Hydriding properties of a nano-/amorphous-structured Mg–Ni–H system

Orimo, Shin Ichi; Fujii, H.; Ikeda, Kazutaka; Fujikawa, Yoshinori; Kitano, Yasuyuki

doi:10.1016/s0925-8388(96)02995-7

Cited by 59 publications

(39 citation statements)

References 14 publications

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“…At this point it becomes interesting to compare the relative charge results for cubic Mg 2 NiH 4 on the one hand and rutile-type MgH 2 on the other hand calculated with the same conditions. In MgH 2 the obtained charges of ∆Q (Mg) = +1.64 and ∆Q(H) = −0.82 show a much more ionic character, close to −1 for H. By contrast, Mg 2 NiH 4 shows results closer to the presently studied model compounds: ∆Q(Mg) = +1.63, ∆Q(Ni) = −0.71 and ∆Q(H) = −0.64. The charge carried by hydrogen is close to the one calculated for MgNiH 2 .…”

Section: Geometry Optimization Cohesive Energies and Charge Transferssupporting

confidence: 46%

“…This result characterizes it as a hydride with 1.9 wt.-% H capacity, smaller than that of Mg 2 NiH 4 (∼ 3.6 wt.-% H). However, from earlier work on amorphous nano-structured Mg-Ni a higher H content of 2.2 wt.-% in the equiatomic region was reported, i. e. with the composition MgNiH 1.84 , close to MgNiH 2 [4]. Yet this amount of maximum hydrogen uptake is the lowest among nickel-based binary equiatomics such as YNi which can absorb up to 4 H per formula unit (FU) [5].…”

Section: Introductionmentioning

confidence: 91%

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Hydrogen Insertion Effects on the Electronic Structure of Equiatomic MgNi Traced by ab initio Calculations

Matar

Alam

Ouaini

2013

Zeitschrift Für Naturforschung B

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For equiatomic MgNi which can be hydrogenated up to the composition MgNiH 1.6 at an absorption/desorption temperature of 200 • C, the effects of hydrogen absorption are approached with the model structures MgNiH, MgNiH 2 and MgNiH 3 . From full geometry optimization and calculated cohesive energies obtained within DFT, the MgNiH 2 composition close to the experimental limit is identified as most stable. Charge density analysis shows an increasingly covalent character of hydrogen: MgNiH (H −0.67 ) → MgNiH 2 (H −0.63 ) → MgNiH 3 (H −0.55 ). While Mg-Ni bonding prevails in MgNi and hydrogenated model phases, extra itinerant low-energy Ni states appear when hydrogen is introduced signaling Ni-H bonding which prevails over Mg-H as evidenced from total energy calculations and chemical bonding analyses.

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Section: Geometry Optimization Cohesive Energies and Charge Transferssupporting

confidence: 46%

Section: Introductionmentioning

confidence: 91%

Hydrogen Insertion Effects on the Electronic Structure of Equiatomic MgNi Traced by ab initio Calculations

Matar

Alam

Ouaini

2013

Zeitschrift Für Naturforschung B

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“…Knowledge of the interaction of hydrogen with metals and intermetallic compounds is not only of great interest due to the excellent hydrogen storage capabilities of many of these materials [1], [2], [3], [4], [5], [6], [7], [8] and [9], but remains a key parameter especially in Pd-catalyzed reactions involving hydrogen. It is well known that Pd readily absorbs hydrogen in its crystal lattice even at low pressure and room temperature [10].…”

Section: Introductionmentioning

confidence: 99%

Hydride formation and stability on a Pd–SiO2 thin-film model catalyst studied by TEM and SAED

