The Role of Carbon in the Hydrogen Storage Kinetics of Lithium Metal Hydrides (original) (raw)
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Destabilization and characterization of LiBH4/MgH2 complex hydride for hydrogen storage
2007
The demands on Hydrogen fuel based technologies is ever increasing for substitution or replacing fossil fuel due to superior energy sustainability, national security and reduced greenhouse gas emissions. Currently, the polymer based proton exchange membrane fuel cell (PEMFC), is strongly considered for on-board hydrogen storage vehicles due to low temperature operation, efficiency and low environmental impact. However, the realization of PEMFC vehicles must overcome the portable hydrogen storage barrier. DOE and FreedomCAR technical hydrogen storage targets for the case of solid state hydrides are: (1) volumetric hydrogen density > 0.045 kgH2/L, (2) gravimetric hydrogen density > 6.0 wt%, (3) operating temperature < 150 degrees C, (4) lifetimes of 1000 cycles, and (5) a fast rate of H2 absorption and desorption. To meet these targets, we have focused on lithium borohydride systems; an alkali metal complex hydride with a high theoretical hydrogen capacity of 18 wt.%. It has ...
LiBH 4 a new hydrogen storage material
Journal of Power Sources, 2003
The challenge in the research on hydrogen storage materials is to pack hydrogen atoms or molecules as close as possible. The density of liquid and solid hydrogen is 70.8 and 70.6 kg m À3 , respectively. Hydrogen absorbed in metals can reach a density of more than 150 kg m À3 (e.g. Mg 2 FeH 6 ) at atmospheric pressure. However, due to the large atomic mass of the transition metals the gravimetric hydrogen density is limited to less than 5 mass%. Light weight group 3 metals, e.g. Al, B, are able to bind four hydrogen atoms and form together with an alkali metal an ionic or at least partially covalent compound. These compounds are rather stable and often desorb the hydrogen only above their melting temperature. Complex hydrides like NaAlH 4 , when catalyzed, decompose already at room temperature. We have investigated LiBH 4 , a complex hydride which consists of 18 mass% of hydrogen. The hydrogen desorption from LiBH 4 was successfully catalyst with SiO 2 and 13.5 mass% of hydrogen were liberated starting already at 200 8C. #
The impact of carbon materials on the hydrogen storage properties of light metal hydrides
Journal of Materials Chemistry, 2011
The safe and efficient storage of hydrogen is still one of the remaining challenges towards fuel cell powered cars. Metal hydrides are a promising class of materials as they allow the storage of large amounts of hydrogen in a small volume at room temperature and low pressures. However, usually the kinetics of hydrogen release and uptake and the thermodynamic properties do not satisfy the requirements for practical applications. Therefore current research focuses on catalysis and the thermodynamic tailoring of metal hydride systems. Surprisingly, carbon materials used as additive or support are very effective to improve the hydrogen storage properties of metal hydrides allowing fast kinetics and even a change in the thermodynamic properties. Even though the underlying mechanisms are not always well understood, the beneficial effect is probably related to the peculiar structure of the carbon materials. This feature article gives an introduction to the different carbon materials, an overview of the preparation strategies to synthesize carbon/hydride nanocomposites, and highlights the beneficial effect of carbon by discussing two important hydrides: MgH 2 and NaAlH 4 .
The Possibility of Lithium Iodide (LiI) as H2 Storage Material: A Conceptual DFT (CDFT) Approach
Zenodo (CERN European Organization for Nuclear Research), 2023
This article deals with the different types of the hydrogen storage process, its thermochemistry, adsorption process, and binding energy, in the light of the computational approach using the conceptual density functional theory (CDFT). This article expresses the view that lithium iodide (LiI) is a viable template for hydrogen storage at low temperatures. The density functional theory (DFT) has been used to investigate the structure and chemical reactivity of the resulting templates. The adsorption process is found to be quasi-sorption in nature. The molecular hydrogen interacts with building blocks (with Li centre) through electrovalent interaction and a single LiI molecule is capable of absorbing 10 H 2 with a high gravimetric wt% value (13.07 wt%) which is found to be a promising system as per standard. The changes in Gibbs free energy indicate that hydrogen adsorption can occur spontaneously at cryogenic temperatures.
