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. [Display omitted] •MC-5/PMS/Vis system achieved a 100% removal of OFX within just 15 min.•1O2, h+, and •O2− were the main reactive radicals involved in the OFX degradation.•MoS2/Co3O4 exhibited rapid transportation and separation of charge carriers.•Co–Mo interaction can further promote the OFX degradation efficiency.•Intermediates of OFX were identified and four degradation pathways were proposed.