Activation barriers of CO oxidation on Pt-M (M = Ru, Sn) alloys

Fuel cells have attracted attention in recent years because they are very energy-efficient. However, we have to face up to a serious problem in that platinum, which is the usual anode electrocatalyst, is readily poisoned by CO. In the case of the Direct Methanol Fuel Cell (DMFC), it is very important to develop new materials for use as electrocatalysts that exhibit good tolerance to CO, since CO is invariably present as an intermediate in the dissociation of methanol. The aim of this study is to examine the mechanism of H ₂O dissociation and of the CO + OH combination reactions in the CO oxidation process by calculating the adsorption energies and the activation barriers. In the case of Pt-Ru alloys, the activation barrier of the H ₂O dissociation reaction is almost the same as it is for pure Pt. The activation energy of the CO + OH combination reaction on Pt-Ru alloy is larger than that on pure Pt. Nevertheless, the adsorption energy of H ₂O is larger than that on pure Pt. On the other hand, the activation barrier and adsorption energies of H ₂O on Pt-Sn alloy are very close to the corresponding values on pure Pt. Moreover, the activation barrier for the CO + OH combination reaction on Pt-Sn alloy is lower than that on pure Pt.