Degradation of LSCF Cathode Induced by SO<sub>2</sub> in Air

Kishimoto, Haruo; Wang, Fangfang; Cho, Do-Hyung; Lv, Peiling; Bagarinao, Katherine Develos; Yamaji, Katsuhiko; Horita, Teruhisa; Yokokawa, Harumi

doi:10.1149/06801.1045ecst

Cited by 13 publications

(7 citation statements)

References 11 publications

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“…Relationship between the R ohmic and R p for the LSCF6428 cathode under 1 ppm SO 2 degradation, which is previously reported in ECS transaction. 16 The data for 0.1 ppm at 1073 K, which is previously reported, 14 is also plotted. Inset: R ohmic and R p .…”

Section: Resultsmentioning

confidence: 80%

“…For the degradation recovery test, LSCF6428 was first exposed to 1 ppm SO 2 for 3 h at operating temperature of either 923 K or 973 K, and the Time dependence of the rate of decrease in current under potentiostatic condition (−0.2 V vs. RE(air)) at each temperature, which is previously reported in ECS transaction. 16 The data for 0.1 ppm at 1073 K, which is previously reported, 14 is also plotted.…”

Section: Methodsmentioning

confidence: 80%

“…Earlier work has focused on the accelerated degradation behavior of LSCF cathodes induced by exposure to SO 2 -air mixture. [12][13][14][15][16] Based on the experimentally derived results and theoretical thermodynamic calculations, 12 it was confirmed that the SO 2 reacts with the Sr component to form SrSO 4 accompanied by precipitation of CoFe 2 O 4 . Moreover, SrSO 4 is easily accumulated in the vicinity of the LSCF/GDC interface under polarization condition.…”

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confidence: 88%

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Interrelation between Sulfur Poisoning and Performance Degradation of LSCF Cathode for SOFCs

Wang

Kishimoto

Develos-Bagarinao

et al. 2016

J. Electrochem. Soc.

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Performance degradation of SOFC cathodes has been partly attributed to sulfur dioxide (SO2), which is one of the major impurities naturally present in air. In this work, the sulfur poisoning behavior of (LaSr)(CoFe)O3 (LSCF) cathodes exposed to 1 ppm of SO2 in air was investigated as a function of time under various operation temperatures of 923 K, 973 K, and 1073 K. Severe performance degradation was observed at low temperatures of 923 K and 973 K. For these cases, only the polarization resistance (Rp) was increased, additionally no sulfur component was detected in the LSCF cathode. At 1073 K, both Rp and ohmic resistance (Rohmic) increased during the progress of degradation and SrSO4 was observed in cathode, especially near the LSCF/GDC interface. Plausible sulfur poisoning mechanisms were proposed based on the observed experimental phenomena.

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Section: Resultsmentioning

confidence: 80%

Section: Methodsmentioning

confidence: 80%

mentioning

confidence: 88%

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Interrelation between Sulfur Poisoning and Performance Degradation of LSCF Cathode for SOFCs

Wang

Kishimoto

Develos-Bagarinao

et al. 2016

J. Electrochem. Soc.

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“…In particular, for the sulfur poisoning of active cathodes, it becomes more difficult to identify whether sulfur poisoning appears or not even when detailed analyses on sulfur accumulation on cathode will be available with SIMS etc. This is because the degradation rate in cathode is not linearly proportional to the amount of sulfur accumulated in cathodes; significant degradations may occur even due to an extremely small amount of sulfur particularly at low temperatures . In such a case, the observed slope in correlation may help in considering possible sources of degradations, since similar correlations were obtained for sulfur poisoning in button cell experiments.…”

Section: Correlation Between Cathode Overpotential and Ohmic Lossmentioning

confidence: 85%

Recent Achievements of NEDO Durability Project with an Emphasis on Correlation Between Cathode Overpotential and Ohmic Loss

et al. 2017

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Long-term performance testes by CRIEPI (Central Research Institute for Electric Power Industry) on six industrial stacks have revealed an interesting correlation between cathode polarization loss and ohmic loss. To make clear the physicochemical meaning of this correlation, detailed analyses were made on the conductivity degradation of YSZ electrolyte in button cells and then on the ohmic losses in the industrial cells in terms of time constants which are determined from speed of the tetragonal transformation through the Y diffusion from the cubic phase to the tetragonal phase. In some cases, shorter time constants (faster degradations) were detected than those expected from the two-time-constant (with and without NiO reduction effects) model, suggesting that additional ohmic losses after subtracting the contribution from the tetragonal transformation must be caused from other sources such as cathode-degradation inducing effects. Main cathode degradations can be ascribed to sulfur poisoning due to contamination in air in the CRIEPI test site. An important feature was extracted as this cathode degradations became more severe when the gadolinium-doped ceria (GDC) interlayers were fabricated into dense film. Plausible mechanisms for cathode degradations were proposed based on the Sr/Co depletion on surface of lanthanum strontium cobalt ferrite (LSFC) in the active area. Peculiar cathode degradations found in stacks are interpreted in term of changes in surface concentration by reactions with sulfur oxide, electrochemical side reactions for water vapor emission or Sr volatilization, and diffusion of Sr/Co from inside LSCF.

