Articulo
New Insight on the Hydrogen Absorption Evolution of the Mg–Fe–H System under Equilibrium Conditions
Autor
Puszkiel, Julián
Castro Riglos, M.
Ramallo López, José Martín
Mizrahi, Martín D.
Gemming, Thomas
Pistidda, Claudio
Arneodo Larochette, Pierre
Bellosta von Colbe, José
Klassen, Thomas
Dornheim, Martin
Gennari, Fabiana
Institución
Resumen
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. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas