Core-shell structured Ni/NiS/NiS2@C(S, N) nanocomposites: A efficient multi-interfaces electrocatalyst for overall urea electrolysis

Herein, we synthesized S, N co-doped graphitic carbon-coated Ni/NiS/NiS2 (Ni/NiS/NiS2@C(S, N)) nanocomposites via the arc-discharge method combined with the sulfidation process. The as-prepared Ni/NiS/NiS2@C(S, N) nanocomposites with unique core-shell structures and multiple interfaces exhibit highly efficient electrocatalytic capacity. They only needed the overpotential of 60 mV to afford the current density of −10 mA cm−2 towards hydrogen evolution reaction (HER). Meanwhile, they required a low potential of 1.381 V at 10 mA cm−2 towards urea oxidation reaction (UOR). Even during urea electrolysis, they only needed the cell voltage of 1.45 V at 10 mA cm−2 and exhibited strong stability in the long-time test. Further, the catalytic mechanism of Ni/NiS/NiS2@C(S, N) nanocomposites was discussed in detail. The superior electrocatalytic capacity of Ni/NiS/NiS2 @C(S, N) nanocomposites towards HER, UOR, and urea electrolysis results from the synergistic effect among multiple interfaces. Such synergistic effect triggers rapid electron transfer, fast rate cleavage of H2O and urea, and improved hydrogen adsorption free energy.