Nitrogen-Doped Nickel Sulfide Composite Array Electrode as an Efficient Electrocatalyst for Hydrogen Evolution Reaction

Transition metal sulfides have become some of the most promising non-precious metal catalysts due to their high specific surface area, unique electronic structure, and rich phase and property modulation methods. However, defects such as high overpotential and slow reaction kinetics hinder their implementation in electrocatalytic applications. Herein, graphene-coated sponge nickel (SNG) supported Ni₉S₈ nanowires were doped with N to adjust the electronic structure and thus improve the electrocatalytic hydrogen evolution performance of the N-Ni₉S₈@SNG core/branch electrode. The N-Ni₉S₈@SNG electrode exhibits excellent hydrogen evolution performance, with an overpotential of 98 mV at 10 mA cm⁻² and long-cycle stability with no significant attenuation of the overpotential after testing at 10 mA cm⁻² for 10 h. The results of photoelectron spectroscopy and density functional theory calculations showed that, due to the higher electronegativity of the nitrogen site, the electron density of the surrounding Ni and S atoms is changed, thereby promoting the dissociation of H₂O and the adsorption/desorption of hydrogen.