Montmorillonite-Regulated C3N4/Co3O4 Interface Enables Sustained Radical-Driven Photocatalytic Peroxymonosulfate Oxidation of Bisphenol A

Abstract Interfacial regulation provides a route to couple charge separation, Co-site chemistry, and peroxymonosulfate (PMS) activation in photocatalytic oxidation. Here, a montmorillonite-regulated C3N4/Co3O4 photocatalyst (MCNCo) was constructed for light-assisted BPA degradation. MCNCo achieved 85.2% BPA removal within 60 min, compared with 70.2% for CNCo, despite its lower specific surface area and substantially lower bulk Co content. KPFM revealed a 0.404 eV work-function difference between C3N4 and Co3O4, while SPV, photocurrent, PL, and EIS measurements consistently showed enhanced photoinduced charge separation after MMT incorporation. Component-control experiments identified Co-containing sites as the primary direct PMS activation centers, with C3N4 supplying photogenerated carriers and MMT regulating the defect-rich interfacial environment and Co-site stability. MCNCo/PMS/Vis followed a photogenerated-charge-assisted radical pathway in which •OH and SO4•–contributed 47.76 and 22.67%, respectively, whereas 1O2 contributed 0.05%. Although MCNCo and CNCo reached the same final PMS decomposition efficiency (80.36%), MCNCo showed the higher PMS utilization index (0.139 versus 0.115), consistent with its sustained BPA oxidation. MCNCo also maintained catalytic activity over ten cycles, and TOC removal increased to 72.63% at 300 min. These results establish layered MMT as an interfacial regulator that couples defect control, charge transfer, and Co-mediated PMS activation.