Two-dimensionally confined Ir/WOx heterointerfaces boost the acidic oxygen evolution reaction for ampere-level stable PEM water electrolysis
Iridium-based materials remain the only commercially viable anode electrocatalysts for the acidic oxygen evolution reaction (OER) in proton exchange membrane water electrolyzers (PEMWE), yet their high cost and insufficient activity necessitate reducing Ir loading while enhancing performance. This work reports the synthesis of ultrathin Ir/WOx hybrid nanosheets (Ir/WOx NSs) featuring abundant two-dimensionally confined heterointerfaces, composed of crystalline Ir nanograins embedded within an amorphous WOx matrix. The Ir/WOx NSs achieve a mass activity of 2.34 A mgIr−1 at an overpotential of 300 mV, approximately 11.1 and 9.8 times higher than Ir NSs and commercial Ir/C, respectively. The 2D-confined interactions establish synergistic bifunctional sites and efficient charge transfer interfaces, accelerating the initial hydrolysis dissociation step. On interfacial Ir atoms, the adsorption of *O and subsequent formation of *OOH intermediates are thermodynamically facilitated, promoting the adsorbate evolution mechanism. The Ir/WOx NSs-based PEMWE delivers a low cell voltage of 1.71 V at 1.0 A cm−2 and exhibits outstanding long-term durability, with a potential decay rate of 2.8 μV h−1 compared to 210 μV h−1 for commercial IrO2. This work demonstrates the engineering of 2D-confined metal-oxide interfacial electrocatalysts for efficient and stable green hydrogen production.