Effects of Titanium-Containing Additives on the Dehydrogenation Properties of LiAlH₄: A Computational and Experimental Study

Abstract

Metal hydrides are attractive materials for use in thermal storage systems to manage excessive transient heat loads and for hydrogen storage applications. This paper presents a combined computational and experimental investigation of the influence of Ti, TiO 2, and TiCl 3 additives on the dehydrogenation properties of milled LiAlH 4 . Density functional theory (DFT) is used to predict the effect of Ti-containing additives on the electronic structure of the region surrounding the additive after its adsorption on the LiAlH 4 (010) surface. The electron distribution and charge transfer within the LiAlH 4 /additive system is evaluated. Electronic structure calculations predict covalent-like bonding between the Ti atom of the adsorbate and surrounding H atoms. The hydrogen (H) binding energy associated with the removal of the first H from the modified LiAlH 4 surface is calculated and compared with experimental dehydration activation energies. It is seen that the weaker H binding corresponds to the larger amount of charge transferred from the Ti atom to adjacent H atoms. A reduction in charge transfer between the Al atom and surrounding H atoms is also observed when compared to charge transfer in the unmodified LiAlH 4 surface. This reduction in charge transfer between Al–H weakens the covalent bond within the [AlH 4 ] − tetrahedron, which in turn reduces the dehydrogenation temperature exhibited by LiAlH 4 when Ti-containing additives are used.