Numerical Simulation of SOFC Electrode Polarization Using Three-Dimensional Microstructure Reconstructed by FIB-SEM
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Numerical Simulation of SOFC Electrode Polarization Using Three-Dimensional Microstructure Reconstructed by FIB-SEM Naoki Shikazono1 and Nobuhide Kasagi2 1 Institute of Industrial Science, The University of Tokyo, Komaba 4-6-1, Meguro-ku, Tokyo, 153-8505, JAPAN. 2 Department of Mechanical Engineering, The University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo 113-8656, JAPAN. ABSTRACT Three-dimensional numerical simulations can provide information which cannot be obtained from experiments and can be a powerful tool for investigating reaction phenomena in solid oxide fuel cell (SOFC) electrodes. In the present study, a dual-beam focused ion beamscanning electron microscope is used to reconstruct the three dimensional microstructures of the SOFC electrodes, and their polarization characteristics are predicted by a lattice Boltzmann method. Predicted overpotentials for Ni-YSZ anode and mixed ionic and electronic conducting cathode (La0.6Sr0.4Co0.2Fe0.8O3-; LSCF6428) are compared with the experimental data for validation. In addition, three-dimensional distributions of electrochemical potential and current densities inside the electrode microstructures are obtained. Large non-uniformities of potential and current distributions are found in the Ni-YSZ anode, while those became much uniform in the LSCF cathode. The present method can be expected as a powerful tool for investigating local potential fields which affect local reactions and diffusion processes as well as local physical properties of the SOFC electrodes. INTRODUCTION Solid oxide fuel cell (SOFC) is anticipated to play a major role in the future energy system because of its superior efficiency and fuel flexibility [1]. However, cost and durability issues must be further improved before market introduction. It is widely known that the electrode microstructure has significant effects upon the cell performance and durability of SOFCs. Thus, the basic understanding of microscopic features of the electrode is indispensible. Recently, direct measurements of three-dimensional SOFC electrode microstructures have been carried out using focused ion beam scanning electron microscopy (FIB-SEM) [2–12] and nano X-ray computed tomography (nano-XCT) [13,14]. As a result, useful quantitative data such as TPB length and tortuosity factor can be obtained from the reconstructed three-dimensional microstructures. On the other hand, numerical simulations have potentials to provide useful information which cannot be obtained from experiments. Recently, large attention has been paid to the lattice Boltzmann method (LBM), which is suitable for simulating complicated porous electrodes. Joshi et al. [15] performed a multi-component LBM simulation in a two dimensional porous media. Asinari et al. [16] also used LBM for solving H2 and H2O diffusion inside the micro pores. Suzue et al. [17] conducted a three-dimensional LBM simulation in a stochastically reconstructed anode microstructure. However, microstructures used in these studies were artificial, which consequently highlighted the import
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