Activated carbon derived from walnut green peel as an electrode material for high-performance supercapacitors

How to dispose agricultural waste walnut green peel has been a hard nut to crack during the ripening season. Transforming walnut green peel into activated carbon as electrode materials for energy storage devices would be a potential avenue to reduce the caused environmental pollution. Here, activated porous biomass carbon was successfully prepared by a simple KOH two-step activation of walnut green peel and applied in supercapacitors. Thereinto, the prepared carbon WGL-7 activated at 700 ºC showed high specific surface area (1404.3 m 2 g −1 ), abundant structural defects and pore structure, modest oxygen doping and wettability, and fast charge-transfer. The capacitance of WGL-7 modified electrodes could achieve 236 F g −1 at 0.5 A g −1 in 6 M KOH electrolyte, and its calculated energy density and power density were 31.8 W h kg −1 and 1003.5 W kg −1 . The capacitance retention rate remained 94.4% after 3000 cycles at 10 A g −1 . These results indicate that walnut green peel-activated carbon as the electrode material of supercapacitor has great capacitive performance.