Nanocarbon-hydride composites for hydrogen storage

Graphite is considered a possible material for solid state hydrogen storage. In this thesis graphite was ball milled for 8hrs under 3 bar H\(_2\), followed by the addition of LiBH\(_4\) at a ratio of 2:1 (graphite:LiBH\(_4\)) and milled for a further 2hrs. Characterization of the as milled material showed the formation of a nanocrsytalline/amorphous mixture of graphite and LiBH\(_4\). Decomposition was performed by heating to 500°C at 2°Cmin\(^{-1}\). Graphite milled for 8 hrs released a small amount of hydrogen at 350°C, though no reaction was observed using DSC. The graphite+LiBH\(_4\) sample, however, exhibited 4 endothermic peaks consistent with a modified LiBH\(_4\) decomposition. The application of an over pressure of hydrogen during heating of the graphite+LiBH\(_4\) was found to suppress the decomposition of LiBH\(_4\). In-situ XRD measurements demonstrated that Li\(_2\)C\(_2\) was formed. Li\(_2\)C\(_2\) is known to be a key decomposition product in making a graphite based system reversible. It was not possible to identify the exact decomposition path due to partial oxidation of the sample during the measurement. Partial reversibility was observed at non optimized conditions of 500°C under 100bar H\(_2\) for 20 minutes