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

The hydrogen oxidation reaction (hor) is studied on a polycrystalline platinum electrode in H2SO4 and HClO4 solutions at different rotation rates in the overpotential region comprised between 0.0 < η/V ≤ 1.1. The experimental polarization curves recorded at steady state are quite similar for both acids. The results are interpreted in the whole overpotential region on the basis of the Tafel–Heyrovsky–Volmer kinetic mechanism, coupled with a reversible water electroadsorption step. The experimental results are correlated with the equations derived from the resolution of the kinetic mechanism. A unique set of kinetic parameters can appropriately simulate the polarization curves obtained in both electrolyte solutions for all 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, adsorbed OH generated from water electroadsorption being most likely responsible for behaviour at high overpotentials.

► Study of the hydrogen oxidation reaction on the complete overpotential range.
► Effect of oxyanions in the inhibition of the reaction at high overpotentials.
► Inhibition of active sites due to the reversible electroadsorption of OH species.
► Correlation of experimental results through a unique set of kinetic parameters.