“Three-in-one”: Triple-engineered charge transfer in Bi4O5Br2/FeS2 hybrid for efficient treatment of cefalexin and real pharmaceutical wastewater

The rational design of heterostructure photocatalysts is of great significance for maximizing the synergistic effects from individual material characteristics during photocatalytic processes. Herein, a triple-engineered Bi 4 O 5 Br 2 /FeS 2 heterojunction was successfully developed via a combined calcination–hydrothermal method. The optimized heterojunction (BOB/FS-21) demonstrated a cefalexin degradation rate of 98.6 % within 60 min, and exhibited exceptional performance in the treatment of real pharmaceutical wastewater, effectively reducing the COD from 7852 mg/L to 1987 mg/L. The superior performance was attributed to the following benefits, either directly or indirectly: i) interfacial S − O bonds built specific charge transfer channels, ii) Z -scheme mode optimized the charge transfer path, iii) photothermal-assisted effect accelerated reaction kinetics and suppressed carrier recombination. Experiments, characterizations, and calculations collectively validated these synergistic benefits driving the efficient and active charge transfer process, realizing a unified “three-in-one” functional system. Besides, the breakdown mechanism of cefalexin was investigated by employing mass spectrometry and DFT methods, and a toxicity evaluation of the intermediate products during degradation was carried out using toxicological assessments. Overall, this work establishes a triple-synergy paradigm for the design of advanced heterogeneous photocatalysts toward sustainable antibiotic remediation.