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Sample records for advanced electrochemical oxidation

  1. ELECTROCHEMICAL ADVANCED OXIDATION PROCESS UTILIZING NB-DOPED TIO2 ELECTRODES

    EPA Science Inventory

    An electrochemical advanced oxidation process has been developed, utilizing electrodes which generate hydroxyl free radical (HO) by oxidizing water. All substrates tested are oxidized, mostly with reaction rates proportional to the corresponding rate constants for reaction with h...

  2. ELECTROCHEMICAL ADVANCED OXIDATION PROCESS UTILIZING NB-DOPED TIO2 ELECTRODES

    EPA Science Inventory

    An electrochemical advanced oxidation process has been developed utilizing electrodes which generate hydroxyl free radical (HO) by oxidizing water. All substrates tested are oxidized, mostly with reaction rates proportional to the corresponding rate constants for reaction with hy...

  3. Remediation of a winery wastewater combining aerobic biological oxidation and electrochemical advanced oxidation processes.

    PubMed

    Moreira, Francisca C; Boaventura, Rui A R; Brillas, Enric; Vilar, Vítor J P

    2015-05-15

    Apart from a high biodegradable fraction consisting of organic acids, sugars and alcohols, winery wastewaters exhibit a recalcitrant fraction containing high-molecular-weight compounds as polyphenols, tannins and lignins. In this context, a winery wastewater was firstly subjected to a biological oxidation to mineralize the biodegradable fraction and afterwards an electrochemical advanced oxidation process (EAOP) was applied in order to mineralize the refractory molecules or transform them into simpler ones that can be further biodegraded. The biological oxidation led to above 97% removals of dissolved organic carbon (DOC), chemical oxygen demand (COD) and 5-day biochemical oxygen demand (BOD5), but was inefficient on the degradation of a bioresistant fraction corresponding to 130 mg L(-1) of DOC, 380 mg O2 L(-1) of COD and 8.2 mg caffeic acid equivalent L(-1) of total dissolved polyphenols. Various EAOPs such as anodic oxidation with electrogenerated H2O2 (AO-H2O2), electro-Fenton (EF), UVA photoelectro-Fenton (PEF) and solar PEF (SPEF) were then applied to the recalcitrant effluent fraction using a 2.2 L lab-scale flow plant containing an electrochemical cell equipped with a boron-doped diamond (BDD) anode and a carbon-PTFE air-diffusion cathode and coupled to a photoreactor with compound parabolic collectors (CPCs). The influence of initial Fe(2+) concentration and current density on the PEF process was evaluated. The relative oxidative ability of EAOPs increased in the order AO-H2O2 < EF < PEF ≤ SPEF. The SPEF process using an initial Fe(2+) concentration of 35 mg L(-1), current density of 25 mA cm(-2), pH of 2.8 and 25 °C reached removals of 86% on DOC and 68% on COD after 240 min, regarding the biologically treated effluent, along with energy consumptions of 45 kWh (kg DOC)(-1) and 5.1 kWh m(-3). After this coupled treatment, color, odor, COD, BOD5, NH4(+), NO3(-) and SO4(2-) parameters complied with the legislation targets and, in addition, a total dissolved polyphenols content of 0.35 mg caffeic acid equivalent L(-1) was found. Respirometry tests revealed low biodegradability enhancement along the SPEF process. PMID:25765168

  4. Post-treatment of reclaimed waste water based on an electrochemical advanced oxidation process

    NASA Technical Reports Server (NTRS)

    Verostko, Charles E.; Murphy, Oliver J.; Hitchens, G. D.; Salinas, Carlos E.; Rogers, Tom D.

    1992-01-01

    The purification of reclaimed water is essential to water reclamation technology life-support systems in lunar/Mars habitats. An electrochemical UV reactor is being developed which generates oxidants, operates at low temperatures, and requires no chemical expendables. The reactor is the basis for an advanced oxidation process in which electrochemically generated ozone and hydrogen peroxide are used in combination with ultraviolet light irradiation to produce hydroxyl radicals. Results from this process are presented which demonstrate concept feasibility for removal of organic impurities and disinfection of water for potable and hygiene reuse. Power, size requirements, Faradaic efficiency, and process reaction kinetics are discussed. At the completion of this development effort the reactor system will be installed in JSC's regenerative water recovery test facility for evaluation to compare this technique with other candidate processes.

  5. Occurrence and Removal of Organic Micropollutants in Landfill Leachates Treated by Electrochemical Advanced Oxidation Processes.

    PubMed

    Oturan, Nihal; van Hullebusch, Eric D; Zhang, Hui; Mazeas, Laurent; Budzinski, Hélène; Le Menach, Karyn; Oturan, Mehmet A

    2015-10-20

    In recent years, electrochemical advanced oxidation processes have been shown to be an effective alternative for the removal of refractory organic compounds from water. This study is focused on the effective removal of recalcitrant organic matter (micropollutants, humic substances, etc.) present in municipal solid waste landfill leachates. A mixture of eight landfill leachates has been studied by the electro-Fenton process using a Pt or boron-doped diamond (BDD) anode and a carbon felt cathode or by the anodic oxidation process with a BDD anode. These processes exhibit great oxidation ability due to the in situ production of hydroxyl radicals ((•)OH), a highly powerful oxidizing species. Both electrochemical processes were shown to be efficient in the removal of dissolved total organic carbon (TOC) from landfill leachates. Regarding the electro-Fenton process, the replacement of the classical anode Pt by the anode BDD allows better performance in terms of dissolved TOC removal. The occurrence and removal yield of 19 polycyclic aromatic hydrocarbons, 15 volatile organic compounds, 7 alkylphenols, 7 polychlorobiphenyls, 5 organochlorine pesticides, and 2 polybrominated diphenyl ethers in landfill leachate were also investigated. Both electrochemical processes allow one to reach a quasicomplete removal (about 98%) of these organic micropollutants. PMID:26378656

  6. Electrochemical advanced oxidation for cold incineration of the pharmaceutical ranitidine: mineralization pathway and toxicity evolution.

    PubMed

    Olvera-Vargas, Hugo; Oturan, Nihal; Brillas, Enric; Buisson, Didier; Esposito, Giovanni; Oturan, Mehmet A

    2014-12-01

    Ranitidine (RNTD) is a widely prescribed histamine H2-receptor antagonist whose unambiguous presence in water sources appointed it as an emerging pollutant. Here, the degradation of 0.1 mM of this drug in aqueous medium was studied by electrochemical advanced oxidation processes (EAOPs) like anodic oxidation with electrogenerated H2O2 and electro-Fenton using Pt/carbon-felt, BDD/carbon-felt and DSA-Ti/RuO2–IrO2/carbon-felt cells. The higher oxidation power of the electro-Fenton process using a BDD anode was demonstrated. The oxidative degradation of RNTD by the electrochemically generated OH radicals obeyed a pseudo-first order kinetics. The absolute rate constant for its hydroxylation reaction was 3.39 × 109 M−1 s−1 as determined by the competition kinetics method. Almost complete mineralization of the RNTN solution was reached by using a BDD anode in both anodic oxidation with electrogenerated H2O2 and electro-Fenton processes. Up to 11 cyclic intermediates with furan moiety were detected from the degradation of RNTD, which were afterwards oxidized to short-chain carboxylic acids before their mineralization to CO2 and inorganic ions such as NH4+, NO3− and SO42−. Based on identified products, a plausible reaction pathway was proposed for RNTD mineralization. Toxicity assessment by the Microtox® method revealed that some cyclic intermediates are more toxic than the parent molecule. Toxicity was quickly removed following the almost total mineralization of the treated solution. Overall results confirm the effectiveness of EAOPs for the efficient removal of RNTD and its oxidation by-products from water. PMID:25461930

  7. Electrochemical advanced oxidation and biological processes for wastewater treatment: a review of the combined approaches.

    PubMed

    Ganzenko, Oleksandra; Huguenot, David; van Hullebusch, Eric D; Esposito, Giovanni; Oturan, Mehmet A

    2014-01-01

    As pollution becomes one of the biggest environmental challenges of the twenty-first century, pollution of water threatens the very existence of humanity, making immediate action a priority. The most persistent and hazardous pollutants come from industrial and agricultural activities; therefore, effective treatment of this wastewater prior to discharge into the natural environment is the solution. Advanced oxidation processes (AOPs) have caused increased interest due to their ability to degrade hazardous substances in contrast to other methods, which mainly only transfer pollution from wastewater to sludge, a membrane filter, or an adsorbent. Among a great variety of different AOPs, a group of electrochemical advanced oxidation processes (EAOPs), including electro-Fenton, is emerging as an environmental-friendly and effective treatment process for the destruction of persistent hazardous contaminants. The only concern that slows down a large-scale implementation is energy consumption and related investment and operational costs. A combination of EAOPs with biological treatment is an interesting solution. In such a synergetic way, removal efficiency is maximized, while minimizing operational costs. The goal of this review is to present cutting-edge research for treatment of three common and problematic pollutants and effluents: dyes and textile wastewater, olive processing wastewater, and pharmaceuticals and hospital wastewater. Each of these types is regarded in terms of recent scientific research on individual electrochemical, individual biological and a combined synergetic treatment. PMID:24965093

  8. Application of electrochemical advanced oxidation processes to the mineralization of the herbicide diuron.

    PubMed

    Pipi, Angelo R F; Sirés, Ignasi; De Andrade, Adalgisa R; Brillas, Enric

    2014-08-01

    Here, solutions with 0.185mM of the herbicide diuron of pH 3.0 have been treated by electrochemical advanced oxidation processes (EAOPs) like electrochemical oxidation with electrogenerated H2O2 (EO-H2O2), electro-Fenton (EF) and UVA photoelectro-Fenton (PEF) or solar PEF (SPEF). Trials were performed in stirred tank reactors of 100mL and in a recirculation flow plant of 2.5L using a filter-press reactor with a Pt or boron-doped diamond (BDD) anode and an air-diffusion cathode for H2O2 electrogeneration. Oxidant hydroxyl radicals were formed from water oxidation at the anode and/or in the bulk from Fenton's reaction between added Fe(2+) and generated H2O2. In both systems, the relative oxidation ability of the EAOPs increased in the sequence EO-H2O2

  9. Toxicological and chemical assessment of arsenic-contaminated groundwater after electrochemical and advanced oxidation treatments.

    PubMed

    Radić, Sandra; Crnojević, Helena; Vujčić, Valerija; Gajski, Goran; Gerić, Marko; Cvetković, Želimira; Petra, Cvjetko; Garaj-Vrhovac, Vera; Oreščanin, Višnja

    2016-02-01

    Owing to its proven toxicity and mutagenicity, arsenic is regarded a principal pollutant in water used for drinking. The objective of this study was the toxicological and chemical evaluation of groundwater samples obtained from arsenic enriched drinking water wells before and after electrochemical and ozone-UV-H2O2-based advanced oxidation processes (EAOP). For this purpose, acute toxicity test with Daphnia magna and chronic toxicity test with Lemna minor L. were employed as well as in vitro bioassays using human peripheral blood lymphocytes (HPBLs). Several oxidative stress parameters were estimated in L.minor. Physicochemical analysis showed that EAOP treatment was highly efficient in arsenic but also in ammonia and organic compound removal from contaminated groundwater. Untreated groundwater caused only slight toxicity to HPBLs and D. magna in acute experiments. However, 7-day exposure of L. minor to raw groundwater elicited genotoxicity, a significant growth inhibition and oxidative stress injury. The observed genotoxicity and toxicity of raw groundwater samples was almost completely eliminated by EAOP treatment. Generally, the results obtained with L. minor were in agreement with those obtained in the chemical analysis suggesting the sensitivity of the model organism in monitoring of arsenic-contaminated groundwater. In parallel to chemical analysis, the implementation of chronic toxicity bioassays in a battery is recommended in the assessment of the toxic and genotoxic potential of such complex mixtures. PMID:26580737

  10. Electrochemical oxidation of cholesterol

    PubMed Central

    2015-01-01

    Summary Indirect cholesterol electrochemical oxidation in the presence of various mediators leads to electrophilic addition to the double bond, oxidation at the allylic position, oxidation of the hydroxy group, or functionalization of the side chain. Recent studies have proven that direct electrochemical oxidation of cholesterol is also possible and affords different products depending on the reaction conditions. PMID:25977713

  11. Recent advances in nanostructured Nb-based oxides for electrochemical energy storage

    NASA Astrophysics Data System (ADS)

    Yan, Litao; Rui, Xianhong; Chen, Gen; Xu, Weichuan; Zou, Guifu; Luo, Hongmei

    2016-04-01

    For the past five years, nanostructured niobium-based oxides have emerged as one of the most prominent materials for batteries, supercapacitors, and fuel cell technologies, for instance, TiNb2O7 as an anode for lithium-ion batteries (LIBs), Nb2O5 as an electrode for supercapacitors (SCs), and niobium-based oxides as chemically stable electrochemical supports for fuel cells. Their high potential window can prevent the formation of lithium dendrites, and their rich redox chemistry (Nb5+/Nb4+, Nb4+/Nb3+) makes them very promising electrode materials. Their unique chemical stability under acid conditions is favorable for practical fuel-cell operation. In this review, we summarized recent progress made concerning the use of niobium-based oxides as electrodes for batteries (LIBs, sodium-ion batteries (SIBs), and vanadium redox flow batteries (VRBs)), SCs, and fuel cell applications. Moreover, crystal structures, charge storage mechanisms in different crystal structures, and electrochemical performances in terms of the specific capacitance/capacity, rate capability, and cycling stability of niobium-based oxides are discussed. Insights into the future research and development of niobium-based oxide compounds for next-generation electrochemical devices are also presented. We believe that this review will be beneficial for research scientists and graduate students who are searching for promising electrode materials for batteries, SCs, and fuel cells.

  12. Recent advances in nanostructured Nb-based oxides for electrochemical energy storage.

    PubMed

    Yan, Litao; Rui, Xianhong; Chen, Gen; Xu, Weichuan; Zou, Guifu; Luo, Hongmei

    2016-04-28

    For the past five years, nanostructured niobium-based oxides have emerged as one of the most prominent materials for batteries, supercapacitors, and fuel cell technologies, for instance, TiNb2O7 as an anode for lithium-ion batteries (LIBs), Nb2O5 as an electrode for supercapacitors (SCs), and niobium-based oxides as chemically stable electrochemical supports for fuel cells. Their high potential window can prevent the formation of lithium dendrites, and their rich redox chemistry (Nb(5+)/Nb(4+), Nb(4+)/Nb(3+)) makes them very promising electrode materials. Their unique chemical stability under acid conditions is favorable for practical fuel-cell operation. In this review, we summarized recent progress made concerning the use of niobium-based oxides as electrodes for batteries (LIBs, sodium-ion batteries (SIBs), and vanadium redox flow batteries (VRBs)), SCs, and fuel cell applications. Moreover, crystal structures, charge storage mechanisms in different crystal structures, and electrochemical performances in terms of the specific capacitance/capacity, rate capability, and cycling stability of niobium-based oxides are discussed. Insights into the future research and development of niobium-based oxide compounds for next-generation electrochemical devices are also presented. We believe that this review will be beneficial for research scientists and graduate students who are searching for promising electrode materials for batteries, SCs, and fuel cells. PMID:27074412

  13. Decolorization and mineralization of Allura Red AC aqueous solutions by electrochemical advanced oxidation processes.

    PubMed

    Thiam, Abdoulaye; Sirés, Ignasi; Garrido, José A; Rodríguez, Rosa M; Brillas, Enric

    2015-06-15

    The decolorization and mineralization of solutions containing 230 mg L(-1) of the food azo dye Allura Red AC at pH 3.0 have been studied upon treatment by electrochemical oxidation with electrogenerated H2O2 (EO-H2O2), electro-Fenton (EF) and photoelectro-Fenton (PEF). Experiments were performed with a stirred tank reactor containing a boron-doped diamond (BDD) or Pt anode and an air-diffusion cathode to generate H2O2. The main oxidants were hydroxyl radicals formed at the anode surface from water oxidation and in the bulk from Fenton's reaction between H2O2 and added Fe(2+). The oxidation ability increased in the sequence EO-H2O2 < EF < PEF and faster degradation was always obtained using BDD. PEF process with BDD yielded almost total mineralization following similar trends in SO4(2-), ClO4(-) and NO3(-) media, whereas in Cl(-) medium, mineralization was inhibited by the formation of recalcitrant chloroderivatives. GC-MS analysis confirmed the cleavage of the −N=N− bond with formation of two main aromatics in SO4(2-) medium and three chloroaromatics in Cl(-) solutions. The effective oxidation of final oxalic and oxamic acids by BDD along with the photolysis of Fe(III)-oxalate species by UVA light accounted for the superiority of PEF with BDD. NH4(+), NO3(-) and SO4(2-) ions were released during the mineralization. PMID:25734532

  14. Electrochemical oxidation of chemical weapons

    SciTech Connect

    Surma, J.E.

    1994-05-01

    Catalyzed electrochemical oxidation (CEO), a low-temperature electrochemical oxidation technique, is being examined for its potential use in destroying chemical warfare agents. The CEO process oxidizes organic compounds to form carbon dioxide and water. A bench-scale CEO system was used in three separate tests sponsored by the US Department of Energy`s (DOE) Office of Intelligence and National Security through the Advanced Concepts Program. The tests examined the effectiveness of CEO in destroying sarin (GB), a chemical nerve agent. The tests used 0.5 mL, 0.95 mL, and 1.0 mL of GB, corresponding to 544 mg, 816 mg, and 1,090 mg, respectively, of GB. Analysis of the off gas showed that, under continuous processing of the GB agent, destruction efficiencies of better than six 9s (99.9999% destroyed) could be achieved.

  15. Electrochemical oxidation of chlorophenols

    SciTech Connect

    Polcaro, A.M.; Palmas, S.

    1997-05-01

    Electrochemical 2-chlorophenol and 2,6-dichlorophenol removal from aqueous solutions using porous carbon felt anodes was investigated. Operating variables including current input, ratio between electrode and solution volumes, and initial pollutant concentration were considered in order to determine their influence on the faradic efficiency of the process. The byproducts of the oxidation reaction were identified, and their concentration was determined during the electrolysis. The experimental results showed that a satisfactory detoxification, consisting of removal of cyclic chlorinated compounds, could be accomplished by means of this electrochemical method with a faradic efficiency of 30% under optimized conditions. A mathematical model based on the reaction between chlorophenols adsorbed on the carbon fibers of the electrode and hydroxyl radicals produced by anodic oxidation of water has been proposed in order to interpret the experimental behavior of the system under different operating conditions.

  16. Solid oxide electrochemical reactor science.

    SciTech Connect

    Sullivan, Neal P.; Stechel, Ellen Beth; Moyer, Connor J.; Ambrosini, Andrea; Key, Robert J.

    2010-09-01

    Solid-oxide electrochemical cells are an exciting new technology. Development of solid-oxide cells (SOCs) has advanced considerable in recent years and continues to progress rapidly. This thesis studies several aspects of SOCs and contributes useful information to their continued development. This LDRD involved a collaboration between Sandia and the Colorado School of Mines (CSM) ins solid-oxide electrochemical reactors targeted at solid oxide electrolyzer cells (SOEC), which are the reverse of solid-oxide fuel cells (SOFC). SOECs complement Sandia's efforts in thermochemical production of alternative fuels. An SOEC technology would co-electrolyze carbon dioxide (CO{sub 2}) with steam at temperatures around 800 C to form synthesis gas (H{sub 2} and CO), which forms the building blocks for a petrochemical substitutes that can be used to power vehicles or in distributed energy platforms. The effort described here concentrates on research concerning catalytic chemistry, charge-transfer chemistry, and optimal cell-architecture. technical scope included computational modeling, materials development, and experimental evaluation. The project engaged the Colorado Fuel Cell Center at CSM through the support of a graduate student (Connor Moyer) at CSM and his advisors (Profs. Robert Kee and Neal Sullivan) in collaboration with Sandia.

  17. Electrochemical oxidation of organic waste

    SciTech Connect

    Almon, A.C.; Buchanan, B.R.

    1990-01-01

    Both silver catalyzed and direct electrochemical oxidation of organic species are examined in analytical detail. This paper describes the mechanisms, reaction rates, products, intermediates, capabilities, limitations, and optimal reaction conditions of the electrochemical destruction of organic waste. A small bench-top electrocell being tested for the treatment of small quantities of laboratory waste is described. The 200-mL electrochemical cell used has a processing capacity of 50 mL per day, and can treat both radioactive and nonradioactive waste. In the silver catalyzed process, Ag(I) is electrochemically oxidized to Ag(II), which attacks organic species such as tributylphosphate (TBP), tetraphenylborate (TPB), and benzene. In direct electrochemical oxidation, the organic species are destroyed at the surface of the working electrode without the use of silver as an electron transfer agent. This paper focuses on the destruction of tributylphosphate (TBP), although several organic species have been destroyed using this process. The organic species are converted to carbon dioxide, water, and inorganic acids.

  18. Electrochemical oxidation of organic waste

    SciTech Connect

    Almon, A.C.; Buchanan, B.R.

    1990-12-31

    Both silver catalyzed and direct electrochemical oxidation of organic species are examined in analytical detail. This paper describes the mechanisms, reaction rates, products, intermediates, capabilities, limitations, and optimal reaction conditions of the electrochemical destruction of organic waste. A small bench-top electrocell being tested for the treatment of small quantities of laboratory waste is described. The 200-mL electrochemical cell used has a processing capacity of 50 mL per day, and can treat both radioactive and nonradioactive waste. In the silver catalyzed process, Ag(I) is electrochemically oxidized to Ag(II), which attacks organic species such as tributylphosphate (TBP), tetraphenylborate (TPB), and benzene. In direct electrochemical oxidation, the organic species are destroyed at the surface of the working electrode without the use of silver as an electron transfer agent. This paper focuses on the destruction of tributylphosphate (TBP), although several organic species have been destroyed using this process. The organic species are converted to carbon dioxide, water, and inorganic acids.

  19. Electrochemical oxidation for landfill leachate treatment

    SciTech Connect

    Deng, Yang Englehardt, James D.

    2007-07-01

    This paper aims at providing an overview of electrochemical oxidation processes used for treatment of landfill leachate. The typical characteristics of landfill leachate are briefly reviewed, and the reactor designs used for electro-oxidation of leachate are summarized. Electrochemical oxidation can significantly reduce concentrations of organic contaminants, ammonia, and color in leachate. Pretreatment methods, anode materials, pH, current density, chloride concentration, and other additional electrolytes can considerably influence performance. Although high energy consumption and potential chlorinated organics formation may limit its application, electrochemical oxidation is a promising and powerful technology for treatment of landfill leachate.

  20. Electrochemical carbon dioxide concentrator advanced technology tasks

    NASA Technical Reports Server (NTRS)

    Schneider, J. J.; Schubert, F. H.; Hallick, T. M.; Woods, R. R.

    1975-01-01

    Technology advancement studies are reported on the basic electrochemical CO2 removal process to provide a basis for the design of the next generation cell, module and subsystem hardware. An Advanced Electrochemical Depolarized Concentrator Module (AEDCM) is developed that has the characteristics of low weight, low volume, high CO2, removal, good electrical performance and low process air pressure drop. Component weight and noise reduction for the hardware of a six man capacity CO2 collection subsystem was developed for the air revitalization group of the Space Station Prototype (SSP).

  1. Dechlorination by combined electrochemical reduction and oxidation.

    PubMed

    Cong, Yan-qing; Wu, Zu-cheng; Tan, Tian-en

    2005-06-01

    Chlorophenols are typical priority pollutants listed by USEPA (U.S. Environmental Protection Agency). The removal of chlorophenol could be carried out by a combination of electrochemical reduction and oxidation method. Results showed that it was feasible to degrade contaminants containing chlorine atoms by electrochemical reduction to form phenol, which was further degraded on the anode by electrochemical oxidation. Chlorophenol removal rate was more than 90% by the combined electrochemical reduction and oxidation at current of 6 mA and pH 6. The hydrogen atom is a powerful reducing agent that reductively dechlorinates chlorophenols. The instantaneous current efficiency was calculated and the results indicated that cathodic reduction was the main contributor to the degradation of chlorophenol. PMID:15909345

  2. Dechlorination by combined electrochemical reduction and oxidation*

    PubMed Central

    Cong, Yan-qing; Wu, Zu-cheng; Tan, Tian-en

    2005-01-01

    Chlorophenols are typical priority pollutants listed by USEPA (U.S. Environmental Protection Agency). The removal of chlorophenol could be carried out by a combination of electrochemical reduction and oxidation method. Results showed that it was feasible to degrade contaminants containing chlorine atoms by electrochemical reduction to form phenol, which was further degraded on the anode by electrochemical oxidation. Chlorophenol removal rate was more than 90% by the combined electrochemical reduction and oxidation at current of 6 mA and pH 6. The hydrogen atom is a powerful reducing agent that reductively dechlorinates chlorophenols. The instantaneous current efficiency was calculated and the results indicated that cathodic reduction was the main contributor to the degradation of chlorophenol. PMID:15909345

  3. Toxicity assessment of the water used for human consumption from the Cameron/Tuba City abandoned uranium mining area prior/after the combined electrochemical treatment/advanced oxidation.

    PubMed

    Gajski, Goran; Oreščanin, Višnja; Gerić, Marko; Kollar, Robert; Lovrenčić Mikelić, Ivanka; Garaj-Vrhovac, Vera

    2015-01-01

    The purpose of this work was detailed physicochemical, radiological, and toxicological characterization of the composite sample of water intended for human consumption in the Cameron/Tuba City abandoned uranium mining area before and after a combined electrochemical/advanced oxidation treatment. Toxicological characterization was conducted on human lymphocytes using a battery of bioassays. On the bases of the tested parameters, it could be concluded that water used for drinking from the tested water sources must be strictly forbidden for human and/or animal consumption since it is extremely cytogenotoxic, with high oxidative stress potential. A combined electrochemical treatment and posttreatment with ozone and UV light decreased the level of all physicochemical and radiological parameters below the regulated values. Consequently, the purified sample was neither cytotoxic nor genotoxic, indicating that the presented method could be used for the improvement of water quality from the sites highly contaminated with the mixture of heavy metals and radionuclides. PMID:25087498

  4. Dual Electrical-Behavior Regulation on Electrocatalysts Realizing Enhanced Electrochemical Water Oxidation.

    PubMed

    Xu, Kun; Ding, Hui; Lv, Haifeng; Chen, Pengzuo; Lu, Xiuli; Cheng, Han; Zhou, Tianpei; Liu, Si; Wu, Xiaojun; Wu, Changzheng; Xie, Yi

    2016-05-01

    Dual electrical-behavior regulation on electrocatalysts is proven to be an effective strategy for realizing enhanced electrochemical water oxidation. Electrical-behavior regulation opens up a promising avenue to design advanced electrocatalysts. PMID:26928560

  5. Fabrication of advanced electrochemical energy materials using sol-gel processing techniques

    NASA Technical Reports Server (NTRS)

    Chu, C. T.; Chu, Jay; Zheng, Haixing

    1995-01-01

    Advanced materials play an important role in electrochemical energy devices such as batteries, fuel cells, and electrochemical capacitors. They are being used as both electrodes and electrolytes. Sol-gel processing is a versatile solution technique used in fabrication of ceramic materials with tailored stoichiometry, microstructure, and properties. The application of sol-gel processing in the fabrication of advanced electrochemical energy materials will be presented. The potentials of sol-gel derived materials for electrochemical energy applications will be discussed along with some examples of successful applications. Sol-gel derived metal oxide electrode materials such as V2O5 cathodes have been demonstrated in solid-slate thin film batteries; solid electrolytes materials such as beta-alumina for advanced secondary batteries had been prepared by the sol-gel technique long time ago; and high surface area transition metal compounds for capacitive energy storage applications can also be synthesized with this method.

  6. Solid oxide electrochemical cell fabrication process

    DOEpatents

    Dollard, Walter J.; Folser, George R.; Pal, Uday B.; Singhal, Subhash C.

    1992-01-01

    A method to form an electrochemical cell (12) is characterized by the steps of thermal spraying stabilized zirconia over a doped lanthanum manganite air electrode tube (14) to provide an electrolyte layer (15), coating conductive particles over the electrolyte, pressurizing the outside of the electrolyte layer, feeding halide vapors of yttrium and zirconium to the outside of the electrolyte layer and feeding a source of oxygen to the inside of the electrolyte layer, heating to cause oxygen reaction with the halide vapors to close electrolyte pores if there are any and to form a metal oxide coating on and between the particles and provide a fuel electrode (16).

  7. Degradation of pharmaceutical beta-blockers by electrochemical advanced oxidation processes using a flow plant with a solar compound parabolic collector.

    PubMed

    Isarain-Chávez, Eloy; Rodríguez, Rosa María; Cabot, Pere Lluís; Centellas, Francesc; Arias, Conchita; Garrido, José Antonio; Brillas, Enric

    2011-08-01

    The degradation of the beta-blockers atenolol, metoprolol tartrate and propranolol hydrochloride was studied by electro-Fenton (EF) and solar photoelectro-Fenton (SPEF). Solutions of 10 L of 100 mg L⁻¹ of total organic carbon of each drug in 0.1 M Na₂SO₄ with 0.5 mM Fe²⁺ of pH 3.0 were treated in a recirculation flow plant with an electrochemical reactor coupled with a solar compound parabolic collector. Single Pt/carbon felt (CF) and boron-doped diamond (BDD)/air-diffusion electrode (ADE) cells and combined Pt/ADE-Pt/CF and BDD/ADE-Pt/CF cells were used. SPEF treatments were more potent with the latter cell, yielding 95-97% mineralization with 100% of maximum current efficiency and energy consumptions of about 0.250 kWh g TOC⁻¹. However, the Pt/ADE-Pt/CF cell gave much lower energy consumptions of about 0.080 kWh g TOC⁻¹ with slightly lower mineralization of 88-93%, then being more useful for its possible application at industrial level. The EF method led to a poorer mineralization and was more potent using the combined cells by the additional production of hydroxyl radicals (•OH) from Fenton's reaction from the fast Fe²⁺ regeneration at the CF cathode. Organics were also more rapidly destroyed at BDD than at Pt anode. The decay kinetics of beta-blockers always followed a pseudo first-order reaction, although in SPEF, it was accelerated by the additional production of •OH from the action of UV light of solar irradiation. Aromatic intermediates were also destroyed by hydroxyl radicals. Ultimate carboxylic acids like oxalic and oxamic remained in the treated solutions by EF, but their Fe(III) complexes were photolyzed by solar irradiation in SPEF, thus explaining its higher oxidation power. NO₃⁻ was the predominant inorganic ion lost in EF, whereas the SPEF process favored the production of NH₄⁺ ion and volatile N-derivatives. PMID:21693380

  8. Electrochemical oxidation of phenol using graphite anodes

    SciTech Connect

    Awad, Y.M.; Abuzaid, N.S.

    1999-02-01

    The effects of current and pH on the electrochemical oxidation of phenol on graphite electrodes is investigated in this study. There was no sign of deterioration of the graphite bed after 5 months of operation. Phenol removal efficiency was a function of the current applied and was around 70% at a current of 2.2 A. The increase of phenol removal efficiency with current is attributed to the increase of ionic transport which increases the rate of electrode reactions responsible for the removal process. The percentage of complete oxidation of phenol increases with current, with a maximum value of about 50%. However, at pH 0.2 it is slightly higher than that at pH 0.5 at all currents. The phenol removal rate increases with increases of current and pH. While the current (CO{sub 2}) efficiency reaches a maximum value in the current range of 1.0--1.2 A, it increases with an increase of acid concentration. The findings of this study have important implications: while anodic oxidation of phenol on graphite can achieve acceptable removal of phenol, the extent of oxidation should not be overlooked.

  9. Electrochemical and microstructural study of oxide films formed electrochemically at microcrystalline Al-Fe-V-Si alloys.

    PubMed

    Thomas, S C; Birss, V I; Steele, D; Tessier, D

    1995-07-01

    A recent advance in metallurgical technology has been the application of rapid solidification techniques to Al alloy production. FVS0812 is the designation given to a microcrystalline Al-based alloy consisting of 8 wt% Fe, 1 wt% V and 2 wt% Si. It is a two-phase alloy, consisting of ca. 27 vol percent of approximately spherical Fe-V-Si-rich dispersoids in an essentially pure Al matrix. The high strength, low density properties of this advanced material, and other related alloys, have not yet been realized, however, due, in part, to the inability of the alloy to form a thick, adherent, abrasion-resistant outer surface oxide film, a feature readily achieved at conventional Al alloys by normal anodizing methods. The present research has involved an electro-chemical study of oxide film growth at the 812 alloy, with the specific goals being to seek an understanding of the origin of the oxide film growth problem and ultimately to propose alternative approaches to the formation of a thick, stable oxide film at this material. The techniques used in this research have included electrochemical methodologies such as cyclic voltammetry and electrochemical impedance spectroscopy. Crucial information has been obtained through transmission electron microscopy (TEM) of ultramicrotomed specimens. Experiments were carried out initially in neutral borate solutions to characterize the compact barrier oxide film formed in this environment and expected to be present beneath the porous oxide film formed in the normal sulfuric acid anodizing medium.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:7549001

  10. Technology advancement of the electrochemical CO2 concentrating process

    NASA Technical Reports Server (NTRS)

    Schubert, F. H.; Heppner, D. B.; Hallick, T. M.; Woods, R. R.

    1979-01-01

    Two multicell, liquid-cooled, advanced electrochemical depolarized carbon dioxide concentrator modules were fabricated. The cells utilized advanced, lightweight, plated anode current collectors, internal liquid cooling and lightweight cell frames. Both were designed to meet the carbon dioxide removal requirements of one-person, i.e., 1.0 kg/d (2.2 lb/d).

  11. Electrochemical oxidation of perfluorinated compounds in water.

    PubMed

    Niu, Junfeng; Li, Yang; Shang, Enxiang; Xu, Zesheng; Liu, Jinzi

    2016-03-01

    Perfluorinated compounds (PFCs) are persistent and refractory organic pollutants that have been detected in various environmental matrices and municipal wastewater. Electrochemical oxidation (EO) is a promising remediation technique for wastewater contaminated with PFCs. A number of recent studies have demonstrated that the "non-active" anodes, including boron-doped diamond, tin oxide, and lead dioxide, are effective in PFCs elimination in wastewater due to their high oxygen evolution potential. Many researchers have conducted experiments to investigate the optimal conditions (i.e., potential, current density, pH value, plate distance, initial PFCs concentration, electrolyte, and other factors) for PFCs elimination to obtain the maximal elimination efficiency and current efficiency. The EO mechanism and pathways of PFCs have been clearly elucidated, which undergo electron transfer, Kolbe decarboxylation or desulfonation, hydrolysis, and radical reaction. In addition, the safety evaluation and energy consumption evaluation of the EO technology have also been summarized to decrease toxic ion release from electrode and reduce the cost of this technique. Although the ultrasonication and hydrothermal techniques combined with the EO process can improve the removal efficiency and current efficiency significantly, these coupled techniques have not been commercialized and applied in industrial wastewater treatment. Finally, key challenges facing EO technology are listed and the directions for further research are pointed out (such as combination with other techniques, treatment for natural waters contaminated by low levels of PFCs, and reactor design). PMID:26745381

  12. Oxidation of artificial sweetener sucralose by advanced oxidation processes: a review.

    PubMed

    Sharma, Virender K; Oturan, Mehmet; Kim, Hyunook

    2014-01-01

    Sucralose, a chlorinated carbohydrate, has shown its increased use as an artificial sweetener and persistently exists in wastewater treatment plant effluents and aquatic environment. This paper aims to review possible degradation of sucralose and related carbohydrates by biological, electrochemical, chemical, and advanced oxidation processes. Biodegradation of sucralose in waterworks did not occur significantly. Electrochemical oxidation of carbohydrates may be applied to seek degradation of sucralose. The kinetics of the oxidation of sucralose and the related carbohydrates by different oxidative species is compared. Free chlorine, ozone, and ferrate did not show any potential to degrade sucralose in water. Advanced oxidation processes, generating highly strong oxidizing agent hydroxyl radicals ((•)OH), have demonstrated effectiveness in transforming sucralose in water. The mechanism of oxidation of sucralose by (•)OH is briefly discussed. PMID:24687789

  13. Electrochemically reduced graphene oxide / sulfonated polyether ether ketone composite membrane for electrochemical applications

    NASA Astrophysics Data System (ADS)

    Seetharaman, S.; Ramya, K.; Dhathathreyan, K. S.

    2013-06-01

    A simple and effective method for the preparation of sulfonated polyether ether ketone (SPEEK) based composites with electrochemical reduced graphene oxide (EGO) as inorganic fillers has been described. The resulting dispersions are homogeneous and the cast membranes show significant improvement on tensile strength and thermal properties. It has high ionic conductivity and is cost effective making it a promising alternative membrane for electrochemical applications.

  14. Tutorial Review: Electrochemical Nitric Oxide Sensors for Physiological Measurements

    PubMed Central

    Privett, Benjamin J.; Shin, Jae Ho; Schoenfisch, Mark H.

    2013-01-01

    Summary The important biological roles of nitric oxide (NO) have prompted the development of analytical techniques capable of sensitive and selective detection of NO. Electrochemical sensing, more than any other NO-detection method, embodies the parameters necessary for quantifying NO in challenging physiological environments such as blood and the brain. Herein, we provide a broad overview of the field of electrochemical NO sensors, including design, fabrication, and analytical performance characteristics. Both electrochemical sensors and biological applications are detailed. PMID:20502795

  15. Advanced materials and electrochemical processes in high-temperature solid electrolytes

    SciTech Connect

    Bates, J.L.; Chick, L.A.; Youngblood, G.E.; Weber, W.J.

    1990-10-01

    Fuel cells for the direct conversion of fossil fuels to electric energy necessitates the use of high-temperature solid electrodes. This study has included: (1) determination of electrical transport, thermal and electrical properties to illucidate the effects of microstructure, phase equilibria, oxygen partial pressure, additives, synthesis and fabrication on these properties; (2) investigation of synthesis and fabrication of advanced oxide materials, such as La{sub 0.9}Sn{sub 0.1}MnO{sub 3}; and (3) application of new analytical techniques using complex impedance coupled with conventional electrochemical methods to study the electrochemical processes and behavior of materials for solid oxide fuel cells and other high-temperature electrolyte electrochemical process. 15 refs., 10 figs., 2 tabs. (BM)

  16. ADVANCED OXIDATION PROCESS

    SciTech Connect

    Dr. Colin P. Horwitz; Dr. Terrence J. Collins

    2003-11-04

    The removal of recalcitrant sulfur species, dibenzothiophene and its derivatives, from automotive fuels is an integral component in the development of cleaner burning and more efficient automobile engines. Oxidative desulfurization (ODS) wherein the dibenzothiophene derivative is converted to its corresponding sulfoxide and sulfone is an attractive approach to sulfur removal because the oxidized species are easily extracted or precipitated and filtered from the hydrocarbon phase. Fe-TAML{reg_sign} activators of hydrogen peroxide (TAML is Tetra-Amido-Macrocyclic-Ligand) catalytically convert dibenzothiophene and its derivatives rapidly and effectively at moderate temperatures (50-60 C) and ambient pressure to the corresponding sulfoxides and sulfones. The oxidation process can be performed in both aqueous systems containing alcohols such as methanol, ethanol, or t-butanol, and in a two-phase hydrocarbon/aqueous system containing tert-butanol or acetonitrile. In the biphasic system, essentially complete conversion of the DBT to its oxidized products can be achieved using slightly longer reaction times than in homogeneous solution. Among the key features of the technology are the mild reaction conditions, the very high selectivity where no over oxidation of the sulfur compounds occurs, the near stoichiometric use of hydrogen peroxide, the apparent lack of degradation of sensitive fuel components, and the ease of separation of oxidized products.

  17. Electrode electrolyte interlayers containing cerium oxide for electrochemical fuel cells

    DOEpatents

    Borglum, Brian P.; Bessette, Norman F.

    2000-01-01

    An electrochemical cell is made having a porous fuel electrode (16) and a porous air electrode (13), with solid oxide electrolyte (15) therebetween, where the air electrode surface opposing the electrolyte has a separate, attached, dense, continuous layer (14) of a material containing cerium oxide, and where electrolyte (16) contacts the continuous oxide layer (14), without contacting the air electrode (13).

  18. Oxide modified air electrode surface for high temperature electrochemical cells

    DOEpatents

    Singh, Prabhakar; Ruka, Roswell J.

    1992-01-01

    An electrochemical cell is made having a porous cermet electrode (16) and a porous lanthanum manganite electrode (14), with solid oxide electrolyte (15) between them, where the lanthanum manganite surface next to the electrolyte contains a thin discontinuous layer of high surface area cerium oxide and/or praseodymium oxide, preferably as discrete particles (30) in contact with the air electrode and electrolyte.

  19. Technology advancement of the electrochemical CO2 concentrating process

    NASA Technical Reports Server (NTRS)

    Schubert, F. H.; Woods, R. R.; Hallick, T. M.; Heppner, D. B.

    1978-01-01

    The overall objectives of the present program are to: (1) improve the performance of the electrochemical CO2 removal technique by increasing CO2 removal efficiencies at pCO2 levels below 400 Pa, increasing cell power output and broadening the tolerance of electrochemical cells for operation over wide ranges of cabin relative humidity; (2) design, fabricate, and assemble development hardware to continue the evolution of the electrochemical concentrating technique from the existing level to an advanced level able to efficiently meet the CO2 removal needs of a spacecraft air revitalization system (ARS); (3) develop and incorporate into the EDC the components and concepts that allow for the efficient integration of the electrochemical technique with other subsystems to form a spacecraft ARS; (4) combine ARS functions to enable the elimination of subsystem components and interfaces; and (5) demonstrate the integration concepts through actual operation of a functionally integrated ARS.

  20. Electrochemical water oxidation with carbon-grafted iridium complexes.

    PubMed

    deKrafft, Kathryn E; Wang, Cheng; Xie, Zhigang; Su, Xin; Hinds, Bruce J; Lin, Wenbin

    2012-02-01

    Hydrogen production from water splitting provides a potential solution to storing harvested solar energy in chemical fuels, but this process requires active and robust catalysts that can oxidize water to provide a source of electrons for proton reduction. Here we report the direct, covalent grafting of molecular Ir complexes onto carbon electrodes, with up to a monolayer coverage. Carbon-grafted Ir complexes electrochemically oxidize water with a turnover frequency of up to 3.3 s(-1) and a turnover number of 644 during the first hour. Electrochemical water oxidation with grafted catalysts gave enhanced rates and stability compared to chemically driven water oxidation with the corresponding molecular catalysts. This strategy provides a way to systematically evaluate catalysts under tunable conditions, potentially providing new insights into electrochemical water oxidation processes and water oxidation catalyst design. PMID:22292527

  1. ADVANCED OXIDATION PROCESS

    SciTech Connect

    Colin P. Horwitz; Terrence J. Collins

    2003-10-22

    The design of new, high efficiency and cleaner burning engines is strongly coupled with the removal of recalcitrant sulfur species, dibenzothiophene and its derivatives, from fuels. Oxidative desulfurization (ODS) wherein these dibenzothiophene derivatives are oxidized to their corresponding sulfoxides and sulfones is an approach that has gained significant attention. Fe-TAML{reg_sign} activators of hydrogen peroxide (TAML is Tetra-Amido-Macrocyclic-Ligand) convert in a catalytic process dibenzothiophene and its derivatives to the corresponding sulfoxides and sulfones rapidly at moderate temperatures (60 C) and ambient pressure. The reaction can be performed in both an aqueous system containing an alcohol (methanol, ethanol, or t-butanol) to solubilize the DBT and in a two-phase hydrocarbon/aqueous system where the alcohol is present in both phases and facilitates the oxidation. Under a consistent set of conditions using the FeBF{sub 2} TAML activator, the degree of conversion was found to be t-butanol > methanol > ethanol. In the cases of methanol and ethanol, both the sulfoxide and sulfone were observed while for t-butanol only the sulfone was detected. In the two-phase system, the alcohol may function as an inverse phase transfer agent. The oxidation was carried out using two different TAML activators. In homogeneous solution, approximately 90% oxidation of the DBT could be achieved using the prototype TAML activator, FeB*, by sonicating the solution at near room temperature. In bi-phasic systems conversions as high as 50% were achieved using the FeB* TAML activator and hydrogen peroxide at 100 C. The sonication method yielded only {approx}6% conversion but this may have been due to mixing.

  2. Technology advancement of the electrochemical CO2 concentrating process

    NASA Technical Reports Server (NTRS)

    Schubert, F. H.; Woods, R. R.; Hallick, T. M.; Heppner, D. B.

    1977-01-01

    A five-cell, liquid-cooled advanced electrochemical depolarized carbon dioxide concentrator module was fabricated. The cells utilized the advanced, lightweight, plated anode current collector concept and internal liquid-cooling. The five cell module was designed to meet the carbon dioxide removal requirements of one man and was assembled using plexiglass endplates. This one-man module was tested as part of an integrated oxygen generation and recovery subsystem.

  3. Electrochemical and partial oxidation of methane

    NASA Astrophysics Data System (ADS)

    Singh, Rahul

    2008-10-01

    Hydrogen has been the most common fuel used for the fuel cell research but there remains challenging technological hurdles and storage issues with hydrogen fuel. The direct electrochemical oxidation of CH4 (a major component of natural gas) in a solid oxide fuel cell (SOFC) to generate electricity has a potential of commercialization in the area of auxiliary and portable power units and battery chargers. They offer significant advantages over an external reformer based SOFC, namely, (i) simplicity in the overall system architecture and balance of plant, (ii) more efficient and (iii) availability of constant concentration of fuel in the anode compartment of SOFC providing stability factor. The extreme operational temperature of a SOFC at 700-1000°C provides a thermodynamically favorable pathway to deposit carbon on the most commonly used Ni anode from CH4 according to the following reaction (CH4 = C + 2H2), thus deteriorating the cell performance, stability and durability. The coking problem on the anode has been a serious and challenging issue faced by the catalyst research community worldwide. This dissertation presents (i) a novel fabricated bi-metallic Cu-Ni anode by electroless plating of Cu on Ni anode demonstrating significantly reduced or negligible coke deposition on the anode for CH4 and natural gas fuel after long term exposure, (ii) a thorough microstructural examination of Ni and Cu-Ni anode exposed to H2, CH4 and natural gas after long term exposure at 750°C by scanning electron microscopy, energy dispersive X-ray spectroscopy and X-ray diffraction and (iii) in situ electrochemical analysis of Ni and Cu-Ni for H2, CH4 and natural gas during long term exposure at 750°C by impedance spectroscopy. A careful investigation of variation in the microstructure and performance characteristics (voltage-current curve and impedance) of Ni and Cu-Ni anode before and after a long term exposure of CH4 and natural gas would allow us to test the validation of a negligible coke formation on the novel fabricated anode by electroless plating process. Hydrogen is an environmentally cleaner source of energy. The recent increase in the demand of hydrogen as fuel for all types of fuel cells and petroleum refining process has boosted the need of production of hydrogen. Methane, a major component of natural gas is the major feedstock for production of hydrogen. The route of partial oxidation of methane to produce syngas (CO + H2) offers significant advantages over commercialized steam reforming process for higher efficiency and lower energy requirements. Partial oxidation of methane was studied by pulsing O2 into a CH4 flow over Rh/Al2O3 in a sequence of in situ infrared (IR) cell and fixed bed reactor at 773 K. The results obtained from the sequence of an IR cell followed by a fixed bed reactor show that (i) adsorbed CO produced possesses a long residence time, indicating that adsorbed oxygen leading to the formation of CO is significantly different from those leading to CO2 and (ii) CO2 is not an intermediate species for the formation of CO. In situ IR of pulse reaction coupled with alternating reactor sequence is an effective approach to study the primary and secondary reactions as well as the nature of their adsorbed species. As reported earlier, hydrogen remains to be the most effective fuel for fuel cells, the production of high purity hydrogen from naturally available resources such as coal, petroleum, and natural gas requires a number of energy-intensive steps, making fuel cell processes for stationary electric power generation prohibitively uneconomic. Direct use of coal or coal gas as the feed is a promising approach for low cost electricity generation. Coal gas solid oxide fuel cell was studied by pyrolyzing Ohio #5 coal to coal gas and transporting to a Cu anode solid oxide fuel cell to generate power. The study of coal-gas solid oxide fuel cell is divided into two sections, i.e., (i) understanding the composition of coal gas by in situ infrared spectroscopy combined with mass spectrometry and (ii) evaluating the performance of coal gas for power generation based on the composition on a Cu-SOFC. The voltage-current performance curve for coal gas suggests that hydrogen and methane rich coal gas performed better than CO2 or D2O concentrated coal gas. A slow rate of reforming reaction of D2O than CO2 with coal and coal gas was observed during pyrolysis reaction. The coal and coke (by-product of pyrolysis) were characterized by Raman spectrometer to reveal the effect of pyrolysis on the structural properties of coal.

  4. Advanced electrochemical concepts for NASA applications

    NASA Astrophysics Data System (ADS)

    Halpert, Gerald; Attia, Alan

    A Jet Propulsion Laboratory (JPL) survey of 23 electrochemical systems for space applications in which experts from universities, industry, and government participated is discussed. They recommended achievable specific energy for these systems and forecast the likelihood of their development of these systems by the year 1995, 2000, and 2005. The highest ranked systems for operation in planetary inner-orbit spacecraft included Na/beta-double prime-alumina/Z, where Z = S, FeCl2 or NiCl2, the upper plateau Li(Al)/FeS2 system, and the H2/O2 alkaline regenerative fuel cell. The achievable specific energy for these as operational batteries was estimated to be 130, 180 and 100 Wh/kg, respectively. For planetary outer-orbit and small geosynchronous (GEO) spacecraft Li/TiS2 (estimated 90 Wh/kg) was the choice.

  5. Costs of the electrochemical oxidation of wastewaters: a comparison with ozonation and Fenton oxidation processes.

    PubMed

    Cañizares, Pablo; Paz, Rubén; Sáez, Cristina; Rodrigo, Manuel A

    2009-01-01

    In the work described here the technical and economic feasibilities of three Advanced Oxidation Processes (AOPs) have been studied: Conductive-Diamond Electrochemical Oxidation (CDEO), Ozonation and Fenton oxidation. The comparison was made by assessing the three technologies with synthetic wastewaters polluted with different types of organic compounds and also with actual wastes (from olive oil mills and from a fine-chemical manufacturing plant). All three technologies were able to treat the wastes, but very different results were obtained in terms of efficiency and mineralization. Only CDEO could achieve complete mineralization of the pollutants for all the wastes. However, the efficiencies were found to depend on the concentration of pollutant (mass transfer control of the oxidation rate). Results obtained in the oxidation with ozone (at pH 12) or by Fenton's reagent were found to depend on the nature of the pollutants, and significant concentrations of oxidation-refractory compounds were usually accumulated during the treatment. Within the discharge limits that all of the technologies can reach, the economic analysis shows that the operating cost of Fenton oxidation is lower than either CDEO or ozonation, although CD\\EO can compete satisfactorily with the Fenton process in the treatment of several kinds of wastes. Likewise, the investment cost for the ozonation process seems to be higher than either CDEO or Fenton oxidation, regardless of the pollutant treated. PMID:18082930

  6. Electrochemical glucose oxidation on dendritic cuprous oxide film fabricated by PSS-assisted electrochemical deposition

    NASA Astrophysics Data System (ADS)

    Yang, Ming; Jin, Xiaoqi; Huang, Qiao

    2011-02-01

    Cuprous oxides (Cu 2O) with different morphologies were deposited on F-doped tin oxide (FTO) covered glass substrates by potentiostatic deposition. The as-deposited samples were characterized by XRD, BET surface area and SEM. The effects of Poly(styrene sulfonic acid) sodium salt (PSS) on the crystal morphologies of Cu 2O were studied. Different crystal morphologies of Cu 2O can be obtained by varying the concentrations of PSS in the electrolytes. The formation of dendritic microstructure in Cu 2O film depends on the concentration of PSS in the electrolyte. Dendritic Cu 2O crystals formed gradually with the increase of the concentration of PSS in the electrolyte from 0 to 4 g L -1. More symmetrical Cu 2O crystals appear when the concentration of PSS is changed from 4 to 8 g L -1. However, the Cu 2O nanoparticles formed instead of dendritic Cu 2O crystals if the concentration of PSS reaches to 12 g L -1, which is due to the slower diffusion rate of reactive species in high concentration of PSS. The as-deposited Cu 2O thin films with different morphologies all exhibit the electrochemical glucose oxidation properties. The improved performance of glucose oxidation is achieved on the dendritic Cu 2O film electrode. The result indicates that the dendritic microstructure is beneficial for decreasing the resistance and improving transportation and diffusion of reactants and products.

  7. Electrochemical oxidation of reverse osmosis concentrate on mixed metal oxide (MMO) titanium coated electrodes.

    PubMed

    Bagastyo, Arseto Y; Radjenovic, Jelena; Mu, Yang; Rozendal, Ren A; Batstone, Damien J; Rabaey, Korneel

    2011-10-15

    Reverse osmosis (RO) membranes have been successfully applied around the world for wastewater reuse applications. However, RO is a physical separation process, and besides the clean water stream (permeate) a reverse osmosis concentrate (ROC) is produced, usually representing 15-25% of the feed water flow and containing the organic and inorganic contaminants at higher concentrations. In this study, electrochemical oxidation was investigated for the treatment of ROC generated during the reclamation of municipal wastewater effluent. Using laboratory-scale two-compartment electrochemical systems, five electrode materials (i.e. titanium coated with IrO2-Ta2O5, RuO2-IrO2, Pt-IrO2, PbO2, and SnO2-Sb) were tested as anodes in batch mode experiments, using ROC from an advanced water treatment plant. The best oxidation performance was observed for Ti/Pt-IrO2 anodes, followed by the Ti/SnO2-Sb and Ti/PbO2 anodes. The effectiveness of the treatment appears to correlate with the formation of oxidants such as active chlorine (i.e. Cl2/HClO/ClO-). As a result, electro-generated chlorine led to the abundant formation of harmful by-products such as trihalomethanes (THMs) and haloacetic acids (HAAs), particularly at Ti/SnO2-Sb and Ti/Pt-IrO2 anodes. The highest concentration of total HAAs (i.e. 2.7 mg L(-1)) was measured for the Ti/SnO2-Sb electrode, after 0.55 Ah L(-1) of supplied specific electrical charge. Irrespective of the used material, electrochemical oxidation of ROC needs to be complemented by a polishing treatment to alleviate the release of halogenated by-products. PMID:21802107

  8. In Situ Electrochemical Oxidation Tuning of Transition Metal Disulfides to Oxides for Enhanced Water Oxidation

    PubMed Central

    2015-01-01

    The development of catalysts with earth-abundant elements for efficient oxygen evolution reactions is of paramount significance for clean and sustainable energy storage and conversion devices. Our group demonstrated recently that the electrochemical tuning of catalysts via lithium insertion and extraction has emerged as a powerful approach to improve catalytic activity. Here we report a novel in situ electrochemical oxidation tuning approach to develop a series of binary, ternary, and quaternary transition metal (e.g., Co, Ni, Fe) oxides from their corresponding sulfides as highly active catalysts for much enhanced water oxidation. The electrochemically tuned cobalt–nickel–iron oxides grown directly on the three-dimensional carbon fiber electrodes exhibit a low overpotential of 232 mV at current density of 10 mA cm–2, small Tafel slope of 37.6 mV dec–1, and exceptional long-term stability of electrolysis for over 100 h in 1 M KOH alkaline medium, superior to most non-noble oxygen evolution catalysts reported so far. The materials evolution associated with the electrochemical oxidation tuning is systematically investigated by various characterizations, manifesting that the improved activities are attributed to the significant grain size reduction and increase of surface area and electroactive sites. This work provides a promising strategy to develop electrocatalysts for large-scale water-splitting systems and many other applications. PMID:27162978

  9. Porous nanoarchitectures of spinel-type transition metal oxides for electrochemical energy storage systems.

    PubMed

    Park, Min-Sik; Kim, Jeonghun; Kim, Ki Jae; Lee, Jong-Won; Kim, Jung Ho; Yamauchi, Yusuke

    2015-12-14

    Transition metal oxides possessing two kinds of metals (denoted as AxB3-xO4, which is generally defined as a spinel structure; A, B = Co, Ni, Zn, Mn, Fe, etc.), with stoichiometric or even non-stoichiometric compositions, have recently attracted great interest in electrochemical energy storage systems (ESSs). The spinel-type transition metal oxides exhibit outstanding electrochemical activity and stability, and thus, they can play a key role in realising cost-effective and environmentally friendly ESSs. Moreover, porous nanoarchitectures can offer a large number of electrochemically active sites and, at the same time, facilitate transport of charge carriers (electrons and ions) during energy storage reactions. In the design of spinel-type transition metal oxides for energy storage applications, therefore, nanostructural engineering is one of the most essential approaches to achieving high electrochemical performance in ESSs. In this perspective, we introduce spinel-type transition metal oxides with various transition metals and present recent research advances in material design of spinel-type transition metal oxides with tunable architectures (shape, porosity, and size) and compositions on the micro- and nano-scale. Furthermore, their technological applications as electrode materials for next-generation ESSs, including metal-air batteries, lithium-ion batteries, and supercapacitors, are discussed. PMID:26549729

  10. Progress in electrochemical synthesis of magnetic iron oxide nanoparticles

    NASA Astrophysics Data System (ADS)

    Ramimoghadam, Donya; Bagheri, Samira; Hamid, Sharifah Bee Abd

    2014-11-01

    Recently, magnetic iron oxide particles have been emerged as significant nanomaterials due to its extensive range of application in various fields. In this regard, synthesis of iron oxide nanoparticles with desirable properties and high potential applications are greatly demanded. Therefore, investigation on different iron oxide phases and their magnetic properties along with various commonly used synthetic techniques are remarked and thoroughly described in this review. Electrochemical synthesis as a newfound method with unique advantages is elaborated, followed by design approaches and key parameters to control the properties of the iron oxide nanoparticles. Additionally, since the dispersion of iron oxide nanoparticles is as important as its preparation, surface modification issue has been a serious challenge which is comprehensively discussed using different surfactants. Despite the advantages of the electrochemical synthesis method, this technique has been poorly studied and requires deep investigations on effectual parameters such as current density, pH, electrolyte concentration etc.

  11. Electrochemical oxidation of textile wastewater and its reuse.

    PubMed

    Mohan, N; Balasubramanian, N; Basha, C Ahmed

    2007-08-17

    It is attempted in the present investigation to treat organic pollutant present in the textile effluent using an electrochemical treatment technique. Experiments are carried out in a batch electrochemical cell covering wide range in operating conditions. Due to the strong oxidizing potential of the chemicals produced, the effluent COD is reduced substantially in this treatment technique. The influence of effluent initial concentration, pH, supporting electrolyte concentration and the anode material on pollutant degradation has been critically examined. It is further attempted in the present investigation to reuse the treated wastewater for dyeing purpose. Several cycles of dyeing operations have been performed with the treated textile wastewater and the dye uptake and water quality have been critically examined at each cycle of dyeing process. The results indicate that the electrochemical method is a feasible technique for treatment of textile wastewater and electrochemically treated wastewater can be effectively reused for dyeing application. PMID:17336454

  12. Corrosion and electrochemical oxidation of a pyrite by Thiobacillus ferrooxidans

    SciTech Connect

    Mustin, C.; Berthelin, J. ); Marion, P.; Donato, P. de )

    1992-04-01

    The oxidation of a pure pyrite by Thiobacillus Ferrooxidans is not really a constant phenomenon; it must be considered to be more like a succession of different steps which need characterization. Electrochemical studies using a combination of a platinum electrode and a specific pyrite electrode (packed-ground-pyrite electrode) revealed four steps in the bioleaching process. Each step can be identified by the electrochemical behavior (redox potentials) of pyrite, which in turn can be related to chemical (leachate content), bacterial (growth), and physical (corrosion patterns) parameters of the leaching process. A comparison of the oxidation rates of iron and sulfur indicated the nonstoichiometric bacterial oxidation of a pure pyrite in which superficial phenomena, aqueous oxidation, and deep crystal dissolution are successively involved.

  13. Corrosion and Electrochemical Oxidation of a Pyrite by Thiobacillus ferrooxidans

    PubMed Central

    Mustin, C.; Berthelin, J.; Marion, P.; de Donato, P.

    1992-01-01

    The oxidation of a pure pyrite by Thiobacillus ferrooxidans is not really a constant phenomenon; it must be considered to be more like a succession of different steps which need characterization. Electrochemical studies using a combination of a platinum electrode and a specific pyrite electrode (packed-ground-pyrite electrode) revealed four steps in the bioleaching process. Each step can be identified by the electrochemical behavior (redox potentials) of pyrite, which in turn can be related to chemical (leachate content), bacterial (growth), and physical (corrosion patterns) parameters of the leaching process. A comparison of the oxidation rates of iron and sulfur indicated the nonstoichiometric bacterial oxidation of a pure pyrite in which superficial phenomena, aqueous oxidation, and deep crystal dissolution are successively involved. Images PMID:16348688

  14. Electrochemical oxidation of imazapyr with BDD electrode in titanium substrate.

    PubMed

    Souza, F L; Teodoro, T Q; Vasconcelos, V M; Migliorini, F L; Lima Gomes, P C F; Ferreira, N G; Baldan, M R; Haiduke, R L A; Lanza, M R V

    2014-12-01

    In this work we have studied the treatment of imazapyr by electrochemical oxidation with boron-doped diamond anode. Electrochemical degradation experiments were performed in a one-compartment cell containing 0.45 L of commercial formulations of herbicide in the pH range 3.0-10.0 by applying a density current between 10 and 150 mA cm(-2) and in the temperature range 25-45 °C. The maximum current efficiencies were obtained at lower current densities since the electrochemical system is under mass transfer control. The mineralization rate increased in acid medium and at higher temperatures. The treatment was able to completely degrade imazapyr in the range 4.6-100.0 mg L(-1), although the current charge required rises along with the increasing initial concentration of the herbicide. Toxicity analysis with the bioluminescent bacterium Vibrio fischeri showed that at higher pollutant concentrations the toxicity was reduced after the electrochemical treatment. To clarify the reaction pathway for imazapyr mineralization by OH radicals, LC-MS/MS analyses we performed together with a theoretical study. Ions analysis showed the formation of high levels of ammonium in the cathode. The main final products of the electrochemical oxidation of imazapyr with diamond thin film electrodes are formic, acetic and butyric acids. PMID:25461923

  15. Method of electrode fabrication for solid oxide electrochemical cells

    SciTech Connect

    Jensen, R.R.

    1990-11-20

    A process for fabricating cermet electrodes for solid oxide electrochemical cells by sintering is disclosed. First, a porous metal electrode is fabricated on a solid oxide cell, such as a fuel cell by, for example, sintering, and is then infiltrated with a high volume fraction stabilized zirconia suspension. A second sintering step is used to sinter the infiltrated zirconia to a high density in order to more securely attach the electrode to the solid oxide electrolyte of the cell. High performance fuel electrodes can be obtained with this process. Further electrode performance enhancement may be achieved if stabilized zirconia doped with cerium oxide, chromium oxide, titanium oxide, and/or praseodymium oxide for electronic conduction is used. 5 figs.

  16. Method of electrode fabrication for solid oxide electrochemical cells

    SciTech Connect

    Jensen, Russell R.

    1990-01-01

    A process for fabricating cermet electrodes for solid oxide electrochemical cells by sintering is disclosed. First, a porous metal electrode is fabricated on a solid oxide cell, such as a fuel cell by, for example, sintering, and is then infiltrated with a high volume fraction stabilized zirconia suspension. A second sintering step is used to sinter the infiltrated zirconia to a high density in order to more securely attach the electrode to the solid oxide electrolyte of the cell. High performance fuel electrodes can be obtained with this process. Further electrode performance enhancement may be achieved if stabilized zirconia doped with cerium oxide, chromium oxide, titanium oxide, and/or praseodymium oxide for electronic conduction is used.

  17. Zinc oxide nanostructures for electrochemical cortisol biosensing

    NASA Astrophysics Data System (ADS)

    Vabbina, Phani Kiran; Kaushik, Ajeet; Tracy, Kathryn; Bhansali, Shekhar; Pala, Nezih

    2014-05-01

    In this paper, we report on fabrication of a label free, highly sensitive and selective electrochemical cortisol immunosensors using one dimensional (1D) ZnO nanorods (ZnO-NRs) and two dimensional nanoflakes (ZnO-NFs) as immobilizing matrix. The synthesized ZnO nanostructures (NSs) were characterized using scanning electron microscopy (SEM), selective area diffraction (SAED) and photoluminescence spectra (PL) which showed that both ZnO-NRs and ZnO-NFs are single crystalline and oriented in [0001] direction. Anti-cortisol antibody (Anti-Cab) are used as primary capture antibodies to detect cortisol using electrochemical impedance spectroscopy (EIS). The charge transfer resistance increases linearly with increase in cortisol concentration and exhibits a sensitivity of 3.078 KΩ. M-1 for ZnO-NRs and 540 Ω. M -1 for ZnO-NFs. The developed ZnO-NSs based immunosensor is capable of detecting cortisol at 1 pM. The observed sensing parameters are in physiological range. The developed sensors can be integrated with microfluidic system and miniaturized potentiostat to detect cortisol at point-of-care.

  18. Decolorization of landfill leachate using electrochemical oxidation technique

    NASA Astrophysics Data System (ADS)

    Jumaah, Majd Ahmed; Othman, Mohamed Rozali

    2015-09-01

    The study was carried out to investigate the electrochemical oxidation of landfill leachate from the Jeram sanitary landfill leachate using charcoal base metallic composite electrodes. The control parameters used were applied voltage, Cl- concentration (as supporting electrolyte) and pH of the solution. The optimum conditions obtained were NaCl concentration of 1.5 % (w/v), applied voltage of 10 V, operating time 180 min and C60CG Co10PVC15 electrode as an anode.15 Electrochemical treatment using charcoal base metallic composite electrode was able to remove color up to 79%.

  19. Electrochemical oxidation of sulphides in paper mill wastewater by using mixed oxide anodes.

    PubMed

    Särkkä, Heikki; Kuhmonen, Kaisa; Vepsäläinen, Mikko; Pulliainen, Martti; Selin, Jukka; Rantala, Pekka; Kukkamäki, Esko; Sillanpää, Mika

    2009-08-01

    In this study, the electrochemical oxidation technique was used to oxidize sulphides present in paper mill wastewater. Inactivation of anaerobic bacteria in wastewater was also investigated. Sulphide oxidation was effective during the experiments, and the best efficiency was achieved by the smallest current density used. One of the main oxidants of sulphides during the experiments was oxygen. Anaerobic bacteria were better inactivated with higher initial chloride concentration in wastewater because of electrochemically generated chlorine/hypochlorite. Dissolved oxygen, redox potential and pH values of the wastewater increased because of electrochemically generated oxygen-based oxidants and oxidation reactions occurring on the anode. In general, it can be said that sulphide removal was successful in the present study. PMID:19803327

  20. Sol-gel Technology and Advanced Electrochemical Energy Storage Materials

    NASA Technical Reports Server (NTRS)

    Chu, Chung-tse; Zheng, Haixing

    1996-01-01

    Advanced materials play an important role in the development of electrochemical energy devices such as batteries, fuel cells, and electrochemical capacitors. The sol-gel process is a versatile solution for use in the fabrication of ceramic materials with tailored stoichiometry, microstructure, and properties. This processing technique is particularly useful in producing porous materials with high surface area and low density, two of the most desirable characteristics for electrode materials. In addition,the porous surface of gels can be modified chemically to create tailored surface properties, and inorganic/organic micro-composites can be prepared for improved material performance device fabrication. Applications of several sol-gel derived electrode materials in different energy storage devices are illustrated in this paper. V2O5 gels are shown to be a promising cathode material for solid state lithium batteries. Carbon aerogels, amorphous RuO2 gels and sol-gel derived hafnium compounds have been studied as electrode materials for high energy density and high power density electrochemical capacitors.

  1. Recent advances on multi-component hybrid nanostructures for electrochemical capacitors

    NASA Astrophysics Data System (ADS)

    Xiong, Pan; Zhu, Junwu; Wang, Xin

    2015-10-01

    With the continuously growing energy demand and ever-escalating environmental problems, the great energy transition from conventional fossil fuels to renewable sources of energy is under way, and requires more efficient and reliable electrochemical energy storage devices, such as electrochemical capacitors (also called as supercapacitors). In order to achieve high energy and power densities of supercapacitors, numerous efforts are devoted to the development of advanced multi-component hybrid electrode materials for realizing high-performance. This review summarizes the most recent progress in the development of nanostructured electrode materials for energy storage, with a particular focus on these nanostructures that integrate carbon materials, metal oxides/hydroxides and conducting polymers for enhancing energy storage performances via taking advantage of each component's unique functionality and their synergetic effects. Finally, we give some perspectives on the challenges and opportunities in this intriguing field.

  2. Electrochemical phase diagrams for Ti oxides from density functional calculations

    NASA Astrophysics Data System (ADS)

    Huang, Liang-Feng; Rondinelli, James M.

    2015-12-01

    Developing an accurate simulation method for the electrochemical stability of solids, as well as understanding the physics related with its accuracy, is critically important for improving the performance of compounds and predicting the stability of new materials in aqueous environments. Herein we propose a workflow for the accurate calculation of first-principles electrochemical phase (Pourbaix) diagrams. With this scheme, we study the electrochemical stabilities of Ti and Ti oxides using density-functional theory. First, we find the accuracy of an exchange-correlation functional in predicting formation energies and electrochemical stabilities is closely related with the electronic exchange interaction therein. Second, the metaGGA and hybrid functionals with a more precise description of the electronic exchange interaction lead to a systematic improvement in the accuracy of the Pourbaix diagrams. Furthermore, we show that accurate Ti Pourbaix diagrams also require that thermal effects are included through vibrational contributions to the free energy. We then use these diagrams to explain various experimental electrochemical phenomena for the Ti-O system, and show that if experimental formation energies for Ti oxides, which contain contributions from defects owing to their generation at high (combustion) temperatures, are directly used to predict room temperature Pourbaix diagrams then significant inaccuracies result. In contrast, the formation energies from accurate first-principles calculations, e.g., using metaGGA and hybrid functionals, are found to be more reliable. Finally, to facilitate the future application of our accurate electrochemical phase equilibria diagrams, the variation of the Ti Pourbaix diagrams with aqueous ion concentration is also provided.

  3. Preparation and electrochemical properties of Ce-Ru-SnO2 ternary oxide anode and electrochemical oxidation of nitrophenols.

    PubMed

    Liu, Yuan; Liu, Huiling; Ma, Jun; Li, Junjing

    2012-04-30

    A cerium doped ternary SnO(2) based oxides anode that is CeO(2)-RuO(2)-SnO(2) (Ce-Ru-SnO(2)) anode, was prepared by facile thermal decomposition technique. XRD was used to characterize the crystal structures of modified SnO(2) anodes. Electrochemical impedance spectroscopy (EIS) and accelerated life test were also utilized to study the electrochemical property of Ce-Ru-SnO(2) anode. The results indicated that Ce-Ru-SnO(2) anode possessed smaller charge transfer resistance and longer service life than other modified SnO(2) anodes. Oxidants, such as hydroxyl radicals, hydrogen peroxide and hypochlorite ions were determined. Electrochemical oxidation of nitrophenols (NPs) were conducted and compared with previous studies. The degradation of nitrophenols revealed two distinguishing laws for mononitrophenol and multinitrophenols. The Ce-Ru-SnO(2) anode is considered to be a promising material for the treatment of organic pollutants due to its high electrochemical activity and benign stability. PMID:22365388

  4. Direct electrochemical reduction of metal-oxides

    DOEpatents

    Redey, Laszlo I.; Gourishankar, Karthick

    2003-01-01

    A method of controlling the direct electrolytic reduction of a metal oxide or mixtures of metal oxides to the corresponding metal or metals. A non-consumable anode and a cathode and a salt electrolyte with a first reference electrode near the non-consumable anode and a second reference electrode near the cathode are used. Oxygen gas is produced and removed from the cell. The anode potential is compared to the first reference electrode to prevent anode dissolution and gas evolution other than oxygen, and the cathode potential is compared to the second reference electrode to prevent production of reductant metal from ions in the electrolyte.

  5. Electrochemical properties of inorganic nanoporous oxide coated electrodes

    NASA Astrophysics Data System (ADS)

    Leonard, Kevin C.

    The ability to produce clean water and produce and store clean energy is essential to society. Hence, technologies that facilitate clean energy and clean water are of great importance. This study focused on utilizing nanoporous insulating oxide materials to alter the chemistry at the electrode/electrolyte interface to improve the performance of a number of clean energy and clean water technologies. Here we have shown that applying a thin-film of SiO2 nanoparticles to an electrochemical capacitor electrode can increase the energy storage capacity by up to 50% at high power ratings. We have developed a geometric model to describe the coating of the porous electrode to explain the increased performance at high power ratings. We have also shown that the coated electrochemical capacitor exhibits a higher capacitance when normalized to BET surface area, suggesting that the coated surface is behaving fundamentally differently than the uncoated surface. We attribute the increase in capacitance to the inherent surface potential of the oxide coating and have shown that if we alter the surface potential of the oxide, we can in turn alter the electrochemical capacitance. In addition, we have determined that when used in capacitive deionization systems, these coatings can increase ion removal and accelerate regeneration, allowing for higher efficiency and less waste water. We have demonstrated that a nanoporous oxide coating can increase the gas production rate and lower the overpotential of the hydrogen evolution reaction via water electrolysis on both stainless steel and carbon electrodes. In addition, this work presents data on utilizing nanoporous oxide coatings on Li-Ion battery cathodes to improve high temperature capacity fade. We also introduce a novel thin-film battery/electrochemical capacitor hybrid device, which can improve the performance of simple thin-film batteries.

  6. An Electrochemical Glucose Sensor Based on Zinc Oxide Nanorods

    PubMed Central

    Marie, Mohammed; Mandal, Sanghamitra; Manasreh, Omar

    2015-01-01

    A glucose electrochemical sensor based on zinc oxide (ZnO) nanorods was investigated. The hydrothermal sol–gel growth method was utilized to grow ZnO nanorods on indium tin oxide-coated glass substrates. The total active area of the working electrode was 0.3 × 0.3 cm2 where titanium metal was deposited to enhance the contact. Well aligned hexagonal structured ZnO nanorods with a diameter from 68 to 116 nm were obtained. The excitonic peak obtained from the absorbance spectroscopy was observed at ~370 nm. The dominant peak of Raman spectroscopy measurement was at 440 cm−1, matching with the lattice vibration of ZnO. The uniform distribution of the GOx and Nafion membrane that has been done using spin coating technique at 4000 rotations per minute helps in enhancing the ion exchange and increasing the sensitivity of the fabricated electrochemical sensor. The amperometric response of the fabricated electrochemical sensor was 3 s. The obtained sensitivity of the fabricated ZnO electrochemical sensor was 10.911 mA/mM·cm2 and the lower limit of detection was 0.22 µM. PMID:26263988

  7. Degradation of conazole fungicides in water by electrochemical oxidation.

    PubMed

    Urzúa, J; González-Vargas, C; Sepúlveda, F; Ureta-Zañartu, M S; Salazar, R

    2013-11-01

    The electrochemical oxidation (EO) treatment in water of three conazole fungicides, myclobutanil, triadimefon and propiconazole, has been carried out at constant current using a BDD/SS system. First, solutions of each fungicide were electrolyzed to assess the effect of the experimental parameters such as current, pH and fungicide concentration on the decay of each compound and total organic carbon abatement. Then a careful analysis of the degradation by-products was made by high performance liquid chromatography, ion chromatography and gas chromatography coupled with mass spectrometry in order to provide a detailed discussion on the original reaction pathways. Thus, during the degradation of conazole fungicides by the electrochemical oxidation process, aromatic intermediates, aliphatic carboxylic acids and Cl(-) were detected prior to their complete mineralization to CO2 while NO3(-) anions remained in the treated solution. This is an essential preliminary step towards the applicability of the EO processes for the treatment of wastewater containing conazole fungicides. PMID:24140400

  8. Playing peekaboo with graphene oxide: a scanning electrochemical microscopy investigation.

    PubMed

    Rapino, Stefania; Treossi, Emanuele; Palermo, Vincenzo; Marcaccio, Massimo; Paolucci, Francesco; Zerbetto, Francesco

    2014-11-01

    Scanning electrochemical microscopy (SECM) can image graphene oxide (GO) flakes on insulating and conducting substrates. The contrast between GO and the substrate is controlled by the electrostatic interactions that are established between the charges of the molecular redox mediator and the charges present in the sheet/substrate. SECM also allows quantitative measurement - at the nano/microscale - of the charge transfer kinetics between single monolayer sheets and agent molecules. PMID:25224581

  9. Sulfur tolerant composite cermet electrodes for solid oxide electrochemical cells

    DOEpatents

    Isenberg, Arnold O.

    1987-01-01

    An electrochemical apparatus is made containing an exterior electrode bonded to the exterior of a tubular, solid, oxygen ion conducting electrolyte where the electrolyte is also in contact with an interior electrode, said exterior electrode comprising particles of an electronic conductor contacting the electrolyte, where a ceramic metal oxide coating partially surrounds the particles and is bonded to the electrolyte, and where a coating of an ionic-electronic conductive material is attached to the ceramic metal oxide coating and to the exposed portions of the particles.

  10. Observable Electrochemical Oxidation of Carbon Promoted by Platinum Nanoparticles.

    PubMed

    Kou, Zongkui; Cheng, Kun; Wu, Hui; Sun, Ronghui; Guo, Beibei; Mu, Shichun

    2016-02-17

    The radical degradation of Pt-based catalysts toward oxygen reduction reaction (ORR), predominantly caused by the oxidation of carbon supports, heavily blocks the commercialization of polymer electrolyte membrane fuel cells (PEMFCs). As reported, the electrochemical oxidation of carbon could be accelerated by Pt catalysts; however, hitherto no direct evidence is present for the promotion of Pt catalysts. Herein, a unique ultrathin carbon layer (approximately 2.9 nm in thickness) covered Pt catalyst (Pt/C-GC) is designed and synthesized by a chemical vapor deposition (CVD) method. This magnifies the catalysis effect of Pt to carbon oxidation due to the greatly increased contact sites between the metal-support, making it easy to investigate the carbon oxidation process by observing the thinning of the carbon layer on Pt nanoparticles from TEM observations. Undoubtedly, this finding can better guide the structural design of the durable metal catalysts for PEMFCs and other applications. PMID:26788962

  11. Electrochemical & Thermochemical Behavior of Cerium(IV) Oxide delta

    NASA Astrophysics Data System (ADS)

    Chueh, William C.

    The mixed-valent nature of nonstoichiometric ceria (CeO2-delta ) gives rise to a wide range of intriguing properties, such as mixed ionic and electronic conduction and oxygen storage. Surface and transport behavior in rare-earth (samaria) doped and undoped ceria were investigated, with particular emphasis on applications in electrochemical and thermochemical energy conversion processes such as fuel cells and solar fuel production. The electrochemical responses of bulk-processed ceria with porous Pt and Au electrodes were analyzed using 1-D and 2-D transport models to decouple surface reactions, near-surface transport and bulk transport. Combined experimental and numerical results indicate that hydrogen electro-oxidation and hydrolysis near open-circuit conditions occur preferentially over the ceria | gas interface rather than over the ceria | gas | metal interface, with the rate-limiting step likely to be either surface reaction or transport through the surface oxygen vacancy depletion layer. In addition, epitaxial thin films of ceria were grown on zirconia substrates using pulsed-laser deposition to examine electrocatalysis over well-defined microstructures. Physical models were derived to analyze the electrochemical impedance response. By varying the film thickness, interfacial and chemical capacitance were decoupled, with the latter shown to be proportional to the small polaron densities. The geometry of microfabricated metal current collectors (metal = Pt, Ni) was also systematically varied to investigate the relative activity of the ceria | gas and the ceria | metal | gas interfaces. The data suggests that the electrochemical activity of the metal-ceria composite is only weakly dependent on the metal due to the relatively high activity of the ceria | gas interface. In addition to electrochemical experiments, thermochemical reduction-oxidation studies were performed on ceria. It was shown that thermally-reduced ceria, upon exposure to H 2O and/or CO2, can be reoxidized to form H2, CO, and/or CH4. Analysis of gas evolution rates confirms that the kinetics of ceria oxidation by H2O and CO2 are dominated by surface reactions, rather than by ambipolar oxygen diffusion. Temperature-programmed oxidation experiments revealed that, even under thermodynamically favored conditions, carbonaceous species do not form on the surface of neat ceria, thereby giving a high CO selectivity when dissociating CO2. A scaled-up ceria-based solar reactor was designed and tested to demonstrate the feasibility of solar fuel production via thermochemical cycling.

