MCO-Coated Interconnects for Mitigation of Cr-Poisoning in Solid Oxide Fuel Cells

Abstract

Chrome species evaporated from stainless steel interconnect are considered to be the major poisoning source for the cathode of solid oxide fuel cells (SOFCs). The poisoning effect is extremely severe when humidity is present in the incoming air. High performance perovskite-oxide type cathodes, such as LSCF and BSCF are subject to deactivation by Cr. To eliminate/mitigate the Cr poisoning effect, conductive coatings on the surface of stainless steel (SS) are employed to block Cr evaporation. In the present study, a Mn-Co oxide (MCO) coating on SS using the dip coating method will be reported. Dip coating was found to be very suitable to fabricate MCO coatings on SS, which in the case of SOFC interconnects are usually specially designed for gas delivery with complex structure. The initial results indicate MCO coating is very effective in blocking Cr evaporation, which was examined in both single cell and stack testing. Single cell tests using MCO-coated cathode SS test hardware resulted in a very low degradation rate of < 4 mV / 1000 hours when tested over thousands of hours with up to 10% H2O in flowing air. This result is very similar to tests without humidity. Stack testing indicates dip coating is feasible for coating specially designed, complex parts such as SOFC interconnects.