Destabilization and characterization of LiBH4/MgH2 complex hydride for hydrogen storage (original) (raw)
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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. #
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.
The Role of Carbon in the Hydrogen Storage Kinetics of Lithium Metal Hydrides
A feasible solution to the problem of urban pollution is hydrogen propelled zero-emission vehicles. The US Department of Energy (DoE) has set the target of 6.5 wt% of H 2 storage capacity and a volumetric energy density of 1.5 kWh/L at an operating temperature and pressure conditions of 50°C and 2.5 bar respectively by 2010.[1] The storage media being studied until now have not been able to successfully achieve these targets and therefore, a compact, light weight hydrogen-storage system for transportation is not available currently. Hydrogen storage is therefore the key enabling technology that should be significantly advanced in terms of performance and cost effectiveness if hydrogen is to become an important part of the world's energy economy. In the present work, fundamental studies of the processes involved in hydrogen adsorption and release by carbon beryllium-containing lithium hydrides are carried out, to enable the design of efficient hydrogen storage materials for transportation applications. This is obtained by studying geometric, energetic, and thermodynamic properties such as the enthalpy of formation ∆H f of ionic metal hydrides Li(C n Be y)H x and Li 2 (C n Be y)H x. Our results indicate that the presence of (C-Be) dopants in Li-H complexes, enhances the desorption kinetics of these compounds lowering the enthalpy of dehydrogenation tremendously.
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
International Journal of Hydrogen Energy, 2010
Multinary complex hydrides comprised of borohydrides, amides and metal hydrides have been synthesized using the solid state mechano-chemical process. After the optimization of the system, it was found that LiBH 4 /LiNH 2 /MgH 2 exhibits potential reversible hydrogen storage behavior (>6 wt.%) at temperatures of 125e175 C. To further improve the hydrogen performance of the system, various nano additives namely, nickel, cobalt, iron, copper, and manganese were investigated. It was observed that some of these additives (Co, Ni) lowered the hydrogen release temperature at least 75e100 C in the major hydrogen decomposition step. While other additives acted as catalysts and increased the rate at which hydrogen was released. Combinatorial addition of selected materials were also investigated and found to have both a positive effect on kinetics and reduction in hydrogen desorption temperature.
Tuning LiBH4 for Hydrogen Storage: Destabilization, Additive, and Nanoconfinement Approaches
Tuning LiBH4 for Hydrogen Storage: Destabilization, Additive, and Nanoconfinement Approaches, 2019
Hydrogen technology has become essential to fulfill our mobile and stationary energy needs in a global low-carbon energy system. The non-renewability of fossil fuels and the increasing environmental problems caused by our fossil fuel-running economy have led to our efforts towards the application of hydrogen as an energy vector. However, the development of volumetric and gravimetric efficient hydrogen storage media is still to be addressed. LiBH4 is one of the most interesting media to store hydrogen as a compound due to its large gravimetric (18.5 wt.%) and volumetric (121 kgH2 m^3) hydrogen densities. In this review, we focus on some of the main explored approaches to tune the thermodynamics and kinetics of LiBH4 : (I) LiBH4 + MgH2 destabilized system, (II) metal and metal hydride added LiBH4 , (III) destabilization of LiBH4 by rare-earth metal hydrides, and (IV) the nanoconfinement of LiBH4 and destabilized LiBH4 hydride systems. Thorough discussions about the reaction pathways, destabilizing and catalytic effects of metals and metal hydrides, novel synthesis processes of rare earth destabilizing agents, and all the essential aspects of nanoconfinement are led.
The complex hydride 2LiNH 2 e1.1MgH 2-0.1LiBH 4-3wt%ZrCoH 3 releases H 2 below 180 C. The complex hydride was combined with an intermetallic one to build an storage tank. The coupled material solution improves H 2 charging and discharging kinetics. A full scale hydrogen storage system was built and coupled with a HT-PEM. The APU was tested on vehicle in realistic conditions. a b s t r a c t The main objective of the SSH2S (Fuel Cell Coupled Solid State Hydrogen Storage Tank) project was to develop a solid state hydrogen storage tank based on complex hydrides and to fully integrate it with a High Temperature Proton Exchange Membrane (HT-PEM) fuel cell stack. A mixed lithium amide/mag-nesium hydride system was used as the main storage material for the tank, due to its high gravimetric storage capacity and relatively low hydrogen desorption temperature. The mixed lithium amide/mag-nesium hydride system was coupled with a standard intermetallic compound to take advantage of its capability to release hydrogen at ambient temperature and to ensure a fast start-up of the system. The hydrogen storage tank was designed to feed a 1 kW HT-PEM stack for 2 h to be used for an Auxiliary Power Unit (APU). A full thermal integration was possible thanks to the high operation temperature of the fuel cell and to the relative low temperature (170 C) for hydrogen release from the mixed lithium amide/magnesium hydride system.
Improved hydrogen storage performance of the LiNH2–MgH2–LiBH4 system by addition of ZrCo hydride
International Journal of Hydrogen Energy, 2010
Significant improvements in the hydrogen absorption/desorption properties of the 2LiNH 2 e1.1MgH 2 e0.1LiBH 4 composite have been achieved by adding 3wt% ZrCo hydride. The composite can absorb 5.3wt% hydrogen under 7.0 MPa hydrogen pressure in 10 min and desorb 3.75wt% hydrogen under 0.1 MPa H 2 pressure in 60 min at 150 C, compared with 2.75wt% and 1.67wt% hydrogen under the same hydrogenation/dehydrogenation conditions without the ZrCo hydride addition, respectively. TPD measurements showed that the dehydrogenation temperature of the ZrCo hydride-doped sample was decreased about 10 C compared to that of the pristine sample. It is concluded that both the homogeneous distribution of ZrCo particles in the matrix observed by SEM and EDS and the destabilized NeH bonds detected by IR spectrum are the main reasons for the improvement of H-cycling kinetics of the 2LiNH 2 e1.1MgH 2 e0.1LiBH 4 system.