Facilitating charge transfer through an atomic coherent interface of a novel direct Z-scheme BiVO₄@Cu₃SnS₄ heterojunction to boost photocatalytic performance

Direct Z-scheme photocatalytic systems are very promising composite photocatalysts, and their photocatalytic performance is highly associated with the quality of the interface within them. Herein, a novel direct Z-scheme heterojunction with a coherent interface has been presented for the first time. Specifically, the heterojunction was constructed by dispersing pre-prepared BiVO₄ crystals into the reaction system to synthesize Cu₃SnS₄, followed by a hydrothermal reaction. It is shown that Cu₃SnS₄ was deposited on the surface of each pre-prepared BiVO₄ crystal as a thin layer via heterogeneous nucleation to acquire a core-shell heterojunction. The BiVO₄@Cu₃SnS₄ heterojunction was found to possess an atomic coherent interface, which is formed through the bonding between the (121) plane of BiVO₄ and the (112) plane of Cu₃SnS₄, originating from the matching in the crystalline lattice between the two planes. The coherent interface facilitated the charge transfer from Cu₃SnS₄ to BiVO₄ owing to the difference in their Fermi levels, thereby forming a built-in electric field pointing from Cu₃SnS₄ to BiVO₄. Reduced fluorescence emission and a shortened carrier lifetime reveal an obvious reduction in the inter-band charge recombination for the optimal BVO@CTS-0.19 sample. Consequently, BVO@CTS-0.19 shows remarkably enhanced photocatalytic performance in MO degradation, Cr⁶⁺ reduction and oxygen evolution. The Z-scheme charge transfer mechanism for BVO@CTS-0.19 was verified by a suite of techniques. This work provides a universal strategy for building a coherent interface to develop high-performance direct Z-scheme heterojunctions.