Editorial

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8 pages, 256 KiB

Open AccessEditorial

State-of-the-Art and Progress in Metal-Hydrogen Systems

by Terry D. Humphries, Craig E. Buckley, Mark Paskevicius and Torben R. Jensen

Inorganics 2023, 11(12), 476; https://doi.org/10.3390/inorganics11120476 - 11 Dec 2023

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Abstract

Hydrogen is heralded as a future global energy carrier [...] Full article

(This article belongs to the Special Issue State-of-the-Art and Progress in Metal-Hydrogen Systems)

Research

Jump to: Editorial, Review

12 pages, 1727 KiB

Open AccessArticle

Electrolytes in Multiple-Phase Hydrogen Storage Reactions

by John J. Vajo, Jasim Uddin, Son-Jong Hwang and Jason Graetz

Inorganics 2023, 11(7), 267; https://doi.org/10.3390/inorganics11070267 - 24 Jun 2023

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Abstract

Multiple-phase hydrogen storage materials such as metal alanates and borohydrides, and destabilized systems offer the possibility of high hydrogen storage capacity with favorable thermodynamics. However, the multiphase nature of these materials intrinsically limits the kinetics due to the required transport of species between [...] Read more.

Multiple-phase hydrogen storage materials such as metal alanates and borohydrides, and destabilized systems offer the possibility of high hydrogen storage capacity with favorable thermodynamics. However, the multiphase nature of these materials intrinsically limits the kinetics due to the required transport of species between phases, which are typically in dry powder form. To address this limitation, the influence of added electrolytes is explored. This approach is motivated by analogy with similar multiphase battery reactions that show reduced kinetic limitations while necessarily containing electrolytes. Previous experimental results showing improved kinetics for MgH₂/Sn (using a LiBH₄/KBH₄ eutectic electrolyte) and NaAlH₄ (using a diglyme electrolyte) are further analyzed in terms of this analogy. The results show that the analogy is useful and rate constants are increased. Importantly, the inclusion of an electrolyte also appears to alleviate the continuously decreasing rates with the extent of reaction, which is characteristic of many multiphase hydrides. Instead, reaction rates are approximately constant until near completion. Together, these effects can lead to >10× shorter overall reaction times. In addition, new results are presented for the hydrogenation of MgB₂ using Li/K/CsI and Li/K/CsCl eutectic electrolytes, where >60% conversion to Mg(BH₄)₂ was demonstrated at 350 bar. Full article

(This article belongs to the Special Issue State-of-the-Art and Progress in Metal-Hydrogen Systems)

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11 pages, 9833 KiB

Open AccessArticle

Hydrogen Release and Uptake of MgH₂ Modified by Ti₃CN MXene

by Xiantun Huang, Chenglin Lu, Yun Li, Haimei Tang, Xingqing Duan, Kuikui Wang and Haizhen Liu

Inorganics 2023, 11(6), 243; https://doi.org/10.3390/inorganics11060243 - 05 Jun 2023

Cited by 6 | Viewed by 1315

Abstract

MgH₂ has a high hydrogen content of 7.6 wt% and possesses good reversibility under normal conditions. However, pristine MgH₂ requires a high temperature above 300 °C to release hydrogen, with very slow kinetics. In this work, we utilized Ti₃CN [...] Read more.

MgH₂ has a high hydrogen content of 7.6 wt% and possesses good reversibility under normal conditions. However, pristine MgH₂ requires a high temperature above 300 °C to release hydrogen, with very slow kinetics. In this work, we utilized Ti₃CN MXene to reduce the operating temperature and enhance the kinetics of MgH₂. The initial temperature of MgH₂ decomposition can be lowered from 322 °C for pristine MgH₂ to 214 °C through the employment of Ti₃CN. The desorbed MgH₂ + 7.5 wt% Ti₃CN can start absorption at room temperature, while the desorbed pristine MgH₂ can only start absorption at 120 °C. The employment of Ti₃CN can significantly improve the hydrogen release kinetics of MgH₂, with the desorption activation energy decreasing from 121 to 80 kJ mol⁻¹. Regarding thermodynamics, the desorption enthalpy changes of MgH₂ and MgH₂ + 7.5 wt% Ti₃CN were 79.3 and 78.8 kJ mol⁻¹, respectively. This indicates that the employment of Ti₃CN does not alter the thermal stability of MgH₂. Phase evolution studies through the use of X-ray diffraction and electron diffraction both confirm that Ti₃CN remains stable during the hydrogen release and uptake process of the composite. This work will help understand the impact of a transition metal carbonitride on the hydrogen storage of MgH₂. Full article

