Supercapacitor Activated Carbon Electrode from Composite of Green Monoliths of KOH-Treated Pre-Carbonized Oil Palm Empty Fruit Bunches and HNO3-Treated Graphite

Abstract

Supercapacitor electrodes in the form of activated carbon monoliths (ACMs) were prepared by carbonization and activation of three different composite of green monoliths (GMs) consisting of (a) self-adhesive carbon grains (SACG) derived from pre-carbonized oil palm empty fruit bunches, KOH and graphite additive, (b) KOH-treated SACG and HNO3-treated graphite additive, and (c) SACG and HNO3-treated graphite additive. The ACM1, ACM2 and ACM3 electrodes produced from their respective GMs were characterized using nitrogen adsorption-desorption technique and the supercapacitor cell fabricated using these electrodes were characterized by galvanostatic charge discharge method. The results showed that the change in the condition of material component in the GMs by acid/alkaline treatment moderately changed the pore characteristics of the electrodes, for example only around 10 % change occurred in the specific surface area of the samples. However, such change gave a larger change in the electrochemical performance of the cells, where the ACM3 exhibit the specific capacitance (119 F g-1) and specific energy (3.5 W h kg-1), which were (66 – 71) % and (28 – 75) % higher than the other cells, and the specific power (63.3 W kg-1), which was 33 % lower than the other cells. These results demonstrate a non-linear dependency of electrochemical performances of the cells on the porosity characteristics of the electrodes resulted from the modification of component materials in the GMs.