Kinetically Constrained Semicrystallization of IrO 2 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.