Switching the reaction mechanisms and pollutant degradation routes through active center size-dependent Fenton-like catalysis

Rationally regulating reaction mechanisms in Fenton-like reactions by tuning the properties of catalysts is of great significance, but still challenging. Herein, we synthesized various active center size-dependent catalysts to realize the switching of reaction mechanisms and pollutant degradation routes in peroxymonosulfate (PMS) activation systems. The results illustrated that the reaction mechanism transformed from radical oxidation (51.64%) to nonradical oxidation (89.92%) with the decrease of active center size from nanoparticle (CoNP-NC) to single atom (CoSA-NC). The evolution of reactive species switched the degradation intermediates and pathway of sulfisoxazole (SIZ). The generation of singlet oxygen (1O2) in CoSA-NC/PMS tends to selectively attack electron-rich site of SIZ, while reaction between radicals and SIZ prefers non-selective oxidation in CoNP-NC/PMS system. Besides, the toxicity tests indicated that the conversion from non-selective to selective oxidation resulted in lower toxicity of effluent after reaction, which can further reduce environmental risks of effluent. [Display omitted] •Controlled synthesis of cobalt active center sites from nanoparticles to single atoms.•The reaction mechanism transformed from radical oxidation to nonradical oxidation.•The degradation routes of SIZ can be switched in active center size-dependent catalysis.•The toxicity of intermediates can be controlled in active center size-dependent catalysis.