Effect of chemical treatment of multi-walled carbon nanotubes on the specific capacitance of supercapacitors

Abstract

To date, the research on carbon nanomaterials has progressed rapidly. More than 400 papers were written in 2021 on the application of carbon nanomaterials in various fields. The high demand for the use of such materials has increased due to a sharp increase in the demand for semiconductor materials and materials for supercapacitor electrodes and other electrical devices. Despite the unique physical properties of carbon nanomaterials, there are limitations to their use. To solve this problem, various methods of modifying the surface, both through chemical interactions and physical adsorption, were proposed. One of these methods is chemical modification. The evaluation of effect of chemical treatment parameters on the properties of carbon nanomaterials is an urgent task due to the fact that the chemistry of the processes is poorly understood. In this work, the effect of concentrated sulfuric and nitric acids on the change of specific surface area, elemental composition, composition of functional groups, and also on the change of specific capacitance was considered. It is believed that both the porosity and the functional groups formed during oxidation contribute to the change in specific capacitance. The specific surface area of all samples decreased on average by a factor of 1.5–3 after the chemical treatment. Different oxygen and sulfur-containing functional groups are observed after the chemical treatment. The highest specific capacitance of the treated carbon nanofibers was 114 F/g.

Treatment of Multi-Walled Carbon Nanotubes with Dichromic Acid: Oxidation and Appearance of Intercalation

“…When comparing the specific capacitance of MWCNTs treated with sulfuric acid, which is one of the most frequently used oxidizers [ 44 ], it can be concluded that the treatment with dichromic acid leads to higher specific capacitance of material as well as lower C:O ratios [ 2 ]. Moreover, sometimes the oxidative treatment with sulfuric acid or nitric acid does not lead to a significant improvement in specific capacitance (the latter varied from 2.9 to 3.67 F g −1 for chemically treated CNT-based textile samples) [ 31 ].…”

“…Carbon nanomaterials have a wide range of applications in various fields and their research is cutting edge nowadays. The main prospective materials from this group are carbon nanotubes, which are interesting to be applied in supercapacitors [ 1 , 2 , 3 , 4 ], membranes [ 5 , 6 ], biosensors [ 7 ], polymer composites [ 8 , 9 ], batteries [ 10 ], gas sensors [ 11 , 12 , 13 ], etc. The creation of novel high-performance supercapacitors is on the way to large-scale production and extensive research should be carried out to overcome many problems towards this direction.…”