Investigation of electrode/electrolyte interface dynamics of solid oxide fuel cells

During the solid oxide fuel cell (SOFC) operation, the non-homogenous reactions and boundary conditions cause temperature gradient in the cell. The stress is generated due to the temperature gradient as a result of the thermal expansion mismatch of the electrolyte and electrodes and delamination and crack occur. In this study, the effects of the SOFC operation parameters on the temperature distribution are investigated experimentally. In this study, the temperature distribution and the corresponding performance variation within the SOFC with industrial sizes are investigated both experimentally and numerically. The most effective parameter that creates a temperature gradient in the cell is found to be current density. The numerical results show good agreement with the experimental results. The experiments show that the cell performance degrades with the operation time depending on the operation temperature. In order to examine the main reasons for the degradation of the cell performance, heat transfer, electrochemical reactions and stresses are numerically investigated for electrolyte/anode interfaces within a small volume of the cell with 5 µm x 5 µm captured from the cell. The micro-geometry used in the numerical analysis, which mimics the real electrode structure, is generated via Dream 3D software. The governing equations representing the conservation of energy and charge, mechanics and electrochemical reactions are numerically solved by COMSOL software. Since 2D model does not agree well with the experimental results, 3D geometry is used. The numerical results reveal that stress is generated at the electrolyte/anode interface and triple phase boundary edges due to the thermal expansion difference and the stress is found to increase with the temperature up to material limits. The stress is found to decrease with the increasing the electrolyte content in the anode and the porosity of the anode.