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Showing papers on "Hydrogen storage published in 2004"


Journal ArticleDOI
TL;DR: The future of a particularly promising class of materials for hydrogen storage, namely the catalytically enhanced complex metal hydrides, is discussed and the predictions are supported by thermodynamics considerations, calculations derived from molecular orbital (MO) theory and backed up by simple chemical insights and intuition.
Abstract: This review focuses on key aspects of the thermal decomposition of multinary or mixed hydride materials, with a particular emphasis on the rational control and chemical tuning of the strategically important thermal decomposition temperature of such hydrides, Tdec. An attempt is also made to predict the thermal stability of as-yet unknown, elusive or even unknown hydrides. The future of a particularly promising class of materials for hydrogen storage, namely the catalytically enhanced complex metal hydrides, is discussed. The predictions are supported by thermodynamics considerations, calculations derived from molecular orbital (MO) theory and backed up by simple chemical insights and intuition.

1,404 citations


Journal ArticleDOI
TL;DR: This paper reviews the various storage methods for hydrogen and highlights their potential for improvement and their physical limitations.
Abstract: Hydrogen exhibits the highest heating value per mass of all chemical fuels. Furthermore, hydrogen is regenerative and environmentally friendly. There are two reasons why hydrogen is not the major fuel of today’s energy consumption. First of all, hydrogen is just an energy carrier. And, although it is the most abundant element in the universe, it has to be produced, since on earth it only occurs in the form of water and hydrocarbons. This implies that we have to pay for the energy, which results in a difficult economic dilemma because ever since the industrial revolution we have become used to consuming energy for free. The second difficulty with hydrogen as an energy carrier is its low critical temperature of 33 K (i.e. hydrogen is a gas at ambient temperature). For mobile and in many cases also for stationary applications the volumetric and gravimetric density of hydrogen in a storage material is crucial. Hydrogen can be stored using six different methods and phenomena: (1) high-pressure gas cylinders (up to 800 bar), (2) liquid hydrogen in cryogenic tanks (at 21 K), (3) adsorbed hydrogen on materials with a large specific surface area (at T<100 K), (4) absorbed on interstitial sites in a host metal (at ambient pressure and temperature), (5) chemically bonded in covalent and ionic compounds (at ambient pressure), or (6) through oxidation of reactive metals, e.g. Li, Na, Mg, Al, Zn with water. The most common storage systems are high-pressure gas cylinders with a maximum pressure of 20 MPa (200 bar). New lightweight composite cylinders have been developed which are able to withstand pressures up to 80 MPa (800 bar) and therefore the hydrogen gas can reach a volumetric density of 36 kg·m−3, approximately half as much as in its liquid state. Liquid hydrogen is stored in cryogenic tanks at 21.2 K and ambient pressure. Due to the low critical temperature of hydrogen (33 K), liquid hydrogen can only be stored in open systems. The volumetric density of liquid hydrogen is 70.8 kg·m−3, and large volumes, where the thermal losses are small, can cause hydrogen to reach a system mass ratio close to one. The highest volumetric densities of hydrogen are found in metal hydrides. Many metals and alloys are capable of reversibly absorbing large amounts of hydrogen. Charging can be done using molecular hydrogen gas or hydrogen atoms from an electrolyte. The group one, two and three light metals (e.g. Li, Mg, B, Al) can combine with hydrogen to form a large variety of metal–hydrogen complexes. These are especially interesting because of their light weight and because of the number of hydrogen atoms per metal atom, which is two in many cases. Hydrogen can also be stored indirectly in reactive metals such as Li, Na, Al or Zn. These metals easily react with water to the corresponding hydroxide and liberate the hydrogen from the water. Since water is the product of the combustion of hydrogen with either oxygen or air, it can be recycled in a closed loop and react with the metal. Finally, the metal hydroxides can be thermally reduced to metals in a solar furnace. This paper reviews the various storage methods for hydrogen and highlights their potential for improvement and their physical limitations.

