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Special Issue "Hydrides: Fundamentals and Applications"

A special issue of Energies (ISSN 1996-1073).

Deadline for manuscript submissions: closed (15 July 2015)

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

Special Issue Editors

Guest Editor
Prof. Dr. Craig M. Jensen

Department of Chemistry, University of Hawaii, Honolulu, HI 96822, USA
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Fax: +1-808-956-5908
Interests: Catalysis, reaction mechanisms, NMR spectroscopy, hydrogen storage materials
Guest Editor
Prof. Dr. Etsuo Akiba

Department of Mechanical Engineering, Kyushu University, Fukuoka, 819-0395, Japan WPI International Institute for Carbon-Neutral Energy Research (WPI-I2CNER), Kyushu University, Fukuoka 819-0395, Japan
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Interests: Materials Science, Hydrogen Energy, Crystal Structure Analysis
Guest Editor
Associate Prof. Dr. Hai-Wen Li

International Research Center for Hydrogen Energy, Kyushu University, Fukuoka 819-0395, Japan WPI International Institute for Carbon-Neutral Energy Research (WPI-I2CNER), Kyushu University, Fukuoka 819-0395, Japan
Website | E-Mail
Interests: hydrogen storage; ionic conductivity; rechargeable battery; functional materials

Special Issue Information

Dear Colleauges,

The reversible elimination of hydrogen from metal hydrides serves as the basis for unique methods of energy transformation. This technology has found widespread practical utilization in applications such as hydrogen compressors, storage, and sensors, as well as batteries. Moreover, it is plausible that metal hydride technology could be utilized to provide practically viable solutions to the challenges of energy storage.  For nearly two decades, an extensive, worldwide research effort has been devoted to complex metal hydrides possessing high volumetric and/or gravimetric hydrogen densities with the goal of their practical utilization as onboard hydrogen storage materials. Additionally, a significant and growing number of efforts have been devoted to developing metal hydrides as advanced sensors and ionic conductors, and for electrochemical and stationary energy storage. This Special Issue will provide a sampling of on-going, state-of-art research on metal hydrides, ranging from fundamental investigations to practical applications with a concentration on topics which are currently of high interest.

Prof. Dr. Craig M. Jensen
Prof. Dr. Etsuo Akiba
Associate Prof. Dr. Hai-Wen Li
Guest Editors

Manuscript Submission Information

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Keywords

  • metal hydride
  • complex hydride
  • hydrogen storage
  • hydrogen sensor
  • electrochemical application
  • ionic conductors
  • energy storage

Published Papers (16 papers)

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Editorial

Jump to: Research, Review

Open AccessEditorial Hydrides: Fundamentals and Applications
Energies 2016, 9(4), 308; doi:10.3390/en9040308
Received: 25 March 2016 / Accepted: 25 March 2016 / Published: 22 April 2016
PDF Full-text (139 KB) | HTML Full-text | XML Full-text
Abstract Both the Japanese and Hawaiian archipelagos are both completely devoid of petroleum resources.[...] Full article
(This article belongs to the Special Issue Hydrides: Fundamentals and Applications) Printed Edition available

