Enhancing the storing capability of activated carbon materials derived from kolanut (cola acuminata) peels as a potential electrode for symmetric supercapacitor: synthesis and characterization of the materials and device fabrication.

Doped activated carbon (DAC) was synthesized from Kolanut peels, a common agricultural waste, using a tube furnace. Potassium hydroxide (KOH) and thiourea (CH?N?S) served as the activating and doping agents, respectively, with an optimized synthesis temperature of 700 °C. Compared to undoped activated carbon (UAC), the DAC exhibited superior physicochemical properties, including perforated wall morphology, a combination of microporous and mesoporous carbon structures, and the successful incorporation of nitrogen atom only. Additionally, the DAC demonstrated an amorphous carbon framework. The electrochemical performance of both DAC and UAC was evaluated in a 2.5 M KNO? electrolyte solution. Notably, the DAC displayed significantly enhanced performance, attributed to a higher proportion of capacitive-controlled energy storage. A symmetric supercapacitor device fabricated using the DAC achieved a maximum specific energy of 16 Wh kg?¹ with a corresponding specific power of 377 W kg?¹ at a current density of 0.5 A g?¹. Furthermore, the device exhibited remarkable cycling stability, with a coulombic efficiency of 99.6% and 90% capacitance retention after 5,000 charge-discharge cycles. These results demonstrate that DAC derived from kolanut peels is a promising material for energy storage applications, offering high performance, sustainability, and cost-effectiveness.

Keywords:  Kolanut peels, Doped activated carbon, Symmetric device, Energy storage

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