  12. Fabrication of solid oxide fuel cell by electrochemical vapor deposition

    DOEpatents

    Riley, B.; Szreders, B.E.

    1988-04-26

    In a high temperature solid oxide fuel cell (SOFC), the deposition of an impervious high density thin layer of electrically conductive interconnector material, such as magnesium doped lanthanum chromite, and of an electrolyte material, such as yttria stabilized zirconia, onto a porous support/air electrode substrate surface is carried out at high temperatures (/approximately/1100/degree/ /minus/ 1300/degree/C) by a process of electrochemical vapor deposition. In this process, the mixed chlorides of the specific metals involved react in the gaseous state with water vapor resulting in the deposit of an impervious thin oxide layer on the support tube/air electrode substrate of between 20--50 microns in thickness. An internal heater, such as a heat pipe, is placed within the support tube/air electrode substrate and induces a uniform temperature profile therein so as to afford precise and uniform oxide deposition kinetics in an arrangement which is particularly adapted for large scale, commercial fabrication of SOFCs.

  13. Fabrication of solid oxide fuel cell by electrochemical vapor deposition

    DOEpatents

    Brian, Riley; Szreders, Bernard E.

    1989-01-01

    In a high temperature solid oxide fuel cell (SOFC), the deposition of an impervious high density thin layer of electrically conductive interconnector material, such as magnesium doped lanthanum chromite, and of an electrolyte material, such as yttria stabilized zirconia, onto a porous support/air electrode substrate surface is carried out at high temperatures (approximately 1100.degree.-1300.degree. C.) by a process of electrochemical vapor deposition. In this process, the mixed chlorides of the specific metals involved react in the gaseous state with water vapor resulting in the deposit of an impervious thin oxide layer on the support tube/air electrode substrate of between 20-50 microns in thickness. An internal heater, such as a heat pipe, is placed within the support tube/air electrode substrate and induces a uniform temperature profile therein so as to afford precise and uniform oxide deposition kinetics in an arrangement which is particularly adapted for large scale, commercial fabrication of SOFCs.

  14. Scalable and sustainable electrochemical allylic C-H oxidation.

    PubMed

    Horn, Evan J; Rosen, Brandon R; Chen, Yong; Tang, Jiaze; Chen, Ke; Eastgate, Martin D; Baran, Phil S

    2016-05-01

    New methods and strategies for the direct functionalization of C-H bonds are beginning to reshape the field of retrosynthetic analysis, affecting the synthesis of natural products, medicines and materials. The oxidation of allylic systems has played a prominent role in this context as possibly the most widely applied C-H functionalization, owing to the utility of enones and allylic alcohols as versatile intermediates, and their prevalence in natural and unnatural materials. Allylic oxidations have featured in hundreds of syntheses, including some natural product syntheses regarded as "classics". Despite many attempts to improve the efficiency and practicality of this transformation, the majority of conditions still use highly toxic reagents (based around toxic elements such as chromium or selenium) or expensive catalysts (such as palladium or rhodium). These requirements are problematic in industrial settings; currently, no scalable and sustainable solution to allylic oxidation exists. This oxidation strategy is therefore rarely used for large-scale synthetic applications, limiting the adoption of this retrosynthetic strategy by industrial scientists. Here we describe an electrochemical C-H oxidation strategy that exhibits broad substrate scope, operational simplicity and high chemoselectivity. It uses inexpensive and readily available materials, and represents a scalable allylic C-H oxidation (demonstrated on 100 grams), enabling the adoption of this C-H oxidation strategy in large-scale industrial settings without substantial environmental impact. PMID:27096371

  15. Treatment of landfill leachate by electrochemical oxidation and anaerobic process.

    PubMed

    Li, Tinggang; Li, Xiufen; Chen, Jian; Zhang, Guoping; Wang, Hongchun

    2007-05-01

    The removal performance of typical refractory organic compounds in landfill leachate was investigated during the electrochemical (EC) oxidation and anaerobic process combined treatment system in this paper. The results indicated that the treatment of landfill leachate by the combined system was highly effective. The toxicity of leachate was notably decreased after the electrochemical oxidation process and the biodegradability was improved. The concentration of the organic acid with low molecular weight in the leachate increased from 28% to 90% based on the biodegradability assays after the EC oxidation process. The anaerobic digestion could further remove the residual organic compounds. At a hydraulic retention time (HRT) of 16 hours and an organic loading rate (OLR) of 8 kg COD/m3 d, the concentration of COD, SS, ALK, VA, N-TKN, N-NH4+ and P-PO4(3)- [corrected] in UASB effluent were 532, 12, 6744, 400, 540, 455 and 11.6 mg/L, respectively, with approximately 90% removal efficiency of COD. The organic compounds in the landfill leachate revealed different degradation characteristics in the combined system. p-chloroaniline, bisphenol A, 6-methyl-2-phenyl-quinoline, dimethylnaphthaline and N'-(2-methyl-4-chlorophenyl)-N-cyclohexyformamidine, classified into the first group in this paper, were completely removed by the EC oxidation and did not reappear in the effluent of the UASB reactor. Phenylacetic acid, 3-methyl-indole and N-cyclohexyl-acetamide, called the second group, were completely removed, but reappeared in the UASB reactor. 4-methyl-phenol, 3,4-dihydroisoquinoline, 2(3H)-benzothiazolone, exo-2-hydroxycineole and benzothiazole, the third group, were degraded little in the EC oxidation process, but extensively removed by the anaerobic process. Benzoic acid, benzenepropanoic acid and 2-cyano-3,5-dimethyl-1-hydroxypyrrole, the fourth group, concentration obviously increased in the EC process, but was completely removed in the UASB reactor. The content of volatile fatty acids (VFAs) markedly increased from 0.68% in the leachate to 16.18% in the effluent from the electrochemical oxidation process (EC(effl)). In addition, the degradation rate of organic compounds from the landfill leachate was different in the EC oxidation and anaerobic process. PMID:17571841

  16. Corner heating in rectangular solid oxide electrochemical cell generators

    DOEpatents

    Reichner, Philip

    1989-01-01

    Disclosed is an improvement in a solid oxide electrochemical cell generator 1 having a rectangular design with four sides that meet at corners, and containing multiplicity of electrically connected fuel cells 11, where a fuel gas is passed over one side of said cells and an oxygen containing gas is passed into said cells, and said fuel is burned to form heat, electricity, and an exhaust gas. The improvement comprises passing the exhaust gases over the multiplicity of cells 11 in such a way that more of the heat in said exhaust gases flows at the corners of the generator, such as through channels 19.

  17. Platinum Electrodeposition at Unsupported Electrochemically Reduced Nanographene Oxide for Enhanced Ammonia Oxidation

    PubMed Central

    2015-01-01

    The electrochemical reduction of highly oxidized unsupported graphene oxide nanosheets and its platinum electrodeposition was done by the rotating disk slurry electrode technique. Avoiding the use of a solid electrode, graphene oxide was electrochemically reduced in a slurry solution with a scalable process without the use of a reducing agent. Graphene oxide nanosheets were synthesized from carbon platelet nanofibers to obtain highly hydrophilic layers of less than 250 nm in width. The graphene oxide and electrochemically reduced graphene oxide/Pt (erGOx/Pt) hybrid materials were characterized through different spectroscopy and microscopy techniques. Pt nanoparticles with 100 facets, clusters, and atoms at erGOx were identified by high resolution transmission electron microscopy (HRTEM). Cyclic voltammetry was used to characterize the electrocatalytic activity of the highly dispersed erGOx/Pt hybrid material toward the oxidation of ammonia, which showed a 5-fold current density increase when compared with commercially available Vulcan/Pt 20%. This is in agreement with having Pt (100) facets present in the HRTEM images of the erGOx/Pt material. PMID:24417177

  18. Platinum electrodeposition at unsupported electrochemically reduced nanographene oxide for enhanced ammonia oxidation.

    PubMed

    Cunci, Lisandro; Velez, Carlos A; Perez, Ivan; Suleiman, Amal; Larios, Eduardo; José-Yacamán, Miguel; Watkins, James J; Cabrera, Carlos R

    2014-02-12

    The electrochemical reduction of highly oxidized unsupported graphene oxide nanosheets and its platinum electrodeposition was done by the rotating disk slurry electrode technique. Avoiding the use of a solid electrode, graphene oxide was electrochemically reduced in a slurry solution with a scalable process without the use of a reducing agent. Graphene oxide nanosheets were synthesized from carbon platelet nanofibers to obtain highly hydrophilic layers of less than 250 nm in width. The graphene oxide and electrochemically reduced graphene oxide/Pt (erGOx/Pt) hybrid materials were characterized through different spectroscopy and microscopy techniques. Pt nanoparticles with 100 facets, clusters, and atoms at erGOx were identified by high resolution transmission electron microscopy (HRTEM). Cyclic voltammetry was used to characterize the electrocatalytic activity of the highly dispersed erGOx/Pt hybrid material toward the oxidation of ammonia, which showed a 5-fold current density increase when compared with commercially available Vulcan/Pt 20%. This is in agreement with having Pt (100) facets present in the HRTEM images of the erGOx/Pt material. PMID:24417177

  19. Three-dimensionally grown thorn-like Cu nanowire arrays by fully electrochemical nanoengineering for highly enhanced hydrazine oxidation.

    PubMed

    Huang, Jianfei; Zhao, Shunan; Chen, Wei; Zhou, Ying; Yang, Xiaoling; Zhu, Yihua; Li, Chunzhong

    2016-03-21

    This communication reports fully electrochemical nanoengineering toward three-dimensionally grown thorn-like Cu nanowire arrays (CNWAs) as a highly efficient and durable electrocatalyst for hydrazine oxidation. Characterized by substantial negative shifting of the onset potential and an enlarged catalytic current density, the CNWAs afforded greatly enhanced hydrazine oxidation activity, even transcending that of the Pt/C catalyst at a higher reaction rate. The parameters of the electrochemical engineering and metallization methods were found to be essentially influential on the microstructure, and thus the electrocatalytic activity of the CNWAs. The present work typifies a flexible and expandible route toward integrated electrodes of metallic 1D nanostructures which are of interest in advancing the performance of cutting-edge electrochemical applications. PMID:26580842

  20. Functionalizing Aluminum Oxide by Ag Dendrite Deposition at the Anode during Simultaneous Electrochemical Oxidation of Al.

    PubMed

    Rafailović, Lidija D; Gammer, Christoph; Rentenberger, Christian; Trišović, Tomislav; Kleber, Christoph; Karnthaler, Hans Peter

    2015-11-01

    A novel synthesis strategy is presented for depositing metallic Ag at the anode during simultaneous electrochemical oxidation of Al. This unexpected result is achieved based on galvanic coupling. Metallic dendritic nanostructures well-anchored in a high surface area supporting matrix are envisioned to open up a new avenue of applications. PMID:26398487

  1. Three-dimensionally grown thorn-like Cu nanowire arrays by fully electrochemical nanoengineering for highly enhanced hydrazine oxidation

    NASA Astrophysics Data System (ADS)

    Huang, Jianfei; Zhao, Shunan; Chen, Wei; Zhou, Ying; Yang, Xiaoling; Zhu, Yihua; Li, Chunzhong

    2016-03-01

    This communication reports fully electrochemical nanoengineering toward three-dimensionally grown thorn-like Cu nanowire arrays (CNWAs) as a highly efficient and durable electrocatalyst for hydrazine oxidation. Characterized by substantial negative shifting of the onset potential and an enlarged catalytic current density, the CNWAs afforded greatly enhanced hydrazine oxidation activity, even transcending that of the Pt/C catalyst at a higher reaction rate. The parameters of the electrochemical engineering and metallization methods were found to be essentially influential on the microstructure, and thus the electrocatalytic activity of the CNWAs. The present work typifies a flexible and expandible route toward integrated electrodes of metallic 1D nanostructures which are of interest in advancing the performance of cutting-edge electrochemical applications.This communication reports fully electrochemical nanoengineering toward three-dimensionally grown thorn-like Cu nanowire arrays (CNWAs) as a highly efficient and durable electrocatalyst for hydrazine oxidation. Characterized by substantial negative shifting of the onset potential and an enlarged catalytic current density, the CNWAs afforded greatly enhanced hydrazine oxidation activity, even transcending that of the Pt/C catalyst at a higher reaction rate. The parameters of the electrochemical engineering and metallization methods were found to be essentially influential on the microstructure, and thus the electrocatalytic activity of the CNWAs. The present work typifies a flexible and expandible route toward integrated electrodes of metallic 1D nanostructures which are of interest in advancing the performance of cutting-edge electrochemical applications. Electronic supplementary information (ESI) available: Experimental details, additional figures and table. See DOI: 10.1039/c5nr06512g

  2. Electrochemically tunable thermal conductivity of lithium cobalt oxide

    NASA Astrophysics Data System (ADS)

    Cho, Jiung; Losego, Mark D.; Zhang, Hui Gang; Kim, Honggyu; Zuo, Jianmin; Petrov, Ivan; Cahill, David G.; Braun, Paul V.

    2014-06-01

    Using time-domain thermoreflectance, the thermal conductivity and elastic properties of a sputter deposited LiCoO2 film, a common lithium-ion cathode material, are measured as a function of the degree of lithiation. Here we report that via in situ measurements during cycling, the thermal conductivity of a LiCoO2 cathode reversibly decreases from ~5.4 to 3.7 W m-1 K-1, and its elastic modulus decreases from 325 to 225 GPa, as it is delithiated from Li1.0CoO2 to Li0.6CoO2. The dependence of the thermal conductivity on lithiation appears correlated with the lithiation-dependent phase behaviour. The oxidation-state-dependent thermal conductivity of electrolytically active transition metal oxides provides opportunities for dynamic control of thermal conductivity and is important to understand for thermal management in electrochemical energy storage devices.

  3. Electrochemically tunable thermal conductivity of lithium cobalt oxide.

    PubMed

    Cho, Jiung; Losego, Mark D; Zhang, Hui Gang; Kim, Honggyu; Zuo, Jianmin; Petrov, Ivan; Cahill, David G; Braun, Paul V

    2014-01-01

    Using time-domain thermoreflectance, the thermal conductivity and elastic properties of a sputter deposited LiCoO2 film, a common lithium-ion cathode material, are measured as a function of the degree of lithiation. Here we report that via in situ measurements during cycling, the thermal conductivity of a LiCoO2 cathode reversibly decreases from ~5.4 to 3.7 W m(-1) K(-1), and its elastic modulus decreases from 325 to 225 GPa, as it is delithiated from Li1.0CoO2 to Li0.6CoO2. The dependence of the thermal conductivity on lithiation appears correlated with the lithiation-dependent phase behaviour. The oxidation-state-dependent thermal conductivity of electrolytically active transition metal oxides provides opportunities for dynamic control of thermal conductivity and is important to understand for thermal management in electrochemical energy storage devices. PMID:24892640

  4. Mediated Electrochemical Oxidation (MEO) based technology. Final report

    SciTech Connect

    1996-07-18

    The goal of this CRADA was the continued research and development by LLNL, and the commercialization by EOSystems, Inc., of the waste treatment technology known as Mediated Electrochemical Oxidation. MEO is a non-thermal electrochemical technology developed in part at LLNL for the destruction of organic waste streams; this technology has wide applications in the government, manufacturing, biomedical and industrial sectors. The system uses an electrochemical cell to generate highly oxidizing {open_quote}mediators{close_quote} in an acidic aqueous solution, which subsequently react with organic waste and convert it to carbon dioxide and water. The broad research responsibilities of LLNL in this CRADA were the investigation of numerous cell electrode materials and materials of construction, the evaluation of the process chemistry, and the testing of a flow visualization cell and a functional prototype. Major deliverables included: a determination of suitable electrode materials, an investigation of the destruction efficiency for numerous organic substrates, the construction and testing of a flow visualization cell, and the testing of a functional prototype commercial cell. The responsibilities of EOSystems included the definition of the market and potential customers, the design and engineering of the flow visualization and prototype cells, and the commercialization of the MEO units. Deliverables included the selection of the process and ancillary systems, the design of a flow visualization cell, and the design and construction of a prototype cell. In general, most of the deliverables were met by both partners, although unexpected technical difficulties delayed some of the delivery dates and forced the adoption of a modified statement of work. However, the primary, original project goals were completed on-time and on-budget.

  5. Selective Electrochemical Generation of Hydrogen Peroxide from Water Oxidation.

    PubMed

    Viswanathan, Venkatasubramanian; Hansen, Heine A; Nørskov, Jens K

    2015-11-01

    Water is a life-giving source, fundamental to human existence, yet over a billion people lack access to clean drinking water. The present techniques for water treatment such as piped, treated water rely on time and resource intensive centralized solutions. In this work, we propose a decentralized device concept that can utilize sunlight to split water into hydrogen and hydrogen peroxide. The hydrogen peroxide can oxidize organics while the hydrogen bubbles out. In enabling this device, we require an electrocatalyst that can oxidize water while suppressing the thermodynamically favored oxygen evolution and form hydrogen peroxide. Using density functional theory calculations, we show that the free energy of adsorbed OH* can be used to determine selectivity trends between the 2e(-) water oxidation to H2O2 and the 4e(-) oxidation to O2. We show that materials which bind oxygen intermediates sufficiently weakly, such as SnO2, can activate hydrogen peroxide evolution. We present a rational design principle for the selectivity in electrochemical water oxidation and identify new material candidates that could perform H2O2 evolution selectively. PMID:26538037

  6. Electrochemical formation of a composite polymer-aluminum oxide film

    NASA Astrophysics Data System (ADS)

    Runge-Marchese, Jude Mary

    1997-10-01

    The formation of polymer films through electrochemical techniques utilizing electrolytes which include conductive polymer is of great interest to the coatings and electronics industries as a means for creating electrically conductive and corrosion resistant finishes. One of these polymers, polyamino-benzene (polyaniline), has been studied for this purpose for over ten years. This material undergoes an insulator-to-metal transition upon doping with protonic acids in an acid/base type reaction. Review of prior studies dealing with polyaniline and working knowledge of aluminum anodization has led to the development of a unique process whereby composite polymer-aluminum oxide films are formed. The basis for the process is a modification of the anodizing electrolyte which results in the codeposition of polyaniline during aluminum anodization. A second process, which incorporates electrochemical sealing of the anodic layer with polyaniline was also developed. The formation of these composite films is documented through experimental processing, and characterized by way of scientific analysis and engineering tests. Analysis results revealed the formation of unique dual phase anodic films with fine microstructures which exhibited full intrusion of the columnar aluminum oxide structure with polyaniline, indicating the polymer was deposited as the metal oxidation proceeded. An aromatic amine derivative of polyaniline with aluminum sulfate was determined to be the reaction product within the aluminum oxide phase of the codeposited films. Scientific characterization determined the codeposition process yields completely chemically and metallurgically bound composite films. Engineering studies determined the films, obtained through a single step, exhibited superior wear and corrosion resistance to conventionally anodized and sealed films processed through two steps, demonstrating the increased manufacturing process efficiency that can be realized with the modification of the conventional anodization process.

  7. Current status of environmental, health, and safety issues of electrochemical capacitors for advanced vehicle applications

    SciTech Connect

    Vimmerstedt, L.J.; Hammel, C.J.

    1997-04-01

    Electrochemical capacitors are a candidate for traction power assists in hybrid electric vehicles (HEVs). Other advanced automotive applications, while not the primary focus of current development efforts, are also possible. These include load leveling high-energy batteries, power conditioning electronics, electrically hated catalysts, electric power steering, and engine starter power. Higher power and longer cycle life are expected for electrochemical capacitors than for batteries. Evaluation of environmental, health, and safety (EH and S) issues of electrochemical capacitors is an essential part of the development and commercialization of electrochemical capacitors for advanced vehicles. This report provides an initial EH and S assessment. This report presents electrochemical capacitor electrochemistry, materials selection, intrinsic material hazards, mitigation of those hazards, environmental requirements, pollution control options, and shipping requirements. Most of the information available for this assessment pertains to commercial devices intended for application outside the advanced vehicle market and to experiment or prototype devices. Electrochemical capacitors for power assists in HEVs are not produced commercially now. Therefore, materials for advanced vehicle electrochemical capacitors may change, and so would the corresponding EH and S issues. Although changes are possible, this report describes issues for likely electrochemical capacitor designs.

  8. Synergetic antibacterial activity of reduced graphene oxide and boron doped diamond anode in three dimensional electrochemical oxidation system

    NASA Astrophysics Data System (ADS)

    Qi, Xiujuan; Wang, Ting; Long, Yujiao; Ni, Jinren

    2015-05-01

    A 100% increment of antibacterial ability has been achieved due to significant synergic effects of boron-doped diamond (BDD) anode and reduced graphene oxide (rGO) coupled in a three dimensional electrochemical oxidation system. The rGO, greatly enhanced by BDD driven electric field, demonstrated strong antibacterial ability and even sustained its excellent performance during a reasonable period after complete power cut in the BDD-rGO system. Cell damage experiments and TEM observation confirmed much stronger membrane stress in the BDD-rGO system, due to the faster bacterial migration and charge transfer by the expanded electro field and current-carrying efficiency by quantum tunnel. Reciprocally the hydroxyl-radical production was eminently promoted with expanded area of electrodes and delayed recombination of the electron-hole pairs in presence of the rGO in the system. This implied a huge potential for practical disinfection with integration of the promising rGO and the advanced electrochemical oxidation systems.

  9. Synergetic antibacterial activity of reduced graphene oxide and boron doped diamond anode in three dimensional electrochemical oxidation system

    PubMed Central

    Qi, Xiujuan; Wang, Ting; Long, Yujiao; Ni, Jinren

    2015-01-01

    A 100% increment of antibacterial ability has been achieved due to significant synergic effects of boron-doped diamond (BDD) anode and reduced graphene oxide (rGO) coupled in a three dimensional electrochemical oxidation system. The rGO, greatly enhanced by BDD driven electric field, demonstrated strong antibacterial ability and even sustained its excellent performance during a reasonable period after complete power cut in the BDD-rGO system. Cell damage experiments and TEM observation confirmed much stronger membrane stress in the BDD-rGO system, due to the faster bacterial migration and charge transfer by the expanded electro field and current-carrying efficiency by quantum tunnel. Reciprocally the hydroxyl-radical production was eminently promoted with expanded area of electrodes and delayed recombination of the electron–hole pairs in presence of the rGO in the system. This implied a huge potential for practical disinfection with integration of the promising rGO and the advanced electrochemical oxidation systems. PMID:25994309

  10. Size-dependent electrochemical oxidation of silver nanoparticles.

    PubMed

    Ivanova, Olga S; Zamborini, Francis P

    2010-01-13

    Here we quantify the electrochemical oxidation of Ag nanoparticles (NPs) as a function of size by electrostatically attaching Ag NPs synthesized by seed-mediated growth in the presence of citrate (diameter = 8 to 50 nm) to amine-functionalized indium-tin oxide coated glass electrodes (Glass/ITO), obtaining a linear sweep voltammogram from 0.1 V, where Ag(0) is stable, up to 1.0 V, and observing the peak potential (E(p)) for oxidation of Ag(0) to Ag(+). Electrostatic attachment to the organic linker presumably removes direct interactions between Ag and ITO and allows control over the total Ag coverage by altering the soaking time. This is important as both metal-electrode interactions and overall Ag coverage can affect E(p). E(p) shifts positive from an average of 275 to 382 mV as the Ag NP diameter increases for a constant Ag coverage and under conditions of planar diffusion, suggesting a shift in E(p) due to a thermodynamic shift in E(0) for the Ag/Ag(+) redox couple with size. The negative shift in E(p) with decreasing Ag NP radius follows the general trend predicted by theory and agrees with previous qualitative experimental observations. A better understanding of metal nanostructure oxidation is crucial considering their potential use in many different applications and the importance of metal corrosion processes at the nanoscale. PMID:20000318

  11. Physical and electrochemical study of cobalt oxide nano- and microparticles

    SciTech Connect

    Alburquenque, D.; Vargas, E.; Denardin, J.C.; Escrig, J.; Marco, J.F.; Gautier, J.L.

    2014-07-01

    Cobalt oxide nanocrystals of size 17–21 nm were synthesized by a simple reaction between cobalt acetate (II) and dodecylamine. On the other hand, micrometric Co{sub 3}O{sub 4} was prepared using the ceramic method. The structural examination of these materials was performed using powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and transmission electron microscopy (TEM and HRTEM). XRD studies showed that the oxides were pure, well-crystallized, spinel cubic phases with a-cell parameter of 0.8049 nm and 0.8069 nm for the nano and micro-oxide, respectively. The average particle size was 19 nm (nano-oxide) and 1250 μm (micro-oxide). Morphological studies carried out by SEM and TEM analyses have shown the presence of octahedral particles in both cases. Bulk and surface properties investigated by X-ray photoelectron spectroscopy (XPS), point zero charge (pzc), FTIR and cyclic voltammetry indicated that there were no significant differences in the composition on both materials. The magnetic behavior of the samples was determined using a vibrating sample magnetometer. The compounds showed paramagnetic character and no coercivity and remanence in all cases. Galvanostatic measurements of electrodes formed with nanocrystals showed better performance than those built with micrometric particles. - Highlights: • Spinel Co{sub 3}O{sub 4} nanoparticles and microparticles with same structure but with different cell parameters, particle size and surface area were synthesized. • Oxide nanoparticles showed better electrochemical behavior than micrometric ones due to area effect.

  12. Enhanced photocatalytic activity of electrochemically synthesized aluminum oxide nanoparticles

    NASA Astrophysics Data System (ADS)

    Pathania, Deepak; Katwal, Rishu; Kaur, Harpreet

    2016-03-01

    In this study, aluminum oxide (Al2O3) nanoparticles (NPs) were synthesized via an electrochemical method. The effects of reaction parameters such as supporting electrolytes, solvent, current and electrolysis time on the shape and size of the resulting NPs were investigated. The Al2O3 NPs were characterized by Fourier transform infrared spectroscopy, X-ray diffraction, transmission electron microscopy, thermogravimetric analysis/differential thermal analysis, energy-dispersive X-ray analysis, and ultraviolet-visible spectroscopy. Moreover, the Al2O3 NPs were explored for photocatalytic degradation of malachite green (MG) dye under sunlight irradiation via two processes: adsorption followed by photocatalysis; coupled adsorption and photocatalysis. The coupled process exhibited a higher photodegradation efficiency (45%) compared to adsorption followed by photocatalysis (32%). The obtained kinetic data was well fitted using a pseudo-first-order model for MG degradation.

  13. Vanadium oxides nanostructures: Hydrothermal synthesis and electrochemical properties

    SciTech Connect

    Mjejri, I.; Etteyeb, N.; Sediri, F.

    2014-12-15

    Highlights: • Vanadium oxides nanostructures were synthesized hydrothermally. • Reversible redox behavior with doping/dedoping process. • Doping/dedoping is easier for Li{sup +} to Na{sup +}. • Energy-related applications such as cathodes in lithium batteries. - Abstract: A facile and template-free one-pot strategy is applied to synthesize nanostructured vanadium oxide particles via a hydrothermal methodology. X-ray diffraction (XRD), scanning electron microscope (SEM), Fourier transforms infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) have been used to characterize the structure and morphology of the samples. The products are gradually changed from sheet-shaped VO{sub 2}(B) to rod-like V{sub 3}O{sub 7}·H{sub 2}O with decreasing cyclohexanediol as both protective and reducing agent. The specific surface area of the VO{sub 2}(B) nanosheets and V{sub 3}O{sub 7}·H{sub 2}O nanorods was found to be 22 and 16 m{sup 2} g{sup −1}, respectively. Thin films of VO{sub 2}(B) and V{sub 3}O{sub 7}·H{sub 2}O deposited on ITO substrates were electrochemically characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The voltammograms show reversible redox behavior with doping/dedoping process corresponding to reversible cation intercalation/de-intercalation into the crystal lattice of the nanorods/nanosheets. This process is easier for the small Li{sup +} cation than larger ones Na{sup +}.

  14. Oxidation of alloys for advanced steam turbines

    SciTech Connect

    Holcomb, Gordon R.; Covino, Bernard S., Jr.; Bullard, Sophie J.; Cramer, Stephen D.; Ziomek-Moroz, M.

    2005-01-01

    Ultra supercritical (USC) power plants offer the promise of higher efficiencies and lower emissions. Current goals of the U.S. Department of Energy’s Advanced Power Systems Initiatives include coal generation at 60% efficiency, which would require steam temperatures of up to 760°C. This research examines the steamside oxidation of advanced alloys for use in USC systems, with emphasis placed on alloys for high- and intermediate-pressure turbine sections.

  15. Electrochemical Water Oxidation of Ultrathin Cobalt Oxide-Based Catalyst Supported onto Aligned ZnO Nanorods.

    PubMed

    Koteeswara Reddy, Nandanapalli; Winkler, Stefanie; Koch, Norbert; Pinna, Nicola

    2016-02-10

    A stable and durable electrochemical water oxidation catalyst based on CoO functionalized ZnO nanorods (NRs) is introduced. ZnO NRs were grown on fluorine-doped tin oxide (FTO) by using a low-temperature chemical solution method and were functionalized with cobalt oxide by electrochemical deposition. The electrochemical water oxidation performance of cobalt oxide functionalized ZnO NRs was studied under alkaline (pH = 10) conditions. From these studies, it is noticed that cobalt oxide functionalized ZnO NRs show electrocatalytic activity toward water oxidation with current density on the order of several mA cm(-2). Further, 30 s CoO deposited ZnO nanorods exhibited excellent galvanostatic stability at a current density of 1 mA cm(-2) and potentiostatic stability at 1.25 V vs Ag/AgCl over an electrolysis period of 1 h. PMID:26784675

  16. Electrochemically Reduced Water Protects Neural Cells from Oxidative Damage

    PubMed Central

    Hamasaki, Takeki; Kinjo, Tomoya; Nakamichi, Noboru; Teruya, Kiichiro; Kabayama, Shigeru

    2014-01-01

    Aging-related neurodegenerative disorders are closely associated with mitochondrial dysfunction and oxidative stresses and their incidence tends to increase with aging. Brain is the most vulnerable to reactive species generated by a higher rate of oxygen consumption and glucose utilization compared to other organs. Electrochemically reduced water (ERW) was demonstrated to scavenge reactive oxygen species (ROS) in several cell types. In the present study, the protective effect of ERW against hydrogen peroxide (H2O2) and nitric oxide (NO) was investigated in several rodent neuronal cell lines and primary cells. ERW was found to significantly suppress H2O2 (50–200 μM) induced PC12 and SFME cell deaths. ERW scavenged intracellular ROS and exhibited a protective effect against neuronal network damage caused by 200 μM H2O2 in N1E-115 cells. ERW significantly suppressed NO-induced cytotoxicity in PC12 cells despite the fact that it did not have the ability to scavenge intracellular NO. ERW significantly suppressed both glutamate induced Ca2+ influx and the resulting cytotoxicity in primary cells. These results collectively demonstrated for the first time that ERW protects several types of neuronal cells by scavenging ROS because of the presence of hydrogen and platinum nanoparticles dissolved in ERW. PMID:25383141

  17. Electrochemical, H2O2-Boosted Catalytic Oxidation System

    NASA Technical Reports Server (NTRS)

    Akse, James R.; Thompson, John O.; Schussel, Leonard J.

    2004-01-01

    An improved water-sterilizing aqueous-phase catalytic oxidation system (APCOS) is based partly on the electrochemical generation of hydrogen peroxide (H2O2). This H2O2-boosted system offers significant improvements over prior dissolved-oxygen water-sterilizing systems in the way in which it increases oxidation capabilities, supplies H2O2 when needed, reduces the total organic carbon (TOC) content of treated water to a low level, consumes less energy than prior systems do, reduces the risk of contamination, and costs less to operate. This system was developed as a variant of part of an improved waste-management subsystem of the life-support system of a spacecraft. Going beyond its original intended purpose, it offers the advantage of being able to produce H2O2 on demand for surface sterilization and/or decontamination: this is a major advantage inasmuch as the benign byproducts of this H2O2 system, unlike those of systems that utilize other chemical sterilants, place no additional burden of containment control on other spacecraft air- or water-reclamation systems.

  18. Improved electrochemical biosensor response via metal oxide pre-oxidation of chemical interferents

    NASA Astrophysics Data System (ADS)

    Houseknecht, Jamie G.; Tapsak, Mark A.

    2007-09-01

    Typical biological samples are inherently complicated. They may contain a myriad of compounds that are electroactive at the same potential as that used in many electrochemical biosensors. Therefore, a biosensor design feature must be included that either eliminates or blocks the interferents from generating false positive signals. The ability to use an insoluble compound, that of MnO II, in order to oxidize interferents such as ascorbic acid, acetaminophen and uric acid, was investigated in a prototype sensor system at a bias potential of 0.6 V versus Ag/AgCl. Unlike previous work with these materials, a difference between the ability for the metal oxide to oxidize the interferents was observed. Most effective was the capability of MnO II to oxidize uric acid. Alternatively, the MnO II had little effect on acetaminophen. The study is both introduced and results are discussed within the context of an implantable glucose sensor.

  19. HANDBOOK ON ADVANCED NONPHOTOCHEMICAL OXIDATION PROCESSES

    EPA Science Inventory

    The purpose of this handbook is to summarize commercial-scale system performance and cost data for advanced nonphotochemical oxidation (ANPO) treatment of contaminated water, air, and soil. Similar information from pilot-and bench-scale evaluations of ANPO processes is also inclu...

  20. HANDBOOK ON ADVANCED PHOTOCHEMICAL OXIDATION PROCESSES

    EPA Science Inventory

    This handbook summarizes commercial-scale system performance and cost data for advanced photochemical oxidation (APO) treatment of contaminated water, air, and solids. Similar information from pilot- and bench-scale evaluations of APO processes is also included to supplement the...

  1. Recent advances in electrochemical biosensors based on graphene two-dimensional nanomaterials.

    PubMed

    Song, Yang; Luo, Yanan; Zhu, Chengzhou; Li, He; Du, Dan; Lin, Yuehe

    2016-02-15

    Graphene as a star among two-dimensional nanomaterials has attracted tremendous research interest in the field of electrochemistry due to their intrinsic properties, including the electronic, optical, and mechanical properties associated with their planar structure. The marriage of graphene and electrochemical biosensors has created many ingenious biosensing strategies for applications in the areas of clinical diagnosis and food safety. This review provides a comprehensive overview of the recent advances in the development of graphene based electrochemical biosensors. Special attention is paid to graphene-based enzyme biosensors, immunosensors, and DNA biosensors. Future perspectives on high-performance graphene-based electrochemical biosensors are also discussed. PMID:26187396

  2. Demonstration of Electrochemical Cell Properties by a Simple, Colorful Oxidation-reduction Experiment.

    ERIC Educational Resources Information Center

    Hendricks, Lloyd J.; And Others

    1982-01-01

    Describes apparatus/methodology and provides background information for an experiment demonstrating electrochemical concepts and properties of electrochemical cells. The color of a solution close to an electrode is changed from that of the bulk solution to either of two contrasting colors depending on whether the reaction is oxidation or…

  3. Advanced Proton Conducting Polymer Electrolytes for Electrochemical Capacitors

    NASA Astrophysics Data System (ADS)

    Gao, Han

    Research on solid electrochemical energy storage devices aims to provide high performance, low cost, and safe operation solutions for emerging applications from flexible consumer electronics to microelectronics. Polymer electrolytes, minimizing device sealing and liquid electrolyte leakage, are key enablers for these next-generation technologies. In this thesis, a novel proton-conducing polymer electrolyte system has been developed using heteropolyacids (HPAs) and polyvinyl alcohol for electrochemical capacitors. A thorough understanding of proton conduction mechanisms of HPAs together with the interactions among HPAs, additives, and polymer framework has been developed. Structure and chemical bonding of the electrolytes have been studied extensively to identify and elucidate key attributes affecting the electrolyte properties. Numerical models describing the proton conduction mechanism have been applied to differentiate those attributes. The performance optimization of the polymer electrolytes through additives, polymer structural modifications, and synthesis of alternative HPAs has achieved several important milestones, including: (a) high proton mobility and proton density; (b) good ion accessibility at electrode/electrolyte interface; (c) wide electrochemical stability window; and (d) good environmental stability. Specifically, high proton mobility has been addressed by cross-linking the polymer framework to improve the water storage capability at normal-to-high humidity conditions (e.g. 50-80% RH) as well as by incorporating nano-fillers to enhance the water retention at normal humidity levels (e.g. 30-60% RH). High proton density has been reached by utilizing additional proton donors (i.e. acidic plasticizers) and by developing different HPAs. Good ion accessibility has been achieved through addition of plasticizers. Electrochemical stability window of the electrolyte system has also been investigated and expanded by utilizing HPAs with different heteroatoms. The optimized polymer electrolyte demonstrated even higher proton conductivity than pure HPAs and the enabled electrochemical capacitors have demonstrated an exceptionally high rate capability of 50 Vs-1 in cyclic voltammograms and a 10 ms time constant in impedance analyses.

  4. Enhanced electrochemical supercapacitance of binder-free nanoporous ternary metal oxides/metal electrode.

    PubMed

    Gao, J J; Qiu, H-J; Wen, Y R; Chiang, F-K; Wang, Y

    2016-07-15

    Free-standing nanoporous Ni-Cu-Mn mixed metal oxides on metal with a high surface area was fabricated by chemically dealloying a Ni8Cu12Mn80 single-phase precursor, followed by electrochemical oxidation in an alkaline solution. Electrochemical analysis shows that first Cu and Mn-based metal oxides formed by the electrochemical oxidation. Ni-based oxides grow later with the increase of electrochemical CV cycles and mix with the Cu/Mn oxides, forming a relatively stable mixed metal oxides thin film on metal ligament network. Due to the different electrochemical properties of each metal and the synergetic effect between them, the mixed ternary metal oxides formed on metal nano-ligament can operate stably between a wide potential window (1.5V) in 1.0M KOH aqueous solution when tested as a free-standing supercapacitor electrode. Due to the high volumetric surface area, wide operating potential window and excellent conductivity, the nanoporous metal oxides@metal composite exhibits a high volumetric capacitance (∼500Fcm(-3)), high energy density (∼38mWhcm(-3)) and good cycling stability. PMID:27089016

  5. Eliminating degradation in solid oxide electrochemical cells by reversible operation

    NASA Astrophysics Data System (ADS)

    Graves, Christopher; Ebbesen, Sune Dalgaard; Jensen, Søren Højgaard; Simonsen, Søren Bredmose; Mogensen, Mogens Bjerg

    2015-02-01

    One promising energy storage technology is the solid oxide electrochemical cell (SOC), which can both store electricity as chemical fuels (electrolysis mode) and convert fuels to electricity (fuel-cell mode). The widespread use of SOCs has been hindered by insufficient long-term stability, in particular at high current densities. Here we demonstrate that severe electrolysis-induced degradation, which was previously believed to be irreversible, can be completely eliminated by reversibly cycling between electrolysis and fuel-cell modes, similar to a rechargeable battery. Performing steam electrolysis continuously at high current density (1 A cm-2), initially at 1.33 V (97% energy efficiency), led to severe microstructure deterioration near the oxygen-electrode/electrolyte interface and a corresponding large increase in ohmic resistance. After 4,000 h of reversible cycling, however, no microstructural damage was observed and the ohmic resistance even slightly improved. The results demonstrate the viability of applying SOCs for renewable electricity storage at previously unattainable reaction rates, and have implications for our fundamental understanding of degradation mechanisms that are usually assumed to be irreversible.

  6. Facile and controllable electrochemical reduction of graphene oxide and its applications

    SciTech Connect

    Shao, Yuyan; Wang, Jun; Engelhard, Mark H.; Wang, Chong M.; Lin, Yuehe

    2010-01-01

    Graphene oxide is electrochemically reduced which is called electrochemically reduced graphene oxide (ER-G). ER-G is characterized with scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, and X-ray diffraction. The oxygen content is significantly decreased and the sp 2 carbon is restored after electrochemical reduction. ER-G exhibits much higher electrochemical capacitance and cycling durability than carbon nanotubes (CNTs) and chemically reduced graphene; the specific capacitance measured with cyclic voltammetry (20 mV/s) is ~165 F/g, ~86 F/g, and ~100 F/g for ER-G, CNTs, and chemically reduced graphene,1 respectively. The electrochemical reduction of oxygen and hydrogen peroxide was greatly enhanced on ER-G electrodes as compared with CNTs. ER-G has shown a good potential for applications in energy storage, biosensors, and electrocatalysis.

  7. Solid-phase electrochemical reduction of graphene oxide films in alkaline solution

    PubMed Central

    2013-01-01

    Graphene oxide (GO) film was evaporated onto graphite and used as an electrode to produce electrochemically reduced graphene oxide (ERGO) films by electrochemical reduction in 6 M KOH solution through voltammetric cycling. Fourier transformed infrared and Raman spectroscopy confirmed the presence of ERGO. Electrochemical impedance spectroscopy characterization of ERGO and GO films in ferrocyanide/ferricyanide redox couple with 0.1 M KCl supporting electrolyte gave results that are in accordance with previous reports. Based on the EIS results, ERGO shows higher capacitance and lower charge transfer resistance compared to GO. PMID:24059434

  8. Degradation of formaldehyde by advanced oxidation processes.

    PubMed

    Guimarães, José Roberto; Farah, Carolina Rittes Turato; Maniero, Milena Guedes; Fadini, Pedro Sérgio

    2012-09-30

    The degradation of formaldehyde in an aqueous solution (400 mg L(-1)) was studied using photolysis, peroxidation and advanced oxidation processes (UV/H(2)O(2), Fenton and photo-Fenton). Photolysis was the only process tested that did not reduce formaldehyde concentration; however, only advanced oxidation processes (AOPs) significantly decreased dissolved organic carbon (DOC). UV/H(2)O(2) and photo-Fenton AOPs were used to degrade formaldehyde at the highest concentrations (1200-12,000 mg L(-1)); the processes were able to reduce CH(2)O by 98% and DOC by 65%. Peroxidation with ultraviolet light (UV/H(2)O(2)) improved the efficiency of treatment of effluent from an anatomy laboratory. The effluent's CH(2)O content was reduced by 91%, DOC by 48%, COD by 46% and BOD by 53% in 420 min of testing. PMID:22595075

  9. Semi-empirical chemical model for indirect advanced oxidation of Acid Orange 7 using an unmodified carbon fabric cathode for H2O2 production in an electrochemical reactor.

    PubMed

    Ramírez, B; Rondán, V; Ortiz-Hernández, L; Silva-Martínez, S; Alvarez-Gallegos, A

    2016-04-15

    A commercial Unidirectional Carbon Fabric piece was used to design an electrode for the cathodic O2 reduction reaction in a divided (by a Nafion(®) 117 membrane) parallel plate reactor. The anode was a commercial stainless steel mesh. Under this approach it is feasible to produce H2O2 at low energy (2.08 kWh kg(-1) H2O2) in low ionic acidic medium. In the catholyte side the H2O2 can be activated with Fe(2+) to develop the Fenton reagent. It was found that Acid Orange 7 (AO7) indirect oxidation (in the concentration range of 0.12-0.24 mM) by Fenton chemistry follows a first order kinetic equation. The energy required for 0.24 mM AO7 degradation is 1.04 kWhm(-3). From each experimental AO7 oxidation the main parameters (a, mM and k, min(-1)) of the first order kinetic equation are obtained. These parameters can be correlated with AO7 concentration in the concentration range studied. Based on this method a semi-empirical chemical model was developed to predict the AO7 abatement, by means of Fenton chemistry. Good AO7 oxidation predictions can be made in the concentration range studied. A detailed discussion of the energy required for oxidizing AO7 and the accuracy of the chemical model to predict its oxidation is included in this paper. PMID:26874037

  10. Non-enzymatic electrochemical glucose sensor based on platinum nanoflowers supported on graphene oxide.

    PubMed

    Wu, Geng-huang; Song, Xin-hong; Wu, Yan-fan; Chen, Xiao-mei; Luo, Feng; Chen, Xi

    2013-02-15

    A non-enzymatic electrochemical method was developed for glucose detection using a glassy carbon electrode modified with platinum nanoflowers supported on graphene oxide (PtNFs-GO). PtNFs-GO was synthesized using a nontoxic, rapid, one-pot and template-free method. Low-cost, green solvent ethanol acted as the reductant, and the advanced and effective 2D carbon material-GO nanosheet acted as the stabilizing material. Their morphologies were characterized using transmission electron microscopy. Cyclic voltammetry and amperometric methods were used to evaluate the electrocatalytic activity towards glucose in neutral media. The modified electrode exhibited strong and sensitive amperometric responses to glucose even in the presence of a high concentration of chloride ions. The response time was within 5s. The interference effects from ascorbic acid and uric acid were comparatively small when operated at suitable potential. Under optimal detection potential (0.47 V with a saturated calomel reference electrode) the PtNFs-GO modified electrode performed a current response towards glucose at a broad concentration range from 2 μM to 20.3mM. Two linear regions could be observed at 2 μM to 10.3mM with a sensitivity of 1.26 μA mM(-1)cm(-2) (correlation coefficient 0.9968), and at 10.3mM to 20.3mM with a sensitivity of 0.64 μA mM(-1)cm(-2)(correlation coefficient 0.9969). The LOD of 2 μM was lower than many non-enzymatic electrochemical glucose sensors. The modified electrode was also applied to the determination of glucose in glucose injection solutions, and the satisfactory results obtained indicated that it was promising for the development of a novel non-enzymatic electrochemical glucose sensor. PMID:23598034

  11. Advances in Mechanisms of Anti-oxidation

    PubMed Central

    Ma, Qiang

    2016-01-01

    Reactive oxygen species (ROS) are a family of molecules that are continuously produced from oxygen consumption in aerobic cells. Controlled generation of ROS in normal cells serves useful purposes to regulate important cellular processes such as cell proliferation, inflammation, and immune response, but overproduction of ROS causes oxidative stress that contributes to the development of cancer, chronic disease, and aging. These hugely different consequences of ROS exposure demand a carefully balanced control of ROS production and disposition, which is largely achieved through the body’s elaborate antioxidant system. The human antioxidant system consists of small antioxidants, antioxidant proteins, ROS-metabolizing enzymes, as well as many regulator proteins that mediate adaptive responses to oxidant stress. How such a complex system reacts with oxidants and achieves the required specificity and sensitivity for proper anti-oxidation is incompletely understood. In this respect, new advances in the understanding of the chemistry that determines the reaction of a given oxidant or antioxidant with a protein target provide considerable insights into these and related questions. The findings hold certain promise for new drug development for preventing and treating diseases associated with oxidant tissue damage. PMID:24641954

  12. Effect of electrochemical redox reaction on biochemical ammonium oxidation and chemical nitrite oxidation.

    PubMed

    Jeon, Bo Young; Seo, Ha Na; Kang, Seung Won; Park, Doo Hyun

    2010-03-01

    A modified graphite felt electrode with neutral red (NRelectrode) was shown to catalyze the chemical oxidation of nitrite to nitrate under aerobic conditions. The electrochemically oxidized NR-electrode (EO-NR-electrode) and reduced NR-electrode (ER-NR-electrode) catalyzed the oxidation of 1,094+/-39 mg/l and 382+/-45 mg/l of nitrite, respectively, for 24 h. The electrically uncharged NRelectrode (EU-NR-electrode) catalyzed the oxidation of 345+/-47 mg/l of nitrite for 24 h. The aerobic bacterial community immobilized in the EO-NR-electrode did not oxidize ammonium to nitrite; however, the aerobic bacterial community immobilized in the ER-NR-electrode bioelectrochemically oxidized 1,412+/-39 mg/l of ammonium for 48 h. Meanwhile, the aerobic bacterial community immobilized on the EU-NR-electrode biochemically oxidized 449+/-22 mg/l of ammonium for 48 h. In the continuous culture system, the aerobic bacterial community immobilized on the ER-NR-electrode bioelectrochemically oxidized a minimal 1,337+/-38 mg/l to a maximal 1,480+/-38 mg/l of ammonium to nitrate, and the community immobilized on the EU-NR-electrode biochemically oxidized a minimal 327+/-23 mg/l to a maximal 412+/-26 mg/l of ammonium to nitrate every two days. The bacterial communities cultivated in the ER-NR-electrode and EU-NR-electrode in the continuous culture system were analyzed by TGGE on the 20th and 50th days of incubation. Some ammoniumoxidizing bacteria were enriched on the ER-NR-electrode, but not on the EU-NR-electrode. PMID:20372016

  13. Route of electrochemical oxidation of the antibiotic sulfamethoxazole on a mixed oxide anode.

    PubMed

    Hussain, Sajjad; Gul, Saima; Steter, Juliana R; Miwa, Douglas W; Motheo, Artur J

    2015-10-01

    The appearance of pharmaceutical compounds and their bioactive transformation products in aquatic environments is becoming an issue of increasing concern. In this study, the electrochemical oxidation of the widely used antibiotic sulfamethoxazole (SMX) was investigated using a commercial mixed oxide anode (Ti/Ru0.3Ti0.7O2) and a single compartment filter press-type flow reactor. The kinetics of SMX degradation was determined as a function of electrolyte composition, applied current density, and initial pH. Almost complete (98 %) degradation of SMX could be achieved within 30 min of electrolysis in 0.1 mol L(-1) NaCl solution at pH 3 with applied current densities ≥20 mA cm(-2). Nine major intermediates of the reaction were identified by LC-ESI-Q-TOF-MS (e.g., C6H9NO2S (m/z = 179), C6H4NOCl (m/z = 141), and C6H6O2 (m/z = 110)). The degradation followed various routes involving cleavage of the oxazole and benzene rings by hydroxyl and/or chlorine radicals, processes that could occur before or after rupture of the N-S bond, followed by oxidation of the remaining moieties. Analysis of the total organic carbon content revealed that the antibiotic was partially mineralized under the conditions employed and some inorganic ions, including NO3 (-) and SO4 (2-), could be identified. The results presented herein demonstrate the efficacy of the electrochemical process using a Ti/Ru0.3Ti0.7O2 anode for the remediation of wastewater containing the antibiotic SMX. PMID:26002364

  14. Induced effects of advanced oxidation processes

    NASA Astrophysics Data System (ADS)

    Liu, Peng; Li, Chaolin; Zhao, Zhuanjun; Lu, Gang; Cui, Haibo; Zhang, Wenfang

    2014-02-01

    Hazardous organic wastes from industrial, military, and commercial activities represent one of the greatest challenges to human beings. Advanced oxidation processes (AOPs) are alternatives to the degradation of those organic wastes. However, the knowledge about the exact mechanisms of AOPs is still incomplete. Here we report a phenomenon in the AOPs: induced effects, which is a common property of combustion reaction. Through analysis EDTA oxidation processes by Fenton and UV-Fenton system, the results indicate that, just like combustion, AOPs are typical induction reactions. One most compelling example is that pre-feeding easily oxidizable organic matter can promote the oxidation of refractory organic compound when it was treated by AOPs. Connecting AOPs to combustion, it is possible to achieve some helpful enlightenment from combustion to analyze, predict and understand AOPs. In addition, we assume that maybe other oxidation reactions also have induced effects, such as corrosion, aging and passivation. Muchmore research is necessary to reveal the possibilities of induced effects in those fields.

  15. Induced effects of advanced oxidation processes.

    PubMed

    Liu, Peng; Li, Chaolin; Zhao, Zhuanjun; Lu, Gang; Cui, Haibo; Zhang, Wenfang

    2014-01-01

    Hazardous organic wastes from industrial, military, and commercial activities represent one of the greatest challenges to human beings. Advanced oxidation processes (AOPs) are alternatives to the degradation of those organic wastes. However, the knowledge about the exact mechanisms of AOPs is still incomplete. Here we report a phenomenon in the AOPs: induced effects, which is a common property of combustion reaction. Through analysis EDTA oxidation processes by Fenton and UV-Fenton system, the results indicate that, just like combustion, AOPs are typical induction reactions. One most compelling example is that pre-feeding easily oxidizable organic matter can promote the oxidation of refractory organic compound when it was treated by AOPs. Connecting AOPs to combustion, it is possible to achieve some helpful enlightenment from combustion to analyze, predict and understand AOPs. In addition, we assume that maybe other oxidation reactions also have induced effects, such as corrosion, aging and passivation. Muchmore research is necessary to reveal the possibilities of induced effects in those fields. PMID:24503715

  16. Induced effects of advanced oxidation processes

    PubMed Central

    Liu, Peng; Li, Chaolin; Zhao, Zhuanjun; Lu, Gang; Cui, Haibo; Zhang, Wenfang

    2014-01-01

    Hazardous organic wastes from industrial, military, and commercial activities represent one of the greatest challenges to human beings. Advanced oxidation processes (AOPs) are alternatives to the degradation of those organic wastes. However, the knowledge about the exact mechanisms of AOPs is still incomplete. Here we report a phenomenon in the AOPs: induced effects, which is a common property of combustion reaction. Through analysis EDTA oxidation processes by Fenton and UV-Fenton system, the results indicate that, just like combustion, AOPs are typical induction reactions. One most compelling example is that pre-feeding easily oxidizable organic matter can promote the oxidation of refractory organic compound when it was treated by AOPs. Connecting AOPs to combustion, it is possible to achieve some helpful enlightenment from combustion to analyze, predict and understand AOPs. In addition, we assume that maybe other oxidation reactions also have induced effects, such as corrosion, aging and passivation. Muchmore research is necessary to reveal the possibilities of induced effects in those fields. PMID:24503715

  17. Electrochemical Oxidative Decarboxylation of Malonic Acid Derivatives: A Method for the Synthesis of Ketals and Ketones.

    PubMed

    Ma, Xiaofeng; Luo, Xiya; Dochain, Simon; Mathot, Charlotte; Mark, Istvn E

    2015-10-01

    A novel electrochemical oxidative decarboxylation of disubstituted malonic acids leading to dimethoxy ketals is described. In the presence of NH3, a wide range of disubstituted malonic acids was transformed into the corresponding ketals in good to excellent yields under electrochemical conditions. When the crude reaction mixture, obtained after electrolysis, was directly treated with 1 M aq HCl, the initially generated ketals were smoothly transformed into the corresponding ketones in a single vessel operation. PMID:26392322

  18. Kinetics of the electrochemical oxidation of 1,1-bis-hydroperoxy-4-methylcyclohexane on platinum

    NASA Astrophysics Data System (ADS)

    Vedenyapina, M. D.; Simakova, A. P.; Platonov, M. M.; Terent'ev, A. O.; Skundin, A. M.; Vedenyapin, A. A.

    2013-03-01

    The electrochemical synthesis of 3,12-dimethyl-7,8,15,16-tetraoxadispiro[5.2.5.2]hexadecane (1,2,4,5-tetraoxane) from 1,1-bis-hydroperoxy-4-methylcyclohexane on platinum electrode in a cell with separated and unseparated cathode and anode space in an aprotic solvent is conducted. The kinetics of electrochemical oxidation of 1,1-bis(hydroperoxy)-4-methylcyclohexane is studied. The current yield of the reaction is determined.

  19. Recent advances in the electrochemical construction of heterocycles

    PubMed Central

    2014-01-01

    Summary Due to the fact that the major portion of pharmaceuticals and agrochemicals contains heterocyclic units and since the overall number of commercially used heterocyclic compounds is steadily growing, heterocyclic chemistry remains in the focus of the synthetic community. Enormous efforts have been made in the last decades in order to render the production of such compounds more selective and efficient. However, most of the conventional methods for the construction of heterocyclic cores still involve the use of strong acids or bases, the operation at elevated temperatures and/or the use of expensive catalysts and reagents. In this regard, electrosynthesis can provide a milder and more environmentally benign alternative. In fact, numerous examples for the electrochemical construction of heterocycles have been reported in recent years. These cases demonstrate that ring formation can be achieved efficiently under ambient conditions without the use of additional reagents. In order to account for the recent developments in this field, a selection of representative reactions is presented and discussed in this review. PMID:25550752

  20. Mapping Electrochemical Heterogeneity at Iron Oxide Surfaces: A Local Electrochemical Impedance Study.

    PubMed

    Lucas, Marie; Boily, Jean-François

    2015-12-22

    Alternating current scanning electrochemical microscopy (AC-SECM) was used for the first time to map key electrochemical attributes of oriented hematite (α-Fe2O3) single crystal surfaces at the micron-scale. Localized electrochemical impedance spectra (LEIS) of the (001) and (012) faces provided insight into the spatial variations of local double layer capacitance (C(dl)) and charge transfer resistance (R(ad)). These parameters were extracted by LEIS measurements in the 0.4-8000 Hz range to probe the impedance response generated by the redistribution of water molecules and charge carriers (ions) under an applied AC. These were attributed to local variations in the local conductivity of the sample surfaces. Comparison with global EIS measurements on the same samples uncovered highly comparable frequency-resolved processes, that were broken down into contributions from the bulk hematite, the interface as well as the microelectrode/tip assembly. This work paves the way for new studies aimed at mapping electrochemical processes at the mesoscale on this environmentally and technologically important material. PMID:26625255

  1. Advances in electrospun carbon fiber-based electrochemical sensing platforms for bioanalytical applications.

    PubMed

    Mao, Xianwen; Tian, Wenda; Hatton, T Alan; Rutledge, Gregory C

    2016-02-01

    Electrochemical sensing is an efficient and inexpensive method for detection of a range of chemicals of biological, clinical, and environmental interest. Carbon materials-based electrodes are commonly employed for the development of electrochemical sensors because of their low cost, biocompatibility, and facile electron transfer kinetics. Electrospun carbon fibers (ECFs), prepared by electrospinning of a polymeric precursor and subsequent thermal treatment, have emerged as promising carbon systems for biosensing applications since the electrochemical properties of these carbon fibers can be easily modified by processing conditions and post-treatment. This review addresses recent progress in the use of ECFs for sensor fabrication and analyte detection. We focus on the modification strategies of ECFs and identification of the key components that impart the bioelectroanalytical activities, and point out the future challenges that must be addressed in order to advance the fundamental understanding of the ECF electrochemistry and to realize the practical applications of ECF-based sensing devices. PMID:26650731

  2. Advanced Electrochemical Technologies for Hydrogen Production by Alternative Thermochemical Cycles

    SciTech Connect

    Lvov, Serguei; Chung, Mike; Fedkin, Mark; Lewis, Michele; Balashov, Victor; Chalkova, Elena; Akinfiev, Nikolay; Stork, Carol; Davis, Thomas; Gadala-Maria, Francis; Stanford, Thomas; Weidner, John; Law, Victor; Prindle, John

    2011-01-06

    Hydrogen fuel is a potentially major solution to the problem of climate change, as well as addressing urban air pollution issues. But a key future challenge for hydrogen as a clean energy carrier is a sustainable, low-cost method of producing it in large capacities. Most of the world's hydrogen is currently derived from fossil fuels through some type of reforming processes. Nuclear hydrogen production is an emerging and promising alternative to the reforming processes for carbon-free hydrogen production in the future. This report presents the main results of a research program carried out by a NERI Consortium, which consisted of Penn State University (PSU) (lead), University of South Carolina (USC), Tulane University (TU), and Argonne National Laboratory (ANL). Thermochemical water decomposition is an emerging technology for large-scale production of hydrogen. Typically using two or more intermediate compounds, a sequence of chemical and physical processes split water into hydrogen and oxygen, without releasing any pollutants externally to the atmosphere. These intermediate compounds are recycled internally within a closed loop. While previous studies have identified over 200 possible thermochemical cycles, only a few have progressed beyond theoretical calculations to working experimental demonstrations that establish scientific and practical feasibility of the thermochemical processes. The Cu-Cl cycle has a significant advantage over other cycles due to lower temperature requirements – around 530 °C and below. As a result, it can be eventually linked with the Generation IV thermal power stations. Advantages of the Cu-Cl cycle over others include lower operating temperatures, ability to utilize low-grade waste heat to improve energy efficiency, and potentially lower cost materials. Another significant advantage is a relatively low voltage required for the electrochemical step (thus low electricity input). Other advantages include common chemical agents and reactions going to completion without side reactions, and lower demands on materials of construction. Three university research groups from PSU, USC, and TU as well as a group from ANL have been collaborating on the development of enabling technologies for the Cu-Cl cycle, including experimental work on the Cu-Cl cycle reactions, modeling and simulation, and particularly electrochemical reaction for hydrogen production using a CuCl electrolyzer. The Consortium research was distributed over the participants and organized in the following tasks: (1) Development of CuCl electrolyzer (PSU), (2) Thermodynamic modeling of anolyte solution (PSU), (3) Proton conductive membranes for CuCl electrolysis (PSU), (4) Development of an analytical method for online analysis of copper compounds in highly concentrated aqueous solutions (USC), (5) Electrodialysis as a means for separation and purification of the streams exiting the electrolyzer in the Cu-Cl cycle (USC), (6) Development of nanostructured electrocatalysts for the Cu-Cl electrolysis (USC), (7) Cu-Cl electrolyzer modeling (USC), (8) Aspen Plus modeling of the Cu-Cl thermochemical cycle (TU), (9) International coordination of research on the development of the Cu-Cl thermochemical cycle (ANL). The results obtained in the project clearly demonstrate that the Cu-Cl alternative thermochemical cycle is a promising and viable technology to produce hydrogen efficiently.

  3. Electrochemical self-assembly of oriented zinc oxide film from polyethylene oxide containing electrolyte.

    PubMed

    Ju, Xiaohui; Feng, Wei; Fujii, Akihiko; Ozaki, Masanori

    2009-03-01

    Oriented nanopillar ZnO crystals were firstly fabricated by the potentiostatic cathodic electrodeposition technique on conducting glass substrates from polyethylene oxide (PEO) containing zinc nitrate solutions at low temperature (343 K). The mechanism for PEO-assisted electrochemical growth of ZnO hexagonal columus was proposed and confirmed by scanning electron microscopy, X-ray diffraction and UV-visible spectrophotometer measurements. It was observed that the concentration of PEO played an important role in the morphology and size of ZnO crystals. The structure and optical studies indicated that the addition of PEO not only influenced crystal growth habit but also improve the optical properties of ZnO. PMID:19435038

  4. Electrochemical oxidation of 2,4,5-trichlorophenoxyacetic acid by metal-oxide-coated Ti electrodes.

    PubMed

    Maharana, Dusmant; Xu, Zesheng; Niu, Junfeng; Rao, Neti Nageswara

    2015-10-01

    Electrochemical oxidation of 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) over metal-oxide-coated Ti anodes, i.e., Ti/SnO2-Sb/Ce-PbO2, Ti/SnO2-Sb and Ti/RuO2, was examined. The degradation efficiency of over 90% was attained at 20 min at different initial concentrations (0.5-20 mg L(-1)) and initial pH values (3.1-11.2). The degradation efficiencies of 2,4,5-T on Ti/SnO2-Sb/Ce-PbO2, Ti/SnO2-Sb and Ti/RuO2 anodes were higher than 99.9%, 97.2% and 91.5% at 30 min, respectively, and the respective total organic carbon removal ratios were 65.7%, 54.6% and 37.2%. The electrochemical degradation of 2,4,5-T in aqueous solution followed pseudo-first-order kinetics. The compounds, i.e., 2,5-dichlorohydroquinone and 2,5-dihydroxy-p-benzoquinone, have been identified as the main aromatic intermediates by liquid chromatography-mass spectrometry. The results showed that the energy efficiencies of 2,4,5-T (20 mg L(-1)) degradation with Ti/SnO2-Sb/Ce-PbO2 anode at the optimal current densities from 2 to 16 mA cm(-2) ranged from 8.21 to 18.73 kWh m(-3). PMID:25981800

  5. Electrochemical characterization and occluded environment analysis of localized corrosion in advanced aluminum alloys

    SciTech Connect

    Wall, F.D.; Stoner, G.E.

    1994-12-31

    In order for advanced aluminum alloys to be used in structural applications it is necessary to understand and mitigate failures that can occur due to localized corrosion events. Mechanical and electrochemical stresses interacting with a microstructural heterogeneity can result in the rapid growth of a flaw in the material; this phenomenon is a form of environmentally assisted cracking (EAC). One possible mechanism of EAC in Al-Li-X alloys is the preferential dissolution of an electrochemically active microstructural feature along a grain or sub-grain boundary. To examine this mechanism it is necessary to obtain information on the occluded environment that develops in a growing crack and the electrochemical behavior of boundary phases in the occluded environment. The electrochemistry of three relevant boundary phases (matrix phase (SHT 2095), T{sub 1} precipitate (Al{sub 2}CuLi) and Cu-depleted zone (99.99% Al)) in several model environments has been documented using a variety of electrochemical techniques including scratching and straining electrode experiments. The electrochemical behavior of these phases has been linked to the SCC behavior of several Al-Li-X alloys using constant load testing under applied potentials in NaCl/Li{sub 2}CO{sub 3} and NaCl/Na{sub 2}CrO{sub 4} environments. The occluded environment model is being evaluated and refined by analysis of occluded chemistries using pH measurements and capillary electrophoresis.

  6. Mediated electrochemical oxidation of organic wastes without electrode separators

    DOEpatents

    Farmer, J.C.; Wang, F.T.; Hickman, R.G.; Lewis, P.R.

    1996-05-14

    An electrochemical cell/electrolyte/mediator combination is described for the efficient destruction of organic contaminants using metal salt mediators in a sulfuric acid electrolyte, wherein the electrodes and mediator are chosen such that hydrogen gas is produced at the cathode and no cell membrane is required. 3 figs.

  7. Synthesis and electrochemical behavior of nanostructured cauliflower-shape Co-Ni/Co-Ni oxides composites

    SciTech Connect

    Gupta, Vinay Kawaguchi, Toshikazu; Miura, Norio

    2009-01-08

    Nanostructured Co-Ni/Co-Ni oxides were electrochemically deposited onto stainless steel electrode by electrochemical method and characterized for their structural and supercapacitive properties. The SEM images indicated that the obtained Co-Ni/Co-Ni oxides had cauliflower-type nanostructure. The X-ray diffraction pattern showed the formation of Co{sub 3}O{sub 4}, NiO, Co and Ni. The EDX elemental mapping images indicated that Ni, Co and O are distributed uniformly. The deposited Co-Ni/Co-Ni oxides showed good supercapacitive characteristics with a specific capacitance of 331 F/g at 1 mA/cm{sup 2} current density in 1 M KOH electrolyte. A mechanism of the formation of cauliflower-shape Co-Ni/Co-Ni oxides was proposed. A variety of promising applications in the fields such as energy storage devices and sensors can be envisioned from Co-Ni/Co-Ni oxides.

  8. Electrochemical oxidation of wine polyphenols in the presence of sulfur dioxide.

    PubMed

    Makhotkina, Olga; Kilmartin, Paul A

    2013-06-12

    Electrochemical oxidation of three representative wine polyphenols (catechin, caffeic acid, and quercetin) in the presence of sulfur dioxide in a model wine solution (pH = 3.3) was investigated. The oxidation was undertaken using chronoamperometry at a rotating glassy carbon rod electrode, and the reaction products were characterized by HPLC-MS. The mechanism of electrochemical oxidation of polyphenols in the presence of sulfur dioxide was proposed to be an ECEC mechanism. The polyphenols first underwent a one-electron oxidation to a semiquinone radical, which can be reduced back to the original polyphenol by sulfur dioxide, or further oxidized to the quinone form. In the cases of caffeic acid and catechin, the quinone combined with sulfur dioxide and produced new derivatives. The quercetin quinone underwent further chemical transformations, producing several new compounds. The proposed mechanisms were confirmed by digital simulation of cyclic voltammograms. PMID:23692398

  9. Electrochemical synthesis of nickel-aluminium oxide system from metals obtained by ore processing

    NASA Astrophysics Data System (ADS)

    Korobochkin, V. V.; Usoltseva, N. V.; Shorokhov, K. G.; Popova, E. V.

    2015-11-01

    Separate and combined electrochemical oxidation of aluminium and nickel has been conducted by alternating current of industrial frequency. Concentration increase of electrolyte solution (sodium chloride) in the range from 3 to 25 wt. % and current density from 0.5 to 1.5 A/cm2 was found to result in the increasing metal oxidation rate, excluding aluminium oxidation which oxidation rate is independent of the electrolyte solution concentration. At the current density of 1.5 A/cm2 the products of separate oxidation of nickel and aluminium are nickel oxyhydroxides, nickel hydroxides and aluminium oxyhydroxide (boehmite), respectively. In addition to these compounds, the nickel-aluminium oxide hydrate is included in the products of nickel and aluminium co-oxidation. Its content grows with the increasing electrolyte solution concentration. Varying the concentration and current density within the limits indicated, the nickel-aluminium oxide system with nickel oxide content from 3 to 10 wt. % is produced.

  10. Development of Advanced Electrochemical Sensors for DNA Detection at the Point of Care

    NASA Astrophysics Data System (ADS)

    Hsieh, Kuangwen

    In the post-genomic era, ever-advancing capabilities in DNA detection and analysis have become vital to the detection of infectious diseases and the diagnosis of genetic abnormalities and inheritable diseases. The benefit of such capabilities, however, has yet to reach patients outside of centralized facilities. There thus exists an increasing need to decentralize DNA detection methods and to administer such diagnostics at the "point of care." Electrochemical-based DNA sensors present a compelling approach, but have yet to deliver satisfactory sensitivity, specificity, miniaturization, and real-time monitoring capability to meet the demand of point-of-care diagnostics. Motivated by their potential and their current limitations, in this dissertation, we present a series of strategies that we have undertaken in order to address the key shortcomings of electrochemical DNA sensors and advance them toward point-of-care applications. First, we report a single-step, single reagent, label-free, isothermal electrochemical DNA sensor based on the phenomenon of enzyme catalyzed target recycling amplification. Using this technique, we achieve improved detection limit in comparison to hybridization-based sensors without amplification. We also demonstrate greater than 16-fold amplification of signal at low target concentrations. Next, we present a novel electrochemical DNA sensor that detects single-nucleotide mismatched targets with unprecedented "polarity-switching" responses. This "bipolar" sensor employs a surface-bound and redox-modified (methylene blue) DNA probe architecture, and outputs a decreased Faradaic current when hybridized to a perfectly matched (PM) target, but conversely reports an increased Faradaic current when hybridized to a single-base mismatched (SM) target. Third, we describe the microfluidic electrochemical dynamic allele specific hybridization (microE-DASH) platform for versatile and rapid detection of single-nucleotide polymorphisms. Implementing electrochemical-based melting curve analysis within the microfluidic device, this platform directly detects PCR amplicon-like targets and distinguishes perfectly matched target from single-base mismatched target and heterozygote combination of both targets in 20 minutes. Finally, we present the microfluidic electrochemical quantitative loop-mediated isothermal amplification (MEQ-LAMP) platform for rapid, sensitive, and quantitative detection of pathogen genomic DNA at the point of care. DNA amplification is electrochemically monitored in real time within a monolithic microfluidic device, enabling the detection of as few as 16 copies of Salmonella genomic DNA via a single-step process in under an hour.

  11. Integrating electrochemical oxidation into forward osmosis process for removal of trace antibiotics in wastewater.

    PubMed

    Liu, Pengxiao; Zhang, Hanmin; Feng, Yujie; Shen, Chao; Yang, Fenglin

    2015-10-15

    During the rejection of trace pharmaceutical contaminants from wastewater by forward osmosis (FO), disposal of the FO concentrate was still an unsolved issue. In this study, by integrating the advantages of forward osmosis and electrochemical oxidation, a forward osmosis process with the function of electrochemical oxidation (FOwEO) was established for the first time to achieve the aim of rejection of trace antibiotics from wastewater and treatment of the concentrate at the same time. Results demonstrated that FOwEO (current density J=1 mA cm(-2)) exhibited excellent rejections of antibiotics (>98%) regardless of different operation conditions, and above all, antibiotics in the concentrate were well degraded (>99%) at the end of experiment (after 3h). A synergetic effect between forward osmosis and electrochemical oxidation was observed in FOwEO, which lies in that antibiotic rejections by FO were enhanced due to the degradation of antibiotics in the concentrate, while the electrochemical oxidation capacity was improved in the FOwEO channel, of which good mass transfer and the assist of indirect oxidation owing to the reverse NaCl from draw solution were supposed to be the mechanism. This study demonstrated that the FOwEO has the capability to thoroughly remove trace antibiotics from wastewater. PMID:25966924

  12. Electrochemical studies on nanometal oxide-activated carbon composite electrodes for aqueous supercapacitors

    NASA Astrophysics Data System (ADS)

    Ho, Mui Yen; Khiew, Poi Sim; Isa, Dino; Chiu, Wee Siong

    2014-11-01

    In present study, the electrochemical performance of eco-friendly and cost-effective titanium oxide (TiO2)-based and zinc oxide-based nanocomposite electrodes were studied in neutral aqueous Na2SO3 electrolyte, respectively. The electrochemical properties of these composite electrodes were studied using cyclic voltammetry (CV), galvanostatic charge-discharge (CD) and electrochemical impedance spectroscopy (EIS). The experimental results reveal that these two nanocomposite electrodes achieve the highest specific capacitance at fairly low oxide loading onto activated carbon (AC) electrodes, respectively. Considerable enhancement of the electrochemical properties of TiO2/AC and ZnO/AC nanocomposite electrodes is achieved via synergistic effects contributed from the nanostructured metal oxides and the high surface area mesoporous AC. Cations and anions from metal oxides and aqueous electrolyte such as Ti4+, Zn2+, Na+ and SO32- can occupy some pores within the high-surface-area AC electrodes, forming the electric double layer at the electrode-electrolyte interface. Additionally, both TiO2 and ZnO nanoparticles can provide favourable surface adsorption sites for SO32- anions which subsequently facilitate the faradaic processes for pseudocapacitive effect. These two systems provide the low cost material electrodes and the low environmental impact electrolyte which offer the increased charge storage without compromising charge storage kinetics.

  13. Synthesis and characterization of a nanocomposite of goethite nanorods and reduced graphene oxide for electrochemical capacitors

    SciTech Connect

    Shou Qingliang; Cheng Jipeng; Zhang Li; Nelson, Bradley J.; Zhang Xiaobin

    2012-01-15

    We report a one-step synthesis of a nanocomposite of goethite ({alpha}-FeOOH) nanorods and reduced graphene oxide (RGO) using a solution method in which ferrous cations serve as a reducing agent of graphite oxide (GO) to graphene and a precursor to grow goethite nanorods. As-prepared goethite nanorods have an average length of 200 nm and a diameter of 30 nm and are densely attached on both sides of the RGO sheets. The electrochemical properties of the nanocomposite were characterized by cyclic voltammetry (CV) and chronopotentiometry (CP) charge-discharge tests. The results showed that goethite/RGO composites have a high electrochemical capacitance of 165.5 F g{sup -1} with an excellent recycling capability making the material promising for electrochemical capacitors. - Graphical abstract: The reduced graphene oxide sheets are decorated with goethite nanorods. The as-prepared composite exhibits a high electrochemical capacitance with good recycling capability, which is promising for supercapacitor applications. Higlights: Black-Right-Pointing-Pointer Ferrous ions act as reductant of graphite oxide and precursor of goethite nanorods. Black-Right-Pointing-Pointer Goethite nanorods are attached on both sides of the reduced graphene oxide sheets. Black-Right-Pointing-Pointer Composite exhibits a high specific capacitance and a good recycling capability. Black-Right-Pointing-Pointer Composite is promising for supercapacitor applications.

  14. Effect of nanostructured graphene oxide on electrochemical activity of its composite with polyaniline titanium dioxide

    NASA Astrophysics Data System (ADS)

    Binh Phan, Thi; Thanh Luong, Thi; Mai, Thi Xuan; Thanh Thuy Mai, Thi; Tot Pham, Thi

    2016-03-01

    Graphene oxide (GO) significantly affects the electrochemical activity of its composite with polyanline titanium dioxide (TiO2). In this work various composites with different GO contents have been successfully synthesized by chemical method to compare not only their material properties but also electrochemical characteristics with each other. The results of an electrochemical impedance study showed that their electrochemical property has been improved due to the presence of GO in a composite matrix. The galvanodynamic polarization explained that among them the composite with GO/Ani ratio in the range of 1-14 exhibits a better performance compared to the other due to yielding a higher current desity (280 μA cm-2). The TEM and SEM images which presented the fibres of a composite bundle with the presence of PANi and TiO2 were examined by IR-spectra and x-ray diffraction, respectively.

  15. Design and Fabrication of Complementary Metal-Oxide-Semiconductor Sensor Chip for Electrochemical Measurement

    NASA Astrophysics Data System (ADS)

    Yamazaki, Tomoyuki; Ikeda, Takaaki; Kano, Yoshiko; Takao, Hidekuni; Ishida, Makoto; Sawada, Kazuaki

    2010-04-01

    An electrochemical sensor has been developed on a single chip in which potentiostat and sensor electrodes are integrated. Sensor chips were fabricated using 5.0 µm complementary metal-oxide-semiconductor (CMOS) technology. All processes including the CMOS process, postprocessing for fabricating sensor electrodes and passivation layers, and packaging were performed at Toyohashi University of Technology. The integration makes it possible to measure electrochemical signals without having to use a bulky external electrochemical system. The potential between the working electrode and the reference electrode was controlled using an on-chip potentiostat composed of CMOS transistors. The chip characteristics were verified by electrochemical measurement, namely, by cyclic voltammetry. Potassium ferricyanide solution was measured to obtain results that fit well to the theoretical formula. A clear proportional relationship between peak height and the concentration of the sample solution was obtained using the proposed sensor chip, and the dynamic range obtained was 0.10 to 8.0 mM.

  16. Design and Fabrication of Complementary Metal-Oxide-Semiconductor Sensor Chip for Electrochemical Measurement

    NASA Astrophysics Data System (ADS)

    Tomoyuki Yamazaki,; Takaaki Ikeda,; Yoshiko Kano,; Hidekuni Takao,; Makoto Ishida,; Kazuaki Sawada,

    2010-04-01

    An electrochemical sensor has been developed on a single chip in which potentiostat and sensor electrodes are integrated. Sensor chips were fabricated using 5.0 μm complementary metal-oxide-semiconductor (CMOS) technology. All processes including the CMOS process, postprocessing for fabricating sensor electrodes and passivation layers, and packaging were performed at Toyohashi University of Technology. The integration makes it possible to measure electrochemical signals without having to use a bulky external electrochemical system. The potential between the working electrode and the reference electrode was controlled using an on-chip potentiostat composed of CMOS transistors. The chip characteristics were verified by electrochemical measurement, namely, by cyclic voltammetry. Potassium ferricyanide solution was measured to obtain results that fit well to the theoretical formula. A clear proportional relationship between peak height and the concentration of the sample solution was obtained using the proposed sensor chip, and the dynamic range obtained was 0.10 to 8.0 mM.

  17. ADVANCED OXIDATION TECHNOLOGIES FOR THE TREATMENT OF CONTAMINATED GROUNDWATER

    EPA Science Inventory

    This paper presents information on two pilot-field appliations of advanced oxidation technologies for contaminated groundwater with organis. The two UV/oxidation technologies were developed by Ultrox International of Santa Ana, California and Peroxidatrion Systems, Inc. of Tucso...

