The Experts below are selected from a list of 267 Experts worldwide ranked by ideXlab platform
Richard G. Compton - One of the best experts on this subject based on the ideXlab platform.
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Sweep voltammetry with a semi-circular potential waveform: Electrode Kinetics
Journal of Electroanalytical Chemistry, 2019Co-Authors: Yuki Uchida, Enno Kätelhön, Richard G. ComptonAbstract:Abstract We introduce a sensitive, novel way to determine the standard electrochemical rate constant, k0, through the application of a semi-circular potential wave at a microdisc Electrode. A one-electron reduction reaction is investigated and simulated for varying rate constants. It is shown that the voltammograms of a semi-circular potential wave exhibit significantly greater sensitivity to the changes in Electrode Kinetics compared to the conventional linear potential wave. A reprogramming of a commercial potentiostat can yield a one order magnitude greater sensitivity and can be used to determine the rate constant of a system under investigation.
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The Marcus-Hush model of Electrode Kinetics at a single nanoparticle
Journal of Electroanalytical Chemistry, 2014Co-Authors: Martin C Henstridge, Kristopher R. Ward, Richard G. ComptonAbstract:Abstract We examine the effect of the Marcus-Hush model of Electrode Kinetics on electron transfer at the surface of a single nanoparticle impacting an electode. Using numerical simulation we demonstrate the possibility of observing a kinetically limited steady state current which is smaller than the mass transport limiting current for such a system.
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a comparison of the butler volmer and asymmetric marcus hush models of Electrode Kinetics at the channel Electrode
Journal of Electroanalytical Chemistry, 2012Co-Authors: Martin C Henstridge, Neil V. Rees, Richard G. ComptonAbstract:Abstract We report a theoretical study of steady-state voltammetry at the channel Electrode comparing the Butler–Volmer and Marcus–Hush (both symmetric and asymmetric) models of Electrode Kinetics. The latter model is shown, for small values of both reorganisation energy and standard rate constant, to exhibit a kinetically-limited steady-state current which is smaller than the mass-transport limiting current given by the Levich equation. However, the combination of parameters required to observe this kinetically-limited current is unlikely to occur in a ‘real’ system. We conclude that the Butler–Volmer model is sufficient to accurately model voltammetry under these conditions.
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giving physical insight into the butler volmer model of Electrode Kinetics application of asymmetric marcus hush theory to the study of the electroreductions of 2 methyl 2 nitropropane cyclooctatetraene and europium iii on mercury microElectrodes
Journal of Electroanalytical Chemistry, 2012Co-Authors: Martin C Henstridge, Eduardo Laborda, Ángela Molina, Neil V. Rees, Yijun Wang, Francisco Martinezortiz, Danu Suwatchara, Richard G. ComptonAbstract:Abstract The asymmetric Marcus–Hush (MH) model for Electrode Kinetics is applied to the kinetic study of the electroreduction of 2-methyl-2-nitropropane in acetonitrile, cyclooctatetraene in dimethylsulfoxide and europium(III) in aqueous solution, using mercury microhemispheres as working Electrodes. This kinetic model includes the possibility of the oxidative and reductive processes having different reorganization energies due to differences between the force constants of the electroactive species. For each redox couple, the response obtained in cyclic and square wave voltammetries can be fitted satisfactorily with the four-parameter asymmetric MH model. From the fitting of the voltammograms the values of the kinetic parameters are extracted and analyzed in terms of physical properties of the electroactive species. A comparison of the asymmetric model against the simpler, phenomenological Butler–Volmer (BV) approach is discussed, as well as a possible physical interpretation for the BV transfer coefficient.
