Photocatalytic peroxymonosulfate activation over S-scheme Co1−xS/g-C3N4 heterostructure toward high-efficiency polyethylene terephthalate degradation

The inherent chemical stability of polyethylene terephthalate (PET) poses significant challenges for its natural degradation, leading to severe environmental accumulation. This study presents an innovative Co 1-x S/g-C 3 N 4 S-scheme heterojunction photocatalyst designed to enhance interfacial electron transfer and promote cobalt redox cycling for efficient peroxymonosulfate (PMS) activation, achieving effective PET degradation. Experimental results demonstrated that the optimized photocatalysis/PMS system achieved a 6.3-fold higher PET degradation efficiency compared to the photocatalysis system alone. The optimized system (30 % Co 1-x S/g-C 3 N 4 with 4 mM PMS and 1 mL H 2 O 2 under irradiation) achieved a remarkable PET degradation efficiency of 80.91 ± 1.30 %. Density functional theory (DFT) calculations unveiled the interfacial electronic structure of Co 1-x S/g-C 3 N 4 , demonstrating hole accumulation on g-C 3 N 4 and electron localization on Co 1-x S. Systematic comparative experiments confirmed the cooperative roles of heterojunction architecture, electron transfer dynamics, cobalt active sites, and H 2 O 2 in PMS activation. Degradation intermediates were identified by gas chromatography spectrometry (GC) and liquid chromatography-mass spectrometry (LC-MS), while electron spin resonance (ESR) and radical trapping experiments established SO 4 •− as the predominant reactive species. This study provides a new approach for the construction of S-scheme heterojunction photocatalysts, the activation by PMS, and the treatment of PET plastic in water.