Soft Nanoscience Letters, 2012, 2, 59-66 http://dx.doi.org/10.4236/snl.2012.24011 Published Online October 2012 (http://www.SciRP.org/journal/snl) 59 Functionalized Exfoliated Graphene Oxide as Supercapacitor Electrodes Prasanna Karthika, Natarajan Rajalakshmi * , Kaveripatnam S. Dhathathreyan Centre for Fuel Cell Technology, International Advanced Research Centre for Powder Metallurgy and New Materials, IITM Re- search Park, Chennai, India. Email: * lakshmiraja2003@yahoo.com Received July 31 st , 2012; revised August 31 st , 2012; accepted September 16 th , 2012 ABSTRACT Functionalized exfoliated graphene oxide (EGO) for supercapacitor electrodes have been synthesized by simple chemi- cal methods from the exfoliated graphite (EG) as precursor. Structural and morphological characterizations of EGO have been carried out using X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), FTIR and Raman spec- troscopy. Electrochemical performance of these electrodes has been investigated using cyclic voltammetry, gal- vanostatic charge-discharge, and electrochemical impedance spectroscopy. The fabricated supercapacitor gave a spe- cific capacitance of 146 Fg –1 and energy density of 20 Wh·kg –1 for a highly oxidized sample with more functional groups compared to pure, lower level oxidized and reduced samples. The single and multi layered graphene oxide sheets produced by this method have a lower degree of agglomeration. We found that the graphene oxide with func- tional oxygen groups of quinine type enhances the capacitance compared to other oxygen functional groups. Keywords: Graphene; Supercapacitor; Functionalization; Exfoliation; Carbon 1. Introduction Supercapacitors based on electrochemical double layer capacitance (EDLC) are electrical energy storage devices that store and release energy by charge separation at the electrochemical interface between an electrode and an electrolyte [1]. These capacitors have an extremely high energy density compared to conventional dielectric capacitors, as the energy stored is inversely proportional to the thickness of the double layer and they are able to store a large amount of charge which can be delivered at much higher power ratings than rechargeable batteries. They can be used in a wide range of energy capture and storage applications and are used stand alone as the primary power source or in combination with batteries or fuel cells due to their advantages like high power capability, long life, a wide thermal operating range, low weight, flexible packaging, and low maintenance. In addition to the EDLCs another class of supercapacitor that is based on pseudocapacitance can also is employed, where the storage mechanism is based on faradic, and redox reactions occur using electrode materials such as electrically conducting polymers and metal oxides. Though the energy densities of pseudocapacitance based devices are greater than EDLCs, the phase changes within the electrode due to the faradic reaction limit their lifetime and power density [2-4]. Supercapacitors use nanoporous electrodes based on carbon materials like VulcanXC, Acetylene Black, Car- bon Nnaotubes etc., to store large amounts of charge on their high surface areas, and use the ions in electrolytes to carry charge into the pores. Their high power density makes them a potentially useful complement to batteries. However, ion transport through long, narrow channels still limits power and efficiency in these devices [5]. Various conducting polymers have also been widely studied as electrode materials for supercapacitors becau- se of their high capacitance, easy production, and low cost. However, poor conductivity and weak flexibility of conducting polymers limit them from usage in high performance flexible supercapacitors. Graphene, a two dimensional carbon material, has attr- acted much research attention due to several breakth- roughs in fundamental research and for practical appli- cations [6-18]. In contrast to the conventional high surfa- ce area materials, the effective surface area of graphene materials as capacitor electrode materials does not depe- nd on the distribution of pores at solid state, which is different from the current supercapacitors fabricated with activated carbons and carbon nanotubes [19]. Graphene oxide, existing as individual layered sheets, can be an ideal electrode material as their graphene sides could be exposed to electrolyte with possibly high surface area * Corresponding author. Copyright © 2012 SciRes. SNL