La substituted Sr2MnO4 as a possible cathode material in SOFC (original) (raw)
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Materials Research Bulletin, 2003
Perovskite type oxides Ln 0.6 Sr 0.4 Co 0.8 Mn 0.2 O 3Àd (Ln ¼ La, Gd, Sm, or Nd) have been prepared by the solid state reaction of corresponding oxides. The crystal parameters of the compositions were determined by XRD powder diffraction, which revealed that all the compositions have orthorhombic structure. The reaction test of all samples with Ce 0.8 Gd 0.2 O 1.9 was carried out at 1200 8C for 48 h, and no reaction product was detected by XRD. The change in mass of La 0.6 Sr 0.4 Co 0.8 Mn 0.2 O 3Àd as a function of temperature was determined by thermogravimetric analysis (TGA). The electrical conductivity of the sintered samples were measured as a function of temperature from 200 to 1000 8C. The highest conductivity of about 1400 S cm À1 was found in La 0.6 Sr 0.4 Co 0.8 Mn 0.2 O 3Àd . The cathodic polarization of these oxides electrodes deposited on Ce 0.8 Gd 0.2 O 1.9 tablet was studied at 500-800 8C in air. #
Review of Cathode Materials for Solid Oxide Fuel Cell
International Journal of Scientific Research in Physics and Applied Sciences, 2018
Proper selection of cathode material for solid oxide fuel cell (SOFC) is more important because of its impact which is noticeable on the performance of SOFC. The cathode is exposed to high temperature and an oxidizing atmosphere which limits the choice of metals and conducting oxides. Normally most common materials for SOFC cathodes belong to the family of the perovskite-type oxides. Cathode material should exhibit high electronic conductivity, high catalytic activity towards the oxygen reduction, it is able to conduct electrons as well as oxide ions, and have a porous microstructure to allow transport of oxygen. Its thermal expansion coefficient should match with that of other components. The most commonly used cathode for SOFCs is δ 3 x x 1 MnO Sr La (LSM).
Ionics, 1995
The influence of A-site deficiency in perovskite materials of the system Lao.s_y-Sro.2MnO3.s on the rate of oxygen reduction at the cathode of the SOFC were investigated. Cathode layers with the compositions Lao.sSro.2MnO3.8 and Lao.75Sro.2MnO3_8 were prepared by sereenprinring and were sintered onto thin sheets of cubic Y-stabilized zirconia. The time dependent response of the cell voltage to changes in current density was found to be different for these two cathode composititons. During cell operation the performance of the Lao.8Sro.2MnO3_8 layer improved slowly and eventually attained values identical to those of the Lao.75Sro.2MnO3.8 layer which reached its final performance comparatively fast. Furthermore, for the Lao.sSro.2MnO3-8 layer, degradation in the performance was observed, if subsequently the applied current density was lowered, i.e. the improvement is reversible. Similar effects were seen for the A-site deficient composition, but to a much smaller degree. The difference in electrochemical performance of these two compositions is attributed to a different reactivity between the electrolyte and the cathode material, a change of the morphology of the Lao.sSro.2MnO3_s layer during operation and/or a change of the electrochemically effective area in the vicinity of the three phase boundary.
Journal of Power Sources, 2012
Our previous study of La 1−x Sr x MnO 3±ı (LSM) infiltrated La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3−␦ (LSCF) cathode suggests that a hybrid phase, La 0.8 Sr 0.2 Co 0.17 Mn 0.83 O 3−␦ (LSMCo), is associated with the observed enhancement in performance and stability of LSCF cathodes. Here we report the properties of LSMCo as a potential cathode for a solid oxide fuel cell (SOFC). The electrical conductivity of LSMCo varies from 118 to 166 S cm −1 at 500-800 • C. The interfacial polarization resistances of an LSMCo cathode on YSZ electrolyte are smaller than those of an LSM cathode at 600-800 • C. The performance of a cell based on an LSMCo cathode is ∼34% higher than that based on an LSM cathode while maintaining comparable long-term stability, indicating that LSMCo is a promising cathode material for intermediate temperature SOFCs.
