Regulating Surface Hydroxyl Groups in CoO _<i>x</i> via Atomically Dispersed Ru for Durable Acidic Oxygen Evolution

Atomically dispersed catalysts significantly enhance active site utilization, reducing the precious metal loading by orders of magnitude. However, their catalytic performance in the acidic oxygen evolution reaction (OER) is often limited by the intrinsic activity and acid corrosion resistance of the support. Herein, we employ CoO x with moderate OER activity as the support and anchor Ru sites (Ru/Co 3 O 4 ) to enhance its durability during acidic OER, achieving outstanding electrochemical performance. Combined experimental and theoretical analyses reveal that the resultant Ru species from high-temperature treatment (≥450 °C) effectively modulate the valence state and electronic structure of CoO x, leading to regulated hydroxyl (*OH) coverage on Co sites. This process effectively mitigates surface deactivation by reducing the *OH coverage, thus enhancing the durability of the Co-based support. Consequently, Ru/Co 3 O 4 demonstrates great OER performance, achieving a low overpotential of 280 mV at 50 mA cm –2 and maintaining negligible potential loss over 1000 h at 50 mA cm –2 in acidic media. In a proton exchange membrane water electrolysis device, it also demonstrates stable operation for 450 h at 0.2 A cm –2 and 200 h at 0.5 A cm –2 . These insights into the mechanism of the OER and structure–activity relationships are crucial for advancing low-noble-metal catalyst systems.