Preparation of highly porous activated carbons from peanut shells as low-cost electrode materials for supercapacitors

The synthesis of three-dimensional porous biomass carbons from the abundant peanut shells is investigated employing K2CO3, KCl, KOH, and NaOH as the activators for the application as low-cost electrode materials for supercapacitors. The results show that KCl-AC and K2CO3-AC are mainly composed of microporous structures, while KOH-AC and NaOH-AC show a well-developed porous structure consisting of both micropores and mesopores, and NaOH activation is more inclined to form mesopores than KOH. KOH-AC achieves the highest specific surface area of 2936.8 m(2) g(-1) and a relatively higher graphitization degree among these samples. At 1 A g(-1), the gravimetric specific capacitances of K2CO3-AC, KCl-AC, NaOH-AC and KOH-AC are 250, 210, 284, and 339 F g(-1) in the three-electrode system. The gravimetric specific capacitance of KOH-AC reaches 440 F g(-1) at 0.1 A g(-1) and retains 286 F g(-1) at 10 A g(-1). In a two-electrode system, KOH-AC exhibits a high specific energy of 39.1 W h kg(-1) at a specific power of 2495.5 W kg(-1). KOH-AC also shows low internal resistance and good charge and discharge performance, and high cycle stability of 80% capacitance retention is achieved for 10000 cycles at 5 A g(-1).