Catalytic activity and selectivity of Cerium-Doped catalysts in dichloromethane oxidation

Chlorinated volatile organic compounds (CVOCs) pose a significant threat to human beings and the ecological environment. Although noble metal catalysts can realize the low-temperature and efficient degradation of CVOCs, their high cost and easy to accumulate carbon and sintering limit the practical application. What’s more, the toxic by-products generated from the reaction are easy to be adsorbed on the catalyst surface, leading to the poisoning of the active sites. Based on this, four cerium-chromium doped catalysts, Ce_1-xCr_xO₂-M, where M stands for rod (R), cube (C), particle (P), and spindle (S), were prepared by a two-step hydrothermal method in the present study to systematically investigate the mechanism of chromium doping on the structural remodeling and catalytic performance of CeO₂. It is shown that chromium doping induces the formation of Ce-O-Cr solid solution, which increases the defect site density and promotes the generation of oxygen vacancies by regulating the oxygen atom arrangement, and significantly enhances the trapping and activation of gas-phase oxygen. Among them, Ce_1-xCr_xO₂-S showed the best DCM degradation performance (T₅₀ = 179 °C, T₉₀ = 304 °C), which was attributed to the high specific surface area of the unique morphology, the high density of acidic sites on the surface to promote the dissociation of the C-Cl bond, and the optimized redox properties to accelerate the generation and conversion of reactive oxygen species, which synergistically achieved the high efficiency and depth of the DCM. The three synergies achieved the efficient deep mineralization of DCM. The process optimization shows that 500 ℃ roasting can effectively maintain the active structure. In addition, Ce_1-xCr_xO₂-S has excellent thermal stability and water resistance.