Mechanism Decoding of an S-Scheme ZnIn₂S₄/H₂WO₄ Heterojunction with Favorable Surface Electronic Potential for...

The rational construction of heterojunction interfaces plays a critical role in enhancing the carrier separation efficiency for photocatalytic hydrogen evolution. In this study, a ZnIn₂S₄/H₂WO₄ S-scheme heterojunction was successfully synthesized via a self-assembly strategy. Compared with conventional WO₃, the H₂WO₄ 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 H₂WO₄ nanosheets within ZnIn₂S₄ nanoflowers provides enhanced interfacial contact, thereby facilitating efficient charge separation and migration. As a result, the optimized ZnIn₂S₄/H₂WO₄ composite demonstrates a hydrogen evolution rate of 138 mmol/g/h, achieving a 4.7-fold enhancement over pristine ZnIn₂S₄ and a 1.9-fold improvement compared to the ZnIn₂S₄/WO₃. 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.