Performance of stainless steel interconnects with (Mn, Co)3O4-Based coating for solid oxide electrolysis. (8th July 2022) - Dogdibegovic, Emir
Abstract: Mixed transition-metal oxide coatings are commonly applied to stainless steel interconnects for solid oxide cell stacks. Such coatings reduce oxidation and Cr evaporation rates, leading to improved degradation rate and stack lifetime. Here, the ChromLok™ MCO-based composition (Mn, Co)3 O4 is applied to Crofer 22 APU stainless steel and evaluated specifically for application in solid oxide electrolyzer stacks operating around 800 °C and utilizing oxygen-ion-conducting solid oxide cells. The MCO coating is found to decrease the stainless steel oxidation rate by about one order of magnitude, and decrease the Cr evaporation rate by fourfold. The coating also dramatically lowers the rate of area-specific resistance increase for stainless steel coupons oxidized for 500 h with constant current applied, from 33 mΩ∗cm 2 kh −1 for an uncoated coupon to less than 4 mΩ∗cm 2 kh −1 for coated coupons. The coating is demonstrated on full-scale interconnects for single-cells, where the coating dramatically reduces degradation rate, and for a stack, which displays stable operation for 700 h. Highlights: MCO coating decreases the stainless-steel oxidation rate by an order of magnitude. MCO coating decreases the Cr evaporation rate of stainless steel by fourfold. The coating dramatically lowers the rate of ASR increase for stainless steel. The coating was demonstrated on full-scale interconnects for single cells. Stack degradation rate was reduced showing stable 700-h electrolysis operation.