Novel strategy for low-temperature vacuum preparation of high-quality graphene

Abstract

Previously, the preparation of graphene often required one or more of strong acid oxidants, reduction temperatures above 1000 ℃,expensive metal catalysts, and accompanied by the problems of low efficiency, high and heavy pollution. Our work provided a novel strategy for low-temperature vacuum preparation of high-quality graphene. Anhydrous AlCl3 and FeCl3 were used as bi-intercalants to prepare stage-1 graphite intercalation compounds (AlCl3-FeCl3-GICs) with accordion-like structure. Vacuum treatment of stage-1 AlCl3-FeCl3-GICs at a relatively low temperature of 180 ℃, low-boiling-point AlCl3 was heated and vaporized to further stretch the graphite sheet to obtain worm-like expanded graphite. The expanded graphite could maintain a loose structure under atmospheric conditions and was not collapsed. The effect of van der Waals force between the sheets of adjacent graphite layers was greatly weakened, which made the expanded graphite easily to be exfoliated. High-quality graphene was obtained by ultrasonic treatment of expanded graphite in solvent using liquid-phase exfoliation method. The preparation process of expanded graphite did not use strong oxidants, and was carried out in an anhydrous and oxygen-free environment. The reaction temperature was also controlled within 180 ℃. The overall preparation conditions were relatively mild and environmentally friendly. The preparation of graphene by the liquid-phase method could avoid the destruction of the graphene lattice structure as much as possible. The scanning electron microscope (SEM), transmission electron microscope (TEM) and atomic force microscope (AFM) were used to observe the microscopic morphology of graphene, and the X-ray powder diffraction (XRD) instrument, ray photoelectron spectroscopy (XPS) instrument and Raman spectrometer were used to characterize the microstructure of graphene. The results show that the prepared graphene has extremely low defects, the sp2 lattice structure still maintains a high degree of regularity, and most graphene layers are within three.

Keywords

• graphene
• high-quality
• graphite intercalation compounds
• low-temperature and vacuum strategy
• liquid-phase exfoliation