Engineering water dissociation sites in MoS₂ nanosheets for accelerated electrocatalytic hydrogen production

Earth-abundant MoS₂ is widely reported as a promising HER electrocatalyst in acidic solutions, but it exhibits extremely poor HER activities in alkaline media due to the slow water dissociation process. Here we present a combined theoretical and experimental approach to improve the sluggish HER kinetics of MoS₂ electrocatalysts through engineering the water dissociation sites by doping Ni atoms into MoS₂ nanosheets. The Ni sites thus introduced can effectively reduce the kinetic energy barrier of the initial water-dissociation step and facilitate the desorption of the ^-OH that are formed. As a result, the developed Ni-doped MoS₂ nanosheets (Ni-MoS₂) show an extremely low HER overpotential of ∼98 mV at 10 mA cm^-2 in 1 M KOH aqueous solution, which is superior to those (>220 mV at 10 mA cm^-2) of reported MoS₂ electrocatalysts.