International Journal of Electrochemical Science
Solid oxide fuel cells (SOFCs) are generally known to be one of the most promising energy conversion devices, offering benefits such as system compactness, high efficiency and low environmental pollution. In this study, La 0.65 Sr 0.3 MnO 3 (LSM) nanoceramic powders were prepared through the citrate-nitrate auto-combustion route with a β-alanine-to-nitrate ratio of 1:1. Thereafter, a Thermolyne 47900 furnace was used to calcine the prepared powders at 900 °C for 4 hrs to remove carbonaceous residues, and then, the prepared powders were characterized using SEM/EDS, XRD, and TGA. Calculations using the Debye-Scherrer equation illustrated that the average crystallite size of the powders was approximately 20-25 nm. There was no loss in weight after reaching a temperature of ~700 °C, as indicated by TGA, signifying the completion of combustion. Electrochemical characterization of the La 0.8 Sr 0.2 MnO 3 (LSM) cathode powders was performed by coating these powders (as the cathode functional layer (CFL) with 40-60 wt% 8YSZ on the bottom and the catalyst layer (CL) on the top) using the screen printing technique on SOFC half-cells (NiO-YSZ+YSZ) obtained from CGCRI (Kolkata, India) with a cell size of 36 mm dia × 1.6 mm (effective electrode area of ~1.13 cm 2). These cells were tested with H 2 and O 2 at 750-800 °C with flow rates of 1.2-1.8 lit min-1 H 2 and 0.4-0.6 lit min-1 O 2 with a hydrogen humidification of 3%. The current density (cd) and power density (pd) were the highest for the CFL containing 60 wt% LSM and 40 wt% YSZ. The cd and pd of the single SOFC cell were 0.8 A cm-2 (at 0.7 V) and 0.6 W cm-2 , respectively, at 800 °C, a hydrogen flow rate of 1.8 lit min-1 and an oxygen flow rate of 0.6 lit min-1 .
Journal of Electronic Materials, 2020
In this study, Ruddlesden-Popper La 0.9 Sr 1.1 Co 1Àx Mo x O 4 (x £ 0.1) powders were successfully synthesized using a modified sol-gel method. The structural analysis revealed that all samples had a tetragonal phase at room temperature. The electrical conductivity measurements showed that all samples had semiconducting behavior in the range of room temperature to 850°C. Moreover, it was found that the electrical conductivity of the ceramics was enhanced with the increase of Mo doping, at temperatures higher than 300°C up to 850°C. This enhancement of the electrical conductivity can be due to Co 3+-O-Mo 5+-O-Co 2+ double-exchange interaction. The EIS measurements of the symmetrical cells were carried out for x = 0, 0.03 and 0.1 samples at 650°C, 750°C and 850°C. The obtained area specific resistance (ASR) values of La 0.9 Sr 1.1 Co 1Àx Mo x O 4 on ceria-gadolinium oxide (CGO) electrolyte at 850°C were 0.36 X cm 2 , 0.35 X cm 2 and 1 X cm 2 for samples x = 0, 0.03 and 0.1, respectively. These results indicate that the electrical conductivity of pure sample (La 0.9 Sr 1.1 CoO 4) has been enhanced by Mo substitution in Co ion sites, but limits the oxygen ion transport.
Electrochemical properties of novel SOFC dual electrode La0.75Sr0.25Cr0.5Mn0.3Ni0.2O3−δ
Solid State Ionics, 2011
The perovskite La 0.75 Sr 0.25 Cr 0.5 Mn 0.3 Ni 0.2 O 3−δ (LSCMMn 0.30 Ni 0.20 ) was evaluated as potential electrode for solid oxide fuel cells. The electrochemical performances of LSCMMn 0.30 Ni 0.20 for hydrogen oxidation and oxygen reduction reactions were studied at 800°C. Symmetrical cells LSCMMn 0.30 Ni 0.20 /YSZ/LSCMMn 0.30 Ni 0.20 were studied by electrochemical impedance spectroscopy. The total conductivity of LSCMMn 0.30 Ni 0.20 is 22 S cm −1 in air and 0.8 S cm −1 under wet 5% H 2 /Ar at 800°C. The area specific resistance (ASR) at 800°C for hydrogen oxidation reaction is 1 Ω cm 2 . The ASR for oxygen reduction reaction is 1.6 Ω cm 2 . An ageing study during 24 h shows a relatively good stability of the electrochemical performances. LSCMMn 0.3 Ni 0.2 seems to be a promising dual electrode for a symmetrical SOFC.
