Freestanding composite electrodes of MnOxembedded carbon nanofibers for high-performance supercapacitors

Manganese oxide/carbon nanofiber (MnOx/CNF) composites were successfully fabricated as freestanding electrodes through incorporating different manganese sources of nanostructured MnO2 or Mn(CH3COO)2·4H2O into polyacrylonitrile (PAN) solution by electrospinning and a subsequent carbonization method. The MnO2 with a rod-like hierarchical core–corona nanostructure was self-prepared by a hydrothermal method using polyvinylpyrrolidone (PVP) to control the size and morphology of nanoparticles. The morphologies and structures of the MnOx/CNF composites were characterized by means of field emission scanning electron microscopy, transmission electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy. MnOx/CNFs produced from Mn(CH3COO)2·4H2O exhibited good flexibility with uniform dispersion of small MnOx particles in the loose structures of the CNFs. In contrast, MnOx/CNFs derived from MnO2 displayed relative brittle mechanical properties. The electrochemical performances of the two composites were investigated by cyclic voltammetry, galvanostatic charging/discharging and impedance measurement techniques. The resulting MnOx/CNFs demonstrated excellent electrochemical performance with great rate capability, low internal resistance and long-term cycling stability. Composites produced from Mn(CH3COO)2·4H2O delivered a specific capacitance of 211 F g−1 at 0.25A g−1 in 0.5 M Na2SO4 electrolyte These results suggest that such freestanding MnOx/CNF composites would be promising electrodes for high-performance supercapacitors.