As a promising cost-effective electrocatalyst for hydrogen evolution reaction (HER), molybdenum disulfide (MoS2) has been drawing more attention. However, the desired performances are restricted by the poor conductivity and inadequate active sites. To address these obstructions, we design an intelligent sandwiched nanostructure of hierarchical hollow nanospheres, which are assembled by Ni-modified MoS2 nanosheets encapsulated into N-doped carbon layers (NC@MoS2/Ni-NC HNSs). The hybrid catalyst exhibits significantly increased electrical conductivity and active area, thereby maximally exposing the rich active sites. Additionally, the sandwiched hierarchy is favorable for preventing the agglomeration of the nanosheets to ensure the excellent stability. Consequently, such NC@MoS2/Ni-NC HNSs show brilliant HER performance with a delightful onset overpotential of ∼16.8 mV and a low overpotential of 82.1 mV to achieve a current density of 10 mA cm−2 in alkaline solution, together with the prominent long-term stability for over 35 h. Theoretical studies underline that metallic Ni doping can not only tune the electronic structures and optimize the appropriate free energy of H* adsorption (ΔGH*), but also play a critical role in activating the catalytic activity in both S edges and basal plane, and lowering the energy barrier for initial water dissociation of Ni-doped MoS2 catalysts, synchronously. This synergy effect for improving the apparent and intrinsic activity can be extended to the design and synthesis strategies for other high-efficiency electrochemical applications.
