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Electrochemical oxidation of glycine by doped nickel hydroxide modified electrode

VIDOTTI, Marcio; TORRESI, Susana I. Cordoba de; KUBOTA, Lauro T.
Fonte: ELSEVIER SCIENCE SA Publicador: ELSEVIER SCIENCE SA
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
46.22%
The electrocatalytic oxidation of glycine by doped nickel hydroxide modified electrodes and their use as sensors are described. The electrode modification was carried out by a simple electrochemical coprecipitation and its electrochemical properties were investigated. The modified electrode presented activity for glycine oxidation after applying a potential required to form NiOOH (similar to 0.45 V vs Ag/AgCl). In these conditions a sensitivity of 0.92 mu A mmol(-1) L and a linear response range from 0.1 up to 1.2 mmol L(-1) were achieved in the electrolytic Solutions at PH 12.6. Limits of detection and quantification were found to be 30 and 110 mu mol L(-1), respectively. Kinetic studies performed with rotating disk electrode (RDE) and by chronoamperometry allowed to determine the heterogeneous rate constant of 4.3 x 10(2) mol(-1) Ls(-1), Suggesting that NiOOH is a good electrocatalyst for glycine oxidation. NiOOH activity to oxidize other amino acids was also investigated, (c) 2008 Elsevier B.V. All rights reserved.; Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); Fapesp; CNPq[152312/2007-2]; Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Oxygen reduction reaction on a Pt/carbon fuel cell catalyst in the presence of trace quantities of ammonium ions: An RRDE study

Lopes, Thiago; Chlistunoff, Jerzy; Sansinena, Jose-Maria; Garzon, Fernando H.
Fonte: PERGAMON-ELSEVIER SCIENCE LTD; OXFORD Publicador: PERGAMON-ELSEVIER SCIENCE LTD; OXFORD
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
46.26%
The effect of trace quantities of ammonia on oxygen reduction reaction (ORR) on carbon-supported platinum catalysts in perchloric acid solutions is assessed using rotating ring disk electrode (RRDE) technique. The study demonstrates that ammonia has detrimental effects on ORR. The most significant effect takes place in the potential region above 0.7 V vs RHE. The effect is explained by the electrochemical oxidation of ammonia, which blocks Pt active sites and increases the formation of H2O2. This leads to losses in the disk currents and increments in the ring currents. The apparent losses in ORR currents may occur in two ways, namely, through the blocking of the active sites for ORR as well as by generating a small anodic current, which is believed to have a lower contribution. In addition, a detrimental effect of sodium cations in the potential range below 0.75 V vs RHE was demonstrated. This effect is most likely due to the co-adsorption of sodium cations and perchlorate anions on the Pt surface. Copyright (C) 2012, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.; U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy; U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy; government agency CAPES [1151-08-8]; government agency CAPES

Influence of normal and radial contributions of local current density on local electrochemical impedance spectroscopy

Ferrari, Jean Vicente; Melo, Hercilio Gomes de; Keddam, M.; Orazem, M. E.; Pébère, Nadine; Tribollet, Bernard; Vivier, V.
Fonte: Pergamon-Elsevier Science Ltd; Oxford Publicador: Pergamon-Elsevier Science Ltd; Oxford
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
46.6%
A new tri-electrode probe is presented and applied to local electrochemical impedance spectroscopy (LEIS) measurements. As opposed to two-probe systems, the three-probe one allows measurement not only of normal, but also of radial contributions of local current densities to the local impedance values. The results concerning the cases of the blocking electrode and the electrode with faradaic reaction are discussed from the theoretical point of view for a disk electrode. Numerical simulations and experimental results are compared for the case of the ferri/ferrocyanide electrode reaction at the Pt working electrode disk. At the centre of the disk, the impedance taking into account both normal and radial contributions was in good agreement with the local impedance measured in terms of only the normal contribution. At the periphery of the electrode, the impedance taking into account both normal and radial contributions differed significantly from the local impedance measured in terms of only the normal contribution. The radial impedance results at the periphery of the electrode are in good agreement with the usual explanation that the associated larger current density is attributed to the geometry of the electrode, which exhibits a greater accessibility at the electrode edge. (C) 2011 Elsevier Ltd. All rights reserved.; CAPES; Charles A. Stokes professorship

