Ultrahigh surface area biomass derived 3D hierarchical porous carbon nanosheet electrodes for high energy density supercapacitors

A simple one step activation method is used to achieve an ultra-high specific surface area of 2943 m(2) g(-1), and abundant pore volume of 1.83 cm(3) g(-1) with a rational micro/meso/macro pore size distributed activated carbon nanosheets from Prosopis Juliflora wood carbon waste blocks. A superior electrochemical performance has been achieved with a specific capacitance of 588 F g(-1) at 0.5 A g(-1) with an excellent stability (retention 92.5% after 6000 cycles) in 6 M KOH electrolyte for a three-electrode approach. The assembled symmetric supercapacitor device outperformed in a neutral aqueous electrolyte compared to an alkaline electrolyte, such as with a gravimetric capacitance of 403 and 426 F g(-1) and superior energy density of 32.9 W h kg(-1) (at 172.7 W kg(-1)) and 56.7 W h kg(-1) (at 248.8 W kg(-1)), and a large electrochemical window of 0-1.4 V in 6 M KOH and 0-2 V in 1 M Na2SO4 electrolyte, respectively. The electrochemical performance has been enhanced by the degree of graphitization, surface functional groups, surface area and pore structure/volume. This work provides a trustworthy approach to produce higher energy density devices from renewable biomass carbon wastes for various energy storage applications. (C) 2020 Elsevier Ltd. All rights reserved.