Yu. A. Dobrovolsky

Achievements in the field of proton-conductive polymer electrolyte membranes

The 2000–2006 achievements in the field of synthesis, property examination, and application of proton-exchange membranes are reviewed on the basis of more than 120 papers.

2-Hydroxy-4-methylbenzenesulfonic acid dihydrate: Crystal structure, vibrational spectra, proton conductivity, and thermal stability

The crystal and molecular structure of 2-hydroxy4-methylbenzenesulfonic acid dihydrate C6H3(CH3)(OHSO−3 H5O2+ (I) was studied by X-ray diffraction and vibrational spectroscopy. The compound crystallized in the monoclinic crystal system; crystal data: a=10.853(2) Å, b=7.937(2) Å, c=12.732(3) Å, β=112.13(3)°, V=1015.9(4)Å3,Z=4,dcalc=1.466g/cm3,spacegroupP21/c,Rf=0.0486,GOOF=1.161.The S-O distances in the sulfonate group differed substantially (S1-O2 1.439(2) Å, S1-O3 1.455(2) Å, and S1-O4 1.464(2) Å. The symmetry of the H5O2 cation decreased due to proton displacement toward one of the two water molecules. XRD data on the asymmetry of H5O2 were confirmed by IR and Raman spectral data. The strong triplet at 2900, 3166, 3377 cm−1 in the IR spectrum of I corresponds to different types of H-bond and shifted to 2185, 2363, 2553 cm−1 after deuteration. The proton conductivity of the compound was measured by impedance spectroscopy: 6 × 10−7 S/cm at 298 K (32 rel %), Eact=0.4±0.01 eV. The conductivity increased to 10-3 S/cm, Eact=0.1 eV when ambient humidity increased to 60 rel %.

Protonic conductivity of neutral and acidic silicotungstates

Abstract The salts of composition Me 4− x H x SiW 12 O 40 · n H 2 O (Me=Na, K, Rb, Cs, NH 4 ) are synthesized; their thermal stability, temperature dependence of proton conductivity and structure of protonhydrate shell are studied. The proton conductivity is shown to depend on both the number of acidic protons and polarizability of salt-forming cation of alkaline metal. The presence of differently hydrated protons is discovered in both acidic and neutral salts of 12-silicotungstic acid.

Thermodynamic equilibria and kinetic reversibility of the solid electrolyte/electron conductor/gas boundary at low temperature

The relation of the concentration dependence of the emf of low-temperature potentiometric gas sensors to the adsorption isotherms of the detected species is considered on the basis of the literature data and the experimental results of the authors. The causes for the deviation of measured emf of the sensors from their theoretical values are discussed. The conditions for the formation of electrochemical products and their elimination from the triphase boundaries of solid electrolyte/electron conductor/gas are also discussed.

Proton conductivity of calix[n]arene-para-sulfonic acids (n = 4, 8)

High proton conductivity in calix[n]arene-para-sulfonic acid hydrates (n = 4, 8) reaching a value of 10−1 Ohm−1 cm−1 at a relative humidity of 80% was revealed for the first time. This value is close to the record conductivity of solid proton conductors and acid water solutions. The dependence of proton transfer parameters and water quantity in the title compounds dependent on the relative humidity of air was investigated.

Quantum chemical modeling of the structure formation and proton transfer in 2-hydroxybenzenesulfonic, 4-hydroxy-1,3-benzenedisulfonic, and 1,3-benzenedisulfonic acids

