Science.gov

Sample records for hydrogen permeable metals

  1. Hydrogen-permeable composite metal membrane and uses thereof

    DOEpatents

    Edlund, David J.; Friesen, Dwayne T.

    1993-06-08

    Various hydrogen production and hydrogen sulfide decomposition processes are disclosed that utilize composite metal membranes that contain an intermetallic diffusion barrier separating a hydrogen-permeable base metal and a hydrogen-permeable coating metal. The barrier is a thermally stable inorganic proton conductor.

  2. Tubular hydrogen permeable metal foil membrane and method of fabrication

    DOEpatents

    Paglieri, Stephen N.; Birdsell, Stephen A.; Barbero, Robert S.; Snow, Ronny C.; Smith, Frank M.

    2006-04-04

    A tubular hydrogen permeable metal membrane and fabrication process comprises obtaining a metal alloy foil having two surfaces, coating the surfaces with a metal or metal alloy catalytic layer to produce a hydrogen permeable metal membrane, sizing the membrane into a sheet with two long edges, wrapping the membrane around an elongated expandable rod with the two long edges aligned and overlapping to facilitate welding of the two together, placing the foil wrapped rod into a surrounding fixture housing with the two aligned and overlapping foil edges accessible through an elongated aperture in the surrounding fixture housing, expanding the elongated expandable rod within the surrounding fixture housing to tighten the foil about the expanded rod, welding the two long overlapping foil edges to one another generating a tubular membrane, and removing the tubular membrane from within the surrounding fixture housing and the expandable rod from with the tubular membrane.

  3. Hydrogen Permeability of Mulitphase V-Ti-Ni Metallic Membranes

    SciTech Connect

    Adams, T. M.; Mickalonis, J.

    2005-10-18

    Development of advanced hydrogen separation membranes in support of hydrogen production processes such as coal gasification and as front end gas purifiers for fuel cell based system is paramount to the successful implementation of a national hydrogen economy. Current generation metallic hydrogen separation membranes are based on Pd-alloys. Although the technology has proven successful, at issue is the high cost of palladium. Evaluation of non-noble metal based dense metallic separation membranes is currently receiving national and international attention. The focal point of the reported work was to evaluate a Group 5A-Ta, Nb, V-based alloy with respect to microstructural features and hydrogen permeability. Electrochemical hydrogen permeation testing of the V-Ti-Ni alloy is reported herein and compared to pure Pd measurements recorded as part of this same study. The V-Ti-Ni was demonstrated to have a steady state hydrogen permeation rate an order of magnitude higher than the pure Pd material in testing conducted at 22 C.

  4. Metal/ceramic composites with high hydrogen permeability

    DOEpatents

    Dorris, Stephen E.; Lee, Tae H.; Balachandran, Uthamalingam

    2003-05-27

    A membrane for separating hydrogen from fluids is provided comprising a sintered homogenous mixture of a ceramic composition and a metal. The metal may be palladium, niobium, tantalum, vanadium, or zirconium or a binary mixture of palladium with another metal such as niobium, silver, tantalum, vanadium, or zirconium.

  5. Permeability of precious metals to hydrogen at 2kb total pressure and elevated temperatures.

    USGS Publications Warehouse

    Chou, I.-Ming

    1986-01-01

    Permeabilities of several commonly used precious metals to hydrogen have been measured at 2kb total pressure and between 450o and 812oC by using the double-capsule oxygen buffer technique.- from Author

  6. Reduced hydrogen permeability at high temperatures

    NASA Technical Reports Server (NTRS)

    Stephens, J. R.; Klopp, W. D.; Misencik, J. A.

    1981-01-01

    CO and CO2 reduce hydrogen loss through iron, nickel, and cobalt based alloy tubes. Method is based on concept that oxide film on metal surface reduces hydrogen permeability through metal; adding CO or CO2 forms oxide films continuously during operation, and hydrogen containment is improved. Innovation enhances prospects for Stirling engine system utilization.

  7. Effect of water on hydrogen permeability

    NASA Technical Reports Server (NTRS)

    Hulligan, David; Tomazic, William A.

    1987-01-01

    Doping of hydrogen with CO and CO2 was developed to reduce hydrogen permeation in Stirling engines by forming a low permeability oxide coating on the inner surface of the heater head tubes. Although doping worked well, under certain circumstances the protective oxide could be chemically reduced by the hydrogen in the engine. Some oxygen is required in the hydrogen to prevent reduction. Eventually, all the oxygen in the hydrogen gas - whatever its source - shows up as water. This is the result of hydrogen reducing the CO, CO2, or the protective inner surface oxides. This water can condense in the engine system under the right conditions. If the concentration of water vapor is reduced to a low enough level, the hydrogen can chemically reduce the oxide coating, resulting in an increase in permeability. This work was done to define the minimum water content required to avoid this reduction in the oxide coating. The results of this testing show that a minimum of approximately 750 ppm water is required to prevent an increase in permeability of CG-27, a high temperature metal alloy selected for Stirling engine heater tubes.

  8. Metallic Hydrogen

    NASA Astrophysics Data System (ADS)

    Silvera, Isaac; Zaghoo, Mohamed; Salamat, Ashkan

    2015-03-01

    Hydrogen is the simplest and most abundant element in the Universe. At high pressure it is predicted to transform to a metal with remarkable properties: room temperature superconductivity, a metastable metal at ambient conditions, and a revolutionary rocket propellant. Both theory and experiment have been challenged for almost 80 years to determine its condensed matter phase diagram, in particular the insulator-metal transition. Hydrogen is predicted to dissociate to a liquid atomic metal at multi-megabar pressures and T =0 K, or at megabar pressures and very high temperatures. Thus, its predicted phase diagram has a broad field of liquid metallic hydrogen at high pressure, with temperatures ranging from thousands of degrees to zero Kelvin. In a bench top experiment using static compression in a diamond anvil cell and pulsed laser heating, we have conducted measurements on dense hydrogen in the region of 1.1-1.7 Mbar and up to 2200 K. We observe a first-order phase transition in the liquid phase, as well as sharp changes in optical transmission and reflectivity when this phase is entered. The optical signature is that of a metal. The mapping of the phase line of this transition is in excellent agreement with recent theoretical predictions for the long-sought plasma phase transition to metallic hydrogen. Research supported by the NSF, Grant DMR-1308641, the DOE Stockpile Stewardship Academic Alliance Program, Grant DE-FG52-10NA29656, and NASA Earth and Space Science Fellowship Program, Award NNX14AP17H.

  9. System level permeability modeling of porous hydrogen storage materials.

    SciTech Connect

    Kanouff, Michael P.; Dedrick, Daniel E.; Voskuilen, Tyler

    2010-01-01

    A permeability model for hydrogen transport in a porous material is successfully applied to both laboratory-scale and vehicle-scale sodium alanate hydrogen storage systems. The use of a Knudsen number dependent relationship for permeability of the material in conjunction with a constant area fraction channeling model is shown to accurately predict hydrogen flow through the reactors. Generally applicable model parameters were obtained by numerically fitting experimental measurements from reactors of different sizes and aspect ratios. The degree of channeling was experimentally determined from the measurements and found to be 2.08% of total cross-sectional area. Use of this constant area channeling model and the Knudsen dependent Young & Todd permeability model allows for accurate prediction of the hydrogen uptake performance of full-scale sodium alanate and similar metal hydride systems.

  10. Liquid metal hydrogen barriers

    DOEpatents

    Grover, George M.; Frank, Thurman G.; Keddy, Edward S.

    1976-01-01

    Hydrogen barriers which comprise liquid metals in which the solubility of hydrogen is low and which have good thermal conductivities at operating temperatures of interest. Such barriers are useful in nuclear fuel elements containing a metal hydride moderator which has a substantial hydrogen dissociation pressure at reactor operating temperatures.

  11. Hydrogen interactions with metals

    NASA Technical Reports Server (NTRS)

    Mclellan, R. B.; Harkins, C. G.

    1975-01-01

    Review of the literature on the nature and extent of hydrogen interactions with metals and the role of hydrogen in metal failure. The classification of hydrogen-containing systems is discussed, including such categories as covalent hydrides, volatile hydrides, polymeric hydrides, and transition metal hydride complexes. The use of electronegativity as a correlating parameter in determining hydride type is evaluated. A detailed study is made of the thermodynamics of metal-hydrogen systems, touching upon such aspects as hydrogen solubility, the positions occupied by hydrogen atoms within the solvent metal lattice, the derivation of thermodynamic functions of solid solutions from solubility data, and the construction of statistical models for hydrogen-metal solutions. A number of theories of hydrogen-metal bonding are reviewed, including the rigid-band model, the screened-proton model, and an approach employing the augmented plane wave method to solve the one-electron energy band problem. Finally, the mechanism of hydrogen embrittlement is investigated on the basis of literature data concerning stress effects and the kinetics of hydrogen transport to critical sites.

  12. Determination of hydrogen permeability in commercial and modified superalloys

    NASA Technical Reports Server (NTRS)

    Bhattacharyya, S.; Peterman, W.

    1983-01-01

    The results of hydrogen permeability measurements on several iron- and cobalt-base alloys as well as on two long-ranged ordered alloys over the range of 705 to 870 C (1300 to 1600 F) are summarized. The test alloys included wrought alloys N-155, IN 800, A-286, 19-9DL, and 19-9DL modifications with aluminum, niobium, and misch metal. In addition, XF-818, CRM-6D, SA-F11, and HS-31 were evaluated. Two wrought long-range ordered alloys, Ni3Al and (Fe,Ni)3(V,Al) were also evaluated. All tests were conducted at 20.7 MPa pressure in either pure and/or 1% CO2-doped H2 for test periods as long as 133 h. Detailed analyses were conducted to determine the relative permeability rankings of these alloys and the effect of doping, exit surface oxidation, specimen design variations, and test duration on permeability coefficient, and permeation activation energies were determined. The two long-range ordered alloys had the lowest permeability coefficients in pure H2 when compared with the eight commercial alloys and their modifications. With CO2 doping, significant decrease in permeability was observed in commercial alloys--no doped tests were conducted with the long-range ordered alloys.

  13. A Quantitative Concept of the Permeability to Hydrogen of Passivating Layers on a Metal at the Apex of the Crack in the Corrosion-induced Cracking of Constructional Materials

    NASA Astrophysics Data System (ADS)

    Marichev, Viktor A.

    1987-05-01

    A general theoretical and methodological approach to the determination of the role of the local anodic dissolution and hydrogen-induced embrittlement in the corrosion-induced cracking of various constructional materials is examined. The possibility of the quantitative estimation of the role of the hydrogen-induced embrittlement in the corrosion-induced cracking of high-strength steels and titanium, aluminium, magnesium, and zirconium alloys is demonstrated. A quantitative concept of the permeability of hydrogen of passivating layers on a metal at the apex of a crack, which has made it possible to determine quantitatively for the first time the relation between the critical concentration of hydrogen and the stress intensity coefficient in the hydrogen-induced embrittlement of steels and titanium and aluminium alloys, has been developed on the basis of several postulates. Two new methods for the investigation of the adsorption of hydrogen and anions at the apex of the crack in corrosion-induced cracking, based on this concept, are proposed. The bibliography includes 47 references.

  14. The interaction of hydrogen with metal alloys

    NASA Technical Reports Server (NTRS)

    Danford, M. D.; Montano, J. W.

    1991-01-01

    Hydrogen diffusion coefficients were measured for several alloys, and these were determined to be about the same at 25 C for all alloys investigated. The relation of structure, both metallurgical and crystallographic, to the observed hydrogen distribution on charging was investigated, as well as the role of hydride formation in the hydrogen resistance of metal alloys. An attempt was made to correlate the structures and compositions of metal alloys as well as other parameters with the ratios of their notched tensile strengths in hydrogen to that in helium, R(H2/He), which are believed to represent a measure of their hydrogen resistance. Evidence supports the belief that hydrogen permeability and hydrogen resistance are increased by smaller grain sizes for a given alloy composition.

  15. Stable catalyst layers for hydrogen permeable composite membranes

    DOEpatents

    Way, J. Douglas; Wolden, Colin A

    2014-01-07

    The present invention provides a hydrogen separation membrane based on nanoporous, composite metal carbide or metal sulfide coated membranes capable of high flux and permselectivity for hydrogen without platinum group metals. The present invention is capable of being operated over a broad temperature range, including at elevated temperatures, while maintaining hydrogen selectivity.

  16. Determination of hydrogen permeability in uncoated and coated superalloys

    NASA Technical Reports Server (NTRS)

    Bhattacharyya, S.; Vesely, E. J., Jr.; Hill, V. L.

    1981-01-01

    Hydrogen permeability, diffusivity, and solubility data were obtained for eight wrought and cast high temperature alloys over the range 650 to 815 C. Data were obtained for both uncoated alloys and wrought alloys coated with four commercially available coatings. Activation energies for permeability, diffusivity and solubility were calculated.

  17. Gas Permeable Chemochromic Compositions for Hydrogen Sensing

    NASA Technical Reports Server (NTRS)

    Bokerman, Gary (Inventor); Mohajeri, Nahid (Inventor); Muradov, Nazim (Inventor); Tabatabaie-Raissi, Ali (Inventor)

    2013-01-01

    A (H2) sensor composition includes a gas permeable matrix material intermixed and encapsulating at least one chemochromic pigment. The chemochromic pigment produces a detectable change in color of the overall sensor composition in the presence of H2 gas. The matrix material provides high H2 permeability, which permits fast permeation of H2 gas. In one embodiment, the chemochromic pigment comprises PdO/TiO2. The sensor can be embodied as a two layer structure with the gas permeable matrix material intermixed with the chemochromic pigment in one layer and a second layer which provides a support or overcoat layer.

  18. Measuring Hydrogen Concentrations in Metals

    NASA Technical Reports Server (NTRS)

    Danford, M. D.

    1985-01-01

    Commercial corrosion-measurement system adapted to electrochemical determination of hydrogen concentrations in metals. New technique based on diffusion of hydrogen through foil specimen of metal. In sample holder, hydrogen produced on one side of foil, either by corrosion reaction or by cathodic current. Hydrogen diffused through foil removed on other side by constant anode potential, which leads to oxidation of hydrogen to water. Anode current is measure of concentration of hydrogen diffusing through foil. System used to study hydrogen uptake, hydrogen elimination by baking, effect of heat treatment, and effect of electroplating on high-strength steels.

  19. Metallization of fluid hydrogen

    SciTech Connect

    Nellis, W.J.; Louis, A.A.; Ashcroft, N.W.

    1997-05-14

    The electrical activity of liquid hydrogen has been measured at the high dynamic pressures, and temperatures that can be achieved with a reverberating shock wave. The resulting data are most naturally interpreted in terms of a continuous transition from a semiconducting to a metallic, largely diatomic fluid, the latter at 140 CPa, (ninefold compression) and 3000 K. While the fluid at these conditions resembles common liquid metals by the scale of its resistivity of 500 micro-ohm-cm, it differs by retaining a strong pairing character, and the precise mechanism by which a metallic state might be attained is still a matter of debate. Some evident possibilities include (i) physics of a largely one-body character, such as a band-overlap transition, (ii) physics of a strong-coupling or many-body character,such as a Mott-Hubbard transition, and (iii) process in which structural changes are paramount.

  20. Hydrogen environment embrittlement of metals

    NASA Technical Reports Server (NTRS)

    Jewett, R. P.; Walter, R. J.; Chandler, W. T.; Frohmberg, R. P.

    1973-01-01

    Hydrogen environment embrittlement refers to metals stressed while exposed to a hydrogen atmosphere. Tested in air, even after exposure to hydrogen under pressure, this effect is not observed on similar specimens. Much high purity hydrogen is prepared by evaporation of liquid hydrogen, and thus has low levels for potential impurities which could otherwise inhibit or poison the absorbent reactions that are involved. High strength steels and nickel-base allows are rated as showing extreme embrittlement; aluminum alloys and the austenitic stainless steels, as well as copper, have negligible susceptibility to this phenomenon. The cracking that occurs appears to be a surface phenomenon, is unlike that of internal hydrogen embrittlement.

  1. Metal salt catalysts for enhancing hydrogen spillover

    DOEpatents

    Yang, Ralph T; Wang, Yuhe

    2013-04-23

    A composition for hydrogen storage includes a receptor, a hydrogen dissociating metal doped on the receptor, and a metal salt doped on the receptor. The hydrogen dissociating metal is configured to spill over hydrogen to the receptor, and the metal salt is configured to increase a rate of the spill over of the hydrogen to the receptor.

  2. Effect of water on hydrogen permeability. [Stirling engines

    NASA Technical Reports Server (NTRS)

    Hulligan, D. D.; Tomazic, W. A.

    1984-01-01

    Doping of hydrogen with CO or CO2 was developed to reduce hydrogen permeation in Stirling engines by forming low permeability oxide coatings in the heater tubes. An end product of this process is water - which can condense in the cold parts of the engine system. If the water vapor is reduced to a low enough level, the hydrogen can reduce the oxide coating resulting in increased permeability. The equilibrium level of water (oxygen bearing gas) required to avoid reduction of the oxide coating was investigated. Results at 720 C and 13.8 MPa have shown that: (1) pure hydrogen will reduce the coating; (2) 500 ppm CO (500 ppm water equivalent) does not prevent the reduction; and (3) 500 ppm CO2 (1000 ppm water) appears to be close to the equilibrium level. Further tests are planned to define the equilibrium level more precisely and to extend the data to 820 C and 3.4, 6.9, and 13.8 MPa.

  3. Effects of hydrogen on metals

    NASA Technical Reports Server (NTRS)

    Cataldo, C. E.

    1969-01-01

    Several rules to guide choice of materials, and methods of welding, electroplating, and heat treatment will provide a method for minimizing failures in storage tanks and related hardware. Failures are caused by high-pressure hydrogen effects, the formation of hydrides in titanium, and hydrogen absorption through various metals processing techniques.

  4. Hydrogen Permeability of Polymer Matrix Composites at Cryogenic Temperatures

    NASA Technical Reports Server (NTRS)

    Grenoble, Ray W.; Gates, Thomas S

    2005-01-01

    This paper presents experimental methods and results of an ongoing study of the correlation between damage state and hydrogen gas permeability of laminated composite materials under mechanical strains and thermal loads. A specimen made from IM-7/977-2 composite material has been mechanically cycled at room temperature to induce microcrack damage. Crack density and tensile modulus were observed as functions of number of cycles. Damage development was found to occur most quickly in the off-axis plies near the outside of the laminate. Permeability measurements were made after 170,000 cycles and 430,000 cycles. Leak rate was found to depend on applied mechanical strain, crack density, and test temperature.

  5. Characterization of tungsten films and their hydrogen permeability

    SciTech Connect

    Nemanič, Vincenc Kovač, Janez; Lungu, Cristian; Porosnicu, Corneliu; Zajec, Bojan

    2014-11-01

    Prediction of tritium migration and its retention within fusion reactors is uncertain due to a significant role of the structural disorder that is formed on the surface layer after plasma exposure. Tungsten films deposited by any of the suitable methods are always disordered and contain a high density of hydrogen traps. Experiments on such films with hydrogen isotopes present a suitable complementary method, which improves the picture of the hydrogen interaction with fusion relevant materials. The authors report on the morphology, composition, and structure of tungsten films deposited by the thermionic vacuum arc method on highly permeable Eurofer substrates. Subsequently, hydrogen permeation studies through these films were carried out in a wide pressure range from 20 to 1000 mbars at 400 °C. The final value of the permeation coefficient for four samples after 24 h at 400 °C was between P = 3.2 × 10{sup −14} mol H{sub 2}/(m s Pa{sup 0.5}) and P = 1.1 × 10{sup −15} mol H{sub 2}/(m s Pa{sup 0.5}). From the time evolution of the permeation flux, it was shown that diffusivity was responsible for the difference in the steady fluxes, as solubility was roughly the same. This is confirmed by XRD data taken on these samples.

  6. Hydrogen permeability degradation of Pd-coated Nb-TiNi alloy caused by its interfacial diffusion

    NASA Astrophysics Data System (ADS)

    Ohtsu, Naofumi; Ishikawa, Kazuhiro; Kobori, Yoshihiro

    2016-01-01

    Pd-coated Nb40Ti30Ni30 (Nb-TiNi) is considered a promising material for hydrogen-permeable membranes because of the low usage of Pd metal. This paper reports the degradation of hydrogen permeability occurring during the permeation experiment above 773 K. Surface analysis using X-ray photoelectron spectroscopy revealed that interdiffusion between the Pd coating and the constituent elements of Nb and Ti progressed during the permeation experiment. The diffused Ti was concentrated near the topmost surface and then formed TiO2, which resulted in a decrease in the Pd concentration at the topmost surface. However, the diffused Nb was observed to bind to Pd in the surface and formed a Pd-Nb alloy beneath the topmost surface. We concluded that these changes caused the decline of the hydrogen permeability at high-temperature conditions.

  7. Composite Metal-hydrogen Electrodes for Metal-Hydrogen Batteries

    SciTech Connect

    Ruckman, M W; Wiesmann, H; Strongin, M; Young, K; Fetcenko, M

    1997-04-01

    The purpose of this project is to develop and conduct a feasibility study of metallic thin films (multilayered and alloy composition) produced by advanced sputtering techniques for use as anodes in Ni-metal hydrogen batteries. The anodes could be incorporated in thin film solid state Ni-metal hydrogen batteries that would be deposited as distinct anode, electrolyte and cathode layers in thin film devices. The materials could also be incorporated in secondary consumer batteries (i.e. type AF(4/3 or 4/5)) which use electrodes in the form of tapes. The project was based on pioneering studies of hydrogen uptake by ultra-thin Pd-capped metal-hydrogen ratios exceeding and fast hydrogen charging and Nb films, these studies suggested that materials with those of commercially available metal hydride materials discharging kinetics could be produced. The project initially concentrated on gas phase and electrochemical studies of Pd-capped niobium films in laboratory-scale NiMH cells. This extended the pioneering work to the wet electrochemical environment of NiMH batteries and exploited advanced synchrotron radiation techniques not available during the earlier work to conduct in-situ studies of such materials during hydrogen charging and discharging. Although batteries with fast charging kinetics and hydrogen-metal ratios approaching unity could be fabricated, it was found that oxidation, cracking and corrosion in aqueous solutions made pure Nb films-and multiiayers poor candidates for battery application. The project emphasis shifted to alloy films based on known elemental materials used for NiMH batteries. Although commercial NiMH anode materials contain many metals, it was found that 0.24 µm thick sputtered Zr-Ni films cycled at least 50 times with charging efficiencies exceeding 95% and [H]/[M] ratios of 0.7-1.0. Multilayered or thicker Zr-Ni films could be candidates for a thin film NiMH battery that may have practical applications as an integrated power source for

  8. Metallic Hydrogen and Nano-Tube Magnets

    NASA Technical Reports Server (NTRS)

    Cole, John W.

    2004-01-01

    When hydrogen is subjected to enough pressure the atoms will be pressed into close enough proximity that each electron is no longer bound to a single proton. The research objectives is to find whether metallic hydrogen can be produced and once produced will the metallic hydrogen be metastable and remain in the metallic form when the pressure is released.

  9. Hydrogen Permeability of Incoloy 800H, Inconel 617, and Haynes 230 Alloys

    SciTech Connect

    Pattrick Calderoni

    2010-07-01

    A potential issue in the design of the NGNP reactor and high-temperature components is the permeation of fission generated tritium and hydrogen product from downstream hydrogen generation through high-temperature components. Such permeation can result in the loss of fission-generated tritium to the environment and the potential contamination of the helium coolant by permeation of product hydrogen into the coolant system. The issue will be addressed in the engineering design phase, and requires knowledge of permeation characteristics of the candidate alloys. Of three potential candidates for high-temperature components of the NGNP reactor design, the hydrogen permeability has been documented well only for Incoloy 800H, but at relatively high partial pressures of hydrogen. Hydrogen permeability data have been published for Inconel 617, but only in two literature reports and for partial pressures of hydrogen greater than one atmosphere, far higher than anticipated in the NGNP reactor. The hydrogen permeability of Haynes 230 has not been published. To support engineering design of the NGNP reactor components, the hydrogen permeability of Inconel 617 and Haynes 230 were determined using a measurement system designed and fabricated at the Idaho National Laboratory. The performance of the system was validated using Incoloy 800H as reference material, for which the permeability has been published in several journal articles. The permeability of Incoloy 800H, Inconel 617 and Haynes 230 was measured in the temperature range 650 to 950 °C and at hydrogen partial pressures of 10-3 and 10-2 atm, substantially lower pressures than used in the published reports. The measured hydrogen permeability of Incoloy 800H and Inconel 617 were in good agreement with published values obtained at higher partial pressures of hydrogen. The hydrogen permeability of Inconel 617 and Haynes 230 were similar, about 50% greater than for Incoloy 800H and with similar temperature dependence.

  10. Method for controlled hydrogen charging of metals

    DOEpatents

    Cheng, Bo-Ching; Adamson, Ronald B.

    1984-05-29

    A method for controlling hydrogen charging of hydride forming metals through a window of a superimposed layer of a non-hydriding metal overlying the portion of the hydride forming metals to be charged.

  11. Effect of oxide films on hydrogen permeability of candidate Stirling engine heater head tube alloys

    NASA Technical Reports Server (NTRS)

    Schuon, S. R.; Misencik, J. A.

    1981-01-01

    The effect of oxide films developed in situ from CO/CO2 doped hydrogen on high pressure hydrogen permeability at 820 C was studied on N-155, A-286, IN 800, 19-9DL, Nitronic 40, HS-188, and IN 718 tubing in a Stirling materials simulator. The hydrogen permeability decreased with increasing dopant levels of CO or CO2 and corresponding decreases in oxide porosity. Minor reactive alloying elements strongly influenced permeability. At high levels of CO or CO2, a liquid oxide formed on alloys with greater than 50 percent Fe. This caused increased permeability. The oxides formed on the inside tube walls were analyzed and their effective permeabilities were calculated.

  12. Hydrogen Permeability of a Polymer Based Composite Tank Material Under Tetra-Axial Strain

    NASA Technical Reports Server (NTRS)

    Stokes, Eric H.

    2003-01-01

    In order to increase the performance of future expendable and reusable launch vehicles and reduce per-pound payload launch costs, weight reductions have been sought in vehicle components. Historically, the cryogenic propellant tanks for launch vehicles have been constructed from metal. These are some of the largest structural components in the vehicle and contribute significantly to the vehicles total dry weight. A successful replacement material will be conformable, have a high strength to weight ratio, and have a low gas-permeability to the cryogens being stored, i.e., oxygen and hydrogen. Polymer-based composites are likely candidates to fill this role. Polymer and polymer-based composites in general are known to have acceptable gas permeation properties in their as-cured state.1 The use of polymer-based composites for this application has been proposed for some time.2 Some successes have been reported with oxygen3, but other than the DC-XA experience, those with hydrogen have been limited. The primary reason for this has been the small molecular diameter of hydrogen, the lower temperatures of the liquid, and that the composite materials examined to date have all been susceptible to microcrack formation in response to the thermal-mechanical cycles experienced in the use-environment. There have been numerous accounts of composite materials with reported acceptable resistance to the formation of microcracks when exposed to various mechanical and/or thermal cycles. However, virtually all of these studies have employed uniaxial loads and there has been no discussion or empirical evidence pertaining to how these loads relate to the biaxial state of stress in the material in its use environment. Furthermore, many of these studies have suffered from a lack of instrument sensitivity in detecting hydrogen permeability, no standards, insufficient documentation of test conditions, testing of cycled materials in their unload state, and/or false assumptions about the nature

  13. Permeability of hydrogen isotopes through nickel-based alloys

    SciTech Connect

    Edge, E.M.; Mitchell, D.J.

    1983-04-01

    Permeabilities and diffusivities of deuterium in several nickel-based alloys were measured in this investigation. Measurements were made by the gas-phase breakthrough technique in the temperature range 200 to 450/sup 0/C with applied pressures ranging from 1 to 100 kPa. The results were extrapolated to predict the permeabilities (K) of the alloys at room temperature. The alloy with the smallest deuterium permeability is Carpenter 49, for which K = 4.3 x 10/sup -18/ mol s/sup -1/ m/sup -1/ Pa/sup -//sup 1/2/ at 22/sup 0/C. The permeability of deuterium in Kovar or Ceramvar is about 80% greater than that for Carpenter 49. Premeabilities of Inconel 625, Inconel 718, Inconel 750 and Monel K-500 are all equal to about 5 x 10/sup -17/ mol m/sup -1/ s/sup -1/ Pa/sup -//sup 1/2/ at 22/sup 0/C. The validity (from a statistical standpoint) of the extrapolation of the permeabilities to room temperature is considered in detail. Published permeabilities of stainless steels and nickel-iron alloys are also reviewed. The greatest differences in permeabilities among the nickel-based alloys appear to be associated with the tendency for some alloys to form protective oxide layers. Permeabilities of deuterium through laminates containing copper are smaller than for any of the iron-nickel alloys.

  14. Using permeable membranes to produce hydrogen and oxygen from water

    NASA Technical Reports Server (NTRS)

    Sanders, A. P.; Williams, R. J.; Downs, W. R.; Mcbryar, H.

    1975-01-01

    Concept may make it profitable to obtain hydrogen fuel from water. Laboratory tests have demonstrated that method enables decomposition of water several orders of magnitude beyond equilibrium state where only small amounts of free hydrogen are present.

  15. Hydrogen trapping and the interaction of hydrogen with metals

    NASA Technical Reports Server (NTRS)

    Danford, Merlin D.

    1987-01-01

    A method has been developed for the determination of trapped hydrogen in metal alloys, involving the determination of mobile hydrogen using the electrochemical method and the determination of total hydrogen with the fusion method, the difference in hydrogen concentrations being due to trapped hydrogen. It has been found that hydrogen enters body-centered cubic structures through the grain bodies rather than through the grain boundaries. Hydrogen also diffuses much more rapidly in body-centered cubic structures on charging than in face-centered cubic structures, the hydrogen distribution being more uniform in nature. The energy necessary to cause hydrogen embrittlement is postulated to arise from the changes in crystal lattice energies brought about through interaction of hydrogen with atoms in the metal lattice. The total energy change is more negative for body-centered cubic structures, believed to be the cause of a greater tendency toward hydrogen embrittlement. Finally, the agreement of hydrogen concentrations obtained at 25 C by the electrochemical method with those obtained by the fusion method are taken as a strong indication of the power and validity of the electrochemical method.

  16. Novel Metallic Membranes for Hydrogen Separation

    SciTech Connect

    Dogan, Omer

    2011-02-27

    To reduce dependence on oil and emission of greenhouse gases, hydrogen is favored as an energy carrier for the near future. Hydrogen can be converted to electrical energy utilizing fuel cells and turbines. One way to produce hydrogen is to gasify coal which is abundant in the U.S. The coal gasification produces syngas from which hydrogen is then separated. Designing metallic alloys for hydrogen separation membranes which will work in a syngas environment poses significant challenges. In this presentation, a review of technical targets, metallic membrane development activities at NETL and challenges that are facing the development of new technologies will be given.

  17. Metal-hydrogen bridge bonding of hydrocarbons on metal surfaces

    PubMed Central

    Gavin, Robert M.; Reutt, Janice; Muetterties, Earl L.

    1981-01-01

    Molecular orbital studies implicate multicenter metal-hydrogen-carbon interactions as contributors to the bonding of chemisorbed hydrocarbons on clean metal surfaces. The most stable geometries appear to be those that achieve the maximum multicenter bonding to the coordinately unsaturated metal atoms in the vicinity of the anchoring metal-carbon interaction. Energy differences between possible surface sites are of the same magnitude as stabilization energies for three-center bonding of hydrogen atoms to the metal surface. Accordingly, secondary interactions of hydrogen with neighboring metal atoms may be significant determining factors in surface structures. The model predictions are compared with known structures and are used to propose a mechanism for hydrocarbon reactions on metal surfaces. These metal-hydrogen-carbon interactions are presumed to be intermediate points or states in C—H bond-breaking processes. PMID:16593041

  18. Novel Composite Hydrogen-Permeable Membranes for Nonthermal Plasma Reactors for the Decomposition of Hydrogen Sulfide

    SciTech Connect

    Morris Argyle; John Ackerman; Suresh Muknahallipatna; Jerry Hamann; Stanislaw Legowski; Gui-Bing Zhao; Sanil John; Ji-Jun Zhang; Linna Wang

    2007-09-30

    The goal of this experimental project was to design and fabricate a reactor and membrane test cell to dissociate hydrogen sulfide (H{sub 2}S) in a nonthermal plasma and to recover hydrogen (H{sub 2}) through a superpermeable multi-layer membrane. Superpermeability of hydrogen atoms (H) has been reported by some researchers using membranes made of Group V transition metals (niobium, tantalum, vanadium, and their alloys), but it was not achieved at the moderate pressure conditions used in this study. However, H{sub 2}S was successfully decomposed at energy efficiencies higher than any other reports for the high H{sub 2}S concentration and moderate pressures (corresponding to high reactor throughputs) used in this study.

  19. METAL HYDRIDE HYDROGEN COMPRESSORS: A REVIEW

    SciTech Connect

    Bowman Jr, Robert C; Yartys, Dr. Volodymyr A.; Lototskyy, Dr. Michael V; Pollet, Dr. B.G.

    2014-01-01

    Metal hydride (MH) thermal sorption compression is an efficient and reliable method allowing a conversion of energy from heat into a compressed hydrogen gas. The most important component of such a thermal engine the metal hydride material itself should possess several material features in order to achieve an efficient performance in the hydrogen compression. Apart from the hydrogen storage characteristics important for every solid H storage material (e.g. gravimetric and volumetric efficiency of H storage, hydrogen sorption kinetics and effective thermal conductivity), the thermodynamics of the metal-hydrogen systems is of primary importance resulting in a temperature dependence of the absorption/desorption pressures). Several specific features should be optimized to govern the performance of the MH-compressors including synchronisation of the pressure plateaus for multi-stage compressors, reduction of slope of the isotherms and hysteresis, increase of cycling stability and life time, together with challenges in system design associated with volume expansion of the metal matrix during the hydrogenation. The present review summarises numerous papers and patent literature dealing with MH hydrogen compression technology. The review considers (a) fundamental aspects of materials development with a focus on structure and phase equilibria in the metal-hydrogen systems suitable for the hydrogen compression; and (b) applied aspects, including their consideration from the applied thermodynamic viewpoint, system design features and performances of the metal hydride compressors and major applications.

  20. Using First-Principles Calculations to Describe Amorphous Metal Films for Hydrogen Purification

    NASA Astrophysics Data System (ADS)

    Hao, Shiqiang; Widom, Mike; Sholl, David

    2009-03-01

    The increasing demand for clean and efficient energy has resulted in an increased global willingness to embrace the proposed hydrogen economy. The use of amorphous metal films as membranes to purify hydrogen has potential to overcome at least some of the disadvantages of existing crystalline metal membranes. We introduce a general strategy combining density functional theory and statistical mechanics to quantitatively predict solubility, diffusivity and permeability of interstitial H in amorphous metals. Our methods make it possible for the first time to quantitatively evaluate the performance of amorphous metal films as hydrogen purification membranes. These methods are introduced by examining amorphous Fe3B and a crystalline analogue with the same composition. A membrane made from the amorphous material is predicted to have a hydrogen permeability 1.5-2 orders of magnitude higher than a crystalline membrane. The methods we introduce here will be useful in accelerating the development of amorphous membranes for practical applications.

  1. Investigation of metal hydride materials as hydrogen reservoirs for metal-hydrogen batteries

    NASA Technical Reports Server (NTRS)

    ONISCHAK

    1976-01-01

    The performance and suitability of various metal hydride materials were examined for use as possible hydrogen storage reservoirs for secondary metal-hydrogen batteries. Lanthanum pentanickel hydride appears as a probable candidate in terms of stable hydrogen supply under feasible thermal conditions. A kinetic model describing the decomposition rate data of the hydride has been developed.

  2. Hydrogen transport membranes

    DOEpatents

    Mundschau, Michael V.

    2005-05-31

    Composite hydrogen transport membranes, which are used for extraction of hydrogen from gas mixtures are provided. Methods are described for supporting metals and metal alloys which have high hydrogen permeability, but which are either too thin to be self supporting, too weak to resist differential pressures across the membrane, or which become embrittled by hydrogen. Support materials are chosen to be lattice matched to the metals and metal alloys. Preferred metals with high permeability for hydrogen include vanadium, niobium, tantalum, zirconium, palladium, and alloys thereof. Hydrogen-permeable membranes include those in which the pores of a porous support matrix are blocked by hydrogen-permeable metals and metal alloys, those in which the pores of a porous metal matrix are blocked with materials which make the membrane impervious to gases other than hydrogen, and cermets fabricated by sintering powders of metals with powders of lattice-matched ceramic.

  3. Pore structure and effective permeability of metallic filters

    NASA Astrophysics Data System (ADS)

    Hejtmánek, Vladimír; Veselý, Martin; Čapek, Pavel

    2013-02-01

    The pore structures (microstructures) of two metallic filters were reconstructed using the stochastic reconstruction method based on simulated annealing. The following microstructural descriptors were included in the description of the real microstructures: the two-point probability function, the lineal-path functions for the void or solid phases, i.e. simulated annealing was constrained by all low-order statistical measures that were accessible through the analysis of images of polished sections. An effect of the microstructural descriptors on the course of reconstruction was controlled by modifying two parameters of the reconstruction procedure [1]. Their values resulted from repeated reconstruction of two-dimensional microstructures in such a way that the reference (experimental) and calculated two-point cluster functions deviated negligibly. It was tacitly assumed that the parameters adjusted during two-dimensional reconstruction had the same influence on the formation of the three-dimensional microstructures. Since connectivity of phases is a critical property of the stochastically reconstructed media, clusters of pore and solid voxels were determined using the Hoshen-Kopelman algorithm. It was found that the solid phase formed one large cluster in accordance with the physical feasibility. The void phase created one large cluster and a few small clusters representing the isolated porosity. The percolation properties were further characterised using the local porosity theory [2]. Effective permeability of the replicas was estimated by solving the Stokes equation for creeping flow of an incompressible liquid in pore space. Calculated permeability values matched well their experimental counterparts.

  4. Metallic Hydrogen: A Game Changing Rocket Propellant

    NASA Technical Reports Server (NTRS)

    Silvera, Isaac F.

    2016-01-01

    The objective of this research is to produce metallic hydrogen in the laboratory using an innovative approach, and to study its metastability properties. Current theoretical and experimental considerations expect that extremely high pressures of order 4-6 megabar are required to transform molecular hydrogen to the metallic phase. When metallic hydrogen is produced in the laboratory it will be extremely important to determine if it is metastable at modest temperatures, i.e. remains metallic when the pressure is released. Then it could be used as the most powerful chemical rocket fuel that exists and revolutionize rocketry, allowing single-stage rockets to enter orbit and chemically fueled rockets to explore our solar system.

  5. Metastable Metal Hydrides for Hydrogen Storage

    DOE PAGESBeta

    Graetz, Jason

    2012-01-01

    The possibility of using hydrogen as a reliable energy carrier for both stationary and mobile applications has gained renewed interest in recent years due to improvements in high temperature fuel cells and a reduction in hydrogen production costs. However, a number of challenges remain and new media are needed that are capable of safely storing hydrogen with high gravimetric and volumetric densities. Metal hydrides and complex metal hydrides offer some hope of overcoming these challenges; however, many of the high capacity “reversible” hydrides exhibit a large endothermic decomposition enthalpy making it difficult to release the hydrogen at low temperatures. Onmore » the other hand, the metastable hydrides are characterized by a low reaction enthalpy and a decomposition reaction that is thermodynamically favorable under ambient conditions. The rapid, low temperature hydrogen evolution rates that can be achieved with these materials offer much promise for mobile PEM fuel cell applications. However, a critical challenge exists to develop new methods to regenerate these hydrides directly from the reactants and hydrogen gas. This spotlight paper presents an overview of some of the metastable metal hydrides for hydrogen storage and a few new approaches being investigated to address the key challenges associated with these materials.« less

  6. Final Report: Metal Perhydrides for Hydrogen Storage

    SciTech Connect

    Hwang, J-Y.; Shi, S.; Hackney, S.; Swenson, D.; Hu, Y.

    2011-07-26

    Hydrogen is a promising energy source for the future economy due to its environmental friendliness. One of the important obstacles for the utilization of hydrogen as a fuel source for applications such as fuel cells is the storage of hydrogen. In the infrastructure of the expected hydrogen economy, hydrogen storage is one of the key enabling technologies. Although hydrogen possesses the highest gravimetric energy content (142 KJ/g) of all fuels, its volumetric energy density (8 MJ/L) is very low. It is desired to increase the volumetric energy density of hydrogen in a system to satisfy various applications. Research on hydrogen storage has been pursed for many years. Various storage technologies, including liquefaction, compression, metal hydride, chemical hydride, and adsorption, have been examined. Liquefaction and high pressure compression are not desired due to concerns related to complicated devices, high energy cost and safety. Metal hydrides and chemical hydrides have high gravimetric and volumetric energy densities but encounter issues because high temperature is required for the release of hydrogen, due to the strong bonding of hydrogen in the compounds. Reversibility of hydrogen loading and unloading is another concern. Adsorption of hydrogen on high surface area sorbents such as activated carbon and organic metal frameworks does not have the reversibility problem. But on the other hand, the weak force (primarily the van der Waals force) between hydrogen and the sorbent yields a very small amount of adsorption capacity at ambient temperature. Significant storage capacity can only be achieved at low temperatures such as 77K. The use of liquid nitrogen in a hydrogen storage system is not practical. Perhydrides are proposed as novel hydrogen storage materials that may overcome barriers slowing advances to a hydrogen fuel economy. In conventional hydrides, e.g. metal hydrides, the number of hydrogen atoms equals the total valence of the metal ions. One Li

  7. Hydrogen production from methane using oxygen-permeable ceramic membranes

    NASA Astrophysics Data System (ADS)

    Faraji, Sedigheh

    Non-porous ceramic membranes with mixed ionic and electronic conductivity have received significant interest in membrane reactor systems for the conversion of methane and higher hydrocarbons to higher value products like hydrogen. However, hydrogen generation by this method has not yet been commercialized and suffers from low membrane stability, low membrane oxygen flux, high membrane fabrication costs, and high reaction temperature requirements. In this dissertation, hydrogen production from methane on two different types of ceramic membranes (dense SFC and BSCF) has been investigated. The focus of this research was on the effects of different parameters to improve hydrogen production in a membrane reactor. These parameters included operating temperature, type of catalyst, membrane material, membrane thickness, membrane preparation pH, and feed ratio. The role of the membrane in the conversion of methane and the interaction with a Pt/CeZrO2 catalyst has been studied. Pulse studies of reactants and products over physical mixtures of crushed membrane material and catalyst have clearly demonstrated that a synergy exists between the membrane and the catalyst under reaction conditions. The degree of catalyst/membrane interaction strongly impacts the conversion of methane and the catalyst performance. During thermogravimetric analysis, the onset temperature of oxygen release for BSCF was observed to be lower than that for SFC while the amount of oxygen release was significantly greater. Pulse injections of CO2 over crushed membranes at 800°C have shown more CO2 dissociation on the BSCF membrane than the SFC membrane, resulting in higher CO formation on the BSCF membrane. Similar to the CO2 pulses, when CO was injected on the samples at 800°C, CO2 production was higher on BSCF than SFC. It was found that hydrogen consumption on BSCF particles is 24 times higher than that on SFC particles. Furthermore, Raman spectroscopy and temperature programmed desorption studies of

  8. Abundant Metals Give Precious Hydrogenation Performance

    SciTech Connect

    Bullock, R. Morris

    2013-11-29

    Homogeneous catalysts based on precious (noble) metals have had a profound influence on modern synthetic methods, enabling highly selective synthesis of organic compounds but typically require precious metal catalysts (Ru, Rh, Ir, Pt, and Pd). Increasing efforts have been devoted to the design and discovery of homogeneous catalysts using base metals (e.g., Mn, Fe, Co, Ni, Cu, Mo). Morris et al. report Fe catalysts for asymmetric hydrogenation of C=O bonds. Cobalt catalysts for asymmetric hydrogenation of C=C bonds are described by Chirik et al., and Beller et al. report new nanoscale iron catalysts for synthesis of functionalized anilines through hydrogenation of nitroarenes. The author’s work in this area is supported as part of the Center for Molecular Electrocatalysis, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences. Pacific Northwest National Laboratory is operated by Battelle for the U.S. Department of Energy.

  9. The effect of a tin barrier layer on the permeability of hydrogen through mild steel and ferritic stainless steel

    SciTech Connect

    Bowker, J.; Piercy, G.R.

    1984-11-01

    Experiments were performed to measure the effectiveness of a commercially electroplated tin layer as a barrier to hydrogen, and to see how this altered when the tin layer was converted to FeSn. The authors measured the permeability of hydrogen through AISI 410 ferritic stainless steel and determined the effectiveness of tin as a surface barrier on it. The measured values for the permeability of hydrogen in iron and ferritic stainless steel are shown.

  10. Noble Metals Would Prevent Hydrogen Embrittlement

    NASA Technical Reports Server (NTRS)

    Paton, N. E.; Frandsen, J. D.

    1987-01-01

    According to proposal, addition of small amounts of noble metals makes iron- and nickel-based alloys less susceptible to embrittlement by hydrogen. Metallurgists demonstrated adding 0.6 to 1.0 percent by weight of Pd or Pt eliminates stress/corrosion cracking in type 4130 steel. Proposal based on assumption that similar levels (0.5 to 1.0 weight percent) of same elements effective against hydrogen embrittlement.

  11. Nanostructures from hydrogen implantation of metals.

    SciTech Connect

    McWatters, Bruce Ray; Causey, Rion A.; DePuit, Ryan J.; Yang, Nancy Y. C.; Ong, Markus D.

    2009-09-01

    This study investigates a pathway to nanoporous structures created by hydrogen implantation in aluminum. Previous experiments for fusion applications have indicated that hydrogen and helium ion implantations are capable of producing bicontinuous nanoporous structures in a variety of metals. This study focuses specifically on hydrogen and helium implantations of aluminum, including complementary experimental results and computational modeling of this system. Experimental results show the evolution of the surface morphology as the hydrogen ion fluence increases from 10{sup 17} cm{sup -2} to 10{sup 18} cm{sup -2}. Implantations of helium at a fluence of 10{sup 18} cm{sup -2} produce porosity on the order of 10 nm. Computational modeling demonstrates the formation of alanes, their desorption, and the resulting etching of aluminum surfaces that likely drives the nanostructures that form in the presence of hydrogen.

  12. Microporous Metal Organic Materials for Hydrogen Storage

    SciTech Connect

    S. G. Sankar; Jing Li; Karl Johnson

    2008-11-30

    We have examined a number of Metal Organic Framework Materials for their potential in hydrogen storage applications. Results obtained in this study may, in general, be summarized as follows: (1) We have identified a new family of porous metal organic framework materials with the compositions M (bdc) (ted){sub 0.5}, {l_brace}M = Zn or Co, bdc = biphenyl dicarboxylate and ted = triethylene diamine{r_brace} that adsorb large quantities of hydrogen ({approx}4.6 wt%) at 77 K and a hydrogen pressure of 50 atm. The modeling performed on these materials agree reasonably well with the experimental results. (2) In some instances, such as in Y{sub 2}(sdba){sub 3}, even though the modeling predicted the possibility of hydrogen adsorption (although only small quantities, {approx}1.2 wt%, 77 K, 50 atm. hydrogen), our experiments indicate that the sample does not adsorb any hydrogen. This may be related to the fact that the pores are extremely small or may be attributed to the lack of proper activation process. (3) Some samples such as Zn (tbip) (tbip = 5-tert butyl isophthalate) exhibit hysteresis characteristics in hydrogen sorption between adsorption and desorption runs. Modeling studies on this sample show good agreement with the desorption behavior. It is necessary to conduct additional studies to fully understand this behavior. (4) Molecular simulations have demonstrated the need to enhance the solid-fluid potential of interaction in order to achieve much higher adsorption amounts at room temperature. We speculate that this may be accomplished through incorporation of light transition metals, such as titanium and scandium, into the metal organic framework materials.

  13. The hydrogen permeability of Pd4S

    SciTech Connect

    O’Brien, Casey P.; Gellman, Andrew J.; Morreale, Bryan D.; Miller, James B.

    2011-04-01

    Hydrogen permeates rapidly through pure Pd membranes, but H2S, a common minor component in hydrogencontaining streams, produces a Pd4S film on the Pd surface that severely retards hydrogen permeation. Hydrogen still permeates through the bi-layered Pd4S/Pd structure, indicating that the Pd4S surface is active for H2 dissociation; the low hydrogen permeability of the Pd4S film is responsible for the decreased rate of hydrogen transport. In this work, the hydrogen permeability of Pd4S was determined experimentally in the 623-773 K temperature range. Bi-layered Pd4S/Pd foils were produced by exposing pure Pd foils to H2S. H2 fluxes through the bi-layered Pd4S/Pd foils were measured during exposure to both pure H2 and a 1000 ppm H2S in H2 gas mixture. Our results show that H2S slows hydrogen permeation through Pd mainly by producing a Pd4S film on the Pd surface that is roughly an order-of-magnitude less permeable to hydrogen (kPd4S = 10-7.5 exp(-0.22 eV/kBT)molH2/m/s/Pa-1/2) than pure Pd. The presence of H2S in the gas stream results in greater inhibition of hydrogen transport than can be explained by the very low permeability of Pd4S. H2S may block H2 dissociation sites at the Pd4S surface.

  14. Process for forming a nickel foil with controlled and predetermined permeability to hydrogen

    DOEpatents

    Engelhaupt, Darell E.

    1981-09-22

    The present invention provides a novel process for forming a nickel foil having a controlled and predetermined hydrogen permeability. This process includes the steps of passing a nickel plating bath through a suitable cation exchange resin to provide a purified nickel plating bath free of copper and gold cations, immersing a nickel anode and a suitable cathode in the purified nickel plating bath containing a selected concentration of an organic sulfonic acid such as a napthalene-trisulfonic acid, electrodepositing a nickel layer having the thickness of a foil onto the cathode, and separating the nickel layer from the cathode to provide a nickel foil. The anode is a readily-corrodible nickel anode. The present invention also provides a novel nickel foil having a greater hydrogen permeability than palladium at room temperature.

  15. Compressibility of liquid-metallic hydrogen

    NASA Astrophysics Data System (ADS)

    MacDonald, A. H.

    1983-05-01

    An expression for the compressibility κ of liquid-metallic hydrogen, derived within adiabatic and linear screening approximations, is presented. Terms in the expression for κ have been associated with Landau parameters of the two-component Fermi liquid. The compressibility found for the liquid state is much larger than the compressibility which would be expected in the solid state.

  16. Metallic Hydrogen - Potentially a High Energy Rocket Propellant

    NASA Technical Reports Server (NTRS)

    Cole, John; Silvera, Ike

    2007-01-01

    Pure metallic hydrogen is predicted to have a specific impulse (Isp) of 1700 seconds, but the reaction temperature is too high for current engine materials. Diluting metallic hydrogen with liquid hydrogen can reduce the reaction temperature to levels compatible with current material limits and still provide an Isp greater than 900 s. Metallic hydrogen has not yet been produced on earth, but experimental techniques exist that may change this situation. This paper will provide a brief description of metallic hydrogen and the status of experiments that may soon produce detectable quantities of this material in the lab. Also provided are some characteristics for diluted metallic hydrogen engines and launch vehicles.

  17. Metal-Catalysed Transfer Hydrogenation of Ketones.

    PubMed

    Štefane, Bogdan; Požgan, Franc

    2016-04-01

    We highlight recent developments of catalytic transfer hydrogenation of ketones promoted by transition metals, while placing it within its historical context. Since optically active secondary alcohols are important building blocks in fine chemicals synthesis, the focus of this review is devoted to chiral catalyst types which are capable of inducing high stereoselectivities. Ruthenium complexes still represent the largest part of the catalysts, but other metals (e.g. Fe) are rapidly penetrating this field. While homogeneous transfer hydrogenation catalysts in some cases approach enzymatic performance, the interest in heterogeneous catalysts is constantly growing because of their reusability. Despite excellent activity, selectivity and compatibility of metal complexes with a variety of functional groups, no universal catalysts exist. Development of future catalyst systems is directed towards reaching as high as possible activity with low catalyst loadings, using "greener" conditions, and being able to operate under mild conditions and in a highly selective manner for a broad range of substrates. PMID:27573143

  18. Hydrogen Storage in Metal-Organic Frameworks

    SciTech Connect

    Omar M. Yaghi

    2012-04-26

    Conventional storage of large amounts of hydrogen in its molecular form is difficult and expensive because it requires employing either extremely high pressure gas or very low temperature liquid. Because of the importance of hydrogen as a fuel, the DOE has set system targets for hydrogen storage of gravimetric (5.5 wt%) and volumetric (40 g L-1) densities to be achieved by 2015. Given that these are system goals, a practical material will need to have higher capacity when the weight of the tank and associated cooling or regeneration system is considered. The size and weight of these components will vary substantially depending on whether the material operates by a chemisorption or physisorption mechanism. In the latter case, metal-organic frameworks (MOFs) have recently been identified as promising adsorbents for hydrogen storage, although little data is available for their sorption behavior. This grant was focused on the study of MOFs with these specific objectives. (1) To examine the effects of functionalization, catenation, and variation of the metal oxide and organic linkers on the low-pressure hydrogen adsorption properties of MOFs. (2) To develop a strategy for producing MOFs with high surface area and porosity to reduce the dead space and increase the hydrogen storage capacity per unit volume. (3) To functionalize MOFs by post synthetic functionalization with metals to improve the adsorption enthalpy of hydrogen for the room temperature hydrogen storage. This effort demonstrated the importance of open metal sites to improve the adsorption enthalpy by the systematic study, and this is also the origin of the new strategy, which termed isoreticular functionalization and metalation. However, a large pore volume is still a prerequisite feature. Based on our principle to design highly porous MOFs, guest-free MOFs with ultrahigh porosity have been experimentally synthesized. MOF-210, whose BET surface area is 6240 m2 g-1 (the highest among porous solids), takes up

  19. Hydrogen storage in metal-hydrogen systems and their derivatives

    NASA Astrophysics Data System (ADS)

    Eberle, U.; Arnold, G.; von Helmolt, R.

    During the last years, the power densities of automotive fuel cell systems have been raised dramatically. However, a major technology improvement is still needed for the on-board fuel storage system since hydrogen exhibits a rather low volumetric energy density (regardless whether it is stored as a liquid at cryogenic temperatures or as a compressed gas). Furthermore, the cost for current hydrogen containers is far from what gasoline tanks cost. Therefore, alternatives like solid-state absorbers of hydrogen (e.g. metal hydrides or complex hydrides) are investigated for their feasibility by the car industry. These kinds of systems show very high volumetric storage densities on a materials basis. Unfortunately, the host compounds are usually quite heavy and thus possess a low gravimetric storage density. Also, the thermodynamics and kinetics of the absorption/desorption reactions and their impact on the tank design in general (and on the heat management in particular) have to be considered. Within the framework of this paper, the properties of the most promising solid-state storage systems are discussed and compared to those of the liquid and compressed gaseous hydrogen technologies.

  20. PERMEABILITY, SOLUBILITY, AND INTERACTION OF HYDROGEN IN POLYMERS- AN ASSESSMENT OF MATERIALS FOR HYDROGEN TRANSPORT

    SciTech Connect

    Kane, M

    2008-02-05

    Fiber-reinforced polymer (FRP) piping has been identified as a leading candidate for use in a transport system for the Hydrogen Economy. Understanding the permeation and leakage of hydrogen through the candidate materials is vital to effective materials system selection or design and development of safe and efficient materials for this application. A survey of the literature showed that little data on hydrogen permeation are available and no mechanistically-based models to quantitatively predict permeation behavior have been developed. However, several qualitative trends in gaseous permeation have been identified and simple calculations have been performed to identify leakage rates for polymers of varying crystallinity. Additionally, no plausible mechanism was found for the degradation of polymeric materials in the presence of pure hydrogen. The absence of anticipated degradation is due to lack of interactions between hydrogen and FRP and very low solubility coefficients of hydrogen in polymeric materials. Recommendations are made to address research and testing needs to support successful materials development and use of FRP materials for hydrogen transport and distribution.

  1. Powered by DFT: Screening methods that accelerate materials development for hydrogen in metals applications.

    PubMed

    Nicholson, Kelly M; Chandrasekhar, Nita; Sholl, David S

    2014-11-18

    CONSPECTUS: Not only is hydrogen critical for current chemical and refining processes, it is also projected to be an important energy carrier for future green energy systems such as fuel cell vehicles. Scientists have examined light metal hydrides for this purpose, which need to have both good thermodynamic properties and fast charging/discharging kinetics. The properties of hydrogen in metals are also important in the development of membranes for hydrogen purification. In this Account, we highlight our recent work aimed at the large scale screening of metal-based systems with either favorable hydrogen capacities and thermodynamics for hydrogen storage in metal hydrides for use in onboard fuel cell vehicles or promising hydrogen permeabilities relative to pure Pd for hydrogen separation from high temperature mixed gas streams using dense metal membranes. Previously, chemists have found that the metal hydrides need to hit a stability sweet spot: if the compound is too stable, it will not release enough hydrogen under low temperatures; if the compound is too unstable, the reaction may not be reversible under practical conditions. Fortunately, we can use DFT-based methods to assess this stability via prediction of thermodynamic properties, equilibrium reaction pathways, and phase diagrams for candidate metal hydride systems with reasonable accuracy using only proposed crystal structures and compositions as inputs. We have efficiently screened millions of mixtures of pure metals, metal hydrides, and alloys to identify promising reaction schemes via the grand canonical linear programming method. Pure Pd and Pd-based membranes have ideal hydrogen selectivities over other gases but suffer shortcomings such as sensitivity to sulfur poisoning and hydrogen embrittlement. Using a combination of detailed DFT, Monte Carlo techniques, and simplified models, we are able to accurately predict hydrogen permeabilities of metal membranes and screen large libraries of candidate alloys

  2. Method for controlling density and permeability of sintered powdered metals

    NASA Technical Reports Server (NTRS)

    Todd, H. H.

    1968-01-01

    Improved, relatively low-cost method has been developed to produce porous metals with predetermined pore size, pore spacing, and density, utilizing powder-metal processes. The method uses angular not spherical tungsten powder.

  3. Supported Molten Metal Membranes for Hydrogen Separation

    SciTech Connect

    Datta, Ravindra; Ma, Yi Hua; Yen, Pei-Shan; Deveau, Nicholas; Fishtik, Ilie; Mardilovich, Ivan

    2013-09-30

    We describe here our results on the feasibility of a novel dense metal membrane for hydrogen separation: Supported Molten Metal Membrane, or SMMM.1 The goal in this work was to develop these new membranes based on supporting thin films of low-melting, non- precious group metals, e.g., tin (Sn), indium (In), gallium (Ga), or their alloys, to provide a flux and selectivity of hydrogen that rivals the conventional but substantially more expensive palladium (Pd) or Pd alloy membranes, which are susceptible to poisoning by the many species in the coal-derived syngas, and further possess inadequate stability and limited operating temperature range. The novelty of the technology presented numerous challenges during the course of this project, however, mainly in the selection of appropriate supports, and in the fabrication of a stable membrane. While the wetting instability of the SMMM remains an issue, we did develop an adequate understanding of the interaction between molten metal films with porous supports that we were able to find appropriate supports. Thus, our preliminary results indicate that the Ga/SiC SMMM at 550 ºC has a permeance that is an order of magnitude higher than that of Pd, and exceeds the 2015 DOE target. To make practical SMM membranes, however, further improving the stability of the molten metal membrane is the next goal. For this, it is important to better understand the change in molten metal surface tension and contact angle as a function of temperature and gas-phase composition. A thermodynamic theory was, thus, developed, that is not only able to explain this change in the liquid-gas surface tension, but also the change in the solid-liquid surface tension as well as the contact angle. This fundamental understanding has allowed us to determine design characteristics to maintain stability in the face of changing gas composition. These designs are being developed. For further progress, it is also important to understand the nature of solution and

  4. Hydrogen Permeability of Palladium Membrane for Steam-Reforming of Bio-Ethanol Using the Membrane Reactor

    NASA Astrophysics Data System (ADS)

    Kinouchi, Kouji; Katoh, Masahiro; Horikawa, Toshihide; Yoshikawa, Takushi; Wada, Mamoru

    A Palladium membrane was prepared by electro-less plating method on porous stainless steel. The catalytic hydrogen production by steam-reforming of biomass-derived ethanol (bio-ethanol) using a Pd membrane was analyzed by comparing it with those for the reaction using reagent ethanol (the reference sample). And the hydrogen permeability of the palladium membrane was investigated using the same palladium membrane (H2/He selectivity = 249, at ΔP = 0.10 MPa, 873 K). As a result, for bio-ethanol, deposited carbon had a negative influence on the hydrogen-permeability of the palladium membrane and hydrogen purity. The sulfur content in the bio-ethanol may have promoted carbon deposition. By using a palladium membrane, it was confirmed that H2 yield (%) was increased. It can be attributed that methane was converted from ethanol and produced more hydrogen by steam reforming, due to the in situ removal of hydrogen from the reaction location.

  5. RF Breakdown of Metallic Surfaces in Hydrogen

    SciTech Connect

    BastaniNejad, M.; Elmustafa, A.A.; Yonehara, K.; Chung, M.; Jansson, A.; Hu, M.; Moretti, A.; Popovic, M.; Alsharo'a, M.; Neubauer, M.; Sah, R.; /Muons Inc., Batavia

    2009-05-01

    In earlier reports, microscopic images of the surfaces of metallic electrodes used in high-pressure gas-filled 805 MHz RF cavity experiments were used to investigate the mechanism of RF breakdown of tungsten, molybdenum, and beryllium electrode surfaces. Plots of remnants were consistent with the breakdown events being due to field emission, due to the quantum mechanical tunnelling of electrons through a barrier as described by Fowler and Nordheim. In the work described here, these studies have been extended to include tin, aluminium, and copper. Contamination of the surfaces, discovered after the experiments concluded, have cast some doubt on the proper qualities to assign to the metallic surfaces. However, two significant results are noted. First, the maximum stable RF gradient of contaminated copper electrodes is higher than for a clean surface. Second, the addition of as little as 0.01% of SF6 to the hydrogen gas increased the maximum stable gradient, which implies that models of RF breakdown in hydrogen gas will be important to the study of metallic breakdown.

  6. Ion beam studies of hydrogen in metals

    SciTech Connect

    Myers, S.M.; Wampler, W.R.; Besenbacher, F.; Robinson, S.L.; Moody, N.R.

    1984-01-01

    Methods based on ion implantation and nuclear reaction analysis were used to investigate the behavior of hydrogen isotopes in metals. The binding enthalpy of deuterium (D) at irradiation effects, He bubbles, D/sub 2/ bubbles, and metal-oxide interfaces was measured for Al, Fe, Ni, Cu, Pd, austenitic stainless steel, Inconel, and amorphous Fe/sub 40/Ni/sub 40/P/sub 14/B/sub 6/. The binding enthalpies determined for the pure metals are in excellent agreement with mechanistic calculations based on effective-medium theory and other information. Surface-limited release of D from Fe, stainless steel, and Inconel was measured as a function of temperature and the state of surface oxidation. The release rate was accurately proportional to the square of the D concentration in solution, permitting the results to be expressed in terms of a surface recombination coefficient. This quantity was up to four orders of magnitude greater for an ion-sputtered surface than for a surface with electropolish oxide. The diffusion coefficient and solid solubility of tritium in stainless steel were measured for the first time at the ice point, thereby extending downward by three orders of magnitude the diffusivities available from conventional permeation experiments. Deuterium concentration profiles resulting from electrochemical charging of Incoloy 903 were measured as a function of charging current, thereby providing a direct, systematic calibration of such charging in an austenitic material where conventional permeation measurements are precluded by the small hydrogen diffusion rate.

  7. Metal hydrides reactors with improved dynamic characteristics for a fast cycling hydrogen compressor

    NASA Astrophysics Data System (ADS)

    Popeneciu, G.; Coldea, I.; Lupu, D.; Misan, I.; Ardelean, O.

    2009-08-01

    This paper presents an investigation of coupled heat and mass transfer process in metal hydrides hydrogen storage reactors. Hydrogen storage and compression performance of our designed and developed reactors are studied by varying the operating parameters and analyzing the effects of metal hydride bed parameters. The metal alloy selected to characterize the cycling behaviour of reactors is LaNi5, material synthesized and characterized by us in the range 20-80°C. Four types of metal hydride reactors were tested with the aim to provide a fast hydrogen absorption-desorption cycle, able to be thermally cycled at rapid rates. Some new technical solutions have been studied to make a step forward in reducing the duration of the reactors cycle, which combines the effective increase of the thermal conductivity and good permeability to hydrogen gas. Dynamic characteristic of developed fast metal hydride reactors is improved using our novel mixture metal hydride-CA conductive additive due to the increased effective thermal conductivity of the alloy bed. The advanced hydride bed design with high heat transfer capabilities can be thermally cycled at a rapid rate, under 120 seconds, in order to process high hydrogen flow rates.

  8. Catalytic arene hydrogenation using early transition metal hydride compounds

    SciTech Connect

    Rothwell, I.P.

    1993-03-15

    Progress was achieved in four areas: development of surface supported Group 5 metal organometallic compounds for catalytic arene hydrogenation, isolation and reactivity of possible intermediates in catalytic arene hydrogenation, synthesis and characterization of new d[sup 0]-metal hydride compounds, and stoichiometric reactivity of d[sup 0] metal hydrido, aryloxide compounds. (DLC)

  9. The permeability of endplate channels to monovalent and divalent metal cations

    PubMed Central

    1980-01-01

    The relative permeability of endplate channels to monovalent and divalent metal ions was determined from reversal potentials. Thallium is the most permeant ion with a permeability ratio relative to Na+ of 2.5. The selectivity among alkali metals is weak with a sequence, Cs+ greater than Rb+ greater than K+ greater than Na+ greater than Li+, and permeability ratios of 1.4, 1.3, 1.1, 1.0, and 0.9. The selectivity among divalent ions is also weak, with a sequence for alkaline earths of Mg++ greater than Ca++ greater than Ba++ greater than Sr++. The transition metal ions Mn++, Co++, Ni++, Zn++, and Cd++ are also permeant. Permeability ratios for divalent ions decreased as the concentration of divalent ion was increased in a manner consistent with the negative surface potential theory of Lewis (1979 J. Physiol. (Lond.). 286: 417--445). With 20 mM XCl2 and 85.5 mM glucosamine.HCl in the external solution, the apparent permeability ratios for the alkaline earth cations (X++) are in the range 0.18--0.25. Alkali metal ions see the endplate channel as a water-filled, neutral pore without high-field-strength sites inside. Their permeability sequence is the same as their aqueous mobility sequence. Divalent ions, however, have a permeability sequence almost opposite from their mobility sequence and must experience some interaction with groups in the channel. In addition, the concentrations of monovalent and divalent ions are increased near the channel mouth by a weak negative surface potential. PMID:6247423

  10. Metallic hydrogen: The most powerful rocket fuel yet to exist

    NASA Astrophysics Data System (ADS)

    Silvera, Isaac F.; Cole, John W.

    2010-03-01

    Wigner and Huntington first predicted that pressures of order 25 GPa were required for the transition of solid molecular hydrogen to the atomic metallic phase. Later it was predicted that metallic hydrogen might be a metastable material so that it remains metallic when pressure is released. Experimental pressures achieved on hydrogen have been more than an order of magnitude higher than the predicted transition pressure and yet it remains an insulator. We discuss the applications of metastable metallic hydrogen to rocketry. Metastable metallic hydrogen would be a very light-weight, low volume, powerful rocket propellant. One of the characteristics of a propellant is its specific impulse, Isp. Liquid (molecular) hydrogen-oxygen used in modern rockets has an Isp of ~460s; metallic hydrogen has a theoretical Isp of 1700s! Detailed analysis shows that such a fuel would allow single-stage rockets to enter into orbit or carry economical payloads to the moon. If pure metallic hydrogen is used as a propellant, the reaction chamber temperature is calculated to be greater than 6000 K, too high for currently known rocket engine materials. By diluting metallic hydrogen with liquid hydrogen or water, the reaction temperature can be reduced, yet there is still a significant performance improvement for the diluted mixture.

  11. How absorbed hydrogen affects the catalytic activity of transition metals.

    PubMed

    Aleksandrov, Hristiyan A; Kozlov, Sergey M; Schauermann, Swetlana; Vayssilov, Georgi N; Neyman, Konstantin M

    2014-12-01

    Heterogeneous catalysis is commonly governed by surface active sites. Yet, areas just below the surface can also influence catalytic activity, for instance, when fragmentation products of catalytic feeds penetrate into catalysts. In particular, H absorbed below the surface is required for certain hydrogenation reactions on metals. Herein, we show that a sufficient concentration of subsurface hydrogen, H(sub) , may either significantly increase or decrease the bond energy and the reactivity of the adsorbed hydrogen, H(ad) , depending on the metal. We predict a representative reaction, ethyl hydrogenation, to speed up on Pd and Pt, but to slow down on Ni and Rh in the presence of H(sub) , especially on metal nanoparticles. The identified effects of subsurface H on surface reactivity are indispensable for an atomistic understanding of hydrogenation processes on transition metals and interactions of hydrogen with metals in general.

  12. The Permeability of the Sodium Channel to Metal Cations in Myelinated Nerve

    PubMed Central

    Hille, Bertil

    1972-01-01

    The relative permeability of sodium channels to eight metal cations is studied in myelinated nerve fibers. Ionic currents under voltage-clamp conditions are measured in Na-free solutions containing the test ion. Measured reversal potentials and the Goldman equation are used to calculate the permeability sequence: Na+ ≈ Li+ > Tl+ > K+. The ratio PK/PNa is 1/12. The permeabilities to Rb+, Cs+, Ca++, and Mg++ are too small to measure. The permeability ratios agree with observations on the squid giant axon and show that the reversal potential ENa differs significantly from the Nernst potential for Na+ in normal axons. Opening and closing rates for sodium channels are relatively insensitive to the ionic composition of the bathing medium, implying that gating is a structural property of the channel rather than a result of the movement or accumulation of particular ions around the channel. A previously proposed pore model of the channel accommodates the permeant metal cations in a partly hydrated form. The observed sequence of permeabilities follows the order expected for binding to a high field strength anion in Eisenman's theory of ion exchange equilibria. PMID:5025743

  13. Technical and economic aspects of hydrogen storage in metal hydrides

    NASA Technical Reports Server (NTRS)

    Schmitt, R.

    1981-01-01

    The recovery of hydrogen from such metal hydrides as LiH, MgH2, TiH2, CaH2 and FeTiH compounds is studied, with the aim of evaluating the viability of the technique for the storage of hydrogen fuel. The pressure-temperature dependence of the reactions, enthalpies of formation, the kinetics of the hydrogen absorption and desorption, and the mechanical and chemical stability of the metal hydrides are taken into account in the evaluation. Economic aspects are considered. Development of portable metal hydride hydrogen storage reservoirs is also mentioned.

  14. Enhanced zero-valent metal permeable wall treatment of contaminated groundwater

    SciTech Connect

    Reinhart, D.R.; Clausen, C.A.; Geiger, C.

    1997-12-31

    On-going research at the University of Central Florida, supported by NASA, is investigating the use of sonicated zero-valent metal permeable treatment walls to remediate chlorinated solvent contaminated groundwater. Use of ultrasound within the treatment wall is proposed to enhance and/or restore the activity of the zero-valent metal. Batch studies designed to evaluate the destruction of chlorinated hydrocarbons using enhanced zero-valent metal reduction found a nearly three-fold increase in reaction rates after ultrasound treatment. Column studies substantiated these results. It is hypothesized that ultrasound serves to remove corrosion products from the iron surface and will prolong the reactive life and efficiency of the permeable treatment wall, thus decreasing long-term costs of wall construction and maintenance.

