Capacitive behaviour of thermally reduced graphene oxide in a novel ionic liquid containing di-cationic charge

• An ionic liquid (IL) with di-cationic group was prepared for evaluation of supercapacitive behaviour.
• Morphology and electrochemistry of graphene oxide (GO) and thermally reduced graphene oxide (rGO) before/after reduction were studied.
• Capacitances of GO and rGO were 23 F g−1 and 155 F g−1, respectively.
• Charge transfer resistances of the rGO electrode were 18.3 Ω in 0.1 M LiClO4, and 12.8 Ω in 0.1 M IL.
• Cycling durability of rGO exhibited 90.6% retention after 2000 cycles in IL, but 64% in 0.1 M LiClO4.

A novel ionic liquid (IL) with di-cationic group was synthesized and used to evaluate the supercapacitive behaviour of a thermally reduced graphene oxide (rGO) in comparison with aqueous LiClO4 electrolyte. The morphological properties of GO and thermally reduced GO were characterized by XRD, TEM, Raman spectroscopy, and rGO was found to have a typical structural nature after thermal reduction. The electrochemical performance of the GO and rGO were studied using cyclic voltammetry, impedance spectroscopy and galvanostatic charge/discharge in two different aqueous electrolytes, 0.1 M C6(TMA)2(BF4)2 and 0.1 M LiClO4, respectively. Superior capacitive properties were observed from rGO in both the electrolytes than that of GO electrode. Maximum specific capacitances of 102 F g−1 and 155 F g−1 from rGO were obtained in 0.1 M LiClO4 and C6(TMA)2(BF4)2, respectively, at a scan rate of 10 mV s−1, and that are higher than that of GO (12 F g−1 and 23 F g−1 in 0.1 M LiClO4 and C6(TMA)2(BF4)2, respectively). The charge transfer resistances of the rGO electrode were 18.3 Ω for 0.1 M LiClO4, and 12.8 Ω for 0.1 M C6(TMA)2(BF4)2. The rGO electrode also exhibited a desirable profile and maintained over 90.6% of its initial capacitance after 2000 cycles, while 63.8% retention was observed in 0.1 M LiClO4, indicating that it has an excellent cycling performance and structural stability in IL compared with the other electrolyte.