ABO3-delta and A2BO4±delta Perovskites as Solid Oxide Fuel Cell Cathode Materials for Reduced Operating Temperatures

• Applicant: Professor Dr. Ulrich Guth
• Subject Area: Inorganic Molecular Chemistry - Synthesis and Characterisation
• Term: from 2004 to 2009
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 5417513

One of the main drawbacks for a broad application of Solid Oxide Fuel Cells (SOFCs) is their cost. Therefore, there is a world-wide search for new high-performance materials that allow the operation at reduced temperatures (650 °C - 750 °C), making it possible to use cheaper materials for some components. The main focus for this has to be on the cathode, as the polarisation losses of todays cathode materials limit the cellperformance. The use of manganese-containing perovskites with structure ABO3-d (e.g. La0.65Sr0.3MnO3-d) is established practically in the fabrication of SOFC cathodes for operating temperatures of 850 - 1000 °C. Replacing these materials by others with reasonable ionic conductivity and better electrocatalytic activity leads to a higher overall cell performance, especially at reduced temperatures. However, this is often associated with lower chemical stability and rising thermal expansion. Alternative materials that meet these requirements are mixed oxides with layered K2NiF4 structure of the general formula A2BO4±d (A=La, Pr, Sm, Gd, Sr, Ca etc., B = Fe, Co, Ni, Cu), which have not yet been explored in depth for application as cathodes. The A2BO4±d - materials offer the possibility of overcoming the disadvantages mentioned above. It is intended to explore the relevant properties for application as SOFC cathodes with A2BO4 structure and with or without A- and B-site cation nonstoichiometry in respect electrical conductivity, thermal expansion and stability, ionic conductivity, catalytic activity, and chemical compatibility with other cell components. It is well known that cationic nonstoichiometry has effects on defect structure, transport properties, and catalytic activity of perovskites with ABO3 structure, hence it can be assumed that the cation nonstochiometry of A2BO4 materials may also play an important role. The research work will be done under the cooperation between Dresden University of Technology (TUD) and Shanghai Institute of Ceramics - Chinese Academy of Sciences (SICCAS). Basing on such research, it is expected to achieve an excellent cathode material with desired performance.

• DFG Programme: Research Grants