A. A. Tomasov

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.

Conductivity compensation in CdZnTe: Cl crystals with variable zinc content

The effect of cadmium vapor pressure during postgrowth annealing on the compensation of conductivity has been studied in semi-insulating Cd1−xZnxTe:Cl crystals with variable zinc content (x = 0.005, 0.01, and 0.05), which are used in nuclear radiation detectors. At a small zinc content (x = 0.005 and 0.01), the main role in the in Cd1−xZnxTe:Cl crystals is played by the cadmium point defects. In crystals with a higher zinc content (x = 0.05), the compensation of charged defects is incompletely controlled by changing the cadmium vapor pressure, which is evidence of a significant influence of the zinc point defects.

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.

Effect of annealing on semi-insulating CdZnTe:Cl crystals with variable zinc content

Semi-insulating Cd1−xZnxTe:C1 crystals with variable zinc content (x = 0.0002, 0.005, 0.01, and 0.1) were grown using the method of horizontal directional solidification. The effect of the conditions of post-growth annealing under controlled cadmium vapor pressure and additional low-temperature annealing on the main parameters responsible for the quality of nuclear radiation detectors based on such crystals were studied.

Exact self-compensation of conduction in Cd0.95Zn0.05Te:Cl crystals in a wide range of Cd vapor pressures

The process of self-compensation in Cd0.95Zn0.05Te:Cl solid-solution crystals has been studied by annealing single crystals under a controlled Cd vapor pressure, with subsequent measurements of the Hall effect, photoluminescence, carrier lifetime and mobility, and photocurrent memory in the annealed crystals. By means of this annealing, conditions of thermal treatment that make it possible to fabricate low-conductivity samples with a low carrier density, 107–1011 cm−3, are defined. In these samples, a p → n conduction inversion is observed at a higher free-carrier density (n, p ≈ 109 cm−3) and the dependence of the electron density on the Cd vapor pressure exhibits a more gentle slope than in the case of CdTe:Cl crystals. The obtained data are discussed in terms of a self-compensation model in which intrinsic point defects act as acceptors with deep levels. This level is attributed to a Zn vacancy, which remains active at high Cd pressure.

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.

Humidity-independent portable air-hydrogen fuel cells with slotted silicon based gas-distributing plates

We have studied the characteristics of small-scale air-hydrogen fuel cells (FCs) operating in a free-breathing cathode regime. The cells are provided with a new gas-distributing element on the cathode side, which is based on a silicon plate with narrow through slots (slotted Si plate). It is shown that the use of a slotted Si plate significantly weakens the dependence of the FC characteristics on the humidity of environment in a broad temperature range. Indeed, at a fixed temperature, the FC power only changed within 10% when the relative humidity of the ambient air varied between 50 and 98%.

Structure of platinum–carbon electrodes containing various forms of nafion proton-conducting polymer

Scanning electron microscopy, atomic force microscopy, and cyclic voltammetry have been used to perform a complex comparative study of the structure of hydrogen fuel cell electrodes consisting of nanostructured platinum on carbon black and electrodes containing a proton-conducting Nafion polymer introduced into the electrode in the form of a solution and in a precoagulated state. It has been shown that, in the latter case, the specific area of electrochemically active platinum increases significantly (by up to two times).