Degradation of a High Performance SOFC Cathode by Cr‐Poisoning at OCV‐Conditions

In this work we investigate the effect of Cr‐poisoning at OCV‐condition by means of electrochemical impedance spectroscopy (EIS). The anode‐supported cell (ASC) is operated in Cr‐free environment for the first 70 h of the cell test at 800 °C supplying air to the cathode and a varying mixture of H2O/H2 to the anode. The performance of the cell is determined by current‐voltage (CV) measurement after the start up. After an operating time of 70 h in the absence of chromium species a Cr‐source was switched on by passing the oxidant (air) through a Crofer22APU powder bed. In order to determine the degradation caused by Cr‐poisoning electrical impedance spectra are collected at every 29 h of operating time. After further 275 h at OCV‐condition in the presence of Cr‐source another CV‐curve is measured. A detailed analysis of the measured impedance spectra by the distribution of relaxation times (DRT) enables a separation of the cathode polarization resistance. During the Cr‐free operation the cathode polarization shows a constant value. After the Cr‐source is switched on a strong increase of the cathode polarization resistance is observed. This unique result shows clearly that Cr‐poisoning of an LSM/8YSZ‐cathode already takes place at OCV‐condition.