Research

Jump to: Editorial, Review

Open AccessArticle Thermal Decomposition of Anhydrous Alkali Metal Dodecaborates M2B12H12 (M = Li, Na, K)
Energies 2015, 8(11), 12429-12438; doi:10.3390/en81112326
Received: 16 July 2015 / Revised: 8 October 2015 / Accepted: 22 October 2015 / Published: 4 November 2015
Cited by 4 | PDF Full-text (2154 KB) | HTML Full-text | XML Full-text
Abstract
Metal dodecaborates M2/nB12H12 are regarded as the dehydrogenation intermediates of metal borohydrides M(BH4)n that are expected to be high density hydrogen storage materials. In this work, thermal decomposition processes of anhydrous alkali metal dodecaborates
[...] Read more.
Metal dodecaborates M2/nB12H12 are regarded as the dehydrogenation intermediates of metal borohydrides M(BH4)n that are expected to be high density hydrogen storage materials. In this work, thermal decomposition processes of anhydrous alkali metal dodecaborates M2B12H12 (M = Li, Na, K) synthesized by sintering of MBH4 (M = Li, Na, K) and B10H14 have been systematically investigated in order to understand its role in the dehydrogenation of M(BH4)n. Thermal decomposition of M2B12H12 indicates multistep pathways accompanying the formation of H-deficient monomers M2B12H12x containing the icosahedral B12 skeletons and is followed by the formation of (M2B12Hz)n polymers. The decomposition behaviors are different with the in situ formed M2B12H12 during the dehydrogenation of metal borohydrides. Full article
(This article belongs to the Special Issue Hydrides: Fundamentals and Applications) Printed Edition available
Open AccessArticle Effect of Magnesium Fluoride on Hydrogenation Properties of Magnesium Hydride
Energies 2015, 8(11), 12546-12556; doi:10.3390/en81112330
Received: 12 July 2015 / Revised: 11 October 2015 / Accepted: 15 October 2015 / Published: 4 November 2015
Cited by 2 | PDF Full-text (5462 KB) | HTML Full-text | XML Full-text
Abstract
A cost effective catalyst is of great importance for consideration of MgH2 as potential hydrogen storage material. In this regard, we investigated the catalytic role of alkaline metal fluoride on the hydrogen storage behavior of MgH2. Samples were synthesized by admixing 5 mol
[...] Read more.
A cost effective catalyst is of great importance for consideration of MgH2 as potential hydrogen storage material. In this regard, we investigated the catalytic role of alkaline metal fluoride on the hydrogen storage behavior of MgH2. Samples were synthesized by admixing 5 mol % MgF2 into MgH2 powder using planetary ball mill. Hydrogenation measurements made at 335 °C showed that in comparison to only 70% absorption by pure MgH2, catalyzed material absorbed 92% of theoretical capacity in less than 20 min and desorbed completely in almost the same time. Sorption studies done at lower temperatures revealed that complete absorption at temperature as low as 145 °C is possible. This is due to uniform distribution of MgF2 nano particles within the MgH2 powder. X-ray diffraction patterns also showed the presence of stable MgF2 phase that does not decompose upon hydrogen absorption-desorption. Cyclic measurements done at 310 °C showed negligible loss in the overall storage capacity with cycling. These results reveal that the presence of the chemically inert and stable MgF2 phase is responsible for good reversible characteristic and improved kinetics. Full article
(This article belongs to the Special Issue Hydrides: Fundamentals and Applications) Printed Edition available
Open AccessArticle Combined X-ray and Raman Studies on the Effect of Cobalt Additives on the Decomposition of Magnesium Borohydride
Energies 2015, 8(9), 9173-9190; doi:10.3390/en8099173
Received: 24 July 2015 / Revised: 18 August 2015 / Accepted: 19 August 2015 / Published: 27 August 2015
Cited by 6 | PDF Full-text (3169 KB) | HTML Full-text | XML Full-text
Abstract
Magnesium borohydride (Mg(BH4)2) is one of the most promising hydrogen storage materials. Its kinetics of hydrogen desorption, reversibility, and complex reaction pathways during decomposition and rehydrogenation, however, present a challenge, which has been often addressed by using transition metal
[...] Read more.
Magnesium borohydride (Mg(BH4)2) is one of the most promising hydrogen storage materials. Its kinetics of hydrogen desorption, reversibility, and complex reaction pathways during decomposition and rehydrogenation, however, present a challenge, which has been often addressed by using transition metal compounds as additives. In this work the decomposition of Mg(BH4)2 ball-milled with CoCl2 and CoF2 additives, was studied by means of a combination of several in-situ techniques. Synchrotron X-ray diffraction and Raman spectroscopy were used to follow the phase transitions and decomposition of Mg(BH4)2. By comparison with pure milled Mg(BH4)2, the temperature for the γ → ε phase transition in the samples with CoF2 or CoCl2 additives was reduced by 10–45 °C. In-situ Raman measurements showed the formation of a decomposition phase with vibrations at 2513, 2411 and 766 cm−1 in the sample with CoF2. Simultaneous X-ray absorption measurements at the Co K-edge revealed that the additives chemically transformed to other species. CoF2 slowly reacted upon heating till ~290 °C, whereas CoCl2 transformed drastically at ~180 °C. Full article
