Construction of WO3/ZnIn2S4 Z-scheme heterojunction by electrostatic self-assembly to enhance charge separation and reactive oxygen species generation

This study successfully fabricated a WO 3 /ZnIn 2 S 4 (WO 3 /ZIS) composite photocatalyst via electrostatic self-assembly under acidic conditions (pH = 4.1). The effect of composite ratio on the material's structure and optoelectronic properties was systematically investigated using multiple characterization techniques, including XRD, SEM, TEM, BET, UV–Vis spectroscopy, and electrochemical measurements. Photocatalytic mechanism studies were conducted using fluvastatin as a model pharmaceutical pollutant. Results confirm the formation of a Z-scheme heterojunction in the WO 3 /ZIS composite. Increasing the proportion of ZnIn 2 S 4 during electrostatic self-assembly effectively enlarges the specific surface area, enhances visible-light absorption, and suppresses the recombination of photogenerated e − -h + pairs, thereby significantly improving photocatalytic performance. The WO 3 /ZIS-30 % composite material exhibited the most stable structure, the largest specific surface area, and the optimal light absorption capacity and charge carrier separation efficiency. Its degradation efficiency for fluvastatin reached 59.81 %, representing a 25.88 % improvement over WO 3 . Radical trapping experiments verify the simultaneous generation of ·OH and ·O 2 − radicals, and the concentrations of ·O 2 − and ·OH were 1.68 × 10 −5  mol/L and 1.61 × 10 −5  mol/Land their synergistic action considerably strengthens the oxidative power of the system. The Z-scheme heterojunction formed by electrostatic self-assembly facilitates spatial separation of photo generated charges and enables multi-radical oxidation, collectively boosting photocatalytic efficiency. This work provides a new strategy for designing highly efficient and stable photocatalysts suited for removing pharmaceutical contaminants from water.