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redox systems obeying marcus hush chidsey Electrode Kinetics do not obey the randles sevcik equation for linear sweep voltammetry
Journal of Electroanalytical Chemistry, 2012Co-Authors: Martin C Henstridge, Eduardo Laborda, Edmund J F Dickinson, Richard G. ComptonAbstract:Abstract The cyclic voltammetry of the reaction of a solution-phase species at a macroElectrode under semi-infinite diffusion is simulated assuming irreversible Electrode Kinetics within the Marcus–Hush–Chidsey model. The resulting peak currents are shown to deviate from the square root dependence on voltage scan rate predicted by the Randles–Sevcik equation. Simulated voltammetry of a surface-bound redox couple also shows deviations from the expected linear dependence of peak current on scan rate. These numerical findings are supported by analytical arguments and they provide simple method for a critical analysis of the kinetic model. In particular the sheer extent of published experimental work containing linear Randles–Sevcik plots suggests the need for significant refinement of the Marcus–Hush–Chidsey model before it is suitable for the analysis of experimental voltammetry.
Alan M. Bond - One of the best experts on this subject based on the ideXlab platform.
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Limitations in Electrochemical Determination of Mass-Transport Parameters: Implications for Quantification of Electrode Kinetics Using Data Optimisation Methods
Australian Journal of Chemistry, 2017Co-Authors: Elena Mashkina, Alan M. Bond, Alexandr N. SimonovAbstract:Voltammetric quantification of the Electrode Kinetics for the quasi-reversible reaction requires detailed experiment–theory comparisons. Ideally, predicted data derived from the theoretical model are fitted to the experimental data by adjusting the reversible potential (E0), heterogeneous electron transfer rate constant at E0 (k0), and charge transfer coefficient α, with mass-transport and other parameters exactly known. However, parameters relevant to mass transport that include Electrode area (A), diffusion coefficient (D), and concentration (c), are usually subject to some uncertainty. Herein, we examine the consequences of having different combinations of errors present in A, D, and c in the estimation of E0, k0, and α on the basis of the a.c. (alternating current) voltammetric experiment–theory comparisons facilitated by the use of a computer-assisted parameter optimisation algorithm. In most cases, experimentally reasonable errors (
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dual frequency alternating current designer waveform for reliable voltammetric determination of Electrode Kinetics approaching the reversible limit
Analytical Chemistry, 2016Co-Authors: Cameron Luke Bentley, Alan M. Bond, Jie ZhangAbstract:Alternating current (ac) voltammetry provides access to faster Electrode Kinetics than direct current (dc) methods. However, difficulties in ac and other methods arise when the heterogeneous electron-transfer rate constant (k0) approaches the reversible limit, because the voltammetric characteristics become insensitive to Electrode Kinetics. Thus, in this near-reversible regime, even small uncertainties associated with bulk concentration (C), diffusion coefficient (D), Electrode area (A), and uncompensated resistance (Ru) can lead to significant systematic error in the determination of k0. In this study, we have introduced a kinetically sensitive dual-frequency designer waveform into the Fourier-transformed large-amplitude alternating current (FTAC) voltammetric method that is made up of two sine waves having the same amplitude but with different frequencies (e.g., 37 and 615 Hz) superimposed onto a dc ramp to quantify the close-to-reversible Fc0/+ process (Fc = ferrocene) in two nonhaloaluminate ionic li...
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Determination of fast Electrode Kinetics facilitated by use of an internal reference.
Analytical chemistry, 2015Co-Authors: Kiran Bano, Alan M. Bond, Jie ZhangAbstract:The concept of using an internal reversible reference process as a calibration in the determination of fast Electrode Kinetics has been developed and applied with the technique of Fourier transformed large amplitude ac voltammetry to minimize the influence of errors arising from uncertainties in parameters such as Electrode area (A), concentration (C), diffusion coefficient (D), and uncompensated resistance (Ru). Since kinetic parameters (electron transfer rate constant, k0, and electron transfer coefficient, α) are irrelevant in the voltammetric characterization of a reversible reaction, parameters such as A, C, D, and Ru can be calibrated using the reversible process prior to quantification of the Electrode Kinetics associated with the fast quasi-reversible process. If required, new values of parameters derived from the calibration exercise can be used for the final determination of k0 and α associated with the process of interest through theory-experimental comparison exercises. Reference to the revers...
