WO2004110922A2

WO2004110922A2 - Field-assisted gas storage materials and fuel cells comprising the same

Info

Publication number: WO2004110922A2
Application number: PCT/US2004/017489
Authority: WO
Inventors: William Paul Minnear; Luke Nathaniel Brewer
Original assignee: General Electric Company
Priority date: 2003-06-10
Filing date: 2004-06-03
Publication date: 2004-12-23
Also published as: WO2004110922A3; CN100391827C; KR20060017640A; EP1638885A2; CN1829655A; AU2004247670A1; JP2007513039A; CA2528629A1

Abstract

Field-assisted gas storage materials having improved gas storage density/solubility and improved gas mobility are described. In some embodiments, the gas storage material comprises a material comprising gas storage space and enough ionic character to sustain an electric dipole during application of an applied field, wherein the applied field does not cause the material to become conductive, and wherein a gas is stored within the gas storage space in the material. In other emdodiments, the gas storage material comprises a meterial comprising gas storage space and enough magnetic character to allow magnetic dipoles therein to be enhanced during application of an applied field, and wherein a gas is stored within the gas storage space in the material. In embodiments, the gas is capable of diffusing through the material, and application of a field allows at least one of the following to be controlled: (a) gas solubility; (b) gas uptake; (c) gas discharge; and (d) gas mobility.

Description

FIELD-ASSISTED GAS STORAGE MATERIALS AND FUEL CELLS COMPRISING SAME

FIELD OF THE INVENTION

The present invention relates generally to field-assisted gas storage materials. More specifically, the present invention relates to field-assisted gas storage materials, wherein the gas storage density or solubility and mobility, as well as the uptake and discharge of gas, can all be controlled by application of a field. Even more specifically, the present invention relates to field-assisted hydrogen storage materials, and fuel cells comprising the same, where the hydrogen density or solubility and mobility, as well as the uptake and discharge of hydrogen, can all be controlled by application of a field.

BACKGROUND OF THE INVENTION

Fuel cell technology is a rapidly growing industry with many potentially far-reaching benefits.. The current market for fuel cells is approximately $218 million, an amount that has been projected to rise to $2.4 billion by 2004, and to $7 billion by 2009. If successfully implemented, fuel cell technology is expected to provide, among other benefits, improved national energy security due to reduced reliance on foreign fossil fuels and enhanced air quality due to markedly reduced emission of airborne pollutants.

Fuel cells are capable of extremely efficient energy conversion, and can be used for both transportation and stationary applications. For transportation applications, fuel cell vehicles present a promising alternative to conventional internal combustion engine vehicles. Fuel cell vehicles may be fueled with hydrogen, and emit only water and energy, whereas conventional internal combustion engine vehicles burn fossil fuels such as gasoline or diesel, and emit harmful particulates and greenhouse gases to the atmosphere. There are many additional advantages to fuel cell vehicles. Fuel cell vehicles may be up to three times or more energy efficient than conventional vehicles. Fuel cell vehicles may convert between 40-45% or more of the energy in the provided fuel into power, where conventional internal combustion engine vehicles convert only about 16% of the energy in the provided fuel into power. Additionally, because fuel cell vehicles operate with electric motors that have very few moving parts (i.e., only those pumps and blowers that are needed to provide fuel and coolant), vehicle vibrations and noise will be vastly reduced in fuel cell vehicles, and routine maintenance (i.e., oil changes, spark plug replacement, etc.) will be eliminated.

Fuel cells operate very much like batteries that can be recharged while power is being drawn. However, while batteries are recharged using electricity, fuels cells are recharged using hydrogen. Typically, hydrogen fuel cells operate by converting the chemical energy in hydrogen and oxygen into water, producing electricity and heat, which is then fed into an electric motor that powers the wheels of a fuel cell vehicle.