(This article belongs to the Special Issue State-of-the-Art and Progress in Metal-Hydrogen Systems)

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10 pages, 2111 KiB

Open AccessArticle

The Role of Bulk Stiffening in Reducing the Critical Temperature of the Metal-to-Hydride Phase Transition and the Hydride Stability: The Case of Zr(Mo_xFe_1−x)₂-H₂

by Isaac Jacob, Dotan Babai, Matvey Bereznitsky and Roni Z. Shneck

Inorganics 2023, 11(6), 228; https://doi.org/10.3390/inorganics11060228 - 25 May 2023

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Abstract

This study aims to shed light on the unusual trend in the stabilities of Zr(Mo_xFe_1−x)₂, 0 ≤ x ≤ 1, hydrides. Both the rule of reversed stability and the crystal volume criterion correlate with the increased hydride [...] Read more.

This study aims to shed light on the unusual trend in the stabilities of Zr(Mo_xFe_1−x)₂, 0 ≤ x ≤ 1, hydrides. Both the rule of reversed stability and the crystal volume criterion correlate with the increased hydride stabilities from x = 0 to x = 0.5, but are in contrast with the destabilization of the end member ZrMo₂ hydride. The pressure-composition isotherms of ZrMo₂-H₂ exhibit very wide solid solubility regions, which may be associated with diminished H–H elastic interaction, u_elas. In order to discern this possibility, we measured the elastic moduli of Zr(Mo_xFe_1−x)₂, x = 0, 0.5, 1. The shear modulus, G, shows a moderate variation in this composition range, while the bulk modulus, B, increases significantly and monotonically from 148.2 GPa in ZrFe₂ to 200.4 GPa in ZrMo₂. The H–H elastic interaction is proportional to B and therefore its increase cannot directly account for a decrease in u_elas. Therefore, we turn our attention to the volume of the hydrogen atom,

v_{H}

, which usually varies in a limited range. Two coexisting phases, a Laves cubic (a = 7.826 Å) and a tetragonal (a = 5.603 Å, c = 8.081 Å) hydride phase are identified in ZrMo₂H_3.5, obtained by cooling to liquid nitrogen temperature at about 50 atm. The volume of the hydrogen atom in these two hydrides is estimated to be 2.2 Å³/(H atom). Some very low

v_{H}

values, have been reported by other investigators. The low

v_{H}

values, as well as the one derived in this work, significantly reduce u_elas for ZrMo₂-H₂, and thus reduce the corresponding critical temperature for the metal-to-hydride phase transition, and the heat of hydride formation. We suggest that the bulk stiffening in ZrMo₂ confines the corresponding hydride expansion and thus reduces the H-H elastic interaction. Full article

(This article belongs to the Special Issue State-of-the-Art and Progress in Metal-Hydrogen Systems)

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9 pages, 2837 KiB

Open AccessArticle

Liquid Channels Built-In Solid Magnesium Hydrides for Boosting Hydrogen Sorption

by Zhi-Kang Qin, Li-Qing He, Xiao-Li Ding, Ting-Zhi Si, Ping Cui, Hai-Wen Li and Yong-Tao Li

Inorganics 2023, 11(5), 216; https://doi.org/10.3390/inorganics11050216 - 17 May 2023

Cited by 2 | Viewed by 1258

Abstract

Realizing rapid and stable hydrogen sorption at low temperature is critical for magnesium-based hydrogen storage materials. Herein, liquid channels are built in magnesium hydride by introducing lithium borohydride ion conductors as an efficient route for improving its hydrogen sorption. For instance, the 5 [...] Read more.

