Incorporation of MnO2-Coated Carbon Nanotubes between Graphene Sheets as Supercapacitor Electrode

Hierarchical graphene-based composite consisting of graphene sheets intercalated by MnO2-coated carbon nanotubes (MnC) was,prepared for high-performance super capacitor electrode. The highly negatively charged graphene oxides reduced by urea (RGO) and the positively charged MnC functionalized with poly(diallyldimethylammonium chloride) created a strong electrostatic interaction, forming a hierarchical nanostructure. The elelctrocapacitive behaviors of MnC/RGO (MnC-G) were systematically investigated by cyclic voltammetry, galvanostatic charge discharge and electrochemical impedance spectroscopy. A maximum specific capacitance of 193 F/g was achieved for the MnC-G composite with 37% RGO, which was almost 3-fold higher than 69 F/g of carbon nanotubes/RGO and 2-fold higher than 89 F/g of MnO2/RGO composite. Moreover, an excellent rate performance, a good capacitance retention (similar to 70%) and a superior Coulombic efficiency (94-96%) were also observed during the continuous 1300 cycles of galvanostatic charge-discharge.