Low content cerium oxide nanoparticles on carbon for hydrogen peroxide electrosynthesis

Assumpcao, M. H. M. T.; Moraes, A.; Souza, R. F. B. de; Gaubeur, I.; Oliveira, R. T. S.; Antonin, V. S.; Malpass, G. R. P.; Rocha, R. S.; Calegaro, M. L.; Lanza, M. R. V.; Santos, M. C.
Fonte: ELSEVIER SCIENCE BV; AMSTERDAM Publicador: ELSEVIER SCIENCE BV; AMSTERDAM
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
46.18%
A comparative study using different proportions of CeO2/C (4%, 9% and 13% CeO2) was performed to produce H2O2, a reagent used in the oxidation of organic pollutants and in electro-Fenton reactions for the production of the hydroxyl radical (OH center dot), a strong oxidant agent used in the electrochemical treatment of aqueous wastewater. The CeO2/C materials were prepared by a modified polymeric precursor method (PPM). X-ray diffraction analysis of the CeO2/C prepared by the PPM identified two phases. CeO2 and CeO2. The average size of the crystallites in these materials was close to 7 nm. The kinetics of the oxygen reduction reaction (ORR) were evaluated by the rotating ring-disk electrode technique. The results showed that the 4% CeO2/C prepared by the PPM was the best composite for the production of H2O2 in a 1 mol L-1 NaOH electrolyte solution. For this material, the number of electrons transferred and the H2O2 percentage efficiency were 3.1 and 44%, respectively. The ring-current of the 4% CeO2/C was higher than that of Vulcan carbon, the reference material for H2O2 production, which produced 41% H2O2 and transferred 3.1 electrons per molecule of oxygen. The overpotential for this reaction on the ceria-based catalyst was substantially lower (approximately 200 mV)...

Electrooxidation and determination of dopamine using a Nafion (R)-cobalt hexacyanoferrate film modified electrode

Castro, Suely S. L.; Mortimer, Roger J.; de Oliveira, Marcelo F.; Stradiotto, Nelson R.
Fonte: Molecular Diversity Preservation Int Publicador: Molecular Diversity Preservation Int
Tipo: Artigo de Revista Científica Formato: 1950-1959
ENG
Relevância na Pesquisa
46.39%
The electrocatalysis of dopamine has been studied using a cobalt hexacyanoferrate film (CoHCFe)-modified glassy carbon electrode. Using a rotating disk CoHCFe-modified electrode, the reaction rate constant for dopamine was found to be 3.5 x 105 cm(3) mol(-1) s(-1) at a concentration of 5.0 x 10(-5) mol L-1. When a Nafion (R) film is applied to the CoHCFe-modified electrode surface a high selectivity for the determination of dopamine over ascorbic acid was obtained. The analytical curve for dopamine presented linear dependence over the concentration range from 1.2 x 10(-5) to 5.0 x 10(-4) mol L-1 with a slope of 23.5 mA mol(-1) L and a linear correlation coefficient of 0.999. The detection limit of this method was 8.9 x 10(-6) mol L-1 and the relative standard deviation for five measurements of 2.5 x 10(-4) mol L-1 dopamine was 0.58%.

