Three-Dimensional Microscopic Modeling and Activation Thickness Analysis of the Anode of Solid Oxide Fuel Cells
Abstract: A solid oxide fuel cell anode microstructure is obtained using X-ray technology. A complete three-dimensional (3D) and fine heterogeneous model is built on the basis of the microstructure. The difference between the simulation results of microscopic and macroscopic models is compared. The physical fields of the heterogeneous model are analyzed and the effects of operating conditions are investigated. The results show that the electrochemical reaction at three-phase boundaries does not cause a high concentration gradient in the pore phase. The H2 molar fraction and concentration overpotential almost linearly decrease with the anode depth. However, the decrease of the H2 molar fraction is small, indicating that fuel supply is sufficient. Compared with activation and ohmic overpotentials, the concentration overpotential is negligible. Given the heterogeneity of the microstructure, the physical fields of the anode would fluctuate. The higher the electrochemical reaction rate, the greater the fluctuation of the physical fields. As shown in the microscopic simulation result, the active thickness of the anode is expressed as the analytical function of the operating conditions and microstructure parameters. The active thickness increases with temperature and H2 molar fraction but slightly decreases with the total overpotential. The active thickness is analytically expressed as the function of electrode parameters and operating conditions, which can improve electrode design and optimization.
Keywords: model / anode / microstructure / active thickness / microscopic / optimization / function / overpotential / molar
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