Realizing rapid and stable hydrogen sorption at low temperature is critical for magnesium-based hydrogen storage materials. Herein, liquid channels are built in magnesium hydride by introducing lithium borohydride ion conductors as an efficient route for improving its hydrogen sorption. For instance, the 5 wt% LiBH₄-doped MgH₂ can release about 7.1 wt.% H₂ within 40 min at 300 °C but pure MgH₂ only desorbs less than 0.7 wt.% H₂, and more importantly it delivers faster desorption kinetics with more than 10 times enhancement to pure MgH₂. The hydrogen absorption capacity of LiBH₄-doped MgH₂ can still be well kept at approximately 7.2 wt.% without obvious capacity degradation even after six absorption and desorption cycles. This approach is not only through building ion transfer channels as a hydrogen carrier for kinetic enhancement but also by inhibiting the agglomeration of MgH₂ particles to obtain stable cyclic performance, which brings further insights to promoting the hydrogen ab-/desorption of other metal hydrides. Full article

(This article belongs to the Special Issue State-of-the-Art and Progress in Metal-Hydrogen Systems)

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11 pages, 8222 KiB

Open AccessArticle

Release of Pure H₂ from Na[BH₃(CH₃NH)BH₂(CH₃NH)BH₃] by Introduction of Methyl Substituents

by Ting Zhang, Timothy Steenhaut, Michel Devillers and Yaroslav Filinchuk

Inorganics 2023, 11(5), 202; https://doi.org/10.3390/inorganics11050202 - 07 May 2023

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Abstract

Over the last 10 years, hydrogen-rich compounds based on five-membered boron–nitrogen chain anions have attracted attention as potential hydrogen storage candidates. In this work, we synthesized Na[BH₃(CH₃NH)BH₂(CH₃NH)BH₃] through a simple mechanochemical approach. The [...] Read more.

Over the last 10 years, hydrogen-rich compounds based on five-membered boron–nitrogen chain anions have attracted attention as potential hydrogen storage candidates. In this work, we synthesized Na[BH₃(CH₃NH)BH₂(CH₃NH)BH₃] through a simple mechanochemical approach. The structure of this compound, obtained through synchrotron powder X-ray diffraction, is presented here for the first time. Its hydrogen release properties were studied by thermogravimetric analysis and mass spectrometry. It is shown here that Na[BH₃(CH₃NH)BH₂(CH₃NH)BH₃], on the contrary of its parent counterpart, Na[BH₃NH₂BH₂NH₂BH₃], is able to release up to 4.6 wt.% of pure hydrogen below 150 °C. These results demonstrate that the introduction of a methyl group on nitrogen atom may be a good strategy to efficiently suppress the release of commonly encountered undesired gaseous by-products during the thermal dehydrogenation of B-N-H compounds. Full article

(This article belongs to the Special Issue State-of-the-Art and Progress in Metal-Hydrogen Systems)

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18 pages, 3810 KiB

Open AccessArticle

Hydrogen Compression Materials with Output Hydrogen Pressure in a Wide Range of Pressures Using a Low-Potential Heat-Transfer Agent

by Xu Zhang, Yu-Yuan Zhao, Bao-Quan Li, Mikhail Prokhorenkov, Elshad Movlaev, Jin Xu, Wei Xiong, Hui-Zhong Yan and Sergey Mitrokhin

Inorganics 2023, 11(5), 180; https://doi.org/10.3390/inorganics11050180 - 24 Apr 2023

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Abstract

In order to meet the demand of metal hydride–hydrogen compressors (MHHC) and their hydrogen compression materials for high-pressure hydrogen filling in a hydrogen energy field, four kinds of hydrogen storage alloys with low-grade heat source (<373 K) heating outputs and different hydrogen pressures [...] Read more.

