Interaction of Au with CeO2(111): A photoemission study

We have studied the adsorption of low dimensional gold on ceria, produced by evaporation onto the surface. The interaction of gold with CeO2(111) layers was investigated with x-ray photoemission spectroscopy, ultraviolet photoemission spectroscopy, and resonant photoelectron spectroscopy (RPES). Gold was deposited in steps onto a 1.5 nm thick CeO2(111) layer epitaxially grown on a Cu(111) substrate. The RPES showed a partial Ce4+→Ce3+ reduction, observed as a resonant enhancement of the 4f level of the Ce3+ species. This can be explained by possible creation of a new Au+ ionic state. The observed effects are stronger for Au deposition at room temperature than at 250 °C. The obtained results are in agreement with already published density functional theory calculations reporting weakening of bond between the oxygen and the Ce atoms in ceria caused by the presence of gold.