General Synthesis of Metal Indium Sulfide Atomic Layers for Photocatalysis

The metal indium sulfides have attracted extensive research interest in photocatalysis due to regulable atomic configuration and excellent optoelectronic properties. However, the synthesis of metal indium sulfide atomic layers is still challenging since intrinsic non-van-der-Waals layered structures of some components. Here, a surfactant self-assembly growth mechanism is proposed to controllably synthesize metal indium sulfide atomic layers. Eleven types of atomic layers with tunable compositions, thickness, and defect concentrations are successfully achieved namely In₂S₃, MgIn₂S₄, CaIn₂S₄, MnIn₂S₄, FeIn₂S₄, ZnIn₂S₄, Zn₂In₂S₅, Zn₄In₁₆S₃₃, CuInS₂, CuIn₅S₈, and CdIn₂S₄. The typical CaIn₂S₄ shows a defect-dependence activity for CO₂ photoreduction. The designed S vacancies in CaIn₂S₄ can serve as catalytic centers to activate CO₂ molecules via localized electrons for π-back-donation. The engineered S vacancies tune the non-covalent interaction with CO₂ and intermediates, manages to tune the free energy, and lower the reaction energy barrier. As a result, the defect-rich CaIn₂S₄ displays 2.82× improved reduction rate than defect-poor CaIn₂S₄. Meantime, other components also display promising photocatalytic performance, such as Zn₂In₂S₅ with a H₂O₂ photosynthesis rate of 292 µmol g^-1 h^-1 and CuInS₂ with N₂-NH₄ ⁺ conversion rate of 54 µmol g^-1 h^-1. This work paves the way for the multidisciplinary exploration of metal indium sulfide atomic layers with unique photocatalysis properties.