Effect of K2TiF6 additive on the hydrogen storage properties of 4MgH2-LiAlH4 destabilized system

In this study, the hydrogen storage properties and reaction mechanism of 4MgH2-LiAlH4 destabilized system with K2TiF6 additive were studied for the first time. It was found that the addition of K2TiF6 resulted in both decreased decomposition temperature, and enhanced sorption kinetics, compared to undoped 4MgH2 + LiAlH4. The onset dehydrogenation temperature of the 10 wt% K2TiF6-doped 4MgH2 + LiAlH4 sample was reduced by about 50 °C compared to the as-milled undoped 4MgH2 + LiAlH4, and the saturation of dehydrogenation process for the K2TiF6-added 4MgH2 + LiAlH4 sample was achieved within 25 min compared with 45 min for the undoped sample. From the Kissinger plot, the activation energy for the MgH2-relevent decomposition was reduced from 126 kJ/mol for 4MgH2-LiAlH4 composite to 107 kJ/mol after addition of K2TiF6. The differential scanning calorimetry measurements indicated that the enthalpy change in the 4MgH2 + LiAlH4 composite system was unaffected by the addition of K2TiF6. It was believed that the formation of Ti-containing and Al-containing species together with a small amount of Li-containing species during the ball milling or the dehydrogenation process might be actually responsible for the catalytic effects, and thus, further improved the dehydrogenation of the K2TiF6-added 4MgH2 + LiAlH4 composite system.