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

• Published in: Journal of power sources Vol. 322; pp. 179 - 186
• Main Authors: Chen, Haipeng, Yu, Hao, Zhang, Qianqian, Liu, Bogu, Liu, Pei, Zhou, Xinpei, Han, Zongying, Zhou, Shixue
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.08.2016
• Subjects: Anions; Anthracite; Atomic clusters; Cations; Dehydriding mechanism; Hydrides; Incorporation; Iron; Magnesium hydride; Performance enhancement; Surface chemistry; Surface structure; Dehydriding mechanism; Incorporation; Magnesium hydride; Surface structure
• ISSN: 0378-7753; 1873-2755
• DOI: 10.1016/j.jpowsour.2016.05.031

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. [Display omitted] •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.