The effect of dopant Cu, Fe, Ni or La on the structures and properties of mesoporous Co-Ce-O compound catalysts

A series of Co-Ce-O mesoporous catalysts doped with Cu, Fe, Ni or La and the undoped one were synthesized by using tri-block copolymer P-123 as the template. These catalysts show wormhole-like structures, high surface areas (144–167 m2/g) and uniform meso-pore size distributions (4.0–4.8 nm) after calcination at 500 °C. The activity for low-temperature CO oxidation and the thermal stability of the mesoporous Co-Ce-O catalyst are largely modified by the dopant Cu, Fe, Ni or La in different ways. It is revealed by in situ diffuse reflectance infrared spectroscopy that CO oxidation over all the samples except the Ni-doped one undergoes carbonates pathway. In this case, the oxidation activities of the catalysts are mainly determined by the mobility of surface lattice oxygen species, which is indicated by the temperature-programmed reduction and desorption results. Doping with Cu greatly enhances the oxidation activity of Co-Ce-O catalyst at the calcination temperatures of 500 °C and 650 °C, and doping with La significantly improves its activity at the calcination temperature of 800 °C. However, doping with Fe always decreases the activity of Co-Ce-O catalyst regardless of the calcination temperature. Largely different from other dopants, the addition of Ni induces a change of the mechanism for CO oxidation and results in a remarkable decrease in the activity.