(This article belongs to the Special Issue Hydrides: Fundamentals and Applications) Printed Edition available
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Open AccessArticle Efficient Synthesis of an Aluminum Amidoborane Ammoniate
Energies 2015, 8(9), 9107-9116; doi:10.3390/en8099107
Received: 6 July 2015 / Revised: 4 August 2015 / Accepted: 6 August 2015 / Published: 26 August 2015
Cited by 4 | PDF Full-text (385 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
A novel species of metal amidoborane ammoniate, [Al(NH2BH3)63−][Al(NH3)63+] has been successfully synthesized in up to 95% via the one-step reaction of AlH3·OEt2 with liquid NH3BH3
[...] Read more.
A novel species of metal amidoborane ammoniate, [Al(NH2BH3)63−][Al(NH3)63+] has been successfully synthesized in up to 95% via the one-step reaction of AlH3·OEt2 with liquid NH3BH3·nNH3 (n = 1~6) at 0 °C. This solution based reaction method provides an alternative pathway to the traditional mechano-chemical ball milling methods, avoiding possible decomposition. MAS 27Al NMR spectroscopy confirms the formulation of the compound as an Al(NH2BH3)63− complex anion and an Al(NH3)63+ cation. Initial dehydrogenation studies of this aluminum based M-N-B-H compound demonstrate that hydrogen is released at temperatures as low as 65 °C, totaling ~8.6 equivalents of H2 (10.3 wt %) upon heating to 105 °C. This method of synthesis offers a promising route towards the large scale production of metal amidoborane ammoniate moieties. Full article
(This article belongs to the Special Issue Hydrides: Fundamentals and Applications) Printed Edition available
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Open AccessArticle Metal Hydrides for High-Temperature Power Generation
Energies 2015, 8(8), 8406-8430; doi:10.3390/en8088406
Received: 7 May 2015 / Accepted: 4 August 2015 / Published: 10 August 2015
Cited by 8 | PDF Full-text (1060 KB) | HTML Full-text | XML Full-text
Abstract
Metal hydrides can be utilized for hydrogen storage and for thermal energy storage (TES) applications. By using TES with solar technologies, heat can be stored from sun energy to be used later, which enables continuous power generation. We are developing a TES technology
[...] Read more.
Metal hydrides can be utilized for hydrogen storage and for thermal energy storage (TES) applications. By using TES with solar technologies, heat can be stored from sun energy to be used later, which enables continuous power generation. We are developing a TES technology based on a dual-bed metal hydride system, which has a high-temperature (HT) metal hydride operating reversibly at 600–800 °C to generate heat, as well as a low-temperature (LT) hydride near room temperature that is used for hydrogen storage during sun hours until there is the need to produce electricity, such as during night time, a cloudy day or during peak hours. We proceeded from selecting a high-energy density HT-hydride based on performance characterization on gram-sized samples scaled up to kilogram quantities with retained performance. COMSOL Multiphysics was used to make performance predictions for cylindrical hydride beds with varying diameters and thermal conductivities. Based on experimental and modeling results, a ~200-kWh/m3 bench-scale prototype was designed and fabricated, and we demonstrated the ability to meet or exceed all performance targets. Full article
(This article belongs to the Special Issue Hydrides: Fundamentals and Applications) Printed Edition available
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Open AccessArticle Increasing Hydrogen Density with the Cation-Anion Pair BH4-NH4+ in Perovskite-Type NH4Ca(BH4)3
Energies 2015, 8(8), 8286-8299; doi:10.3390/en8088286
Received: 3 March 2015 / Revised: 19 June 2015 / Accepted: 22 July 2015 / Published: 6 August 2015
Cited by 4 | PDF Full-text (1119 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
A novel metal borohydride ammonia-borane complex Ca(BH4)2·NH3BH3 is characterized as the decomposition product of the recently reported perovskite-type metal borohydride NH4Ca(BH4)3, suggesting that ammonium-based metal borohydrides release hydrogen gas via
[...] Read more.
A novel metal borohydride ammonia-borane complex Ca(BH4)2·NH3BH3 is characterized as the decomposition product of the recently reported perovskite-type metal borohydride NH4Ca(BH4)3, suggesting that ammonium-based metal borohydrides release hydrogen gas via ammonia-borane-complexes. For the first time the concept of proton-hydride interactions to promote hydrogen release is applied to a cation-anion pair in a complex metal hydride. NH4Ca(BH4)3 is prepared mechanochemically from Ca(BH4)2 and NH4Cl as well as NH4BH4 following two different protocols, where the synthesis procedures are modified in the latter to solvent-based ball-milling using diethyl ether to maximize the phase yield in chlorine-free samples. During decomposition of NH4Ca(BH4)3 pure H2 is released, prior to the decomposition of the complex to its constituents. As opposed to a previously reported adduct between Ca(BH4)2 and NH3BH3, the present complex is described as NH3BH3-stuffed α-Ca(BH4)2. Full article
(This article belongs to the Special Issue Hydrides: Fundamentals and Applications) Printed Edition available
Figures

