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).