NMR studies of conduction mechanisms in electrolyte materials for fuel cells
Murray, Eoin (2007) NMR studies of conduction mechanisms in electrolyte materials for fuel cells. PhD thesis, Dublin City University.
Full text available as:
Fuel cells are clean and efficient electrochemical energy conversion devices which have garnered much scientific attention in recent years as clean renewable sources of energy. However, development is currently restrained by materials limitations, particularly those associated with the electrolyte. A number of liquid electrolytes are currently in use in commercial applications but solid electrolytes are preferable as they are more robust, more efficient and less susceptible to corrosion. In this work, a number of solid conducting materials which have potential to be applied in fuel cells were studied by NMR techniques. By gaining detailed mechanistic insight into charge transport we hope to contribute to the development of these materials.
In the first part of this thesis charge conduction mechanisms is investigated in ionic conductors. In Chapter 3 19F NMR relaxometry is applied to investigate fluoride ion dynamics in the fluoride conducting superionic material, PbSnF4 and in Chapter 4 1H NMR relaxometry is used to examine proton motions along hydrogen bonds in the novel superprotonic material, Cs6(HSO4)3(H2PO4)4. The results of the NMR analysis show good agreement with bulk physical properties from diffraction and conductivity techniques for both materials and a new mechanism for fluoride ion conduction in PbSnF4 is proposed.
In the second part of this thesis, the synthesis and analysis of conducting polyaniline is presented. In Chapter 5 the synthesis of amorphous polyaniline samples with varying dopant content is presented and in Chapter 6 a number of methods for the synthesis of nano-structured doped polyaniline are examined. Both amorphous and semi-crystalline polymers are analysed by 19F and 1H NMR relaxometery and show similar dependence on the dimensionality of charge carriers through the heterogeneous regions of the material. The dimensionality of this motion is shown to be dependent on both the conductivity and the relative dopant concentration. In an appendix, preliminary NMR relaxometry results on molecular dynamics in ionic liquids are presented.
Archive Staff Only: edit this record