Oxygen Vacancies Engineering of Co₃O₄ to Modulate the Adjacent Environment: Boosted Singlet Oxygen Generation in Peroxymonosulfate-Mediated 2-Chlorophenol Degradation

Peroxymonosulfate-based advanced oxidation processes are promising for removing organic pollutants but precisely generating singlet oxygen (1O2) as nonradical reactive oxygen species is difficult. Herein, a porous Co3O4 nanosheet was synthesized and further tailored by the bulk doping of Mn and the surface loading of Ru. The abundant oxygen vacancies (Ov) could be created by the Mn doping and then facilitated the precise anchoring of Ru, which in turn contributed to the construction of the adjacent heteronuclear diatomic adsorbed sites (Co-Ov-Ru). In the base MnCoOx/peroxymonosulfate (PMS) system, the electron transfer occurred between the ≡Co(III)-(O)OSO3- complex and free HSO5- to produce the O2•- and subsequently the adjacent O2•- trapped on the Ov disproportionates into 1O2, whereas the anchoring of Ru occupied the Ov and high-selectively boosted the self-combined generation of 1O2 through the heteronuclear diatomic-adsorbed PMS (SO5•--Co-Ov-Ru-SO5•-). The optimized Ru/MnCoOx demonstrated wide pH adaptability, high efficiency, and salinity tolerance for the degradation of 2-chlorophenol, and it removes over 99% of contaminants in complex water matrices even after 36 h in fixed-bed operation. This work provided a new protocol for PMS activation through a distinctively structured and easily scaled Co3O4-based catalyst and contributed to understand the tuning generation of singlet oxygen and guide the design of metal oxide catalysts.