Synthesis of Two-Dimensional\nHigh-Entropy Transition\nMetal Dichalcogenide Single Crystals

Two-dimensional (2D) high-entropy\ntransition metal dichalcogenides\n(HETMDs) have gained significant interest due to their structural\nproperties and correlated possibilities for high-end devices. However,\nthe controlled synthesis of 2D HETMDs presents substantial challenges\nowing to the distinction in the inherent characteristics among diverse\nmetal elements in the synthesis, such as saturated vapor pressure\nof precursors and formation energy of products. Here, we present the\nsynthesis of a 2D HETMD single crystal with 0.92 nm thickness through\na liquid-phase reaction system, where the metal elements are fed uniformly\nand simultaneously. The rapid codeposition of different precursors\nfacilitates the formation of high-entropy products, thereby preventing\nphase separation. The method can be expanded to produce a variety\nof 2D HETMDs, such as quinary (MoNbTaV)S<sub>2</sub>, hexahydroxy\n(MoWNbTaV)S<sub>2</sub>, and multichalcogenide (MoWNb)SSe. The as-prepared\n2D HETMD is an excellent catalyst for the hydrogen evolution reaction\n(HER), demonstrating the overpotential of 84 mV at 10 mA cm<sup>–2</sup> of an individual crystal, which is much better than that of pristine\nMoS<sub>2</sub> (260 mV at 10 mA cm<sup>–2</sup>). The strategy\noffers the flexibility to artificially design the element selectivity\nand properties of HETMD single crystals in the 2D limit, enabling\napplications across a wide range of advanced fields.