Efficient photocatalytic hydrogen evolution: synergistic triple heterojunctions based on ZnIn2S4, Co3O4 and SiC@g-C3N5

Abstract

The production of hydrogen through photocatalytic technology has become a very attractive way to alleviate the problem of environmental pollution. In this work, A ZnIn₂S₄Co₃O₄-(SiC@g-C₃N₅) triple heterojunctions structure was constructed. In this structure, a P-N heterojunction is formed by Co₃O₄ with ZIS, a Z-type heterojunction is constructed by ZIS with CN5, and a II-type heterojunction is formed by CN5 with SiC. The three are synergistically used to optimize the carrier migration path. Under this synergistic mechanism, Co₃O₄ increases the concentration of photogenerated electrons in the ZIS conduction band. It allows the photogenerated electrons to participate in the H⁺ reduction hydrogen generation reaction. Meanwhile, SiC facilitates further electron enrichment in the CN5 conduction band via the type - II heterojunction.SiC also boosts carrier migration efficiency through the Z - type pathway. In the ZnIn₂S₄ - Co₃O₄-(SiC@g - C₃N₅) system, the consumption rate of useless photogenerated electron - hole pairs per unit time is much higher than that in the ZIS - CN5 system with only one Z - type heterojunction. The number of photogenerated electrons on ZIS in the ZnIn₂S₄ - Co₃O₄-(SiC@g - C₃N₅) system is much higher than that in the ZIS - CN5 system. This greatly reduces the probability of the system's photogenerated carrier complexation. It also increases the charge separation efficiency. As a result, the photocatalytic efficiency is significantly improved. 20ZIS-Co-(SiC@CN5) composites exhibited efficient hydrogen production (13655μmol·g^-1-h^-1) in hydrogen production experiments. The ZIS - Co - (SiC@CN5) composites enable efficient separation and directional migration of photogenerated carriers via the collaborative action of the multilevel heterojunction. This action offers a scalable concept for designing highly efficient and stable photocatalysts for hydrogen production.