▎ 摘　　要

The catalytic nature of iron-nitrogen-graphene (Fe-N-G) heterocatalysts with regards to the oxygen evolution reaction (OER) and the oxygen reduction reaction (ORR) were studied. By performing systematic density functional theory calculations of fourteen different atomic structures of iron/nitrogen/carbon compounds, multiple reaction active sites are found and compared, and manifold reaction pathways and relevant reaction mechanisms are defined. This study indicates that among various iron/nitrogen/carbon compounds, square planar Fe-N-G heterocatalysts are the most promising electrocatalysts for the OER and the ORR that favor dissociative reaction pathways. In addition, the crucial role of high mobility pi electrons in ortho-C atoms near embedded metal atoms is revealed via the molecular orbital theory. This study presents a new perspective with which to understand the catalytic mechanism of single-metal-atom embedded in graphene-based materials, which has become the most competitive catalyst with traditional electrocatalysts for renewable energy industries.