Tuning catalytic properties of bimetallic surfaces: Oxygen adsorption on pseudomorphic Pt/Ru overlayers

The adsorption of atomic and molecular oxygen on bimetallic Pt/Ru overlayer systems has been studied by periodic density functional theory calculations. A strong interaction between the Pt and the Ru layers is found resulting in a hcp stacking for the first Pt layer on Ru. The chemical properties of the Pt/Ru overlayers are beyond those of the single constituents Pt and Ru. Both the compression of the Pt overlayers as well as the strong direct interaction between Pt and Ru, which reaches up to the second Pt layer, reduce the atomic and molecular oxygen adsorption energies compared to pure Pt and Ru surfaces. Although the influence of the electrolyte and any external electric field are neglected, the results should still be relevant in the electrochemical context. The consequences of the theoretical findings for the oxygen reduction reaction in electrocatalysis are discussed.