Key role of yttrium doping on Cu/CeO2 (111) in water–gas shift reaction: Promotion of cluster dispersity

Abstract

Conventional theoretical models of electronic metal-support interaction (EMSI) often assume uniform metal dispersion, leading to conclusions conflicting with experimental observations. It highlights the critical need to incorporate metal dispersion effects in EMSI studies. Here, we investigate how Y³⁺ doping regulates Cu cluster dispersion on CeO₂(1 1 1) for the water–gas shift reaction (WGSR) using density functional theory (DFT), mean-field microkinetic modeling (MF-MKM), and kinetic Monte Carlo (kMC) simulations. Cohesion energy analysis reveals that on undoped ceria, bilayer clusters predominate. However, Y³⁺ (compared to Ce⁴⁺) possesses a smaller radius and lower redox capability, which differentiates loading sites but obstructs EMSI. Excessive doping even restricts the formation of spillover oxygen (O_sp), thereby favoring 3D clusters. The presence of surface spillover oxygen partially compensates for the EMSI weakening. This compensation effect causes the cohesive energy difference between bilayer and O_sp planar-type clusters to become positive, resulting in the advantage of O_sp planar-type clusters at lightly doping level. Kinetic simulations identify O_sp-type planar copper clusters as functional active phases for undoped/lightly doped ceria, while heavily doped systems are regular planar clusters without O_sp. O_sp-type planar clusters exhibit extraordinary catalytic activity due to O_sp-mediated adsorption and reactivity promotion, whereas bilayer clusters manifest low activity. Comprehensive analysis of cluster dispersion and structure–activity relationships discloses non-monotonic WGSR activity dependence on Y-doping: activity of sub-nanometer copper clusters peaks at low doping amount before declining at higher doping levels, aligning with experiments This work highlights the necessity of identifying both dispersion and activity of clusters for specific doping levels. These findings provide critical insights for the design of doped-supported catalysts and establish a theoretical framework for optimizing EMSI in heterogeneous catalysis.