Long‐Term Testing of SOFC Stacks at Forschungszentrum Jülich

Blum, Ludger; Packbier, Ute; Vinke, Izaak C.; Haart, L.G.J. de

doi:10.1002/fuce.201200151

Cited by 89 publications

(70 citation statements)

References 10 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…4) Although LSM/YSZ containing SOFC has exhibited long-term chemical and mechanical stability during full cell/stack testing under normal cathode exposure environment, slight increase of polarization resistance has led to minor performance degradation. 5) Cathodic polarization considerably contributes to the energy loss, more at low operating temperatures. 6) Compressed environment air with water (³3% representing 100% relative humidity at room temperature) and carbon dioxide (³350 ppm) is used as cathode gas.…”

Section: Introductionmentioning

confidence: 99%

Performance regeneration in lanthanum strontium manganite cathode during exposure to H2O and CO2 containing ambient air atmospheres

Mahapatra

Singh

2015

J. Ceram. Soc. Japan

View full text Add to dashboard Cite

The regenerability and stability of lanthanum strontium manganite (LSM)/yttria doped zirconia (YSZ)/LSM symmetrical cells have been examined after the cells were exposed to real-world air environment containing H 2 O and CO 2 . An alternate exposure experiment in 20% H 2 O-air and dry air has been conducted to test the reversibility of the cell degradation in H 2 O/air. Long-term experiment in 3% H 2 O-0.5% CO 2 -air, dry air, 0.5% CO 2 -air, and 10% CO 2 -air has shown the stability and regenerability of the cell performance. Additional experiments show that periodic water content fluctuation causes the cell performance fluctuation. Electrochemical performance measurements and post-test microstructure analysis indicate that the segregation of SrO on the LSM surface and formation of La 2 Zr 2 O 7 at the LSM/YSZ interface degraded the electrochemical performance by increasing the polarization resistance. The cell performance degradation can be partially recovered by exposure to dry air. Thermogravimetric analysis (TGA) has been conducted for the LSM as well as its constituent oxides to elucidate degradation mechanisms. Mechanisms related to the performance degradation and regenerability have been proposed.

show abstract

Section: Introductionmentioning

confidence: 99%

Performance regeneration in lanthanum strontium manganite cathode during exposure to H2O and CO2 containing ambient air atmospheres

Mahapatra

Singh

2015

J. Ceram. Soc. Japan

View full text Add to dashboard Cite

show abstract

“…[6][7][8][9] Recently, a short stack achieved a 10 years lifetime, and remains in operation. 10 With proper protective coating, a voltage degradation rate of less than 0.3%/kh and lifetime of more than 40,000 h at 700…”

mentioning

confidence: 99%

Electrochemical Performance and Preliminary Post-Mortem Analysis of a Solid Oxide Cell Stack with 20,000 h of Operation

Fang

Frey

Menzler

et al. 2018

J. Electrochem. Soc.

View full text Add to dashboard Cite

A long-term test with a two-layer solid oxide cell stack was carried out for more than 20,000 hours. The stack was mainly characterized in a furnace environment in electrolysis mode, with 50% humidification of H 2 at 800 • C. The endothermic operation was carried out with a current density of −0.5 Acm −2 and steam conversion rate of 50%. Electrolysis at lower temperatures (i.e., 700 • C and 750 • C) and fuel cell operation (with 0.5 Acm −2 and fuel utilization of 50%) at 800 • C were also carried out (<2000 h each) for comparison. The voltage and area specific resistance degradation rates were ∼0.6%/kh and 8.2%/kh after ∼18,460 hours of operation. In total, the stack was operated above 700 • C for more than 20,000 hours. Impedance measurement and analysis showed that the increase of ohmic resistance was the main degradation phenomenon, while electrode polarizations were kept nearly constant before a severe burning took place in one layer. Ni-depletion in fuel electrodes was confirmed during post-mortem analysis, which was assumed to be the major degradation mechanism observed. The stack performance and degradation analysis under different working conditions, as well as the results of preliminary post-mortem analysis will be presented. One of the critical challenges to the application and commercialization of solid oxide cell (SOC) technology is the long-term stability of complete systems, stacks and single components. Despite the fact that accelerating methods have long been under discussion, the time-consuming and costly endurance tests of stacks and cells under relevant conditions are still necessary for reliable degradation analyses and lifetime prediction. Compared to the tests with single cell or other stack and system component, the results of long-term degradation tests with stacks are quite limited. [1][2][3][4][5] Previous results have shown stable performance of stacks working in the temperature range of 700-800• C in SOFC mode. [6][7][8][9] Recently, a short stack achieved a 10 years lifetime, and remains in operation. 10 With proper protective coating, a voltage degradation rate of less than 0.3%/kh and lifetime of more than 40,000 h at 700• C is possible with current stack design and components. In contrast to the low degradation rate in SOFC mode, higher degradation rates of ∼0.6-1.5%/kh were observed with similar types of cells in the same stack design in SOEC mode, as described by Nguyen et al. 11 Therefore, the functionality and optimization potential of the cells and stacks, as well as their long-term degradation behavior and mechanisms in SOEC mode, needs to be further investigated. Amongst the stacks operated in SOEC mode, a two-layer stack was operated under different stationary conditions for more than 20,000 h. The stack performance was regularly monitored by open circuit voltage, voltage-current curves and impedance measurements. After cooling down, one third of the stack was embedded in resin for cross-section preparation, and the rest was disassembled for visual inspection. The prelim...

