Interlayer-expanded and defect-rich metal dichalcogenide (MX2) nanosheets for active and stable hydrogen evolution

Layered metal dichalcogenides (MX2) constructed from 2D covalently bonded monolayers are an exciting family as promising low-cost electrocatalysts towards the hydrogen evolution reaction (HER). Defect engineering of layered lattices to fully utilize MX2 nanosheets is highly desirable. Herein, we report a universal synthesis of defective MX2 nanosheets by modulating both the basal planes and the interlayers. A series of basal plane-disordered and interlayer-expanded MX2 (M = Mo, W, Sn; X = S, Se) nanosheets are synthesized. Interlayer spacings of the MX2 nanosheets are significantly enlarged to 0.93-1.05 nm with an increase of 0.34-0.40 nm, owing to species intercalation. Abundant defects resulting from the wide interlayer expansion and the disordered basal planes offer extensive unsaturated chalcogen atoms as active sites for HER. Consequently, interlayer-expanded and defect-rich (IEDR) MX2 catalysts exhibit striking activities, delivering small Tafel slopes, low onset overpotentials, large cathodic current densities and excellent long-term stabilities. Our work paves a new pathway to improve the electrocatalytic HER activity by defect modulation.