Potentials and challenges of a Li-RHC based Tank

The potential of a LiBH4 - MgH2 hydrogen storage tank is discussed, on the basis of the Lab tests concerning the thermodynamic and kinetic properties of the composite and of the preliminary simulation results on the large scale capacity

Thermodynamic and kinetic characterization of the catalysed LiBH4 - MgH2 system

The LiBH4 – MgH2 system is of particular interest among the reactive hydride composites due to its high gravimetric capacity and the full reversibility of the sorption reactions. With the aim to realize a hydrogen storage tank based on this material, a full physico-chemical characterization of the 2:1 molar ratio composition has been undertaken, in order to obtain data fundamental for the simulation of the sorption processes and the design of the system. In particular, the reaction enthalpy, entropy and activation energy for all the sorption steps have been evaluated by PCT and coupled manometric – calorimetric measurements. Optical microscopy has been used to confirm the evolution of the different physico-chemical processes involving liquid and gas phases. Concerning the response of the system to the exothermal absorption and endothermal desorption reaction, the thermal conductivity of the composite in the charged and discharged state has been measured by the transient source method as a function of the temperature and the density, modified by compaction, of the samples. The effect of the density on the sorption properties and the cycling of the materials has been explored by kinetic measurements and scanning electron microscope investigations up to 20 full charging/discharging cycles on pellets compacted at pressure as high as 900 MPa. A strong effect has been noticed on the number of the so-called activation cycles and on the absorption kinetic performance, while no decrepitation and disaggregation effects have been observed, in spite of the presence of the borohydride liquid phase

Physico-chemical properties and sorption behaviour of the catalysed LiBH4 - MgH2 reactive hydride composite

In the last 20 years, enormous efforts have been devoted to the research and development of materials having, at the same time, high hydrogen gravimetric and volumetric capacities and favourable thermodynamic and kinetic sorption properties for practical applications as hydrogen tank. In particular, the quest to find a high capacity reversible hydride has shifted the interest towards alanate, amide and borohydride compounds. Currently, alkaline and alkaline-earth metal borohydrides are considered the most attractive materials for automotive applications. Despite a high gravimetric and volumetric capacity, the thermodynamics of the reversible dehydrogenation of many complex borohydrides doesn't meet the targets required for a practical on board hydrogen carrier. Moreover, all of these materials are plagued by high kinetics barriers to dehydrogenation and/or rehydrogenation in the solid state. Therefore, a valid approach was established in order to tune the dehydrogenation thermodynamic properties (i.e. reducing decomposition enthalpy) of the borohydrides, by incorporating a second or third specie into the reaction to stabilize the reaction products. In this study, the kinetic and thermodynamic properties of the sorption steps characterizing the binary LiBH4-MgH2 system have been investigated in detail by combined manometric – calorimetric measurements, in situ and ex situ X-Ray powder diffraction analyses and in-situ Synchrotron Radiation Powder X-ray Diffraction (SR-PXD). The system is well known in literature concerning the good reversibility of the sorption reaction and the high gravimetric capacity, but no chemico-physical characterization has been made up to now. By DSC measurements it has been shown that LiBH4 phase transition and melting take place (at 100 °C and 240 °C respectively) before any dehydrogenation step. Subsequently, MgH2 decomposes (at around 320 °C) and free Mg reacts with the borohydride to give MgB2 (380 °C). This last compound re-hydrogenates in one step giving, through the simultaneous reaction with LiH, the two starting hydrides. The total gravimetric capacity is 9 wt %. Absorption and desorption enthalpies and activation energies have been determined, together with the heat capacity and the thermal conductivity, fundamental data for the sketching and the realization of the hydrogen storage tank. The influence of the density of the samples on the hydrogen sorption properties and on the thermal conductivity has been evaluated too

Compaction pressure influence on material properties and sorption behaviour of LiBH4-MgH2 composite

Among different Reactive Hydride Composites (RHCs), the combination of LiBH4 and MgH2 is a promising one for hydrogen storage, providing a high reversible storage capacity. During desorption of both LiBH4 and MgH2, the formation of MgB2 lowers the overall reaction enthalpy. In this work, the material was compacted to pellets for further improvement of the volumetric hydrogen capacity. The influence of compaction pressure on the apparent density, thermal conductivity and sorption behaviour for the Li-based RHC during cycling was investigated for the first time. Although LiBH4 melts during cycling, decrepitation or disaggregation of the pellets is not observed for any of the investigated compaction pressures. However, a strong influence of the compaction pressure on the apparent hydrogen storage capacity is detected. The influence on the reaction kinetics is rather low. To provide explanations for the observed correlations, SEM analysis before and after each sorption step was performed for different compaction pressures. Thus, the low hydrogen sorption in the first cycles and the continuously improving sorption for low pressure compacted pellets with cycling may be explained by some surface observations, along with the form stability of the pellets

