Studies of Solid Oxide Fuel Cell Electrode Evolution Using 3D Tomography

Yakal-Kremski, Kyle; Cronin, J. Scott; Chen-Wiegart, Yu Chen Karen; Wang, J.; Barnett, Scott A.

doi:10.1002/fuce.201200177

Cited by 28 publications

(19 citation statements)

References 41 publications

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“…2.2 Three-Dimensional Electron Microscopy. The interface between the YSZ electrolyte and the Ni-YSZ electrode was imaged by 3D FIB-SEM serial sectioning [20][21][22] (Zeiss Crossbeam 540). Samples were extracted near the middle along the flow path in the tested cells, except for the SOFC segmented-cell (segment 12).…”

Section: Methodsmentioning

confidence: 99%

Evolution of the Morphology Near Triple-Phase Boundaries in Ni–Yttria Stabilized Zirconia Electrodes Upon Cathodic Polarization

Nakajo

Rinaldi

Caliandro

et al. 2020

Journal of Electrochemical Energy Conversion and Storage

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Microstructural changes in Ni–yttria stabilized zirconia (YSZ) near the YSZ electrolyte were examined by three-dimensional (3D) electron microscopy after electrolysis and fuel cell operation up to 10,700 h and 15,000 h, respectively. The depletion of Ni and three-phase boundaries (TPBs) close to the electrolyte was detected upon cathodic polarization. It corresponded to spatial variations of dihedral angles (θ) at TPBs and Ni surface curvature along the direction perpendicular to the electrolyte, which comport with electrowetting and Zener pinning theory on several aspects. θNi decreased by up to 6 deg next to the electrolyte after electrolysis but remained uniform after fuel cell operation. This is in line with predictions from electrowetting theory with capacitances measured by electrochemical impedance spectroscopy and distribution of relaxation times. The decrease in θNi was concurrent to transition toward concave Ni/pore interfacial shapes and lower genus of the Ni phase, which suggests the pinch-off of Ni ligaments following surface diffusion-controlled Rayleigh instability. The increase in absolute mean curvature near the electrolyte interface is a driving force for outward transport of Ni. The decrease in θYSZ further suggests that TPB lines relocate on YSZ surface features that provide higher Zener pinning force. In contrast, few localized contact losses between Ni and YSZ that can also occur under high cathodic polarization and trigger Ni depletion were detected. The results are expected to advance the understanding of the driving forces that cause Ni depletion near the electrolyte in electrolysis for the design of improved solid oxide cell electrode microstructures.

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Section: Methodsmentioning

confidence: 99%

Evolution of the Morphology Near Triple-Phase Boundaries in Ni–Yttria Stabilized Zirconia Electrodes Upon Cathodic Polarization

Nakajo

Rinaldi

Caliandro

et al. 2020

Journal of Electrochemical Energy Conversion and Storage

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“…Structural and electrochemical changes of these pre-aged anodes are then observed after further ageing. TXM is utilized to obtain quantitative three-dimensional (3D) electrode microstructural images [5][6][7][8][9]. Electrochemical characterization is done on full cells utilizing electrochemical impedance spectroscopy (EIS) and equivalent circuit fitting to isolate the anode components of the impedance responses.…”

Section: Introductionmentioning

confidence: 99%

Combined electrochemical and X-ray tomography study of the high temperature evolution of Nickel – Yttria Stabilized Zirconia solid oxide fuel cell anodes

Kennouche

Chen-Wiegart

Riscoe

et al. 2016

Journal of Power Sources

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Accelerated ageing of Ni-Yttria Stabilized Zirconia (YSZ) anode functional layers (AFLs) in solid oxide fuel cells (SOFCs) is carried out at 1000-1200°C, the resulting morphological changes are investigated using transmission X-ray microscopy (TXM), and properties are characterized using electrochemical impedance spectroscopy (EIS). Prior to ageing, the as prepared NiO-YSZ AFLs are reduced to Ni-YSZ and then aged at 1100°C for 100 h in order to eliminate early-stage morphological changes. Measured particle size and three phase boundary (TPB) density changes with ageing time and temperature are fit reasonably well using a power-law coarsening model. This model is also used in conjunction with an electrochemical model to predict changes in the anode charge-transfer polarization resistance.

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“… TPB lengths in Ni-YSZ anodes as a function of volume analyzed from literature [ 7 , 8 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 ] (data table with references are given in the supplementary material, Table S1 ). Independent from the fabrication method, the TPB lengths increase significantly for some of the analyses that are taken on a very small volume (which is probably due to limitations of representativeness).…”

Section: Introductionmentioning

confidence: 99%

3D Microstructure Effects in Ni-YSZ Anodes: Influence of TPB Lengths on the Electrochemical Performance

et al. 2015

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3D microstructure-performance relationships in Ni-YSZ anodes for electrolyte-supported cells are investigated in terms of the correlation between the triple phase boundary (TPB) length and polarization resistance (Rpol). Three different Ni-YSZ anodes of varying microstructure are subjected to eight reduction-oxidation (redox) cycles at 950 °C. In general the TPB lengths correlate with anode performance. However, the quantitative results also show that there is no simplistic relationship between TPB and Rpol. The degradation mechanism strongly depends on the initial microstructure. Finer microstructures exhibit lower degradation rates of TPB and Rpol. In fine microstructures, TPB loss is found to be due to Ni coarsening, while in coarse microstructures reduction of active TPB results mainly from loss of YSZ percolation. The latter is attributed to weak bottlenecks associated with lower sintering activity of the coarse YSZ. The coarse anode suffers from complete loss of YSZ connectivity and associated drop of TPBactive by 93%. Surprisingly, this severe microstructure degradation did not lead to electrochemical failure. Mechanistic scenarios are discussed for different anode microstructures. These scenarios are based on a model for coupled charge transfer and transport, which allows using TPB and effective properties as input. The mechanistic scenarios describe the microstructure influence on current distributions, which explains the observed complex relationship between TPB lengths and anode performances. The observed loss of YSZ percolation in the coarse anode is not detrimental because the electrochemical activity is concentrated in a narrow active layer. The anode performance can be predicted reliably if the volume-averaged properties (TPBactive, effective ionic conductivity) are corrected for the so-called short-range effect, which is particularly important in cases with a narrow active layer.

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Studies of Solid Oxide Fuel Cell Electrode Evolution Using 3D Tomography

Cited by 28 publications

References 41 publications

Evolution of the Morphology Near Triple-Phase Boundaries in Ni–Yttria Stabilized Zirconia Electrodes Upon Cathodic Polarization

Evolution of the Morphology Near Triple-Phase Boundaries in Ni–Yttria Stabilized Zirconia Electrodes Upon Cathodic Polarization

Combined electrochemical and X-ray tomography study of the high temperature evolution of Nickel – Yttria Stabilized Zirconia solid oxide fuel cell anodes

3D Microstructure Effects in Ni-YSZ Anodes: Influence of TPB Lengths on the Electrochemical Performance

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