Sodium metal reacts with water explosively to generate hydrogen. Therefore, sodium metal can have an important role as a hydrogen storage material. Seawater contains water most and sodium second. Seawater is electrolyzed by offshore wind or solar cell power generation to produce sodium; which is transported to a thermoelectric power plant on land and then is reacted with water to produce hydrogen for electric power generation. Sodium hydroxide, a by-product, is used as a raw material for soda industries. In the sodium production process, many by-products such as fresh water, magnesium, sodium hydroxide, hydrochloric acid, and sulfuric acid are produced. Thus, sodium metal is an economical, renewable, and sustainable fuel that discharges neither CO2 nor radioactivity.

Several hydrides of Nd2Ni2In with various H concentrations up to 6 H atoms/f.u. have been synthesized. Nd2Ni2In crystallizes in the tetragonal Mo2FeB2 structure type which can be changed upon hydrogenation to an orthorhombic structure, space group Pbma. The unit-cell volume increases by 15.5 % for Nd2Ni2InH4.5 and by 21.6 % for Nd2Ni2InH6. The triangular rare-earth lattice can give rise to magnetic frustration in case of antiferromagnetic interactions in Nd2Ni2In. The frustration is removed upon hydrogenation due to the orthorhombic distortion. The magnetic ordering temperature decreases with H concentration from 8 K in Nd2Ni2In down to 3.5 K in Nd2Ni2InH6.

Hydrogen storage in metallic nanoparticles was investigated by classical molecular dynamics and parameter physics. We observed phenomenological variation due to the differences in potential parameters of metal-hydrogen pair and crystal lattices. Three patterns of hydrogen distribution in both b.c.c. and f.c.c. nanoparticles were observed: non-absorbing, homogeneously-absorbing and heterogeneously-absorbing. In the last case, hydrogen atoms distribute just beneath the particle surface to form a hydrogen-rich layer. This layer prevents the diffusive motions of hydrogen atoms into the nanoparticle. We also carried out long simulation runs up to 1 nm to observed the structural variation of nanoparticles due to hydrogenation. Generation of grain boundaries was observed in b.c.c nanoparticles with the condition of strong metal–hydrogen interaction. Most of the grain boundaries were symmetric-tilt type and migrated inside the particle to reduce the interface energies. Formation of grain boundary was not observed in f.c.c. nanoparticles.

Hydrogen vacancy effect on the activation energy for self-diffusion is investigated by NEB method. The path was calculated by moving a hydrogen atom from a nearby complex into the vacancy in another complex. Compared with the substitution enthalpy of hydrogen vacancy, the activation energy for self-diffusion is easier to achieve during the dehydrogenation process.

A parallel high-sensitivity hydrogen sorption, and in situ Raman/IR emissivity measurement system has been developed using a stainless-steel sample cell with a sapphire window to act as a bridge between the PCT and optical measurements. The cell can be pressurized up to 4.5 MPa and heated up to 723 K. The system can measure small changes in hydrogen content, down to 0.5 μg, allowing for characterization of small quantities of powers and thin films. Hydrogen desorption in LiNH2 - LiBH4 - MgH2 nanocomposites has been studied by in-situ Raman and PCT measurement, while that of MgH2 powers and thin films has been studied by in-situ PCT and IR emissivity. In powder samples, qualitative trend is observed between changes in the Raman peak intensity/IR emissivity and the amount of hydrogen absorbed or desorbed.

With relatively high gravimetric and volumetric hydrogen storage capacities, borohydrides have attracted interest as potential hydrogen storage media. Lithium borohydride has a maximum theoretical gravimetric hydrogen storage density of 18.4 wt%, and has been shown to be reversible when heated to 600°C in 350 bar hydrogen1. It is hoped that a greater understanding of the decomposition and reformation mechanisms, may lead to the development of LiBH4-based materials that can absorb and desorb hydrogen under less extreme conditions. However, these studies have proved a challenge: currently most in-situ investigations have used x-ray diffraction or neutron diffraction however these cannot readily give information on non-crystalline or liquid phases. The preparation of samples measured ex-situ via XRD, NMR2 and Raman3 have shown the reaction products and stable intermediates during the thermal decomposition, however, it is very difficult to detect short lived intermediate (or byproduct) species. Raman spectroscopy has the advantages that: materials with only short-range order can be analysed; and by focusing the laser on regions in a sample the reaction path can be monitored with changing temperature with a rapid scan rate.

