Interaction of Zr with CeO2(111) Thin Film and Its Influence on Supported Ag Nanoparticles

Metal-support interaction plays a crucial role in modulating the activity and selectivity of oxide-supported metal nanoparticles in heterogonous catalysis. Zr-doped ceria is a critical component in automotive three-way catalysts. In order to understand the doping effect and Zr-CeO2 interaction at the atomic level, here we employed X-ray photoelectron spectroscopy (XPS) and scanning tunneling microscopy (STM) to comprehensively investigate the structures, morphologies, and interfacial electronic properties of submonolayer coverage of Zr deposited onto 2 nm thick well-ordered CeO2(111) thin films grown on Cu(111) at different temperatures and its effect on Ag growth under ultrahigh vacuum conditions. The strong Zr CeO2 interaction leads to a two-dimensional (2D) growth of Zr on the CeO2(111) surface and the formation of a homogeneous Zr-O-Ce mixed oxide layer at room temperature, accompanied by partial reduction of Ce from 4+ to 3+ state. At high temperature, both XPS and STM results indicate that the reverse oxygen spillover from ceria substrate to Zr clusters occurs, leading to the formation of reconstructed zirconia and further reduction of ceria. Deposition of Ag onto the Zr predeposited CeO2(111) surface results in a three-dimensional growth of Ag nanoparticles with a higher particle density and smaller particle size compared to those on the pure CeO2(111) surface under same conditions. In addition, an enhanced thermal stability of Ag particles upon annealing was observed on such mixed oxide surface.