Hydrogen storage properties and mechanisms of as-cast, homogenized and ECAP processed Mg98.5Y1Zn0.5 alloys containing LPSO phase

In this work, three different states (as-cast, homogenized and ECAP processed) of Mg98.5Y1Zn0.5 alloys with high theoretical hydrogen storage capacity (7.2 wt%) were prepared and comminuted into chips by filing. Then their hydrogen storage properties and underlying mechanisms were systematically investigated through experimental and first-principles calculations approaches. The results show that the activation properties of these alloys are enhanced in the order of homogenized, as-cast and ECAP processed states, which is closely associated with the size of filed chips. After activation, the as-cast and ECAP processed samples exhibit the superior hydrogen adsorption/desorption kinetics compared with the homogenized one. Interestingly, the as-cast sample presents the similar or even better kinetics relative to the ECAP processed one. This should be attributed to the more uniform dispersion of in-situ formed YH2 nanohydride in the as-cast alloy, which remarkably boosts the reversible hydrogen storage properties of Mg matrix by the synergistic pinning and catalytic effects. First-principles calculations reveal that the doping of Y not only reduces the activation energy of H-2 dissociation on Mg surface, but also decreases the hydrogen removal energy of H atom from MgH2 bulk, which accounts well for the excellent hydrogen sorption kinetics of Mg98.5Y1Zn0.5 alloys. (C) 2020 Elsevier Ltd. All rights reserved.

Automated summary

This study systematically investigated the hydrogen storage properties of Mg98.5Y1Zn0.5 alloys in different states, finding that the activated as-cast and ECAP processed samples showed superior kinetics compared to the homogenized one, with the as-cast sample exhibiting even better performance than the ECAP processed one. The more uniform dispersion of YH2 nanohydride in the as-cast alloy significantly enhanced the reversible hydrogen storage properties of Mg matrix.