Open AccessArticle The improved Hydrogen Storage Performances of the Multi-Component Composite: 2Mg(NH2)2–3LiH–LiBH4
Energies 2015, 8(7), 6898-6909; doi:10.3390/en8076898
Received: 25 May 2015 / Revised: 28 June 2015 / Accepted: 30 June 2015 / Published: 10 July 2015
Cited by 6 | PDF Full-text (4435 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
2Mg(NH2)2–3LiH–LiBH4 composite exhibits an improved kinetic and thermodynamic properties in hydrogen storage in comparison with 2Mg(NH2)2–3LiH. The peak temperature of hydrogen desorption drops about 10 K and the peak width shrinks about 50 K
[...] Read more.
2Mg(NH2)2–3LiH–LiBH4 composite exhibits an improved kinetic and thermodynamic properties in hydrogen storage in comparison with 2Mg(NH2)2–3LiH. The peak temperature of hydrogen desorption drops about 10 K and the peak width shrinks about 50 K compared with the neat 2Mg(NH2)2–3LiH. Its isothermal dehydrogenation and re-hydrogenation rates are respectively 2 times and 18 times as fast as those of 2Mg(NH2)2–3LiH. A slope desorption region with higher equilibrium pressure is observed. By means of X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance (NMR) analyses, the existence of Li2BNH6 is identified and its roles in kinetic and thermodynamic enhancement are discussed. Full article
(This article belongs to the Special Issue Hydrides: Fundamentals and Applications) Printed Edition available
Open AccessArticle Dehydriding Process and Hydrogen–Deuterium Exchange of LiBH4–Mg2FeD6 Composites
Energies 2015, 8(6), 5459-5466; doi:10.3390/en8065459
Received: 30 April 2015 / Revised: 28 May 2015 / Accepted: 2 June 2015 / Published: 8 June 2015
Cited by 3 | PDF Full-text (576 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
The dehydriding process and hydrogen–deuterium exchange (H–D exchange) of xLiBH4 + (1 − x)Mg2FeD6 (x = 0.25, 0.75) composites has been studied in detail. For the composition with x = 0.25, only one overlapping mass peak
[...] Read more.
The dehydriding process and hydrogen–deuterium exchange (H–D exchange) of xLiBH4 + (1 − x)Mg2FeD6 (x = 0.25, 0.75) composites has been studied in detail. For the composition with x = 0.25, only one overlapping mass peak of all hydrogen and deuterium related species was observed in mass spectrometry. This implied the simultaneous dehydriding of LiBH4 and Mg2FeD6, despite an almost 190 °C difference in the dehydriding temperatures of the respective discrete complex hydrides. In situ infrared spectroscopy measurements indicated that H–D exchange between [BH4] and [FeD6]4− had occurred during ball-milling and was promoted upon heating. The extent of H–D exchange was estimated from the areas of the relevant mass signals: immediately prior to the dehydriding, more than two H atoms in [BH4] was replaced by D atoms. For x = 0.75, H–D exchange also occurred and about one to two H atoms in [BH4] was replaced by D atoms immediately before the dehydriding. In contrast to the situation for x = 0.25, firstly LiBH4 and Mg2FeD6 dehydrided simultaneously with a special molar ratio = 1:1 at x = 0.75, and then the remaining LiBH4 reacted with the Mg and Fe derived from the dehydriding of Mg2FeD6. Full article
(This article belongs to the Special Issue Hydrides: Fundamentals and Applications) Printed Edition available
Open AccessArticle Enhanced Hydrogen Generation Properties of MgH2-Based Hydrides by Breaking the Magnesium Hydroxide Passivation Layer
Energies 2015, 8(5), 4237-4252; doi:10.3390/en8054237
Received: 28 February 2015 / Revised: 15 April 2015 / Accepted: 4 May 2015 / Published: 11 May 2015
Cited by 18 | PDF Full-text (1074 KB) | HTML Full-text | XML Full-text
Abstract
Due to its relatively low cost, high hydrogen yield, and environmentally friendly hydrolysis byproducts, magnesium hydride (MgH2) appears to be an attractive candidate for hydrogen generation. However, the hydrolysis reaction of MgH2 is rapidly inhibited by the formation of a
[...] Read more.
