Catalytic Hydrolysis–Oxidation of Halogenated Methanes over Phase- and Defect-Engineered CePO₄: Halogenated Byproduct-Free and Stable Elimination

Abstract

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 4 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 H 2 O. Hexagonal and defective CePO 4 with more structural H 2 O and Brønsted/Lewis acid sites was more reactive and durable compared with monoclinic CePO 4 . Based on the phase and defect engineering of CePO 4 , in situ diffuse reflectance infrared Fourier transform spectra (DRIFTS), and kinetic isotope effect experiments, a hydrolysis−oxidation pathway characterized by the direct involvement of H 2 O 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 4 . The structure−performance-dependent relationships of the engineered CePO 4 contributed to the rational design of efficient catalysts for HVOC elimination, and this pioneering work on external electric fieldassisted catalytic hydrolysis−oxidation established an innovative HVOC elimination route.