Universal Method for Large-Scale Synthesis of Layered Transition Metal Dichalcogenides.

Abstract

The layered transition metal dichalcogenides are currently amongst the most intensively investigated materials. These compounds constitute a broad family of materials, with characteristic layered structures, covering both semiconductors and metallic materials. The great attention arises from the possibility to exfoliate these materials down to single layers with many unique properties, such as thickness dependent band-gap energy, and the possibility of tuning transport properties by phase transitions. The research in the field of transition metal dichalcogenides is also motivated by their high electrocatalytic activity towards several industrially important reactions, such as the hydrogen evolution reaction, as well as many other applications in nano- and optoelectronics. Although these materials are studied intensively, their availability is extremely limited and only disulfides of molybdenum and tungsten are broadly commercially available. Here an optimized procedure for simple direct synthesis of transition metal dichalcogenides using powder metals and elemental chalcogens is reported. The optimized thermal treatment allowed the synthesis scaling of the sulfides, selenides and tellurides of 4th, 5th, 6th, and 7th group of layered-structure dichalcogenides. The synthesized transition metal dichalcogenides were single phase. The phase purity, structure, and morphology were investigated in detail by electron microscopy and EDS, X-ray diffraction, and Raman spectroscopy.