Sr2−XLaXMgMoO6 and Sr2−XLaXMgNbO6 for Use as Sulfur-Tolerant Anodes Without a Buffer Layer

• Published in: Journal of the American Ceramic Society Vol. 97; no. 11; pp. 3636 - 3642
• Main Authors: Howell, Thomas G., Kuhnell, Cory P., Reitz, Thomas L., Eigenbrodt, Bryan C., Singh, Raj N.
• Format: Journal Article
• Language: English
• Published: Blackwell Publishing Ltd 01-11-2014
• Subjects: Anodes; Buffer layers; Diffusion; Electrochemical analysis; Electrolytes; Electronics; Solid oxide fuel cells; Stability
• ISSN: 0002-7820; 1551-2916
• DOI: 10.1111/jace.13208

The objective of this effort is to synthesize and characterize a series of lanthanum‐(La) doped Sr2MgMoO6 (SMMO) and La‐doped Sr2MgNbO6 (SMNO) anode materials which can be used in combination with lanthanum‐containing electrolytes to mitigate the effects of lanthanum poisoning in solid oxide fuel cells (SOFCs). Currently, an La0.4Ce0.6O1.8 (LDC) buffer layer is used with many perovskite‐based anode materials to prevent La diffusion into the anode from the La0.8Sr0.2Ga0.8Mg0.2O2.8 (LSGM) electrolyte which can create a resistive La species that impedes electrochemical performance. The LDC buffer layer, with diminished electronic conductivity, adds an extra level of complexity in the SOFC manufacturing process. Further, this extraneous layer presents an added experimental challenge when assessing anode material performance. Overall electrochemical performance could be improved if the resistive buffer layer could be removed, thereby allowing the anode material to have direct contact with the electrolyte. To accomplish this, a new class of anode materials was synthesized with the goal of balancing “La” chemical potential between these neighboring materials. La‐doped SMMO and SMNO were prepared and studied. It was hypothesized that by incorporating La into the anode, the gradient of chemical activity between the anode and electrolyte would decrease, which would prevent La diffusion. These anode materials were synthesized via a sol–gel methodology and characterized with X‐ray diffraction to assess phase purity. The conductivity of the materials was analyzed in the presence of both H2 and 100 ppm H2S/H2 to determine the stability and performance of these materials during device operation. The stability experiments demonstrated that 40% La‐doped SMNO is stable in all pertinent environments while not reacting with the LSGM electrolyte.