Microstructure degradation of cermet anodes for solid oxide fuel cells: Quantification of nickel grain growth in dry and in humid atmospheres

Holzer, Lorenz; Iwanschitz, Boris; Hocker, Thomas; Münch, Beat; Prestat, Michel; Wiedenmann, Daniel; Vogt, Uli; Holtappels, Peter; Sfeir, Joseph; Mai, Andreas; Graule, Thomas

doi:10.1016/j.jpowsour.2010.08.017

Cited by 311 publications

(266 citation statements)

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“…This type of transport is of importance for modern energy conversion technologies, which attempt to harvest green energy sources (e.g. transport of charged species in electrodes of fuel cells, solar cells or batteries) [8][9][10][11][12]. Thereby, it is necessary to understand which microstructural features influence the charge-transport, to improve the electrode performance by a controlled optimization of the microstructure.…”

Section: Introductionmentioning

confidence: 99%

The influence of constrictivity on the effective transport properties of porous layers in electrolysis and fuel cells

et al. 2012

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The aim of the present investigation is to define microstructure parameters, which control the effective transport properties in porous materials for energy technology. Recent improvements in 3D-imaging (FIB-nanotomography, synchrotron X-ray tomography) and image analysis (skeletonization and graph analysis, transport simulations) open new possibilities for the study of microstructure effects. In this study, we describe novel procedures for a quantitative analysis of constrictivity, which characterizes the so-called bottleneck effect. In a first experimental part, methodological tests are performed using a porous (La,Sr)CoO 3 material (SOFC cathode). The tests indicate that the proposed procedure for quantitative analysis of constrictivity gives reproducible results even for samples with inhomogeneous microstructures (cracks, gradient of porosity). In the second part, 3D analyses are combined with measurements of ionic conductivity by impedance spectroscopy. The investigations are preformed on membranes of electrolysis cells with porosities between 0.27 and 0.8. Surprisingly, the tortuosities remain nearly constant (1.6) for the entire range of porosity. In contrast, the constrictivities vary strongly and correlate well with the measured transport resistances. Hence, constrictivity represents the dominant microstructure parameter, which controls the effective transport properties in the analysed membrane materials. An empirical relationship is then derived for the calculation of effective transport properties based on phase volume fraction, tortuosity, and constrictivity.

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confidence: 99%

The influence of constrictivity on the effective transport properties of porous layers in electrolysis and fuel cells

et al. 2012

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“…Na Figura 1(a) tem-se um anodo convencional, evidenciando a natureza porosa da microestrutura, a qual é essencial para proporcionar percolação e difusão dos gases e o estabelecimento da RTF, proporcionando também estabilidade térmica ao dispositivo. Com efeito, as características da região de transição entre o anodo poroso e o denso eletrólito, as quais caracterizam a interface Ni-YSZ/YSZ, são críticas para a otimização do desempenho e da estabilidade de uma CaCOS [5,7]. Estas características devem ser tais que proporcionem conexão elétrica disponível para o transporte iônico nesta interface, sem a existência de descontinuidades que resultam no estabelecimento de impedâncias locais.…”

Section: Resultsunclassified

Desenvolvimento De Cerâmicos E Conjugados Metal-Cerâmica Para Células a Combustível De Óxido Sólido

Ponseggi¹,

Dias²,

Furtado³

2018

ABM Proceedings

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ResumoO desenvolvimento dos materiais dos eletrodos (anodo e catodo) e do eletrólito de células a combustível de óxido sólido (SOFC) com o intuito de que estas possam operar de forma estável com combustíveis diferentes do hidrogênio é um objetivo central da pesquisa em SOFC. Dessa forma, o objetivo deste trabalho é evidenciar as características microestruturais e o desempenho de materiais para uso de combustíveis hidrocarbônicos e alcoóis em SOFC. Neste trabalho são avaliados, à luz da caracterização eletroquímica e elétrica de SOFC unitárias e estruturas em bicamadas anodo-eletrólito, sistemas materiais do tipo Ni/Cu-Céria/YSZ-LSM sob a alimentação de diferentes combustíveis. Os melhores resultados foram obtidos com o uso de hidrogênio ou etanol, mas novos desenvolvimentos em engenharia microestrutural são prementes. Também ficou evidenciado os problemas de degradação e instabilidade advindos da presença de sulfurados no biogás combustível. Palavras-chave: Células a combustível; Eletrodos funcionais; Eletrólitos sólidos. DEVELOPMENT OF CERAMICS AND METAL-CERAMIC COMPOSITES FOR SOLID OXIDE FUEL CELLS AbstractThe development of materials of electrodes (anode and cathode) and the electrolyte so that they can operate stably with fuels other than hydrogen is a central goal of research in SOFC. Thus, the aim of this work is to show the microstructural characteristics and performance of materials for use of hydrocarbon and alcohol fuels in SOFC. In this work are evaluated in light of electrical and electrochemical characterization of single SOFC and anode-electrolyte bilayer structures material systems Ni/Cu-ceria/LSM-YSZ with different fuels. The best results were obtained with the use of hydrogen or ethanol, but new developments in microstructural engineering are also considered. It is also evident problems of degradation and instability arising from the presence of sulfur in biogas fuel.

