Diffusion rates of reactants and components in solid oxide cells

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Abstract

The electrochemical performance of solid oxide electrolysis cells (SOECs) is very dependent on diffusion rates of the gaseous reactants through the porous electrodes, and the degradation rate of SOEC Ni/YSZ electrodes can be dependent on Ni-migration. The Ni-migration is dependent on electrode polarization and diffusion rate of Ni-containing minority species impact the migration. The electrode polarization as well as the diffusion rate of minority Ni-species are dependent on the partial pressure and pressure gradient of H2O as well as on electrochemical potential gradients. Thus, the H2O diffusion gradient resulting from the electrical load of the cell is expected to affect the Ni migration.
Therefore, this contribution first evaluates and discusses the diffusion rates of H2/H2O and CO/CO2 in porous Ni-YSZ composites. A 10 kh durability test with electrochemical impedance spectroscopy recorded at the beginning and end of the test show significant signs of change in the diffusion resistance.
Next, the diffusion rate of Ni-species is evaluated based on observed migration of Ni in the electrochemical active Ni-YSZ layer with sub-micron Ni particles. This is compared with catalysis research literature and models for Ni particle diffusivity [1].
Based on the presented results and literature study a modified hypothesis for Ni-migration is provided.
Original languageEnglish
Title of host publicationProceedings of the 13th European SOFC & SOE Forum 2018
PublisherEuropean Fuel Cell Forum AG
Publication date2018
Pages71-82
Article numberB1208
ISBN (Electronic)978-3-905592-23-8
Publication statusPublished - 2018
Event13th EUROPEAN SOFC & SOE FORUM - Kultur- und Kongresszentrum Luzern, Lucerne, Switzerland
Duration: 3 Jul 20186 Jul 2018
Conference number: 13
http://www.efcf.com/

Conference

Conference13th EUROPEAN SOFC & SOE FORUM
Number13
LocationKultur- und Kongresszentrum Luzern
CountrySwitzerland
CityLucerne
Period03/07/201806/07/2018
Internet address

Cite this

Jensen, S. H., Hauch, A., Sun, X., Chen, M., Ebbesen, S. D., & Mogensen, M. B. (2018). Diffusion rates of reactants and components in solid oxide cells. In Proceedings of the 13th European SOFC & SOE Forum 2018 (pp. 71-82). [B1208] European Fuel Cell Forum AG.