On the oxidation degree of few-layer graphene oxide sheets obtained from chemically oxidized multiwall carbon nanotubes

Multiwall carbon nanotubes (MWCNT), generated by catalytic decomposition of methane using a Fe–Mo/MgO catalyst, were subjected to oxidation and exfoliation obtaining aqueous suspensions of few-layer graphene oxides (FLGO). FLGO with different oxidation ratios were obtained using a modified Hummers method by varying the amount of oxidizing agent (KMnO₄), followed by ultrasonic exfoliation. The exhaustive characterization of the resulting materials clearly showed surface functional groups evolution during oxidation and structural and morphological changes. Oxidation caused expansion and separation of the graphene layers by oxygenated groups formation and water intercalation. The full opening of the MWCNT resulted in FLGO as carbon nanoribbons and sheets from a KMnO₄/MWCNT ratio of 6.