The effect of K2SiF6 on the MgH2 hydrogen storage properties

Abstract The catalytic effect of K2SiF6 on MgH2 was first timely studied. The MgH2 + 5 wt.% K2SiF6 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 MgH2 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 MgH2. 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, Mg2Si, MgF2 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.