Tailoring the thickness of MoSe2 layer of the hierarchical double-shelled N-doped carbon@MoSe2 hollow nanoboxes for efficient and stable hydrogen evolution reaction.

• Double-shelled hierarchical hollow NC@MoSe 2 nanobox has been synthesized for HER. • The NC@MoSe 2 with the optimum shell thickness shows the best HER activity. • The excellent HER activity is beneficial from the abundant exposed active edges. • It is also attributed to strong electronic coupling between MoSe 2 and NC layer. • DFT calculation results reveal the strong synergistic effect between NC and MoSe 2. Large-scale production of H 2 through water electrolysis is limited by the lack of efficient and crust-abundant low-cost electrocatalysts. Here, MoSe 2 and N-doped carbon (NC) is successfully constructed into a double-shelled hierarchical hollow nanobox. The obtained NC@MoSe 2 is demonstrated to be an active catalyst for hydrogen evolution reaction (HER). The NC@MoSe 2 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@MoSe 2 with the optimum thickness of MoSe 2 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 MoSe 2 nanosheets with small size, the overall hierarchical hollow architecture and strong electronic coupling between MoSe 2 and NC layer. Density functional theory (DFT) calculation results have well supported the experimental observations, revealing the strong synergistic effect between NC and MoSe 2 , thus the increased carrier density around the Fermi level and reduced hydrogen adsorption free energy (ΔG H*) for MoSe 2 composited with NC. [ABSTRACT FROM AUTHOR]