Temperature dependence of graphene oxide reduced by hydrazine hydrate

Abstract

Graphene oxide (GO) was successfully prepared by a modified Hummer’smethod. The reduction effect and mechanism of the as-prepared GO reducedwith hydrazine hydrate at different temperatures and time were characterized byx-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy(FTIR), elemental analysis (EA), x-ray diffractions (XRD), Raman spectroscopy andthermo-gravimetric analysis (TGA). The results showed that the reduction effect of GOmainly depended on treatment temperature instead of treatment time. Desirablereduction of GO can only be obtained at high treatment temperature. Reduced at95 °C for 3 h, theC/O atomicratio of GO increased from 3.1 to 15.1, which was impossible to obtain at low temperatures, such as 80,60 or 15 °C, even for longer reduction time. XPS, 13C NMR and FTIR results show that most of theepoxide groups bonded to graphite during the oxidation were removed from GO and form thesp2 structure after being reduced by hydrazine hydrate at high temperature (>60 °C), leading to the electric conductivity of GO increasing from1.5 × 10 − 6 to5 S cm − 1, while the hydroxyls on the surface of GO were not removed by hydrazine hydrate even athigh temperature. Additionally, the FTIR, XRD and Raman spectrum indicate that theGO reduced by hydrazine hydrate can not be entirely restored to the pristine graphitestructures. XPS and FTIR data also suggest that carbonyl and carboxyl groups can bereduced by hydrazine hydrate and possibly form hydrazone, but not a C = C structure.