Effect of activated alloys on hydrogen discharge kinetics of MgH2 nanocrystals

Abstract

Effect of activated alloys on hydrogen discharge kinetics of MgH₂ nanocrystals AbstractActivated alloys synthesized by arc-melting were examined as catalysts for improving the hydrogen sorption characteristics of nanostructured magnesium hydride, proposed as a reversible hydrogen storage material. The MgH 2 -catalyst absorbing materials were prepared by ball milling of pure MgH 2 with hydrided Zr 47 Ni 53 ,Zr 9 Ni 11 , and other investigated alloys. The nanostructured MgH 2 -intermetallic systems were tested at 250 • C and catalyst addition of eutectoid Zr 47 Ni 53 resulted in the fastest desorption time and highest initial desorption rate. Also, the catalyzed Mg-hydride with activated Zr 9 Ni 11 and Zr 7 Ni 10 phases showed fast desorption kinetics. Moreover, the results demonstrated that the composition of dispersed Zr x Ni y catalysts has a strong influence on the amount of accumulated hydrogen and desorption rate of Mg-nanocomposite.

Effect of LaNi5 and additional catalysts on hydrogen storage properties of Mg

“…Thereby, the energy from ball milling has been probably used to form a new phase instead of reducing the particle size. Similar effects on hydrogenation properties of MgH 2 powders have also been observed by employing other Ni-rich alloys [11].…”

“…However, it is more difficult to improve the desorption kinetics, and it has been mostly investigated at high temperatures (≥280 • C). More recently, Dehouche et al [11] reported that activated Zr Ni alloys have significant effect in enhancing the desorption kinetics of ball milled MgH 2 at 250 • C. Moreover, a remarkable improvement in desorption kinetics of ball milled MgH 2 at 200 • C under vacuum was also reported by Kojima et al [12] using nano-Ni/Al 2 O 5 /C catalysts composite.…”

Thermodynamic Properties, Hysteresis Behavior and Stress-Strain Analysis of MgH2 Thin Films, Studied over a Wide Temperature Range

“…At high temperatures, T ≥ 523 K, the ratio between absorption and desorption equilibrium pressures in films becomes essentially the same as in bulk [3,26], i.e., P abs /P des ≈ 2, proving that thin film optical results are in line with the bulk volumetric data. At lower temperatures (T < 423 K) the difference in hysteresis between thin films and bulk becomes much more pronounced.…”

“…The enthalpy of hydride decomposition, −71.0 ± 4.2 kJ/molH 2 , is relatively close to the electrochemistry data, but in a disagreement with the hydrogenography. [3] and MgH 2 -V 3at.%-Ti 2at.% [26], thin [24] and thick MgH 2 films [25] are shown for comparison. Red diamonds are the calculated absorption and desorption equilibrium pressures from the Van't Hoff equation using Pedersen [22] and Stampfer [11] thermodynamic parameters, respectively.…”

Hydrogen sorption kinetics of magnesium hydride enhanced by the addition of Zr 8 Ni 21 alloy

“…Dehouche et al observed that MgH 2 ball-milled with some Zr-Ni alloys exhibited an improved a/d kinetics, which also depended on the stoichiometry of the alloy [11]. More precisely, the eutectoid composition Zr 36 Ni 64 formed by the two crystalline phases Zr 7 Ni 10 and Zr 8 Ni 21 [12] showed a faster kinetics than Zr 7 Ni 10 and Zr 9 Ni 11 .…”