Flow injection amperometric determination of persulfate in cosmetic products using a Prussian Blue film-modified electrode

De Oliveira, Marcelo F.; Saczk, Adelir A.; Neto, Jose A. Gomes; Roldan, Paulo S.; Stradiotto, Nelson R.
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Artigo de Revista Científica Formato: 371-380
ENG
Relevância na Pesquisa
46.18%
A flow-injection system with a glassy carbon disk electrode modified with Prussian Blue film is proposed for the determination of persulfate in commercial samples of hair bleaching boosters by amperometry. The detection was obtained by chronoamperometric technique and the sample is injected into the electrochemical cell in a wall jet configuration. Potassium chloride at concentration of 0.1 mol L-1 acted as sample carrier at a flow rate of 4.0 mL min-1 and supporting-electrolyte. For 0.025 V (vs. Ag/AgCl) applied voltage, the proposed system handles ca. 160 samples per hour (1.0 10-4 - 1.0 10-3 mol L-1 of persulfate), consuming about 200 μL sample and 11 mg KCl per determination. Typical linear correlations between electrocatalytic current and persulfate concentration was ca. 0.9998. The detection limit is 9.0 10-5 mol L-1 and the calculated amperometric sensibility 3.6 103 μA L mol -1. Relative standard deviation (n =12) of a 1.0 10-4 mol L-1 sample is about 2.2%. The method was applied to persulfate determination in commercial hair-bleaching samples and results are in agreement with those obtained by titrimetry at 95% confidence level and good recoveries (95 - 112%) of spiked samples were found. © 2003 by MDPI.

Study of electrochemical oxidation and determination of albendazole using a glassy carbon-rotating disk electrode

Santos, André L.; Takeuchi, Regina M.; Mariotti, Marcela P.; De Oliveira, Marcelo F.; Zanoni, Maria Valnice Boldrin; Stradiotto, Nelson R.
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Artigo de Revista Científica Formato: 671-674
ENG
Relevância na Pesquisa
66.41%
In this work, electrochemical oxidation of albendazole (ABZ) was carried out using a glassy carbon-rotating disk electrode. Development of electroanalytical methodology for ABZ quantification in pharmaceutical formulations was also proposed by using linear sweep voltammetric technique. Electrochemical oxidation is observed for ABZ at E 1/2 = 0.99:V vs. Ag/AgCl sat, when an anodic wave is observed. Kinetic parameters obtained for ABZ oxidation exhibited a standard heterogeneous rate constant for the electrodic process equal to (1.51 ± 0.07) ± 10 -5:cm:s -1, with a αn a value equal to 0.76. Limiting current dependence against ABZ concentration exhibited linearity on 5.0 ± 10 -5 to 1.0 ± 10 -2:mol:l -1 range, being obtained a detection limit of 2.4 ± 10 -5:mol:l -1. Proposed methodology was applied to ABZ quantification in pharmaceutical formulations. © 2005 Elsevier SAS. All rights reserved.

Influence of the preparation method and the support on H2O 2electrogeneration using cerium oxide nanoparticles

Assumpcão, M. H M T; Moraes, A.; De Souza, R. F B; Calegaro, M. L.; Lanza, M. R V; Leite, E. R.; Cordeiro, M. A L; Hammer, P.; Santos, M. C.
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Artigo de Revista Científica Formato: 339-343
ENG
Relevância na Pesquisa
46.18%
This work describes the influence of the preparation method and the carbon support using a low contentof cerium oxide nanoparticles (CeO2/C 4%) on H2O2electrogeneration via the oxygen reduction reac-tion (ORR). For this purpose, the polymeric precursor (PPM) and sol-gel (SGM) methods with Vulcan XC72R (V) and Printex L6 (P) supports were employed. The materials were characterized by X-ray diffrac-tion (XRD), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). TheXRD analysis identified two phases comprising CeO2and CeO 2-x. The smallest mean crystallite size wasexhibited for the 4% CeO2/C PPM P material, which was estimated using the Debye-Scherrer equation tobe 6 nm and 4 nm for the CeO2and the CeO 2-xphases, respectively, and was determined by TEM to be5.9 nm. XPS analysis was utilized to compare the oxygen content of the 4% CeO2/C PPM P to Printex L6.The electrochemical analysis was accomplished using a rotating ring-disk electrode. The results showedthat the 4% CeO2/C specimen, prepared by PPM and supported on Printex L6, was the best electrocatalystfor H2O2production in 1 mol L -1NaOH. This material showed the highest ring current, producing 88%H2O2and transferring 2.2 electrons per O 2molecule via the ORR at the lowest onset potential. Addition-ally...

