A Single-Phase FeCoNiMnMo High-Entropy Alloy Oxygen Evolution Anode Working in Alkaline Solution for over 1000 h

Mo is beneficial to improving oxygen evolution performance, but it is very soluble in an alkaline environment. High-entropy alloys (HEAs) can inhibit the dissolution of metals, but it is difficult for elements with large differences in physical properties (e.g., electronegativity, atomic radius, and melting point) to be uniformly dissolved together. Herein, we prepare a homogeneous face-centered cubic FeCoNiMnMo HEA by electrolyzing the solid oxide mixture in molten salt at 900 °C. The concomitant solid-state electrometallization and alloying process prevent the phase segregation that usually happens in the repeated melting method. More importantly, the as-prepared FeCoNiMnMo shows a good electrocatalytic activity for oxygen evolution reaction (OER) (overpotential (η) = 279 mV, j = 10 mA cm–2) and excellent stability for over 1000 h without significant decay. Experimental analysis and density functional theory calculations reveal that Mo is a crucial enabler in achieving a high electrocatalytic activity and durability. The high-entropy effect significantly reduces the leaching rate of Mo and thereby maintains the thickness of the catalytic layer. In addition, the FeCoNiMnMo HEA electrode can perform stably under industrial conditions (6 M KOH, 60 °C, and 400 mA cm–2) for more than 300 h, demonstrating the ability to serve under industrial conditions. The preparation and design of the single-phase FeCoNiMnMo HEA electrode offer infinite OER candidates for enabling efficient water electrolysis.