Manganese Oxide/Carbon Nanofibers-Embedded Graphene Sheets for Capacitors

We report the fabrication of a ternary nanoarchitecture consisting of manganese oxide (MnO), carbon nanofibers (CNFs), and reduced graphene oxide sheets and their application to supercapacitor electrodes. MnO nanoclustersdecorated CNFs (MCNFs) with diameters of about 50 nm were prepared via single-nozzle co-electrospinning. The MCNFs were readily embedded into graphene sheets via hydrophobic interaction in aqueous solution. Importantly, this straightforward synthesis process readily affords product on a scale of tens of grams. The embedded MCNFs prevent the irreversible aggregation of graphene sheets and allow an opened microstructure inside the nanoarchitectures. The specific capacitances of the resulting nanoarchitectures were examined in an acidic electrolyte and found to be 50 to 200 F g−1 depending on the amount of reduced graphene oxide. The capacitances were higher than those of control samples (only reduced graphene oxide or MCNFs), which was probably due to the synergistic effect of the individual components. Moreover, the graphene sheets separated by the MCNFs boost the electrochemical performance of the nanoarchitecture electrodes. These electrodes exhibit enhanced specific capacitances compared with a sheet electrode fabricated of MCNF-only or RGO-only. The RGO sheet acts as a conductive channel inside the nanoarchitecture, while the intercalated MCNFs increase the efficiency of the ion and charge transfer in the nanoarchitecture. The ultrathin CNFs, which might be a promising alternative to carbon nanotubes, overcome the low electrical conductivity of the excellent pseudocapacitive component, MnO. It is expected that these structural characteristics will make the ternary nanoarchitectures promising candidates for various applications in the areas of composite science, separation/filtration, and energy conversion/storage.