Interfacial charge steering in CdS/nitrogen-deficient g-C3N4 heterojunctions boosts solar-driven persulfate activation for PPCPs decontamination

Abstract

The persistence of pharmaceuticals and personal care products (PPCPs) in aquatic ecosystems poses severe environmental risks, primarily owing to their incomplete removal by conventional treatment methods and potential for inducing bacterial resistance. While CdS/g-C₃N₄ heterojunctions exhibit promise for photocatalytic degradation, the role of nitrogen-defect engineering in steering interfacial charge behavior to synergize photocatalysis with persulfate (PS)-based advanced oxidation remains unexplored. Herein, a nitrogen-deficient Z-scheme CdS/g-C₃N₄ (CdS/N-CN) heterojunction was designed via hydrothermal synthesis to enable solar-driven cooperative photocatalysis and PS activation for PPCPs degradation. The optimized system achieved complete degradation of 10 mg/L sulfamethoxazole (SMX) within 60 min under visible light, achieving a rate constant (0.157 min⁻¹) 29 times higher than pristine g-C₃N₄. Mechanistic investigations demonstrated dual-pathway operation: a built-in electric field drove Z-scheme charge transfer, migrating electrons from N-CN to CdS while holes in N-CN served as primary oxidants. Meanwhile, electrons from CdS activated PS to generate sulfate and hydroxyl radicals, with the latter transforming into singlet oxygen for supplementary oxidation. This synergistic photocatalysis-PS activation system maintained efficient redox activity while enhancing charge separation, ultimately enabling effective PPCPs decontamination. This research presents a novel strategy for leveraging solar-driven heterojunctions and persulfate chemistry for sustainable water remediation.