In this work, a scalable method was developed to produce graphene oxide (GO) via high-shearing of pre-oxidized graphite. Various oxidation states of pre-oxidized graphite were obtained following different oxidation periods through a modified Hummers’ method. The oxidized graphite flakes were investigated by X-ray diffractometry, Fourier transform infrared spectroscopy, and Raman spectroscopy. Instead of a prolonged oxidation period of more than 24 hours, the graphite sample that underwent 6 hours of oxidation was selected for the high-shearing process to obtain exfoliated GO. The transmission electron microscopy and atomic force microscopy results confirmed that large-area and single-layer GO can be produced by the high-shear exfoliation method with pre-oxidized graphite flakes. This modified
procedure enables the remarkably simple, fast, and effective production of high-quality GO.