Catalytic effects of metal (Ti) addition on the dehydrogenation properties of aluminium hydride

Due to its high hydrogen capacity (10.1 wt.%), aluminium hydride (AlH₃) is considered as a possible material for on-board hydrogen storage applications. However, several factors, such as a high decomposition temperature and sluggish desorption kinetics, limit this benefit and render this material unmarketable. To overcome these limitations, numerous studies have been conducted, such as using mechanical ball milling to reduce the particle size and adding dopants or catalysts. In this work, the effect of metal (Ti) on the dehydrogenation properties of AlH₃ has been investigated for the first time. The results show that Ti lowered the initial decomposition temperature and sped up the process of AlH₃ desorption. The 10 wt.% Ti-doped AlH₃ sample's initial decomposition temperature dropped from 145 °C to 120 °C compared to that of as-received AlH₃. For the desorption kinetic measurements at 100 °C, the 10 wt.% Ti-doped AlH₃ sample could desorb about 4.0 wt.% of H₂ in 20 min compared to 0.1 wt.% for the as-received AlH₃. After Ti was added, the activation energy for the dehydrogenation process of AlH₃ that was determined by Kissinger analysis decreased. From the X-ray diffraction analysis, we found that Ti did not react with AlH₃ during the mechanical milling and heating (desorption) processes. Ti is believed to play a catalytic role by inducing Ti-H interaction and weakening Al-H bonding, thus improving the dehydrogenation properties of AlH₃.