FeCo2O4/hollow graphene spheres hybrid with enhanced electrocatalytic activities for oxygen reduction and oxygen evolution reaction

Efficient bi-functional electrocatalysts with high durability are essential to the development of metal–air batteries, the performance of which is limited by the slow kinetics of oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) at the cathode. In this work, a covalently coupled FeCo2O4/hollow reduced graphene oxide spheres (FCO/HrGOS) hybrid with a 3D architecture has been fabricated step by step via an electrostatically induced assembly method. The covalent coupling between FCO and HrGOS along with the 3D architecture of FCO/HrGOS not only provides an efficient electron transport path but also facilitate the transport of electrolyte and O2 during the ORR and OER process in 0.1 M KOH aqueous solution. The ORR on FCO/HrGOS is mainly dominated by a 4e− reaction pathway. The as-prepared FCO/HrGOS exhibits comparable ORR activity and superior OER activity as compared to commercial Pt/C (20 wt.% Pt). Meanwhile, the stabilities of FCO/HrGOS toward both the ORR and OER are significantly higher than those of commercial Pt/C. The high electrocatalytic activity and durability of FCO/HrGOS hybrid are attributed to the covalent coupling between FCO and HrGOS as well as the 3D architecture of FCO/HrGOS built from the hollow graphene sphere.