  18. Electrochemical protection of zirconium in oxidizing hydrochloric acid solutions

    SciTech Connect

    Yuu, T-L.; Maguire, M.

    1984-06-01

    An electrochemical protection technique using cathodic polarization to maintain zirconium below its critical repassivation potential was used to avoid pitting and stress corrosion cracking (SCC) in hydrochloric acid (HCI) containing ferric ions (Fe/sup +3/). Corrosion and pit penetration rates are reported for pickled, abraded, and as-received surface conditions in 10, 20, and 37% HCI containing 50, 100, or 500 ppm Fe/sup +3/ at temperatures to boiling. The pickled surface was the least susceptible to pitting in the 64 day tests. Electrochemical protection is then evaluated for total immersion, partial immersion, U-bend, and constant strain rate tensile tests. Protection is effective in eliminating pitting and SCC in 10 and 20% HCI containing Fe/sup +3/.

  19. Electrochemical protection of Zr against SCC by oxidizing HCl solutions

    SciTech Connect

    Yaiu, T.; Maguire, M.

    1985-07-01

    Results are reported for electrochemical protection of zirconium in HCl containing 500 ppm ferric ions. Corrosion rate and pit propagation rate data as a function of acid concentration (10 to 37%) and temperature (25 to 107 C) are presented first as a basis for observations of SCC and/or intergranular attack associated with weld metals. U-bend, C-ring, sustained load tensile, and slow strain-rate tests were used and compared to define conditions where SCC occurs. Along with electrochemical protection, heat treatment and reducing the ferric ion concentration are presented as ways to alleviate local attack. Metallography was used both to define the mode of attack and to show the benefits of protection techniques.

  20. Electrochemical functionalization of polypyrrole through amine oxidation of poly(amidoamine) dendrimers: Application to DNA biosensor.

    PubMed

    Miodek, Anna; Mejri-Omrani, Nawel; Khoder, Rabih; Korri-Youssoufi, Hafsa

    2016-07-01

    Electrochemical patterning method has been developed to fabricate composite based on polypyrrole (PPy) film and poly(amidoamine) dendrimers of fourth generation (PAMAM G4). PPy layer was generated using electrochemical polymerization of pyrrole on a gold electrode. PPy film was then modified with PAMAM G4 using amines electro-oxidation method. Covalent bonding of PAMAM G4 and the formation of PPy-PAMAM composite was characterized using Fourier Transform Infrared Spectroscopy (FT-IR) and X-ray Photoelectron Spectroscopy (XPS). Ferrocenyl groups were then attached to such surface as a redox marker. Electrochemical properties of the modified nanomaterial (PPy-PAMAM-Fc) were studied using both amperometric and impedimetric methods to demonstrate the efficiency of electron transfer through the modified PPy layer. The obtained electrical and electrochemical properties were compared to a composite where PPy bearing carboxylic acid functions was chemically modified with PAMAM G4 by covalent attachment through formation of amid bond (PPy-CONH-PAMAM). The above mentioned studies showed that electrochemical patterning does not disturb the electronic properties of PPy. The effect of the number of functional groups introduced by the electrochemical patterning was demonstrated through the association of various compounds (ethylenediamine, PAMAM G2 and PAMAM G6). We demonstrated that such compounds could be applied in the biosensors technology. The modified PPy-PAMAM-Fc was evaluated as a platform for DNA sensing. High performance in the DNA detection by variation of the electrochemical signal of ferrocene was obtained with detection limit of 0.4 fM. Furthermore, such approach of electrochemical patterning by oxidation of amines could be applied for chemical modification of PPy and open a new way in various biosensing application involving functionalized PPy. PMID:27154698

  1. Preparation, characterization, and electrochemical application of mesoporous copper oxide

    SciTech Connect

    Cheng, Liang; Anhui Key Laboratory of Functional Molecular Solids, and College of Chemistry and Materials Science, Anhui Normal University, Wuhu 241000 ; Shao, Mingwang; Anhui Key Laboratory of Functional Molecular Solids, and College of Chemistry and Materials Science, Anhui Normal University, Wuhu 241000 ; Chen, Dayan; Zhang, Yuzhong

    2010-02-15

    Mesoporous CuO was successfully synthesized via thermal decomposition of CuC{sub 2}O{sub 4} precursors. These products had ring-like morphology, which was made up of nanoparticles with the average diameter of 40 nm. The electrochemical experiments showed that the mesoporous CuO decreased the overvoltage of the electrode and increased electron transference in the measurement of dopamine.

  2. Synthesis and electrochemical capacitance of long tungsten oxide nanorod arrays grown vertically on substrate

    SciTech Connect

    Park, Sun Hwa; Kim, Young Heon; Lee, Tae Geol; Shon, Hyun Kyong; Park, Hyun Min; Korea Research Institute of Standards and Science, Daejeon 305-340 ; Song, Jae Yong

    2012-11-15

    Highlights: ► Growth of long amorphous tungsten oxide nanorods on a substrate. ► Formation of single-crystalline tungsten oxide nanorods by a heat-treatment. ► High electrochemical pseudocapacitance of 2.8 mF cm{sup −2}. ► Excellent cyclability of psuedocapacitance up to 1000 cycles. -- Abstract: Long tungsten oxide nanorods are vertically grown on Al/W/Ti coated silicon substrates using a two-step anodization process. The first anodization of the Al film forms a mesh-like mask of anodic aluminum oxide, and the second anodization of the W film results in the formation of a buffer layer, a bottom nanorod, and a top nanorod of amorphous tungsten oxide. A pore-widening process prior to the second anodization leads to the enhancement of nanorod length above approximately 500 nm. After a heat-treatment, the tungsten oxide nanorods are crystallized to form a single crystalline structure while the buffer layer forms a polycrystalline structure. The crystalline tungsten oxide nanorods show a cyclic voltammogram retaining the quasi-rectangular shape of an electrochemically reversible faradaic redox reaction, i.e., a typical pseudocapacitive behavior. The maximum electrochemical capacitance per apparent surface area reaches approximately 2.8 mF cm{sup −2} at the voltage scan rate of 20 mV s{sup −1}, and the excellent cyclability of charge–discharge process is maintained up to 1000 cycles.

  3. Effects of Salts and Metal Oxides on Electrochemical and Optical Properties of Streptococcus mutans

    NASA Astrophysics Data System (ADS)

    Kawai, Tsuyoshi; Nagame, Seigo; Kambara, Masaki; Yoshino, Katsumi

    1994-10-01

    The effects of calcium salts and metal oxide powders on electrochemical, optical and biological properties of Streptococcus mutans have been studied as a novel method to determine the strain. Electrochemical signals of Streptococcus mutans show remarkable decrease in the presence of saturated calcium salts such as CaHPO4, Ca3(PO4)2, and Ca5(PO4)3OH depending on the strains of Streptococcus mutans: Ingbritt, NCTC-10449, or GS-5. The number of viable cells also decreases upon addition of these powders. The effects of metal oxides such as ZnO and BaTiO3 on the electrochemical characteristics and photoluminescence of Streptococcus mutans have also been studied.

  4. Photo-electrochemical Oxidation of Organic C1 Molecules over WO3 Films in Aqueous Electrolyte: Competition Between Water Oxidation and C1 Oxidation.

    PubMed

    Reichert, Robert; Zambrzycki, Christian; Jusys, Zenonas; Behm, R Jürgen

    2015-11-01

    To better understand organic-molecule-assisted photo-electrochemical water splitting, photo-electrochemistry and on-line mass spectrometry measurements are used to investigate the photo-electrochemical oxidation of the C1 molecules methanol, formaldehyde, and formic acid over WO3 film anodes in aqueous solution and its competition with O2 evolution from water oxidation O2 (+) and CO2 (+) ion currents show that water oxidation is strongly suppressed by the organic species. Photo-electro-oxidation of formic acid is dominated by formation of CO2 , whereas incomplete oxidation of formaldehyde and methanol prevails, with the selectivity for CO2 formation increasing with increasing potential and light intensity. The mechanistic implications for the photo-electro-oxidation of the organic molecules and its competition with water oxidation, which could be derived from this novel approach, are discussed. PMID:26382643

  5. Electrochemical detection of nitric oxide production in perfused pig coronary artery: comparison of the performances of two electrochemical sensors.

    PubMed

    Villeneuve, N; Bedioui, F; Voituriez, K; Avaro, S; Vilaine, J P

    1998-08-01

    In situ direct measurement of nitric oxide (NO) in biological media is now possible by means of electrochemical detection. In the literature, there are principally two amperometric approaches based on the direct oxidation of NO either on a sensor made from platinum/ iridium (Pt/Ir) alloy coated with a three-layered membrane or on a nickel porphyrin and Nafion-coated carbon fiber electrode. Nonetheless, the exact nature of the experimental amperometric signal obtained with the Pt/Ir system was never authenticated as being related to NO. This study compared responses of two sensors to the inhibition effect of Nomega-nitro-L-arginine (L-NA) as the amperometric signals produced by 5-hydroxytryptamine (5-HT) on isolated pig coronary preparations. These amperometric signals could be attributed to NO only for the nickel porphyrin and Nafion-coated carbon fiber electrode. Indeed, voltammetric characterization of the electrochemical response demonstrated only variations of the baseline current upon additions of either SNAP or NO on the Pt/Ir electrode instead of anodic peak current displayed at 0.63-0.75 V for the other system. Nitrites induced baseline current variations with the Pt/Ir electrode, similar to those obtained with S-nitroso-N-acetyl-dl-penicillamine (SNAP) or NO. This study highlights the potential hazards and pitfalls that may be associated with the use of a Pt/Ir sensor calibrated with SNAP solutions for the detection of NO production in various biological systems. PMID:10100498

  6. Electrochemical oxidation stability of anions for modern battery electrolytes: a CBS and DFT study.

    PubMed

    Jónsson, Erlendur; Johansson, Patrik

    2015-02-01

    The electrochemical stability vs. oxidation is a crucial property of anions in order to be suitable as components in lithium-ion batteries. Here the applicability of a number of computational approaches and methods to assess this property, employing a wide selection of DFT functionals, has been studied using the CCSD(T)/CBS method as the reference. In all, the vertical anion oxidation potential, ΔEv, is a fair way to calculate the stability vs. oxidation, however, a functional of at least hybrid quality is recommended. In addition, the chemical hardness, η, is identified as a novel approach to calculate the stability vs. oxidation. PMID:25557392

  7. Synthesis, optical and electrochemical properties of ZnO nanowires/graphene oxide heterostructures

    PubMed Central

    2013-01-01

    Large-scale vertically aligned ZnO nanowires with high crystal qualities were fabricated on thin graphene oxide films via a low temperature hydrothermal method. Room temperature photoluminescence results show that the ultraviolet emission of nanowires grown on graphene oxide films was greatly enhanced and the defect-related visible emission was suppressed, which can be attributed to the improved crystal quality and possible electron transfer between ZnO and graphene oxide. Electrochemical property measurement results demonstrated that the ZnO nanowires/graphene oxide have large integral area of cyclic voltammetry loop, indicating that such heterostructure is promising for application in supercapacitors. PMID:23522184

  8. Electrochemically triggered release of human insulin from an insulin-impregnated reduced graphene oxide modified electrode.

    PubMed

    Teodorescu, Florina; Rolland, Laure; Ramarao, Viswanatha; Abderrahmani, Amar; Mandler, Daniel; Boukherroub, Rabah; Szunerits, Sabine

    2015-09-28

    An electrochemical insulin-delivery system based on reduced graphene oxide impregnated with insulin is described. Upon application of a potential pulse of -0.8 V for 30 min, up to 70 ± 4% of human insulin was released into a physiological medium while preserving its biological activity. PMID:26257079

  9. Electrochemical studies of hydrogen evolution, storage and oxidation on carbon nanotube electrodes

    NASA Astrophysics Data System (ADS)

    Prosini, Pier Paolo; Pozio, Alfonso; Botti, Sabina; Ciardi, Roberto

    Carbon nanotube films produced on a Si(1 0 0) substrate without any metal catalyst were used as electrodes in galvanic cells. The electrochemical mechanism of hydrogen evolution, storage and oxidation was studied using cyclic voltammetry and galvanostatic polarisation. Cyclic voltammetry showed that hydrogen is easily produced on the carbon nanotube surface, but a significant overvoltage was observed for hydrogen oxidation. The kinetics of hydrogen evolution influenced the quantity of hydrogen stored in the nanotube, which increased with increasing discharge currents.

  10. Degradation of methylparathion in aqueous solution by electrochemical oxidation.

    PubMed

    Vlyssides, Apostolos; Barampouti, Elli Maria; Mai, Sofia; Arapoglou, Dimitris; Kotronarou, Anastasia

    2004-11-15

    The electrochemical degradation of methylparathion has been investigated by using Ti/Pt as anode, Stainless Steel 304 as cathode, and sodium chloride as electrolyte. The pesticide is rapidly degraded, but full mineralization is not observed. Degradation products have been monitored through gas chromatography and mass spectrometry, and the overall degradation process has been monitored through dissolved and particulate organic carbon, sulfur, and phosphorus measurements. Several intermediates have been identified, and oxalic, formic, and acetic acids as well as tetraphosphorus trisulfide have been recognized as final products of the degradation process. A proposed mechanism of the process is presented. PMID:15573616

  11. Oxygen vacancy diffusion across cathode/electrolyte interface in solid oxide fuel cells: An electrochemical phase-field model

    NASA Astrophysics Data System (ADS)

    Hong, Liang; Hu, Jia-Mian; Gerdes, Kirk; Chen, Long-Qing

    2015-08-01

    An electrochemical phase-field model is developed to study electronic and ionic transport across the cathode/electrolyte interface in solid oxide fuel cells. The influences of local current density and interfacial electrochemical reactions on the transport behaviors are incorporated. This model reproduces two electrochemical features. Nernst equation is satisfied through the thermodynamic equilibriums of the electron and oxygen vacancy. The distributions of charged species around the interface induce charge double layer. Moreover, we verify the nonlinear current/overpotential relationship. This model facilitates the exploration of problems in solid oxide fuel cells, which are associated with transport of species and electrochemical reactions at high operating temperature.

  12. Vanadium oxide nanodisks: Synthesis, characterization, and electrochemical properties

    SciTech Connect

    Ren, Ling; Cao, Minhua; Shi, Shufeng; Hu, Changwen

    2012-01-15

    Highlights: Black-Right-Pointing-Pointer Highly crystallined VO{sub 1.6}{center_dot}H{sub 2}O nanodisks have been synthesized by using a novel solid-solution-solid growth process. Black-Right-Pointing-Pointer The nanodisks are assembled from nanoparticles. Black-Right-Pointing-Pointer PEG-4000 plays an important role for the formation of the nanodisks. Black-Right-Pointing-Pointer The as-synthesized nanodisks exhibit good electrochemical behavior. -- Abstract: Highly crystallined VO{sub 1.6}{center_dot}H{sub 2}O nanodisks assembled from nanoparticles have been successfully fabricated under hydrothermal conditions by using bulk V{sub 2}O{sub 5} and Na{sub 2}S{sub 2}O{sub 3} as the starting materials in the presence of surfactant polyethylene glycol 4000 (PEG-4000). The nanodisks have a diameter of 200 nm and thickness of 40 nm. Hollow nanodisks are occasionally observed, which is similar to Chinese ancient copper coins. The formation of nanodisks can be ascribed to a novel solid-solution-solid growth mechanism. Compared with other methods, the solid state transformation method is simple and economic. In addition, the nanodisks exhibit good electrochemical behavior and promising to be used in lithium-ion battery.

  13. Synthesis and Microstructural Characterization of Manganese Oxide Electrodes for Application as Electrochemical Supercapacitors

    NASA Astrophysics Data System (ADS)

    Babakhani, Banafsheh

    The aim of this thesis work was to synthesize Mn-based oxide electrodes with high surface area structures by anodic electrodeposition for application as electrochemical capacitors. Rod-like structures provide large surface areas leading to high specific capacitances. Since templated electrosynthesis of rods is not easy to use in practical applications, it is more desirable to form rod-like structures without using any templates. In this work, Mn oxide electrodes with rod-like structures (˜1.5 µm in diameter) were synthesized from a solution of 0.01 M Mn acetate under galvanostatic control without any templates, on Au coated Si substrates. The electrochemical properties of the synthesized nanocrystalline electrodes were investigated to determine the effect of morphology, chemistry and crystal structure on the corresponding electrochemical behavior of Mn oxide electrodes. Mn oxides prepared at different current densities showed a defective antifluoritetype crystal structure. The rod-like Mn oxide electrodes synthesized at low current densities (5 mAcm.2) exhibited a high specific capacitance due to their large surface areas. Also, specific capacity retention after 250 cycles in an aqueous solution of 0.5 M Na2SO4 at 100 mVs -1 was about 78% of the initial capacity (203 Fg-1 ). To improve the electrochemical capacitive behavior of Mn oxide electrodes, a sequential approach and a one-step method were adopted to synthesize Mn oxide/PEDOT electrodes through anodic deposition on Au coated Si substrates from aqueous solutions. In the former case, free standing Mn oxide rods (about 10 µm long and less than 1.5 µm in diameter) were first synthesized, then coated by electro-polymerization of a conducting polymer (PEDOT) giving coaxial rods. The one-step, co-electrodeposition method produced agglomerated Mn oxide/PEDOT particles. The electrochemical behavior of the deposits depended on the morphology and crystal structure of the fabricated electrodes, which were affected by the composition and pH of the electrolyte, temperature, current density and polymer deposition time. Mn oxide/PEDOT coaxial core/shell rods consisted of MnO2 with an antifluorite-type structure coated with amorphous PEDOT. The Mn oxide/PEDOT coaxial core/shell electrodes prepared by the sequential method showed significantly better specific capacity and redox performance properties relative to both uncoated Mn oxide rods and co- electrodeposited Mn oxide/PEDOT electrodes. The best specific capacitance for Mn oxide/PEDOT rods produced sequentially was ˜295 F g-1 with ˜92% retention after 250 cycles in 0.5 M Na2SO4 at 100 mV s-1. To further improve the electrochemical capacitive behavior of Mn oxide electrodes, Co-doped and Fe-doped Mn oxide electrodes with a rod-like morphology and antifluorite-type crystal structure were synthesized by anodic electrodeposition, on Au coated Si substrates, from dilute solutions of Mn acetate and Co sulphate and Mn acetate and Fe chloride. Also, Mn-Co oxide/PEDOT coaxial core/shell rods were synthesized by applying a shell of PEDOT on Mn-Co oxide electrodes. Mn-Co oxide/PEDOT electrodes consisted of MnO2, with partial Co 2+ and Co3+ ion substitution for Mn4+, and amorphous PEDOT. Mn-Fe oxide electrodes consisted of MnO2, with partial Fe2+ and Fe3+ ion substitution for Mn4+. Electrochemical analysis showed that the capacitance values for all deposits increased with increasing scan rate to 100 mVs -1, and then decreased after 100 mVs-1. The Mn-Co oxide/PEDOT electrodes showed improved specific capacity and electrochemical cyclability relative to uncoated Mn-Co oxides and Mn-Fe oxides. Mn-Co oxide/PEDOT electrodes with rod-like structures had high capacitances (up to 310 Fg -1) at a scan rate of 100 mVs-1 and maintained their capacitance after 500 cycles in 0.5 M Na2SO4 (91% retention). Capacitance reduction for the deposits was mainly due to the loss of Mn ions by dissolution in the electrolyte solution. To better understand the nucleation and growth mechanisms of Mn oxide electrodes, the effects of supersaturation ratio on the morphology and crystal structure of electrodeposited Mn oxide were studied. By changing deposition parameters, including deposition current density, electrolyte composition, pH and temperature, a series of nanocrystalline Mn oxide electrodes with various morphologies (continuous coatings, rod-like structures, aggregated rods and thin sheets) and an antifluorite-type crystal structure was obtained. Mn oxide thin sheets showed instantaneous nucleation and single crystalline growth; rods had a mix of instantaneous/progressive nucleation and polycrystalline growth and continuous coatings formed by progressive nucleation and polycrystalline growth. Electrochemical analysis revealed the best capacitance behaviour obtained for Mn oxide thin sheets followed by Mn oxide rods, with dimensions on the microscale, and then continuous coatings. The highest specific capacitance (˜230 Fg-1) and capacitance retention rates (˜88%) were obtained for Mn oxide thin sheets after 250 cycles in 0.5 M Na2 SO4 at 20 mVs-1.

  14. Copper-substituted perovskite compositions for solid oxide fuel cell cathodes and oxygen reduction electrodes in other electrochemical devices

    DOEpatents

    Rieke, Peter C.; Coffey, Gregory W.; Pederson, Larry R.; Marina, Olga A.; Hardy, John S.; Singh, Prabhaker; Thomsen, Edwin C.

    2010-07-20

    The present invention provides novel compositions that find advantageous use in making electrodes for electrochemical cells. Also provided are electrochemical devices that include active oxygen reduction electrodes, such as solid oxide fuel cells, sensors, pumps and the like. The compositions comprises a copper-substituted ferrite perovskite material. The invention also provides novel methods for making and using the electrode compositions and solid oxide fuel cells and solid oxide fuel cell assemblies having cathodes comprising the compositions.

  15. Cerium-modified doped strontium titanate compositions for solid oxide fuel cell anodes and electrodes for other electrochemical devices

    DOEpatents

    Marina, Olga A [Richland, WA; Stevenson, Jeffry W [Richland, WA

    2010-03-02

    The present invention provides novel compositions that find advantageous use in making electrodes for electrochemical cells and electrochemical devices such as solid oxide fuel cells, electrolyzers, sensors, pumps and the like, the compositions comprising cerium-modified doped strontium titanate. The invention also provides novel methods for making and using anode material compositions and solid oxide fuel cells and solid oxide fuel cell assemblies having anodes comprising the compositions.

  16. Cerium-modified doped strontium titanate compositions for solid oxide fuel cell anodes and electrodes for other electrochemical devices

    DOEpatents

    Marina, Olga A [Richland, WA; Stevenson, Jeffry W [Richland, WA

    2010-11-23

    The present invention provides novel compositions that find advantageous use in making electrodes for electrochemical cells and electrochemical devices such as solid oxide fuel cells, electrolyzers, sensors, pumps and the like, the compositions comprising cerium-modified doped strontium titanate. The invention also provides novel methods for making and using anode material compositions and solid oxide fuel cells and solid oxide fuel cell assemblies having anodes comprising the compositions.

  17. Modified cermet fuel electrodes for solid oxide electrochemical cells

    DOEpatents

    Ruka, Roswell J.; Spengler, Charles J.

    1991-01-01

    An exterior porous electrode (10), bonded to a solid oxygen ion conducting electrolyte (13) which is in contact with an interior electrode (14), contains coarse metal particles (12) of nickel and/or cobalt, having diameters from 3 micrometers to 35 micrometers, where the coarse particles are coated with a separate, porous, multiphase layer (17) containing fine metal particles of nickel and/or cobalt (18), having diameters from 0.05 micrometers to 1.75 micrometers and conductive oxide (19) selected from cerium oxide, doped cerium oxide, strontium titanate, doped strontium titanate and mixtures thereof.

  18. Electrochemical analysis of transparent oxide-less photovoltaic cell with perforation patterned metal substrate

    NASA Astrophysics Data System (ADS)

    Kim, Myoung; You, In-Kyu; Lee, Kyoung-Won; Lee, In-Hwan; Yun, Ho-Gyeong

    2013-05-01

    In terms of electrochemical behaviour, a transparent conductive oxide (TCO)-less dye-sensitized solar cell (DSSC) with two metal foils was compared with those of a metal foil-based DSSC with a TCO-coated substrate. By virtue of electrochemical impedance spectroscopy, intensity modulated photocurrent spectroscopy, intensity modulated photovoltage spectroscopy, open-circuit voltage decay, and photocurrent transient measurements, it was clearly confirmed that the limited performance of the TCO-less DSSC was caused by the restricted transport of ion species in the electrolyte due to the perforation patterned metal foil.

  19. Electrochemically Exfoliated Graphene and Graphene Oxide for Energy Storage and Electrochemistry Applications.

    PubMed

    Ambrosi, Adriano; Pumera, Martin

    2016-01-01

    Top-down methods are of key importance for large-scale graphene and graphene oxide preparation. Electrochemical exfoliation of graphite has lately gained much interest because of the simplicity of execution, the short process time, and the good quality of graphene that can be obtained. Here, we test three different electrolytes, that is, H2 SO4 , Na2 SO4 , and LiClO4 , with a common exfoliation procedure to evaluate the difference in structural and chemical properties that result for the graphene. The properties are analyzed by means of scanning transmission electron microscopy (STEM), Raman spectroscopy, and X-ray photoelectron spectroscopy. We then tested the graphene materials for electrochemical applications, measuring the heterogeneous electron transfer (HET) rates with a Fe(CN)6 (3-/4-) redox probe, and their capacitive behavior in alkaline solutions. We correlate the electrochemical features with the presence of structural defects and oxygen functionalities on the graphene materials. In particular, the use of LiClO4 during the electrochemical exfoliation of graphite allowed the formation of highly oxidized graphene with a C/O ratio close to 4.0 and represents a possible avenue for the mass production of graphene oxide as valid alternative to the current laborious and dangerous chemical procedures, which also have limited scalability. PMID:26441292

  20. Development of graphene-nanometre-sized cerium oxide-incorporated aluminium and its electrochemical evaluation

    NASA Astrophysics Data System (ADS)

    Ashraf, P. Muhamed; Thomas, Saly N.; Edwin, Leela

    2016-02-01

    Graphene-nanometre-sized cerium oxide-incorporated aluminium was prepared and its electrochemical and surface morphological characteristics were studied. The atomic force micrographs and scanning electron micrographs evaluation highlighted that the graphene and nanometre-sized cerium oxide in aluminium had decreased the surface roughness and improved the surface morphological characteristics. The graphene: nanometre-sized cerium oxide (ratios 1:2 or 2:1) with lesser amounts of particle in the matrix showed excellent corrosion resistance in the marine environment as evidenced by linear polarization, electrochemical impedance and weight loss studies. Introduction of graphene in the aluminium matrix showed a barrier separation between the outermost layer and inner layer, increased roughness and increased corrosion. The material is found to be a potential candidate for use in marine environment.

  1. Polyaniline-grafted reduced graphene oxide for efficient electrochemical supercapacitors.

    PubMed

    Kumar, Nanjundan Ashok; Choi, Hyun-Jung; Shin, Yeon Ran; Chang, Dong Wook; Dai, Liming; Baek, Jong-Beom

    2012-02-28

    An alternative and effective route to prepare conducting polyaniline-grafted reduced graphene oxide (PANi-g-rGO) composite with highly enhanced properties is reported. In order to prepare PANi-g-rGO, amine-protected 4-aminophenol was initially grafted to graphite oxide (GO) via acyl chemistry where a concomitant partial reduction of GO occurred due to the refluxing and exposure of GO to thionyl chloride vapors and heating. Following the deprotection of amine groups, an in situ chemical oxidative grafting of aniline in the presence of an oxidizing agent was carried out to yield highly conducting PANi-g-rGO. Electron microscopic studies demonstrated that the resultant composite has fibrillar morphology with a room-temperature electrical conductivity as high as 8.66 S/cm and capacitance of 250 F/g with good cycling stability. PMID:22276770

  2. Advanced oxidation technologies for chemical demilitarization

    SciTech Connect

    Rosocha, L.A.; Korzekwa, R.A.; Monagle, M.; Coogan, J.J.; Tennant, R.A.; Brown, L.F.; Currier, R.P.

    1996-12-31

    This is the final report of a one-year, Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory. The main project objective was to establish a technical basis for future program development in the area of chemical warfare agent destruction using a Los Alamos-developed advanced oxidation process: a two-stage device consisting of thermal packed-bed reactor (PBR) and a nonthermal plasma (NTP) reactor. Various compounds were evaluated as potential surrogates for chemical warfare (CW) agents. Representative effluent mass balances were projected for future comparisons with incinerators. The design and construction of lab-scale PBR/NTP reactors (consisting of a liquid injection and metering system, electric furnace, condensers, chemical traps, plasma reactors, power supplies, and chemical diagnostics) has been completed. This equipment, the experience gained from chemical-processing experiments, process modeling, and an initial demonstration of the feasibility of closed-loop operation, have provided a technical basis for further demonstrations and program development efforts.

  3. Ruthenium Oxide Electrochemical Super Capacitor Optimization for Pulse Power Applications

    NASA Technical Reports Server (NTRS)

    Merryman, Stephen A.; Chen, Zheng

    2000-01-01

    Electrical actuator systems are being pursued as alternatives to hydraulic systems to reduce maintenance time, weight and costs while increasing reliability. Additionally, safety and environmental hazards associated with the hydraulic fluids can be eliminated. For most actuation systems, the actuation process is typically pulsed with high peak power requirements but with relatively modest average power levels. The power-time requirements for electrical actuators are characteristic of pulsed power technologies where the source can be sized for the average power levels while providing the capability to achieve the peak requirements. Among the options for the power source are battery systems, capacitor systems or battery-capacitor hybrid systems. Battery technologies are energy dense but deficient in power density; capacitor technologies are power dense but limited by energy density. The battery-capacitor hybrid system uses the battery to supply the average power and the capacitor to meet the peak demands. It has been demonstrated in previous work that the hybrid electrical power source can potentially provide a weight savings of approximately 59% over a battery-only source. Electrochemical capacitors have many properties that make them well-suited for electrical actuator applications. They have the highest demonstrated energy density for capacitive storage (up to 100 J/g), have power densities much greater than most battery technologies (greater than 30kW/kg), are capable of greater than one million charge-discharge cycles, can be charged at extremely high rates, and have non-explosive failure modes. Thus, electrochemical capacitors exhibit a combination of desirable battery and capacitor characteristics.

  4. Performance Evaluation of SOFC System usingElectrochemical Direct Oxidation of Methane

    NASA Astrophysics Data System (ADS)

    Yokoo, Masayuki; Take, Tetsuo; Ohtsu, Satoshi

    We evaluated the performance of systems composed of a solid oxide fuel cell (SOFC) using electrochemical direct oxidation of methane and a conventional steam-reforming-type SOFC (SRSOFC). Net thermal efficiency in an atmospheric partial-oxidation-type SOFC (POSOFC)-SRSOFC system was 8% higher than that in a simple SRSOFC system in the output range of more than 35 kW. The efficiency in a pressurized POSOFC-SRSOFC-gas-turbine (GT) system was slightly higher than that in a pressurized SRSOFC-GT system.

  5. Boosting supercapacitor performance of carbon fibres using electrochemically reduced graphene oxide additives.

    PubMed

    Cao, Yachang; Zhu, Miao; Li, Peixu; Zhang, Rujing; Li, Xinming; Gong, Qianming; Wang, Kunling; Zhong, Minlin; Wu, Dehai; Lin, Feng; Zhu, Hongwei

    2013-12-01

    Modifying conventional materials with new recipes represents a straightforward yet efficient way to realize large-scale applications of new materials. Electrochemically reduced graphene oxide (ERGO) coated carbon fibres (CFs), prepared as fibre-like supercapacitor electrodes, exhibited excellent electrochemical energy storage performance. Upon addition of only a small amount (~1 wt%) of ERGO, the hybrid fibres showed superior electrochemical capacitances (nearly three orders of magnitude enhanced) compared to pure CFs in both aqueous and gel electrolytes. Meanwhile, the energy density did not decrease notably as the power density increased. The superior capacitive performance could be attributed to the synergistic effect between wrinkled and porous ERGO sheets and highly conductive CFs. This fibre electrode material also offered advantages such as easy operation, mass production capability, mechanical flexibility and robustness, and could have an impact on a wide variety of potential applications in energy and electronic fields. PMID:24141749

  6. Mechanistic Study for Facile Electrochemical Patterning of Surfaces with Metal Oxides.

    PubMed

    Jones, Evan C; Liu, Qihan; Suo, Zhigang; Nocera, Daniel G

    2016-05-24

    Reactive interface patterning promoted by lithographic electrochemistry serves as a method for generating submicrometer scale structures. We use a binary-potential step on a metallic overlayer on silicon to fabricate radial patterns of cobalt oxide on the nanoscale. The mechanism for pattern formation has heretofore been ill-defined. The binary potential step allows the electrochemical boundary conditions to be controlled such that initial conditions for a scaling analysis are afforded. With the use of the scaling analysis, a mechanism for producing the observed pattern geometry is correlated to the sequence of electrochemical steps involved in the formation of the submicrometer structures. The patterning method is facile and adds to electrochemical micromachining techniques employing a silicon substrate. PMID:27072117

  7. Chemical and electrochemical oxidation of small organic molecules

    NASA Astrophysics Data System (ADS)

    Smart, Marshall C.

    Direct oxidation fuel cells using proton-exchange membrane electrolytes have long been recognized as being an attractive mode of power generation. The current work addresses the electro-oxidation characteristics of a number of potential fuels on Pt-based electrodes which can be used in direct oxidation fuel cells, including hydrocarbons and oxygenated molecules, such as alcohols, formates, ethers, and acetals. Promising alternative fuels which were identified, such as trimethoxymethane and dimethoxymethane, were then investigated in liquid-feed PEM-based fuel cells. In addition to investigating the nature of the anodic electro-oxidation of organic fuels, effort was also devoted to developing novel polymer electrolyte membranes which have low permeability to organic molecules, such as methanol. This research was initiated with the expectation of reducing the extent of fuel crossover from the anode to the cathode in the liquid-feed design fuel cell which results in lower fuel efficiency and performance. Other work involving efforts to improve the performance of direct oxidation fuel cell includes research focused upon improving the kinetics of oxygen reduction. There is continued interest in the identification of new, safe, non-toxic, and inexpensive reagents which can be used in the oxidation of organic compounds. Urea-hydrogen peroxide (UHP), a hydrogen bonded adduct, has been shown to serve as a valuable source of hydrogen peroxide in a range of reactions. UHP has been shown to be ideal for the monohydroxylation of aromatics, including toluene, ethylbenzene, p-xylene, m-xylene, and mesitylene, as well as benzene, in the presence of trifluoromethanesulfonic acid. It was also found that aniline was converted to a mixture containing primarily azobenzene, azoxybenzene and nitrobenzene when reacted with UHP in glacial acetic acid. A number of aniline derivatives have been investigated and it was observed that the corresponding azoxybenzene derivatives could be generated as the major products in good to excellent yields. The oxidation of other organic substrates was also investigated using urea-hydrogen peroxide as an oxidation reagent, including cyclohexylamine, 1-adamantaneamine, and adamantane.

  8. Microfluidic electrochemical sensor for on-line monitoring of aerosol oxidative activity.

    PubMed

    Sameenoi, Yupaporn; Koehler, Kirsten; Shapiro, Jeff; Boonsong, Kanokporn; Sun, Yele; Collett, Jeffrey; Volckens, John; Henry, Charles S

    2012-06-27

    Particulate matter (PM) air pollution has a significant impact on human morbidity and mortality; however, the mechanisms of PM-induced toxicity are poorly defined. A leading hypothesis states that airborne PM induces harm by generating reactive oxygen species in and around human tissues, leading to oxidative stress. We report here a system employing a microfluidic electrochemical sensor coupled directly to a particle-into-liquid sampler (PILS) system to measure aerosol oxidative activity in an on-line format. The oxidative activity measurement is based on the dithiothreitol (DTT) assay, where, after being oxidized by PM, the remaining reduced DTT is analyzed by the microfluidic sensor. The sensor consists of an array of working, reference, and auxiliary electrodes fabricated in a poly(dimethylsiloxane)-based microfluidic device. Cobalt(II) phthalocyanine-modified carbon paste was used as the working electrode material, allowing selective detection of reduced DTT. The electrochemical sensor was validated off-line against the traditional DTT assay using filter samples taken from urban environments and biomass burning events. After off-line characterization, the sensor was coupled to a PILS to enable on-line sampling/analysis of aerosol oxidative activity. Urban dust and industrial incinerator ash samples were aerosolized in an aerosol chamber and analyzed for their oxidative activity. The on-line sensor reported DTT consumption rates (oxidative activity) in good correlation with aerosol concentration (R(2) from 0.86 to 0.97) with a time resolution of approximately 3 min. PMID:22651886

  9. Microfluidic Electrochemical Sensor for On-line Monitoring of Aerosol Oxidative Activity

    PubMed Central

    Sameenoi, Yupaporn; Koehler, Kirsten; Shapiro, Jeff; Boonsong, Kanokporn; Sun, Yele; Collett, Jeffrey; Volckens, John; Henry, Charles S.

    2012-01-01

    Particulate matter (PM) air pollution has a significant impact on human morbidity and mortality; however, the mechanisms of PM-induced toxicity are poorly defined. A leading hypothesis states that airborne PM induces harm by generating reactive oxygen species (ROS) in and around human tissues, leading to oxidative stress. We report here, a system employing a microfluidic electrochemical sensor coupled directly to a Particle-into-Liquid-Sampler (PILS) system to measure aerosol oxidative activity in an on-line format. The oxidative activity measurement is based on the dithiothreitol assay (DTT assay) where after oxidized by PM, the remaining reduced DTT was analyzed by the microfluidic sensor. The sensor consists of an array of working, reference, and auxiliary electrodes fabricated in a poly(dimethylsiloxane) (PDMS)-based microfluidic device. Cobalt (II) phthalocyanine (CoPC)-modified carbon paste was used as the working electrode material allowing selective detection of reduced DTT. The electrochemical sensor was validated off-line against the traditional DTT assay using filter samples taken from urban environments and biomass burning events. After off-line characterization, the sensor was coupled to a PILS to enable on-line sampling/analysis of aerosol oxidative activity. Urban dust and industrial incinerator ash samples were aerosolized in an aerosol chamber and analyzed for their oxidative activity. The on-line sensor reported DTT consumption rates (oxidative activity) in good correlation with aerosol concentration (R2 from 0.86–.97) with a time-resolution of approximately 3 minutes. PMID:22651886

  10. Graphene electrode modified with electrochemically reduced graphene oxide for label-free DNA detection.

    PubMed

    Li, Bing; Pan, Genhua; Avent, Neil D; Lowry, Roy B; Madgett, Tracey E; Waines, Paul L

    2015-10-15

    A novel printed graphene electrode modified with electrochemically reduced graphene oxide was developed for the detection of a specific oligonucleotide sequence. The graphene oxide was immobilized onto the surface of a graphene electrode via π-π bonds and electrochemical reduction of graphene oxide was achieved by cyclic voltammetry. A much higher redox current was observed from the reduced graphene oxide-graphene double-layer electrode, a 42% and 36.7% increase, respectively, in comparison with that of a bare printed graphene or reduced graphene oxide electrode. The good electron transfer activity is attributed to a combination of the large number of electroactive sites in reduced graphene oxide and the high conductivity nature of graphene. The probe ssDNA was further immobilized onto the surface of the reduced graphene oxide-graphene double-layer electrode via π-π bonds and then hybridized with its target cDNA. The change of peak current due to the hybridized dsDNA could be used for quantitative sensing of DNA concentration. It has been demonstrated that a linear range from 10(-7)M to 10(-12)M is achievable for the detection of human immunodeficiency virus 1 gene with a detection limit of 1.58 × 10(-13)M as determined by three times standard deviation of zero DNA concentration. PMID:26002015

  11. Treatment of papermaking tobacco sheet wastewater by electrocoagulation combined with electrochemical oxidation.

    PubMed

    Ma, Xiangjuan; Gao, Yang; Huang, Hanping

    2015-01-01

    Attempts were made in this study to examine the efficiency of electrocoagulation (EC) using aluminum (Al) anode and stainless steel net cathode combined with electrochemical oxidation with a β-PbO₂anode or a mixed metal oxide (MMO) anode for treatment of papermaking tobacco sheet wastewater, which has the characteristics of high content of suspended solids (SS), intensive color, and low biodegradability. The wastewater was first subjected to the EC process under 40 mA/cm² of current density, 2.5 g/L of NaCl, and maintaining the original pH of wastewater. After 6 minutes of EC process, the effluent was further treated by electrochemical oxidation. The results revealed that the removal of SS during the EC process was very beneficial to mass transfer of organics during electrochemical oxidation. After the combined process, 83.9% and 82.8% of chemical oxygen demand (COD) removal could be achieved on the β-PbO₂and MMO anodes, respectively. The main components of the final effluent were biodegradable organic acids, such as acetic acid, propionic acid, butyric acid, valeric acid, and hexahyl carbonic acid; the 5-day biochemical oxygen demand/chemical oxygen demand (BOD₅/COD) ratio increased from 0.06 to 0.85 (Al + β-PbO₂) or 0.80 (Al + MMO). Therefore, this integrated process is a promising alternative for pretreatment of papermaking tobacco sheet wastewater prior to biological treatment. PMID:25909726

  12. Electroless deposition of conformal nanoscale iron oxide on carbon nanoarchitectures for electrochemical charge storage.

    PubMed

    Sassin, Megan B; Mansour, Azzam N; Pettigrew, Katherine A; Rolison, Debra R; Long, Jeffrey W

    2010-08-24

    We describe a simple self-limiting electroless deposition process whereby conformal, nanoscale iron oxide (FeO(x)) coatings are generated at the interior and exterior surfaces of macroscopically thick ( approximately 90 microm) carbon nanofoam paper substrates via redox reaction with aqueous K(2)FeO(4). The resulting FeO(x)-carbon nanofoams are characterized as device-ready electrode structures for aqueous electrochemical capacitors and they demonstrate a 3-to-7 fold increase in charge-storage capacity relative to the native carbon nanofoam when cycled in a mild aqueous electrolyte (2.5 M Li(2)SO(4)), yielding mass-, volume-, and footprint-normalized capacitances of 84 F g(-1), 121 F cm(-3), and 0.85 F cm(-2), respectively, even at modest FeO(x) loadings (27 wt %). The additional charge-storage capacity arises from faradaic pseudocapacitance of the FeO(x) coating, delivering specific capacitance >300 F g(-1) normalized to the content of FeO(x) as FeOOH, as verified by electrochemical measurements and in situ X-ray absorption spectroscopy. The additional capacitance is electrochemically addressable within tens of seconds, a time scale of relevance for high-rate electrochemical charge storage. We also demonstrate that the addition of borate to buffer the Li(2)SO(4) electrolyte effectively suppresses the electrochemical dissolution of the FeO(x) coating, resulting in <20% capacitance fade over 1000 consecutive cycles. PMID:20731433

  13. Moisture effects on the electrochemical reaction and resistance switching at Ag/molybdenum oxide interfaces.

    PubMed

    Yang, Chuan-Sen; Shang, Da-Shan; Chai, Yi-Sheng; Yan, Li-Qin; Shen, Bao-Gen; Sun, Young

    2016-05-14

    An important potential application of solid state electrochemical reactions is in redox-based resistive switching memory devices. Based on the fundamental switching mechanisms, the memory has been classified into two modes, electrochemical metallization memory (ECM) and valence change memory (VCM). In this work, we have investigated a solid state electrochemical cell with a simple Ag/MoO3-x/fluorine-doped tin oxide (FTO) sandwich structure, which shows a normal ECM switching mode after an electroforming process. While in the lower voltage sweep range, the switching behavior changes to VCM-like mode with the opposite switching polarity to the ECM mode. By current-voltage measurements under different ambient atmospheres and X-ray photoemission spectroscopy analysis, electrochemical anodic passivation of the Ag electrode and valence change of molybdenum ions during resistance switching have been demonstrated. The crucial role of moisture adsorption in the switching mode transition has been clarified based on the Pourbaix diagram for the Ag-H2O system for the first time. These results provide a fundamental insight into the resistance switching mechanism model in solid state electrochemical cells. PMID:26996952

  14. Elementary reaction modeling of solid oxide electrolysis cells: Main zones for heterogeneous chemical/electrochemical reactions

    NASA Astrophysics Data System (ADS)

    Li, Wenying; Shi, Yixiang; Luo, Yu; Cai, Ningsheng

    2015-01-01

    A theoretical model of solid oxide electrolysis cells considering the heterogeneous elementary reactions, electrochemical reactions and the transport process of mass and charge is applied to study the relative performance of H2O electrolysis, CO2 electrolysis and CO2/H2O co-electrolysis and the competitive behavior of heterogeneous chemical and electrochemical reactions. In cathode, heterogeneous chemical reactions exist near the outside surface and the electrochemical reactions occur near the electrolyte. According to the mathematical analysis, the mass transfer flux D ∇c determines the main zone size of heterogeneous chemical reactions, while the charge transfer flux σ ∇V determines the other one. When the zone size of heterogeneous chemistry is enlarged, more CO2 could react through heterogeneous chemical pathway, and polarization curves of CO2/H2O co-electrolysis could be prone to H2O electrolysis. Meanwhile, when the zone size of electrochemistry is enlarged, more CO2 could react through electrochemical pathway, and polarization curves of CO2/H2O co-electrolysis could be prone to CO2 electrolysis. The relative polarization curves, the ratio of CO2 participating in electrolysis and heterogeneous chemical reactions, the mass and charge transfer flux and heterogeneous chemical/electrochemical reaction main zones are simulated to study the effects of cathode material characteristics (porosity, particle diameter and ionic conductivity) and operating conditions (gas composition and temperature).

  15. Advanced EMU electrochemically regenerable CO2 and moisture absorber module breadboard

    NASA Technical Reports Server (NTRS)

    Lee, M. C.; Sudar, M.; Chang, B. J.

    1988-01-01

    The applicability of the Electrochemically Regenerable Carbon Dioxide and Moisture Absorption Technology to the advanced extravehicular mobility unit was demonstrated by designing, fabricating, and testing a breadboard Absorber Module and an Electrochemical Regenerator. Test results indicated that the absorber module meets or exceeds the carbon dioxide removal requirements specified for the design and can meet the moisture removal requirement when proper cooling is provided. CO2 concentration in the vent gas stream was reduced from 0.52 to 0.027 kPa (3.9 to 0.20 mm Hg) for the full five hour test period. Vent gas dew point was reduced from inlet values of 294 K (69 F) to 278 K (41 F) at the outlet. The regeneration of expended absorbent was achieved by the electrochemical method employed in the testing. An absorbent bed using microporous hydrophobic membrane sheets with circulating absorbent is shown to be the best approach to the design of an Absorber Module based on sizing and performance. Absorber Module safety design, comparison of various absorbents and their characteristics, moisture absorption and cooling study and subsystem design and operation time-lining study were also performed.

  16. Mechanistic studies of water electrolysis and hydrogen electro-oxidation on high temperature ceria-based solid oxide electrochemical cells.

    PubMed

    Zhang, Chunjuan; Yu, Yi; Grass, Michael E; Dejoie, Catherine; Ding, Wuchen; Gaskell, Karen; Jabeen, Naila; Hong, Young Pyo; Shavorskiy, Andrey; Bluhm, Hendrik; Li, Wei-Xue; Jackson, Gregory S; Hussain, Zahid; Liu, Zhi; Eichhorn, Bryan W

    2013-08-01

    Through the use of ambient pressure X-ray photoelectron spectroscopy (APXPS) and a single-sided solid oxide electrochemical cell (SOC), we have studied the mechanism of electrocatalytic splitting of water (H2O + 2e(-) → H2 + O(2-)) and electro-oxidation of hydrogen (H2 + O(2-) → H2O + 2e(-)) at ∼700 °C in 0.5 Torr of H2/H2O on ceria (CeO2-x) electrodes. The experiments reveal a transient build-up of surface intermediates (OH(-) and Ce(3+)) and show the separation of charge at the gas-solid interface exclusively in the electrochemically active region of the SOC. During water electrolysis on ceria, the increase in surface potentials of the adsorbed OH(-) and incorporated O(2-) differ by 0.25 eV in the active regions. For hydrogen electro-oxidation on ceria, the surface concentrations of OH(-) and O(2-) shift significantly from their equilibrium values. These data suggest that the same charge transfer step (H2O + Ce(3+) <-> Ce(4+) + OH(-) + H(•)) is rate limiting in both the forward (water electrolysis) and reverse (H2 electro-oxidation) reactions. This separation of potentials reflects an induced surface dipole layer on the ceria surface and represents the effective electrochemical double layer at a gas-solid interface. The in situ XPS data and DFT calculations show that the chemical origin of the OH(-)/O(2-) potential separation resides in the reduced polarization of the Ce-OH bond due to the increase of Ce(3+) on the electrode surface. These results provide a graphical illustration of the electrochemically driven surface charge transfer processes under relevant and nonultrahigh vacuum conditions. PMID:23822749

  17. Electrochemically deposited gallium oxide nanostructures on silicon substrates.

    PubMed

    Ghazali, Norizzawati Mohd; Mahmood, Mohamad Rusop; Yasui, Kanji; Hashim, Abdul Manaf

    2014-01-01

    We report a synthesis of β-Ga2O3 nanostructures on Si substrate by electrochemical deposition using a mixture of Ga2O3, HCl, NH4OH, and H2O. The presence of Ga3+ ions contributed to the deposition of Ga2O3 nanostructures on the Si surface with the assistance of applied potentials. The morphologies of the grown structures strongly depended on the molarity of Ga2O3 and pH level of electrolyte. β-Ga2O3 nanodot-like structures were grown on Si substrate at a condition with low molarity of Ga2O3. However, Ga2O3 nanodot structures covered with nanorods on top of their surfaces were obtained at higher molarity, and the densities of nanorods seem to increase with the decrease of pH level. High concentration of Ga3+ and OH- ions may promote the reaction of each other to produce Ga2O3 nanorods in the electrolyte. Such similar nature of Ga2O3 nanorods was also obtained by using hydrothermal process. The grown structures seem to be interesting for application in electronic and optoelectronic devices as well as to be used as a seed structure for subsequent chemical synthesis of GaN by thermal transformation method. PMID:24629107

  18. Electrochemically deposited gallium oxide nanostructures on silicon substrates

    NASA Astrophysics Data System (ADS)

    Ghazali, Norizzawati Mohd; Mahmood, Mohamad Rusop; Yasui, Kanji; Hashim, Abdul Manaf

    2014-03-01

    We report a synthesis of β-Ga2O3 nanostructures on Si substrate by electrochemical deposition using a mixture of Ga2O3, HCl, NH4OH, and H2O. The presence of Ga3+ ions contributed to the deposition of Ga2O3 nanostructures on the Si surface with the assistance of applied potentials. The morphologies of the grown structures strongly depended on the molarity of Ga2O3 and pH level of electrolyte. β-Ga2O3 nanodot-like structures were grown on Si substrate at a condition with low molarity of Ga2O3. However, Ga2O3 nanodot structures covered with nanorods on top of their surfaces were obtained at higher molarity, and the densities of nanorods seem to increase with the decrease of pH level. High concentration of Ga3+ and OH- ions may promote the reaction of each other to produce Ga2O3 nanorods in the electrolyte. Such similar nature of Ga2O3 nanorods was also obtained by using hydrothermal process. The grown structures seem to be interesting for application in electronic and optoelectronic devices as well as to be used as a seed structure for subsequent chemical synthesis of GaN by thermal transformation method.

  19. AES and TDS studies of electrochemically oxidized Pt(100)

    NASA Astrophysics Data System (ADS)

    Wagner, F. T.; Ross, P. N.

    Anodic films formed on Pt(100) in 0.3M HF using a quasi thin-layer electrochemical cell within a vacuum envelope were transferred to ultra-high vacuum for study by AES and TDS. Films generated at potentials above 1.1 V (RHE) survived emersion and pumpdown in a hydrated state. As the emersion potential increased, the integrated H 2O and O 2 thermal desorption signals increased in parallel, indicating a constant stoichiometry consistent with the formation of a platinum hydroxide layer. The oxygen TDS and AES signals after holding the electrode at constant potentials above 1.9 V (RHE) for several minutes saturated with formation of a surface phase containing 2.3 O/Pt (desorbing as O 2) and 2 H 2O/Pt. Much thicker films could be grown by AC polarization. XPS analysis combined with TDS indicated the most likely chemical state of the saturation layer to be Pt(OH) 4. Water evolved from all films at 400 K and higher, temperatures much higher than that reported for surface adsorbed hydroxyl groups produced by low-temperature gas-phase coadsorption of O 2 and h 2O [G.B. Fisher and B.A. Sexton, Phys. Rev. Letters 44 (1980) 683]. The higher temperature desorption is ascribed to the incorporation of hydroxyls into a surface phase involving place-exchange between Pt and OH.

  20. Effect of additives on electrochemical performance of lithium nickel cobalt manganese oxide at high temperature

    NASA Astrophysics Data System (ADS)

    Kang, Kyoung Seok; Choi, Suneui; Song, JunHo; Woo, Sang-Gil; Jo, Yong Nam; Choi, Jungkyu; Yim, Taeeun; Yu, Ji-Sang; Kim, Young-Jun

    2014-05-01

    Lithium-nickel-cobalt-manganese oxide, Li[NixCoyMnz]O2 (NCM) is a low-cost cathode material with a high capacity and a moderately high rate capability, however, it still suffers from poor electrochemical performance. In this study, several types of additives are attempted to enhance the surface stability of high-Ni-content (Ni ≥ 60%) cathodes and the most effective additive turns out to be PS. The cycle performance in the presence of 2% PS is much improved at a high temperature of 60 °C: (1) 98.9% of its initial capacity is preserved, (2) the increase in thickness is only 17.9%, preventing undesired swellings, and (3) gases are not generated in large amounts with the internal pressure being 56.4 kPa. The FT-IR spectroscopy results suggest that the surface of the cathode in the presence of 2% PS is covered with a film of alkyl sulfone components (RSOSR and RSO2SR), which is possibly formed by the electrochemical oxidation of PS. The current results confirm that the electrochemical performance of Ni-rich cathodes can be improved via the appropriate use of additives. They also indicate that among the tested additive candidates in this study, PS is highly desirable for enhancing the electrochemical performance of Ni-rich cathodes.

  1. Electrolytic destruction of spent tributylphosphate extractant using silver catalyzed electrochemical oxidation

    SciTech Connect

    Almon, A.C.; Buchanan, B.R.

    1990-01-01

    Silver catalyzed electrochemical oxidation of organic species is examined in analytical detail. This paper describes the mechanisms, reactions rates, products, intermediates, capabilities, limitations, and optimal reaction conditions of the electrochemical destruction of organic waste. A small bench-top electrocell being tested for the treatment of small quantity laboratory waste is described. The 200 mL electrochemical cell used has a processing capacity of 50 mL per day, and can treat both radioactive and non-radioactive waste. In the silver catalyzed process, Ag(I) is electrochemically oxidized to Ag(II) which attacks organic species such as tributylphosphate (TBP), tetraphenylborate (TPB), and benzene {sup 1,2}. This paper focuses on the destruction of tributylphosphate (TBP) although several organic species have been destroyed using this process. The organic species are converted to carbon dioxide, water, and inorganic acids. The process has the potential for RCRA (Resource Conservation and Recovery Act) waste treatment as well as disposal of large amounts of radioactive organic waste.

  2. Electrochemical oxidation of cyanide in the hydrocyclone cell

    SciTech Connect

    Dhamo, N.

    1996-12-31

    A diluted electroplating cyanide rinse water has been used to test the use of the hydrocyclone cell (HCC) in batch recycle mode of operation for the simultaneous oxidation of cyanide during the electrodeposition of silver. The results obtained in this work with regard to the final products, current efficiency and the number of transferred electrons per CN{sup {minus}} helped to establish a probable reaction scheme. According to this, the process occurs mainly with one-electron transfer, through cyanate and cyanogen as intermediate species. Meanwhile, under conditions where the electrolyte circulates in an open bath and flows successively through the cathodic and the anodic compartments, as in the case of the HCC system, the cyanate could be produced by the direct oxidation through air and/or generated peroxide and CN could be lost as HCN (g).

  3. Degradation of the commercial surfactant nonylphenol ethoxylate by advanced oxidation processes.

    PubMed

    da Silva, Salatiel Wohlmuth; Klauck, Cláudia Regina; Siqueira, Marco Antônio; Bernardes, Andréa Moura

    2015-01-23

    Four different oxidation process, namely direct photolysis (DP) and three advanced oxidation processes (heterogeneous photocatalysis - HP, eletrochemical oxidation - EO and photo-assisted electrochemical oxidation - PEO) were applied in the treatment of wastewater containing nonylphenol ethoxylate (NPnEO). The objective of this work was to determine which treatment would be the best option in terms of degradation of NPnEO without the subsequent generation of toxic compounds. In order to investigate the degradation of the surfactant, the processes were compared in terms of UV/Vis spectrum, mineralization (total organic carbon), reaction kinetics, energy efficiency and phytotoxicity. A solution containing NPnEO was prepared as a surrogate of the degreasing wastewater, was used in the processes. The results showed that the photo-assisted processes degrade the surfactant, producing biodegradable intermediates in the reaction. On the other hand, the electrochemical process influences the mineralization of the surfactant. The process of PEO carried out with a 250W lamp and a current density of 10mA/cm(2) showed the best results in terms of degradation, mineralization, reaction kinetics and energy consumption, in addition to not presenting phytotoxicity. Based on this information, this process can be a viable alternative for treating wastewater containing NPnEO, avoiding the contamination of water resources. PMID:25262384

  4. Strongly improved electrochemical cycling durability by adding iridium to electrochromic nickel oxide films.

    PubMed

    Wen, Rui-Tao; Niklasson, Gunnar A; Granqvist, Claes G

    2015-05-13

    Anodically colored nickel oxide (NiO) thin films are of much interest as counter electrodes in tungsten oxide based electrochromic devices such as "smart windows" for energy-efficient buildings. However, NiO films are prone to suffering severe charge density degradation upon prolonged electrochemical cycling, which can lead to insufficient device lifetime. Therefore, a means to improve the durability of NiO-based films is an important challenge at present. Here we report that the incorporation of a modest amount of iridium into NiO films [Ir/(Ir + Ni) = 7.6 atom %] leads to remarkable durability, exceeding 10000 cycles in a lithium-conducting electrolyte, along with significantly improved optical modulation during extended cycling. Structure characterization showed that the face-centered-cubic-type NiO structure remained after iridium addition. Moreover, the crystallinity of these films was enhanced upon electrochemical cycling. PMID:25919917

  5. Electrochemical reactions of S-, Se-, and Te-containing organic compounds. XV. Oxidation of selenoanisole derivatives

    SciTech Connect

    Latypova, V.Z.; Kargin, Yu.M.; Zhuikov, V.V.; Chmutova, G.A.; Lisitsyn, Yu.A.

    1986-03-10

    The electrochemical oxidation of a number of derivatives of selenoanisole RC/sub 6/H/sub 4/SeCH/sub 3/ in acetonitrile on a platinum rotating disk electrode takes place according to a two-electron elimination mechanism with the formation of an intermediate unstable radical cation, which undergoes a first-order reaction (deprotonation, dealkylation, or an interaction with macrocomponents of the solution). A comparison of the results of the electrochemical oxidation and the spectrophotometry of CT complexes with the use of the methods of sigma-rho analysis demonstrated the constancy of the kinetic components of E/sub 1/2/ (R not equal to p-NH/sub 2/) and the distorting influence of adsorption effects on it. The compound with R = p-NH/sub 2/ reacts like other substituted anilines. The electrophilic constant of the p-SeCH/sub 3/ substituent has been evaluated (sigma/sup +/ = 0.59 +/- 0.05).

  6. Electrochemical sensing chemical oxygen demand based on the catalytic activity of cobalt oxide film.

    PubMed

    Wang, Jinqi; Wu, Can; Wu, Kangbing; Cheng, Qin; Zhou, Yikai

    2012-07-29

    Cobalt oxide sensing film was in situ prepared on glassy carbon electrode surface via constant potential oxidation. Controlling at 0.8 V in NaOH solution, the high-valence cobalt catalytically oxidized the reduced compounds, decreasing its surface amount and current signal. The current decline was used as the response signal of chemical oxygen demand (COD) because COD represents the summation of reduced compounds in water. The surface morphology and electrocatalytic activity of cobalt oxide were readily tuned by variation of deposition potential, time, medium and Co(2+) concentration. As confirmed from the atomic force microscopy measurements, the cobalt oxide film, that prepared at 1.3 V for 40 s in pH 4.6 acetate buffer containing 10 mM Co(NO(3))(2), possesses large surface roughness and numerous three-dimensional structures. Electrochemical tests indicated that the prepared cobalt oxide exhibited high electrocatalytic activity to the reduced compounds, accompanied with strong COD signal enhancement. As a result, a novel electrochemical sensor with high sensitivity, rapid response and operational simplicity was developed for COD. The detection limit was as low as 1.1 mg L(-1). The analytical application was studied using a large number of lake water samples, and the accuracy was tested by standard method. PMID:22769005

  7. Electrochemical treatment of wastewater: A case study of reduction of DNT and oxidation of chlorinated phenols

    SciTech Connect

    Rodgers, J.D.; Bunce, N.J.; Jedral, W.

    1999-07-01

    Electrochemical treatment is under consideration as a treatment option for several recalcitrant compounds. In this work the authors investigate the oxidation of chlorophenols and the reduction of nitroaromatics. In the case of chlorinated phenols, they explore the problem of anode fouling which has hampered electrolytic treatment of phenolic compounds by examining phenols differing in the extent of chlorination, according to the mechanism of oxidation at different electrode types. Linear sweep voltammograms at a Pt anode were interpreted in terms of deposition of oligomers on the anode surface. Passivation increased in parallel with the uncompensated resistance of the solution and occurred only at potentials at which water is oxidized, suggesting that the formation of the oligomer film involves attack of hydroxyl radicals on electrochemically oxidized substrate. Relative reactivities of congeners were anode-dependent, due to different mechanisms of oxidation: direct electron transfer oxidation at PbO{sub 2} and hydroxyl radical attack at SnO{sub 2} and IrO{sub 2}. Voltammetry of 2,6-dinitrotoluene (DNT) was consistent with literature values. DNT was reduced at several cathodes with the most promising result at Ni-plated Ni wire. At current densities {lt} 0.1 mA cm{sup {minus}2}, current efficiencies {gt} 50% could be achieved with 4-chlorophenol at all three anodes and for 2,6-DNT at Ni-plated Ni wire.

  8. An electrochemical approach to graphene oxide coated sulfur for long cycle life

    NASA Astrophysics Data System (ADS)

    Moon, Joonhee; Park, Jungjin; Jeon, Cheolho; Lee, Jouhahn; Jo, Insu; Yu, Seung-Ho; Cho, Sung-Pyo; Sung, Yung-Eun; Hong, Byung Hee

    2015-07-01

    Owing to the possibilities of achieving high theoretical energy density and gravimetric capacity, sulfur has been considered as a promising cathode material for rechargeable lithium batteries. However, sulfur shows rapid capacity fading due to the irreversible loss of soluble polysulfides and the decrease in active sites needed for conducting agents. Furthermore, the low electrical conductivity of sulfur hampers the full utilization of active materials. Here we report that graphene oxide coated sulfur composites (GO-S/CB) exhibit improved electrochemical stability as well as enhanced rate performance, evidenced by various electrochemical analyses. The cyclic voltammetry and the galvanostatic cycling analysis revealed that the GO plays key roles in homogenizing the nanocomposite structures of the electrodes, in improving the electrochemical contact, and in minimizing the loss of soluble polysulfide intermediates. An electrochemical impedance spectroscopy analysis also confirms the enhanced structural stability of the GO-S/CB composites after battery operation. As a result, the GO-S/CB exhibited excellent cycle stability and specific capacity as high as ~723.7 mA h g-1 even after 100 cycles at 0.5 C.Owing to the possibilities of achieving high theoretical energy density and gravimetric capacity, sulfur has been considered as a promising cathode material for rechargeable lithium batteries. However, sulfur shows rapid capacity fading due to the irreversible loss of soluble polysulfides and the decrease in active sites needed for conducting agents. Furthermore, the low electrical conductivity of sulfur hampers the full utilization of active materials. Here we report that graphene oxide coated sulfur composites (GO-S/CB) exhibit improved electrochemical stability as well as enhanced rate performance, evidenced by various electrochemical analyses. The cyclic voltammetry and the galvanostatic cycling analysis revealed that the GO plays key roles in homogenizing the nanocomposite structures of the electrodes, in improving the electrochemical contact, and in minimizing the loss of soluble polysulfide intermediates. An electrochemical impedance spectroscopy analysis also confirms the enhanced structural stability of the GO-S/CB composites after battery operation. As a result, the GO-S/CB exhibited excellent cycle stability and specific capacity as high as ~723.7 mA h g-1 even after 100 cycles at 0.5 C. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr01951f

  9. Electrochemically regenerable metabolic CO2 and moisture control system for an advanced EMU application

    NASA Technical Reports Server (NTRS)

    Lee, M. C.; Beckstrom, P. S.; Cusick, R. J.

    1988-01-01

    Regenerable CO2 and moisture removal techniques that reduce expendables and logistics requirements are needed to sustain people undertaking extravehicular activities for the Space Station. NASA has been investigating ways to advance the Electrochemically Regenerable CO2 and Moisture Absorption (ERCA) technology to replace the nonregenerable solid lithium hydroxide absorber for the advanced Portable Life Support System (PLSS). The ERCA technology, due to its use of liquid absorbent, has the ability to effectively satisfy the high metabolic CO2 and moisture removal requirements of PLSS applications. This paper defines the ERCA technology concept and its advantages for the PLSS application, reviews breadboard and subscale testdata and presents the results of design concepts for a prototype Absorber Module of improved performance and the physical characteristics of the projected flight hardware.

  10. Mediated electrochemical oxidation of organic wastes using a Co(III) mediator in a neutral electrolyte

    DOEpatents

    Balazs, G.B.; Lewis, P.R.

    1999-07-06

    An electrochemical cell with a Co(III) mediator and neutral pH anolyte provides efficient destruction of organic and mixed wastes. The organic waste is concentrated in the anolyte reservoir, where the cobalt mediator oxidizes the organics and insoluble radioactive species and is regenerated at the anode until all organics are converted to carbon dioxide and destroyed. The neutral electrolyte is non-corrosive, and thus extends the lifetime of the cell and its components. 2 figs.

  11. Mediated electrochemical oxidation of organic wastes using a Co(III) mediator in a neutral electrolyte

    DOEpatents

    Balazs, G. Bryan; Lewis, Patricia R.

    1999-01-01

    An electrochemical cell with a Co(III) mediator and neutral pH anolyte provides efficient destruction of organic and mixed wastes. The organic waste is concentrated in the anolyte reservoir, where the cobalt mediator oxidizes the organics and insoluble radioactive species and is regenerated at the anode until all organics are converted to carbon dioxide and destroyed. The neutral electrolyte is non-corrosive, and thus extends the lifetime of the cell and its components.

  12. An Investigation into the Effect of a Post-electroplating Electrochemical Oxidation Treatment on Tin Whisker Formation

    NASA Astrophysics Data System (ADS)

    Ashworth, M. A.; Haspel, D.; Wu, L.; Wilcox, G. D.; Mortimer, R. J.

    2015-01-01

    Since the `cracked oxide theory' was proposed by Tu in 1994,1 there has only been a limited number of studies that have sought to investigate the effect of the Sn oxide on whisker growth. The current study has used electrochemical oxidation to produce oxide films, which has enabled the effect of the surface oxide thickness on whisker growth to be established. The effect of oxide thickness on whisker growth has been investigated for tin electrodeposits on both Cu and brass substrates. The influence of applied oxidation potential on the thickness of the Sn oxide film has been investigated using x-ray photoelectron spectroscopy (XPS) for potassium bicarbonate-carbonate and borate buffer electrolyte solutions. Whisker growth from electrochemically oxidised Sn-Cu deposits on Cu and Sn deposits on brass has been investigated and compared with samples left to develop a native air-formed oxide. XPS studies show that the thickness of the electrochemically formed Sn oxide film is dependent on the applied oxidation potential and the total charge passed. Subsequent whisker growth studies demonstrate that electrochemically oxidised Sn-Cu deposits on Cu and Sn deposits on brass are significantly less susceptible to whisker growth than those having a native oxide film. For Sn deposits on brass, the electrochemically formed Sn oxide greatly reduces Zn oxide formation at the surface of the tin deposit, which results in whisker mitigation. For Sn-Cu deposits on Cu, the reduction in whisker growth must simply derive from the increased thickness of the Sn oxide, i.e. the Sn oxide film has an important role in stemming the development of whiskers.

  13. Lipid advanced glycosylation: pathway for lipid oxidation in vivo.

    PubMed Central

    Bucala, R; Makita, Z; Koschinsky, T; Cerami, A; Vlassara, H

    1993-01-01

    To address potential mechanisms for oxidative modification of lipids in vivo, we investigated the possibility that phospholipids react directly with glucose to form advanced glycosylation end products (AGEs) that then initiate lipid oxidation. Phospholipid-linked AGEs formed readily in vitro, mimicking the absorbance, fluorescence, and immunochemical properties of AGEs that result from advanced glycosylation of proteins. Oxidation of unsaturated fatty acid residues, as assessed by reactive aldehyde formation, occurred at a rate that paralleled the rate of lipid advanced glycosylation. Aminoguanidine, an agent that prevents protein advanced glycosylation, inhibited both lipid advanced glycosylation and oxidative modification. Incubation of low density lipoprotein (LDL) with glucose produced AGE moieties that were attached to both the lipid and the apoprotein components. Oxidized LDL formed concomitantly with AGE-modified LDL. Of significance, AGE ELISA analysis of LDL specimens isolated from diabetic individuals revealed increased levels of both apoprotein- and lipid-linked AGEs when compared to specimens obtained from normal, nondiabetic controls. Circulating levels of oxidized LDL were elevated in diabetic patients and correlated significantly with lipid AGE levels. These data support the concept that AGE oxidation plays an important and perhaps primary role in initiating lipid oxidation in vivo. PMID:8341651

  14. Biological treatment of a textile effluent after electrochemical oxidation of reactive dyes.

    PubMed

    Vilaseca, Mercè; Gutiérrez, Maria-Carmen; López-Grimau, Victor; López-Mesas, Montserrat; Crespi, Martí

    2010-02-01

    In this work, a synthetic textile effluent containing a reactive dye (C.I. Reactive Orange 4) was treated in an electrochemical cell with titanium covered by platinum oxide (Ti/PtOx) electrodes to remove color. The discolored effluent was mixed with other textile mill process effluents (scouring, bleaching, washing, etc.), according to the rate of each effluent in the mill, and was submitted to biological treatment (activated sludge plant). Two biological plants were run simultaneously to evaluate the influence of oxidant products generated during the electrochemical treatment. The final chemical oxygen demand (COD) removal in both plants was 65 to 72%. The yield of the activated sludge plants was not affected by the addition of 10% of the discolored dyeing effluent (even when oxidants products were not removed), which indicates that the previous electrochemical treatment do not produce inhibition effects on the biological plant. However, in the case of direct addition of the discolored effluent, the biological treatment plant required a longer adaptation period. In addition, the electrolytic respirometry tests showed that all the biodegradable organic matter was removed, which implies that the yield in organic matter removal was the maximum possible for this type of treatment. PMID:20183984

  15. COD and color removal of reactive orange 16 dye solution by electrochemical oxidation and adsorption method

    NASA Astrophysics Data System (ADS)

    Zakaria, Zuhailie; Ahmad, Wan Yaacob Wan; Yusop, Muhammad Rahimi; Othman, Mohamed Rozali

    2015-09-01

    Degradation of Reactive Orange 16 (RO16) dye was investigated using electrochemical oxidation and adsorption (batch method) using mixture of coconut trunk charcoal-graphite-tin-polyvinyl chloride(PVC). In batch studies for adsorbents pellet and powder form of the charcoal mixture were used. RO16 was chosen as the model dye because of its high resistance towards conventional treatment methods. NaCl and RO16 concentration, treatment duration, weight of electrode and adsorbent and volume of solution were kept constant for both methods. The effectiveness of the treatments were compared and evaluated by percentage of RO16 decolorization and chemical oxygen demand (COD) removal and results indicated that electrochemical oxidation method ables to decolorized RO16 dye up to 98.5% after 20 minutes electrolysis time while pellet and powder in batch method only removed 17.1 and 33.6% of RO16 color respectively. However, only 45.6% of COD can be removed using electrochemical oxidation method while pellet and powder in batch method removed 47.8 and 49.6% of COD respectively. The decolorization and COD removal of RO16 was determined using UV-Vis spectrophotometer (by the changes of absorption spectrum intensity of azo chromophore (-N=N-) at λ=388 and 492.50 nm and Hach spectrophotometer respectively. FTIR was used to determine functional groups present in the coconut trunk charcoal.

  16. Electrochemical oxidation of the poultry manure anaerobic digested effluents for enhancing pollutants removal by Chlorella vulgaris.

    PubMed

    Wang, Mengzi; Cao, Wei; Wu, Yu; Lu, Haifeng; Li, Baoming

    2016-06-01

    The mechanisms and pseudo-kinetics of the electrochemical oxidation for wastewater treatment and the synergistic effect of combining algal biological treatment were investigated. NaCl, Na2SO4 and HCl were applied to compare the effect of electrolyte species on nutrients removal. NaCl was proved to be more efficient in removing ammonia ([Formula: see text]), total phosphorus (TP), total organic carbon (TOC) and inorganic carbon (IC). [Formula: see text] oxidation by using Ti/Pt-IrO2 electrodes was modelled, which indicates that the [Formula: see text] removal followed the zero-order kinetic with sufficient Cl(-) and the first-order kinetic with insufficient Cl(-), respectively. The feasibility of combining electrochemical oxidation with microalgae cultivation for wastewater treatment was also determined. A 2 h electrochemical pretreatment reduced 57% [Formula: see text], 76% TP, 72% TOC and 77% IC from the digested effluent, which is applied as feedstock for algae cultivation, and resulted in increasing both the biomass production and pollutants removal efficiencies of the algal biological process. PMID:26853507

  17. SULFATE RADICAL-BASED ADVANCED OXIDATION PROCESSES- ACS MEETING

    EPA Science Inventory

    This paper will present an overview of sulfate radical-based advanced oxidation technologies for the destruction of environmentally toxic chemicals in wastewater, industrial water, groundwater and sources of water supply. The paper will include fundamental aspects of the generati...

  18. ADVANCED OXIDATION PROCESSES (AOP'S FOR THE TREATMENT OF CCL CHEMICALS

    EPA Science Inventory

    Research on treatment of Contaminant Candidate List (CCL) chemicals is being conducted. Specific groups of contaminants on the CCL will be evaluated using numerous advanced oxidation processes (AOPs). Initially, these CCL contaminants will be evaluated in groups based on chemical...

  19. Writable electrochemical energy source based on graphene oxide.

    PubMed

    Wei, Di

    2015-01-01

    Graphene oxide (GO) was mainly used as raw material for various types of reduced graphene oxide (rGO) as a cost effective method to make graphene like materials. However, applications of its own unique properties such as extraordinary proton conductivity and super-permeability to water were overlooked. Here GO based battery-like planar energy source was demonstrated on arbitrary insulating substrate (e.g. polymer sheet/paper) by coating PEDOT, GO ink and rGO on Ag charge collectors. Energy from such GO battery depends on its length and one unit cell with length of 0.5 cm can generate energy capacity of 30 Ah/L with voltage up to 0.7 V when room temperature ionic liquid (RTIL) is added. With power density up to 0.4 W/cm(3) and energy density of 4 Wh/L, GO battery was demonstrated to drive an electrochromic device. This work is the first attempt to generate decent energy using the fast transported water molecules inside GO. It provides very safe energy source that enables new applications otherwise traditional battery technology can not make including building a foldable energy source on paper and platform for futuristic wearable electronics. A disposable energy source made of GO was also written on a plastic glove to demonstrate wearability. PMID:26462557

  20. Cobalt Oxide Nanoflowers for Electrochemical Determination of Glucose

    NASA Astrophysics Data System (ADS)

    Balouch, Quratulain; Ibupoto, Zafar Hussain; Khaskheli, Ghulam Qadir; Soomro, Razium Ali; Sirajuddin; Samoon, Muhammad Kashif; Deewani, Vinod Kumar

    2015-10-01

    This study reports a simple, economic, and efficient approach for synthesis of cobalt oxide (Co3O4) nanostructures by a low-temperature aqueous chemical growth method. The synthesized Co3O4 nanostructures were characterized by various techniques such as x-ray diffraction, x-ray photoelectron spectroscopy, and scanning electron microscopy. The synthesized nanostructures exhibited flower-shaped morphology with thickness of each pellet in the range of 200 to 300 nm. The synthesized Co3O4 nanostructures with excellent structural features exhibited high electrocatalytic activity towards the oxidation of glucose in alkaline solution. This enabled development of a highly sensitive (1618.71 µA mM-1 cm-2), stable and reproducible non-enzymatic glucose sensor. The developed sensor demonstrated high anti-interference capability against common interferents such as dopamine, ascorbic acid and uric acid. Furthermore, the applicability of the developed sensor for the determination of glucose from human blood serum provides an alternative approach for the routine glucose analysis.

  1. Writable electrochemical energy source based on graphene oxide

    PubMed Central

    Wei, Di

    2015-01-01

    Graphene oxide (GO) was mainly used as raw material for various types of reduced graphene oxide (rGO) as a cost effective method to make graphene like materials. However, applications of its own unique properties such as extraordinary proton conductivity and super-permeability to water were overlooked. Here GO based battery-like planar energy source was demonstrated on arbitrary insulating substrate (e.g. polymer sheet/paper) by coating PEDOT, GO ink and rGO on Ag charge collectors. Energy from such GO battery depends on its length and one unit cell with length of 0.5 cm can generate energy capacity of 30 Ah/L with voltage up to 0.7 V when room temperature ionic liquid (RTIL) is added. With power density up to 0.4 W/cm3 and energy density of 4 Wh/L, GO battery was demonstrated to drive an electrochromic device. This work is the first attempt to generate decent energy using the fast transported water molecules inside GO. It provides very safe energy source that enables new applications otherwise traditional battery technology can not make including building a foldable energy source on paper and platform for futuristic wearable electronics. A disposable energy source made of GO was also written on a plastic glove to demonstrate wearability. PMID:26462557

  2. Writable electrochemical energy source based on graphene oxide

    NASA Astrophysics Data System (ADS)

    Wei, Di

    2015-10-01

    Graphene oxide (GO) was mainly used as raw material for various types of reduced graphene oxide (rGO) as a cost effective method to make graphene like materials. However, applications of its own unique properties such as extraordinary proton conductivity and super-permeability to water were overlooked. Here GO based battery-like planar energy source was demonstrated on arbitrary insulating substrate (e.g. polymer sheet/paper) by coating PEDOT, GO ink and rGO on Ag charge collectors. Energy from such GO battery depends on its length and one unit cell with length of 0.5 cm can generate energy capacity of 30 Ah/L with voltage up to 0.7 V when room temperature ionic liquid (RTIL) is added. With power density up to 0.4 W/cm3 and energy density of 4 Wh/L, GO battery was demonstrated to drive an electrochromic device. This work is the first attempt to generate decent energy using the fast transported water molecules inside GO. It provides very safe energy source that enables new applications otherwise traditional battery technology can not make including building a foldable energy source on paper and platform for futuristic wearable electronics. A disposable energy source made of GO was also written on a plastic glove to demonstrate wearability.

  3. Experimental study on electrochemical hydrogen pump of SrZrO{sub 3}-based oxide

    SciTech Connect

    Tanaka, M.; Asakura, Y.; Uda, T.

    2008-07-15

    The electrochemical hydrogen pump properties of the SrZr{sub 0.8}In{sub 0.2}O{sub 3-{alpha}} proton conducting oxide were evaluated under various atmospheres, temperatures and the effect of oxygen gas in the cathode for the recovery of hydrogen isotopes. It was found that high temperature is not necessarily required and protonic conductivity of the proton conducting oxide rather than total conductivity should be observed to improve the performance of the hydrogen pump. Furthermore, the presence of oxygen in the cathode compartment plays an important role in the enhancement of the hydrogen pump performance. (authors)

  4. Method of making sulfur tolerant composite cermet electrodes for solid oxide electrochemical cells

    DOEpatents

    Isenberg, Arnold O.