747 citations


Journal ArticleDOI
TL;DR: A novel MMOM structure and its room-temperature hydrogen adsorption properties are reported and it is reported that these materials possess physical characteristics similar to those of single-walled carbon nanotubes but also exhibit a number of improved features.
Abstract: Advancement in hydrogen storage techniques represents one of the most important areas of today's materials research. While extensive efforts have been made to the existing techniques, there is no viable storage technology capable of meeting the DOE cost and performance targets at the present time. New materials with significantly improved hydrogen adsorption capability are needed. Microporous metal coordination materials (MMOM) are promising candidates for use as sorbents in hydrogen adsorption. These materials possess physical characteristics similar to those of single-walled carbon nanotubes (SWNTs) but also exhibit a number of improved features. Here, we report a novel MMOM structure and its room-temperature hydrogen adsorption properties.

615 citations


Journal ArticleDOI
TL;DR: This review will discuss the different possibilities for chemical storage of hydrogen and the focus on the presently most advanced system with respect to storage capacity and kinetics, i.e. catalyzed alanates, especially NaAlH(4).

592 citations


Journal ArticleDOI
TL;DR: In this paper, a new storage material has been developed, which is from the partial substitution of lithium by magnesium in the nitride/imide system, with a plateau pressure of about 30bar and 200°C with a H capacity of 4.5% and possibly higher.

477 citations


Journal ArticleDOI
TL;DR: An overview of recent advances in the application of non-carbonaceous nanostructured and composite materials in hydrogen storage is presented in this paper, where the main focus is on complex hydrides, non-graphitic nanotubes, and other porous composite and framework materials.
Abstract: An overview of recent advances in the application of non-carbonaceous nanostructured and composite materials in hydrogen storage is presented in this review. The main focus is on complex hydrides, non-graphitic nanotubes, and other porous composite and framework materials, since carbon nanotubes have been the subject of numerous other reviews. Recent advances in the area of alanates show a promising reversible absorption capability of up to 5 %, closing in on the projected Department of Energy (DOE) target of 6 %. Non-carbon nanotubes mainly showed a sorption capacity of 1–3 wt.-%, although a promising level of 4.2 wt.-% is shown by boron nitride nanotubes after collapse of their walls. Other interesting materials included here are lithium nitride and porous metallo-organic frameworks.

441 citations


Journal ArticleDOI
TL;DR: In this paper, LiH/Si alloying with Si is shown to destabilize the strongly bound hydrides LiH and MgH2, causing the equilibrium hydrogen pressure at 490 °C to increase from approximately 5 × 10-5 to 1 bar.
Abstract: Alloying with Si is shown to destabilize the strongly bound hydrides LiH and MgH2. For the LiH/Si system, a Li2.35Si alloy forms upon dehydrogenation, causing the equilibrium hydrogen pressure at 490 °C to increase from approximately 5 × 10-5 to 1 bar. For the MgH2/Si system, Mg2Si forms upon dehydrogenation, causing the equilibrium pressure at 300 °C to increase from 1.8 to >7.5 bar. Thermodynamic calculations indicate equilibrium pressures of 1 bar at approximately 20 °C and 100 bar at approximately 150 °C. These conditions indicate that the MgH2/Si system, which has a hydrogen capacity of 5.0 wt %, could be practical for hydrogen storage at reduced temperatures. The LiH/Si system is reversible and can be cycled without degradation. Absorption/desorption isotherms, obtained at 400−500 °C, exhibited two distinct flat plateaus with little hysteresis. The plateaus correspond to formation and decomposition of various Li silicides. The MgH2/Si system was not readily reversible. Hydrogenation of Mg2Si appears...

415 citations


Journal ArticleDOI
TL;DR: In this article, Li2NH was modified by adding Ca and Mg in order to form ternary systems, and hydrogen absorption and desorption over these materials were found to take place at much reduced temperatures.
Abstract: Lithium nitride and imide were found to possess remarkable hydrogen storage capacity under moderate temperatures and pressures [1]. For lithium imide, as an example, ~7wt% of hydrogen can be theoretically absorbed. To release hydrogen at equilibrium pressure of one bar, temperature has to be raised to above 270oC, which is on the higher side for practical application. To lower down the operation temperatures, thermodynamic parameters of the material should be altered. Here we report the recent progresses in the development of ternary imides for hydrogen storage. Binary imide, Li2NH, was modified by adding Ca and Mg in order to form ternary systems. Hydrogen absorption and desorption over these materials were found to take place at much reduced temperatures. For Li-Mg-N-H systems temperature as low as 170 oC was achieved. P-C isotherms of the ternary systems have been determined and the structural changes before and after hydrogen storage were investigated.

