From elemental metals to synergistic electrocatalysis: Comparative theoretical and experimental insights into FeNiCoCuMo high-entropy alloy for alkaline oxygen evolution reaction

Self-supported, hot-pressed FeNiCoCuMo high-entropy alloy (HEA) electrodes were fabricated and characterized by X-ray diffraction (XRD), high-resolution transmission electron microscopy (HR-TEM), and energy dispersive spectroscopy (EDS), confirming a face-centered cubic (FCC) matrix with minor body-centered cubic (BCC) phase (~1wt%). We map the redox behavior of the individual constituents (Fe, Ni, Co, Cu, and Mo) and compare it with HEA to reveal solid-solution synergy (“cocktail effect”). Electrochemistry (cyclic voltammetry (CV)/linear sweep voltammetry (LSV)/Tafel in 1.0 M KOH) and X-ray photoelectron spectroscopy (XPS) show broadened redox features for HEA and Ni/Co-rich (oxy)hydroxide signatures with MoO_x contributions. Triplicate electrodes (M1–M3) deliver an average overpotential of 370 mV at 10 mA·cm⁻² and a Tafel slope of 78 mV·dec⁻¹, outperforming monometallic references and remaining competitive with the literature-reported RuO₂. Chronopotentiometry 100 h evidence stable operation; post-mortem XRD indicates a thin reconstructed surface while the bulk remains FCC-dominated. Density functional theory (DFT) supports broadened electronic states near the Fermi level and enhanced charge transfer. Overall, structure and computation link compositional disorder, surface reconstruction, and oxygen evolution reaction (OER) kinetics in a robust anode for alkaline oxygen evolution.