Geometric properties of nanostructured solid oxide fuel cell electrodes

Abstract

3D microstructures for nanostructured solid oxide fuel cell (SOFC) electrodes fabricated by infiltration/impregnation method are constructed numerically, by using a phenomenological procedure. Key geometric properties of the constructed electrodes are calculated at various infiltration loadings, including the percolation probabilities of pores and infiltrated nanoparticles, the total and active three-phase boundary (TPB) length, backbone and nanoparticles surface areas, and backbone-nanoparticles boundary area. The effects of backbone particle size, backbone porosity, nanoparticle size, and its aggregation risk are studied systematically. Analytical models are developed to predict these geometric properties, and agree well with the numerical infiltration results, as well as the literature data. It is found that the peak TPB length can be achieved at 63% coverage of the backbone surface by infiltrated nanoparticles. More interestingly, the backbone structure has little effect on nanoparticles surface area, but significantly affects TPB length, suggesting an strategy to identify electrode reaction mechanisms. Decreasing infiltrated particle size increases its surface area, enhances the peak TPB length, and decreases the optimal infiltration loading, indicating small infiltrated particles essentially benefits electrode performance. The results provide valuable information for understanding the geometric properties of the infiltrated SOFC electrodes and contribute to the design of high performance SOFC electrodes.