Constructing Spatially Separated Cage-Like Z-scheme Heterojunction Photocatalyst for Enhancing Photocatalytic H2 Evolution

Heterojunctions coupled into micro-mesoscopic structures is an attractive strategy to optimize the light harvesting and carrier separation of semiconductor photocatalysts. A self-templating method of ion exchange is reported to synthesize an exquisite hollow cage-structured Ag2S@CdS/ZnS that direct Z-scheme heterojunction photocatalyst. On the ultrathin shell of the cage, Ag2S, CdS, and ZnS with Zn-vacancies (V-Zn) are arranged sequentially from outside to inside. Among them, the photogenerated electrons are excited by ZnS to the V-Zn energy level and then recombine with the photogenerated holes that are generated by CdS, while the electrons remained in the CdS conduction band are further transferred to Ag2S. The ingenious cooperation of the Z-scheme heterojunction with the hollow structure optimizes the photogenerated charges transport channel, spatially separated the oxidation and reduction half-reactions, decreases the charge recombination probability, and simultaneously improves the light harvesting efficiency. As a result, the photocatalytic hydrogen evolution activity of the optimal sample is 136.6 and 17.3 times higher than that of cage-like ZnS with V-Zn and CdS by, respectively. This unique strategy demonstrates the tremendous potential of the incorporation of heterojunction construction to morphology design of photocatalytic materials, and also provided a reasonable route for designing other efficient synergistic photocatalytic reactions.