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Sample records for electrochemical oxidation treatment

  1. 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.

  2. Treatment of Radioactive Organic Wastes by an Electrochemical Oxidation

    SciTech Connect

    Kim, K.H.; Ryue, Y.G.; Kwak, K.K.; Hong, K.P.; Kim, D.H.

    2007-07-01

    A waste treatment system by using an electrochemical oxidation (MEO, Mediated Electrochemical Oxidation) was installed at KAERI (Korea Atomic Energy Research Institute) for the treatment of radioactive organic wastes, especially EDTA (Ethylene Diamine Tetraacetic Acid) generated during the decontamination activity of nuclear installations. A cerium and silver mediated electrochemical oxidation technique method has been developed as an alternative for an incineration process. An experiment to evaluate the applicability of the above two processes and to establish the conditions to operate the pilot-scale system has been carried out by changing the concentration of the catalyst and EDTA, the operational current density, the operating temperature, and the electrolyte concentration. As for the results, silver mediated oxidation was more effective in destructing the EDTA wastes than the cerium mediated oxidation process. For a constant volume of the EDTA wastes, the treatment time for the cerium-mediated oxidation was 9 hours and its conversion ratio of EDTA to water and CO{sub 2} was 90.2 % at 80 deg. C, 10 A, but the treatment time for the silver-mediated oxidation was 3 hours and its conversion ratio was 89.2 % at 30 deg. C, 10 A. (authors)

  3. 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

  4. STEP wastewater treatment: a solar thermal electrochemical process for pollutant oxidation.

    PubMed

    Wang, Baohui; Wu, Hongjun; Zhang, Guoxue; Licht, Stuart

    2012-10-01

    A solar thermal electrochemical production (STEP) pathway was established to utilize solar energy to drive useful chemical processes. In this paper, we use experimental chemistry for efficient STEP wastewater treatment, and suggest a theory based on the decreasing stability of organic pollutants (hydrocarbon oxidation potentials) with increasing temperature. Exemplified by the solar thermal electrochemical oxidation of phenol, the fundamental model and experimental system components of this process outline a general method for the oxidation of environmentally stable organic pollutants into carbon dioxide, which is easily removed. Using thermodynamic calculations we show a sharply decreasing phenol oxidation potential with increasing temperature. The experimental results demonstrate that this increased temperature can be supplied by solar thermal heating. In combination this drives electrochemical phenol removal with enhanced oxidation efficiency through (i) a thermodynamically driven decrease in the energy needed to fuel the process and (ii) improved kinetics to sustain high rates of phenol oxidation at low electrochemical overpotential. The STEP wastewater treatment process is synergistic in that it is performed with higher efficiency than either electrochemical or photovoltaic conversion process acting alone. STEP is a green, efficient, safe, and sustainable process for organic wastewater treatment driven solely by solar energy. PMID:22965739

  5. 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

  6. 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

  7. Highly efficient and energy-saving sectional treatment of landfill leachate with a synergistic system of biochemical treatment and electrochemical oxidation on a boron-doped diamond electrode.

    PubMed

    Zhao, Guohua; Pang, Yaning; Liu, Lei; Gao, Junxia; Lv, Baoying

    2010-07-15

    In this paper, a synergistic combination of the biochemical treatment and electrochemical oxidation (SBEO) of landfill leachate with sectional treatment on a boron-doped diamond (BDD) electrode is proposed. The first stage involves the synergistic system of biochemical treatment and electrochemical oxidation. Then, the second stage is followed by individual biochemical treatment. Comparisons among the SBEO, electrochemical oxidation, biochemical treatment and biochemical treatment with the pretreatment of electrochemical oxidation are made systematically, which show that this method is both highly efficient and energy-saving. The higher TOC removal and low energy cost on the BDD electrode can be explained by the conversion of the bio-refractory pollutants to biodegradable organics in the electrochemical oxidation process, improving the current efficiency and reducing the energy cost. The treated wastewater is degraded only with biochemical treatment in the second stage, which further improves efficiency and reduced the energy cost. PMID:20413218

  8. 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.

  9. 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

  10. 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

  11. 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

  12. 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

  13. 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 ? and a sulfide concentration of 250 mg L(-1). PMID:25463589

  14. Water disinfection by electrochemical treatment.

    PubMed

    Feng, Chuanping; Suzuki, Keitaro; Zhao, Shuyun; Sugiura, Norio; Shimada, Satoru; Maekawa, Takaaki

    2004-08-01

    The electrochemical disinfection of germinated brown rice (GBR) circulating water and cooling tower water containing Legionella bacteria was investigated. Results showed the total aerobic plate counts (APC) in the treated GBR circulating water decreased significantly and the turbidity was largely improved at a pulse voltage of 1.0 kV; Legionella bacteria were also disinfected effectively at 1.0 kV. The disinfection was attributed to the synergistic effects of the oxide anode, the electric field, and the radicals formed during the electrochemical treatment. This suggests that electrochemical treatment could be applicable to the disinfection of water from other sources. PMID:15081482

  15. Incorporation of electrochemical advanced oxidation processes in a multistage treatment system for sanitary landfill leachate.

    PubMed

    Moreira, Francisca C; Soler, J; Fonseca, Amlia; Saraiva, Isabel; Boaventura, Rui A R; Brillas, Enric; Vilar, Vtor J P

    2015-09-15

    The current study has proved the technical feasibility of including electrochemical advanced oxidation processes (EAOPs) in a multistage strategy for the remediation of a sanitary landfill leachate that embraced: (i) first biological treatment to remove the biodegradable organic fraction, oxidize ammonium and reduce alkalinity, (ii) coagulation of the bio-treated leachate to precipitate humic acids and particles, followed by separation of the clarified effluent, and (iii) oxidation of the resulting effluent by an EAOP to degrade the recalcitrant organic matter and increase its biodegradability so that a second biological process for removal of biodegradable organics and nitrogen content could be applied. The influence of current density on an UVA photoelectro-Fenton (PEF) process was firstly assessed. The oxidation ability of various EAOPs such as electro-Fenton (EF) with two distinct initial total dissolved iron concentrations ([TDI]0), PEF and solar PEF (SPEF) was further evaluated and these processes were compared with their analogous chemical ones. A detailed assessment of the two first treatment stages was made and the biodegradability enhancement during the SPEF process was determined by a Zahn-Wellens test to define the ideal organics oxidation state to stop the EAOP and apply the second biological treatment. The best current density was 200mAcm(-2) for a PEF process using a BDD anode, [TDI]0 of 60mgL(-1), pH 2.8 and 20C. The relative oxidation ability of EAOPs increased in the order EF with 12mg [TDI]0L(-1)

  16. 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.

  17. 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.

  18. Electrochemical oxidation of tetracycline antibiotics using a Ti/IrO2 anode for wastewater treatment of animal husbandry.

    PubMed

    Miyata, M; Ihara, I; Yoshid, G; Toyod, K; Umetsu, K

    2011-01-01

    In animal husbandry, antibiotics are widely used to treat and prevent diseases or to promote growth. The use of antibiotics for domestic animals enables to promote safety of livestock products and enhance productivity. Tetracycline antibiotics (TCs) are one of the primarily used groups of antibiotics for cattle and swine. However, the unintentional spreading of antibiotics from animal waste to the environment may leave out drug residues, promoting resistant strains of bacteria, and will adversely affect the ecosystem and human health. To prevent the spread of veterinary antibiotics in the environment, it is required to treat residual antibiotics in livestock wastewater. In this study, we investigated the electrochemical oxidation of TCs to treat livestock wastewater. The concentrations of TCs in aqueous solutions were reduced from 100 mg/L to less than 0.6 mg/L by 6 h of electrochemical treatment using a Ti/IrO2 anode with Na2SO4 electrolyte. The concentration of oxytetracycline (OTC) in livestock wastewater was also reduced from 100 mg/L to less than 0.7 mg/L by the same treatment. Thus, the electrochemical oxidation using a Ti/IrO2 anode with Na2SO4 electrolyte was found to be effective for degradation of TCs. The results suggest that the electrochemical oxidation method is a promising treatment for TCs in livestock wastewater. PMID:21278467

  19. 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.

  20. 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

  1. 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.

  2. 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

  3. 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.

  4. Low-cost electrochemical treatment of indium tin oxide anodes for high-efficiency organic light-emitting diodes

    SciTech Connect

    Hui Cheng, Chuan Shan Liang, Ze; Gang Wang, Li; Dong Gao, Guo; Zhou, Ting; Ming Bian, Ji; Min Luo, Ying; Tong Du, Guo

    2014-01-27

    We demonstrate a simple low-cost approach as an alternative to conventional O{sub 2} plasma treatment to modify the surface of indium tin oxide (ITO) anodes for use in organic light-emitting diodes. ITO is functionalized with F{sup −} ions by electrochemical treatment in dilute hydrofluoric acid. An electrode with a work function of 5.2 eV is achieved following fluorination. Using this electrode, a maximum external quantum efficiency of 26.0% (91 cd/A, 102 lm/W) is obtained, which is 12% higher than that of a device using the O{sub 2} plasma-treated ITO. Fluorination also increases the transparency in the near-infrared region.

  5. Sequential treatment of diluted olive pomace leachate by digestion in a pilot scale UASB reactor and BDD electrochemical oxidation.

    PubMed

    Katsoni, Alphathanasia; Mantzavinos, Dionissios; Diamadopoulos, Evan

    2014-06-15

    The efficiency of the anaerobic treatment of olive pomace leachate (OPL) at mesophilic conditions was investigated. Daily and cumulative biogas production was measured during the operational period. The maximum biogas flowrate was 65L/d, of which 50% was methane. In addition, the applicability of electrochemical oxidation as an advanced post-treatment method for the complete removal of chemical oxygen demand (COD) from the anaerobically treated OPL was evaluated. The diluted OPL, having a pH of 6.5 and a total COD of 5g/L, was first treated in a 600L, pilot-scale up-flow anaerobic sludge blanket (UASB) reactor. The UASB reactor was operated for 71 days at mesophilic conditions (322C) in a temperature-controlled environment at a hydraulic retention time of 3 days, and organic loading rates (OLR) between 0.33 and 1.67g COD/(L.d). The UASB process led to a COD removal efficiency between 35 and 70%, 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 18 A and in the presence of 0.17% NaCl as the supporting electrolyte, complete removal of COD was attained after 7h of treatment predominantly through total oxidation reactions. During electrochemical experiments, three groups of organo-chlorinated 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, along with the residual chlorine are thought to increase the matrix ecotoxicity to Artemia salina. PMID:24704905

  6. Mediated electrochemical oxidation treatment for Rocky Flats combustible low-level mixed waste. Final report, FY 1993 and 1994

    SciTech Connect

    Chiba, Z.; Lewis, P.R.; Murguia, L.C.

    1994-09-01

    Mediated Electrochemical Oxidation (MEO) is an aqueous process which destroys hazardous organics by oxidizing a mediator at the anode of an electrochemical cell; the mediator in turn oxidizes the organics within the bulk of the electrolyte. With this process organics can be nearly completely destroyed, that is, the carbon and hydrogen present in the hydrocarbon are almost entirely mineralized to carbon dioxide and water. The MEO process is also capable of dissolving radioactive materials, including difficult-to-dissolve compounds such as plutonium oxide. Hence, this process can treat mixed wastes, by destroying the hazardous organic components of the waste, and dissolving the radioactive components. The radioactive material can be recovered if desired, or disposed of as non-mixed radioactive waste. The process is inherently safe, since the hazardous and radioactive materials are completely contained in the aqueous phase, and the system operates at low temperatures (below 80{degree}C) and at ambient pressures.

  7. Antitumor effects of electrochemical treatment

    PubMed Central

    Gonzlez, Maraelys Morales; Zamora, Lisset Ortz; Cabrales, Luis Enrique Bergues; Sierra Gonzlez, Gustavo Victoriano; de Oliveira, Luciana Oliveira; Zanella, Rodrigo; Buzaid, Antonio Carlos; Parise, Orlando; Brito, Luciana Macedo; Teixeira, Cesar Augusto Antunes; Gomes, Marina das Neves; Moreno, Gleyce; Feo da Veiga, Venicio; Tell, Marcos; Holandino, Carla

    2013-01-01

    Electrochemical treatment is an alternative modality for tumor treatment based on the application of a low intensity direct electric current to the tumor tissue through two or more platinum electrodes placed within the tumor zone or in the surrounding areas. This treatment is noted for its great effectiveness, minimal invasiveness and local effect. Several studies have been conducted worldwide to evaluate the antitumoral effect of this therapy. In all these studies a variety of biochemical and physiological responses of tumors to the applied treatment have been obtained. By this reason, researchers have suggested various mechanisms to explain how direct electric current destroys tumor cells. Although, it is generally accepted this treatment induces electrolysis, electroosmosis and electroporation in tumoral tissues. However, action mechanism of this alternative modality on the tumor tissue is not well understood. Although the principle of Electrochemical treatment is simple, a standardized method is not yet available. The mechanism by which Electrochemical treatment affects tumor growth and survival may represent more complex process. The present work analyzes the latest and most important research done on the electrochemical treatment of tumors. We conclude with our point of view about the destruction mechanism features of this alternative therapy. Also, we suggest some mechanisms and strategies from the thermodynamic point of view for this therapy. In the area of Electrochemical treatment of cancer this tool has been exploited very little and much work remains to be done. Electrochemical treatment constitutes a good therapeutic option for patients that have failed the conventional oncology methods. PMID:23592904

  8. 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.

  9. Electrochemical oxidation of resorcinol for wastewater treatment using Ti/TiO2-RuO2-IrO2 electrode.

    PubMed

    Rajkumar, D; Palanivelu, K; Mohan, N

    2001-01-01

    Electrochemical oxidation of resorcinol for wastewater treatment in the presence of chloride was investigated. Titanium Substrate Insoluble Anode (TSIA) coated with TiO2-RuO2-IrO2 was used as an anode and graphite carbon sheet was used as a cathode. The extent of resorcinol electrochemical oxidation was determined in terms of COD removal. The Box-Behnken second order composite design was used to study the effect of operating parameters such as initial pH, chloride concentration, initial concentration of resorcinol and charge input. The experimental values were in good correlation with predicted values, and the correlation coefficient was found to be good. The effect of current density on resorcinol oxidation, the AOX level during the electrochemical treatment and TOC removal were also studied for selected conditions. It has been observed that the extended electrolysis brings down the AOX concentration to lower levels. The maximum current efficiency was observed at higher resorcinol concentration, higher chloride concentration and increasing current density. PMID:11759910

  10. Electrochemical treatment of mixed and hazardous waste

    SciTech Connect

    Dziewinski, J.; Marczak, S.; Smith, W.; Nuttall, E.

    1995-12-31

    Los Alamos National Laboratory (LANL) and The University of New Mexico are jointly developing an electrochemical process for treating hazardous and radioactive wastes. The wastes treatable by the process include toxic metal solutions, cyanide solutions, and various organic wastes that may contain chlorinated organic compounds. The main component of the process is a stack of electrolytic cells with peripheral equipment such as a rectifier, feed system, tanks with feed and treated solutions, and a gas-venting system. During the treatment, toxic metals are deposited on the cathode, cyanides are oxidized on the anode, and organic compounds are anodically oxidized by direct or mediated electrooxidation, depending on their type. Bench scale experimental studies have confirmed the feasibility of applying electrochemical systems to processing of a great variety of hazardous and mixed wastes. The operating parameters have been defined for different waste compositions using surrogate wastes. Mixed wastes are currently treated at bench scale as part of the treatability study.

  11. Electrochemical nitric oxide sensors for physiological measurements.

    PubMed

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

    2010-06-01

    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. In this tutorial review, 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

  12. Direct electrochemical oxidation of ammonia on graphite as a treatment option for stored source-separated urine.

    PubMed

    Zllig, Hanspeter; Fritzsche, Cristina; Morgenroth, Eberhard; Udert, Kai M

    2015-02-01

    Electrolysis can be a viable technology for ammonia removal from source-separated urine. Compared to biological nitrogen removal, electrolysis is more robust and is highly amenable to automation, which makes it especially attractive for on-site reactors. In electrolytic wastewater treatment, ammonia is usually removed by indirect oxidation through active chlorine which is produced in-situ at elevated anode potentials. However, the evolution of chlorine can lead to the formation of chlorate, perchlorate, chlorinated organic by-products and chloramines that are toxic. This study focuses on using direct ammonia oxidation on graphite at low anode potentials in order to overcome the formation of toxic by-products. With the aid of cyclic voltammetry, we demonstrated that graphite is active for direct ammonia oxidation without concomitant chlorine formation if the anode potential is between 1.1 and 1.6V vs. SHE (standard hydrogen electrode). A comparison of potentiostatic bulk electrolysis experiments in synthetic stored urine with and without chloride confirmed that ammonia was removed exclusively by continuous direct oxidation. Direct oxidation required high pH values (pH>9) because free ammonia was the actual reactant. In real stored urine (pH=9.0), an ammonia removal rate of 2.90.3gNm(-2)d(-1) was achieved and the specific energy demand was 42WhgN(-1) at an anode potential of 1.31V vs. SHE. The measurements of chlorate and perchlorate as well as selected chlorinated organic by-products confirmed that no chlorinated by-products were formed in real urine. Electrode corrosion through graphite exfoliation was prevented and the surface was not poisoned by intermediate oxidation products. We conclude that direct ammonia oxidation on graphite electrodes is a treatment option for source-separated urine with three major advantages: The formation of chlorinated by-products is prevented, less energy is consumed than in indirect ammonia oxidation and readily available and cheap graphite can be used as the electrode material. PMID:25497427

  13. 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

  14. 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

  15. 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

  16. 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

  17. Influences of both carbon supports and heat-treatment of supported catalyst on electrochemical oxidation of methanol

    SciTech Connect

    Uchida, Makoto; Aoyama, Yuko; Tanabe, Mieko; Yanagihara, Nobuyuki; Eda, Nobuo; Ohta, Akira

    1995-08-01

    The effects of carbon supports for platinum-ruthenium (Pt-Ru) catalysts on anode performance of direct methanol fuel cells (DMFC) were investigated. Good polarization characteristics of the methanol electrode were obtained for a Pt-Ru catalyst supported on an acetylene black with high specific surface area and a pore size distribution in the range of 3 to 8 nm. The performance of the methanol electrode increased with the increase in pore volume for the pore size distribution of 3 to 8 nm. Analyses of various carbon blacks and supported catalysts were carried out with several techniques: N{sub 2} adsorption (Brunauer-Emmett-Teller (BET) and Barrett-Joyner-Halenda (BJH) methods), CO adsorption, transmission electron microscope, and scanning electron microscope observations. The effects of the heat-treating temperature, time, and atmosphere on the polarization curves of the methanol electrodes with the acetylene black were investigated. The heat-treatment in air at 370 C improved not only methanol oxidation but the durability of the Pt-Ru catalyst.

  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. 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

  20. Electrochemical treatment of mixed (hazardous and radioactive) wastes

    SciTech Connect

    Dziewinski, J.; Zawodzinski, C.; Smith, W.H.

    1995-02-01

    Electrochemical treatment technologies for mixed hazardous waste are currently under development at Los Alamos National Laboratory. For a mixed waste containing toxic components such as heavy metals and cyanides in addition to a radioactive component, the toxic components can be removed or destroyed by electrochemical technologies allowing for recovery of the radioactive component prior to disposal of the solution. Mixed wastes with an organic component can be treated by oxidizing the organic compound to carbon dioxide and then recovering the radioactive component. The oxidation can be done directly at the anode or indirectly using an electron transfer mediator. This work describes the destruction of isopropanol, acetone and acetic acid at greater than 90% current efficiency using cobalt +3 or silver +2 as the electron transfer mediator. Also described is the destruction of cellulose based cheesecloth rags with electrochemically generated cobalt +3, at an overall efficiency of approximately 20%.

  1. A review on the electrochemical treatment of the salty organic wastewater

    NASA Astrophysics Data System (ADS)

    Du, Xianjun

    2015-07-01

    Electrochemical technologies have proved to be useful for the treatment of wastewater, and recent years, there are growing interests in electrochemical treatment of the salty organic wastewater. The aim of this paper is to mainly present the source of the salty organic wastewater, the mechanism of direct and indirect oxidation process, and the research advances of electrochemical technologies in the salty organic wastewater by literature reports review.

  2. Solid oxide electrochemical cell fabrication process

    DOEpatents

    Dollard, Walter J. (Churchill Borough, PA); Folser, George R. (Lower Burrell, PA); Pal, Uday B. (Cambridge, MA); Singhal, Subhash C. (Murrysville, PA)

    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).

  3. 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.

  4. Electrochemical treatment of landfill leachate: Oxidation at Ti/PbO{sub 2} and Ti/SnO{sub 2} anodes

    SciTech Connect

    Cossu, R.; Polcaro, A.M.; Mascia, M.; Palmas, S.; Renoldi, F.; Lavagnolo, M.C.

    1998-11-15

    Leachate originating in landfills where municipal solid wastes are disposed is a wastewater with a complex composition that could have a high environmental impact. The primary goal of this research was to investigate the feasibility of removing refractory organic pollutants and ammonium nitrogen from landfill leachate by electrochemical oxidation. The effects of current density, pH, and chloride concentration on the removal of both chemical oxygen demand (COD) and ammonium nitrogen were investigated. Titanium coated with lead dioxide (PbO{sub 2}) or tin dioxide (SnO{sub 2}) was used as the anode. An effective process was achieved in which the leachate was decolorized, COD was removed up to a value of 100 mg L{sup {minus}1}, and ammonia was totally eliminated. Average current efficiency of about 30% was measured for a decrease of COD from 1200 to 150 mg L{sup {minus}1}, while efficiency of about 10% was measured for a near complete removal of ammonium nitrogen, starting from an initial value of 380 mg L{sup {minus}1}. Results indicated that the organic load was removed by both direct and indirect oxidation. Indirect oxidation by chlorine or hypochlorite originating from oxidation of chlorides is believed to be mainly responsible for the nitrogen removal.

  5. 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.

  6. 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

  7. Method and electrochemical cell for synthesis and treatment of metal monolayer electrocatalysts metal, carbon, and oxide nanoparticles ion batch, or in continuous fashion

    DOEpatents

    Adzic, Radoslav; Zhang, Junliang; Sasaki, Kotaro

    2015-04-28

    An apparatus and method for synthesis and treatment of electrocatalyst particles in batch or continuous fashion is provided. In one embodiment, the apparatus comprises a sonication bath and a two-compartment chamber submerged in the sonication bath. The upper and lower compartments are separated by a microporous material surface. The upper compartment comprises a cover and a working electrode (WE) connected to a Pt foil contact, with the foil contact connected to the microporous material. The upper chamber further comprises reference counter electrodes. The lower compartment comprises an electrochemical cell containing a solution of metal ions. In one embodiment, the method for synthesis of electrocatalysts comprises introducing a plurality of particles into the apparatus and applying sonication and an electrical potential to the microporous material connected to the WE. After the non-noble metal ions are deposited onto the particles, the non-noble metal ions are displaced by noble-metal ions by galvanic displacement.

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

    DOEpatents

    Borglum, Brian P. (Edgewood, PA); Bessette, Norman F. (N. Huntingdon, PA)

    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).

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

    DOEpatents

    Singh, Prabhakar (Export, PA); Ruka, Roswell J. (Churchill Boro, Allegheny County, PA)

    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.

  10. Innovative oxide materials for electrochemical energy conversion

    NASA Astrophysics Data System (ADS)

    Wachsman, Eric D.

    2012-02-01

    Research in functional materials has progressed from those materials exhibiting structural to electronic functionality. The study of ion conducting ceramics ushers in a new era of ``chemically functional materials.'' This chemical functionality arises out of the defect equilibria of these materials, and results in the ability to transport chemical species and actively participate in chemical reactions at their surface. Moreover, this chemical functionality provides a promise for the future whereby the harnessing of our natural hydrocarbon energy resources can shift from inefficient and polluting combustion - mechanical methods to direct electrochemical conversion. The unique properties of these materials and their applications will be described. The focus will be on the application of ion conducting ceramics to energy conversion and storage, chemical sensors, chemical separation and conversion, and life support systems. Results presented will include development of record high power density (3 kW/kg) solid oxide fuel cells, NOx/CO species selective solid-state sensors, high yield membrane reactors, and regenerative life support systems that reduce CO2 to O2 and solid C.

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

    PubMed

    Viswanathan, Venkatasubramanian; Hansen, Heine A; Nrskov, 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

  12. 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.

  13. 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

  14. Basic Principles of the Electrochemical Mineralization of Organic Pollutants for Wastewater Treatment

    NASA Astrophysics Data System (ADS)

    Kapa?ka, Agnieszka; Fti, Gyrgy; Comninellis, Christos

    The electrochemical mineralization of organic pollutants is a new technology for treatment of dilute wastewater (COD < 5 g/L). In this method, utilizing the electrical energy, a complete oxidation of pollutants can be achieved on high oxidation power anodes. An ideal anode for this type of treatment is a boron-doped diamond electrode (BDD) characterized by a high reactivity toward organics oxidation. In the present work, both thermodynamic and kinetic aspects of organics mineralization are discussed. The proposed theoretical kinetic model of organics mineralization on BDD anodes is in excellent agreement with the experimental results. In addition, the economical aspect of electrochemical organics mineralization is reported.

  15. 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.

  16. Electrochemical oxidation and reuse of tannery saline wastewater.

    PubMed

    Sundarapandiyan, S; Chandrasekar, R; Ramanaiah, B; Krishnan, S; Saravanan, P

    2010-08-15

    In this present work, electrochemical treatment of saline wastewater with organic (protein) load was studied. The influence of the critical parameters of electro-oxidation such as pH, period, salt concentration and current density on the reduction of organic load was studied using graphite electrodes. It was found that current density of 0.024 A/cm(2) for a period of 2 h at pH 9.0 rendered best results in terms of reduction in COD and TKN. The energy requirement for the reduction of 1 kg of TKN and 1 kg of COD are 22.45 kWh and 0.80 kWh respectively at pH 9 and 0.024 A/cm(2). Reuse experiments were conducted at commercial scale. One of the saline waste streams in leather manufacturing process, pickling was treated and reused continuously thrice. The characteristics of the waste stream and the quality of the leathers indicate that the reuse of saline streams with intermittent electrochemical treatment is feasible. PMID:20435417

  17. Spectroscopic study of SERS- and SEIRA-activity of copper large-scaled surface substrates prepared by electrochemical deposition: What is the role of oxidation-reduction cycle treatment?

    NASA Astrophysics Data System (ADS)

    Prokopec, Vadym; Dendisová-Vyškovská, Marcela; Kokaislová, Alžběta; Čejková, Jitka; Člupek, Martin; Matějka, Pavel

    2011-05-01

    Surface-enhanced Raman scattering (SERS) and surface-enhanced infrared absorption (SEIRA) are powerful analytical techniques used for the study and characterization of ultrathin films and monolayers of organic compounds adsorbed on the nanostructured surface of several metals. The main requirement which has to be met for the SERS- and SEIRA-activity is the proper morphology of the surface in nanoscale, which can be tailored by the preparation procedure. In the present work different electrochemical preparation procedures of copper substrates (cathodic reduction from electrochemical baths or its combination with oxidation-reduction cycles (ORC) treatment) were developed with the aim of fabrication of the substrate with both SERS- and SEIRA-activity for the selected model analyte. The diffuse reflectance methodology was designed to study SEIRA-activity on large-scaled nanostructured surfaces. The nanostructure of the copper surface was characterized using Scanning Electron Microscopy (SEM). The effect of different ORC treatments on the surface morphology as well as on SERS- and SEIRA-activity is discussed. The interpretation of SERS and SEIRA spectra has been made in terms of the comparison of these two types of surface-enhanced spectra with normal infrared and Raman spectra and DFT calculation elucidating the orientation of the molecule on the surface.

  18. Modification of the surface morphology of the silicon substrate for boron-doped diamond electrodes in electrochemical wastewater treatment applications

    NASA Astrophysics Data System (ADS)

    Bak, Ji-Yoon; Lee, Choong-Hyun; Kim, Jung-Do; Lim, Dae-Soon

    2016-01-01

    For electrochemical wastewater treatment applications, textured boron-doped diamond (BDD) electrodes were fabricated by using a simple and cost-effective etching process. On the basis of the surface area measurement, the etching time was optimized in order to achieve higher electrochemical wastewater treatment performance. The surface structure, electrochemical properties, and electrochemical oxidation performance of the electrodes were characterized by using Raman spectroscopy and atomic force microscopy, in addition to electrochemical techniques. The textured BDD electrode demonstrated a dense and large surface area with no change in the film's properties. The effective surface area of the textured BDD electrode was approximately twice as large as that of the planar BDD electrode. The electrochemical results clearly demonstrate that the enhanced surface area of the BDD electrode achieves a higher current efficiency and much lower energy consumption in the electrochemical oxidation of methyl-orange.

  19. Photocatalytic and electrochemical combined treatment of textile wash water.

    PubMed

    Neelavannan, M G; Revathi, M; Ahmed Basha, C

    2007-10-22

    Various chemical and physical processes for treatment of textile effluent are not destructive but they only transfer the contaminants from one form to another. The presence of high concentration of organic dye and total dissolved solids (TDS) in the effluent that are not removed by biological treatment must be eliminated by an alternative method to the conventional ones is the advanced oxidation process (AOP). A procion blue dye effluent was treated by photo and electrochemical oxidation process as well as by combining photocatalytic degradation using TiO2 suspensions. Chemical oxygen demand (COD) and colour removal can be used to follow the degradation of the organic pollutant. The effects of pH, current density, flow rate of effluent that passes into the reactor and supporting electrolyte were studied. Comparative studies were carried out on photocatalytic and electrochemical process to degrade the procion blue. The maximum COD reduction and colour removal were 96 and 100%, respectively. Photodegradation efficiency of dye was high when photolysis was carried out in the presence of 40 mg/l of TiO2. PMID:17509754

  20. Electrochemical oxidation of carbon fibers: Properties, surface chemistry and morphology

    NASA Astrophysics Data System (ADS)

    Jiang, Wenbo

    1999-10-01

    A series of PAN-based T300 carbon fibers was continuously, electrochemically oxidized in aqueous and organic media. A 30% fiber weight loss was obtained at an extent of oxidation of 10,600 C/g. Acidic functional groups were produced on fiber surfaces in amounts from 0 to 2640 mumol/g as the extent of oxidation increased from 0 to 10600 C/g. These surface functions were further reacted with diethylenetriamine to introduce amine functions onto fibers. The oxidation extended far deeper than the XPS detection limit (<100 A). N 2 BET at 77K gave very low fiber specific surface area in contrast to CO2 DR measurements at 273 K which confirmed large increases in surface area with oxidation. No heavy damage or macro-/mesopores were found in scanning electron micrographs. An ultramicropore structure was characterized by the CO2 DR method combined with nonlocal density functional theory. The average pore diameter was about 1.2 nm with a dominant pore diameter of 0.4 nm. CCl4, methylene blue, I2, AgNO3, and Ni(NO3)2 adsorption studies were performed. A pH-dependent swelling model was discussed. In basic media, a solvation/swelling process allows small molecules to penetrate the microporous channels and react with fiber functional groups. A remote site silver reduction/adsorption model was confirmed based upon high AgNO3 adsorption and qualitative experiments. Single filament breaking and fragmentation tests and fiber/epoxy composite mechanical tests were conducted. Fiber/epoxy matrix adhesion was improved by oxidation although the fiber tensile strength decreased. Post-heat treatment causes further weight loss and the loss of oxygen-containing surface functional groups.

  1. Cobalt vanadium oxide thin nanoplates: primary electrochemical capacitor application

    PubMed Central

    Zhang, Youjuan; Liu, Yuanying; Chen, Jing; Guo, Qifei; Wang, Ting; Pang, Huan

    2014-01-01

    Co3V2O8 thin nanoplates are firstly described as a kind of electrode material for supercapacitors. More importantly, from electrochemical measurements, the obtained Co3V2O8 nanoplate electrode shows a good specific capacitance (0.5?A g?1, 739?F g?1) and cycling stability (704?F g?1 retained after 2000 cycles). This study essentially offers a new kind of metal vanadium oxides as electrochemical active material for the development of supercapacitors. PMID:25023373

  2. Design of electrochemical processes for treatment of unusual waste streams

    SciTech Connect

    Farmer, J.C.

    1998-01-01

    UCRL- JC- 129438 PREPRINT This document was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor the University of California nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise, does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or the University of California. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or the University of California, and shall not be used for advertising or product endorsement purposes. Introduction. An overview of work done on the development of three electrochemical processes that meet the specific needs of low- level waste treatment is presented. These technologies include: mediated electrochemical oxidation [I- 4]; bipolar membrane electrodialysis [5]; and electrosorption of carbon aerogel electrodes [6- 9]. Design strategies are presented to assess the suitability of these electrochemical processes for Mediated electrochemical oxidation. Mixed wastes include both hazardous and radioactive components. It is desirable to reduce the overall volume of the waste before immobilization and disposal in repositories. While incineration is an attractive technique for the destruction of organic fractions of mixed wastes, such high-temperature thermal processes pose the threat of volatilizing various radionuclides. By destroying organics in the aqueous phase at low temperature and ambient pressure, the risk of volatilization can be reduced. One approach that is attractive is the use of eiectrochemically generated mediators such as Ag( ll), Co( Ill) and Fe( III). These oxidants react with organicsin Bipolar membrane electrodialysis. in the aqueous processing of nuclear materials, process steps arise that require the neutralization of an acidic stream with a strong base. Ultimately, these neutralized salt solutions become aqueous waste streams, requiring further treatment and disposal. By "splitting" such neutralized salt solutions into their acid and base components, the generation of aqueous mixed waste can be greatly reduced. At LLNL, a bipolar membrane electrodialysis cell has been used to separate neutral solutions of NaCl, NaNO1 and Na, SO, into product streams of NaOH, HCI, HNOj and H2S0,, which could be recycled. The eftlciency of this particular process will be discussed, as well as practical limitations of the technology. Basic principles of engineering design of such systems will be reviewed.

  3. Electrochemical reduction of nickel from oxide melts

    NASA Astrophysics Data System (ADS)

    Mikhailov, A. I.; Vatolin, A. N.

    2010-08-01

    The electrochemical behavior of nickel ions in melted sodium borosilicate and calcium alumino-silicate with NiO additions (0.25-4 wt %), which cover the entire solubility region, is studied using I- V characteristics and an electrolytic method.

  4. 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.

  5. Electrochemical treatment of the effluent of a fine chemical manufacturing plant.

    PubMed

    Caizares, P; Paz, R; Lobato, J; Sez, C; Rodrigo, M A

    2006-11-01

    In this work, the electrochemical oxidation of an actual industrial wastewater with conductive-diamond anodes has been studied. The wastewater is the effluent of a fine chemicals plant. This effluent consists of an aqueous solution of solvents (ketones and alcohols) with a high concentration of aromatic compounds coming from the raw materials, intermediates and products of the different processes of the plant and its COD is around 6000 mg dm(-3). The electrolyses were carried out in a discontinuous operation mode under galvanostatic conditions, using a bench-scale plant equipped with a single compartment electrochemical flow cell. The conductive-diamond electrochemical oxidation (CDEO) allowed achieving the complete mineralization of the waste with high current efficiencies. These efficiencies seem to strongly depend on the concentration, pH and temperature but not on the current density (in the range studied). This confirms that besides the hydroxyl radicals mediated oxidation, CDEO combines other important oxidation processes such as the direct electrooxidation on the diamond surface and the oxidation mediated by other electrochemically formed compounds generated on this electrode. Other two advanced oxidation processes (ozonation and Fenton oxidation) have been also studied in this work for comparison purposes. Both technologies were able to treat the wastes, but they obtained very different results in terms of efficiency and mineralization. The efficiency of ozonation and electrochemical oxidation were very similar (especially during the first stages), although the energy consumption required by the electrochemical process to remove at fixed percentage of COD or TOC was significantly smaller than that of ozonation. The possible accumulation of carboxylic acid as final products excludes the use of Fenton oxidation as a sole treatment technology. PMID:16806682

  6. Fractional surface termination of diamond by electrochemical oxidation.

    PubMed

    Hoffmann, Ren; Obloh, Harald; Tokuda, Norio; Yang, Nianjun; Nebel, Christoph E

    2012-01-10

    The crystalline form of sp(3)-hybridized carbon, diamond, offers various electrolyte-stable surface terminations. The H-termination-selective attachment of nitrophenyl diazonium, imaged by AFM, shows that electrochemical oxidation can control the fractional hydrogen/oxygen surface termination of diamond on the nanometer scale. This is of particular interest for all applications relying on interfacial electrochemistry, especially for biointerfaces. PMID:22172282

  7. 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

  8. Development of a system for treatment of coconut industry wastewater using electrochemical processes followed by Fenton reaction.

