Facile preparation of graphene sheets from synthetic graphite

Graphene sheets were prepared from the raw graphite by 67–70% HNO3 oxidation under refluxing at 140 °C for 4 h, followed by the treatment with KOH powder in an automatic mortar at room temperature for 1 h and subjecting to the 1-methyl-2-pyrrolidinone (NMP) solution for exfoliation. The obtained graphene sheets were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), Raman spectroscopy, atom force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). The KOH in the process was found to play a key role in the preparation of the graphene sheets and can be regarded as a reducing agent.

► A facile method for preparation of graphene sheets was developed.
► The KOH was found to play a key role in preparation of graphene sheets.
► The KOH in the process can be regarded as a reducing agent.