Enriched Electrophilic Oxygen Species on Ru Optimize Acidic Water Oxidation

Abstract Ruthenium oxide (RuO 2 ) is considered one of the most promising catalysts for replacing iridium oxide (IrO 2 ) in the acidic oxygen evolution reaction (OER). Nevertheless, the performance of RuO 2 remains unacceptable due to the dissolution of Ru and the lack of *OH in acidic environments. This paper reports a grain boundary (GB)‐rich porous RuO 2 electrocatalyst for the efficient and stable acidic OER. The involvement of GB regulates the valence state of Ru and weakens the interaction between Ru and O, effectively facilitating *OH adsorption and *OOH formation. Notably, achieved a record‐high catalytic activity (145 mV at 10 mA cm −2 ) with a low Tafel slope (40.9 mV dec −1 ) and a remarkable mass activity of 332 mA mg −1 Ru at 1.5 V versus reversible hydrogen electrode is achieved. Additionally, the porous RuO 2 exhibits superb stability with an ultra‐low degradation rate of 26 µV h −1 over a 50‐day durability test. This study opens a viable pathway for the development of efficient and robust Ru‐based acidic OER electrocatalysts.