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For electrochemical systems such as solid oxide fuel cells (SOFCs) or solid oxide electrolyzer cells (SOECs), perovskites are widely used as cathode material for the reduction of molecular oxygen. At present, strontium-substituted lanthanum manganite, La1-xSrxMnO3-δ (LSM), is used as standard SOFC cathode material for operation at high temperatures, whereas strontium-substituted lanthanum ferrite (LSF) is alternatively explored for medium-temperature SOFCs. Moreover, LSF is considered to be a potential candidate for oxygen separation membranes as the material reported interesting electrical properties. The design of new perovskite-type La transition-metal oxides is of significant technological importance in order to reduce the operating temperature to 600-800 °C and thus to reduce the SOFC system cost. For investigations on a new material class, (La1-xSrx)yFe1-z(Ni,Cu)zO3-δ was synthesized by a spray-pyrolysis process and modified on the A-site in both stoichiometric and nonstoichiometric configurations and on the B-site by substituting Fe with Ni and Cu. [ABSTRACT FROM AUTHOR]

In solid oxide fuel cells, doped strontium titinates have been widely studied as anode materials due to their high n-type conductivity. They are used as current conducting backbones as an alternative to nickel-cermets, which suffer degradation due to coking, sulphur poisoning, and low tolerance to redox cycling. In this work, anode backbone materials were synthesized from La0.2Sr0.25Ca0.45TiO3−δ (LSCTA-), modified with 5 wt.% Zn, and infiltrated with nickel (Ni)/ceria gadolinium-doped cerium oxide (CGO), Fe, and Co. The electrodes were further studied for their electrochemical performance using electrochemical impedance spectroscopy (EIS) at open circuit voltage (OCV) in different hydrogen to steam ratios and at various operating temperatures (850–650 °C). Infiltration of electrocatalysts significantly reduced the polarization resistance and among the studied infiltrates, at all operating temperatures, Ni-CGO showed excellent electrode performance. The polarization resistances in 3% and 50% H2O/H2 atmosphere were found to be 0.072 and 0.025 Ω cm2, respectively, at 850 °C, and 0.091 and 0.076 Ω cm2, respectively, at 750 °C, with Ni-CGO. These values are approximately three orders of magnitude smaller than the polarization resistance (25 Ω cm2) of back bone material measured at 750 °C. [ABSTRACT FROM AUTHOR]

All ceramic anode supported half cells of technically relevant scale were fabricated in this study, using a novel strontium titanate anode material. The use of this material would be highly advantageous in solid oxide fuel cells due to its redox tolerance and resistance to coking and sulphur poisoning. Successful fabrication was possible through aqueous tape casting of both anode support and electrolyte layers and subsequent lamination. Screen printing of electrolyte layers onto green anode tapes was also attempted but resulted in cracked electrolyte layers upon firing. Microstructural, electrical and mechanical properties of anode supports and half cells will be discussed. The use of two different commercial titanate powders with nominal identical, but in reality different stoichiometries, strongly affect electrical and mechanical properties. Careful consideration of such variations between powder suppliers, and batches of the same supplier, is critical for the successful implementation of ceramic anode supported solid oxide fuel cells. [ABSTRACT FROM AUTHOR]

Abstract: Tubular membranes of La0.6Ca0.4Fe0.75Co0.25O3−δ and La0.5Sr0.5Fe1−y Ti y O3−δ (y =0, 0.2) for the application of partial oxidation of methane to syngas were produced by thermoplastic extrusion and investigated by oxygen permeation measurements. The optimum ceramic content in the feedstock for extrusion was found to be 51vol% as a result of rheology measurements. Tubes with an outer diameter of 4.8–5.5mm and thickness of 0.25–0.47mm were produced with densities higher than 95% of the theoretical density. The oxygen permeation flux of the tubular membranes was measured with air on one side and Ar or Ar+CH4 mixture on the other side. The oxygen permeation rate decreased with Ti-substitution while it was considerably increased by introduction of 5% methane into the system. The normalized oxygen fluxes in air/Ar gradient at 900°C were measured to be 0.06, 0.051, and 0.012μmolcm−2 s−1 for LCFC, LSF, and LSFT2, respectively, and 0.18μmolcm−2 s−1 for LSFT2 with 5% methane. [Copyright &y& Elsevier]