Role of Ti-based catalysts in the dehydrogenation mechanism of magnesium borohydride: A cluster approach

The role of Ti and Ti-based catalysts such as TiCl3 and TiF3 in the dehydrogenation of Mg(BH4)2 has been studied using a cluster approach and density functional theory. The optimized geometry of Mg(BH4)2 clusters mimics the structure it has in the crystalline form, but undergoes significant geometric distortion as well as changes in the natural bond orbital (NBO) charge after the addition of the catalysts. While all the catalysts lower the hydrogen desorption energy, elemental Ti appears to be the best catalyst followed by TiCl3 and TiF3. The lowering of the hydrogen desorption is shown to be due to the weakening of the BH bond which is caused by the interaction of Ti with H and Mg.

► Ti acts as a better catalyst than either TiCl3and TiF3.
► The catalyst weakens the B–H bonding.
► The H atoms need less energy for desorption.