A comparative study on Ce-Pr and Ce-Mn mixed oxide catalysts toward soot catalytic combustion

CePr and CeMn mixed oxide catalysts were synthesized by inserting Pr and Mn atoms into CeO2. Catalytic performance on soot combustion was investigated, and several characterizations were carried out using X-ray photoelectron spectroscopy, Brunauer-Emmett-Teller surface area analysis, H-2 temperature-programmed reduction, and X-ray diffraction. Results show that a cubic fluorite structure solid solution can be formed with Pr and Mn doped into CeO2 lattice. Three oxygen species, namely, lattice oxygen O-I (O2-), defect oxygen species O-II (O-2(-), O-2(2-), and O-), and hydroxyl-like groups and adsorbed molecular water O-III, exist in the solid solution structure. In general, the defect oxygen species O-II is responsible for soot combustion. CePr exhibits fast oxidation rate because of the presence of open oxygen migration channel (O-I <-> O-II <-> O-III), and reactive oxygen species O-II can continue to be replenished. CeMn possesses a large amount of surface active oxygen, which results in excellent low-temperature catalytic activity.