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Metals 2018, 8(11), 967; https://doi.org/10.3390/met8110967

New Insight on the Hydrogen Absorption Evolution of the Mg–Fe–H System under Equilibrium Conditions

1
Department of Physical Chemistry of Materials, Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET) and Centro Atómico Bariloche, Av. Bustillo km 9500, San Carlos de Bariloche P.C. 8400, Argentina
2
Department of Nanotechnology, Institute of Materials Research, Helmholtz–Zentrum Geesthacht, Max-Planck-Straße 1, 21502 Geesthacht, Germany
3
Department of Metalphysics, Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET) and Centro Atómico Bariloche, Av. Bustillo km 9500, San Carlos de Bariloche P.C. 8400, Argentina
4
Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas, INIFTA (CCT La Plata-CONICET, UNLP), Diagonal 113 y Calle 64, 1900 La Plata, Argentina
5
IFW Dresden, Helmholtzstr. 20, 01069 Dresden, Germany
6
Institute of Materials Technology, Helmut Schmidt University, Holstenhofweg 85, 22043 Hamburg, Germany
*
Author to whom correspondence should be addressed.
Received: 11 October 2018 / Revised: 31 October 2018 / Accepted: 12 November 2018 / Published: 19 November 2018
(This article belongs to the Special Issue Metals in Hydrogen Technology)
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Abstract

Mg2FeH6 is regarded as potential hydrogen and thermochemical storage medium due to its high volumetric hydrogen (150 kg/m3) and energy (0.49 kWh/L) densities. In this work, the mechanism of formation of Mg2FeH6 under equilibrium conditions is thoroughly investigated applying volumetric measurements, X-ray diffraction (XRD), X-ray absorption near edge structure (XANES), and the combination of scanning transmission electron microscopy (STEM) with energy-dispersive X-ray spectroscopy (EDS) and high-resolution transmission electron microscopy (HR-TEM). Starting from a 2Mg:Fe stoichiometric powder ratio, thorough characterizations of samples taken at different states upon hydrogenation under equilibrium conditions confirm that the formation mechanism of Mg2FeH6 occurs from elemental Mg and Fe by columnar nucleation of the complex hydride at boundaries of the Fe seeds. The formation of MgH2 is enhanced by the presence of Fe. However, MgH2 does not take part as intermediate for the formation of Mg2FeH6 and acts as solid-solid diffusion barrier which hinders the complete formation of Mg2FeH6. This work provides novel insight about the formation mechanism of Mg2FeH6. View Full-Text
Keywords: magnesium-iron complex hydride; equilibrium conditions; transmission electron microscopy; X-ray spectroscopy; hydrogen-energy storage magnesium-iron complex hydride; equilibrium conditions; transmission electron microscopy; X-ray spectroscopy; hydrogen-energy storage
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Puszkiel, J.; Castro Riglos, M.V.; Ramallo-López, J.M.; Mizrahi, M.; Gemming, T.; Pistidda, C.; Arneodo Larochette, P.; Bellosta von Colbe, J.; Klassen, T.; Dornheim, M.; Gennari, F. New Insight on the Hydrogen Absorption Evolution of the Mg–Fe–H System under Equilibrium Conditions. Metals 2018, 8, 967.

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