403 citations


Journal ArticleDOI
TL;DR: In this paper, a hydrogen clathrate hydrate, H2(H2O)2, was synthesized at 200-300 MPa and 240-249 K, which can be preserved to ambient P at 77 K.
Abstract: At low temperature (T) and high pressure (P), gas molecules can be held in ice cages to form crystalline molecular compounds that may have application for energy storage. We synthesized a hydrogen clathrate hydrate, H2(H2O)2, that holds 50 g/liter hydrogen by volume or 5.3 wt %. The clathrate, synthesized at 200–300 MPa and 240–249 K, can be preserved to ambient P at 77 K. The stored hydrogen is released when the clathrate is warmed to 140 K at ambient P. Low T also stabilizes other molecular compounds containing large amounts of molecular hydrogen, although not to ambient P, e.g., the stability field for H2(H2O) filled ice (11.2 wt % molecular hydrogen) is extended from 2,300 MPa at 300 K to 600 MPa at 190 K, and that for (H2)4CH4 (33.4 wt % molecular hydrogen) is extended from 5,000 MPa at 300 K to 200 MPa at 77 K. These unique characteristics show the potential of developing low-T molecular crystalline compounds as a new means for hydrogen storage.

400 citations


Journal ArticleDOI
TL;DR: In this paper, mechanical alloying was used to process powder mixtures of MgH2 with 8 mol % M (M=Al, Ti, Fe, Ni, Ni and Cu) in order to modify hydrogen storage properties of the Mg hydride.

375 citations


Journal ArticleDOI
TL;DR: In this article, a stand-alone renewable energy system based on energy storage as hydrogen has been developed and installed at the Hydrogen Research Institute, and successfully tested for autonomous operation with developed control system and power conditioning devices.
Abstract: Electrolytic hydrogen offers a promising alternative for long-term energy storage of renewable energy (RE). A stand-alone RE system based on energy storage as hydrogen has been developed and installed at the Hydrogen Research Institute, and successfully tested for autonomous operation with developed control system and power conditioning devices. The excess energy produced, with respect to the load requirement, has been sent to the electrolyzer for hydrogen production. When energy produced from the RE sources became insufficient, with respect to the load requirement, the stored hydrogen was fed to a fuel cell to produce electricity. The RE system components have substantially different voltage-current characteristics and they are integrated through power conditioning devices on a dc bus for autonomous operation by using a developed control system. The developed control system has been successfully tested for autonomous operation and energy management of the system. The experimental results clearly indicate that a stand-alone RE system based on hydrogen production is safe and reliable.

Journal ArticleDOI
TL;DR: In this article, the hydrogen storage properties of a ball-milled mixture of 3Mg(NH2)2 and 8LiH after first synthesizing MgNH22 by ball milling MgH2 under an atmosphere of NH3 gas at room temperature were investigated.
Abstract: We have investigated the hydrogen storage properties of a ball-milled mixture of 3Mg(NH2)2 and 8LiH after first synthesizing Mg(NH2)2 by ball milling MgH2 under an atmosphere of NH3 gas at room temperature. The thermal desorption mass spectra of the mixture without any catalysts indicated that a large amount of hydrogen (∼7 wt %) was desorbed from 140 °C, and the desorption peaked at ∼190 °C under a heating rate of 5 °C/min with almost no ammonia emission. Moreover, the reversibility of the hydrogen absorption/desorption reactions was confirmed to be complete. The above results indicate that this system is one of the promising metal−N−H systems for hydrogen storage.

