Electrochemically driven cation segregation in the mixed conductor La0.6Sr0.4Co0.2Fe0.8O3−δ

Finsterbusch, Martin; Lussier, A.; Schaefer, J.A.; Idzerda, Y. U.

doi:10.1016/j.ssi.2012.02.006

Cited by 60 publications

(77 citation statements)

References 17 publications

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“…This indicates the SrCrO 4 formation at the LSCF cathode surface by the following possible reactions: 1) trapping of Cr and deposition of Cr are accelerated at the Pt-mesh/LSCF interface during cathode reaction and 2) Sr-transports to the surface of LSCF porous structures to form SrCrO 4 . Sr-segregation in LSCF has been reported by several authors [17][18][19], and the present result can be related with the instability of LSCF cathode under polarized condition. If we assume grain boundary diffusion of Sr in LSCF, relatively long distance diffusion of Sr is calculated through the porous LSCF cathode.…”

Section: Methodssupporting

confidence: 79%

Degradation Mechanism of SOFC Cathodes under CrO₃ and SO₂ Impurity Exposures

et al. 2013

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The effects of Cr-and S-impurities on the cathode performances were examined at the mixed ionic-electronic conducting La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3 (LSCF) cathode. Under exposures to CrO 3 and SO 2 , the cathode performance decreased drastically by forming SrCrO 4 and SrSO 4 at the LSCF grain surfaces and electrochemical active sites. The main degradation factors of LSCF cathode was the decrease of surface reaction rates by the impurities. The Sr-diffusion and depletion in the LSCF structures can affect the cathode performance degradation. Relatively large amounts of Sr were depleted in the LSCF grains under CrO 3 exposures by forming a thick SrCrO 4 at the Pt-mesh/LSCF cathode interfaces, while small amounts of Sr-depletion in the LSCF grains under SO 2 exposures.

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Section: Methodssupporting

confidence: 79%

Degradation Mechanism of SOFC Cathodes under CrO₃ and SO₂ Impurity Exposures

et al. 2013

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“…17 Many perovskite materials, including common SOFC cathodes such as LSC, LSCF and LSM ((La,Sr)MnO 3 ), display this segregation of Sr from the perovskite lattice to the surface. [18][19][20] It is driven by high temperature and mechanical stress 21,22 as well as by relaxation of crystal defects. 23 The Sr from the perovskite lattice forms SrO crystals on the entire available cathode surface, which is a possible reaction partner for volatile Cr species.…”

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confidence: 99%

Insight into the Reaction Mechanism of (La_0.58Sr_0.40)(Co_0.20Fe_0.80)O_3-δCathode with Volatile Chromium Species at High Current Density in a Solid Oxide Fuel Cell Stack

Beez

Yin

Menzler

et al. 2017

J. Electrochem. Soc.

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Anode-supported solid oxide fuel cells with different Cr protection layers on the metallic interconnect were operated in a short stack at 700 • C for 1240 h. The current density was raised sequentially from 0.5 A cm −2 during the first 240 h of operation to 0.75 A cm −2 for a further 1000 h. After operation, the (La,Sr)(Co,Fe)O 3-δ (LSCF) cathode layers were analyzed with respect to Cr interaction by both wet chemical and microstructural methods. For cells equipped with interconnects coated with a dense APS protection layer, the amount of Cr on the cathode was in the range of a few μg. For cells with a porous WPS coating on the interconnect, the amount of Cr was in the range of 110-160 μg cm −2 and Cr-containing phases were detected by SEM analysis both on top of the cathode layer and also at the LSCF/GDC interface, which has rarely been observed before. In addition, a deterioration of the cathode microstructure near the LSCF/GDC interface was observed. With respect to the high current density during operation, a theory was developed which explains both the Cr deposition at the LSCF/GDC interface and also the deterioration of the cathode. Climate change, limitation of resources, technical and political obstacles associated with nuclear power and changes in the global energy economy are only a few reasons why the world needs alternative concepts for its future energy supply. One key technology offering decentralized energy supply is solid oxide fuel cells (SOFC).1 Their high efficiency; fuel flexibility and scalability allows them to be used as decentralized power plants or, on a smaller scale, in auxiliary power units or range extenders in mobile applications. 2-4During the development and optimization of SOFC stacks and systems, attention was not only focused on performance but also on the application of cost-efficient materials. One major improvement was the establishment of metallic interconnects, offering high electronic and thermal conductivity and mechanical stability while also decreasing the price per repeating unit compared to full ceramic stack designs.5 However, the preferentially used Cr-containing steels lead to pronounced performance degradation due to the evaporation of Cr compounds, which then react with the cathode. Under the oxidizing conditions on the cathode side, hexavalent Cr species such as CrO 3 and CrO 2 (OH) 2 evaporate from the oxide scale of the interconnect or balance-of-plant components and react with the LSCF cathode material to form a Sr-and Cr-containing oxide scale thereby decreasing cell performance. 3,6,7 This effect is known to be influenced by parameters such as Cr partial pressure, air humidity and temperature. [8][9][10] To avoid this Cr-related degradation, different strategies have been developed to either reduce the Cr partial pressure to an acceptable level for the desired operating time or to increase the Cr tolerance of the cathode material itself. The most promising technique for avoiding Cr poisoning is to coat the interconnect steel with a preferentially dense pro...