Due to its relatively low cost, high hydrogen yield, and environmentally friendly hydrolysis byproducts, magnesium hydride (MgH2) appears to be an attractive candidate for hydrogen generation. However, the hydrolysis reaction of MgH2 is rapidly inhibited by the formation of a magnesium hydroxide passivation layer. To improve the hydrolysis properties of MgH2-based hydrides we investigated three different approaches: ball milling, synthesis of MgH2-based composites, and tuning of the solution composition. We demonstrate that the formation of a composite system, such as the MgH2/LaH3 composite, through ball milling and in situ synthesis, can improve the hydrolysis properties of MgH2 in pure water. Furthermore, the addition of Ni to the MgH2/LaH3 composite resulted in the synthesis of LaH3/MgH2/Ni composites. The LaH3/MgH2/Ni composites exhibited a higher hydrolysis rate—120 mL/(g·min) of H2 in the first 5 min—than the MgH2/LaH3 composite— 95 mL/(g·min)—without the formation of the magnesium hydroxide passivation layer. Moreover, the yield rate was controlled by manipulation of the particle size via ball milling. The hydrolysis of MgH2 was also improved by optimizing the solution. The MgH2 produced 1711.2 mL/g of H2 in 10 min at 298 K in the 27.1% ammonium chloride solution, and the hydrolytic conversion rate reached the value of 99.5%. Full article
(This article belongs to the Special Issue Hydrides: Fundamentals and Applications) Printed Edition available
Open AccessArticle Temperature Dependence of the Elastic Modulus of (Ni0.6Nb0.4)1−xZrx Membranes: Effects of Thermal Treatments and Hydrogenation
Energies 2015, 8(5), 3944-3954; doi:10.3390/en8053944
Received: 27 February 2015 / Accepted: 20 April 2015 / Published: 6 May 2015
Cited by 6 | PDF Full-text (692 KB) | HTML Full-text | XML Full-text
Abstract
Amorphous (Ni0.6Nb0.4)1−xZrx membranes were investigated by means of X-ray diffraction, thermogravimetry, differential thermal analysis and tensile modulus measurements. Crystallization occurs only above 673 K, and even after hydrogenation the membranes retain their mainly amorphous nature. However,
[...] Read more.
Amorphous (Ni0.6Nb0.4)1−xZrx membranes were investigated by means of X-ray diffraction, thermogravimetry, differential thermal analysis and tensile modulus measurements. Crystallization occurs only above 673 K, and even after hydrogenation the membranes retain their mainly amorphous nature. However, after exposure to gaseous hydrogen, the temperature dependence of the tensile modulus, M, displays large variations. The modulus of the hydrogen reacted membrane is higher with respect to the pristine samples in the temperature range between 298 K and 423 K. Moreover, a sharp drop in M is observed upon heating to approximately 473 K, well below the glass transition temperature of these glasses. We propose that the changes in the moduli as a function of temperature on the hydrogenated samples are due to the formation of nanocrystalline phases of Zr hydrides in (Ni0.6Nb0.4)1−xZrx-H membanes. Full article
(This article belongs to the Special Issue Hydrides: Fundamentals and Applications) Printed Edition available
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Open AccessArticle Hydrogen Storage in Pristine and d10-Block Metal-Anchored Activated Carbon Made from Local Wastes
Energies 2015, 8(5), 3578-3590; doi:10.3390/en8053578
Received: 18 November 2014 / Revised: 15 January 2015 / Accepted: 20 April 2015 / Published: 28 April 2015
Cited by 2 | PDF Full-text (1997 KB) | HTML Full-text | XML Full-text
Abstract
Activated carbon has been synthesized from local palm shell, cardboard and plastics municipal waste in the Kingdom of Saudi Arabia. It exhibits a surface area of 930 m2/g and total pore volume of 0.42 cm3/g. This pristine activated carbon
[...] Read more.
Activated carbon has been synthesized from local palm shell, cardboard and plastics municipal waste in the Kingdom of Saudi Arabia. It exhibits a surface area of 930 m2/g and total pore volume of 0.42 cm3/g. This pristine activated carbon has been further anchored with nickel, palladium and platinum metal particles by ultrasound-assisted impregnation. Deposition of nanosized Pt particles as small as 3 nm has been achieved, while for Ni and Pd their size reaches 100 nm. The solid-gas hydrogenation properties of the pristine and metal-anchored activated carbon have been determined. The pristine material exhibits a reversible hydrogen storage capacity of 2.3 wt% at 77 K and 3 MPa which is higher than for the doped ones. In these materials, the spillover effect due to metal doping is of minor importance in enhancing the hydrogen uptake compared with the counter-effect of the additional mass of the metal particles and pore blocking on the carbon surface. Full article
