Effect of morphology on the catalytic oxidation of dichloromethane over CeO2 catalysts

The catalytic oxidation of CVOCs has emerged as a prominent and challenging research frontier in environmental science. This study systematically investigated the influence of CeO2 morphology on the oxidation of dichloromethane (DCM), a representative and recalcitrant CVOC. Through solvothermal synthesis, we successfully fabricated CeO2 catalysts with four distinct morphologies: cubes, nanorods, nanosheets, and nanospheres. These nanostructured catalysts were evaluated for their catalytic performance in DCM oxidation, revealing significant morphology-dependent activity. CeO2-Nanosheets emerged as the most effective catalyst, achieving a T90 of 384°C, with the highest CO2 yield and the lowest chlorine-containing by-products. It maintained stable performance over 48 h with minimal decline in DCM conversion and CO2 selectivity. Characterization revealed that the nanosheet morphology possessed several advantageous features: high concentrations of reactive oxygen species, abundant Ce3+ active sites, enhanced redox capacity and optimal surface acidity. These characteristics collectively contributed to the exceptional catalytic activity and selectivity. In situ DRIFTS experiments were conducted to elucidate the reaction mechanism, identifying three key intermediates in the oxidation process: methoxy, formaldehyde and formate species. These findings not only provide a detailed understanding of the reaction pathway but also offer valuable insights for optimizing catalyst design.