Analysis of Polarization and Impedance Under Phosphine Induced Anode Degradation in a Planer SOFC

Abstract

An in house three dimensional computational model for planar solid oxide fuel cells, DREAM SOFC, is used to predict the phosphine induced performance degradation in large planar cells. The empirical model parameters are calibrated for one dimensional button cell code by using available experimental data for button cell. These parameters are used in DREAM SOFC to perform degradation simulations for planar cells. These calculations are based on a cell level model which includes anode, electrolyte, cathode, and interconnect components of the cell. The V-I curves obtained at different points on the degradation curve shows that while PH3 coverage increases the voltage losses increase, slowly at first and sharply after some time. The impedance curves predicted for a typical button cell shows impedance response of anode supported the cell while anode is exposed to phosphine. Anode and cathode losses are significantly visible from the impedance calculations. These impedance calculations show that the increase in the activation losses in the anode is the major loss for the cell degradation and they increase sharply during faster degradation regime. This study focus on a similar study on a relatively large planar cell.