The effects of Nafion film thickness and Pt loading on the kinetics of hydrogen oxidation reaction at the Nafion/Pt-black thin-film electrodes immersed in 0.5 M H2SO4 electrolyte were investigated using a rotating disk electrode configuration. The Nafion coating (<= 8.0 mu m) had a negligible effect on the electrochemical active surface area measured. The diffusional resistance for H-2 in the Nafion film was negligible when the film was thinner than 0.2 mu m. The modified Koutecky-Levich equation was used to determine the kinetic parameters. The H-2 permeability in the Nafion film was 2.4 x 10(-11) mol/cm s, which is close to that in 0.5 M H2SO4. Due to the fast intrinsic reaction rate of H-2 oxidation on the Pt catalyst, the diffusion of H-2 in the catalyst layer affected the overall reaction rate to a higher extent when the Pt loading or overpotential increased. The effect of H-2 diffusion in the catalyst layer on the overall reaction rate was accounted for using the effectiveness factor. The corrected exchange current density for the Pt-black catalyst was determined to be 0.49 mA/cm(2), based on the real Pt surface area. These results might contribute to the determination on the intrinsic electrocatalytic activity of a high-surface-area fuel cell catalyst. (C) 2012 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.
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JOURNAL OF THE TAIWAN INSTITUTE OF CHEMICAL ENGINEERS Volume: 44 Issue: 3 Pages: 393-401
