In situ growth of monodisperse Fe3O4 nanoparticles on graphene as flexible paper for supercapacitor

A well-organized Fe3O4/graphene sheet composite (GS/Fe3O4) paper has been constructed via a universal three-step method. A graphene oxide/Fe2O3 composite (GO/Fe2O3) dispersion is prepared followed by vacuum filtration of the dispersion to obtain a GO/Fe2O3 composite paper. Finally, heat treatment of the GO/Fe2O3 paper produces the GS/Fe3O4 paper. Fe3O4 nanoparticles of similar to 5 nm are grown in situ and uniformly anchored on graphene sheets by covalent chemical bonding. The three-dimensional (3-D) conductive paper provides good electrical contact and improves the dispersion of well-adhered Fe3O4 nanoparticles, further boosting the accessible capacity. Therefore, the GS/Fe3O4 paper exhibits excellent rate performance and cyclic stability as a flexible anode material for supercapacitors. The optimized GS/Fe3O4 paper could achieve a high specific capacitance of 368 F g(-1) at 1 A g(-1) and remain 245 F g(-1) at 5 A g(-1) after 1000 cycles, suggesting a promising application in the fabrication of flexible energy storage devices. This work opens up new insights into the design of GS/metal oxide paper as a flexible electrode.