Abstract
This PhD thesis concerns the field of hydrogen storage and more specifically solid-sate hydrogen storage materials. Magnesium borohydride, Mg(BH4)2, is a compound of strong interest because of its high hydrogen gravimetric capacity (14.8 %) and was the subject of this study. The literature on the decomposition of this compound is actually very inconsistent and reveals numerous contradictions. Different synthesis routes of Mg(BH4)2 were studied during the thesis in order to produce the purest possible compound and at a lower cost. A mechanical milling-assisted metathesis reaction produced Mg(BH4)2 from NaBH4 and MgCl2 precursors with an excellent yield. The hydrogen desorption properties of Mg(BH4)2 were then improved by a dual approach of catalytic additions and nano-confinement into mesoporous carbons. Core-shell Ni-Pt nanoparticles of about 1.9 nm in diameter were used as catalysts. These particles were dispersed in a carbon having mesoporous channels of 4 nm in diameter prepared by hard templating of SBA-15 silica. The results showed that the combined effect of both nano-confinement and catalysis allows the final decomposition temperature of Mg(BH4)2 to be reduced by more than 100°C while obtaining faster hydrogen desorption kinetics