Preparation of an Electric Double Layer Capacitor (EDLC) Using Miscanthus-Derived Biocarbon

Commercially available biocarbon (BC) derived from Miscanthus was activated by potassium hydroxide (KOH) at different BC/KOH ratios of 1:3, 1:4, and 1:5. The structural and morphological changes and the porosity developed in the resultant products were investigated. In addition, the electrochemical performance of the assembled electric double layer capacitors (EDLCs) incorporating these carbonaceous materials was determined using galvanostatic, voltammetric, and impedance spectroscopy techniques. Compared with pristine BC samples, these KOH-activated BC samples exhibited a significant increase in the surface area from 98 to 3024 m2 g–1, which was mainly attributed to the well-developed micropores. By employing the activated BC as an electrode material for EDLCs, comparable capacitance values up to 110.8 F g–1 at a scan rate of 0.05 V s–1 and 65.4 F g–1 at a current density of 1 A g–1 were obtained during operation in an organic electrolyte. The variations in the electrochemical behavior were considered in relation to the surface area and the porous characteristics.