Kim, Youdong Rand, Peter Brim, Elliot Meisel, Charlie Goldy, Steven R. Yang, Jayoon Sanders, Michael Kim, Hyun Sik Jo, Kanghee Lee, Heesoo Tucker, Garritt J. V. Ciobanu, Cristian Richards, Ryan M. Sullivan, Neal P. O'Hayre, Ryan 2025-07-18T06:30:12Z 2025-07-18T06:30:12Z 2025-07-18 2025-12 0926-3373 https://pubs.kist.re.kr/handle/201004/152774 Due to their high efficiency and versatility, solid oxide electrochemical cells (SOCs) are poised to play a significant role in future energy conversion and storage applications. In recent years, SOCs have bifurcated into two distinct categories: traditional oxygen-ion conducting SOCs that typically operate from similar to 650850 degrees C and the more recent proton-conducting ceramic (PCC) SOCs that typically operate from similar to 400650 degrees C. Current performance and lifetime of both oxygen-ion conducting SOCs and PCCs is primarily limited by the air/steam electrode, which facilitates the oxygen reduction reaction (ORR) during fuel cell operation and must also facilitate the oxygen evolution reaction (OER) during electrolysis operation. Here, we present a newly designed high-entropy double perovskite oxide suitable as a universal ORR/OER electrode for both oxygen-ion conducting SOCs and PCCs. Machine learning methods are applied to identify chemical descriptors for highly catalytic high-entropy double perovskite oxides (AA'B2O6) across a large compositional space. Based on the machine-learning guidance, we ultimately converge on Ba0.9Cs0.1(Ca0.2Gd0.2La0.2Pr0.2Sr0.2)Co1.5Fe0.5O6 (CsBaHEO) as a universal air/steam electrode. Structure stabilization is accomplished by an equimolar five-cation high-entropy composition on the A'-site, while cesium substitution on the A-site enhances the electrical conductivity and leads to a higher oxygen vacancy concentration. This material exhibits versatility and high performance in reversible oxygen-ion SOCs, reversible PCCs, and also large-scale tubular PCCs. For example, the CsBaHEO-based PCC reaches 1018 mW center dot cm(-2) at 600 degrees C, while a large-scale tubular PCC using CsBaHEO for electrolysis achieves a hydrogen production rate of 21.314 ML center dot min(-1) at 600 degrees C. English Elsevier BV Machine learning informed rational design of high entropy double perovskite oxide universal air/steam electrodes for solid oxide electrochemical cells Article 10.1016/j.apcatb.2025.125590 1 Applied Catalysis B: Environment and Energy, v.378 Applied Catalysis B: Environment and Energy 378 Y scie scopus 001513140800001 Chemistry, Physical Engineering, Environmental Engineering, Chemical Chemistry Engineering Article HIGH-PERFORMANCE CATHODE CERAMIC FUEL-CELLS OXYGEN REDUCTION TEMPERATURE EFFICIENT GENERATION STABILITY OXIDATION Hydrogen production Solid oxide electrolysis cell Protonic ceramic electrochemical Cell Machine learning High-entropy perovskite oxide