A. A. Nechitailov

Specific features of operation of a membrane-electrode assembly of an air-hydrogen fuel cell

Specific features of the operation of the membrane-electrode assembly with high catalytic activity that are a part of the simplified design of a low-temperature air-hydrogen fuel cell under conditions of forced and natural convection of air on the cathode are studied. The governing effect of water balance on the specific power of the fuel cell in the stationary mode (∼1 h) is shown, and the range of the operating conditions of the cell with self-control is determined. The power of the fuel cell at an efficiency of ∼50% and the surface density of platinum on a cathode of ≈0.2 mg/cm2 is 200–250 and 100 mW/cm2 in the forced and natural air-convection modes, respectively, which is comparable with the advanced results.

Specific features of oxygen electroreduction on platinized carbon black-functionalized carbon nanotube composite

The electrochemical behavior of multiwalled carbon nanotubes (MWCNTs) containing functional surface groups has been studied by the methods of cyclic voltammetry and direct-current polarography with stationary and rotating disk electrodes. The surface catalytic activity of supported platinum in the reaction of molecular oxygen electroreduction and the influence of functionalized MWCNTs on this process were determined.

Thermal oxidation of carbon nanomaterials

The process of the thermal oxidation of various carbon nanomaterials (multiwalled carbon nanotubes, carbon black, nanoporous carbon and graphite) used in the catalytic layers of electrochemical energy converters (electrolyzers, fuel cells) has been studied. The thermal stability of these materials has been determined. Relationships between the structural characteristics of carbon nanomaterials and the parameters of their thermal oxidation in air have determined using the methods of differential thermal analysis and adsorption-structure analysis.

Mass transport at the cathode of a hydrogen fuel cell in the presence of carbon nanotubes

The influence of carbon nanotubes (CNTs) in the composition of a porous cathode on the increase in the current density of the corresponding standard cathode is studied during the operation of an oxygen–hydrogen fuel cell. The influence of CNTs caused by structure and mass exchange is investigated.

Cathode of hydrogen fuel cell, with modified structure and hydrophobicity

Relationship between the composition of the cathode of a hydrogen fuel cell with a proton-conducting membrane, the porosity, and the diffusion properties upon introduction into the cathode of functional additives of a hydrophobizing agent and carbon nanotubes.

Membrane-electrode assemblies with high specific power based on functionalized carbon nanotubes

It is demonstrated that the efficiency of catalysis and platinum usage in electrochemical energy converters can be improved by employing chemically functionalized multiwalled carbon tubes. On this basis, membrane-electrode assemblies for air-hydrogen fuel cells with specific powers up to 581 mW/cm2 have been obtained.

Impurity defects in Cr-doped Bi12SiO20 and Bi12TiO20 crystals

Bi12SiO20 and Bi12TiO20 crystals doped with l0-5 to 2 x 10-2 wt % Cr were grown by the Czochralski technique. The Cr content of the crystals and the valence state of Cr ions were determined by a new analytical technique with the use of 1,5-diphenylcarbazide. Correlations were revealed between the segregation coefficient of the dopant, the charge state of Cr ions, and the absorption coefficient of the crystals. Doping with Cr was found to shift the intrinsic edge to longer wavelengths and to give rise to a new absorption band in the near-IR region. The results are interpreted as indicating that the Cr ions in the sillenite crystals studied are in at least two oxidation states and occupy inequivalent sites in the sillenite cell.

Technology and structural characteristics of electrode material in the Pt/C–Taunite-MD–Nafion system

Laboratory technique was developed for fabrication of an electrode material containing a platinized carbon black, carbon nanofibers, and proton-conducting polymer Nafion. Scanning and transmission electron microscopy was used to study the structure of the material and experimental dependences were obtained that relate the properties and structure of the electrode material to its structure and fabrication technique and make it possible to obtain a material with prescribed service characteristics.

A voltammetric method of measuring the specific surface area and amount of platinum in microsamples of electrode material and membrane-electrode assembly of hydrogen fuel cells

A method based on cyclic voltammetry is proposed for determining platinum content, measuring the specific area of the active surface of platinum nanoparticles, and studying the dynamics of these values in a small amount (micrograms) of sample material.

Influence of the purity of the starting materials on the recording of dynamic holograms in Bi12TiO20 crystals

The parameters of Bi12TiO20 crystals grown with bismuth oxide of different degrees of purity were measured by a holographic recording technique in an external ac electric field and were compared with a crystal specially doped with chromium. Various crystal parameters such as the diffusion length of the photoexcited carriers and the Debye screening length were determined. It was found that the absorption spectrum of the material and the holographic recording efficiency were strongly influenced by light chromium doping and by insufficient purity of the starting mixture.