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2 Conversion with SOCs 5
Published in Yun Zheng, Bo Yu, Jianchen Wang, Jiujun Zhang, Carbon Dioxide Reduction through Advanced Conversion and Utilization Technologies, 2019
Yun Zheng, Bo Yu, Jianchen Wang, Jiujun Zhang
As mentioned above, LSC has excellent mixed conductivity, but at the same time, its exhibits a high TEC due to the low-spin to high-spin transition associated with the Co3+ ions. In order to improve the match with electrolyte materials and maintain catalytic activity in the meantime, the common trade-off is partially substituting Co with Fe in La1−xSrxCo1−yFeyO3-δ. For an LSCF system, the bond energy of Fe-O is stronger than that of Co-O; therefore, there exists a tighter combination among the atoms that alleviates the lattice expansion caused by heating. In addition, the doping of Fe means a decrease in the Co content. Therefore, the effect on TEC arising from the spin of Co3+ ions can also decline accordingly66. Due to the presence of a large amount of oxygen vacancies, LSCF has a superior ionic conductivity (approximately 0.18 S cm−1, 900°C), and simultaneously owns a desired electronic conductivity.40,46,67–69 Therefore, LSCF performs well in property and is commonly used as a SOC electrode.70,71
Solid Oxide Fuel Cells: Electrode Materials and Membrane Formations
Published in Toshio Naito, Functional Materials, 2019
Yoshiteru Itagaki, Hidenori Yahiro
However, these oxides have a relatively low oxygen diffusion coefficient (D = 3 × 10−12 cm2 s−1 at 900°C for La0.5Sr0.5MnO3) [26], and cathodic overpotential tends to be large at a low temperature. Recently, (La, Sr)(Co, Fe)O3 oxides (lanthanum strontium cobalt ferrite, LSCF) have been mostly adopted as a common cathode material for an intermediate-temperature solid oxide fuel cell (IT-SOFC). The LSCF oxides have a high oxygen transportation property (D = 5 × 10−7 cm2 s−1 at 900°C for La0.5Sr0.5Co0.8Fe0.2O3) [26].
Why Do We Need to Control Humidity?
Published in Ghenadii Korotcenkov, Handbook of Humidity Measurement, 2018
Basing of the example of the humidity influence on the solid oxide fuel cell cathodes, one can judge how strong and overall could be the humidity influence on the material properties and the device parameters. For example, Hardy et al. (2015) established that for La0.8Sr0.2MnO3 (LSM), La0.6Sr0.4Co0.2Fe0.8O3 (LSCF), and Yttria-stabilized zirconia (YSZ)-based cathodes the following effects can be observed: Humidity in the cathode air can cause an immediate increase in the polarization resistance of LSM/YSZ cathodes; this effect is reversible when the humidity is removed.Humidity in the cathode air can produce an increase in the LSM/YSZ cathode performance degradation rate, with the effect being more pronounced at higher current densities.Chemical effects of humidity on LSM/YSZ cathodes can include Mn interdiffusion, Mn oxide formation at the LSM-YSZ interfaces, Mn enrichment at the YSZ grain boundaries, and expansion of LSM lattice parameters.Humidity in the cathode air can cause an increase in the polarization resistance of LSCF cathodes; the effect is more pronounced at lower temperatures.Humidity in the cathode air can cause an increased degradation rate in LSCF at temperatures below 700°C–750°C, but can result in a decreased degradation rate at higher temperatures.Humidity can lead to increased Sr or Co segregation in the LSCF cathodes as well as an increased rate of compositional evolution of minor iron cobalt spinel phases.Infiltration is a possible mean of mitigating the effects of humidity on the LSM/YSZ and LSCF cathodes.
Flat-tubular solid oxide fuel cells and stacks: a review
Published in Journal of Asian Ceramic Societies, 2021
Muhammad Zubair Khan, Asim Iltaf, Hafiz Ahmad Ishfaq, Fahd Nawaz Khan, Waqas Hassan Tanveer, Rak-Hyun Song, Muhammad Taqi Mehran, Mohsin Saleem, Amjad Hussain, Zubair Masaud
Large cathodic polarization, due to the high activation energy required for oxygen reduction reaction (ORR) is a major issue associated with the FT-SOFCs cathode materials. A cathode material should exhibit enough electronic conductivity (ionic conductivity is added advantage) to minimize the polarization losses. The TEC should be matched well with electrolyte materials and it should be stable during long-term SOFC operation. Multi-layered cathode composed of LSM-YSZ composite and LSCF was widely used as cathode material in FT-SOFCs and coated on the electrolyte co-sintered flat substrate by a dip-coating method [74,91,102,117,119]. Park et al. [73] also used LSM-YSZ composite cathode for monolithic FT-SOFCs using a spray coating method. LSCF is an important MIEC cathode material that plays a very vital role in the commercialization and development of SOFC technologies. T. Suzuki et al. [124] used a cost-effective dip-coating technique to coat the composite air electrode of LSCF-GDC (Ce0.9Gd0.1O1.95) on the GDC interlayer for the fabrication of 1.3 cm wide and 0.2 cm thick micro FT-SOFCs.