Journal ArticleDOI
TL;DR: A new generation of materials to maximize reversible H2 storage at room temperature and modest pressures is proposed and it is found that the Li pillared graphene sheet system can take up 6.5 mass% of H2 at 20 bars and room temperature, which satisfies the DOE target of hydrogen-storage materials for transportation.
Abstract: We propose a new generation of materials to maximize reversible H2 storage at room temperature and modest pressures ( < 20 bars). We test these materials using grand canonical Monte Carlo simulations with a first-principles-derived force field and find that the Li pillared graphene sheet system can take up 6.5 mass% of H2 (a density of 62: 9k g=m 3 at 20 bars and room temperature. This satisfies the DOE (Department of Energy) target of hydrogen-storage materials for transportation. We also suggest ways to synthesize these systems. In addition we show that Li-doped pillared single-wall nanotubes can lead to a hydrogen-storage capacity of 6.0 mass% and 61: 7k g=m 3 at 50 bars and room temperature storage, which is close to the DOE target.

Journal ArticleDOI
TL;DR: In this article, the basic properties in the 1:1 mixture of lithium amide LiNH2 and lithium hydride LiH as a candidate of reversible hydrogen storage materials were examined.

Journal ArticleDOI
TL;DR: In this article, a systematic investigation of various carbon supports was used to better understand how hydrogen spillover affects hydrogen storage on carbon materials and showed that the baseline adsorption of the carbon was the predominant factor in the magnitude of overall hydrogen uptake.
Abstract: Hydrogen storage in carbon materials can be increased by hydrogen spillover from a supported catalyst; a systematic investigation of various carbon supports was used to better understand how hydrogen spillover affects hydrogen storage on carbon materials. Secondary spillover experiments effectively eliminated experimental variables associated with primary spillover, evidenced by materials clustering around the carbon type for a variety of supported catalyst-carbon mixtures. Providing a supported catalyst to act as a hydrogen source enhances the overall hydrogen uptake of a carbon material; for example, simple mixing of carbon nanotubes with supported palladium increased the uptake of the carbons by a factor of three. However, the baseline adsorption of the carbon was the predominant factor in the magnitude of the overall hydrogen uptake, even when hydrogen spillover was active. Three observations illustrated that a dynamic steady-state model is needed for predictive capacity of hydrogen spillover.

Journal ArticleDOI
TL;DR: In this paper, the role of charging the electrical double layer is carefully considered during the process of hydrogen insertion and deinsertion into carbon, i.e. electroreduction and electrooxidation, respectively.
Abstract: The mechanism of electrochemical hydrogen storage in a nanostructured carbon electrode using the electrodecomposition of KOH and H2SO4 aqueous solutions has been investigated by means of galvanostatic and voltammetry techniques. The role of charging the electrical double layer is carefully considered during the process of hydrogen insertion and deinsertion into carbon, i.e. electroreduction and electrooxidation, respectively. Once the electrode potential becomes lower than the equilibrium potential, hydrogen in the zero oxidation state is formed by the reduction of water in alkaline solution or the reduction of hydronium ions H3O+ in acidic medium. In the next step, hydrogen is physically adsorbed (Had) onto the carbon surface and diffuses into the bulk of the carbon material with an efficiency which depends on the type of electrolyte. A higher amount of hydrogen is stored using the KOH medium, and the galvanostatic oxidation shows a well-defined plateau around -0.5 V vs. Normal Hydrogen Electrode (NHE). Due to the high overvoltage value in KOH (η=0.55 V), the recombination steps of Had leading to molecular hydrogen evolution through the chemical (Tafel) or electrochemical (Heyrovsky) reactions are less favoured than in an H2SO4 medium (η=0.32 V). Hence, a meaningful sorption of hydrogen is observed only in the basic electrolyte which shows a reversible capacity of 350 mA h/g (i.e. 1.3 wt. %) with a good electrical efficiency. Such performance demonstrates that nanostructured activated carbons might be a promising alternative to metallic alloys for electrochemical hydrogen storage.

Journal ArticleDOI
TL;DR: A survey of utilization of boron for hydrogen storage can be found in this paper, where a brief summary of hydrogen storage technology in general and focus on possible uses of BORON and its compounds is presented.


