Vacancy engineering of single-layer lateral heterojunction for efficient Z-scheme photocatalytic water reduction

Optimizing the Z-scheme charge transmission of lateral heterojunction constructed by single-layer (SL) nanosheets is an appealing yet challenging tactics to boost photocatalytic efficiency for solar fuel production and environmental remediation. Herein, we reported the edge/corner-specific growth of SL ZnIn₂S₄-MoSe₂ lateral heterojunction with intensified Z-scheme charge transmission through intimate Mo-S connection and S vacancies (V_S) engineering. The Mo-S chemical bonds inside ZnIn₂S₄-MoSe₂ heterojunction offer a speedy channel for Z-scheme charge transmission as confirmed via surface photovoltage spectroscopy, radical production, and in situ photo-irradiated X-ray photoelectron spectroscopy tests as well as density functional theory calculation, while V_S engineering enlarges Fermi level difference between ZnIn₂S₄ and MoSe₂ to strengthen internal electric field and driving force for photo-carriers transmission, resulting in an excellent photocatalytic H₂ evolution (PHE) capability. Isotopic labeling experiment verified the photocatalytic water reduction by ZnIn₂S₄-MoSe₂ heterojunction, which exhibited a visible-light-driven PHE rate up to 55.70 mmol g^-1h^-1 (or 550.70 micromol/10 mg/h) with an apparent quantum yield reaching 38.9 % at 400 nm. Moreover, the ZnIn₂S₄-MoSe₂ heterojunction also possessed a robust stability during long-term photocatalytic reaction. The research findings could inspire new idea to enhance the photocatalytic capability of two-dimensional (2D) heterojunction by strengthening Z-scheme charge transmission at atomic level.