Hollow Sandwiched Structure of Ni-Modified MoS₂ Wrapped into Symmetrical N-Doped Carbon toward a Superior Hydrogen Evolution Electrocatalyst

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, herein, we design and fabricate 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 and durability 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 release inert basal plane to activated sites, leading to the boosted HER performance.