Low tungsten content of nanostructured material supported on carbon for the degradation of phenol

Assumpção, M. H M T; De Souza, R. F B; Reis, R. M.; Rocha, R. S.; Steter, J. R.; Hammer, P.; Gaubeur, I.; Calegaro, M. L.; Lanza, M. R V; Santos, M. C.
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Artigo de Revista Científica Formato: 479-486
ENG
Relevância na Pesquisa
46.33%
A comparative study using different mass proportions of WO3/C (1%, 5%, 10% and 15%) for H2O2 electrogeneration and subsequent phenol degradation was performed. To include the influence of the carbon substrate and the preparation methods, all synthesis parameters were evaluated. The WO3/C materials were prepared by a modified polymeric precursor method (PPM) and the sol-gel method (SGM) on Vulcan XC 72R and Printex L6 carbon supports, verifying the most efficient metal/carbon proportion. The materials were physically characterized by X-ray diffraction (XRD) and by X-ray photoelectron spectroscopy (XPS) techniques. The XRD and the XPS techniques identified just one phase containing WO3 and elevated oxygen concentration on carbon with the presence of WO3. The oxygen reduction reaction (ORR), studied by the rotating ring-disk electrode technique, showed that WO3/C material with the lowest tungsten content (1% WO3/C), supported on Vulcan XC 72R and prepared by SGM, was the most promising electrocatalyst for H2O2 electrogeneration. This material was then analyzed using a gas diffusion electrode (GDE) and 585mgL-1 of H2O2 was produced in acid media. This GDE was employed as a working electrode in an electrochemical cell to promote phenol degradation by an advanced oxidative process. The most efficient method applied was the photo-electro-Fenton; this method allowed for 65% degradation and 11% mineralization of phenol during a 2-h period. Following 12h of exhaustive electrolysis using the photo-electro-Fenton method...

Sulfite induced autoxidation of Cu(II)/tetra/ penta and hexaglycine complexes: spectrophotometric and rotating-ring-disk glassy carbon electrode studies and analytical potentialities

Alipázaga,Maria V.; Bonifácio,Rodrigo L.; Kosminsky,Luis; Bertotti,Mauro; Coichev,Nina
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/10/2003 EN
Relevância na Pesquisa
46.46%
The oxidation of Cu(II) complexes with tetra, penta and hexaglycine in borate buffer aqueous solution, by dissolved oxygen is strongly accelerated by sulfite. The formation of Cu(III) complexes with maximum absorbances at 250 nm (e = 9000 mol-1 L cm-1) and 365 nm (e = 7120 mol-1 L cm-1) was also characterized by using rotating ring-disk voltammetry, whose anodic and cathodic components were observed in voltammograms recorded in solutions containing Cu(II). Voltammograms, obtained at various rotation speeds, showed that the Cu(III) species electrochemically generated is not stable over the entire time window of the experiment and in solutions containing tetraglycine the overall limiting current is controlled by the kinetics of an equilibrium involving Cu(II) species.The calculated first order rate constant of the decomposition was 4.37x10-3 s-1. Electrochemical experiments carried out in Cu(II) solutions after the addition of relatively small amounts of sulfite demonstrated that the Cu(III) species formed in the chemical reaction is the same as the one collected at the ring electrode when Cu(II) is oxidized at the disk electrode in ring-disk voltammetry. The concentration of Cu(III) complexes is proportional to the amount of added sulfite and the results indicated that indirect analytical methods for sulfite may be developed by means of spectrophotometric or amperometric detection of the chemically generated product.