  15. Heavy metal uptake and leaching from polluted soil using permeable barrier in DTPA-assisted phytoextraction.

    PubMed

    Zhao, Shulan; Shen, Zhiping; Duo, Lian

    2015-04-01

    Application of sewage sludge (SS) in agriculture is an alternative technique of disposing this waste. But unreasonable application of SS leads to excessive accumulation of heavy metals in soils. A column experiment was conducted to test the availability of heavy metals to Lolium perenne grown in SS-treated soils following diethylene triamine penta acetic acid (DTPA) application at rates of 0, 10 and 20 mmol kg(-1) soil. In order to prevent metal leaching in DTPA-assisted phytoextraction process, a horizontal permeable barrier was placed below the treated soil, and its effectiveness was also assessed. Results showed that DTPA addition significantly increased metal uptake by L. perenne shoots and metal leaching. Permeable barriers increased metal concentrations in plant shoots and effectively decreased metal leaching from the treated soil. Heavy metals in SS-treated soils could be gradually removed by harvesting L. perenne many times in 1 year and adding low dosage of DTPA days before each harvest.

  16. Catalytic hydrogenation and gas permeation properties of metal-containing poly(phenylene oxide) and polysulfone

    SciTech Connect

    Hanrong Gao; Yun Xu; Shijian Liao; Ren Liu; Daorong Yu . Dalian Inst. of Chemical Physics)

    1993-11-10

    Metal-containing polymers, PPL-DPP-Pd, PPO-CPA-Pd, PSF-DPP-Pd, PSF-CPA-Pd (PDD = diphenylphosphinyl, CPA = o-carboxy phenyl amino), PPO-M (M = Pd,Cu,Co,Ni), and PSF-Pd, were prepared by incorporating metal chloride with either modified or unmodified poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) and polysulfone (PSF). The Pd-containing polymers exhibit catalytic activity in the hydrogenation of cyclopentadiene under mild conditions both in alcohol solution and in the gas phase. The selectivity in the hydrogenation of diene to monoene in the gas phase can be controlled by adjusting the hydrogen partial pressure. The metal-containing polymers, PPL-M and PSF-Pd, can be cast easily into the membranes. The H[sub 2]/N[sub 2] permselectivity for PPO-M is higher than that for unmodified PPO, whereas the permeability of H[sub 2] changes slightly. The H[sub 2] permeability and H[sub 2]/N[sub 2] permselectivity for the PPO-Pd membrane are up to 67.5 barrers and 135, respectively.

  17. Noble metal-free hydrogen evolution catalysts for water splitting.

    PubMed

    Zou, Xiaoxin; Zhang, Yu

    2015-08-01

    Sustainable hydrogen production is an essential prerequisite of a future hydrogen economy. Water electrolysis driven by renewable resource-derived electricity and direct solar-to-hydrogen conversion based on photochemical and photoelectrochemical water splitting are promising pathways for sustainable hydrogen production. All these techniques require, among many things, highly active noble metal-free hydrogen evolution catalysts to make the water splitting process more energy-efficient and economical. In this review, we highlight the recent research efforts toward the synthesis of noble metal-free electrocatalysts, especially at the nanoscale, and their catalytic properties for the hydrogen evolution reaction (HER). We review several important kinds of heterogeneous non-precious metal electrocatalysts, including metal sulfides, metal selenides, metal carbides, metal nitrides, metal phosphides, and heteroatom-doped nanocarbons. In the discussion, emphasis is given to the synthetic methods of these HER electrocatalysts, the strategies of performance improvement, and the structure/composition-catalytic activity relationship. We also summarize some important examples showing that non-Pt HER electrocatalysts could serve as efficient cocatalysts for promoting direct solar-to-hydrogen conversion in both photochemical and photoelectrochemical water splitting systems, when combined with suitable semiconductor photocatalysts.

  18. Hydrogenation of coal liquid utilizing a metal carbonyl catalyst

    DOEpatents

    Feder, Harold M.; Rathke, Jerome W.

    1979-01-01

    Coal liquid having a dissolved transition metal, catalyst as a carbonyl complex such as Co.sub.2 (CO.sub.8) is hydrogenated with hydrogen gas or a hydrogen donor. A dissociating solvent contacts the coal liquid during hydrogenation to form an immiscible liquid mixture at a high carbon monoxide pressure. The dissociating solvent, e.g. ethylene glycol, is of moderate coordinating ability, while sufficiently polar to solvate the transition metal as a complex cation along with a transition metal, carbonyl anion in solution at a decreased carbon monoxide pressure. The carbon monoxide pressure is reduced and the liquids are separated to recover the hydrogenated coal liquid as product. The dissociating solvent with the catalyst in ionized form is recycled to the hydrogenation step at the elevated carbon monoxide pressure for reforming the catalyst complex within fresh coal liquid.

  19. Mechanical properties and permeability of hydrogen isotopes through CrNi35WTiAl alloy, containing radiogenic helium

    SciTech Connect

    Maksimkin, I.P.; Yukhimchuk, A.A.; Boitsov, I.Y.; Malkov, I.L.; Musyaev, R.K.; Baurin, A.Y.; Shevnin, E.V.; Vertey, A.V.

    2015-03-15

    The long-term contact of structural materials (SM) with tritium-containing media makes their properties in terms of kinetic permeability of hydrogen isotopes change. This change is the consequence of the defect formation in SM due to the result of {sup 3}He build-up generated by the radioactive decay of tritium dissolved in SM. This paper presents the experimental results concerning the permeability of hydrogen isotopes through CrNi35WTiAl alloy containing {sup 3}He and the impact of the presence of {sup 3}He and H on its mechanical properties. Tensile tests of cylindrical samples containing various concentrations of {sup 3}He (90, 230 and 560 appm) have been performed in inert and hydrogen atmospheres. The build-up of {sup 3}He has been made using the 'helium trick' technique. The maximal decrease in the plastic characteristics of the CrNi35WTiAl alloy occurs in samples with the highest {sup 3}He (560 appm) content at 873 K. The permeability of deuterium through the CrNi35WTiAl alloy in the initial state and that with 560 appm of {sup 3}He content was explored. The presence of this {sup 3}He concentration has shown an increase in deuterium permeability, evidently due to structural changes in the material under the impact of radiogenic helium.

  20. Effect of microsolvation on hydrogen trapping potential of metal ions

    NASA Astrophysics Data System (ADS)

    Das, Ranjita; Bandaru, Sateesh; D'mello, Viola Caroline; Chattaraj, Pratim Kumar

    2013-03-01

    A thorough analysis is carried out to understand how the microsolvation affects the hydrogen adsorbing capacity of metal ions in the presence as well as absence of the counter ions. Calculations are done at different levels of theory by using different functionals and basis sets and also by using the BSSE correction. The Be2+ ion doped systems exhibit stronger interaction with the hydrogen molecule than the other metal doped systems. The extent of interaction is less affected by the method of computation. The reaction free energy values imply that adsorption on alkaline earth metal doped systems is spontaneous at room temperature. Interaction energies are favorable for hydrogen adsorption on the systems containing alkaline earth metal ions and the gravimetric density of adsorbed hydrogen molecule is more in those containing the alkali metal ions.

  1. High-Pressure Multi-Mbar Conductivity Experiments on Hydrogen: The Quest for Solid Metallic Hydrogen

    SciTech Connect

    Jackson, D

    2007-02-07

    Ultra-dense hydrogen has long been the subject of intense experimental and theoretical research due to the fascinating physics which arises from this supposedly simple system. The properties of ultra-dense hydrogen also have important implications for planetary physics, since the interiors of the giant planets Jupiter and Saturn are believed to consist of cores of dense, metallic hydrogen. Finally, ultra-dense hydrogen is of direct programmatic interest, and multiple-shock compression experiments on hydrogen to the metallic state have stimulated the accelerated development of new hydrogen equation-of-state (EOS) models used for ICF and other applications. The focus of our research has often been described as the ''Holy Grail'' of high-pressure physics research: The metallization of solid hydrogen. Metallic hydrogen has long been considered to be the prototypical system for the study of insulator-to-metal (I-M) transitions. Although metallic hydrogen (Z=1) may superficially appear to be a very simple material, it is in fact an extremely challenging system for theoretical analysis due to the presence of large zero-point atomic motions and the complete absence of any core electrons. Thus, solid metallic hydrogen promises to be a fascinating material. Among its predicted properties is the possibility of being a high temperature superconductor with a critical temperature T{sub c} of the order of {approx} 100K [1]. The successful metallization of solid hydrogen would be a groundbreaking scientific discovery and open up new frontiers in science and possibly technology as well.

  2. Metal Dichalcogenides Monolayers: Novel Catalysts for Electrochemical Hydrogen Production

    PubMed Central

    Pan, Hui

    2014-01-01

    Catalyst-driven electrolysis of water is considered as a “cleanest” way for hydrogen production. Finding cheap and abundant catalysts is critical to the large-scale implementation of the technology. Two-dimensional metal dichalcogenides nanostructures have attracted increasing attention because of their catalytic performances in water electrolysis. In this work, we systematically investigate the hydrogen evolution reduction of metal dichalcogenides monolayers based on density-functional-theory calculations. We find that metal disulfide monolayers show better catalytic performance on hydrogen production than other metal dichalcogenides. We show that their hydrogen evolution reduction strongly depends on the hydrogen coverage and the catalytic performance reduces with the increment of coverage because of hydrogenation-induced lower conductivity. We further show that the catalytic performance of vanadium disulfide monolayer is comparable to that of Pt at lower hydrogen coverage and the performance at higher coverage can be improved by hybridizing with conducting nanomaterials to enhance conductivity. These metal disulfide monolayers with lower overpotentials may apply to water electrolysis for hydrogen production. PMID:24967679

  3. Novel Composite Hydrogen-Permeable Membranes for Non-Thermal Plasma Reactors for the Decomposition of Hydrogen Sulfide

    SciTech Connect

    Morris D. Argyle; John F. Ackerman; Suresh Muknahallipatna; Jerry C. Hamann; Stanislaw Legowski; Guibling Zhao; Ji-Jun Zhang; Sanil John

    2005-10-01

    The goal of this experimental project is to design and fabricate a reactor and membrane test cell to dissociate hydrogen sulfide (H{sub 2}S) in a non-thermal plasma and recover hydrogen (H{sub 2}) through a superpermeable multi-layer membrane. Superpermeability of hydrogen atoms (H) has been reported by some researchers using membranes made of Group V transition metals (niobium, tantalum, vanadium, and their alloys), although it has yet to be confirmed in this study. A pulsed corona discharge (PCD) reactor has been fabricated and used to dissociate H{sub 2}S into hydrogen and sulfur. A nonthermal plasma cannot be produced in pure H{sub 2}S with our reactor geometry, even at discharge voltages of up to 30 kV, because of the high dielectric strength of pure H{sub 2}S ({approx}2.9 times higher than air). Therefore, H{sub 2}S was diluted in another gas with lower breakdown voltage (or dielectric strength). Breakdown voltages of H{sub 2}S in four balance gases (Ar, He, N{sub 2} and H{sub 2}) have been measured at different H{sub 2}S concentrations and pressures. Breakdown voltages are proportional to the partial pressure of H{sub 2}S and the balance gas. H{sub 2}S conversion and the reaction energy efficiency depend on the balance gas and H{sub 2}S inlet concentrations. With increasing H{sub 2}S concentrations, H{sub 2}S conversion initially increases, reaches a maximum, and then decreases. H{sub 2}S conversion in atomic balance gases, such as Ar and He, is more efficient than that in diatomic balance gases, such as N{sub 2} and H{sub 2}. These observations can be explained by the proposed reaction mechanism of H{sub 2}S dissociation in different balance gases. The results show that nonthermal plasmas are effective for dissociating H{sub 2}S into hydrogen and sulfur.

  4. Development and application of techniques for the microstructural characterization of hydrogen permeability in zirconium oxides

    NASA Astrophysics Data System (ADS)

    Glavicic, Michael G.

    Equipment and techniques have been developed for the microstructural characterization of Zirconium Oxide films grown on Zr-2.5%Nb pressure tubes. A thin film texture apparatus was constructed and used to measure the texture and stress present in thin zirconium oxide films. The general techniques developed employ a grazing incidence geometry which allows the texture and stress present in thin films (<1mum) of any type to be examined. In addition, a technique for the quantitative phase analysis of textured ZrO2 films grown on zirconium alloys using pole figure data has also been developed. Moreover, equipment was constructed to determine the relative porosity of oxide films grown on a metal substrate using an electrochemical method that measures the effective non-porous oxide thickness. The described equipment and techniques were then used to characterize a test matrix of specimens whose relative hydrogen pick-up was measured by Differential Scanning Calorimetry. The application of beat treatments to the substrates prior to oxide growth was found to have a pronounced effect upon the sharpness of the oxide texture. A correlation between the degree of sharpness of the oxide texture and hydrogen pick-up and corrosion rate of the substrate was also determined. In addition, based upon the new techniques developed it was determined that the tetragonal phase of the oxide is stress stabilized in a region close to the metal/oxide interface.

  5. Disposal pathway for tritiated reactive metals and tritiated hydrogen gas

    SciTech Connect

    Antoniazzi, A. B.; Morton, C. S.

    2008-07-15

    Kinectrics and its predecessor company Ontario Hydro Research Div. (a division of Ontario Hydro) had a fully operational tritium laboratory on site since the early 1980's. During those years numerous projects and experiments were undertaken using hydrogen and tritium for the most part. Metals with an affinity for hydrogen are commonly employed as scavengers of hydrogenic gases from process streams or as hydrogen storage mediums. The two most common of these metals used were depleted uranium and a zirconium-iron alloy (SAES St198). The break-up of Ontario Hydro through deregulation activities resulted in the building of a new, smaller, tritium laboratory and the decommissioning of the original tritium laboratory. Decommissioning activities resulted in the need to safely dispose of these reactive metals. Disposal of these metals is not straight forward. For safe, long term, disposal it has been decided to oxidize the metals in a controlled fashion. The oxidized beds, containing the metals, will be sent to a radioactive waste site for long term storage. Options for disposal of tritiated hydrogen gas are presented and discussed. This paper provides a disposal pathway for tritiated reactive metals and hydrogen thereby closing the loop in tritium handling. (authors)

  6. Hydrogen evolution by a metal-free electrocatalyst

    NASA Astrophysics Data System (ADS)

    Zheng, Yao; Jiao, Yan; Zhu, Yihan; Li, Lu Hua; Han, Yu; Chen, Ying; Du, Aijun; Jaroniec, Mietek; Qiao, Shi Zhang

    2014-04-01

    Electrocatalytic reduction of water to molecular hydrogen via the hydrogen evolution reaction may provide a sustainable energy supply for the future, but its commercial application is hampered by the use of precious platinum catalysts. All alternatives to platinum thus far are based on nonprecious metals, and, to our knowledge, there is no report about a catalyst for electrocatalytic hydrogen evolution beyond metals. Here we couple graphitic-carbon nitride with nitrogen-doped graphene to produce a metal-free hybrid catalyst, which shows an unexpected hydrogen evolution reaction activity with comparable overpotential and Tafel slope to some of well-developed metallic catalysts. Experimental observations in combination with density functional theory calculations reveal that its unusual electrocatalytic properties originate from an intrinsic chemical and electronic coupling that synergistically promotes the proton adsorption and reduction kinetics.

  7. Gas chromatographic separation of hydrogen isotopes using metal hydrides

    SciTech Connect

    Aldridge, F.T.

    1984-05-09

    A study was made of the properties of metal hydrides which may be suitable for use in chromatographic separation of hydrogen isotopes. Sixty-five alloys were measured, with the best having a hydrogen-deuterium separation factor of 1.35 at 60/sup 0/C. Chromatographic columns using these alloys produced deuterium enrichments of up to 3.6 in a single pass, using natural abundance hydrogen as starting material. 25 references, 16 figures, 4 tables.

  8. NOVEL COMPOSITE HYDROGEN-PERMEABLE MEMBRANES FOR NON-THERMAL PLASMA REACTORS FOR THE DECOMPOSITION OF HYDROGEN SULFIDE

    SciTech Connect

    Morris D. Argyle; John F. Ackerman; Suresh Muknahallipatna; Jerry C. Hamann; Stanislaw Legowski; Ji-Jun Zhang; Guibing Zhao; Robyn J. Alcanzare; Linna Wang; Ovid A. Plumb

    2004-07-01

    The goal of this experimental project is to design and fabricate a reactor and membrane test cell to dissociate hydrogen sulfide (H{sub 2}S) in a non-thermal plasma and recover hydrogen (H{sub 2}) through a superpermeable multi-layer membrane. Superpermeability of hydrogen atoms (H) has been reported by some researchers using membranes made of Group V transition metals (niobium, tantalum, vanadium, and their alloys), although it has yet to be confirmed in this study. Experiments involving methane conversion reactions were conducted with a preliminary pulsed corona discharge reactor design in order to test and improve the reactor and membrane designs using a non-toxic reactant. This report details the direct methane conversion experiments to produce hydrogen, acetylene, and higher hydrocarbons utilizing a co-axial cylinder (CAC) corona discharge reactor, pulsed with a thyratron switch. The reactor was designed to accommodate relatively high flow rates (655 x 10{sup -6} m{sup 3}/s) representing a pilot scale easily converted to commercial scale. Parameters expected to influence methane conversion including pulse frequency, charge voltage, capacitance, residence time, and electrode material were investigated. Conversion, selectivity and energy consumption were measured or estimated. C{sub 2} and C{sub 3} hydrocarbon products were analyzed with a residual gas analyzer (RGA). In order to obtain quantitative results, the complex sample spectra were de-convoluted via a linear least squares method. Methane conversion as high as 51% was achieved. The products are typically 50%-60% acetylene, 20% propane, 10% ethane and ethylene, and 5% propylene. First Law thermodynamic energy efficiencies for the system (electrical and reactor) were estimated to range from 38% to 6%, with the highest efficiencies occurring at short residence time and low power input (low specific energy) where conversion is the lowest (less than 5%). The highest methane conversion of 51% occurred at a

  9. Hydrogen adsorption in metal-decorated silicon carbide nanotubes

    NASA Astrophysics Data System (ADS)

    Singh, Ram Sevak; Solanki, Ankit

    2016-09-01

    Hydrogen storage for fuel cell is an active area of research and appropriate materials with excellent hydrogen adsorption properties are highly demanded. Nanotubes, having high surface to volume ratio, are promising storage materials for hydrogen. Recently, silicon carbide nanotubes have been predicted as potential materials for future hydrogen storage application, and studies in this area are ongoing. Here, we report a systematic study on hydrogen adsorption properties in metal (Pt, Ni and Al) decorated silicon carbide nanotubes (SiCNTs) using first principles calculations based on density functional theory. The hydrogen adsorption properties are investigated by calculations of adsorption energy, electronic band structure, density of states (DOS) and Mulliken charge population analysis. Our findings show that hydrogen adsorptions on Pt, Ni and Al-decorated SiCNTs undergo spontaneous exothermic reactions with significant modulation of electronic structure of SiCNTs in all cases. Importantly, according to the Mulliken charge population analysis, dipole-dipole interaction causes chemisorptions of hydrogen in Pt, Ni and Al decorated SiCNTs with formation of chemical bonds. The study is a platform for the development of metal decorated SiCNTs for hydrogen adsorption or hydrogen storage application.

  10. Interactions of Hydrogen Isotopes and Oxides with Metal Tubes

    SciTech Connect

    Glen R. Longhurst

    2008-08-01

    Understanding and accounting for interaction of hydrogen isotopes and their oxides with metal surfaces is important for persons working with tritium systems. Reported data from several investigators have shown that the processes of oxidation, adsorption, absorption, and permeation are all coupled and interactive. A computer model has been developed for predicting the interaction of hydrogen isotopes and their corresponding oxides in a flowing carrier gas stream with the walls of a metallic tube, particularly at low hydrogen concentrations. An experiment has been constructed to validate the predictive model. Predictions from modeling lead to unexpected experiment results.

  11. Graphenes in the absence of metals as carbocatalysts for selective acetylene hydrogenation and alkene hydrogenation

    NASA Astrophysics Data System (ADS)

    Primo, Ana; Neatu, Florentina; Florea, Mihaela; Parvulescu, Vasile; Garcia, Hermenegildo

    2014-10-01

    Catalysis makes possible a chemical reaction by increasing the transformation rate. Hydrogenation of carbon-carbon multiple bonds is one of the most important examples of catalytic reactions. Currently, this type of reaction is carried out in petrochemistry at very large scale, using noble metals such as platinum and palladium or first row transition metals such as nickel. Catalysis is dominated by metals and in many cases by precious ones. Here we report that graphene (a single layer of one-atom-thick carbon atoms) can replace metals for hydrogenation of carbon-carbon multiple bonds. Besides alkene hydrogenation, we have shown that graphenes also exhibit high selectivity for the hydrogenation of acetylene in the presence of a large excess of ethylene.

  12. DEVELOPMENT OF A NON-NOBLE METAL HYDROGEN PURIFICATION SYSTEM

    SciTech Connect

    Korinko, P; Kyle Brinkman, K; Thad Adams, T; George Rawls, G

    2008-11-25

    Development of advanced hydrogen separation membranes in support of hydrogen production processes such as coal gasification and as front end gas purifiers for fuel cell based system is paramount to the successful implementation of a national hydrogen economy. Current generation metallic hydrogen separation membranes are based on Pd-alloys. Although the technology has proven successful, at issue is the high cost of palladium. Evaluation of non-noble metal based dense metallic separation membranes is currently receiving national and international attention. The focus of the reported work was to develop a scaled reactor with a VNi-Ti alloy membrane to replace a production Pd-alloy tube-type purification/diffuser system.

  13. Production of negative hydrogen ions on metal grids

    SciTech Connect

    Oohara, W.; Maetani, Y.; Takeda, Takashi; Takeda, Toshiaki; Yokoyama, H.; Kawata, K.

    2015-03-15

    Negative hydrogen ions are produced on a nickel grid with positive-ion irradiation. In order to investigate the production mechanism, a copper grid without the chemisorption of hydrogen atoms and positive helium ions without negative ionization are used for comparison. Positive hydrogen ions reflected on the metal surface obtain two electrons from the surface and become negatively ionized. It is found that the production yield of negative ions by desorption ionization of chemisorbed hydrogen atoms seems to be small, and the production is a minor mechanism.

  14. Production of negative hydrogen ions on metal grids

    NASA Astrophysics Data System (ADS)

    Oohara, W.; Maetani, Y.; Takeda, Takashi; Takeda, Toshiaki; Yokoyama, H.; Kawata, K.

    2015-03-01

    Negative hydrogen ions are produced on a nickel grid with positive-ion irradiation. In order to investigate the production mechanism, a copper grid without the chemisorption of hydrogen atoms and positive helium ions without negative ionization are used for comparison. Positive hydrogen ions reflected on the metal surface obtain two electrons from the surface and become negatively ionized. It is found that the production yield of negative ions by desorption ionization of chemisorbed hydrogen atoms seems to be small, and the production is a minor mechanism.

  15. Hydrogen separation membrane on a porous substrate

    DOEpatents

    Song, Sun-Ju; Lee, Tae H.; Chen, Ling; Dorris, Stephen E.; Balachandran, Uthamalingam

    2011-06-14

    A hydrogen permeable membrane is disclosed. The membrane is prepared by forming a mixture of metal oxide powder and ceramic oxide powder and a pore former into an article. The article is dried at elevated temperatures and then sintered in a reducing atmosphere to provide a dense hydrogen permeable portion near the surface of the sintered mixture. The dense hydrogen permeable portion has a higher initial concentration of metal than the remainder of the sintered mixture and is present in the range of from about 20 to about 80 percent by volume of the dense hydrogen permeable portion.

  16. Influence of gaseous hydrogen on metals

    NASA Technical Reports Server (NTRS)

    Walter, R. J.; Chandler, W. T.

    1973-01-01

    Tensile, fracture toughness, threshold stress intensity for sustained-load crack growth, and cyclic and sustained load crack growth rate measurements were performed on a number of alloys in high-pressure hydrogen and helium environments. The results of tensile tests performed in 34.5 MN/m2 (5000 psi) hydrogen indicated that Inconel 625 was considerable embrittled at ambient temperature but was not embrittled at 144 K (-200 F). The tensile properties of AISI 321 stainless steel were slightly reduced at ambient temperature and 144 K (-200 F). The tensile properties of Ti-5Al-2.5 Sn ELI were essentially unaffected by hydrogen at 144 K (-200 F). OFHC copper was not embrittled by hydrogen at ambient temperature or at 144 K (-200 F).

  17. Thermochemical Ablation Therapy of VX2 Tumor Using a Permeable Oil-Packed Liquid Alkali Metal

    PubMed Central

    Guo, Ziyi; Zhang, Qiang

    2015-01-01

    Objective Alkali metal appears to be a promising tool in thermochemical ablation, but, it requires additional data on safety is required. The objective of this study was to explore the effectiveness of permeable oil-packed liquid alkali metal in the thermochemical ablation of tumors. Methods Permeable oil-packed sodium–potassium (NaK) was prepared using ultrasonic mixing of different ratios of metal to oil. The thermal effect of the mixture during ablation of muscle tissue ex vivo was evaluated using the Fluke Ti400 Thermal Imager. The thermochemical effect of the NaK-oil mixture on VX2 tumors was evaluated by performing perfusion CT scans both before and after treatment in 10 VX2 rabbit model tumors. VX2 tumors were harvested from two rabbits immediately after treatment to assess their viability using trypan blue and hematoxylin and eosin (H.E.) staining. Results The injection of the NaK–oil mixture resulted in significantly higher heat in the ablation areas. The permeable oil controlled the rate of heat released during the NaK reaction with water in the living tissue. Perfusion computed tomography and its parameter map confirmed that the NaK–oil mixture had curative effects on VX2 tumors. Both trypan blue and H.E. staining showed partial necrosis of the VX2 tumors. Conclusions The NaK–oil mixture may be used successfully to ablate tumor tissue in vivo. With reference to the controlled thermal and chemical lethal injury to tumors, using a liquid alkali in ablation is potentially an effective and safe method to treat malignant tumors. PMID:25885926

  18. Determination of the Darcy permeability of porous media including sintered metal plugs

    NASA Technical Reports Server (NTRS)

    Frederking, T. H. K.; Hepler, W. A.; Yuan, S. W. K.; Feng, W. F.

    1986-01-01

    Sintered-metal porous plugs with a normal size of the order of 1-10 microns are used to evaluate the Darcy permeability of laminar flow at very small velocities in laminar fluids. Porous media experiment results and data adduced from the literature are noted to support the Darcy law analog for normal fluid convection in the laminar regime. Low temperature results suggest the importance of collecting room temperature data prior to runs at liquid He(4) temperatures. The characteristic length diagram gives a useful picture of the tolerance range encountered with a particular class of porous media.

  19. Non-conventional hydrogen bonds: pterins-metal anions.

    PubMed

    Vargas, Rubicelia; Martínez, Ana

    2011-07-28

    In this paper, we present an analysis of the interaction of metal ions (Cu, Ag and Au) with three different pterins (pterin, isoxanthopterin and sepiapterin) to provide insights concerning the formation of conventional and non-conventional H bonds. Density functional theory calculations were performed in order to reveal the optimized structures of pterin molecules, dimers and tetramers compounds, both with and without metal anions (M). The interaction with small metal clusters (M(3)) is also considered. The formation of different systems is characterized in terms of the structural parameters and hydrogen binding energies (HBE). The HBE values for pterin-M systems presented in this study lie between 22 and 60 kcal mol(-1) and can therefore be classified as strong conventional and strong non-conventional hydrogen bonds. The HBE with small metal clusters (pterin-M(3)) are smaller than the HBE with metal atoms. Vertical electron detachment energies (VEDEs) are also reported in order to analyze the influence of the hydrogen bond on electronic properties. A direct correlation between VEDEs and HBE was found for pterin-M and pterin-M(3) complexes; i.e. as the VEDEs increase, the HBE also augment. The only exception is with Ag(3). The main conclusion derived from this study is that the strong non-conventional hydrogen bonds formed between pterins, dimers and tetramers do not affect the formation of conventional hydrogen bonds between pterins but they do influence the VEDEs. PMID:21695329

  20. Metal-functionalized silicene for efficient hydrogen storage.

    PubMed

    Hussain, Tanveer; Chakraborty, Sudip; Ahuja, Rajeev

    2013-10-21

    First-principles calculations based on density functional theory are used to investigate the electronic structure along with the stability, bonding mechanism, band gap, and charge transfer of metal-functionalized silicene to envisage its hydrogen-storage capacity. Various metal atoms including Li, Na, K, Be, Mg, and Ca are doped into the most stable configuration of silicene. The corresponding binding energies and charge-transfer mechanisms are discussed from the perspective of hydrogen-storage compatibility. The Li and Na metal dopants are found to be ideally suitable, not only for strong metal-to-substrate binding and uniform distribution over the substrate, but also for the high-capacity storage of hydrogen. The stabilities of both Li- and Na-functionalized silicene are also confirmed through molecular dynamics simulations. It is found that both of the alkali metals, Li(+) and Na(+), can adsorb five hydrogen molecules, attaining reasonably high storage capacities of 7.75 and 6.9 wt %, respectively, with average adsorption energies within the range suitable for practical hydrogen-storage applications.

  1. Use of triphenyl phosphate as risk mitigant for metal amide hydrogen storage materials

    DOEpatents

    Cortes-Concepcion, Jose A.; Anton, Donald L.

    2016-04-26

    A process in a resulting product of the process in which a hydrogen storage metal amide is modified by a ball milling process using an additive of TPP. The resulting product provides for a hydrogen storage metal amide having a coating that renders the hydrogen storage metal amide resistant to air, ambient moisture, and liquid water while improving useful hydrogen storage and release kinetics.

  2. The temperature variation of hydrogen diffusion coefficients in metal alloys

    NASA Technical Reports Server (NTRS)

    Danford, M. D.

    1990-01-01

    Hydrogen diffusion coefficients were measured as a function of temperature for a few metal alloys using an electrochemical evolution technique. Results from these measurements are compared to those obtained by the time-lag method. In all cases, diffusion coefficients obtained by the electrochemical method are larger than those by the time-lag method by an order of magnitude or more. These differences are attributed mainly to hydrogen trapping.

  3. Interaction of hydrogen with metal nitrides and imides

    NASA Astrophysics Data System (ADS)

    Chen, Ping; Xiong, Zhitao; Luo, Jizhong; Lin, Jianyi; Tan, Kuang Lee

    2002-11-01

    The pursuit of a clean and healthy environment has stimulated much effort in the development of technologies for the utilization of hydrogen-based energy. A critical issue is the need for practical systems for hydrogen storage, a problem that remains unresolved after several decades of exploration. In this context, the possibility of storing hydrogen in advanced carbon materials has generated considerable interest. But confirmation and a mechanistic understanding of the hydrogen-storage capabilities of these materials still require much work. Our previously published work on hydrogen uptake by alkali-doped carbon nanotubes cannot be reproduced by others. It was realized by us and also demonstrated by Pinkerton et al. that most of the weight gain was due to moisture, which the alkali oxide picked up from the atmosphere. Here we describe a different material system, lithium nitride, which shows potential as a hydrogen storage medium. Lithium nitride is usually employed as an electrode, or as a starting material for the synthesis of binary or ternary nitrides. Using a variety of techniques, we demonstrate that this compound can also reversibly take up large amounts of hydrogen. Although the temperature required to release the hydrogen at usable pressures is too high for practical application of the present material, we suggest that more investigations are needed, as the metal-N-H system could prove to be a promising route to reversible hydrogen storage.

  4. Hydrogen evolution from water through metal sulfide reactions

    NASA Astrophysics Data System (ADS)

    Saha, Arjun; Raghavachari, Krishnan

    2013-11-01

    Transition metal sulfides play an important catalytic role in many chemical reactions. In this work, we have conducted a careful computational study of the structures, electronic states, and reactivity of metal sulfide cluster anions M2SX- (M = Mo and W, X = 4-6) using density functional theory. Detailed structural analysis shows that these metal sulfide anions have ground state isomers with two bridging sulfide bonds, notably different in some cases from the corresponding oxides with the same stoichiometry. The chemical reactivity of these metal sulfide anions with water has also been carried out. After a thorough search on the reactive potential energy surface, we propose several competitive, energetically favorable, reaction pathways that lead to the evolution of hydrogen. Selectivity in the initial water addition and subsequent hydrogen migration are found to be the key steps in all the proposed reaction channels. Initial adsorption of water is most favored involving a terminal metal sulfur bond in Mo2S4- isomers whereas the most preferred orientation for water addition involves a bridging metal sulfur bond in the case of W2S4- and M2S5- isomers. In all the lowest energy H2 elimination steps, the interacting hydrogen atoms involve a metal hydride and a metal hydroxide (or thiol) group. We have also observed a higher energy reaction channel where the interacting hydrogen atoms in the H2 elimination step involve a thiol (-SH) and a hydroxyl (-OH) group. For all the reaction pathways, the Mo sulfide reactions involve a higher barrier than the corresponding W analogues. We observe for both metals that reactions of M2S4- and M2S5- clusters with water to liberate H2 are exothermic and involve modest free energy barriers. However, the reaction of water with M2S6- is highly endothermic with a considerable barrier due to saturation of the local bonding environment.

  5. Hydrogen evolution from water through metal sulfide reactions.

    PubMed

    Saha, Arjun; Raghavachari, Krishnan

    2013-11-28

    Transition metal sulfides play an important catalytic role in many chemical reactions. In this work, we have conducted a careful computational study of the structures, electronic states, and reactivity of metal sulfide cluster anions M2S(X)(-) (M = Mo and W, X = 4-6) using density functional theory. Detailed structural analysis shows that these metal sulfide anions have ground state isomers with two bridging sulfide bonds, notably different in some cases from the corresponding oxides with the same stoichiometry. The chemical reactivity of these metal sulfide anions with water has also been carried out. After a thorough search on the reactive potential energy surface, we propose several competitive, energetically favorable, reaction pathways that lead to the evolution of hydrogen. Selectivity in the initial water addition and subsequent hydrogen migration are found to be the key steps in all the proposed reaction channels. Initial adsorption of water is most favored involving a terminal metal sulfur bond in Mo2S4(-) isomers whereas the most preferred orientation for water addition involves a bridging metal sulfur bond in the case of W2S4(-) and M2S5(-) isomers. In all the lowest energy H2 elimination steps, the interacting hydrogen atoms involve a metal hydride and a metal hydroxide (or thiol) group. We have also observed a higher energy reaction channel where the interacting hydrogen atoms in the H2 elimination step involve a thiol (-SH) and a hydroxyl (-OH) group. For all the reaction pathways, the Mo sulfide reactions involve a higher barrier than the corresponding W analogues. We observe for both metals that reactions of M2S4(-) and M2S5(-) clusters with water to liberate H2 are exothermic and involve modest free energy barriers. However, the reaction of water with M2S6(-) is highly endothermic with a considerable barrier due to saturation of the local bonding environment.

  6. Membrane for hydrogen recovery from streams containing hydrogen sulfide

    DOEpatents

    Agarwal, Pradeep K.

    2007-01-16

    A membrane for hydrogen recovery from streams containing hydrogen sulfide is provided. The membrane comprises a substrate, a hydrogen permeable first membrane layer deposited on the substrate, and a second membrane layer deposited on the first layer. The second layer contains sulfides of transition metals and positioned on the on a feed side of the hydrogen sulfide stream. The present invention also includes a method for the direct decomposition of hydrogen sulfide to hydrogen and sulfur.

  7. Hydrogen storage by physisorption on Metal Organic Frameworks

    NASA Astrophysics Data System (ADS)

    Dailly, Anne

    2008-03-01

    Cryo-adsorption systems based on materials with high specific surface areas have the main advantage that they can store and release hydrogen with fast kinetics and high reversibility over multiples cycles. Recently Metal Organic Frameworks (MOFs) have been proposed as promising adsorbents for hydrogen. These crystallographically well organized hybrid solids resulting from the three dimensional connection of inorganic clusters using organic linkers show the largest specific surface areas of all known crystalline solids. The determination of the relationships between physical properties (chemistry, structure, surface area ) of the MOFs and their hydrogen storage behavior is a key step in the characterization of these materials, if they are to be designed for hydrogen storage applications. Excess hydrogen sorption measurements for different MOFs will be presented. We show that maximum hydrogen uptake at high pressure and 77K does not always scale with the specific surface area. A linear correlation trend only apply within a class of specific materials and breaks down when the surface area measurement does not represent the surface sites that are available to H2. The influence of pore size and shape will also be discussed by comparing several MOFs with different structure types. The hydrogen adsorption and binding energy at low pressure are strongly dependent on the metal ions and the pore size.

  8. Optical hydrogen sensors based on metal-hydrides

    NASA Astrophysics Data System (ADS)

    Slaman, M.; Westerwaal, R.; Schreuders, H.; Dam, B.

    2012-06-01

    For many hydrogen related applications it is preferred to use optical hydrogen sensors above electrical systems. Optical sensors reduce the risk of ignition by spark formation and are less sensitive to electrical interference. Currently palladium and palladium alloys are used for most hydrogen sensors since they are well known for their hydrogen dissociation and absorption properties at relatively low temperatures. The disadvantages of palladium in sensors are the low optical response upon hydrogen loading, the cross sensitivity for oxygen and carbon, the limited detection range and the formation of micro-cracks after some hydrogen absorption/desorption cycles. In contrast to Pd, we find that the use of magnesium or rear earth bases metal-hydrides in optical hydrogen sensors allow tuning of the detection levels over a broad pressure range, while maintaining a high optical response. We demonstrate a stable detection layer for detecting hydrogen below 10% of the lower explosion limit in an oxygen rich environment. This detection layer is deposited at the bare end of a glass fiber as a micro-mirror and is covered with a thin layer of palladium. The palladium layer promotes the hydrogen uptake at room temperature and acts as a hydrogen selective membrane. To protect the sensor for a long time in air a final layer of a hydrophobic fluorine based coating is applied. Such a sensor can be used for example as safety detector in automotive applications. We find that this type of fiber optic hydrogen sensor is also suitable for hydrogen detection in liquids. As example we demonstrate a sensor for detecting a broad range of concentrations in transformer oil. Such a sensor can signal a warning when sparks inside a high voltage power transformer decompose the transformer oil over a long period.

  9. Bridged transition-metal complexes and uses thereof for hydrogen separation, storage and hydrogenation

    DOEpatents

    Lilga, M.A.; Hallen, R.T.

    1991-10-15

    The present invention constitutes a class of organometallic complexes which reversibly react with hydrogen to form dihydrides and processes by which these compounds can be utilized. The class includes bimetallic complexes in which two cyclopentadienyl rings are bridged together and also separately [pi]-bonded to two transition metal atoms. The transition metals are believed to bond with the hydrogen in forming the dihydride. Transition metals such as Fe, Mn or Co may be employed in the complexes although Cr constitutes the preferred metal. A multiple number of ancillary ligands such as CO are bonded to the metal atoms in the complexes. Alkyl groups and the like may be substituted on the cyclopentadienyl rings. These organometallic compounds may be used in absorption/desorption systems and in facilitated transport membrane systems for storing and separating out H[sub 2] from mixed gas streams such as the product gas from coal gasification processes. 3 figures.

  10. Bridged transition-metal complexes and uses thereof for hydrogen separation, storage and hydrogenation

    DOEpatents

    Lilga, M.A.; Hallen, R.T.

    1990-08-28

    The present invention constitutes a class of organometallic complexes which reversibly react with hydrogen to form dihydrides and processes by which these compounds can be utilized. The class includes bimetallic complexes in which two cyclopentadienyl rings are bridged together and also separately [pi]-bonded to two transition metal atoms. The transition metals are believed to bond with the hydrogen in forming the dihydride. Transition metals such as Fe, Mn or Co may be employed in the complexes although Cr constitutes the preferred metal. A multiple number of ancillary ligands such as CO are bonded to the metal atoms in the complexes. Alkyl groups and the like may be substituted on the cyclopentadienyl rings. These organometallic compounds may be used in absorption/desorption systems and in facilitated transport membrane systems for storing and separating out H[sub 2] from mixed gas streams such as the producer gas from coal gasification processes. 3 figs.

  11. Bridged transition-metal complexes and uses thereof for hydrogen separation, storage and hydrogenation

    DOEpatents

    Lilga, Michael A.; Hallen, Richard T.

    1990-01-01

    The present invention constitutes a class of organometallic complexes which reversibly react with hydrogen to form dihydrides and processes by which these compounds can be utilized. The class includes bimetallic complexes in which two cyclopentadienyl rings are bridged together and also separately .pi.-bonded to two transition metal atoms. The transition metals are believed to bond with the hydrogen in forming the dihydride. Transition metals such as Fe, Mn or Co may be employed in the complexes although Cr constitutes the preferred metal. A multiple number of ancilliary ligands such as CO are bonded to the metal atoms in the complexes. Alkyl groups and the like may be substituted on the cyclopentadienyl rings. These organometallic compounds may be used in absorption/desorption systems and in facilitated transport membrane systems for storing and separating out H.sub.2 from mixed gas streams such as the produce gas from coal gasification processes.

  12. Bridged transition-metal complexes and uses thereof for hydrogen separation, storage and hydrogenation

    DOEpatents

    Lilga, Michael A.; Hallen, Richard T.

    1991-01-01

    The present invention constitutes a class of organometallic complexes which reversibly react with hydrogen to form dihydrides and processes by which these compounds can be utilized. The class includes bimetallic complexes in which two cyclopentadienyl rings are bridged together and also separately .pi.-bonded to two transition metal atoms. The transition metals are believed to bond with the hydrogen in forming the dihydride. Transition metals such as Fe, Mn or Co may be employed in the complexes although Cr constitutes the preferred metal. A multiple number of ancilliary ligands such as CO are bonded to the metal atoms in the complexes. Alkyl groups and the like may be substituted on the cyclopentadienyl rings. These organometallic compounds may be used in absorption/desorption systems and in facilitated transport membrane systems for storing and separating out H.sub.2 from mixed gas streams such as the product gas from coal gasification processes.

  13. Hydrogen storage in microporous metal-organic frameworks with exposed metal sites.

    PubMed

    Dincă, Mircea; Long, Jeffrey R

    2008-01-01

    Owing to their high uptake capacity at low temperature and excellent reversibility kinetics, metal-organic frameworks have attracted considerable attention as potential solid-state hydrogen storage materials. In the last few years, researchers have also identified several strategies for increasing the affinity of these materials towards hydrogen, among which the binding of H(2) to unsaturated metal centers is one of the most promising. Herein, we review the synthetic approaches employed thus far for producing frameworks with exposed metal sites, and summarize the hydrogen uptake capacities and binding energies in these materials. In addition, results from experiments that were used to probe independently the metal-hydrogen interaction in selected materials will be discussed.

  14. Composite metal-hydrogen electrodes for metal-hydrogen batteries. Final report, October 1, 1993--April 15, 1997

    SciTech Connect

    Ruckman, M.W.; Strongin, M.; Weismann, H.

    1997-04-01

    The purpose of this project is to develop and conduct a feasibility study of metallic thin films (multilayered and alloy composition) produced by advanced sputtering techniques for use as anodes in Ni-metal hydrogen batteries that would be deposited as distinct anode, electrolyte and cathode layers in thin film devices. The materials could also be incorporated in secondary consumer batteries (i.e. type AF(4/3 or 4/5)) which use electrodes in the form of tapes. The project was based on pioneering studies of hydrogen uptake by ultra-thin Pd-capped Nb films, these studies suggested that materials with metal-hydrogen ratios exceeding those of commercially available metal hydride materials and fast hydrogen charging and discharging kinetics could be produced. The project initially concentrated on gas phase and electrochemical studies of Pd-capped niobium films in laboratory-scale NiMH cells. This extended the pioneering work to the wet electrochemical environment of NiMH batteries and exploited advanced synchrotron radiation techniques not available during the earlier work to conduct in-situ studies of such materials during hydrogen charging and discharging. Although batteries with fast charging kinetics and hydrogen-metal ratios approaching unity could be fabricated, it was found that oxidation, cracking and corrosion in aqueous solutions made pure Nb films and multilayers poor candidates for battery application. The project emphasis shifted to alloy films based on known elemental materials used for NiMH batteries. Although commercial NiMH anode materials contain many metals, it was found that 0.24 {mu}m thick sputtered Zr-Ni films cycled at least 50 times with charging efficiencies exceeding 95% and [H]/[M] ratios of 0.7-1.0. Multilayered or thicker Zr-Ni films could be candidates for a thin film NiMH battery that may have practical applications as an integrated power source for modern electronic devices.

  15. HYDROGEN EMBRITTLEMENT OF METALS: A PRIMER FOR THE FAILURE ANALYST

    SciTech Connect

    Louthan, M

    2008-01-31

    Hydrogen reduces the service life of many metallic components. Such reductions may be manifested as blisters, as a decrease in fatigue resistance, as enhanced creep, as the precipitation of a hydride phase and, most commonly, as unexpected, macroscopically brittle failure. This unexpected, brittle fracture is commonly termed hydrogen embrittlement. Frequently, hydrogen embrittlement occurs after the component has been is service for a period of time and much of the resulting fracture surface is distinctly intergranular. Many failures, particularly of high strength steels, are attributed to hydrogen embrittlement simply because the failure analyst sees intergranular fracture in a component that served adequately for a significant period of time. Unfortunately, simply determining that a failure is due to hydrogen embrittlement or some other form of hydrogen induced damage is of no particular help to the customer unless that determination is coupled with recommendations that provide pathways to avoid such damage in future applications. This paper presents qualitative and phenomenological descriptions of the hydrogen damage processes and outlines several metallurgical recommendations that may help reduce the susceptibility of a particular component or system to the various forms of hydrogen damage.

  16. Dependence of hydrogen permeabilities of isotropic graphites on the pore structure

    NASA Astrophysics Data System (ADS)

    Yamawaki, M.; Yamaguchi, K.; Suzuki, Y.; Tanaka, S.

    1991-03-01

    The permeation behavior of molecular hydrogen through isotropic graphites is investigated. The observed dependences of the permeation rate on pressure, specimen thickness, temperature and molecular weight suggest that hydrogen permeates by molecular flow, probably through open pores. A simple pore structure model is developed and is compared with the experimental results. It is revealed that hydrogen permeation through isotropic graphites depends not only on the pore size or the porosity, but also on the pore size distribution and tortuosity.

  17. Using Hydrogen Balloons to Display Metal Ion Spectra

    ERIC Educational Resources Information Center

    Maynard, James H.

    2008-01-01

    We have optimized a procedure for igniting hydrogen-filled balloons containing metal salts to obtain the brightest possible flash while minimizing the quantity of airborne combustion products. We report air quality measurements in a lecture hall immediately after the demonstration. While we recommend that this demonstration be done outdoors or in…

  18. Nanoporous, Metal Carbide, Surface Diffusion Membranes for High Temperature Hydrogen Separations

    SciTech Connect

    Way, J.; Wolden, Colin

    2013-09-30

    Colorado School of Mines (CSM) developed high temperature, hydrogen permeable membranes that contain no platinum group metals with the goal of separating hydrogen from gas mixtures representative of gasification of carbon feedstocks such as coal or biomass in order to meet DOE NETL 2015 hydrogen membrane performance targets. We employed a dual synthesis strategy centered on transition metal carbides. In the first approach, novel, high temperature, surface diffusion membranes based on nanoporous Mo{sub 2}C were fabricated on ceramic supports. These were produced in a two step process that consisted of molybdenum oxide deposition followed by thermal carburization. Our best Mo{sub 2}C surface diffusion membrane achieved a pure hydrogen flux of 367 SCFH/ft{sup 2} at a feed pressure of only 20 psig. The highest H{sub 2}/N{sub 2} selectivity obtained with this approach was 4.9. A transport model using “dusty gas” theory was derived to describe the hydrogen transport in the Mo{sub 2}C coated, surface diffusion membranes. The second class of membranes developed were dense metal foils of BCC metals such as vanadium coated with thin (< 60 nm) Mo{sub 2}C catalyst layers. We have fabricated a Mo{sub 2}C/V composite membrane that in pure gas testing delivered a H{sub 2} flux of 238 SCFH/ft{sup 2} at 600 °C and 100 psig, with no detectable He permeance. This exceeds the 2010 DOE Target flux. This flux is 2.8 times that of pure Pd at the same membrane thickness and test conditions and over 79% of the 2015 flux target. In mixed gas testing we achieved a permeate purity of ≥99.99%, satisfying the permeate purity milestone, but the hydrogen permeance was low, ~0.2 SCFH/ft{sup 2}.psi. However, during testing of a Mo{sub 2}C coated Pd alloy membrane with DOE 1 feed gas mixture a hydrogen permeance of >2 SCFH/ft{sup 2}.psi was obtained which was stable during the entire test, meeting the permeance associated with the 2010 DOE target flux. Lastly, the Mo{sub 2}C/V composite

  19. Geochemistry of a permeable reactive barrier for metals and acid mine drainage

    SciTech Connect

    Benner, S.G.; Blowes, D.W.; Herbert, R.B. Jr.; Ptacek, C.J.; Gould, W.D.

    1999-08-15

    A permeable reactive barrier, designed to remove metals and generate alkalinity by promoting sulfate reduction and metal sulfide precipitation, was installed in August 1995 into an aquifer containing effluent from mine tailings. Passage of groundwater through the barrier results in striking improvement in water quality. Dramatic changes in concentrations of SO{sub 4}, Fe, trace metals, and alkalinity are observed. Populations of sulfate reducing bacteria are 10,000 times greater, and bacterial activity, as measured by dehydrogenase activity, is 10 times higher within the barrier compared to the up-gradient aquifer. Dissolved sulfide concentrations increase by 0.2--120 mg/L, and the isotope {sup 34}S is enriched relative to {sup 32}S in the dissolved phase SO{sub 4}{sup 2{minus}} within the barrier. Water chemistry, coupled with geochemical speciation modeling, indicates the pore water in the barrier becomes supersaturated with respect to amorphous Fe sulfide. Solid phase analysis of the reactive mixture indicates the accumulation of Fe monosulfide precipitates. Shifts in the saturated states of carbonate, sulfate, and sulfide minerals and most of the observed changes in water chemistry in the barrier and down-gradient aquifer can be attributed, either directly or indirectly, to bacterially mediated sulfate reduction.

  20. Metal hydride hydrogen compression: Recent advances and future prospects

    DOE PAGESBeta

    Bowman, Jr., Robert C.; Yartys, Volodymyr A.; Lototskyy, Mykhaylo V.; Linkov, Vladimir; Grant, David; Stuart, Alastair; Eriksen, Jon; Denys, Roman

    2016-03-17

    Metal hydride (MH) thermal sorption compression is one of the more important applications of the metal hydrides. The present paper reviews recent advances in the field based on the analysis of the fundamental principles of this technology. The performances when boosting hydrogen pressure, along with two- and three-step compression units are analyzed. The paper includes also a theoretical modeling of a two-stage compressor aimed at both describing the performance of the experimentally studied systems, but, also, on their optimization and design of more advanced MH compressors. Business developments in the field are reviewed for the Norwegian company HYSTORSYS AS andmore » the South African Institute for Advanced Materials Chemistry. Finally, future prospects are outlined presenting the role of the metal hydride compression in the overall development of the hydrogen driven energy systems. Lastly, the work is based on the analysis of the development of the technology in Europe, USA and South Africa.« less

  1. Replacing precious metals with carbide catalysts for hydrogenation reactions

    DOE PAGESBeta

    Ruijun, Hou; Chen, Jingguang G.; Chang, Kuan; Wang, Tiefeng

    2015-03-03

    Molybdenum carbide (Mo₂C and Ni/Mo₂C) catalysts were compared with Pd/SiO₂ for the hydrogenation of several diene molecules, 1,3- butadiene, 1,3- and 1,4-cyclohexadiene (CHD). Compared to Pd/SiO₂, Mo₂C showed similar hydrogenation rate for 1,3-butadiene and 1,3-CHD and even higher rate for 1,4-CHD, but with significant deactivation rate for 1,3-CHD hydrogenation. However, the hydrogenation activity of Mo₂C could be completely regenerated by H₂ treatment at 723 K for the three molecules. The Ni modified Mo₂C catalysts retained similar activity for 1,3-butadiene hydrogenation with significantly enhanced selectivity for 1-butene production. The 1-butene selectivity increased with increasing Ni loading below 15%. Among the Nimore » modified Mo₂C catalysts, 8.6%Ni/Mo₂C showed the highest selectivity to 1-butene, which was even higher selectivity than that over Pd/SiO₂. Compared to Pd/SiO₂, both Mo₂C and Ni/Mo₂C showed combined advantages in hydrogenation activity and catalyst cost reduction, demonstrating the potential to use less expensive carbide catalysts to replace precious metals for hydrogenation reactions.« less

  2. Replacing precious metals with carbide catalysts for hydrogenation reactions

    SciTech Connect

    Ruijun, Hou; Chen, Jingguang G.; Chang, Kuan; Wang, Tiefeng

    2015-03-03

    Molybdenum carbide (Mo₂C and Ni/Mo₂C) catalysts were compared with Pd/SiO₂ for the hydrogenation of several diene molecules, 1,3- butadiene, 1,3- and 1,4-cyclohexadiene (CHD). Compared to Pd/SiO₂, Mo₂C showed similar hydrogenation rate for 1,3-butadiene and 1,3-CHD and even higher rate for 1,4-CHD, but with significant deactivation rate for 1,3-CHD hydrogenation. However, the hydrogenation activity of Mo₂C could be completely regenerated by H₂ treatment at 723 K for the three molecules. The Ni modified Mo₂C catalysts retained similar activity for 1,3-butadiene hydrogenation with significantly enhanced selectivity for 1-butene production. The 1-butene selectivity increased with increasing Ni loading below 15%. Among the Ni modified Mo₂C catalysts, 8.6%Ni/Mo₂C showed the highest selectivity to 1-butene, which was even higher selectivity than that over Pd/SiO₂. Compared to Pd/SiO₂, both Mo₂C and Ni/Mo₂C showed combined advantages in hydrogenation activity and catalyst cost reduction, demonstrating the potential to use less expensive carbide catalysts to replace precious metals for hydrogenation reactions.

  3. The Interaction of Hydrogen with Simple and Noble Metals Surfaces

    NASA Astrophysics Data System (ADS)

    Sprunger, Phillip T.

    The basic concepts of adsorption are illustrated by the investigation of a simple adsorbate (hydrogen) with the "simplest" metals (simple and noble metals). Theoretically tractable, these systems serve as an excellent test of our basic understanding of chemisorption. The interaction of atomic and molecular hydrogen with the surfaces of Mg(0001), Mg(1120), Li(110), K(110), Ag(110), and Ag(111) have been studied with a variety of experimental probes. In all cases, no evidence for H_2 associative or dissociative adsorption is observed at the substrate temperature investigated (>=q90 K). In the case of the simple metals below 150 K, atomic hydrogen is bound to the surfaces in a strongly chemisorbed state (hydride). For Mg and Li, the hydride is localized to the surface wherein the substrate electron density is lower than the bulk. Because of the low electron density, hydrogen is absorbed into the bulk of K at low temperatures and forms a bulk-hydride phase. However, these low-temperature phases are metastable. In the case of Mg, hydrogen moves into lower energy configuration bonding sites which are closer to or below the surface plane. However, the hydride characteristics are absent; the H atom is effectively screened because of the higher jellium density. In contrast, upon annealing, hydrogen is absorbed into the bulk of Li and K and phase separation occurs forming regions of clean metal and bulk hydride areas. The results are compared to theoretical studies; the propensity for absorption over adsorption is understood in terms of jellium-based models. In the case of silver, at 100 K, atomic hydrogen bonds in trigonal sites on both the (110) and (111) surfaces. As a function of H concentration, a sequence of lattice gas superstructures is observed; these phases are accompanied by small H-induced displacements of the substrate surface atoms. In the case of Ag(110), the low-temperature phase is metastable; upon annealing, hydrogen desorption from low energy states is

  4. Noble-metal-free plasmonic photocatalyst: hydrogen doped semiconductors

    PubMed Central

    Ma, Xiangchao; Dai, Ying; Yu, Lin; Huang, Baibiao

    2014-01-01

    The unique capacity of localized surface plasmon resonance (LSPR) offers a new opportunity to overcome the limited efficiency of semiconductor photocatalyst. Here we unravel that LSPR, which usually occurs in noble metal nanoparticles, can be realized by hydrogen doping in noble-metal-free semiconductor using TiO2 as a model photocatalyst. Moreover, its LSPR is located in infrared region, which supplements that of noble metal whose LSPR is generally in the visible region, making it possible to extend the light response of photocatalyst to infrared region. The near field enhancement is shown to be comparable with that of noble-metal nanoparticles, indicating that highly enhanced light absorption rate can be expected. The present work can provide a key guideline for the creation of highly efficient noble-metal-free plasmonic photocatalysts and have a much wider impact in infrared bioimaging and spectroscopy where infrared LSPR is essential. PMID:24496400

  5. Nanoparticulate gellants for metallized gelled liquid hydrogen with aluminum

    NASA Technical Reports Server (NTRS)

    Palaszewski, Bryan; Starkovich, John; Adams, Scott

    1996-01-01

    Gelled liquid hydrogen was experimentally formulated using sol-gel technology. As a follow-on to work with cryogenic simulants, hydrogen was gelled with an alkoxide material: BTMSE. Initial results demonstrated that gellants with a specific surface area of 1000 m(exp 2)/g could be repeatably fabricated. Gelled hexane and metallized gelled hexane (with 13.8-wt% Al) were produced. Propellant settling testing was conducted for acceleration levels of 2 to 10 times normal gravity and a minimum gellant percentage was determined for stable gelled hexane and metalized gelled hexane. A cryogenic capillary rheometer was also designed, constructed, and used to determine the viscosity of gelled hydrogen. Small volumes of liquid hydrogen were gelled with a 7- to 8-wt% gellant level. The gelled H2 viscosity was 1.5 to 3.7 times that of liquid hydrogen: 0.048 to 0.116 mPa-s versus 0.03 mPa-s for liquid H2 (at 16 K and approximately 1 atm pressure).

  6. Improved metal hydride technology for the storage of hydrogen

    SciTech Connect

    Sapru, K.; Ming, L.; Ramachandran, S.

    1995-09-01

    Low cost, high density storage of hydrogen will remove the most serious barrier to large-scale utilization of hydrogen as a non-polluting, zero-emission fuel. An important challenge for the practical use of Mg-based, high capacity hydrogen storage alloys has been the development of a low-cost, bulk production technique. Two difficulties in preparation of Mg-based alloys are the immiscibility of Mg with many transition metals and the relatively high volatility of Mg compared to many transition metals. These factors preclude the use of conventional induction melting techniques for the Mg-based alloy preparation. A mechanical alloying technique, in which Mg immiscibility and volatility do not present a problem, was developed and shows great promise for production of Mg-based alloys. A number of Mg-based alloys were prepared via modified induction melting and mechanical alloying methods. The alloys were tested for gas phase hydrogen storage properties, composition, structure and morphology. The mechanically alloyed samples are multi-component, multi-phase, highly disordered materials in their as-prepared state. These unoptimized alloys have shown reversible H-storage capacity of more than 5 wt.% hydrogen. After 2000 absorption/desorption cycles, the alloys show no decline in storage capacity or desorption kinetics. The alloys have also demonstrated resistance to CH{sub 4} and CO poisoning in preliminary testing. Upon annealing, with an increase in crystallinity, the H-storage capacity decreases, indicating the importance of disorder.

  7. Treatment of percolate from metal sulfide mine tailings with a permeable reactive barrier of transformed red mud.

    PubMed

    Zijlstra, J J P; Dessì, R; Peretti, R; Zucca, A

    2010-04-01

    Metal sulfide tailings of the Sardinian (Italy) abandoned Baccu Locci arsenic mine show high concentrations of aluminum, arsenic, cadmium, copper, manganese, lead, and zinc in acid percolate (pH = 4) and have been classified as "dangerous waste." This paper shows that the release of toxic metals can be strongly reduced when the tailings are placed on a reactive permeable bed (7 wt %) of porous, alkaline pellets of transformed red mud (TRM). During a laboratory percolation test, two columns with 80 kg of waste, of which one contained a bottom layer of TRM pellets, were each alimented with 600 L of de-ionized water. Comparing pH, electroconductivity, metal, and sulfate concentrations of collected percolate from both columns demonstrates efficient neutralization (pH = 7.4) and removal of metals (80 to 99%) for the column with the permeable reactive bottom layer. PMID:20432649

  8. Structural tailoring of hydrogen-bonded poly(acrylic acid)/poly(ethylene oxide) multilayer thin films for reduced gas permeability.

    PubMed

    Xiang, Fangming; Ward, Sarah M; Givens, Tara M; Grunlan, Jaime C

    2015-02-01

    Hydrogen bonded poly(acrylic acid) (PAA)/poly(ethylene oxide) (PEO) layer-by-layer assemblies are highly elastomeric, but more permeable than ionically bonded thin films. In order to expand the use of hydrogen-bonded assemblies to applications that require a better gas barrier, the effect of assembling pH on the oxygen permeability of PAA/PEO multilayer thin films was investigated. Altering the assembling pH leads to significant changes in phase morphology and bonding. The amount of intermolecular hydrogen bonding between PAA and PEO is found to increase with increasing pH due to reduction of COOH dimers between PAA chains. This improved bonding leads to smaller PEO domains and lower gas permeability. Further increasing the pH beyond 2.75 results in higher oxygen permeability due to partial deprotonation of PAA. By setting the assembling pH at 2.75, the negative impacts of COOH dimer formation and PAA ionization on intermolecular hydrogen bonding can be minimized, leading to a 50% reduction in the oxygen permeability of the PAA/PEO thin film. A 20 bilayer coating reduces the oxygen transmission rate of a 1.58 mm natural rubber substrate by 20 ×. These unique nanocoatings provide the opportunity to impart a gas barrier to elastomeric substrates without altering their mechanical behavior.

  9. Hot Hydrogen Testing of Refractory Metals and Ceramics

    NASA Technical Reports Server (NTRS)

    Zee, Ralph; Chin, Bryan; Cohron, Jon

    1993-01-01

    The objective of this investigation is to develop a technique with which refractory metal carbide samples can be exposed to hydrogen containing gases at high temperatures, and to use various microstructural and analytical techniques to determine the chemical and rate processes involved in hydrogen degradation in these materials. Five types of carbides were examined including WC, NbC, HfC, ZrC, and TaC. The ceramics were purchased and were all monolithic in nature. The temperature range investigated was from 850 to 1600 C with a hydrogen pressure of one atmosphere. Control experiments, in vacuum, were also conducted for comparison so that the net effects due to hydrogen could be isolated. The samples were analyzed prior to and after exposure. Gas samples were collected in selected experiments and analyzed using gas chromography. Characterization of the resulting microstructure after exposure to hydrogen was conducted using optical microscopy, x-ray diffraction, scanning electron microscopy, and weight change. The ceramics were purchased and were all monolithic in nature. It was found that all samples lost weight after exposure, both in hydrogen and vacuum. Results from the microstructure analyses show that the degradation processes are different among the five types of ceramics involved. In addition, the apparent activation energy for the degradation process is a function of temperature even within the same material. This indicates that there are more than one mechanism involved in each material, and that the mechanisms are temperature dependent.

  10. Hydrogen evolution from water through metal sulfide reactions

    SciTech Connect

    Saha, Arjun; Raghavachari, Krishnan

    2013-11-28

    Transition metal sulfides play an important catalytic role in many chemical reactions. In this work, we have conducted a careful computational study of the structures, electronic states, and reactivity of metal sulfide cluster anions M{sub 2}S{sub X}{sup −} (M = Mo and W, X = 4–6) using density functional theory. Detailed structural analysis shows that these metal sulfide anions have ground state isomers with two bridging sulfide bonds, notably different in some cases from the corresponding oxides with the same stoichiometry. The chemical reactivity of these metal sulfide anions with water has also been carried out. After a thorough search on the reactive potential energy surface, we propose several competitive, energetically favorable, reaction pathways that lead to the evolution of hydrogen. Selectivity in the initial water addition and subsequent hydrogen migration are found to be the key steps in all the proposed reaction channels. Initial adsorption of water is most favored involving a terminal metal sulfur bond in Mo{sub 2}S{sub 4}{sup −} isomers whereas the most preferred orientation for water addition involves a bridging metal sulfur bond in the case of W{sub 2}S{sub 4}{sup −} and M{sub 2}S{sub 5}{sup −} isomers. In all the lowest energy H{sub 2} elimination steps, the interacting hydrogen atoms involve a metal hydride and a metal hydroxide (or thiol) group. We have also observed a higher energy reaction channel where the interacting hydrogen atoms in the H{sub 2} elimination step involve a thiol (–SH) and a hydroxyl (–OH) group. For all the reaction pathways, the Mo sulfide reactions involve a higher barrier than the corresponding W analogues. We observe for both metals that reactions of M{sub 2}S{sub 4}{sup −} and M{sub 2}S{sub 5}{sup −} clusters with water to liberate H{sub 2} are exothermic and involve modest free energy barriers. However, the reaction of water with M{sub 2}S{sub 6}{sup −} is highly endothermic with a considerable

  11. Composite hydrogen separation element and module

    DOEpatents

    Edlund, D.J.

    1996-03-12

    There are disclosed improvements in multicomponent composite metal membranes useful for the separation of hydrogen, the improvements comprising the provision of a flexible porous intermediate layer between a support layer and a nonporous hydrogen-permeable coating metal layer, and the provision of a textured coating metal layer. 15 figs.

  12. Hydrogen-Rich Medium Attenuated Lipopolysaccharide-Induced Monocyte-Endothelial Cell Adhesion and Vascular Endothelial Permeability via Rho-Associated Coiled-Coil Protein Kinase.

    PubMed

    Xie, Keliang; Wang, Weina; Chen, Hongguang; Han, Huanzhi; Liu, Daquan; Wang, Guolin; Yu, Yonghao

    2015-07-01

    Sepsis is the leading cause of death in critically ill patients. In recent years, molecular hydrogen, as an effective free radical scavenger, has been shown a selective antioxidant and anti-inflammatory effect, and it is beneficial in the treatment of sepsis. Rho-associated coiled-coil protein kinase (ROCK) participates in junction between normal cells, and regulates vascular endothelial permeability. In this study, we used lipopolysaccharide to stimulate vascular endothelial cells and explored the effects of hydrogen-rich medium on the regulation of adhesion of monocytes to endothelial cells and vascular endothelial permeability. We found that hydrogen-rich medium could inhibit adhesion of monocytes to endothelial cells and decrease levels of adhesion molecules, whereas the levels of transepithelial/endothelial electrical resistance values and the expression of vascular endothelial cadherin were increased after hydrogen-rich medium treatment. Moreover, hydrogen-rich medium could lessen the expression of ROCK, as a similar effect of its inhibitor Y-27632. In addition, hydrogen-rich medium could also inhibit adhesion of polymorphonuclear neutrophils to endothelial cells. In conclusion, hydrogen-rich medium could regulate adhesion of monocytes/polymorphonuclear neutrophils to endothelial cells and vascular endothelial permeability, and this effect might be related to the decreased expression of ROCK protein.

  13. Atomic interactions and phase transition in hydrogen metal systems

    SciTech Connect

    Shirley, A.I.

    1985-01-01

    The statistical mechanical behavior of H in pure metals and metal alloys is investigated using elasticity theory and lattice-gas models. The interactions between H atoms are separated into elastic and electronic contributions, and only the elastic contributions are evaluated. Three studies are reported: trapping of H by interstitial and substitutional impurities in bbc metals; modeling of H in impure metals; and modeling of H in concentration metal hydrides. The elastic interactions between H and interstitial and substitutional impurities in bbc metals are calculated using the method of lattice statics. Comparison with experimentally-measured trapping energies indicates that trapping by interstitial impurities is due solely to elastic energy, whereas both elastic and electronic interactions contribute to trapping by substitutional impurities. To include the effect of substitutional trapping on the phase transitions of H in metal alloys, the random-field lattice-gas model is developed. Interactions between H atoms are determined using the effective metal atom approximation. Hydrogen-impurity interactions are treated as a random field, in analogy with the random-field Ising model. Phase diagrams of the Nb/sub .95/Mo/sub .05/-H and Nb/sub .85/Mo/sub .15/-H systems are calculated by Monte Carlo simulation using the random-field model. The model gives qualitatively correct predictions of the phase behavior when the random field is included.

  14. CO2 hydrogenation on a metal hydride surface.

    PubMed

    Kato, Shunsuke; Borgschulte, Andreas; Ferri, Davide; Bielmann, Michael; Crivello, Jean-Claude; Wiedenmann, Daniel; Parlinska-Wojtan, Magdalena; Rossbach, Peggy; Lu, Ye; Remhof, Arndt; Züttel, Andreas

    2012-04-28

    The catalytic hydrogenation of CO(2) at the surface of a metal hydride and the corresponding surface segregation were investigated. The surface processes on Mg(2)NiH(4) were analyzed by in situ X-ray photoelectron spectroscopy (XPS) combined with thermal desorption spectroscopy (TDS) and mass spectrometry (MS), and time-of-flight secondary ion mass spectrometry (ToF-SIMS). CO(2) hydrogenation on the hydride surface during hydrogen desorption was analyzed by catalytic activity measurement with a flow reactor, a gas chromatograph (GC) and MS. We conclude that for the CO(2) methanation reaction, the dissociation of H(2) molecules at the surface is not the rate controlling step but the dissociative adsorption of CO(2) molecules on the hydride surface. PMID:22433948

  15. Hydrogen Peroxide, Signaling in Disguise during Metal Phytotoxicity

    PubMed Central

    Cuypers, Ann; Hendrix, Sophie; Amaral dos Reis, Rafaela; De Smet, Stefanie; Deckers, Jana; Gielen, Heidi; Jozefczak, Marijke; Loix, Christophe; Vercampt, Hanne; Vangronsveld, Jaco; Keunen, Els

    2016-01-01

    Plants exposed to excess metals are challenged by an increased generation of reactive oxygen species (ROS) such as superoxide (O2•-), hydrogen peroxide (H2O2) and the hydroxyl radical (•OH). The mechanisms underlying this oxidative challenge are often dependent on metal-specific properties and might play a role in stress perception, signaling and acclimation. Although ROS were initially considered as toxic compounds causing damage to various cellular structures, their role as signaling molecules became a topic of intense research over the last decade. Hydrogen peroxide in particular is important in signaling because of its relatively low toxicity, long lifespan and its ability to cross cellular membranes. The delicate balance between its production and scavenging by a plethora of enzymatic and metabolic antioxidants is crucial in the onset of diverse signaling cascades that finally lead to plant acclimation to metal stress. In this review, our current knowledge on the dual role of ROS in metal-exposed plants is presented. Evidence for a relationship between H2O2 and plant metal tolerance is provided. Furthermore, emphasis is put on recent advances in understanding cellular damage and downstream signaling responses as a result of metal-induced H2O2 production. Finally, special attention is paid to the interaction between H2O2 and other signaling components such as transcription factors, mitogen-activated protein kinases, phytohormones and regulating systems (e.g. microRNAs). These responses potentially underlie metal-induced senescence in plants. Elucidating the signaling network activated during metal stress is a pivotal step to make progress in applied technologies like phytoremediation of polluted soils. PMID:27199999

  16. Direct versus hydrogen assisted CO dissociation on metal surfaces

    NASA Astrophysics Data System (ADS)

    Alfonso, Dominic

    2012-02-01

    We present investigations of the formation of precursor hydrocarbon species relevant to production of liquid hydrocarbons on low index surfaces of various important noble and transition metals. The formation could occur via the so-called carbide mechanism where direct CO dissociation takes place, followed by stepwise hydrogenation of C yielding CHx species. Formation of precursor CHx species could also potentially take place through hydrogenated CO intermediates. First-principles calculations of energetics and barriers of CO conversion to hydrocarbons species were performed using plane-wave periodic density functional theory. Our calculations indicate that the two pathways are generally competitive on transition metals. A microkinetic model, with input thermodynamics and kinetic parameters estimated from electronic structure calculations, has been developed. The two pathways will be further examined using microkinetic approach to determine whether the aforementioned finding holds at realistic conditions.

  17. Metallization and electrical conductivity of hydrogen in Jupiter.

    PubMed

    Nellis, W J; Weir, S T; Mitchell, A C

    1996-08-16

    Electrical conductivities of molecular hydrogen in Jupiter were calculated by scaling electrical conductivities measured at shock pressures in the range of 10 to 180 gigapascals (0.1 to 1.8 megabars) and temperatures to 4000 kelvin, representative of conditions inside Jupiter. Jupiter's magnetic field is caused by convective dynamo motion of electrically conducting fluid hydrogen. The data imply that Jupiter should become metallic at 140 gigapascals in the fluid, and the electrical conductivity in the jovian molecular envelope at pressures up to metallization is about an order of magnitude larger than expected previously. The large magnetic field is produced in the molecular envelope closer to the surface than previously thought. PMID:8688072

  18. Metal-free transfer hydrogenation of olefins via dehydrocoupling catalysis

    PubMed Central

    Pérez, Manuel; Caputo, Christopher B.; Dobrovetsky, Roman; Stephan, Douglas W.

