Oxygen vacancies induced heterogeneous catalysis of peroxymonosulfate by Ni-doped AgFeO2 materials: Evolution of reactive oxygen species and mechanism

Oxygen vacancies (OVs) modulation has emerged as a prevalent strategy to optimize the performance of Fenton-like catalysts. Nevertheless, the OVs-induced evolution of reactive oxygen species (ROSs) and associated mechanisms in the Fenton-like process remain insufficient. Herein, a series of oxygen-defective AgFe1-xNixO2 were synthesized to enhance peroxymonosulfate (PMS) decomposition and efficient degradation of bisphenol A (BPA) in water. The total amounts of OVs were regulated by varying the ratio of Ni dopant. Compared with original AgFeO2, the AgFe1-xNixO2 with rich OVs exhibited a better redox potential for PMS interaction and a lower reaction energy barrier of PMS decomposition. Superoxide radical (O-2(center dot-)) and singlet oxygen (O-1(2)) worked as the dominant ROSs during the oxidation, rather than traditional sulfate radical (SO4 center dot-) or hydroxyl radical (% OH). Notably, in situ electron spin resonance witnessed the evolution of growing O-2(center dot-) and O-1(2), as well as lessened SO4 center dot- and %OH with increasing OVs content. It was mainly attributed to the preferential dissociation of PMS into O-2 on the OVs, additionally, OVs facilitated the superior surface oxygen mobility and electrical conductivity, which also gave rise to a significant enhancement in O-2(center dot-) and O-1(2) generation. Consequently, an OVsdependent PMS activation mechanism was proposed.