Abstract: For heterogeneous catalysts, the build-up of interface contacts can influence markedly their activities. Being different from the conventional supported metal/oxide catalysts, the reverse type of oxide/metal structures, e.g. the ceria/Pt composite, have emerged as novel catalytic materials in many fields. However, it remains challenging to determine the optimal interface structure and/or the metal-oxide synergistic effect that can boost catalytic activities. In this work, we conducted density functional theory calculations with on-site Coulomb interaction correction to determine the optimal structures and investigate the physical as well as catalytic properties of various CeO₂/Pt(111) composites containing CeO₂(111) monolayer, bilayer, and trilayer at Pt(111). We found that the interaction strength between CeO₂(111) and Pt(111) substrate first reduces as the ceria slab grows from monolayer to bilayer, and then largely gets converged when the trilayer occurs. Such trend was well rationalized by analyzing the number and distances of O-Pt bonds at the interface. Calculated Bader charges uncovered the significant charge redistribution occurring around the interface, whereas the net electron transfer across the interface is non-significant and decreases as ceria thickness increases. Moreover, comparative calculations on oxygen vacancy formation energies clarified that oxygen removal can be promoted on the CeO₂/Pt(111) composites, especially at the interface. We finally employed CO oxidation as a model reaction to probe the surface reactivity, and determined an intrinsic activity order of monolayer CeO₂(111) > monolayer CeO₂(111)/Pt(111) > regular CeO₂(111). More importantly, we emphasized the significant role of the moderate ceria-Pt interaction at the interface that endows the CeO₂/Pt reverse catalyst both good thermostability and high catalytic activity. The monolayer CeO₂(111)/Pt(111) composite was theoretically predicted highly efficient for catalyzing CO oxidation.

Key words: CeO₂/Pt reverse catalyst, Interface structure, Oxygen vacancy, CO oxidation, Density functional theory