Ni-Co Nanoparticles@Ni3S2/Co9S8 Heterostructure Nanowire Arrays for Efficient Bifunctional Overall Water Splitting

This work develops a novel Ni-Co nanoparticles coupled with Ni3S2 and Co9S8 phases on nickel foam (denoted as Ni-Co NPS@Ni3S2/Co9S8/NF) hybrid structure material as a bifunctional water electrolysis catalyst. The self-assembly Ni-Co alloy phases enhance electrical conductivity, while the synergistic interactions among the three components (Ni-Co, Ni3S2 and Co9S8) optimize the lattice parameters and electronic environment for boosting both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). The catalyst achieves low overpotentials of 106 mV for HER and 185 mV for OER at 10 mA·cm−2 in 1M KOH, along with a very low charge-transfer resistance. Density functional theory (DFT) calculations reveal that the multi-component interaction narrows the band gap and optimizes the hydrogen adsorption free energy (ΔGH*) as well as the adsorption free energies of OER intermediates (ΔGOH*). This work identifies the hybrid structure as the key to the enhanced activity and offers a promising strategy for designing efficient nickel–cobalt-based electrocatalysts.