Due to the material benefits in the reduction of the operating temperatures of SOFCs, development of novel electrolyte and electrode materials is deemed to be essential for SOFC performance optimisation at intermediate temperatures. Iron-based perovskites were previously overlooked as anode materials due to their instability in reducing atmospheres at SOFC operating temperatures, although substantial research has been conducted into the use of these materials as SOFC cathodes. The reduction in operating temperature allows for use of materials, such as iron-based perovskites, which lack the requisite thermal or redox stability for high temperature operation. Synthesis of iron rich strontium molybdenum ferrite double perovskites determined that the previously observed performance of these materials was intrinsically linked to initial high temperature reduction, thus reducing the utility of these materials at intermediate temperatures. XRD and DC conductivity measurements determined that doping of SrFeO₃₋δ with titanium and niobium produced the optimal balance between conductivity and stability for SrFe₀.₉(Ti,Nb)₀.₁O₃₋δ. Introduction of transition metal dopants further increased the electronic conductivity with copper doping exhibiting the highest electronic conductivity of the redox stable SrFe₃₋₀₉ ̣₁₈₆₄₂₇⁻²°₀.₈-x(TM)x(Ti,Nb)₀.₁O₃-δ materials. Increasing the copper content of SrFe₀.₈-xCu₀.₁+xNb₀.₁O₃-δ resulted in a reduction of the electronic conductivity. A-site doping with lanthanum replicated the structure and conductivity observed previously in the literature, with redox stability at intermediate temperature observed for both La₀.₆0.6Sr₀.₄FeO₃-δ and La₀.₈Sr₀.₂FeO₃-δ. Replacement of lanthanum with yttrium elicited a reduction in the electronic conductivity, with Y₀.₃Sr₀.₇FeO₃-δ exhibiting the highest electronic conductivity of the redox stable materials. Symmetrical fuel cell testing with 60:40 SrFe₀.₉Ti₀.₁O₃-δ-Gd₀.₂Ce₀.₈O₂-δ, 55:45 La₀.₆Sr₀.₄FeO₃-δ-Gd₀.₂Ce₀.₈O₂-δ and SrFe₀.₈Cu₀.₁Nb₀.₁O₃-δ electrodes recorded performances of 22 mWcm⁻², 80 mWcm⁻² and 306 mWcm⁻² respectively at 700 °C. The fuel cell performance of a symmetrical SrFe₀.₈Cu₀.₁Nb₀.₁O₃-δ-Gd₀.₂Ce₀.₈O₂-δ- SrFe₀.₈Cu₀.₁Nb₀.₁O₃-δ fuel cell was an improvement on the symmetrical fuel cell performance from the literature.
|Date of Award||7 Oct 2015|
- University Of Strathclyde
|Supervisor||Shanwen Tao (Supervisor) & Carl Schaschke (Supervisor)|