Amorphous IrO_x buffer layer stabilizes low-valence Ir centers and reinforces IrO hybridization in hierarchical...

Developing high activity and stable low-Ir-loading electrocatalysts for anodic oxygen evolution reaction (OER) in acidic media remains a formidable challenge. Herein, amorphous IrO_x-shelled metallic Ir nanoparticles were successfully anchored onto spinel Co₃O₄ framework (Ir-IrCoO_x), yielding a hierarchical Ir/IrO_x/Co₃O₄ multilayer architecture with the hollow nanobox morphology. Operando infrared absorption spectroscopy combined with ex-situ X-ray adsorption spectroscopy reveal that the IrO_x buffer layer functions as a protective and electronic-regulating interface that suppresses over-oxidation of both the Ir centers and the oxide scaffold, thereby stabilizing a low Ir oxidation state and reinforcing IrO hybridization, enabling the target catalyst follows an adsorbate evolution mechanism pathway. Consequently, thus-prepared Ir-IrCoO_x catalyst delivers a favorable mass activity (120.28 A g_Ir^-1) and turnover frequency (0.18 s^-1), which is significantly superior to commercial IrO₂ (32.91 A g_Ir^-1 and 0.01 s^-1). This work demonstrates that interface-coupling engineering effectively suppresses Ir dissolution and offers a general design paradigm for acidic OER electrocatalysts.