BiOI/Bi₄O₅Br₂/BiOBr double S-scheme heterostructure applied in photocatalysis antimicrobial and degradation:...

The development of high-performance photocatalytic materials is of great significance for addressing water pollution challenges. In this work, a double S-scheme BiOI/Bi₄O₅Br₂/BiOBr heterojunction was successfully fabricated via a combination of hydrothermal and room-temperature deposition strategies. The phase composition, micromorphology, and chemical valence states were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). The optical and photoelectrochemical properties were investigated using ultraviolet-visible diffuse reflectance spectroscopy (UV-vis DRS), photoluminescence (PL) spectroscopy, photocurrent measurement, electron paramagnetic resonance (EPR), and electrochemical impedance spectroscopy (EIS). Under light-emitting diode (LED) light irradiation, the optimized BiOI/Bi₄O₅Br₂/BiOBr composite (denoted as IBrB-50) exhibited strong photocatalytic activity, achieving complete inactivation of Escherichia coli (E. coli), Pseudomonas aeruginosa (P. aeruginosa), and Staphylococcus aureus (S. aureus), along with a 75.1% removal rate of tetracycline (TC). The excellent performance is attributed to the double S-scheme heterojunction, which reduces interfacial charge transfer resistance and promotes the efficient separation of photogenerated electron-hole pairs, as confirmed by the enhanced photocurrent and reduced PL intensity. Radical trapping experiments revealed that holes (h⁺) and superoxide anion radicals (•O₂^-) were the dominant active species driving the photocatalytic reaction. The IBrB-50 composite also demonstrated good stability across four degradation cycles, with XRD confirming the intact crystal structure. Thus, this work provides an effective strategy for water remediation and offers a new material for simultaneous bacterial disinfection and organic pollutant elimination.