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R J Behm - One of the best experts on this subject based on the ideXlab platform.

  • oxygen reduction on a high surface area pt vulcan carbon catalyst a thin film rotating ring Disk Electrode study
    Journal of Electroanalytical Chemistry, 2001
    Co-Authors: U A Paulus, Thomas J Schmidt, Hubert A Gasteiger, R J Behm
    Abstract:

    We describe the adaptation of the recently developed thin-film rotating Disk Electrode method and its application in a rotating ring Disk configuration (RRDE) to the investigation of the oxygen reduction reaction (orr) on a supported catalyst powder (Pt/Vulcan XC 72 carbon). This allows the determination of kinetic data, such as reaction orders or apparent activation energies, for the orr directly without mathematical modeling. Collection experiments reveal a potential and rotation rate independent collection efficiency. RRDE measurements allow, for the first time, the direct determination of the fraction of peroxide production during oxygen reduction on supported catalysts. Finally, comparison of measurements in 0.5 M H2SO4 and 0.5 M HClO4, respectively, reveals a significant effect of (bi)sulfate adsorption on the orr activity. On the basis of the present results, predictions are made on the kinetic limit of the orr in polymer electrolyte fuel cells, in the absence of ohmic and mass transport resistances at 100% utilization.

  • rotating Disk Electrode measurements on the co tolerance of a high surface area pt vulcan carbon fuel cell catalyst
    Journal of The Electrochemical Society, 1999
    Co-Authors: Thomas J Schmidt, Hubert A Gasteiger, R J Behm
    Abstract:

    The authors examine the electrocatalytic properties of a Pt/Vulcan carbon catalyst toward the electro-oxidation of CO and CO/H{sub 2} mixtures under proton exchange membrane fuel cell (PEMFC) relevant conditions (60 to 80 C, continuous reactant flow), employing rotating Disk Electrode (RDE) measurements. They demonstrate that the recently introduced thin-film RDE technique can be applied to predict the performance of real fuel cell anodes operating on CO-contaminated H{sub 2}. The method involves attaching the catalyst particles to a glassy carbon RDE via a thin Nafion film. The thin-film RDE technique opens the possibility for the mass-transport-free determination of the Electrode kinetics at 100% catalyst utilization. At identical mass-specific current densities, the overpotentials for CO/H{sub 2} oxidation measured with the thin-film RDE technique are in excellent agreement with performance data from PEMFC anodes. The kinetics of pure CO oxidation were investigated with CO/N{sub 2} mixtures, revealing that the CO oxidation activity increases with decreasing CO partial pressure (negative reaction order). The observed ignition potential for CO oxidation was the same for both the CO/N{sub 2} and the CO/H{sub 2} mixtures. Two H{sub 2} oxidation mechanisms in the presence of CO can be distinguished: (1) a high Tafel slope region at low overpotentials,more » where H{sub 2} oxidation occurs in vacancies of the CO adlayer; and (2) a low Tafel slope region at high overpotentials where H{sub 2} and CO oxidation occur simultaneously.« less

  • characterization of high surface area electrocatalysts using a rotating Disk Electrode configuration
    Journal of The Electrochemical Society, 1998
    Co-Authors: Thomas J Schmidt, Hubert A Gasteiger, G D Stab, Peter Urban, D M Kolb, R J Behm
    Abstract:

    A newly developed method is presented which allows the characterization of the electrocatalytic properties of highly dispersed electrocatalysts in a true rotating Disk Electrode (RDE) configuration by attaching the catalyst powder on a glossy carbon Electrode via a thin Nafion film. Complete utilization and high reproducibility of both the Electrode preparation and the catalyst loading could be shown via voltammetry and CO stripping voltammetry. Furthermore RDE measurements on the electro‐oxidation of hydrogen on Pt/Vulcan showed that the effect of diffusion through the Nation film can be avoided by proper Electrode preparation. Therefore, the Electrode kinetics for fuel cell relevant reactions under continuous flow conditions can be measured directly without mathematical modeling.

