Thermal Exfoliation of Natural Cellulosic Material for Graphene Synthesis

Hibiscus flower petals have been used as a cheap natural resource precursor for cost-effective synthesis of high quality graphene by thermal exfoliation process. In order to compare the quality of graphene obtained from the flower petals directly with the flower petals pretreated with nickel(II) chloride, Raman spectroscopic technique has been used as the structural probe. The role of temperature and the effect of nickel on thermal exfoliation process have been examined. It has been observed that graphene obtained via nickel incorporation is of better quality because NI²⁺ ions that get dispersed in the layered-structured cellulose at elevated temperatures get reduced to the metallic state, which in turn push the graphitic layers during thermal exfoliation to produce good quality graphene. In contrast, no such driving force is present in cellulose and hemi-cellulose of flower petals that contain lignin.