Special Issue "Metals in Hydrogen Technology"

A special issue of Metals (ISSN 2075-4701).

Deadline for manuscript submissions: 30 September 2019

Special Issue Editor

Guest Editor
Dr. Claudio Pistidda

Department of Nanotechnology, Helmholtz-Zentrum Geesthacht, Germany
Website | E-Mail
Interests: material science; hydrogen technology; renewable energy; mechanochemistry

Special Issue Information

Dear Colleagues,

The world transition to a sustainable and reliable carbon free economy is the greatest challenge of the 21st century. The growing environmental awareness of climate changes and health diseases caused by the massive use of fossil fuels supplies, calls for immediate and radical changes. In view of long-term energy provision solution, the only available alternative to the production of energy from fossil fuels is to harvest it from renewable energy sources, such as sunlight, wind, tide and biomasses. Because of their intermittent nature and uneven availability on Earth, a complete exploitation of renewable energy sources is difficult. Therefore, energy storage media are needed. Hydrogen is widely considered as a key element for a potential energy solution. The possibility to produce hydrogen utilizing renewable energy sources and to store in it energy, presents multiple advantages. On the one hand, energy will be harvested and stored nearly without the production of harmful pollutants, and on the other hand the security of energy supply will be granted. In addition, the implementation of hydrogen as “energy carrier” is expected to result in an effective and synergic utilization of renewable energy sources. In order to achieve these aims, hydrogen storage technology is a key roadblock towards the use of H2 as an energy carrier. The shift from conventional fuels to hydrogen triggers great challenges that must be addressed quickly. Although, in the last decades enormous progress has been made in the development of hydrogen storage materials and hydrogen infrastructures, a lot still has to be done to efficiently support such epochal transition. In this regard, the study of interaction between metals, metal alloys and metal-based compounds and hydrogen is of primary importance. In fact, metals are essential components of materials for hydrogen production, hydrogen storage, and the entire infrastructure connected with the hydrogen distribution.

Dr. Claudio  Pistidda
Guest Editor

Manuscript Submission Information

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Keywords

  • Technological development/challenges in hydrogen technology

  • Hydrogen storage in metal containing systems

  • Metals in hydrogen production

  • Metal as additives for hydrogen production and storage

  • Metal hydrides in energy storage applications

Published Papers (6 papers)

