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Sample records for indirect electrochemical oxidation

  1. 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

  2. Study on superoxide and hydroxyl radicals generated in indirect electrochemical oxidation by chemiluminescence and UV-Visible spectra.

    PubMed

    Zhang, Bo-Tao; Zhao, Li-Xia; Lin, Jin-Ming

    2008-01-01

    The generation and transformation of radicals on the cathode of indirect electrochemical oxidation were studied by chemiluminescence (CL) and UV-Visible spectra in the reactor with a salt bridge that connected the separated chambers. The CL intensity of 4 x 10(-9) mol/L luminol on the cathode with bubbling oxygen was about seven times that of the intensity without it, which was because of the generation of reactive oxygen species (ROS). The existence of ROS, especially the generation of the superoxide radical, could be affirmed by the fact that the CL intensity of 4 x 10(-9) mol/L 2-methyl-6-(4-methoxyphenyl)-3,7-dihydroimidazo[1,2-a]pyrazin-3-one with bubbling oxygen was about four times that of the intensity without it. However, there was no chemiluminescence on the anode under the same condition. The change in the UV-Visible spectra of nitro blue tetrazolium and N,N-dimethyl-4-nitrosoaniline at the cathode chamber affirmed the transformation from oxygen to superoxide and hydroxyl radicals. The mechanism of the superoxide and hydroxyl radical generation and transformation on the cathode was discussed with the help of the experimental results and relative references.

  3. 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. Copyright © 2015 Elsevier B.V. All rights reserved.

  4. The indirect electrochemical refining of lunar ores

    NASA Technical Reports Server (NTRS)

    Semkow, Krystyna W.; Sammells, Anthony F.

    1987-01-01

    Recent work performed on an electrolytic cell is reported which addresses the implicit limitations in various approaches to refining lunar ores. The cell uses an oxygen vacancy conducting stabilized zirconia solid electrolyte to effect separation between a molten salt catholyte compartment where alkali metals are deposited, and an oxygen-evolving anode of composition La(0.89)Sr(0.1)MnO3. The cell configuration is shown and discussed along with a polarization curve and a steady-state current-voltage curve. In a practical cell, cathodically deposited liquid lithium would be continuously removed from the electrolytic cell and used as a valuable reducing agent for ore refining under lunar conditions. Oxygen would be indirectly electrochemically extracted from lunar ores for breathing purposes.

  5. The indirect electrochemical refining of lunar ores

    NASA Technical Reports Server (NTRS)

    Semkow, Krystyna W.; Sammells, Anthony F.

    1987-01-01

    Recent work performed on an electrolytic cell is reported which addresses the implicit limitations in various approaches to refining lunar ores. The cell uses an oxygen vacancy conducting stabilized zirconia solid electrolyte to effect separation between a molten salt catholyte compartment where alkali metals are deposited, and an oxygen-evolving anode of composition La(0.89)Sr(0.1)MnO3. The cell configuration is shown and discussed along with a polarization curve and a steady-state current-voltage curve. In a practical cell, cathodically deposited liquid lithium would be continuously removed from the electrolytic cell and used as a valuable reducing agent for ore refining under lunar conditions. Oxygen would be indirectly electrochemically extracted from lunar ores for breathing purposes.

  6. Electrochemical oxidation of methylenedioxyamphetamines.

    PubMed

    Squella, J A; Cassels, B K; Arata, M; Bavestrello, M P; Nuñez-Vergara, L J

    1993-09-01

    Four amphetamine derivatives bearing a methylenedioxy group at positions 3 and 4 of the benzene ring and differing in their substitution at C(6) were studied by differential pulse voltammetry in aqueous media. These experiments showed a single oxidation peak for the C(6)-H, -Br and -Cl compounds, while the C(6)-NO(2) analogue was not oxidized. The oxidation peak is interpreted as due to the removal of one electron from the aromatic electrophore with formation of a radical cation stabilized by the dioxole ring. The linear relationship between the peak current and the concentration of the derivatives is appropriate for development of a quantitative method for their determination. pK' values were determined using both electrochemical and spectrophotometric methods.

  7. Direct electrochemical oxidation of polyacrylates.

    PubMed

    Bellagamba, Riccardo; Comninellis, Christos; Vatistas, Nicolaos

    2002-10-01

    A promising elimination treatment of non-biodegradable organic pollutants is the direct electro-oxidation. In this work has been proposed the electrochemical elimination of polyacrylates by using boron-doped diamond (BDD) as anodic material. The complete elimination of organic contaminants has been obtained and this is the first case of successful electrochemical treatment of polymeric and bio-refractory species. The tests of the electrochemical oxidation have been conducted at constant current conditions and a complete elimination of organic species has been reached. The decrease of the COD value with time follows the behaviour of an ideal anode as in the case of low molecular organic compounds.

  8. Electrochemical oxidation of chemical weapons

    SciTech Connect

    Surma, J.E.

    1994-05-01

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

  9. 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.

  10. 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.

  11. 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

  12. 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.

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

    PubMed

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

    2016-04-15

    A commercial Unidirectional Carbon Fabric piece was used to design an electrode for the cathodic O2 reduction reaction in a divided (by a Nafion(®) 117 membrane) parallel plate reactor. The anode was a commercial stainless steel mesh. Under this approach it is feasible to produce H2O2 at low energy (2.08 kWh kg(-1) H2O2) in low ionic acidic medium. In the catholyte side the H2O2 can be activated with Fe(2+) to develop the Fenton reagent. It was found that Acid Orange 7 (AO7) indirect oxidation (in the concentration range of 0.12-0.24 mM) by Fenton chemistry follows a first order kinetic equation. The energy required for 0.24 mM AO7 degradation is 1.04 kWhm(-3). From each experimental AO7 oxidation the main parameters (a, mM and k, min(-1)) of the first order kinetic equation are obtained. These parameters can be correlated with AO7 concentration in the concentration range studied. Based on this method a semi-empirical chemical model was developed to predict the AO7 abatement, by means of Fenton chemistry. Good AO7 oxidation predictions can be made in the concentration range studied. A detailed discussion of the energy required for oxidizing AO7 and the accuracy of the chemical model to predict its oxidation is included in this paper. Copyright © 2016 Elsevier Ltd. All rights reserved.

  14. [Effect of pH for the electrochemical oxidation products and oxidation pathways of ammonia].

    PubMed

    Chen, Jin-luan; Shi, Han-chang; Xu, Li-li

    2008-08-01

    The electrochemical oxidation of ammonia in wastewater was investigated in a flow electrochemical cell. The effect of pH on ammonia removal efficiency, oxidation products and oxidation pathways was elucidated. The experimental results indicated that, the higher production efficiency of free chlorine and hydroxyl radical can be obtained under the moderate alkaline condition, and the electrochemical oxidation rate of ammonia was higher in this condition. In existence of chloride ions, chloramines produced during the electrolysis of ammonia. The constituent of chloramines related with the pH of reaction system. When pH was higher than 9, monochloramine was dominant; When pH was equal to 7, monochloramine and dichloramine existed at the same time and the concentration of the two chloramines was an approximation of the same; When pH was smaller than 5, most of the production was dichloramine. The production of nitrogen trichloride can be avoided when pH was higher than 5. Under the current density of 20 mA/cm2, the concentration of hydroxyl radical produced by electrolysis was smaller than 5 x 10(-15) mol/L. The indirect oxidation was the dominant reaction in the two pathways of electrochemical oxidation of ammonia.

  15. Electrochemical Oxidation of Alkylnitro Compounds PP-1345

    DTIC Science & Technology

    2004-08-17

    dinitropropanol (DNPOH, the precursor to the energetic plasticizer BDNPA/F) yield as byproducts large amounts of chemical process waste in the form...these chemistries and the significantly large resulting waste streams requiring treatment and disposal after the manufacturing chemistry is completed...fielded materials and many others, and thus avoid their byproducts and large waste streams. This proven electrochemical oxidation technology, employed

  16. Direct and Indirect Phototransformation of Graphene Oxide in Sunlight

    EPA Science Inventory

    Direct and indirect (with added H202 that serves as OH precursor) photoreactions of grapheme oxide (GO) were examined under sunlight exposure. The results indicate that GO photoreacts under both conditions, leading to significant alterations in GO's physicochemical properties. In...

  17. Direct and Indirect Phototransformation of Graphene Oxide in Sunlight

    EPA Science Inventory

    Direct and indirect (with added H202 that serves as OH precursor) photoreactions of grapheme oxide (GO) were examined under sunlight exposure. The results indicate that GO photoreacts under both conditions, leading to significant alterations in GO's physicochemical properties. In...

  18. Solid oxide electrochemical cell fabrication process

    DOEpatents

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

    1992-01-01

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

  19. Electrochemical and photocatalytic oxidation of hydrocarbons

    NASA Astrophysics Data System (ADS)

    Rismanchian, Azadeh

    This study demonstrates the development of a stable anode for electrochemical oxidation of hydrocarbons in solid oxide fuel cell (SOFC) and a highly active TiO2 based catalyst for photocatalytic reactions. The Ni/YSZ anode of SOFC was modified by Cu electroless plating. The catalytic activity toward H2 and CH4 oxidation were compared by the Faraday resistance (RF) obtained from the impedance spectroscopy. The RF ratio of Cu-Ni/YSZ in CH4 to H2 was greater than that of Ni/YSZ, indicating low catalytic activity of Cu-Ni/YSZ toward CH4 oxidation. The addition of Cu decreased the catalytic activity, but increased stability to 138 h in dry CH4. Characterization of the carbon type with Raman spectroscopy and temperature programmed oxidation showed that Cu formed disordered carbon rather than graphitic carbon which is the precursor to coking. Addition of CO2 to CH4 was studied as another approach to prevent coking. Electrochemical performance and mass spectrometry of the reactor effluent showed that the CH4-CO2 SOFC generated electricity from CO and H2, products of dry reforming reaction, with CO as the major contributor to current generation. CH4-CO 2 decreased the activation polarization but showed a limiting current due to the fuel depletion at the interlayer-electrolyte interface. Anode interlayer was modified by reducing the particle size to 2 mum. The fine microstructure increased the three phase boundary length and reduced the activation polarization. The pore loss in the fine microstructure resulted in diffusion limitation and a limiting current in CH4 which was eliminated by adding 4 wt% of pore former at interlayer. Further addition of pore former lowered the performance by creating discontinuity at electrolyte-interlayer interface. The photocatalytic oxidation of ethanol on TiO2 and TiO 2 modified with Ag and Au nanoparticles was studied by in-situ IR spectroscopy. Au and Ag increased the surface hydroxyl groups, which further served as active species to

  20. Vanadium oxide electrode synthesized by electroless deposition for electrochemical capacitors

    NASA Astrophysics Data System (ADS)

    Wu, Haoran; Lian, Keryn

    2014-12-01

    A thin film vanadium oxide electrode was synthesized by a simple electroless deposition method. Surface and structural analyses revealed that the deposited oxide is a mixture of amorphous V2O5 and VO2. Electrochemical characterizations of the synthesized vanadium oxide showed capacitive behavior with good cycle life. The electroless deposition of vanadium oxide is inexpensive, easy to process, and environmentally benign, offering a promising route for electrode development for electrochemical capacitors.

  1. 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.

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

    PubMed

    Gözmen, 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

  3. Mineralization of the biocide chloroxylenol by electrochemical advanced oxidation processes.

    PubMed

    Skoumal, Marcel; Arias, Conchita; Cabot, Pere Lluís; Centellas, Francesc; Garrido, José Antonio; Rodríguez, Rosa María; Brillas, Enric

    2008-04-01

    Electrochemical advanced oxidation processes (EAOPs) are environmentally friendly methods based on the destruction of organic pollutants in wastewaters with in situ electrogenerated hydroxyl radical. This species is formed in anodic oxidation (AO) from water oxidation at the anode and in indirect electro-oxidation methods like electro-Fenton (EF) and photoelectro-Fenton (PEF) also from reaction between catalytic Fe2+ and H2O2 continuously produced at the O2-diffusion cathode. The PEF method involves the irradiation of the treated solution with UVA light to enhance the photolysis of organics including Fe(III) complexes. In this work, the oxidation power of such EAOPs to decontaminate synthetic wastewaters of the biocide chloroxylenol (4-chloro-3,5-dimethylphenol) at pH 3.0 is comparatively examined with an undivided electrolytic cell containing a Pt or boron-doped diamond (BDD) anode and a stainless steel or O2-diffusion cathode. The initial chlorine is released as Cl(-) ion, which remains stable in the medium using Pt or is oxidized to Cl2 on BDD. The biocide solutions can be completely decontaminated using AO with a BDD anode, as well as PEF with a Pt or BDD anode. The PEF procedure with a BDD anode is the most powerful method leading to total mineralization in about 300 min, practically independent of current density. When current density rises, the degradation rate of processes increases, but they become less efficient due to the larger enhancement of waste reactions of oxidants. Chloroxylenol is much more rapidly removed in EF and PEF than in AO. 2,6-dimethylhydroquinone, 2,6-dimethyl-p-benzoquinone and 3,5-dimethyl-2-hydroxy-p-benzoquinone are identified as aromatic by-products, and maleic, malonic, pyruvic, acetic and oxalic acids are found as generated carboxylic acids. A general pathway for chloroxylenol mineralization by all EAOPs including the above by-products is proposed.

  4. Electrochemical degradation of carbaryl on oxide electrodes.

    PubMed

    Miwa, D W; Malpass, G R P; Machado, S A S; Motheo, A J

    2006-10-01

    This paper presents the study of a prospective electrochemical treatment system for the pesticide carbaryl. Three different dimensionally stable anodes were employed (Ti/Ru0.3 Ti0.7 O2, Ti/Ru0.3 Sn0.7 O2 and Ti/Ir0.3 Ti0.7 O2) and the effect of current density (10, 20, 40 and 60 mA cm(-2)) and supporting electrolyte (0.1 mol L(-1) NaCl and 0.033 mol L(-1) H2SO4) is discussed. All the electrodes present a low level of carbaryl and total organic carbon removal in H2SO4, even at highly positive potentials, indicating that the application of current is not, in itself, sufficient to promote effective oxidation of the pesticide and its products. However, in the presence of NaCl all the electrodes used present rapid diminishing of the carbaryl and total organic carbon content, thus suggesting enhanced activity. The results demonstrate the participation of partially oxidised Cl- species at the electrode surface, which act as an intermediate in the electron transfer between the pesticide molecule and the electrode. Thus, under such conditions, the feasibility of the electrochemical route for the treatment (total or partial) of waste that contains carbaryl is evident.

  5. Mediated electrochemical oxidation of mixed wastes

    SciTech Connect

    Chiba, Z.

    1993-04-01

    The Mediated Electrochemical Oxidation (MEO) process was studied for destroying low-level combustible mixed wastes at Rocky Flats Plant. Tests were performed with non-radioactive surrogate materials: Trimsol for contaminated cutting oils, and reagent-grade cellulose for contaminated cellulosic wastes. Extensive testing was carried out on Trimsol in both small laboratory-scale apparatus and on a large-scale system incorporating an industrial-size electrochemical cell. Preliminary tests were also carried out in the small-scale system with cellulose. Operating and system parameters that were studied were: use of a silver-nitric acid versus a cobalt-sulfuric acid system, effect of electrolyte temperature, effect of acid concentration, and effect of current density. Destruction and coulombic efficiencies were calculated using data obtained from continuous carbon dioxide monitors and total organic carbon (TOC) analysis of electrolyte samples. For Trimsol, the best performance was achieved with the silver-nitrate system at high acid concentrations, temperatures, and current densities. Destruction efficiencies of 99% or greater, and coulombic efficiencies up to 70% were obtained. For the cellulose, high destruction efficiencies and reasonable coulombic efficiencies were obtained for both silver-nitrate and cobalt-sulfate systems.

  6. 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.

  7. 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).

  8. Oxalic acid mineralization by electrochemical oxidation processes.

    PubMed

    Huang, Yao-Hui; Shih, Yu-Jen; Liu, Cheng-Hong

    2011-04-15

    In this study, two electrochemical oxidation processes were utilized to mineralize oxalic acid which was a major intermediate compound in the oxidation of phenols and other aromatic compounds. The anode rod and cathode net were made of a titanium coated with RuO(2)/IrO(2) (Ti-DSA) and stainless steel (S.S. net, SUS304), respectively. First, the Fered-Fenton process, which used H(2)O(2) and Fe(2+) as additive reagents, achieved 85% of TOC removal. It proceeded with ligand-to-metal charge-transfer (LMCT), which was evidenced by the accumulation of metallic foil on the selected cathode. However, in the absence of H(2)O(2)/Fe(2+), it showed a higher TOC removal efficiency while using Cl(-) only as an additive reagent due to the formation of hypochlorite on the anode. It was also found that the mineralization of oxalic acid by electrolysis generated hypochlorite better than the dosage of commercial hypochlorite without electricity. Also, pH value was a major factor that affected the mineralization efficiency of the oxalic acid due to the chlorine chemistry. 99% TOC removal could be obtained by Cl(-) electrolysis in an acidic environment.

  9. Forensic electrochemistry: indirect electrochemical sensing of the components of the new psychoactive substance "Synthacaine".

    PubMed

    Cumba, Loanda R; Kolliopoulos, Athanasios V; Smith, Jamie P; Thompson, Paul D; Evans, Peter R; Sutcliffe, Oliver B; do Carmo, Devaney R; Banks, Craig E

    2015-08-21

    "Synthacaine" is a New Psychoactive Substance which is, due to its inherent psychoactive properties, reported to imitate the effects of cocaine and is therefore consequently branded as "legal cocaine". The only analytical approach reported to date for the sensing of "Synthacaine" is mass spectrometry. In this paper, we explore and evaluate a range of potential analytical techniques for its quantification and potential use in the field screening "Synthacaine" using Raman spectroscopy, presumptive (colour) testing, High Performance Liquid Chromatography (HPLC) and electrochemistry. HPLC analysis of street samples reveals that "Synthacaine" comprises a mixture of methiopropamine (MPA) and 2-aminoindane (2-AI). Raman spectroscopy and presumptive (colour) tests, the Marquis, Mandelin, Simon's and Robadope test, are evaluated towards a potential in-the-field screening approach but are found to not be able to discriminate between the two when they are both present in the same sample, as is the case in the real street samples. We report for the first time a novel indirect electrochemical protocol for the sensing of MPA and 2-AI which is independently validated in street samples with HPLC. This novel electrochemical approach based upon one-shot disposable cost effective screen-printed graphite macroelectrodes holds potential for in-the-field screening for "Synthacaine".

  10. 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. Copyright © 2015 Elsevier B.V. All rights reserved.

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

    DOEpatents

    Borglum, Brian P.; Bessette, Norman F.

    2000-01-01

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

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

    DOEpatents

    Singh, Prabhakar; Ruka, Roswell J.

    1992-01-01

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

  13. Review on landfill leachate treatment by electrochemical oxidation: Drawbacks, challenges and future scope.

    PubMed

    Mandal, Pubali; Dubey, Brajesh K; Gupta, Ashok K

    2017-08-30

    Various studies on landfill leachate treatment by electrochemical oxidation have indicated that this process can effectively reduce two major pollutants present in landfill leachate; organic matter and ammonium nitrogen. In addition, the process is able to enhance the biodegradability index (BOD/COD) of landfill leachate, which make mature or stabilized landfill leachate suitable for biological treatment. The elevated concentration of ammonium nitrogen especially observed in bioreactor landfill leachate can also be reduced by electrochemical oxidation. The pollutant removal efficiency of the system depends upon the mechanism of oxidation (direct or indirect oxidation) which depends upon the property of anode material. Applied current density, pH, type and concentration of electrolyte, inter-electrode gap, mass transfer mode, total anode area to volume of effluent to be treated ratio, temperature, flow rate or flow velocity, reactor geometry, cathode material and lamp power during photoelectrochemical oxidation may also influence the system performance. In this review paper, past and present scenarios of landfill leachate treatment efficiencies and costs of various lab scale, pilot scale electrochemical oxidation studies asa standalone system or integrated with biological and physicochemical processes have been reviewed with the conclusion that electrochemical oxidation can be employed asa complementary treatment system with biological process for conventional landfill leachate treatment as well asa standalone system for ammonium nitrogen removal from bioreactor landfill leachate. Furthermore, present drawbacks of electrochemical oxidation process asa landfill leachate treatment system and relevance of incorporating life cycle assessment into the decision-making process besides process efficiency and cost, have been discussed. Copyright © 2017 Elsevier Ltd. All rights reserved.

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

    PubMed

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

    2012-02-01

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

  15. Electron transfer of Pseudomonas aeruginosa CP1 in electrochemical reduction of nitric oxide.

    PubMed

    Zhou, Shaofeng; Huang, Shaobin; He, Jiaxin; Li, Han; Zhang, Yongqing

    2016-10-01

    This study reports catalytic electro-chemical reduction of nitric oxide (NO) enhanced by Pseudomonas aeruginosa strain CP1. The current generated in the presence of bacteria was 4.36times that in the absence of the bacteria. The strain was able to catalyze electro-chemical reduction of NO via indirect electron transfer with an electrode, revealed by a series of cyclic voltammetry experiments. Soluble electron shuttles secreted into solution by live bacteria were responsible for the catalytic effects. The enhancement of NO reduction was also confirmed by detection of nitrous oxide; the level of this intermediate was 46.4% higher in the presence of bacteria than in controls, illustrated that the electron transfer pathway did not directly reduce nitric oxide to N2. The findings of this study may offer a new model for bioelectrochemical research in the field of NO removal by biocatalysts.

  16. 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.

  17. Solution synthesis of metal oxides for electrochemical energy storage applications.

    PubMed

    Xia, Xinhui; Zhang, Yongqi; Chao, Dongliang; Guan, Cao; Zhang, Yijun; Li, Lu; Ge, Xiang; Bacho, Ignacio Mínguez; Tu, Jiangping; Fan, Hong Jin

    2014-05-21

    This article provides an overview of solution-based methods for the controllable synthesis of metal oxides and their applications for electrochemical energy storage. Typical solution synthesis strategies are summarized and the detailed chemical reactions are elaborated for several common nanostructured transition metal oxides and their composites. The merits and demerits of these synthesis methods and some important considerations are discussed in association with their electrochemical performance. We also propose the basic guideline for designing advanced nanostructure electrode materials, and the future research trend in the development of high power and energy density electrochemical energy storage devices.

  18. Porous nickel oxide films for electrochemical capacitors

    SciTech Connect

    Liu, K.C.; Anderson, M.A.

    1995-12-31

    NiO/Ni composite thin films consisting of nano-sized particles have been found to perform as good electrodes in electrochemical capacitor applications. These films can provide a specific capacitance of 25--40 F/g. The low cost of raw materials and easy manufacturing process of this system should allow one to produce low-cost electrochemical capacitors.

  19. 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

  20. An electrochemically reduced graphene oxide-based electrochemical immunosensing platform for ultrasensitive antigen detection.

    PubMed

    Haque, Al-Monsur Jiaul; Park, Hyejin; Sung, Daekyung; Jon, Sangyong; Choi, Sung-Yool; Kim, Kyuwon

    2012-02-21

    We present an electrochemically reduced graphene oxide (ERGO)-based electrochemical immunosensing platform for the ultrasensitive detection of an antigen by the sandwich enzyme-linked immunosorbent assay (ELISA) protocol. Graphene oxide (GO) sheets were initially deposited on the amine-terminated benzenediazonium-modified indiun tin oxide (ITO) surfaces through both electrostatic and π-π interactions between the modified surfaces and GO. This deposition was followed by the electrochemical reduction of graphene oxide (GO) for preparing ERGO-modified ITO surfaces. These surfaces were then coated with an N-acryloxysuccinimide-activated amphiphilic polymer, poly(BMA-r-PEGMA-r-NAS), through π-π stacking interactions between the benzene ring tethered to the polymer and ERGO. After covalent immobilization of a primary antibody on the polymer-modified surfaces, sandwich ELISA was carried out for the detection of an antigen by use of a horseradish peroxidase (HRP)-labeled secondary antibody. Under the optimized experimental conditions, the developed electrochemical immunosensor exhibited a linear response over a wide range of antigen concentrations with a very low limit of detection (ca. 100 fg/mL, which corresponds to ca. 700 aM). The high sensitivity of the electrochemical immunosensor may be attributed not only to the enhanced electrocatalytic activity owing to ERGO but also to the minimized background current owing to the reduced nonspecific binding of proteins.

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

    PubMed Central

    2015-01-01

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

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

    DOE PAGES

    Chen, Wei; Wang, Haotian; Li, Yuzhang; ...

    2015-07-15

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

  3. [Research on synergy of combining electrochemical oxidation and catalytic wet oxidation].

    PubMed

    Wang, Hua; Li, Guang-Ming; Zhang, Fang; Huang, Ju-Wen

    2009-07-15

    A new catalytic wet oxidation fixed-bed reactor combined with three-dimensional electric-field was developed to investigate catalytic wet oxidation, electrochemical oxidation and electroassisted catalytic wet oxidation of the solution containing phenol in the presence of a catalyst Mn-Sn-Sb-3/gamma-Al2O3. Good electroassisted catalytic wet oxidation efficiency was obtained in the setup for the combination system even at mild conditions (T = 130 degrees C, po2 = 1.0 MPa) that the phenol conversion and TOC reduction were up to 94.0% and 88.4% after 27 min treatment, respectively. The result also shows that the rate constants of electroassisted catalytic wet oxidation are much higher than that of not only both catalytic wet oxidation and electrochemical oxidation process alone but also additive efficiencies of catalytic wet oxidation and electrochemical oxidation processes, which indicates an apparent synergetic effect between CWO and ECO processes.

  4. Nucleophilic aromatic substitution for heteroatoms: an oxidative electrochemical approach.

    PubMed

    Gallardo, Iluminada; Guirado, Gonzalo; Marquet, Jordi

    2002-04-19

    The nucleophilic aromatic substitution for heteroatom through electrochemical oxidation of the intermediate sigma-complexes (Meisenheimer complexes) in simple nitroaromatic compounds is reported for the first time (NASX process). The studies have been carried out with hydride, cyanide, fluoride, methoxy, and ethanethiolate anions and n-butylamine as a nucleophile, at the cyclic voltammetry (CV) and preparative electrolysis level. The cyclic voltammetry experiments allow for detection and characterization of the sigma-complexes and they have led us to a proposal for the mechanism of the oxidation step. Furthermore, the power of the CV technique in the analysis of the reaction mixture throughout the whole chemical and electrochemical process is described.

  5. DEVELOPMENT OF ELECTROCHEMICAL REDUCTION TECHNOLOGY FOR SPENT OXIDE FUELS

    SciTech Connect

    Hur, Jin-Mok; Seo, Chung-Seok; Kim, Ik-Soo; Hong, Sun-Seok; Kang, Dae-Seung; Park, Seong-Won

    2003-02-27

    The Advanced Spent Fuel Conditioning Process (ACP) has been under development at Korea Atomic Energy Research Institute (KAERI) since 1997. The concept is to convert spent oxide fuel into metallic form and to remove high heat-load fission products such as Cs and Sr from the spent fuel. The heat power, volume, and radioactivity of spent fuel can decrease by a factor of a quarter via this process. For the realization of ACP, a concept of electrochemical reduction of spent oxide fuel in Li2O-LiCl molten salt was proposed and several cold tests using fresh uranium oxides have been carried out. In this new electrochemical reduction process, electrolysis of Li2O and reduction of uranium oxide are taking place simultaneously at the cathode part of electrolysis cell. The conversion of uranium oxide to uranium metal can reach more than 99% ensuring the feasibility of this process.

  6. Advanced treatment of biologically pretreated coking wastewater by electrochemical oxidation using boron-doped diamond electrodes.

    PubMed

    Zhu, Xiuping; Ni, Jinren; Lai, Peng

    2009-09-01

    Electrochemical oxidation is a promising technology to treatment of bio-refractory wastewater. Coking wastewater contains high concentration of refractory and toxic compounds and the water quality usually cannot meet the discharge standards after conventional biological treatment processes. This paper initially investigated the electrochemical oxidation using boron-doped diamond (BDD) anode for advanced treatment of coking wastewater. Under the experimental conditions (current density 20-60mAcm(-2), pH 3-11, and temperature 20-60 degrees C) using BDD anode, complete mineralization of organic pollutants was almost achieved, and surplus ammonia-nitrogen (NH(3)-N) was further removed thoroughly when pH was not adjusted or at alkaline value. Moreover, the TOC and NH(3)-N removal rates in BDD anode cell were much greater than those in other common anode systems such as SnO(2) and PbO(2) anodes cells. Given the same target to meet the National Discharge Standard of China, the energy consumption of 64kWhkgCOD(-1) observed in BDD anode system was only about 60% as much as those observed in SnO(2) and PbO(2) anode systems. Further investigation revealed that, in BDD anode cell, organic pollutants were mainly degraded by reaction with free hydroxyl radicals and electrogenerated oxidants (S(2)O(8)(2-), H(2)O(2), and other oxidants) played a less important role, while direct electrochemical oxidation and indirect electrochemical oxidation mediated by active chlorine can be negligible. These results showed great potential of BDD anode system in engineering application as a final treatment of coking wastewater.

  7. Electrochemical study of DNA damaged by oxidation stress.

    PubMed

    Zitka, Ondrej; Krizkova, Sona; Skalickova, Sylvie; Kopel, Pavel; Babula, Petr; Adam, Vojtech; Kizek, Rene

    2013-02-01

    Many compounds can interact with DNA leading to changes of DNA structure as point mutation and bases excision, which could trigger some metabolic failures, which leads to the changes in DNA structure resulting in cancer. Oxidation of nucleic acid bases belongs to the one of the mostly occurred type of DNA damaging leading to the above mentioned phenomena. The investigation of processes of DNA oxidation damage is topical and electrochemical methods include a versatile and sensitive tool for these purposes. 8-hydroxydeoxyguanosine (8-OHdG) is the most widely accepted marker of DNA damage. Oxidative damage to DNA by free radicals and exposure to ionizing radiation generate several other products within the double helix besides mentioned oxidation products of nucleic acid bases. The basic electrochemical behaviour of nucleic acids bases on various types of carbon electrodes is reviewed. Further, we address our attention on description of oxidation mechanisms and on detection of the most important products of nucleic bases oxidation. The miniaturization of detector coupled with some microfluidic devices is suggested and discussed. The main aim of this review is to report the advantages and features of the electrochemical detection of guanine oxidation product as 8-OHdG and other similarly produced molecules as markers for DNA damage.

  8. 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)

  9. Electrochemical oxidation of COD from real textile wastewaters: Kinetic study and energy consumption.

    PubMed

    Zou, Jiaxiu; Peng, Xiaolan; Li, Miao; Xiong, Ying; Wang, Bing; Dong, Faqin; Wang, Bin

    2017-03-01

    In the present study, the electrochemical oxidation of real wastewaters discharged by textile industry was carried out using a boron-doped diamond (BDD) anode. The effect of operational variables, such as applied current density (20-100 mA·cm(-2)), NaCl concentration added to the real wastewaters (0-3 g·L(-1)), and pH value (2.0-10.0), on the kinetics of COD oxidation and on the energy consumption was carefully investigated. The obtained experimental results could be well matched with a proposed kinetic model, in which the indirect oxidation mediated by electrogenerated strong oxidants would be described through a pseudo-first-order kinetic constant k. Values of k exhibited a linear increase with increasing applied current density and decreasing pH value, and an exponential increase with NaCl concentration. Furthermore, high oxidation kinetics resulted in low specific energy consumption, but this conclusion was not suitable to the results obtained under different applied current density. Under the optimum operational conditions, it only took 3 h to complete remove the COD in the real textile wastewaters and the specific energy consumption could be as low as 11.12 kWh·kg(-1) COD. The obtained results, low energy consumption and short electrolysis time, allowed to conclude that the electrochemical oxidation based on BDD anodes would have practical industrial application for the treatment of real textile wastewater.

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

    PubMed Central

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

    1992-01-01

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

  11. High Temperature Oxidation and Electrochemical Studies Related to Hot Corrosion

    DTIC Science & Technology

    1989-12-01

    thin film of liquid sodium sulfate. It appears that the initial formation of metal oxides is necessary for the initial reaction and the transport of...compounds in the silica film allow transport of alkali metal cations under an electrochemical driving force with essentially no electronic conduction

  12. Electrochemical advanced oxidation processes: today and tomorrow. A review.

    PubMed

    Sirés, Ignasi; Brillas, Enric; Oturan, Mehmet A; Rodrigo, Manuel A; Panizza, Marco

    2014-01-01

    In recent years, new advanced oxidation processes based on the electrochemical technology, the so-called electrochemical advanced oxidation processes (EAOPs), have been developed for the prevention and remediation of environmental pollution, especially focusing on water streams. These methods are based on the electrochemical generation of a very powerful oxidizing agent, such as the hydroxyl radical ((•)OH) in solution, which is then able to destroy organics up to their mineralization. EAOPs include heterogeneous processes like anodic oxidation and photoelectrocatalysis methods, in which (•)OH are generated at the anode surface either electrochemically or photochemically, and homogeneous processes like electro-Fenton, photoelectro-Fenton, and sonoelectrolysis, in which (•)OH are produced in the bulk solution. This paper presents a general overview of the application of EAOPs on the removal of aqueous organic pollutants, first reviewing the most recent works and then looking to the future. A global perspective on the fundamentals and experimental setups is offered, and laboratory-scale and pilot-scale experiments are examined and discussed.

  13. 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.

  14. Method of electrode fabrication for solid oxide electrochemical cells

    DOEpatents

    Jensen, Russell R.

    1990-01-01

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

  15. 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.

  16. Zinc oxide nanostructures for electrochemical cortisol biosensing

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

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

  17. Hydrophilic graphene surface prepared by electrochemically reduced micellar graphene oxide as a platform for electrochemical sensor.

    PubMed

    Akkarachanchainon, Nontapol; Rattanawaleedirojn, Pranee; Chailapakul, Orawon; Rodthongkum, Nadnudda

    2017-04-01

    Graphene is one of the promising hydrophobic carbon-based nanomaterials used for electrode modification in electrochemical sensor. However, hydrophobicity of graphene makes it incompatible with aqueous electrolyte solution, leading to significant impediment to the electron transfer process. Here, we aim to alter graphene property to be hydrophilicity by using an electrochemically reduced micellar graphene oxide for electrode surface modification. Then, this system was applied for the simultaneous determination of toxic pesticides (e.g. carbofuran and carbendazim). Interestingly, the modified electrode offers an improved electrochemical sensitivity, verified by a drastic increase in current signal of carbofuran (4 times) and carbendazim (12 times) compared to an unmodified electrode. Under the optimal conditions, low detection limits of carbofuran and carbendazim were found to be 10µgL(-1) and 5µgL(-1), respectively. Ultimately, this system was successfully applied for the sensitive and simultaneous determination of carbofuran and carbendazim residues in various agricultural products.

  18. 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

  19. Solid oxide materials research accelerated electrochemical testing

    SciTech Connect

    Windisch, C.; Arey, B.

    1995-08-01

    The objectives of this work were to develop methods for accelerated testing of cathode materials for solid oxide fuel cells under selected operating conditions. The methods would be used to evaluate the performance of LSM cathode material.

  20. Improved Electrochemical Detection of Zinc Ions Using Electrode Modified with Electrochemically Reduced Graphene Oxide

    PubMed Central

    Kudr, Jiri; Richtera, Lukas; Nejdl, Lukas; Xhaxhiu, Kledi; Vitek, Petr; Rutkay-Nedecky, Branislav; Hynek, David; Kopel, Pavel; Adam, Vojtech; Kizek, Rene

    2016-01-01

    Increasing urbanization and industrialization lead to the release of metals into the biosphere, which has become a serious issue for public health. In this paper, the direct electrochemical reduction of zinc ions is studied using electrochemically reduced graphene oxide (ERGO) modified glassy carbon electrode (GCE). The graphene oxide (GO) was fabricated using modified Hummers method and was electrochemically reduced on the surface of GCE by performing cyclic voltammograms from 0 to −1.5 V. The modification was optimized and properties of electrodes were determined using electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). The determination of Zn(II) was performed using differential pulse voltammetry technique, platinum wire as a counter electrode, and Ag/AgCl/3 M KCl reference electrode. Compared to the bare GCE the modified GCE/ERGO shows three times better electrocatalytic activity towards zinc ions, with an increase of reduction current along with a negative shift of reduction potential. Using GCE/ERGO detection limit 5 ng·mL−1 was obtained. PMID:28787832

  1. 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.

  2. Electrochemical deposition of conducting ruthenium oxide films from solution

    SciTech Connect

    Anderson, D.P.; Warren, L.F.

    1984-02-01

    In the last decade, ruthenium oxide, RuO /sub x/ (x less than or equal to 2), has been used extensively as the active anode electrocatalyst constituent for Cl/sub 2/ and O/sub 2/ evolution reactions, in chlorate production, and in metal electrowinning from mixed chloride-sulfate solutions. More recently, this material has been incorporated in several light-induced water electrolysis schemes and apparently possesses the ability to inhibit CdS photocorrosion by acting as a hole scavenger. The numerous applications for this catalyst material certainly warrant further studies of its electrochemical properties on a variety of substrates, e.g., semiconductors. The lack of a simple technique for controlled deposition of ruthenium oxide onto conducting substrates prompted us to investigate an electrochemical approach to this problem. We describe here a new way to electrochemically deposit conducting films of hydrated ruthenium oxide from an aqueous solution of the benzeneruthenium (II)aqua complex. The films slowly dissolve in aqueous electrolytes upon potential cycling, yet appear to be catalytic with regards to water oxidation.

  3. 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.

  4. Direct electrochemical reduction of metal-oxides

    DOEpatents

    Redey, Laszlo I.; Gourishankar, Karthick

    2003-01-01

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

  5. Electrochemical deposition of zinc oxide nanorods for hybrid solar cells

    NASA Astrophysics Data System (ADS)

    Torres Damasco Ty, Jennifer; Yanagi, Hisao

    2015-04-01

    Zinc oxide (ZnO) nanorod arrays for inorganic/organic hybrid solar cells were electrochemically deposited on indium tin oxide (ITO) substrates with a rotating disk electrode setup. The addition of a ZnO seed layer on the ITO prior to electrochemical deposition improved the morphology of the nanorods, resulting in nanorods with smaller and homogenous diameters as well as a higher degree of vertical orientation on to the substrate. The ZnO films deposited on the seeded ITO substrates had higher optical transmittance and lower concentration of defects. Chronoamperometric transient curves show that nucleation and coalescence occurred later for bare ITO substrates, indicating lower densities of initial nuclei, resulting in the growth of nanorods with larger diameters. The solar cell characteristics of the devices fabricated from the seeded ITO substrates were better. The seed layer also acts as a hole-blocking layer, preventing the direct contact between the hole-transporting polymer material and the ITO.

  6. Nitrogen-doped reduced graphene oxide electrodes for electrochemical supercapacitors.

    PubMed

    Nolan, Hugo; Mendoza-Sanchez, Beatriz; Ashok Kumar, Nanjundan; McEvoy, Niall; O'Brien, Sean; Nicolosi, Valeria; Duesberg, Georg S

    2014-02-14

    Herein we use Nitrogen-doped reduced Graphene Oxide (N-rGO) as the active material in supercapacitor electrodes. Building on a previous work detailing the synthesis of this material, electrodes were fabricated via spray-deposition of aqueous dispersions and the electrochemical charge storage mechanism was investigated. Results indicate that the functionalised graphene displays improved performance compared to non-functionalised graphene. The simplicity of fabrication suggests ease of up-scaling of such electrodes for commercial applications.

  7. 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.

  8. 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, 38°C 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. Copyright © 2014 Elsevier Ltd. All rights reserved.

  9. 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.

  10. Oxidation of enrofloxacin with conductive-diamond electrochemical oxidation, ozonation and Fenton oxidation: a comparison.

    PubMed

    Guinea, Elena; Brillas, Enric; Centellas, Francesc; Cañizares, Pablo; Rodrigo, Manuel A; Sáez, Cristina

    2009-05-01

    The treatment of enrofloxacin synthetic wastewaters using conductive-diamond electrochemical oxidation (CDEO), ozonation and Fenton oxidation has been studied. Results show that the three technologies can reduce the organic content of enrofloxacin synthetic wastewaters but with different performances. CDEO was the most efficient technology in terms of mineralization but not on COD removal, which was more efficiently achieved by ozonation. This indicates that ozonation is efficient in the breakage of the complex molecules but not on the removal of final carboxylic acids. The high initial efficiency in terms of oxidant-use obtained by Fenton oxidation evidences that it is very efficient in the removal of the enrofloxacin, although it rapidly leads to the formation of refractory compounds to the treatment. This indicates the significance of other oxidation mechanisms (e.g. coagulation) that enhance the results obtained by the expected hydroxyl-mediated oxidation. Ammonium ions were the primary product species in CDEO and nitrate ions in ozonation, whereas Fenton effluents contained similar amounts of both nitrogen ionic species.

  11. Electrochemical oxidation by square-wave potential pulses in the imitation of oxidative drug metabolism.

    PubMed

    Nouri-Nigjeh, Eslam; Permentier, Hjalmar P; Bischoff, Rainer; Bruins, Andries P

    2011-07-15

    Electrochemistry combined with mass spectrometry (EC-MS) is an emerging analytical technique in the imitation of oxidative drug metabolism at the early stages of new drug development. Here, we present the benefits of electrochemical oxidation by square-wave potential pulses for the oxidation of lidocaine, a test drug compound, on a platinum electrode. Lidocaine was oxidized at constant potential and by square-wave potential pulses with different cycle times, and the reaction products were analyzed by liquid chromatography-mass spectrometry [LC-MS(/MS)]. Application of constant potentials of up to +5.0 V resulted in relatively low yields of N-dealkylation and 4-hydroxylation products, while oxidation by square-wave potential pulses generated up to 50 times more of the 4-hydroxylation product at cycle times between 0.2 and 12 s (estimated yield of 10%). The highest yield of the N-dealkylation product was obtained at cycle times shorter than 0.2 s. Tuning of the cycle time is thus an important parameter to modulate the selectivity of electrochemical oxidation reactions. The N-oxidation product was only obtained by electrochemical oxidation under air atmosphere due to reaction with electrogenerated hydrogen peroxide. Square-wave potential pulses may also be applicable to modulate the selectivity of electrochemical reactions with other drug compounds in order to generate oxidation products with greater selectivity and higher yield based on the optimization of cycle times and potentials. This considerably widens the scope of direct electrochemistry-based oxidation reactions for the imitation of in vivo oxidative drug metabolism.

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

    DOEpatents

    Brian, Riley; Szreders, Bernard E.

    1989-01-01

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

  13. 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.

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

    PubMed

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

    2016-05-05

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

  15. Electrochemical oxidation of an azo dye in aqueous media investigation of operational parameters and kinetics.

    PubMed

    Parsa, J Basiri; Rezaei, M; Soleymani, A R

    2009-09-15

    In this research two types of electrochemical reactors for the treatment of simulated wastewaters containing Direct blue 71 azo dye (DB71) were used: (1) Laboratory scale undivided electrolysis cell system (450 mL volume) with one 2 cm x 2 cm platinum plate as the anode placed in the middle of the cell and two 2 cm x 8 cm steel plates (SS-304) as cathodes placed in the sides of the cell 2 cm from the central anode. (2) Pilot scale reactor (9L volume), equipped with two 3 cm x 23 cm stainless steel plates as anode and cathode, with distance of 3 cm apart. The influence of supporting electrolyte, applied voltage and pH were studied. The UV-vis spectra of samples during the electrochemical oxidation showed the rapid decolorization of the dye solution. During the process, the COD and current were measured in order to evaluate the degree of mineralization, energy consumption, current and anode efficiencies. The optimum supporting electrolyte and applied voltage were NaCl (5 g L(-1)) and 15 V. Using the lab scale reactor resulted in complete decolorization and mineralization of the dye solutions after ca. 90 and 120 min, respectively. Similar results were obtained using the pilot plant reactor under the same conditions. The good fit of the data to pseudo-first-order kinetics for COD removal at all applied voltages (except 20 V) was taken as proof of the involvement of indirect oxidation pathways in the process.

  16. Impact of the oxidant chemistry description on direct and indirect aerosol forcing estimates

    NASA Astrophysics Data System (ADS)

    Olivié, D.; Sand, M.; Berntsen, T.; Seland; Kirkevåg, A.; Iversen, T.

    2011-12-01

    Sulfate aerosol is formed as a consequence of the oxidation of dimethyl sulfide (DMS) and sulfur dioxide (SO2) by the hydroxyl radical (OH), ozone (O3), hydrogen peroxide (H2O2) and the nitrate radical (NO3). In addition, the amount of particulate organic matter (POM) is also influenced by the atmospheric oxidant concentrations. Oxidant levels can therefore have a considerable impact on aerosols and on their direct and indirect forcing. Here we study the impact of the description of these oxidation reactions. The model which is used is the CAM-Oslo model, which contains an aerosol module describing the evolution of DMS, SO2, sea-salt, dust, BC, POM, and sulfate. It also describes the interaction of the aerosols with radiation and clouds, and therefore gives estimates of the direct and indirect forcing of aerosols. In the standard version of the aerosol module, the oxidation rates are calculated using prescribed monthly fields of OH, O3, H2O2 and NO3. In the new version, we use oxidant fields calculated on-line by a full tropospheric chemistry scheme. On-line OH, O3, H2O2 and NO3 distributions induce both lower sulfate concentrations (-10 %) and lower POM concentrations (-2.5 %). The impact on the direct and indirect forcing is +0.065 and +0.185 W/m2 respectively, underlining the importance of the oxidant description for the estimation of the direct and indirect aerosol forcing.

  17. Electrochemical Detection of Nitric Oxide in Plant Cell Suspensions.

    PubMed

    Griveau, Sophie; Besson-Bard, Angélique; Bedioui, Fethi; Wendehenne, David

    2016-01-01

    Nitric oxide is a hydrophobic radical acting as a physiological mediator in plants. Because of its unique properties, the detection of NO in plant tissues and cell suspensions remains a challenge. For this purpose, several techniques are used, each having certain advantages and limitations such as interferences with other species, questionable sensitivity, and/or selectivity or ex situ measurement. Here we describe a very attractive approach for tracking NO in plant cell suspensions using a NO-sensitive homemade platinum/iridium-based electrochemical microsensor. This method constitutes the absolute real-time proof of the production of free NO in physiological conditions.

  18. 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.

  19. Scalable and Sustainable Electrochemical Allylic C–H Oxidation

    PubMed Central

    Chen, Yong; Tang, Jiaze; Chen, Ke; Eastgate, Martin D.; Baran, Phil S.

