Structural and Electrochemical Properties of Physically and Chemically Activated Carbon Nanoparticles for Supercapacitors

The demand for supercapacitors has been high during the integration of renewable energy devices into the electrical grid. Although activated carbon materials have been widely utilized as supercapacitor electrodes, the need for economic and sustainable processes to extract and activate carbon nanomaterials is still crucial. In this work, the biomass waste of date palm fronds is converted to a hierarchical porous nanostructure of activated carbon using simple ball-milling and sonication methods. Chemical and physical activation agents of NaOH and CO2, receptively, were applied on two samples separately. Compared with the specific surface area of 603.5 m2/g for the CO2-activated carbon, the NaOH-activated carbon shows a higher specific surface area of 1011 m2/g with a finer nanostructure. Their structural and electrochemical properties are functionalized to enhance electrode–electrolyte contact, ion diffusion, charge accumulation, and redox reactions. Consequently, when used as electrodes in an H2SO4 electrolyte for supercapacitors, the NaOH-activated carbon exhibits an almost two-fold higher specific capacitance (125.9 vs. 56.8 F/g) than that of the CO2-activated carbon at the same current density of 1 A/g. Moreover, using carbon cloth as a current collector provides mechanical flexibility to our electrodes. Our practical approach produces cost-effective, eco-friendly, and flexible activated carbon electrodes with a hierarchical porous nanostructure for supercapacitor applications.