Tea-leaves based nitrogen-doped porous carbons for high-performance supercapacitors electrode

Nitrogen-doped porous activated carbons have been fabricated through a simple and efficient carbonization method at 700 A degrees 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 similar to 1143.9 m(2) 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.