Jenewein¹,

Penner²,

Gabasch³

et al. 2006

Journal of Catalysis

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Hydride formation was studied on Pd particles supported on SiO 2 , and the results were evaluated with reference to a corresponding ZnO-promoted Pd/SiO 2 catalyst reported recently. Pd particles (mean size, ~5 nm) were epitaxially grown on NaCl(001) cleavage faces and subsequently covered by a layer of amorphous SiO 2 , thereby maintaining their epitaxial orientation. The films were subjected to various hydrogen and annealing treatments in the temperature regime of 373-873 K, and their stability in an O 2 environment (373-573 K) was also tested. The structural and morphological changes were followed by transmission electron microscopy and selected area electron diffraction. Reduction at 523 K increased the mean particle size considerably and converted the Pd particles into an amorphous hydride phase that decomposed at and above 673 K either by reduction in hydrogen or by annealing in He environment, forming a crystalline Pd 2 Si phase. Oxidative treatments of the Pd-H phase at temperatures above 523 K induce transformation into partially oriented Pd particles. The Pd 2 Si phase was stable under reductive conditions up to 873 K and decomposed into disoriented Pd particles on oxidation at temperatures at and above 573 K. Although the Pd/SiO 2 catalyst can be readily converted into an amorphous hydride phase, it loses its hydrogen storage capability on entering the silicide state at 673 K, and hence no hydride formation was observed. These results are in contrast to previous observations on a corresponding Pd/ZnO/SiO 2 catalyst, where the formation of a well-ordered PdZn alloy prevented the formation of the hydride phase and significantly enhanced the structural stability of the catalyst and its resistance against sintering. In contrast, the Pd/SiO 2 system was converted into the amorphous hydride state under "real" catalytic conditions, for example, during CO 2 hydrogenation at around 523 K.

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“…Orimoi et al [10] produced a large volume of disordered grain boundaries among the grain boundary region of Mg2Ni alloy on the condition of mechanical milling, not only increased the hydrogen storage capacity, but also remain the overall structure of nanocrystals same. Additionally, a large number of theoretical studies discovered that it is useful for Mg2Ni alloy to improve hydrogen storage properties accompanied by the amorphous of disordered grain boundary [11][12]. In addition, Kohn et al [13] found that Mg2Ni exhibit superior hydrogen absorption properties due to its nanocrystalline structure.…”

Section: Introductionmentioning

confidence: 99%

Thermal Stability of the Mg2Ni-Based Hydrogen Storage Alloy Doped Ti Element

Li¹,

Zhang²,

Kong³

et al. 2016

IJHT

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Crystal structures, electronic structures, thermal stability and dehydrogenation energy of Mg-based hydrogen storage materials were investigated via the first-principle calculations, and the calculations of bonding properties, electronic structure, band structure, density of state, charge density difference and electronic structure of Mg2Ni alloy were examined. Namely, the work mainly took account of doping metal elements Ti to replace Mg and Ni elements in different proportions portion, and then form different crystals, including Mg12Ni6, Mg1.5NiTiMg(2)1/2, Mg5/3NiTiMg(2)1/3, Mg2NiH4, Mg2Ni3/4Ti1/4H4 aimed to improve the hydrogen storage characteristics of Mg-based metal hydrides. The results manifested Ti elements may hold the center position of octahedral sites, and the investigation further indicated that the hydrogen release performance and the thermal stability of hydrogen became lower through calculating absorption reaction enthalpy. Additionally, the metals Ti with high electronegativity interstitially exhibit useful effects on the characteristics of Mg-based hydrogen storage, which is beneficial to find the impact of the mechanism in terms of the electronic structure, and provide the theoretical support for designing new hydrogen storage materials.

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Hydriding properties of a nano-/amorphous-structured Mg–Ni–H system

Cited by 59 publications

References 14 publications

Hydrogen Insertion Effects on the Electronic Structure of Equiatomic MgNi Traced by ab initio Calculations

Hydrogen Insertion Effects on the Electronic Structure of Equiatomic MgNi Traced by ab initio Calculations

Hydride formation and stability on a Pd–SiO2 thin-film model catalyst studied by TEM and SAED

Thermal Stability of the Mg2Ni-Based Hydrogen Storage Alloy Doped Ti Element

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