Mn 2 O 3 Supported RuO 2 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 Mn 2 O 3 supported RuO 2 electrocatalyst featuring short-range-ordered RuO 2 domains that synergistically combines high activity and durability for acidic oxygen evolution. Hydrothermal Ru deposition followed by calcination enables uniform RuO 2 dispersion on Mn 2 O 3, yielding edge-rich RuO 2 domains with limited long-range crystallinity. Structural characterization shows that RuO 2 /Mn 2 O 3 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, RuO 2 /Mn 2 O 3 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, RuO 2 /Mn 2 O 3 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.