Molybdenum and rhenium disulfide synthesis via high-pressure carbonate melt

Various applications of transition metal dichalcogenides (TMDs) require preparation by exfoliation of precursor bulk materials. However, bulk TMDs are not always available in suitable forms and current synthesis methods may not result in appropriate crystals. This study reports synthesis of large crystals (50-100 μm) of MoS₂ and ReS₂, by recrystallisation of MoS₂ powder or reaction of sulfate with perrhenic acid, respectively. The reactions have been performed at high pressure and temperature (≥1 GPa; ≥800 °C) in a liquid Ca-carbonate flux. The resulting crystals were characterised by electron microscopy imaging, EDS and WDS chemical analyses, and Raman spectroscopy. The carbonate matrix can be easily dissolved to recover the product TMDs. This method allows synthesis of large well-crystalline TMD compositions that are otherwise challenging to obtain.