    2016-01-01

    New methods and strategies for the direct functionalization of C–H bonds are beginning to reshape the fabric of retrosynthetic analysis, impacting the synthesis of natural products, medicines, and even materials1. The oxidation of allylic systems has played a prominent role in this context as possibly the most widely applied C–H functionalization due to the utility of enones and allylic alcohols as versatile intermediates, along with their prevalence in natural and unnatural materials2. Allylic oxidations have been featured in hundreds of syntheses, including some natural product syntheses regarded as “classics”3. Despite many attempts to improve the efficiency and practicality of this powerful transformation, the vast majority of conditions still employ highly toxic reagents (based around toxic elements such as chromium, selenium, etc.) or expensive catalysts (palladium, rhodium, etc.)2. These requirements are highly problematic in industrial settings; currently, no scalable and sustainable solution to allylic oxidation exists. As such, this oxidation strategy is rarely embraced for large-scale synthetic applications, limiting the adoption of this important retrosynthetic strategy by industrial scientists. In this manuscript, we describe an electrochemical solution to this problem that exhibits broad substrate scope, operational simplicity, and high chemoselectivity. This method employs inexpensive and readily available materials, representing the first example of a scalable allylic C–H oxidation (demonstrated on 100 grams), finally opening the door for the adoption of this C–H oxidation strategy in large-scale industrial settings without significant environmental impact. PMID:27096371

  20. Electrochemical degradation, kinetics & performance studies of solid oxide fuel cells

    NASA Astrophysics Data System (ADS)

    Das, Debanjan

    Linear and Non-linear electrochemical characterization techniques and equivalent circuit modelling were carried out on miniature and sub-commercial Solid Oxide Fuel Cell (SOFC) stacks as an in-situ diagnostic approach to evaluate and analyze their performance under the presence of simulated alternative fuel conditions. The main focus of the study was to track the change in cell behavior and response live, as the cell was generating power. Electrochemical Impedance Spectroscopy (EIS) was the most important linear AC technique used for the study. The distinct effects of inorganic components usually present in hydrocarbon fuel reformates on SOFC behavior have been determined, allowing identification of possible "fingerprint" impedance behavior corresponding to specific fuel conditions and reaction mechanisms. Critical electrochemical processes and degradation mechanisms which might affect cell performance were identified and quantified. Sulfur and siloxane cause the most prominent degradation and the associated electrochemical cell parameters such as Gerisher and Warburg elements are applied respectively for better understanding of the degradation processes. Electrochemical Frequency Modulation (EFM) was applied for kinetic studies in SOFCs for the very first time for estimating the exchange current density and transfer coefficients. EFM is a non-linear in-situ electrochemical technique conceptually different from EIS and is used extensively in corrosion work, but rarely used on fuel cells till now. EFM is based on exploring information obtained from non-linear higher harmonic contributions from potential perturbations of electrochemical systems, otherwise not obtained by EIS. The baseline fuel used was 3 % humidified hydrogen with a 5-cell SOFC sub-commercial planar stack to perform the analysis. Traditional methods such as EIS and Tafel analysis were carried out at similar operating conditions to verify and correlate with the EFM data and ensure the validity of the

  1. 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.

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

    PubMed

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

    2013-11-01

    The electrochemical oxidation (EO) treatment in water of three conazole fungicides, myclobutanil, triadimefon and propiconazole, has been carried out at constant current using a BDD/SS system. First, solutions of each fungicide were electrolyzed to assess the effect of the experimental parameters such as current, pH and fungicide concentration on the decay of each compound and total organic carbon abatement. Then a careful analysis of the degradation by-products was made by high performance liquid chromatography, ion chromatography and gas chromatography coupled with mass spectrometry in order to provide a detailed discussion on the original reaction pathways. Thus, during the degradation of conazole fungicides by the electrochemical oxidation process, aromatic intermediates, aliphatic carboxylic acids and Cl(-) were detected prior to their complete mineralization to CO2 while NO3(-) anions remained in the treated solution. This is an essential preliminary step towards the applicability of the EO processes for the treatment of wastewater containing conazole fungicides. Copyright © 2013 Elsevier Ltd. All rights reserved.

  3. Selective electrochemical generation of hydrogen peroxide from water oxidation

    DOE PAGES

    Viswanathan, Venkatasubramanian; Hansen, Heine A.; Norskov, Jens K.

    2015-10-08

    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, wemore » 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. Furthermore, we present a rational design principle for the selectivity in electrochemical water oxidation and identify new material candidates that could perform H2O2 evolution selectively.« less

  4. Selective electrochemical generation of hydrogen peroxide from water oxidation

    SciTech Connect

    Viswanathan, Venkatasubramanian; Hansen, Heine A.; Norskov, Jens K.

    2015-10-08

    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. Furthermore, we present a rational design principle for the selectivity in electrochemical water oxidation and identify new material candidates that could perform H2O2 evolution selectively.

  5. Degradation of caffeine by conductive diamond electrochemical oxidation.

    PubMed

    Indermuhle, Chloe; Martín de Vidales, Maria J; Sáez, Cristina; Robles, José; Cañizares, Pablo; García-Reyes, Juan F; Molina-Díaz, Antonio; Comninellis, Christos; Rodrigo, Manuel A

    2013-11-01

    The use of Conductive-Diamond Electrochemical Oxidation (CDEO) and Sonoelectrochemical Oxidation (CDSEO) has been evaluated for the removal of caffeine of wastewater. Effects of initial concentration, current density and supporting electrolyte on the process efficiency are assessed. Results show that caffeine is very efficiently removed with CDEO and that depletion of caffeine has two stages depending on its concentration. At low concentrations, opposite to what it is expected in a mass-transfer controlled process, the efficiency increases with current density very significantly, suggesting a very important role of mediated oxidation processes on the removal of caffeine. In addition, the removal of caffeine is faster than TOC, indicating the formation of reaction intermediates. The number and relative abundance of them depend on the operating conditions and supporting electrolyte used. In chloride media, removal of caffeine is faster and more efficiently, although the occurrence of more intermediates takes place. CDSEO does not increase the efficiency of caffeine removal, but it affects to the formation of intermediates. A detailed characterization of intermediates by liquid chromatography time-of-flight mass spectrometry seems to indicate that the degradation of caffeine by CDEO follows an oxidation pathway similar to mechanism proposed by other advanced oxidation processes.

  6. Electrochemical production of hydrogen coupled with the oxidation of arsenite.

    PubMed

    Kim, Jungwon; Kwon, Daejung; Kim, Kitae; Hoffmann, Michael R

    2014-01-01

    The production of hydrogen accompanied by the simultaneous oxidation of arsenite (As(III)) was achieved using an electrochemical system that employed a BiOx-TiO2 semiconductor anode and a stainless steel (SS) cathode in the presence of sodium chloride (NaCl) electrolyte. The production of H2 was enhanced by the addition of As(III) during the course of water electrolysis. The synergistic effect of As(III) on H2 production can be explained in terms of (1) the scavenging of reactive chlorine species (RCS), which inhibit the production of H2 by competing with water molecules (or protons) for the electrons on the cathode, by As(III) and (2) the generation of protons, which are more favorably reduced on the cathode than water molecules, through the oxidation of As(III). The addition of 1.0 mM As(III) to the electrolyte at a constant cell voltage (E cell) of 3.0 V enhanced the production of H2 by 12% even though the cell current (I cell) was reduced by 5%. The net effect results in an increase in the energy efficiency (EE) for H2 production (ΔEE) by 17.5%. Furthermore, the value ΔEE, which depended on As(III) concentration, also depended on the applied E cell. For example, the ΔEE increased with increasing As(III) concentration in the micromolar range but decreased as a function of E cell. This is attributed to the fact that the reactions between RCS and As(III) are influenced by both RCS concentration depending on E cell and As(III) concentration in the solution. On the other hand, the ΔEE decreased with increasing As(III) concentration in the millimolar range due to the adsorption of As(V) generated from the oxidation of As(III) on the semiconductor anode. In comparison to the electrochemical oxidation of certain organic compounds (e.g., phenol, 4-chlorophenol, 2-chlorophenol, salicylic acid, catechol, maleic acid, oxalate, and urea), the ΔEE obtained during As(III) oxidation (17.5%) was higher than that observed during the oxidation of the above organic compounds

  7. 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.

  8. Pre-eminence of the Indirect Channel in the Resonant Inverse Photoelectron Spectroscopy of Cerium Oxide

    SciTech Connect

    Tobin, J. G.; Yu, S. -W.; Chung, B. W.; Waddill, G. D.

    2012-04-01

    We recently reported a strong resonance in the inverse photoelectron spectroscopy (IPES) of cerium oxide. Here, we showed that dominance of the indirect channel of the resonant inverse photoelectron spectroscopy (RIPES) is so complete that the photon energy dependence can be explained in terms of emission associated with a single photon energy.

  9. Electrochemical oxidation for the treatment of textile industry wastewater.

    PubMed

    Radha, K V; Sridevi, V; Kalaivani, K

    2009-01-01

    This study elucidates the reduction of organics from textile effluents through electrochemical oxidation technique. Effect of pH and current intensity were investigated in this system. It was found that degradation was maximum at the current intensity of 0.6 A and at a pH of 1.3. Under the same experimental conditions the removal of chemical oxygen demand (COD), total solids, total dissolved solids and total organic carbon were found to be approximately 68%, 49.2%, 50.7% and 96.8%, respectively. Effect of current intensity on color removal was also investigated as a function of electrolysis time (30-210 minutes) and it showed that maximum removal efficiency (96%) was reached within 60 minutes at 0.6 A. While studying the effect of pH on COD removal, it was observed that a decrease in pH to an optimum of 1.3 showed maximum COD reduction of 68%. These results suggest an important role of these parameters in electrochemical process for removing organic pollutants.

  10. 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.

  11. 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.

  12. Research Update: Nanoscale electrochemical transistors in correlated oxides

    NASA Astrophysics Data System (ADS)

    Kanki, Teruo; Tanaka, Hidekazu

    2017-04-01

    Large reversible changes of the electronic transport properties of solid-state oxide materials induced by electrochemical fields have received much attention as a new research avenue in iontronics. In this research update, dramatic transport changes in vanadium dioxide (VO2) nanowires were demonstrated by electric field-induced hydrogenation at room temperature through the nanogaps separated by humid air in a field-effect transistor structure with planar-type gates. This unique structure allowed us to investigate hydrogen intercalation and diffusion behavior in VO2 channels with respect to both time and space. Our results will contribute to further strategic researches to examine fundamental chemical and physical properties of devices and develop iontronic applications, as well as offering new directions to explore emerging functions for sensing, energy, and neuromorphologic devices combining ionic and electronic behaviors in solid-state materials.

  13. Direct electrochemical reduction of graphene oxide on ionic liquid doped screen-printed electrode and its electrochemical biosensing application.

    PubMed

    Ping, Jianfeng; Wang, Yixian; Fan, Kai; Wu, Jian; Ying, Yibin

    2011-10-15

    A novel electrochemical biosensing platform using electrochemically reduced graphene oxide (ER-GNO) modified electrode was proposed. This modified electrode was prepared by one-step electrodeposition of the exfoliated GNO sheets onto the ionic liquid doped screen-printed electrode (IL-SPE). The resulting ER-GNO/IL-SPE brought new capabilities for electrochemical devices by combining the advantages of ER-GNO and disposable electrode. Two important biomolecules, nicotinamide adenine dinucleotide (NADH) and hydrogen peroxide (H(2)O(2)), were employed to study the electrochemical performance of the ER-GNO/IL-SPE, which exhibited more favorable electron transfer kinetics than the bare IL-SPE. On the basis of the greatly enhanced electrochemical reactivity of H(2)O(2) at the developed electrode, ER-GNO and glucose oxidase constructed disposable biosensor showed better analytical performance for the glucose detection compared with the IL-SPE based biosensor. The linear range for the detection of glucose was from 5.0 μM to 12.0 mM with a detection limit of 1.0 μM. This work provides a useful avenue for implementing ER-GNO as a new generation of electrochemical transducer in disposable electrode, which could expand the scope of graphene constructed electrochemical biosensing devices and hold great promise for routine sensing applications.

  14. Preliminary studies using hybrid mediated electrochemical oxidation (HMEO) for the removal of persistent organic pollutants (POPs).

    PubMed

    Chung, S J; Balaji, S; Matheswaran, M; Ramesh, T; Moon, I S

    2007-01-01

    This study investigates the hybrid mediated electrochemical oxidation (HMEO) technology, which is a newly developed non thermal electrochemical oxidation process for organic destruction. A combination of ozone and ultrasonication processes to the mediated electrochemical oxidation (MEO) process is termed as hybrid mediated electrochemical oxidation. The electrochemical cell was developed in this laboratory. In the present study, several organic compounds, such as phenol, benzoquinone and ethylenediaminetetraacetic acid (EDTA), were chosen as the model organic pollutants to be destructed by the hybrid process. The organic destruction was monitored based on the CO2 generation and total organic carbon (TOC) reduction. The HMEO process was found to be extremely effective in the destruction of all the target organics chosen in this study. The information obtained from this study will provide an insight in adopting this technique for dealing with more recalcitrant organics (POPs).

  15. 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 +}.

  16. Ruthenium Oxide-Based Microelectrochemical Devices: Electrochemical Behavior of the Oxide Formed by Reduction of RuO4(2-)

    DTIC Science & Technology

    1988-08-15

    579 I i1. TITLE (include Security Classification) Ruthemium Oxide-Based Microelectrochemical Devices : Electrochem. _Behavior of the Oxide Formed by...Ruthenium Oxide-Based Microelectrochemical Devices : Electrochemical Behavior of the Oxide Formed by Reduction of RuO4 2- by Djonald F. Lyons, Martin 0...RUTHENIUM OXIDE-BASED MICROELECTROCHEMICAL DEVICES : ELECTROCHEMICAL BEHAVIOR OF THE OXIDE FORMED BY REDUCTION OF Ruo4 2- Donald F. Lyons, Martin 0

  17. 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 π-π 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.

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

    PubMed

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

    2012-08-24

    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 π-π 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.

  19. Industrial solution contaminated by polyacrylates: their elimination by electrochemical combustion.

    PubMed

    Masci, M; Chiti, L; De Lorenzo, A; Mantione, D; De Battisti, A; Vatistas, N

    2001-01-01

    The electrochemical combustion of polyacrylates was studied through both direct and indirect oxidation. The obtained results indicate the non elimination of the polyacrylates with the direct oxidation, while the indirect oxidation with NaCl completely eliminates these organic compounds. In the last case the effects of different initial concentrations of NaCl, anode materials and current densities was studied.

  20. 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.

  1. Treatment and toxicity evaluation of methylene blue using electrochemical oxidation, fly ash adsorption and combined electrochemical oxidation-fly ash adsorption.

    PubMed

    Wang, Kai-sung; Wei, Ming-Chi; Peng, Tzu-Huan; Li, Heng-Ching; Chao, Shu-Ju; Hsu, Tzu-Fang; Lee, Hong-Shen; Chang, Shih-Hsien

    2010-08-01

    Treatment of a basic dye, methylene blue, by electrochemical oxidation, fly ash adsorption, and combined electrochemical oxidation-fly ash adsorption was compared. Methylene blue at 100 mgL(-1) was used in this study. The toxicity was also monitored by the Vibrio fischeri light inhibition test. When electrochemical oxidation was used, 99% color and 84% COD were removed from the methylene blue solution in 20 min at a current density of 428 Am(-2), NaCl of 1000 mgL(-1), and pH(0) of 7. However, the decolorized solution showed high toxicity (100% light inhibition). For fly ash adsorption, a high dose of fly ash (>20,000 mgL(-1)) was needed to remove methylene blue, and the Freundlich isotherm described the adsorption behavior well. In the combined electrochemical oxidation-fly ash adsorption treatment, the addition of 4000 mgL(-1) fly ash effectively reduced intermediate toxicity and decreased the COD of the electrochemical oxidation-treated methylene blue solution. The results indicated that the combined process effectively removed color, COD, and intermediate toxicity of the methylene blue solution.

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

    NASA Astrophysics Data System (ADS)

    Houseknecht, Jamie G.; Tapsak, Mark A.

    2007-09-01

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

  3. 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…

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

    PubMed

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

    2009-01-01

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

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

    PubMed

    Bagastyo, Arseto Y; Radjenovic, Jelena; Mu, Yang; Rozendal, René 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. Copyright © 2011 Elsevier Ltd. All rights reserved.

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

    PubMed

    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.

  7. 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): 0-2 g/L and electrolysis time (t): 10-130 min 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.

  8. 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.

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

    PubMed

    Basirun, Wan J; Sookhakian, Mehran; Baradaran, Saeid; Mahmoudian, Mohammad R; Ebadi, Mehdi

    2013-09-24

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

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

    PubMed Central

    2013-01-01

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

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

    NASA Astrophysics Data System (ADS)

    Basirun, Wan J.; Sookhakian, Mehran; Baradaran, Saeid; Mahmoudian, Mohammad R.; Ebadi, Mehdi

    2013-09-01

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

  12. Electrochemical corrosion of a noble metal-bearing alloy-oxide composite

    DOE PAGES

    Chen, X; Ebert, W. L.; Indacochea, Ernesto

    2017-08-01

    The effects of added Ru and Pd on the microstructure and electrochemical behaviour of a composite material made by melting those metals with AISI 410 stainless steel, Zr, Mo, and lanthanide oxides were assessed using electrochemical and microscopic methods The lanthanide oxides reacted with Zr to form durable lanthanide zirconates and Mo alloyed with steel to form FeMoCr intermetallics. The noble metals alloyed with the steel to provide solid solution strengthening and inhibit carbide/nitride formation. A passive film formed during electrochemical tests in acidic NaCl solution, but became less effective as corrosion progressed and regions over the intermetallics eventually failed.

  13. Alkaline electrochemical advanced oxidation process for chromium oxidation at graphitized multi-walled carbon nanotubes.

    PubMed

    Xue, Yudong; Zheng, Shili; Sun, Zhi; Zhang, Yi; Jin, Wei

    2017-09-01

    Alkaline electrochemical advanced oxidation processes for chromium oxidation and Cr-contaminated waste disposal were reported in this study. The highly graphitized multi-walled carbon nanotubes g-MWCNTs modified electrode was prepared for the in-situ electrochemical generation of HO2(-). RRDE test results illustrated that g-MWCNTs exhibited much higher two-electron oxygen reduction activity than other nanocarbon materials with peak current density of 1.24 mA cm(-2), %HO2(-) of 77.0% and onset potential of -0.15 V (vs. Hg/HgO). It was originated from the highly graphitized structure and good electrical conductivity as illustrated from the Raman, XRD and EIS characterizations, respectively. Large amount of reactive oxygen species (HO2(-) and ·OH) were in-situ electro-generated from the two-electron oxygen reduction and chromium-induced alkaline electro-Fenton-like reaction. The oxidation of Cr(III) was efficiently achieved within 90 min and the conversion ratio maintained more than 95% of the original value after stability test, offering an efficient and green approach for the utilization of Cr-containing wastes. Copyright © 2017 Elsevier Ltd. All rights reserved.

  14. On-site wood-chip bioreactors could reduce indirect nitrous oxide emissions from tile drain waters

    USDA-ARS?s Scientific Manuscript database

    Indirect nitrous oxide (N2O) emissions originating from nitrate-laden agricultural drainage waters represent approximately 21% of total N2O emissions in the USA. Typical strategies to mitigate indirect N2O emissions are either improving fertilization methods or on-site treatment of drainage water. R...

  15. Mitigating Sources of Indirect Nitrous Oxide Emissions from Tile Drain by On-Site Wood-Chip Bioreactors

    USDA-ARS?s Scientific Manuscript database

    Indirect nitrous oxide (N2O) emissions originating from nitrate-laden agricultural drainage waters represent a substantial fraction of total N2O emissions in the USA. Typical strategies to mitigate indirect N2O emissions are either improving fertilization methods or on-site treatment of drainage wat...

  16. Electrochemical Stripping of Atomic Oxygen on Single-Crystalline Platinum: Bridging Gas-Phase and Electrochemical Oxidation

    PubMed Central

    2017-01-01

    To understand the interaction between Pt and surface oxygenated species in electrocatalysis, this paper correlates the electrochemistry of atomic oxygen on Pt formed in the gas phase with electrochemically generated oxygen species on a variety of single-crystal platinum surfaces. The atomic oxygen adsorbed on single-crystalline Pt electrodes, made by thermal dissociation of molecular oxygen, is used for voltammetry measurements in acidic electrolytes (HClO4 and H2SO4). The essential knowledge of coverage, binding energy, and surface construction of atomic oxygen is correlated with the charge, potential, and shape of voltammograms, respectively. The differences of the voltammograms between the oxide made by thermal dissociation of molecular oxygen and electrochemical oxidation imply that atomic oxygen is not an intermediate of the electrochemical oxidation of Pt(111). The reconstruction of (100) terrace and step and the low-potential stripping of atomic oxygen on (111) step site provide insight into the first stages of degradation of Pt-based electrocatalysts. PMID:28225278

  17. 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.

  18. Electrochemical oxidation of fluoroquinolone antibiotics: Mechanism, residual antibacterial activity and toxicity change.

    PubMed

    Zhu, Linyan; Santiago-Schübel, Beatrix; Xiao, Hongxia; Hollert, Henner; Kueppers, Stephan

    2016-10-01

    In this paper, we studied the electrochemical oxidation mechanisms of three typical fluoroquinolone antibiotics (FQs), and investigated residual antibacterial activity and toxicity changes after oxidation processes. Electrochemistry coupled to mass spectrometry (EC-MS) was used to study the oxidation processes of ciprofloxacin (CIP), norfloxacin (NOR) and ofloxacin (OFL). Eight oxidation products for each parent compound were identified and their chemical structures were elucidated. The transformation trend of each product, with the continuous increase of voltage from 0 to 3000 mV, was recorded by online EC-MS. The oxidation pathways were proposed based on the structural information and transformation trends of oxidation products. We found the oxidation mechanisms of FQs consisted of the hydroxylation and cleavage of piperazinyl ring via reactions with hydroxyl radicals, while the fluoroquinolone core remained intact. The antibacterial activity of the parent compounds and their oxidation mixtures was estimated using zone inhibition tests for gram-negative bacteria Salmonella typhimurium. It was found that the oxidation mixtures of CIP and NOR retained the antibacterial properties with lower activity compared to their parent compounds, while the antibacterial activity of OFL was almost eliminated after oxidation. Furthermore, the toxicity of the three FQs and their oxidation mixtures were evaluated using algal growth inhibition test (Desmodesmus subspicatus). The median effective concentration (EC50) values for the algal inhibition tests were calculated for the end point of growth rate. The toxicity of CIP and NOR to green algae after electrochemical oxidation, remained unchanged, while that of OFL significantly increased. The results presented in this paper contribute to an understanding of the electrochemical oxidation mechanisms of FQs, and highlight the potential environmental risks of FQs after electrochemical oxidation processes. Copyright © 2016 Elsevier

  19. Indirect emissions of nitrous oxide from regional aquifers in the United Kingdom.

    PubMed

    Hiscock, K M; Bateman, A S; Mühlherr, I H; Fukada, T; Dennis, P F

    2003-08-15

    Diffuse pollution of groundwater by agriculture has caused elevated concentrations of nitrate (NO3-) and nitrous oxide (N2O) in regional aquifers. N2O is an important "greenhouse" gas, yet there are few estimates of indirect emissions of N2O from regional aquifers. In this study, high concentrations of N2O (mean 602 nM) were measured in the unconfined Chalk aquifer of eastern England, in an area of intensive agriculture. In contrast, pristine groundwaters from upland regions of England and Scotland, with predominantly natural vegetation cover, were found to have much lower concentrations of N2O (mean 27 nM). A positive relationship between N2O and NO3- concentrations and delta18O-NO3 values of between 3.36 and 16.00/1000 suggest that nitrification is the principal source of N2O. A calculated emission factor (EF5-g) of 0.0019 for indirect losses of N2O from Chalk groundwater is an order of magnitude lower than the value of 0.015 currently used in the Intergovernmental Panel on Climate Change (IPCC) methodology for assessing agricultural emissions. A flux of N2O from the major UK aquifers of 0.04 kg N2O-N ha(-1) a(-1) has been calculated using two approaches and suggests that indirect losses of N2O from regional aquifers are much less significant (<1%) than direct emissions from agricultural soils.

  20. Graphene oxide sheet-prussian blue nanocomposites: green synthesis and their extraordinary electrochemical properties.

    PubMed

    Liu, Xiao-Wang; Yao, Zi-Jian; Wang, Yue-Feng; Wei, Xian-Wen

    2010-12-01

    A facile and green method for the synthesis of graphene oxide sheets (GOs)-prussian blue nanocomposites has been presented via a spontaneous redox reaction in a aqueous solution containing FeCl3, K3[Fe(CN)6] and graphene oxide sheets. Electrochemical property investigation demonstrates PB nanocubes formed on the surface of GOs retain their excellent electrochemical activity and the GOs can enhance the electron transfer between PB and GC electrode. Moreover, the obtained nanocomposites even have shown a higher sensitivity toward the electrocatalytical reduction of H2O2 than that of multiwalled carbon nanotube/PB nanocomposites. Given their extraordinary electrochemical properties and the green preparation, as-prepared GO-PB nanocomposites have great potential in the field of electrochemical sensor and biofuel cell.

  1. 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; Markò, István E

    2015-10-02

    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.

  2. Fertilizer management effects on nitrate leaching and indirect nitrous oxide emissions in irrigated potato production.

    PubMed

    Venterea, Rodney T; Hyatt, Charles R; Rosen, Carl J

    2011-01-01

    Potato ( L.) is a N-intensive crop, with high potential for nitrate (NO) leaching, which can contribute to both water contamination and indirect nitrous oxide (NO) emissions. Two approaches that have been considered for reducing N losses include conventional split application (CSA) of soluble fertilizers and single application of polymer-coated urea (PCU). The objectives of this study were to: (i) compare NO leaching using CSA and two PCUs (PCU-1 and PCU-2), which differed in their polymer formulations, and (ii) use measured NO leaching rates and published emissions factors to estimate indirect NO emissions. Averaged over three growing seasons (2007-2009), NO leaching rates were not significantly different among the three fertilizer treatments. Using previously reported direct NO emissions data from the same experiment, total direct plus indirect growing season NO emissions with PCU-1 were estimated to be 30 to 40% less than with CSA. However, PCU-1 also resulted in greater residual soil N after harvest in 2007 and greater soil-water NO in the spring following the 2008 growing season. These results provide evidence that single PCU applications for irrigated potato production do not increase growing season NO leaching compared with multiple split applications of soluble fertilizers, but have the potential to increase N losses after the growing season and into the following year. Estimates of indirect NO emissions ranged from 0.8 to 64% of direct emissions, depending on what value was assumed for the emission factor describing off-site conversion of NO to NO. Thus, our results also demonstrate how more robust models are needed to account for off-site conversion of NO to NO, since current emission factor models have an enormous degree of uncertainty. Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.

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

    PubMed

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

    2015-10-01

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

  4. Next-Generation Electrochemical Energy Materials for Intermediate Temperature Molten Oxide Fuel Cells and Ion Transport Molten Oxide Membranes.

    PubMed

    Belousov, Valery V

    2017-02-21

    High temperature electrochemical devices such as solid oxide fuel cells (SOFCs) and oxygen separators based on ceramic materials are used for efficient energy conversion. These devices generally operate in the temperature range of 800-1000 °C. The high operating temperatures lead to accelerated degradation of the SOFC and oxygen separator materials. To solve this problem, the operating temperatures of these electrochemical devices must be lowered. However, lowering the temperature is accompanied by decreasing the ionic conductivity of fuel cell electrolyte and oxygen separator membrane. Therefore, there is a need to search for alternative electrolyte and membrane materials that have high ionic conductivity at lower temperatures. A great many opportunities exist for molten oxides as electrochemical energy materials. Because of their unique electrochemical properties, the molten oxide innovations can offer significant benefits for improving energy efficiency. In particular, the newly developed electrochemical molten oxide materials show high ionic conductivities at intermediate temperatures (600-800 °C) and could be used in molten oxide fuel cells (MOFCs) and molten oxide membranes (MOMs). The molten oxide materials containing both solid grains and liquid channels at the grain boundaries have advantages compared to the ceramic materials. For example, the molten oxide materials are ductile, which solves a problem of thermal incompatibility (difference in coefficient of thermal expansion, CTE). Besides, the outstanding oxygen selectivity of MOM materials allows us to separate ultrahigh purity oxygen from air. For their part, the MOFC electrolytes show the highest ionic conductivity at intermediate temperatures. To evaluate the potential of molten oxide materials for technological applications, the relationship between the microstructure of these materials and their transport and mechanical properties must be revealed. This Account summarizes the latest results on

  5. Capsid protein oxidation in feline calicivirus using an electrochemical inactivation treatment.

    PubMed

    Shionoiri, Nozomi; Nogariya, Osamu; Tanaka, Masayoshi; Matsunaga, Tadashi; Tanaka, Tsuyoshi

    2015-01-01

    Pathogenic viral infections are an international public health concern, and viral disinfection has received increasing attention. Electrochemical treatment has been used for treatment of water contaminated by bacteria for several decades, and although in recent years several reports have investigated viral inactivation kinetics, the mode of action of viral inactivation by electrochemical treatment remains unclear. Here, we demonstrated the inactivation of feline calicivirus (FCV), a surrogate for human noroviruses, by electrochemical treatment in a developed flow-cell equipped with a screen-printed electrode. The viral infectivity titer was reduced by over 5 orders of magnitude after 15 min of treatment at 0.9V vs. Ag/AgCl. Proteomic study of electrochemically inactivated virus revealed oxidation of peptides located in the viral particles; oxidation was not observed in the non-treated sample. Furthermore, transmission electron microscopy revealed that viral particles in the treated sample had irregular structures. These results suggest that electrochemical treatment inactivates FCV via oxidation of peptides in the structural region, causing structural deformation of virus particles. This first report of viral protein damage through electrochemical treatment will contribute to broadening the understanding of viral inactivation mechanisms. Copyright © 2014 Elsevier B.V. All rights reserved.

  6. Electrochemical and spectroscopic studies of the oxidation mechanism of the herbicide propanil.

    PubMed

    Garrido, E M; Lima, J L F C; Delerue-Matos, C; Borges, F; Silva, A M S; Piedade, J A P; Oliveira Brett, A M

    2003-02-12

    Electrochemical oxidation of propanil in deuterated solutions was studied by cyclic, differential pulse, and square wave voltammetry using a glassy carbon microelectrode. The oxidation of propanil in deuterated acid solutions occurs at the nitrogen atom of the amide at a potential of +1.15 V vs Ag/AgCl. It was also found that, under the experimental conditions used, protonation at the oxygen atom of propanil occurs, leading to the appearance of another species in solution which oxidizes at +0.60 V. The anodic peak found at +0.79 V vs Ag/AgCl in deuterated basic solutions is related to the presence of an anionic species in which a negative charge is on the nitrogen atom. The electrochemical data were confirmed by the identification of all the species formed in acidic and basic deuterated solutions by means of NMR spectroscopy. The results are supported by electrochemical and spectroscopic studies of acetanilide in deuterated solutions.

  7. Oxidative stabilization of polyacrylonitrile nanofibers and carbon nanofibers containing graphene oxide (GO): a spectroscopic and electrochemical study

    PubMed Central

    Gergin, İlknur; Ismar, Ezgi

    2017-01-01

    In this study, a precursor for carbon nanofibers (CNF) was fabricated via electrospinning and carbonized through a thermal process. Before carbonization, oxidative stabilization should be applied, and the oxidation mechanism also plays an important role during carbonization. Thus, the understanding of the oxidation mechanism is an essential part of the production of CNF. The oxidation process of polyacrylonitrile was studied and nanofiber webs containing graphene oxide (GO) are obtained to improve the electrochemical properties of CNF. Structural and morphological characterizations of the webs are carried out by using attenuated total reflectance Fourier transform infrared spectroscopy and Raman spectroscopy, scanning electron microscopy, atomic force microscopy and transmission electron microscopy. Mechanical tests are performed with a dynamic mechanical analyzer, and thermal studies are conducted by using thermogravimetric analysis. Electrochemical impedance spectroscopy, and cyclic voltammetry are used to investigate capacitive behavior of the products. The proposed equivalent circuit model was consistent with charge-transfer processes taking place at interior pores filled with electrolyte. PMID:28875098

  8. 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

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

    PubMed

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

    2015-10-01

    Electrochemical oxidation of 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) over metal-oxide-coated Ti anodes, i.e., Ti/SnO2-Sb/Ce-PbO2, Ti/SnO2-Sb and Ti/RuO2, was examined. The degradation efficiency of over 90% was attained at 20 min at different initial concentrations (0.5-20 mg L(-1)) and initial pH values (3.1-11.2). The degradation efficiencies of 2,4,5-T on Ti/SnO2-Sb/Ce-PbO2, Ti/SnO2-Sb and Ti/RuO2 anodes were higher than 99.9%, 97.2% and 91.5% at 30 min, respectively, and the respective total organic carbon removal ratios were 65.7%, 54.6% and 37.2%. The electrochemical degradation of 2,4,5-T in aqueous solution followed pseudo-first-order kinetics. The compounds, i.e., 2,5-dichlorohydroquinone and 2,5-dihydroxy-p-benzoquinone, have been identified as the main aromatic intermediates by liquid chromatography-mass spectrometry. The results showed that the energy efficiencies of 2,4,5-T (20 mg L(-1)) degradation with Ti/SnO2-Sb/Ce-PbO2 anode at the optimal current densities from 2 to 16 mA cm(-2) ranged from 8.21 to 18.73 kWh m(-3). Copyright © 2015 Elsevier Ltd. All rights reserved.

  10. 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.

  11. Mediated electrochemical oxidation of organic wastes without electrode separators

    DOEpatents

    Farmer, Joseph C.; Wang, Francis T.; Hickman, Robert G.; Lewis, Patricia R.

    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.

  12. 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.

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

    PubMed

    Makhotkina, Olga; Kilmartin, Paul A

    2013-06-12

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

  14. Nanoscale electrochemical patterning reveals the active sites for catechol oxidation at graphite surfaces.

    PubMed

    Patel, Anisha N; McKelvey, Kim; Unwin, Patrick R

    2012-12-19

    Graphite-based electrodes (graphite, graphene, and nanotubes) are used widely in electrochemistry, and there is a long-standing view that graphite step edges are needed to catalyze many reactions, with the basal surface considered to be inert. In the present work, this model was tested directly for the first time using scanning electrochemical cell microscopy reactive patterning and shown to be incorrect. For the electro-oxidation of dopamine as a model process, the reaction rate was measured at high spatial resolution across a surface of highly oriented pyrolytic graphite. Oxidation products left behind in a pattern defined by the scanned electrochemical cell served as surface-site markers, allowing the electrochemical activity to be correlated directly with the graphite structure on the nanoscale. This process produced tens of thousands of electrochemical measurements at different locations across the basal surface, unambiguously revealing it to be highly electrochemically active, with step edges providing no enhanced activity. This new model of graphite electrodes has significant implications for the design of carbon-based biosensors, and the results are additionally important for understanding electrochemical processes on related sp(2)-hybridized materials such as pristine graphene and nanotubes.

  15. Electrochemical and photoelectrochemical oxidation of 5-hydroxymethylfurfural to 2,5-furandicarboxylic acid and 2,5-diformylfuran

    DOEpatents

    Choi, Kyoung-Shin; Cha, Hyun Gil

    2017-03-21

    Electrochemical and photoelectrochemical cells for the oxidation of 5-hydroxymethylfurfural to 2,5-furandicarboxylic acid and/or 2,5-diformylfuran are provided. Also provided are methods of using the cells to carry out the electrochemical and photoelectrochemical oxidation of 5-hydroxymethylfurfural to 2,5-furandicarboxylic acid and/or 2,5-diformylfuran.

  16. 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.

  17. Annealing of indium tin oxide (ITO) coated optical fibers for optical and electrochemical sensing purposes

    NASA Astrophysics Data System (ADS)

    Dominik, Magdalena; Siuzdak, Katarzyna; Niedziałkowski, Paweł; Stranak, Vitezslav; Sezemsky, Petr; Sobaszek, Michał; Bogdanowicz, Robert; Ossowski, Tadeusz; Śmietana, Mateusz

    2016-12-01

    Glass and fiber structures with Indium Tin Oxide (ITO) coating were subjected to annealing in order to identify impact of the thermal treatment on their optical and electrochemical properties. It is shown that the annealing process significantly modifies optical properties and thickness of the films, which are crucial for performance of optical fiber sensors. Moreover, it visibly improves electrochemical activity of ITO on glass slides and thicker (∅=400 μm) ITO-coated fibers, whereas in the case of thinner fibers (∅=125 μm) it could lead to a loss of their electrochemical activity. Depending on the applied substrate and the annealing process, the investigated structures with ITO coating can be further used as fiber-based sensors with integrated opto-electrochemical readout.

  18. Phytic acid/graphene oxide nanocomposites modified electrode for electrochemical sensing of dopamine.

    PubMed

    Wang, Donglei; Xu, Fei; Hu, Jiajie; Lin, Meng

    2017-02-01

    An electrochemical sensor for determining dopamine was developed by modifying phytic acid/graphene oxide (PA/GO) nanocomposites onto a glassy carbon electrode (GCE). PA functionalized GO was prepared by an ultra-sonication method. Subsequently, the PA/GO nanocomposites were drop-casted on a glassy carbon substrate. The structural feature of the PA/GO modified GCE was confirmed by attenuated total reflection infrared (ATR-IR) spectroscopy. The proposed electrochemical sensor was applied to detect various concentrations of DA by differential pulse voltammetry (DPV). The PA/GO/GCE was considered to be highly sensitive to DA in the range of 0.05-10μM. In addition, the PA/GO/GCE demonstrated high electrochemical selectivity toward DA in the presence of ascorbic acid (AA) and uric acid (UA). The prepared electrochemical DA sensor was applied for detection of DA in dopamine hydrochloride injection and spiked samples of human urine with satisfactory results.

  19. 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.

  20. 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.

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

    PubMed

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

    2016-07-01

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

  2. News in Regions of Electrochemical Synthesis of Oxidizers

    DTIC Science & Technology

    of compounds: chlorine oxides, persulfuric acid, ammonium persulfate, manganese oxides, bichromates, bromates, iodates, iodic acid, perborates , percarbonates, and lead tetra-acetate. A bibliography of 95 items is included.

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

    SciTech Connect

    Cheng, Liang; Shao, Mingwang; 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.

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

    NASA Astrophysics Data System (ADS)

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

    1994-10-01

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

  6. In operando studies on the electrochemical oxidation of water mediated by molecular catalysts.

    PubMed

    Hetterscheid, Dennis G H

    2017-09-12

    Homogeneous reactions in general are relatively easy to study with respect to heterogeneous systems since all catalytic sites are uniform and can be addressed simultaneously. The latter feature is fully out of the window in an electrochemical context, where only the few catalytic species that are sufficiently close to the electrode undergo redox reactions. Especially in the water oxidation reaction where harsh reaction conditions are employed, a clear picture of what is the active species, what products are formed, how one can steer this, and how it all depends on the exact reaction conditions is important to be able to fully unravel the key reaction paths. The combination of electrochemical experiments with on-line detection of the catalytic species and reaction products is a powerful approach to successfully address these questions. Recently, a significant progress has been made in on-line studies on molecular water oxidation catalysts during electrochemical experiments. These are reviewed here.

  7. Chemical composition and direct electrochemical oxidation of table olive processing wastewater using high oxidation power anodes.

    PubMed

    Gargouri, Boutheina; Gargouri, Olfa Dridi; Khmakhem, Ibtihel; Ammar, Sonda; Abdelhèdi, Ridha; Bouaziz, Mohamed

    2017-01-01

    Table olive processing wastewater (TOW) is a notoriously polluting due to its high organic and phenol content. To reduce them, an electrochemical process has been studied for the treatment of this effluent. Experiments were performed with a cell equipped with lead dioxide (PbO2) or boron-doped diamond (BDD) as anode and platinum as cathode, where Table Olive Wastewater (TOW) were destroyed by hydroxyl radicals formed at the anode surface from water oxidation. The comparative study of both systems shows the performance of the BDD anode compared to PbO2, explained by the large amounts of hydroxyl radicals generated effective at BDD anode and its synthesis characteristics. Using LC/MS analysis, it was possible to determine hydroxytyrosol, as major phenolic compounds, in table olive processing wastewater and its concentration reach 890 mg L(-1). A possible reaction mechanism oxidation for hydroxytyrosol was proposed. The kinetics decays for hydroxytyrosol degradation on PbO2 anode follows a pseudo-first order reaction with a rate constant 0.9 h(-1) for japp value 20 mA cm(-2).

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

    PubMed

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

    2015-02-07

    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.

  9. Mercury Underpotential Deposition to Determine Iridium and Iridium Oxide Electrochemical Surface Areas

    SciTech Connect

    Alia, Shaun M.; Hurst, Katherine E.; Kocha, Shyam S.; Pivovar, Bryan S.

    2016-06-02

    Determining the surface areas of electrocatalysts is critical for separating the key properties of area-specific activity and electrochemical surface area from mass activity. Hydrogen underpotential deposition and carbon monoxide oxidation are typically used to evaluate iridium (Ir) surface areas, but are ineffective on oxides and can be sensitive to surface oxides formed on Ir metals. Mercury underpotential deposition is presented in this study as an alternative, able to produce reasonable surface areas on Ir and Ir oxide nanoparticles, and able to produce similar surface areas prior to and following characterization in oxygen evolution. Reliable electrochemical surface areas allow for comparative studies of different catalyst types and the characterization of advanced oxygen evolution catalysts. Lastly, they also enable the study of catalyst degradation in durability testing, both areas of increasing importance within electrolysis and electrocatalysis.

  10. Mercury Underpotential Deposition to Determine Iridium and Iridium Oxide Electrochemical Surface Areas

    DOE PAGES

    Alia, Shaun M.; Hurst, Katherine E.; Kocha, Shyam S.; ...

    2016-06-02

    Determining the surface areas of electrocatalysts is critical for separating the key properties of area-specific activity and electrochemical surface area from mass activity. Hydrogen underpotential deposition and carbon monoxide oxidation are typically used to evaluate iridium (Ir) surface areas, but are ineffective on oxides and can be sensitive to surface oxides formed on Ir metals. Mercury underpotential deposition is presented in this study as an alternative, able to produce reasonable surface areas on Ir and Ir oxide nanoparticles, and able to produce similar surface areas prior to and following characterization in oxygen evolution. Reliable electrochemical surface areas allow for comparativemore » studies of different catalyst types and the characterization of advanced oxygen evolution catalysts. Lastly, they also enable the study of catalyst degradation in durability testing, both areas of increasing importance within electrolysis and electrocatalysis.« less

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

    PubMed

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

    2015-11-01

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

  12. Intermediate stages of electrochemical oxidation of single-crystalline platinum revealed by in situ Raman spectroscopy

    PubMed Central

    Huang, Yi-Fan; Kooyman, Patricia J.; Koper, Marc T. M.

    2016-01-01

    Understanding the atomistic details of how platinum surfaces are oxidized under electrochemical conditions is of importance for many electrochemical devices such as fuel cells and electrolysers. Here we use in situ shell-isolated nanoparticle-enhanced Raman spectroscopy to identify the intermediate stages of the electrochemical oxidation of Pt(111) and Pt(100) single crystals in perchloric acid. Density functional theory calculations were carried out to assist in assigning the experimental Raman bands by simulating the vibrational frequencies of possible intermediates and products. The perchlorate anion is suggested to interact with hydroxyl phase formed on the surface. Peroxo-like and superoxo-like two-dimensional (2D) surface oxides and amorphous 3D α-PtO2 are sequentially formed during the anodic polarization. Our measurements elucidate the process of the electrochemical oxidation of platinum single crystals by providing evidence for the structure-sensitive formation of a 2D platinum-(su)peroxide phase. These results may contribute towards a fundamental understanding of the mechanism of degradation of platinum electrocatalysts. PMID:27514695

  13. 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.

  14. Intermediate stages of electrochemical oxidation of single-crystalline platinum revealed by in situ Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Huang, Yi-Fan; Kooyman, Patricia J.; Koper, Marc T. M.

    2016-08-01

    Understanding the atomistic details of how platinum surfaces are oxidized under electrochemical conditions is of importance for many electrochemical devices such as fuel cells and electrolysers. Here we use in situ shell-isolated nanoparticle-enhanced Raman spectroscopy to identify the intermediate stages of the electrochemical oxidation of Pt(111) and Pt(100) single crystals in perchloric acid. Density functional theory calculations were carried out to assist in assigning the experimental Raman bands by simulating the vibrational frequencies of possible intermediates and products. The perchlorate anion is suggested to interact with hydroxyl phase formed on the surface. Peroxo-like and superoxo-like two-dimensional (2D) surface oxides and amorphous 3D α-PtO2 are sequentially formed during the anodic polarization. Our measurements elucidate the process of the electrochemical oxidation of platinum single crystals by providing evidence for the structure-sensitive formation of a 2D platinum-(su)peroxide phase. These results may contribute towards a fundamental understanding of the mechanism of degradation of platinum electrocatalysts.

  15. CO oxidation on stepped-Pt(111) under electrochemical conditions: insights from theory and experiment.

    PubMed

    Busó-Rogero, C; Herrero, E; Bandlow, J; Comas-Vives, A; Jacob, Timo

    2013-11-14

    The co-adsorption of CO and OH on two Pt stepped surfaces vicinal to the (111) orientation has been evaluated by means of density functional theory (DFT) calculations. Focusing on Pt(533) and Pt(221), which contain (100) and (111)-steps, respectively, we find that (111)-steps should be more reactive towards CO oxidation than surfaces containing (100)-steps. The DFT results are compared with electrochemical experiments on the CO adsorption and oxidation on these vicinal surfaces.

  16. 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.

  17. Direct and indirect effects of kisspeptin on liver oxidant and antioxidant systems in young male rats.

    PubMed

    Aydin, M; Oktar, S; Yonden, Z; Ozturk, O H; Yilmaz, B

    2010-06-01

    Kisspeptin is a recently discovered hypothalamic peptide which plays an important role in the central control of reproductive functions. We have investigated direct and indirect effects of kisspeptin on the liver oxidative stress in young male rats. Twenty-four rats were divided into four groups (n = 6/group). First group served as control and received saline. Kisspeptin-10 was administered to the animals in the second group (20 nmol/rat/day), for a period of 7 days. Rats were given only one dose gosereline (0.9 mg/rat), a GnRH agonist in the third group. The last group received kisspeptin-10 with gosereline. The activities of catalase, superoxide dismutase (SOD), xanthine oxidase (XO), adenosine deaminase (AD) and level of malondialdehyde were studied in liver tissue. Serum samples were separated for total antioxidant capacity (TAC), total oxidant status (TOS), alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase, blood urea nitrogen (BUN), colesterol, high-density lipoprotein (HDL) and triglyceride. Kisspeptin increased the activities of SOD and catalase (p < 0.05). When compared to the control group, the levels of malondialdehyde, TOS and AST were lower, but levels of BUN, cholesterole, HDL and AD were higher in the other three groups (p < 0.05). In conclusion, our findings suggest that kisspeptin may have antioxidant and thus protective effects on the liver tissue. 2010 John Wiley & Sons, Ltd.

  18. 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.

  19. Electrochemical preparation of activated graphene oxide for the simultaneous determination of hydroquinone and catechol.