    PubMed

    Gomes, Lcio de Moura; Duarte, Jos Leandro da Silva; Pereira, Nathalia Marcelino; Martnez-Huitle, Carlos A; Tonholo, Josealdo; Zanta, Carmen Lcia de Paiva E Silva

    2014-01-01

    The coconut processing industry generates a significant amount of liquid waste. New technologies targeting the treatment of industrial effluents have emerged, including advanced oxidation processes, the Fenton reaction, and electrochemical processes, which produce strong oxidizing species to remove organic matter. In this study we combined the Fenton reaction and electrochemical process to treat wastewater generated by the coconut industry. We prepared a synthetic wastewater consisting of a mixture of coconut milk and water and assessed how the Fenton reagents' concentration, the cathode material, the current density, and the implementation of associated technologies affect its treatment. Electrochemical treatment followed by the Fenton reaction diminished turbidity and chemical oxygen demand (COD) by 85 and 95%, respectively. The Fenton reaction followed by the electrochemical process reduced turbidity and COD by 93 and 85%, respectively. Therefore, a combination of the Fenton and electrochemical technologies can effectively treat the effluent from the coconut processing industry. PMID:24901620

  9. Method of electrode fabrication for solid oxide electrochemical cells

    DOEpatents

    Jensen, Russell R. (Murrysville, PA)

    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.

  10. Method of electrode fabrication for solid oxide electrochemical cells

    DOEpatents

    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.

  11. Electrochemical Treatment of Alkaline Nuclear Wastes. Innovative Technology Summary Report

    SciTech Connect

    2001-01-01

    Nitrate and nitrite are two of the major hazardous non-radioactive species present in Hanford and Savannah River (SR) high-level waste (HLW). Electrochemical treatment processes have been developed to remove these species by converting aqueous sodium nitrate/nitrite into sodium hydroxide and chemically reducing the nitrogen species to gaseous ammonia, nitrous oxide and nitrogen. Organic complexants and other organic compounds found in waste can be simultaneously oxidized to gaseous carbon dioxide and water, thereby reducing flammability and leaching risks as well as process interferences in subsequent radionuclide separation processes. Competing technologies include thermal, hydrothermal and chemical destruction. Unlike thermal and hydrothermal processes that typically operate at very high temperatures and pressures, electrochemical processes typically operate at low temperatures (<100 C) and atmospheric pressure. Electrochemical processes effect chemical transformations by the addition or removal of electrons and, thus, do not add additional chemicals, as is the case with chemical destruction processes. Hanford and SR have different plans for disposal of the low-activity waste (LAW) that results when radioactive Cs{sup 137} has been removed from the HLW. At SR, the decontaminated salt solution will be disposed in a cement waste form referred to as Saltstone, whereas at Hanford the waste will be vitrified as a borosilicate glass. Destruction of the nitrate and nitrite before disposing the decontaminated salt solution in Saltstone would eliminate possible groundwater contamination that could occur from the leaching of nitrate and nitrite from the cement waste form. Destruction of nitrate and nitrite before vitrification at Hanford would significantly reduce the size of the off-gas system by eliminating the formation of NO{sub x} gases in the melter. Throughout the 1990's, the electrochemical conversion process has been extensively studied at SR, the University of Sou th Carolina, and elsewhere. Testing at the bench-scale has been completed using both surrogate and actual waste streams. A pilot-scale test facility was constructed and operated briefly at SR. This document contains information on the above-mentioned technology, including description, applicability, cost, and performance data.

  12. 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 K?. M-1 for ZnO-NRs and 540 ?. 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.

  13. 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

  14. 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.

  15. 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.

  16. 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.

  17. An Electrochemical Glucose Sensor Based on Zinc Oxide Nanorods.

    PubMed

    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/mMcm2 and the lower limit of detection was 0.22 M. PMID:26263988

  18. 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 solgel 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/mMcm2 and the lower limit of detection was 0.22 M. PMID:26263988

  19. Electrochemical oxidation of textile industry wastewater by graphite electrodes.

    PubMed

    Bhatnagar, Rajendra; Joshi, Himanshu; Mall, Indra D; Srivastava, Vimal C

    2014-01-01

    In the present article, studies have been performed on the electrochemical (EC) oxidation of actual textile industry wastewater by graphite electrodes. Multi-response optimization of four independent parameters namely initial pH (pHo): 4-10, current density (j): 27.78-138.89 A/m(2), NaCl concentration (w): 0-2g/L and electrolysis time (t): 10-130min have been performed using Box-Behnken (BB) experimental design. It was aimed to simultaneously maximize the chemical oxygen demand (COD) and color removal efficiencies and minimize specific energy consumption using desirability function approach. Pareto analysis of variance (ANOVA) showed a high coefficient of determination value for COD (R(2) = 0.8418), color (R(2) = 0.7010) and specific energy (R(2) = 0.9125) between the experimental values and the predicted values by a second-order regression model. Maximum COD and color removal and minimum specific energy consumed was 90.78%, 96.27% and 23.58 kWh/kg COD removed, respectively, were observed at optimum conditions. The wastewater, sludge and scum obtained after treatment at optimum condition have been characterized by various techniques. UV-visible study showed that all azo bonds of the dyes present in the wastewater were totally broken and most of the aromatic rings were mineralized during EC oxidation with graphite electrode. Carbon balance showed that out of the total carbon eroded from the graphite electrodes, 27-29.2% goes to the scum, 71.1-73.3% goes into the sludge and rest goes to the treated wastewater. Thermogravimetric analysis showed that the generated sludge and scum can be dried and used as a fuel in the boilers/incinerators. PMID:24766597

  20. Electrochemical water-splitting based on hypochlorite oxidation.

    PubMed

    Macounov, Kate?ina Minhov; Simic, Nina; Ahlberg, Elisabet; Krtil, Petr

    2015-06-17

    Effective catalytic water-splitting can be electrochemically triggered in an alkaline solution of sodium hypochlorite. Hypochlorite oxidation on polycrystalline platinum yields ClO radicals, which initiate a radical-assisted water-splitting, yielding oxygen, hydrogen peroxide, and protons. The efficiency of the O2 production corresponds to about two electrons per molecule of the produced O2 and is controlled primarily by the hypochlorite concentration and pH. PMID:26030185

  1. Electrochemical treatment of evaporated residue of soak liquor generated from leather industry.

    PubMed

    Boopathy, R; Sekaran, G

    2013-09-15

    The organic and suspended solids present in soak liquor, generated from leather industry, demands treatment. The soak liquor is being segregated and evaporated in solar evaporation pans/multiple effect evaporator due to non availability of viable technology for its treatment. The residue left behind in the pans/evaporator does not carry any reuse value and also faces disposal threat due to the presence of high concentration of sodium chloride, organic and bacterial impurities. In the present investigation, the aqueous evaporated residue of soak liquor (ERSL) was treated by electrochemical oxidation. Graphite/graphite and SS304/graphite systems were used in electrochemical oxidation of organics in ERSL. Among these, graphite/graphite system was found to be effective over SS304/graphite system. Hence, the optimised conditions for the electrochemical oxidation of organics in ERSL using graphite/graphite system was evaluated by response surface methodology (RSM). The mass transport coefficient (km) was calculated based on pseudo-first order rate kinetics for both the electrode systems (graphite/graphite and SS304/graphite). The thermodynamic properties illustrated the electrochemical oxidation was exothermic and non-spontaneous in nature. The calculated specific energy consumption at the optimum current density of 50 mA cm(-2) was 0.41 kWh m(-3) for the removal of COD and 2.57 kWh m(-3) for the removal of TKN. PMID:23770619

  2. Electrochemical Oxidation of Synthetic Dyes in Simulated Wastewaters

    NASA Astrophysics Data System (ADS)

    Gallios, G.; Violintzis, X.; Voinovskii, I.; Voulgaropoulos, A.

    An electrochemical oxidation method for the degradation of synthetic reactive azodyes found in textile wastewaters is discussed. Four commercial synthetic dyes (black, blue, red and yellow) commonly used in dying operations were studied in single, binary and ternary mixtures. Low (100 mg/L) and high (500, 1,000 and 2,000 mg/L) initial dye concentrations were studied. The effect of various sodium chloride concentrations (as supporting electrolyte) on the effectiveness of electrochemical oxidation was examined. The effect of current intensity (1.5, 2.5 and 3.0 A) and pH (vales 3, 5, 7 and 10) was studied as well. The kinetics of the electrochemical oxidation for each dye were studied and compared. The conditions for effective dye degradation even from 2,000 mg/L initial concentration were established. The method was proved very effective even with binary and ternary mixtures of basic synthetic dyes. The Chemical Oxygen Demand (COD) and the Total Organic Carbon (TOC) were reduced by 60% and 25% respectively, meaning that the treated solutions were friendlier to the environment.

  3. [Modeling the oxidative detoxication function of the liver using electrochemical oxidation reactions].

    PubMed

    Zhirnov, G F; Izotov, M V; Karuzina, I I; Lopukhin, Iu M; Archakov, A I

    1979-01-01

    An electrochemical system is developed, which permits to simulate oxidative reactions, processing in presence of cytochrome P-450. The system, combined with a dialyzing apparatus, may be used for oxidation and elimination of various hydrophobic substances of exoand endogenous origin from animal and human organisms. PMID:442594

  4. 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.

  5. 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

  6. 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.

  7. 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

  8. 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...

  9. 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...

  10. Case Studies in the Electrochemical Treatment of Wastewater Containing Organic Pollutants Using BDD

    NASA Astrophysics Data System (ADS)

    Polcaro, Anna Maria; Mascia, M.; Palmas, S.; Vacca, A.

    A critical review is presented in this chapter on the possible applications of boron-doped diamond (BDD) as anode material to perform oxidation of organic compounds in aqueous solution. The oxidation of model substances is studied as well as that of the main classes of pollutants, such as phenols, dyes, pesticides and drugs, surfactants, which make some problems of degradation with the traditional wastewater treatments. The presented results indicate that organic compounds refractory to other oxidation techniques are successfully oxidized at BDD, even if the reaction mechanism is differently dependent on the organic compound and the electrolyte composition. Economic considerations reveal that electrochemical oxidations at BDD are less expensive than other advanced oxidation processes, indicating that in the near future this technology can become a competitive treatment for the removal of refractory compounds from wastewater.

  11. OXIDATIVE TREATMENT OF INDUSTRIAL WASTEWATER

    EPA Science Inventory

    This paper defines industrial waste treatment process as falling into categories of oxidative destruction, reductive destruction, and non-destructive, separation operations. The various oxidative approaches, including biological, chemical and thermal methods, are then discussed i...

  12. Simultaneous Electrochemical Reduction and Delamination of Graphene Oxide Films.

    PubMed

    Wang, Xiaohan; Kholmanov, Iskandar; Chou, Harry; Ruoff, Rodney S

    2015-09-22

    Here we report an electrochemical method to simultaneously reduce and delaminate graphene oxide (G-O) thin films deposited on metal (Al and Au) substrates. During the electrochemical reaction, interface charge transfer between the G-O thin film and the electrode surface was found to be important in eliminating oxygen-containing groups, yielding highly reduced graphene oxide (rG-O). In the meantime, hydrogen bubbles were electrochemically generated at the rG-O film/electrode interface, propagating the film delamination. Unlike other metal-based G-O reduction methods, the metal used here was either not etched at all (for Au) or etched a small amount (for Al), thus making it possible to reuse the substrate and lower production costs. The delaminated rG-O film exhibits a thickness-dependent degree of reduction: greater reduction is achieved in thinner films. The thin rG-O films having an optical transmittance of 90% (? = 550 nm) had a sheet resistance of 6390 447 ?/? (ohms per square). rG-O-based stretchable transparent conducting films were also demonstrated. PMID:26257072

  13. 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.

  14. Simultaneous hydrogen production and electrochemical oxidation of organics using boron-doped diamond electrodes.

    PubMed

    Jiang, Juyuan; Chang, Ming; Pan, Peng

    2008-04-15

    This paper presents advantages of using a boron-doped diamond (BDD) electrode for hydrogen production and wastewater treatment in a single electrochemical cell. Results indicated that the BDD electrode possessed the widest known electrochemical window, allowing new possibilities for both anodic and cathodic reactions to simultaneously take place. The BDD electrode exhibited high anodic potential, generating high oxidation state radicals that facilitated oxidation of toxic waste organic compounds such as 4-nitrophenols. In contrast, because of widening of potential windows, the rate of hydrogen evolution at the cathode was significantly increased. Time-on-stream concentrations of reaction intermediates were monitored to elucidate mechanism involved in 4-nitrophenol oxidation. Spalling, fouling, or reduction in the thickness of thin-film diamond coating was not observed. Overall, the BDD electrode exhibits unique properties including chemical inertness, anticorrosion, and extended service life. These properties are especially important in wastewater treatment. Economic advantages were attributed to the low cost and long duration BDD electrode and the valuable hydrogen byproduct produced. Analysis has shown that technology associated with the BDD electrode could be effectively implemented with minimum energy input and capital requirements. When combined with solar energy and fuel cells, electrochemical wastewater processing can become energy efficient and cost-effective. PMID:18497166

  15. 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

  16. Wet Electrolytic Oxidation of Organics and Application for Sludge Treatment

    NASA Astrophysics Data System (ADS)

    Serikawa, Roberto M.

    Wet electrolytic oxidation (WEO) is electrochemical oxidation conducted at subcritical water temperature and pressure. Under these conditions, the electrolytic reaction of water is very different from the reaction usually seen in water electrolysis. Electrolysis of an aqueous NaCl solution at 250°C proceeds without the evolution of any oxygen, chlorine or even hydrogen. Rapid oxidation of organics to CO2 occurs in WEO with the production of hydrogen. Further addition of an oxidizer enhances the electrochemical oxidation of organics with the suppression of hydrogen evolution. AOX compounds found in usual electrooxidation are not formed in WEO treatment. When WEO is applied to sludge treatment, colors are drastically reduced and there is an increase in the yield of organic acids. The biodegradability increases by up to 50% and the treated water shows higher methane yields during anaerobic fermentation.

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

    NASA Astrophysics Data System (ADS)

    Riley, Brian; Szreders, Bernard E.

    1988-04-01

    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 (approx. 1100 to 1300 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 and 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.

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

    DOEpatents

    Brian, Riley (Willimantic, CT); Szreders, Bernard E. (Oakdale, CT)

    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.

  19. 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.

  20. The electrochemical oxidation of organic selenides and selenoxides

    SciTech Connect

    Ryan, M.D.; Yau, J.; Hack, M.

    1997-06-01

    The electrochemical oxidation of alkyl and aryl selenides was investigated in acetonitrile. The oxidation of diphenyl selenide and di(4-methylphenyl) selenide led primarily to the formation of their respective selenoxides, which were identified by exhaustive coulometric oxidation and {sup 1}H and {sup 13}C analysis of the products. The selenoxide itself was not observed in the cyclic voltammetry of the selenide for two reasons: first, the protonation of the selenoxide by the acid formed from the reaction of water with the cation radical and second, the formation of a selenoxide hydrate. The formation of the hydrate with diphenyl selenoxide was verified by isolation of the dimethoxy derivative. In addition to the selenoxide, selenonium compounds, formed by the coupling of the oxidized material, were also observed. The alkyl selenides were generally oxidized at a lower potential than the aryl selenides. This trend is different from the sulfur analogues, where the aryl sulfides are easier to oxidize than their alkyl counterparts. As a result, the difference in their redox potentials is relatively small. These differences may occur because the oxidation of aryl sulfides is more likely to take place on the aromatic ring, which leads to a greater yield of the coupled products (about 100%) when compared to the selenide analogue.

  1. 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

  2. Treatment of dilute methylene blue-containing wastewater by coupling sawdust adsorption and electrochemical regeneration.

    PubMed

    Bouaziz, I; Chiron, C; Abdelhedi, R; Savall, A; Groenen Serrano, K

    2014-01-01

    In the present work, the coupling of adsorption and electrochemical oxidation on a boron-doped diamond (BDD) electrode to treat solutions containing dyes is studied. This coupling may be convenient for the treatment of diluted pollutant that is limited by the low rate of electrooxidation due to mass-transfer limitation. A pre-concentration step by adsorption could minimize the design of the electrochemical reactor. The adsorbent chosen was mixed with softwood sawdust, and methylene blue was chosen as the model dye molecule. Isotherms of adsorption and kinetics were investigated as well as the effects of current density and regeneration time. The BDD electrochemical oxidation of methylene blue adsorbed onto sawdust led simultaneously to its degradation and sawdust regeneration for the next adsorption. It was observed that multiple adsorption and electrochemical regeneration cycles led to an enhancement of adsorption capacity of the sawdust. This study demonstrated that adsorption–electrochemical degradation coupling offers a promising approach for the efficient elimination of organic dyes from wastewater. PMID:24659458

  3. 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.

  4. 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

  5. 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

  6. Challenges and Opportunities for Electrochemical Processes as Next-Generation Technologies for the Treatment of Contaminated Water.

    PubMed

    Radjenovic, Jelena; Sedlak, David L

    2015-10-01

    Electrochemical processes have been extensively investigated for the removal of a range of organic and inorganic contaminants. The great majority of these studies were conducted using nitrate-, perchlorate-, sulfate-, and chloride-based electrolyte solutions. In actual treatment applications, organic and inorganic constituents may have substantial effects on the performance of electrochemical treatment. In particular, the outcome of electrochemical oxidation will depend on the concentration of chloride and bromide. Formation of chlorate, perchlorate, chlorinated, and brominated organics may compromise the quality of the treated effluent. A critical review of recent research identifies future opportunities and research needed to overcome major challenges that currently limit the application of electrochemical water treatment systems for industrial and municipal water and wastewater treatment. Given the increasing interest in decentralized wastewater treatment, applications of electrolytic systems for treatment of domestic wastewater, greywater, and source-separated urine are also included. To support future adoption of electrochemical treatment, new approaches are needed to minimize the formation of toxic byproducts and the loss of efficiency caused by mass transfer limitations and undesired side reactions. Prior to realizing these improvements, recognition of the situations where these limitations pose potential health risks is a necessary step in the design and operation of electrochemical treatment systems. PMID:26370517

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

    PubMed

    Rafailovi?, Lidija D; Gammer, Christoph; Rentenberger, Christian; Triovi?, 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

  8. Importance of Electrode Material in the Electrochemical Treatment of Wastewater Containing Organic Pollutants

    NASA Astrophysics Data System (ADS)

    Panizza, Marco

    Electrochemical oxidation is a promising method for the treatment of wastewaters containing organic compounds. As a general rule, the electrochemical incineration of organics at a given electrode can take place at satisfactory rates and without electrode deactivation only at high anodic potentials in the region of the water discharge due to the participation of the intermediates of oxygen evolution. The nature of the electrode material strongly influences both the selectivity and the efficiency of the process. In particular, anodes with low oxygen evolution overpotential (i.e., good catalysts for oxygen evolution reactions), such as graphite, IrO2, RuO2, and Pt only permit the partial oxidation of organics, while anodes with high oxygen evolution overpotential (i.e., anodes that are poor catalysts for oxygen evolution reactions), such as SnO2, PbO2, and boron-doped diamond (BDD) favor the complete oxidation of organics to CO2 and so are ideal electrodes for wastewater treatment.However, the application of SnO2 and PbO2 anodes may be limited by their short service life and the risk of lead contamination, while BDD electrodes exhibit good chemical and electrochemical stability, a long life, and a wide potential window for water discharge, and are thus promising anodes for industrial-scale wastewater treatment.

  9. Electrochemical treatment of olive mill wastewater: treatment extent and effluent phenolic compounds monitoring using some uncommon analytical tools.

    PubMed

    Belaid, Chokri; Khadraoui, Moncef; Mseddii, Salma; Kallel, Monem; Elleuch, Boubaker; Fauvarque, Jean Frangois

    2013-01-01

    Problems related with industrials effluents can be divided in two parts: (1) their toxicity associated to their chemical content which should be removed before discharging the wastewater into the receptor media; (2) and the second part is linked to the difficulties of pollution characterisation and monitoring caused by the complexity of these matrixes. This investigation deals with these two aspects, an electrochemical treatment method of an olive mill wastewater (OMW) under platinized expanded titanium electrodes using a modified Grignard reactor for toxicity removal as well as the exploration of the use of some specific analytical tools to monitor effluent phenolic compounds elimination. The results showed that electrochemical oxidation is able to remove/mitigate the OMW pollution. Indeed, 87% of OMW color was removed and all aromatic compounds were disappeared from the solution by anodic oxidation. Moreover, 55% of the chemical oxygen demand (COD) and the total organic carbon (TOC) were reduced. On the other hand, UV-Visible spectrophotometry, Gaz chromatography/mass spectrometry, cyclic voltammetry and 13C Nuclear Magnetic Resonance (NMR) showed that the used treatment seems efficaciously to eliminate phenolic compounds from OMW. It was concluded that electrochemical oxidation in a modified Grignard reactor is a promising process for the destruction of all phenolic compounds present in OMW. Among the monitoring analytical tools applied, cyclic voltammetry and 13C NMR a re among th e techniques that are introduced for thefirst time to control the advancement of the OMW treatment and gave a close insight on polyphenols disappearance. PMID:23586318

  10. ELECTROCHEMICAL PROCESSES FOR IN-SITU TREATMENT OF CONTAMINATED SOILS

    EPA Science Inventory

    This project will study electrochemical processes for the in situ treatment of soils contaminated by mixed wastes, i.e., organic and inorganic. Soil samples collected from selected DOE waste sites will be characterized for specific organic and metal contaminants and hydraulic per...

  11. Chemical, electrochemical and photochemical molecular water oxidation catalysts.

    PubMed

    Bofill, Roger; Garca-Antn, Jordi; Escriche, Llus; Sala, Xavier

    2015-11-01

    Hydrogen release from the splitting of water by simply using sunlight as the only energy source is an old human dream that could finally become a reality. This process involves both the reduction and oxidation of water into hydrogen and oxygen, respectively. While the first process has been fairly overcome, the conversion of water into oxygen has been traditionally the bottleneck process hampering the development of a sustainable hydrogen production based on water splitting. Fortunately, a revolution in this field has occurred during the past decade, since many research groups have been conducting an intense research in this area. Thus, while molecular, well-characterized catalysts able to oxidize water were scarce just five years ago, now a wide range of transition metal based compounds has been reported as active catalysts for this transformation. This review reports the most prominent key advances in the field, covering either examples where the catalysis is triggered chemically, electrochemically or photochemically. PMID:25547287

  12. High-efficient treatment of wastewater contained the carcinogen naphthylamine by electrochemical oxidation with ?-Al2O3 supported MnO2 and Sb-doped SnO2 catalyst.

    PubMed

    Chen, Fengtao; Yu, Sanchuan; Dong, Xiaoping; Zhang, Shishen

    2012-08-15

    1-Naphthylamine wastewater causes severe environmental pollution because of its acute toxicity and carcinogenicity in humans, which makes it difficult to reuse by conventional technologies. In this study, we report an investigation of the electrochemical catalytic oxidation of 1-naphthylamine in synthetic wastewater in a 150 mL electrolytic batch reactor with Ti/Sb-SnO(2)/PbO(2) as anode and steel plate as cathode, where the reaction was assisted by MnO(2) and Sn(1-x)Sb(x)O(2) composite materials as the catalyst and ?-Al(2)O(3) as the carrier (MnO(2)-Sn(1-x)Sb(x)O(2)/?-Al(2)O(3)). The catalyst was synthesized by impregnating process and was characterized by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The effects of pH and current density on the efficiency of the electrochemical degradation process were also studied. It was found that MnO(2)-Sn(1-x)Sb(x)O(2)/?-Al(2)O(3) exhibited excellent catalytic activity in the electrochemical degradation of 1-naphthylamine wastewater. The results showed that the refractory organics in wastewater can be effectively removed by this process, and a chemical oxygen demand (COD) removal efficiency of 92.2% was obtained in 20 min at pH 7.0 and current density was equal to 50 mA cm(-2). According to the experimental results, a hypothetical mechanism of electrochemical catalytic degradation was also proposed. PMID:22652320

  13. 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.

  14. Integrated biological and electro-chemical treatment of swine manure.

    PubMed

    Chae, K J; Yim, S K; Choi, K H; Kim, S K; Park, W K

    2004-01-01

    A full-scale biogas plant was applied to the processing of 10 m3/d of swine manure. The plant consisted of an anaerobic digester and an engine-generator. The digester operation resulted in an 81% of COD removal, a 55% of VS reduction, and methane-rich biogas production that is used to generate electrical and thermal energies. To further treat the digested manure, for compliance with discharge limits, an electro-chemical oxidation with a dimensionally sable anode was investigated for the simultaneous elimination of both the remaining COD and ammonia nitrogen. It was able to reduce NH4+-N levels from as high as 1552 down to 25 mg/L in 160 min, and the COD from 1542 to 0.21 mg/L under the experimental conditions of 8 V, 30 A and 20,000 microS/cm. The amount of electricity required for a 90% removal of the residual COD and ammonia in 1 m3 of filtered digester manure, via electrochemical oxidation, were approximately 153 and 151 kWh, respectively. These values exceed the maximum potential capacity of the biogas-originated electricity through the digestion of swine manure containing normal VS content. However, approximately 50% of the required electricity for the electrochemical oxidation could be supplied from the engine-generator. PMID:15137454

  15. Research trends in electrochemical technology for water and wastewater treatment

    NASA Astrophysics Data System (ADS)

    Zheng, Tianlong; Wang, Juan; Wang, Qunhui; Meng, Huimin; Wang, Lihong

    2015-03-01

    It is difficult to completely degrade wastewater containing refractory pollutants without secondary pollution by biological treatment, as well as physical-chemical process. Therefore, electrochemical technology has attracted much attention for its environmental compatibility, high removal efficiency, and potential cost effectiveness, especially on the industrial wastewater treatment. An effective bibliometric analysis based on the Science Citation Index Core Collection database was conducted to evaluate electrochemical technology for water and wastewater treatment related research from 1994 to 2013. The amount of publications significantly increased in the last two decades. Journal of the Electrochemical Society published the most articles in this field with a top h-index of 90, taking 5.8 % of all, followed by Electrochimica Acta and Journal of Electroanalytical Chemistry. The researchers focused on categories of chemistry, electrochemistry, and materials science. China and Chinese Academy of Sciences were the most productive country and institution, respectively, while the USA, with the most international collaborative articles and highest h-index of 130, was the major collaborator with 15 other countries in top 20 most productive countries. Moreover, based on the analysis of author keywords, title, abstract, and `KeyWords Plus', a new method named "word cluster analysis" was successfully applied to trace the research hotspot. Nowadays, researchers mainly focused on novel anodic electrode, especially on its physiochemical and electrochemical properties.

  16. 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

  17. 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.

  18. Bismuth oxide coated amorphous manganese dioxide for electrochemical capacitors

    NASA Astrophysics Data System (ADS)

    Li, Xiaofeng; Zhang, Linsen; Dong, Huichao; Xia, Tongchi; Huang, Zhigang

    2015-05-01

    With MnSO4, NaOH and K2S2O8 as the raw materials, the amorphous and ?-type manganese dioxide (MnO2) is separately prepared by using different chemical precipitation-oxidation methods. The results of charge-discharge and electrochemical impedance spectroscopy (EIS) tests show that (i) the specific capacitance of the amorphous MnO2 reaches to 301.2 F g-1 at a current density of 200 mA g-1 and its capacitance retention rate after 2000 cycles is 97%, which is obviously higher than 250.8 F g-1 and 71% of the ?-type one, respectively; (ii) good electrochemical capacitance properties of the amorphous MnO2 should be contributed to easy insertion/extraction of ions within the material; (iii) when 5 wt% Bi2O3 is coated on the amorphous MnO2, its specific capacitance increases to 352.8 F g-1 and the capacitance retention rate is 90% after 2000 cycles.

  19. 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.

  20. Synthesis and electrochemical properties of lithium molybdenum oxides

    NASA Astrophysics Data System (ADS)

    Kobayashi, Hironori; Tabuchi, Mitsuharu; Shikano, Masahiro; Yasuo Nishimura; Kageyama, Hiroyuki; Ishida, Tadashi; Nakamura, Hideo; Kurioka, Yutaka; Kanno, Ryoji

    Layered oxides Li 2MoO 3 were synthesized at 923 K (sample A), 1023 K (sample B), and 1073 K (sample C) and characterized by X-ray diffractometry, magnetic and electrochemical measurements. All Li 2MoO 3 showed rhombohedral symmetry with an ?-NaFeO 2-related structure and paramagnetic behavior down to 83 K. Lithium deintercalation from samples B and C proceeded to x=1.2 in Li 2- xMoO 3. The Li/Li 2MoO 3 (samples B and C) cells showed cycling capacities of 150 mAh/g in the voltage range of 1.5-4.3 V after 10 cycles. Samples B and C showed better cycle reversibility than sample A. The different charge and discharge characteristics between samples A-C might be caused by structural differences which were indicated by X-ray diffraction measurements.

  1. Spectroscopic And Electrochemical Studies Of Electrochromic Hydrated Nickel Oxide Films

    NASA Astrophysics Data System (ADS)

    Yu, P. C.; Nazri, G.; Lampert, C. M.

    1986-09-01

    The electrochrcrnic properties of hydrated nickel oxide thin films electrochemically deposited by anodization onto doped tin oxide-coated glass have been studied by transmittance measurements, cyclic voltammetry, Fourier-transform infrared spectroscopy, and ion-backscattering spectrometry. The spectral transmittance is reported for films switched in both the bleached and colored states. The photopic transmittance (Tp) can be switched from T (bleached) = 0.77 to T (colored) = 0.21, and the solar transmittance (Ts) can be switched from Ts(bleached) = 0.73 to TS (colored) = 0.35. Also reported is the near-infrared transmittance (TNIR)which was found to switch fran T N,IR (bleached) = 0.72 to TNIR (colored) = 0.55. The bleached condition is noted to have very low solar absorption in both the visible and solar regions. Ion-backscattering spectrometry was performed on the hydrated nickel oxide film, yielding a camposition of Ni01.0 (dehydrated) and a film thickness of 125 A. Cyclic voltammetry showed that, for films in the bleached or colored state, the reversible reaction is Ni(0H), = NiOOH + H+ + e . Voltammnetry also showed that the switching of the film is controlled by the diffusion or protons, where OH plays a role in the reaction mechanism. Analysis of the hydrated nickel-oxide thin films by Fourier-transform infrared spectroscopy revealed that both the bleached and colored states contain lattice water and hydroxyl groups. The surface hydroxyl groups play an important role in the coloration and bleaching of the anodically deposited nickel oxide thin films.

  2. 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 +}.

  3. Electrochemical anodic oxidation of nitrogen doped carbon nanowall films: X-ray photoelectron and Micro-Raman spectroscopy study

    NASA Astrophysics Data System (ADS)

    Achour, A.; Vizireanu, S.; Dinescu, G.; Le Brizoual, L.; Djouadi, M.-A.; Boujtita, M.

    2013-05-01

    Unintentional nitrogen doped carbon nanowall (CNW) films were oxidized through anodic polarization in different applied potential windows, in a mild neutral K2SO4 electrolyte solution. Applied potentials in the range of [0-1], [0-1.5] and [0-2] V vs. SCE were explored. The films were characterized with X-ray photoelectron (XPS) and Micro-Raman spectroscopy, in order to investigate the surface chemistry and structural changes after treatment, respectively. The XPS analysis revealed that this electrochemical treatment leads to an increase of oxygen functional groups, and influences the nitrogen proportion and bonding configuration (such as pyridinic/pyridonic nitrogen) on the film surface at room temperature. In particular, an obvious enhancement of pyrrolic/pyridonic nitrogen doping of CNWs via electrochemical cycling in the range of [0-1.5] and [0-2] V vs. SCE was achieved. Such enhancement happened, because of the oxidation of nitrogen atoms in pyridine as a result of OH ions injection upon electrochemical cycling. Micro-Raman analysis indicates structural quality degradation with increasing the applied potential window. Moreover, the electrochemical capacitance of CNW films was increased after treatment in the range of [0-1] and [0-1.5] and decreased in the range of [0-2] V vs. SCE. The results show that harsh oxidation happened in the range [0-2] V.

  4. 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.

  5. Electrochemical treatment of mouse Ehrlich tumor with direct electric current.

    PubMed

    Cabrales, L B; Ciria, H C; Bruzn, R P; Quevedo, M S; Aldana, R H; De Oca, L M; Salas, M F; Pea, O G

    2001-07-01

    Electrochemical treatment of cancer utilizes direct electric current (DEC) to produce direct alterations and chemical changes in tumors. However, the DEC treatment is not established and mechanisms are not well understood. In vivo studies were conducted to evaluate the effectiveness of DEC on animal tumor models. Ehrlich tumors were implanted subcutaneously in sixty male BALB/c mice. When the tumor volumes reached 850 mm(3), four platinum electrodes were inserted into the tumors. DEC of 4 mA was applied for 21 min to the treated group; the total charge was 5 C. The healthy and sick control groups were subjected to the same conditions but without DEC. Hematological and chemical parameters as well as histopathological and peritumoral findings were studied. After the electrochemical therapy it was observed that both tumor volume decrease and necrosis percentage increase were significant in the treated group. Moreover, 24 h after treatment an acute inflammatory response, as well as sodium ion decrease, and potassium ion and spleen weight increase were observed in this group. It was concluded that both electrochemical reactions (fundamentally those in which reactive oxygen species are involved), and immune system stimulation induced by cytotoxic action of the DEC could constitute the most important antitumor mechanisms. PMID:11424154

  6. A reduced graphene oxide based electrochemical biosensor for tyrosine detection

    NASA Astrophysics Data System (ADS)

    Wei, Junhua; Qiu, Jingjing; Li, Li; Ren, Liqiang; Zhang, Xianwen; Chaudhuri, Jharna; Wang, Shiren

    2012-08-01

    In this paper, a green and safe hydrothermal method has been used to reduce graphene oxide and produce hemin modified graphene nanosheet (HGN) based electrochemical biosensors for the determination of l-tyrosine levels. The as-fabricated HGN biosensors were characterized by UV-visible absorption spectra, fluorescence spectra, Fourier transform infrared spectroscopy (FTIR) spectra and thermogravimetric analysis (TGA). The experimental results indicated that hemin was successfully immobilized on the reduced graphene oxide nanosheet (rGO) through ?-? interaction. TEM images and EDX results further confirmed the attachment of hemin on the rGO nanosheet. Cyclic voltammetry tests were carried out for the bare glass carbon electrode (GCE), the rGO electrode (rGO/GCE), and the hemin-rGO electrode (HGN/GCE). The HGN/GCE based biosensor exhibits a tyrosine detection linear range from 5 10-7 M to 2 10-5 M with a detection limitation of 7.5 10-8 M at a signal-to-noise ratio of 3. The sensitivity of this biosensor is 133 times higher than that of the bare GCE. In comparison with other works, electroactive biosensors are easily fabricated, easily controlled and cost-effective. Moreover, the hemin-rGO based biosensors demonstrate higher stability, a broader detection linear range and better detection sensitivity. Study of the oxidation scheme reveals that the rGO enhances the electron transfer between the electrode and the hemin, and the existence of hemin groups effectively electrocatalyzes the oxidation of tyrosine. This study contributes to a widespread clinical application of nanomaterial based biosensor devices with a broader detection linear range, improved stability, enhanced sensitivity and reduced costs.