A novel catalytic route for hydrogenation dehydrogenation of 2LiH MgB2 via in situ formed core shell LixTiO2 nanoparticles

A novel catalytic route for hydrogenation dehydrogenation of 2LiH MgB2 via in situ formed core shell LixTiO2 nanoparticles Aiming to improve the hydrogen storage properties of 2LiH MgB2 Li RHC , the effect of TiO2 addition to Li RHC is investigated. The presence of TiO2 leads to the in situ formation of core shell LixTiO2 nanoparticles during milling and upon heating. These nanoparticles markedly enhance the hydrogen storage properties of Li RHC. Throughout hydrogenation dehydrogenation cycling at 400 C a 1 mol TiO2 doped Li RHC material shows sustainable hydrogen capacity of 10 wt and short hydrogenation and dehydrogenation times of just 25 and 50 minutes, respectively. The in situ formed core shell LixTiO2 nanoparticles confer proper microstructural refinement to the Li RHC, thus preventing the material s agglomeration upon cycling. An analysis of the kinetic mechanisms shows that the presence of the core shell LixTiO2 nanoparticles accelerates the one dimensional interface controlled mechanism during hydrogenation owing to the high Li mobility through the LixTiO2 lattice. Upon dehydrogenation, the in situ formed core shell LixTiO2 nanoparticles do not modify the dehydrogenation thermodynamic properties of the Li RHC itself. A new approach by the combination of two kinetic models evidences that the activation energy of both MgH2 decomposition and MgB2 formation is reduced. These improvements are due to a novel catalytic mechanism via Li source sink reversible reaction

A novel catalytic route for hydrogenation-dehydrogenation of 2LiH + MgB2: Via in situ formed core-shell LixTiO2 nanoparticles

Aiming to improve the hydrogen storage properties of 2LiH + MgB2 (Li-RHC), the effect of TiO2 addition to Li-RHC is investigated. The presence of TiO2 leads to the in situ formation of core-shell LixTiO2 nanoparticles during milling and upon heating. These nanoparticles markedly enhance the hydrogen storage properties of Li-RHC. Throughout hydrogenation-dehydrogenation cycling at 400 °C a 1 mol% TiO2 doped Li-RHC material shows sustainable hydrogen capacity of ∼10 wt% and short hydrogenation and dehydrogenation times of just 25 and 50 minutes, respectively. The in situ formed core-shell LixTiO2 nanoparticles confer proper microstructural refinement to the Li-RHC, thus preventing the material's agglomeration upon cycling. An analysis of the kinetic mechanisms shows that the presence of the core-shell LixTiO2 nanoparticles accelerates the one-dimensional interface-controlled mechanism during hydrogenation owing to the high Li+ mobility through the LixTiO2 lattice. Upon dehydrogenation, the in situ formed core-shell LixTiO2 nanoparticles do not modify the dehydrogenation thermodynamic properties of the Li-RHC itself. A new approach by the combination of two kinetic models evidences that the activation energy of both MgH2 decomposition and MgB2 formation is reduced. These improvements are due to a novel catalytic mechanism via Li+ source/sink reversible reactions.Fil: Puszkiel, Julián Atilio. Comision Nacional de Energia Atomica. Gerencia D/area de Energia Nuclear. Gerencia Materiales.; Argentina. Helmholtz–Zentrum Geesthacht; Alemania. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; ArgentinaFil: Castro Riglos, Maria Victoria. Comision Nacional de Energía Atómica. Gerencia de Área Investigaciones y Aplicaciones no Nucleares. Gerencia de Física (Centro Atómico Bariloche). División Física de Metales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; ArgentinaFil: Ramallo Lopez, Jose Martin. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; ArgentinaFil: Mizrahi, Martin Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; ArgentinaFil: Karimi, F.. Helmholtz–Zentrum Geesthacht; AlemaniaFil: Santoru, Antonio. Helmholtz–Zentrum Geesthacht; AlemaniaFil: Hoell, Armin. Helmholtz-zentrum Berlin; AlemaniaFil: Gennari, Fabiana Cristina. Comision Nacional de Energia Atomica. Gerencia D/area de Energia Nuclear. Gerencia Materiales.; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; ArgentinaFil: Arneodo Larochette, Pierre Paul. Comision Nacional de Energia Atomica. Gerencia D/area de Energia Nuclear. Gerencia Materiales.; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; ArgentinaFil: Pistidda, Claudio. Helmholtz–Zentrum Geesthacht; AlemaniaFil: Klassen, Thomas. Helmut Schmidt University; AlemaniaFil: Bellosta Von Colbe, J.M.. Helmholtz–Zentrum Geesthacht; AlemaniaFil: Dornheim, M.. Helmholtz–Zentrum Geesthacht; Alemani