Showing papers on "Hydrogen storage published in 2000"

Hydrogen storage in single-walled carbon nanotubes

Abstract: We perform density-functional calculations to search for hydrogen adsorption sites and predict maximum storage capacity in single-walled carbon nanotubes. We find two chemisorption sites at top sites of the exterior and the interior of the tube wall. We further find that a form of H2 molecule can exist in an empty space inside nanotubes. The storage capacity of hydrogen in an empty space increases linearly with tube diameter. The maximum storage capacity is limited by the repulsive energies between H2 molecules inside nanotubes and those between H2 molecules and the tube wall. We predict that hydrogen storage capacity in (10,10) nanotube can exceed 14 wt % (160 kg H2/m3).

Catalyzed alanates for hydrogen storage

Abstract: The discovery that hydrogen can be reversibly absorbed and desorbed from complex hydrides (the alanates) by the addition of catalysts has created an entirely new prospect for lightweight hydrogen storage. Unlike the interstitial intermetallic hydrides, these compounds release hydrogen through a series of decomposition/recombination reactions e.g.: NaAlH{sub 4} {Leftrightarrow} 1/3Na{sub 3}AlH{sub 6} + 2/3Al + H{sub 2} {Leftrightarrow} NaH + Al + 3/2H{sub 2}. Initial work resulted in improved catalysts, advanced methods of preparation and a better understanding of the hydrogen absorption and desorption processes. Recent studies have clarified some of the fundamental material properties as well as the engineering characteristics of catalyst enhanced sodium alanate. Phase transitions observed real-time through in situ X-ray powder diffraction demonstrate that the decomposition reactions occur through long-range transport of metal species. SEM imaging and EDS analysis verify aluminum segregation to the surface of the material during decomposition. The equilibrium thermodynamics of decomposition have now been measured down to room temperature. They show a plateau pressure for the first reaction of 1 atm at 33 C, which suggest that, thermodynamically, this material is ideally suited to onboard hydrogen storage for fuel cell vehicles. Room temperature desorption with slow but measurable kinetics has been recorded for the first time. Studies at elevated temperatures (125-165 C), approaching that found in fuel cell operations, were performed on a scaled-up test bed. The bed demonstrated surprisingly good kinetics and other positive material properties. However, these studies also pointed to the need to develop new non-alkoxide based catalysts and doping methods to increase capacity and reduce the level of hydrocarbon impurities found in the desorbed hydrogen. For this reason, new Ti-Cl catalysts and doping processes are being developed which show higher capacities and improved kinetics. An overview of the current state-of-the-art will be presented along with our own studies and the implications for the viability of these materials in on-board hydrogen storage applications.

High Adsorptive Property of Opened Carbon Nanotubes at 77 K

Abstract: Hydrogen adsorption in porous materials is one of the methods actively being studied to store hydrogen on board vehicles driven by fuel cells Recent experiments and numerical simulations have shown that adsorbent materials appropriate to hydrogen storage could be made up of carbon nanotubes In this work we study the properties of such materials By Monte Carlo simulations, we compute the hydrogen adsorption in two arrangements of opened single-walled carbon nanotubes at a temperature of 77 K and pressures up to 15 MPa A quantitative comparison is made between simulation data and experimental results The studied nanotube arrangements seem able to adsorb hydrogen gas in amounts required for their use in fuel cell vehicles

Hydrogen Storage in Single-Walled Carbon Nanotubes at Room Temperature.

Abstract: Masses of single-walled carbon nanotubes (SWNTs) with a large mean diameter of about 1.85 nanometers, synthesized by a semicontinuous hydrogen arc discharge method, were employed for hydrogen adsorption experiments in their as-prepared and pretreated states. A hydrogen storage capacity of 4.2 weight percent, or a hydrogen to carbon atom ratio of 0.52, was achieved reproducibly at room temperature under a modestly high pressure (about 10 megapascal) for a SWNT sample of about 500 milligram weight that was soaked in hydrochloric acid and then heat-treated in vacuum. Moreover, 78.3 percent of the adsorbed hydrogen (3.3 weight percent) could be released under ambient pressure at room temperature, while the release of the residual stored hydrogen (0.9 weight percent) required some heating of the sample. Because the SWNTs can be easily produced and show reproducible and modestly high hydrogen uptake at room temperature, they show promise as an effective hydrogen storage material.

Hydrogen-based ecosystem

Abstract: A complete infrastructure system for the generation (32), storage (34) transportation (35), and delivery (36) of hydrogen which makes a hydrogen ecosystem possible. The infrastructure system utilizes high capacity, low cost, light weight thermal hydrogen storage alloy materials (42) having fast kinetics. Also, a novel hydrogen storage bed design which includes a support/heat-transfer component (41) which is made from a highly porous, high thermal conductivity, solid material such as a high thermal conductivity graphitic foam. Finally a material including at least one particle having atomically engineered local chemical and electronic environments, characterized in that the local environments providing bulk nucleation.

Production of single-walled carbon nanotubes by a hydrogen arc discharge method

Abstract: A method for producing a single-walled carbon nanotube product by a hydrogen arc discharge method includes providing an anode including graphite powder, catalyst metal, and a growth promoter in an atmosphere containing hydrogen; providing a cathode in the atmosphere; and inducing an electric arc across the anode and cathode to thereby consume the anode and produce the single-walled carbon nanotube product Additionally, the single-walled carbon nanotube product may be soaked in an acid or an oxidative reactant and heated under vacuum to produce a hydrogen storage material

Hydrogen Storage and Electrode Properties of V‐Based Solid Solution Type Alloys Prepared by a Thermic Process

Abstract: A vanadium-based solid-solution-type alloy V 4 TiNi 0.65 Co 0.05 Nb 0.047 Ta 0.047 with a large discharge capacity was obtained using a low-cost precursor of V 4 Ni 0.65 Nb 0.047 produced by aluminothermic reduction from V 2 O 5 , Nb 2 O 5 , and Ni, The alloy was deoxidized to a low level by adding mischmetal as a reducing agent when the precursor was alloyed with Ti, Co, and Ta. The alloy showed a hydrogen absorption behavior similar to an alloy prepared from high-purity constituent metals. Moreover, the Mm-Ni-O phase was precipitated as spherical particles along the TiNi network phase in the alloy, remarkably improving the electrode rate capability because of enhanced catalytic ability of the network phase.

Nanoparticles for hydrogen storage, transportation, and distribution

Abstract: This invention uses nanoparticles to broaden the range of economic materials, improve performance across this broader range, and thereby lower costs of hydride and other storage systems. Nanoparticles can have dramatically different mechanical, chemical, electrical, thermodynamic, and/or other properties than their parent (precursor) materials. Because of this fundamental characteristic, nanophase materials can greatly improve the range of possibilities of materials selection, performance, cost, and practicality for hydride storage systems, advancing the early commerciality of such systems for hydrogen fuel cells or other applications. Among such hydrogen storage improvements are cheaper and better-performing metals, alloys, and/or compounds; lower weight; and reduced storage volumes.