Electro-purification of carbon nanotube networks without damaging the assembly structure and crystallinity

Fe-containing nanoparticles are of a high mass fraction in the as-grown carbon nanotube (CNT) network. By controlling the S-to-Fe atom ratio in the growth feedstock and introducing water as a weak oxidant, highly crystalline few-walled CNT network can be obtained, with a mass fraction of over 20 wt% for the Fe-containing nanoparticles. We report here an electron-oxidation-based purification method to efficiently remove the Fe-containing nanoparticles without inducing clear damage to either the assembly structure or the tube crystallinity. The purification could increase the ratio between Raman D and G peak intensities slightly from 0.08 to 0.12, decrease the specific conductivity from 0.31 to 0.24 S m2/g and the Fe content from >20 wt% to ≈1 wt%, and modify the capacitance just by about 13 F/g. All these indicate that the CNT network was well maintained by such gentle electro-oxidation-based purification. In addition, the purified CNT network can exhibit advantages in mechanical and electrical applications.