Low-temperature CO oxidation on CuO/CeO2 catalysts: the significant effect of copper precursor and calcination temperature

CuO/CeO2 catalysts for CO oxidation were prepared by impregnation using different Cu precursors (acetate, nitrate, chloride, and sulfate) and calcined at 500 or 800 degrees C. Their physicochemical properties were characterized by TG-DSC, XRD, TEM, N-2 adsorption, Raman, XPS, H-2-TPR, CO-TPD, and DRIFTS. The results show that CuO is the dominant Cu species in all cases except for copper sulfate calcined at 500 degrees C, under which temperature some Cu-2(OH)(3)Cl are also obtained from copper chloride. CuO/CeO2 prepared from copper acetate and calcined at 500 degrees C shows the best activity for CO oxidation, due to the presence of more finely dispersed CuO and stronger synergistic effects. The synergistic effects can induce the formation of Cu+ (the better CO adsorption sites) and activate the lattice oxygen, thus exerting a crucial role in the catalytic process. However, the residual Cl- and SO42- have a negative effect on the synergistic effects, resulting in low activity in CO oxidation.