Hydrate clusters of 2-hydroxybenzenesulfonic and 1,3-benzenedisulfonic acids were calculated in terms of the density functional theory (DFT) by the B3LYP/6-31G** method. The process of water adsorption on the crystal surface of 4-hydroxy-1,3-benzenedisulfonic acid dihydrate was simulated using the generalized gradient approximation (DFT/PBE) and periodic boundary conditions. For the model system (OHC6H4SO3−)·H5O2+, the activation barriers for the proton transfer were calculated depending on the distance between the O atoms and the deviation of the proton from the O...O bond line. The presence of one H2O molecule per SO3H group is energetically most favorable for the formation of clusters of 1,3-benzenedisulfonic acid containing a stoichiometric amount of water. The simulation of the hydration of 4-hydroxy-1,3-benzenedisulfonic acid dihydrate (OHC6H3(SO3H)2·2 H2O + n H2O, n = 1–3) showed that the superstoichiometric H2O molecule is adsorbed on the crystal surface of this dihydrate with energy release of 0.75–0.95 eV. The position of this water molecule is less favorable in the bulk than on the surface.

Low-temperature proton conductivity in hydrated and nonhydrated tin dioxide.

Abstract The protonic and electronic conductivity of the specimens SnO 2 · n H 2 O, SnO 2 ·Sb 2 O 4 · n H 2 O and SnO 2 at the temperature range from −20 to +60°C and the processes of ion transport through the interface SnO 2 · n H 2 O|Pt in hydrogen containing environments are investigated. A similarity of mechanisms of protonic transport in hydrated and non-hydrated specimens is shown.

The Structure and Properties of Phenol-2,4-disulfonic Acid Dihydrate

The crystal and molecular structure of phenol-2,4-disulfonic acid dihydrate was determined by X-ray structure analysis. All hydrogen positions in the crystal structure were found using difference Fourier syntheses. Oxonium cations and acid anions were linked in the crystal structure by short H-bonds, and the phenol OH group participated in two weak H-bonds with sulfo group oxygens simultaneously. The IR frequency corresponding to νs, as (H3O+) vibrations decreased to 2700 cm−1 under the influence of short H-bonds between oxonium cations and anions. The contour of the corresponding absorption band became anomalously broad. A discrete maximum was observed at 3412 cm−1 on the high-frequency wing of this band; this maximum was assigned to OH stretching vibrations of the phenol group. The protonic conductivity of the compound measured by impedance spectroscopy was 2.5 × 10−6 Ω−1 cm−1 at 298 K in a vacuum, Ea = 0.37 ± 0.01 eV. An increase in the humidity of the environment to 15% at room temperature increased conductivity from 10−6 to 10−5 Ω−1 cm−1, Ea = 0.27 ± 0.02 eV.

Oxide supported platinum electrocatalysts for hydrogen and alcohol fuel cells

Efficient oxide supported electrocatalysts for hydrogen and alcohol fuel cells are developed. They are characterized by a low content of platinum, exhibit high activity in the oxidation of low-molecular alcohols and tolerance to the CO poisoning. It is shown that the application of catalysts developed (Pt/SnO2-SbOx) enables one to raise the power of fuel cells operating on ethanol approximately by two times as compared with similar fuel cells with commercial PtRu/C catalysts.

Chemical and electrochemical processes in low-temperature superionic hydrogen sulfide sensors

Effect the morphology of the surface of the working electrode (PbS) exerts on the sensitivity of a low-temperature potentiometric hydrogen sulfide sensor is studied. The sensor, which is based on electrochemical cell NaxWO3/NASICON/PbS, may be used for fast selective detection of hydrogen sulfide in air in natural conditions. It is demonstrated that the sensors with PbS that are deposited out of solution have a faster response than the pressed-to ones. The dependence of EMF on the hydrogen sulfide concentration for the former is linear in semilogarithmic coordinates. Thus difference is explained by the microstructure of the lead sulfide layer. It is shown that the lead sulfide interaction with hydrogen sulfide involves a reversible partial reduction of sulfur and lead at the surface. The species that form in so doing contain sulfur atoms in lower oxidation degrees (poly-and oligo sulfides, sulfite). A mechanism of the sensor operation is proposed on the basis of data yielded by experiment and quantum-chemical simulation. The mechanism includes reversible transport of hydrogen from sulfur atoms to oxygen atoms.