Electrochemical capacitance characteristics of patterned ruthenium dioxide-carbon nanotube nanocomposites grown onto graphene

In this study, graphene was used as a conductive substrate for vertically aligned carbon nanotube (CNT) bundle arrays growth, to be used as an electrode for electrochemical double layer capacitor (EDLC), as graphene and CNT exhibit good conductivity and excellent chemical stability. Both of them are composed of carbon, therefore making a superior adhesion between them. The configuration of bundle arrays provided a relatively higher specific surface area in contact with electrolyte, thereby resulting in demonstratively higher capacitance. Moreover, as the RuO2 nanostructures have good pseudocapacitance characteristics, they were coated onto vertically aligned CNT bundle arrays in order to effectively enhance the EDLC performances. The characteristics of CNT/graphene, CNT bundle/graphene, and RuO2/CNT bundle/graphene electrodes were examined with the use of scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Raman spectroscopy. Furthermore, their electrochemical properties were investigated by an electrochemical analyzer. The specific capacitances of CNT/graphene, CNT bundle/graphene, and RuO2/CNT bundle/graphene were 4.64, 6.65, and 128.40 F/g at the scan rate of 0.01 V/s, respectively.