Carbothermal Synthesis of Nitrogen-Doped Graphene Composites for Energy Conversion and Storage Devices

Metal oxides and carbonaceous composites are both promising materials for electrochemical energy conversion and storage devices, such as secondary rechargeable batteries, fuel cells and electrochemical capacitors. In this study, Fe₃O₄ nanoparticles wrapped in nitrogen-doped (N-doped) graphene nanosheets (Fe₃O₄@G) were fabricated by a facile one-step carbothermal reduction method derived from Fe₂O₃ and liquid-polyacrylonitrile (LPAN). The unique two-dimensional structure of N-doped graphene nanosheets, can not only accommodate the volume changes during lithium intercalation/extraction processes and suppress the particles aggregation but also act as an electronically conductive matrix to improve the electrochemical performance of Fe₃O₄ anode, especially the rate capability. What's more, by etching Fe₃O₄@G to remove the iron-based oxide template, porous N-doped graphene composites (NGCs) were prepared and presented abundant pore structure with high specific surface area, delivering a specific capacitance of 172 F·g^-1 at 0.5 A·g^-1. In this way, Fe₂O₃ was both template and activator to adjust the pore size of graphene. And the effect of specific surface area and pore size tuned by the Fe₂O₃ activator were also revealed.