Enhanced hydrogen storage performance of LiAlH 4–MgH 2–TiF 3 composite

Abstract

The mutual destabilization of LiAlH 4 and MgH 2 in the reactive hydride composite LiAlH 4–MgH 2 is attributed to the formation of intermediate compounds, including Li–Mg and Mg–Al alloys, upon dehydrogenation. TiF 3 was doped into the composite for promoting this interaction and thus enhancing the hydrogen sorption properties. Experimental analysis on the LiAlH 4–MgH 2–TiF 3 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 LiAlH 4–MgH 2–TiF 3 composite (mole ratio 1:1:0.05), the dehydrogenation temperature range starts from about 60 °C, which is 100 °C lower than for LiAlH 4–MgH 2. At 300 °C, the LiAlH 4–MgH 2–TiF 3 composite can desorb 2.48 wt% hydrogen in 10 min during its second stage dehydrogenation, corresponding to the decomposition of MgH 2. In contrast, 20 min was required for the LiAlH 4–MgH 2 sample to release so much hydrogen capacity under the same conditions. The hydrogen absorption properties of the LiAlH 4–MgH 2–TiF 3 composite were also improved significantly as compared to the LiAlH 4–MgH 2 composite. A hydrogen absorption capacity of 2.68 wt% under 300 °C and 20 atm H 2 pressure was reached after 5 min in the LiAlH 4–MgH 2–TiF 3 composite, which is larger than that of LiAlH 4–MgH 2 (1.75 wt%). XRD results show that the MgH 2 and LiH were reformed after rehydrogenation.