Synergistic Co-Doping of Barium and Cobalt Enables Stable and Active RuO₂ for Acidic Water Oxidation

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 RuO₂ catalysts (Ba/Co-RuO₂) 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 H₂SO₄ with negligible decay. More importantly, a proton exchange membrane electrolyzer using Ba/Co-RuO₂ 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.