Improvement of hydrogen-storage properties of MgH2 by Ni, LiBH4, and Ti addition

Abstract

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–2LiBH4–2Ti was prepared by reactive mechanical grinding. MgH2–10Ni–2LiBH4–2Ti after reactive mechanical grinding contained MgH2, Mg, Ni, TiH1.924, and MgO phases. The activation of MgH2–10Ni–2LiBH4–2Ti for hydriding and dehydriding reactions was not required. At the number of cycles, n = 2, MgH2–10Ni–2LiBH4–2Ti 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 H2. At n = 1, MgH2–10Ni–2LiBH4–2Ti 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 H2. The PCT (Pressure–Composition–Temperature) curve at 593 K for MgH2–10Ni–2LiBH4–2Ti 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–2LiBH4–2Ti at n = 1 was analyzed.