No abstract

Solid Oxide Electrolysis (SOE) can be used to produce hydrogen with very high efficiencies at remarkable hydrogen production rates. Through microstructural and compositional modification, conventional low cost Solid Oxide Fuel Cell (SOFC) materials have been used to create a Solid Oxide Electrolysis Cell (SOEC) that can achieve remarkable current density at cell voltages allowing higher conversion efficiency than current commercial electrolysers. Current densities in excess of 6 A/cm2 have been achieved at 800°C with a cell voltage of < 1.67 V. This cell shows a more than 3-fold increase in hydrogen production rate at higher efficiency than established commercial electrolysers.

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% H 2 O 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.

Coating development at FuelCell Energy (FCE) is a continuous activity looking at optimizing chemistry, application process and features of the coating for longer life of the solid oxide fuel cell (SOFC) stack in high humidity environment. Cathode interconnects surfaces are protected with manganese cobalt oxide (MCO) coatings to minimize chrome evaporation and poisoning of the fuel cell.Protecting the surface of cathode interconnects becomes necessary to extend the SOFC life. Two different coatings have been studied at FCE. MCO was either deposited as a perovskite by dip coating or formed in situ during stack operation. A direct comparison of the two methods was studied after hundreds of hours in SOFC stack testing both in dry and humid air environment. The stacks were tested in normal conditions with dry air in cathode and also in air with additional humidity. A significant improvement in degradation rate and cell stability has been observed and achieved with those stacks.