Toward Practical Water Decontaminations via Peroxymonosulfate Nonradical Oxidation: The Role of Cocatalyst MoS₂ with Sulfur Vacancies

Abstract

Molybdenum disulfide (MoS2) is a prevalent cocatalyst for peroxymonosulfate (PMS) activation with iron-based materials. The contribution of molybdenum atoms in cocatalyst MoS2 to iron regeneration during PMS activation has been broadly known, though the role of sulfur atoms remains explored. Here, we applied a one-step, facile means to prepare particulate Fe3O4 supported by wrinkled MoS2 with discernible sulfur vacancies (SV), forming a flower-like Fe3O4–MoS2 composite catalyst. We demonstrated, for the first time, a strong affinity of SV to PMS, facilitating the formation of an intermediate FeIII–PMS* while modulating the generation of pivotal nonradical species. Using an extensive characterization, we confirmed the simultaneous generation of high-valent iron-oxo species (FeIVO) and singlet oxygen (1O2) during PMS activation with the Fe3O4–MoS2 catalysts. In addition, we proposed that the FeIVO stemmed from the FeIII–PMS* precursor, which underwent heterolytic cleavage of the O–O bonds and concomitant rearrangement of oxygen atoms. Meanwhile, 1O2 is excited by PMS and formed by active oxygen (O*) liberated from iron oxides. Consequently, the Fe3O4–MoS2 catalysts showed impressive performance in removing typical micropollutants from real water sources, such as secondary effluent from wastewater treatment plants, tap water, and surface water stream. Our study provides new insights into a nonradical pathway for PMS activation with Sv-containing MoS2, clearing the way for developing high-performance MoS2 catalysts for water decontamination.