Hydrogen is considered in the art to be an ideal fuel for fuel cell vehicles. Hydrogen is the most plentiful element in the universe, is the third most plentiful element on Earth, can be derived from multiple renewable energies, and, when consumed as fuel in a fuel cell, produces only water without the production of greenhouse gases such as carbon dioxide. Conventional means of storing hydrogen for end use delivery include: (1) liquid or gaseous hydrogen, (2) hydrocarbon fuels (i.e., fossil fuels), and (3) solid materials (i.e., metal hydrides).

Using liquid or gaseous hydrogen as the energy source in a fuel cell is not ideal. Hydrogen is highly flammable and requires a low hydrogen-to-air concentration for combustion. Furthermore, hydrogen is harder to transport and store than other liquid fuels. Additionally, there is currently only a very limited infrastructure available for distributing hydrogen to the public.

To avoid the disadvantages presented by the use of pure hydrogen as a fuel, many fuel cell designs focus on using hydrocarbon or alcohol fuels, such as methanol, natural gas and petroleum distillates. However, these designs present disadvantages of their own, such as, for example, the need for fuel reformers, which break down the hydrocarbon fuel into hydrogen, carbon dioxide and water. The hydrogen produced by such reformers is not pure, which lowers the efficiency of the fuel cell. Furthermore, adding a reformer to convert hydrocarbon fuel into hydrogen may drop the overall efficiency of the fuel cell to about 30 to 40 percent. Additional disadvantages of using hydrocarbon fuels include: (1) onboard reformers add to the complexity, cost and maintenance of the fuel cell system; (2) if the reformer allows carbon dioxide to reach the fuel cell anode, the performance of the cell will be gradually decreased; and (3) reformers produce greenhouse gases and other air pollutants.

Hydrogen storage materials, which chemically store the hydrogen fuel, are considered to be an advantageous source of hydrogen for fuel cells in a wide range of potential applications. However, getting sufficient hydrogen solubility, storage density, and mobility in such materials has proven to be difficult. Furthermore, the ability to control the rates of hydrogen uptake and release over a broad range of power output for applications such as fuel cells has not yet been achieved. Therefore, improved hydrogen storage materials are desired for a variety of applications, including selective hydrogen separation from other gases, catalysis, and fuel cells for vehicles, personal power generation, and stationary power generation.

Extensive research activity in the past 30 or so years has focused on storing hydrogen in the form of solid metal hydrides. Metal hydrides are typically generated exothermically when metals and alloys are exposed to hydrogen. Most of the hydrogen reacts with these metals and/or alloys and forms new compounds, while a smaller portion of the hydrogen decomposes into atomic hydrogen in the exothermic reaction and subsequently enters interstices in the metal lattice. The hydrogen can be recovered for use from therein by heating, by electrolytic oxidation of the hydride, or by a reaction with an oxide or water. One advantage of using a metal hydride for hydrogen storage is that the volume density for hydrogen storage in metal hydrides is relatively large in comparison to other storage media. However, recovering the hydrogen from the hydride is difficult, as is regenerating the metal. Moreover, the metal adds significant weight to the fuel cell system. Examples of well-known hydrogen storage materials include metal hydrides, such as FeTiH₂ and LaNi₅H₆, which contain about 1.9 and about 1.5 percent by weight hydrogen respectively, that release hydrogen upon heating. Even though FeTiH₂ and LaNi₅H₆ have acceptable recovery temperatures, the hydrogen content in terms of weight percent is too low for use in vehicular fuel cell applications. Other metal hydrides, such as MgH₂ and TiH₂, have higher hydrogen contents, about 7.6 and about 4.0 percent by weight respectively, but must be heated to high temperatures (i.e., above about 100⁰C) in order to recover the hydrogen. Other drawbacks to the use of metal hydrides as gas storage materials include disproportionation, poisoning, accompanying losses of capacity, and the need for regeneration of some of the storage alloys.

Carbon nanotubes are another potential hydrogen storage material that has been studied extensively. Carbon nanotubes are fullerene-related structures that consist of seamless graphite cylinders closed at either end with caps containing pentagonal rings. Carbon nanotube powders tend to pack inefficiently and have poor volumetric efficiency. Furthermore, carbon nanotubes are very expensive to produce, and currently are not available in the quantities that are needed for commercial hydrogen storage applications.

