A defect engineered Z-scheme polymeric C₃N₄/CdS heterojunction mediated by Ag boosts dual-channel H₂O₂ production...

The clean production of hydrogen peroxide (H₂O₂) with simultaneous degradation of antibiotic pollutants using an efficient photocatalytic system is a promising, economical and environmentally friendly strategy to alleviate the increasingly serious energy and environmental problems at present. In this study, a novel Z-scheme Ag-loaded polymeric C₃N₄/sulfur-vacancy CdS (Ag-PCN/Vs-CdS) heterojunction was successfully constructed by growing sulfur vacancy-rich CdS (Vs-CdS) nanoparticles on Ag-loaded PCN nanosheets, which exhibited excellent photocatalytic activity for H₂O₂ production from amoxicillin (AMX) wastewater. The optimized 10-Ag-PCN/Vs-CdS presented a H₂O₂ generation rate of 2070.4 μmol g^-1 h^-1 in AMX solution, which was 67.9 and 14.2 times higher than those of Ag-PCN (30.5 μmol g^-1 h^-1) and Vs-CdS (145.7 μmol g^-1 h^-1). In addition, the yield of H₂O₂ could reach 3888.9 μM in 16 h in AMX wastewater far exceeding that in pure water; meanwhile, the efficiency of AMX degradation could reach 78.1%. The results indicated that the Ag-PCN/Vs-CdS heterojunction possessed sustainable activity for producing H₂O₂ and simultaneously degrading antibiotics. Furthermore, the mechanism of H₂O₂ production through the dual channels of an oxygen reduction reaction (ORR) and a water oxidation reaction (WOR) and the photodegradation of AMX by the Z-scheme Ag-PCN/Vs-CdS heterostructure are carefully proposed. Toxicological analysis results showed that the water solubility and toxicity of AMX degradation products were significantly reduced. The synergistic effects of doping of Ag, introduction of S vacancies, the sacrificial effect of AMX and the Z-scheme heterojunction greatly boosted the electron delocalization effect, promoted charge separation and optimized the redox capacity, thus greatly increasing the photocatalytic activity. This research would provide new insights for the synthesis of novel catalysts for the green production of H₂O₂ and the simultaneous degradation of antibiotic pollutants, which was of great significance for the production of clean chemicals and environmental remediation.