Solid oxide fuel cells (SOFCs) show great promise as a technology capable of reducing both fuel consumption and CO2 emissions, due to their ability to convert many types of fuels to electricity at high efficiencies. An SOFC consists of porous anode and cathode electrodes separated by a solid electrolyte. The technical challenges surrounding SOFCs concern their high operating temperature, and how this negatively impacts operating cost, reliability, and start up time. Traditional SOFC anode materials contain Ni to catalyze hydrogen gas oxidation, however, degradation of these materials due to reactions between Ni and components of the fuel gas at high temperatures drive efforts to develop more robust alternatives. Ni-free double perovskites have been investigated in recent years as possible replacements for traditional Ni-containing cermets. In this study, a series of Sr2MMoO6-δ double perovskite materials (where M = Fe, Co, or Ni) were synthesized, and the changes in their morphologies and electrical performances under relevant SOFC operating conditions were explored. X-ray techniques are ideal for characterizing the morphology of materials, therefore ultra-small angle, small angle and wide angle X-ray scattering (USAXS/SAXS/WAXS) was conducted to monitor changes in the microstructures of the anode materials at high temperatures and under reducing atmosphere over time. Meanwhile, electrical impedance spectroscopy (EIS) was conducted to measure electrical performance losses under similar conditions. The stability of the double perovskite structure was found to be highly dependent on the identity of the cation M, such that when M = Fe, the material remained stable over the course of the experiments. However, when M = Co or Ni, much more structural and performance degradation occurred over time. Future work will focus on the development of a high temperature electrochemical cell that is compatible with the X-ray beam line, such that EIS and USAXS/SAXS/WAXS measurements may be conducted simultaneously and in-operando. Such measurements will allow for the direct comparison of electrical and morphological changes occurring in the material under operating conditions. Furthermore, similar experiments will be conducted on additive manufactured SOFCs to explore the effects of the manufacturing method on the resulting morphology of the cell components and overall performance.

Ni-free double perovskites as alternative solid oxide fuel cell anode materials: In situ structural and performance characterization

2019 Fall National Meeting

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