Fabrication and Characterisation of Carbon-Based Electrodes for Supercapacitor Applications Using Agricultural Waste from Kano State

Background: Supercapacitors are high-power energy storage devices with growing applications in renewable energy systems and electronics. Agricultural waste-derived carbon materials from North West Nigeria offer a sustainable and low-cost electrode source. Aim: This study fabricated and characterised carbon-based supercapacitor electrodes using groundnut shell biomass from Kano State. Methods: Groundnut shells were carbonised at 800 degrees Celsius under nitrogen atmosphere and activated using potassium hydroxide. Electrodes were fabricated from the activated carbon, carbon black, and PVDF binder. Electrochemical characterisation was performed using cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopy in 1M KOH electrolyte. Results: Specific capacitance of 218 F/g was achieved at 1 A/g current density. Capacitance retention was 91% after 5,000 charge-discharge cycles. Specific surface area of the activated carbon was 1,420 m2/g by BET analysis. Conclusion: Groundnut shell-derived activated carbon from Kano State is a viable precursor for high-performance supercapacitor electrodes. The findings support development of sustainable energy storage materials from Nigerian agricultural waste streams. Keywords: supercapacitor, activated carbon, agricultural waste, Kano, electrochemical energy storage.