  7. 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

  8. 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

  9. Electrochemically reduced water protects neural cells from oxidative damage.

    PubMed

    Kashiwagi, Taichi; Yan, Hanxu; Hamasaki, Takeki; Kinjo, Tomoya; Nakamichi, Noboru; Teruya, Kiichiro; Kabayama, Shigeru; Shirahata, Sanetaka

    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??M) induced PC12 and SFME cell deaths. ERW scavenged intracellular ROS and exhibited a protective effect against neuronal network damage caused by 200??M 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 Ca(2+) 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

  10. 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.

  11. Influence of electrochemical reduction and oxidation processes on the decolourisation and degradation of C.I. Reactive Orange 4 solutions.

    PubMed

    del Ro, 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. Response surface optimization of electrochemical treatment of textile dye wastewater.

    PubMed

    Krbahti, Bahadir K

    2007-06-25

    The electrochemical treatment of textile dye wastewater containing Levafix Blue CA, Levafix Red CA and Levafix Yellow CA reactive dyes was studied on iron electrodes in the presence of NaCl electrolyte in a batch electrochemical reactor. The wastewater was synthetically prepared in relatively high dye concentrations between 400mg/L and 2000mg/L. The electrochemical treatment of textile dye wastewater was optimized using response surface methodology (RSM), where current density and electrolyte concentration were to be minimized while dye removal and turbidity removal were maximized at 28 degrees C reaction temperature. Optimized conditions under specified cost driven constraints were obtained for the highest desirability at 6.7mA/cm(2), 5.9mA/cm(2) and 5.4mA/cm(2) current density and 3.1g/L, 2.5g/L and 2.8g/L NaCl concentration for Levafix Blue CA, Levafix Red CA and Levafix Yellow CA reactive textile dyes, respectively. PMID:17184910

  13. 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

  14. Electrochemical treatment of human urine for its storage and reuse as flush water.

    PubMed

    Ikematsu, Mineo; Kaneda, Kazuhiro; Iseki, Masahiro; Yasuda, Masashi

    2007-08-15

    We proposed the electrochemical treatment of human urine to enable its storage without the accompanying unpleasant odor. This urine can then be reused as flush water in toilets as a means to tackle water shortage problems. In laboratory-scale experiments, the time-dependent variation in the pH of human urine, after the addition of urease, could be suppressed by chlorine produced via the electrochemical treatment of diluted human urine. Ureolysis was quantified by pH increase within 100 h. This suppression occurred as a result of an irreversible change in the conformation of urease that resulted in its inactivation at an oxidation-reduction potential (ORP) of ca. 240 mV or above. Due to the electrochemical inactivation of urease during the entire storage period of urine, the hydrolysis of urea in urine, which results in the production of the unpleasant odor due to ammonia formation, can be avoided. Thus, the treatment enables the storage of urine for its reuse as flush water in toilets. PMID:17462709

  15. Study of the electrochemical oxidation and reduction of C.I. Reactive Orange 4 in sodium sulphate alkaline solutions.

    PubMed

    del Ro, 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

  16. 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-H2O2treatment with BDD was the most potent method, yielding 93% mineralization after 360 min at 100 mA cm(-2). In the flow plant, the SPEF process attained a maximum mineralization of 70% at 100 mA cm(-2). Lower current densities slightly reduced the mineralization degree in SPEF, enhancing the current efficiency and dropping the energy consumption. The diuron decay always obeyed a pseudo-first-order kinetics, with a much greater apparent rate constant in EF and SPEF compared to EO-H2O2. Oxalic and oxamic acids were detected as final carboxylic acids. Ammonium and chloride ions were also released, the latter ion being partially converted into chlorate and perchlorate ions at the BDD surface. PMID:24873706

  17. 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.

  18. 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.

  19. Electrochemical therapy to treat cancer (in vivo treatment).

    PubMed

    Tell, M; Oliveira, L; Parise, O; Buzaid, A C; Oliveira, R T; Zanella, R; Cardona, A

    2007-01-01

    The aim of this paper is to present the evaluations and results attained by our research group from the clinical applications of Electrochemical Therapy (EChT in short) on tumors, specifically of cats and dogs. Our in vivo results indicate that EChT is an effective cancer treatment. Application of EChT in human beings was approved by National Health Surveillance Agency, which is linked to the Brazilian Ministry of Health. To make EChT available for cancer patients in the Brazil, basic studies were conducted and a Phase I clinical trial was started. PMID:18002757

  20. 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

  1. 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.

  2. Electrochemical oxidation of synthetic tannery wastewater in chloride-free aqueous media.

    PubMed

    Costa, Carla Regina; Montilla, Francisco; Moralln, Emilia; Olivi, Paulo

    2010-08-15

    The electrochemical treatment of a synthetic tannery wastewater, prepared with several compounds used by finishing tanneries, was studied in chloride-free media. Boron-doped diamond (Si/BDD), antimony-doped tin dioxide (Ti/SnO(2)-Sb), and iridium-antimony-doped tin dioxide (Ti/SnO(2)-Sb-Ir) were evaluated as anode. The influence of pH and current density on the treatment was assessed by means of the parameters used to measure the level of organic contaminants in the wastewater; i.e., total phenols, chemical oxygen demand (COD), total organic carbon (TOC), and absorbance. Results showed that faster decrease in these parameters occurred when the Si/BDD anode was used. Good results were obtained with the Ti/SnO(2)-Sb anode, but its complete deactivation was reached after 4h of electrolysis at 25 mA cm(-2), indicating that the service life of this electrode is short. The Ti/SnO(2)-Sb-Ir anode is chemically and electrochemically more stable than the Ti/SnO(2)-Sb anode, but it is not suitable for the electrochemical treatment under the studied conditions. No significant changes were observed for electrolyses performed at different pH conditions with Si/BDD, and this electrode led to almost complete mineralization after 4h of electrolysis at 100 mA cm(-2). The increase in current density resulted in faster wastewater oxidation, with lower current efficiency and higher energy consumption. Si/BBD proved to be the best electrodic material for the direct electrooxidation of tannery wastewaters. PMID:20452722

  3. 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.

  4. Optimization of Electrochemical Treatment Process Conditions for Distillery Effluent Using Response Surface Methodology

    PubMed Central

    Arulmathi, P.; Elangovan, G.; Begum, A. Farjana

    2015-01-01

    Distillery industry is recognized as one of the most polluting industries in India with a large amount of annual effluent production. In this present study, the optimization of electrochemical treatment process variables was reported to treat the color and COD of distillery spent wash using Ti/Pt as an anode in a batch mode. Process variables such as pH, current density, electrolysis time, and electrolyte dose were selected as operation variables and chemical oxygen demand (COD) and color removal efficiency were considered as response variable for optimization using response surface methodology. Indirect electrochemical-oxidation process variables were optimized using Box-Behnken response surface design (BBD). The results showed that electrochemical treatment process effectively removed the COD (89.5%) and color (95.1%) of the distillery industry spent wash under the optimum conditions: pH of 4.12, current density of 25.02 mA/cm2, electrolysis time of 103.27 min, and electrolyte (NaCl) concentration of 1.67 g/L, respectively. PMID:26491716

  5. 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.

  6. Treatment of wastewater from pulp and paper mill industry by electrochemical methods in membrane reactor.

    PubMed

    Chanworrawoot, Kanjana; Hunsom, Mali

    2012-12-30

    The treatment of wastewater from a pulp and paper mill plant using electrochemical methods was performed at a laboratory bench-scale at ambient temperature (~30 °C). The effects of wastewater dilution (10- to 100-fold), circulating water flow rate (0-3.95 l/min), current density (1.90-3.80 mA/cm(2)) and sodium chloride concentration (0-3.75 g/l) were ascertained. The results demonstrated that this methods can facilitate the disappearance of the oxidative coupling unit of lignin as well as other organic and inorganic compounds, measured in terms of the removal of color, total biological- and total chemical oxygen demand (BOD and COD), and the total suspended and dissolved solids (TSS and TSD). In addition, the electrochemical method was more effective at reducing the pollutant levels, produced a smaller quantity of low-density sludge and had a low operating cost per unit quantity of COD. After optimization, the electrochemical method operating in a batch mode enhanced the removal of color, BOD and COD at around 98%, 98% and 97%, respectively, whilst in a continuous mode at the steady state condition (8 h after the start-up time) the color, BOD and COD levels were reduced by around 91%, 83% and 86%, respectively. PMID:23062272

  7. Characterization of internal oxide layers in 3% Si grain-oriented steel by electrochemical methods

    NASA Astrophysics Data System (ADS)

    Toda, H.; Sato, K.; Komatsubara, M.

    1997-12-01

    The structure of internal oxide layers in decarburized sheet was studied using a newly developed electrochemical method. Dissolving potential profiles indicated the amount of fayalite (Fe2SiO4) and silica (SiO2) in the layers. The quantitative data for the contents of fayalite and silica in the internal oxide layers can be easily obtained by this method.

  8. Status of test results of electrochemical organic oxidation of a tank 241-SY-101 simulated waste

    SciTech Connect

    Colby, S.A.

    1994-06-01

    This report presents scoping test results of an electrochemical waste pretreatment process to oxidize organic compounds contained in the Hanford Site`s radioactive waste storage tanks. Electrochemical oxidation was tested on laboratory scale to destroy organics that are thought to pose safety concerns, using a nonradioactive, simulated tank waste. Minimal development work has been applied to alkaline electrochemical organic destruction. Most electrochemical work has been directed towards acidic electrolysis, as in the metal purification industry, and silver catalyzed oxidation. Alkaline electrochemistry has traditionally been associated with the following: (1) inefficient power use, (2) electrode fouling, and (3) solids handling problems. Tests using a laboratory scale electrochemical cell oxidized surrogate organics by applying a DC electrical current to the simulated tank waste via anode and cathode electrodes. The analytical data suggest that alkaline electrolysis oxidizes the organics into inorganic carbonate and smaller carbon chain refractory organics. Electrolysis treats the waste without adding chemical reagents and at ambient conditions of temperature and pressure. Cell performance was not affected by varying operating conditions and supplemental electrolyte additions.

  9. 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

  10. Detoxification of methyl-parathion pesticide in aqueous solutions by electrochemical oxidation.

    PubMed

    Arapoglou, D; Vlyssides, A; Israilides, C; Zorpas, A; Karlis, P

    2003-03-17

    Commercial methyl-parathion (MeP) was detoxified using an electrochemical method that employed a Ti/Pt anode and stainless steel 304 as cathode. Sodium chloride was added as electrolyte and the mixture was passed through an electrolytic cell for 2 h. Due to the strong oxidizing potential of the produced chemicals, the organic pollutants were wet oxidized to carbon dioxide and water. A number of experiments were run at laboratory scale. Reductions of COD and BOD(5) were both over 80% and the mean energy consumption was 18-8 kWh per kg(-1) COD reduced (COD(r)). The degradation of MeP was more effective when the pH of the brine solution was in the acid range than when it was in the alkaline range. From the results it can be concluded that electrolysis could be used as an oxidation pre-treatment stage for detoxification of toxic wastes with MeP. PMID:12628787

  11. Electrochemical study of the catechol-modified chitosan system for clozapine treatment monitoring.

    PubMed

    Winkler, Thomas E; Ben-Yoav, Hadar; Chocron, Sheryl E; Kim, Eunkyoung; Kelly, Deanna L; Payne, Gregory F; Ghodssi, Reza

    2014-12-01

    This work presents a thorough electrochemical and reliability analysis of a sensing scheme for the antipsychotic clozapine. We have previously demonstrated a novel detection approach for this redox-active drug, highly effective in schizophrenia treatment, based on a catechol-modified chitosan film. The biomaterial film enables amplification of the oxidative current generated by clozapine through redox cycling. Here, we study critical electrochemical and material aspects of the redox cycling system to overcome barriers in point-of-care monitoring in complex biological samples. Specifically, we explore the electrochemical parameter space, showing that enhanced sensing performance depends on the presence of a reducing mediator as well as the electrochemical technique applied. These factors account for up to 1.75-fold and 2.47-fold signal enhancement, respectively. Looking at potential interferents, we illustrate that the redox cycling system allows for differentiation between selected redox-active species, clozapine's structurally largely analogous metabolite norclozapine as well as the representative catecholamine dopamine. Furthermore, we investigate material stability and fouling with reuse as well as storage. We find no evidence of film fouling due to clozapine; slow overall biomaterial degradation with successive use accounts for a 2.2% absolute signal loss and can be controlled for. Storage of the redox cycling system appears feasible over weeks when kept in solution with only 0.26%/day clozapine signal degradation, while ambient air exposure of three or more days reduces performance by 58%. This study not only advances our understanding of the catechol-modified chitosan system, but also further establishes the viability of applying it toward sensing clozapine in a clinical setting. Such point-of-care monitoring will allow for broader use of clozapine by increasing convenience to patients as well as medical professionals, thus improving the lives of people affected by schizophrenia through personalized medicine. PMID:25383917

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

    PubMed

    Lucas, Marie; Boily, Jean-Franois

    2015-12-22

    Alternating current scanning electrochemical microscopy (AC-SECM) was used for the first time to map key electrochemical attributes of oriented hematite (?-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 (Cdl) and charge transfer resistance (Rad). 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

  13. 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

  14. Electrochemical oxidation of berberine and mass spectrometric identification of its oxidation products.

    PubMed

    Skopalov, Jana; Vacek, Jan; Papoukov, Barbora; Jirovsk, David; Maier, Vt?zslav; Ranc, Vclav

    2012-10-01

    Electrochemical oxidation of the isoquinoline alkaloid berberine in aqueous medium was studied by cyclic and differential pulse voltammetry at a glassy carbon electrode (GCE). Two anodic peaks of the quaternary form of berberine were observed at +1.2V and +1.4V (vs. SCE) in acidic and neutral solutions. When the anodic polarization exceeded the value of +1.1 V, the redox active film is formed on the GCE surface. The formation of adsorbed film was well-documented by quasireversible redox couple at +0.25 V which was studied in redox cycling experiments. In alkaline medium, a new anodic peak at +0.5 V appeared due to oxidation of berberine pseudobase to 8-oxoberberine. Solutions of berberine at different pH were subjected to controlled potential electrolysis on platinum gauze electrode and analyzed using liquid chromatography (HPLC) equipped with electrospray ionization/quadrupole time-of-flight mass spectrometry. The main water soluble monomeric product of berberine oxidation under physiological-near experimental conditions, OP1, was identified as demethyleneberberine cation (2,3-dihydroxy-9,10-dimethoxy-5,6-dihydroisoquinolino[3,2-a]isoquinolin-7-ium). PMID:21963270

  15. 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

  16. Mediated electrochemical oxidation as an alternative to incineration for mixed wastes

    SciTech Connect

    Chiba, Z.; Schumacher, B.; Lewis, P.; Murguia, L.

    1995-02-01

    Mediated Electrochemical Oxidation (MEO) is an aqueous process which oxidizes organics electrochemically at low temperatures and ambient pressures. The process can be used to treat mixed wastes containing hazardous organics by destroying the organic components of the wastes. The radioactive components of the wastes are dissolved in the electrolyte where they can be recovered if desired, or immobilized for disposal. The process of destroying organics is accomplished via a mediator, which is in the form of metallic ions in solution. At Lawrence Livermore National Laboratory (LLNL) we have worked with worked with several mediators, including silver, cobalt and cerium. We have tested mediators in nitric as well as sulfuric acids. We have recently completed extensive experimental studies on cobalt-sulfuric acid and silver-nitric acid systems for destroying the major organic components of Rocky Flats Plant combustible mixed wastes. Organics tested were: Trimsol (a cutting oil), cellulose (including paper and cloth), rubber (latex), plastics (Tyvek, polyethylene and polyvinyl chloride) and biomass (bacteria). The process was capable of destroying almost all of the organics tested, attaining high destruction efficiencies at reasonable coulombic efficiencies. The only exception was polyvinyl chloride, which was destroyed very slowly resulting in poor coulombic efficiencies. Besides the process development work mentioned above, we are working on the design of a pilot-plant scale integrated system to be installed in the Mixed Waste Management Facility (MWMF) at LLNL. The system will also be completely integrated with upstream and downstream processes (for example, feed preparation, off-gas and water treatment, and final forms encapsulation). The conceptual design for the NEO-MWMF system has been completed and preliminary design work has been initiated. Demonstration of the process with low-level mixed wastes is expected to commence in 1998.

  17. Removal of arsenic, phosphates and ammonia from well water using electrochemical/chemical methods and advanced oxidation: a pilot plant approach.

    PubMed

    Orescanin, Visnja; Kollar, Robert; Nad, Karlo; Halkijevic, Ivan; Kuspilic, Marin; Findri Gustek, Stefica

    2014-01-01

    The purpose of this work was to develop a pilot plant purification system and apply it to groundwater used for human consumption, containing high concentrations of arsenic and increased levels of phosphates, ammonia, mercury and color. The groundwater used was obtained from the production well in the Vinkovci County (Eastern Croatia). Due to a complex composition of the treated water, the purification system involved a combined electrochemical treatment, using iron and aluminum electrode plates with simultaneous ozonation, followed by a post-treatment with UV, ozone and hydrogen peroxide. The removal of the contaminant with the waste sludge collected during the electrochemical treatment was also tested. The combined electrochemical and advanced oxidation treatment resulted in the complete removal of arsenic, phosphates, color, turbidity, suspended solids and ammonia, while the removal of other contaminants of interest was up to 96.7%. Comparable removal efficiencies were obtained by using waste sludge as a coagulant. PMID:24798899

  18. Mediated electrochemical oxidation of organic wastes without electrode separators

    DOEpatents

    Farmer, Joseph C. (Newtown, PA); Wang, Francis T. (Danville, CA); Hickman, Robert G. (Livermore, CA); Lewis, Patricia R. (Livermore, CA)

    1996-01-01

    An electrochemical cell/electrolyte/mediator combination 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.

  19. 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.

  20. Tunable photoluminescence from sheet-like black phosphorus crystal by electrochemical oxidation

    NASA Astrophysics Data System (ADS)

    Gan, Z. X.; Sun, L. L.; Wu, X. L.; Meng, M.; Shen, J. C.; Chu, Paul K.

    2015-07-01

    An electrochemical method to prepare two-dimensional (2D) layered black phosphorus oxide with an inhomogeneous and non-stoichiometric structure is developed and described. The localized oxygen-related electronic states induce tunable photoluminescence (PL) between 620 and 670 nm. After oxidation, several new Raman modes with frequencies below 300 cm-1 emerge and the Ag 1 mode splits into two sub-bands. The frequency difference between the two sub-bands (?) exhibits a monotonic dependence on the emission wavelength suggesting that PL is determined by the degree of oxidation. Similar to graphene oxide, phosphorene oxide is a promising 2D structure with many potential applications.

  1. Characterization of oxide structures on stainless steel sternal wires by electrochemical reduction

    NASA Astrophysics Data System (ADS)

    Su, Yea-Yang; Shih, Chun-Che; Chen, Lung-Ching; Shih, Chun-Ming; Lin, Shing-Jong

    2012-01-01

    Different oxide structures can be formed on passive stainless steel sternal wires by various surface modifications. Oxide structure has a significant influence on the efficacy and biocompatibility of the medical devices. In this study, cathodic reduction was used to distinguish the oxide structures on 316L stainless steel sternal wires in a buffered phosphate electrolyte. TEM, Auger depth profile, XPS, and SEM were applied to examine the oxide structures. Interfacial resistance was measured using electrochemical impedance spectroscopy. Results indicate that cathodic reduction profiles have the capability to identify oxide structures on the passivated medical devices.

  2. Oxidation pond for municipal wastewater treatment

    NASA Astrophysics Data System (ADS)

    Butler, Erick; Hung, Yung-Tse; Suleiman Al Ahmad, Mohammed; Yeh, Ruth Yu-Li; Liu, Robert Lian-Huey; Fu, Yen-Pei

    2015-04-01

    This literature review examines process, design, and cost issues related to using oxidation ponds for wastewater treatment. Many of the topics have applications at either full scale or in isolation for laboratory analysis. Oxidation ponds have many advantages. The oxidation pond treatment process is natural, because it uses microorganisms such as bacteria and algae. This makes the method of treatment cost-effective in terms of its construction, maintenance, and energy requirements. Oxidation ponds are also productive, because it generates effluent that can be used for other applications. Finally, oxidation ponds can be considered a sustainable method for treatment of wastewater.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. 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

  9. Electrochemical processes for in-situ treatment of contaminated soils. 1998 annual progress report

    SciTech Connect

    Huang, C.P.

    1998-06-01

    'This research project is to develop electrochemical processes for in-situ treatment of contaminated soils. Specifically, it is to study electrokinetic (EK) and electro-Fento (EF) processes and to integrate these processes for the treatment of soils containing mixed contaminants. The objectives are: (1) To study important parameters controlling the mobilization and the transport of selected organics and metals in soils by the electrokinetic (EK) process. Factors to be studied include field strength, pH, ionic strength, soil washing agents, types of organic and metal contaminants, and soil surface properties such as cation exchange capacity(CEC), soil organic content, soil moisture content, soil composition, and surface charge. (2) To study the important factors governing the oxidation of selected organic contaminants by the electro-Fenton (EF) process. Parameters such as pH, surface area and the configuration of working electrode, oxygen concentration, ferrous ion, and temperature that may affect the performance of the EF process will be investigated. (3) To understand the mechanism of the oxidation of selected organic contaminants by the electro-Fenton oxidation process.'

  10. 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.

  11. 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.

  12. 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

  13. 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 Jrgen

    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

  14. Nanostructured Mn-based oxides for electrochemical energy storage and conversion.

    PubMed

    Zhang, Kai; Han, Xiaopeng; Hu, Zhe; Zhang, Xiaolong; Tao, Zhanliang; Chen, Jun

    2015-02-01

    Batteries and supercapacitors as electrochemical energy storage and conversion devices are continuously serving for human life. The electrochemical performance of batteries and supercapacitors depends in large part on the active materials in electrodes. As an important family, Mn-based oxides have shown versatile applications in primary batteries, secondary batteries, metal-air batteries, and pseudocapacitors due to their high activity, high abundance, low price, and environmental friendliness. In order to meet future market demand, it is essential and urgent to make further improvements in energy and power densities of Mn-based electrode materials with the consideration of multiple electron reaction and low molecular weight of the active materials. Meanwhile, nanomaterials are favourable to achieve high performance by means of shortening the ionic diffusion length and providing large surface areas for electrode reactions. This article reviews the recent efforts made to apply nanostructured Mn-based oxides for batteries and pseudocapacitors. The influence of structure, morphology, and composition on electrochemical performance has been systematically summarized. Compared to bulk materials and notable metal catalysts, nanostructured Mn-based oxides can promote the thermodynamics and kinetics of the electrochemical reactions occurring at the solid-liquid or the solid-liquid-gas interface. In particular, nanostructured Mn-based oxides such as one-dimensional MnO2 nanostructures, MnO2-conductive matrix nanocomposites, concentration-gradient structured layered Li-rich Mn-based oxides, porous LiNi0.5Mn1.5O4 nanorods, core-shell structured LiMnSiO4@C nanocomposites, spinel-type Co-Mn-O nanoparticles, and perovskite-type CaMnO3 with micro-nano structures all display superior electrochemical performance. This review should shed light on the sustainable development of advanced batteries and pseudocapacitors with nanostructured Mn-based oxides. PMID:25200459

  15. Advantages of electrodes with dendrimer-protected platinum nanoparticles and carbon nanotubes for electrochemical methanol oxidation.

    PubMed

    Siriviriyanun, Ampornphan; Imae, Toyoko

    2013-04-14

    Electrochemical sensors consisting of electrodes loaded with carbon nanotubes and Pt nanoparticles (PtNPs) protected by dendrimers have been developed using a facile method to fabricate them on two types of disposable electrochemical printed chips with a screen-printed circular gold or a screen-printed circular glassy carbon working electrode. The electrochemical performance of these sensors in the oxidation of methanol was investigated by cyclic voltammetry. It was revealed that such sensors possess stable durability and high electrocatalytic activity: the potential and the current density of an anodic peak in the oxidation of methanol increased with increasing content of PtNPs on the electrodes, indicating the promotion of electrocatalytic activity in relation to the amount of catalyst. The low anodic potential suggests the easy electrochemical reaction, and the high catalyst tolerance supports the almost complete oxidation of methanol to carbon dioxide. The significant performance of these sensors in the detection of methanol oxidation comes from the high electrocatalytic ability of PtNPs, excellent energy transfer of carbon nanotubes and the remarkable ability of dendrimers to act as binders. Thus these systems are effective for a wide range of applications as chemical, biomedical, energy and environmental sensors and as units of direct methanol fuel cells. PMID:23435635

  16. 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

  17. Characterization of internal oxide layers in 3% Si grain-oriented steel by electrochemical methods

    SciTech Connect

    Toda, H.; Sato, K.; Komatsubara, M.

    1997-12-01

    The structure of internal oxide layers in decarburized sheet was studied using a newly developed electrochemical method. Dissolving potential profiles indicated the amount of fayalite (Fe{sub 2}SiO{sub 4}) and silica (SiO{sub 2}) in the layers. The quantitative data for the contents of fayalite and silica in the internal oxide layers can be easily obtained by this method.

  18. Electrochemical treatment of mouse and rat fibrosarcomas with direct current

    SciTech Connect

    Chou, C.K.; McDougall, J.A.; Ahn, C.; Vora, N.

    1997-03-01

    Electrochemical treatment (ECT) of cancer utilizes direct current to produce chemical changes in tumors. ECT has been suggested as an effective alternative local cancer therapy. However, a methodology is not established, and mechanisms are not well studied. In vivo studies were conducted to evaluate the effectiveness of ECT on animal tumor models. Radiation-induced fibrosarcomas were implanted subcutaneously in 157 female C3H/HeJ mice. Larger rat fibrosarcomas were implanted on 34 female Fisher 344 rats. When the spheroidal tumors reached 10 mm in the mice, two to five platinum electrodes were inserted into the tumors at various spacings and orientations. Ten rats in a pilot group were treated when their ellipsoidal tumors were about 25 mm long; electrode insertion was similar to the later part of the mouse study; i.e., two at the base and two at the center. A second group of 24 rats was treated with six or seven electrodes when their tumors were about 20 mm long; all electrodes were inserted at the tumor base. Of the 24 rats, 12 of these were treated once, 10 were treated twice, and 2 were treated thrice. All treated tumors showed necrosis and regression for both mice and rats; however, later tumor recurrence reduced long-term survival. When multiple treatments were implemented, the best 3 month mouse tumor cure rate was 59.3%, and the best 6 month rat tumor cure rate was 75.0%. These preliminary results indicate that ECT is effective on the radiation-induced fibrosarcoma (RIF-1) mouse tumor and rat fibrosarcoma. The effectiveness is dependent on electrode placement and dosage.

  19. 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.

  20. 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

  1. 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.

  2. Chemical and electrochemical study of fabrics coated with reduced graphene oxide

    NASA Astrophysics Data System (ADS)

    Molina, J.; Fernndez, J.; del Ro, A. I.; Bonastre, J.; Cases, F.

    2013-08-01

    Polyester fabrics coated with reduced graphene oxide (RGO) have been obtained and later characterized by means of chemical and electrochemical techniques. X-ray photoelectron spectroscopy showed a decrease of the oxygen content as well as an increase of the sp2 fraction after chemical reduction of graphene oxide (GO). The electrical conductivity was measured by electrochemical impedance spectroscopy (EIS) and showed a decrease of 5 orders of magnitude in the resistance (?) when GO was reduced to RGO. The phase angle also changed from 90 for PES-GO (capacitative behavior) to 0 for RGO coated fabrics (resistive behavior). In general an increase in the number of RGO layers produced an increase of the conductivity of the fabrics. EIS measurements in metal/sample/electrolyte configuration showed better electrocatalytic properties and faster diffusion rate for RGO specimens. Scanning electrochemical microscopy was employed to test the electroactivity of the different fabrics obtained. The sample coated with GO was not conductive since negative feedback was obtained. When GO was reduced to RGO the sample behaved like a conducting material since positive feedback was obtained. Approach curves indicated that the redox mediator had influence on the electrochemical response. The Fe(CN)63-/4- redox mediator produced a higher electrochemical response than Ru(NH3)63+/2+ one.

  3. 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.

  4. Electrochemical treatment of cork boiling wastewater with a boron-doped diamond anode.

    PubMed

    Fernandes, Annabel; Santos, Diana; Pacheco, Maria José; Ciríaco, Lurdes; Simões, Rogério; Gomes, Arlindo C; Lopes, Ana

    2015-01-01

    Anodic oxidation at a boron-doped diamond anode of cork boiling wastewater was successfully used for mineralization and biodegradability enhancement required for effluent discharge or subsequent biological treatment, respectively. The influence of the applied current density (30-70 mA/cm2) and the background electrolyte concentration (0-1.5 g/L Na2SO4) on the performance of the electrochemical oxidation was investigated. The supporting electrolyte was required to achieve conductivities that enabled anodic oxidation at the highest current intensities applied. The results indicated that pollutant removal increased with the applied current density, and after 8 h, reductions greater than 90% were achieved for COD, dissolved organic carbon, total phenols and colour. The biodegradability enhancement was from 0.13 to 0.59 and from 0.23 to 0.72 for the BOD/COD ratios with BOD of 5 and 20 days' incubation period, respectively. The tests without added electrolyte were performed at lower applied electrical charges (15 mA/cm2 or 30 V) with good organic load removal (up to 80%). For an applied current density of 30 mA/cm2, there was a minimum of electric conductivity of 1.9 mS/cm (corresponding to 0.75 g/L of Na2SO4), which minimized the specific energy consumption. PMID:25409580

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

    DOEpatents

    Rieke, Peter C. (Pasco, WA); Coffey, Gregory W. (Richland, WA); Pederson, Larry R. (Kennewick, WA); Marina, Olga A. (Richland, WA); Hardy, John S. (Richland, WA); Singh, Prabhaker (Richland, WA); Thomsen, Edwin C. (Richland, WA)

    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.

  6. 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.

  7. 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.

  8. Electrochemical treatment of industrial wastewater containing 5-amino-6-methyl-2-benzimidazolone: toward an electrochemical-biological coupling.

    PubMed

    Torres, Ricardo A; Sarria, Victor; Torres, Walter; Peringer, Paul; Pulgarin, Cesar

    2003-07-01

    We studied the electrochemical oxidation, on Pt anodes, of industrial wastewaters containing 5-amino-6-methyl-2-benzimidazolone (AMBI). Electrolysis of this non-biodegradable effluent produces simultaneous oxidation of AMBI and chloride ions. Highly oxidative chlorine intermediate species further boost the degradation of AMBI. Solution temperature, pH and current density affect little the degradation of AMBI. At our best conditions, AMBI was 100% degraded in 45 min. However, because the reaction intermediates exhibited high toxicity and non-biodegradability, the electrolysis had to continue for 3 more hours in order to obtain a biocompatible solution. Then, complete mineralization of the outputs from the electrolytic cells was readily achieved in a fixed bed biological reactor. PMID:14509698

  9. Modified cermet fuel electrodes for solid oxide electrochemical cells

    DOEpatents

    Ruka, Roswell J. (Churchill Boro, PA); Spengler, Charles J. (Murrysville, PA)

    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.

  10. 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

  11. 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.

  12. 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

  13. Coating of tips for electrochemical scanning tunneling microscopy by means of silicon, magnesium, and tungsten oxides.

    PubMed

    Salerno, Marco

    2010-09-01

    Different combinations of metal tips and oxide coatings have been tested for possible operation in electrochemical scanning tunneling microscopy. Silicon and magnesium oxides have been thermally evaporated onto gold and platinum-iridium tips, respectively. Two different thickness values have been explored for both materials, namely, 40 and 120 nm for silicon oxide and 20 and 60 nm for magnesium oxide. Alternatively, tungsten oxide has been grown on tungsten tips via electrochemical anodization. In the latter case, to seek optimal results we have varied the pH of the anodizing electrolyte between one and four. The oxide coated tips have been first inspected by means of scanning electron microscopy equipped with microanalysis to determine the morphological results of the coating. Second, the coated tips have been electrically characterized ex situ for stability in time by means of cyclic voltammetry in 1 M aqueous KCl supporting electrolyte, both bare and supplemented with K(3)[Fe(CN)(6)] complex at 10 mM concentration in milliQ water as an analyte. Only the tungsten oxide coated tungsten tips have shown stable electrical behavior in the electrolyte. For these tips, the uncoated metal area has been estimated from the electrical current levels, and they have been successfully tested by imaging a gold grating in situ, which provided stable results for several hours. The successful tungsten oxide coating obtained at pH=4 has been assigned to the WO(3) form. PMID:20886983

  14. Coating of tips for electrochemical scanning tunneling microscopy by means of silicon, magnesium, and tungsten oxides

    NASA Astrophysics Data System (ADS)

    Salerno, Marco

    2010-09-01

    Different combinations of metal tips and oxide coatings have been tested for possible operation in electrochemical scanning tunneling microscopy. Silicon and magnesium oxides have been thermally evaporated onto gold and platinum-iridium tips, respectively. Two different thickness values have been explored for both materials, namely, 40 and 120 nm for silicon oxide and 20 and 60 nm for magnesium oxide. Alternatively, tungsten oxide has been grown on tungsten tips via electrochemical anodization. In the latter case, to seek optimal results we have varied the pH of the anodizing electrolyte between one and four. The oxide coated tips have been first inspected by means of scanning electron microscopy equipped with microanalysis to determine the morphological results of the coating. Second, the coated tips have been electrically characterized ex situ for stability in time by means of cyclic voltammetry in 1 M aqueous KCl supporting electrolyte, both bare and supplemented with K3[Fe(CN)6] complex at 10 mM concentration in milliQ water as an analyte. Only the tungsten oxide coated tungsten tips have shown stable electrical behavior in the electrolyte. For these tips, the uncoated metal area has been estimated from the electrical current levels, and they have been successfully tested by imaging a gold grating in situ, which provided stable results for several hours. The successful tungsten oxide coating obtained at pH=4 has been assigned to the WO3 form.

  15. Morphological and Electrochemical Properties of Crystalline Praseodymium Oxide Nanorods

    PubMed Central

    2010-01-01

    Highly crystalline Pr6O11 nanorods were prepared by a simple precipitation method of triethylamine complex at 500C. Synthesized Pr6O11 nanorods were uniformly grown with the diameter of 1215 nm and the length of 100150 nm without any impurities of unstable PrO2 phase. The Pr6O11 nanorod electrodes attained a high electrical conductivity of 0.954 Scm?1 with low activation energy of 0.594 eV at 850C. The electrochemical impedance study showed that the resistance of electrode was significantly decreased at high temperature, which resulted from its high conductivity and low activation energy. The reduced impedance and high electrical conductivity of Pr6O11 nanorod electrodes are attributed to the reduction of grain boundaries and high space charge width. PMID:20672103

  16. Electrochemical Deposition of Iron Nanoneedles on Titanium Oxide Nanotubes

    SciTech Connect

    Gan Y. X.; Zhang L.; Gan B.J.

    2011-10-01

    Iron as a catalyst has wide applications for hydrogen generation from ammonia, photodecomposition of organics, and carbon nanotube growth. Tuning the size and shape of iron is meaningful for improving the catalysis efficiency. It is the objective of this work to prepare nanostructured iron with high surface area via electrochemical deposition. Iron nanoneedles were successfully electrodeposited on Ti supported TiO2 nanotube arrays in a chlorine-based electrolyte containing 0.15 M FeCl2 {center_dot} 4H2O and 2.0 M HCl. Transmission electron microscopic analysis reveals that the average length of the nanoneedles is about 200 nm and the thickness is about 10 nm. It has been found that a high overpotential at the cathode made of Ti/TiO2 nanotube arrays is necessary for the formation of the nanoneedles. Cyclic voltammetry test indicates that the electrodeposition of iron nanoneedles is a concentration-limited process.

