Direct electrodeposition of NiFe-based high-entropy compounds on nickel foam advanced electrocatalysts for the oxygen evolution reaction

Abstract

Electrochemical water splitting for hydrogen production is highly dependent on the efficiency of the oxygen evolution reaction (OER). While NiFe-based electrocatalysts are widely studied, their performance is often constrained by limited active sites and structural stability. This study presents a novel NiFe high-entropy compound synthesized via a facile one-step electrodeposition method. By systematically tuning the Ni/Fe atomic ratio, the optimized NiFe-2 : 1 electrode exhibits exceptional OER performance, achieving an ultralow overpotential of 232 mV at 10 mA cm⁻² and a Tafel slope of 56.70 mV dec⁻¹ in 1.0 M KOH. Structural and spectroscopic analyses (XRD, XPS, and TEM) confirm the formation of an amorphous structure with mixed valence states (Ni⁰/Ni²⁺ and Fe⁰/Fe²⁺), which facilitates electron transfer and optimizes adsorption energetics. Mott–Schottky analysis further reveals that NiFe-2 : 1 exhibits a high acceptor concentration (7.71 × 10¹⁷ cm⁻³) and p-type semiconductor behavior, contributing to enhanced charge transport and catalytic kinetics. The electrode also demonstrates outstanding long-term stability, maintaining its activity over 100 h without structural degradation. This work highlights the significance of electronic structure modulation through compositional engineering in high-entropy electrocatalysts, offering a scalable and efficient strategy for advancing alkaline water electrolysis.