International Journal of Hydrogen Energy, Vol.38, No.4, 1910-1917, 2013
Improvement of hydrogen-storage properties of MgH2 by Ni, LiBH4, and Ti addition
In this work, differently from our previous work, MgH2 instead of Mg was used as a starting material. Ni, Ti, and LiBH4 with a high hydrogen-storage capacity of 18.4 wt% were added. A sample with a composition of MgH2-10Ni-2LiBH(4)-2Ti was prepared by reactive mechanical grinding. MgH2-10Ni-2LiBH(4)-2Ti after reactive mechanical grinding contained MgH2, Mg, Ni, TiH1.924, and MgO phases. The activation of MgH2-10Ni-2LiBH(4)-2Ti for hydriding and dehydriding reactions was not required. At the number of cycles, n = 2, MgH2-10Ni-2LiBH(4)-2Ti absorbed 4.09 wt% H for 5 min, 4.25 wt% H for 10 min, and 4.44 wt % H for 60 min at 573 K under 12 bar H-2. At n = 1, MgH2-10Ni-2LiBH(4)-2Ti desorbed 0.13 wt % H for 10 min, 0.54 wt% H for 20 min, 1.07 wt% H for 30 min, and 1.97 wt% H for 60 min at 573 K under 1.0 bar H-2. The PCT (Pressure-Composition-Temperature) curve at 593 K for MgH2-10Ni-2LiBH(4)-2Ti showed that its hydrogen-storage capacity was 5.10 wt%. The inverse dependence of the hydriding rate on temperature is partly due to a decrease in the pressure differential between the applied hydrogen pressure and the equilibrium plateau pressure with the increase in temperature. The rate-controlling step for the dehydriding reaction of the MgH2-10Ni-2LiBH(4)-2Ti at n = 1 was analyzed. Copyright (C) 2012, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.
Keywords:Starting material MgH2;Ni;LiBH4;and Ti addition;Reactive mechanical grinding;Activation;Mg2Ni formation