    2014-01-01

    A major advance in main-group chemistry in recent years has been the emergence of the reactivity of main-group species that mimics that of transition metal complexes. In this report, the Lewis acidic phosphonium salt [(C6F5)3PF][B(C6F5)4] 1 is shown to catalyze the dehydrocoupling of silanes with amines, thiols, phenols, and carboxylic acids to form the Si-E bond (E = N, S, O) with the liberation of H2 (21 examples). This catalysis, when performed in the presence of a series of olefins, yields the concurrent formation of the products of dehydrocoupling and transfer hydrogenation of the olefin (30 examples). This reactivity provides a strategy for metal-free catalysis of olefin hydrogenations. The mechanisms for both catalytic reactions are proposed and supported by experiment and density functional theory calculations. PMID:25002489

  19. Silane plus molecular hydrogen as a possible pathway to metallic hydrogen

    PubMed Central

    Yao, Yansun; Klug, Dennis D.

    2010-01-01

    The high-pressure behavior of silane, SiH4, plus molecular hydrogen was investigated using a structural search method and ab initio molecular dynamics to predict the structures and examine the physical origin of the pressure-induced drop in hydrogen intramolecular vibrational (vibron) frequencies. A structural distortion is predicted at 15 GPa from a slightly strained fcc cell to a rhombohedral cell that involves a small volume change. The predicted equation of state and the pressure-induced drop in the hydrogen vibron frequencies reproduces well the experimental data (Strobel TA, Somayazulu M, Hemley RJ (2009) Phys Rev Lett 103:065701). The bond weakening in H2 is induced by intermolecular interactions between the H2 and SiH4 molecules. A significant feature of the high-pressure structures of SiH4(H2)2 is the dynamical behavior of the H2 molecules. It is found that H2 molecules are rotating in this pressure range whereas the SiH4 molecules remain rigid. The detailed nature of the interactions of molecular hydrogen with SiH4 in SiH4(H2)2 is therefore strongly influenced by the dynamical behavior of the H2 molecules in the high-pressure structure. The phase with the calculated structure is predicted to become metallic near 120 GPa, which is significantly lower than the currently suggested pressure for metallization of bulk molecular hydrogen. PMID:21078957

  20. Zero-Temperature Structures of Atomic Metallic Hydrogen

    NASA Astrophysics Data System (ADS)

    McMahon, Jeffrey; Ceperley, David

    2011-03-01

    Since the first prediction of an atomic metallic phase of hydrogen by Wigner and Huntington over 75 years ago, there have been many theoretical efforts aimed at determining the crystal structures of the zero-temperature phases. We present results from ab initio random structure searching with density functional theory performed to determine the ground state structures from 500 GPa to 5 TPa. We estimate that molecular hydrogen dissociates into a monatomic body-centered tetragonal structure near 500 GPa (rs = 1.225), which then remains stable to 2.5 TPa (rs = 0.969). At higher pressures, hydrogen stabilizes in an . . . ABCABC . . . planar structure that is remarkably similar to the ground state of lithium, which compresses to the face-centered cubic lattice beyond 5 TPa (rs < 0.86). Our results provide a complete ab initio description of the atomic metallic crystal structures of hydrogen, resolving one of the most fundamental and long outstanding issues concerning the structures of the elements.

  1. A van der Waals density functional theory comparison of metal decorated graphene systems for hydrogen adsorption

    NASA Astrophysics Data System (ADS)

    Wong, Janet; Yadav, Shwetank; Tam, Jasmine; Veer Singh, Chandra

    2014-06-01

    Previous Density Functional Theory (DFT) studies on metal decorated graphene generally use local density approximation (LDA) or generalized gradient approximation (GGA) functionals which can cause inaccuracies in hydrogen binding energies as they neglect van der Waals (vdW) interactions and are difficult to compare due to their widely varying simulation parameters. We investigated the hydrogen binding ability of several metals with a consistent set of simulations using the GGA functional and incorporated vdW forces through the vdW-DF2 functional. Metal adatom anchoring on graphene and hydrogen adsorption ability for both single and double sided decoration were studied for eight metals (Al, Li, Na, Ca, Cu, Ni, Pd, and Pt). It was found that the vdW correction can have a significant impact on both metal and hydrogen binding energies. The vdW-DF2 functional led to stronger metal adatom and hydrogen binding for light metals in comparison to GGA results, while heavier transition metals displayed the opposite behaviour but still produced stronger hydrogen binding energies than light metals. Nickel was found to be the best balance between hydrogen binding ability for reversible storage and low weight. The effects on hydrogen binding energy and maximum achievable hydrogen gravimetric density were analyzed for Ni-graphene systems with varying metal coverage. Lower metal coverage was found to improve hydrogen binding but decrease hydrogen gravimetric density. The highest achieved Ni-graphene system gravimetric density was 6.12 wt. %.

  2. Hydrogen and Dihydrogen Bonds in the Reactions of Metal Hydrides.

    PubMed

    Belkova, Natalia V; Epstein, Lina M; Filippov, Oleg A; Shubina, Elena S

    2016-08-10

    The dihydrogen bond-an interaction between a transition-metal or main-group hydride (M-H) and a protic hydrogen moiety (H-X)-is arguably the most intriguing type of hydrogen bond. It was discovered in the mid-1990s and has been intensively explored since then. Herein, we collate up-to-date experimental and computational studies of the structural, energetic, and spectroscopic parameters and natures of dihydrogen-bonded complexes of the form M-H···H-X, as such species are now known for a wide variety of hydrido compounds. Being a weak interaction, dihydrogen bonding entails the lengthening of the participating bonds as well as their polarization (repolarization) as a result of electron density redistribution. Thus, the formation of a dihydrogen bond allows for the activation of both the MH and XH bonds in one step, facilitating proton transfer and preparing these bonds for further transformations. The implications of dihydrogen bonding in different stoichiometric and catalytic reactions, such as hydrogen exchange, alcoholysis and aminolysis, hydrogen evolution, hydrogenation, and dehydrogenation, are discussed. PMID:27285818

  3. Predicted energy densitites for nickel-hydrogen and silver-hydrogen cells embodying metallic hydrides for hydrogen storage

    NASA Technical Reports Server (NTRS)

    Easter, R. W.

    1974-01-01

    Simplified design concepts were used to estimate gravimetric and volumetric energy densities for metal hydrogen battery cells for assessing the characteristics of cells containing metal hydrides as compared to gaseous storage cells, and for comparing nickel cathode and silver cathode systems. The silver cathode was found to yield superior energy densities in all cases considered. The inclusion of hydride forming materials yields cells with very high volumetric energy densities that also retain gravimetric energy densities nearly as high as those of gaseous storage cells.

  4. Magnetic Permeability Imaging of Metals with a Scanning Near-Field Microwave Microscope

    NASA Astrophysics Data System (ADS)

    Lee, Sheng-Chiang; Vlahacos, C. P.; Feenstra, B. J.; Schwartz, Andrew; Steinhauer, David; Wellstood, Fredrick; Anlage, Steven

    2001-03-01

    We extended the use of our scanning near-field microwave microscope to measure the local magnetic properties of metallic samples in a spatially-resolved manner. We use a small loop probe to detect magnetic perturbations in thin film and bulk samples. We demonstrate qualitative and quantitative understanding of permeability imaging through spatially-resolved ferromagnetic resonance experiments on a single crystal of the colossal magneto-resistive material La_0.8Sr_0.2MnO_3. The experimental results are well described by a simple model of the system. We also modified this microscope to image the ferromagnetic resonance field over a ferromagnetic sample in the presence of external magnetic field. The spatial resolution is on the order of the size of the loop, currently 200 μ m. Results demonstrating FMR imaging on La_0.8Sr_0.2MnO3 and amorphous magnetic tapes will be presented. Reference: S.C. Lee, C P. Vlahacos, B. J. Feenstra, Andrew Schwartz, D. E. Steinhauer, F. C. Wellstood, and Steve M. Anlage, Appl. Phys. Lett., December 18 (2000)

  5. Combining Nitrilotriacetic Acid and Permeable Barriers for Enhanced Phytoextraction of Heavy Metals from Municipal Solid Waste Compost by and Reduced Metal Leaching.

    PubMed

    Zhao, Shulan; Jia, Lina; Duo, Lian

    2016-05-01

    Phytoextraction has the potential to remove heavy metals from contaminated soil, and chelants can be used to improve the capabilities of phytoextraction. However, environmentally persistent chelants can cause metal leaching and groundwater pollution. A column experiment was conducted to evaluate the viability of biodegradable nitrilotriacetic acid (NTA) to increase the uptake of heavy metals (Cd, Cr, Ni, Pb, Cu, and Zn) by L. in municipal solid waste (MSW) compost and to evaluate the effect of two permeable barrier materials, bone meal and crab shell, on metal leaching. The application of NTA significantly increased the concentrations and uptake of heavy metals in . The enhancement was more pronounced at higher dosages of NTA. In the 15 mmol kg NTA treatment using a crab shell barrier, the Cr and Ni concentrations in the plant shoots increased by approximately 8- and 10-fold, respectively, relative to the control. However, the addition of NTA also caused significant heavy metal leaching from the MSW compost. Bone meal and crab shell barriers positioned between the compost and the subsoil were effective in preventing metal leaching down through the soil profile by the retention of metals in the barrier. The application of a biodegradable chelant and the use of permeable barriers is a viable form of enhanced phytoextraction to increase the removal of metals and to reduce possible leaching. PMID:27136160

  6. Combining Nitrilotriacetic Acid and Permeable Barriers for Enhanced Phytoextraction of Heavy Metals from Municipal Solid Waste Compost by and Reduced Metal Leaching.

    PubMed

    Zhao, Shulan; Jia, Lina; Duo, Lian

    2016-05-01

    Phytoextraction has the potential to remove heavy metals from contaminated soil, and chelants can be used to improve the capabilities of phytoextraction. However, environmentally persistent chelants can cause metal leaching and groundwater pollution. A column experiment was conducted to evaluate the viability of biodegradable nitrilotriacetic acid (NTA) to increase the uptake of heavy metals (Cd, Cr, Ni, Pb, Cu, and Zn) by L. in municipal solid waste (MSW) compost and to evaluate the effect of two permeable barrier materials, bone meal and crab shell, on metal leaching. The application of NTA significantly increased the concentrations and uptake of heavy metals in . The enhancement was more pronounced at higher dosages of NTA. In the 15 mmol kg NTA treatment using a crab shell barrier, the Cr and Ni concentrations in the plant shoots increased by approximately 8- and 10-fold, respectively, relative to the control. However, the addition of NTA also caused significant heavy metal leaching from the MSW compost. Bone meal and crab shell barriers positioned between the compost and the subsoil were effective in preventing metal leaching down through the soil profile by the retention of metals in the barrier. The application of a biodegradable chelant and the use of permeable barriers is a viable form of enhanced phytoextraction to increase the removal of metals and to reduce possible leaching.

  7. The solubility of hydrogen and deuterium in alloyed, unalloyed and impure plutonium metal

    SciTech Connect

    Richmond, Scott; Bridgewater, Jon S; Ward, John W; Allen, Thomas H

    2010-01-01

    Hydrogen is exothermically absorbed in many transition metals, all rare earths and the actinides. The hydrogen gas adsorbs, dissociates and diffuses into these metals as atomic hydrogen. Absorbed hydrogen is generally detrimental to Pu, altering its properties and greatly enhancing corrosion. Measuring the heat of solution of hydrogen in Pu and its alloys provides significant insight into the thermodynamics driving these changes. Hydrogen is present in all Pu metal unless great care is taken to avoid it. Heats of solution and formation are provided along with evidence for spinodal decomposition.

  8. Ternary Amides Containing Transition Metals for Hydrogen Storage: A Case Study with Alkali Metal Amidozincates.

    PubMed

    Cao, Hujun; Richter, Theresia M M; Pistidda, Claudio; Chaudhary, Anna-Lisa; Santoru, Antonio; Gizer, Gökhan; Niewa, Rainer; Chen, Ping; Klassen, Thomas; Dornheim, Martin

    2015-11-01

    The alkali metal amidozincates Li4 [Zn(NH2)4](NH2)2 and K2[Zn(NH2)4] were, to the best of our knowledge, studied for the first time as hydrogen storage media. Compared with the LiNH2-2 LiH system, both Li4 [Zn(NH2)4](NH2)2-12 LiH and K2[Zn(NH2)4]-8 LiH systems showed improved rehydrogenation performance, especially K2[Zn(NH2)4]-8 LiH, which can be fully hydrogenated within 30 s at approximately 230 °C. The absorption properties are stable upon cycling. This work shows that ternary amides containing transition metals have great potential as hydrogen storage materials.

  9. Transport properties of liquid metal hydrogen under high pressures

    NASA Technical Reports Server (NTRS)

    Brown, R. C.; March, N. H.

    1972-01-01

    A theory is developed for the compressibility and transport properties of liquid metallic hydrogen, near to its melting point and under high pressure. The interionic force law is assumed to be of the screened Coulomb type, because hydrogen has no core electrons. The random phase approximation is used to obtain the structure factor S(k) of the system in terms of the Fourier transform of this force law. The long wavelenth limit of the structure factor S(o) is related to the compressibility, which is much lower than that of alkali metals at their melting points. The diffusion constant at the melting point is obtained in terms of the Debye frequency, using a frequency spectrum analogous with the phonon spectrum of a solid. A similar argument is used to obtain the combined shear and bulk viscosities, but these depend also on S(o). The transport coefficients are found to be about the same size as those of alkali metals at their melting points.

  10. Hydrogen storage material and process using graphite additive with metal-doped complex hydrides

    DOEpatents

    Zidan, Ragaiy; Ritter, James A.; Ebner, Armin D.; Wang, Jun; Holland, Charles E.

    2008-06-10

    A hydrogen storage material having improved hydrogen absorbtion and desorption kinetics is provided by adding graphite to a complex hydride such as a metal-doped alanate, i.e., NaAlH.sub.4. The incorporation of graphite into the complex hydride significantly enhances the rate of hydrogen absorbtion and desorption and lowers the desorption temperature needed to release stored hydrogen.

  11. Phase separation of metallic hydrogen-helium alloys

    NASA Technical Reports Server (NTRS)

    Straus, D. M.; Ashcroft, N. W.; Beck, H.

    1976-01-01

    Calculations are presented for the thermodynamic functions and phase separation boundaries of solid metallic hydrogen helium alloys at temperatures between 0 K and 19,000 K and at pressures between 15 and 90 megabars. Expressions for the band structure energy of a randomly disordered alloy (including third order in the electron ion interaction) are derived and evaluated. Short and long range order are included by the quasi-chemical method, and lattice dynamics in the virtual crystal harmonic approximation. We conclude that at temperatures below 4,000 K there is complete phase separation of hydrogen helium alloys, and that a miscibility gap remains at the highest temperatures and pressures considered. The relevance of these results to models of the deep interior of Jupiter is briefly discussed.

  12. Capture of liquid hydrogen boiloff with metal hydride absorbers

    NASA Technical Reports Server (NTRS)

    Rosso, M. J.; Golben, P. M.

    1984-01-01

    A procedure which uses metal hydrides to capture some of this low pressure (,1 psig) hydrogen for subsequent reliquefaction is described. Of the five normally occurring sources of boil-off vapor the stream associated with the off-loading of liquid tankers during dewar refill was identified as the most cost effective and readily recoverable. The design, fabrication and testing of a proof-of-concept capture device, operating at a rate that is commensurate with the evolution of vapor by the target stream, is described. Liberation of the captured hydrogen gas at pressure .15 psig at normal temperatures (typical liquefier compressor suction pressure) are also demonstrated. A payback time of less than three years is projected.

  13. Metal hydride hydrogen compression: recent advances and future prospects

    NASA Astrophysics Data System (ADS)

    Yartys, Volodymyr A.; Lototskyy, Mykhaylo; Linkov, Vladimir; Grant, David; Stuart, Alastair; Eriksen, Jon; Denys, Roman; Bowman, Robert C.

    2016-04-01

    Metal hydride (MH) thermal sorption compression is one of the more important applications of the MHs. The present paper reviews recent advances in the field based on the analysis of the fundamental principles of this technology. The performances when boosting hydrogen pressure, along with two- and three-step compression units, are analyzed. The paper includes also a theoretical modelling of a two-stage compressor aimed at describing the performance of the experimentally studied systems, their optimization and design of more advanced MH compressors. Business developments in the field are reviewed for the Norwegian company HYSTORSYS AS and the South African Institute for Advanced Materials Chemistry. Finally, future prospects are outlined presenting the role of the MH compression in the overall development of the hydrogen-driven energy systems. The work is based on the analysis of the development of the technology in Europe, USA and South Africa.

  14. The transition to the metallic state in low density hydrogen.

    PubMed

    McMinis, Jeremy; Morales, Miguel A; Ceperley, David M; Kim, Jeongnim

    2015-11-21

    Solid atomic hydrogen is one of the simplest systems to undergo a metal-insulator transition. Near the transition, the electronic degrees of freedom become strongly correlated and their description provides a difficult challenge for theoretical methods. As a result, the order and density of the phase transition are still subject to debate. In this work, we use diffusion quantum Monte Carlo to benchmark the transition between paramagnetic and anti-ferromagnetic body centered cubic atomic hydrogen in its ground state. We locate the density of the transition by computing the equation of state for these two phases and identify the phase transition order by computing the band gap near the phase transition. These benchmark results show that the phase transition is continuous and occurs at a Wigner-Seitz radius of rs = 2.27(3) a0. We compare our results to previously reported density functional theory, Hedin's GW approximation, and dynamical mean field theory results. PMID:26590549

  15. Three Permeable Pavements Performances for Priority Metal Pollutants and Metals associated with Deicing Chemicals from Edison Parking Lot, NJ - abstract

    EPA Science Inventory

    The U.S. Environmental Protection Agency constructed a 4000-m2 parking lot in Edison, New Jersey in 2009. The parking lot is surfaced with three permeable pavements [permeable interlocking concrete pavers (PICP), pervious concrete (PC), and porous asphalt (PA)]. Samples of each p...

  16. Three Permeable Pavements Performances for Priority Metal Pollutants and Metals Associated with Deicing Chemicals from Edison Parking Lot, NJ

    EPA Science Inventory

    The U.S. Environmental Protection Agency constructed a 4000-m2 parking lot in Edison, New Jersey in 2009. The parking lot is surfaced with three permeable pavements [permeable interlocking concrete pavers (PICP), pervious concrete (PC), and porous asphalt (PA)]. Samples of each p...

  17. Catalytic arene hydrogenation using early transition metal hydride compounds. Progress report

    SciTech Connect

    Rothwell, I.P.

    1993-03-15

    Progress was achieved in four areas: development of surface supported Group 5 metal organometallic compounds for catalytic arene hydrogenation, isolation and reactivity of possible intermediates in catalytic arene hydrogenation, synthesis and characterization of new d{sup 0}-metal hydride compounds, and stoichiometric reactivity of d{sup 0} metal hydrido, aryloxide compounds. (DLC)

  18. Distinct metallization and atomization transitions in dense liquid hydrogen.

    PubMed

    Mazzola, Guglielmo; Sorella, Sandro

    2015-03-13

    We perform molecular dynamics simulations driven by accurate quantum Monte Carlo forces on dense liquid hydrogen. There is a recent report of a complete atomization transition between a mixed molecular-atomic liquid and a completely dissociated fluid in an almost unaccessible pressure range [Nat. Commun. 5, 3487 (2014)]. Here, instead, we identify a different transition between the fully molecular liquid and the mixed-atomic fluid at ∼400  GPa, i.e., in a much more interesting pressure range. We provide numerical evidence supporting the metallic behavior of this intermediate phase. Therefore, we predict that the metallization at finite temperature occurs in this partially dissociated molecular fluid, well before the complete atomization of the liquid. At high temperature this first-order transition becomes a crossover, in very good agreement with the experimental observation. Several systematic tests supporting the quality of our large scale calculations are also reported.

  19. Control of redox reactivity of flavin and pterin coenzymes by metal ion coordination and hydrogen bonding.

    PubMed

    Fukuzumi, Shunichi; Kojima, Takahiko

    2008-03-01

    The electron-transfer activities of flavin and pterin coenzymes can be fine-tuned by coordination of metal ions, protonation and hydrogen bonding. Formation of hydrogen bonds with a hydrogen-bond receptor in metal-flavin complexes is made possible depending on the type of coordination bond that can leave the hydrogen-bonding sites. The electron-transfer catalytic functions of flavin and pterin coenzymes are described by showing a number of examples of both thermal and photochemical redox reactions, which proceed by controlling the electron-transfer reactivity of coenzymes with metal ion binding, protonation and hydrogen bonding.

  20. Metal-Hydrogen Phase Diagrams in the Vicinity of Melting Temperatures

    SciTech Connect

    Shapovalov, V.I.

    1999-01-06

    Hydrogen-metal interaction phenomena belong to the most exciting challenges of today's physical metallurgy and physics of solids due to the uncommon behavior of hydrogen in condensed media and to the need for understanding hydrogen's strong negative impact on properties of some high-strength steels and.alloys. The paper cites and summarizes research data on fundamental thermodynamic characteristics of hydrogen in some metals that absorb it endothermally at elevated temperatures. For a number of metal-hydrogen systems, information on some phase diagrams previously not available to the English-speaking scientific community is presented.

  1. Performance study of a hydrogen powered metal hydride actuator

    NASA Astrophysics Data System (ADS)

    Mainul Hossain Bhuiya, Md; Kim, Kwang J.

    2016-04-01

    A thermally driven hydrogen powered actuator integrating metal hydride hydrogen storage reactor, which is compact, noiseless, and able to generate smooth actuation, is presented in this article. To test the plausibility of a thermally driven actuator, a conventional piston type actuator was integrated with LaNi5 based hydrogen storage system. Copper encapsulation followed by compaction of particles into pellets, were adopted to improve overall thermal conductivity of the reactor. The operation of the actuator was thoroughly investigated for an array of operating temperature ranges. Temperature swing of the hydride reactor triggering smooth and noiseless actuation over several operating temperature ranges were monitored for quantification of actuator efficiency. Overall, the actuator generated smooth and consistent strokes during repeated cycles of operation. The efficiency of the actuator was found to be as high as 13.36% for operating a temperature range of 20 °C-50 °C. Stress-strain characteristics, actuation hysteresis etc were studied experimentally. Comparison of stress-strain characteristics of the proposed actuator with traditional actuators, artificial muscles and so on was made. The study suggests that design modification and use of high pressure hydride may enhance the performance and broaden the application horizon of the proposed actuator in future.

  2. Molecular metal-Oxo catalysts for generating hydrogen from water

    SciTech Connect

    Long, Jeffrey R; Chang, Christopher J; Karunadasa, Hemamala I

    2015-02-24

    A composition of matter suitable for the generation of hydrogen from water is described, the positively charged cation of the composition having the general formula [(PY5W.sub.2)MO].sup.2+, wherein PY5W.sub.2 is (NC.sub.5XYZ)(NC.sub.5H.sub.4).sub.4C.sub.2W.sub.2, M is a transition metal, and W, X, Y, and Z can be H, R, a halide, CF.sub.3, or SiR.sub.3, where R can be an alkyl or aryl group. The two accompanying counter anions, in one embodiment, can be selected from the following Cl.sup.-, I.sup.-, PF.sub.6.sup.-, and CF.sub.3SO.sub.3.sup.-. In embodiments of the invention, water, such as tap water containing electrolyte or straight sea water can be subject to an electric potential of between 1.0 V and 1.4 V relative to the standard hydrogen electrode, which at pH 7 corresponds to an overpotential of 0.6 to 1.0 V, with the result being, among other things, the generation of hydrogen with an optimal turnover frequency of ca. 1.5 million mol H.sub.2/mol catalyst per h.

  3. Hydrogenated - Metal Oxide Nanohybrids: AN Inventiveness Plinth for Sensing Devices

    NASA Astrophysics Data System (ADS)

    Baraneedharan, P.; Ramaprabhu, S.

    Graphene- a two dimensional sheet of sp2 hybridized carbon atoms has been considered as promising materials in sensor design for detection of target molecule. Charge carriers in graphene obey linear dispersion relation and it behaves like mass less relativistic particles which act as base for enhanced electron transport. Thus the electrons move ballistically without scattering giving higher mobility even at room temperature. Further, the presence of oxygen containing functional group and crystal defects assisted via hydrogenation process take vital part in electrochemical adsorption of electro active species and catalyses the same. Though issues with selectivity, stability and sensitivity are limited for several nanostructured metal oxides sensing, the hybrid system started its effective role in design of sensing platform. Thus considering the potential important of hydrogenated graphene -metal oxide systems, a nanohybrid system is developed and its structural, morphological and optical properties were understood using respective characterization tool. Further, the prepared hybrid nanosystem used as a platform for bimolecule detection, where the sensor exhibits higher range of sensitivity and selectivity.

  4. Physics of Hydrogen Storage in Metal-Hydrides

    NASA Astrophysics Data System (ADS)

    Abdelfattah-Zidan, Ragaiy

    Physical aspects of the hydrogenation-dehydrogenation mechanisms of metal-metal hydride systems were examined. Experimental investigation was conducted for magnesium hydride as a case study. Theoretical analysis and computational study were carried out. The kinetics of hydrogenation-dehydrogenation of traditionally prepared Mg-MgH_2 and chemically synthesized Mg-MgH_2 were experimentally investigated. A detailed investigation was carried out to determine the reasons for the improved performance of a chemically synthesized Mg-MgH _2 previously reported by Bogdanovic and co-workers. A scanning electron microscope was used to examine the surface morphology of the samples. The surface of chemically prepared samples appeared to be covered with micro-spheroidal beads ranging in radius between 0.5 μm and 0.05 μm formed in a fractal-like configuration. Theoretical analysis indicated that the unusual surface structure of the chemically prepared samples could be responsible for the rapid uptake and release of hydrogen. The uptake and release enhancement is believed to be partially due to the substantial increase in the surface area and partially due fast diffusion into the smaller particles. The effect of the addition of nickel to the surface was also investigated. Theoretical analysis was carried out. Models for the process at the surface as well as in the bulk were developed. Diffusion equation was examined taking into account the diffusion coefficient being function of concentration. A non-linear differential equation resulted for this case. The differential equation was numerically solved.

  5. Synthesis of transition-metal phosphides from oxidic precursors by reduction in hydrogen plasma

    SciTech Connect

    Guan Jie; Wang Yao; Qin Minglei; Yang Ying; Li Xiang; Wang Anjie

    2009-06-15

    A series of transition metal phosphides, including MoP, WP, CoP, Co{sub 2}P, and Ni{sub 2}P, were synthesized from their oxidic precursors by means of hydrogen plasma reduction under mild conditions. The effects of reduction conditions, such as metal to phosphorus molar ratio, power input, and reduction time, on the synthesis of metal phosphides were investigated. The products were identified by means of XRD characterization. It is indicated that metal phosphides were readily synthesized stoichiometrically from their oxides in hydrogen plasma under mild conditions. - Graphical abstract: Metal phosphides were obtained stoichiometrically from their oxidic precursors by hydrogen plasma reaction under mild conditions.

  6. Theory of catalytic dissociation of hydrogen atoms on a metal surface

    SciTech Connect

    Konstantinov, O. V. Dymnikov, V. D.; Mittsev, M. A.

    2008-08-15

    The model of hydrogen atom ionization near a metal surface is discussed on the basis of a comparison between the metal work function and the atom ionization energy. In the theoretical calculation, it is shown that the hydrogen atom ionization energy decreases when the atom approaches the metal surface. The ionization energy vanishes when the distance between proton and the metal surface is somewhat less than the Bohr radius.

  7. Hydrogen Sensors Using Nitride-Based Semiconductor Diodes: The Role of Metal/Semiconductor Interfaces

    PubMed Central

    Irokawa, Yoshihiro

    2011-01-01

    In this paper, I review my recent results in investigating hydrogen sensors using nitride-based semiconductor diodes, focusing on the interaction mechanism of hydrogen with the devices. Firstly, effects of interfacial modification in the devices on hydrogen detection sensitivity are discussed. Surface defects of GaN under Schottky electrodes do not play a critical role in hydrogen sensing characteristics. However, dielectric layers inserted in metal/semiconductor interfaces are found to cause dramatic changes in hydrogen sensing performance, implying that chemical selectivity to hydrogen could be realized. The capacitance-voltage (C–V) characteristics reveal that the work function change in the Schottky metal is not responsible mechanism for hydrogen sensitivity. The interface between the metal and the semiconductor plays a critical role in the interaction of hydrogen with semiconductor devises. Secondly, low-frequency C–V characterization is employed to investigate the interaction mechanism of hydrogen with diodes. As a result, it is suggested that the formation of a metal/semiconductor interfacial polarization could be attributed to hydrogen-related dipoles. In addition, using low-frequency C–V characterization leads to clear detection of 100 ppm hydrogen even at room temperature where it is hard to detect hydrogen by using conventional current-voltage (I–V) characterization, suggesting that low-frequency C–V method would be effective in detecting very low hydrogen concentrations. PMID:22346597

  8. Hydrogen sensors using nitride-based semiconductor diodes: the role of metal/semiconductor interfaces.

    PubMed

    Irokawa, Yoshihiro

    2011-01-01

    In this paper, I review my recent results in investigating hydrogen sensors using nitride-based semiconductor diodes, focusing on the interaction mechanism of hydrogen with the devices. Firstly, effects of interfacial modification in the devices on hydrogen detection sensitivity are discussed. Surface defects of GaN under Schottky electrodes do not play a critical role in hydrogen sensing characteristics. However, dielectric layers inserted in metal/semiconductor interfaces are found to cause dramatic changes in hydrogen sensing performance, implying that chemical selectivity to hydrogen could be realized. The capacitance-voltage (C-V) characteristics reveal that the work function change in the Schottky metal is not responsible mechanism for hydrogen sensitivity. The interface between the metal and the semiconductor plays a critical role in the interaction of hydrogen with semiconductor devises. Secondly, low-frequency C-V characterization is employed to investigate the interaction mechanism of hydrogen with diodes. As a result, it is suggested that the formation of a metal/semiconductor interfacial polarization could be attributed to hydrogen-related dipoles. In addition, using low-frequency C-V characterization leads to clear detection of 100 ppm hydrogen even at room temperature where it is hard to detect hydrogen by using conventional current-voltage (I-V) characterization, suggesting that low-frequency C-V method would be effective in detecting very low hydrogen concentrations. PMID:22346597

  9. Surface studies of metals after interaction with hydrogen isotopes

    NASA Astrophysics Data System (ADS)

    Silver, David Samuel

    1998-12-01

    The objective of this research is to characterize surfaces of metals after interaction with hydrogen isotopes. Iron, which does not readily bond with hydrogen, and palladium, which strongly bonds with hydrogen, were studied. Observations of surfaces are used to determine the nature of their metamorphosis due to such exposures. An experimental study of pure iron foil (99.99%) exposed to a hot, dense hydrogen and argon gas mixture in a ballistic compressor yielded evidence for new structural and compositional changes of the metal due to the exposure. Atomic force microscope (AFM) studies demonstrated surfaces to be highly uneven, where height variations were often 2 mum for many micron-sized regions scanned. An iron foil exposed to argon gases alone revealed unique dendritic patterns but negligible height variations for micron-size scans. A cold rolled single crystal palladium cathode was electrolyzed in a solution of Dsb2O and 15% Hsb2SOsb4 by volume for 12 minutes. The cathode bent toward the anode during electrolysis. Examination of both concave and convex surfaces using the scanning electron microscope (SEM), scanning tunneling microscope (STM), and AFM revealed rimmed craters with faceted crystals inside and multi-textured surfaces. Also pairs of cold rolled polycrystalline palladium cathodes underwent electrolysis for six minutes or less, in Dsb2O and Hsb2O solutions, each solution containing 15% Hsb2SOsb4, by volume. Surface morphologies of the heavy water electrolyzed samples revealed asperities, craters, and nodules, and evidence of recrystallization and crystal planes. After 1.5 years, new AFM studies of the same Pd surfaces exposed to heavy water electrolyte exhibited loose, nanometer-sized particles. However, the surfaces of Pd cathodes exposed to light water electrolyte remained nearly identical to morphologies of foils not electrolyzed, and did not change with time. No surface asperities or loose grains were observed on the latter. Secondary ion mass

  10. Transport of hydrogen in metals with occupancy dependent trap energies

    SciTech Connect

    Schmid, K. Toussaint, U. von; Schwarz-Selinger, T.

    2014-10-07

    Common diffusion trapping models for modeling hydrogen transport in metals are limited to traps with single de-trapping energies and a saturation occupancy of one. While they are successful in predicting typical mono isotopic ion implantation and thermal degassing experiments, they fail at describing recent experiments on isotope exchange at low temperatures. This paper presents a new modified diffusion trapping model with fill level dependent de-trapping energies that can also explain these new isotope exchange experiments. Density function theory (DFT) calculations predict that even mono vacancies can store between 6 and 12 H atoms with de-trapping energies that depend on the fill level of the mono vacancy. The new fill level dependent diffusion trapping model allows to test these DFT results by bridging the gap in length and time scale between DFT calculations and experiment.

  11. Frustrated Lewis pairs: metal-free hydrogen activation and more.

    PubMed

    Stephan, Douglas W; Erker, Gerhard

    2010-01-01

    Sterically encumbered Lewis acid and Lewis base combinations do not undergo the ubiquitous neutralization reaction to form "classical" Lewis acid/Lewis base adducts. Rather, both the unquenched Lewis acidity and basicity of such sterically "frustrated Lewis pairs (FLPs)" is available to carry out unusual reactions. Typical examples of frustrated Lewis pairs are inter- or intramolecular combinations of bulky phosphines or amines with strongly electrophilic RB(C(6)F(5))(2) components. Many examples of such frustrated Lewis pairs are able to cleave dihydrogen heterolytically. The resulting H(+)/H(-) pairs (stabilized for example, in the form of the respective phosphonium cation/hydridoborate anion salts) serve as active metal-free catalysts for the hydrogenation of, for example, bulky imines, enamines, or enol ethers. Frustrated Lewis pairs also react with alkenes, aldehydes, and a variety of other small molecules, including carbon dioxide, in cooperative three-component reactions, offering new strategies for synthetic chemistry. PMID:20025001

  12. An electrochemical method for determining hydrogen concentrations in metals and some applications

    NASA Technical Reports Server (NTRS)

    Danford, M. D.

    1983-01-01

    An electrochemical method was developed for the determination of hydrogen in metals using the EG&G-PARC Model 350A Corrosion Measurement Console. The method was applied to hydrogen uptake, both during electrolysis and electroplating, and to studies of hydrogen elimination and the effect of heat treatment on elimination times. Results from these studies are presented.

  13. The transition to the metallic state in low density hydrogen

    SciTech Connect

    McMinis, Jeremy; Morales, Miguel A.; Ceperley, David M.; Kim, Jeongnim

    2015-11-21

    Solid atomic hydrogen is one of the simplest systems to undergo a metal-insulator transition. Near the transition, the electronic degrees of freedom become strongly correlated and their description provides a difficult challenge for theoretical methods. As a result, the order and density of the phase transition are still subject to debate. In this work, we use diffusion quantum Monte Carlo to benchmark the transition between paramagnetic and anti-ferromagnetic body centered cubic atomic hydrogen in its ground state. We locate the density of the transition by computing the equation of state for these two phases and identify the phase transition order by computing the band gap near the phase transition. These benchmark results show that the phase transition is continuous and occurs at a Wigner-Seitz radius of r{sub s} = 2.27(3) a{sub 0}. We compare our results to previously reported density functional theory, Hedin’s GW approximation, and dynamical mean field theory results.

  14. The transition to the metallic state in low density hydrogen

    DOE PAGESBeta

    McMinis, Jeremy; Morales, Miguel A.; Ceperley, David M.; Kim, Jeongnim

    2015-11-18

    Solid atomic hydrogen is one of the simplest systems to undergo a metal-insulator transition. Near the transition, the electronic degrees of freedom become strongly correlated and their description provides a difficult challenge for theoretical methods. As a result, the order and density of the phase transition are still subject to debate. In this work we use diffusion quantum Monte Carlo to benchmark the transition between the paramagnetic and anti-ferromagnetic phases of ground state body centered cubic atomic hydrogen. We locate the density of the transition by computing the equation of state for these two phases and identify the phase transitionmore » order by computing the band gap near the phase transition. These benchmark results show that the phase transition is continuous and occurs at a Wigner-Seitz radius of rs = 2.27(3)a0. As a result, we compare our results to previously reported density functional theory, Hedin s GW approximation, and dynamical mean field theory results.« less

  15. The transition to the metallic state in low density hydrogen

    SciTech Connect

    McMinis, Jeremy; Morales, Miguel A.; Ceperley, David M.; Kim, Jeongnim

    2015-11-18

    Solid atomic hydrogen is one of the simplest systems to undergo a metal-insulator transition. Near the transition, the electronic degrees of freedom become strongly correlated and their description provides a difficult challenge for theoretical methods. As a result, the order and density of the phase transition are still subject to debate. In this work we use diffusion quantum Monte Carlo to benchmark the transition between the paramagnetic and anti-ferromagnetic phases of ground state body centered cubic atomic hydrogen. We locate the density of the transition by computing the equation of state for these two phases and identify the phase transition order by computing the band gap near the phase transition. These benchmark results show that the phase transition is continuous and occurs at a Wigner-Seitz radius of rs = 2.27(3)a0. As a result, we compare our results to previously reported density functional theory, Hedin s GW approximation, and dynamical mean field theory results.

  16. Stainless Steel Permeability

    SciTech Connect

    Buchenauer, Dean A.; Karnesky, Richard A.

    2015-09-01

    An understanding of the behavior of hydrogen isotopes in materials is critical to predicting tritium transport in structural metals (at high pressure), estimating tritium losses during production (fission environment), and predicting in-vessel inventory for future fusion devices (plasma driven permeation). Current models often assume equilibrium diffusivity and solubility for a class of materials (e.g. stainless steels or aluminum alloys), neglecting trapping effects or, at best, considering a single population of trapping sites. Permeation and trapping studies of the particular castings and forgings enable greater confidence and reduced margins in the models. For FY15, we have continued our investigation of the role of ferrite in permeation for steels of interest to GTS, through measurements of the duplex steel 2507. We also initiated an investigation of the permeability in work hardened materials, to follow up on earlier observations of unusual permeability in a particular region of 304L forgings. Samples were prepared and characterized for ferrite content and coated with palladium to prevent oxidation. Issues with the poor reproducibility of measurements at low permeability were overcome, although the techniques in use are tedious. Funding through TPBAR and GTS were secured for a research grade quadrupole mass spectrometer (QMS) and replacement turbo pumps, which should improve the fidelity and throughput of measurements in FY16.

  17. New vistas in the determination of hydrogen in aerospace engine metal alloys

    NASA Technical Reports Server (NTRS)

    Danford, M. D.

    1986-01-01

    The application of diffusion theory to the analysis of hydrogen desorption data has been studied. From these analyses, important information concerning hydrogen solubilities and the nature of the hydrogen distributions in the metal has been obtained. Two nickel base alloys, Rene' 41 and Waspaloy, and one ferrous alloy, 4340 steel, were studied in this work. For the nickel base alloys, it was found that the hydrogen distributions after electrolytic charging conformed closely to those which would be predicted by diffusion theory. The hydrogen distributions in electrolytically charged 4340 steel, on the other hand, were essentially uniform in nature, which would not be predicted by diffusion theory. Finally, it has been found that the hydrogen desorption is completely explained by the nature of the hydrogen distribution in the metal, and that the 'fast' hydrogen is not due to surface and subsurface hydride formation, as was originally proposed.

  18. Hydrogen storage in Pd nanocrystals covered with a metal-organic framework

    NASA Astrophysics Data System (ADS)

    Li, Guangqin; Kobayashi, Hirokazu; Taylor, Jared M.; Ikeda, Ryuichi; Kubota, Yoshiki; Kato, Kenichi; Takata, Masaki; Yamamoto, Tomokazu; Toh, Shoichi; Matsumura, Syo; Kitagawa, Hiroshi

    2014-08-01

    Hydrogen is an essential component in many industrial processes. As a result of the recent increase in the development of shale gas, steam reforming of shale gas has received considerable attention as a major source of H2, and the more efficient use of hydrogen is strongly demanded. Palladium is well known as a hydrogen-storage metal and an effective catalyst for reactions related to hydrogen in a variety of industrial processes. Here, we present remarkably enhanced capacity and speed of hydrogen storage in Pd nanocrystals covered with the metal-organic framework (MOF) HKUST-1 (copper(II) 1,3,5-benzenetricarboxylate). The Pd nanocrystals covered with the MOF have twice the storage capacity of the bare Pd nanocrystals. The significantly enhanced hydrogen storage capacity was confirmed by hydrogen pressure-composition isotherms and solid-state deuterium nuclear magnetic resonance measurements. The speed of hydrogen absorption in the Pd nanocrystals is also enhanced by the MOF coating.

  19. Chemical bonding of hydrogen molecules to transition metal complexes

    SciTech Connect

    Kubas, G.J.

    1990-01-01

    The complex W(CO){sub 3}(PR{sub 3}){sub 2}(H{sub 2}) (CO = carbonyl; PR{sub 3} = organophosphine) was prepared and was found to be a stable crystalline solid under ambient conditions from which the hydrogen can be reversibly removed in vacuum or under an inert atmosphere. The weakly bonded H{sub 2} exchanges easily with D{sub 2}. This complex represents the first stable compound containing intermolecular interaction of a sigma-bond (H-H) with a metal. The primary interaction is reported to be donation of electron density from the H{sub 2} bonding electron pair to a vacant metal d-orbital. A series of complexes of molybdenum of the type Mo(CO)(H{sub 2})(R{sub 2}PCH{sub 2}CH{sub 2}PR{sub 2}){sub 2} were prepared by varying the organophosphine substitutent to demonstrate that it is possible to bond either dihydrogen or dihydride by adjusting the electron-donating properties of the co-ligands. Results of infrared and NMR spectroscopic studies are reported. 20 refs., 5 fig.

  20. Chemomechanical Origin of Hydrogen Trapping at Grain Boundaries in fcc Metals.

    PubMed

    Zhou, Xiao; Marchand, Daniel; McDowell, David L; Zhu, Ting; Song, Jun

    2016-02-19

    Hydrogen embrittlement of metals is widely observed, but its atomistic origins remain little understood and much debated. Combining a unique identification of interstitial sites through polyhedral tessellation and first-principles calculations, we study hydrogen adsorption at grain boundaries in a variety of face-centered cubic metals of Ni, Cu, γ-Fe, and Pd. We discover the chemomechanical origin of the variation of adsorption energetics for interstitial hydrogen at grain boundaries. A general chemomechanical formula is established to provide accurate assessments of hydrogen trapping and segregation energetics at grain boundaries, and it also offers direct explanations for certain experimental observations. The present study deepens our mechanistic understanding of the role of grain boundaries in hydrogen embrittlement and points to a viable path towards predictive microstructure engineering against hydrogen embrittlement in structural metals.

  1. Hydrogen absorption induced metal deposition on palladium and palladium-alloy particles

    DOEpatents

    Wang, Jia X.; Adzic, Radoslav R.

    2009-03-24

    The present invention relates to methods for producing metal-coated palladium or palladium-alloy particles. The method includes contacting hydrogen-absorbed palladium or palladium-alloy particles with one or more metal salts to produce a sub-monoatomic or monoatomic metal- or metal-alloy coating on the surface of the hydrogen-absorbed palladium or palladium-alloy particles. The invention also relates to methods for producing catalysts and methods for producing electrical energy using the metal-coated palladium or palladium-alloy particles of the present invention.

  2. Effect Of Water On Permeation By Hydrogen

    NASA Technical Reports Server (NTRS)

    Tomazic, William A.; Hulligan, David

    1988-01-01

    Water vapor in working fluid equilibrates with permeability-reducing oxides in metal parts. Report describes study of effects of water on permeation of heater-head tubes by hydrogen in Stirling engine. Experiments performed to determine minimum concentration of oxygen and/or oxygen-bearing gas maintaining oxide coverage adequate for low permeability. Tests showed 750 ppm or more of water effective in maintaining stable, low permeability.

  3. Miniaturized metal (metal alloy)/ PdO.sub.x/SiC hydrogen and hydrocarbon gas sensors

    NASA Technical Reports Server (NTRS)

    Hunter, Gary W. (Inventor); Xu, Jennifer C. (Inventor); Lukco, Dorothy (Inventor)

    2011-01-01

    A miniaturized Schottky diode hydrogen and hydrocarbon sensor and the method of making same is disclosed and claimed. The sensor comprises a catalytic metal layer, such as palladium, a silicon carbide substrate layer and a thin barrier layer in between the catalytic and substrate layers made of palladium oxide (PdO.sub.x ). This highly stable device provides sensitive gas detection at temperatures ranging from at least 450 to 600.degree. C. The barrier layer prevents reactions between the catalytic metal layer and the substrate layer. Conventional semiconductor fabrication techniques are used to fabricate the small-sized sensors. The use of a thicker palladium oxide barrier layer for other semiconductor structures such as a capacitor and transistor structures is also disclosed.

  4. Miniaturized Metal (Metal Alloy)/PdO(x)/SiC Hydrogen and Hydrocarbon Gas Sensors

    NASA Technical Reports Server (NTRS)

    Hunter, Gary W. (Inventor); Xu, Jennifer C. (Inventor); Lukco, Dorothy (Inventor)

    2008-01-01

    A miniaturized Schottky diode hydrogen and hydrocarbon sensor and the method of making same is disclosed and claimed. The sensor comprises a catalytic metal layer, such as palladium, a silicon carbide substrate layer and a thin barrier layer in between the catalytic and substrate layers made of palladium oxide (PdO(x)). This highly stable device provides sensitive gas detection at temperatures ranging from at least 450 to 600 C. The barrier layer prevents reactions between the catalytic metal layer and the substrate layer. Conventional semiconductor fabrication techniques are used to fabricate the small-sided sensors. The use of a thicker palladium oxide barrier layer for other semiconductor structures such as a capacitor and transistor structures is also disclosed.

  5. Miniaturized metal (metal alloy)/ PdO.sub.x/SiC hydrogen and hydrocarbon gas sensors

    NASA Technical Reports Server (NTRS)

    Hunter, Gary W. (Inventor); Xu, Jennifer C. (Inventor); Lukco, Dorothy (Inventor)

    2008-01-01

    A miniaturized Schottky diode hydrogen and hydrocarbon sensor and the method of making same is disclosed and claimed. The sensor comprises a catalytic metal layer, such as palladium, a silicon carbide substrate layer and a thin barrier layer in between the catalytic and substrate layers made of palladium oxide (PdO.sub.x). This highly stable device provides sensitive gas detection at temperatures ranging from at least 450 to 600.degree. C. The barrier layer prevents reactions between the catalytic metal layer and the substrate layer. Conventional semiconductor fabrication techniques are used to fabricate the small-sized sensors. The use of a thicker palladium oxide barrier layer for other semiconductor structures such as a capacitor and transistor structures is also disclosed.

  6. In-situ Hydrogen Sorption 2D-ACAR Facility for the Study of Metal Hydrides for Hydrogen Storage

    NASA Astrophysics Data System (ADS)

    Legerstee, W. J.; de Roode, J.; Anastasopol, A.; Falub, C. V.; Eijt, S. W. H.

    We developed a dedicated hydrogen sorption setup coupled to a positron 2D-ACAR (two-dimensional Angular Correlation of Annihilation Radiation) setup employing a 22Na-source, which will enable to collect 2D-ACAR momentum distributions in-situ as a function of temperature, hydrogen pressure and hydrogen content. In parallel, a dedicated glovebox was constructed for handling air-sensitive metal and metal hydride samples, with a special entrance for the 2D-ACAR sample insert. The 2D-ACAR setup was tested in first measurements on a Pd0.75Ag0.25 foil and on a ball-milled MgH2 powder in both the hydrogen loaded and desorbed states. The hydrogen loaded Pd0.75Ag0.25Hx sample was kept under a 1 bar hydrogen pressure to prevent partial desorption during measurements at room temperature. The collected 2D-ACAR distributions of Pd0.75Ag0.25 and Pd0.75Ag0.25Hx showed similar features as observed in previous studies. The broadening of the ACAR distributions observed for the Mg to MgH2 metal-insulator transition was compared in a quantitative manner to ab-initio calculations reported in the literature.

  7. Hydrogen Adsorption, Absorption and Diffusion on and in Transition Metal Surfaces: A DFT Study

    SciTech Connect

    Ferrin, Peter A.; Kandoi, Shampa; Nilekar, Anand U.; Mavrikakis, Manos

    2012-01-04

    Periodic, self-consistent DFT-GGA(PW91) calculations are used to study the interaction of hydrogen with different facets of seventeen transition metals—the (100) and (111) facets of face-centered cubic (fcc) metals, the (0001) facet of hexagonal-close packed (hcp) metals, and the (100) and (110) facets of body-centered cubic (bcc) metals. Calculated geometries and binding energies for surface and subsurface hydrogen are reported and are, in general, in good agreement with both previous modeling studies and experimental data. There are significant differences between the binding on the close-packed and more open (100) facets of the same metal. Geometries of subsurface hydrogen on different facets of the same metal are generally similar; however, binding energies of hydrogen in the subsurface of the different facets studied showed significant variation. Formation of surface hydrogen is exothermic with respect to gas-phase H₂ on all metals studied with the exception of Ag and Au. For each metal studied, hydrogen in its preferred subsurface state is always less stable than its preferred surface state. The magnitude of the activation energy for hydrogen diffusion from the surface layer into the first subsurface layer is dominated by the difference in the thermodynamic stability of these two states. Diffusion from the first subsurface layer to one layer further into the bulk does not generally have a large thermodynamic barrier but still has a moderate kinetic barrier. Despite the proximity to the metal surface, the activation energy for hydrogen diffusion from the first to the second subsurface layer is generally similar to experimentally-determined activation energies for bulk diffusion found in the literature. There are also some significant differences in the activation energy for hydrogen diffusion into the bulk through different facets of the same metal.

  8. Strain effects on hydrogen storage capability of metal-decorated graphene: A first-principles study

    NASA Astrophysics Data System (ADS)

    Zhou, Miao; Lu, Yunhao; Zhang, Chun; Feng, Yuan Ping

    2010-09-01

    We report an investigation on strain-engineered adsorption of metal atoms on graphene and hydrogen storage capabilities of metal-decorated graphene by using first-principles approach based on density functional theory. We show that an applied strain not only stabilizes the supported metal atoms and prevents them from clustering but further increases the hydrogen storage capacity. Specifically, a tensile strain of 10% in graphene increases the adsorption energy of Li (Ti) atom by around 75% (71%) and the gravimetric density of hydrogen storage up to 15.4 wt % (9.5 wt %), with a binding energy of ˜0.2 eV/H2.

  9. Heat energy from hydrogen-metal nuclear interactions

    NASA Astrophysics Data System (ADS)

    Hadjichristos, John; Gluck, Peter

    2013-11-01

    The discovery of the Fleischmann-Pons Effect in 1989, a promise of an abundant, cheap and clean energy source was premature in the sense that theoretical knowledge, relative technologies and the experimental tools necessary for understanding and for scale-up still were not available. Therefore the field, despite efforts and diversification remained quasi-stagnant, the effect (a scientific certainty) being of low intensity leading to mainstream science to reject the phenomenon and not supporting its study. Recently however, the situation has changed, a new paradigm is in statunascendi and the obstacles are systematically removed by innovative approaches. Defkalion, a Greek company (that recently moved in Canada for faster progress) has elaborated an original technology for the Ni-H system [1-3]. It is about the activation of hydrogen and creation of nuclear active nano-cavities in the metal through a multi-stage interaction, materializing some recent breakthrough announcements in nanotechnology, superconductivity, plasma physics, astrophysics and material science. A pre-industrial generator and a novel mass-spectrometry instrumentations were created. Simultaneously, a meta-theory of phenomena was sketched in collaboration with Prof. Y. Kim (Purdue U).

  10. Critical concentration for hydrogen bubble formation in metals.

    PubMed

    Sun, Lu; Jin, Shuo; Zhou, Hong-Bo; Zhang, Ying; Zhang, Wenqing; Ueda, Y; Lee, H T; Lu, Guang-Hong

    2014-10-01

    Employing a thermodynamic model with previously calculated first-principle energetics as inputs, we determined the hydrogen (H) concentration at the interstitial and monovacancy as well as its dependence on temperature and pressure in tungsten and molybdenum. Based on this, we predicted the critical H concentration for H bubble formation at different temperatures. The critical concentration, defined as the value when the concentration of H at a certain mH-vacancy complex first became equal to that of H at the interstitial, was 24 ppm/7.3 GPa and 410 ppm/4.7 GPa at 600 K in tungsten and molybdenum in the case of a monovacancy. Beyond the critical H concentration, numerous H atoms accumulated in the monovacancy, leading to the formation and rapid growth of H-vacancy complexes, which was considered the preliminary stage of H bubble formation. We expect that the proposed approach will be generally used to determine the critical H concentration for H bubble formation in metals.

  11. Oxidative Dissolution of Nickel Metal in Hydrogenated Hydrothermal Solutions

    SciTech Connect

    Ziemniak, S. E.; Guilmette, P. A.; Turcotte, R. A.; Tunison, H. M.

    2007-03-27

    A platinum-lined, flowing autoclave facility is used to investigate the solubility behavior of metallic nickel in hydrogenated ammonia and sodium hydroxide solutions between 175 and 315 C. The solubility measurements were interpreted by means of an oxidative dissolution reaction followed by a sequence of Ni(II) ion hydrolysis reactions: Ni(s) + 2H+(aq) = Ni2+(aq) + H2(g) and Ni{sup 2+}(aq) + nH{sub 2}O = Ni(OH){sub n}{sup 2-n}(aq) + nH{sup +}(aq) where n = 1 and 2. Gibbs energies associated with these reaction equilibria were determined from a least-squares analysis of the data. The extracted thermochemical properties ({Delta}fG{sup 0}, {Delta}fH{sup 0} and S{sup 0}) for Ni2{sup +}(aq), Ni(OH){sup +}(aq) and Ni(OH){sub 2}(aq) were found to be consistent with those determined in a previous solubility study of NiO/Ni(OH){sub 2} conducted in our laboratory. The thermodynamic basis of the Ni/NiO phase boundary in aqueous solutions is examined to show that Ni(s) is stable relative to NiO(s) in solutions saturated at 25 C with 1 atm H{sub 2} for temperatures below 309 C.

  12. Heat energy from hydrogen-metal nuclear interactions

    SciTech Connect

    Hadjichristos, John; Gluck, Peter

    2013-11-13

    The discovery of the Fleischmann-Pons Effect in 1989, a promise of an abundant, cheap and clean energy source was premature in the sense that theoretical knowledge, relative technologies and the experimental tools necessary for understanding and for scale-up still were not available. Therefore the field, despite efforts and diversification remained quasi-stagnant, the effect (a scientific certainty) being of low intensity leading to mainstream science to reject the phenomenon and not supporting its study. Recently however, the situation has changed, a new paradigm is in statunascendi and the obstacles are systematically removed by innovative approaches. Defkalion, a Greek company (that recently moved in Canada for faster progress) has elaborated an original technology for the Ni-H system [1-3]. It is about the activation of hydrogen and creation of nuclear active nano-cavities in the metal through a multi-stage interaction, materializing some recent breakthrough announcements in nanotechnology, superconductivity, plasma physics, astrophysics and material science. A pre-industrial generator and a novel mass-spectrometry instrumentations were created. Simultaneously, a meta-theory of phenomena was sketched in collaboration with Prof. Y. Kim (Purdue U)

  13. Hydrogen storage in the form of metal hydrides

    NASA Technical Reports Server (NTRS)

    Zwanziger, M. G.; Santana, C. C.; Santos, S. C.

    1984-01-01

    Reversible reactions between hydrogen and such materials as iron/titanium and magnesium/ nickel alloy may provide a means for storing hydrogen fuel. A demonstration model of an iron/titanium hydride storage bed is described. Hydrogen from the hydride storage bed powers a converted gasoline electric generator.

  14. Design of Hydrogen Storage Alloys/Nanoporous Metals Hybrid Electrodes for Nickel-Metal Hydride Batteries

    NASA Astrophysics Data System (ADS)

    Li, M. M.; Yang, C. C.; Wang, C. C.; Wen, Z.; Zhu, Y. F.; Zhao, M.; Li, J. C.; Zheng, W. T.; Lian, J. S.; Jiang, Q.

    2016-06-01

    Nickel metal hydride (Ni-MH) batteries have demonstrated key technology advantages for applications in new-energy vehicles, which play an important role in reducing greenhouse gas emissions and the world’s dependence on fossil fuels. However, the poor high-rate dischargeability of the negative electrode materials—hydrogen storage alloys (HSAs) limits applications of Ni-MH batteries in high-power fields due to large polarization. Here we design a hybrid electrode by integrating HSAs with a current collector of three-dimensional bicontinuous nanoporous Ni. The electrode shows enhanced high-rate dischargeability with the capacity retention rate reaching 44.6% at a discharge current density of 3000 mA g‑1, which is 2.4 times that of bare HSAs (18.8%). Such a unique hybrid architecture not only enhances charge transfer between nanoporous Ni and HSAs, but also facilitates rapid diffusion of hydrogen atoms in HSAs. The developed HSAs/nanoporous metals hybrid structures exhibit great potential to be candidates as electrodes in high-performance Ni-MH batteries towards applications in new-energy vehicles.

  15. Design of Hydrogen Storage Alloys/Nanoporous Metals Hybrid Electrodes for Nickel-Metal Hydride Batteries.

    PubMed

    Li, M M; Yang, C C; Wang, C C; Wen, Z; Zhu, Y F; Zhao, M; Li, J C; Zheng, W T; Lian, J S; Jiang, Q

    2016-01-01

    Nickel metal hydride (Ni-MH) batteries have demonstrated key technology advantages for applications in new-energy vehicles, which play an important role in reducing greenhouse gas emissions and the world's dependence on fossil fuels. However, the poor high-rate dischargeability of the negative electrode materials-hydrogen storage alloys (HSAs) limits applications of Ni-MH batteries in high-power fields due to large polarization. Here we design a hybrid electrode by integrating HSAs with a current collector of three-dimensional bicontinuous nanoporous Ni. The electrode shows enhanced high-rate dischargeability with the capacity retention rate reaching 44.6% at a discharge current density of 3000 mA g(-1), which is 2.4 times that of bare HSAs (18.8%). Such a unique hybrid architecture not only enhances charge transfer between nanoporous Ni and HSAs, but also facilitates rapid diffusion of hydrogen atoms in HSAs. The developed HSAs/nanoporous metals hybrid structures exhibit great potential to be candidates as electrodes in high-performance Ni-MH batteries towards applications in new-energy vehicles. PMID:27270184

  16. Design of Hydrogen Storage Alloys/Nanoporous Metals Hybrid Electrodes for Nickel-Metal Hydride Batteries

    PubMed Central

    Li, M. M.; Yang, C. C.; Wang, C. C.; Wen, Z.; Zhu, Y. F.; Zhao, M.; Li, J. C.; Zheng, W. T.; Lian, J. S.; Jiang, Q.

    2016-01-01

    Nickel metal hydride (Ni-MH) batteries have demonstrated key technology advantages for applications in new-energy vehicles, which play an important role in reducing greenhouse gas emissions and the world’s dependence on fossil fuels. However, the poor high-rate dischargeability of the negative electrode materials—hydrogen storage alloys (HSAs) limits applications of Ni-MH batteries in high-power fields due to large polarization. Here we design a hybrid electrode by integrating HSAs with a current collector of three-dimensional bicontinuous nanoporous Ni. The electrode shows enhanced high-rate dischargeability with the capacity retention rate reaching 44.6% at a discharge current density of 3000 mA g−1, which is 2.4 times that of bare HSAs (18.8%). Such a unique hybrid architecture not only enhances charge transfer between nanoporous Ni and HSAs, but also facilitates rapid diffusion of hydrogen atoms in HSAs. The developed HSAs/nanoporous metals hybrid structures exhibit great potential to be candidates as electrodes in high-performance Ni-MH batteries towards applications in new-energy vehicles. PMID:27270184

  17. Design of Hydrogen Storage Alloys/Nanoporous Metals Hybrid Electrodes for Nickel-Metal Hydride Batteries.

    PubMed

    Li, M M; Yang, C C; Wang, C C; Wen, Z; Zhu, Y F; Zhao, M; Li, J C; Zheng, W T; Lian, J S; Jiang, Q

    2016-06-07

    Nickel metal hydride (Ni-MH) batteries have demonstrated key technology advantages for applications in new-energy vehicles, which play an important role in reducing greenhouse gas emissions and the world's dependence on fossil fuels. However, the poor high-rate dischargeability of the negative electrode materials-hydrogen storage alloys (HSAs) limits applications of Ni-MH batteries in high-power fields due to large polarization. Here we design a hybrid electrode by integrating HSAs with a current collector of three-dimensional bicontinuous nanoporous Ni. The electrode shows enhanced high-rate dischargeability with the capacity retention rate reaching 44.6% at a discharge current density of 3000 mA g(-1), which is 2.4 times that of bare HSAs (18.8%). Such a unique hybrid architecture not only enhances charge transfer between nanoporous Ni and HSAs, but also facilitates rapid diffusion of hydrogen atoms in HSAs. The developed HSAs/nanoporous metals hybrid structures exhibit great potential to be candidates as electrodes in high-performance Ni-MH batteries towards applications in new-energy vehicles.

  18. Protective effects of hydrogen-rich medium on lipopolysaccharide-induced monocytic adhesion and vascular endothelial permeability through regulation of vascular endothelial cadherin.

    PubMed

    Yu, Y; Wang, W N; Han, H Z; Xie, K L; Wang, G L; Yu, Y H

    2015-06-11

    We observed the effect of hydrogen-rich medium on lipopolysaccharide (LPS)-induced human umbilical vein endothelial cells (HUVECs), hyaline leukocyte conglutination, and permeability of the endothelium. Endotheliocytes were inoculated on 6-well plates and randomly divided into 4 groups: control, H2, LPS, LPS+H2, H2, and LPS+H2 in saturated hydrogen-rich medium. We applied Wright's stain-ing to observe conglutination of hyaline leukocytes and HUVECs, flow cytometry to determine the content of vascular cell adhesion protein 1 (VCAM-1) and intercellular adhesion molecule 1 (ICAM-1), enzyme-linked immunosorbent assay to measure the E-selectin concentration in the cell liquor, the transendothelial electrical resistance (TEER) to test the permeability of endothelial cells, and Western blot and immunofluorescence to test the expression and distribution of vascular endothelial (VE)-cadherin. Compared with control cells, there was an increase in endothelium-hyaline leukocyte conglutination, a reduction in VCAM-1, ICAM-1, and E-selectin, and the TEER value increased obviously. Compared with LPS, there was an obvious reduction in the conglutination of LPS+H2 cells, a reduction in VCAM-1, ICAM-1, and E-selectin levels, and a reduction in the TEER-resistance value, while the expression of VE-cadherin increased. Fluorescence results showed that, compared with control cells, the VE-cadherin in LPS cells was in-complete at the cell joints. Compared with LPS cells, the VE-cadherin in LPS+H2 cells was even and complete at the cell joints. Liquid rich in hydrogen could reduce LPS-induced production of adhesion molecules and endothelium-hyaline leukocyte conglutination, and influence the expression and distribution of VE-cadherin to regulate the permeability of the endothelium.

  19. Optimization of neutron tomography for rapid hydrogen concentration inspection of metal castings

    SciTech Connect

    Gibbons, M. R., LLNL

    1998-02-03

    Hydrogen embrittlement describes a group of phenomena leading to the degradation of metal alloy properties. The hydrogen concentration in the alloy can be used as an indicator for the onset of embrittlement. A neutron tomography system has been optimized to perform nondestructive detection of hydrogen concentration in titanium aircraft engine compressor blades. Preprocessing of back projection images and postprocessing of tomographic reconstructions are used to achieve hydrogen concentration sensitivity below 200 ppm weight. This paper emphasizes the postprocessing techniques which allow automated reporting of hydrogen concentration.

  20. Polymerization Effect of Electrolytes on Hydrogen-Bonding Cryoprotectants: Ion–Dipole Interactions between Metal Ions and Glycerol

    PubMed Central

    2015-01-01

    Protectants which are cell membrane permeable, such as glycerol, have been used effectively in the cryopreservation field for a number of decades, for both slow cooling and vitrification applications. In the latter case, the glass transition temperature (Tg) of the vitrification composition is key to its application, dictating the ultimate storage conditions. It has been observed that the addition of some electrolytes to glycerol, such as MgCl2, could elevate the Tg of the mixture, thus potentially providing more storage condition flexibility. The microscopic mechanisms that give rise to the Tg-enhancing behavior of these electrolytes are not yet well understood. The current study focuses on molecular dynamics simulation of glycerol mixed with a variety of metal chlorides (i.e., NaCl, KCl, MgCl2, and CaCl2), covering a temperature range that spans both the liquid and glassy states. The characteristics of the ion–dipole interactions between metal cations and hydroxyl groups of glycerol were analyzed. The interruption of the original hydrogen-bonding network among glycerol molecules by the addition of ions was also investigated in the context of hydrogen-bonding quantity and lifetime. Divalent metal cations were found to significantly increase the Tg by strengthening the interacting network in the electrolyte/glycerol mixture via strong cation–dipole attractions. In contrast, monovalent cations increased the Tg insignificantly, as the cation–dipole attraction was only slightly stronger than the original hydrogen-bonding network among glycerol molecules. The precursor of crystallization of NaCl and KCl was also observed in these compositions, potentially contributing to weak Tg-enhancing ability. The Tg-enhancing mechanisms elucidated in this study suggest a structure-enhancing role for divalent ions that could be of benefit in the design of protective formulations for biopreservation purposes. PMID:25405831

  1. Influence of N deficiency and salinity on metal (Pb, Zn and Cu) accumulation and tolerance by Rhizophora stylosa in relation to root anatomy and permeability.

    PubMed

    Cheng, Hao; Wang, You-Shao; Ye, Zhi-Hong; Chen, Dan-Ting; Wang, Yu-Tu; Peng, Ya-Lan; Wang, Li-Ying

    2012-05-01

    Effects of N deficiency and salinity on root anatomy, permeability and metal (Pb, Zn and Cu) translocation and tolerance were investigated using mangrove seedlings of Rhizophora stylosa. The results showed that salt could directly reduce radial oxygen loss (ROL) by stimulation of lignification within exodermis. N deficiency, oppositely, would reduce lignification. Such an alteration in root permeability may also influence metal tolerance by plants. The data indicated that a moderate salinity could stimulate a lignified exodermis that delayed the entry of metals into the roots and thereby contributed to a higher metal tolerance, while N deficiency would aggravate metal toxicity. The results from sand pot trail further confirmed this issue. This study provides a barrier property of the exodermis in dealing with environments. The plasticity of root anatomy is likely an adaptive strategy to regulate the fluxes of gases, nutrients and toxins at root-soil interface. PMID:22361050

  2. Influence of N deficiency and salinity on metal (Pb, Zn and Cu) accumulation and tolerance by Rhizophora stylosa in relation to root anatomy and permeability.

    PubMed

    Cheng, Hao; Wang, You-Shao; Ye, Zhi-Hong; Chen, Dan-Ting; Wang, Yu-Tu; Peng, Ya-Lan; Wang, Li-Ying

    2012-05-01

    Effects of N deficiency and salinity on root anatomy, permeability and metal (Pb, Zn and Cu) translocation and tolerance were investigated using mangrove seedlings of Rhizophora stylosa. The results showed that salt could directly reduce radial oxygen loss (ROL) by stimulation of lignification within exodermis. N deficiency, oppositely, would reduce lignification. Such an alteration in root permeability may also influence metal tolerance by plants. The data indicated that a moderate salinity could stimulate a lignified exodermis that delayed the entry of metals into the roots and thereby contributed to a higher metal tolerance, while N deficiency would aggravate metal toxicity. The results from sand pot trail further confirmed this issue. This study provides a barrier property of the exodermis in dealing with environments. The plasticity of root anatomy is likely an adaptive strategy to regulate the fluxes of gases, nutrients and toxins at root-soil interface.

  3. Metal-activated histidine carbon donor hydrogen bonds contribute to metalloprotein folding and function.

    PubMed

    Schmiedekamp, Ann; Nanda, Vikas

    2009-07-01

    Carbon donor hydrogen bonds are typically weak interactions that contribute less than 2 kcal/mol, and provide only modest stabilization in proteins. One exception is the class of hydrogen bonds donated by heterocyclic side chain carbons. Histidine is capable of particularly strong interactions through the Cepsilon(1) and Cdelta(2) carbons when the imidazole is protonated or bound to metal. Given the frequent occurrence of metal-bound histidines in metalloproteins, we characterized the energies of these interactions through DFT calculations on model compounds. Imidazole-water hydrogen bonding could vary from -11.0 to -17.0 kcal/mol, depending on the metal identity and oxidation state. A geometric search of metalloprotein structures in the PDB identified a number of candidate His C-H...O hydrogen bonds which may be important for folding or function. DFT calculations on model complexes of superoxide reductase show a carbon donor hydrogen bond positioning a water molecule above the active site.

  4. A New Venue Toward Predicting the Role of Hydrogen Embrittlement on Metallic Materials

    NASA Astrophysics Data System (ADS)

    Bal, Burak; Sahin, Ibrahim; Uzun, Alper; Canadinc, Demircan

    2016-11-01

    This paper presents a new crystal plasticity formulation to predict the role of hydrogen embrittlement on the mechanical behavior of metallic materials. Specifically, a series of experiments were carried out to monitor the role of hydrogen interstitial content on the uniaxial tensile deformation response of iron alloyed with hydrogen, and the classical Voce hardening scheme was modified to account for the shear stresses imposed on arrested dislocations due to the surrounding hydrogen interstitials. The proposed set of physically grounded crystal plasticity formulations successfully predicted the deformation response of iron in the presence of different degrees of hydrogen embrittlement. Moreover, the combined experimental and modeling effort presented herein opens a new venue for predicting the alterations in the performance of metallic materials, where the hydrogen embrittlement is unavoidable.

  5. Metal-inorganic-organic matrices as efficient sorbents for hydrogen storage.

    PubMed

    Azzouz, Abdelkrim; Nousir, Saadia; Bouazizi, Nabil; Roy, René

    2015-03-01

    Stabilization of metal nanoparticles (MNPs) without re-aggregation is a major challenge. An unprecedented strategy is developed for achieving high dispersion of copper(0) or palladium(0) on montmorillonite-supported diethanolamine or thioglycerol. This results in novel metal-inorganic-organic matrices (MIOM) that readily capture hydrogen at ambient conditions, with easy release under air stream. Hydrogen retention appears to involve mainly physical interactions, slightly stronger on thioglycerol-based MIOM (S-MIOM). Thermal enhancement of desorption suggests also a contribution of chemical interactions. The increase of hydrogen uptake with prolonged contact times arises from diffusion hindrance, which appears to be beneficial by favoring hydrogen entrapment. Even with compact structures, MIOMs act as efficient sorbents with much higher efficiency factor (1.14-1.17 mmol H 2 m(-2)) than many other sophisticated adsorbents reported in the literature. This opens new prospects for hydrogen storage and potential applications in microfluidic hydrogenation reactions.

  6. Heavy metals removal and hydraulic performance in zero-valent iron/pumice permeable reactive barriers.

    PubMed

    Moraci, Nicola; Calabrò, Paolo S

    2010-11-01

    Long-term behaviour is a major issue related to the use of zero-valent iron (ZVI) in permeable reactive barriers for groundwater remediation; in fact, in several published cases the hydraulic conductivity and removal efficiency were progressively reduced during operation, potentially compromising the functionality of the barrier. To solve this problem, the use of granular mixtures of ZVI and natural pumice has recently been proposed. This paper reports the results of column tests using aqueous nickel and copper solutions of various concentrations. Three configurations of reactive material (ZVI only, granular mixture of ZVI and pumice, and pumice and ZVI in series) are discussed. The results clearly demonstrate that iron-pumice granular mixtures perform well both in terms of contaminant removal and in maintaining the long-term hydraulic conductivity. Comparison with previous reports concerning copper removal by ZVI/sand mixtures reveals higher performance in the case of ZVI/pumice.

