Phase Engineering of Metastable Transition Metal Dichalcogenides via Ionic Liquid Assisted Synthesis.

Metallic group VIB transition metal dichalcogenides (1T-TMDs) have attracted great interest because of their outstanding performance in electrocatalysis, supercapacitors, batteries, and so on, whereas the strict fabrication conditions and thermodynamical metastability of 1T-TMDs greatly restrict their extensive applications. Therefore, it is significant to obtain stable and high-concentration 1T-TMDs in a simple and large-scale strategy. Herein, we report a facile and large-scale synthesis of high-concentration 1T-TMDs via an ionic liquid (IL) assisted hydrothermal strategy, including 1T-MoS ₂ (the obtained MoS ₂ sample was denoted as MoS ₂ -IL), 1T-WS ₂ , 1T-MoSe ₂ , and 1T-WSe ₂ . More importantly, we found that IL can adsorb on the surface of 1T-MoS ₂ , where the steric hindrance, π-π stacking, and hydrogen bonds of ionic liquid collectively induce the formation of the 1T-MoS ₂ . In addition, DFT calculation reveals that electrons are transferred from [BMIM]SCN (1-butyl-3-methylimidazolium thiocyanate) to 1T-MoS ₂ layers by hydrogen bonds, which enhances the stability of 1T-MoS ₂ , so the MoS ₂ -IL performs with high stability for 180 days at room temperature without obvious change. Furthermore, the MoS ₂ -IL exhibits excellent HER performance with an overpotential of 196 mV at 10 mA cm ^-2 in acid conditions.