Optimization of the cathode porosity via mechanochemical synthesis with carbon black

Journal of Solid State Electrochemistry - Nanostructured carbon–coated composite cathode materials LiFe0.5Mn0.5PO4/C (LFMP/C) are prepared by the mechanochemically assisted solid-state...     

Conducting properties of a gel ionite modified with zirconium hydrophosphate nanoparticles

The organo-inorganic composites based on a strongly acid gel resin including zirconium hydro-phosphate nanoparticles and their aggregates were studied by impedance spectroscopy, electron microscopy, and standard contact porosimetry. The porous structure of the polymer was transformed under the action of the inorganic filler. The nanoparticles in the transport pores provided a three- to fivefold increase in the electric conductivity of the nanocomposites compared with the conductivity of the nonmodified ionite and a decrease in the percolation threshold. The nanocomposite ionites demonstrated stability against the accumulation of organic substances during electrodeionization to extract Na⁺ from low-concentrated solutions.     

Electrochemical,Structural, and Thermogravimetric Studies of Activated Supercapacitor Electrodes Based on Carbonized Cellulose Cloth

Russian Journal of Physical Chemistry A - The high–temperature reagentless activation of carbonized cellulose cloth is used to manufacture supercapacitor (SC) electrodes with different fast...     

Effect of the functionalizing of carbon nanotubes on the electrodeposited catalysts’ structure and catalytic properties

The structure and hydrophilic-hydrophobic properties of functionalized single-wall carbon nanotubes are studied by the standard porosimetry method. It is shown that the functionalized nanotubes have highly hydrophilic surface; at that the summary surface area measured “by octane” decreased, as a result of the functionalizing, due to the blocking of the nanotubes’ inner channels by the functional groups located at the nanotubes’ ends. The nanotubes’ capacitive properties are studied; their charging-discharging curves appeared being highly reversible, unlike those of other carbonaceous materials. Catalytic properties of the functionalized nanotubes are studied, with particular tendency toward their using as a carrier of platinum catalysts for the methanol oxidation and oxygen electroreduction reactions. When minor amounts (5–10 μg cm⁻²) of platinum or platinum-ruthenium alloy are deposited onto the nanotubes’ hydrophilic surface, uniform layer of the catalyst is formed, with specific surface area up to 150–300 m² g⁻¹; high current of the methanol oxidation or oxygen electroreduction is observed at these catalysts. When the catalyst deposit mass increased, its specific surface area decreased, as well as the specific current of the reactions occurring thereon. When the current is related to the electrochemically active unit surface, the catalytic activity is nearly the same both for different catalyst mass deposited onto the nanotubes and the same catalyst mass at different carbonaceous carriers.     

Carbon electrodes with high pseudocapacitance for supercapacitors

Electrochemical properties of electrodes on the basis of CH900-20 activated carbon (AC) cloth were studied in concentrated H₂SO₄ solutions in a wide range of potentials from −0.8 to +1 V RHE. Cyclic voltammetric curves measured in two ranges of potentials were analyzed: in the reversibility range (from 0.1 to 0.9 V) and in the deep cathodic charging range (from −0.8 to 1 V). Electric double layer (EDL) charging occurs in the reversibility range, while faradaic processes of hydrogen chemisorption and its intercalation into carbon take place in the range of negative potentials (<−0.1 V). The intercalation process is controlled by slow solid-phase hydrogen diffusion. For the first time, the maximum value of specific discharge capacity of 1560 C/g was obtained, which is much higher than the values known from the literature for carbon electrodes. On the basis of this value and Faraday’s law, it was assumed that the compound of C₆H is formed in the limiting case of AC deep cathodic charging. The specific charge value grows at an increase in the concentration of H₂SO₄. The mechanism of double intercalation of sulfuric acid and hydrogen into the AC is suggested. The data obtained are used to develop a mathematical charging-discharge model for an AC electrode taking into account the EDL charging, chemisorption, and hydrogen intercalation.     

Electrochemical Properties of Carbon Black AD-100 and AD-100 Promoted with Pyropolymer of Cobalt Tetra(p-methoxyphenyl)porphyrin

Carbon black AD-100: initial, activated, and promoted with pyropolymer of cobalt tetra(p-methoxyphenyl)porphyrin is characterized by a complex of electrochemical (floating electrode, rotating disk electrode, rotating ring-disk electrode, electrochemical impedance) and structural (standard porosimetry, BET) methods of investigation. Procedures for the AD-100 activation and promotion and the preparation of thin layers of the material to be studied and deposited on disk electrodes are described. The effect of the activation and promotion of carbon black on the surface and electrocatalytic activity of materials under study in the reduction of oxygen and hydrogen peroxide is shown. The ratio of constants of oxygen reduction directly to water and through intermediate formation of hydrogen peroxide is determined. A path for the oxygen reduction is discussed.     

Electrochemical dehalogenation of polytrifluorochloroethylene

The electrochemical reduction of polytrifluorochloroethylene suspended in an electrolyte using organic electron transfer mediators led to surface modification of the polymer. Pyrolysis of the reduction product was accompanied by the formation of a highly porous thermally stable polycarbon material with pore sizes in a very wide range, approximately from 1 to 10⁵ nm.     

Carbon nanofiber paper cathode modification for higher performance of phosphoric acid fuel cells on polybenzimidazole membrane

Entire carbon nanofiber mats (carbon nanofiber paper) based on polyacrylonitrile pyropolymer composite were prepared by the preliminary oxidation (stabilization) of the initial polymer at 250–350°C in air and following pyrolysis at 800–1200°C under vacuum. The mats were tested as cathodes in a fuel cell on polybenzimidazole membrane. Properties of the pyropolymers which were obtained by polymer carbonization could be significantly changed by the addition of specific additives to polyacrylonitrile and also by changing thermal treatment. Particularly, the addition of Ketjen Black® or Vulcan® XC72 carbon blacks and polyvinyl pyrrolidone during electrospinning step resulted in increase of material electrical conductivity and inner porosity, which is important for improving fuel cell performance. Depending on oxidation and pyrolysis temperature, the physical properties of platinated carbon nanofiber paper and the efficiency of a fuel cell on polybenzimidazole membrane significantly change.     

Effect of the porous structure of polymer on the kinetics of Ni<Superscript>2+</Superscript> exchange on hybrid inorganic-organic ionites

Hybrid organic-inorganic ion exchangers are obtained by incorporating amorphous zirconium hydrophosphate into the gel of strong acidic cation exchange resin. Hybrid organic-inorganic ion exchangers are obtained by modifying strong acidic cation exchange resin with amorphous zirconium hydrophosphate. The synthesized materials are studied by standard porometry contact. It is found that raising the inorganic component content to 34 wt % diminishes the microporosity of the samples and simultaneously enhances the of meso- and macropore volume. Experiments establish that modification of a polymer matrix lowers the self-diffusion coefficient of Ni²⁺ from 8.1 × 10⁻¹² to 2.4 × 10⁻¹²–4.1 × 10⁻¹² m² s⁻¹; nevertheless, an inorganic ion exchanger minimizes the inhibitory effect of co-ions on the Ni²⁺ → H⁺ exchange rate. One possible mechanism for of filling of the matrix by with particles of zirconium hydrophosphate is discussed.