Understanding and controlling the formation of single-atom site from supported Cu cluster by tuning CeO reducibility: Theoretical insight into the Gd-doping effect on electronic metal-support interaction.

Controlling the formation of single-atom (SA) sites from supported metal clusters is an important and interesting issue to effectively improve the catalytic performance of heterogeneous catalysts. For extensively studied CO oxidation over metal/CeO systems, the SA formation and stabilization under reaction conditions is generally attributed to CO adsorption, however, the pivotal role played by the reducible CeO support and the underlying electronic metal-support interaction (EMSI) are not yet fully understood. Based on a ceria-supported Cu catalyst model, we performed density functional theory calculations to investigate the intrinsic SA formation mechanism and discussed the synergistic effect of Gd-doped CeO and CO adsorption on the SA formation. The CeO reducibility is tuned with doped Gd content ranging from 12.5 % ∼ 25 %. Based on ab initio thermodynamic and ab initio molecular dynamics, the critical condition for SA formation was identified as 21.875 % Gd-doped CeO with CO-saturated adsorption on Cu. Electronic analysis revealed that the open-shell lattice O (δ < 2) generated by Gd doping facilitates the charge transfer from the bottom-corner Cu (Cu) to CeO. The CO-saturated adsorption further promotes this charge transfer process and enhances the EMSI between Cu and CeO, leading to the disintegration of Cu from Cu and subsequent formation of the active SA site.