I. N. Burmistrov

Sr0.75Y0.25Co0.5Mn0.5O3 − y Perovskite Cathode for Solid Oxide Fuel Cells

The Sr 0.75 Y 0 . 25 Co 0.5 Mn 0.5 O 3-y , (SYCM) oxide with a cubic perovskite structure was examined as a promising cathode material for intermediate temperature solid oxide fuel cells (IT-SOFCs). The electrical conductivity, thermal expansion coefficient (TEC), and reactivity with gadolinia-doped ceria (GDC) or yttria-stabilized zirconia (YSZ) were studied. Reflections from SrZrO 3 (~6 wt %) after heat-treatment of the SYCM:YSZ mixture at 900°C for 48 h and no reaction after heat-treatment with GDC were observed. In the low and intermediate temperature region (473-873 K), the TEC value is 13.3 ppm K -1 and most closely matches the common IT-SOFC electrolyte material GDC, but the TEC value increases to 19.6 ppm K -1 at 873-1073 K. The investigations of the electrochemical properties of the model SOFCs at 900°C with the SYCM cathode show that substituting the SYCM cathode for the standard (La,Sr)Mn03 cathode improves the cell performance.

Kinetics of NiO reduction and morphological changes in composite anodes of solid oxide fuel cells: Estimate using Raman scattering technique

The kinetics of nickel reduction and morphological changes in Ni–10Sc1CeSZ composite anodes in intermediate-temperature solid oxide fuel cells (SOFC) are studied using the Raman spectroscopy technique with the help of application of optically transparent single crystal solid electrolyte membranes and also the thermogravimetric analysis technique. It is shown that the first reduction cycle differs considerably from all the further ones, which is related to morphological changes of nickel grains occurring during the first reduction cycle. A general scheme of occurrence of the process is suggested in studies of model cells using the Raman spectroscopy technique and also in the case of thermogravimetric analysis of powders; it explains the causes for significant differences between the total duration of the process as measured using different techniques. The results of the work can be used for optimization of the mode of initial reduction of the anodic SOFC electrode.

Synthesis and properties of fuel cell anodes based on (La0.5 + xSr0.5 − x)1 − yMn0.5Ti0.5O3 − δ (x = 0–0.25, y = 0–0.03)

Results are presented of studying electrochemical properties of perovskite-like solid solutions (La0.5 + xSr0.5 − x)1 − yMn0.5Ti0.5O3 − δ (x = 0–0.25, y = 0–0.03) synthesized using the citrate technique and studied as oxide anodic materials for solid oxide fuel cells (SOFC). X-ray diffraction (XRD) analysis is used to establish that the materials are stable in a wide range of oxygen chemical potential, stable in the presence of 5 ppm H2S in the range of intermediate temperatures, and also chemically compatible with the solid electrolyte of La0.8Sr0.2Ga0.8Mg0.15Co0.05O3 − δ (LSGMC). It is shown that transition to a reducing atmosphere results in a decrease in electron conductivity that produced a significant effect on the electrochemical activity of porous electrodes. Model cells of planar SOFC on a supporting solid-electrolyte membrane (LSGMC) with anodes based on (La0.6Sr0.4)0.97Mn0.5Ti0.5O3 − δ and (La0.75Sr0.25)0.97Mn0.5Ti0.5O3 − δ and a cathode of Sm0.5Sr0.5CoO3 − δ are manufactured and tested using the voltammetry technique.

Preparation of membrane-electrode assemblies of solid oxide fuel cells by co-sintering of electrodes

The results of the development of procedures for forming membrane-electrode assemblies (MEAs) of solid oxide fuel cells (SOFCs) by co-sintering of electrodes and electrochemical tests of MEAs were described. Plates of Hionic™ material (Fuel Cell Materials, United States) with an area of 50 × 50 mm2 were used as a solid electrolyte membrane. The cathode layers were prepared from cation-deficient lanthanum-strontium manganite and the anion conductor 89 mol % ZrO2–10 mol % Sc2O3–1 mol % CeO2 (10Sc1CeSZ) with a carbon black addition for control over the microstructure. The anode layers were formed from the composite NiO/10Sc1CeSZ and by introducing rice starch as a pore-forming agent in the anode current-collecting layer. The thermal treatment mode was optimized based on thermogravimetry and scanning electron microscopy data and the results of testing the electrochemical characteristics of SOFCs to provide the formation of electrochemically active electrodes using one thermal cycle.

Fabrication of membrane–electrode assemblies for solid-oxide fuel cells by joint sintering of electrodes at high temperature

The results on optimizing the procedure of preparation of the electrode system within membrane–electrode assemblies (MEA) of solid-oxide fuel cells (SOFC) by joint sintering of electrodes at the enhanced temperature close to that of anode sintering are presented. The MEA are prepared based on membranes of the anionic conductor HionicTM (Fuel Cell Materials, USA); the cathode is formed based on cation–deficient lanthanum-strontium manganite (La0.8Sr0.2)0.95MnO3 with addition of activated carbon for optimizing its microstructure; the anode is formed on the basis of cermet NiO/10Sc1CeSZ (89 mol % ZrO2, 10 mol % Sc2O3, 1 mol % CeO2). The results of electrochemical testing of model MEA are also shown.

Ceramic membranes based on scandium-stabilized ZrO2 obtained by tape casting technique

Results of studies of solid-electrolyte membranes with the composition of 89 mol % ZrO2-10 mol % Sc2O3-1 mol % CeO2 obtained using the technique of slip casting on a moving tape are presented. Optimization of technological parameters of membrane casting and sintering allowed manufacturing parallel plane gastight plates with the thickness of 200–250 μm that were tested in model solid oxide fuel cells (SOFC) of planar design with standard electrodes based on nickel-containing cermets and lanthanum-strontium manganite. It is shown that though conductivity of such membranes is lower as compared to that of compacted and sintered compacted samples due to diffusion of the aluminum oxide admixture in the course of the manufacturing process, power density of SOFC is sufficiently high and reaches 430 mW/cm2 at 850°C.