Both the cubic C15-type and the hexagonal C14-type Laves phase compounds HoMn2 were successfully prepared. We found that they absorbed hydrogen up to 3.4 atoms per formula unit at room temperature and discharged it at around 490 K, reversibly. Structural and hydriding/dehydriding properties of the host HoMn2 and their hydrides HoMn2Hx have been investigated by powder X-ray diffraction (XRD) and thermogravimetry/differential thermal analysis (TG/DTA). With increasing the hydrogen content, the host C15-type HoMn2 is distorted into a rhombohedral phase at above x = 2.9, while the host C14-type one keeps the hexagonal structure up to x = 3.4. The experimental results obtained from TG/DTA measurement suggest that two possible interstitial sites with different activation energies for hydrogen desorption exist in the C14 HoMn2, while one site in the C15 HoMn2.

We have studied the effect of synthesis conditions on the nanostructure of advanced carbons that show moderate to high hydrogen storage. We have performed in situ studies of the dynamic pyrolysis of palladium catalyzed multifunctional polymers (MFP) in nitrogen environments, to understand the effect of process parameters and to utilize the results in the development of optimum nanostructures to meet the storage requirements. Carbon sorbents have been synthesized from polysaccharides including chitosan, chitin, and cellulose. Pyrolysis in a hydrogen atmosphere at 1373 K and 24 h has lead to microporous carbons with an optimum surface area and pore volume exceeding 2000 m2 g−1 and 2.0 cc g−1, respectively. Gravimetric microbalance studies indicate that these materials physically absorb hydrogen and store between 7 to 10 mass percent at 10 bar and 100 K. TEM micrographs indicate that the amorphous carbon shows additional ordering with prolonged hydrogen treatment from 2 to 24 h which has proven beneficial in increasing hydrogen storage. X-ray diffraction, TEM analysis, and porosimetry measurements also indicate that extending hydrogen exposure beyond 24 h leads to decreasing hydrogen storage due to the continuation of a loss in carbon relative to metal contaminants (P, Ca, Na) in the starting materials and increased crystallinity. Comparison of the results have shown that for advanced carbons derived from polymers or natural products treated with hydrogen at high temperatures, the optimum nanostructure is substantially disordered (turbostratic) graphite, whereas for materials derived from MFP, it is primarily amorphous carbon. The experiments have also revealed the optimum temperature region for storage where sorption/desorption curves show evidence of capillary condensation/densification.

We have used the density functional theory to study the H adsorption phenomena on Rh (110) surface with H coverage from 0.33 to 2.00 mono-layers. We found H atom favors the three-fold coordinated site as observed experimentally. We confirmed the existence of 1x3-H (0.33 H coverage), 1x2-H (0.5 H coverage), 1x3-2H (0.66 H coverage), 1x1-2H (2.0 H coverage) ordered structures. We also found that the proposed 1x3-2H structure for H coverage of 0.66 is not the lowest energy configuration. We have proposed a new 1x3-2H structure which needs to be tested by future experiments. This is a preliminary report and a more detailed description of the work will be published later.

We reported the relationship between the structure of metal-organic frameworks (MOFs) and the capability of hydrogen uptake. The QSPR (quantitative structure-property relationship) method was used to find out the factor which affects the adsorption amount of hydrogen molecule on the MOFs. The derivatives which were substituted by functionalized aromatic rings showed the effect of polarization within the identical topology of the frame and similar lattice constants. And the typical series of MOFs with different topology of the frames were investigated to examine the influence of topological change. For the consideration of saturation of hydrogen adsorption amounts, the result of fitting the adsorption curve with Langmuir-Freundlich equation was used to the QSPR approach additionally. We found out that the polar surface area plays a key role on the adsorption amount of hydrogen molecule into the MOFs and the specific value of electrostatic potential surface was calculated to indicate the interaction between hydrogen molecule and MOF.

Experimental wet chemical approaches to complex an iron atom with two C60 fullerenes, representing a new molecule, dubbed a “bucky dumbbell,” have been demonstrated. The structure of this molecule has been determined by 13C solid-state nuclear magnetic resonance (NMR) and electron paramagnetic resonance (EPR). Furthermore, this structure has been shown to have unique binding sites for dihydrogen molecules with the technique of temperature programmed desorption (TPD). The new adsorption sites have binding energies that are stronger than that observed for hydrogen physisorbed on planar graphite, but significantly weaker than a chemical C-H bond. Further development of these molecules could make them ideal candidates for onboard vehicular hydrogen storage.

Clathrate hydrates of structure II with organic cyclic oxides were identified to have the ability to include molecular hydrogen into their empty small cages at near-ambient temperature and moderate pressure. Solid-state NMR and Raman spectroscopy of the included hydrogen molecules indicate that the small cavities are both singly and doubly occupied by hydrogen molecules in the mixed hydrates. The inclusion mechanism can be derived from the critical progression of the cage occupancies as determined from in-situ kinetic experiments on formation and decomposition. The inclusion ability of hydrogen molecules was observed for several organic clathrate hydrate formers such as THF (tetrahydrofuran) and 1,4-dioxane, suggesting this to be a general property. A structural transition of the simple amine hydrate was suggested to produce a novel double CH4 + t-BuNH2 hydrate as confirmed by using microscopic analytical methods. The corresponding hydrate compositions were determined by using NMR spectroscopy to describe a tuning mechanism to increase the storage capacity.

