Enhanced hydrogen storage performance of LiAlH4–MgH2–TiF3 composite
The mutual destabilization of LiAlH4 and MgH2 in the reactive hydride composite LiAlH4–MgH2 is attributed to the formation of intermediate compounds, including Li–Mg and Mg–Al alloys, upon dehydrogenation. TiF3 was doped into the composite for promoting this interaction and thus enhancing the hydrogen sorption properties. Experimental analysis on the LiAlH4–MgH2–TiF3 composite was performed via temperature-programmed desorption (TPD), differential scanning calorimetry (DSC), isothermal sorption, pressure-composition isotherms (PCI), and powder X-ray diffraction (XRD). For LiAlH4–MgH2–TiF3 composite (mole ratio 1:1:0.05), the dehydrogenation temperature range starts from about 60 °C, which is 100 °C lower than for LiAlH4–MgH2. At 300 °C, the LiAlH4–MgH2–TiF3 composite can desorb 2.48 wt% hydrogen in 10 min during its second stage dehydrogenation, corresponding to the decomposition of MgH2. In contrast, 20 min was required for the LiAlH4–MgH2 sample to release so much hydrogen capacity under the same conditions. The hydrogen absorption properties of the LiAlH4–MgH2–TiF3 composite were also improved significantly as compared to the LiAlH4–MgH2 composite. A hydrogen absorption capacity of 2.68 wt% under 300 °C and 20 atm H2 pressure was reached after 5 min in the LiAlH4–MgH2–TiF3 composite, which is larger than that of LiAlH4–MgH2 (1.75 wt%). XRD results show that the MgH2 and LiH were reformed after rehydrogenation.