A flexible graphene/multiwalled carbon nanotube film as a high performance electrode material for supercapacitors

Highlights: → A flexible graphene/multiwalled carbon nanotube (GN/MWCNT) film fabricated by flow-directed assembly and hydrazine to reduce. → The MWCNTs in the obtained composite film not only efficiently increase the basal spacing but also bridge the defects for electron transfer between GN sheets. → The freestanding GN/MWCNT film has a potential application in flexible energy storage devices. - Abstract: A flexible graphene/multiwalled carbon nanotube (GN/MWCNT) film has been fabricated by flow-directed assembly from a complex dispersion of graphite oxide (GO) and pristine MWCNTs followed by the use of gas-based hydrazine to reduce the GO into GN sheets. The GN/MWCNT (16 wt.% MWCNTs) film characterized by Fourier transformation infrared spectra, X-ray diffraction and scanning electron microscope has a layered structure with MWCNTs uniformly sandwiched between the GN sheets. The MWCNTs in the obtained composite film not only efficiently increase the basal spacing but also bridge the defects for electron transfer between GN sheets, increasing electrolyte/electrode contact area and facilitating transportation of electrolyte ion and electron into the inner region of electrode. Electrochemical data demonstrate that the GN/MWCNT film possesses a specific capacitance of 265 F g-1 at 0.1 A g-1 and a good rate capability (49% capacity retention at 50 A g-1), and displays an excellent specific capacitance retention of 97% after 2000 continuous charge/discharge cycles. The results of electrochemical measurements indicate that the freestanding GN/MWCNT film has a potential application in flexible energy storage devices.