Noncovalently-functionalized reduced graphene oxide sheets by water-soluble methyl green for supercapacitor application

• MG–RGO composites were firstly prepared through non-covalent modification.
• The mass ratio in composites is a key for achieving high specific capacitance.
• MG–RGO 5:4 exhibits the highest specific capacitance of 341 F g−1.
• MG–RGO 5:4 shows excellent rate capability and long life cycle.

In the present work, water-soluble electroactive methyl green (MG) has been used to non-covalently functionalize reduced graphene oxide (RGO) for enhancing supercapacitive performance. The microstructure, composition and morphology of MG–RGO composites are systematically characterized by UV–vis absorption, field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD). The electrochemical performances are investigated by cyclic voltammetry (CV), galvanostatic charge/discharge and electrochemical impedance spectroscopy (EIS). The fast redox reactions from MG could generate additional pseudocapacitance, which endows RGO higher capacitances. As a result, the MG–RGO composite (with the 5:4 mass ratio of MG:RGO) achieve a maximum value of 341 F g−1 at 1 A g−1 within the potential range from −0.25 to 0.75 V and provide a 180% enhancement in specific capacitance in comparison with pure RGO. Furthermore, excellent rate capability (72% capacitance retention from 1 A g−1 to 20 A g−1) and long life cycle (12% capacitance decay after 5000 cycles) are achieved for the MG–RGO composite electrode.

Electroactive methyl green (MG) is selected to functionalize reduced graphene oxide (RGO) through non-covalent modification and the composite achieves high specific capacitance, good rate capability and excellent long life cycle.Figure optionsDownload as PowerPoint slide