▎ 摘　　要

Solid electrocatalysts of iron phthalocyanine (FePc) embedded in 3D porous N-doped graphene aerogel (NGA) are designed and applied as cathode catalysts for non-aqueous lithium-oxygen (Li-O-2) batteries. Two composites with different axial bonding types between FePc and NGA, including a coordinate covalent bond (FePc/NGA-c) and non-covalent pi-pi stacking interaction (FePc/NGA-pi), are fabricated by reflux and physical mixing methods, respectively. Systematical characterizations confirmed the FePc/NGA-c composite using axial coordination between FePc and NGA substrate via the Fe-N-C bond exhibited more thermal stability and less stack and aggregation of FePc molecules in the composite. Combining the bifunctional catalytic activity of the FePc molecule with oxygen reduction reaction/oxygen evolution reaction (ORR/OER) processes and a flexible porous 3D structure and N-doping in NGA, the electrochemical test demonstrated both FePc anchored on NGA composites display higher activity as bifunctional catalysts for O-2 electrodes in Li-O-2 batteries. However, the FePc/NGA-c electrode displays better electrochemical performance than the FePc/NGA-pi composite due to the axial covalent connection of the FePc catalyst with NGA substrate, leading to higher electrocatalytic activity and exceptional structural durability during cycling for FePc/NGA-c. This work provides new insight into the steric effect of the coordination bond between FePc and NGA on the electrocatalytic activity of O-2 electrodes. These results indicate our unique structural design of FePc/NGA-c using solid FePc axially anchored on NGA via covalent bonding is a promising cathode material for high performance of rechargeable Li-O-2 batteries. (C) 2018 Elsevier Ltd. All rights reserved.