Functionally graded composite cathodes for solid oxide fuel cells

Hart, Noam; Brandon, NP; Day, Michael; Lapeña-Rey, N.

doi:10.1016/s0378-7753(01)01035-7

Cited by 142 publications

(95 citation statements)

References 12 publications

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“…Complex materials containing transition metal and cerium cations have been considered as catalysts, electrodes in fuel cells, and batteries [1][2][3][4][5][6][7][8][9][10][11][12]. A high activity with respect to a certain catalytic or electrode process could relate to an optimal surface concentration of Ce cations and their involvement in the reversible redox cycle (Ce 3+ ↔ Ce 4+ ) [13].…”

Section: Introductionmentioning

confidence: 99%

“…The perovskite-fluorite interface in composite cathodes in fuel cells is responsible for oxygen sorption and reduction, surface mobility of oxygen vacancies, fast oxygen ion exchange between the surface and bulk of grains, and for optimum distribution of catalysts over surface (which depends on wetting characteristics of the interface) [8][9][10][11][12]. A recent computational study showed that transition metal cations are responsible for the electrocatalytic activity for oxygen reduction [35], suggesting that a high surface concentration of transition metal cations could facilitate surface processes.…”

Section: Introductionmentioning

confidence: 99%

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Identification of surface composition and chemical states in composites comprised of phases with fluorite and perovskite structures by X-ray photoelectron spectroscopy

Konysheva

Francis

2013

Applied Surface Science

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Keywords:X-ray photoelectron spectroscopy (XPS) Surface composition Composites with perovskite and fluorite structures Oxidation state of cerium cations Binding energy a b s t r a c t X-ray photoelectron spectroscopy (XPS) has been used to explore the cation rearrangement between the surface and bulk of grains and the surface chemical states of Ce, Mn, Co, Sr, and O ions in the single phase CeO 2 -based solid solutions and in the two phase (100 − x)La 0.6 Sr 0.4 CoO 3 -xCeO 2 (LSCCx) and (100 − x)La 0.8 Sr 0.2 MnO 3 -xCeO 2 (LSMCx) composites. The well-resolved Ce 3d 5/2 and Ce 3d 3/2 spin-orbit components were determined to study the Ce 4+ to Ce 3+ electronic transition at the surface. The surface of the LSCCx and LSMCx (x = 8-40 mol%) composites is depleted in cerium. Both Ce 4+ and Ce 3+ cations were revealed. The surface fraction of Ce 4+ cations increases with the rise in CeO 2 content in both systems, but it is higher by about a factor of two in the LSCC composites. A strong enrichment of the surface by Co cations was observed for the composites LSCCx (x = 8-40 mol%), implying that the presence of cerium could facilitate the Co surface segregation. A slight Sr surface enrichment compared to the nominal stoichiometry was found for La 0.6 Sr 0.4 CoO 3 , CeO 2 -based solid solutions, LSCC57, and LSMCx (x = 10-57) composites. In contrast, the surface of the LSCCx (x = 10-37) composites is slightly depleted in strontium cations. The O 1s spectra of the LSCC and LSMC composites contain several contributions associated with the lattice oxygen related to the phases with the perovskite and fluorite structures as well as with different surface states. Their contributions vary with CeO 2 content and a chemical origin of the transition metal cations on the B-site in the perovskite structure. The Ce 2 (CO 3 ) 3 -based phase seems to exist at the surface of grains and crystallites in the LSCC57 and LSCM composites.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Identification of surface composition and chemical states in composites comprised of phases with fluorite and perovskite structures by X-ray photoelectron spectroscopy

Konysheva

Francis

2013

Applied Surface Science

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“…Most of the analysis reported in the literature is performed on compositionally graded LSM-YSZ cathodes 34 . In some of the proposed models, the porosity gradient through the cathode layer is also incorporated 26,32,[35][36][37] . It is of great interest that the grading will reduce the coefficient of thermal expansion (CTE) mismatch between the electrode and the electrolyte substrate resulting in improvement of adhesion, durability and mechanical stability of the cell components.…”

