Synthesis and characterization of activated carbon derived from agricultural waste (cocoa pod husks) as potential electrode for symmetric supercapacitor

Biomass waste of cocoa pod husks is adopted as starting material to synthesize Activated carbon (ACC) using a tube furnace via KOH activation with temperature ranging from 500 °C to 800 °C. The activated carbon prepared at 600 °C (ACC 600 °C) shows improved qualities than the other prepared samples, according to the physico-chemical analyses. A sponge-like morphology, amorphous structure, and microporous and mesoporous carbon are observed in the synthesized material. Trasatti approach is adopted to verify the storage mechanism of the activated carbon material (ACC 600 °C) with the percentage contribution of capacitive and diffusion-controlled effect as 92.4732% and 7.5268% for positive electrode while the negative electrode possesses 75.565% and 24.435% at scan rate of 50 mVs⁻¹. A symmetric device is fabricated from the ACC 600 °C, which gives a maximum specific energy (S.E.) of 19 Wh kg⁻¹ with a corresponding specific power (S.P.) of 453 W kg⁻¹ at a specific current of 0.5 A g⁻¹ in 2.5 M KNO₃ solution. The coulombic efficiency of the device is 99.6% after 10000 cycles with 72% capacitance retention. The obtained results suggest that the activated carbon derived from cocoa pod husks could be used as a promising material for supercapacitor's application.