Abstract
Magnesium based alloys are promising solid materials for hydrogen storage. However, it is a real challenge to synthesise hydrogen storage materials with high hydrogen storage capacity and low dehydrogenation temperature. Here, we have performed extensively structural searches for ternary magnesium-based hydrogen storage compounds of with n ranging from 16 to 25 by calypso method and first-principles calculations. We readily identified the experimentally observed hydride and uncovered a stable stoichiometry of with high hydrogen storage capacity of 6.7 wt% and low dehydrogenation temperature of 273 K. The remarkable decrease of the hydrogen release temperature is attributed to the atomic rearrangements in , which forms H-H pairs and has weakened metal-hydrogen chemical bonds compared to the stable and compounds. Our calculations show that undergoes a structural phase transition from its phase to a phase at 75 GPa, and the phase is a potential polyhydride superconductor. The present findings offer insights for understanding the hydrogen storage and release of Mg-Nb-H ternary magnesium-based hydrogen storage compounds, which open avenues for the design and synthesis of magnesium-based hydrogen storage material.
- Received 16 August 2021
- Revised 3 December 2021
- Accepted 13 December 2021
DOI:https://doi.org/10.1103/PhysRevB.104.224510
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