Enhancement in dehydriding performance of magnesium hydride by iron incorporation: A combined experimental and theoretical investigation

• Atomic Fe from milling balls can be incorporated onto MgH2 surface.
• Atomic Fe and H anions can form atomic clusters FeH4/FeH2 on MgH2 surface.
• MgH2 with Fe incorporation shows a dropped dehydriding energy barrier.
• Catalytic reason of atomic Fe lies in its moderate strength of electron attraction.

Structural change and dehydriding mechanism of MgH2 with atomic Fe incorporation from reactive ball milling are characterized and simulated by first-principles calculation. Two kinds of hydrides β- and γ-MgH2 are formed from Mg powders under hydrogen atmosphere by 3.0 h of milling with pretreated anthracite as milling aid. Experimental studies suggest that the atomic Fe can be incorporated onto MgH2 surface by the shearing effect of Fe-based milling balls on Mg/MgH2 particles. The incorporated Fe has a high dispersity on MgH2 surface and can form atomic clusters FeH4/FeH2 by combining with H anions. The dehydriding reaction of the Fe-incorporated MgH2 begins at hydride surface and shows an enhanced performance with apparent activation energy of 110.3 kJ mol−1. Theoretical studies suggest that the incorporated Fe can act as a bridge that contributes to electron transfer from H anion to Mg cation before H2 molecule formation. The intrinsic reason of atomic Fe in catalyzing dehydriding reaction of MgH2 lies in its moderate strength of electron attraction.

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