Gold-Triggered Restructuring of Interfacial Water on Ir Nanoclusters Switches Oxygen Evolution Pathways toward Stable Acidic Electrocatalysis

Abstract Ir-based anodes for proton exchange membrane water electrolysis (PEMWE) often degrade when lattice oxygen participates in acidic OER, accelerating Ir dissolution. Here, we engineer the interfacial water microenvironment by alloying Au with low-crystallinity Ir nanoclusters on TiO2 (IrAu0.12@TiO2). The Ir-Au work-function mismatch induces interfacial electronic polarization, strengthens metal–water interactions, facilitates rapid water activation, and reorganizes the hydrogen (H)-bond network to enrich weakly H-bonded (“free”) H2O at active sites. Operando Raman spectroscopy captures, at lower potentials, the accelerated conversion of H-bonded water into free-H2O, while 18O differential electrochemical mass spectrometry confirms markedly suppressed lattice-oxygen contributions from the surface oxide layer, indicating a shift from the LOM (lattice oxygen mechanism) to the AEM (adsorbate evolution mechanism)-dominated pathway. Kinetic isotope effects, Tafel-isotope analyses, and thermodynamic–kinetic simulations further reveal lowered barriers for water dissociation and accelerated proton-coupled electron transfer. Consequently, IrAu0.12@TiO2 delivers 10 mA cm–2 at 230 mV and a mass activity of 633.7 A gIr–1 at 275 mV and sustains PEMWE operation for 510 h at 1 A cm–2 with 98.2% retention. This work highlights interfacial water microenvironment engineering as a generalizable route to couple high activity with long-term durability in acidic OER electrocatalysts for PEMWE anodes.