The low H content portion of the PCT absorption curves of the 40Ti-xV-(50-x)Mn-10Cr alloys exhibits a plateau, whose pressure has been determined together with the solubility limit of H in the α–phase (solid solution). The chemical (Dc) and Einstein (DE) diffusion coefficients of H have been deduced from H absorption kinetics (273 K-1100 K) and from mechanical spectroscopy (150 K-200 K), which has revealed a Snoek-type of anelastic relaxation. The combined Arrhenius plot of DE and Dc gives the following parameters for H diffusion: W=0.318±0.005 eV, D0=(4±1)×10−7 m2/s (36 V alloy) and W=0.352±0.005 eV, D0=(5±1)10−7 m2/s (32 V alloy).

Emissions from fossil fuel combustion alter the composition of the atmosphere and have been touted as a major cause of climate change. The amount of carbon dioxide in the atmosphere, for example, has increased by more than 30% since pre-industrial times. Average global surface temperature has increased by approximately 0.6 ± 0.2°C since the late 19th Century, and surface temperature records indicate that the 1990s are likely to have been the warmest decade of the last millennium. The anthropogenically-induced warming is superimposed on natural climatic variability. Proxy records show a regular oscillation, on a roughly 100,000-year cycle, between glacials and interglacials. Superimposed on these long-term oscillations are shorter scale variations. It is thought that changes in the seasonality and location of radiation from the Sun trigger the onset or end of glaciation, and the change is then amplified by feedbacks in the earth-atmosphere system. A firm link between atmospheric composition and temperature has been established from ice core records spanning the last 420,000 years, which show that changes in time of global temperature and atmospheric concentrations of carbon dioxide and methane are tightly coupled. Global average surface temperature is projected to increase by between 1.4 and 5.8°C by 2100, with the warming being greatest over land and polar regions. Precipitation is predicted to increase in the tropical, mid- and high-latitude regions, but to decrease in the subtropical regions. Alternative energy technologies such as hydrogen fuel cell vehicles will lower greenhouse gas emissions and reduce climate problems and costs.

Nano-particles of Pr and Mn-doped ceria have been prepared by mixing nitrate solutions and hexamethylenetetramine as an oxidizing agent, and their thermal stability has been investigated. The particle size was evaluated by means of XRD, BET and dynamic light scattering techniques. The particle size of Pr and Mn-doped ceria was found to be approximately 3 nm as prepared. Even though the particle size of doped ceria increases with increasing annealing temperature, the size of less than 15 nm was kept after annealing at 873 K for 10 h. On the other hand, the lattice constant of nano-sized ceria, for example 0.544 nm for 3 nm-size particles, decreases and reaches to the value of bulk material (0.541 nm) as annealing temperature increases. This suggests that the valence state of cerium and the amount of oxygen vacancies strongly depend on the particle size.

We carried out molecular dynamics simulations with Tersoff-Brenner potentials in order to investigate the hydrogen uptake mechanisms and storage capacity of carbon nanoscrolls (CNSs). CNSs are jelly roll-like structures formed by wrapping graphene layers. Interlayer adsorption is an option for this material, which does not exist for single and multiwalled carbon nanotubes. We analyzed the processes of hydrogen physisorption and uptake mechanisms. We observed incorporation of hydrogen molecules in both external and internal scroll surfaces. Insertion in the internal cavity and between the scroll layers is responsible for 40% of the total hydrogen adsorption at 77 K.

