Electrocatalysis of oxygen reduction and hydrogen oxidation in platinum dispersed on tungsten carbide in acid medium

Abstract

Tungsten carbide dispersed on a high surface area carbon (W2C/C) prepared by a sonochemical method was used as the support of a Pt-based electrocatalyst (Pt-W2C/C). The resulting materials were tested for two important reactions with practical interest in fuel cells, that is, the oxygen reduction and hydrogen oxidation reactions, in acid medium. The electrochemical techniques considered were cyclic voltammetry, linear sweep voltammetry, and steady-state polarization curves, obtained utilizing an ultrathin catalyst layer in a rotating ring–disk electrode. The results showed that the Pt-W2C/C catalyst led to a remarkable enhancement of the oxygen reduction in acid medium, when compared to the standard Pt/C, both following a four-electron mechanism. The hydrogen oxidation reaction showed similar kinetics on Pt-W2C/C and Pt/C following the direct discharge mechanism on both catalysts. The W2C/C support presented remarkable activity for the hydrogen oxidation reaction, most probably after the Heyrovsky–Volmer mechanism at low overpotential and the direct discharge irreversible mechanism at high overpotentials.