Synthesis of Hierarchically Structured Nickel–Iron Sulfide on Nickel Foam as a Catalyst for Efficient Oxygen Evolution Reaction

A nickel-iron sulfide nanosheets modified nickel foam electrode NiFeS/NF was prepared via a facial one-step hydrothermal method. The NiFeS/NF showed a hierarchical porous structure with nanosheet-constructed flower-like clusters with a large surface area. The composite catalyst NiFeS/NF exhibited high oxygen-evolution activity in 1 M KOH electrolyte. It had an overpotential of 170 mV at 10 mA/cm² with a low Tafel slope of 86 mV dec^-1. After 100 h of oxygen evolution at 100 mA cm⁻², the electrode maintained good stability. Density functional theory calculations show that NiFeS/NF exhibits superior OER activity in alkaline media due to the optimization of Gibbs free energy ΔG_OER and a more favorable O₂ desorption process.