A three-dimensional heterogeneity analysis of electrochemical energy conversion in SOFC anodes using electron nanotomography and mathematical modeling

Tomasz A. Prokop, Katarzyna Berent, Hiroshi Iwai, Janusz S.Szmyd, Grzegorz Brus - AGH University of Science and Technology, Faculty of Energy and Fuels, AGH University of Science and Technology, Academic Centre for Materials and Nanotechnology, Krakow, Poland , Kyoto University, Department of Aeronautics and Astronautics, Kyoto, Japan

In this paper a fully three dimensional, multiphase, micro-scale solid oxide fuel cellanode transport phenomena numerical model is proposed and verified. The Butler-Volmer model was combined with empirical relations for conductivity and diffusivity – notably the Fuller-Shetler-Giddings equation, and the Fickian modelfor transport of gas reagents. FIB-SEM tomography of a commercial SOFC stack anode was performed and the resulting images were processed to acquire input data. A novel method for estimating local values of Triple Phase Boundary length density for use in a three-phase, three-dimensional numerical mesh was proposed. The model equations are solved using an in-house code and the results were verified by comparison to an analytical solution within the range of its applicability. A limited parametric study was performed to qualitatively assess simulation performance and impact of heterogeneity. Despite the high dependence of the SOFC anode performance on the geometry of its anisotropic, three-phase microstructure there are very few micro-scale numerical models simulating transport phenomena within these electrodes.

How Amira-Avizo Software is used

The reconstructed 3D model of anode
microstructure is prepared through the process of stacking
2D SEM images. AVIZO algorithms allow the output images
to be resampled in such a way, that pixel edge length is equal
to the thickness of the corresponding layers. This functionality has been used to ensure the cubic shape of voxels,
which in turn allows for the straightforward construction of
regular, orthogonal and uniform mesh.