After heating lithium borohydride through its phase change and melting point, shifts in peak position and peak width were observed, which agreed with other studies4. A sample was also heated to 500°C (under 1 bar Ar) to decompose the sample. A number of intermediates and reaction products have been predicted and observed ex situ. This work shows the in situ formation of lithium dodecaborane (Li2B12H12) and amorphous boron from liquid lithium borohydride. It is therefore possible to determine at what temperatures certain intermediates and products form.

In this proceeding, we discuss measurements of the vibrational properties of hydrides using inelastic neutron scattering (INS) and the impact of the vibrational modes on the thermodynamic properties. We compare the heat capacity of PdH0.63 and LiBH4 as measured calorimetrically to that derived form INS spectra. We show that the vibrational properties of Ca(BH4)2 depend on the specific phase and hitherto determine their stability.

We describe the growth of novel ultrathin Mg crystalline nanoblades by oblique angle vapor deposition. These nanoblades were then coated with catalyst Pd and hydrogenated into magnesium hydride MgH2. In situ thermal desorption spectroscopy study showed a low H desorption temperature at ∼365 K. In situ reflection high energy electron diffraction patterns were used to study the temperature dependent structure and composition changes during the de-hydrogenation of Pd coated MgH2 nanoblades. The diffraction rings reveal the formation of alloys of Pd and Mg when the temperature is over ∼480 K. Transmission electron microscopy diffraction also supports the formation of Pd and Mg alloys. This alloying reduces the cycling capability of Mg hydride. The de-hydrogenation of MgH2 introduces a strain at the bilayer interface between MgH2 and Mg resultant from 30% volume reduction from MgH2 to Mg and formed curved nanoblades as evident by scanning electron microscopy images. Designing factors of recyclable simple hydrides will be discussed.

The phonon distribution of hydrogen storage α-LaNi5H with 4h, 6m, 12n, and 12o interstitial hydrogen was calculated by using first-principles potential surfaces with a 2×2×2 supercell model in order to investigate structural and thermodynamic properties. Frequency shifts due to the phonon contribution from the internal energies of 12n < 6m < 12o < 4h appeared in specific modes originating from interstitial hydrogen and in the upper-edge modes with nickel-lattice motion. The thermodynamic stability of 12n interstitial hydrogen in α-LaNi5H due to the wide XZ storage space can be explained by its phonon amplitudes and the charge density around nickel-bonded hydrogen.

In-situ observation of the reaction between light weight hydride LiH and NH3 gas was performed by means of TEM (Transmission Electron Microscopy) with an environmental cell. This environmental cell was designed for the observation of the gas-solid reaction under 0 ∼ 0.2 MPa gas atmosphere at 20 ∼ 150 °C. It has been confirmed a volume expansion and generation of LiNH2, that is the reaction between LiH and NH3. Moreover, it was revealed that LiNH2 was generated at the surface of LiH particle at first process of the reactions.

In the present work we study theoretically hydrogen incorporated into several positions in the zirconia cubic and tetragonal lattices. These are positions in the interstitial space and in the zirconium vacancy (VZr). We examine the structure of such configurations and for VZr-related defects we also calculate selected positron characteristics in order to assess their capability of trapping positrons. It is shown that hydrogen atoms do not prefer to stay in the center of the largest interstitial space nor of VZr and they rather tend to create bonds with neighboring oxygen atoms. The positron lifetime of the VZr+1H complex is shorter than that for non-decorated VZr and positron trapping in VZr+1H complexes could, in principle, explain experimental lifetime data.

Three different classes of boron and nitrogen containing light metal complex hydrides have been investigated, resulting from the reactions of LiNH2 with LiBH4, NaNH2 with NaBH4 and MHx (where M = Li, Na and Ca) with NH3BH3. A rich variety of new phases has been identified, which exhibit modified decomposition pathways and onset temperatures of hydrogen desorption as low as 40°C. In each case the composition of phases formed has been examined in detail and the products of thermal decomposition—solid and gaseous—have been determined.