    PubMed

    Velmurugan, Murugan; Karikalan, Natarajan; Chen, Shen-Ming; Cheng, Yi-Hui; Karuppiah, Chelladurai

    2017-03-31

    This paper describes the electrochemical preparation of highly electrochemically active and conductive activated graphene oxide (aGO). Afterwards, the electrochemical properties of aGO was studied towards the simultaneous determination of hydroquinone (HQ) and catechol (CC). This aGO is prepared by the electrochemical activation of GO by various potential treatments. The resultant aGOs are examined by various physical and electrochemical characterizations. The high potential activation (1.4 to -1.5) process results a highly active GO (aGO1), which manifest a good electrochemical behavior towards the determination of HQ and CC. This aGO1 modified screen printed carbon electrode (SPCE) was furnished the sensitive detection of HQ and CC with linear concentration range from 1 to 312μM and 1 to 350μM. The aGO1 modified SPCE shows the lowest detection limit of 0.27μM and 0.182μM for the HQ and CC, respectively. The aGO1 modified SPCE reveals an excellent selectivity towards the determination of HQ and CC in the presence of 100 fold of potential interferents. Moreover, the fabricated disposable aGO1/SPCE sensor was demonstrated the determination of HQ and CC in tap water and industrial waste water.

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

    NASA Astrophysics Data System (ADS)

    Molina, J.; Fernández, J.; del Río, 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 (Ω) 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.

  1. 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.

  2. 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

  3. Boron-doped diamond electrodes for the electrochemical oxidation and cleavage of peptides.

    PubMed

    Roeser, Julien; Alting, Niels F A; Permentier, Hjalmar P; Bruins, Andries P; Bischoff, Rainer

    2013-07-16

    Electrochemical oxidation of peptides and proteins is traditionally performed on carbon-based electrodes. Adsorption caused by the affinity of hydrophobic and aromatic amino acids toward these surfaces leads to electrode fouling. We compared the performance of boron-doped diamond (BDD) and glassy carbon (GC) electrodes for the electrochemical oxidation and cleavage of peptides. An optimal working potential of 2000 mV was chosen to ensure oxidation of peptides on BDD by electron transfer processes only. Oxidation by electrogenerated OH radicals took place above 2500 mV on BDD, which is undesirable if cleavage of a peptide is to be achieved. BDD showed improved cleavage yield and reduced adsorption for a set of small peptides, some of which had been previously shown to undergo electrochemical cleavage C-terminal to tyrosine (Tyr) and tryptophan (Trp) on porous carbon electrodes. Repeated oxidation with BDD electrodes resulted in progressively lower conversion yields due to a change in surface termination. Cathodic pretreatment of BDD at a negative potential in an acidic environment successfully regenerated the electrode surface and allowed for repeatable reactions over extended periods of time. BDD electrodes are a promising alternative to GC electrodes in terms of reduced adsorption and fouling and the possibility to regenerate them for consistent high-yield electrochemical cleavage of peptides. The fact that OH-radicals can be produced by anodic oxidation of water at elevated positive potentials is an additional advantage as they allow another set of oxidative reactions in analogy to the Fenton reaction, thus widening the scope of electrochemistry in protein and peptide chemistry and analytics.

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

    SciTech Connect

    Marina, Olga A; Stevenson, Jeffry W

    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.

  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. Metal Oxide Materials and Collector Efficiency in Electrochemical Supercapacitors

    DTIC Science & Technology

    2010-12-01

    composites can be deposited sponta- neously on carbon substrates, (iv) thin film mixed oxide systems showed promising power densities, especially in...Materials Characterization . . . . . . . . . . . . . . . . . . . . . 18 5 Thin film mixed oxide electrodes...titanium substrate. . . . . . . . . . . . . . . . . . . 26 Figure 17: X-ray diffraction patterns for RuxMn1-xO2 thin film coated titanium substrates The

  8. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2013-05-01

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

  10. Direct correlation of electrochemical behaviors with anti-thrombogenicity of semiconducting titanium oxide films.

    PubMed

    Wan, Guojiang; Lv, Bo; Jin, Guoshou; Maitz, Manfred F; Zhou, Jianzhang; Huang, Nan

    2014-01-01

    Biomaterials-associated thrombosis is dependent critically upon electrochemical response of fibrinogen on material surface. The relationship between the response and anti-thrombogenicity of biomaterials is not well-established. Titanium oxide appears to have good anti-thrombogenicity and little is known about its underlying essential chemistry. We correlate their anti-thrombogenicity directly to electrochemical behaviors in fibrinogen containing buffer solution. High degree of inherent n-type doping was noted to contribute the impedance preventing charge transfer from fibrinogen into film (namely its activation) and consequently reduced degree of anti-thrombogenicity. The impedance was the result of high donor carrier density as well as negative flat band potential.

  11. Polymer-directed synthesis of metal oxide-containing nanomaterials for electrochemical energy storage.

    PubMed

    Mai, Yiyong; Zhang, Fan; Feng, Xinliang

    2014-01-07

    Metal oxide-containing nanomaterials (MOCNMs) of controllable structures at the nano-scale have attracted considerable interest because of their great potential applications in electrochemical energy storage devices, such as lithium-ion batteries (LIBs) and supercapacitors. Among many structure-directing agents, polymers and macromolecules, including block copolymers (BCPs) and graphene, exhibit distinct advantages in the template-assisted synthesis of MOCNMs. In this feature article, we introduce the controlled preparation of MOCNMs employing BCPs and graphene as structure-directing agents. Typical synthetic strategies are presented for the control of structures and sizes as well as the improvement of physical properties and electrochemical performance of MOCNMs in LIBs and supercapacitors.

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

    PubMed

    Ambrosi, Adriano; Pumera, Martin

    2016-01-04

    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. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. Ammonium nitrogen removal from wastewater with a three-dimensional electrochemical oxidation system.

    PubMed

    Ding, Jing; Zhao, Qing-Liang; Wei, Liang-Liang; Chen, Yang; Shu, Xin

    2013-01-01

    Ammonium-containing wastewater could cause the promotion of eutrophication and a hindrance to the disinfection of water supplies. In this study, the feasibility of removing low-concentration ammonium nitrogen from synthetic and real wastewater by electrochemical oxidation was investigated. Using laboratory-scale electrochemical systems, the effects of chloride concentration, current density, anode materials, cathode materials, electrode gap, initial ammonium concentration and three-dimensional particles on the removal of ammonium nitrogen and current efficiency (CE) were evaluated. Ammonium nitrogen removal was mainly dependent upon anode materials and current density. The performance of two- and three-dimensional electrochemical oxidation systems was comparatively discussed. Both particle electrodes could enhance ammonium nitrogen removal and increase CE. However, the mechanism of the process seemed to be different. Moreover, the interaction of zeolites adsorption and electrochemical oxidation on the anode in a three-dimensional system could favor the regeneration of zeolites. Surface morphology of the used Ru-Ir-Sn/Ti anode revealed its longer working life of electrocatalysis. The result of ammonium degradation for a real wastewater treatment plant effluent showed the degradation rates in a three-dimensional system increased by 1.4 times those in a two-dimensional system.

  14. Electrochemical and theoretical characterization of the electro-oxidation of dimethoxycurcumin

    NASA Astrophysics Data System (ADS)

    Arrue, Lily; Barra, Tomas; Camarada, María Belén; Zarate, Ximena; Schott, Eduardo

    2017-06-01

    Dimethoxycurcumin (DMC) ((1E,6E)-1-(3,4-dimethoxycyclohexyl)-7-(3,4-dimethoxyphenyl) hepta-1,6- diene-3,5-dione) is a natural polyphenolic compound that appears together with curcumin in turmeric. Both molecules have wide range biological activities as antioxidant, anti-inflammatory and anti-carcinogenic agent. To evaluate the oxidation process and kinetics for DMC, the rate constant, electron transfer and diffusion coefficients for the electrochemical oxidation were determined. Therefore, its electrochemical behavior over a platinum electrode in anhydrous media was investigated. Furthermore, DFT calculations were performed to give a rational explanation to the obtained results. All the results support the fact that the central sbnd CH2sbnd group is the most reactive against an oxidation process.

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

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

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

  16. Electrochemical treatment of aqueous wastes containing pyrogallol by BDD-anodic oxidation.

    PubMed

    Nasr, Bensalah; Hsen, Trabelsi; Abdellatif, Gadri

    2009-01-01

    In this work, the electrochemical oxidation of pyrogallol (1,2,3-trihydroxybenzene) on boron-doped diamond anodes has been studied. The voltammetric results showed that pyrogallol oxidation takes place in the same potential region as that of phenol where the supporting electrolyte is stable. Synthetic wastewaters containing pyrogallol have been treated in a bench-scale electrolysis plant. This plant operates in a discontinuous mode by recirculating the waste continuously through a single-chamber electrochemical flow cell. The complete mineralization of pyrogallol and the electro-generated pollutants is obtained in the electrolytic device. HPLC analyses show the formation of carboxylic acids as the main intermediates. The efficiency of the electrochemical process was found to depend mainly on the pollutant concentration present in the waste and on the applied current density. The high efficiency of this technology can be explained in terms of the direct electro-oxidation at the BDD surface and the oxidation carried out by hydroxyl radicals and other electro-generated oxidants.

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

    PubMed

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

    2016-04-28

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

  18. Evaluation of three simple direct or indirect carbonyl detection methods for characterization of oxidative modifications of proteins.

    PubMed

    Vásquez-Garzón, Verónica R; Rouimi, Patrick; Jouanin, Isabelle; Waeg, Georg; Zarkovic, Neven; Villa-Treviño, Saul; Guéraud, Françoise

    2012-05-01

    Among disruptions induced by oxidative stress, modifications of proteins, particularly irreversible carbonylation, are associated with the development of several diseases, including cardiovascular diseases, neurodegenerative diseases, and cancer. Carbonylation of proteins can occur directly or indirectly through the adduction of lipid oxidation products. In this study, three classical and easy-to-perform techniques to detect direct or indirect carbonylation of proteins were compared. A model protein apomyoglobin and a complex mixture of rat liver cytosolic proteins were exposed to cumene hydroperoxide oxidation or adduction to the lipid peroxidation product 4-hydroxynonenal in order to test direct or indirect carbonylation, respectively. The technique using a specific anti-4-hydroxynonenal-histidine adduct antibody was effective to detect in vitro modification of model apomyoglobin and cytosolic proteins by 4-hydroxynonenal but not by direct carbonylation which was achieved by techniques using biotin-coupled hydrazide or dinitrophenylhydrazine derivatization of carbonyls. Sequential use of these methods enabled the detection of both direct and indirect carbonyl modification in proteins, although constitutively biotinylated proteins were detected by biotin-hydrazide. Although rather classical and efficient, methods for carbonyl detection on proteins in oxidative stress studies may be biased by some artifactual detections and complicated by proteins multimerizations. The use of more and more specific available antibodies is recommended to complete detection of lipid peroxidation product adducts on proteins.

  19. Fasting substrate oxidation at rest assessed by indirect calorimetry: is prior dietary macronutrient level and composition a confounder?

    PubMed

    Miles-Chan, J L; Dulloo, A G; Schutz, Y

    2015-07-01

    Indirect calorimetry, the measurement of O₂ consumption and CO₂ production, constitutes an invaluable tool as the most common method for analyzing whole-body energy expenditure, and also provides an index of the nature of macronutrient substrate oxidation--namely, carbohydrate (CHO) versus fat oxidation. The latter constitutes a key etiological factor in obesity as this condition can only develop when total fat oxidation is chronically lower than total exogenous fat intake. The standardization of indirect calorimetry measurements is essential for accurately tracking the relative proportion of energy expenditure derived from CHO and fat oxidation. Here we analyze literature data to show that the average fasting respiratory quotient typically shifts from approximately 0.80 to 0.90 (indicating a doubling of resting CHO oxidation) in response to a switch in dietary CHO intake (as % energy) from 30 to 60%. This underscores the importance of taking into account dietary macronutrient composition prior to indirect calorimetry studies in the interpretation of data on substrate utilization and oxidation.

  20. Modified cermet fuel electrodes for solid oxide electrochemical cells

    DOEpatents

    Ruka, Roswell J.; Spengler, Charles J.

    1991-01-01

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

  1. Theoretical investigation of the activity of cobalt oxides for the electrochemical oxidation of water.

    PubMed

    Bajdich, Michal; García-Mota, Mónica; Vojvodic, Aleksandra; Nørskov, Jens K; Bell, Alexis T

    2013-09-11

    The presence of layered cobalt oxides has been identified experimentally in Co-based anodes under oxygen-evolving conditions. In this work, we report the results of theoretical investigations of the relative stability of layered and spinel bulk phases of Co oxides, as well as the stability of selected surfaces as a function of applied potential and pH. We then study the oxygen evolution reaction (OER) on these surfaces and obtain activity trends at experimentally relevant electro-chemical conditions. Our calculated volume Pourbaix diagram shows that β-CoOOH is the active phase where the OER occurs in alkaline media. We calculate relative surface stabilities and adsorbate coverages of the most stable low-index surfaces of β-CoOOH: (0001), (0112), and (1014). We find that at low applied potentials, the (1014) surface is the most stable, while the (0112) surface is the more stable at higher potentials. Next, we compare the theoretical overpotentials for all three surfaces and find that the (1014) surface is the most active one as characterized by an overpotential of η = 0.48 V. The high activity of the (1014) surface can be attributed to the observation that the resting state of Co in the active site is Co(3+) during the OER, whereas Co is in the Co(4+) state in the less active surfaces. Lastly, we demonstrate that the overpotential of the (1014) surface can be lowered further by surface substitution of Co by Ni. This finding could explain the experimentally observed enhancement in the OER activity of Ni(y)Co(1-y)O(x) thin films with increasing Ni content. All energetics in this work were obtained from density functional theory using the Hubbard-U correction.

  2. Co(III) as mediator in phenol destruction using electrochemical oxidation

    NASA Astrophysics Data System (ADS)

    Herlina, Herlina; Derlini, Derlini; Muhammad, Razali

    2017-03-01

    Mediated electrochemical oxidation is one of the method for oxidation of organic compound by using a mediator. This method has been developed because have several advantages which low cost and efficient, the exhaust gas does not contain toxic materials and hazardous waste and the process take place at a relatively low temperature. Electrochemical oxidation of organic compounds using metal ion mediator is one alternative method that is appropriate for the treatment of organic waste. Co(III) is a strong oxidizing agent used as a mediator has been prepared in Pt electrodes. The concentration of Co(III) formed during oxidation determined by potentiometric titration where Co(III) aliquot was added into Fe(II) excess solution and the remaining Fe(II) which did not react has been titrated with Ce(IV). In optimum condition, Co(III) was then used to oxidize the organic compound into carbon dioxide. The parameters has been studied are the standard oxidation potential of mediator, acid concentration and temperature. The results obtained at potential of 6 Volt, with nitric acid 4 M and temperature of 25°C give result 23.86% where Co (II) is converted to Co(III) within 2 hours. The addition of silver nitrate can increase the concentration of Co(III). At the optimum conditions, the mediator ion Co(III) can destructed to 66.44% of phenol compound oxidized into carbon dioxide.

  3. 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.

  4. Surface properties of nanostructured NiO undergoing electrochemical oxidation in 3-methoxy-propionitrile

    NASA Astrophysics Data System (ADS)

    Bonomo, Matteo; Marrani, Andrea Giacomo; Novelli, Vittoria; Awais, Muhammad; Dowling, Denis P.; Vos, Johannes G.; Dini, Danilo

    2017-05-01

    Nanostructured nickel oxide (NiO) was deposited in the configuration of thin film (thickness, l = 2-6 μm) onto fluorine-doped tin oxide (FTO) substrates via plasma-assisted rapid discharge sintering (RDS). Electrochemical cycling of RDS NiO in 3-methoxy-propionitrile (3-MPN) revealed two characteristic peaks of NiO oxidation which were associated to the surface-confined redox processes Ni(II) → Ni(III) and Ni(III) → Ni(IV). Grazing angle X-ray photoelectron spectroscopy (XPS) was conducted ex-situ on NiO electrodes in both pristine and oxidized states. Oxidized NiO samples for XPS experiments were obtained in the potentiostatic mode through the polarization of NiO at its two characteristic potentials of oxidation. The XPS analysis allowed to ascertain the electronic structure of the nanoporous NiO framework, and verify the adsorption of perchlorate and chloride anions onto NiO surface due to the compensation of the charge stored in oxidized NiO. XPS also revealed that the spectrum within the region characteristic of Ni 2p ionization does not vary considerably with the state of charge of the nickel centres. This finding is in evident contrast to what has been observed for the same system when it undergoes electrochemical oxidation in aqueous electrolyte.

  5. Morphological and electrochemical properties of crystalline praseodymium oxide nanorods.

    PubMed

    Shamshi Hassan, M; Shaheer Akhtar, M; Shim, Kyung-Bo; Yang, O-Bong

    2010-02-05

    Highly crystalline Pr6O11 nanorods were prepared by a simple precipitation method of triethylamine complex at 500°C. Synthesized Pr6O11 nanorods were uniformly grown with the diameter of 12-15 nm and the length of 100-150 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 850°C. 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.

  6. 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.

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

    PubMed Central

    2010-01-01

    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 μA mM−1 cm−2), low detection limit (0.2 μM) and high selectivity with the apparent Michaelis–Menten constant estimated to be as small as 33.9 μM. 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. PMID:20596358

  8. 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 μA mM-1 cm-2), low detection limit (0.2 μM) and high selectivity with the apparent Michaelis-Menten constant estimated to be as small as 33.9 μM. 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.

  9. 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.

  10. Immobilization of methylviologen between well-ordered multilayers of manganese oxide during their electrochemical assembly.

    PubMed

    Nakayama, Masaharu; Hoyashita, Ryo; Komatsu, Hiroyuki; Muneyama, Etsuhiro; Shoda, Kaoru; Kunishige, Atsuhiro

    2007-03-13

    Methylviologen dications (MV2+) were immobilized between layers of manganese oxide during their electrochemical assembly by an anodic route in a homogeneous aqueous Mn2+ solution. This approach yielded a well-ordered multilayer film on a platinum substrate as a result of dense packing of planar MV2+ molecules to stabilize the layered framework. A grazing angle in-plane X-ray diffraction study revealed that the manganese oxide sheets and the molecular planes of inserted MV2+ ions are oriented parallel to the electrode surface. Cyclic voltammetry of the product film indicated an electron transfer from the underlying Pt substrate to inserted methylviologen ions through the manganese oxide sheets.

  11. 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.

  12. Enhancing electrochemical detection on graphene oxide-CNT nanostructured electrodes using magneto-nanobioprobes

    PubMed Central

    Sharma, Priyanka; Bhalla, Vijayender; Dravid, Vinayak; Shekhawat, Gajendera; Jinsong-Wu, J W; Prasad, E. Senthil; Suri, C. Raman

    2012-01-01

    Graphene and related materials have come to the forefront of research in electrochemical sensors during recent years due to the promising properties of these nanomaterials. Further applications of these nanomaterials have been hampered by insufficient sensitivity offered by these nanohybrids for the type of molecules requiring lower detection ranges. Here, we report a signal amplification strategy based on magneto-electrochemical immunoassay which combines the advantages of carbon nanotube and reduced graphene oxide together with electrochemical bursting of magnetic nanoparticles into a large number of metal ions. Sensitive detection was achieved by precisely designing the nanohybrid and correlating the available metal ions with analyte concentration. We confirmed the ultrahigh sensitivity of this method for a new generation herbicide diuron and its analogues up to sub-picomolar concentration in standard water samples. The novel immune-detection platform showed the excellent potential applicability in rapid and sensitive screening of environmental pollutants or toxins in samples. PMID:23166860

  13. [Degradation of aniline by a dual-electrode electrochemical oxidation process].

    PubMed

    Cen, Shi-Hong; Song, Xiao-Yan; Chu, Yan-Yang

    2011-08-01

    The efficiency and the mechanism of aniline degradation by an electrochemical oxidation process using a Ti/SnO2-Sb2O5 electrode as the anode and a graphite electrode as the cathode, were studied in two aqueous electrolytes with/without Fe2+. The results showed that the reasonable anodic potential was about 2.0 V +/- 0.1 V for Ti/SnO2-Sb2O5 electrode to oxidize organic compounds, while the optimum cathodic potential was -0.65 V for graphite electrode to reduce O2 generating H2O2. The oxidation degradation of aniline could not take place only by the single action of H2O2. Anodic oxidation was accounted for the degradation of aniline in the absence of Fe2+, while in the presence of Fe2+ both electro-Fenton oxidation and anodic oxidation (dual-electrode electrochemical oxidation) could degradate aniline effectively, and in this case the former was the main mechanism. Under the conditions of -0.65 V cathodic potential, pH 3.0 and 0.5 mmol x L(-1) Fe2+, the removal rate of COD was 77.5% after 10 h treatment and a current efficiency of 97.8% for COD removal could be obtained. This work indicates that the dual-electrode electrochemical oxidation is feasible for the degradation of organic compounds with a high current efficiency by using Ti/SnO2-Sb2O5 as anode as well as the reasonable anodic and cathodic potentials.

  14. 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. Copyright © 2014 Elsevier Ltd. All rights reserved.

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

    PubMed

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

    2015-10-15

    A novel printed graphene electrode modified with electrochemically reduced graphene oxide was developed for the detection of a specific oligonucleotide sequence. The graphene oxide was immobilized onto the surface of a graphene electrode via π-π bonds and electrochemical reduction of graphene oxide was achieved by cyclic voltammetry. A much higher redox current was observed from the reduced graphene oxide-graphene double-layer electrode, a 42% and 36.7% increase, respectively, in comparison with that of a bare printed graphene or reduced graphene oxide electrode. The good electron transfer activity is attributed to a combination of the large number of electroactive sites in reduced graphene oxide and the high conductivity nature of graphene. The probe ssDNA was further immobilized onto the surface of the reduced graphene oxide-graphene double-layer electrode via π-π bonds and then hybridized with its target cDNA. The change of peak current due to the hybridized dsDNA could be used for quantitative sensing of DNA concentration. It has been demonstrated that a linear range from 10(-7)M to 10(-12)M is achievable for the detection of human immunodeficiency virus 1 gene with a detection limit of 1.58 × 10(-13)M as determined by three times standard deviation of zero DNA concentration. Copyright © 2015 Elsevier B.V. All rights reserved.

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

    NASA Astrophysics Data System (ADS)

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

    2015-01-01

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

  17. 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.

  18. Destruction of commercial pesticides by cerium redox couple mediated electrochemical oxidation process in continuous feed mode.

    PubMed

    Balaji, Subramanian; Chung, Sang Joon; Ryu, Jae-Yong; Moon, Il Shik

    2009-12-30

    Mediated electrochemical oxidation was carried out for the destruction of commercial pesticide formulations using cerium(IV) in nitric acid as the mediator electrolyte solution in a bench scale set up. The mediator oxidant was regenerated in situ using an electrochemical cell. The real application of this sustainable process for toxic organic pollutant destruction lies in its ability for long term continuous operation with continuous organic feeding and oxidant regeneration with feed water removal. In this report we present the results of fully integrated MEO system. The task of operating the continuous feed MEO system for a long time was made possible by continuously removing the feed water using an evaporator set up. The rate of Ce(IV) regeneration in the electrochemical cell and the consumption for the pesticide destruction was matched based on carbon content of the pesticides. It was found that under the optimized experimental conditions for Ce(III) oxidation, organic addition and water removal destruction efficiency of ca. 99% was obtained for all pesticides studied. It was observed that the Ce(IV) concentration was maintained nearly the same throughout the experiment. The stable operation for 6h proved that the process can be used for real applications and for possible scale up for the destruction of larger volumes of toxic organic wastes.

  19. 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.

  20. [Examination of the oral cavities of patients with cancer: clinical evaluation and indirect measurement of the nitric oxide level].

    PubMed

    de Carvalho, Emilia Campos; Cárnio, Evelin Capellari; Khouri, Vivian Youssef; Guilherme, Caroline; dos Santos, Claudia Benedita; Pace, Mariangela Aparecida

    2013-02-01

    This observational study aimed to verify the association between the clinical state of the oral cavity (based on the Index of Decayed, Missing, and Filled Teeth and the Simplified Oral Hygiene Index) and the indirectly determined nitric oxide level in patients with oncologic and hematologic diseases. This study included 20 hospitalized patients who were in the evaluation phase prior to starting chemotherapy and who had been diagnosed with leukemia (35%), lymphoma (50%) or myeloma (15%). Fifty percent of these patients had normal oral health (no injury or trauma), and most had satisfactory (35%) or typical (35%) hygiene, but 30% had poor or very poor hygiene. The indirectly measured levels of nitric oxide ranged from 13.34 to 257. The nitric oxide level was not associated with other parameters, and there was great variability in its level. Further studies are necessary given the potential of using this indicator in the early detection of oral diseases.

  1. Alzheimer's disease amyloid beta peptides in vitro electrochemical oxidation.

    PubMed

    Enache, Teodor Adrian; Oliveira-Brett, Ana Maria

    2017-04-01

    The oxidative behaviour of the human amyloid beta (Aβ1-40 and Aβ1-42) peptides and a group of similar peptides: control inverse (Aβ40-1 and Aβ42-1), mutants (Aβ1-40Phe(10) and Aβ1-40Nle(35)), rat Aβ1-40Rat, and fragments (Aβ1-28, Aβ1-16, Aβ10-20, Aβ12-28, and Aβ17-42), in solution or adsorbed, at a glassy carbon electrode, by cyclic and differential pulse voltammetry, were investigated and compared. Structurally the Aβ1-40 and Aβ1-42 sequences contain five electroactive amino acid residues, one tyrosine (Tyr(10)), three histidines (His(6), His(13) and His(14)) and one methionine (Met(35)). The Aβ peptide 3D structure influenced the exposure of the redox residues to the electrode surface and their oxidation peak currents. Depending on the amino acid sequence length and content, the Aβ peptides gave one or two oxidation peaks. The first electron transfer reaction corresponded to the tyrosine amino acid residue oxidation, and the second to both histidines and methionine amino acid residues. The highest contribution to the second oxidation peak current was from His(13), followed by His(14) and His(6) residues, and Met(35) residue had the lowest contribution. The Aβ peptides electron transfer depended on peptide hydrophobicity and 3D structure, the redox residues position in the sequence, the redox residues close to N-termini giving the highest oxidation peak currents.

  2. Chemical and electrochemical oxidation of small organic molecules

    NASA Astrophysics Data System (ADS)

    Smart, Marshall C.

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

  3. Zn2+-Doped Polyaniline/Graphene Oxide as Electrode Material for Electrochemical Supercapacitors

    NASA Astrophysics Data System (ADS)

    Xu, Hui; Tang, Jing; Chen, Yong; Liu, Jian; Pu, Jinjuan; Li, Qi

    2017-10-01

    Electrodes based on Zn2+-doped polyaniline/graphene oxide (Zn2+/PANI/GO) were synthesized on stainless steel mesh substrates in H2SO4 solution via electrochemical codeposition. Different concentrations of graphene oxide (GO) were incorporated into the films to improve the electrochemical performance of the electrodes. Electrochemical properties of the films were tested by cyclic voltammetry, galvanostatic charge-discharge tests, and electrochemical impedance spectroscopy, in a three-electrode system. The maximum specific capacitance of the Zn2+/PANI/GO film with a GO concentration of 15 mg L-1 was found to be 1266 F g-1 at a scan rate of 3 mV s-1. This value was higher than that of a Zn2+ doped polyaniline (Zn2+/PANI) film (814 F g-1). The Zn2+/PANI/GO film also showed good cycling stability, retaining over 86% of its initial capacitance after 1000 cycles. These results indicate that the Zn2+/PANI/GO composites can be applied as high performance supercapacitor electrodes.

  4. Electrochemical Alcohol Oxidation Mediated by TEMPO‐like Nitroxyl Radicals

    PubMed Central

    Ciriminna, Rosaria; Ghahremani, Mina

    2017-01-01

    Abstract The electrocatalytic oxidation of alcohols mediated by TEMPO‐like nitroxyl radicals is an economically and industrially viable method that will shortly find commercial application in the synthesis of valued substances including active pharmaceutical ingredients (APIs), valued natural product derivatives, fine chemicals, and valued nanomaterials. PMID:28168142

  5. Electrochemically deposited gallium oxide nanostructures on silicon substrates.

    PubMed

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

    2014-03-17

    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.

  6. Electrochemically deposited gallium oxide nanostructures on silicon substrates

    NASA Astrophysics Data System (ADS)

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

    2014-03-01

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

  7. Electrochemically deposited gallium oxide nanostructures on silicon substrates

    PubMed Central

    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

  8. Facile synthesis of cuprous oxide nanowires decorated graphene oxide nanosheets nanocomposites and its application in label-free electrochemical immunosensor.

    PubMed

    Wang, Huan; Zhang, Yong; Wang, Yulan; Ma, Hongmin; Du, Bin; Wei, Qin

    2017-01-15

    In this work, the assembly between one-dimensional (1D) nanomaterials and two-dimensional (2D) nanomaterials was achieved by a simple method. Cuprous oxide nanowires decorated graphene oxide nanosheets (Cu2O@GO) nanocomposites were synthesized for the first time by a simple electrostatic self-assembly process. The nanostructure was well confirmed by scanning electron microscope (SEM) and transmission electron microscope (TEM) images. Taking advantages of good electrocatalytic activity and high specific surface area of Cu2O@GO nanocomposites, a label-free electrochemical immunosensor was developed by employing Cu2O@GO as signal amplification platform for the quantitative detection of alpha fetoprotein (AFP). In addition, toluidine blue (TB) was used as the electron transfer mediator to provide the electrochemical signal, which was adsorbed on graphene oxide nanosheets (GO NSs) by electrostatic attraction. The detection mechanism was based on the monitoring of the electrochemical current response change of TB by the square wave voltammetry (SWV) when immunoreaction occurred on the surface of electrode. Under optimal conditions, the proposed immunosensor displayed a high sensitivity and a low detection limit. This designed method may provide an effective method in the clinical diagnosis of AFP and other tumor markers.

  9. The sensor based on oxidized multi-walled carbon nanotubes prepared by electrochemical method and its application

    NASA Astrophysics Data System (ADS)

    Song, Y. Z.; Yang, L.; Jiang, Q. Y.

    2015-07-01

    The sensor based on oxidized multi-walled carbon nanotubes was prepared by electrochemical method. The behavior of norepinephrine tartrate at the modified electrode was studied. It was demonstrated that modified sensor is a good electrocatalyst for norepinephrine tartrate.

  10. 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.

  11. Electrochemical degradation of 4-chlorophenol at nickel-antimony doped tin oxide electrode.

    PubMed

    Wang, Y H; Chan, K Y; Li, X Y; So, S K

    2006-11-01

    The effectiveness of a novel nickel-antimony doped tin oxide electrode for electrochemical degradation of organic pollutants was investigated using 4-chlorophenol (4-CP) as a model toxic organic. The experimental results demonstrate that the optimal Ni content was at Ni:Sn=1:500 in atomic ratio in the precursor coating solution, whereas the Sb:Sn ratio was set at 8:500. Using the electrode prepared with the optimal Ni doping ratio for 4-CP degradation, the charge-based efficiencies were up to 89 microg C(-1) for 4-CP destruction and 15 microg C(-1) for TOC removal, which were considerably higher than the efficiencies observed for other electrodes. It is suggested that the enhancement of the electrode for electrochemical oxidation of organics could be attributed to the production of hydroxyl radicals in anodic water electrolysis.

  12. 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.

  13. 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.

  14. 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

  15. Electrochemical properties of poly(vinyl alcohol) and graphene oxide composite for supercapacitor applications

    NASA Astrophysics Data System (ADS)

    Theophile, Niyitanga; Jeong, Hae Kyung

    2017-02-01

    Poly(vinyl alcohol), PVA, polymer was successfully combined with graphene oxide (GO) and thermally reduced graphene oxide (RGO), respectively, to make composites and characterized for supercapacitor applications. PVA-RGO composite shows excellent electrochemical properties compared to PVA-GO composite. The capacitance of 190 Fg-1 is obtained from PVA-RGO composite which is larger than that (13 Fg-1) of PVA-GO composite. Electrochemical impedance of PVA-RGO is more than ten times smaller than that of PVA-GO at 20 kHz, demonstrating that PVA-RGO composite has a great advantage for supercapacitor applications compared to PVA, GO, RGO, and PVA-GO composite.

  16. Imaging of a thin oxide film formation from the combination of surface reflectivity and electrochemical methods.

    PubMed

    Chakri, Sara; Patel, Anisha N; Frateur, Isabelle; Kanoufi, Frédéric; Sutter, Eliane Marie Madeleine; Tran, T T Mai; Tribollet, Bernard; Vivier, Vincent

    2017-04-13

    Electrochemical methods (cyclic voltammetry (CV), potential steps, and electrochemical impedance spectroscopy), were successfully combined with in situ reflectometry measurements for a detailed analysis of the passive layer evolution as a function of the electrode potential. Interestingly, both EIS and surface reflectivity allowed a film thickness in the nanometer range to be readily determined. In addition, transient analyses of the reflectivity simultaneously recorded with CVs show the formation of both Fe2O3 and Fe3O4 oxides. The image analysis showed that the steel surface reactivity is heterogeneous and presents micrometric islands coated with thicker oxide layer than the surrounding surface. The in situ combination of these techniques thus offers a powerful analytical description of the interface on local scale and its transient response to a perturbation.

  17. A molecularly imprinted polymer with incorporated graphene oxide for electrochemical determination of quercetin.

    PubMed

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

    2013-04-25

    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.

  18. Electrochemical sensing of glucose by reduced graphene oxide-zinc ferrospinels

    NASA Astrophysics Data System (ADS)

    Shahnavaz, Zohreh; Woi, Pei Meng; Alias, Yatimah

    2016-08-01

    We have developed ZnFe2O4 magnetic nanoparticles/reduced graphene oxide nanosheets modified glassy carbon (ZnFe2O4/rGO/GCE) electrode as a novel system for the electrochemical glucose sensing. Via a facile in situ hydrothermal route, the reduction of GO and the formation of ZnFe2O4 nanoparticles occurred simultaneously. This enables the ZnFe2O4 nanoparticles dispersed on the reduced graphene sheet. Characterization of nanocomposite by X-ray diffraction (XRD) and transmission electron microscopy (TEM) clearly demonstrate the successful attachment of ZnFe2O4 nanoparticles to graphene sheets. Electrochemical studies revealed that the ZnFe2O4/rGO/GCE possess excellent electrocatalytic activities toward the oxidation of glucose and the performance of sensor is enhanced by integration of graphene nanosheets with ZnFe2O4 nanoparticles.

  19. 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

  20. Electrochemical reaction and oxidation of lecithin under pulsed electric fields (PEF) processing.

    PubMed

    Zhao, Wei; Yang, Ruijin; Liang, Qi; Zhang, Wenbin; Hua, Xiao; Tang, Yali

    2012-12-12

    Pulsed electric fields (PEF) processing is a promising nonthermal food preservation technology, which is ongoing from laboratory and pilot plant scale levels to the industrial level. Currently, greater attention has been paid to side effects occurring during PEF treatment and the influences on food qualities and food components. The present study investigated the electrochemical reaction and oxidation of lecithin under PEF processing. Results showed that electrochemical reaction of NaCl solutions at different pH values occurred during PEF processing. Active chlorine, reactive oxygen, and free radicals were detected, which were related to the PEF parameters and pH values of the solution. Lecithin extracted from yolk was further selected to investigate the oxidation of food lipids under PEF processing, confirming the occurrence of oxidation of lecithin under PEF treatment. The oxidative agents induced by PEF might be responsible for the oxidation of extracted yolk lecithin. Moreover, this study found that vitamin C as a natural antioxidant could effectively quench free radicals and inhibit the oxidation of lipid in NaCl and lecithin solutions as model systems under PEF processing, representing a way to minimize the impact of PEF treatment on food qualities.

  1. 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).

  2. The electrochemical oxidation of chalcopyrite in ammoniacal solutions

    NASA Astrophysics Data System (ADS)

    Warren, G. W.; Wadsworth, M. E.

    1984-06-01

    The anodic dissolution of chalcopyrite in ammoniacal solutions was investigated using electrochemical methods. At low overvoltages, the formation of a copper deficient sulfide layer, Cu1-xFeS2 through a charge transfer reaction is proposed based upon the dependence of the rest or open circuit potential on solution composition and the presence of a Tafel region of appropriate slope. In addition, a current peak that occurs at 10-4 A/cm2 is a function of the square root of the voltage scanning speed and is explained in terms of a charge transfer reaction. At larger overvoltages, constant potential experiments and mass balances performed at various anodic potentials indicate that the dissolution is consistent with the overall reaction, CuFeS2 + 4NH3 + 9OH- = Cu(NH3){4/+2} + Fe(OH)3 + S2O{3/=} + 3H2O + 9e -, although some copper may be released to solution in the cuprous state and some ferrous iron has been identified in the product film. Current vs time data taken during constant potential experiments were found to obey a linear rate relationship. This was interpreted in terms of the formation of a layer of constant thickness which is corroded at the outer interface at the same rate it is formed at the inner interface.. The model proposed is typical of the corrosion of some metals. An examination of the polarization curves shows the dissolution reaction to be first order with respect to [OH-]. The lack of dependence on [Cu2+] indicates that the catalytic effect of cupric ion during oxygen pressure leaching is related only to the cathodic reduction of O2 in agreement with the results of previous investigations.

  3. 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.

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

    DOEpatents

    Balazs, G. Bryan; Lewis, Patricia R.

    1999-01-01

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

  5. Electrochemically oxidized electronic and ionic conducting nanostructured block copolymers for lithium battery electrodes.

    PubMed

    Patel, Shrayesh N; Javier, Anna E; Balsara, Nitash P

    2013-07-23

    Block copolymers that can simultaneously conduct electronic and ionic charges on the nanometer length scale can serve as innovative conductive binder material for solid-state battery electrodes. The purpose of this work is to study the electronic charge transport of poly(3-hexylthiophene)-b-poly(ethylene oxide) (P3HT-PEO) copolymers electrochemically oxidized with lithium bis(trifluoromethanesulfonyl) imide (LiTFSI) salt in the context of a lithium battery charge/discharge cycle. We use a solid-state three-terminal electrochemical cell that enables simultaneous conductivity measurements and control over electrochemical doping of P3HT. At low oxidation levels (ratio of moles of electrons removed to moles of 3-hexylthiophene moieties in the electrode), the electronic conductivity (σe,ox) increases from 10(-7) S/cm to 10(-4) S/cm. At high oxidation levels, σe,ox approaches 10(-2) S/cm. When P3HT-PEO is used as a conductive binder in a positive electrode with LiFePO4 active material, P3HT is electrochemically active within the voltage window of a charge/discharge cycle. The electronic conductivity of the P3HT-PEO binder is in the 10(-4) to 10(-2) S/cm range over most of the potential window of the charge/discharge cycle. This allows for efficient electronic conduction, and observed charge/discharge capacities approach the theoretical limit of LiFePO4. However, at the end of the discharge cycle, the electronic conductivity decreases sharply to 10(-7) S/cm, which means the "conductive" binder is now electronically insulating. The ability of our conductive binder to switch between electronically conducting and insulating states in the positive electrode provides an unprecedented route for automatic overdischarge protection in rechargeable batteries.

  6. Electrochemical oxidation of xanthosine. Isolation and structure elucidation of a new dimeric xanthine nucleoside

    SciTech Connect

    Xinhua Ji; Subramanian, P.; van der Helm, D.; Dryhurst, G. )

    1990-02-16

    Electrochemical oxidation of xanthosine (2) at pH 2 at a pyrolytic graphite electrode generates an electrophilic radical cation intermediate. Nucleophilic attack by 2 on this radical results, ultimately, in formation of 3-(8-xanthosyl)xanthosine (7). Hydrolytic cleavage of one ribose residue from 7 in acidic solution leads to 3-(8-xanthosyl)xanthine (8). The structure of 8, a new dimeric xanthine nucleoside, has been established using spectral and X-ray diffraction methods.

  7. 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.

  8. Membrane electro-oxidizer: A new hybrid membrane system with electrochemical oxidation for enhanced organics and fouling control.

    PubMed

    Mameda, Naresh; Park, Hyung-June; Choo, Kwang-Ho

    2017-09-05

    The synergistic combination of membrane filtration with advanced oxidation is of particular interest for next-generation wastewater treatment technologies. A membrane electro-oxidizer (MEO) hybridizing a submerged microfilter and an electrochemical cell was developed and investigated for tertiary treatment of secondary industrial (textile) wastewater effluent. Laboratory- and pilot-scale MEO systems were designed and evaluated for treatment efficiency and membrane fouling control. The MEO achieved substantial removal of color (50-90%), turbidity (>90%), and bacteria (>4 log) as well as chemical oxygen demand (13-31%) and 1,4-dioxane (∼25-53%). Fluorescence-based parallel factor analysis disclosed the degradation of humic-like organics with fluorophores. Size exclusion chromatograms with organic carbon detection confirmed the removal of specific organic molecules with ∼100 Da. While investigating the effects of oxidant quenching agents, reactive chlorine species and hydrogen peroxide were found to be most responsible for the anodic oxidation of secondary effluent organics. The efficacy of membrane fouling mitigation by the MEO was greater when higher electric current densities were applied, but was not dependent on the number of electrochemical cells installed. The MEO is a promising technology for enhanced organics removal with simultaneous fouling control due to its multifunctional active oxidants. Copyright © 2017 Elsevier Ltd. All rights reserved.

  9. 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.

  10. 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.

  11. 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

    2016-01-01

    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.

  12. 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.

  13. A Zinc Oxide Nanoflower-Based Electrochemical Sensor for Trace Detection of Sunset Yellow

    PubMed Central

    Ya, Yu; Jiang, Cuiwen; Li, Tao; Liao, Jie; Fan, Yegeng; Wei, Yuning; Yan, Feiyan; Xie, Liping

    2017-01-01

    Zinc oxide nanoflower (ZnONF) was synthesized by a simple process and was used to construct a highly sensitive electrochemical sensor for the detection of sunset yellow (SY). Due to the large surface area and high accumulation efficiency of ZnONF, the ZnONF-modified carbon paste electrode (ZnONF/CPE) showed a strong enhancement effect on the electrochemical oxidation of SY. The electrochemical behaviors of SY were investigated using voltammetry with the ZnONF-based sensor. The optimized parameters included the amount of ZnONF, the accumulation time, and the pH value. Under optimal conditions, the oxidation peak current was linearly proportional to SY concentration in the range of 0.50–10 μg/L and 10–70 μg/L, while the detection limit was 0.10 μg/L (signal-to-noise ratio = 3). The proposed method was used to determine the amount of SY in soft drinks with recoveries of 97.5%–103%, and the results were in good agreement with the results obtained by high-performance liquid chromatography. PMID:28282900

  14. Electrochemical regeneration of a reduced graphene oxide/magnetite composite adsorbent loaded with methylene blue.

    PubMed

    Sharif, Farbod; Gagnon, Luke R; Mulmi, Suresh; Roberts, Edward P L

    2017-05-01

    In this work, two different reduced graphene oxide/iron oxide (rGO-IO) nanocomposites with different iron oxide loadings were fabricated using a one-step solvothermal method. The structure, properties and applications of the synthesized nanocomposites were evaluated with Raman spectroscopy, attenuated total reflectance Fourier transform infrared spectroscopy, thermogravimetric analysis, X-ray diffraction, electron microscopy, and energy-dispersive X-ray spectroscopy. The iron oxide is in the form of magnetite (Fe3O4), so that the resultant adsorbent can readily be separated from the treated water using a magnetic field. The ability of the nanocomposites to remove methylene blue (MB) from water by adsorption was investigated. The highest adsorptive capacity observed was 39 mg g(-1), for the composite containing 60 wt% iron oxide. The adsorptive capacity of the rGO-IO decreased to 26 mg g(-1) when the mass fraction of iron oxide was increased to 75 wt%. Electrochemical regeneration of MB loaded rGO-IO was also investigated. The electrochemical regeneration was found to be rapid and with low electrical energy consumption relative to conventional adsorbents, due to the high electrical conductivity and nonporous surface of the rGO. A regeneration efficiency of 100% was obtained after 30 min of electrochemical treatment using a 2 mm thick bed of rGO-IO loaded with 39 mg g(-1) MB, using a current density of 10 mA cm(-2). Multiple adsorption-electrochemical regeneration cycles demonstrated that the surface of the rGO was modified leading to increase in the adsorptive capacity to around 80 mg g(-1) after the second regeneration cycle. The morphology of the rGO was observed to change significantly after electrochemical regeneration, suggesting that the rGO based adsorbent materials could only be used for a few cycles. Copyright © 2017 Elsevier Ltd. All rights reserved.

  15. Hydrogeological Controls on Regional-Scale Indirect Nitrous Oxide Emission Factors for Rivers.

    PubMed

    Cooper, Richard J; Wexler, Sarah K; Adams, Christopher A; Hiscock, Kevin M

    2017-09-19

    Indirect nitrous oxide (N2O) emissions from rivers are currently derived using poorly constrained default IPCC emission factors (EF5r) which yield unreliable flux estimates. Here, we demonstrate how hydrogeological conditions can be used to develop more refined regional-scale EF5r estimates required for compiling accurate national greenhouse gas inventories. Focusing on three UK river catchments with contrasting bedrock and superficial geologies, N2O and nitrate (NO3(-)) concentrations were analyzed in 651 river water samples collected from 2011 to 2013. Unconfined Cretaceous Chalk bedrock regions yielded the highest median N2O-N concentration (3.0 μg L(-1)), EF5r (0.00036), and N2O-N flux (10.8 kg ha(-1) a(-1)). Conversely, regions of bedrock confined by glacial deposits yielded significantly lower median N2O-N concentration (0.8 μg L(-1)), EF5r (0.00016), and N2O-N flux (2.6 kg ha(-1) a(-1)), regardless of bedrock type. Bedrock permeability is an important control in regions where groundwater is unconfined, with a high N2O yield from high permeability chalk contrasting with significantly lower median N2O-N concentration (0.7 μg L(-1)), EF5r (0.00020), and N2O-N flux (2.0 kg ha(-1) a(-1)) on lower permeability unconfined Jurassic mudstone. The evidence presented here demonstrates EF5r can be differentiated by hydrogeological conditions and thus provide a valuable proxy for generating improved regional-scale N2O emission estimates.

  16. Electrodeposition and electrochemical reduction of epitaxial metal oxide thin films and superlattices

    NASA Astrophysics Data System (ADS)

    He, Zhen

    The focus of this dissertation is the electrodeposition and electrochemical reduction of epitaxial metal oxide thin films and superlattices. The electrochemical reduction of metal oxides to metals has been studied for decades as an alternative to pyrometallurgical processes for the metallurgy industry. However, the previous work was conducted on bulk polycrystalline metal oxides. Paper I in this dissertation shows that epitaxial face-centered cubic magnetite (Fe3O4 ) thin films can be electrochemically reduced to epitaxial body-centered cubic iron (Fe) thin films in aqueous solution on single-crystalline Au substrates at room temperature. This technique opens new possibilities to produce special epitaxial metal/metal oxide heterojunctions and a wide range of epitaxial metallic alloy films from the corresponding mixed metal oxides. Electrodeposition, like biomineralization, is a soft solution processing method which can produce functional materials with special properties onto conducting or semiconducting solid surfaces. Paper II in this dissertation presents the electrodeposition of cobalt-substituted magnetite (CoxFe3-xO4, 0 of cobalt-substituted magnetite (CoxFe3-xO4, 0oxide (Co3O4) thin films on stainless steel and Au single-crystalline substrates. The crystalline Co3O4 thin films exhibit high catalytic activity towards the oxygen evolution reaction in an alkaline solution. A possible application of the electrodeposited Co 3O4 is the fabrication of highly active and low-cost photoanodes for photoelectrochemical water-splitting cells.

