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

Abstract

In this work, MgH2 was employed as a starting material rather than Mg. Samples with compositions of 94 wt% MgH2-6 wt% Ni and 85 wt% MgH2-15 wt% Ni were prepared by reactive mechanical grinding. They were named MgH2-6Ni and MgH2-15Ni, respectively. Their hydriding and dehydriding properties were then examined and compared. The activation of MgH2-6Ni and MgH2-15Ni was completed after just the first hydriding (under 12 bar H2)-dehydriding (in vacuum) cycle at 573 K. MgH2-6Ni after reactive mechanical grinding has a larger specific area and a slightly smaller mean particle size (37㎡/g, 1.22 μm) than MgH2-15Ni after reactive mechanical grinding (30㎡/g, 1.24 μm). The activated MgH2-15Ni has slightly lower hydriding rates and a smaller quantity of hydrogen absorbed for 60 min at 573 K under 12 bar H2 than MgH2-6Ni. At 573 K under 1.0 bar H2, the activated MgH2-6Ni at first had a higher dehydriding rate than the activated MgH2-15Ni; however, the activated MgH2-15Ni had higher dehydriding rates after approximately 10 min and a larger quantity of hydrogen desorbed for 60 min than the activated MgH2-6Ni. 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 MgH2. (Received November 2, 2012)