Showing papers on "Hydrogen storage published in 2006"
TL;DR: Use of the tritopic bridging ligand 1,3,5-benzenetristetrazolate (BTT3-) enables formation ofDMF, featuring a porous metal-organic framework with a previously unknown cubic topology.
Abstract: 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.
1,057 citations
TL;DR: In this paper, a hydrogen storage system using a metal-organic framework is described, where each metal cluster includes one or more metal ions and at least one open metal site, and the metal clusters are connected by charged multidentate linking ligands connecting adjacent metal clusters.
Abstract: A gas storage material contains a metal-organic framework that includes a plurality of metal clusters and a plurality of charged multidentate linking ligands that connect adjacent metal clusters. Each metal cluster includes one or more metal ions and at least one open metal site. The metal-organic framework includes one or more sites for storing molecular hydrogen. A hydrogen storage system using the hydrogen storage material is provided.
1,047 citations
TL;DR: It is demonstrated that for maximum delivery of the gas the optimum adsorbent must be homogeneous, and that introduction of heterogeneity, such as by ball milling, irradiation, and other means, can only provide small increases in physisorption-related delivery for hydrogen.
Abstract: The storage of gases in porous adsorbents, such as activated carbon and carbon nanotubes, is examined here thermodynamically from a systems viewpoint, considering the entire adsorption-desorption cycle. The results provide concrete objective criteria to guide the search for the "Holy Grail" adsorbent, for which the adsorptive delivery is maximized. It is shown that, for ambient temperature storage of hydrogen and delivery between 30 and 1.5 bar pressure, for the optimum adsorbent the adsorption enthalpy change is 15.1 kJ/mol. For carbons, for which the average enthalpy change is typically 5.8 kJ/mol, an optimum operating temperature of about 115 K is predicted. For methane, an optimum enthalpy change of 18.8 kJ/mol is found, with the optimum temperature for carbons being 254 K. It is also demonstrated that for maximum delivery of the gas the optimum adsorbent must be homogeneous, and that introduction of heterogeneity, such as by ball milling, irradiation, and other means, can only provide small increases in physisorption-related delivery for hydrogen. For methane, heterogeneity is always detrimental, at any value of average adsorption enthalpy change. These results are confirmed with the help of experimental data from the literature, as well as extensive Monte Carlo simulations conducted here using slit pore models of activated carbons as well as atomistic models of carbon nanotubes. The simulations also demonstrate that carbon nanotubes offer little or no advantage over activated carbons in terms of enhanced delivery, when used as storage media for either hydrogen or methane.
932 citations
744 citations
TL;DR: In this article, the charge storage mechanism of manganese oxide and activated carbon has been studied in aqueous medium in order to optimise an asymmetric (or hybrid) supercapacitor based on these two materials as positive and negative electrode, respectively.
695 citations
679 citations
TL;DR: In this article, the authors provide an overview of experimental work on such systems together with an outline of theoretical studies that have been undertaken to estimate the practical limits to the amount of hydrogen that could be stored per unit weight.
654 citations
TL;DR: In this paper, hydrogen adsorption in two different metal-organic frameworks (MOFs), MOF-5 and Cu-BTC (BTC: benzene-1,3,5-tricarboxylate), with Zn2+ and Cu2+ as central metal ions, were investigated at temperatures ranging from 77 K to room temperature.
Abstract: Hydrogen adsorption in two different metal–organic frameworks (MOFs), MOF-5 and Cu-BTC (BTC: benzene-1,3,5-tricarboxylate), with Zn2+ and Cu2+ as central metal ions, respectively, is investigated at temperatures ranging from 77 K to room temperature. The process responsible for hydrogen storage in these MOFs is pure physical adsorption with a heat of adsorption of approximately –4 kJ mol–1. With a saturation value of 5.1 wt.-% for the hydrogen uptake at high pressures and 77 K, MOF-5 shows the highest storage capacity ever reported for crystalline microporous materials. However, at low pressures Cu-BTC shows a higher hydrogen uptake than MOF-5, making Cu-based MOFs more promising candidates for potential storage materials. Furthermore, the hydrogen uptake is correlated with the specific surface area for crystalline microporous materials, as shown for MOFs and zeolites.
612 citations
TL;DR: NMR studies in conjunction with DFT/GIAO chemical shift calculations indicate that both polyaminoborane and the diammoniate of diborane, [(NH3)2BH2+]BH4-, are initial products in the reactions.
