Understanding the oxygen-containing functional groups on multiwall carbon nanotubes toward supercapacitors

Typical functionalization treatment by strong acid is used to introduce functional groups into/onto the multiwall carbon nanotubes (MWCNTs), to enhance the desired redox activity for electrochemical applications. The influence of various functional groups on the redox of MWCNT has been studied in recent years. Different functional groups on MWCNT can be removed selectively using different thermal annealing temperatures. By this method, it is recognized that carboxyl, anhydride, and phenol groups play essential roles in the redox reaction. A designed carboxyl/anhydride-rich defective MWCNT is fabricated with a superior specific areal capacitance of 34.55 mF/cm2. These results provide more information for the study of the MWCNTs' electrochemical applications toward supercapacitors and batteries.