In-situ observation on the catalytic effect of Nb2O5 in MgH2 was carried out by using transmission electron microscopy (TEM). We prepared two kinds of samples, because we tried to observe the reaction from two kinds of viewpoints. MgH2 catalyzed with 1 mol% of Nb2O5 was prepared for an overall viewpoint on the desorption process of MgH2 with catalyst by conventional TEM. The dehydrogenation of the 1 mol% sample started at 150 °C and Mg nano-size particles were formed. However, Nb2O5 was not confirmed in diffraction patterns and images, because it was highly dispersed by ball-milled. So MgH2 catalyzed with 10 mol% of Nb2O5 was prepared for local viewpoint to focus the boundary between the catalyst and the Mg phase by high voltage electron micro scope (HVEM). The sample mixed in mortar was prepared for this, because it was difficult to find the boundary in the sample ball-milled. The high resolution images of the 10 mol% sample revealed that the dehydrogenation started from the interface of MgH2 and Nb2O5. The result suggested that the dehydrogenation could proceed with hydrogen diffusion from MgH2 phase to the interface between Mg and Nb2O5.

We report the synthesis of nanostructured stage-2 potassium graphite, KC24, by intercalation of turbostratic graphite nanofibers produced from an electrospun polymer, and compare its properties with exfoliated graphite-based KC24. The nanostructured KC24 sample has low crystalline order and slightly increased interlayer spacing of 8.76 Å, compared with 8.65 Å in the bulk sample, indicating minimal registration of the graphite planes. Time-resolved time-of-flight neutron diffraction on both nanostructured and bulk KC24 under ammoniation is suggestive of a more homogeneous and faster pressure-modulated phase transition to the ternary ammoniated potassium-graphite in the nanostructured material. Following ammoniation, negligible hydrogen uptake is observed at 50 K.

Interaction between nitrogen-substituted graphene-like compounds and hydrogen was investigated using ab initio molecular orbital method in the aspect of hydrogen storage. We adopted coronene as a model compound for fragmented graphene-like carbon materials and compared the interaction between hydrogen and pure or N-substituted coronenes by changing nitrogen positions. Among the assumed 19 N-substituted models, polarozabilities and HOMO–LUMO gaps were compared to evaluate physisorption and chemisorption energies. As for chemisorption, two N-substituted models were selected and closely examined to reveal the dependence on both nitrogen-substitution and hydrogen-adsorption positions. Potential energy surfaces as a function of H–H bond length and H2–coronen distance showed that the barrier height for hydrogen chemisorption strongly depends on N-substitution positions. The chemisorbed products of N-substituted coronenes are stabilized or destabilized compared with the pure carbon case depending on the sites of N-substitution and H-adsorption. These results suggest that N-substitution at certain positions possibly improve hydrogen storage properties of graphene-like materials.

This paper presents a brief review of recent developments in the studies of fully hydrogenated graphene sheets, also known as “graphane,” and related initial results on partially hydrogenated structures. For the fully hydrogenated case, some important discrepancies exist between published first-principles calculations, and between calculations and experiment, with qualitative differences on whether or not the graphene sheet expands or contracts upon hydrogenation. The lattice change has important effects on partially hydrogenated structures. First-principles calculations of ribbon structures, with interfaces between graphane and graphene regions, show that the interfaces have substantial misfit strains. Calculating the interfacial energy must carefully account for the strain energy in the neighboring regions, and for sufficiently large regions between interfaces, defects at the interface that relieve the strain may be energetically preferable. Tight-binding simulations show that at ambient temperatures, segments of graphene sheets may spontaneously combine with atomic hydrogen to form regions of graphane. Small amounts of chemisorbed hydrogen distort the graphene layer, due to the lattice misfit.