Electrocatalytic oxidation of thiosulfate at glassy carbon electrode chemically modified with cobalt pentacyanonitrosylferrate

Sabzi,Reza E.
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/12/2005 EN
Relevância na Pesquisa
46.28%
An electroactive thin film of Cobalt pentacyanonitrosylferrate (CoPCNF) was electrodeposited on a glassy carbon electrode by cyclic voltammetry. The modified electrode exhibits good electrocatalytic activity toward oxidation of thiosulfate. The electrocatalytic oxidation of thiosulfate at glassy carbon electrode modified with CoPCNF as a working electrode has been studied by using cyclic voltammetry, rotating disk electrode (RDE) voltammetry and chronoamperometry in a solution of 0.25 mol L-1 KNO3 as a supporting electrolyte. A Tafel plot, derived from voltammograms indicated a one-electron charge transfer process, at rate determining step in the catalytic oxidation of thiosulfate. The kinetics of catalytic reaction was investigated and the average value of the rate constant (k), for the catalytic reaction and the diffusion coefficient (D) were evaluated by different approaches for thiosulfate and found to be (5.61 ± 0.14) ´10² (mol L-1)-1s-1 and (6.59 ± 0.70) ´10-6 cm²s-1 respectively.

Rotating Disk Electrode Voltammetric Measurements of Serotonin Transporter Kinetics in Synaptosomes

Hagan, Catherine E.; Neumaier, John F.; Schenk, James O.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
46.27%
Altered serotonin (5-HT) signaling is implicated in several neuropsychiatric disorders, including depression, anxiety, obsessive-compulsive disorder, and autism. The 5-HT transporter (SERT) modulates 5-HT neurotransmission strength and duration. This is the first study using rotating disk electrode voltammetry (RDEV) to measure 5-HT clearance. SERT kinetics were measured in whole brain synaptosomes. Uptake kinetics of exogenous 5-HT were measured using glassy carbon electrodes rotated in 500 uL glass chambers containing synaptosomes from SERT-knockout (−/−), heterozygous (+/−), or wild-type (+/+) mice. RDEV detected 5-HT concentrations of 5 nM and higher. Initial velocities were kinetically resolved with Km and Vmax values of 99 ± 35 standard error of regression (SER) nM and 181 ± 11 SER fmol / (s x mg protein), respectively in wild-type synaptosomes. The method enables control over drug and chemical concentrations, facilitating interpretation of results. Results are compared in detail to other techniques used to measure SERT kinetics, including tritium labeled assays, chronoamperometry, and fast scan cyclic voltammetry. RDEV exhibits decreased 5-HT detection limits, decreased vulnerability to 5-HT oxidation products that reduce electrode sensitivity...

A comparison of charge-transfer mechanisms at rotated disk electrode for biomimetic binuclear and tetranuclear oxo-manganese complex in aqueous solution

Martin, Cibely S.; Teixeira, Marcos F. S.
Fonte: Elsevier B.V. Publicador: Elsevier B.V.
Tipo: Artigo de Revista Científica Formato: 76-82
ENG
Relevância na Pesquisa
66.35%
Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq); Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); Processo FAPESP: 2009/11079-1; Processo FAPESP: 2010/12524-6; Many high-valence multinuclear mu-oxo-bridged manganese complexes have been synthesized to mimic the active site of the natural enzymes. The electrochemical and kinetic parameters were determined for two mimicking complexes ([(Mn2O2)-O-IV(terpy)(2)(H2O)(2)](4+) and [(Mn4O5)-O-IV(terpy)(4)(H2O)(2)](6+)) by cyclic voltammetry and linear sweep voltammetry using a rotating disk electrode (RDE). Stability and kinetic behavior are directly related to mu-oxo bridges, where the mu-oxo-bridge provides a fast electron transition between metal centers due to stabilization of dx(2) - y(2) orbitals by the oxygen bond. On the other hand, when the dx(2) - y(2) orbitals are stabilized by aqua ligands by a coordination bond, a displacement of oxidation potential to more positive potential was observed. A shift of the potential to more negative values with increase in rotation rate was observed, which can be ascribed to a chemical step. The chemical step involves the dimerization process of the binuclear oxo-manganese complex to tetranuclear oxo-manganeses complex. (C) 2014 Elsevier B.V. All rights reserved.

