Comparison of chromium poisoning among solid oxide fuel cell cathode materials

Abstract

Chromium poisoning phenomena of solid oxide fuel cells (SOFCs) were investigated using (La0.8Sr0.2)0.98MnO3 (LSM), Pr0.8Sr0.2MnO3 (PrSM), Nd0.8Sr0.2MnO3 (NdSM), and Br0.5Sr0.5Co0.8Fe0.2O3 (BSCF) for the cathode materials and yttria-stabilized zirconia (YSZ) as the electrolyte material at 700°C under constant cathode polarization conditions. Deposition of chromium increased with increasing cathode polarization similarly for the four cathodes, although position of the deposition was different for the BSCF cathode. Chromium deposited near the cathode/electrolyte interface for the LSM cathode, the PrSM cathode and the NdSM cathode. Chromium deposition on the surface of the zirconia electrolyte was observed for the PrSM cathode and the NdSM cathode as previously observed in the LSM cathode. Oxygen deficiency in the deposited chromium on the surface of the zirconia electrolyte was also observed, thus the reaction mechanism of chromium vapor with the oxygen vacancy induced by cathode polarization was supported. The oxygen vacancy on the surface of the zirconia electrolyte seemed to be generated via metal oxides such as manganese oxide or neodymium oxide segregated from the cathode materials. Chromium deposited on the surface of the BSCF cathode. Cathode polarization seems to increase reactivity of BSCF and enhance trapping of chromium vapor near the cathode surface.