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 degrees C, which is 100 degrees C lower than for LiAlH4-MgH2. At 300 degrees 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 degrees C and 20 atm H-2 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. Copyright (C) 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.