Assembled graphene oxide and single-walled carbon nanotube ink for stable supercapacitors

We describe the synthesis and fabrication of a graphene oxide (GO) and single-walled carbon nanotube (SWCNT) composite ink (GO–SWCNT ink) for electrochemically stable supercapacitors. Atomic force microscopy and scanning electron microscopy studies demonstrate that the obtained GO flakes are single layer with size distribution from 100 nm to 20 μm. SWCNTs are dispersed using a GO aqueous solution (2 mg/mL) with sonication support to achieve a SWCNT concentration of 12 mg/mL, the highest reported value so far without surfactant assistance. Raman spectroscopy studies indicate that the full-width at half-maximum of the G band increases with the mixing of SWCNT and GO indicating that electronic structure changes via π–π interactions of GO sheets and SWCNTs. Paper-based electrodes of supercapacitor were conveniently fabricated with GO–SWCNT composite ink via a dip casting method. By using different concentrations of SWCNT in the ink, the paper electrodes provide different capacitance values. The highest value of specific capacitance reaches 295 F/g at a current density of 0.5 A/g with a GO/SWCNT weight ratio of 1:5. The cycling stability for the GO–SWCNT paper electrode supercapacitors indicates capacitance retention of 85% over 60,000 cycles.