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Among the factors which restrict the large-scale utilization of magnesium-based hydride as a hydrogen storage medium, the high operating temperature, slow kinetics, and air stability in particular are key obstacles. In this work, a novel method, namely hydriding combustion synthesis plus short-term mechanical milling followed by air exposure, was proposed to synthesize air stable and autocatalytic magnesium nickel hydride (Mg2NiH4), which shows excellent hydrogen absorption/desorption kinetics, capacity retention and oxidation resistance. The short-term-milled Mg2NiH4 can desorb 2.97 wt.% hydrogen within 500 s at 230 °C. Even after exposure under air atmosphere for 67 days, it can still desorb 2.88 wt.% hydrogen within 500 s at 230 °C. The experimental and theoretical results both indicated that the surface of as-milled Mg2NiH4 was easy to be oxidized under air atmosphere. However, the in-situ formed Ni during air exposure of Mg2NiH4 improved the hydrogen desorption kinetics, and the formed surface passivation layer maintained the hydrogen storage capacity and avoided further poisoning, which we called autocatalytic and self-protective effect. Such a novel dual effect modified the reaction activity and oxidation resistance of the air-exposed Mg2NiH4. Our findings provide useful insights into the design and preparation of air stable metal-based hydride for large-scale utilization and long-term storage.

Publication history
Copyright
Acknowledgements

Publication history

Received: 09 July 2021
Revised: 13 August 2021
Accepted: 26 August 2021
Published: 05 October 2021
Issue date: March 2022

Copyright

© Tsinghua University Press and Springer-Verlag GmbH Germany, part of Springer Nature 2021

Acknowledgements

Acknowledgements

This work was supported by the National Natural Science Foundation of China (Nos. 51771092, 52071177, and 21975125), Six Talent Peaks Project in Jiangsu Province (No. 2018-XNY-020) and the Priority Academic Program Development (PAPD) of Jiangsu Higher Education Institutions. The computational resources generously provided by the High Performance Computing Center of Nanjing Tech University are greatly appreciated.

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