Air side contamination in Solid Oxide Fuel Cell stack testing

Schuler, J. Andreas; Gehrig, Christian; Wuillemin, Zacharie; Schuler, A. J.; Wochele, J.; Ludwig, Christian; Hessler-Wyser, Aïcha; herle, Jan Van

doi:10.1016/j.jpowsour.2010.10.058

Cited by 61 publications

(63 citation statements)

References 37 publications

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“…From the present experiences, also kinetic information regarding individual sulphur oxidation steps can be accessed, because the time for reaching stable fluorescence signal after changing the SOFC temperature took longer than the shortest data accumulation period practised here (w30 min). Developed an operando SOFC-XAS cell is versatile as it also allows studying contamination effects at the air-fed cathode side, including Cr [56] poisoning and alkaline elements if appropriate X-ray windows for higher oxygen partial pressures are applied. The presented cell allows also to obtain the metal (in the present case Ni and Ce) absorption edges, which may facilitate the identification of Ni-and CeO 2 -related reaction products with sulphur.…”

Section: Discussionmentioning

confidence: 99%

Redox dynamics of sulphur with Ni/GDC anode during SOFC operation at mid- and low-range temperatures: An operando S K-edge XANES study

Nurk

Huthwelker

Braun

et al. 2013

Journal of Power Sources

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h i g h l i g h t s g r a p h i c a l a b s t r a c tAn operando SOFC anode S-poisoning XAS experiment at 550 C to 250 C was performed. S K-edge XANES spectral information at Ni/GDC outer surface was collected.Intermediates with different sulphur oxidation states (6þ, 4þ, 0, 2À) were observed. Proportion of oxidation states changed as a function of temperature. Differences between TD calculations and XAS information were observed and discussed. a r t i c l e i n f o a b s t r a c t Sulphur poisoning of nickelebased solid oxide fuel cell (SOFC) anode catalysts is a well-documented shortcoming, but not yet fully understood. Here, a novel experiment is demonstrated to obtain spectroscopic information at operando conditions, in particular the molecular structure of sulphur species in the sulphur K-shell X-ray absorption near edge structure (XANES) region for a SOFC anode under realistic operando conditions, thus, with the flux of O 2À from cathode to anode. Cooling from T ¼ 550 C stepwise down to 250 C, 5 ppm H 2 S/H 2 reacting with Ni-gadolinium doped ceria (GDC) anode resulted in several sulphur species in different oxidation states (6þ, 4þ, 0, À2) and in amounts being at a minimum at high temperature. According to sulphur speciation analysis, the species could either relate to eSO 4 2À or SO 3 (g), eSO 3 2À or SO 2 (g), S 2 (g) or surface-adsorbed S atoms, and, Ni or Ce sulphides, respectively. The coexistence of different sulphur oxidation states as a function of temperature was analysed in the context of thermodynamic equilibrium calculations. Deviations between experimental results and calculations are most likely due to limitations in the speed of some intermediate oxidation steps as well as due to differences between stoichiometric CeO 2 used in calculations and partially reduced Ce 0.9 Gd 0.1 O 2Àd .

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Section: Discussionmentioning

confidence: 99%

Redox dynamics of sulphur with Ni/GDC anode during SOFC operation at mid- and low-range temperatures: An operando S K-edge XANES study

Nurk

Huthwelker

Braun

et al. 2013

Journal of Power Sources

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“…In the case of interconnects protective layers -either applied as a thin coating or developed in-situ through high-temperature scale formation -are used as a countermeasure but cannot completely suppress the emission of Cr-species into the gas phase [3,4]. Similar degradation issues may be caused by poisoning of the cathode with silicon species released into the gas stream from silicate-based glass sealing materials or heat-resistant alloys used in BOP-components [5][6][7][8][9][10].…”