Section: Research Objectives and Motivationmentioning

confidence: 99%

“…Grading can be classified in three ways: (1) composition grading (volumetric ratio of electronic conducting particles to ionic conducting particles), (2) particle size grading, and (3) porosity grading. In either ways, the goal is to enhance the electrochemical reactivity and increase the electronic/ ionic conductivity of the electrode, to minimize the mass transport resistance to gas mixtures and thus concentration polarization inside the porous electrode and to increase mechanical stability by, for instance, avoiding sharp discontinuities in thermal expansion coefficients, which could result in delamination during thermal cycling 33,36,56 .…”

Section: Functionally Graded Materials (Fgms)mentioning

confidence: 99%

Microstructure Sensitive Design and Processing in Solid Oxide Electrolyzer Cell

Garmestani¹,

Herring²

2009

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SUMMARYThe aim of this study was to develop an inexpensive manufacturing process for deposition of functionally graded thin films of LSM oxides with porosity graded microstructures for use as IT-SOFCs cathode. The spray pyrolysis method was chosen as a low-temperature processing technique for deposition of porous LSM films onto dense YSZ substrates. The effort was directed toward the optimization of the processing conditions for deposition of high quality LSM films with variety of morphologies in the range of dense to porous microstructures. Results of optimization studies of spray parameters revealed that the substrate surface temperature is the most critical parameter influencing the roughness and morphology, porosity, cracking and crystallinity of the film. Physical and chemical properties of deposited thin films such as porosity, morphology, phase crystallinity and compositional homogeneity have shown to be extensively dependent on the preparation conditions. Detailed analysis of the film formation mechanisms have been discussed in this work. It is suggested that using volatile metal-organic precursors as in CVD would alter the film formation mechanism to MOCVD process in which films of high quality can be processed. Novel electrode microstructures currently include a graded microstructure wherein the large pores are made close to the surface in outer layers for maximum mass transport into the electrode structure and smaller pores and particles close to the electrolyte interface would create maximum number of active reaction sites. Taking the advantage of simplicity of spray pyrolysis technique combined with using metal-organic compounds, the conventional ultrasonic spray system was upgraded to a novel system whereby highly crystalline multiMicrostructure Sensitive Design for Materials in Solid Oxide Electrolyzer Cell, Garmestani vi layered porosity graded LSM cathode with columnar morphology with good electrical conductivity in the range of 500-700 °C was fabricated through a multi-step spray and via optimizing spray parameters. This achievement for the current graded LSM cathode would allow its use in IT-SOFCs.Microstructure Sensitive Design for Materials in Solid Oxide Electrolyzer Cell, Garmestani 7

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“…cisalhamento, indicado para materiais cerâmicos utilizado por esta técnica (77) . (114) e a temperatura e tempo de sinterização foi relatado no trabalho de PIAO et al (85) , otimizando em ambos os trabalhos com a técnica de conformação de filme impressão sobre tela.…”

Section: Grupo Espacial R-3chunclassified

Síntese, processamento e caracterização das meia-células de óxido sólido catodo/eletrólito de manganito de lantânio dopado com estrôncio/zircônia estabilizada com ítria

Chiba¹

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Functionally graded composite cathodes for solid oxide fuel cells

Cited by 142 publications

References 12 publications

Identification of surface composition and chemical states in composites comprised of phases with fluorite and perovskite structures by X-ray photoelectron spectroscopy

Identification of surface composition and chemical states in composites comprised of phases with fluorite and perovskite structures by X-ray photoelectron spectroscopy

Microstructure Sensitive Design and Processing in Solid Oxide Electrolyzer Cell

Síntese, processamento e caracterização das meia-células de óxido sólido catodo/eletrólito de manganito de lantânio dopado com estrôncio/zircônia estabilizada com ítria

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