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.