Dimagnesium iron(II) hydride, Mg2FeH6, containing octahedral FeH64- anions

Didisheim, J.-J.; Zolliker, Peter; Yvon, K.; Fischer, P.; Schefer, J.; Gubelmann, M.; Williams, A. F.

doi:10.1021/ic00181a032

Cited by 295 publications

(208 citation statements)

References 3 publications

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“…The similarity between the spectra of the Fe-Mg and MnMg hydrides is due to the fact that both ternary hydrides contain an octahedral MH 6 unit. The higher frequencies of the FeH 6 4-vibrations relative to those for MnH 6 5-are consistent with the higher positive charge on Fe (+2) vs. Mn (+1), and shorter Fe-H bond length (1.49 Å vs. 1.63 Å). In all cases, the frequency ratios between corresponding peaks in the hydride and deuteride spectra range from 1.25 to 1.37.…”

supporting

confidence: 70%

“…3 In all of these systems, a thin Pd overlayer (generally > 5 nm) is applied to catalyze absorption and desorption of hydrogen and to protect the readily oxidized rare earth and/or Mg from oxidation. Infrared internal reflectance spectroscopy was used to characterize the transparent Ni-Mg hydride films as a mixture of Mg 2 8 and Mg 2 FeH 6 (E g = 1.8 eV) 9 support experimental evidence 4,6 for semiconductor behavior in these materials. Mg 3 MnH 7 (calculated Eg = 2.56 eV) 10 is orange in color, 7 and is also presumably semiconducting.…”

mentioning

confidence: 84%

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Mixed metal films with switchable optical properties

Richardson¹,

Slack²,

Farangis³

et al. 2002

Applied Physics Letters

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Thin, Pd-capped metallic films containing magnesium and first row transition metals (Mn, Fe, Co) switch reversibly from their initial reflecting state to visually transparent states when exposed to gaseous hydrogen or following cathodic polarization in an alkaline electrolyte. Reversion to the reflecting state is achieved by exposure to air or by anodic polarization. The films were prepared by co-sputtering from one magnesium target and one manganese, iron, or cobalt target. Both the dynamic optical switching range and the speed of the transition depend on the magnesium-transition metal ratio. Infrared spectra of films in the transparent, hydrided (deuterided) states support the presence of the intermetallic hydride phases Mg 3 MnH 7 , Mg 2 FeH 6 , and Mg 2 CoH 5 . * Following the discovery of the switchable mirror phenomenon in yttrium and lanthanum hydrides by Huiberts et al., 1 similar behavior was reported in rare earth-magnesium alloy films. 2 Recently, metaltransparent hydride switching was also found in nickel-magnesium thin films. 3 In all of these systems, a thin Pd overlayer (generally > 5 nm) is applied to catalyze absorption and desorption of hydrogen and to protect the readily oxidized rare earth and/or Mg from oxidation. Infrared internal reflectance spectroscopy was used to characterize the transparent Ni-Mg hydride films as a mixture of Mg 2 NiH 4 and MgH 2 . 3 Other ternary hydrides containing magnesium and a first row transition metal include Mg

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supporting

confidence: 70%

mentioning

confidence: 84%

Mixed metal films with switchable optical properties

Richardson¹,

Slack²,

Farangis³

et al. 2002

Applied Physics Letters

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show abstract

“…A green color was also reported when sintering process was used to synthesize Mg 2 FeH 6 from a 2Mg-Fe composition 3,4 . Figure 7a shows that the 3Mg-Fe powder is mainly constituted by the Mg 2 FeH 6 phase, having a mean crystallite size of 13 nm.…”

Section: Reactive Milling Of 3mg-fementioning

confidence: 78%

“…Magnesium powder (-20 + 100 mesh, 99.8%), iron powder (-22 mesh, 99.998%) and iron granules (1-2 mm, 99.98%), were provided by Alfa Aesar. Magnesium was mixed with granulated or powdered iron and loaded into a stainless steel vial of 160 cm 3 . After three atmosphere cleaning cycles, consisting of evacuation and argon injection, the milling vial was filled with hydrogen (99.999%) at 3MPa of pressure.…”

Section: Methodsmentioning

confidence: 99%

Mg2FeH6-based nanocomposites with high capacity of hydrogen storage processed by reactive milling

et al. 2012

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The compound Mg 2 FeH 6 was synthesized from a 2Mg-Fe mixture in a single process through high-energy ball milling under hydrogen atmosphere at room temperature. The complex hydride was prepared from Mg powder and granulated or powdered Fe using a planetary mill. The phase evolution during different milling times was performed by X-rays diffraction technique. The dehydrogenation behavior of the hydride was investigated through simultaneous thermal analyses of differential scanning calorimetry and thermogravimetry coupled with mass spectrometer. The use of powdered iron as starting material promoted conversion to complex hydride at shorter milling times than when granulated iron was used, nevertheless, after 24 hours of milling the 2Mg-Fe (powdered or granulated) mixtures presented similar dehydrogenation behavior. The hydrogen absorption during milling was on average 3.2 wt. (%), however, changing the proportions of the reagents to 3Mg-Fe a Mg 2 FeH 6 -MgH 2 based nanocomposite with higher density of hydrogen (5.2 wt. (%)) was obtained.

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“…For the preparation of Mg 2 FeH 6 compounds, many methods such as sintering the 2Mg+Fe mixture under high pressure hydrogen 5,6) and mechanical milling the 2Mg+Fe or 2MgH 2 +Fe mixture [7][8][9][10][11][12][13][14] have been developed. The Mg 2 FeH 6 compound has been first synthesized and described in 1984.…”

Section: Introductionmentioning

confidence: 99%

Synthesis and Hydrogen Storage Behaviour of Pure Mg<SUB>2</SUB>FeH<SUB>6</SUB> at Nanoscale

et al. 2011

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Pure Mg 2 FeH 6 compounds with two different morphologies have been successfully synthesized directly by mechanical milling (MM) and sintering of a mixture of 2Mg+Fe nanoparticles under an H 2 atmosphere, respectively. The successful preparation of pure Mg 2 FeH 6 can be attributed to the small particle sizes of Mg and Fe nanoparticles prepared by hydrogen plasma-metal reaction (HPMR), which provides shorter diffusion distance for hydrogen and the metals. The X-ray diffraction (XRD) and scanning electron microscopy (SEM) results show that the Mg 2 FeH 6 synthesized by mechanical milling has larger particle size but smaller crystallite size compared with the Mg 2 FeH 6 synthesized by sintering. The Mg 2 FeH 6 synthesized by mechanical milling can desorb more than 4.5 mass% hydrogen in 10 min under an initial hydrogen pressure of 0.001 bar at 573 K. Compared with the Mg 2 FeH 6 synthesized by sintering under the same conditions as the Mg 2 FeH 6 synthesized by mechanical milling, it is suggested that decrease of crystallite size is beneficial for enhancing desorption property of Mg 2 FeH 6 .

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Dimagnesium iron(II) hydride, Mg2FeH6, containing octahedral FeH64- anions

Cited by 295 publications

References 3 publications

Mixed metal films with switchable optical properties

Mixed metal films with switchable optical properties

Mg2FeH6-based nanocomposites with high capacity of hydrogen storage processed by reactive milling

Synthesis and Hydrogen Storage Behaviour of Pure Mg<SUB>2</SUB>FeH<SUB>6</SUB> at Nanoscale

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