Preparation and characterization of high value-added activated carbon derived from biowaste walnut shell by KOH activation for supercapacitor electrode

Walnut shell, a renewable and easy-accessible agricultural biowaste, was utilized as a precursor for the preparation of activated carbon materials with KOH activation in this study. After a series of activation processes, therefore, the activated carbon derived from walnut shells achieved a specific surface area of 1016.4 m 2 /g. With the advantage of low cost and environmental friendly, the prepared carbon materials have superior electrochemical performance and excellent prospects in the application of supercapacitor electrodes. The morphology and textural properties of the AC samples were examined by N 2 adsorption–desorption, scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and FTIR spectra. All the electrode samples exhibited excellent electrochemical performance. The AC-650 electrode achieved a maximum specific capacitance of 169.2 F/g at current density of 0.5 A/g in 6 M KOH electrolyte. This work provided an effective approach for the treatment and utilization of agricultural biowastes, which was worthwhile for economic, environmental, and societal viewpoints.