Hydrogen Evolution Catalyzed by a Molybdenum Sulfide Two-Dimensional Structure with Active Basal Planes.

Molybdenum disulfide has been demonstrated as a promising catalyst for hydrogen evolution reaction (HER). However, its performance is limited by fractional active edge sites and the strong dependence on hydrogen coverage. In this study, we find an enhanced HER performance in a two-dimensional substoichiometric molybdenum sulfide. Both first-principles calculations and experimental results demonstrate that the basal plane is catalytically active toward HER, as evidenced by an optimum Gibbs free energy and a low reaction overpotential. More interestingly, the HER performance is insensitive to hydrogen coverage and can be improved under compressive in-plane biaxial strains. Our results suggest not only an improved HER performance of substoichiometric molybdenum sulfide due to its chemical reactive basal plane but also a way to tune the performance.