文摘
Nitrogen-doped porous activated carbons have been fabricated through a simple and efficient carbonization method at 700 °C with the waste tea-leaves as carbon precursor and ZnCl2 as activating agent. The average pore size and specific surface area are in the ranges of 2.3–6.6 nm and 10.3 ~ 1143.9 m2 g−1, with the ZnCl2 to tea-leaves weight ratio from 0 to 3. As an electrode material for supercapacitors, the TPACs-2 (the ZnCl2 to tea-leaves weight ratio is 2) which has 3.0 wt% nitrogen content, possesses a large specific capacitance of 296 F g−1 at 0.5 A g−1 and excellent rate capability (74 % retention at 10 A g−1) in 2 mol L−1 KOH. Furthermore, the symmetric supercapacitor fabricated with TPACs-2 electrodes delivers a high energy density of 13.5 Wh kg−1 at a power density of 221 W kg−1 and superior cycle stability (only 9 % loss after 5000 cycles), operating in the wide voltage range of 0–1.8 V in 0.5 mol L−1 Na2SO4 aqueous electrolyte. The results demonstrate TPACs-2 is a promising candidate for the electrode material of supercapacitors.