Strain‐Directed Ru Redistribution to Form RuO ₂ /Pt Mosaic Heterointerfaces for Acid‐Stable Water Oxidation

ABSTRACT Doping Ru oxides with heteroatoms such as Pt can mitigate their intrinsic redox instability by redistributing charge at the interface during acidic OER conditions; however, achieving atomically intimate Pt–Ru configurations remains challenging because conventional synthesis routes cannot reliably juxtapose the two elements at structurally compatible catalytic sites. Here, we report a strain‐driven atomic migration strategy that enables controlled redistribution of Ru from the exterior to the interior of PtNi multiframe during thermal oxidation. Redox‐induced Ni oxidation generates lattice strain that drives inward Ru migration, leading to the formation of RuO ₂ /Pt mosaic heterointerfaces throughout the open framework. These heterointerfaces create a Pt‐biased redox environment that stabilizes Ru ⁴⁺ while strongly suppressing lattice oxygen participation. Operando XAFS and ¹⁸ O‐labeled DEMS reveal that this Pt–Ru redox asymmetry underpins the remarkable stability, while interfacial electronic modulation steers the reaction toward an adsorbate evolution mechanism‐dominated pathway with more favorable intermediate energetics. Consequently, the catalyst delivers an ultralow overpotential of 168 mV at 10 mA cm ⁻² and maintains stable operation for over 540 h. Overall, this work establishes strain‐directed atomic migration as a versatile post‐synthetic route for constructing redox‐stabilized heterointerfaces, providing a broadly applicable design principle for highly active and durable water‐splitting electrocatalysts.