    1989-01-01

    An electrochemical apparatus is made containing an exterior electorde bonded to the exterior of a tubular, solid, oxygen ion conducting electrolyte where the electrolyte is also in contact with an interior electrode, said exterior electrode comprising particles of an electronic conductor contacting the electrolyte, where a ceramic metal oxide coating partially surrounds the particles and is bonded to the electrolyte, and where a coating of an ionic-electronic conductive material is attached to the ceramic metal oxide coating and to the exposed portions of the particles.

  5. Preparation of silver nanoparticles/graphene nanosheets as a catalyst for electrochemical oxidation of methanol

    SciTech Connect

    Han, Kun; Miao, Peng; Tang, Yuguo; Tong, Hui; Zhu, Xiaoli; Liu, Tao; Cheng, Wenbo

    2014-02-03

    In this report, silver nanoparticles (AgNPs) decorated graphene nanosheets have been prepared based on the reduction of Ag ions by hydroquinone, and their catalytic performance towards the electrochemical oxidation of methanol is investigated. The synthesis of the nano-composite is confirmed by transmission electron microscope measurements and UV-vis absorption spectra. Excellent electrocatalytic performance of the material is demonstrated by cyclic voltammograms. This material also contributes to the low peak potential of methanol oxidation compared with most of the other materials.

  6. Enhanced electro-oxidation of alcohols at electrochemically treated polycrystalline palladium surface

    NASA Astrophysics Data System (ADS)

    Wang, Lianqin; Bevilacqua, Manuela; Chen, Yan-Xin; Filippi, Jonathan; Innocenti, Massimo; Lavacchi, Alessandro; Marchionni, Andrea; Miller, Hamish; Vizza, Francesco

    2013-11-01

    The present study demonstrates the effectiveness of an electrochemical treatment consisting in cycles of constant potential oxidation and reduction of polycrystalline palladium surface in the enhancement of the electro-oxidation of ethanol, ethylene glycol and glycerol. The rise of the activity after the treatment has been ascribed to the increase of both surface area and density of low coordination surface atoms. FTIR spectra showed that a change in the reaction products distribution also occurs, resulting, in some cases, in an increased tendency to cleave the C-C bond.

  7. Electrochemical investigations of advanced materials for microelectronic and energy storage devices

    NASA Astrophysics Data System (ADS)

    Goonetilleke, Pubudu Chaminda

    A broad range of electrochemical techniques are employed in this work to study a selected set of advanced materials for applications in microelectronics and energy storage devices. The primary motivation of this study has been to explore the capabilities of certain modern electrochemical techniques in a number of emerging areas of material processing and characterization. The work includes both aqueous and non-aqueous systems, with applications in two rather general areas of technology, namely microelectronics and energy storage. The sub-systems selected for investigation are: (i) Electrochemical mechanical and chemical mechanical planarization (ECMP and CMP, respectively), (ii) Carbon nanotubes in combination with room temperature ionic liquids (ILs), and (iii) Cathode materials for high-performance Li ion batteries. The first group of systems represents an important building block in the fabrication of microelectronic devices. The second and third groups of systems are relevant for new energy storage technologies, and have generated immense interests in recent years. A common feature of these different systems is that they all are associated with complex surface reactions that dictate the performance of the devices based on them. Fundamental understanding of these reactions is crucial to further development and expansion of their associated technologies. It is the complex mechanistic details of these surface reactions that we address using a judicious combination of a number of state of the art electrochemical techniques. The main electrochemical techniques used in this work include: (i) Cyclic voltammetry (CV) and slow scan cyclic voltammetry (SSCV, a special case of CV); (ii) Galvanostatic (or current-controlled) measurements; (iii) Electrochemical impedance spectroscopy (EIS), based on two different methodologies, namely, Fourier transform EIS (FT-EIS, capable of studying fast reaction kinetics in a time-resolved mode), and EIS using frequency response analysis (employed to study slow reactions such as solid state diffusion of Li). The designs of both the experimental equipment and the control variables change for studying the different aqueous and non-aqueous systems. The protocols for data analysis also change depending on the systems. In addition, it often becomes necessary to combine different aspects of the different experimental methods to obtain the necessary information about the system(s) under study. The experimental strategies and the associated theoretical considerations for developing these strategies are discussed in appropriate contexts of this work. CNT electrodes in combination with IL electrolytes are potentially important for electrochemical super-capacitors. We have carried out electrochemical investigation of such a system involving a paper-electrode of multiwall CNT in the IL of 1-Ethyl-3-methyl imidazolium ethylsulfate (EMIM-EtSO4). Our study concentrated on the analytical aspects of cyclic voltammetry (CV) to probe the double layer capacitance of these relatively unconventional systems. (that involve rather large charge-discharge time constants). Both theoretical and experimental aspects of CV for such systems have been discussed, focusing in particular, on the effects of faradaic side-reactions, electrolyte resistance and voltage scan speeds. The results have been analyzed using an electrode equivalent circuit model, demonstrating a method to account for the typical artifacts expected in CV of CNT-IL interfaces. Chemical-mechanical planarization (CMP) of copper has now become an integral part of modern semiconductor fabrication technology. Recently, electrochemical-mechanical planarization (ECMP) has emerged as a possible extension of CMP, where through voltage-activated removal of Cu surface layers, one can substantially minimize the down-force necessary for mechanical polishing However, the detailed electrochemical factors that are central to designing efficient abrasive-free electrolytes for ECMP are not clearly understood at the present time. The present work has addressed this issue by studying the relative electrochemical effects of selected different chemical additives. Controlling the surface reactions (that is controlling the voltage-induced material removal) in ECMP requires a carefully designed combination of a number of electrochemical input variables (voltage activation program and electrolyte composition). We have studied the main experimental factors for designing these parameters, using triangular and rectangular-voltage-pulse modulated dissolution of Cu in electrolytes of different chemical compositions. Applications of rechargeable Li ion batteries have considerably expanded in recent years. As a result, research activities involving material-fabrication and characterization for these batteries also have expanded during this period. The importance of studying these specific materials lies in the fact that the cathode plays a major role in its contribution to the battery performance LiMn2O4 cathodes are being considered for next generation of Li ion batteries. The current work focuses on a specific problem commonly associated with Li cathode systems, namely surface film formation on the cathodes. LiMn2O4 cathodes tend to develop native surface films in carbonate electrolytes. By combining D.C. SSCV with A.C. EIS, we have studied how these films would react with an electrolyte of LiBF4 in ethylene and diethyl carbonates. We have demonstrated that such reactions could affect the measurement of the characteristic electrochemical parameters of the cathode, namely the intercalation capacitance, initial capacity-loss, coulometric titration profiles, and the solid state diffusion coefficient of Li+. A generalized framework for data analysis, based on the considerations of electrode equivalent circuits, has been used to combine the results of the D.C. and A.C. measurements.

  8. Conductive diamond electrochemical oxidation of caffeine-intensified biologically treated urban wastewater.

    PubMed

    Martín de Vidales, María J; Millán, María; Sáez, Cristina; Pérez, José F; Rodrigo, Manuel A; Cañizares, Pablo

    2015-10-01

    In this work, the usefulness of Conductive Diamond Electrochemical Oxidation (CDEO) to degrade caffeine in real urban wastewater matrixes was assessed. The oxidation of actual wastewater intensified with caffeine (from 1 to 100 mg L(-1)) was studied, paying particular attention to the influence of the initial load of caffeine and the differences observed during the treatment of caffeine in synthetic wastewater. The results showed that CDEO is a technology that is capable of efficiently degrading this compound even at very low concentrations and that it can even be completely depleted. Profiles of the ionic species of S (SO4(2-)), N (NH4(+), NO3(-)) and Cl (ClO(-), ClO3(-) and ClO4(-)) were monitored and explained for plausible oxidation mechanisms. It was observed that the efficiency achieved is higher in the treatment of real wastewater than in the oxidation of synthetic wastewater because of the contribution of electrogenerated oxidant species such as hypochlorite. The formation of chlorate and perchlorate during electrochemical processes was observed, and a combined strategy to prevent this important drawback was successfully tested based on the application of low current densities with the simultaneous dosing of hydrogen peroxide. PMID:26048815

  9. High-temperature "spectrochronopotentiometry": correlating electrochemical performance with in situ Raman spectroscopy in solid oxide fuel cells.

    PubMed

    Kirtley, John D; Halat, David M; McIntyre, Melissa D; Eigenbrodt, Bryan C; Walker, Robert A

    2012-11-20

    Carbon formation or "coking" on solid oxide fuel cell (SOFC) anodes adversely affects performance by blocking catalytic sites and reducing electrochemical activity. Quantifying these effects, however, often requires correlating changes in SOFC electrochemical efficiency measured during operation with results from ex situ measurements performed after the SOFC has been cooled and disassembled. Experiments presented in this work couple vibrational Raman spectroscopy with chronopotentiometry to observe directly the relationship between graphite deposited on nickel cermet anodes and the electrochemical performance of SOFCs operating at 725 °C. Raman spectra from Ni cermet anodes at open circuit voltage exposed to methane show a strong vibrational band at 1556 cm(-1) assigned to the "G" mode of highly ordered graphite. When polarized in the absence of a gas-phase fuel, these carbon-loaded anodes operate stably, oxidizing graphite to form CO and CO(2). Disappearance of graphite intensity measured in the Raman spectra is accompanied by a steep ∼0.8 V rise in the cell potential needed to keep the SOFC operating under constant current conditions. Continued operation leads to spectroscopically observable Ni oxidation and another steep rise in cell potential. Time-dependent spectroscopic and electrochemical measurements pass through correlated equivalence points providing unequivocal, in situ evidence that identifies how SOFC performance depends on the chemical condition of its anode. Chronopotentiometric data are used to quantify the oxide flux necessary to eliminate the carbon initially present on the SOFC anode, and data show that the oxidation mechanisms responsible for graphite removal correlate directly with the electrochemical condition of the anode as evidenced by voltammetry and impedance measurements. Electrochemically oxidizing the Ni anode damages the SOFC significantly and irreversibly. Anodes that have been reconstituted following electrochemical oxidation of carbon and Ni show qualitatively different kinetics of carbon removal, and the electrochemical performance of these systems is characterized by low maximum currents and large polarization resistances. PMID:23046116

  10. Removal of the X-ray contrast media diatrizoate by electrochemical reduction and oxidation.

    PubMed

    Radjenovic, Jelena; Flexer, Victoria; Donose, Bogdan C; Sedlak, David L; Keller, Jurg

    2013-01-01

    Due to their resistance to biological wastewater treatment, iodinated X-ray contrast media (ICM) have been detected in municipal wastewater effluents at relatively high concentrations (i.e., up to 100 μg L(-1)), with hospitals serving as their main source. To provide a new approach for reducing the concentrations of ICMs in wastewater, electrochemical reduction at three-dimensional graphite felt and graphite felt doped with palladium nanoparticles was examined as a means for deiodination of the common ICM diatrizoate. The presence of palladium nanoparticles significantly enhanced the removal of diatrizoate and enabled its complete deiodination to 3,5-diacetamidobenzoic acid. When the system was employed in the treatment of hospital wastewater, diatrizoate was reduced, but the extent of electrochemical reduction decreased as a result of competing reactions with solutes in the matrix. Following electrochemical reduction of diatrizoate to 3,5-diacetamidobenzoic acid, electrochemical oxidation with boron-doped diamond (BDD) anodes was employed. 3,5-Diacetamidobenzoic acid disappeared from solution at a rate that was similar to that of diatrizoate, but it was more readily mineralized than the parent compound. When electrochemical reduction and oxidation were coupled in a three-compartment reactor operated in a continuous mode, complete deiodination of diatrizoate was achieved at an applied cathode potential of -1.7 V vs SHE, with the released iodide ions electrodialyzed in a central compartment with 80% efficiency. The resulting BDD anode potential (i.e., +3.4-3.5 V vs SHE) enabled efficient oxidation of the products of the reductive step. The presence of other anions (e.g., chloride) was likely responsible for a decrease in I(-) separation efficiency when hospital wastewater was treated. Reductive deiodination combined with oxidative degradation provides benefits over oxidative treatment methods because it does not produce stable iodinated intermediates. Nevertheless, the process must be further optimized for the conditions encountered in hospital wastewater to improve the separation efficiency of halide ions prior to the electrooxidation step. PMID:24261992

  11. Coupling digestion in a pilot-scale UASB reactor and electrochemical oxidation over BDD anode to treat diluted cheese whey.

    PubMed

    Katsoni, Alphathanasia; Mantzavinos, Dionissios; Diamadopoulos, Evan

    2014-11-01

    The efficiency of the anaerobic treatment of cheese whey (CW) at mesophilic conditions was investigated. In addition, the applicability of electrochemical oxidation as an advanced post-treatment for the complete removal of chemical oxygen demand (COD) from the anaerobically treated cheese whey was evaluated. The diluted cheese whey, having a pH of 6.5 and a total COD of 6 g/L, was first treated in a 600-L, pilot-scale up-flow anaerobic sludge blanket (UASB) reactor. The UASB process, which was operated for 87 days at mesophilic conditions (32 ± 2 °C) at a hydraulic retention time (HRT) of 3 days, led to a COD removal efficiency between 66 and 97 %, while the particulate matter of the wastewater was effectively removed by entrapment in the sludge blanket of the reactor. When the anaerobic reactor effluent was post-treated over a boron-doped diamond (BDD) anode at 9 and 18 A and in the presence of NaCl as the supporting electrolyte, complete removal of COD was attained after 3-4 h of reaction. During electrochemical experiments, three groups of organochlorinated compounds, namely trihalomethanes (THMs), haloacetonitriles (HANs), and haloketons (HKs), as well as 1,2-dichloroethane (DCA) and chloropicrin were identified as by-products of the process; these, alongside free chlorine, are thought to increase the matrix ecotoxicity to Artemia salina. PMID:24793070

  12. Electrochemical oxidation of 243Am(III) in nitric acid by a terpyridyl-derivatized electrode

    SciTech Connect

    Dares, C. J.; Lapides, A. M.; Mincher, B. J.; Meyer, T. J.

    2015-11-05

    A high surface area, tin-doped indium oxide electrode surface-derivatized with a terpyridine ligand has been applied to the oxidation of trivalent americium to Am(V) and Am(VI) in nitric acid. Potentials as low as 1.8 V vs. the saturated calomel electrode are used, 0.7 V lower than the 2.6 V potential for one-electron oxidation of Am(III) to Am(IV) in 1 M acid. This simple electrochemical procedure provides, for the first time, a method for accessing the higher oxidation states of Am in non-complexing media for developing the coordination chemistries of Am(V) and Am(VI) and, more importantly, for separation of americium from nuclear waste streams.

  13. Electrochemical properties of highly degenerate and low cost cadmium oxide thin films

    NASA Astrophysics Data System (ADS)

    Mundinamani, S. P.; Rabinal, M. K.

    2015-11-01

    In the present work, we describe a simple and easy method for the deposition of nanostructured cadmium oxide films on glass by spray pyrolysis. The electrochemical capacitive properties of these films have been studied for different electrolyte species under the different scan rates. The present results show a high value of specific capacitance of 18 F g-1 in 1 M NaOH electrolyte for the scan rate of 10 mV s-1. This value of specific capacitance is the highest ever reported value for cadmium oxide thin films. These results emphasize that the ion diffusion between the electrode and the electrolyte is significantly high due to the highly porous nanostructure of cadmium oxide and these results confirms the cadmium oxide as a capacitive material. The constructed devices were stable even after the 1000 cycle.

  14. Electrochemical properties of tin oxide anodes for sodium-ion batteries

    NASA Astrophysics Data System (ADS)

    Lu, Ying Ching; Ma, Chuze; Alvarado, Judith; Kidera, Takafumi; Dimov, Nikolay; Meng, Ying Shirley; Okada, Shigeto

    2015-06-01

    Few tin (Sn)-oxide based anode materials have been found to have large reversible capacity for both sodium (Na)-ion and lithium (Li)-ion batteries. Herein, we report the synthesis and electrochemical properties of Sn oxide-based anodes for sodium-ion batteries: SnO, SnO2, and SnO2/C. Among them, SnO is the most suitable anode for Na-ion batteries with less first cycle irreversibility, better cycle life, and lower charge transfer resistance. The energy storage mechanism of the above-mentioned Sn oxides was studied, which suggested that the conversion reaction of the Sn oxide anodes is reversible in Na-ion batteries. The better anode performance of SnO is attributed by the better conductivity.

  15. Oxidation-Reduction Resistance of Advanced Copper Alloys

    NASA Technical Reports Server (NTRS)

    Greenbauer-Seng, L. (Technical Monitor); Thomas-Ogbuji, L.; Humphrey, D. L.; Setlock, J. A.

    2003-01-01

    Resistance to oxidation and blanching is a key issue for advanced copper alloys under development for NASA's next generation of reusable launch vehicles. Candidate alloys, including dispersion-strengthened Cu-Cr-Nb, solution-strengthened Cu-Ag-Zr, and ODS Cu-Al2O3, are being evaluated for oxidation resistance by static TGA exposures in low-p(O2) and cyclic oxidation in air, and by cyclic oxidation-reduction exposures (using air for oxidation and CO/CO2 or H2/Ar for reduction) to simulate expected service environments. The test protocol and results are presented.

  16. Preparation and electrochemical performances of nanoporous/cracked cobalt oxide layer for supercapacitors

    NASA Astrophysics Data System (ADS)

    Gobal, Fereydoon; Faraji, Masoud

    2014-12-01

    Nanoporous/cracked structures of cobalt oxide (Co3O4) electrodes were successfully fabricated by electroplating of zinc-cobalt onto previously formed TiO2 nanotubes by anodizing of titanium, leaching of zinc in a concentrated alkaline solution and followed by drying and annealing at 400 °C. The structure and morphology of the obtained Co3O4 electrodes were characterized by X-ray diffraction, EDX analysis and scanning electron microscopy. The results showed that the obtained Co3O4 electrodes were composed of the nanoporous/cracked structures with an average pore size of about 100 nm. The electrochemical capacitive behaviors of the nanoporous Co3O4 electrodes were investigated by cyclic voltammetry, galvanostatic charge-discharge studies and electrochemical impedance spectroscopy in 1 M NaOH solution. The electrochemical data demonstrated that the electrodes display good capacitive behavior with a specific capacitance of 430 F g-1 at a current density of 1.0 A g-1 and specific capacitance retention of ca. 80 % after 10 days of being used in electrochemical experiments, indicating to be promising electroactive materials for supercapacitors. Furthermore, in comparison with electrodes prepared by simple cathodic deposition of cobalt onto TiO2 nanotubes(without dealloying procedure), the impedance studies showed improved performances likely due to nanoporous/cracked structures of electrodes fabricated by dealloying of zinc, which provide fast ion and electron transfer routes and large reaction surface area with the ensued fast reaction kinetics.

  17. Effect of surfactant on the electrochemical performance of graphene/iron oxide electrode for supercapacitor

    NASA Astrophysics Data System (ADS)

    Ghasemi, Shahram; Ahmadi, Fatemeh

    2015-09-01

    In this study, reduced graphene oxide- Fe3O4 (RGO-Fe3O4) nanocomposite is fabricated using simple electrophoretic deposition (EPD) method followed by an electrochemical reduction process. It is characterized using atomic force microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy and scanning electron microscopy. Fe3O4 nanoparticles with 20-50 nm in diameter are uniformly formed on RGO. Electrochemical properties of nanocomposite are characterized by cyclic voltammetery, galvanostatic charge/discharge and electrochemical impedance spectroscopy. According to the galvanostatic charge/discharge analysis, RGO-Fe3O4/SS presents specific capacitance (Cs) of 154 F g-1 at current density of 1 A g-1, which is higher than that of RGO/SS (81 F g-1) in Na2SO4 electrolyte. Also, the electrochemical behaviors show that addition of three kind of surfactant, i.e. sodium dodecyl sulphate, cetyltrimethylammonium bromide, t-octyl phenoxy polyethoxyethanol (Triton X-100) to Na2SO4 aqueous solution can improve the Cs of RGO-Fe3O4/SS electrodes. RGO-Fe3O4/SS in Na2SO4 electrolyte containing Triton X-100 shows maximum Cs of 236 F g-1 at 1 A g-1 which retains 97% of initial capacitance after 500 cycles.

  18. Combinatorial electrochemical synthesis and screening of Pt-WO3 catalysts for electro-oxidation of methanol

    NASA Astrophysics Data System (ADS)

    Jayaraman, Shrisudersan; Baeck, Sung-Hyeon; Jaramillo, Thomas F.; Kleiman-Shwarsctein, Alan; McFarland, Eric W.

    2005-06-01

    An automated system for high-throughput electrochemical synthesis and screening of fuel cell electro-oxidation catalysts is described. This system consists of an electrode probe that contains counter and reference electrodes that can be positioned inside an array of electrochemical cells created within a polypropylene block. The electrode probe is attached to an automated of X-Y-Z motion system. An externally controlled potentiostat is used to apply the electrochemical potential to the catalyst substrate. The motion and electrochemical control are integrated using a user-friendly software interface. During automated synthesis the deposition potential and/or current may be controlled by a pulse program triggered by the software using a data acquisition board. The screening includes automated experiments to obtain cyclic voltammograms. As an example, a platinum-tungsten oxide (Pt-WO3) library was synthesized and characterized for reactivity towards methanol electro-oxidation.

  19. Charge Transport Properties of P3HT-PEO block copolymers that are Electrochemically Oxidized in the Solid-State

    NASA Astrophysics Data System (ADS)

    Patel, Shrayesh; Javier, Anna; Balsara, Nitash

    2013-03-01

    We report on the relationship between morphology and electronic/ionic charge transport of Poly(3-hexylthiophene)- b-Poly(ethylene oxide) (P3HT- b-PEO) and lithium bis-(trifluoromethanesulfonyl) imide (LiTFSI) mixtures. Using ac impedance spectroscopy, we show that P3HT- b-PEO/LiTFSI mixtures can conduct electronic and ionic charges simultaneously. The electronic resistance of P3HT- b-PEO can be controlled through the electrochemical oxidation of P3HT with LiTFSI. We designed an all solid-state electrochemical cell with three terminals to measure the electronic conductivity of P3HT- b-PEO under applied potentials. The addition of a third terminal within the P3HT- b-PEO layer allows for the in-situ measurement of the electronic conductivity as a function of the P3HT electrochemical oxidation level. Our experimental setup is unique in that electrochemical oxidation occurs in the presence of solid-polymer electrolyte. Previous studies on the electrochemical oxidation of polythiophenes have been done in the presence of a liquid electrolyte. The results of the in-situ electronic conductivity measurements as a function of electrochemical doping level and block copolymer composition will be presented.

  20. Amorphous mixed-metal hydroxide nanostructures for advanced water oxidation catalysts

    NASA Astrophysics Data System (ADS)

    Gao, Y. Q.; Liu, X. Y.; Yang, G. W.

    2016-02-01

    The design of highly efficient, durable, and earth-abundant catalysts for the oxygen evolution reaction (OER) is crucial in order to promote energy conversion and storage processes. Here, we synthesize amorphous mixed-metal (Ni-Fe) hydroxide nanostructures with a homogeneous distribution of Ni/Fe as well as a tunable Ni/Fe ratio by a simple, facile, green and low-cost electrochemical technique, and we demonstrate that the synthesized amorphous nanomaterials possess ultrahigh activity and super long-term cycle stability in the OER process. The amorphous Ni0.71Fe0.29(OH)x nanostructure affords a current density of 10 mA cm-2 at an overpotential of a mere 0.296 V and a small Tafel slope of 58 mV dec-1, while no deactivation is detected in the CV testing even up to 30 000 cycles, which suggests the promising application of these amorphous nanomaterials in electrochemical oxidation. Meanwhile, the distinct catalytic activities among these amorphous Ni-Fe hydroxide nanostructures prompts us to take notice of the composition of the alloy hydroxides/oxides when studying their catalytic properties, which opens an avenue for the rational design and controllable preparation of such amorphous nanomaterials as advanced OER electrocatalysts.The design of highly efficient, durable, and earth-abundant catalysts for the oxygen evolution reaction (OER) is crucial in order to promote energy conversion and storage processes. Here, we synthesize amorphous mixed-metal (Ni-Fe) hydroxide nanostructures with a homogeneous distribution of Ni/Fe as well as a tunable Ni/Fe ratio by a simple, facile, green and low-cost electrochemical technique, and we demonstrate that the synthesized amorphous nanomaterials possess ultrahigh activity and super long-term cycle stability in the OER process. The amorphous Ni0.71Fe0.29(OH)x nanostructure affords a current density of 10 mA cm-2 at an overpotential of a mere 0.296 V and a small Tafel slope of 58 mV dec-1, while no deactivation is detected in the CV testing even up to 30 000 cycles, which suggests the promising application of these amorphous nanomaterials in electrochemical oxidation. Meanwhile, the distinct catalytic activities among these amorphous Ni-Fe hydroxide nanostructures prompts us to take notice of the composition of the alloy hydroxides/oxides when studying their catalytic properties, which opens an avenue for the rational design and controllable preparation of such amorphous nanomaterials as advanced OER electrocatalysts. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr08989a

  1. ADVANCED OXIDATION: OXALATE DECOMPOSITION TESTING WITH OZONE

    SciTech Connect

    Ketusky, E.; Subramanian, K.

    2012-02-29

    At the Savannah River Site (SRS), oxalic acid is currently considered the preferred agent for chemically cleaning the large underground Liquid Radioactive Waste Tanks. It is applied only in the final stages of emptying a tank when generally less than 5,000 kg of waste solids remain, and slurrying based removal methods are no-longer effective. The use of oxalic acid is preferred because of its combined dissolution and chelating properties, as well as the fact that corrosion to the carbon steel tank walls can be controlled. Although oxalic acid is the preferred agent, there are significant potential downstream impacts. Impacts include: (1) Degraded evaporator operation; (2) Resultant oxalate precipitates taking away critically needed operating volume; and (3) Eventual creation of significant volumes of additional feed to salt processing. As an alternative to dealing with the downstream impacts, oxalate decomposition using variations of ozone based Advanced Oxidation Process (AOP) were investigated. In general AOPs use ozone or peroxide and a catalyst to create hydroxyl radicals. Hydroxyl radicals have among the highest oxidation potentials, and are commonly used to decompose organics. Although oxalate is considered among the most difficult organic to decompose, the ability of hydroxyl radicals to decompose oxalate is considered to be well demonstrated. In addition, as AOPs are considered to be 'green' their use enables any net chemical additions to the waste to be minimized. In order to test the ability to decompose the oxalate and determine the decomposition rates, a test rig was designed, where 10 vol% ozone would be educted into a spent oxalic acid decomposition loop, with the loop maintained at 70 C and recirculated at 40L/min. Each of the spent oxalic acid streams would be created from three oxalic acid strikes of an F-area simulant (i.e., Purex = high Fe/Al concentration) and H-area simulant (i.e., H area modified Purex = high Al/Fe concentration) after nearing dissolution equilibrium, and then decomposed to {le} 100 Parts per Million (ppm) oxalate. Since AOP technology largely originated on using ultraviolet (UV) light as a primary catalyst, decomposition of the spent oxalic acid, well exposed to a medium pressure mercury vapor light was considered the benchmark. However, with multi-valent metals already contained in the feed, and maintenance of the UV light a concern; testing was conducted to evaluate the impact from removing the UV light. Using current AOP terminology, the test without the UV light would likely be considered an ozone based, dark, ferrioxalate type, decomposition process. Specifically, as part of the testing, the impacts from the following were investigated: (1) Importance of the UV light on the decomposition rates when decomposing 1 wt% spent oxalic acid; (2) Impact of increasing the oxalic acid strength from 1 to 2.5 wt% on the decomposition rates; and (3) For F-area testing, the advantage of increasing the spent oxalic acid flowrate from 40 L/min (liters/minute) to 50 L/min during decomposition of the 2.5 wt% spent oxalic acid. The results showed that removal of the UV light (from 1 wt% testing) slowed the decomposition rates in both the F & H testing. Specifically, for F-Area Strike 1, the time increased from about 6 hours to 8 hours. In H-Area, the impact was not as significant, with the time required for Strike 1 to be decomposed to less than 100 ppm increasing slightly, from 5.4 to 6.4 hours. For the spent 2.5 wt% oxalic acid decomposition tests (all) without the UV light, the F-area decompositions required approx. 10 to 13 hours, while the corresponding required H-Area decompositions times ranged from 10 to 21 hours. For the 2.5 wt% F-Area sludge, the increased availability of iron likely caused the increased decomposition rates compared to the 1 wt% oxalic acid based tests. In addition, for the F-testing, increasing the recirculation flow rates from 40 liter/minute to 50 liter/minute resulted in an increased decomposition rate, suggesting a better use of ozone.

  2. Optimization and electrochemical characterization of RF-sputtered iridium oxide microelectrodes for electrical stimulation

    NASA Astrophysics Data System (ADS)

    Kang, Xiaoyang; Liu, Jingquan; Tian, Hongchang; Yang, Bin; NuLi, Yanna; Yang, Chunsheng

    2014-02-01

    A reactively sputtered iridium oxide (IrOx) thin film has been developed as electrochemical modification material for microelectrodes to obtain high stability and charge storage capacity (CSC) in functional electrical stimulation. The effect of the oxygen flow and oxygen to argon ratio during sputtering process on the microstructure and electrochemical properties of the IrOx film is characterized. After optimization, the activated IrOx microelectrode shows the highest CSC of 36.15 mC cm-2 at oxygen flow of 25 sccm and oxygen to argon ratio of (2.5:1). Because the deposition process of the reactively sputtered iridium oxide is an exothermic reaction, it is difficult to form film patterning by the lift-off process. The lift-off process was focused on the partially carbonized photoresist (PR) and normal PR. The higher of the carbonization degree of PR reaches, the longer the immersion duration. However, the patterning process of the iridium oxide film becomes feasible when the sputtering pressure is increasing. The experimental results show that the iridium oxide films forms the pattern with the lowest duration of ultrasonic agitation when the deposition pressure is 4.2 Pa and pressure ratio between O2 and Ar pressure is 3:4.

  3. Tetradentate Schiff base ligands and their complexes: synthesis, structural characterization, thermal, electrochemical and alkane oxidation.

    PubMed

    Ceyhan, Gökhan; Köse, Muhammet; McKee, Vickie; Uruş, Serhan; Gölcü, Ayşegül; Tümer, Mehmet

    2012-09-01

    Three Schiff base ligands (H(2)L(1)-H(2)L(3)) with N(2)O(2) donor sites were synthesized by condensation of 1,5-diaminonapthalene with benzaldehyde derivatives. A series of Cu(II), Co(II), Ni(II), Mn(II) and Cr(III) complexes were prepared and characterized by spectroscopic and analytical methods. Thermal, electrochemical and alkane oxidation reactions of the ligands and their metal complexes were investigated. Extensive application of 1D ((1)H, (13)C NMR) and 2D (COSY, HETCOR, HMBC and TOSCY) NMR techniques were used to characterize the structures of the ligands and establish the (1)H and (13)C resonance assignments of the three ligands. Ligands H(2)L(1) and H(2)L(3) were obtained as single crystals from THF solution and characterized by X-ray diffraction. Both molecules are centrosymmetric and asymmetric unit contains one half of the molecule. Catalytic alkane oxidation reactions with the transition metal complexes investigated using cyclohexane and cyclooctane as substrates. The Cu(II) and Cr(III) complexes showed good catalytic activity in the oxidation of cyclohexane and cyclooctane to desired oxidized products. Electrochemical and thermal properties of the compounds were also investigated. PMID:22571942

  4. Preparation and Characterization of a PEDOT-Manganese Oxide Composite, and Its Application to Electrochemical Sensing

    NASA Astrophysics Data System (ADS)

    Arena, A.

    2016-03-01

    Stable and transparent aqueous dispersions of a hybrid organic-inorganic composite, are prepared by electrochemically doping Manganese Oxide into Polyethylendioxythiophene (PEDOT). Films deposited from the PEDOT-MnOx dispersions, are characterized by means of electrical and optical measurements, and by means of Atomic Force Microscopy (AFM) investigations. The PEDOT-MnOx composite is then used to modify one of the gold electrodes of a simple electrochemical cell, in which Nafion is used as a solid electrolyte. The cell is characterized using time domain electrical measurements. It is found that distinguishable redox peaks arise in the current-voltage loops of the cell, as nanomolar amounts of either acetic acid and ammonia, are added to the deionized water into which the cell is immersed. The intensity of such current peaks, is linearly related to the concentration of the analytes, in the nanomolar range of concentrations.

  5. Reduced graphene oxide-yttria nanocomposite modified electrode for enhancing the sensitivity of electrochemical genosensor.

    PubMed

    Rasheed, P Abdul; Radhakrishnan, Thulasi; Shihabudeen, P K; Sandhyarani, N

    2016-09-15

    Reduced graphene oxide-yttria nanocomposite (rGO:Y) is applied as electrochemical genosensor platform for ultrahigh sensitive detection of breast cancer 1 (BRCA1) gene for the first time. The sensor is based on the sandwich assay in which gold nanoparticle cluster labeled reporter DNA hybridize to the target DNA. Glassy carbon electrode modified with rGO-yttria serves as the immobilization platform for capture probe DNA. The sensor exhibited a fine capability of sensing BRCA1 gene with linear range of 10attomolar (aM) to 1nanomolar (nM) and a detection limit of 5.95attomolar. The minimum distinguishable response concentration is down to the attomolar level with a high sensitivity and selectivity. We demonstrated that the use of rGO:Y modified electrode along with gold nanoparticle cluster (AuNPC) label leads to the highly sensitive electrochemical detection of BRCA1 gene. PMID:27153526

  6. High performance solid oxide fuel cell cathode fabricated by electrochemical vapor deposition

    SciTech Connect

    Suzuki, Minoru; Sasaki, Hirokazu; Otoshi, Shoji; Kajimura, Atsuko; Sugiura, Nozomi; Ippommatsu, Masamichi . Fundamental Research Labs.)

    1994-07-01

    La(Sr)MnO[sub 3] cathodes have been investigated as high temperature oxygen reduction electrodes in the solid oxide fuel cells (SOFCs). The cathodes consist of 10 mole percent of yttria stabilized zirconia (YSZ) thin film electrolyte layer deposited on a porous La[sub 0.81]Sr[sub 0.09]MnO[sub 3] tube using the electrochemical vapor deposition method. The La(Sr)MnO[sub 3]/YSZ cathodes have different electrochemical properties from those fabricated with the sintering method. The cathode polarization was about 1 mV at a current density of 1.5 A/cm[sup 2] in oxygen at 1,000 C. This type of cathode has an extremely large phase boundary and large interfacial capacitance (more than 1 F/cm[sup 2]) which is approximately proportional to the oxygen partial pressure.

  7. Electroless Deposition of Conformed Nanoscale Iron Oxide on Carbon Nanoarchitectures for Electrochemical Charge Storage

    SciTech Connect

    Sassin, M.; Mansour, A; Pettigrew, K; Rolison, D; Long, J

    2010-01-01

    We describe a simple self-limiting electroless deposition process whereby conformal, nanoscale iron oxide (FeO{sub x}) coatings are generated at the interior and exterior surfaces of macroscopically thick ({approx}90 {micro}m) carbon nanofoam paper substrates via redox reaction with aqueous K{sub 2}FeO{sub 4}. The resulting FeO{sub x}-carbon nanofoams are characterized as device-ready electrode structures for aqueous electrochemical capacitors and they demonstrate a 3-to-7 fold increase in charge-storage capacity relative to the native carbon nanofoam when cycled in a mild aqueous electrolyte (2.5 M Li{sub 2}SO{sub 4}), yielding mass-, volume-, and footprint-normalized capacitances of 84 F g{sup -1}, 121 F cm{sup -3}, and 0.85 F cm{sup -2}, respectively, even at modest FeO{sub x} loadings (27 wt %). The additional charge-storage capacity arises from faradaic pseudocapacitance of the FeO{sub x} coating, delivering specific capacitance >300 F g{sup -1} normalized to the content of FeO{sub x} as FeOOH, as verified by electrochemical measurements and in situ X-ray absorption spectroscopy. The additional capacitance is electrochemically addressable within tens of seconds, a time scale of relevance for high-rate electrochemical charge storage. We also demonstrate that the addition of borate to buffer the Li{sub 2}SO{sub 4} electrolyte effectively suppresses the electrochemical dissolution of the FeO{sub x} coating, resulting in <20% capacitance fade over 1000 consecutive cycles.

  8. Morphology, structural and optical properties of iron oxide thin film photoanodes in photoelectrochemical cell: Effect of electrochemical oxidation

    NASA Astrophysics Data System (ADS)

    Maabong, Kelebogile; Machatine, Augusto G.; Hu, Yelin; Braun, Artur; Nambala, Fred J.; Diale, Mmantsae

    2016-01-01

    Hematite (α-Fe2O3) is a promising semiconductor as photoanode in solar hydrogen production from photoelectrolysis of water due to its appropriate band gap, low cost and high electrochemical stability in aqueous caustic electrolytes. Operation of such photoanode in a biased photoelectrochemical cell constitutes an anodization with consequent redox reactions at the electrode surface. α-Fe2O3 thin film photoanodes were prepared by simple and inexpensive dip coating method on fluorine doped tin oxide (FTO) glass substrate, annealed in air at 500 °C for 2 h, then electrochemically oxidized (anodized) in 1 M KOH at 500 mV for 1 min in dark and light conditions. Changes in structural properties and morphology of α-Fe2O3 nanoparticles films were investigated by XRD, Raman spectroscopy and a high resolution FE-SEM. The average grain size was observed to increase from ~57 nm for pristine samples to 73 and 77 nm for anodized samples in dark and light respectively. Broadening and red shift in Raman spectra in anodized samples may be attributed to lattice expansion upon oxidation. The UV-visible measurements revealed enhanced absorption in the photoanodes after the treatment. The findings suggest that the anodization of the photoelectrode in a biased cell causes not only changes of the molecular structure at the surface, but also changes in the crystallographic structure which can be detected with x-ray diffractometry.

  9. Facile and novel electrochemical preparation of a graphene-transition metal oxide nanocomposite for ultrasensitive electrochemical sensing of acetaminophen and phenacetin

    NASA Astrophysics Data System (ADS)

    Jiang, Lin; Gu, Shuqing; Ding, Yaping; Jiang, Feng; Zhang, Zhen

    2013-12-01

    A facile and novel preparation strategy based on electrochemical techniques for the fabrication of electrodeposited graphene (EGR) and zinc oxide (ZnO) nanocomposite was developed. The morphology and structure of the EGR-based nanocomposite were investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (XPS) and Raman spectroscopy. Meanwhile, the electrochemical performance of the nanocomposite was demonstrated with cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Due to the synergistic effect of EGR and ZnO nanoparticles, an ultrasensitive electrochemical sensor for acetaminophen (AC) and phenacetin (PCT) was successfully fabricated. The linearity ranged from 0.02 to 10 μM for AC and 0.06 to 10 μM for PCT with high sensitivities of 54 295.82 μA mM-1 cm2 for AC and 21 344.66 μA mM-1 cm2 for PCT, respectively. Moreover, the practical applicability was validated to be reliable and desirable in pharmaceutical detections. The excellent results showed the promise of the proposed preparation strategy of EGR-transition metal oxide nanocomposite in the field of electroanalytical chemistry.A facile and novel preparation strategy based on electrochemical techniques for the fabrication of electrodeposited graphene (EGR) and zinc oxide (ZnO) nanocomposite was developed. The morphology and structure of the EGR-based nanocomposite were investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (XPS) and Raman spectroscopy. Meanwhile, the electrochemical performance of the nanocomposite was demonstrated with cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Due to the synergistic effect of EGR and ZnO nanoparticles, an ultrasensitive electrochemical sensor for acetaminophen (AC) and phenacetin (PCT) was successfully fabricated. The linearity ranged from 0.02 to 10 μM for AC and 0.06 to 10 μM for PCT with high sensitivities of 54 295.82 μA mM-1 cm2 for AC and 21 344.66 μA mM-1 cm2 for PCT, respectively. Moreover, the practical applicability was validated to be reliable and desirable in pharmaceutical detections. The excellent results showed the promise of the proposed preparation strategy of EGR-transition metal oxide nanocomposite in the field of electroanalytical chemistry. Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr03620k

  10. Recent Advances in Electrochemical Biosensors Based on Fullerene-C60 Nano-Structured Platforms

    PubMed Central

    Pilehvar, Sanaz; De Wael, Karolien

    2015-01-01

    Nanotechnology is becoming increasingly important in the field of (bio)sensors. The performance and sensitivity of biosensors is greatly improved with the integration of nanomaterials into their construction. Since its first discovery, fullerene-C60 has been the object of extensive research. Its unique and favorable characteristics of easy chemical modification, conductivity, and electrochemical properties has led to its tremendous use in (bio)sensor applications. This paper provides a concise review of advances in fullerene-C60 research and its use as a nanomaterial for the development of biosensors. We examine the research work reported in the literature on the synthesis, functionalization, approaches to nanostructuring electrodes with fullerene, and outline some of the exciting applications in the field of (bio)sensing. PMID:26610583

  11. Recent Advances in Electrochemical Biosensors Based on Fullerene-C60 Nano-Structured Platforms.

    PubMed

    Pilehvar, Sanaz; De Wael, Karolien

    2015-12-01

    Nanotechnology is becoming increasingly important in the field of (bio)sensors. The performance and sensitivity of biosensors is greatly improved with the integration of nanomaterials into their construction. Since its first discovery, fullerene-C60 has been the object of extensive research. Its unique and favorable characteristics of easy chemical modification, conductivity, and electrochemical properties has led to its tremendous use in (bio)sensor applications. This paper provides a concise review of advances in fullerene-C60 research and its use as a nanomaterial for the development of biosensors. We examine the research work reported in the literature on the synthesis, functionalization, approaches to nanostructuring electrodes with fullerene, and outline some of the exciting applications in the field of (bio)sensing. PMID:26610583

  12. Steam Oxidation of Advanced Steam Turbine Alloys

    SciTech Connect

    Holcomb, Gordon R.

    2008-01-01

    Power generation from coal using ultra supercritical steam results in improved fuel efficiency and decreased greenhouse gas emissions. Results of ongoing research into the oxidation of candidate nickel-base alloys for ultra supercritical steam turbines are presented. Exposure conditions range from moist air at atmospheric pressure (650°C to 800°C) to steam at 34.5 MPa (650°C to 760°C). Parabolic scale growth coupled with internal oxidation and reactive evaporation of chromia are the primary corrosion mechanisms.

  13. Simultaneous Electrochemical Detection of Dopamine and Ascorbic Acid Using an Iron Oxide/Reduced Graphene Oxide Modified Glassy Carbon Electrode

    PubMed Central

    Peik-See, Teo; Pandikumar, Alagarsamy; Nay-Ming, Huang; Hong-Ngee, Lim; Sulaiman, Yusran

    2014-01-01

    The fabrication of an electrochemical sensor based on an iron oxide/graphene modified glassy carbon electrode (Fe3O4/rGO/GCE) and its simultaneous detection of dopamine (DA) and ascorbic acid (AA) is described here. The Fe3O4/rGO nanocomposite was synthesized via a simple, one step in-situ wet chemical method and characterized by different techniques. The presence of Fe3O4 nanoparticles on the surface of rGO sheets was confirmed by FESEM and TEM images. The electrochemical behavior of Fe3O4/rGO/GCE towards electrocatalytic oxidation of DA was investigated by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) analysis. The electrochemical studies revealed that the Fe3O4/rGO/GCE dramatically increased the current response against the DA, due to the synergistic effect emerged between Fe3O4 and rGO. This implies that Fe3O4/rGO/GCE could exhibit excellent electrocatalytic activity and remarkable electron transfer kinetics towards the oxidation of DA. Moreover, the modified sensor electrode portrayed sensitivity and selectivity for simultaneous determination of AA and DA. The observed DPVs response linearly depends on AA and DA concentration in the range of 1–9 mM and 0.5–100 μM, with correlation coefficients of 0.995 and 0.996, respectively. The detection limit of (S/N = 3) was found to be 0.42 and 0.12 μM for AA and DA, respectively. PMID:25195850

  14. The kinetics of the oxidation of pyrite by ferric ions and dissolved oxygen: An electrochemical study

    SciTech Connect

    Holmes, P.R.; Crundwell, F.K.

    2000-01-01

    The dissolution of pyrite is important in the geochemical cycling of iron and sulphur, in the formation of acid mine drainage, and in the extraction of metals by bacterial leaching. Many researchers have studied the kinetics of dissolution, and the rate of dissolution has often been found to be half-order in ferric ions or oxygen. Previous work has not adequately explained the kinetics of dissolution of pyrite. The dissolution of pyrite is an oxidation-reduction reaction. The kinetics of the oxidation and reduction half-reactions was studied independently using electrochemical techniques of voltammetry. The kinetics of the overall reaction was studied by the electrochemical technique of potentiometry, which consisted of measuring the mixed potential of a sample of corroding pyrite in solutions of different compositions. The kinetics of the half reactions are related to the kinetics of the overall dissolution reaction by the condition that there is no accumulation of charge. This principle is used to derive expressions for the mixed potential and the rate of dissolution, which successfully describe the mixed potential measurements and the kinetics of dissolution reported in the literature. It is shown that the observations of half-order kinetics and that the oxygen in the sulphate product arises from water are both a direct consequence of the electrochemical mechanism. Thus it is concluded that the electrochemical reaction steps occurring at the mineral-solution interface control the rate of dissolution. Raman spectroscopy was used to analyze reaction products formed on the pyrite surface. The results indicated that small amounts of polysulphides form on the surface of the pyrite. However, it was also found that the mixed (corrosion) potential does not change over a 14-day leaching period. This indicates that even though polysulphide material is present on the surface, it does not influence the rate of the reactions occurring at the surface. Measurement of the sulphur yields as a function of electrode potential indicate that thiosulphate is not the only source of the sulphur product.

  15. Reduced graphene oxide anchored Cu(OH)2 as a high performance electrochemical supercapacitor.

    PubMed

    Pramanik, Atin; Maiti, Sandipan; Mahanty, Sourindra

    2015-09-01

    Developing new materials for electrochemical supercapacitors with higher energy density has recently gained tremendous impetus in the context of effective utilization of renewable energy. Herein, we report a simple one-pot synthesis of bundled nanorods of Cu(OH)2 embedded in a matrix of reduced graphene oxide (Cu(OH)2@RGO) under mild hydrothermal conditions of 80 °C for 1 h. The synthesized material shows a high BET surface area of 78.7 m(2) g(-1) and a mesoporous nature with a broad pore-size distribution consisting of structural pores as well as inter-particle pores. Raman spectroscopy suggests an intimate interaction between Cu(OH)2 and reduced graphene oxide (RGO) creating more defects by destruction of sp(2) domains which would help the defect-assisted charge transport during electrochemical processes. When investigated as an electrochemical supercapacitor, Cu(OH)2@RGO shows a high capacitance of 602 F g(-1) at 0.2 A g(-1) in 1 M KOH in a three-electrode cell configuration. Detailed electrochemical studies indicate that the Faradic processes are diffusion controlled and follow a quasi-reversible kinetics. Further, a two-electrode symmetric cell shows good energy density and power density (84.5 Wh kg(-1) at 0.55 kW kg(-1) and 20.5 Wh kg(-1) at 5.5 kW kg(-1)) characteristics demonstrating superior application potential of this common low-cost transition metal hydroxide for high performance energy storage devices. PMID:26208312

  16. Advanced launch system. Advanced development oxidizer turbopump program

    NASA Astrophysics Data System (ADS)

    1993-10-01

    On May 19, 1989, Pratt & Whitney was awarded contract NAS8-37595 by the National Aeronautics and Space Administration, Marshall Space Flight Center, Huntsville Alabama for an Advanced Development Program (ADP) to design, develop and demonstrate a highly reliable low cost, liquid oxygen turbopump for the Advanced Launch System (ALS). The ALS had an overall goal of reducing the cost of placing payloads in orbit by an order of magnitude. This goal would require a substantial reduction in life cycle costs, with emphasis on recurring costs, compared to current launch vehicles. Engine studies supporting these efforts were made for the Space Transportation Main Engine (STME). The emphasis on low cost required design simplification of components and subsystems such that the ground maintenance and test operations was minimized. The results of the Oxygen Turbopump ADP technology effort would provide data to be used in the STME. Initially the STME baseline was a gas generator cycle engine with a vacuum thrust level of 580,000 lbf. This was later increased to 650,000 lbf and the oxygen turbopump design approach was changed to reflect the new thrust level. It was intended that this ADP program be conducted in two phases. Phase 1, a basic phase, would encompass the preliminary design effort, and Phase II, an optional contract phase to cover design, fabrication and test evaluation of an oxygen turbopump at a component test facility at the NASA John C. Stennis Space Center in Mississippi. The basic phase included preliminary design and analysis, evaluation of low cost concepts, and evaluation of fabrication techniques. The option phase included design of the pump and support hardware, analysis of the final configuration to ensure design integrity, fabrication of hardware to demonstrate low cost, DVS Testing of hardware to verify the design, assembly of the turbopump and full scale turbopump testing. In December 1990, the intent of this ADP to support the design and development was changed. The design effort for the oxygen turbopump became part of the STME Phase B contract. The status of the pump design funded through this ADP was presented at the Preliminary Design Review (PDR) at the MSFC on October 24, 1990. Advancements in the design of the pump were subsequently continued under the Phase B Contract. The emphasis of this ADP became the demonstration of individual technologies that would have the greatest potential for reducing the recurring cost and increasing reliability. In October of 1992, overall program funding was reduced and work on this ADP was terminated.

  17. Advanced launch system. Advanced development oxidizer turbopump program

    NASA Technical Reports Server (NTRS)

    1993-01-01

    On May 19, 1989, Pratt & Whitney was awarded contract NAS8-37595 by the National Aeronautics and Space Administration, Marshall Space Flight Center, Huntsville Alabama for an Advanced Development Program (ADP) to design, develop and demonstrate a highly reliable low cost, liquid oxygen turbopump for the Advanced Launch System (ALS). The ALS had an overall goal of reducing the cost of placing payloads in orbit by an order of magnitude. This goal would require a substantial reduction in life cycle costs, with emphasis on recurring costs, compared to current launch vehicles. Engine studies supporting these efforts were made for the Space Transportation Main Engine (STME). The emphasis on low cost required design simplification of components and subsystems such that the ground maintenance and test operations was minimized. The results of the Oxygen Turbopump ADP technology effort would provide data to be used in the STME. Initially the STME baseline was a gas generator cycle engine with a vacuum thrust level of 580,000 lbf. This was later increased to 650,000 lbf and the oxygen turbopump design approach was changed to reflect the new thrust level. It was intended that this ADP program be conducted in two phases. Phase 1, a basic phase, would encompass the preliminary design effort, and Phase II, an optional contract phase to cover design, fabrication and test evaluation of an oxygen turbopump at a component test facility at the NASA John C. Stennis Space Center in Mississippi. The basic phase included preliminary design and analysis, evaluation of low cost concepts, and evaluation of fabrication techniques. The option phase included design of the pump and support hardware, analysis of the final configuration to ensure design integrity, fabrication of hardware to demonstrate low cost, DVS Testing of hardware to verify the design, assembly of the turbopump and full scale turbopump testing. In December 1990, the intent of this ADP to support the design and development was changed. The design effort for the oxygen turbopump became part of the STME Phase B contract. The status of the pump design funded through this ADP was presented at the Preliminary Design Review (PDR) at the MSFC on October 24, 1990. Advancements in the design of the pump were subsequently continued under the Phase B Contract. The emphasis of this ADP became the demonstration of individual technologies that would have the greatest potential for reducing the recurring cost and increasing reliability. In October of 1992, overall program funding was reduced and work on this ADP was terminated.

  18. Cobalt (hydro)oxide electrodes under electrochemical conditions: a first principle study

    NASA Astrophysics Data System (ADS)

    Chen, Jia; Selloni, Annabella

    2013-03-01

    There is currently much interest in photoelectrochemical water splitting as a promising pathway towards sustainable energy production. A major issue of such photoelectrochemical devices is the limited efficiency of the anode, where the oxygen evolution reaction (OER) takes place. Cobalt (hydro)oxides, particularly Co3O4 and Co(OH)2, have emerged as promising candidates for use as OER anode materials. Interestingly, recent in-situ Raman spectroscopy studies have shown that Co3O4 electrodes undergo progressive oxidation and transform into oxyhydroxide, CoO(OH), under electrochemical working conditions. (Journal of the American Chemical Society 133, 5587 (2011))Using first principle electronic structure calculations, we provide insight into these findings by presenting results on the structural, thermodynamic, and electronic properties of cobalt oxide, hydroxide and oxydroxide CoO(OH), and on their relative stabilities when in contact with water under external voltage.

  19. Development of a tritium monitor combined with an electrochemical tritium pump using a proton conducting oxide

    SciTech Connect

    Tanaka, M.; Sugiyama, T.

    2015-03-15

    The detection of low level tritium is one of the key issues for tritium management in tritium handling facilities. Such a detection can be performed by tritium monitors based on proton conducting oxide technique. We tested a tritium monitoring system composed of a commercial proportional counter combined with an electrochemical hydrogen pump equipped with CaZr{sub 0.9}In{sub 0.1}O{sub 3-α} as proton conducting oxide. The hydrogen pump operated at 973 K under electrolysis conditions using tritiated water vapor (HTO). The proton conducting oxide extracts tritium molecules (HT) from HTO and tritium concentration is measured by the proportional counter. The advantage of the proposed tritium monitoring system is that it is able to convert HTO into molecular hydrogen.

  20. Amorphous Ni-Co Binary Oxide with Hierarchical Porous Structure for Electrochemical Capacitors.

    PubMed

    Long, Chao; Zheng, Mingtao; Xiao, Yong; Lei, Bingfu; Dong, Hanwu; Zhang, Haoran; Hu, Hang; Liu, Yingliang

    2015-11-11

    A simple and outstanding approach is provided to fabricate amorphous structure Ni-Co binary oxide as supercapacitors electrode materials. We can easily obtain porous Ni-Co oxides composite materials via chemical bath deposition and subsequent calcination without any template or complicate operation procedures. The amorphous porous Ni-Co binary oxide exhibits brilliant electrochemical performance: first, the peculiar porous structure can effectively transport electrolytes and shorten the ion diffusion path; second, binary composition and amorphous character introduce more surface defects for redox reactions. It shows a high specific capacitance up to 1607 F g(-1) and can be cycled for 2000 cycles with 91% capacitance retention. In addition, the asymmetric supercapacitor delivers superior energy density of 28 W h kg(-1), and the maximum power density of 3064 W kg(-1) with a high energy density of 10 W h kg(-1). PMID:26099689

  1. Novel quasi-symmetric solid oxide fuel cells with enhanced electrochemical performance

    NASA Astrophysics Data System (ADS)

    Chen, Yonghong; Cheng, Zhuanxia; Yang, Yang; Gu, Qingwen; Tian, Dong; Lu, Xiaoyong; Yu, Weili; Lin, Bin

    2016-04-01

    Symmetrical solid oxide fuel cell (SSOFC) using same materials as both anode and cathode simultaneously has gained extensively attentions, which can simplify fabrication process, minimize inter-diffusion between components, enhance sulfur and coking tolerance by operating the anode as the cathode in turn. With keeping the SSOFC's advantages, a novel quasi-symmetrical solid oxide fuel cell (Q-SSOFC) is proposed to further improve the performance, which optimally combines two different SSOFC electrode materials as both anode and cathode simultaneously. PrBaFe2O5+δ (PBFO) and PrBaFe1.6Ni0.4O5+δ (PBFNO, Fe is partially substituted by Ni.) are prepared and applied as both cathode and anode for SSOFC, which exhibit desirable chemical and thermal compatibility with Sm0.8Ce0.2O1.9 (SDC) electrolyte. PBFO cathode exhibits higher oxygen reduction reaction (ORR) activity than PBFNO cathode in air, whereas PBFNO anode exhibits higher hydrogen oxidation reaction (HOR) activity than PBFO anode in H2. The as-designed Q-SSOFC of PBFNO/SDC/PBFO exhibits higher electrochemical performance than the conventional SSOFCs of both PBFO/SDC/PBFO and PBFNO/SDC/PBFNO. The superior performance of Q-SSOFC is attributed to the lowest polarization resistance (Rp). The newly developed Q-SSOFCs open doors for further improvement of electrochemical performance in SSOFC, which hold more promise for various potential applications.

  2. Activated carbon electrodes: electrochemical oxidation coupled with desalination for wastewater treatment.

    PubMed

    Duan, Feng; Li, Yuping; Cao, Hongbin; Wang, Yi; Crittenden, John C; Zhang, Yi

    2015-04-01

    The wastewater usually contains low-concentration organic pollutants and some inorganic salts after biological treatment. In the present work, the possibility of simultaneous removal of them by combining electrochemical oxidation and electrosorption was investigated. Phenol and sodium chloride were chosen as representative of organic pollutants and inorganic salts and a pair of activated carbon plate electrodes were used as anode and cathode. Some important working conditions such as oxygen concentration, applied potential and temperature were evaluated to reach both efficient phenol removal and desalination. Under optimized 2.0 V of applied potential, 38C of temperature, and 500 mL min(-1) of oxygen flow, over 90% of phenol, 60% of TOC and 20% of salinity were removed during 300 min of electrolysis time. Phenol was removed by both adsorption and electrochemical oxidation, which may proceed directly or indirectly by chlorine and hypochlorite oxidation. Chlorophenols were detected as degradation intermediates, but they were finally transformed to carboxylic acids. Desalination was possibly attributed to electrosorption of ions in the pores of activated carbon electrodes. The charging/regeneration cycling experiment showed good stability of the electrodes. This provides a new strategy for wastewater treatment and recycling. PMID:25585871

  3. Advanced oxidation processes coupled with electrocoagulation for the exhaustive abatement of Cr-EDTA.

    PubMed

    Durante, Christian; Cuscov, Marco; Isse, Abdirisak Ahmed; Sandonà, Giancarlo; Gennaro, Armando

    2011-02-01

    Using Cr-EDTA as a model system, a two-step method has been investigated for the abatement of persistent chromium complexes in water. The treatment consists of an oxidative decomposition of the organic ligands by means of ozonization or electrochemical oxidation at a boron doped diamond (BDD) electrode, followed by removal of the metal via electrochemical coagulation. In the designed synthetic waste, EDTA has been used both as a chelating agent and as a mimic of the organic content of a typical wastewater provided by a purification leather plant. A crucial point evaluated is the influence of the oxidative pretreatment on the chemical modification of the synthetic waste and hence on the electrocoagulation efficacy. Because of the great stability of Cr complexes, such as Cr-EDTA, the classical coagulation methods, based on ligand exchange between Cr(III) and Fe(II) or Fe(III), are ineffective toward Cr abatement in the presence of organic substances. On the contrary, when advanced oxidation processes (AOPs), such as ozonization or electrooxidation at a BDD anode are applied in series with electrocoagulation (EC), complete abatement of the recalcitrant Cr fraction can be achieved. ECs have been carried out by using Fe sacrificial anodes, with alternating polarization and complete Cr abatement (over 99%) has been obtained with modest charge consumption. It has been found that Cr(III) is first oxidized to Cr(VI) in the AOP preceding EC. Then, during EC, Cr(VI) is mainly reduced back to Cr(III) by electrogenerated Fe(II). Thus, Cr is mainly eliminated as Cr(III). However, a small fraction of Cr(VI) goes with the precipitate as confirmed by XPS analysis of the sludge. PMID:21255817

  4. Characterization of electro-oxidation catalysts using scanning electrochemical and mass spectral methods

    NASA Astrophysics Data System (ADS)

    Jambunathan, Krishnakumar

    Low temperature fuel cells have many potential benefits, including high efficiency, high energy density and environmental friendliness. However, logistically appealing fuels for this system, such as reformed hydrocarbons or alcohols, exhibit poor performance because of catalyst poisoning that occurs during oxidation at the anode. This research focuses on the analysis of several model fuels and catalyst materials to understand the impact of catalyst poisoning on reactivity. Two novel experimental tools were developed based upon the local measurement of catalyst performance using scanning, reactivity mapping probes. The Scanning Electrochemical Microscope (SECM) was used to directly measure the rate constant for hydrogen oxidation in the presence and absence of dissolved CO. The Scanning Differential Electrochemical Mass Spectrometer (SDEMS) was exploited to measure the partial and complete oxidation products of methanol and ethanol oxidation. The reactivity of Pt and Pt/Ru catalysts towards the hydrogen oxidation reaction in the absence and presence of adsorbed CO was elucidated using the SECM. Steady state rate constant measurements in the absence of CO showed that the rate of hydrogen oxidation reaction exceeded 1 cms-1 . Steady state rate constant measurements in the presence of CO indicated that the platinum surface is completely inactive due to adsorbed CO. Addition of as little as 6% Ru to the Pt electrode was found to significantly improve the activity of the electrode towards CO removal. SDEMS was used to study the electro-oxidation of methanol on Pt xRuy electrodes at different electrode potentials and temperatures. Screening measurements performed with the SDEMS showed that PtxRu y electrodes containing 6--40% Ru had the highest activity for methanol oxidation. Current efficiencies for CO2 were also calculated under different conditions. SDEMS was also used to study the electro-oxidation of ethanol on Pt xRuy electrodes. The reaction was found to occur more slowly than the methanol oxidation reaction. Addition of 22%--40% Ru to the Pt electrode was found to increase the current densities and lower the onset potentials. The reaction was found to occur though a parallel path mechanism, which was confirmed by the detection of ethanol and acetic acid apart from CO2.

  5. Morphological, rheological and electrochemical studies ofpoly(ethylene oxide) electrolytes containing fumed silicananoparticles

    SciTech Connect

    Xie, Jiangbing; Kerr, John B.; Duan, Robert G.; Han, Yongbong

    2003-06-01

    In this paper, the rheology and crystallization of composite Poly(Ethylene Oxide) (PEO) electrolytes were studied by dynamic mechanical analysis, DSC and polarized light microscopy. The effects of fumed silica nanoparticles on the conductivities of the polymer electrolytes at temperatures above and below their melting point were measured and related to their rheology and crystallization behavior, respectively. The electrolyte/electrode interfacial properties and cycling performances of the composite polymer electrolytes in Li/Li cells are also discussed. The measured electrochemical properties were found to depend heavily on the operational environments and sample processing history.

  6. Electrophoretically deposited graphene oxide and carbon nanotube composite for electrochemical capacitors

    NASA Astrophysics Data System (ADS)

    Ajayi, Obafunso A.; Guitierrez, Daniel H.; Peaslee, David; Cheng, Arthur; Gao, Theodore; Wong, Chee Wei; Chen, Bin

    2015-10-01

    We report a scalable one-step electrode fabrication approach for synthesizing composite carbon-based supercapacitors with synergistic outcomes. Multi-walled carbon nanotubes (MWCNTs) were successfully integrated into our modified electrophoretic deposition process to directly form composite MWCNT-GO electrochemical capacitor electrodes (where GO is graphene oxide) with superior performance to solely GO electrodes. The measured capacitance improved threefold, reaching a maximum specific capacitance of 231 F g-1. Upon thermal reduction, MWCNT-GO electrode sheet resistance decreased by a factor of 8, significantly greater than the 2× decrease of those without MWCNTs.

  7. Electrophoretically deposited graphene oxide and carbon nanotube composite for electrochemical capacitors.

    PubMed

    Ajayi, Obafunso A; Guitierrez, Daniel H; Peaslee, David; Cheng, Arthur; Gao, Theodore; Wong, Chee Wei; Chen, Bin

    2015-10-16

    We report a scalable one-step electrode fabrication approach for synthesizing composite carbon-based supercapacitors with synergistic outcomes. Multi-walled carbon nanotubes (MWCNTs) were successfully integrated into our modified electrophoretic deposition process to directly form composite MWCNT-GO electrochemical capacitor electrodes (where GO is graphene oxide) with superior performance to solely GO electrodes. The measured capacitance improved threefold, reaching a maximum specific capacitance of 231 F g(-1). Upon thermal reduction, MWCNT-GO electrode sheet resistance decreased by a factor of 8, significantly greater than the 2× decrease of those without MWCNTs. PMID:26403850

  8. Effects of Potential and Mechanical Stimulation on Oxidation of Tantalum During Electrochemical Mechanical Polishing

    NASA Astrophysics Data System (ADS)

    Gao, F.; Liang, Hong

    2012-03-01

    Metal oxidation under stress plays a significant role in many industrial applications, particularly in chemical mechanical polishing (CMP). Here we report effects of mechanical stimulation on tantalum (Ta) oxidation during CMP. A tantalum surface was polished at various anodic potentials and under different mechanical forces. A potentiostat was used to measure the anodic reaction current during electrochemical mechanical polishing (ECMP). The material removal rate (MRR) measured using atomic force microscopy (AFM) was compared with that calculated using Faraday's law. Relationship was linked (or established) between the anodic potential and a mechanical force. The MRR was a second-order polynomial function of potential at constant mechanical force, followed by a logarithmic function. It was found that more suboxides were present at extreme potentials (low and high), while substantial pentoxide was generated under intermediate potentials. A model is proposed to explain the oxidation process of Ta during ECMP. The oxidation of Ta was a function of the anodic potential and mechanical force. The ex situ method used in this study fulfilled the in situ observation on Ta oxidation in polishing. Additionally, this technique can be used to investigate oxidation of other metals.

  9. Decolourisation of simulated reactive dyebath effluents by electrochemical oxidation assisted by UV light.

    PubMed

    López-Grimau, V; Gutiérrez, M C

    2006-01-01

    This study is focused on the optimisation of the electrochemical decolourisation of textile effluents containing reactive dyes with the aim of making feasible-technically and economically-this method at industrial scale. Coloured waters were treated in continuous at low current density, to reduce the electrical consumption. Ti/PtO(x) electrodes were used to oxidize simulated dyebaths prepared with an azo/dichlorotriazine reactive dye (C.I. Reactive Orange 4). The decolourisation yield was dependent on the dyeing electrolyte (NaCl or Na(2)SO(4)). Dyeing effluents which contained from 0.5 to 20 gl(-1) of NaCl reached a high decolourisation yield, depending on the current density, immediately after the electrochemical process. These results were improved when the effluents were stored for several hours under solar light. After the electrochemical treatment the effluents were stored in a tank and exposed under different lighting conditions: UV light, solar light and darkness. The evolution of the decolourisation versus the time of storage was reported and kinetic constants were calculated. The time of storage was significantly reduced by the application of UV light. A dye mineralization study was also carried out on a concentrated dyebath. A TOC removal of 81% was obtained when high current density was applied for a prolonged treatment with recirculation. This treatment required a high electrical consumption. PMID:15893798

  10. Flexible conducting polymer/reduced graphene oxide films: synthesis, characterization, and electrochemical performance

    NASA Astrophysics Data System (ADS)

    Yang, Wenyao; Zhao, Yuetao; He, Xin; Chen, Yan; Xu, Jianhua; Li, Shibin; Yang, Yajie; Jiang, Yadong

    2015-05-01

    In this paper, we demonstrate the preparation of a flexible poly (3,4-ethylenedioxythiophene) -poly (styrenesulfonate)/reduced graphene oxide (PEDOT-PSS/RGO) film with a layered structure via a simple vacuum filtered method as a high performance electrochemical electrode. The PEDOT-PSS/RGO films are characterized by scanning electron microscopy (SEM), X-ray diffraction, Raman spectroscopy, and Fourier transform infrared (FT-IR) spectrometry. The results indicate that a layer-ordered structure is constructed in this nanocomposite during the vacuum filtering process. The electrochemical performances of the flexible films are characterized by electrochemical impedance spectroscopy, cyclic voltammetry, and galvanostatic charge/discharge. The results reveal that a 193.7 F/g highly specific capacitance of nanocomposite film is achieved at a current density of 500 mA/g. This flexible and self-supporting nanocomposite film exhibits excellent cycling stability, and the capacity retention is 90.6 % after 1000 cycles, which shows promising application as high-performance electrode materials for flexible energy-storage devices.

  11. Electrochemical tuning of layered lithium transition metal oxides for improvement of oxygen evolution reaction

    NASA Astrophysics Data System (ADS)

    Lu, Zhiyi; Wang, Haotian; Kong, Desheng; Yan, Kai; Hsu, Po-Chun; Zheng, Guangyuan; Yao, Hongbin; Liang, Zheng; Sun, Xiaoming; Cui, Yi

    2014-07-01

    Searching for low-cost and efficient catalysts for the oxygen evolution reaction has been actively pursued owing to its importance in clean energy generation and storage. While developing new catalysts is important, tuning the electronic structure of existing catalysts over a wide electrochemical potential range can also offer a new direction. Here we demonstrate a method for electrochemical lithium tuning of catalytic materials in organic electrolyte for subsequent enhancement of the catalytic activity in aqueous solution. By continuously extracting lithium ions out of LiCoO2, a popular cathode material in lithium ion batteries, to Li0.5CoO2 in organic electrolyte, the catalytic activity is significantly improved. This enhancement is ascribed to the unique electronic structure after the delithiation process. The general efficacy of this methodology is demonstrated in several mixed metal oxides with similar improvements. The electrochemically delithiated LiCo0.33Ni0.33Fe0.33O2 exhibits a notable performance, better than the benchmark iridium/carbon catalyst.

  12. Electrochemical tuning of layered lithium transition metal oxides for improvement of oxygen evolution reaction.

    PubMed

    Lu, Zhiyi; Wang, Haotian; Kong, Desheng; Yan, Kai; Hsu, Po-Chun; Zheng, Guangyuan; Yao, Hongbin; Liang, Zheng; Sun, Xiaoming; Cui, Yi

    2014-01-01

    Searching for low-cost and efficient catalysts for the oxygen evolution reaction has been actively pursued owing to its importance in clean energy generation and storage. While developing new catalysts is important, tuning the electronic structure of existing catalysts over a wide electrochemical potential range can also offer a new direction. Here we demonstrate a method for electrochemical lithium tuning of catalytic materials in organic electrolyte for subsequent enhancement of the catalytic activity in aqueous solution. By continuously extracting lithium ions out of LiCoO2, a popular cathode material in lithium ion batteries, to Li0.5CoO2 in organic electrolyte, the catalytic activity is significantly improved. This enhancement is ascribed to the unique electronic structure after the delithiation process. The general efficacy of this methodology is demonstrated in several mixed metal oxides with similar improvements. The electrochemically delithiated LiCo0.33Ni0.33Fe0.33O2 exhibits a notable performance, better than the benchmark iridium/carbon catalyst. PMID:24993836

  13. Electrochemical codeposition of vanadium oxide and polypyrrole for high-performance supercapacitor with high working voltage.

    PubMed

    Bai, Ming-Hua; Bian, Li-Jun; Song, Yu; Liu, Xiao-Xia

    2014-08-13

    Electrochemical codeposition of vanadium oxide (V2O5) and polypyrrole (PPy) is conducted from vanadyl sulfate (VOSO4) and pyrrole in their aqueous solution to get V2O5-PPy composite, during which one-dimensional growth of polypyrrole (PPy) is directed. X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR) are used to characterize the composite, while scanning electron microscopy (SEM) is used to investigate their morphologies. Cyclic voltammetry (CV), chronopotentiometry (CP) for galvanostatic charge-discharge and electrochemical impedance spectroscopy (EIS) are used to study electrochemical activities and pseudocapacitive properties of the composite. The influences of VOSO4 to pyrrole ratio in the electro-codeposition solution on morphologies and pseudocapacitive properties of the composite are discussed. Due to the organic-inorganic synergistic effect, V2O5-PPy composite exhibits good charge-storage properties in a large potential window from -1.4 to 0.6 V vs SCE, with a specific capacitance of 412 F/g at 4.5 mA/cm(2). A model supercapacitor assembled by using the V2O5-PPy composite as the electrode materials displays a high operating voltage of 2 V and so a high energy density of 82 Wh/kg (at the power density of 800 W/kg). PMID:25010464

  14. Controllable Synthesis of Formaldehyde Modified Manganese Oxide Based on Gas-Liquid Interfacial Reaction and Its Application of Electrochemical Sensing.

    PubMed

    Bai, Wushuang; Sheng, Qinglin; Nie, Fei; Zheng, Jianbin

    2015-12-30

    Controllable synthesis of manganese oxides was performed via a simple one-step synthetic method. Then obtained manganese oxides which exhibit flower-like, cloud-like, hexagon-like, and rod-like morphologies were modified by formaldehyde based on a simple self-made gas-liquid reaction device respectively and the modified manganese oxides with coral-like, scallop-like and rod-like morphology were synthesized accordingly. The obtained materials were characterized and the formation mechanism was also researched. Then the modified manganese oxides were used to fabricate electrochemical sensors to detect H2O2. Comparison of electrochemical properties between three kinds of modified manganese oxides was investigated and the best one has been successfully employed as H2O2 sensor which shows a low detection limit of 0.01 μM, high sensitivity of 162.69 μA mM(-1) cm(-2), and wide linear range of 0.05 μM-12.78 mM. The study provides a new method for controllable synthesis of metal oxides, and electrochemical application of formaldehyde modified manganese oxides will provides a new strategy for electrochemical sensing with high performance, low cost, and simple fabrication. PMID:26647786

  15. New advanced surface modification technique: titanium oxide ceramic surface implants: long-term clinical results

    NASA Astrophysics Data System (ADS)

    Szabo, Gyorgy; Kovacs, Lajos; Barabas, Jozsef; Nemeth, Zsolt; Maironna, Carlo

    2001-11-01

    The purpose of this paper is to discuss the background to advanced surface modification technologies and to present a new technique, involving the formation of a titanium oxide ceramic coating, with relatively long-term results of its clinical utilization. Three general techniques are used to modify surfaces: the addition or removal of material and the change of material already present. Surface properties can also be changed without the addition or removal of material, through the laser or electron beam thermal treatment. The new technique outlined in this paper relates to the production of a corrosion-resistant 2000-2500 A thick, ceramic oxide layer with a coherent crystalline structure on the surface of titanium implants. The layer is grown electrochemically from the bulk of the metal and is modified by heat treatment. Such oxide ceramic-coated implants have a number of advantageous properties relative to implants covered with various other coatings: a higher external hardness, a greater force of adherence between the titanium and the oxide ceramic coating, a virtually perfect insulation between the organism and the metal (no possibility of metal allergy), etc. The coated implants were subjected to various physical, chemical, electronmicroscopic, etc. tests for a qualitative characterization. Finally, these implants (plates, screws for maxillofacial osteosynthesis and dental root implants) were applied in surgical practice for a period of 10 years. Tests and the experience acquired demonstrated the good properties of the titanium oxide ceramic-coated implants.

  16. Enhanced electrochemical performance of a crosslinked polyaniline-coated graphene oxide-sulfur composite for rechargeable lithium-sulfur batteries

    NASA Astrophysics Data System (ADS)

    Moon, San; Jung, Young Hwa; Kim, Do Kyung

    2015-10-01

    Due to the extraordinarily high theoretical capacity of sulfur (1675 mAh g-1), the lithium-sulfur (Li-S) battery has been considered a promising candidate for future high-energy battery applications. Li-S batteries, however, have suffered from limited cycle lives, mainly due to the formation of soluble polysulfides, which prevent the practical application of this attractive technology. The encapsulation of sulfur with various conductive materials has addressed this issue to some extent. Nevertheless, most approaches still present partial encapsulation of sulfur and moreover require a large quantity of conductive material (typically, >30 wt%), making the use of sulfur less desirable from the viewpoint of capacity. Here, we address these chronic issues of Li-S cells by developing a graphene oxide-sulfur composite with a thin crosslinked polyaniline (PANI) layer. Graphene oxide nanosheets with large surface area, high conductivity and a uniform conductive PANI layer, which are synthesized by a layer-by-layer method, have a synergetic interaction with a large portion of the sulfur in the active material. Furthermore, a simple crosslinking process efficiently prevents polysulfide dissolution, resulting in unprecedented electrochemical performance, even with a high sulfur content (∼75%): a high capacity retention of ∼80% is observed, in addition to 97.53% of the average Coulombic efficiency being retained after 500 cycles. The performance we demonstrate represents an advance in the field of lithium-sulfur batteries for applications such as power tools.

  17. Facile and novel electrochemical preparation of a graphene-transition metal oxide nanocomposite for ultrasensitive electrochemical sensing of acetaminophen and phenacetin.

    PubMed

    Jiang, Lin; Gu, Shuqing; Ding, Yaping; Jiang, Feng; Zhang, Zhen

    2014-01-01

    A facile and novel preparation strategy based on electrochemical techniques for the fabrication of electrodeposited graphene (EGR) and zinc oxide (ZnO) nanocomposite was developed. The morphology and structure of the EGR-based nanocomposite were investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (XPS) and Raman spectroscopy. Meanwhile, the electrochemical performance of the nanocomposite was demonstrated with cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Due to the synergistic effect of EGR and ZnO nanoparticles, an ultrasensitive electrochemical sensor for acetaminophen (AC) and phenacetin (PCT) was successfully fabricated. The linearity ranged from 0.02 to 10 μM for AC and 0.06 to 10 μM for PCT with high sensitivities of 54,295.82 μA mM(-1) cm(2) for AC and 21,344.66 μA mM(-1) cm(2) for PCT, respectively. Moreover, the practical applicability was validated to be reliable and desirable in pharmaceutical detections. The excellent results showed the promise of the proposed preparation strategy of EGR-transition metal oxide nanocomposite in the field of electroanalytical chemistry. PMID:24201458

  18. Amorphous mixed-metal hydroxide nanostructures for advanced water oxidation catalysts.

    PubMed

    Gao, Y Q; Liu, X Y; Yang, G W

    2016-02-25

    The design of highly efficient, durable, and earth-abundant catalysts for the oxygen evolution reaction (OER) is crucial in order to promote energy conversion and storage processes. Here, we synthesize amorphous mixed-metal (Ni-Fe) hydroxide nanostructures with a homogeneous distribution of Ni/Fe as well as a tunable Ni/Fe ratio by a simple, facile, green and low-cost electrochemical technique, and we demonstrate that the synthesized amorphous nanomaterials possess ultrahigh activity and super long-term cycle stability in the OER process. The amorphous Ni0.71Fe0.29(OH)x nanostructure affords a current density of 10 mA cm(-2) at an overpotential of a mere 0.296 V and a small Tafel slope of 58 mV dec(-1), while no deactivation is detected in the CV testing even up to 30 000 cycles, which suggests the promising application of these amorphous nanomaterials in electrochemical oxidation. Meanwhile, the distinct catalytic activities among these amorphous Ni-Fe hydroxide nanostructures prompts us to take notice of the composition of the alloy hydroxides/oxides when studying their catalytic properties, which opens an avenue for the rational design and controllable preparation of such amorphous nanomaterials as advanced OER electrocatalysts. PMID:26864279

  19. Recent advances in heterogeneous selective oxidation catalysis for sustainable chemistry.

    PubMed

    Guo, Zhen; Liu, Bin; Zhang, Qinghong; Deng, Weiping; Wang, Ye; Yang, Yanhui

    2014-05-21

    Oxidation catalysis not only plays a crucial role in the current chemical industry for the production of key intermediates such as alcohols, epoxides, aldehydes, ketones and organic acids, but also will contribute to the establishment of novel green and sustainable chemical processes. This review is devoted to dealing with selective oxidation reactions, which are important from the viewpoint of green and sustainable chemistry and still remain challenging. Actually, some well-known highly challenging chemical reactions involve selective oxidation reactions, such as the selective oxidation of methane by oxygen. On the other hand some important oxidation reactions, such as the aerobic oxidation of alcohols in the liquid phase and the preferential oxidation of carbon monoxide in hydrogen, have attracted much attention in recent years because of their high significance in green or energy chemistry. This article summarizes recent advances in the development of new catalytic materials or novel catalytic systems for these challenging oxidation reactions. A deep scientific understanding of the mechanisms, active species and active structures for these systems are also discussed. Furthermore, connections among these distinct catalytic oxidation systems are highlighted, to gain insight for the breakthrough in rational design of efficient catalytic systems for challenging oxidation reactions. PMID:24553414

  20. Influence of hydrogen-oxidizing bacteria on the corrosion of low carbon steel: Local electrochemical investigations.

    PubMed

    Moreira, Rebeca; Schütz, Marta K; Libert, Marie; Tribollet, Bernard; Vivier, Vincent

    2014-06-01

    Low carbon steel has been considered a suitable material for component of the multi-barrier system employed on the geological disposal of high-level radioactive waste (HLW). A non negligible amount of dihydrogen (H2) is expected to be produced over the years within the geological repository due to the anoxic corrosion of metallic materials and also to the water radiolysis. The influence of the activity of hydrogen-oxidizing bacteria (HOB) and iron-reducing bacteria (IRB) on carbon steel corrosion is considered in this study because of the high availability of energetic nutriments (H2, iron oxides and hydroxides) produced in anoxic disposal conditions. Local electrochemical techniques were used for investigating the activity of IRB as a promoter of local corrosion in the presence of H2 as electron donor. A local consumption of H2 by the bacteria has been evidenced and impedance measurements indicate the formation of a thick layer of corrosion products. PMID:24177135

  1. Electrochemical analysis of polyethylenimine-modified graphene oxide supports for Pt nanoparticles catalyst electrode.

