Methanol Oxidation Reaction on α-Tungsten Carbide Versus Platinum (1 1 1) Surfaces: A DFT Electrochemical Study

A density functional study of Gibbs free energy profiles for the methanol oxidation reaction (MOR) on Pt and α-WC surfaces provides a solid basis for the rationalisation that transition metal carbides represent excellent alternative materials to Pt as fuel cell anodes. Furthermore, this study shows that a strategy to enhance the activity of the WC surfaces is by doping with an excess of electronic charge. Although on the neutral surface the preferred pathway is through the dissociation of the methanol O-H bond with no formation of CO, on the electron-rich surface the reaction goes quite easily to CO, which is then transformed to CO2 by applying an onset potential of only 0.49 V (computed with reference to a standard hydrogen electrode). This is almost exactly the potential required to achieve full oxidation to CO2 on the Pt (1 1 1) surface (computed to be 0.48 V) through a direct CH mechanism (dissociation of the methanol C-H bond). This analysis is corroborated by the excellent agreement between the computed and experimental onset potentials.