High‑Entropy Perovskite Anodes for Efficient Water Oxidation Reaction in Protonic Ceramic Electrolysis Cells

ABSTRACT Protonic ceramic electrolysis cells (PCECs) have emerged as promising energy conversion devices due to their high efficiency and environmental friendliness. However, the development of excellent anodes with high catalytic activity of water oxidation reaction, ionic conductivity and durability remains a critical challenge. In this study, high‐entropy oxides (HEOs) of La(Co 0.4‐ x Fe 0.2 Ni 0.2 Cr 0.2 Sc x )O 3‐ δ were reported as anodes for PCECs. The effects of Sc on the phase structure, microstructure, catalytic activity, and electrochemical performance of the HEOs were systematically investigated. The HEO‐Sc3 ( x = 0.3) oxide exhibited the highest catalytic activity with an area‐specific resistance of 0.34 Ω cm −2 at 600°C, concluded by analyzing the oxygen vacancy concentration, hydrated proton concentration, and free energy of the oxygen evolution reaction. Besides, the diversification at the B‑site of perovskite and increased Sc dopant significantly reduced the thermal expansion coefficient and maintained long‑term material stability. Finally, a single cell based on the HEO‐Sc3 anode achieved a current density of 2.31 A cm −2 under 1.3 V and 600°C. This work not only highlights the pivotal function of Sc incorporation within HEO anodes, but also introduces a rational design pathway for constructing highly active and durable HEOs to the water oxidation reaction in PCECs.