  17. Electrochemical oxidation and protein adduct formation of aniline: a liquid chromatography/mass spectrometry study.

    PubMed

    Melles, Daniel; Vielhaber, Torsten; Baumann, Anne; Zazzeroni, Raniero; Karst, Uwe

    2012-04-01

    Historically, skin sensitization tests are typically based on in vivo animal tests. However, for substances used in cosmetic products, these tests have to be replaced according to the European Commission regulation no. 1223/2009. Modification of skin proteins by electrophilic chemicals is a key process associated with the induction of skin sensitization. The present study investigates the capabilities of a purely instrumental setup to determine the potential of commonly used non-electrophilic chemicals to cause skin sensitization by the generation of electrophilic species from the parent compound. In this work, the electrophiles were generated by the electrochemical oxidation of aniline, a basic industrial chemical which may also be released from azo dyes in cosmetics. The compound is a known sensitizer and was oxidized in an electrochemical thin-layer cell which was coupled online to electrospray ionization-mass spectrometry. The electrochemical oxidation was performed on a boron-doped diamond working electrode, which is able to generate hydroxyl radicals in aqueous solutions at high potentials. Without any pretreatment, the oxidation products were identified by electrospray ionization/time-of-flight mass spectrometry (ESI-ToF-MS) using their exact masses. A mass voltammogram was generated by plotting the obtained mass spectra against the applied potential. Oligomerization states with up to six monomeric units in different redox states of aniline were observed using this setup. This approach was extended to generate adducts between the oxidation products of aniline and the tripeptide glutathione. Two adducts were identified with this trapping experiment. Protein modification was carried out subsequently: Aniline was oxidized at a constant potential and was allowed to react with β-lactoglobulin A (β-LGA) or human serum albumin (HSA), respectively. The generated adducts were analyzed by liquid chromatography coupled to ESI-ToF-MS. For both β-LGA and HSA, aniline

  18. Electrochemical synthesis of tetragonal oxide tungsten bronze nanofilms on platinum

    NASA Astrophysics Data System (ADS)

    Kosov, A. V.; Semerikova, O. L.; Vakarin, S. V.; Pankratov, A. A.; Plaksin, S. V.; Korzun, I. V.; Akashev, L. A.; Zaykov, Yu. P.

    2017-02-01

    We are the first to synthesize nanofilms of tetragonal oxide tungsten bronze (OTB) on a Pt(110) substrate by the electrolysis of the K2WO4-Na2WO4-WO3 melt at 700 and 750°C. The composition and the morphology of OTB are shown to depend on the deposition potential and the WO3 concentration in the melt. The laws of formation of tetragonal OTB films are discussed. The synthesized OTB samples are found to have a good thermal stability in the temperature range 20-800°C.

  19. Measurement of oxidized and methylated DNA bases by HPLC with electrochemical detection.

    PubMed

    Kaur, H; Halliwell, B

    1996-08-15

    Oxidative DNA damage is thought to be an important contributor to cancer development and to be affected by dietary constituents, so its accurate measurement is important. DNA methylation is recognized as an important mechanism affecting gene expression. In the present paper we describe an HPLC-with-electrochemical-detection procedure that allows rapid and sensitive measurement of four oxidized (2,6-diamino-4-hydroxy-5-formamidopyrimidine, 5-hydroxyuracil, 8-hydroxyguanine, 8-hydroxyadenine) and three methylated (7-methylguanine, 1-methylguanine, O6-methylguanine) bases in acid hydrolysates of DNA. Guanine was also detected, but was clearly separated from the other bases.

  20. 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.

  1. Electrochemically-Controlled Compositional Oscillations of Oxide Surfaces

    SciTech Connect

    Mutoro, Eva; Crumlin, Ethan; Pöpke, Hendrik; Luerssen, Bjoern; Amati, Matteo; Abyaneh, Majid; Biegalski, Michael D; Christen, Hans M; Gregoratti, Luca; Janek, Jürgen; Shao-Horn, Yang

    2012-01-01

    Perovskite oxides can exhibit a wide range of interesting characteristics such as being catalytically active and electronically and/or ionically conducting, and thus they have been used in a number of solid-state devices such as solid oxide fuel cells and sensors. As the surface compositions of perovskites can greatly influence the catalytic properties, knowing and controlling their surface chemistries is crucial to enhance device performance. In this study, we demonstrate that the surface strontium (Sr) and cobalt (Co) concentrations of perovskite-based thin films can be controlled reversibly at elevated temperatures by applying small electrical potential biases. The surface chemistry changes of La0.8Sr0.2CoO3 (LSC113), LaSrCoO4 (LSC214), and LSC214-decorated LSC113 films (LSC113/214) were investigated in situ by utilizing synchrotron-based X-ray photoelectron spectroscopy (XPS), where the largest changes of surface Sr was found for the LSC113/214 surface. These findings offer the potential of reversibly controlling the surface functionality of perovskites.

  2. Electrochemical properties of iodine-containing lithium manganese oxide spinel

    NASA Astrophysics Data System (ADS)

    Han, Chi-Hwan; Hong, Young-Sik; Hong, Hyun-Sil; Kim, Keon

    Iodine-containing, cation-deficient, lithium manganese oxides (ICCD-LMO) are prepared by reaction of MnO 2 with LiI. The MnO 2 is completely transformed into spinel-structured compounds with a nominal composition of Li 1- δMn 2-2 δO 4I x. A sample prepared at 800 °C, viz. Li 0.99Mn 1.98O 4I 0.02, exhibits an initial discharge capacity of 113 mA h g -1 with good cycleability and rate capability in the 4-V region. Iodine-containing, lithium-rich lithium manganese oxides (ICLR-LMO) are also prepared by reaction of LiMn 2O 4 with LiI, which results in a nominal composition of Li 1+ xMn 2- xO 4I x. Li 1.01Mn 1.99O 4I 0.02 shows a discharge capacity of 124 mA h g -1 on the first cycle and 119 mA h g -1 a on the 20th cycle. Both results indicate that a small amount of iodine species helps to maintain cycle performance.

  3. A dual electrochemical sensor for nitrite and nitric oxide.

    PubMed

    Zen, J M; Kumar, A S; Wang, H F

    2000-12-01

    Nafion/lead-ruthenate pyrochlore chemically modified electrode (NPyCME) showed a remarkable dual sensing activity toward NO2- oxidation and NO reduction as demonstrated by cyclic voltammetry (CV), ac-impedance spectroscopy and flow injection analysis (FIA). The mechanistic parameters of current function, charge transfer resistance and exchange current for the NPyCME, GCE and Nafion-coated GCE were evaluated and compared. The disproportionation reaction of NIIIO2- into NIVO3- + NIIO in acidic solution was used as a model system for testing the dual sensing ability of the NPyCME. The obtained crossover peak response for NO2- oxidation and NO reduction in pH 1.65 buffer solution gave the direct proof for the applicability of the NPyCME in the dual electrocatalytic action. By flow injection analysis, under optimized conditions, the calibration curve was linear in the range of 100 nM-100 microM and 800 nM-63.3 microM and the detection limit (S/N = 3) was 4.8 nM and 15.6 nM for NO2- and NO, respectively.

  4. 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.

  5. Writable electrochemical energy source based on graphene oxide.

    PubMed

    Wei, Di

    2015-10-14

    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.

  6. 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

  7. 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.

  8. 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

  9. Electrochemical oxidation of oxalic acid at highly boron-doped diamond electrodes.

    PubMed

    Ivandini, Tribidasari A; Rao, Tata N; Fujishima, Akira; Einaga, Yasuaki

    2006-05-15

    Electrochemical oxidation of oxalic acid has been investigated at bare, highly boron-doped diamond electrodes. Cyclic voltammetry and flow injection analysis with amperometric detection were used to study the electrochemical reaction. Hydrogen-terminated diamonds exhibited well-defined peaks of oxalic acid oxidation in a wide pH range. A good linear response was observed for a concentration range from 50 nM to 10 microM, with an estimated detection limit of approximately 0.5 nM (S/N = 3). In contrast, oxygen-terminated diamonds showed no response for oxalic acid oxidation inside the potential window, indicating that surface termination contributed highly to the control of the oxidation reaction. An investigation with glassy carbon electrodes was conducted to confirm the surface termination effect on oxalic acid oxidation. Although a hydrogen-terminated glassy carbon electrode showed an enhancement of signal-to-background ratio in comparison with untreated glassy carbon, less stability of the current responses was observed than that at hydrogen-terminated diamond.

  10. 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. Copyright © 2015 Elsevier Ltd. All rights reserved.

  11. Formation and electrochemical characterization of anodic ZrO2-WO3 mixed oxide nanotubular arrays

    NASA Astrophysics Data System (ADS)

    Whitman, Stuart R.; Raja, Krishnan S.

    2014-06-01

    ZrO2-WO3 mixed oxide nanotubes were synthesized by a simple electrochemical anodization route. The oxide nanotubes contained a mixture of metastable hexagonal WO3 and monoclinic (and orthorhombic) ZrO2 phases, as well as a mixed-oxide ZrW2O8 phase that showed a metastable tetragonal symmetry. Evaluation of photo-activity of the materials showed generation of photo-potentials of -85 mV and -230 mV in the as-anodized and annealed conditions. Because of the mismatch in the band edge positions of the WO3 and ZrO2 phases and the resultant relaxation of photo-generated charge carriers, no significant photo-current density could be observed. The arrays of oxide nanotubes are considered for electrochemical capacitor application because of their morphology-assisted fast charge/discharge kinetics and large surface area. Presence of a large concentration of charge defects (on the order of 1021 cm-3) and the reported high proton conductivity of the ZrO2-WO3 mixed oxide rendered high capacitance, which decreased with an increase in the scan rate of cyclic voltammetry. The highest measured capacitance was 40.03 mF/cm2 at a scan rate of 10 mV/s and the lowest was 1.93 mF/cm2 at 1 V/s in 1 M sulfuric acid solution.

  12. Chitosan-iron oxide nanocomposite based electrochemical aptasensor for determination of malathion.

    PubMed

    Prabhakar, Nirmal; Thakur, Himkusha; Bharti, Anu; Kaur, Navpreet

    2016-10-05

    An electrochemical aptasensor based on chitosan-iron oxide nanocomposite (CHIT-IO) film deposited on fluorine tin Oxide (FTO) was developed for the detection of malathion. Iron oxide nanoparticles were prepared by co-precipitation method and characterized by Transmission electron microscopy and UV-Visible spectroscopy. The biotinylated DNA aptamer sequence specific to the malathion was immobilized onto the iron oxide doped-chitosan/FTO electrode by using streptavidin as linking molecule. Various characterization studies like Field Emission-Scanning Electron Microscopy (FE-SEM), Fourier Transform Infrared Spectroscopy (FT-IR), and Electrochemical studies were performed to attest the successful fabrication of bioelectrodes. Experimental parameters like aptamer concentration, response time, stability of electrode and reusability studies were optimized. Aptamer immobilized chitosan-iron oxide nanocomposite (APT/SA/CHIT-IO/FTO) bioelectrodes exhibited LOD of about 0.001 ng/mL within 15 min and spike-in studies revealed about 80-92% recovery of malathion from the lettuce leaves and soil sample. Copyright © 2016 Elsevier B.V. All rights reserved.

  13. Direct electrochemical reduction of solid uranium oxide in molten fluoride salts

    NASA Astrophysics Data System (ADS)

    Gibilaro, Mathieu; Cassayre, Laurent; Lemoine, Olivier; Massot, Laurent; Dugne, Olivier; Malmbeck, Rikard; Chamelot, Pierre

    2011-07-01

    The direct electrochemical reduction of UO 2 solid pellets was carried out in LiF-CaF 2 (+2 mass.% Li 2O) at 850 °C. An inert gold anode was used instead of the usual reactive sacrificial carbon anode. In this case, oxidation of oxide ions present in the melt yields O 2 gas evolution on the anode. Electrochemical characterisations of UO 2 pellets were performed by linear sweep voltammetry at 10 mV/s and reduction waves associated to oxide direct reduction were observed at a potential 150 mV more positive in comparison to the solvent reduction. Subsequent, galvanostatic electrolyses runs were carried out and products were characterised by SEM-EDX, EPMA/WDS, XRD and microhardness measurements. In one of the runs, uranium oxide was partially reduced and three phases were observed: nonreduced UO 2 in the centre, pure metallic uranium on the external layer and an intermediate phase representing the initial stage of reduction taking place at the grain boundaries. In another run, the UO 2 sample was fully reduced. Due to oxygen removal, the U matrix had a typical coral-like structure which is characteristic of the pattern observed after the electroreduction of solid oxides.

  14. Surface functionalization of fluorine-doped tin oxide samples through electrochemical grafting.

    PubMed

    Lamberti, F; Agnoli, S; Brigo, L; Granozzi, G; Giomo, M; Elvassore, N

    2013-12-26

    Transparent conductive oxides are emerging materials in several fields, such as photovoltaics, photoelectrochemistry, and optical biosensing. Their high chemical inertia, which ensured long-term stability on one side, makes challenging the surface modification of transparent conductive oxides; long-term robust modification, high yields, and selective surface modifications are essential prerequisite for any further developments. In this work, we aim at inducing chemical functionality on fluorine-doped tin oxide surfaces (one of the most inexpensive transparent conductive oxide) by means of electrochemical grafting of aryl diazonium cations. The grafted layers are fully characterized by photoemission spectroscopy, cyclic voltammetry, and atomic force microscopy showing linear correlation between surface coverage and degree of modification. The electrochemical barrier effect of modified surfaces was studied at different pH to characterize the chemical nature of the coating. We showed immuno recognition of biotin complex built onto grafted fluorine-doped tin oxides, which opens the perspective of integrating FTO samples with biological-based devices.

  15. Boron-doped cobalt oxide thin films and its electrochemical properties

    NASA Astrophysics Data System (ADS)

    Kerli, S.

    2016-09-01

    The cobalt oxide and boron-doped cobalt oxide thin films were produced by spray deposition method. All films were obtained onto glass and fluorine-doped tin oxide (FTO) substrates at 400∘C and annealed at 550∘C. We present detailed analysis of the morphological and optical properties of films. XRD results show that boron doping disrupts the structure of the films. Morphologies of the films were investigated by using a scanning electron microscopy (SEM). Optical measurements indicate that the band gap energies of the films change with boron concentrations. The electrochemical supercapacitor performance test has been studied in aqueous 6 M KOH electrolyte and with scan rate of 5 mV/s. Measurements show that the largest capacitance is obtained for 3% boron-doped cobalt oxide film.

  16. Electrochemical oxidation of hydrazine and its derivatives on the surface of metal electrodes in alkaline media

    NASA Astrophysics Data System (ADS)

    Asazawa, Koichiro; Yamada, Koji; Tanaka, Hirohisa; Taniguchi, Masatoshi; Oguro, Keisuke

    Electrochemical oxidation of hydrazine and its derivatives on the surface of various metal electrodes in alkaline media was investigated. A comparison of various polycrystalline metal electrodes (Ni, Co, Fe, Cu, Ag, Au, and Pt) showed that Co and Ni electrodes have a lower onset potential for hydrazine oxidation than the Pt electrode. The onset oxidation potential of APA (aminopolyacrylamide), a hydrazine derivative (-0.127 V vs. reversible hydrogen electrode, RHE), was similar to that of hydrazine hydrate (-0.178 V vs. RHE) in the case of the Co electrode. APA oxidation was possible because of hydrazine desorption that was caused by APA hydrolysis. The hydrolysis reaction was brought about by a heat treatment. This result suggests that the hydrazine hydrolysis reaction of hydrazine derivatives makes it possible to store hydrazine hydrate safely.

  17. Solar-powered electrochemical oxidation of organic compounds coupled with the cathodic production of molecular hydrogen.

    PubMed

    Park, Hyunwoong; Vecitis, Chad D; Hoffmann, Michael R

    2008-08-21

    A Bi-doped TiO2 anode, which is prepared from a mixed metal oxide coating deposited on Ti metal, is shown to be efficient for conventional water splitting. In this hybrid photovoltaic-electrochemical system, a photovoltaic (PV) cell is used to convert solar light to electricity, which is then used to oxidize a series of phenolic compounds at the semiconductor anode to carbon dioxide with the simultaneous production of molecular hydrogen from water/proton reduction at the stainless steel cathode. Degradation of phenol in the presence of a background NaCl electrolyte produces chlorinated phenols as reaction intermediates, which are subsequently oxidized completely to carbon dioxide and low-molecular weight carboxylic acids. The anodic current efficiency for the complete oxidation of phenolic compounds ranges from 3% to 17%, while the cathodic current efficiency and the energy efficiency for hydrogen gas generation range from 68% to 95% and 30% to 70%, respectively.

  18. Mediated electrochemical oxidation of Rocky Flats combustible low level mixed wastes

    SciTech Connect

    Chiba, Z.

    1992-12-01

    Mediated Electrochemical Oxidation (MEO) was originally developed for dissolution of difficult to dissolve forms of plutonium oxide. It was also found to be effective for oxidizing non-polymerized organic materials. MEO is an inherently safe process since the hazardous and radioactive materials are completely contained in the aqueous phase, and operating temperatures and pressures of the system are low (well below 100 {degree}C and 30 psig). The most commonly used mediator-electrolyte combination is silver in nitric acid. The process produces divalent silver ion, a strong oxidizing agent, which dissolves the radioactive components of mixed wastes and destroys the organic components. In the past, work at LLNL has been focused on understanding the basic science and modeling the dissolution and destruction mechanisms. Reaction rates of water with Ag(H) were measured using spectrophotometric methods, and the diffusivity of silver ions in nitric acid was estimated using a rotating disk electrode.

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

    SciTech Connect

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

    2015-11-05

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

  20. 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.

  1. Analysis of geometric and electrochemical characteristics of lithium cobalt oxide electrode with different packing densities

    DOE PAGES

    Lim, Cheolwoong; Yan, Bo; Kang, Huixiao; ...

    2016-08-06

    In order to investigate geometric and electrochemical characteristics of Li ion battery electrode with different packing densities, lithium cobalt oxide (LiCoO2) cathode electrodes were fabricated from a 94:3:3 (wt%) mixture of LiCoO2, polymeric binder, and super-P carbon black and calendered to different densities. A synchrotron X-ray nano-computed tomography system with a spatial resolution of 58.2 nm at the Advanced Photon Source of the Argonne National Laboratory was employed to obtain three dimensional morphology data of the electrodes. The morphology data were then quantitatively analyzed to characterize their geometric properties, such as porosity, tortuosity, specific surface area, and pore size distribution.more » The geometric and electrochemical analysis reveal that high packing density electrodes have smaller average pore size and narrower pore size distribution, which improves the electrical contact between carbon-binder matrix and LiCoO2 particles. The better contact improves the capacity and rate capability by reducing the possibility of electrically isolated LiCoO2 particles and increasing the electrochemically active area. The results show that increase of packing density results in higher tortuosity, but electrochemically active area is more crucial to cell performance than tortuosity at up to 3.6 g/cm3 packing density and 4 C rate.« less

  2. Analysis of geometric and electrochemical characteristics of lithium cobalt oxide electrode with different packing densities

    SciTech Connect

    Lim, Cheolwoong; Yan, Bo; Kang, Huixiao; Song, Zhibin; Lee, Wen Chao; De Andrade, Vincent; De Carlo, Francesco; Yin, Leilei; Kim, Youngsik; Zhu, Likun

    2016-08-06

    In order to investigate geometric and electrochemical characteristics of Li ion battery electrode with different packing densities, lithium cobalt oxide (LiCoO2) cathode electrodes were fabricated from a 94:3:3 (wt%) mixture of LiCoO2, polymeric binder, and super-P carbon black and calendered to different densities. A synchrotron X-ray nano-computed tomography system with a spatial resolution of 58.2 nm at the Advanced Photon Source of the Argonne National Laboratory was employed to obtain three dimensional morphology data of the electrodes. The morphology data were then quantitatively analyzed to characterize their geometric properties, such as porosity, tortuosity, specific surface area, and pore size distribution. The geometric and electrochemical analysis reveal that high packing density electrodes have smaller average pore size and narrower pore size distribution, which improves the electrical contact between carbon-binder matrix and LiCoO2 particles. The better contact improves the capacity and rate capability by reducing the possibility of electrically isolated LiCoO2 particles and increasing the electrochemically active area. The results show that increase of packing density results in higher tortuosity, but electrochemically active area is more crucial to cell performance than tortuosity at up to 3.6 g/cm3 packing density and 4 C rate.

  3. Analysis of Geometric and Electrochemical Characteristics of Lithium Cobalt Oxide Electrode with Different Packing Densities

    SciTech Connect

    Lim, Cheolwoong; Yan, Bo; Kang, Huixiao; Song, Zhibin; Lee, Wen Chao; De Andrade, Vincent; De Carlo, Francesco; Yin, Leilei; Kim, Youngsik; Zhu, Likun

    2016-10-01

    To investigate geometric and electrochemical characteristics of Li ion battery electrode with different packing densities, lithium cobalt oxide (LiCoO2) cathode electrodes were fabricated from a 94:3:3 (wt%) mixture of LiCoO2, polymeric binder, and super-P carbon black and calendered to different densities. A synchrotron X-ray nano-computed tomography system with a spatial resolution of 58.2 nm at the Advanced Photon Source of the Argonne National Laboratory was employed to obtain three dimensional morphology data of the electrodes. The morphology data were quantitatively analyzed to characterize their geometric properties, such as porosity, tortuosity, specific surface area, and pore size distribution. The geometric and electrochemical analysis reveal that high packing density electrodes have smaller average pore size and narrower pore size distribution, which improves the electrical contact between carbon-binder matrix and LiCoO2 particles. The better contact improves the capacity and rate capability by reducing the possibility of electrically isolated LiCoO2 particles and increasing the electrochemically active area. The results show that increase of packing density results in higher tortuosity, but electrochemically active area is more crucial to cell performance than tortuosity at up to 3.6 g/cm3 packing density and 4 C rate.

  4. Analysis of geometric and electrochemical characteristics of lithium cobalt oxide electrode with different packing densities

    NASA Astrophysics Data System (ADS)

    Lim, Cheolwoong; Yan, Bo; Kang, Huixiao; Song, Zhibin; Lee, Wen Chao; De Andrade, Vincent; De Carlo, Francesco; Yin, Leilei; Kim, Youngsik; Zhu, Likun

    2016-10-01

    To investigate geometric and electrochemical characteristics of Li ion battery electrode with different packing densities, lithium cobalt oxide (LiCoO2) cathode electrodes were fabricated from a 94:3:3 (wt%) mixture of LiCoO2, polymeric binder, and super-P carbon black and calendered to different densities. A synchrotron X-ray nano-computed tomography system with a spatial resolution of 58.2 nm at the Advanced Photon Source of the Argonne National Laboratory was employed to obtain three dimensional morphology data of the electrodes. The morphology data were quantitatively analyzed to characterize their geometric properties, such as porosity, tortuosity, specific surface area, and pore size distribution. The geometric and electrochemical analysis reveal that high packing density electrodes have smaller average pore size and narrower pore size distribution, which improves the electrical contact between carbon-binder matrix and LiCoO2 particles. The better contact improves the capacity and rate capability by reducing the possibility of electrically isolated LiCoO2 particles and increasing the electrochemically active area. The results show that increase of packing density results in higher tortuosity, but electrochemically active area is more crucial to cell performance than tortuosity at up to 3.6 g/cm3 packing density and 4 C rate.

  5. 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.

  6. Zinc oxide/redox mediator composite films-based sensor for electrochemical detection of important biomolecules.

    PubMed

    Tang, Chun-Fang; Kumar, S Ashok; Chen, Shen-Ming

    2008-09-15

    Electrochemical oxidation of serotonin (SN) onto zinc oxide (ZnO)-coated glassy carbon electrode (GCE) results in the generation of redox mediators (RMs) that are strongly adsorbed on electrode surface. The electrochemical properties of zinc oxide-electrogenerated redox mediator (ZnO/RM) (inorganic/organic) hybrid film-coated electrode has been studied using cyclic voltammetry (CV). The scanning electron microscope (SEM), atomic force microscope (AFM), and electrochemical techniques proved the immobilization of ZnO/RM core/shell microparticles on the electrode surface. The GCE modified with ZnO/RM hybrid film showed two reversible redox peaks in acidic solution, and the redox peaks were found to be pH dependent with slopes of -62 and -60 mV/pH, which are very close to the Nernst behavior. The GCE/ZnO/RM-modified electrode exhibited excellent electrocatalytic activity toward the oxidations of ascorbic acid (AA), dopamine (DA), and uric acid (UA) in 0.1M phosphate buffer solution (PBS, pH 7.0). Indeed, ZnO/RM-coated GCE separated the anodic oxidation waves of DA, AA, and UA with well-defined peak separations in their mixture solution. Consequently, the GCE/ZnO/RMs were used for simultaneous detection of DA, AA, and UA in their mixture solution. Using CV, calibration curves for DA, AA, and UA were obtained over the range of 6.0 x 10(-6) to 9.6 x 10(-4)M, 1.5 x 10(-5) to 2.4 x 10(-4)M, and 5.0 x 10(-5) to 8 x 10(-4)M with correlation coefficients of 0.992, 0.991, and 0.989, respectively. Moreover, ZnO/RM-modified GCE had good stability and antifouling properties.

  7. Solar-mediated thermo-electrochemical oxidation of sodium dodecyl benzene sulfonate by modulating the effective oxidation potential and pathway for green remediation of wastewater

    PubMed Central

    Gu, Di; Gao, Simeng; Jiang, TingTing; Wang, Baohui

    2017-01-01

    To match the relentless pursuit of three research hot points - efficient solar utilization, green and sustainable remediation of wastewater and advanced oxidation processes, solar-mediated thermo-electrochemical oxidation of surfactant was proposed and developed for green remediation of surfactant wastewater. The solar thermal electrochemical process (STEP), fully driven with solar energy to electric energy and heat and without an input of other energy, sustainably serves as efficient thermo-electrochemical oxidation of surfactant, exemplified by SDBS, in wastewater with the synergistic production of hydrogen. The electrooxidation-resistant surfactant is thermo-electrochemically oxidized to CO2 while hydrogen gas is generated by lowing effective oxidation potential and suppressing the oxidation activation energy originated from the combination of thermochemical and electrochemical effect. A clear conclusion on the mechanism of SDBS degradation can be proposed and discussed based on the theoretical analysis of electrochemical potential by quantum chemical method and experimental analysis of the CV, TG, GC, FT-IR, UV-vis, Fluorescence spectra and TOC. The degradation data provide a pilot for the treatment of SDBS wastewater that appears to occur via desulfonation followed by aromatic-ring opening. The solar thermal utilization that can initiate the desulfonation and activation of SDBS becomes one key step in the degradation process. PMID:28294180

  8. Solar-mediated thermo-electrochemical oxidation of sodium dodecyl benzene sulfonate by modulating the effective oxidation potential and pathway for green remediation of wastewater

    NASA Astrophysics Data System (ADS)

    Gu, Di; Gao, Simeng; Jiang, Tingting; Wang, Baohui

    2017-03-01

    To match the relentless pursuit of three research hot points - efficient solar utilization, green and sustainable remediation of wastewater and advanced oxidation processes, solar-mediated thermo-electrochemical oxidation of surfactant was proposed and developed for green remediation of surfactant wastewater. The solar thermal electrochemical process (STEP), fully driven with solar energy to electric energy and heat and without an input of other energy, sustainably serves as efficient thermo-electrochemical oxidation of surfactant, exemplified by SDBS, in wastewater with the synergistic production of hydrogen. The electrooxidation-resistant surfactant is thermo-electrochemically oxidized to CO2 while hydrogen gas is generated by lowing effective oxidation potential and suppressing the oxidation activation energy originated from the combination of thermochemical and electrochemical effect. A clear conclusion on the mechanism of SDBS degradation can be proposed and discussed based on the theoretical analysis of electrochemical potential by quantum chemical method and experimental analysis of the CV, TG, GC, FT-IR, UV-vis, Fluorescence spectra and TOC. The degradation data provide a pilot for the treatment of SDBS wastewater that appears to occur via desulfonation followed by aromatic-ring opening. The solar thermal utilization that can initiate the desulfonation and activation of SDBS becomes one key step in the degradation process.

  9. Solar-mediated thermo-electrochemical oxidation of sodium dodecyl benzene sulfonate by modulating the effective oxidation potential and pathway for green remediation of wastewater.

    PubMed

    Gu, Di; Gao, Simeng; Jiang, TingTing; Wang, Baohui

    2017-03-15

    To match the relentless pursuit of three research hot points - efficient solar utilization, green and sustainable remediation of wastewater and advanced oxidation processes, solar-mediated thermo-electrochemical oxidation of surfactant was proposed and developed for green remediation of surfactant wastewater. The solar thermal electrochemical process (STEP), fully driven with solar energy to electric energy and heat and without an input of other energy, sustainably serves as efficient thermo-electrochemical oxidation of surfactant, exemplified by SDBS, in wastewater with the synergistic production of hydrogen. The electrooxidation-resistant surfactant is thermo-electrochemically oxidized to CO2 while hydrogen gas is generated by lowing effective oxidation potential and suppressing the oxidation activation energy originated from the combination of thermochemical and electrochemical effect. A clear conclusion on the mechanism of SDBS degradation can be proposed and discussed based on the theoretical analysis of electrochemical potential by quantum chemical method and experimental analysis of the CV, TG, GC, FT-IR, UV-vis, Fluorescence spectra and TOC. The degradation data provide a pilot for the treatment of SDBS wastewater that appears to occur via desulfonation followed by aromatic-ring opening. The solar thermal utilization that can initiate the desulfonation and activation of SDBS becomes one key step in the degradation process.

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

    NASA Astrophysics Data System (ADS)

    Patel, Shrayesh; Javier, Anna; Balsara, Nitash

    2013-03-01

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

  11. Efficient electrochemical oxidation of perfluorooctanoate using a Ti/SnO2-Sb-Bi anode.

    PubMed

    Zhuo, Qiongfang; Deng, Shubo; Yang, Bo; Huang, Jun; Yu, Gang

    2011-04-01

    The electrochemical decomposition of persistent perfluorooctanoate (PFOA) with a Ti/SnO2-Sb-Bi electrode was demonstrated in this study. After 2 h electrolysis, over 99% of PFOA (25 mL of 50 mg·L(-1)) was degraded with a first-order kinetic constant of 1.93 h(-1). The intermediate products including short-chain perfluorocarboxyl anions (CF3COO-, C2F5COO-, C3F7COO-, C4F9COO-, C5F11COO-, and C6F13COO-) and F- were detected in the aqueous solution. The electrochemical oxidation mechanism was revealed, that PFOA decomposition first occurred through a direct one electron transfer from the carboxyl group in PFOA to the anode at the potential of 3.37 V (vs saturated calomel electrode, SCE). After that, the PFOA radical was decarboxylated to form perfluoroheptyl radical which allowed a defluorination reaction between perfluoroheptyl radical and hydroxyl radical/O2. Electrospray ionization (ESI) mass spectrum further confirmed that the oxidation of PFOA on the Ti/SnO2-Sb-Bi electrode proceeded from the carboxyl group in PFOA rather than C-C cleavage, and the decomposition processes followed the CF2 unzipping cycle. The electrochemical technique with the Ti/SnO2-Sb-Bi electrode provided a potential method for PFOA degradation in the aqueous solution.

  12. Boron doped ZnO embedded into reduced graphene oxide for electrochemical supercapacitors

    NASA Astrophysics Data System (ADS)

    Alver, Ü.; Tanrıverdi, A.

    2016-08-01

    In this work, reduced graphene oxide/boron doped zinc oxide (RGO/ZnO:B) composites were fabricated by a hydrothermal process and their electrochemical properties were investigated as a function of dopant concentration. First, boron doped ZnO (ZnO:B) particles was fabricated with different boron concentrations (5, 10, 15 and 20 wt%) and then ZnO:B particles were embedded into RGO sheets. The physical properties of sensitized composites were characterized by XRD and SEM. Characterization indicated that the ZnO:B particles with plate-like structure in the composite were dispersed on graphene sheets. The electrochemical properties of the RGO/ZnO:B composite were investigated through cyclic voltammetry, galvanostatic charge/discharge measurements in a 6 M KOH electrolyte. Electrochemical measurements show that the specific capacitance values of RGO/ZnO:B electrodes increase with increasing boron concentration. RGO/ZnO:B composite electrodes (20 wt% B) display the specific capacitance as high as 230.50 F/g at 5 mV/s, which is almost five times higher than that of RGO/ZnO (52.71 F/g).

  13. Electrochemical oxidation of biological pretreated and membrane separated landfill leachate concentrates on boron doped diamond anode

    NASA Astrophysics Data System (ADS)

    Zhou, Bo; Yu, Zhiming; Wei, Qiuping; Long, HangYu; Xie, Youneng; Wang, Yijia

    2016-07-01

    In the present study, the high quality boron-doped diamond (BDD) electrodes with excellent electrochemical properties were deposited on niobium (Nb) substrates by hot filament chemical vapor deposition (HFCVD) method. The electrochemical oxidation of landfill leachate concentrates from disc tube reverse osmosis (DTRO) process over a BDD anode was investigated. The effects of varying operating parameters, such as current density, initial pH, flow velocity and cathode material on degradation efficiency were also evaluated following changes in chemical oxygen demand (COD) and ammonium nitrogen (NH3sbnd N). The instantaneous current efficiency (ICE) was used to appraise different operating conditions. As a result, the best conditions obtained were as follows, current density 50 mA cm-2, pH 5.16, flow velocity 6 L h-1. Under these conditions, 87.5% COD and 74.06% NH3sbnd N removal were achieved after 6 h treatment, with specific energy consumption of 223.2 kWh m-3. In short, these results indicated that the electrochemical oxidation with BDD/Nb anode is an effective method for the treatment of landfill leachate concentrates.

  14. Bio-functionalized graphene-graphene oxide nanocomposite based electrochemical immunosensing.

    PubMed

    Sharma, Priyanka; Tuteja, Satish K; Bhalla, Vijayender; Shekhawat, G; Dravid, Vinayak P; Suri, C Raman

    2013-01-15

    We report a novel in-situ electrochemical synthesis approach for the formation of functionalized graphene-graphene oxide (fG-GO) nanocomposite on screen-printed electrodes (SPE). Electrochemically controlled nanocomposite film formation was studied by transmission electron microscopy (TEM) and Raman spectroscopy. Further insight into the nanocomposite has been accomplished by the Fourier transformed infrared spectroscopy (FTIR), thermal gravimetric analysis (TGA) and X-ray diffraction (XRD) spectroscopy. Configured as a highly responsive screen-printed immunosensor, the fG-GO nanocomposite on SPE exhibits electrical and chemical synergies of the nano-hybrid functional construct by combining good electronic properties of functionalized graphene (fG) and the facile chemical functionality of graphene oxide (GO) for compatible bio-interface development using specific anti-diuron antibody. The enhanced electrical properties of nanocomposite biofilm demonstrated a significant increase in electrochemical signal response in a competitive inhibition immunoassay format for diuron detection, promising its potential applicability for ultra-sensitive detection of range of target analytes. Copyright © 2012 Elsevier B.V. All rights reserved.

  15. Electrochemical regeneration of Fe2+ in Fenton oxidation processes.

    PubMed

    Qiang, Zhimin; Chang, Jih-Hsing; Huang, Chin-Pao

    2003-03-01

    This study is to establish optimal conditions for the minimization of iron sludge produced in Fenton oxidation processes by electro-regenerating Fe(2+) with constant potential (CPM) or constant current mode (CCM). Results indicate that the optimal cathodic potential for Fe(2+) regeneration is -0.1 V vs. the saturated calomel electrode (SCE) in terms of current efficiency. Keeping the initial Fe(3+) concentration ([Fe(3+)](0)) constant, the average current density produced at -0.1 V vs. SCE (CPM) is approximately equal to the optimal current density applied in the CCM. The suitable pH range is below the pH value determined by Fe(3+) hydrolysis. As expected, increasing cathode surface area and solution temperature notably increases Fe(2+) regeneration rate. At the optimal potential, the average current density increases linearly with [Fe(3+)](0), exhibiting a slope of 8.48 x 10(-3)(A/m(2))(mg/L)(-1). The average current efficiency varies with [Fe(3+)](0), e.g., 75% and 96-98% at 100 and > or = 500 mg/L [Fe(3+)](0), respectively. Once reaching 75% of Fe(2+) regeneration capacity, further regeneration becomes difficult due to Fe(3+) mass transfer limitation. Fe(2+) can also be effectively regenerated by dissolving iron sludge at low pH (usually

  16. A novel method for photodegradation of high-chroma dye wastewater via electrochemical pre-oxidation.

    PubMed

    Zhao, Kunjiao; Zhao, Guohua; Li, Peiqiang; Gao, Junxia; Lv, Baoying; Li, Dongming

    2010-06-01

    A new two-step process involving the electrocatalytic (EC) pre-oxidation and the following photoelectrocatalytic synergistic (PEC) oxidation is proposed to treat the high concentration and high-chroma methyl orange dye wastewater, which cannot be degraded by photocatalytic oxidation (PC) directly. The SnO(2)/TiO(2)-NTs/Ti electrode simultaneously possessing the outstanding PC oxidation properties of TiO(2)-NTs and the excellent EC oxidation abilities of the Sb doped SnO(2) was synthesized by impregnating Sb doped SnO(2) nanoparticles into TiO(2)-NTs. In the pre-oxidation process as the first stage, the high-color dye wastewater is decolorized with electrochemical method to some extent. Then, the wastewater becomes a light transmission system. It provides a suitable condition for PC oxidation reaction in the second stage. The synergistic effects of PC and EC oxidation led to the high PEC efficiency and the complete mineralization of dye wastewater is achieved. This two-step process is fast and efficient, which is worthy to study and explore in the practical environmental treatment.

  17. Nanoporous gold supported cobalt oxide microelectrodes as high-performance electrochemical biosensors.

    PubMed

    Lang, Xing-You; Fu, Hong-Ying; Hou, Chao; Han, Gao-Feng; Yang, Ping; Liu, Yong-Bing; Jiang, Qing

    2013-01-01

    Tremendous demands for electrochemical biosensors with high sensitivity and reliability, fast response and excellent selectivity have stimulated intensive research on developing versatile materials with ultrahigh electrocatalytic activity. Here we report flexible and self-supported microelectrodes with a seamless solid/nanoporous gold/cobalt oxide hybrid structure for electrochemical nonenzymatic glucose biosensors. As a result of synergistic electrocatalytic activity of the gold skeleton and cobalt oxide nanoparticles towards glucose oxidation, amperometric glucose biosensors based on the hybrid microelectrodes exhibit multi-linear detection ranges with ultrahigh sensitivities at a low potential of 0.26 V (versus Ag/AgCl). The sensitivity up to 12.5 mA mM⁻¹ cm⁻² with a short response time of less than 1 s gives rise to ultralow detection limit of 5 nM. The outstanding performance originates from a novel nanoarchitecture in which the cobalt oxide nanoparticles are incorporated into pore channels of the seamless solid/nanoporous Au microwires, providing excellent electronic/ionic conductivity and mass transport for the enhanced electrocatalysis.

  18. Electrochemical Water Oxidation by a Catalyst-Modified Metal-Organic Framework Thin Film

    SciTech Connect

    Lin, Shaoyang; Pineda-Galvan, Yuliana; Maza, William A.; Epley, Charity C.; Zhu, Jie; Kessinger, Matthew C.; Pushkar, Yulia; Morris, Amanda J.

    2016-12-15

    Water oxidation, a key component in artificial photosynthesis, requires high overpotentials and exhibits slow reaction kinetics that necessitates the use of stable and efficient heterogeneous water-oxidation catalysts (WOCs). Here, we report the synthesis of UiO-67 metal–organic framework (MOF) thin films doped with [Ru(tpy)(dcbpy)OH2]2+ (tpy=2,2':6',2''-terpyridine, dcbpy=5,5'-dicarboxy-2,2'-bipyridine) on conducting surfaces and their propensity for electrochemical water oxidation. The electrocatalyst oxidized water with a turnover frequency (TOF) of (0.2±0.1) s-1 at 1.71 V versus the normal hydrogen electrode (NHE) in buffered solution (pH~7) and exhibited structural and electrochemical stability. The electroactive sites were distributed throughout the MOF thin film on the basis of scan-ratedependent voltammetry studies. This work demonstrates a promising way to immobilize large concentrations of electroactive WOCs into a highly robust MOF scaffold and paves the way for future photoelectrochemical water-splitting systems.

  19. 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.

  20. Electrochemical DNA biosensors based on thin gold films sputtered on capacitive nanoporous niobium oxide.

    PubMed

    Rho, Sangchul; Jahng, Deokjin; Lim, Jae Hoon; Choi, Jinsub; Chang, Jeong Ho; Lee, Sang Cheon; Kim, Kyung Ja

    2008-01-18

    Electrochemical DNA biosensors based on a thin gold film sputtered on anodic porous niobium oxide (Au@Nb(2)O(5)) are studied in detail here. We found that the novel DNA biosensor based on Au@Nb(2)O(5) is superior to those based on the bulk gold electrode or niobium oxide electrode. For example, the novel method does not require any time-consuming cleaning step in order to obtain reproducible results. The adhesion of gold films on the substrate is very stable during electrochemical biosensing, when the thin gold films are deposited on anodically prepared nanoporous niobium oxide. In particular, the novel biosensor shows enhanced biosensing performance with a 2.4 times higher resolution and a three times higher sensitivity. The signal enhancement is in part attributed to capacitive interface between gold films and nanoporous niobium oxide, where charges are accumulated during the anodic and cathodic scanning, and is in part ascribed to the structural stability of DNA immobilized at the sputtered gold films. The method allows for the detection of single-base mismatch DNA as well as for the discrimination of mismatch positions.

  1. High quality reduced graphene oxide flakes by fast kinetically controlled and clean indirect UV-induced radical reduction

    NASA Astrophysics Data System (ADS)

    Flyunt, Roman; Knolle, Wolfgang; Kahnt, Axel; Halbig, Christian E.; Lotnyk, Andriy; Häupl, Tilmann; Prager, Andrea; Eigler, Siegfried; Abel, Bernd

    2016-03-01

    This work highlights a surprisingly simple and kinetically controlled highly efficient indirect method for the production of high quality reduced graphene oxide (rGO) flakes via UV irradiation of aqueous dispersions of graphene oxide (GO), in which the GO is not excited directly. While the direct photoexcitation of aqueous GO (when GO is the only light-absorbing component) takes several hours of reaction time at ambient temperature (4 h) leading only to a partial GO reduction, the addition of small amounts of isopropanol and acetone (2% and 1%) leads to a dramatically shortened reaction time by more than two orders of magnitude (2 min) and a very efficient and soft reduction of graphene oxide. This method avoids the formation of non-volatile species and in turn contamination of the produced rGO and it is based on the highly efficient generation of reducing carbon centered isopropanol radicals via the reaction of triplet acetone with isopropanol. While the direct photolysis of GO dispersions easily leads to degradation of the carbon lattice of GO and thus to a relatively low electric conductivity of the films of flakes, our indirect photoreduction of GO instead largely avoids the formation of defects, keeping the carbon lattice intact. Mechanisms of the direct and indirect photoreduction of GO have been elucidated and compared. Raman spectroscopy, XPS and conductivity measurements prove the efficiency of the indirect photoreduction in comparison with the state-of-the-art reduction method for GO (hydriodic acid/trifluoroacetic acid). The rapid reduction times and water solvent containing only small amounts of isopropanol and acetone may allow easy process up-scaling for technical applications and low-energy consumption.This work highlights a surprisingly simple and kinetically controlled highly efficient indirect method for the production of high quality reduced graphene oxide (rGO) flakes via UV irradiation of aqueous dispersions of graphene oxide (GO), in which the

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

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

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

  3. Self-Powered Electrochemical Oxidation of 4-Aminoazobenzene Driven by a Triboelectric Nanogenerator.

    PubMed

    Gao, Shuyan; Su, Jingzhen; Wei, Xianjun; Wang, Miao; Tian, Miao; Jiang, Tao; Wang, Zhong Lin

    2017-01-24

    A rotary disc-structured triboelectric nanogenerator (rd-TENG) on the basis of free-standing electrification has been designed, where the aluminum composite panel has not been tailored to the stator becauseit is commercially available and cost-effective, has good electronic conductivity, and is easily processed. With the rotating speed increasing from 200 to 1000 rpm, the short-circuit current (Isc) is sharply enhanced from 50 μA to 200 μA, while the measured open-circuit voltage (Voc) and transferred charge (Qtr) almost keep constant, 600 V and 0.4 μC, respectively. The matched load for the rd-TENG at a rotating speed of 600 rpm is 2.7 MΩ, generating a maximum power of 19.75 mW, which corresponds to a maximum power density of 2.28 W m(-2). Using the electric power generated by such a rd-TENG, highly toxic and carcinogenic 4-aminoazobenzene can be selectively treated to produce CO2 or an oligomer via reasonably controlling electrochemical oxidation potentials. The underlying mechanism is tentatively proposed based on the cyclic voltammogram, gas chromatograph-mass spectrometer, electrochemical impedance spectroscopy, and UV-vis spectra. Here the electrochemical degradation in a single-compartment cell is more valid, preferable, and feasible. The output Voc and rectified current of rd-TENG guarantee its extensive application to self-power electrochemical degradation of other azo compounds, i.e., 2-(4-dimethylaminophenylazo) benzoic acid, to CO2. This work suggests that rd-TENG, sustainable energy, can be feasibly designed to self-power a practical electrochemical treatment of dyeing wastewater by harvesting vibration energy.

  4. Investigate electrochemical immunosensor of cortisol based on gold nanoparticles/magnetic functionalized reduced graphene oxide.

    PubMed

    Sun, Bolu; Gou, Yuqiang; Ma, Yuling; Zheng, Xiaoping; Bai, Ruibin; Ahmed Abdelmoaty, Ahmed Attia; Hu, Fangdi

    2017-02-15

    A sensitively competitive electrochemical immunosensor for the detection of cortisol was successfully developed based on gold nanoparticles and magnetic functionalized reduced graphene oxide (AuNPs/MrGO). In order to construct the base of the immunosensor, the MrGO was initially fabricated by chemical cross-linking and used to modify the nafion pretreated glassy carbon electrode. Subsequently, the surface of electrode was modified by AuNPs via electrochemical deposition. A variety of cortisol (Cor) can be firmly loaded in the AuNPs/MrGO with large specific surface area and good bioactivity to construct the basic electrode (Cor/AuNPs/MrGO/Nafion@GCE), which was characterized by the cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS), respectively. Due to the cortisol on the surface of basic electrode and samples can competitively combine with the cortisol antibody labelled by horseradish peroxidase (HRP-Strept-Biotin-Ab). Finally, the detection signal of electrochemical immunosensor (HRP-Strept-Biotin-Ab-Cor/AuNPs/MrGO/Nafion@GCE) in the test liquid had negative correlations with the concentration of cortisol in samples. The AuNPs/MrGO with excellent electrical conductivity being applied, the electrochemical response of the immunosensor was immensely amplified. The immunosensor displayed excellent analytical performance for the detection of cortisol range from 0.1 to 1000ng/mL with a detection limit of 0.05ng/mL at 3σ. Moreover, compared the developed immunoassay with commercially available enzyme linked immunosorbent assay, the proposed method showed good precision, acceptable stability and reproducibility, indicating the immunosensor could be used for the sensitive, efficient and real-time detection of cortisol in real samples. Therefore, the present strategy provides a novel and convenient method for clinical determination of cortisol. Copyright © 2016 Elsevier B.V. All rights reserved.

