The dehydrogenation kinetics and reversibility improvements of Mg(BH4)2 doped with Ti nano-particles under mild conditions

Magnesium borohydride , Mg(BH 4 ) 2 , is ball-milled with Ti nano-particles. Such catalyzed Mg(BH 4 ) 2 releases more hydrogen than pristine Mg(BH 4 ) 2 does during isothermal dehydrogenation at 270, 280, and 290 °C. The catalyzed Mg(BH 4 ) 2 also exhibits better dehydrogenation kinetics than the pristine Mg(BH 4 ) 2 . Based on kinetics model fitting, the activation energy ( E a ) of the catalyzed Mg(BH 4 ) 2 is calculated to be lower than pristine Mg(BH 4 ) 2 . During partial dehydrogenation , the catalyzed Mg(BH 4 ) 2 releases 4.23 wt % (wt%) H 2 for the second dehydrogenation at 270 °C, comparing to 4.05, and 3.75 wt% H 2 at 280, and 290 °C. The reversibility of 4.23 wt% capacity is also one of the highest for Mg(BH 4 ) 2 dehydrogenation under mild conditions such as 270 °C as reported. 4 cycles of Mg(BH 4 ) 2 dehydrogenation are conducted at 270 °C. The capacities degrade during 4 cycles and tend to be stable at about 3.0 wt% for the last two cycles. By analyzing the hydrogen de/absorption products of the catalyzed sample, Mg(BH 4 ) 2 is found to be regenerated after rehydrogenation according to Fourier Transform Infrared (FTIR) spectroscopy. Ti nano-particles can react with Mg(BH 4 ) 2 during ball-milling and de/rehydrogenation. The products include TiH 1.924 , TiB, and TiB 2 , which can improve the dehydrogenation properties of Mg(BH 4 ) 2 from a multiple aspect.