Interface oxygen vacancies (OVs) is commonly used to improve the catalytic performance of activators in persulfate-based advanced oxidation processes, but the underlying mechanism was not fully explored due to the coexisted of OVs and reducing metal active sites. This work reports a facile heat treatment method to regulate OVs in MoO3-x to elucidate the mechanism of peroxymonosulfate (PMS) activated by OVs to degrade organic pollutants Electron spin resonance, free radical quenching, X-ray photoelectron spectroscopy, and Raman spectroscopy confirmed that both reducing Mo species and OVs of MoO3-x surface were responsible for PMS activation. Further experiments and Density Function Theory (DFT) calculation suggest that OVs in MoO3-x induced the formation of superoxide radical (O2●−), and then O2●− was transformed into singlet oxygen (1O2) or mediated PMS activation to generate radicals for pollutants degradation. The stead-state concentrations of free radical calculated with kinetics model shows that OVs were more favorable to mediate PMS to generate hydroxyl radicals (●OH) and reducing Mo species would like to induce PMS to produce sulfate radicals (SO4●−). Furthermore, OVs mediate ●OH generation under oxic conditions, while reducing Mo species induce SO4●− formation under both oxic and anoxic conditions. Overall, this study is dedicated to a new insight into the in-depth mechanism of PMS activation by OVs-rich catalysts and provides a novel strategy for reactive species regulation in PMS based oxidation process.

Oxygen vacancies-dominated reactive species generation from peroxymonosulfate activated by MoO3-x for pollutant degradation

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