Large area few-layer graphene with scalable preparation from waste biomass for high-performance supercapacitor

Carbonaceous materials with high surface area and a sheet-like structure promote fast ion-transport kinetics, making them an ideal choice to be used in supercapacitors. Few-layer graphene (FLG)-like nanosheets with abundance of micro as well as mesopores are achieved via mechanical exfoliation method from an agricultural waste biomass: peanut shell (PS). A well-known elementary method of probe-sonication, for the achievement of FLG sheets from renewable sources, is introduced in this study for the very first time. The Peanut shell-derived FLG (PS-FLG) possesses remarkably high specific surface area (2070 m² g^-1) with a sufficiently large pore volume of 1.33 cm³ g^-1. For the fabrication of a binder-free supercapacitor, the PS-FLG-based electrodes exhibited a high specific capacity of 186 F g^-1 without the use of any binder in 1 M H₂SO₄ as supporting electrolyte. The highest energy density of 58.125 W h Kg^-1 and highest power density of 37.5 W Kg^-1 was achieved by the material. Surprisingly, the working potential increased to 2.5 V in an organic electrolyte leading to an obvious increase in the energy density to 68 W h Kg^-1. Solid-state-supercapacitor was fabricated with this material for the possible use of low-cost, high energy promising energy storage device.