Sustainable Porous Carbon from Ziziphus Fruit Waste for High Specific Capacity Electrode Materials

The growing demand for efficient energy storage for renewable systems requires low-cost, high-performance electrode materials. Supercapacitors offer fast charge-discharge but suffer from low energy density. Biomass-derived porous carbon is a sustainable alternative to commercial activated carbon. This study aims to synthesize hierarchical N,O-doped porous carbon from Ziziphus spina-christi fruit waste in order to evaluate the effect of alkali agent and activation time on porosity and supercapacitor performance. The carbon was prepared via carbonization at 600°C followed by chemical activation with KOH or NaOH at 800°C for 2 h and 3 h. The materials were characterized by FE-SEM, XRD, Raman, and N 2 adsorption-desorption. The electrochemical tests were conducted in 3-electrode system. The optimized ZSCFC-3h-KOH exhibited a high specific surface area of 917.5 m 2 g - 1 , a hierarchical micro-mesoporous structure, and an ID/IG ratio of 0.98. In a 3-electrode system, it delivered a specific capacitance of 231.6 F g - 1 at 1 A g - 1 with an IR drop of only 0.03 V. The electrode showed excellent stability, retaining 94.3% of its capacitance after 10,000 cycles at 5 A g - 1 . Z. spina-christi fruit waste is a viable, sustainable precursor for high-capacitance supercapacitor electrodes. KOH activation for 3 h is optimal for creating accessible pore networks for ion storage.