N-Doped Carbon Nanosheets from Biomass for Ultra Long-Cycling and High Energy Density Symmetric Supercapacitors

The demand for high performance energy storage devices has stimulated much interests in developing high-energy density supercapacitors. Herein, we report N-doped peanut hull derived activated carbon (PHAC) nanosheets as high-performance supercapacitor electrode by low-cost approach. Electron microscope and physiochemical characterization of PHAC confirm multi-layered sheet like nanostructures with self-doped nitrogen. Tuning of KOH activation temperature in a narrow range between 700 degrees C and 750 degrees C has a significant effect over specific surface area which increases up to similar to 2300 m(2)g(-1) for 720 degrees C activated PHAC compared to 501 m(2)g(-1) for 700 degrees C treated sample. Investigation of PHACs as supercapacitor electrode in 1.0 M H2SO4 electrolyte delivers high capacitance of 195 Fg(-1) at an applied current density of 1 Ag-1 with superior capacitance retention of 98.6% after 15000 cycles. More importantly, PHACs electrode shows high stability even at a current density of 50 Ag-1 with an impressive capacitive retention of 49.2%. In a symmetric cell configuration, the PHAC constructed electrode shows a maximum power density of 25 KW kg(-1) with energy density of 8.96 Wh kg(-1). Such an exquisite charge storage performance of N-doped peanut hull based carbon nanosheets is attributed to very large surface area, porosity, high N-content vis-a-vis electrical conductivity. (C) 2021 The Electrochemical Society ("ECS"). Published on behalf of ECS by IOP Publishing Limited.