Highly crystalline graphene formation from graphene oxides by ultrahigh temperature process using solar furnace

Abstract

This work reports the efficient structural restoration of defective graphene oxide (GO) to a crystalline graphene by an ultrahigh temperature process at around 1800 °C achieved by a solar furnace. The GO samples were treated at high temperature by irradiating concentrated sunlight and focusing it on the sample under an inert nitrogen environment at atmospheric and reduced pressure. The structural restoration of GO was analyzed by Raman spectra, and the features of their D- and 2D-bands were remarkably improved at ultrahigh temperatures. The restoration was induced not by a photochemical reaction but dominantly by a thermally stimulated reaction. The process under reduced pressure gives rise to significantly better features in the Raman spectra than that of the atmospheric condition. This tendency shows that a trace amount of impurities contained in pure nitrogen gas are not negligible and attack the GO surfaces to induce considerable defects. These results indicate the superiority of the ultrahigh temperature process at reduced pressure for efficient GO restoration and the formation of highly crystalline graphene.

Anomalous restoration of graphitic layers from graphene oxide in ethanol environment at ultrahigh temperature using solar furnace

“…Solar furnaces are very handy and simple to operate, and can easily be applied to reactive environments since they only heat samples at specific positions at around 2000 °C. 22) We applied a solar furnace to heat GO under an ethanol environment at a reduced pressure for the first time and compared the effect of the ethanol environment in ultrahigh-temperature annealing on the stacking structure of GO with that of an inert environment.…”