In-situ preparation of Fe3O4/graphene nanocomposites and their electrochemical performances for supercapacitor

Fe3O4 has a broad application prospect in electrode materials of supercapacitors due to its high theoretical specific capacitance, low cost, and environmental friendliness. However, its easy agglomeration property and low charge/discharge cycle stability limit its further application. In order to overcome these issues, the preparation conditions for Fe3O4 nanoparticles with high specific capacitance were optimized. Then the Fe3O4 was used as the feedstock to prepare the Fe3O4/graphene nanocomposites using solvothermal method for the in-situ reduction of graphene oxide and the combination of Fe3O4 nanoparticles with graphene. The Fe3O4 nanoparticles, graphene oxides and Fe3O4/graphene nanocomposites were characterized by X-ray diffraction (XRD), N2 adsorption, Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM). The capacitance and stability of these samples were obtained from charge/discharge curves and cyclic voltammograms. The results show that during preparation process, Fe3+ ions could combine with the O-containing functional groups on the surface of graphene oxide to form Fe3O4 nanoparticles, and the graphene oxide could be in-situ reduced to form graphene simultaneously. This could effectively prevent aggregation of Fe3O4 and stacking of graphene as electrode materials. Moreover, the optimal conditions for preparing Fe3O4/graphene nanocomposites (BF24G60) are 60% of graphene theoretical percentage in Fe3O4/graphene nanocomposites, 205 °C of preparation temperature, and 24 h of reaction time. For the BF24G60 sample, it has excellent cycle stability (93% after 500 cycles) and specific capacitance (300 F/g at 0.4 A/g), which is higher than that of the single graphene (77 F/g) and Fe3O4 nanoparticles (222 F/g).