Abstract
Anode-supported solid oxide fuel cells with different Cr protection layers on the metallic interconnect were operated in a short stack at 700°C for 1240 h. The current density was raised sequentially from 0.5 A cm−2 during the first 240 h of operation to 0.75 A cm−2 for a further 1000 h. After operation, the (La,Sr)(Co,Fe)O3-δ (LSCF) cathode layers were analyzed with respect to Cr interaction by both wet chemical and microstructural methods. For cells equipped with interconnects coated with a dense APS protection layer, the amount of Cr on the cathode was in the range of a few μg. For cells with a porous WPS coating on the interconnect, the amount of Cr was in the range of 110–160 μg cm−2 and Cr-containing phases were detected by SEM analysis both on top of the cathode layer and also at the LSCF/GDC interface, which has rarely been observed before. In addition, a deterioration of the cathode microstructure near the LSCF/GDC interface was observed. With respect to the high current density during operation, a theory was developed which explains both the Cr deposition at the LSCF/GDC interface and also the deterioration of the cathode.
Highlights
JES FOCUS ISSUE ON OXYGEN REDUCTION AND EVOLUTION REACTIONS FOR HIGH TEMPERATURE ENERGY CONVERSION AND STORAGE
Apart from the increased degradation rate, the trend of the degradation process of layer 1 is quite similar to layer 3, which has an interconnect coating prepared by wet powder spraying (WPS)
Anode-supported solid oxide fuel cells were tested in a four-layer JU LICH F-design stack
Summary
JES FOCUS ISSUE ON OXYGEN REDUCTION AND EVOLUTION REACTIONS FOR HIGH TEMPERATURE ENERGY CONVERSION AND STORAGE. The most promising technique for avoiding Cr poisoning is to coat the interconnect steel with a preferentially dense protection layer This layer either prevents the Cr scale coming into contact with the gas phase or serves as a Cr getter by offering a reaction partner to form a more stable product phase thereby decreasing the Cr partial pressure in the cathode compartment.[11,12] In particular, dense layers applied by atmospheric plasma spraying (APS) have proven. Due to the segregation of Sr they are prone to Cr-related degradation.[17]
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