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

Abstract

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 (O_v) 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–O_v–Ru). In the base MnCoO_x/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 O_v disproportionates into ¹O₂, whereas the anchoring of Ru occupied the O_v and high-selectively boosted the self-combined generation of ¹O₂ through the heteronuclear diatomic-adsorbed PMS (SO₅^•––Co–O_v–Ru–SO₅^•–). The optimized Ru/MnCoO_x 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.