Dependence of Electrolyte Medium to Performance of Reduced Graphene Oxide (R-GO) based Supercapacitor

Abstract

Supercapacitors (SCs) play a crucial role in energy storage applications. SCs store and release energy by maintaining an electrostatic charge at the interface between the electrode and an electrolyte solution. Key advantages of SCs include their high capacitance, long cycle life and high power density. However, they typically have lower energy density compared to traditional batteries. Reduced graphene oxide (R GO) is a highly significant electrode material for SCs due to its unique combination of properties such as high electrical conductivity, large surface area, chemical stability and easy functionalization that enhance the performance of SCs. The electrolyte is responsible for facilitating the movement of ions between the electrodes during the charging and discharging cycles. In this study, R-GO was synthesized from natural graphite using the modified Hummers method. The process began with the oxidation of graphite powder using a mixture of oxidizing agents, 98% concentrated sulfuric acid (H2SO4) and potassium permanganate and sodium nitrate. A reducing agent, hydrogen peroxide was employed to chemically reduce the GO. Creating an electrode for the SC was begun by dispersing R-GO in dimethylformamide (DMF). Titanium dioxide (TiO2) was used as binder. R-GO/TiO2 suspension was coated onto a conductive substrate, fluorine-doped tin oxide (FTO). Upon deposition, the DMF solvent was evaporated, leaving behind a well-structured R-GO layer on the substrate. 2M H2SO4 and Lithium trifluoromethenesulfonate (LiCF3SO3) were used as electrolytes separately. This study explores the performance of SCs utilizing acidic electrolytes in comparison to ionic liquid electrolytes. This research reveals that R-GO based SCs exhibit the highest specific capacitance values of 146 F g-1 and 59 F g-1 at 2 mV s-1 with H2SO4 and LiCF3SO3 electrolytes respectively. Moreover, the study demonstrates the maximum energy density is 17.07 Wh kg-1 and 2.39 Wh kg-1 at 0.5 mA current for acidic and ionic liquid electrolytes respectively, emphasizing their capability to deliver and absorb energy. The study also shows the maximum power density 17.57 kW kg-1 achieved with ionic liquid electrolyte and 81.5 kW kg-1 with acidic electrolyte at 5 mA. In conclusion, this abstract underscores the pivotal role of electrolyte selection in determining the performance of R-GO based SCs. Additionally, the study reveals that R-GO-based SC shows higher performance with acidic electrolytes.