Mechanism Decoding of an S-Scheme ZnIn2S4/H2WO4 Heterojunction with Favorable Surface Electronic Potential for Enhanced and Anti-Corrosion Photocatalytic Hydrogen Evolution

The rational construction of heterojunction interfaces plays a critical role in enhancing the carrier separation efficiency for photocatalytic hydrogen evolution. In this study, a ZnIn 2 S 4 /H 2 WO 4 S-scheme heterojunction was successfully synthesized via a self-assembly strategy. Compared with conventional WO 3, the H 2 WO 4 component exhibits a lower work function, which significantly promotes surface electron overflow and establishes an optimized S-scheme charge transfer pathway. Structural characterization reveals that the intimate integration of H 2 WO 4 nanosheets within ZnIn 2 S 4 nanoflowers provides enhanced interfacial contact, thereby facilitating efficient charge separation and migration. As a result, the optimized ZnIn 2 S 4 /H 2 WO 4 composite demonstrates a hydrogen evolution rate of 138 mmol/g/h, achieving a 4.7-fold enhancement over pristine ZnIn 2 S 4 and a 1.9-fold improvement compared to the ZnIn 2 S 4 /WO 3 . This work highlights the dual requirements for oxidation photocatalysts in S-scheme systems: precise band gap alignment and favorable surface electronic properties, both essential for enabling efficient electron overflow and ensuring effective S-scheme charge migration channels.