Large-scale production of H-2 through water electrolysis is limited by the lack of efficient and crust-abundant low-cost electrocatalysts. Here, MoSe2 and N-doped carbon (NC) is successfully constructed into a double-shelled hierarchical hollow nanobox. The obtained NC@MoSe2 is demonstrated to be an active catalyst for hydrogen evolution reaction (HER). The NC@MoSe2 delicately combine the structural and functional advantages of two-dimensional layered transition metal dichalcogenides (TMDs) and NC, which yield the striking synergistic effect to endow them with extremely enhanced electrochemical activity to efficiently catalyze the evolution of H-2. Remarkably, the NC@MoSe2 with the optimum thickness of MoSe2 shell can exhibit a fairly low onset potential of 61 mV, an extremely small overpotential of 164 mV vs. RHE at 10 mA cm (2), a greatly reduced Tafel slope of 55 mV dec (1), and a higher exchange current density of 0.102 mA cm (2). Specifically, this is mainly beneficial from the abundant exposed active edges from the edge-terminated ultrathin MoSe2 nanosheets with small size, the overall hierarchical hollow architecture and strong electronic coupling between MoSe2 and NC layer. Density functional theory (DFT) calculation results have well supported the experimental observations, revealing the strong synergistic effect between NC and MoSe2, thus the increased carrier density around the Fermi level and reduced hydrogen adsorption free energy (DGH*) for MoSe2 composited with NC. (C) 2019 Elsevier Inc. All rights reserved.