Catalytic Hydrolysis-Oxidation of Halogenated Methanes over Phase- and Defect-Engineered CePO₄: Halogenated...

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 CePO₄ 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 H₂O. Hexagonal and defective CePO₄ with more structural H₂O and Brønsted/Lewis acid sites was more reactive and durable compared with monoclinic CePO₄. Based on the phase and defect engineering of CePO₄, in situ diffuse reflectance infrared Fourier transform spectra (DRIFTS), and kinetic isotope effect experiments, a hydrolysis-oxidation pathway characterized by the direct involvement of H₂O 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 CePO₄. The structure-performance-dependent relationships of the engineered CePO₄ 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.