Spatial Distribution of Oxygen Chemical Potential under Potential Gradients and Theoretical Maximum Power Density with 8YSZ Electrolyte

Abstract

The maximum power density of SOFC with 8YSZ electrolyte as the function of thickness was calculated by integrating partial conductivities of charge carriers under various DC bias conditions at a fixed oxygen chemical potential gradient at both sides of the electrolyte. The partial conductivities were successfully taken using the Hebb-Wagner polarization method as a function of temperature and oxygen partial pressure, and the spatial distribution of oxygen partial pressure across the electrolyte was calculated based on Choudhury and Pattersonâ model by considering zero electrode polarization. At positive voltage conditions corresponding to SOFC and SOEC, the high conductivity region was expanded, but at negative cell voltage condition, the low conductivity region near n-type to p-type transition was expanded. In addition, the maximum power density calculated from the current-voltage characteristic showed approximately 5.76 W/cm 2 at 700° C with 10 Î 1/4m thick-8YSZ, while the oxygen partial pressure of the cathode and anode sides maintained∼0.21 and 10 -22 atm.