Strain Modulated Charge Transfer of (0D–2D) ZnS/ZnIn₂S₄ Heterostructure Through a Facile In Situ Synthesis for Efficient Solar to Fuel Conversion

Forming an intermediate electric field at the interface of two semiconductors to facilitate charge transfer and isolate redox reactions is still challenging for catalysis applications. However, great progress has been achieved regarding the rational design of different dimensional semiconductors, the in-situ growth of the heterostructure is considered the best choice to achieve a high-quality interface. In this study, we fabricate a ZnS/ZnIn₂S₄(0D–2D) heterostructure catalyst, where cubic ZnS crystals are decorating a hexagonal ZnIn₂S₄ (ZIS) layer structured with a high difference in the solubility product constant K_sp, using a single pot hydrothermal approach. We used XRD, HRTEM, and band alignment studies to determine the origin of the interfacial charge transfer mechanism, which is based on lattice mismatch and related interfacial microstrain. The structural strain at the interface was caused by lattice mismatch in the composites caused by heterostructuring between two lattices due to the interatomic distances and different crystal symmetries. In addition, this interfacial mismatch strain can induce mid-gap states at the interface that facilitate electron and hole recombination forming a Z-scheme configuration. The low-temperature photoluminescence study was studied to reveal the nature of the defect state at the interface and to provide a clear explanation for the charge carriers' mechanism. The microstructure and spectroscopy analysis both disclose that the optimum ratio of ZnS and ZIS with this (0D–2D) catalyst exhibits improved charge carrier separation and shows significantly enhanced photochemical CO₂ reduction and hydrogen evolution.