Synthesis of graphene oxide: Effect of sonication during oxidation

The oxidation of graphite to graphene oxide (GO) is a widely used approach to exfoliate graphite. Nevertheless, achieving precise control over the degree of oxidation and the resulting properties of GO has considerable challenges. In this study, we demonstrate that using sonication during the oxidation of graphite by Hummers' method alters the chemistry and properties of the GO. Contrary to our expectations, we found that sonication slows the oxidation of graphite by impeding the intercalation of sulfuric acid. This results in fewer oxygen-containing functional groups on the GO and minimizes functionalization of the basal plane of the graphene oxide sheets, leading to superior electrochemical and mechanical properties of GO-based composites compared to GO synthesized without sonication. In this study, we use X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), Fourier Transform Infrared spectroscopy (FTIR), cyclic voltammetry, and compression testing to quantify the effects of sonication during oxidation and propose the mechanism leading to those effects.