Improved Dehydrogenation Properties of Ti-Doped LiAlH₄: Role of Ti Precursors

Abstract

The dehydrogenation properties of LiAlH₄ doped with different Ti precursors (Ti, TiO₂, and TiCl₃) via ball milling are investigated. The results not only show significant decreases in the decomposition temperatures (<i>T</i>_dec) and activation energies (<i>E</i>_A) of the first two dehydrogenation reaction steps of LiAlH₄ by doping with TiO₂ or TiCl₃, but also reveal how each Ti precursor affects the dehydrogenation process. Although doping LiAlH₄ with TiCl₃ induced the largest decrease in <i>T</i>_dec and <i>E</i>_A, TiO₂-doped LiAlH₄ produced a decrease in <i>T</i>_dec and <i>E</i>_A that is quite close to the TiCl₃-doped sample as well as superior short-term stability, suggesting that doping with TiO₂ has certain advantages over doping with TiCl₃. Further, the underlying mechanisms associated with the Ti precursors during the dehydrogenation reaction of LiAlH₄ have been studied using quasi in situ X-ray photoelectron spectroscopy. The results reveal that the Ti⁴⁺ and Ti³⁺ reduction processes and the segregation of Li cations to the surface of LiAlH₄ during ball milling play critical roles in the improved dehydrogenation properties observed