Kinetic study of the hydrogen oxidation reaction on Pt over the complete overpotential range

Abstract

The hydrogen oxidation reaction (hor) was studied on a polycrystalline platinum electrode in H2SO4 and HClO4 solutions at different rotation rates in the overpotentials region between 0.0 and 1.1 V. The experimental polarization curves recorded on steady state are quite similar for both acids. The results were interpreted in the whole overpotentials region on the basis of the Tafel-Heyrovsky-Volmer kinetic mechanism, coupled with a reversible water electroadsorption step. The experimental results were correlated with the equations derived from the resolution of the kinetic mechanism. It was found that a unique set of kinetic parameters can appropriately simulate the polarization curves obtained in both electrolyte solutions and for all the rotation rates, indicating that the proposed mechanism is suitable for the description of the reaction in the whole range of overpotentials. Moreover, the results indicate that the oxyanions do not play a decisive role in the inhibition of the active sites involved in the reaction, being adsorbed OH generated from water electroadsorption the most likely responsible for the behaviour at high overpotentials.