The coaxial nanostructure of ruthenium oxide thin films coated onto the vertically grown graphitic nanofibers for electrochemical supercapacitor

In this work, the coaxial nanostructure of ruthenium oxide (RuOx) thin films coated onto the surface of the vertical graphitic nanofibers (GNFs) was developed and employed as electrodes for electrochemical supercapacitor. The vertically aligned GNFs were directly grown on the fluorine doped tin oxide glass via the chemical vapor deposition, and the RuOx thin films were prepared by an easy cyclic voltammetric electrochemical deposition. The morphologies and nanostructures of the coaxial-nanostructure RuOx/GNFs were investigated by the field emission gun scanning electron microscopy and the high-resolution transmission electron microscopy, respectively. Raman spectrum was used to examine the characteristic features of the RuOx/GNFs. The electrochemical properties were examined by cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectra. The directly grown GNFs not only played the attractive template that offered a large surface area to promote the loading of RuOx for enhancing electrochemical activity, but also provided a high-speed pathway that promoted charge transport and transfer. The macroporous structure of the vertically coaxial-nanostructure RuOx/GNFs avoided the self-aggregation, thus allowed the electrolyte can easily diffuse through the open space between them to enhance the electrochemical performance. The electrochemical measurements revealed that the excellent charge storage properties of the RuOx/GNFs can be obtained, the good electrochemical performance was attributed to the unique macroporous structure and the coaxial nanostructure of RuOx/GNFs.