Structural evolutions under surface oxidation of AgPd Alloy: From Orientation, composition and strain effects to catalytic application

The surface oxidation of AgPd alloys can significantly impact their catalytic activity, however, the detailed understanding of such dynamic mechanism and the prediction of catalytic activity is still lacking. Herein, a comprehensive investigation combining ab initio molecular dynamics simulations with experimental observations is performed. The surface oxidation of AgPd alloys is highly dependent on oxygen concentration, where AgO_x forms in oxygen-poor environment and PdO_x forms in oxygen-rich environment, and shows highly reliance on the orientation, composition and strain state. The oxidation level of Ag, Pd and AgPd alloys follows the trend of (1 1 1) < (1 0 0) < (1 1 0) under 1.0 ML of O coverage. Both Pd single-atom and Ag matrix atoms in PdAg single-atom alloys are susceptible to oxidation under 0.5 ML of O coverage, with the increase of Pd atom number, only AgO_x forms. Tensile strain promotes the oxidation of Ag(1 1 1) surface by facilitating the inward diffusion of O atoms, while compressive strain promotes the oxidation of Pd(1 1 1) and AgPd(1 1 1) surfaces by facilitating the outward migration of Ag/Pd atoms. The oxidized AgPd(1 1 1) surface with tensile strain under 0.5 ML of O coverage exhibits the optimum electrocatalytic activity toward formate oxidation reaction.