Cathodes interaction with contact materials

Besides the glass seal interfaces, interactions have also been reported at the interfaces of the metallic interconnect with electrical contact layers, which are inserted between the cathode and the interconnect to minimize interfacial electrical resistance and facilitate stack assembly. For example, perovskites that are typically used for cathodes and considered as potential contact materials have been reported to react with interconnect alloys. Reaction between manganites- and chromia-forming alloys lead to formation of a manganese-containing spinel interlayer that appears to help minimize the contact ASR [219,220], Sr in the perovskite conductive oxides can react with the chromia scale on alloys to form SrCr04 [219,221],... 

During SOFC operation, interconnects interact with surrounding gaseous environments on both the cathode and anode side, as well as with adjacent components such as sealing materials, electrodes, and electrical contact layers inserted between interconnects and electrodes. These interactions potentially cause corrosion of metallic interconnects and affect their stability and performance. 

However, reliable information about dependence of the functional properties of complex nickelates on their chemical composition and structure is still absent, while any straightforward and accelerated design of cathode materials is to be based upon reliable (and independent upon their interaction with electrolyte) characterization of the ability of then-surface sites to catalyze the oxygen reduction as well as of oxygen mobility in the bulk. Several lanthanum-nickel-iron mixed oxides with perovskite structure have demonstrated promising performance as cathodes for IT SOFC with traditional YSZ and GDC electrolytes [111-112]. However, studies of the behavior of electrode materials in contact with ATLS electrolytes or that of ATLS-based composites are veiy scarce [113]. 

When the operating temperature is about 1000°C, interconnects need to be made of ceramic materials. Although excellent performances of fuel cells based on ceramic interconnects have been proved, costs are still a relevant restriction. At reduced temperature, the use of less expensive materials, like for instance stainless steel, is possible. Several organizations are currently investigating the interaction of different metals with the electrodes (De Jonghe et al. 2004, Zahid et al. 2004, Pedersen et al. 2004). The two main issues to overcome are the oxidation of the metal when in contact with air at the cathode side and the interaction of the chromium vapors with the cathode. 

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