Controlled Syntheses and Multifunctional Applications of Two-Dimensional Metallic Transition Metal Dichalcogenides

Among two-dimensional (2D) layered materials, metallic transition metal dichalcogenides (MTMDCs) are emerging as promising candidates in many application aspects (e.g., electronics, spintronics, and energy related fields, etc.) in view of their ultrahigh electronic conductivities, newfangled room-temperature ferromagnetism (e.g., VSe2, VTe2), and excellent catalytic activities. Specially, 2D TaX2 and VX2 (X = S, Se, Te) materials stand in a vital place on account of their exotic physical and chemical properties. Notably, the controlled synthesis of such materials is the premise for exploring the aforementioned properties and applications. Among the reported preparation methods, chemical vapor deposition (CVD) is proven to be a promising approach in view of its scalability, simple operation, low cost, etc. This method has been employed to synthesize various 2D layered materials and heterostructures in a well-controlled fashion. Nevertheless, in view of the complicated growth mechanism and process, the CVD growth of ultrathin TaX2 and VX2 nanosheets/films remains extremely challenging. In addition, the application explorations of 2D TaX2 and VX2 in the energy related fields and electronic devices are still in the primary stage. In this Account, we review the up-to-date advances regarding the CVD syntheses of 2D TaX2 and VX2 (e.g., TaS2, TaSe2, VS2, VSe2, and VTe2, etc.) and air-stable MTMDCs (e.g., PtSe2, NiTe2), as well as their multifunctional applications in the energy related fields and electronic devices. First, the CVD growth of TaX2 and VX2 nanosheets/films with tunable thicknesses/domain sizes and the MTMDCs/semiconducting TMDCs vertical heterostructures are systematically summarized. Second, the application explorations of CVD-synthesized 2D TaX2 and VX2 as high-performance electrode materials in electrocatalytic hydrogen evolution reaction (HER) and electronic devices are introduced, respectively. Third, the CVD syntheses of 2D MTMDCs with robust environmental stability and novel physical properties (e.g., semimetal-semiconductor transition, magnetism) are discussed. In the end, the challenges regarding the preparations and multifunctional applications of 2D MTMDCs are highlighted, and the future research directions are also proposed. We believe that this Account is comprehensive and insightful for the CVD syntheses of high-quality 2D MTMDCs materials toward versatile applications.