Lithium amidoborane (LiAB) is known as an efficient hydrogen storage material. The dehydrogenation reaction of LiAB was studied employing temperature-programmed desorption methods at varying temperature and H 2 pressure. As the dehydroge-nation products are in amorphous form, the XRD technique is not useful for their identification. The two-step decomposition temperatures (74 and 118 °C) were found to hardly change in the 1–80 bar pressure range. This is related either to kinetic effects or to thermal dependence of the reaction enthalpy. Further, the possible joint decomposition of LiNH 2 BH 3 with LiBH 4 or MgH 2 was investigated. Indeed LiBH 4 proved to destabilize LiAB, producing a 10 °C decrease of the first-step decomposition temperature, whereas no significant effect was observed by the addition of MgH 2. The 5LiNH 2 BH 3 + LiBH 4 assemblage shows improved hydrogen storage properties with respect to pure lithium amidoborane. Keywords Lithium amidoborane · Hydrogen storage · Destabilization · Lithium borohydride · Magnesium hydride
Improved thermodynamic properties of doped LiBH 4 for hydrogen storage: First-principal calculation
International Journal of Hydrogen Energy, 2019
First-principles calculations have been performed on lithium borohydride LiBH4 using the ultrasoft pseudopotential method, which is a potential candidate for hydrogen-storage materials due to its extremely large gravimetric capacity of 18 mass % hydrogen. We focus on an orthorhombic phase observed at ambient conditions and predict its fundamental properties; De-hydrogenation and electronic properties of doped Li1+xB1-xH4 by Li (with 0<x<0.75); to be used as a material for hydrogen-storage; are studied from density-functional theory based first-principles calculations. The results suggest that the substitution of B by Li decrease the desorption enthalpy of hydrogen from 75 kJ/mol.l to 40. Our calculation results show the function of Li in improving thermodynamics, which provides a favorable thermodynamic modification.
LITHIUM BOROHYDRIDE AS A HYDROGEN STORAGE MATERIAL: A REVIEW
The major obstacle in transition to the hydrogen economy is the problem of onboard hydrogen storage. Solid-state hydrogen storage is the safest and most efficient method for hydrogen storage. Most of the metal hydrides exhibit very large volumetric storage density but less than 5 wt % gravimetric hydrogen density. Light metals such as Al, B bind with four hydrogen atoms and form together with an alkali metal an ionic or partially covalent compound called complex hydride. LiBH4 is a complex hydride with 18.5 mass % gravimetric hydrogen density and 121 kg/m3 volumetric hydrogen storage capacity. The desorption temperature of LiBH4 is greater than 470°C, thus making it difficult to use for storage applications. In addition, the conditions for reversible reaction are unfavorable. Modification of thermodynamics of the hydrogenation and dehydrogenation reaction is possible by using additives which could destabilize LiBH4 by stabilizing the dehydrogenated state. This could decrease the heat of reaction and reduce the desorption temperature at the same time, making the conditions for reversible reaction more optimum. Several additives which could destabilize LiBH4 have been reviewed.
Journal of Computational Electronics, 2023
Renewable energy prices are decreasing, making it easier to make energy systems that are good for the environment. Highdensity storage for renewable energy is possible with hydrogen. This work focuses on the theoretical study of LiXH 3 (where X = Ti, Mn, and Cu), including their structural, electronic, mechanical, thermoelectric, and hydrogen storage properties, using first-principles calculations. LiCuH 3 is more stable than LiMnH 3 and LiTiH 3 , based on the optimization graph. The electronic properties show the metallic nature of these studied hydrides. Born's criterion indicates that all studied hydrides are brittle for various mechanical applications. LiTiH 3 , LiMnH 3 , and LiCuH 3 are all thought to be able to store hydrogen with gravimetric storage capacities of 5.22%, 4.66%, and 4.11%, respectively. Based on how their thermoelectric properties change with temperature, all the materials under study can absorb heat energy, which shows that they are both electrically and thermally conductive.