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 (O2−) and singlet oxygen (1O2) worked as the dominant ROSs during the oxidation, rather than traditional sulfate radical (SO4−) or hydroxyl radical (OH). Notably, in situ electron spin resonance witnessed the evolution of growing O2− and 1O2, as well as lessened SO4− and OH with increasing OVs content. It was mainly attributed to the preferential dissociation of PMS into O2 on the OVs, additionally, OVs facilitated the superior surface oxygen mobility and electrical conductivity, which also gave rise to a significant enhancement in O2− and 1O2 generation. Consequently, an OVs-dependent PMS activation mechanism was proposed.