Novel 2D/2D/2D heterojunction of ZnIn2S4/g-C3N4/MoS2 for enhanced photocatalytic hydrogen evolution reaction

Photocatalysts for hydrogen evolution reaction (HER) have widely been explored but fine-tuning and engineering multiphase photocatalyst components are still challenging. Among catalysts, ZnIn2S4 has shown promise but maximizing the use of ZnIn2S4-photogenerated carriers and enhancing quantum yield still require further investigation. One way to achieve this is by enhancing the photon utilization and reducing the recombination of shallow carriers in ZnIn2S4. Accordingly, novel ZnIn2S4/g-C3N4/MoS2 type-II heterojunction composites with 2D/2D/2D structures (abbreviated ZIS/CN/MS) were synthesized in the present work by simple thermal condensation-solvothermal method. The optimized ZIS/CN/MS exhibited a photocatalytic hydrogen evolution rate of 13.6 mmol g(-1) h(-1) under visible light (lambda >= 420 nm) irradiation, a value much higher than those of pure-phases ZIS and CN, as well as the binary composite of ZIS/CN. The apparent quantum efficiency of the optimized ZIS/CN/MS at a wavelength of 420 nm reached 27.0 % coupled with excellent cycling stability. The significantly improved photocatalytic performance and the excellent stability can mainly be attributed to the unique 2D/2D/2D arrangement of the ternary components of ZIS, CN, and MS in ZIS/CN/MS photocatalyst, providing a large number of close interfacial contacts between the components for shortened migration distance of photogenerated charges and more pathways for electron separation and transport in type-II heterostructures. Overall, the proposed methodology and ZIS/CN/MS composites with type-II heterojunction and 2D/2D/2D structures have great potential for use in solar-to-hydrogen energy conversion and can be extended to the preparation of other photocatalysts.