Synthesis and structural/electrochemical evaluation of N, S co-doped activated porous carbon spheres as efficient electrode material for supercapacitors

Micrometer size activated porous carbon spheres doped with nitrogen and sulfur (NSAPC) are synthesized hydrothermally by using saccharose as the carbon precursor and l-cysteine as the doping agent, followed by KOH activation. These doped porous carbon spheres possess a high specific surface area (SSA) and porosity (mainly microporous) suitable for efficient charge storage. Additionally, doping with nitrogen and sulfur significantly changes the surface chemistry. When tested as electrode material for supercapacitor, the co-doped porous carbons outperformed the undoped carbon. NSAPC spheres show a high specific capacitance of 270 F/g at a current density of 1 A/g in 1 M H2SO4 and exhibit excellent charge-discharge cycling stability over 5000 cycles. The enhanced electrochemical performance can be attributed to the combined effect of high specific surface area, presence of micro and mesopores along with nitrogen and sulfur heteroatoms.