Cold rolling reduction, microstructural changes induced by cold rolling and subsequent heat treatment, hydrogen permeability (Φ) of Nb-Ti-Ni duplex phase alloys have been investigated using a rolling machine, a scanning electron microscope (SEM), an X-ray diffractometer (XRD) and a gas flow technique. The Nb-Ti-Ni alloys on the line connecting the TiNi compound and the Nb90Ti10 solid solution alloy show higher rolling reduction of 70 % or more at room temperature. The value of Φ for the Nb40Ti30Ni30 alloy, which is higher than that of pure Pd at 673K, decreases with increasing rolling reduction and attains to one third of that of the original one by the 50 % rolling reduction. The eutectic microstructure consisting of {TiNi+(Nb, Ti)} phases disappears and is replaced by the (Nb, Ti) phase embedded in the TiNi matrix by heat treatment 1073 K or more and for 605ks in a vacuum. However, its Φ value remains as it was by annealing at 1273 K or less, while it increases with increasing annealing periods at 1373 K or more and recovers to the original value after annealing for 605ks. These experimental results indicate that rolling and annealing techniques are the useful method for the preparation of a hydrogen permeable Nb-Ti-Ni alloy membrane.

The conventional Fenton mechanism is reviewed and then slightly modified to incorporate additional data. Following the DuPont attack mechanism closely, we explain why the FER is proportional to the carboxylic acid end-group concentration in Fenton tests. We then make a case that in-cell testing introduces additional decay reactions operating locally in the membrane. These additional reactions explain the shape of the FER vs. time curve and why the FER is nearly independent of the carboxylate end group concentration. A semi-quantitative model is introduced to support the self consistency of the proposed reaction scheme.

Heteropoly silicotungstic acid (STA)-based, cross-linked hybrid proton exchange membranes for intermediate-temperature (80°-120°C) fuel cell applications were fabricated by incorporating STA in a host matrix of binding silane, SiO2 sol gel, ethylene methacrylate copolymer containing glycidyl methacrylate groups (PMG), and molecular cross-linker. The STA loading level relative to the sum of the PMG and a cross-linker exceeded 100 weight%. Upon curing at 145° under pressure, the composite membranes were nearly 100% cross-linked and were flexible, showed high thermal and chemical stability against Fenton’s reagent, and exhibited a break-in behavior during cyclic voltammetric (CV) scans. The best proton conductivity, which was obtained from CV results, decreased from ∼8-15 mS/cm at 80°C and 100% relative humidity (RH), to ∼1.5 mS/cm at 100°C and 46% RH, and ∼0.25 mS/cm at 120°C and 23%RH.

Light weight hydrogen storage systems are indeed essential for the on-board automotive vehicular applications. Complex chemical hydrides bearing light elements such as Li, Na, Mg etc. and their catalytic doping with transition metal species are presently being investigated. The Li- modified Mg2FeH6 structure have been thermally characterized using DSC and TGA techniques. It is interesting to notice that the reduction in the decomposition temperature of about 100° C has been unambiguously observed for the Li modified Mg2FeH6. Besides, there is an enhancement in sorption kinetics for the Ti- doped Mg2FeH6. The role of Ti- species on the dehydrogenation and rehdyrogenation properties of NaAlH4 have been explored by heat flow measurements using high pressure differential scanning calorimetry. We have also developed the Li-amide/LiH system by sonicated process and studied their PCT characteristics. A new class of hydrogen storage system Zn(BH4)2 with theoretical hydrogen capacity of 8.4 wt.% have been synthesized and we have determined their gravimetric and volumetric characteristics.

We describe a study of the dynamics of hydrogen in Pr2Fe17H4, where isolated hexagons formed by the interstitial tetrahedral (t) sites of the metal lattice are populated by mobile hydrogen atoms. An activation energy of 0.10 eV has been determined for a localized jump process involving the hopping of these hydrogen atoms among adjacent vertices of each hexagon, slightly lower than that for hydrogen hopping in Pr2Fe17H5, where each hexagon is occupied by two hydrogen atoms.