Abstract: Ionic liquids are shown to provide advantageous media for amineborane-based chemical hydrogen storage systems. Both the extent and rate of hydrogen release from ammonia borane dehydrogenation are significantly increased at 85, 90, and 95 degrees C when the reactions are carried out in 1-butyl-3-methylimidazolium chloride compared to analogous solid-state reactions. NMR studies in conjunction with DFT/GIAO chemical shift calculations indicate that both polyaminoborane and the diammoniate of diborane, [(NH3)2BH2+]BH4-, are initial products in the reactions.
580 citations
TL;DR: Using density functional theory, it is found that an isolated Li(12)C(60) cluster where Li atoms are capped onto the pentagonal faces of the fullerene not only is very stable but also can store up to 120 hydrogen atoms in molecular form with a binding energy of 0.075 eV/H(2).
Abstract: Solid state materials capable of storing hydrogen with high gravimetric (9 wt %) and volumetric density (70 g/L) are critical for the success of a new hydrogen economy. In addition, an ideal storage system should be able to operate under ambient thermodynamic conditions and exhibit fast hydrogen sorption kinetics. No materials are known that meet all these requirements. While recent theoretical efforts showed some promise for transition-metal-coated carbon fullerenes, later studies demonstrated that these metal atoms prefer to cluster on the fullerene surface, thus reducing greatly the weight percentage of stored hydrogen. Using density functional theory we show that Li-coated fullerenes do not suffer from this constraint. In particular, we find that an isolated Li12C60 cluster where Li atoms are capped onto the pentagonal faces of the fullerene not only is very stable but also can store up to 120 hydrogen atoms in molecular form with a binding energy of 0.075 eV/H2. In addition, the structural integrity ...
509 citations
TL;DR: Substantially increased hydrogen storage capacities of modified MOFs are reported by using a simple technique that causes and facilitates hydrogen spillover.
Abstract: The possible utilization of hydrogen as the energy source for fuel-cell vehicles is limited by the lack of a viable hydrogen storage system. Metal−organic frameworks (MOFs) belong to a new class of microporous materials that have recently been shown to be potential candidates for hydrogen storage; however, no significant hydrogen storage capacity has been achieved in MOFs at ambient temperature. Here we report substantially increased hydrogen storage capacities of modified MOFs by using a simple technique that causes and facilitates hydrogen spillover. Thus, the storage of 4 wt % is achieved at room temperature and 100 atm for the modified IRMOF-8. The adsorption is reversible, and the rates are fast. That has made MOFs truly promising for hydrogen storage application.
TL;DR: The United States Department of Energy has established three centers of excellence for hydrogen storage materials development as mentioned in this paper, focusing on complex metal hydrides that can be regenerated onboard a vehicle, chemical hydride that require off-board reprocessing, and carbon-based storage materials.
TL;DR: This work reports, for the first time, significant amounts of hydrogen storage in MOF-5 and IRMOF-8 at ambient temperature by using a very simple technique via hydrogen dissociation and spillover, and suggests that the technique is suitable for hydrogenstorage in a variety of MOF materials because of their similar structures.
Abstract: The utilization of hydrogen in fuel-cell powered vehicles is limited by the lack of a safe and effective system for hydrogen storage. At the present time, there is no viable storage technology capable of meeting the DOE targets. Porous metal-organic frameworks (MOFs) are novel and potential candidates for hydrogen storage. Until now it is still not possible to achieve any significant hydrogen storage capacity in MOFs at ambient temperature. Here, we report, for the first time, significant amounts of hydrogen storage in MOF-5 and IRMOF-8 at ambient temperature by using a very simple technique via hydrogen dissociation and spillover. Thus, hydrogen uptakes for MOF-5 and IRMOF-8 can be enhanced by a factor of 3.3 and 3.1, respectively (to nearly 2 wt % at 10 MPa and 298 K). Furthermore, the isotherms are totally reversible. These findings suggest that our technique is suitable for hydrogen storage in a variety of MOF materials because of their similar structures as MOF-5 and IRMOF-8.
TL;DR: Three structurally diverse polymers of intrinsic microporosity reversibly adsorb significant quantities of hydrogen and represent the first examples of a new type of purely organic hydrogen storage material, which can be tailored to meet the specific requirements of hydrogen physisorption.
Abstract: Three structurally diverse polymers of intrinsic microporosity reversibly adsorb significant quantities of hydrogen (1.4–1.7 % by mass at 77 K) and represent the first examples of a new type of purely organic hydrogen storage material, which can be tailored to meet the specific requirements of hydrogen physisorption.
TL;DR: In this paper, the authors review the current technology for the storage of hydrogen on board a fuel cell-propelled vehicle and outline the inherent difficulties with gas pressure and liquid hydrogen storage, leading to the development of metal hydride batteries.
