Kinetics of hydrogen oxidation reaction on Nafion-coated Pt/C electrodes under high overpotentials

The influences of the Nafion film thickness and Pt loading on the kinetics of the hydrogen oxidation reaction on Nafion-coated 20 wt% Pt/C electrodes immersed in 0.5 M H2SO4 were investigated using a rotating disk electrode configuration. The coating of a Nafion film (≦8 μm) had a negligible effect on the electrochemical surface area of an electrode. The kinetic parameters were estimated at an overpotential of 0.4 V; the values obtained were shown to vary with the method of data treatment. The diffusional resistance for H2 in the Nafion film was negligible when the film was thinner than 0.2 μm. The permeability of H2 in the Nafion film ranged from 2.4 × 10−5 to 4.8 × 10−5 mM cm2/s. The error analysis demonstrated that the apparent kinetic current estimated was resulted from experimental errors, instead of resulting from a chemical process as proposed by some previous investigators.