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new insights into the analysis of the Electrode Kinetics of flavin adenine dinucleotide redox center of glucose oxidase immobilized on carbon Electrodes
Langmuir, 2014Co-Authors: Alexandr N. Simonov, Elena Mashkina, Willo Grosse, Blair Bethwaite, Jeff Tan, David Abramson, Gordon G Wallace, Simon E Moulton, Alan M. BondAbstract:New insights into electrochemical Kinetics of the flavin adenine dinucleotide (FAD) redox center of glucose-oxidase (GlcOx) immobilized on reduced graphene oxide (rGO), single- and multiwalled carbon nanotubes (SW and MWCNT), and combinations of rGO and CNTs have been gained by application of Fourier transformed AC voltammetry (FTACV) and simulations based on a range of models. A satisfactory level of agreement between experiment and theory, and hence establishment of the best model to describe the redox chemistry of FAD, was achieved with the aid of automated e-science tools. Although still not perfect, use of Marcus theory with a very low reorganization energy (≤0.3 eV) best mimics the experimental FTACV data, which suggests that the process is gated as also deduced from analysis of FTACV data obtained at different frequencies. Failure of the simplest models to fully describe the Electrode Kinetics of the redox center of GlcOx, including those based on the widely employed Laviron theory is demonstrated, as is substantial kinetic heterogeneity of FAD species. Use of a SWCNT support amplifies the kinetic heterogeneity, while a combination of rGO and MWCNT provides a more favorable environment for fast communication between FAD and the Electrode.
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Fourier‐Transformed Large‐Amplitude AC Voltammetric Study of Tetrathiafulvalene (TTF): Electrode Kinetics of the TTF0/TTF.+ and TTF.+/TTF2+ Processes
ChemElectroChem, 2013Co-Authors: Alan M. Bond, Kiran Bano, Shaimaa Adeel, Lisandra L. Martin, Jie ZhangAbstract:Large-amplitude Fourier-transformed (FT) AC voltammetry was used at high frequency to study the Electrode Kinetics of tetrathiafulvalene (TTF), its radical cation TTF.+ and that of the dication TTF2+ in acetonitrile (0.1 M Bu4NPF6). The two oxidized forms were prepared by quantitative bulk electrolysis of TTF under dry-box conditions. A high frequency of 233 Hz was used at glassy carbon (GC) and platinum (Pt) macro disk Electrodes to enhance the kinetic sensitivity and hence upper limit of the measurable heterogeneous charge transfer rate constant (k0). Difficulties associated with the use of high frequencies at macro disk Electrodes are discussed. Comparison of experimental data with simulations is used to extract k0 and other parameters for each of the TTF0/.+ and TTF.+/2+ processes from both reduction and oxidation perspectives. k0 values for TTF0/.+and TTF.+/0 processes are ≥1.0 cm s−1 and consequently regarded as reversible under the AC conditions used. However, the significantly slower quasi-reversible behaviour observed for the TTF.+/2+ redox couple, with k0 being 0.3±0.05 cm s−1, can be precisely estimated.
Henricus J M Bouwmeester - One of the best experts on this subject based on the ideXlab platform.
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Electrode properties of sr doped lamno3 on yttria stabilized zirconia ii Electrode Kinetics
Journal of The Electrochemical Society, 1997Co-Authors: F H Van Heuveln, Henricus J M BouwmeesterAbstract:A series of six cathodes Sr0.15La0.85MnO3 (SLM) on yttria-stabilized zirconia with different morphology of the Electrode/electrolyte interface were characterized by ac impedance and dc polarization measurements. It is found that the Electrode Kinetics at elevated temperature (945°C) are governed by two serial processes. An activation process can be identified to occur at high cathodic overpotential, whereas a transport process competes with charge-transfer at comparatively low overpotential. Attention is drawn to the profound change in the electrocatalytic properties of Sr0.15La0.85MnO3 upon current passage and its influence in elucidation of the interfacial Kinetics.