Hydrogen is under consideration by several countries for its potential as an energy carrier for transportation applications. In order to compete with vehicles in use today, hydrogen-powered vehicles will require a driving range of greater than 300-miles in order to meet customer needs and expectations. For the overall vehicular light-duty fleet, this dictates that a range of 5 to 13 kg of hydrogen be stored on-board (assuming a fuel cell power plant) within stringent system weight, volume, and cost constraints. Vehicular hydrogen storage thus constitutes a major scientific and technological challenge. To meet this challenge, the U.S. Department of Energy (DOE) initiated a “National Hydrogen Storage Project” with roughly 40 universities, 15 companies and 10 federal laboratories, actively engaged in hydrogen storage research. Centers of Excellence in metal hydrides, chemical hydrides, and carbon-based materials have been established, as well as independent university and industry projects in the areas of new concepts/materials, hydrogen storage testing, and storage system analysis. Recent technical progress in each of these areas is discussed.

Microstructure, crystal structure and hydrogen permeability (Φ) of Nb-Ti-Ni alloys on the straight line connecting the compositions of the eutectic and the primary (Nb, Ti) phase have been investigated to develop the alloys showing high hydrogen permeability with a scanning electron microscope (SEM), an X-ray diffractometer (XRD), and a gas permeation apparatus, respectively. These alloys consist of the B2-TiNi compound and the bcc- (Nb, Ti) solid solution and are hydrogen permeable when they contain much amount of the eutectic phase. The values of Φ for these alloys increase with increasing temperature and Nb content. The Nb68Ti17Ni15 alloy shows the highest Φ of [molH2m−1s−1Pa−0.5] at 673 K, which is 3.1 times higher than that of pure Pd. The present work demonstrates that the alloys showing the high Φ values are obtained on the straight line connecting the compositions of the eutectic and the primary phase.

To enhance the visible light absorption of anatase TiO2 photo-electrodes, the material was doped with carbon by two different methods: i) by spray pyrolysis under a CO2 atmosphere, and ii) by a post-deposition thermal treatment in a hexane-containing environment. For the hexane-treated samples, most of the carbon is located at the surface, from which it can be removed by re-oxidation at elevated temperatures. In addition, both methods seem to result in the presence of small amounts of carbon in the bulk of the material, as deduced from a small red-shift of the absorption edge of TiO2.

We propose core-shell InP-CdS and InP-ZnTe nanorods as photoelectrodes in the efficient photoelectrochemical hydrogen production. Based on our systematic study using strain-dependent k.p theory, we find that in these heterostructures both energies and wave-function distributions of electrons and holes can be favorably tailored to a considerable extent by exploiting the interplay between quantum confinement and strain. Consequently, these core-shell nanorods with proper dimensions (height, core radius, and shell thickness) can simultaneously satisfy all criteria for effective photoelectrodes in solar-based hydrogen production.

In order to clarify the charge transfer characteristics for H2 generation, photoelectrochemical properties of n-type GaN in HCl solution were investigated. The flatband potential under illumination and the onset voltages of photocurrent located approximately the same position. From the result, we concluded that the positively charged surface by hole capture is the main reason of the extra voltage requirement for H2 generation. The carrier concentration in n-type GaN also affects the photocurrent.

Sulfonated poly ether ether ketone (SPEEK) with a high degree of sulfonation (DS = 0.9) was mixed with a modified silane bearing a sulfonic acid function (sulfonated diphenylsilanediole, SDPDO).

Homogeneous composite membranes with several SPEEK:SDPDO ratios, were obtained. The addition of the ormosil significantly improved the water uptake and solubility properties of pure SPEEK.

The structural and electrochemical characteristics of the composite membranes were investigated by means of thermogravimetric analysis (TG), field emission scanning electron microscopy (FE-SEM), and electrochemical impedance spectroscopy (EIS). The conductivity values of the composites SPEEK/SDPDO demonstrated that they possess good proton transport characteristics, thus being suitable for application in Polymer Electrolyte Fuel Cells operating at intermediate temperature.

