Activating the Bifunctionality of a Perovskite Oxide toward Oxygen Reduction and Oxygen Evolution Reactions.

This article presents a facile and effective approach to activate the bifunctionality of calcium-manganese perovskites toward the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). We substituted Nb into the Mn site of CaMnO (CMO) and treated the material with H. The as-obtained CaMnNbO (H-CMNO) displays the same structure as that of CMO, and compared to that of CMO, H-CMNO exhibits significantly improved OER performance, including a lower overpotential, a reduced Tafel slope, a higher mass activity, and enhanced stability. In addition, the ORR performance of H-CMNO is also greatly enhanced, relative to CMO, with a higher ORR activity and a more efficient electron-transfer pathway. H-CMNO shows an even higher activity-per-catalyst cost and superior stability than that of state-of-the-art materials, such as IrO and Pt/C. This great enhancement in ORR and OER activity of H-CMNO is attributed to several factors, including phase stabilization, optimized e filling, better OH adsorption, and improved electrical conductivity.