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Electrode Properties of Sr‐Doped LaMnO3 on Yttria‐Stabilized Zirconia II. Electrode Kinetics
Journal of The Electrochemical Society, 1997Co-Authors: F.h. Van Heuveln, Henricus J M BouwmeesterAbstract:A series of six cathodes Sr0.15La0.85MnO3 (SLM) on yttria-stabilized zirconia with different morphology of the Electrode/electrolyte interface were characterized by ac impedance and dc polarization measurements. It is found that the Electrode Kinetics at elevated temperature (945°C) are governed by two serial processes. An activation process can be identified to occur at high cathodic overpotential, whereas a transport process competes with charge-transfer at comparatively low overpotential. Attention is drawn to the profound change in the electrocatalytic properties of Sr0.15La0.85MnO3 upon current passage and its influence in elucidation of the interfacial Kinetics.
Martin C Henstridge - One of the best experts on this subject based on the ideXlab platform.
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The Marcus-Hush model of Electrode Kinetics at a single nanoparticle
Journal of Electroanalytical Chemistry, 2014Co-Authors: Martin C Henstridge, Kristopher R. Ward, Richard G. ComptonAbstract:Abstract We examine the effect of the Marcus-Hush model of Electrode Kinetics on electron transfer at the surface of a single nanoparticle impacting an electode. Using numerical simulation we demonstrate the possibility of observing a kinetically limited steady state current which is smaller than the mass transport limiting current for such a system.
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a comparison of the butler volmer and asymmetric marcus hush models of Electrode Kinetics at the channel Electrode
Journal of Electroanalytical Chemistry, 2012Co-Authors: Martin C Henstridge, Neil V. Rees, Richard G. ComptonAbstract:Abstract We report a theoretical study of steady-state voltammetry at the channel Electrode comparing the Butler–Volmer and Marcus–Hush (both symmetric and asymmetric) models of Electrode Kinetics. The latter model is shown, for small values of both reorganisation energy and standard rate constant, to exhibit a kinetically-limited steady-state current which is smaller than the mass-transport limiting current given by the Levich equation. However, the combination of parameters required to observe this kinetically-limited current is unlikely to occur in a ‘real’ system. We conclude that the Butler–Volmer model is sufficient to accurately model voltammetry under these conditions.
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giving physical insight into the butler volmer model of Electrode Kinetics application of asymmetric marcus hush theory to the study of the electroreductions of 2 methyl 2 nitropropane cyclooctatetraene and europium iii on mercury microElectrodes
Journal of Electroanalytical Chemistry, 2012Co-Authors: Martin C Henstridge, Eduardo Laborda, Ángela Molina, Neil V. Rees, Yijun Wang, Francisco Martinezortiz, Danu Suwatchara, Richard G. ComptonAbstract:Abstract The asymmetric Marcus–Hush (MH) model for Electrode Kinetics is applied to the kinetic study of the electroreduction of 2-methyl-2-nitropropane in acetonitrile, cyclooctatetraene in dimethylsulfoxide and europium(III) in aqueous solution, using mercury microhemispheres as working Electrodes. This kinetic model includes the possibility of the oxidative and reductive processes having different reorganization energies due to differences between the force constants of the electroactive species. For each redox couple, the response obtained in cyclic and square wave voltammetries can be fitted satisfactorily with the four-parameter asymmetric MH model. From the fitting of the voltammograms the values of the kinetic parameters are extracted and analyzed in terms of physical properties of the electroactive species. A comparison of the asymmetric model against the simpler, phenomenological Butler–Volmer (BV) approach is discussed, as well as a possible physical interpretation for the BV transfer coefficient.
