Interfacial Confinement Enables Conformal IrOx Nanofilms for Low-Ir-Loading PEM Water Electrolysis

Abstract Terawatt-scale deployment of proton-exchange membrane water electrolyzers (PEMWEs) requires low iridium (Ir) loading, which disrupts the catalyst layer’s in-plane electronic percolation network and severely degrades performance. Here, we overcome this bottleneck via an interfacial confinement strategy that electrostatically enriches cationic Ir intermediates on the negatively charged, oxygen-deficient TiOx surface, thereby redirecting Ir deposition from three-dimensional island growth to a two-dimensional conformal film on TiO2 supports. The resulting IrOx-NF@TiO2 catalyst with low Ir packing density maintains long-range in-plane electron percolation, reducing reliance on the high Ir loading typically required by conventional IrOx nanoparticle catalysts to establish quasi-continuous conductive pathways. At a loading of 0.166 mgIr cm−2, blade-coated membrane electrode assemblies incorporating this architecture feature ∼7 μm-thick catalyst layers with an Ir packing density of only ∼0.25 gIr cm–3, allowing an ∼84% reduction in Ir use while achieving performance comparable to that of commercial IrO2. This work highlights the potential of supported conformal IrOx catalysts as competitive candidates for next-generation low-Ir PEMWEs.