Graphene preparation and process parameters by pre-intercalation assisted electrochemical exfoliation of graphite

Among all the preparation methods, electrochemical exfoliation of graphite in neutral aqueous solution to prepare high-quality graphene is a hot research topic due to many advantages, such as high efficiency, environmental friendly, fewer defects, and convenient operation with simple equipment. In this work, the graphene was prepared by pre-intercalation assisted electrochemical exfoliation of graphite foil, in which one pre-intercalation stage was performed at the low voltage to moderately enlarge the interlayer distance of graphite foil, and then graphite electrode was electrochemically exfoliated to produce graphene nanosheets in an aqueous inorganic salt solution of (NH 4 ) 2 SO 4 . Through comparing two pretreatment methods of graphite foil (pre-expansion with liquid nitrogen and pre-intercalation by electrochemical intercalation), the electrochemical pre-intercalation process was confirmed to avoid the serious loss of the graphite electrode during the liquid nitrogen pretreatment and facilitate electrochemical exfoliation. Meanwhile, the optimum parameters of pre-intercalation were determined. Subsequently, the effect of applied voltage on the quality of obtained graphene (such as the number of layers, defects, size, composition) during the exfoliation stage was investigated systematically, and especially the effect of applied voltage on the quality and yield of graphene was discussed in detail. The graphene nanosheets with a small number of layers (60% is less than 5 layers) were obtained through two stages of electrochemical pre-intercalation and exfoliation. The structure, morphology, and composition of the graphene were analyzed by using the XRD, SEM, TEM, AFM, and XPS.