Influence of TiF3 catalyst on the enhancement of hydrogen storage properties of Mg-Na-Al-Li-B composite system

Abstract

This study emphasizes the catalytic function of TiF3 on hydrogen storage properties and the reaction mechanism of the MgH2-Na3AlH6-LiBH4 produced by employing the ball-milling technique, which has a molar ratio of 1:1:4. It discovered that the mixture of Na3AlH6 and LiBH4 reacted through a metathesis reaction and transformed into Li3AlH6 and NaBH4 composite upon the ball milling procedure. MgH2-Li3AlH6-NaBH4 destabilized system with TiF3 catalyst has displayed four decomposition tiers throughout the heating procedure. The initial tier of hydrogen release in the composite occurs at temperatures of 100 °C and 75 °C lower than in the catalyst-free composite. Continuous heating resulted in two through four dehydrogenation tiers, with an overall capacity of 10.1 wt% hydrogens released (at temperatures of 200 °C, 350 °C, and 400 °C, respectively). In contrast to the Mg-Na-Al-Li-B-H catalyst-free composite, incorporating the TiF3 catalyst demonstrates a faster hydrogen uptake and release rate. The apparent activation energy (Ea) for the dissociation of Li3AlH6, MgH2, and NaBH4 in the composite with TiF3 catalyst was remarkably abridged compared to the catalyst-free ternary system (Kissinger plot; 23, 20, and 13 kJ/mol, respectively for doped composite). TiF3's considerable catalytic performance is ascribed to the in-situ production of AlTi and AlF phases during the dehydrogenation process of TiF3 and Li3AlH6. Once generated, the AlTi and AlF phase serves as a genuine catalyst in the MgH2-Na3AlH6-4LiBH4-TiF3 ternary system.