Redox behaviour of CeO2 and Ce0.5Zr0.5O2 supported CuO catalysts for CO oxidation

The reduction-oxidation behaviour of supported copper oxide catalysts has been investigated by temperature-programmed reduction. For the CuO/CeO2 catalyst there are three reducible copper oxide species; alpha and beta peaks are attributed to the reduction of highly dispersed copper oxide species; a gamma(1) peak is ascribed to the reduction of bulk CuO. The order of reduction of three copper oxide species is found to be alpha-beta-gamma(1), which is consistent with the order of reoxidation of copper species on a reduced CuO/CeO2 catalyst. For the CuO/Ce0.5Zr0.5O2 catalyst, three copper oxide species are also observed, an alpha peak is attributed to the dispersed copper oxide species; gamma(1) and gamma(2) peaks are ascribed to the bulk CuO. The reduction of the CuO/CeO2 catalyst is easier than for CuO/Ce0.5Zr0.5O2; the oxidation of the reduced CuO/CeO2 catalyst is also easier than for the reduced CuO/Ce0.5Zr0.5O2 catalyst. CuO dispersion on a CeO2 support is larger than on Ce0.5Zr0.5O2. The catalytic activity of CuO/CeO2 for CO oxidation is higher than that of CuO/Ce0.5Zr0.5O2, which is consistent with the dispersion and the reduction of CuO.