Direct Syntheses of 2D Noble Transition Metal Dichalcogenides Toward Electronics, Optoelectronics, and...

2D noble transition metal dichalcogenides (nTMDCs, PdX₂ and PtX₂, where X═S, Se, Te) have emerged as a new class of 2D materials, owing to their unique puckered pentagonal structure in 2D PdS₂ and PdSe₂, largely tunable band structures or band gaps with decreasing the layer thickness at the 2D limit, strong interlayer interactions, superior optoelectronic properties, high edge catalytic properties, etc. Directly synthesizing 2D nTMDCs domains or thin films with large-area uniformity, tunable thickness, and high crystalline quality is the premise for exploring these salient properties and developing a wide range of applications. Hereby, this review summarizes recent progress in the direct syntheses and characterizations of 2D nTMDCs, mainly focusing on the thermally assisted conversion (TAC) and chemical vapor deposition (CVD) methods, by using various metal and chalcogen-contained precursors. Meanwhile, the applications of directly synthesized 2D nTMDCs in various fields, such as high-performance field effect transistors (FETs), broadband photodetectors, superior catalysts in hydrogen evolution reactions, and ultra-sensitive piezo resistance sensors, are also discussed. Finally, challenges and prospects regarding the direct syntheses of high-quality 2D nTMDCs and their applications in next-generation electronic and optoelectronic devices, as well as novel catalysts beyond noble metals are overviewed.