▎ 摘　　要

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. (C) 2020 Published by Elsevier B.V.