  7. In situ Raman spectroscopy study of metal-enhanced hydrogenation and dehydrogenation of VO2.

    PubMed

    Wu, Hao; Fu, Qiang; Bao, Xinhe

    2016-11-01

    Vanadium dioxide (VO2) has a phase transition from insulator to metal at 340 K, and this transition can be strongly modified by hydrogenation. In this work, two dimensional (2D) VO2 sheets have been grown on Si(1 1 1) surfaces through chemical vapor deposition, and metal (Au, Pt) thin films were deposited on VO2 surfaces by sputtering. The hydrogenation and dehydrogenation of VO2 and metal-decorated VO2 structures in H2 and in air were in situ studied by Raman. We found that hydrogenation and dehydrogenation temperatures have been significantly decreased with the VO2 surface decorated by Au and Pt. The enhanced hydrogenation and dehydrogenation reactions can be attributed to catalytic dissociation of H2 and O2 molecules on metal surfaces and subsequent spillover of dissociated H and O atoms to the oxide surfaces. PMID:27603090

  8. In situ Raman spectroscopy study of metal-enhanced hydrogenation and dehydrogenation of VO2

    NASA Astrophysics Data System (ADS)

    Wu, Hao; Fu, Qiang; Bao, Xinhe

    2016-11-01

    Vanadium dioxide (VO2) has a phase transition from insulator to metal at 340 K, and this transition can be strongly modified by hydrogenation. In this work, two dimensional (2D) VO2 sheets have been grown on Si(1 1 1) surfaces through chemical vapor deposition, and metal (Au, Pt) thin films were deposited on VO2 surfaces by sputtering. The hydrogenation and dehydrogenation of VO2 and metal-decorated VO2 structures in H2 and in air were in situ studied by Raman. We found that hydrogenation and dehydrogenation temperatures have been significantly decreased with the VO2 surface decorated by Au and Pt. The enhanced hydrogenation and dehydrogenation reactions can be attributed to catalytic dissociation of H2 and O2 molecules on metal surfaces and subsequent spillover of dissociated H and O atoms to the oxide surfaces.

  9. Highly mobile and reactive state of hydrogen in metal oxide semiconductors at room temperature.

    PubMed

    Chen, Wan Ping; He, Ke Feng; Wang, Yu; Chan, Helen Lai Wah; Yan, Zijie

    2013-01-01

    Hydrogen in metal oxides usually strongly associates with a neighboring oxygen ion through an O-H bond and thus displays a high stability. Here we report a novel state of hydrogen with unusually high mobility and reactivity in metal oxides at room temperature. We show that freshly doped hydrogen in Nb₂O₅ and WO₃ polycrystals via electrochemical hydrogenation can reduce Cu²⁺ ions into Cu⁰ if the polycrystals are immersed in a CuSO₄ solution, while this would not happen if the hydrogenated polycrystals have been placed in air for several hours before the immersion. Time-dependent studies of electrochemically hydrogenated rutile single crystals reveal two distinct states of hydrogen: one as protons covalently bonded to oxygen ions, while the other one is highly unstable with a lifetime of just a few hours. Observation of this mobile and reactive state of hydrogen will provide new insight into numerous moderate and low temperature interactions between metal oxides and hydrogen.

  10. Highly mobile and reactive state of hydrogen in metal oxide semiconductors at room temperature

    NASA Astrophysics Data System (ADS)

    Chen, Wan Ping; He, Ke Feng; Wang, Yu; Chan, Helen Lai Wah; Yan, Zijie

    2013-11-01

    Hydrogen in metal oxides usually strongly associates with a neighboring oxygen ion through an O-H bond and thus displays a high stability. Here we report a novel state of hydrogen with unusually high mobility and reactivity in metal oxides at room temperature. We show that freshly doped hydrogen in Nb2O5 and WO3 polycrystals via electrochemical hydrogenation can reduce Cu2+ ions into Cu0 if the polycrystals are immersed in a CuSO4 solution, while this would not happen if the hydrogenated polycrystals have been placed in air for several hours before the immersion. Time-dependent studies of electrochemically hydrogenated rutile single crystals reveal two distinct states of hydrogen: one as protons covalently bonded to oxygen ions, while the other one is highly unstable with a lifetime of just a few hours. Observation of this mobile and reactive state of hydrogen will provide new insight into numerous moderate and low temperature interactions between metal oxides and hydrogen.

  11. Oxidation by hydrogen in the chemistry and physics of the rare-earth metals.

    PubMed

    Simon, Arndt

    2012-04-27

    Rare-earth metals (RE) easily react with hydrogen. For decades the bonding of hydrogen has been discussed controversially in terms of either the "proton model" or the "anion model". Detailed investigations of metal-rich compounds of the rare-earth metals provide clear evidence for the incorporation of hydrogen as a hydride anion. Several categories of compounds can be distinguished regarding their behavior towards hydrogen. Low-valence compounds with metal-metal bonding frequently provide their excess electrons to form hydride ions as found with the halide hydrides REXH(n). However, there are exceptions, such as, LaI which does not react with hydrogen as a result of special electronic and electrostatic conditions. The opposite is true with La(2)C(3) although this compound does not provide excess metal valence electrons. An amorphous phase La(2)C(3)H(1.5) forms at very low temperature, around 450 K. The presence of hydrogen strongly influences the electrical and magnetic properties, for example, spin-glass formation and colossal magneto resistance arising in the presence of 4f(n) cores with the lanthanoid elements.

  12. A metal-free strategy to release chemisorbed H2 from hydrogenated boron nitride nanotubes.

    PubMed

    Roy, Lisa; Bhunya, Sourav; Paul, Ankan

    2014-11-10

    Chemisorbed hydrogen on boron nitride nanotubes (BNNT) can only be released thermally at very high temperatures above 350 °C. However, no catalyst has been identified that could liberate H2 from hydrogenated BN nanotubes under moderate conditions. Using different density functional methods we predict that the desorption of chemisorbed hydrogen from hydrogenated BN nanotubes can be facilitated catalytically by triflic acid at low free-energy activation barriers and appreciable rates under metal free conditions and mildly elevated temperatures (40-50 °C). Our proposed mechanism shows that the acid is regenerated in the process and can further facilitate similar catalytic release of H2 , thus suggesting all the chemisorbed hydrogen on the surface of the hydrogenated nanotube can be released in the form of H2 . These findings essentially raise hope for the development of a sustainable chemical hydrogen storage strategy in BN nanomaterials. PMID:25132421

  13. Enhanced chitosan beads-supported Fe(0)-nanoparticles for removal of heavy metals from electroplating wastewater in permeable reactive barriers.

    PubMed

    Liu, Tingyi; Yang, Xi; Wang, Zhong-Liang; Yan, Xiaoxing

    2013-11-01

    The removal of heavy metals from electroplating wastewater is a matter of paramount importance due to their high toxicity causing major environmental pollution problems. Nanoscale zero-valent iron (NZVI) became more effective to remove heavy metals from electroplating wastewater when enhanced chitosan (CS) beads were introduced as a support material in permeable reactive barriers (PRBs). The removal rate of Cr (VI) decreased with an increase of pH and initial Cr (VI) concentration. However, the removal rates of Cu (II), Cd (II) and Pb (II) increased with an increase of pH while decreased with an increase of their initial concentrations. The initial concentrations of heavy metals showed an effect on their removal sequence. Scanning electron microscope images showed that CS-NZVI beads enhanced by ethylene glycol diglycidyl ether (EGDE) had a loose and porous surface with a nucleus-shell structure. The pore size of the nucleus ranged from 19.2 to 138.6 μm with an average aperture size of around 58.6 μm. The shell showed a tube structure and electroplating wastewaters may reach NZVI through these tubes. X-ray photoelectron spectroscope (XPS) demonstrated that the reduction of Cr (VI) to Cr (III) was complete in less than 2 h. Cu (II) and Pb (II) were removed via predominant reduction and auxiliary adsorption. However, main adsorption and auxiliary reduction worked for the removal of Cd (II). The removal rate of total Cr, Cu (II), Cd (II) and Pb (II) from actual electroplating wastewater was 89.4%, 98.9%, 94.9% and 99.4%, respectively. The findings revealed that EGDE-CS-NZVI-beads PRBs had the capacity to remediate actual electroplating wastewater and may become an effective and promising technology for in situ remediation of heavy metals.

  14. Improved retort for cleaning metal powders with hydrogen

    NASA Technical Reports Server (NTRS)

    Arias, A.

    1969-01-01

    Improved cleaning retort produces uniform temperature distribution in the heated zone and minimizes hydrogen channeling through the powder bed. Retort can be used for nonmetallic powders, sintering in a reducing atmosphere, and for cleaning powders in reduction atmospheres other than hydrogen.

  15. Hydrogen storage materials: room-temperature wet-chemistry approach toward mixed-metal borohydrides.

    PubMed

    Jaroń, Tomasz; Orłowski, Piotr A; Wegner, Wojciech; Fijałkowski, Karol J; Leszczyński, Piotr J; Grochala, Wojciech

    2015-01-19

    The poor kinetics of hydrogen evolution and the irreversibility of the hydrogen discharge hamper the use of transition metal borohydrides as hydrogen storage materials, and the drawbacks of current synthetic methods obstruct the exploration of these systems. A wet-chemistry approach, which is based on solvent-mediated metathesis reactions of precursors containing bulky organic cations and weakly coordinating anions, leads to mixed-metal borohydrides that contain only a small amount of "dead mass". The applicability of this method is exemplified by Li[Zn2(BH4)5] and M[Zn(BH4)3] salts (M=Na, K), and its extension to other systems is discussed.

  16. Transition-metal-catalyzed hydrogen-transfer annulations: access to heterocyclic scaffolds.

    PubMed

    Nandakumar, Avanashiappan; Midya, Siba Prasad; Landge, Vinod Gokulkrishna; Balaraman, Ekambaram

    2015-09-14

    The ability of hydrogen-transfer transition-metal catalysts, which enable increasingly rapid access to important structural scaffolds from simple starting materials, has led to a plethora of research efforts on the construction of heterocyclic scaffolds. Transition-metal-catalyzed hydrogen-transfer annulations are environmentally benign and highly atom-economical as they release of water and hydrogen as by-product and utilize renewable feedstock alcohols as starting materials. Recent advances in this field with respect to the annulations of alcohols with various nucleophilic partners, thus leading to the formation of heterocyclic scaffolds, are highlighted herein.

  17. Catalytic hydrogenation using complexes of base metals with tridentate ligands

    DOEpatents

    Vasudevan, Kalyan V.; Zhang, Guoqi; Hanson, Susan K.

    2016-09-06

    Complexes of cobalt and nickel with tridentate ligand PNHP.sup.R are effective for hydrogenation of unsaturated compounds. Cobalt complex [(PNHP.sup.Cy)Co(CH.sub.2SiMe.sub.3)]BAr.sup.F.sub.4 (PNHP.sup.Cy=bis[2-(dicyclohexylphosphino)ethyl]amine, BAr.sup.F.sub.4=B(3,5-(CF.sub.3).sub.2C.sub.6H.sub.3).sub.4)) was prepared and used with hydrogen for hydrogenation of alkenes, aldehydes, ketones, and imines under mild conditions (25-60.degree. C., 1-4 atm H.sub.2). Nickel complex [(PNHP.sup.Cy)Ni(H)]BPh.sub.4 was used for hydrogenation of styrene and 1-octene under mild conditions. (PNP.sup.Cy)Ni(H) was used for hydrogenating alkenes.

  18. Hydrogen generation using silicon nanoparticles and their mixtures with alkali metal hydrides

    NASA Astrophysics Data System (ADS)

    Patki, Gauri Dilip

    mole of Si. We compare our silicon nanoparticles (˜10nm diameter) with commercial silicon nanopowder (<100nm diameter) and ball-milled silicon powder (325 mesh). The increase in rate upon decreasing the particle size to 10 nm was even greater than would be expected based upon the increase in surface area. While specific surface area increased by a factor of 6 in going from <100 nm to ˜10 nm particles, the hydrogen production rate increased by a factor of 150. However, in all cases, silicon requires a base (e.g. NaOH, KOH, hydrazine) to catalyze its reaction with water. Metal hydrides are also promising hydrogen storage materials. The optimum metal hydride would possess high hydrogen storage density at moderate temperature and pressure, release hydrogen safely and controllably, and be stable in air. Alkali metal hydrides have high hydrogen storage density, but exhibit high uncontrollable reactivity with water. In an attempt to control this explosive nature while maintaining high storage capacity, we mixed our silicon nanoparticles with the hydrides. This has dual benefits: (1) the hydride- water reaction produces the alkali hydroxide needed for base-catalyzed silicon oxidation, and (2) dilution with 10nm coating by, the silicon may temper the reactivity of the hydride, making the process more controllable. Initially, we analyzed hydrolysis of pure alkali metal hydrides and alkaline earth metal hydrides. Lithium hydride has particularly high hydrogen gravimetric density, along with faster reaction kinetics than sodium hydride or magnesium hydride. On analysis of hydrogen production we found higher hydrogen yield from the silicon nanoparticle—metal hydride mixture than from pure hydride hydrolysis. The silicon-hydride mixtures using our 10nm silicon nanoparticles produced high hydrogen yield, exceeding the theoretical yield. Some evidence of slowing of the hydride reaction rate upon addition of silicon nanoparticles was observed.

  19. Sub-Nanostructured Non Transition Metal Complex Grids for Hydrogen Storage

    SciTech Connect

    Dr. Orhan Talu; Dr. Surendra N. Tewari

    2007-10-27

    This project involved growing sub-nanostructured metal grids to increase dynamic hydrogen storage capacity of metal hydride systems. The nano particles of any material have unique properties unlike its bulk form. Nano-structuring metal hydride materials can result in: {sm_bullet}Increased hydrogen molecule dissociation rate, {sm_bullet} Increased hydrogen atom transport rate, {sm_bullet} Decreased decrepitation caused by cycling, {sm_bullet} Increased energy transfer in the metal matrix, {sm_bullet} Possible additional contribution by physical adsorption, and {sm_bullet} Possible additional contribution by quantum effects The project succeeded in making nano-structured palladium using electrochemical growth in templates including zeolites, mesoporous silica, polycarbonate films and anodized alumina. Other metals were used to fine-tune the synthesis procedures. Palladium was chosen to demonstrate the effects of nano-structuring since its bulk hydrogen storage capacity and kinetics are well known. Reduced project funding was not sufficient for complete characterization of these materials for hydrogen storage application. The project team intends to seek further funding in the future to complete the characterization of these materials for hydrogen storage.

  20. Enviro-Friendly Hydrogen Generation from Steel Mill-Scale via Metal-Steam Reforming

    ERIC Educational Resources Information Center

    Azad, Abdul-Majeed; Kesavan, Sathees

    2006-01-01

    An economically viable and environmental friendly method of generating hydrogen for fuel cells is by the reaction of certain metals with steam, called metal-steam reforming (MSR). This technique does not generate any toxic by-products nor contributes to the undesirable greenhouse effect. From the standpoint of favorable thermodynamics, total…

  1. Aqueous-phase hydrogenation of acetic acid over transition metal catalysts

    SciTech Connect

    Olcay, Hakan; Xu, Lijun; Xu, Ye; Huber, George

    2010-01-01

    Catalytic hydrogenation of acetic acid to ethanol has been carried out in aqueous phase on several metals, with ruthenium being the most active and selective. DFT calculations suggest that the initial CO bond scission yielding acetyl is the key step and that the intrinsic reactivity of the metals accounts for the observed activity.

  2. Determination of the Molar Volume of Hydrogen from the Metal-Acid Reaction: An Experimental Alternative.

    ERIC Educational Resources Information Center

    de Berg, Kevin; Chapman, Ken

    1996-01-01

    Describes an alternative technique for determining the molar volume of hydrogen from the metal-acid reaction in which the metal sample is encased in a specially prepared cage and a pipette filler is used to fill an inverted burette with water. Eliminates some difficulties encountered with the conventional technique. (JRH)

  3. In situ study of the initiation of hydrogen bubbles at the aluminium metal/oxide interface.

    PubMed

    Xie, De-Gang; Wang, Zhang-Jie; Sun, Jun; Li, Ju; Ma, Evan; Shan, Zhi-Wei

    2015-09-01

    The presence of excess hydrogen at the interface between a metal substrate and a protective oxide can cause blistering and spallation of the scale. However, it remains unclear how nanoscale bubbles manage to reach the critical size in the first place. Here, we perform in situ environmental transmission electron microscopy experiments of the aluminium metal/oxide interface under hydrogen exposure. It is found that once the interface is weakened by hydrogen segregation, surface diffusion of Al atoms initiates the formation of faceted cavities on the metal side, driven by Wulff reconstruction. The morphology and growth rate of these cavities are highly sensitive to the crystallographic orientation of the aluminium substrate. Once the cavities grow to a critical size, the internal gas pressure can become great enough to blister the oxide layer. Our findings have implications for understanding hydrogen damage of interfaces.

  4. In situ study of the initiation of hydrogen bubbles at the aluminium metal/oxide interface

    NASA Astrophysics Data System (ADS)

    Xie, De-Gang; Wang, Zhang-Jie; Sun, Jun; Li, Ju; Ma, Evan; Shan, Zhi-Wei

    2015-09-01

    The presence of excess hydrogen at the interface between a metal substrate and a protective oxide can cause blistering and spallation of the scale. However, it remains unclear how nanoscale bubbles manage to reach the critical size in the first place. Here, we perform in situ environmental transmission electron microscopy experiments of the aluminium metal/oxide interface under hydrogen exposure. It is found that once the interface is weakened by hydrogen segregation, surface diffusion of Al atoms initiates the formation of faceted cavities on the metal side, driven by Wulff reconstruction. The morphology and growth rate of these cavities are highly sensitive to the crystallographic orientation of the aluminium substrate. Once the cavities grow to a critical size, the internal gas pressure can become great enough to blister the oxide layer. Our findings have implications for understanding hydrogen damage of interfaces.

  5. Change in soft magnetic properties of Fe-based metallic glasses during hydrogen absorption and desorption

    SciTech Connect

    Novak, L.; Lovas, A.; Kiss, L.F.

    2005-08-15

    The stress level can be altered in soft magnetic amorphous alloys by hydrogen absorption. The resulting changes in the soft magnetic parameters are reversible or irreversible, depending on the chemical composition. Some of these effects are demonstrated in Fe-B, Fe-W-B, and Fe-V-B glassy ribbons, in which various magnetic parameters are measured mainly during hydrogen desorption. The rate of hydrogen desorption is also monitored by measuring the pressure change in a hermetically closed bomb. The observed phenomena are interpreted on the basis of induced stresses and chemical interactions between the solute metal and hydrogen.

  6. High-pressure chemistry of hydrogen in metals: in situ study of iron hydride.

    PubMed

    Badding, J V; Hemley, R J; Mao, H K

    1991-07-26

    Optical observations and x-ray diffraction measurements of the reaction between iron and hydrogen at high pressure to form iron hydride are described. The reaction is associated with a sudden pressure-induced expansion at 3.5 gigapascals of iron samples immersed in fluid hydrogen. Synchrotron x-ray diffraction measurements carried out to 62 gigapascals demonstrate that iron hydride has a double hexagonal close-packed structure, a cell volume up to 17% larger than pure iron, and a stoichiometry close to FeH. These results greatly extend the pressure range over which the technologically important iron-hydrogen phase diagram has been characterized and have implications for problems ranging from hydrogen degradation and embrittlement of ferrous metals to the presence of hydrogen in Earth's metallic core.

  7. Hot hydrogen testing of metallic turbo pump materials

    NASA Technical Reports Server (NTRS)

    Zee, Ralph; Chin, Bryan; Inamdar, Rohit

    1993-01-01

    The objectives of this investigation are to expose heat resistant alloys to hydrogen at elevated temperatures and to use various microstructural and analytical techniques to determine the chemical and rate process involved in degradation of these materials due to hydrogen environment. Inconel 718 and NASA-23 (wrought and cast) are candidate materials. The degradation of these materials in the presence of 1 to 5 atmospheric pressure of hydrogen from 450 C to 1100 C was examined. The hydrogen facility at Auburn University was used for this purpose. Control experiments were also conducted wherein the samples were exposed to vacuum so that a direct comparison of the results would separate the thermal contribution from the hydrogen effects. The samples were analyzed prior to and after exposure. A residual gas collection system was used to determine the gaseous species produced by any chemical reaction that may have occurred during the exposure. Analysis of this gas sample shows only the presence of H2 as expected. Analyses of the samples were conducted using optical microscopy, x-ray diffraction, scanning electron microscopy, and weight change. There appears to be no change in weight of the samples as a result of hydrogen exposure. In addition no visible change on the surface structure was detected. This indicates that the materials of interest do not have strong interaction with hot hydrogen. This is consistent with the microstructure results.

  8. Membrane permeability of redox active metal chelators: an important element in reducing hydroxyl radical induced NAD+ depletion in neuronal cells.

    PubMed

    Jayasena, T; Grant, R S; Keerthisinghe, N; Solaja, I; Smythe, G A

    2007-03-01

    There is substantial evidence implicating increased production of the hydroxyl radical and oxidative stress in the pathogenesis of neurodegenerative diseases such as Alzheimer's disease (AD). Significant amounts of hydroxyl radicals will be produced in the presence of hydrogen peroxide and redox active iron via Fenton chemistry. Increased iron levels within the cytoplasm of vulnerable neurons suggest that this may also be an important site of oxidative activity. We investigated the likelihood that intracellular, rather than extracellular chelation of ferrous or ferric iron may be more effective in reducing hydroxyl radical induced cell damage and preserving NAD(+) levels and cell viability. Using intracellular NAD(H) measurements as an indicator of cell viability we found that membrane permeable ferrous chelators were most efficient in preserving cellular NAD(+) levels. Hydrophilic, ferrous or ferric chelators and lipophilic ferric chelators were essentially ineffective in preventing cellular NAD(+) depletion when added at physiological concentrations. We propose that lipophilic ferrous chelators, due to their actions inside the cell, are effective agents for moderating neuronal damage in conditions such as AD where intracellular oxidative stress plays a significant role in disease pathology. PMID:17210195

  9. Synchrotron radiation photoemission study of metal overlayers on hydrogenated amorphous silicon at room temperature

    SciTech Connect

    Pi, J.

    1990-09-21

    In this dissertation, metals deposited on a hydrogenated amorphous silicon (a-Si:H) film at room temperature are studied. The purpose of this work is mainly understanding the electronic properties of the interface, using high-resolution synchrotron radiation photoemission techniques as a probe. Atomic hydrogen plays an important role in passivating dangling bonds of a-Si:H films, thus reducing the gap-state distribution. In addition, singly bonded hydrogen also reduces states at the top of the valence band which are now replaced by deeper Si-H bonding states. The interface is formed by evaporating metal on an a-Si:H film in successive accumulations at room temperature. Au, Ag, and Cr were chosen as the deposited metals. Undoped films were used as substrates. Since some unique features can be found in a-Si:H, such as surface enrichment of hydrogen diffused from the bulk and instability of the free surface, we do not expect the metals/a-Si:H interface to behave exactly as its crystalline counterpart. Metal deposits, at low coverages, are found to gather preferentially around regions deficient in hydrogen. As the thickness is increased, some Si atoms in those regions are likely to leave their sites to intermix with metal overlayers like Au and Cr. 129 refs., 30 figs.

  10. Hydrogen-induced surface metallization of SrTiO3(001).

    PubMed

    D'Angelo, M; Yukawa, R; Ozawa, K; Yamamoto, S; Hirahara, T; Hasegawa, S; Silly, M G; Sirotti, F; Matsuda, I

    2012-03-16

    Surface metallization of SrTiO3(001) by hydrogen adsorption is experimentally confirmed for the first time by photoemission spectroscopy and surface conductivity measurements. The metallic state is assigned to a quantized state in the space-charge layer induced by electron doping from hydrogen atoms. The measured two-dimensional (2D) conductivity is well above the 2D Ioffe-Regel limit indicating that the system is in a metallic conduction regime. The mean free path of the surface electron is estimated to be several nanometers at room temperature. PMID:22540498

  11. Single walled carbon nanotube-metal oxide nanocomposites for reversible and reproducible storage of hydrogen.

    PubMed

    Silambarasan, D; Surya, V J; Vasu, V; Iyakutti, K

    2013-11-13

    Composite material consisting of single walled carbon nanotubes (SWCNTs) and metal oxide nanoparticles has been prepared and their hydrogen storage performance is evaluated. Metal oxides such as tin oxide (SnO2), tungsten trioxide (WO3), and titanium dioxide (TiO2) are chosen as the composite constituents. The composites have been prepared by means of ultrasonication. Then, the composite samples are deposited on alumina substrates and at 100 °C in a Sieverts-like hydrogenation setup. Characterization techniques such as transmission electron microscopy (TEM), Raman spectroscopy, scanning electron microscopy (SEM), powder X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, energy dispersive spectroscopy (EDS), CHN elemental analysis, and thermogravimetric (TG) measurements are used to analyze the samples at various stages of experiments. Hydrogen storage capacity of the composites namely, SWCNT-SnO2, SWCNT-WO3, and SWCNT-TiO2 are found to be 1.1, 0.9, and 1.3 wt %, respectively. Hydrogenated composite samples are stable at room temperature and desorption of hydrogen is found to be 100% reversible. Desorption temperature ranges and binding energy ranges of hydrogen have been measured from the desorption studies. The hydrogenation, dehydrogenation temperature, and binding energy of hydrogen fall in the recommended range of a suitable hydrogen storage medium applicable for fuel cell applications. Reproducibility and deterioration level of the composite samples have also been examined. PMID:24117025

  12. Permeability and Strength Measurements on Sintered, Porous, Hollow Turbine Blades Made by the American Electro Metal Corporation under Office of Naval Research Contract N-ONR-295 (01)

    NASA Technical Reports Server (NTRS)

    Richards, Hadley T.; Livingood, N.B.

    1954-01-01

    An experimental investigation was made to determine the permeability and strength characteristics of a number of sintered, porous, hollow turbine rotor blades and to determine the effectiveness of the blade fabrication method on permeability control. The test blades were fabricated by the American Electro Metal Corporation under a contract with the Office of Naval Research, Department of the Navy, and were submitted to the NACA for testing. Of the 22 test blades submitted, ten were sintered but not coined, five were sintered and coined, and seven were sintered and not coined but contained perforated reinforcements integral with the blade shells. Representative samples of each group of blades were tested. Large variations in permeability in both chordwise and spanwise directions were found. Local deviations as large as 155 to -85 percent from prescribed values were found in chordwise permeability. Only one blade, an uncoined one, had a chordwise permeability variations which reasonably approached that specified. Even for this blade, local deviations exceeded 10 percent. Spanwise permeability, specified to be held constant, varied as much as 50 percent from root to tip for both an uncoined and a coined blade. Previous NACA analyses have shown that in order to maintain proper control of blade wall temperatures, permeability variations must not exceed plus or minus 10 percent. Satisfactory control of permeability in either the chordwise or the spanwise direction was not achieved in the blades tested. Spin tests made at room temperature for six blades revealed the highest material rupture strength to be 8926 pounds per square inch. This value is about one third the strength required for rotor blades in present-day turbojet engines. The lowest value of blade strength was 1436 pounds per square inch.

  13. Method of producing metallized chloroplasts and use thereof in the photochemical production of hydrogen and oxygen

    DOEpatents

    Greenbaum, Elias

    1987-01-01

    The invention is primarily a metallized chloroplast composition for use in a photosynthetic reaction. A catalytic metal is precipitated on a chloroplast membrane at the location where a catalyzed reduction reaction occurs. This metallized chloroplast is stabilized by depositing it on a support medium such as fiber so that it can be easily handled. A possible application of this invention is the splitting of water to form hydrogen and oxygen that can be used as a renewable energy source.

  14. Method of CO and/or CO.sub.2 hydrogenation using doped mixed-metal oxides

    SciTech Connect

    Shekhawat, Dushyant; Berry, David A.; Haynes, Daniel J.; Abdelsayed, Victor; Smith, Mark W.; Spivey, James J.

    2015-10-06

    A method of hydrogenation utilizing a reactant gas mixture comprising a carbon oxide and a hydrogen agent, and a hydrogenation catalyst comprising a mixed-metal oxide containing metal sites supported and/or incorporated into the lattice. The mixed-metal oxide comprises a perovskite, a pyrochlore, a fluorite, a brownmillerite, or mixtures thereof doped at the A-site or the B-site. The metal site may comprise a deposited metal, where the deposited metal is a transition metal, an alkali metal, an alkaline earth metal, or mixtures thereof. Contact between the carbon oxide, hydrogen agent, and hydrogenation catalyst under appropriate conditions of temperature, pressure and gas flow rate generate a hydrogenation reaction and produce a hydrogenated product made up of carbon from the carbon oxide and some portion of the hydrogen agent. The carbon oxide may be CO, CO.sub.2, or mixtures thereof and the hydrogen agent may be H.sub.2. In a particular embodiment, the hydrogenated product comprises an alcohol, an olefin, an aldehyde, a ketone, an ester, an oxo-product, or mixtures thereof.

  15. Molten metal reactor and method of forming hydrogen, carbon monoxide and carbon dioxide using the molten alkaline metal reactor

    DOEpatents

    Bingham, Dennis N.; Klingler, Kerry M.; Turner, Terry D.; Wilding, Bruce M.

    2012-11-13

    A molten metal reactor for converting a carbon material and steam into a gas comprising hydrogen, carbon monoxide, and carbon dioxide is disclosed. The reactor includes an interior crucible having a portion contained within an exterior crucible. The interior crucible includes an inlet and an outlet; the outlet leads to the exterior crucible and may comprise a diffuser. The exterior crucible may contain a molten alkaline metal compound. Contained between the exterior crucible and the interior crucible is at least one baffle.

  16. Metal sulfite/sulfate reactions in thermochemical hydrogen cycles

    SciTech Connect

    Mason, C.F.V.; Bowman, M.G.

    1980-01-01

    The thermochemical cycles which have been most extensively developed all involve the thermal decomposition of sulfuric acid which is corrosive. Metal sulfate cycles have been studied as a means of circumventing handling corrosive mixtures at high temperatures. However, these metal sulfate cycles still use an electrochemical step to produce H/sub 2/. Alternate H/sub 2/ producing steps to be used in conjunction with metal sulfates are examined.

  17. Empirical Method to Estimate Hydrogen Embrittlement of Metals as a Function of Hydrogen Gas Pressure at Constant Temperature

    NASA Technical Reports Server (NTRS)

    Lee, Jonathan A.

    2010-01-01

    High pressure Hydrogen (H) gas has been known to have a deleterious effect on the mechanical properties of certain metals, particularly, the notched tensile strength, fracture toughness and ductility. The ratio of these properties in Hydrogen as compared to Helium or Air is called the Hydrogen Environment Embrittlement (HEE) Index, which is a useful method to classify the severity of H embrittlement and to aid in the material screening and selection for safety usage H gas environment. A comprehensive world-wide database compilation, in the past 50 years, has shown that the HEE index is mostly collected at two conveniently high H pressure points of 5 ksi and 10 ksi near room temperature. Since H embrittlement is directly related to pressure, the lack of HEE index at other pressure points has posed a technical problem for the designers to select appropriate materials at a specific H pressure for various applications in aerospace, alternate and renewable energy sectors for an emerging hydrogen economy. Based on the Power-Law mathematical relationship, an empirical method to accurately predict the HEE index, as a function of H pressure at constant temperature, is presented with a brief review on Sievert's law for gas-metal absorption.

  18. Heats of solution and lattice-expansion and trapping energies of hydrogen in transition metals

    NASA Astrophysics Data System (ADS)

    Griessen, R.

    1988-08-01

    The heat of hydrogen solution in a metal at infinite dilution ΔH¯∞ is shown to depend on (1) the distance R between a hydrogen atom and its metallic nearest neighbors, (2) the characteristic band-structure energy ΔE=EF-Es, where EF is the Fermi energy and Es basically the center of the lowest conduction band of the host metal, and (3) the width Wd of the d band of the host metal. The semiempirical relation ΔH¯∞=αΔE W1/2d [with α=18.6 (kJ/mol H)(AṨ eV-3/2) and β=-90 kJ/mol H if ΔE, Wd, and R are given in units of eV and Å, respectively] reproduces the experimental values of ΔH¯∞ remarkably well. It also reproduces the volume expansion accompanying hydrogen absorption and predicts the correct interstitial site occupancy of hydrogen in a transition metal. Furthermore, it makes it possible to estimate the binding energy of hydrogen to a vacancy.

  19. [Regulation of sulfates, hydrogen sulfide and heavy metals in technogenic reservoirs by sulfate-reducing bacteria].

    PubMed

    Hudz', S P; Peretiatko, T B; Moroz, O M; Hnatush, S O; Klym, I R

    2011-01-01

    Sulfate-reducing bacteria Desulfovibrio desulfuricans Ya-11 in the presence of sulfates and organic compounds in the medium reduce sulfates to hydrogen sulfide (dissimilatory sulfate reduction). Heavy metals in concentration over 2 mM inhibit this process. Pb2+, Zn2+, Ni2+, Co2+, Fe2+ and Cd2+ ions in concentration 1-1.5 mM display insignificant inhibiting effect on sulfate reduction process, and metals precipitate in the form of sulfides. At concentrations of heavy metals 2-3 mM one can observe a decrease of sulfates reduction intensity, and a percent of metals binding does not exceed 72%. Obtained results give reason to confirm, that sulfate-reducing bacteria play an important role in regulation of the level of sulfates, hydrogen sulfide and heavy metals in reservoirs and they may be used for purification of water environment from these compounds.

  20. DWPF Hydrogen Generation Study-Form of Noble Metal SRAT Testing

    SciTech Connect

    Bannochie, C

    2005-09-01

    The Defense Waste Processing Facility, DWPF, has requested that the Savannah River National Laboratory, SRNL, investigate the factors that contribute to hydrogen generation to determine if current conservatism in setting the DWPF processing window can be reduced. A phased program has been undertaken to increase understanding of the factors that influence hydrogen generation in the DWPF Chemical Process Cell, CPC. The hydrogen generation in the CPC is primarily due to noble metal catalyzed decomposition of formic acid with a minor contribution from radiolytic processes. Noble metals have historically been added as trim chemicals to process simulations. The present study investigated the potential conservatism that might be present from adding the catalytic species as trim chemicals to the final sludge simulant versus co-precipitating the noble metals into the insoluble sludge solids matrix. Two sludge simulants were obtained, one with co-precipitated noble metals and one without noble metals. Co-precipitated noble metals were expected to better match real waste behavior than using trimmed noble metals during CPC simulations. Portions of both sludge simulants were held at 97 C for about eight hours to qualitatively simulate the effects of long term storage on particle morphology and speciation. The two original and two heat-treated sludge simulants were then used as feeds to Sludge Receipt and Adjustment Tank, SRAT, process simulations. Testing was done at relatively high acid stoichiometries, {approx}175%, and without mercury in order to ensure significant hydrogen generation. Hydrogen generation rates were monitored during processing to assess the impact of the form of noble metals. The following observations were made on the data: (1) Co-precipitated noble metal simulant processed similarly to trimmed noble metal simulant in most respects, such as nitrite to nitrate conversion, formate destruction, and pH, but differently with respect to hydrogen generation: (A

  1. Ab initio investigation on hydrogen adsorption capability in Zn and Cu-based metal organic frameworks

    NASA Astrophysics Data System (ADS)

    Tanuwijaya, V. V.; Hidayat, N. N.; Agusta, M. K.; Dipojono, H. K.

    2015-09-01

    One of the biggest challenge in material technology for hydrogen storage application is to increase hydrogen uptake in room temperature and pressure. As a class of highly porous material, Metal-Organic Frameworks (MOF) holds great potential with its tunable structure. However, little is known about the effect of metal cluster to its hydrogen storage capability. Investigation on this matter has been carried out carefully on small cluster of Zn and Cu-based MOF using first principles method. The calculation of two distinct building units of MOFs, namely octahedral and paddle-wheel models, have been done with B3LYP density functional method using 6-31G(d,p) and LANL2DZ basis sets. From geometry optimization of Zn-based MOF linked by benzene-dicarboxylate (MOF-5), it is found that hydrogen tends to keep distance from metal cluster group and stays above benzene ring. In the other hand, hydrogen molecule prefers to stay atop of the exposed Cu atom in Cu-based MOF system linked by the same linker group (Cu-bdc). Calculated hydrogen binding enthalpies for Zn and Cu octahedral cages at ZnO3 sites are 1.64kJ/mol and 2.73kJ/mol respectively, while hydrogen binding enthalpies for Zn and Cu paddle-wheel cages calculated on top of metal atoms are found to be at 6.05kJ/mol and 6.10kJ/mol respectively. Major difference between Zn-MOF-5 and Cu-bdc hydrogen uptake performance might be caused by unsaturated metal sites present in Cu-bdc system and the influence of their geometric structures, although a small difference on binding energy in the type of transition metal used is also observed. The comparison between Zn and Cu-based MOF may contribute to a comprehensive understanding of metal clusters and the importance of selecting best transition metal for design and synthesis of metal-organic frameworks.

  2. Ab initio investigation on hydrogen adsorption capability in Zn and Cu-based metal organic frameworks

    SciTech Connect

    Tanuwijaya, V. V.; Hidayat, N. N. Agusta, M. K. Dipojono, H. K.

    2015-09-30

    One of the biggest challenge in material technology for hydrogen storage application is to increase hydrogen uptake in room temperature and pressure. As a class of highly porous material, Metal-Organic Frameworks (MOF) holds great potential with its tunable structure. However, little is known about the effect of metal cluster to its hydrogen storage capability. Investigation on this matter has been carried out carefully on small cluster of Zn and Cu-based MOF using first principles method. The calculation of two distinct building units of MOFs, namely octahedral and paddle-wheel models, have been done with B3LYP density functional method using 6-31G(d,p) and LANL2DZ basis sets. From geometry optimization of Zn-based MOF linked by benzene-dicarboxylate (MOF-5), it is found that hydrogen tends to keep distance from metal cluster group and stays above benzene ring. In the other hand, hydrogen molecule prefers to stay atop of the exposed Cu atom in Cu-based MOF system linked by the same linker group (Cu-bdc). Calculated hydrogen binding enthalpies for Zn and Cu octahedral cages at ZnO{sub 3} sites are 1.64kJ/mol and 2.73kJ/mol respectively, while hydrogen binding enthalpies for Zn and Cu paddle-wheel cages calculated on top of metal atoms are found to be at 6.05kJ/mol and 6.10kJ/mol respectively. Major difference between Zn-MOF-5 and Cu-bdc hydrogen uptake performance might be caused by unsaturated metal sites present in Cu-bdc system and the influence of their geometric structures, although a small difference on binding energy in the type of transition metal used is also observed. The comparison between Zn and Cu-based MOF may contribute to a comprehensive understanding of metal clusters and the importance of selecting best transition metal for design and synthesis of metal-organic frameworks.

  3. Nickel-hydrogen. [metal hydrides, electrochemical corrosion, and structural design

    NASA Technical Reports Server (NTRS)

    Mchenry, E. J.

    1977-01-01

    Because of the disintegration of LaNi5 as the lattice expands on absorbing hydrogen, a nickel hydrogen cell similar to a nickel cadmium cell was designed. The positive electrode is wrapped in a microporous separator and the leads are insulated. A negative conducting grid is inserted and welded to the top of the can into an open ended container which is then turned upside down and filled so that LiNa5 powder occupies all the space not used by the rest of the components. The bottom of the can is then welded on. A fill tube is located either on the bottom or on the top of the can. When welded shut, the cell is put into a pressure bomb and the lanthanum nickel is activated at about 1,000 pounds of hydrogen. Electrolytes are added to the cell as well as whatever amount of hydrogen precharge desired, and the cell is sealed. Advantages and disadvantages of the cell are discussed.

  4. Stability of noble metal catalysts for the hydrogen-oxygen reaction.

    NASA Technical Reports Server (NTRS)

    Armstrong, W. E.; Jennings, T. J.; Voge, H. H.

    1972-01-01

    Stability of various supported noble metal catalysts for initiation of the hydrogen-oxygen reaction was tested by means of steam-hydrogen treatment at 1000-1200 C followed by a simple activity test. Many catalysts were stable to 1100 C, but all lost some activity at 1200 C. The most active with very good stability was an iridium/alumina catalyst of high iridium content.

  5. Graphene from Alginate Pyrolysis as a Metal-Free Catalyst for Hydrogenation of Nitro Compounds.

    PubMed

    Trandafir, Mihaela-Mirela; Florea, Mihaela; Neaţu, Florentina; Primo, Ana; Parvulescu, Vasile I; García, Hermenegildo

    2016-07-01

    Graphene obtained by pyrolysis of alginate at 900 °C under inert atmosphere and exfoliation is used as a metal-free catalyst for reduction of nitro to amino groups with hydrogen as a reagent. The process is general for aromatic and aliphatic, conjugated and isolated nitro groups, and occurs with low selectivity over hydrogenation of carbon-carbon double bonds. PMID:27246529

  6. A Biomimetic Approach to New Adsorptive Hydrogen Storage Metal-Organic Frameworks

    SciTech Connect

    Zhou, Hongcai J

    2015-08-12

    In the past decades, there has been an escalation of interest in the study of MOFs due to their fascinating structures and intriguing application potentials. Their exceptionally high surface areas, uniform yet tunable pore sizes, and well-defined adsorbate-MOF interaction sites make them suitable for hydrogen storage. Various strategies to increase the hydrogen capacity of MOFs, such as constructing pore sizes comparable to hydrogen molecules, increasing surface area and pore volume, utilizing catenation, and introducing coordinatively unsaturated metal centers (UMCs) have been widely explored to increase the hydrogen uptake of the MOFs. MOFs with hydrogen uptake approaching the DOE gravimetric storage goal under reasonable pressure but cryo- temperature (typically 77 K) were achieved. However, the weak interaction between hydrogen molecules and MOFs has been the major hurdle limiting the hydrogen uptake of MOFs at ambient temperature. Along the road, we have realized both high surface area and strong interaction between framework and hydrogen are equally essential for porous materials to be practically applicable in Hydrogen storage. Increasing the isosteric heats of adsorption for hydrogen through the introduction of active centers into the framework could have great potential on rendering the framework with strong interaction toward hydrogen. Approaches on increasing the surface areas and improving hydrogen affinity by optimizing size and structure of the pores and the alignment of active centers around the pores in frameworks have been pursued, for example: (a) the introduction of coordinatively UMC (represents a metal center missing multiple ligands) with potential capability of multiple dihydrogen-binding (Kubas type, non-dissociative) per UMC, (b) the design and synthesis of proton-rich MOFs in which a + H3 binds dihydrogen just like a metal ion does, and (c) the preparation of MOFs and PPNs with well aligned internal electric fields. We believe the

  7. Strategies for Hydrogen Storage in Nanoporous Metal-Organic Framework Materials

    NASA Astrophysics Data System (ADS)

    Snurr, Randall

    2011-03-01

    Storing hydrogen by physisorption in porous materials is a challenging problem of great interest for future vehicle technology. Metal-organic frameworks (MOFs) are a new class of nanoporous materials that have demonstrated exciting potential for solving this problem. MOFs are synthesized by the self-assembly of metal nodes and connecting organic linker molecules to create stable, porous frameworks. The synthetic chemistry opens the possibility to create an almost unlimited number of MOFs and to tailor them for particular applications, such as hydrogen storage. The diversity of MOFs also creates an opportunity to learn more about the fundamentals of hydrogen adsorption in porous materials. We have used a combination of classical Monte Carlo simulations and quantum mechanical approaches to investigate fundamental questions about hydrogen storage in MOFs and to design new materials with improved storage capabilities. Relationships have been elucidated between hydrogen uptake and properties such as the MOF surface area, void volume, degree of catenation, enthalpy of adsorption, and cation content. Introduction of cations is a promising strategy to improve hydrogen uptake at room temperature, and different metal cations and different strategies for introducing them into MOFs have been screened computationally.

  8. Systematic DFT-GGA study of hydrogen adsorption on transition metals

    NASA Astrophysics Data System (ADS)

    Vasić, D.; Ristanović, Z.; Pašti, I.; Mentus, S.

    2011-12-01

    Computational study of hydrogen adsorption on (111) surface of transition metals with face centered cubic (fcc) lattice is reported and the results are compared with available experimental and theoretical data. In addition, dissociative adsorption of hydrogen on Pt(111), Pt(100) and Pt(110) is studied in the range of coverage from 0.25 to 1 monolayer. In the case of Pt(111) preferential adsorption site was found to be three-coordinated fcc-hollow site, while on Pt(100) and Pt(110) surface hydrogen settles on two-coordinated bridge and short bridge site, respectively. Hydrogen adsorption energy was found to decrease with the increasing coverage. Structural changes of studied Pt surfaces upon hydrogen adsorption have been compared with the experimental data existing in the literature and good qualitative agreement has been obtained.

  9. Predicting distinct regimes of hydrogen behavior at nano-cavities in metals

    NASA Astrophysics Data System (ADS)

    Hayward, Erin; Hayward, Robert; Fu, Chu-Chun

    2016-08-01

    Hydrogen interacts strongly with structural defects and is often implicated in degradation of materials. Precise conditions and local structures favoring the formation of H2 molecules are unclear so far, and not directly accessible experimentally. We present a computational and theoretical study of properties and behavior of hydrogen at nano-cavities based on the saturation of the vacancy cluster surfaces. A predictive model is developed which characterizes two regimes of behavior: in the undersaturated regime, non-interacting atomic hydrogen decorates the surface of a nano-cavity. In the oversaturated regime, the surface is maximally covered, and stable molecular hydrogen can be formed within the bubble. We verify this model with ab initio Monte Carlo simulations to extensively explore low energy states of small vacancy clusters containing multiple hydrogen atoms. The present model is expected to be easily transferable to the study of H in other metallic systems.

  10. Metal-organic frameworks for the storage and delivery of biologically active hydrogen sulfide

    SciTech Connect

    Allan, Phoebe K; Wheatley, Paul S; Aldous, David; Mohideen, M Infas; Tang, Chiu; Hriljac, Joseph A; Megson, Ian L; Chapman, Karena W; De Weireld, Guy; Vaesen, Sebastian; Morris, Russell E

    2012-04-02

    Hydrogen sulfide is an extremely toxic gas that is also of great interest for biological applications when delivered in the correct amount and at the desired rate. Here we show that the highly porous metal-organic frameworks with the CPO-27 structure can bind the hydrogen sulfide relatively strongly, allowing the storage of the gas for at least several months. Delivered gas is biologically active in preliminary vasodilation studies of porcine arteries, and the structure of the hydrogen sulfide molecules inside the framework has been elucidated using a combination of powder X-ray diffraction and pair distribution function analysis.

  11. Transition metal dichalcogenides as a catalyst for hydrogen-evolution reaction

    NASA Astrophysics Data System (ADS)

    Lee, Jun-Ho; Son, Young-Woo; Seok, Jinbong; Yang, Heejun

    Hydrogen evolution using electrochemical reaction of water with specific catalysts has been considered as next-generation energy resources. The best-well known and most productive electrochemical catalyst is platinum. However, there has been a continuous struggle to replace the precious Pt-based catalysts by inexpensive and earth-abundant materials such as transition metal dichalcogenides (TMDs). We investigated catalytic performances of various TMDs for hydrogen-evolution reaction (HER) by using first-principles density functional theory calculation. We calculate Gibbs free energy, most widely used descriptor of catalytic activity, of hydrogen atom on TMDs and analyze an origin of significant performance of HER.

  12. Catalytic Metal Free Production of Large Cage Structure Carbon Particles: A Candidate for Hydrogen Storage

    NASA Technical Reports Server (NTRS)

    Kimura, Yuki; Nuth, Joseph A., III; Ferguson, Frank T.

    2005-01-01

    We will demonstrate that carbon particles consisting of large cages can be produced without catalytic metal. The carbon particles were produced in CO gas as well as by introduction of 5% methane gas into the CO gas. The gas-produced carbon particles were able to absorb approximately 16.2 wt% of hydrogen. This value is 2.5 times higher than the 6.5 wt% goal for the vehicular hydrogen storage proposed by the Department of Energy in the USA. Therefore, we believe that this carbon particle is an excellent candidate for hydrogen storage for fuel cells.

  13. The storage of hydrogen in the form of metal hydrides: An application to thermal engines

    NASA Technical Reports Server (NTRS)

    Gales, C.; Perroud, P.

    1981-01-01

    The possibility of using LaNi56, FeTiH2, or MgH2 as metal hydride storage sytems for hydrogen fueled automobile engines is discussed. Magnesium copper and magnesium nickel hydrides studies indicate that they provide more stable storage systems than pure magnesium hydrides. Several test engines employing hydrogen fuel have been developed: a single cylinder motor originally designed for use with air gasoline mixture; a four-cylinder engine modified to run on an air hydrogen mixture; and a gas turbine.

  14. Solubility of hydrogen and its isotopes in metals from mixed gases

    NASA Astrophysics Data System (ADS)

    San Marchi, C.; Somerday, B. P.; Larson, R. S.; Rice, S. F.

    2008-01-01

    This short communication reviews the classical thermodynamics governing dissolution of hydrogen in metals. Classical thermodynamics is then applied to equilibrium dissolution of hydrogen and its isotopes in metals from mixtures of their diatomic gases. For simplicity in presentation, we use the specific example of H 2 and D 2 gas mixtures to demonstrate the general principles of equilibrium solubility; however, other systems may be treated analogously. The formation of HD gas is shown to have a significant effect on equilibrium solubility since it affects the chemical potentials of the H 2 and D 2 gases. Finally, we compare this thermodynamic analysis with empirical solutions from the literature.

  15. Dynamic high pressure: Why it makes metallic fluid hydrogen

    NASA Astrophysics Data System (ADS)

    Nellis, W. J.

    2015-09-01

    Metallic fluid H has been made by dynamic compression decades after Wigner and Huntington (WH) predicted its existence in 1935. The density at which it was made is within a few percent of the density predicted by WH. Metallic fluid H was achieved by multiple-shock compression of liquid H2, which is quasi-isentropic and thermally equilibrated. That is, the compressions were isentropic but for enough temperature and entropy to drive the crossover to completion from H2 to H at 9-fold compression. The metallic fluid is highly degenerate: T/TF≈0.014. The basic ideas of dynamic compression, also known as supersonic, adiabatic, nonlinear hydrodynamics, were developed in the last half of the Nineteenth Century in European universities. Today dynamic compression is generally unfamiliar to the scientific community, which impedes general understanding as to why fluid H becomes metallic at a pressure observable in a laboratory. The purposes of this paper are to (i) present a brief review of dynamic compression and its affects on materials, (ii) review considerations that led to the sample holder designed specifically to make metallic fluid H, and (iii) present a brief inter-comparison of dynamic and static methods to achieve high pressure relative to their prospects for making metallic H.

  16. Vanadium diaphragm electrode serves as hydrogen diffuser in lithium hydride cell

    NASA Technical Reports Server (NTRS)

    Crouthamel, C. E.; Heinrich, R. R.; Johnson, C. E.

    1967-01-01

    Lithium hydride cell uses vanadium diaphragm electrode as a hydrogen diffuser. Vanadium is high in hydrogen gas solubility and permeability, is least sensitive to adverse surface effects, maintains good mechanical strength in hydrogen atmospheres, and appears to be compatible with all alkali-halide electrolytes and lithium metals.

  17. Study on the electronic structure and hydrogen adsorption by transition metal decorated single wall carbon nanotubes.

    PubMed

    Modak, P; Chakraborty, Brahmananda; Banerjee, S

    2012-05-01

    The ground state geometry and electronic structure of various 4d transition metal (TM) atom (Y, Zr, Nb and Mo) decorated single wall carbon nanotubes (SWCNTs) are obtained using density functional theory and the projector augmented wave (PAW) method. We found a systematic change in the adsorption site of the transition metal atom with increasing number of d electrons. We also predicted that Y and Zr decorated SWCNTs are metallic whereas Nb and Mo decorated SWCNTs are semiconducting. From detailed electronic structure and Bader charge analysis we found that the systematic variation of the adsorption site with the number of d electrons is related to the decreasing amount of charge transfer from the TM atom to the SWCNT along the 4d series. We have also studied the hydrogen adsorption capabilities of these decorated SWCNTs to understand the role of transition metal d electrons in binding the hydrogen molecules to the system. We found that metallic SWCNT + TM systems are better hydrogen adsorbers. We showed that the hydrogen adsorption by a TM decorated SWCNT will be maximum when all the adsorptions are physisorption and that the retention of magnetism by the system is crucial for physisorption.

  18. Hydrogen-induced cracking along the fusion boundary of dissimilar metal welds

    SciTech Connect

    Rowe, M.D.; Nelson, T.W.; Lippold, J.C.

    1999-02-01

    Presented here are the results from a series of experiments in which dissimilar metals welds were made using the gas tungsten arc welding process with pure argon or argon-6% hydrogen shielding gas. The objective was to determine if cracking near the fusion boundary of dissimilar metal welds could be caused by hydrogen absorbed during welding and to characterize the microstructures in which cracking occurred. Welds consisted of ER308 and ER309LSi austenitic stainless steel and ERNiCr-3-nickel-based filler metals deposited on A36 steel base metal. Cracking was observed in welds made with all three filler metals. A ferrofluid color metallography technique revealed that cracking was confined to regions in the weld metal containing martensite. Microhardness indentations indicated that martensitic regions in which cracking occurred had hardness values from 400 to 550 HV. Cracks did not extend into bulk weld metal with hardness less than 350 HV. Martensite formed near the fusion boundary in all three filler metals due to regions of locally increased base metal dilution.

  19. High Flux Metallic Membranes for Hydrogen Recovery and Membrane Reactors

    SciTech Connect

    Buxbaum, Robert

    2010-06-30

    We made and tested over 250 new alloys for use as lower cost, higher flux hydrogen extraction membrane materials. Most of these were intermetallic, or contained significant intermetallic content, particularly based on B2 alloy compositions with at least one refractory component; B2 intermetallics resemble BCC alloys, in structure, but the atoms have relatively fixed positions, with one atom at the corners of the cube, the other at the centers. The target materals we were looking for would contain little or no expensive elements, no strongly toxic or radioactive elements, would have high flux to hydrogen, while being fabricable, brazable, and relatively immune to hydrogen embrittlement and corrosion in operation. The best combination of properties of the membrane materials we developed was, in my opinion, a Pd-coated membrane consisting of V -9 atomic % Pd. This material was relatively cheap, had 5 times the flux of Pd under the same pressure differential, was reasonably easy to fabricate and braze, and not bad in terms of embrittlement. Based on all these factors we project, about 1/3 the cost of Pd, on an area basis for a membrane designed to last 20 years, or 1/15 the cost on a flux basis. Alternatives to this membrane replaced significant fractions of the Pd with Ni and or Co. The cost for these membranes was lower, but so was the flux. We produced successful brazed products from the membrane materials, and made them into flat sheets. We tested, unsuccessfully, several means of fabricating thematerials into tubes, and eventually built a membrane reactor using a new, flat-plate design: a disc and doughnut arrangement, a design that seems well- suited to clean hydrogen production from coal. The membranes and reactor were tested successfully at Western Research. A larger equipment company (Chart Industries) produced similar results using a different flat-plate reactor design. Cost projections of the membrane are shown to be attractive.

  20. Wigner and Huntington: the long quest for metallic hydrogen

    NASA Astrophysics Data System (ADS)

    Nellis, W. J.

    2013-06-01

    In 1935, Wigner and Huntington (WH) predicted that at a density D Met=0.62 mole H/cm3, 'very low temperatures', and a pressure greater than 25 GPa, body-centered cubic H2 would undergo an isostructural phase transition directly to H with an associated insulator-metal transition (IMT). WH also predicted an H2 structure type that might occur if the simple H2/H dissociative IMT does not exist: 'It is possible … that a layer-like lattice … is obtainable under high pressure'. In 1991, Ashcroft predicted that the 'geometric and dynamic nature of the (H-H) pairing', possibly in a layered graphite-like structure, would substantially impede achieving metallic H2. In 1996, metallic fluid H was made under dynamic compression at 0.64 mole H/cm3, 140 GPa and T/T F≪1, where T F is Fermi temperature. In 2012, a layer-like lattice, called Phase IV, was discovered above ∼220 GPa static pressure. Phase IV is insulating and possibly semi-metallic up to ∼360 GPa, above which it has been predicted to become metallic. This paper is a historical perspective - a comparison of WH's predictions with recent dynamic, static and theoretical high pressure results. WH did extremely well.

  1. Pressure effects on hydrogen atoms near the metal plane in the HCP phase of rare-earth metal trihydrides

    NASA Astrophysics Data System (ADS)

    Tunghathaithip, N.; Pakornchote, T.; Phaisangittisakul, N.; Bovornratanaraks, T.; Pinsook, U.

    2016-04-01

    Rare-earth metal trihydrides, REH3 (RE=Sc, Y, La), in the hcp phase were investigated under high pressure by the ab initio method. We concentrated on the behavior of hydrogen atoms which is affected by pressure. Two-thirds of the hydrogen atoms near the metal plane (Hm) were found to displace away from the metal plane as pressure increases. The trajectory of these squeezed hydrogen atoms is from a site near the metal plane, and moves past the plane of the tetragonal sites, and heads toward the nearest octahedral site. However, the rate of displacement depends on the local environment. LaH3 exhibits the least impediment on the Hm displacement while YH3 and ScH3 exhibit stronger impediment. Furthermore, our calculated Raman and IR active modes are in general agreement with the experimental data. The displacement of Hm can be used to explain the behavior of the Ov peak in Raman spectra, where it exists at low pressure and disappears at higher pressure in YH3 and ScH3.

  2. Systems and methods for selective hydrogen transport and measurement

    DOEpatents

    Glatzmaier, Gregory C

    2013-10-29

    Systems and methods for selectively removing hydrogen gas from a hydrogen-containing fluid volume are disclosed. An exemplary system includes a proton exchange membrane (PEM) selectively permeable to hydrogen by exclusively conducting hydrogen ions. The system also includes metal deposited as layers onto opposite sides or faces of the PEM to form a membrane-electrode assembly (MEA), each layer functioning as an electrode so that the MEA functions as an electrochemical cell in which the ionic conductors are hydrogen ions, and the MEA functioning as a hydrogen selective membrane (HSM) when located at the boundary between a hydrogen-containing fluid volume and a second fluid.

  3. Observation of Hydrogen Distribution Around Non-Metallic Inclusions in Steels with Tritium Microautoradiography

    SciTech Connect

    Otsuka, Teppei; Hanada, Hitoshi; Nakashima, Hidehiko; Sakamoto, Kan; Hayakawa, Masao; Hashizume, Kenichi; Sugisaki, Masayasu

    2005-07-15

    Hydrogen distributions around non-metallic inclusions in steels are successfully characterized with high-resolution tritium autoradiography. The autoradiographs show that hydrogen accumulation characteristics around the inclusions depend on types of the inclusions. In the case of MnS, hydrogen was inhomogeneously distributed in the ferrite matrix surrounding the MnS inclusion, probably because hydrogen is trapped in defects formed around MnS. The inhomogeneous distribution of hydrogen may be originated from the asymmetric stress field produced by a contraction of the MnS phase in the heat treatment, i.e. the inhomogeneous volumetric change of MnS owing to its larger thermal expansion than that of the ferrite phase. In the case of Al{sub 2}O{sub 3}, hydrogen was intensely localized at boundary layers of the ferrite matrix surrounding the Al{sub 2}O{sub 3} inclusion. This could be attributed to hydrogen trapping at defects introduced by a residual stress in the boundary layers of the ferrite matrix due to larger contraction of the ferrite phase than that of the Al{sub 2}O{sub 3} phase on cooling. Similarly hydrogen was accumulated in the surrounding ferrite matrix but more widely distributed around Cr carbide probably because difference in the thermal expansion between the Cr carbide and ferrite phases is less than that between the Al{sub 2}O{sub 3} and ferrite phases.

  4. Metal chelator combined with permeability enhancer ameliorates oxidative stress-associated neurodegeneration in rat eyes with elevated intraocular pressure.

    PubMed

    Liu, P; Zhang, M; Shoeb, M; Hogan, D; Tang, Luosheng; Syed, M F; Wang, C Z; Campbell, G A; Ansari, N H

    2014-04-01

    Because as many as half of glaucoma patients on intraocular pressure (IOP)-lowering therapy continue to experience optic nerve toxicity, it is imperative to find other effective therapies. Iron and calcium ions play key roles in oxidative stress, a hallmark of glaucoma. Therefore, we tested metal chelation by means of ethylenediaminetetraacetic acid (EDTA) combined with the permeability enhancer methylsulfonylmethane (MSM) applied topically on the eye to determine if this noninvasive treatment is neuroprotective in rat optic nerve and retinal ganglion cells exposed to oxidative stress induced by elevated IOP. Hyaluronic acid (HA) was injected into the anterior chamber of the rat eye to elevate the IOP. EDTA-MSM was applied topically to the eye for 3 months. Eyeballs and optic nerves were processed for histological assessment of cytoarchitecture. Protein-lipid aldehyde adducts and cyclooxygenase-2 (COX-2) were detected immunohistochemically. HA administration increased IOP and associated oxidative stress and inflammation. Elevated IOP was not affected by EDTA-MSM treatment. However, oxidative damage and inflammation were ameliorated as reflected by a decrease in formation of protein-lipid aldehyde adducts and COX-2 expression, respectively. Furthermore, EDTA-MSM treatment increased retinal ganglion cell survival and decreased demyelination of optic nerve compared with untreated eyes. Chelation treatment with EDTA-MSM ameliorates sequelae of IOP-induced toxicity without affecting IOP. Because most current therapies aim at reducing IOP and damage occurs even in the absence of elevated IOP, EDTA-MSM has the potential to work in conjunction with pressure-reducing therapies to alleviate damage to the optic nerve and retinal ganglion cells. PMID:24509160

  5. Dynamic high pressure: why it makes metallic fluid hydrogen

    NASA Astrophysics Data System (ADS)

    Nellis, William

    2015-06-01

    Metallic fluid H (MFH) was made by dynamic compression decades after Wigner and Huntington (WH) predicted it in 1935. The density of MFH is within a few percent of the density predicted by WH. MFH was made by multiple-shock compression of liquid H2, which process is quasi-isentropic and thermally equilibrated. The compressions were isentropic but produced enough dissipation as temperature T and entropy S to drive the crossover from insulating H2 to metallic H at 9-fold compressed atomic H density. T and S were tuned by temporally shaping the applied pressure pulse such that H2 dissociated to H at sufficiently high density to make a highly degenerate metal. The basic ideas of dynamic compression, also known as supersonic, adiabatic, nonlinear hydrodynamics, were developed in the last half of the Nineteenth Century. Our purposes are to (i) present a brief review of dynamic compression and its affects on materials, (ii) review considerations that led to the sample holder designed specifically to make MFH, and (iii) present a inter-comparison of dynamic and static methods relative to their prospects for making metallic H.

  6. The hydrogenation of metals upon interaction with water

    NASA Technical Reports Server (NTRS)

    Andreyev, L. A.; Gelman, B. G.; Zhukhovitskiy, A. A.; Polosina, Y. Y.

    1979-01-01

    Hydrogen evolution at 600 deg and 5 x 10 to the 7th power - 10 to the 6th power torr from AVOOO Al samples, which were pickled in 10 percent NaOH, is discussed. An H evolution kinetic equation is derived for samples of equal vol. and different surfaces (5 and 20 sq cm). The values of the H evolution coefficient K indicated an agreement with considered H diffusion mechanism through an oxide layer. The activation energy for the H evolution process, obtained from the K-temp. relation, was 13,000 2000 cal/g-atom.

  7. Nanochemistry at the atomic scale revealed in hydrogen-induced semiconductor surface metallization

    NASA Astrophysics Data System (ADS)

    Derycke, Vincent; Soukiassian, Patrick G.; Amy, Fabrice; Chabal, Yves J.; D'Angelo, Marie D.; Enriquez, Hanna B.; Silly, Mathieu G.

    2003-04-01

    Passivation of semiconductor surfaces against chemical attack can be achieved by terminating the surface-dangling bonds with a monovalent atom such as hydrogen. Such passivation invariably leads to the removal of all surface states in the bandgap, and thus to the termination of non-metallic surfaces. Here we report the first observation of semiconductor surface metallization induced by atomic hydrogen. This result, established by using photo-electron and photo-absorption spectroscopies and scanning tunnelling techniques, is achieved on a Si-terminated cubic silicon carbide (SiC) surface. It results from competition between hydrogen termination of surface-dangling bonds and hydrogen-generated steric hindrance below the surface. Understanding the ingredient for hydrogen-stabilized metallization directly impacts the ability to eliminate electronic defects at semiconductor interfaces critical for microelectronics, provides a means to develop electrical contacts on high-bandgap chemically passive materials, particularly for interfacing with biological systems, and gives control of surfaces for lubrication, for example of nanomechanical devices.

  8. Nanochemistry at the atomic scale revealed in hydrogen-induced semiconductor surface metallization.

    PubMed

    Derycke, Vincent; Soukiassian, Patrick G; Amy, Fabrice; Chabal, Yves J; D'angelo, Marie D; Enriquez, Hanna B; Silly, Mathieu G

    2003-04-01

    Passivation of semiconductor surfaces against chemical attack can be achieved by terminating the surface-dangling bonds with a monovalent atom such as hydrogen. Such passivation invariably leads to the removal of all surface states in the bandgap, and thus to the termination of non-metallic surfaces. Here we report the first observation of semiconductor surface metallization induced by atomic hydrogen. This result, established by using photo-electron and photo-absorption spectroscopies and scanning tunnelling techniques, is achieved on a Si-terminated cubic silicon carbide (SiC) surface. It results from competition between hydrogen termination of surface-dangling bonds and hydrogen-generated steric hindrance below the surface. Understanding the ingredient for hydrogen-stabilized metallization directly impacts the ability to eliminate electronic defects at semiconductor interfaces critical for microelectronics, provides a means to develop electrical contacts on high-bandgap chemically passive materials, particularly for interfacing with biological systems, and gives control of surfaces for lubrication, for example of nanomechanical devices.

  9. Trends in Selective Hydrogen Peroxide Production on Transition Metal Surfaces from First Principles

    SciTech Connect

    Rankin, Rees B.; Greeley, Jeffrey P.

    2012-10-19

    We present a comprehensive, Density Functional Theory-based analysis of the direct synthesis of hydrogen peroxide, H2O2, on twelve transition metal surfaces. We determine the full thermodynamics and selected kinetics of the reaction network on these metals, and we analyze these energetics with simple, microkinetically motivated rate theories to assess the activity and selectivity of hydrogen peroxide production on the surfaces of interest. By further exploiting Brønsted-Evans-Polanyi relationships and scaling relationships between the binding energies of different adsorbates, we express the results in the form of a two dimensional contour volcano plot, with the activity and selectivity being determined as functions of two independent descriptors, the atomic hydrogen and oxygen adsorption free energies. We identify both a region of maximum predicted catalytic activity, which is near Pt and Pd in descriptor space, and a region of selective hydrogen peroxide production, which includes Au. The optimal catalysts represent a compromise between activity and selectivity and are predicted to fall approximately between Au and Pd in descriptor space, providing a compact explanation for the experimentally known performance of Au-Pd alloys for hydrogen peroxide synthesis, and suggesting a target for future computational screening efforts to identify improved direct hydrogen peroxide synthesis catalysts. Related methods of combining activity and selectivity analysis into a single volcano plot may be applicable to, and useful for, other aqueous phase heterogeneous catalytic reactions where selectivity is a key catalytic criterion.

  10. Photoelectron Spectroscopy of Transition Metal Hydride Cluster Anions and Their Roles in Hydrogenation Reactions

    NASA Astrophysics Data System (ADS)

    Zhang, Xinxing; Bowen, Kit

    The interaction between transition metals and hydrogen has been an intriguing research topic for such applications as hydrogen storage and catalysis of hydrogenation and dehydrogenation. Special bonding features between TM and hydrogen are interesting not only because they are scarcely reported but also because they could help to discover and understand the nature of chemical bonding. Very recently, we discovered a PtZnH5- cluster which possessed an unprecedented planar pentagonal coordination between the H5- moiety and Pt, and exhibited special σ-aromaticity. The H5-kernel as a whole can be viewed as a η5-H5 ligand for Pt. As the second example, an H2 molecule was found to act as a ligand in the PdH3-cluster, in which two H atoms form a η2-H2 type of ligation to Pd. These transition metal hydride clusters were considered to be good hydrogen sources for hydrogenation. The reactions between PtHn- and CO2 were investigated. We observed formate in the final product H2Pt(HCO2)- .

  11. Hydrogen Doped Metal Oxide Semiconductors with Exceptional and Tunable Localized Surface Plasmon Resonances.

    PubMed

    Cheng, Hefeng; Wen, Meicheng; Ma, Xiangchao; Kuwahara, Yasutaka; Mori, Kohsuke; Dai, Ying; Huang, Baibiao; Yamashita, Hiromi

    2016-07-27

    Heavily doped semiconductors have recently emerged as a remarkable class of plasmonic alternative to conventional noble metals; however, controlled manipulation of their surface plasmon bands toward short wavelengths, especially in the visible light spectrum, still remains a challenge. Here we demonstrate that hydrogen doped given MoO3 and WO3 via a facile H-spillover approach, namely, hydrogen bronzes, exhibit strong localized surface plasmon resonances in the visible light region. Through variation of their stoichiometric compositions, tunable plasmon resonances could be observed in a wide range, which hinge upon the reduction temperatures, metal species, the nature and the size of metal oxide supports in the synthetic H2 reduction process as well as oxidation treatment in the postsynthetic process. Density functional theory calculations unravel that the intercalation of hydrogen atoms into the given host structures yields appreciable delocalized electrons, enabling their plasmonic properties. The plasmonic hybrids show potentials in heterogeneous catalysis, in which visible light irradiation enhanced catalytic performance toward p-nitrophenol reduction relative to dark condition. Our findings provide direct evidence for achieving plasmon resonances in hydrogen doped metal oxide semiconductors, and may allow large-scale applications with low-price and earth-abundant elements.

  12. Phonons in quantum solids with defects. [lattice vacancies and interstitials in solid helium and metallic hydrogen

    NASA Technical Reports Server (NTRS)

    Jacobi, N.; Zmuidzinas, J. S.

    1974-01-01

    A formalism was developed for temperature-dependent, self-consistent phonons in quantum solids with defects. Lattice vacancies and interstitials in solid helium and metallic hydrogen, as well as electronic excitations in solid helium, were treated as defects that modify properties of these systems. The information to be gained from the modified phonon spectrum is discussed.

  13. Butterfly valve with metal seals controls flow of hydrogen from cryogenic through high temperatures

    NASA Technical Reports Server (NTRS)

    Johnson, L. D.

    1967-01-01

    Butterfly valve with metal seals operates over a temperature range of minus 423 degrees to plus 440 degrees F with hydrogen as a medium and in a radiation environment. Media flow is controlled by an internal butterfly disk which is rotated by an actuation shaft.

  14. Method for hydrogen production and metal winning, and a catalyst/cocatalyst composition useful therefor

    DOEpatents

    Dhooge, Patrick M.

    1987-10-13

    A catalyst/cocatalyst/organics composition of matter is useful in electrolytically producing hydrogen or electrowinning metals. Use of the catalyst/cocatalyst/organics composition causes the anode potential and the energy required for the reaction to decrease. An electrolyte, including the catalyst/cocatalyst composition, and a reaction medium composition further including organic material are also described.

