## 1 Introduction  
With the growing concerns regarding climate change and the depletion of fossil fuels, researchers have paid a great deal of attention towards developing high-performance energy storage devices. As an energy device, supercapacitors have drawn a great deal of interest from the point of view of research and applications because of their merits--their high power density, excellent efficiency, wide range of operation temperatures, long cycle life, and requiring very little maintenance [1; 2]. One type of a supercapacitor, called the electrical double layer capacitor (EDLC), stores energy in an electrical double layer through fast ion adsorption and desorption process at the interface between the electrolyte and electrode. Therefore, it would be vital to obtain an understanding of the charge dynamics of the ions, in both the electrode and electrolyte [3]. Our earlier investigations on the charge dynamics of ionic liquid between two electrodes reveal that, during the charging process, the mobile ions that participate in energy storage are mainly from the region near the electrode, rather than from the bulk of the electrolyte [4; 5]. Furthermore, the charging of the electrode is a combination effect of both the attractive and repulsive interactions, depending on the polarity of the ions [4; 6]. Therefore, the ionic species intercalated on, or near, the electrode would play an essential role in the performance of EDLC. However, based on the physical relation, the energy density is E = 0.5 CV\({}^{2}\), where C is the capacitance of the cell related to the surface area of the electrode and V is the applied voltage. Therefore, the improvements in EDLC cells are centered on developing highly conductive porous materials, discovering electrolytes with wide electrochemical windows and modifying the electrode/electrolyte interface properties. For high-performance electrolytes, a particular group of molten salts, called ionic liquids (ILs), are becoming favorable for EDLC applications. ILs possess qualities includinghigh conductivity, a wide electrochemical window, low viscosity, low volatility and a capacity for high stability at high temperatures [7,8]. However, ILs comprise of both cations and anions, and the size of these comprising ions could be large, which may hinder the ability of ILs regarding accessing small pores. On the other hand, reduced graphene oxide (RGO) is a promising high specific surface area materials for ion storage because of its high electrical conductivity and large, theoretical, specific surface area (2630 m\({}^{2}\)/g). Since graphene oxide (GO) can be obtained by the chemical oxidation of natural graphite particles, RGO has the potential to be mass produced [9,10]. GO is an amphiphile as a result of the defects and the attached hydrophilic oxygen groups that are introduced to the hydrophobic basal plane of graphene during the oxidation process. These attached hydrophilic oxygen functional groups could isolate the electrical conduction between GO particles and could disperse the GO as a few layers of sheets in water [11], whereas the thermal reduction process, provides an easy way for converting GO into thermally-reduced graphene oxides (TRG) by removing the attached oxygen groups at elevated temperatures. Without the use of strong chemical bases, it is a chemically free and environmentally-friendly process [12,13]. However, without the oxygen groups, the hydrophobic nature of TRG is almost water insoluble, thus hampering further processing of the material composites [11]. In the existing literature, ionic surfactants are often utilized to stabilize RGO suspensions in water and avoid the restacking of RGO in a solid form [14,15]. Ionic surfactants are amphiphilic compounds because they are composed of ionic hydrophilic head groups and extended apolar, hydrophobic tails. Thus, the surfactant can interact with the RGO surfactant through the static forces between the charged head groups and the residual oxygen groups.