17 research outputs found
Nanoconfined 2LiBH4eMgH2eTiCl3 in carbon aerogel scaffold for reversible hydrogen storage
No full textNanoconfinement of 2LiBH4–MgH2–TiCl3 in resorcinol–formaldehyde carbon aerogel scaffold (RF–CAS) for reversible hydrogen storage applications is proposed. RF–CAS is encapsulated with approximately 1.6 wt. % TiCl3 by solution impregnation technique, and it is further nanoconfined with bulk 2LiBH4–MgH2 via melt infiltration. Faster dehydrogenation kinetics is obtained after TiCl3 impregnation, for example, nanoconfined 2LiBH4–MgH2–TiCl3 requires ∼1 and 4.5 h, respectively, to release 95% of the total hydrogen content during the 1st and 2nd cycles, while nanoconfined 2LiBH4–MgH2 (∼2.5 and 7 h, respectively) and bulk material (∼23 and 22 h, respectively) take considerably longer. Moreover, 95–98.6% of the theoretical H2 storage capacity (3.6–3.75 wt. % H2) is reproduced after four hydrogen release and uptake cycles of the nanoconfined 2LiBH4–MgH2–TiCl3. The reversibility of this hydrogen storage material is confirmed by the formation of LiBH4 and MgH2 after rehydrogenation using FTIR and SR-PXD techniques, respectively.Fil: Gosalawit Utke, Rapee. Helmholtz-Zentrum Geesthacht; Alemania. Suranaree University of Technology; TailandiaFil: Milanese, Chiara. Universita degli Studi di Pavia; ItaliaFil: Javadian, Payam. University Aarhus; DinamarcaFil: Jepsen, Julian. Helmholtz-Zentrum Geesthacht; AlemaniaFil: Laipple, Daniel. Helmholtz-Zentrum Geesthacht; AlemaniaFil: Karmi, Fahim. Helmholtz-Zentrum Geesthacht; AlemaniaFil: Puszkiel, Julián Atilio. Helmholtz-Zentrum Geesthacht; Alemania. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Jensen, Torben. University Aarhus; DinamarcaFil: Marini, Amedeo. Universita degli Studi di Pavia; ItaliaFil: Klassen, Thomas. Helmholtz-Zentrum Geesthacht; AlemaniaFil: Dornheim, Martin. Helmholtz-Zentrum Geesthacht; Alemani
2LiBH4–MgH2–0.13TiCl4 confined in nanoporous structure of carbon aerogel scaffold for reversible hydrogen storage
No full textThe investigations based on kinetic improvement and reaction mechanisms during melt infiltration, dehydrogenation, and rehydrogenation of nanoconfined 2LiBH4-MgH2-0.13TiCl4 in carbon aerogel scaffold (CAS) are proposed. It is found that TiCl4 and LiBH4 are successfully nanoconfined in CAS, while MgH2 proceeds partially. In the same temperature (25-500ºC) and time (0?5 h at constant temperature) ranges nanoconfined 2LiBH4-MgH2-0.13TiCl4 dehydrogenates completely 99% of theoretical H2 storage capacity, while that of nanoconfined 2LiBH4?MgH2 is only 94%. Nanoconfined 2LiBH4-MgH2-0.13TiCl4 performs three-step dehydrogenation at 140, 240, and 380ºC. Onset (the first-step) dehydrogenation temperature (140ºC), significantly lower than those of nanoconfined sample of 2LiBH4-MgH2 and 2LiBH4-MgH2-TiCl3 (DT = 140 and 110ºC, respectively) is in agreement with the decomposition of eutectic LiBH4-Mg(BH4)2 and lithium?titanium borohydride. For the second and third steps (240 and 380ºC),decompositions of LiBH4 destabilized