show abstract

“…18 Also, SOFC stacks with LSCF cathodes have been shown to provide reasonably stable long-term performance, 19 an observation that appears to be at odds with the Sr segregation and related degradation observed for thin-film LSCF.…”

mentioning

confidence: 99%

“…Although the measured properties of well-prepared polycrystalline thin-film electrodes normally agree reasonably well with values from bulk materials, 17 in some cases such as epitaxial thin film electrodes, properties may deviate significantly. 18 Also, SOFC stacks with LSCF cathodes have been shown to provide reasonably stable long-term performance, 19 an observation that appears to be at odds with the Sr segregation and related degradation observed for thin-film LSCF.…”

mentioning

confidence: 99%

Mechanisms of Performance Degradation of (La,Sr)(Co,Fe)O_3-δSolid Oxide Fuel Cell Cathodes

Wang

Yakal-Kremski

Yeh

et al. 2016

J. Electrochem. Soc.

131

View full text Add to dashboard Cite

Symmetric cells with porous La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3-δ (LSCF) electrodes on Gd 0.1 Ce 0.9 O 1.95 (GDC) electrolytes were aged at 800 • C for 800 hours in ambient air. Electrochemical impedance spectroscopy (EIS) measurements performed periodically at 700 • C showed a continuous increase of the polarization resistance from 0.15 to 0.34 · cm 2 . Three-dimensional (3D) tomographic analysis using focused ion beam-scanning electron microscopy (FIB-SEM) showed negligible changes due to the ageing, suggesting that the observed resistance increase was not caused by electrode morphological evolution. However, an increased amount, by a factor of 3, of a water-soluble Sr rich surface phase on the aged LSCF electrode was detected by an etching procedure coupled with inductively coupled plasma-optical emission spectrometry (ICP-OES). The electrochemical analysis in combination with the microstructural parameters determined by FIB-SEM was used to examine the effect of Sr segregation on the rate of oxygen surface exchange, based on the Adler-Lane-Steele (ALS) model. 1-6However, a number of MIEC materials including LSCF exhibit Sr surface segregation, which has been proposed to hinder the oxygen surface exchange process. [7][8][9][10][11] This is believed to be an important issue for the stability of advanced SOFCs utilizing MIEC cathodes. Still, most of the Sr segregation observations have been made on thin film samples, where it is straightforward to measure surface composition using techniques such as X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES), and secondary ion mass spectrometry (SIMS).12-15 Recently Rupp et al. 16 reported a novel technique utilizing chemical etching with on-line inductively coupled plasma optical emission spectrometry (ICP-OES) detection to successfully quantify Sr-rich surface phases on dense La 0.6 Sr 0.4 CoO 3-δ (LSC) thin films. There is only one report of a measurement of a practical porous LSCF electrode that showed Sr segregation, measured via XPS, along with electrochemical performance degradation. 11The distinction between thin film and bulk electrode samples is potentially important. Thin films are often characterized by columnar growth with very high grain boundary densities, they may exhibit significant stress, and the thermal history is usually very different from that of porous electrodes (preparation mostly below 800• C). Although the measured properties of well-prepared polycrystalline thin-film electrodes normally agree reasonably well with values from bulk materials, 17 in some cases such as epitaxial thin film electrodes, properties may deviate significantly.18 Also, SOFC stacks with LSCF cathodes have been shown to provide reasonably stable long-term performance, 19 an observation that appears to be at odds with the Sr segregation and related degradation observed for thin-film LSCF.In this work, we investigated the degradation mechanisms, especially Sr surface segregation, of porous LSCF cathodes. LSCF symmetric-electrode cells with Gd 0.1 Ce 0.9 ...

show abstract

Long‐Term Testing of SOFC Stacks at Forschungszentrum Jülich

Cited by 89 publications

References 10 publications

Performance regeneration in lanthanum strontium manganite cathode during exposure to H<sub>2</sub>O and CO<sub>2</sub> containing ambient air atmospheres

Performance regeneration in lanthanum strontium manganite cathode during exposure to H<sub>2</sub>O and CO<sub>2</sub> containing ambient air atmospheres

Electrochemical Performance and Preliminary Post-Mortem Analysis of a Solid Oxide Cell Stack with 20,000 h of Operation

Mechanisms of Performance Degradation of (La,Sr)(Co,Fe)O_3-δSolid Oxide Fuel Cell Cathodes

Contact Info

Product

Resources

About

Long‐Term Testing of SOFC Stacks at Forschungszentrum Jülich

Cited by 89 publications

References 10 publications

Performance regeneration in lanthanum strontium manganite cathode during exposure to H<sub>2</sub>O and CO<sub>2</sub> containing ambient air atmospheres

Performance regeneration in lanthanum strontium manganite cathode during exposure to H<sub>2</sub>O and CO<sub>2</sub> containing ambient air atmospheres

Electrochemical Performance and Preliminary Post-Mortem Analysis of a Solid Oxide Cell Stack with 20,000 h of Operation

Mechanisms of Performance Degradation of (La,Sr)(Co,Fe)O3-δSolid Oxide Fuel Cell Cathodes

Contact Info

Product

Resources

About

Mechanisms of Performance Degradation of (La,Sr)(Co,Fe)O_3-δSolid Oxide Fuel Cell Cathodes