Two-dimensional electrochemical model for mixed conductors: a study of ceria

A two-dimensional small bias model has been developed for a patterned metal current collector | mixed oxygen ion and electronic conductor (MIEC) | patterned metal current collector electrochemical cell in a symmetric gas environment. Specifically, we compute the electrochemical potential distributions of oxygen vacancies and electrons in the bulk and near the surface for Pt|Sm0.15Ce0.85O1.925|Pt symmetric cell in a H2− H2O−Ar (reducing) atmosphere from 500 to 650 C. Using a two-dimensional finiteelement model, we show that two types of electronic current exist within the cell: an in-plane drift-diffusion current that flows between the gas | ceria chemical reaction site and the metal current collector, and a cross-plane current that flows between the two metal electrodes on the opposite side of the cell. By fitting the surface reaction constant k̃ f to experimental electrode resistance values while fixing material properties such as bulk ionic and electronic equilibrium defect concentrations and mobilities, we are able to separate the electrode polarization into the surface reaction component and the in-plane electron drift-diffusion component. We show that for