  15. Investigation of the Alkaline Electrochemical Interface and Development of Composite Metal/Metal-Oxides for Hydrogen and Oxygen Electrodes

    NASA Astrophysics Data System (ADS)

    Bates, Michael

    Understanding the fundamentals of electrochemical interfaces will undoubtedly reveal a path forward towards a society based on clean and renewable energy. In particular, it has been proposed that hydrogen can play a major role as an energy carrier of the future. To fully utilize the clean energy potential of a hydrogen economy, it is vital to produce hydrogen via water electrolysis, thus avoiding co-production of CO2 inherent to reformate hydrogen. While significant research efforts elsewhere are focused on photo-chemical hydrogen production from water, the inherent low efficiency of this method would require a massive land-use footprint to achieve sufficient hydrogen production rates to integrate hydrogen into energy markets. Thus, this research has primarily focused on the water splitting reactions on base-metal catalysts in the alkaline environment. Development of high-performance base-metal catalysts will help move alkaline water electrolysis to the forefront of hydrogen production methods, and when paired with solar and wind energy production, represents a clean and renewable energy economy. In addition to the water electrolysis reactions, research was conducted to understand the de-activation of reversible hydrogen electrodes in the corrosive environment of the hydrogen-bromine redox flow battery. Redox flow batteries represent a promising energy storage option to overcome the intermittency challenge of wind and solar energy production methods. Optimization of modular and scalable energy storage technology will allow higher penetration of renewable wind and solar energy into the grid. In Chapter 1, an overview of renewable energy production methods and energy storage options is presented. In addition, the fundamentals of electrochemical analysis and physical characterization of the catalysts are discussed. Chapter 2 reports the development of a Ni-Cr/C electrocatalyst with unprecedented mass-activity for the hydrogen evolution reaction (HER) in alkaline

  16. Metal-Carbon Hybrid Electrocatalysts Derived from Ion-Exchange Resin Containing Heavy Metals for Efficient Hydrogen Evolution Reaction.

    PubMed

    Zhou, Yucheng; Zhou, Weijia; Hou, Dongman; Li, Guoqiang; Wan, Jinquan; Feng, Chunhua; Tang, Zhenghua; Chen, Shaowei

    2016-05-01

    Transition metal-carbon hybrids have been proposed as efficient electrocatalysts for hydrogen evolution reaction (HER) in acidic media. Herein, effective HER electrocatalysts based on metal-carbon composites are prepared by controlled pyrolysis of resin containing a variety of heavy metals. For the first time, Cr2 O3 nanoparticles of 3-6 nm in diameter homogeneously dispersed in the resulting porous carbon framework (Cr-C hybrid) is synthesized as efficient HER electrocatalyst. Electrochemical measurements show that Cr-C hybrids display a high HER activity with an onset potential of -49 mV (vs reversible hydrogen electrode), a Tafel slope of 90 mV dec(-1) , a large catalytic current density of 10 mA cm(-2) at -123 mV, and the prominent electrochemical durability. X-ray photoelectron spectroscopic measurements confirm that electron transfer occurs from Cr2 O3 into carbon, which is consistent with the reported metal@carbon systems. The obtained correlation between metals and HER activities may be exploited as a rational guideline in the design and engineering of HER electrocatalysts. PMID:27061759

  17. Metal-Carbon Hybrid Electrocatalysts Derived from Ion-Exchange Resin Containing Heavy Metals for Efficient Hydrogen Evolution Reaction.

    PubMed

    Zhou, Yucheng; Zhou, Weijia; Hou, Dongman; Li, Guoqiang; Wan, Jinquan; Feng, Chunhua; Tang, Zhenghua; Chen, Shaowei

    2016-05-01

    Transition metal-carbon hybrids have been proposed as efficient electrocatalysts for hydrogen evolution reaction (HER) in acidic media. Herein, effective HER electrocatalysts based on metal-carbon composites are prepared by controlled pyrolysis of resin containing a variety of heavy metals. For the first time, Cr2 O3 nanoparticles of 3-6 nm in diameter homogeneously dispersed in the resulting porous carbon framework (Cr-C hybrid) is synthesized as efficient HER electrocatalyst. Electrochemical measurements show that Cr-C hybrids display a high HER activity with an onset potential of -49 mV (vs reversible hydrogen electrode), a Tafel slope of 90 mV dec(-1) , a large catalytic current density of 10 mA cm(-2) at -123 mV, and the prominent electrochemical durability. X-ray photoelectron spectroscopic measurements confirm that electron transfer occurs from Cr2 O3 into carbon, which is consistent with the reported metal@carbon systems. The obtained correlation between metals and HER activities may be exploited as a rational guideline in the design and engineering of HER electrocatalysts.

  18. Hydrogen sulfide removal from coal gas by the metal-ferrite sorbents made from the heavy metal wastewater sludge.

    PubMed

    Tseng, Ting Ke; Chang, Han Ching; Chu, Hsin; Chen, Hung Ta

    2008-12-30

    The metal-ferrite (chromium-ferrite and zinc-ferrite) sorbents made from the heavy metal wastewater sludge have been developed for the hydrogen sulfide removal from coal gas. The high temperature absorption of hydrogen sulfide from coal gas with the metal-ferrite sorbent in a fixed bed reactor was conducted in this study. The metal-ferrite powders were the products of the ferrite process for the heavy metal wastewater treatment. The porosity analysis results show that the number of micropores of the sorbents after sulfidation and regeneration process decreases and the average pore size increases due to the acute endothermic and exothermic reactions during the sulfidation-regeneration process. The FeS, ZnS, and MnS peaks are observed on the sulfided sorbents, and the chromium extraction of the CFR6 can fulfill the emission standard of Taiwan EPA. The suitable sulfidation temperature range for chromium-ferrite sorbent is at 500-600 degrees C. In addition, effects of various concentrations of H2 and CO were also conducted in the present work at different temperatures. By increasing the H2 concentration, the sulfur sorption capacity of the sorbent decreases and an adverse result is observed in the case of increasing CO concentration. This can be explained via water-shift reaction.

  19. The kinetic and mechanical aspects of hydrogen-induced failure in metals. Ph.D. Thesis, 1971

    NASA Technical Reports Server (NTRS)

    Nelson, H. G.

    1972-01-01

    Premature hydrogen-induced failure observed to occur in many metal systems involves three stages of fracture: (1) crack initiation, (2) stable slow crack growth, and (3) unstable rapid crack growth. The presence of hydrogen at some critical location on the metal surface or within the metal lattice was shown to influence one or both of the first two stages of brittle fracture but has a negligible effect on the unstable rapid crack growth stage. The relative influence of the applied parameters of time, temperature, etc., on the propensity of a metal to exhibit hydrogen induced premature failure was investigated.

  20. Phase transition into the metallic state in hypothetical (without molecules) dense atomic hydrogen

    SciTech Connect

    Khomkin, A. L. Shumikhin, A. S.

    2013-10-15

    A simple physical model of the metal-dielectric (vapor-liquid) phase transition in hypothetical (without molecules) atomic hydrogen is proposed. The reason for such a transition is the quantum collective cohesive energy occurring due to quantum electron-electron exchange similar to the cohesive energy in the liquid-metal phase of alkali metals. It is found that the critical parameters of the transition are P{sub c} ∼ 41000 atm, ρ{sub c} ∼ 0.1 g/cm{sup 3}, and T{sub c} ∼ 9750 K.

  1. Active and Durable Hydrogen Evolution Reaction Catalyst Derived from Pd-Doped Metal-Organic Frameworks.

    PubMed

    Chen, Jitang; Xia, Guoliang; Jiang, Peng; Yang, Yang; Li, Ren; Shi, Ruohong; Su, Jianwei; Chen, Qianwang

    2016-06-01

    The water electrolysis is of critical importance for sustainable hydrogen production. In this work, a highly efficient and stable PdCo alloy catalyst (PdCo@CN) was synthesized by direct annealing of Pd-doped metal-organic frameworks (MOFs) under N2 atmosphere. In 0.5 M H2SO4 solution, PdCo@CN displays remarkable electrocatalytic performance with overpotential of 80 mV, a Tafel slope of 31 mV dec(-1), and excellent stability of 10 000 cycles. Our studies reveal that noble metal doped MOFs are ideal precursors for preparing highly active alloy electrocatalysts with low content of noble metal.

  2. Post-synthetic Ti Exchanged UiO-66 Metal-Organic Frameworks that Deliver Exceptional Gas Permeability in Mixed Matrix Membranes

    PubMed Central

    Smith, Stefan J. D.; Ladewig, Bradley P.; Hill, Anita J.; Lau, Cher Hon; Hill, Matthew R.

    2015-01-01

    Gas separation membranes are one of the lowest energy technologies available for the separation of carbon dioxide from flue gas. Key to handling the immense scale of this separation is maximised membrane permeability at sufficient selectivity for CO2 over N2. For the first time it is revealed that metals can be post-synthetically exchanged in MOFs to drastically enhance gas transport performance in membranes. Ti-exchanged UiO-66 MOFs have been found to triple the gas permeability without a loss in selectivity due to several effects that include increased affinity for CO2 and stronger interactions between the polymer matrix and the Ti-MOFs. As a result, it is also shown that MOFs optimized in previous works for batch-wise adsorption applications can be applied to membranes, which have lower demands on material quantities. These membranes exhibit exceptional CO2 permeability enhancement of as much as 153% when compared to the non-exchanged UiO-66 mixed-matrix controls, which places them well above the Robeson upper bound at just a 5 wt.% loading. The fact that maximum permeability enhancement occurs at such low loadings, significantly less than the optimum for other MMMs, is a major advantage in large-scale application due to the more attainable quantities of MOF needed. PMID:25592747

  3. Grain-boundary engineering markedly reduces susceptibility to intergranular hydrogen embrittlement in metallic materials

    SciTech Connect

    Bechtle, Sabine; Kumar, Mukul; Somerday, Brian P.; Launey, Maximilien E.; Ritchie, Robert O.

    2009-05-10

    The feasibility of using 'grain-boundary engineering' techniques to reduce the susceptibility of a metallic material to intergranular embrittlement in the presence of hydrogen is examined. Using thermomechanical processing, the fraction of 'special' grain boundaries was increased from 46% to 75% (by length) in commercially pure nickel samples. In the presence of hydrogen concentrations between 1200 and 3400 appm, the high special fraction microstructure showed almost double the tensile ductility; also, the proportion of intergranular fracture was significantly lower and the J{sub c} fracture toughness values were some 20-30% higher in comparison with the low special fraction microstructure. We attribute the reduction in the severity of hydrogen-induced intergranular embrittlement to the higher fraction of special grain boundaries, where the degree of hydrogen segregation at these boundaries is reduced.

  4. Partially Hydrogenated Graphene Materials Exhibit High Electrocatalytic Activities Related to Unintentional Doping with Metallic Impurities.

    PubMed

    Jankovský, Ondřej; Libánská, Alena; Bouša, Daniel; Sedmidubský, David; Matějková, Stanislava; Sofer, Zdeněk

    2016-06-13

    Partially hydrogenated graphene materials, synthesized by the chemical reduction/hydrogenation of two different graphene oxides using zinc powder in acidic environment or aluminum powder in alkaline environment, exhibit high electrocatalytic activities, as well as electrochemical sensing properties. The starting graphene oxides and the resultant hydrogenated graphenes were characterized in detail. Their electrocatalytic activity was examined in the oxygen reduction reaction, whereas sensing properties towards explosives were tested by using picric acid as a redox probe. Findings indicate that the high electrocatalytic performance originates not only from the hydrogenation of graphene, but also from unintentional contamination of graphene with manganese and other metals during synthesis. A careful evaluation of the obtained data and a detailed chemical analysis are necessary to identify the origin of this anomalous electrocatalytic activity. PMID:27167069

  5. Combinatorial Search of Hydrogen Catalysts Based on Transition Metal Embedded Graphitic Carbons

    NASA Astrophysics Data System (ADS)

    Choi, Woon Ih; Wood, Brandon; Schwegler, Eric; Ogitsu, Tadashi; Quantum Simulation Group Team

    2015-03-01

    To find right d-orbital configuration for hydrogen catalyst among embedded transition metal (TM) atoms into the lattice of graphene, we performed high-throughput computational search out of 300 combinatorial material pools. Theoretical criteria, so called descriptors regarding material stability and catalytic activity are considered and we were able to narrow down to ten materials for hydrogen evolution, two for hydrogen oxidation reaction. Since catalytically active sites are isolated to single TM atom, Volmer-Kubas type of new reaction pathway is expected for hydrogen evolution. Earth-abundant element Mo, bulk form of which doesn't show good catalytic activity at all, turns into catalytically active site as it is dispersed atomically and its d-orbitals splits by the symmetry of local coordination at the binding sites.

  6. Highly effective hydrogen isotope separation in nanoporous metal-organic frameworks with open metal sites: direct measurement and theoretical analysis.

    PubMed

    Oh, Hyunchul; Savchenko, Ievgeniia; Mavrandonakis, Andreas; Heine, Thomas; Hirscher, Michael

    2014-01-28

    Separating gaseous mixtures that consist of very similar size is one of the critical issues in modern separation technology. Especially, the separation of the isotopes hydrogen and deuterium requires special efforts, even though these isotopes show a very large mass ratio. Conventionally, H/D separation can be realized through cryogenic distillation of the molecular species or the Girdler-sulfide process, which are among the most energy-intensive separation techniques in the chemical industry. However, costs can be significantly reduced by using highly mass-selective nanoporous sorbents. Here, we describe a hydrogen isotope separation strategy exploiting the strongly attractive open metal sites present in nanoporous metal-organic frameworks of the CPO-27 family (also referred to as MOF-74). A theoretical analysis predicts an outstanding hydrogen isotopologue separation at open metal sites due to isotopal effects, which has been directly observed through cryogenic thermal desorption spectroscopy. For H2/D2 separation of an equimolar mixture at 60 K, the selectivity of 12 is the highest value ever measured, and this methodology shows extremely high separation efficiencies even above 77 K. Our theoretical results imply also a high selectivity for HD/H2 separation at similar temperatures, and together with catalytically active sites, we propose a mechanism to produce D2 from HD/H2 mixtures with natural or enriched deuterium content. PMID:24359584

  7. Highly effective hydrogen isotope separation in nanoporous metal-organic frameworks with open metal sites: direct measurement and theoretical analysis.

    PubMed

    Oh, Hyunchul; Savchenko, Ievgeniia; Mavrandonakis, Andreas; Heine, Thomas; Hirscher, Michael

    2014-01-28

    Separating gaseous mixtures that consist of very similar size is one of the critical issues in modern separation technology. Especially, the separation of the isotopes hydrogen and deuterium requires special efforts, even though these isotopes show a very large mass ratio. Conventionally, H/D separation can be realized through cryogenic distillation of the molecular species or the Girdler-sulfide process, which are among the most energy-intensive separation techniques in the chemical industry. However, costs can be significantly reduced by using highly mass-selective nanoporous sorbents. Here, we describe a hydrogen isotope separation strategy exploiting the strongly attractive open metal sites present in nanoporous metal-organic frameworks of the CPO-27 family (also referred to as MOF-74). A theoretical analysis predicts an outstanding hydrogen isotopologue separation at open metal sites due to isotopal effects, which has been directly observed through cryogenic thermal desorption spectroscopy. For H2/D2 separation of an equimolar mixture at 60 K, the selectivity of 12 is the highest value ever measured, and this methodology shows extremely high separation efficiencies even above 77 K. Our theoretical results imply also a high selectivity for HD/H2 separation at similar temperatures, and together with catalytically active sites, we propose a mechanism to produce D2 from HD/H2 mixtures with natural or enriched deuterium content.

  8. Vapor phase hydrogenation of furfural over nickel mixed metal oxide catalysts derived from layered double hydroxides

    DOE PAGESBeta

    Sulmonetti, Taylor P.; Pang, Simon H.; Claure, Micaela Taborga; Lee, Sungsik; Cullen, David A.; Agrawal, Pradeep K.; Jones, Christopher W.

    2016-03-09

    The hydrogenation of furfural is investigated over various reduced nickel mixed metal oxides derived from layered double hydroxides (LDHs) containing Ni-Mg-Al and Ni-Co-Al. Upon reduction, relatively large Ni(0) domains develop in the Ni-Mg-Al catalysts, whereas in the Ni-Co-Al catalysts smaller metal particles of Ni(0) and Co(0), potentially as alloys, are formed, as evidenced by XAS, XPS, STEM and EELS. All the reduced Ni catalysts display similar selectivities towards major hydrogenation products (furfuryl alcohol and tetrahydrofurfuryl alcohol), though the side products varied with the catalyst composition. The 1.1Ni-0.8Co-Al catalyst showed the greatest activity per titrated site when compared to the othermore » catalysts, with promising activity compared to related catalysts in the literature. In conclusion, the use of base metal catalysts for hydrogenation of furanic compounds may be a promising alternative to the well-studied precious metal catalysts for making biomass-derived chemicals if catalyst selectivity can be improved in future work by alloying or tuning metal-oxide support interactions.« less

  9. Evidence of a first-order phase transition to metallic hydrogen

    NASA Astrophysics Data System (ADS)

    Zaghoo, Mohamed; Salamat, Ashkan; Silvera, Isaac F.

    2016-04-01

    The insulator-metal transition in hydrogen is one of the most outstanding problems in condensed-matter physics. The high-pressure metallic phase is now predicted to be liquid atomic from the low-temperature limit with the system in the ground state to very high temperatures. We have conducted measurements of optical properties of hot dense hydrogen in the region of 1.1-1.7 Mbars and up to 2200 K. We present evidence supportive of a first-order phase transition accompanied by changes in transmittance and reflectance, characteristic of a metal. The phase line of this transition has a negative slope in agreement with theories of the so-called plasma phase transition.

  10. 2D Transition-Metal-Dichalcogenide-Nanosheet-Based Composites for Photocatalytic and Electrocatalytic Hydrogen Evolution Reactions.

    PubMed

    Lu, Qipeng; Yu, Yifu; Ma, Qinglang; Chen, Bo; Zhang, Hua

    2016-03-01

    Hydrogen (H2) is one of the most important clean and renewable energy sources for future energy sustainability. Nowadays, photocatalytic and electrocatalytic hydrogen evolution reactions (HERs) from water splitting are considered as two of the most efficient methods to convert sustainable energy to the clean energy carrier, H2. Catalysts based on transition metal dichalcogenides (TMDs) are recognized as greatly promising substitutes for noble-metal-based catalysts for HER. The photocatalytic and electrocatalytic activities of TMD nanosheets for the HER can be further improved after hybridization with many kinds of nanomaterials, such as metals, oxides, sulfides, and carbon materials, through different methods including the in situ reduction method, the hot-injection method, the heating-up method, the hydro(solvo)thermal method, chemical vapor deposition (CVD), and thermal annealing. Here, recent progress in photocatalytic and electrocatalytic HERs using 2D TMD-based composites as catalysts is discussed.

  11. Characterization and high throughput analysis of metal hydrides for hydrogen storage

    NASA Astrophysics Data System (ADS)

    Barcelo, Steven James

    Efficient hydrogen storage is required for fuel cell vehicles to be competitive with those driven by internal combustion engines. Current methods of storage such as compressed gas and liquid hydrogen cannot meet this standard, so novel hydrogen storage materials such as metal hydrides are required. No simple metal hydride meets the required specifications. Research is required to find new materials or improve existing materials. This thesis describes the research practices necessary to achieve legitimate and repeatable results in laboratories across the world. Examples of experiments using these techniques are presented, such as a high throughput technique to optimize materials systems with up to three components such as calcium borohydride with titanium catalyst and magnesium hydride with nickel and aluminum as destabilizing elements and catalysts. Thin films composed of gradients of each material were deposited by sputtering, creating a single thin film sample covering all potential material combinations. Optical properties of the samples under hydrogen pressure were monitored to identify the regions with largest and fastest hydrogen uptake. In the Ca-B-Ti system, titanium did not sufficiently catalyze the borohydride formation reaction at low temperature. Substantial hydrogen uptake was shown in the Mg-Ni region of the Mg-Ni-Al films. Al did not participate in the reaction at low temperature. Further investigation of the role of catalysts and destabilizing elements in improving hydrogen storage performance through X-ray Absorption and Emission Spectroscopy measurements of the Mg-Ni system during hydrogenation is presented. Typical X-ray spectroscopy measurements use a synchrotron radiation source and require ultra high vacuum conditions. For these experiments we designed a chamber which can be inserted into a vacuum chamber allowing in situ measurements of a sample under hydrogen pressure, providing information on the role of Ni in hydrogen absorption of Mg

  12. Experimental design and simulation of a metal hydride hydrogen storage system

    NASA Astrophysics Data System (ADS)

    Gadre, Sarang Ajit

    Metal hydrides, as a hydrogen storage medium, have been under consideration for many years because they have the ability to store hydrogen reversibly in the solid state at relatively low pressures and ambient temperatures. The utility of metal hydrides as a hydrogen storage medium was demonstrated recently by the Savannah River Technology Center (SRTC) in an on-board hydrogen storage system for a hybrid electric bus project. The complex geometry and the intricate design of the SRTC bed presents quite a challenge to the development of a mathematical model that can be used for design and optimization. In a new approach introduced here, the reversible reaction kinetics and the empirical Van't Hoff relationship used in a typical reactor model are replaced by a solid phase diffusion equation and one of the two semi-empirical equilibrium P-C-T relationships based on modified virial and composite Langmuir isotherm expressions. Starting with the simplest mathematical formulation, which resulted in an analytical expression, various models were developed and successively improved by relaxing certain assumptions, eventually resulting in the most rigorous model yet developed for this system. All of these models were calibrated using experimental pressure and temperature histories obtained from a bench scale hydrogen storage test facility. The heat and mass transfer coefficients or the thermal conductivity were the only adjustable parameters in these models. A design of experiments approach was also used for studying the effect of various factors on the performance of this bench scale hydrogen storage unit. Overall, the results of this study demonstrated that even a fairly simple numerical model could do a reasonable job in predicting the discharge behavior of a fairly complicated, metal hydride hydrogen storage bed over a wide range of operating conditions. The more rigorous 2-D model gave considerable insight into the dynamics of the hydrogen discharge process from an

  13. Partial and complete reduction of O2 by hydrogen on transition metal surfaces

    SciTech Connect

    Ford, Denise; Nilekar, Anand Udaykumar; Xu, Ye; Mavrikakis, Manos

    2010-01-01

    The metal-catalyzed reduction of di-oxygen (O{sub 2}) by hydrogen is at the heart of direct synthesis of hydrogen peroxide (HOOH) and power generation by proton exchange membrane fuel cells. Despite its apparent simplicity, how the reaction proceeds on different metals is not yet well understood. We present a systematic study of O{sub 2} reduction on the (111) facets of eight transition metals (Rh, Ir, Ni, Pd, Pt, Cu, Ag, and Au) based on periodic density functional theory (DFT-GGA) calculations. Analysis of ten surface elementary reaction steps suggests three selectivity regimes as a function of the binding energy of atomic oxygen (BEO), delineated by the opposite demands to catalyze O-O bond scission and O-H bond formation: The dissociative adsorption of O{sub 2} prevails on Ni, Rh, Ir, and Cu; the complete reduction to water via associative (peroxyl, peroxide, and aquoxyl) mechanisms prevails on Pd, Pt, and Ag; and HOOH formation prevails on Au. The reducing power of hydrogen is decreased electrochemically by increasing the electrode potential. This hinders the hydrogenation of oxygen species and shifts the optimal selectivity for water to less reactive metals. Our results point to the important role of the intrinsic reactivity of metals in the selectivity of O{sub 2} reduction, provide a unified basis for understanding the metal-catalyzed reduction of O{sub 2} to H{sub 2}O and HOOH, and offer useful insights for identifying new catalysts for desired oxygen reduction products.

  14. Proposed Ligand-Centered Electrocatalytic Hydrogen Evolution and Hydrogen Oxidation at a Noninnocent Mononuclear Metal-Thiolate.

    PubMed

    Haddad, Andrew Z; Kumar, Davinder; Ouch Sampson, Kagna; Matzner, Anna M; Mashuta, Mark S; Grapperhaus, Craig A

    2015-07-29

    The noninnocent coordinatively saturated mononuclear metal-thiolate complex ReL3 (L = diphenylphosphinobenzenethiolate) serves as an electrocatalyst for hydrogen evolution or hydrogen oxidation dependent on the presence of acid or base and the applied potential. ReL3 reduces acids to H2 in dichloromethane with an overpotential of 380 mV and a turnover frequency of 32 ± 3 s(-1). The rate law displays a second-order dependence on acid concentration and a first-order dependence on catalyst concentration with an overall third-order rate constant (k) of 184 ± 2 M(-2) s(-1). Reactions with deuterated acid display a kinetic isotope effect of 9 ± 1. In the presence of base, ReL3 oxidizes H2 with a turnover frequency of 4 ± 1 s(-1). The X-ray crystal structure of the monoprotonated species [Re(LH)L2](+), an intermediate in both catalytic H2 evolution and oxidation, has been determined. A ligand-centered mechanism, which does not require metal hydride intermediates, is suggested based on similarities to the redox-regulated, ligand-centered binding of ethylene to ReL3. PMID:26161802

  15. Recent advances in transition metal phosphide nanomaterials: synthesis and applications in hydrogen evolution reaction.

    PubMed

    Shi, Yanmei; Zhang, Bin

    2016-03-21

    The urgent need of clean and renewable energy drives the exploration of effective strategies to produce molecular hydrogen. With the assistance of highly active non-noble metal electrocatalysts, electrolysis of water is becoming a promising candidate to generate pure hydrogen with low cost and high efficiency. Very recently, transition metal phosphides (TMPs) have been proven to be high performance catalysts with high activity, high stability, and nearly ∼100% Faradic efficiency in not only strong acidic solutions, but also in strong alkaline and neutral media for electrochemical hydrogen evolution. In this tutorial review, an overview of recent development of TMP nanomaterials as catalysts for hydrogen generation with high activity and stability is presented. The effects of phosphorus (P) on HER activity, and their synthetic methods of TMPs are briefly discussed. Then we will demonstrate the specific strategies to further improve the catalytic efficiency and stability of TMPs by structural engineering. Making use of TMPs as cocatalysts and catalysts in photochemical and photoelectrochemical water splitting is also discussed. Finally, some key challenges and issues which should not be ignored during the rapid development of TMPs are pointed out. These strategies and challenges of TMPs are instructive for designing other high-performance non-noble metal catalysts.

  16. Dissolution of Uranium Metal Without Hydride Formation or Hydrogen Gas Generation

    SciTech Connect

    Soderquist, Chuck Z.; Oliver, Brian M.; McNamara, Bruce K.

    2008-09-01

    This study shows that metallic uranium will cleanly dissolve in carbonate-peroxide solution without generation of hydrogen gas or uranium hydride. Metallic uranium shot, 0.5 to 1 mm diameter, were reacted with ammonium carbonate - hydrogen peroxide solution ranging in concentration from 0.13M to 1.0M carbonate and 0.50M to 2.0M peroxide. The uranium beads were weighed before and after reacting with the etch solution, and from the weights of the beads, their diameters were calculated, before and after the etch. The etch rate on the beads was then calculated from the reduction in bead diameter, and independently by uranium analysis of the solution. The calculated etch rate ranged from about 4 x 10-4 to 8 x 10-4 cm per hour, dependent primarily on the peroxide concentration. A hydrogen analysis of the etched beads showed that no detectable hydrogen was introduced into the uranium metal by the etching process.

  17. Hydrogen Spillover between Single Gold Nanorods and Metal Oxide Supports: A Surface Plasmon Spectroscopy Study.

    PubMed

    Collins, Sean S E; Cittadini, Michela; Pecharromán, Carlos; Martucci, Alessandro; Mulvaney, Paul

    2015-08-25

    We used dark field spectroscopy to monitor the dissociation of hydrogen on single gold nanoparticles embedded in metal oxide supports. Individual gold nanorods were monitored in real time to reveal the peak position, the full width at half-maximum, and the relative intensity of the surface plasmon resonances during repeated N2-H2-N2 and air-H2-air cycles. Shifts in the spectra are shown to be due to changes in electron density and not to refractive index shifts in the environment. We demonstrate that hydrogen does not dissociate on gold nanorods (13 nm × 40 nm) at room temperature when in contact with silica and that electrons or hydrogen atoms migrate from Pt nanoparticles to Au nanoparticles through the supporting metal oxide at room temperature. However, this spillover mechanism only occurs for semiconducting oxides (anatase TiO2 and ZnO) and does not occur for Au and Pt nanoparticles embedded in silica. Finally, we show that hydrogen does dissociate directly on anatase surfaces at room temperature during air-H2-air cycles. Our results show that hydrogen spillover, surface dissociation of reactants, and surface migration of chemical intermediates can be detected and monitored in real time at the single particle level.

  18. The Role of Water in the Storage of Hydrogen in Metals

    NASA Technical Reports Server (NTRS)

    Hampton, Michael D.; Lomness, Janice K.; Giannuzzi, Lucille A.

    2001-01-01

    One major problem with the use of hydrogen is safe and efficient storage. In the pure form, bulky and heavy containers are required greatly reducing the efficiency of its use. Safety is also a great concern. Storage of hydrogen in the form of a metal hydride offers distinct advantages both in terms of volumetric efficiency and in terms of safety. As a result, an enormous amount of research is currently being done on metal-hydrogen systems. Practical application of these systems to storage of hydrogen can only occur when they are very well understood. In this paper, the preliminary results of a study of the surfaces of magnesium nickel alloys will be presented. Alloys that have been rendered totally unreactive with hydrogen as well as those that have been activated with liquid water and with water vapor were studied. Data obtained from XPS (X-ray Photoelectron Spectrometer) analysis, with samples held in vacuum for the shortest possible time to minimize the hydroxide degradation will be presented. Furthermore, TEM data on samples prepared in a new way that largely protects the surface from the high vacuum will be discussed.

  19. Integrating hydrogen generation and storage in a novel compact electrochemical system based on metal hydrides

    NASA Astrophysics Data System (ADS)

    Rangel, C. M.; Fernandes, V. R.; Slavkov, Y.; Bozukov, L.

    The development of efficient and reliable energy storage systems based on hydrogen technology represents a challenge to seasonal storage based on renewable hydrogen. State of the art renewable energy generation systems include separate units such as electrolyzer, hydrogen storage vessel and a fuel cell system for the conversion of H 2 back into electricity, when required. In this work, a novel electrochemical system has been developed which integrates hydrogen production, storage and compression in only one device, at relatively low cost and high efficiency. The developed prototype comprises a six-electrode cell assembly using an AB 5-type metal hydride and Ni plates as counter electrodes, in a 35-wt% KOH solution. Metal hydride electrodes with chemical composition LaNi 4.3Co 0.4Al 0.3 were prepared by high frequency vacuum melting followed by high temperature annealing. X-ray phase analysis showed typical hexagonal structure and no traces of other intermetallic compounds belonging to the La-Ni phase diagram. Thermodynamic study has been performed in a Sieverts type of apparatus produced by Labtech Int. During cycling, the charging/discharging process was studied in situ using a gas chromatograph from Agilent. It is anticipated that the device will be integrated as a combined hydrogen generator and storage unit in a stand-alone system associated to a 1-kW fuel cell.

  20. Metal complexes with varying intramolecular hydrogen bonding networks

    PubMed Central

    Lacy, David C.; Mukherjee, Jhumpa; Lucas, Robie L.; Day, Victor W.; Borovik, A.S.

    2013-01-01

    Alfred Werner described the attributes of the primary and secondary coordination spheres in his development of coordination chemistry. To examine the effects of the secondary coordination sphere on coordination chemistry, a series of tripodal ligands containing differing numbers of hydrogen bond (H-bond) donors were used to examine the effects of H-bonds on Fe(II), Mn(II)–acetato, and Mn(III)–OH complexes. The ligands containing varying numbers of urea and amidate donors allowed for systematic changes in the secondary coordination spheres of the complexes. Two of the Fe(II) complexes that were isolated as their Bu4N+ salts formed dimers in the solid-state as determined by X-ray diffraction methods, which correlates with the number of H-bonds present in the complexes (i.e., dimerization is favored as the number of H-bond donors increases). Electron paramagnetic resonance (EPR) studies suggested that the dimeric structures persist in acetonitrile. The Mn(II) complexes were all isolated as their acetato adducts. Furthermore, the synthesis of a rare Mn(III)–OH complex via dioxygen activation was achieved that contains a single intramolecular H-bond; its physical properties are discussed within the context of other Mn(III)–OH complexes. PMID:24904193

  1. Hydrogen-transparent metal surfaces produced by use of molten salts with very low oxygen and water activities

    SciTech Connect

    Deublein, G.; Huggins, R.A. . Dept. of Materials Science and Engineering)

    1989-08-01

    One can employ simple thermodynamic principles to predict conditions under which metals will not form hydrogen-blocking surface oxide layers in electrolyte environments. These principles are used to show that very low oxygen and water activities can be produced in some halide-based molten salt systems by the incorporation of alkali hydrides. Under these conditions, some normally very reactive metals will not form oxide surface layers. As a result, rapid interfacial and surface/bulk equilibria with hydrogen can be attained. Experiments are presented that verify these principles in the titanium-hydrogen and vanadium-hydrogen systems by using electro chemical methods to measure the thermodynamic and kinetic aspects of the solution of hydrogen and the formation of metal hydrides. In addition, it is shown that interfacial equilibrium is obtained very rapidly upon iron and aluminum in such metals.

  2. First principles assessment of ideal fracture energies of materials with mobile impurities: implications for hydrogen embrittlement of metals

    SciTech Connect

    Jiang, D.E.; Carter, Emily A. . E-mail: eac@chem.ucla.edu

    2004-09-20

    We propose that the ideal fracture energy of a material with mobile bulk impurities can be obtained within the framework of a Born-Haber thermodynamic cycle. We show that such a definition has the advantage of initial and final states at equilibrium, connected by well-defined and measurable energetic quantities, which can also be calculated from first principles. Using this approach, we calculate the ideal fracture energy of metals (Fe and Al) in the presence of varying amounts of hydrogen, using periodic density functional theory. We find that the metal ideal fracture energy decreases almost linearly with increasing hydrogen coverage, dropping by {approx}45% at one-half monolayer of hydrogen, indicating a substantial reduction of metal crystal cohesion in the presence of hydrogen atoms and providing some insight into the cohesion-reduction mechanism of hydrogen embrittlement in metals.

  3. Hydrogenation and dehydrogenation iron pincer catalysts capable of metal-ligand cooperation by aromatization/dearomatization.

    PubMed

    Zell, Thomas; Milstein, David

    2015-07-21

    The substitution of expensive and potentially toxic noble-metal catalysts by cheap, abundant, environmentally benign, and less toxic metals is highly desirable and in line with green chemistry guidelines. We have recently discovered a new type of metal-ligand cooperation, which is based on the reversible dearomatization/aromatization of different heteroaromatic ligand cores caused by deprotonation/protonation of the ligand. More specifically, we have studied complexes of various transition metals (Ru, Fe, Co, Rh, Ir, Ni, Pd, Pt, and Re) bearing pyridine- and bipyridine-based PNP and PNN pincer ligands, which have slightly acidic methylene protons. In addition, we have discovered long-range metal-ligand cooperation in acridine-based pincer ligands, where the cooperation takes place at the electrophilic C-9 position of the acridine moiety leading to dearomatization of its middle ring. This type of metal-ligand cooperation was used for the activation of chemical bonds, including H-H, C-H (sp(2) and sp(3)), O-H, N-H, and B-H bonds. This unusual reactivity likely takes place in various catalytic hydrogenation, dehydrogenation, and related reactions. In this Account, we summarize our studies on novel bifunctional iron PNP and PNN pincer complexes, which were designed on the basis of their ruthenium congeners. Iron PNP pincer complexes serve as efficient (pre)catalysts for hydrogenation and dehydrogenation reactions under remarkably mild conditions. Their catalytic applications include atom-efficient and industrially important hydrogenation reactions of ketones, aldehydes, and esters to the corresponding alcohols. Moreover, they catalyze the hydrogenation of carbon dioxide to sodium formate in the presence of sodium hydroxide, the selective decomposition of formic acid to carbon dioxide and hydrogen, and the E-selective semihydrogenation of alkynes to give E-alkenes. These catalysts feature, compared to other iron-based catalysts, very high catalytic activities which in

  4. Solar hydrogen production with semiconductor metal oxides: new directions in experiment and theory.

    PubMed

    Valdés, Álvaro; Brillet, Jeremie; Grätzel, Michael; Gudmundsdóttir, Hildur; Hansen, Heine A; Jónsson, Hannes; Klüpfel, Peter; Kroes, Geert-Jan; Le Formal, Florian; Man, Isabela C; Martins, Rafael S; Nørskov, Jens K; Rossmeisl, Jan; Sivula, Kevin; Vojvodic, Aleksandra; Zäch, Michael

    2012-01-01

    An overview of a collaborative experimental and theoretical effort toward efficient hydrogen production via photoelectrochemical splitting of water into di-hydrogen and di-oxygen is presented here. We present state-of-the-art experimental studies using hematite and TiO(2) functionalized with gold nanoparticles as photoanode materials, and theoretical studies on electro and photo-catalysis of water on a range of metal oxide semiconductor materials, including recently developed implementation of self-interaction corrected energy functionals. PMID:22083224

  5. SOLUBILITY OF WATER ICE IN METALLIC HYDROGEN: CONSEQUENCES FOR CORE EROSION IN GAS GIANT PLANETS

    SciTech Connect

    Wilson, H. F.; Militzer, B.

    2012-01-20

    Using ab initio simulations we investigate whether water ice is stable in the cores of giant planets, or whether it dissolves into the layer of metallic hydrogen above. By Gibbs free energy calculations we find that for pressures between 10 and 40 Mbar the ice-hydrogen interface is thermodynamically unstable at temperatures above approximately 3000 K, far below the temperature of the core-mantle boundaries in Jupiter and Saturn. This implies that the dissolution of core material into the fluid layers of giant planets is thermodynamically favored, and that further modeling of the extent of core erosion is warranted.

  6. Considerations for Storage of High Test Hydrogen Peroxide (HTP) Utilizing Non-Metal Containers

    NASA Technical Reports Server (NTRS)

    Moore, Robin E.; Scott, Joseph P.; Wise, Harry

    2005-01-01

    When working with high concentrations of hydrogen peroxide, it is critical that the storage container be constructed of the proper materials, those which will not degrade to the extent that container breakdown or dangerous decomposition occurs. It has been suggested that the only materials that will safely contain the peroxide for a significant period of time are metals of stainless steel construction or aluminum use as High Test Hydrogen Peroxide (HTP) Containers. The stability and decomposition of HTP will be also discussed as well as various means suggested in the literature to minimize these problems. The dangers of excess oxygen generation are also touched upon.

  7. Scattering influences in quantitative fission neutron radiography for the in situ analysis of hydrogen distribution in metal hydrides

    NASA Astrophysics Data System (ADS)

    Börries, S.; Metz, O.; Pranzas, P. K.; Bücherl, T.; Söllradl, S.; Dornheim, M.; Klassen, T.; Schreyer, A.

    2015-10-01

    In situ neutron radiography allows for the time-resolved study of hydrogen distribution in metal hydrides. However, for a precise quantitative investigation of a time-dependent hydrogen content within a host material, an exact knowledge of the corresponding attenuation coefficient is necessary. Additionally, the effect of scattering has to be considered as it is known to violate Beer's law, which is used to determine the amount of hydrogen from a measured intensity distribution. Within this study, we used a metal hydride inside two different hydrogen storage tanks as host systems, consisting of steel and aluminum. The neutron beam attenuation by hydrogen was investigated in these two different setups during the hydrogen absorption process. A linear correlation to the amount of absorbed hydrogen was found, allowing for a readily quantitative investigation. Further, an analysis of scattering contributions on the measured intensity distributions was performed and is described in detail.

  8. Metallization of hydrogen and the essential differences between dynamic and static compression

    NASA Astrophysics Data System (ADS)

    Nellis, W.

    2013-06-01

    In 1935 Wigner and Huntington (WH) predicted that at density DThry = 0.62 mole H/cm3, ``very low temperatures,'' and a pressure greater than 25 GPa, bcc H2 undergoes an isostructural phase transition directly to H with an associated insulator-metal transition (IMT). In 1996 metallic fluid H was made under dynamic compression in a cross over from H2 to H that completes at Dexp = 0.64 mole H/cm3, 140 GPa and T ~ 2600 K. The Free-electron Fermi temperature TF = 220,000 K and T/TF = 0.012 << 1 , as for ordinary metals at 300 K. To date solid metallic hydrogen has yet to be made at static pressures up to ~360 GPa at T ~ 300 K. This difference between electrical conductivity of H2 compressed dynamically and statistically begs the question of why fluid H at 140 GPa and ~3000 K becomes metallic at 0.64 mol H/cm3, the density predicted by WH for their IMT at low T; whereas metallization of solid H2 or H near 300 K is yet to be achieved experimentally at pressures up to ~360 GPa? The answer is systematic differences induced by the rate of application of pressure in the two methods. Slow compression at ~300 K strengthens solid H2 by inducing intermolecular bonds, which impede dissociation, metallization and perhaps even thermal equilibrium. Fast dynamic compression of liquid H2 up to ~3000 K precludes formation of intermolecular H-H bonds, which permits fluid H2 to weaken to dissociation and thus metallization at 140 GPa. Dynamic- and static-compression effects on materials will be compared in the context of how they effect metallization of hydrogen.

  9. Graphene oxide/metal nanocrystal multilaminates as the atomic limit for safe and selective hydrogen storage

    DOE PAGESBeta

    Cho, Eun Seon; Ruminski, Anne M.; Aloni, Shaul; Liu, Yi-Sheng; Guo, Jinghua; Urban, Jeffrey J.

    2016-02-23

    Interest in hydrogen fuel is growing for automotive applications; however, safe, dense, solid-state hydrogen storage remains a formidable scientific challenge. Metal hydrides offer ample storage capacity and do not require cryogens or exceedingly high pressures for operation. However, hydrides have largely been abandoned because of oxidative instability and sluggish kinetics. We report a new, environmentally stable hydrogen storage material constructed of Mg nanocrystals encapsulated by atomically thin and gas-selective reduced graphene oxide (rGO) sheets. This material, protected from oxygen and moisture by the rGO layers, exhibits exceptionally dense hydrogen storage (6.5 wt% and 0.105 kg H2 per litre in themore » total composite). As rGO is atomically thin, this approach minimizes inactive mass in the composite, while also providing a kinetic enhancement to hydrogen sorption performance. In conclusion, these multilaminates of rGO-Mg are able to deliver exceptionally dense hydrogen storage and provide a material platform for harnessing the attributes of sensitive nanomaterials in demanding environments.« less

  10. Graphene oxide/metal nanocrystal multilaminates as the atomic limit for safe and selective hydrogen storage

    PubMed Central

    Cho, Eun Seon; Ruminski, Anne M.; Aloni, Shaul; Liu, Yi-Sheng; Guo, Jinghua; Urban, Jeffrey J.

    2016-01-01

    Interest in hydrogen fuel is growing for automotive applications; however, safe, dense, solid-state hydrogen storage remains a formidable scientific challenge. Metal hydrides offer ample storage capacity and do not require cryogens or exceedingly high pressures for operation. However, hydrides have largely been abandoned because of oxidative instability and sluggish kinetics. We report a new, environmentally stable hydrogen storage material constructed of Mg nanocrystals encapsulated by atomically thin and gas-selective reduced graphene oxide (rGO) sheets. This material, protected from oxygen and moisture by the rGO layers, exhibits exceptionally dense hydrogen storage (6.5 wt% and 0.105 kg H2 per litre in the total composite). As rGO is atomically thin, this approach minimizes inactive mass in the composite, while also providing a kinetic enhancement to hydrogen sorption performance. These multilaminates of rGO-Mg are able to deliver exceptionally dense hydrogen storage and provide a material platform for harnessing the attributes of sensitive nanomaterials in demanding environments. PMID:26902901

  11. DIRECT DECOMPOSITION OF METHANE TO HYDROGEN ON METAL LOADED ZEOLITE CATALYST

    SciTech Connect

    Lucia M. Petkovic; Daniel M. Ginosar; Kyle C. Burch; Harry W. Rollins

    2005-08-01

    The manufacture of hydrogen from natural gas is essential for the production of ultra clean transportation fuels. Not only is hydrogen necessary to upgrade low quality crude oils to high-quality, low sulfur ultra clean transportation fuels, hydrogen could eventually replace gasoline and diesel as the ultra clean transportation fuel of the future. Currently, refinery hydrogen is produced through the steam reforming of natural gas. Although efficient, the process is responsible for a significant portion of refinery CO2 emissions. This project is examining the direct catalytic decomposition of methane as an alternative to steam reforming. The energy required to produce one mole of hydrogen is slightly lower and the process does not require water-gas-shift or pressure-swing adsorption units. The decomposition process does not produce CO2 emissions and the product is not contaminated with CO -- a poison for PEM fuel cells. In this work we examined the direct catalytic decomposition of methane over a metal modified zeolite catalyst and the recovery of catalyst activity by calcination. A favorable production of hydrogen was obtained, when compared with previously reported nickel-zeolite supported catalysts. Reaction temperature had a strong influence on catalyst activity and on the type of carbon deposits. The catalyst utilized at 873 and 973 K could be regenerated without any significant loss of activity, however the catalyst utilized at 1073 K showed some loss of activity after regeneration.

  12. Graphene oxide/metal nanocrystal multilaminates as the atomic limit for safe and selective hydrogen storage.

    PubMed

    Cho, Eun Seon; Ruminski, Anne M; Aloni, Shaul; Liu, Yi-Sheng; Guo, Jinghua; Urban, Jeffrey J

    2016-02-23

    Interest in hydrogen fuel is growing for automotive applications; however, safe, dense, solid-state hydrogen storage remains a formidable scientific challenge. Metal hydrides offer ample storage capacity and do not require cryogens or exceedingly high pressures for operation. However, hydrides have largely been abandoned because of oxidative instability and sluggish kinetics. We report a new, environmentally stable hydrogen storage material constructed of Mg nanocrystals encapsulated by atomically thin and gas-selective reduced graphene oxide (rGO) sheets. This material, protected from oxygen and moisture by the rGO layers, exhibits exceptionally dense hydrogen storage (6.5 wt% and 0.105 kg H2 per litre in the total composite). As rGO is atomically thin, this approach minimizes inactive mass in the composite, while also providing a kinetic enhancement to hydrogen sorption performance. These multilaminates of rGO-Mg are able to deliver exceptionally dense hydrogen storage and provide a material platform for harnessing the attributes of sensitive nanomaterials in demanding environments.

  13. Graphene oxide/metal nanocrystal multilaminates as the atomic limit for safe and selective hydrogen storage

    NASA Astrophysics Data System (ADS)

    Cho, Eun Seon; Ruminski, Anne M.; Aloni, Shaul; Liu, Yi-Sheng; Guo, Jinghua; Urban, Jeffrey J.

    2016-02-01

    Interest in hydrogen fuel is growing for automotive applications; however, safe, dense, solid-state hydrogen storage remains a formidable scientific challenge. Metal hydrides offer ample storage capacity and do not require cryogens or exceedingly high pressures for operation. However, hydrides have largely been abandoned because of oxidative instability and sluggish kinetics. We report a new, environmentally stable hydrogen storage material constructed of Mg nanocrystals encapsulated by atomically thin and gas-selective reduced graphene oxide (rGO) sheets. This material, protected from oxygen and moisture by the rGO layers, exhibits exceptionally dense hydrogen storage (6.5 wt% and 0.105 kg H2 per litre in the total composite). As rGO is atomically thin, this approach minimizes inactive mass in the composite, while also providing a kinetic enhancement to hydrogen sorption performance. These multilaminates of rGO-Mg are able to deliver exceptionally dense hydrogen storage and provide a material platform for harnessing the attributes of sensitive nanomaterials in demanding environments.

  14. Application of alkali metal-doped carbons for hydrogen recovery and isotope separation.

    PubMed

    Akuzawa, N; Okano, Y; Iwashita, T; Matsumoto, R; Soneda, Y

    2011-10-01

    Hydrogen-sorption isotherms of alkali metal-doped carbons at 77 K were determined for promoting application of these materials as hydrogen-recovery and isotope-separation agent. The hydrogen-sorption behavior of rubidium-doped Grafoil, with composition of RbC24, showed high sorption ability against hydrogen at low pressure. Taking into account the fact that sorption-desorption was fast and reversible, and the equilibrium pressure at half coverage was very low, i.e., 40 Pa, RbC24 prepared from Grafoil is promising as a recovery agent for hydrogen gas at low pressure. The hydrogen (H2)/deuterium(D2)-sorption isotherms of potassium-doped carbons with composition of KC10, prepared from multi wall carbon nanotube (MWCNT) and carbons derived from petroleum cokes with heat-treatment temperatures of 1000 and 1500 degrees C, were also determined. Isotope separation coefficient was estimated from those isotherms. A very large isotope effect was found for KC10 prepared from MWCNT, comparable to those prepared from carbons with heat-treatment temperatures of 1000 or 1500 degrees C. However, a severe problem was found for KC10 (MWCNT) that repetition of the sorption-desorption cycles resulted in the decrease of the sorbed amount of H2 and D2.

  15. Cleavage of hydrogen by activation at a single non-metal centre - towards new hydrogen storage materials.

    PubMed

    Grabowski, Sławomir J

    2015-05-28

    Molecular surfaces of non-metal species are often characterized by both positive and negative regions of electrostatic potential (EP) at a non-metal centre. This centre may activate molecular hydrogen which further leads to the addition reaction. The positive EP regions at the non-metal centres correspond to σ-holes; the latter sites are enhanced by electronegative substituents. This is why the following simple moieties; PFH2, SFH, AsFH2, SeFH, BrF3, PF(CH3)2 and AsF(CH3)2, were chosen here to analyze the H2 activation and its subsequent splitting at the P, As, S, Se and Br centres. Also the reverse H-H bond reforming process is analyzed. MP2/aug-cc-pVTZ calculations were performed for systems corresponding to different stages of these processes. The sulphur centre in the SFH moiety is analyzed in detail since the potential barrier height for the addition reaction for this species is the lowest of the moieties analyzed here. The results of calculations show that the SFH + H2 → SFH3 reaction in the gas phase is endothermic but it is exothermic in polar solvents. PMID:25939477

  16. Cleavage of hydrogen by activation at a single non-metal centre - towards new hydrogen storage materials.

    PubMed

    Grabowski, Sławomir J

    2015-05-28

    Molecular surfaces of non-metal species are often characterized by both positive and negative regions of electrostatic potential (EP) at a non-metal centre. This centre may activate molecular hydrogen which further leads to the addition reaction. The positive EP regions at the non-metal centres correspond to σ-holes; the latter sites are enhanced by electronegative substituents. This is why the following simple moieties; PFH2, SFH, AsFH2, SeFH, BrF3, PF(CH3)2 and AsF(CH3)2, were chosen here to analyze the H2 activation and its subsequent splitting at the P, As, S, Se and Br centres. Also the reverse H-H bond reforming process is analyzed. MP2/aug-cc-pVTZ calculations were performed for systems corresponding to different stages of these processes. The sulphur centre in the SFH moiety is analyzed in detail since the potential barrier height for the addition reaction for this species is the lowest of the moieties analyzed here. The results of calculations show that the SFH + H2 → SFH3 reaction in the gas phase is endothermic but it is exothermic in polar solvents.

  17. Bifacial Base-Pairing Behaviors of 5-Hydroxyuracil DNA Bases through Hydrogen Bonding and Metal Coordination.

    PubMed

    Takezawa, Yusuke; Nishiyama, Kotaro; Mashima, Tsukasa; Katahira, Masato; Shionoya, Mitsuhiko

    2015-10-12

    A novel bifacial ligand-bearing nucleobase, 5-hydroxyuracil (U(OH) ), which forms both a hydrogen-bonded base pair (U(OH) -A) and a metal-mediated base pair (U(OH) -M-U(OH) ) has been developed. The U(OH) -M-U(OH) base pairs were quantitatively formed in the presence of lanthanide ions such as Gd(III) when U(OH) -U(OH) pairs were consecutively incorporated into DNA duplexes. This result established metal-assisted duplex stabilization as well as DNA-templated assembly of lanthanide ions. Notably, a duplex possessing U(OH) -A base pairs was destabilized by addition of Gd(III) ions. This observation suggests that the hybridization behaviors of the U(OH) -containing DNA strands are altered by metal complexation. Thus, the U(OH) nucleobase with a bifacial base-pairing property holds great promise as a component for metal-responsive DNA materials.

  18. Metallic contamination in hydrogen plasma immersion ion implantation of silicon

    NASA Astrophysics Data System (ADS)

    Chu, Paul K.; Fu, Ricky K. Y.; Zeng, Xuchu; Kwok, Dixon T. K.

    2001-10-01

    In plasma immersion ion implantation (PIII), ions bombard all surfaces inside the PIII vacuum chamber, especially the negatively pulsed biased sample stage and to a lesser extent the interior of the vacuum chamber. As a result, contaminants sputtered from these exposed surfaces can be reimplanted into or adsorb on the silicon wafer. Using particle-in-cell theoretical simulation, we determine the relative ion doses incident on the top, side, and bottom surfaces of three typical sample chuck configurations: (i) a bare conducting stage with the entire sample platen and high-voltage feedthrough/supporting rod exposed and under a high voltage, (ii) a stage with only the sample platen exposed to the plasma but the high-voltage feedthrough protected by an insulating quartz shroud, and (iii) a bare stage with a silicon extension or guard ring to reduce the number of ions bombarding the side and bottom of the sample platen. Our simulation results reveal that the ratio of the incident dose impacting the top of the sample platen to that impacting the side and bottom of the sample stage can be improved to 49% using a guard ring. To corroborate our theoretical results, we experimentally determine the amounts of metallic contaminants on 100 mm silicon wafers implanted using a bare chuck and with a 150 mm silicon wafer inserted between the 100 mm wafer and sample stage to imitate the guard ring. We also discuss the effectiveness of a replaceable all-silicon liner inside the vacuum chamber to address the second source of contamination, that from the interior wall of the vacuum chamber. Our results indicate a significant improvement when an all-silicon liner and silicon guard ring are used simultaneously.

  19. Cryogenic Gellant and Fuel Formulation for Metallized Gelled Propellants: Hydrocarbons and Hydrogen with Aluminum

    NASA Technical Reports Server (NTRS)

    Wong, Wing; Starkovich, John; Adams, Scott; Palaszewski, Bryan; Davison, William; Burt, William; Thridandam, Hareesh; Hu-Peng, Hsiao; Santy, Myrrl J.

    1994-01-01

    An experimental program to determine the viability of nanoparticulate gellant materials for gelled hydrocarbons and gelled liquid hydrogen was conducted. The gellants included alkoxides (BTMSE and BTMSH) and silica-based materials. Hexane, ethane, propane and hydrogen were gelled with the newly-formulated materials and their rheological properties were determined: shear stress versus shear rate and their attendant viscosities. Metallized hexane with aluminum particles was also rheologically characterized. The propellant and gellant formulations were selected for the very high surface area and relatively-high energy content of the gellants. These new gellants can therefore improve rocket engine specific impulse over that obtained with traditional cryogenic-fuel gellant materials silicon dioxide, frozen methane, or frozen ethane particles. Significant reductions in the total mass of the gellant were enabled in the fuels. In gelled liquid hydrogen, the total mass of gellant was reduced from 10-40 wt percent of frozen hydrocarbon particles to less that 8 wt percent with the alkoxide.

  20. Metal-encapsulated organolead halide perovskite photocathode for solar-driven hydrogen evolution in water

    NASA Astrophysics Data System (ADS)

    Crespo-Quesada, Micaela; Pazos-Outón, Luis M.; Warnan, Julien; Kuehnel, Moritz F.; Friend, Richard H.; Reisner, Erwin

    2016-09-01

    Lead-halide perovskites have triggered the latest breakthrough in photovoltaic technology. Despite the great promise shown by these materials, their instability towards water even in the presence of low amounts of moisture makes them, a priori, unsuitable for their direct use as light harvesters in aqueous solution for the production of hydrogen through water splitting. Here, we present a simple method that enables their use in photoelectrocatalytic hydrogen evolution while immersed in an aqueous solution. Field's metal, a fusible InBiSn alloy, is used to efficiently protect the perovskite from water while simultaneously allowing the photogenerated electrons to reach a Pt hydrogen evolution catalyst. A record photocurrent density of -9.8 mA cm-2 at 0 V versus RHE with an onset potential as positive as 0.95+/-0.03 V versus RHE is obtained. The photoelectrodes show remarkable stability retaining more than 80% of their initial photocurrent for ~1 h under continuous illumination.

  1. Magnetic Properties and Magnetocaloric Effect of Hydrogen Treated Gd-BASED Bulk Metallic Glass

    NASA Astrophysics Data System (ADS)

    Zheng, Q.; Fu, H.; Wang, M. X.

    The metallic glass Gd52.5Co18.5Al28Zr1 preserves the amorphous structure after hydrogenation at 473 K for 48 h. The absorption of hydrogen leads to the reduction of the magnetic transition temperature due to the expansion of the interatomic distance. The magnetic anisotropy is introduced and the coercivity and remanence are 352 Oe and 12.5 emu/g at 1.8 K, respectively. The maxima of magnetic entropy changes are 11.3 and 7.5 J/kg K with the magnetic field changes of 0 to 70 kOe and 0 to 50 kOe, respectively. The decline of the magnetic entropy changes can be attributed to the disappearance of the collinear ferromagnetic characteristics and the difficulty of saturation for the magnetization after hydrogenation.

  2. Computational modeling of the mechanism of hydrogen embrittlement (HE) and stress corrosion cracking (SCC) in metals

    NASA Astrophysics Data System (ADS)

    Cendales, E. D.; Orjuela, F. A.; Chamarraví, O.

    2016-02-01

    In this article theoretical models and some existing data sets were examined in order to model the two main causes (hydrogen embrittlement and corrosion-cracking under stress) of the called environmentally assisted cracking phenomenon (EAC). Additionally, a computer simulation of flat metal plate subject to mechanical stress and cracking due both to hydrogen embrittlement and corrosion was developed. The computational simulation was oriented to evaluate the effect on the stress-strain behavior, elongation percent and the crack growth rate of AISI SAE 1040 steel due to three corrosive enviroments (H2 @ 0.06MPa; HCl, pH=1.0; HCl, pH=2.5). From the computer simulation we conclude that cracking due to internal corrosion of the material near to the crack tip limits affects more the residual strength of the flat plate than hydrogen embrittlement and generates a failure condition almost imminent of the mechanical structural element.

  3. Hydrogen storage properties of light metal adatoms (Li, Na) decorated fluorographene monolayer.

    PubMed

    Hussain, T; Islam, M S; Rao, G S; Panigrahi, P; Gupta, D; Ahuja, Rajeev

    2015-07-10

    Owing to its high energy density, the potential of hydrogen (H2) as an energy carrier has been immense, however its storage remains a big obstacle and calls for an efficient storage medium. By means of density functional theory (DFT) in spin polarized generalized gradient approximation (GGA), we have investigated the structural, electronic and hydrogen storage properties of a light alkali metal (Li, Na) functionalized fluorographene monolayer (FG). Metal adatoms bind to the FG with significantly high binding energy, much higher than their cohesive energies, which helps to achieve a uniform distribution of metal adatoms on the monolayer and consequently ensure reversibility. Due to a difference of electronegativities, each metal adatom transfers a substantial amount of its charge to the FG monolayer and attains a partial positive state, which facilitates the adsorption of multiple H2 molecules around the adatoms by electrostatic as well as van der Waals interactions. To get a better description of H2 adsorption energies with metal-doped systems, we have also performed calculations using van der Waals corrections. For both the functionalized systems, the results indicate a reasonably high H2 storage capacity with H2 adsorption energies falling into the range for the practical applications.

  4. Local atomic structure modulations activate metal oxide as electrocatalyst for hydrogen evolution in acidic water.

    PubMed

    Li, Yu Hang; Liu, Peng Fei; Pan, Lin Feng; Wang, Hai Feng; Yang, Zhen Zhong; Zheng, Li Rong; Hu, P; Zhao, Hui Jun; Gu, Lin; Yang, Hua Gui

    2015-08-19

    Modifications of local structure at atomic level could precisely and effectively tune the capacity of materials, enabling enhancement in the catalytic activity. Here we modulate the local atomic structure of a classical but inert transition metal oxide, tungsten trioxide, to be an efficient electrocatalyst for hydrogen evolution in acidic water, which has shown promise as an alternative to platinum. Structural analyses and theoretical calculations together indicate that the origin of the enhanced activity could be attributed to the tailored electronic structure by means of the local atomic structure modulations. We anticipate that suitable structure modulations might be applied on other transition metal oxides to meet the optimal thermodynamic and kinetic requirements, which may pave the way to unlock the potential of other promising candidates as cost-effective electrocatalysts for hydrogen evolution in industry.

  5. Effect of metal and nonmetal on adsorption of hydrogen in torus-type C120

    NASA Astrophysics Data System (ADS)

    Zhou, Caihua; Ma, Ning; Fan, Guang; Ma, Zhanying

    2016-02-01

    The hydrogen adsorption properties for the torus-type C120, and the changes of adsorption influenced by nonmetal and metal have been systematically investigated. The results show that, in the pristine torus-type C120, the inner carbon atoms have more negative static potential than the outer ones. H2 intends to accumulate at the area near inner carbon atoms. However, torus-type C120 is modified by nonmetal (N and O) or metal (Li), the accumulated fields of H2 are changed. Li can evidently enhance the hydrogen storage capacity. The most gravimetric density is predicted to be 7.21 wt% for the 8Li-C120 in 77 K and 1200 kPa.

  6. Local atomic structure modulations activate metal oxide as electrocatalyst for hydrogen evolution in acidic water

    PubMed Central

    Li, Yu Hang; Liu, Peng Fei; Pan, Lin Feng; Wang, Hai Feng; Yang, Zhen Zhong; Zheng, Li Rong; Hu, P.; Zhao, Hui Jun; Gu, Lin; Yang, Hua Gui

    2015-01-01

    Modifications of local structure at atomic level could precisely and effectively tune the capacity of materials, enabling enhancement in the catalytic activity. Here we modulate the local atomic structure of a classical but inert transition metal oxide, tungsten trioxide, to be an efficient electrocatalyst for hydrogen evolution in acidic water, which has shown promise as an alternative to platinum. Structural analyses and theoretical calculations together indicate that the origin of the enhanced activity could be attributed to the tailored electronic structure by means of the local atomic structure modulations. We anticipate that suitable structure modulations might be applied on other transition metal oxides to meet the optimal thermodynamic and kinetic requirements, which may pave the way to unlock the potential of other promising candidates as cost-effective electrocatalysts for hydrogen evolution in industry. PMID:26286479

  7. Two-component Fermi-liquid theory - Equilibrium properties of liquid metallic hydrogen

    NASA Technical Reports Server (NTRS)

    Oliva, J.; Ashcroft, N. W.

    1981-01-01

    It is reported that the transition of condensed hydrogen from an insulating molecular crystal phase to a metallic liquid phase, at zero temperature and high pressure, appears possible. Liquid metallic hydrogen (LMH), comprising interpenetrating proton and electron fluids, would constitute a two-component Fermi liquid with both a very high component-mass ratio and long-range, species-dependent bare interactions. The low-temperature equilibrium properties of LMH are examined by means of a generalization to the case of two components of the phenomenological Landau Fermi-liquid theory, and the low-temperature specific heat, compressibility, thermal expansion coefficient and spin susceptibility are given. It is found that the specific heat and the thermal expansion coefficient are vastly greater in the liquid than in the corresponding solid, due to the presence of proton quasiparticle excitations in the liquid.

  8. Investigation of multi-metal catalysts for stable hydrogen production via urea electrolysis

    NASA Astrophysics Data System (ADS)

    King, Rebecca L.; Botte, Gerardine G.

    It has been shown that urea electrolysis is a viable method for wastewater remediation and simultaneous production of valuable hydrogen. Inexpensive nickel catalyst is optimal for the oxidation of urea in alkaline media but improvements are needed to minimize surface blockage and increase current density. Multi-metal catalysts were investigated by depositing platinum group metals on a nickel substrate. Rhodium and nickel proved synergistic to reduce surface blockage and increase catalyst stability. Rh-Ni electrodes reduced the overpotential for the electro-oxidation of urea and improved the current density by a factor of 200 compared to a Ni catalyst.

  9. Simulation studies of a model of high-density metallic hydrogen

    NASA Technical Reports Server (NTRS)

    Mon, K. K.; Chester, G. V.; Ashcroft, N. W.

    1980-01-01

    Upper bounds for the ground-state energies of liquid and solid phases of metallic hydrogen and metallic deuterium have been calculated with variational methods and Monte Carlo techniques. At four densities (0.8, 1.2, 1.36, and 1.488) crystalline phases are clearly preferred in the sense that the energy difference, when compared to the liquid, is in excess of the errors inherent in the numerical procedures. At a fifth density (1.6), the energy differences between solid and liquid phases are smaller than these errors.

  10. Evaluation of the performance and applications of a metal hydride hydrogen compressor

    NASA Astrophysics Data System (ADS)

    Klausner, M.; McMillan, J.; Wickham, D.

    1984-09-01

    Low-grade energy from geothermal, solar or industrial process heat sources may be utilized to power a metal hydride compressor. A four-stage compressor, containing rare-earth metal alloys, compressed 35 standard liters per minute (SLPM) of hydrogen from 0.35 MPa (45 psia) to 3.5 MPa (480 psia), using 680 kg/h (3 GPM) of 80 C water. A computer model was written to simulate compressor performance. The application of the compressor in power cycles (Brayton gas cycles), and the economics of compressor operation were examined.

  11. Anion Binding in Metal-Organic Frameworks Functionalized with Urea Hydrogen-Bonding Groups

    SciTech Connect

    Custelcean, Radu; Moyer, Bruce A; Bryantsev, Vyacheslav S.; Hay, Benjamin P.

    2006-01-01

    A series of metal-organic frameworks (MOFs) functionalized with urea hydrogen-bonding groups has been synthesized and structurally analyzed by single-crystal X-ray diffraction to evaluate the efficacy of anion coordination by urea within the structural constraints of the MOFs. We found that urea-based functionalities may be used for anion binding within metal-organic frameworks when the tendency for urea{hor_ellipsis}urea self-association is decreased by strengthening the intramolecular CH{hor_ellipsis}O hydrogen bonding of N-phenyl substituents to the carbonyl oxygen atom. Theoretical calculations indicate that N,N'-bis(m-pyridyl)urea (BPU) and N,N'-bis(m-cyanophenyl)urea (BCPU) should have enhanced hydrogen-bonding donor abilities toward anions and decreased tendencies to self-associate into hydrogen-bonded tapes compared to other disubstituted ureas. Accordingly, BPU and BCPU were incorporated in MOFs as linkers through coordination of various Zn, Cu, and Ag transition metal salts, including Zn(ClO{sub 4}){sub 2}, ZnSO{sub 4}, Cu(NO{sub 3}){sub 2}, Cu(CF{sub 3}SO{sub 3}){sub 2}, AgNO{sub 3}, and AgSO{sub 3}CH{sub 3}. Structural analysis by single-crystal X-ray diffraction showed that these linkers are versatile anion binders, capable of chelate hydrogen bonding to all of the oxoanions explored. Anion coordination by the urea functionalities was found to successfully compete with urea self-association in all cases except for that of charge-diffuse perchlorate.

  12. TREATMENT OF METALS IN GROUND WATER USING AN ORGANIC-BASED SULFATE-REDUCING PERMEABLE REACTIVE BARRIER

    EPA Science Inventory

    A pilot permeable reactive barrier (PRB) consisting of a mixture of leaf compost, zero-valent iron (ZVI) filings, limestone and pea gravel was evaluated at a former phosphate fertilizer manufacturing facility in Charleston, S.C. The PRB is designed to treat arsenic and heavy met...

  13. Phase, microstructure and hydrogen storage properties of Mg-Ni materials synthesized from metal nanoparticles

    NASA Astrophysics Data System (ADS)

    Shao, Huaiyu; Chen, Chunguang; Liu, Tong; Li, Xingguo

    2014-04-01

    After Mg and Ni nanoparticles were fabricated by hydrogen plasma metal reaction, Mg-rich MgxNi100-x(75 < x < 90) materials were synthesized from these metal nanoparticles to study the synergistic effects for hydrogen storage in these samples to show both good kinetics and high capacity. These MgxNi100-x materials may absorb hydrogen with a capacity of around 3.3-5.1 wt% in 1 min at 573 K. The Mg90Ni10 sample shows a hydrogen capacity of 6.1 wt%. The significant kinetic enhancement is thought to be due to the unique nanostructure from the special synthesis route, the catalytic effect of the Mg2Ni nano phase, and the synergistic effects between the Mg2Ni and Mg phases in the materials. An interesting phenomenon which has never been reported before was observed during pressure composition isotherm (PCT) measurements. One steep step in the absorption process and two obviously separated steps in the desorption process during PCT measurements of Mg80Ni20 and Mg90Ni10 samples were observed and a possible reason from the kinetic performance of the Mg2Ni and Mg phases in absorption and desorption processes was explained. These MgxNi100-x materials synthesized from Mg and Ni nanoparticles show high capacity and good kinetics, which makes these materials very promising candidates for thermal storage or energy storage and utilization for renewable power.

  14. Phase, microstructure and hydrogen storage properties of Mg-Ni materials synthesized from metal nanoparticles.

    PubMed

    Shao, Huaiyu; Chen, Chunguang; Liu, Tong; Li, Xingguo

    2014-04-01

    After Mg and Ni nanoparticles were fabricated by hydrogen plasma metal reaction, Mg-rich MgxNi₁₀₀₋x(75 < x < 90) materials were synthesized from these metal nanoparticles to study the synergistic effects for hydrogen storage in these samples to show both good kinetics and high capacity. These MgxNi₁₀₀₋x materials may absorb hydrogen with a capacity of around 3.3-5.1 wt% in 1 min at 573 K. The Mg₉₀Ni₁₀ sample shows a hydrogen capacity of 6.1 wt%. The significant kinetic enhancement is thought to be due to the unique nanostructure from the special synthesis route, the catalytic effect of the Mg₂Ni nano phase, and the synergistic effects between the Mg₂Ni and Mg phases in the materials. An interesting phenomenon which has never been reported before was observed during pressure composition isotherm (PCT) measurements. One steep step in the absorption process and two obviously separated steps in the desorption process during PCT measurements of Mg₈₀Ni₂₀ and Mg₉₀Ni₁₀ samples were observed and a possible reason from the kinetic performance of the Mg₂Ni and Mg phases in absorption and desorption processes was explained. These MgxNi₁₀₀₋x materials synthesized from Mg and Ni nanoparticles show high capacity and good kinetics, which makes these materials very promising candidates for thermal storage or energy storage and utilization for renewable power.

  15. Integrating photobiological hydrogen production with dye-metal bioremoval from simulated textile wastewater.

    PubMed

    Kaushik, Anubha; Mona, Sharma; Kaushik, C P

    2011-11-01

    The study reports production of hydrogen in photobioreactors with free (PBR(Fr)) and immobilized (PBR(Imm)) Nostoc biomass at enhanced and sustained rates. Before running the photobioreactors, effects of different immobilization matrices and cyanobacterial dose on hydrogen production were studied in batch mode. As hydrogen production in the PBRs declined spent biomass from the photobioreactors were collected and utilized further for column biosorption of highly toxic dyes (Reactive Red 198+Crystal Violet) and metals (hexavalent chromium and bivalent cobalt) from simulated textile wastewater. Breakthrough time, adsorption capacity and exhaustion time of the biosorption column were studied. The photobioreactors with free and immobilized cyanobacterium produced hydrogen at average rates of 101 and 151 μmol/h/mg Chl a, respectively over 15 days, while the adsorption capacity of the spent biomass was up to 1.4 and 0.23 mg/g for metals and 15 and 1.75 mg/g for the dyes, respectively in continuous column mode.

