| 1. |
- Gosalawit-Utke, Rapee, et al.
(författare)
-
Ca(BH4)(2)-MgF2 Reversible Hydrogen Storage: Reaction Mechanisms and Kinetic Properties
- 2011
-
Ingår i: Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 115:9, s. 3762-3768
-
Tidskriftsartikel (refereegranskat)abstract
- A composite of Ca(BH4)(2)-MgF2 is proposed as a reversible hydrogen storage system. The dehydrogenation and rehydrogenation reaction mechanisms are investigated by in situ time-resolved synchrotron radiation powder X-ray diffraction (SR-PXD) and Raman spectroscopy. The formation of an intermediate phase (CaF2-xHx) is observed during rehydrogenation. The hydrogen content of 4.3 wt % is obtained within 4 h during the first dehydrogenation at isothermal and isobaric conditions of 330 degrees C and 0.5 bar H-2, respectively. The cycling efficiency is evaluated by three release and uptake cycles together with absorbed hydrogen content in the range 5.1-5.8 wt % after 2.5 h (T = 330 degrees C and p(H-2) = 130 bar). The kinetic properties on the basis of hydrogen absorption are comparable for all cycles. As compared to pure Ca(BH4)(2) and Ca(BH4)(2)-MgH2 composite, Ca(BH4)(2)-MgF2 composite reveals the kinetic destabilization and the reproducibility of hydrogen storage capacities during cycling, respectively.
|
|
| 2. |
- Minella, Christian Bonatto, et al.
(författare)
-
Effect of Transition Metal Fluorides on the Sorption Properties and Reversible Formation of Ca(BH4)(2)
- 2011
-
Ingår i: Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 115:5, s. 2497-2504
-
Tidskriftsartikel (refereegranskat)abstract
- Light metal borohydrides are considered as promising materials for solid state hydrogen storage. Because of the high hydrogen content of 11.5 wt % and the rather low dehydrogenation enthalpy of 32 kJ mol(-1)H(2), Ca(BH4)(2) is considered to be one of the most interesting compounds in this class of materials. In the present work, the effect of selected TM-fluoride (TM = transition metal) additives on the reversible formation of Ca(BH4)(2) was investigated by means of thermovolumetric, calorimetric, Fourier transform infrared spectroscopy, and ex situ, and in situ synchrotron radiation powder X-ray diffraction (SR-PXD) measurements. Furthermore, selected desorbed samples were analyzed by B-11{H-1} solid state magic angle spinning nuclear magnetic resonance (MAS NMR). Under the conditions used in this study (145 bar H-2 pressure and 350 degrees C), TiF4 and NbF5 were the only additives causing partial reversibility. In these two cases, B-11{H-1} MAS NMR analyses detected CaB6 and likely CaB12H12 in the dehydrogenation products. Elemental boron was found in the decomposition products of Ca(BH4)(2) samples with VF4, TiF3, and VF3. The results indicate an important role of CaB6 for the reversible formation of Ca(BH4)(2).
|
|
| 3. |
- Pasquini, Luca, et al.
(författare)
-
Magnesium- and intermetallic alloys-based hydrides for energy storage : modelling, synthesis and properties
- 2022
-
Ingår i: Progress in Energy. - : Institute of Physics Publishing (IOPP). - 2516-1083. ; 4:3
-
Forskningsöversikt (refereegranskat)abstract
- Hydrides based on magnesium and intermetallic compounds provide a viable solution to the challenge of energy storage from renewable sources, thanks to their ability to absorb and desorb hydrogen in a reversible way with a proper tuning of pressure and temperature conditions. Therefore, they are expected to play an important role in the clean energy transition and in the deployment of hydrogen as an efficient energy vector. This review, by experts of Task 40 'Energy Storage and Conversion based on Hydrogen' of the Hydrogen Technology Collaboration Programme of the International Energy Agency, reports on the latest activities of the working group 'Magnesium- and Intermetallic alloys-based Hydrides for Energy Storage'. The following topics are covered by the review: multiscale modelling of hydrides and hydrogen sorption mechanisms; synthesis and processing techniques; catalysts for hydrogen sorption in Mg; Mg-based nanostructures and new compounds; hydrides based on intermetallic TiFe alloys, high entropy alloys, Laves phases, and Pd-containing alloys. Finally, an outlook is presented on current worldwide investments and future research directions for hydrogen-based energy storage.
|
|
| 4. |
- Pistidda, Claudio, et al.
(författare)
-
Pressure Effect on the 2NaH+MgB2 Hydrogen Absorption Reaction
- 2010
-
Ingår i: Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 114:49, s. 21816-21823
-
Tidskriftsartikel (refereegranskat)abstract
- The hydrogen absorption mechanism of the 2NaH + MgB2 system has been investigated in detail. Depending on the applied hydrogen pressure, different intermediate phases are observed. In the case of absorption measurements performed under 50 bar of hydrogen pressure, NaBH4 is found not to be formed directly. Instead, first an unknown phase is formed, followed upon further heating by the formation of NaMgH3 and a NaH-NaBH4 molten salt mixture; only at the end after heating to 380 degrees C do the reflections of the crystalline NaBH4 appear. In contrast, measurements performed at lower hydrogen pressure (5 bar of H-2), but under the same temperature conditions, demonstrate that the synthesis of NaBH4 is possible without occurrence of the unknown phase and of NaMgH3. This indicates that the reaction path can be tuned by the applied hydrogen pressure. The formation of a NaH-NaBH4 molten salt mixture is observed also for the measurement performed under 5 bar of hydrogen pressure with the formation of free Mg. However, under this pressure condition the formation of crystalline NaBH4 is observed only during cooling at 367 degrees C. For none of the applied experimental conditions has it been possible to achieve the theoretical gravimetric hydrogen capacity of 7.8 wt %.
|
|
| 5. |
- Pistidda, Claudio, et al.