In order to meet the demand of metal hydride–hydrogen compressors (MHHC) and their hydrogen compression materials for high-pressure hydrogen filling in a hydrogen energy field, four kinds of hydrogen storage alloys with low-grade heat source (<373 K) heating outputs and different hydrogen pressures (up to 80 MPa) were developed as hydrogen compression materials. The preliminary compositions of the hydrogen storage alloys were determined by using a statistical model and research experience. The rare earth series AB₅ and Ti/Zr base AB₂ hydrogen storage alloys were prepared using a high-temperature melting method. The composition, structure, and hydrogenation/dehydrogenation plateau characteristics of the alloys were tested by an inductively coupled plasma mass spectrometer (ICP-MAS), X-ray diffractometer (XRD), and pressure–composition isothermal (PCT) tester. The median output pressures of the four-stage hydrogen storage alloys at 363 K were 8.90 MPa, 25.04 MPa, 42.97 MPa, and 84.73 MPa, respectively, which met the requirements of the 20 MPa, 35 MPa, and 70 MPa high-pressure hydrogen injections for the MHHCs. In fact, due to the tilted pressure plateau of the PCT curve, the synergy between the adjacent two alloys still needed to be adjusted. Full article

(This article belongs to the Special Issue State-of-the-Art and Progress in Metal-Hydrogen Systems)

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9 pages, 3112 KiB

Open AccessArticle

Exploring Proton Pair Motion Away from the Global Proton–Tuple Energy Minimum in Yttrium-Doped Barium Zirconate

by Yiqing Pan, Minh Tam Hoang, Sanaa Mansoor and Maria Alexandra Gomez

Inorganics 2023, 11(4), 160; https://doi.org/10.3390/inorganics11040160 - 09 Apr 2023

Cited by 1 | Viewed by 1081

Abstract

Yttrium-doped barium zirconate is one of the fastest solid-state proton conductors. While previous studies suggest that proton–tuples move as pairs in yttrium-doped barium zirconate, a systematic catalog of possible close proton–tuple moves is missing. Such a catalog is essential to simulating dual proton [...] Read more.

Yttrium-doped barium zirconate is one of the fastest solid-state proton conductors. While previous studies suggest that proton–tuples move as pairs in yttrium-doped barium zirconate, a systematic catalog of possible close proton–tuple moves is missing. Such a catalog is essential to simulating dual proton conduction effects. Density functional theory with the Perdew–Burke–Ernzerhof functional is utilized to obtain the total electronic energy for each proton–tuple. The conjugate gradient and nudged elastic band methods are used to find the minima and transition states for proton–tuple motion. In the lowest-energy configuration, protons are in close proximity to each other and the dopant, significantly affecting the backbone structure. The map of moves away from the global minimum proton–tuple shows that the most critical move for long-range proton conduction is a rotation with a barrier range of 0.31–0.41 eV when the two protons are in close proximity. Full article

(This article belongs to the Special Issue State-of-the-Art and Progress in Metal-Hydrogen Systems)

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15 pages, 3255 KiB

Open AccessArticle

Destabilization of the LiBH₄–NaBH₄ Eutectic Mixture through Pore Confinement for Hydrogen Storage

by Filippo Peru, Seyedhosein Payandeh, Torben R. Jensen, Georgia Charalambopoulou and Theodore Steriotis

Inorganics 2023, 11(3), 128; https://doi.org/10.3390/inorganics11030128 - 18 Mar 2023

Cited by 2 | Viewed by 1427

Abstract

Both LiBH₄ and NaBH₄ are well known for having high hydrogen contents, but also high decomposition temperatures and slow hydrogen absorption–desorption kinetics, preventing their use for hydrogen storage applications. The low melting temperature (219 °C) of their eutectic mixture 0.71 LiBH [...] Read more.

