Tamara Kharlamova

Design and Characterization of Nanocomposites Based on Complex Perovskites and Doped Ceria as Advanced Materials for Solid Oxide Fuel Cell Cathodes and Membranes

La 0.8 Sr 0.2 Fe 0.6 Ni 0.4 O 3-x - Ce 0.9 Gd 0.1 O 2-x and La 0.8 Sr 0.2 Fe 0.8 Co 0.2 O 3-x - Ce 0.9 Gd 0.1 O 2-x nanocomposites were synthesized via ultrasonic dispersion of nanocrystalline powders of perovskite and fluorite oxides in acetone with addition of a surfactant, followed by drying and sintering at temperatures up to 1200°C. The evolution of the structure of samples with sintering temperature was studied by XRD and TEM with EDX and compared with the data on conductivity, oxygen isotope exchange, O 2 TPD, H 2 and CH 4 TPR. Preliminary testing of button-size cells with cathodes supported on thin YSZ layer covering Ni/YSZ cermet demonstrated a high and stable performance of LSNF–GDC composite promising for the practical application.

Synthesis and physicochemical and catalytic properties of apatite-type lanthanum silicates

Undoped and aluminum-doped lanthanum silicates with an apatite structure have been synthesized using mechanical activation, and their structure, microstructure, and catalytic properties in the oxidative coupling of methane have been investigated. The phase composition, structure, and microstructure of the silicates have been determined by X-ray diffraction, IR spectroscopy, X-ray photoelectron spectroscopy, low-temperature nitrogen adsorption, and scanning and transmission electron microscopy. The catalytic activity of silicates have been investigated in a catalytic flow reactor at 700–800°C, a CH4: O2 molar ratio of 3.8: 1 in the feed, and a residence time of 0.04 s. The catalytic properties of apatite-type lanthanum silicates can be tuned by varying the number of cationic vacancies and/or interstitial oxygen ions through isomorphic substitution of atoms with a smaller oxidation number for silicon in the apatite lattice.

Structural Features and Transport Properties of La(Sr)Fe1-xNixO3-δ– Ce0.9Gd0.1O2-δ Nanocomposites—Advanced Materials for IT SOFC Cathodes

Mixed ionic−electronic conducting nanocomposites comprising complex oxides - perovskite (lanthanum-strontium nickelate-ferrite [LSFN]) and gadolinium-doped ceria (GDC) have been prepared via ultrasonic dispersion of nanocrystalline powders of LSFNx and GDC in organic solvent with addition of surfactant, followed by drying and sintering up to 1300°C. Their structural and surface properties have been studied by x-ray diffraction, ultraviolet–visible (UV-vis) electron spectroscopy, transmission electron microscopy with elemental analysis, and x-ray photoelectron spectroscopy. Results of impedance spectroscopy, oxygen isotope exchange, O2 temperature-programmed desorption, weight, and conductivity relaxation experiments have revealed a strong positive effect of perovskite−fluorite nanodomain interfaces in composite on the oxygen mobility and reactivity. Testing in wet H2/air feeds for a button-size cell with functionally graded LSFN0.4–GDC cathode layer supported on a thin YSZ layer covering Ni/YSZ cermet has demonstrated high and stable performance, promising for the practical application in the intermediate temperature range.

Perovskite and Composite Materials for Intermediate Temperatures Solid Oxide Fuel Cells

La 0.8 Sr 0.2 Fe 0.6 Ni 0.4 O 2.9 (LSFN) and LSFN-La 9.83 Si 4.5 Fe 1.5 O 26 (LSiF) nanocomposite were synthesized and investigated as cathode materials for intermediate temperature (IT) solid oxide fuel cells (SOFC). Phase and structure evolution with sample sintering temperature as well as their transport properties and catalytic activity in oxygen reduction were studied.

Redox and Catalytic Properties of Copper Molybdates with Various Composition

Using XRD and temperature-programmed reduction (TPR), phase and structural transformations of copper molybdates Cu3Mo2O9 and CuMoO4 were investigated in the course of their treatment with hydrogen, carbon monoxide or soot. The catalytic properties of copper molybdates Cu3Mo2O9 and CuMoO4 were studied in model oxidation reactions of carbon monoxide and soot. Phase and structural transformations of the molybdates, in particular formation of Cu4–xMo3O12 and Cu6Mo5O18 phases, was shown to have a significant impact on the formation of active state of the catalysts in the model reactions considered.

Supported MgO–V 2 O 5 /Al 2 O 3 catalysts for oxidative propane dehydration: Effect of the molar Mg : V ratio on the phase composition and catalytic properties of samples

The physicochemical properties of V2O5/Al2O3 and MgO–V2O5/Al2O3 supported catalysts (Mg : V = 1 : 1, 2 : 1, and 3 : 2) obtained by consecutive impregnation of the support with solutions of vanadium and magnesium precursors are studied using a complex of mutually complementary methods (XRD, Raman spectroscopy, UV–Vis spectrometry, and TPR-H2). The effect of the formation of surface magnesium vanadates of various composition and structure on the catalytic properties of the supported vanadium oxide catalysts in the oxidative dehydrogenation of propane is studied. The introduction of magnesium in the samples and an increase in its content, accompanied by a change in the structure of the surface vanadium oxide phases from polymeric VO6/VO5 species to surface metavanadate species, magnesium metavanadate, and further to magnesium divanadate, significantly affects their catalytic properties in the reaction of the oxidative dehydrogenation of propane to propylene.

Textural Characteristics and Structural Peculiarities of Supported Vanadium Oxide Materials Prepared by the NH4VO3 Aqueous Solution Wetness Impregnation

Textural characteristics and structural peculiarities of materials based on supported vanadium oxide are considered. The materials were prepared by the incipient wetness impregnation of SiO2, TiO2, γ-Al2O3 and carbon-modified γ-Al2O3 supports using an aqueous solution of NH4VO3. Samples were characterized by low temperature N2 adsorption, XRD, IR, Raman and US-Vis DR spectroscopy and H2-TPR.