Constructed NiS-Mn2SnS4/g-C3N4 dual-stage type-II heterojunction with high-specific-surface-area for synergistically enhanced photocatalytic hydrogen production performance

In light of the energy and environmental crises humanity faces, photocatalytic hydrogen production has emerged as one of the effective solutions. Nevertheless, the development of high-performance, low-energy-consumption, and long-lasting stable photocatalysts remains extremely urgent. In this study, a NiS-Mn 2 SnS 4 /g-C 3 N 4 composite with efficient photocatalytic hydrogen evolution performance is synthesized via a simple physical mixing method and calcination process. The introduction of NiS and Mn 2 SnS 4 significantly increases the specific surface area of the g-C 3 N 4 composite, and a dual Type-II heterojunction capable of efficiently separating electron-hole pairs is formed between the components and g-C 3 N 4 . Under 300 W xenon lamp irradiation, the NiS-Mn 2 SnS 4 /g-C 3 N 4 composite achieves a hydrogen evolution rate of 7672.45 μmol·g −1 ·h −1 , corresponding to 3.76, 59.74, and 254.64 times enhancements compared to bare g-C 3 N 4 , NiS, and Mn 2 SnS 4 , respectively. After four cycles, the hydrogen production of NiS-Mn 2 SnS 4 /g-C 3 N 4 still reaches 91 % of the rate in the first cycle. Photoelectrochemical property characterization demonstrates that the composite samples can generate more active sites, reduce the overpotential for H 2 evolution, and enhance light absorption efficiency. Combined with density functional theory (DFT) calculations and band structure analysis, it is confirmed that a strong electronic coupling effect exists among NiS, Mn 2 SnS 4 , and g-C 3 N 4 , and the electron transfer follows a Type-II pathway. This study provides important references and insights for constructing high-activity and high-specific-surface-area g-C 3 N 4 -based photocatalysts.