Surface-Related Effects Limiting the Performance of Solid Oxide Fuel Cell Cathodes

Bucher, Edith

doi:10.1007/s00501-011-0030-3

Cited by 8 publications

(6 citation statements)

References 21 publications

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“…The effects of chromium poisoning were simulated by placing a chromium pellet upstream close to the specimen thus exposing the sample to chromia-containing gas flows. A more detailed description of the experimental procedure is given elsewhere [29].…”

Section: Electrical Conductivity Relaxation Measurementsmentioning

confidence: 99%

Long-term stability of the IT-SOFC cathode materials La0.6Sr0.4CoO3−δ and La2NiO4+δ against combined chromium and silicon poisoning

et al. 2015

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Long-term degradation effects of combined Cr-and Si-poisoning on the promising IT-SOFC cathode materials La 0.6 Sr 0.4 CoO 3-δ and La 2 NiO 4+δ were investigated at 700°C in dry and humid atmospheres for subsequent periods of 1000 hours using dcconductivity relaxation measurements. Degradation-induced changes in chemical composition and morphology of the contaminated sample surfaces were studied by atomic force microscopy, X-ray photoelectron spectroscopy and scanning electron microscopy with energy and wavelength dispersive X-ray analysis. Upon exposure to humid, Cr-and Si-containing gas flows both materials exhibit a strong decrease of the chemical surface exchange coefficient of oxygen by a factor 110 and 40 for La 0.6 Sr 0.4 CoO 3-δ and La 2 NiO 4+δ , respectively, which can be attributed to the formation of Cr-containing crystallites on the degraded sample surfaces. Post-test analyses confirm large amounts of Cr accompanied by a Sr-enrichment within the first 600 nm of the surface of La 0.6 Sr 0.4 CoO 3-δ , indicating the decomposition of the perovskite phase by SrCrO 4 -formation. For La 2 NiO 4+δ the penetration depth of chromium is significantly less and Cr-traces up to a depth of up to 140 nm were determined by depth profiling. For both compounds silicon was found to spread in small patches across the entire sample surface as determined by elemental mapping analysis.

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Section: Electrical Conductivity Relaxation Measurementsmentioning

confidence: 99%

Long-term stability of the IT-SOFC cathode materials La0.6Sr0.4CoO3−δ and La2NiO4+δ against combined chromium and silicon poisoning

et al. 2015

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“…If the relative humidity and testing temperature are increased to 60% and 700 °C, respectively, the decay of the exchange kinetics reaches as large as two orders of magnitudes. The decayed property is attributed to the change in surface composition and Si poisoning which is pronouncedly enhanced under H 2 O‐containing atmosphere as suggested in references. Furthermore, the presence of gaseous H 2 O also makes contribution to the poisoning process with Cr.…”

Section: Effect Of the Surface Poisoning And Degradationmentioning

confidence: 71%

Factors influencing the measured surface reaction kinetics parameters

Xia

2016

Asia-Pacific J Chem Eng

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Further understanding of the cathode oxygen reduction reaction mechanism is one of the most important challenges for the development of solid oxide fuel cells at low and intermediate temperature. Determining the surface reaction kinetics parameters such as the surface exchange coefficient and bulk diffusion coefficient is critical to reveal the cathode process. However, the reported results from different literatures are widely divergent and sometimes the variation can reach as high as over one order of magnitude even for the same cathode material. The various original data make it difficult to judge the reaction property and possibly weaken the reliability of the parameters. In this review paper, the recent progress of the oxygen reduction reaction kinetics parameters is comprehensively summarized for typical cathode material La 1Àx Sr x Co 1Ày Fe y O 3Àδ regarding the experimental methods and principles. Emphasis is also placed on the main influenced factors which may result in the reported variation. The main purpose of this paper is to provide a summary of recent progress and reveal the possible difference source for the surface reaction kinetics of oxygen reduction reaction.