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

    NASA Astrophysics Data System (ADS)

    Arena, A.

    2016-03-01

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

  6. The influence of large cations on the electrochemical properties of tunnel-structured metal oxides

    NASA Astrophysics Data System (ADS)

    Yuan, Yifei; Zhan, Chun; He, Kun; Chen, Hungru; Yao, Wentao; Sharifi-Asl, Soroosh; Song, Boao; Yang, Zhenzhen; Nie, Anmin; Luo, Xiangyi; Wang, Hao; Wood, Stephen M.; Amine, Khalil; Islam, M. Saiful; Lu, Jun; Shahbazian-Yassar, Reza

    2016-11-01

    Metal oxides with a tunnelled structure are attractive as charge storage materials for rechargeable batteries and supercapacitors, since the tunnels enable fast reversible insertion/extraction of charge carriers (for example, lithium ions). Common synthesis methods can introduce large cations such as potassium, barium and ammonium ions into the tunnels, but how these cations affect charge storage performance is not fully understood. Here, we report the role of tunnel cations in governing the electrochemical properties of electrode materials by focusing on potassium ions in α-MnO2. We show that the presence of cations inside 2 × 2 tunnels of manganese dioxide increases the electronic conductivity, and improves lithium ion diffusivity. In addition, transmission electron microscopy analysis indicates that the tunnels remain intact whether cations are present in the tunnels or not. Our systematic study shows that cation addition to α-MnO2 has a strong beneficial effect on the electrochemical performance of this material.

  7. Methylene blue intercalated into calcium phosphate - Electrochemical properties and an ascorbic acid oxidation study

    NASA Astrophysics Data System (ADS)

    Lazarin, Angélica M.; Airoldi, Claudio

    2008-09-01

    Methylene blue (MB) was intercalated inside the cavity of a layered calcium phosphate host. The dye is strongly retained and not easily leached from the matrix. The intercalated dye material was incorporated into a carbon paste electrode and by means of cyclic voltammetry and amperometry, its electrochemical properties were investigated. In various electrolyte solutions, on changing the pH between 3 and 9, the midpoint potential remained practically constant at -0.15 V. This is not the usual behavior for MB, since it is known that in the solution phase the midpoint potential changes considerably with pH, indicating that, in the present case, methylene blue is a guest molecule intercalated inside the lamellar structure of the calcium phosphate. An electrode made with this material was used to study the electrochemical oxidation of ascorbic acid and then applied to commercial samples, with excellent agreement within the 95% confidence level.

  8. Controllable synthesis of metal hydroxide and oxide nanostructures by ionic liquids assisted electrochemical corrosion method

    NASA Astrophysics Data System (ADS)

    Liu, Na; Wu, Di; Wu, Haoxi; Luo, Fang; Chen, Ji

    2008-08-01

    Cu(OH) 2 nanowires have been synthesized by anodic oxidation of copper through a simple electrolysis process employing ionic liquid as an electrolyte. Controlling the electrochemical conditions can qualitatively modulate the lengths, amounts, and shapes of Cu(OH) 2 nanostructures. A rational mechanism based on coordination self-assembly and oriented attachment is proposed for the selective formation of the polycrystalline Cu(OH) 2 nanowires. In addition, the FeOOH nanoribbons, Ni(OH) 2 nanosheets, and ZnO nanospheres were also synthesized by this route, indicative of the universality of the electrochemical route presented herein. The morphologies and structures of the synthesized nanostructures have been characterized by transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM), powder X-ray diffraction (XRD), Fourier transform infrared spectra (FT-IR), and thermogravimetric (TG).

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

    PubMed

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

    2016-09-15

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

  10. Direct electrochemistry and electrocatalysis of lobetyolin via magnetic functionalized reduced graphene oxide film fabricated electrochemical sensor.

    PubMed

    Sun, Bolu; Gou, Xiaodan; Bai, Ruibin; Abdelmoaty, Ahmed Attia Ahmed; Ma, Yuling; Zheng, Xiaoping; Hu, Fangdi

    2017-05-01

    A novel lobetyolin electrochemical sensor based on a magnetic functionalized reduced graphene oxide/Nafion nanohybrid film has been introduced in this work. The magnetic functionalized reduced graphene oxide was characterized by fourier transform infrared spectroscopy, atomic force microscope, X-ray diffraction, transmission electron microscopy and thermogravimetric analysis. The scanning electron microscopy characterized the morphology and microstructure of the prepared sensors, and the electrochemical effective surface areas of the prepared sensors were also calculated by chronocoulometry method. The electrochemical behavior of lobetyolin on the magnetic functionalized reduced graphene oxide/Nafion nanohybrid modified glassy carbon electrode was investigated by cyclic voltammetry and differential pulse voltammetry in a phosphate buffer solution of pH6.0. The electron-transfer coefficient (α), electron transfer number (n), and electrode reaction rate constant (Κs) were calculated as 0.78, 0.73, and 4.63s(-1), respectively. Under the optimized conditions, the sensor based on magnetic functionalized reduced graphene oxide/Nafion showed a linear voltammetric response to the lobetyolin concentration at 1.0×10(-7) to 1.0×10(-4)mol/L with detection limit (S/N=3)of 4.3×10(-8)mol/L. The proposed sensor also displayed acceptable reproducibility, long-term stability, and high selectivity, and performs well for analysis of lobetyolin in real samples. The voltammetric sensor was successfully applied to detect lobetyolin in Codonopsis pilosula with recovery values in the range of 96.12%-102.66%.

  11. High quality reduced graphene oxide flakes by fast kinetically controlled and clean indirect UV-induced radical reduction.

    PubMed

    Flyunt, Roman; Knolle, Wolfgang; Kahnt, Axel; Halbig, Christian E; Lotnyk, Andriy; Häupl, Tilmann; Prager, Andrea; Eigler, Siegfried; Abel, Bernd

    2016-04-14

    This work highlights a surprisingly simple and kinetically controlled highly efficient indirect method for the production of high quality reduced graphene oxide (rGO) flakes via UV irradiation of aqueous dispersions of graphene oxide (GO), in which the GO is not excited directly. While the direct photoexcitation of aqueous GO (when GO is the only light-absorbing component) takes several hours of reaction time at ambient temperature (4 h) leading only to a partial GO reduction, the addition of small amounts of isopropanol and acetone (2% and 1%) leads to a dramatically shortened reaction time by more than two orders of magnitude (2 min) and a very efficient and soft reduction of graphene oxide. This method avoids the formation of non-volatile species and in turn contamination of the produced rGO and it is based on the highly efficient generation of reducing carbon centered isopropanol radicals via the reaction of triplet acetone with isopropanol. While the direct photolysis of GO dispersions easily leads to degradation of the carbon lattice of GO and thus to a relatively low electric conductivity of the films of flakes, our indirect photoreduction of GO instead largely avoids the formation of defects, keeping the carbon lattice intact. Mechanisms of the direct and indirect photoreduction of GO have been elucidated and compared. Raman spectroscopy, XPS and conductivity measurements prove the efficiency of the indirect photoreduction in comparison with the state-of-the-art reduction method for GO (hydriodic acid/trifluoroacetic acid). The rapid reduction times and water solvent containing only small amounts of isopropanol and acetone may allow easy process up-scaling for technical applications and low-energy consumption.

  12. Catalytic and electrochemical behaviour of solid oxide fuel cell operated with simulated-biogas mixtures

    NASA Astrophysics Data System (ADS)

    Dang-Long, T.; Quang-Tuyen, T.; Shiratori, Y.

    2016-06-01

    Being produced from organic matters of wastes (bio-wastes) through a fermentation process, biogas mainly composed of CH4 and CO2 and can be considered as a secondary energy carrier derived from solar energy. To generate electricity from biogas through the electrochemical process in fuel cells is a state-of-the-art technology possessing higher energy conversion efficiency without harmful emissions compared to combustion process in heat engines. Getting benefits from high operating temperature such as direct internal reforming ability and activation of electrochemical reactions to increase overall system efficiency, solid oxide fuel cell (SOFC) system operated with biogas becomes a promising candidate for distributed power generator for rural applications leading to reductions of environmental issues caused by greenhouse effects and bio-wastes. CO2 reforming of CH4 and electrochemical oxidation of the produced syngas (H2-CO mixture) are two main reaction processes within porous anode material of SOFC. Here catalytic and electrochemical behavior of Ni-ScSZ (scandia stabilized-zirconia) anode in the feed of CH4-CO2 mixtures as simulated-biogas at 800 °C were evaluated. The results showed that CO2 had strong influences on both reaction processes. The increase in CO2 partial pressure resulted in the decrease in anode overvoltage, although open-circuit voltage was dropped. Besides that, the simulation result based on a power-law model for equimolar CH4-CO2 mixture revealed that coking hazard could be suppressed along the fuel flow channel in both open-circuit and closed-circuit conditions.

  13. Catalytic and electrochemical behaviour of solid oxide fuel cell operated with simulated-biogas mixtures

    SciTech Connect

    Dang-Long, T.; Quang-Tuyen, T.; Shiratori, Y.

    2016-06-03

    Being produced from organic matters of wastes (bio-wastes) through a fermentation process, biogas mainly composed of CH{sub 4} and CO{sub 2} and can be considered as a secondary energy carrier derived from solar energy. To generate electricity from biogas through the electrochemical process in fuel cells is a state-of-the-art technology possessing higher energy conversion efficiency without harmful emissions compared to combustion process in heat engines. Getting benefits from high operating temperature such as direct internal reforming ability and activation of electrochemical reactions to increase overall system efficiency, solid oxide fuel cell (SOFC) system operated with biogas becomes a promising candidate for distributed power generator for rural applications leading to reductions of environmental issues caused by greenhouse effects and bio-wastes. CO{sub 2} reforming of CH{sub 4} and electrochemical oxidation of the produced syngas (H{sub 2}–CO mixture) are two main reaction processes within porous anode material of SOFC. Here catalytic and electrochemical behavior of Ni-ScSZ (scandia stabilized-zirconia) anode in the feed of CH{sub 4}–CO{sub 2} mixtures as simulated-biogas at 800 °C were evaluated. The results showed that CO{sub 2} had strong influences on both reaction processes. The increase in CO{sub 2} partial pressure resulted in the decrease in anode overvoltage, although open-circuit voltage was dropped. Besides that, the simulation result based on a power-law model for equimolar CH{sub 4}−CO{sub 2} mixture revealed that coking hazard could be suppressed along the fuel flow channel in both open-circuit and closed-circuit conditions.

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

    SciTech Connect

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

    2000-01-01

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

  15. Arsenic(III) detection using electrochemical-chemical-chemical redox cycling at bare indium-tin oxide electrodes.

    PubMed

    Jeong, Jinkyo; Das, Jagotamoy; Choi, Moonjung; Jo, Jinkyung; Aziz, Md Abdul; Yang, Haesik

    2014-11-21

    Sensitive As(III) detection in ground water is of great importance for evaluating the quality of drinking water. We report a sensitive electrochemical method for As(III) detection based on electrochemical-chemical-chemical (ECC) redox cycling involving Ru(IV) [an oxidized species of Ru(III)(NH3)5NH2(2+)], As(III), and tris(3-carboxyethyl)phosphine (TCEP). Electrochemical oxidation of Ru(III)(NH3)5NH2(2+) formed from Ru(III)(NH3)6(3+) generates Ru(IV), which quickly oxidizes As(III). This electro-mediated oxidation of As(III) produces As(V), which is reduced back to As(III) by TCEP. Electrochemically generated Ru(IV) then reoxidizes As(III), allowing ECC redox cycling to occur at a high rate on bare indium-tin oxide (ITO) electrodes without modifying the surfaces with electrocatalytic materials. Because most interfering metal ions precipitate in a carbonate buffer, water samples are mixed with carbonate buffers prior to electrochemical measurements, rendering the effects of Cu(+), Cu(2+), Fe(2+), Fe(3+), and Pb(2+) insignificant. The detection limit calculated by ECC redox cycling using a chronocoulogram is 1.2 μM, much lower than that obtained using only the electro-mediated oxidation of As(III) (90 μM).

  16. 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.

  17. 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.

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

    PubMed Central

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

    2015-01-01

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

  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

    2015-05-21

    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.

  20. Amplified electrochemical determination of maltol in food based on graphene oxide-wrapped tin oxide@carbon nanospheres.

    PubMed

    Gan, Tian; Sun, Junyong; Yu, Miaomiao; Wang, Kaili; Lv, Zhen; Liu, Yanming

    2017-01-01

    The study presents a new approach for rapid and ultrasensitive detection of maltol using a glassy carbon electrode (GCE) modified with graphene oxide-wrapped tin oxide@carbon nanospheres (SnO2@C@GO). The morphological and components properties of SnO2@C@GO nanocomposites were investigated by means of X-ray diffraction spectroscopy, Raman spectroscopy, field emission scanning electron microscopy, high resolution transmission electron microscopy, and electrochemical impedance spectroscopy. SnO2@C@GO nanocomposite on a GCE had a synergetic effect on the electrochemical oxidation of maltol by means of square wave voltammetry. Under the optimum conditions, anodic peak current response of maltol was linear with its concentration in the range of 80nM-10μM, and a detection limit of 12nM was achieved for maltol. The experiment results presented that the method showed good selectivity, sensitivity, reproducibility, and long-term stability, as well as excellent potential for use as an ideal inexpensive voltammetric method applicable for complex food matrices.

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

    PubMed Central

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

    2014-01-01

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

  2. Redox deposition of nanoscale metal oxides on carbon for next-generation electrochemical capacitors.

    PubMed

    Sassin, Megan B; Chervin, Christopher N; Rolison, Debra R; Long, Jeffrey W

    2013-05-21

    Transition metal oxides that mix electronic and ionic conductivity are essential active components of many electrochemical charge-storage devices, ranging from primary alkaline cells to more advanced rechargeable Li-ion batteries. In these devices, charge storage occurs via cation-insertion/deinsertion mechanisms in conjunction with the reduction/oxidation of metal sites in the oxide. Batteries that incorporate such metal oxides are typically designed for high specific energy, but not necessarily for high specific power. Electrochemical capacitors (ECs), which are typically composed of symmetric high-surface-area carbon electrodes that store charge via double-layer capacitance, deliver their energy in time scales of seconds, but at much lower specific energy than batteries. The fast, reversible faradaic reactions (typically described as "pseudocapacitance") of particular nanoscale metal oxides (e.g., ruthenium and manganese oxides) provide a strategy for bridging the power/energy performance gap between batteries and conventional ECs. These processes enhance charge-storage capacity to boost specific energy, while maintaining the few-second timescale of the charge-discharge response of carbon-based ECs. In this Account, we describe three examples of redox-based deposition of EC-relevant metal oxides (MnO2, FeOx, and RuO2) and discuss their potential deployment in next-generation ECs that use aqueous electrolytes. To extract the maximum pseudocapacitance functionality of metal oxides, one must carefully consider how they are synthesized and subsequently integrated into practical electrode structures. Expressing the metal oxide in a nanoscale form often enhances electrochemical utilization (maximizing specific capacitance) and facilitates high-rate operation for both charge and discharge. The "wiring" of the metal oxide, in terms of both electron and ion transport, when fabricated into a practical electrode architecture, is also a critical design parameter for

  3. 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.

  4. 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.

  5. 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.

  6. Efficient removal of insecticide "imidacloprid" from water by electrochemical advanced oxidation processes.

    PubMed

    Turabik, Meral; Oturan, Nihal; Gözmen, Belgin; Oturan, Mehmet A

    2014-01-01

    The oxidative degradation of imidacloprid (ICP) has been carried out by electrochemical advanced oxidation processes (EAOPs), anodic oxidation, and electro-Fenton, in which hydroxyl radicals are generated electrocatalytically. Carbon-felt cathode and platinum or boron-doped diamond (BDD) anodes were used in electrolysis cell. To determine optimum operating conditions, the effects of applied current and catalyst concentration were investigated. The decay of ICP during the oxidative degradation was well fitted to pseudo-first-order reaction kinetics and absolute rate constant of the oxidation of ICP by hydroxyl radicals was found to be k abs(ICP) = 1.23 × 10(9) L mol(-1) s(-1). The results showed that both anodic oxidation and electro-Fenton process with BDD anode exhibited high mineralization efficiency reaching 91 and 94% total organic carbon (TOC) removal at 2 h, respectively. For Pt-EF process, mineralization efficiency was also obtained as 71%. The degradation products of ICP were identified and a plausible general oxidation mechanism was proposed. Some of the main reaction intermediates such as 6-chloronicotinic acid, 6-chloronicotinaldehyde, and 6-hydroxynicotinic acid were determined by GC-MS analysis. Before complete mineralization, formic, acetic, oxalic, and glyoxylic acids were identified as end-products. The initial chlorine and organic nitrogen present in ICP were found to be converted to inorganic anions Cl(-), NO₃(-), and NH₄(+).

  7. DMS atmospheric concentrations and sulphate aerosol indirect radiative forcing: a sensitivity study to the DMS source representation and oxidation

    NASA Astrophysics Data System (ADS)

    Boucher, O.; Moulin, C.; Belviso, S.; Aumont, O.; Bopp, L.; Cosme, E.; von Kuhlmann, R.; Lawrence, M. G.; Pham, M.; Reddy, M. S.; Sciare, J.; Venkataraman, C.

    2003-01-01

    The global sulphur cycle has been simulated using a general circulation model with a focus on the source and oxidation of atmospheric dimethylsulphide (DMS). The sensitivity of atmospheric DMS to the oceanic DMS climatology, the parameterisation of the sea-air transfer and to the oxidant fields have been studied. The importance of additional oxidation pathways (by O3 in the gas- and aqueous-phases and by BrO in the gas phase) not incorporated in global models has also been evaluated. While three different climatologies of the oceanic DMS concentration produce rather similar global DMS fluxes to the atmosphere at 24-27 Tg S yr -1, there are large differences in the spatial and seasonal distribution. The relative contributions of OH and NO3 radicals to DMS oxidation depends critically on which oxidant fields are prescribed in the model. Oxidation by O3 appears to be significant at high latitudes in both hemispheres. Oxidation by BrO could be significant even for BrO concentrations at sub-pptv levels in the marine boundary layer. The impact of such refinements on the DMS chemistry onto the indirect radiative forcing by anthropogenic sulphate aerosols is also discussed.

  8. Photochemical, electrochemical, and photoelectrochemical water oxidation catalyzed by water-soluble mononuclear ruthenium complexes.

    PubMed

    Li, Ting-Ting; Zhao, Wei-Liang; Chen, Yong; Li, Fu-Min; Wang, Chuan-Jun; Tian, Yong-Hua; Fu, Wen-Fu

    2014-10-20

    Two mononuclear ruthenium complexes [Ru(H2tcbp)(isoq)2] (1) and [Ru(H2tcbp)(pic)2] (2) (H4tcbp=4,4',6,6'-tetracarboxy-2,2'-bipyridine, isoq=isoquinoline, pic=4-picoline) are synthesized and fully characterized. Two spare carboxyl groups on the 4,4'-positions are introduced to enhance the solubility of 1 and 2 in water and to simultaneously allow them to tether to the electrode surface by an ester linkage. The photochemical, electrochemical, and photoelectrochemical water oxidation performance of 1 in neutral aqueous solution is investigated. Under electrochemical conditions, water oxidation is conducted on the deposited indium-tin-oxide anode, and a turnover number higher than 15,000 per water oxidation catalyst (WOC) 1 is obtained during 10 h of electrolysis under 1.42 V vs. NHE, corresponding to a turnover frequency of 0.41 s(-1). The low overpotential (0.17 V) of electrochemical water oxidation for 1 in the homogeneous solution enables water oxidation under visible light by using [Ru(bpy)3](2+) (P1) (bpy=2,2'-bipyridine) or [Ru(bpy)2(4,4'-(COOEt)2-bpy)](2+) (P2) as a photosensitizer. In a three-component system containing 1 or 2 as a light-driven WOC, P1 or P2 as a photosensitizer, and Na2S2O8 or [CoCl(NH3)5]Cl2 as a sacrificial electron acceptor, a high turnover frequency of 0.81 s(-1) and a turnover number of up to 600 for 1 under different catalytic conditions are achieved. In a photoelectrochemical system, the WOC 1 and photosensitizer are immobilized together on the photoanode. The electrons efficiently transfer from the WOC to the photogenerated oxidizing photosensitizer, and a high photocurrent density of 85 μA cm(-2) is obtained by applying 0.3 V bias vs. NHE.

  9. Graphene oxide functionalized with silver nanoparticles as conducting electrodes for solar cells and electrochemical energy storage devices

    NASA Astrophysics Data System (ADS)

    Reddy, Kakarla Raghava; Alonso-Marroquin, Fernando

    2017-06-01

    We present the development of novel electrochemical supercapacitor and sensor based on silver (Ag) nanoparticles coated graphene oxide (GO). 10-20 nm diameter of Ag nanoparticles were well dispersed on the surface of graphene oxide through the chemical reduction method. Ag-coated GO nanohybrids were characterized by transmission electron microscopy (TEM), X-ray diffraction, Raman spectroscopy, electrical and an electrochemical analysis for the energy storage (supercapacitors), energy conversion (solar cells) and sensor applications. It is found that nanohybrid electrodes showed good specific capacitance and electrochemical sensing performance in comparison to pristine GO. The improvement in the electrochemical characteristics can be attributed to the sensitizing effect between Ag nanparticles and GO. These GO/Ag hybrid transparent conducting films also show low resistance and good transmittance, suggesting they are good electrodes for the opto-electronic devices (e.g. solar cells).

  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 175μM, with a detection limit of 39nM, and it is free from common interferences such as uric acid and ascorbic acid. Copyright © 2014 Elsevier B.V. All rights reserved.

  11. Indirect oxidation of the antitumor agent procarbazine by tyrosinase--possible application in designing anti-melanoma prodrugs.

    PubMed

    Gasowska-Bajger, Beata; Wojtasek, Hubert

    2008-06-01

    The interaction of tyrosinase with the anticancer drug procarbazine has been investigated. In the presence of the enzyme alone no oxidation of this dialkylhydrazine above the background level was observed. However, when phenolic substrates (4-tert-butylcatechol or N-acetyl-l-tyrosine) were included in the reaction mixture, procarbazine was rapidly degraded. Oxygen consumption measurements showed that in a mixture both the phenolic substrate and the drug were oxidized. The major product of procarbazine degradation was isolated and identified as azoprocarbazine, the first active metabolite of this drug detected in previous in vivo and in vitro studies. This indirect oxidation of the hydrazine group in this anticancer agent indicates possible application of a hydrazine linker in construction of tyrosinase-activated anti-melanoma prodrugs.

  12. High-performance symmetric electrochemical capacitor based on graphene foam and nanostructured manganese oxide

    NASA Astrophysics Data System (ADS)

    Bello, Abdulhakeem; Fashedemi, Omobosede O.; Lekitima, Joel N.; Fabiane, Mopeli; Dodoo-Arhin, David; Ozoemena, Kenneth I.; Gogotsi, Yury; Charlie Johnson, Alan T.; Manyala, Ncholu

    2013-08-01

    We have fabricated a symmetric electrochemical capacitor with high energy and power densities based on a composite of graphene foam (GF) with ˜80 wt% of manganese oxide (MnO2) deposited by hydrothermal synthesis. Raman spectroscopy and X-ray diffraction measurements showed the presence of nanocrystalline MnO2 on the GF, while scanning and transmission electron microscopies showed needle-like manganese oxide coated and anchored onto the surface of graphene. Electrochemical measurements of the composite electrode gave a specific capacitance of 240 Fg-1 at a current density of 0.1 Ag-1 for symmetric supercapacitors using a two-electrode configuration. A maximum energy density of 8.3 Whkg-1 was obtained, with power density of 20 kWkg-1 and no capacitance loss after 1000 cycles. GF is an excellent support for pseudo-capacitive oxide materials such as MnO2, and the composite electrode provided a high energy density due to a combination of double-layer and redox capacitance mechanisms.

  13. ZnO Nanorods Grown Electrochemically on Different Metal Oxide Underlays

    NASA Astrophysics Data System (ADS)

    Gromyko, I.; Dedova, T.; Krunks, M.; Syritski, V.; Mere, A.; Mikli, V.; Unt, T.; Oja Acik, I.

    2015-03-01

    In this study we present results on electrochemically grown ZnO nanorods on different metal oxide underlays, such as ZnO seed layers with different morphologies, ZnS and TiO2 compact thin films produced by spray pyrolysis on transparent conductive oxide (TCO) substrates. Also in this work we present results on ZnO nanorods directly deposited on some chosen TCO substrates. The relationship between nanorod formation and substrate properties were studied. All ZnO nanorod layers were grown electrochemically using ZnCl2 aqueous solutions (c=0.2 mmol/L) at the bath temperature of 80 °C during one hour. The structural properties and morphology of metal oxide underlays and ZnO nanorods grown on them were studied by scanning electron microscopy (SEM), x-ray diffraction spectroscopy (XRD). Depending on the substrate morphology, ZnO rods with different dimension, orientation, shape and density were obtained. For instance, larger rods (d~200 nm, l~700 nm) were obtained on substrates, such as ITO/glass, FTO/glass and ZnO:In/ITO/glass. Smaller rods (d~60 nm, l~350 nm) were obtained on smooth, uniform and fine-grained underlays, such as ZnS and TiO2.

  14. Electrochemical oxidation of the polycyclic aromatic hydrocarbons in polluted concrete of the residential buildings.

    PubMed

    Aćimović, Danka D; Karić, Slavko D; Nikolić, Željka M; Brdarić, Tanja P; Tasić, Gvozden S; Marčeta Kaninski, Milica P; Nikolić, Vladimir M

    2017-01-01

    Polycyclic aromatic hydrocarbons (PAH) have been listed by the United States Environmental Protection Agency (US EPA) and by the European Community as priority environmental pollutants. The removal of PAHs from soils, sediments and waste water has attracted attention of scientists and engineers for several decades. Electrochemical oxidation of PAH compounds in water, is receiving increasing attention, due to its convenience and simplicity. In this study we performed electrochemical oxidation of 16 EPA PAHs mixture in 10% NaCl aqueous solution in potentiostatic conditions, at voltage 1 V. Decrease of concentration of some individual PAHs, up to 70% referred to their starting concentration, after 60 min of electrolysis, was confirmed by UPLC/PDA analysis. In further work investigation was extrapolated to in situ removal of PAHs from concrete, as the medium where, to our knowledge, such way of PAH removal has not been investigated before. High concentrations of PAH contamination occurred in the concrete structure of the residential buildings in Belgrade in 2014. Application of DC voltage of 50 V between nickel and stainless steel electrodes packed in the concrete wall, moisturized with the 10% NaCl solution, led to considerable removal of the pollutants by oxidation process throughout the concrete. Copyright © 2016 Elsevier Ltd. All rights reserved.

  15. Retarding of electrochemical oxidation of formate on the platinum anode by a coat of Nafion membrane

    NASA Astrophysics Data System (ADS)

    Zhang, Rui; Lv, Weixin; Li, Guanghua; Mezaal, Mohammed Adnan; Li, Xiaojing; Lei, Lixu

    2014-12-01

    It has been found that the faradaic efficiency is decreasing with the electrolysis time for electrochemical reduction of CO2 to formate on a Sn cathode with a Pt anode in an undivided electrolytic cell, because the oxidation of formed formate takes place on the Pt anode, which also limits seriously the highest concentration of formate in the system. Here, we report that a coat of Nafion membrane on the Pt anode can retard the oxidation of formate: even if the concentration of the formate in the electrolyte reaches to 0.12 mol L-1, the faradaic efficiency still maintains above 61.3%; in contrast, the oxidation reaction of the formate on the naked Pt electrode is very fast, when the concentration of the formate in the electrolyte reaches to 0.023 mol L-1, the faradaic efficiency decreases to 35.3%. This is very important because the separation of formic acid could not be economical when its concentration is not high enough, and it is also costly if the depleted solution allows too less of its concentration because the solution has to be reused in the electrochemical process.

  16. Label-free detection of telomerase activity using guanine electrochemical oxidation signal.

    PubMed

    Eskiocak, Ugur; Ozkan-Ariksoysal, Dilsat; Ozsoz, Mehmet; Oktem, Huseyin Avni

    2007-11-15

    Telomerase is an important biomarker for cancer cells and its activation in 85% of all cancer types confers a clinical diagnostic value. A label-free electrochemical assay based on guanine oxidation signal to measure telomerase activity is described. This developed technology combined with a disposable sensor, carbon graphite electrode (CGE), and differential pulse voltammetry (DPV) was performed by using PCR amplicons with/without telomeric repeats as the guanine oxidation signal observed at +1.0 V measured after the immobilization of PCR products. Guanine oxidation signal was chosen as a measure of telomerase activity because a substantial increase in the number of guanines was introduced by the action of telomerase which adds hexameric repeats (TTAGGG)n that contain 50% guanine. The developed assay was shown to specifically measure telomerase activity from cell extracts, and elongation rates increased linearly in a concentration dependent manner. Telomerase activity could be detected in cell extracts containing as low as 100 ng/microL of protein. All of the electrochemical measurements were also confirmed with the conventional TRAP-silver staining assay. Rapidity, simplicity, and the label-free nature of the developed assay make it suitable for practical use in quantitative determination of telomerase activity from clinical samples for diagnosis of cancer.

  17. Mechanistic Study of the Validity of Using Hydroxyl Radical Probes To Characterize Electrochemical Advanced Oxidation Processes.

    PubMed

    Jing, Yin; Chaplin, Brian P

    2017-02-21

    The detection of hydroxyl radicals (OH(•)) is typically accomplished by using reactive probe molecules, but prior studies have not thoroughly investigated the suitability of these probes for use in electrochemical advanced oxidation processes (EAOPs), due to the neglect of alternative reaction mechanisms. In this study, we investigated the suitability of four OH(•) probes (coumarin, p-chlorobenzoic acid, terephthalic acid, and p-benzoquinone) for use in EAOPs. Experimental results indicated that both coumarin and p-chlorobenzoic acid are oxidized via direct electron transfer reactions, while p-benzoquinone and terephthalic acid are not. Coumarin oxidation to form the OH(•) adduct product 7-hydroxycoumarin was found at anodic potentials lower than that necessary for OH(•) formation. Density functional theory (DFT) simulations found a thermodynamically favorable and non-OH(•) mediated pathway for 7-hydroxycoumarin formation, which is activationless at anodic potentials > 2.10 V/SHE. DFT simulations also provided estimates of E° values for a series of OH(•) probe compounds, which agreed with voltammetry results. Results from this study indicated that terephthalic acid is the most appropriate OH(•) probe compound for the characterization of electrochemical and catalytic systems.

  18. Electrochemically Formed Ultrafine Metal Oxide Nanocatalysts for High-Performance Lithium–Oxygen Batteries

    SciTech Connect

    Liu, Bin; Yan, Pengfei; Xu, Wu; Zheng, Jianming; He, Yang; Luo, Langli; Bowden, Mark E.; Wang, Chong-Min; Zhang, Ji-Guang

    2016-08-10

    Lithium-oxygen (Li-O2) battery has an extremely high theoretical specific energy density as compared with conventional energy storage systems. However, practical application of Li-O2 battery system still faces significant challenges, especially its poor cyclability. In this work, we report a new approach to synthesis ultrafine metal oxide nanocatalysts through an electrochemical pre-lithiation process. This process reduces the size of NiCo2O4 (NCO) particles from 20~30 nm to a uniformly distributed domain of ~ 2 nm and largely improved their catalytic activity. Structurally, the pre-lithiated NCO NWs are featured by ultrafine NiO/CoO nanoparticles, which show high stability during prolonged cycles in terms of morphology and the particle size, therefore maintaining an excellent catalytic effect to oxygen reduction and evolution reactions. Li-O2 battery using this catalyst has demonstrated an initial capacity of 29,280 mAh g-1 and has retained a stable capacity of over 1,000 mAh g-1 after 100 cycles based on the weight of NCO active material. Direct in-situ TEM observation conclusively reveals the lithiation/delithiation process of as-prepared NCO NWs, clarifying the NCO/Li electrochemical reaction mechanism that can be extended to other transition-metal oxides and providing the in depth understandings on the catalysts and battery chemistries of other ternary transition-metal oxides.

  19. Electrochemical determination of estradiol using a thin film containing reduced graphene oxide and dihexadecylphosphate.

    PubMed

    Janegitz, Bruno C; dos Santos, Fabrício A; Faria, Ronaldo C; Zucolotto, Valtencir

    2014-04-01

    Graphene is a material that has attracted attention with regard to sensing and biosensing applications in recent years. Here, we report a novel treatment (using ultrasonic bath and ultrasonic tip) to obtain graphene oxide (GO) and a new stable conducting film using reduced graphene oxide (RGO) and dihexadecylphosphate film (DHP). The GO was obtained by chemical exfoliation and it was reduced using NaBH4. Subsequently, RGO-DHP dispersion was prepared and it was dropped onto a glassy carbon electrode by casting technique. The electrode was characterized by cyclic voltammetry and electrochemical spectroscopy impedance. The voltammetric behavior of the RGO-DHP/GC electrode in the presence of estradiol was studied, and the results reported an irreversible oxidation peak current at 0.6V. Under the optimal experimental conditions, using linear sweep adsorptive stripping voltammetry, the detection limit obtained for this hormone was 7.7×10(-8)mol L(-1). The proposed electrode can be attractive for applications as electrochemical sensors and biosensors.

  20. Influence of laser-generated surface structures on electrochemical performance of lithium cobalt oxide

    NASA Astrophysics Data System (ADS)

    Kohler, R.; Proell, J.; Ulrich, S.; Przybylski, M.; Seifert, H. J.; Pfleging, W.

    2012-03-01

    The further development of energy storage devices especially of lithium-ion batteries plays an important role in the ongoing miniaturization process towards lightweight, flexible mobile devices. To improve mechanical stability and to increase the power density of electrode materials while maintaining the same footprint area, a three-dimensional battery design is necessary. In this study different designs of three-dimensional cathode materials are investigated with respect to the electrochemical performance. Lithium cobalt oxide is considered as a standard cathode material, since it has been in use since the first commercialization of lithium-ion batteries. Various electrode designs were manufactured in lithium cobalt oxide electrodes via laser micro-structuring. Laser ablation experiments in ambient air were performed to obtain hierarchical and high aspect surface structures. Laser structuring using mask techniques as well as the formation of self-organized conical surface structures were studied in detail. In the latter case a density of larger than twenty million microstructures per square centimeter was obtained with a significant increase of active surface area. Laser annealing was applied for the control of the average grain size and the adjustment of a crystalline phase which exhibits electrochemical capacities in the range of the practical capacity known for lithium cobalt oxide. An investigation of cycling stability with respect to annealing parameters such as annealing time and temperature was performed using a diode laser operating at 940 nm. Information on the phase and crystalline structure were obtained using Raman spectroscopy and X-ray diffraction analysis. The electrochemical performance of the laser modified cathodes was studied via cyclic voltammetry and galvanostatic testing using a lithium anode and a standard liquid electrolyte.

  1. Electrochemical oxidation of cisatracurium on carbon paste electrode and its analytical applications.

    PubMed

    Torres, R F; Mochón, M C; Sánchez, J C; Bello López, M A; Pérez, A G

    2001-03-16

    The electrochemical oxidation of cisatracurium was investigated by cyclic voltammetry and differential pulse voltammetry at a carbon paste electrode and the experimental parameters have been optimized in order to obtain the optimum analytical signal. A differential pulse voltammetric method with carbon paste electrode is described for the determination of cisatracurium with detection limit of 0.38 mug/ml and quantitation limit of 1.26 mug/ml. The proposed method was applied to determine the content of cisatracurium in human urine and human serum, obtaining accurate and precise results.

  2. 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.

  3. Dynamic electrochemical investigations of hydrogen oxidation and production by enzymes and implications for future technology.

    PubMed

    Armstrong, Fraser A; Belsey, Natalie A; Cracknell, James A; Goldet, Gabrielle; Parkin, Alison; Reisner, Erwin; Vincent, Kylie A; Wait, Annemarie F

    2009-01-01

    This tutorial review describes studies of hydrogen production and oxidation by biological catalysts--metalloenzymes known as hydrogenases--attached to electrodes. It explains how the electrocatalytic properties of hydrogenases are studied using specialised electrochemical techniques and how the data are interpreted to allow assessments of catalytic rates and performance under different conditions, including the presence of O2, CO and H2S. It concludes by drawing some comparisons between the enzyme active sites and platinum catalysts and describing some novel proof-of-concept applications that demonstrate the high activities and selectivities of these 'alternative' catalysts for promoting H2 as a fuel.

  4. Electrochemical behavior and voltammetric determination of acetaminophen based on glassy carbon electrodes modified with poly(4-aminobenzoic acid)/electrochemically reduced graphene oxide composite films.

    PubMed

    Zhu, Wencai; Huang, Hui; Gao, Xiaochun; Ma, Houyi

    2014-12-01

    Poly(4-aminobenzoic acid)/electrochemically reduced graphene oxide composite film modified glassy carbon electrodes (4-ABA/ERGO/GCEs) were fabricated by a two-step electrochemical method. The electrochemical behavior of acetaminophen at the modified electrode was investigated by means of cyclic voltammetry. The results indicated that 4-ABA/ERGO composite films possessed excellent electrocatalytic activity towards the oxidation of acetaminophen. The electrochemical reaction of acetaminophen at 4-ABA/ERGO/GCE is proved to be a surface-controlled process involving the same number of protons and electrons. The voltammetric determination of acetaminophen performed with the 4-ABA/ERGO modified electrode presents a good linearity in the range of 0.1-65 μM with a low detection limit of 0.01 μM (S/N=3). In the case of using the 4-ABA/ERGO/GCE, acetaminophen and dopamine can be simultaneously determined without mutual interference. Furthermore, the 4-ABA/ERGO/GCE has good reproducibility and stability, and can be used to determine acetaminophen in tablets.

  5. Electrochemically reduced graphene oxide-based electrochemical sensor for the sensitive determination of ferulic acid in A. sinensis and biological samples.

    PubMed

    Liu, Linjie; Gou, Yuqiang; Gao, Xia; Zhang, Pei; Chen, Wenxia; Feng, Shilan; Hu, Fangdi; Li, Yingdong

    2014-09-01

    An electrochemically reduced graphene oxide (ERGO) modified glassy carbon electrode (GCE) was used as a new voltammetric sensor for the determination of ferulic acid (FA). The morphology and microstructure of the modified electrodes were characterized by scanning electron microscopy (SEM) and Raman spectroscopy analysis, and the electrochemical effective surface areas of the modified electrodes were also calculated by chronocoulometry method. Sensing properties of the electrochemical sensor were investigated by means of cyclic voltammetry (CV) and differential pulse voltammetry (DPV). It was found that ERGO was electrodeposited on the surface of GCE by using potentiostatic method. The proposed electrode exhibited electrocatalytic activity to the redox of FA because of excellent electrochemical properties of ERGO. The transfer electron number (n), electrode reaction rate constant (ks) and electron-transfer coefficient (α) were calculated as 1.12, 1.24s(-1), and 0.40, respectively. Under the optimized conditions, the oxidation peak current was proportional to FA concentration at 8.49 × 10(-8)mol L(-1) to 3.89 × 10(-5)mol L(-1) with detection limit of 2.06 × 10(-8)mol L(-1). This fabricated sensor also displayed acceptable reproducibility, long-term stability, and high selectivity with negligible interferences from common interfering species. The voltammetric sensor was successfully applied to detect FA in A. sinensis and biological samples with recovery values in the range of 99.91%-101.91%.

  6. A study of the characteristics of indium tin oxide after chlorine electro-chemical treatment

    SciTech Connect

    Kim, Moonsoo; Kim, Jongmin; Cho, Jaehee; Kim, Hyunwoo; Lee, Nayoung; Choi, Byoungdeog

    2016-10-15

    Graphical abstract: The presence of Chlorine in the outer surface resulted in a highly electro-negative surface states and an increase in the vacuum energy level. - Highlights: • We investigated the influence of chlorine surface treatment on ITO properties. • Chlorination induced the change of the electro-static potential in the outer surface. • Chlorine electro-chemical treatment of ITO is a simple, fast and effective technique. - Abstract: In this work, we investigate the influence of a chlorine-based electro-chemical surface treatment on the characteristics of indium tin oxide (ITO) including the work function, chemical composition, and phase transition. The treated ITOs were characterized using X-ray photoelectron spectroscopy (XPS), ultra-violet photoelectron spectroscopy (UPS), 4-point probe measurements, and grazing incidence X-ray diffraction (GI-XRD). We confirmed a change of the chemical composition in the near-surface region of the ITO and the formation of indium-chlorine (In-Cl) bonds and surface dipoles (via XPS). In particular, the change of the electro-static potential in the outer surface was caused by chlorination. Due to the vacuum-level shift after the electro-chemical treatment in a dilute hydrochloric acid, the ITO work function was increased by ∼0.43 eV (via UPS); furthermore, the electro-negativity of the chlorine anions attracted electrons to emit them from the hole transport layer (HTL) to the ITO anodes, resulting in an increase of the hole-injection efficiency.

  7. Electrochemical Oxidation of EDTA in Nuclear Wastewater Using Platinum Supported on Activated Carbon Fibers

    PubMed Central

    Zhao, Bo; Zhu, Wenkun; Mu, Tao; Hu, Zuowen; Duan, Tao

    2017-01-01

    A novel Pt/ACF (Pt supported on activated carbon fibers) electrode was successfully prepared with impregnation and electrodeposition method. Characterization of the electrodes indicated that the Pt/ACF electrode had a larger effective area and more active sites. Electrochemical degradation of ethylenediaminetetra-acetic acid (EDTA) in aqueous solution with Pt/ACF electrodes was investigated. The results showed that the 3% Pt/ACF electrode had a better effect on EDTA removal. The operational parameters influencing the electrochemical degradation of EDTA with 3% Pt/ACF electrode were optimized and the optimal removal of EDTA and chemical oxygen demand (COD) were 94% and 60% after 100 min on condition of the electrolyte concentration, initial concentration of EDTA, current density and initial value of pH were 0.1 mol/L, 300 mg/L, 40 mA/cm2 and 5.0, respectively. The degradation intermediates of EDTA in electrochemical oxidation with 3% Pt/ACF electrode were identified by gas chromatography-mass spectrum (GC-MS). PMID:28754016

  8. Effect of morphology and defect density on electron transfer of electrochemically reduced graphene oxide

    NASA Astrophysics Data System (ADS)

    Zhang, Yan; Hao, Huilian; Wang, Linlin

    2016-12-01

    Electrochemically reduced graphene oxide (ERGO) is widely used to construct electrochemical sensors. Understanding the electron transfer behavior of ERGO is essential for its electrode material applications. In this paper, different morphologies of ERGO were prepared via two different methods. Compared to ERGO/GCEs prepared by electrochemical reduction of pre-deposited GO, more exposed edge planes of ERGO are observed on the surface of ERGO-GCE that was constructed by electrophoretic deposition of GO. The defect densities of ERGO were controlled by tuning the mass or concentration of GO. The electron transfer kinetics (k0) of GCE with different ERGOs was comparatively investigated. Owing to increased surface areas and decreased defect density, the k0 values of ERGO/GCE initially increase and then decrease with incrementing of GO mass. When the morphology and surface real areas of ERGO-GCE are the same, an increased defect density induces an accelerated electron transfer rate. k0 valuesof ERGO-GCEs are about 1 order of magnitude higher than those of ERGO/GCEs due to the difference in the amount of edge planes. This work demonstrates that both defect densities and edge planes of ERGO play crucial roles in electron transfer kinetics.

  9. Zinc oxide nanowires-based electrochemical biosensor for L-lactic acid amperometric detection

    NASA Astrophysics Data System (ADS)

    Zhao, Yanguang; Yan, Xiaoqin; Kang, Zhuo; Fang, Xiaofei; Zheng, Xin; Zhao, Lanqing; Du, Hongwu; Zhang, Yue

    2014-05-01

    In this work, zinc oxide (ZnO) nanowires-based electrochemical biosensor is designed and fabricated for the detection of L-lactic acid. ZnO nanowires were successfully synthesized via the chemical vapor deposition method. The morphology and structure of the prepared products were characterized, and the average diameter of synthesized ZnO samples was 500 nm. The fluorescence characterization was performed to verify the immobilization of lactate oxidase onto the ZnO surface. Biosensors based on large-area ZnO nanowires were then constructed, and a series of electrochemical experiments showed that ZnO could provide the efficient electron transfer channel between the enzymic active sites and the electrode surface. The proposed electrochemical biosensor exhibited a sensitivity of 15.6 µA cm-2 mM-1, a wide linear range of 12 µM-1.2 mM with a low-detection limit of 12 µM for L-lactic acid detection. This study has indicated the potential applications for ZnO nanowires to construct the simple and economic nano-bio devices for the detection of biological species.

  10. Graphene oxide sheet-mediated silver enhancement for application to electrochemical biosensors.

    PubMed

    Wan, Yi; Wang, Yi; Wu, Jiajia; Zhang, Dun

    2011-02-01

    Functionalized graphene oxide (GO) sheets coupled with a signal amplification method based on the nanomaterial-promoted reduction of silver ions for the sensitive and selective detection of bacteria. This paper aims to develop an electrochemical route combined with GO sheet-mediated Ag enhancement for biological/chemical analyte detection. A linear relationship between the stripping response and the logarithm of the bacterial concentration was obtained using an electrochemical technique for concentrations ranging from 1.8 × 10(2) to 1.8 × 10(8) cfu mL(-1), with a slope of 15.28 and a correlation coefficient of 0.995. Dot blot assay was used as a conventional immunoassay method for comparison with the electrochemical method, as well as to observe the quality of the anti-sulfate-reducing bacteria (SRB) antibody (Ab) used in the immunosensor. The GO sheet-mediated silver enhancement holds great potential for the rapid analysis of protein, DNA, and pathogens.

  11. Rapid online nonenzymatic protein digestion combining microwave heating acid hydrolysis and electrochemical oxidation.

    PubMed

    Basile, Franco; Hauser, Nicolas

    2011-01-01

    We report an online nonenzymatic method for site-specific digestion of proteins to yield peptides that are well suited for collision-induced dissociation tandem mass spectrometry. The method combines online microwave heating acid hydrolysis at aspartic acid and online electrochemical oxidation at tryptophan and tyrosine. The combined microwave/electrochemical digestion is reproducible and produces peptides with an average sequence length of 10 amino acids. This peptide length is similar to the average peptide length of 9 amino acids obtained by digestion of proteins with the enzyme trypsin. As a result, the peptides produced by this novel nonenzymatic digestion method, when analyzed by electrospray ionization mass spectrometry, produce protonated molecules with mostly +1 and +2 charge states. The combination of these two nonenzymatic methods overcomes shortcomings with each individual method in that (i) peptides generated by the microwave-hydrolysis method have an average amino acid length of 16 amino acids and (ii) the electrochemical-cleavage method is unable to reproducibly digest proteins with molecular masses above 4 kDa. Preliminary results are presented on the application and utility of this rapid online digestion (total of 6 min of digestion time) on a series of standard peptides and proteins as well as an Escherichia coli protein extract.