  17. Tin Oxide Nanorod Array-Based Electrochemical Hydrogen Peroxide Biosensor

    NASA Astrophysics Data System (ADS)

    Liu, Jinping; Li, Yuanyuan; Huang, Xintang; Zhu, Zhihong

    2010-07-01

    SnO2 nanorod array grown directly on alloy substrate has been employed as the working electrode of H2O2 biosensor. Single-crystalline SnO2 nanorods provide not only low isoelectric point and enough void spaces for facile horseradish peroxidase (HRP) immobilization but also numerous conductive channels for electron transport to and from current collector; thus, leading to direct electrochemistry of HRP. The nanorod array-based biosensor demonstrates high H2O2 sensing performance in terms of excellent sensitivity (379 ?A mM-1 cm-2), low detection limit (0.2 ?M) and high selectivity with the apparent Michaelis-Menten constant estimated to be as small as 33.9 ?M. Our work further demonstrates the advantages of ordered array architecture in electrochemical device application and sheds light on the construction of other high-performance enzymatic biosensors.

  18. 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.

  19. A combined CaO/electrochemical treatment of the landfill leachate from different sanitary landfills in Croatia.

    PubMed

    Orescanin, Visnja; Kollar, Robert; Ruk, Damir; Nad, Karlo; Mikulic, Nenad

    2012-01-01

    The aim of this research was development of appropriate procedure for the treatment of landfill leachate taken from the Visevac, Mraclinska Dubrava and Piskornica sanitary landfills. Due to the complex nature of the effluents a combined treatment approach was applied. The pretreatment step included simultaneous treatment with calcium oxide and electrocoagulation/electrooxidation by stainless steel electrode set. The main treatment included electrocoagulation/electrooxidation using the set of stainless steel, iron and aluminum electrodes. The pretreatment allowed the destruction and/or coagulation of the high molecular weight organic substances as well as optimization of pH values for the formation of reactive oxidative species, and the transformation of NH(4)-N into volatile NH(3)-N. In the presence of added calcium oxide and electrochemically generated coagulant the removal of the fluorides, phosphates and heavy metals occur through the formation of poorly soluble fluorapatite, hydroxyl apatite, and various hydroxides. During the main treatment electrochemically generated reactive oxidative species carried out rapid decomposition of the organic matter and ammonia, resulting in the removal of COD from 74.9% to 94.2%, color from 98.8% to 99.7%, turbidity from 98.4% to 99.3%, suspended solids from 97.1% to 99.3%, and ammonia from 99.6% to 99.7%. Slightly better results for the removal efficiency of color, turbidity and suspended solids were obtained in the case of Piskornica landfill compared with the other two landfills, while the COD removal efficiency decreases in the following order: Piskornica >Mraclinska Dubrava >Visevac. This could be related to the age of the landfill, which increases in the same order. Consequently, with the increasing age of the landfill the degree of degradability of the organic matter reduces significantly. Applied treatment approach resulted in clear, colorless and odorless effluent with the values of all measured parameters significantly lower compared to the upper permissible limit for discharge into the environment. PMID:22755521

  20. 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

  1. Chitosan/graphene oxide nanocomposite films with enhanced interfacial interaction and their electrochemical applications

    NASA Astrophysics Data System (ADS)

    He, Linghao; Wang, Hongfang; Xia, Guangmei; Sun, Jing; Song, Rui

    2014-09-01

    A series of chitosan (CS) nanocomposites incorporated with graphene oxide (GO) nanosheets were facilely prepared by sonochemical method. Characterized by scanning electron microscopy, the obtained nanocomposites showed fine dispersion of GO in the CS matrix. Meanwhile, a marked interfacial interaction was also revealed as the values of glass transition temperature, the decomposition temperature and the storage modulus were significantly increased with the addition of GO. Furthermore, the well dispersed GO nanosheets could significantly improve the electrochemical activity of the CS as demonstrated by the electrochemical behaviors of pure CS and the GO/CS composite electrodes. Hence, the GO/CS nanocomposites film could be a promising candidate in the fabrication of electrochemical biosensors.

  2. Characterization of the catalytic films formed on stainless steel anodes employed for the electrochemical treatment of cuprocyanide wastewaters.

    PubMed

    Szpyrkowicz, Lidia; Ricci, Francesco; Montemor, M Ftima; Souto, Ricardo M

    2005-03-17

    Surface composition changes at stainless steel anodes in an electrochemical reactor applied for the electrochemical treatment of cuprocyanide-containing wastewaters operating under different hydrodynamic conditions were investigated. Under highly alkaline conditions in situ generation of a surface film on the anode with catalytic properties towards cyanide electrolysis was observed. X-ray photoelectron spectroscopy (XPS) results demonstrated that only copper oxi-hydroxide compounds constitute the surface film developed on the stainless steel anodes, as no traces of N- and C-containing compounds were observed. The collected XPS spectra revealed relevant details concerning the oxidation states of copper in the film, and the products Cu2O, CuO and Cu(OH)2 were identified on the surface of the anodes. However, the quantitative proportions of the individual products differ and depend on the type of mixing employed during reactor operation. PMID:15752859

  3. Influence of electrolytes (TEABF4 and TEMABF4) on electrochemical performance of graphite oxide derived from needle coke.

    PubMed

    Yang, Sunhye; Kim, Ick-Jun; Choi, In-Sik; Bae, Mi-Kyeong; Kim, Hyun-Soo

    2013-05-01

    The structure of needle coke was changed to graphite oxide structure after oxidation treatment with 70 wt.% of nitric acid and sodium chlorate (NaClO3), and the inter-layer distance of the oxidized needle coke was expanded to 6.9 angstroms. The first charge profile of the oxidized needle coke-cell with 1.2 M TEMABF4/acetonitrile solution displayed that the intercalation of electrolyte ions into the inter-layer occurred at 1.0 V, which value is lower than 1.3 V of the oxidized needle coke-cell with 1.2 M TEABF4/acetonitrile solution. After first charge/discharge, the cell using TEMABF4 electrolyte exhibited smaller electrode resistance of 0.05 omega, and larger specific volume capacitance of 25.5 F/ml at the two-electrode system in the potential range 0-2.5 V than those of the cell using TEABF4 electrolyte. Compared to the TEABF4 electrolyte, better electrochemical performance of the TEMABF4 electrolyte in the oxidized needle coke may be caused by the smaller cation (TEMA+) size and better ion mobility in the nanopores between inter-layers. PMID:23858941

  4. Catalytic oxidation of anionic surfactants by electrochemical oxidation with CuO-Co2O3-PO4(3-) modified kaolin.

    PubMed

    Gu, Lin; Wang, Bo; Ma, Hongzhu; Kong, Wuping

    2006-09-21

    A new catalytic oxidation of anionic surfactants by electrochemistry method was designed and used to investigate the removal of anionic surfactant from simulated wastewater. Synergetic effect on COD removal was studied when integrating the electrochemical reactor, using porous graphite as anode and cathode, with the effective CuO-Co2O3-PO4(3-) modified kaolin catalyst in a single undivided cell. The result showed that this combined process could effectively remove anionic surfactant. Its COD removal efficiency was much higher than those individual processes and could reach up to 90% in 60 min. The operating parameters such as initial pH, cell voltage, and current intensity were also investigated. Possible theory for COD removal was also proposed to predict the role of modified kaolin, electro-catalysis and oxidation in the combined process. The pollutants in wastewater could be decreased by the high reactive OH* that produced on the surface of catalyst by the decomposition of electrochemical generated H2O2. The result indicates that the catalytic oxidation by electrochemistry method is a promising wastewater treatment technique. PMID:16621257

  5. ENGINEERING BULLETIN: CHEMICAL OXIDATION TREATMENT

    EPA Science Inventory

    Oxidation destroys hazardous contaminants by chemically converting them to nonhazardous or less toxic compounds that are ideally more stable, less mobile, and/or inert. However, under some conditions, other hazardous compounds may be formed. The oxidizing agents most commonly use...

  6. 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

  7. 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 ? ?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).

  8. 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

  9. Destruction of hazardous and mixed wastes using mediated electrochemical oxidation in a Ag(II)HNO3 bench scale system

    SciTech Connect

    Balazs, B.; Chiba, Z.; Hsu, P.; Lewis, P.; Murguia, L.; Adamson, M.

    1997-02-01

    Mediated Electrochemical Oxidation (MEO) is a promising technology for the destruction of organic containing wastes and the remediation of mixed wastes containing transuranic components. The combination of a powerful oxidant and an acid solution allows the conversion of nearly all organics, whether present in hazardous or in mixed waste, to carbon dioxide. Insoluble transuranics are dissolved in this process and may be recovered by separation and precipitation. The oxidant, or mediator, is a multivalent transition metal ion which is cleanly recycled in a number of charge transfer steps in an electrochemical cell. The MEO technique offers several advantages which are inherent in the system. First, the oxidation/dissolution processes are accomplished at near ambient pressures and temperatures (30-70{degrees}C). Second, all waste stream components and oxidation products (with the exception of evolved gases) are contained in an aqueous environment. This electrolyte acts as an accumulator for inorganics which were present in the original waste stream, and the large volume of electrolyte provides a thermal buffer for the energy released during oxidation of the organics. Third, the generation of secondary waste is minimal, as the process needs no additional reagents. Finally, the entire process can be shut down by simply turning off the power, affording a level of control unavailable in some other techniques. Although the oxidation of organics and the dissolution of transuranics by higher valency metal ions has been known for some time, applying the MEO technology to waste treatment is a relatively recent development. Numerous groups, both in the United States and Europe, have made substantial progress in the last decade towards understanding the mechanistic pathways, kinetics, and engineering aspects of the process. At Lawrence Livermore National Laboratory, substantial contributions have been made to this knowledge base in these areas and others. Conceptual design and engineering development have been completed for a pilot plant-scale MEO system, and numerous data have been gathered on the efficacy of the process for a wide variety of anticipated waste components. This presentation will review the data collected at LLNL for a bench scale system based primarily on the use of a Ag(II) mediator in a nitric acid electrolyte; results from several other mediator/acid combinations will be included. Data obtained on the chemical, electrochemical, and engineering aspects will be presented. The topics of organics destruction, transuranic recovery, and some of the ancillary systems will be addressed, and areas requiring further study will be mentioned.

  10. 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

  11. 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

  12. 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.

  13. Electrochemically deposited gallium oxide nanostructures on silicon substrates.

    TOXLINE Toxicology Bibliographic Information

    Ghazali NM; Mahmood MR; Yasui K; Hashim AM

    2014-01-01

    We report a synthesis of ?-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. ?-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.

  14. 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 ?-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. ?-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.

  15. Electrochemically deposited gallium oxide nanostructures on silicon substrates

    PubMed Central

    2014-01-01

    We report a synthesis of ?-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. ?-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

  16. 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.

  17. Macroporous metal oxides: Synthesis, characterization and application in catalysis and electrochemical power sources

    NASA Astrophysics Data System (ADS)

    Sokolov, Sergey

    New approaches to the synthesis of magnesium, aluminum and nickel oxides with three-dimensionally ordered macroporous (3DOM) structure by colloidal crystal templating were explored. Such metal oxides were characterized by powder X-ray diffraction, scanning and transmission electron microscopy, thermogravimetric analysis, differential scanning calorimetry and nitrogen gas adsorption. Interconnected macropores, either organized in periodic arrays or positioned randomly, varied in diameter from 275 to 950 nm. The effect of the pore size on sintering behavior of the material was studied on macroporous alpha-Al2O3. Having a free diffusion path inherent to 3DOM structure, such morphology offers the advantage of highly accessible surfaces, which makes it an interesting candidate for catalyst supports. A silver catalyst supported on 3DOM alpha-Al 2O3 was tested in epoxidation of ethylene and its performance was compared to that of the catalyst prepared on commercial alumina support. The procedure successfully used for the preparation of macroporous alpha-Al 2O3 was adopted for the synthesis of 3DOM lithium aluminates. Namely, a mixture of LiAl5O8 and gamma-LiAlO 2, as well as pure beta- and gamma-LiAlO2 phases were obtained. Correlations between the manner in which the lithium precursor was introduced, the molar ratio between lithium and aluminum precursors, the heat treatment conditions and the morphology and phase composition of the product were established. With their open pore structures and thin walls, these materials may have potential applications as breeder materials for fusion reactors or as ceramic matrixes in molten carbonate fuel cells. As a part of a related project targeting a nano-assembled lithium solid state battery, proposed cathode material, LiCoO2, was obtained in a form of macroporous thin films prepared by electrostatic spray deposition on Pt-coated quartz substrates and electrochemical measurements were performed on these films.

  18. Electrochemical synthesis of oxide thick film on the stabilized zirconia surface in molten salt

    SciTech Connect

    Shan, Y.J.; Nakamura, Tetsuro; Inaguma, Yoshiyuki; Itoh, Mitsuru

    1995-07-01

    A new method for the electrochemical synthesis of oxide thick film in molten salt was developed. The following galvanic cell was assembled, and the electrolysis was carried out at 973 K: Pt, metal{vert_bar}(50{minus}x/2) mole percent (m/o) KCl{minus}(50{minus}x/2) m/o NaCl{minus}x m/o additive{vert_bar}(O{sup 2{minus}})YSZ{vert_bar}O{sub 2}, Pt where the additive was an oxide or a chloride containing the metal ions of the anode. When the additive was dissolved and ionized in the molten salt, its oxide film formed on the stabilized zirconia surface. At this time, metal ions derived from the additive were carried to the stabilized zirconia surface under an electric field, and reacted with oxide ions, coming from the oxygen electrode through zirconia solid electrolyte, to form the oxide film.

  19. Electrochemical oxidation of ?Am(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

  20. 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).

  1. A Molecularly Imprinted Polymer with Incorporated Graphene Oxide for Electrochemical Determination of Quercetin

    PubMed Central

    Sun, Si; Zhang, Mengqi; Li, Yijun; He, Xiwen

    2013-01-01

    The molecularly imprinted polymer based on polypyrrole film with incorporated graphene oxide was fabricated and used for electrochemical determination of quercetin. The electrochemical behavior of quercetin on the modified electrode was studied in detail using differential pulse voltammetry. The oxidation peak current of quercetin in B-R buffer solution (pH = 3.5) at the modified electrode was regressed with the concentration in the range from 6.0 10?7 to 1.5 10?5 mol/L (r2 = 0.997) with a detection limit of 4.8 10?8 mol/L (S/N = 3). This electrode showed good stability and reproducibility. In the above mentioned range, rutin or morin which has similar structures and at the same concentration as quercetin did not interfere with the determination of quercetin. The applicability of the method for complex matrix analysis was also evaluated. PMID:23698263

  2. 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).

  3. Glucose oxidase catalysed oxidation of glucose in a dialysis membrane electrochemical reactor (D-MER).

    PubMed

    Bassguy, R; Dlcouls-Servat, K; Bergel, A

    2004-04-01

    The purpose of this work was to evaluate the effectiveness of a new Membrane Electrochemical Reactor (MER) for the production of gluconic acid by glucose oxidase (GOD) catalysed glucose oxidation. The GOD was confined against the electrode surface with a dialysis membrane. The role of the electrochemical step was to eliminate by oxidation the hydrogen peroxide that appeared as a by-product of the reaction and strongly inhibited and/or inactivated GOD. The dialysis MER gave a transformation ratio of 30% with an initial glucose concentration of around 300 mM. This result is significantly better than the maximum of 10% obtained when hydrogen peroxide was eliminated by addition of a large excess of catalase in solution, as is generally done. The D-MER also revealed unexpected properties of the enzyme kinetics, such as an oscillatory behaviour, which were discussed. PMID:15015074

  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. Surface protonation and electrochemical activity of oxides in aqueous solution

    SciTech Connect

    Goodenough, J.B.; Manoharan, R.; Paranthaman, M. )

    1990-03-14

    Measurements of the pH dependence of the surface-charge density on oxide particles are correlated with the pH dependence of the cyclic voltammograms and of the chemical activity of the oxide for electrolysis/fuel cell reactions. Studies of the pyrochlores Pb{sub 2}M{sub 2{minus}x}Pb{sub x}O{sub 7{minus}y} and the rutiles in MO{sub 2} (M = Ru or Ir) and of the perovskite Sr{sub 1{minus}x}NbO{sub 3{minus}{delta}} show that (1) the oxygen-reduction reaction, found on the pyrochlores in alkaline solution, occurs by exchange of a surface OH{sup {minus}} species at an O{prime} site with an adsorbed O{sub 2}{sup {minus}} solution species, (2) the oxygen-evolution and chlorine-evolution reactions occur at a surface O{sup {minus}} species made accessible by surface oxidation of a redox couple lying close to the top of the O{sup 2{minus}}:2p{sup 6} valence band, and (3) the hydrogen-evolution reaction occurs at the surface OH{sub 2} species bonded to cations with a surface redox couple lying close to the H{sup +}/H{sub 2} level in solution.

  6. Electrochemical activation of Cp* iridium complexes for electrode-driven water-oxidation catalysis.

    PubMed

    Thomsen, Julianne M; Sheehan, Stafford W; Hashmi, Sara M; Campos, Jess; Hintermair, Ulrich; Crabtree, Robert H; Brudvig, Gary W

    2014-10-01

    Organometallic iridium complexes bearing oxidatively stable chelate ligands are precursors for efficient homogeneous water-oxidation catalysts (WOCs), but their activity in oxygen evolution has so far been studied almost exclusively with sacrificial chemical oxidants. In this report, we study the electrochemical activation of Cp*Ir complexes and demonstrate true electrode-driven water oxidation catalyzed by a homogeneous iridium species in solution. Whereas the Cp* precursors exhibit no measurable O2-evolution activity, the molecular species formed after their oxidative activation are highly active homogeneous WOCs, capable of electrode-driven O2 evolution with high Faradaic efficiency. We have ruled out the formation of heterogeneous iridium oxides, either as colloids in solution or as deposits on the surface of the electrode, and found indication that the conversion of the precursor to the active molecular species occurs by a similar process whether carried out by chemical or electrochemical methods. This work makes these WOCs more practical for application in photoelectrochemical dyads for light-driven water splitting. PMID:25188635

  7. 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

  8. 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.

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

    DOEpatents

    Balazs, G. Bryan (Livermore, CA); Lewis, Patricia R. (Livermore, CA)

    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.

  10. Assessment of Electrodes Prepared from Wafers of Boron-doped Diamond for the Electrochemical Oxidation of Waste Lubricants

    SciTech Connect

    Taylor, G.T.; Sullivan, I.A.; Newey, A.W.E.

    2006-07-01

    Electrochemical oxidation using boron-doped diamond electrodes is being investigated as a treatment process for radioactively contaminated oily wastes. Previously, it was shown that electrodes coated with a thin film of diamond were able to oxidise a cutting oil but not a mineral oil. These tests were inconclusive, because the electrodes lost their diamond coating during operation. Accordingly, an electrode prepared from a 'solid' wafer of boron-doped diamond is being investigated to determine whether it will oxidise mineral oils. The electrode has been tested with sucrose, a cutting oil and an emulsified mineral oil. Before and after each test, the state of the electrode was assessed by cyclic voltammetry with the ferro/ferricyanide redox couple. Analysis of the cyclic voltammogram suggested that material accumulated on the surface of the electrode during the tests. The magnitude of the effect was in the order: - emulsified mineral oil > cutting oil > sucrose. Despite this, the results indicated that the electrode was capable of oxidising the emulsified mineral oil. Confirmatory tests were undertaken in the presence of alkali to trap the carbon dioxide, but they had to be abandoned when the adhesive holding the diamond in the electrode was attacked by the alkali. Etching of the diamond wafer was also observed at the end of the tests. Surface corrosion is now regarded as an intrinsic part of the electrochemical oxidation on diamond, and it is expected that the rate of attack will determine the service life of the electrodes. (authors)

  11. Radiofrequency-oxidation treatment of sewage sludge.

    PubMed

    Srinivasan, Asha; Young, Chris; Liao, Ping H; Lo, Kwang V

    2015-12-01

    A novel thermal-chemical treatment technology using radiofrequency heating and oxidants (hydrogen peroxide, ozone and a combination of both) was used for the treatment of sewage sludge. This was to evaluate the process effectiveness on cell disintegration and nutrient release of sludge, physical property changes such as particle size distribution, dewaterability and settleability, and their inter-relationships. The effectiveness of treatment processes was in the following order, from the most to least: thermal-oxidation process, oxidation process and thermal process. The thermal-oxidation process greatly increased cell disintegration and nutrient release, improved settleability, and decreased particle sizes. The treatment scheme involving ozone addition followed by hydrogen peroxide and radiofrequency heating yielded the highest soluble chemical oxygen demand, volatile fatty acids, ammonia and metals, while proffering the shortest capillary suction time and excellent settling properties. PMID:26233925

  12. 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

  13. 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.

  14. 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.

  15. 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

  16. 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.

  17. 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)

  18. 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

  19. 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.

  20. 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.

  1. 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.

  2. 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.

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

    PubMed

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

    2015-08-21

    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. PMID:26196857

  4. A graphene oxide-based electrochemical sensor for sensitive determination of 4-nitrophenol.

    PubMed

    Li, Junhua; Kuang, Daizhi; Feng, Yonglan; Zhang, Fuxing; Xu, Zhifeng; Liu, Mengqin

    2012-01-30

    A graphene oxide (GO) film coated glassy carbon electrode (GCE) was fabricated for sensitive determination of 4-nitrophenol (4-NP). The GO-based sensor was characterized by scanning electron microscope, atomic force microscopy and electrochemical impedance spectroscopy. The electrochemical behaviors of 4-NP at the GO-film coated GCE were investigated in detail. In 0.1M acetate buffer with a pH of 4.8, 4-NP yields a very sensitive and well-defined reduction peak at the GO-modified GCE. It is found that the GO film exhibits obvious electrocatalytic activity toward the reduction of 4-NP since it not only increases the reduction peak current but also lowers the reduction overpotential. Based on this, an electrochemical method was proposed for the direct determination of 4-NP. Various kinetic parameters such as transfer electron number, transfer proton number and standard heterogeneous rate constant were calculated, and various experimental parameters were also optimized. Under the optimal conditions, the reduction peak current varies linearly with the concentration of 4-NP ranging from 0.1 to 120 ?M, and the detection limit is 0.02 ?M at the signal noise ratio of 3. Moreover, the fabricated sensor presented high selectivity and long-term stability. This electrochemical sensor was further applied to determine 4-NP in real water samples, and it showed great promise for simple, sensitive, and quantitative detection of 4-NP. PMID:22178284

  5. 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

  6. Oxidative particle mixtures for groundwater treatment

    DOEpatents

    Siegrist, Robert L.; Murdoch, Lawrence C.

    2000-01-01

    The invention is a method and a composition of a mixture for degradation and immobilization of contaminants in soil and groundwater. The oxidative particle mixture and method includes providing a material having a minimal volume of free water, mixing at least one inorganic oxidative chemical in a granular form with a carrier fluid containing a fine grained inorganic hydrophilic compound and injecting the resulting mixture into the subsurface. The granular form of the inorganic oxidative chemical dissolves within the areas of injection, and the oxidative ions move by diffusion and/or advection, therefore extending the treatment zone over a wider area than the injection area. The organic contaminants in the soil and groundwater are degraded by the oxidative ions, which form solid byproducts that can sorb significant amounts of inorganic contaminants, metals, and radionuclides for in situ treatment and immobilization of contaminants. The method and composition of the oxidative particle mixture for long-term treatment and immobilization of contaminants in soil and groundwater provides for a reduction in toxicity of contaminants in a subsurface area of contamination without the need for continued injection of treatment material, or for movement of the contaminants, or without the need for continuous pumping of groundwater through the treatment zone, or removal of groundwater from the subsurface area of contamination.

  7. In situ DNA oxidative damage by electrochemically generated hydroxyl free radicals on a boron-doped diamond electrode.

    PubMed

    Oliveira, S Carlos B; Oliveira-Brett, Ana Maria

    2012-03-13

    In situ DNA oxidative damage by electrochemically generated hydroxyl free radicals has been directly demonstrated on a boron-doped diamond electrode. The DNA-electrochemical biosensor incorporates immobilized double-stranded DNA (dsDNA) as molecular recognition element on the electrode surface, and measures in situ specific binding processes with dsDNA, as it is a complementary tool for the study of bimolecular interaction mechanisms of compounds binding to DNA and enabling the screening and evaluation of the effect caused to DNA by radicals and health hazardous compounds. Oxidants, particularly reactive oxygen species (ROS), play an important role in dsDNA oxidative damage which is strongly related to mutagenesis, carcinogenesis, autoimmune inflammatory, and neurodegenerative diseases. The hydroxyl radical is considered the main contributing ROS to endogenous oxidation of cellular dsDNA causing double-stranded and single-stranded breaks, free bases, and 8-oxoguanine occurrence. The dsDNA-electrochemical biosensor was used to study the interaction between dsDNA immobilized on a boron-doped diamond electrode surface and in situ electrochemically generate hydroxyl radicals. Non-denaturing agarose gel-electrophoresis of the dsDNA films on the electrode surface after interaction with the electrochemically generated hydroxyl radicals clearly showed the occurrence of in situ dsDNA oxidative damage. The importance of the dsDNA-electrochemical biosensor in the evaluation of the dsDNA-hydroxyl radical interactions is clearly demonstrated. PMID:22335175

  8. Development of an Electrochemical Oxidation Method for Probing Higher Order Protein Structure with Mass Spectrometry

    SciTech Connect

    McClintock, Carlee; Kertesz, Vilmos; Hettich, Robert {Bob} L

    2008-01-01

    We report here the novel use of electrochemistry to generate covalent oxidative labels on intact proteins in both non-native and physiologically relevant solutions as a surface mapping probe of higher order protein structure. Two different electrodes were tested across a range of experimental parameters including voltage, flow rate, and solution electrolyte composition to affect the extent of oxidation on intact proteins, as measured both on-line and off-line with mass spectrometry. Oxidized proteins were collected off-line for proteolytic digestion followed by LC-MS/MS analysis. Peptide MS/MS data were searched with the InsPecT scoring algorithm for forty-six oxidative mass shifts previously reported in the literature. Preliminary data showed agreement between solvent accessibility and the oxidation status of many ubiquitin residues in aqueous buffer, while more buried residues were found to be oxidized in non-native solution. Our results indicate that electrochemical oxidation using a boron-doped diamond electrode has the potential to become a useful and easily accessible tool for conducting oxidative surface mapping experiments.

  9. Changes in the redox state of iridium oxide clusters and their relation to catalytic water oxidation. Radiolytic and electrochemical studies

    SciTech Connect

    Nahor, G.S.; Hapiot, P.; Neta, P. ); Harriman, A. )

    1991-01-24

    Radiolytically prepared iridium oxide (IrO{sub x}{center dot}nH{sub 2}O) clusters have been shown to catalyze the photochemical oxidation of water. These catalysts have been oxidized by radiolytic or electrochemical methods and the changes in their optical absorptions and redox states have been studied. The clusters contain four or five Ir atoms in a mixture of Ir{sup III} and Ir{sup IV} states, formally described as Ir{sup 3.2+}. Time-resolved pulse-radiolytic studies revealed three processes in the subsecond time scale. The first step produces a short-lived intermediate ({lambda}{sub max} {approximately} 360 nm), possibly an OH adduct, that is transformed to more stable oxidized species ({lambda}{sub max} 340 and 580 nm). In the third step, there is a rise in the 580-nm absorption. The same species were observed in {gamma}-radiolysis and in spectroelectrochemical experiments. Cyclic voltammetric and coulometric measurements suggest that the initial IrO{sub x} cluster is oxidized in two stages, from Ir{sup 3.2+} to Ir{sup 3.8+} and then to Ir{sup 4+}. Further oxidation of the cluster leads to oxidation of water to O{sub 2}.

  10. 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.

  11. Influence of synthesis conditions on the electrochemical properties of nanostructured amorphous manganese oxide cryogels

    NASA Astrophysics Data System (ADS)

    Yang, Jingsi; Xu, Jun John

    Amorphous manganese oxides have received increasing attention in recent years as intercalation cathodes for rechargeable lithium batteries. The sol-gel method is a versatile method for achieving nanostructured amorphous oxides. In this paper, two different sol-gel routes are investigated, where nanostructured amorphous manganese oxide cryogels are obtained via freeze drying Mn(IV) oxide hydrogels formed in situ. In one route the hydrogels are formed by reaction between a solution of sodium permanganate and a solution of disodium fumarate, and in the other route by reaction between a solution of sodium permanganate and solid fumaric acid. Highly homogeneous monolithic manganese oxide hydrogels are obtained from both synthesis routes with precursor concentrations between 0.1 and 0.2 M. The freeze drying method proves to be an efficient method for obtaining nanostructured amorphous manganese oxide cryogels out of the hydrogels. Depending on the synthesis conditions of the hydrogels, the resultant cryogels can yield very high specific capacities for lithium intercalation and excellent rate performance. The cryogel with the best performance exhibits 289 mAh/g at a C/100 rate and 174 mAh/g at a 2 C rate. Strong dependence of electrochemical properties of the cryogels on the synthesis conditions of the parent hydrogels has been observed. The different electrochemical properties are believed to be due to different surface areas and local structures of the cryogels derived from hydrogels synthesized under different conditions. This strong dependence gives rise to the possibility of achieving promising intercalation materials through tailoring the surface area and the local structure of amorphous manganese oxides by adjusting sol-gel synthesis conditions.

  12. 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

  13. Electrochemical degradation of polycyclic aromatic hydrocarbons in creosote solution using ruthenium oxide on titanium expanded mesh anode.

    PubMed

    Tran, Lan-Huong; Drogui, Patrick; Mercier, Guy; Blais, Jean-Franois

    2009-05-30

    In this study, expanded titanium (Ti) covered with ruthenium oxide (RuO(2)) electrode was used to anodically oxidize polycyclic aromatic hydrocarbons (PAH) in creosote solution. Synthetic creosote-oily solution (COS) was prepared with distilled water and a commercial creosote solution in the presence of an amphoteric surfactant; Cocamidopropylhydroxysultaine (CAS). Electrolysis was carried out using a parallelepipedic electrolytic 1.5-L cell containing five anodes (Ti/RuO(2)) and five cathodes (stainless steel, 316 L) alternated in the electrode pack. The effects of initial pH, temperature, retention time, supporting electrolyte, current density and initial PAH concentration on the process performance were examined. Experimental results revealed that a current density of 9.23 mA cm(-2) was beneficial for PAH oxidation. The sum of PAH concentrations for 16 PAHs could be optimally diminished up to 80-82% while imposing a residence time in the electrolysis cell of 90 min. There was not a significant effect of the electrolyte (Na(2)SO(4)) concentration on oxidation efficiency in the investigated range of 500-4000 mg/L. However, an addition of 500 mg Na(2)SO(4)L(-1) was required to reduce the energy consumption and the treatment cost. Besides, there was no effect of initial PAH concentration on oxidation efficiency in the investigated range of 270-540 mg PAHL(-1). Alkaline media was not favourable for PAH oxidation, whereas high performance of PAH degradation could be recorded without initial pH adjustment (original pH around 6.0). Likewise, under optimal conditions, 84% of petroleum hydrocarbon (C(10)-C(50)) was removed, whereas removal yields of 69% and 62% have been measured for O&G and COD, respectively. Microtox and Daphnia biotests showed that electrochemical oxidation using Ti/RuO(2) could be efficiently used to reduce more than 90% of the COS toxicity. PMID:18926633

  14. 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.

  15. Co-Ni alloy nanowires prepared by anodic aluminum oxide template via electrochemical deposition.

    PubMed

    Kwag, Yong-Gyu; Ha, Jong-Keun; Kim, Hye-Sung; Cho, Hyoung-Jin; Cho, Kwon-Koo

    2014-12-01

    The alloy nanowires are more prospective magnetic and shape memory materials. Fabrication of binary or more alloy nanowires using electrochemical deposition process is generally challenging due to the different synthesis conditions of individual elements. In the present work, binary NiCo alloy nanowire arrays have been fabricated by electrochemical deposition using anodic aluminum oxide template medium technique. The optimum conditions (temperature, voltage and time) for synthesis of NiCo alloy nanowire array were achieved based on the ideal experimental conditions of single Ni and Co nanowire arrays. The synthesized NiCo alloy nanowire arrays were characterized by X-ray diffraction, field emission scanning electron microscopy and energy dispersive X-ray spectrometer. The amorphous NiCo alloy nanowires were crystallized by annealing of 800 degrees C for 1 hour in argon atmosphere. The controlled composition of electrolyte provided to achieve a uniformly distributed chemical composition of Ni and Co (49.26:50.74) in nanowires. PMID:25970984

  16. Superior Catalytic Activity of Electrochemically Reduced Graphene Oxide Supported Iron Phthalocyanines toward Oxygen Reduction Reaction.

    PubMed

    Liu, Dong; Long, Yi-Tao

    2015-11-01

    Structure and surface properties of supporting materials are of great importance for the catalytic performance of the catalysts. Herein, we prepared the iron phthalocyanine (FePc) functionalized electrochemically reduced graphene oxide (ERGO) by the electrochemical reduction of FePc/GO. The resultant FePc/ERGO exhibits higher catalytic activity toward ORR than that of FePc/graphene. More importantly, the onset potential for ORR at FePc/ERGO positively shifts by 45 mV compared with commercial Pt/C in alkaline media. Besides, FePc/ERGO displays enhanced durability and selectivity toward ORR. The superior catalytic performance of FePc/ERGO for ORR are ascribed to the self-supported structure of ERGO, uniformly morphology and size of FePc nanoparticles. PMID:26477473

  17. 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.

  18. Electrochemical treatment of simulated textile wastewater with industrial components and Levafix Blue CA reactive dye: optimization through response surface methodology.

    PubMed

    Körbahti, Bahadir K; Tanyolaç, Abdurrahman

    2008-03-01

    The electrochemical oxidation of simulated textile wastewater was studied on iron electrodes in the presence of NaCl electrolyte in a batch electrochemical reactor. The simulated textile wastewater was prepared from industrial components based on the real mercerized and non-mercerized cotton and viscon process, being first in literature. The highest COD, color and turbidity removals were achieved as 93.9%, 99.5%, and 82.9%, respectively, at 40% pollution load, 8 V applied potential, 37.5 g/L electrolyte concentration and 30 degrees C reaction temperature. The electrochemical treatment of industrial textile wastewater was optimized using response surface methodology (RSM), where applied potential and electrolyte concentration were to be minimized while COD, color and turbidity removal percents were maximized at 100% pollution load. In a specific batch run under the optimum conditions of 30 degrees C reaction temperature, 25 g/L electrolyte concentration and 8 V applied potential applied with 35.5 mA/cm2 current density at 100% pollution load, COD, color and turbidity removals were realized as 61.6%, 99.6% and 66.4%, respectively. PMID:17656018

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

    PubMed

    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

  20. 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.

  1. 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 electronhole 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

  2. 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 19 mM and 0.5100 ?M, 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 ?M for AA and DA, respectively. PMID:25195850

  3. 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

  4. 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.

  5. Field emission characteristics of electrochemically synthesized nickel nanowires with oxygen plasma post-treatment

    NASA Astrophysics Data System (ADS)

    Joo, Jinsoo; Lee, Sun Jeong; Park, Dong Hyuk; Kim, Young Soo; Lee, Yeonhee; Lee, Cheol Jin; Lee, Seong-Rae

    2006-07-01

    The field emissive, electrical, magnetic, and structural characteristics of nickel (Ni) nanowires synthesized using the electrochemical deposition method with an alumina nanoporous template are reported. The synthesis and formation of Ni nanowires were confirmed by XRD, SEM, and HR-TEM experiments. Ferromagnetic hysteresis curves and the metallic temperature dependence of the current-voltage characteristics were observed for the Ni nanowire systems. The nanotip emitters of the field emission cells of the Ni nanowires after O2 plasma treatment were easily patterned using the solution drop casting (SDC) method, in which the Ni nanowires were homogeneously dispersed in organic solvents, and then dropped and dried on an n-type doped Si substrate as the cathode. For the O2 plasma treated Ni nanowires, we observed that the inhomogeneous oxidized layer on their surface was reduced, that the current density of the field emission cell increased from ~3.0 10-9 to ~1.0 10-3 A cm-2 due to field emission, and that the lowest threshold electric field was ~4 V m-1. The field enhancement factor was estimated as ~1300 for the O2 plasma treated Ni nanowires. The evolution of the field emission obtained from the phosphor screen was observed at different applied electric fields.

