Exfoliation of Graphite into Graphene by a Rotor–Stator in Supercritical CO₂: Experiment and Simulation

Abstract

High-shear-induced exfoliation of graphite into graphene using a rotor–stator mixer in supercritical CO2 is a promising approach to massively produce high-quality graphene. The exfoliation mechanism of the rotor–stator and its geometry influence on the exfoliation yield were investigated in this work. The results showed that the active region of peeling off graphite to graphene was located between the rotor (including the rotating fluid) and the stator, in which the velocity gradient was the highest. The exfoliation time was valid only when the graphite particles fell in the active region. The volume of the effective area and the active exfoliation time affected the graphene yield significantly. The optimal ratio of the wall area of the stator is about 80%. Both the lengthened rotor–stator and the multiwall stators increased the yield by 40%. Also, the similar results were obtained in other solvents like water and NMP by the optimal structure of the rotor–stator in terms of exfoliation efficiency. The findings pave the way to scale up the approach of a rotor–stator mixer in supercritical CO2 for the industrial-scale production of graphene.