The work in this thesis describes the synthesis and characterisation of direct and indirect hydrogen storage materials. The main experimental techniques used have been Powder X-ray Diffraction (PXD), Powder Neutron Diffraction (PND) and Temperature Programmed Desorption (TPD).
The Magnesium ammines, Mg(NH3)6X2 (where X= Cl, Br, I) are interesting materials for use as an indirect H2 storage material (by the splitting of NH3) due to their high H2 gravimetric capacities. These ammines have been synthesised at room temperature through the reaction of the starting salt with NH3 and are cubic (Fm3m). TPD investigations have revealed that the ammines deammoniate in a three step process, with the chloride ammine possessing the most favourable deammoniation temperatures. Ex-situ PND has been used to refine the structure and in-situ PND has been employed to study the deammoniation processes in more detail.
‘H2 release’ systems have been examined as a potential solution for H2 storage. Mg(NH3)6Cl2 has been mixed with LiH or MgH2 at room temperature and studied using TPD with the LiH system the most encouraging in terms of the H2 release temperature. In-Situ PND has also been employed to understand the mechanism of H2 release. The Mg(OH)2 –LiH ‘H2 release’ system has also been studied using both bulk starting materials and microstructured materials.
Microplates of Mg(OH)2 have been synthesised by a new MW (microwave) heating process in 6 mins. The employment of microstructured materials has reduced the onset reaction temperature from 147 oC in the bulk materials to 79oC when the starting materials are mixed for 10 mins
