Sinki-derived activated carbon for dual applications in supercapacitors and dye removal

• Activated carbon derived from sinki (AC-S) demonstrated a high surface area of 1278 m 2 /g. • 3D structure with combined micropores and mesopores. • The AC-S exhibited a specific capacitance of 192 F/g at the current density of 0.5 A/g. • 107 % capacitance retention after 5000 cycles. • Effective adsorptive removal of methylene blue (MB) dye. Transforming food waste into activated carbon for use as a supercapacitor electrode material and dye adsorption represents an effective approach to meeting energy requirements and addressing environmental challenges. In this study, activated carbon was synthesized from sinki, a traditional Nepalese dish produced by fermenting radish roots, through carbonization and activation under a nitrogen atmosphere. The resulting activated carbon from sinki (AC-S) exhibited a three-dimensional (3D) porous structure comprising both micro- and mesopores, with a specific surface area of 1278 m 2 /g. X-ray diffraction (XRD), Raman spectroscopy, and Fourier-transform infrared spectroscopy (FTIR) confirmed the formation of both amorphous and crystalline carbon structures. When used as a supercapacitor electrode, the AC-S demonstrated favorable electrochemical behavior, attaining a specific capacitance of 192 F/g at 0.5 A/g and a notable enhancement in cyclic stability, reaching 107.5% after 5000 cycles. Furthermore, the ACS was evaluated for its dye-adsorption efficiency in aqueous solution, showing promising results for removing methylene blue (MB) from water. These findings suggested that the sinki serves as a novel, sustainable, cost-effective precursor for producing multifunctional activated carbon.