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Hydrogen release from Mg(NH2)2-MgH2 through mechanochemical reaction.
Jianjiang Hu1, Guotao Wu, Yongfeng Liu
1Department of Physics, National University of Singapore, Singapore 117542.
The Journal of Physical Chemistry. B
|July 28, 2006
Summary
Mechanical ball milling released 7.4 wt % hydrogen from magnesium amide and hydride. This process formed magnesium imide, which then converted to magnesium nitride and hydrogen via a mild endothermic reaction.
Area of Science:
- Materials Science
- Chemical Engineering
- Hydrogen Storage
Background:
- Magnesium-based materials are promising for hydrogen storage.
- Understanding the reaction pathways is crucial for optimizing hydrogen release.
Purpose of the Study:
- To investigate hydrogen release from a magnesium amide and magnesium hydride mixture.
- To elucidate the intermediate phases and reaction mechanisms during ball milling.
Main Methods:
- Mechanical ball milling of magnesium amide and magnesium hydride (1:2 molar ratio).
- Fourier Transform Infrared Spectroscopy (FTIR) and X-ray Diffraction (XRD) for material characterization.
- Monitoring hydrogen release at various milling stages.
Main Results:
- Achieved 7.4 wt % hydrogen release.
- Identified magnesium imide as an intermediate, formed first.
- Confirmed conversion of magnesium imide and hydride to magnesium nitride and hydrogen.
- Thermodynamic calculations indicated a mild endothermic reaction (3.5 kJ/mol H2).
Conclusions:
- Mechanical ball milling effectively releases hydrogen from magnesium amide and hydride mixtures.
- The reaction proceeds through magnesium imide intermediate formation.
- The process is thermodynamically favorable under mild conditions, suitable for hydrogen storage applications.