Fe3O4@C core-shell microspheres: synthesis, characterization, and application as supercapacitor electrodes

Fe3O4@C microspheres with diameter of about 400 nm and carbon layer thickness of about 30 nm have been successfully prepared through solvothermal reactions and subsequent calcination under the protection of Ar. The composition, structure, and morphological characteristics were studied by X-ray diffraction (XRD), energy-dispersive spectrometry (EDX), field emission scanning electron microscopy (FESEM), and transmission electron microscopy (TEM). The Fe3O4@C microspheres can maintain a maximum specific capacitance of 110.8 F g(-1) at current density of 0.5 A g(-1), higher than pure Fe3O4 (67.9 F g(-1)). After 2,000 electrochemical cycles, the Fe3O4@C electrode still remaining 95.6 % of the highest specific capacitance, indicating its good cycle stability. The results show that the Fe3O4@C microspheres are promising electrode materials for high performance supercapacitors.