Chlorine Poisoning of SOFC Ni-Cermet Anodes

Haga, Kengo; Shiratori, Yusuke; Ito, Kohei; Sasaki, Kazunari

doi:10.1149/1.2980521

Cited by 58 publications

(45 citation statements)

References 22 publications

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“…Such Ni particle precipitation on zirconia grains has also been reported in chlorine poisoning of a Ni-based cermet anode. 18 The decrease in the amount of Ni near the triple-phase boundary results in a decrease in the electrochemical activity due to the loss of electrochemical reaction sites with cycling. The increase in anode Ni grain size and the number of isolated Ni particles on the zirconia grains leads to cell performance degradation.…”

Section: Degradation During the Shutdown Protocolmentioning

confidence: 99%

SOFC Durability against Standby and Shutdown Cycling

Hanasaki

Uryu

Daio

et al. 2014

J. Electrochem. Soc.

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To simulate realistic operating conditions in SOFC systems, we investigate the influence of thermal cycling on the performance of electrolyte-supported planar SOFCs. Thermal cycling is often associated with interruption of fuel supply, with three main modes; hot standby, cold standby, and shutdown. Cell performance degradation is most significant during shutdown cycles. Nickel oxidation and agglomeration are more pronounced when SOFCs are subjected to lower temperatures for longer periods of time, leading to significant performance degradation. Ostwald ripening at the anode leads to degradation as Ni grains increase in size with cycling. Ni particle precipitation on the anode zirconia grains and along electrolyte grain boundaries is found for the first time in shutdown cycling tests. When H 2 S is mixed with the fuel, the internal reforming reactions and electrode reactions are inhibited by sulfur poisoning of the Ni anodes, accelerating degradation. The SOFC cycling degradation mechanisms are discussed in detail. Solid oxide fuel cells (SOFCs) have several advantages including high efficiency, fuel flexibility, and utilization of non-noble metal, Pt-free catalysts, due to their relatively high operation temperature. Commercialization of SOFC systems for residential electric power applications began in Japan in 2011. Such systems are frequently stopped and restarted in normal operation, e.g. when power is not required, or in an emergency. Such start-stop operation results in thermal cycling, and is often associated with an interruption in fuel supply. Although it is well known that thermal and redox cycling under startstop operation deteriorates SOFC electrochemical performance, [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15] there are only a limited number of studies that systematically focus on this technologically relevant issue.Continuous SOFC stack operation with constant power output generally results in a gradual degradation in performance during long-term operation (SOFCs should run for up to a decade). However, SOFCs can suffer to a greater degree from changes in operation conditions. Due to thermal expansion mismatch between the different components, the cells can suffer from mechanical degradation mechanisms, such as delamination and crack formation with simple thermal cycling. Changes in atmosphere can result in more serious degradation. The influences of thermal cycling and current density cycling on cell degradation have been previously investigated.1-4 The change in volume causes Ni agglomeration. [5][6][7] Redox cycles are typically associated with oxidation of Ni particles at the anode. [8][9][10][11][12] Furthermore, redox cycling results in the formation of Ni hydroxides at a certain vapor pressure in oxidizing atmosphere, with a high water vapor concentration. 13,14 In real residential SOFC power units, cells and stacks are not subjected to these different conditions independently; the changes occur much more dynamically. Therefore, cycle durability studies should be performed using reali...

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Section: Degradation During the Shutdown Protocolmentioning

confidence: 99%

SOFC Durability against Standby and Shutdown Cycling

Hanasaki

Uryu

Daio

et al. 2014

J. Electrochem. Soc.

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“…Of primary concern to the fuel cell system are halocarbons, as they convert to acid gas that can corrode catalytic surfaces [22][23][24]. For Molten Carbonate Fuel Cells (MCFC's), degradation due to halogens is also a long term effect; halogens react with the electrolyte, thereby affecting the performance of the MCFC over time [23,25].…”

Section: Volatile Organic Compounds (Voc)mentioning

confidence: 99%

Fuel quality issues in stationary fuel cell systems.

Papadias¹,

Ahmed²

2012

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“…Among the reactions listed above, methane cracking (7) and Boudouard reaction (8) are those identified in the literature as the major pathways for carbon deposition on Ni-based catalysts and SOFC anodes [28,39]. Therefore, only these reactions have been included in the model presented.…”

Section: Carbon Deposition Studymentioning

confidence: 99%

Reporting Degradation from Different Fuel Contaminants in Ni‐anode SOFCs

et al. 2017

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The real-life operation of solid oxide fuel cell (SOFC) system has to deal with fuel contaminants which might reduce even significantly the lifetime of reformer and stack depending on the type and amount of contaminant present in the feed stream. From a system perspective, detecting and correlating observed stack and reformer performance degradation with fuel contamination is fundamental to implement correctional procedures (e.g., change of clean-up vessels catalysts) and/or trigger alarms to prevent a further contamination of the fuel cell. In this work, based on own experiments with several fuel contaminants (H 2 S, HCl, tars, siloxanes), we have developed empirical degradation models which are able to quantitatively correlate the range of degradation rate resulting from known amounts of a certain contaminant type in the fuel stream. Degradation induced by carbon deposition is also assessed using a simulation model. The techno-economic trade-off of having ultra-stringent purification requirements on the fuel clean-up unit due to additional operating costs (e.g., for frequent catalysts change) or capital costs (e.g., for vessel over-sizing to accommodate a larger amount of catalysts and possibly of different types) versus the lifetime of the fuel cell stacks is eventually analyzed.

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Chlorine Poisoning of SOFC Ni-Cermet Anodes

Cited by 58 publications

References 22 publications

SOFC Durability against Standby and Shutdown Cycling

SOFC Durability against Standby and Shutdown Cycling

Fuel quality issues in stationary fuel cell systems.

Reporting Degradation from Different Fuel Contaminants in Ni‐anode SOFCs

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