Abstract: Elucidation of the CuO_x-CeO₂ interactions is of great interest and importance in understanding complex CuO_x-CeO₂ interfacial catalysis in various reactions. In the present work, we have investigated structures and catalytic activity in CO oxidation of CuO_x species on CeO₂ rods, cubes and polyhedra predominantly exposing {110}+{100}, {100} and {111} facets by the incipient wetness impregnation method with the lowest Cu loading of 0.025%. The structural evolution of CuO_x species was found to depend on both the Cu loading and the CeO₂ morphology. As the Cu loading increases, CuO_x species are deposited preferentially on the surface defect of CeO₂ and then aggregate and grow, accompanied by the formation of isolated Cu ions, CuO_x clusters strongly/weakly interacting with the CeO₂, highly dispersed CuO nanoparticles, and large CuO nanoparticles. The isolated Cu⁺ species and CuO_x clusters weakly interacting with the CeO₂ were observed mainly on the O-terminated CeO₂{100} facets. Meanwhile, more Cu(I) species are stabilized during CO reduction processes in CuO_x/c-CeO₂ catalysts than in CuO_x/r-CeO₂ and CuO_x/p-CeO₂ catalysts. The catalytic activities of various CuO_x/CeO₂ catalysts in CO oxidation vary with both the CuO_x species and the CeO₂ morphology. These results comprehensively elucidate the CuO_x-CeO₂ interactions and exemplify their morphology-dependence.

Key words: CeO₂ nanocrystals, CuO_x/CeO₂ catalysts, Metal-support interactions, CO oxidation, Morphology effect