Both LiBH₄ and NaBH₄ are well known for having high hydrogen contents, but also high decomposition temperatures and slow hydrogen absorption–desorption kinetics, preventing their use for hydrogen storage applications. The low melting temperature (219 °C) of their eutectic mixture 0.71 LiBH₄–0.29 NaBH₄ allowed the synthesis of a new composite material through the melt infiltration of the hydrides into the ~5 nm diameter pores of a CMK-3 type carbon. A composite of 0.71 LiBH₄–0.29 NaBH₄ and non-porous graphitic carbon discs was also prepared by similar methods for comparison. Both composites showed improved kinetics and a partial reversibility of the dehydrogenation/rehydrogenation reactions. However, the best results were observed for the CMK-3 nanoconfined hydrides; a consistent uptake of about 3.5 wt.% H₂ was recorded after five hydrogenation/dehydrogenation cycles for an otherwise non-reversible system. The improved hydrogen release kinetics are attributed to carbon–hydride surface interactions rather than nanoconfinement, while enhanced heat transfer due to the carbon support may also play a role. Likewise, the carbon–hydride contact proved beneficial in terms of reversibility, without, however, ruling out the potential positive effect of pore confinement. Full article

(This article belongs to the Special Issue State-of-the-Art and Progress in Metal-Hydrogen Systems)

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11 pages, 2763 KiB

Open AccessCommunication

Investigation on the Formation of Rare-Earth Metal Phenoxides via Metathesis

by Jintao Wang, Qijun Pei, Yang Yu, Jirong Cui, Shangshang Wang, Khai Chen Tan, Jiaquan Guo, Teng He and Ping Chen

Inorganics 2023, 11(3), 115; https://doi.org/10.3390/inorganics11030115 - 10 Mar 2023

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Abstract

A number of alkali organometallic complexes with suitable thermodynamic properties and high capacity for hydrogen storage have been synthesized; however, few transition metal–organic complexes have been reported for hydrogen storage. Moreover, the synthetic processes of these transition metal–organic complexes via metathesis were not [...] Read more.

A number of alkali organometallic complexes with suitable thermodynamic properties and high capacity for hydrogen storage have been synthesized; however, few transition metal–organic complexes have been reported for hydrogen storage. Moreover, the synthetic processes of these transition metal–organic complexes via metathesis were not well characterized previously, leading to a lack of understanding of the metathesis reaction. In the present study, yttrium phenoxide and lanthanum phenoxide were synthesized via metathesis of sodium phenoxide with YCl₃ and LaCl₃, respectively. Quasi in situ NMR, UV-vis, and theoretical calculations were employed to characterize the synthetic processes and the final products. It is revealed that the electron densities of phenoxides in rare-earth phenoxides are lower than in sodium phenoxide due to the stronger Lewis acidity of Y³⁺ and La³⁺. The synthetic process may follow a pathway of stepwise formation of dichloride, monochloride, and chloride-free species. Significant decreases in K-band and R-band absorption were observed in UV-vis, which may be due to the weakened conjugation effect between O and the aromatic ring after rare-earth metal substitution. Two molecular structures, i.e., planar and nonplanar, are identified by theoretical calculations for each rare-earth phenoxide. Since these two structures have very close single-point energies, they may coexist in the materials. Full article

(This article belongs to the Special Issue State-of-the-Art and Progress in Metal-Hydrogen Systems)

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8 pages, 1543 KiB

Open AccessCommunication

Collectable Single Pure-Pd Metal Membrane with High Strength and Flexibility Prepared through Electroplating for Hydrogen Purification

by Naruki Endo, Yumi Kaneko, Norikazu Dezawa, Yasuhiro Komo and Masanobu Higuchi

Inorganics 2023, 11(3), 111; https://doi.org/10.3390/inorganics11030111 - 09 Mar 2023

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Abstract

Among the various film preparation methods, electroplating is one of the simplest and most economical methods. However, it is challenging to collect a dense single Pd film through plating, owing to the accumulation of stress in the film during the process. Therefore, the [...] Read more.

