Energies

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Open AccessEditorial

Hydrides: Fundamentals and Applications

by Craig M. Jensen, Etsuo Akiba and Hai-Wen Li

Energies 2016, 9(4), 308; https://doi.org/10.3390/en9040308 - 22 Apr 2016

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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)

Research

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5462 KiB

Open AccessArticle

Effect of Magnesium Fluoride on Hydrogenation Properties of Magnesium Hydride

by Pragya Jain, Viney Dixit, Ankur Jain, Onkar N. Srivastava and Jacques Huot

Energies 2015, 8(11), 12546-12556; https://doi.org/10.3390/en81112330 - 4 Nov 2015

Cited by 22 | Viewed by 7380

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)

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2154 KiB

Open AccessArticle

Thermal Decomposition of Anhydrous Alkali Metal Dodecaborates M₂B₁₂H₁₂ (M = Li, Na, K)

by Liqing He, Hai-Wen Li and Etsuo Akiba

Energies 2015, 8(11), 12429-12438; https://doi.org/10.3390/en81112326 - 4 Nov 2015

Cited by 19 | Viewed by 6400

Abstract

Metal dodecaborates M_2/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 M_2/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 M₂B₁₂H₁₂₋_x containing the icosahedral B₁₂ skeletons and is followed by the formation of (M₂B₁₂H_z)_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)

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3169 KiB

Open AccessArticle

Combined X-ray and Raman Studies on the Effect of Cobalt Additives on the Decomposition of Magnesium Borohydride

by Olena Zavorotynska, Stefano Deledda, Jenny G. Vitillo, Ivan Saldan, Matylda N. Guzik, Marcello Baricco, John C. Walmsley, Jiri Muller and Bjørn C. Hauback

Energies 2015, 8(9), 9173-9190; https://doi.org/10.3390/en8099173 - 27 Aug 2015

Cited by 30 | Viewed by 7280

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)

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385 KiB

Open AccessArticle

Efficient Synthesis of an Aluminum Amidoborane Ammoniate

by Junzhi Yang, Paul R. Beaumont, Terry D. Humphries, Craig M. Jensen and Xingguo Li

Energies 2015, 8(9), 9107-9116; https://doi.org/10.3390/en8099107 - 26 Aug 2015

Cited by 16 | Viewed by 5442

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)

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1060 KiB

Open AccessArticle

Metal Hydrides for High-Temperature Power Generation

by Ewa C. E. Rönnebro, Greg Whyatt, Michael Powell, Matthew Westman, Feng (Richard) Zheng and Zhigang Zak Fang

Energies 2015, 8(8), 8406-8430; https://doi.org/10.3390/en8088406 - 10 Aug 2015

Cited by 71 | Viewed by 8305

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)

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1119 KiB

Open AccessArticle

Increasing Hydrogen Density with the Cation-Anion Pair BH₄⁻-NH₄⁺ in Perovskite-Type NH₄Ca(BH₄)₃

by Pascal Schouwink, Fabrice Morelle, Yolanda Sadikin, Yaroslav Filinchuk and Radovan Černý

Energies 2015, 8(8), 8286-8299; https://doi.org/10.3390/en8088286 - 6 Aug 2015

Cited by 16 | Viewed by 11986

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)

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4435 KiB

Open AccessArticle

The improved Hydrogen Storage Performances of the Multi-Component Composite: 2Mg(NH₂)₂–3LiH–LiBH₄

by Han Wang, Hujun Cao, Guotao Wu, Teng He and Ping Chen

Energies 2015, 8(7), 6898-6909; https://doi.org/10.3390/en8076898 - 10 Jul 2015

Cited by 21 | Viewed by 5550

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)

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576 KiB

Open AccessArticle

Dehydriding Process and Hydrogen–Deuterium Exchange of LiBH₄–Mg₂FeD₆ Composites

by Guanqiao Li, Motoaki Matsuo, Katsutoshi Aoki, Tamio Ikeshoji and Shin-ichi Orimo

Energies 2015, 8(6), 5459-5466; https://doi.org/10.3390/en8065459 - 8 Jun 2015

Cited by 6 | Viewed by 5017

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)