  6. 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

  7. 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.

  8. 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.

  9. Oxidation of coals in the course of mechanical treatment

    SciTech Connect

    A.G. Proidakov; G.A. Kalabin

    2009-04-15

    The results of a study of coal oxidation under stationary conditions and during mechanical treatment are presented. A considerable increase in the reaction rate constants of coal oxidation during mechanical treatment because of oxidative mechanical degradation was found.

  10. Enhanced catalytic and dopamine sensing properties of electrochemically reduced conducting polymer nanocomposite doped with pure graphene oxide.

    PubMed

    Wang, Wenting; Xu, Guiyun; Cui, Xinyan Tracy; Sheng, Ge; Luo, Xiliang

    2014-08-15

    Significantly enhanced catalytic activity of a nanocomposite composed of conducting polymer poly (3,4-ethylenedioxythiophene) (PEDOT) doped with graphene oxide (GO) was achieved through a simple electrochemical reduction process. The nanocomposite (PEDOT/GO) was electrodeposited on an electrode and followed by electrochemical reduction, and the obtained reduced nanocomposite (PEDOT/RGO) modified electrode exhibited lowered electrochemical impedance and excellent electrocatalytic activity towards the oxidation of dopamine. Based on the excellent catalytic property of PEDOT/RGO, an electrochemical sensor capable of sensitive and selective detection of DA was developed. The fabricated sensor can detect DA in a wide linear range from 0.1 to 175?M, with a detection limit of 39nM, and it is free from common interferences such as uric acid and ascorbic acid. PMID:24632460

  11. 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

  12. Indirect electrochemical treatment of bisphenol A in water via electrochemically generated Fenton's reagent.

    PubMed

    Gzmen, Belgin; Oturan, Mehmet A; Oturan, Nihal; Erbatur, Oktay

    2003-08-15

    Bisphenol A (BPA) has been treated with electrochemically generated Fenton's reagent in aqueous medium. Hydroxyl radicals that were formed in Fenton's reagent reacted with the organic substrate producing two different isomers of monohydroxylated product and, upon successive hydroxylation, mainly one dihydroxylated product. Further hydroxylation first degraded one of the aromatic rings, and the side chain thus formed was then cleaved off the other aromatic ring. The second aromatic ring was also degraded upon successive hydroxylations. Small saturated and unsaturated aliphatic acids were the last products prior to mineralization. It was found that use of cuprous/cupric ion pair resulted a faster conversion of BPA and faster mineralization when compared using ferrous/ferric ions, but this happened at the expence of excess electrical charge utilized for an equivalent conversion or mineralization. Degradation by using ferrous/ferric ions was more efficient than cuprous/cupric ions case in terms of total mineralization versus charge utilized, and a mineralization of 82% had been achieved by applying 107.8 mF of charge to a 0.7 mM BPA solution of 0.200 dm3. The rate constant of the monohydroxylation of BPA in the presence of ferrous/ferric ions had been determined as 1.0 x 10(10) M(-1) s(-1) where BPA and salicylic acid competitively reacted with hydroxyl radicals in aqueous medium with the initial concentrations of Fe2+, BPA, and SA of 1.0, 0.5, and 0.5 mM, respectively. In a similar experiment where the initial concentrations of Cu2+, BPA, and SA were 1.0, 0.5, and 0.5 mM, respectively, the corresponding rate constant was determined to be the same as the rate constant obtained for Fe2+ (i.e., 1.0 x 10(10) M(-1) s(-1)). While the use of Cu2+ cannot be advised for processing BPA and similar substrates by using the electro-Fenton technique for both technical and economical reasons, the use of [Fe2+]/[BPA]0 values in the range 3-4 will be sufficient to achieve an efficient mineralization of BPA and similar substrates by the electro-Fenton process in aqueous medium. PMID:12953886

  13. 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.

  14. Modelling temporal kinetic oscillations for electrochemical oxidation of formic acid on Pt

    NASA Astrophysics Data System (ADS)

    Okamoto, Hiroshi; Tanaka, Naoki; Naito, Masayoshi

    1996-01-01

    A model is presented which suitably reproduces the observed kinetic potential oscillations for the electrochemical oxidation of formic acid on Pt. Coupled ordinary differential equations are formulated concerning three variables: the electrode potential and the amounts of adsorbed water and carbon monoxide. Two points prove to be essential in this model to an obtain oscillation behavior similar to the observed behavior: the interaction between the two adsorbed species increases with the electrode potential and the saturation surface coverage of the adsorbed carbon monoxide is less than 1. These two points are consistent with experimental observations.

  15. 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

  16. 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.

  17. Electrochemical Processes for In-Situ Treatment of Contaminated Soils - Final Report - 09/15/1996 - 01/31/2001

    SciTech Connect

    Huang, Chin-Pao

    2001-05-31

    This project will study electrochemical processes for the in situ treatment of soils contaminated by mixed wastes, i.e., organic and inorganic. Soil samples collected form selected DOE waste sites will be characterized for specific organic and metal contaminants and hydraulic permeability. The soil samples are then subject to desorption experiments under various physical-chemical conditions such as pH and the presence of surfactants. Batch electro-osmosis experiments will be conducted to study the transport of contaminants in the soil-water systems. Organic contaminants that are released from the soil substrate will be treated by an advanced oxidation process, i.e., electron-Fantan. Finally, laboratory reactor integrating the elector-osmosis and elector-Fantan processes will be used to study the treatment of contaminated soil in situ.

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

    PubMed

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

    2015-01-01

    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 193.7F/g highly specific capacitance of nanocomposite film is achieved at a current density of 500mA/g. This flexible and self-supporting nanocomposite film exhibits excellent cycling stability, and the capacity retention is 90.6% after 1000cycles, which shows promising application as high-performance electrode materials for flexible energy-storage devices. PMID:26019698

  19. Fabrication of highly catalytic silver nanoclusters/graphene oxide nanocomposite as nanotag for sensitive electrochemical immunoassay.

    PubMed

    Wang, Jiamian; Wang, Xiuyun; Wu, Shuo; Song, Jie; Zhao, Yanqiu; Ge, Yanqiu; Meng, Changgong

    2016-02-01

    Silver nanoclusters and graphene oxide nanocomposite (AgNCs/GRO) is synthesized and functionalized with detection antibody for highly sensitive electrochemical sensing of carcinoembryonic antigen (CEA), a model tumor marker involved in many cancers. AgNCs with large surface area and abundant amount of low-coordinated sites are synthesized with DNA as template and exhibit high catalytic activity towards the electrochemical reduction of H2O2. GRO is employed to assemble with AgNCs because it has large specific surface area, super electronic conductivity and strong ?-? stacking interaction with the hydrophobic bases of DNA, which can further improve the catalytic ability of the AgNCs. Using AgNCs/GRO as signal amplification tag, an enzyme-free electrochemical immunosensing protocol is designed for the highly sensitive detection of CEA on the capture antibody functionalized immunosensing interface. Under optimal conditions, the designed immunosensor exhibits a wide linear range from 0.1pgmL(-1) to 100ngmL(-1) and a low limit of detection of 0.037pgmL(-1). Practical sample analysis reveals the sensor has good accuracy and reproducibility, indicating the great application prospective of the AgNCs/GRO in fabricating highly sensitive immunosensors, which can be extended to the detection of various kinds of low abundance disease related proteins. PMID:26772127

  20. Simple and label-free electrochemical impedance Amelogenin gene hybridization biosensing based on reduced graphene oxide.

    PubMed

    Benvidi, Ali; Rajabzadeh, Nooshin; Mazloum-Ardakani, Mohammad; Heidari, Mohammad Mehdi; Mulchandani, Ashok

    2014-08-15

    The increasing desire for sensitive, easy, low-cost, and label free methods for the detection of DNA sequences has become a vital matter in biomedical research. For the first time a novel label-free biosensor for sensitive detection of Amelogenin gene (AMEL) using reduced graphene oxide modified glassy carbon electrode (GCE/RGO) has been developed. In this work, detection of DNA hybridization of the target and probe DNA was investigated by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). The optimum conditions were found for the immobilization of probe on RGO surface and its hybridization with the target DNA. CV and EIS carried out in an aqueous solution containing [Fe(CN)6](3-/4-) redox pair have been used for the biosensor characterization. The biosensor has a wide linear range from 1.010(-20) to 1.010(-14)M with the lower detection limit of 3.210(-21)M. Moreover, the present electrochemical detection offers some unique advantages such as ultrahigh sensitivity, simplicity, and feasibility for apparatus miniaturization in analytical tests. The excellent performance of the biosensor is attributed to large surface-to-volume ratio and high conductivity of RGO, which enhances the probe absorption and promotes direct electron transfer between probe and the electrode surface. This electrochemical DNA sensor could be used for the detection of specific ssDNA sequence in real biological samples. PMID:24632459

  1. 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.

  2. 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

  3. 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.

  4. 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 ?M, high sensitivity of 162.69 ?A mM(-1) cm(-2), and wide linear range of 0.05 ?M-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

  5. Summary technical report on the electrochemical treatment of alkaline nuclear wastes

    SciTech Connect

    Hobbs, D.T.

    1994-07-30

    This report summarizes the laboratory studies investigating the electrolytic treatment of alkaline solutions carried out under the direction of the Savannah River Technology Center from 1985-1992. Electrolytic treatment has been demonstrated at the laboratory scale to be feasible for the destruction of nitrate and nitrite and the removal of radioactive species such as {sup 99}Tc and {sup 106}Ru from Savannah River Site (SRS) decontaminated salt solution and other alkaline wastes. The reaction rate and current efficiency for the removal of these species are dependent on cell configuration, electrode material, nature of electrode surface, waste composition, current density, and temperature. Nitrogen, ammonia, and nitrous oxide have been identified as the nitrogen-containing reaction products from the electrochemical reduction of nitrate and nitrite under alkaline conditions. The reaction mechanism for the reduction is very complex. Voltammetric studies indicated that the electrode reactions involve surface phenomena and are not necessarily mass transfer controlled. In an undivided cell, results suggest an electrocatalytic role for oxygen via the generation of the superoxide anion. In general, more efficient reduction of nitrite and nitrate occurs at cathode materials with higher overpotentials for hydrogen evolution. Nitrate and nitrite destruction has also been demonstrated in engineering-scale flow reactors. In flow reactors, the nitrate/nitrite destruction efficiency is improved with an increase in the current density, temperature, and when the cell is operated in a divided cell configuration. Nafion{reg_sign} cation exchange membranes have exhibited good stability and consistent performance as separators in the divided-cell tests. The membranes were also shown to be unaffected by radiation at doses approximating four years of cell operation in treating decontaminated salt solution.

  6. Electrochemical oxidation of tramadol in low-salinity reverse osmosis concentrates using boron-doped diamond anodes.

    PubMed

    Lütke Eversloh, Christian; Schulz, Manoj; Wagner, Manfred; Ternes, Thomas A

    2015-04-01

    The electrochemical treatment of low-salinity reverse osmosis (RO) concentrates was investigated using tramadol (100 μM) as a model substance for persistent organic contaminants. Galvanostatic degradation experiments using boron-doped diamond electrodes at different applied currents were conducted in RO concentrates as well as in ultra-pure water containing either sodium chloride or sodium sulfate. Kinetic investigations revealed a significant influence of in-situ generated active chlorine besides direct anodic oxidation. Therefore, tramadol concentrations decreased more rapidly at elevated chloride content. Nevertheless, reduction of total organic carbon (TOC) was found to be comparatively low, demonstrating that transformation rather than mineralization was taking place. Early stage product formation could be attributed to both direct and indirect processes, including demethylation, hydroxylation, dehydration, oxidative aromatic ring cleavage and halogenation reactions. The latter led to various halogenated derivatives and resulted in AOX (adsorbable organic halogens) formation in the lower mg/L-range depending on the treatment conditions. Characterisation of transformation products (TPs) was achieved via MS(n) experiments and additional NMR measurements. Based on identification and quantification of the main TPs in different matrices and on additional potentiostatic electrolysis, a transformation pathway was proposed. PMID:25660808

  7. 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 mol1). This significant energy reduction opens routes to the development of nonaqueous hydrogen energy technology. PMID:24720359

  8. 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.

  9. 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

  10. Electrochemical and electrochromic properties of niobium oxide thin films fabricated by pulsed laser deposition

    SciTech Connect

    Fu, Z.W.; Kong, J.J.; Qin, Q.Z.

    1999-10-01

    Niobium oxide thin films have been successfully fabricated on the indium-tin oxide coated glasses by pulsed laser deposition in an O{sub 3}/O{sub 2} gas mixture. Films are characterized by X-ray diffraction and Raman spectrometry. Electrochemical and electrochromic properties of Nb{sub 2}O{sub 5} films are examined by cyclic voltammogram and potential step coupled with an in situ charge-coupled device spectrophotometer. The unique characteristics of absorption spectra of Nb{sub 2}O{sub 5} films are observed for the first time, and the optical absorption from the trapped electrons in the surface states plays an important role in the electrochromic phenomenon.

  11. Electrochemical investigation of polyhalide ion oxidation-reduction on carbon nanotube electrodes for redox flow batteries

    SciTech Connect

    Shao, Yuyan; Engelhard, Mark H.; Lin, Yuehe

    2009-10-01

    Polyhalide ions (Br-/BrCl2-) are an important redox couple for redox flow batteries. The oxidation-reduction behavior of polyhalide ions on a carbon nanotube (CNT) electrode has been investigated with cyclic voltammetry and electrochemical impedance spectroscopy. The onset oxidation potential of Br-/BrCl2- is negatively shifted by >100 mV, and the redox current peaks are greatly enhanced on a CNT electrode compared with that on the most widely-used graphite electrode. The reaction resistance of the redox couple (Br-/BrCl2-) is decreased on a CNT electrode. The redox reversibility is increased on a CNT electrode even though it still needs further improvement. CNT is a promising electrode material for redox flow batteries.

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

    PubMed

    Moreira, Rebeca; Schtz, 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

  13. In-situ generated H?O? induced efficient visible light photo-electrochemical catalytic oxidation of PCP-Na with TiO?.

    PubMed

    Liu, Wei; Liu, Huichao; Ai, Zhihui

    2015-05-15

    In this study, we developed a novel photo-electrochemical catalytic oxidation wastewater treatment system by interacting the cathodic in-situ generated H?O? with TiO? suspension to form interfacial ? Ti(IV)OOH species, which endowed the PEC system with superior efficiency for degrading sodium pentachlorophenate (PCP-Na) under visible light irradiation at neutral pH. The apparent PCP-Na degradation rate constant of the PEC system was more than 10 times that of the electrochemical oxidation counterpart. In the PEC system, the interfacial ? Ti(IV)OOH species injected electrons to the conduction band of TiO? to initiate the activation of O? and the in-situ generated H?O? adsorbed on the surface of TiO?, lead to producing reactive oxygen species of superoxide anions and hydroxyl radicals, which were responsible for the dechlorination and mineralization of PCP-Na during the PEC process, respectively. The dosage of TiO? catalyst and the current intensity applied on PCP-Na degradation were optimized. This study develops a high efficient PEC oxidation system for wastewater treatment and provides new insight into the role of cathodic in-situ generated H?O? on PEC oxidation of PCP-Na with TiO? under visible light irradiation. PMID:25698570

  14. Evidence for Decoupled Electron and Proton Transfer in the Electrochemical Oxidation of Ammonia on Pt(100).

    PubMed

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

    2016-02-01

    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 that incorporates a deprotonation step occurring prior to the electron transfer. The deprotonation step yields a negatively charged surface-adsorbed species that 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. Ammonia oxidation is a new example of a bond-forming reaction on (100) terraces that involves decoupled proton-electron transfer. PMID:26757266

  15. 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

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

    DOEpatents

    Balachandran, Uthamalingam (Hinsdale, IL); Poeppel, Roger B. (Glen Ellyn, IL); Kleefisch, Mark S. (Naperville, IL); Kobylinski, Thaddeus P. (Lisle, IL); Udovich, Carl A. (Joliet, IL)

    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.

  17. 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

  18. 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.

  19. Effect of nitro substituent on electrochemical oxidation of phenols at boron-doped diamond anodes.

    PubMed

    Jiang, Yi; Zhu, Xiuping; Li, Hongna; Ni, Jinren

    2010-02-01

    In order to investigate nitro-substitutent's effect on degradation of phenols at boron-doped diamond (BDD) anodes, cyclic voltammetries of three nitrophenol isomers: 2-nitrophenol (2NP), 3-nitrophenol (3NP) and 4-nitrophenol (4NP) were studied, and their bulk electrolysis results were compared with phenol's (Ph) under alkaline condition. The voltammetric study showed nitrophenols could be attacked by hydroxyl radicals and nitro-group was released from the aromatic ring. Results of bulk electrolysis showed degradation of all phenols were fit to a pseudo first-order equation and followed in this order: 2NP>4NP>3NP>Ph. Molecular structures, especially carbon atom charge, significantly influenced the electrochemical oxidation of these isomers. Intermediates were analyzed during the electrolysis process, and were mainly catechol, resorcinol, hydroquinone, and carboxylic acids, such as acetic acid and oxalic acid. A simple degradation pathway was proposed. Moreover, a linear increasing relationship between degradation rates and Hammett constants of the studied phenols was observed, which demonstrated that electrochemical oxidation of these phenols was mainly initiated by electrophilic attack of hydroxyl radicals at BDD anodes. PMID:20060999

  20. Processing, microstructural evolution and electrochemical performance relationships in solid oxide fuel cells

    NASA Astrophysics Data System (ADS)

    Sarikaya, Ayhan

    The relationships between the processing parameters, microstructures and electrochemical performance of solid oxide fuel cell (SOFC) components were investigated. The operating regimes (i.e., reducing vs. oxidizing) as well as the elevated temperatures (e.g. 800C) for their operation introduce several material challenges. Therefore, composite materials are employed to withstand operating conditions while providing sufficient electrochemical performance for fuel cell operation. Analyses on lanthanum-strontium manganite (LSM) - yttria stabilized zirconia (YSZ) compositions (45 vol%-55 vol%) by impedance spectroscopy demonstrated that two competing polarization mechanisms (i.e. charge-exchange and surface adsorption-diffusion of oxygen) limit performance. Optimization of microstructures resulted in total resistances as low as 0.040 Ohm cm2. Studies on Ag composites revealed that incorporation of up to 25 vol% oxide particles (LSM and YSZ) with sizes comparable to the Ag grains (~0.5 microm) can minimize the densification and coarsening of the Ag matrix. While the powder based oxide additions increased the stability limit of porous Ag composites from <550C to 800C, the use of nanostructured coatings increased the stability limit to 900C for cathodes and current collectors. Investigations of Ni-YSZ anode microstructures demonstrated that uniform distribution of percolating isometric pores (>5 microm) allows forming desired continuous percolation of all phases (Ni, YSZ and pores) lowering activation polarization below 0.100 Ohm cm2 and maintaining significant electrical conductivity (>1000 S/cm). Identification of polarization mechanisms by deconvolution of impedance spectra and tailoring the corresponding microstructures was demonstrated as an effective method for optimization of SOFC components.

  1. Microwave oxidation treatment of sewage sludge.

    PubMed

    Lo, Kwang V; Srinivasan, Asha; Liao, Ping H; Bailey, Sam

    2015-01-01

    Microwave-oxidation treatment of sewage sludge using various oxidants was studied. Two treatment schemes with a combination of hydrogen peroxide and ozone were examined: hydrogen peroxide and ozone were introduced into the sludge simultaneously, followed by microwave heating. The other involved the ozonation first, and then the resulting solution was subjected to microwave and hydrogen peroxide treatment. The set with ozonation followed by hydrogen peroxide plus microwave heating yielded higher soluble materials than those of the set with hydrogen peroxide plus ozone first and then microwave treatment. No settling was observed for all treatments in the batch operation, except ozone/microwave plus hydrogen peroxide set at 120°C. The pilot-scale continuous-flow 915 MHz microwave study has demonstrated that microwave-oxidation process is feasible for real-time industrial application. It would help in providing key data for the design of a full-scale system for treating sewage sludge and the formulation of operational protocols. PMID:26030695

  2. 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 113% 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 500C. 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 600C.

  3. 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

  4. Electrochemical properties of iron oxides/carbon nanotubes as anode material for lithium ion batteries

    NASA Astrophysics Data System (ADS)

    Zeng, Zhipeng; Zhao, Hailei; Lv, Pengpeng; Zhang, Zijia; Wang, Jie; Xia, Qing

    2015-01-01

    A composited anode material with combined Fe3O4/FeO nanotube and carbon shell is synthesized by a facile hydrothermal method with subsequent CVD heat treatment. The as-prepared Fe3O4/FeO/C composite shows excellent cycle stability and rate capability as lithium ion battery anode. We study the effect of FeO on the electrochemical performances of the Fe3O4/FeO/C electrode. A capacity climbing phenomenon can be observed for the Fe3O4/FeO/C electrodes, which tends to be more evident with increasing FeO content. The "extra capacity" is correlated with the reversible formation of polymeric gel-like film on the particle surface of active materials, which is electrochemical active towards Li ions. The FeO component presents a certain extent of catalytic role in assisting the formation of the gel-like film. Transmission electron microscope (TEM) and electrochemical impedance spectroscopy (EIS) analytical technique are combined to further confirm the reversible growth of the SEI gel-like film. High temperature promotes the formation of gel-like film, while the resistance from the film decreases remarkably with temperature due to the enhanced lithium ion conductivity. The film contributes little to the whole EIS resistance of Fe3O4/FeO nanotube/carbon electrode. Tentative explanations based on the current experiments and existing literature are made to explain such unusual finding.

  5. Use of electrochemical oxidation and model peptides to study nucleophilic biological targets of reactive metabolites: the case of rimonabant.

    PubMed

    Thorsell, Annika; Isin, Emre M; Jurva, Ulrik

    2014-10-20

    Electrochemical oxidation of drug molecules is a useful tool to generate several different types of metabolites. In the present study we developed a model system involving electrochemical oxidation followed by characterization of the oxidation products and their propensity to modify peptides. The CB1 antagonist rimonabant was chosen as the model drug. Rimonabant has previously been shown to give high covalent binding to proteins in human liver microsomes and hepatocytes and the iminium ion and/or the corresponding aminoaldehyde formed via P450 mediated ?-carbon oxidation of rimonabant was proposed to be a likely contributor. This proposal was based on the observation that levels of covalent binding were significantly reduced when iminium species were trapped as cyanide adducts but also following addition of methoxylamine expected to trap aldehydes. Incubation of electrochemically oxidized rimonabant with peptides resulted in peptide adducts to the N-terminal amine with a mass increment of 64 Da. The adducts were shown to contain an addition of C5H4 originating from the aminopiperidine moiety of rimonabant. Formation of the peptide adducts required further oxidation of the iminium ion to short-lived intermediates, such as dihydropyridinium species. In addition, the metabolites and peptide adducts generated in human liver microsomes were compared with those generated by electrochemistry. Interestingly, the same peptide modification was found when rimonabant was coincubated with one of the model peptides in microsomes. This clearly indicated that reactive metabolite(s) of rimonabant identical to electrochemically generated species are also present in the microsomal incubations. In summary, electrochemical oxidation combined with peptide trapping of reactive metabolites identified a previously unobserved bioactivation pathway of rimonabant that was not captured by traditional trapping agents and that may contribute to the in vitro covalent binding. PMID:25210840

  6. Surface structure effects on the electrochemical oxidation of ethanol on platinum single crystal electrodes.

    PubMed

    Colmati, Flavio; Tremiliosi-Filho, Germano; Gonzalez, Ernesto R; Bern, Antonio; Herrero, Enrique; Feliu, Juan M

    2008-01-01

    Ethanol oxidation has been studied on Pt(111), Pt(100) and Pt(110) electrodes in order to investigate the effect of the surface structure and adsorbing anions using electrochemical and FTIR techniques. The results indicate that the surface structure and anion adsorption affect significantly the reactivity of the electrode. Thus, the main product of the oxidation of ethanol on the Pt(111) electrode is acetic acid, and acetaldehyde is formed as secondary product. Moreover, the amount of CO formed is very small, and probably associated with the defects present on the electrode surface. For that reason, the amount of CO2 is also small. This electrode has the highest catalytic activity for the formation of acetic acid in perchloric acid. However, the formation of acetic acid is inhibited by the presence of specifically adsorbed anions, such as (bi)sulfate or acetate, which is the result of the formation of acetic acid. On the other hand, CO is readily formed at low potentials on the Pt(100) electrode, blocking completely the surface. Between 0.65 and 0.80 V, the CO layer is oxidized and the production of acetaldehyde and acetic acid is detected. The Pt(110) electrode displays the highest catalytic activity for the splitting of the C-C bond. Reactions giving rise to CO formation, from either ethanol or acetaldehyde, occur at high rate at any potential. On the other hand, the oxidation of acetaldehyde to acetic acid has probably the lower reaction rate of the three basal planes. PMID:19213328

  7. In situ XPS studies of perovskite oxide surfaces under electrochemical polarization.

    PubMed

    Vovk, Greg; Chen, Xiaohua; Mims, Charles A

    2005-02-17

    An in situ XPS study of oxidation-reduction processes on three perovskite oxide electrode surfaces was carried out by incorporating the materials in an electrochemical cell mounted on a heated sample stage in an ultrahigh vacuum (UHV) chamber. Electrodes made of powdered LaCr(1-x)Ni(x)O(3-delta) (x = 0.4, 1) showed changes in the XPS features of all elements upon redox cycling between formal Ni3+ and Ni2+ oxidation stoichiometries, indicating the delocalized nature of the electronic states involved and strong mixing of O 2p to Ni 3d levels to form band states. The surface also showed changes in adsorption capacity for CO2 upon reduction as a result of increased nucleophilicity of surface oxygen. Another perovskite oxide, La(0.5)Sr(0.5)CoO(3-delta), laser deposited as highly oriented thin films on (100) oriented yttria-stabilized zirconia (YSZ), also showed evidence of both local and nonlocal effects in the XPS features upon redox cycling. In contrast to LaCr(1-x)Ni(x)O(3-delta), redox cycling mainly affected the XPS features of cobalt with little effect on oxygen. This signifies reduced participation of O 2p states in the conduction band of this material. Small changes in surface cation stoichiometry in this film were observed and attributed to mobility of the A-site Sr dopant under polarization. PMID:16851240

  8. 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.

  9. Study of degradation intermediates formed during electrochemical oxidation of pesticide residue 2,6-dichlorobenzamide (BAM) in chloride medium at boron doped diamond (BDD) and platinum anodes.

    PubMed

    Madsen, Henrik Tkker; Sgaard, Erik Gydesen; Muff, Jens

    2015-02-01

    For electrochemical oxidation to become applicable in water treatment outside of laboratories, a number of challenges must be elucidated. One is the formation and fate of degradation intermediates of targeted organics. In this study the degradation of the pesticide residue 2,6-dichlorobenzamide, an important groundwater pollutant, was investigated in a chloride rich solution with the purpose of studying the effect of active chlorine on the degradation pathway. To study the relative importance of the anodic oxidation and active chlorine oxidation in the bulk solution, a non-active BDD and an active Pt anode were compared. Also, the effect of the active chlorine oxidation on the total amount of degradation intermediates was investigated. We found that for 2,6-dichlorobenzamide, active chlorine oxidation was determining for the initial step of the degradation, and therefore yielded a completely different set of degradation intermediates compared to an inert electrolyte. For the Pt anode, the further degradation of the intermediates was also largely dependent on active chlorine oxidation, while for the BDD anode anodic oxidation was most important. It was also found that the presence of active chlorine led to fewer degradation intermediates compared to treatment in an inert electrolyte. PMID:25465959

  10. 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.

  11. 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

  12. 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

  13. 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.

  14. Conducting polypyrrole films as a potential tool for electrochemical treatment of azo dyes in textile wastewaters.

    PubMed

    Haque, Md Mominul; Smith, Warren T; Wong, Danny K Y

    2015-01-01

    In this paper, we demonstrate conducting polypyrrole films as a potential green technology for electrochemical treatment of azo dyes in wastewaters using Acid Red 1 as a model analyte. These films were synthesised by anodically polymerising pyrrole in the presence of Acid Red 1 as a supporting electrolyte. In this way, the anionic Acid Red 1 is electrostatically attracted to the cationic polypyrrole backbone formed to maintain electroneutrality, and is thus entrapped in the film. These Acid Red 1-entrapped polypyrrole films were characterised by electrochemical, microscopic and spectroscopic techniques. Based on a two-level factorial design, the solution pH, Acid Red 1 concentration and polymerisation duration were identified as significant parameters affecting the entrapment efficiency. The entrapment process will potentially aid in decolourising Acid Red 1-containing wastewaters. Similarly, in a cathodic process, electrons are supplied to neutralise the polypyrrole backbone, liberating Acid Red 1 into a solution. In this work, following an entrapment duration of 480 min in 2000 mg L(-1) Acid Red 1, we estimated 21% of the dye was liberated after a reduction period of 240 min. This allows the recovery of Acid Red 1 for recycling purposes. A distinctive advantage of this electrochemical Acid Red 1 treatment, compared to many other techniques, is that no known toxic by-products are generated in the treatment. Therefore, conducting polypyrrole films can potentially be applied as an environmentally friendly treatment method for textile effluents. PMID:25262487

  15. Layer by Layer Ex-Situ Deposited Cobalt-Manganese Oxide as Composite Electrode Material for Electrochemical Capacitor

    PubMed Central

    Rusi; Chan, P. Y.; Majid, S. R.

    2015-01-01

    The composite metal oxide electrode films were fabricated using ex situ electrodeposition method with further heating treatment at 300C. The obtained composite metal oxide film had a spherical structure with mass loading from 0.13 to 0.21 mg cm-2. The structure and elements of the composite was investigated using X-ray diffraction (XRD) and energy dispersive X-ray (EDX). The electrochemical performance of different composite metal oxides was studied by cyclic voltammetry (CV) and galvanostatic charge-discharge (CD). As an active electrode material for a supercapacitor, the Co-Mn composite electrode exhibits a specific capacitance of 285 Fg-1 at current density of 1.85 Ag-1 in 0.5M Na2SO4 electrolyte. The best composite electrode, Co-Mn electrode was then further studied in various electrolytes (i.e., 0.5M KOH and 0.5M KOH/0.04M K3Fe(CN) 6 electrolytes). The pseudocapacitive nature of the material of Co-Mn lead to a high specific capacitance of 2.2 x 103 Fg-1 and an energy density of 309 Whkg-1 in a 0.5MKOH/0.04MK3Fe(CN) 6 electrolyte at a current density of 10 Ag-1. The specific capacitance retention obtained 67% of its initial value after 750 cycles. The results indicate that the ex situ deposited composite metal oxide nanoparticles have promising potential in future practical applications. PMID:26158447

  16. Layer by Layer Ex-Situ Deposited Cobalt-Manganese Oxide as Composite Electrode Material for Electrochemical Capacitor.

    PubMed

    Rusi; Chan, P Y; Majid, S R

    2015-01-01

    The composite metal oxide electrode films were fabricated using ex situ electrodeposition method with further heating treatment at 300C. The obtained composite metal oxide film had a spherical structure with mass loading from 0.13 to 0.21 mg cm(-2). The structure and elements of the composite was investigated using X-ray diffraction (XRD) and energy dispersive X-ray (EDX). The electrochemical performance of different composite metal oxides was studied by cyclic voltammetry (CV) and galvanostatic charge-discharge (CD). As an active electrode material for a supercapacitor, the Co-Mn composite electrode exhibits a specific capacitance of 285 Fg(-1) at current density of 1.85 Ag(-1) in 0.5 M Na2SO4 electrolyte. The best composite electrode, Co-Mn electrode was then further studied in various electrolytes (i.e., 0.5 M KOH and 0.5 M KOH/0.04 M K3Fe(CN) 6 electrolytes). The pseudocapacitive nature of the material of Co-Mn lead to a high specific capacitance of 2.2 x 10(3) Fg(-1) and an energy density of 309 Whkg(-1) in a 0.5 M KOH/0.04 M K3Fe(CN) 6 electrolyte at a current density of 10 Ag(-1). The specific capacitance retention obtained 67% of its initial value after 750 cycles. The results indicate that the ex situ deposited composite metal oxide nanoparticles have promising potential in future practical applications. PMID:26158447

  17. Electrochemical incineration of wastes

    NASA Technical Reports Server (NTRS)

    Kaba, L.; Hitchens, G. D.; Bockris, J. O'M.

    1989-01-01

    A low temperature electrolysis process has been developed for the treatment of solid waste material and urine. Experiments are described in which organic materials are oxidized directly at the surface of an electrode. Also, hypochlorite is generated electrochemically from chloride component of urine. Hypochlorite can act as a strong oxidizing agent in solution. The oxidation takes place at 30-60 C and the gaseous products from the anodic reaction are carbon dioxide, nitrogen, oxygen. Hydrogen is formed at the cathode. Carbon monoxide, and nitrogen oxides and methane were not detected in the off gases. Chlorine was evolved at the anode in relatively low amounts.

  18. The kinetics and electrochemical rate-determining step of aqueous pyrite oxidation

    NASA Astrophysics Data System (ADS)

    Williamson, Mark A.; Rimstidt, J. Donald

    1994-12-01

    Rate data available in the literature have been compiled for the reaction of pyrite with dissolved oxygen (DO) to produce a rate law that is applicable over four orders of magnitude in DO concentration over the pH range 2-10. The valid rate law is ? where r is the rate of pyrite destruction in units of mol m -2 s -1. A series of batch and mixed flow reactor experiments were performed to determine the effect of SO 42-, Cl -, ionic strength, and dissolved oxygen on the rate of reaction of pyrite with ferric iron. Of these, only dissolved oxygen was found to have any appreciable effect. Experimental results of the present study were combined with kinetic data reported in the literature to formulate rate laws that are applicable over a six order of magnitude range in Fe 3+ and Fe 2+ concentration for the pH range 0.5-3.0. In N 2-purged solution, the rate law is ? and when dissolved oxygen is present, ? where r is the rate of pyrite destruction in mol m -2 s -1. Experiments were also performed in which a single pyrite sample was repeatedly reacted with ferric iron solutions of the same composition and identical surface area to mass of solution ratio (A/M). For each subsequent experiment, the rate of reaction slowed and the original behavior of the pyrite could not be reestablished by washing the pyrite with concentrated HNO3 or EDTA. This behavior was interpreted as representative of a change in the electrochemical properties of the solid pyrite. Pretreating pyrite samples with aqueous solutions of ferrous iron and EDTA did not change the reaction rate with ferric iron; however, pretreatment with hydroxylamine hydrochloride lowered the rate significantly. The data presented are best modeled by a nonsite-specific Freundlich multilayer isotherm. Good correlation was found between Eh and rate for the aqueous oxidation of pyrite with DO and ferric iron. Because the fractional orders of reaction are difficult to explain with a purely molecular-based mechanism, a cathodic-anodic electrochemical mechanism is favored to explain the transfer of the electron from pyrite to the aqueous oxidant. Mechanistically, the results of this study suggest a nonsite specific interaction between dissolved oxidants and the pyrite surface. Rate correlates strongly with Eh ({Fe3+}/{Fe2+} ratio or DO concentration) and is consistent with an electrochemical mechanism where anodic and cathodic reactions occur at different places on the pyrite surface.