Among the various film preparation methods, electroplating is one of the simplest and most economical methods. However, it is challenging to collect a dense single Pd film through plating, owing to the accumulation of stress in the film during the process. Therefore, the characteristics of a single plated film have not been clearly identified, although pure Pd is widely used in metallic-hydrogen-purification membranes. In this study, stress concentration in film during preparation was reduced by optimizing the plating process, and a dense single flat film was successfully collected. No impurities were detected. Thus, a high-purity Pd film was prepared. Its surface texture was found to be significantly different from that of the rolled film, and several approximately 5 μm sized aggregates were observed on the surface. The plated film is reported to have mechanical properties superior to those of the rolled film, with twice the displacement and four times the breaking point strength. The hydrogen permeabilities of the plated film (5.4 × 10⁻⁹–1.1 × 10⁻⁸ mol·m⁻¹·s⁻¹·Pa^−1/2 at 250–450 °C) were comparable to those of the rolled and reported films, indicating that the surface texture does not have a strong effect on hydrogen permeability. The results of this study promote the practical use of Pd-based membranes through electroplating. Full article

(This article belongs to the Special Issue State-of-the-Art and Progress in Metal-Hydrogen Systems)

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11 pages, 4653 KiB

Open AccessArticle

Study of Phase Composition in TiFe + 4 wt.% Zr Alloys by Scanning Photoemission Microscopy

by Sabrina Sartori, Matteo Amati, Luca Gregoratti, Emil Høj Jensen, Natalia Kudriashova and Jacques Huot

Inorganics 2023, 11(1), 26; https://doi.org/10.3390/inorganics11010026 - 03 Jan 2023

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Abstract

The alloy TiFe is widely used as hydrogen storage material. However, the first hydrogenation is difficult. It was found that the addition of zirconium greatly improves the kinetic of first hydrogenation, but the mechanism is not well understood. In this paper, we report [...] Read more.

The alloy TiFe is widely used as hydrogen storage material. However, the first hydrogenation is difficult. It was found that the addition of zirconium greatly improves the kinetic of first hydrogenation, but the mechanism is not well understood. In this paper, we report the use of scanning photoemission microscopy to investigate the composition and chemical state of the various phases present in this alloy and how they change upon hydrogenation/dehydrogenation. We found the presence of different oxide phases that were not seen by conventional SEM investigation. The nature of these oxides phases seems to change upon hydrogenation/dehydrogenation cycle. This indicates that oxide phases may play a more significant role in the hydrogen absorption as what was previously believed. Full article

(This article belongs to the Special Issue State-of-the-Art and Progress in Metal-Hydrogen Systems)

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12 pages, 2631 KiB

Open AccessArticle

Synthesis, Structure and Mg²⁺ Ionic Conductivity of Isopropylamine Magnesium Borohydride

by Lasse G. Kristensen, Mads B. Amdisen, Mie Andersen and Torben R. Jensen

Inorganics 2023, 11(1), 17; https://doi.org/10.3390/inorganics11010017 - 30 Dec 2022

Cited by 1 | Viewed by 1960

Abstract

The discovery of new inorganic magnesium electrolytes may act as a foundation for the rational design of novel types of solid-state batteries. Here we investigated a new type of organic-inorganic metal hydride, isopropylamine magnesium borohydride, Mg(BH₄)₂∙(CH₃)₂ [...] Read more.

The discovery of new inorganic magnesium electrolytes may act as a foundation for the rational design of novel types of solid-state batteries. Here we investigated a new type of organic-inorganic metal hydride, isopropylamine magnesium borohydride, Mg(BH₄)₂∙(CH₃)₂CHNH₂, with hydrophobic domains in the solid state, which appear to promote fast Mg²⁺ ionic conductivity. A new synthetic strategy was designed by combination of solvent-based methods and mechanochemistry. The orthorhombic structure of Mg(BH₄)₂∙(CH₃)₂CHNH₂ was solved ab initio by the Rietveld refinement of synchrotron X-ray powder diffraction data and density functional theory (DFT) structural optimization in space group I2₁2₁2₁ (unit cell, a = 9.8019(1) Å, b = 12.1799(2) Å and c = 17.3386(2) Å). The DFT calculations reveal that the three-dimensional structure may be stabilized by weak dispersive interactions between apolar moieties and that these may be disordered. Nanoparticles and heat treatment (at T > 56 °C) produce a highly conductive composite, σ(Mg²⁺) = 2.86 × 10⁻⁷, and 2.85 × 10⁻⁵ S cm⁻¹ at −10 and 40 °C, respectively, with a low activation energy, E_a = 0.65 eV. Nanoparticles stabilize the partially eutectic molten state and prevent recrystallization even at low temperatures and provide a high mechanical stability of the composite. Full article

