Experimental and Modeling Study of the Impedance of Ni/YSZ Cermet Anodes

We present a combined experimental and modeling study of the impedance of Ni/YSZ cermet anodes. Experiments are performed using symmetrical cells with 30 mu m electrodes and 195 mu m YSZ electrolyte. Impedance spectra are recorded in H-2/H2O/N-2/He atmospheres over a wide range of operating conditions (650-900 degrees C, 4-46% H2O). The data are analyzed by both, an equivalent circuit model consisting of 4 RQ elements, and a two-dimensional detailed-chemistry kinetic model. The combined results allow a detailed insight into the coupled electrochemical and transport processes. This enables identification of the physical origin of the impedance features: 1) charge-transfer (hydrogen spillover reaction) and electrical double layer; 2) gas diffusion in the supply channels; 3) gas diffusion in the current collector mesh.