The past decade has witnessed a remarkable growth of research interests in two-dimensional (2D) layered nanomaterials. Composed of layered MX2 (M is a transition metal of groups 4?10 and X is a chalcogen) crystals, 2D transition metal chalcogenides (TMCs) offer versatile and appealing chemical properties that are promising for a variety of applications including electronics, sensing, energy storage and catalysis. Synthesis of 2D TMCs, however, has largely been limited to physical/chemical exfoliation of bulk crystals (top?down) and chemical vapor deposition (CVD) on appropriate substrates. Despite the progress that has been made, reliable production of 2D TMCs with control over the size, layer thickness, composition and structure has been challenging with existing methods. Moreover, feasible methods for manipulation of these 2D nanomaterials for functional applications are yet to be developed. These problems have become the main obstacles for practical implementation of the 2D nanomaterials in large scale.Our group has been dedicated to the development of organic solution synthesis of 2D nanomaterials. Previously this method has been demonstrated to robust for the preparation of monodisperse and uniform colloidal nanocrystals, including zero-dimensional (0D) nanoparticles and one-dimensional (1D) nanorods and nanowires. Recently we have developed a two-step method for the synthesis of 2D TMCs in organic solutions. Transition metal or transition metal oxide nanoparticles were first synthesized, and then applied as seeds for chalcogenation to form TMC nanoparticles. 2D TMCs were produced either by in situ solvothermal exfoliation, or by post-synthesis liquid exfoliation. Control over the size, shape and stacking degree of produced nanosheets was achieved by tuning the morphology of the seeding nanoparticle and reaction conditions (e.g., temperature, stabilizing ligands) for chalcogenation/exfoliation. In addition, starting with composite metal or metal oxide nanostructures (e.g., alloy and core/shell nanoparticles), bimetallic 2D TMCs were obtained with control over composition. The obtained 2D TMCs were further demonstrated to be efficient electrocatalysts for the hydrogen evolution reaction (HER) and oxygen reduction reaction (ORR).

Organic solution synthesis of 2D transition metal chalcogenides

247th National Meeting (2014)

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