    PubMed

    Park, Jae Young; Kim, Seok

    2014-03-01

    Polyethylenimine-modified graphene oxide supported platinum electro-catalyst was synthesized by a modified sodium borohydride reduction method. As a modifier agent, polyethylenimine (PEI) was used to form coating layer onto graphene surface. To ascertain the electrochemical behavior, PEI-reduced graphene oxide (PEI-RGO) was compared with changing the PEI/RGO weight ratio of 1:0.5, 1:1 and 1:2, respectively. The morphology of electro-catalysts was observed by transmission electron microscope (TEM) and scanning electron microscope (SEM) images. In addition, lattice parameters and particle size of electro-catalysts were measured by X-ray diffraction (XRD). FT-IR spectra of catalysts were used to ascertain existence and functional group of the PEI branches on GO surface. PMID:24745236

  2. Cuprous Sulfide/Reduced Graphene Oxide Hybrid Nanomaterials: Solvothermal Synthesis and Enhanced Electrochemical Performance

    NASA Astrophysics Data System (ADS)

    He, Zhanjun; Zhu, Yabo; Xing, Zheng; Wang, Zhengyuan

    2016-01-01

    The cuprous sulfide nanoparticles (CuS NPs)-decorated reduced graphene oxide (rGO) nanocomposites have been successfully prepared via a facile and efficient solvothermal synthesis method. Scanning electron microscopy and transmission electron microscopy images demonstrated that CuS micronspheres composed of nanosheets and distributed on the rGO layer in well-monodispersed form. Fourier-transform infrared spectroscopy analyses and x-ray photoelectron spectroscopy showed that graphene oxide (GO) had been reduced to rGO. The electrochemical performances of CuS/rGO nanocomposites were investigated by cyclic voltammetry and charge/discharge techniques, which showed that the specific capacitance of CuS/rGO nanocomposites was enhanced because of the introduction of rGO.

  3. An Electrochemical Study of Frustrated Lewis Pairs: A Metal-Free Route to Hydrogen Oxidation

    PubMed Central

    2014-01-01

    Frustrated Lewis pairs have found many applications in the heterolytic activation of H2 and subsequent hydrogenation of small molecules through delivery of the resulting proton and hydride equivalents. Herein, we describe how H2 can be preactivated using classical frustrated Lewis pair chemistry and combined with in situ nonaqueous electrochemical oxidation of the resulting borohydride. Our approach allows hydrogen to be cleanly converted into two protons and two electrons in situ, and reduces the potential (the required energetic driving force) for nonaqueous H2 oxidation by 610 mV (117.7 kJ mol–1). This significant energy reduction opens routes to the development of nonaqueous hydrogen energy technology. PMID:24720359

  4. LABORATORY EVALUATION OF A MICROFLUIDIC ELECTROCHEMICAL SENSOR FOR AEROSOL OXIDATIVE LOAD

    PubMed Central

    Koehler, Kirsten; Shapiro, Jeffrey; Sameenoi, Yupaporn; Henry, Charles; Volckens, John

    2014-01-01

    Human exposure to particulate matter (PM) air pollution is associated with human morbidity and mortality. The mechanisms by which PM impacts human health are unresolved, but evidence suggests that PM intake leads to cellular oxidative stress through the generation of reactive oxygen species (ROS). Therefore, reliable tools are needed for estimating the oxidant generating capacity, or oxidative load, of PM at high temporal resolution (minutes to hours). One of the most widely reported methods for assessing PM oxidative load is the dithiothreitol (DTT) assay. The traditional DTT assay utilizes filter-based PM collection in conjunction with chemical analysis to determine the oxidation rate of reduced DTT in solution with PM. However, the traditional DTT assay suffers from poor time resolution, loss of reactive species during sampling, and high limit of detection. Recently, a new DTT assay was developed that couples a Particle-Into-Liquid-Sampler with microfluidic-electrochemical detection. This ‘on-line’ system allows high temporal resolution monitoring of PM reactivity with improved detection limits. This study reports on a laboratory comparison of the traditional and on-line DTT approaches. An urban dust sample was aerosolized in a laboratory test chamber at three atmospherically-relevant concentrations. The on-line system gave a stronger correlation between DTT consumption rate and PM mass (R2 = 0.69) than the traditional method (R2 = 0.40) and increased precision at high temporal resolution, compared to the traditional method. PMID:24711675

  5. Evidence for decoupled electron and proton transfer in the electrochemical oxidation of ammonia on Pt(100)

    DOE PAGESBeta

    Katsounaros, Ioannis; Chen, Ting; Gewirth, Andrew A.; Markovic, Nenad M.; Koper, Marc T. M.

    2016-01-12

    The two traditional mechanisms of the electrochemical ammonia oxidation consider only concerted proton-electron transfer elementary steps and thus they predict that the rate–potential relationship is independent of the pH on the pH-corrected RHE potential scale. In this letter we show that this is not the case: the increase of the solution pH shifts the onset of the NH3-to-N2 oxidation on Pt(100) to lower potentials and also leads to higher surface concentration of formed NOad before the latter is oxidized to nitrite. Therefore, we present a new mechanism for the ammonia oxidation which incorporates a deprotonation step occurring prior to themore » electron transfer. The deprotonation step yields a negatively charged surface-adsorbed species which is discharged in a subsequent electron transfer step before the N–N bond formation. The negatively charged species is thus a precursor for the formation of N2 and NO. The new mechanism should be a future guide for computational studies aiming at the identification of intermediates and corresponding activation barriers for the elementary steps. As a result, ammonia oxidation is a new example of a bond-forming reaction on (100) terraces which involves decoupled proton-electron transfer.« less

  6. Cross-flow electrochemical reactor cells, cross-flow reactors, and use of cross-flow reactors for oxidation reactions

    DOEpatents

    Balachandran, Uthamalingam; Poeppel, Roger B.; Kleefisch, Mark S.; Kobylinski, Thaddeus P.; Udovich, Carl A.

    1994-01-01

    This invention discloses cross-flow electrochemical reactor cells containing oxygen permeable materials which have both electron conductivity and oxygen ion conductivity, cross-flow reactors, and electrochemical processes using cross-flow reactor cells having oxygen permeable monolithic cores to control and facilitate transport of oxygen from an oxygen-containing gas stream to oxidation reactions of organic compounds in another gas stream. These cross-flow electrochemical reactors comprise a hollow ceramic blade positioned across a gas stream flow or a stack of crossed hollow ceramic blades containing a channel or channels for flow of gas streams. Each channel has at least one channel wall disposed between a channel and a portion of an outer surface of the ceramic blade, or a common wall with adjacent blades in a stack comprising a gas-impervious mixed metal oxide material of a perovskite structure having electron conductivity and oxygen ion conductivity. The invention includes reactors comprising first and second zones seprated by gas-impervious mixed metal oxide material material having electron conductivity and oxygen ion conductivity. Prefered gas-impervious materials comprise at least one mixed metal oxide having a perovskite structure or perovskite-like structure. The invention includes, also, oxidation processes controlled by using these electrochemical reactors, and these reactions do not require an external source of electrical potential or any external electric circuit for oxidation to proceed.

  7. Formation of electrochemically reduced graphene oxide on melamine electrografted layers and its application toward the determination of methylxanthines.

    PubMed

    Kesavan, Srinivasan; Raj, M Amal; John, S Abraham

    2016-03-01

    The current study describes the electrografting of 2,4-diamino-1,3,5-triazine (AT) groups at the surfaces of glassy carbon electrode (GCE) and indium tin oxide (ITO) through in situ diazotization of melamine. The presence of AT groups at the surface of the electrode was confirmed by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS), and cyclic voltammetry (CV). Furthermore, graphene oxide (GO) was self-assembled on AT grafted GCE. The oxygen functional groups present on the surface of GO were electrochemically reduced to form an electrochemically reduced graphene oxide (ERGO) on AT grafted electrode surface. Raman spectra show the characteristic D and G bands at 1340 and 1605 cm(-1), respectively, which confirms the successful attachment of GO on AT grafted surface, and the ratio of D and G bands was increased after the electrochemical reduction of GO. EIS shows that the electron transfer reaction of [Fe(CN)6](3-/4-) was higher at the ERGO modified electrode than at bare, AT grafted, and GO modified GCEs. The electrocatalytic activity of ERGO was investigated toward the oxidation of methylxanthines. It shows excellent electrocatalytic activity toward these methylxanthines by not only shifting their oxidation potentials toward less positive potentials but also enhancing their oxidation currents. PMID:26717896

  8. Effect of hydrothermal reaction time and alkaline conditions on the electrochemical properties of reduced graphene oxide

    NASA Astrophysics Data System (ADS)

    Vermisoglou, E. C.; Giannakopoulou, T.; Romanos, G.; Giannouri, M.; Boukos, N.; Lei, C.; Lekakou, C.; Trapalis, C.

    2015-12-01

    Reduced graphene oxide sheets (rGO) were prepared by hydrothermal treatment of aqueous dispersions of graphite oxide (GtO) applied for short (4 h) and prolonged reaction times (19-24 h). The effect of process duration as well as the alkaline conditions (pH ∼10) by addition of K2CO3 on the quality characteristics of the produced rGO materials was investigated. Both reduction and exfoliation occurred during this process as it was evidenced by FTIR and XRD data. SEM, TEM and HRTEM microscopy displayed highly exfoliated rGO materials. XPS verified that the re-establishment of the conjugated graphene network is more extensive for prolonged times of hydrothermal processing in accordance to Raman spectroscopy measurements. The sample produced under alkaline conditions bore fewer defects and almost 5 times higher BET surface area (∼181 m2/g) than the sample with no pH adjustment (∼34 m2/g) for the same hydrothermal reaction time (19 h), attributed to the developed microporosity. The specific capacitance of this material estimated by electrochemical impedance using three-electrode cell and KCl aqueous solution as an electrolyte was ∼400-500 F/g. When EDLC capacitors were fabricated from rGO materials the electrochemical testing in organic electrolyte i.e. TEABF4 in PC, revealed that the shortest hydrothermal reaction time (4 h) was more efficient resulting in capacitance around 60 F/g.

  9. Selective oxidation of ethane using the Au|YSZ|Ag electrochemical membrane system

    SciTech Connect

    Hamakawa, Satoshi; Sato, Koichi; Hayakawa, Takashi; York, A.P.E.; Tsunoda, Tatsuo; Suzuki, Kunio; Shimizu, Masao; Takehira, Katsuomi

    1997-01-01

    The catalytic conversion of ethane to acetaldehyde on an inert gold electrode has been studied using the electrochemical membrane reactor with yttria-stabilized zirconia (YSZ) solid electrolyte at 475 C. On applying a direct current to the reaction cell, 5% ethane in N{sub 2}, Au|YSZ|Ag, 100% O{sub 2}, acetaldehyde was formed and the formation rate increased linearly with increasing current. Selectivities to acetaldehyde and carbon dioxide were 45 and 55%, respectively. The addition of oxygen to the ethane-mixed gas in the anode space did not affect the acetaldehyde formation. The use of YSZ powder as a fixed bed catalyst under the mixed gas flow of ethane and oxygen at 450 to 600 C resulted in the formation of carbon monoxide, carbon dioxide, and ethene. Even the use of N{sub 2}O instead of oxygen resulted in no formation of acetaldehyde. Hence, it is likely that partial oxidation of ethane to acetaldehyde was carried out by the oxygen species transferred electrochemically through the YSZ which appeared at the gold-YSZ-gas triple-phase boundary. From the results of ethanol oxidation over the Au|YSZ|Ag system, the following mechanism was proposed: ethane is dehydrogenated to an ethyl radical, then converted to ethoxide, and finally to acetaldehyde by the oxygen species transferred through the YSZ.

  10. Joining of Oxide Dispersion Strengthened Steels for Advanced Reactors

    NASA Astrophysics Data System (ADS)

    Baker, B. W.; Brewer, L. N.

    2014-12-01

    The design, manufacture, and experimental analysis of structural materials capable of operation in the high temperatures, corrosive environments, and radiation damage spectra of future reactor designs remain one of the key pacing items for advanced reactor designs. The most promising candidate structural materials are vanadium-based refractory alloys, silicon carbide composites and oxide dispersion strengthened steels. Of these, oxide dispersion strengthened steels are a likely near-term candidate to meet required demands. This paper reviews different variants of oxide dispersion strengthened steels and discusses their capability with regard to high-temperature strength, corrosion resistance, and radiation damage resistance. Additionally, joining of oxide dispersion strengthened steels, which has been cited as a limiting factor preventing their use, is addressed and reviewed. Specifically, friction stir welding of these steels is reviewed as a promising joining method for oxide dispersion strengthened steels.

  11. Recent advances of lanthanum-based perovskite oxides for catalysis

    DOE PAGESBeta

    Zhu, Huiyuan; Zhang, Pengfei; Dai, Sheng

    2015-09-21

    There is a need to reduce the use of noble metal elements especially in the field of catalysis, where noble metals are ubiquitously applied. To this end, perovskite oxides, an important class of mixed oxide, have been attracting increasing attention for decades as potential replacements. Benefiting from the extraordinary tunability of their compositions and structures, perovskite oxides can be rationally tailored and equipped with targeted physical and chemical properties e.g. redox behavior, oxygen mobility, and ion conductivity for enhanced catalysis. Recently, the development of highly efficient perovskite oxide catalysts has been extensively studied. This review article summarizes the recent developmentmore » of lanthanum-based perovskite oxides as advanced catalysts for both energy conversion applications and traditional heterogeneous reactions.« less

  12. Recent advances of lanthanum-based perovskite oxides for catalysis

    SciTech Connect

    Zhu, Huiyuan; Zhang, Pengfei; Dai, Sheng

    2015-09-21

    There is a need to reduce the use of noble metal elements especially in the field of catalysis, where noble metals are ubiquitously applied. To this end, perovskite oxides, an important class of mixed oxide, have been attracting increasing attention for decades as potential replacements. Benefiting from the extraordinary tunability of their compositions and structures, perovskite oxides can be rationally tailored and equipped with targeted physical and chemical properties e.g. redox behavior, oxygen mobility, and ion conductivity for enhanced catalysis. Recently, the development of highly efficient perovskite oxide catalysts has been extensively studied. This review article summarizes the recent development of lanthanum-based perovskite oxides as advanced catalysts for both energy conversion applications and traditional heterogeneous reactions.

  13. Nanoporous zeolite and solid-state electrochemical devices for nitrogen-oxide sensing

    NASA Astrophysics Data System (ADS)

    Yang, Jiun-Chan

    Solid-state electrochemical gas sensing devices composed of stabilized-zirconia electrolyte have used extensively in the automobile and chemical industry. Two types of electrochemical devices, potentiometric and amperometric, were developed in this thesis for total NOx (NO + NO2) detection in harsh environments. In potentiometric devices, Pt covered with Pt containing zeolite Y (PtY) and WO3 were examined as the two electrode materials. Significant reactivity differences toward NOx between PtY and WO 3 led to the difference in non-electrochemical reactions and resulted in a electrode potential. With gases passing through a PtY filter, it was possible to remove interferences from 2000 ppm CO, 800 ppm propane, 10 ppm NH3, as well as to minimize effects of 1˜13% O2, CO2, and H2O. Total NOx concentration was measured by maintaining a temperature difference between the filter and the sensor. The sensitivity was significantly improved by connecting sensors in series. Amperometic devices were also developed to detect NOx passing through the PtY filter. By applying a low anodic potential of 80 mV, NO in the NOx equilibrated mixture can be oxidized at a Pt working electrode on the YSZ electrolyte at 500°C. The PtY can be held separate from the YSZ or coated onto the YSZ as a film. This design was demonstrated to exhibit total-NOx detection capability, a low NOx detection limit (< 1 ppm), high NOx selectivity relative to CO and oxygen, and linear dependence on NOx concentration. The non-electrochemical reactions around the triple-phase boundary were studied to understand the origin of the superior performance of WO3 on potentiometric NOx sensing. From TPD, DRIFTS, XRD, Raman, and catalytic activity measurements, the interfacial reactions between WO 3 and YSZ were found to dramatically reduce the NOx catalytic activity of YSZ. WO3 reacted with surface Y2O3 on YSZ and formed less catalytically active yttrium tungsten oxides and monoclinic ZrO2, which suppressed the non-electrochemical reactions around the triple-phase boundary. These two products also decreased the oxygen vacancy density around the triple-phase boundary, slowed down the electrochemical oxygen reduction reaction, and in turn increased the NOx signal. The surface nanostructure of electrodes was modified by wet chemical processes to change the non-electrochemical NOx reactions. A thin WO3 coating prepared from the peroxytungstate solution with well-defined triple-phase boundaries resulted in higher sensitivity and better response times than the electrode fabricated from commercial WO3 powders. The electrodeposited porous Pt layer greatly increased the surface area and led to a similar catalytic activity with PtY on NOx sensing. The modified electrodes demonstrated the importance of the surface nanostructure and interfacial species for potentiometric NOx sensing. The sensors composed of tungsten/H2O2 deposited sensing electrodes and more hydrothermal stable Pt-loaded siliceous zeolite Y (PtSY) reference electrodes have stable NO2 signal at 5-10% water in 600°C.

  14. Electrochemical measurements bearing on the oxidation state of the Skaergaard Layered Intrusion

    NASA Astrophysics Data System (ADS)

    Kersting, Annie B.; Arculus, Richard J.; Delano, John W.; Loureiro, Daniel

    1989-07-01

    The oxygen fugacities (fO2's) of magnetically-concentrated fractions (MCF) of three rock samples from the Skaergaard Layered Intrusion were measured between 800 1150° C using oxygen-specific, solid zirconia electrolytes at atmospheric pressure. Two of the bulk rock samples (an oxide cumulate and an oxide-bearing gabbro) are from the Middle Zone (MZ) and the other (an olivine plagioclase orthocumulate) is from the Lower Zone (LZ). All MCF define fO2 versus T arrays that lie 1.5 0.5 log units above the fayalite-magnetite-quartz (FMQ) buffer. Experiments with different cell-imposed initial redox states (one from a reduced direction and one from an oxidized direction) were run on each sample in an attempt to achieve experimental reversibility. This was accomplished by imposing a known redox memory on the galvanic cell prior to loading each sample. Reversibility for each sample agreed to better than 0.2 of a log unit. Irreversible autoreduction of 0.2 of a log unit was observed on the two MZ samples at temperatures exceeding 1065° C. Scanning electron microscope and electron microprobe study of pre- and post-run products shows that reaction and textural re-equilibration occurred among the oxide phase assemblages under the experimental conditions employed. Careful characterization of pre- and post-run assemblages is clearly necessary before adequate interpretation of the experimental results can be made in these types of electrochemical studies. Different approaches to investigations of the fO2 of the Skaergaard Intrusion, be it thermodynamic calculations or experimental methods, should yield concordant results or at least understandable discrepancies. Calculated fO2's using thermobarometry applied to the ilmenite-magnetite pairs in the post-experimental assemblages agree with the experimentally determined fO2's to within one log unit at a given temperature. These results are also consistent with previously calculated fO2 values (Buddington and Lindsley 1964; Morse et al. 1980), but are considerably more oxidized than a previous electrolyte-based fO2 study of a different sample suite from the Skaergaard (Sato and Valenza 1980) that include values close to the iron-wustite (IW) buffer from both MZ and LZ oxide separates. Differences between this electrochemical study and that of Sato and Valenza (1980) may be due to variations in the level of indigenous (or curatorially-introduced) carbon in the samples studied. Despite a number of experimental difficulties, electrochemical cells can provide an accurate and precise method of determining the oxygen fugacity of naturally occurring, complex oxide assemblages. Tight experimental reversals and reproducible values obtained in heating and cooling cycles are an indication of the precision and accuracy of the data recoverable with electrochemical cells.

  15. Studies on electrochemical recovery of silver from simulated waste water from Ag(II)/Ag(I) based mediated electrochemical oxidation process.

    PubMed

    Chandrasekara Pillai, K; Chung, Sang Joon; Moon, Il-Shik

    2008-11-01

    In the Ag(II)/Ag(I) based mediated electrochemical oxidation (MEO) process, the spent waste from the electrochemical cell, which is integrated with the scrubber columns, contains high concentrations of precious silver as dissolved ions in both the anolyte and the catholyte. This work presents an electrochemical developmental study for the recovery of silver from simulated waste water from Ag(II)/Ag(I) based MEO process. Galvanostatic method of silver deposition on Ti cathode in an undivided cell was used, and the silver recovery rate kinetics of silver deposition was followed. Various experimental parameters, which have a direct bearing on the metal recovery efficiency, were optimized. These included studies with the nitric acid concentration (0.75-6M), the solution stirring rate (0-1400 rpm), the inter-electrode distance between the anode and the cathode (2-8 cm), the applied current density (29.4-88.2 mA cm(-2)), and the initial Ag(I) ion concentration (0.01-0.2M). The silver recovered by the present electrodeposition method was re-dissolved in 6M nitric acid and subjected to electrooxidation of Ag(I) to Ag(II) to ascertain its activity towards Ag(II) electrogeneration from Ag(I), which is a key factor for the efficient working of MEO process. Our studies showed that the silver metal recovered by the present electrochemical deposition method could be reused repeatedly for MEO process with no loss in its electrochemical activity. Some work on silver deposition from sulfuric acid solution of different concentrations was also done because of its promising features as the catholyte in the Ag(II) generating electrochemical cell used in MEO process, which include: (i) complete elimination of poisonous NO(x) gas liberation in the cathode compartment, (ii) reduced Ag(+) ion migration across Nafion membrane from anolyte to catholyte thereby diminished catholyte contamination, and (iii) lower cell voltage and hence lesser power consumption. PMID:18762320

  16. Advanced oxidation processes with coke plant wastewater treatment.

    PubMed

    Krzywicka, A; Kwarciak-Koz?owska, A

    2014-01-01

    The aim of this study was to determine the most efficient method of coke wastewater treatment. This research examined two processes - advanced oxidation with Fenton and photo-Fenton reaction. It was observed that the use of ultraviolet radiation with Fenton process had a better result in removal of impurities. PMID:24804662

  17. Direct electrochemical oxidation of S-captopril using gold electrodes modified with graphene-AuAg nanocomposites

    PubMed Central

    Pogacean, Florina; Biris, Alexandru R; Coros, Maria; Lazar, Mihaela Diana; Watanabe, Fumiya; Kannarpady, Ganesh K; Al Said, Said A Farha; Biris, Alexandru S; Pruneanu, Stela

    2014-01-01

    In this paper, we present a novel approach for the electrochemical detection of S-captopril based on graphene AuAg nanostructures used to modify an Au electrode. Multi-layer graphene (Gr) sheets decorated with embedded bimetallic AuAg nanoparticles were successfully synthesized catalytically with methane as the carbon source. The two catalytic systems contained 1.0 wt% Ag and 1.0 wt% Au, while the second had a larger concentration of metals (1.5 wt% Ag and 1.5 wt% Au) and was used for the synthesis of the Gr-AuAg-1 and Gr-AuAg-1.5 multicomponent samples. High-resolution transmission electron microscopy analysis indicated the presence of graphene flakes that had regular shapes (square or rectangular) and dimensions in the tens to hundreds of nanometers. We found that the size of the embedded AuAg nanoparticles varied between 5 and 100 nm, with the majority being smaller than 20 nm. Advanced scanning transmission electron microscopy studies indicated a bimetallic characteristic of the metallic clusters. The resulting Gr-AuAg-1 and Gr-AuAg-1.5 samples were used to modify the surface of commonly used Au substrates and subsequently employed for the direct electrochemical oxidation of S-captopril. By comparing the differential pulse voltammograms recorded with the two modified electrodes at various concentrations of captopril, the peak current was determined to be well-defined, even at relatively low concentration (10−5 M), for the Au/Gr-AuAg-1.5 electrode. In contrast, the signals recorded with the Au/Gr-AuAg-1 electrode were poorly defined within a 5×10−6 to 5×10−3 M concentration range, and many of them overlapped with the background. Such composite materials could find significant applications in nanotechnology, sensing, or nanomedicine. PMID:24596464

  18. Surface Composition, Work Function, and Electrochemical Characteristics of Gallium-Doped Zinc Oxide

    SciTech Connect

    Ratcliff, E. L.; Sigdel, A. K.; Macech, M. R.; Nebesny, K.; Lee, P. A.; Ginley, D. S.; Armstrong, N. R.; Berry, J. J.

    2012-06-30

    Gallium-doped zinc oxide (GZO) possesses the electric conductivity, thermal stability, and earth abundance to be a promising transparent conductive oxide replacement for indium tin oxide electrodes in a number of molecular electronic devices, including organic solar cells and organic light emitting diodes. The surface chemistry of GZO is complex and dominated by the hydrolysis chemistry of ZnO, which influences the work function via charge transfer and band bending caused by adsorbates. A comprehensive characterization of the surface chemical composition and electrochemical properties of GZO electrodes is presented, using both solution and surface adsorbed redox probe molecules. The GZO surface is characterized using monochromatic X-ray photoelectron spectroscopy and ultraviolet photoelectron spectroscopy after the following pretreatments: (i) hydriodic acid etch, (ii) potassium hydroxide etch, (iii) RF oxygen plasma etching, and (iv) high-vacuum argon-ion sputtering. The O 1s spectra for the GZO electrodes have contributions from the stoichiometric oxide lattice, defects within the lattice, hydroxylated species, and carbonaceous impurities, with relative near-surface compositions varying with pretreatment. Solution etching procedures result in an increase of the work function and ionization potential of the GZO electrode, but yield different near surface Zn:Ga atomic ratios, which significantly influence charge transfer rates for a chemisorbed probe molecule. The near surface chemical composition is shown to be the dominant factor in controlling surface work function and significantly influences the rate of electron transfer to both solution and tethered probe molecules.

  19. Advanced Launch System advanced development oxidizer turbopump program: Technical implementation plan

    NASA Technical Reports Server (NTRS)

    Ferlita, F.

    1989-01-01

    The Advanced Launch Systems (ALS) Advanced Development Oxidizer Turbopump Program has designed, fabricated and demonstrated a low cost, highly reliable oxidizer turbopump for the Space Transportation Engine that minimizes the recurring cost for the ALS engines. Pratt and Whitney's (P and W's) plan for integrating the analyses, testing, fabrication, and other program efforts is addressed. This plan offers a comprehensive description of the total effort required to design, fabricate, and test the ALS oxidizer turbopump. The proposed ALS oxidizer turbopump reduces turbopump costs over current designs by taking advantage of design simplicity and state-of-the-art materials and producibility features without compromising system reliability. This is accomplished by selecting turbopump operating conditions that are within known successful operating regions and by using proven manufacturing techniques.

  20. Study and characterization of porous copper oxide produced by electrochemical anodization for radiometric heat absorber

    PubMed Central

    2014-01-01

    The aim of this work is to optimize the different parameters for realization of an absorbing cavity to measure the incident absolute laser energy. Electrochemical oxidation is the background process that allowed the copper blackening. A study of the blackened surface quality was undertaken using atomic force microscopy (AFM) analysis and ultraviolet-visible-infrared spectrophotometry using a Shimadzu spectrophotometer. A two-dimensional and three-dimensional visualization by AFM of the formed oxide coating showed that the copper surfaces became porous after electrochemical etching with different roughness. This aspect is becoming more and more important with decreasing current density anodization. In a 2 mol L -1 of NaOH solution, at a temperature of 90°C, and using a 16 mA cm2 constant density current, the copper oxide formed has a reflectivity of around 3% in the spectral range between 300 and 1,800 nm. Using the ‘mirage effect’ technique, the obtained Cu2O diffusivity and thermal conductivity are respectively equal to (11.5 ± 0.5) 10 to 7 m2 s-1 and (370 ± 20) Wm-1 K-1. This allows us to consider that our Cu2O coating is a good thermal conductor. The results of the optical and thermal studies dictate the choice of the cavity design. The absorbing cavity is a hollow cylinder machined to its base at an angle of 30°. If the included angle of the plane is 30° and the interior surface gives specular reflection, an incoming ray parallel to the axis will undergo five reflections before exit. So the absorption of the surface becomes closely near 0.999999. PMID:25349555

  1. Study and characterization of porous copper oxide produced by electrochemical anodization for radiometric heat absorber

    NASA Astrophysics Data System (ADS)

    Ben Salem, Sonia; Achour, Zahra Ben; Thamri, Kamel; Touayar, Oualid

    2014-10-01

    The aim of this work is to optimize the different parameters for realization of an absorbing cavity to measure the incident absolute laser energy. Electrochemical oxidation is the background process that allowed the copper blackening. A study of the blackened surface quality was undertaken using atomic force microscopy (AFM) analysis and ultraviolet-visible-infrared spectrophotometry using a Shimadzu spectrophotometer. A two-dimensional and three-dimensional visualization by AFM of the formed oxide coating showed that the copper surfaces became porous after electrochemical etching with different roughness. This aspect is becoming more and more important with decreasing current density anodization. In a 2 mol L -1 of NaOH solution, at a temperature of 90°C, and using a 16 mA cm2 constant density current, the copper oxide formed has a reflectivity of around 3% in the spectral range between 300 and 1,800 nm. Using the `mirage effect' technique, the obtained Cu2O diffusivity and thermal conductivity are respectively equal to (11.5 ± 0.5) 10 to 7 m2 s-1 and (370 ± 20) Wm-1 K-1. This allows us to consider that our Cu2O coating is a good thermal conductor. The results of the optical and thermal studies dictate the choice of the cavity design. The absorbing cavity is a hollow cylinder machined to its base at an angle of 30°. If the included angle of the plane is 30° and the interior surface gives specular reflection, an incoming ray parallel to the axis will undergo five reflections before exit. So the absorption of the surface becomes closely near 0.999999.

  2. Study and characterization of porous copper oxide produced by electrochemical anodization for radiometric heat absorber.

    PubMed

    Ben Salem, Sonia; Achour, Zahra Ben; Thamri, Kamel; Touayar, Oualid

    2014-01-01

    The aim of this work is to optimize the different parameters for realization of an absorbing cavity to measure the incident absolute laser energy. Electrochemical oxidation is the background process that allowed the copper blackening. A study of the blackened surface quality was undertaken using atomic force microscopy (AFM) analysis and ultraviolet-visible-infrared spectrophotometry using a Shimadzu spectrophotometer. A two-dimensional and three-dimensional visualization by AFM of the formed oxide coating showed that the copper surfaces became porous after electrochemical etching with different roughness. This aspect is becoming more and more important with decreasing current density anodization. In a 2 mol L(-1) of NaOH solution, at a temperature of 90°C, and using a 16 mA cm(2) constant density current, the copper oxide formed has a reflectivity of around 3% in the spectral range between 300 and 1,800 nm. Using the 'mirage effect' technique, the obtained Cu2O diffusivity and thermal conductivity are respectively equal to (11.5 ± 0.5) 10 to 7 m(2) s(-1) and (370 ± 20) Wm(-1) K(-1). This allows us to consider that our Cu2O coating is a good thermal conductor. The results of the optical and thermal studies dictate the choice of the cavity design. The absorbing cavity is a hollow cylinder machined to its base at an angle of 30°. If the included angle of the plane is 30° and the interior surface gives specular reflection, an incoming ray parallel to the axis will undergo five reflections before exit. So the absorption of the surface becomes closely near 0.999999. PMID:25349555

  3. Composite electrodes for advanced electrochemical applications. Quarterly report for the period July 1 - September 30, 1999

    SciTech Connect

    Kovach, Chris

    1999-10-01

    The electrochemical industry is one of the most highly energy-intensive industries today. However, there have been no significant advances in the electrodes that these industries use. The dimensionally stable anode (DSA), which ELTECH introduced under a license agreement, has been the industry standard for the past twenty-five years. But, DSAs are nearing the end of their technological prevalence. The principal problems with DSAs include high capital and operating cost, and the proprietary nature of the technology. In addition, DSAs experience problems that include contamination of the process solution by anode materials, failure when the electrocatalytic coating peels from under attack, generally low anode performance due to inherent limitations in operating current density, and short anode lifetime because of corrosion. The proposed innovation combines the low electrical resistance of copper with the corrosion resistance of electrically conductive diamond to achieve energy-efficient, long-lifetime electrodes for electrochemistry. The proposed work will ultimately develop a composite electrode that consists of a copper substrate, a conductive diamond coating, and a catalytic precious metal coating. The scope of the current work includes preparation, testing, and evaluation of diamond-coated titanium electrodes.

  4. Development of Advanced Electrochemical Emission Spectroscopy for Monitoring Corrosion in Simulated DOE Liquid Waste

    SciTech Connect

    Macdonald, Digby D.; Liu, Sue; Sikora, Elizbieta; Liu, Jun

    2001-06-01

    Fracture of AISI 4340 steel in concentrated sodium hydroxide solution has been monitored by measuring the coupling current that flows between the crack and the external surfaces. The results clearly demonstrate that positive current flows from the crack to the external cathodes (through the solution) during crack growth of AISI 4340 steel in concentrated (6 to12 M) sodium hydroxide solution at 70 C. The (electron) coupling current contains periodic noise that is attributed to fracture events occurring at the crack front, with the amplitude of the noise and the mean current increasing with crack growth rate. The characteristic shape of the individual transients in the noise at lower SCC crack growth rate is a rapid drop followed by slow recovery. The form of the noise in the coupling current during SCC at high NaOH concentration (8 M and 12 M) is attributed to overlap of many cracks propagating simultaneously through micro fracture events along grain boundaries. The discrete events, which have a dimension of about 49 {micro}m, are postulated to be hydrogen induced, and the mechanism of caustic cracking of AISI 4340 steel is considered to be hydrogen embrittlement along grain boundaries. Measurement of the electrochemical noise is shown to be capable of detecting and distinguishing between uniform corrosion and stress corrosion cracking in the steel/NaOH system. The coupling current data are consistent with a hydrogen embrittlement mechanism for crack advance.

  5. V{sub 2}O{sub 5} xerogel-poly(ethylene oxide) hybrid material: Synthesis, characterization, and electrochemical properties

    SciTech Connect

    Guerra, Elidia M.; Ciuffi, Katia J.; Oliveira, Herenilton P. . E-mail: herepo@ffclrp.usp.br

    2006-12-15

    In this work, we report the synthesis, characterization, and electrochemical properties of vanadium pentoxide xerogel-poly(ethylene oxide) (PEO) hybrid materials obtained by varying the average molecular weight of the organic component as well as the components' ratios. The materials were characterized by X-ray diffraction, ultraviolet/visible and infrared spectroscopies, thermogravimetric analysis, scanning electron microscopy, electron paramagnetic resonance, and cyclic voltammetry. Despite the presence of broad and low intensity peaks, the X-ray diffractograms indicate that the lamellar structure of the vanadium pentoxide xerogel is preserved, with increase in the interplanar spacing, giving evidence of a low-crystalline structure. We found that the electrochemical behaviour of the hybrid materials is quite similar to that found for the V{sub 2}O{sub 5} xerogel alone, and we verified that PEO leads to stabilization and reproducibility of the Li{sup +} electrochemical insertion/de-insertion into the V{sub 2}O{sub 5} xerogel structure, which makes these materials potential components of lithium ion batteries. - Graphical abstract: The synthesis, structural and electrochemical properties of vanadium pentoxide xerogel-poly(ethylene oxide) hybrid materials have been described. Despite the presence of broad and low intensity peaks, the X-ray diffractograms indicate that the lamellar structure of the vanadium pentoxide xerogel is preserved. The cy voltammetry technique demonstrated that PEO intercalation provides an improvement in the electrochemical properties, mainly with respect to the lithium electroinsertion process into the oxide matrix.

  6. Effluent characteristics of advanced treatment for biotreated coking wastewater by electrochemical technology using BDD anodes.

    PubMed

    Wang, Chunrong; Zhang, Mengru; Liu, Wei; Ye, Min; Su, Fujin

    2015-05-01

    Effluent of biotreated coking wastewater comprises hundreds of organic and inorganic pollutants and has the characteristics of high toxicity and difficult biodegradation; thus, its chemical oxygen demand cannot meet drainage standards in China. A boron-doped diamond anode was selected for advanced treatment of biotreated coking wastewater, and considering the efficiency of the removal of total organic carbon and energy consumption, optimal conditions were obtained as current density of 75 mA cm(-2), electrolysis time of 1.5 h, and an electrode gap of 1.0 cm in an orthogonal test. Effluent characteristics were investigated at different electrolysis times. The ratio of the 5-day biochemical oxygen demand (BOD5) to the chemical oxygen demand increased from an initial value of 0.05 to 0.65 at 90 min. Fluorescence spectra were used to evaluate the evolution of refractory organics. Two fluorescence peaks for raw wastewater, corresponding to an aromatic protein-like substance II and humic acid-like substance, weakened at 30 and at 90 min, only the former was detected. The specific oxygen uptake rate was used to assess effluent toxicity, and an obvious inhibition effect was found at 15 min; then, it was significantly faded at 30 and 45 min. The BOD5/NO3 (-)-N ratio increased from an initial value of 0.48 to 1.25 at 45 min and then gradually dropped to 0.69 at 90 min. According to the above effluent characteristics, it is strongly suggested that electrochemical technology using boron-doped diamond anodes is combined with biological denitrification technology for the advanced treatment of biotreated coking wastewater. PMID:25432427

  7. Oxidative Lipidomics Coming of Age: Advances in Analysis of Oxidized Phospholipids in Physiology and Pathology

    PubMed Central

    Pitt, Andrew R.

    2015-01-01

    Abstract Significance: Oxidized phospholipids are now well recognized as markers of biological oxidative stress and bioactive molecules with both pro-inflammatory and anti-inflammatory effects. While analytical methods continue to be developed for studies of generic lipid oxidation, mass spectrometry (MS) has underpinned the advances in knowledge of specific oxidized phospholipids by allowing their identification and characterization, and it is responsible for the expansion of oxidative lipidomics. Recent Advances: Studies of oxidized phospholipids in biological samples, from both animal models and clinical samples, have been facilitated by the recent improvements in MS, especially targeted routines that depend on the fragmentation pattern of the parent molecular ion and improved resolution and mass accuracy. MS can be used to identify selectively individual compounds or groups of compounds with common features, which greatly improves the sensitivity and specificity of detection. Application of these methods has enabled important advances in understanding the mechanisms of inflammatory diseases such as atherosclerosis, steatohepatitis, leprosy, and cystic fibrosis, and it offers potential for developing biomarkers of molecular aspects of the diseases. Critical Issues and Future Directions: The future in this field will depend on development of improved MS technologies, such as ion mobility, novel enrichment methods and databases, and software for data analysis, owing to the very large amount of data generated in these experiments. Imaging of oxidized phospholipids in tissue MS is an additional exciting direction emerging that can be expected to advance understanding of physiology and disease. Antioxid. Redox Signal. 22, 1646–1666. PMID:25694038

  8. Effect of additive on electrochemical corrosion properties of plasma electrolytic oxidation coatings formed on CP Ti under different processing frequency

    NASA Astrophysics Data System (ADS)

    Babaei, Mahdi; Dehghanian, Changiz; Vanaki, Mojtaba

    2015-12-01

    The plasma electrolytic oxidation (PEO) coating containing zirconium oxide was fabricated on CP Ti at different processing frequencies viz., 100 Hz and 1000 Hz in a (Na2ZrO3, Na2SiO3)-additive containing NaH2PO4-based solution, and long-term electrochemical corrosion behavior of the coatings was studied using electrochemical impedance spectroscopy (EIS) in 3.5 wt.% NaCl solution. Electrochemical degradation behavior of two-layered coatings formed at different frequencies was turned out to be governed by concentration of electrolyte additive. With increasing additive concentration, the coating obtained at frequency of 1000 Hz exhibited enhanced corrosion resistance. However, corrosion resistance of the coating prepared at 100 Hz was found to decrease with increased additive, which was attributed to intensified microdischarges damaging the protective effect of inner layer. Nevertheless, the electrolyte additive was found to mitigate the long-term degradation of the coatings to a significant extent.

  9. Spontaneous electrochemical treatment for sulfur recovery by a sulfide oxidation/vanadium(V) reduction galvanic cell.

    PubMed

    Kijjanapanich, Pimluck; Kijjanapanich, Pairoje; Annachhatre, Ajit P; Esposito, Giovanni; Lens, Piet N L

    2015-02-01

    Sulfide is the product of the biological sulfate reduction process which gives toxicity and odor problems. Wastewaters or bioreactor effluents containing sulfide can cause severe environmental impacts. Electrochemical treatment can be an alternative approach for sulfide removal and sulfur recovery from such sulfide rich solutions. This study aims to develop a spontaneous electrochemical sulfide oxidation/vanadium(V) reduction cell with a graphite electrode system to recover sulfide as elemental sulfur. The effects of the internal and external resistance on the sulfide removal efficiency and electrical current produced were investigated at different pH. A high surface area of the graphite electrode is required in order to have as less internal resistance as possible. In this study, graphite powder was added (contact area >633 cm(2)) in order to reduce the internal resistance. A sulfide removal efficiency up to 91% and electrical charge of more than 400 C were achieved when using five graphite rods supplemented with graphite powder as the electrode at an external resistance of 30 Ω and a sulfide concentration of 250 mg L(-1). PMID:25463589

  10. Electrochemically reduced graphene oxide/carbon nanotubes composites as binder-free supercapacitor electrodes

    NASA Astrophysics Data System (ADS)

    Yang, Qin; Pang, Siu-Kwong; Yung, Kam-Chuen

    2016-04-01

    Binder-free composites of electrochemically reduced graphene oxide (ecrGO) and multiwalled carbon nanotubes (MWCNTs) were fabricated as supercapacitors electrodes operating in aqueous systems. GO was found to be electrochemically reduced according to the XRD and Raman data. Therefore, this facile and controllable method was applied to reduce GO in the GO/MWCNTs composites, generating ecrGO/MWCNTs composites. The ecrGO/MWCNTs composites exhibit higher specific capacitance (Csp) than ecrGO because the intercalation of MWCNTs into ecrGO sheets increases the surface areas, according to the TEM, XRD and N2 adsorption-desorption results. The composites with different mass ratios of GO to MWCNTs (10:1, 5:1, 1:1, 1:5, 1:10) were investigated. The ecrGO/MWCNTs composite (GO: MWCNTs = 5:1) showed the highest Csp from the cyclic voltammetry results at a scan rate of 10 mV s-1, and it expressed Csp of 165 F g-1 at a current density of 1 A g-1 and 93% retention after 4000 cycles of charge/discharge. When the mass ratio of GO to MWCNTs further decreases to 1:10, the Csp of the composites declines, and the ecrGO/MWCNTs composite (GO: MWCNTs = 1:10) performs a nearly pure double-layer capacitor. However, the composites containing more MWCNTs can maintain better capacitive behavior at higher rates of charge/discharge.

  11. Defect physics vis-à-vis electrochemical performance in layered mixed-metal oxide cathode materials

    NASA Astrophysics Data System (ADS)

    Hoang, Khang; Johannes, Michelle

    Layered mixed-metal oxides with different compositions of (Ni,Co,Mn) [NCM] or (Ni,Co,Al) [NCA] have been used in commercial lithium-ion batteries. Yet their defect physics and chemistry is still not well understood, despite having important implications for the electrochemical performance. In this presentation, we report a hybrid density functional study of intrinsic point defects in the compositions LiNi1/3Co1/3Mn1/3O2 (NCM1/3) and LiNi1/3Co1/3Al1/3O2 (NCA1/3) which can also be regarded as model compounds for NCM and NCA. We will discuss defect landscapes in NCM1/3 and NCA1/3 under relevant synthesis conditions with a focus on the formation of metal antisite defects and its implications on the electrochemical properties and ultimately the design of NCM and NCA cathode materials.

  12. Multi-resistive Reduced Graphene Oxide Diode with Reversible Surface Electrochemical Reaction induced Carrier Control

    PubMed Central

    Seo, Hyungtak; Ahn, Seungbae; Kim, Jinseo; Lee, Young-Ahn; Chung, Koo-Hyun; Jeon, Ki-Joon

    2014-01-01

    The extended application of graphene-based electronic devices requires a bandgap opening in order to realize the targeted device functionality. Since the bandgap tuning of pristine graphene is limited to 360 meV, the chemical modification of graphene is considered essential to achieve a large bandgap opening at the expense of electrical properties degradation. Reduced graphene oxide (RGO) has attracted significant interest for fabricating graphene-based semiconductors since it has several advantages over other forms of chemically modified graphene; such as tunable bandgap opening, decent electrical properties, and easy synthesis. Because of the reduced bonding nature of RGO, the role of metastable oxygen in the RGO matrix is recently highlighted and it may offer emerging ionic devices. In this study, we show that multi-resistivity RGO/n-Si diodes can be obtained by controlling the RGO thickness at a nanometer scale. This is made possible by (1) a metastable lattice-oxygen drift within bulk RGO and (2) electrochemical ambient hydroxyl (OH) formation at the RGO surface. The effect demonstrated in a p-RGO/n-Si heterojunction diode is equivalent to electrochemically driven reversible electronic manipulation and therefore provides an important basis for the application of O bistability in RGO for chemical sensors and electrocatalysis. PMID:25007942

  13. Exhaled nitric oxide monitoring by quantum cascade laser: comparison with chemiluminescent and electrochemical sensors

    NASA Astrophysics Data System (ADS)

    Mandon, Julien; Högman, Marieann; Merkus, Peter J. F. M.; van Amsterdam, Jan; Harren, Frans J. M.; Cristescu, Simona M.

    2012-01-01

    Fractional exhaled nitric oxide (FENO) is considered an indicator in the diagnostics and management of asthma. In this study we present a laser-based sensor for measuring FENO. It consists of a quantum cascade laser (QCL) combined with a multi-pass cell and wavelength modulation spectroscopy for the detection of NO at the sub-part-per-billion by volume (ppbv, 1∶10-9) level. The characteristics and diagnostic performance of the sensor were assessed. A detection limit of 0.5 ppbv was demonstrated with a relatively simple design. The QCL-based sensor was compared with two market sensors, a chemiluminescent analyzer (NOA 280, Sievers) and a portable hand-held electrochemical analyzer (MINO®, Aerocrine AB, Sweden). FENO from 20 children diagnosed with asthma and treated with inhaled corticosteroids were measured. Data were found to be clinically acceptable within 1.1 ppbv between the QCL-based sensor and chemiluminescent sensor and within 1.7 ppbv when compared to the electrochemical sensor. The QCL-based sensor was tested on healthy subjects at various expiratory flow rates for both online and offline sampling procedures. The extended NO parameters, i.e. the alveolar region, airway wall, diffusing capacity, and flux were calculated and showed a good agreement with the previously reported values.

  14. Synthesis of Electrochemically Reduced Graphene Oxide Bonded to Thiodiazole-Pd and Applications to Biosensor.

    PubMed

    You, Jung-Min; Han, Hyoung Soon; Jeon, Seungwon

    2015-08-01

    A novel biosensor for the determination of hydrogen peroxide and glucose was developed based on EGN-TDZ-Pd, as an electrocatalyst. The preparation of graphene oxide (GO) nanosheets was functionalized by combining it with 5-amino-1,3,4-thiadiazole-2-thiol (TDZ) and by covalently bonding it to palladium (Pd) nanoparticles (GO-TDZ-Pd). In the electrochemical investigation, EGN-TDZ-Pd was characterized via scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and electrochemical impedance spectroscopy (EIS). Cyclic voltammetry (CV) and chronoamperometry (CA) were used to characterize the performance of EGN-TDZ-Pd. The proposed H2O2 biosensor exhibited a wide linear range from 10 µM to 6.5 mM. Also, a glucose biosensor was prepared using glucose oxidase and EGN-TDZ-Pd placed onto a glassy carbon electrode (GCE). The GOx/EGN-TDZ-Pd/GCE was easily prepared using a rapid and simple procedure, and it was utilized for highly sensitive glucose determination. PMID:26369140

  15. Label-free electrochemical immunosensor based on cerium oxide nanowires for Vibrio cholerae O1 detection.

    PubMed

    Tam, Phuong Dinh; Thang, Cao Xuan

    2016-01-01

    This paper developed a label-free immunosensor based on cerium oxide nanowire for Vibrio cholerae O1 detection application. The CeO2 nanowires were synthesized by hydrothermal reaction. The immobilization of Anti-V. cholerae O1 onto CeO2 nanowire-deposited sensor was performed via an amino ester, which was created by using 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide, and sulfo-N-hydroxysuccinimide. The electrochemical responses of the immunosensor were studied by electrochemical impedance spectroscopy with [Fe (CN) 6] (3-/4-) as redox probe. A linear response in electron transfer resistance for cell of V. cholerae O1 concentration was found in the range of 1.0 10(2)CFU/mL to 1.0 10(4)CFU/mL. The detection limit of the immunosensor was 1.0 10(2)CFU/mL. The immunosensor sensitivity was 56.82 ?/CFU mL(-1). Furthermore, the parameters affecting immunosensor response were also investigated, as follows: pH value, immunoreaction time, incubation temperature, and anti-V. cholerae O1 concentration. PMID:26478391

  16. Electrochemical effect of lithium tungsten oxide modification on LiCoO2 thin film electrode

    NASA Astrophysics Data System (ADS)

    Hayashi, Tetsutaro; Okada, Jiro; Toda, Eiji; Kuzuo, Ryuichi; Matsuda, Yasutaka; Kuwata, Naoaki; Kawamura, Junichi

    2015-07-01

    We fabricated a lithium tungsten oxide (LWO)-modified LiCoO2 (LCO) thin film electrode by pulsed laser deposition and investigated the reason for its lower resistance as compared with a bare LCO electrode. X-ray diffraction revealed that the LWO layer has a randomly oriented Li2WO4 structure with tetragonal symmetry. Scanning electron microscopy and energy-dispersive X-ray spectroscopy (EDX) indicated that the LWO modification changes the LCO particle surface, and the electrochemical impedance spectroscopy demonstrated that the LWO modification on LCO decreases the lithium ion transfer resistance at the interface between the positive electrode and the liquid electrolyte and increases the frequency factor at the interface. X-ray photoemission spectroscopy, EDX, and electron energy loss spectroscopy (EELS) indicated the presence of phosphate on the surface of the unmodified LCO electrode after electrochemical tests, but EDX and EELS did not indicate the presence of phosphate in the LWO-modified LCO electrode. The absence of phosphates apparently alleviates the hindrance of Li+ ion diffusion and increases the frequency factor in LCO, resulting in lowered Li+ ion transfer resistance at the interface.

  17. Multi-resistive Reduced Graphene Oxide Diode with Reversible Surface Electrochemical Reaction induced Carrier Control

    NASA Astrophysics Data System (ADS)

    Seo, Hyungtak; Ahn, Seungbae; Kim, Jinseo; Lee, Young-Ahn; Chung, Koo-Hyun; Jeon, Ki-Joon

    2014-07-01

    The extended application of graphene-based electronic devices requires a bandgap opening in order to realize the targeted device functionality. Since the bandgap tuning of pristine graphene is limited to 360 meV, the chemical modification of graphene is considered essential to achieve a large bandgap opening at the expense of electrical properties degradation. Reduced graphene oxide (RGO) has attracted significant interest for fabricating graphene-based semiconductors since it has several advantages over other forms of chemically modified graphene; such as tunable bandgap opening, decent electrical properties, and easy synthesis. Because of the reduced bonding nature of RGO, the role of metastable oxygen in the RGO matrix is recently highlighted and it may offer emerging ionic devices. In this study, we show that multi-resistivity RGO/n-Si diodes can be obtained by controlling the RGO thickness at a nanometer scale. This is made possible by (1) a metastable lattice-oxygen drift within bulk RGO and (2) electrochemical ambient hydroxyl (OH) formation at the RGO surface. The effect demonstrated in a p-RGO/n-Si heterojunction diode is equivalent to electrochemically driven reversible electronic manipulation and therefore provides an important basis for the application of O bistability in RGO for chemical sensors and electrocatalysis.

  18. Multi-resistive reduced graphene oxide diode with reversible surface electrochemical reaction induced carrier control.

    PubMed

    Seo, Hyungtak; Ahn, Seungbae; Kim, Jinseo; Lee, Young-Ahn; Chung, Koo-Hyun; Jeon, Ki-Joon

    2014-01-01

    The extended application of graphene-based electronic devices requires a bandgap opening in order to realize the targeted device functionality. Since the bandgap tuning of pristine graphene is limited to 360 meV, the chemical modification of graphene is considered essential to achieve a large bandgap opening at the expense of electrical properties degradation. Reduced graphene oxide (RGO) has attracted significant interest for fabricating graphene-based semiconductors since it has several advantages over other forms of chemically modified graphene; such as tunable bandgap opening, decent electrical properties, and easy synthesis. Because of the reduced bonding nature of RGO, the role of metastable oxygen in the RGO matrix is recently highlighted and it may offer emerging ionic devices. In this study, we show that multi-resistivity RGO/n-Si diodes can be obtained by controlling the RGO thickness at a nanometer scale. This is made possible by (1) a metastable lattice-oxygen drift within bulk RGO and (2) electrochemical ambient hydroxyl (OH) formation at the RGO surface. The effect demonstrated in a p-RGO/n-Si heterojunction diode is equivalent to electrochemically driven reversible electronic manipulation and therefore provides an important basis for the application of O bistability in RGO for chemical sensors and electrocatalysis. PMID:25007942

  19. Exhaled nitric oxide monitoring by quantum cascade laser: comparison with chemiluminescent and electrochemical sensors.

    PubMed

    Mandon, Julien; Hgman, Marieann; Merkus, Peter J F M; van Amsterdam, Jan; Harren, Frans J M; Cristescu, Simona M

    2012-01-01

    Fractional exhaled nitric oxide (F(E)NO) is considered an indicator in the diagnostics and management of asthma. In this study we present a laser-based sensor for measuring F(E)NO. It consists of a quantum cascade laser (QCL) combined with a multi-pass cell and wavelength modulation spectroscopy for the detection of NO at the sub-part-per-billion by volume (ppbv, 110(-9)) level. The characteristics and diagnostic performance of the sensor were assessed. A detection limit of 0.5 ppbv was demonstrated with a relatively simple design. The QCL-based sensor was compared with two market sensors, a chemiluminescent analyzer (NOA 280, Sievers) and a portable hand-held electrochemical analyzer (MINO, Aerocrine AB, Sweden). F(E)NO from 20 children diagnosed with asthma and treated with inhaled corticosteroids were measured. Data were found to be clinically acceptable within 1.1 ppbv between the QCL-based sensor and chemiluminescent sensor and within 1.7 ppbv when compared to the electrochemical sensor. The QCL-based sensor was tested on healthy subjects at various expiratory flow rates for both online and offline sampling procedures. The extended NO parameters, i.e. the alveolar region, airway wall, diffusing capacity, and flux were calculated and showed a good agreement with the previously reported values. PMID:22352669

  20. Development of a Silver-Copper Oxide Braze for Joining Metallic and Ceramic Components in Electrochemical Devices

    SciTech Connect

    Weil, K. Scott; Hardy, John S.; Kim, Jin Yong Y.

    2003-10-30

    One of the challenges in manufacturing solid-state electrochemical devices, such as planar solid oxide fuel cells (pSOFC) and oxygen generators, is in hermetically sealing the ceramic and metallic components such that the resulting joint remains rugged and stable under continuous high temperature operation in an oxidizing atmosphere. A well proven method of joining dissimilar materials is by brazing. Unfortunately many of the commercially available ceramic-to-metal braze alloys exhibit oxidation properties which are unacceptable for use in these applications. This paper outlines an alternative brazing technique, reactive air brazing (RAB), that is being developed specifically for use in an oxidizing environment.

  1. Nanoelectrical investigation and electrochemical performance of nickel-oxide/carbon sphere hybrids through interface manipulation.

    PubMed

    Yang, Xiaogang; Zhang, Yan'ge; Wu, Guodong; Zhu, Congxu; Zou, Wei; Gao, Yuanhao; Tian, Jie; Zheng, Zhi

    2016-05-01

    Advanced hetero-nanostructured materials for electrochemical devices, such as Li-ion batteries (LiBs), dramatically depend on each functional component and their interfaces to transport and storage charges, where the bottleneck is the sluggish one in series. In this work, we prepare Ni(OH)2@C hybrids through a continuous feeding in reflux and followed by a hydrothermal treatment. The as-prepared Ni(OH)2@C can be further converted into NiO@C hybrids after thermal annealing. As a control, Ni(OH)2&C and NiO&C nanocomposites have also been prepared. Peakforce Tuna measurement shows the conductivity of the NiO@C hybrids is higher than that of NiO&C composites in nanoscale. To further investigate the quality of the interface, 100 charge/discharge cycles of the hybrids are performed in LiBs. The capacity retention of hybrid materials has significantly improved than the simple carbon composites. The enhancement of the electrochemical performance is attributed to the better electric conductivity and smaller charge transfer impedance and strong covalent interface between nickel species and carbon spheres obtained through the controlled seeded deposition. PMID:26897565

  2. Impact of leachate composition on the advanced oxidation treatment.

    PubMed

    Oulego, Paula; Collado, Sergio; Laca, Adriana; Díaz, Mario

    2016-01-01

    Advanced oxidation processes (AOPs) are gaining importance as an alternative to the biological or physicochemical treatments for the management of leachates. In this work, it has been studied the effect of the characteristics of the leachate (content in humic acids, landfill age and degree of stabilization) on the wet oxidation process and final quality of the treated effluent. A high concentration of humic acids in the leachate had a positive effect on the COD removal because this fraction is more easily oxidizable. Additionally, it has been demonstrated that the simultaneous presence of humic acid and the intermediates generated during the oxidation process improved the degradation of this acid, since such intermediates are stronger initiators of free radicals than the humic acid itself. Similar values of COD removals (49% and 51%) and biodegradability indices (0.30 and 0.35) were observed, after 8 h of wet oxidation, for the stabilised leachate (biologically pretreated) and the raw one, respectively. Nevertheless, final colour removal was much higher for the stabilised leachate, achieving values up to 91%, whereas for the raw one only 56% removal was attained for the same reaction time. Besides, wet oxidation treatment was more efficient for the young leachate than for the old one, with final COD conversions of 60% and 37%, respectively. Eventually, a triangular "three-lump" kinetic model, which considered direct oxidation to CO2 and partial oxidation through intermediate compounds, was here proposed. PMID:26517790

  3. One-step electrochemical synthesis of nitrogen and sulfur co-doped, high-quality graphene oxide.

    PubMed

    Parvez, Khaled; Rincón, Rosalba A; Weber, Nils-Eike; Cha, Kitty C; Venkataraman, Shyam S

    2016-04-14

    High-quality graphene oxide (GO) with high crystallinity and electrical conductivity as well as in situ doped with nitrogen and sulfur is obtained via the electrochemical exfoliation of graphite. Furthermore, iron incorporated GO sheets show promising catalytic activity and stable methanol tolerance durability when used as electrocatalysts for the oxygen reduction reaction. PMID:27040326

  4. Development of Advanced Electrochemical Emission Spectroscopy for Monitoring Corrosion in Simulated DOE Liquid Waste

    SciTech Connect

    Digby Macdonald; Brian Marx; Balaji Soundararajan; Morgan Smith

    2005-07-28

    The different tasks that have been carried out under the current program are as follows: (1) Theoretical and experimental assessment of general corrosion of iron/steel in borate buffer solutions by using electrochemical impedance spectroscopy (EIS), ellipsometry and XPS techniques; (2) Development of a damage function analysis (DFA), which would help in predicting the accumulation of damage due to pitting corrosion in an environment prototypical of DOE liquid waste systems; (3) Experimental measurement of crack growth rate, acoustic emission signals, and coupling currents for fracture in carbon and low alloy steels as functions of mechanical (stress intensity), chemical (conductivity), electrochemical (corrosion potential, ECP), and microstructural (grain size, precipitate size, etc) variables in a systematic manner, with particular attention being focused on the structure of the noise in the current and its correlation with the acoustic emissions; (4) Development of fracture mechanisms for carbon and low alloy steels that are consistent with the crack growth rate, coupling current data and acoustic emissions; (5) Inserting advanced crack growth rate models for SCC into existing deterministic codes for predicting the evolution of corrosion damage in DOE liquid waste storage tanks; (6) Computer simulation of the anodic and cathodic activity on the surface of the steel samples in order to exactly predict the corrosion mechanisms; (7) Wavelet analysis of EC noise data from steel samples undergoing corrosion in an environment similar to that of the high level waste storage containers, to extract data pertaining to general, pitting and stress corrosion processes, from the overall data. The work has yielded a number of important findings, including an unequivocal demonstration of the role of chloride ion in passivity breakdown on nickel in terms of cation vacancy generation within the passive film, the first detection and characterization of individual micro fracture events in stress corrosion cracking, and the determination of kinetic parameters for the generation and annihilation of point defects in the passive film on iron. The existence of coupling between the internal crack environment and the external cathodic environment, as predicted by the coupled environment fracture model (CEFM), has also been indisputably established for the AISI 4340/NaOH system. It is evident from the studies that analysis of coupling current noise is a very sensitive tool for studying the crack tip processes in relation to the chemical, mechanical, electrochemical, and microstructural properties of the system. Experiments are currently being carried out to explore these crack tip processes by simultaneous measurement of the acoustic activity at the crack tip in an effort to validate the coupling current data. These latter data are now being used to deterministically predict the accumulation of general and localized corrosion damage on carbon in prototypical DOE liquid waste storage tanks. Computer simulation of the cathodic and anodic activity on the steel surfaces is also being carried out in an effort to simulate the actual corrosion process. Wavelet analysis of the coupling current data promises to be a useful tool to differentiate between the different corrosion mechanisms. Hence, wavelet analysis of the coupling current data from the DOE waste containers is also being carried out to extract data pertaining to general, pitting and stress corrosion processes, from the overall data which is bound to contain noise fluctuations due to any or all of the above mentioned processes.

  5. High efficiencies in the electrochemical oxidation of an anthraquinonic dye with conductive-diamond anodes.

    PubMed

    Aquino, José Mario; Rocha-Filho, Romeu C; Sáez, Cristina; Cañizares, Pablo; Rodrigo, Manuel A

    2014-01-01

    Oxidation of anthraquinonic dye Acid Blue 62 by electrolysis with conductive-diamond electrodes is studied in this work. COD, TOC, and color have been selected to monitor the degradation of the molecule as a function of several operating inputs (current density, pH, temperature, and NaCl concentration). Results show that the electrochemical oxidation of this model of large molecules follows a first order kinetics in all the conditions assessed, and it does not depend on the pH and temperature. The occurrence of chloride ions in wastewaters increases the rate of color and COD removal as a consequence of the mediated oxidation promoted by the chlorinated oxidizing species. However, chloride occurrence does not have an influence on the mineralization rate. First-order kinetic-constants for color depletion (attack to chromophores groups), oxidation (COD removal), and mineralization (TOC removal) were found to depend on the current density and to increase significantly with its value. A single model was proposed to explain these changes in terms of the mediated oxidation processes. Rate of mineralization remained very close to that expected for a purely mass transfer-controlled process. This was explained assuming that mediated oxidation does not have a significant influence on the mineralization in spite it has some effect on intermediate oxidation stages. The efficiency of the oxidation was found to depend mainly on the concentration of COD being negligible the effect of the other inputs assessed except for the occurrence of chloride ions. Opposite, the efficiency of mineralization depends on concentration of TOC and current density and it did not depend on the chloride occurrence. This observation was found to have an important influence on the power required to remove a given percentage of the initial TOC or COD. To decrease COD efficiently, the occurrence of chloride in the solution is very important, while to remove TOC efficiently, it is more important to work at low current densities and chloride effect is negligible. Energy consumption could be decreased by folds using the proper conditions. PMID:24652577

  6. Polyethylene oxide (PEO)-ammonium sulfate ((NH 4) 2SO 4) complexes and electrochemical cell performance

    NASA Astrophysics Data System (ADS)

    Ali, A. M. M.; Mohamed, N. S.; Arof, A. K.

    The PEO-(NH 4) 2SO 4 systems with different NH 4+/EO ratio have been prepared by the solution-cast technique and investigated by X-ray diffraction, infrared spectroscopy and impedance spectroscopy. The highest conductivity (2.7×10 -6 S cm -1) is obtained from the film with a NH 4+/EO ratio of 0.050. Some electrochemical cells are then fabricated using the film with the highest electrical conductivity as the electrolyte. Different metal oxides and their combination are used as the cathode active materials. The highest open-circuit voltage (OCV) of 1.059 V is provided by the cell with configuration (Zn+ZnSO 4·7H 2O)/PEO-(NH 4) 2SO 4/(0.02 g PbO 2+0.02 g MnO 2). The short-circuit current of this cell is 97 μA.

  7. Electrochemically reduced graphene oxide multilayer films as efficient counter electrode for dye-sensitized solar cells.

    PubMed

    Xu, Xiaobao; Huang, Dekang; Cao, Kun; Wang, Mingkui; Zakeeruddin, Shaik M; Grätzel, Michael

    2013-01-01

    We report on a new counter electrode for dye-sensitized solar cells (DSCs), which is prepared using layer-by-layer assembly of negatively charged graphene oxide and positively charged poly (diallyldimethylammonium chloride) followed by an electrochemical reduction procedure. The DSC devises using the heteroleptic Ru complex C106TBA as sensitizer and this new counter electrode reach power conversion efficiencies of 9.5% and 7.6% in conjunction with low volatility and solvent free ionic liquid electrolytes, respectively. The new counter electrode exhibits good durability (60°C for 1000 h in a solar simulator, 100 mW cm(-2)) during the accelerated tests when used in combination with an ionic liquid electrolyte. This work identifies a new class of electro-catalysts with potential for low cost photovoltaic devices. PMID:23508212

  8. Graphene oxide as nanocarrier for sensitive electrochemical immunoassay of clenbuterol based on labeling amplification strategy.

    PubMed

    Lai, Yanjun; Bai, Jing; Shi, Xinhao; Zeng, Yanbo; Xian, Yuezhong; Hou, Jie; Jin, Litong

    2013-03-30

    A novel electrochemical immunosensor for sensitive detection of clenbuterol (CLB) is fabricated using glucose oxidase (GOD)-functionalized grahene oxide (GO) nanocomposites to label CLB. The immunosensor was constructed by layer-by-layer assembly colloidal prussian blue (PB), multiwalled carbon nanotubes (MWCNTs) and CLB antibodies (Abs) on a glassy carbon electrode (GCE). In this competitive immunoassay system, PB acts as the redox mediator to reduce H2O2 originated from the catalyst cycle of GOD. The high ratio of GOD to GO effectively amplified the signal for this competitive-type immunoassay. Under optimized conditions, the immunosensor shows a wide linear range from 0.5 to 1,000 ng/mL with a low detection limit of 0.25 ng/mL. The dual signal amplification of GOD-functionalized GO nanocomposites as a label is promising to be applied to design other sensitive immunosenseors. PMID:23598209

  9. Indium tin oxide based chip for optical and electrochemical characterization of protein-cell interaction

    NASA Astrophysics Data System (ADS)

    Choi, Yong Hyun; Min, Junhong; Cho, Sungbo

    2015-06-01

    Analysis on the interaction between proteins and cells is required for understanding the cellular behaviour and response. In this article, we characterized the adhesion and growth of 293/GFP cells on fetal bovine serum (FBS) coated indium tin oxide (ITO) electrode. Using optical and electrochemical measurement, it was able to detect the adsorption of the protein on the surface of the ITO electrode dependent on the concentration of the protein in the immersing solution or the immersing time. An increase in the amount of the adsorbed serum protein resulted in a decrease in anodic peak current and an increase in the charge transfer resistance extracted from the equivalent circuit fitting analysis. More cells adhered and proliferated on the ITO electrode which was pre-immersed in FBS medium rather than bare electrode. The effect of the FBS on cell behaviors was reflected in the impedance monitoring of cells at 21.5 kHz.

  10. In-situ quantification of solid oxide fuel cell electrode microstructure by electrochemical impedance spectroscopy

    NASA Astrophysics Data System (ADS)

    Zhang, Yanxiang; Chen, Yu; Chen, Fanglin

    2015-03-01

    Three-dimensional (3D) microstructure of solid oxide fuel cell electrodes plays critical roles in determining fuel cell performance. The state-of-the-art quantification technique such as X-ray computed tomography enables direct calculation of geometric factors by 3D microstructure reconstruction. Taking advantages of in-situ, fast-responding and low cost, electrochemical impedance spectroscopy represented by distribution of relaxation time (DRT) is a novel technique to estimate geometric properties of fuel cell electrodes. In this study, we employed the anode supported cells with the cell configuration of Ni-YSZ || YSZ || LSM-YSZ as an example and compared the tortuosity factor of pores of the anode substrate layer by X-ray computed tomography and DRT analysis. Good agreement was found, validating the feasibility of in-situ microstructural quantification by using the DRT technique.

  11. Electrochemically Reduced Graphene Oxide Multilayer Films as Efficient Counter Electrode for Dye-Sensitized Solar Cells

    PubMed Central

    Xu, Xiaobao; Huang, Dekang; Cao, Kun; Wang, Mingkui; Zakeeruddin, Shaik M.; Grätzel, Michael

    2013-01-01

    We report on a new counter electrode for dye-sensitized solar cells (DSCs), which is prepared using layer-by-layer assembly of negatively charged graphene oxide and positively charged poly (diallyldimethylammonium chloride) followed by an electrochemical reduction procedure. The DSC devises using the heteroleptic Ru complex C106TBA as sensitizer and this new counter electrode reach power conversion efficiencies of 9.5% and 7.6% in conjunction with low volatility and solvent free ionic liquid electrolytes, respectively. The new counter electrode exhibits good durability (60°C for 1000 h in a solar simulator, 100 mW cm−2) during the accelerated tests when used in combination with an ionic liquid electrolyte. This work identifies a new class of electro-catalysts with potential for low cost photovoltaic devices. PMID:23508212

  12. Solid oxide electrolysis cell analysis by means of electrochemical impedance spectroscopy: A review

    NASA Astrophysics Data System (ADS)

    Nechache, A.; Cassir, M.; Ringuedé, A.

    2014-07-01

    High temperature water electrolysis based on Solid Oxide Electrolysis Cell (SOEC) is a very promising solution to produce directly pure hydrogen. However, degradation issues occurring during operation still represent a scientific and technological barrier in view of its development at an industrial scale. Electrochemical Impedance Spectroscopy (EIS) is a powerful in-situ fundamental tool adapted to the study of SOEC systems. Hence, after a quick presentation of EIS principle and data analysis methods, this review demonstrates how EIS can be used: (i) to characterize the performance and mechanisms of SOEC electrodes; (ii) as a complementary tool to study SOEC degradation processes for different cell configurations, in addition to post-test tools such as scanning electron microscopy (SEM) or X-ray diffraction (XRD). The use of EIS to establish a systematic SOEC analysis is introduced as well.

  13. TiO2 nanotube arrays via electrochemical anodic oxidation: Prospective electrode for sensing phenyl hydrazine

    NASA Astrophysics Data System (ADS)

    Ameen, Sadia; Shaheer Akhtar, M.; Seo, Hyung-Kee; Shin, Hyung-Shik

    2013-08-01

    The TiO2 nanotube (NT) arrays were grown on Ti foil substrate by electrochemical anodic oxidation and utilized as working electrode to fabricate a highly sensitive and reproducible chemical sensor for the detection of harmful phenyl hydrazine chemical. The fabricated chemical sensor based on TiO2 NT arrays electrode exhibited high sensitivity of ˜40.9μA mM-1 cm-2 and detection limit of ˜0.22 μM with short response time (10 s). The enhanced sensing properties were attributed to the presence of depleted oxygen layer on the surface of grown TiO2 NT arrays and its high electron transfer process via good electrocatalytic activity towards phenyl hydrazine chemical.

  14. A Novel Electrochemical Detector using Prussian Blue Modified Indium Tin Oxide Electrode

    NASA Astrophysics Data System (ADS)

    Yi, In-Je; Kim, Ju-Ho; Kang, C. J.; Choi, Y. J.; Lee, Kisay; Kim, Yong-Sang

    2006-01-01

    We propose a novel electrochemical detector (ECD) to catalyze redox efficiently by electrodepositing Prussian blue (PB, ferric hexacyanoferrate) on the indium tin oxide (ITO) electrode. Capillary electrophoresis (CE) and amperometric methods were used. We investigated the PB surface properties by topography from atomic force microscopy (AFM). The PB film on dense and smooth surfaces could catalyze redox reaction efficiently. Compared with CE-ECD microchips using a bare-ITO electrode, the proposed CE-ECD microchip using a PB modified electrode has shown better sensitivity of the electropherograms. It has been verified that wide-ranging detection can be performed under the limits of 0.01 mM of dopamine and catechol respectively when we use a PB modified electrode.

  15. Mössbauer study of electrochemically deposited amorphous iron-sulfide-oxide thin films

    NASA Astrophysics Data System (ADS)

    Ichimura, Masaya; Kajima, Takahiro; Kawai, Shoichi; Mibu, Ko

    2016-03-01

    Iron-sulfide-oxide thin films, which are promising candidates for solar cell materials, were deposited by electrochemical deposition. As-deposited and annealed films were characterized by Mössbauer spectroscopy, X-ray diffraction (XRD), and Raman scattering at room temperature. The as-deposited film is amorphous, and the oxygen content is about 1/4 of the sulfur content (S/Fe ≈ 1.5, O/Fe ≈ 0.4). The Mössbauer spectrum for the as-deposited film is a doublet with a broad line profile having hyperfine parameters similar to those of FeS2 pyrite or marcasite. This indicates that Fe atoms are in the Fe2+ low-spin state, as in FeS2.

  16. Electrochemical oxidation of methanol on Pt nanoparticles composited MnO 2 nanowire arrayed electrode

    NASA Astrophysics Data System (ADS)

    Zhao, Guang-Yu; Li, Hu-Lin

    2008-03-01

    By use of the membrane-template synthesis route, MnO 2 nanowire arrayed electrodes are successfully synthesized by means of the anodic deposition technique. The Pt nanoparticles composited MnO 2 nanowire arrayed electrodes (PME) are obtained through depositing Pt on MnO 2 nanowire arrayed electrode by cathode deposition technique. For comparison of electrochemical performance, Pt nanowire arrayed electrodes which have the same amount of Pt with PME are also prepared. The electro-oxidation of methanol on PME and Pt nanowire arrayed electrodes is investigated at room temperature by cyclic voltammetry, which show that about 110 mV decreased overpotential and 2.1-fold enhanced votammetric current are achieved on PME. The chronoamperometry result demonstrates that the resistance to carbon monoxide for PME is improved.

  17. Synthesis and Electrochemical Analyses of Manganese Oxides for Super-Capacitors.

    PubMed

    Kim, Taewoo; Hwang, Hyein; Jang, Jaeyong; Park, Inyeong; Shim, Sang Eun; Baeck, Sung-Hyeon

    2015-11-01

    δ-Phase and α-phase manganese oxides were prepared using a hydrothermal method and their electrochemical properties were characterized. The influence of calcination temperature on the properties of manganese oxides was studied. Crystallinities were studied by X-ray diffraction, and scanning and transmission electron microscopy were utilized to examine morphologies. Average pore sizes and specific surface areas of samples were analyzed using the Barret-Joyner-Halenda and Brunauer-Emmett-Teller methods, respectively. After calcination in the range 300 degrees C to 600 degrees C, changes in morphology and crystallinity were observed. The flower-like shape of as synthesized samples became nanorod-like and the δ-phase changed to the α-phase. These changes may have been due to the removal of water during calcination. Furthermore, a transition stage in which the two phases coexisted was observed. Synthesized manganese oxides were mixed with carbon by sonification, to increase electric conductivity and to induce a synergistic effect between pseudo-capacitor and electric double layer capacitor (EDLC). Specific capacitances and rate durability of each composite were investigated by cyclic voltammetry in 1 M Na2SO4 electrolyte at different scan rates. MnO2 calcined at 400 degrees C exhibited the highest capacitance, probably due to its high surface area and more porous structure. PMID:26726613

  18. Electrochemical synthesis of new magnetic mixed oxides of Sr and Fe: Composition, magnetic properties, and microstructure

    SciTech Connect

    Amigo, R.; Asenjo, J.; Krotenko, E.; Torres, F.; Tejada, J.; Brillas, E.

    2000-02-01

    An electrochemical method for the preparation of magnetic nanoparticles of new Sr-Fe oxides is presented in this work. It consists of the electrolysis of nitrate or chloride solutions with Sr{sup 2+} and Fe{sup 3+} salts using commercial Fe electrodes. Magnetic materials are collected as precipitates from nitrate media in the pH range 1-3 and from chloride media within the pH range 1--12. The presence of 100--300 ppm aniline in acidic nitrate media yields a decrease in energy cost and particle size. Inductively coupled plasma analysis of materials and energy-dispersive X-ray spectrometry of single particles confirm that they are composed of mixed oxides of Sr and Fe. All synthesized materials crystallize as inverse cubic spinels, usually with intermediate structures between magnetite and maghemite. They are formed by nanoparticles with average sizes from 2 nm to {approximately} 50 nm, as observed by scanning electron microscopy. The electrogenerated mixed oxides have higher saturation magnetization, but lower remanent magnetization and coercive field, than commercial strontium hexaferrite with micrometric particle size.

  19. Reversible oxygen scavenging at room temperature using electrochemically reduced titanium oxide nanotubes

    NASA Astrophysics Data System (ADS)

    Close, Thomas; Tulsyan, Gaurav; Diaz, Carlos A.; Weinstein, Steven J.; Richter, Christiaan

    2015-05-01

    A material capable of rapid, reversible molecular oxygen uptake at room temperature is desirable for gas separation and sensing, for technologies that require oxygen storage and oxygen splitting such as fuel cells (solid-oxide fuel cells in particular) and for catalytic applications that require reduced oxygen species (such as removal of organic pollutants in water and oil-spill remediation). To date, however, the lowest reported temperature for a reversible oxygen uptake material is in the range of 200-300 °C, achieved in the transition metal oxides SrCoOx (ref. 1) and LuFe2O4+x (ref. 2) via thermal cycling. Here, we report rapid and reversible oxygen scavenging by TiO2-x nanotubes at room temperature. The uptake and release of oxygen is accomplished by an electrochemical rather than a standard thermal approach. We measure an oxygen uptake rate as high as 14 mmol O2 g-1 min-1, ˜2,400 times greater than commercial, irreversible oxygen scavengers. Such a fast oxygen uptake at a remarkably low temperature suggests a non-typical mechanistic pathway for the re-oxidation of TiO2-x. Modelling the diffusion of oxygen, we show that a likely pathway involves ‘exceptionally mobile’ interstitial oxygen produced by the oxygen adsorption and decomposition dynamics, recently observed on the surface of anatase.

