One-step green and scalable dry synthesis of nitrogen-doped graphene-encapsulated Fe3O4 nanoparticles as high-performance supercapacitor electrode

Advanced electrode materials are of vital importance to the application of high-performance supercapacitors. However, most of the electrode materials are limited by their low specific capacitance and/or poor cycling stability. In this work, nitrogen-doped graphene-encapsulated Fe3O4 nanoparticles (Fe3O4@NG) were synthesized through a simple one-step green and scalable dry pyrolysis method, in which the uniform growth of Fe3O4 nanoparticles with a diameter of about 30–60 nm, the reduction of graphene oxide (GO), and the introduction of nitrogen atoms on graphene could be achieved simultaneously. The structure, composition, and electrochemical performance of the Fe3O4@NG samples were systematically characterized. Compared to pristine Fe3O4, Fe3O4@NG showed superior electrochemical performances, including an ultra-high specific capacitance of up to 740 F g−1 at the current density of 1 A g−1, a greatly improved rate capability of 56.8% with the increase in current density from 1 to 20 A g−1, and an excellent cycling stability with the retention ratio of 90.9% after 3000 cycles. Furthermore, after being placed in the external environment for one year, the specific capacitance retention of Fe3O4@NG could be as high as 98%, proving again that the as-prepared Fe3O4@NG exhibited perfect structural stability and excellent stable electrochemical properties. All of the results demonstrate an extraordinary performance of Fe3O4@NG, thus being potential for future practical applications.