Modeling the impedance response of mixed-conducting thin film electrodes

In this paper a novel numerical impedance model is developed for mixed-conducting thin films working as electrodes for solid oxide fuel cells. The relative importance of interfaces is considered by incorporating double layer contributions at the film/gas boundary. Simulations are performed on a model system, namely doped ceria, in a symmetric cell configuration using geometrically well-defined patterned metal current collectors. Results reveal that experimentally consistent bulk impedances and surface capacitances can be extracted using the model. The impedance response depends strongly on the pattern spacing of the current collector, and is attributed to the electronic in-plane drift-diffusion as well as to the interplay between the surface reaction resistance and the electronic/ionic bulk drift-diffusion resistance.