Surface Chemistry Of Ceria And Its Application In Catalysis: A First-principle DFT+U Investigation

Ceria substrate can induce metal nanoparticles by strong metal-support bondingto exhibit extraordinary catalytic activities in many important reactions, such as COoxidation reaction, water-gas-shift reaction and hydrogen production reaction.Numerous efforts have been made to investigate the key factors that dominate theircatalytic activities. These factors include the dimensionality and morphology of goldnanoparticles, the fluxionality and electronic state of gold clusters, the presence ofgold NP-support interfaces. Although some progress has been achieved in the pastdecade, the dominant factors for the high activity of ceria-supported gold catalystshave not been fully resolved due to the lack of their precise atomic structures.In this work, we employ density functional theory with the inclusion of theon-site Coulomb interaction (DFT+U) to investigate the structure evolution ofsmall-sized gold (Au、Au4、Au8and Au12) clusters on reduced CeO2(111) surfaceswith single surface oxygen vacancy (SSV), linear surface oxygen vacancy trimer(LSVT), double linear surface oxygen vacancy cluster with a surface vacancy dimerand a subsurface vacancy (dLSVC), and triangular surface oxygen vacancy trimer(TSVT). Our results indicate the relative stabilities of multilayer (3D) structures arestrengthened gradually comparing to the monolayer (2D) structures with theincreasing of numbers of gold atoms. Different reduced ceria surfaces transferdifferent charges to gold clusters, which causes2D-3D structure transition of goldclusters occurring in the orders of Au2D→3D@CeO2-TSVT> Au2D→3D@CeO2-dLSVC~Au2D→3D@CeO2-LSVT> Au2D→3D@CeO2-SSV. Meanwhile, two competitivenucleation patterns are observed, fcc-like nucleation and hcp-like nucleation, whichhighly influence the morphology of supported gold clusters. Further site-by-siteinvestigations indicate the coordination number and the charges of Au atom are thedominant factors to influence the adsorption strength of CO and O2, and the interfaceplays a relative minor role. These findings not only enrich the knowledge of therelationship among the surface defects, the gold cluster structures and small molecules’adsorptions, but provide a theoretical perspective to help design the optimal Au/CeO2systems with high catalytic efficiency.