Yu. A. Dobrovolskii

Median Chebyshev spectroscopy of electrochemical noise

An algorithm for analyzing electrochemical noise based on Chebyshev spectroscopy using the sample median is presented. Chebyshev spectroscopy with the sample median nicely complements Chebyshev spectroscopy with the sample mean. Chebyshev noise spectroscopy with the sample median can be used to distinguish between corrosion processes, which cannot be achieved using Chebyshev spectroscopy with the sample mean. This “median Chebyshev spectroscopy” can be effectively used to diagnose the electrochemical noise of corrosion systems and electrochemical power sources.

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.

Crystal Structure and Properties of Acid Salt of Orthoperiodic Acid CsH9I2O12

The acid salt of orthoperiodic acid CsH9I2O12crystallizes in the monoclinic system: base-centered unit cell, space group Cc. Unit cell parameters: a=18.473(5) Å, b= 5.439(2) Å, c= 10.481(3) Å, β = 99.73°. The crystal structure consists of layers parallel to the yzcrystallographic axis. The layers are formed by the Cs+ions, the molecules of orthoperiodic acid IO(OH)5, and by the IO2(OH)–4ions and are joined via hydrogen bonds. The studies of proton conductivity of ceramics reveal their transition into a superionic state at temperatures above 40°C.

Features of electrochemical and thermal properties of CsHSO4-C60 composite materials

New composite proton-conducting materials based on cesium hydrosulfate with fullerite C60 were synthesized. The concentration dependence of the proton conductivity and thermal properties of synthesized materials with C60 contents from 0 to 50 vol % was studied. It was found that these dependences are nonmonotonic with extrema at C60 contents of ∼2 and 30 vol %. The conductivity of the composite material with a C60 content of ∼2 vol % is almost twice higher than the conductivity of pure CsHSO4 due to the formation of a new surface phase, which is confirmed by thermal analysis methods.

Mixed Salt Cs2[I(OH)3O3] · CsSO4(H)H5IO6: Synthesis, Crystal Structure, and Properties

The mixed salt Cs2[I(OH)3O3] · CsSO4(H)H5IO6 (I) was synthesized for the first time, and its structure and properties were studied by X-ray diffraction, IR and Raman spectroscopies, impedance measurements and DTA method. It crystallizes in trigonal system: a = 7.503(2) Å, c = 16.631(3) Å, space group P3, Z = 2. The crystal structure consists of octahedral IO6 and tetrahedral SO4 fragments, linked by a three-dimensional network of hydrogen bonds, and of the Cs+ ions.

Synthesis, Crystal Structure, and Properties of Mixed Salt Cs2SO4 · H6TeO6

Mixed salt Cs2SO4 · H6TeO6 (I) is synthesized and its structure and properties are studied by X-ray diffraction analysis, IR and Raman spectroscopies, impedance measurements, and differential thermal analysis. Compound I crystallizes in hexagonal system with unit cell parameters a = 7.455(1) Å, c = 33.303(7) Å, space group R3c, Z = 6. Its crystal structure consists of the H6TeO6 molecules and SO42- anions united by network of hydrogen bonds and Cs+ cations.

Quantum-Chemical Simulation of the Proton Transport in Mono- and Disubstituted Salts with Octahedral Anions

Salts Rb2H3IO6, Rb4H6I2O12, and Rb4H2I2O10 and adducts CsHSO4· H6TeO6 and Cs2SO4· H6TeO6 of the salt · acid type are calculated within density functional theory B3LYP. Calculations for Te, I, Rb, and Cs atoms make use of basis set LanL2DZ complemented by polarization d,p-functions and pseudopotential LanL2; for Li, O, and H atoms, basis set 6-31G** is used. The activation energy for the proton migration is commensurate with that for the water molecule abstraction in the salts and is smaller in rubidium salts than in cesium salts.

Field-Effect Transistor Based on the Proton Conductivity of Graphene Oxide and Nafion Films

Proton conductivity in graphene oxide and Nafion films depending on humidity and voltages across electrodes is studied in the model of a field-effect transistor. The electrical characteristics of the films are similar to one another, but the mobility of positive charges in Nafion and the current gain are higher by 2–3 orders of magnitude compared with graphene oxide. The negative ion current in graphene-oxide films at positive bias voltage is significant compared with the proton current (up to ~10%), while it is almost lacking in Nafion films (<1%).

Effect of External Electric Field on the Proton Conductivity of Nafion Films

The current-voltage characteristics of Nafion films were studied depending on the ambient humidity, electrode voltage, and temperature. It was shown that the film can contain free (polarization current) and bound water; the latter can be completely removed under vacuum conditions. The current decreased with time at constant electrode voltage because of water removal from the film in the absence of electrochemical processes. A theoretical model in the form of the Nernst–Planck equation was considered; it describes the proton transport through the film in an electric field. The inverse problem of restoring the diffusion coefficient from the experimental proton conductivity was solved.

Crystal Structure and Properties of Rb4H2I2O10 · 4H2O

Single crystals of the Rb4H2I2O10· 4H2O were synthesized for the first time and studied by X-ray diffraction analysis. The crystals are monoclinic, a = 7.321(6) Å, b = 12.599(8) Å, c = 8.198(8) Å, β = 96.30(7)°, Z = 2, space group P21/c. The H2I2O104– anion is formed by the edge-sharing IO6 octahedra. The anions are united by hydrogen bonds into a chain running along the x axis. The chains are combined by water molecules into a three-dimensional structure through hydrogen bonds. The compound is a proton conductor. The conductivity values measured at 20–60°C vary within 10–6 to 10–4 ohm–1 cm–1.