Journal ArticleDOI
TL;DR: The effect of substitutional doping and structural defects on hydrogen adsorption on boron nitride nanotubes has been studied in this article, where the pseudopotential density functional method was used to calculate the binding energy and distance of adsorbed hydrogen.
Abstract: The adsorption of molecular hydrogen on boron nitride nanotubes is studied with the use of the pseudopotential density functional method. The binding energy and distance of adsorbed hydrogen is particularly calculated. It is found that the binding energy of hydrogen on boron nitride nanotubes is increased by as much as $40%$ compared to that on carbon nanotubes, which is attributed to heteropolar bonding in boron nitride. The effect of substitutional doping and structural defects on hydrogen adsorption is also studied and we find a substantial enhancement of the binding energy from that on perfect boron nitride. The current study demonstrates a pathway to the finding of proper media that can hold hydrogen at ambient conditions through physisorption.

Journal ArticleDOI
TL;DR: In this paper, the authors investigated the relationship between BH atomistic vibrations in [BH 4 ] − -anion and melting temperatures of MBH 4 (M=Li, Na, and K) as indexes of hydrogen desorption (decomposition) temperatures.

Patent
06 May 2004
TL;DR: In this paper, a substantially reversible catalytic hydrogenation of extended pi-conjugated substrates is described, in which the hydrogen, contained in the at least partially hydrogenated form of the extended polycyclic aromatic system, can be facilely released for use by a catalytic dehydrogenation of the latter in the presence of a de-hydrogenation catalyst which can be effected by lowering the hydrogen gas pressure, generally to pressures greater than 0.1 bar or raising the temperature to less than 250° C. or less.
Abstract: Processes are provided for the storage and release of hydrogen by means of a substantially reversible catalytic hydrogenation of extended pi-conjugated substrates which include large polycyclic aromatic hydrocarbons, polycyclic aromatic hydrocarbons with nitrogen heteroatoms, polycyclic aromatic hydrocarbons with oxygen heteroatoms, polycyclic aromatic hydrocarbons with alkyl, alkoxy, nitrile, ketone, ether or polyether substituents, pi-conjugated molecules comprising 5 membered rings, pi-conjugated molecules comprising six and five membered rings with nitrogen or oxygen hetero atoms, and extended pi-conjugated organic polymers. The hydrogen, contained in the at least partially hydrogenated form of the extended pi-conjugated system, can be facilely released for use by a catalytic dehydrogenation of the latter in the presence of a dehydrogenation catalyst which can be effected by lowering the hydrogen gas pressure, generally to pressures greater than 0.1 bar or raising the temperature to less than 250° C. or less, or by a combination of these two process parameters.

Journal ArticleDOI
B. Liao1, Y.Q Lei1, L.X. Chen1, Guohua Lu1, H.G. Pan1, Qiuyan Wang1 
TL;DR: In this paper, the effect of La/Mg ratio on the structure and electrochemical properties of La x Mg 3− x Ni 9 (x =16-22) ternary alloys was investigated.

Journal ArticleDOI
TL;DR: In this article, the thermal stability and hydrogen storage properties of Mg-based alloys have been investigated and it was found that mechanical alloying results in a supersaturated solid solution of some elements in the Mg phase.

Journal ArticleDOI
TL;DR: In this paper, the influence of alloying elements on the stability of magnesium dihydride was investigated through calculations of the total energy of the considered systems, and it was shown that the alloying element considered here decrease the heat of formation of (Mg,X)H-2-i.e., destabilizing the hydride with decreasing order of effect from Cu, Ni, Al, Nb, and Fe to Ti.
Abstract: MgH2 is a promising compound for hydrogen storage. Its relatively high stability has been the main obstacle for practical applications. Here, first-principles calculations of MgH2 and MgH2-X (X=Al, Ti, Fe, Ni, Cu, or Nb) were carried out to investigate the influences of selected alloying elements on the stability of the magnesium hydride. The full-potential linearized augmented plane-wave method within the generalized gradient approximation was used in the present study. The influence of alloying elements on the stability of magnesium dihydride was investigated through calculations of the total energy of the considered systems. It was shown that the alloying elements considered here decrease the heat of formation of (Mg,X)H-2-i.e., destabilizing the hydride-with decreasing order of effect from Cu, Ni, Al, Nb, and Fe to Ti. The destabilization of the magnesium hydride by the alloying elements was due to a weakened bonding between magnesium and hydrogen atoms. Hence, the dehydrogenation properties of MgH2 are expected to be improved to a different extent by the addition of alloying elements.

