Lattice‐Matched Rutile Support Stabilizes Low‐Iridium Catalyst for Industrial PEM Water Electrolysis

The terawatt‐scale deployment of proton exchange membrane water electrolyzers (PEMWEs) is fundamentally bottlenecked by the catastrophic dissolution of iridium (Ir) during the acidic oxygen evolution reaction (OER) at high current densities. Here, we present an epitaxial‐like phase‐engineering strategy that transcends the longstanding activity‐stability trade‐off by constructing a structurally coherent rutile‐on‐rutile interface. By precisely tailoring the crystalline phase of Nb‐doped TiO 2 (RNTO) from anatase to a lattice‐matched rutile structure (R800NTO), we unlock a potent and durable Strong Oxide‐Support Interaction (SOSI) for a unique rutile‐on‐rutile configuration (IrO 2 @R800NTO). This lattice‐coherent anchoring effect not only optimizes the Ir d‐band center (−1.79 eV) to streamline reaction kinetics but also elevates the thermodynamic barrier for IrO 3 leaching (3.85 eV), as evidenced by operando Raman spectroscopy and DFT calculations. Critically, in a practical PEMWE device with a low Ir loading (0.15 mg cm −2 ), the IrO 2 @R800NTO anode delivers an industrial‐level current density of 3 A cm −2 at only 1.77 V, decisively surpassing the U.S. DOE 2026 target. This work establishes lattice coherence as a critical interfacial descriptor, providing a transformative paradigm for engineering ultra‐durable and cost‐effective catalytic systems for large‐scale energy conversion.