Carbon Fiber/Epoxy Composite Ring-disk Electrode: Fabrication, Characterization and Application to Electrochemical Detection in Capillary High Performance Liquid Chromatography

Xu, Xiaomi; Weber, Stephen G.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em 15/05/2009 EN
Relevância na Pesquisa
46.57%
Carbon fiber/epoxy composite materials, which are manufactured using the pultrusion process, are commercially available in various shapes and sizes at very low cost. Here we demonstrate the application of such a material as an electrochemical detector in a flow system. Cyclic voltammetry shows that the material's electrochemical behavior resembles that of glassy carbon. Using tube and rod composites, we successfully fabricated a ring-disk electrode with a 20 μm gap between the ring and the disk. The narrow gap is favorable for mass transfer in the generator-collector experiment. This composite ring-disk electrode is assembled in a thin-layer radial-flow cell and used as an electrochemical detector. The disk electrode, placed directly opposite to the flow inlet, is operated as a generator electrode with the ring electrode being a collector. The high collection efficiency on the ring electrode (0.8 for a chemically reversible species) enhances the detection selectivity.

Limitations for current production in Geobacter sulfurreducens biofilms

Bonanni, P. Sebastian; Bradley, Dan F.; Schrott, Germán David; Busalmen, Juan Pablo
Fonte: Wiley Vch Verlag Publicador: Wiley Vch Verlag
Tipo: info:eu-repo/semantics/article; info:ar-repo/semantics/artículo; info:eu-repo/semantics/publishedVersion Formato: application/pdf
ENG
Relevância na Pesquisa
46.27%
Devices that exploit electricity produced by electroactive bacteria such as Geobacter sulfurreducens have not yet been demonstrated beyond the laboratory scale. The current densities are far from the maximum that the bacteria can produce because fundamental properties such as the mechanism of extracellular electron transport and factors limiting cell respiration remain unclear. In this work, a strategy for the investigation of electroactive biofilms is presented. Numerical modeling of the response of G. sulfurreducens biofilms cultured on a rotating disk electrode has allowed for the discrimination of different limiting steps in the process of current production within a biofilm. The model outputs reveal that extracellular electron transport limits the respiration rate of the cells furthest from the electrode to the extent that cell division is not possible. The mathematical model also demonstrates that recent findings such as the existence of a redox gradient in actively respiring biofilms can be explained by an electron hopping mechanism but not when considering metallic-like conductivities.; Fil: Bonanni, P. Sebastian. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Mar del Plata. Instituto de Investigación en Ciencia y Tecnología de Materiales (i); Argentina; Universidad Nacional de Mar del Plata. Facultad de Ingenieria; Argentina;; Fil: Bradley...

A rotating ring disk electrode study of the oxygen reduction reaction in lithium containing non aqueous electrolyte

Calvo, Ernesto Julio; Mozhzhukhina, Nataliia
Fonte: Elsevier Publicador: Elsevier
Tipo: info:eu-repo/semantics/article; info:ar-repo/semantics/artículo; info:eu-repo/semantics/publishedVersion Formato: application/pdf
ENG
Relevância na Pesquisa
46.4%
We show the effect of a very small addition of LiClO4 to tetraethyl ammonium perchlorate (TEAP) in acetonitrile on the electro-reduction of molecular oxygen (ORR) at a rotating ring (Pt) glassy carbon (GC) disk electrode. While TEA+ cations stabilize the first electron reduction product in acetonitrile, superoxide O2 −, in the absence of Li+ the ORR proceeds by two one-electron sequential steps to the stabilized peroxide. Addition of 10 μM LiClO4 (b1:800 Li+ to TEA+ ratio) strongly affects the ORR mechanism: Both disk (ID) and ring (IR) currents strongly decrease, with less than 0.5% O2 − produced at the GC disk reaching the ring electrode, but still IR follows the same potential dependence as ID. On the other hand, addition of DMSO to acetonitrile 0.1 M LiClO4 stabilizes soluble O2 − detected at the ring since DMSO preferentially solvates Li+ preventing disproportionation of LiO2 into O2 and passivating Li2O2.; Fil: Calvo, Ernesto Julio. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía; Argentina;; Fil: Mozhzhukhina, Nataliia. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química...

