Tiny Ni3S2 boosting MoS2 hydrogen evolution in alkali by enlarging coupling boundaries and stimulating basal plane.

The relatively slow reaction kinetics of the hydrogen evolution reaction (HER) by water electrolysis in alkali hinder its large-scale industrial production. To improve the HER activity in alkaline media, a novel Ni3S2/MoS2/CC catalytic electrode was synthesized by a simple two-step hydrothermal method in this work. The modification of MoS2 by Ni3S2 could facilitate the adsorption and dissociation of water, thus accelerating the alkaline HER kinetics. Moreover, the unique morphology of small Ni3S2 nanoparticles grown on MoS2 nanosheets not only increased the interface coupling boundaries, which acted as the most efficient active sites for the Volmer step in alkaline medium, but also sufficiently activated the MoS2 basal plane, thus providing more active sites. Consequently, Ni3S2/MoS2/CC only needed overpotentials of 189.4 and 240 mV to drive current densities of 100 and 300 mA·cm-2, respectively. More importantly, its catalytic performance of Ni3S2/MoS2/CC even exceeded that of Pt/C at a high current density after 261.7 mA·cm-2 in 1.0 M KOH.