(This article belongs to the Special Issue Hydrides: Fundamentals and Applications) Printed Edition available
Open AccessArticle LaNi5-Assisted Hydrogenation of MgNi2 in the Hybrid Structures of La1.09Mg1.91Ni9D9.5 and La0.91Mg2.09Ni9D9.4
Energies 2015, 8(4), 3198-3211; doi:10.3390/en8043198
Received: 26 February 2015 / Revised: 6 April 2015 / Accepted: 13 April 2015 / Published: 21 April 2015
Cited by 6 | PDF Full-text (1270 KB) | HTML Full-text | XML Full-text
Abstract
This work focused on the high pressure PCT and in situ neutron powder diffraction studies of the LaMg2Ni9-H2 (D2) system at pressures up to 1,000 bar. LaMg2Ni9 alloy was prepared by a powder
[...] Read more.
This work focused on the high pressure PCT and in situ neutron powder diffraction studies of the LaMg2Ni9-H2 (D2) system at pressures up to 1,000 bar. LaMg2Ni9 alloy was prepared by a powder metallurgy route from the LaNi9 alloy precursor and Mg powder. Two La3−xMgxNi9 samples with slightly different La/Mg ratios were studied, La1.1Mg1.9Ni9 (sample 1) and La0.9Mg2.1Ni9 (sample 2). In situ neutron powder diffraction studies of the La1.09Mg1.91Ni9D9.5 (1) and La0.91Mg2.09Ni9D9.4 (2) deuterides were performed at 25 bar D2 (1) and 918 bar D2 (2). The hydrogenation properties of the (1) and (2) are dramatically different from those for LaNi3. The Mg-containing intermetallics reversibly form hydrides with DHdes = 24.0 kJ/molH2 and an equilibrium pressure of H2 desorption of 18 bar at 20 °C (La1.09Mg1.91Ni9). A pronounced hysteresis of H2 absorption and desorption, ~100 bar, is observed. The studies showed that LaNi5-assisted hydrogenation of MgNi2 in the LaMg2Ni9 hybrid structure takes place. In the La1.09Mg1.91Ni9D9.5 (1) and La0.91Mg2.09Ni9D9.4 (2) (a = 5.263/5.212; c = 25.803/25.71 Å) D atoms are accommodated in both Laves and CaCu5-type slabs. In the LaNi5 CaCu5-type layer, D atoms fill three types of interstices; a deformed octahedron [La2Ni4], and [La(Mg)2Ni2] and [Ni4] tetrahedra. The overall chemical compositions can be presented as LaNi5H5.6/5.0 + 2*MgNi2H1.95/2.2 showing that the hydrogenation of the MgNi2 slab proceeds at mild H2/D2 pressure of just 20 bar. A partial filling by D of the four types of the tetrahedral interstices in the MgNi2 slab takes place, including [MgNi3] and [Mg2Ni2] tetrahedra. Full article
(This article belongs to the Special Issue Hydrides: Fundamentals and Applications) Printed Edition available
Open AccessArticle Melting Behavior and Thermolysis of NaBH4−Mg(BH4)2 and NaBH4−Ca(BH4)2 Composites
Energies 2015, 8(4), 2701-2713; doi:10.3390/en8042701
Received: 12 March 2015 / Revised: 31 March 2015 / Accepted: 1 April 2015 / Published: 8 April 2015
Cited by 8 | PDF Full-text (1518 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
The physical properties and the hydrogen release of NaBH4–Mg(BH4)2 and NaBH4−Ca(BH4)2 composites are investigated using in situ synchrotron radiation powder X-ray diffraction, thermal analysis and temperature programmed photographic analysis. The composite, xNaBH
[...] Read more.
The physical properties and the hydrogen release of NaBH4–Mg(BH4)2 and NaBH4−Ca(BH4)2 composites are investigated using in situ synchrotron radiation powder X-ray diffraction, thermal analysis and temperature programmed photographic analysis. The composite, xNaBH4–(1 − x)Mg(BH4)2, x = 0.4 to 0.5, shows melting/frothing between 205 and 220 °C. However, the sample does not become a transparent molten phase. This behavior is similar to other alkali-alkaline earth metal borohydride composites. In the xNaBH4–(1 − x)Ca(BH4)2 system, eutectic melting is not observed. Interestingly, eutectic melting in metal borohydrides systems leads to partial thermolysis and hydrogen release at lower temperatures and the control of sample melting may open new routes for obtaining high-capacity hydrogen storage materials. Full article
(This article belongs to the Special Issue Hydrides: Fundamentals and Applications) Printed Edition available

