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

Abstract

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 µm, 330 µm and 7 µm, 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.

Keywords:

• Graphene oxide
• spheroidal graphite
• epoxy groups

Credit author statement

All authors: writing, reviewing, and editing. JMR: overall supervision, original draft writing and supervision. JMR, OK, and RG: conceptualization. GGCS: investigation.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

The research work is carried out under the project “SmarthouB/M-ERA.net (100581056)” funded by Sächsische Aufbaubank (SAB), FAPESP/MERA 2020/08322-0, and FAPESP/PITE 2020/12204-3. The authors gratefully acknowledge the financial support received from these funds and R.G. also acknowledges support from NEXT Generation-EU under the MUR-Innovation ecosystems grant ECS00000041-Vitality (spoke9).