Design of Highly Active and Stable Bifunctional Electrocatalysts for Oxygen Reactions

Abstract

A new design strategy for the development of bifunctional electrocatalysts capable of catalyzing both the oxygen evolution reaction (OER) and the oxygen reduction reaction (ORR) is proposed. In this strategy, the MnOx lattice is doped with either electropositive (Sr, Ba) or electronegative (Bi, Pb) elements that results in the coincorporation of electron-rich donor (Mn2+) and electron-poor acceptor (Mn4+) defects in the same parent (Mn3+) lattice. These defects effectively catalyze the reduction (ORR) and oxidation (OER) processes on the same electrode surface. This study is based on the results of a previous study on Mn2O3 that showed Mn2+ and Mn4+ as the active sites for ORR and OER processes, respectively. Our results show that BiMnOx is the most promising bifunctional catalyst with OER/ORR activities that are comparable to the individual activities of state-of-the-art commercial Pt or RuO2 catalysts. Stability tests show the catalyst to be stable for more than 3 h of continuous OER or ORR polarization. This work provides a pathway for the individual tuning of defects to control electrocatalytic activities, which opens up new possibilities for the rational design of many perovskite-based oxides.