Vertically Aligned MoS2/Mo2C hybrid Nanosheets Grown on Carbon Paper for Efficient Electrocatalytic Hydrogen Evolution

Maximizing and creating active sites has been a broad strategy to increase the performance of a catalyst. Because of the high electrocatalytic hydrogen evolution reactivity (HER) of ultrafine Mo₂C nanocrystals and edges of two-dimensional MoS₂, an electrode with a synergistic integration of these two nanomaterials is expected to show a better HER performance. In this work we report this hybrid nanostructure of vertically aligned MoS₂/Mo₂C nanosheets on conductive carbon paper. It was revealed that the original structure of MoS₂ nanosheets remains intact after the carburization, but the surfaces are incorporated with either Mo₂C nanodomains or a heteroatomic mixture of S and C. The hybrid catalyst exhibits a much lower HER overpotential in comparison to those of the corresponding Mo₂C and MoS₂ alone. Its high activity is congruent with DFT calculations, which show that multiple S and C coordinated Mo sites with near zero Gibbs free energy of hydrogen adsorption exist. Hence, the low overpotential of this binder-free hybrid catalyst is a result of active sites of Mo–S–C and highly dispersed Mo₂C nanodomains on the original edges and basal planes of MoS₂. Our prediction and realization of active HER sites with this hybrid two-dimensional nanostructure opens up a route toward the development of more active HER catalysts.