A Complex Oxide Containing Inherent Peroxide Ions for Catalyzing Oxygen Evolution Reactions in Acid.

Proton exchange membrane water electrolyzers powered by sustainable energy represent a cutting-edge technology for renewable hydrogen generation, while slow anodic oxygen evolution reaction (OER) kinetics still remains a formidable obstacle that necessitates basic comprehension for facilitating electrocatalysts' design. Here, we report a low-iridium complex oxide La _1.2 Sr _2.7 IrO _7.33 with a unique hexagonal structure consisting of isolated Ir(V)O ₆ octahedra and true peroxide O ₂ ^2- groups as a highly active and stable OER electrocatalyst under acidic conditions. Remarkably, La _1.2 Sr _2.7 IrO _7.33 , containing 59 wt % less iridium relative to the benchmark IrO ₂ , shows about an order of magnitude higher mass activity, 6-folds higher intrinsic activity than the latter, and also surpasses the state-of-the-art Ir-based oxides ever reported. Combined electrochemical, spectroscopic, and density functional theory investigations reveal that La _1.2 Sr _2.7 IrO _7.33 follows the peroxide-ion participation mechanism under the OER condition, where the inherent peroxide ions with accessible nonbonded oxygen states are responsible for the high OER activity. This discovery offers an innovative strategy for designing advanced catalysts for various catalytic applications.