Triple phase boundary specific pathway analysis for quantitative characterization of solid oxide cell electrode microstructure

Jørgensen, Peter Stanley; Ebbehøj, Søren Lyng

doi:10.1016/j.jpowsour.2015.01.054

Cited by 51 publications

(63 citation statements)

References 21 publications

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“…Previous 3D-reconstructions of similar Ni-stabilized zirconia electrodes have shown that electrodes having same phase fractions, similar PSDs and even comparable percolating TPB densities can have significantly different critical pathway radii for the Ni network, tortuosity for the percolating Ni path and significant differences in the number of percolating paths from the electrode/electrolyte interface to the outer circuit. These parameters were shown to affect the electrochemical performance significantly [22]. Based on those results and the observation of the microstructural changes in Cell D we therefore hypothesize that also the necking between Ni-Ni particles and the Ni-YSZ…”

Section: Select Test Conditions Based On Electrode Overpotentialmentioning

confidence: 56%

“…This reduction procedure was chosen to make the NiO reduction procedure similar to several previously reported SOEC test (e.g. [7,10,12] ) and kept constant as previously reported results of 3D reconstructions of fuel electrodes show that the reduction profile can affect the fuel electrode microstructure significantly [22]. Hereafter performance characterization via iV-curves and electrochemical impedance spectroscopy (EIS) was conducted.…”

Section: Test Procedures and Operating Conditionsmentioning

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: Select Test Conditions Based On Electrode Overpotentialmentioning

confidence: 56%

Section: Test Procedures and Operating Conditionsmentioning

confidence: 99%

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

et al. 2016

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“…4) The fast marching method calculates the shortest path through the analysed phase by creating a distance map between the starting and end boundary of a propagating front. The shortest path between the two boundaries of the sample is then read out of the distance map and divided by the Euclidean distance of the starting and end boundary to calculate the geometric tortuosity (Jørgensen et al, 2011;Jørgensen et al, 2015;Taiwo et al, 2016a).…”

Section: Image-based Tortuosity Calculation Approachesmentioning

confidence: 99%

Contradictory concepts in tortuosity determination in porous media in electrochemical devices

Tjaden

Finegan

Lane³

et al. 2017

Chemical Engineering Science

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Porous media are a vital component in almost every electrochemical device in the form of electrode, support or gas diffusion layers. Microstructural parameters of porous layers such as tortuosity, porosity and pore size diameter are of high importance and crucial for diffusive mass transport calculations. Among these parameters, the tortuosity remains ill-defined in the field of electrochemistry, resulting in a wide range of different calculation approaches. Here, we present a systematic approach of calculating the tortuosity of different porous samples using image and diffusion cell experimental-based methods. Image-based analyses include a selection of geometric and flux-based tortuosity calculation algorithms. Differences between the image and diffusion cell-based results are encountered and attributed to the small pore diameters and thereby induced Knudsen effects within the samples which govern the diffusion flux. Highlights Microstructural analysis of oxygen transport membrane porous supports.  Correlative tortuosity determinations via X-ray tomography and diffusion cell experiments.  Evaluation of the effect of tortuosity, porosity and sample thickness on diffusion resistance.  Visible differences between different tortuosity calculation approaches are encountered.  Diffusion cell experiments yield the highest and geometric-based image quantification algorithms result in the lowest tortuosity values.

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“…High electrochemical performance required a high TPB in the anode, because increasing the TPB density will enhance the kinetics of the oxidation reaction that occurs between oxygen ions and methane fuel on the anode side of the cell, and thus increase cell performance. Using 3D imaging techniques like FIB-SEM [14,[30][31][32][33], the nanocomposite anodes with optimized electrode microstructure exhibit substantially higher TPB density, leading to higher cell performance and better stability [15,16,[34][35][36]. Therefore, the new double-pore NiO-SDC anode with a wider TPB area is much more promising for direct-methane solid oxide fuel cells, compared with the conventional single-pore NiO-SDC anode.…”

Section: Electrochemical Performance Of Single Cellsmentioning

confidence: 99%

“…Recently, some new microstructure for NiO-SDC anodes were investigated as alternative anode materials for direct use with methane fuels, such as surface modification of NiO-SDC anode by impregnation [9][10][11]. This results have indicated that the adjustment of NiO-SDC anodes are very effective in suppressing catalytic carbon formation by blocking methane from approaching the nickel, which is catalytically active towards methane pyrolysis [13][14][15][16].…”

Section: Introductionmentioning

confidence: 99%

A robust NiO–Sm0.2Ce0.8O1.9 anode for direct-methane solid oxide fuel cell

Tian

Liu

Chen

et al. 2015

Materials Research Bulletin

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A robust NiO-Sm0.2Ce0.8O1.9 anode for direct-methane solid oxide fuel cell, Materials Research Bulletin http://dx.doi.org/10. 1016/j.materresbull.2015.06.042 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. Graphical abstractHighlights  Robust NiO-SDC anode is synthesized by co-assembly for direct-methane SOFC. The cell performance was improved by 40%-45% with the new NiO-SDC anode. No significant degradation of the cell performance was observed after 60 hours. The double-pore NiO-SDC anode with higher TPB is promising for SOFC. AbstractIn order to directly use methane without a reforming process, NiO-Sm 0.2 Ce 0.8 O 1.9 (NiO-SDC) nanocomposite anode are successfully synthesized via a one-pot, surfactant-assisted co-assembly approach for direct-methane solid oxide fuel cells.Both NiO with cubic phase and SDC with fluorite phase are obtained at 550°C. Both 2 NiO nanoparticles and SDC nanoparticles are highly monodispersed in size with nearly spherical shapes. Based on the as-synthesized NiO-SDC, two kinds of single cells with different micro/macro-porous structure are successfully fabricated. As a result, the cell performance was improved by 40%-45% with the new double-pore NiO-SDC anode relative to the cell performance with the conventional NiO-SDC anode due to a wider triple-phase-boundary (TPB) area. In addition, no significant degradation of the cell performance was observed after 60 hours, which means an increasing of long term stability. Therefore, the as-synthesized NiO-SDC nanocomposite is a promising anode for direct-methane solid oxide fuel cells.

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Triple phase boundary specific pathway analysis for quantitative characterization of solid oxide cell electrode microstructure

Cited by 51 publications

References 21 publications

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

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

Contradictory concepts in tortuosity determination in porous media in electrochemical devices

A robust NiO–Sm0.2Ce0.8O1.9 anode for direct-methane solid oxide fuel cell

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