Carbon electrode material from peanut shell by one-step synthesis for high performance supercapacitor

Activated carbons (ACs) derived from biomass have become one of the most promising electrode materials for supercapacitors due to their reproducibility and low cost. In this study, peanut shell is used as the precursor to prepare AC via one-step synthesis method activated by ZnCl₂, FeCl₃ and their mixture in N₂ atmosphere at 700 °C. The characteristics and structure of the obtained ACs were studied by SEM, HR-TEM, BET, FT-IR, XRD and Raman spectroscopy. The prepared AC materials showed high specific surface area and large amount of micropores, and the maximum specific surface area reached 1481.59 m²/g. The etching effect of iron oxide and zinc chloride on the carbon skeleton facilitated the formation of micropores. The XRD pattern and Raman spectra indicated that all samples were amorphous carbons with some graphitic crystalline structures. In addition, FT-IR analysis illustrated that the surface of AC materials possessed a large number of oxygen-containing functional groups, which were beneficial to their electrochemical performance. From the electrochemical performance of the AC materials, it was observed that better electrochemical properties were achieved at a weight ratio of biomass to activator of 2:1 in comparison with 0.8:1 and 4:1 for all the activators. The obtained AC showed a high specific capacitance of 239.88 F/g at the current density of 0.5 A/g in 1 M Na₂SO₄ electrolyte and exhibited excellent cycling performance with 94.55% capacity retention after 5000 cycles.