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

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 RuZrCoCrCeO₂ 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 H₂), and operates stably for 600 h at 200 mA cm_geo ^-2, demonstrating its practical potential for scalable, Ir-free PEM electrolyzers.