Breaking the Activity‐Stability Trade‐Off of RuO ₂ via Metallic Ru Bilateral Regulation for Acidic Oxygen Evolution Reaction

Abstract Developing highly efficient acidic oxygen evolution reaction (OER) electrocatalysts is crucial for proton exchange membrane water electrolyzer. RuO 2 electrocatalysts, which followed a kinetically favorable lattice oxygen mechanism, perform a preferable intrinsic activity, but poor stability for acidic OER. Recent work often sacrifices the intrinsic activity of RuO 2 to enhance stability. The balance between the activity and stability of RuO 2 ‐based catalysts is still overlooked in current research. Here, we report a controlled method to introduce metallic Ru onto RuO 2 catalysts to form the Ru 4+ ─O─Ru 0 interfacial structure for decreasing the Ru 4+ oxidation state and promoting deprotonation kinetics. Metallic Ru can serve as the electron donor to lower the oxidation state of *V o ‐RuO 4 2− in Ru/RuO 2 for stabilizing the structure of *V o ‐RuO 4 2− ‐Ru/RuO 2 to favour the acidic OER stability. Moreover, the deprotonation kinetics via the interfacial oxygen site between Ru 4+ and Ru 0 is significantly enhanced on Ru/RuO 2 catalysts to improve the acidic OER activity. This work offers a unique perspective to balance the acidic OER activity and stability of RuO 2 .