Doping and interface engineering accelerating spatial charge separation and transfer on 2D/2D Sn-In2S3/CdS Z-scheme heterojunction for efficient light-to‑hydrogen conversion

Two-dimensional (2D) β-In₂S₃, with significant advantages of broad spectral response, suitable conduction band position, high carrier mobility, and low toxicity, displays great potential in photocatalytic hydrogen production. However, its high charge recombination rate has severely constrained its practical application in photocatalysis. Here, we employ a heteroatom doping and interface engineering strategy to in situ deposit CdS nanosheets onto Sn⁴⁺ doped In₂S₃ to construct an ultrathin 2D/2D Sn-In₂S₃/CdS Z-scheme heterojunction with a sulfur-shared interface. This unique structure not only enhances interfacial interactions but also establishes a direct Z-scheme charge-transfer pathway, significantly suppressing electron-hole recombination while accelerating carrier migration. Simultaneously, Sn⁴⁺ doping narrows the bandgap of In₂S₃, inducing a spectral redshift to broaden the visible absorption range and fortify the photocatalytic stability. The optimized Sn-In₂S₃/CdS heterojunction (SIC3) achieves a remarked hydrogen evolution rate of 5.119 mmol·g^-1·h^-1 under visible light, representing a 66.8- and 37.0-fold enhancement over pure CdS and Sn-In₂S₃, respectively. Furthermore, its apparent quantum efficiency reaches 5.1 % at 420 nm. Additionally, experimental characterizations and density functional theory calculations demonstrate a Z-scheme heterojunction photocatalytic mechanism. This work demonstrates that the dual strategy of metal doping and interfacial engineering provides an effective approach to designing stable, ultrathin heterojunction photocatalysts for high-efficiency solar hydrogen generation.