Nanostructured porous carbons with high rate cycling and floating performance for supercapacitor application

Biomass-derived activated carbon from cork (Quercus Suber) (ACQS) was prepared via a two-step environment-friendly route using mild KHCO3 as the activating agent. This synthesis route makes the material produced less toxic for usage as electrode material for energy storage application. The ACQS has well-defined microporous and mesoporous structures and a specific surface area of 1056.52 m2 g-1 and pore volume of 0.64 cm3 g-1. Three-electrode tests were performed in 6 M KOH, 1 M H2SO4 and 3 M KNO3 aqueous electrolytes, to analyse the material performance in acidic, basic, and neutral media. Specific capacitance values (Cs) of 133 F g-1/167 F g-1 at 1.0 A g-1 was obtained in 3 M KNO3 in the positive/negative potential windows. Due to the observed best performance in neutral 3 M KNO3, further electrochemical analysis of the symmetric device was carried out using the same electrolyte. The device displayed a Cs value of 122 F g-1, energy and power densities of ∼14 W h kg-1 and 450 W kg-1 respectively; at 0.5 A g-1. The device also displayed an excellent stability after potentiostatic floating at a maximum voltage of 1.8 V for 120 h and ∼100% capacitance retention after 10,000 charge-discharge cycles. The excellent stability makes the cork-derived material a potential excellent, cost-effective material for supercapacitor application.