Adsorption Properties of Ce/Ag System

Cerium nanopowders doped by a small amount of silver exhibit interesting catalytic properties towards the low temperature oxidation of CO. It is generally believed that a metal support interaction plays an important role in a catalytic process. Therefore in our study we examined electronic and adsorption properties of cerium deposited onto a polycrystalline silver substrate. Layers of approximately one monolayer of cerium deposited on a clean silver substrate were examined in situ using surface sensitive techniques - by X-ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy (UPS) and low energy ion scattering (LEIS). Especially UPS confirmed the strong metal substrate interaction; results of XPS were not so straightforward. CO molecular adsorption was observed by XPS and UPS, LEIS experimental results exhibited CO adsorption on Ce atoms. Oxygen adsorption on deposited layers led to strong oxidation, stoichiometry of oxidized layers was given by amount of adsorbed oxygen and by temperature. CO oxidation on Ag/CeO powder catalyst prepared by decomposition of organic precursors on nanostructural cerium oxide particles was performed in a flow tube reactor using the mixture of Ar, O and CO, production elements were measured by a mass spectrometer. Significant lowering of CO oxidation temperature was observed in comparison with the pure CeO powder. 2