  16. HYDROGEN SEPARATION MEMBRANES

    SciTech Connect

    Donald P. McCollor; John P. Kay

    1999-08-01

    A likely membrane for future testing of high-temperature hydrogen separation from a gasification product stream was targeted as an inorganic analog of a dense-metal membrane, where the hydrogen would dissolve into and diffuse through the membrane structure. An amorphous membrane such as zinc sulfide appeared to be promising. Previously, ZnS film coating tests had been performed using an electron-beam vacuum coating instrument, with zinc films successfully applied to glass substrates. The coatings appeared relatively stable in air and in a simple simulated gasification atmosphere at elevated temperature. Because the electron-beam coating instrument suffered irreparable breakdown, several alternative methods were tested in an effort to produce a nitrogen-impermeable, hydrogen-permeable membrane on porous sintered steel substrates. None of the preparation methods proved successful in sealing the porous substrate against nitrogen gas. To provide a nitrogen-impermeable ZnS material to test for hydrogen permeability, two ZnS infrared sample windows were purchased. These relatively thick ''membranes'' did not show measurable permeation of hydrogen, either due to lack of absorption or a negligible permeation rate due to their thickness. To determine if hydrogen was indeed adsorbed, thermogravimetric and differential thermal analyses tests were performed on samples of ZnS powder. A significant uptake of hydrogen gas occurred, corresponding to a maximum of 1 mole H{sub 2} per 1 mole ZnS at a temperature of 175 C. The hydrogen remained in the material at ambient temperature in a hydrogen atmosphere, but approximately 50% would be removed in argon. Reheating in a hydrogen atmosphere resulted in no additional hydrogen uptake. Differential scanning calorimetry indicated that the hydrogen uptake was probably due to the formation of a zinc-sulfur-hydrogen species resulting in the formation of hydrogen sulfide. The zinc sulfide was found to be unstable above approximately 200 C

  17. Nucleosynthesis of the elements and the liquid metallic hydrogen model of the Sun

    NASA Astrophysics Data System (ADS)

    Robitaille, Pierre-Marie

    2012-10-01

    Modern nucleosynthesis theory stems from the anticipated life cycle of stellar objects. Within this framework, the Sun, as a relatively young and light main sequence star, is unable to synthesize any element beyond helium. All metallic elements in our solar system have consequently been hypothesized to arise from the explosion of early stars which previously populated this region of the galaxy. Much of nucleosynthesis theory currently rests on gaseous stellar models and has developed in a direction consistent which such objects. In this presentation, the problem of nucleosynthesis is briefly reconsidered within the context of a condensed Sun. Such an object, built from liquid metallic hydrogen provides a new avenue for nucleosynthesis. Nuclei and protons contained within a metallic hydrogen lattice, will be subjected to vibrational modes which should be conducive to promoting internuclear reaction. The pressures within the Sun should make the synthesis of all the elements possible based on the combination of lighter elements. In stark contrast to current theory, it is advanced that all elements, beyond hydrogen, can be made within such a thermonuclear furnace.

  18. Alloys for hydrogen storage in nickel/hydrogen and nickel/metal hydride batteries

    NASA Technical Reports Server (NTRS)

    Anani, Anaba; Visintin, Arnaldo; Petrov, Konstantin; Srinivasan, Supramaniam; Reilly, James J.; Johnson, John R.; Schwarz, Ricardo B.; Desch, Paul B.

    1993-01-01

    Since 1990, there has been an ongoing collaboration among the authors in the three laboratories to (1) prepare alloys of the AB(sub 5) and AB(sub 2) types, using arc-melting/annealing and mechanical alloying/annealing techniques; (2) examine their physico-chemical characteristics (morphology, composition); (3) determine the hydrogen absorption/desorption behavior (pressure-composition isotherms as a function of temperature); and (4) evaluate their performance characteristics as hydride electrodes (charge/discharge, capacity retention, cycle life, high rate capability). The work carried out on representative AB(sub 5) and AB(sub 2) type modified alloys (by partial substitution or with small additives of other elements) is presented. The purpose of the modification was to optimize the thermodynamics and kinetics of the hydriding/dehydriding reactions and enhance the stabilities of the alloys for the desired battery applications. The results of our collaboration, to date, demonstrate that (1) alloys prepared by arc melting/annealing and mechanical alloying/annealing techniques exhibit similar morphology, composition and hydriding/dehydriding characteristics; (2) alloys with the appropriate small amounts of substituent or additive elements: (1) retain the single phase structure, (2) improve the hydriding/dehydriding reactions for the battery applications, and (3) enhance the stability in the battery environment; and (3) the AB(sub 2) type alloys exhibit higher energy densities than the AB(sub 5) type alloys but the state-of-the-art, commercialized batteries are predominantly manufactured using Ab(sub 5) type alloys.

  19. Mitigation of Hydrogen Gas Generation from the Reaction of Water with Uranium Metal in K Basins Sludge

    SciTech Connect

    Sinkov, Sergey I.; Delegard, Calvin H.; Schmidt, Andrew J.

    2010-01-29

    Means to decrease the rate of hydrogen gas generation from the chemical reaction of uranium metal with water were identified by surveying the technical literature. The underlying chemistry and potential side reactions were explored by conducting 61 principal experiments. Several methods achieved significant hydrogen gas generation rate mitigation. Gas-generating side reactions from interactions of organics or sludge constituents with mitigating agents were observed. Further testing is recommended to develop deeper knowledge of the underlying chemistry and to advance the technology aturation level. Uranium metal reacts with water in K Basin sludge to form uranium hydride (UH3), uranium dioxide or uraninite (UO2), and diatomic hydrogen (H2). Mechanistic studies show that hydrogen radicals (H·) and UH3 serve as intermediates in the reaction of uranium metal with water to produce H2 and UO2. Because H2 is flammable, its release into the gas phase above K Basin sludge during sludge storage, processing, immobilization, shipment, and disposal is a concern to the safety of those operations. Findings from the technical literature and from experimental investigations with simple chemical systems (including uranium metal in water), in the presence of individual sludge simulant components, with complete sludge simulants, and with actual K Basin sludge are presented in this report. Based on the literature review and intermediate lab test results, sodium nitrate, sodium nitrite, Nochar Acid Bond N960, disodium hydrogen phosphate, and hexavalent uranium [U(VI)] were tested for their effects in decreasing the rate of hydrogen generation from the reaction of uranium metal with water. Nitrate and nitrite each were effective, decreasing hydrogen generation rates in actual sludge by factors of about 100 to 1000 when used at 0.5 molar (M) concentrations. Higher attenuation factors were achieved in tests with aqueous solutions alone. Nochar N960, a water sorbent, decreased hydrogen

  20. Curvature and ionization-induced reversible hydrogen storage in metalized hexagonal B36.

    PubMed

    Liu, Chun-Sheng; Wang, Xiangfu; Ye, Xiao-Juan; Yan, Xiaohong; Zeng, Zhi

    2014-11-21

    The synthesis of quasiplanar boron clusters (B36) with a central hexagonal hole provides the first experimental evidence that a single-atomic-layer borophene with hexagonal vacancies is potentially viable [Z. Piazza, H. Hu, W. Li, Y. Zhao, J. Li, and L. S. Wang, Nat. Commun. 5, 3113 (2014)]. However, owing to the hexagonal holes, tunning the electronic and physical properties of B36 through chemical modifications is not fully understood. Based on (van der Waals corrected-) density functional theory, we show that Li adsorbed on B36 and B36 (-) clusters can serve as reversible hydrogen storage media. The present results indicate that the curvature and ionization of substrates can enhance the bond strength of Li due to the energetically favorable B 2p-Li 2p orbitals hybridization. Both the polarization mechanism and the orbital hybridization between H-s orbitals and Li-2s2p orbitals contribute to the adsorption of H2 molecules and the resulting adsorption energy lies between the physisorbed and chemisorbed states. Interestingly, the number of H2 in the hydrogen storage medium can be measured by the appearance of the negative differential resistance behavior at different bias voltage regions. Furthermore, the cluster-assembled hydrogen storage materials constructed by metalized B36 clusters do not cause a decrease in the number of adsorbed hydrogen molecules per Li. The system reported here is favorable for the reversible hydrogen adsorption/desorption at ambient conditions. PMID:25416890

  1. High performance hydrogen storage from Be-BTB metal-organic framework at room temperature.

    PubMed

    Lim, Wei-Xian; Thornton, Aaron W; Hill, Anita J; Cox, Barry J; Hill, James M; Hill, Matthew R

    2013-07-01

    The metal-organic framework beryllium benzene tribenzoate (Be-BTB) has recently been reported to have one of the highest gravimetric hydrogen uptakes at room temperature. Storage at room temperature is one of the key requirements for the practical viability of hydrogen-powered vehicles. Be-BTB has an exceptional 298 K storage capacity of 2.3 wt % hydrogen. This result is surprising given that the low adsorption enthalpy of 5.5 kJ mol(-1). In this work, a combination of atomistic simulation and continuum modeling reveals that the beryllium rings contribute strongly to the hydrogen interaction with the framework. These simulations are extended with a thermodynamic energy optimization (TEO) model to compare the performance of Be-BTB to a compressed H2 tank and benchmark materials MOF-5 and MOF-177 in a MOF-based fuel cell. Our investigation shows that none of the MOF-filled tanks satisfy the United States Department of Energy (DOE) storage targets within the required operating temperatures and pressures. However, the Be-BTB tank delivers the most energy per volume and mass compared to the other material-based storage tanks. The pore size and the framework mass are shown to be contributing factors responsible for the superior room temperature hydrogen adsorption of Be-BTB.

  2. Curvature and ionization-induced reversible hydrogen storage in metalized hexagonal B36.

    PubMed

    Liu, Chun-Sheng; Wang, Xiangfu; Ye, Xiao-Juan; Yan, Xiaohong; Zeng, Zhi

    2014-11-21

    The synthesis of quasiplanar boron clusters (B36) with a central hexagonal hole provides the first experimental evidence that a single-atomic-layer borophene with hexagonal vacancies is potentially viable [Z. Piazza, H. Hu, W. Li, Y. Zhao, J. Li, and L. S. Wang, Nat. Commun. 5, 3113 (2014)]. However, owing to the hexagonal holes, tunning the electronic and physical properties of B36 through chemical modifications is not fully understood. Based on (van der Waals corrected-) density functional theory, we show that Li adsorbed on B36 and B36 (-) clusters can serve as reversible hydrogen storage media. The present results indicate that the curvature and ionization of substrates can enhance the bond strength of Li due to the energetically favorable B 2p-Li 2p orbitals hybridization. Both the polarization mechanism and the orbital hybridization between H-s orbitals and Li-2s2p orbitals contribute to the adsorption of H2 molecules and the resulting adsorption energy lies between the physisorbed and chemisorbed states. Interestingly, the number of H2 in the hydrogen storage medium can be measured by the appearance of the negative differential resistance behavior at different bias voltage regions. Furthermore, the cluster-assembled hydrogen storage materials constructed by metalized B36 clusters do not cause a decrease in the number of adsorbed hydrogen molecules per Li. The system reported here is favorable for the reversible hydrogen adsorption/desorption at ambient conditions.

  3. Selectivity of layered double hydroxides and their derivative mixed metal oxides as sorbents of hydrogen sulfide.

    PubMed

    Othman, Mohamed A; Zahid, Waleed M; Abasaeed, Ahmed E

    2013-06-15

    In the context of finding high efficient sorbent materials for removing hydrogen sulfide (H2S) from air stream, a screening study was performed to find the best combination of metals for the synthesis of layered double hydroxides (LDHs) and their derivative mixed metal oxides. Based on selectivity of 998 natural mineral species of sulfur-containing compounds, Cu(2+), Ni(2+) and Zn(2+) were selected as divalent metals, and Fe(3+), Al(3+) and Cr(3+) as trivalent metals to synthesis the LDHs sorbents. 10 LDHs materials and their calcined mixed metal oxides, Ni(0.66)Al(0.34), Cu(0.35)Ni(0.32)Al(0.33), Zn(0.66)Al(0.34), Cu(0.36)Zn(0.32)Al(0.32), Ni(0.64)Fe(0.36), Cu(0.35)Ni(0.31)Fe(0.34), Ni(0.66)Cr(0.34), Cu(0.35)Ni(0.31)Cr(0.34), Zn(0.66)Cr(0.34), Cu(0.33)Zn(0.32)Cr(0.35) were synthesized, characterized chemically and physically, and then tested using breakthrough test to determine their sulfur uptake. Ni(0.64)Fe(0.36) mixed metal oxides was found to have the best uptake of hydrogen sulfide (136 mg H₂S/g). Regeneration of spent Ni(0.64)Fe(0.36) mixed metal oxides was studied using two different mixture solutions, NaCl/NaOH and acetate-buffer/NaCl/NaOH. The latter mixture successfully desorbed the sulfur from the Ni0.64Fe0.36 sorbent for 2 cycles of regeneration/sorption.

  4. Investigation of the feasibility of developing low permeability polymeric films

    NASA Technical Reports Server (NTRS)

    Hoggatt, J. T.

    1971-01-01

    The feasibility of reducing the gas permeability rate of Mylar and Kapton films without drastically effecting their flexibility characteristics at cryogenic temperatures was considered. This feasibility was established using a concept of diffusion bonding two layers of metallized films together forming a film-metal-film sandwich laminate. The permeability of kapton film to gaseous helium was reduced from a nominal ten = to the minus 9 power cc-mm/sq cm sec. cm Hg to ten to the minus 13 power cc-mm/ sq cm - sec. cm Hg with some values as low as ten to the minus 15 power cc - mm/sq cm m-sec - cm Hg being obtained. Similar reductions occurred in the liquid hydrogen permeability at -252 C. In the course of the program the permeability, flexibility and bond strength of plain, metalized and diffusion bond film were determined at +25 C, -195 C and -252 C. The cryogenic flexibility of Kapton film was reduced slightly due to the metallization process but no additional loss in flexibility resulted from the diffusion bonding process.

  5. A permeable reactive barrier (PRB) media sequence for the remediation of heavy metal and hydrocarbon contaminated water: A field assessment at Casey Station, Antarctica.

    PubMed

    Statham, Tom M; Stark, Scott C; Snape, Ian; Stevens, Geoffrey W; Mumford, Kathryn A

    2016-03-01

    A field trial was conducted at Casey Station, Antarctica to assess the suitability of a permeable reactive barrier (PRB) media sequence for the remediation of sites containing both hydrocarbon and heavy metal contamination. An existing PRB was modified to assess a sequence consisting of three sections: (i) Nutrient release/hydrocarbon sorption using ZeoPro™ and granular activated carbon; (ii) Phosphorus and heavy metal capture by granular iron and sand; (iii) Nutrient and excess iron capture by zeolite. The media sequence achieved a greater phosphorus removal capacity than previous Antarctic PRB configurations installed on site. Phosphorus concentrations were reduced during flow through the iron/sand section and iron concentrations were reduced within the zeolite section. However, non-ideal flow was detected during a tracer test and supported by analysis of media and liquid samples from the second summer of operation. Results indicate that the PRB media sequence trialled might be appropriate for other locations, especially less environmentally challenging contaminated sites.

  6. Modular Attachment of Appended Boron Lewis Acids to a Ruthenium Pincer Catalyst: Metal-Ligand Cooperativity Enables Selective Alkyne Hydrogenation.

    PubMed

    Tseng, Kuei-Nin T; Kampf, Jeff W; Szymczak, Nathaniel K

    2016-08-24

    A new series of bifunctional Ru complexes with pendent Lewis acidic boranes were prepared by late-stage modification of an active hydrogen-transfer catalyst. The appended boranes modulate the reactivity of a metal hydride as well as catalytic hydrogenations. After installing acidic auxiliary groups, the complexes become multifunctional and catalyze the cis-selective hydrogenation of alkynes with higher rates, conversions, and selectivities compared with the unmodified catalyst. PMID:27472301

  7. Hydrogen sulfide preconditioning protects rat liver against ischemia/reperfusion injury by activating Akt-GSK-3β signaling and inhibiting mitochondrial permeability transition.

    PubMed

    Zhang, Qingqing; Fu, Hailong; Zhang, Hao; Xu, Fengying; Zou, Zui; Liu, Meng; Wang, Quanxing; Miao, Mingyong; Shi, Xueyin

    2013-01-01

    Hydrogen sulfide (H2S) is the third most common endogenously produced gaseous signaling molecule, but its impact on hepatic ischemia/reperfusion (I/R) injury, especially on mitochondrial function, remains unclear. In this study, rats were randomized into Sham, I/R, ischemia preconditioning (IPC) or sodium hydrosulfide (NaHS, an H2S donor) preconditioning groups. To establish a model of segmental (70%) warm hepatic ischemia, the hepatic artery, left portal vein and median liver lobes were occluded for 60 min and then unclamped to allow reperfusion. Preconditioning with 12.5, 25 or 50 μmol/kg NaHS prior to the I/R insult significantly increased serum H2S levels, and, similar to IPC, NaHS preconditioning decreased alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels in the plasma and prevented hepatocytes from undergoing I/R-induced necrosis. Moreover, a sub-toxic dose of NaHS (25 μmol/kg) did not disrupt the systemic hemodynamics but dramatically inhibited mitochondrial permeability transition pore (MPTP) opening and thus prevented mitochondrial-related cell death and apoptosis. Mechanistic studies revealed that NaHS preconditioning markedly increased the expression of phosphorylated protein kinase B (p-Akt), phosphorylated glycogen synthase kinase-3 beta (p-GSK-3β) and B-cell lymphoma-2 (Bcl-2) and decreased the release of mitochondrial cytochrome c and cleaved caspase-3/9 levels. Therefore, NaHS administration prior to hepatic I/R ameliorates mitochondrial and hepatocellular damage through the inhibition of MPTP opening and the activation of Akt-GSK-3β signaling. Furthermore, this study provides experimental evidence for the clinical use of H2S to reduce liver damage after perioperative I/R injury. PMID:24058562

  8. Hydrogen Sulfide Preconditioning Protects Rat Liver against Ischemia/Reperfusion Injury by Activating Akt-GSK-3β Signaling and Inhibiting Mitochondrial Permeability Transition

    PubMed Central

    Zhang, Hao; Xu, Fengying; Zou, Zui; Liu, Meng; Wang, Quanxing; Miao, Mingyong; Shi, Xueyin

    2013-01-01

    Hydrogen sulfide (H2S) is the third most common endogenously produced gaseous signaling molecule, but its impact on hepatic ischemia/reperfusion (I/R) injury, especially on mitochondrial function, remains unclear. In this study, rats were randomized into Sham, I/R, ischemia preconditioning (IPC) or sodium hydrosulfide (NaHS, an H2S donor) preconditioning groups. To establish a model of segmental (70%) warm hepatic ischemia, the hepatic artery, left portal vein and median liver lobes were occluded for 60 min and then unclamped to allow reperfusion. Preconditioning with 12.5, 25 or 50 μmol/kg NaHS prior to the I/R insult significantly increased serum H2S levels, and, similar to IPC, NaHS preconditioning decreased alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels in the plasma and prevented hepatocytes from undergoing I/R-induced necrosis. Moreover, a sub-toxic dose of NaHS (25 μmol/kg) did not disrupt the systemic hemodynamics but dramatically inhibited mitochondrial permeability transition pore (MPTP) opening and thus prevented mitochondrial-related cell death and apoptosis. Mechanistic studies revealed that NaHS preconditioning markedly increased the expression of phosphorylated protein kinase B (p-Akt), phosphorylated glycogen synthase kinase-3 beta (p-GSK-3β) and B-cell lymphoma-2 (Bcl-2) and decreased the release of mitochondrial cytochrome c and cleaved caspase-3/9 levels. Therefore, NaHS administration prior to hepatic I/R ameliorates mitochondrial and hepatocellular damage through the inhibition of MPTP opening and the activation of Akt-GSK-3β signaling. Furthermore, this study provides experimental evidence for the clinical use of H2S to reduce liver damage after perioperative I/R injury. PMID:24058562

  9. Mn in misch-metal based superlattice metal hydride alloy - Part 1 structural, hydrogen storage and electrochemical properties

    NASA Astrophysics Data System (ADS)

    Young, K.; Wong, D. F.; Wang, L.; Nei, J.; Ouchi, T.; Yasuoka, S.

    2015-03-01

    The structural, gaseous phase hydrogen storage, and electrochemical properties of a series of Mn-modified misch-metal based superlattice metal hydride alloys were investigated in part one of this two-part series of papers. X-ray diffraction analysis showed that these alloys are all multi-phased compositions with different abundances of AB2, AB3, A2B7, AB4, and AB5 phases. Substitution of Ni in the B-site by Mn promotes AB5 phase formation and decreases both gaseous phase and electrochemical capacities due to the reduction in the abundance of main hexagonal A2B7 phase. AC impedance and magnetic susceptibility measurement were employed to characterize the surface of Mn-free and Mn-modified alloys and show deterioration in surface catalytic ability as the Mn-content increases. Mn-modification adversely affected misch-metal based superlattice metal hydride alloy properties such as phase homogeneity, capacity, cycle stability, high-rate performance, and surface reaction.

  10. Efficient hydrogen evolution in transition metal dichalcogenides via a simple one-step hydrazine reaction

    PubMed Central

    Cummins, Dustin R.; Martinez, Ulises; Sherehiy, Andriy; Kappera, Rajesh; Martinez-Garcia, Alejandro; Schulze, Roland K.; Jasinski, Jacek; Zhang, Jing; Gupta, Ram K.; Lou, Jun; Chhowalla, Manish; Sumanasekera, Gamini; Mohite, Aditya D.; Sunkara, Mahendra K.; Gupta, Gautam

    2016-01-01

    Hydrogen evolution reaction is catalysed efficiently with precious metals, such as platinum; however, transition metal dichalcogenides have recently emerged as a promising class of materials for electrocatalysis, but these materials still have low activity and durability when compared with precious metals. Here we report a simple one-step scalable approach, where MoOx/MoS2 core-shell nanowires and molybdenum disulfide sheets are exposed to dilute aqueous hydrazine at room temperature, which results in marked improvement in electrocatalytic performance. The nanowires exhibit ∼100 mV improvement in overpotential following exposure to dilute hydrazine, while also showing a 10-fold increase in current density and a significant change in Tafel slope. In situ electrical, gate-dependent measurements and spectroscopic investigations reveal that hydrazine acts as an electron dopant in molybdenum disulfide, increasing its conductivity, while also reducing the MoOx core in the core-shell nanowires, which leads to improved electrocatalytic performance. PMID:27282871

  11. Active and Durable Hydrogen Evolution Reaction Catalyst Derived from Pd-Doped Metal-Organic Frameworks.

    PubMed

    Chen, Jitang; Xia, Guoliang; Jiang, Peng; Yang, Yang; Li, Ren; Shi, Ruohong; Su, Jianwei; Chen, Qianwang

    2016-06-01

    The water electrolysis is of critical importance for sustainable hydrogen production. In this work, a highly efficient and stable PdCo alloy catalyst (PdCo@CN) was synthesized by direct annealing of Pd-doped metal-organic frameworks (MOFs) under N2 atmosphere. In 0.5 M H2SO4 solution, PdCo@CN displays remarkable electrocatalytic performance with overpotential of 80 mV, a Tafel slope of 31 mV dec(-1), and excellent stability of 10 000 cycles. Our studies reveal that noble metal doped MOFs are ideal precursors for preparing highly active alloy electrocatalysts with low content of noble metal. PMID:27112733

  12. Porous molybdenum carbide nano-octahedrons synthesized via confined carburization in metal-organic frameworks for efficient hydrogen production

    PubMed Central

    Wu, Hao Bin; Xia, Bao Yu; Yu, Le; Yu, Xin-Yao; Lou, Xiong Wen (David)

    2015-01-01

    Electrochemical water splitting has been considered as a promising approach to produce clean and sustainable hydrogen fuel. However, the lack of high-performance and low-cost electrocatalysts for hydrogen evolution reaction hinders the large-scale application. As a new class of porous materials with tunable structure and composition, metal-organic frameworks have been considered as promising candidates to synthesize various functional materials. Here we demonstrate a metal-organic frameworks-assisted strategy for synthesizing nanostructured transition metal carbides based on the confined carburization in metal-organic frameworks matrix. Starting from a compound consisting of copper-based metal-organic frameworks host and molybdenum-based polyoxometalates guest, mesoporous molybdenum carbide nano-octahedrons composed of ultrafine nanocrystallites are successfully prepared as a proof of concept, which exhibit remarkable electrocatalytic performance for hydrogen production from both acidic and basic solutions. The present study provides some guidelines for the design and synthesis of nanostructured electrocatalysts. PMID:25758159

  13. Porous molybdenum carbide nano-octahedrons synthesized via confined carburization in metal-organic frameworks for efficient hydrogen production

    NASA Astrophysics Data System (ADS)

    Wu, Hao Bin; Xia, Bao Yu; Yu, Le; Yu, Xin-Yao; Lou, Xiong Wen (David)

    2015-03-01

    Electrochemical water splitting has been considered as a promising approach to produce clean and sustainable hydrogen fuel. However, the lack of high-performance and low-cost electrocatalysts for hydrogen evolution reaction hinders the large-scale application. As a new class of porous materials with tunable structure and composition, metal-organic frameworks have been considered as promising candidates to synthesize various functional materials. Here we demonstrate a metal-organic frameworks-assisted strategy for synthesizing nanostructured transition metal carbides based on the confined carburization in metal-organic frameworks matrix. Starting from a compound consisting of copper-based metal-organic frameworks host and molybdenum-based polyoxometalates guest, mesoporous molybdenum carbide nano-octahedrons composed of ultrafine nanocrystallites are successfully prepared as a proof of concept, which exhibit remarkable electrocatalytic performance for hydrogen production from both acidic and basic solutions. The present study provides some guidelines for the design and synthesis of nanostructured electrocatalysts.

  14. Porous molybdenum carbide nano-octahedrons synthesized via confined carburization in metal-organic frameworks for efficient hydrogen production.

    PubMed

    Wu, Hao Bin; Xia, Bao Yu; Yu, Le; Yu, Xin-Yao; Lou, Xiong Wen David

    2015-03-11

    Electrochemical water splitting has been considered as a promising approach to produce clean and sustainable hydrogen fuel. However, the lack of high-performance and low-cost electrocatalysts for hydrogen evolution reaction hinders the large-scale application. As a new class of porous materials with tunable structure and composition, metal-organic frameworks have been considered as promising candidates to synthesize various functional materials. Here we demonstrate a metal-organic frameworks-assisted strategy for synthesizing nanostructured transition metal carbides based on the confined carburization in metal-organic frameworks matrix. Starting from a compound consisting of copper-based metal-organic frameworks host and molybdenum-based polyoxometalates guest, mesoporous molybdenum carbide nano-octahedrons composed of ultrafine nanocrystallites are successfully prepared as a proof of concept, which exhibit remarkable electrocatalytic performance for hydrogen production from both acidic and basic solutions. The present study provides some guidelines for the design and synthesis of nanostructured electrocatalysts.

  15. Micro-machined thin film hydrogen gas sensor, and method of making and using the same

    NASA Technical Reports Server (NTRS)

    DiMeo, Jr., Frank (Inventor); Bhandari, Gautam (Inventor)

    2001-01-01

    A hydrogen sensor including a thin film sensor element formed, e.g., by metalorganic chemical vapor deposition (MOCVD) or physical vapor deposition (PVD), on a microhotplate structure. The thin film sensor element includes a film of a hydrogen-interactive metal film that reversibly interacts with hydrogen to provide a correspondingly altered response characteristic, such as optical transmissivity, electrical conductance, electrical resistance, electrical capacitance, magnetoresistance, photoconductivity, etc., relative to the response characteristic of the film in the absence of hydrogen. The hydrogen-interactive metal film may be overcoated with a thin film hydrogen-permeable barrier layer to protect the hydrogen-interactive film from deleterious interaction with non-hydrogen species. The hydrogen sensor of the invention may be usefully employed for the detection of hydrogen in an environment susceptible to the incursion or generation of hydrogen and may be conveniently configured as a hand-held apparatus.

  16. Metal-and hydrogen-bonding competition during water absorption on Pd(111) and Ru(0001)

    SciTech Connect

    Tatarkhanov, Mouslim; Ogletree, D. Frank; Rose, Franck; Mitsui, Toshiyuki; Fomin, Evgeny; Rose, Mark; Cerda, Jorge I.; Salmeron, Miquel

    2009-09-03

    The initial stages of water adsorption on the Pd(111) and Ru(0001) surfaces have been investigated experimentally by Scanning Tunneling Microscopy in the temperature range between 40 K and 130 K, and theoretically with Density Functional Theory (DFT) total energy calculations and STM image simulations. Below 125 K water dissociation does not occur at any appreciable rate and only molecular films are formed. Film growth starts by the formation of flat hexamer clusters where the molecules bind to the metal substrate through the O-lone pair while making H-bonds with neighboring molecules. As coverage increases, larger networks of linked hexagons are formed with a honeycomb structure, which requires a fraction of the water molecules to have their molecular plane perpendicular to the metal surface with reduced water-metal interaction. Energy minimization favors the growth of networks with limited width. As additional water molecules adsorb on the surface they attach to the periphery of existing islands, where they interact only weakly with the metal substrate. These molecules hop along the periphery of the clusters at intermediate temperatures. At higher temperatures they bind to the metal to continue the honeycomb growth. The water-Ru interaction is significantly stronger than the water-Pd interaction, which is consistent with the greater degree of hydrogen-bonded network formation and reduced water-metal bonding observed on Pd relative to Ru.

  17. Hydrogen physisorption on metal-organic framework linkers and metalated linkers: a computational study of the factors that control binding strength.

    PubMed

    Tsivion, Ehud; Long, Jeffrey R; Head-Gordon, Martin

    2014-12-24

    In order for hydrogen gas to be used as a fuel, it must be stored in sufficient quantity on board the vehicle. Efforts are being made to increase the hydrogen storage capabilities of metal-organic frameworks (MOFs) by introducing unsaturated metal sites into their linking element(s), as hydrogen adsorption centers. In order to devise successful hydrogen storage strategies there is a need for a fundamental understanding of the weak and elusive hydrogen physisorption interaction. Here we report our findings from the investigation of the weak intermolecular interactions of adsorbed hydrogen molecules on MOF-linkers by using cluster models. Since physical interactions such as dispersion and polarization have a major contribution to attraction energy, our approach is to analyze the adsorption interaction using energy decomposition analysis (EDA) that distinguishes the contribution of the physical interactions from the charge-transfer (CT) "chemical" interaction. Surprisingly, it is found that CT from the adsorbent to the σ*(H2) orbital is present in all studied complexes and can contribute up to approximately -2 kJ/mol to the interaction. When metal ions are present, donation from the σ(H2) → metal Rydberg-like orbital, along with the adsorbent → σ*(H2) contribution, can contribute from -2 to -10 kJ/mol, depending on the coordination mode. To reach a sufficient adsorption enthalpy for practical usage, the hydrogen molecule must be substantially polarized. Ultimately, the ability of the metalated linker to polarize the hydrogen molecule is highly dependent on the geometry of the metal ion coordination site where a strong electrostatic dipole or quadrupole moment is required.

  18. Synthetic and mechanistic studies of metal-free transfer hydrogenations applying polarized olefins as hydrogen acceptors and amine borane adducts as hydrogen donors.

    PubMed

    Yang, Xianghua; Fox, Thomas; Berke, Heinz

    2012-01-28

    Metal-free transfer hydrogenation of polarized olefins (RR'C=CEE': R, R' = H or organyl, E, E' = CN or CO(2)Me) using amine borane adducts RR'NH-BH(3) (R = R' = H, AB; R = Me, R' = H, MAB; R = (t)Bu, R' = H, tBAB; R = R' = Me, DMAB) as hydrogen donors, were studied by means of in situ NMR spectroscopy. Deuterium kinetic isotope effects and the traced hydroboration intermediate revealed that the double H transfer process occurred regio-specifically in two steps with hydride before proton transfer characteristics. Studies on substituent effects and Hammett correlation indicated that the rate determining step of the H(N) transfer is in agreement with a concerted transition state. The very reactive intermediate [NH(2)=BH(2)] generated from AB was trapped by addition of cyclohexene into the reaction mixture forming Cy(2)BNH(2). The final product borazine (BHNH)(3) is assumed to be formed by dehydrocoupling of [NH(2)=BH(2)] or its solvent stabilized derivative [NH(2)=BH(2)]-(solvent), rather than by dehydrogenation of cyclotriborazane (BH(2)NH(2))(3) which is the trimerization product of [NH(2)=BH(2)]. PMID:22124505

  19. SOLUBILITY OF IRON IN METALLIC HYDROGEN AND STABILITY OF DENSE CORES IN GIANT PLANETS

    SciTech Connect

    Wahl, Sean M.; Wilson, Hugh F.; Militzer, Burkhard

    2013-08-20

    The formation of the giant planets in our solar system, and likely a majority of giant exoplanets, is most commonly explained by the accretion of nebular hydrogen and helium onto a large core of terrestrial-like composition. The fate of this core has important consequences for the evolution of the interior structure of the planet. It has recently been shown that H{sub 2}O, MgO, and SiO{sub 2} dissolve in liquid metallic hydrogen at high temperature and pressure. In this study, we perform ab initio calculations to study the solubility of an innermost metallic core. We find dissolution of iron to be strongly favored above 2000 K over the entire pressure range (0.4-4 TPa) considered. We compare with and summarize the results for solubilities on other probable core constituents. The calculations imply that giant planet cores are in thermodynamic disequilibrium with surrounding layers, promoting erosion and redistribution of heavy elements. Differences in solubility behavior between iron and rock may influence evolution of interiors, particularly for Saturn-mass planets. Understanding the distribution of iron and other heavy elements in gas giants may be relevant in understanding mass-radius relationships, as well as deviations in transport properties from pure hydrogen-helium mixtures.

  20. Percolative metal-organic framework/carbon composites for hydrogen storage

    NASA Astrophysics Data System (ADS)

    Xie, Shuqian; Hwang, Jiann-Yang; Sun, Xiang; Shi, Shangzhao; Zhang, Zheng; Peng, Zhiwei; Zhai, Yuchun

    2014-05-01

    Percolative Metal-organic framework/Carbon (MOFAC) composites are synthesized by IRMOF8 (isoreticular metal-organic frameworks) directly depositing on activated carbon via heterogeneous nucleation. Carbon content is calculated by TGA (Thermogravimetric analysis) tests. XRD (X-ray diffraction) and FESEM (Field emission-scanning electron microscope) are carried out to characterize the structures of the samples. BET surface areas and the pore size distribution are measured. The dielectric constant is measured with impedance analyzer and a specially designed sample holder. The dielectric constants of the MOFAC composites rise with increasing the carbon content, and the composites possess the insulator-conductor transition as the carbon content increases from 17.77 wt% to 22.2 wt%. The composites are further tested for hydrogen storage capability under assist of the PMN-PT (single crystal lead magnesium niobate-lead titanate) generated electric field. With help from the PMN-PT, the hydrogen uptake capability is increased about 31.5% over the MOFAC3 (MOF-Carbon composite with 22.2 wt% of carbon) without PMN-PT, which is elucidated by the charge distribution mechanisms. The improved storage is due to a stronger electrostatic interaction between IRMOF8 and hydrogen molecule caused by field polarization. Meanwhile, rapid adsorption/desorption kinetics and total reversibility on the samples are observed in the present or absence of external electric field.

  1. Electrostatically enhanced FF interactions through hydrogen bonding, halogen bonding and metal coordination: an ab initio study.

    PubMed

    Bauzá, Antonio; Frontera, Antonio

    2016-07-27

    In this manuscript the ability of hydrogen and halogen bonding interactions, as well as metal coordination to enhance FF interactions involving fluorine substituted aromatic rings has been studied at the RI-MP2/def2-TZVPD level of theory. We have used 4-fluoropyridine, 4-fluorobenzonitrile, 3-(4-fluorophenyl)propiolonitrile and their respective meta derivatives as aromatic compounds. In addition, we have used HF and IF as hydrogen and halogen bond donors, respectively, and Ag(i) as the coordination metal. Furthermore, we have also used HF as an electron rich fluorine donor entity, thus establishing FF interactions with the above mentioned aromatic systems. Moreover, a CSD (Cambridge Structural Database) search has been carried out and some interesting examples have been found, highlighting the impact of FF interactions involving aromatic fluorine atoms in solid state chemistry. Finally, cooperativity effects between FF interactions and both hydrogen and halogen bonding interactions have been analyzed and compared. We have also used Bader's theory of "atoms in molecules" to further describe the cooperative effects.

  2. The Contrasting Character of Early and Late Transition Metal Fluorides as Hydrogen Bond Acceptors.

    PubMed

    Smith, Dan A; Beweries, Torsten; Blasius, Clemens; Jasim, Naseralla; Nazir, Ruqia; Nazir, Sadia; Robertson, Craig C; Whitwood, Adrian C; Hunter, Christopher A; Brammer, Lee; Perutz, Robin N

    2015-09-16

    The association constants and enthalpies for the binding of hydrogen bond donors to group 10 transition metal complexes featuring a single fluoride ligand (trans-[Ni(F)(2-C5NF4)(PR3)2], R = Et 1a, Cy 1b, trans-[Pd(F)(4-C5NF4)(PCy3)2] 2, trans-[Pt(F){2-C5NF2H(CF3)}(PCy3)2] 3 and of group 4 difluorides (Cp2MF2, M = Ti 4a, Zr 5a, Hf 6a; Cp*2MF2, M = Ti 4b, Zr 5b, Hf 6b) are reported. These measurements allow placement of these fluoride ligands on the scales of organic H-bond acceptor strength. The H-bond acceptor capability β (Hunter scale) for the group 10 metal fluorides is far greater (1a 12.1, 1b 9.7, 2 11.6, 3 11.0) than that for group 4 metal fluorides (4a 5.8, 5a 4.7, 6a 4.7, 4b 6.9, 5b 5.6, 6b 5.4), demonstrating that the group 10 fluorides are comparable to the strongest organic H-bond acceptors, such as Me3NO, whereas group 4 fluorides fall in the same range as N-bases aniline through pyridine. Additionally, the measurement of the binding enthalpy of 4-fluorophenol to 1a in carbon tetrachloride (-23.5 ± 0.3 kJ mol(-1)) interlocks our study with Laurence's scale of H-bond basicity of organic molecules. The much greater polarity of group 10 metal fluorides than that of the group 4 metal fluorides is consistent with the importance of pπ-dπ bonding in the latter. The polarity of the group 10 metal fluorides indicates their potential as building blocks for hydrogen-bonded assemblies. The synthesis of trans-[Ni(F){2-C5NF3(NH2)}(PEt3)2], which exhibits an extended chain structure assembled by hydrogen bonds between the amine and metal-fluoride groups, confirms this hypothesis.

  3. Degradation of metallic surfaces under space conditions, with particular emphasis on Hydrogen recombination processes

    NASA Astrophysics Data System (ADS)

    Sznajder, Maciej; Geppert, Ulrich; Dudek, Mirosław

    2015-07-01

    The widespread use of metallic structures in space technology brings risk of degradation which occurs under space conditions. New types of materials dedicated for space applications, that have been developed in the last decade, are in majority not well tested for different space mission scenarios. Very little is known how material degradation may affect the stability and functionality of space vehicles and devices during long term space missions. Our aim is to predict how the solar wind and electromagnetic radiation degrade metallic structures. Therefore both experimental and theoretical studies of material degradation under space conditions have been performed. The studies are accomplished at German Aerospace Center (DLR) in Bremen (Germany) and University of Zielona Góra (Poland). The paper presents the results of the theoretical part of those studies. It is proposed that metal bubbles filled with Hydrogen molecular gas, resulting from recombination of the metal free electrons and the solar protons, are formed on the irradiated surfaces. A thermodynamic model of bubble formation has been developed. We study the creation process of H2 -bubbles as function of, inter alia, the metal temperature, proton dose and energy. Our model has been verified by irradiation experiments completed at the DLR facility in Bremen. Consequences of the bubble formation are changes of the physical and thermo-optical properties of such degraded metals. We show that a high surface density of bubbles (up to 108cm-2) with a typical bubble diameter of ∼ 0.4 μm will cause a significant increase of the metallic surface roughness. This may have serious consequences to any space mission. Changes in the thermo-optical properties of metallic foils are especially important for the solar sail propulsion technology because its efficiency depends on the effective momentum transfer from the solar photons onto the sail structure. This transfer is proportional to the reflectivity of a sail. Therefore

  4. OPTIMIZATION OF INTERNAL HEAT EXCHANGERS FOR HYDROGEN STORAGE TANKS UTILIZING METAL HYDRIDES

    SciTech Connect

    Garrison, S.; Tamburello, D.; Hardy, B.; Anton, D.; Gorbounov, M.; Cognale, C.; van Hassel, B.; Mosher, D.

    2011-07-14

    Two detailed, unit-cell models, a transverse fin design and a longitudinal fin design, of a combined hydride bed and heat exchanger are developed in COMSOL{reg_sign} Multiphysics incorporating and accounting for heat transfer and reaction kinetic limitations. MatLab{reg_sign} scripts for autonomous model generation are developed and incorporated into (1) a grid-based and (2) a systematic optimization routine based on the Nelder-Mead downhill simplex method to determine the geometrical parameters that lead to the optimal structure for each fin design that maximizes the hydrogen stored within the hydride. The optimal designs for both the transverse and longitudinal fin designs point toward closely-spaced, small cooling fluid tubes. Under the hydrogen feed conditions studied (50 bar), a 25 times improvement or better in the hydrogen storage kinetics will be required to simultaneously meet the Department of Energy technical targets for gravimetric capacity and fill time. These models and methodology can be rapidly applied to other hydrogen storage materials, such as other metal hydrides or to cryoadsorbents, in future work.

  5. Impact of metal and anion substitutions on the hydrogen storage properties of M-BTT metal-organic frameworks.

    PubMed

    Sumida, Kenji; Stück, David; Mino, Lorenzo; Chai, Jeng-Da; Bloch, Eric D; Zavorotynska, Olena; Murray, Leslie J; Dincă, Mircea; Chavan, Sachin; Bordiga, Silvia; Head-Gordon, Martin; Long, Jeffrey R

    2013-01-23

    Microporous metal-organic frameworks are a class of materials being vigorously investigated for mobile hydrogen storage applications. For high-pressure storage at ambient temperatures, the M(3)[(M(4)Cl)(3)(BTT)(8)](2) (M-BTT; BTT(3-) = 1,3,5-benzenetristetrazolate) series of frameworks are of particular interest due to the high density of exposed metal cation sites on the pore surface. These sites give enhanced zero-coverage isosteric heats of adsorption (Q(st)) approaching the optimal value for ambient storage applications. However, the Q(st) parameter provides only a limited insight into the thermodynamics of the individual adsorption sites, the tuning of which is paramount for optimizing the storage performance. Here, we begin by performing variable-temperature infrared spectroscopy studies of Mn-, Fe-, and Cu-BTT, allowing the thermodynamics of H(2) adsorption to be probed experimentally. This is complemented by a detailed DFT study, in which molecular fragments representing the metal clusters within the extended solid are simulated to obtain a more thorough description of the structural and thermodynamic aspects of H(2) adsorption at the strongest binding sites. Then, the effect of substitutions at the metal cluster (metal ion and anion within the tetranuclear cluster) is discussed, showing that the configuration of this unit indeed plays an important role in determining the affinity of the framework toward H(2). Interestingly, the theoretical study has identified that the Zn-based analogs would be expected to facilitate enhanced adsorption profiles over the compounds synthesized experimentally, highlighting the importance of a combined experimental and theoretical approach to the design and synthesis of new frameworks for H(2) storage applications.

  6. Hydrogen purifier module and method for forming the same

    DOEpatents

    DeVries, Peter David

    2012-02-07

    A hydrogen purifier utilizing a hydrogen permeable membrane, and a gas-tight seal, where the seal is uses a low temperature melting point metal, which upon heating above the melting point subsequently forms a seal alloy with adjacent metals, where the alloy has a melting point above the operational temperature of the purifier. The purifier further is constructed such that a degree of isolation exists between the metal that melts to form the seal and the active area of the purifier membrane, so that the active area of the purifier membrane is not corrupted. A method of forming a hydrogen purifier utilizing a hydrogen permeable membrane with a seal of the same type is also disclosed.

  7. Turning aluminium into a noble-metal-like catalyst for low-temperature activation of molecular hydrogen.

    PubMed

    Chopra, Irinder S; Chaudhuri, Santanu; Veyan, Jean François; Chabal, Yves J

    2011-11-01

    Activation of molecular hydrogen is the first step in producing many important industrial chemicals that have so far required expensive noble-metal catalysts and thermal activation. We demonstrate here that aluminium doped with very small amounts of titanium can activate molecular hydrogen at temperatures as low as 90 K. Using an approach that uses CO as a probe molecule, we identify the atomistic arrangement of the catalytically active sites containing Ti on Al(111) surfaces, combining infrared reflection-absorption spectroscopy and first-principles modelling. CO molecules, selectively adsorbed on catalytically active sites, form a complex with activated hydrogen that is removed at remarkably low temperatures (115 K; possibly as a molecule). These results provide the first direct evidence that Ti-doped Al can carry out the essential first step of molecular hydrogen activation under nearly barrierless conditions, thereby challenging the monopoly of noble metals in hydrogen activation. PMID:21946610

  8. A Transition to Metallic Hydrogen: Evidence of the Plasma Phase Transition

    NASA Astrophysics Data System (ADS)

    Silvera, Isaac; Zaghoo, Mohamed; Salamat, Ashkan

    The insulator-metal transition in hydrogen is one of the most outstanding problems in condensed matter physics. The high-pressure metallic phase is now predicted to be liquid atomic from T =0 K to very high temperatures. We have conducted measurements of optical properties of hot dense hydrogen in the region of 1.1-1.7 Mbar and up to 2200 K in a diamond anvil cell using pulsed laser heating of the sample. We present evidence in two forms: a plateau in the heating curves (average laser power vs temperature) characteristic of a first-order phase transition with latent heat, and changes in transmittance and reflectance characteristic of a metal for temperatures above the plateau temperature. For thick films the reflectance saturates at ~0.5. The phase line of this transition has a negative slope in agreement with theories of the so-called plasma phase transition. The NSF, Grant DMR-1308641, the DOE Stockpile Stewardship Academic Alliance Program, Grant DE-FG52-10NA29656, and NASA Earth and Space Science Fellowship Program, Award NNX14AP17H supported this research.

  9. Molecular metal-Nx centres in porous carbon for electrocatalytic hydrogen evolution

    NASA Astrophysics Data System (ADS)

    Liang, Hai-Wei; Brüller, Sebastian; Dong, Renhao; Zhang, Jian; Feng, Xinliang; Müllen, Klaus

    2015-08-01

    Replacement of precious platinum with efficient and low-cost catalysts for electrocatalytic hydrogen evolution at low overpotentials holds tremendous promise for clean energy devices. Here we report a novel type of robust cobalt-nitrogen/carbon catalyst for the hydrogen evolution reaction (HER) that is prepared by the pyrolysis of cobalt-N4 macrocycles or cobalt/o-phenylenediamine composites and using silica colloids as a hard template. We identify the well-dispersed molecular CoNx sites on the carbon support as the active sites responsible for the HER. The CoNx/C catalyst exhibits extremely high turnover frequencies per cobalt site in acids, for example, 0.39 and 6.5 s-1 at an overpotential of 100 and 200 mV, respectively, which are higher than those reported for other scalable non-precious metal HER catalysts. Our results suggest the great promise of developing new families of non-precious metal HER catalysts based on the controlled conversion of homogeneous metal complexes into solid-state carbon catalysts via economically scalable protocols.

  10. Uranium metal reactions with hydrogen and water vapour and the reactivity of the uranium hydride produced

    SciTech Connect

    Godfrey, H.; Broan, C.; Goddard, D.; Hodge, N.; Woodhouse, G.; Diggle, A.; Orr, R.

    2013-07-01

    Within the nuclear industry, metallic uranium has been used as a fuel. If this metal is stored in a hydrogen rich environment then the uranium metal can react with the hydrogen to form uranium hydride which can be pyrophoric when exposed to air. The UK National Nuclear Laboratory has been carrying out a programme of research for Sellafield Limited to investigate the conditions required for the formation and persistence of uranium hydride and the reactivity of the material formed. The experimental results presented here have described new results characterising uranium hydride formed from bulk uranium at 50 and 160 C. degrees and measurements of the hydrolysis kinetics of these materials in liquid water. It has been shown that there is an increase in the proportion of alpha-uranium hydride in material formed at lower temperatures and that there is an increase in the rate of reaction with water of uranium hydride formed at lower temperatures. This may at least in part be attributable to a difference in the reaction rate between alpha and beta-uranium hydride. A striking observation is the strong dependence of the hydrolysis reaction rate on the temperature of preparation of the uranium hydride. For example, the reaction rate of uranium hydride prepared at 50 C. degrees was over ten times higher than that prepared at 160 C. degrees at 20% extent of reaction. The decrease in reaction rate with the extent of reaction also depended on the temperature of uranium hydride preparation.

  11. Complexes of earth-abundant metals for catalytic electrochemical hydrogen generation under aqueous conditions.

    PubMed

    Thoi, V Sara; Sun, Yujie; Long, Jeffrey R; Chang, Christopher J

    2013-03-21

    Growing global energy demands and climate change motivate the development of new renewable energy technologies. In this context, water splitting using sustainable energy sources has emerged as an attractive process for carbon-neutral fuel cycles. A key scientific challenge to achieving this overall goal is the invention of new catalysts for the reductive and oxidative conversions of water to hydrogen and oxygen, respectively. This review article will highlight progress in molecular electrochemical approaches for catalytic reduction of protons to hydrogen, focusing on complexes of earth-abundant metals that can function in pure aqueous or mixed aqueous-organic media. The use of water as a reaction medium has dual benefits of maintaining high substrate concentration as well as minimizing the environmental impact from organic additives and by-products.

  12. Visible-light-driven hydrogen production in a dye sensitized polyoxometalate system without noble metals

    NASA Astrophysics Data System (ADS)

    Liu, Xing; Li, Yuexiang; Peng, Shaoqin; Lai, Hua; Yi, Zhengji

    2016-05-01

    In this work, a noble-metal-free homogeneous system was constructed in one step with Keggin-type polyoxometalate (POM) SiW12O404- as a catalyst, Eosin Y as a photosensitizer, and triethanolamine (TEOA) as a sacrificial electron donor for water splitting to produce hydrogen under visible-light irradiation. A two-electron reduced heteropoly blue SiW12O406- is produced by photosensitization under visible-light irradiation. The effect of various component concentrations and POMs with different central atoms (PW12O403-, GeW12O404-, etc.) on hydrogen production was discussed. This simple system made of earth-abundant elements is expected to contribute toward the development of functional and efficient artificial photosynthetic system.

  13. Stable isolated metal atoms as active sites for photocatalytic hydrogen evolution.

    PubMed

    Xing, Jun; Chen, Jian Fu; Li, Yu Hang; Yuan, Wen Tao; Zhou, Ying; Zheng, Li Rong; Wang, Hai Feng; Hu, P; Wang, Yun; Zhao, Hui Jun; Wang, Yong; Yang, Hua Gui

    2014-02-17

    The process of using solar energy to split water to produce hydrogen assisted by an inorganic semiconductor is crucial for solving our energy crisis and environmental problems in the future. However, most semiconductor photocatalysts would not exhibit excellent photocatalytic activity without loading suitable co-catalysts. Generally, the noble metals have been widely applied as co-catalysts, but always agglomerate during the loading process or photocatalytic reaction. Therefore, the utilization efficiency of the noble co-catalysts is still very low on a per metal atom basis if no obvious size effect exists, because heterogeneous catalytic reactions occur on the surface active atoms. Here, for the first time, we have synthesized isolated metal atoms (Pt, Pd, Rh, or Ru) stably by anchoring on TiO2 , a model photocatalystic system, by a facile one-step method. The isolated metal atom based photocatalysts show excellent stability for H2 evolution and can lead to a 6-13-fold increase in photocatalytic activity over the metal clusters loaded on TiO2 by the traditional method. Furthermore, the configurations of isolated atoms as well as the originality of their unusual stability were analyzed by a collaborative work from both experiments and theoretical calculations.

  14. Surface science and electrochemical studies of metal-modified carbides for fuel cells and hydrogen production

    NASA Astrophysics Data System (ADS)

    Kelly, Thomas Glenn

    Carbides of the early transition metals have emerged as low-cost catalysts that are active for a wide range of reactions. The surface chemistry of carbides can be altered by modifying the surface with small amounts of admetals. These metal-modified carbides can be effective replacements for Pt-based bimetallic systems, which suffer from the drawbacks of high cost and low thermal stability. In this dissertation, metal-modified carbides were studied for reactions with applications to renewable energy technologies. It is demonstrated that metal-modified carbides possess high activity for alcohol reforming and electrochemical hydrogen production. First, the surface chemistry of carbides towards alcohol decomposition is studied using density functional theory (DFT) and surface science experiments. The Vienna Ab initio Simulation Package (VASP) was used to calculate the binding energies of alcohols and decomposition intermediates on metal-modified carbides. The calculated binding energies were then correlated to reforming activity determined experimentally using temperature programmed desorption (TPD). In the case of methanol decomposition, it was found that tungsten monocarbide (WC) selectively cleaved the C-O bond to produce methane. Upon modifying the surface with a single layer of metal such as Ni, Pt, or Rh, the selectivity shifted towards scission of the C-H bonds while leaving the C-O bond intact, producing carbon monoxide (CO) and H2. High resolution energy loss spectroscopy (HREELS) was used to examine the bond breaking sequence as a function of temperature. From HREELS, it was shown that the surfaces followed an activity trend of Rh > Ni > Pt. The Au-modified WC surface possessed too low of a methanol binding energy, and molecular desorption of methanol was the most favorable pathway on this surface. Next, the ability of Rh-modified WC to break the C-C bond of C2 and C3 alcohols was demonstrated. HREELS showed that ethanol decomposed through an acetaldehyde

  15. Anion Coordination in Metal-Organic Frameworks Functionalized with Urea Hydrogen-Bonding Groups

    SciTech Connect

    Custelcean, Radu; Moyer, Bruce A.; Bryantsev, Vyacheslav; Hay, Benjamin P.

    2005-12-15

    A series of metal-organic frameworks (MOFs) functionalized with urea hydrogen-bonding groups have been designed, synthesized, and structurally analyzed by single crystal X-ray diffraction to evaluate the efficacy of anion binding within the structural constraints of the MOFs. We found that urea-based functionalities may be used for anion binding within metal-organic frameworks when the tendency for urea???urea self-association is decreased by strengthening the intramolelcular CH???O hydrogen bonding of N-phenyl substituents to the carbonyl oxygen atom. Theoretical calculations indicate that N,N?-bis(m-pyridyl)urea (BPU) and N,N?-bis(m-cyanophenyl)urea (BCPU) should have enhanced hydrogen-bonding donor abilities toward anions and decreased tendencies to self-associate into hydrogen-bonded chains compared to other disubstituted ureas. Accordingly, BPU and BCPU were incorporated in MOFs as linkers through coordination of various Zn, Cu, and Ag transition metal salts, including Zn(ClO4)2, ZnSO4, Cu(NO3)2, Cu(CF3SO3)2, AgNO3 and AgSO3CH3. Structural analysis by single-crystal X-ray diffraction showed that these linkers are versatile anion binders, capable of chelate hydrogen bonding to all of the oxoanions explored. Anion binding by the urea functionalities was found to successfully compete with urea self-association in all cases except for that of charge-diffuse perchlorate. This research was sponsored by the Division of Chemical Sciences, Geosciences, and Biosciences, Office of Basic Energy Sciences of the U.S. Department of Energy, under contract number DE-AC05-00OR22725 with Oak Ridge National Laboratory (managed by UT-Battelle, LLC), and performed at Oak Ridge National laboratory and Pacific Northwest National Laboratory (managed by Battelle for the U.S. Department of Energy under contract DE-AC05-76RL01830). This research was performed in part using the Molecular Science Computing Facility (MSCF) in the William R. Wiley Environmental Molecular Sciences laboratory

  16. Quasi-two-dimensional metallic hydrogen inside di-phosphide at high pressure

    NASA Astrophysics Data System (ADS)

    Degtyarenko, N. N.; Mazur, E. A.

    2016-09-01

    The method of mathematical modelling was used for the calculation of the structural, electronic, phononic, and other characteristics of various normal phases of phosphorus hydrides with stoichiometry PHk. It was shown that the di-phosphine may form 2D lattice of the metallic hydrogen in it, stabilized by phosphorus atoms under high hydrostatic pressure. The resulting structure with the elements of H-P-H has a locally stable (or metastable) phonon spectrum. The properties of di-phosphine were compared with the properties of similar structures such as the sulphur hydrides.

  17. Universal transition state scaling relations for (de)hydrogenation over transition metals.

    PubMed

    Wang, S; Petzold, V; Tripkovic, V; Kleis, J; Howalt, J G; Skúlason, E; Fernández, E M; Hvolbæk, B; Jones, G; Toftelund, A; Falsig, H; Björketun, M; Studt, F; Abild-Pedersen, F; Rossmeisl, J; Nørskov, J K; Bligaard, T

    2011-12-14

    We analyse the transition state energies for 249 hydrogenation/dehydrogenation reactions of atoms and simple molecules over close-packed and stepped surfaces and nanoparticles of transition metals using Density Functional Theory. Linear energy scaling relations are observed for the transition state structures leading to transition state scaling relations for all the investigated reactions. With a suitable choice of reference systems the transition state scaling relations form a universality class that can be approximated with one single linear relation describing the entire range of reactions over all types of surfaces and nanoclusters. PMID:21996683

  18. Coupled Electron-Ion Monte Carlo Calculations of Dense Metallic Hydrogen

    NASA Astrophysics Data System (ADS)

    Pierleoni, Carlo; Ceperley, David M.; Holzmann, Markus

    2004-09-01

    We present an efficient new Monte Carlo method which couples path integrals for finite temperature protons with quantum Monte Carlo calculations for ground state electrons, and we apply it to metallic hydrogen for pressures beyond molecular dissociation. We report data for the equation of state for temperatures across the melting of the proton crystal. Our data exhibit more structure and higher melting temperatures of the proton crystal than do Car-Parrinello molecular dynamics results. This method fills the gap between high temperature electron-proton path integral and ground state diffusion Monte Carlo methods and should have wide applicability.

  19. Scaling Properties of Adsorption Energies for Hydrogen-Containing Molecules on Transition-Metal Surfaces

    NASA Astrophysics Data System (ADS)

    Abild-Pedersen, F.; Greeley, J.; Studt, F.; Rossmeisl, J.; Munter, T. R.; Moses, P. G.; Skúlason, E.; Bligaard, T.; Nørskov, J. K.

    2007-07-01

    Density functional theory calculations are presented for CHx, x=0,1,2,3, NHx, x=0,1,2, OHx, x=0,1, and SHx, x=0,1 adsorption on a range of close-packed and stepped transition-metal surfaces. We find that the adsorption energy of any of the molecules considered scales approximately with the adsorption energy of the central, C, N, O, or S atom, the scaling constant depending only on x. A model is proposed to understand this behavior. The scaling model is developed into a general framework for estimating the reaction energies for hydrogenation and dehydrogenation reactions.

  20. Work function shifts of catalytic metals under hydrogen gas visualized by terahertz chemical microscopy.

    PubMed

    Kiwa, Toshihiko; Hagiwara, Takafumi; Shinomiya, Mitsuhiro; Sakai, Kenji; Tsukada, Keiji

    2012-05-21

    Terahertz chemical microscopy (TCM) was applied to visualize the distribution of the work function shift of catalytic metals under hydrogen gas. TCM measures the chemical potential on the surface of a SiO(2)/Si/sapphire sensing plate without any contact with the plate. By controlling the bias voltage between an electrode on the SiO(2)/ surface and the Si layer, the relationship between the voltage and the THz amplitude from the sensing plate can be obtained. As a demonstration, two types of structures were fabricated on the sensing plate, and the work function shifts due to catalytic reactions were visualized.

  1. Discovery of Novel Complex Metal Hydrides for Hydrogen Storage through Molecular Modeling and Combinatorial Methods

    SciTech Connect

    Lesch, David A; Adriaan Sachtler, J.W. J.; Low, John J; Jensen, Craig M; Ozolins, Vidvuds; Siegel, Don; Harmon, Laurel

    2011-02-14

    UOP LLC, a Honeywell Company, Ford Motor Company, and Striatus, Inc., collaborated with Professor Craig Jensen of the University of Hawaii and Professor Vidvuds Ozolins of University of California, Los Angeles on a multi-year cost-shared program to discover novel complex metal hydrides for hydrogen storage. This innovative program combined sophisticated molecular modeling with high throughput combinatorial experiments to maximize the probability of identifying commercially relevant, economical hydrogen storage materials with broad application. A set of tools was developed to pursue the medium throughput (MT) and high throughput (HT) combinatorial exploratory investigation of novel complex metal hydrides for hydrogen storage. The assay programs consisted of monitoring hydrogen evolution as a function of temperature. This project also incorporated theoretical methods to help select candidate materials families for testing. The Virtual High Throughput Screening served as a virtual laboratory, calculating structures and their properties. First Principles calculations were applied to various systems to examine hydrogen storage reaction pathways and the associated thermodynamics. The experimental program began with the validation of the MT assay tool with NaAlH4/0.02 mole Ti, the state of the art hydrogen storage system given by decomposition of sodium alanate to sodium hydride, aluminum metal, and hydrogen. Once certified, a combinatorial 21-point study of the NaAlH4 LiAlH4Mg(AlH4)2 phase diagram was investigated with the MT assay. Stability proved to be a problem as many of the materials decomposed during synthesis, altering the expected assay results. This resulted in repeating the entire experiment with a mild milling approach, which only temporarily increased capacity. NaAlH4 was the best performer in both studies and no new mixed alanates were observed, a result consistent with the VHTS. Powder XRD suggested that the reverse reaction, the regeneration of the

  2. Curvature and ionization-induced reversible hydrogen storage in metalized hexagonal B{sub 36}

    SciTech Connect

    Liu, Chun-Sheng Wang, Xiangfu; Yan, Xiaohong; Ye, Xiao-Juan; Zeng, Zhi

    2014-11-21

    The synthesis of quasiplanar boron clusters (B{sub 36}) with a central hexagonal hole provides the first experimental evidence that a single-atomic-layer borophene with hexagonal vacancies is potentially viable [Z. Piazza, H. Hu, W. Li, Y. Zhao, J. Li, and L. S. Wang, Nat. Commun. 5, 3113 (2014)]. However, owing to the hexagonal holes, tunning the electronic and physical properties of B{sub 36} through chemical modifications is not fully understood. Based on (van der Waals corrected-) density functional theory, we show that Li adsorbed on B{sub 36} and B{sub 36}{sup −} clusters can serve as reversible hydrogen storage media. The present results indicate that the curvature and ionization of substrates can enhance the bond strength of Li due to the energetically favorable B 2p-Li 2p orbitals hybridization. Both the polarization mechanism and the orbital hybridization between H-s orbitals and Li-2s2p orbitals contribute to the adsorption of H{sub 2} molecules and the resulting adsorption energy lies between the physisorbed and chemisorbed states. Interestingly, the number of H{sub 2} in the hydrogen storage medium can be measured by the appearance of the negative differential resistance behavior at different bias voltage regions. Furthermore, the cluster-assembled hydrogen storage materials constructed by metalized B{sub 36} clusters do not cause a decrease in the number of adsorbed hydrogen molecules per Li. The system reported here is favorable for the reversible hydrogen adsorption/desorption at ambient conditions.

  3. Beyond Metal-Hydrides: Non-Transition-Metal and Metal-Free Ligand-Centered Electrocatalytic Hydrogen Evolution and Hydrogen Oxidation.

    PubMed

    Haddad, Andrew Z; Garabato, Brady D; Kozlowski, Pawel M; Buchanan, Robert M; Grapperhaus, Craig A

    2016-06-29

    A new pathway for homogeneous electrocatalytic H2 evolution and H2 oxidation has been developed using a redox active thiosemicarbazone and its zinc complex as seminal metal-free and transition-metal-free examples. Diacetyl-bis(N-4-methyl-3-thiosemicarbazone) and zinc diacetyl-bis(N-4-methyl-3-thiosemicarbazide) display the highest reported TOFs of any homogeneous ligand-centered H2 evolution catalyst, 1320 and 1170 s(-1), respectively, while the zinc complex also displays one of the highest reported TOF values for H2 oxidation, 72 s(-1), of any homogeneous catalyst. Catalysis proceeds via ligand-centered proton-transfer and electron-transfer events while avoiding traditional metal-hydride intermediates. The unique mechanism is consistent with electrochemical results and is further supported by density functional theory. The results identify a new direction for the design of electrocatalysts for H2 evolution and H2 oxidation that are not reliant on metal-hydride intermediates. PMID:27326672

  4. Metallization and Dissociation of Fluid Hydrogen and Other Diatomics at 100 GPa Pressures

    SciTech Connect

    Nellis, W J

    2002-09-20

    Dynamic compression of diatomic liquids using both single-shock (Hugoniot) and multiple-shock (reverberating-shock) compression achieves pressures which range up to a few 100 GPa (Mbar), densities as high as tenfold of initial liquid density in hydrogen, and temperatures up to several 1000 K. Single-shock compression produces substantial heating, which causes a limiting compression. Multiple-shock compression is quasi-isentropic, which achieves lower temperatures and higher densities than single shocks, and has no limiting compression. Diatomic fluids have universal behaviors under dynamic compression. Under multiple-shock compression, these fluids undergo a density-driven nonmetal-metal Mott transitions with common density scaling. Under single-shock compression, these fluids have essentially the same Hugoniot in velocity space. D{sub 2} undergoes temperature-driven dissociation to a poor metal at {approx}50 GPa. These results provide insight into which of the two published D{sub 2} Hugoniots is probably correct.

  5. Hydrogen storage in a microporous metal-organic framework with exposed Mn2+ coordination sites.

    PubMed

    Dincă, Mircea; Dailly, Anne; Liu, Yun; Brown, Craig M; Neumann, Dan A; Long, Jeffrey R

    2006-12-27

    Use of the tritopic bridging ligand 1,3,5-benzenetristetrazolate (BTT3-) enables formation of [Mn(DMF)6]3[(Mn4Cl)3(BTT)8(H2O)12]2.42DMF.11H2O.20CH3OH, featuring a porous metal-organic framework with a previously unknown cubic topology. Crystals of the compound remain intact upon desolvation and show a total H2 uptake of 6.9 wt % at 77 K and 90 bar, which at 60 g H2/L provides a storage density 85% of that of liquid hydrogen. The material exhibits a maximum isosteric heat of adsorption of 10.1 kJ/mol, the highest yet observed for a metal-organic framework. Neutron powder diffraction data demonstrate that this is directly related to H2 binding at coordinatively unsaturated Mn2+ centers within the framework.

  6. Solar Metal Sulfate-Ammonia Based Thermochemical Water Splitting Cycle for Hydrogen Production

    NASA Technical Reports Server (NTRS)

    Huang, Cunping (Inventor); T-Raissi, Ali (Inventor); Muradov, Nazim (Inventor)

    2014-01-01

    Two classes of hybrid/thermochemical water splitting processes for the production of hydrogen and oxygen have been proposed based on (1) metal sulfate-ammonia cycles (2) metal pyrosulfate-ammonia cycles. Methods and systems for a metal sulfate MSO.sub.4--NH3 cycle for producing H2 and O2 from a closed system including feeding an aqueous (NH3)(4)SO3 solution into a photoctalytic reactor to oxidize the aqueous (NH3)(4)SO3 into aqueous (NH3)(2)SO4 and reduce water to hydrogen, mixing the resulting aqueous (NH3)(2)SO4 with metal oxide (e.g. ZnO) to form a slurry, heating the slurry of aqueous (NH4)(2)SO4 and ZnO(s) in the low temperature reactor to produce a gaseous mixture of NH3 and H2O and solid ZnSO4(s), heating solid ZnSO4 at a high temperature reactor to produce a gaseous mixture of SO2 and O2 and solid product ZnO, mixing the gaseous mixture of SO2 and O2 with an NH3 and H2O stream in an absorber to form aqueous (NH4)(2)SO3 solution and separate O2 for aqueous solution, recycling the resultant solution back to the photoreactor and sending ZnO to mix with aqueous (NH4)(2)SO4 solution to close the water splitting cycle wherein gaseous H2 and O2 are the only products output from the closed ZnSO4--NH3 cycle.

  7. Hydrogen Storage in metal-modified single-walled carbon nanotubes

    SciTech Connect

    Dr. Ahn

    2004-04-30

    It has been known for over thirty years that potassium-intercalated graphites can readily adsorb and desorb hydrogen at {approx}1 wt% at 77 K. These levels are much higher than can be attained in pure graphite, owing to a larger thermodynamic enthalpy of adsorption. This increased enthalpy may allow hydrogen sorption at higher temperatures. Potassium has other beneficial effects that enable the design of a new material: (a) Increased adsorption enthalpy in potassium-intercalated graphite compared to pure graphite reduces the pressure and increases the temperature required for a given fractional coverage of hydrogen adsorption. We expect the same effects in potassium-intercalated SWNTs. (b) As an intercalant, potassium separates c-axis planes in graphite. Potassium also separates the individual tubes of SWNTs ropes producing swelling and increased surface area. Increased surface area provides more adsorption sites, giving a proportionately higher capacity. The temperature of adsorption depends on the enthalpy of adsorption. The characteristic temperature is roughly the adsorption enthalpy divided by Boltzmann's constant, k{sub B}. For the high hydrogen storage capacity of SWNTs to be achieved at room temperature, it is necessary to increase the enthalpy of adsorption. Our goal for this project was to use metal modifications to the carbon surface of SWNTs in order to address both enhanced adsorption and surface area. For instance, the enthalpy of sorption of hydrogen on KC8 is 450 meV/H{sub 2}, whereas it is 38 meV/H{sub 2} for unmodified SWNTs. By adsorption thermodynamics we expect approximately that the same performance of SWNTs at 77 K will be achieved at a temperature of [450/38] 77 K = 900 K. This is a high temperature, so we expect that adsorption on nearly all the available sites for hydrogen will occur at room temperature under a much lower pressure. This pressure can be estimated conveniently, since the chemical potential of hydrogen is approximately

  8. Energy decomposition analysis of cation-π, metal ion-lone pair, hydrogen bonded, charge-assisted hydrogen bonded, and π-π interactions.

    PubMed

    Sharma, Bhaskar; Srivastava, Hemant Kumar; Gayatri, Gaddamanugu; Sastry, Garikapati Narahari

    2015-03-30

    This study probes the nature of noncovalent interactions, such as cation-π, metal ion-lone pair (M-LP), hydrogen bonding (HB), charge-assisted hydrogen bonding (CAHB), and π-π interactions, using energy decomposition schemes-density functional theory (DFT)-symmetry-adapted perturbation theory and reduced variational space. Among cation-π complexes, the polarization and electrostatic components are the major contributors to the interaction energy (IE) for metal ion-π complexes, while for onium ion-π complexes (NH4+, PH4+, OH3+, and SH3+) the dispersion component is prominent. For M-LP complexes, the electrostatic component contributes more to the IE except the dicationic metal ion complexes with H2 S and PH3 where the polarization component dominates. Although electrostatic component dominates for the HB and CAHB complexes, dispersion is predominant in π-π complexes.

  9. Tailoring the properties of ammine metal borohydrides for solid-state hydrogen storage.

    PubMed

    Jepsen, Lars H; Ley, Morten B; Filinchuk, Yaroslav; Besenbacher, Flemming; Jensen, Torben R

    2015-04-24

    A series of halide-free ammine manganese borohydrides, Mn(BH4 )2 ⋅nNH3 , n=1, 2, 3, and 6, a new bimetallic compound Li2 Mn(BH4 )4 ⋅6NH3 , and the first ammine metal borohydride solid solution Mg1-x Mnx (BH4 )2 ⋅6NH3 are presented. Four new crystal structures have been determined by synchrotron radiation powder X-ray diffraction and the thermal decomposition is systematically investigated for all the new compounds. The solid-gas reaction between Mn(BH4 )2 and NH3 provides Mn(BH4 )2 ⋅6NH3 . The number of NH3 per Mn has been varied by mechanochemical treatment of Mn(BH4 )2 ⋅6NH3 -Mn(BH4 )2 mixtures giving rise to increased hydrogen purity for n/m≤1 for M(BH4 )m ⋅nNH3 . The structures of Mg(BH4 )2 ⋅3NH3 and Li2 Mg(BH4 )4 ⋅6NH3 have been revisited and new structural models are presented. Finally, we demonstrate that ammonia destabilizes metal borohydrides with low electronegativity of the metal (χp <∼1.6), while metal borohydrides with high electronegativity (χp >∼1.6) are generally stabilized.

