Low-cost, scalable preparation of high-quality graphene has been a critical challenge that hampers its large-scale application. We here propose a novel, scalable liquid phase exfoliation method in which the intercalation, expansion and exfoliation of graphite are achieved all under ambient conditions, not involving any heating or high-temperature treatment. We demonstrate that such room-temperature liquid-phase intercalation and expansion allow graphite flakes to expand up to 1000 times. Significantly different from thermally expanded graphite, the resulting chemically expanded graphite (CEG) exhibits a uniform, open, porous structure with a specific surface area (847 m²/g) comparable to the theoretical value of 3-layer graphene. The CEG obtained is able to be exfoliated under mild conditions to give high-quality graphene with a yield of 70% relative to the starting graphite. The exfoliated graphene sheets have very few defects, with an atomic ratio of carbon to oxygen (C/O ratio) of 28. The as-prepared graphene exhibits an electrical conductivity of 1.17×105 S/m and the corresponding transparent films also reveal superior optical and electrical performance.

This work was published on Chemistry of Materials, see details: Shan Lin, Lei Dong, Jiajia Zhang and Hongbin Lu*, Room-Temperature Intercalation and #1000-fold Chemical Expansion for Scalable Preparation of High Quality Graphene, Chem. Mater., 2016, DOI:10.1021/acs.chemmater.5b05043.