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

Abstract

A simple one step activation method is used to achieve an ultra-high specific surface area of 2943 m2 g−1, and abundant pore volume of 1.83 cm3 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.