Hydrogen synthesis and segregation from water splitting with simultaneous partial oxidation of methane can be achieved using MIEC membranes that conduct oxygen ions and electrons. The process offers hydrocarbon free hydrogen production on the feed side of the membrane (steam side) and syn-gas on the permeate side (methane side). A composite MIECs system comprising GdxCe1−xO2−x/2 (GDC) and GdxSr1−xTi1−yAlyO3 (GSTA) has been used and the hydrogen flux has been estimated. The oxygen diffusion coeffcient for oxygen transport through the bulk of the membrane and surface exchange coefficient of oxygen at the solid/gas interface were obtained using electrical conductivity relaxation (ECR) experiments and the hydrogen generation flux was measured for membranes of different thicknesses, with and without surface exchange catalysts for various experimental conditions.

To clarify the effect of Sn substitution for Ni of LaNi5 on the lattice defect formation during the hydrogenation and dehydrogenation processes, in-situ positron lifetime measurements were per-formed in LaNi4.93Sn0.27. During the hydrogenation, the mean positron lifetime, τm, monotonically increased up to 175 ps which is almost same as calculated positron lifetime for vacancy. This shows vacancy introduction by hydrogenation. The τm mean positron lifetime decreased down to 135 ps with hydrogen content during the dehydrogenation. It shows that the vacancies are removed from the lattice during the dehydrogenation. These results show that vacancies in LaNi4.93Sn0.27 are intro-duced and removed reversibly during the hydrogenation and dehydrogenation. The concentra-tions of vacancy and dislocation were 1 × 10−5 and 6 × 109 cm−2, respectively. These values are two orders lower than those in LaNi5.

The discovery that dopants, such as Ti, cause NaAlH4 to reversibly desorb H2 at mild conditions has spurred a great deal of research into complex metal hydrides. However, no complex hydride meets the targets for automotive hydrogen storage. Our approach is to accelerate the rate of discovery of improved hydrides and dopants through the combination of Virtual High Throughput Screening (VHTS) and Combinatorial Synthesis and Screening (CSS). Our CSS methods will allow us to screen thousands of samples in a year. These samples will be prepared by ball milling mixtures of hydrides and dopants similar to the established method of preparing Ti doped NaAlH4. VHTS exploits a molecular mechanics method to screen a thousand phases in a month. The combination of combinatorial methods and VHTS will help us discover the most promising complex hydrides for hydrogen storage. We will show the results of our medium throughput CSS and VHTS as applied to the NaAlH4–LiAlH4 – Mg(AlH4)2 mixed alanate compositions.

Si-Ce-O mixed solids (50, 30, 10 and 5, Si/Ce molar ratio) were prepared by using Ce(NO3)3·6H2O as cerium source, tetraethyl orthosilicate (TEOS) as Si precursor and cetyltrimethylammonium bromide (CTABr) as synthesis template. The Ni catalysts were prepared by impregnation of the supports using Ni-acetilacetonate (30 wt.% Ni) as Ni source. The samples were characterized by: X-ray diffraction, temperature-programmed reduction (TPR), and TEM. The nickel reduction degree decreased with the addition of cerium, even in low concentration. When methane was decomposed over all the catalysts only hydrogen was obtained as a gaseous product. The addition of cerium brought about a significant increase in stability compared with Ni/SiO2 catalyst. These preliminary results indicated that CeO2 addition improves the dispersion of Ni particles leading to a better distribution of deposited carbon and increasing the lifetime of Ni particles.

This paper describes preparation and methane reforming characteristics of a proto-type reformer based on a composite-type oxygen permeable membrane. The tape-cast membrane of Sm-doped CeO2 and 15 vol% MnFe2O4 composite was combined with ferric stainless steel separator with a same thermal expansion coefficient. For the reformer module, high CH4 conversion, CO and H2 selectivity of 96%, 84% and 89% were achieved, respectively. Based on C, H and O balances, oxygen permeation flux was found to be 5.7 mu-mol/cm2s. Joule heat caused by the oxygen permeation was estimated to be approximately 17.5 W, and this covered most part of heat required for reforming reactions.