Efficient ofloxacin degradation via peroxymonosulfate activation using an S-scheme MoS2/Co3O4 heterojunction composite under visible light: Performance and mechanistic insights

Sulfate-radical-mediated photocatalysis technology peroxymonosulfate (PMS) activation via visible light irradiation shows great promise for water treatment applications. However, its effectiveness largely depends on the bifunctional performance of photocatalysis and PMS activation provided by the catalysts. In this study, we successfully synthesized a novel S-scheme MoS₂/Co₃O₄ (MC) heterojunction composite by a hydrothermal method and employed it for the first time to activate PMS for ofloxacin (OFX) degradation under visible light irradiation. The MC-5/PMS/Vis system achieved an impressive 85.11% OFX degradation efficiency within 1 min and complete OFX removal within 15 min under optimal conditions, with an apparent first-order kinetics rate constant of 0.429 min⁻¹. Reactive species trapping experiments and electron spin resonance analysis identified ¹O₂, h⁺, and •O₂⁻ as the primary active species responsible for OFX degradation. Photoelectrochemical analyses and density functional theory calculations indicated the formation of a built-in electric field between MoS₂ and Co₃O₄, which enhanced the separation and migration of photoinduced carriers. Additionally, the Co–Mo interaction further increased the yield of dominant reactive species, thereby boosting photocatalytic activity. This work underscores the potential of visible-light-assisted PMS-mediated photocatalysis using Co₃O₄-based catalysts for effective pollutant control.