Interaction of cobalt with ceria thin films and its influence on supported Au nanoparticles

Abstract

The interaction of Co with ceria thin films and its influence on the sintering behavior of Au were investigated by scanning tunneling microscopy (STM), synchrotron radiation photoemission spectroscopy (SRPES) and X-ray photoelectron spectroscopy (XPS). The strong interaction between Co and CeO2(111) leads to oxidation of Co to Co2+ at 300K, accompanied by partial reduction of ceria surface at low Co coverages. Subsequent Co deposition results in an increasing fraction of metallic Co. Annealing to high temperatures induces Co2+ ions diffuse into the CeO2 film, while the small metallic Co islands agglomerate into larger ones. The bimetallic Co–Au particles were prepared by deposition of Au on the existing Co particles on ceria surfaces. The sintering behavior of Co–Au bimetallic surfaces is found to be highly determined by the stoichiometry of ceria supports. The addition of Co to the Au/CeO2 surface suppresses the sintering of Au particles at high temperatures in comparison with that of pure Au particles. However, Au particles are less stable on the Co/CeO1.82 layer than on CeO1.82 surface.