Ekaterina A. Arkhipova

Catalytic conversion of aliphatic alcohols on carbon nanomaterials: The roles of structure and surface functional groups

Carbon nanomaterials with the structure of graphene and different compositions of the surface groups are used as catalysts for the conversion of С2–С4 aliphatic alcohols. The conversions of ethanol, propanol- 1, propanol-2, butanol-1, butanol-2, and tert-butanol on carbon nanotubes, nanoflakes, and nanoflakes doped with nitrogen are investigated. Oxidized and nonoxidized multiwalled carbon nanotubes, nanoflakes, and nanoflakes doped with nitrogen are synthesized. X-ray diffraction analysis, X-ray photoelectron spectroscopy, scanning and transmission electronic microscopies, Brunauer–Emmett–Teller method, derivatographic analyses, and the pulsed microcatalytic method are used to characterize comprehensively the prepared catalysts. It was established that all of the investigated carbon nanomaterials (with the exception of nondoped carbon nanoflakes) are bifunctional catalysts for the conversion of aliphatic alcohols, and promote dehydration reactions with the formation of olefins and dehydrogenation reactions with the formation of aldehydes or ketones. Nanoflakes doped with nitrogen are inert with respect to secondary alcohols and tert-butanol. The role of oxygen-containing and nitrogen-containing surface groups, and of the geometrical structure of the carbon matrix of graphene nanocarbon materials in the catalytic conversion of aliphatic alcohols, is revealed. Characteristics of the conversion of aliphatic alcohols that are associated with their structure are identified.

Pseudocapacity of N-doped and polymer modified carbon nanomaterials in non-aqueous media

Abstract Present work deals with the pseudocapacitance of carbon nanomaterials modified by nitrogen heterosubstitution and electroactive polymers taking place in ionic liquids and lithium salts solutions in organic media. It is shown that N-doped materials, where nitrogen atoms are located within grahene layers, due to excess of electrons and variation of specific cooperation demonstrates higher capacitance than non-doped samples in the whole range of voltage applied, restricted by electrochemical stability window of electrolyte. The values were found to mostly depend on correlations of the ions size and pore size in the material. For composites of carbon nanotubes with electroactive polypyrrole, obtained electrochemically in the ionic liquid, the capacitance can increase more than 3 times due to reversible red-ox processes. In case of high purity of components there were no polymer degradation process observed. The possibility of implementation of mixed electrolytes based on solutions of high voltage ionic liquids with symmetrical electrochemical stability window and lithium salts in dry acetonitrile for realization of pseudocapacitance effect together with ion-pore size correlations is proposed.

Effect of the morphology of structured carbon nanomaterials on their oxidizability

The oxidation of multi-walled carbon nanotubes (MCNTs), nanofibers (CNFs), and few-layer graphite fragments (FLGFs) with a nitric acid solution was studied. The oxygen content in the functionalized derivatives was determined by X-ray photoelectron spectroscopy and thermal analysis. The results were correlated with the structural features of the nanomaterials revealed by high-resolution transmission electron microscopy and X-ray diffraction. The highest content of carboxyl groups was achieved by functionalization of carbon nanotubes with the conical position of graphene layers.