Hydrogen release from Mg(NH2)2-MgH2 through mechanochemical 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.