Journal
INTERNATIONAL JOURNAL OF HYDROGEN ENERGY
Volume 46, Issue 7, Pages 5441-5448Publisher
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.ijhydene.2020.11.044
Keywords
Hydrogen storage; Magnesium alloys; Crystal structure; Phase transformations; High pressure
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The study investigated the formation of metastable gamma-MgH2 under ultra-high pressure, which has a lower dehydrogenation temperature and high hydrogen storage capacity compared to alpha-MgH2. Application of ultra-high pressure facilitated the formation of gamma-MgH2, showing its potential as a future hydrogen storage material.
The formation of metastable gamma-MgH2 upon application of ultra-high pressure and its dehydrogenation properties were studied. Magnesium-nickel alloy (14 wt.% Ni) was hydrogenated and compressed at ultra-high pressures of 2.5 and 4 GPa. The phase composition and desorption properties of the products were investigated. Powder X-ray diffraction indicated that some alpha-MgH2 converted to gamma-MgH2 during compression. This resulted in the onset of hydrogen desorption at 60 degrees C under vacuum. Our findings thus show that application of ultra-high pressure can facilitate the formation of gamma-MgH2, which has a lower dehydrogenation temperature (<= 200 degrees C) than alpha-MgH2, which desorbs at temperatures above 300 degrees C. The metastable phase possessed a high hydrogen storage capacity of at least 4.5 wt.%. These properties revealed the potential of gamma-MgH2 as a future hydrogen storage material. (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.
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