Impact of spheroidal graphite morphology on the functionalization of graphene oxide surface

This study conducted a comparative analysis of graphene oxide (GO) surfaces generated using the modified Hummers method at low temperature, employing spheroidal, flake, and micronized graphite with d50 values of approximately 49 mu m, 330 mu m and 7 mu m, respectively. The characterization of the resulting GOs involved TGA, HRTEM, AFM, as well as UV-vis, FTIR, XPS and Raman spectroscopy. Spheroidal graphite produced GO sheets with a thickness of only 1 nm, displaying a zeta potential of -41 mV after 3 h of intercalation and oxidation reaction. In contrast, flake and micronized graphite also yielded 1-nm-thick GO sheets but exhibited a wider size distribution, with zeta potential values of -32 mV and -35 mV, respectively. Moreover, the GO surface derived from spheroidal graphite showed an increased presence of epoxy groups and a reduced concentration of oxidative debris compared to GOs from other graphite types. The curvature of graphite crystals within spheroidal graphite had a more pronounced impact on graphite oxidation than on graphene layer exfoliation. This research highlights the significance of considering graphite sheet curvature as a crucial variable in GO production, providing insights into the novel and noteworthy role that graphite sheet curvature can play in GO materials.