Correcting the Hydrogen Diffusion Limitation in Rotating Disk Electrode Measurements of Hydrogen Evolution Reaction Kinetics

Zheng, Jie; Yan, Yushan; Xu, Bingjun
Fonte: The Electrochemical Society Publicador: The Electrochemical Society
Tipo: Artigo de Revista Científica
EN_US
Relevância na Pesquisa
46.47%
Pulsiher's PDF; Rotating disk electrode (RDE) method is widely employed in studies on the hydrogen oxidation/evolution reaction (HOR/HER) owing to its well-defined mass transport behaviors. While it is accepted that the measured HOR current is controlled by both the electrode kinetics and the diffusion of H2, HER is typically assumed to be free of diffusion limitation. Here we demonstrate that HER could also be diffusion limited when the electrode kinetics is fast, as evidenced by the rotation speed dependent HER current on Pt in acid (pH = 1) and the overlap of the HER polarization curve with the concentration overpotential curve. The HER diffusion limitation originates from the insufficient mass transport of produced H2 from the electrode surface to the bulk electrolyte and the highly reversible nature of HOR/HER. Kinetic analyses based on HER polarization curves on Pt in acid without correcting for the diffusion limitation could lead to inaccurate Tafel slopes and mechanistic interpretations, and significantly underestimated HER activities. A general data analysis protocol based on the reversible Koutecky-Levich equation is developed to obtain accurate kinetic information of HOR/HER even when electrode kinetics is facile. This new method is compared with other existing methods on Pt disk electrodes at different pHs and thin-film electrodes with different Pt loadings.; University of Delaware. Center for Catalytic Science & Technology.

Convolutive modelling of the disk electrode geometry under reversible conditions

Mahon, Peter; Oldham, Keith
Fonte: Pergamon-Elsevier Ltd Publicador: Pergamon-Elsevier Ltd
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
46.46%
The disk electrode is one of the most readily constructed electrode geometries but the perimetric discontinuity complicates the theoretical analysis. Under reversible conditions, this system simplifies to a situation that can be described by a convolution expression and can therefore be modelled by the method known as convolutive modelling. Convolutive modelling is here employed to simulate cyclic voltammograms at a disk electrode; those results are compared to fast quasi-explicit finite difference digital simulations. The inaccuracy of the latter method is thereby exposed. In addition, current reversal chronopotentiometry at a disk is modelled.

Diffusion-controlled chronoamperometry at a disk electrode

Mahon, Peter; Oldham, Keith
Fonte: American Chemical Society Publicador: American Chemical Society
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
56.26%
An accurate formula exists for describing the decay of the current following the imposition of extreme concentration polarization on a disk electrode under diffusion-controlled conditions. It has been amply validated by diverse simulations and is presented here in a more compact form than hitherto. The formula finds application beyond the realm of potential-step chronoamperometry.

Modeling of Catalytic Reaction in Protein-Film Linear Scan Voltammetry at Rotating Disk Electrode

Lovri,Milivoj
Fonte: Sociedade Portuguesa de Electroquímica Publicador: Sociedade Portuguesa de Electroquímica
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2009 EN
Relevância na Pesquisa
66.41%
The numerical method for the simulation of linear scan voltammetry on the rotating disk electrode is adjusted to the problem of irreversible redox reaction between the adsorbed catalyst and the dissolved reactant under transient conditions. The response consists of the wave and the maximum. The peak current depends on the scan rate in linear scan voltammetry, while the limiting current of the wave depends on the rate of rotation of the working electrode. The rate constant of catalytic reaction is determined from the kinetic current under steady-state conditions