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

A special issue of Inorganics (ISSN 2304-6740). This special issue belongs to the section "Inorganic Materials".

Deadline for manuscript submissions: closed (31 October 2023) | Viewed by 31817

Printed Edition Available!
A printed edition of this Special Issue is available here.

Special Issue Editors

Dr. Terry Humphries

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Guest Editor
Physics and Astronomy, Curtin University, GPO Box U1987, Perth, WA 6845, Australia
Interests: hydrogen storage; energy storage materials; thermal energy storage materials; inorganic synthesis; thermal analysis
Special Issues, Collections and Topics in MDPI journals
Prof. Dr. Craig Buckley

E-Mail Website
Guest Editor
Physics and Astronomy, Curtin University, GPO Box U1987, Perth, WA 6845, Australia
Interests: hydrogen storage; energy storage materials; thermal energy storage materials; metal hydrides; thermodynamics
Special Issues, Collections and Topics in MDPI journals
Dr. Mark Paskevicius

E-Mail Website
Guest Editor
Physics and Astronomy, Curtin University, GPO Box U1987, Perth, WA 6845, Australia
Interests: hydrogen storage; energy storage materials; thermal energy storage materials; ion conductors; electrochemistry
Special Issues, Collections and Topics in MDPI journals
Prof. Dr. Torben R. Jensen

E-Mail Website
Guest Editor
Interdisciplinary Nanoscience Center and Department of Chemistry, Aarhus University, DK-8000 Aarhus C, Denmark
Interests: synthesis and characterization of inorganic materials; structural, chemical and physical properties; energy storage as hydrogen or electricity in novel types of batteries; multivalent solid state batteries
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Hydrogen is heralded as a future global energy carrier. The National Hydrogen Strategy of Australia has set a target for a clean, innovative, safe and competitive hydrogen industry with expectations to become a major exporter in the hydrogen industry by 2030. As such, there is increasing interest from major industries to integrate hydrogen technology into their energy portfolio and supply chains. Metal hydrides have received much interest over the past several decades, which is obvious from a previous related Special Issue published in Inorganics: "Functional Materials Based on Metal Hydrides". Reversible solid-state hydrogen storage at ambient conditions with moderate energy exchange with the surroundings is the ultimate challenge to realise a hydrogen-based society. Varieties of novel materials have been investigated in recent decades, which has provided many novel compositions, fascinating structures and functionalities. Today, metal hydrides are explored for a range of applications from hydrogen export, remote-area power systems, solid-state batteries, thermochemical energy storage and hydrogen diffusion.

The aim of this Special Issue of Inorganics, entitled ‘State-of-the-Art and Progress in Metal-Hydrogen Systems’, is to inspire continued research within this important class of materials, in particular for energy-related applications. This Special Issue also serves as a collection of contributions presented at the International Symposium on Metal-Hydrogen Systems, held in Perth, Western Australia, 30 October–4 November 2022. This meeting, MH2022, is the 17th meeting in a distinguished series of conferences dating back to 1968.

Dr. Terry D. Humphries
Prof. Dr. Craig E. Buckley
Dr. Mark Paskevicius
Prof. Dr. Torben R. Jensen
Guest Editors

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Keywords

  • metal hydride
  • hydrogen
  • interstitial hydride
  • ionic hydride
  • complex hydride
  • organic hydride
  • hydrogen storage
  • hydrogen diffusion
  • thermochemical energy storage
  • solid-state batteries
  • solid-state electrolyte
  • extreme conditions
  • physisorption
  • chemisorption
  • nanoconfinement
  • nanoporous materials
  • kinetics
  • thermodynamics
  • ab initio model
  • catalysis
  • electrochemical reaction
  • energy storage
  • crystal structures
  • surface and interface effects
  • hydrogen production
  • hydrogen purification

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Editorial

Jump to: Research, Review

8 pages, 256 KiB  
Editorial
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
Viewed by 2470
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  
Article
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
Viewed by 1132
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  
Article
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 - 5 Jun 2023
Cited by 17 | Viewed by 2118
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  
Article
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(MoxFe1−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
Viewed by 1071
Abstract
This study aims to shed light on the unusual trend in the stabilities of Zr(MoxFe1−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(MoxFe1−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, uelas. In order to discern this possibility, we measured the elastic moduli of Zr(MoxFe1−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 uelas. Therefore, we turn our attention to the volume of the hydrogen atom, vH, 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 ZrMo2H3.5, 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 vH values, have been reported by other investigators. The low vH values, as well as the one derived in this work, significantly reduce uelas 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  
Article
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 4 | Viewed by 1720
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  
Article
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 - 7 May 2023
Viewed by 1417
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  
Article
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
Viewed by 2360
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  
Article
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 - 9 Apr 2023
Cited by 1 | Viewed by 1462
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  
Article
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 3 | Viewed by 1839
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  
Communication
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
Viewed by 1640
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  
Communication
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 - 9 Mar 2023
Cited by 1 | Viewed by 1923
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  
Article
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 - 3 Jan 2023
Viewed by 3548
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  
Article
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 3 | Viewed by 2473
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, Ea = 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  
Article
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 - 9 Oct 2022
Cited by 1 | Viewed by 1735
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  
Review
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 9 | Viewed by 3497
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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