Boosting Photocatalytic H2 Evolution Performance of ZnIn2S4 via S-Scheme Heterostructuring With ZnMoO4

Step-scheme (S-scheme) heterojunctions offer significant potential for enhancing photocatalytic hydrogen evolution (PHE) by promoting charge separation while preserving high redox capabilities. Herein, theoretical calculations predict that constructing a ZnMoO₄@ZnIn₂S₄ S-scheme (ZMO@ZIS) heterojunction significantly lowers the Gibbs free energy for H₂ evolution compared to the individual monomers, indicating a thermodynamically and kinetically favored pathway. Guided by this prediction, we synthesized the ZMO@ZIS heterojunction by in situ anchoring ZnIn₂S₄ nanosheets onto ZnMoO₄ hexagonal platform, with the expectation of achieving excellent photocatalytic H₂ evolution performance. This unique trans-scale assembly strategy spontaneously organizes ZIS into a hierarchical porous network, markedly increasing the surface area and providing abundant accessible active sites and efficient mass transfer channels. Comprehensive experimental characterization combined with detailed theoretical simulation provides compelling evidence confirming the S-scheme electron transfer mechanism and establishment of an internal electric field, where high-potential electrons in ZIS and holes in ZMO are retained for PHE. Consequently, the ZMO@ZIS-13 S-scheme heterojunction achieves an exceptional visible-light PHE rate of 5.045 mmol g⁻¹ h⁻¹ under visible light, representing a 10.7-fold improvement compared to that of pure ZnIn₂S₄. This study demonstrates the efficacy of theory-guided design and trans-scale assembly for creating efficient S-scheme photocatalysts with optimized charge dynamics.