Effects of Oxidation by Hydrogen Peroxide on the Structures of Multiwalled Carbon Nanotubes

Abstract

We studied the effects of H 2 O 2 oxidation without metal catalysts and under neutral conditions on morphologies and structures of the multiwalled carbon nanotubes (MWNTs). The formation of surface functional groups and changes in nanotube structures, morphology, and thermal stability during oxidation were analysized by X-ray photoelectron spectroscopy, X-ray diffraction, Raman spectra, high-resolution transmission electron microscopy, and thermogravimetric analysis. Several functional groups such as carboxylic (-COOH), carbonyl (-CdO), and hydroxyl (-OH) groups were formed on the surface of MWNTs; however, hydroxyl groups were preferentially formed and reached a maximum atomic concentration of about 46% in 4 days of oxidation. The graphitization degree decreased in the first day of oxidation; however, it readily increased in the continued oxidation days.

An efficient method for the carboxylation of few-wall carbon nanotubes with little damage to their sidewalls

“…Experimentally, room temperature oxidation of carbon nanotubes with hydrogen peroxide alone has been explored by Peng and col. [38]. Their results are in agreement with calculations made by Luque and col. [37]: hydroxylation takes place very slowly along several days preferentially on network defects and in a subsequent stage, eOH and lactone groups transform into carboxylic groups and CO 2 with removal of impurities.…”

“…The slight reduction in thermal stability is in accord with the results of Yun and col. [38] but not sufficiently explained in the literature. One possible explanation considers that oxidation process starts with decarboxylation and CO 2 generation creating a hole in the graphene sheet and inducing a cascade of events that ultimately collapses the carbon structure and its combustion.…”

Room Temperature Purification of Few-Walled Carbon Nanotubes with High Yield

“…Most reactions stud-ied thus were carried out in boiling H 2 O 2 for quick purification. 29 However, the selectivity at such conditions is still not optimized, resulting in the sacrifice of a significant amount of carbon nanotubes in order to reach high purity. In this study, we sacrificed the reaction time for more selectivity and higher yield by carrying out the reaction in a homogeneous H 2 O 2 solution at room temperature under constant stirring.…”

Dry Oxidation and Vacuum Annealing Treatments for Tuning the Wetting Properties of Carbon Nanotube Arrays

“…[18][19][20] These wet oxidation techniques are difficult to be scaled up to industrial level because of safety and environmental issues and the considerable amount of time to complete the oxidation process. In addition, a critical point drying method may need to be employed to minimize the effect of capillary forces that may destroy the microscopic structure and overall alignment of the CNT array during the drying process.…”