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 mu g 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.

Automated summary

Ir-based perovskite oxides have shown promise as electrocatalysts for oxygen evolution reaction (OER) in an acidic medium, but their uncontrollable surface amorphization and structural instability have been major challenges. In this study, we report a high-yield chemical exfoliation method to obtain protonated colloidal nanosheets with an undamaged perovskite framework from Ruddlesden-Popper layered perovskite Sr2IrO4. These protonated perovskite nanosheets show potential to overcome the trade-off between OER activity and structural stability. The 2D morphology and uniformity of these nanosheets enable the fabrication of an ultralow-Ir-loading catalyst film with significantly higher activity and comparable Ir leaching to the IrO2 catalyst film during OER. The presence of structural hydroxyl groups on the surface of protonated nanosheets is found to contribute to the catalytic cycle of OER, representing a non-traditional adsorbate evolution mechanism for the protonated layered perovskite framework.