Ir single atoms unlock bridging-oxygen microenvironment enhances ultrastable OER in PEMWE at ampere-level current densities

Catalyst development for proton exchange membrane water electrolysis (PEMWE) has long been focused on a metal-site-centric paradigm, with Ru or Ir centers regarded as the primary lever for tuning oxygen evolution through adsorption and electronic-structure engineering. Yet, meaningful gains in device performance remain elusive. This paradox suggests that alternative strategies beyond the metal active site may play a crucial role in governing the oxygen evolution reaction in PEMWE. Here, we report a strategy that activates the latent functionality of bridging oxygen by engineering a tailored microenvironment within Ru-O_bri-Ir motifs. This configuration enhances the basicity of bridging oxygen, transforming it from a passive lattice spectator into an active basic site that promotes deprotonation in the rate-determining step (RDS), thereby accelerating oxygen evolution reaction (OER) kinetics under acidic conditions. Meanwhile, the regulated microenvironment suppresses excessive oxidation and lattice oxygen loss, leading to substantially improved stability. The Ir_SA-RuO₂ catalyst requires an overpotential of only 196 mV to deliver 10 mA cm⁻² and maintains stable operation for over 1500 h in 0.5 M H₂SO₄. When integrated into a proton exchange membrane electrolyzer, it sustains continuous operation at 1 A cm⁻² for 2325 h (over three month) under 80 °C pure-water.