Dual Function of Mn Doping for Active and Robust Acidic Water Oxidation on RuO₂

Developing cost-effective and acid-stable oxygen evolution reaction (OER) catalysts is vital for the advancement of proton-exchange membrane (PEM) water electrolysis. Herein, we report a Mn-modified RuO₂electrocatalyst derived from a Mn₃O₄spinel precursor that exhibits exceptional OER activity and long-term durability under acidic conditions. Through a templated synthesis strategy, Mn₃O₄nanostructures direct the formation of Mn–RuO₂nanospheres with uniform Mn incorporation and complete phase transformation, overcoming the limitations of conventional bulk doping approaches. The optimized catalyst exhibits a low overpotential of 200 mV at 10 mA cm^–2in 0.5 M H₂SO₄and maintains stable performance over 600 h of continuous operation, with minimal degradation (83 μV h^–1). Mechanistic investigations, including kinetic isotope effect analysis and methanol oxidation probing, reveal that Mn incorporation does not alter the rate-determining *OOH formation step but enhances *OH coverage and mitigates Ru overoxidation through electronic modulation and sacrificial oxidation. This dual role of Mn, in enhancing activity and stabilizing the RuO₂structure, provides valuable insights for the design of robust Ru-based electrocatalysts for acidic water oxidation.