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 CeO 2 (111)-supported Pd-based bimetallic nanorods was investigated using density functional theory calculations corrected by on-site Coulomb interactions. We studied a series of CeO 2 (111)-supported Pd-based bimetallic nanorods (Pd–X, where X = Ag, Au, Cu, Pt, Rh, Ru) and found that Pd–Ag/CeO 2 and Pd–Cu/CeO 2 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/CeO 2 system is more effective for catalyzing CO oxidation as compared to Pd–Cu/CeO 2 because both CeO 2 lattice oxygen atoms and adsorbed oxygen molecules at Ag sites can oxidize CO with low energy barriers. Both the Pd–Ag and Pd–CeO 2 interfaces in Pd–Ag/CeO 2 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–CeO 2 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.