Dual modulation of BiOCl: enhancing photocatalytic antibiotic degradation through Co surface bonding and a WS ₂ heterojunction

The persistence of fluoroquinolone antibiotics like norfloxacin in aquatic environments necessitates advanced treatment solutions. Photocatalysis emerges as an effective strategy, wherein BiOCl has garnered significant attention due to its unique layered structure and favorable band characteristics. However, the performance of BiOCl is limited by narrow visible-light absorption and rapid charge recombination. Traditional modification methods involving prolonged high-temperature/pressure treatments risk damaging its intrinsic structure. This study innovatively presents a mild sonochemical strategy that establishes Co surface bonding and constructs a BiOCl/WS₂ heterojunction, realizing the introduction of hybrid energy levels and the regulation of heterostructure formation simultaneously. The Co-BiOCl/WS₂ composite demonstrated the successful formation of Co-Cl bonds and WS₂ heterojunction integration, with a 0.35 eV bandgap reduction alongside significantly enhanced visible-light absorption and charge separation efficiency. The Co-BiOCl/WS₂ composite achieved 92.37% norfloxacin degradation within 60 min under visible light with a reaction rate constant 1.95 times higher than that of BiOCl, while maintaining excellent stability across various environmental conditions. The degradation pathways were elucidated by combining Fukui function calculations predicting the piperazine ring's vulnerability with HPLC-MS analysis. This work provides a facile strategy for dual-functional modification of BiOCl under mild conditions and offers valuable insights for designing efficient photocatalysts for antibiotic wastewater treatment.