Low‐Cost Self‐Reconstructed High Entropy Oxide as an Ultra‐Durable OER Electrocatalyst for Anion Exchange Membrane Water Electrolyzer

Abstract Future energy loss can be minimized to a greater extent via developing highly active electrocatalysts for alkaline water electrolyzers. Incorporating an innovative design like high entropy oxides, dealloying, structural reconstruction, in situ activation can potentially reduce the energy barriers between practical and theoretical potentials. Here, a Fd‐3m spinel group high entropy oxide is developed via a simple solvothermal and calcination approach. The developed (FeCoMnZnMg) 3 O 4 electrocatalyst shows a near equimolar distribution of all the metal elements resulting in higher entropy (ΔS ≈1.61R) and higher surface area. The self‐reconstructed spinel high entropy oxide (S‐HEO) catalyst exhibited a lower overpotential of 240 mV to reach 10 mA cm −2 and enhanced reaction kinetics (59 mV dec −1 ). Noticeably, the S‐HEO displayed an outstanding durability of 1000 h without any potential loss, significantly outperforming most of the reported OER electrocatalysts. Further, S‐HEO is evaluated as the anode catalyst for an anion exchange membrane water electrolyzer (AEMWE) in 1 m , 0.1 m KOH, and DI water at 20 and 60 °C. These results demonstrate that S‐HEO is a highly attractive, non‐noble class of materials for high active oxygen evolution reaction (OER) electrocatalysts allowing fine‐tuning beyond the limits of bi‐ or trimetallic oxides.