by LiCl solvation and MgH2 are accomplished, respectively. In conclusion, dehydrogenation products are B, Mg, LiH, and TiH. Reversibility of nanoconfined 2LiBH4-MgH2-0.13TiCl4 sample is confirmed by the recovery of LiBH4 after rehydrogenation together with the formation of [B12H12] derivatives. The superior kinetics during the 2nd, 3rd, and 4th cycles of nanoconfined2LiBH4-MgH2-0.13TiCl4 to the nanoconfined 2LiBH4-MgH2 can be due to the formations of Ti-MgH2 alloys (Mg0.25Ti0.75H2 and Mg6TiH2) during the 1st rehydrogenation.Fil: Gosalawit Utke, Rapee. Institute of Materials Research; Alemania. Suranaree University of Technology; TailandiaFil: Milanese, Chiara. University of Pavia; ItaliaFil: Javadian, Payam. University of Aarhus; DinamarcaFil: Girella, Alessandro. University of Pavia; ItaliaFil: Laipple, Daniel. Institute of Materials Research; AlemaniaFil: Puszkiel, Julián Atilio. Institute of Materials Research; Alemania. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Cattaneo, Alice S.. University of Aarhus; DinamarcaFil: Ferrara, Chiara. University of Aarhus; DinamarcaFil: Wittayakhun, Jatuporn. Suranaree University of Technology; TailandiaFil: Skibsted, Jørgen. University of Aarhus; DinamarcaFil: Jensen, Torben R.. University of Aarhus; DinamarcaFil: Marini, Amedeo. University of Pavia; ItaliaFil: Klassen, Thomas. Institute of Materials Research; AlemaniaFil: Dornheim, Martin. Institute of Materials Research; Alemani
Nanoconfined 2LiBH4 - MgH2 in nanoporous carbon aerogel scaffolds for reversible hydrogen storage
No full textNanoconfined 2 LiBH4 - MgH2 is prepared with and without catalyst (TiCl3) by direct melt infiltration of bulk 2 LiBH4 - MgH2 into an inert carbon aerogel scaffold material. Homogeneous dispersion of MgH2, LiBH4 and TiCl3 in the nanoporous structure of carbon scaffold is assured by several means, such as SEM-EDS via focus ion beam technique, in situ synchrotron radiation powder X-Ray diffraction, and N2 adsorption-desorption. The nanoconfined 2LiBH4-MgH2 system with and without catalyst release 100% hydrogen storage capacity within 100 and 200 min respectively, while the time for the bulk material is 30 h. A reversible 10.8 wt % H2 with respect to the metal hydride content over 4 hydrogen release and uptake cycles is preserved from both the nanoconfined systems
Destabilization of LiBH4 by Nanoconfinement in PMMA–co–BM Polymer Matrix for Reversible Hydrogen Storage
No full textDestabilization of LiBH4 by nanoconfinement in poly (methyl methacrylate)-co-butyl meth-acrylate (PMMA-co-BM), denoted as nano LiBH4-PMMA-co-BM, is proposed for reversible
hydrogen storage. The onset dehydrogenation temperature of nano LiBH4-PMMA-co-BM is reduced to 80C (DeltaT=340 and170
°C as compared with milled LiBH4 and nanoconfined LiBH4
in carbon aerogel,respectively).At120°C under vacuum,nanoLiBH4-PMMA-co-BM releases 8.8 wt.% H2
with respect to LiBH4 content within 4 h during the 1st dehydrogenation, while milled LiBH4
performs no dehydrogenation at the same temperature and pressure condition.