  19. Enhanced Conversion Efficiency of Cu(In,Ga)Se2 Solar Cells via Electrochemical Passivation Treatment.

    PubMed

    Tsai, Hung-Wei; Thomas, Stuart R; Chen, Chia-Wei; Wang, Yi-Chung; Tsai, Hsu-Sheng; Yen, Yu-Ting; Hsu, Cheng-Hung; Tsai, Wen-Chi; Wang, Zhiming M; Chueh, Yu-Lun

    2016-03-30

    Defect control in Cu(In,Ga)Se2 (CIGS) materials, no matter what the defect type or density, is a significant issue, correlating directly to PV performance. These defects act as recombination centers and can be briefly categorized into interface recombination and Shockley-Read-Hall (SRH) recombination, both of which can lead to reduced PV performance. Here, we introduce an electrochemical passivation treatment for CIGS films that can lower the oxygen concentration at the CIGS surface as observed by X-ray photoelectron spectrometer analysis. Temperature-dependent J-V characteristics of CIGS solar cells reveal that interface recombination is suppressed and an improved rollover condition can be achieved following our electrochemical treatment. As a result, the surface defects are passivated, and the power conversion efficiency performance of the solar cell devices can be enhanced from 4.73 to 7.75%. PMID:26815164

  20. 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.

  1. 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

  2. [Treatment of Petrochemical Treatment Plant Secondary Effluent by Fenton Oxidation].

    PubMed

    Wang, Yi; Wu, Chang-yong; Zhou, Yue-xi; Zhang, Xue; Dong, Bo; Chen, Xue-min

    2015-07-01

    Fenton oxidation was applied to treat the petrochemical treatment plant secondary effluent by the continuous flow configuration. The effect of Fenton agent dosage on the COD and phosphorus removal and the variation of the dissolved organic matter characteristics during the treatment process were investigated. The results showed the average COD and PO(4)3- -P concentrations were 64.8 mg.L-1 and 0. 79 mg.L-1, respectively. When the dosage of H2O (30%), FeSO4.7H2O and PAM were 0. 4 mL.L-1, 0. 8 mg.L-1 and 0. 9 mg.L-1 and the residence time was 30 min, the average removal rate of COD and PO(4)3- -P were 24. 3% and 95. 5% respectively. The effluent COD was lower than 50 mg.L-1. The percentage of dissolved organic matters with molecular weight less than 1 x 10(3) was 80. 4% in the raw wastewater, however, the percentage increased to 95. 6% when treated by Fenton oxidation. Three-dimensional fluorescence analysis showed that the Fenton oxidation can effectively remove protein and phenols. GC-MS results showed that there were about 117 kinds of organic matters detected in the secondary effluent, while the number reduced to 27 after oxidation by Fenton. The organics containing unsaturated bond had a better removal than those of other types of organics. Fenton oxidation can be used in the advanced treatment of petrochemical secondary effluent. PMID:26489330

  3. 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.

  4. 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.

  5. Electrochemical deposition of silver on manganese dioxide coated reduced graphene oxide for enhanced oxygen reduction reaction

    NASA Astrophysics Data System (ADS)

    Lee, Kyungmi; Ahmed, Mohammad Shamsuddin; Jeon, Seungwon

    2015-08-01

    We have prepared a reduced graphene oxide (rGO)-supported silver (Ag) and manganese dioxide (MnO2) deposited porous-like catalyst (denoted as rGO/MnO2/Ag) through a facile electrochemical deposition route and have been used as a cathode catalyst for oxygen reduction reaction (ORR) in alkaline fuel cells. The physical properties of rGO/MnO2/Ag have been investigated via several instrumental methods. This material exhibits a polycrystalline structure characterized by Ag/MnO2 microsphere formation as a result of Ostwald ripening. The X-ray diffraction and X-ray photoelectron spectroscopy data reveal that the MnO2 and Ag have been slightly alloyed and Mn presents with the dioxide form on rGO. The electrochemical properties of the electrocatalyst have been studied via several voltammetric methods. The results demonstrated that the rGO/MnO2/Ag has an excellent catalytic activity for ORR in alkaline media compared to the other tested electrodes. Particularly, it shows 1.2 times higher current density and better electron transfer rate at 0.3 V per O2 than that of 20 wt% Pt/C. The other kinetic analysis reveals that the O2 has reduced directly to H2O through a nearly four-electron pathway with better anodic fuel tolerance and duration performance than that of 20% Pt/C.

  6. 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 M 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

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

    NASA Astrophysics Data System (ADS)

    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 (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.

  8. 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

  9. 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

  10. Behavior of molybdenum nitrides as materials for electrochemical capacitors: Comparison with ruthenium oxide

    SciTech Connect

    Liu, T.C.; Pell, W.G.; Conway, B.E.; Roberson, S.L.

    1998-06-01

    Ruthenium oxide (RuO{sub 2}), formed as a thin film on a Ru or Ti metal substrate, exhibits a large specific (cm{sup {minus}2}) and almost constant, electrochemical capacitance over a 1.35 V range in aqueous H{sub 2}SO{sub 4}. This behavior has led to its investigation and use as a material for fabrication of supercapacitor devices. However, its cost has encouraged search for other materials exhibiting similar behavior. Work reported in the present paper evaluates two nitrides of Mo, Mo{sub 2}N and MoN, as substitutes for RuO{sub 2}. It is shown that very similar capacitance behavior to that of RuO{sub 2} films arises, e.g., in cyclic voltammetry and dc charging curves; in the former, almost mirror-image anodic and cathodic current-response profiles, characteristic of a capacitor, arise. However, the nitride materials have a substantially smaller voltage operating range of only some 0.7 V due to electrochemical decomposition above ca. 0.7 V vs. RHE. This limits their usefulness as a substitute for RuO{sub 2}. Of interest is that the nitride films exhibit potential-decay and potential-recovery on open circuit after respective charge and forced discharge. The decay and recovery processes are logarithmic in time, indicating the role of internal faradaic charge redistribution processes.

  11. Direct and environmentally benign synthesis of manganese oxide/graphene composites from graphite for electrochemical capacitors

    NASA Astrophysics Data System (ADS)

    Lee, Hae-Min; Jeong, Gyoung Hwa; Kang, Doo Won; Kim, Sang-Wook; Kim, Chang-Koo

    2015-05-01

    We develop a direct and environmentally benign method to prepare manganese oxide (Mn3O4)/graphene composites via one-step hydrothermal synthesis from graphite without using strong acids and toxic reducing agents. Structural and morphological analyses reveals that the irregularly shaped Mn3O4 nanoparticles are well-dispersed on the graphene flakes. Cyclic voltammetry and galvanostatic charge-discharge tests indicate that the charge-storing mechanism of the Mn3O4/graphene composites is pseudocapacitive. The Mn3O4/graphene composite exhibits a specific capacitance of 367 F/g at a current density of 5 A/g. After 3000 charge-discharge cycles, the Mn3O4/graphene electrode retains 91.8% of its initial specific capacitance. From electrochemical impedance spectra, it is evident that the changes in both the equivalent series resistance and charge-transfer resistance of the Mn3O4/graphene electrode before and after 3000 charge-discharge cycles are small, indicating good cycling and electrochemical stability of the Mn3O4/graphene electrode.

  12. Thromboresistant/anti-biofilm catheters via electrochemically modulated nitric oxide release.

    PubMed

    Ren, Hang; Colletta, Alessandro; Koley, Dipankar; Wu, Jianfeng; Xi, Chuanwu; Major, Terry C; Bartlett, Robert H; Meyerhoff, Mark E

    2015-08-01

    Inexpensive nitric oxide (NO) release strategies to prevent thrombosis and bacterial infections are desirable for implantable medical devices. Herein, we demonstrate the utility of electrochemically modulated NO release from a catheter model using an inner copper wire working electrode and an inorganic nitrite salt solution reservoir. These catheters generate NO surface fluxes of >1.0 10(-10)mol min(-1) cm(-2) for more than 60 h. Catheters with an NO flux of 1.1 10(-10)mol min(-1) cm(-2) are shown to significantly reduce surface thrombus formation when implanted in rabbit veins for 7h. Further, the ability of these catheters to exhibit anti-biofilm properties against bacterial species commonly causing bloodstream and urinary catheter infections is examined. Catheters releasing NO continuously during the 2d growth of Staphylococcus aureus exhibit a 6 log-unit reduction in viable surface bacteria. We also demonstrate that catheters generating NO for only 3h at a flux of 1.0 10(-10)mol min(-1) cm(-2) lower the live bacterial counts of both 2d and 4d pre-formed Escherichia coli biofilms by >99.9%. Overall, the new electrochemical NO-release devices could provide a cost-effective strategy to greatly enhance the biocompatibility and antimicrobial properties of intravascular and urinary catheters, as well as other implantable medical devices. PMID:25588885

  13. 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

  14. 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

  15. Electrochemical oxidation of glucose on gold nanoparticle-modified reduced graphene oxide electrodes in alkaline solutions

    NASA Astrophysics Data System (ADS)

    Shi, Qiaofang; Diao, Guowang; Mu, Shaolin

    2015-12-01

    A given amount of gold is electrodeposited on the reduced graphene oxide (RGO)/glassy carbon (GC) electrodes to form Au/RGO/GC electrodes, which are carried out at different potentials. The Au/RGO/GC electrode with Au loading of 250 ?g cm-2 prepared at a constant potential of -0.30 V exhibits the best electrocatalytic activity to glucose oxidation in alkaline solutions because of homogeneous dispersion of gold nanoparticles with smaller sizes. This electrode shows long-term stability, rapid charge transfer ability, and higher current density compared to other gold electrodes reported previously.

  16. Electrochemical behavior of palmatine and its sensitive determination based on an electrochemically reduced l-methionine functionalized graphene oxide modified electrode.

    PubMed

    Qiao, Wenhua; Wang, Lu; Ye, Baoxian; Li, Gaiping; Li, Jianjun

    2015-12-01

    A new and sensitive voltammetric sensor for palmatine, based on an electrochemically reduced l-methionine functionalized graphene oxide modified glassy carbon electrode (l-Met-ERGO/GCE), is reported. The electrochemical characteristics of palmatine at the proposed sensor were studied systematically and some dynamic parameters were calculated for the first time. A reasonable reaction mechanism for palmatine on the l-Met-ERGO/GCE electrode was proposed and discussed, and this could be a reference for the pharmacological action of palmatine in clinical study. Under optimized conditions, the peak current had a linear relationship with palmatine concentration in the range of 1 10(-7) to 5 10(-5) mol L(-1) with a detection limit of 6 10(-8) mol L(-1). Additionally, the proposed method was also used to detect palmatine in human urine samples, medicinal tablets and the Chinese herb Fibraurea recisa Pierre with satisfactory results. PMID:26517817

  17. Electrochemical wastewater treatment directly powered by photovoltaic panels: electrooxidation of a dye-containing wastewater.

    PubMed

    Valero, David; Ortiz, Juan M; Expósito, Eduardo; Montiel, Vicente; Aldaz, Antonio

    2010-07-01

    Electrochemical technologies have proved to be useful for the treatment of wastewater, but to enhance their green characteristics it seems interesting to use a green electric energy such as that provided by photovoltaic (PV) cells, which are actually under active research to decrease the economic cost of solar kW. The aim of this work is to demonstrate the feasibility and utility of using an electrooxidation system directly powered by a photovoltaic array for the treatment of a wastewater. The experimental system used was an industrial electrochemical filter press reactor and a 40-module PV array. The influence on the degradation of a dye-containing solution (Remazol RB 133) of different experimental parameters such as the PV array and electrochemical reactor configurations has been studied. It has been demonstrated that the electrical configuration of the PV array has a strong influence on the optimal use of the electric energy generated. The optimum PV array configuration changes with the intensity of the solar irradiation, the conductivity of the solution, and the concentration of pollutant in the wastewater. A useful and effective methodology to adjust the EO-PV system operation conditions to the wastewater treatment is proposed. PMID:20540540

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

    PubMed

    Aquino, Jos Mario; Rocha-Filho, Romeu C; Sez, Cristina; Caizares, 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

  19. Solid flexible electrochemical supercapacitor using Tobacco mosaic virus nanostructures and ALD ruthenium oxide

    NASA Astrophysics Data System (ADS)

    Gnerlich, M.; Pomerantseva, E.; Gregorczyk, K.; Ketchum, D.; Rubloff, G.; Ghodssi, R.

    2013-11-01

    An all-solid electrochemical supercapacitor has been developed using a nanostructured nickel and titanium nitride template that is coated with ruthenium oxide by atomic layer deposition (ALD). The electrode morphology was based on a high surface area biotemplate of genetically modified Tobacco mosaic virus. The biotemplate automatically self-assembles at room temperature in aqueous solution. Nafion perfluorosulfonate ionomer dispersion was cast on the electrodes and used as a solid proton-conducting electrolyte. A 5.8 F g-1 gravimetric capacity (578 F cm-2 based on footprint) was achieved in Nafion electrolyte, and the device retained 80% of its capacity after 25?000 cycles. The technology presented here will enable thin, solid, flexible supercapacitors that are compatible with standard microfabrication techniques.

  20. 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

  1. 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.

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

    NASA Astrophysics Data System (ADS)

    Nechache, A.; Cassir, M.; Ringued, 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.

  3. 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.

  4. Nanocrystalline indium tin oxide fabricated via sol-gel combustion for electrochemical luminescence cells.

    PubMed

    Chaoumead, Accarat; Kim, Tae-Woo; Park, Min-Woo; Sung, Youl-Moon

    2012-04-01

    Nanoporous indium tin oxide (ITO) was synthesized via a sol-gel combustion hybrid method using Ketjenblack as a fuel. The effects of the sol-gel combustion conditions on the structures and morphology of the ITO particles were studied. The size of the nanoporous powder was found to be 20-30 nm in diameter. The layer of the nanoporous ITO electrode (-10 microm thickness) with large surface area (-360 m2/g) was fabricated for an electrochemical luminescence (ECL) cell. At 4 V bias, the ECL efficiency of the cell consisting of the nanoporous ITO layer was approximately 1050 cd/m2, which is significantly higher than the cell using only the FTO electrode (450 cd/m2). The nanoporous ITO layer was effective in increasing the ECL intensities. PMID:22849163

  5. Mechanism for resistive switching in an oxide-based electrochemical metallization memory

    NASA Astrophysics Data System (ADS)

    Peng, Shanshan; Zhuge, Fei; Chen, Xinxin; Zhu, Xiaojian; Hu, Benlin; Pan, Liang; Chen, Bin; Li, Run-Wei

    2012-02-01

    A comparison of the asymmetric OFF-state current-voltage characteristics between Cu/ZnO/Pt and Cu/ZnO/Al-doped ZnO (AZO) electrochemical metallization memory (ECM) cells demonstrates that the Cu filament rupture and rejuvenation occur at the ZnO/Pt (or AZO) interface, i.e., the cathodic interface. Therefore, the filament is most likely to have a conical shape, with wider and narrower diameters formed at the anodic and cathodic interfaces, respectively. It is inferred that the filament growth starts at the anode surface and stops at the cathode surface. Our results indicate that oxide-based ECM cells strongly differ from sulfide- and selenide-based ones in the resistive switching mechanism.

  6. Spinel manganese-nickel-cobalt ternary oxide nanowire array for high-performance electrochemical capacitor applications.

    PubMed

    Li, Lu; Zhang, Yongqi; Shi, Fan; Zhang, Yijun; Zhang, Jiaheng; Gu, Changdong; Wang, Xiuli; Tu, Jiangping

    2014-10-22

    Aligned spinel Mn-Ni-Co ternary oxide (MNCO) nanowires are synthesized by a facile hydrothermal method. As an electrode of supercapacitors, the MNCO nanowire array on nickel foam shows an outstanding specific capacitance of 638 F g(-1) at 1 A g(-1) and excellent cycling stability. This exceptional performance benefits from its nanowire architecture, which can provide large reaction surface area, fast ion and electron transfer, and good structural stability. Furthermore, an asymmetric supercapacitor (ASC) with high energy density is assembled successfully by employing the MNCO nanowire array as positive electrode and carbon black as negative electrode. The excellent electrochemical performances indicate the promising potential application of the ASC device in the energy storage field. PMID:25247606

  7. Electrochemical regeneration of sodium hypochlorite in the absorption-oxidation method of desorbing waste gases

    SciTech Connect

    Znamenskii, Yu.D.; Perchugov, G.Ya.

    1988-07-10

    The electrochemical synthesis of sodium hypochlorite from a solution with a reduced concentration of sodium chloride is efficiently carried out with the use of ruthenium oxide-titanium anodes (ROTA). In this context they investigated the electrolysis of a solution of sodium chloride with concentrations equal to 20 and 50 kg/m/sup 3/ in a single cell flow-type electrolyzer with an ROTA and, for comparison, with a graphite anode under laboratory conditions. A flow-type electrolyzer was selected in view of the fact that it most closely satisfies the purposes of gas purification. The current efficiency with respect to sodium hypochlorite was almost two times higher, and the specific consumption of electrical energy was 1.6-1.8 times lower in the case of the ROTA than in the case of the graphite electrode. The yield of sodium chlorate remained on the same level in both cases.

  8. Template-Free Synthesis of Ruthenium Oxide Nanotubes for High-Performance Electrochemical Capacitors.

    PubMed

    Kim, Ji-Young; Kim, Kwang-Heon; Kim, Hyun-Kyung; Park, Sang-Hoon; Roh, Kwang Chul; Kim, Kwang-Bum

    2015-08-01

    One-dimensional, hydrous ruthenium oxide nanotubes (RuO21.84H2O) have been successfully achieved using a template-free, microwave-hydrothermal process. These were found to be amorphous in nature and have a large specific surface area of 250 m(2)g(-1), producing a specific and volumetric capacitance of 511 Fg(-1) and 531 Fcm(-3), respectively, at a discharging current density of 0.5 Ag(-1). When used as an electrode material in an electrochemical capacitor or ultracapacitor, they produced a significant improvement in capacitance, rate capability, and cyclability that can be attributed to the hollow nature of tubes allowing greater contact between the active surface of the electrode and the electrolyte. PMID:26161814

  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. Electrochemical oxide nanotube formation on the Ti-35Ta-xHf alloys for dental materials.

    PubMed

    Moon, Byung-Hak; Jeong, Yong-Hoon; Choe, Han-Cheol

    2011-08-01

    In this study, we investigated the electrochemical oxide nanotube formation on the Ti-35Ta-xHf alloys for dental materials. The Ti-35Ta-xHf alloys contained from 3 wt.% to 15 wt.% Hf were manufactured by arc melting furnace. The nanotube oxide layers were formed on Ti-35Ta-xHf alloy by anodic oxidation method in 1 M H3PO4 electrolytes containing 0.5 wt.% NaF and 0.8 wt.% NaF at room temperature. The surface characteristics of Ti-35Ta-xHf alloy and nanotube morphology were determined by FE-SEM, STEM, and XRD. The nano-porous surface of Ti-35Ta-xHf alloys showed in 0.5 wt% NaF solution and nanotubular surface showed in 0.8 wt% NaF solution, respectively. The highly ordered nanotube layer without regular knots was formed on the Ti-35Ta-15Hf alloy in the 0.5 wt% NaF solution compared to on Ti-35Ta-3Hf and Ti-35Ta-7Hf alloys in 0.8 wt% NaF solution. Also, the nanotube length of Ti-35Ta-xHf alloys increased as Hf content increased. PMID:22103212

  11. 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

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. Inactivation of Pseudomonas aeruginosa in electrochemical advanced oxidation process with diamond electrodes.

    PubMed

    Griessler, M; Knetsch, S; Schimpf, E; Schmidhuber, A; Schrammel, B; Wesner, W; Sommer, R; Kirschner, A K T

    2011-01-01

    The electrochemical advanced oxidation process (EAOP) with diamond electrodes may serve as an additional technology to the currently approved methods for water disinfection. Only few data exist on the microbicidal effect of the EAOP. The aim of our study was to investigate the microbicidal effect of a flow-through oxidation cell with diamond electrodes, using Pseudomonas aeruginosa as the test organism. Without electrical current the EAOP had no measurable effect on investigated microbiological and chemical parameters. For direct electrical current a stronger impact was observed at low flow rate than at higher flow rate. Depending on the contact time of the oxidants and the type of quenching reagent added, inactivation of P. aeruginosa was in the range log 1.6-3.6 at the higher flow rate and log 2.4-4.4 at the lower rate. Direct electrical current showed a stronger microbicidal effect than alternating current (maximum reduction log 4.0 and log 2.9, respectively). The microbiological results of experiments with this EAOP prototype revealed higher standard deviations than expected, based on our experience with standard water disinfection methods. Safe use of an EAOP system requires operating parameters to be defined and used accurately, and thus specific monitoring tests must be developed. PMID:21902043

  17. 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.

  18. 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 ? 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 chargedischarge 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.

  19. 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.

  20. Corrosion resistance and bioactivity of titanium after surface treatment by three different methods: ion implantation, alkaline treatment and anodic oxidation.

    PubMed

    Krupa, D; Baszkiewicz, J; Kozubowski, J A; Mizera, J; Barcz, A; Sobczak, J W; Biliński, A; Rajchel, B

    2005-02-01

    The paper compares the effects of various surface modifications, ion implantation, alkaline treatment and anodic oxidation, upon the corrosion resistance and bioactivity of titanium. The chemical composition of the surface layers thus produced was determined by XPS, SIMS and EDS coupled with SEM. The structure of the layers was examined by TEM, and their phase composition by XRD. The corrosion resistance was determined by electrochemical methods after the samples were exposed to the test conditions for 13 h. The bioactivity of titanium was evaluated in a simulated body fluid at a temperature of 37 degrees C after various exposure time. PMID:15723257

  1. Effect of plasma nitriding treatment on structural, tribological and electrochemical properties of commercially pure titanium.

    PubMed

    elik, ?lhan; Karakan, Mehmet

    2016-02-01

    In this study, plasma nitriding treatment was applied to commercially pure titanium (Grade 2). Structural properties, electrochemical and tribological behaviours of the nitrided pure titanium specimens were comparatively investigated. Microstructure and morphology of the plasma nitrided specimens were analysed by X-ray diffraction and scanning electron microscopy. Furthermore, corrosion tests were conducted in Ringer's solution, which represents a human body environment, to determine electrochemical properties. Then, tribological and frictional properties were investigated using pin-on-disc tribometer, and a micro-hardness tester was used to measure the hardness of the coatings. The results showed that plasma nitrided specimens exhibited higher surface hardness than the untreated specimens did. In addition, the plasma nitrided specimens at 700?C presented significantly better performance than the other plasma nitrided specimens (at 500?C and 600?C) under dry wear conditions. Moreover, corrosion test results showed that corrosion behaviours of untreated and nitrided samples had similar characteristic. PMID:26666885

  2. Improvement in electrochemical capacitance of activated carbon from scrap tires by nitric acid treatment

    NASA Astrophysics Data System (ADS)

    Han, Yan; Zhao, Ping-Ping; Dong, Xiao-Ting; Zhang, Cui; Liu, Shuang-Xi

    2014-12-01

    Activated carbon (AC) obtained from the industrial pyrolytic tire char is treated by concentrated nitric acid (AC-HNO3) and then used as the electrode material for supercapacitors. Surface properties and electrochemical capacitances of AC and ACHNO3 are studied. It is found that the morphology and the porous texture for AC and AC-HNO3 have little difference, while the oxygen content increases and functional groups change after the acid treatment. Electrochemical results demonstrate that the AC-HNO3 electrode displays higher specific capacitance, better stability and cycling performance, and lower equivalent series resistance, indicating that AC obtained from the industrial pyrolytic tire char treated by concentrated nitric acid is applicable for supercapacitors.

  3. Coupling extraction-flotation with surfactant and electrochemical degradation for the treatment of PAH contaminated hazardous wastes.

    PubMed

    Tran, Lan-Huong; Drogui, Patrick; Mercier, Guy; Blais, Jean-Franois

    2009-10-30

    The performance of a two-stage process combining extraction of polycyclic aromatic hydrocarbons (PAHs) with an amphoteric surfactant (CAS) followed by electro-oxidation of PAH-foam concentrate was studied for the decontamination of aluminum industry wastes (AIW) and polluted soils. The PAH suspensions extracted from AIW and soils were treated in a 2L-parallelepipedic electrolytic cell containing Ti/RuO2 anodes and stainless steel cathodes. Current densities varying from 4.6 to 18.5 mA cm(-2) have been tested with and without addition of a supporting electrolyte (6.25 to 50 kg Na2SO4 t(-1) of dry waste). The best performance for PAH degradation was obtained while the electrolytic cell was operated during 90 min at a current density of 9.2 mA cm(-2), with a total solids concentration of 2.0%, and in presence 12.5 kg Na(2)SO(4)t(-1). The application of the process on AIW (initial PAH content: 3424 mg kg(-1)) allowed extracting 42% of PAH, whereas 50% of PAH was electrochemically degraded in the resulting foam suspensions. By comparison, 44% to 60% of PAH was extracted from polluted soils (initial PAH content: 1758 to 4160 mg kg(-1)) and 21% to 55% of PAH was oxidized in the foam suspensions. The electrochemical treatment cost (including only electrolyte and energy consumption) recorded in the best experimental conditions varied from 99 to 188 USD $ t(-1) of soils or AIW treated. PMID:19525064

  4. 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

  5. The oriented growth of tungsten oxide in ordered mesoporous carbon and their electrochemical performance

    NASA Astrophysics Data System (ADS)

    Wang, Tao; Tang, Jing; Fan, Xiaoli; Zhou, Jianhua; Xue, Hairong; Guo, Hu; He, Jianping

    2014-04-01

    Electrocatalysts for hydrogen oxidation and methanol oxidation are the heart of the proton exchange membrane fuel cell. In spite of tremendous efforts, developing low-cost anodic electrocatalysts with high catalytic activity and corrosion resistance is still a great challenge. Here, we report a nanocomposite consisting of oriented WO3 nanorods grown in ordered mesoporous carbon as a high-performance functional catalyst carrier for proton exchange membrane fuel cells. As a result of the catalytic graphitization effect of tungsten compounds, the degree of graphitization and conductivity of mesoporous carbon film were improved even at a low temperature. Furthermore, compared with ordered mesoporous carbon, ordered mesoporous C-WO3 nanocomposites possess favorable hydrophilicity, excellent corrosion resistance and notable electrocatalytic activities. The unusual electrocatalytic activities arise from the ideal physical properties of the carrier and synergetic catalysis between Pt and WO3.Electrocatalysts for hydrogen oxidation and methanol oxidation are the heart of the proton exchange membrane fuel cell. In spite of tremendous efforts, developing low-cost anodic electrocatalysts with high catalytic activity and corrosion resistance is still a great challenge. Here, we report a nanocomposite consisting of oriented WO3 nanorods grown in ordered mesoporous carbon as a high-performance functional catalyst carrier for proton exchange membrane fuel cells. As a result of the catalytic graphitization effect of tungsten compounds, the degree of graphitization and conductivity of mesoporous carbon film were improved even at a low temperature. Furthermore, compared with ordered mesoporous carbon, ordered mesoporous C-WO3 nanocomposites possess favorable hydrophilicity, excellent corrosion resistance and notable electrocatalytic activities. The unusual electrocatalytic activities arise from the ideal physical properties of the carrier and synergetic catalysis between Pt and WO3. Electronic supplementary information (ESI) available: Additional structural characterizations and electrochemical measurements. See DOI: 10.1039/c4nr00396a

  6. 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.

  7. 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

  8. 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

  9. 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.

  10. 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

  11. Electrochemical Oxidation of NADH at Highly Boron-Doped Diamond Electrodes.

    PubMed

    Rao, T N; Yagi, I; Miwa, T; Tryk, D A; Fujishima, A

    1999-07-01

    Conductive boron-doped chemical vapor-deposited diamond thin films, already known to have superior properties for general electroanalysis, including low background current and a wide potential window, are here shown to have additional advantages with respect to electrochemical oxidation of nicotinamide adenine dinucleotide (NADH), including high resistance to deactivation and insensitivity to dissolved oxygen. Cyclic voltammetry, amperometry, and the rotating disk electrode technique were used to study the reaction in neutral pH solution. Highly reproducible cyclic voltammograms for NADH oxidation were obtained at as-deposited diamond electrodes. The response was stable over several months of storage in ambient air, in contrast to glassy carbon electrodes, which deactivated within 1 h. The diamond electrode exhibited very high sensitivity for NADH, with an amperometric detection limit of 10 nM (S/N = 7). The response remained stable, even in the very low concentration range, for several months. In addition, interference effects due to ascorbic acid were minimal when the concentrations of NADH and ascorbic acid were comparable. An NADH-mediated dehydrogenese-based ethanol biosensor incorporating an unmodified diamond electrode is demonstrated. The present results indicate that diamond is a useful electrode material for the analytical detection of NADH, making it attractive for use in sensors based on enzyme-catalyzed reactions involving NADH as a cofactor. PMID:21662795

  12. Morphological and substrate effects on the electrochemical behaviour of doped tin oxide anodes

    NASA Astrophysics Data System (ADS)

    Miljkovic, Bojan

    Films of Sb-doped SnO2 were successfully fabricated on a Ti substrate through precursor application by spin coating followed by a thermal decomposition process. The dependence of film characteristics on fabrication temperature was studied in the range of 500 to 800C. An optimum electrocatalytic response was found for a firing temperature of 600C. This was attributed to a balance between Sb-doping effects, titanium substrate oxidation, and film morphological development. This was determined through observation of the morphology, crystallographic texture, and electrochemical characteristics, such as the oxygen evolution potential (OEP), ferri/ferrocyanide electron transfer reaction, and phenol oxidation. Polymerization of phenol and the subsequent deactivation of the anode surface was related to the active surface area of the SnO2 film. Preliminary studies on the effect of Ni-Sb and Zn-Sb co-doping of SnO2 were conducted. The addition of Ni was shown to decrease the film conductivity while maintaining the OEP. Inclusion of Zn resulted in the formation of a second phase, Zn2SnO4 , which effectively inhibited oxygen evolution causing an increase in the OEP.

  13. 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.

  14. Electrochemical Urea Biosensor Based on Sol-gel Derived Nanostructured Cerium Oxide

    NASA Astrophysics Data System (ADS)

    Ansari, Anees A.; Azahar, Md; Malhotra, B. D.

    2012-04-01

    Urease (Urs) and glutamate dehydrogenase (GLDH) have been co-immobilized onto a nanostructured-cerium oxide (Nano-CeO2) film deposited onto a indium-tin-oxide (ITO) coated glass substrate by dip-coating via sol-gel process for urea detection. This nanostructured film has characterized using X-ray diffraction (XRD), Fourier transform infrared (FTIR), Scanning electron microscope (SEM) and electrochemical techniques, respectively. The particle size of the Nano-CeO2 film has been found to be 23 nm. Electrochemcial response (CV) studies show that Ur-GLDH/Nano-CeO2/ITO bioelectrode is found to be sensitive in the 10-80 mg/dL urea concentration range and can detect urea concentration upto 0.1 mg/dL level. The value of Michaelis-Menten constant (Km) estimated using Lineweaver-Burke plot found as 6.09 mg/dL indicates enhancement in the affinity and/or activity of enzyme attached to their nanobiocomposite. This bioelectrode retained 95% of enzyme activity after 6 months at 4C.

  15. Electrochemical, Optical and Electronic Properties of Iridium Tin Oxide Thin Film as Counter Electrode of Electrochromic Device

    NASA Astrophysics Data System (ADS)

    Niwa, Tatsuo; Takai, Osamu

    2010-10-01

    Iridium tin oxide films (IRTOFs) containing dispersed iridium oxide in a tin oxide matrix were prepared by an ion-plating process. The optical, electrochemical, and electronic properties of the films were measured by varying the iridium concentration in the films. The cyclic voltammogram characteristic of the films showed good reproducibility. The coloration efficiency of the IRTOFs increased with an increase in the concentration of iridium. The change ranges of the conductivity become more than 108 times. The activation energy increased with increasing iridium concentration in the iridium concentration range in which the conductivity decreased. The characteristics of an all-solid-state electrochromic device with an IRTOF counter electrode were measured.

  16. 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.

  17. 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 ? 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

  18. 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.

  19. 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.

  20. Applicability of an electrochemical Fenton-type process to actual wastewater treatment.

    PubMed

    Kishimoto, Naoyuki; Kitamura, Takuya; Nakamura, Yu

    2015-01-01

    The applicability of an electrochemical Fenton-type process (EF-HOCl-ReFe) to the treatment of three actual wastewaters, namely wastewater from an automobile factory (automobile wastewater), metal scrap-cleansing wastewater, and municipal wastewater, is discussed in this research. The EF-HOCl-ReFe successfully removed the chemical oxygen demand (COD) from automobile wastewater pre-treated by a coagulation process without any inhibition. The apparent current efficiency reached 86%, 46% of which was ascribed to the electrochemical Fenton-type mechanism. The metal scrap-cleansing wastewater had a yellow colour and high concentrations of COD (6550 mg/L) and Cl(-) (1560 mM). The EF-HOCl-ReFe could achieve almost complete COD removal and decolourization after 48 h of treatment, although a temporary intensification of colour was observed before the decolourization. The EF-HOCl-ReFe was also effective in the removal of 1,4-dioxane from municipal wastewater pre-treated by activated sludge and coagulation processes, which were unable to remove 1,4-dioxane. The 1,4-dioxane removal efficiency after 30 min of treatment reached 68.5%. Thus, the EF-HOCl-ReFe was applicable to the treatment of these actual wastewaters. PMID:26360743

  1. 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

  2. Investigation of anodic oxide coatings on zirconium after heat treatment

    NASA Astrophysics Data System (ADS)

    Sowa, Maciej; Dercz, Grzegorz; Suchanek, Katarzyna; Simka, Wojciech

    2015-08-01

    Herein, results of heat treatment of zirconium anodised under plasma electrolytic oxidation (PEO) conditions at 500-800 C are presented. The obtained oxide films were investigated by means of SEM, XRD and Raman spectroscopy. The corrosion resistance of the zirconium specimens was evaluated in Ringer's solution. A bilayer oxide coatings generated in the course of PEO of zirconium were not observed after the heat treatment. The resulting oxide layers contained a new sublayer located at the metal/oxide interface is suggested to originate from the thermal oxidation of zirconium. The corrosion resistance of the anodised metal was improved after the heat treatment.

  3. Effects of anodic oxidation of a substoichiometric titanium dioxide reactive electrochemical membrane on algal cell destabilization and lipid extraction.

    PubMed

    Hua, Likun; Guo, Lun; Thakkar, Megha; Wei, Dequan; Agbakpe, Michael; Kuang, Liyuan; Magpile, Maraha; Chaplin, Brian P; Tao, Yi; Shuai, Danmeng; Zhang, Xihui; Mitra, Somenath; Zhang, Wen

    2016-03-01

    Efficient algal harvesting, cell pretreatment and lipid extraction are the major steps challenging the algal biofuel industrialization. To develop sustainable solutions for economically viable algal biofuels, our research aims at devising innovative reactive electrochemical membrane (REM) filtration systems for simultaneous algal harvesting and pretreatment for lipid extraction. The results in this work particularly demonstrated the use of the Ti4O7-based REM in algal pretreatment and the positive impacts on lipid extraction. After REM treatment, algal cells exhibited significant disruption in morphology and photosynthetic activity due to the anodic oxidation. Cell lysis was evidenced by the changes of fluorescent patterns of dissolved organic matter (DOM) in the treated algal suspension. The lipid extraction efficiency increased from 15.2±0.6g-lipidg-algae(-1) for untreated algae to 23.4±0.7g-lipidg-algae(-1) for treated algae (p<0.05), which highlights the potential to couple algal harvesting with cell pretreatment in an integrated REM filtration process. PMID:26722810

  4. 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

  5. Detection of the short-lived cation radical intermediate in the electrochemical oxidation of N,N-dimethylaniline by scanning electrochemical microscopy.

