Post-Test Characterization of an SOFC Short-Stack after 17,000 Hours of Steady Operation

Menzler, Norbert H.; Batfalsky, Peter; Groß, Sonja M.; Shemet, V.; Tietz, Frank

doi:10.1149/1.3569994

Cited by 58 publications

(33 citation statements)

References 9 publications

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“…This indicates that the Cr species remained localized at the top of the cathode layer during cell operation as intended. From this result, it was concluded that the solid phase poisoning led to the same kind of Cr poisoning as reported in the literature for LSCF cathodes independent if they are used in real stack tests or single cell measurements (Menzler et al, 2011;Konysheva, 2014).…”

Section: Microstructural Analysissupporting

confidence: 73%

“…The amount of Cr 2 O 3 powder in the paste was calculated considering the wet layer thickness of the screen used for the screen printing process. It was targeted to achieve a Cr deposition, which is comparable to average Cr contents found in LSCF cathodes after several thousand hours of stack operation with JÜLICH specific stack design (∼100-200 µg cm −2 ) (Menzler et al, 2011;Beez et al, 2017). The Cr content of the paste was adjusted to 6.2 wt.-% (equals 0.1 g Cr 2 O 3 per 1 g organic matrix) with the aim to achieve a Cr deposition of ∼100 µg cm −2 .…”

Section: Experimental Paste Preparationmentioning

confidence: 99%

“…The amount of Cr in the samples was measured using a wet chemical method, which is described in more detail in the literature (Menzler et al, 2011).…”

Section: Solid State Poisoningmentioning

confidence: 99%

“…Gaseous hexavalent Cr species can evaporate from the metallic interconnect or balance-of-plant components and interact with the ceramic air electrode thereby leading to a loss of performance (Menzler et al, 2011). The preferred cathode materials for SOFC are mainly mixed ionic and electronic conducting (MIEC) perovskites like (La,Sr)(Co,Fe)O 3−δ (LSCF) and (La,Sr)CoO 3−δ (LSC).…”

Section: Introductionmentioning

confidence: 99%

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Accelerated Testing of Chromium Poisoning of Sr-Containing Mixed Conducting Solid Oxide Cell Air Electrodes

et al. 2018

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A straightforward method for accelerated testing of Cr poisoning phenomena on mixed ionic and electronic conducting (MIEC) Solid Oxide Cell (SOC) air electrode materials was developed. Cr 2 O 3 -powder is mixed with an organic matrix and screen printed onto anode-supported button cells with (La,Sr)(Co,Fe)O 3−δ (LSCF) cathode. Then, a thermal treatment was conducted to achieve the formation of a well-defined amount of SrCrO 4 on the cathode surface within only a few hours. For the proof of concept, single cell measurements were done to investigate the influence of this new kind of Cr deposition. As reference, a cell poisoned via gas phase diffusion and a cell without any Cr contamination were characterized in the same manner. According to the impedance data, the polarization resistance for both cells, which were contaminated with Cr species, increased. The expected relationship between deposited amount of Cr and increase of polarization resistance was found. ICP-OES analysis proves the high reproducibility of the method as the Cr content is only a function of the Cr paste composition and almost independent of external poisoning conditions. Due to its scalability and reproducibility, this method is proposed to be a new tool for screening of cathode materials and the investigation of different stages of Cr poisoning prior to more sophisticated and time consuming investigations like stack tests.

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Section: Microstructural Analysissupporting

confidence: 73%

Section: Experimental Paste Preparationmentioning

confidence: 99%

“…The amount of Cr in the samples was measured using a wet chemical method, which is described in more detail in the literature (Menzler et al, 2011).…”

Section: Solid State Poisoningmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Accelerated Testing of Chromium Poisoning of Sr-Containing Mixed Conducting Solid Oxide Cell Air Electrodes

et al. 2018

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“…[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.

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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...

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Post‐Test Characterization of Solid Oxide Fuel‐Cell Stacks

Menzler

Batfalsky

2012

Fuel Cell Science and Engineering

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Post-Test Characterization of an SOFC Short-Stack after 17,000 Hours of Steady Operation

Cited by 58 publications

References 9 publications

Accelerated Testing of Chromium Poisoning of Sr-Containing Mixed Conducting Solid Oxide Cell Air Electrodes

Accelerated Testing of Chromium Poisoning of Sr-Containing Mixed Conducting Solid Oxide Cell Air Electrodes

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

Post‐Test Characterization of Solid Oxide Fuel‐Cell Stacks

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