Mechanochemical oxidation of graphite for graphene-hydrogel applications: Pitfalls and benefits

Next to being a precursor for the mass production of graphene, graphene oxide (GO) has itself raised considerable scientific and technological interest for a wide range of future device applications. Mass production of GO remains a challenge as its preparation on a large scale is mostly based on the liquid-phase Hummers method or its modified versions, which are time-consuming and use excessive amounts of toxic chemicals. It is therefore desirable to devise faster, inexpensive, as well as cleaner and sustainable synthetic routes for its preparation. Here we describe preparation of graphene oxide, by means of mechanochemistry, that is of sufficient quality to produce stable 3D graphene aerogels. We also describe problems, which we have persistently encountered, related to the reproducibility of mechanochemical synthesis. The as-prepared graphene oxide and the target graphene aerogels have been studied by powder X-ray diffraction, scanning electron microscopy, atomic force microscopy, Raman spectroscopy, Fourier-transform infrared spectroscopy, UV-vis spectrophotometry and thermogravimetric analysis. We tentatively relate characteristics of GO to its performance in graphene hydrogel preparation.