Defect‐Engineered IrO _x @Perovskite Heterostructures via Thermal Reconstruction for Acid‐Stable Oxygen Evolution Catalysis

ABSTRACT Perovskite‐type oxides hold promise as supports for Ir‐based acidic oxygen evolution reaction (OER) catalysts, yet their instability under harsh conditions limits practical application. Defect engineering of IrO _x ‐perovskite heterostructures offers new opportunities for acidic oxygen evolution catalysis. Here, we demonstrate thermal‐reconstructed oxygen defect regulation in IrO _x @La _1.2 Sr _0.8 Ni _0.6 Fe _0.4 O _4+δ (IrO _x @LSNF) catalysts, where controlled calcination induces in situ growth of oxygen‐deficient amorphous IrO _x on Ruddlesden‐Popper perovskite. Thermal reconstruction at 250°C generates oxygen‐defect‐rich amorphous IrO _x on LSNF (IrO _x @LSNF‐250), creating strong metal‐metal oxides support interaction (MMSI) that enhances active‐site utilization while favoring the lattice oxygen participation mechanism (LOM) for superior OER activity. Remarkably, the perovskite‐anchored IrO _x heterostructure maintains considerable durability in half‐cell acidic media against LOM‐induced collapse, demonstrating how defect‐engineered thermal reconstruction simultaneously addresses activity‐stability trade‐offs in acidic OER catalysis. The optimized OER performance of IrO _x @LSNF‐250 in acidic media are attributed to perovskite‐anchored Ir species suppressing dissolution, together with thermal‐reconstruction‐enriched oxygen defects optimizing LOM. This work establishes a paradigm for defect‐engineered heterostructures via thermal reconstruction, advancing perovskite‐based OER catalysts beyond conventional stability‐activity trade‐offs in acidic media.