The effects of mass transfer on the kinetics of the hydrogen oxidation reaction at the Nafion covered Pt/C electrodes immersed in 0.5 M H(2)SO(4) was investigated using a rotating disk electrode configuration. The hydrodynamic voltammograms were analyzed to determine the kinetic parameters using the modified Koutecky-Levich equation. The permeability of H(2) in the Nafion film was determined to be 2.0 x 10(-5) mM cm(2) s(-1), which is close to that in 0.5 M H(2)SO(4). 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 the 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 20 wt% Pt/C catalyst was determined to be about 0.96 mA cm(-2), based on the real Pt surface area. The results of this work may contribute to the measurement on the intrinsic electrocatalytic activity of a high surface area catalyst used in proton exchange membrane fuel cells. (C) 2011 Elsevier B.V. All rights reserved.
