Abstract
ABSTRACT Activated carbon derived from rice husk was prepared by carbonization followed by KOH activation at 850°C, and the effect of NaOH pretreatment to remove silica on its structural, textural, and electrochemical properties was systematically investigated. Two carbon materials were synthesized under identical carbonization and KOH activation conditions, differing only in the NaOH pretreatment step, allowing the specific contribution of silica removal to pore development and capacitance performance to be assessed. NaOH pretreatment increased the BET specific surface area from 2034.98 to 3031.68 m² g - ¹ and the total pore volume from approximately 1.39 to 2.69 cm³ g - ¹. SEM, XRD, and Raman analyses further confirmed the significant structural modification of the carbon after pretreatment. The improved porous structure was accompanied by improved electrochemical performance: NaOH-pretreated carbon provided a specific capacitance of approximately 215 F g - ¹ and maintained stable charge-discharge behavior for 7000 cycles at 2 A g - ¹. Additionally, the symmetrical cell achieved a maximum calculated energy density of 13.94 Wh kg - ¹ at 75 W kg - ¹ and a maximum investigated cell voltage of 1.5 V, although electrochemical analysis showed an increase in parasitics near this upper voltage limit.. These results establish a direct link between the removal of silica prior to KOH activation, improved pore development, and increased surface area accessible to the electrolyte, demonstrating an effective strategy for targeted modification of the electrochemical properties of rice husk-derived porous carbon.