Electrocatalytic active sites along the Mo-terminated edge of molybdenum disulfide (MoS2) are responsible for the promising hydrogen evolution reaction (HER) activity but poor electrical convey, and scarcity of active sites may inhibit its electrocatalytic performance. Therefore, enhancing the electronic conductivity and increasing the active sites in basal plane are required to realize more efficient hydrogen evolution activity for layered MoS2. Herein, by the incorporation of heterophase SnS2 quantum dots into the basal plane to form atomic-level heterostructure, we dramatically report the enhanced HER activity from MoS2 with current density of -10 mA cm(-2) at a lowered overpotential of 240 mV, a reduced Tafel slope of 65 mV/dec and a long-term durability over 18 h operation. Structural characterization and electrochemical studies reveal the incorporation of heterophase SnS2 quantum dots can efficaciously realize the disorder engineering in the atomic level to regulate the electronic structure, optimize the energy barrier of hydrogen adsorption/desorption, and proliferate the catalytic active sites density, thus activating the basal plane of MoS2 for hydrogen evolution. Density functional theory (DFT) calculation reveals the inception of the improved electrocatalytic activity stemmed from an astronomically immense reduction of the kinetic energy barrier of hydrogen adsorption on and desorption from sulfur sites and sulfur vacancies in the basal plane upon SnS2 incorporation and Sn doping. Our work engenders an efficient method to active the basal plane of 2H-MoS2 by the incorporation of SnS2 heterophase into the atomic layer inducing atomic dislocation and electronic structure optimization. (C) 2019 Elsevier Ltd. All rights reserved.