Structure of the Metal-Support Interface and Oxidation State of Gold Nanoparticles Supported on Ceria

An Au/CeO2 model catalyst was prepared by deposition-precipitation, with the aim of obtaining a sample suitable for a detailed X-ray absorption fine structure (XAFS) analysis of the gold-ceria interface structure. The results demonstrate the existence of a large interface between the gold particle and the support oxide, characterized by well-defined Au-O and Au-Ce interactions extending up to similar to 6.4 angstrom. The complex interface structure is retained after CO treatment up to 250 degrees C and subsequent reoxidation at 400 degrees C. The analysis of the XANES spectra, and the Au-O distance of 2.21 angstrom, longer than Au-O bond lengths previously reported for Au/ceria catalysts, suggest a low oxidation state for the gold atoms placed at the interface between Au and ceria.