  20. Electrochemical gas-electricity cogeneration through direct carbon solid oxide fuel cells

    NASA Astrophysics Data System (ADS)

    Xie, Yongmin; Cai, Weizi; Xiao, Jie; Tang, Yubao; Liu, Jiang; Liu, Meilin

    2015-03-01

    Solid oxide fuel cells (SOFCs), with yttrium stabilized zirconia (YSZ) as electrolyte, composite of strontium-doped lanthanum manganate (LSM) and YSZ as cathode, and cermet of silver and gadolinium-doped ceria (GDC) as anode, are prepared and tested with 5wt% Fe-loaded activated carbon as fuel and ambient air as oxidant. It is found that electricity and CO gas can be cogenerated in the direct carbon SOFCs through the electrochemical oxidation of CO and the Boudouard reaction. The gas-electricity cogeneration performances are investigated by taking the operating time of the DC-SOFCs as a measure of rate decrease of the Boudouard reaction. Three single cells and a two-cell-stack are tested and characterized in terms of electrical power output, CO production rate, electrical conversion efficiency, and overall conversion efficiency. It turns out that a rapid rate of the Boudouard reaction is necessary for getting high electrical power and CO production. Taking the emitted CO as part of the power output, an overall efficiency of 76.5% for the single cell, and of 72.5% for the stack, is obtained.

  1. Redox activity of surface oxygen anions in oxygen-deficient perovskite oxides during electrochemical reactions.

    PubMed

    Mueller, David N; Machala, Michael L; Bluhm, Hendrik; Chueh, William C

    2015-01-01

    Surface redox-active centres in transition-metal oxides play a key role in determining the efficacy of electrocatalysts. The extreme sensitivity of surface redox states to temperatures, to gas pressures and to electrochemical reaction conditions renders them difficult to investigate by conventional surface-science techniques. Here we report the direct observation of surface redox processes by surface-sensitive, operando X-ray absorption spectroscopy using thin-film iron and cobalt perovskite oxides as model electrodes for elevated-temperature oxygen incorporation and evolution reactions. In contrast to the conventional view that the transition metal cations are the dominant redox-active centres, we find that the oxygen anions near the surface are a significant redox partner to molecular oxygen due to the strong hybridization between oxygen 2p and transition metal 3d electronic states. We propose that a narrow electronic state of significant oxygen 2p character near the Fermi level exchanges electrons with the oxygen adsorbates. This result highlights the importance of surface anion-redox chemistry in oxygen-deficient transition-metal oxides. PMID:25598003

  2. Redox activity of surface oxygen anions in oxygen-deficient perovskite oxides during electrochemical reactions

    NASA Astrophysics Data System (ADS)

    Mueller, David N.; Machala, Michael L.; Bluhm, Hendrik; Chueh, William C.

    2015-01-01

    Surface redox-active centres in transition-metal oxides play a key role in determining the efficacy of electrocatalysts. The extreme sensitivity of surface redox states to temperatures, to gas pressures and to electrochemical reaction conditions renders them difficult to investigate by conventional surface-science techniques. Here we report the direct observation of surface redox processes by surface-sensitive, operando X-ray absorption spectroscopy using thin-film iron and cobalt perovskite oxides as model electrodes for elevated-temperature oxygen incorporation and evolution reactions. In contrast to the conventional view that the transition metal cations are the dominant redox-active centres, we find that the oxygen anions near the surface are a significant redox partner to molecular oxygen due to the strong hybridization between oxygen 2p and transition metal 3d electronic states. We propose that a narrow electronic state of significant oxygen 2p character near the Fermi level exchanges electrons with the oxygen adsorbates. This result highlights the importance of surface anion-redox chemistry in oxygen-deficient transition-metal oxides.

  3. Boron-doped cadmium oxide composite structures and their electrochemical measurements

    SciTech Connect

    Lokhande, B.J.; Ambare, R.C.; Mane, R.S.; Bharadwaj, S.R.

    2013-08-01

    Graphical abstract: Conducting nano-fibrous 3% boron doped cadmium oxide thin films were prepared by SILAR and its super capacitive properties were studied. - Highlights: • Samples are of nanofibrous nature. • All samples shows pseudocapacitive behavior. • 3% B doped CdO shows good specific capacitance. • 3% B doped CdO shows maximum 74.93% efficiency at 14 mA/cm{sup 2}. • 3% B doped CdO shows 0.8 Ω internal resistance. - Abstract: Boron-doped and undoped cadmium oxide composite nanostructures in thin film form were prepared onto stainless steel substrates by a successive ionic layer adsorption and reaction method using aqueous solutions of cadmium nitrate, boric acid and 1% H{sub 2}O{sub 2}. As-deposited films were annealed at 623 K for 1 h. The X-ray diffraction study shows crystalline behavior for both doped and undoped films with a porous topography and nano-wires type architecture, as observed in SEM image. Wettability test confirms the hydrophilic surface with 58° contact angle value. Estimated band gap energy is around 1.9 eV. Electrochemical behavior of the deposited films is attempted in 1 M KOH electrolyte using cyclic voltammetry (CV), electrochemical impedance spectroscopy and galvanostatic charge–discharge tests. Maximum values of the specific capacitance, specific energy and specific power obtained for 3% B doped CdO film at 2 mV/s scan rate are 20.05 F/g, 1.22 Wh/kg and 3.25 kW/kg, respectively.

  4. Mechanical and electrochemical characterization of intermediate temperature micro-tubular solid oxide fuel cell

    NASA Astrophysics Data System (ADS)

    Pusz, Jakub

    Solid oxide fuel cells (SOFCs) are attributed for being highly efficient in their energy conversion capabilities and fuel flexibility. The primary objective of this study was to develop an operating solid oxide fuel cell using innovative and cost-effective fabrication techniques. The secondary objective of this research aimed at improving mechanical and electrochemical properties of the cell through utilization of electrode materials characterized by different morphology. The system studied was a micro-tubular, anode supported SOFC operated on both hydrogen and internally-reformed methane at the temperature range of 800-850°C. The research studied different anode poreformers and the utilization of anode powders with different morphologies. Anode supports, fabricated using an extrusion process, were based on a standard composition of 50/50 vol% of NiO/8YSZ powder. Procedures were developed to deposit a 2-5 mum thin and dense 8YSZ electrolyte film via a quick and cost-effective vacuum infiltration process. Two different materials were utilized to fabricate anode supports. The first anode powder consisted of small, nano-size, particles, while the second powder was a sub-micron size powder. Vastly improved power density and redox cycling results were observed from a fuel cell fabricated using a fine powder. For example a power density of >0.5 W cm-2 at 800°C was observed. The performance data of an SOFC operating on internally-reformed methane is presented. A response of the fuel cell set up using two different sealing designs, a cold-seal design and a hot-seal design, is also explained. The electrochemical activity of Gd0.5Sr0.5CoO 3-x cathode fabricated using a standard glycine-nitrate pyrolysis technique and a technique allowing direct deposition of cathode material on top of electrolyte powder was tested. The thesis concludes with recommendations for further work.

  5. 3D CFD ELECTROCHEMICAL AND HEAT TRANSFER MODEL OF AN INTERNALLY MANIFOLDED SOLID OXIDE ELECTROLYSIS CELL

    SciTech Connect

    Grant L. Hawkes; James E. O'Brien; Greg Tao

    2011-11-01

    A three-dimensional computational fluid dynamics (CFD) electrochemical model has been created to model high-temperature electrolysis cell performance and steam electrolysis in an internally manifolded planar solid oxide electrolysis cell (SOEC) stack. This design is being evaluated at the Idaho National Laboratory for hydrogen production from nuclear power and process heat. Mass, momentum, energy, and species conservation and transport are provided via the core features of the commercial CFD code FLUENT. A solid-oxide fuel cell (SOFC) model adds the electrochemical reactions and loss mechanisms and computation of the electric field throughout the cell. The FLUENT SOFC user-defined subroutine was modified for this work to allow for operation in the SOEC mode. Model results provide detailed profiles of temperature, operating potential, steam-electrode gas composition, oxygen-electrode gas composition, current density and hydrogen production over a range of stack operating conditions. Single-cell and five-cell results will be presented. Flow distribution through both models is discussed. Flow enters from the bottom, distributes through the inlet plenum, flows across the cells, gathers in the outlet plenum and flows downward making an upside-down ''U'' shaped flow pattern. Flow and concentration variations exist downstream of the inlet holes. Predicted mean outlet hydrogen and steam concentrations vary linearly with current density, as expected. Effects of variations in operating temperature, gas flow rate, oxygen-electrode and steam-electrode current density, and contact resistance from the base case are presented. Contour plots of local electrolyte temperature, current density, and Nernst potential indicate the effects of heat transfer, reaction cooling/heating, and change in local gas composition. Results are discussed for using this design in the electrolysis mode. Discussion of thermal neutral voltage, enthalpy of reaction, hydrogen production, cell thermal efficiency, cell electrical efficiency, and Gibbs free energy are discussed and reported herein.

  6. Study of the electrochemical oxidation and reduction of C.I. Reactive Orange 4 in sodium sulphate alkaline solutions.

    PubMed

    del Río, A I; Molina, J; Bonastre, J; Cases, F

    2009-12-15

    Synthetic solutions of hydrolysed C.I. Reactive Orange 4, a monoazo textile dye commercially named Procion Orange MX-2R (PMX2R) and colour index number C.I. 18260, was exposed to electrochemical treatment under galvanostatic conditions and Na2SO4 as electrolyte. The influence of the electrochemical process as well as the applied current density was evaluated. Ti/SnO2-Sb-Pt and stainless steel electrodes were used as anode and cathode, respectively, and the intermediates generated on the cathode during electrochemical reduction were investigated. Aliquots of the solutions treated were analysed by UV-visible and FTIR-ATR spectroscopy confirming the presence of aromatic structures in solution when an electro-reduction was carried out. Electro-oxidation degraded both the azo group and aromatic structures. HPLC measures revealed that all processes followed pseudo-first order kinetics and decolourisation rates showed a considerable dependency on the applied current density. CV experiments and XPS analyses were carried out to study the behaviour of both PMX2R and intermediates and to analyse the state of the cathode after the electrochemical reduction, respectively. It was observed the presence of a main intermediate in solution after an electrochemical reduction whose chemical structure is similar to 2-amino-1,5-naphthalenedisulphonic acid. Moreover, the analysis of the cathode surface after electrochemical reduction reveals the presence of a coating layer with organic nature. PMID:19647934

  7. Electrochemical capacitance of iron oxide nanotube (Fe-NT): effect of annealing atmospheres

    NASA Astrophysics Data System (ADS)

    Sarma, Biplab; Jurovitzki, Abraham L.; Ray, Rupashree S.; Smith, York R.; Mohanty, Swomitra K.; Misra, Mano

    2015-07-01

    The effect of annealing atmosphere on the supercapacitance behavior of iron oxide nanotube (Fe-NT) electrodes has been explored and reported here. Iron oxide nanotubes were synthesized on a pure iron substrate through an electrochemical anodization process in an ethylene glycol solution containing 3% H2O and 0.5 wt.% NH4F. Subsequently, the annealing of the nanotubes was carried out at 500 °C for 2 h in various gas atmospheres such as air, oxygen (O2), nitrogen (N2), and argon (Ar). The morphology and crystal phases evolved after the annealing processes were examined via field emission scanning electron microscopy, x-ray diffraction, Raman spectroscopy, and x-ray photoelectron spectroscopy. The electrochemical capacitance properties of the annealed Fe-NT electrodes were evaluated by conducting cyclic voltammetry (CV), galvanostatic charge-discharge, and electrochemical impedance spectroscopy tests in the Li2SO4 electrolyte. Based on these experiments, it was found that the capacitance of the Fe-NT electrodes annealed in air and O2 atmospheres shows mixed behavior comprising both the electric double layer and pseudocapacitance. However, annealing in N2 and Ar environments resulted in well-defined redox peaks in the CV profiles of the Fe-NT electrodes, which are therefore attributed to the relatively higher pseudonature of the capacitance in these electrodes. Based on the galvanostatic charge-discharge studies, the specific capacitance achieved in the Fe-NT electrode after annealing in Ar was about 300 mF cm-2, which was about twice the value obtained for N2-annealed Fe-NTs and three times higher than those annealed in air and O2. The experiments also demonstrated excellent cycle stability for the Fe-NT electrodes with 83%-85% capacitance retention, even after many charge-discharge cycles, irrespective of the gas atmospheres used during annealing. The increase in the specific capacitance was discussed in terms of increased oxygen vacancies as a result of the enhanced transformation of the hematite (α-Fe2O3) phase to the magnetite (Fe3O4) phase for the electrodes annealed in the N2 and Ar atmospheres.

  8. Evaluation of advanced oxidation process for the treatment of groundwater

    SciTech Connect

    Garland, S.B. II ); Peyton, G.R. ); Rice, L.E. . Kansas City Div.)

    1990-01-01

    An advanced oxidation process utilizing ozone, ultraviolet radiation, and hydrogen peroxide was selected for the removal of chlorinated hydrocarbons, particularly trichlorethene and 1,2-dichlorethene, from groundwater underlying the US Department of Energy Kansas City Plant. Since the performance of this process for the removal of organics from groundwater is not well-documented, an evaluation was initiated to determine the performance of the treatment plant, document the operation and maintenance costs experience, and evaluate contaminant removal mechanisms. 11 refs., 3 figs.

  9. Facile electrochemical oxidation of polyaromatic hydrocarbons to surface-confined redox-active quinone species on a multiwalled carbon nanotube surface.

    PubMed

    Barathi, Palani; Kumar, Annamalai Senthil

    2013-02-11

    Polyaromatic hydrocarbon (PAH) oxidation: PAHs, which are considered major environmental pollutants, are carcinogenic, and cannot be electrochemically oxidized on conventional electrodes (gold, platinum, and glassy carbon), can be electrochemically oxidized on multiwalled carbon nanotube surfaces at a potential of 1 V versus Ag/AgCl at pH 7. This results in the formation of stable surface-confined quinone systems (see scheme; AN = anthracene; AQ = anthraquinone). PMID:23296450

  10. Alloys for advanced steam turbines--Oxidation behavior

    SciTech Connect

    Holcomb, G.R.

    2007-10-01

    Advanced or ultra supercritical (USC) steam power plants offer the promise of higher efficiencies and lower emissions. Current goals of the U.S. Department of Energy (DOE) include power generation from coal at 60% efficiency, which would require steam temperatures of up to 760°C. Current research on the oxidation of candidate materials for advanced steam turbines is presented with a focus on a methodology for estimating chromium evaporation rates from protective chromia scales. The high velocities and pressures of advanced steam turbines lead to evaporation predictions as high as 5 × 10-8 kg m-2s-1 of CrO2(OH)2(g) at 760°C and 34.5 MPa. This is equivalent to 0.077 mm per year of solid Cr loss.

  11. Influence of electrochemical reduction and oxidation processes on the decolourisation and degradation of C.I. Reactive Orange 4 solutions.

    PubMed

    del Río, A I; Molina, J; Bonastre, J; Cases, F

    2009-06-01

    The electrochemical treatment of wastewaters from textile industry is a promising treatment technique for substances which are resistant to biodegradation. This paper presents the results of the electrochemical decolourisation and degradation of C.I. Reactive Orange 4 synthetic solutions (commercially known as Procion Orange MX2R). Electrolyses were carried out under galvanostatic conditions in a divided or undivided electrolytic cell. Therefore, oxidation, reduction or oxido-reduction experiences were tested. Ti/SnO(2)-Sb-Pt and stainless steel electrodes were used as anode and cathode, respectively. Degradation of the dye was followed by TOC, total nitrogen, COD and BOD(5) analyses. TOC removal after an oxidation process was higher than after oxido-reduction while COD removal after this last process was about 90%. Besides, the biodegradability of final samples after oxido-reduction process was studied and an improvement was observed. UV-Visible spectra revealed the presence of aromatic structures in solution when an electro-reduction was carried out while oxido-reduction process degraded both azo group and aromatic structures. HPLC analyses indicated the presence of a main intermediate after the reduction process with a chemical structure closely similar to 2-amine-1, 5-naphthalenedisulfonic acid. The lowest decolourisation rate corresponded to electrochemical oxidation. In these experiences a higher number of intermediates were generated as HPLC analysis demonstrated. The decolourisation process for the three electrochemical processes studied presented a pseudo-first order kinetics. PMID:19345978

  12. Decolorization of C. I. Reactive Orange 4 and Textile Effluents by Electrochemical Oxidation Technique using Silver-Carbon Composite Electrode.

    PubMed

    Nordin, Norazzizi; Fathrita Mohd Amir, Siti; Rahimi Yusop, Muhammad; Rozali Othman, Mohamed

    2015-01-01

    In this study, the electrochemical oxidation of C. I. Reactive Orange 4 (RO4) on a silver-carbon composite (AgC-PVC) electrode was studied using the cyclic voltammetry, potential liner V, and electrolysis methods. The AgC-PVC electrode was used as the working electrode in the electrochemical measurement of RO4 in the presence of NaCl as a supporting electrolyte. The UV-Vis spectra of RO4 after the electrochemical oxidation showed the complete decolorization of the solution. The electrolysis products were characterized using FTIR and GC-MS. The results showed that in the presence of OCl- as an active oxidant, RO4 molecules are broken down into several lower-molecular-weight molecules by the electrochemical technique. The electrode used was also able to reduce the COD, BOD(5) and surfactant contents in the textile effluents using a pilot scale reactor. This proved that the prepared AgC-PVC electrode was beneficial for removing both the color and other pollutants from textile effluents. PMID:26454599

  13. Synthesis of Pt nanoparticles on electrochemically reduced graphene oxide by potentiostatic and alternate current methods

    SciTech Connect

    Molina, J.; Fernández, J.; Río, A.I. del; Bonastre, J.; Cases, F.

    2014-03-01

    Reduced graphene oxide (RGO) has been synthesized on Pt wires by means of a potentiodynamic method between + 0.6 V and − 1.4 V for 20 scans. Cyclic voltammetry characterization of the coatings showed the typical capacitative behavior of graphene. Pt nanoparticles were synthesized on Pt–RGO electrodes by means of potentiostatic methods and a comparison between different synthesis potentials (− 0.16, 0, + 0.2 and + 0.4 V) for the same synthesis charge (mC·cm{sup −2}) was established. The electrodes obtained were characterized in 0.5 M H{sub 2}SO{sub 4} solution to observe the characteristic oxidation and reduction processes of the Pt surface. A 0.5 M H{sub 2}SO{sub 4}/0.5 M CH{sub 3}OH solution was used to measure the catalytic properties of the deposits against methanol oxidation. The most appropriate potential to perform the synthesis was 0 V followed by − 0.16 V and + 0.2 V. The morphology of the coatings varied depending on the potential applied as observed by scanning electron microscopy. Alternate current methods were also used to synthesize Pt nanoparticles and compare the results with the traditional potentiostatic method. Different frequencies were used: 0.1, 1, 10, 100, 1000 and 10 000 Hz. Alternate current synthesis is more efficient than traditional potentiostatic methods, obtaining more electroactive coatings with less effective synthesis time. - Highlights: • Reduced graphene oxide has been obtained by electrochemical reduction on Pt wires. • Pt nanoparticles have been obtained potentiostatically at different potentials. • Pt nanoparticles have been obtained by ac methods with different frequencies. • ac synthesis is a better synthesis method than potentiostatic synthesis.

  14. Probing Structural Changes in Poly(3-hexylthiophene) (P3HT) During Electrochemical Oxidation with In Situ X-ray Scattering

    NASA Astrophysics Data System (ADS)

    Thelen, Jacob L.; Patel, Shrayesh N.; Javier, Anna E.; Balsara, Nitash P.

    2014-03-01

    Mixtures of poly(3-hexylthiophene)-b-poly(ethylene oxide) (P3HT-b-PEO) block copolymer and lithium bis(trifluromethanesulfonyl) imide (LiTFSI) salt can microphase separate into electron (P3HT) and ion (PEO/LiTFSI) conducting domains. P3HT is a semicrystalline polymer with intrinsically semiconducting electronic properties. Electrochemical oxidation (doping) of the P3HT block provides the P3HT-b-PEO/LiTFSI mixtures with electronic conductivity suitable for lithium battery operation. Due to the presence of the solid-state electrolyte (PEO/LiTFSI) in intimate contact with the microphase separated P3HT domains, electrochemical oxidation of P3HT can be performed entirely in the solid state; therefore, P3HT-b-PEO/LiTFSI provides a unique opportunity to study the structural changes in P3HT induced by oxidation. We use in situ x-ray scattering techniques to probe structural changes in P3HT during electrochemical oxidation and correlate these changes with previously observed enhancements in electron mobility. Supported by the Joint Center for Energy Storage Research (JCESR).

  15. Kinetics and mechanism of the electrochemical formation of iron oxidation products on steel immersed in sour acid media.

    PubMed

    Hernndez-Espejel, Antonio; Palomar-Pardav, Manuel; Cabrera-Sierra, Romn; Romero-Romo, Mario; Ramrez-Silva, Mara Teresa; Arce-Estrada, Elsa M

    2011-03-01

    From electrochemical techniques (cyclic voltammetry, potential steps, and EIS), XRD, and SEM-EDX, the kinetics and mechanism of anodic film formation applying anodic potential steps on steel immersed in sour acid media was determined. It was found, from a thermodynamic analysis, based on equilibrium phase diagrams of the system considered in this work, that iron oxidation may produce different new solid phases, depending on the applied potential, the first being the iron oxidation associated with formation of FeS((c)) species, which in turn can be reoxidized to FeS(2(c)) or even to Fe(2)O(3(c)) at higher potential values. From analysis of the corresponding experimental potentiostatic current density transients, it was concluded that the electrochemical anodic film formation involves an E(1)CE(2) mechanism, whereby the first of the two simultaneous processes were the Fe electrochemical oxidation (E(1)) followed by FeS precipitation (C) that occurs by 3D nucleation and growth limited by mass transfer reaction and FeS oxidation (E(2)) forming a mix of different stoichiometry iron sulphides and oxides. From EIS measurements, it was revealed that the anodic film's charge transfer resistance diminishes as the potential applied for its formation becomes more anodic, thus behaving poorly against corrosion. PMID:21302956

  16. Measuring fundamental properties in operating solid oxide electrochemical cells by using in situ X-ray photoelectron spectroscopy

    NASA Astrophysics Data System (ADS)

    Zhang, Chunjuan; Grass, Michael E.; McDaniel, Anthony H.; Decaluwe, Steven C.; Gabaly, Farid El; Liu, Zhi; McCarty, Kevin F.; Farrow, Roger L.; Linne, Mark A.; Hussain, Zahid; Jackson, Gregory S.; Bluhm, Hendrik; Eichhorn, Bryan W.

    2010-11-01

    Photoelectron spectroscopic measurements have the potential to provide detailed mechanistic insight by resolving chemical states, electrochemically active regions and local potentials or potential losses in operating solid oxide electrochemical cells (SOCs), such as fuel cells. However, high-vacuum requirements have limited X-ray photoelectron spectroscopy (XPS) analysis of electrochemical cells to ex situ investigations. Using a combination of ambient-pressure XPS and CeO2-x/YSZ/Pt single-chamber cells, we carry out in situ spectroscopy to probe oxidation states of all exposed surfaces in operational SOCs at 750°C in 1mbar reactant gases H2 and H2O. Kinetic energy shifts of core-level photoelectron spectra provide a direct measure of the local surface potentials and a basis for calculating local overpotentials across exposed interfaces. The mixed ionic/electronic conducting CeO2-x electrodes undergo Ce3+/Ce4+ oxidation-reduction changes with applied bias. The simultaneous measurements of local surface Ce oxidation states and electric potentials reveal the active ceria regions during H2 electro-oxidation and H2O electrolysis. The active regions extend ~150μm from the current collectors and are not limited by the three-phase-boundary interfaces associated with other SOC materials. The persistence of the Ce3+/Ce4+ shifts in the ~150μm active region suggests that the surface reaction kinetics and lateral electron transport on the thin ceria electrodes are co-limiting processes.

  17. Facile synthesis of cobalt oxide/reduced graphene oxide composites for electrochemical capacitor and sensor applications

    NASA Astrophysics Data System (ADS)

    Nguyen, Thi Toan; Nguyen, Van Hoa; Deivasigamani, Ranjith Kumar; Kharismadewi, Dian; Iwai, Yoshio; Shim, Jae-Jin

    2016-03-01

    Reduced graphene oxide sheets decorated with cobalt oxide nanoparticles (Co3O4/rGO) were produced using a hydrothermal method without surfactants. Both the reduction of GO and the formation of Co3O4 nanoparticles occurred simultaneously under this condition. At the same current density of 0.5 A g-1, the Co3O4/rGO nanocomposites exhibited much a higher specific capacitance (545 F g-1) than that of bare Co3O4 (100 F g-1). On the other hand, for the detection of H2O2, the peak current of Co3O4/rGO was 4 times higher than that of Co3O4. Moreover, the resulting composite displayed a low detection limit of 0.62 μM and a high sensitivity of 28,500 μA mM-1cm-2 for the H2O2 sensor. These results suggest that the Co3O4/rGO nanocomposite is a promising material for both supercapacitor and non-enzymatic H2O2 sensor applications.

  18. Aerosol synthesis and electrochemical analysis of niobium mixed-metal oxides for the ethanol oxidation reaction in acid and alkaline electrolyte

    NASA Astrophysics Data System (ADS)

    Konopka, Daniel A.

    Direct ethanol fuel cells are especially important among emerging electrochemical power systems with the potential to offset a great deal of the energy demand currently met through the use of fossil fuels. Ethanol can be refined from petroleum sources or attained from renewable biomass, and is more easily and safely stored and transported than hydrogen, methanol or gasoline. The full energy potential of ethanol in fuel cells can only be realized if the reaction follows a total oxidation pathway to produce CO2. This must be achieved by the development of advanced catalysts that are electrically conductive, stable in corrosive environments, contain a high surface area on which the reaction can occur, and exhibit a bi-functional effect for the ethanol oxidation reaction (EOR). The latter criterion is achievable in mixed-metal systems. Platinum is an effective metal for catalyzing surface reactions of many adsorbates and is usually implemented in the form of Pt nanoparticles supported on inexpensive carbon. This carbon is believed to be neutral in the catalysis of Pt. Instead, carbon can be replaced with carefully designed metals and metal oxides as co-catalysis or support structures that favorably alter the electronic structure of Pt slightly through a strong metal support interaction, while also acting as an oxygen source near adsorbates to facilitate the total oxidation pathway. Niobium mixed-metal-oxides were explored in this study as bi-functional catalyst supports to Pt nanoparticles. We developed a thermal aerosol synthesis process by which mesoporous powders of mixed-metal-oxides decorated with Pt nanoparticles could be obtained from liquid precursors within ˜5 seconds or less, followed by carefully refined chemical and thermal post-treatments. Exceptionally high surface areas of 170--180m2/g were achieved via a surfactant-templated 3D wormhole-type porosity, comparable on a per volume basis to commercial carbon blacks and high surface area silica supports. For the first time, in situ FTIR measurements in acid electrolyte showed that highly dispersed Pt nanoparticles (2--5nm) on NbRuyO z (at% 8Nb:1Ru) catalyze the formation of CO2 from ethanol in greater yield, and 0.35--0.4V lower, than Pt(111). Compared to conventional Pt/carbon, this indicates that, (1) Pt supported on NbRuyO z can be more effective at splitting the C---C bond in ethanol and, (2) the scission occurs at potentials more ideal for a higher efficiency fuel cell anode. Ex situ-microscopy revealed the polarization-induced two- and three-dimensional formation of Pt-NbOx interfacial adsorption sites responsible for the facilitation of the total oxidation pathway of ethanol. The results show that synthesis and post-treatment of niobia supports can bias the utility of Pt/niobia systems towards the ethanol oxidation reaction at the anode or the oxygen reduction reaction at the cathode. Experimental and computational-theoretical analyses indicate that the mechanism of interfacial site formation is dependent upon the local oxygen concentration, as well as the availability of multiple, energetically accessible oxidation states like those inherent to niobia. Future directions for the development of highly active, niobium-based materials tailored for efficient catalysis of the total oxidation pathway of ethanol are discussed.

  19. Electrochemical enzyme-less urea sensor based on nano-tin oxide synthesized by hydrothermal technique.

    PubMed

    Ansari, S G; Fouad, H; Shin, Hyung-Shik; Ansari, Z A

    2015-12-01

    Nano-Tin oxide was synthesized using hydrothermal method at 150C for 6h and then thin films were deposited by electrophoretic method at an optimized voltage of 100V for 5min on electropolished aluminum substrate. Spherical particles of about 30-50nm diameters are observed with partial agglomeration when observed under electron microscope, which are tetragonal rutile structure. XPS results showed peaks related to Sn 4d, Sn 3d, O 1s & C 1s with spin-orbit splitting of 8.4eV for Sn 3d. Feasibility studies of enzyme less urea sensing characteristics of nano-tin oxide thin films are exhibited herein. The deposited films have been used for enzyme less urea sensing from 1 to 20mM concentration in buffer solution. The sensors were characterized electrochemically to obtain cyclic voltammogram as a function of urea concentration and scan rate. The sensitivity is estimated as 18.9?A/mM below 5mM and 2.31?A/mM above 5mM with a limit of detection of 0.6mM. PMID:26381425

  20. THERMAL AND ELECTROCHEMICAL THREE DIMENSIONAL CFD MODEL OF A PLANAR SOLID OXIDE ELECTROLYSIS CELL

    SciTech Connect

    Grant Hawkes; Jim O'Brien; Carl Stoots; Steve Herring; Mehrdad Shahnam

    2005-07-01

    A three-dimensional computational fluid dynamics (CFD) model has been created to model high-temperature steam electrolysis in a planar solid oxide electrolysis cell (SOEC). The model represents a single cell, as it would exist in an electrolysis stack. Details of the model geometry are specific to a stack that was fabricated by Ceramatec , Inc. and tested at the Idaho National Laboratory. Mass, momentum, energy, and species conservation and transport are provided via the core features of the commercial CFD code FLUENT2. A solid-oxide fuel cell (SOFC) model adds the electrochemical reactions and loss mechanisms and computation of the electric field throughout the cell. The FLUENT SOFC user-defined subroutine was modified for this work to allow for operation in the SOEC mode. Model results provide detailed profiles of temperature, Nernst potential, operating potential, anode-side gas composition, cathode-side gas composition, current density and hydrogen production over a range of stack operating conditions. Mean model results are shown to compare favorably with experimental results obtained from an actual ten-cell stack tested at INL.

  1. Electrochemical oxidation of landfill leachate in a flow reactor: optimization using response surface methodology.

    PubMed

    Silveira, Jefferson E; Zazo, Juan A; Pliego, Gema; Bidóia, Edério D; Moraes, Peterson B

    2015-04-01

    Response surface methodology based on Box-Behnken (BBD) design was successfully applied to the optimization in the operating conditions of the electrochemical oxidation of sanitary landfill leachate aimed for making this method feasible for scale up. Landfill leachate was treated in continuous batch-recirculation system, where a dimensional stable anode (DSA(©)) coated with Ti/TiO2 and RuO2 film oxide were used. The effects of three variables, current density (milliampere per square centimeter), time of treatment (minutes), and supporting electrolyte dosage (moles per liter) upon the total organic carbon removal were evaluated. Optimized conditions were obtained for the highest desirability at 244.11 mA/cm(2), 41.78 min, and 0.07 mol/L of NaCl and 242.84 mA/cm(2), 37.07 min, and 0.07 mol/L of Na2SO4. Under the optimal conditions, 54.99% of chemical oxygen demand (COD) and 71.07 ammonia nitrogen (NH3-N) removal was achieved with NaCl and 45.50 of COD and 62.13 NH3-N with Na2SO4. A new kinetic model predicted obtained from the relation between BBD and the kinetic model was suggested. PMID:25339535

  2. The electrochemical approach to concerted proton—electron transfers in the oxidation of phenols in water

    PubMed Central

    Costentin, Cyrille; Louault, Cyril; Robert, Marc; Savéant, Jean-Michel

    2009-01-01

    Establishing mechanisms and intrinsic reactivity in the oxidation of phenol with water as the proton acceptor is a fundamental task relevant to many reactions occurring in natural systems. Thanks to the easy measure of the reaction kinetics by the current and the setting of the driving force by the electrode potential, the electrochemical approach is particularly suited to this endeavor. Despite challenging difficulties related to self-inhibition blocking the electrode surface, experimental conditions were established that allowed a reliable analysis of the thermodynamics and mechanisms of the proton-coupled electron-transfer oxidation of phenol to be carried out by means of cyclic voltammetry. The thermodynamic characterization was conducted in buffer media whereas the mechanisms were revealed in unbuffered water. Unambiguous evidence of a concerted proton–electron transfer mechanism, with water as proton acceptor, was thus gathered by simulation of the experimental data with appropriately derived theoretical relationships, leading to the determination of a remarkably large intrinsic rate constant. The same strategy also allowed the quantitative analysis of the competition between the concerted proton–electron transfer pathway and an OH−-triggered stepwise pathway (proton transfer followed by electron transfer) at high pHs. Investigation of the passage between unbuffered and buffered media with the example of the PO4H2−/PO4H2− couple revealed the prevalence of a mechanism involving a proton transfer preceding an electron transfer over a PO4H2−-triggered concerted process. PMID:19822746

  3. Surface characteristics and electrochemical corrosion behavior of a pre-anodized microarc oxidation coating on titanium alloy.

    PubMed

    Cui, W F; Jin, L; Zhou, L

    2013-10-01

    A porous bioactive titania coating on biomedical β titanium alloy was prepared by pre-anodization followed by micro arc oxidation technology. The effects of pre-anodization on the phase constituent, morphology and electrochemical corrosion behavior of the microarc oxidation coating were investigated. The results show that pre-anodization has less influence on the phase constituent and the surface morphology of the microarc oxidation coating, but improves the inner layer density of the microarc oxidation coating. The decrease of plasma discharge strength due to the presence of the pre-anodized oxide film contributes to the formation of the compact inner layer. The pre-anodized microarc oxidation coating effectively inhibits the penetration of the electrolyte in 0.9% NaCl solution and thus increases the corrosion resistance of the coated titanium alloy in physiological solution. PMID:23910276

  4. Bipolar plating of metal contacts onto oxide interconnection for solid oxide electrochemical cell

    DOEpatents

    Isenberg, A.O.

    1987-03-10

    Disclosed is a method of forming an adherent metal deposit on a conducting layer of a tube sealed at one end. The tube is immersed with the sealed end down into an aqueous solution containing ions of the metal to be deposited. An ionically conducting aqueous fluid is placed inside the tube and a direct current is passed from a cathode inside the tube to an anode outside the tube. Also disclosed is a multi-layered solid oxide fuel cell tube which consists of an inner porous ceramic support tube, a porous air electrode covering the support tube, a non-porous electrolyte covering a portion of the air electrode, a non-porous conducting interconnection covering the remaining portion of the electrode, and a metal deposit on the interconnection. 1 fig.

  5. Bipolar plating of metal contacts onto oxide interconnection for solid oxide electrochemical cell

    DOEpatents

    Isenberg, Arnold O.

    1987-01-01

    Disclosed is a method of forming an adherent metal deposit on a conducting layer of a tube sealed at one end. The tube is immersed with the sealed end down into an aqueous solution containing ions of the metal to be deposited. An ionically conducting aqueous fluid is placed inside the tube and a direct current is passed from a cathode inside the tube to an anode outside the tube. Also disclosed is a multi-layered solid oxide fuel cell tube which consists of an inner porous ceramic support tube, a porous air electrode covering the support tube, a non-porous electrolyte covering a portion of the air electrode, a non-porous conducting interconnection covering the remaining portion of the electrode, and a metal deposit on the interconnection.

  6. Synthesis of gallium nitride nanostructures by nitridation of electrochemically deposited gallium oxide on silicon substrate

    NASA Astrophysics Data System (ADS)

    Ghazali, Norizzawati Mohd; Yasui, Kanji; Hashim, Abdul Manaf

    2014-12-01

    Gallium nitride (GaN) nanostructures were successfully synthesized by the nitridation of the electrochemically deposited gallium oxide (Ga2O3) through the utilization of a so-called ammoniating process. Ga2O3 nanostructures were firstly deposited on Si substrate by a simple two-terminal electrochemical technique at a constant current density of 0.15 A/cm2 using a mixture of Ga2O3, HCl, NH4OH and H2O for 2 h. Then, the deposited Ga2O3 sample was ammoniated in a horizontal quartz tube single zone furnace at various ammoniating times and temperatures. The complete nitridation of Ga2O3 nanostructures at temperatures of 850°C and below was not observed even the ammoniating time was kept up to 45 min. After the ammoniating process at temperature of 900°C for 15 min, several prominent diffraction peaks correspond to hexagonal GaN (h-GaN) planes were detected, while no diffraction peak of Ga2O3 structure was detected, suggesting a complete transformation of Ga2O3 to GaN. Thus, temperature seems to be a key parameter in a nitridation process where the deoxidization rate of Ga2O3 to generate gaseous Ga2O increase with temperature. The growth mechanism for the transformation of Ga2O3 to GaN was proposed and discussed. It was found that a complete transformation can not be realized without a complete deoxidization of Ga2O3. A significant change of morphological structures takes place after a complete transformation of Ga2O3 to GaN where the original nanorod structures of Ga2O3 diminish, and a new nanowire-like GaN structures appear. These results show that the presented method seems to be promising in producing high-quality h-GaN nanostructures on Si.

  7. Removal of caffeine from aqueous solution by indirect electrochemical oxidation using a graphite-PVC composite electrode: A role of hypochlorite ion as an oxidising agent.

    PubMed

    Al-Qaim, Fouad F; Mussa, Zainab H; Othman, Mohamed R; Abdullah, Md P

    2015-12-30

    The electrochemical oxidation of caffeine, a widely over-the-counter stimulant drug, has been investigated in effluent wastewater and deionized water (DIW) using graphite-poly vinyl chloride (PVC) composite electrode as anode. Effects of initial concentration of caffeine, chloride ion (Cl(-)) loading, presence of hydrogen peroxide (H2O2), sample volume, type of sample and applied voltage were determined to test and to validate a kinetic model for the oxidation of caffeine by the electrochemical oxidation process. The results revealed that the electrochemical oxidation rates of caffeine followed pseudo first-order kinetics, with rate constant values ranged from 0.006 to 0.23 min(-1) depending on the operating parameters. The removal efficiency of caffeine increases with applied voltage very significantly, suggesting a very important role of mediated oxidation process. However, the consumption energy was considered during electrochemical oxidation process. In chloride media, removal of caffeine is faster and more efficiently, although occurrence of more intermediates takes place. The study found that the adding H2O2 to the NaCl solution will inhibit slightly the electrochemical oxidation rate in comparison with only NaCl in solution. Liquid chromatography-time of flight-mass spectrometry (LC-TOF-MS) technique was applied to the identification of the by-products generated during electrochemical oxidation, which allowed to construct the proposed structure of by-products. PMID:26218306

  8. Vanadium Oxide Electrochemical Capacitors: An Investigation into Aqueous Capacitive Degradation, Alternate Electrolyte-Solvent Systems, Whole Cell Performance and Graphene Oxide Composite Electrodes

    NASA Astrophysics Data System (ADS)

    Engstrom, Allison Michelle

    Vanadium oxide has emerged as a potential electrochemical capacitor material due to its attractive pseudocapacitive performance; however, it is known to suffer from capacitive degradation upon sustained cycling. In this work, the electrochemical cycling behavior of anodically electrodeposited vanadium oxide films with various surface treatments in aqueous solutions is investigated at different pH. Quantitative compositional analysis and morphological studies provide additional insight into the mechanism responsible for capacitive degradation. Furthermore, the capacitance and impedance behavior of vanadium oxide electrochemical capacitor electrodes is compared for both aqueous and nonaqueous electrolyte-solvent systems. Alkali metal chloride and bromide electrolytes were studied in aqueous systems, and nonaqueous systems containing alkali metal bromides were studied in polar aprotic propylene carbonate (PC) or dimethyl sulfoxide (DMSO) solvents. The preferred aqueous and nonaqueous systems identified in the half-cell studies were utilized in symmetric vanadium oxide whole-cells. An aqueous system utilizing a 3.0 M NaCl electrolyte at pH 3.0 exhibited an excellent 96% capacitance retention over 3000 cycles at 10 mV s-1. An equivalent system tested at 500 mV s-1 displayed an increase in capacitance over the first several thousands of cycles, and eventually stabilized over 50,000 cycles. Electrodes cycled in nonaqueous 1.0 M LiBr in PC exhibited mostly non-capacitive charge-storage, and electrodes cycled in LiBr-DMSO exhibited a gradual capacitive decay over 10,000 cycles at 500 mV s-1. Morphological and compositional analyses, as well as electrochemical impedance modeling, provide additional insight into the cause of the cycing behavior. Lastly, reduced graphene oxide and vanadium oxide nanowire composites have been successfully synthesized using electrophoretic deposition for electrochemical capacitor electrodes. The composite material was found to perform with a higher capacitance than electrodes containing only vanadium oxide nanowires by a factor of 4.0 at 10 mV s-1 and 7.5 at 500 mV s-1. The thermally reduced composite material was examined in both symmetric and asymmetric whole cell electrochemical capacitor devices, and although the asymmetric cell achieved both higher energy and power density, the symmetric cell retained a higher capacitance over 50,000 cycles at 200 mV s-1.

  9. A non-oxidative electrochemical approach to online measurements of dopamine release through laccase-catalyzed oxidation and intramolecular cyclization of dopamine.

    PubMed

    Lin, Yuqing; Zhang, Zipin; Zhao, Lingzhi; Wang, Xiang; Yu, Ping; Su, Lei; Mao, Lanqun

    2010-02-15

    A new electrochemical approach to selective online measurements of dopamine (DA) release in the cerebral microdialysate is demonstrated with a non-oxidative mechanism based on the distinct reaction properties of DA and the excellent biocatalytic activity of laccase. To make the successful transition of the distinct sequential reaction properties of DA from a conceptual determination protocol to a practical online analytical system, laccase enzyme is immobilized onto magnetite nanoparticles and the nanoparticles are confined into a fused-silica capillary through an external magnetic field to fabricate a magnetic microreactor. The microreactor is placed in the upstream of the thin-layer electrochemical flow cell to efficiently catalyze the oxidation of DA into its quinonoid form and thereby initialize the sequential reactions including deprotonation, intramolecular cyclization, disproportionation and/or oxidation to finally give 5,6-dihydroxyindoline quinone. The electrochemical reduction of the produced 5,6-dihydroxyindoline quinone at bare glassy carbon electrode is used as the readout for the DA measurement. The laccase-immobilized microreactor is also found to catalyze the oxidation of ascorbic acid (AA) and 3,4-dihydroxyphenylacetic acid (DOPAC) into electroinactive species and, as such, to eliminate the great interference from both species. Moreover, the successful transition of the mechanism for DA detection from the conventional oxidative electrochemical approach to the non-oxidative one substantially enables the measurements virtually interference-free from physiological levels of uric acid, 5-hydroxytryptamine, norepinephrine, and epinephrine. The current response is linear with DA concentration within a concentration range from 1 to 20 microM with a sensitivity of 3.97 nA/microM. The detection limit, based on a signal-to-noise ratio of 3, is calculated to be 0.3 microM. The high selectivity and the good linearity as well as the high stability of the online method make it very potential for continuous monitoring of cerebral DA release in physiological and pathological processes. PMID:19926273

  10. Enhanced Osseointegration of Hierarchical Micro/Nanotopographic Titanium Fabricated by Microarc Oxidation and Electrochemical Treatment.

    PubMed

    Li, Guanglong; Cao, Huiliang; Zhang, Wenjie; Ding, Xun; Yang, Guangzheng; Qiao, Yuqin; Liu, Xuanyong; Jiang, Xinquan

    2016-02-17

    Rapid osseointegration is recognized as a critical factor in determining the success rate of orthopedic and dental implants. Microarc oxidation (MAO) fabricated titanium oxide coatings with a porous topography have been proven to be a potent approach to enhance osteogenic capacity. Now we report two kinds of new hierarchical coatings with similar micromorphologies but different nanotopographies (i.e., MAO and MAO-AK coatings), and both coatings significantly promote cell attachment and osteogenic differentiation through mediating the integrin ?1 signaling pathway. In this study, titanium with a unique hierarchical micro/nanomorphology surface was fabricated by a novel duplex coating process, that is, the first a titanium oxide layer was coated by MAO, and then the coating was electrochemically reduced in alkaline solution (MAO-AK). A series of in vitro stem cell differentiation and in vivo osseointegration experiments were carried out to evaluate the osteogenic capacity of the resulting coatings. In vitro, the initial adhesion of the canine bone marrow stem cells (BMSCs) seeded on the MAO and MAO-AK coatings was significantly enhanced, and cell proliferation was promoted. In addition, the expression levels of osteogenesis-related genes, osteorix, alkaline phosphates (ALP), osteopontin, and osteocalcin, in the canine BMSCs, were all up-regulated after incubation on these coatings, especially on the MAO-AK coating. Also, the in vitro ALP activity and mineralization capacity of canine BMSC cultured on the MAO-AK group was better than that on the MAO group. Furthermore, 6 weeks after insertion of the titanium implants into canine femurs, both the bone formation speed and the bone-implant contact ratio of the MAO-AK group were significantly higher than those of the MAO group. All these results suggest that this duplex coating process is promising for engineering titanium surfaces to promote osseointegration for dental and orthopedic applications. PMID:26789077

  11. Thermodynamic and kinetic study of mixed metal oxide cathode material for lithium organic polymer electrolyte electrochemical cells

    NASA Astrophysics Data System (ADS)

    Atwater, Terrill Bradford

    1997-09-01

    The thermodynamics and discharge kinetics of the lithium/bismuth modified manganese dioxide electrochemical couple was investigated. These investigations coupled with biased impedance spectroscopy studies lead to the establishment of a model of the electrochemical interfaces of the system. Biased impedance spectroscopy allows for the study of the electrodes during open circuit and discharge conditions. This ability to study the electrode interface during discharge allowed for the development of an equivalent circuit and description of the complex interface of the mixed metal oxide. The results of these techniques were the establishment of a theory of the discharge mechanism of the lithium/bismuth modified manganese dioxide electrochemical cell and the processes involved. Equivalent circuit analysis of materials provides data for comparison. Equivalent circuit analysis when used with biased impedance spectroscopy provides valued component data for lithium battery cathode material. The model, therefore, provides an invaluable tool in the investigation of new materials for use as lithium battery cathodes. Kinetic measurements were used to determine the catalytic nature of the bismuth phase in bismuth modified manganese dioxide lithium primary battery cathode material. A reduction in activation energy for lithium cells was identified in the bismuth manganese mixed metal oxide as compared to manganese dioxide. Impedance spectroscopy allowed for the identification of an additional process linked to the catalytic behavior of the bismuth oxide phase of the bismuth manganese mixed metal oxide. An additional part of the studies focused on the thermodynamics and kinetics of the lithium polymer electrolyte cells with bismuth manganese mixed metal oxide cathodes. This study resulted in the determination of thermodynamic properties of the electrochemical couple. Discharge kinetic measurements lead to the establishment of optimum cathode formulations. This optimization considered both gravimetric and volumetric efficiencies. Measurements examined the relationship between discharge characteristics and cathode material concentration and cathode thickness.

  12. Advanced low carbon-to-nitrogen ratio wastewater treatment by electrochemical and biological coupling process.

    PubMed

    Deng, Shihai; Li, Desheng; Yang, Xue; Zhu, Shanbin; Xing, Wei

    2016-03-01

    Nitrogen pollution in ground and surface water significantly affects the environment and its organisms, thereby leading to an increasingly serious environmental problem. Such pollution is difficult to degrade because of the lack of carbon sources. Therefore, an electrochemical and biological coupling process (EBCP) was developed with a composite catalytic biological carrier (CCBC) and applied in a pilot-scale cylindrical reactor to treat wastewater with a carbon-to-nitrogen (C/N) ratio of 2. The startup process, coupling principle, and dynamic feature of the EBCP were examined along with the effects of hydraulic retention time (HRT), dissolved oxygen (DO), and initial pH on nitrogen removal. A stable coupling system was obtained after 51 days when plenty of biofilms were cultivated on the CCBC without inoculation sludge. Autotrophic denitrification, with [Fe(2+)] and [H] produced by iron-carbon galvanic cells in CCBC as electron donors, was confirmed by equity calculation of CODCr and nitrogen removal. Nitrogen removal efficiency was significantly influenced by HRT, DO, and initial pH with optimal values of 3.5 h, 3.5 ± 0.1 mg L(-1), and 7.5 ± 0.1, respectively. The ammonia, nitrate, and total nitrogen (TN) removal efficiencies of 90.1 to 95.3 %, 90.5 to 99.0 %, and 90.3 to 96.5 % were maintained with corresponding initial concentrations of 40 ± 2 mg L(-1) (NH3-N load of 0.27 ± 0.01 kg NH3-N m(-3) d(-1)), 20 ± 1 mg L(-1), and 60 ± 2 mg L(-1) (TN load of 0.41 ± 0.02 kg TN m(-3) d(-1)). Based on the Eckenfelder model, the kinetics equation of the nitrogen transformation along the reactor was N e  = N 0 exp (-0.04368 h/L(1.8438)). Hence, EBCP is a viable method for advanced low C/N ratio wastewater treatment. PMID:26564190

  13. Virtual electrochemical nitric oxide analyzer using copper, zinc superoxide dismutase immobilized on carbon nanotubes in polypyrrole matrix.

    PubMed

    Madasamy, Thangamuthu; Pandiaraj, Manickam; Balamurugan, Murugesan; Karnewar, Santosh; Benjamin, Alby Robson; Venkatesh, Krishna Arun; Vairamani, Kanagavel; Kotamraju, Srigiridhar; Karunakaran, Chandran

    2012-10-15

    In this work, we have designed and developed a novel and cost effective virtual electrochemical analyzer for the measurement of NO in exhaled breath and from hydrogen peroxide stimulated endothelial cells using home-made potentiostat. Here, data acquisition system (NI MyDAQ) was used to acquire the data from the electrochemical oxidation of NO mediated by copper, zinc superoxide dismutase (Cu,ZnSOD). The electrochemical control programs (graphical user-interface software) were developed using LabVIEW 10.0 to sweep the potential, acquire the current response and process the acquired current signal. The Cu,ZnSOD (SOD1) immobilized on the carbon nanotubes in polypyrrole modified platinum electrode was used as the NO biosensor. The electrochemical behavior of the SOD1 modified electrode exhibited the characteristic quasi-reversible redox peak at the potential, +0.06 V vs. Ag/AgCl. The biological interferences were eliminated by nafion coated SOD1 electrode and then NO was measured selectively. Further, this biosensor showed a wide linear range of response over the concentration of NO from 0.1 μM to 1 mM with a detection limit of 0.1 μM and high sensitivity of 1.1 μA μM(-1). The electroanalytical results obtained here using the developed virtual electrochemical instrument were also compared with the standard cyclic voltammetry instrument and found in agreement with each other. PMID:23141325

  14. Virtual electrochemical nitric oxide analyzer using copper, zinc superoxide dismutase immobilized on carbon nanotubes in polypyrrole matrix.

    TOXLINE Toxicology Bibliographic Information

    Madasamy T; Pandiaraj M; Balamurugan M; Karnewar S; Benjamin AR; Venkatesh KA; Vairamani K; Kotamraju S; Karunakaran C

    2012-10-15

    In this work, we have designed and developed a novel and cost effective virtual electrochemical analyzer for the measurement of NO in exhaled breath and from hydrogen peroxide stimulated endothelial cells using home-made potentiostat. Here, data acquisition system (NI MyDAQ) was used to acquire the data from the electrochemical oxidation of NO mediated by copper, zinc superoxide dismutase (Cu,ZnSOD). The electrochemical control programs (graphical user-interface software) were developed using LabVIEW 10.0 to sweep the potential, acquire the current response and process the acquired current signal. The Cu,ZnSOD (SOD1) immobilized on the carbon nanotubes in polypyrrole modified platinum electrode was used as the NO biosensor. The electrochemical behavior of the SOD1 modified electrode exhibited the characteristic quasi-reversible redox peak at the potential, +0.06 V vs. Ag/AgCl. The biological interferences were eliminated by nafion coated SOD1 electrode and then NO was measured selectively. Further, this biosensor showed a wide linear range of response over the concentration of NO from 0.1 μM to 1 mM with a detection limit of 0.1 μM and high sensitivity of 1.1 μA μM(-1). The electroanalytical results obtained here using the developed virtual electrochemical instrument were also compared with the standard cyclic voltammetry instrument and found in agreement with each other.

  15. Preparation and characterization of zinc oxide nanoparticles and their sensor applications for electrochemical monitoring of nucleic acid hybridization.

    PubMed

    Yumak, Tugrul; Kuralay, Filiz; Muti, Mihrican; Sinag, Ali; Erdem, Arzum; Abaci, Serdar

    2011-09-01

    In this study, ZnO nanoparticles (ZNP) of approximately 30 nm in size were synthesized by the hydrothermal method and characterized by X-ray diffraction (XRD), Braun-Emmet-Teller (BET) N2 adsorption analysis and transmission electron microscopy (TEM). ZnO nanoparticles enriched with poly(vinylferrocenium) (PVF+) modified single-use graphite electrodes were then developed for the electrochemical monitoring of nucleic acid hybridization related to the Hepatitis B Virus (HBV). Firstly, the surfaces of polymer modified and polymer-ZnO nanoparticle modified single-use pencil graphite electrodes (PGEs) were characterized using scanning electron microscopy (SEM). The electrochemical behavior of these electrodes was also investigated using differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS). Subsequently, the polymer-ZnO nanoparticle modified PGEs were evaluated for the electrochemical detection of DNA based on the changes at the guanine oxidation signals. Various modifications in DNA oligonucleotides and probe concentrations were examined in order to optimize the electrochemical signals that were generated by means of nucleic acid hybridization. After the optimization studies, the sequence-selective DNA hybridization was investigated in the case of a complementary amino linked probe (target), or noncomplementary (NC) sequences, or target and mismatch (MM) mixture in the ratio of (1:1). PMID:21600741

  16. Development of Advanced Electrochemical Emission Spectroscopy for Monitoring Corrosion in Simulated DOE Liquid Waste

    SciTech Connect

    Digby D. Macdonald; Brian M. Marx; Sejin Ahn; Julio de Ruiz; Balaji Soundararaja; Morgan Smith; and Wendy Coulson

    2008-01-15

    Various forms of general and localized corrosion represent principal threats to the integrity of DOE liquid waste storage tanks. These tanks, which are of a single wall or double wall design, depending upon their age, are fabricated from welded carbon steel and contain a complex waste-form comprised of NaOH and NaNO{sub 3}, along with trace amounts of phosphate, sulfate, carbonate, and chloride. Because waste leakage can have a profound environmental impact, considerable interest exists in predicting the accumulation of corrosion damage, so as to more effectively schedule maintenance and repair. The different tasks that are being carried out under the current program are as follows: (1) Theoretical and experimental assessment of general corrosion of iron/steel in borate buffer solutions by using electrochemical impedance spectroscopy (EIS), ellipsometry and XPS techniques; (2) Development of a damage function analysis (DFA) which would help in predicting the accumulation of damage due to pitting corrosion in an environment prototypical of DOE liquid waste systems; (3) Experimental measurement of crack growth rate, acoustic emission signals and coupling currents for fracture in carbon and low alloy steels as functions of mechanical (stress intensity), chemical (conductivity), electrochemical (corrosion potential, ECP), and microstructural (grain size, precipitate size, etc) variables in a systematic manner, with particular attention being focused on the structure of the noise in the current and its correlation with the acoustic emissions; (4) Development of fracture mechanisms for carbon and low alloy steels that are consistent with the crack growth rate, coupling current data and acoustic emissions; (5) Inserting advanced crack growth rate models for SCC into existing deterministic codes for predicting the evolution of corrosion damage in DOE liquid waste storage tanks; (6) Computer simulation of the anodic and cathodic activity on the surface of the steel samples in order to exactly predict the corrosion mechanisms; (7) Wavelet analysis of EC noise data from steel samples undergoing corrosion in an environment similar to that of the high level waste storage containers, to extract data pertaining to general, pitting and stress corrosion processes, from the overall data. The Point Defect Model (PDM) is directly applied as the theoretical assessment method for describing the passive film formed on iron/steels. The PDM is used to describe general corrosion in the passive region of iron. In addition, previous work suggests that pit formation is due to the coalescence of cation vacancies at the metal/film interface which would make it possible to use the PDM parameters to predict the onset of pitting. This previous work suggests that once the critical vacancy density is reached, the film ruptures to form a pit. Based upon the kinetic parameters derived for the general corrosion case, two parameters relating to the cation vacancy formation and annihilation can be calculated. These two parameters can then be applied to predict the transition from general to pitting corrosion for iron/mild steels. If cation vacancy coalescence is shown to lead to pitting, it can have a profound effect on the direction of future studies involving the onset of pitting corrosion. The work has yielded a number of important findings, including an unequivocal demonstration of the role of chloride ion in passivity breakdown on nickel in terms of cation vacancy generation within the passive film, the first detection and characterization of individual micro fracture events in stress corrosion cracking, and the determination of kinetic parameters for the generation and annihilation of point defects in the passive film on iron. The existence of coupling between the internal crack environment and the external cathodic environment, as predicted by the coupled environment fracture model (CEFM), has also been indisputably established for the AISI 4340/NaOH system. It is evident from the studies that analysis of coupling current noise is a very sensitive tool for studying the crack tip processes in relation to the chemical, mechanical, electrochemical and microstructural properties of the system. Experiments are currently being carried out to explore these crack tip processes by simultaneous measurement of the acoustic activity at the crack tip in an effort to validate the coupling current data. These latter data are now being used to deterministically predict the accumulation of general and localized corrosion damage on carbon in prototypical DOE liquid waste storage tanks. Computer simulation of the cathodic and anodic activity on the steel surfaces is also being carried out in an effort to simulate the actual corrosion process. Wavelet analysis of the coupling current data promises to be a useful tool to differentiate between the different corrosion mechanisms.

  17. Enriching distinctive microbial communities from marine sediments via an electrochemical-sulfide-oxidizing process on carbon electrodes.

    PubMed

    Li, Shiue-Lin; Nealson, Kenneth H

    2015-01-01

    Sulfide is a common product of marine anaerobic respiration, and a potent reactant biologically and geochemically. Here we demonstrate the impact on microbial communities with the removal of sulfide via electrochemical methods. The use of differential pulse voltammetry revealed that the oxidation of soluble sulfide was seen at +30 mV (vs. SHE) at all pH ranges tested (from pH = 4 to 8), while non-ionized sulfide, which dominated at pH = 4 was poorly oxidized via this process. Two mixed cultures (CAT and LA) were enriched from two different marine sediments (from Catalina Island, CAT; from the Port of Los Angeles, LA) in serum bottles using a seawater medium supplemented with lactate, sulfate, and yeast extract, to obtain abundant biomass. Both CAT and LA cultures were inoculated in electrochemical cells (using yeast-extract-free seawater medium as an electrolyte) equipped with carbon-felt electrodes. In both cases, when potentials of +630 or +130 mV (vs. SHE) were applied, currents were consistently higher at +630 then at +130 mV, indicating more sulfide being oxidized at the higher potential. In addition, higher organic-acid and sulfate conversion rates were found at +630 mV with CAT, while no significant differences were found with LA at different potentials. The results of microbial-community analyses revealed a decrease in diversity for both CAT and LA after electrochemical incubation. In addition, some bacteria (e.g., Clostridium and Arcobacter) not well-known to be capable of extracellular electron transfer, were found to be dominant in the electrochemical cells. Thus, even though the different mixed cultures have different tolerances for sulfide, electrochemical-sulfide removal can lead to major population changes. PMID:25741331

  18. Enriching distinctive microbial communities from marine sediments via an electrochemical-sulfide-oxidizing process on carbon electrodes

    PubMed Central

    Li, Shiue-Lin; Nealson, Kenneth H.

    2015-01-01

    Sulfide is a common product of marine anaerobic respiration, and a potent reactant biologically and geochemically. Here we demonstrate the impact on microbial communities with the removal of sulfide via electrochemical methods. The use of differential pulse voltammetry revealed that the oxidation of soluble sulfide was seen at +30 mV (vs. SHE) at all pH ranges tested (from pH = 4 to 8), while non-ionized sulfide, which dominated at pH = 4 was poorly oxidized via this process. Two mixed cultures (CAT and LA) were enriched from two different marine sediments (from Catalina Island, CAT; from the Port of Los Angeles, LA) in serum bottles using a seawater medium supplemented with lactate, sulfate, and yeast extract, to obtain abundant biomass. Both CAT and LA cultures were inoculated in electrochemical cells (using yeast-extract-free seawater medium as an electrolyte) equipped with carbon-felt electrodes. In both cases, when potentials of +630 or +130 mV (vs. SHE) were applied, currents were consistently higher at +630 then at +130 mV, indicating more sulfide being oxidized at the higher potential. In addition, higher organic-acid and sulfate conversion rates were found at +630 mV with CAT, while no significant differences were found with LA at different potentials. The results of microbial-community analyses revealed a decrease in diversity for both CAT and LA after electrochemical incubation. In addition, some bacteria (e.g., Clostridium and Arcobacter) not well-known to be capable of extracellular electron transfer, were found to be dominant in the electrochemical cells. Thus, even though the different mixed cultures have different tolerances for sulfide, electrochemical-sulfide removal can lead to major population changes. PMID:25741331

  19. Development of advanced mixed oxide fuels for plutonium management

    SciTech Connect

    Eaton, S.; Beard, C.; Buksa, J.; Butt, D.; Chidester, K.; Havrilla, G.; Ramsey, K.

    1997-06-01

    A number of advanced Mixed Oxide (MOX) fuel forms are currently being investigated at Los Alamos National Laboratory that have the potential to be effective plutonium management tools. Evolutionary Mixed Oxide (EMOX) fuel is a slight perturbation on standard MOX fuel, but achieves greater plutonium destruction rates by employing a fractional nonfertile component. A pure nonfertile fuel is also being studied. Initial calculations show that the fuel can be utilized in existing light water reactors and tailored to address different plutonium management goals (i.e., stabilization or reduction of plutonium inventories residing in spent nuclear fuel). In parallel, experiments are being performed to determine the feasibility of fabrication of such fuels. Initial EMOX pellets have successfully been fabricated using weapons-grade plutonium.

  20. Comparison of different advanced oxidation processes for phenol degradation.

    PubMed

    Esplugas, Santiago; Gimnez, Jaime; Contreras, Sandra; Pascual, Esther; Rodrguez, Miguel

    2002-02-01

    Advanced Oxidation Processes (O3, O3/H2O2, UV, UV/O3, UV/H2O2, O3/UV/H2O2, Fe2+ /H2O2 and photocatalysis) for degradation of phenol in aqueous solution have been studied in earlier works. In this paper, a comparison of these techniques is undertaken: pH influence, kinetic constants, stoichiometric coefficient and optimum oxidant/pollutant ratio. Of the tested processes, Fenton reagent was found to the fastest one for phenol degradation. However, lower costs were obtained with ozonation. In the ozone combinations, the best results were achieved with single ozonation. As for the UV processes, UV/H2O2 showed the highest degradation rate. PMID:11848342

  1. Recent advances in the use of ionic liquids for electrochemical sensing.

    PubMed

    Silvester, Debbie S

    2011-12-01

    Ionic Liquids are salts that are liquid at (or just above) room temperature. They possess several advantageous properties (e.g. high intrinsic conductivity, wide electrochemical windows, low volatility, high thermal stability and good solvating ability), which make them ideal as non-volatile electrolytes in electrochemical sensors. This mini-review article describes the recent uses of ionic liquids in electrochemical sensing applications (covering the last 3 years) in the context of voltammetric sensing at solid/liquid, liquid/liquid interfaces and carbon paste electrodes, as well as their use in gas sensing, ion-selective electrodes, and for detecting biological molecules, explosives and chemical warfare agents. A comment on the future direction and challenges in this field is also presented. PMID:22013585

  2. Advanced Oxide Dispersion Strengthened and Nanostructured Ferritic Alloys

    SciTech Connect

    Miller, Michael K.; Parish, Chad M.; Li, Qian

    2013-10-01

    Nanostructured ferritic alloy is a subcategory of oxide dispersion strengthened steels intended for advanced reactor applications. The complex ultrafine grained microstructure of an advanced nanostructured ferritic alloy, as determined by electron microscopy and atom probe tomography, is summarised. Three distinct populations of precipitates were observed: 20–50 nm Ti(N,O,C), 5–10 nm diameter Y2Ti2O7/Y2TiO5 and 1–4 nm diameter Ti,Y,O enriched nanoclusters. The first two populations were predominantly located along grain boundaries together with Cr, W and C segregation. A dense population of nanoclusters was observed both in the grain interior as well as on the grain boundaries. These nanoclusters are highly tolerant to high dose irradiation at elevated temperatures.

  3. Electrochemical oxidation of reverse osmosis concentrate on boron-doped diamond anodes at circumneutral and acidic pH.

    PubMed

    Bagastyo, Arseto Y; Batstone, Damien J; Kristiana, Ina; Gernjak, Wolfgang; Joll, Cynthia; Radjenovic, Jelena

    2012-11-15

    Electrochemical processes have been widely investigated for degrading organic contaminants present in wastewater. This study evaluated the performance of electrochemical oxidation using boron-doped diamond (BDD) electrodes by forming OH() for the treatment of reverse osmosis concentrate (ROC) from secondary-treated wastewater effluents. Since oxidation by OH() and active chlorine species (HClO/ClO(-)) is influenced by pH, the electrochemical oxidation of ROC was evaluated at controlled pH 6-7 and at pH 1-2 (no pH adjustment). A high concentration of chloride ions in the ROC enhanced the oxidation, and 7-11% of Coulombic efficiency for chemical oxygen demand (COD) removal was achieved with 5.2 Ah L(-1) of specific electrical charge. Complete COD removal was observed after 5.2 and 6.6 Ah L(-1), yet the corresponding dissolved organic carbon (DOC) removal was only 48% (at acidic pH) and 59% (at circumneutral pH). Although a higher operating pH seemed to enhance the participation of OH() in oxidation mechanisms, high concentrations of chloride resulted in the formation of significant concentrations of adsorbable organic chlorine (AOCl) after electrochemical oxidation at both pH. While adsorbable organic bromine (AOBr) was degraded at a higher applied electrical charge, a continuous increase in AOCl concentration (up to 0.88 mM) was observed until the end of the experiments (i.e. 10.9 Ah L(-1)). In addition, total trihalomethanes (tTHMs) and total haloacetic acids (tHAAs) were further degraded with an increase in electrical charge under both pH conditions, to final total concentrations of 1 and 4 μM (tTHMs), and 12 and 22 μM (tHAAs), at acidic and circumneutral pH, respectively. In particular, tHAAs were still an order of magnitude above their initial concentration in ROC after further electrooxidation. Where high chloride concentrations are present, it was found to be necessary to separate chloride from ROC prior to electrochemical oxidation in order to avoid the formation of chlorinated by-products. PMID:22995242

  4. Electrochemical oxidation of ²⁴³Am(III) in nitric acid by a terpyridyl-derivatized electrode.

    PubMed

    Dares, Christopher J; Lapides, Alexander M; Mincher, Bruce J; Meyer, Thomas J

    2015-11-01

    Selective oxidation of trivalent americium (Am) could facilitate its separation from lanthanides in nuclear waste streams. Here, we report the application of a high-surface-area, tin-doped indium oxide electrode surface-derivatized with a terpyridine ligand to the oxidation of Am(III) to Am(V) and Am(VI) in nitric acid. Potentials as low as 1.8 volts (V) versus the saturated calomel electrode were applied, 0.7 V lower than the 2.6 V potential for one-electron oxidation of Am(III) to Am(IV) in 1 molar acid. This simple electrochemical procedure provides a method to access the higher oxidation states of Am in noncomplexing media for the study of the associated coordination chemistry and, more important, for more efficient separation protocols. PMID:26542564

  5. Novel Signal-Amplified Fenitrothion Electrochemical Assay, Based on Glassy Carbon Electrode Modified with Dispersed Graphene Oxide.

    PubMed

    Wang, Limin; Dong, Jinbo; Wang, Yulong; Cheng, Qi; Yang, Mingming; Cai, Jia; Liu, Fengquan

    2016-01-01

    A novel signal-amplified electrochemical assay for the determination of fenitrothion was developed, based on the redox behaviour of organophosphorus pesticides on a glassy carbon working electrode. The electrode was modified using graphene oxide dispersion. The electrochemical response of fenitrothion at the modified electrode was investigated using cyclic voltammetry, current-time curves, and square-wave voltammetry. Experimental parameters, namely the accumulation conditions, pH value, and volume of dispersed material, were optimised. Under the optimum conditions, a good linear relationship was obtained between the oxidation peak current and the fenitrothion concentration. The linear range was 1-400 ng·mL(-1), with a detection limit of 0.1 ng·mL(-1) (signal-to-nose ratio = 3). The high sensitivity of the sensor was demonstrated by determining fenitrothion in pakchoi samples. PMID:27003798

  6. Novel Signal-Amplified Fenitrothion Electrochemical Assay, Based on Glassy Carbon Electrode Modified with Dispersed Graphene Oxide

    NASA Astrophysics Data System (ADS)

    Wang, Limin; Dong, Jinbo; Wang, Yulong; Cheng, Qi; Yang, Mingming; Cai, Jia; Liu, Fengquan

    2016-03-01

    A novel signal-amplified electrochemical assay for the determination of fenitrothion was developed, based on the redox behaviour of organophosphorus pesticides on a glassy carbon working electrode. The electrode was modified using graphene oxide dispersion. The electrochemical response of fenitrothion at the modified electrode was investigated using cyclic voltammetry, current-time curves, and square-wave voltammetry. Experimental parameters, namely the accumulation conditions, pH value, and volume of dispersed material, were optimised. Under the optimum conditions, a good linear relationship was obtained between the oxidation peak current and the fenitrothion concentration. The linear range was 1–400 ng·mL‑1, with a detection limit of 0.1 ng·mL‑1 (signal-to-nose ratio = 3). The high sensitivity of the sensor was demonstrated by determining fenitrothion in pakchoi samples.

  7. Novel Signal-Amplified Fenitrothion Electrochemical Assay, Based on Glassy Carbon Electrode Modified with Dispersed Graphene Oxide

    PubMed Central

    Wang, Limin; Dong, Jinbo; Wang, Yulong; Cheng, Qi; Yang, Mingming; Cai, Jia; Liu, Fengquan

    2016-01-01

    A novel signal-amplified electrochemical assay for the determination of fenitrothion was developed, based on the redox behaviour of organophosphorus pesticides on a glassy carbon working electrode. The electrode was modified using graphene oxide dispersion. The electrochemical response of fenitrothion at the modified electrode was investigated using cyclic voltammetry, current-time curves, and square-wave voltammetry. Experimental parameters, namely the accumulation conditions, pH value, and volume of dispersed material, were optimised. Under the optimum conditions, a good linear relationship was obtained between the oxidation peak current and the fenitrothion concentration. The linear range was 1–400 ng·mL−1, with a detection limit of 0.1 ng·mL−1 (signal-to-nose ratio = 3). The high sensitivity of the sensor was demonstrated by determining fenitrothion in pakchoi samples. PMID:27003798

  8. Selective Separation of Cs and Sr from LiCl-Based Salt for Electrochemical Processing of Oxide Spent Nuclear Fuel

    SciTech Connect

    P Sachdev

    2008-07-01

    Electrochemical processing technology is currently being used for the treatment of metallic spent fuel from the Experimental Breeder Reactor-II at Idaho National Laboratory. The treatment of oxide-based spent nuclear fuel via electrochemical processing is possible provided there is a front-end oxide reduction step. During this reduction process, certain fission products, including Cs and Sr, partition into the salt phase and form chlorides. Both solid state and molten LiCl-zeolite-A ion exchange tests were conducted for selectively removing Cs and Sr from LiCl-based salt. The solid-state tests produced in excess of 99% removal of Cs and Sr. The molten state tests failed due to phase transformation of the zeolite structure when in contact with the molten LiCl salt.

  9. Use of high-temperature gas-tight electrochemical cells to measure electronic transport and thermodynamics in metal oxides

    SciTech Connect

    Park, J.H.; Ma, B.; Park, E.T.

    1997-10-01

    By using a gas-tight electrochemical cell, the authors can perform high-temperature coulometric titration and measure electronic transport properties to determine the electronic defect structure of metal oxides. This technique reduces the time and expense required for conventional thermogravimetric measurements. The components of the gas-tight coulometric titration cell are an oxygen sensor, Pt/yttria stabilized zirconia (YSZ)/Pt, and an encapsulated metal oxide sample. Based on cell design, both transport and thermodynamic measurements can be performed over a wide range of oxygen partial pressures (pO{sub 2} = 10{sup {minus}35} to 1 atm). This paper describes the high-temperature gas-tight electrochemical cells used to determine electronic defect structures and transport properties for pure and doped-oxide systems, such as YSZ, doped and pure ceria (Ca-CeO{sub 2} and CeO{sub 2}), copper oxides, and copper-oxide-based ceramic superconductors, transition metal oxides, SrFeCo{sub 0.5}O{sub x}, and BaTiO{sub 3}.

  10. More accurate macro-models of solid oxide fuel cells through electrochemical and microstructural parameter estimation - Part II: Parameter estimation

    NASA Astrophysics Data System (ADS)

    Boigues-Muñoz, Carlos; Pumiglia, Davide; McPhail, Stephen J.; Santori, Giulio; Montinaro, Dario; Comodi, Gabriele; Carlini, Maurizio; Polonara, Fabio

    2015-07-01

    This paper presents a systematic synergetic approach between experimental measurements, equivalent circuit modelling (described in Part I) and macro-scale modelling theory which has proved to be instrumental for the estimation of microstructural and electrochemical features of a Ni-YSZ|YSZ|Pr2NiO4+δ - GDC solid oxide fuel cell (SOFC). The aforementioned parameters have been used to generate a more accurate CFD macro-model which has been validated against the experimental results (presented in Part III).

  11. Formation of Co3O4 microframes from MOFs with enhanced electrochemical performance for lithium storage and water oxidation.

    PubMed

    Feng, Yi; Yu, Xin-Yao; Paik, Ungyu

    2016-05-01

    Co3O4 microframes are synthesized through a template-engaged strategy via the etching of Co-Co Prussian blue analogue microcubes with ammonia solution and subsequent annealing treatment. Benefitting from their unique structural merits including 3D open structure and high porosity, these Co3O4 microframes exhibit enhanced electrochemical properties for both lithium-ion batteries and water oxidation. PMID:27078114

  12. Electrochemical promotion of propane oxidation on Pt deposited on a dense β"-Al2O3 ceramic Ag+ conductor

    NASA Astrophysics Data System (ADS)

    Tsampas, Michail; Kambolis, Anastasios; Obeid, Emil; Lizarraga, Leonardo; Sapountzi, Foteini; Vernoux, Philippe

    2013-08-01

    A new kind of electrochemical catalyst based on a Pt porous catalyst film deposited on a β"-Al2O3 ceramic Ag+ conductor was developed and evaluated during propane oxidation. It was observed that upon anodic polarization, the rate of propane combustion was significantly electropromoted up to 400%. Moreover, for the first time, exponential increase of the catalytic rate was evidenced during galvanostatic transient experiment in excellent agreement with EPOC equation.

  13. Electrochemical capacitor

    DOEpatents

    Anderson, Marc A.; Liu, Kuo -Chuan; Mohr, Charles M.

    1999-10-05

    An inexpensive porous metal oxide material having high surface area, good conductivity and high specific capacitance is advantageously used in an electrochemical capacitor. The materials are formed in a sol-gel process which affords control over the properties of the resultant metal oxide materials.

  14. Electrochemical and biological characterization of coatings formed on Ti-15Mo alloy by plasma electrolytic oxidation.

    PubMed

    Kazek-Kęsik, Alicja; Krok-Borkowicz, Małgorzata; Pamuła, Elżbieta; Simka, Wojciech

    2014-10-01

    β-Type titanium alloys are considered the future materials for bone implants. To improve the bioactivity of Ti-15Mo, the surface was modified using the plasma electrolytic oxidation (PEO) process. Tricalcium phosphate (TCP, Ca3PO4), wollastonite (CaSiO3) and silica (SiO2) were selected as additives in the anodizing bath to enhance the bioactivity of the coatings formed during the PEO process. Electrochemical analysis of the samples was performed in Ringer's solution at 37°C. The open-circuit potential (EOCP) as a function of time, corrosion potential (ECORR), corrosion current density (jCORR) and polarization resistance (Rp) of the samples were determined. Surface modification improved the corrosion resistance of Ti-15Mo in Ringer's solution. In vitro studies with MG-63 osteoblast-like cells were performed for 1, 3 and 7 days. After 24h, the cells were well adhered on the entire surfaces, and their number increased with increasing culture time. The coatings formed in basic solution with wollastonite exhibited better biological performance compared with the as-ground sample. PMID:25175202

  15. The growth and electrochemical properties of metal-oxide thin films: lithium intercalation

    NASA Astrophysics Data System (ADS)

    Julien, C.; El-Farh, L.; Balkanski, M.; Hussain, O. M.; Nazri, G. A.

    1993-03-01

    Transition-metal oxides such as MoO 3 and V 6O 13 can undergo reversible lithium intercalation at ambient temperature and are used as cathode materials for secondary lithium batteries. Thin films of these compounds have been prepared by employing flash and thermal evaporation techniques. The films are systematically characterized by studying structural, optical and electrical properties in relation with the growth conditions. Electrochemical properties of lithium galvanic thin film cells of 100 μA h capacity are investigated. Thermodynamic data show that microbatteries fabricated with films formed at moderate temperature exhibit a monotonous discharge voltage indicating that the material remains in the single phase even for large intercalation ratio. The lithium diffusivity increases with the temperature Ts of preparation of the film and reaches a value of 10 -11 cm 2 s -1 in Li xMoO 3 and 10 -9 cm 2 s -1 in Li xV 6 O 13 for Ts = 250°C.

  16. Synthesis of Au/Graphene Oxide Composites for Selective and Sensitive Electrochemical Detection of Ascorbic Acid

    NASA Astrophysics Data System (ADS)

    Song, Jian; Xu, Lin; Xing, Ruiqing; Li, Qingling; Zhou, Chunyang; Liu, Dali; Song, Hongwei

    2014-12-01

    In this work, we present a novel ascorbic acid (AA) sensor applied to the detection of AA in human sera and pharmaceuticals. A series of Au nanoparticles (NPs) and graphene oxide sheets (Au NP/GO) composites were successfully synthesized by reduction of gold (III) using sodium citrate. Then the Au NP/GO composites were used to construct nonenzymatic electrodes in practical AA measurement. The electrode that has the best performance presents attractive analytical features, such as a low working potential of +0.15 V, a high sensitivity of 101.86 μA mM-1 cm-2 to AA, a low detection limit of 100 nM, good reproducibility and excellent selectivity. And more,it was also employed to accurately and practically detect AA in human serum and clinical vitamin C tablet with the existence of some food additive. The enhanced AA electrochemical properties of the Au NP/GO modified electrode in our work can be attributed to the improvement of electroactive surface area of Au NPs and the synergistic effect from the combination of Au NPs and GO sheets. This work shows that the Au NP/GO/GCEs hold the prospect for sensitive and selective determination of AA in practical clinical application.

  17. Electrochemical immunosensor for ethinylestradiol using diazonium salt grafting onto silver nanoparticles-silica-graphene oxide hybrids.