Hubert A Gasteiger - One of the best experts on this subject based on the ideXlab platform.

  • electrocatalytic measurement methodology of oxide catalysts using a thin film rotating Disk Electrode
    Journal of The Electrochemical Society, 2010
    Co-Authors: Jin Suntivich, Hubert A Gasteiger, Naoaki Yabuuchi, Yang Shaohorn
    Abstract:

    Transition-metal oxides can exhibit high electrocatalytic activity for reactions such as the oxygen reduction reaction (ORR) in alkaline media. It is often difficult to measure and compare the activities of oxide catalysts on either per mass or per surface area basis, because of the poorly defined oxygen transport to and within porous oxide Electrodes of several tens of micrometers thickness. In this study, a methodology was developed to compare the ORR activities of submicrometer-sized transition-metal oxides. Thin films of LaNiO 3 , LaCu 0.5 Mn 0.5 O 3 , and La 0.75 Ca 0.25 FeO 3 oxide particles were bonded to glassy carbon via an ion-exchanged Nafion binder, and their mass and specific ORR activities were extracted from rotating Disk Electrode measurements. We found that the specific activity of LaNi0 3 was much higher than that of La 0.75 Ca 0.25 FeO 3 and LaCu 0.5 Mn 0.5 O 3 . The projection of LaNiO 3 in the actual fuel cell cathode was presented, which was shown to be competitive with current platinum-based cathodes.

  • oxygen reduction on a high surface area pt vulcan carbon catalyst a thin film rotating ring Disk Electrode study
    Journal of Electroanalytical Chemistry, 2001
    Co-Authors: U A Paulus, Thomas J Schmidt, Hubert A Gasteiger, R J Behm
    Abstract:

    We describe the adaptation of the recently developed thin-film rotating Disk Electrode method and its application in a rotating ring Disk configuration (RRDE) to the investigation of the oxygen reduction reaction (orr) on a supported catalyst powder (Pt/Vulcan XC 72 carbon). This allows the determination of kinetic data, such as reaction orders or apparent activation energies, for the orr directly without mathematical modeling. Collection experiments reveal a potential and rotation rate independent collection efficiency. RRDE measurements allow, for the first time, the direct determination of the fraction of peroxide production during oxygen reduction on supported catalysts. Finally, comparison of measurements in 0.5 M H2SO4 and 0.5 M HClO4, respectively, reveals a significant effect of (bi)sulfate adsorption on the orr activity. On the basis of the present results, predictions are made on the kinetic limit of the orr in polymer electrolyte fuel cells, in the absence of ohmic and mass transport resistances at 100% utilization.

  • rotating Disk Electrode measurements on the co tolerance of a high surface area pt vulcan carbon fuel cell catalyst
    Journal of The Electrochemical Society, 1999
    Co-Authors: Thomas J Schmidt, Hubert A Gasteiger, R J Behm
    Abstract:

    The authors examine the electrocatalytic properties of a Pt/Vulcan carbon catalyst toward the electro-oxidation of CO and CO/H{sub 2} mixtures under proton exchange membrane fuel cell (PEMFC) relevant conditions (60 to 80 C, continuous reactant flow), employing rotating Disk Electrode (RDE) measurements. They demonstrate that the recently introduced thin-film RDE technique can be applied to predict the performance of real fuel cell anodes operating on CO-contaminated H{sub 2}. The method involves attaching the catalyst particles to a glassy carbon RDE via a thin Nafion film. The thin-film RDE technique opens the possibility for the mass-transport-free determination of the Electrode kinetics at 100% catalyst utilization. At identical mass-specific current densities, the overpotentials for CO/H{sub 2} oxidation measured with the thin-film RDE technique are in excellent agreement with performance data from PEMFC anodes. The kinetics of pure CO oxidation were investigated with CO/N{sub 2} mixtures, revealing that the CO oxidation activity increases with decreasing CO partial pressure (negative reaction order). The observed ignition potential for CO oxidation was the same for both the CO/N{sub 2} and the CO/H{sub 2} mixtures. Two H{sub 2} oxidation mechanisms in the presence of CO can be distinguished: (1) a high Tafel slope region at low overpotentials,more » where H{sub 2} oxidation occurs in vacancies of the CO adlayer; and (2) a low Tafel slope region at high overpotentials where H{sub 2} and CO oxidation occur simultaneously.« less

