Magnetite ultrafine particles/porous reduced graphene oxide grown onto Ni foam as a binder-free electrode for supercapacitors.

Here, we report a simple and green electrochemical route to fabricate a porous network of a FeO nanoparticle-porous reduced graphene oxide (p-rGO) nanocomposite supported on a nickel-foam substrate, which is directly used as a binder-free charge storage electrode. Through this method, pristine FeO NPs/Ni, p-rGO/Ni and FeO NPs@p-rGO/Ni electrodes are fabricated and compared. In the fabricated FeO NPs@p-rGO/Ni electrode, the porous rGO sheets served as a conductive network to facilitate the collection and transportation of electrons during the charge/discharge cycles, improving the conductivity of magnetite NPs and providing a larger specific surface area. As a result, the FeO NPs@p-rGO/Ni exhibited a specific capacitance of 1323 F g at 0.5 A g and 79% capacitance retention when the current density is increased 20 times, where the FeO NPs/Ni electrode showed low specific capacitance of 357 F g and 43% capacity retention. Furthermore, the composite electrode kept 95.1% and 86.7% of its initial capacitances at the current densities of 1 and 4 A g, respectively, which were higher than those of a FeO/NF electrode at similar loads ( 80.4% and 65.9% capacitance retentions at 1 and 4 A g, respectively). These beneficial effects proved the synergistic contribution between p-rGO and FeO. Hence, such ultrafine magnetite particles grown onto a porous reduced GO network directly imprinted onto a Ni substrate could be a promising candidate for high performance energy storage aims.