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Research

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Open AccessArticle
The Dehydrogenation Mechanism and Reversibility of LiBH4 Doped by Active Al Derived from AlH3
Metals 2019, 9(5), 559; https://doi.org/10.3390/met9050559
Received: 10 April 2019 / Revised: 9 May 2019 / Accepted: 10 May 2019 / Published: 13 May 2019
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Abstract
A detailed analysis of the dehydrogenation mechanism and reversibility of LiBH4 doped by as-derived Al (denoted Al*) from AlH3 was performed by thermogravimetry (TG), differential scanning calorimetry (DSC), mass spectral analysis (MS), powder X-ray diffraction (XRD), scanning electronic microscopy (SEM), and [...] Read more.
A detailed analysis of the dehydrogenation mechanism and reversibility of LiBH4 doped by as-derived Al (denoted Al*) from AlH3 was performed by thermogravimetry (TG), differential scanning calorimetry (DSC), mass spectral analysis (MS), powder X-ray diffraction (XRD), scanning electronic microscopy (SEM), and Fourier transform infrared spectroscopy (FTIR). The results show that the dehydrogenation of LiBH4/Al* is a five-step reaction: (1) LiBH4 + Al → LiH + AlB2 + “Li-Al-B-H” + B2H6 + H2; (2) the decomposition of “Li-Al-B-H” compounds liberating H2; (3) 2LiBH4 + Al → 2LiH + AlB2 + 3H2; (4) LiBH4 → LiH + B + 3/2H2; and (5) LiH + Al → LiAl + 1/2H2. Furthermore, the reversibility of the LiBH4/Al* composite is based on the following reaction: LiH + LiAl + AlB2 + 7/2H2 ↔ 2LiBH4 + 2Al. The extent of the dehydrogenation reaction between LiBH4 and Al* greatly depends on the precipitation and growth of reaction products (LiH, AlB2, and LiAl) on the surface of Al*. A passivation shell formed by these products on the Al* is the kinetic barrier to the dehydrogenation of the LiBH4/Al* composite. Full article
(This article belongs to the Special Issue Metals in Hydrogen Technology)
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Open AccessFeature PaperArticle
Effect of the Process Parameters on the Energy Transfer during the Synthesis of the 2LiBH4-MgH2 Reactive Hydride Composite for Hydrogen Storage
Metals 2019, 9(3), 349; https://doi.org/10.3390/met9030349
Received: 22 February 2019 / Revised: 12 March 2019 / Accepted: 16 March 2019 / Published: 19 March 2019
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Abstract
Several different milling parameters (additive content, rotation velocity, ball-to-powder ratio, degree of filling, and time) affect the hydrogen absorption and desorption properties of a reactive hydride composite (RHC). In this paper, these effects were thoroughly tested and analyzed. The milling process investigated in [...] Read more.
Several different milling parameters (additive content, rotation velocity, ball-to-powder ratio, degree of filling, and time) affect the hydrogen absorption and desorption properties of a reactive hydride composite (RHC). In this paper, these effects were thoroughly tested and analyzed. The milling process investigated in such detail was performed on the 2LiH-MgB2 system doped with TiCl3. Applying an upgraded empirical model, the transfer of energy to the material during the milling process was determined. In this way, it is possible to compare the obtained experimental results with those from processes at different scales. In addition, the different milling parameters were evaluated independently according to their individual effect on the transferred energy. Their influence on the reaction kinetics and hydrogen capacity was discussed and the results were correlated to characteristics like particle and crystallite size, specific surface area, presence of nucleation sites and contaminants. Finally, an optimal value for the transferred energy was determined, above which the powder characteristics do not change and therefore the RHC system properties do not further improve. Full article
(This article belongs to the Special Issue Metals in Hydrogen Technology)
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Open AccessArticle
New Insight on the Hydrogen Absorption Evolution of the Mg–Fe–H System under Equilibrium Conditions
Metals 2018, 8(11), 967; https://doi.org/10.3390/met8110967
Received: 11 October 2018 / Revised: 31 October 2018 / Accepted: 12 November 2018 / Published: 19 November 2018
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Abstract
Mg2FeH6 is regarded as potential hydrogen and thermochemical storage medium due to its high volumetric hydrogen (150 kg/m3) and energy (0.49 kWh/L) densities. In this work, the mechanism of formation of Mg2FeH6 under equilibrium conditions [...] Read more.
Mg2FeH6 is regarded as potential hydrogen and thermochemical storage medium due to its high volumetric hydrogen (150 kg/m3) and energy (0.49 kWh/L) densities. In this work, the mechanism of formation of Mg2FeH6 under equilibrium conditions is thoroughly investigated applying volumetric measurements, X-ray diffraction (XRD), X-ray absorption near edge structure (XANES), and the combination of scanning transmission electron microscopy (STEM) with energy-dispersive X-ray spectroscopy (EDS) and high-resolution transmission electron microscopy (HR-TEM). Starting from a 2Mg:Fe stoichiometric powder ratio, thorough characterizations of samples taken at different states upon hydrogenation under equilibrium conditions confirm that the formation mechanism of Mg2FeH6 occurs from elemental Mg and Fe by columnar nucleation of the complex hydride at boundaries of the Fe seeds. The formation of MgH2 is enhanced by the presence of Fe. However, MgH2 does not take part as intermediate for the formation of Mg2FeH6 and acts as solid-solid diffusion barrier which hinders the complete formation of Mg2FeH6. This work provides novel insight about the formation mechanism of Mg2FeH6. Full article
(This article belongs to the Special Issue Metals in Hydrogen Technology)
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Open AccessArticle
Quantitative and Qualitative Analysis of Hydrogen Accumulation in Hydrogen-Storage Materials Using Hydrogen Extraction in an Inert Atmosphere
Metals 2018, 8(9), 672; https://doi.org/10.3390/met8090672
Received: 10 July 2018 / Revised: 21 August 2018 / Accepted: 21 August 2018 / Published: 28 August 2018
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Abstract
Currently, standard samples with high hydrogen concentrations that meet the requirements of hydrogen extraction in an inert atmosphere are not currently available on the market. This article describes the preparation of Ti-H standard samples and the calibration of RHEN602, a hydrogen analyzer, using [...] Read more.
Currently, standard samples with high hydrogen concentrations that meet the requirements of hydrogen extraction in an inert atmosphere are not currently available on the market. This article describes the preparation of Ti-H standard samples and the calibration of RHEN602, a hydrogen analyzer, using LECO (LECO, Saint Joseph, MI, USA). Samples of technically pure titanium alloy were chosen as the material for sample production. The creation procedure includes five main steps: sample preparation (polishing to an average roughness of 0.04 μm using sandpaper), annealing, hydrogenation, maintenance in an inert gas atmosphere, and characterization of the samples. The absolute hydrogen concentration in the samples was determined by two methods: volumetric and mass change after the introduction of hydrogen. Furthermore, in-situ X-ray diffraction, temperature programmed desorption (TPD) analysis, and thermogravimetric analysis were used during measurements to investigate the phase transitions in the samples. As a result of this work, a series of calibration samples were prepared in a concentration range up to 4 wt % hydrogen, optimal parameters for measuring high concentrations of hydrogen. The calibration line was obtained and the calibration error was 10%. Full article
(This article belongs to the Special Issue Metals in Hydrogen Technology)
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Open AccessFeature PaperArticle
Techno-Economic Analysis of High-Pressure Metal Hydride Compression Systems
Metals 2018, 8(6), 469; https://doi.org/10.3390/met8060469
Received: 1 June 2018 / Revised: 16 June 2018 / Accepted: 18 June 2018 / Published: 20 June 2018
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Abstract
Traditional high-pressure mechanical compressors account for over half of the car station’s cost, have insufficient reliability, and are not feasible for a large-scale fuel cell market. An alternative technology, employing a two-stage, hybrid system based on electrochemical and metal hydride compression technologies, represents [...] Read more.
Traditional high-pressure mechanical compressors account for over half of the car station’s cost, have insufficient reliability, and are not feasible for a large-scale fuel cell market. An alternative technology, employing a two-stage, hybrid system based on electrochemical and metal hydride compression technologies, represents an excellent alternative to conventional compressors. The high-pressure stage, operating at 100–875 bar, is based on a metal hydride thermal system. A techno-economic analysis of the metal hydride system is presented and discussed. A model of the metal hydride system was developed, integrating a lumped parameter mass and energy balance model with an economic model. A novel metal hydride heat exchanger configuration is also presented, based on minichannel heat transfer systems, allowing for effective high-pressure compression. Several metal hydrides were analyzed and screened, demonstrating that one selected material, namely (Ti0.97Zr0.03)1.1Cr1.6Mn0.4, is likely the best candidate material to be employed for high-pressure compressors under the specific conditions. System efficiency and costs were assessed based on the properties of currently available materials at industrial levels. Results show that the system can reach pressures on the order of 875 bar with thermal power provided at approximately 150 °C. The system cost is comparable with the current mechanical compressors and can be reduced in several ways as discussed in the paper. Full article
(This article belongs to the Special Issue Metals in Hydrogen Technology)
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Review

