Manganese as Electron Reservoir Stabilized RuMnO x @RuO x with Enhanced Activity and Robust Durability for Acidic Water Oxidation

Designing highly active and durable electrocatalysts with low noble-metal mass-loading to boost the sluggish oxygen evolution reaction is crucial for hydrogen production. Herein, a Ru-enriched surface and oxygen-defective RuMnO x @RuO x -1.5 catalyst is developed with enhanced activity and robust stability through MnO x serving as an electron reservoir. This RuMnO x @RuO x -1.5 catalyst with an ultralow mass-loading of 91.2 μg Ru cm −2 delivers 1645 A g Ru −1 @1.5 V versus RHE and long-term operational stability exceeding 240 h with a high stability number (6.22 × 10 4 ) in 0.5 M H 2 SO 4 . Characterizations and theoretical calculations reveal that the sacrificial spaced Mn dissolution makes the adjacent Mn serve as an electron reservoir to replenish electrons on active Ru sites and suppress the overoxidation of Ru extending the robust stability. The crystalline−amorphous heterointerfaces, abundant oxygen vacancies, and stable Ru−O−Mn motifs simultaneously facilitate superior activity. The weaker adsorption between Ru sites and oxo-intermediates lowers the energy barrier from O* to *OOH following the adsorbate evolution mechanism (AEM) pathway. This work provides a promising perspective on designing cost-effective OER electrocatalysts for proton exchange membrane water electrolysis.