Spectroscopic techniques such as IR and Raman are very powerful to understand guest-host interactions. Although these techniques are complementary, Raman spectroscopy has not been widely implemented as a tool to characterize these interactions. This study illustrates the use of Raman spectroscopy not only to probe the interactions experienced by a guest molecule but also to detect structural changes occurring in the framework upon loading. Weak interactions of adsorbed molecules with the framework are reflected in frequency and intensity variations in both Raman and IR absorption lines, as shown for the case of CO2, N2 and CH4 with Zn(bdc)(ted)0.5.

Hydrogen (H2) sensing property of AgInSbTe (AIST)-SiO2 nanocomposite thin film prepared by target-attachment sputtering method was investigated in this work. The sample subjected to a 400°C-annealing for 90 sec exhibits a significant sensitivity (58.9 %) and short response time (75 sec) upon the exposure to an ambient containing 200 ppm H2 at 75°C. The gas sensing capability is ascribed to the presence of antimony oxides, e.g., Sb2O3 and Sb2O5, in nanocomposite layer which provide the charge carriers for sensing reactions. Moreover, the high specific-surface-area (SSA) feature of AIST nanocrystals in nanocomoposite layer provided numerous sites for reduction/oxidation reactions and thus a good H2 gas sensing property can be achieved.

An experimental study of hydrogen adsorption in a variety of high-surface area adsorbent materials has been conducted at room temperature and pressures up to 500 bar on high surface area activated carbons, zeolite templated carbons (ZTC), and metal organic frameworks (MOFs). For all materials, excess hydrogen adsorption isotherms were measured up to 500 bar and have been analyzed in terms of the BET surface area and pore size distribution. The materials were also evaluated for their increase in hydrogen storage density over compressed gas. It was determined that, due to the lower excess adsorption and skeletal densities for the microstructured materials, MOF-177 and ZTC have worse storage densities than compressed gas at most pressures, even when assuming a bed compaction factor of two, while the activated carbons offer marginal increases in storage density over the pressure range investigated.

The morphological evolution of Mg based powders during repeated absorption-desorption reactions with hydrogen has been studied by Scanning Electron Microscopy. The main feature observed is the presence, after several cycles, of surface protrusions probably constituted by the base Mg material without the presence of a catalyst. The effect is present both in catalyzed and non-catalyzed materials and it is considered an indication of the tendency of the base material to exit from the oxide shell surrounding the Mg powder particles. This tendency is confirmed by the observation of empty MgO boxes indicating that the effect can push until a complete expulsion of the base material. This effect can represent the base for an innovative method for cleaning the surface of a tank material by an “in situ” procedure.

Hydrogen absorption in metallic nanoparticles was investigated by classical molecular dynamics (MD) simulation. We used a simple model composed of an isolated f.c.c. or b.c.c. nanoparticle of 1, 1.4, 2, 4, 6, 8 and 10 nm in diameter and surrounding hydrogen atoms. The simulated particle sizes are which correspond to about 50 to 44000 atoms. In the case of f.c.c. nanoparticles, atomic configuration with five-fold symmetries was observed in both hydrogenfree and hydrogenated particles smaller than 2 nm. The f.c.c. structure was maintained in larger particles than 4 nm with lattice deformation which varies with M-H interaction. The b.c.t. structure was observed in hydrogenated b.c.c. nanoparticles. Number of H atoms absorbed in a nanoparticle varies depending on particle size and M-H interaction: it increases with increasing particle size and M-H bond strength.

Novel Mg-Zr-A (A=Na, Li and K) hydrides have been synthesized by the gigapascal hydrogen pressure method. Their crystal structures were analyzed based on synchrotron X-ray diffraction (XRD) patterns. In the Mg-Zr-H system, the Mg-Zr hydride with FCC structure was formed under 8 GPa and 873 K. In the case of Mg-Zr-Li and Mg-Zr-K systems, the quaternary hydrides were formed and these retained the same crystal structure, FCC structure, up to x = 1.0 While in the Mg-Zr-Na system, the quaternary hydrides were formed and these retained the FCC structure, up to x = 0.3. With the addition of 0.5 NaH, a hydride with the Ca7Ge type structure was formed instead of the FCC structure. The Mg-Zr-(Li, Na, K) hydrides can reversibly absorb and desorb hydrogen. The hydrogen desorption temperatures of those hydrides decrease with the increasing ionic radius of the alkali metal.

Entrapping hydrogen molecules within the nanopores of solid adsorbents serves as a unique alternative for on-board storing of hydrogen for transportation purposes. The key advantage of the physisorption process for hydrogen storage is the higher density values achieved with the adsorbed gas, compared to that of the compressed phase, translating into higher storage capacities at lower pressures. The necessary condition for effective adsorption is the presence of narrow micropores of < 2 nm in width which provide the most suitable environment of hydrogen adsorption. Despite numerous theoretical calculations or indirect experimental estimations, there has not been a direct experimental measurement of the density of adsorbed hydrogen as a function of pressure and/or pore size. In the present study, we report on the use of in-situ small angle neutron scattering (SANS) to study the phase behavior of hydrogen confined in narrow micropores. We provide for the first time direct experimental measurements of the effect of pore size and pressure on hydrogen adsorbed on a polyfurfuryl alcohol-derived activated carbon (PFAC), at room temperature and pressures up to 207 bar. SANS studies were carried out at the General-Purpose Small-Angle Neutron Scattering spectrometer of the High Flux Isotope Reactor at Oak Ridge National Laboratory. The measurements covered the Q-range from 0.01 to 0.8 Å-1, covering the pores in the range of 9 to 34 Å of the PFAC material. Initial results suggest that the density of adsorbed hydrogen is higher than the density of bulk hydrogen gas and increases with decreasing pore size.

Crystal and local structures and hydrogen occupation of Mg containing materials, (Mg,Ca)Nix (x = 2, 3) intermetallic compounds and a MgCo metastable alloy, have been investigated using in-situ and ex-situ X-ray/neutron diffraction and total scattering.

A C15 Laves phase (Mg0.67Ca0.33)Ni2 showed isotropic lattice expansion upon hydrogenation. Mg and Ca occupied the same site randomly. It has two hydrogen sites, Mg(Ca)2Ni2 site and M(Ca)Ni3 site.

Mg2CaNi9, MgCa2Ni9, and CaNi3 compounds consisted of MgZn2-type (Mg,Ca)2Ni4 cell and CaCu5-type CaNi5 cell stacking along the c-axis. The MgZn2-type cell was occupied by only Mg in Mg2CaNi9, and randomly occupied by both Mg and Ca in MgCa2Ni9. Expansion of this cell strongly depended on the composition: larger expansion was observed in a Ca-rich composition.

Local structure of a Mg-Co alloy synthesized by mechanical alloying has been studied using the PDF (Pair Distribution Function) method. The analysis suggested that material contained two 1-2 nm domains with different compositions and local structures, i.e. Mg-rich and Co-rich domains, and hydrogen was located only in the Mg-rich domain.