Evaluation of SOFC anode polarization simulation using three-dimensional microstructures reconstructed by FIB tomography

Abstract

In order to evaluate the numerical simulation method for solid oxide fuel cell anode polarization, three-dimensional lattice Boltzmann method simulation is carried out using Ni–YSZ microstructures reconstructed by a focused ion beam scanning electron microscope. The effects of reconstructed sample volume size on the three phase boundary length, tortuosity factors and overpotential are first investigated. The YSZ tortuosity factor has remained nearly unchanged when the cross-sectional area exceeds approximately 200 μm 2, while the pore tortuosity factor is almost independent of the sample volume size. On the other hand, the Ni tortuosity shows very large variation regardless of the sample volume size. The overpotential predicted with the largest volume size sample is slightly larger than those of smaller volume samples. Two exchange current models based on patterned electrodes are assessed presently. Both models give weaker dependence on the steam concentration than the experimental data. From the predicted three-dimensional current stream lines, it is found that the mirrored computational structure gives a thinner reactive layer because of the factitious connection of Ni phase. Thus, it is recommended to use larger volume size samples which can cover whole reactive thickness when discussing the local potential and flux distributions.