Strain-Induced Dynamic Surface Exchange in Ternary Alloy Nanosponges for Stable PEM Water Electrolysis

The anodic oxygen evolution reaction (OER) in proton exchange membrane water electrolysis (PEMWE) struggles against a persistent trilemma: achieving low iridium loading without sacrificing activity or stability. To overcome this, we design ultrafine IrRuCu ternary alloy nanosponges featuring an "artery-capillary" hierarchical mass-transfer network, synthesized via surfactant-assisted ethylene glycol reduction and selective etching. This catalyst exhibits a distinct gradient core-shell architecture, where lattice mismatch from the Cu/Ru-rich core triggers significant tensile strain in the outer active Ir shell. Integrating a series of comprehensive in situ characterization and DFT calculations, we uncover a novel, non-destructive strain-induced dynamic surface exchange mechanism. Tensile strain upshifts the Ir d-band center from -2.3 to -1.7 eV, amplifying the covalency and electrophilicity of surface Ir-O bonds to assemble a dense hydroxyl network at open-circuit potential. This geometric-electronic modulation slashes the rate-determining ^*O to ^*OOH barrier. Active surface oxygen directly accelerates kinetics, while rapid water refilling prevents bulk dissolution. Consequently, the alloy nanosponges require a 220 mV overpotential at 10 mA cm^-2, boasting a mass-specific activity 59.2 times that of commercial benchmarks. Demonstrating over 4500 h of stability in industrial-scale PEMWE full-cells, this paradigm offers a compelling route toward economical green hydrogen.