Computational Design of a CeO2-Supported Pd-Based Bimetallic Nanorod for CO Oxidation

Engineering a bimetallic system with complementary chemical properties can be an effective way of tuning catalytic activity. In this work, CO oxidation on CeO2(111)-supported Pd-based bimetallic nanorods was investigated using density functional theory calculations corrected by on-site Coulomb interactions. We studied a series of CeO2(111)-supported Pd-based bimetallic nanorods (Pd-X, where X = Ag, Au, Cu, Pt, Rh, Ru) and found that Pd-Ag/CeO2 and Pd-Cu/CeO2 are the two systems where the binding sites of CO and O-2 are distinct; that is, in these two systems, CO and O-2 do not compete for the same binding sites. An analysis of the CO oxidation mechanisms suggests that the Pd-Ag/CeO2 system is more effective for catalyzing CO oxidation as compared to Pd-Cu/CeO2 because both CeO2 lattice oxygen atoms and adsorbed oxygen molecules at Ag sites can oxidize CO with low energy barriers. Both the Pd-Ag and PdCeO2 interfaces in Pd-Ag/CeO2 were found to play important roles in CO oxidation. The Pd-Ag interface, which combines the different chemical nature of the two metals, not only separates the binding sites of CO and O-2 but also opens up active reaction pathways for CO oxidation. The strong metal-support interaction at the Pd-CeO2 interface facilitates CO oxidation by the Mars-van Krevelen mechanism. Our study provides theoretical guidance for designing highly active metal/oxide catalysts for CO oxidation.