Graphene Oxide Formation Mechanism and Organosulfates Interlayer Bridging

ABSTRACT A kinetic investigation of graphite oxidation using a modified Hummers method was conducted to clarify the structural evolution of graphene oxide (GO) and the formation of sulfur‐containing functionalities. Graphite was oxidized for 2, 12, and 28 h, producing graphite oxides referred to as GrO‐2 h, GrO‐12 h, and GrO‐28 h. Structural and chemical characterization was performed using xX‐ray diffraction (XRD), Raman spectroscopy, atomic force microscopy (AFM), X‐ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), solid‐state 13 C NMR (SSNMR), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and energy‐dispersive spectroscopy (EDS). The results showed that prolonged oxidation did not significantly increase the oxidation degree but instead promoted defect formation, sulfur incorporation, and structural reorganization. Experimental evidence suggests that sulfate/organosulfate species are introduced during the early stages of oxidation and may subsequently participate in interlayer interactions, potentially involving sulfate‐bridging configurations between GO sheets. A mechanistic model based on nucleophilic substitution reactions is proposed to describe the formation of hydroxyl, epoxide, and sulfate functionalities during graphite oxidation. These findings provide new insights into the kinetics of GO formation and contribute to improved control over GO synthesis.