Dynamic amorphous confinement stabilizes crystalline IrO2 for ultra-durable proton exchange membrane water electrolysis

Abstract Crystalline IrO 2 exhibits high conductivity and structural robustness but suffers from limited active-site exposure, whereas amorphous IrO x provides abundant active motifs yet rapidly degrades during operation. Here we report a crystalline–amorphous hybrid IrO 2 catalyst in which conductive crystalline IrO 2 nanodomains are confined within a porous amorphous iridium oxide matrix. The catalyst achieves 6.4 A cm − 2 at 2.0 V in a proton exchange membrane water electrolysis cell with an ultralow Ir loading of 0.2 mg Ir cm − 2 and exhibits negligible degradation over 3400 hours at 3 A cm − 2 . Operando spectroscopy reveals that the amorphous framework enables reversible surface reconstruction of crystalline IrO 2 into active oxyhydroxide species while suppressing irreversible coarsening and dissolution. Density functional theory calculations suggest that the crystalline–amorphous architecture strengthens Ir–O electronic coupling and facilitates *OOH formation. This work demonstrates that dynamically stabilized crystalline–amorphous interfaces can overcome the conventional activity–stability limitation of acidic oxygen evolution catalysts.