Section: Introductionmentioning

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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“…Numerous studies (e.g. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20]) have considered the severity of chromium poisoning of (La,Sr)MnO 3 -based cathodes depending on whether the SOFC is operated under load or is held at open-circuit, whether the air supplied to the cathode is dry or humidified, and depending on the interconnect metallic alloy used (Inconel 600, Cr5Fe1Y 2 O 3 , Crofer22APU, RA446, 17-4 stainless steel, AISI 441, SUS430, ITM or ZMG232).…”

Section: Introductionmentioning

confidence: 99%

“…Assuming slow kinetics, the non-observation of chromium-substituted (La,Sr)MnO 3 is not surprising considering that exposure times in all but one (Menzler et al [13], 8,000 h exposure time) of the above-cited chromium poisoning studies were ≤ 3,000 h and therefore short compared to SOFC system lifetime requirements, which exceed 40,000 h [20,22]. Moreover, it would be nearly impossible to distinguish any chromium-substituted (La,Sr)MnO 3 formed from (La,Sr)MnO 3 using the common technique of X-ray diffractometry (XRD), since these materials are isostructural on account of the fact that the ionic radii [23] of VI-coordinate (high spin) Mn 3+ (0.645 Å) and Cr 3+ (0.615 Å) are similar.…”

Section: Introductionmentioning

confidence: 99%

Conductivity and oxygen reduction activity changes in lanthanum strontium manganite upon low-level chromium substitution

Tsekouras

Braun

2014

Solid State Ionics

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On the timescale of solid oxide fuel cell (SOFC) system lifetime requirements, the thermodynamically predicted low-level substitution of chromium on the B-site of (La,Sr)MnO 3 could be a source of cathode degradation underlying more overt and well-known chromium poisoning mechanisms. To study this phenomenon in isolation, electronic conductivity (σ) and electrochemical oxygen reduction activity of the (La 0.8 Sr 0.2 ) 0.98 Cr x Mn 1−x O 3 model series (x = 0, 0.02, 0.05 or 0.1) were measured in air between 850 and 650 °C. Depending on the extent of chromium substitution and the measurement temperature, electrochemical impedance spectroscopy (EIS) results could be deconvoluted into a maximum of three contributions reflecting possible limiting processes such as oxide ion transport and dissociative adsorption. Chromium substitution resulted in lowered σ (from 174 S cm − 1 (x = 0) to 89 S cm − 1 (x = 0.1) at 850 °C) and a steady rise in associated activation energy (E a ) (from 0.105 ± 0.001 eV (x = 0) to 0.139 ± 0.001 eV (x = 0.1)). From EIS analyses, ohmic and polarisation resistances increased, whilst Ea for the overall oxygen reduction reaction also increased from 1.39 ± 0.04 eV (x = 0) to 1.48-1.54 ± 0.04 eV upon chromium substitution.Keywords level, conductivity, oxygen, reduction, activity, changes, chromium, lanthanum, substitution, strontium, manganite, upon, low Depending on the extent of chromium substitution and the measurement temperature, electrochemical impedance spectroscopy (EIS) results could be deconvoluted into a maximum of three contributions 2 reflecting possible limiting processes such as oxide ion transport and dissociative adsorption. Chromium substitution resulted in lowered  (from 174 S cm -1 (x = 0) to 89 S cm -1 (x = 0.1) at 850 °C) and a steady rise in associated activation energy (E a ) (from 0.105 ± 0.001 eV (x = 0) to 0.139 ± 0.001 eV (x = 0.1)). From EIS analysis, ohmic and polarisation resistances increased, whilst E a for the overall oxygen reduction reaction also increased from 1.39 ± 0.04 eV (x = 0) to 1.48-1.54 ± 0.04 eV upon chromium substitution.

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Air side contamination in Solid Oxide Fuel Cell stack testing

Cited by 61 publications

References 37 publications

Redox dynamics of sulphur with Ni/GDC anode during SOFC operation at mid- and low-range temperatures: An operando S K-edge XANES study

Redox dynamics of sulphur with Ni/GDC anode during SOFC operation at mid- and low-range temperatures: An operando S K-edge XANES study

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

Conductivity and oxygen reduction activity changes in lanthanum strontium manganite upon low-level chromium substitution

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