Size-controllable synthesis of monodispersed nitrogen-doped carbon nanospheres from polydopamine for high-rate supercapacitors

Monodispersed nitrogen-doped carbon nanospheres with tunable particle size (100–230 nm) were synthesized via self-polymerization of biochemical dopamine in the presence of hexamethylenetetramine as a buffer and F127 as a size controlling agent. Hexamethylenetetramine can mildly release NH 3 , which in turn initiates the polymerization reaction of dopamine. The carbon nanospheres obtained exhibited a significant energy storage capability of 265 F·g −1 at 0.5 A·g −1 and high-rate performance of 82% in 6 mol·L −1 KOH (20 A·g −1 ), which could be attributed to the presence of abundant micro-mesoporous structure, doped nitrogen functional groups and the small particle size. Moreover, the fabricated symmetric supercapacitor device displayed a high stability of 94% after 5000 cycles, revealing the considerable potential of carbon nanospheres as electrode materials for energy storage.