Journal ArticleDOI
TL;DR: In this article, massive ZnO nanowires with the mean diameter of 20 nm have been synthesized by evaporation of metal zinc at 900°C in the quartz tube.
Abstract: Massive ZnO nanowires with the mean diameter of 20 nm have been rapid synthesized by evaporation of metal zinc at 900 °C in the quartz tube. Metal catalyst, graphite additive, and vacuum are not necessary, and, more importantly, it is very convenient and effective for large-scale industrialization. The hydrogen storage characteristics of the synthesized ZnO nanowires are investigated at room temperature. The highest storage capacity of 0.83 wt% is achieved under the pressure of about 3.03 Mpa, and about 71% of the stored hydrogen can be released under ambient pressure at room temperature.

Journal ArticleDOI
Yugang Sun1, Zhanliang Tao1, Jun Chen1, Thurston Herricks1, Younan Xia1 
TL;DR: When the surfaces of Ag nanowires were coated with thin sheaths of Pd/Ag alloys, they exhibited hydrogen absorption/desorption behaviors and capacities similar to those of pure Pd powders or nanotubes.
Abstract: When the surfaces of Ag nanowires were coated with thin sheaths of Pd/Ag alloys, they exhibited hydrogen absorption/desorption behaviors and capacities similar to those of pure Pd powders or nanotubes. The stronger mechanical strengths of these cable-like nanostructures also allowed them to undergo more absorption/desorption cycles with no morphological changes. These nanostructures can be used as a good model system to study the interaction between hydrogen and metal alloys with relatively low concentrations of Pd (<10%) with respect to structural, thermodynamic, and kinetic features.

Journal ArticleDOI
TL;DR: In this paper, the effect of graphitic carbon on the desorption and absorption of MgH2 was examined, and the results showed that graphite poses little influence on the de-sorption properties of the milled powder, but does benefit the absorption process.

Journal ArticleDOI
TL;DR: In this paper, the physicisorption energy of molecular hydrogen on flat carbon nanoparticles (graphitic platelets) and polycyclic aromatic hydrocarbons (PAHs) is determined to be attractive between 3.5 and 7.2 kJ mol−1, depending on the orientation of H2 and on the particle size.
Abstract: The physisorption energy of molecular hydrogen (H2) on flat carbon nanoparticles (graphitic platelets) and polycyclic aromatic hydrocarbons (PAHs) is determined to be attractive between 3.5 and 7.2 kJ mol−1, depending on the orientation of H2 and on the particle size. Entropy, estimated from experimental data, reduces the interaction energy by 3.4 kJ mol−1 at room temperature. Therefore, nanostructured graphitic platelets might be suitable for hydrogen storage. Computations have been carried out for PAHs from benzene to coronene using second order Moller–Plesset (MP2) theory at the basis set limit, and the results are extrapolated to graphene layers.

Journal ArticleDOI
TL;DR: In this paper, the results obtained considering a model of a stand-alone energy system supplied just with renewable sources of energy (RES) composed by an electrolyzer, a hydrogen tank and a proton exchange membrane fuel cell are exposed.

Journal ArticleDOI
B. Liao1, Y.Q Lei1, Chen Leifeng1, Guohua Lu1, H.G. Pan1, Qiuyan Wang1 
TL;DR: The effect of replacing part of the Ni by a metallic element in La 2 MgNi 9 on the structure and electrochemical properties of the thus formed quaternary alloys (M = Co, Mn, Fe, Al, Cu, Sn) was investigated as discussed by the authors.