Formation of Mg2Ni/Cu phase and de-/hydrogenation behavior of Mg91Ni9-xCux alloy at moderate temperatures

Xin Ding, Ruirun Chen, Xiaoyu Chen, Wenchao Cao, Yanqing Su, Hongsheng Ding and Jingjie Guo

Renewable Energy, 2020, vol. 166, issue C, 81-90

Abstract: The addition of Cu is proved effective to improve the hydrogen storage property of hypoeutectic Mg–Ni alloy. In this study, Mg91Ni9-xCux (x = 3, 4.5, and 6) alloys are prepared by melting, and their isothermal de-/hydrogenation properties are characterized, especially at moderate temperatures. The results show that a much thicker eutectic structure is formed in Mg91Ni3Cu6 alloy, and the hydrogen storage properties deteriorate gradually with the Cu addition. Cu atoms can increase the lattice constants of Mg2Ni and Mg6.33Ni by replacing Ni atoms. After repeated absorption and desorption cycles, Mg2Ni/Cu crystals are preserved by forming high-density Mg2Ni/Cu nanophases, and the diffusion of H atoms and nucleation of hydrides are facilitated. Also, the nucleation of hydrides in Mg91Ni6Cu3 alloy are facilitated by the “synergistic effect”. Comparing with the Mg91Ni4.5Cu4.5 and Mg91Ni3Cu6 alloys, the Mg91Ni6Cu3 alloy shows a higher hydrogen capacity of 5.60 wt % with faster kinetic property at 175 °C under 1 MPa hydrogen. The Mg91Ni6Cu3 hydride shows the faster desorption rate at 225 °C. In Mg91Ni4.5Cu4.5 and Mg91Ni3Cu6 alloys, the Mg2Ni/Cu phases gradually transform into Mg2Cu-like phases, and the independent hydrogenation processes lead to their reduced hydrogen storage capacities.

Keywords: Hydrogen storage; Mg–Ni–Cu alloy; Eutectic structure; Dehydrogenation kinetics (search for similar items in EconPapers)
Date: 2020
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Persistent link: https://EconPapers.repec.org/RePEc:eee:renene:v:166:y:2020:i:c:p:81-90

DOI: 10.1016/j.renene.2020.11.120

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