Experimental investigation of the important influence of pretreatment process of thermally exfoliated graphene on their microstructure and supercapacitor performance

Thermal exfoliation is a popular approach to prepare thin-layered graphene in large scale. Generally believed that the microstructure and surface chemistry of the products could tailored by the variation of ambient gas pressure, temperature, acid and organic substances during thermal exfoliation of graphite oxide (GO). In this work, we investigated the effect of physical pre-treatment process and acid assisting on the texture, surface state and electrochemical performance of the resulting thermal exfoliated graphene, and found that the different physical pre-treatment process had great influence on the microstructure and specific surface area of graphene. Especially the graphene formed by sonication treatment consisted by thin layers with lots of wrinkles delivered the highest specific surface area of 678 m2/g. Adding volatile acid in the process of pre-treatment could decrease their specific surface area. But the graphene obtained with acid assisting was possessed of larger pore volume and improved conductivity which promoted their electrochemical performance effectively. The important role of physical pre-treatment process and acid assisting process in expansion-exfoliation of GO was discussed in detail in this work.