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redox systems obeying marcus hush chidsey Electrode Kinetics do not obey the randles sevcik equation for linear sweep voltammetry
Journal of Electroanalytical Chemistry, 2012Co-Authors: Martin C Henstridge, Eduardo Laborda, Edmund J F Dickinson, Richard G. ComptonAbstract:Abstract The cyclic voltammetry of the reaction of a solution-phase species at a macroElectrode under semi-infinite diffusion is simulated assuming irreversible Electrode Kinetics within the Marcus–Hush–Chidsey model. The resulting peak currents are shown to deviate from the square root dependence on voltage scan rate predicted by the Randles–Sevcik equation. Simulated voltammetry of a surface-bound redox couple also shows deviations from the expected linear dependence of peak current on scan rate. These numerical findings are supported by analytical arguments and they provide simple method for a critical analysis of the kinetic model. In particular the sheer extent of published experimental work containing linear Randles–Sevcik plots suggests the need for significant refinement of the Marcus–Hush–Chidsey model before it is suitable for the analysis of experimental voltammetry.
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A comparison of the Butler–Volmer and asymmetric Marcus–Hush models of Electrode Kinetics at the channel Electrode
Journal of Electroanalytical Chemistry, 2012Co-Authors: Martin C Henstridge, Neil V. Rees, Richard G. ComptonAbstract:Abstract We report a theoretical study of steady-state voltammetry at the channel Electrode comparing the Butler–Volmer and Marcus–Hush (both symmetric and asymmetric) models of Electrode Kinetics. The latter model is shown, for small values of both reorganisation energy and standard rate constant, to exhibit a kinetically-limited steady-state current which is smaller than the mass-transport limiting current given by the Levich equation. However, the combination of parameters required to observe this kinetically-limited current is unlikely to occur in a ‘real’ system. We conclude that the Butler–Volmer model is sufficient to accurately model voltammetry under these conditions.
Charles R Martin - One of the best experts on this subject based on the ideXlab platform.
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Electrode Kinetics of oxygen reduction at carbon supported and unsupported platinum microcrystallite nafion interfaces
Journal of Electroanalytical Chemistry, 1992Co-Authors: Arvind Parthasarathy, S. Srinivasan, John A Appleby, Charles R MartinAbstract:The Electrode Kinetics of oxygen reduction at the platinum microcrystallite/Nafion® interface was investigated as a function of temperature and pressure. These studies were conducted using porous gas-diffusion Electrodes, containing unsupported platinum (10 Mg cm−2) or carbon-supported platinum (0.4 mg cm−2), in proton exchange membrane fuel cells, using H2 and O2 as reactants. The effects of platinum loading and of Nafion impregnation on the Electrode kinetic parameters were elucidated. Over the range of current densities from 1 to 1000 mA cm−2 (geometric), the Tafel slope was ca. −60 mV per decade and was practically independent of temperature, O2 pressure, and type of Electrode. The platinum Electrode was still in the potential regime where oxygenated species are present on the surface (Temkin conditions). The reaction order with respect to O2 is unity and the activation energy for O2-reduction was ca. 80 kJ mol−1. These Electrode kinetic parameters are in good agreement with those obtained at the platinum microElectrode/Nafion interface, as previously determined in our laboratories.
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Electrode Kinetics of oxygen reduction at carbon-supported and unsupported platinum microcrystallite/Nafion® interfaces
Journal of Electroanalytical Chemistry, 1992Co-Authors: Arvind Parthasarathy, Supramaniam Srinivasan, A. John Appleby, Charles R MartinAbstract:The Electrode Kinetics of oxygen reduction at the platinum microcrystallite/Nafion® interface was investigated as a function of temperature and pressure. These studies were conducted using porous gas-diffusion Electrodes, containing unsupported platinum (10 Mg cm−2) or carbon-supported platinum (0.4 mg cm−2), in proton exchange membrane fuel cells, using H2 and O2 as reactants. The effects of platinum loading and of Nafion impregnation on the Electrode kinetic parameters were elucidated. Over the range of current densities from 1 to 1000 mA cm−2 (geometric), the Tafel slope was ca. −60 mV per decade and was practically independent of temperature, O2 pressure, and type of Electrode. The platinum Electrode was still in the potential regime where oxygenated species are present on the surface (Temkin conditions). The reaction order with respect to O2 is unity and the activation energy for O2-reduction was ca. 80 kJ mol−1. These Electrode kinetic parameters are in good agreement with those obtained at the platinum microElectrode/Nafion interface, as previously determined in our laboratories.