Investigation of the Active Thickness of Solid Oxide Fuel Cell Cathode

In solid oxide fuel cell (SOFC) electrode, electrochemical reaction only occurs in a narrow region near the interface of electrode and electrolyte, which is regarded as the “active thickness”. However, as a key parameter for SOFC electrode microstructure design and optimization, the active thickness of SOFC cathode reported by different research groups vary significantly (from 13 μm [1] to 253 μm [2]) due to different measuring conditions or simulation assumptions.

In this study, a detailed SOFC model is developed, in which the dusty gas model (DGM), Ohm’s law and the concentration related Butler-Volmer equation are used to describe the gas diffusion in pores, ion and electron conduction in electrolyte and electrodes, and electrochemical reaction kinetics, respectively. The effective ionic conductivity, electronic conductivity and the TPB length are calculated with the percolation theory and coordinate number theory [3]. Current density distribution in cathode is investigated under various operating conditions and 99% total current density is used as the indicator of the active thickness. This work could provide useful information for SOFC cathode microstructure optimization and for performance enhancement.

Keywords: Solid oxide fuel cell; Cathode thickness; Triple phase boundary length

[1]     Lu, Z., Hardy, J. S., Templeton, J. W., & Stevenson, J. W. (2012).Extended reaction zone of La0.6Sr0. 4Co0.2Fe0. 8O3 cathode for solid oxide fuel cell. Journal of Power Sources, 198: 90-94.

[2]     Jiang, Z. Y., Xia, C. R., & Chen, F. L. (2010). Efficient thickness of solid oxide fuel cell composite electrode. Chinese Journal of Chemical Physics, 23(2), 217.

[3]     Chen, D., Bi, W., Kong, W., & Lin, Z. (2010). Combined micro-scale and macro-scale modeling of the composite electrode of a solid oxide fuel cell. Journal of Power Sources, 195(19), 6598-6610.