Effects of double substitution on MgH2 hydrogen storage properties: An Ab initio study

Simultaneous improvement of kinetics and thermodynamics based on SrF2 and SrF2@Gr additives on hydrogen sorption in MgH2

“…Therefore, formation of MgF 2 and the associated compound SrH 2 will take place. MgH 2 exhibits an ioniccovalent bond42 with charge densities as Mg 1.509+ and H -0.754 . Khatabi et al42 have shown that the bonding between Mg and H can be weakened by using a suitable catalyst having active d orbitals.MgF 2 type compounds have active d orbitals in their orbital geometry 43 .…”

“…MgH 2 exhibits an ioniccovalent bond42 with charge densities as Mg 1.509+ and H -0.754 . Khatabi et al42 have shown that the bonding between Mg and H can be weakened by using a suitable catalyst having active d orbitals.MgF 2 type compounds have active d orbitals in their orbital geometry 43 . MgF 2 is highly ionic owing to the elemental electronegativity difference of 2.67 (Mg: 1.31, F: 3.98), which is higher as 24 compared to the electronegativity difference for MgH 2 which is 0.79 (Mg: 1.31, H: 2.10) being a polar molecule with high electronegative character and dominant contribution of d orbital will readily interact with polar covalent MgH 2 and destabilize Mg-H bond and improve the kinetics.The MgF 2 because of the above reason will play dominant role in improving the kinetics.…”

Experimentally Observed Nucleation and Growth Behavior of Mg/MgH2 during De/Hydrogenation of MgH2/Mg: A Review

“…Gabis et al [59] believed that for the dehydrogenation of non-metallic (ion-covalent) hydrides, the morphology of "nucleation and growth" is typical due to the fact that only a few nuclei appear relatively slowly and rarely form a skin as a result of the slow (compared to metals) hydrogen desorption, while for metallic ones, the "shrinking core" morphology is more common due to the fact that so many nuclei of the new phase appear and later form a solid skin of the new phase as a result of the fast desorption from the entire surface of the metal parent phase. This can lead to two suggestions: (1) The dehydrogenation of MgH 2 should be controlled by the "nucleation and growth" mechanism because MgH 2 is a semiconductor with a relatively large energy gap of 4.16 eV [60][61][62]; (2) The nucleation rate of Mg from MgH 2 is the major cause that poses the argument between the "nucleation and growth" mechanism and the "shrinking core" mechanism, i.e., the difference in the nucleation rate in various MgH 2 dehydrogenation experiments led to the fact that some experimental results were successfully explained by the "nucleation and growth" model while others by the "shrinking core" model. The evidence for the rationality of the last suggestion may also be served by the finding of Nogita et al [55].…”

Structural, mechanical and thermodynamic stability of the CaIn intermetallic compound for promising hydrogen storage: ab-initio calculations

“…One of the most important applications of intermetallic compounds is hydrogen storage. Hydrogen can be stored in intermetallic compounds, such as AB-type, AB 2 -type and AB 5 -type compounds; some intermetallics that have been studied include magnesium hydrides (MgH 2 ) [9], TiFe, NaAl and LaNi 5 [10,11], where it can be safely and securely stored in a solid-state form. This makes intermetallic compounds an ideal solution for hydrogen storage, as they are able to absorb large amounts of hydrogen at relatively low pressures.…”