    PubMed

    Cincotto, Fernando H; Martínez-García, Gonzalo; Yáñez-Sedeño, Paloma; Canevari, Thiago C; Machado, S A S; Pingarrón, José M

    2016-01-15

    This work describes the preparation of an electrochemical immunosensor for ethinylestradiol (EE2) based on grafting of diazonium salt of 4-aminobenzoic acid onto a glassy carbon electrode modified with silver nanoparticles/SiO2/graphene oxide hybrid followed by covalent binding of anti-ethinylestradiol (anti-EE2) to activated carboxyl groups. A competitive immunoassay was developed for the determination of the hormone using peroxidase-labeled ethinylestradiol (HRP-EE2) and measurement of the amperometric response at -200mV in the presence of hydroquinone (HQ) as redox mediator. The calibration curve for EE2 exhibited a linear range between 0.1 and 50ng/mL (r(2)=0.996), with a detection limit of 65pg/mL. Interference studies with other hormones related with EE2 revealed the practical specificity of the developed method for the analyte. A good reproducibility, with RSD=4.5% (n=10) was also observed. The operating stability of a single bioelectrode modified with anti-EE2 was maintained at least for 15 days when it was stored at 4°C under humid conditions between measurements. The developed immunosensor was applied to the analysis of spiked urine with good results. PMID:26592615

  18. Highly Selective Oxidation of Carbohydrates in an Efficient Electrochemical Energy Converter: Cogenerating Organic Electrosynthesis.

    PubMed

    Holade, Yaovi; Servat, Karine; Napporn, Teko W; Morais, Cláudia; Berjeaud, Jean-Marc; Kokoh, Kouakou B

    2016-02-01

    The selective electrochemical conversion of highly functionalized organic molecules into electricity, heat, and added-value chemicals for fine chemistry requires the development of highly selective, durable, and low-cost catalysts. Here, we propose an approach to make catalysts that can convert carbohydrates into chemicals selectively and produce electrical power and recoverable heat. A 100 % Faradaic yield was achieved for the selective oxidation of the anomeric carbon of glucose and its related carbohydrates (C1-position) without any function protection. Furthermore, the direct glucose fuel cell (DGFC) enables an open-circuit voltage of 1.1 V in 0.5 m NaOH to be reached, a record. The optimized DGFC delivers an outstanding output power Pmax =2 mW cm(-2) with the selective conversion of 0.3 m glucose, which is of great interest for cogeneration. The purified reaction product will serve as a raw material in various industries, which thereby reduces the cost of the whole sustainable process. PMID:26777210

  19. Application of electrochemically reduced graphene oxide on screen-printed ion-selective electrode.

    PubMed

    Ping, Jianfeng; Wang, Yixian; Ying, Yibin; Wu, Jian

    2012-04-01

    In this study, a novel disposable all-solid-state ion-selective electrode using graphene as the ion-to-electron transducer was developed. The graphene film was prepared on screen-printed electrode directly from the graphene oxide dispersion by a one-step electrodeposition technique. Cyclic voltammetry and electrochemical impedance spectroscopy were employed to demonstrate the large double layer capacitance and fast charge transfer of the graphene film modified electrode. On the basis of these excellent properties, an all-solid-state calcium ion-selective electrode as the model was constructed using the calcium ion-selective membrane and graphene film modified electrode. The mechanism about the graphene promoting the ion-to-electron transformation was investigated in detail. The disposable electrode exhibited a Nernstian slope (29.1 mV/decade), low detection limit (10(-5.8) M), and fast response time (less than 10 s). With the high hydrophobic character of graphene materials, no water film was formed between the ion-selective membrane and the underlying graphene layer. Further studies revealed that the developed electrode was insensitive to light, oxygen, and redox species. The use of the disposable electrode for real sample analysis obtained satisfactory results, which made it a promising alternative in routine sensing applications. PMID:22380625

  20. Electrocatalysis of NADH oxidation using electrochemically activated fluphenazine on carbon nanotube electrode.

    PubMed

    Sobczak, Agnieszka; Rębiś, Tomasz; Milczarek, Grzegorz

    2015-12-01

    Electrocatalytic determination of NADH using a hybrid surface-modified electrode with multi-wall carbon nanotubes (MWCNTs) and a novel electrogenerated redox mediator is described. The redox mediator precursor - fluphenazine (Flu) was adsorbed on MWCNT-modified glassy carbon (GC) electrode which was then subjected to electrochemical activation in 0.1 M H2SO4 using cyclic voltammetry (CV) over a range of potentials -0.2 to 1.5 V vs. Ag/AgCl (6 scans at 100 mV s(-1)). Cyclic voltammograms of Flu indicated the formation of a stable electroactive material presenting one reversible redox couple at the formal potential of -0.115 vs. Ag/AgCl in a phosphate buffer (pH7.0) as a supporting electrolyte. The peaks increased linearly with increasing scan rate indicating electroactive molecules anchored to the electrode surface. The GC/MWCNT/Flu electrode efficiently catalyzed the oxidation of NADH with a decrease in the overpotential of about 600 mV and 150 mV compared to the bare GC and GC/MWCNT electrode, respectively. This modified electrode was successfully used as the working electrode in the chronoamperometric analysis. The peak current response to NADH was linear over its concentration range from 15 μM to 84 μM, and correlation coefficient 0.998. The limits of detection (5 μM) and quantitation (15 μM) were evaluated. PMID:26211441

  1. Synthesis of Au/Graphene Oxide Composites for Selective and Sensitive Electrochemical Detection of Ascorbic Acid

    PubMed Central

    Song, Jian; Xu, Lin; Xing, Ruiqing; Li, Qingling; Zhou, Chunyang; Liu, Dali; Song, Hongwei

    2014-01-01

    In this work, we present a novel ascorbic acid (AA) sensor applied to the detection of AA in human sera and pharmaceuticals. A series of Au nanoparticles (NPs) and graphene oxide sheets (Au NP/GO) composites were successfully synthesized by reduction of gold (III) using sodium citrate. Then the Au NP/GO composites were used to construct nonenzymatic electrodes in practical AA measurement. The electrode that has the best performance presents attractive analytical features, such as a low working potential of +0.15 V, a high sensitivity of 101.86 μA mM−1 cm−2 to AA, a low detection limit of 100 nM, good reproducibility and excellent selectivity. And more,it was also employed to accurately and practically detect AA in human serum and clinical vitamin C tablet with the existence of some food additive. The enhanced AA electrochemical properties of the Au NP/GO modified electrode in our work can be attributed to the improvement of electroactive surface area of Au NPs and the synergistic effect from the combination of Au NPs and GO sheets. This work shows that the Au NP/GO/GCEs hold the prospect for sensitive and selective determination of AA in practical clinical application. PMID:25515430

  2. Electrochemical studies on the oxidation of guanine and adenine at cyclodextrin modified electrodes.

    PubMed

    Abbaspour, Abdolkarim; Noori, Abolhassan

    2008-12-01

    An electrochemical sensor for guanine and adenine using cyclodextrin-modified poly(N-acetylaniline) (PNAANI) on a carbon paste electrode has been developed. The oxidation mechanism of guanine and adenine on the surface of the electrode was investigated by cyclic voltammetry. It was found that the electrode processes are irreversible, pH dependent, and involve several reaction products. The electron transfer process occurs in consecutive steps with the formation of a strongly adsorbed intermediate on the electrode surface. Also, a new method for estimating the apparent formation constants of guanine and adenine with the immobilized cyclodextrins, through the change of surface coverage of studied analytes has been reported. Both guanine and adenine showed linear concentrations in the range of 0.1-10 microM by using differential pulse voltammetry, with an experimental limit of detection down to 0.05 microM. Linear concentration ranges of 2-150 microM for guanine and 6-104 microM for adenine have been found when cyclic voltammetry was used for determination of both analytes. PMID:19082068

  3. Synthesis of Au/graphene oxide composites for selective and sensitive electrochemical detection of ascorbic acid.

    PubMed

    Song, Jian; Xu, Lin; Xing, Ruiqing; Li, Qingling; Zhou, Chunyang; Liu, Dali; Song, Hongwei

    2014-01-01

    In this work, we present a novel ascorbic acid (AA) sensor applied to the detection of AA in human sera and pharmaceuticals. A series of Au nanoparticles (NPs) and graphene oxide sheets (Au NP/GO) composites were successfully synthesized by reduction of gold (III) using sodium citrate. Then the Au NP/GO composites were used to construct nonenzymatic electrodes in practical AA measurement. The electrode that has the best performance presents attractive analytical features, such as a low working potential of +0.15 V, a high sensitivity of 101.86 μA mM(-1) cm(-2) to AA, a low detection limit of 100 nM, good reproducibility and excellent selectivity. And more,it was also employed to accurately and practically detect AA in human serum and clinical vitamin C tablet with the existence of some food additive. The enhanced AA electrochemical properties of the Au NP/GO modified electrode in our work can be attributed to the improvement of electroactive surface area of Au NPs and the synergistic effect from the combination of Au NPs and GO sheets. This work shows that the Au NP/GO/GCEs hold the prospect for sensitive and selective determination of AA in practical clinical application. PMID:25515430

  4. Effect of electrochemical oxidation on biodegradability and toxicity of batik industry wastewater

    NASA Astrophysics Data System (ADS)

    Subramaniam, Devagi; Halim, Azhar A.

    2014-09-01

    This study was conducted to investigate the increase in biodegradability and reduction in toxicity level in the batik wastewater treatment. Basically, the wastewater treatment from batik industry contained chemicals especially dyes which are not biodegradable and contains higher toxicity level because of the chemical compartment which comes out during the wastewater discharge and this could lead high risk in health wise to humans and all the aquatic living organisms. Thus, this research was carried to enhance the effectiveness of the electrochemical oxidation method by using the batik wastewater. Optimal parameters such as pH, time, distance between graphite electrodes and sodium chloride (NaCl) concentration as it activates as the electrolyte was done to obtain the removal of BOD, COD and color in the batik wastewater. The research study found that the removal of COD and color was high in the acidic conditions which are pH 5 with the removal of COD, 89.71% and color 93.89%. The ratio of BOD5/ COD successfully increased from 0.015 to 0.271 which mean it increase by 94.46% and the toxicity level using Toxtrax method (10017) also successfully reduced from 1.195% to 0.129% which means the samples which were slightly toxic were reduced to non-toxic level.

  5. Seedless growth of zinc oxide flower-shaped structures on multilayer graphene by electrochemical deposition

    PubMed Central

    2014-01-01

    A seedless growth of zinc oxide (ZnO) structures on multilayer (ML) graphene by electrochemical deposition without any pre-deposited ZnO seed layer or metal catalyst was studied. A high density of a mixture of vertically aligned/non-aligned ZnO rods and flower-shaped structures was obtained. ML graphene seems to generate the formation of flower-shaped structures due to the stacking boundaries. The nucleation of ZnO seems to be promoted at the stacking edges of ML graphene with the increase of applied current density, resulting in the formation of flower-shaped structures. The diameters of the rods/flower-shaped structures also increase with the applied current density. ZnO rods/flower-shaped structures with high aspect ratio over 5.0 and good crystallinity were obtained at the applied current densities of −0.5 and −1.0 mA/cm2. The growth mechanism was proposed. The growth involves the formation of ZnO nucleation below 80°C and the enhancement of the growth of vertically non-aligned rods and flower-shaped structures at 80°C. Such ZnO/graphene hybrid structure provides several potential applications in sensing devices. PMID:25024694

  6. A Highly Controllable Electrochemical Anodization Process to Fabricate Porous Anodic Aluminum Oxide Membranes

    NASA Astrophysics Data System (ADS)

    Lin, Yuanjing; Lin, Qingfeng; Liu, Xue; Gao, Yuan; He, Jin; Wang, Wenli; Fan, Zhiyong

    2015-12-01

    Due to the broad applications of porous alumina nanostructures, research on fabrication of anodized aluminum oxide (AAO) with nanoporous structure has triggered enormous attention. While fabrication of highly ordered nanoporous AAO with tunable geometric features has been widely reported, it is known that its growth rate can be easily affected by the fluctuation of process conditions such as acid concentration and temperature during electrochemical anodization process. To fabricate AAO with various geometric parameters, particularly, to realize precise control over pore depth for scientific research and commercial applications, a controllable fabrication process is essential. In this work, we revealed a linear correlation between the integrated electric charge flow throughout the circuit in the stable anodization process and the growth thickness of AAO membranes. With this understanding, we developed a facile approach to precisely control the growth process of the membranes. It was found that this approach is applicable in a large voltage range, and it may be extended to anodization of other metal materials such as Ti as well.

  7. Electrochemical detection of catecholamine exocytosis using planar iridium oxide electrodes in nanoliter microfluidic cell culture volumes

    PubMed Central

    Ges, Igor A.; Currie, Kevin P.M.; Baudenbacher, Franz

    2013-01-01

    Release of neurotransmitters and hormones by Ca2+ regulated exocytosis is a fundamental cellular/molecular process that is disrupted in a variety of psychiatric, neurological, and endocrine disorders. Therefore, this area represents a relevant target for drug and therapeutic development, efforts that will be aided by novel analytical tools and devices that provide mechanistically rich data with increased throughput. Toward this goal, we have electrochemically deposited iridium oxide (IrOx) films onto planar thin film platinum electrodes (20300m2) and utilized these for quantitative detection of catecholamine exocytosis from adrenal chromaffin cells trapped in a microfluidic network. The IrOx electrodes show a linear response to norepinephrine in the range of 0400M, with a sensitivity of 23.10.5mA/(Mmm2). The sensitivity of the IrOx electrodes does not change in the presence of ascorbic acid, a substance commonly found in biological samples. A replica molded polydimethylsiloxane (PDMS) microfluidic device with nanoliter sensing volumes was aligned and sealed to a glass substrate with the sensing electrodes. Small populations of chromaffin cells were trapped in the microfluidic sensing chamber and stimulated by rapid perfusion with high potassium (50mM) containing Tyrodes solution at a flow rate of 1nL/s. Stimulation of the cells produced a rapid increase in current due to oxidation of the released catecholamines, with an estimated maximum concentration in the microfluidic device ~52M. Thus, we demonstrate the utility of an integrated microfluidic network with IrOx electrodes for real-time quantitative detection of catecholamines released from small populations of cells. PMID:22398270

  8. Treatment of synthetic urine by electrochemical oxidation using conductive-diamond anodes.

    PubMed

    Dbira, Sondos; Bensalah, Nasr; Bedoui, Ahmed; Cañizares, Pablo; Rodrigo, Manuel A

    2015-04-01

    In this work, the electrochemical oxidation of synthetic urine by anodic oxidation using boron-doped diamond as anode and stainless steel as cathode was investigated. Results show that complete depletion of chemical oxygen demand (COD) and total organic carbon (TOC) can be attained regardless of the current density applied in the range 20-100 mA cm(-2). Oxalic and oxamic acids, and, in lower concentrations, creatol and guanidine were identified as the main intermediates. Chloride ions play a very important role as mediators and contribute not only to obtain a high efficiency in the removal of the organics but also to obtain an efficient removal of nitrogen by the transformation of the various raw nitrogen species into gaseous nitrogen through chloramine formation. The main drawback of the technology is the formation of chlorates and perchlorates as final chlorine products. The increase of current density from 20 to 60 mA cm(-2) led to an increase in the rate of COD and TOC removals although the process becomes less efficient in terms of energy consumption (removals of COD and TOC after applying 18 Ah dm(-3) were 93.94 and 94.94 %, respectively, at 20 mA cm(-2) and 89.17 and 86.72 %, respectively, at 60 mA cm(-2)). The most efficient conditions are low current densities and high temperature reaching total mineralization at an applied charge as low as 20 kAh m(-3). This result confirmed that the electrolysis using diamond anodes is a very interesting technology for the treatment of urine. PMID:25399531

  9. In-situ X-Ray Absorption Spectroscopy (XAS) Investigation of a Bifunctional Manganese Oxide Catalyst with High Activity for Electrochemical Water Oxidation and Oxygen Reduction

    PubMed Central

    Benck, Jesse D.; Gul, Sheraz; Webb, Samuel M.; Yachandra, Vittal K.; Yano, Junko; Jaramillo, Thomas F.

    2013-01-01

    In-situ x-ray absorption spectroscopy (XAS) is a powerful technique that can be applied to electrochemical systems, with the ability to elucidate the chemical nature of electrocatalysts under reaction conditions. In this study, we perform in-situ XAS measurements on a bifunctional manganese oxide (MnOx) catalyst with high electrochemical activity for the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER). Using x-ray absorption near edge structure (XANES) and extended x-ray absorption fine structure (EXAFS), we find that exposure to an ORR-relevant potential of 0.7 V vs. RHE produces a disordered Mn3II,III,IIIO4 phase with negligible contributions from other phases. After the potential is increased to a highly anodic value of 1.8 V vs. RHE, relevant to the OER, we observe an oxidation of approximately 80% of the catalytic thin film to form a mixed MnIII,IV oxide, while the remaining 20% of the film consists of a less oxidized phase, likely corresponding to unchanged Mn3II,III,IIIO4. XAS and electrochemical characterization of two thin film catalysts with different MnOx thicknesses reveals no significant influence of thickness on the measured oxidation states, at either ORR or OER potentials, but demonstrates that the OER activity scales with film thickness. This result suggests that the films have porous structure, which does not restrict electrocatalysis to the top geometric layer of the film. As the portion of the catalyst film that is most likely to be oxidized at the high potentials necessary for the OER is that which is closest to the electrolyte interface, we hypothesize that the MnIII,IV oxide, rather than Mn3II,III,IIIO4, is the phase pertinent to the observed OER activity. PMID:23758050

  10. A novel approach for analyzing electrochemical properties of mixed conducting solid oxide fuel cell anode materials by impedance spectroscopy.

    PubMed

    Nenning, A; Opitz, A K; Huber, T M; Fleig, J

    2014-10-28

    For application of acceptor-doped mixed conducting oxides as solid oxide fuel cell (SOFC) anodes, high electrochemical surface activity as well as acceptable electronic and ionic conductivity are crucial. In a reducing atmosphere, particularly the electronic conductivity of acceptor-doped oxides can become rather low and the resulting complex interplay of electrochemical reactions and charge transport processes makes a mechanistic interpretation of impedance measurements very complicated. In order to determine all relevant resistive and capacitive contributions of mixed conducting electrodes in a reducing atmosphere, a novel electrode design and impedance-based analysis technique is therefore introduced. Two interdigitating metallic current collectors are placed in a microelectrode, which allows in-plane measurements within the electrode as well as electrochemical measurements versus a counter electrode. Equivalent circuit models for quantifying the spectra of both measurement modes are developed and applied to simultaneously fit both spectra, using the same parameter set. In this manner, the electronic and ionic conductivity of the material as well as the area-specific resistance of the surface reaction and the chemical capacitance can be determined on a single microelectrode in a H2-H2O atmosphere. The applicability of this new tool was demonstrated in SrTi0.7Fe0.3O(3-δ) (STFO) thin film microelectrodes, deposited on single-crystalline yttria-stabilized zirconia (YSZ) substrates. All materials parameters that contribute to the polarization resistance of STFO electrodes in a reducing atmosphere could thus be quantified. PMID:25219525

  11. One-pot synthesis of NiFe layered double hydroxide/reduced graphene oxide composite as an efficient electrocatalyst for electrochemical and photoelectrochemical water oxidation

    NASA Astrophysics Data System (ADS)

    Youn, Duck Hyun; Park, Yoon Bin; Kim, Jae Young; Magesh, Ganesan; Jang, Youn Jeong; Lee, Jae Sung

    2015-10-01

    As an efficient non-precious metal catalyst for oxygen evolution reaction (OER) in electrochemical and photoelectrochemical water splitting, NiFe layered double hydroxide (LDH)/reduced graphene oxide (NiFe/RGO) composite is synthesized by a simple solvothermal method in one-pot. NiFe LDHs are uniformly deposited on RGO layers of high electrical conductivity and large surface area. In electrochemical water splitting, NiFe/RGO shows superior OER performance compared to bare NiFe and reference IrO2 with a lower benchmark η10 value (required overpotential to drive 10 mA cm-2) of 0.245 V. Furthermore, NiFe/RGO substantially increases the performance of a hematite photoanode in photoelectrochemical water oxidation, demonstrating its potential as an OER co-catalyst for photoelectrodes.

  12. Mediated electrochemical oxidation of organic wastes using a Co (III) mediator in a nitric acid based system

    DOEpatents

    Balazs, G. Bryan; Chiba, Zoher; Lewis, Patricia R.; Nelson, Norvell; Steward, G. Anthony

    1999-01-01

    An electrochemical cell with a Co(III) mediator and nitric acid electrolyte provides efficient destruction of organic and mixed wastes. The organic waste is concentrated in the anolyte reservoir, where the mediator oxidizes the organics and insoluble transuranic compounds and is regenerated at the anode until the organics are converted to CO.sub.2. The nitric acid is an excellent oxidant that facilitates the destruction of the organic components. The anode is not readily attacked by the nitric acid solution, thus the cell can be used for extended continual operation without electrode replacement.

  13. Mediated electrochemical oxidation of organic wastes using a Co (III) mediator in a nitric acid based system

    DOEpatents

    Balazs, G.B.; Chiba, Z.; Lewis, P.R.; Nelson, N.; Steward, G.A.

    1999-06-15

    An electrochemical cell with a Co(III) mediator and nitric acid electrolyte provides efficient destruction of organic and mixed wastes. The organic waste is concentrated in the anolyte reservoir, where the mediator oxidizes the organics and insoluble transuranic compounds and is regenerated at the anode until the organics are converted to CO[sub 2]. The nitric acid is an excellent oxidant that facilitates the destruction of the organic components. The anode is not readily attacked by the nitric acid solution, thus the cell can be used for extended continual operation without electrode replacement. 2 figs.

  14. Synthesis and electrocatalytic effect of Ag@Pt core-shell nanoparticles supported on reduced graphene oxide for sensitive and simple label-free electrochemical aptasensor.

    PubMed

    Mazloum-Ardakani, Mohammad; Hosseinzadeh, Laleh; Taleat, Zahra

    2015-12-15

    Bimetallic Ag@Pt core-shell nanoparticles supported on reduced graphene oxide nanosheets (Ag@Pt-GRs) was synthesized and used as novel desirable sensor platform and electrocatalyst for catechol as probe in aptasensor. Gold screen-printed electrodes modified with Ag@Pt-GRs and applied to advance enzyme-free and label-free electrochemical aptasensor for detection of protein biomarker tumor necrosis factor-alpha (TNF-α). The morphology of the Ag@Pt-GRs could be characterized by transmission electron microscopy, X-ray diffraction and UV-vis spectra. The results showed that these nanocomposite exhibited attractive electrocatalytic activity and also yielded large surface area, which improve the amount of immobilized TNF-α aptamer. Due to the excellent electrocatalytic activity of Ag@Pt-GRs towards the oxidation of catechol, determination of TNF-α antigen was based on its obstruction to the electrocatalytic oxidation of catechol by Ag@Pt-GRs after binding to the surface of electrode through interaction with the aptamer. The calibration curve was obtained by differential pulse voltammetry and square wave voltammetry. Under optimum conditions, the results demonstrated that this electrochemical aptasensor possessed a dynamic range from 0.0 pg/mL to 60 pg/mL with a low detection limit of 2.07 pg/mL for TNF-α. The analytical usefulness of the aptasensor was finally demonstrated analyzing serum samples. The simple fabrication method, high sensitivity, specificity, good reproducibility and stability as well as acceptable accuracy for TNF-α detection in human serum samples are the main advantages of this aptasensor, which might have broad applications in protein diagnostics and bioassay. PMID:26094037

  15. CoOx thin film deposited by CVD as efficient water oxidation catalyst: change of oxidation state in XPS and its correlation to electrochemical activity.

    PubMed

    Weidler, Natascha; Paulus, Sarina; Schuch, Jona; Klett, Joachim; Hoch, Sascha; Stenner, Patrick; Maljusch, Artjom; Brötz, Joachim; Wittich, Carolin; Kaiser, Bernhard; Jaegermann, Wolfram

    2016-04-20

    To reduce energy losses in water electrolysers a fundamental understanding of the water oxidation reaction steps is necessary to design efficient oxygen evolution catalysts. Here we present CoOx/Ti electrocatalytic films deposited by thermal and plasma enhanced chemical vapor deposition (CVD) onto titanium substrates. We report electrochemical (EC), photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) measurements. The electrochemical behavior of the samples was correlated with the chemical and electronic structure by recording XPS spectra before and after each electrochemical treatment (conditioning and cyclovoltammetry). The results show that the electrochemical behavior of CoOx/Ti strongly depends on the resulting electronic structure and composition. The thermal deposition leads to the formation of a pure Co(ii)Ox which transforms to a mixed Co(ii)Co(iii)Ox during the OER. This change in oxidation state is coupled with a decrease in overpotential from η = 0.57 V to η = 0.43 V at 5 mA cm(-2). Plasma deposition in oxygen leads to a Co(iii)-dominated mixed CoOx, that has a lower onset potential as deposited due to a higher Co(iii) content in the initial deposited material. After the OER XPS results of the CoOx/Ti indicate a partial formation of hydroxides and oxyhydroxides on the oxide surface. Finally the plasma deposition in air, results in a CoOxOH2 surface, that is able to completely oxidizes during OER to an oxyhydroxide Co(iii)OOH. With the in situ formed CoOOH we present a highly active catalyst for the OER (η = 0.34 at 5 mA cm(-2); η = 0.37 V at 10 mA cm(-2)). PMID:26694730

  16. Synthesis of gallium nitride nanostructures by nitridation of electrochemically deposited gallium oxide on silicon substrate

    PubMed Central

    2014-01-01

    Gallium nitride (GaN) nanostructures were successfully synthesized by the nitridation of the electrochemically deposited gallium oxide (Ga2O3) through the utilization of a so-called ammoniating process. Ga2O3 nanostructures were firstly deposited on Si substrate by a simple two-terminal electrochemical technique at a constant current density of 0.15 A/cm2 using a mixture of Ga2O3, HCl, NH4OH and H2O for 2 h. Then, the deposited Ga2O3 sample was ammoniated in a horizontal quartz tube single zone furnace at various ammoniating times and temperatures. The complete nitridation of Ga2O3 nanostructures at temperatures of 850°C and below was not observed even the ammoniating time was kept up to 45 min. After the ammoniating process at temperature of 900°C for 15 min, several prominent diffraction peaks correspond to hexagonal GaN (h-GaN) planes were detected, while no diffraction peak of Ga2O3 structure was detected, suggesting a complete transformation of Ga2O3 to GaN. Thus, temperature seems to be a key parameter in a nitridation process where the deoxidization rate of Ga2O3 to generate gaseous Ga2O increase with temperature. The growth mechanism for the transformation of Ga2O3 to GaN was proposed and discussed. It was found that a complete transformation can not be realized without a complete deoxidization of Ga2O3. A significant change of morphological structures takes place after a complete transformation of Ga2O3 to GaN where the original nanorod structures of Ga2O3 diminish, and a new nanowire-like GaN structures appear. These results show that the presented method seems to be promising in producing high-quality h-GaN nanostructures on Si. PMID:25593562

  17. Synthesis of gallium nitride nanostructures by nitridation of electrochemically deposited gallium oxide on silicon substrate.

    PubMed

    Ghazali, Norizzawati Mohd; Yasui, Kanji; Hashim, Abdul Manaf

    2014-01-01

    Gallium nitride (GaN) nanostructures were successfully synthesized by the nitridation of the electrochemically deposited gallium oxide (Ga2O3) through the utilization of a so-called ammoniating process. Ga2O3 nanostructures were firstly deposited on Si substrate by a simple two-terminal electrochemical technique at a constant current density of 0.15 A/cm(2) using a mixture of Ga2O3, HCl, NH4OH and H2O for 2 h. Then, the deposited Ga2O3 sample was ammoniated in a horizontal quartz tube single zone furnace at various ammoniating times and temperatures. The complete nitridation of Ga2O3 nanostructures at temperatures of 850°C and below was not observed even the ammoniating time was kept up to 45 min. After the ammoniating process at temperature of 900°C for 15 min, several prominent diffraction peaks correspond to hexagonal GaN (h-GaN) planes were detected, while no diffraction peak of Ga2O3 structure was detected, suggesting a complete transformation of Ga2O3 to GaN. Thus, temperature seems to be a key parameter in a nitridation process where the deoxidization rate of Ga2O3 to generate gaseous Ga2O increase with temperature. The growth mechanism for the transformation of Ga2O3 to GaN was proposed and discussed. It was found that a complete transformation can not be realized without a complete deoxidization of Ga2O3. A significant change of morphological structures takes place after a complete transformation of Ga2O3 to GaN where the original nanorod structures of Ga2O3 diminish, and a new nanowire-like GaN structures appear. These results show that the presented method seems to be promising in producing high-quality h-GaN nanostructures on Si. PMID:25593562

  18. Electronic defects and interface potentials for Al oxide films on Al and their relationship to electrochemical properties

    SciTech Connect

    SULLIVAN,JOHN P.; DUNN,ROBERTO G.; BARBOUR,J. CHARLES; WALL,FREDERICK D.; MISSERT,NANCY A.; BUCHHEIT,R.G.

    2000-06-01

    The relative electronic defect densities and oxide interface potentials were determined for naturally-occurring and synthetic Al oxides on Al. In addition, the effect of electrochemical treatment on the oxide electrical properties was assessed. The measurements revealed (1) that the open circuit potential of Al in aqueous solution is inversely correlated with the oxide electronic defect density (viz., lower oxide conductivities are correlated with higher open circuit potentials), and (2) the electronic defect density within the Al oxide is increased upon exposure to an aqueous electrolyte at open circuit or applied cathodic potentials, while the electronic defect density is reduced upon exposure to slight anodic potentials in solution. This last result, combined with recent theoretical predictions, suggests that hydrogen may be associated with electronic defects within the Al oxide, and that this H may be a mobile species, diffusing as H{sup +}. The potential drop across the oxide layer when immersed in solution at open circuit conditions was also estimated and found to be 0.3 V, with the field direction attracting positive charge towards the Al/oxide interface.

  19. A highly sensitive electrochemical biosensor for catechol using conducting polymer reduced graphene oxide-metal oxide enzyme modified electrode.

    PubMed

    Sethuraman, V; Muthuraja, P; Anandha Raj, J; Manisankar, P

    2016-10-15

    The fabrication, characterization and analytical performances were investigated for a catechol biosensor, based on the PEDOT-rGO-Fe2O3-PPO composite modified glassy carbon (GC) electrode. The graphene oxide (GO) doped conducting polymer poly (3,4-ethylenedioxythiophene) (PEDOT) was prepared through electrochemical polymerization by potential cycling. Reduction of PEDOT-GO was carried out by amperometric method. Fe2O3 nanoparticles were synthesized in ethanol by hydrothermal method. The mixture of Fe2O3, PPO and glutaraldehyde was casted on the PEDOT-rGO electrode. The surface morphology of the modified electrodes was studied by FE-SEM and AFM. Cyclic voltammetric studies of catechol on the enzyme modified electrode revealed higher reduction peak current. Determination of catechol was carried out successfully by Differential Pulse Voltammetry (DPV) technique. The fabricated biosensor investigated shows a maximum current response at pH 6.5. The catechol biosensor exhibited wide sensing linear range from 4×10(-8) to 6.20×10(-5)M, lower detection limit of 7×10(-9)M, current maxima (Imax) of 92.55µA and Michaelis-Menten (Km) constant of 30.48µM. The activation energy (Ea) of enzyme electrode is 35.93KJmol(-1) at 50°C. There is no interference from d-glucose and l-glutamic acid, ascorbic acid and o-nitrophenol. The PEDOT-rGO-Fe2O3-PPO biosensor was stable for at least 75 days when stored in a buffer at about 4°C. PMID:26751827

  20. Electrochemical and spectroscopic studies of some less stable oxidation states of selected lanthanide and actinide elements

    SciTech Connect

    Hobart, D. E.

    1981-06-01

    Simultaneous observation of electrochemical and spectroscopic properties (spectroelectrochemistry) at optically transparent electrodes (OTE's) was used to study some less stable oxidation states of selected lanthanide and actinide elements. Cyclic voltammetry at microelectrodes was used in conjunction with spectroelectrochemistry for the study of redox couples. Additional analytical techniques were used. The formal reduction potential (E/sup 0/') values of the M(III)/M(II) redox couples in 1 M KCl at pH 6 were -0.34 +- 0.01 V for Eu, -1.18 +- 0.01 V for Yb, and -1.50 +- 0.01 V for Sm. Spectropotentiostatic determination of E/sup 0/' for the Eu(III)/Eu(II) redox couple yielded a value of -0.391 +- 0.005 V. Spectropotentiostatic measurement of the Ce(IV)/Ce(III) redox couple in concentrated carbonate solution gave E/sup 0/' equal to 0.051 +- 0.005 V, which is about 1.7 V less positive than the E/sup 0/' value in noncomplexing solution. This same difference in potential was observed for the E/sup 0/' values of the Pr(IV)/Pr(III) and Tb(IV)/Tb(III) redox couples in carbonate solution, and thus Pr(IV) and Tb(IV) were stabilized in this medium. The U(VI)/U(V)/U(IV) and U(IV)/U(III) redox couples were studied in 1 M KCl at OTE's. Spectropotentiostatic measurement of the Np(VI)/Np(V) redox couple in 1 M HClO/sub 4/ gave an E/sup 0/' value of 1.140 +- 0.005 V. An E/sup 0/' value of 0.46 +- 0.01 V for the Np(VII)/Np(VI) couple was found by voltammetry. Oxidation of Am(III) was studied in concentrated carbonate solution, and a reversible cyclic voltammogram for the Am(IV)/Am(III) couple yielded E/sup 0/' = 0.92 +- 0.01 V in this medium; this value was used to estimate the standard reduction potential (E/sup 0/) of the couple as 2.62 +- 0.01 V. Attempts to oxidize Cm(III) in concentrated carbonate solution were not successful which suggests that the predicted E/sup 0/ value for the Cm(IV)/Cm(III) redox couple may be in error.

  1. Unraveling a two-step oxidation mechanism in electrochemical Cu-MOF synthesis.

    PubMed

    Schäfer, Philipp; van der Veen, Monique A; Domke, Katrin F

    2016-03-17

    To employ the full potential of electrochemical (ec) synthesis to grow metal-organic frameworks (MOFs) in more complex organizations at the mesoscale, it is vital to understand the underlying crystallization reaction pathway. For the MOF most typically grown electrochemically, CuBTC, we systematically investigated the role of oxygen species in the synthesis. PMID:26954845

  2. 2,4-Toluene diisocyanate detection in liquid and gas environments through electrochemical oxidation in an ionic liquid.

    PubMed

    Lin, Lu; Rehman, Abdul; Chi, Xiaowei; Zeng, Xiangqun

    2016-02-01

    The electrochemical oxidation of 2,4-toluene diisocyanate (2,4-TDI) in an ionic liquid (IL) has been systematically characterized to determine plausible electrochemical and chemical reaction mechanisms and to define the optimal detection methods for such a highly significant analyte. It has been found that the use of an IL as the electrolyte allows the oxidation of 2,4-TDI to occur at a less positive anodic potential with no side reactions as compared to traditional acetonitrile based electrolytes. UV-Vis, FT-IR, cyclic voltammetry and Electrochemical Impedance Spectroscopy (EIS) studies have revealed the unique mechanisms of dimerization of 2,4-TDI at the electrode interface by self-addition reactions, which can be utilized to improve the selectivity of detection. The study of 2,4-TDI redox chemistry further facilitates the development of a robust amperometric sensing methodology by selecting a hydrophobic IL ([C4mpy][NTf2]) and by restricting the potential window to only include the oxidation process. Thus, this innovative electrochemical sensor is capable of avoiding the two most ubiquitous interferents in ambient conditions (i.e. humidity and oxygen), thereby enhancing the sensor performance and reliability for real world applications. The method was established to detect 2,4-TDI in both liquid and gas phases. The limits of detection (LOD) values were 130.2 ppm and 0.7862 ppm, respectively, for the two phases, and are comparable to the safety standards reported by NIOSH. The as-developed 2.4-TDI amperometric sensor exhibits a sensitivity of 1.939 μA ppm(-1). Moreover, due to the simplicity of design and the use of an IL both as a solvent and non-volatile electrolyte, the sensor has the potential to be miniaturized for smart sensing protocols in distributed sensor applications. PMID:26763507

  3. Measuring fundamental properties in operating solid oxide electrochemical cells by using in situ X-ray photoelectron spectroscopy.

    PubMed

    Zhang, Chunjuan; Grass, Michael E; McDaniel, Anthony H; DeCaluwe, Steven C; El Gabaly, Farid; Liu, Zhi; McCarty, Kevin F; Farrow, Roger L; Linne, Mark A; Hussain, Zahid; Jackson, Gregory S; Bluhm, Hendrik; Eichhorn, Bryan W

    2010-11-01

    Photoelectron spectroscopic measurements have the potential to provide detailed mechanistic insight by resolving chemical states, electrochemically active regions and local potentials or potential losses in operating solid oxide electrochemical cells (SOCs), such as fuel cells. However, high-vacuum requirements have limited X-ray photoelectron spectroscopy (XPS) analysis of electrochemical cells to ex situ investigations. Using a combination of ambient-pressure XPS and CeO(2-x)/YSZ/Pt single-chamber cells, we carry out in situ spectroscopy to probe oxidation states of all exposed surfaces in operational SOCs at 750 °C in 1 mbar reactant gases H(2) and H(2)O. Kinetic energy shifts of core-level photoelectron spectra provide a direct measure of the local surface potentials and a basis for calculating local overpotentials across exposed interfaces. The mixed ionic/electronic conducting CeO(2-x) electrodes undergo Ce(3+)/Ce(4+) oxidation-reduction changes with applied bias. The simultaneous measurements of local surface Ce oxidation states and electric potentials reveal the active ceria regions during H(2) electro-oxidation and H(2)O electrolysis. The active regions extend ~150 μm from the current collectors and are not limited by the three-phase-boundary interfaces associated with other SOC materials. The persistence of the Ce(3+)/Ce(4+) shifts in the ~150 μm active region suggests that the surface reaction kinetics and lateral electron transport on the thin ceria electrodes are co-limiting processes. PMID:20871607

  4. UTILITY OF MECHANISTIC MODELS FOR DIRECTING ADVANCED SEPARATIONS RESEARCH & DEVELOPMENT ACTIVITIES: Electrochemically Modulated Separation Example

    SciTech Connect

    Schwantes, Jon M.

    2009-06-01

    The objective for this work was to demonstrate the utility of mechanistic computer models designed to simulate actinide behavior for use in efficiently and effectively directing advanced laboratory R&D activities associated with developing advanced separations methods.

  5. Electrochemical abatement of pollutants NO sub x and SO sub x in a solid-oxide electrolyte reactor

    SciTech Connect

    Stevenson, D.A.; Frank, C.W.

    1990-11-01

    The present research program is a basic study of the electrocatalysis of the electrochemical decomposition of gaseous pollutant species NOx and SOx. The effective removal of these species is a worthy goal for utilizing coal combustion systems in order to minimize the impact of acid rain and photochemical smog. These electrochemical devices show great promise: they have no moving parts, they are quiet, and the relevant materials can tolerate the harsh conditions of exhaust systems. The heart of these devices are the solid electrolytes which already are applied in similar environments for exhaust sensors and for fuel cells. In contrast to the exhaust sensor which operates a solid electrolyte electrochemical cell in an open circuit sensor mode and the fuel cell which is a galvanic cell, the abatement cell is a electrolytic cell, with a DC power source used to reduce NOx and SOx to elemental nitrogen and sulfur, respectively at the cathode. The critical practical issues for this application are the extent of reaction of the pollutant gases, the capital costs of the systems, the lifetime cost of the system, and the operation costs. This basic study addresses the last issue, the power requirements for the operation of these cells. The authors have carried out fundamental studies of the electrolytic conductivity and electrochemical kinetics for these abatement reactions. They have investigated two electrolytes, yttria stabilized zirconia (YSZ) and erbia stabilized bismuth oxide (ESB). Individual sections have been indexed separately for inclusion on the data base.

  6. Electrochemical immunosensor for sensitive determination of the anorexigen peptide YY at grafted reduced graphene oxide electrode platforms.

    PubMed

    Guerrero, S; Martínez-García, G; Serafín, V; Agüí, L; Yáñez-Sedeño, P; Pingarrón, J M

    2015-11-21

    The first electrochemical immunosensor for the determination of peptide YY is reported in this paper. A novel electrochemical platform, prepared by the electrochemical grafting of the diazonium salt of 4-aminobenzoic acid onto a reduced graphene oxide-modified glassy carbon electrode, was used, on which the covalent immobilization of specific anti-PYY antibodies was accomplished. The HOOC-Phe-rGO/GCEs were characterized using cyclic voltammetry and electrochemical impedance spectroscopy. The different variables affecting the preparation of the modified electrodes and the performance of the immunosensor were optimized. Under the optimized conditions, a calibration plot for PYY showing a linear range extending between 10(-4) and 10(2) ng mL(-1) was found. This range is adequate for the determination of this protein in real samples, since the expected concentration in human serum is around 100 pg mL(-1). The limit of detection was 0.01 pg mL(-1) of PYY. The immunosensor exhibited good reproducibility of the PYY measurements, excellent storage stability and selectivity, as well as a shorter assay time than those of ELISA kits. The usefulness of the immunosensor for the analysis of real samples was demonstrated by analyzing human serum samples spiked with PYY at three concentration levels. PMID:26258180

  7. Understanding the mechanism of surface modification through enhanced thermal and electrochemical stabilities of N-doped graphene oxide

    NASA Astrophysics Data System (ADS)

    Mehetre, Shantilal S.; Maktedar, Shrikant S.; Singh, Man

    2016-03-01

    The kinetically active two dimensional surface of graphene oxide (GrO) plays an important role in understanding the chemistry of graphene. The GrO is comprises of carbon and oxygen while the f-(6-AIND) GrO contains nitrogen along with carbon and oxygen. The prominent thermal instability of GrO is widely explored. However, due to the synergistic impact of their constituting elements, the thermal and electrochemical stability of f-(6-AIND) GrO enhances after N-doping with nitrogen containing heterocycles like 6-Aminoindazole. Hence it is essential to probe the mutual impact of various functionalities present over the surface of GrO, to understand the mechanism of direct functionalization of GrO with thermal and electrochemical stabilities. Therefore, the decomposition kinetics of discrete atomic domains and their effect on thermal stability of f-(6-AIND) GrO was revealed with spectroscopic analysis and thermal assessment. Additionally, the mechanism of thermal transformation is precisely developed to demonstrate the impact of heat on weight loss due to the mass transfer. Likewise, the electrochemical properties can be well understood with the help of mechanism of electrochemical activity and cyclic voltammetry experiments. Also, the f-(6-AIND) GrO is confirmed with the help of various surface analysis techniques like FTIR, EDS, HR-XPS, HR-TEM, CV, SAED, TGA, DSC and UV-vis.

  8. Advanced oxidation of bleached eucalypt kraft pulp mill effluent.

    PubMed

    Mounteer, A H; Pereira, R O; Morais, A A; Ruas, D B; Silveira, D S A; Viana, D B; Medeiros, R C

    2007-01-01

    In this study a poorly biodegradable (BOD/COD = 0.3) industrial alkaline ECF bleaching filtrate was treated using different advanced oxidation processes to evaluate their use in combined chemical-biological treatment aimed at increasing recalcitrant COD removal and improving final effluent quality. Oxidative treatments included ozonation combined with hydrogen peroxide (2, 5, 10, 20 mmol L(-1) O3/0.7, 2, 5, 10 mmol L(-1) H2O2) and photocatalysis with hydrogen peroxide (UV/2, 4 and 8 mmolL(-1) H2O2) and with TiO2 (UV/TiO2/0.7 and 4 mmol L(-1) H2O2). The O3/H2O2 process increased effluent biodegradability by up to 68% as a result of increasing BOD and decreasing COD. Increasing the O3 dose had a greater effect on biodegradability improvement and lignin and colour removal efficiencies than increasing the H2O2 dose. A combined oxidant dose of 5 mmol L(-1) O3 and 2 mmol L(-1) H2O2 resulted in 75% lignin removal, 40% colour removal and 6% carbohydrate loss without mineralizing the organic carbon. The photocatalytic processes led to a decrease in effluent biodegradability through combined decrease in BOD and increase in COD and did not result in efficient lignin or colour removal. Photocatalytic oxidation was apparently inhibited by the high chloride and COD levels in the alkaline filtrate, and may be more efficient in recalcitrant COD removal if performed after biological. PMID:17486841

  9. Development of Advanced Electrochemical Emission Spectroscopy for Monitoring Corrosion in Simulated DOE Liquid Waste

    SciTech Connect

    MacDonald, Digby D.

    2005-06-01

    In this work, the examination of electrochemical noise data comprised three main approaches: one, a computer simulation of the anodic and cathodic activity relating to corrosion on a metal surface; two, experimental modeling of the electrochemical environment inside nuclear waste storage containers and collection of EN generated; and three, Wavelet analysis of the EN data from the first two parts. The simulation of EN proved to be effective in replicating the EN data of both general and pitting corrosion. Using competition mechanisms for the anodic and cathodic sites on the surface, the long-term, low-frequency data generated by localized pitting corrosion was reproduced. Disabling one or more of the rules of the simulation eliminated the low-frequency character of the data, and eliminating all of the rules effectively reproduced general corrosion noise. The simulation accuracy benefited from comparison to experimental data, and conversely, it improved the EN analysis by providing theory for the underlying mechanisms. The experimental electrochemical cell modeled the important factors in nuclear waste storage containers for this EN study; mainly increased temperature and the concentrations of corrosion-inducing or inhibiting chemicals. It also provided a platform for studying how the EN was affected by the competing chemicals.

  10. Review: advances in electrochemical genosensors-based methods for monitoring blooms of toxic algae.

    PubMed

    Orozco, Jahir; Medlin, Linda K

    2013-10-01

    Harmful algal blooms (HABs), which have expanded worldwide in their occurrence and frequency, are a serious menace to aquatic ecosystems and humans. The development of rapid, accurate and cost-effective detection systems for toxic algal monitoring in aquatic environments is urgently required. Although many efforts have been devoted to develop reliable tools to monitor the entire spectrum of existing toxic algae, a portable semi-automated system that enables HAB monitoring at a low cost is still not available for general purchase. This work reviews the challenges and opportunities in translating the remarkable progress of electrochemical genosensors-based methods towards practical in situ HAB monitoring applications. It is specifically focused on reviewing the optimised methods for a detection system based on a sandwich hybridisation assay (SHA) performed over transducer platforms of different materials, geometries and dimensions and presenting the diverse advantages and disadvantages among them. Probe design and specificity and optimisation of the genosensor in terms of hybridisation conditions and electrochemical signal are discussed as well as their long-term stability and storage and semi-automation attempts. With continuous innovation and attention to key challenges, we expect semi-automatic devices containing DNA-based electrochemical biosensors to have an important impact upon monitoring of serious HAB events. PMID:23097073

  11. Comparative studies on single-layer reduced graphene oxide films obtained by electrochemical reduction and hydrazine vapor reduction

    PubMed Central

    2012-01-01

    The comparison between two kinds of single-layer reduced graphene oxide (rGO) sheets, obtained by reduction of graphene oxide (GO) with the electrochemical method and hydrazine vapor reduction, referred to as E-rGO and C-rGO, respectively, is systematically studied. Although there is no morphology difference between the E-rGO and C-rGO films adsorbed on solid substrates observed by AFM, the reduction process to obtain the E-rGO and C-rGO films is quite different. In the hydrazine vapor reduction, the nitrogen element is incorporated into the obtained C-rGO film, while no additional element is introduced to the E-rGO film during the electrochemical reduction. Moreover, Raman spectra show that the electrochemical method is more effective than the hydrazine vapor reduction method to reduce the GO films. In addition, E-rGO shows better electrocatalysis towards dopamine than does C-rGO. This study is helpful for researchers to understand these two different reduction methods and choose a suitable one to reduce GO based on their experimental requirements. PMID:22373422

  12. Electrochemical sensor for Isoniazid based on the glassy carbon electrode modified with reduced graphene oxide-Au nanomaterials.

    PubMed

    Guo, Zhuo; Wang, Ze-Yu; Wang, Hui-Hua; Huang, Guo-Qing; Li, Meng-Meng

    2015-12-01

    A sensitive electrochemical sensor has been fabricated to detect Isoniazid (INZ) using reduced graphene oxide (RGO) and Au nanocomposites (RGO-Au). RGO-Au nanocomposites were synthesized by a solution-based approach of chemical co-reduction of Au(III) and graphene oxide (GO), and were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy, and Fourier transform infrared (FT-IR). The Au nanoparticles separate the RGO sheets in the precipitate and prevent RGO sheets from aggregation upon π-π stacking interactions. RGO-Au nanocomposites were used to modify the glassy carbon electrode (GCE). The electrochemical properties of RGO-Au/GCE were investigated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS), and the RGO-Au/GCE exhibited remarkably strong electrocatalytic activities towards INZ. Under the optimized conditions, there was linear relationships between the peak currents and the concentrations in the range of 1.0×10(-7)M to 1.0×10(-3)M for INZ, with the limit of detection (LOD) (based on S/N=3) of 1.0×10(-8)M for INZ. PMID:26354255

  13. Electrochemical oxidation of ampicillin antibiotic at boron-doped diamond electrodes and process optimization using response surface methodology.

    PubMed

    Körbahti, Bahadır K; Taşyürek, Selin

    2015-03-01

    Electrochemical oxidation and process optimization of ampicillin antibiotic at boron-doped diamond electrodes (BDD) were investigated in a batch electrochemical reactor. The influence of operating parameters, such as ampicillin concentration, electrolyte concentration, current density, and reaction temperature, on ampicillin removal, COD removal, and energy consumption was analyzed in order to optimize the electrochemical oxidation process under specified cost-driven constraints using response surface methodology. Quadratic models for the responses satisfied the assumptions of the analysis of variance well according to normal probability, studentized residuals, and outlier t residual plots. Residual plots followed a normal distribution, and outlier t values indicated that the approximations of the fitted models to the quadratic response surfaces were very good. Optimum operating conditions were determined at 618 mg/L ampicillin concentration, 3.6 g/L electrolyte concentration, 13.4 mA/cm(2) current density, and 36 °C reaction temperature. Under response surface optimized conditions, ampicillin removal, COD removal, and energy consumption were obtained as 97.1 %, 92.5 %, and 71.7 kWh/kg CODr, respectively. PMID:24906830

  14. Zinc oxide nanoring embedded lacey graphene nanoribbons in symmetric/asymmetric electrochemical capacitive energy storage

    NASA Astrophysics Data System (ADS)

    Sahu, Vikrant; Goel, Shubhra; Sharma, Raj Kishore; Singh, Gurmeet

    2015-12-01

    This article describes the synthesis and characterization of ZnO nanoring embedded graphene nanoribbons. Patterned holes (mesopore dia.) in graphene nanoribbons are chemically generated, leading to a high density of the edge planes. These planes carry negatively charged surface groups (like -COOH and -OH) and therefore anchor the metal ions in a cordial fashion forming a string of metal ions along the edge planes. These strings of imbibed metal ions precipitate as tiny ZnO nanorings over lacey graphene nanoribbons. The thus obtained graphene nanoribbon (GNR) based hierarchical ZnO mesoporous structures are three dimensionally accessible to the electrolyte and demonstrate high performance in capacitive energy storage. The ZnO/GNR nanocomposite electrode in an asymmetric supercapacitor device with lacey reduced graphene oxide nanoribbons (LRGONRs) as a negative electrode exhibits a 2.0 V potential window in the aqueous electrolyte and an ultra-short time constant (0.08 s). The wide potential window consequently increased the energy density from 6.8 Wh kg-1 (ZnO/GNR symmetric) to 9.4 Wh kg-1 (ZnO/GNR||LRGONR asymmetric). The relaxation time constant obtained for the asymmetric supercapacitor device was three orders of magnitude less compared to the ZnO (symmetric, 33 s) supercapacitor device. The high cycling stability of ZnO/GNR||LRGONR up to 96.7% capacitance retention, after 5000 GCD cycles at 2 mA cm-2, paves the way to a high performance aqueous electrochemical supercapacitive energy storage.This article describes the synthesis and characterization of ZnO nanoring embedded graphene nanoribbons. Patterned holes (mesopore dia.) in graphene nanoribbons are chemically generated, leading to a high density of the edge planes. These planes carry negatively charged surface groups (like -COOH and -OH) and therefore anchor the metal ions in a cordial fashion forming a string of metal ions along the edge planes. These strings of imbibed metal ions precipitate as tiny ZnO nanorings over lacey graphene nanoribbons. The thus obtained graphene nanoribbon (GNR) based hierarchical ZnO mesoporous structures are three dimensionally accessible to the electrolyte and demonstrate high performance in capacitive energy storage. The ZnO/GNR nanocomposite electrode in an asymmetric supercapacitor device with lacey reduced graphene oxide nanoribbons (LRGONRs) as a negative electrode exhibits a 2.0 V potential window in the aqueous electrolyte and an ultra-short time constant (0.08 s). The wide potential window consequently increased the energy density from 6.8 Wh kg-1 (ZnO/GNR symmetric) to 9.4 Wh kg-1 (ZnO/GNR||LRGONR asymmetric). The relaxation time constant obtained for the asymmetric supercapacitor device was three orders of magnitude less compared to the ZnO (symmetric, 33 s) supercapacitor device. The high cycling stability of ZnO/GNR||LRGONR up to 96.7% capacitance retention, after 5000 GCD cycles at 2 mA cm-2, paves the way to a high performance aqueous electrochemical supercapacitive energy storage. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr06083d

  15. Screen-printed calcium-birnessite electrodes for water oxidation at neutral pH and an "electrochemical harriman series".

    PubMed

    Lee, Seung Y; González-Flores, Diego; Ohms, Jonas; Trost, Tim; Dau, Holger; Zaharieva, Ivelina; Kurz, Philipp

    2014-12-01

    A mild screen-printing method was developed to coat conductive oxide surfaces (here: fluorine-doped tin oxide) with micrometer-thick layers of presynthesized calcium manganese oxide (Ca-birnessite) particles. After optimization steps concerning the printing process and layer thickness, electrodes were obtained that could be used as corrosion-stable water-oxidizing anodes at pH 7 to yield current densities of 1 mA cm(-2) at an overpotential of less than 500 mV. Analyses of the electrode coatings of optimal thickness (≈10 μm) indicated that composition, oxide phase, and morphology of the synthetic Ca-birnessite particles were hardly affected by the screen-printing procedure. However, a more detailed analysis by X-ray absorption spectroscopy revealed small modifications of both the Mn redox state and the structure at the atomic level, which could affect functional properties such as proton conductivity. Furthermore, the versatile new screen-printing method was used for a comparative study of various transition-metal oxides concerning electrochemical water oxidation under "artificial leaf conditions" (neutral pH, fairly low overpotential and current density), for which a general activity ranking of RuO2 >Co3 O4 ≈(Ca)MnOx ≈NiO was observed. Within the group of screened manganese oxides, Ca-birnessite performed better than "Mn-only materials" such as Mn2 O3 and MnO2 . PMID:25346273

  16. Formation of Mosaic Silicon Oxide Structure during Metal-Assisted Electrochemical Etching of Silicon at High Current Density

    NASA Astrophysics Data System (ADS)

    Cao, Dao Tran; Anh, Cao Tuan; Ngan, Luong Truc Quynh

    2016-05-01

    We have used constant-current, metal-assisted electrochemical etching of silicon in HF/H2O2/ethanol electrolyte to fabricate porous silicon. We found that, at large enough current density, the sponge-like porous silicon structure is replaced by a mosaic structure, which includes islands of various shapes emerging between trenches that have been etched downward. Energy-dispersive x-ray analysis showed that the surface of the mosaic pieces was covered with silicon oxide, while little silicon oxide developed on the surface of trenches. We suggest that the appearance of the mosaic structure can be explained by the increase in the oxidation rate of silicon when the anodic current density increases, combined with no change in the dissolution rate of silicon oxide into the solution. Consequently, above a certain value of anodic current density, there is sufficient residual silicon oxide on the etched surface to create a continuous thin film. However, if the silicon oxide layer is too thick (e.g., due to too high anodic current density or too long etching time), it will become cracked (formation of mosaic pieces), likely due to differences in thermal expansion coefficient between the amorphous silicon oxide layer and crystalline silicon substrate. The oxide is cracked at locations with many defects, and the cracks reveal the silicon substrate. Therefore, at the locations where cracks occur, etching will go sideways and downward, creating trenches.

  17. Formation of Mosaic Silicon Oxide Structure during Metal-Assisted Electrochemical Etching of Silicon at High Current Density

    NASA Astrophysics Data System (ADS)

    Cao, Dao Tran; Anh, Cao Tuan; Ngan, Luong Truc Quynh

    2016-03-01

    We have used constant-current, metal-assisted electrochemical etching of silicon in HF/H2O2/ethanol electrolyte to fabricate porous silicon. We found that, at large enough current density, the sponge-like porous silicon structure is replaced by a mosaic structure, which includes islands of various shapes emerging between trenches that have been etched downward. Energy-dispersive x-ray analysis showed that the surface of the mosaic pieces was covered with silicon oxide, while little silicon oxide developed on the surface of trenches. We suggest that the appearance of the mosaic structure can be explained by the increase in the oxidation rate of silicon when the anodic current density increases, combined with no change in the dissolution rate of silicon oxide into the solution. Consequently, above a certain value of anodic current density, there is sufficient residual silicon oxide on the etched surface to create a continuous thin film. However, if the silicon oxide layer is too thick (e.g., due to too high anodic current density or too long etching time), it will become cracked (formation of mosaic pieces), likely due to differences in thermal expansion coefficient between the amorphous silicon oxide layer and crystalline silicon substrate. The oxide is cracked at locations with many defects, and the cracks reveal the silicon substrate. Therefore, at the locations where cracks occur, etching will go sideways and downward, creating trenches.

  18. Metal-free dihydrogen oxidation by a borenium cation: a combined electrochemical/frustrated Lewis pair approach.

    PubMed

    Lawrence, Elliot J; Herrington, Thomas J; Ashley, Andrew E; Wildgoose, Gregory G

    2014-09-01

    In order to use H2 as a clean source of electricity, prohibitively rare and expensive precious metal electrocatalysts, such as Pt, are often used to overcome the large oxidative voltage required to convert H2 into 2 H(+) and 2 e(-). Herein, we report a metal-free approach to catalyze the oxidation of H2 by combining the ability of frustrated Lewis pairs (FLPs) to heterolytically cleave H2 with the in situ electrochemical oxidation of the resulting borohydride. The use of the NHC-stabilized borenium cation [(IiPr2)(BC8H14)](+) (IiPr2=C3H2(NiPr)2, NHC=N-heterocyclic carbene) as the Lewis acidic component of the FLP is shown to decrease the voltage required for H2 oxidation by 910 mV at inexpensive carbon electrodes, a significant energy saving equivalent to 175.6 kJ mol(-1). The NHC-borenium Lewis acid also offers improved catalyst recyclability and chemical stability compared to B(C6F5)3, the paradigm Lewis acid originally used to pioneer our combined electrochemical/frustrated Lewis pair approach. PMID:25044562

  19. Effect of ammonium-salt solutions on the surface properties of carbon fibers in electrochemical anodic oxidation

    NASA Astrophysics Data System (ADS)

    Qian, Xin; Wang, Xuefei; Ouyang, Qin; Chen, Yousi; Yan, Qing

    2012-10-01

    The surfaces of polyacrylonitrile-based carbon fibers were treated by an electrochemical anodic method. Three different kinds of ammonium-salt solutions namely NH4HCO3, (NH4)2CO3 and (NH4)3PO4 were respectively chosen as the electrolytes. The effect of these electrolytes on the surface structure was studied by scanning electron microscopy (SEM), atomic force microscopy (AFM), and X-ray photoelectron spectroscopy (XPS). The results showed that longitudinal grooves on the fiber surface became more well-defined and much deeper after surface treatment, and the root mean square roughness (RMS) of carbon fiber surface increased from 4.6 nm for untreated fibers to 13.5 nm for treated fibers in (NH4)3PO4 electrolytes. The concentration of oxygen and nitrogen atomic on the fiber surface increased after surface treatment. The tensile strength of oxidized fibers had an obvious decrease, whereas the interlaminar shear strength (ILSS) value of corresponding carbon fiber reinforced polymers (CFRPs) increased in a large extent. The intensity of oxidative reaction varied with the change of ammonium-salt solutions and electrochemical oxidation in (NH4)3PO4 electrolyte was of the most violence. The corresponding mechanism was also discussed and the result showed that the higher the concentration of OH- ions in the electrolytes, the violent the oxidative reaction happened.

  20. Electrochemical Synthesis of Binary and Ternary Niobium-Containing Oxide Electrodes Using the p-Benzoquinone/Hydroquinone Redox Couple.

    PubMed

    Papa, Christopher M; Cesnik, Anthony J; Evans, Taylor C; Choi, Kyoung-Shin

    2015-09-01

    New electrochemical synthesis methods have been developed to obtain layered potassium niobates, KNb3O8 and K4Nb6O17, and perovskite-type KNbO3 as film-type electrodes. The electrodes were synthesized from aqueous solutions using the redox chemistry of p-benzoquinone and hydroquinone to change the local pH at the working electrode to trigger deposition of desired phases. In particular, the utilization of electrochemically generated acid via the oxidation of hydroquinone for inorganic film deposition was first demonstrated in this study. The layered potassium niobates could be converted to (H3O)Nb3O8 and (H3O)4Nb6O17 by cationic exchange, which, in turn, could be converted to Nb2O5 by heat treatment. The versatility of the new deposition method was further demonstrated for the formation of CuNb2O6 and AgNbO3, which were prepared by the deposition of KNb3O8 and transition metal oxides, followed by thermal and chemical treatments. Considering the lack of solution-based synthesis methods for Nb-based oxide films, the methods reported in this study will contribute greatly to studies involving the synthesis and applications of Nb-based oxide electrodes. PMID:26293515

  1. Metal-Free Dihydrogen Oxidation by a Borenium Cation: A Combined Electrochemical/Frustrated Lewis Pair Approach**

    PubMed Central

    Lawrence, Elliot J; Herrington, Thomas J; Ashley, Andrew E; Wildgoose, Gregory G

    2014-01-01

    In order to use H2 as a clean source of electricity, prohibitively rare and expensive precious metal electrocatalysts, such as Pt, are often used to overcome the large oxidative voltage required to convert H2 into 2 H+ and 2 e−. Herein, we report a metal-free approach to catalyze the oxidation of H2 by combining the ability of frustrated Lewis pairs (FLPs) to heterolytically cleave H2 with the in situ electrochemical oxidation of the resulting borohydride. The use of the NHC-stabilized borenium cation [(IiPr2)(BC8H14)]+ (IiPr2=C3H2(NiPr)2, NHC=N-heterocyclic carbene) as the Lewis acidic component of the FLP is shown to decrease the voltage required for H2 oxidation by 910 mV at inexpensive carbon electrodes, a significant energy saving equivalent to 175.6 kJ mol−1. The NHC–borenium Lewis acid also offers improved catalyst recyclability and chemical stability compared to B(C6F5)3, the paradigm Lewis acid originally used to pioneer our combined electrochemical/frustrated Lewis pair approach. PMID:25044562

  2. Sonophotocatalysis in advanced oxidation process: a short review.

    PubMed

    Joseph, Collin G; Li Puma, Gianluca; Bono, Awang; Krishnaiah, Duduku

    2009-06-01

    Sonophotocatalysis involves the use of a combination of ultrasonic sound waves, ultraviolet radiation and a semiconductor photocatalyst to enhance a chemical reaction by the formation of free radicals in aqueous systems. Researchers have used sonophotocatalysis in a variety of investigations i.e. from water decontamination to direct pollutant degradation. This degradation process provides an excellent opportunity to reduce reaction time and the amount of reagents used without the need for extreme physical conditions. Given its advantages, the sonophotocatalysis process has a futuristic application from an engineering and fundamental aspect in commercial applications. A detailed search of published reports was done and analyzed in this paper with respect to sonication, photocatalysis and advanced oxidation processes. PMID:19282232

  3. Zinc oxide nanoring embedded lacey graphene nanoribbons in symmetric/asymmetric electrochemical capacitive energy storage.

    PubMed

    Sahu, Vikrant; Goel, Shubhra; Sharma, Raj Kishore; Singh, Gurmeet

    2015-12-28

    This article describes the synthesis and characterization of ZnO nanoring embedded graphene nanoribbons. Patterned holes (mesopore dia.) in graphene nanoribbons are chemically generated, leading to a high density of the edge planes. These planes carry negatively charged surface groups (like -COOH and -OH) and therefore anchor the metal ions in a cordial fashion forming a string of metal ions along the edge planes. These strings of imbibed metal ions precipitate as tiny ZnO nanorings over lacey graphene nanoribbons. The thus obtained graphene nanoribbon (GNR) based hierarchical ZnO mesoporous structures are three dimensionally accessible to the electrolyte and demonstrate high performance in capacitive energy storage. The ZnO/GNR nanocomposite electrode in an asymmetric supercapacitor device with lacey reduced graphene oxide nanoribbons (LRGONRs) as a negative electrode exhibits a 2.0 V potential window in the aqueous electrolyte and an ultra-short time constant (0.08 s). The wide potential window consequently increased the energy density from 6.8 Wh kg(-1) (ZnO/GNR symmetric) to 9.4 Wh kg(-1) (ZnO/GNR||LRGONR asymmetric). The relaxation time constant obtained for the asymmetric supercapacitor device was three orders of magnitude less compared to the ZnO (symmetric, 33 s) supercapacitor device. The high cycling stability of ZnO/GNR||LRGONR up to 96.7% capacitance retention, after 5000 GCD cycles at 2 mA cm(-2), paves the way to a high performance aqueous electrochemical supercapacitive energy storage. PMID:26597970

  4. Tunable Mixed Ionic/Electronic Conductivity and Permittivity of Graphene Oxide Paper for Electrochemical Energy Conversion.

    PubMed

    Bayer, Thomas; Bishop, Sean R; Perry, Nicola H; Sasaki, Kazunari; Lyth, Stephen M

    2016-05-11

    Graphene oxide (GO) is a two-dimensional graphitic carbon material functionalized with oxygen-containing surface functional groups. The material is of interest in energy conversion, sensing, chemical processing, gas barrier, and electronics applications. Multilayer GO paper has recently been applied as a new proton conducting membrane in low temperature fuel cells. However, a detailed understanding of the electrical/dielectric properties, including separation of the ionic vs electronic contributions under relevant operating conditions, has so far been lacking. Here, the electrical conductivity and dielectric permittivity of GO paper are investigated in situ from 30 to 120 °C, and from 0 to 100% relative humidity (RH) using impedance spectroscopy. These are related to the water content, measured by thermogravimetric analysis. With the aid of electron blocking measurements, GO is demonstrated to be a mixed electronic-protonic conductor, and the ion transference number is derived for the first time. For RH > 40%, conductivity is dominated by proton transport (with a maximum of 0.5 mS/cm at 90 °C and 100% RH). For RH < 40%, electronic conductivity dominates (with a maximum of 7.4 mS/cm at ∼80 °C and 0% RH). The relative permittivity of GO paper increases with decreasing humidity, from ∼10 at 100% RH to several 1000 at 10% RH. These results underline the potential of GO for application not only as a proton conducting electrolyte but also as a mixed conducting electrode material under appropriate conditions. Such materials are highly applicable in electrochemical energy conversion and storage devices such as fuel cells and electrolyzers. PMID:27088238

  5. Batch fabrication of mesoporous boron-doped nickel oxide nanoflowers for electrochemical capacitors

    SciTech Connect

    Yang, Jing-He; Yu, Qingtao; Li, Yamin; Mao, Liqun; Ma, Ding

    2014-11-15

    Highlights: • A new facile liquid-phase method has been employed for synthesis boron-doped NiO nanoflowers. • The specific surface area of NiO is as high as 200 m{sup 2} g{sup −1}. • NiO nanoflowers exhibit a high specific capacitance of ∼1309 F g{sup −1} at a charge and discharge current density of 3 A g{sup −1}. • NiO nanoflowers have excellent cycling ability and even after 2500 cycles there is no significant reduction in specific capacitance. - Abstract: Boron-doped nickel oxide (B-NiO) nanoflowers are prepared by simple thermal decomposition of nickel hydroxide. B-NiO is porous sphere with a diameter of about 400 nm. B-NiO nanoflowers are composed of approximately 30 nm nanoplates and the thickness of the nanosheets is approximately 3 nm. The specific surface area of the material is as high as 200 m{sup 2} g{sup −1} and the pore size distribution curves of B-NiO has three typical peaks in the range of mesoporous (5 nm, 13 nm and 18 nm). As an electrode for supercapacitors, the crystalline B-NiO nanoflowers have favorable characteristics, for instance, a specific capacitance of 1309 F g{sup −1} at a current density of 3 A g{sup −1} and no significant reduction in Coulombic efficiency after 2500 cycles at 37.5 A g{sup −1}. This remarkable electrochemical performance will make B-NiO nanoflowers a promising electrode material for high performance supercapacitors.

  6. Electrochemical study of lithiated transition metal oxide composite for single layer fuel cell

    NASA Astrophysics Data System (ADS)

    Hu, Huiqing; Lin, Qizhao; Muhammad, Afzal; Zhu, Bin

    2015-07-01

    This study analyzed the effect of various semiconductors of transition metal oxides in modified lithiated NiO on the electrochemical performance of a single layer fuel cell (SLFC). A typical ionic conductor Ce0.8Sm0.2O2-δ (SDC) and three types of semiconductors Li0.3Ni0.6Cu0.07Sr0.03O2-δ (LNCuS), Li0.3Ni0.6Mn0.07Sr0.03O2-δ (LNMnS) and Li0.3Ni0.6Co0.07Sr0.03O2-δ (LNCoS), were the fundamental components of the SLFCs. The components were characterized by using X-ray diffraction (XRD), a scanning electron microscope (SEM), and an energy-dispersive X-ray spectrometer (EDS). The stability of the synthesized materials was evaluated using thermal gravity analysis (TGA). The ohmic resistances at 500 °C were 0.36, 0.48 and 0.58 Ω cm2 for 6SDC-4LNMnS, 6SDC-4LNCoS and 6SDC-4LNCuS, respectively. Among the three SLFCs, the single cell with 6SDC-4LNMnS achieves the highest power density (422 mW cm-2) but the lowest temperature stability, while the single cell with 6SDC-4LNCuS achieved the lowest power density (331 mW cm-2) but the highest temperature stability during the operation temperature.

  7. More accurate macro-models of solid oxide fuel cells through electrochemical and microstructural parameter estimation - Part I: Experimentation

    NASA Astrophysics Data System (ADS)

    Boigues Muñoz, Carlos; Pumiglia, Davide; McPhail, Stephen J.; Montinaro, Dario; Comodi, Gabriele; Santori, Giulio; Carlini, Maurizio; Polonara, Fabio

    2015-10-01

    The distributed relaxation times (DRT) method has been employed in order to deconvolute the electrochemical impedance spectroscopy (EIS) measurements carried out on a Ni-YSZ|YSZ|Pr2NiO4+δ - GDC solid oxide fuel cell (SOFC). This has enabled to shed light on the diverse physicochemical processes occurring within the aforementioned cell by individuating the characteristic relaxation times of these by means of a specifically designed experimental campaign where temperature and gas compositions in anode and cathode were varied one at a time. A comprehensive equivalent circuit model (ECM) has thus been generated based on the processes observed in the DRT spectra. This ECM has proved to be instrumental for the obtainment of parameters which describe the microstructural and electrochemical properties of the SOFC when used contemporaneously with experimental results and modelling theory (described in Part II of this work).

  8. Hybrid nickel manganese oxide nanosheet-3D metallic dendrite percolation network electrodes for high-rate electrochemical energy storage

    NASA Astrophysics Data System (ADS)

    Nguyen, Tuyen; Eugénio, Sónia; Boudard, Michel; Rapenne, Laetitia; Carmezim, M. João; Silva, Teresa M.; Montemor, M. Fátima

    2015-07-01

    This work reports the fabrication, by electrodeposition and post-thermal annealing, of hybrid electrodes for high rate electrochemical energy storage composed of nickel manganese oxide (Ni0.86Mn0.14O) nanosheets over 3D open porous dendritic NiCu foams. The hybrid electrodes are made of two different percolation networks of nanosheets and dendrites, and exhibit a specific capacitance value of 848 F g-1 at 1 A g-1. The electrochemical tests revealed that the electrodes display an excellent rate capability, characterized by capacitance retention of approximately 83% when the applied current density increases from 1 A g-1 to 20 A g-1. The electrodes also evidenced high charge-discharge cycling stability, which attained 103% after 1000 cycles.

  9. Influence of albumin and inorganic ions on electrochemical corrosion behavior of plasma electrolytic oxidation coated magnesium for surgical implants

    NASA Astrophysics Data System (ADS)

    Wan, Peng; Lin, Xiao; Tan, LiLi; Li, Lugee; Li, WeiRong; Yang, Ke

    2013-10-01

    Magnesium and its alloys are of great interest for biodegradable metallic devices. However, the degradation behavior and mechanisms of magnesium treated with coating in physiological environment in the presence of organic compound such as albumin have not been elucidated. In this study, the plasma electrolytic oxidation coated magnesium immersed in four different simulated body fluids: NaCl, PBS and with the addition of albumin to investigate the influence of protein and inorganic ions on degradation behavior by electrochemical methods. The results of electrochemical tests showed that aggressive corrosion took place in 0.9 wt.% NaCl solution; whereas albumin can act as an inhibitor, its adsorption impeded further dissolution of the coating. The mechanism was attributed to the synergistic effect of protein adsorption and precipitation of insoluble salts.

  10. First-principles density functional calculation of electrochemical stability of fast Li ion conducting garnet-type oxides.

    PubMed

    Nakayama, Masanobu; Kotobuki, Masashi; Munakata, Hirokazu; Nogami, Masayuki; Kanamura, Kiyoshi

    2012-07-28

    The research and development of rechargeable all-ceramic lithium batteries are vital to realize their considerable advantages over existing commercial lithium ion batteries in terms of size, energy density, and safety. A key part of such effort is the development of solid-state electrolyte materials with high Li(+) conductivity and good electrochemical stability; lithium-containing oxides with a garnet-type structure are known to satisfy the requirements to achieve both features. Using first-principles density functional theory (DFT), we investigated the electrochemical stability of garnet-type Li(x)La(3)M(2)O(12) (M = Ti, Zr, Nb, Ta, Sb, Bi; x = 5 or 7) materials against Li metal. We found that the electrochemical stability of such materials depends on their composition and structure. The electrochemical stability against Li metal was improved when a cation M was chosen with a low effective nuclear charge, that is, with a high screening constant for an unoccupied orbital. In fact, both our computational and experimental results show that Li(7)La(3)Zr(2)O(12) and Li(5)La(3)Ta(2)O(12) are inert to Li metal. In addition, the linkage of MO(6) octahedra in the crystal structure affects the electrochemical stability. For example, perovskite-type La(1/3)TaO(3) was found, both experimentally and computationally, to react with Li metal owing to the corner-sharing MO(6) octahedral network of La(1/3)TaO(3), even though it has the same constituent elements as garnet-type Li(5)La(3)Ta(2)O(12) (which is inert to Li metal and features isolated TaO(6) octahedra). PMID:22711381

  11. Allylic ionic liquid electrolyte-assisted electrochemical surface passivation of LiCoO2 for advanced, safe lithium-ion batteries

    PubMed Central

    Mun, Junyoung; Yim, Taeeun; Park, Jang Hoon; Ryu, Ji Heon; Lee, Sang Young; Kim, Young Gyu; Oh, Seung M.

    2014-01-01

    Room-temperature ionic liquid (RTIL) electrolytes have attracted much attention for use in advanced, safe lithium-ion batteries (LIB) owing to their nonvolatility, high conductivity, and great thermal stability. However, LIBs containing RTIL-electrolytes exhibit poor cyclability because electrochemical side reactions cause problematic surface failures of the cathode. Here, we demonstrate that a thin, homogeneous surface film, which is electrochemically generated on LiCoO2 from an RTIL-electrolyte containing an unsaturated substituent on the cation (1-allyl-1-methylpiperidinium bis(trifluoromethanesulfonyl)imide, AMPip-TFSI), can avert undesired side reactions. The derived surface film comprised of a high amount of organic species from the RTIL cations homogenously covered LiCoO2 with a <25 nm layer and helped suppress unfavorable thermal reactions as well as electrochemical side reactions. The superior performance of the cell containing the AMPip-TFSI electrolyte was further elucidated by surface, electrochemical, and thermal analyses. PMID:25168309

  12. Allylic ionic liquid electrolyte-assisted electrochemical surface passivation of LiCoO2 for advanced, safe lithium-ion batteries.

    PubMed

    Mun, Junyoung; Yim, Taeeun; Park, Jang Hoon; Ryu, Ji Heon; Lee, Sang Young; Kim, Young Gyu; Oh, Seung M

    2014-01-01

    Room-temperature ionic liquid (RTIL) electrolytes have attracted much attention for use in advanced, safe lithium-ion batteries (LIB) owing to their nonvolatility, high conductivity, and great thermal stability. However, LIBs containing RTIL-electrolytes exhibit poor cyclability because electrochemical side reactions cause problematic surface failures of the cathode. Here, we demonstrate that a thin, homogeneous surface film, which is electrochemically generated on LiCoO2 from an RTIL-electrolyte containing an unsaturated substituent on the cation (1-allyl-1-methylpiperidinium bis(trifluoromethanesulfonyl)imide, AMPip-TFSI), can avert undesired side reactions. The derived surface film comprised of a high amount of organic species from the RTIL cations homogenously covered LiCoO2 with a <25 nm layer and helped suppress unfavorable thermal reactions as well as electrochemical side reactions. The superior performance of the cell containing the AMPip-TFSI electrolyte was further elucidated by surface, electrochemical, and thermal analyses. PMID:25168309

  13. Allylic ionic liquid electrolyte-assisted electrochemical surface passivation of LiCoO2 for advanced, safe lithium-ion batteries

    NASA Astrophysics Data System (ADS)

    Mun, Junyoung; Yim, Taeeun; Park, Jang Hoon; Ryu, Ji Heon; Lee, Sang Young; Kim, Young Gyu; Oh, Seung M.

    2014-08-01

    Room-temperature ionic liquid (RTIL) electrolytes have attracted much attention for use in advanced, safe lithium-ion batteries (LIB) owing to their nonvolatility, high conductivity, and great thermal stability. However, LIBs containing RTIL-electrolytes exhibit poor cyclability because electrochemical side reactions cause problematic surface failures of the cathode. Here, we demonstrate that a thin, homogeneous surface film, which is electrochemically generated on LiCoO2 from an RTIL-electrolyte containing an unsaturated substituent on the cation (1-allyl-1-methylpiperidinium bis(trifluoromethanesulfonyl)imide, AMPip-TFSI), can avert undesired side reactions. The derived surface film comprised of a high amount of organic species from the RTIL cations homogenously covered LiCoO2 with a <25 nm layer and helped suppress unfavorable thermal reactions as well as electrochemical side reactions. The superior performance of the cell containing the AMPip-TFSI electrolyte was further elucidated by surface, electrochemical, and thermal analyses.

  14. Oxidative stress in aging: advances in proteomic approaches.

    PubMed

    Ortuño-Sahagún, Daniel; Pallàs, Mercè; Rojas-Mayorquín, Argelia E

    2014-01-01

    Aging is a gradual, complex process in which cells, tissues, organs, and the whole organism itself deteriorate in a progressive and irreversible manner that, in the majority of cases, implies pathological conditions that affect the individual's Quality of Life (QOL). Although extensive research efforts in recent years have been made, the anticipation of aging and prophylactic or treatment strategies continue to experience major limitations. In this review, the focus is essentially on the compilation of the advances generated by cellular expression profile analysis through proteomics studies (two-dimensional [2D] electrophoresis and mass spectrometry [MS]), which are currently used as an integral approach to study the aging process. Additionally, the relevance of the oxidative stress factors is discussed. Emphasis is placed on postmitotic tissues, such as neuronal, muscular, and red blood cells, which appear to be those most frequently studied with respect to aging. Additionally, models for the study of aging are discussed in a number of organisms, such as Caenorhabditis elegans, senescence-accelerated probe-8 mice (SAMP8), naked mole-rat (Heterocephalus glaber), and the beagle canine. Proteomic studies in specific tissues and organisms have revealed the extensive involvement of reactive oxygen species (ROS) and oxidative stress in aging. PMID:24688629

  15. Oxidative Stress in Aging: Advances in Proteomic Approaches

    PubMed Central

    Ortuño-Sahagún, Daniel; Pallàs, Mercè; Rojas-Mayorquín, Argelia E.