Review

Jump to: Editorial, Research

Open AccessReview Hydrazine Borane and Hydrazinidoboranes as Chemical Hydrogen Storage Materials
Energies 2015, 8(4), 3118-3141; doi:10.3390/en8043118
Received: 27 January 2015 / Revised: 20 February 2015 / Accepted: 7 April 2015 / Published: 20 April 2015
Cited by 15 | PDF Full-text (1651 KB) | HTML Full-text | XML Full-text
Abstract
Hydrazine borane N2H4BH3 and alkali derivatives (i.e., lithium, sodium and potassium hydrazinidoboranes MN2H3BH3 with M = Li, Na and K) have been considered as potential chemical hydrogen storage materials. They belong
[...] Read more.
Hydrazine borane N2H4BH3 and alkali derivatives (i.e., lithium, sodium and potassium hydrazinidoboranes MN2H3BH3 with M = Li, Na and K) have been considered as potential chemical hydrogen storage materials. They belong to the family of boron- and nitrogen-based materials and the present article aims at providing a timely review while focusing on fundamentals so that their effective potential in the field could be appreciated. It stands out that, on the one hand, hydrazine borane, in aqueous solution, would be suitable for full dehydrogenation in hydrolytic conditions; the most attractive feature is the possibility to dehydrogenate, in addition to the BH3 group, the N2H4 moiety in the presence of an active and selective metal-based catalyst but for which further improvements are still necessary. However, the thermolytic dehydrogenation of hydrazine borane should be avoided because of the evolution of significant amounts of hydrazine and the formation of a shock-sensitive solid residue upon heating at >300 °C. On the other hand, the alkali hydrazinidoboranes, obtained by reaction of hydrazine borane with alkali hydrides, would be more suitable to thermolytic dehydrogenation, with improved properties in comparison to the parent borane. All of these aspects are surveyed herein and put into perspective. Full article
(This article belongs to the Special Issue Hydrides: Fundamentals and Applications) Printed Edition available
Open AccessReview Recent Advances in the Use of Sodium Borohydride as a Solid State Hydrogen Store
Energies 2015, 8(1), 430-453; doi:10.3390/en8010430
Received: 22 October 2014 / Accepted: 15 December 2014 / Published: 13 January 2015
Cited by 13 | PDF Full-text (817 KB) | HTML Full-text | XML Full-text
Abstract
The development of new practical hydrogen storage materials with high volumetric and gravimetric hydrogen densities is necessary to implement fuel cell technology for both mobile and stationary applications. NaBH4, owing to its low cost and high hydrogen density (10.6 wt%), has
[...] Read more.
The development of new practical hydrogen storage materials with high volumetric and gravimetric hydrogen densities is necessary to implement fuel cell technology for both mobile and stationary applications. NaBH4, owing to its low cost and high hydrogen density (10.6 wt%), has received extensive attention as a promising hydrogen storage medium. However, its practical use is hampered by its high thermodynamic stability and slow hydrogen exchange kinetics. Recent developments have been made in promoting H2 release and tuning the thermodynamics of the thermal decomposition of solid NaBH4. These conceptual advances offer a positive outlook for using NaBH4-based materials as viable hydrogen storage carriers for mobile applications. This review summarizes contemporary progress in this field with a focus on the fundamental dehydrogenation and rehydrogenation pathways and properties and on material design strategies towards improved kinetics and thermodynamics such as catalytic doping, nano-engineering, additive destabilization and chemical modification. Full article
(This article belongs to the Special Issue Hydrides: Fundamentals and Applications) Printed Edition available

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