Solid State Ionics, 2012
La 0.5 Sr 0.5 CoO 3 − δ and La 0.6 Sr 0.4 CoO 3 − δ are characterized with respect to application as cathode materials in intermediate temperature solid oxide fuel cells (IT-SOFCs). Surface exchange and transport parameters of oxygen are determined by the conductivity relaxation technique between 525°C and 725°C at oxygen partial pressures of 0.1, 0.01 and 0.001 bar. Electrical conductivities of both compounds range between 1000 and 2400 S cm -1 and are slightly higher for La 0.6 Sr 0.4 CoO 3 − δ . However, La 0.5 Sr 0.5 CoO 3 − δ shows superior performance with regard to oxygen diffusion, ionic conductivity and oxygen surface exchange within the investigated range of temperatures and oxygen partial pressures. At 725°C the chemical surface exchange coefficient of oxygen is 2 × 10 -3 cm s -1 for La 0.5 Sr 0.5 CoO 3 − δ and 4 × 10 -4 cm s -1 for La 0.6 Sr 0.4 CoO 3 − δ . At lower oxygen partial pressures a strong decrease in the surface exchange coefficient is observed and diffusion data cannot be obtained from relaxation measurements. Oxygen vacancy diffusion coefficients are similar for both compounds and range between 10 -6 and 10 -8 cm 2 s -1 with activation energies around 100 kJmol -1 . At 725°C and 0.1 bar oxygen partial pressure, the ionic conductivity of La 0.5 Sr 0.5 CoO 3 − δ is 1 × 10 -2 S cm -1 with an activation energy of 118 kJmol -1 . The results show that both compositions meet the requirements for the application as IT-SOFC cathodes in the short-term range.
Materials, 2022
The high efficiency of solid oxide fuel cells with La0.8Sr0.2MnO3−δ (LSM) cathodes working in the range of 800–1000 °C, rapidly decreases below 800 °C. The goal of this study is to improve the properties of LSM cathodes working in the range of 500–800 °C by the addition of YFe0.5Co0.5O3 (YFC). Monophasic YFC is synthesized and sintered at 950 °C. Composite cathodes are prepared on Ce0.8Sm0.2O1.9 electrolyte disks using pastes containing YFC and LSM powders mixed in 0:1, 1:19, and 1:1 weight ratios denoted LSM, LSM1, and LSM1, respectively. X-ray diffraction patterns of tested composites reveal the presence of pure perovskite phases in samples sintered at 950 °C and the presence of Sr4Fe4O11, YMnO3, and La0.775Sr0.225MnO3.047 phases in samples sintered at 1100 °C. Electrochemical impedance spectroscopy reveals that polarization resistance increases from LSM1, by LSM, to LSM2. Differences in polarization resistance increase with decreasing operating temperatures because activation ene...
Preparation of La 0.9 Sr 0.1 MnO 3-δ (LSM) Thin Films by Spray Pyrolysis Technique for SOFC Cathode
Strontium-doped lanthanum manganite (La 0.9 Sr 0.1 MnO 3-δ) were synthesized by spray pyrolysis technique in the thin film form on alumina substrate. The La 0.9 Sr 0.1 MnO 3-δ (LSM) thin films were sintered in the step of 150 o C from 600 o C to 900 o C. X-ray diffraction study confirmed phase formation of LSM and Infrared spectroscopy confirmed perovskite structure. Morphology of LSM has been studied by using Scanning electron microscopy and Atomic force microscopy, shown porosity within homogeneous grain structure. TGA/DSC and DTA study exhibits stable crystallization after 700 o C. Dielectric study shows mixed electrical conduction at the grain boundary interface in the sample.