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

    PubMed

    López-Grimau, V; Gutiérrez, M C

    2006-01-01

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

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

    PubMed

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

    2015-12-30

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

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

    NASA Astrophysics Data System (ADS)

    Gao, F.; Liang, Hong

    2012-03-01

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

  15. Mechanism of enhanced removal of quinonic intermediates during electrochemical oxidation of Orange II under ultraviolet irradiation.

    PubMed

    Li, Fazhan; Li, Guoting; Zhang, Xiwang

    2014-03-01

    The effect of ultraviolet irradiation on generation of radicals and formation of intermediates was investigated in electrochemical oxidation of the azo-dye Orange II using a TiO2-modified β-PbO2 electrode. It was found that a characteristic absorbance of quinonic compounds at 255 nm, which is responsible for the rate-determining step during aromatics degradation, was formed only in electrocatalytic oxidation. The dye can be oxidized by either HO radicals or direct electron transfer. Quinonic compounds were produced concurrently. The removal of TOC by photo-assisted electrocatalytic oxidation was 1.56 times that of the sum of the other two processes, indicating a significant synergetic effect. In addition, once the ultraviolet irradiation was introduced into the process of electrocatalytic oxidation, the degradation rate of quinonic compounds was enhanced by as much as a factor of two. The more efficient generation of HO radicals resulted from the introduction of ultraviolet irradiation in electrocatalytic oxidation led to the significant synergetic effect as well as the inhibiting effect on the accumulation of quinonic compounds.

  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-H2O2

  17. Electrochemical study on the adsorption of carbon oxides and oxidation of their adsorption products on platinum group metals and alloys.

    PubMed

    Siwek, Hanna; Lukaszewski, Mariusz; Czerwiński, Andrzej

    2008-07-07

    CO(2) reduction and CO adsorption on noble metals (Pt, Rh, Pd) and their alloys (Pt-Rh, Pd-Pt, Pd-Rh, Pd-Pt-Rh) prepared as thin rough deposits have been studied by chronoamperometry (CA), cyclic voltammetry (CV) and the electrochemical quartz crystal microbalance (EQCM). The influence of alloy surface composition on the values of surface coverage, eps (electron per site) and potential of the oxidation of CO(2) reduction and CO adsorption products is shown. The oxidation of the adsorbate on Pt-Rh alloys proceeds more easily (at lower potentials) than on pure metals. On the other hand, in the case of Pd-Pt and Pd-Rh alloys the adsorbate oxidation is more difficult and requires higher potentials than on Pt or Rh. The analysis of the EQCM signal is presented for the case of adsorption and oxidation of carbon oxide adsorption products on the electrodes studied. The comparison of adsorption parameters and the EQCM response obtained for platinum group metals and alloys leads to the conclusion that reduced CO(2) cannot be totally identified with adsorbed CO.

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

    PubMed

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

    2014-06-01

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

  19. Stabilization of ultrathin (hydroxy)oxide films on transition metal substrates for electrochemical energy conversion

    NASA Astrophysics Data System (ADS)

    Zeng, Zhenhua; Chang, Kee-Chul; Kubal, Joseph; Markovic, Nenad M.; Greeley, Jeffrey

    2017-06-01

    Design of cost-effective electrocatalysts with enhanced stability and activity is of paramount importance for the next generation of energy conversion systems, including fuel cells and electrolysers. However, electrocatalytic materials generally improve one of these properties at the expense of the other. Here, using density functional theory calculations and electrochemical surface science measurements, we explore atomic-level features of ultrathin (hydroxy)oxide films on transition metal substrates and demonstrate that these films exhibit both excellent stability and activity for electrocatalytic applications. The films adopt structures with stabilities that significantly exceed bulk Pourbaix limits, including stoichiometries not found in bulk and properties that are tunable by controlling voltage, film composition, and substrate identity. Using nickel (hydroxy)oxide/Pt(111) as an example, we further show how the films enhance activity for hydrogen evolution through a bifunctional effect. The results suggest design principles for this class of electrocatalysts with simultaneously enhanced stability and activity for energy conversion.

  20. Electrochemical performance of Ag nanoparticle decorated reduced graphene oxide in determination of anticancer drug flutamide

    NASA Astrophysics Data System (ADS)

    Banerjee, Sanchari; Mondal, Shrabani; Madhuri, Rashmi; Sharma, Prashant K.

    2017-05-01

    Ag nanoparticle decorated reduced graphene oxide (rGO-Ag) have been synthesized successfully by simultaneously reducing graphene oxide and AgNO3 with hydrazine hydrate as reducing agent. The synthesized rGO-Ag has been characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and fourier transformed infrared (FTIR) spectroscopy to study the structural properties and finally utilized for the electrochemical detection of anti-cancer drug flutamide (FLT). The prominent peak at the position of around 0.07 V is observed in the voltammogram which indicates the catalytic reduction of NO2 group of FLT by rGO-Ag. The fabricated sensor posses a linear detection range of 0.1 to 0.3 mM with a detection limit as low as 1.16 μM.

  1. Electrochemical synthesis of birnessite-type layered manganese oxides for rechargeable lithium batteries

    NASA Astrophysics Data System (ADS)

    Nakayama, Masaharu; Kanaya, Taku; Lee, Jong-Won; Popov, Branko N.

    Layered manganese dioxide (MnO 2) films intercalated with Li +, Na + or Mg 2+ ions were synthesized by a one-step electrochemical method. The electrodeposition was potentiostatically performed by applying an anodic potential of 1.0 V vs. Ag/AgCl in an aqueous MnSO 4 solution containing a perchlorate salt of the cation. The electrodeposited oxide films have a birnessite-type layered structure with alkali cations and water molecules between manganese oxide layers. The galvanostatic charge-discharge experiments performed in 1 M LiPF 6-DME/PC solution indicated that the Mg 2+-intercalated MnO 2 electrode exhibits an initial discharge capacity as large as 140 mAh g -1 and it shows a better capacity retention during cycling as compared with the Li +- or Na +-intercalated MnO 2 electrode.

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

    PubMed Central

    2014-01-01

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

  3. 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.

  4. Advanced treatment of wet-spun acrylic fiber manufacturing wastewater using three-dimensional electrochemical oxidation.

    PubMed

    Zheng, Tianlong; Wang, Qunhui; Shi, Zhining; Fang, Yue; Shi, Shanshan; Wang, Juan; Wu, Chuanfu

    2016-12-01

    A three-dimensional electrochemical oxidation (3D-EC) reactor with introduction of activated carbon (AC) as particle micro-electrodes was applied for the advanced treatment of secondary wastewater effluent of a wet-spun acrylic fiber manufacturing plant. Under the optimized conditions (current density of 500A/m(2), circulation rate of 5mL/min, AC dosage of 50g, and chloride concentration of 1.0g/L), the average removal efficiencies of chemical oxygen demand (CODcr), NH3-N, total organic carbon (TOC), and ultraviolet absorption at 254nm (UV254) of the 3D-EC reactor were 64.5%, 60.8%, 46.4%, and 64.8%, respectively; while the corresponding effluent concentrations of CODcr, NH3-N, TOC, and UV254 were 76.6, 20.1, and 42.5mg/L, and 0.08Abs/cm, respectively. The effluent concentration of CODcr was less than 100mg/L, which showed that the treated wastewater satisfied the demand of the integrated wastewater discharge standard (GB 8978-1996). The 3D-EC process remarkably improved the treatment efficiencies with synergistic effects for CODcr, NH3-N, TOC, and UV254 during the stable stage of 44.5%, 38.8%, 27.2%, and 10.9%, respectively, as compared with the sum of the efficiencies of a two-dimensional electrochemical oxidation (2D-EC) reactor and an AC adsorption process, which was ascribed to the numerous micro-electrodes of AC in the 3D-EC reactor. Gas chromatography mass spectrometry (GC-MS) analysis revealed that electrochemical treatment did not generate more toxic organics, and it was proved that the increase in acute biotoxicity was caused primarily by the production of free chlorine.

  5. 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.

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

    DOEpatents

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

    1994-01-01

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

  7. Temperature effect on electrochemical promotion of syngas cogeneration in direct-methane solid oxide fuel cells

    NASA Astrophysics Data System (ADS)

    Huang, Ta-Jen; Huang, Meng-Chin

    Syngas cogeneration in direct-methane solid oxide fuel cells with Ni-yttria-stabilized zirconia (YSZ) anodes was studied with temperature varying from 700 to 900 °C. A phenomenon of electrochemical promotion of bulk lattice-oxygen extraction from the YSZ electrolyte was observed. With increasing temperature, this promotion effect increases while both the rate enhancement ratios of CO and CO 2 formations decrease. The activation energy of CO and CO 2 formation under close circuit is lower than that under open circuit. The activation energy for the lattice-oxygen extraction from the YSZ bulk is higher than that for the oxygen transport through the YSZ bulk. The process of lattice-oxygen extraction from YSZ is rate determining in direct-methane oxidation under the condition of either close circuit or open circuit. The dependence of CO formation rate on the oxygen supply rate is stronger than that of CO 2 formation rate. Electrochemical promotion of bulk lattice-oxygen extraction enhances syngas cogeneration.

  8. Hydrogen production aided solid oxide electrochemical reformer fed with octane: A theoretical analysis

    NASA Astrophysics Data System (ADS)

    Murashkina, A. A.; Maragou, V. I.; Demin, A. K.; Pikalova, E. Yu.; Tsiakaras, P. E.

    In the present work the possibility of pure hydrogen production by a solid oxide electrochemical reformer (SOER) is examined. Initial reagents are water steam, flowing into the cathode channel and octane flowing into the anode channel. Three modes of reforming are considered: (i) steam reforming (SR-mode), (ii) preliminary octane partial oxidation (PO-mode) and (iii) preliminary octane reforming by exhaust anode gas recycling (EAGR-mode). A parametric analysis is carried out that can be easily applied for various hydrocarbons. It was found that the electromotive force (EMF) value depends mainly on the ratio of steam moles' number supplied to the cathode space to the number of hydrogen output moles (k-parameter). It was also found that EMF increases with k increase, while is weakly affected from the temperature and the heat losses amount. Moreover, the EMF average value under the PO-mode is lower than that under the SR-mode. Finally, it is shown that the SOER optimum characteristics can be reached under the EAGR-mode, since it provides the most favorable combination of the reforming efficiency and the rate of the electrochemical process.

  9. 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. Copyright (c) 2009 Elsevier Ltd. All rights reserved.

  10. Amine functionalized graphene oxide/CNT nanocomposite for ultrasensitive electrochemical detection of trinitrotoluene.

    PubMed

    Sablok, Kavita; Bhalla, Vijayender; Sharma, Priyanka; Kaushal, Roohi; Chaudhary, Shilpa; Suri, C Raman

    2013-03-15

    Binding of electron-deficient trinitrotoluene (TNT) to the electron rich amine groups on a substrate form specific charge-transfer Jackson-Meisenheimer (JM) complex. In the present work, we report formation of specific JM complex on amine functionalized reduced graphene oxide/carbon nanotubes- (a-rGO/CNT) nanocomposite leading to sensitive detection of TNT. The CNT were dispersed using graphene oxide that provides excellent dispersion by attaching to CNT through its hydrophobic domains and solubilizes through the available OH and COOH groups on screen printed electrode (SPE). The GO was reduced electrochemically to form reduced graphene that remarkably increases electrochemical properties owing to the intercalation of high aspect CNT on graphene flakes as shown by TEM micrograph. The surface amine functionalization of dropcasted and rGO/CNT was carried out using a bi-functional cross linker ethylenediamine. The extent of amine functionalization on modified electrodes was confirmed using energy dispersive X-ray (EDX), X-ray photoelectron spectroscopy (XPS) and confocal microscopy. The FTIR and Raman spectra further suggested the formation of JM complex between amine functionalized electrodes and TNT leading to a shift in peak intensity together with peak broadening. The a-rGO/CNT nanocomposite prepared electrode surface leads to ultra-trace detection of TNT upto 0.01 ppb with good reproducibility (n=3). The a-rGO/CNT sensing platform could be an alternate for sensitive detection of TNT explosive for various security and environmental applications.

  11. Electrochemically Formed Ultrafine Metal Oxide Nanocatalysts for High-Performance Lithium-Oxygen Batteries.

    PubMed

    Liu, Bin; Yan, Pengfei; Xu, Wu; Zheng, Jianming; He, Yang; Luo, Langli; Bowden, Mark E; Wang, Chong-Min; Zhang, Ji-Guang

    2016-08-10

    Lithium-oxygen (Li-O2) batteries have an extremely high theoretical specific energy density when compared with conventional energy-storage systems. However, practical application of the Li-O2 battery system still faces significant challenges. In this work, we report a new approach for synthesis of ultrafine metal oxide nanocatalysts through an electrochemical prelithiation process. This process reduces the size of NiCo2O4 (NCO) particles from 20-30 nm to a uniformly distributed domain of ∼2 nm and significantly improves their catalytic activity. Structurally, the prelithiated NCO nanowires feature ultrafine NiO/CoO nanoparticles that are highly stable during prolonged cycles in terms of morphology and particle size, thus maintaining an excellent catalytic effect to oxygen reduction and evolution reactions. A Li-O2 battery using this catalyst demonstrated an initial capacity of 29 280 mAh g(-1) and retained a capacity of >1000 mAh g(-1) after 100 cycles based on the weight of the NCO active material. Direct in situ transmission electron microscopy observations conclusively revealed the lithiation/delithiation process of as-prepared NCO nanowires and provided in-depth understanding for both catalyst and battery chemistries of transition-metal oxides. This unique electrochemical approach could also be used to form ultrafine nanoparticles of a broad range of materials for catalyst and other applications.

  12. High-throughput synthesis and electrochemical screening of a library of modified electrodes for NADH oxidation.

    PubMed

    Pinczewska, Aleksandra; Sosna, Maciej; Bloodworth, Sally; Kilburn, Jeremy D; Bartlett, Philip N

    2012-10-31

    We report the combinatorial preparation and high-throughput screening of a library of modified electrodes designed to catalyze the oxidation of NADH. Sixty glassy carbon electrodes were covalently modified with ruthenium(II) or zinc(II) complexes bearing the redox active 1,10-phenanthroline-5,6-dione (phendione) ligand by electrochemical functionalization using one of four different linkers, followed by attachment of one of five different phendione metal complexes using combinatorial solid-phase synthesis methodology. This gave a library with three replicates of each of 20 different electrode modifications. This library was electrochemically screened in high-throughput (HTP) mode using cyclic voltammetry. The members of the library were evaluated with regard to the surface coverage, midpeak potential, and voltammetric peak separation for the phendione ligand, and their catalytic activity toward NADH oxidation. The surface coverage was found to depend on the length and flexibility of the linker and the geometry of the metal complex. The choices of linker and metal complex were also found to have significant impact on the kinetics of the reaction between the 1,10-phenanthroline-5,6-dione ligand and NADH. The rate constants for the reaction were obtained by analyzing the catalytic currents as a function of NADH concentration and scan rate, and the influence of the surface molecular architecture on the kinetics was evaluated.

  13. Bioactive plasma electrolytic oxidation coatings--the role of the composition, microstructure, and electrochemical stability.

    PubMed

    Mohedano, M; Guzman, R; Arrabal, R; López Lacomba, J-L; Matykina, E

    2013-11-01

    A Plasma electrolytic oxidation (PEO) process was used to produce bioactive coatings on Ti. PEO coatings with Ca/P atomic ratio of 1.7 and 4.0 were fabricated and characterized with respect to their morphology, composition, and microstructure. AC and DC electrochemical tests were used to evaluate the effect of (i) organic additives (amino acids, proteins, vitamins, and antibiotics) in alpha-minimum essential medium (α-MEM) on electrochemical stability of noncoated and PEO-coated Ti and (ii) coating composition, microstructure, and corrosion behavior on the cell response in α-MEM. PEO-coated Ti showed higher corrosion resistance than the noncoated Ti in MEM with and without organic additives by an order of magnitude. The corrosion resistance in α-MEM decreased with time for nonmodified Ti and increased for PEO-coated Ti; the latter was because of the adsorption of the proteins in the coating pores which increased the diffusion resistance. The presence of Ca and P in titanium oxide coating at the Ca/P ratio exceeding that of any stoichiometric Ca-P-O and Ca-P-O-H compounds facilitates faster osteoblast cell adhesion.

  14. 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.

  15. Highly hydrogenated graphene through microwave exfoliation of graphite oxide in hydrogen plasma: towards electrochemical applications.

    PubMed

    Eng, Alex Yong Sheng; Sofer, Zdenek; Šimek, Petr; Kosina, Jiri; Pumera, Martin

    2013-11-11

    Hydrogenated graphenes exhibit a variety of properties with potential applications in devices, ranging from a tunable band gap to fluorescence, ferromagnetism, and the storage of hydrogen. We utilize a one-step microwave-irradiation process in hydrogen plasma to create highly hydrogenated graphene from graphite oxides. The procedure serves the dual purposes of deoxygenation and concurrent hydrogenation of the carbon backbone. The effectiveness of the hydrogenation process is investigated on three different graphite oxides (GOs), which are synthesized by using the Staudenmaier, Hofmann, and Hummers methods. A systematic characterization of our hydrogenated graphenes is performed using UV/Vis spectroscopy, SEM, AFM, Raman spectroscopy, FTIR spectroscopy, X-ray photoelectron spectroscopy (XPS), combustible elemental analysis, and electrical conductivity measurements. The highest hydrogenation extent is observed in hydrogenated graphene produced from the Hummers-method GO, with a hydrogen content of 19 atomic % in the final product. In terms of the removal of oxygen groups, microwave exfoliation yields graphenes with very similar oxygen contents despite differences in their parent GOs. In addition, we examine the prospective application of hydrogenated graphenes as electrochemical transducers through a cyclic voltammetry (CV) study. The highly hydrogenated graphenes exhibit fast heterogeneous electron-transfer rates, suggestive of their suitability for electrochemical applications in electrodes, supercapacitors, batteries, and sensors. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Treatment of winery wastewater by electrochemical methods and advanced oxidation processes.

    PubMed

    Orescanin, Visnja; Kollar, Robert; Nad, Karlo; Mikelic, Ivanka Lovrencic; Gustek, Stefica Findri

    2013-01-01

    The aim of this research was development of new system for the treatment of highly polluted wastewater (COD = 10240 mg/L; SS = 2860 mg/L) originating from vine-making industry. The system consisted of the main treatment that included electrochemical methods (electro oxidation, electrocoagulation using stainless steel, iron and aluminum electrode sets) with simultaneous sonication and recirculation in strong electromagnetic field. Ozonation combined with UV irradiation in the presence of added hydrogen peroxide was applied for the post-treatment of the effluent. Following the combined treatment, the final removal efficiencies of the parameters color, turbidity, suspended solids and phosphates were over 99%, Fe, Cu and ammonia approximately 98%, while the removal of COD and sulfates was 77% and 62%, respectively. A new approach combining electrochemical methods with ultrasound in the strong electromagnetic field resulted in significantly better removal efficiencies for majority of the measured parameters compared to the biological methods, advanced oxidation processes or electrocoagulation. Reduction of the treatment time represents another advantage of this new approach.

  17. Removal of colour and COD from wastewater containing acid blue 22 by electrochemical oxidation.

    PubMed

    Panizza, Marco; Cerisola, Giacomo

    2008-05-01

    Electrochemical oxidation of synthetic wastewater containing acid blue 22 on a boron-doped diamond electrode (BDD) was studied, using cyclic voltammetry and bulk electrolysis. The influence of current density, dye concentration, flow rate, and temperature was investigated, in order to find the best conditions for COD and colour removal. It was found that, during oxidation, a polymeric film, causing BDD deactivation, was formed in the potential region of water stability, and that it was removed by anodic polarisation at high potentials in the region of O(2) evolution. Bulk electrolysis results showed that the electrochemical process was suitable for completely removing COD and effectively decolourising wastewaters, due to the production of hydroxyl radicals on the diamond surface. In particular, under optimal experimental conditions of flow rates (i.e. 300 dm(3) h(-1)) and current density (i.e. 20 mA cm(-2)), 97% of COD was removed in 12h electrolysis, with 70 kWh m(-3) energy consumption.

  18. Electrochemical oxidation of polyethylene glycol in electroplating solution using paraffin composite copper hexacyanoferrate modified (PCCHM) anode.

    PubMed

    Bejankiwar, Rajesh S; Basu, Abir; Cementi, Max

    2004-01-01

    Electrochemical oxidation of polyethylene glycol (PEG) in an acidic (pH 0.18 to 0.42) and high ionic strength electroplating solution was investigated. The electroplating solution is a major source of wastewater in the printing wiring board industry. A paraffin composite copper hexacyanoferrate modified (PCCHM) electrode was used as the anode and a bare graphite electrode was used as the cathode. The changes in PEG and total organic carbon (TOC) concentrations during the course of the reaction were monitored. The efficiency of the PCCHM anode was compared with bare graphite anode and it was found that the former showed significant electrocatalytic property for PEG and TOC removal. Chlorides present in the solution were found to contribute significantly in the overall organic removal process. Short chain organic compounds like acetic acid, oxalic acid, formic acid and ethylene glycol formed during electrolysis were identified by HPLC method. Anode surface area and applied current density were found to influence the electro-oxidation process, in which the former was found to be dominating. Investigations of the kinetics for the present electrochemical reaction suggested that the two stage first-order kinetic model provides a much better representation of the overall mechanism of the process if compared to the generalized kinetic model.

  19. Ionic and electrochemical phenomena induced by structural and chemical defects in oxide thin films

    NASA Astrophysics Data System (ADS)

    Aruta, Carmela

    Interactions at the surfaces/interfaces between complex oxides and gaseous environment are fundamental for the efficiency of many environmental friendly systems and applications. Such interactions can be modified by the intricate interrelationship between microstructure and chemical substitution defects, being their role on functional properties, such as ionic conductivity and surface reaction rates, as particularly relevant as difficult to discriminate. New possibilities in thin film fabrication allow growth of oxide thin films with a more precise control of the structure and chemical stoichiometry, thus unveiling new perspectives in the study of electrochemical effects for physical functionalities, through nanoscale characterizations by complementary state-of-art techniques. As an example of interfacial structural defect effects, we will discuss the case of yttrium doped barium zirconate thin films, where the cation substitutions represent a viable mechanism, alternative to the formation of dislocations near the interface, to relieve the strain building up in the film growing on a highly mismatched substrate, thus providing fast transport pathways together with enhanced interface electrochemical reactivity. The effect of the chemical defects will be further presented in the case of samarium-doped ceria films with different doping concentration. We will explain the role of the trivalent doping on the conduction mechanism, i.e. proton or oxygen ion, which in turns may greatly influence the surface reactivity.

  20. 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.

  1. Microwave synthesis and electrochemical characterization of Mn/Ni mixed oxide for supercapacitor application

    SciTech Connect

    Prasankumar, T.; Jose, Sujin P.; Ilangovan, R.; Venkatesh, K. S.

    2015-06-24

    Nanostructured Mn/Ni mixed metal oxide was synthesized at ambient temperature by facile microwave irradiation technique. The crystal structure and surface morphology were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. X-ray diffraction analysis confirmed the formation of Mn/Ni mixed oxide in rhombohedral phase and the grain size calculated was found to be 87 nm. The irregular spherical morphology of the prepared sample was exhibited by the SEM images. The characteristic peaks of FTIR at about 630 cm{sup −1} and 749 cm{sup −1} were attributed to the Mn-O and Ni-O stretching vibrations respectively. The presence of both Mn and Ni in the prepared sample was validated by the EDS spectra which in turn confirmed the formation of mixed oxide. Cyclic voltammetry and galvanostatic chargedischarge measurements were employed to investigate the electrochemical performance of the mixed oxide. The cyclic voltammetry curves demonstrated good capacitive performance of the sample in the potential window −0.2V to 0.9V. The charge discharge study revealed the suitability of the prepared mixed oxide for the fabrication of supercapacitor electrode.

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

    SciTech Connect

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

    2016-01-12

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

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

    DOE PAGES

    Katsounaros, Ioannis; Chen, Ting; Gewirth, Andrew A.; ...

    2016-01-12

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

  4. Estimation of the composition parameter of electrochemically colored amorphous hydrogen tungsten oxide films

    NASA Astrophysics Data System (ADS)

    Kaneko, Hiroko; Miyake, Kiyoshi

    1989-07-01

    The electrical and optical steady state observed in electrochemical coloration has been studied using asymmetric cells consisting of evaporated amorphous tungsten oxide films with 350-6000 Å thickness. The counter electrode used is indium wire, steel wire, or antimony-tin oxide film, and the electrolyte is a 1-N H2SO4 aqueous solution containing 10 vol % glycerol. The current and optical transmittance of the cells decrease with increasing time during coloration, and simultaneously reach a steady state. The optical density (λ=0.5 μm) in the steady state is proportional to the thickness of the tungsten oxide film, and the absorption coefficient at λ=0.5 μm of the colored oxide film in the state is approximately 9.0×104 cm-1. The effective charges which contribute to the coloration of films calculated from the charge injected until the electro-optical steady state were found to be 1.03-1.20×103 C/cm3. Assuming that the evaporated tungsten oxide films used have a distorted ReO3 structure, and that a hydrogen tungsten bronze HxWO3 is formed by coloration, the composition parameter x calculated from the average value of the effective charge, is 0.36, which is comparable with that of hydrogen tungsten bronze H0.33WO3 obtained for the colored crystalline WO3 films.

  5. 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.

  6. Degradation of atrazine by electrochemical advanced oxidation processes using a boron-doped diamond anode.

    PubMed

    Borràs, Núria; Oliver, Ramon; Arias, Conchita; Brillas, Enric

    2010-06-24

    Solutions of 30 mg L(-1) of the herbicide atrazine have been degraded by environmentally friendly electrochemical advanced oxidation processes (EAOPs) such as anodic oxidation (AO), electro-Fenton (EF), and photoelectro-Fenton (PEF) using a small open and cylindrical cell with a boron-doped diamond (BDD) anode. AO has been carried out either with a stainless steel cathode or an O(2) diffusion cathode able to generate H(2)O(2). Hydroxyl radicals ((*)OH) formed at the BDD surface in all EAOPs and in the bulk from Fenton's reaction between added Fe(2+) and electrogenerated H(2)O(2) in EF and PEF are the main oxidants. All treatments yielded almost overall mineralization, although the rate for total organic carbon (TOC) removal is limited by the oxidation of persistent byproducts with (*)OH at the BDD surface. In AO, TOC abatement is enhanced by parallel electrochemical reduction of organics at the stainless steel cathode, while in PEF, it also increases from additional photolysis of intermediates by UVA light under the synergistic action of (*)OH in the bulk. The effect of current and pH on the degradative behavior of EAOPs has been examined to determine their optimum values. Atrazine decay always follows a pseudo-first-order reaction, being more rapidly destroyed from (*)OH in the bulk than at the BDD surface. Aromatic intermediates such as desethylatrazine, desethyldesisopropylatrazine, and cyanuric acid and short linear carboxylic acids such as formic, oxalic, and oxamic have been identified and quantified by reversed-phase and ion-exclusion HPLC, respectively. Released inorganic ions such as Cl(-), NO(3)(-), and NH(4)(+) have been followed by ionic chromatography.

  7. 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.

  8. Nitrogen-doped graphene: effect of graphite oxide precursors and nitrogen content on the electrochemical sensing properties.

    PubMed

    Megawati, Monica; Chua, Chun Kiang; Sofer, Zdenek; Klímová, Kateřina; Pumera, Martin

    2017-06-21

    Graphene, produced via chemical methods, has been widely applied for electrochemical sensing due to its structural and electrochemical properties as well as its ease of production in large quantity. While nitrogen-doped graphenes are widely studied materials, the literature showing an effect of graphene oxide preparation methods on nitrogen quantity and chemical states as well as on defects and, in turn, on electrochemical sensing is non-existent. In this study, the properties of nitrogen-doped graphene materials, prepared via hydrothermal synthesis using graphite oxide produced by various classical methods using permanganate or chlorate oxidants Staudenmaier, Hummers, Hofmann and Brodie oxidation methods, were studied; the resulting nitrogen-doped graphene oxides were labeled as ST-GO, HU-GO, HO-GO and BR-GO, respectively. The electrochemical oxidation of biomolecules, such as ascorbic acid, uric acid, dopamine, nicotinamide adenine nucleotide and DNA free bases, was carried out using cyclic voltammetry and differential pulse voltammetry techniques. The nitrogen content in doped graphene oxides increased in the order ST-GO < BR-GO < HO-GO < HU-GO. In the same way, the pyridinic form of nitrogen increased and the electrocatalytic effect of N-doped graphene followed this trend, as shown in the cyclic voltammograms. This is a very important finding that provides insight into the electrocatalytic effect of N-doped graphene. The nitrogen-doped graphene materials exhibited improved sensitivity over bare glassy carbon for ascorbic acid, uric acid and dopamine detection. These studies will enhance our understanding of the effects of graphite oxide precursors on the electrochemical sensing properties of nitrogen-doped graphene materials.

  9. Electrochemical lithium intercalation chemistry of condensed molybdenum metal cluster oxide: LiMo4O6

    NASA Astrophysics Data System (ADS)

    Lim, Sung-Chul; Chae, Munseok S.; Heo, Jongwook W.; Hong, Seung-Tae

    2017-10-01

    The electrochemical lithium-ion intercalation properties of molybdenum metal-cluster oxide LixMo4O6 (0.33 ≤ x ≤ 1.0) in an organic electrolyte of 1.0 M LiPF6 in ethylene carbonate/dimethyl carbonate (1:2 v/v) were characterized for the first time. Li0.66Mo4O6 (tetragonal, P4/mbm, a = 9.5914(3) Å, c = 2.8798(1) Å, V = 264.927(15) Å3, Z = 2) was prepared via ion-exchange of indium and lithium ions from InMo4O6 (tetragonal, P4/mbm, a = 9.66610(4) Å, c = 2.86507(2) Å, V = 267.694(2) Å3, Z = 2), which was first synthesized from a stoichiometric mixture of In, Mo, and MoO3 via a solid-state reaction for 11 h at 1100 °C. Then, Li0.33Mo4O6 was obtained via electrochemical charge of the electrode at 3.4 V vs. Li. The electrochemical lithium-ion insertion into Li0.33Mo4O6 occurs stepwise: three separate peaks were observed in the cyclic voltammogram and three quasi-plateaus in the galvanostatic profile, indicating a complicated intercalation mechanism. However, examination of the structural evolution of LixMo4O6 during the electrochemical cycle indicated a reversible reaction over the measured voltage range (2.0-3.2 V) and x range (0.33 ≤ x ≤ 1.00). Despite the excellent electrochemical reversibility, LixMo4O6 showed poor rate performance with a low capacity of 36.3 mAh g-1 at a rate of 0.05 C. Nonetheless, this work demonstrates a new structural class of lithium cathode materials with condensed metal clusters and 1D tunnels, and provides a host material candidate for multivalent-ion batteries.

  10. Solid state tungsten oxide hydrate/tin oxide hydrate electrochromic device prepared by electrochemical reactions

    NASA Astrophysics Data System (ADS)

    Nishiyama, Kentaro; Matsuo, Ryo; Sasano, Junji; Yokoyama, Seiji; Izaki, Masanobu

    2017-03-01

    The solid state electrochromic device composed of tungsten oxide hydrate (WO3(H2O)0.33) and tin oxide hydrate (Sn(O,OH)) has been constructed by anodic deposition of WO3(H2O)0.33 and Sn(O,OH) layers and showed the color change from clear to blue by applying voltage through an Au electrode.

  11. Electrochemical metallization switching with a platinum group metal in different oxides

    NASA Astrophysics Data System (ADS)

    Wang, Zhongrui; Jiang, Hao; Hyung Jang, Moon; Lin, Peng; Ribbe, Alexander; Xia, Qiangfei; Yang, J. Joshua

    2016-07-01

    In a normal electrochemical metallization (ECM) switch, electrochemically active metals, such as Ag and Cu are used to provide mobile ions for the conducting filament. In both ECM and valence change memory (VCM) devices, platinum group metals, such as Pt and Pd, are typically used as the counter electrode and assumed to be chemically and physically inert. In this study, we explore whether the so-called inert metal itself can form a conducting filament and result in repeatable resistance switching. Pd and different oxide host matrices are used for this purpose. We have observed that the transport of oxygen anions dominates over Pd metal cations in ALD deposited AlOx and HfOx. However, in sputtered SiOx, Pd cation transport was revealed, accompanied by the formation of nano-crystalline Pd filament(s) in the junctions. Based on these observations, memristors with reversible and repeatable switching were obtained by using Pd doped SiOx as the switching material.In a normal electrochemical metallization (ECM) switch, electrochemically active metals, such as Ag and Cu are used to provide mobile ions for the conducting filament. In both ECM and valence change memory (VCM) devices, platinum group metals, such as Pt and Pd, are typically used as the counter electrode and assumed to be chemically and physically inert. In this study, we explore whether the so-called inert metal itself can form a conducting filament and result in repeatable resistance switching. Pd and different oxide host matrices are used for this purpose. We have observed that the transport of oxygen anions dominates over Pd metal cations in ALD deposited AlOx and HfOx. However, in sputtered SiOx, Pd cation transport was revealed, accompanied by the formation of nano-crystalline Pd filament(s) in the junctions. Based on these observations, memristors with reversible and repeatable switching were obtained by using Pd doped SiOx as the switching material. Electronic supplementary information (ESI) available

  12. Enhanced electrochemical characteristics of lithium manganese oxide thin film cathodes for lithium-ion rechargeable microbatteries

    NASA Astrophysics Data System (ADS)

    Kim, Won-Seok

    Spinel LiMn2O4 (average oxidation state of Mn = 3.5) thin film has been introduced for a promising cathode of thin film lithium-ion microbatteries because of its advantages over other cathodes. Thus, many research groups have been investigating the thin film lithium manganese oxide cathode using several different techniques but only a few of them achieved acceptable electrochemical properties required for a thin film cathode for 4 V region. However, for 3 V application the wide applications of LiMn2O 4 film as a cathode in rechargeable microbatteries have been restricted by electrochemically unfavorable facts such as capacity fade on cycling and poor rate capability at high rates. In this study, we examined the mechanisms responsible for capacity fade on cycling and rate capability of LiMn 2O4 thin film cathodes with the help of pulsed laser deposition (PLD) technique. In an attempt to address these issues, a three-part experimental procedure has been designed to look at the effect of structure and compositions of the thin film cathodes on their electrochemical characteristics. First, the effect of growth temperature of the thin film cathodes has been investigated. Next, LiMn2O4 thin film cathodes doped with aluminum, which replaces Mn3+ in the spinet structure, have been synthesized and characterized as a function of the amount of aluminum substituted. Finally, ultraviolet radiation was added to a PLD system for in situ ultraviolet-assisted PLD (UVPLD) growth of cathode films. Through the addition of ultraviolet radiation, highly reactive oxygen species are generated which alter the oxygenation conditions and dynamically alter the films properties such as crystallinity and composition. A variety of characterization techniques indicate that LiMn2O 4 thin film cathodes grown at 400˜500°C exhibit the optimized electrochemical characteristics in terms of capacity, capacity retention, and rate capability. Al-doped LiMn2O4 thin films show a more stable structure

  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. 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.

  15. Degradation of herbicide 4-chlorophenoxyacetic acid by advanced electrochemical oxidation methods.

    PubMed

    Boye, Birame; Dieng, Momar M; Brillas, Enric

    2002-07-01

    The herbicide 4-chlorophenoxyacetic acid (4-CPA) has been degraded in aqueous medium by advanced electrochemical oxidation processes such as electro-Fenton and photoelectro-Fenton with UV light, using an undivided cell containing a Pt anode. In these environmentally clean methods, the main oxidant is the hydroxyl radical produced from Fenton's reaction between Fe2+ added to the medium and H2O2 electrogenerated from an 02-diffusion cathode. Solutions of a 4-CPA concentration <400 ppm within the pH range of 2.0-6.0 at 35 degrees C can be completely mineralized at low current by photoelectro-Fenton, while electro-Fenton leads to ca. 80% of mineralization. 4-CPA is much more slowly degraded by anodic oxidation in the absence and presence of electrogenerated H2O2. 4-Chlorophenol, 4-chlorocatechol, and hydroquinone are identified as aromatic intermediates by CG-MS and quantified by reverse-phase chromatography. Further oxidation of these chloroderivatives yields stable chloride ions. Generated carboxylic acids such as glycolic, glyoxylic, formic, malic, maleic, fumaric, and oxalic are followed by ion exclusion chromatography. The highest mineralization rate found for photoelectro-Fenton is accounted for by the fast photodecomposition of complexes of Fe3+ with such short-chain acids, mainly oxalic acid, under the action of UV light.

  16. Electrochemical capacitor performance of hydrous ruthenium oxide/mesoporous carbon composite electrodes

    NASA Astrophysics Data System (ADS)

    Jang, Jong H.; Han, Sangjin; Hyeon, Taeghwan; Oh, Seung M.

    Ruthenium/carbon composite materials are prepared by impregnating ruthenium(III) acetylacetonate into a mesoporous carbon (average pore diameter=12 mn, pore volume=3.6 cm 3 g -1) and then heat treatment at 320 °C for 2 h under an argon atmosphere. The metallic ruthenium nanoparticles are converted to pseudo-capacitive hydrous ruthenium oxide by electrochemical oxidation at 0.75 V (versus SCE) for 2 h in 2.0 M H 2SO 4. The specific capacitance of the composite electrodes, which is the sum of the double-layer capacitance of mesoporous carbon and the pseudo-capacitance of hydrous ruthenium oxide, reaches 243 F g -1 with heavy loading. As the loading is increased, however, the degree of ruthenium utilization for a pseudo-capacitor becomes poorer, presumably due to a limited conversion to the hydrous oxide form. The rate capability of composite electrodes also decreases with increase in ruthenium loading, due to an increase in both the equivalent series resistance (ESR) and the overall capacitance value. The ESR enlargement is caused mainly an increase in the electrolyte resistance within pores which, in turn, results from a pore narrowing with ruthenium loading Hindered ionic motion in narrowed pores can explain this feature. An increase in the RC time constant with ruthenium loading is further verified by ac impedance measurements.

  17. Fabrication of ultrafine manganese oxide-decorated carbon nanofibers for high-performance electrochemical capacitors

    SciTech Connect

    Yang, Ying; Lee, Sungsik; Brown, Dennis E.; Zhao, Hairui; Li, Xinsong; Jiang, Daqiang; Hao, Shijie; Zhao, Yongxiang; Cong, Daoyong; Zhang, Xin; Ren, Yang

    2016-09-01

    Ultrafine manganese oxide-decorated carbon nanofibers (MnOn-CNF) as a new type of electrode materials are facilely fabricated by direct conversion of Mn, Zn-trimesic acid (H3BTC) metal organic framework fibers (Mn-ZnBTC). The construction and evolution of Mn-ZnBTC precursors are investigated by SEM and in situ high-energy XRD. The manganese oxides are highly dispersed onto the porous carbon nanofibers formed simultaneously, verified by TEM, X-ray absorption fine structure (XAFS), Raman, ICP-AES and N2 adsorption techniques. As expected, the resulting MnOn-CNF composites are highly stable, and can be cycled up to 5000 times with a high capacitance retention ratio of 98% in electrochemical capacitor measurements. They show a high capacitance of up to 179 F g–1 per mass of the composite electrode, and a remarkable capacitance of up to 18290 F g–1 per active mass of the manganese(IV) oxide, significantly exceeding the theoretical specific capacitance of manganese(IV) oxide (1370 F g–1). The maximum energy density is up to 19.7 Wh kg–1 at the current density of 0.25 A g–1, even orders higher than those of reported electric double-layer capacitors and pseudocapacitors. The excellent capacitive performance can be ascribed to the joint effect of easy accessibility, high porosity, tight contact and superior conductivity integrated in final MnOn-CNF composites.

  18. 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.

  19. Electrochemical Characterization of a Solid Oxide Membrane Electrolyzer for Production of High-Purity Hydrogen

    NASA Astrophysics Data System (ADS)

    Pati, Soobhankar; Yoon, Kyung Joong; Gopalan, Srikanth; Pal, Uday B.

    2009-12-01

    A laboratory-scale solid oxide membrane (SOM) steam electrolyzer that can potentially use energy value in waste or any source of carbon or hydrocarbon to produce high-purity hydrogen has been fabricated and evaluated. The SOM electrolyzer comprises an oxygen-ion-conducting yttria-stabilized zirconia (YSZ) electrolyte with a Ni-YSZ cermet cathode coated on one side and liquid-metal anode on the other side. The SOM electrolyzer is operated at 1000 °C by providing a steam-rich gas feed to the Ni-YSZ cermet cathode and feeding a reductant source into the liquid-metal anode. The steam is reduced over the cathode, and oxygen ions are transported through the YSZ electrolyte and are oxidized at the molten metal electrode by the reductant feed. The advantage of SOM electrolyzer over the state-of-the-art solid oxide electrolyzer is its ability to use solid, liquid, and gaseous reductant feed in the liquid-metal anode to reduce the oxygen chemical potential and drive the reaction for hydrogen production. In this study, an electrochemical process model for a SOM electrolyzer was developed. The condition of the liquid-metal anode with reductant was simulated by bubbling humidified hydrogen (3 pct H2O) in the liquid metal, and the electrochemical performance of the SOM electrolyzer was modeled. The experimental data were curve-fitted into the model to identify the various polarization losses. It showed that the performance of the SOM electrolyzer was dominated by the ohmic resistance of the YSZ membrane. Based on the results of this study, future work is needed toward increasing the performance efficiency of the SOM electrolyzer.

  20. 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.

  1. Oxidative stress response to acute hypobaric hypoxia and its association with indirect measurement of increased intracranial pressure: a field study

    PubMed Central

    Strapazzon, Giacomo; Malacrida, Sandro; Vezzoli, Alessandra; Dal Cappello, Tomas; Falla, Marika; Lochner, Piergiorgio; Moretti, Sarah; Procter, Emily; Brugger, Hermann; Mrakic-Sposta, Simona

    2016-01-01

    High altitude is the most intriguing natural laboratory to study human physiological response to hypoxic conditions. In this study, we investigated changes in reactive oxygen species (ROS) and oxidative stress biomarkers during exposure to hypobaric hypoxia in 16 lowlanders. Moreover, we looked at the potential relationship between ROS related cellular damage and optic nerve sheath diameter (ONSD) as an indirect measurement of intracranial pressure. Baseline measurement of clinical signs and symptoms, biological samples and ultrasonography were assessed at 262 m and after passive ascent to 3830 m (9, 24 and 72 h). After 24 h the imbalance between ROS production (+141%) and scavenging (−41%) reflected an increase in oxidative stress related damage of 50–85%. ONSD concurrently increased, but regression analysis did not infer a causal relationship between oxidative stress biomarkers and changes in ONSD. These results provide new insight regarding ROS homeostasis and potential pathophysiological mechanisms of acute exposure to hypobaric hypoxia, plus other disease states associated with oxidative-stress damage as a result of tissue hypoxia. PMID:27579527

  2. Influences of graphene oxide support on the electrochemical performances of graphene oxide-MnO2 nanocomposites

    PubMed Central

    2011-01-01

    MnO2 supported on graphene oxide (GO) made from different graphite materials has been synthesized and further investigated as electrode materials for supercapacitors. The structure and morphology of MnO2-GO nanocomposites are characterized by X-ray diffraction, X-ray photoemission spectroscopy, scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, and Nitrogen adsorption-desorption. As demonstrated, the GO fabricated from commercial expanded graphite (denoted as GO(1)) possesses more functional groups and larger interplane gap compared to the GO from commercial graphite powder (denoted as GO(2)). The surface area and functionalities of GO have significant effects on the morphology and electrochemical activity of MnO2, which lead to the fact that the loading amount of MnO2 on GO(1) is much higher than that on GO(2). Elemental analysis performed via inductively coupled plasma optical emission spectroscopy confirmed higher amounts of MnO2 loading on GO(1). As the electrode of supercapacitor, MnO2-GO(1) nanocomposites show larger capacitance (307.7 F g-1) and better electrochemical activity than MnO2-GO(2) possibly due to the high loading, good uniformity, and homogeneous distribution of MnO2 on GO(1) support. PMID:21951643

  3. 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.

  4. Investigation of the charge-storage behavior of electrochemically activated graphene oxide on supercapacitor electrodes in acidic electrolyte

    NASA Astrophysics Data System (ADS)

    Kim, Jaekwang; Choi, Eunmi; Lee, Ilbok; Kim, Daeun; Han, Seunghee; Pyo, Sung Gyu; Yoon, Songhun

    2017-09-01

    Herein, charge storage behavior of graphene oxide electrode was investigated after its electrochemical activation. X-ray photoelectron spectroscopy (XPS), cyclic voltammetry (CV), galvanostatic chargedischarge method (GCD), and electrochemical impedance spectroscopy (EIS) were employed for this analysis. From XPS analysis, a decrease of atomic ratio of C=C bond was observed after electrochemical activation from 86.94 to 79.64%. Also, enhancement of specific capacitance appeared from 54.1 to 65.7 F g-1 at 20 mV s-1, and rectangular shape in CV became more collapsed in activated grapheme oxide electrode. In the GCD profiles, similarly, difference of resistance values at high and low cut-off potential became larger after activation, indicative of increased polarization. From EIS, detailed resistance components were compared, which reflected that the increased resistance and higher capacitance after activation was probably attributed to larger amount of surface functional groups after activation. [Figure not available: see fulltext.

  5. Hydrothermal preparation of reduced graphene oxide-silver nanocomposite using Plectranthus amboinicus leaf extract and its electrochemical performance.

    PubMed

    Zheng, Yuhong; Wang, Aiwu; Cai, Wen; Wang, Zhong; Peng, Feng; Liu, Zhong; Fu, Li

    2016-12-01

    Graphene based nanocomposites are receiving increasing attention in many fields such as material chemistry, environmental science and pharmaceutical science. In this study, a facial synthesis of a reduced graphene oxide-silver nanocomposite (RGO-Ag) was carried out from Plectranthus amboinicus leaf extract. The synthesized nanocomposite was characterized by using X-ray diffraction, scanning electron microscope, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, transmission electron microscope and UV-vis spectroscopy for structural confirmation. The reduction of graphene oxide and silver ions was achieved simultaneously due to the reducibility of the Plectranthus amboinicus leaf extract. We further investigated the electrochemical properties of the biosynthesized RGO-Ag nanocomposite. A nonenzymatic H2O2 electrochemical sensor was shown to be successfully fabricated by using biosynthesized RGO-Ag nanocomposite. Moreover, the fabricated electrochemical sensor also showed good selectivity.

