Iron incorporation and sulfur modification synergistically enhance oxygen evolution in nickel–cobalt hydroxide electrocatalysts

Abstract

The development of efficient, stable, and low-cost non-precious metal electrocatalysts is pivotal for advancing water electrolysis for hydrogen production, where the oxygen evolution reaction (OER) remains the kinetic bottleneck. Herein, we report a self-supported S–NiCoFe(OH)_x/NF electrode with Fe incorporation and S modification. The results reveal that the incorporation of Fe significantly boosts the intrinsic catalytic activity of the material, while the modification of S further enhances charge transfer efficiency and accelerates reaction kinetics. Electrochemical tests demonstrated that the S–NiCoFe(OH)_x/NF electrode exhibited outstanding OER performance in 1.0 M KOH, requiring an overpotential of only 283 mV to achieve a current density of 100 mA cm⁻², with a Tafel slope of 36.2 mV·dec⁻¹. X-ray photoelectron spectroscopy (XPS) depth profiling confirms a gradient distribution of Fe and S from the surface to the bulk phase of the composite: Fe content increases from the surface to the bulk, whereas S is primarily enriched on the surface. This synergistic regulation of elemental composition and spatial distribution not only resolves the trade-off between activity and conductivity but also provides a versatile design principle for the development of high-performance hydroxide-based electrocatalysts toward practical water electrolysis.