Preparation of activated carbon from waste Camellia oleifera shell for supercapacitor application

The cost-effective activated carbons derived from waste Camellia oleifera shell (COS) by ZnCl2 activation method are investigated as the active electrode material in electric double-layer capacitors (EDLCs) for the first time. The activation temperature and ZnCl2/COS impregnation ratio are two key factors affecting the surface area and pore structure of the prepared activated carbons, which accordingly affect their capacitive performances. Electrochemical investigations indicate that the activated carbon (AC-3-600) obtained at the activation temperature of 600 °C and impregnation ratio of 3 shows the maximum specific capacitance of 374 and 266 F g−1 in 1 mol L−1 H2SO4 and 6 mol L−1 KOH electrolytes at 0.2 A g−1, respectively. The high capacitance of the AC-3-600 is attributed to its high surface area (1,935 m2 g−1), high total pore volume (1.02 cm3 g−1), and especially the large percentage of micropores (735 m2 g−1). Meanwhile, the activated carbon presents good cycle stability in both acid and alkaline electrolytes during 5,000 cycles at a fair current density of 4 A g−1. So, we had reasons to believe that the activated carbons from waste COS by ZnCl2 activation might be one of the innovative carbon electrode materials for EDLCs application.