Shape-Engineered Synthesis of Atomically Thin 1T-SnS2 Catalyzed by Potassium Halides.

Shape engineering plays a crucial role in the application of two-dimensional (2D) layered metal dichalcogenide (LMD) crystalline materials in terms of physical and chemical property modulation. However, controllable growth of 1T phase tin disulfide (SnS2) with multifarious morphologies has rarely been reported and remains challenging. Herein, we report a direct synthesis of large-size, uniform, and atomically thin 1T-SnS2 with multiple morphologies by adding potassium halides via a facile chemical vapor deposition process. A variety of morphologies, i.e., from hexagon, triangle, windmill, and dendritic to coralloid, corresponding to fractal dimensions from 1.01 to 1.81 are accurately controlled by growth conditions. Moreover, the Sn concentration controls the morphology change of SnS2. The edge length of the SnS2 dendritic flake can grow larger than 500 μm in 5 min. Potassium halides can significantly reduce the surface migration barrier of the SnS2 cluster and enhance the SnS2 adhesion force with substrate to facilitate efficient high in-plane growth of monolayer SnS2 compared to sodium halides by density functional theory calculations. More branched SnS2 with higher fractal dimension provides more active sites for enhancing hydrogen evolution reactions. Importantly, we prove that potassium halides are preferable for 1T-phase LMDs structures, while sodium halides are more suitable for 2H-phase materials. The growth mechanism proposed here provides a general approach for controllable-phase synthesis of 2D LMD crystals and related heterostructures. Shape engineering of 2D materials also provides a strategy to tune LMD properties for demanding applications.