  6. Validation study of nasal nitric oxide measurements using a hand-held electrochemical analyser.

    PubMed

    Maniscalco, M; de Laurentiis, G; Weitzberg, E; Lundberg, J O; Sofia, M

    2008-03-01

    Exhaled nitric oxide (NO) measurement is a simple and non-invasive method for monitoring airway inflammation. Similarly, nasal NO has been proposed as a surrogate marker in inflammatory diseases of the upper airways, e.g. allergic rhinitis. A new portable analyser using an electrochemical sensor has been developed for measurements of exhaled NO, and its reproducibility and comparison with other analysers has been tested recently in healthy subjects and in patients with lower airways disease. The application of this hand-held analyser in nasal NO analysis was tested and compared to the gold standard represented by a chemiluminescence analyser. Thirty subjects including 15 patients with allergic rhinitis (AR) and 15 healthy subjects (HS) were studied. The intraindividual variability, calculated as the difference in nasal NO levels between two measurements from a single nasally exhaled breath manoeuvre, and the comparison between the electrochemical analyser (NIOX MINO, Aerocrine) and a chemiluminescence analyser (NOA, Sievers) were performed. In AR patients mean nasal NO was 59.0 +/- 16.3 p.p.b. with the MINO and 58.3 +/- 15.6 p.p.b. with the NOA. In HS nasal NO was 49.1 +/- 10.8 p.p.b. with the MINO and 49.8 +/- 8.2 p.p.b. with the NOA. The Bland-Altman analysis showed bias values of 0.005 +/- 3.6 with the 95% limits of agreement from -6.97 to 6.98 p.p.b. Measurements of nasal NO levels with a hand-held electrochemical analyser are reproducible and the results are comparable to a stationary chemiluminescence analyser.

  7. All-Graphene Oxide Flexible Solid-State Supercapacitors with Enhanced Electrochemical Performance.

    PubMed

    Ogata, Chikako; Kurogi, Ruriko; Awaya, Keisuke; Hatakeyama, Kazuto; Taniguchi, Takaaki; Koinuma, Michio; Matsumoto, Yasumichi

    2017-08-09

    The rapid development of flexible and wearable electronics has led to an increase in the demand for flexible supercapacitors with enhanced electrochemical performance. Graphene oxide (GO) and reduced GO (rGO) exhibit several key properties required for supercapacitor components. Although solid-state rGO/GO/rGO supercapacitors with unique structures are promising, their moderate capacitance is inadequate for practical applications. Herein, we report a flexible solid-state rGO/GO/rGO supercapacitor comprising H2SO4-intercalated GO electrolyte/separator and pseudocapacitive rGO electrodes, which demonstrate excellent electrochemical performance. The resulting supercapacitor delivered an areal capacitance of 14.5 mF cm(-2), which is among the highest values achieved for any rGO/GO/rGO supercapacitor. High ionic concentration and fast ion conduction in the H2SO4-intercalated GO electrolyte/separator and abundant CH defects, which serve as pseudocapacitive sites on the rGO electrode, were responsible for the high capacitance of this device. The rGO electrode, well separated by the H2SO4 molecular spacer, supplied highly efficient ion transport channels, leading to excellent rate capability. The highly packed rGO electrode and high specific capacitance resulted in a high volumetric energy density (1.24 mWh cm(-3)) observed in this supercapacitor. The structure, without a clear interface between GO and rGO, provides extremely low resistance and flexibility for devices. Our device operated in air (25 °C 40%) without the use of external electrolytes, conductive additives, and binders. Furthermore, we demonstrate a simple and versatile technique for supercapacitor fabrication by combining photoreduction and electrochemical treatment. These advantages are attractive for developing novel carbon-based energy devices with high device performance and low fabrication costs.

  8. Bone reactions to oxidized titanium implants with electrochemical anion sulphuric acid and phosphoric acid incorporation.

    PubMed

    Sul, Young-Taeg; Johansson, Carina B; Kang, Yunmo; Jeon, Dong-Gyun; Albrektsson, Tomas

    2002-01-01

    The importance of the surface properties of implants for a successful osseointegration has been emphasized. It is generally known that bone response to implant surfaces is considerably related to the various surface properties. The purpose of this study was to investigate bone tissue reactions to multifactorial biocompatibility of the surface oxide of electrochemically oxidized titanium implants. The ultimate objective was to improve surface quality, resulting in enhancement of clinical outcomes of osseointegrated implants. Three different surface types of commercially pure titanium (c.p. Ti) implants were prepared. Turned implants were used for controls and test implants were prepared by the micro arc oxidation (MAO) method, either in sulphuric acid (S implants) or in phosphoric acid (P implants). Implants were inserted in the femur and tibia of 10 mature New Zealand White rabbits. The bone response was evaluated by biomechanical tests, histology, and histomorphometry. The follow-up time was 6 weeks. The mean peak values of the removal torque showed significant differences between control and test S implants (p =.022) but showed no significant differences between control and test P implants (p =.195) or between test S and test P implants (p =.457). In addition, the histomorphometric comparisons of the bone-to-metal contact around entire implants demonstrated 186% increase in S implants (p =.028) and 232% increase in P implants (p =.028) compared with the paired control groups. Quantification of the bone area in the threads did not show any significant differences. The present results suggest that the primary mode of action in strong bone response to S implants is mechanical interlocking, and to P implants, it is biochemical interaction. It is possible that the phosphate groups in the titanium oxide of P implants provide potential chemical bonding sites for calcium ions and hydroxyapatite of the bone matrix during biologic mineralization. key words: bone responses

  9. Nanostructured Metal Oxide Coatings for Electrochemical Energy Conversion and Storage Electrodes

    NASA Astrophysics Data System (ADS)

    Cordova, Isvar Abraxas

    The realization of an energy future based on safe, clean, sustainable, and economically viable technologies is one of the grand challenges facing modern society. Electrochemical energy technologies underpin the potential success of this effort to divert energy sources away from fossil fuels, whether one considers alternative energy conversion strategies through photoelectrochemical (PEC) production of chemical fuels or fuel cells run with sustainable hydrogen, or energy storage strategies, such as in batteries and supercapacitors. This dissertation builds on recent advances in nanomaterials design, synthesis, and characterization to develop novel electrodes that can electrochemically convert and store energy. Chapter 2 of this dissertation focuses on refining the properties of TiO2-based PEC water-splitting photoanodes used for the direct electrochemical conversion of solar energy into hydrogen fuel. The approach utilized atomic layer deposition (ALD); a growth process uniquely suited for the conformal and uniform deposition of thin films with angstrom-level thickness precision. ALD's thickness control enabled a better understanding of how the effects of nitrogen doping via NH3 annealing treatments, used to reduce TiO2's bandgap, can have a strong dependence on TiO2's thickness and crystalline quality. In addition, it was found that some of the negative effects on the PEC performance typically associated with N-doped TiO2 could be mitigated if the NH 3-annealing was directly preceded by an air-annealing step, especially for ultrathin (i.e., < 10 nm) TiO2 films. ALD was also used to conformally coat an ultraporous conductive fluorine-doped tin oxide nanoparticle (nanoFTO) scaffold with an ultrathin layer of TiO2. The integration of these ultrathin films and the oxide nanoparticles resulted in a heteronanostructure design with excellent PEC water oxidation photocurrents (0.7 mA/cm2 at 0 V vs. Ag/AgCl) and charge transfer efficiency. In Chapter 3, two innovative

  10. Nonradical oxidation from electrochemical activation of peroxydisulfate at Ti/Pt anode: Efficiency, mechanism and influencing factors.

    PubMed

    Song, Haoran; Yan, Linxia; Ma, Jun; Jiang, Jin; Cai, Guangqiang; Zhang, Wenjuan; Zhang, Zhongxiang; Zhang, Jiaming; Yang, Tao

    2017-06-01

    Electrochemical activation of peroxydisulfate (PDS) at Ti/Pt anode was systematically investigated for the first time in this work. The synergistic effect produced from the combination of electrolysis and the addition of PDS demonstrates that PDS can be activated at Ti/Pt anode. The selective oxidation towards carbamazepine (CBZ), sulfamethoxazole (SMX), propranolol (PPL), benzoic acid (BA) rather than atrazine (ATZ) and nitrobenzene (NB) was observed in electrochemical activation of PDS process. Moreover, addition of excess methanol or tert-butanol had negligible impact on CBZ (model compound) degradation, demonstrating that neither sulfate radical (SO4(-)) nor hydroxyl radical (HO) was produced in electrochemical activation of PDS process. Direct oxidation (PDS oxidation alone and electrolysis) and nonradical oxidation were responsible for the degradation of contaminants. The results of linear sweep voltammetry (LSV) and chronoamperometry suggest that electric discharge may integrate PDS molecule with anode surface into a unique transition state structure, which is responsible for the nonradical oxidation in electrochemical activation of PDS process. Adjustment of the solution pH from 1.0 to 7.0 had negligible effect on CBZ degradation. Increase of either PDS concentration or current density facilitated the degradation of CBZ. The presence of chloride ion (Cl(-)) significantly enhanced CBZ degradation, while addition of bicarbonate (HCO3(-)), phosphate (PO4(3-)) and humic acid (HA) all inhibited CBZ degradation with the order of HA > HCO3(-) > PO4(3-). The degradation products of CBZ and chlorinated products were also identified. Electrochemical activation of PDS at Ti/Pt anode may serve as a novel technology for selective oxidation of organic contaminants in water and soil. Copyright © 2017. Published by Elsevier Ltd.

  11. 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.

  12. 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

  13. 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

    2015-12-07

    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.

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

    PubMed

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

    2012-01-01

    Fractional exhaled nitric oxide (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.

  15. 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

  16. Green synthesis of manganese oxide nanoparticles for the electrochemical sensing of p-nitrophenol

    NASA Astrophysics Data System (ADS)

    Kumar, Vineet; Singh, Kulvinder; Panwar, Shaily; Mehta, Surinder Kumar

    2017-03-01

    Manganese oxide (MnO) NPs are widely used in contaminant sensing, drug delivery, data storage, catalysis and biomedical imaging. Green synthesis of NPs is important due to increased concern of environmental pollution. Green chemistry based synthesis of NPs is preferred due to its ecofriendly nature. In this study, MnO NPs of different sizes were synthesized in aqueous medium using clove, i.e., Syzygium aromaticum extract (CE) as reducing and stabilizing agents. These NPs were used for the electrochemical sensing of p-nitrophenol (PNP). The synthesis of MnO NPs was over in 30 min. MnO NPs of different sizes were obtained by varying metal ion concentration, metal ion volume ratio, CE concentration, CE volume ratio, and incubation temperature. Selectively, 4 nm MnO NPs were used for electrochemical sensing of paranitrophenol. The MnO NPs modified gold electrodes detected PNP with good sensitivity, 0.16 µA µM-1 cm2. The limit of PNP detection was 15.65 µM. The MnO NPs prepared using CE based green chemistry approach is useful for PNP sensing. These NPs can also be useful for various in vivo applications in which the NPs come in human contact.

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

    NASA Astrophysics Data System (ADS)

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

    2012-01-01

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

  18. 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.

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

    NASA Astrophysics Data System (ADS)

    Hoang, Khang; Johannes, Michelle

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

  20. A comparison study of macrocyclic hosts functionalized reduced graphene oxide for electrochemical recognition of tadalafil.

    PubMed

    Zhao, Hui; Yang, Long; Li, Yucong; Ran, Xin; Ye, Hanzhang; Zhao, Genfu; Zhang, Yanqiong; Liu, Feng; Li, Can-Peng

    2017-03-15

    The present work described the comparison of β-cyclodextrin (β-CD) and p-sulfonated calix[6]arene (SCX6) functionalized reduced graphene oxide (RGO) for recognition of tadalafil. In this study, tadalafil and two macrocycles (β-CD and SCX6) were selected as the guest and host molecules, respectively. The inclusion complexes of β-CD/tadalafil and SCX6/tadalafil were studied by UV spectroscopy and molecular simulation calculations, proving the higher supermolecular recognition capability of SCX6 than β-CD towards tadalafil. The β-CD@RGO and SCX6@RGO composites were prepared by a wet-chemical route. The obtained composites were characterized by Fourier transform infrared spectrometry, thermogravimetric analysis, atomic force microscopy, and zeta potential. The SCX6@RGO showed a higher electrochemical response than β-CD@RGO, which was caused by the higher recognition capability of SCX6 than β-CD. By combining the merits of SCX6 and the RGO, a sensitive electrochemical sensing platform was developed based on the SCX6@RGO nanohybrids. A linear response range of 0.1-50 μM and 50-1000 μM for tadalafil with a low detection limit of 0.045 μM (S/N=3) was obtained by using this method. The constructed sensing platform was successfully used to determine tadalafil in herbal sexual health products and spiked human serum samples, suggesting its promising analytical applications for the trace level determination of tadalafil.

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

    PubMed

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

    2014-07-10

    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.

  2. Enhancement of corrosion resistance of polypyrrole using metal oxide nanoparticles: Potentiodynamic and electrochemical impedance spectroscopy study.

    PubMed

    Hosseini, Marzieh; Fotouhi, Lida; Ehsani, Ali; Naseri, Maryam

    2017-11-01

    We introduce a simple and facile strategy for dispersing of nanoparticles within a p-type conducting polymer matrix by in situ electropolymerization using oxalic acid as the supporting electrolyte. Coatings prepared from polypyrrole-nano-metal oxide particles synthesized by in situ polymerization were found to exhibit excellent corrosion resistance much superior to polypyrrole (Ppy) in aggressive environments. The anti-corrosion behavior of polypyrrole films in different states and the presence of TiO2, Mn2O3 and ZnO nanoparticles synthesized by electropolymerization on Al electrodes have been investigated in corrosive solutions using potentiodynamic polarization and electrochemical impedance spectroscopy. The electrochemical response of the coated electrodes in polymer and nanocomposite state was compared with bare electrodes. The use of TiO2 nanoparticles has proved to be a great improvement in the performances of polypyrrole films for corrosion protection of Al samples. The polypyrrole synthesized in the presence of TiO2 nanoparticles coated electrodes offered a noticeable enhancement of protection against corrosion processes. The exceptional improvement of performance of these coatings has been associated with the increase in barrier to diffusion, prevention of charge transport by the nanosize TiO2, redox properties of polypyrrole as well as very large surface area available for the liberation of dopant due to nano-size additive. Copyright © 2017 Elsevier Inc. All rights reserved.

  3. Electrochemical Synthesis of Mesoporous CoPt Nanowires for Methanol Oxidation

    PubMed Central

    Serrà, Albert; Montiel, Manuel; Gómez, Elvira; Vallés, Elisa

    2014-01-01

    A new electrochemical method to synthesize mesoporous nanowires of alloys has been developed. Electrochemical deposition in ionic liquid-in-water (IL/W) microemulsion has been successful to grow mesoporous CoPt nanowires in the interior of polycarbonate membranes. The viscosity of the medium was high, but it did not avoid the entrance of the microemulsion in the interior of the membrane’s channels. The structure of the IL/W microemulsions, with droplets of ionic liquid (4 nm average diameter) dispersed in CoPt aqueous solution, defined the structure of the nanowires, with pores of a few nanometers, because CoPt alloy deposited only from the aqueous component of the microemulsion. The electrodeposition in IL/W microemulsion allows obtaining mesoporous structures in which the small pores must correspond to the size of the droplets of the electrolytic aqueous component of the microemulsion. The IL main phase is like a template for the confined electrodeposition. The comparison of the electrocatalytic behaviours towards methanol oxidation of mesoporous and compact CoPt nanowires of the same composition, demonstrated the porosity of the material. For the same material mass, the CoPt mesoporous nanowires present a surface area 16 times greater than compact ones, and comparable to that observed for commercial carbon-supported platinum nanoparticles.

  4. Graphene oxide integrated sensor for electrochemical monitoring of mitomycin C-DNA interaction.

    PubMed

    Erdem, Arzum; Muti, Mihrican; Papakonstantinou, Pagona; Canavar, Ece; Karadeniz, Hakan; Congur, Gulsah; Sharma, Surbhi

    2012-05-07

    We present a graphene oxide (GO) integrated disposable electrochemical sensor for the enhanced detection of nucleic acids and the sensitive monitoring of the surface-confined interactions between the anticancer drug mitomycin C (MC) and DNA. Interfacial interactions between immobilized calf thymus double-stranded (dsDNA) and anticancer drug MC were investigated using differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS) techniques. Based on three repetitive voltammetric measurements of 120 μg mL(-1) DNA immobilized on GO-modified electrodes, the RSD % (n = 3) was calculated as 10.47% and the detection limit (DL) for dsDNA was found to be 9.06 μg mL(-1). EIS studies revealed that the binding of the drug MC to dsDNA leads to a gradual decrease of its negative charge. As a consequence of this interaction, the negative redox species were allowed to approach the electrode, and thus increase the charge transfer kinetics. On the other hand, DPV studies exploited the decrease of the guanine signal due to drug binding as the basis for specifically probing the biointeraction process between MC and dsDNA.

  5. Simultaneous reduction of nitrate and oxidation of by-products using electrochemical method.

    PubMed

    Li, Miao; Feng, Chuanping; Zhang, Zhenya; Lei, Xiaohui; Chen, Rongzhi; Yang, Yinan; Sugiura, Norio

    2009-11-15

    Electrochemical denitrification was studied with an objective to enhance the selectivity of nitrate to nitrogen gas and to remove the by-products in an undivided electrochemical cell, in which Cu-Zn cathode and Ti/IrO(2)-Pt anode were assembled. In the presence of 0.50 g/L NaCl as supporting electrolyte, the NO(3)(-)-N decreased from 100.0 to 9.7 mg/L after 300 min electrolysis; no ammonia and nitrite were detected in the treated solution. The surface of the cathode was appeared to be rougher than unused after electrolysis at initial pH 6.5 and 12.0. After electrolysis of 5h at the initial pH 3.0, passivation of the Cu-Zn cathode was observed. The reduction rate slightly increased with increasing current density in the range of 10-60 mA/cm(2) and temperatures had little effect on nitrate reduction. Nitrate could be completely removed by the simultaneous reduction and oxidation developed in this study, which is suitable for deep treatment of nitrate polluted water.

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

    PubMed

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

    2015-02-01

    Sulfide is the product of the biological sulfate reduction process which gives toxicity and odor problems. Wastewaters or bioreactor effluents containing sulfide can cause severe environmental impacts. Electrochemical treatment can be an alternative approach for sulfide removal and sulfur recovery from such sulfide rich solutions. This study aims to develop a spontaneous electrochemical sulfide oxidation/vanadium(V) reduction cell with a graphite electrode system to recover sulfide as elemental sulfur. The effects of the internal and external resistance on the sulfide removal efficiency and electrical current produced were investigated at different pH. A high surface area of the graphite electrode is required in order to have as less internal resistance as possible. In this study, graphite powder was added (contact area >633 cm(2)) in order to reduce the internal resistance. A sulfide removal efficiency up to 91% and electrical charge of more than 400 C were achieved when using five graphite rods supplemented with graphite powder as the electrode at an external resistance of 30 Ω and a sulfide concentration of 250 mg L(-1). Copyright © 2014 Elsevier Ltd. All rights reserved.

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

    SciTech Connect

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

    2003-10-30

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

  8. Electrochemical reduction of porous 17 kg uranium oxide pellets by selection of an optimal cathode/anode surface area ratio

    NASA Astrophysics Data System (ADS)

    Choi, Eun-Young; Hur, Jin-Mok; Choi, In-Kyu; Kwon, Seon Gil; Kang, Dae-Seung; Hong, Sun Seok; Shin, Ho-Sup; Yoo, Min A.; Jeong, Sang Mun

    2011-11-01

    This study examines how the cathode/anode surface area ratio affects the electrochemical reduction of uranium oxide in a molten Li 2O-LiCl electrolyte. A bench-scale test showed that a low cathode/anode surface area ratio is helpful for efficiently attaining a high current density and producing metallic uranium from uranium oxide in an Li 2O-LiCl electrolyte. A 17 kg uranium oxide electrolysis cell was set up with a cathode/anode surface area ratio of 2.6, and uranium oxide was successfully reduced to metallic uranium.

  9. Indirect nitrous oxide emissions from streams within the US Corn Belt scale with stream order

    USDA-ARS?s Scientific Manuscript database

    Nitrous oxide (N2O) is an important greenhouse gas and the primary stratospheric ozone depleting substance. Its deleterious effects on the environment have prompted appeals to regulate emissions from agriculture, which represents the primary source in the global N2O budget. Successful implementation...

  10. Destination of organic pollutants during electrochemical oxidation of biologically-pretreated dye wastewater using boron-doped diamond anode.

    PubMed

    Zhu, Xiuping; Ni, Jinren; Wei, Junjun; Xing, Xuan; Li, Hongna

    2011-05-15

    Electrochemical oxidation of biologically-pretreated dye wastewater was performed in a boron-doped diamond (BDD) anode system. After electrolysis of 12h, the COD was decreased from 532 to 99 mg L(-1) (<100 mg L(-1), the National Discharge Standard of China). More importantly, the destination of organic pollutants during electrochemical oxidation process was carefully investigated by molecular weight distribution measurement, resin fractionation, ultraviolet-visible spectroscopy, HPLC and GC-MS analysis, and toxicity test. As results, most organic pollutants were completely removed by electrochemical oxidation and the rest was primarily degraded to simpler compounds (e.g., carboxylic acids and short-chain alkanes) with less toxicity, which demonstrated that electrochemical oxidation of biologically-pretreated dye wastewater with BDD anode was very effective and safe. Especially, the performance of BDD anode system in degradation of large molecular organics such as humic substances makes it very promising in practical applications as an advanced treatment of biologically-pretreated wastewaters. Copyright © 2011 Elsevier B.V. All rights reserved.

  11. Electrochemical degradation of the antihypertensive losartan in aqueous medium by electro-oxidation with boron-doped diamond electrode.

    PubMed

    Salazar, Claudio; Contreras, Nicole; Mansilla, Héctor D; Yáñez, Jorge; Salazar, Ricardo

    2016-12-05

    In this work the electrochemical oxidation of losartan, an emerging pharmaceutical pollutant, was studied. Electrochemical oxidation was carried out in batch mode, in an open and undivided cell of 100cm(3) using a boron-doped diamond (BDD)/stainless steel system. With Cl(-) medium 56% of mineralization was registered, while with the trials containing SO4(2-) as supporting electrolyte a higher mineralization yield of 67% was reached, even obtaining a total removal of losartan potassium at 80mAcm(-2) and 180min of reaction time at pH 7.0. Higher losartan potassium concentrations enhanced the mineralization degree and the efficiency of the electrochemical oxidation process. During the mineralization up to 4 aromatic intermediates were identified by ultra high performance liquid chromatography tandem mass spectrometry (UHPLC-MS/MS). Moreover, short-linear carboxylic acids, like oxalic, succinic and oxamic were detected and quantified by ion-exclusion HPLC. Finally, the ability of the electrochemical oxidation process to mineralize dissolved commercial tablets containing losartan was achieved, obtaining TOC removal up to 71% under optimized conditions (10mAcm(-2), 0.05M Na2SO4, pH 7.0 and 25°C and 360min of electrolysis). Copyright © 2016 Elsevier B.V. All rights reserved.

  12. Electrospun manganese (III) oxide nanofiber based electrochemical DNA-nanobiosensor for zeptomolar detection of dengue consensus primer.

    PubMed

    Tripathy, Suryasnata; Krishna Vanjari, Siva Rama; Singh, Vikrant; Swaminathan, S; Singh, Shiv Govind

    2017-04-15

    Nanoscale biosensors, owing to their high-sensitivity and extremely low limits-of-detection, have enabled the realization of highly complex and sophisticated miniaturized platforms for several important healthcare applications, the most predominant one being disease diagnosis. In particular, nanomaterial facilitated electrochemical detection of DNA hybridization has had an exceptional impact on fields such as genetics and cancerous mutation detection Here we report an ultrasensitive electrochemical platform using electrospun semi-conducting Manganese (III) Oxide (Mn2O3) nanofibers for DNA Hybridization detection. The proposed platform coalesces the inherent advantages of metal-oxide nanofibers and electrochemical transduction techniques, resulting in label-free zeptomolar detection of DNA hybridization. As proof of concept, we demonstrate zeptomolar detection of Dengue consensus primer (limit of detection: 120×10(-21)M) both in control as well as spiked serum samples. Our reported detection limit is superior in comparison with previously reported electrochemical DNA hybridization sensors for Dengue virus detection, spanning both labeled and label-free transductions. This ultra-sensitivity, we believe, is a result of synthesizing a low bandgap electrospun metal-oxide nanomaterial corresponding to a specific oxidation state of Manganese. This methodology can be extended for detection of any hybridization of interest by simply adapting an appropriate functionalization protocol and thus is very generic in nature. Copyright © 2016 Elsevier B.V. All rights reserved.

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

    PubMed

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

    2014-01-01

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

  14. 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.

  15. SOLID OXIDE FUEL CELL CATHODES: Polarization Mechanisms and Modeling of the Electrochemical Performance

    NASA Astrophysics Data System (ADS)

    Fleig, Jurgen

    2003-08-01

    Several recent experimental and numerical investigations have contributed to the improved understanding of the electrochemical mechanisms taking place at solid oxide fuel cell (SOFC) cathodes and yielded valuable information on the relationships between alterable parameters (geometry/material) and the cathodic polarization resistance. Efforts to reduce the polarization resistance in SOFCs can benefit from these results, and some important aspects of the corresponding studies are reviewed. Experimental results, particularly measurements using geometrically well-defined Sr-doped LaMnO3 (LSM) cathodes, are discussed. In regard to simulations, the different levels of sophistication used in SOFC electrode modeling studies are summarized and compared. Exemplary simulations of mixed conducting cathodes that show the capabilities and limits of different modeling levels are described.

  16. Synthesis and characterization of zinc-molybdenum oxide photocatalysts using an electrochemical-thermal process

    NASA Astrophysics Data System (ADS)

    Goveas, J. J.; Gonsalves, R. A.; Rao, P.; Pinto, R.

    2016-05-01

    Dyes act as major pollutants in water and can be degraded by photocatalysis. This paper establishes the role of electrochemically generated nanostructures of Zinc-Molybdenum oxides (ZMO) as photocatalysts by degrading EBT (Eriochrome Black- T) taken as a model pollutant under UV light. A facile, rapid and low cost process to synthesize these nanostructures (ZMO) is presented. Various factors that affect the synthesis and photocatalytic activity of these nanostructures are discussed. The role of calcination temperature and pulverization on the photocatalytic action has also been established. Particles have been synthesized in pure form as well as using surfactants such as cetrimide (cetyl trimethyl ammonium bromide), polyethylene glycol (PEG) and SDS (sodium dodecyl sulphate) to enhance their photocatalytic action. This paper also discusses the characterization of these nanoparticles by powder XRD, SEM, FT-IR and UV-Visible spectroscopy. Decolourisation was achieved to completion under optimum experimental conditions at room temperature ascertaining the application of these nanostructures as effective photocatalysts.

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

    NASA Astrophysics Data System (ADS)

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

    2006-01-01

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

  18. 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

  19. 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.

  20. 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.

  1. Enhanced electrochemical oxidation of Acid Red 3R wastewater with iron phosphomolybdate supported catalyst.

    PubMed

    Wang, Li; Yue, Lin; Shi, Feng; Guo, Jianbo; Yang, Jingliang; Lian, Jing; Luo, Xiao; Guo, Yankai

    2015-01-01

    Electrochemical oxidation of Acid Red 3R (AR3R) was investigated with the new catalyst of iron phosphomolybdate (FePMo12) supported on modified molecular sieves type 4 Å (4A) as packing materials in the reactor. The results of the Fourier transform infrared spectroscopy and X-ray diffraction indicated that the heteropolyanion had a Keggin structure. The optimal conditions for decolorization of simulated AR3R wastewater were as follows: current density 35 mA/cm², initial pH 4.0, airflow 0.08 m³/hour and inter-electrode distance 3.0 cm. With the addition of NaCl to the system, the decolorization efficiency increased. But Na₂SO₄had a negative effect on the decolorization efficiency, which was attributed to the negative salt effect. The degradation mechanisms of AR3R were also discussed in detail.

  2. Pd Nanoparticles Coupled to WO2.72 Nanorods for Enhanced Electrochemical Oxidation of Formic Acid.

    PubMed

    Xi, Zheng; Erdosy, Daniel P; Mendoza-Garcia, Adriana; Duchesne, Paul N; Li, Junrui; Muzzio, Michelle; Li, Qing; Zhang, Peng; Sun, Shouheng

    2017-04-12

    We synthesize a new type of hybrid Pd/WO2.72 structure with 5 nm Pd nanoparticles (NPs) anchored on 50 × 5 nm WO2.72 nanorods. The strong Pd/WO2.72 coupling results in the lattice expansion of Pd from 0.23 to 0.27 nm and the decrease of Pd surface electron density. As a result, the Pd/WO2.72 shows much enhanced catalysis toward electrochemical oxidation of formic acid in 0.1 M HClO4; it has a mass activity of ∼1600 mA/mgPd in a broad potential range of 0.4-0.85 V (vs RHE) and shows no obvious activity loss after a 12 h chronoamperometry test at 0.4 V. Our work demonstrates an important strategy to enhance Pd NP catalyst efficiency for energy conversion reactions.

  3. Real-Time Electrochemical Impedance Spectroscopy Diagnosis of the Marine Solid Oxide Fuel Cell

    NASA Astrophysics Data System (ADS)

    Nakajima, Hironori; Kitahara, Tatsumi

    2016-09-01

    We have investigated the behavior of an operating solid oxide fuel cell (SOFC) with supplying a simulated syngas to develop SOFC diagnosis method for marine SOFC units fueled with liquefied natural gas. We analyse the characteristics of syngas fueled anode of an intermediate temperature microtubular SOFC at 500 °C as a model case by electrochemical impedance spectroscopy (EIS) to find parameters useful for the diagnosis. EIS analyses are performed with an equivalent circuit model consisting of several resistances and capacitances attributed to the anode and cathode processes. The characteristic changes of those circuit parameters by internal reforming and anode degradation show that they can be used for the real-time diagnosis of operating SOFCs.

  4. 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 µF 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.

  5. Removal of perfluorinated compounds in wastewater treatment plant effluents by electrochemical oxidation.

    PubMed

    Zhang, Chunhui; Wang, Liangliang; Li, Juan; Su, Peidong; Peng, Chen

    2015-01-01

    The presence of perfluorinated compounds (PFCs) in the effluents of a wastewater treatment plant (WWTP) in Beijing was investigated in the current study. Perfluorooctanoate acid and perfluorooctane sulfonate were the predominant PFCs in wastewater, accounting for 19-27% and 18-31%, respectively. The concentrations of PFCs with long chains were much lower than those PFCs with short chains (≤C8). An electrochemical oxidation reactor was employed for advanced treatment of PFCs in WWTP effluents using stainless steel plates as anode and cathode electrodes. It was concluded that the removal efficiency of PFCs was improved accordingly with the increasing applied current density. The removal efficiencies of target PFCs ranged from 23.53 to 51.79% with a reaction time of 30 minutes, current density of 20 mA/cm(2), electrode plate distance of 1.0 cm and electrode plate amounts of five pairs.

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

    NASA Astrophysics Data System (ADS)

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

    2016-03-01

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

  7. 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.

  8. A facile graphene oxide based sensor for electrochemical detection of neonicotinoids.

    PubMed

    Urbanová, Veronika; Bakandritsos, Aristides; Jakubec, Petr; Szambó, Tamás; Zbořil, Radek

    2017-03-15

    The increasing use of neonicotinoids in systematic seed treatment to crops is a serious cause of pollution of water resources and environment. Consequently, food sources can get eventually contaminated. To this end, it is desirable to develop suitable and effective platforms in order to obtain low-cost and sensitive sensors for neonicotinoids detection. In this work, graphene oxide modified electrodes were used as highly efficient electrochemical sensors for detection of two common insecticides - thiamethoxam and imidacloprid. The proposed sensor responded linearly in the concentration range of 10-200µmolL(-1) for both analytes and the detection limits were determined as low as 8.3µmolL(-1) and 7.9µmolL(-1) for thiamethoxam and imidacloprid, respectively. Analytical performance was also evaluated on spiked water and honey samples.

  9. Synthesis and characterization of zinc-molybdenum oxide photocatalysts using an electrochemical-thermal process

    SciTech Connect

    Goveas, J. J. Gonsalves, R. A.; Rao, P.; Pinto, R.

    2016-05-23

    Dyes act as major pollutants in water and can be degraded by photocatalysis. This paper establishes the role of electrochemically generated nanostructures of Zinc-Molybdenum oxides (ZMO) as photocatalysts by degrading EBT (Eriochrome Black- T) taken as a model pollutant under UV light. A facile, rapid and low cost process to synthesize these nanostructures (ZMO) is presented. Various factors that affect the synthesis and photocatalytic activity of these nanostructures are discussed. The role of calcination temperature and pulverization on the photocatalytic action has also been established. Particles have been synthesized in pure form as well as using surfactants such as cetrimide (cetyl trimethyl ammonium bromide), polyethylene glycol (PEG) and SDS (sodium dodecyl sulphate) to enhance their photocatalytic action. This paper also discusses the characterization of these nanoparticles by powder XRD, SEM, FT-IR and UV-Visible spectroscopy. Decolourisation was achieved to completion under optimum experimental conditions at room temperature ascertaining the application of these nanostructures as effective photocatalysts.

  10. 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

    2015-08-05

    One-dimensional, hydrous ruthenium oxide nanotubes (RuO2·1.84H2O) 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 F·g(-1) and 531 F·cm(-3), respectively, at a discharging current density of 0.5 A·g(-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.

  11. 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.

  12. Synthesis, characterization, and electrochemical response of iron oxide nanoparticles for sensing acetaminophen

    NASA Astrophysics Data System (ADS)

    Pal Singh, Beer; Kumar, Arun; Duarte, Armando P.; Rojas, Segundo J.; Crespo-Medina, Marielys; Areizaga-Martinez, Hector I.; Vega-Olivencia, Carmen A.; Tomar, M. S.

    2016-10-01

    Magnetite (Fe3O4) and hematite (α-Fe2O3) iron oxide nanoparticles were synthesized using the co-precipitation method via subsequent heat treatment using ferrous chloride (FeCl2.4H2O) as a source of iron. The synthesized powder was annealed at high temperature in an air atmosphere to promote the formation of the hematite (α-Fe2O3) phase. Both oxide phases of iron oxide were characterized using x-ray diffraction, thermogravimetric, and differential scanning calorimetric analysis, and Raman spectroscopy. The phases of as-synthesized nanoparticles were confirmed by XRD and Raman studies. The thermal behavior and weight loss of the initial powdered Fe3O4 to α-Fe2O3 was studied using TG-DSC analysis. In the present case, the Fe3O4 and α-Fe2O3 nanoparticles were used for the electrochemical sensing of acetaminophen (C6H9NO2). The sensing of acetaminophen was performed by Fe3O4 and α-Fe2O3 modified glassy carbon electrode, using a potential controlled cyclic voltammetric technique. The Fe3O4 and α-Fe2O3 nanoparticles exhibited electrocatalytic ability for sensing acetaminophen. Detailed results are included.

  13. 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.

  14. Critical review of electrochemical advanced oxidation processes for water treatment applications.

    PubMed

    Chaplin, Brian P

    2014-05-01

    Electrochemical advanced oxidation processes (EAOPs) have emerged as novel water treatment technologies for the elimination of a broad-range of organic contaminants. Considerable validation of this technology has been performed at both the bench-scale and pilot-scale, which has been facilitated by the development of stable electrode materials that efficiently generate high yields of hydroxyl radicals (OH˙) (e.g., boron-doped diamond (BDD), doped-SnO2, PbO2, and substoichiometic- and doped-TiO2). Although a promising new technology, the mechanisms involved in the oxidation of organic compounds during EAOPs and the corresponding environmental impacts of their use have not been fully addressed. In order to unify the state of knowledge, identify research gaps, and stimulate new research in these areas, this review critically analyses published research pertaining to EAOPs. Specific topics covered in this review include (1) EAOP electrode types, (2) oxidation pathways of select classes of contaminants, (3) rate limitations in applied settings, and (4) long-term sustainability. Key challenges facing EAOP technologies are related to toxic byproduct formation (e.g., ClO4(-) and halogenated organic compounds) and low electro-active surface areas. These challenges must be addressed in future research in order for EAOPs to realize their full potential for water treatment.

  15. Hydrothermally Oxidized Single-Walled Carbon Nanotube Networks for High Volumetric Electrochemical Energy Storage.

    PubMed

    Liu, Tianyuan; Davijani, Amir A Bakhtiary; Sun, Jingying; Chen, Shuo; Kumar, Satish; Lee, Seung Woo

    2016-07-01

    Improving volumetric energy density is one of the major challenges in nanostructured carbon electrodes for electrochemical energy storage device applications. Herein, a simple hydrothermal oxidation process of single-walled carbon nanotube (SWNT) networks in dilute nitric acid is reported, enabling simultaneous physical densification and chemical functionalization of the as-assembled randomly-packed SWNT films. After the hydrothermal oxidation process, the density of the SWNT films increases from 0.63 to 1.02 g cm(-3) and a considerable amount of redox-active oxygen functional groups are introduced on the surface of the SWNTs. The functionalized SWNT films are used as positive electrodes against Li metal negative electrodes for potential Li-ion capacitors or Li-ion battery applications. The functionalized SWNT electrodes deliver high volumetric as well as gravimetric capacities, 154 Ah L(-1) and 152 mAh g(-1) , respectively, owing to the surface redox reactions between the introduced oxygen functional groups and Li ions. In addition, these electrodes exhibit a remarkable rate-capability by retaining its high capacity of 94 Ah L(-1) (92 mAh g(-1) ) at a high discharge rate of 10 A g(-1) . These results demonstrate the simple hydrothermal oxidation process as an attractive strategy for improving the volumetric performance of nanostructured carbon electrodes. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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

    PubMed

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

    2015-01-19

    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.

  17. Nano-scale islands of ruthenium oxide as an electrochemical sensor for iodate and periodate determination.

    PubMed

    Chatraei, Fatemeh; Zare, Hamid R

    2013-03-01

    In this study, a promising electrochemical sensor was fabricated by the electrodeposition of nano-scale islands of ruthenium oxide (ruthenium oxide nanoparticles, RuON) on a glassy carbon electrode (RuON-GCE). Then, the electrocatalytic oxidation of iodate and periodate was investigated on it, using cyclic voltammetry, chronoamperometry and amperometry as diagnostic techniques. The charge transfer coefficient, α, and the charge transfer rate constant, ks, for electron transfer between RuON and GCE were calculated as 0.5 ± 0.03 and 9.0 ± 0.7 s(-1) respectively. A comparison of the data obtained from the electrocatalytic reduction of iodate and periodate at a bare GCE (BGCE) and RuON-GCE clearly shows that the unique electronic properties of nanoparticles definitely improve the characteristics of iodate and periodate electrocatalytic reduction. The kinetic parameters such as the electron transfer coefficient, α, and the heterogeneous electron transfer rate constant, k', for the reduction of iodate and periodate at RuON-GCE surface were determined using cyclic voltammetry. Amperometry revealed a good linear relationship between the peak current and the concentration of iodate and periodate. The detection limits of 0.9 and 0.2 μM were calculated for iodate and periodate respectively.

  18. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2015-05-01

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

  20. An electrochemical dopamine aptasensor incorporating silver nanoparticle, functionalized carbon nanotubes and graphene oxide for signal amplification.

    PubMed

    Bahrami, Shokoh; Abbasi, Amir Reza; Roushani, Mahmoud; Derikvand, Zohreh; Azadbakht, Azadeh

    2016-10-01

    In this work, immobilization of a dopamine (DA) aptamer was performed at the surface of an amino functionalized silver nanoparticle-carbon nanotube graphene oxide (AgNPs/CNTs/GO) nanocomposite. A 58-mer DA-aptamer was immobilized through the formation of phosphoramidate bonds between the amino group of chitosan and the phosphate group of the aptamer at the 5' end. An AgNPs/CNTs/GO nanocomposite was employed as a highly catalytic label for electrochemical detection of DA based on electrocatalytic activity of the nanocomposite toward hydrogen peroxide (H2O2). Interaction of DA with the aptamer caused conformational changes of the aptamer which, in turn, decreased H2O2 oxidation and reduction peak currents. On the other hand, the presumed folding of the DA-aptamer complexes on the sensing interface inhibited the electrocatalytic activity of AgNPs/CNTs/GO toward H2O2. Sensitive quantitative detection of DA was carried out by monitoring the decrease of differential pulse voltammetric (DPV) responses of AgNPs/CNTs/GO nanocomposite toward H2O2 oxidation. The DPV signal linearly decreased with increased concentration of DA from 3 to 110nmolL(-1) with a detection limit of 700±19.23pmolL(-1). Simple preparation, low operation cost, speed and validity are the decisive factors of this method motivating its application to biosensing investigation.

  1. 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.

  2. Açaí (Euterpe oleracea Mart.) Modulates Oxidative Stress Resistance in Caenorhabditis elegans by Direct and Indirect Mechanisms

    PubMed Central

    Bonomo, Larissa de Freitas; Silva, David Nunes; Boasquivis, Patrícia Ferreira; Paiva, Franciny Aparecida; Guerra, Joyce Ferreira da Costa; Martins, Talita Alves Faria; de Jesus Torres, Álvaro Gustavo; de Paula, Igor Thadeu Borges Raposo; Caneschi, Washington Luiz; Jacolot, Philippe; Grossin, Nicolas; Tessier, Frederic J.; Boulanger, Eric; Silva, Marcelo Eustáquio; Pedrosa, Maria Lúcia; de Paula Oliveira, Riva

    2014-01-01

    Açaí (Euterpe oleracea Mart.) has recently emerged as a promising source of natural antioxidants. Despite its claimed pharmacological and nutraceutical value, studies regarding the effects of açaí in vivo are limited. In this study, we use the Caenorhabditis elegans model to evaluate the in vivo antioxidant properties of açaí on an organismal level and to examine its mechanism of action. Supplementation with açaí aqueous extract (AAE) increased both oxidative and osmotic stress resistance independently of any effect on reproduction and development. AAE suppressed bacterial growth, but this antimicrobial property did not influence stress resistance. AAE-increased stress resistance was correlated with reduced ROS production, the prevention of sulfhydryl (SH) level reduction and gcs-1 activation under oxidative stress conditions. Our mechanistic studies indicated that AAE promotes oxidative stress resistance by acting through DAF-16 and the osmotic stress response pathway OSR-1/UNC-43/SEK-1. Finally, AAE increased polyglutamine protein aggregation and decreased proteasome activity. Our findings suggest that natural compounds available in AAE can improve the antioxidant status of a whole organism under certain conditions by direct and indirect mechanisms. PMID:24594796

  3. Mechanical and electrochemical characterization of intermediate temperature micro-tubular solid oxide fuel cell

    NASA Astrophysics Data System (ADS)

    Pusz, Jakub

    Solid oxide fuel cells (SOFCs) are attributed for being highly efficient in their energy conversion capabilities and fuel flexibility. The primary objective of this study was to develop an operating solid oxide fuel cell using innovative and cost-effective fabrication techniques. The secondary objective of this research aimed at improving mechanical and electrochemical properties of the cell through utilization of electrode materials characterized by different morphology. The system studied was a micro-tubular, anode supported SOFC operated on both hydrogen and internally-reformed methane at the temperature range of 800-850°C. The research studied different anode poreformers and the utilization of anode powders with different morphologies. Anode supports, fabricated using an extrusion process, were based on a standard composition of 50/50 vol% of NiO/8YSZ powder. Procedures were developed to deposit a 2-5 mum thin and dense 8YSZ electrolyte film via a quick and cost-effective vacuum infiltration process. Two different materials were utilized to fabricate anode supports. The first anode powder consisted of small, nano-size, particles, while the second powder was a sub-micron size powder. Vastly improved power density and redox cycling results were observed from a fuel cell fabricated using a fine powder. For example a power density of >0.5 W cm-2 at 800°C was observed. The performance data of an SOFC operating on internally-reformed methane is presented. A response of the fuel cell set up using two different sealing designs, a cold-seal design and a hot-seal design, is also explained. The electrochemical activity of Gd0.5Sr0.5CoO 3-x cathode fabricated using a standard glycine-nitrate pyrolysis technique and a technique allowing direct deposition of cathode material on top of electrolyte powder was tested. The thesis concludes with recommendations for further work.

  4. Design of a new nanocomposite between bismuth nanoparticles and graphene oxide for development of electrochemical sensors.

    PubMed

    Bindewald, Eduardo H; Schibelbain, Arthur F; Papi, Maurício A P; Neiva, Eduardo G C; Zarbin, Aldo J G; Bergamini, Márcio F; Marcolino-Júnior, Luiz H

    2017-10-01

    This study describes a new route for preparation of a nanocomposite between graphene oxide (GO) and bismuth nanoparticles (BiNPs) and its evaluation as modifier electrode for development of electrochemical sensors. BiNPs were synthesized under ultrasound conditions using Bi(NO3)3 as metal precursor and ascorbic acid (AA) as reducing agent/passivating. Some experimental parameters of BiNPs synthesis such as Bi(3+):AA molar ratio and reaction time were conducted aiming the best voltammetric performance of the sensor. Glassy carbon electrodes (GCE) were modified by drop-casting with the BiNPs dispersions and anodic stripping voltammetry measurements were performed and revealed an improvement in the sensitivityfor determination of Cd(II) and Pb(II) compared to an unmodified electrode. The best electrochemical response was obtained for a BiNPs synthesis with Bi(3+):AA molar ratio of 1:6 and reaction time of 10min, which yielded Bi metallic nanoparticles with average size of 5.4nm confirmed by XRD and TEM images, respectively. GO was produced by graphite oxidation using potassium permanganate and exfoliated with an ultrasound tip. GO-BiNPs nanocomposite was obtained by a simple mixture of GO and BiNPs dispersions in water and kept under ultrasonic bath for 1h. GCE were modified with a nanocomposite suspension containing 0.3 and 1.5mgmL(-1) of GO and BiNPs in water, respectively. Under optimized conditions, the proposed nanocomposite was evaluated on the voltammetric determination of Pb (II) and Cd (II), leading to a linear response range between 0.1 and 1.4μmolL(-1) for both cations, with limit of detection of 30 and 27nmolL(-1), respectively. These results indicate the great potential of the GO-BiNPs nanocomposite for improving the sensitivity of voltammetric procedures. Copyright © 2017 Elsevier B.V. All rights reserved.

  5. Boron-doped cadmium oxide composite structures and their electrochemical measurements

    SciTech Connect

    Lokhande, B.J.; Ambare, R.C.; Mane, R.S.; Bharadwaj, S.R.

    2013-08-01

    Graphical abstract: Conducting nano-fibrous 3% boron doped cadmium oxide thin films were prepared by SILAR and its super capacitive properties were studied. - Highlights: • Samples are of nanofibrous nature. • All samples shows pseudocapacitive behavior. • 3% B doped CdO shows good specific capacitance. • 3% B doped CdO shows maximum 74.93% efficiency at 14 mA/cm{sup 2}. • 3% B doped CdO shows 0.8 Ω internal resistance. - Abstract: Boron-doped and undoped cadmium oxide composite nanostructures in thin film form were prepared onto stainless steel substrates by a successive ionic layer adsorption and reaction method using aqueous solutions of cadmium nitrate, boric acid and 1% H{sub 2}O{sub 2}. As-deposited films were annealed at 623 K for 1 h. The X-ray diffraction study shows crystalline behavior for both doped and undoped films with a porous topography and nano-wires type architecture, as observed in SEM image. Wettability test confirms the hydrophilic surface with 58° contact angle value. Estimated band gap energy is around 1.9 eV. Electrochemical behavior of the deposited films is attempted in 1 M KOH electrolyte using cyclic voltammetry (CV), electrochemical impedance spectroscopy and galvanostatic charge–discharge tests. Maximum values of the specific capacitance, specific energy and specific power obtained for 3% B doped CdO film at 2 mV/s scan rate are 20.05 F/g, 1.22 Wh/kg and 3.25 kW/kg, respectively.

