High performance supercapacitors based on reduced graphene oxide in aqueous and ionic liquid electrolytes

Partially reduced graphene oxide (RGO) has been fabricated using hydrobromic acid. Since hydrobromic acid is a weak reductant, some oxygen functional groups which are relatively stable for electrochemical systems remain in RGO. Therefore, RGO can be re-dispersed in water and 2–3 layers of graphene can be observed by transmission electron microscopy, showing excellent affinity with water. RGO facilitates the penetration of aqueous electrolyte and introduces pseudocapacitive effects. Moreover, its capacitive nature is enhanced after cycling measurements. It is concluded that the increase of capacitance is due to the reduction of the oxygen functional groups by the cyclic voltammetry and electrochemical impedance spectroscopy analysis. The electrochemical properties in the ionic liquid electrolyte, 1-butyl-3-methylimidazolium hexafluorophosphate (BMIPF6), are also investigated. At a current density of 0.2 A g−1, the maximum capacitance values of 348 and 158 F g−1 are obtained in 1 M H2SO4 and BMIPF6, respectively.

The partially reduced graphene oxide which can be re-dispersed in water has been fabricated using hydrobromic acid. It is revealed that the oxygen groups remained in RGO introduces pseudocapacitance to enhance its capacitance and life time performance. The maximum capacitance values are 348 and 158 F g−1 in 1 M H2SO4 and BMIPF6, respectively at 0.2 A g−1.Figure optionsDownload as PowerPoint slideResearch highlights
► The RGO colloids in water are stable for several days. 2–3 layers of graphene plane have been detected in RGO.
► The maximum capacitance values reach 348 and 158 F g−1 in 1 M H2SO4 and BMIPF6, respectively at 0.2 A g−1.
► RGO shows an amazing life-time behavior in the aqueous system.