Hierarchical urchin-like peapoded core-shell-structured NiCo2@Ni1/3Co2/3S2@C catalyst with synergistically high-efficiency electrocatalytic properties toward hydrogen evolution reaction

Abstract Designing and developing earth-abundant, low-price and high-efficiency catalysts for hydrogen evolution reaction (HER) is remaining a great challenge from the standpoint of energy. Herein, we have synthesized, firstly, three-dimensional (3D) urchin-like NiCo2@Ni1/3Co2/3S2 @C catalyst composed of one-dimensional (1D) peapod-like structure, in which the nanoparticles of the peapod are characterized with a special structure: NiCo 2 alloy as the core and thin Ni1/3Co2/3S2 layer as the shell. Notably, the internal NiCo2 core offers efficient routes for electron transfer and the external Ni1/3Co2/3S2 shell provides a great number of active sites for HER. Owing to the synergistic effect between the inner core and the outer shell, NiCo2@Ni1/3Co2/3S2@C catalyst displays excellent catalytic performance, including a low overpotential of ∼41.0 mV at 10 mA cm−2, a corresponding small Tafel slope of ∼39.2 mV dec−1 , and an excellent stability in acidic medium for 200 h, which is greater than many reported transition metal chalcogenides (TMCs). Simultaneously, the free energy of H ∗ adsorption (ΔGH∗) for NiCo2@Ni1/3Co2/3S2@C (about −0.10 eV) is extremely near to that for Pt (∼0.09 eV) by density functional theory (DFT) calculated results, which is significantly beneficial to HER performance.