Electrochemical Behavior of Multi Walled Carbon Nanotubes Modified by Ammonia

Niemodyfikowane oraz utlenione wielościenne nanorurki węglowe (MWCNT) poddane zostały wygrzewaniu w temperaturze 500 oraz 900°C w strumieniu amoniaku. Wykonano badania fizykochemiczne, mające na celu ocenę jakościową efektów modyfikacji. Ponadto badano zachowanie elektrochemiczne uzyskanych materiałów węglowych metodą trójelektrodowej cyklowoltamperometrii w środowisku niewodnym, gdzie elektrodą pracującą była sedymentacyjna warstwa nanorurek węglowych. Wykazano, że azot wiąże się trwale z powierzchnią nanorurek, gdy wygrzewaniu w strumieniu amoniaku w temperaturze 500°C poddano wielościenne nanorurki wstępnie utlenione. Atomy azotu najprawdopodobniej wiążą się z powierzchnią w postaci soli amoniowych oraz amidów o różnej rzędowości. W tych warunkach prawdopodobnie część azotu jest wbudowana w struktury aromatyczne (aromatyczne heterocykliczne, azo-aromatyczne).Unmodified and oxidized multi walled carbon nanotubes (MWCNT) were heated (500°C and 900°C) in a stream of ammonia. The characteristics of the physicochemical properties of the samples obtained were estimated using various experimental methods. Cyclic voltammetry studies of nano-carbon electrodes in non-aqueous electrolyte were carried out to evaluate the electrochemical behavior of modified MWCNTs. The results of this work conclusively demonstrate the generation of nitrogen-containing moieties on the MWCNT surface only in case of heating at 500°C in a stream of ammonia previously oxidized carbon nanotubes. Probably the nitrogen atoms were bound to the nanotubes surface as ammonium salts, amides with different order of a nitrogen atom and aromatic structures (aromatic heterocyclic, azo-aromatic)

An Attempt to Apply Analogs of the Dubinin-Radushkevich and Freundlich Equations for Describing Isotherms of Adsorption from Binary Liquid Solutions of Non-Electrolytes with Unlimited Miscibility

An extention of the Dabrowski and Jaroniec concept of describing adsorption from binary liquid solutions of non-electrolytes on solids in terms of the Dubinin-Radushkevich (DR) and Freundlich (F) equations is presented. A new solution has been advanced based on the definition of the chemical affinity of the process of generation of equilibrium bulk phase from the pure components of the solution. The real adsorption isotherm equation has been formulated in which particular cases are the quasi-DR equation and the quasi-F equation. Some adsorption systems are described

Changes in the Surface Chemistry and Adsorptive Properties of Active Carbon Previously Oxidised and Heat-Treated at Various Temperatures. II. Electrochemical Investigations of Surface Chemistry

Thermal treatment of oxidised active carbon under vacuum conditions led to changes in the chemical nature of its surface, e.g. a stepwise decrease in the total oxygen content and an increase in the pH of the carbon slurry. Annealing reduced the number of surface oxygen-containing groups and increased the overall number of basic groups. The results of the cyclic voltammetric studies analysed in this paper clearly indicate only a weak relationship between the presence and number of cathodic/anodic peaks, i.e. reduction/oxidation of electroactive surface groups, forming during cyclisation and the degree of surface oxidation (regulated by heat treatment) of the carbon samples tested. The electrochemical behaviour of powdered carbon suggested electro-oxidation of the surface of the electrode material with participation of adsorbed hydroxy ions and water molecules. The possible electrochemical reactions and mechanisms of the surface processes were discussed in order to explain the observed phenomena

Description of Adsorption of Iodine from Non-Aqueous Solutions on Active Carbon

A description is proposed of iodine adsorption on active carbon from solutions in six different organic solvents in terms of general criteria of thermodynamic equilibrium in liquid solutions of limited miscibility of the components. The numerical values of the parameters of the excess adsorption isotherm equation have been determined and the distribution function of the adsorption potential difference of the components, which characterizes the global adsorption heterogeneity of the system, has been calculated under the assumption that the tested mixtures behave like ideal solutions