| Zdroj: |
Dou, X, Kuang, X, Sun, W, Jiang, G, Lu, C & Hermann, A 2021, ' Ternary Mg-Nb-H polyhydrides under high pressure ', Physical Review B, vol. 104, no. 22, 0224510 . https://doi.org/10.1103/PhysRevB.104.224510 |
| Popis: |
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 Mg7NbHn with n ranging from 16 to 25 by calypso method and first-principles calculations. We readily identified the experimentally observed Mg7NbH16 hydride and uncovered a stable stoichiometry of Mg7NbH19 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 Mg7NbH19, which forms H-H pairs and has weakened metal-hydrogen chemical bonds compared to the stable Mg7NbH16 and MgH2 compounds. Our calculations show that Mg7NbH16 undergoes a structural phase transition from its P¯42m phase to a Fm¯3m phase at 75 GPa, and the Fm¯3m 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. |
