Synergistic Co‐Doping of Barium and Cobalt Enables Stable and Active RuO 2 for Acidic Water Oxidation

Abstract Developing acid‐stable and active non‐iridium oxygen evolution reaction (OER) electrocatalysts is crucial to facilitating the cost‐effective and large‐scale applications of proton exchange membrane water electrolysis (PEMWE) for hydrogen production. However, the instability of Ru sites and lattice oxygen loss limit their further application, imposing a significant challenge to designing Ru‐based catalysts with both high activity and long‐term stability. Here, cobalt and barium co‐doped RuO 2 catalysts (Ba/Co‐RuO 2 ) are developed, exhibiting a low overpotential of 166 mV and exceptional durability, maintaining OER operation for over 1500 h at 10 mA cm −2 in 0.5 M H 2 SO 4 with negligible decay. More importantly, a proton exchange membrane electrolyzer using Ba/Co‐RuO 2 as the anode also demonstrates excellent performance, achieving 3 A cm −2 at 1.87 V and sustaining durability for over 300 h at 800 mA cm −2 . In situ and ex situ experimental characterizations, together with computational analyses, confirm that the remarkable activity and stability originate from Ba and Co co‐doping, which induces lattice strain and electron redistribution. These effects effectively stabilize the catalyst's structure and synergistically regulate the adsorption/desorption of oxygen intermediates. This work provides an efficient co‐doping strategy to design high‐performance electrocatalysts for PEMWE.