The role of exfoliating solvents for control synthesis of few-layer graphene-like nanosheets in energy storage applications: Theoretical and experimental investigation

Control synthesis of graphene is the need of the hour for versatile applications in the energy sector. A novel yet facile mechanical exfoliation technique has been developed here for the synthesis of high-quality few-layer graphene (FLG)-like nanosheets from a biowaste material, peanut shells. Biowastes, on the other hand, is one of the most abundant natural resources for carbon, which needs to be recycled. Therefore, careful selection of biomass as well as proper synthesis engineering can provide a sustainable route to attain mass-scale graphene-like nanosheet production. Liquid-phase mechanical exfoliation in various solvent systems such as an organic solvent, isopropyl alcohol (IPA), water and hydrogen peroxide (as the best medium for cavitation), as well as an inorganic acidic solution of phosphoric acid which caused the exfoliation by intercalation, has been explored. Depending on the nature of solvents, reduction in dimensions of the as-derived exfoliated peanut-shell derived graphene-like nanosheets (EPSGs) occur, which ensures the number of layers of the sheets. In order to elucidate the role of exfoliating solvents, DFT-based computational studies have also been performed in detail. The assynthesized EPSGs were tested for their subsequent applications in supercapacitor. The electrochemical results are consistent with the theoretical finding that organic solvents, like IPA, has a better exfoliating effect in the liquid-phase exfoliation and has shown excellent specific capacitance (323 F g(-1)) as well as energy density (101 W h kg(-1)).