KOH activated peanut shell derived porous carbons for high-performance supercapacitor applications

Biomass-derived activated carbons are being increasingly investigated as sustainable electrode materials for energy storage because of their adjustable porosity and conductivity. In this work, peanut shells (PS) were transformed into activated carbon through conventional pyrolysis followed by a chemical activation process. The peanut shell-derived activated carbon was synthesized with a mass ratio of 1:1 (Biochar: KOH). The sample activated at 800 °C shows a high BET surface area of 414.5 m²/g and pore volume of 0.33 cm³/g, values which are significantly higher than many other reported agricultural-waste carbons (< 300 m²/g). The X-ray diffraction measurement reveals that the synthesized samples possess both amorphous and graphitic carbon phases, and Raman spectroscopy confirms this with distinct defective (D) and graphitic (G) bands near 1335 cm⁻¹ and 1584 cm⁻¹, respectively. Remarkably, the PSNK-800 sample delivers an impressive specific capacitance of 288 F/g in a 1 M H₂SO₄ electrolyte, surpassing several reported biomass-derived carbons (typically 150–250 F/g). Further, it demonstrates a coulombic efficiency of 95% over 4200 cycles. In the practical aspect, the fabricated prototype symmetric supercapacitor demonstrated a C_s value of 56 F/g at 1 A/g in 1 M H₂SO₄. The calculated specific energy and power densities stand at 7.2 Wh/kg and 900 W/kg, underscoring the material’s efficiency. Moreover, the device exhibits an intrinsic resistance (R_s) of 2.1 Ω, which is ideally suited for cutting-edge electronic applications.