Mn₂O₃ Supported RuO₂ with Short-Range-Ordered Domains for Durable Oxygen Evolution in PEM Water Electrolysis

Developing efficient and durable anode electrocatalysts is essential for translating proton exchange membrane water electrolysis (PEMWE) into practical hydrogen production. Here, we report an Mn₂O₃ supported RuO₂ electrocatalyst featuring short-range-ordered RuO₂ domains that synergistically combines high activity and durability for acidic oxygen evolution. Hydrothermal Ru deposition followed by calcination enables uniform RuO₂ dispersion on Mn₂O₃, yielding edge-rich RuO₂ domains with limited long-range crystallinity. Structural characterization shows that RuO₂/Mn₂O₃ retained stable Ru speciation and an almost constant oxygen vacancy fraction after extended OER operation, consistent with suppressed anodic degradation. Operando spectroscopy captures the key *OOH and *OO intermediates, supporting an adsorbate evolution mechanism (AEM) under acidic conditions. Building on the identified AEM pathway and the stabilized catalyst structure, RuO₂/Mn₂O₃ achieves an overpotential of 150 mV at 10 mA cm^-2, a Tafel slope of 44.6 mV dec^-1, and stable operation for >400 h in acidic electrolyte. In PEMWE tests, RuO₂/Mn₂O₃ delivers 1.0 A cm^-2 at 1.61 V and operates stably for 100 h at 200 mA cm^-2, highlighting its promise for practical acidic water electrolysis.