Moreover,nanoLiBH4-PMMA-coBM can be rehydrogenated at the mildest condition(140°C under50 barH2 for12h) among other modifiedLiBH4 reportedinthepreviousliterature
Nanoconfined 2LiBH4-MgH2 for Reversible Hydrogen Storages: Reaction Mechanisms, Kinetics and Thermodynamics
No full textSamples of nanoconfined Reactive Hydride Composites in resorcinol–formaldehyde (RF) aerogel scaffolds are prepared by (i) direct melt infiltration of bulk 2LiBH4–MgH2; and (ii)
MgH2 impregnation and LiBH4 melt infiltration. The reaction mechanisms, kinetics and thermodynamics of the systems are determined. Activation energy (EA) and LiBH4 and MgH2
dehydrogenation enthalpies (Hdes, MgH2+ Hdes, LiBH4) of the nanoconfined 2LiBH4–MgH2 are in this work of interest. The hydrogen sorption reactions in both nanoconfined samples are reversible as shown by the recovering of LiBH4 and MgH2 after rehydrogenation. The titration results show the remarkable improvement in desorption kinetics of both nanoconfined samples over the bulk material, such as more than 90 % of overall hydrogen storage capacity is obtained
within 2 h for the nanoconfined samples during the 1st dehydrogenation, while that of bulk material needs more than 16 h. The activation energy of the composites decreases by 84–150 kJ/mol (EA) due to nanoconfinement. For thermodynamics, the dehydrogenation enthalpies of
LiBH4 and MgH2 (Hdes, MgH2+ Hdes, LiBH4) obtained from the nanoconfined sample reduces up to 10.61 kJ/mol H2 with respect to the bulk material
Chemico-physical characterization and hydrogen sorption properties of chemical hydrides confined into mesoporous scaffolds
No full textWithin the widespread activity in the development of innovative hydrogen storage materials, rising attention has been recently addressed to the sorption properties of nanosized materials confined into the mesoporous networks of matrixes with different chemical nature. Improvements of the thermodynamic properties and kinetics of hydrogen release and uptake are expected through the reduction to nanometer scale and the control of grain size of hydrides particles. As a further beneficial effect, the undesired grain growth and particle agglomeration would be avoided.
In this work, the possibility to infiltrate single and multicomponent chemical hydrides into Si- and C- matrices is explored. In particular, NaBH4 and NaBH4 - MgH2 mixtures were embedded in Si-based and C-based high surface matrixes and LiBH4-MgH2 mixtures in C aerogel matrices by wet chemical impregnation and melting infiltration. Structural characterization was performed by X-Ray diffraction, small angle neutron scattering and transmission electron microscopy in order to estimate the efficiency of impregnation techniques. The thermodynamics and kinetics of the absorption and desorption processes and the chemical nature of the released gas were analyzed by high-pressure calorimetry, manometric measurements and mass spectroscopy.
A noticeable reduction in the temperature of the sorption steps, in the desorption enthalpies and in the activation energies with respect to the mixtures in powder form is evident for both the explored systems. Full reversibility of the sorption processes has been demonstrated for the Li-containing system
Effect of Transition Metal Fluorides on the Sorption Properties and Reversible Formation of Ca(BH(4))(2) RID C-7241-2011 RID B-3019-2009 RID A-2096-2009 RID B-4391-2009
No full textLight 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-1H 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 11B{1H} solid state magic angle spinning nuclear magnetic resonance (MAS NMR). Under the conditions used in this study (145 bar H 2 pressure and 350 °C), TiF4 and NbF5 were the only additives causing partial reversibility. In these two cases, 11B{1H} 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
LiF-MgB2 System for Reversible Hydrogen Storage
No full textLiF-MgB2 composites are proposed for reversible hydrogen storage. With respect to pure LiBH4, a significantly kinetic destabilization regarding hydrogenation and dehydrogenation is accomplished. The reversible hydrogen storage capacity is up to 6.4 wt %. The kinetic properties are improved significantly during cycling. The formations of the hydridofluoride phases (LiBa4-yFy and LiH1-xFx) are observed by in situ synchrotron X-ray diffraction (XRD) and attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR). Hydrogenation and dehydrogenation mechanisms are described on the basis of the formation and decomposition of the hydridofluoride phases, respectively
Sorption behavior of the MgH2-Mg2FeH6 hydride storage system synthesized by mechanical milling followed by sintering
No full textThe 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