  • characterization of high surface area electrocatalysts using a rotating Disk Electrode configuration
    Journal of The Electrochemical Society, 1998
    Co-Authors: Thomas J Schmidt, Hubert A Gasteiger, G D Stab, Peter Urban, D M Kolb, R J Behm
    Abstract:

    A newly developed method is presented which allows the characterization of the electrocatalytic properties of highly dispersed electrocatalysts in a true rotating Disk Electrode (RDE) configuration by attaching the catalyst powder on a glossy carbon Electrode via a thin Nafion film. Complete utilization and high reproducibility of both the Electrode preparation and the catalyst loading could be shown via voltammetry and CO stripping voltammetry. Furthermore RDE measurements on the electro‐oxidation of hydrogen on Pt/Vulcan showed that the effect of diffusion through the Nation film can be avoided by proper Electrode preparation. Therefore, the Electrode kinetics for fuel cell relevant reactions under continuous flow conditions can be measured directly without mathematical modeling.

Thomas J Schmidt - One of the best experts on this subject based on the ideXlab platform.

  • oxygen reduction on a high surface area pt vulcan carbon catalyst a thin film rotating ring Disk Electrode study
    Journal of Electroanalytical Chemistry, 2001
    Co-Authors: U A Paulus, Thomas J Schmidt, Hubert A Gasteiger, R J Behm
    Abstract:

    We describe the adaptation of the recently developed thin-film rotating Disk Electrode method and its application in a rotating ring Disk configuration (RRDE) to the investigation of the oxygen reduction reaction (orr) on a supported catalyst powder (Pt/Vulcan XC 72 carbon). This allows the determination of kinetic data, such as reaction orders or apparent activation energies, for the orr directly without mathematical modeling. Collection experiments reveal a potential and rotation rate independent collection efficiency. RRDE measurements allow, for the first time, the direct determination of the fraction of peroxide production during oxygen reduction on supported catalysts. Finally, comparison of measurements in 0.5 M H2SO4 and 0.5 M HClO4, respectively, reveals a significant effect of (bi)sulfate adsorption on the orr activity. On the basis of the present results, predictions are made on the kinetic limit of the orr in polymer electrolyte fuel cells, in the absence of ohmic and mass transport resistances at 100% utilization.

  • rotating Disk Electrode measurements on the co tolerance of a high surface area pt vulcan carbon fuel cell catalyst
    Journal of The Electrochemical Society, 1999
    Co-Authors: Thomas J Schmidt, Hubert A Gasteiger, R J Behm
    Abstract:

    The authors examine the electrocatalytic properties of a Pt/Vulcan carbon catalyst toward the electro-oxidation of CO and CO/H{sub 2} mixtures under proton exchange membrane fuel cell (PEMFC) relevant conditions (60 to 80 C, continuous reactant flow), employing rotating Disk Electrode (RDE) measurements. They demonstrate that the recently introduced thin-film RDE technique can be applied to predict the performance of real fuel cell anodes operating on CO-contaminated H{sub 2}. The method involves attaching the catalyst particles to a glassy carbon RDE via a thin Nafion film. The thin-film RDE technique opens the possibility for the mass-transport-free determination of the Electrode kinetics at 100% catalyst utilization. At identical mass-specific current densities, the overpotentials for CO/H{sub 2} oxidation measured with the thin-film RDE technique are in excellent agreement with performance data from PEMFC anodes. The kinetics of pure CO oxidation were investigated with CO/N{sub 2} mixtures, revealing that the CO oxidation activity increases with decreasing CO partial pressure (negative reaction order). The observed ignition potential for CO oxidation was the same for both the CO/N{sub 2} and the CO/H{sub 2} mixtures. Two H{sub 2} oxidation mechanisms in the presence of CO can be distinguished: (1) a high Tafel slope region at low overpotentials,more » where H{sub 2} oxidation occurs in vacancies of the CO adlayer; and (2) a low Tafel slope region at high overpotentials where H{sub 2} and CO oxidation occur simultaneously.« less

