Kinetically Constrained Semicrystallization of IrO₂ with Balanced Activity and Stability for Acidic Oxygen Evolution Reaction

The activity–stability trade-off for IrO₂ constrains the development of proton exchange membrane water electrolyzers (PEMWEs). Conventionally, high IrO₂ crystallinity ensures oxygen evolution reaction (OER) stability while compromising activity, while amorphous structure offers high OER activity while sacrificing durability. Herein, we develop a kinetically constrained amorphization strategy using high-temperature thermal shock to precisely tune IrO₂ crystallinity, capturing an ideal intermediate state: low-crystallinity IrO₂ (LC-IrO₂). LC-IrO₂ merges the high activity of amorphous IrO₂ derived from the short-range order and the robust stability of crystalline IrO₂ with structural rigidity. Consequently, the LC-IrO₂ catalyst simultaneously achieves excellent catalytic activity and stability for acidic OER. A PEMWE using a LC-IrO₂ anode requires only 1.69 V to reach 1 A cm^–2 at 60 °C and maintains steady operation for 500 h with a negligible degradation rate. This study demonstrates kinetic crystallinity control as a new paradigm for electrocatalyst design.