Embedding Sub‐1 nm Ru‐Based High‐Entropy Clusters on Oxyphilic Cerium Oxide for Durable Intermittent Anion Exchange Membrane Water Electrolysis

ABSTRACT The development of efficient and durable platinum‐free electrocatalysts for the hydrogen evolution reaction (HER) is crucial for advancing anion exchange membrane water electrolyzer (AEMWE) powered by intermittent renewable energy. Herein, we report ultra‐stable sub‐1 nm Ru‐based high‐entropy clusters embedded on oxyphilic cerium oxide for alkaline HER, which achieves low overpotentials of 25 and 66 mV at 10 and 100 mA cm −2 , with mass activity (4543 mA mg −1 Ru ) and turnover frequency (2.38 H 2 s −1 ) exceeding Pt/C by 16.5 and 8.5 times. When integrated into an AEMWE, it attains 1.0 and 2.0 A cm −2 at 1.75 and 1.95 V with negligible degradation over 1300 h. Experimental and theoretical results reveal that the strong electron metal‐support interaction (EMSI) mediated by Ru─O─Ce bonds not only activates an efficient dual interfacial Ce‐Ru water dissociation site, accelerating the rate‐limiting Volmer step, but also optimizes the electronic structure of Ru sites, yielding a near‐ideal hydrogen adsorption free energy and enhancing resistance to hydroxyl species poisoning. Most importantly, the combined high‐entropy effect and EMSI‐induced confinement provide dual thermodynamic and kinetic stabilization of the clusters, suppressing the degradation under intermittent operating conditions. This study offers a new design principle for developing robust electrocatalysts suited for dynamic renewable energy systems.