Reverse-Micelle-Induced Exfoliation of Graphite into Graphene Nanosheets with Assistance of Supercritical CO2

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Mass production of graphene with low cost and excellent properties is essential for its practical applications in energy, composites, biotechnology, and electronics. Here for the first time we demonstrate that graphite powder can be efficiently exfoliated into monolayered and few-layered nanosheets based on the driving forces originating from the phase inversion, i.e., from micelles to reverse micelles in the emulsion microenvironment built by supercritical carbon dioxide (SC CO2). A series of surfactants have been studied, and the experimental results indicate that efficient exfoliation of graphene depends on the suitable surfactant chosen in the SC CO2 solution system. In this work, polyvinylpyrrolidone (PVP) is confirmed to be an excellent surfactant to play the critical role on exfoliation of graphite, which leads to a high-yield graphene nanosheets (87.7%, ≤3 layers) with concentration of 1.93 mg/mL, large lateral size (up to 5 μm) and low oxidation degree (a C/O ratio of 20.28). And the dispersible ...