Protonated Iridate Nanosheets with a Highly Active and Stable Layered Perovskite Framework for Acidic Oxygen Evolution

Ir-based perovskite oxides show great promise for next-generation oxygen evolution reaction (OER) electrocatalysts in an acidic medium, but they are generally stuck with their uncontrollable surface amorphization and thus structural instability (e.g., serious Ir leaching) during OER. Herein, we report the high-yield chemical exfoliation of Ruddlesden-Popper layered perovskite Sr₂IrO₄ into protonated colloidal nanosheets with an undamaged perovskite framework. We further demonstrate the potential of protonated perovskite nanosheets to evade the trade-off between OER activity and structural stability. The 2D morphological benefit and nice monodispersity of these protonated perovskite nanosheets enable the facile fabrication of an ultralow-Ir-loading catalyst film (30 μg cm^-2), which exhibits about 10 times higher activity than the IrO₂ catalyst film and undergoes almost as much Ir leaching during OER. Our joint experimental and theoretical results also reveal that structural hydroxyl groups on the surface of protonated nanosheets participate in the catalytic cycle of OER, and the protonated layered perovskite framework represents an example of OER electrocatalyst that works with a non-traditional adsorbate evolution mechanism.