Hydrogen-Storage Property Enhancement of Magnesium Hydride by Nickel Addition via Reactive Mechanical Grinding

摘要

In this work, MgH_2 was employed as a starting material rather than Mg. Samples with compositions of 94 wt% MgH_2-6 wt% Ni and 85 wt% MgH_2-15 wt% Ni were prepared by reactive mechanical grinding. They were named MgH_2-6Ni and MgH_2-15Ni, respectively. Their hydriding and dehydriding properties were then examined and compared. The activation of MgH_2-6Ni and MgH_2-15Ni was completed after just the first hydriding (under 12 bar EU-dehydriding (in vacuum) cycle at 573 K. MgH_2-6Ni after reactive mechanical grinding has a larger specific area and a slightly smaller mean particle size (37 m~2/g, 1.22 μm) than MgH_2-15Ni after reactive mechanical grinding (30 m /g, 1.24 μm). The activated MgH_2-15Ni has slightly lower hydriding rates and a smaller quantity of hydrogen absorbed for 60 min at 573 K under 12 bar H_2 than MgH_2-6Ni. At 573 K under 1.0 bar H_2, the activated MgH_2-6Ni at first had a higher dehydriding rate than the activated MgH_2-15Ni; however, the activated MgH_2-15Ni had higher dehydriding rates after approximately 10 min and a larger quantity of hydrogen desorbed for 60 min than the activated MgH_2-6Ni. The decrease in particle size and creation of defects due to Ni addition via reactive mechanical grinding are considered to increase the hydriding and dehydriding rates of MgH_2.