Improvement of hydrogenation kinetics and catalytic effects of TiCl3 and TiO2 on MgH2 with LiH metal hydride synthesized by high energy ball milling
K_S. Jung, G_J. Lee, K_S. Lee
Hanyang University, KR
magnesium hydride, lithium hydride, catalyst, TiCl3, TiO2
MgH2 -X wt.% LiH (X=1, 3, 5 and 7) composites were synthesized by high-energy ball milling in order to improve the hydrogenation properties of magnesium hydride. MgH2-3 wt.% LiH sample exhibited the highest hydrogen desorption capacity of 6.44 wt.% at the 1st cycle at 400, but the capacity decreased to 4.58 wt.% after the 5th cycle. This capacity is still lower than that of pure magnesium, however, the kinetics of hydrogen absorption was greatly enhanced from 0.0002 wt.%/sec for pure magnesium to 0.0793 wt.%/sec for the MgH2-3 wt% LiH. To increase the hydrogenation properties of the MgH2-3 wt.% LiH sample, 1 mol % of TiCl3 and TiO2 (rutile) were added as a catalyst. The sample with TiO2 did not change the dehydrogenation temperature, but exhibited better cycle stability showing 5.71 wt.% of hydrogen absorption capacity after the 5th cycle. In case of sample with TiCl3, dehydrogenation temperature of the sample was slightly decreased from 380 to 350 and the hydrogenation kinetics and capacity were greatly enhanced as 0.102 wt.%/sec with capacity of 5.88 wt.% at 250 and 40 atm.
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