Modeling of Gas Diffusion in Ni/YSZ Electrodes in CO2 and Co-electrolysis

Jakob Dragsbæk Duhn, Anker Degn Jensen, Stig Wedel, Christian Wix

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Abstract

Carbon formation may occur during CO2 and CO2/H2O electrolysis using solid oxide electrolyzer cells due to the Boudouard reaction (2CO →  CO2 + C(s)). Formed carbon may disintegrate the cell structure and it is therefore of importance to be able to predict when carbon is formed, and take actions to prevent its formation. For prediction of carbon formation, the gas composition in the electrode must be known. In this work, the diffusion of gases in the electrode has been modeled with the dusty gas model in 1 and 2 dimensions, and the effect of tortuosity, porosity, temperature, electrode thickness, pore diameter, current density, pitch and rib width has been investigated. It is shown that diffusion limitations on reactant/product transport may lead to carbon formation. The parameters describing the microstructure and the dimensions of the cathode channels and interconnect ribs are found to have a large effect on the carbon formation propensity. Given a set of parameters, a simple correlation between the CO mole fraction in the channel and under the interconnect rib, and current density during CO2-electrolysis can be derived. This correlation makes it possible to efficiently integrate the calculation of carbon formation risk in existing electrolyzer cell models.
Original languageEnglish
JournalFuel Cells
Volume17
Issue number4
Pages (from-to)442-456
ISSN1615-6846
DOIs
Publication statusPublished - 2017
Event12th European SOFC & SOE Forum - Lucerne, Switzerland
Duration: 5 Jul 20168 Jul 2016
Conference number: 12
http://www.efcf.com/index.php?id=1954

Conference

Conference12th European SOFC & SOE Forum
Number12
CountrySwitzerland
CityLucerne
Period05/07/201608/07/2016
Internet address

Keywords

  • Boudouard Reaction
  • Carbon Formation
  • Diffusive Mass Transport
  • Electrolysis
  • Fuel Cell
  • Mathematical Modeling
  • Solid Oxide Electrolysis Cell

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