    2014-01-01

    Aging is a gradual, complex process in which cells, tissues, organs, and the whole organism itself deteriorate in a progressive and irreversible manner that, in the majority of cases, implies pathological conditions that affect the individual's Quality of Life (QOL). Although extensive research efforts in recent years have been made, the anticipation of aging and prophylactic or treatment strategies continue to experience major limitations. In this review, the focus is essentially on the compilation of the advances generated by cellular expression profile analysis through proteomics studies (two-dimensional [2D] electrophoresis and mass spectrometry [MS]), which are currently used as an integral approach to study the aging process. Additionally, the relevance of the oxidative stress factors is discussed. Emphasis is placed on postmitotic tissues, such as neuronal, muscular, and red blood cells, which appear to be those most frequently studied with respect to aging. Additionally, models for the study of aging are discussed in a number of organisms, such as Caenorhabditis elegans, senescence-accelerated probe-8 mice (SAMP8), naked mole-rat (Heterocephalus glaber), and the beagle canine. Proteomic studies in specific tissues and organisms have revealed the extensive involvement of reactive oxygen species (ROS) and oxidative stress in aging. PMID:24688629

  16. Great-enhanced performance of Pt nanoparticles by the unique carbon quantum dot/reduced graphene oxide hybrid supports towards methanol electrochemical oxidation

    NASA Astrophysics Data System (ADS)

    Hong, Tian-Zeng; Xue, Qiong; Yang, Zhi-Yong; Dong, Ya-Ping

    2016-01-01

    The Pt-carbon quantum dot (CQD)/reduced graphene oxide (RGO) catalysts are prepared by one pot reduction method and demonstrate ultraefficient performance towards methanol oxidation reaction (MOR). In the high content CQD products, Pt nanoparticles around 2-3 nm are dispersed uniformly on supporting materials. And the X-ray photoelectron spectroscopy analysis indicates that in the high content CQD products a large part of surface oxygen groups is contributed by CQD. The electrochemical tests reveal that the catalyst with the saturated CQD exhibits best performance in MOR: the mass and specific activity at forward peak position, the potential close to fuel cell operation and 3600 s of chronoamperometric curve are roughly 2-3 folds of the commercial Pt/C. Furthermore, the electrochemical data on the series of catalysts with different quantity of CQD disclose the improving tendency of MOR performance with the increasing content of CQD evidently. Overview the electrochemical and characterization results, we suggest CQD play multiple roles in the enhancement of Pt performance: present abundant nucleating and anchoring points to facilitate the formation of small size and uniform distributed Pt particles; act as spacer to alleviate restacking of RGO sheets; and provide fruitful surface oxygen groups to improve the antipoisonous ability of Pt.

  17. Electrochemical oxidation of methanol using dppm-bridged Ru/Pd, Ru/Pt and Ru/Au catalysts.

    PubMed

    Yang, Ying; McElwee-White, Lisa

    2004-08-01

    The electrochemical oxidation of methanol was carried out using a series of dppm-bridged Ru/Pd, Ru/Pt and Ru/Au heterobimetallic complexes as catalysts. The major oxidation products were formaldehyde dimethyl acetal (dimethoxymethane, DMM) and methyl formate (MF). The Ru/Pd and Ru/Pt bimetallic catalysts generally afforded lower product ratios of DMM/MF and higher current efficiencies than the Ru/Au catalysts. The Ru/Au bimetallics exhibited product ratios and current efficiencies similar to those obtained from the Ru mononuclear compound CpRu(PPh(3))(2)Cl. Increasing the methanol concentration afforded higher current efficiencies, while the addition of water to the samples shifted the product distribution toward the more highly oxidized product, MF. PMID:15278130

  18. The electrochemical oxidation of toluene catalysed by Co(II) in N-butyl-N-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide.

    PubMed

    Balaji, S; Kannan, K; Moon, I S

    2015-12-14

    The electrochemical oxidation of toluene in N-butyl-N-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide ([bmpyr](+)[Ntf2](-)) was investigated by using cyclic voltammetry and galvanostatic electrolysis in the presence of Co(II) at a Pt disc working electrode. Cyclic voltammetry (CV) investigations revealed that Co(II)-Co(III) oxidation is a diffusion controlled electron transfer process. The diffusion coefficient values of Co(II) were found to increase from 0.38 × 10(-7) to 1.9 × 10(-7) cm(2) s(-1) as the temperature was increased from 25 °C to 80 °C. The CV peak current for toluene electro-oxidation increased by nearly 7 fold in the presence of Co(II) demonstrating a good catalytic effect. Co(II) catalysed galvanostatic electrolysis of toluene at room temperature has shown that benzaldehyde was formed along with a small quantity of 3-methyl-1-hexanol. PMID:26538114

  19. A new method for manufacturing graphene and electrochemical characteristic of graphene-supported Pt nanoparticles in methanol oxidation

    NASA Astrophysics Data System (ADS)

    Kakaei, Karim; Zhiani, Mohammad

    2013-03-01

    We report a Pt/graphene catalyst for the methanol oxidation. Graphene is synthesized from graphite electrodes using ionic liquid-assisted electrochemical exfoliation. Graphene-supported Pt electrocatalyst is then reduced by sodium borohydride with ethylenediaminetetraacetic acid disodium salt (EDTA-2Na) as a stabilizing agent to prepare highly dispersed Pt nanoparticles on carbon graphene to use as methanol oxidation in direct methanol fuel cell (DMFC) catalysts. X-ray diffractometer and scanning electron microscopy technique are used to investigate the crystallite size and the surface morphologies respectively. The electrochemical characteristics of the Pt/graphene and commercial Pt/C catalysts are investigated by cyclic voltammetry (CV) in nitrogen saturated sulfuric acid aqueous solutions and in mixed sulfuric acid and methanol aqueous solutions. The catalytic activities of the Pt/graphene and Pt/C electrodes for methanol oxidation is 1315 A g-1 Pt and 725 A g-1 Pt, which can be revealed the particular properties of the exfoliated graphene supports. Furthermore, Pt/graphene exhibited a better sensitivity, signal-to-noise ratio, and stability than commercial Pt/C.

  20. Analysis of diffusion-controlled stochastic events of iridium oxide single nanoparticle collisions by scanning electrochemical microscopy.

    PubMed

    Kwon, Seong Jung; Bard, Allen J

    2012-04-25

    We investigated the electrochemical detection of single iridium oxide nanoparticle (IrO(x) NP) collisions at the NaBH(4)-treated Pt ultramicroelectrode (UME) in a scanning electrochemical microscope (SECM) over an insulating surface. The NP collision events were monitored by observing the electrocatalytic water oxidation reaction at potentials where it does not take place on the Pt UME. These collisions occurred stochastically, resulting in a transient response ("blip") for each collision. The frequency of the collisions is proportional to the flux of NPs to the UME tip, and thus equivalent to the SECM current. A plot of collision frequency versus distance followed the theoretical approach curve behavior for negative feedback for a high concentration of mediator, demonstrating that the collisions were diffusion-controlled and that single-particle measurements of mass transport are equivalent to ensemble ones. When the SECM was operated with a Pt substrate at the same potential as the tip, the behavior followed that expected of the shielding mode. These studies and additional ones result in a model where the IrO(x) NP collision on the Pt UME is adsorptive, with oxygen produced by the catalyzed water oxidation causing a current decay. This results in a blip current response, with the current decay diminished in the presence of the oxygen scavenger, sulfite ion. Random walk and theoretical bulk simulations agreed with the proposed mechanism of IrO(x) NP collision, adsorption, and subsequent deactivation. PMID:22452267

  1. Electrochemical tuning of oxygen-containing groups on graphene oxides: towards control of the performance for the analysis of biomarkers.

    PubMed

    Lim, Chee Shan; Ambrosi, Adriano; Pumera, Martin

    2014-06-28

    Graphene materials are very popular in the field of biosensing owing to their distinctive characteristics. However, oxygen-containing groups are known to exist intrinsically in graphene-related materials. These groups influence the electrochemical properties of graphene materials and therefore affect the sensing performance of graphene-based electrodes when used to detect redox active biomarkers. A well-defined carbon/oxygen (C/O) ratio can be obtained upon applying different reduction potentials to graphene oxide (GO) films for a controlled removal of redox active oxygen functionalities. Here, we show that a precise control of the oxygen functionalities on the graphene oxide films allows the tuning of the biosensing capabilities of the electrodes for the analysis of two significant biomarkers, uric acid and ascorbic acid, as well as two DNA bases, guanine and adenine. Both the catalytic properties and the sensitivity of the reduced GO film electrodes (ERGOs) are evaluated by measuring the oxidation potential and the peak current, respectively. We demonstrate that each biomarker requires different optimal conditions which can be easily matched by varying the electrochemical pre-treatment of the sensing GO film. PMID:24817612

  2. Electrochemical preparation of nickel and copper oxides-decorated graphene composite for simultaneous determination of dopamine, acetaminophen and tryptophan.

    PubMed

    Liu, Bingdi; Ouyang, Xiaoqian; Ding, Yaping; Luo, Liqing; Xu, Duo; Ning, Yanqun

    2016-01-01

    In the present work, transition metal oxides decorated graphene (GR) have been fabricated for simultaneous determination of dopamine (DA), acetaminophen (AC) and tryptophan (Trp) using square wave voltammetry. Electro-deposition is a facile preparation strategy for the synthesis of nickel oxide (NiO) and copper oxide (CuO) nanoparticles. GR can be modified by using citric acid to produce more functional groups, which is conducive to the deposition of dispersed metal particles. The morphologies and interface properties of the obtained NiO-CuO/GR nanocomposite were examined by scanning electron microscopy, energy dispersive X-ray spectroscopy and Raman spectroscopy. Moreover, the electrochemical performances of the composite film were investigated by cyclic voltammetry and electrochemical impedance spectroscopy. The modified electrode exhibited that the linear response ranges for detecting DA, AC and Trp were 0.5-20 μM, 4-400 μM and 0.3-40 μM, respectively, and the detection limits were 0.17 μM, 1.33 μM and 0.1 μM (S/N=3). Under optimal conditions, the sensor displayed high sensitivity, excellent stability and satisfactory results in real samples analysis. PMID:26695242

  3. Treatment of real industrial wastewater using the combined approach of advanced oxidation followed by aerobic oxidation.

    PubMed

    Ramteke, Lokeshkumar P; Gogate, Parag R

    2016-05-01

    Fenton oxidation and ultrasound-based pretreatment have been applied to improve the treatment of real industrial wastewater based on the use of biological oxidation. The effect of operating parameters such as Fe(2+) loading, contact time, initial pH, and hydrogen peroxide loading on the extent of chemical oxygen demand (COD) reduction and change in biochemical oxygen demand (BOD5)/COD ratio has been investigated. The optimum operating conditions established for the pretreatment were initial pH of 3.0, Fe(2+) loading of 2.0, and 2.5 g L(-1) for the US/Fenton/stirring and Fenton approach, respectively, and temperature of 25 °C with initial H2O2 loading of 1.5 g L(-1). The use of pretreatment resulted in a significant increase in the BOD5/COD ratio confirming the production of easily digestible intermediates. The effect of the type of sludge in the aerobic biodegradation was also investigated based on the use of primary activated sludge (PAS), modified activated sludge (MAS), and activated sludge (AS). Enhanced removal of the pollutants as well as higher biomass yield was observed for MAS as compared to PAS and AS. The use of US/Fenton/stirring pretreatment under the optimized conditions followed by biological oxidation using MAS resulted in maximum COD removal at 97.9 %. The required hydraulic retention time for the combined oxidation system was also significantly lower as compared to only biological oxidation operation. Kinetic studies revealed that the reduction in the COD followed a first-order kinetic model for advanced oxidation and pseudo first-order model for biodegradation. The study clearly established the utility of the combined technology for the effective treatment of real industrial wastewater. PMID:26846248

  4. Iron(3) oxide-based nanoparticles as catalysts in advanced organic aqueous oxidation.

    PubMed

    Zelmanov, Grigory; Semiat, Raphael

    2008-01-01

    Water contaminated with dissolved organic matter is an important issue to resolve for all-purpose uses. The catalytic behavior of iron-based nanocatalysts was investigated for the treatment of contaminated water in the advanced chemical oxidation process. In this study, typical organic contaminants, such as ethylene glycol and phenol, were chosen to simulate common contaminants. It was shown that the two substances are efficiently destroyed by the Fenton-like reaction using iron(3) oxide-based nanocatalysts in the presence of hydrogen peroxide without the need for UV or visible radiation sources at room temperature. A strong effect of nanocatalyst concentration on reaction rate was shown. The kinetic reaction was found and the reaction rate coefficient k was calculated. PMID:17714754

  5. High Surface Area Antimony-Doped Tin Oxide Electrodes Templated by Graft Copolymerization. Applications in Electrochemical and Photoelectrochemical Catalysis.

    PubMed

    Luo, Hanlin; Fang, Zhen; Song, Na; Garvey, Timothy; Lopez, Rene; Meyer, Thomas J

    2015-11-18

    Mesoporous ATO nanocrystalline electrodes of micrometer thicknesses have been prepared from ATO nanocrystals and the grafted copolymer templating agents poly vinyl chloride-g-poly(oxyethylene methacrylate). As-obtained electrodes have high interfacial surface areas, large pore volumes, and rapid intraoxide electron transfer. The resulting high surface area materials are useful substrates for electrochemically catalyzed water oxidation. With thin added shells of TiO2 deposited by atomic layer deposition (ALD) and a surface-bound Ru(II) polypyridyl chromophore, they become photoanodes for hydrogen generation in the presence of a reductive scavenger. PMID:26488595

  6. Electrochemical modification of the passive oxide layer on a Ti film observed by in situ neutron reflectometry

    SciTech Connect

    Tun, Z.; Noeel, J.J.; Shoesmith, D.W.

    1999-03-01

    Anodization and the effect of subsequently applying cathodic potential to a thin-film Ti electrode in an aqueous NaCl solution have been studied with in situ neutron reflectometry. This new technique provides further insight into the processes underlying anodic oxide formation and hydrogen absorption under cathodic polarization. The results (Pilling-Bedworth ratio, anodization ratio, the onset of fluctuations in electrode current under cathodic potential, etc.) are generally in agreement with the literature, but this new technique provides further insight into the electrochemical processes. The anodized oxide is observed to be not porous, and has the density of the rutile structure for its entire thickness. However, it comprises two distinct regions: an inner region similar in thickness and composition to the original air-grown oxide, and an outer region containing a significant amount of hydrogen. The similarity of the inner region to the original oxide suggests that the underlying oxide growth mechanism for Ti is the point-defect model. Under applied cathodic potentials the overall oxide thickness remains constant, but the inner region is gradually converted to a material similar in hydrogen content to the outer region. The onset of massive hydrogen penetration seems to occur when the conversion is complete, or when the inner region has been reduced to only a few atomic layers.

  7. Hydroxyapatite/gelatin functionalized graphene oxide composite coatings deposited on TiO2 nanotube by electrochemical deposition for biomedical applications

    NASA Astrophysics Data System (ADS)

    Yan, Yajing; Zhang, Xuejiao; Mao, Huanhuan; Huang, Yong; Ding, Qiongqiong; Pang, Xiaofeng

    2015-02-01

    Graphene oxide cross-linked gelatin was employed as reinforcement fillers in hydroxyapatite coatings by electrochemical deposition process on TiO2 nanotube arrays (TNs). The TNs were grown on titanium by electrochemical anodization in hydrofluoric electrolyte using constant voltage. Fourier transform infrared spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, Field emission scanning electron microscopy equipped with energy dispersive X-ray analysis and biological studies were used to characterize the coatings. The corrosion resistance of the coatings was also investigated by electrochemical method in simulated body fluid solution.

  8. Cobalt-Porphyrin-Platinum-Functionalized Reduced Graphene Oxide Hybrid Nanostructures: A Novel Peroxidase Mimetic System For Improved Electrochemical Immunoassay

    PubMed Central

    Shu, Jian; Qiu, Zhenli; Wei, Qiaohua; Zhuang, Junyang; Tang, Dianping

    2015-01-01

    5,10,15,20-Tetraphenyl-21H,23H-porphine cobalt flat stacking on the reduced graphene oxide with platinum nanoparticles (PtNPs/CoTPP/rGO) were first synthesized and functionalized with monoclonal rabbit anti-aflatoxin B1 antibody (anti-AFB1) for highly efficient electrochemical immunoassay of aflatoxin B1 (AFB1) in this work. Transmission electron microscopy (TEM), atomic force microscope (AFM) and spectral techniques were employed to characterize the PtNPs/CoTPP/rGO hybrids. Using anti-AFB1-conjugated PtNPs/CoTPP/rGO as the signal-transduction tag, a novel non-enzymatic electrochemical immunosensing system was designed for detection of target AFB1 on the AFB1-bovine serum albumin-functionalized sensing interface. Experimental results revealed that the designed immunoassay could exhibit good electrochemical responses for target analyte and allowed the detection of AFB1 at a concentration as low as 5.0 pg mL−1 (5.0 ppt). Intra- and inter-assay coefficients of variation were below 10%. Importantly, the methodology was further validated for analyzing naturally contaminated or spiked blank peanut samples with consistent results obtained by AFB1 ELISA kit, thus providing a promising approach for quantitative monitoring of organic pollutants. PMID:26462136

  9. Cobalt-Porphyrin-Platinum-Functionalized Reduced Graphene Oxide Hybrid Nanostructures: A Novel Peroxidase Mimetic System For Improved Electrochemical Immunoassay

    NASA Astrophysics Data System (ADS)

    Shu, Jian; Qiu, Zhenli; Wei, Qiaohua; Zhuang, Junyang; Tang, Dianping

    2015-10-01

    5,10,15,20-Tetraphenyl-21H,23H-porphine cobalt flat stacking on the reduced graphene oxide with platinum nanoparticles (PtNPs/CoTPP/rGO) were first synthesized and functionalized with monoclonal rabbit anti-aflatoxin B1 antibody (anti-AFB1) for highly efficient electrochemical immunoassay of aflatoxin B1 (AFB1) in this work. Transmission electron microscopy (TEM), atomic force microscope (AFM) and spectral techniques were employed to characterize the PtNPs/CoTPP/rGO hybrids. Using anti-AFB1-conjugated PtNPs/CoTPP/rGO as the signal-transduction tag, a novel non-enzymatic electrochemical immunosensing system was designed for detection of target AFB1 on the AFB1-bovine serum albumin-functionalized sensing interface. Experimental results revealed that the designed immunoassay could exhibit good electrochemical responses for target analyte and allowed the detection of AFB1 at a concentration as low as 5.0 pg mL-1 (5.0 ppt). Intra- and inter-assay coefficients of variation were below 10%. Importantly, the methodology was further validated for analyzing naturally contaminated or spiked blank peanut samples with consistent results obtained by AFB1 ELISA kit, thus providing a promising approach for quantitative monitoring of organic pollutants.

  10. Cobalt-Porphyrin-Platinum-Functionalized Reduced Graphene Oxide Hybrid Nanostructures: A Novel Peroxidase Mimetic System For Improved Electrochemical Immunoassay.

    PubMed

    Shu, Jian; Qiu, Zhenli; Wei, Qiaohua; Zhuang, Junyang; Tang, Dianping

    2015-01-01

    5,10,15,20-Tetraphenyl-21H,23H-porphine cobalt flat stacking on the reduced graphene oxide with platinum nanoparticles (PtNPs/CoTPP/rGO) were first synthesized and functionalized with monoclonal rabbit anti-aflatoxin B1 antibody (anti-AFB1) for highly efficient electrochemical immunoassay of aflatoxin B1 (AFB1) in this work. Transmission electron microscopy (TEM), atomic force microscope (AFM) and spectral techniques were employed to characterize the PtNPs/CoTPP/rGO hybrids. Using anti-AFB1-conjugated PtNPs/CoTPP/rGO as the signal-transduction tag, a novel non-enzymatic electrochemical immunosensing system was designed for detection of target AFB1 on the AFB1-bovine serum albumin-functionalized sensing interface. Experimental results revealed that the designed immunoassay could exhibit good electrochemical responses for target analyte and allowed the detection of AFB1 at a concentration as low as 5.0 pg mL(-1) (5.0 ppt). Intra- and inter-assay coefficients of variation were below 10%. Importantly, the methodology was further validated for analyzing naturally contaminated or spiked blank peanut samples with consistent results obtained by AFB1 ELISA kit, thus providing a promising approach for quantitative monitoring of organic pollutants. PMID:26462136

  11. Enhancing electrochemical performance by control of transport properties in buffer layers--solid oxide fuel/electrolyser cells.

    PubMed

    Ramasamy, Devaraj; Nasani, Narendar; Brandão, Ana D; Pérez Coll, Domingo; Fagg, Duncan P

    2015-05-01

    The current work demonstrates how tailoring the transport properties of thin ceria-based buffer layers in solid oxide fuel or electrolyser cells can provide the necessary phase stability against chemical interaction at the electrolyte/electrode interface, while also providing radical improvements in the electrochemical performance of the oxygen electrode. Half cells of Ce0.8R0.2O2-δ + 2 mol% Co buffer layers (where R = Gd, Pr) with Nd2NiO4+δ electrodes were fabricated by spin coating on dense YSZ electrolyte supports. Dramatic decreases in polarization resistance, Rp, of up to an order of magnitude, could be achieved in the order, Pr ≪ Gd < no buffer layer. The current article shows how this improvement can be related to increased levels of ambipolar conductivity in the mixed conducting buffer layer, which provides an additional parallel path for electrochemical reaction. This is an important breakthrough as it shows how electrode polarization resistance can be substantially improved, in otherwise identical electrochemical cells, solely by tailoring the transport properties of thin intermediate buffer layers. PMID:25857870

  12. Metallic oxide CdIn2O4 films for the label free electrochemical detection of DNA hybridization.

    PubMed

    Zebda, A; Stambouli, V; Labeau, M; Guiducci, C; Diard, J-P; Le Gorrec, B

    2006-08-15

    DNA functionalised semiconductor metallic oxide electrodes have been developed for the direct electrochemical detection of DNA hybridization, without labelling or the introduction of a redox couple. Conductive CdIn(2)O(4) thin films with controlled properties were deposited on glass substrates using an aerosol pyrolysis technique. The films exhibit a polycrystalline microstructure with a surface roughness of 1.5 nm (r.m.s.) and an electrical resistivity ranging between 1 and 3 x 10(-3) Omega cm. These electrodes were functionalised using hydroxylation and silanisation steps, to allow the binding of DNA probe sequences (20 bases). The electrical detection of DNA hybridization with complementary sequences has been performed using electrochemical impedance spectrometry (EIS) measuring the variation of impedance before and after hybridization. Two set-ups were used, a standard set-up including three electrodes and a set-up including two symmetrical electrodes. In both configurations, a significant increase of the impedance modulus, more particularly of the real part of the impedance (160-225% according to the electrochemical cell used) has been obtained over a frequency range of 10-10(5)Hz. DNA hybridization has also been systematically confirmed using the fluorescence spectrometry. This study emphasizes the high sensitivity of the CdIn(2)O(4) as a working electrode for the detection of biological events occurring at the electrode surface. PMID:16434177

  13. Molecular Cobalt Clusters as Precursors of Distinct Active Species in Electrochemical, Photochemical, and Photoelectrochemical Water Oxidation Reactions in Phosphate Electrolytes.

    PubMed

    Li, Xiaobo; Clatworthy, Edwin B; Masters, Anthony F; Maschmeyer, Thomas

    2015-11-01

    Three cobalt model molecular compounds, Co-cubane ([Co4 (3 -O)4 (-OAc)4 py4 ]), Co-trimer ([Co3 (?3 -O)(-OAc)6 py3 ]PF6 ), and Co-dimer ([Co2 (?-OH)2 (-OAc)(OAc)2 py4 ]PF6 ), are investigated as water oxidation reaction (WOR) catalysts, using electrochemical, photochemical, and photoelectrochemical methodologies in phosphate electrolyte. The actual species contributing to the catalytic activity observed in the WOR are derived from the transformation of these cobalt compounds. The catalytic activity observed is highly dependent on the initial compound structure and on the particular WOR methodology used. Co-cubane shows no activity in the electrochemical WOR and negligible activity in the photochemical WOR, but is active in the photoelectrochemical WOR, in which it behaves as a precursor to catalytically active species. Co-dimer also shows no activity in the electrochemical WOR, but behaves as a precursor to catalytically active species in both the photochemical and photoelectrochemical WOR experiments. Co-trimer behaves as a precursor to catalytically active species in all three of the WOR methodologies. PMID:26404053

  14. Amplified inhibition of the electrochemical signal of ferrocene by enzyme-functionalized graphene oxide nanoprobe for ultrasensitive immunoassay.

    PubMed

    Lai, Guosong; Cheng, Hui; Xin, Dinghong; Zhang, Haili; Yu, Aimin

    2016-01-01

    A nanoprobe-induced signal inhibition mechanism was designed for ultrasensitive electrochemical immunoassay at a chitosan-ferrocene (CS-Fc) based immunosensor. The nanoprobe was prepared by covalently loading signal antibody and high-content horseradish peroxidase (HRP) on the graphene oxide (GO) nanocarrier. The immunosensor was prepared through the stepwise assembly of gold nanoparticles (Au NPs) and capture antibody at a CS-Fc modified electrode. After sandwich immunoreaction, the GO-HRP nanoprobes were quantitatively captured onto the immunosensor surface and thus induced the production of a layer of insoluble film through the enzymatically catalytic reaction of the HRP labels. Both the dielectric immunocomplex formed on the immunosensor surface and the enzymatic precipitate with low electroconductivity led to the electrochemical signal decease of the Fc indicator, which was greatly amplified by the multi-enzyme signal amplification of the nanoprobe. Based on this amplified signal inhibition mechanism, a new ultrasensitive electrochemical immunoassay method was developed. Using carcinoembryonic antigen as a model analyte, this method showed a wide linear range over 5 orders of magnitude with a detection limit down to 0.54 pg/mL. Besides, the immunosensor showed good specificity, acceptable reproducibility and stability as well as satisfactory reliability for the serum sample analysis. PMID:26703270

  15. An ultrasensitive electrochemical DNA biosensor based on a copper oxide nanowires/single-walled carbon nanotubes nanocomposite

    NASA Astrophysics Data System (ADS)

    Chen, Mei; Hou, Changjun; Huo, Danqun; Yang, Mei; Fa, Huanbao

    2016-02-01

    Here, we developed a novel and sensitive electrochemical biosensor to detect specific-sequence target DNA. The biosensor was based on a hybrid nanocomposite consisting of copper oxide nanowires (CuO NWs) and carboxyl-functionalized single-walled carbon nanotubes (SWCNTs-COOH). The resulting CuO NWs/SWCNTs layers exhibited a good differential pulse voltammetry (DPV) current response for the target DNA sequences, which we attributed to the properties of CuO NWs and SWCNTs. CuO NWs and SWCNTs hybrid composites with highly conductive and biocompatible nanostructure were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), and cyclic voltammetry (CV). Immobilization of the probe DNA on the electrode surface was largely improved due to the unique synergetic effect of CuO NWs and SWCNTs. DPV was applied to monitor the DNA hybridization event, using adriamycin as an electrochemical indicator. Under optimal conditions, the peak currents of adriamycin were linear with the logarithm of target DNA concentrations (ranging from 1.0 × 10-14 to 1.0 × 10-8 M), with a detection limit of 3.5 × 10-15 M (signal/noise ratio of 3). The biosensor also showed high selectivity to single-base mismatched target DNA. Compared with other electrochemical DNA biosensors, we showed that the proposed biosensor is simple to implement, with good stability and high sensitivity.

  16. Characterizing mechanisms of extracellular electron transport in sulfur and iron-oxidizing electrochemically active bacteria isolated from marine sediments

    NASA Astrophysics Data System (ADS)

    Rowe, A. R.; Bird, L. J.; Lam, B. R.; Nealson, K. H.

    2014-12-01

    Lithotrophic reactions, including the oxidation of mineral species, are often difficult to detect in environmental systems. This could be due to the nature of substrate or metabolite quantification or the rapid consumption of metabolic end products or intermediates by proximate biological or abiotic processes. Though recently genetic markers have been applied to detecting these processes in environmental systems, our knowledge of lithotrophic markers are limited to those processes catalyzed by organisms that have been cultured and physiologically characterized. Here we describe the use of electrochemical enrichment techniques to isolate marine sediment-dwelling microbes capable of the oxidation or insoluble forms of iron and sulfur including both the elemental species. All the organisms isolated fall within the Alphaproteobacteria and Gammaproteobacteria and are capable of acquiring electrons from an electrode while using either oxygen or nitrate as a terminal electron acceptor. Electrochemical analysis of these microbes has demonstrated that, though they have similar geochemical abilities (either sulfur or iron oxidation), they likely utilize different biochemical mechanisms demonstrated by the variability in dominant electron transfer modes or interactions (i.e., biofilm, planktonic or mediator facilitated interactions) and the wide range of midpoint potentials observed for dominant redox active cellular components (ranging from -293 to +50 mV vs. Ag/AgCl). For example, organisms isolated on elemental sulfur tended to have higher midpoint potentials than iron-oxidizing microbes. A variety of techniques are currently being applied to understanding the different mechanisms of extracellular electron transport for oxidizing an electrode or corresponding insoluble electron donor including both genomic and genetic manipulation experiments. The insight gained from these experiments is not limited to the physiology of the organisms isolated but will also aid in identification of genetic targets to better understand the ecologic importance of lithotrophs and the role solid substrates may play in their metabolism.

  17. Graphene-Based Hybrids with Manganese Oxide Polymorphs as Tailored Interfaces for Electrochemical Energy Storage: Synthesis, Processing, and Properties

    NASA Astrophysics Data System (ADS)

    Gupta, S.; van Meveren, M. M.; Jasinski, J.

    2015-01-01

    Technological progress is determined to a greater extent by developments of novel materials or new combinations of known materials with different dimensionality and diverse functionality. In this work, we report on the synthesis and characterization of graphene-based hybrid nanomaterials coupled with transition-metal oxide polymorphs (nano/micro-manganese oxides, i.e., β-MnO2 [Mn(IV)] and Mn3O4 [Mn(II, III)]). This lays the groundwork for high-performance electrochemical electrodes for alternative energy devices owing to their higher specific capacitance, wide operational potential window and stability through charge-discharge cycling, environmentally benignity, cost-effectiveness, easy processing, and reproducibility on a larger scale. To accomplish this, we strategically designed these hybrids by direct anchoring or physical adsorption of β-MnO2 and Mn3O4 on variants of graphene, namely graphene oxide and its reduced form, via mixing dispersions of the constituents under mild ultrasonication and drop-casting, resulting in four different combinations. This facile approach affords strong chemical/physical attachment and is expected to result in coupling between the pseudocapacitive transition-metal oxides and supercapacitive nanocarbons showing enhanced activity/reactivity and reasonable areal density of tailored interfaces. We used a range of complementary analytical characterization tools to determine the structure and physical properties, such as scanning electron microscopy combined with energy-dispersive x-ray spectroscopy, atomic force microscopy, x-ray diffraction, resonance Raman spectroscopy combined with elemental Raman mapping, and transmission electron microscopy in conjunction with selected-area electron diffraction. All of these techniques reveal surface morphology, local (lattice dynamical) and average structure, and local charge transfer due to the physically (or chemically) adsorbed manganese oxide of synthesized hybrids that helps to establish microscopic structure-property-function correlations highlighting the surface structure and interfaces to further investigate their electrochemical supercapacitor properties.

  18. Oxidative stress to the cornea, changes in corneal optical properties, and advances in treatment of corneal oxidative injuries.

    PubMed

    Cejka, Cestmir; Cejkova, Jitka

    2015-01-01

    Oxidative stress is involved in many ocular diseases and injuries. The imbalance between oxidants and antioxidants in favour of oxidants (oxidative stress) leads to the damage and may be highly involved in ocular aging processes. The anterior eye segment and mainly the cornea are directly exposed to noxae of external environment, such as air pollution, radiation, cigarette smoke, vapors or gases from household cleaning products, chemical burns from splashes of industrial chemicals, and danger from potential oxidative damage evoked by them. Oxidative stress may initiate or develop ocular injury resulting in decreased visual acuity or even vision loss. The role of oxidative stress in the pathogenesis of ocular diseases with particular attention to oxidative stress in the cornea and changes in corneal optical properties are discussed. Advances in the treatment of corneal oxidative injuries or diseases are shown. PMID:25861412

  19. Identification and Analysis of Electrochemical Instrumentation Limitations through the Study of Platinum Surface Oxide Formation and Reduction.

    PubMed

    McMath, Ashley A; van Drunen, Julia; Kim, Jutae; Jerkiewicz, Gregory

    2016-03-15

    Anodic polarization of Pt electrodes in aqueous H2SO4 leads to the formation of a surface oxide (PtO). Herein, the surface oxide growth is accomplished using three different approaches: (i) chronoamperometry (CA); (ii) chronocoulometry (CC); and (iii) a combination of cyclic voltammetry (CV) and CA. The PtO reduction is accomplished potentiodynamically using voltammetry. The oxide growth takes place at defined polarization potentials (Ep), polarization times (tp), and temperatures (T). The oxide charge density (qox) is determined for both the formation (qox,form) and reduction (qox,red) processes. The oxide reduction CV profiles are integrated to determine the charge density values for oxide reduction (qox,red,CV) which are compared with the qox,form,CA and qox,form,CC values. The values of qox,form,CC are greater than those of qox,form,CA, but both potentiotatic methods (CA and CC) produce qox,form values that are consistently lower than those of qox,red,CV. In the case of oxide formation with combined CV and CA, the values of qox,form,CV+CA are found to be lower than the values of qox,red,CV, although the difference is small. Electrochemical quartz crystal nanobalance (EQCN) is used to monitor the mass variation at the electrode surface during the oxide formation and reduction process at Ep = 1.20 V with various tp values. Equal mass changes during oxide formation and reduction are detected by the EQCN. The nature of the differences in qox,form and qox,red encountered with the different experimental methods are discussed in terms of instrumental limitations. PMID:26877259

  20. Nanostructures and Lithium Electrochemical Reactivity of Lithium Titanites and Titanium Oxides: A Review

    SciTech Connect

    Yang, Zhenguo; Choi, Daiwon; Kerisit, Sebastien N.; Rosso, Kevin M.; Wang, Donghai; Zhang, Jiguang; Graff, Gordon L.; Liu, J.

    2009-07-15

    Being inherently safe and chemically compatible with the electrolyte, titanium oxidebased materials, including both Li-titanites and various TiO2-polymorphs, are considered alternatives to carbonaceous anodes in Li-ion batteries. Given the commercial success of the spinel lithium titanites, TiO2-polymorphs, in particular in nanostructured forms, have been fabricated and investigated for the applications. Nanostructuring leads to increased reaction areas, shortened Li+ diffusion and potentially enhanced solubility/capacity. Integration with an electron conductive second phase into the TiO2-based nanostructures eases the electron transport, resulting in further improved lithium electrochemical activity and the overall electrochemical performance. This paper reviews structural characteristics and Li-electrochemical reactivity, along with synthetic approaches, of nanostructures and nano-composites based on lithium titanites and TiO2-polymorphs that include rutile, anatase, bronze and brookite.

  1. Applications of advanced oxidation processes: present and future.

    PubMed

    Suty, H; De Traversay, C; Cost, M

    2004-01-01

    The use of advanced oxidation processes (AOPs) to remove pollutants in various water treatment applications has been the subject of study for around 30 years. Most of the available processes (Fenton reagent, O3 under basic conditions, O3/H2O2, O3/UV, O3/solid catalyst, H2O2/M(n+), H2O2/UV, photo-assisted Fenton, H2O2/solid catalyst, H2O2/NaClO, TiO2/UV etc.) have been investigated in depth and a considerable body of knowledge has been built up about the reactivity of many pollutants. Various industrial applications have been developed, including ones for ground remediation (TCE, PCE), the removal of pesticides from drinking water, the removal of formaldehyde and phenol from industrial waste water and a reduction in COD from industrial waste water. The development of such AOP applications has been stimulated by increasingly stringent regulations, the pollution of water resources through agricultural and industrial activities and the requirement that industry meet effluent discharge standards. Nevertheless, it is difficult to obtain an accurate picture of the use of AOPs and its exact position in the range of water treatment processes has not been determined to date. The purpose of this overview is to discuss those processes and provide an indication of future trends. PMID:15077976

  2. A straightforward implementation of in situ solution electrochemical C NMR spectroscopy for studying reactions on commercial electrocatalysts: ethanol oxidation.

    PubMed

    Huang, L; Sorte, E G; Sun, S-G; Tong, Y Y J

    2015-05-11

    Identifying and quantifying electrocatalytic-reaction-generated solution species, be they reaction intermediates or products, are highly desirable in terms of understanding the associated reaction mechanisms. We report herein a straightforward implementation of in situ solution electrochemical (13)C NMR spectroscopy for the first time that enables in situ studies of reactions on commercial fuel-cell electrocatalysts (Pt and PtRu blacks). Using ethanol oxidation reaction (EOR) as a working example, we discovered that (1) the complete oxidation of ethanol to CO2 only took place dominantly at the very beginning of a potentiostatic chronoamperometric (CA) measurement and (2) the PtRu had a much higher activity in catalysing oxygen insertion reaction that leads to acetic acid. PMID:25868425

  3. Ascorbic Acid Assisted Synthesis of Cobalt Oxide Nanostructures, Their Electrochemical Sensing Application for the Sensitive Determination of Hydrazine

    NASA Astrophysics Data System (ADS)

    Tahira, Aneela; Nafady, Ayman; Baloach, Quarratulain; Sirajuddin; Sherazi, Syed Tufail Hussain; Shaikh, Tayyaba; Arain, Munazza; Willander, Magnus; Ibupoto, Zafar Hussain

    2016-04-01

    This study describes, the synthesis of cobalt oxide nanostructures using ascorbic acid as a growth directing agent by the hydrothermal method. Ascorbic acid is used for the first time for the synthesis of cobalt oxide nanostructures and a unique morphology is prepared in the present study. The cobalt oxide nanostructures were characterized by scanning electron microcopy, x-ray diffraction, and x-ray photoelectron spectroscopy techniques. These analytical techniques demonstrated well defined morphology, good crystalline quality, and high purity of as prepared cobalt oxide nanostructures. The glassy carbon electrode was modified with cobalt oxide nanostructures for the development of a sensitive and selective electrochemical hydrazine sensor. The developed hydrazine sensor exhibits a linear range of 2-24 μM. The sensitivity and limit of detection of presented hydrazine sensors are 12,734 μA/mM/cm2 and 0.1 μM respectively. The developed hydrazine sensor is highly selective, stable, and reproducible. The proposed sensor is successfully applied for the detection of hydrazine from different water samples. The present study provides the development of an alternative tool for the reliable monitoring of hydrazine from environmental and biological samples.

  4. A New Mechanism in Electrochemical Process for Arsenic Oxidation: Production of H2O2 from Anodic O2 Reduction on the Cathode under Automatically Developed Alkaline Conditions.

    PubMed

    Qian, Ao; Yuan, Songhu; Zhang, Peng; Tong, Man

    2015-05-01

    Electrochemical cathodes are often used to reduce contaminants or produce oxidizing substances (i.e., H2O2). Alkaline conditions develop automatically around the cathode in electrochemical processes, and O2 diffuses onto the cathode easily. However, limited attention is paid to contaminant transformation by the reactive species produced on the cathode under oxic and alkaline conditions due to the inapplicability of pH for Fenton reaction. In this study, a new oxidation mechanism on the cathode is presented for contaminant transformation under automatically developed alkaline conditions. In an electrochemical sand column, 6.67 μM As(III) was oxidized by 36% when it passed through the cathode under the conditions of 30 mA current, an initial pH of 7.5 and a flow rate of 2 mL/min. Under the alkaline conditions (pH 10.0-11.0) that developed automatically around the cathode, the reduction potential of As(III) decreased greatly, allowing a pronounced oxidation by the small quantities of H2O2 produced from O2 reduction on the cathode. As(III) oxidation was further increased by the presence of soil pore water and groundwater solutes of HCO3-, Ca2+, Mg2+ and humic acid. The new oxidation mechanism found for the cathode under localized alkaline conditions supplements the fundamentals of contaminant transformation in electrochemical processes. PMID:25853500

  5. Platinum/mesoporous WO3 as a carbon-free electrocatalyst with enhanced electrochemical activity for methanol oxidation.

    PubMed

    Cui, Xiangzhi; Shi, Jianlin; Chen, Hangrong; Zhang, Lingxia; Guo, Limin; Gao, Jianhua; Li, Jingbo

    2008-09-25

    A new type of carbon-free electrode catalyst, Pt/mesoporous WO3 composite, has been prepared and its electrochemical activity for methanol oxidation has been investigated. The mesoporous tungsten trioxide support was synthesized by a replicating route and the mesoporous composties with Pt loaded were characterized by using X-ray diffraction (XRD), nitrogen sorption, field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM) and energy-dispersive X-ray spectroscopy (EDS) techniques. Cyclic voltammetry (CV), line scan voltammetry (LSV) and chronoamperometry (CA) were adopted to characterize the electrochemical activities of the composites. The mesoporous WO3 showed high surface area, ordered pore structure, and nanosized wall thickness of about 6-7 nm. When a certain amount of Pt nanoparticles were dispersed in the pore structure of mesoporous WO3, the resultant mesostructured Pt/WO3 composites exhibit high electro-catalytic activity toward methanol oxidation. The overall electro-catalytic activities of 20 wt % Pt/WO3 composites are significantly higher than that of commercial 20 wt % Pt/C catalyst and are comparable to the 20 wt % PtRu/C catalyst in the potential region of 0.5-0.7 V. The enhanced electro-catalytic activity is attributed to be resulted from the assistant catalytic effect and the mesoporous structure of WO3 supports. PMID:18754636

  6. Non-covalent functionalization of graphene oxide by polyindole and subsequent incorporation of Ag nanoparticles for electrochemical applications

    NASA Astrophysics Data System (ADS)

    Dubey, Prashant; Kumar, Ashish; Prakash, Rajiv

    2015-11-01

    Reduced graphene oxide (r-GO) sheets have been modified by polyindole (PIn) via in situ chemical oxidation method to obtain stable dispersion in water and furthermore incorporation of Ag nanoparticles (Ag NPs); the resulting Ag NPs/PIn-r-GO nanocomposite is demonstrated for electrochemical applications. Ag NPs/r-GO and PIn/GO nanocomposites have also been prepared for its comparative study with Ag NPs/PIn-r-GO. Non-covalent functionalization of GO by PIn polymer leads to PIn-GO dispersion, which is stable for several months without any precipitation. This dispersed solution is used for formation of Ag NPs/PIn-r-GO nanocomposite. Various experimental tools like UV-vis, FTIR and TEM have been used to characterize as-synthesized materials. Thereafter electrochemical performance of as-synthesized nanocomposites have been compared for their charge capacitive behaviour (without its poisoning compared to Ag NPs/r-GO) which leads to be an excellent candidate for the possible applications such as electrocatalysis, charge storage devices, etc. We observed that Ag NPs/PIn-r-GO nanocomposite exhibits better processability and electroactivity as electrode material in comparison to Ag NPs/r-GO and PIn/GO nanocomposites due to synergistic effect of individual components.

  7. The effect of As, Co, and Ni impurities on pyrite oxidation kinetics: An electrochemical study of synthetic pyrite

    NASA Astrophysics Data System (ADS)

    Lehner, Stephen; Savage, Kaye; Ciobanu, Madalina; Cliffel, David E.

    2007-05-01

    Synthetic pyrite crystals doped with As, Co, or Ni, undoped pyrite, and natural arsenian pyrite from Leadville, Colorado were investigated with electrochemical techniques and solid-state measurements of semiconducting properties to determine the effect of impurity content on pyrite's oxidation behavior. Potential step experiments, cyclic voltammetry, and AC voltammetry were performed in a standard three-electrode electrochemical cell setup. A pH 1.78 sulfuric acid solution containing 1 mM ferric iron, open to atmospheric oxygen, was chosen to approximate water affected by acid drainage. Van der Pauw/Hall effect measurements determined resistivity, carrier concentration and carrier mobility. The anodic dissolution of pyrite and the reduction of ferric iron half-reactions are taken as proxies for natural pyrite oxidation. Pyrite containing no impurities is least reactive. Pyrite with As is more reactive than pyrite with either Ni or Co despite lower dopant concentration. As, Co, and Ni impurities introduce bulk defect states at different energy levels within the band gap. Higher reactivity of impure pyrite suggests that introduced defect levels lead to higher density of occupied surface states at the solid-solution interface and increased metallic behavior. The current density generated from potential step experiments increased with increasing As concentration. The higher reactivity of As-doped pyrite may be related to p-type conductivity and corrosion by holes. The results of this study suggest that considering the impurity content of pyrite in mining waste may lead to more accurate risk assessment of acid producing potential.

  8. Polyaniline-iron oxide nanohybrid film as multi-functional label-free electrochemical and biomagnetic sensor for catechol.

    PubMed

    Chandra, Sudeshna; Lang, Heinrich; Bahadur, Dhirendra

    2013-09-17

    Polyaniline-iron oxide magnetic nanohybrid was synthesized and characterized using various spectroscopic, microstructural and electrochemical techniques. The smart integration of Fe3O4 nanoparticles within the polyaniline (PANI) matrix yielded a mesoporous nanohybrid (Fe3O4@PANI) with high surface area (94 m(2) g(-1)) and average pore width of 12.8 nm. Catechol is quasi-reversibly oxidized to o-quinone and reduced at the Fe3O4@PANI modified electrodes. The amperometric current response toward catechol was evaluated using the nanohybrid and the sensitivity and detection limit were found to be 312 μA μL(-1) and 0.2 nM, respectively. The results from electrochemical impedance spectroscopy (EIS) indicated that the increased solution resistance (Rs) was due to elevated adsorption of catechol on the modified electrodes. Photoluminescence spectra showed ligand-to-metal charge transfer (LMCT) between p-π orbitals of the phenolate oxygen in catechol and the d-σ* metal orbital of Fe3O4@PANI nanohybrid. Potential dependent spectroelectrochemical behavior of Fe3O4@PANI nanohybrid toward catechol was studied using UV/vis/NIR spectroscopy. The binding activity of the biomagnetic particles to catechol through Brownian relaxation was evident from AC susceptibility measurements. The proposed sensor was used for successful recovery of catechol in tap water samples. PMID:23998532

  9. Nickel hydroxide nanoparticles-reduced graphene oxide nanosheets film: layer-by-layer electrochemical preparation, characterization and rifampicin sensory application.

    PubMed

    Rastgar, Shokoufeh; Shahrokhian, Saeed

    2014-02-01

    Electrochemical deposition, as a well-controlled synthesis procedure, has been used for subsequently layer-by-layer preparation of nickel hydroxide nanoparticle-reduced graphene oxide nanosheets (Ni(OH)2-RGO) on a graphene oxide (GO) film pre-cast on a glassy carbon electrode surface. The surface morphology and nature of the nano-hybrid film (Ni(OH)2-RGO) was thoroughly characterized by scanning electron and atomic force microscopy, spectroscopy and electrochemical techniques. The modified electrode appeared as an effective electro-catalytic model for analysis of rifampicin (RIF) by using linear sweep voltammetry (LSV). The prepared modified electrode exhibited a distinctly higher activity for electro-oxidation of RIF than either GO, RGO nanosheets or Ni(OH)2 nanoparticles. Enhancement of peak currents is ascribed to the fast heterogeneous electron transfer kinetics that arise from the synergistic coupling between the excellent properties of RGO nanosheets (such as high density of edge plane sites, subtle electronic characteristics and attractive π-π interaction) and unique properties of metal nanoparticles. Under the optimized analysis conditions, the modified electrode showed two oxidation processes for rifampicin at potentials about 0.08 V (peak I) and 0.69 V (peak II) in buffer solution of pH 7.0 with a wide linear dynamic range of 0.006-10.0 µmol L(-1) and 0.04-10 µmol L(-1) with a detection limit of 4.16 nmol L(-1) and 2.34 nmol L(-1) considering peaks I and II as an analytical signal, respectively. The results proved the efficacy of the fabricated modified electrode for simple, low cost and highly sensitive medicine sensor well suited for the accurate determinations of trace amounts of rifampicin in the pharmaceutical and clinical preparations. PMID:24401398

  10. Amperometric detection and electrochemical oxidation of aliphatic amines and ammonia on silver-lead oxide thin-film electrodes

    SciTech Connect

    Ge, Jisheng

    1996-01-08

    This thesis comprises three parts: Electrocatalysis of anodic oxygen-transfer reactions: aliphatic amines at mixed Ag-Pb oxide thin-film electrodes; oxidation of ammonia at anodized Ag-Pb eutectic alloy electrodes; and temperature effects on oxidation of ethylamine, alanine, and aquated ammonia.

  11. Electrochemical methane sensor

    DOEpatents

    Zaromb, S.; Otagawa, T.; Stetter, J.R.

    1984-08-27

    A method and instrument including an electrochemical cell for the detection and measurement of methane in a gas by the oxidation of methane electrochemically at a working electrode in a nonaqueous electrolyte at a voltage about 1.4 volts vs R.H.E. (the reversible hydrogen electrode potential in the same electrolyte), and the measurement of the electrical signal resulting from the electrochemical oxidation.

  12. Effects of Tungsten Oxide Addition on the Electrochemical Performance of Nanoscale Tantalum Oxide-Based Electrocatalysts for Proton Exchange Membrane PEM Fuel Cells

    SciTech Connect

    Oh, Tak Keun; Kim, Jin Yong; Shin, Yongsoon; Engelhard, Mark H.; Weil, K. Scott

    2011-08-01

    In the present study, the properties of a series of non-platinum based nanoscale tantalum oxide/tungsten oxide-carbon composite catalysts was investigated for potential use in catalyzing the oxygen reduction reaction (ORR) on the cathode side of a PEM fuel cell membrane electrode assembly. Electrochemical performance was measured using a half-cell test set up with a rotating disc electrode and compared with a commercial platinum-on-carbon (Pt/C) catalyst. Overall, all of the oxide-based composite catalysts exhibit high ORR on-set potentials, comparable to that of the baseline Pt/C catalyst. The addition of tungsten oxide as a dopant to tantalum oxide greatly improved mass specific current density. Maximum performance was achieved with a catalyst containing 32 mol% of tungsten oxide, which exhibited a mass specific current density ~8% that of the Pt/C catalyst at 0.6 V vs. the normal hydrogen electrode (NHE) and ~35% that of the Pt/C catalyst at 0.2 V vs. NHE. Results from X-ray photoelectron spectroscopy analysis indicated that the tungsten cations in the composite catalysts exist in the +6 oxidation state, while the tantalum displays an average valence of +5, suggesting that the addition of tungsten likely creates an oxygen excess in the tantalum oxide structure that influences its oxygen absorption kinetics. When the 32mol% tungsten doped catalyst loading on the working electrode was increased to five times that of the original loading (which was equivalent to that of the baseline Pt/C catalyst), the area specific current density improved four fold, achieving an area specific current density ~35% that of the Pt/C catalyst at 0.6 V vs. NHE.

  13. Advances in the identification of electrochemical transfer function models using Prony analysis

    SciTech Connect

    Trudnowski, D.J.; Donnelly, M.K.; Hauer, J.F.

    1993-02-01

    This paper further advances the usefulness and understanding of Prony analysis as a tool for identification of power system electromechanical oscillation models. These linear models are developed by analyzing power system ring-down data. The presented results allow more generality in the assumed model formulation. In addition, a comparison is made between Prony analysis and autoregressive moving-average (KARMA) modeling, which has also been proposed for analysis of system oscillations. Under the conditions investigated, the Prony algorithm performed more accurate identification.

  14. Feasibility of steam tunnel oxide for advanced non volatile memories

    NASA Astrophysics Data System (ADS)

    Ghidini, G.; Tosi, M.; Clementi, C.

    1997-07-01

    In order to reduce dopant diffusion to obtain device scaling, a decrease of any thermal treatment is required. Therefore, to substitute dry thermal oxides for tunnel application in Flash Memories, the possibility of using steam oxides grown at low temperatures was studied, considering, in addition, scaling of these oxides for future generations. Results concerning oxide reliability and charge trapping for elementary structures are presented and correlated with device performance.

  15. Electrochemically induced far-infrared difference spectroscopy on metalloproteins using advanced synchrotron technology.

    PubMed

    Vita, Nicolas; Brubach, Jean-Blaise; Hienerwadel, Rainer; Bremond, Nicolas; Berthomieu, Dorothée; Roy, Pascale; Berthomieu, Catherine

    2013-03-01

    New information on a protein's structure, intra- and intermolecular hydrogen bonds, or metal-ligand bond properties can be unraveled in the far-infrared (far-IR)-terahertz-domain (600-3 cm(-1) or 18-0.1 THz). In this study, we compare the performances of thermal sources with synchrotron far-IR to record reaction-induced Fourier transform infrared (FT-IR) difference signals with proteins in solution. Using the model protein Cu-azurin placed in a short path length electrochemical cell adapted for transmission spectroscopy in vacuum-purged optics, we show that minute spectral shifts induced by metal isotope labeling or temperature changes are detected using the far-IR beamline AILES of the synchrotron SOLEIL. On one hand, these data allow us to identify modes involving Cu-ligand vibrations and pave the way for the analysis of metal sites or metal redox states of proteins not amenable to resonance Raman spectroscopy. On another hand, small band shifts or changes in band intensity upon temperature modifications show that far-IR difference spectroscopy allows one to extract from a complex background hydrogen-bonding signatures directly relevant to the protein function. For Cu-azurin, a temperature-sensitive IR mode involving Cu(II)-His vibrations points to the role of a hydrogen bond between a Cu histidine ligand and the water solvent in tuning the Cu(II)-histidine bond properties. Furthermore, these experimental data support the possible role of a His117-water interaction in electron-transfer activity of Cu-azurin proposed by theoretical studies. PMID:23360365

  16. Modular advanced oxidation process enabled by cathodic hydrogen peroxide production.

    PubMed

    Barazesh, James M; Hennebel, Tom; Jasper, Justin T; Sedlak, David L

    2015-06-16

    Hydrogen peroxide (H2O2) is frequently used in combination with ultraviolet (UV) light to treat trace organic contaminants in advanced oxidation processes (AOPs). In small-scale applications, such as wellhead and point-of-entry water treatment systems, the need to maintain a stock solution of concentrated H2O2 increases the operational cost and complicates the operation of AOPs. To avoid the need for replenishing a stock solution of H2O2, a gas diffusion electrode was used to generate low concentrations of H2O2 directly in the water prior to its exposure to UV light. Following the AOP, the solution was passed through an anodic chamber to lower the solution pH and remove the residual H2O2. The effectiveness of the technology was evaluated using a suite of trace contaminants that spanned a range of reactivity with UV light and hydroxyl radical (HO(•)) in three different types of source waters (i.e., simulated groundwater, simulated surface water, and municipal wastewater effluent) as well as a sodium chloride solution. Irrespective of the source water, the system produced enough H2O2 to treat up to 120 L water d(-1). The extent of transformation of trace organic contaminants was affected by the current density and the concentrations of HO(•) scavengers in the source water. The electrical energy per order (EEO) ranged from 1 to 3 kWh m(-3), with the UV lamp accounting for most of the energy consumption. The gas diffusion electrode exhibited high efficiency for H2O2 production over extended periods and did not show a diminution in performance in any of the matrices. PMID:26039560

  17. Modular Advanced Oxidation Process Enabled by Cathodic Hydrogen Peroxide Production

    PubMed Central

    2015-01-01

    Hydrogen peroxide (H2O2) is frequently used in combination with ultraviolet (UV) light to treat trace organic contaminants in advanced oxidation processes (AOPs). In small-scale applications, such as wellhead and point-of-entry water treatment systems, the need to maintain a stock solution of concentrated H2O2 increases the operational cost and complicates the operation of AOPs. To avoid the need for replenishing a stock solution of H2O2, a gas diffusion electrode was used to generate low concentrations of H2O2 directly in the water prior to its exposure to UV light. Following the AOP, the solution was passed through an anodic chamber to lower the solution pH and remove the residual H2O2. The effectiveness of the technology was evaluated using a suite of trace contaminants that spanned a range of reactivity with UV light and hydroxyl radical (HO•) in three different types of source waters (i.e., simulated groundwater, simulated surface water, and municipal wastewater effluent) as well as a sodium chloride solution. Irrespective of the source water, the system produced enough H2O2 to treat up to 120 L water d–1. The extent of transformation of trace organic contaminants was affected by the current density and the concentrations of HO• scavengers in the source water. The electrical energy per order (EEO) ranged from 1 to 3 kWh m–3, with the UV lamp accounting for most of the energy consumption. The gas diffusion electrode exhibited high efficiency for H2O2 production over extended periods and did not show a diminution in performance in any of the matrices. PMID:26039560

  18. Experimental Approach to Controllably Vary Protein Oxidation While Minimizing Electrode Adsorption for Boron-Doped Diamond Electrochemical Surface Mapping Applications

    SciTech Connect

    McClintock, Carlee; Hettich, Robert {Bob} L

    2013-01-01

    Oxidative protein surface mapping has become a powerful approach for measuring the solvent accessibility of folded protein structures. A variety of techniques exist for generating the key reagent hydroxyl radicals for these measurements; however, many of these approaches require use of radioactive sources or caustic oxidizing chemicals. The purpose of this research was to evaluate and optimize the use of boron-doped diamond (BDD) electrochemistry as a highly accessible tool for producing hydroxyl radicals as a means to induce a controllable level of oxidation on a range of intact proteins. These experiments utilize a relatively high flow rates to reduce protein residence time inside the electrochemical flow chamber, along with a unique cell activation approach to improve control over the intact protein oxidation yield. Studies were conducted to evaluate the level of protein adsorption onto the electrode surface. This report demonstrates a robust protocol for the use of BDD electrochemistry and high performance LC-MS/MS as a high-throughput experimental pipeline for probing higher order protein structure, and illustrates how it is complementary to predictive computational modeling efforts.

  19. Simultaneous electrochemical determination of dopamine and paracetamol on multiwalled carbon nanotubes/graphene oxide nanocomposite-modified glassy carbon electrode.

    PubMed

    Cheemalapati, Srikanth; Palanisamy, Selvakumar; Mani, Veerappan; Chen, Shen-Ming

    2013-12-15

    In the present study, multiwalled carbon nanotubes (MWCNT)/graphene oxide (GO) nanocomposite was prepared by homogenous dispersion of MWCNT and GO and used for the simultaneous voltammetric determination of dopamine (DA) and paracetamol (PA). The TEM results confirmed that MWCNT walls were wrapped well with GO sheets. The MWCNT/GO nanocomposite showed superior electrocatalytic activity towards the oxidation of DA and PA, when compared with either pristine MWCNT or GO. The major reason for the efficient simultaneous detection of DA and PA at nanocomposite was the synergistic effect between MWCNT and GO. The electrochemical oxidation of DA and PA was investigated by cyclic voltammetry, differential pulse voltammetry and amperometry. The nanocomposite modified electrode showed electrocatalytic oxidation of DA and PA in the linear response range from 0.2 to 400 µmol L(-1) and 0.5 to 400 µmol L(-1) with the detection limit of 22 nmol L(-1) and 47 nmol L(-1) respectively. The proposed sensor displayed good selectivity, sensitivity, stability with appreciable consistency and precision. PMID:24209344

  20. Raman and electrochemical impedance studies of sol-gel titanium oxide and single walled carbon nanotubes composite films.

    PubMed

    Rincón, M E; Trujillo-Camacho, M E; Miranda-Hernández, M; Cuentas-Gallegos, A K; Orozco, G

    2007-01-01

    Titanium oxide grown by a sol-gel route on single-walled carbon nanotubes was studied by Raman and Electrochemical Impedance techniques and compared with mixtures obtained by mechanical grinding. In spite of the superior dispersion of single-walled carbon nanotubes bundles in sol-gel composites, the lost of the small-diameter carbon nanotubes in the oxidizing sol-gel bath was inferred from their Raman spectra and the lower capacitive current of the voltammograms in 0.1 M H2SO4. We proposed proton electrosorption as the main charge storage mechanism for sol-gel composites, favoured by the hydroxylation and n-type conductivity of the oxide, while electrodes based on mixtures were dominated by double-layer charging, developing some pseudocapacitance with potential cycling due to the reversible oxidation of carbon nanotubes. Comparsion with TiO2/Carbon Blacks composites shows the effective role of single-walled carbon nanotubes as templates to control the mesoporous nature of sol-gel composite electrodes. PMID:17450931

  1. An advanced tunnel oxide layer process for 65 nm NOR floating-gate flash memories

    NASA Astrophysics Data System (ADS)

    Chiu, Shengfen; Xu, Yue; Ji, Xiaoli; Liao, Yiming; Wu, Fuwei; Yan, Feng

    2015-10-01

    An advanced tunnel oxide layer process for 65 nm NOR-type floating-gate flash memory is proposed to improve tunnel oxide quality by an additive sacrificial oxide layer growth. The sacrificial oxide layer process effectively controls the thickness variation of tunnel oxide and improves the flatness of the SiO2/Si interface across the active area. The interface traps generation during program/erase cycling of flash cells is found to be reduced, and the reliability property is significantly improved as compared to flash cells without the sacrificial oxide layer process. The technology is applicable to further scaled floating-gate flash memories.

  2. Spray absorption and electrochemical reduction of nitrogen oxides from flue gas.

    PubMed

    Guo, Qingbin; Sun, Tonghua; Wang, Yalin; He, Yi; Jia, Jinping

    2013-08-20

    This work developed an electrochemical reduction system which can effectively scrub NO× from flue gas by using aqueous solution of Fe(II)(EDTA) (ethylenediaminetetraacetate) as absorbent and electrolyte. This new system features (a) complete decomposition of NOX to harmless N2; and (b) fast regeneration of Fe(II)(EDTA) through electrochemical reaction. The Fe(II)(EDTA) solution was recycled and reused continuously during entire process, and no harmful waste was generated. The reaction mechanism was thoroughly investigated by using voltammetric, chromatographic and spectroscopic approaches. The operating conditions of the system were optimized based on NOX removal efficiency. Approximately 98% NO removal was obtained at the optimal condition. The interference of SO2 in flue gas and the system operating stability was also evaluated. PMID:23875953

  3. Electrochemical synthesis of nanoparticles of magnetic mixed oxides of Sr-Fe and Sr-Co-Fe.

    PubMed

    Asenjo, J; Amigó, R; Krotenko, E; Torres, F; Tejada, J; Brillas, E; Sardin, G

    2001-12-01

    The electrochemical synthesis of magnetic nanoparticles of new Sr-Fe and Sr-Co-Fe oxides using an undivided cell with two Fe electrodes is reported in this work. These materials are collected as precipitates by electrolyzing acidic solutions containing mixtures of chlorides and nitrates of Sr2+, Fe3+ and, optionally, Co2+ at temperatures between 40 degrees C and 80 degrees C. Sr-Fe oxides are produced with energy costs lower than 2.7 kWh kg-1 in the pH range 2.0-6.0 at 50 mA cm-2, whereas Sr-Co-Fe oxides are obtained with a cost of 3.0 kWh kg-1 at pH 1.5 and at 35 mA cm-2. Inductively coupled plasma analysis of materials and energy dispersive X-ray microanalysis of single particles confirm that they are composed of pure mixed oxides, without metallic Fe impurities. All synthesized compounds crystallize as inverse cubic spinels, with structures similar to those of maghemite and magnetite. They are formed by round-shape nanoparticles with sizes lower than 50 nm, as observed by transmission electron microscopy. Thermal desorption spectrometry allows us to detect the presence of hydrogen and volatiles proceeding from water decomposition in their lattices. After heating the electrogenerated materials at 300 degrees C during 1 h to eliminate such species, Sr-Co-Fe oxides with similar magnetic properties to those of hard ferrites are obtained, but magnetic Sr-Fe oxides only behave as soft ferrites. PMID:12914086

  4. Fully solar-driven thermo- and electrochemistry for advanced oxidation processes (STEP-AOPs) of 2-nitrophenol wastewater.

    PubMed

    Nie, Chunhong; Shao, Nan; Wang, Baohui; Yuan, Dandan; Sui, Xin; Wu, Hongjun

    2016-07-01

    The STEP (Solar Thermal Electrochemical Process) for Advanced Oxidation Processes (AOPs, combined to STEP-AOPs), fully driven by solar energy without the input of any other forms of energy and chemicals, is introduced and demonstrated from the theory to experiments. Exemplified by the persistent organic pollutant 2-nitrophenol in water, the fundamental model and practical system are exhibited for the STEP-AOPs to efficiently transform 2-nitrophenol into carbon dioxide, water, and the other substances. The results show that the STEP-AOPs system performs more effectively than classical AOPs in terms of the thermodynamics and kinetics of pollutant oxidation. Due to the combination of solar thermochemical reactions with electrochemistry, the STEP-AOPs system allows the requisite electrolysis voltage of 2-nitrophenol to be experimentally decreased from 1.00 V to 0.84 V, and the response current increases from 18 mA to 40 mA. STEP-AOPs also greatly improve the kinetics of the oxidation at 30 °C and 80 °C. As a result, the removal rate of 2-nitrophenol after 1 h increased from 19.50% at 30 °C to 32.70% at 80 °C at constant 1.90 V. Mechanistic analysis reveals that the oxidation pathway is favorably changed because of thermal effects. The tracking of the reaction displayed that benzenediol and hydroquinone are initial products, with maleic acid and formic acid as sequential carboxylic acid products, and carbon dioxide as the final product. The theory and experiments on STEP-AOPs system exemplified by the oxidation of 2-nitrophenol provide a broad basis for extension of the STEP and AOPs for rapid and efficient treatment of organic wastewater. PMID:27093694

  5. Advanced Cu chemical displacement technique for SiO2-based electrochemical metallization ReRAM application

    PubMed Central

    2014-01-01

    This study investigates an advanced copper (Cu) chemical displacement technique (CDT) with varying the chemical displacement time for fabricating Cu/SiO2-stacked resistive random-access memory (ReRAM). Compared with other Cu deposition methods, this CDT easily controls the interface of the Cu-insulator, the switching layer thickness, and the immunity of the Cu etching process, assisting the 1-transistor-1-ReRAM (1T-1R) structure and system-on-chip integration. The modulated shape of the Cu-SiO2 interface and the thickness of the SiO2 layer obtained by CDT-based Cu deposition on SiO2 were confirmed by scanning electron microscopy and atomic force microscopy. The CDT-fabricated Cu/SiO2-stacked ReRAM exhibited lower operation voltages and more stable data retention characteristics than the control Cu/SiO2-stacked sample. As the Cu CDT processing time increased, the forming and set voltages of the CDT-fabricated Cu/SiO2-stacked ReRAM decreased. Conversely, decreasing the processing time reduced the on-state current and reset voltage while increasing the endurance switching cycle time. Therefore, the switching characteristics were easily modulated by Cu CDT, yielding a high performance electrochemical metallization (ECM)-type ReRAM. PMID:25364318

  6. The mechanical, electrochemical, and morphological characteristics of passivating oxide films covering cobalt-chromium-molybdenum alloys: A study of five microstructures

    NASA Astrophysics Data System (ADS)

    Megremis, Spiro John

    2001-07-01

    Cobalt-chromium-molybdenum (Co-Cr-Mo) alloys possess a combination of properties that make them well suited for employment as biomaterials, such as high-strength and excellent wear and corrosion resistance. They receive this excellent corrosion resistance from passive oxide films which cover their surface. Because of the important role these oxide films play in protecting Co-Cr Mo alloys used in biological applications, there is a need to better understand them. This thesis investigated the structural and physical properties of the passivating oxide films covering Co-Cr Mo alloys with five different microstructures. The Co-Cr-Mo alloys were separated into the following groups: cast, wrought high carbon, wrought high carbon aged, forged high carbon, and forged low carbon. Electrochemical scratch tests were performed which provided information on the electrochemical kinetics of oxide fracture and repassivation for the different Co-Cr-Mo alloys. Furthermore, the stability and mechanical integrity of the oxide films covering the alloys were also evaluated. Step-polarization impedance spectroscopy tests were also performed on the different Co-Cr-Mo alloys, which provided valuable information about their electrochemical behavior when immersed in phosphate buffered saline (PBS) solution. For instance, it was observed that the corrosion properties of the different alloy types did not vary significantly with respect to the behavior of their individual polarization curves. Likewise, impedance values (maximum early resistance, maximum polarization resistance, and minimum capacitance) for the five alloy groups did not reveal any statistically meaningful differences. The similar passive electrochemical behavior of the five alloy groups suggests that the oxide films covering them were not significantly altered by changes in carbon content and processing. This research also showed that it was possible to monitor changes in the surface morphology of the cast Co-Cr-Mo alloys over a wide range of potentials using in-situ electrochemical atomic force microscopy. In addition, the collection of SPIS information in conjunction with the AFM images revealed several distinct relationships between surface morphology and electrochemical behavior for the alloys. Thus, it was demonstrated that the combination of electrochemical atomic force microscopy with simultaneous SPIS allowed careful, direct correlation of surface structure and electrochemical properties.

  7. Separators for electrochemical cells

    SciTech Connect

    Carlson, Steven Allen; Anakor, Ifenna Kingsley

    2014-11-11

    Provided are separators for use in an electrochemical cell comprising (a) an inorganic oxide and (b) an organic polymer, wherein the inorganic oxide comprises organic substituents. Preferably, the inorganic oxide comprises an hydrated aluminum oxide of the formula Al.sub.2O.sub.3.xH.sub.2O, wherein x is less than 1.0, and wherein the hydrated aluminum oxide comprises organic substituents, preferably comprising a reaction product of a multifunctional monomer and/or organic carbonate with an aluminum oxide, such as pseudo-boehmite and an aluminum oxide. Also provided are electrochemical cells comprising such separators.

  8. Evaluation of Resin Dissolution Using an Advanced Oxidation Process - 13241

    SciTech Connect

    Goulart de Araujo, Leandro; Vicente de Padua Ferreira, Rafael; Takehiro Marumo, Julio; Passos Piveli, Roque; Campos, Fabio

    2013-07-01

    The ion-exchange resin is widely used in nuclear reactors, in cooling water purification and removing radioactive elements. Because of the long periods of time inside the reactor system, the resin becomes radioactive. When the useful life of them is over, its re-utilization becomes inappropriate, and for this reason, the resin is considered radioactive waste. The most common method of treatment is the immobilization of spent ion exchange resin in cement in order to form a solid monolithic matrix, which reduces the radionuclides release into the environment. However, the characteristic of contraction and expansion of the resin limits its incorporation in 10%, resulting in high cost in its direct immobilization. Therefore, it is recommended the utilization of a pre-treatment, capable of reducing the volume and degrading the resin, which would increase the load capacity in the immobilization. This work aims to develop a method of degradation of ion spent resins from the nuclear research reactor of Nuclear and Energy Research Institute (IPEN/CNEN-SP), Brazil, using the Advanced Oxidative Process (AOP) with Fenton's reagent (hydrogen peroxide and ferrous sulphate as catalyst). The resin evaluated was a mixture of cationic (IR 120P) and anionic (IRA 410) resins. The reactions were conducted by varying the concentration of the catalyst (25, 50, 100 e 150 mM) and the volume of the hydrogen peroxide, at three different temperatures, 50, 60 and 70 deg. C. The time of reaction was three hours. Total organic carbon content was determined periodically in order to evaluate the degradation as a function of time. The concentration of 50 mM of catalyst was the most effective in degrading approximately 99%, using up to 330 mL of hydrogen peroxide. The most effective temperature was about 60 deg. C, because of the decomposition of hydrogen peroxide in higher temperatures. TOC content was influenced by the concentration of the catalyst, interfering in the beginning of the degradation process. It was possible to correlate it with the final amount of non-degraded resins. These results show that these conditions were favorable to destroy the resins, indicating to be the AOP an effective technique to reduce the volume of the waste. (authors)

  9. The utilization of SiNWs/AuNPs-modified indium tin oxide (ITO) in fabrication of electrochemical DNA sensor.

    PubMed

    Rashid, Jahwarhar Izuan Abdul; Yusof, Nor Azah; Abdullah, Jaafar; Hashim, Uda; Hajian, Reza

    2014-12-01

    This work describes the incorporation of SiNWs/AuNPs composite as a sensing material for DNA detection on indium tin-oxide (ITO) coated glass slide. The morphology of SiNWs/AuNPs composite as the modifier layer on ITO was studied by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX). The morphological studies clearly showed that SiNWs were successfully decorated with 20 nm-AuNPs using self-assembly monolayer (SAM) technique. The effective surface area for SiNWs/AuNPs-modified ITO enhanced about 10 times compared with bare ITO electrode. SiNWs/AuNPs nanocomposite was further explored as a matrix for DNA probe immobilization in detection of dengue virus as a bio-sensing model to evaluate its performance in electrochemical sensors. The hybridization of complementary DNA was monitored by differential pulse voltammetry (DPV) using methylene blue (MB) as the redox indicator. The fabricated biosensor was able to discriminate significantly complementary, non-complementary and single-base mismatch oligonucleotides. The electrochemical biosensor was sensitive to target DNA related to dengue virus in the range of 9.0-178.0 ng/ml with detection limit of 3.5 ng/ml. In addition, SiNWs/AuNPs-modified ITO, regenerated up to 8 times and its stability was up to 10 weeks at 4°C in silica gel. PMID:25491829

  10. Graphene oxide nanoribbon-based sensors for the simultaneous bio-electrochemical enantiomeric resolution and analysis of amino acid biomarkers.

    PubMed

    Martín, Aída; Batalla, Pilar; Hernández-Ferrer, Javier; Martínez, María Teresa; Escarpa, Alberto

    2015-06-15

    In this work, a straightforward in-situ measurement of L and D-amino acids (AAs) has been developed using disposable graphene oxide nanoribbon (GON) screen printed electrodes. For that, we took advantage of the electroactivity of certain clinically relevant AAs, such as tyrosine (Tyr) and methionine (Met), which are involved in important bacterial diseases (Bacillus subtilis and Vibrio cholera, respectively). The strategy is based on a dual electrochemical and enzymatic approach. The D-AA with the class enzyme D amino acid oxidase (DAAO) generates H2O2. This H2O2 is simultaneously detected with the L-AA, electroactive molecule by differential pulse voltammetry (DPV). These GON disposable platforms use just 50 μL of sample and a total analysis time of 360 s. Both L and D enantiomers calibration and quantitative analysis were explored and were simultaneously detected with accuracy and precision in urine samples. Any interference of uric acid and other electroactive AAs was noticed. This proposed electrochemical GON-based enantiomeric bio-sensor becomes a highly promising tool as future point of care for fast and reliable early diagnosis of diseases related to the presence of D-AAs. PMID:25562744

  11. Highly sensitive amperometric biosensor based on electrochemically-reduced graphene oxide-chitosan/hemoglobin nanocomposite for nitromethane determination.

    PubMed

    Wen, Yunping; Wen, Wei; Zhang, Xiuhua; Wang, Shengfu

    2016-05-15

    Nitromethane (CH3NO2) is an important organic chemical raw material with a wide variety of applications as well as one of the most common pollutants. Therefore it is pretty important to establish a simple and sensitive detection method for CH3NO2. In our study, a novel amperometric biosensor for nitromethane (CH3NO2) based on immobilization of electrochemically-reduced graphene oxide (rGO), chitosan (CS) and hemoglobin (Hb) on a glassy carbon electrode (GCE) was constructed. Scanning electron microscopy, infrared spectroscopy and electrochemical methods were used to characterize the Hb-CS/rGO-CS composite film. The effects of scan rate and pH of phosphate buffer on the biosensor have been studied in detail and optimized. Due to the graphene and chitosan nanocomposite, the developed biosensor demonstrating direct electrochemistry with faster electron-transfer rate (6.48s(-1)) and excellent catalytic activity towards CH3NO2. Under optimal conditions, the proposed biosensor exhibited fast amperometric response (<5s) to CH3NO2 with a wide linear range of 5μM~1.46mM (R=0.999) and a low detection limit of 1.5μM (S/N=3). In addition, the biosensor had high selectivity, reproducibility and stability, providing the possibility for monitoring CH3NO2 in complex real samples. PMID:26800205

  12. Enhanced Yields of Iron-Oxidizing Bacteria by In Situ Electrochemical Reduction of Soluble Iron in the Growth Medium

    PubMed Central

    Blake, Robert C.; Howard, Gary T.; McGinness, Stephen

    1994-01-01

    An electrochemical apparatus for culturing chemolithotrophic bacteria that respire aerobically on ferrous ions is described. Enhanced yields of the bacteria were achieved by the in situ electrochemical reduction of soluble iron in the growth medium. When subjected to a direct current of 30 A for 60 days, a 45-liter culture of Thiobacillus ferrooxidans grew from 6 × 107 to 9.5 × 109 cells per ml. Growth of the bacterium within the electrolytic bioreactor was linear with time. A final cell density corresponding to 4.7 g of wet cell paste per liter was achieved, and a total of 320 g of wet cell paste was harvested from one culture. The apparatus was designed to deliver protons concomitantly with electrons; therefore, the pH of the culture remained stable at 1.6 ± 0.1 for the duration of growth. This laboratory-scale apparatus may be readily adapted to pilot or production scale. It is thus anticipated that abundant numbers of iron-oxidizing bacteria may be obtained for both fundamental and applied studies. PMID:16349344

  13. Electrochemical oxidation of recalcitrant organic compounds in biologically treated municipal solid waste leachate in a flow reactor.

    PubMed

    Quan, Xuejun; Cheng, Zhiliang; Chen, Bo; Zhu, Xincai

    2013-10-01

    Biologically-treated municipal solid waste (MSW) leachate still contains many kinds of bio-recalcitrant organic matter. A new plate and frame electrochemical reactor was designed to treat these materials under flow conditions. In the electrochemical oxidation process, NH3 and color could be easily removed by means of electro-generated chlorine/hypochlorite within 20 min. The effects of major process parameters on the removal of organic pollutants were investigated systematically. Under experimental conditions, the optimum operation parameters were current density of 65 mA/cm2, flow velocity of 2.6 cm/sec in electrode gap, and initial chloride ion concentration of 5000 mg/L. The COD in the leachate could be reduced below 100 mg/L after 1 hr of treatment. The kinetics and mechanism of COD removal were investigated by simultaneously monitoring the COD change and chlorine/hypochlorite production. The kinetics of COD removal exhibited a two-stage kinetic model, and the decrease of electro-generated chlorine/hypochlorite production was the major mechanism for the slowing down of the COD removal rate in the second stage. The narrowing of the electrode gap is beneficial for COD removal and energy consumption. PMID:24494488

  14. Facial-shape controlled precursors for lithium cobalt oxides and the electrochemical performances in lithium ion battery

    NASA Astrophysics Data System (ADS)

    Shim, Jae-Hyun; Cho, Sang-Woo; Missiul, Aleksandr; Jung, Hyun-Ok; Lee, Sanghun

    2015-01-01

    Two types of lithium cobalt oxides (LiCoO2) as cathode materials for lithium ion batteries are synthesized from two cobalt sources of different facial-shapes (octahedral and truncated-octahedral Co3O4) and Li2CO3 using solid state synthesis. From X-ray diffraction and scanning electron microscopy measurements, the reaction mechanism of the formation of LiCoO2 is investigated. It is revealed that LiCoO2 from octahedral Co3O4 with only {111} surfaces grows in one direction whereas the crystal orientation of LiCoO2 from truncated-octahedral Co3O4 with {111} and {100} surfaces is not unique and the spinel intermediates of LixCo2O4 are formed during synthesis. They show largely unequal rate and cycling performances for lithium ion battery, even though their outer appearances are nearly identical. Almost single-cryst