Few-Layer ZnIn₂S₄/Laponite Heterostructures: Role of Mg²⁺ Leaching in Zn Defect Formation

Designing nanostructures with extended light absorption via defect engineering is a useful approach for the synthesis of efficient photocatalysts. Herein, ZnIn₂S₄ was grown hydrothermally in the modified interlayer space of Laponite, resulting in lamellae consisting of Zn-defective ZnIn₂S₄ several unit cells thick. In the process it was found that Mg²⁺ leached from Laponite during synthesis led to the formation of Zn defects in ZnIn₂S₄. This resulted in nanohybrids with light absorption extended across the visible spectrum and in improved charge transfer due to the layered structure formed via confined growth. Compared with pure ZnIn₂S₄, Zn-defective ZnIn₂S₄-Laponite hybrids have increased photocurrent generation and photocatalytic performance. The leaching of Mg²⁺ and the resulting formation of Zn defects was attenuated by addition of 4 mM Mg²⁺ to the reaction, due to a combination of shifting of the equilibrium of Mg²⁺ leaching toward stability, and increased ionic strength. In summary, this work demonstrates the growth of ∼1 nm thick lamellae of ZnIn₂S₄, presents a unique strategy to generate cation defects in nanomaterials and the mechanism behind it, and also provides an approach to mitigate Mg²⁺ leaching in such syntheses.