Step-doped disulfide vacancies and functional groups synergistically enhance photocatalytic activity of S-scheme CuSnS/L-BiOBr towards ciprofloxacin degradation.

Development of efficient photocatalysts for efficient recalcitrant organic pollutants degradation is of great significance. Herein, the step-doped disulfide vacancies S-scheme CuSnS/L-BiOBr (CTS/L-BiOBr) heterojunction photocatalyst was prepared for ciprofloxacin (CIP) degradation. X-ray photoelectron spectroscopy (XPS) analysis, ultraviolet photo-electron spectroscopy (UPS) analysis, band structure and dominant radicals' identification together verified that the transfer of photogenerated carriers conformed to the S-scheme mechanism. Benefited from the interfacial electric field (IEF) of the S-scheme heterojunction and incorporation of L-cysteine with introducing S-vacancies and surface functional groups (-NH, -COO), photogenerated charges generation and separation of the CTS/L-BiOBr were greatly improved. With ·OH and h as dominant reactive species, CIP removal reached 93% using CTS/L-BiOBr within 180 min of visible light irradiation, which was 3.5 times and 2.6 times of pristine CuSnS and L-BiOBr, respectively. Moreover, possible CIP degradation pathways were proposed and the degradation intermediates ecotoxicity were evaluated. This study could provide reference for designing efficient S-scheme photocatalysts for recalcitrant wastewater treatment.