Mn0.75Ru0.25O2 with Low Ru Concentration for Active and Durable Acidic Oxygen Evolution

Ruthenium has emerged as a promising alternative to iridium in water-splitting anodes. However, it becomes overoxidized and dissolves at industry-relevant working conditions. To enhance the activity and stability of electrocatalysts for oxygen evolution reaction, an isostructural rutile MnRu oxide with low Ru concentration (Mn_0.75Ru_0.25O₂) is synthesized and an asymmetric Mn-O-Ru dual-site active center is developed. It exhibits 154 mV overpotential at 10 mA cm⁻² and can operate stably at 200 mA cm⁻² for 670 h with a degradation rate of 29 uV/h⁻¹. A proton exchange membrane water electrolyzer achieves stable operation at 1 A cm⁻² for 700 h with a degradation rate of 53 uV h⁻¹. Structural analysis and isotopic labeling correlate the asymmetric nature of the Mn-O-Ru dual-site active center, which facilitates the oxygen evolution reaction along the radical coupling pathway, with the stabilization of the cations and the lattice oxygen in isostructural rutile Mn_0.75Ru_0.25O₂.