Exfoliation of bulk 2H-MoS2 into bilayer 1T-phase nanosheets via ether-induced superlattices

The exfoliation of bulk 2H-molybdenum disulfide (2H-MoS2) into few-layer nanosheets with 1T-phase and controlled layers represents a daunting challenge towards the device applications of MoS2. Conventional ion intercalation assisted exfoliation needs the use of hazardous n-butyllithium and/or elaborate control of the intercalation potential to avoid the decomposition of the MoS2. This work reports a facile strategy by intercalating Li ions electrochemically with ether-based electrolyte into the van der Waals (vdW) channels of MoS2, which successfully avoids the decomposition of MoS2 at low potentials. The co-intercalation of Li+ and the ether solvent into MoS2 makes a first-order phase transformation, forming a superlattice phase, which preserves the layered structure and hence enables the exfoliation of bulk 2H-MoS2 into bilayer nanosheets with 1T-phase. Compared with the pristine 2H-MoS2, the bilayer 1T-MoS2 nanosheets exhibit better electrocatalytic performance for the hydrogen evolution reaction (HER). This facile method should be easily extended to the exfoliation of various transition metal dichalcogenides (TMDs).