Degradation of Solid Oxide Fuel Cell Performance by Cr-Poisoning

Performance and stability of solid oxide fuel cells (SOFC) have been continuously improved over the past 10 years. But whenever the individual cells are connected by a metallic interconnector (MIC), the stack performance undergoes a pronounced performance and degradation. Possible cause, inter alia, is the effect of Cr-evaporation from the MIC and, thus, Cr-poisoning of the cathode. In this work we examined the difference in cell performance and short-term stability during a galvanostatic test for 280h by using an inert or a flowfield made of Crofer22APU (chromia forming alloy). A detailed analysis of the impedance spectra by the distribution of relaxation times (DRT) and a subsequent Complex Nonlinear Least Squares (CLNS) fit enabled the separation of anodic and cathodic polarization resistance. During the test, the cathode polarization resistance increased about +144 % in the presence of Crofer22APU. In contrast, the polarization resistance decreased by 3.2% in the absence of Crofer22APU.