Stabilizing Grain-Boundary-Rich RuO ₂ by Atomic Iridium-Doping To Achieve High-Performance Oxygen Evolution for Ampere-Level PEM Water Electrolysis

Defect-rich RuO2 catalysts, although possessing high electrocatalytic activity, are inherently unstable for the anode oxygen evolution reaction (OER) in proton exchange membrane water electrolysis (PEMWE) due to rapid lattice oxygen depletion. Here we report an atomically Ir-doped, grain-boundary-rich RuO2 catalyst (Ir-GB-RuO2) that suppresses overactivation of lattice oxygen by forming robust Ru–O–Ir bridging motifs at grain boundaries, achieving high-performance acidic OER electrocatalysis and ampere-level stable PEMWE. The induced electronic modulation shifts the catalytic mechanism from a pure lattice oxygen mechanism (LOM) to a balanced coexistence of LOM and the adsorbate evolution mechanism (AEM), thereby achieving robust stability while preserving high intrinsic activity. The primary Ir-GB-RuO2 catalyst requires only 191 mV overpotential to achieve 10 mA cm–2 and exhibits a prolonged durability exceeding 1000 h at 100 mA cm–2. In a PEM electrolyzer, it attains the current density of 1.0 A cm–2 at a notably low cell voltage (1.67 V) and exhibits a minimal potential decay rate of only 55.3 μV h–1 over 1500 h of continuous operation. This work overcomes the intrinsic activity–stability trade-off in defect-rich Ru-based catalysts for industrial PEMWE.