Low-Temperature Chromium Poisoning of SOFC Cathode

Abstract

Chromium poisoning of SOFC cathode has been studied at 650 °C utilizing an electrochemical half-cell configuration (Air-3%H2O-CrOxHy /LSM//YSZ/Ag/Air). While the cell performance and electrode impedance show continued improvement with time under standard conditions (3% H2O-air), cell performance degrades rapidly in the presence of gaseous chromium as indicated by increase in the electrode polarization and reduction in the current with time. Scanning electron microscopy (SEM)/energy dispersive X-ray spectroscopy (EDS) analyses for the cell exposed to chromium vapor shows chromium deposition on the cathode/electrolyte interface, no chromium was detected on the cathode surface and the interface of the cathode/electrolyte for the standard cell. Calculated equilibrium vapor pressures of chromium vapor species formed from pure chromium oxide (Cr2O3) under flowing humidified air (3% H2O-air) show that the partial pressure of major chromium specie namely CrO2(OH)2 at low temperature still remains appreciable and a cause for concern during long term operation of low-temperature SOFC.