Improved hydrogen storage properties of LiAlH₄ by mechanical milling with TiF₃

Dehydrogenation behavior of LiAlH₄ (lithium alanate) admixed with TiF₃ is investigated by pressure-composition-temperature (PCT), fourier transform infrared spectroscopy (FTIR), X-ray Diffraction (XRD), differential scanning calorimetry (DSC) and temperature programmed desorption (TPD). The TiF₃ addition enhances kinetics of LiAlH₄ and decreases the decomposition temperature. The LiAlH₄-2 mol % TiF₃ sample starts to release hydrogen at about 35 °C and the dehydrogenation rate reaches a maximum value at 108.4 °C, compared with 145 °C and 179.9 °C for the as-received LiAlH₄. As for the dehydrogenation kinetics, the LiAlH₄-2 mol % TiF₃ sample releases about 7.0 wt % H₂ at 140 °C within 80 min. In comparison, the as-received LiAlH₄ sample releases only 0.8 wt % hydrogen under the same conditions. The existence of proposed catalyst, Al₃Ti formed in-situ in the process of dehydrogenation, has been confirmed experimentally by XRD measurements. The activation energy of LiAlH₄-2 mol % TiF₃ composite is deduced to be 66.76 kJ mol⁻¹ and 88.21 kJ mol⁻¹ for the first and second reaction stages of LiAlH₄ dehydrogenation. - Highlights: • TiF₃ considerably enhances the dehydrogenation kinetics of LiAlH₄. • TiF₃-doped LiAlH₄ dehydrogenates even at room temperature. • Low activation energy of the dehydrogenation reaction. • Al₃Ti formed in-situ helps to explain the dehydrogenation mechanism