(författare)
-
Synthesis of amorphous Mg(BH4)(2) from MgB2 and H-2 at room temperature
- 2010
-
Ingår i: Journal of Alloys and Compounds. - : Elsevier BV. - 0925-8388. ; 508:1, s. 212-215
-
Tidskriftsartikel (refereegranskat)abstract
- Due to its high hydrogen content and its favourable overall thermodynamics magnesium tetrahydroborate has been considered interesting for hydrogen storage applications. In this work we show that unsolvated amorphous magnesium tetrahydroborate can be obtained by reactive ball milling of commercial MgB2 under 100 bar hydrogen atmosphere. The material was characterized by solid-state NMR which showed the characteristic features of Mg(BH4)(2), together with those of higher borohydride species. High pressure DSC and TPD-MS showed thermal behaviour similar to that of Mg(BH4)(2) but with broadened signals. In situ synchrotron X-ray powder diffraction confirmed the amorphous state of the material and showed the typical crystalline decomposition products of Mg(BH4)(2) at elevated temperatures. (C) 2010 Elsevier B.V. All rights reserved.
|
|
| 6. |
- Puszkiel, Julian, et al.
(författare)
-
Hydrogen storage in Mg-LiBH4 composites catalyzed by FeF3
- 2014
-
Ingår i: Journal of Power Sources. - : Elsevier BV. - 1873-2755 .- 0378-7753. ; 267, s. 799-811
-
Tidskriftsartikel (refereegranskat)abstract
- Mg-10 mol% LiBH4 composite plus small amounts of FeF3 is investigated in the present work. The presence of LiBH4 during the milling process noticeably modifies the size and morphology of the Mg agglomerates, leading to faster hydrogenation and reaching almost the theoretical hydrogen capacity owing to enhanced hydrogen diffusion mechanism. However, the dehydrogenation of the system at low temperatures (<= 300 degrees C) is still slow. Thus, FeF3 addition is proposed to improve the dehydrogenation kinetic behavior. From experimental results, it is found that the presence of FeF3 results in an additional size reduction of the Mg agglomerates between similar to 10 and similar to 100 mu m and the formation of stable phases such as MgF2, LiF and FeB. The FeB species might have a catalytic effect upon the MgH2 decomposition. As a further result of the FeF3 addition, the Mg-10 mol%LiBH4-5 mol% FeF3 material shows improved dehydrogenation properties: reduced dehydrogenation activation energy, faster hydrogen desorption rate and reversible hydrogen capacities of about 5 wt% at 275 degrees C. (C) 2014 Elsevier B.V. All rights reserved.
|
|
| 7. |
- Puszkiel, Julian, et al.
(författare)
-
Sorption behavior of the MgH2-Mg2FeH6 hydride storage system synthesized by mechanical milling followed by sintering
- 2013
-
Ingår i: International Journal of Hydrogen Energy. - : Elsevier BV. - 1879-3487 .- 0360-3199. ; 38:34, s. 14618-14630
-
Tidskriftsartikel (refereegranskat)abstract
- The hydrogen sorption behavior of the Mg2FeH6-MgH2 hydride system is investigated via in-situ synchrotron and laboratory powder X-ray diffraction (SR-PXD), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), particle size distribution (PSD) and volumetric techniques. The Mg2FeH6-MgH2 hydride system is obtained by mechanical milling in argon atmosphere followed by sintering at high temperature and hydrogen pressure. In-situ SR-PXD results show that upon hydriding MgH2 is a precursor for Mg2FeH6 formation and remained as hydrided phase in the obtained material. Diffusion constraints preclude the further formation of Mg2FeH6. Upon dehydriding, our results suggest that MgH2 and Mg2FeH6 decompose independently in a narrow temperature range between 275 and 300 degrees C. Moreover, the decomposition behavior of both hydrides in the Mg2FeH6-MgH2 hydride mixture is influenced by each other via dual synergetic-destabilizing effects. The final hydriding/dehydriding products and therefore the kinetic behavior of the Mg2FeH6-MgH2 hydride system exhibits a strong dependence on the temperature and pressure conditions. Copyright (C) 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.
|
|
| 8. |
- Saldan, Ivan, et al.
(författare)
-
Hydrogen Sorption in the LiH-LiF-MgB2 System
- 2013
-
Ingår i: Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 117:33, s. 17360-17366
-
Tidskriftsartikel (refereegranskat)abstract
- A composite material in the LiH-LiF-MgB2 system has been synthesized by high-energy ball milling. Some peaks in addition to that of the binary 2LiH-MgB2 and 2LiF-MgB2 systems are observed for the composite material by high-pressure differential scanning calorimetry (HP-DSC), indicating the formation of intermediate phases. In situ synchrotron radiation powder X-ray diffraction (SR-PXD) performed at 60 bar of H-2 and 390 degrees C shows a superposition of both reaction pathways that are typical for 2LiH-MgB2 and 2LiF-MgB2. After hydrogen absorption of the LiH-LiF-MgB2 composite the vibrational modes of LiBH4 were observed by attenuated total reflection infrared (ATR-IR) spectroscopy. The F-19 MAS NMR spectrum of the LiF-LiBH4 sample after heat treatment in hydrogen is strongly dominated by the centerband and spinning sidebands from LiF; in addition, a low-intensity resonance, very similar to that of [BF4](-) ion, is identified.
|
|
