Synthesis of electrolyte and electrode materials for solid oxide fuel cells

• Main Author: Keenan, Philip J.
• Published: University of Birmingham 2017
• Subjects: 621.31; QD Chemistry
• Online Access: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.704823

In this PhD thesis, new materials for solid oxide fuel cells have been researched. It focuses on both the cathode and electrolyte components. Two general systems, the perovskite-type ABO3 and apatite-type M10-x(XO4)6O2+y structures, have been investigated. The structural characteristics, conductivity and stability have been examined. The perovskite work for the cathode uses doping strategies to introduce disorder into the system and change the conduction characteristics through a structure change to cubic. It has been shown that only small amounts of dopants are required to cause this structural change and effect the conductivity. In addition, thermal and chemical compatibility tests, along with ASR tests with known fluorite and apatite electrolytes, have been investigated. Their stability in a CO2 containing environment was tested and a full-scale production of a fuel cell was attempted (Chapters 3 and 4). The electrolyte investigations focussed on doping the Ba2Sc2O5 sample to form a perovskite structure that possesses both oxide ion and protonic conductivity. The doping has decreased the amount of scandium present with cheaper elements such as rare earth Yb3+, or transition metals Fe4+ and Ti4+, all in an attempt to form the cubic structure that results in high oxide ion/proton conductivity and increased stability in CO2 environments (Chapter 5). The final chapter focuses on phosphate and rare earth doping of BaPrO3, to form the cubic perovskite structure. These samples were seen to have increased water incorporation and stability in CO2. However, this was at the expense of the ionic conductivity due to vacancy trapping.