  • characterization of high surface area electrocatalysts using a rotating Disk Electrode configuration
    Journal of The Electrochemical Society, 1998
    Co-Authors: Thomas J Schmidt, Hubert A Gasteiger, G D Stab, Peter Urban, D M Kolb, R J Behm
    Abstract:

    A newly developed method is presented which allows the characterization of the electrocatalytic properties of highly dispersed electrocatalysts in a true rotating Disk Electrode (RDE) configuration by attaching the catalyst powder on a glossy carbon Electrode via a thin Nafion film. Complete utilization and high reproducibility of both the Electrode preparation and the catalyst loading could be shown via voltammetry and CO stripping voltammetry. Furthermore RDE measurements on the electro‐oxidation of hydrogen on Pt/Vulcan showed that the effect of diffusion through the Nation film can be avoided by proper Electrode preparation. Therefore, the Electrode kinetics for fuel cell relevant reactions under continuous flow conditions can be measured directly without mathematical modeling.

Yu Morimoto - One of the best experts on this subject based on the ideXlab platform.

  • an accurate evaluation for the activity of nano sized electrocatalysts by a thin film rotating Disk Electrode oxygen reduction on pt c
    Electrochimica Acta, 2012
    Co-Authors: Kazutaka Hiroshima, Yuji Kamitaka, Tatsuya Hatanaka, Yu Morimoto
    Abstract:

    Abstract Up to now, it remains to be a challenge to accurately and reproducibly evaluate the oxygen reduction reaction (ORR) activity by a thin-film rotating Disk Electrode (TF-RDE) and results in literatures often disagree. In this work, we developed an “intermittently microcontact-coating fine-droplets” method of preparing homogeneous thin-film to guarantee the accuracy of electro-catalytic activity evaluation by a TF-RDE, in which the measured Electrode current is controlled by both the diffusion of the reactant from the electrolyte bulk to the surface of the electro-catalyst and the kinetic process on the surface of the electro-catalyst. By precisely controlling the distribution and varying the loading of nano-sized Pt/C particles on a smooth glassy carbon substrate with an in-house-developed automated Electrode-preparation device, we investigated the effect of the distribution of the particles on the accuracy of compensating for diffusion limitations of ORR in an aqueous acid solution. As a reference, a smooth Pt bulk Disk Electrode was evaluated under the same environment to clarify the effect of the within-thin-film diffusion, which may occur in the TF-RDE. The results show that, the accuracy of correction for diffusion limitations cannot be guaranteed by only a linear relation of 1/I versus (rotation rate)−1/2 in Koutecky–Levich plot and significantly depends on the distribution of the particles on the substrate. Some criteria for judging the accuracy of the compensation and optimization of the thin-film structure have been systematically discussed.

