Thin films of carbon nanotubes and chemically reduced graphenes for electrochemical micro-capacitors

We report the making of chemically reduced graphene (CRG) sheets separated by layer-by-layer-assembled multi-walled carbon nanotubes (MWCNTs) for electrochemical micro-capacitor applications. Submicron thin films of amine-functionalized MWCNTs (MWCNT-NH2) and CRG derived from graphene oxides, were shown to be cross-linked with amide bonds having high packing densities of similar to 70%. These carbon-only electrodes were found to have large volumetric capacitance of similar to 160 F/cm(electrode)(3) in an acidic electrolyte (0.5 M H2SO4). The electrode capacitance in a neutral electrolyte (1 M KCl) was found much lower, which supported the hypothesis that the observed high capacitances in the acidic electrolyte can be attributed primarily to redox reactions between protons and surface oxygen-containing groups on carbon. (C) 2010 Elsevier Ltd. All rights reserved.