Electronic structure engineering and a cascade electron transfer channel in a Ni2P/1T-WS2/ZnIn2S4 ternary heterojunction for enhanced photocatalytic hydrogen evolution: construction, kinetics, and mechanistic insights†

Achieving high performance electronic structure engineering in multi-component photocatalysts to effectively coordinate photoinduced carrier migration and surface reaction dynamics is still a key obstacle for solar-driven hydrogen production. Herein, well-defined ZnIn₂S₄ nanosheets modified with metallic 1T-phase WS₂ and Ni₂P dual cocatalysts with superior photoactivity and stability were fabricated by two-step ultrasonic self-assembly processes. A series of photoelectrochemical characterization studies revealed that the metallic phase 1T-WS₂ with excellent conductivity can effectively lower the charge transport resistance and enhance electron transfer efficiency, while Ni₂P with abundant active sites can efficiently promote the surface H₂-production reaction dynamics in this dual cocatalyst system. Moreover, the synergistic effects of the 1T-WS₂ and Ni₂P dual cocatalysts can boost the oxidation efficiency of the sacrificial regents (lactic acid) by elevating the valence band levels of ZnIn₂S₄, which in turn promotes the separation of photocarriers. As a result, the optimized tandem Ni₂P/1T-WS₂/ZnIn₂S₄ ternary heterojunction with a cascade electron transfer pathway achieved a peak hydrogen generation rate of 17.01 mmol g⁻¹ h⁻¹, roughly 3.34, 1.56 and 1.36 times greater than those of bare ZnIn₂S₄, binary 1T-WS₂/ZnIn₂S₄ and Ni₂P/ZnIn₂S₄, respectively. This work not only provides mechanistic insights into how dual cocatalysts influence electronic structure engineering and charge transfer dynamics but also establishes a versatile framework for the design of multi-component heterojunctions for more efficient and sustainable solar-to-fuel conversion.