Effect of ZnCl2 concentration on the performance of supercapacitor cell electrodes from shallot leaf waste (Allium ascalonicum L.)

Abstract

The development of carbon electrodes for supercapacitors requires pore structure optimization to enhance energy storage performance through chemical activation. This study aims to analyze the effect of varying ZnCl₂ activator concentrations on the physical characteristics and electrochemical performance of carbon electrodes derived from red onion biomass. The concentrations used were 0.1 M, 0.3 M, 0.5 M, and 0.7 M, with the synthesis steps including pre-carbonization at 200°C for 2 hours, chemical activation using ZnCl₂, carbonization at 800°C in a N₂ gas flow, and physical activation using CO₂ gas at 850°C. The physical characterization performed involved measuring density and SEM analysis to examine morphology. The characterization results showed that the SL-0.7 sample exhibited the highest density reduction of 0.39 g/cm³, the SL-0.7 sample also exhibited a more uniform pore morphology and a more open surface based on SEM. Electrochemical testing via Cyclic Voltammetry and Galvanostatic Charge-Discharge methods yielded the highest specific capacitance of 233.68 F/g and 113.82 F/g for the SL-0.7 sample, indicating that an increase in ZnCl₂ concentration significantly affects the physical characteristics and performance of carbon electrodes in supercapacitor applications.