TL;DR: In this paper, metal ammine salts were proposed as safe, reversible, high-density and low-cost hydrogen carriers, which could provide a platform for using ammonia as a fuel for the hydrogen economy.
TL;DR: The results verify in both theoretical levels that SiCNTs seem to be more suitable materials for hydrogen storage than pure CNTs.
Abstract: A multiscale theoretical approach is used for the investigation of hydrogen storage in silicon-carbon nanotubes (SiCNTs). First, ab initio calculations at the density functional level of theory (DFT) showed an increase of 20% in the binding energy of H2 in SiCNTs compared with pure carbon nanotubes (CNTs). This is explained by the alternative charges that exist in the SiCNT walls. Second, classical Monte Carlo simulation of nanotube bundles showed an even larger increase of the storage capacity in SiCNTs, especially in low temperature and high-pressure conditions. Our results verify in both theoretical levels that SiCNTs seem to be more suitable materials for hydrogen storage than pure CNTs.
TL;DR: It has been demonstrated that the bismuth sulfide's morphology and the constant charge-discharge current density had a noticeable influence on their capacity of electrochemical hydrogen storage.
Abstract: Bi2S3 flowerlike patterns with well-aligned nanorods were synthesized using a facile solution-phase biomolecule-assisted approach in the presence of L-cysteine (an ordinary and cheap amino acid), which turned out to serve as both the S source and the directing molecule in the formation of bismuth sulfide nanostructures. Emphatically, no nauseous scent (H2S) appeared in our experiments, which could not be avoided in other previous reports. The morphology, structure, and phase composition of the as-prepared Bi2S3 products were characterized using various techniques (scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, selected area electron diffraction, and high-resolution transmission electron microscopy). The formation mechanism for the bismuth sulfide flowerlike assemblies with well-arranged nanorods was also discussed. In addition, other Bi2S3 homogeneous nanostructures (e.g., networklike nanoflakes, nanorod-based bundles, and nanoflakes) were obtained through varying the experimental parameters. Interestingly, we have found that these synthesized bismuth sulfide nanostructures using the biomoleucle-assisted approach could electrochemically charge and discharge with the capacity of 142 (mA h)/g (corresponding to 0.51 wt % hydrogen in single-walled carbon nanotubes) under normal atmosphere at room temperature. A novel two-plateau phenomenon was observed in the synthesized Bi2S3 nanostructures, suggesting that there were two independent steps in the charging process. It has been demonstrated that the bismuth sulfide's morphology and the constant charge-discharge current density had a noticeable influence on their capacity of electrochemical hydrogen storage. These differences in hydrogen storage capacity are likely due to the size and density of space/pores as well as the morphology of different Bi2S3 nanostructures. The novel Bi2S3 nanomaterials may find potential applications in hydrogen storage, high-energy batteries, luminescence, optoelectronic and catalytic fields, as well as in the studies of structure-property relationships. This facile, environmentally benign, and solution-phase biomolecule-assisted method can be potentially extended to the preparation of other metal chalcogenides including FeS, CuS, NiS, PbS, MnS, and CoS nanostructures.
TL;DR: In this article, a series of nanoporous synthetic polymers has been studied for hydrogen adsorption, including hypercrosslinked Hypersol-Macronet MN200 resins.
Abstract: Hydrogen adsorption using a series of nanoporous synthetic polymers has been studied. Promising results were obtained during the screening of commercially available porous polymer beads; of the polymers considered, hypercrosslinked Hypersol-Macronet MN200 resin exhibited the highest adsorption capacity for hydrogen. This initial success triggered the development of our own high surface area hypercrosslinked materials. Subjecting gel-type and macroporous vinylbenzyl chloride-based precursors swollen in dichloroethane to a Friedel−Crafts reaction catalyzed by iron trichloride afforded beads with surface areas of 1 930 and 1 300 m2/g, respectively, as calculated using the BET equation. The former polymer reversibly stores up to 1.5 wt % H2 at a pressure of 0.12 MPa and a temperature of 77.3 K. The initial heat of adsorption of hydrogen molecules onto this polymer is 6.6 kJ/mol.
TL;DR: In this paper, the authors predict that a single ethylene molecule can form a stable complex with two transition metals (TM) such as Ti, and the resulting TM-ethylene complex then absorbs up to ten hydrogen molecules, reaching to gravimetric storage capacity.
