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

Developing highly efficient acidic oxygen evolution reaction (OER) electrocatalysts is crucial for proton exchange membrane water electrolyzer. RuO 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 to enhance stability. The balance between the activity and stability of RuO-based catalysts is still overlooked in current research. Here, we report a controlled method to introduce metallic Ru onto RuO catalysts to form the Ru─O─Ru interfacial structure for decreasing the Ru oxidation state and promoting deprotonation kinetics. Metallic Ru can serve as the electron donor to lower the oxidation state of *V-RuO in Ru/RuO for stabilizing the structure of *V-RuO -Ru/RuO to favour the acidic OER stability. Moreover, the deprotonation kinetics via the interfacial oxygen site between Ru and Ru is significantly enhanced on Ru/RuO catalysts to improve the acidic OER activity. This work offers a unique perspective to balance the acidic OER activity and stability of RuO.