Nitrogen-doped porous carbons through KOH activation with superior performance in supercapacitors

A series of nitrogen-doped porous carbons are prepared through KOH activation of a nonporous nitrogen-enriched carbon which is synthesized by pyrolysis of the polymerized ethylenediamine and carbon tetrachloride. The porosity and nitrogen content of the nitrogen-doped porous carbons depend strongly on the weight ratio of KOH/carbon. As the weight ratio of KOH/carbon increases from 0.5 to 2, the specific surface area increases from 521 to 1913 m2 g−1, while the nitrogen content decreases from 10.8 to 1.1 wt.%. The nitrogen-doped porous carbon prepared with a moderate KOH/carbon weight ratio of 1, which possesses a balanced specific surface area (1463 m2 g−1) and nitrogen content (3.3 wt.%), exhibits the largest specific capacitance of 363 F g−1 at a current density of 0.1 A g−1 in 1 M H2SO4 aqueous electrolyte, attributed to the co-contribution of double-layer capacitance and pseudocapacitance. Moreover, it shows excellent rate capability (182 F g−1 remained at 20 A g−1) and good cycling stability (97% capacitance retention over 5000 cycles), making it a promising electrode material for supercapacitors.