Correlation between structure of titanium additives and dehydrogenation reaction of magnesium borohydride studied by continuous observation of x-ray absorption spectroscopy

Local structure of Ti-based additives in Mg(BH4)2 was studied by X-ray absorption fine structure spectroscopy with conventional and dispersive mode in order to understand the correlation between the structure of the additives and dehydrogenation property of Mg(BH4)2. Simultaneous measurement of the dehydrogenation curve and the X-ray absorption spectroscopy by the dispersive optics revealed that a part of TiCl3 additive is converted to TixMg1-3x/2(BH4)2 (x=0-0.67) just after ball milling mixture and then promptly resolved to TiB2 at 100-150degC with the first dehydrogenation peak. TiO2 additive is slowly converted to lower oxidation state in wide temperature range around the second dehydrogenation peak at 350degC where the main dehydrogenation reaction of Mg(BH4)2 occurs. (author)