The effect of K2SiF6 on the MgH2 hydrogen storage properties.

The catalytic effect of K 2 SiF 6 on MgH 2 was first timely studied. The MgH 2 + 5 wt.% K 2 SiF 6 was prepared via the ball milling technique. The catalyst had lessened the initial decomposition temperature by 134 °C and 48 °C as compared to both pristine and milled MgH 2 samples, respectively. In 2 minutes, 4.5 wt.% of hydrogen was absorbed (250 °C) by the doped composite, which was 0.8 wt.% higher than the milled MgH 2. Meanwhile, for the desorption kinetics (320 °C, 1 atm), the amount of desorbed hydrogen was increased by 2.4 wt.% and 2.3 wt.% for the first 10 and 20 minutes. Besides, contracting volume and Johnson-Mehl-Avrami models were used to analyse the kinetics sorptions. The decomposition activation energy calculated based on Kissinger equation was 114 kJ/mol. As for the active species, Mg 2 Si, MgF 2 and KH were formed during the heating process. These active species are speculated to be responsible for the improvement of the hydrogenation properties of the composite. [ABSTRACT FROM AUTHOR]