S-scheme V3O7-ZnIn2S4 and VO2-ZnIn2S4 heterojunctions: The role of vanadium oxide in photocatalytic hydrogen evolution

Solar-driven photocatalytic hydrogen evolution is crucial for sustainable energy conversion but is limited by insufficient charge separation and weak redox capability. Herein, VO 2 -ZnIn 2 S 4 (ZIS) and V 3 O 7 -ZIS heterojunctions were rationally constructed via a two-step synthesis, anchoring ZIS nanosheets onto VO 2 nanorods and V 3 O 7 nanowires. Optimized V 3 O 7 -ZIS-150 achieves an exceptional H 2 evolution rate of 30.14 mmol g −1 h −1 , 2.72 times higher than VO 2 -ZIS. X-ray Photoelectron Spectroscopy (XPS), electrochemical, and electron spin resonance (ESR) analyses reveal S-scheme configurations for both heterojunctions: electrons transfer from the V 3 O 7 conduction band (CB) to the ZIS valence band (VB), and from the ZIS CB to the VO 2 VB, preserving strong reduction/oxidation potentials. V 3 O 7 -ZIS has a more negative VB potential than VO 2 -ZIS, enhancing hole oxidation and •O 2− /•OH generation, thereby boosting H 2 activity. This comparative study demonstrates that engineering V 3 O 7 -based S-scheme heterojunctions is effective for high-performance photocatalysts, providing mechanistic insights for sustainable energy applications.