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1074 KiB

Open AccessArticle

Enhanced Hydrogen Generation Properties of MgH₂-Based Hydrides by Breaking the Magnesium Hydroxide Passivation Layer

by Liuzhang Ouyang, Miaolian Ma, Minghong Huang, Ruoming Duan, Hui Wang, Lixian Sun and Min Zhu

Energies 2015, 8(5), 4237-4252; https://doi.org/10.3390/en8054237 - 11 May 2015

Cited by 104 | Viewed by 10640

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)

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692 KiB

Open AccessArticle

Temperature Dependence of the Elastic Modulus of (Ni_0.6Nb_0.4)_1−xZr_x Membranes: Effects of Thermal Treatments and Hydrogenation

by Oriele Palumbo, Sergio Brutti, Francesco Trequattrini, Suchismita Sarker, Michael Dolan, Dhanesh Chandra and Annalisa Paolone

Energies 2015, 8(5), 3944-3954; https://doi.org/10.3390/en8053944 - 6 May 2015

Cited by 16 | Viewed by 6118

Abstract

Amorphous (Ni_0.6Nb_0.4)_1−xZr_x 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 (Ni_0.6Nb_0.4)_1−xZr_x 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 (Ni_0.6Nb_0.4)_1−xZr_x-H membanes. Full article

(This article belongs to the Special Issue Hydrides: Fundamentals and Applications)

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1997 KiB

Open AccessArticle

Hydrogen Storage in Pristine and d10-Block Metal-Anchored Activated Carbon Made from Local Wastes

by Mohamed F. Aly Aboud, Zeid A. ALOthman, Mohamed A. Habila, Claudia Zlotea, Michel Latroche and Fermin Cuevas

Energies 2015, 8(5), 3578-3590; https://doi.org/10.3390/en8053578 - 28 Apr 2015

Cited by 22 | Viewed by 7042

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)

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1270 KiB

Open AccessArticle

LaNi₅-Assisted Hydrogenation of MgNi₂ in the Hybrid Structures of La_1.09Mg_1.91Ni₉D_9.5 and La_0.91Mg_2.09Ni₉D_9.4

by Roman V. Denys, Volodymyr A. Yartys, Evan MacA. Gray and Colin J. Webb

Energies 2015, 8(4), 3198-3211; https://doi.org/10.3390/en8043198 - 21 Apr 2015

Cited by 14 | Viewed by 7061

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 La_3−xMg_xNi₉ samples with slightly different La/Mg ratios were studied, La_1.1Mg_1.9Ni₉ (sample 1) and La_0.9Mg_2.1Ni₉ (sample 2). In situ neutron powder diffraction studies of the La_1.09Mg_1.91Ni₉D_9.5 (1) and La_0.91Mg_2.09Ni₉D_9.4 (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 DH_des = 24.0 kJ/mol_H2 and an equilibrium pressure of H₂ desorption of 18 bar at 20 °C (La_1.09Mg_1.91Ni₉). 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 La_1.09Mg_1.91Ni₉D_9.5 (1) and La_0.91Mg_2.09Ni₉D_9.4 (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 LaNi₅H_5.6/5.0 + 2*MgNi₂H_1.95/2.2 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)

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1518 KiB

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Melting Behavior and Thermolysis of NaBH₄−Mg(BH₄)₂ and NaBH₄−Ca(BH₄)₂ Composites

by Morten B. Ley, Elsa Roedern, Peter M. M. Thygesen and Torben R. Jensen

Energies 2015, 8(4), 2701-2713; https://doi.org/10.3390/en8042701 - 8 Apr 2015

Cited by 26 | Viewed by 6650

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)

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Open AccessReview

Hydrazine Borane and Hydrazinidoboranes as Chemical Hydrogen Storage Materials

by Romain Moury and Umit B. Demirci

Energies 2015, 8(4), 3118-3141; https://doi.org/10.3390/en8043118 - 20 Apr 2015

Cited by 68 | Viewed by 11093

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)

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817 KiB

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Recent Advances in the Use of Sodium Borohydride as a Solid State Hydrogen Store

by Jianfeng Mao and Duncan H. Gregory

Energies 2015, 8(1), 430-453; https://doi.org/10.3390/en8010430 - 13 Jan 2015

Cited by 101 | Viewed by 11177

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)

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