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“…These reactions are strongly affected by modifications of the electrode surface induced either directly by H 2 O (g) or indirectly by poisoning with critical impurities (Cr, Si, etc. ), due to their enhanced gas phase transport in humid atmospheres .…”

Section: Resultsmentioning

confidence: 99%

“…It might be due to SO 2 ‐impurities on a ppb‐level in the test gases and trace amounts of Cr‐residues in the test reactor, which might accumulate within the electrode in the course of the long‐term experiment. It is well known that gas phase transport of Cr‐species is significantly enhanced in humid atmospheres , , . Large‐scale blocking of active areas of the inner backbone surface by insulating secondary phases is expected to critically affect the electrode performance.…”

Section: Resultsmentioning

confidence: 99%

“…This is a strong indication that gas phase transport of silicon in humid atmospheres occurred during the long-term experiment, with the most likely Si source being the quartz glass reactor. The fact that Si is found preferably in the porous layers of the spincoated electrode can be explained by the gas phase transport and deposition mechanisms [53,56,63] and the fact that Si readily forms silicate layers on the surface but does not diffuse into the bulk of the perovskite structure [55,64]. Surface accumulation of silicate species clearly reduces the oxygen surface exchange activity of electrode materials and is thus assumed to be the main cause for the electrochemical degradation observed in this study, though separating its contribution from grain coarsening effects within the spin-coated layers is difficult.…”

Section: Post-test Analysismentioning

confidence: 99%

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Effect of Microstructure on the Degradation of La_0.6Sr_0.4CoO_3–_δ Electrodes in Dry and Humid Atmospheres

et al. 2019

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La0.6Sr0.4CoO3–δ electrode layers with three different microstructures were manufactured by screen‐printing, spin‐coating and infiltration into a porous Ce0.9Gd0.1O1.95 backbone. Electrode performance was monitored at 700 °C in 20% O2 over periods of 1,600 to 3,860 h by means of electrochemical impedance spectroscopy under open circuit conditions. Reference measurements were performed in dry atmospheres, where significant electrode activation was observed for cells with spin‐coated and infiltrated electrodes. Subsequently, the relative humidity level in the surrounding atmosphere was set to 30% and further raised to 60%, thus simulating SOFC operation with ambient air without pre‐drying. While no performance loss could be observed in dry atmospheres, significant degradation occurred in humid atmospheres with pronounced differences between degradation rates of half cells with different electrode microstructures. Post‐test analyses by scanning electron microscopy (SEM) and transmissionscanning electron microscopy (STEM) were employed to identify the causes for the observed differences in degradation behavior. For screen‐printed cells, the surface of the degraded electrodes was covered with small crystallites, probably consisting of SrO formed by Sr‐segregation and surface precipitation, where humidity was found to be a crucial factor. For spin‐coated and infiltrated electrodes, poisoning by impurities (Si, Cr, S) and particle coarsening were identified as potential causes.

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Surface-Related Effects Limiting the Performance of Solid Oxide Fuel Cell Cathodes

Cited by 8 publications

References 21 publications

Long-term stability of the IT-SOFC cathode materials La0.6Sr0.4CoO3−δ and La2NiO4+δ against combined chromium and silicon poisoning

Long-term stability of the IT-SOFC cathode materials La0.6Sr0.4CoO3−δ and La2NiO4+δ against combined chromium and silicon poisoning

Factors influencing the measured surface reaction kinetics parameters

Effect of Microstructure on the Degradation of La_0.6Sr_0.4CoO_3–_δ Electrodes in Dry and Humid Atmospheres

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Surface-Related Effects Limiting the Performance of Solid Oxide Fuel Cell Cathodes

Cited by 8 publications

References 21 publications

Long-term stability of the IT-SOFC cathode materials La0.6Sr0.4CoO3−δ and La2NiO4+δ against combined chromium and silicon poisoning

Long-term stability of the IT-SOFC cathode materials La0.6Sr0.4CoO3−δ and La2NiO4+δ against combined chromium and silicon poisoning

Factors influencing the measured surface reaction kinetics parameters

Effect of Microstructure on the Degradation of La0.6Sr0.4CoO3–δ Electrodes in Dry and Humid Atmospheres

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Effect of Microstructure on the Degradation of La_0.6Sr_0.4CoO_3–_δ Electrodes in Dry and Humid Atmospheres