Catalytic Hydrolysis-Oxidation of Halogenated Methanes over Phase- and Defect-Engineered CePO: Halogenated Byproduct-Free and Stable Elimination.

Catalytic elimination of halogenated volatile organic compound (HVOC) emissions was still a huge challenge through conventional catalytic combustion technology, such as the formation of halogenated byproducts and the destruction of the catalyst structure; hence, more efficient catalysts or a new route was eagerly desired. In this work, crystal phase- and defect-engineered CePO was rationally designed and presented abundant acid sites, moderate redox ability, and superior thermal/chemical stability; the halogenated byproduct-free and stable elimination of HVOCs was achieved especially in the presence of HO. Hexagonal and defective CePO with more structural HO and Brønsted/Lewis acid sites was more reactive and durable compared with monoclinic CePO. Based on the phase and defect engineering of CePO, in situ diffuse reflectance infrared Fourier transform spectra (DRIFTS), and kinetic isotope effect experiments, a hydrolysis-oxidation pathway characterized by the direct involvement of HO was proposed. Initiatively, an external electric field (5 mA) significantly accelerated the elimination of HVOCs and even 90% conversion of dichloromethane could be obtained at 170 °C over hexagonal CePO. The structure-performance-dependent relationships of the engineered CePO contributed to the rational design of efficient catalysts for HVOC elimination, and this pioneering work on external electric field-assisted catalytic hydrolysis-oxidation established an innovative HVOC elimination route.