Physical and Electrochemical Properties of Supercapacitor Electrodes Derived from Carbon Nanotube and Biomass Carbon

Abstract

Green monoliths (GMs) were prepared from mixtures of KOH (5% by weight), carbon nanotubes (5%) and self-adhesive carbon grains (90%) from oil palm empty fruit bunch fibers. The GMs were carbonized up to 600, 700 and 800°C under an N2 gas environment, and activated by CO2 gas at 800°C for one hour to produce activated carbon monoliths (ACMs), designated as ACM6, ACM7 and ACM8, respectively. The characterization of the ACMs showed a notable effect of the carbonization temperature on the structure, microstructure, electrical conductivity and porosity of the ACMs. Consequently, three independent methods, galvanostatic charge-discharge, cyclic voltammetry and electrochemical impedance spectroscopy, used for the electrochemical characterization of supercapacitor cells fabricated using the ACMs as their electrodes, consistently found that the ACM7 and ACM8 cells have higher specific capacitance (77 Fg-1 and 85 Fg-1, respectively), specific energy (2.2 Wh kg-1 and 2.1 Wh kg-1, respectively) and specific power (156 W kg-1 and 161 W kg-1, respectively) compared to the ACM6 cell. These results suggest that carbonization should be performed at temperatures closer or equal to the activation temperature for the preparation of supercapacitor electrodes composed of biomass precursors.