We study deuterated tetrahydroborate LiBH4 in the low-temperature (LT) phase, focusing on the BH (BD) stretching vibrations, by infrared (IR) and IR-pump-probe spectroscopy. Calculated infrared spectra by density functional theory allow us to disentangle the contributions coming from all the coexisting BH4-nDn (n = 0…4) molecular units. We report on anharmonicity and vibrational lifetime (1.6 ps) of the BD vibrations, as well as on the BH2D2 orientational relaxation by polarization anisotropy IR-pump-probe measurements. We find a constant anisotropy for at least 5 ps confirming the slow reorientational motion and low thermal disorder of the BH4 unit in the LT phase of this potential hydrogen storage material.

The aim of this work is the investigation of the metal-hydride transformation in magnesium (Mg) nanoparticles both as a function of particle size and in response to surface functionalization by clusters of transition metals (TM): Pd, Ni, Ti.

Mg nanoparticles were synthesized by the inert-gas condensation technique, which yields single crystals with six-fold symmetry whose average size can be controlled by tuning the inert gas pressure. After the synthesis the nanoparticles were passivated by slow exposure to oxygen, obtaining a core-shell morphology where a metallic core is coated by a MgO shell of about 5 nm thickness.

The material structure was investigated by Transmission Electron Microscopy (TEM), also in High Resolution (HRTEM) mode, and by X-Ray Diffraction (XRD). The sorption kinetics were analysed by a volumetric Sievert apparatus, which also allowed for a determination of the activation energies.

Small nanoparticles (≈35 nm) display interesting kinetics with gravimetric capacity of 4.5 wt.% at saturation, limited by the oxide fraction. Hydride formation proceeds by one-dimensional growth controlled by diffusion through the hydride, while the reverse transformation to metal involves interface-controlled three-dimensional growth of nuclei formed at constant rate.

On the contrary, large nanoparticles (≈450 nm) exhibit very low reactivity due to reduced probability of hydrogen dissociation/recombination and nucleation at the particle surface. For this reason, large nanoparticles were surface-decorated by TM through in situ evaporation in the inert-gas condensation chamber. This procedure results in clusters of 3-4 nm located over a portion of the MgO shell, as shown by XRD and HRTEM on Pd-decorated sample. This treatment results in dramatically improved hydrogen sorption behavior. In fact, previously inert nanoparticles now exhibit of up to 5.6 wt.%.

Real-time diffraction studies using Synchrotron Radiation were carried out during hydrogen desorption on the Pd-decorated nanoparticles. We clearly show that a Mg-Pd intermetallic phase is formed after the first heating treatment and takes active part in the transformation.

Phase transformations in epitaxial yttrium films grown on (0001)Ti//(0001)Al2O3 Ti-buffered sapphire substrates and hydrogenated for 10 min were characterized using transmission electron microscopy. After hydrogen charging, dense twin lamellae form during α(Y(H))-to-β(YH2) phase transition with twin boundaries predominately parallel to the interface between Y and a substrate. High densities of Shockley partial dislocations are present at the twin boundaries, their glides during phase transformation are responsible for the formation of twin lamellae. Electron diffraction from YH2 phase shows superlattice reflections, which suggests a new type of ordering on octahedral interstitial sites.

Carbon nanocones are the fifth allotropic form of carbon, first synthesized in 1997. They have been selected for investigating hydrogen storage capacity, because initial temperature programmed desorption experiments found a significant amount of hydrogen was evolved at ambient temperatures. The aim of this work was to study the effect of impregnation conditions on metal catalyst dispersion and to investigate whether the metal loaded cones had improved hydrogen storage characteristics. Pre-treatment of carbon nanocones with hydrogen peroxide was carried out, followed by metal decoration in aqueous solution by an incipient wetness technique. Two methods of reducing the metal catalyst have been applied: in hydrogen at room temperature (RT) and in an aqueous solution of NaBH4. XRD confirmed the complete metal reduction and TEM showed that the reduction technique affected the catalyst dispersion. Very fine dispersions of ca. 1 nm diameter metal clusters at catalyst loadings of 5 wt.% were achieved and high dispersions were retained for loadings as high as 15 wt.%. Hydrogen uptakes at RT were measured and an increase with metal loading was observed.