文摘
Cerium oxide films equivalent to 2 ML of CeO2 were grown at 520 K in an oxygen atmosphere on a cleanCu(111) substrate in order to prepare a model catalytic system. This "inverse model catalyst" was characterizedby low-energy electron diffraction (LEED), X-ray photoelectron spectroscopy (XPS) of core levels, and resonantphotoelectron spectroscopy (RPES) of the valence band. Samples annealed at 770 K exhibited a LEED patterncorresponding to the (1.5 × 1.5) CeO2(111)/Cu(111) structure that can be interpreted as formation of a flat,well-ordered cerium oxide overlayer aligned with the principal crystallographic axes of the substrate. Themodel catalytic system corresponds well to a copper-loaded ceria nanopowder catalyst that exhibits growthof Cu(111) film structure on CeO2(111) planes. Lowering of the CO oxidation temperature due to the Culoading is explained by CO adsorption on copper in the vicinity of highly active ceria planes providing oxygenfor the reaction.