• Flow domain mesophase structure in the coke precursor favours the formation of graphite oxide. • The degree of graphitization strongly controls oxidation efficiency, oxygen incorporation, and exfoliation behaviour. • Highly graphitized cokes and graphite form well-ordered graphite oxide with labile interlayer oxygen groups. • Thermal reduction yields few-layer graphene-like materials with expanded lamellar morphology and low residual oxygen content. Graphene and graphene oxide are commonly synthesized from highly graphitized precursors, whose preparation requires extreme temperatures and entails high energy consumption. In this study, graphite oxide and graphene-like materials were prepared by the Hummers method using petroleum-derived cokes as low-cost pre-graphitic precursors. Vacuum residue (VR) and decanted oil (DO) cokes with different mesophase structures were heat-treated between 650 and 2300 °C and compared with a commercial graphite reference. The structural and morphological evolution of the precursors and derived materials was investigated by X-ray diffraction, thermal analysis coupled with mass spectrometry, X-ray photoelectron spectroscopy, Raman spectroscopy, and electron microscopy. The degree of graphitization was found to depend strongly on both the mesophase structure of the coke and the heat-treatment temperature. The efficiency of Hummers oxidation was highly dependent on the precursor structure: more graphitized materials incorporated larger amounts of oxygen-containing groups, which decomposed during reduction and promoted exfoliation, whereas less graphitized cokes exhibited limited oxygen uptake and poorer exfoliation. Raman analysis indicates that oxidation severely disrupts long-range graphitic order, yielding reduced oxide materials composed of defect-rich sp 2 domains regardless of the precursor origin. Electron microscopy confirms partial delamination into sheet-like domains composed of few-layer graphene crystallites for materials derived from highly graphitized cokes and commercial graphite.
Pardines et al. (Wed,) studied this question.