(This article belongs to the Special Issue State-of-the-Art and Progress in Metal-Hydrogen Systems)

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10 pages, 2692 KiB

Open AccessArticle

Stress Reduction of a V-Based BCC Metal Hydride Bed Using Silicone Oil as a Glidant

by Xin Zheng, Hanyang Kong, Desheng Chu, Faping Hu, Yao Wang, Yigang Yan and Chaoling Wu

Inorganics 2022, 10(10), 167; https://doi.org/10.3390/inorganics10100167 - 09 Oct 2022

Viewed by 1194

Abstract

The large volume expansion and self-locking phenomenon of metal hydride particles during hydrogen sorption often leads to a high stress concentration on the walls of a container, which may cause the collapse of the container. In present study, silicone oil was investigated as [...] Read more.

The large volume expansion and self-locking phenomenon of metal hydride particles during hydrogen sorption often leads to a high stress concentration on the walls of a container, which may cause the collapse of the container. In present study, silicone oil was investigated as a glidant for a V-based BCC metal hydride bed to alleviate the stress concentration during hydrogen sorption. The results indicated that the addition of 5 wt% silicone oil slightly reduced the initial hydrogen storage capacity of V₄₀Ti₂₆Cr₂₆Fe₈ (particle size: ~325 μm) but improved the absorption reversibility, regardless of the oil viscosity. It was observed that silicone oil formed a thin oil layer of 320~460 nm in thickness on the surface of the V₄₀Ti₂₆Cr₂₆Fe₈ particles, which might improve the fluidity of the powder, reduce the self-locking phenomenon and alleviate the stress concentration on the container walls. Consequently, the maximum strain on the surface of the hydrogen storage container decreased by ≥22.5% after adding 5 wt% silicone oil with a viscosity of 1000 cSt. Full article

(This article belongs to the Special Issue State-of-the-Art and Progress in Metal-Hydrogen Systems)

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Review

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17 pages, 1734 KiB

Open AccessReview

Metal Hydride Composite Structures for Improved Heat Transfer and Stability for Hydrogen Storage and Compression Applications

by Liang Liu, Alexander Ilyushechkin, Daniel Liang, Ashleigh Cousins, Wendy Tian, Cherry Chen, Jon Yin and Liezl Schoeman

Inorganics 2023, 11(5), 181; https://doi.org/10.3390/inorganics11050181 - 24 Apr 2023

Cited by 5 | Viewed by 2164

Abstract

Metal alloys and intermetallic compounds offer an attractive method for safely storing hydrogen (H₂). The metal alloys absorb H₂ into their structure, often swelling and fracturing as a result of phase transformation during hydride formation/decomposition cycles. The absorption of H [...] Read more.

Metal alloys and intermetallic compounds offer an attractive method for safely storing hydrogen (H₂). The metal alloys absorb H₂ into their structure, often swelling and fracturing as a result of phase transformation during hydride formation/decomposition cycles. The absorption of H₂ is an exothermic process, requiring the effective and efficient removal of heat. This can be challenging as heat transfer to/from powdered beds is notoriously difficult, and often limited by poor thermal conductivity. Hence, the observed reaction kinetics for absorption and desorption of H₂ is dominated by heat flow. The most common method for improving the thermal conductivity of the alloy powders is to prepare them into composite structures with other high thermal conductivity materials, such as carbons and expanded natural graphite. Such composite structures, some also combined with polymers/resins, can also mitigate safety issues related to swelling and improve cyclic durability. This paper reviews the methods that have been used to prepare such composite structures and evaluates the observed impact on thermal conductivity. Full article

(This article belongs to the Special Issue State-of-the-Art and Progress in Metal-Hydrogen Systems)

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