N. Mezentseva

La0.8Sr0.2Ni0.4Fe0.6O3–Ce0.8Gd0.2O2–δ Nanocomposite as Mixed Ionic–Electronic Conducting Material for SOFC Cathode and Oxygen Permeable Membranes: Synthesis and Properties

Mixed ionic–electronic conducting nanocomposite La0.8Sr0.2Ni0.4Fe0.6O3 (LSNF)–Ce0.8Gd0.2O2– δ (GDC) was prepared via ultrasonic dispersion of nanocrystalline powders of perovskite and fluorite oxides in water with addition of surfactant, followed by drying and sintering up to 1300°C. Analysis of the real structure of nanocomposite (studied by XRD and TEM with EDX) and its surface composition (studied by XPS) revealed moderate redistribution of elements between phases favoring their epitaxy. Results of impedance spectroscopy, oxygen isotope exchange, O2 TPD and H2 TPR experiments revealed a positive effect of composite interfaces on the oxygen mobility and reactivity agreeing with the ambipolar transport behavior of MIEC composite. Preliminary testing of button-size cell with functionally graded LSNF–GDC cathode layer supported on thin YSZ layer covering Ni/YSZ cermet demonstrated high and stable performance, which is promising for its practical application.

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 of mesoporous complex framework zirconium phosphates via organic- inorganic nanocomposites: genesis of structure, adsorption and catalytic properties

This work presents the first results of synthesis of framework binary phosphates of zirconium and transition metal cations (Co, Cu, Ce) via nanocomposites of starting inorganic salts with citric acid and studies of their structure genesis. Nanoparticles of layered Zr phosphates with typical sizes in the range of 18-24 Ǻ are formed at the mixing stage. Less basic Cu and Co cations are mainly octa-coordinated with both phosphate groups of those nanoparticles and citric acid molecules. At subsequent thermal treatment, Cu and Co cations are incorporated within Zr phosphate nanoparticles acquiring a low coordination approaching a tetrahedral one while rearranging the nuclei structure into that of a framework type. Removal of citric acid by heating under air at 200—300 o C preserves the size of nanoparticles while their ordered stacking forms mesoporous structure with a narrow pore size distribution ~ 50 A and specific surface area up to 200 m 2 /g after calcination at 600 o C. The binary phosphates promoted by a small amount of Pt were found to be effective catalysts of NOx selective reduction by decane in the oxygen excess not subjected to coking with a high and stable performance at high space velocities in the presence of steam.