Fabrication of graphene/polypyrrole nanotube/MnO2 nanotube composite and its supercapacitor application

A novel composite is fabricated through hybridizing graphene with polypyrrole (PPY) nanotube and manganese dioxide (MnO2) nanotube to comprehensively utilize the electrical double layer capacitance and pseudo-capacitance. Scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Raman spectroscopy are employed to characterize its structure. The SEM and TEM images illustrate that graphene/PPY nanotube/MnO2 nanotube composite (GPM) presents interconnected structure. The result of Raman analysis demonstrates the intimate interactions among PPY, graphene and MnO2. In addition, cyclic voltammetry (CV), galvanostatic charge-discharge and electrochemical impedance spectroscopy (EIS) techniques are used to measure the electrochemical properties. It is revealed that GPM presents excellent high-rate performance and its capacitance is as high as 469.5 Fg(-1) at a current density of 0.3 Ag-1, higher than that of PPY and chemically reduced graphene sheet as well as the materials reported in the literature. Furthermore, long-term charge-discharge cycle test confirms that the fabrication of GPM can effectively merge the merits of graphene, PPY and MnO2. Additionally, EIS analysis illustrates that the presence of conductive graphene as well as the intimate interactions among graphene, PPY and MnO2 lead to the good electrochemical stability.