A model study on correlation between microstructure-gas diffusion and Cr deposition in porous LSM/YSZ cathodes of solid oxide fuel cells

The deposition of Cr on cathode materials in solid oxide fuel cells (SOFCs) is complex and impacted by multiple factors. In this report, a mathematical model based on electrochemical Cr-poisoning mechanism is developed to investigate the correlation between gas transport and Cr deposition in porous strontium doped lanthanum manganite/yttria stabilized zirconia (LSM/YSZ) cathode. Time evolution of cathode pore size and three phase boundaries (TPBs) in different cathode regions with Cr₂O₃ deposition is analyzed. The distribution of local current density in the cathode, the lifetime, the concentration polarization, the activation polarization and area specific resistance of SOFC cathodes are subsequently assessed quantitatively. Three types of LSM/YSZ cathode structures with uniform, ascending and descending gradient pore-size distributions are compared. The results show that uniform pore distribution contributes to the best performance when all the cathodes own TPBs with the same initial length.