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.

Graphical abstractThis described the increase of specific capacitance in activated N-doped carbon/MWNT electrodes with increasing microporosity.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Carbon layer coated carbon nanotubes were fabricated as new electrode materials. ► N-doped carbons layers (N/C) were obtained via carbonization of melamine layer. ► N/C-carbon nanotubes were further activated using potassium hydroxide (KOH). ► Activated N/C-CNTs showed highest specific capacitance value (262 F/g). ► It was due to easy ion transfer by micropores and redox reaction of the electrodes.