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“…[6][7][8][9][10] In addition to Cr species, sulfur, most likely from the air stream, can deposit at the cathode side, poisoning and degrading the cell performance. [11][12][13][14][15][16][17] La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3-δ (LSCF) perovskite material has been extensively studied and regarded as one of the most promising cathode candidates for IT-SOFCs due to its high mixed electronic and ionic conductivities and high catalytic activity for the O 2 reduction reaction. [18][19][20] However, despite the promising potential of the LSCF material as the IT-SOFC cathode, few studies have been reported on the interaction between the LSCF electrode and sulfur dioxide and there are significant discrepancies in the mechanism of the sulfur deposition and poisoning for the O 2 reduction reaction at the LSCF cathode.…”

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confidence: 99%

Effect of SO₂Poisoning on the Electrochemical Activity of La_0.6Sr_0.4Co_0.2Fe_0.8O_3-δCathodes of Solid Oxide Fuel Cells

Wang

Chen

et al. 2017

J. Electrochem. Soc.

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The effect of sulfur deposition and poisoning on the electrochemical activity of La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3-δ (LSCF) cathode of solid oxide fuel cells (SOFCs) for the O 2 reduction reaction is studied under accelerated experimental conditions. EDS, FIB-STEM and XRD analysis clearly show the sulfur deposition occurs on the surface as well as in the bulk of the electrode, forming SrSO 4 , CoFe 2 O 4 and La 2 (SO 4 ) 3 . The sulfur deposition is random and the intensity of sulfur deposition increases with the decrease in operation temperatures. This is consistent with the significantly high poisoning effect of SO 2 in air on the electrocatalytic activity of LSCF electrodes for oxygen reduction reaction at low temperatures. After polarization at 200 mAcm −2 and 600 • C for 20 h in 10 ppm SO 2 -containing air, electrode polarization potential, E Cathode increased from 750 mV to ∼2500 mV, an increase of 1750 mV, substantially higher than 135 and 48 mV for the reaction at 700 and 800 • C. Sulfur deposition causes the increase of electrode polarization as well as ohmic resistances of LSCF cathodes for the O 2 reduction reaction. Moreover, sulfur deposition and poisoning on the LSCF cathodes is not reversible and the irreversibility of sulfur poisoning increases with the decrease of temperature. Computational calculation indicates that the interaction between LSCF and SO 2 is thermodynamically favorable, leading to complete decomposition of LSCF perovskite structure, which is in excellent agreement with the experimental results as shown in this study. Kinetically, sulfur deposition is most likely initiated by the nucleation reaction between the gaseous SO 2 and segregated SrO on the surface of LSCF electrode, which accelerates depletion of Sr and leads to the decomposition of LSCF perovskite structure.

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Degradation of LSCF Cathode Induced by SO₂ in Air

Cited by 13 publications

References 11 publications

Interrelation between Sulfur Poisoning and Performance Degradation of LSCF Cathode for SOFCs

Interrelation between Sulfur Poisoning and Performance Degradation of LSCF Cathode for SOFCs

Recent Achievements of NEDO Durability Project with an Emphasis on Correlation Between Cathode Overpotential and Ohmic Loss

Effect of SO₂Poisoning on the Electrochemical Activity of La_0.6Sr_0.4Co_0.2Fe_0.8O_3-δCathodes of Solid Oxide Fuel Cells

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Degradation of LSCF Cathode Induced by SO2 in Air

Cited by 13 publications

References 11 publications

Interrelation between Sulfur Poisoning and Performance Degradation of LSCF Cathode for SOFCs

Interrelation between Sulfur Poisoning and Performance Degradation of LSCF Cathode for SOFCs

Recent Achievements of NEDO Durability Project with an Emphasis on Correlation Between Cathode Overpotential and Ohmic Loss

Effect of SO2Poisoning on the Electrochemical Activity of La0.6Sr0.4Co0.2Fe0.8O3-δCathodes of Solid Oxide Fuel Cells

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Degradation of LSCF Cathode Induced by SO₂ in Air

Effect of SO₂Poisoning on the Electrochemical Activity of La_0.6Sr_0.4Co_0.2Fe_0.8O_3-δCathodes of Solid Oxide Fuel Cells