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.