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“…La 1-x Sr x MnO 3 (LSM) or (La, Sr)(Co, Fe)O 3 (LSCF), as cathode material, SOFC usually operates at relatively high temperature, i.e. between 600• C to 1000• C, 1 due to the large activation energy for oxygen ion diffusion 6 and oxygen reduction reaction (ORR).7 This high operating temperature makes SOFC free from noble metal catalyst and highly flexible to a wide range of fuels.8 However, it also makes SOFC vulnerable to degradations caused by, for example, coarsening, secondary phase formation and Cr poisoning, [9][10][11] which limit the long-term stability of SOFC.Coarsening has been found to be one of the degradation mode in LSM-based SOFC cathode above 850• C. 11 The increased polarization resistance after coarsening suggests its impact on the ORR in the cathode. There are two possible pathways for ORR on LSM, i.e.…”

mentioning

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“…8 However, it also makes SOFC vulnerable to degradations caused by, for example, coarsening, secondary phase formation and Cr poisoning, [9][10][11] which limit the long-term stability of SOFC.…”

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Linking Initial Microstructure to ORR Related Property Degradation in SOFC Cathode: A Phase Field Simulation

Lei

Cheng

Wen

2017

J. Electrochem. Soc.

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Microstructure evolution driven by thermal coarsening is an important factor for the loss of oxygen reduction reaction rates in SOFC cathode. In this work, the effect of an initial microstructure on the microstructure evolution in SOFC cathode is investigated using a recently developed phase field model. Specifically, we tune the phase fraction, the average grain size, the standard deviation of the grain size and the grain shape in the initial microstructure, and explore their effect on the evolution of the grain size, the density of triple phase boundary, the specific surface area and the effective conductivity in LSM-YSZ cathodes. It is found that the degradation rate of triple phase boundary density and specific surface area of LSM is lower with less LSM phase fraction (with constant porosity assumed) and greater average grain size, while the degradation rate of effective conductivity can also be tuned by adjusting the standard deviation of grain size distribution and grain aspect ratio. Solid oxide fuel cell (SOFC) is a promising candidate to achieve clean electricity generation with high efficiency.1-5 Using ionic conductor, e.g. yttria stabilized zirconia (YSZ), as electrolyte, and perovskite oxides, e.g. La 1-x Sr x MnO 3 (LSM) or (La, Sr)(Co, Fe)O 3 (LSCF), as cathode material, SOFC usually operates at relatively high temperature, i.e. between 600• C to 1000• C, 1 due to the large activation energy for oxygen ion diffusion 6 and oxygen reduction reaction (ORR).7 This high operating temperature makes SOFC free from noble metal catalyst and highly flexible to a wide range of fuels.8 However, it also makes SOFC vulnerable to degradations caused by, for example, coarsening, secondary phase formation and Cr poisoning, [9][10][11] which limit the long-term stability of SOFC.Coarsening has been found to be one of the degradation mode in LSM-based SOFC cathode above 850• C. 11 The increased polarization resistance after coarsening suggests its impact on the ORR in the cathode. There are two possible pathways for ORR on LSM, i.e. the electrode surface pathway and the bulk pathway. 7,12,13 Due to the small ionic conductivity of LSM, the electrode surface pathway is considered to be dominating in the conventional composite cathode of LSM and YSZ. In this pathway, the oxygen molecule is converted to oxygen intermediates on the LSM surface, diffuses to the triple phase boundary (TPB) through surface diffusion and incorporates into YSZ at TPB. The rate determining step is still under debate, and it might depend on the operational condition and the microstructure. But it is known that both the TPB density and specific surface area (SSA) of LSM can influence the rate of the electrode surface pathway in the SOFC cathode.7,13 Previous experiments and simulations have shown that the coarsening in SOFC electrode leads to the loss of both the TPB density and the SSA of electrode phase, 14-17 which increases the polarization resistance in cathode. In addition, coarsening is known to increase the ohmic resistance in SOFC elect...

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Microstructure degradation of cermet anodes for solid oxide fuel cells: Quantification of nickel grain growth in dry and in humid atmospheres

Cited by 311 publications

References 37 publications

The influence of constrictivity on the effective transport properties of porous layers in electrolysis and fuel cells

The influence of constrictivity on the effective transport properties of porous layers in electrolysis and fuel cells

Desenvolvimento De Cerâmicos E Conjugados Metal-Cerâmica Para Células a Combustível De Óxido Sólido

Linking Initial Microstructure to ORR Related Property Degradation in SOFC Cathode: A Phase Field Simulation

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