Acid‐Stable Ruthenium‐Based Solid Solution for Oxygen Evolution in Proton Exchange Membrane Electrolyzers

Abstract Proton exchange membrane (PEM) water electrolysis offers a promising route for green hydrogen production, yet balancing catalytic activity and durability remains challenging for oxygen evolution reaction (OER) catalysts in acid, particularly for non‐Ir‐based catalysts. Herein, we develop a template‐guided strategy to synthesize the metal–organic framework (MOF)‐derived RuZrCoCrCeO 2 solid solution with tunable multi‐metal heteroatom regulation. The catalyst demonstrates outstanding acidic OER performance, requiring only 179 mV overpotential to achieve 10 mA cm geo −2 and remarkable durability over 1500 h at 50 mA cm geo −2 with a negligible decay of 30.67 µV h −1 . An “electronic buffer” effect facilitates electron transfer from atomically dispersed Zr to Ru, forming asymmetric Ru─O─Zr bonds with enhanced metal–oxygen covalency, thereby preventing excessive oxidation of Ru species. A vicinal deprotonation mechanism was proposed, where lattice oxygen assists *OOH deprotonation with a lower energy barrier on Ru─O─M sites. A PEM electrolyzer with low Ru loading (0.37 mg Ru cm −2 ) achieves an industrial‐level current density of 1 A cm −2 at 1.66 V, corresponding to a low hydrogen cost of US$0.89 kg −1 below the US DOE target (US$2 per kg of H 2 ), and operates stably for 600 h at 200 mA cm geo −2 , demonstrating its practical potential for scalable, Ir‐free PEM electrolyzers.