Ferromagnetic ordering correlated strong metal–oxygen hybridization for superior oxygen reduction reaction activity

Abstract

The efficiency of transition-metal oxide materials toward oxygen-related electrochemical reactions is classically controlled by metal–oxygen hybridization. Recently, the unique magnetic exchange interactions in transition-metal oxides are proposed to facilitate charge transfer and reduce activation barrier in electrochemical reactions. Such spin/magnetism-related effects offer a new and rich playground to engineer oxide electrocatalysts, but their connection with the classical metal–oxygen hybridization theory remains an open question. Here, using the Mn x V y O z family as a platform, we show that ferromagnetic (FM) ordering is intrinsically correlated with the strong manganese (Mn)–oxygen (O) hybridization of Mn oxides, thus significantly increasing the oxygen reduction reaction (ORR) activity. We demonstrate that this enhanced Mn–O hybridization in FM Mn oxides is closely associated with the generation of active Mn sites on the oxide surface and obtaining favorable reaction thermodynamics under operating conditions. As a result, FM-Mn 2 V 2 O 7 with a high degree of Mn–O hybridization achieves a record high ORR activity. Our work highlights the potential applications of magnetic oxide materials with strong metal–oxygen hybridization in energy devices.