Synergetic contribution of Co3+/Co2+ and FeNC in CoFe@CoFe2O4 toward efficient electrocatalysts for oxygen reduction reaction

Abstract

The design and synthesis of non-noble metal nanomaterials as highly activity and durability electrocatalysts for oxygen reduction reaction (ORR) is of great importance for realizing practical applications of many electrochemical energy conversion and storage devices. Here, we report a Co3+/Co2+ redox couple tuned FeNC electrocatalysts with highly activity toward ORR. The electrons at the Fe-N active site are redistributed and Fe-N binding energy is negatively shifted about 2 eV due to the addition of the proper Co3+/Co2+ redox couple, resulting in a great increase of the specific content of pyrrolic N. Owing to the synergetic contribution of Co3+/Co2+ redox couple and FeNpyrrolicC, CoFe@CoFe2O4-N-C electrocatalysts after modulating the active site structure show better electrochemical performance than the electrocatalysts with monometallic FeNpyridinicC or CoNpyrrolicC component, and outperform the commercial Pt/C catalysts. KSCN poison measurements furtherly reveal that the increased Fe2+ content facilitates the activity of FeNpyrrolicC. This work not only opens up a new strategy to tailor the charge distribution of an active site toward enhanced activity but also provides insights into the fundamental understanding of the synergetic contribution of bimetal for ORR electrocatalysis.