  10. How Hydrogen Bonds Affect the Growth of Reverse Micelles around Coordinating Metal Ions.

    PubMed

    Qiao, Baofu; Demars, Thomas; Olvera de la Cruz, Monica; Ellis, Ross J

    2014-04-17

    Extensive research on hydrogen bonds (H-bonds) have illustrated their critical role in various biological, chemical and physical processes. Given that existing studies are predominantly performed in aqueous conditions, how H-bonds affect both the structure and function of aggregates in organic phase is poorly understood. Herein, we investigate the role of H-bonds on the hierarchical structure of an aggregating amphiphile-oil solution containing a coordinating metal complex by means of atomistic molecular dynamics simulations and X-ray techniques. For the first time, we show that H-bonds not only stabilize the metal complex in the hydrophobic environment by coordinating between the Eu(NO3)3 outer-sphere and aggregating amphiphiles, but also affect the growth of such reverse micellar aggregates. The formation of swollen, elongated reverse micelles elevates the extraction of metal ions with increased H-bonds under acidic condition. These new insights into H-bonds are of broad interest to nanosynthesis and biological applications, in addition to metal ion separations.

  11. Structure and energetics of hydrogen-bonded networks of methanol on close packed transition metal surfaces

    NASA Astrophysics Data System (ADS)

    Murphy, Colin J.; Carrasco, Javier; Lawton, Timothy J.; Liriano, Melissa L.; Baber, Ashleigh E.; Lewis, Emily A.; Michaelides, Angelos; Sykes, E. Charles H.

    2014-07-01

    Methanol is a versatile chemical feedstock, fuel source, and energy storage material. Many reactions involving methanol are catalyzed by transition metal surfaces, on which hydrogen-bonded methanol overlayers form. As with water, the structure of these overlayers is expected to depend on a delicate balance of hydrogen bonding and adsorbate-substrate bonding. In contrast to water, however, relatively little is known about the structures methanol overlayers form and how these vary from one substrate to another. To address this issue, herein we analyze the hydrogen bonded networks that methanol forms as a function of coverage on three catalytically important surfaces, Au(111), Cu(111), and Pt(111), using a combination of scanning tunneling microscopy and density functional theory. We investigate the effect of intermolecular interactions, surface coverage, and adsorption energies on molecular assembly and compare the results to more widely studied water networks on the same surfaces. Two main factors are shown to direct the structure of methanol on the surfaces studied: the surface coverage and the competition between the methanol-methanol and methanol-surface interactions. Additionally, we report a new chiral form of buckled hexamer formed by surface bound methanol that maximizes the interactions between methanol monomers by sacrificing interactions with the surface. These results serve as a direct comparison of interaction strength, assembly, and chirality of methanol networks on Au(111), Cu(111), and Pt(111) which are catalytically relevant for methanol oxidation, steam reforming, and direct methanol fuel cells.

  12. Metal-encapsulated organolead halide perovskite photocathode for solar-driven hydrogen evolution in water

    PubMed Central

    Crespo-Quesada, Micaela; Pazos-Outón, Luis M.; Warnan, Julien; Kuehnel, Moritz F.; Friend, Richard H.; Reisner, Erwin

    2016-01-01

    Lead-halide perovskites have triggered the latest breakthrough in photovoltaic technology. Despite the great promise shown by these materials, their instability towards water even in the presence of low amounts of moisture makes them, a priori, unsuitable for their direct use as light harvesters in aqueous solution for the production of hydrogen through water splitting. Here, we present a simple method that enables their use in photoelectrocatalytic hydrogen evolution while immersed in an aqueous solution. Field's metal, a fusible InBiSn alloy, is used to efficiently protect the perovskite from water while simultaneously allowing the photogenerated electrons to reach a Pt hydrogen evolution catalyst. A record photocurrent density of −9.8 mA cm−2 at 0 V versus RHE with an onset potential as positive as 0.95±0.03 V versus RHE is obtained. The photoelectrodes show remarkable stability retaining more than 80% of their initial photocurrent for ∼1 h under continuous illumination. PMID:27595974

  13. Self-Printing on Graphitic Nanosheets with Metal Borohydride Nanodots for Hydrogen Storage

    NASA Astrophysics Data System (ADS)

    Li, Yongtao; Ding, Xiaoli; Zhang, Qingan

    2016-08-01

    Although the synthesis of borohydride nanostructures is sufficiently established for advancement of hydrogen storage, obtaining ultrasmall (sub-10 nm) metal borohydride nanocrystals with excellent dispersibility is extremely challenging because of their high surface energy, exceedingly strong reducibility/hydrophilicity and complicated composition. Here, we demonstrate a mechanical-force-driven self-printing process that enables monodispersed (~6 nm) NaBH4 nanodots to uniformly anchor onto freshly-exfoliated graphitic nanosheets (GNs). Both mechanical-forces and borohydride interaction with GNs stimulate NaBH4 clusters intercalation/absorption into the graphite interlayers acting as a ‘pen’ for writing, which is accomplished by exfoliating GNs with the ‘printed’ borohydrides. These nano-NaBH4@GNs exhibit favorable thermodynamics (decrease in ∆H of ~45%), rapid kinetics (a greater than six-fold increase) and stable de-/re-hydrogenation that retains a high capacity (up to ~5 wt% for NaBH4) compared with those of micro-NaBH4. Our results are helpful in the scalable fabrication of zero-dimensional complex hydrides on two-dimensional supports with enhanced hydrogen storage for potential applications.

  14. Structure and energetics of hydrogen-bonded networks of methanol on close packed transition metal surfaces.

    PubMed

    Murphy, Colin J; Carrasco, Javier; Lawton, Timothy J; Liriano, Melissa L; Baber, Ashleigh E; Lewis, Emily A; Michaelides, Angelos; Sykes, E Charles H

    2014-07-01

    Methanol is a versatile chemical feedstock, fuel source, and energy storage material. Many reactions involving methanol are catalyzed by transition metal surfaces, on which hydrogen-bonded methanol overlayers form. As with water, the structure of these overlayers is expected to depend on a delicate balance of hydrogen bonding and adsorbate-substrate bonding. In contrast to water, however, relatively little is known about the structures methanol overlayers form and how these vary from one substrate to another. To address this issue, herein we analyze the hydrogen bonded networks that methanol forms as a function of coverage on three catalytically important surfaces, Au(111), Cu(111), and Pt(111), using a combination of scanning tunneling microscopy and density functional theory. We investigate the effect of intermolecular interactions, surface coverage, and adsorption energies on molecular assembly and compare the results to more widely studied water networks on the same surfaces. Two main factors are shown to direct the structure of methanol on the surfaces studied: the surface coverage and the competition between the methanol-methanol and methanol-surface interactions. Additionally, we report a new chiral form of buckled hexamer formed by surface bound methanol that maximizes the interactions between methanol monomers by sacrificing interactions with the surface. These results serve as a direct comparison of interaction strength, assembly, and chirality of methanol networks on Au(111), Cu(111), and Pt(111) which are catalytically relevant for methanol oxidation, steam reforming, and direct methanol fuel cells.

  15. Self-Printing on Graphitic Nanosheets with Metal Borohydride Nanodots for Hydrogen Storage.

    PubMed

    Li, Yongtao; Ding, Xiaoli; Zhang, Qingan

    2016-08-03

    Although the synthesis of borohydride nanostructures is sufficiently established for advancement of hydrogen storage, obtaining ultrasmall (sub-10 nm) metal borohydride nanocrystals with excellent dispersibility is extremely challenging because of their high surface energy, exceedingly strong reducibility/hydrophilicity and complicated composition. Here, we demonstrate a mechanical-force-driven self-printing process that enables monodispersed (~6 nm) NaBH4 nanodots to uniformly anchor onto freshly-exfoliated graphitic nanosheets (GNs). Both mechanical-forces and borohydride interaction with GNs stimulate NaBH4 clusters intercalation/absorption into the graphite interlayers acting as a 'pen' for writing, which is accomplished by exfoliating GNs with the 'printed' borohydrides. These nano-NaBH4@GNs exhibit favorable thermodynamics (decrease in ∆H of ~45%), rapid kinetics (a greater than six-fold increase) and stable de-/re-hydrogenation that retains a high capacity (up to ~5 wt% for NaBH4) compared with those of micro-NaBH4. Our results are helpful in the scalable fabrication of zero-dimensional complex hydrides on two-dimensional supports with enhanced hydrogen storage for potential applications.

  16. Self-Printing on Graphitic Nanosheets with Metal Borohydride Nanodots for Hydrogen Storage

    PubMed Central

    Li, Yongtao; Ding, Xiaoli; Zhang, Qingan

    2016-01-01

    Although the synthesis of borohydride nanostructures is sufficiently established for advancement of hydrogen storage, obtaining ultrasmall (sub-10 nm) metal borohydride nanocrystals with excellent dispersibility is extremely challenging because of their high surface energy, exceedingly strong reducibility/hydrophilicity and complicated composition. Here, we demonstrate a mechanical-force-driven self-printing process that enables monodispersed (~6 nm) NaBH4 nanodots to uniformly anchor onto freshly-exfoliated graphitic nanosheets (GNs). Both mechanical-forces and borohydride interaction with GNs stimulate NaBH4 clusters intercalation/absorption into the graphite interlayers acting as a ‘pen’ for writing, which is accomplished by exfoliating GNs with the ‘printed’ borohydrides. These nano-NaBH4@GNs exhibit favorable thermodynamics (decrease in ∆H of ~45%), rapid kinetics (a greater than six-fold increase) and stable de-/re-hydrogenation that retains a high capacity (up to ~5 wt% for NaBH4) compared with those of micro-NaBH4. Our results are helpful in the scalable fabrication of zero-dimensional complex hydrides on two-dimensional supports with enhanced hydrogen storage for potential applications. PMID:27484735

  17. Structure and energetics of hydrogen-bonded networks of methanol on close packed transition metal surfaces.

    PubMed

    Murphy, Colin J; Carrasco, Javier; Lawton, Timothy J; Liriano, Melissa L; Baber, Ashleigh E; Lewis, Emily A; Michaelides, Angelos; Sykes, E Charles H

    2014-07-01

    Methanol is a versatile chemical feedstock, fuel source, and energy storage material. Many reactions involving methanol are catalyzed by transition metal surfaces, on which hydrogen-bonded methanol overlayers form. As with water, the structure of these overlayers is expected to depend on a delicate balance of hydrogen bonding and adsorbate-substrate bonding. In contrast to water, however, relatively little is known about the structures methanol overlayers form and how these vary from one substrate to another. To address this issue, herein we analyze the hydrogen bonded networks that methanol forms as a function of coverage on three catalytically important surfaces, Au(111), Cu(111), and Pt(111), using a combination of scanning tunneling microscopy and density functional theory. We investigate the effect of intermolecular interactions, surface coverage, and adsorption energies on molecular assembly and compare the results to more widely studied water networks on the same surfaces. Two main factors are shown to direct the structure of methanol on the surfaces studied: the surface coverage and the competition between the methanol-methanol and methanol-surface interactions. Additionally, we report a new chiral form of buckled hexamer formed by surface bound methanol that maximizes the interactions between methanol monomers by sacrificing interactions with the surface. These results serve as a direct comparison of interaction strength, assembly, and chirality of methanol networks on Au(111), Cu(111), and Pt(111) which are catalytically relevant for methanol oxidation, steam reforming, and direct methanol fuel cells. PMID:25005297

  18. Self-Printing on Graphitic Nanosheets with Metal Borohydride Nanodots for Hydrogen Storage.

    PubMed

    Li, Yongtao; Ding, Xiaoli; Zhang, Qingan

    2016-01-01

    Although the synthesis of borohydride nanostructures is sufficiently established for advancement of hydrogen storage, obtaining ultrasmall (sub-10 nm) metal borohydride nanocrystals with excellent dispersibility is extremely challenging because of their high surface energy, exceedingly strong reducibility/hydrophilicity and complicated composition. Here, we demonstrate a mechanical-force-driven self-printing process that enables monodispersed (~6 nm) NaBH4 nanodots to uniformly anchor onto freshly-exfoliated graphitic nanosheets (GNs). Both mechanical-forces and borohydride interaction with GNs stimulate NaBH4 clusters intercalation/absorption into the graphite interlayers acting as a 'pen' for writing, which is accomplished by exfoliating GNs with the 'printed' borohydrides. These nano-NaBH4@GNs exhibit favorable thermodynamics (decrease in ∆H of ~45%), rapid kinetics (a greater than six-fold increase) and stable de-/re-hydrogenation that retains a high capacity (up to ~5 wt% for NaBH4) compared with those of micro-NaBH4. Our results are helpful in the scalable fabrication of zero-dimensional complex hydrides on two-dimensional supports with enhanced hydrogen storage for potential applications. PMID:27484735

  19. Metal-encapsulated organolead halide perovskite photocathode for solar-driven hydrogen evolution in water.

    PubMed

    Crespo-Quesada, Micaela; Pazos-Outón, Luis M; Warnan, Julien; Kuehnel, Moritz F; Friend, Richard H; Reisner, Erwin

    2016-01-01

    Lead-halide perovskites have triggered the latest breakthrough in photovoltaic technology. Despite the great promise shown by these materials, their instability towards water even in the presence of low amounts of moisture makes them, a priori, unsuitable for their direct use as light harvesters in aqueous solution for the production of hydrogen through water splitting. Here, we present a simple method that enables their use in photoelectrocatalytic hydrogen evolution while immersed in an aqueous solution. Field's metal, a fusible InBiSn alloy, is used to efficiently protect the perovskite from water while simultaneously allowing the photogenerated electrons to reach a Pt hydrogen evolution catalyst. A record photocurrent density of -9.8 mA cm(-2) at 0 V versus RHE with an onset potential as positive as 0.95±0.03 V versus RHE is obtained. The photoelectrodes show remarkable stability retaining more than 80% of their initial photocurrent for ∼1 h under continuous illumination. PMID:27595974

  20. Metal-free photochemical silylations and transfer hydrogenations of benzenoid hydrocarbons and graphene

    NASA Astrophysics Data System (ADS)

    Papadakis, Raffaello; Li, Hu; Bergman, Joakim; Lundstedt, Anna; Jorner, Kjell; Ayub, Rabia; Haldar, Soumyajyoti; Jahn, Burkhard O.; Denisova, Aleksandra; Zietz, Burkhard; Lindh, Roland; Sanyal, Biplab; Grennberg, Helena; Leifer, Klaus; Ottosson, Henrik

    2016-10-01

    The first hydrogenation step of benzene, which is endergonic in the electronic ground state (S0), becomes exergonic in the first triplet state (T1). This is in line with Baird's rule, which tells that benzene is antiaromatic and destabilized in its T1 state and also in its first singlet excited state (S1), opposite to S0, where it is aromatic and remarkably unreactive. Here we utilized this feature to show that benzene and several polycyclic aromatic hydrocarbons (PAHs) to various extents undergo metal-free photochemical (hydro)silylations and transfer-hydrogenations at mild conditions, with the highest yield for naphthalene (photosilylation: 21%). Quantum chemical computations reveal that T1-state benzene is excellent at H-atom abstraction, while cyclooctatetraene, aromatic in the T1 and S1 states according to Baird's rule, is unreactive. Remarkably, also CVD-graphene on SiO2 is efficiently transfer-photohydrogenated using formic acid/water mixtures together with white light or solar irradiation under metal-free conditions.

  1. Metal-free photochemical silylations and transfer hydrogenations of benzenoid hydrocarbons and graphene

    PubMed Central

    Papadakis, Raffaello; Li, Hu; Bergman, Joakim; Lundstedt, Anna; Jorner, Kjell; Ayub, Rabia; Haldar, Soumyajyoti; Jahn, Burkhard O.; Denisova, Aleksandra; Zietz, Burkhard; Lindh, Roland; Sanyal, Biplab; Grennberg, Helena; Leifer, Klaus; Ottosson, Henrik

    2016-01-01

    The first hydrogenation step of benzene, which is endergonic in the electronic ground state (S0), becomes exergonic in the first triplet state (T1). This is in line with Baird's rule, which tells that benzene is antiaromatic and destabilized in its T1 state and also in its first singlet excited state (S1), opposite to S0, where it is aromatic and remarkably unreactive. Here we utilized this feature to show that benzene and several polycyclic aromatic hydrocarbons (PAHs) to various extents undergo metal-free photochemical (hydro)silylations and transfer-hydrogenations at mild conditions, with the highest yield for naphthalene (photosilylation: 21%). Quantum chemical computations reveal that T1-state benzene is excellent at H-atom abstraction, while cyclooctatetraene, aromatic in the T1 and S1 states according to Baird's rule, is unreactive. Remarkably, also CVD-graphene on SiO2 is efficiently transfer-photohydrogenated using formic acid/water mixtures together with white light or solar irradiation under metal-free conditions. PMID:27708336

  2. First-Principles Modeling of Hydrogen Storage in Metal Hydride Systems

    SciTech Connect

    J. Karl Johnson

    2011-05-20

    The objective of this project is to complement experimental efforts of MHoCE partners by using state-of-the-art theory and modeling to study the structure, thermodynamics, and kinetics of hydrogen storage materials. Specific goals include prediction of the heats of formation and other thermodynamic properties of alloys from first principles methods, identification of new alloys that can be tested experimentally, calculation of surface and energetic properties of nanoparticles, and calculation of kinetics involved with hydrogenation and dehydrogenation processes. Discovery of new metal hydrides with enhanced properties compared with existing materials is a critical need for the Metal Hydride Center of Excellence. New materials discovery can be aided by the use of first principles (ab initio) computational modeling in two ways: (1) The properties, including mechanisms, of existing materials can be better elucidated through a combined modeling/experimental approach. (2) The thermodynamic properties of novel materials that have not been made can, in many cases, be quickly screened with ab initio methods. We have used state-of-the-art computational techniques to explore millions of possible reaction conditions consisting of different element spaces, compositions, and temperatures. We have identified potentially promising single- and multi-step reactions that can be explored experimentally.

  3. Electrical conductivity of metallic hydrogen in the nearly-free-electron model

    NASA Astrophysics Data System (ADS)

    Shvets, V. T.

    2007-04-01

    The electrical resistivity of metallic hydrogen has been calculated. To do this, the perturbation theory in terms of electron-proton interaction for the reciprocal relaxation time characterizing the electrical conductivity has been employed. The second-and third-order terms as well as an approximate expression for the series sum have been calculated in detail. In doing so, the random-phase approximation with allowance for exchange interaction and correlations in the local-field approximation has been used for an electron subsystem and the exact solution of the Percus-Yevick equation for the hard-sphere model has been employed for the proton subsystem. In this case, at given density and temperature, the only parameter of the theory is the hard-sphere diameter. To determine this parameter, the effective pairwise interproton interaction has been calculated. The hard-sphere diameter has been determined from the dependence of the interproton interaction on the distance and the known temperature of the system. The dependence of the resistivity of metallic hydrogen on the density and temperature has been examined in a wide range of the latter quantities. In the entire range of densities and temperatures considered, the resistivity proves to be close to its limiting value for which the nearly-free-electron model is applicable.

  4. Hydrogen Assisted Crack in Dissimilar Metal Welds for Subsea Service under Cathodic Protection

    NASA Astrophysics Data System (ADS)

    Bourgeois, Desmond

    Dissimilar metal welds (DMWs) are routinely used in the oil and gas industries for structural joining of high strength steels in order to eliminate the need for post weld heat treatment (PWHT) after field welding. There have been reported catastrophic failures in these DMWs, particularly the AISI 8630 steel - Alloy 625 DMW combination, during subsea service while under cathodic protection (CP). This is due to local embrittlement that occurs in susceptible microstructures that are present at the weld fusion boundary region. This type of cracking is known as hydrogen assisted cracking (HAC) and it is influenced by base/filler metal combination, and welding and PWHT procedures. DMWs of two material combinations (8630 steel -- Alloy 625 and F22 steel -- Alloy 625), produced with two welding procedures (BS1 and BS3) in as welded and PWHT conditions were investigated in this study. The main objectives included: 1) evaluation of the effect of materials composition, welding and PWHT procedures on the gradients of composition, microstructure, and properties in the dissimilar transition region and on the susceptibility to HAC; 2) investigation of the influence of microstructure on the HAC failure mechanism and identification of microstructural constituents acting as crack nucleation and propagation sites; 3) assessment of the applicability of two-step PWHT to improve the resistance to HAC in DMWs; 4) establishment of non-failure criterion for the delayed hydrogen cracking test (DHCT) that is applicable for qualification of DMWs for subsea service under cathodic protection (CP).

  5. First-Principles Study of Electronic Structure and Hydrogen Adsorption of 3d Transition Metal Exposed Paddle Wheel Frameworks

    SciTech Connect

    Bak, J. H.; Le, V. D.; Kang, J.; Wei, S. H.; Kim, Y. H.

    2012-04-05

    Open-site paddle wheels, comprised of two transition metals bridged with four carboxylate ions, have been widely used for constructing metal-organic frameworks with large surface area and high binding energy sites. Using first-principles density functional theory calculations, we have investigated atomic and electronic structures of various 3d transition metal paddle wheels before and after metal exposure and their hydrogen adsorption properties at open metal sites. Notably, the hydrogen adsorption is impeded by covalent metal-metal bonds in early transition metal paddle wheels from Sc to Cr and by the strong ferromagnetic coupling of diatomic Mn and Fe in the paddle wheel configurations. A significantly enhanced H{sub 2} adsorption is predicted in the nonmagnetic Co{sub 2} and Zn{sub 2} paddle wheel with the binding energy of {approx}0.2 eV per H{sub 2}. We also propose the use of two-dimensional Co{sub 2} and Zn{sub 2} paddle wheel frameworks that could have strongly adsorbed dihydrogen up to 1.35 wt % for noncryogenic hydrogen storage applications.

  6. Transition metal catalysts for the conversion of ortho- to para-hydrogen

    SciTech Connect

    Brooks, C.J.

    1993-01-01

    The chemistry of the catalytic conversion of ortho- to para-hydrogen was pursued in this study by the preparation and characterization of transition metal silicates as well as ruthenium supported on silica. A plug flow reactor system was designed to test the conversion of ortho- to para-H[sub 2] from room temperature to [minus]196[degrees]C. This involved both the design and modification of an overall reactor system as well as individual reactor tubes. The system was calibrated to allow the measurement of conversion by thermal conductivity and measured catalytic activity such that they could be compared with other catalysts in the literature. Metal silicates of nickel, iron, chromium, and manganese were prepared by the coprecipitation or sol-gel methods. The study involved the optimization of activities at [minus]196[degrees]C by the variation of the catalyst preparation method. These changes, which increased the total surface area and total pore volume of the silicate, also increased the activity. Nitrogen adsorption confirmed the changes in the physical structure of the silicate. Ruthenium catalysts were prepared through traditional impregnation methods as well as through inpregnation of a ruthenium ammine intermediate. It was found that the traditional catalysts had a maximum activity at [approx][minus]158[degrees]C. This is most likely caused by the increasing strength of the Ru-H interaction at decreasing temperatures. Activity could be increased by heating the catalyst to high temperature and then cooling to the reaction temperature in helium. High temperature is felt to desorb a strongly bound hydrogen layer, while low temperature cooling does not allow as great of a readsorption of hydrogen. Chlorine containing precursors enhance this effect by residual surface chlorine increasing the strong H[sub 2] adsorption activation energy. Ruthenium ammine catalysts showed greatly enhanced activities relative to the traditionally prepared ruthenium catalysts.

  7. Metal and Precursor Effect during 1-Heptyne Selective Hydrogenation Using an Activated Carbon as Support

    PubMed Central

    Lederhos, Cecilia R.; Badano, Juan M.; Carrara, Nicolas; Coloma-Pascual, Fernando; Almansa, M. Cristina; Liprandi, Domingo; Quiroga, Mónica

    2013-01-01

    Palladium, platinum, and ruthenium supported on activated carbon were used as catalysts for the selective hydrogenation of 1-heptyne, a terminal alkyne. All catalysts were characterized by temperature programmed reduction, X-ray diffraction, transmission electron microscopy, and X-ray photoelectron spectroscopy. TPR and XPS suggest that the metal in all catalysts is reduced after the pretreatment with H2 at 673 K. The TPR trace of the PdNRX catalyst shows that the support surface groups are greatly modified as a consequence of the use of HNO3 during the catalyst preparation. During the hydrogenation of 1-heptyne, both palladium catalysts were more active and selective than the platinum and ruthenium catalysts. The activity order of the catalysts is as follows: PdClRX > PdNRX > PtClRX ≫ RuClRX. This superior performance of PdClRX was attributed in part to the total occupancy of the d electronic levels of the Pd metal that is supposed to promote the rupture of the H2 bond during the hydrogenation reaction. The activity differences between PdClRX and PdNRX catalysts could be attributed to a better accessibility of the substrate to the active sites, as a consequence of steric and electronic effects of the superficial support groups. The order for the selectivity to 1-heptene is as follows: PdClRX = PdNRX > RuClRX > PtClRX, and it can be mainly attributed to thermodynamic effects. PMID:24348168

  8. Y3+, La3+, and some bivalent metals inhibited the opening of the Tl+-induced permeability transition pore in Ca2+-loaded rat liver mitochondria.

    PubMed

    Korotkov, Sergey; Konovalova, Svetlana; Emelyanova, Larisa; Brailovskaya, Irina

    2014-12-01

    We showed earlier that diminution of 2,4-dinitrophenol (DNP)-stimulated respiration and increase of both mitochondrial swelling and electrochemical potential (ΔΨmito) dissipation in medium containing TlNO3 and KNO3 were caused by opening of Tl(+)-induced mitochondrial permeability transition pore (MPTP) in the inner membrane of Ca(2+)-loaded rat liver mitochondria. The MPTP opening was studied in the presence of bivalent metal ions (Sr(2+), Ba(2+), Mn(2+), Co(2+) and Ni(2+)), trivalent metal ions (Y(3+) and La(3+)), and ruthenium red. We found that these metal ions (except Ba(2+) and Co(2+)) as well as ruthenium red inhibited to the MPTP opening that manifested in preventing both diminution of the DNP-stimulated respiration and increase of the swelling and of the ΔΨmito dissipation in medium containing TlNO3, KNO3, and Ca(2+). Inhibition of the MPTP opening by Sr(2+) and Mn(2+) is suggested because of their interaction with high affinity Ca(2+) sites, facing the matrix side and participating in the MPTP opening. The inhibitory effects of metal ions (Y(3+), La(3+), and Ni(2+)), and ruthenium red are accordingly discussed in regard to competitive and noncompetitive inhibition of the mitochondrial Ca(2+)-uniporter. High concentrations (50μM) of Y(3+) and La(3+) favored of MPTP opening in the inner membrane of rat liver mitochondria in Ca(2+) free medium containing TlNO3. The latter MPTP opening was markedly eliminated by MPTP inhibitors (cyclosporine A and ADP).

  9. Calcium as a superior coating metal in functionalization of carbon fullerenes for high-capacity hydrogen storage

    SciTech Connect

    Yoon, Mina; Yang, Shenyuan; Hicke, Christian; Wang, Enge; Geohegan, David B; Zhang, Zhenyu

    2008-01-01

    We explore theoretically the feasibility of functionalizing carbon nanostructures for hydrogen storage, focusing on the coating of C60 fullerenes with light alkaline-earth metals. Our first-principles density functional theory studies show that both Ca and Sr can bind strongly to the C60 surface, and highly prefer monolayer coating, thereby explaining existing experimental observations. The strong binding is attributed to an intriguing charge transfer mechanism involving the empty d levels of the metal elements. The charge redistribution, in turn, gives rise to electric fields surrounding the coated fullerenes, which can now function as ideal attractors upon molecular hydrogen adsorption with binding strengths strong enough for potential room temperature applications but weak enough to avoid H2 dissociation. With a hydrogen uptake of >8.4wt% on Ca32C60, Ca is superior to all the recently suggested metal coating elements.

  10. Hydrogen from formic acid through its selective disproportionation over sodium germanate--a non-transition-metal catalysis system.

    PubMed

    Amos, Ruth I J; Heinroth, Falk; Chan, Bun; Zheng, Sisi; Haynes, Brian S; Easton, Christopher J; Masters, Anthony F; Radom, Leo; Maschmeyer, Thomas

    2014-10-13

    A robust catalyst for the selective dehydrogenation of formic acid to liberate hydrogen gas has been designed computationally, and also successfully demonstrated experimentally. This is the first such catalyst not based on transition metals, and it exhibits very encouraging performance. It represents an important step towards the use of renewable formic acid as a hydrogen-storage and transport vector in fuel and energy applications. PMID:25169798

  11. A coordinatively saturated sulfate encapsulated in a metal-organic framework functionalized with urea hydrogen-bonding groups

    SciTech Connect

    Custelcean, Radu; Moyer, Bruce A.; Hay, Benjamin P.

    2005-10-14

    A functional coordination polymer decorated with urea hydrogen-bonding donor groups has been designed for optional binding of sulfate; self-assembly of a tripodal tri-urea linker with Ag2SO4 resulted in the formation of a 1D metal-organic framework that encapsulated SO42- anions via twelve complementary hydrogen bonds, which represents the highest coordination number observed for sulfate in a natural or synthetic host.

  12. Universal dependence of hydrogen oxidation and evolution reaction activity of platinum-group metals on pH and hydrogen binding energy

    PubMed Central

    Zheng, Jie; Sheng, Wenchao; Zhuang, Zhongbin; Xu, Bingjun; Yan, Yushan

    2016-01-01

    Understanding how pH affects the activity of hydrogen oxidation reaction (HOR) and hydrogen evolution reaction (HER) is key to developing active, stable, and affordable HOR/HER catalysts for hydroxide exchange membrane fuel cells and electrolyzers. A common linear correlation between hydrogen binding energy (HBE) and pH is observed for four supported platinum-group metal catalysts (Pt/C, Ir/C, Pd/C, and Rh/C) over a broad pH range (0 to 13), suggesting that the pH dependence of HBE is metal-independent. A universal correlation between exchange current density and HBE is also observed on the four metals, indicating that they may share the same elementary steps and rate-determining steps and that the HBE is the dominant descriptor for HOR/HER activities. The onset potential of CO stripping on the four metals decreases with pH, indicating a stronger OH adsorption, which provides evidence against the promoting effect of adsorbed OH on HOR/HER. PMID:27034988

  13. Universal dependence of hydrogen oxidation and evolution reaction activity of platinum-group metals on pH and hydrogen binding energy.

    PubMed

    Zheng, Jie; Sheng, Wenchao; Zhuang, Zhongbin; Xu, Bingjun; Yan, Yushan

    2016-03-01

    Understanding how pH affects the activity of hydrogen oxidation reaction (HOR) and hydrogen evolution reaction (HER) is key to developing active, stable, and affordable HOR/HER catalysts for hydroxide exchange membrane fuel cells and electrolyzers. A common linear correlation between hydrogen binding energy (HBE) and pH is observed for four supported platinum-group metal catalysts (Pt/C, Ir/C, Pd/C, and Rh/C) over a broad pH range (0 to 13), suggesting that the pH dependence of HBE is metal-independent. A universal correlation between exchange current density and HBE is also observed on the four metals, indicating that they may share the same elementary steps and rate-determining steps and that the HBE is the dominant descriptor for HOR/HER activities. The onset potential of CO stripping on the four metals decreases with pH, indicating a stronger OH adsorption, which provides evidence against the promoting effect of adsorbed OH on HOR/HER.

  14. Universal dependence of hydrogen oxidation and evolution reaction activity of platinum-group metals on pH and hydrogen binding energy.

    PubMed

    Zheng, Jie; Sheng, Wenchao; Zhuang, Zhongbin; Xu, Bingjun; Yan, Yushan

    2016-03-01

    Understanding how pH affects the activity of hydrogen oxidation reaction (HOR) and hydrogen evolution reaction (HER) is key to developing active, stable, and affordable HOR/HER catalysts for hydroxide exchange membrane fuel cells and electrolyzers. A common linear correlation between hydrogen binding energy (HBE) and pH is observed for four supported platinum-group metal catalysts (Pt/C, Ir/C, Pd/C, and Rh/C) over a broad pH range (0 to 13), suggesting that the pH dependence of HBE is metal-independent. A universal correlation between exchange current density and HBE is also observed on the four metals, indicating that they may share the same elementary steps and rate-determining steps and that the HBE is the dominant descriptor for HOR/HER activities. The onset potential of CO stripping on the four metals decreases with pH, indicating a stronger OH adsorption, which provides evidence against the promoting effect of adsorbed OH on HOR/HER. PMID:27034988

  15. Heavy metal removal from MSWI fly ash by electrokinetic remediation coupled with a permeable activated charcoal reactive barrier.

    PubMed

    Huang, Tao; Li, Dongwei; Kexiang, Liu; Zhang, Yuewei

    2015-10-21

    This paper presents the investigations into the feasibility of the application of a remediation system that couples electrokinetic remediation (EKR) with the permeable reactive barrier (PRB) concept for municipal solid waste incineration (MSWI) fly ash with activated charcoal as the PRB material. The experimental results of this study showed that the proposed combined method can effectively improve the remediation efficiency and that the addition of the oxalic acid to the PRB media before the coupled system can further enhance the remediation process. In the optimization tests, the maximum removals of Zn, Pb, Cu and Cd were achieved under different experimental conditions. The voltage gradient and processing time were shown to have significant effects on the removal of Cu and Cd, whereas the addition of the oxalic acid had a more significant influence on the removal of Pb. Generally, the processing time is the most significant factor in changing the removal rates of HMs in the enhanced coupled system. In terms of the leaching toxicity, the specimen remediated by ENEKR + PRB showed the lowest leaching value for each HM in the S2 and S3 regions.

  16. Heavy metal removal from MSWI fly ash by electrokinetic remediation coupled with a permeable activated charcoal reactive barrier.

    PubMed

    Huang, Tao; Li, Dongwei; Kexiang, Liu; Zhang, Yuewei

    2015-01-01

    This paper presents the investigations into the feasibility of the application of a remediation system that couples electrokinetic remediation (EKR) with the permeable reactive barrier (PRB) concept for municipal solid waste incineration (MSWI) fly ash with activated charcoal as the PRB material. The experimental results of this study showed that the proposed combined method can effectively improve the remediation efficiency and that the addition of the oxalic acid to the PRB media before the coupled system can further enhance the remediation process. In the optimization tests, the maximum removals of Zn, Pb, Cu and Cd were achieved under different experimental conditions. The voltage gradient and processing time were shown to have significant effects on the removal of Cu and Cd, whereas the addition of the oxalic acid had a more significant influence on the removal of Pb. Generally, the processing time is the most significant factor in changing the removal rates of HMs in the enhanced coupled system. In terms of the leaching toxicity, the specimen remediated by ENEKR + PRB showed the lowest leaching value for each HM in the S2 and S3 regions. PMID:26486449

  17. Heavy metal removal from MSWI fly ash by electrokinetic remediation coupled with a permeable activated charcoal reactive barrier

    NASA Astrophysics Data System (ADS)

    Huang, Tao; Li, Dongwei; Kexiang, Liu; Zhang, Yuewei

    2015-10-01

    This paper presents the investigations into the feasibility of the application of a remediation system that couples electrokinetic remediation (EKR) with the permeable reactive barrier (PRB) concept for municipal solid waste incineration (MSWI) fly ash with activated charcoal as the PRB material. The experimental results of this study showed that the proposed combined method can effectively improve the remediation efficiency and that the addition of the oxalic acid to the PRB media before the coupled system can further enhance the remediation process. In the optimization tests, the maximum removals of Zn, Pb, Cu and Cd were achieved under different experimental conditions. The voltage gradient and processing time were shown to have significant effects on the removal of Cu and Cd, whereas the addition of the oxalic acid had a more significant influence on the removal of Pb. Generally, the processing time is the most significant factor in changing the removal rates of HMs in the enhanced coupled system. In terms of the leaching toxicity, the specimen remediated by ENEKR + PRB showed the lowest leaching value for each HM in the S2 and S3 regions.

  18. Heavy metal removal from MSWI fly ash by electrokinetic remediation coupled with a permeable activated charcoal reactive barrier

    PubMed Central

    Huang, Tao; Li, Dongwei; Kexiang, Liu; Zhang, Yuewei

    2015-01-01

    This paper presents the investigations into the feasibility of the application of a remediation system that couples electrokinetic remediation (EKR) with the permeable reactive barrier (PRB) concept for municipal solid waste incineration (MSWI) fly ash with activated charcoal as the PRB material. The experimental results of this study showed that the proposed combined method can effectively improve the remediation efficiency and that the addition of the oxalic acid to the PRB media before the coupled system can further enhance the remediation process. In the optimization tests, the maximum removals of Zn, Pb, Cu and Cd were achieved under different experimental conditions. The voltage gradient and processing time were shown to have significant effects on the removal of Cu and Cd, whereas the addition of the oxalic acid had a more significant influence on the removal of Pb. Generally, the processing time is the most significant factor in changing the removal rates of HMs in the enhanced coupled system. In terms of the leaching toxicity, the specimen remediated by ENEKR + PRB showed the lowest leaching value for each HM in the S2 and S3 regions. PMID:26486449

  19. Hydrogenation-controlled phase transition on two-dimensional transition metal dichalcogenides and their unique physical and catalytic properties

    PubMed Central

    Qu, Yuanju; Pan, Hui; Kwok, Chi Tat

    2016-01-01

    Two-dimensional (2D) transition metal dichalcogenides (TMDs) have been widely used from nanodevices to energy harvesting/storage because of their tunable physical and chemical properties. In this work, we systematically investigate the effects of hydrogenation on the structural, electronic, magnetic, and catalytic properties of 33 TMDs based on first-principles calculations. We find that the stable phases of TMD monolayers can transit from 1T to 2H phase or vice versa upon the hydrogenation. We show that the hydrogenation can switch their magnetic and electronic states accompanying with the phase transition. The hydrogenation can tune the magnetic states of TMDs among non-, ferro, para-, and antiferro-magnetism and their electronic states among semiconductor, metal, and half-metal. We further show that, out of 33 TMD monolayers, 2H-TiS2 has impressive catalytic ability comparable to Pt in hydrogen evolution reaction in a wide range of hydrogen coverages. Our findings would shed the light on the multi-functional applications of TMDs. PMID:27686869

  20. Hydrogenation-controlled phase transition on two-dimensional transition metal dichalcogenides and their unique physical and catalytic properties

    NASA Astrophysics Data System (ADS)

    Qu, Yuanju; Pan, Hui; Kwok, Chi Tat

    2016-09-01

    Two-dimensional (2D) transition metal dichalcogenides (TMDs) have been widely used from nanodevices to energy harvesting/storage because of their tunable physical and chemical properties. In this work, we systematically investigate the effects of hydrogenation on the structural, electronic, magnetic, and catalytic properties of 33 TMDs based on first-principles calculations. We find that the stable phases of TMD monolayers can transit from 1T to 2H phase or vice versa upon the hydrogenation. We show that the hydrogenation can switch their magnetic and electronic states accompanying with the phase transition. The hydrogenation can tune the magnetic states of TMDs among non-, ferro, para-, and antiferro-magnetism and their electronic states among semiconductor, metal, and half-metal. We further show that, out of 33 TMD monolayers, 2H-TiS2 has impressive catalytic ability comparable to Pt in hydrogen evolution reaction in a wide range of hydrogen coverages. Our findings would shed the light on the multi-functional applications of TMDs.

  1. A permeable reactive barrier (PRB) media sequence for the remediation of heavy metal and hydrocarbon contaminated water: A field assessment at Casey Station, Antarctica.

    PubMed

    Statham, Tom M; Stark, Scott C; Snape, Ian; Stevens, Geoffrey W; Mumford, Kathryn A

    2016-03-01

    A field trial was conducted at Casey Station, Antarctica to assess the suitability of a permeable reactive barrier (PRB) media sequence for the remediation of sites containing both hydrocarbon and heavy metal contamination. An existing PRB was modified to assess a sequence consisting of three sections: (i) Nutrient release/hydrocarbon sorption using ZeoPro™ and granular activated carbon; (ii) Phosphorus and heavy metal capture by granular iron and sand; (iii) Nutrient and excess iron capture by zeolite. The media sequence achieved a greater phosphorus removal capacity than previous Antarctic PRB configurations installed on site. Phosphorus concentrations were reduced during flow through the iron/sand section and iron concentrations were reduced within the zeolite section. However, non-ideal flow was detected during a tracer test and supported by analysis of media and liquid samples from the second summer of operation. Results indicate that the PRB media sequence trialled might be appropriate for other locations, especially less environmentally challenging contaminated sites. PMID:26774301

  2. Density Functional Theory Study of Hydrogen Adsorption in a Ti-Decorated Mg-Based Metal-Organic Framework-74.

    PubMed

    Suksaengrat, Pitphichaya; Amornkitbamrung, Vittaya; Srepusharawoot, Pornjuk; Ahuja, Rajeev

    2016-03-16

    The Ti-binding energy and hydrogen adsorption energy of a Ti-decorated Mg-based metal-organic framework-74 (Mg-MOF-74) were evaluated by using first-principles calculations. Our results revealed that only three Ti adsorption sites were found to be stable. The adsorption site near the metal oxide unit is the most stable. To investigate the hydrogen-adsorption properties of Ti-functionalized Mg-MOF-74, the hydrogen-binding energy was determined. For the most stable Ti adsorption site, we found that the hydrogen adsorption energy ranged from 0.26 to 0.48 eV H2 (-1) . This is within the desirable range for practical hydrogen-storage applications. Moreover, the hydrogen capacity was determined by using ab initio molecular dynamics simulations. Our results revealed that the hydrogen uptake by Ti-decorated Mg-MOF-74 at temperatures of 77, 150, and 298 K and ambient pressure were 1.81, 1.74, and 1.29 H2  wt %, respectively. PMID:26717417

  3. From hydrogen bonding to metal coordination and back: Porphyrin-based networks on Ag(111)

    SciTech Connect

    Studener, F. Müller, K.; Stöhr, M.; Marets, N.; Bulach, V. Hosseini, M. W.

    2015-03-14

    The self-assembly of a metal-free porphyrin bearing two pyridyl coordinating sites and two pentyl chains at trans meso positions was investigated under ultrahigh vacuum on a Ag(111) surface by scanning tunneling microscopy (STM). The STM measurements revealed a well-ordered close-packed structure with a rhombic unit cell for coverages ≤1 monolayer with their molecular plane parallel to the surface. The growth direction of the molecular islands is aligned along the step edges, which are restructured due to molecule-substrate interactions. The shorter unit cell vector of the molecular superstructure follows the 〈1-10〉 direction of the Ag(111) substrate. Hydrogen bonds between pyridyl and pyrrole groups of neighboring molecules as well as weak van der Waals forces between the pentyl chains stabilize the superstructure. Deposition of cobalt atoms onto the close-packed structure at room temperature leads to the formation of a hexagonal porous network stabilized by metal-ligand bonding between the pyridyl ligands and the cobalt atoms. Thermal annealing of the Co-coordination network at temperatures >450 K results in the transformation of the hexagonal network into a second close-packed structure. Changes in the molecule-substrate interactions due to metalation of the porphyrin core with Co as well as intermolecular interactions can explain the observed structural transformations.

  4. Enhanced hydrogen evolution catalysis from chemically exfoliated metallic MoS2 nanosheets.

    PubMed

    Lukowski, Mark A; Daniel, Andrew S; Meng, Fei; Forticaux, Audrey; Li, Linsen; Jin, Song

    2013-07-17

    Promising catalytic activity from molybdenum disulfide (MoS2) in the hydrogen evolution reaction (HER) is attributed to active sites located along the edges of its two-dimensional layered crystal structure, but its performance is currently limited by the density and reactivity of active sites, poor electrical transport, and inefficient electrical contact to the catalyst. Here we report dramatically enhanced HER catalysis (an electrocatalytic current density of 10 mA/cm(2) at a low overpotential of -187 mV vs RHE and a Tafel slope of 43 mV/decade) from metallic nanosheets of 1T-MoS2 chemically exfoliated via lithium intercalation from semiconducting 2H-MoS2 nanostructures grown directly on graphite. Structural characterization and electrochemical studies confirmed that the nanosheets of the metallic MoS2 polymorph exhibit facile electrode kinetics and low-loss electrical transport and possess a proliferated density of catalytic active sites. These distinct and previously unexploited features of 1T-MoS2 make these metallic nanosheets a highly competitive earth-abundant HER catalyst. PMID:23790049

  5. Pure and stable metallic phase molybdenum disulfide nanosheets for hydrogen evolution reaction.

    PubMed

    Geng, Xiumei; Sun, Weiwei; Wu, Wei; Chen, Benjamin; Al-Hilo, Alaa; Benamara, Mourad; Zhu, Hongli; Watanabe, Fumiya; Cui, Jingbiao; Chen, Tar-Pin

    2016-01-01

    Metallic-phase MoS2 (M-MoS2) is metastable and does not exist in nature. Pure and stable M-MoS2 has not been previously prepared by chemical synthesis, to the best of our knowledge. Here we report a hydrothermal process for synthesizing stable two-dimensional M-MoS2 nanosheets in water. The metal-metal Raman stretching mode at 146 cm(-1) in the M-MoS2 structure, as predicted by theoretical calculations, is experimentally observed. The stability of the M-MoS2 is associated with the adsorption of a monolayer of water molecules on both sides of the nanosheets, which reduce restacking and prevent aggregation in water. The obtained M-MoS2 exhibits excellent stability in water and superior activity for the hydrogen evolution reaction, with a current density of 10 mA cm(-2) at a low potential of -175 mV and a Tafel slope of 41 mV per decade.

  6. Pure and stable metallic phase molybdenum disulfide nanosheets for hydrogen evolution reaction.

    PubMed

    Geng, Xiumei; Sun, Weiwei; Wu, Wei; Chen, Benjamin; Al-Hilo, Alaa; Benamara, Mourad; Zhu, Hongli; Watanabe, Fumiya; Cui, Jingbiao; Chen, Tar-Pin

    2016-01-01

    Metallic-phase MoS2 (M-MoS2) is metastable and does not exist in nature. Pure and stable M-MoS2 has not been previously prepared by chemical synthesis, to the best of our knowledge. Here we report a hydrothermal process for synthesizing stable two-dimensional M-MoS2 nanosheets in water. The metal-metal Raman stretching mode at 146 cm(-1) in the M-MoS2 structure, as predicted by theoretical calculations, is experimentally observed. The stability of the M-MoS2 is associated with the adsorption of a monolayer of water molecules on both sides of the nanosheets, which reduce restacking and prevent aggregation in water. The obtained M-MoS2 exhibits excellent stability in water and superior activity for the hydrogen evolution reaction, with a current density of 10 mA cm(-2) at a low potential of -175 mV and a Tafel slope of 41 mV per decade. PMID:26861766

  7. Hydrogen gas sensor based on metal oxide nanoparticles decorated graphene transistor

    NASA Astrophysics Data System (ADS)

    Zhang, Zhangyuan; Zou, Xuming; Xu, Lei; Liao, Lei; Liu, Wei; Ho, Johnny; Xiao, Xiangheng; Jiang, Changzhong; Li, Jinchai

    2015-05-01

    In this work, in order to enhance the performance of graphene gas sensors, graphene and metal oxide nanoparticles (NPs) are combined to be utilized for high selectivity and fast response gas detection. Whether at the relatively optimal temperature or even room temperature, our gas sensors based on graphene transistors, decorated with SnO2 NPs, exhibit fast response and short recovery times (~1 seconds) at 50 °C when the hydrogen concentration is 100 ppm. Specifically, X-ray photoelectron spectroscopy and conductive atomic force microscopy are employed to explore the interface properties between graphene and SnO2 NPs. Through the complimentary characterization, a mechanism based on charge transfer and band alignment is elucidated to explain the physical originality of these graphene gas sensors: high carrier mobility of graphene and small energy barrier between graphene and SnO2 NPs have ensured a fast response and a high sensitivity and selectivity of the devices. Generally, these gas sensors will facilitate the rapid development of next-generation hydrogen gas detection.In this work, in order to enhance the performance of graphene gas sensors, graphene and metal oxide nanoparticles (NPs) are combined to be utilized for high selectivity and fast response gas detection. Whether at the relatively optimal temperature or even room temperature, our gas sensors based on graphene transistors, decorated with SnO2 NPs, exhibit fast response and short recovery times (~1 seconds) at 50 °C when the hydrogen concentration is 100 ppm. Specifically, X-ray photoelectron spectroscopy and conductive atomic force microscopy are employed to explore the interface properties between graphene and SnO2 NPs. Through the complimentary characterization, a mechanism based on charge transfer and band alignment is elucidated to explain the physical originality of these graphene gas sensors: high carrier mobility of graphene and small energy barrier between graphene and SnO2 NPs have ensured a

  8. A Phenomenological Study of the Metal-Oxide Interface: The Role of Catalysis in Hydrogen Production from Renewable Resources

    SciTech Connect

    Idriss, H.; Llorca, J; Chan, S; Blackford, M; Pas, S; Hill, A; Alamgir, F; Rettew, R; Petersburg, C; Barteau, M

    2008-01-01

    The truth about Cats: The metal-oxide interface of a Pd-Rh/CeO{sub 2} catalyst was studied in the context of developing active, selective and durable solid catalytic materials for the production of hydrogen from renewables. The presence of a stable contact between finely dispersed transition-metal clusters (Pd and Rh) on the nanoparticles of the CeO{sub 2} support leads to a highly active and stable catalyst for the steam reforming of ethanol.

  9. Rydberg hydrogen atom near a metallic surface: Stark regime and ionization dynamics

    SciTech Connect

    Inarrea, Manuel; Salas, J. Pablo; Lanchares, Victor; Pascual, Ana Isabel; Palacian, Jesus F.; Yanguas, Patricia

    2007-11-15

    We investigate the classical dynamics of a hydrogen atom near a metallic surface in the presence of a uniform electric field. To describe the atom-surface interaction we use a simple electrostatic image model. Owing to the axial symmetry of the system, the z-component of the canonical angular momentum P{sub {phi}} is an integral and the electronic dynamics is modeled by a two degrees of freedom Hamiltonian in cylindrical coordinates. The structure and evolution of the phase space as a function of the electric field strength is explored extensively by means of numerical techniques of continuation of families of periodic orbits and Poincare surfaces of section. We find that, due to the presence of the electric field, the atom is strongly polarized through two consecutive pitchfork bifurcations that strongly change the phase space structure. Finally, by means of the phase space transition state theory and the classical spectral theorem, the ionization dynamics of the atom is studied.

  10. Methods for producing hydrogen (BI) sulfide and/or removing metals

    DOEpatents

    Truex, Michael J [Richland, WA; Peyton, Brent M [Pullman, WA; Toth, James J [Kennewick, WA

    2002-05-14

    The present invention is a process wherein sulfide production by bacteria is efficiently turned on and off, using pH adjustment. The adjustment of pH impacts sulfide production by bacteria by altering the relative amounts of H.sub.2 S and HS-- in solution and thereby control the inhibition of the bacterial metabolism that produces sulfide. This process can be used to make a bioreactor produce sulfide "on-demand" so that the production of sulfide can be matched to its use as a metal precipitation reagent. The present invention is of significance because it enables the use of a biological reactor, a cost effective sulfide production system, by making the biological reactor produce hydrogen sulfide "on demand", and therefore responsive to production schedules, waste stream generation rate, and health and safety requirements/goals.

  11. Morphological Engineering of CVD-Grown Transition Metal Dichalcogenides for Efficient Electrochemical Hydrogen Evolution.

    PubMed

    Ji, Qingqing; Zhang, Yu; Shi, Jianping; Sun, Jingyu; Zhang, Yanfeng; Liu, Zhongfan

    2016-08-01

    2D layered transition metal dichalcogenides (TMDCs) have emerged as new possibilites beyond conventional particulate catalysts in facilitating efficient electrochemical hydrogen evolution. This is mainly mediated by the ultrahigh surface-to-volume ratio and the effective coupling of all active sites with supporting electrodes. Especially, the facile chemical vapor deposition (CVD) method has enabled morphological engineering of monolayer TMDC catalysts toward development of abundant active edge sites within the 2D plane. Here, two pathways to achieve such purpose are highlighted, either by non-equilibrium growth of MoS2 dendrites or throughout high-density nucleation of MoS2 nanoflakes directly on the electrode materials. Furthermore, future research directions have also been proposed and discussed to further enhance the efficiency of such unique catalysts.

  12. Resonant charge transfer of hydrogen Rydberg atoms incident at a metallic sphere

    NASA Astrophysics Data System (ADS)

    Gibbard, J. A.; Softley, T. P.

    2016-06-01

    A wavepacket propagation study is reported for the charge transfer of low principal quantum number (n = 2) hydrogen Rydberg atoms incident at an isolated metallic sphere. Such a sphere acts as a model for a nanoparticle. The three-dimensional confinement of the sphere yields discrete surface-localized ‘well-image’ states, the energies of which vary with sphere radius. When the Rydberg atom energy is degenerate with one of the quantized nanoparticle states, charge transfer is enhanced, whereas for off-resonant cases little to no charge transfer is observed. Greater variation in charge-transfer probability is seen between the resonant and off-resonant examples in this system than for any other Rydberg-surface system theoretically investigated thus far. The results presented here indicate that it may be possible to use Rydberg-surface ionization as a probe of the surface electronic structure of a nanoparticle, and nanostructures in general.

  13. Hydrogen Sulfide Induced Carbon Dioxide Activation by Metal-Free Dual Catalysis.

    PubMed

    Kumar, Manoj; Francisco, Joseph S

    2016-03-18

    The role of metal free dual catalysis in the hydrogen sulfide (H2S)-induced activation of carbon dioxide (CO2) and subsequent decomposition of resulting monothiolcarbonic acid in the gas phase has been explored. The results suggest that substituted amines and monocarboxylic type organic or inorganic acids via dual activation mechanisms promote both activation and decomposition reactions, implying that the judicious selection of a dual catalyst is crucial to the efficient C-S bond formation via CO2 activation. Considering that our results also suggest a new mechanism for the formation of carbonyl sulfide from CO2 and H2S, these new insights may help in better understanding the coupling between the carbon and sulfur cycles in the atmospheres of Earth and Venus.

  14. Charge separation technique for metal-oxide-silicon capacitors in the presence of hydrogen deactivated dopants

    SciTech Connect

    Witczak, Steven C.; Winokur, Peter S.; Lacoe, Ronald C.; Mayer, Donald C.

    2000-06-01

    An improved charge separation technique for metal-oxide-silicon (MOS) capacitors is presented which accounts for the deactivation of substrate dopants by hydrogen at elevated irradiation temperatures or small irradiation biases. Using high-frequency capacitance-voltage measurements, radiation-induced inversion voltage shifts are separated into components due to oxide trapped charge, interface traps, and deactivated dopants, where the latter is computed from a reduction in Si capacitance. In the limit of no radiation-induced dopant deactivation, this approach reduces to the standard midgap charge separation technique used widely for the analysis of room-temperature irradiations. The technique is demonstrated on a p-type MOS capacitor irradiated with {sup 60}Co {gamma} rays at 100 degree sign C and zero bias, where the dopant deactivation is significant.(c) 2000 American Institute of Physics.

  15. Hydrogen spillover enhanced hydroxyl formation and catalytic activity toward CO oxidation at the metal/oxide interface.

    PubMed

    Jin, Yuekang; Sun, Guanghui; Xiong, Feng; Ding, Liangbing; Huang, Weixin

    2015-03-01

    H2-promoted catalytic activity of oxide-supported metal catalysts in low-temperature CO oxidation is of great interest but its origin remains unknown. Employing an FeO(111)/Pt(111) inverse model catalyst, we herewith report direct experimental evidence for the spillover of H(a) adatoms on the Pt surface formed by H2 dissociation to the Pt-FeO interface to form hydroxyl groups that facilely oxidize CO(a) on the neighboring Pt surface to produce CO2. Hydroxyl groups and coadsorbed water play a crucial role in the occurrence of hydrogen spillover. These results unambiguously identify the occurrence of hydrogen spillover from the metal surface to the noble metal/metal oxide interface and the resultant enhanced catalytic activity of the metal/oxide interface in low-temperature CO oxidation, which provides a molecular-level understanding of both H2-promoted catalytic activity of metal/oxide ensembles in low-temperature CO oxidation and hydrogen spillover.

  16. A porous proton-relaying metal-organic framework material that accelerates electrochemical hydrogen evolution

    PubMed Central

    Hod, Idan; Deria, Pravas; Bury, Wojciech; Mondloch, Joseph E.; Kung, Chung-Wei; So, Monica; Sampson, Matthew D.; Peters, Aaron W.; Kubiak, Cliff P.; Farha, Omar K.; Hupp, Joseph T.

    2015-01-01

    The availability of efficient hydrogen evolution reaction (HER) catalysts is of high importance for solar fuel technologies aimed at reducing future carbon emissions. Even though Pt electrodes are excellent HER electrocatalysts, commercialization of large-scale hydrogen production technology requires finding an equally efficient, low-cost, earth-abundant alternative. Here, high porosity, metal-organic framework (MOF) films have been used as scaffolds for the deposition of a Ni-S electrocatalyst. Compared with an MOF-free Ni-S, the resulting hybrid materials exhibit significantly enhanced performance for HER from aqueous acid, decreasing the kinetic overpotential by more than 200 mV at a benchmark current density of 10 mA cm−2. Although the initial aim was to improve electrocatalytic activity by greatly boosting the active area of the Ni-S catalyst, the performance enhancements instead were found to arise primarily from the ability of the proton-conductive MOF to favourably modify the immediate chemical environment of the sulfide-based catalyst. PMID:26365764

  17. Carborane-Based Metal-Organic Framework with High Methane and Hydrogen Storage Capacities

    SciTech Connect

    Kennedy, RD; Krungleviciute, V; Clingerman, DJ; Mondloch, JE; Peng, Y; Wilmer, CE; Sarjeant, AA; Snurr, RQ; Hupp, JT; Yildirim, T; Farha, OK; Mirkin, CA

    2013-09-10

    A Cu-carborane-based metal organic framework (MOF), NU-135, which contains a quasi-spherical para-carborane moiety, has been synthesized and characterized. NU-135 exhibits a pore volume of 1.02 cm(3)/g and a gravimetric BET surface area of ca. 2600 m(2)/g, and thus represents the first highly porous carborane-based MOF. As a consequence of the, unique geometry of the carborane unit, NU-135 has a very high volumetric BET surface area of ca. 1900 m(2)/cm(3). CH4, CO2, and H-2 adsorption isotherms were measured over a broad range of pressures and temperatures and are in good agreement with computational predictions. The methane storage capacity of NU-135 at 35 bar and 298 K is ca. 187 v(STP)/v. At 298 K, the pressure required to achieve a methane storage density comparable to that of a compressed natural gas (CNG) tank pressurized to 212 bar, which is a typical storage pressure, is only 65 bar. The methane working capacity (5-65 bar) is 170 v(STP)/v. The volumetric hydrogen storage capacity at 55 bar and 77 K is 49 g/L. These properties are comparable to those of current record holders in the area of methane and hydrogen storage. This initial example lays the groundwork for carborane-based materials with high surface areas.

  18. Hydrogen gas sensor based on metal oxide nanoparticles decorated graphene transistor.

    PubMed

    Zhang, Zhangyuan; Zou, Xuming; Xu, Lei; Liao, Lei; Liu, Wei; Ho, Johnny; Xiao, Xiangheng; Jiang, Changzhong; Li, Jinchai

    2015-06-14

    In this work, in order to enhance the performance of graphene gas sensors, graphene and metal oxide nanoparticles (NPs) are combined to be utilized for high selectivity and fast response gas detection. Whether at the relatively optimal temperature or even room temperature, our gas sensors based on graphene transistors, decorated with SnO2 NPs, exhibit fast response and short recovery times (∼1 seconds) at 50 °C when the hydrogen concentration is 100 ppm. Specifically, X-ray photoelectron spectroscopy and conductive atomic force microscopy are employed to explore the interface properties between graphene and SnO2 NPs. Through the complimentary characterization, a mechanism based on charge transfer and band alignment is elucidated to explain the physical originality of these graphene gas sensors: high carrier mobility of graphene and small energy barrier between graphene and SnO2 NPs have ensured a fast response and a high sensitivity and selectivity of the devices. Generally, these gas sensors will facilitate the rapid development of next-generation hydrogen gas detection. PMID:25978618

  19. Hydrogen segregation and its roles in structural stability and metallization: silane under pressure

    PubMed Central

    Cui, Wenwen; Shi, Jingming; Liu, Hanyu; Yao, Yansun; Wang, Hui; Iitaka, Toshiaki; Ma, Yanming

    2015-01-01

    We present results from first-principles calculations on silane (SiH4) under pressure. We find that a three dimensional P-3 structure becomes the most stable phase above 241 GPa. A prominent structural feature, which separates the P-3 structure from previously observed/predicted SiH4 structures, is that a fraction of hydrogen leaves the Si-H bonding environment and forms segregated H2 units. The H2 units are sparsely populated in the system and intercalated with a polymeric Si-H framework. Calculations of enthalpy of formation suggest that the P-3 structure is against the decomposition into Si-H binaries and/or the elemental crystals. Structural stability of the P-3 structure is attributed to the electron-deficient multicenter Si-H-Si interactions when neighboring silicon atoms are linked together through a common hydrogen atom. Within the multicenter bonds, electrons are delocalized and this leads to a metallic state, possibly also a superconducting state, for SiH4. An interesting outcome of the present study is that the enthalpy sum of SiH4 (P-3 structure) and Si (fcc structure) appears to be lower than the enthalpy of disilane (Si2H6) between 200 and 300 GPa (for all previously predicted crystalline forms of Si2H6), which calls for a revisit of the stability of Si2H6 under high pressure. PMID:26266340

  20. Effect of hydrogenation on magnetic properties of heavy transition-metal dichalcogenides

    NASA Astrophysics Data System (ADS)

    Manchanda, Priyanka; Liou, S.-H.; Enders, Axel; Sellmyer, D. J.; Skomski, Ralph

    Two-dimensional transition-metal dichalcogenides (2D TMDs) are emerging as a unique class of materials because of their underlying fundamental physics and technological applications in electronics, sensors, energy storage, photonics, and spintronics. The outstanding electronic properties of 2D TMDs can be further tuned by various external means, such as control of external electric field, chemical functionalization, alloying, and strain. The electronic and magnetic properties of chemical functionalized 2D TMDs is of special interest. Experimentally, adsorbed fluorine has been shown very recently to create a small magnetic moment of 0.06 emu/g in MoS2 nanosheets. Although several studies as well as review articles on the properties of TMDs have been published in the past few years, Mo and W chalcogenides are most widely studied among the ``beyond-graphene'' 2D TMDs. However, studies of chemical functionalization on TMDs containing heavy TMDs such as Ta and Pt are still infancy. In the present work, we investigate the effect of hydrogenation on the magnetism of PtSe2 monolayers using density-functional theory. We find that the hydrogen induces a magnetic moment of 0.7 µB per unitcell. This work has been supported by ARO, and DOE-BES. This work has been supported by ARO, and DOE-BES.

  1. A porous proton-relaying metal-organic framework material that accelerates electrochemical hydrogen evolution

    SciTech Connect

    Hod, Idan; Deria, Pravas; Bury, Wojciech; Mondloch, Joseph E.; Kung, Chung-Wei; So, Monica; Sampson, Matthew D.; Peters, Aaron W.; Kubiak, Cliff P.; Farha, Omar K.; Hupp, Joseph T.

    2015-09-14

    The availability of efficient hydrogen evolution reaction (HER) catalysts is of high importance for solar fuel technologies aimed at reducing future carbon emissions. Even though Pt electrodes are excellent HER electrocatalysts, commercialization of large-scale hydrogen production technology requires finding an equally efficient, low-cost, earth-abundant alternative. Here, high porosity, metal-organic framework (MOF) films have been used as scaffolds for the deposition of a Ni-S electrocatalyst. Compared with an MOF-free Ni-S, the resulting hybrid materials exhibit significantly enhanced performance for HER from aqueous acid, decreasing the kinetic overpotential by more than 200 mV at a benchmark current density of 10 mA cm−2. In conclusion, although the initial aim was to improve electrocatalytic activity by greatly boosting the active area of the Ni-S catalyst, the performance enhancements instead were found to arise primarily from the ability of the proton-conductive MOF to favourably modify the immediate chemical environment of the sulfide-based catalyst.

  2. A porous proton-relaying metal-organic framework material that accelerates electrochemical hydrogen evolution

    DOE PAGESBeta

    Hod, Idan; Deria, Pravas; Bury, Wojciech; Mondloch, Joseph E.; Kung, Chung-Wei; So, Monica; Sampson, Matthew D.; Peters, Aaron W.; Kubiak, Cliff P.; Farha, Omar K.; et al

    2015-09-14

    The availability of efficient hydrogen evolution reaction (HER) catalysts is of high importance for solar fuel technologies aimed at reducing future carbon emissions. Even though Pt electrodes are excellent HER electrocatalysts, commercialization of large-scale hydrogen production technology requires finding an equally efficient, low-cost, earth-abundant alternative. Here, high porosity, metal-organic framework (MOF) films have been used as scaffolds for the deposition of a Ni-S electrocatalyst. Compared with an MOF-free Ni-S, the resulting hybrid materials exhibit significantly enhanced performance for HER from aqueous acid, decreasing the kinetic overpotential by more than 200 mV at a benchmark current density of 10 mA cm−2. In conclusion, althoughmore » the initial aim was to improve electrocatalytic activity by greatly boosting the active area of the Ni-S catalyst, the performance enhancements instead were found to arise primarily from the ability of the proton-conductive MOF to favourably modify the immediate chemical environment of the sulfide-based catalyst.« less

  3. Hydrogen adsorption in metal-organic frameworks: The role of nuclear quantum effects

    SciTech Connect

    Wahiduzzaman, Mohammad; Walther, Christian F. J.; Heine, Thomas

    2014-08-14

    The role of nuclear quantum effects on the adsorption of molecular hydrogen in metal-organic frameworks (MOFs) has been investigated on grounds of Grand-Canonical Quantized Liquid Density-Functional Theory (GC-QLDFT) calculations. For this purpose, we have carefully validated classical H{sub 2}-host interaction potentials that are obtained by fitting Born-Oppenheimer ab initio reference data. The hydrogen adsorption has first been assessed classically using Liquid Density-Functional Theory and the Grand-Canonical Monte Carlo methods. The results have been compared against the semi-classical treatment of quantum effects by applying the Feynman-Hibbs correction to the Born-Oppenheimer-derived potentials, and by explicit treatment within the GC-QLDFT. The results are compared with experimental data and indicate pronounced quantum and possibly many-particle effects. After validation calculations have been carried out for IRMOF-1 (MOF-5), GC-QLDFT is applied to study the adsorption of H{sub 2} in a series of MOFs, including IRMOF-4, -6, -8, -9, -10, -12, -14, -16, -18, and MOF-177. Finally, we discuss the evolution of the H{sub 2} quantum fluid with increasing pressure and lowering temperature.

  4. Hydrogen adsorption in metal-organic frameworks: the role of nuclear quantum effects.

    PubMed

    Wahiduzzaman, Mohammad; Walther, Christian F J; Heine, Thomas

    2014-08-14

    The role of nuclear quantum effects on the adsorption of molecular hydrogen in metal-organic frameworks (MOFs) has been investigated on grounds of Grand-Canonical Quantized Liquid Density-Functional Theory (GC-QLDFT) calculations. For this purpose, we have carefully validated classical H2-host interaction potentials that are obtained by fitting Born-Oppenheimer ab initio reference data. The hydrogen adsorption has first been assessed classically using Liquid Density-Functional Theory and the Grand-Canonical Monte Carlo methods. The results have been compared against the semi-classical treatment of quantum effects by applying the Feynman-Hibbs correction to the Born-Oppenheimer-derived potentials, and by explicit treatment within the GC-QLDFT. The results are compared with experimental data and indicate pronounced quantum and possibly many-particle effects. After validation calculations have been carried out for IRMOF-1 (MOF-5), GC-QLDFT is applied to study the adsorption of H2 in a series of MOFs, including IRMOF-4, -6, -8, -9, -10, -12, -14, -16, -18, and MOF-177. Finally, we discuss the evolution of the H2 quantum fluid with increasing pressure and lowering temperature. PMID:25134591

  5. Hydrogen segregation and its roles in structural stability and metallization: silane under pressure.

    PubMed

    Cui, Wenwen; Shi, Jingming; Liu, Hanyu; Yao, Yansun; Wang, Hui; Iitaka, Toshiaki; Ma, Yanming

    2015-01-01

    We present results from first-principles calculations on silane (SiH4) under pressure. We find that a three dimensional P-3 structure becomes the most stable phase above 241 GPa. A prominent structural feature, which separates the P-3 structure from previously observed/predicted SiH4 structures, is that a fraction of hydrogen leaves the Si-H bonding environment and forms segregated H2 units. The H2 units are sparsely populated in the system and intercalated with a polymeric Si-H framework. Calculations of enthalpy of formation suggest that the P-3 structure is against the decomposition into Si-H binaries and/or the elemental crystals. Structural stability of the P-3 structure is attributed to the electron-deficient multicenter Si-H-Si interactions when neighboring silicon atoms are linked together through a common hydrogen atom. Within the multicenter bonds, electrons are delocalized and this leads to a metallic state, possibly also a superconducting state, for SiH4. An interesting outcome of the present study is that the enthalpy sum of SiH4 (P-3 structure) and Si (fcc structure) appears to be lower than the enthalpy of disilane (Si2H6) between 200 and 300 GPa (for all previously predicted crystalline forms of Si2H6), which calls for a revisit of the stability of Si2H6 under high pressure.

  6. Hydrogen gas sensor based on metal oxide nanoparticles decorated graphene transistor.

    PubMed

    Zhang, Zhangyuan; Zou, Xuming; Xu, Lei; Liao, Lei; Liu, Wei; Ho, Johnny; Xiao, Xiangheng; Jiang, Changzhong; Li, Jinchai

    2015-06-14

    In this work, in order to enhance the performance of graphene gas sensors, graphene and metal oxide nanoparticles (NPs) are combined to be utilized for high selectivity and fast response gas detection. Whether at the relatively optimal temperature or even room temperature, our gas sensors based on graphene transistors, decorated with SnO2 NPs, exhibit fast response and short recovery times (∼1 seconds) at 50 °C when the hydrogen concentration is 100 ppm. Specifically, X-ray photoelectron spectroscopy and conductive atomic force microscopy are employed to explore the interface properties between graphene and SnO2 NPs. Through the complimentary characterization, a mechanism based on charge transfer and band alignment is elucidated to explain the physical originality of these graphene gas sensors: high carrier mobility of graphene and small energy barrier between graphene and SnO2 NPs have ensured a fast response and a high sensitivity and selectivity of the devices. Generally, these gas sensors will facilitate the rapid development of next-generation hydrogen gas detection.

  7. Platinum-nickel frame within metal-organic framework fabricated in situ for hydrogen enrichment and molecular sieving

    NASA Astrophysics Data System (ADS)

    Li, Zhi; Yu, Rong; Huang, Jinglu; Shi, Yusheng; Zhang, Diyang; Zhong, Xiaoyan; Wang, Dingsheng; Wu, Yuen; Li, Yadong

    2015-09-01

    Developing catalysts that provide the effective activation of hydrogen and selective absorption of substrate on metal surface is crucial to simultaneously improve activity and selectivity of hydrogenation reaction. Here we present an unique in situ etching and coordination synthetic strategy for exploiting a functionalized metal-organic framework to incorporate the bimetallic platinum-nickel frames, thereby forming a frame within frame nanostructure. The as-grown metal-organic framework serves as a `breath shell' to enhance hydrogen enrichment and activation on platinum-nickel surface. More importantly, this framework structure with defined pores can provide the selective accessibility of molecules through its one-dimensional channels. In a mixture containing four olefins, the composite can selectively transport the substrates smaller than its pores to the platinum-nickel surface and catalyse their hydrogenation. This molecular sieve effect can be also applied to selectively produce imines, which are important intermediates in the reductive imination of nitroarene, by restraining further hydrogenation via cascade processes.

