Electrochemical behavior of graphene nanosheets in alkylimidazolium tetrafluoroborate ionic liquid electrolytes: influences of organic solvents and the alkyl chains

Abstract

In this study, the electrochemical properties of graphene nanosheets (GNSs) in alkylimidazolium tetrafluoroborate ionic liquids/organic solvent electrolytes are investigated by cyclic voltammetry (CV), galvanostatic charge/discharge and electrochemical impedance spectroscopy (EIS). The organic solvents with different functional groups exhibit a significant influence on the electrochemical properties of the GNSs. From series of organic solvents, in 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIMBF₄)/N,N-dimethylformamide (DMF, C₃H₇NO) electrolyte the GNS electrode shows the best electrochemical performance. Furthermore, the effect of the alkyl chains of ionic liquids on the electrochemical properties of GNSs was also evaluated through the electrochemical tests. The electrochemical properties of GNS electrode in 1-methyl-3-methylimidazolium tetrafluoroborate (MMIMBF₄)/DMF electrolyte are better than those in EMIMBF₄/DMF and 1-butyl-3-methylimidazolium tetrafluoroborate (BMIMBF₄)/DMF electrolytes. This may be attributed to the difference in the length of the alkyl chain on the imidazole ring, which results in the structural change of the electrode/ionic liquid interface and thus affects the electrochemical performance of the GNS electrode.