Abstract: From first-principles calculations, we predict that a single ethylene molecule can form a stable complex with two transition metals (TM) such as Ti. The resulting TM-ethylene complex then absorbs up to ten hydrogen molecules, reaching to gravimetric storage capacity of $\ensuremath{\sim}14\text{ }\text{ }\mathrm{wt}\text{ }%$. Dimerization, polymerizations, and incorporation of the TM-ethylene complexes in nanoporous carbon materials are also discussed. Our results are quite remarkable and open a new approach to high-capacity hydrogen-storage materials discovery.
TL;DR: First principles density functional theory calculations are used to predict the reaction enthalpies for more than 100 destabilization reactions that have not previously been reported, identifying five promising reaction schemes that merit experimental study.
Abstract: Hydrides of period 2 and 3 elements are promising candidates for hydrogen storage but typically have heats of reaction that are too high to be of use for fuel cell vehicles. Recent experimental wor...
TL;DR: In this paper, the authors developed a dehydrogenation catalyst using a simple fixed-bed reactor that has a high stability and sufficient performance, which can generate hydrogen from methylcyclohexane with a conversion > 95 %, toluene selectivity > 99.9 %, hydrogen generation rate > 1000 Nm 3 / h / m 3 cat under the reasonable conditions of 593 K, ambient pressure, LHSV:2.0/h and co-feed hydrogen 5-20% in the feed.
TL;DR: The findings show that zeolite-templated carbons are attractive for hydrogen storage and highlight the potential benefits of functionalization (nitrogen-doping).
Abstract: Carbon materials have been prepared using zeolite 13X or zeolite Y as template and acetonitrile or ethylene as carbon source via chemical vapor deposition (CVD) at 550-1000 degrees C. Materials obtained from acetonitrile at 750-850 degrees C (zeolite 13X) or 750-900 degrees C (zeolite Y) have high surface area (1170-1920 m(2)/g), high pore volume (0.75-1.4 cm(3) g(-1)), and exhibit some structural ordering replicated from the zeolite templates. Templating with zeolite Y generally results in materials with higher surface area. High CVD temperature (> or =900 degrees C) results in low surface area materials that have significant proportions of graphitic carbon and no zeolite-type structural ordering. The nitrogen content of the samples derived from acetonitrile varies between 5 and 8 wt %. When ethylene is used as a carbon precursor, high surface area (800-1300 m(2)/g) materials are only obtained at lower CVD temperature (550-750 degrees C). The ethylene-derived carbons retain some zeolite-type pore channel ordering but also exhibit significant levels of graphitization even at low CVD temperature. In general, the carbon materials retain the particle morphology of the zeolite templates, with solid-core particles obtained at 750-850 degrees C while hollow shells are generated at higher CVD temperature (> or =900 degrees C). We observed hydrogen uptake of up to 4.5 wt % and 45 g H(2)/L (volumetric density) at -196 degrees C and 20 bar for the carbon materials. The hydrogen uptake was found to be dependent on surface area and was therefore influenced by the choice of zeolite template and carbon source. Zeolite Y-templated N-doped carbons had the highest hydrogen uptake capacity. Gravimetric and volumetric methods gave similar uptake capacity at 1 bar (i.e., 1.6 and 2.0 wt % for zeolite 13X and Y-templated N-doped carbons, respectively). Our findings show that zeolite-templated carbons are attractive for hydrogen storage and highlight the potential benefits of functionalization (nitrogen-doping).
TL;DR: The reversible hydrogen storage capacity of the oxide-modified lithium borohydrides decreased gradually during hydriding/dehydriding cycling, but this can be prevented by changing the dehydriding path using appropriate additives.
Abstract: In an attempt to develop lithium borohydrides as reversible hydrogen storage materials with high hydrogen storage capacities, the feasibility of reducing the dehydrogenation temperature of the lithium borohydride and moderating rehydrogenation conditions was explored The lithium borohydride was modified by ball milling with metal oxides and metal chlorides as additives The modified lithium borohydrides released 9 wt % hydrogen starting from 473 K The dehydrided modified lithium borohydrides absorbed 7-9 wt % hydrogen at 873 K and 7 MPa The modification with additives reduced the dehydriding starting temperature from 673 to 473 K and moderated the rehydrogenation conditions from 923 K/15 MPa to 873 K/7 MPa XRD and SEM analysis revealed the formation of an intermediate compound that might play a key role in changing the reaction path, resulting in the lower dehydriding temperature and reversibility The reversible hydrogen storage capacity of the oxide-modified lithium borohydrides decreased gradually during hydriding/dehydriding cycling One of the possible reasons for this effect might be the loss of boron during dehydrogenation, but this can be prevented by changing the dehydriding path using appropriate additives The additives reduced the dehydriding temperature and improved the reversibility, but they also reduced the hydrogen storage capacity The best compromise can be reached by selecting appropriate additives, optimizing the additive loading, and using new synthesis processes other than ball milling
TL;DR: The catalytic mechanisms of transition-metal compounds during the hydrogen sorption reaction of magnesium-based hydrides were investigated through relevant experiments and found to be influenced by four distinct physico-thermodynamic properties.
