Biomass-derived porous activated carbon from Syzygium cumini fruit shells and Chrysopogon zizanioides roots for high-energy density symmetric supercapacitors

Synthesis of biomass derived microporous activated carbon materials has fascinated attention in the emerging field of energy storage due to its high specific surface area, excellent electrical conductivity, low cost and environmental benevolence. Herein, we report facile and cost-effective method to produce porous activated carbons for the first time by physical activation method using two different biomass sources Syzygium cumini fruit shells (SCFS) and Chrysopogon zizanioides roots (CZR) for fabrication of symmetric supercapacitors. Biomass-derived activated carbon (BAC) materials were obtained via a two-step synthesis: (i) carbonization at 700 °C in N2 atmosphere (ii) CO2 activation at 700 °C in N2 atmosphere. The formation of high surface area and disordered micropores on the carbon by CO2 activation was identified by N2 adsorption-desorption and FE-SEM techniques. SCFS-AC and CZR-AC exhibit enhanced electrochemical performances in three-electrode configuration showing their high specific capacitances with good capacitance retention. These biomass derived activated carbon (BAC) based symmetric supercapacitors deliver energy density maximum of 27.22 W h kg−1 (SCFS-AC) and 16.72 W h kg−1 (CZR-AC) at 200 W kg−1 power density with an outstanding cycling stability over 5000 cycles. This work offers an environmentally safe and innovative approach to control the porosity in BAC for energy storage applications.