Prompt gamma-ray activation analysis (PGAA) is an important technique for analyzing materials that may impact the hydrogen economy. An instrument for cold neutron PGAA, located at the NIST Center for Neutron Research (NCNR), has proven useful for the measurement of hydrogen and other elements in a variety of such materials. The detection limit for hydrogen is less than 10 mg/kg for most materials. PGAA has been used to characterize materials with potential for hydrogen storage (e.g. single wall carbon nanohorns, lithium magnesium imides, and zirconium beryllium hydrides), to measure hydrogen uptake by solid proton conductors, and to characterize stoichiometries of Nafion films used as membranes in fuel cells. Future upgrades to the instrument will improve detection limits, applicability, and user interface.

Several solid state NMR techniques including magic-angle-spinning (MAS) and multiple-quantum (MQ) MAS experiments have been used to characterize various AlH3 samples. MAS-NMR spectra for the 1H and 27Al nuclei have been obtained on a variety of AlH3 samples that include the β- and γ- phases as well as the most stable α-phase. While the dominant components in these NMR spectra correspond to the aluminum hydride phases, other species were found that include Al metal, molecular hydrogen (H2), as well as peaks that can be assigned to Al-O species in different configurations. The occurrence and concentration of these extraneous components are dependent upon the initial AlH3 phase composition and preparation procedures. Both the β-AlH3 and γ-AlH3 phases were found to generate substantial amounts of Al metal when the materials were stored at room temperature while the α-phase materials do not exhibit these changes.

Ammonia borane (NH3BH3) is a molecular solid with a high volumetric and gravimetric density of hydrogen. We report room temperature structural data which shows how the freely rotating NH3 and BH3 groups allow a N-H…H-B dihydrogen bond in which hydrogen atoms on adjacent molecules are separated by only 1.90Å. The initial decomposition of ammonia borane at 80-100°C into (NH2BH2)n and H2 has been studied by in-situ nmr spectroscopy and kinetic studies using isotopic substitution. The reaction proceeds by a bimolecular pathway involving a [NH3BH2NH3]+BH4− intermediate with an activation energy of 136kJmol−1.

We report the synthesis by ‘chimie douce’ route of high surface area (200 m2/g) nano crystalline Nb2O5 (so called p-Nb2O5) and the importance of its addition to enhance the hydrogen sorption properties of MgH2. All of the prepared Nb2O5 catalysts induce faster kinetics, up to twice the desorption rate, than commonly used commercial Nb2O5. Among them, both p-Nb2O5 and Nb2O5:350 (p-Nb2O5 heated to 350 °C) exhibit the best catalytic activity, since a 5.2 wt% hydrogen desorption was achieved at 300 °C for (MgH2)p−Nb2O5, as compared to less than 4 wt.% for commercial Nb2O5 added MgH2, (MgH2)c−Nb2O5, within 12 min. Furthermore, due to the addition of high surface area Nb2O5, the desorption temperature was successfully lowered down to 200 °C, with a significant amount of desorbed hydrogen (4.5 wt%). In contrast at this “low” temperature, (MgH2)c−Nb2O5 shows no desorption.

A Sieverts apparatus for small quantity samples has been implemented by employing a very small volume pressure reservoir and a sample chamber of less than 1 ml. The hydrogen storage capacity of a commercially available, HiPco (high pressure CO conversion) single-wall carbon nanotube (SWNT) was measured over a hydrogen pressure range of 0-35 Bar at room temperature. The sample contained approximately 5 wt% of residual Fe catalyst, and showed 0.17 wt% of hydrogen uptake capacity at 30 Bar of hydrogen pressure. Palladium nanoparticles were deposited on the SWNT via electrochemical method (EC) from H2PdCl4 solution. The storage capacity of the SWNT with EC-doped Pd was increased to 0.52 wt% at 30 Bar, which corresponds to the capacity enhancement by a factor between 2.8 and 3.1.

Mechano-chemical synthesis has been employed to prepare new light weight complex borohydrides. The precursor complex borohydrides such as NaBH4 and LiBH4 have been used since these materials posses high hydrogen storage capacity of 13.0 and 19.6 wt.%. This advanced materials based technology will meet the US-DOE grand challenge technical targets. The thermal calorimetric and gravimetric analysis of these complex borohydrides exhibits the hydrogen decomposition temperature (Tdec) of 100–150° C with theoretical capacity of ∼8.0-10.0 wt%. The catalysts (e.g. ZnCl2, TiFx3) doping and destabilization of the borohydride by reacting with binary hydride (MgH2) reveals the enhancement of decomposition kinetics and reversible dehydrogenation-rehydrogenation behavior.

A new type of hydrogen storage tank has been developed for fuel cell vehicles FCHV. The tank design is based on the 35MPa high-pressure cylinder vessel and the heat exchanger module including hydrogen absorbing alloy with high dissociation pressure is integrated in it. To hydrogen absorbing alloy, for example, Ti-Cr-Mn alloy with AB2 laves phase is applied. Its effective hydrogen weight capacity is 1.9 wt% and reaction enthalpy is −2 kJ/molH2. To optimize the heat exchanger, thermal analyzing method was developed to predict the amount of hydrogen absorption or desorption. The simulation consists of heat and mass balance. Heat balance is made by the hydrogen absorbing alloy, heat exchanger and coolant each other. Also reaction heat of the hydrogen absorbing alloy and compressed heat are considered. The reaction heat is calculated from the equation of reaction rate that is derived experimentally.

Furthermore, an additional simulation to predict the charging performance of on-board high-pressure MH tank system by the radiator cooling will be reported. With this simulation, it will become possible to make parameter studies to investigate how the operating conditions influence the performance of tank system.

Recent progresses on two series of light-element hydrides are briefly explained from the viewpoint of 1) prevention/suppression of gas-phase ammonia from mixtures of Mg(NH2)2 and LiH, and also 2) occurrences of reversible dehydriding and rehydriding reactions in NaMgH3.