Electrochemical Behavior of Carbon Nanostructured Electrode Material for Supercapacitor Application

Electrochemical capacitors or supercapacitor (SCs) have been considered as one of the most promising energy storage devices for portable electronics, hybrid electric vehicles and stand-by power system. Especially in electric vehicles, SCs can couple with a fuel cell or battery to store and deliver the energy at a short period of time. Since, SC stores energy by electrostatic interaction between electrode-electrolyte interfaces based on the Electrical double layer phenomenon, so the amount of charge stored directly dependent on the surface area of any electrode material [1,2]. Porous carbon material recognized as a potential electrode material for SC owing to large surface area, chemical stability and low cost [3]. A large variety of porous carbons, such as activated carbons, aerogels, templated carbons, carbide-derived, carbon nanotubes, graphene and carbon nanofibers have been studied as EC electrode materials. However, many of the carbonaceous materials showed disadvantages such as the high ionic resistance, low electrical conductivity and low compatibility of conductive pathways to store charge, which unfavorable for high energy storage and high power devices criteria. So the performance of ECs does not only depends on the physical, but also intimately on the chemical properties of the electrode material. So the strategy of pseudocapacitance is required in the carbon framework. It has been reported that hetero atom (N, S, P and B) doping on carbon structure enhances the surface wettability as well as the electronic conductivity of the materials without compromising the long term cycle stability [4].

In the present work, we have investigated the morphological effect of nitrogen doped three different carbon nano-structures. Different nano-structures electrode materials such as rod, hollow and boat shaped are prepared using a coaxial electro-spinning technique and followed by carbonization, under inert (Ar.) atmosphere. The x-ray diffraction, Raman spectroscopy, x-ray photo-electron microscopy and high resolution transmission electron microscopy results reveal the synthesized carbon materials exhibit turbo-static carbon with poor sp² graphitic carbon. The electrochemical properties of all the three electrode materials have been studied using cyclic voltammogram and galvanostatic charge-discharge using a symmetric type two electrode system configuration with  aqueous as electrolyte medium, and analyzed to know their electrochemical properties. Long term cycle stability tests show excellent capacity retention.

References

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(2). R. Kotz, M. Carlen, Electrochim. Acta., 45, (2000) 2483-2489.

(3). E. Frackowiak, F. Be´guin, Carbon, 39 (2001) 937-950.

(4). D. Hulicova, M. Kodama, H. Hatori, Chem. Mater., 18 (2006) 2318-2326.