Enriched Electrophilic Oxygen Species on Ru Optimize Acidic Water Oxidation.

Ruthenium oxide (RuO) is considered one of the most promising catalysts for replacing iridium oxide (IrO) in the acidic oxygen evolution reaction (OER). Nevertheless, the performance of RuO 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 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) with a low Tafel slope (40.9 mV dec) and a remarkable mass activity of 332 mA mg at 1.5 V versus reversible hydrogen electrode is achieved. Additionally, the porous RuO exhibits superb stability with an ultra-low degradation rate of 26 µV h over a 50-day durability test. This study opens a viable pathway for the development of efficient and robust Ru-based acidic OER electrocatalysts.