  8. Platinum–nickel frame within metal-organic framework fabricated in situ for hydrogen enrichment and molecular sieving

    PubMed Central

    Li, Zhi; Yu, Rong; Huang, Jinglu; Shi, Yusheng; Zhang, Diyang; Zhong, Xiaoyan; Wang, Dingsheng; Wu, Yuen; Li, Yadong

    2015-01-01

    Developing catalysts that provide the effective activation of hydrogen and selective absorption of substrate on metal surface is crucial to simultaneously improve activity and selectivity of hydrogenation reaction. Here we present an unique in situ etching and coordination synthetic strategy for exploiting a functionalized metal-organic framework to incorporate the bimetallic platinum–nickel frames, thereby forming a frame within frame nanostructure. The as-grown metal-organic framework serves as a ‘breath shell' to enhance hydrogen enrichment and activation on platinum–nickel surface. More importantly, this framework structure with defined pores can provide the selective accessibility of molecules through its one-dimensional channels. In a mixture containing four olefins, the composite can selectively transport the substrates smaller than its pores to the platinum–nickel surface and catalyse their hydrogenation. This molecular sieve effect can be also applied to selectively produce imines, which are important intermediates in the reductive imination of nitroarene, by restraining further hydrogenation via cascade processes. PMID:26391605

  9. Optimization and comprehensive characterization of metal hydride based hydrogen storage systems using in-situ Neutron Radiography

    NASA Astrophysics Data System (ADS)

    Börries, S.; Metz, O.; Pranzas, P. K.; Bellosta von Colbe, J. M.; Bücherl, T.; Dornheim, M.; Klassen, T.; Schreyer, A.

    2016-10-01

    For the storage of hydrogen, complex metal hydrides are considered as highly promising with respect to capacity, reversibility and safety. The optimization of corresponding storage tanks demands a precise and time-resolved investigation of the hydrogen distribution in scaled-up metal hydride beds. In this study it is shown that in situ fission Neutron Radiography provides unique insights into the spatial distribution of hydrogen even for scaled-up compacts and therewith enables a direct study of hydrogen storage tanks. A technique is introduced for the precise quantification of both time-resolved data and a priori material distribution, allowing inter alia for an optimization of compacts manufacturing process. For the first time, several macroscopic fields are combined which elucidates the great potential of Neutron Imaging for investigations of metal hydrides by going further than solely 'imaging' the system: A combination of in-situ Neutron Radiography, IR-Thermography and thermodynamic quantities can reveal the interdependency of different driving forces for a scaled-up sodium alanate pellet by means of a multi-correlation analysis. A decisive and time-resolved, complex influence of material packing density is derived. The results of this study enable a variety of new investigation possibilities that provide essential information on the optimization of future hydrogen storage tanks.

  10. Hydrogen production and metal-dye bioremoval by a Nostoc linckia strain isolated from textile mill oxidation pond.

    PubMed

    Mona, Sharma; Kaushik, Anubha; Kaushik, C P

    2011-02-01

    Biohydrogen production by Nostoc linckia HA-46, isolated from a textile-industry oxidation-pond was studied by varying light/dark period, pH, temperature and ratio of carbon-dioxide and argon in the gas-mixture. Hydrogen production rates were maximum under 18 h of light and 6 h of darkness, pH 8.0, 31°C, a CO(2):Ar ratio 2:10. Hydrogen production of the strain acclimatized to 20 mg/L of chromium/cobalt and 100 mg/L of Reactive red 198/crystal violet dye studied in N-supplemented/deficient medium was 6-10% higher in the presence of 1.5 g/L of NaNO(3). Rates of hydrogen production in the presence of dyes/metals by the strain (93-105 μmol/h/mg Chlorophyll) were significantly higher than in medium without metals/dyes serving as control (91.3 μmol/h/mg Chlorophyll). About 58-60% of the two metals and 35-73% of dyes were removed by cyanobacterium. Optimal conditions of temperature, pH and metals/dyes concentration for achieving high hydrogen production and wastewater treatment were found practically applicable as similar conditions are found in the effluent of regional textile-mills.

  11. Modifications of boronic ester pro-chelators triggered by hydrogen peroxide tune reactivity to inhibit metal-promoted oxidative stress.

    PubMed

    Charkoudian, Louise K; Pham, David M; Kwon, Ashley M; Vangeloff, Abbey D; Franz, Katherine J

    2007-11-21

    Several new analogs of salicylaldehyde isonicotinoyl hydrazone (SIH) and salicylaldehyde benzoyl hydrazone (SBH) that contain an aryl boronic ester (BSIH, BSBH) or acid (BASIH) in place of an aryl hydroxide have been synthesized and characterized as masked metal ion chelators. These pro-chelators show negligible interaction with iron(III), although the boronic acid versions exhibit some interaction with copper(II), zinc(II) and nickel(II). Hydrogen peroxide oxidizes the aryl boronate to phenol, thus converting the pro-chelators to tridentate ligands with high affinity metal binding properties. An X-ray crystal structure of a bis-ligated iron(III) complex, [Fe(SBH(m-OMe)(3))(2)]NO(3), confirms the meridonal binding mode of these ligands. Modifications of the aroyl ring of the chelators tune their iron affinity, whereas modifications on the boron-containing ring of the pro-chelators attenuate their reaction rates with hydrogen peroxide. Thus, the methoxy derivative pro-chelator (p-OMe)BASIH reacts with hydrogen peroxide nearly 5 times faster than the chloro derivative (m-Cl)BASIH. Both the rate of pro-chelator to chelator conversion as well as the metal binding affinity of the chelator influence the overall ability of these molecules to inhibit hydroxyl radical formation catalyzed by iron or copper in the presence of hydrogen peroxide and ascorbic acid. This pro-chelator strategy has the potential to improve the efficacy of medicinal chelators for inhibiting metal-promoted oxidative stress. PMID:17992288

  12. AB initio free energy calculations of the solubility of silica in metallic hydrogen and application to giant planet cores

    SciTech Connect

    González-Cataldo, F.; Wilson, Hugh F.; Militzer, B.

    2014-05-20

    By combining density functional molecular dynamics simulations with a thermodynamic integration technique, we determine the free energy of metallic hydrogen and silica, SiO{sub 2}, at megabar pressures and thousands of degrees Kelvin. Our ab initio solubility calculations show that silica dissolves into fluid hydrogen above 5000 K for pressures from 10 and 40 Mbars, which has implications for the evolution of rocky cores in giant gas planets like Jupiter, Saturn, and a substantial fraction of known extrasolar planets. Our findings underline the necessity of considering the erosion and redistribution of core materials in giant planet evolution models, but they also demonstrate that hot metallic hydrogen is a good solvent at megabar pressures, which has implications for high-pressure experiments.

  13. Response Behaviour of a Hydrogen Sensor Based on Ionic Conducting Polymer-metal Interfaces Prepared by the Chemical Reduction Method

    PubMed Central

    Sakthivel, Mariappan; Weppner, Werner

    2006-01-01

    A solid-state amperometric hydrogen sensor based on a protonated Nafion membrane and catalytic active electrode operating at room temperature was fabricated and tested. Ionic conducting polymer-metal electrode interfaces were prepared chemically by using the impregnation-reduction method. The polymer membrane was impregnated with tetra-ammine platinum chloride hydrate and the metal ions were subsequently reduced by using either sodium tetrahydroborate or potassium tetrahydroborate. The hydrogen sensing characteristics with air as reference gas is reported. The sensors were capable of detecting hydrogen concentrations from 10 ppm to 10% in nitrogen. The response time was in the range of 10-30 s and a stable linear current output was observed. The thin Pt films were characterized by XRD, Infrared Spectroscopy, Optical Microscopy, Atomic Force Microscopy, Scanning Electron Microscopy and EDAX.

  14. Photoelectrochemical water splitting for hydrogen production with metal oxide (hematite and cupric oxide) based photocatalysts

    NASA Astrophysics Data System (ADS)

    Tang, Houwen

    Solar hydrogen is one ideal energy source to replace fossil fuel, as it is sustainable and environmentally friendly. Solar hydrogen can be generated in a number of ways. Photoelectrochemical (PEC) water splitting is one of the most promising methods for solar-to-chemical energy conversion. In this research project, metal oxide-based photocatalysts, especially hematite (α-Fe 2O3) and cupric oxide (CuO), were investigated for use as electrodes in PEC water splitting for solar hydrogen production. In our research project of hematite-based electrodes, we started with the incorporation of transition metal, particularly titanium (Ti), in hematite thin films to modify the valence and conduction band edges of hematite. We found that Ti impurities improve the electron conductivity of hematite and consequently lead to significantly enhanced photocurrents. We further investigated the Ti and Mg co-alloyed hematite. In this case, Ti is the donor and Mg is the acceptor in hematite. The co-alloying approach enhanced the solubility of Mg and Ti, which led to reduced electron effective mass and therefore increased electron mobility. Also, co-alloying tunes the carrier density and therefore allows the optimization of electrical conductivity. The densities of charged defects were found to be reduced, and therefore carrier recombinations were reduced. As a result, the Ti and Mg co-alloyed hematite thin films exhibited much improved performance in PEC water splitting as compared to pure hematite thin films. For the study of cupric oxide-based electrodes, we first investigated the possibility of reducing the electrode corrosion of cupric oxide in aqueous solutions by incorporating Ti as an electrode corrosion inhibitor. We found that Ti alloying can enhance the stability of cupric oxide in base solutions at the cost of reducing its crystallinity and optical absorption, and consequently lowering its photon-to-electron conversion efficiency. In order to balance the stability and the

  15. Electrocatalytic Hydrogenation of Oxygenates using Earth-Abundant Transition-Metal Nanoparticles under Mild Conditions.

    PubMed

    Carroll, Kyler J; Burger, Thomas; Langenegger, Lukas; Chavez, Steven; Hunt, Sean T; Román-Leshkov, Yuriy; Brushett, Fikile R

    2016-08-01

    Electrocatalytic hydrogenation (ECH) is a sustainable pathway for the synthesis of value-added organic compounds, provided affordable catalysts with high activity, selectivity and durability are developed. Here, we synthesize Cu/C, Ni/C, and CuNi/C nanoparticles and compare their performance to Pt/C, Ru/C, PtRu/C for the ECH of hydroxyacetone, a bio-derived feedstock surrogate containing a carbonyl and a hydroxyl functional group. The non-precious metal electrocatalysts show promising conversion-time behavior, product selectivities, and Faradaic efficiencies. Ni/C forms propylene glycol with a selectivity of 89 % (at 80 % conversion), while Cu/C catalyzes ECH (52 % selectivity) and hydrodeoxygenation (HDO, 48 % selectivity, accounting for evaporation). CuNi/C shows increased turnover frequencies but reduced ECH selectivity (80 % at 80 % conversion) as compared to the Ni/C catalyst. Importantly, stability studies show that the non-precious metal catalysts do not leach at operating conditions. PMID:27337680

  16. Pure and stable metallic phase molybdenum disulfide nanosheets for hydrogen evolution reaction

    PubMed Central

    Geng, Xiumei; Sun, Weiwei; Wu, Wei; Chen, Benjamin; Al-Hilo, Alaa; Benamara, Mourad; Zhu, Hongli; Watanabe, Fumiya; Cui, Jingbiao; Chen, Tar-pin

    2016-01-01

    Metallic-phase MoS2 (M-MoS2) is metastable and does not exist in nature. Pure and stable M-MoS2 has not been previously prepared by chemical synthesis, to the best of our knowledge. Here we report a hydrothermal process for synthesizing stable two-dimensional M-MoS2 nanosheets in water. The metal–metal Raman stretching mode at 146 cm−1 in the M-MoS2 structure, as predicted by theoretical calculations, is experimentally observed. The stability of the M-MoS2 is associated with the adsorption of a monolayer of water molecules on both sides of the nanosheets, which reduce restacking and prevent aggregation in water. The obtained M-MoS2 exhibits excellent stability in water and superior activity for the hydrogen evolution reaction, with a current density of 10 mA cm−2 at a low potential of −175 mV and a Tafel slope of 41 mV per decade. PMID:26861766

  17. First-Principles Design of Hydrogen Dissociation Catalysts Based on Isoelectronic Metal Solid Solutions.

    PubMed

    Seo, Dong-Hwa; Shin, Hyeyoung; Kang, Kisuk; Kim, Hyungjun; Han, Sang Soo

    2014-06-01

    We report an innovative route for designing novel functional alloys based on first-principles calculations, which is an isoelectronic solid solution (ISS) of two metal elements to create new characteristics that are not native to the constituent elements. Neither Rh nor Ag exhibits hydrogen storage properties, whereas the Rh50Ag50 ISS exhibits properties similar to Pd; furthermore, Au cannot dissociate H2, and Ir has a higher energy barrier for the H2 dissociation reaction than Pt, whereas the Ir50Au50 ISS can dissociate H2 in a similar way to Pt. In the periodic table, Pd is located between Rh and Ag, and Pt is located between Ir and Au, leading to similar atomic and electronic structures between the pure metals (Pd and Pt) and the ISS alloys (Rh50Ag50 and Ir50Au50). From a practical perspective, the Ir-Au ISS would be more cost-effective to use than pure Pt, and could exhibit catalytic activity equivalent to Pt. Therefore, the Ir50Au50 ISS alloy can be a potential catalyst candidate for the replacement of Pt. PMID:26273859

  18. Hydrogen purifier module with membrane support

    DOEpatents

    A hydrogen purifier utilizing a hydrogen-permeable membrane to purify hydrogen from mixed gases containing hydrogen is disclosed. Improved mechanical support for the permeable membrane is described, enabling forward or reverse differential pressurization of the membrane, which further stabilizes the membrane from wrinkling upon hydrogen uptake.

    2012-07-24

    A hydrogen purifier utilizing a hydrogen-permeable membrane to purify hydrogen from mixed gases containing hydrogen is disclosed. Improved mechanical support for the permeable membrane is described, enabling forward or reverse differential pressurization of the membrane, which further stabilizes the membrane from wrinkling upon hydrogen uptake.

  19. Metal-free oxidation of aromatic carbon-hydrogen bonds through a reverse-rebound mechanism.

    PubMed

    Yuan, Changxia; Liang, Yong; Hernandez, Taylor; Berriochoa, Adrian; Houk, Kendall N; Siegel, Dionicio

    2013-07-11

    Methods for carbon-hydrogen (C-H) bond oxidation have a fundamental role in synthetic organic chemistry, providing functionality that is required in the final target molecule or facilitating subsequent chemical transformations. Several approaches to oxidizing aliphatic C-H bonds have been described, drastically simplifying the synthesis of complex molecules. However, the selective oxidation of aromatic C-H bonds under mild conditions, especially in the context of substituted arenes with diverse functional groups, remains a challenge. The direct hydroxylation of arenes was initially achieved through the use of strong Brønsted or Lewis acids to mediate electrophilic aromatic substitution reactions with super-stoichiometric equivalents of oxidants, significantly limiting the scope of the reaction. Because the products of these reactions are more reactive than the starting materials, over-oxidation is frequently a competitive process. Transition-metal-catalysed C-H oxidation of arenes with or without directing groups has been developed, improving on the acid-mediated process; however, precious metals are required. Here we demonstrate that phthaloyl peroxide functions as a selective oxidant for the transformation of arenes to phenols under mild conditions. Although the reaction proceeds through a radical mechanism, aromatic C-H bonds are selectively oxidized in preference to activated Csp3-H bonds. Notably, a wide array of functional groups are compatible with this reaction, and this method is therefore well suited for late-stage transformations of advanced synthetic intermediates. Quantum mechanical calculations indicate that this transformation proceeds through a novel addition-abstraction mechanism, a kind of 'reverse-rebound' mechanism as distinct from the common oxygen-rebound mechanism observed for metal-oxo oxidants. These calculations also identify the origins of the experimentally observed aryl selectivity.

  20. 3d-transition metal induced enhancement of molecular hydrogen adsorption on Mg(0001) surface: An Ab-initio study

    NASA Astrophysics Data System (ADS)

    Banerjee, Paramita; Das, G. P.

    2016-05-01

    In our effort to do first principles design of suitable materials for hydrogen storage, we have explored the interaction characteristics of a hydrogen molecule with pure as well as a 3d-transition metal (TM) atom doped Mg(0001) surface using density functional theory (DFT) based approach. Doping of a 3d-TM atom by creating a vacancy on the top most layer of Mg(0001) surface, enhances the molecular hydrogen adsorption efficiency of this surface by ~ 6 times. The TM atom gains some charge from the defected site of the Mg(0001) surface, becomes anionic and adsorbs the hydrogen molecule via Anti Kubas-type interaction. The interaction energy of this H2 molecule, including van der Waals dispersion correction, turns out to be ~ 0.4 eV, which falls in the right energy window between physisorption and chemisorption. On full coverage of this 3d-TM atom doped Mg(0001) surface with hydrogen molecules, the gravimetric density of hydrogen has been estimated to be ~ 5.6 wt %, thereby satisfying the criteria set by the department of energy (DOE) for efficient hydrogen storage.

  1. A new class of electrocatalysts for hydrogen production from water electrolysis: metal monolayers supported on low-cost transition metal carbides.

    PubMed

    Esposito, Daniel V; Hunt, Sean T; Kimmel, Yannick C; Chen, Jingguang G

    2012-02-15

    This work explores the opportunity to substantially reduce the cost of hydrogen evolution reaction (HER) catalysts by supporting monolayer (ML) amounts of precious metals on transition metal carbide substrates. The metal component includes platinum (Pt), palladium (Pd), and gold (Au); the low-cost carbide substrate includes tungsten carbides (WC and W(2)C) and molybdenum carbide (Mo(2)C). As a platform for these studies, single-phase carbide thin films with well-characterized surfaces have been synthesized, allowing for a direct comparison of the intrinsic HER activity of bare and Pt-modified carbide surfaces. It is found that WC and W(2)C are both excellent cathode support materials for ML Pt, exhibiting HER activities that are comparable to bulk Pt while displaying stable HER activity during chronopotentiometric HER measurements. The findings of excellent stability and HER activity of the ML Pt-WC and Pt-W(2)C surfaces may be explained by the similar bulk electronic properties of tungsten carbides to Pt, as is supported by density functional theory calculations. These results are further extended to other metal overlayers (Pd and Au) and supports (Mo(2)C), which demonstrate that the metal ML-supported transition metal carbide surfaces exhibit HER activity that is consistent with the well-known volcano relationship between activity and hydrogen binding energy. This work highlights the potential of using carbide materials to reduce the costs of hydrogen production from water electrolysis by serving as stable, low-cost supports for ML amounts of precious metals. PMID:22280370

  2. A new class of electrocatalysts for hydrogen production from water electrolysis: metal monolayers supported on low-cost transition metal carbides.

    PubMed

    Esposito, Daniel V; Hunt, Sean T; Kimmel, Yannick C; Chen, Jingguang G

    2012-02-15

    This work explores the opportunity to substantially reduce the cost of hydrogen evolution reaction (HER) catalysts by supporting monolayer (ML) amounts of precious metals on transition metal carbide substrates. The metal component includes platinum (Pt), palladium (Pd), and gold (Au); the low-cost carbide substrate includes tungsten carbides (WC and W(2)C) and molybdenum carbide (Mo(2)C). As a platform for these studies, single-phase carbide thin films with well-characterized surfaces have been synthesized, allowing for a direct comparison of the intrinsic HER activity of bare and Pt-modified carbide surfaces. It is found that WC and W(2)C are both excellent cathode support materials for ML Pt, exhibiting HER activities that are comparable to bulk Pt while displaying stable HER activity during chronopotentiometric HER measurements. The findings of excellent stability and HER activity of the ML Pt-WC and Pt-W(2)C surfaces may be explained by the similar bulk electronic properties of tungsten carbides to Pt, as is supported by density functional theory calculations. These results are further extended to other metal overlayers (Pd and Au) and supports (Mo(2)C), which demonstrate that the metal ML-supported transition metal carbide surfaces exhibit HER activity that is consistent with the well-known volcano relationship between activity and hydrogen binding energy. This work highlights the potential of using carbide materials to reduce the costs of hydrogen production from water electrolysis by serving as stable, low-cost supports for ML amounts of precious metals.

  3. The Grapevine Uncharacterized Intrinsic Protein 1 (VvXIP1) Is Regulated by Drought Stress and Transports Glycerol, Hydrogen Peroxide, Heavy Metals but Not Water.

    PubMed

    Noronha, Henrique; Araújo, Diogo; Conde, Carlos; Martins, Ana P; Soveral, Graça; Chaumont, François; Delrot, Serge; Gerós, Hernâni

    2016-01-01

    A MIP (Major Intrinsic Protein) subfamily called Uncharacterized Intrinsic Proteins (XIP) was recently described in several fungi and eudicot plants. In this work, we cloned a XIP from grapevine, VvXIP1, and agrobacterium-mediated transformation studies in Nicotiana benthamiana revealed that the encoded aquaporin shows a preferential localization at the endoplasmic reticulum membrane. Stopped-flow spectrometry in vesicles from the aqy-null yeast strain YSH1172 overexpressing VvXIP1 showed that VvXIP1 is unable to transport water but is permeable to glycerol. Functional studies with the ROS sensitive probe CM-H2DCFDA in intact transformed yeasts showed that VvXIP1 is also able to permeate hydrogen peroxide (H2O2). Drop test growth assays showed that besides glycerol and H2O2, VvXIP1 also transports boric acid, copper, arsenic and nickel. Furthermore, we found that VvXIP1 transcripts were abundant in grapevine leaves from field grown plants and strongly repressed after the imposition of severe water-deficit conditions in potted vines. The observed downregulation of VvXIP1 expression in cultured grape cells in response to ABA and salt, together with the increased sensitivity to osmotic stress displayed by the aqy-null yeast overexpressing VvXIP1, corroborates the role of VvXIP1 in osmotic regulation besides its involvement in H2O2 transport and metal homeostasis. PMID:27504956

  4. The Grapevine Uncharacterized Intrinsic Protein 1 (VvXIP1) Is Regulated by Drought Stress and Transports Glycerol, Hydrogen Peroxide, Heavy Metals but Not Water

    PubMed Central

    Conde, Carlos; Martins, Ana P.; Soveral, Graça; Chaumont, François; Delrot, Serge

    2016-01-01

    A MIP (Major Intrinsic Protein) subfamily called Uncharacterized Intrinsic Proteins (XIP) was recently described in several fungi and eudicot plants. In this work, we cloned a XIP from grapevine, VvXIP1, and agrobacterium-mediated transformation studies in Nicotiana benthamiana revealed that the encoded aquaporin shows a preferential localization at the endoplasmic reticulum membrane. Stopped-flow spectrometry in vesicles from the aqy-null yeast strain YSH1172 overexpressing VvXIP1 showed that VvXIP1 is unable to transport water but is permeable to glycerol. Functional studies with the ROS sensitive probe CM-H2DCFDA in intact transformed yeasts showed that VvXIP1 is also able to permeate hydrogen peroxide (H2O2). Drop test growth assays showed that besides glycerol and H2O2, VvXIP1 also transports boric acid, copper, arsenic and nickel. Furthermore, we found that VvXIP1 transcripts were abundant in grapevine leaves from field grown plants and strongly repressed after the imposition of severe water-deficit conditions in potted vines. The observed downregulation of VvXIP1 expression in cultured grape cells in response to ABA and salt, together with the increased sensitivity to osmotic stress displayed by the aqy-null yeast overexpressing VvXIP1, corroborates the role of VvXIP1 in osmotic regulation besides its involvement in H2O2 transport and metal homeostasis. PMID:27504956

  5. The Grapevine Uncharacterized Intrinsic Protein 1 (VvXIP1) Is Regulated by Drought Stress and Transports Glycerol, Hydrogen Peroxide, Heavy Metals but Not Water.

    PubMed

    Noronha, Henrique; Araújo, Diogo; Conde, Carlos; Martins, Ana P; Soveral, Graça; Chaumont, François; Delrot, Serge; Gerós, Hernâni

    2016-01-01

    A MIP (Major Intrinsic Protein) subfamily called Uncharacterized Intrinsic Proteins (XIP) was recently described in several fungi and eudicot plants. In this work, we cloned a XIP from grapevine, VvXIP1, and agrobacterium-mediated transformation studies in Nicotiana benthamiana revealed that the encoded aquaporin shows a preferential localization at the endoplasmic reticulum membrane. Stopped-flow spectrometry in vesicles from the aqy-null yeast strain YSH1172 overexpressing VvXIP1 showed that VvXIP1 is unable to transport water but is permeable to glycerol. Functional studies with the ROS sensitive probe CM-H2DCFDA in intact transformed yeasts showed that VvXIP1 is also able to permeate hydrogen peroxide (H2O2). Drop test growth assays showed that besides glycerol and H2O2, VvXIP1 also transports boric acid, copper, arsenic and nickel. Furthermore, we found that VvXIP1 transcripts were abundant in grapevine leaves from field grown plants and strongly repressed after the imposition of severe water-deficit conditions in potted vines. The observed downregulation of VvXIP1 expression in cultured grape cells in response to ABA and salt, together with the increased sensitivity to osmotic stress displayed by the aqy-null yeast overexpressing VvXIP1, corroborates the role of VvXIP1 in osmotic regulation besides its involvement in H2O2 transport and metal homeostasis.

  6. Advanced Hydrogen Transport Membranes for Vision 21 Fossil Fuel Plants

    SciTech Connect

    Carl R. Evenson; Richard N. Kleiner; James E. Stephan; Frank E. Anderson

    2006-04-30

    Eltron Research Inc. and team members CoorsTek, Sued Chemie, Argonne National Laboratory, and NORAM are developing an environmentally benign, inexpensive, and efficient method for separating hydrogen from gas mixtures produced during industrial processes, such as coal gasification. This project was motivated by the National Energy Technology Laboratory (NETL) Vision 21 initiative, which seeks to economically eliminate environmental concerns associated with the use of fossil fuels. Currently, this project is focusing on four basic categories of dense membranes: (1) mixed conducting ceramic/ceramic composites, (2) mixed conducting ceramic/metal (cermet) composites, (3) cermets with hydrogen permeable metals, and (4) layered composites containing hydrogen permeable alloys. Ultimately, these materials must enable hydrogen separation at practical rates under ambient and high-pressure conditions, without deactivation in the presence of feedstream components such as carbon dioxide, water, and sulfur. During this final quarter of the no cost extension several planar membranes of a cermet composition referred to as EC101 containing a high permeability metal and a ceramic phase were prepared and permeability testing was performed.

  7. Trends in Ground-State Entropies for Transition Metal Based Hydrogen Atom Transfer Reactions

    SciTech Connect

    Mader, Elizabeth A.; Manner, Virginia W.; Markle, Todd F.; Wu, Adam; Franz, James A.; Mayer, James M.

    2009-03-10

    Reported herein are thermochemical studies of hydrogen atom transfer (HAT) reactions involving transition metal H-atom donors MIILH and oxyl radicals. [FeII(H2bip)3]2+, [FeII(H2bim)3]2+, [CoII(H2bim)3]2+ and RuII(acac)2(py-imH) [H2bip = 2,2’-bi-1,4,5,6-tetrahydro¬pyrimidine, H2bim = 2,2’-bi-imidazoline, acac = 2,4-pentandionato, py-imH = 2-(2’-pyridyl)¬imidazole)] each react with TEMPO (2,2,6,6-tetramethyl-1-piperidinoxyl) or tBu3PhO• (2,4,6-tri-tert-butylphenoxyl) to give the deprotonated, oxidized metal complex MIIIL, and TEMPOH or tBu3PhOH. Solution equilibrium measurements for the reactions of Co and Fe complexes with TEMPO show a large, negative ground-state entropy for hydrogen atom transfer: ΔSºHAT = -30 ± 2 cal mol-1 K-1 for the two iron complexes and -41 ± 2 cal mol-1 K-1 for [CoII(H2bim)3]2+. The ΔSºHAT for TEMPO + RuII(acac)2(py-imH) is much closer to zero, 4.9 ± 1.1 cal mol-1 K-1. Calorimetric measurements quantitatively confirm the enthalpy of reaction for [FeII(H2bip)3]2+ + TEMPO, thus also confirming ΔSºHAT. Calorimetry on TEMPOH + tBu3PhO• gives ΔHºHAT = 11.2 ± 0.5 kcal mol-1 which matches the enthalpy predicted from the difference in literature solution BDEs. An evaluation of the literature BDEs of both TEMPOH and tBu3PhOH is briefly presented and new estimates are included on the relative enthalpy of solvation for tBu3PhO• vs. tBu3PhOH. The primary contributor to the large magnitude of the ground-state entropy |ΔSºHAT| for the metal complexes is vibrational entropy, ΔSºvib. The common assumption that ΔSºHAT ≈ 0 for HAT reactions, developed for organic and small gas phase molecules, does not hold for transition metal based HAT reactions. The trend in magnitude of |ΔSºHAT| for reactions with TEMPO, RuII(acac)2(py-imH) << [FeII(H2bip)3]2+ = [FeII(H2bim)3]2+ < [CoII(H2bim)3]2+, is surprisingly well predicted by the trends for electron transfer half-reaction entropies, ΔSºET, in aprotic solvents. ΔSºET and

  8. Kinetic and mechanistic studies of carbon-to-metal hydrogen atom transfer involving Os-centered radicals: evidence for tunneling.

    PubMed

    Lewandowska-Andralojc, Anna; Grills, David C; Zhang, Jie; Bullock, R Morris; Miyazawa, Akira; Kawanishi, Yuji; Fujita, Etsuko

    2014-03-01

    We have investigated the kinetics of novel carbon-to-metal hydrogen atom transfer reactions, in which homolytic cleavage of a C-H bond is accomplished by a single metal-centered radical. Time-resolved IR spectroscopic measurements revealed efficient hydrogen atom transfer from xanthene, 9,10-dihydroanthracene, and 1,4-cyclohexadiene to Cp(CO)2Os(•) and (η(5)-(i)Pr4C5H)(CO)2Os(•) radicals, formed by photoinduced homolysis of the corresponding osmium dimers. The rate constants for hydrogen abstraction from these hydrocarbons are in the range 1.5 × 10(5) M(-1) s(-1) to 1.7 × 10(7) M(-1) s(-1) at 25 °C. For the first time, kinetic isotope effects for carbon-to-metal hydrogen atom transfer were determined. Large primary deuterium kinetic isotope effects of 13.4 ± 1.0 and 16.8 ± 1.4 were observed for the hydrogen abstraction from xanthene to form Cp(CO)2OsH and (η(5)-(i)Pr4C5H)(CO)2OsH, respectively, at 25 °C. Temperature-dependent measurements of the kinetic isotope effects over a 60 °C temperature range were carried out to obtain the difference in activation energies (E(D) - E(H)) and the pre-exponential factor ratio (A(H)/A(D)). For hydrogen atom transfer from xanthene to (η(5)-(i)Pr4C5H)(CO)2Os(•), the (E(D) - E(H)) = 3.3 ± 0.2 kcal mol(-1) and A(H)/A(D) = 0.06 ± 0.02 values suggest a quantum mechanical tunneling mechanism.

  9. The corrosion behavior of Alloy 52 weld metal in cyclic hydrogenated and oxygenated water chemistry in high temperature aqueous environment

    NASA Astrophysics Data System (ADS)

    Xu, Jian; Shoji, Tetsuo

    2015-06-01

    The corrosion behavior of Alloy 52 weld metal in cyclic hydrogenated and oxygenated water chemistry in high temperature water is studied by in situ monitoring corrosion potential (Ecorr), contact electric resistance (CER) and electrochemical impedance measurements (EIS), and ex situ scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) analysis. The Ecorr and film resistance show large change when the environment is changed from hydrogenated water to oxygenated water and changeable with changing environment while the morphology and composition only show obvious distinction in the first cycle. The main factor controlling the electric/electrochemical properties of the oxide film is Ecorr.

  10. Studies on metal-organic frameworks of Cu(II) with isophthalate linkers for hydrogen storage.

    PubMed

    Yan, Yong; Yang, Sihai; Blake, Alexander J; Schröder, Martin

    2014-02-18

    Hydrogen (H2) is a promising alternative energy carrier because of its environmental benefits, high energy density, and abundance. However, development of a practical storage system to enable the "Hydrogen Economy" remains a huge challenge. Metal-organic frameworks (MOFs) are an important class of crystalline coordination polymers constructed by bridging metal centers with organic linkers. MOFs show promise for H2 storage owing to their high surface area and tuneable properties. In this Account, we summarize our research on novel porous materials with enhanced H2 storage properties and describe frameworks derived from 3,5-substituted dicarboxylates (isophthalates) that serve as versatile molecular building blocks for the construction of a range of interesting coordination polymers with Cu(II) ions. We synthesized a series of materials by connecting linear tetracarboxylate linkers to {Cu(II)2} paddlewheel moieties. These materials exhibit high structural stability and permanent porosity. Varying the organic linker modulates the pore size, geometry, and functionality to control the overall H2 adsorption. Our top-performing material in this series has a H2 storage capacity of 77.8 mg g(-1) at 77 K, 60 bar. H2 adsorption at low, medium, and high pressures correlates with the isosteric heat of adsorption, surface area, and pore volume, respectively. Another series, using tribranched C3-symmetric hexacarboxylate ligands with Cu(II), gives highly porous (3,24)-connected frameworks incorporating {Cu(II)2} paddlewheels. Increasing the length of the hexacarboxylate struts directly tunes the porosity of the resultant material from micro- to mesoporosity. These materials show exceptionally high H2 uptakes owing to their high surface area and pore volume. The first member of this family reported adsorbs 111 mg g(-1) of H2, or 55.9 g L(-1), at 77 K, 77 bar, while at 77 K, 1 bar, the material adsorbs 2.3 wt % H2. We and others have since achieved enhanced H2 adsorption in these

  11. Microporous metal-organic frameworks incorporating 1,4-benzeneditetrazolate: syntheses, structures, and hydrogen storage properties.

    PubMed

    Dinca, Mircea; Yu, Anta F; Long, Jeffrey R

    2006-07-12

    The potential of tetrazolate-based ligands for forming metal-organic frameworks of utility in hydrogen storage is demonstrated with the use of 1,4-benzeneditetrazolate (BDT(2)(-)) to generate a series of robust, microporous materials. Reaction of H(2)BDT with MnCl(2).4H(2)O and Mn(NO(3))(2).4H(2)O in N,N-diethylformamide (DEF) produces the two-dimensional framework solids Mn(3)(BDT)(2)Cl(2)(DEF)(6) (1) and Mn(4)(BDT)(3)(NO(3))(2)(DEF)(6) (2), whereas reactions with hydrated salts of Mn(2+), Cu(2+), and Zn(2+) in a mixture of methanol and DMF afford the porous, three-dimensional framework solids Zn(3)(BDT)(3)(DMF)(4)(H(2)O)(2).3.5CH(3)OH (3), Mn(3)(BDT)(3)(DMF)(4)(H(2)O)(2).3CH(3)OH.2H(2)O.DMF (4), Mn(2)(BDT)Cl(2)(DMF)(2).1.5CH(3)OH.H(2)O (5), and Cu(BDT)(DMF).CH(3)OH.0.25DMF (6). It is shown that the method for desolvating such compounds can dramatically influence the ensuing gas sorption properties. When subjected to a mild evacuation procedure, compounds 3-6 exhibit permanent porosity, with BET surface areas in the range 200-640 m(2)/g. The desolvated forms of 3-5 store between 0.82 and 1.46 wt % H(2) at 77 K and 1 atm, with enthalpies of adsorption in the range 6.0-8.8 kJ/mol, among the highest so far reported for metal-organic frameworks. In addition, the desolvated form of 6 exhibits preferential adsorption of O(2) over H(2) and N(2), showing promise for gas separation and purification applications.

  12. Supported transition metal catalysts for para- to ortho-hydrogen conversion

    NASA Technical Reports Server (NTRS)

    Brooks, Christopher J.; Wang, Wei; Eyman, Darrell P.

    1994-01-01

    The main goal of this study was to develop and improve on existing catalysts for the conversion of ortho- to para-hydrogen. Starting with a commercially available Air Products nickel silicate, which had a beta value of 20, we were trying to synthesize catalysts that would be an improvement to AP. This was accomplished by preparing silicates with various metals as well as different preparation methods. We also prepared supported ruthenium catalysts by various techniques using several metal precursors to improve present technology. What was also found was that the activation conditions prior to catalytic testing was highly important for both the silicates and the supported ruthenium catalysts. While not the initial focus of the research, we made some interesting observations into the adsorption of H2 on ruthenium. This helped us to get a better understanding of how ortho- to para-H2 conversion takes place, and what features in a catalyst are important to optimize activity. Reactor design was the final area in which some interesting conclusions were drawn. As discussed earlier, the reactor catalyst bed must be constructed using straight 1/8 feet OD stainless steel tubing. It was determined that the use of 1/4 feet OD tubing caused two problems. First, the radius from the center of the bed to the wall was too great for thermal equilibrium. Since the reaction of ortho- to para-H2 is exothermic, the catalyst bed center was warmer than the edges. Second, the catalyst bed was too shallow using a 1/4 feet tube. This caused reactant blow-by which was thought to decrease the measured activity when the flow rate was increased. The 1/8 feet tube corrected both of these concerns.

  13. A comparative theoretical study of metal functionalized carbon nanocones and carbon nanocone sheets as potential hydrogen storage materials.

    PubMed

    Shalabi, A S; Soliman, K A; Taha, H O

    2014-09-28

    The hydrogen storage of Ti functionalized carbon nanocones and carbon nanocone sheets is investigated by using the state-of-the-art density functional theory calculations. The Ti atom prefers to bind at the hollow site of the hexagonal ring. The average adsorption energies corrected for dispersion forces are -0.54 and -0.39 eV per hydrogen molecule. With no metal clustering, the system gravimetric capacities are expected to be as large as 9.31 and 11.01 wt%. The hydrogen storage reactions are characterized in terms of simulated infrared spectra, projected densities of states, kinetics, and statistical thermodynamics. The free energies and enthalpies of the Ti functionalized carbon nanocone meet the ultimate targets of the Department of Energy for all temperatures and pressures. The closest reactions to zero free energy occur at 378.15 K/2.961 atm for carbon nanocones and 233.15 K/2.961 atm for carbon nanocone sheets. The translational component is found to exert a dominant effect on the total entropy change with temperature. More promising thermodynamics are assigned to the hydrogenation of Ti functionalized carbon nanocone sheets at 233.15 K. As the temperature is increased, the lifetimes of the hydrogen molecules adsorbed at the surface drop and the rate constants increase. At fixed pressure, the rate constants of hydrogenation of Ti functionalized carbon nanocones are smaller than those of Ti functionalized carbon nanocone sheets, while the lifetimes are greater.

  14. Concentration of Hydrogen Peroxide

    NASA Technical Reports Server (NTRS)

    Parrish, Clyde F. (Inventor)

    2006-01-01

    Methods for concentrating hydrogen peroxide solutions have been described. The methods utilize a polymeric membrane separating a hydrogen peroxide solution from a sweep gas or permeate. The membrane is selective to the permeability of water over the permeability of hydrogen peroxide, thereby facilitating the concentration of the hydrogen peroxide solution through the transport of water through the membrane to the permeate. By utilizing methods in accordance with the invention, hydrogen peroxide solutions of up to 85% by volume or higher may be generated at a point of use without storing substantial quantities of the highly concentrated solutions and without requiring temperatures that would produce explosive mixtures of hydrogen peroxide vapors.

  15. Tristate electrochemical metallization memory based in the hydrogenated nanocrystalline silicon films

    SciTech Connect

    Yan, X. B.; Chen, Y. F.; Hao, H.; Zhang, E. P.; Shi, S. S.; Lou, J. Z.; Liu, Q.

    2014-08-18

    The hydrogenated nanocrystalline silicon (nc-Si:H) films have been fabricated as resistive switching medium by radio frequency plasma enhanced chemical vapor deposition technology. The constructed Ag/nc-Si:H/Pt structure exhibits stable three nonvolatile resistance states. Tristate resistive states with large ratio 10{sup 2} and 10{sup 5}, less variation of resistance, and long retention exceeding 2.3 × 10{sup 5 }s are observed in Ag/nc-Si:H/Pt stack. The temperature dependence of high resistance state (HRS) and intermediate resistance state (IRS) both show semiconductor behavior, and the temperature dependence of low resistance state (LRS) represents metallic property. Fitting results demonstrated that the conduction mechanism of HRS, IRS, and LRS showed space charge limited conduction (SCLC), tunneling, and ohmic characteristics, respectively. The discrete Ag filament with Si nanocrystalline and complete Ag filament is proposed to be responsible for the performance IRS and LRS. We supposed that the Ag{sup +} ions prefer to be reduced to Ag atoms near the Si nanocrystalline location. Si nanocrystalline between Ag nanoparticles contribute to the current transport at IRS.

  16. In situ Neutron Reflectometry Measurements of Hydrogen Absorption in Thin Metal Films

    NASA Astrophysics Data System (ADS)

    Munter, A. E.; Heuser, B. J.; Guillermo, N. R.

    1996-03-01

    The absorption of hydrogen and deuterium from the gas phase in thin films of Pd has been measured with neutron reflectometry. 500ÅPd films were magnetron sputtered on polished silicon substrates. At room temperature, H and D were observed to absorb into the Pd film at gas pressures of 60 torr and 1 atm respectively. Genetic algorithm fits to the data indicate an expansion of the metal lattice in the direction normal to the surface plane upon uptake. This may be the result of the hydride phase transformation, but the results are inconclusive. Both H and D appear to be preferentially excluded from the film-substrate interface, with a peak in the concentration profile occuring between the air/film interface and the midpoint of the film. Peak concentrations of 0.6 H/Pd and 0.8 D/Pd were determined from the fits. The effect of H absorption appears to be at least partially reversible upon annealing. The discussion will include expansion of the thin films after absorption, depth profiles of the H and D concentrations, and reversibility. Results for H and D absorption in Nb will be presented as well.

  17. A noble-metal-free system for photocatalytic hydrogen production from water.

    PubMed

    Mejía, Esteban; Luo, Shu-Ping; Karnahl, Michael; Friedrich, Aleksej; Tschierlei, Stefanie; Surkus, Annette-Enrica; Junge, Henrik; Gladiali, Serafino; Lochbrunner, Stefan; Beller, Matthias

    2013-11-18

    A series of heteroleptic copper(I) complexes with bidentate PP and NN chelate ligands was prepared and successfully applied as photosensitizers in the light-driven production of hydrogen, by using [Fe3(CO)12] as a water-reduction catalyst (WRC). These systems efficiently reduces protons from water/THF/triethylamine mixtures, in which the amine serves as a sacrificial electron donor (SR). Turnover numbers (for H) up to 1330 were obtained with these fully noble-metal-free systems. The new complexes were electrochemically and photophysically characterized. They exhibited a correlation between the lifetimes of the MLCT excited state and their efficiency as photosensitizers in proton-reduction systems. Within these experiments, considerably long excited-state lifetimes of up to 54 μs were observed. Quenching studies with the SR, in the presence and absence of the WRC, showed that intramolecular deactivation was more efficient in the former case, thus suggesting the predominance of an oxidative quenching pathway. PMID:24123302

  18. Metal-polypyridyl catalysts for electro- and photochemical reduction of water to hydrogen.

    PubMed

    Zee, David Z; Chantarojsiri, Teera; Long, Jeffrey R; Chang, Christopher J

    2015-07-21

    Climate change, rising global energy demand, and energy security concerns motivate research into alternative, sustainable energy sources. In principle, solar energy can meet the world's energy needs, but the intermittent nature of solar illumination means that it is temporally and spatially separated from its consumption. Developing systems that promote solar-to-fuel conversion, such as via reduction of protons to hydrogen, could bridge this production-consumption gap, but this effort requires invention of catalysts that are cheap, robust, and efficient and that use earth-abundant elements. In this context, catalysts that utilize water as both an earth-abundant, environmentally benign substrate and a solvent for proton reduction are highly desirable. This Account summarizes our studies of molecular metal-polypyridyl catalysts for electrochemical and photochemical reduction of protons to hydrogen. Inspired by concept transfer from biological and materials catalysts, these scaffolds are remarkably resistant to decomposition in water, with fast and selective electrocatalytic and photocatalytic conversions that are sustainable for several days. Their modular nature offers a broad range of opportunities for tuning reactivity by molecular design, including altering ancillary ligand electronics, denticity, and/or incorporating redox-active elements. Our first-generation complex, [(PY4)Co(CH3CN)2](2+), catalyzes the reduction of protons from a strong organic acid to hydrogen in 50% water. Subsequent investigations with the pentapyridyl ligand PY5Me2 furnished molybdenum and cobalt complexes capable of catalyzing the reduction of water in fully aqueous electrolyte with 100% Faradaic efficiency. Of particular note, the complex [(PY5Me2)MoO](2+) possesses extremely high activity and durability in neutral water, with turnover frequencies at least 8500 mol of H2 per mole of catalyst per hour and turnover numbers over 600 000 mol of H2 per mole of catalyst over 3 days at an

  19. A Theoretical Study of Methanol Synthesis from CO(2) Hydrogenation on Metal-doped Cu(111) Surfaces

    SciTech Connect

    Liu P.; Yang, Y.; White, M.G.

    2012-01-12

    Density functional theory (DFT) calculations and Kinetic Monte Carlo (KMC) simulations were employed to investigate the methanol synthesis reaction from CO{sub 2} hydrogenation (CO{sub 2} + 3H{sub 2} {yields} CH{sub 3}OH + H{sub 2}O) on metal-doped Cu(111) surfaces. Both the formate pathway and the reverse water-gas shift (RWGS) reaction followed by a CO hydrogenation pathway (RWGS + CO-Hydro) were considered in the study. Our calculations showed that the overall methanol yield increased in the sequence: Au/Cu(111) < Cu(111) < Pd/Cu(111) < Rh/Cu(111) < Pt/Cu(111) < Ni/Cu(111). On Au/Cu(111) and Cu(111), the formate pathway dominates the methanol production. Doping Au does not help the methanol synthesis on Cu(111). Pd, Rh, Pt, and Ni are able to promote the methanol production on Cu(111), where the conversion via the RWGS + CO-Hydro pathway is much faster than that via the formate pathway. Further kinetic analysis revealed that the methanol yield on Cu(111) was controlled by three factors: the dioxomethylene hydrogenation barrier, the CO binding energy, and the CO hydrogenation barrier. Accordingly, two possible descriptors are identified which can be used to describe the catalytic activity of Cu-based catalysts toward methanol synthesis. One is the activation barrier of dioxomethylene hydrogenation, and the other is the CO binding energy. An ideal Cu-based catalyst for the methanol synthesis via CO{sub 2} hydrogenation should be able to hydrogenate dioxomethylene easily and bond CO moderately, being strong enough to favor the desired CO hydrogenation rather than CO desorption but weak enough to prevent CO poisoning. In this way, the methanol production via both the formate and the RWGS + CO-Hydro pathways can be facilitated.

  20. Metal aminoboranes

    DOEpatents

    Burrell, Anthony K.; Davis, Benjamin J.; Thorn, David L.; Gordon, John C.; Baker, R. Thomas; Semelsberger, Troy Allen; Tumas, William; Diyabalanage, Himashinie Vichalya Kaviraj; Shrestha, Roshan P.

    2010-05-11

    Metal aminoboranes of the formula M(NH.sub.2BH.sub.3).sub.n have been synthesized. Metal aminoboranes are hydrogen storage materials. Metal aminoboranes are also precursors for synthesizing other metal aminoboranes. Metal aminoboranes can be dehydrogenated to form hydrogen and a reaction product. The reaction product can react with hydrogen to form a hydrogen storage material. Metal aminoboranes can be included in a kit.

  1. Evaluation of Metal Halide, Plasma, and LED Lighting Technologies for a Hydrogen Fuel Cell Mobile Light (H 2 LT)

    DOE PAGESBeta

    Miller, L. B.; Donohoe, S. P.; Jones, M. H.; White, W. A.; Klebanoff, L. E.; Velinsky, S. A.

    2015-04-22

    This article reports on the testing and comparison of a prototype hydrogen fuel cell light tower (H2LT) and a conventional diesel-powered metal halide light trailer for use in road maintenance and construction activities. The prototype was originally outfitted with plasma lights and then with light-emitting diode (LED) luminaires. Light output and distribution, lighting energy efficiency (i.e., efficacy), power source thermal efficiency, and fuel costs are compared. The metal halide luminaires have 2.2 and 3.1 times more light output than the plasma and LED luminaires, respectively, but they require more power/lumen to provide that output. The LED luminaires have 1.6 timesmore » better light efficacy than either the metal halide or plasma luminaires. The light uniformity ratios produced by the plasma and LED towers are acceptable. The fuel cell thermal efficiency at the power required to operate the plasma lights is 48%, significantly higher than the diesel generator efficiency of 23% when operating the metal halide lights. Due to the increased efficiency of the fuel cell and the LED lighting, the fuel cost per lumen-hour of the H2LT is 62% of the metal halide diesel light tower assuming a kilogram of hydrogen is twice the cost of a gallon of diesel fuel.« less

  2. N,P-Codoped Carbon Networks as Efficient Metal-free Bifunctional Catalysts for Oxygen Reduction and Hydrogen Evolution Reactions.

    PubMed

    Zhang, Jintao; Qu, Liangti; Shi, Gaoquan; Liu, Jiangyong; Chen, Jianfeng; Dai, Liming

    2016-02-01

    The high cost and scarcity of noble metal catalysts, such as Pt, have hindered the hydrogen production from electrochemical water splitting, the oxygen reduction in fuel cells and batteries. Herein, we developed a simple template-free approach to three-dimensional porous carbon networks codoped with nitrogen and phosphorus by pyrolysis of a supermolecular aggregate of self-assembled melamine, phytic acid, and graphene oxide (MPSA/GO). The pyrolyzed MPSA/GO acted as the first metal-free bifunctional catalyst with high activities for both oxygen reduction and hydrogen evolution. Zn-air batteries with the pyrolyzed MPSA/GO air electrode showed a high peak power density (310 W g(-1) ) and an excellent durability. Thus, the pyrolyzed MPSA/GO is a promising bifunctional catalyst for renewable energy technologies, particularly regenerative fuel cells. PMID:26709954

  3. N,P-Codoped Carbon Networks as Efficient Metal-free Bifunctional Catalysts for Oxygen Reduction and Hydrogen Evolution Reactions.

    PubMed

    Zhang, Jintao; Qu, Liangti; Shi, Gaoquan; Liu, Jiangyong; Chen, Jianfeng; Dai, Liming

    2016-02-01

    The high cost and scarcity of noble metal catalysts, such as Pt, have hindered the hydrogen production from electrochemical water splitting, the oxygen reduction in fuel cells and batteries. Herein, we developed a simple template-free approach to three-dimensional porous carbon networks codoped with nitrogen and phosphorus by pyrolysis of a supermolecular aggregate of self-assembled melamine, phytic acid, and graphene oxide (MPSA/GO). The pyrolyzed MPSA/GO acted as the first metal-free bifunctional catalyst with high activities for both oxygen reduction and hydrogen evolution. Zn-air batteries with the pyrolyzed MPSA/GO air electrode showed a high peak power density (310 W g(-1) ) and an excellent durability. Thus, the pyrolyzed MPSA/GO is a promising bifunctional catalyst for renewable energy technologies, particularly regenerative fuel cells.

  4. Selective reduction of biomass by hydriodic acid and its in situ regeneration from iodine by metal/hydrogen.

    PubMed

    Yang, Weiran; Grochowski, Matthew R; Sen, Ayusman

    2012-07-01

    HI returns: Hydroiodic acid is a highly selective reducing reagent for a wide variety of substrates. Its application is limited by the formation of iodine and the difficulty in reconverting that iodione back to HI in situ. We report the facile conversion of I(2) to HI by metal-catalyzed hydrogenation in the presence of water, and demonstrate the utility of this process in the conversion of fructose to 5-methyfurfural and glycerol to 2-iodopropane. PMID:22492614

  5. Monolayer MoS2 films supported by 3D nanoporous metals for high-efficiency electrocatalytic hydrogen production.

    PubMed

    Tan, Yongwen; Liu, Pan; Chen, Luyang; Cong, Weitao; Ito, Yoshikazu; Han, Jiuhui; Guo, Xianwei; Tang, Zheng; Fujita, Takeshi; Hirata, Akihiko; Chen, Mingwei W

    2014-12-17

    The "edge-free" monolayer MoS2 films supported by 3D nanoporous gold show high catalytic activities towards hydrogen evolution reaction (HER), originating from large out-of-plane strains that are geometrically required to manage the 3D curvature of bicontinuous nanoporosity. The large lattice bending leads to local semiconductor-to-metal transition of 2H MoS2 and the formation of catalytically active sites for HER.

  6. Hydrogen storage studies on palladium-doped carbon materials (AC, CB, CNMs) @ metal-organic framework-5.

    PubMed

    Viditha, V; Srilatha, K; Himabindu, V

    2016-05-01

    Metal organic frameworks (MOFs) are a rapidly growing class of porous materials and are considered as best adsorbents for their high surface area and extraordinary porosity. The MOFs are synthesized by using various chemicals like triethylamine, terepthalic acid, zinc acetate dihydrate, chloroform, and dimethylformamide (DMF). Synthesized MOFs are intercalated with palladium/activated carbon, carbon black, and carbon nanomaterials by chemical reduction method for the purpose of enhancing the hydrogen adsorption capacities. We have observed that the palladium doped activated carbon on MOF-5 showed high hydrogen storage capacity. This may be due to the affinity of the palladium toward hydrogen molecule. The samples are characterized by X-ray diffraction, scanning electron microscopy (SEM), and Brunauer-Emmett-Teller (BET) surface area analysis. We have observed a clear decrease in the BET surface area and pore volume. The obtained results show a better performance for the synthesized sample. To our best knowledge, no one has reported the work on palladium-doped carbon materials (activated carbon, carbon black, carbon nanomaterials) impregnated to the metal-organic framework-5. We have attempted to synthesize carbon nanomaterials using indigenously fabricated chemical vapor deposition (CVD) unit as a support. We have observed an increase in the hydrogen storage capacities.

  7. Ultrasonic degradation of Rhodamine B in the presence of hydrogen peroxide and some metal oxide.

    PubMed

    Mehrdad, Abbas; Hashemzadeh, Robab

    2010-01-01

    In this research, degradation of Rodamine B in the presence of (hydrogen peroxide), (hydrogen peroxide+ultrasound), (hydrogen peroxide+aluminum oxide), (hydrogen peroxide+aluminum oxide+ultrasound with different ultrasound power), (hydrogen peroxide+iron oxide) and (hydrogen peroxide+iron oxide+ultrasound with different ultrasound power) were investigated at 25 degrees C. The apparent rate constants for the examined systems were calculated by pseudo-first-order kinetics. The results indicate that the rate of degradation was accelerated by ultrasound. The rate of degradation was increased by increasing power ultrasound. The efficiency of the (hydrogen peroxide+iron oxide+ultrasound) system for degradation of Rodamine B was higher than the others examined.

  8. A high stability Ni-La0.5Ce0.5O2-δ asymmetrical metal-ceramic membrane for hydrogen separation and generation

    NASA Astrophysics Data System (ADS)

    Zhu, Zhiwen; Sun, Wenping; Wang, Zhongtao; Cao, Jiafeng; Dong, Yingchao; Liu, Wei

    2015-05-01

    In this work, hydrogen permeation properties of Ni-La0.5Ce0.5O2-δ (LDC) asymmetrical cermet membrane are investigated, including hydrogen fluxes (JH2) under different hydrogen partial pressures, the influence of water vapor on JH2 and the long-term stability of the membrane operating under the containing-CO2 atmosphere. Ni-LDC asymmetrical membrane shows the best hydrogen permeability among LDC-based hydrogen separation membranes, inferior to Ni-BaZr0.1Ce0.7Y0.2O3-δ asymmetrical membrane. The water vapor in feed gas is beneficial to hydrogen transport process, which promote an increase of JH2 from 5.64 × 10-8 to 6.83 × 10-8 mol cm-2 s-1 at 900 °C. Stability testing of hydrogen permeation suggests that Ni-LDC membrane remains stable against CO2. A dual function of combining hydrogen separation and generation can be realized by humidifying the sweep gas and enhance the hydrogen output by 1.0-1.5 times. Ni-LDC membrane exhibits desirable performance and durability in dual-function mode. Morphologies and phase structures of the membrane after tests are also characterized by SEM and XRD.

  9. Flexible Sandwich Diaphragms Are Less Permeable

    NASA Technical Reports Server (NTRS)

    Michalovic, John G.; Vassallo, Franklin A.

    1993-01-01

    Diaphragms for use in refrigerator compressors made as laminates of commercially available elastomers and metals. Diaphragms flexible, but less permeable by chlorofluorocarbon refrigerant fluids than diaphragms made of homogeneous mixtures of materials.

  10. The carburization of transition metal molybdates (MxMoO₄, M= Cu, Ni or Co) and the generation of highly active metal/carbide catalysts for CO₂ hydrogenation

    DOE PAGESBeta

    Rodriguez, Jose A.; Xu, Wenqian; Ramirez, Pedro J.; Stachiola, Dario; Brito, Joaquin L.

    2015-05-06

    A new approach has been tested for the preparation of metal/Mo₂C catalysts using mixed-metal oxide molybdates as precursors. Synchrotron-based in situ time-resolved X-ray diffraction was used to study the reduction and carburization processes of Cu₃(MoO₄)₂(OH)₂, a-NiMoO₄ and CoMoO₄•nH₂O by thermal treatment under mixtures of hydrogen and methane. In all cases, the final product was β-Mo₂C and a metal phase (Cu, Ni, or Co), but the transition sequence varied with the different metals, and it could be related to the reduction potential of the Cu²⁺, Ni²⁺ and Co²⁺ cations inside each molybdate. The synthesized Cu/Mo₂C, Ni/Mo₂C and Co/Mo₂C catalysts were highlymore » active for the hydrogenation of CO₂. The metal/Mo₂C systems exhibited large variations in the selectivity towards methanol, methane and CnH₂n₊₂ (n > 2) hydrocarbons depending on the nature of the supported metal and its ability to cleave C-O bonds. Cu/Mo₂C displayed a high selectivity for CO and methanol production. Ni/Mo₂C and Co/Mo₂C were the most active catalysts for the activation and full decomposition of CO₂, showing high selectivity for the production of methane (Ni case) and CnH₂n₊₂ (n > 2) hydrocarbons (Co case).« less

  11. The carburization of transition metal molybdates (MxMoO₄, M= Cu, Ni or Co) and the generation of highly active metal/carbide catalysts for CO₂ hydrogenation

    SciTech Connect

    Rodriguez, Jose A.; Xu, Wenqian; Ramirez, Pedro J.; Stachiola, Dario; Brito, Joaquin L.

    2015-05-06

    A new approach has been tested for the preparation of metal/Mo₂C catalysts using mixed-metal oxide molybdates as precursors. Synchrotron-based in situ time-resolved X-ray diffraction was used to study the reduction and carburization processes of Cu₃(MoO₄)₂(OH)₂, a-NiMoO₄ and CoMoO₄•nH₂O by thermal treatment under mixtures of hydrogen and methane. In all cases, the final product was β-Mo₂C and a metal phase (Cu, Ni, or Co), but the transition sequence varied with the different metals, and it could be related to the reduction potential of the Cu²⁺, Ni²⁺ and Co²⁺ cations inside each molybdate. The synthesized Cu/Mo₂C, Ni/Mo₂C and Co/Mo₂C catalysts were highly active for the hydrogenation of CO₂. The metal/Mo₂C systems exhibited large variations in the selectivity towards methanol, methane and CnH₂n₊₂ (n > 2) hydrocarbons depending on the nature of the supported metal and its ability to cleave C-O bonds. Cu/Mo₂C displayed a high selectivity for CO and methanol production. Ni/Mo₂C and Co/Mo₂C were the most active catalysts for the activation and full decomposition of CO₂, showing high selectivity for the production of methane (Ni case) and CnH₂n₊₂ (n > 2) hydrocarbons (Co case).

  12. Pt-Ti-O gate silicon-metal-insulator-semiconductor field-effect transistor hydrogen gas sensors in harsh environments

    NASA Astrophysics Data System (ADS)

    Usagawa, Toshiyuki; Ueda, Kazuhiro; Nambu, Akira; Yoneyama, Akio; Kikuchi, Yota; Watanabe, Atsushi

    2016-06-01

    The influence of radiation damages to developed hydrogen gas sensor chips from γ-rays (60Co) and/or X-rays (synchrotron radiation) is manageably avoided for sensor operations even at extremely high integral doses such as 1.8 and/or 18 MGy. Platinum-titanium-oxygen (Pt-Ti-O) gate silicon-metal-insulator-semiconductor field-effect transistor (Si-MISFET) hydrogen gas sensors can work stably as hydrogen sensors up to about 270 °C and also show environmental hardness as follows: When nitrogen-diluted 10-ppm hexamethyldisiloxane (HMDS) was exposed to the sensor FETs for 40 min at a working temperature of 115 °C, large sensing amplitude (ΔV g) changed little within repetition errors before and after HMDS exposures. The variations of ΔV g among relative humidity of 20 and 80% are very small within ±4.4% around 50% under 40 °C atmosphere. The Pt-Ti-O sensors have been found to show large ΔV g of 624.4 mV with σΔV g of 7.27 mV for nine times repeated measurements under nitrogen-diluted 1.0%-hydrogen gas, which are nearly the same values of 654.5 mV with σΔV g of 3.77 mV under air-diluted 1.0%-hydrogen gas.

  13. Structural and kinetic studies of metal hydride hydrogen storage materials using thin film deposition and characterization techniques

    NASA Astrophysics Data System (ADS)

    Kelly, Stephen Thomas

    Hydrogen makes an attractive energy carrier for many reasons. It is an abundant chemical fuel that can be produced from a wide variety of sources and stored for very long periods of time. When used in a fuel cell, hydrogen emits only water at the point of use, making it very attractive for mobile applications such as in an automobile. Metal hydrides are promising candidates for on-board reversible hydrogen storage in mobile applications due to their very high volumetric storage capacities---in most cases exceeding even that of liquid hydrogen. The United States Department of Energy (DOE) has set fuel system targets for an automotive hydrogen storage system, but as of yet no single material meets all the requirements. In particular, slow reaction kinetics and/or inappropriate thermodynamics plague many metal hydride hydrogen storage materials. In order to engineer a practical material that meets the DOE targets, we need a detailed understanding of the kinetic and thermodynamic properties of these materials during the phase change. In this work I employed sputter deposited thin films as a platform to study materials with highly controlled chemistry, microstructure and catalyst placement using thin film characterization techniques such as in situ x-ray diffraction (XRD) and neutron reflectivity. I observed kinetic limitations in the destabilized Mg2Si system due to the slow diffusion of the host Mg and Si atoms while forming separate MgH2 and Si phases. Conversely, I observed that the presence of Al in the Mg/Al system inhibits hydrogen diffusion while the host Mg and Al atoms interdiffuse readily, allowing the material to fall into a kinetic and/or thermodynamic trap by forming intermetallic compounds such as Mg17Al 12. By using in situ XRD to analyze epitaxial Mg films grown on (001) oriented Al2O3 substrates I observed hydride growth consistent with a model of a planar hydride layer growing into an existing metal layer. Subsequent film cycling changes the hydrogen

  14. Hydrogen transmission/storage with a metal hydride/organic slurry

    SciTech Connect

    Breault, R.W.; Rolfe, J.; McClaine, A.

    1998-08-01

    Thermo Power Corporation has developed a new approach for the production, transmission, and storage of hydrogen. In this approach, a chemical hydride slurry is used as the hydrogen carrier and storage media. The slurry protects the hydride from unanticipated contact with moisture in the air and makes the hydride pumpable. At the point of storage and use, a chemical hydride/water reaction is used to produce high-purity hydrogen. An essential feature of this approach is the recovery and recycle of the spent hydride at centralized processing plants, resulting in an overall low cost for hydrogen. This approach has two clear benefits: it greatly improves energy transmission and storage characteristics of hydrogen as a fuel, and it produces the hydrogen carrier efficiently and economically from a low cost carbon source. The preliminary economic analysis of the process indicates that hydrogen can be produced for $3.85 per million Btu based on a carbon cost of $1.42 per million Btu and a plant sized to serve a million cars per day. This compares to current costs of approximately $9.00 per million Btu to produce hydrogen from $3.00 per million Btu natural gas, and $25 per million Btu to produce hydrogen by electrolysis from $0.05 per Kwh electricity. The present standard for production of hydrogen from renewable energy is photovoltaic-electrolysis at $100 to $150 per million Btu.

  15. Polymer/Silicate Nanocomposites Used to Manufacture Gas Storage Tanks With Reduced Permeability

    NASA Technical Reports Server (NTRS)

    Campbell, Sandi G.; Johnston, Chris

    2004-01-01

    Over the past decade, there has been considerable research in the area of polymer-layered silicate nanocomposites. This research has shown that the dispersion of small amounts of an organically modified layered silicate improves the polymer strength, modulus, thermal stability, and barrier properties. There have been several reports on the dispersion of layered silicates in an epoxy matrix. Potential enhancements to the barrier properties of epoxy/silicate nanocomposites make this material attractive for low permeability tankage. Polymer matrix composites (PMCs) have several advantages for cryogenic storage tanks. They are lightweight, strong, and stiff; therefore, a smaller fraction of a vehicle's potential payload capacity is used for propellant storage. Unfortunately, the resins typically used to make PMC tanks have higher gas permeability than metals. This can lead to hydrogen loss through the body of the tank instead of just at welds and fittings. One approach to eliminate this problem is to build composite tanks with thin metal liners. However, although these tanks provide good permeability performance, they suffer from a substantial mismatch in the coefficient of thermal expansion, which can lead to failure of the bond between the liner and the body of the tank. Both problems could be addressed with polymersilicate nanocomposites, which exhibit reduced hydrogen permeability, making them potential candidates for linerless PMC tanks. Through collaboration with Northrop Grumman and Michigan State University, nanocomposite test tanks were manufactured for the NASA Glenn Research Center, and the helium permeability was measured. An organically modified silicate was prepared at Michigan State University and dispersed in an epoxy matrix (EPON 826/JeffamineD230). The epoxy/silicate nanocomposites contained either 0 or 5 wt% of the organically modified silicate. The tanks were made by filament winding carbon fibers with the nanocomposite resin. Helium permeability

  16. The use of palladium to obtain reproducible boundary conditions for permeability measurements using galvanostatic charging

    NASA Astrophysics Data System (ADS)

    Bowker, J.; Piercy, G. R.

    1985-05-01

    The diffusion current of hydrogen through palladium in an electrochemical cell initially rises linearly with the charging current, reaches a steady “plateau” value, and then rises again. The diffusivity of hydrogen in palladium was measured using standard transient techniques in the initial region of low current density. Combining this value with the measured value of diffusion current at the plateau level gave a concentration of hydrogen at the entrance surface of the palladium that was the same for three different palladium thicknesses, and was equal to the saturation value in α palladium. It is proposed that this can be used as a known and reproducible effective hydrogen pressure (0.019 atm) if palladium is plated onto other metals before measuring their permeability in an electrochemical cell. Experimental evidence for this was obtained from permeability measurements made on several thicknesses of iron. Permeation studies were also made on AISI 410 stainless steel and tin plated mild steel. The measured value for electrolytic tinplate was 107 times that expected from extrapolation of high temperature data. This could be attributed to grain boundaries or porosity covering 0.003 pct of the area. The permeability values of iron and stainless steel are 8.4 x 1012 and 2.8 x 1013 H atom/cm • s • √atm, respectively.

  17. A Pt-Ti-O gate Si-metal-insulator-semiconductor field-effect transistor hydrogen gas sensor

    NASA Astrophysics Data System (ADS)

    Usagawa, Toshiyuki; Kikuchi, Yota

    2010-10-01

    A hydrogen gas sensor based on platinum-titanium-oxygen (Pt-Ti-O) gate silicon-metal-insulator-semiconductor field-effect transistors (Si-MISFETs) was developed. The sensor has a unique gate structure composed of titanium and oxygen accumulated around platinum grains on top of a novel mixed layer of nanocrystalline TiOx and superheavily oxygen-doped amorphous titanium formed on SiO2/Si substrates. The FET hydrogen sensor shows high reliability and high sensing amplitude (Δ Vg) defined by the magnitude of the threshold voltage shift. Δ Vg is well fitted by a linear function of the logarithm of air-diluted hydrogen concentration C (ppm), i.e., Δ Vg(V) =0.355 log C(ppm ) -0.610 , between 100 ppm and 1%. This high gradient coefficient of Δ Vg for the wide sensing range demonstrates that the sensor is suitable for most hydrogen-safety-monitoring sensor systems. The Pt-Ti-O structures of the sensor are typically realized by annealing Pt (15 nm)/Ti (5 nm)-gate Si-metal-oxide-semiconductor structures in air at 400 °C for 2 h. The Pt-Ti-O gate MIS structures were analyzed by transmission electron microscope (TEM), x-ray diffraction, Auger electron spectroscopy, and TEM energy dispersive x-ray spectroscopy. From the viewpoint of practical sensing applications, hydrogen postannealing of the Pt-Ti-O gate Si-MISFETs is necessary to reduce the residual sensing amplitudes with long tailing profiles.

  18. Strongly coupled hybrid nanostructures for selective hydrogen detection - understanding the role of noble metals in reducing cross-sensitivity

    NASA Astrophysics Data System (ADS)

    Liu, Bin; Cai, Daoping; Liu, Yuan; Wang, Dandan; Wang, Lingling; Xie, Wuyuan; Li, Qiuhong; Wang, Taihong

    2014-04-01

    Noble metal-semiconductor hybrid nanostructures can offer outperformance to gas sensors in terms of sensitivity and selectivity. In this work, a catalytically activated (CA) hydrogen sensor is realized based on strongly coupled Pt/Pd-WO3 hybrid nanostructures constructed by a galvanic replacement participated solvothermal procedure. The room-temperature operation and high selectivity distinguish this sensor from the traditional ones. It is capable of detecting dozens of parts per million (ppm) hydrogen in the presence of thousands of ppm methane gas. An insight into the role of noble metals in reducing cross-sensitivity is provided by comparing the sensing properties of this sensor with a traditional thermally activated (TA) one made from the same pristine WO3. Based on both experimental and density functional theory (DFT) calculation results, the cross-sensitivity of the TA sensor is found to have a strong dependence on the highest occupied molecular orbital (HOMO) level of the hydrocarbon molecules. The high selectivity of the CA sensor comes from the reduced impact of gas frontier orbitals on the charge transfer process by the nano-scaled metal-semiconductor (MS) interface. The methodology demonstrated in this work indicates that rational design of MS hybrid nanostructures can be a promising strategy for highly selective gas sensing applications.Noble metal-semiconductor hybrid nanostructures can offer outperformance to gas sensors in terms of sensitivity and selectivity. In this work, a catalytically activated (CA) hydrogen sensor is realized based on strongly coupled Pt/Pd-WO3 hybrid nanostructures constructed by a galvanic replacement participated solvothermal procedure. The room-temperature operation and high selectivity distinguish this sensor from the traditional ones. It is capable of detecting dozens of parts per million (ppm) hydrogen in the presence of thousands of ppm methane gas. An insight into the role of noble metals in reducing cross

  19. Metal-containing fluoropolymer films produced by simultaneous plasma etching and polymerization: Effects of hydrogen or oxygen

    NASA Astrophysics Data System (ADS)

    Kay, E.; Dilks, A.; Seybold, D.

    1980-11-01

    The formation of metal-containing fluoropolymer films by simultaneous plasma etching and polymerization in a radiofrequency diode reactor configuration is investigated as a function of additive scavenger gases. The addition of oxygen to plasmas excited in tetrafluoroethylene or perfluoropropane is found to enhance the etching rate at the excitation metal electrode and diminish the polymer film deposition rate at the grounded electrode. The overall effect is to increase the metal content of the films. The addition of hydrogen to plasmas excited in tetrafluoromethane or perfluoropropane has the opposite effect. X-ray photoelectron spectroscopy is employed to determine the composition and structure of the films, and this coupled with mass spectrometric analysis of the plasma gas phase chemistry has allowed the identification of the likely precursors to plasma polymerization for the systems studied.

  20. Measuring Permeability of Composite Cryotank Laminants

    NASA Technical Reports Server (NTRS)

    Oliver, Stanley T.; Selvidge, Shawn; Watwood, Michael C.

    2004-01-01

    This paper describes a test method developed to identify whether certain materials and material systems are suitable candidates for large pressurized reusable cryogenic tanks intended for use in current and future manned launch systems. It provides a quick way to screen numerous candidate materials for permeability under anticipated loading environments consistent with flight conditions, as well as addressing reusability issues. cryogenic tank, where the major design issue was hydrogen permeability. It was successfully used to evaluate samples subjected to biaxial loading while maintaining test temperatures near liquid hydrogen. After each sample was thermally preconditioned, a cyclic pressure load was applied to simulate the in-plane strain. First permeability was measured while a sample was under load. Then the sample was unloaded and allowed to return to ambient temperature. The test was repeated to simulate reusability, in order to evaluate its effects on material permeability.