A computational investigation of oxygen storage and migration in energy materials

Abstract

This thesis describes a computational investigation into the oxygen storage material copper doped ceria and electrolyte material Ge₅O(PO₄)₆ for use in Solid Oxide Fuel Cells.

In Chapter 1, a background on fuel cells is given along with explanations and examples of different oxygen migration mechanisms. After this, a background on the materials Ge₅O(PO₄)₆ and copper doped ceria is given,.

Chapter 2 presents background on the computational techniques used. This includes discussion of first principles techniques and an explanation of the CALPHAD method.

Chapter 3 presents the detailed results of the investigation into copper doped ceria. This investigation concentrated on the stability of copper ceria as well as on the ionic makeup of the material. The main findings of this investigation are that Cu¹⁺ and Cu²⁺ ions can be doped into ceria with the maximum doping reaching 0.09 mole fraction Cu.

In Chapter 4 the details of the computation investigation into Ge₅O(PO₄)₆ are given. This investigation looked at the possible oxygen migration pathways. From the findings of this investigation we were able to rule out several different possible pathways through the structure.

Chapter 5 gives a brief overview of the findings of each of the projects and provides recommendations on future work that may be carried out on each of the systems.

Appendix A provides supplementary data on the copper doped ceria project, specifically the coding of the thermodynamic database created during the project.