Abstract: The catalytic mechanisms of transition-metal compounds during the hydrogen sorption reaction of magnesium-based hydrides were investigated through relevant experiments. Catalytic activity was found to be influenced by four distinct physico-thermodynamic properties of the transition-metal compound: a high number of structural defects, a low stability of the compound, which however has to be high enough to avoid complete reduction of the transition metal under operating conditions, a high valence state of the transition-metal ion within the compound, and a high affinity of the transition-metal ion to hydrogen. On the basis of these results, further optimization of the selection of catalysts for improving sorption properties of magnesium-based hydrides is possible. In addition, utilization of transition-metal compounds as catalysts for other hydrogen storage materials is considered.
TL;DR: These data clearly demonstrate a significant interaction of hydrogen with doped polyaniline and may be relevant to recent claims of hydrogen storage by polyanile, as well as a deuterium isotope effect on the sensor response.
Abstract: Hydrogen causes a reversible decrease in the resistance of a thin film of camphorsulfonic acid doped polyaniline nanofibers. For a 1% mixture of hydrogen in nitrogen, a 3% decrease in resistance is observed (DeltaR/R = -3%). The hydrogen response is completely suppressed in the presence of humidity. In contrast, oxygen does not inhibit the hydrogen response. A deuterium isotope effect on the sensor response is observed in which hydrogen gives a larger response than deuterium: (DeltaR/R)H/(DeltaR/R)D = 4.1 +/- 0.4. Mass sensors using nanofiber films on a quartz crystal microbalance also showed a comparable deuterium isotope effect: DeltamH/DeltamD = 2.3 +/- 0.2 or DeltanH/DeltanD = 4.6 +/- 0.4 on a molar basis. The resistance change of polyaniline nanofibers is about an order of magnitude greater than conventional polyaniline, consistent with a porous, high-surface-area nanofibrillar film structure that allows for better gas diffusion into the film. A plausible mechanism involves hydrogen bonding to the amine nitrogens along the polyaniline backbone and subsequent dissociation. The inhibitory effect of humidity is consistent with a stronger interaction of water with the polyaniline active sites that bind to hydrogen. These data clearly demonstrate a significant interaction of hydrogen with doped polyaniline and may be relevant to recent claims of hydrogen storage by polyaniline.
TL;DR: Thermogravimetric analysis and X-ray thermodiffractometry indicate that MIL-102 is stable up to approximately 300 degrees C and shows zeolitic behavior and a hydrogen storage capacity of approximately 1.0 wt % at 77 K when loaded at 3.5 MPa.
Abstract: A new three-dimensional chromium(III) naphthalene tetracarboxylate, CrIII3O(H2O)2F{C10H4(CO2)4}1.5·6H2O (MIL-102), has been synthesized under hydrothermal conditions from an aqueous mixture of Cr(NO3)3·9H2O, naphthalene-1,4,5,8-tetracarboxylic acid, and HF. Its structure, solved ab initio from X-ray powder diffraction data, is built up from the connection of trimers of trivalent chromium octahedra and tetracarboxylate moieties. This creates a three-dimensional structure with an array of small one-dimensional channels filled with free water molecules, which interact through hydrogen bonds with terminal water molecules and oxygen atoms from the carboxylates. Thermogravimetric analysis and X-ray thermodiffractometry indicate that MIL-102 is stable up to ∼300 °C and shows zeolitic behavior. Due to topological frustration effects, MIL-102 remains paramagnetic down to 5 K. Finally, MIL-102 exhibits a hydrogen storage capacity of ∼1.0 wt % at 77 K when loaded at 3.5 MPa (35 bar). The hydrogen uptake is discussed...
TL;DR: In this article, the authors investigated the kinetic energy of hydrogen absorption and desorption reactions on the MgH 2 composite doped with 1/mol% Nb 2 O 5 as a catalyst by ballmilling.
TL;DR: Hydrogen storage was not increased upon decreasing the THF concentration below the stoichiometric 5.6 mol % solution to 0.5 mol %, at constant pressure, even after one week, providing strong evidence that THF preferentially occupies the large 5(12)6(4) cavity over hydrogen, for the range of experimental conditions tested.
Abstract: The hydrogen storage capacity of binary THF−H2 clathrate hydrate has been determined as a function of formation pressure, THF composition, and time. The amount of hydrogen stored in the stoichiomet...