Enhancement Effect of Bimetallic Amide K<sub>2</sub>Mn(NH<sub>2</sub>)<sub>4</sub> and In-Situ Formed KH and Mn<sub>4</sub>N on the Dehydrogenation/Hydrogenation Properties of Li–Mg–N–H System
oleh: Gökhan Gizer, Hujun Cao, Julián Puszkiel, Claudio Pistidda, Antonio Santoru, Weijin Zhang, Teng He, Ping Chen, Thomas Klassen, Martin Dornheim
| Format: | Article |
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| Diterbitkan: | MDPI AG 2019-07-01 |
Deskripsi
In this work, we investigated the influence of the K<sub>2</sub>Mn(NH<sub>2</sub>)<sub>4</sub> additive on the hydrogen sorption properties of the Mg(NH<sub>2</sub>)<sub>2</sub> + 2LiH (Li−Mg−N−H) system. The addition of 5 mol% of K<sub>2</sub>Mn(NH<sub>2</sub>)<sub>4</sub> to the Li−Mg−N−H system leads to a decrease of the dehydrogenation peak temperature from 200 °C to 172 °C compared to the pristine sample. This sample exhibits a constant hydrogen storage capacity of 4.2 wt.% over 25 dehydrogenation/rehydrogenation cycles. Besides that, the in-situ synchrotron powder X-ray diffraction analysis performed on the as prepared Mg(NH<sub>2</sub>)<sub>2</sub> + 2LiH containing K<sub>2</sub>Mn(NH<sub>2</sub>)<sub>4</sub> indicates the presence of Mn<sub>4</sub>N. However, no crystalline K-containing phases were detected. Upon dehydrogenation, the formation of KH is observed. The presence of KH and Mn<sub>4</sub>N positively influences the hydrogen sorption properties of this system, especially at the later stage of rehydrogenation. Under the applied conditions, hydrogenation of the last 1 wt.% takes place in only 2 min. This feature is preserved in the following three cycles.