▎ 摘　　要

Transition-metal-coordinated nitrogen-doped carbon (M-N-C) materials have been regarded as the most promising oxygen reduction reaction (ORR) catalysts. However, the ambiguity of the exact active sites seriously hampered the understanding of the structure-performance correlation and the further activity improvement of M-N-C catalysts. Herein, we designed and synthesized a three-dimensional graphene aerogel (GA) supported FeN5 composite with an explicit five-coordinated Fe-N bond. In this composite, pyridine groups were covalently grafted on the graphene surface to anchor iron phthalocyanine (FePc) molecules (FePc/AP-GA). The ORR performance of this catalyst showed a half-wave potential of -0.035 V (vs. Hg/HgO) in an alkaline electrolyte, which surpassed those of the benchmark Pt/C and most pyrolyzed or non-pyrolyzed nonprecious metal catalysts. Additionally, the FePc/AP-GA composite also exhibited a high kinetic current density of 20.01 mA cm(-2) at -0.1 V, good durability, and high tolerance to methanol poisoning effects. X-ray absorption spectroscopy results revealed that the five-coordinated Fe-N bond dominated in the FePc/AP-GA composite with an elongated bond length. This geometric and electronic structure of the iron atom in the FePc/AP-GA composite is believed to facilitate the adsorption of O-2 and intermediates and thus to enhance ORR activity and durability. Our results provided a promising target active site for the rational design of highly efficient M-N-C catalysts for fuel cells and metal-air batteries.