Maximizing and creating active sites has been a general 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. Here 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. Thus, 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.

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