    PubMed

    Cao, Fahe; Kim, Jiyeon; Bard, Allen J

    2014-12-31

    The short-lived intermediate N,N-dimethylaniline (DMA) cation radical, DMA(+), was detected during the oxidation of DMA in MeCN with 0.1 M tetra-n-butylammonium hexafluorophosphate. The detection was accomplished at steady state by scanning electrochemical microscopy (SECM) with ultramicroelectrodes using the tip generation/substrate collection mode. Cyclic voltammetry (CV) with a 2 mm Pt electrode indicates that DMA oxidation in acetonitrile is followed by a dimerization and two electrochemical reactions, which is consistent with previous results. The DMA(+) intermediate is detected by SECM, where the DMA(+) generated at the ca. 500 nm radius Pt tip is collected on a 5 ?m radius Pt substrate when the gap between the tip and the substrate is a few hundred nanometers. Almost all of the DMA(+) is reduced at the substrate when the gap is 200 nm or less, yielding a dimerization rate constant of 2.5 10(8) M(-1)s(-1) based on a simulation. This is roughly 3 orders of magnitude larger than the value estimated by fast-scan CV. We attribute this discrepancy to the effects of double-layer capacitance charging and adsorbed species in the high scan rate CV. PMID:25478724

  6. 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.

  7. 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

  8. 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

  9. 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

  10. Electrochemical enhancement of nitric oxide removal from simulated lean-burn engine exhaust via solid oxide fuel cells.

    PubMed

    Huang, Ta-Jen; Wu, Chung-Ying; Lin, Yu-Hsien

    2011-07-01

    A solid oxide fuel cell (SOFC) unit is constructed with Ni-YSZ as the anode, YSZ as the electrolyte, and La(0.6)Sr(0.4)CoO(3)-Ce(0.9)Gd(0.1)O(1.95) as the cathode. The SOFC operation is performed at 600 C with a cathode gas simulating the lean-burn engine exhaust and at various fixed voltage, at open-circuit voltage, and with an inert gas flowing over the anode side, respectively. Electrochemical enhancement of NO decomposition occurs when an operating voltage is generated; higher O(2) concentration leads to higher enhancement. Smaller NO concentration results in larger NO conversion. Higher operating voltage and higher O(2) concentration can lead to both higher NO conversion and lower fuel consumption. The molar rate of the consumption of the anode fuel can be very much smaller than that of NO to N(2) conversion. This makes the anode fuel consumed in the SOFC-DeNO(x) process to be much less than the equivalent amount of ammonia consumed in the urea-based selective catalytic reduction process. Additionally, the NO conversion increases with the addition of propylene and SO(2) into the cathode gas. These are beneficial for the application of the SOFC-DeNO(x) technology on treating diesel and other lean-burn engine exhausts. PMID:21667969

  11. Exploiting a new electrochemical sensor for biofilm monitoring and water treatment optimization.

    PubMed

    Pavanello, Giovanni; Faimali, Marco; Pittore, Massimiliano; Mollica, Angelo; Mollica, Alessandro; Mollica, Alfonso

    2011-02-01

    Bacterial biofilm development is a serious problem in many fields, and the existing biofilm monitoring sensors often turn out to be inadequate. In this perspective, a new sensor (ALVIM) has been developed, exploiting the natural marine and freshwater biofilms electrochemical activity, proportional to surface covering. The results presented in this work, obtained testing the ALVIM system both in laboratory and in an industrial environment, show that the sensor gives a fast and accurate response to biofilm growth, and that this response can be used to optimize cleaning treatments inside pipelines. Compared to the existing biofilm sensors, the proposed system show significant technological innovations, higher sensitivity and precision. PMID:21186042

  12. Exploiting a new electrochemical sensor for biofilm monitoring and water treatment optimization.

    TOXLINE Toxicology Bibliographic Information

    Pavanello G; Faimali M; Pittore M; Mollica A; Mollica A; Mollica A

    2011-02-01

    Bacterial biofilm development is a serious problem in many fields, and the existing biofilm monitoring sensors often turn out to be inadequate. In this perspective, a new sensor (ALVIM) has been developed, exploiting the natural marine and freshwater biofilms electrochemical activity, proportional to surface covering. The results presented in this work, obtained testing the ALVIM system both in laboratory and in an industrial environment, show that the sensor gives a fast and accurate response to biofilm growth, and that this response can be used to optimize cleaning treatments inside pipelines. Compared to the existing biofilm sensors, the proposed system show significant technological innovations, higher sensitivity and precision.

  13. DEMONSTRATION BULLETIN: PEROX-PURE CHEMICAL OXIDATION TREATMENT

    EPA Science Inventory

    Technology Description: The perox-pure™ chemical oxidation treatment technology was developed by Peroxidation Systems, Inc. (PSI), to destroy dissolved organic contaminants in water. The technology uses ultraviolet (UV) radiation and hydrogen peroxide to oxidize organic co...

  14. DEMONSTRATION BULLETIN: PEROX-PURE CHEMICAL OXIDATION TREATMENT

    EPA Science Inventory

    Technology Description: The perox-pure chemical oxidation treatment technology was developed by Peroxidation Systems, Inc. (PSI), to destroy dissolved organic contaminants in water. The technology uses ultraviolet (UV) radiation and hydrogen peroxide to oxidize organic co...

  15. 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

  16. 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

  17. [The clinical manifestations of the electrochemical processes due to the finishing treatment of dentures made from stainless steel].

    PubMed

    Gozhi?, A G; Sagatelian, G R; Gozhaia, L D; Bol'shakov, G V

    1998-01-01

    The authors propose to treat stainless steel dentures by grinding on organosilicon binding followed by 2 polishing procedures: with diamond paste and paste based on ultradispersed aluminum oxide powder. This technology improves the corrosion resistance of dentures and eliminates signs of diseases caused by electrochemical processes in the oral cavity more effectively than basic technology (vulcanite grinding and polishing with GOI paste). PMID:9643115

  18. 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}.

  19. A combined CaO/electrochemical treatment of the acid mine drainage from the "Robule" Lake.

    PubMed

    Orescanin, Visnja; Kollar, Robert

    2012-01-01

    The purpose of this work was development and application of the purification system suitable for the treatment of the acid mine drainage (AMD) accumulated in the "Robule" Lake, which represents the part of the Bor copper mining and smelting complex, Serbia. The study was undertaken in order to minimize adverse effect on the environment caused by the discharge of untreated AMD, which was characterized with low pH value (2.63) and high concentration of heavy metals (up to 610 mg/L) and sulfates (up to 12,000 mg/L). The treatment of the effluent included pretreatment/pH adjustment with CaO followed by electrocoagulation using iron and aluminum electrode sets. Following the final treatment, the decrease in the concentration of heavy metals ranged from 40 up to 61000 times depending on the metal and its initial concentration. The parameters, color and turbidity were removed completely in the pretreatment step, while the removal efficiencies for other considered parameters were as follows: EC = 55.48%, SO(4) (2-) = 70.83%, Hg = 98.36%, Pb = 97.50%, V = 98.43%, Cr = 99.86%, Mn = 97.96%, Fe = 100.00%, Co = 99.96%, Ni = 99.78%, Cu = 99.99% and Zn = 99.94%. Because the concentrations of heavy metals in the electrochemically treated AMD (ranging from 0.001 to 0.336 mg/L) are very low, the negative impact of this effluent on the aquatic life and humans is not expected. The sludge generated during the treatment of AMD is suitable for reuse for at least two purposes (pretreatment of AMD and covering of the flotation waste heap). From the presented results, it could be concluded that electrochemical treatment is a suitable approach for the treatment of AMD. PMID:22506711

  20. Constraints on the oxidation state of the mantle: An electrochemical and 57Fe Mssbauer study of mantle-derived ilmenites

    NASA Astrophysics Data System (ADS)

    Virgo, David; Luth, Robert W.; Moats, Mark A.; Ulmer, Gene C.

    1988-07-01

    Ilmenite samples from four kimberlite localities were studied using electrochemical, Mssbauer spectroscopic, and microprobe analytical techniques in order to infer the oxidation state of their source regions in the mantle. The values of Fe 3+/?Fe calculated from analyses, using three different electron microanalytical instruments assuming ilmenite stoichiometry, are consistently higher than those derived from the Mssbauer data, by as much as 100%. Furthermore, the range in Fe 3+/?Fe calculated using the analyses from different instruments and/or different correction schemes is nearly as large. Thus Fe 3+/?Fe calculated from microprobe analyses should be taken with caution, even if the precision appears high. An yttria-doped zirconia, double-cell electrochemical apparatus was used to measure the oxygen fugacity ( O 2) of ilmenite as a function of temperature. Samples that contain carbon show irreversible, "auto-oxidation" trends of sharply increasing O 2 with increasing temperature upon initial heating. The one sample that lacked C did not "autooxidize". 57Fe Mssbauer spectroscopy on the electrochemical experiment run products demonstrates that Fe 3+/?Fe is significantly lower than it is for the natural C-bearing ilmenites. In contrast, the ilmenite that lacked C did not change Fe 3+/?Fe during the electrochemical experiment. Examination of the reduced samples with SEM established that the natural, single-phase ilmenites exsolved during the electrochemical experiment to form ilmenite ss, + spinel ss. Reduction-exsolution was caused by reaction with C, which shifted the bulk composition from the stability field of ilmenite ss along an oxygen reaction line into the two-phase stability field of ilmenite ss + spinel ss that lies between the ilmenite-hematite and the ulvspinel-magnetite joins in the TiO 2-(Fe,Mg)O-(Fe,Al) 2O 3 system. The initial, reduced trends in the electrochemical experiments for the C-bearing ilmenites are attributed to disequilibrium interactions between the decomposing sample and the evolved gas in the electrochemical cell and do not represent the quenched "mantle memory" nor the intrinsic o 2 of the sample prior to reduction. Futhermore, the oxidized o 2 trend is interpreted, for the carbon-bearing samples, as representing the o 2 of the ilmenite ss + spinel ss assemblage and not the intrinsic o 2 of the mantle-derived ilmenite ss.

  1. 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).

  2. 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

  3. A Highly Controllable Electrochemical Anodization Process to Fabricate Porous Anodic Aluminum Oxide Membranes.

    PubMed

    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. PMID:26706687

  4. 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

  5. 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??A 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

  6. 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

  7. 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.

  8. 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.

  9. Electrocatalysis of NADH oxidation using electrochemically activated fluphenazine on carbon nanotube electrode.

    PubMed

    Sobczak, Agnieszka; R?bi?, 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 ?M to 84 ?M, and correlation coefficient 0.998. The limits of detection (5 ?M) and quantitation (15 ?M) were evaluated. PMID:26211441

  10. 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

  11. Electrochemical immunosensor for ethinylestradiol using diazonium salt grafting onto silver nanoparticles-silica-graphene oxide hybrids.

    PubMed

    Cincotto, Fernando H; Martnez-Garca, Gonzalo; Yez-Sedeo, Paloma; Canevari, Thiago C; Machado, S A S; Pingarrn, Jos 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 4C under humid conditions between measurements. The developed immunosensor was applied to the analysis of spiked urine with good results. PMID:26592615

  12. Electrochemical oxidation of amphetamine-like drugs and application to electroanalysis of ecstasy in human serum.

    PubMed

    Garrido, E M P J; Garrido, J M P J; Milhazes, N; Borges, F; Oliveira-Brett, A M

    2010-08-01

    Amphetamine and amphetamine-like drugs are popular recreational drugs of abuse because they are powerful stimulants of the central nervous system. Due to a dramatic increase in the abuse of methylenedioxylated derivatives, individually and/or in a mixture, and to the incoherent and contradictory interpretation of the electrochemical data available on this subject, a comprehensive study of the redox properties of amphetamine-like drugs was accomplished. The oxidative behaviour of amphetamine (A), methamphetamine (MA), methylenedioxyamphetamine (MDA) and methylenedioxymethamphetamine (MDMA) was studied in different buffer systems by cyclic, differential pulse and square-wave voltammetry using a glassy carbon electrode. A quantitative electroanalytical method was developed and successfully applied to the determination of MDMA in seized samples and in human serum. Validation parameters, such as sensitivity, precision and accuracy, were evaluated. The results found using the developed electroanalytical methodology enabled to gather some information about the content and amount of MDMA present in ecstasy tablets found in Portugal. Moreover, the data found in this study outlook the possibility of using the voltammetric methods to investigate the potential harmful effects of interaction between drugs such as MDMA and methamphetamine and other substances often used together in ecstasy tablets. PMID:20051327

  13. 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

  14. 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

  15. 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

  16. 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-?) (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

  17. "One-step" simplified electrochemical sensing of TATP based on its acid treatment.

    PubMed

    Munoz, Rodrigo A A; Lu, Donglai; Cagan, Avi; Wang, Joseph

    2007-06-01

    A fast, simple and sensitive electrochemical method for sensing peroxide-based explosives based on their acid treatment is reported. The method relies on the high electrocatalytic activity of Prussian-blue (PB)-modified electrodes towards the acid-generated hydrogen peroxide in the harsh acidic medium (down to pH 0.3) used for releasing hydrogen peroxide. Such effective operation of PB electrochemical sensors in strongly acidic media eliminates the need for an additional neutralization step required in analogous peroxidase-based assays (due to acid-induced enzyme deactivation processes). Factors affecting the efficiency of the acid pre-treatment of triacetone triperoxide (TATP) have been examined and optimized to allow its sensitive measurement down to the 50 ng level within 60 s. Chronoamperometric detection of microgram amounts of solid TATP, following a one-minute acid mixing and placing a 20 microL droplet onto a disposable PB-modified screen-printed electrode is illustrated. Similar results were obtained for the peroxide explosive hexamethylene triperoxide diamine (HMTD). By greatly simplifying the analytical procedure, such an acid-operated "artificial peroxidase" electrocatalytic transducer holds great promise for designing "one-step", user-friendly, miniaturized, cost-effective devices for field screening of peroxide explosives. PMID:17525813

  18. 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 ?10 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.

  19. 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.

  20. 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.

  1. 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

  2. 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

  3. The effect of metallic oxide deposition on the electrochemical behaviour of Al-Zn-Mg-Sn alloy in natural tropical seawater

    NASA Astrophysics Data System (ADS)

    Din Yati, M. S.; Nazree Derman, Mohd; Isa, M. C.; Y Ahmad, M.; Yusoff, N. H. N.; Muhammad, M. M.; Nain, H.

    2014-06-01

    The potential of aluminium alloys as anode materials in cathodic protection system has been explored and a significant improvement has been achieved. However, for marine application, it is quite difficult to maintain continuous activation process due to passivation behavior of aluminum alloys. Therefore, to choose the best activation mechanism for aluminium alloy in marine environment, it has to be considered from various points such as alloy composition and surface treatment. This paper report the effect of metallic ruthenium oxide (RuO2) deposition on the surface of as-cast Al-Zn-Mg-Sn alloy and to study the effect of its presence on the electrochemical behavior using direct current (DC) electrochemical polarization and current capacity measurement. The morphology and topography of corroded surface were studied by the aid of scanning electron microscope (SEM) and confocal laser scanning microscope (CLSM) respectively. Results from this study showed that the presence of intermetallic compound (Mg2Sn) and also mixed metal oxide compound (Al2O3 and RuO2) on the alloy surface has been very useful in improving electrochemical reaction and charge transfer activities in chloride containing solution. This study also showed that RuO2 catalytic coating applied on the surface of Al-Zn-Mg-Sn alloy has slightly increased the corrosion current density compared to Al-Zn-Mg-Sn without RuO2. The corrosion morphology and topography of corroded surface of Al-Zn-Mg-Sn alloy deposited with RuO2 was found more uniform corrosion attack with the formation of porous and fibrous mud-like crack on outer layer. Based on surface morphology and 3D topographic studies, these features were believed to facilitate ionic species adsorption and diffusion through corrosion product layer at solution-alloy interface. Deposited RuO2 films also was found to increase of current efficiency by more than 10%.

  4. Iron Oxide Hyperthermia And Radiation Cancer Treatment

    PubMed Central

    Cassim, SM; Giustini, AJ; Petryk, AA; Strawbridge, RA; Hoopes, PJ

    2014-01-01

    It is established that heat can enhance the effect of radiation cancer treatment. Due to the ability to localize thermal energy using nanoparticle hyperthermia, as opposed to other, less targeted, hyperthermia modalities, it appears such enhancement could be accomplished without complications normally associated with systemic or regional hyperthermia. This study employs non-curative (suboptimal), doses of heat and radiation, in an effort to determine the therapeutic enhancement potential for IONP hyperthermia and radiation. Methods MTG-B murine breast adenocarcinoma cell are inoculated into the right flanks of female CH3/HEJ mice and grown to volumes of 150mm3 +/? 40 mm3. A single dose of 15 Gy (6 MeV) radiation was uniformly delivered to the tumor. A pre-defined thermal dose is delivered by direct injection of iron oxide nanoparticles into the tumor. By adjusting the field strength of the 160 KHz alternating magnetic field (AMF) an intra-tumoral temperature between 41.5 and 43 degrees Celsius was maintained for 10min. The alternating magnetic field was delivered by a water-cooled 36mm diameter square copper tube induction coil operating at 160 kHz with variable magnet field strengths up to 450 Oe. The primary endpoint of the study is the number of days required for the tumor to achieve a volume 3 fold greater than the volume at the time of treatment (tumor regrowth delay). Results Preliminary results suggest the addition of a modest IONP hyperthermia to 15 Gy radiation achieved an approximate 50% increase in tumor regrowth delay as compared to a 15 Gy radiation treatment alone. The therapeutic effects of IONP heat and radiation combined were considered additive, however in mice that demonstrated complete response (no tumor present after 30 days), the effect was considered superadditive or synergistic. Although this data is very encouraging from a multimodality cancer therapy standpoint, additional temporal and dose related information is clearly necessary to optimize the therapy. PMID:25346582

  5. 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.

  6. 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 ?A 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

  7. High-sensitivity paracetamol sensor based on Pd/graphene oxide nanocomposite as an enhanced electrochemical sensing platform.

    PubMed

    Li, Junhua; Liu, Jinlong; Tan, Gongrong; Jiang, Jianbo; Peng, Sanjun; Deng, Miao; Qian, Dong; Feng, Yonglan; Liu, Youcai

    2014-04-15

    Well-dispersed Pd nanoparticles were facilely anchored on graphene oxide (Pd/GO) via a one-pot chemical reduction of the Pd(2+) precursor without any surfactants and templates. The morphology and composition of the Pd/GO nanocomposite were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR) and energy dispersive analysis of X-ray (EDX). The stepwise fabrication process of the Pd/GO modified electrode and its electrochemical sensing performance towards paracetamol was evaluated using electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The experimental results indicate that the as-synthesized Pd nanoparticles are relatively uniform in size (5-10 nm) without large aggregation and uniformly distributed in the carbon matrix with the overall Pd content of 28.77 wt% in Pd/GO. Compared with the GO modified electrode, the Pd/GO modified electrode shows a better electrocatalytic activity to the oxidation of paracetamol with lower oxidation potential and larger peak current, so the Pd/GO nanocomposite can be used as an enhanced sensing platform for the electrochemical determination of paracetamol. The kinetic parameters of the paracetamol electro-oxidation at Pd/GO electrode were studied in detail, and the determination conditions were optimized. Under the optimal conditions, the oxidation peak current is linear to the paracetamol concentration in the ranges of 0.005-0.5 ?M and 0.5-80.0 ?M with a detection limit of 2.2 nM. Based on the high sensitivity and good selectivity of the Pd/GO modified electrode, the proposed method was successfully applied to the determination of paracetamol in commercial tablets and human urines, and the satisfactory results confirm the applicability of this sensor in practical analysis. PMID:24315879

  8. Phase Transformation and Morphology of Calcium Phosphate Prepared by Electrochemical Deposition Process Through Alkali Treatment and Calcination

    NASA Astrophysics Data System (ADS)

    Chen, Hui-Ting; Wang, Moo-Chin; Chang, Kuo-Ming; Wang, Szu-Hao; Shih, Wei-Jen; Li, Wong-Long

    2014-04-01

    The phase transformation and morphology of calcium phosphate prepared by the electrochemical deposition (ECD) process through alkali treatment and calcination have been characterized using X-ray diffraction (XRD), thermogravimetry and differential thermal analyses (TG/DTA), and scanning electron microscopy (SEM). At the ECD process, when the excess OH- was produced, the reaction of 10Ca2++6PO{4/3-}+2OH-?Ca10(PO4)6(OH)2 takes place on the Ti-6Al-4V and the HA is deposited. The XRD results reveal that the as-deposit was mostly composed of dicalcium phosphate dehydrate (Ca2H4P2O9; DCPD) and the minor phase of hydroxyapatite (Ca10(PO4)6(OH)2; HA). After NaOH treatment, all DCPD were converted to HA. Moreover, the content of HA phase increases with ECD potential. After being calcined at 673 K and 873 K (400 C and 600 C) for 4 hours, the phase of HA maintained the major phase for an alkali-treated deposited sample. After being calcined at 1073 K (800 C) for 4 hours, some HA decomposed and caused the minor phases of ?-tricalcium phosphate ( ?-Ca3(PO4)2; ?-TCP), calcium pyrophosphate (Ca2P2O7; CPP), and calcium oxide (CaO) formation. The ?-TCP becomes the major phase with residual HA and CaO after being calcined at 1273 K (1000 C) for 4 hours. The crack forms due to the release of absorbed water from the interior to top surface of sample. For the as-alkali treatment samples, the microstructures were affected by ECD potentials; when the deposited samples after alkali treatment and calcined at 1073 K (800 C) for 4 hours, the microstructure presents the need-like "preforming HA" (pre-HA) from the matrix of plate-like postforming HA (post-HA).

  9. 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.

  10. Improved in vivo performance of amperometric oxygen (PO2) sensing catheters via electrochemical nitric oxide generation/release.

    PubMed

    Ren, Hang; Coughlin, Megan A; Major, Terry C; Aiello, Salvatore; Rojas Pena, Alvaro; Bartlett, Robert H; Meyerhoff, Mark E

    2015-08-18

    A novel electrochemically controlled release method for nitric oxide (NO) (based on electrochemical reduction of nitrite ions) is combined with an amperometric oxygen sensor within a dual lumen catheter configuration for the continuous in vivo sensing of the partial pressure of oxygen (PO2) in blood. The on-demand electrochemical NO generation/release method is shown to be fully compatible with amperometric PO2 sensing. The performance of the sensors is evaluated in rabbit veins and pig arteries for 7 and 21 h, respectively. Overall, the NO releasing sensors measure both venous and arterial PO2 values more accurately with an average deviation of -2 11% and good correlation (R(2) = 0.97) with in vitro blood measurements, whereas the corresponding control sensors without NO release show an average deviation of -31 28% and poor correlation (R(2) = 0.43) at time points >4 h after implantation in veins and >6 h in arteries. The NO releasing sensors induce less thrombus formation on the catheter surface in both veins and arteries (p < 0.05). This electrochemical NO generation/release method could offer a new and attractive means to improve the biocompatibility and performance of implantable chemical sensors. PMID:26201351

  11. Nitrogen doped holey graphene as an efficient metal-free multifunctional electrochemical catalyst for hydrazine oxidation and oxygen reduction

    NASA Astrophysics Data System (ADS)

    Yu, Dingshan; Wei, Li; Jiang, Wenchao; Wang, Hong; Sun, Bo; Zhang, Qiang; Goh, Kunli; Si, Rongmei; Chen, Yuan

    2013-03-01

    Electrocatalysts for anode or cathode reactions are at the heart of electrochemical energy conversion and storage devices. Molecular design of carbon based nanomaterials may create the next generation electrochemical catalysts for broad applications. Herein, we present the synthesis of a three-dimensional (3D) nanostructure with a large surface area (784 m2 g-1) composed of nitrogen doped (up to 8.6 at.%) holey graphene. The holey structure of graphene sheets (~25% of surface area is attributed to pores) engenders more exposed catalytic active edge sites. Nitrogen doping further improves catalytic activity, while the formation of the 3D porous nanostructure significantly reduces graphene nanosheet stacking and facilitates the diffusion of reactants/electrolytes. The three factors work together, leading to superb electrochemical catalytic activities for both hydrazine oxidation (its current generation ability is comparable to that of 10 wt% Pt-C catalyst) and oxygen reduction (its limiting current is comparable to that of 20 wt% Pt-C catalyst) with four-electron transfer processes and excellent durability.Electrocatalysts for anode or cathode reactions are at the heart of electrochemical energy conversion and storage devices. Molecular design of carbon based nanomaterials may create the next generation electrochemical catalysts for broad applications. Herein, we present the synthesis of a three-dimensional (3D) nanostructure with a large surface area (784 m2 g-1) composed of nitrogen doped (up to 8.6 at.%) holey graphene. The holey structure of graphene sheets (~25% of surface area is attributed to pores) engenders more exposed catalytic active edge sites. Nitrogen doping further improves catalytic activity, while the formation of the 3D porous nanostructure significantly reduces graphene nanosheet stacking and facilitates the diffusion of reactants/electrolytes. The three factors work together, leading to superb electrochemical catalytic activities for both hydrazine oxidation (its current generation ability is comparable to that of 10 wt% Pt-C catalyst) and oxygen reduction (its limiting current is comparable to that of 20 wt% Pt-C catalyst) with four-electron transfer processes and excellent durability. Electronic supplementary information (ESI) available: AFM images of GO sheets, nitrogen physisorption isotherms, XPS spectrum of RG, RDE curves of electrodes, CV curves of electrodes, and determination of the number of total electrons (n) involved in hydrazine oxidation. See DOI: 10.1039/c3nr34267k

  12. Evaluation of an integrated continuous stirred microbial electrochemical reactor: Wastewater treatment, energy recovery and microbial community.

    PubMed

    Wang, Haiman; Qu, Youpeng; Li, Da; Zhou, Xiangtong; Feng, Yujie

    2015-11-01

    A continuous stirred microbial electrochemical reactor (CSMER) was developed by integrating anaerobic digestion (AD) and microbial electrochemical system (MES). The system was capable of treating high strength artificial wastewater and simultaneously recovering electric and methane energy. Maximum power density of 5839, 5627, 53310 and 5726 mW m(-2) were obtained by each cell in a four-independent circuit mode operation at an OLR of 12 kg COD m(-3) d(-1). COD removal and energy recovery efficiency were 87.1% and 32.1%, which were 1.6 and 2.5 times higher than that of a continuous stirred tank reactor (CSTR). Larger amount of Deltaproteobacteria (5.3%) and hydrogenotrophic methanogens (47%) can account for the better performance of CSMER, since syntrophic associations among them provided more degradation pathways compared to the CSTR. Results demonstrate the CSMER holds great promise for efficient wastewater treatment and energy recovery. PMID:26094049

  13. Effects of direct current on dog liver: Possible mechanisms for tumor electrochemical treatment

    SciTech Connect

    Li, K.H.; Gu, Y.N.; Xu, B.I.; Fan, D.J.; Ni, B.F.; Xin, Y.L.

    1997-03-01

    Mechanisms of tumor electrochemical treatment (ECT) were studied using normal dog liver. Five physical and chemical methods were used. Two platinum electrodes were inserted into an anesthetized dog`s liver at 3 cm separation. A voltage of 8.5 V direct current (DC) at an average current of 30 mA was applied for 69 min; total charge was 124 coulombs. Concentrations of selected ions near the anode and cathode were measured. The concentrations of Na{sup +} and K{sup +} ions were higher around the cathode, whereas the concentration of Cl{sup {minus}} ions was higher around the anode. Water contents and pH were determined near the anode and the cathode at the midpoint between the two electrodes and in an untreated area away from the electrodes. Hydration occurred around the cathode, and dehydration occurred around the anode. The pH values were 2.1 near the anode and 12.9 near the cathode. Spectrophotometric scans of the liver sample extract were obtained, and the released gases were identified by gas chromatography as chlorine at the anode and hydrogen at the cathode. These results indicate that a series of electrochemical reactions take place during ECT. The cell metabolism and its environment are severely disturbed. Both normal and tumor cells are rapidly and completely destroyed in this altered environment. The authors believe that the above reactions are the ECT mechanisms for treating tumors.

  14. Electrochemical oxidation of ampicillin antibiotic at boron-doped diamond electrodes and process optimization using response surface methodology.

    PubMed

    Krbahti, Bahad?r K; Ta?yrek, 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

  15. 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

  16. Electrochemical detection of Cu2+ through Ag nanoparticle assembly regulated by copper-catalyzed oxidation of cysteamine.

    PubMed

    Cui, Lin; Wu, Jie; Li, Jie; Ge, Yanqiu; Ju, Huangxian

    2014-05-15

    A highly sensitive and selective electrochemical sensor was developed for the detection of Cu(2+) by the assembly of Ag nanoparticles (AgNPs) at dithiobis[succinimidylpropionate] encapsulated Au nanoparticles (DSP-AuNPs), which was regulated by copper-catalyzed oxidation of cysteamine (Cys). The electrochemical sensor was constructed by layer-by-layer modification of glassy carbon electrode with carbon nanotubes, poly(amidoamine) dendrimers and DSP-AuNPs. In the absence of Cu(2+), Cys could bind to the surface of citrate-stabilized AgNPs via Ag-S bond, thus AgNPs could be assembled on the sensor surface through the reaction between DSP and Cys. In contrast, the copper-catalyzed oxidation of Cys by dissolved oxygen in the presence of Cu(2+) inhibited the Cys-induced aggregation of AgNPs, leading to the decrease of the electrochemical stripping signal of AgNPs. Under the optimized conditions, this method could detect Cu(2+) in the range of 1.0-1000 nM with a detection limit of 0.48 nM. The proposed Cu(2+) sensor showed good reproducibility, stability and selectivity. It has been satisfactorily applied to determine Cu(2+) in water samples. PMID:24389390

  17. Tailoring the structural and microstructural properties of nanosized tantalum oxide for high temperature electrochemical gas sensors.

    PubMed

    Bonavita, Anna; Di Bartolomeo, Elisabetta; Chevallier, Laure; D'Ottavi, Cadia; Licoccia, Silvia; Traversa, Enrico

    2009-07-01

    Ta2O5 nanopowders to be used as sensing electrodes in high temperature electrochemical gas sensors for hydrocarbons detection were synthesized using a sol-gel method and their structural and microstructural properties were investigated. The as-synthesized powders were heated at different temperatures in the range 250-1000 degrees C and characterized by TG-DTA, XRD, SEM, TEM and FT-IR. This investigation allowed to identify the correct thermal treatments to achieve the microstructural, textural and functional stability of materials working at high temperature, preserving their nano-metric grain size. Planar sensors fabricated by using Ta2O5 powders treated at 750 degrees C showed promising results for the selective detection of propylene at high temperature (700 degrees C). The good stability of the sensing response after gas exposure at high temperature was correlated to the stable microstructure the electrodes. Thus, Ta2O5 powders seems good candidate as sensing electrode for sensors for automotive exhausts monitoring. PMID:19916469

  18. 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

  19. 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

  20. High performance liquid chromatography coupled with post-column electrochemical oxidation for the detection of PSP toxins.

    PubMed

    Boyer, G L; Goddard, G D

    1999-01-01

    High Performance Liquid Chromatography (HPLC) is an important tool for the study of PSP toxins. It provides an alternative to bioassays and gives the concentration of individual toxin isomers. The current HPLC protocol uses a post-column chemical reaction system (PCRS) to oxidize the saxitoxin ring system to form a fluorescent chromophore. This oxidation is sensitive to changes in the flow rate, temperature, pH and age of the reagents. We have previously shown that this oxidation can be accomplished using electrochemical techniques. Termed the electrochemical oxidation system (ECOS), this approach provides a simpler alternative to the traditional PCRS-based HPLC system. A detailed description of the construction and maintenance of an HPLC-ECOS system for the analysis of PSP toxins is presented. Comparisons of the mouse bioassay, HPLC-PCRS and HPLC-ECOS system are presented for three different sample matrices: toxic dinoflagellates (Alexandrium tamarense), geoduck (Panopea generosa) and scallops (Placopectin magellanicus). In all three cases, the correlation of the HPLC-ECOS system to the mouse bioassay is similar to that obtained using the HPLC-PCRS system for the analysis of PSP toxins. PMID:11122529

  1. 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

  2. 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-? (SDC) and three types of semiconductors Li0.3Ni0.6Cu0.07Sr0.03O2-? (LNCuS), Li0.3Ni0.6Mn0.07Sr0.03O2-? (LNMnS) and Li0.3Ni0.6Co0.07Sr0.03O2-? (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 ? 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.

  3. 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.

  4. NITROUS OXIDE EMISSIONS FROM RIPARIAN BUFFERS AND TREATMENT WETLANDS

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Riparian buffers and treatment wetlands are used throughout the world for the protection of water bodies from nonpoint source pollution, particularly nitrogen. Yet, relatively few studies of riparian or treatment wetland denitrification consider the production of nitrous oxide. Nitrous oxide emissio...

  5. Green synthesis of silver nanoparticles-graphene oxide nanocomposite and its application in electrochemical sensing of tryptophan.

    PubMed

    Li, Junhua; Kuang, Daizhi; Feng, Yonglan; Zhang, Fuxing; Xu, Zhifeng; Liu, Mengqin; Wang, Deping

    2013-04-15

    A new kind of nanocomposite based on silver nanoparticles (AgNPs)/graphene oxide (GO) was conveniently achieved through a green and low-cost synthesis approach using glucose as a reducing and stabilizing agent, and the synthetic procedure can be easily used for the construction of a disposable electrochemical sensor on glassy carbon electrode (GCE). The nanocomposite was detailedly characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX), Fourier transform infrared spectroscopy (FTIR) and electrochemical impedance spectroscopy (EIS). The experimental results demonstrated that the nanocomposite possessed the specific features of both silver nanoparticles and graphene, and the intrinsic high specific area and the fast electron transfer rate ascribed to the nanohybrid structure could improve its electrocatalytic performance greatly. Cyclic voltammetry (CV) and differential pulse voltammetry (DPV) were employed to evaluate the electrochemical properties of AgNPs/GO/GCE towards tryptophan, and the AgNPs/GO film exhibited a distinctly higher activity for the electro-oxidation of tryptophan than GO film with tenfold enhancement of peak current. The oxidation mechanism and the kinetic parameters were investigated, and analysis operation conditions were optimized. Under the selected experimental conditions, the oxidation peak currents were proportional to tryptophan concentrations over the range of 0.01 ?M to 50.0 ?M and 50.0 ?M to 800.0 ?M, respectively. The detection limit was 2.0 nM (S/N=3). Moreover, the proposed method is free of interference from tyrosine and other coexisting species. The resulting sensor displays excellent repeatability and long-term stability; finally it was successfully applied to detect tryptophan in real samples with good recoveries, ranging from 99.0% to 103.0%. PMID:23202352

  6. Hybrid nickel manganese oxide nanosheet-3D metallic dendrite percolation network electrodes for high-rate electrochemical energy storage.

    PubMed

    Nguyen, Tuyen; Eugnio, Snia; Boudard, Michel; Rapenne, Laetitia; Carmezim, M Joo; Silva, Teresa M; Montemor, M Ftima

    2015-08-01

    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. PMID:26135715

  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; Eugnio, Snia; Boudard, Michel; Rapenne, Laetitia; Carmezim, M. Joo; Silva, Teresa M.; Montemor, M. Ftima

    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. Electrochemical oxidation of trace organic contaminants in reverse osmosis concentrate using RuO2/IrO2-coated titanium anodes.

