Significantly improved dehydrogenation of LiBH4 destabilized by TiF3

Abstract

The hydrogen storage properties of LiBH₄ ball milled with TiF₃ were investigated. It was found that the LiBH₄–TiF₃ mixture exhibited significantly improved dehydrogenation properties. For example, the LiBH₄–TiF₃ (mole ratio: 3 : 1) sample started to release hydrogen at around 100 °C, and the hydrogen desorption capacity reached 5.0 wt% at 250 °C. Furthermore, the dehydrogenated product can be partially rehydrogenated at 100 atm H₂ and 350 °C. X-Ray diffraction (XRD), infrared (IR) spectroscopy and X-ray photoelectron spectroscopy (XPS) characterizations revealed that the decreased dehydrogenation conditions in the LiBH₄–TiF₃ system resulted from an exothermic reaction of 3LiBH₄ + TiF₃ → 3LiF + TiB₂ + B + 6H₂, which improved both its thermodynamics and kinetics. As the above reaction is exothermic, the reverse reaction is not feasible, further investigations indicated that the rehydrogenation may be due to the formation of another borohydride.