Critical Review: Hydrothermal Synthesis of 1T-MoS2 – an Important Route to a Promising Material

The unique anisotropy, polytypism, and abundance of molybdenum disulfide make it a singularly versatile material for a range of catalytic, electrochemical, and tribological applications. By employing a hydrothermal synthesis, a high surface area, optionally-supported, gas-repellent metallic MoS2 (1T-MoS2) has been reported to be produced from benign reagents at scale. This hydrothermally produced material has been shown to exhibit outstanding performance as a capacitor, and as an electrocatalyst (e.g. for the hydrogen evolution reaction). However, synthetic ambiguity and sample mischaracterizations are extremely common within the literature of reports of hydrothermally produced 1T-MoS2, and these occur across a range of analysis techniques such as Raman spectroscopy, X-ray diffraction, magnetic susceptibility, and X-ray photoelectron spectroscopy. These oversights have led to significant inconsistencies in the prevalent understanding of 1T-MoS2. In most cases in the literature it is unclear whether MoS2 or an intercalated (Mn+)(1/n)MoIIIS2− variant is produced. Given the high potential of this material for many cutting-edge applications, it is important to clarify the literature to help facilitate rapid progress. In this context the review presents a way forward, by setting out to provide clear and unambiguous synthetic and analytical strategies.