    PubMed

    Radjenovic, Jelena; Bagastyo, Arseto; Rozendal, Ren A; Mu, Yang; Keller, Jrg; Rabaey, Korneel

    2011-02-01

    During membrane treatment of secondary effluent from wastewater treatment plants, a reverse osmosis concentrate (ROC) containing trace organic contaminants is generated. As the latter are of concern, effective and economic treatment methods are required. Here, we investigated electrochemical oxidation of ROC using Ti/Ru(0.7)Ir(0.3)O(2) electrodes, focussing on the removal of dissolved organic carbon (DOC), specific ultra-violet absorbance at 254 nm (SUVA(254)), and 28 pharmaceuticals and pesticides frequently encountered in secondary treated effluents. The experiments were conducted in a continuously fed reactor at current densities (J) ranging from 1 to 250 A m(-2) anode, and a batch reactor at J = 250 A m(-2). Higher mineralization efficiency was observed during batch oxidation (e.g. 25.1 2.7% DOC removal vs 0% removal in the continuous reactor after applying specific electrical charge, Q = 437.0 A h m(-3) ROC), indicating that DOC removal is depending on indirect oxidation by electrogenerated oxidants that accumulate in the bulk liquid. An initial increase and subsequent slow decrease in SUVA(254) during batch mode suggests the introduction of auxochrome substituents (e.g. -Cl, NH(2)Cl, -Br, and -OH) into the aromatic compounds. Contrarily, in the continuous reactor ring-cleaving oxidation products were generated, and SUVA(254) removal correlated with applied charge. Furthermore, 20 of the target pharmaceuticals and pesticides completely disappeared in both the continuous and batch experiments when applying J ? 150 A m(-2) (i.e. Q ? 461.5 A h m(-3)) and 437.0 A h m(-3) (J = 250 A m(-2)), respectively. Compounds that were more persistent during continuous oxidation were characterized by the presence of electrophilic groups on the aromatic ring (e.g. triclopyr) or by the absence of stronger nucleophilic substituents (e.g. ibuprofen). These pollutants were oxidized when applying higher specific electrical charge in batch mode (i.e. 1.45 kA h m(-3) ROC). However, baseline toxicity as determined by Vibrio fischeri bioluminescence inhibition tests (Microtox) was increasing with higher applied charge during batch and continuous oxidation, indicating the formation of toxic oxidation products, possibly chlorinated and brominated organic compounds. PMID:21167547

  12. Electrochemical treatment of perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS) in groundwater impacted by aqueous film forming foams (AFFFs).

    PubMed

    Schaefer, Charles E; Andaya, Christina; Urtiaga, Ana; McKenzie, Erica R; Higgins, Christopher P

    2015-09-15

    Laboratory experiments were performed to evaluate the use of electrochemical treatment for the decomposition of perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS), as well as other perfluoroalkyl acids (PFAAs), in aqueous film forming foam (AFFF)-impacted groundwater collected from a former firefighter training area and PFAA-spiked synthetic groundwater. Using a commercially-produced Ti/RuO2 anode in a divided electrochemical cell, PFOA and PFOS decomposition was evaluated as a function of current density (0-20 mA/cm(2)). Decomposition of both PFOA and PFOS increased with increasing current density, although the decomposition of PFOS did not increase as the current density was increased above 2.5 mA/cm(2). At a current density of 10 mA/cm(2), the first-order rate constants, normalized for current density and treatment volume, for electrochemical treatment of both PFOA and PFOS were 46 10(-5) and 70 10(-5) [(min(-1)) (mA/cm(2))(-1) (L)], respectively. Defluorination was confirmed for both PFOA and PFOS, with 58% and 98% recovery as fluoride, respectively (based upon the mass of PFOA and PFOS degraded). Treatment of other PFAAs present in the groundwater also was observed, with shorter chain PFAAs generally being more recalcitrant. Results highlight the potential for electrochemical treatment of PFAAs, particularly PFOA and PFOS, in AFFF-impacted groundwater. PMID:25909497

  13. An electrochemical and computational study for discrimination of D- and L-cystine by reduced graphene oxide/?-cyclodextrin.

    PubMed

    Zor, Erhan; Bingol, Haluk; Ramanaviciene, Almira; Ramanavicius, Arunas; Ersoz, Mustafa

    2015-01-01

    Here, we report a novel enantioselective electrochemical biosensor for the discrimination of cystine enantiomers (d- and l-cystine) using a chiral interface for the specific recognition of d- and l-cystine. The biosensor is based on reduced graphene oxide modified by ?-cyclodextrin (rGO/?-CD) at the GCE surface. During the preparation of rGO/?-CD/GCE, the modified electrode surfaces were characterized by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM). The electrochemical behaviours of the d- and l-cystine were investigated using the rGO/?-CD/GCE by CV and compared to bare GCE. A clear separation between the oxidation peak potentials of d- and l-cystine was observed at 1.32 and 1.42 V, respectively. The electrochemical discrimination performance of the fabricated chiral sensor was also examined by differential pulse voltammetry (DPV) in a mixed solution of d- and l-cystine. In addition, the DPV technique was used for the determination of d- and l-cystine at low concentration values in the range of 1.0-10.0 ?M. To investigate the amperometric response of rGO/?-CD/GCE towards d- and l-cystine, the chronoamperometry technique was used in the concentration range of 10.0-100.0 ?M. The interactions of the enantiomers with rGO/?-CD were modelled by molecular docking using AutoDock Vina, and the interaction energies were predicted to be -4.8 and -5.3 kcal mol(-1) for d- and l-cystine, respectively. The corresponding values of binding constants were calculated to be 3.32 10(3) and 7.71 10(3) M(-1), respectively. The experimental and molecular docking results indicate that the rGO/?-CD/GCE has a different affinity for each enantiomer. PMID:25382195

  14. A Novel Electrochemical Membrane Bioreactor as a Potential Net Energy Producer for Sustainable Wastewater Treatment

    PubMed Central

    Wang, Yun-Kun; Sheng, Guo-Ping; Shi, Bing-Jing; Li, Wen-Wei; Yu, Han-Qing

    2013-01-01

    One possible way to address both water and energy shortage issues, the two of major global challenges, is to recover energy and water resource from wastewater. Herein, a novel electrochemical membrane bioreactor (EMBR) was developed to recover energy from wastewater and meantime harvest clean water for reuse. With the help of the microorganisms in the biocatalysis and biodegradation process, net electricity could be recovered from a low-strength synthetic wastewater after estimating total energy consumption of this system. In addition, high-quality clean water was obtained for reuse. The results clearly demonstrate that, under the optimized operating conditions, it is possible to recover net energy from wastewater, while at the same time to harvest high-quality effluent for reuse with this novel wastewater treatment system. PMID:23689529

  15. 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.

  16. Comparative study of the effect of pharmaceutical additives on the elimination of antibiotic activity during the treatment of oxacillin in water by the photo-Fenton, TiO2-photocatalysis and electrochemical processes.

    PubMed

    Serna-Galvis, Efraim A; Silva-Agredo, Javier; Giraldo, Ana L; Flórez-Acosta, Oscar A; Torres-Palma, Ricardo A

    2016-01-15

    Synthetic pharmaceutical effluents loaded with the β-lactam antibiotic oxacillin were treated using advanced oxidation processes (the photo-Fenton system and TiO2 photocatalysis) and chloride mediated electrochemical oxidation (with Ti/IrO2 anodes). Combinations of the antibiotic with excipients (mannitol or tartaric acid), an active ingredient (calcium carbonate, i.e. bicarbonate ions due to the pH) and a cleaning agent (sodium lauryl ether sulfate) were considered. Additionally, urban wastewater that had undergone biological treatment was doped with oxacillin and treated with the tested systems. The evolution of antimicrobial activity was monitored as a parameter of processes efficiency. Although the two advanced oxidation processes (AOPs) differ only in the way they produce OH, marked differences were observed between them. There were also differences between the AOPs and the electrochemical system. Interestingly, each additive had a different effect on each treatment. For water loaded with mannitol, electrochemical treatment was the most suitable option because the additive did not significantly affect the efficiency of the system. Due to the formation of a complex with Fe(3+), tartaric acid accelerated the elimination of antibiotic activity during the photo-Fenton process. For TiO2 photocatalysis, the presence of bicarbonate ions contributed to antibiotic activity elimination through the possible formation of carbonate and bicarbonate radicals. Sodium lauryl ether sulfate negatively affected all of the processes. However, due to the higher selectivity of HOCl compared with OH, electrochemical oxidation showed the least inhibited efficiency. For the urban wastewater doped with oxacillin, TiO2 photocatalysis was the most efficient process. These results will help select the most suitable technology for the treatment of water polluted with β-lactam antibiotics. PMID:26479916

  17. 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

    2015-11-18

    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

  18. 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

  19. Electrochemical Sensor Based on Carbon Paste Electrode Modified with Nanostructured Crypotomelane-Type Manganese Oxides for Detection of Heavy Metals

    SciTech Connect

    Cui, Xiaoli; Liu, Guodong; Li, Liyu; Yantasee, Wassana; Lin, Yuehe

    2005-02-03

    A carbon paste electrode modified with nanostructured crypotomelane type manganese oxides was evaluated as new electrochemical sensor for the detection of heavy metal ions in aqueous media. The crypotomelane type manganese oxides are nanofibrous crystals with sub-nanometer tunnels which provide excellent sites for ion-exchanges. The adsorptive stripping voltammetry (ASV) technique involves preconcentration of the metal ions into nanostructured crypotomelane type manganese oxides under an open circuit, then electrolysis of the preconcentrated species, followed by a square-wave potential sweep towards positive values. Factors affecting the preconcentration process were investigated using lead ion as the model analyte. The voltammetric responses increased with the preconcentration time from 2 to 30 min, and also linearly with lead ion concentrations ranging from 50 to 1200 ppb. The detection limits of target metal ion were 10 ppb after 4 min preconcentration and improved to 1 ppb after 20 min preconcentration. The potential for simultaneous detection of copper, silver and lead is also discussed.

  20. Degradation of 1-hydroxy-2,4-dinitrobenzene from aqueous solutions by electrochemical oxidation: role of anodic material.

    PubMed

    Quiroz, Marco A; Snchez-Salas, Jos L; Reyna, Silvia; Bandala, Erick R; Peralta-Hernndez, Juan M; Martnez-Huitle, Carlos A

    2014-03-15

    Electrochemical oxidation (ECOx) of 1-hydroxy-2,4-dinitrobenzene (or 2,4-dinitrophenol: 2,4-DNP) in aqueous solutions by electrolysis under galvanostatic control was studied at Pb/PbO2, Ti/SnO2, Ti/IrxRuySnO2 and Si/BDD anodes as a function of current density applied. Oxidative degradation of 2,4-DNP has clearly shown that electrode material and the current density applied were important parameters to optimize the oxidation process. It was observed that 2,4-DNP was oxidized at few substrates to CO2 with different results, obtaining good removal efficiencies at Pb/PbO2, Ti/SnO2 and Si/BDD anodes. Trends in degradation way depend on the production of hydroxyl radicals (OH) on these anodic materials, as confirmed in this study. Furthermore, HPLC results suggested that two kinds of intermediates were generated, polyhydroxylated intermediates and carboxylic acids. The formation of these polyhydroxylated intermediates seems to be associated with the denitration step and substitution by OH radicals on aromatic rings, this being the first proposed step in the reaction mechanism. These compounds were successively oxidized, followed by the opening of aromatic rings and the formation of a series of carboxylic acids which were at the end oxidized into CO2 and H2O. On the basis of these information, a reaction scheme was proposed for each type of anode used for 2,4-D oxidation. PMID:24462986

  1. A wind-powered BDD electrochemical oxidation process for the removal of herbicides.

    PubMed

    Souza, F L; Lanza, M R V; Llanos, J; Sáez, C; Rodrigo, M A; Cañizares, P

    2015-08-01

    In the search for greener treatment technologies, this work studies the coupling of a wind turbine energy supply with an electrolytic cell (CWTEC device) for the remediation of wastewater polluted with pesticide 2,4-dichlorophenoxyacetic acid (2,4-D). The discontinuous and unforeseeable supply of energy is the main challenge inspiring this new proposal, which aims at reducing the environmental impact of electrolytic treatment by using a green energy supply. The results obtained using the coupled technologies are compared with those obtained by powering the electrolyser with a traditional power supply with a similar current intensity. The mineralisation of wastewater can be accomplished independently of how the electrolytic cell is powered, although differences in performance are clearly observed in the total organic carbon (TOC) and 2,4-D decays. These changes can be explained in terms of the changing profile of the current intensity, which influences the concentrations of the oxidants produced and thereby the mediated electrolytic process. PMID:25950835

  2. Chemical and electrochemical oxidation of thiophene-pyridine and thiophene-pyrimidine co-oligomers in solutions.

    PubMed

    Kumagai, Akira; Fukumoto, Hiroki; Yamamoto, Takakazu

    2007-07-19

    Chemical and electrochemical oxidation (or p-doping) of three types of pi-conjugated co-oligomers, Py-Th-(Th)n-Th-Py (Py = pyridine unit; Th = thiophene unit; 5a, n = 1; 6a, n = 2), Th-Py-(Th)n-Py-Th (5b: n = 1; 6b: n = 2), and Pym-Th-(Th)n-Th-Pym (Pym = pyrimidine unit; 5c: n = 1; 6c: n = 2), in solution systems has been studied. The chemical oxidation with NOBF(4) proceeded with isosbestic points in the UV-vis spectrum. The UV-vis absorption peak of 5a at 418 nm in CH(2)Cl(2) shifted to 456 nm after oxidation of 5a with NOBF(4). The oxidized 5a was easily reduced by N(2)H(4) to give the original UV-vis spectrum of 5a, and 5b, 6b, and 5c behaved similarly in the oxidation and reduction. In the oxidation by NOBF4, an (oxidized co-oligomer)/(original neutral co-oligomer) ratio of 1 was attained at [NOBF4] = 1.3 x 10(-6), 4 x 10(-6), 7 x 10(-6), and 9 x 10(-6) M for 5a, 6b, 5b, and 5c, respectively. The obtained data are considered to reflect the ease of oxidation of the co-oligomer, which is affected by the electron-accepting nature of the N-containing aromatic unit in the co-oligomer and effective pi-conjugated length of the co-oligomer. The cyclic voltammogram of 5a showed three redox couples with anodic peak current potentials of Epa = 0.75, 1.10, and 1.34 V versus Ag+/Ag, respectively. The first oxidation peak was assigned to one-electron oxidation of 5a, and electronic current of the first anodic peak (i) of 5a and 5c was proportional to (scanning rate)1/2. From the i- (scanning rate)1/2 relationship, diffusion constants, D's, of 5a and 5c were estimated to be 9.6 x 10(-6) and 1.7 x 10(-5) cm2 s(-1), respectively. CV data of 5b with the terminal thiophene units indicated occurrence of electrochemical oxidative polymerization of 5b. PMID:17590042

  3. Composition of simulants used in the evaluation of electrochemical processes for the treatment of high-level wastes

    SciTech Connect

    Hobbs, D.T.

    1994-06-27

    Four simulants are being used in the evaluation of electrochemical processes for the treatment of high-level wastes (HLW). These simulants represent waste presently stored at the Hanford, Idaho Falls, Oak Ridge, and Savannah River sites. Three of the simulants are highly alkaline salt solutions (Hanford, Oak Ridge, and Savannah River), and one is highly acidic (Idaho Falls).

  4. Electrochemical deposition and behavior of mixed-valent molybdenum oxide film at glassy carbon and ITO electrodes

    NASA Astrophysics Data System (ADS)

    Koak, Sleyman; Erta?, Fatma Nil; Dursun, Zekerya

    2013-01-01

    The effect of solution composition and the type of the anionic species on the electrochemical formation of mixed-valent molybdenum oxide on a glassy carbon and ITO electrode surfaces was elucidated. Susccessive recording of the voltammograms has shown that anionic species display different stabilizing effect on the reductive formation of hydrogen molybdenum bronzes [MoO3-x (OH)x] and chloroacetic acid buffer has given the best results. The deposit was built upon cycling the potential between 0 and -0.9 V (vs. Ag/AgCl) via reduction of Mo(VI) to Mo(V) on the electrode surface in pH 3.0 chloroacetic acid solution. Electrochemical impedance measurements carried out in this medium revealed a shift in potential zero charge values from -0.2 V to -0.55 V after the potential of the GCE had been cycled for 30 min. An establishment of mixed-valent molybdenum oxide deposit by time on the gold electrode surface was proved by quartz crystal microbalance measurements. Atomic force and scanning electron microscopy techniques were made use of so as to characterize the surface structures of the electrodes. X-ray photoelectron spectroscopy studies confirmed that the deposit contains both Mo(V) and Mo(VI). The deposited films exhibited unique catalytic activity towards nitrite oxidation consistent with the change in peak characteristics.

  5. 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.

  6. 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

  7. 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?M, 4-400?M and 0.3-40?M, respectively, and the detection limits were 0.17?M, 1.33?M and 0.1?M (S/N=3). Under optimal conditions, the sensor displayed high sensitivity, excellent stability and satisfactory results in real samples analysis. PMID:26695242

  8. Real-time investigation of antibiotics-induced oxidative stress and superoxide release in bacteria using an electrochemical biosensor.

    PubMed

    Liu, Xiaobo; Marrakchi, Mouna; Jahne, Michael; Rogers, Shane; Andreescu, Silvana

    2016-02-01

    The involvement of oxidative stress in the mechanism of antibiotics-meditated cell death is unclear and subject to debate. The kinetic profile and a quantitative relationship between the release of reactive oxygen species (ROS), bacteria and antibiotic type remain elusive. Here we report direct measurements and analytical quantification of the release of superoxide radicals (O2(-)), a major contributor to ROS, in antibiotics-treated bacterial cultures using a cytochrome c electrochemical biosensor. The specificity of electrochemical measurements was established by the addition of superoxide dismutase (SOD) which decreased the O2()(-) signal. Measurements using a general ROS-specific fluorescence dye and colony forming units (CFU) assays were performed side-by-side to determine the total ROS and establish the relationship between ROS and the degree of lethality. Exposure of Escherichia coli and Listeria monocytogenes cultures to antibiotics increased the release of O2(-) radicals in a dose-dependent manner, suggesting that the transmembrane generation of ROS may occur as part of the antibiotic action. The study provides a quantitative methodology and fundamental knowledge to further explore the role of oxidative stress in antibiotics-meditated bacterial death and to assess physiological changes associated with the complex metabolic events related to oxidative stress and bacterial resistance. PMID:26655038

  9. An electrochemical study of the oxidation of hydrogen at platinum electrodes in several room temperature ionic liquids.

    PubMed

    Silvester, Debbie S; Aldous, Leigh; Hardacre, Christopher; Compton, Richard G

    2007-05-10

    The electrochemical oxidation of dissolved hydrogen gas has been studied in a range of room-temperature ionic liquids (RTILs), namely [C(2)mim][NTf(2)], [C(4)mim][NTf(2)], [N(6,2,2,2)][NTf(2)], [P(14,6,6,6)][NTf(2)], [C(4)mpyrr][NTf(2)], [C(4)mim][BF(4)], [C(4)mim][PF(6)], [C(4)mim][OTf], and [C(6)mim]Cl on a platinum microdisk electrode of diameter 10 microm. In all cases, except [C(6)mim]Cl, a broad quasi-electrochemically reversible oxidation peak between 0.3 to 1.3 V vs Ag was seen prior to electrode activation ([C(6)mim]Cl showed an almost irreversible wave). When the electrode was pre-anodized ("activated") at 2.0 V vs Ag for 1 min, the peak separations became smaller, and the peak shape became more electrochemically reversible. It is thought that the electrogenerated protons chemically combine with the anions (A-) of the RTIL. The appearance and position of the reverse (reduction) peak on the voltammograms is thought to depend on three factors: (1) the stability of the protonated anion, HA, (2) the position of equilibrium of the protonation reaction HA<==> H+ + A- , and (3) any follow-up chemistry, e.g., dissociation or reaction of the protonated anion, HA. This is discussed for the five different anions studied. The reduction of HNTf(2) was also studied in two [NTf(2)]- -based RTILs and was compared to the oxidation waves from hydrogen. The results have implications for the defining of pKa in RTIL media, for the development of suitable reference electrodes for use in RTILs, and in the possible amperometric sensing of H2 gas. PMID:17284067

  10. Electrochemically induced oxidative removal of As(III) from groundwater in a dual-anode sand column.

    PubMed

    Tong, Man; Yuan, Songhu; Wang, Zimeng; Luo, Mingsen; Wang, Yanxin

    2016-03-15

    In situ treatment of high-arsenic groundwater cost-effectively is still challenging. We proposed an in situ treatment approach which utilizes O2 produced from groundwater electrolysis to increase the redox potential for oxidative removal of arsenic. A sand column was configured to simulate groundwater flow in an aquifer, and a stable anode, a stable cathode and an iron anode were arrayed in an upward mode in the column to evaluate the performance on arsenic removal from the groundwater induced by the oxidative precipitation of Fe(2+) by O2. As(III) at 500μg/L was efficiently oxidized to As(V) by the stable anode followed by the reactive oxidants produced from Fe(II)-O2, and total As were completely removed by the newly formed amorphous iron hydroxides. Quantitative models for the dependence of As(III) oxidation, total As removal and Fe(II) oxidative precipitation on the flow rate and the current density applied to Fe anode were developed. The presence of humic substance promoted the oxidation of As(III) on the stable anode but inhibited the oxidation and removal induced by Fe(II) oxidative precipitation. A stable performance on As(III) oxidation and removal was observed in a 10-day continuous operation. Results from this study prove that groundwater electrolysis could be applicable for oxidative removal of As(III) in porous media, with a controllable and lasting treatment efficiency. PMID:26642445

  11. Oxidation state-differentiated measurement of aqueous inorganic arsenic by continuous flow electrochemical arsine generation coupled to gas-phase chemiluminescence detection.

    PubMed

    Sengupta, Mrinal K; Dasgupta, Purnendu K

    2011-12-15

    The electrochemical reduction of inorganic As on a graphite cathode depends on the current density. We observed that while only inorganic As(III) is reduced to AsH(3) at low current densities, at high current densities both forms of inorganic As are reduced. We describe a unique electrochemical reactor in which the cylindrical anode compartment is isolated from the outer concentric cathode compartment by a Nafion tube in which a hole is deliberately made and the entire anode compartment is inside the cylindrical cavity of a small volume (?115 ?L) cathode chamber. The evolved arsine is then quantitated by gas-phase chemiluminescence (GPCL) reaction with ozone; the latter is generated from oxygen formed during electrolysis. For the dimensions used, inorganic As(III) can be selectively determined at a current of 0.1 A while total inorganic As (both As(III) and As(V)) respond equally at an applied electrolysis current at 0.85 A, without any sample treatment. For a 1-mL sample, the system provides a limit of detection (LOD, S/N = 3) of 0.09 ?g/L for total As (i = 0.85 A) and an LOD of 0.76 ?g/L for As(III) (i = 0.10 A); As(V) is obtained by difference. Comparison of ICP-MS results for total As in groundwater samples that span a large range of concentration and total inorganic As determined by the present method showed a high correlation (r(2) = 0.9975) and a near unity slope. The basic electrochemical arsine generation technique and current-differentiated oxidation state speciation should be applicable as the front end to many other arsenic measurements techniques, including atomic spectrometry. PMID:22035322

  12. 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

  13. Electrochemical thinning of silicon

    DOEpatents

    Medernach, J.W.

    1994-01-11

    Porous semiconducting material, e.g. silicon, is formed by electrochemical treatment of a specimen in hydrofluoric acid, using the specimen as anode. Before the treatment, the specimen can be masked. The porous material is then etched with a caustic solution or is oxidized, depending of the kind of structure desired, e.g. a thinned specimen, a specimen, a patterned thinned specimen, a specimen with insulated electrical conduits, and so on. Thinned silicon specimen can be subjected to tests, such as measurement of interstitial oxygen by Fourier transform infra-red spectroscopy (FTIR). 14 figures.

  14. Electrochemical thinning of silicon

    DOEpatents

    Medernach, John W. (Albuquerque, NM)

    1994-01-01

    Porous semiconducting material, e.g. silicon, is formed by electrochemical treatment of a specimen in hydrofluoric acid, using the specimen as anode. Before the treatment, the specimen can be masked. The porous material is then etched with a caustic solution or is oxidized, depending of the kind of structure desired, e.g. a thinned specimen, a specimen, a patterned thinned specimen, a specimen with insulated electrical conduits, and so on. Thinned silicon specimen can be subjected to tests, such as measurement of interstitial oxygen by Fourier transform infra-red spectroscopy (FTIR).

  15. Occurrence and behaviour of dissolved, nano-particulate and micro-particulate iron in waste waters and treatment systems: new insights from electrochemical analysis.

    PubMed

    Matthies, R; Aplin, A C; Horrocks, B R; Mudashiru, L K

    2012-04-01

    Cyclic-, Differential Pulse- and Steady-state Microdisc Voltammetry (CV, DPV, SMV) techniques have been used to quantify the occurrence and fate of dissolved Fe(ii)/Fe(iii), nano-particulate and micro-particulate iron over a 12 month period in a series of net-acidic and net-alkaline coal mine drainages and passive treatment systems. Total iron in the mine waters is typically 10-100 mg L(-1), with values up to 2100 mg L(-1). Between 30 and 80% of the total iron occurs as solid phase, of which 20 to 80% is nano-particulate. Nano-particulate iron comprises 20 to 70% of the nominally "dissolved" (i.e. <0.45 ?m) iron. Since coagulation and sedimentation are the only processes required to remove solid phase iron, these data have important implications for the generation or consumption of acidity during water treatment. In most waters, the majority of truly dissolved iron occurs as Fe(ii) (average 64 22%). Activities of Fe(ii) do not correlate with pH and geochemical modelling shows that no Fe(ii) mineral is supersaturated. Removal of Fe(ii) must proceed via oxidation and hydrolysis. Except in waters with pH < 4.4, activities of Fe(iii) are strongly and negatively correlated with pH. Geochemical modelling suggests that the activity of Fe(iii) is controlled by the solubility of hydrous ferric oxides and oxyhydroxysulfates, supported by scanning and transmission electron microscopic analysis of solids. Nevertheless, the waters are generally supersaturated with respect to ferrihydrite and schwertmannite, and are not at redox equilibrium, indicating the key role of oxidation and hydrolysis kinetics on water treatment. Typically 70-100% of iron is retained in the treatment systems. Oxidation, hydrolysis, precipitation, coagulation and sedimentation occur in all treatment systems and - independent of water chemistry and the type of treatment system - hydroxides and oxyhydroxysulfates are the main iron sinks. The electrochemical data thus reveal the rationale for incomplete iron retention in individual systems and can thus inform future design criteria. The successful application of this low cost and rapid electrochemical method demonstrates its significant potential for real-time, on-site monitoring of iron-enriched waters and may in future substitute traditional analytical methods. PMID:22370608

  16. 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.

  17. 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.

  18. 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

  19. Enhancing electrochemical performance by control of transport properties in buffer layers--solid oxide fuel/electrolyser cells.

    PubMed

    Ramasamy, Devaraj; Nasani, Narendar; Brando, Ana D; Prez 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-? + 2 mol% Co buffer layers (where R = Gd, Pr) with Nd2NiO4+? 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

  20. 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

  1. 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.

  2. 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 0.54pg/mL. Besides, the immunosensor showed good specificity, acceptable reproducibility and stability as well as satisfactory reliability for the serum sample analysis. PMID:26703270

  3. 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

  4. 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.

  5. 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.

  6. 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.

  7. Enhanced electrochemical expansion of graphite for in situ electrochemical functionalization.

    PubMed

    Zhong, Yu Lin; Swager, Timothy M

    2012-10-31

    An all electrochemical route to functionalized graphene directly from a graphite electrode is described herein obviating the need for defect inducing oxidative or prolonged sonication treatments. Enhanced electrochemical expansion of graphite is achieved by sequential treatment, beginning with the established method of expansion by electrolysis in a Li(+) containing electrolyte, and then with the much larger tetra-n-butylammonium. The result is a hyperexpansion of the graphite basal planes. As a demonstration of the utility of this method, we successfully performed a subsequent in situ electrochemical diazonium functionalization of the hyperexpanded graphite basal planes to give functional graphene sheets. This potential controlled process is more effective than chemical processes and also provides a means of controlling the degree of functionalization. We have further demonstrated that the functionalized graphene could be converted to a pristine low defect form via laser ablation of the funtional groups. As a result, this method presents a potentially scalable approach for graphene circuit patterning. PMID:23075388

  8. Electrochemical treatment of anionic surfactants in synthetic wastewater with three-dimensional electrodes.

    PubMed

    Kong, Wuping; Wang, Bo; Ma, Hongzhu; Gu, Lin

    2006-10-11

    The electrochemical oxidation of anionic surfactants (sodium dodecyl benzene sulfonate, DBS) contained in simulated wastewater treated by three-dimensional electrode system with combined modified kaolin served as packed bed particle electrodes and Ti/Co/SnO(2)-Sb(2)O(3) anode was studied, the chemical oxygen demand (COD) removal of pollutants in the solutions was also investigated. The results showed that the three-dimensional electrodes in combined process could effectively decompose anionic surfactants. The COD removal efficiency can reach 86%, much higher than that of Ti/Co/SnO(2)-Sb(2)O(3) electrodes used singly or modified kaolin employed singly (graphite as anode and cathode) on the same condition of pH 3 and 38.1 mA/cm(2) current density. The current efficiency and kinetic constant were calculated and energy consumption was studied. At the same time the influence of pH and current density on COD removal efficiency with combined three-dimensional electrodes was also investigated, respectively. The optimal initial pH value of degradation is 3 (acid condition), and a minor COD removal increase follows higher current density. PMID:16730897

  9. Final Report: Fiscal Year 1997 demonstration of omnivorous non-thermal mixed waste treatment: Direct chemical oxidation of organic solids and liquids using peroxydisulfate

    SciTech Connect

    Cooper, J.F.

    1998-01-01

    Direct Chemical Oxidation (DCO) is a non-thermal, ambient pressure, aqueous-based technology for the oxidative destruction of the organic components of hazardous or mixed waste streams. The process has been developed for applications in waste treatment, chemical demilitarization and decontamination at LLNL since 1992. The process uses solutions of the peroxydisulfate ion (typically sodium or ammonium salts) to completely mineralize the organics to carbon dioxide and water. The expended oxidant may be electrolytically regenerated to minimize secondary waste. The paper briefly describes: free radical and secondary oxidant formation; electrochemical regeneration; offgas stream; and throughput.

  10. Effect of ammonia plasma treatment on graphene oxide LB monolayers

    SciTech Connect

    Singh, Gulbagh; Botcha, V. Divakar; Narayanam, Pavan K.; Sutar, D. S.; Talwar, S. S.; Major, S. S.; Srinivasa, R. S.

    2013-02-05

    Graphene oxide monolayer sheets were transferred on Si and SiO{sub 2}/Si substrates by Langmuir-Blodgett technique and were exposed to ammonia plasma at room temperature. The monolayer character of both graphene oxide and plasma treated graphene oxide sheets were ascertained by atomic force microscopy. X-ray photoelectron spectroscopy and Raman spectroscopy revealed that ammonia plasma treatment results in enhancement of graphitic carbon content along with the incorporation of nitrogen. The conductivity of graphene oxide monolayers, which was in the range of 10{sup -6}-10{sup -7} S/cm, increased to 10{sup -2}-10{sup -3} S/cm after the ammonia plasma treatment. These results indicate that the graphene oxide was simultaneously reduced and N-doped during ammonia plasma treatment, without affecting the morphological stability of sheets.

  11. Continuous electrochemical treatment of simulated industrial textile wastewater from industrial components in a tubular reactor.

    PubMed

    Krbahti, Bahadir K; Tanyola, Abdurrahman

    2009-10-30

    The continuous electrochemical treatment of industrial textile wastewater in a tubular reactor was investigated. The synthetic wastewater was based on the real process information of pretreatment and dyeing stages of the industrial mercerized and non-mercerized cotton and viscon production. The effects of residence time on chemical oxygen demand (COD), color and turbidity removals and pH change were studied under response surface optimized conditions of 30 degrees C, 25 g/L electrolyte concentration and 3505 mg/L COD feed concentration with 123.97 mA/cm(2) current density. Increasing residence time resulted in steady profiles of COD and color removals with higher treatment performances. The best column performance was realized at 3h of residence time as 53.5% and 99.3% for COD and color removals, respectively, at the expense of 193.1 kWh/kg COD with a mass transfer coefficient of 9.47 x 10(-6) m/s. PMID:19524357

  12. 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

  13. 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...

  14. Microbial As(III) Oxidation in Water Treatment Plant Filters

    EPA Science Inventory

    Arsenic exists in two oxidation states in water - arsenite [As(III)] and arsenate [As(V)]. As(III) is relatively mobile in water and difficult to remove by arsenic-removal treatment processes. Source waters that contain As(III) must add a strong oxidant such as free chlorine or p...

  15. Experimental approach to controllably vary protein oxidation while minimizing electrode adsorption for boron-doped diamond electrochemical surface mapping applications.

    PubMed

    McClintock, Carlee S; Hettich, Robert 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 (i.e., hydroxyl radicals) for these measurements; however, these approaches range significantly in their complexity and expense of operation. This research expands upon earlier work to enhance the controllability of boron-doped diamond (BDD) electrochemistry as an easily accessible tool for producing hydroxyl radicals in order to oxidize a range of intact proteins. Efforts to modulate the oxidation level while minimizing the adsorption of protein to the electrode involved the use of relatively high flow rates to reduce protein residence time inside the electrochemical flow chamber. Additionally, a different cell activation approach using variable voltage to supply a controlled current allowed us to precisely tune the extent of oxidation in a protein-dependent manner. In order to gain perspective on the level of protein adsorption onto the electrode surface, studies were conducted to monitor protein concentration during electrolysis and gauge changes in the electrode surface between cell activation events. This report demonstrates the successful use of BDD electrochemistry for greater precision in generating a target number of oxidation events upon intact proteins. PMID:23210708

  16. 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

  17. Electrochemical assay for the determination of nitric oxide metabolites using copper(II) chlorophyllin modified screen printed electrodes.

    PubMed

    Balamurugan, Murugesan; Madasamy, Thangamuthu; Pandiaraj, Manickam; Bhargava, Kalpana; Sethy, Niroj Kumar; Karunakaran, Chandran

    2015-06-01

    This work presents a novel electrochemical assay for the collective measurement of nitric oxide (NO) and its metabolites nitrite (NO2(-)) and nitrate (NO3(-)) in volume miniaturized sample at low cost using copper(II) chlorophyllin (CuCP) modified sensor electrode. Zinc oxide (ZnO) incorporated screen printed carbon electrode (SPCE) was used as a host matrix for the immobilization of CuCP. The morphological changes of the ZnO and CuCP modified electrodes were investigated using scanning electron microscopy. The electrochemical characterization of CuCP-ZnO-SPCE exhibited the characteristic quasi-reversible redox peaks at the potential +0.06 V versus Ag/AgCl. This biosensor electrode showed a wide linear range of response over NO concentrations from 200 nM to 500 ?M with a detection limit of 100 nM and sensitivity of 85.4 nA ?M(-1). Furthermore, NO2(-) measurement showed linearity of 100 nM to 1mM with a detection limit of 100 nM for NO2(-) and sensitivity of 96.4 nA ?M(-1). Then, the concentration of NO3(-) was measured after its enzymatic conversion into NO2(-). Using this assay, the concentrations of NO, NO2(-), and NO3(-) present in human plasma samples before and after beetroot supplement were estimated using suitable membrane coated CuCP-ZnO-SPCE and validated with the standard Griess method. PMID:25700865

  18. A new cleaning process combining non-ionic surfactant with diamond film electrochemical oxidation for polished silicon wafers

    NASA Astrophysics Data System (ADS)

    Baohong, Gao; Yadong, Zhu; Yuling, Liu; Shengli, Wang; Qiang, Zhou; Xiaoyan, Liu

    2010-07-01

    This paper presents a new cleaning process for particle and organic contaminants on polished silicon wafer surfaces. It combines a non-ionic surfactant with boron-doped diamond (BDD) film anode electrochemical oxidation. The non-ionic surfactant is used to remove particles on the polished wafer's surface, because it can form a protective film on the surface, which makes particles easy to remove. The effects of particle removal comparative experiments were observed by metallographic microscopy, which showed that the 1% v/v non-ionic surfactant achieved the best result. However, the surfactant film itself belongs to organic contamination, and it eventually needs to be removed. BDD film anode electrochemical oxidation (BDD-EO) is used to remove organic contaminants, because it can efficiently degrade organic matter. Three organic contaminant removal comparative experiments were carried out: the first one used the non-ionic surfactant in the first step and then used BDD-EO, the second one used BDD-EO only, and the last one used RCA cleaning technique. The XPS measurement result shows that the wafer's surface cleaned by BDD-EO has much less organic residue than that cleaned by RCA cleaning technique, and the non-ionic surfactant can be efficiently removed by BDD-EO.

  19. 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 bee