Oxygen adsorption on Pt-Pd nanoclusters by DFT and ab initio atomistic thermodynamics

Monometallic Pt and Pd, and bimetallic Pt-core/Pd12-shell and Pd-core/Pt12-shell were built and geometrically optimized by density functional theory calculations in consideration of oxygen adsorption. The different oxygen adsorption sites on the cluster were considered: top site on one shell atom, bridge site between two shell atoms and hollow site among three shell atoms. For each adsorption site, a few coverages were considered, both oxygen-rich condition and oxygen-poor condition. The pressure-temperature phase diagrams were determined for 13-atom Pt-Pd clusters with adsorbed oxygens in terms of ab initio atomistic thermodynamics method. The most stable phase structure and adsorption of oxygen at certain temperature and pressure were illustrated. Additionally the results showed that the cluster structures were most likely to be changed under oxygen-poor condition. This study is helpful to understand their catalyst processes in a few oxygen-involved reactions such as formic acid electro-oxidation, direct methanol fuel cell, oxygen reduction reaction in fuel cells, oxidation of sulfur dioxide and diesel oxidation and so on.