▎ 摘　　要

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 O-2 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. (C) 2015 Elsevier Ltd. All rights reserved.