Bi-S Bond Mediated Direct Z-Scheme BiOCl/Cu₂SnS₃ Heterostructure for Efficient Photocatalytic Hydrogen Generation

The advancement of photocatalytic technology for solar-driven hydrogen (H₂) production remains hindered by several challenges in developing efficient photocatalysts. A key issue is the rapid recombination of charge carriers, which significantly limits the light-harvesting ability of materials like BiOCl and Cu₂SnS₃ quantum dots (CTS QDs), despite the faster charge mobility and quantum confinement effect, respectively. Herein, a BiOCl/CTS (BCTS) heterostructure was synthesized by loading CTS QDs onto BiOCl 2D nanosheets (NSs), that demonstrated excellent photocatalytic activity under visible light irradiation. The improved hydrogen generation rate (HGR) was primarily due to an interfacial Bi-S bond formation, which facilitates the creation of direct Z-scheme heterojunction and an internal electric field at the interface, promoting efficient charge transfer between BiOCl and CTS. Moreover, due to the amalgamation of Bi-S bond formation and interfacial electric field, the optimized BCTS-5% heterostructure exhibited a high HGR of 8.27 mmol g^-1 h^-1, and an apparent quantum yield (AQY) of 61 %, ~4 times higher than pristine BiOCl. First-principle density functional theory (DFT) calculations further revealed the presence of a Bi-S bond with a bond length of ~2.85 Å and a minimal work function of 2.37 eV for the heterostructure, both of which are critical for enhancing H₂ generation efficiency.