Two-dimensionally confined Ir/WOx heterointerfaces boost the acidic oxygen evolution reaction for ampere-level stable PEM water electrolysis

Iridium (Ir)-based materials are the only commercializable class of anode electrocatalysts for acidic oxygen evolution reaction (OER) in proton exchange membrane water electrolyzers (PEMWE). Intending to large-scale implement of PEMWE, it is urgent to improve their OER performances for reducing the usage of high-cost Ir element. Herein, we report an elaborate synthesis of ultrathin Ir/WO_x hybrid nanosheets equipped with abundant 2D-confined heterointerfaces (denoted as Ir/WO_x NSs), which are composed of ultrathin Ir nanograins embedded in amorphous WO_x matrix, to substantially enhance the acidic OER. The Ir/WO_x NSs achieve a notable mass activity of 2.34 A mg_Ir⁻¹ at an overpotential of 300 mV, which is approximately 11.1 and 9.8 times higher than those of Ir NSs and commercial Ir/C, respectively. The 2D-confined interactions between crystalline Ir nanograins and amorphous WO_x matrix establish synergistic bifunctional sites and efficient charge transfer interfaces, which effectively accelerate the initial hydrolysis dissociation step. Moreover, on interfacial Ir atoms, the adsorption of *O and subsequent formation of *OOH intermediates are thermodynamically facilitated, making the OER process more favorable through the adsorbate evolution mechanism. Finally, the Ir/WO_x NSs based PEMWE demonstrates a low cell voltage of only 1.71 V to deliver 1.0 A cm⁻² current density as well as an outstanding long-term durability, realizing efficient and stable green hydrogen production. This work highlights the engineering of 2D-confined metal-oxide interfacial electrocatalysts for efficient energy conversion applications.