Towards active and stable oxygen reduction cathodes: a density functional theory survey on Pt2M skin alloys

Pt metal, when used as a cathode for oxygen reduction (O2 + 4H+ + 4e− → 2H2O), suffers from high overpotential and catalyst corrosion. Here, first-principles based theoretical methods for electrochemical systems are utilized to identify the critical factors affecting cathode performance. By analyzing a large set of Pt alloys, we show that alloys are in general less stable than Pt at the same O coverage under electrochemical conditions, and that maintaining a zero O coverage at the working potentials (e.g. 0.9 V) is key to achieve both high activity and stability. Two quantities, i.e. the surface corrosion energy and the free energy barrier to OOH dissociation, are found to be the main descriptors for the stability and activity. A Pt2Mo skin alloy is discovered to be a good candidate for an oxygen reduction cathode. The theoretical framework provides a new route for the rational design of oxygen reduction catalysts.