Effect of LaCl3 addition on the hydrogen storage properties of MgH2

In this study, the effect of LaCl3 on the hydrogen storage properties of MgH2 prepared by ball milling was investigated for the first time. It was found that the MgH2 + 10 wt.% LaCl3 sample started to decompose at around 300 degrees C, which was 50 C lower than in as-milled MgH2. For desorption kinetics, the LaCl3-doped MgH2 composite sample released about 4.2 wt.% hydrogen at 320 degrees C after 5 min dehydrogenation, while the as-milled MgH2 only released about 0.2 wt.% hydrogen for the same temperature and time. Meanwhile, a hydrogen absorption capacity of 5.1 wt.% was reached at 300 degrees C in 2 min for the LaCl3-doped MgH2 sample. In contrast, the ball-milled MgH2 only absorbed 3.8 wt.% hydrogen at 300 degrees C in 2 min. The activation energy of dehydrogenation was 166.0 14/mol for the as-milled MgH2 and 143.0 klimol for the 10 wt.% LaCl3-added MgH2, indicating that the LaCl3 additive decreased the activation energy for the hydrogen desorption of the MgH2. The improved hydrogen storage properties of the MgH2 in the presence of LaCl3 is believed to be due to the catalytic effects of the La Mg alloy and MgCl2 that were formed in situ during the heating process. (C) 2014 Elsevier Ltd. All rights reserved.