  • reconsideration of the quantitative characterization of the reaction intermediate on electrocatalysts by a rotating ring Disk Electrode the intrinsic yield of h2o2 on pt c
    Electrochimica Acta, 2011
    Co-Authors: Tatsuya Hatanaka, Yu Morimoto
    Abstract:

    To solve the problem of the catalyst-loading-effect on quantifying the reaction intermediates on the surface of electrocatalysts with a rotating ring-Disk Electrode, we studied the formation of hydrogen peroxide in the oxygen reduction reaction on Pt/C with various sample loadings and then proposed an extrapolation model for measuring the intrinsic yield of H2O2, which can quantitatively reflect the characteristics of the surface of a given catalyst. In the extrapolation model, the catalyst loading effect can be compensated by taking the catalyst loading-dependent probability of the re-adsorption + further reaction of the desorbed H2O2 into consideration. The core concept in this extrapolation model is that the probability of the re-adsorption + reaction of the desorbed H2O2 becomes zero if there is no other active site available (i.e., at the extrapolated hypothetical point of zero catalyst loading) for re-adsorption of the desorbed H2O2. The intrinsic yield of H2O2 by extrapolation was much higher than that measured by the conventional model, in which the re-adsorption + reaction of the desorbed H2O2 is not considered, and thus the catalyst loading-dependent apparent yield of H2O2 does not properly reflect the intrinsic characteristics of the surface of a given catalyst.

Joerg Strutwolf - One of the best experts on this subject based on the ideXlab platform.

  • use of the saul yev method for the digital simulation of chronoamperometry at the Disk Electrode in the presence of homogeneous chemical reactions
    Electrochimica Acta, 2018
    Co-Authors: Dieter Britz, Joerg Strutwolf
    Abstract:

    Abstract The two-dimensional Saul'yev method of simulating processes at a Disk Electrode is tested in the presence of homogeneous chemical reactions. The catalytic EC′ reaction can produce a thin reaction layer, which is a test of any simulation method. The second-order Birk/Perone (B/P) reaction is similarly a test because of the nonlinear term appearing in the kinetic equations (although it does not give rise to a thin reaction layer). The Saul'yev method handles these with no special problems and is competitive, in terms of speed, with implicit methods at similar accuracy (and faster in the case of the nonlinear B/P case).

  • digital simulation of chronoamperometry at a Disk Electrode under a flat polymer film containing an enzyme
    Electrochimica Acta, 2015
    Co-Authors: Dieter Britz, Joerg Strutwolf
    Abstract:

    Abstract Current-time and steady state current behaviour were simulated for an ultramicroDisk Electrode (UMDE) inlaid flush with an insulating plane and overlaid by a flat film of polymer containing an enzyme, of various film thicknesses and essentially infinite extent. Steady state currents go through a maximum for some film thickness H , and then approach a constant value for thicker films. This constant value is the same as that for the diffusion limited current at an UMDE in a semi-infinite medium. Response times to 95% of the steady state current, for thin films are shorter than can be achieved using a flat Disk Electrode and a hemispherical polymer drop, but for large H they are slightly longer for comparable film thicknesses/radii. A hemispherical Electrode under a hemispherical polymer drop, however, behaves much like the present arrangement.

  • digital simulation of chronoamperometry at an Electrode within a hemispherical polymer drop containing an enzyme comparison of a hemispherical with a flat Disk Electrode
    Biosensors and Bioelectronics, 2013
    Co-Authors: Dieter Britz, Joerg Strutwolf
    Abstract:

    Abstract Current-time and steady state current behaviour was simulated for the cases of a hemispherical and flat inlaid Disk Electrodes located under a hemispherical polymer drop containing an enzyme which converts a substrate diffusing into the drop into a product that is electroactive at the Electrode. As well, a cylindrical Electrode with length much greater than its diameter and coated with a layer of polymer/enzyme was treated. The ratio of steady state currents at the hemispherical to the Disk Electrode is not, as has sometimes been assumed, always equal to π / 2 ; indeed this is only approached for polymer drops with large spillover ratio, that is, having a radius much larger than that of the Electrodes. Steady state currents for all Electrode geometries (including the cylinder) go through a maximum for some spillover ratio and then approach a constant value for larger spillover ratios. This constant value is the same as that for the diffusion limited current in a semi-infinite medium. For a cylindrical Electrode, the steady state current tends towards zero for large spillover ratios.