Preparation of graphene from graphite by supercritical CO_2 exfoliation assisted with fluid shear
LI Lei;LI GengHui;LI YongFeng;GAO JinSen;XU ChunMing;State Key Laboratory of Heavy Oil Processing,China University of Petroleum;
Recently graphene has attracted a great interest in scientific research due to its excellent electronic,mechanical,optical,and thermal properties. Many methods have been explored for preparation of high-quality graphene efficiently. However,it still remains a great challenge for the scalable production of graphene with low cost. Graphite oxide reduction was commonly recognized as the most promising method,but many oxygen-containing groups such as hydroxyl(-OH) and carboxyl(-COOH) are introduced into the graphene framework during the process,which dramatically decreases the quality of graphene. As a green solvent,supercritical CO2 possesses excellent characteristics of high diffusivity and high permeability. In this work,supercritical CO2 is employed as medium for the exfoliation of graphite. The diffusion and exfoliation process are intensively enhanced with the assistance of fluid shear,which strikingly facilitates the graphite exfoliation,resulting in an improvement of graphene yield. The graphene obtained in our work exhibits intact lattice structure and high electronic conductivity. Moreover,it is found that the graphene synthesized by supercritical CO2 exfoliation consists of 90% exfoliated sheets with less than 10 layers. Our work can provide a clean and low-cost way to commercially produce graphene with high quality.