Significantly enhanced performance of rGO/TiO2 nanosheet composite electrodes based 1.8 V symmetrical supercapacitor with use of redox additive electrolyte

Abstract

The role of redox additive electrolytes in supercapacitors is gaining an increased significance. The present research work, for the first time, investigates the supercapacitor performance of a rGO/TiO2 nanosheet composite (prepared via facile one step hydrothermal reaction route) electrode in combination with a redox additive electrolyte, i.e., 0.2 M K3[Fe(CN)6] in 1 M Na2SO4. The synergistic effects between the porous rGO/TiO2 nanosheet electrode and the optimized redox electrolyte have helped to achieve a significantly high specific capacitance of 1565 F/g at a current density of 3 A/g (working potential window = −0.1–0.5 V). This value of specific capacitance is much higher than achievable with the application of a plain aqueous electrolyte (e.g., 1 M Na2SO4). Furthermore, rGO/TiO2 nanosheet electrodes have been used to fabricate a symmetrical supercapacitor device which has delivered an excellent specific capacitance value of 204.5 F/g at a current density of 1.5 A/g. The device also yielded promising values of energy density (15.5 Wh/kg) and power density (1.1 kW/kg) apart from showing a long-term cyclic stability (∼87%) even after 1000 continuous charge-discharge cycles.