Other well-known hydrogen storage materials include zeolites, which are highly porous crystalline aluminosilicates. However, the hydrogen storage capacity of zeolites, in terms of mass of hydrogen per unit weight of zeolite, is inadequate for vehicular fuel cell applications. Additionally, zeolites must be heated to trigger the release of hydrogen therefrom, and the response time in large cross sections of zeolites is limited by thermal diffusion.

The future hydrogen economy requires efficient ways to store and transport hydrogen for automobile and distributed power fuel cell applications, and numerous other applications. Several methods have been proposed for hydrogen storage, including those discussed above, but currently, none of the materials or methods has demonstrated the desired hydrogen solubility and storage density, hydrogen mobility, and/or hydrogen uptake/release capability needed for commercial applications. Therefore, it would be desirable to have hydrogen storage materials that do not have all the drawbacks of the current hydrogen storage materials.

Additionally, while hydrogen storage materials have been described above, various other gases may also be stored in gas storage materials, and such gas storage materials can be utilized for a variety of purposes, such as for gas separation, emissions sequestration, and drying of gas flows. Improved gas storage materials, capable of storing gas other than hydrogen, are also desired.

Therefore, it would be desirable to have gas storage materials that are light, compact, relatively inexpensive, safe, and easy to use. It would be further desirable to have gas storage materials that provide higher gas solubility (i.e., higher gas storage densities) and higher gas mobility than currently possible. It would also be desirable to have such materials comprise a mechanism that allows the charging/uptake and releasing of gas to be well controlled.

SUMMARY OF THE INVENTION

These and other needs are addressed by embodiments of the present invention. Gas storage materials used in the embodiments described herein include a wide variety of material compositions and types, and are light, compact, relatively inexpensive, safe, easy to use. Moreover, embodiments of the present invention may provide for more efficient and controlled storage and retrieval of gas from gas storage materials, at temperatures below those required by conventional gas storage materials.

Embodiments of this invention comprise gas storage materials having high gas storage density and high gas mobility. These gas storage materials may comprise a material comprising gas storage space and enough ionic character to sustain an electric dipole during application of an applied field, wherein the application of the applied field does not cause the material to become conductive; and a gas stored within the gas storage space in the material, wherein the gas is capable of diffusing through the material. The applied field herein is comprised of an electric field, possibly combined with a stress field or a strain field. Other embodiments of this invention comprise high capacity gas storage materials. These gas storage materials may comprise a material comprising a crystal structure and enough ionic character to sustain an electric dipole during application of an applied field, wherein the application of the applied field does not cause the material to become conductive; and gas stored within the material, wherein the crystal structure comprises a specifically engineered crystal structure that comprises dipoles that allow the engineered crystal structure to hold a predetermined amount of stored gas; and wherein the stored gas bonds with the engineered crystal structure, reducing the free energy of the material, thereby increasing the effective gas solubility of the material. These gas storage materials may further comprise a mechanism for controlling uptake of gas thereto and release of gas therefrom. The mechanism may comprise an applied field (i.e., an electric field, a stress field, a strain field, and combinations of these).

The gas storage materials utilizing an applied electric field may comprise a dielectric material, a piezoelectric material, a ferroelectric material, a ceramic material, a non- metal material, a polymer material, a semiconductor material, and/or any other suitable material.

Yet other embodiments of this invention comprise gas storage materials having a high gas storage density and high gas mobility. These gas storage materials may comprise a material comprising gas storage space and enough magnetic character to allow magnetic dipoles therein to be aligned during application of an applied field; and a gas stored within the gas storage space in the material, wherein the gas is capable of diffusing through the material. The applied field in these embodiments may comprise a magnetic field alone or combined with a stress field, and/or a strain field. These gas storage materials may comprise a magnetic material comprising ferromagnetic elements, wherein the magnetic material is incorporated into a solid-state material, a metal, a ceramic, a polymer, and/or a composite of magnetic and non-magnetic materials.