  6. 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.

  7. Effect of preadsorbed sulfur on the electrochemical reduction of nitric oxide

    SciTech Connect

    Foral, M.J.

    1988-01-01

    The effect of adsorbed sulfur on platinum black/Teflon gas diffusion electrodes has been studied. The controlled deposition and characterization of intermediate coverages of sulfur (fractional sulfur coverages, {Theta}, between 0 and 1.0, based on the total number of Pt surface sites) was first studied, followed by an investigation of the effects of this preadsorbed sulfur on the electrogenerative (i.e. galvanic) reduction of pure and dilute (3%) NO feeds. These effects are discussed in terms of possible applications for electrogenerative NO reduction, especially hydroxylamine production and flue gas scrubbing applications. Sulfur was deposited through electrochemical reduction of sulfur dioxide which had bene previously adsorbed from SO{sub 2}-containing aqueous sulfuric acid solutions. The sulfur layers deposited in this manner were electrochemically characterized using linear sweep and cyclic voltammetry. Sulfur/hydrogen coadsorption coverage plots constructed from coulometric measurements were studied and yielded evidence that a sulfur bilayer is formed on the electrode. In the presence of adsorbed sulfur (0.2 < {Theta} < 1.0) the current generated by the nitric oxide-hydrogen electrogenerative cell was diminished. This effect was more pronounced with pure NO feeds. The decreased cell current involved not only diminished NO conversion, but also a change in product distribution brought about by adsorbed sulfur. At low sulfur coverages and low cell potentials ammonia is the predominant product, but at higher sulfur coverages selectivity shifts to favor hydroxylamine production. Nitrous oxide is formed only at high cell potentials at all sulfur coverages, and nitrogen formation is allowed at lower sulfur coverages but inhibited at higher coverages.

  8. 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

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

    PubMed

    del Río, A I; Molina, J; Bonastre, J; Cases, F

    2009-12-15

    Synthetic solutions of hydrolysed C.I. Reactive Orange 4, a monoazo textile dye commercially named Procion Orange MX-2R (PMX2R) and colour index number C.I. 18260, was exposed to electrochemical treatment under galvanostatic conditions and Na2SO4 as electrolyte. The influence of the electrochemical process as well as the applied current density was evaluated. Ti/SnO2-Sb-Pt and stainless steel electrodes were used as anode and cathode, respectively, and the intermediates generated on the cathode during electrochemical reduction were investigated. Aliquots of the solutions treated were analysed by UV-visible and FTIR-ATR spectroscopy confirming the presence of aromatic structures in solution when an electro-reduction was carried out. Electro-oxidation degraded both the azo group and aromatic structures. HPLC measures revealed that all processes followed pseudo-first order kinetics and decolourisation rates showed a considerable dependency on the applied current density. CV experiments and XPS analyses were carried out to study the behaviour of both PMX2R and intermediates and to analyse the state of the cathode after the electrochemical reduction, respectively. It was observed the presence of a main intermediate in solution after an electrochemical reduction whose chemical structure is similar to 2-amino-1,5-naphthalenedisulphonic acid. Moreover, the analysis of the cathode surface after electrochemical reduction reveals the presence of a coating layer with organic nature.

  10. Electrochemical characterization of Fe-air rechargeable oxide battery in planar solid oxide cell stacks

    NASA Astrophysics Data System (ADS)

    Fang, Qingping; Berger, Cornelius M.; Menzler, Norbert H.; Bram, Martin; Blum, Ludger

    2016-12-01

    Iron-air rechargeable oxide batteries (ROB) comprising solid oxide cells (SOC) as energy converters and Fe/metal-oxide redox couples were characterized using planar SOC stacks. The charge and discharge of the battery correspond to the operations in the electrolysis and fuel cell modes, respectively, but with a stagnant atmosphere consisting of hydrogen and steam. A novel method was employed to establish the stagnant atmosphere for battery testing during normal SOC operation without complicated modification to the test bench and stack/battery concept. Manipulation of the gas compositions during battery operation was not necessary, but the influence of the leakage current from the testing system had to be considered. Batteries incorporating Fe2O3/8YSZ, Fe2O3/CaO and Fe2O3/ZrO2 storage materials were characterized at 800 °C. A maximum charge capacity of 30.4 Ah per layer (with an 80 cm2 active cell area) with ∼0.5 mol Fe was reached with a current of 12 A. The charge capacity lost 11% after ∼130 ROB cycles due to the increased agglomeration of active materials and formation of a dense oxide layer on the surface. The round trip efficiencies of the tested batteries were ≤84% due to the large internal resistance. With state-of-the-art cells, the round trip efficiency can be further improved.

  11. Electrochemical capacitance of iron oxide nanotube (Fe-NT): effect of annealing atmospheres.

    PubMed

    Sarma, Biplab; Jurovitzki, Abraham L; Ray, Rupashree S; Smith, York R; Mohanty, Swomitra K; Misra, Mano

    2015-07-03

    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

  12. Graphene oxide functionalized with silver@silica-polyethylene glycol hybrid nanoparticles for direct electrochemical detection of quercetin.

    PubMed

    Veerapandian, Murugan; Seo, Yeong-Tai; Yun, Kyusik; Lee, Min-Ho

    2014-08-15

    A direct electrochemical detection of quercetin based on functionalized graphene oxide modified on gold-printed circuit board chip was demonstrated in this study. Functionalized graphene oxide materials are prepared by the covalent reaction of graphene oxide with silver@silica-polyethylene glycol nanoparticles (~12.35nm). Functionalized graphene oxide electrode shows a well-defined voltammetric response in phosphate buffered saline and catalyzes the oxidation of quercetin to quinone without the need of an enzyme. Significantly, the functionalized graphene oxide modified electrode exhibited a higher sensitivity than pristine gold-printed circuit board and graphene oxide electrodes, a wide concentration range of 7.5 to 1040nM and detection limit of 3.57nM. Developed biosensor platform is selective toward quercetin in the presence of an interferent molecule. Copyright © 2014 Elsevier B.V. All rights reserved.

  13. High Power Electrochemical Capacitors

    DTIC Science & Technology

    2012-03-23

    electrochemical properties of vanadium oxide aerogels prepared by a freeze-drying process. Journal of the Electrochemical Society, 2004. 151(5): p...Electrochemical Society, 2002. 149(1): p. A26-A30. 12. Rolison, D.R. and B. Dunn, Electrically conductive oxide aerogels : new materials in...surface area vanadium oxide aerogels . Electrochemical and Solid-State Letters, 2000. 3(10): p. 457-459. 14. Shembel, E., et al., Synthesis, investigation

  14. Indirect nitrous oxide emissions from streams within the US Corn Belt scale with stream order

    PubMed Central

    Turner, Peter A.; Griffis, Timothy J.; Lee, Xuhui; Baker, John M.; Venterea, Rodney T.; Wood, Jeffrey D.

    2015-01-01

    N2O is an important greenhouse gas and the primary stratospheric ozone depleting substance. Its deleterious effects on the environment have prompted appeals to regulate emissions from agriculture, which represents the primary anthropogenic source in the global N2O budget. Successful implementation of mitigation strategies requires robust bottom-up inventories that are based on emission factors (EFs), simulation models, or a combination of the two. Top-down emission estimates, based on tall-tower and aircraft observations, indicate that bottom-up inventories severely underestimate regional and continental scale N2O emissions, implying that EFs may be biased low. Here, we measured N2O emissions from streams within the US Corn Belt using a chamber-based approach and analyzed the data as a function of Strahler stream order (S). N2O fluxes from headwater streams often exceeded 29 nmol N2O-N m−2⋅s−1 and decreased exponentially as a function of S. This relation was used to scale up riverine emissions and to assess the differences between bottom-up and top-down emission inventories at the local to regional scale. We found that the Intergovernmental Panel on Climate Change (IPCC) indirect EF for rivers (EF5r) is underestimated up to ninefold in southern Minnesota, which translates to a total tier 1 agricultural underestimation of N2O emissions by 40%. We show that accounting for zero-order streams as potential N2O hotspots can more than double the agricultural budget. Applying the same analysis to the US Corn Belt demonstrates that the IPCC EF5r underestimation explains the large differences observed between top-down and bottom-up emission estimates. PMID:26216994

  15. Odin/SMR nitric oxide observations and its contribution to a better understanding of energetic particle precipitation indirect effect

    NASA Astrophysics Data System (ADS)

    Perot, Kristell; Urban, Joachim; Murtagh, Donal

    The Sub-Millimeter Radiometer (SMR) on board the Odin platform, launched in 2001, is a limb emission sounder measuring trace gases in the stratosphere, mesosphere, and lower thermosphere. Odin is a Swedish-led satellite project funded jointly by Sweden (SNSB), Canada (CSA), Finland (TEKES), and France (CNES), with support by the 3rd party mission programme of the European Space Agency (ESA). Energetic Particle Precipitation (EPP) refers to the process by which energetic protons and electrons affect the Earth’s middle atmosphere. The precipitation of magnetospheric electrons into the polar atmosphere during geomagnetic perturbations leads to nitric oxide (NO) formation in the polar upper mesosphere and lower thermosphere (MLT). During polar winter, EPP-generated NO can be transported downward into the stratosphere by the meridional circulation, where it can affect the ozone concentration. This important solar-terrestrial coupling mechanism is called the EPP indirect effect (EPP IE). Odin/SMR supplies the scientific community with a 10 year NO data set, and measurements of several other related species. The analysis of these long term observations shows that EPP IE is strongly dependent on dynamical activity. Very strong NO downward transport events are observed during most of the winters characterized by a major midwinter stratospheric sudden warming (SSW). SMR is involved in the SPARC project HEPPA-MMI (High Energy Particle Precipitation in the Atmosphere - Model-Measurement Inter-comparison). The goal of this international working group is to get a better understanding of EPP-induced middle atmospheric changes, and to assess the ability of current models to reproduce those phenomena. The work is based on inter-comparisons between measurements from several instruments and results from different models, focusing on the 2008/2009 northern hemisphere polar winter. This period was characterized by peculiar dynamical conditions, with a particularly strong SSW

  16. Elucidation of the factors affecting the oxidative activity of Acremonium sp. HI-25 ascorbate oxidase by an electrochemical approach

    SciTech Connect

    Murata, Kenichi; Nakamura, Nobuhumi Ohno, Hiroyuki

    2008-03-07

    Steady-state kinetics of Acremonium sp. HI-25 ascorbate oxidase toward p-hydroquinone derivatives have been examined by using an electrochemical analysis based on the theory of steady-state bioelectrocatalysis. The electrochemical technique has enabled one to examine the influence of electronic and chemical properties of substrates on the activity. It was proven that the oxidative activity of ascorbate oxidase was dominated by the highly selective substrate-binding affinity based on electrostatic interaction beyond the one-electron redox potential difference between ascorbate oxidase's type 1 copper site and substrate.

  17. Elucidation of the factors affecting the oxidative activity of Acremonium sp. HI-25 ascorbate oxidase by an electrochemical approach.

    PubMed

    Murata, Kenichi; Nakamura, Nobuhumi; Ohno, Hiroyuki

    2008-03-07

    Steady-state kinetics of Acremonium sp. HI-25 ascorbate oxidase toward p-hydroquinone derivatives have been examined by using an electrochemical analysis based on the theory of steady-state bioelectrocatalysis. The electrochemical technique has enabled one to examine the influence of electronic and chemical properties of substrates on the activity. It was proven that the oxidative activity of ascorbate oxidase was dominated by the highly selective substrate-binding affinity based on electrostatic interaction beyond the one-electron redox potential difference between ascorbate oxidase's type 1 copper site and substrate.

  18. 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.

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

    PubMed

    del Río, A I; Molina, J; Bonastre, J; Cases, F

    2009-06-01

    The electrochemical treatment of wastewaters from textile industry is a promising treatment technique for substances which are resistant to biodegradation. This paper presents the results of the electrochemical decolourisation and degradation of C.I. Reactive Orange 4 synthetic solutions (commercially known as Procion Orange MX2R). Electrolyses were carried out under galvanostatic conditions in a divided or undivided electrolytic cell. Therefore, oxidation, reduction or oxido-reduction experiences were tested. Ti/SnO(2)-Sb-Pt and stainless steel electrodes were used as anode and cathode, respectively. Degradation of the dye was followed by TOC, total nitrogen, COD and BOD(5) analyses. TOC removal after an oxidation process was higher than after oxido-reduction while COD removal after this last process was about 90%. Besides, the biodegradability of final samples after oxido-reduction process was studied and an improvement was observed. UV-Visible spectra revealed the presence of aromatic structures in solution when an electro-reduction was carried out while oxido-reduction process degraded both azo group and aromatic structures. HPLC analyses indicated the presence of a main intermediate after the reduction process with a chemical structure closely similar to 2-amine-1, 5-naphthalenedisulfonic acid. The lowest decolourisation rate corresponded to electrochemical oxidation. In these experiences a higher number of intermediates were generated as HPLC analysis demonstrated. The decolourisation process for the three electrochemical processes studied presented a pseudo-first order kinetics.

  20. Chemically Reduced Graphene Oxide for the Assessment of Food Quality: How the Electrochemical Platform Should Be Tailored to the Application.

    PubMed

    Chng, Chu'Er; Ambrosi, Adriano; Chua, Chun Kiang; Pumera, Martin; Bonanni, Alessandra

    2017-02-03

    Graphene platforms have been drawing considerable attention in electrochemistry for the detection of various electroactive probes. Depending on the chemical composition and properties of the probe, graphene materials with diverse structural features may be required to achieve an optimal electrochemical performance. This work comprises a comparative study on three chemically modified graphenes, obtained from the same starting material and with different oxygen functionalities and structural defects (graphene oxide (GO), chemically reduced graphene oxide (CRGO), and thermally reduced graphene oxide (TRGO)) towards the electrochemical detection of quinine, an important flavoring agent present in tonic-based beverages. In general, the reduced graphenes, namely CRGO and TRGO, showed enhanced performance in terms of calibration sensitivity and selectivity, due to the improved heterogeneous electron-transfer rates on their surfaces. In particular, CRGO provided the best overall electrochemical performance, which can be attributed to its higher density of structural defects and reduced amount of oxygen functionalities. For this reason, CRGO was employed for the electrochemical detection of quinine in commercial tonic drink samples, showing high sensitivity and selectivity, and therefore representing a valid low-cost alternative to more complicated and time consuming traditional analytical methods.

  1. Electrochemical Synthesis of Polypyrrole, Reduced Graphene Oxide, and Gold Nanoparticles Composite and Its Application to Hydrogen Peroxide Biosensor

    PubMed Central

    Wu, Baoyan; Zhao, Na; Hou, Shihua; Zhang, Cong

    2016-01-01

    Here we report a facile eco-friendly one-step electrochemical approach for the fabrication of a polypyrrole (PPy), reduced graphene oxide (RGO), and gold nanoparticles (nanoAu) biocomposite on a glassy carbon electrode (GCE). The electrochemical behaviors of PPy–RGO–nanoAu and its application to electrochemical detection of hydrogen peroxide were investigated by cyclic voltammetry. Graphene oxide and pyrrole monomer were first mixed and casted on the surface of a cleaned GCE. After an electrochemical processing consisting of the electrooxidation of pyrrole monomer and simultaneous electroreduction of graphene oxide and auric ions (Au3+) in aqueous solution, a PPy–RGO–nanoAu biocomposite was synthesized on GCE. Each component of PPy–RGO–nanoAu is electroactive without non-electroactive substance. The obtained PPy–RGO–nanoAu/GCE exhibited high electrocatalytic activity toward hydrogen peroxide, which allows the detection of hydrogen peroxide at a negative potential of about −0.62 V vs. SCE. The amperometric responses of the biosensor displayed a sensitivity of 40 µA/mM, a linear range of 32 µM–2 mM, and a detection limit of 2.7 µM (signal-to-noise ratio = 3) with good stability and acceptable reproducibility and selectivity. The results clearly demonstrate the potential of the as-prepared PPy–RGO–nanoAu biocomposite for use as a highly electroactive matrix for an amperometric biosensor. PMID:28335348

  2. Electrochemical Synthesis of Polypyrrole, Reduced Graphene Oxide, and Gold Nanoparticles Composite and Its Application to Hydrogen Peroxide Biosensor.

    PubMed

    Wu, Baoyan; Zhao, Na; Hou, Shihua; Zhang, Cong

    2016-11-21

    Here we report a facile eco-friendly one-step electrochemical approach for the fabrication of a polypyrrole (PPy), reduced graphene oxide (RGO), and gold nanoparticles (nanoAu) biocomposite on a glassy carbon electrode (GCE). The electrochemical behaviors of PPy-RGO-nanoAu and its application to electrochemical detection of hydrogen peroxide were investigated by cyclic voltammetry. Graphene oxide and pyrrole monomer were first mixed and casted on the surface of a cleaned GCE. After an electrochemical processing consisting of the electrooxidation of pyrrole monomer and simultaneous electroreduction of graphene oxide and auric ions (Au(3+)) in aqueous solution, a PPy-RGO-nanoAu biocomposite was synthesized on GCE. Each component of PPy-RGO-nanoAu is electroactive without non-electroactive substance. The obtained PPy-RGO-nanoAu/GCE exhibited high electrocatalytic activity toward hydrogen peroxide, which allows the detection of hydrogen peroxide at a negative potential of about -0.62 V vs. SCE. The amperometric responses of the biosensor displayed a sensitivity of 40 µA/mM, a linear range of 32 µM-2 mM, and a detection limit of 2.7 µM (signal-to-noise ratio = 3) with good stability and acceptable reproducibility and selectivity. The results clearly demonstrate the potential of the as-prepared PPy-RGO-nanoAu biocomposite for use as a highly electroactive matrix for an amperometric biosensor.

  3. 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.

  4. The impact of match-play tennis in a hot environment on indirect markers of oxidative stress and antioxidant status

    PubMed Central

    Knez, Wade L; Périard, JP

    2014-01-01

    Objectives The purpose of this study was to determine the impact of changes in oxidative stress and antioxidant status in response to playing tennis in HOT (∼36°C and 35% relative humidity (RH)) and COOL (∼22°C and 70% RH) conditions. Methods 10 male tennis players undertook two matches for an effective playing time (ie, ball in play) of 20 min, corresponding to ∼122 and ∼107 min of total play in HOT and COOL conditions, respectively. Core body temperature, body mass and indirect markers of oxidative stress (diacrons reactive oxygen metabolic test) and antioxidant status (biological antioxidant potential test) were assessed immediately prematch, midmatch and postmatch, and 24 and 48 h into recovery. Results Regardless of the condition, oxidative stress remained similar throughout play and into recovery. Likewise, match-play tennis in the COOL had no impact on antioxidant status. However, antioxidants status increased significantly in the HOT compared with COOL environment (p<0.05). Body mass losses (∼0.5 kg) were similar between conditions. Rectal temperature increased during both matches (p<0.05), but with a greater magnitude in the HOT (39.3±0.5°C) versus COOL (38.7±0.2°C) environment (p<0.05). Conclusions Match-play tennis in the heat does not exacerbate the development of oxidative stress, but significantly increases antioxidant status. These data suggest that the heat stress observed in the HOT environment may provide a necessary signal for the upregulation of antioxidant defence, dampening cellular damage. PMID:24668382

  5. Preparation of AAO-CeO2 nanotubes and their application in electrochemical oxidation desulfurization of diesel.

    PubMed

    Du, Xiaoqing; Yang, Yumeng; Yi, Chenxi; Chen, Yu; Cai, Chao; Zhang, Zhao

    2017-02-10

    The coaxial arrays of AAO-CeO2 NTs have been successfully galvanostatically deposited on an anode, characterized and adopted as a catalyst for removing organic sulfurs from diesel. The influence of the main electrochemical oxidation factors on the efficiency of desulfurization have also been investigated. The results show that the fabrication process of AAO-CeO2 NTs is accompanied by the formation of a new phase, namely Al3Ce, and the main oxidation products of the diesel are soluble inorganic sulphides, especially Ce2(SO4)3. When compared with dibenzothiophene and 4, 6-dimethyldibenzothiophene, benzothiophene is much more easily removed, with a removal efficiency that reaches 87.2%. Finally, a possible electrochemical oxidation desulfurization pathway for diesel is proposed.

  6. Preparation of AAO-CeO2 nanotubes and their application in electrochemical oxidation desulfurization of diesel

    NASA Astrophysics Data System (ADS)

    Du, Xiaoqing; Yang, Yumeng; Yi, Chenxi; Chen, Yu; Cai, Chao; Zhang, Zhao

    2017-02-01

    The coaxial arrays of AAO-CeO2 NTs have been successfully galvanostatically deposited on an anode, characterized and adopted as a catalyst for removing organic sulfurs from diesel. The influence of the main electrochemical oxidation factors on the efficiency of desulfurization have also been investigated. The results show that the fabrication process of AAO-CeO2 NTs is accompanied by the formation of a new phase, namely Al3Ce, and the main oxidation products of the diesel are soluble inorganic sulphides, especially Ce2(SO4)3. When compared with dibenzothiophene and 4, 6-dimethyldibenzothiophene, benzothiophene is much more easily removed, with a removal efficiency that reaches 87.2%. Finally, a possible electrochemical oxidation desulfurization pathway for diesel is proposed.

  7. Probing Structural Changes in Poly(3-hexylthiophene) (P3HT) During Electrochemical Oxidation with In Situ X-ray Scattering

    NASA Astrophysics Data System (ADS)

    Thelen, Jacob L.; Patel, Shrayesh N.; Javier, Anna E.; Balsara, Nitash P.

    2014-03-01

    Mixtures of poly(3-hexylthiophene)-b-poly(ethylene oxide) (P3HT-b-PEO) block copolymer and lithium bis(trifluromethanesulfonyl) imide (LiTFSI) salt can microphase separate into electron (P3HT) and ion (PEO/LiTFSI) conducting domains. P3HT is a semicrystalline polymer with intrinsically semiconducting electronic properties. Electrochemical oxidation (doping) of the P3HT block provides the P3HT-b-PEO/LiTFSI mixtures with electronic conductivity suitable for lithium battery operation. Due to the presence of the solid-state electrolyte (PEO/LiTFSI) in intimate contact with the microphase separated P3HT domains, electrochemical oxidation of P3HT can be performed entirely in the solid state; therefore, P3HT-b-PEO/LiTFSI provides a unique opportunity to study the structural changes in P3HT induced by oxidation. We use in situ x-ray scattering techniques to probe structural changes in P3HT during electrochemical oxidation and correlate these changes with previously observed enhancements in electron mobility. Supported by the Joint Center for Energy Storage Research (JCESR).

  8. Kinetics and mechanism of the electrochemical formation of iron oxidation products on steel immersed in sour acid media.

    PubMed

    Hernández-Espejel, Antonio; Palomar-Pardavé, Manuel; Cabrera-Sierra, Román; Romero-Romo, Mario; Ramírez-Silva, María Teresa; Arce-Estrada, Elsa M

    2011-03-03

    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.

  9. 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.

  10. Fe3O4 magnetic nanoparticles/reduced graphene oxide nanosheets as a novel electrochemical and bioeletrochemical sensing platform.

    PubMed

    Teymourian, Hazhir; Salimi, Abdollah; Khezrian, Somayeh

    2013-11-15

    We have developed Fe3O4 magnetic nanoparticles/reduced graphene oxide nanosheets modified glassy carbon (Fe3O4/r-GO/GC) electrode as a novel system for the preparation of electrochemical sensing platform. Decorating Fe3O4 nanoparticles on graphene sheets was performed via a facile one-step chemical reaction strategy, where the reduction of GO and the in-situ generation of Fe3O4 nanoparticles occurred simultaneously. Characterization of as-made nanocomposite using X-ray diffraction (XRD), transmission electron microscopy (TEM) and alternative gradient force magnetometry (AGFM) clearly demonstrate the successful attachment of monodisperse Fe3O4 nanoparticles to graphene sheets. Electrochemical studies revealed that the Fe3O4/r-GO/GC electrode possess excellent electrocatalytic activities toward the low potential oxidation of NADH (0.05 V vs. Ag/AgCl) as well as the catalytic reduction of O2 and H2O2 at reduced overpotentials. Via immobilization of lactate dehydrogenase (LDH) as a model dehydrogenase enzyme onto the Fe3O4/r-GO/GC electrode surface, the ability of modified electrode for biosensing lactate was demonstrated. In addition, using differential pulse voltammetry (DPV) to investigate the electrochemical oxidation behavior of ascorbic acid (AA), dopamine (DA) and uric acid (UA) at Fe3O4/r-GO/GC electrode, the high electrocatalytic activity of the modified electrode toward simultaneous detection of these compounds was indicated. Finally, based on the strong electrocatalytic action of Fe3O4/r-GO/GC electrode toward both oxidation and reduction of nitrite, a sensitive amperometric sensor for nitrite determination was proposed. The Fe3O4/r-GO hybrid presented here showing favorable electrochemical features may hold great promise to the development of electrochemical sensors, molecular bioelectronic devices, biosensors and biofuel cells.

  11. Recent advances in metal oxide-based electrode architecture design for electrochemical energy storage.

    PubMed

    Jiang, Jian; Li, Yuanyuan; Liu, Jinping; Huang, Xintang; Yuan, Changzhou; Lou, Xiong Wen David

    2012-10-02

    Metal oxide nanostructures are promising electrode materials for lithium-ion batteries and supercapacitors because of their high specific capacity/capacitance, typically 2-3 times higher than that of the carbon/graphite-based materials. However, their cycling stability and rate performance still can not meet the requirements of practical applications. It is therefore urgent to improve their overall device performance, which depends on not only the development of advanced electrode materials but also in a large part "how to design superior electrode architectures". In the article, we will review recent advances in strategies for advanced metal oxide-based hybrid nanostructure design, with the focus on the binder-free film/array electrodes. These binder-free electrodes, with the integration of unique merits of each component, can provide larger electrochemically active surface area, faster electron transport and superior ion diffusion, thus leading to substantially improved cycling and rate performance. Several recently emerged concepts of using ordered nanostructure arrays, synergetic core-shell structures, nanostructured current collectors, and flexible paper/textile electrodes will be highlighted, pointing out advantages and challenges where appropriate. Some future electrode design trends and directions are also discussed. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. Electrochemical oxidation of bisphenol-A from aqueous solution using graphite electrodes.

    PubMed

    Govindaraj, M; Rathinam, R; Sukumar, C; Uthayasankar, M; Pattabhi, S

    2013-01-01

    Electrochemical oxidation of bisphenol-A (BPA) from aqueous solution using graphite electrodes has been investigated. The effect of the types and concentration of supporting electrolytes, initial pH and applied current density on the performance of the process were examined. During electrolysis, concentration of BPA has been monitored and determined using UV-vis spectra, chemical oxygen demand (COD) and energy consumption. NaCl has been considered as the best supporting electrolyte among the electrolytes used in the present study. Initial pH 5.0, higher concentration (0.01 to 0.1 M) of supporting electrolyte and higher applied current density (4 to 20 mA cm(-2)) facilitate the treatment process. The maximum COD removal of 78.3% has been achieved under the optimal experimental conditions such as NaCl concentration of 0.05 M, applied current density of 12 mA cm(-2), initial pH 5.0 and electrolysis time of 120 min. When the energy consumption has been found to be decreasing with increasing NaCl concentration, it has increased with increasing applied current density. SEM-EDAX analysis has confirmed that the gases such as oxygen and chlorine are produced during the anodic oxidation in graphite anode. The result of UV-vis spectrum analysis confirms the degradation of BPA from aqueous solution at the end of the treatment.

  13. Multivariate optimization for electrochemical oxidation of methyl orange: Pathway identification and toxicity analysis.

    PubMed

    Pillai, Indu M Sasidharan; Gupta, Ashok K; Tiwari, Manoj K

    2015-01-01

    Electrochemical oxidation of methyl orange (Sodium 4-[(4-dimethylamino) phenyldiazenyl] benzenesulfonate) with lead dioxide coated on mild steel was modelled using response surface methodology (RSM) to analyze the influence of pH, NaCl dose and current on color and chemical oxygen demand (COD) removal. Higher current, acidic pH and 0.8-1.2 g L(-1) NaCl dose had an enhancing effect on the removal efficiencies. Interaction effect of the variables highlights the action of (•)OH and HOCl in the oxidation of methyl orange, where HOCl has effect at lower current range. More than 90% COD removal efficiency and ∼100% color removal efficiency was obtained in 5 h at optimum conditions for an initial concentration of 50 mg L(-1). High performance liquid chromatography-mass spectroscopy (HPLC-MS) analysis carried out to identify degradation intermediates revealed the absence of chlorinated intermediates, which was further verified with Fourier transform infrared spectroscopy (FTIR) analysis. The postulated pathway of degradation indicated breakdown through dealkylation, deamination, desulfonation and cleavage of an azo bond and benzene ring. The degradation of methyl orange to smaller compounds was also confirmed by Ion Chromatography (IC). Cytotoxicity analysis on HaCaT cells revealed the intermediates to be more cytotoxic than the dye, possibly due to the aromatic amines and diazines formed during the degradation process.

  14. 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

    2015-12-05

    Nano-Tin oxide was synthesized using hydrothermal method at 150 °C for 6 h and then thin films were deposited by electrophoretic method at an optimized voltage of 100 V for 5 min on electropolished aluminum substrate. Spherical particles of about 30-50 nm 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 8.4 eV 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 20 mM 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 μA/mM below 5 mM and 2.31 μA/mM above 5 mM with a limit of detection of 0.6 mM.

  15. 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 800°C. An optimum electrocatalytic response was found for a firing temperature of 600°C. 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.

  16. Stabilization of ultrathin (hydroxy)oxide films on transition metal substrates for electrochemical energy conversion

    DOE PAGES

    Zeng, Zhenhua; Chang, Kee-Chul; Kubal, Joseph; ...

    2017-05-08

    Design of cost-effective electrocatalysts with enhanced stability and activity is of paramount importance for the next generation of energy conversion systems, including fuel cells and electrolyzers. However, electrocatalytic materials generally improve one of these properties at the expense of the other. Here, using Density Functional Theory calculations and electrochemical surface science measurements, we explore atomic-level features of ultrathin (hydroxy)oxide films on transition metal substrates and demonstrate that these films exhibit both excellent stability and activity for electrocatalytic applications. The films adopt structures with stabilities that significantly exceed bulk Pourbaix limits, including stoichiometries not found in bulk and properties that aremore » tunable by controlling voltage, film composition, and substrate identity. Using nickel (hydroxy)oxide/Pt(111) as an example, we further show how the films enhance activity for hydrogen evolution through a bifunctional effect. Finally, the results suggest design principles for a new class of electrocatalysts with simultaneously enhanced stability and activity for energy conversion.« less

  17. Removal of herbicidal ionic liquids by electrochemical advanced oxidation processes combined with biological treatment.

    PubMed

    Pęziak-Kowalska, Daria; Fourcade, Florence; Niemczak, Michał; Amrane, Abdeltif; Chrzanowski, Łukasz; Lota, Grzegorz

    2017-05-01

    Recently a new group of ionic liquids (ILs) with herbicidal properties has been proposed for use in agriculture. Owing to the design of specific physicochemical properties, this group, referred to as herbicidal ionic liquids (HILs), allows for reducing herbicide field doses. Several ILs comprising phenoxy herbicides as anions and quaternary ammonium cations have been synthesized and tested under greenhouse and field conditions. However, since they are to be introduced into the environment, appropriate treatment technologies should be developed in order to ensure their proper removal and avoid possible contamination. In this study, didecyldimethylammonium (4-chloro-2-methylphenoxy) acetate was selected as a model HIL to evaluate the efficiency of a hybrid treatment method. Electrochemical oxidation or electro-Fenton was considered as a pretreatment step, whereas biodegradation was selected as the secondary treatment method. Both processes were carried out in current mode, at 10 mA with carbon felt as working electrode. The efficiency of degradation, oxidation and mineralization was evaluated after 6 h. Both processes decreased the total organic carbon and chemical oxygen demand (COD) values and increased the biochemical oxygen demand (BOD5) on the COD ratio to a value close to 0.4, showing that the electrolyzed solutions can be considered as 'readily biodegradable.'

  18. Parabens abatement from surface waters by electrochemical advanced oxidation with boron doped diamond anodes.

    PubMed

    Domínguez, Joaquín R; Muñoz-Peña, Maria J; González, Teresa; Palo, Patricia; Cuerda-Correa, Eduardo M

    2016-10-01

    The removal efficiency of four commonly-used parabens by electrochemical advanced oxidation with boron-doped diamond anodes in two different aqueous matrices, namely ultrapure water and surface water from the Guadiana River, has been analyzed. Response surface methodology and a factorial, composite, central, orthogonal, and rotatable (FCCOR) statistical design of experiments have been used to optimize the process. The experimental results clearly show that the initial concentration of pollutants is the factor that influences the removal efficiency in a more remarkable manner in both aqueous matrices. As a rule, as the initial concentration of parabens increases, the removal efficiency decreases. The current density also affects the removal efficiency in a statistically significant manner in both aqueous matrices. In the water river aqueous matrix, a noticeable synergistic effect on the removal efficiency has been observed, probably due to the presence of chloride ions that increase the conductivity of the solution and contribute to the generation of strong secondary oxidant species such as chlorine or HClO/ClO (-). The use of a statistical design of experiments made it possible to determine the optimal conditions necessary to achieve total removal of the four parabens in ultrapure and river water aqueous matrices.

  19. Decolorization and degradation of reactive yellow HF aqueous solutions by electrochemical advanced oxidation processes.

    PubMed

    Bedolla-Guzman, A; Feria-Reyes, R; Gutierrez-Granados, S; Peralta-Hernández, Juan M

    2016-07-29

    Textile manufacturing is the one responsible for water bodies' contamination through the discharge of colored wastes. This work presents the study of reactive yellow HF (RYHF) dye degradation under two different electrochemical advanced oxidation processes (EAOP), namely anodic oxidation (AO) and electro-Fenton (EF)/boron-doped diamond (BDD) process. For the AO, 100 and 300 mg/L solutions using Pt and BDD as anodes in a 100 mL stirred tank cell were used, with a supporting electrolyte of 0.05 mol/L of Na2SO4 at pH 3 under 30 and 50 mA/cm(2) current density. The EF/BDD process was carried out in a flow reactor at 4 and 7 L/min to degrade 100, 200, and 300 mg/L RYHF solutions under 50 and 80 mA/cm(2). UV-Vis determinations were used for decolorization evaluation, while high-performance liquid chromatography (HPLC) method provided information on dye degradation rate.

  20. Electrochemical Characteristics of Tin Oxide-Graphite as Anode Material for Lithium-ion Cells

    NASA Astrophysics Data System (ADS)

    Hasanaly, Siti Munirah

    2010-03-01

    Tin oxide anode materials used in lithium-ion cells experience large volume changes during charging and discharging which cause substantial losses in capacity. In this work, the tin oxide-graphite composite is proposed as an alternative anode material to overcome this problem. The composite was synthesised from a solution of tin chloride dihydrate and graphite powders with citric acid as the chelating agent. In this sol-gel method, a solid phase is formed through a chemical reaction in a liquid phase at moderate temperature. The technique offers several advantages compared to the solid state synthesis technique such as the ability to maintain the homogeneous mixture of precursors during synthesis and to produce small particles. The electrochemical behaviour of the anode material was investigated by means of galvanostatic charge discharge technique. An initial reversible capacity of 748 mAh/g is obtained and nearly 600 mAh/g was retained upon the reaching the fifth cycle. This study shows that the presence of graphite is able to minimise the agglomeration of tin particles that causes large volume changes during cycling, thereby improving cyclability of the anode material.

  1. 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.

  2. Electrochemical oxidation and detection of paeonol on modified electrode with acetylene black nanoparticles.

    PubMed

    Zhang, Huajie; Gao, Miaomiao; Yang, Xiaofeng

    2011-10-15

    With an aim to construct a sensing platform for the electrochemical detection of paeonol, we modified the glassy carbon electrode with acetylene black nanoparticle (AB). A sensitive oxidation peak of paeonol was observed with remarkably increased peak current on the modified electrode because the electrode has a big surface area due to three dimensional structure of AB nanoparticles. The optimization of detection conditions was performed, including pH value of the buffer, the amount of AB nanoparticles on the electrode surface, the accumulation potential and time of paeonol. Under the optimized conditions, the oxidation peak current of paeonol increased linearly with its concentration over the range from 5×10(-7) to 1×10(-4) M. The detection limit was calculated to be 1×10(-7) M. The modified electrode was successfully applied to detect the content of paeonol in cortex moutan, a common traditional Chinese medicine. The method is new, sensitive, rapid and convenient for the detection of paeonol. Copyright © 2011 Elsevier B.V. All rights reserved.

  3. Characterization and electrochemical application of carbon materials based on poly(phenylene oxide)

    NASA Astrophysics Data System (ADS)

    Gray, Hunter

    Carbon materials possess excellent electrical and surface properties for the next generation of energy storage devices. Polymers provide a carbon rich and tailorable precursor for the production of carbon materials. Therefore, activated carbons were prepared from poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) via a three step process: thermal oxidation, carbonization, and activation with KOH. The activated carbons are predominately microporous with BET specific surface areas up to 2638 m2/g. Impedance spectroscopy revealed these carbons possess electrical conductivities comparable to commercial carbon blacks and consequently were employed in thin-film composite electrodes in electrochemical double-layer capacitors. Cyclic voltammetry confirmed maximum specific capacitances of 13.23 F/g and 2.848 F/g for aqueous and organic electrolyte systems, respectively. Additionally, carbon nanotubes were synthesized from PPO and other polymers with a nickel catalyst via chemical vapor deposition as revealed by transmission electron microscopy. This is the first report of carbon nanotubes produced from PPO.

  4. 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 4°C.

  5. Ferrate(VI) as a greener oxidant: Electrochemical generation and treatment of phenol.

    PubMed

    Sun, Xuhui; Zhang, Qi; Liang, He; Ying, Li; Xiangxu, Meng; Sharma, Virender K

    2016-12-05

    Ferrate(VI) (Fe(VI)O4(2-), Fe(VI)) is a greener oxidant in the treatment of drinking water and wastewater. The electrochemical synthesis of Fe(VI) may be considered environmentally friendly because it involves one-step process to convert Fe(0) to Fe(VI) without using harmful chemicals. Electrolysis was performed by using a sponge iron as an anode in NaOH solution at different ionic strengths. The cyclic voltammetric (CV) curves showed that the sponge iron had higher electrical activity than the grey cast iron. The optimum current density was 0.054mAcm(-2) in 10M NaOH solution, which is much lower than the electrolyte concentrations used in other electrode materials. A comparison of current efficiency and energy consumption was conducted and is briefly discussed. The generated ferrate solution was applied to degrade phenol in water at two levels (2mgL(-1) and 5mgL(-1)). The maximum removal efficiency was ∼70% and the optimum pH for phenol treatment was 9.0. Experiments on phenol removal using conventional coagulants (ferric chloride (FeCl3) and polyaluminium chloride (PAC)) were performed independently to demonstrate that removal of phenol by Fe(VI) occurred mainly by oxidative transformation. A combination of Fe(VI) and coagulant may be advantageous in enhancing removal efficiency, adjusting pH, and facilitating flocculation.

  6. Removal of artificial sweetener aspartame from aqueous media by electrochemical advanced oxidation processes.

    PubMed

    Lin, Heng; Oturan, Nihal; Wu, Jie; Sharma, Virender K; Zhang, Hui; Oturan, Mehmet A

    2017-01-01

    The degradation and mineralization of aspartame (ASP) in aqueous solution were investigated, for the first time, by electrochemical advanced oxidation processes (EAOPs) in which hydroxyl radicals were formed concomitantly in the bulk from Fenton reaction via in situ electrogenerated Fenton's reagent and at the anode surface from the water oxidation. Experiments were performed in an undivided cylindrical glass cell with a carbon-felt cathode and a Pt or boron-doped diamond (BDD) anode. The effect of Fe(2+) concentration and applied current on the degradation and mineralization kinetics of ASP was evaluated. The absolute rate constant for the reaction between ASP and OH was determined as (5.23 ± 0.02) × 10(9) M(-1) s(-1) by using the competition kinetic method. Almost complete mineralization of ASP was achieved with BDD anode at 200 mA constant current electrolysis. The formation and generation of the formed carboxylic acids (as ultimate end products before complete mineralization) and released inorganic ion were monitored by ion-exclusion high performance liquid chromatography (HPLC) and ion chromatography techniques, respectively. The global toxicity of the treated ASP solution during treatment was assessed by the Microtox(®) method using V. fischeri bacteria luminescence inhibition. Copyright © 2016 Elsevier Ltd. All rights reserved.

  7. Concurrent electropolymerization of aniline and electrochemical deposition of tungsten oxide for supercapacitor

    NASA Astrophysics Data System (ADS)

    Geng, Jin-Wang; Ye, Yin-Jian; Guo, Di; Liu, Xiao-Xia

    2017-02-01

    Polyaniline-tungsten oxide composite films (PANI-WOx) were prepared through concurrent electropolymerization of aniline and electrochemical deposition of tungsten oxide on partial exfoliated graphite (Ex-GF) for pseudocapacitive materials. The influence of aniline to WOx precursor ratio on pseudocapacitive properties of the afforded PANI-WOx/Ex-GF composite was investigated. PW-2:1/Ex-GF made from the solution containing aniline and WOx precursor in 2:1 ratio displayed a high specific capacitance (408 F g-1/408 mF cm-2 at 1 A g-1/1 mA cm-2) in a wide charge storage potential window of -0.6-0.7 V vs. SCE, leading to a high energy density of 95.8 Wh kg-1 at 650 W kg-1. Due to the synergistic effect between WOx and PANI, the composite showed much improved cyclic stability (91.6% capacitance retention after 5000 galvanostatic charge-discharge cycles) compared to similarly prepared PANI/Ex-GF (69.1% capacitance after 5000 charge-discharge cycles). The assembled symmetric model supercapacitor, by using PW-2:1/Ex-GF as both of the electrodes, also displayed good stability and high energy density, demonstrating that the PANI-WOx composite is promising electrode material for high-performance supercapacitor.

  8. Phase equilibria in electrochemically oxidized La 2CuO 4δ. Transport measurements versus chemical analysis

    NASA Astrophysics Data System (ADS)

    Ondoño-Castillo, S.; Michel, C. R.; Seffar, A.; Fontcuberta, J.; Casañ-Pastor, N.

    1994-12-01

    A comparative study of physical and chemical methods for the analysis of the number and identity of holes in electrochemically oxidized La 2CuO 4+δ is reported. A combination of TGA and iodometric chemical analyses shows the existence of two species with different oxidation potentials. Susceptibility and resistivity measurements show the existence of at least two segregated superconducting phases, while Seebeck measurements shows a large change in the number of carriers for a constant value of δ; this atypical behavior is consistent though with the chemical data and implies the existence of a phase equilibrium within the oxide.

  9. Electrochemical Characterization and Modeling of a Solid Oxide Membrane-Based Electrolyzer for Production of Magnesium and Oxygen

    NASA Astrophysics Data System (ADS)

    Guan, Xiaofei; Pal, Uday B.; Gopalan, Srikanth; Powell, Adam C.

    This paper reports a solid oxide membrane (SOM) electrolysis experiment using an LSM-Inconel inert anode current collector for production of Mg and O2 at 1423K. The electrochemical performance of the SOM cell was evaluated by using various electrochemical techniques including electrochemical impedance spectroscopy, potentiodynamic scans, and potentiostatic electrolysis. The effects of Mg solubility in the flux on the current efficiency and the YSZ membrane stability during SOM electrolysis were discussed and examined through experiment and modeling. The electronic transference number of the flux were measured to assess the Mg dissolution in the flux during SOM electrolysis. A negative correlation between the electronic transference number of the flux and the current efficiency of the SOM electrolysis was observed.

  10. Synthesis of gallium nitride nanostructures by nitridation of electrochemically deposited gallium oxide on silicon substrate

    NASA Astrophysics Data System (ADS)

    Ghazali, Norizzawati Mohd; Yasui, Kanji; Hashim, Abdul Manaf

    2014-12-01

    Gallium nitride (GaN) nanostructures were successfully synthesized by the nitridation of the electrochemically deposited gallium oxide (Ga2O3) through the utilization of a so-called ammoniating process. Ga2O3 nanostructures were firstly deposited on Si substrate by a simple two-terminal electrochemical technique at a constant current density of 0.15 A/cm2 using a mixture of Ga2O3, HCl, NH4OH and H2O for 2 h. Then, the deposited Ga2O3 sample was ammoniated in a horizontal quartz tube single zone furnace at various ammoniating times and temperatures. The complete nitridation of Ga2O3 nanostructures at temperatures of 850°C and below was not observed even the ammoniating time was kept up to 45 min. After the ammoniating process at temperature of 900°C for 15 min, several prominent diffraction peaks correspond to hexagonal GaN (h-GaN) planes were detected, while no diffraction peak of Ga2O3 structure was detected, suggesting a complete transformation of Ga2O3 to GaN. Thus, temperature seems to be a key parameter in a nitridation process where the deoxidization rate of Ga2O3 to generate gaseous Ga2O increase with temperature. The growth mechanism for the transformation of Ga2O3 to GaN was proposed and discussed. It was found that a complete transformation can not be realized without a complete deoxidization of Ga2O3. A significant change of morphological structures takes place after a complete transformation of Ga2O3 to GaN where the original nanorod structures of Ga2O3 diminish, and a new nanowire-like GaN structures appear. These results show that the presented method seems to be promising in producing high-quality h-GaN nanostructures on Si.

  11. Electrochemical selective ion separation in capacitive deionization with sodium manganese oxide.

    PubMed

    Kim, Seonghwan; Yoon, Hansun; Shin, Dongyoon; Lee, Jaehan; Yoon, Jeyong

    2017-11-15

    Electrochemical selective ion separation via capacitive deionization, for example, separation of lithium resource from brine, using lithium ion batteries is proposed and demonstrated to have the potential for separating specific ions selectively from a solution containing diverse ions. This separation method is of great industrial concern because of applicability in various fields such as deionization, water softening, purification, heavy metal removal, and resource recovery. Nevertheless, besides the selectivity of materials for lithium ion batteries toward Li(+), there is very little investigation on the selectivity of the materials for sodium ion batteries toward Na(+). Here, the electrochemical selectivity of sodium manganese oxide (Na0.44MnO2), one of the most widely used material in sodium ion batteries, for Na(+) and other cations (K(+), Mg(2+), and Ca(2+)) is investigated. Selective Na(+) separation using the system consisting of Na0.44MnO2 and a Ag/AgCl electrode is successfully demonstrated from a solution containing diverse cations (Na(+), K(+), Mg(2+), and Ca(2+)) via a two-step process that involves a capturing step (charging process) and a releasing step (discharging process). The results showed that Na0.44-xMnO2 has over 13 times higher selectivity for Na(+) than for K(+) and 6-8times higher selectivity for Na(+) than for Mg(2+) and Ca(2+)