Mechanism of Thermal Defunctionalization of Oxidized Carbon Nanotubes

Abstract

The mechanism of thermal defunctionalization of multiwalled carbon nanotubes (CNTs) oxidized by nitric acid was studied. X-ray photoelectron spectroscopy and thermal analysis under different heating rates combined with mass spectrometry of evolved gases (TGA–MS) were used to reveal the transformations on the CNT surface. Hydrogen–deuterium exchange and mathematical handling of TGA–MS curves were carried out to evaluate the impact of a small amount of residual oxygen on CNT defunctionalization. Water, CO, CO2, and NO/CH2O mass curves recorded during TGA–MS study were curve fitted. The resultant peaks were attributed to the different stages of CNT defunctionalization. Deuterium exchanged CNTs allowed one to reveal the mechanism of water release during heating. Kissinger’s model was applied to estimate the activation energy of the decomposition of different functional groups on the surface of CNTs.

Carbon Fibers Obtained from Flax and Their Adsorption Performance in the Removal of Cu(II) and Co(II) from Aqueous Solutions

“…This values is comparable to other non‐oxidized carbon materials, e.g. activated carbon, carbon nanotubes, graphene sheets . The presented trend is non‐linear, however, the total acidity gradually rises with an increase of nitric acid concentration.…”

Ultrafast all-fibre laser mode-locked by polymer-free carbon nanotube film

“…It is equally pertinent to note that essential properties of CNT themselves may also be affected by oxidation in air [18,19] or elevated temperatures [20]. In order to avoid such modification, free-standing CNT films must be isolated from air (for instance, by placing them inside a sealed fibre connector, between whose ferrules a free-standing CNT film is clamped) and used in conditions ensuring that the laser radiation absorbed within the CMT film does not result in excessive heating of the film.…”

Carbon Dioxide Reduction with Hydrogen on Carbon‐Nanotube‐Supported Catalysts under Supercritical Conditions

“…Multi‐walled carbon nanotubes obtained by pyrolytic synthesis and used as catalytic supports can be represented as defect‐embedded cylinders with the thickness in the range 10–25 nm and inner channels of 2–4 nm . The survey X‐ray photoelectron spectrum of the carrier is shown in Figure .…”

“…The content of oxygen in the sample of the carbon nanotube turned out to be 8.2 wt%. To study the composition of functional groups, the spectrum in the region of C1s was deconvoluted into the following components: C—C (sp 2 ) at the binding energy (BE) 284.3 eV, C—C (sp 3 ) at BE = 285.0 eV, C—O at BE = 286.4 eV, C═O at BE = 287.2 eV, and O—C═O at BE = 288.6 eV . The major part of oxygen was found in the form of carboxylate and hydroxyl groups, whereas carbonyl groups were virtually absent, which is typical for the treatment of carbon nanotubes with an aqueous solution of nitric acid.…”