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

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 (T-dec) and activation energies (E-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 T-dec and E-A, TiO2-doped LiAlH4 produced a decrease in T-dec and E-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.