Speaker
Description
Macadamia shell waste from the production of snacks and desserts in Thailand was converted into porous carbon materials through chemical activation with po-tassium hydroxide (KOH) to add value to the residues. Carbonized macadamia shells were mixed with KOH at the ratios of 1:1, 1:2, and 1:3, and pyrolyzed at 800 °C under Ar flow. Scanning electron microscopy images revealed an in-creased roughness and porosity of the activated carbons at higher KOH contents. X-ray diffraction and Raman spectroscopy indicated an amorphous carbon na-ture. Fourier-transform infrared spectroscopy and X-ray photoelectron spectros-copy confirmed the presence of chemical functional groups and elemental compo-sitions of activated carbons. The specific surface area increased from 715 to 1024 m2/g with an increasing KOH ratio from 1:1 to 1:3. A three-electrode system was used to electrochemically test the samples by cyclic voltammetry and galvanostat-ic charge-discharge tests in 6 M KOH electrolyte. The 1:1, 1:2, and 1:3 activated carbons demonstrated an electrical double-layer capacitor behavior with specific capacitances of 153, 154, and 169 F/g, respectively. The 1:3 activated carbon was further used to fabricate symmetric supercapacitor electrodes, using a 6 M KOH electrolyte. The 1:3 activated carbon coin cell exhibited an energy density of 16 Wh/kg and a power density of 2451 W/kg at 5 A/g. After 10,000 charge-discharge cycles, the specific capacitance increased to 102% due to enhanced sur-face wettability. Finally, KOH-activated carbons derived from macadamia shells are promising materials for supercapacitors, providing a sustainable solution for waste utilization.
