Interfacial Effects of CeO2-Supported Pd Nanorod in Catalytic CO Oxidation: A Theoretical Study

Understanding the interfacial effects of metal/support catalysts is of great significance in heterogeneous catalysis. In this work, we performed density functional theory calculations corrected by on-site Coulomb interactions (DFT+U) to study CO oxidation on a CeO 2 (111)-supported Pd nanorod. Three different reaction mechanisms for CO oxidation were systematically studied, namely the Pd–Ce 3+ dual sites mechanism, the Mars-van Krevelen (M-vK) mechanism, and the Pd-only mechanism. On the basis of energetic analysis, we concluded that the dominant reaction pathway at low temperatures is the Pd–Ce 3+ dual sites mechanism, whereas the M-vK mechanism would be dominant at higher temperatures. The interfacial effects play a crucial role and strongly affect the catalytic activity in these two mechanisms. The origin of the interfacial effects can be understood by analyzing the geometric and electronic properties. From the geometric perspective, the interaction between Pd nanorod and ceria support elongates the Ce–O bonds at the interface, enhancing the mobility and activity of interfacial lattice O atoms. From the electronic perspective, there occurs electron transfer from the Pd nanorod to the interfacial Ce 4+ cation, leading to the formation of Ce 3+, and subsequent electron transfer from Ce 3+ to the adsorbed O 2 at the Pd–Ce 3+ dual sites significantly promotes the formation of active oxygen species for CO oxidation. Our study provides atomic-scale insights into the nature of active sites and the interfacial effects that determine CO oxidation on Pd/CeO 2 catalysts.