9000 Hours Operation of a 25 Solid Oxide Cells Stack in Steam Electrolysis Mode

Corre, Gaël; Brisse, Annabelle

doi:10.1149/06801.3481ecst

Cited by 23 publications

(19 citation statements)

References 3 publications

(3 reference statements)

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“…Figure 10 -inspired by Schefold and co-workes [38] -illustrates the importance in decreasing the long-term degradation rate from e.g. around 2 %/kh as reported by Schefold and co-workes [38] and Corre and Brisse [45] to the long-term degradation rate of 0.3-0.4 %/kh reported here for Cell C at similar test conditions. …”

Section: Microstructures Of Soec Long-term Tested At 125 A/cmsupporting

confidence: 69%

“…fuel cell mode operation) has shown advantageous for the performance of SOC [4,5]; it should be emphasized that at higher electrolysis current densities irreversible degradation phenomena takes place which are not likely to be recoverable by SOFC operation of the SOC [6,7]. Long-term stability needs to be improved even considering promising results such as reported by Tietz, Corre and Hjalmarsson [8][9][10][11] if SOFC systems, and later SOEC systems, are to operate profitable for several years. Recent work has shown that at high current density (high fuel electrode overpotential) the SOEC experiences long-term, roughly linear, irreversible degradation; typically associated with an increase in the ohmic resistance [7,8,12].…”

Section: Introductionmentioning

confidence: 99%

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Ni/YSZ electrodes structures optimized for increased electrolysis performance and durability

et al. 2016

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Cermet Ni/YSZ electrodes are the most commonly applied fuel electrode for solid oxide cells (SOC) both when targeting solid oxide fuel cell (SOFC) applications and when used as solid oxide electrolysis cell (SOEC). In this work we report on the correlation between initial Ni/YSZ microstructure and the resulting electrochemical performance both initially and during long-term electrolysis testing at high current density and high p(H2O) inlet. Especially, this work focuses on microstructure optimization to hinder Ni mobility and migration during long-term operation and illustrates the key-role of electrode over-potential on the degradation of the Ni/YSZ electrodes in SOEC. We find that for long-term stability for electrolysis at high current densities and high p(H2O) the as-produced NiO/YSZ precursor electrode should be: 1) As dense as possible, 2) as fine particle and pore sized as possible and 3) the three phases (Ni, YSZ and pore phase) shall be size-matched and welldispersed. Applying such microstructure optimized Ni/YSZ electrode we show SOEC test results with long-term degradation rate as low as 0.3-0.4 %/kh at 1 A/cm 2 , 800 C and inlet gas mixture of p(H2O)/p(H2):90/10. This enables SOEC operation of such cell for more than 5 years below thermo-neutral potential at these operating conditions.

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Section: Microstructures Of Soec Long-term Tested At 125 A/cmsupporting

confidence: 69%

Section: Introductionmentioning

confidence: 99%

Ni/YSZ electrodes structures optimized for increased electrolysis performance and durability

et al. 2016

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“…In particular, Holzer et al [14] analyzed the effect of humidity for a H 2 O/H 2 mixture in fuel cell mode. The coarsening of Ni enhanced in high humidity conditions would cause a displacement of nickel particles from the triple phase boundary (TPB) to the inner part of the electrode through volatile Ni(OH) 2 . Lastly, this implies a growth of the effective electrolyte thickness and a reduction of electrochemically active TPB, which leads to an inactive Ni-YSZ region [15,16].…”

Section: Fuel Electrode -Cathodementioning

confidence: 99%

Post‐test Analysis on a Solid Oxide Cell Stack Operated for 10,700 Hours in Steam Electrolysis Mode

et al. 2017

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A solid oxide short stack composed of 6 Ni-YSZ supported cells, YSZ electrolyte and GDC-LSC oxygen electrode has been tested for 10,700 hours in steam electrolysis. Initial degradation was followed by a global stabilization of the performance after lowering the current density, with a degradation rate below 0.5% kh -1 .Post-test analysis has been conducted on two repeating units (RUs) to highlight the most significant microstructure alterations. Nickel depletion was observed in the hydrogen electrode close to the interface with the electrolyte. Formation of small pores in the electrolyte was detected along the grain boundaries. A consequent detachment related to this phenomenon was observed in proximity of the GDC compatibility layer. At the oxygen electrode side, the formation of ã 1 mm dense mixed layer of GDC and YSZ was observed. Strontium from the LSC electrode migrated through GDC pores and reacted with YSZ, forming evident SrZrO 3 inclusions. Distinct accumulation of silicon at the Ni/YSZ interface and chromium on the GDC barrier layer have been observed in both RUs. Despite this range of alterations observed, the stack degradation remained limited, testified from the fact that performance decay between 4,000 and 10,000 hours of operation was virtually nil.

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“…Degradation phenomena must also be identified, understood and eliminated or reduced. Over the last few years, some reports on solid oxide electrolysis stacks have been published (1)(2)(3)(4)(5)(6)(7)(8)(9). To our knowledge, only a limited number of studies on the detailed post analysis of a stack have been published so far.…”

Section: Introductionmentioning

confidence: 99%

A Detailed Post Mortem Analysis of Solid Oxide Electrolyzer Cells after Long-Term Stack Operation

Frey

Sebold

Menzler

et al. 2018

J. Electrochem. Soc.

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A long-term test with a two-layer solid oxide electrolyzer stack was carried out for more than 20 000 hours. The stack was mainly operated in a furnace environment in electrolysis mode, with 50% humidification of H2 at 800 °C, a current density of -0.5 Acm -2 and steam conversion rate of 50%. After ~18 000 hours of operation in electrolysis mode, the voltage and area specific resistance degradation rates were ~0.6%/kh and 8.2%/kh, respectively. A detailed post mortem analysis of cells including ICP-OES and microstructural analysis was conducted. Two main degradation phenomena were observed in the cells: In the fuel electrode, the depletion and agglomeration of nickel were visible. At the air electrode, demixing of the air electrode and diffusion of strontium took place. This was observed in the formation of strontium zirconate at the interface between the electrolyte and the GDC barrier layer as well as in the formation of strontium oxide and strontium chromate on top of the cells. Strontium oxide was even found in pores on top of the electrolyte.

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9000 Hours Operation of a 25 Solid Oxide Cells Stack in Steam Electrolysis Mode

Cited by 23 publications

References 3 publications

Ni/YSZ electrodes structures optimized for increased electrolysis performance and durability

Ni/YSZ electrodes structures optimized for increased electrolysis performance and durability

Post‐test Analysis on a Solid Oxide Cell Stack Operated for 10,700 Hours in Steam Electrolysis Mode

A Detailed Post Mortem Analysis of Solid Oxide Electrolyzer Cells after Long-Term Stack Operation

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