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Open AccessFeature PaperReview
Solid State Hydrogen Storage in Alanates and Alanate-Based Compounds: A Review
Metals 2018, 8(8), 567; https://doi.org/10.3390/met8080567
Received: 20 June 2018 / Revised: 17 July 2018 / Accepted: 18 July 2018 / Published: 24 July 2018
Cited by 7 | PDF Full-text (273 KB) | HTML Full-text | XML Full-text
Abstract
The safest way to store hydrogen is in solid form, physically entrapped in molecular form in highly porous materials, or chemically bound in atomic form in hydrides. Among the different families of these compounds, alkaline and alkaline earth metals alumino-hydrides (alanates) have been [...] Read more.
The safest way to store hydrogen is in solid form, physically entrapped in molecular form in highly porous materials, or chemically bound in atomic form in hydrides. Among the different families of these compounds, alkaline and alkaline earth metals alumino-hydrides (alanates) have been regarded as promising storing media and have been extensively studied since 1997, when Bogdanovic and Schwickardi reported that Ti-doped sodium alanate could be reversibly dehydrogenated under moderate conditions. In this review, the preparative methods; the crystal structure; the physico-chemical and hydrogen absorption-desorption properties of the alanates of Li, Na, K, Ca, Mg, Y, Eu, and Sr; and of some of the most interesting multi-cation alanates will be summarized and discussed. The most promising alanate-based reactive hydride composite (RHC) systems developed in the last few years will also be described and commented on concerning their hydrogen absorption and desorption performance. Full article
(This article belongs to the Special Issue Metals in Hydrogen Technology)
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