A. E. Ukshe

Proton conductivity of calix[4]arene-para-sulfonic acids

The proton conductivity of hydrates of calix[4]arene-para-sulfonic acids is studied. The high proton conductivity is observed at ambient temperatures in the wide ranges of environmental humidity and, correspondingly, water content in the hydrate. For the air humidity of 10 rel. %, the conductivity of compounds is 10−4-10−3 S cm−1 and approaches 10−2-10−1 S cm−1 as the humidity increases up to 70 rel. %.

Electrochemical noise diagnostics: Analysis of algorithm of orthogonal expansions

The algorithm of orthogonal expansions is applied to the problem of extraction of diagnostic information from random noise. It is shown that the spectral analysis of electrochemical noise can be performed by a unified algorithm regardless of the type of orthogonal expansion used. A multi-channel indicator of color of electrochemical noise can be constructed on the basis of the orthogonal expansions. It is concluded that the algorithm of orthogonal expansions is an advantageous tool for noise monitoring and noise diagnostics of practically important electrochemical devices, including the devices of electrochemical energetics and systems of protection against corrosion.

Electrochemical noise spectroscopy: Method of secondary Chebyshev spectrum

A new method of electrochemical noise diagnostics is presented: the method of the secondary Chebyshev spectrum based on the splitting of an individual spectral line in the primary Chebyshev spectrum with formation of a system of spectral lines of the secondary Chebyshev spectrum. Algorithm for calculation of the secondary Chebyshev spectrum is developed. The suggested method based on analysis of noises measured in a specific electrochemical system is tested. It is shown that the new method allows determining the differences in the state of the electrochemical system more reliably, than the method of primary Chebyshev noise spectra.

Effect of the structure of calix[4]arene-para-sulfonic acid on its transport properties

The effect of a change in the ambient temperature and humidity on the behavior of calix(4)arene-para-sulfonic acid was studied. For the calixarene under study, at least two stable hydrates were observed: tetra- and octahydrate. The number of water molecules in the crystalline hydrate of the acid was confirmed by simultaneous thermal analysis data and the shape of the IR spectra and diffraction patterns. The change in the composition of the hydrate from n = 4 to n = 20 affected the conductivity but slightly; in the region of phase transitions between the hydrates, the activation energy of conductivity changed abruptly.

Percolation model of conductivity of calix[n]arene-p-sulfonic acids

Proton conductivity of special class of aromatic sulfonic acids is described, in particular, calixarene sulfonic acids that consist of flat anionic layers interlinked by labile two-dimensional hydrogen-bond network. High proton conductivity of their hydrates was observed earlier. The dependence of their transport characteristics (the proton conductivity, the activation energy of conductivity) was shown to have threshold character. The studied systems’ behavior is described on basis of percolation model that assumes changing of the proton transport mechanism at low water content in the structure.

Materials for bipolar plates for proton-conducting membrane fuel cells

The review is devoted to the present state of research and development in the field of construction materials for bipolar plates for hydrogen-air fuel cells with polymeric proton-conducting membranes. Principal requirements for such materials are considered and criteria for their selection are formulated.

Variability of discrete Chebyshev spectra of electrochemical noise

A new characteristic of the electrochemical noise spectrum, namely, the variability of an individual line in the discrete Chebyshev spectrum, is discussed. For Chebyshev transforms that have the normal (Gaussian) probability distribution, the proposed variability is 1. In a model experiment, the effect of the lowfrequency harmonic disturbance (drift) and the high-frequency harmonic disturbance (aliasing component) on the variability of an individual line in the Chebyshev noise spectrum is studied. The potentialities of the new approach are demonstrated for a noise electrochemical system involving corrosion processes. The variability of the corrosion process is shown to exceed the variability of the Gaussian noise by a factor of 1.5. The proposed characteristic of electrochemical noise spectrum, namely, the variability of individual line in the discrete Chebyshev spectrum can be a useful informative parameter for the electrochemical noise diagnosis in various electrochemical systems including chemical power sources and fuel cells in which electrochemical corrosion processes can occur.

Electrochemical sensors based on platinized Ti1 − xRuxO2

Electrocatalysts based on platinized titania modified with ruthenia (0–9 mol %) were studied. The synthesized materials were investigated as working electrodes in potentiometric sensors sensitive to hydrogen and carbon monoxide. All electrocatalysts showed reproducible behavior at pure gas concentrations from 400 to 4000 ppm. In CO-H2 mixtures with comparable concentrations of both gases, the sensors were selective toward hydrogen at ≥0.05 mol % Ru, but not selective to hydrogen or CO at less than 0.05 mol % Ru in the substrate.

Platinized-heteropolycompound-based nanostructured catalysts for low-temperature hydrogen-air fuel cells

Heteropoly acids CsxH3 − xPW12O40 · nH2O with different cesium content are synthesized as nanostructured compositions. Their actual composition and specific surface are determined, microstructure studied and proton conductivity measured. Composite electrocatalytic systems based on platinized cesium salt of phosphorus-tungsten heteropolyacid Cs2.3H0.7PW12O40 · nH2O are prepared with admixture of Vulcan XC-72 carbon black. Mixed electronic-ionic conduction of the composite systems with different carbon black content is studied. Platinum-based nanostructured electrocatalyst based on the Cs2.3H0.7PW12O40 · nH2O-materials as support is synthesized and studied. The possible effective using of the studied nanocomposite as electrode for low-temperature hydrogen-air fuel cells is demonstrated. Electrochemical studies of catalytic properties of the Pt-Cs2.3H0.7PW12O40 · nH2O-C-electrodes in hydrogen and air are carried out by example of the prepared materials with different carbon black content.

Portable sensors for hydrogen analysis

Presently available methods for the determination of hydrogen in the gas phase are analyzed. Various procedures for the detection of hydrogen both at pre-explosion and at very low (less than 50 ppm) concentrations by means of thermocatalytic, semiconductor, amperometric, and potentiometric electrochemical sensors are considered.