Breaking the Mutual-Constraint of Bifunctional Oxygen Electrocatalysis via Direct O─O Coupling on High-Valence Ir Single-Atom on MnOx.

Abstract

Insufficient bifunctional activity of electrocatalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is the major obstruction to the application of rechargeable metal-air batteries. The primary reason is the mutual constraint of ORR and OER mechanism, involving the same oxygen-containing intermediates and demonstrating the scaling limitations of the adsorption energies. Herein, it is reported a high-valence Ir single atom anchored on manganese oxide (Ir_SA-MnO_x) bifunctional catalyst showing independent pathways for ORR and OER, i.e., associated 4e^- pathway on high-valence Ir site for ORR and a novel chemical-activated concerted mechanism for OER, where a distinct spontaneous chemical activation process triggers direct O─O coupling. The Ir_SA-MnO_x therefore delivers outstanding bifunctional activities with remarkably low potential difference (0.635 V) between OER potential at 10 mA cm^-2 and ORR half-wave potential in alkaline solution. This work breaks the scaling limitations and provides a new avenue to design efficient and multifunctional electrocatalysts.