Synthesis and high electrochemical capacitance of N-doped microporous carbon/carbon nanotubes for supercapacitor

Nitrogen-enriched carbon layer-coated multi-walled carbon nanotubes (N/C-MWNTs) composed of core MWNTs and carbon shells were prepared to obtain a new type of carbon electrode materials, and then chemically activated using KOH. After carbonization and activation, the activated N/C-MWNTs (A-N/C-MWNTs) contained about 18% nitrogen and showed a 1-D structure like MWNTs. In addition, the A-N/C-MWNTs exhibited superior electrochemical performance to that of pristine MWNTs and N/C-MWNTs; the highest specific capacitance (262 F/g) of the A-N/C-MWNTs was obtained at a current density of 0.5 A/g, as compared to 66 F/g for MWNTs and 161 F/g for N/C-MWNTs. This superior performance was attributed to the combination effect between improved EDLC features via microporosity developed by chemical activation and increased redox reaction by high nitrogen content of basic A-N/C-MWNTs in acidic electrolyte.