Influence of preparation methods on CuO-CeO2 mixed oxide on the oxidation of CO

Abstract

Influence of preparation methods (combustion and impregnation) on the oxidation of CO over CuO-CeO₂ catalysts has been investigated. Both samples are characterized by means of H₂-temperature-programmed reduction (H₂-TPR) and Raman spectroscopy. CuO-CeO_2­ prepared by combustion shows that there are three CuO species in the mixed oxide: the Cu²⁺ is mostly exist in the Cu_xCe_1-xO_2-dsolid solution and the left in the bulk CuO and finely dispersed CuO species on the surface of CeO₂. CuO-CeO_2­ prepared by impregnation shows that there are two CuO species in the mixed oxide: the Cu²⁺ is mostly exist in the finely dispersed CuO species on the surface of CeO₂ and the left in the Cu_xCe_1-xO_2-dsolid solution. The calculating results of the oxygen vacancy concentration in CuO-CeO₂ mixed oxide from Gaussian deconvolution of Raman spectra showed that, oxygen vacancy concentration in                                  CuO-CeO₂–combustion and CuO-CeO₂–impregnation are 12.7 % and 29.7 %, respectively. The catalyst prepared by impregnation is more active for the oxidation of CO, which caused significant differences in the redox properties and the dispersion of copper species. The discrepancies in the dispersion of copper species and the degree of interaction between copper species and ceria determined the reversible redox properties, and consequently the catalytic performance.