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“…In particular, mixed conducting oxides with simple perovskite structure have been studied as alternative cathode materials for intermediate-temperature (IT)-SOFCs, including Sm 0.5 Sr 0.5 CoO 3− δ (SSC)12, Ba 0.5 Sr 0.5 Co 0.8 Fe 0.2 O 3− δ (BSCF)13, and La 0.6 Sr 0.4 Co 1− x Fe x O 3− δ (LSCF)14. Among them, BSCF was reported to have very low area-specific resistance (ASR), about 0.05 ~ 0.08 Ω cm 2 at 600°C.…”

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confidence: 99%

Highly efficient and robust cathode materials for low-temperature solid oxide fuel cells: PrBa0.5Sr0.5Co2−xFexO5+δ

Choi

Yoo

Kim

et al. 2013

Sci Rep

318

222

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Solid oxide fuel cells (SOFC) are the cleanest, most efficient, and cost-effective option for direct conversion to electricity of a wide variety of fuels. While significant progress has been made in anode materials with enhanced tolerance to coking and contaminant poisoning, cathodic polarization still contributes considerably to energy loss, more so at lower operating temperatures. Here we report a synergistic effect of co-doping in a cation-ordered double-perovskite material, PrBa0.5Sr0.5Co2−xFexO5+δ, which has created pore channels that dramatically enhance oxygen ion diffusion and surface oxygen exchange while maintaining excellent compatibility and stability under operating conditions. Test cells based on these cathode materials demonstrate peak power densities ~2.2 W cm−2 at 600°C, representing an important step toward commercially viable SOFC technologies.

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Electrochemically driven cation segregation in the mixed conductor La0.6Sr0.4Co0.2Fe0.8O3−δ

Cited by 60 publications

References 17 publications

Degradation Mechanism of SOFC Cathodes under CrO₃ and SO₂ Impurity Exposures

Degradation Mechanism of SOFC Cathodes under CrO₃ and SO₂ Impurity Exposures

Insight into the Reaction Mechanism of (La_0.58Sr_0.40)(Co_0.20Fe_0.80)O_3-δCathode with Volatile Chromium Species at High Current Density in a Solid Oxide Fuel Cell Stack

Highly efficient and robust cathode materials for low-temperature solid oxide fuel cells: PrBa0.5Sr0.5Co2−xFexO5+δ

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Electrochemically driven cation segregation in the mixed conductor La0.6Sr0.4Co0.2Fe0.8O3−δ

Cited by 60 publications

References 17 publications

Degradation Mechanism of SOFC Cathodes under CrO3 and SO2 Impurity Exposures

Degradation Mechanism of SOFC Cathodes under CrO3 and SO2 Impurity Exposures

Insight into the Reaction Mechanism of (La0.58Sr0.40)(Co0.20Fe0.80)O3-δCathode with Volatile Chromium Species at High Current Density in a Solid Oxide Fuel Cell Stack

Highly efficient and robust cathode materials for low-temperature solid oxide fuel cells: PrBa0.5Sr0.5Co2−xFexO5+δ

Contact Info

Product

Resources

About

Degradation Mechanism of SOFC Cathodes under CrO₃ and SO₂ Impurity Exposures

Degradation Mechanism of SOFC Cathodes under CrO₃ and SO₂ Impurity Exposures

Insight into the Reaction Mechanism of (La_0.58Sr_0.40)(Co_0.20Fe_0.80)O_3-δCathode with Volatile Chromium Species at High Current Density in a Solid Oxide Fuel Cell Stack