Chemical activation induced modifications in copra meal derived carbon nanodots and their electrochemical implications

This work explores the synthesis and electrochemical enhancement of carbon nanodots (CNDs) derived from coconut oil mill waste (copra meal), with a focus on activation-induced structural and functional modifications for supercapacitor applications. Pristine CNDs were fabricated via hydrothermal carbonization and subsequently activated using KOH, H₃PO₄, and ZnCl₂ to investigate the role of chemical activation in tuning surface area, porosity, and electrochemical behavior. The activated carbon nanodots (ACNDs), particularly those treated with KOH, demonstrated significant increases in BET surface area of 106.91 m²/g and pore volume of 24.563 cm-3 g-1(STP), as well as improved electrochemical double-layer capacitance. Electrochemical performance was evaluated in symmetrical electric double-layer capacitors (EDLCs) using acidic (3 M H₂SO₄), neutral (deep eutectic solvent), and basic (3 M KOH) electrolytes. The best performance was observed in the basic system with KOH-CNDs, delivering a specific capacitance of 160.3 F g⁻¹, an energy density of 7.15 Wh kg⁻¹, and a power density of 449.4 W kg⁻¹. These enhancements are attributed to the synergistic effects of chemical activation and electrolyte compatibility, promoting efficient ion diffusion and improved electrode–electrolyte interaction. In contrast, pristine CNDs outperformed activated forms in acidic and neutral media, suggesting activation-induced degradation under those conditions. This work highlights the potential of copra meal-derived CNDs as low-cost, tunable materials for sustainable supercapacitor electrodes, offering a viable alternative to conventional carbon sources for high-performance energy storage devices.