Transition metal dichalcogenides based electrocatalysts have been proposed as substitutes for noble metals to generate hydrogen in electrolysis of water, but these alternatives usually suffer from their inferior performance of intrinsic semiconducting property and inert basal plane. Here, Zn dopants are proved to can intrigue the catalytic activity of MoS2 nanosheets with the low overpotential of 140 mV at 100 mA/cm(2) and Tafel slope of 35 mV/dec. Density functional theory calculations are performed to unravel the underlying mechanism, revealing that the inert basal plane is activated by Zn dopants with the H adsorption free energy (Delta G(H)*) of -0.07. Further, the charge distribution spreading over the basal plane induced by strong hybridizations of metal d-states and sulphurous p-states play a key role for promoting H atom adsorption and desorption kinetics simultaneously. This study opens new opportunities for the designing and understanding of MoS2-based catalysts for water splitting or other applications. (C) 2017 Elsevier Ltd. All rights reserved.