Development of lanthanum ferrite SOFC cathodes

Simner, Steven P.; Bonnett, Jeff F.; Canfield, Nathan L.; Meinhardt, Kerry D.; Shelton, Jayne P.; Sprenkle, Vince L.; Stevenson, Jeffry W.

doi:10.1016/s0378-7753(02)00455-x

Cited by 299 publications

(185 citation statements)

References 18 publications

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“…In addition to providing more TPB sites, the use of composites is also advantageous for mechanical stability, since it alleviates the problem of thermal expansion coefficient mismatch between the electrolyte and electronic conductor. [13][14][15] Alternative perovskites with mixed ionic and electronic conductivity (MIEC), such as LSF (La 1Àx Sr x FeO 3 ) or LSCF (La 1Àx Sr x Co 1-y Fe y O 3 ) have also been proposed as cathode materials for SOFCs, especially for operation at lower temperatures, 873-1073 K. [16][17][18][19][20][21][22][23][24][25] The ionic conductivity of LSF is significantly higher than that of LSM (8.3 Â 10 À4 S/cm at 973 K), 26 so that oxygen adsorption and reduction do not have to be spatially confined to the TPB sites. 3,15,27 However, the ionic conductivity of MIECs is still much lower than that of the YSZ (1.8 Â 10 À2 S/cm at 973 K).…”

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confidence: 99%

Effect of the Ionic Conductivity of the Electrolyte in Composite SOFC Cathodes

Vohs

Gorte

2011

J. Electrochem. Soc.

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Solid oxide fuel cell (SOFC) cathodes were prepared by infiltration of 35 wt % La0.8Sr0.2FeO3 (LSF) into porous scaffolds of three, zirconia-based electrolytes in order to determine the effect of the ionic conductivity of the electrolyte material on cathode impedances. The electrolyte scaffolds were 10 mol % Sc2O3-stabilized zirconia (ScSZ), 8 mol % Y2O3-stabilized zirconia (YSZ), and 3 mol % Y2O3- 20 mol % Al2O3-doped zirconia (YAZ), prepared by tape casting with graphite pore formers. Each electrolyte scaffold was 65% porous, with identical pore structures as determined by scanning electron microscopy (SEM). Both symmetric cells and fuel cells were prepared and tested between 873 and 1073 K, using LSF composites that had been calcined to 1123 or 1373 K. Literature values for the electrolyte conductivities were confirmed using the ohmic losses from the impedance spectra. The electrode impedances decreased with increasing electrolyte conductivity, with the dependence being between to the power of 0.5 and 1.0, depending on the operating temperature and LSF calcination temperature.

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confidence: 99%

Effect of the Ionic Conductivity of the Electrolyte in Composite SOFC Cathodes

Vohs

Gorte

2011

J. Electrochem. Soc.

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“…Subsequently, LSCF slurry was screen printed or brush painted on the GDC buffer layer, followed by firing at 1080°C in air for 2 hours. [12] Cells from Delphi LSCF based button cells without cathode current collectors were received from Delphi Inc.. The electrode active area was 0.3 cm 2 .…”

Section: (B) Anode-supported Cells With Ysz Electrolytementioning

confidence: 99%

Functionally Graded Cathodes for Solid Oxide Fuel Cells

Yang¹,

Liu²,

Wang³

et al. 2008

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The main objective of this DOE project is to demonstrate that the performance and long-term stability of the state-of-the-art LSCF cathode can be enhanced by a catalytically active coating (e.g., LSM or SSC).We have successfully developed a methodology for reliably evaluating the intrinsic surface catalytic properties of cathode materials. One of the key components of the test cell is a dense LSCF film, which will function as the current collector for the electrode material under evaluation to eliminate the effect of ionic and electronic transport. Since it is dense, the effect of geometry would be eliminated as well.From the dependence of the electrode polarization resistance on the thickness of a dense LSCF electrode and on partial pressure of oxygen, we have confirmed that the surface catalytic activity of LSCF limits the performances of LSCF-based cathodes. Further, we have demonstrated, using test cells of different configurations, that the performance of LSCF-based electrodes can be significantly enhanced by infiltration of a thin film of LSM or SSC. In addition, the stability of LSCF-based cathodes was also improved by infiltration of LSM or SSC.While the concept feasibility of the electrode architecture is demonstrated, many details are yet to be determined. For example, it is not clear how the surface morphology, composition, and thickness of the coatings change under operating conditions over time, how these changes influence the electrochemical behavior of the cathodes, and how to control the microscopic details of the coatings in order to optimize the performance. The selection of the catalytic materials as well as the detailed microstructures of the porous LSCF and the catalyst layer may critically impact the performance of the proposed cathodes.Further, other fundamental questions still remain; it is not clear why the degradation rates of LSCF cathodes are relatively high, why a LSM coating improves the stability of LSCF cathodes, which catalysts would be most effective for LSCF, and how to achieve further enhancement of the performance and stability of SOFC cathodes.4

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“…The diameter of the cathode was 1.6 cm. Details of the fabrication of the button-sized cells used in this study can be found in reference [25] . One benefit of collaborating with PNNL is the ability to work with materials having extremely reproducible materials preparation, tape-casting, tape-laminating and thin-film screen printing fabrication procedures [26] .…”

Section: B-5 Test-bed Application #2: Mass Transfer Effects Sofc Testsmentioning

confidence: 99%

Advanced Measurement and Modeling Techniques for Improved SOFC Cathodes

Adler¹,

Dunyushkina²,

Huff³

et al. 2006

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The goal of this project was to develop an improved understanding of factors governing performance and degradation of mixed-conducting SOFC cathodes. Two new diagnostic tools were developed to help achieve this goal: 1) microelectrode half-cells for improved isolation of cathode impedance on thin electrolytes, and 2) nonlinear electrochemical impedance spectroscopy (NLEIS), a variant of traditional impedance that allows workers to probe nonlinear rates as a function of frequency. After reporting on the development and efficacy of these tools, this document reports on the use of these and other tools to better understand performance and degradation of cathodes based on the mixed conductor La 1-x Sr x CoO 3-δ (LSC) on gadolinia or samaria-doped ceria (GDC or SDC). We describe the use of NLEIS to measure O 2 exchange on thin-film LSC electrodes, and show that O 2 exchange is most likely governed by dissociative adsorption. We also describe parametric studies of porous LSC electrodes using impedance and NLEIS. Our results suggest that O 2 exchange and ion transport co-limit performance under most relevant conditions, but it is O 2 exchange that is most sensitive to processing, and subject to the greatest degradation and sample-to-sample variation. We recommend further work that focuses on electrodes of well-defined or characterized geometry, and probes the details of surface structure, composition, and impurities. Parallel work on primarily electronic conductors (LSM) would also be of benefit to developers, and to improved understanding of surface vs. bulk diffusion.

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Development of lanthanum ferrite SOFC cathodes

Cited by 299 publications

References 18 publications

Effect of the Ionic Conductivity of the Electrolyte in Composite SOFC Cathodes

Effect of the Ionic Conductivity of the Electrolyte in Composite SOFC Cathodes

Functionally Graded Cathodes for Solid Oxide Fuel Cells

Advanced Measurement and Modeling Techniques for Improved SOFC Cathodes

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