High performance of activated multi-walled carbon nanotube composite electrode in KI redox electrolyte

Abstract

High performance electrodes for supercapacitor usually are achieved by compositing conductive and redox materials, the former such as multi-walled carbon nanotubes (MWCNTs), graphene, etc., provide the electrical double-layer capacitances that far less than pseudo-capacitances of the later (metal oxide, polyaniline, and so on). Here, carbonaceous composite electrode of MWCNTs and the redox electrolyte are combined into an electrochemical system for high synergetic effect of capacitance. MWCNT is activated by acid treatment and its structures are characterized by scanning electron microscope, X-ray diffraction, and Infrared spectroscopy analyses. The electrochemical measurements of resultant electrodes showed an excellent synergetic effect. The acid-activated MWCNTs electrode exhibited the maximum specific capacitance of 682 F/g in 0.2 M KI redox electrolytes, which is about 2–20 times larger than MWCNTs and its composite electrode in universal electrolyte without KI.

Keywords:

• MWCNTs
• KI solution
• specific capacitance
• acid treatment
• redox electrolyte

Funding

This work was supported by the National Natural Science Foundation of China (NSFC) [grant number 21271031], [grant number 51573021], [grant number 51063009], [grant number 51203012]; the Beijing Natural Science Foundation of China [grant number 2092013], [grant number 2132009], [grant number 2122015]; and the State Key Laboratory of Organic-Inorganic Composites of China.