Enhancement of the Hydrogen-Storage Characteristics of Mg by Adding Mg2Ni and Ni to MgH2 via High Energy Ball Milling in Hydrogen Atmosphere

Abstract

In this work, Mg2Ni and Ni were added to MgH2 in order to improve the hydrogen-storage properties of Mg. A 94 wt% MgH2+5 wt% Mg2Ni+1wt% Ni (named 94MgH2+5Mg2Ni+1Ni) sample was prepared by milling in a hydrogen atmosphere in a planetary ball mill for 5 h. The Mg2Ni was hydrided during milling in a hydrogen atmosphere. The 94MgH2+5Mg2Ni+1Ni had an effective hydrogen-storage capacity (the quantity of hydrogen absorbed for 60 min) of near 5 wt%. At n=1, the sample released 0.18 wt% for 2 min, 2.14 wt% for 5 min, 4.65 wt% for 10 min, and 5.46 wt% for 60 min at 648 K. The reactive mechanical grinding of MgH2 with Mg2Ni and Ni is believed to facilitate nucleation (by creating defects, which serve as active sites for nucleation, on the surfaces and inside the Mg particles), increase reactivity with hydrogen (by making clean surfaces), and decrease the diffusion distances of hydrogen atoms (by reducing the particle size of Mg). (Received April 10, 2017; Accepted July 28, 2017)