Still other embodiments of this invention comprise gas storage materials having a high gas storage density and high gas mobility. These gas storage materials may comprise: a material comprising: (a) gas storage space; (b) enough ionic character to sustain an electric dipole during application of an applied electric field; and (c) enough magnetic character to allow magnetic dipoles therein to be enhanced during application of an applied magnetic field; and a gas stored within the gas storage space in the material, wherein the gas is capable of diffusing through the material and wherein application of the applied electric field and the applied magnetic field allows at least one of the following to be controlled: (a) gas solubility of the gas storage material; (b) gas uptake to the gas storage material; (c) gas discharge from the gas storage material; and (d) gas mobility within the gas storage material.

In the gas storage materials of this invention, application of the applied field allows one or more of the following things to be controlled: (a) gas solubility of the gas storage material; (b) gas uptake to the gas storage material; (c) gas discharge from the gas storage material; and (d) gas mobility within the gas storage material.

The gases stored within any of these gas storage materials may comprise hydrogen, a gas with a permanent dipole (i.e., carbon dioxide), a polarizable gas capable of molecular or atomic transport through the storage material (i.e., nitrogen in zeolites), and/or any other suitable gas.

In embodiments of this invention, the average occupancy rate of gas molecules per available gas storage space is greater than about 25%.

The diffusion paths in the gas storage materials of this invention may comprise grain boundaries, porosity (i.e., natural or engineered porosity), defects (i.e., a dislocation in the crystal lattice structure of the material, a planar defect in the crystal lattice structure of the material, a surface impurity, a step in the crystal lattice structure of the material, etc.), intrinsic structure of the gas storage material, and/or bulk of the gas storage material.

In embodiments, the gas storage space or gas storage density may be at least partially created in many ways, such as for example by: (a) chemically altering the crystal lattice structure of the material by substituting aliovalent cations and anions; (b) creating defects in the crystal lattice structure of the material so interstitials exist in sublattices of the material; (c) creating defects in the crystal lattice structure of the material so vacancies exist in sublattices of the material; (d) selectively altering the crystal lattice structure of the material so as to provide gas diffusion paths that allow gas mobility within the material; and/or (e) introducing dipoles into the material via the applied field, or the like.

Other embodiments of this invention comprise fuel cells comprising the gas storage materials discussed above.

Further features, aspects and advantages of the present invention will be more readily apparent to those skilled in the art during the course of the following description, wherein references are made to the accompanying figures which illustrate some preferred forms of the present invention, and wherein like characters of reference designate like parts throughout the drawings.

DESCRIPTION OF THE DRAWINGS

The systems and methods of the present invention are described herein below with reference to various figures, in which:

Figure 1 is a diagram showing the dissociation of molecular hydrogen and its storage in a hydrogen storage material as atomic hydrogen, as utilized in embodiments of this invention;

Figure 2 is a diagram showing the dissociation of molecular hydrogen and its storage in a hydrogen storage material as protonic hydrogen, as utilized in embodiments of this invention; and

Figure 3 is a diagram showing the storage of molecular hydrogen in a hydrogen storage material, as utilized in embodiments of this invention.

DETAILED DESCRIPTION OF THE INVENTION

For the purposes of promoting an understanding of the invention, reference will now be made to some embodiments of the present invention as illustrated in FIGURES 1-3 and specific language used to describe the same. The terminology used herein is for the purpose of description, not limitation. Specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a basis for the claims as a representative basis for teaching one skilled in the art to variously employ the present invention. Any modifications or variations in the depicted support structures and methods of making same, and such further applications of the principles of the invention as illustrated herein, as would normally occur to one skilled in the art, are considered to be within the spirit of this invention.

In accordance with one embodiment of the invention, a gas storage system 8 comprising at least one gas storage material 14 and at least one field 10 applied upon the gas storage material 14 to control the gas solubility of the gas storage material 14, is shown in FIGS 1-3. Typically, although not necessarily, the gas stored within gas storage system 8 comprises hydrogen. Hydrogen comprises ionic hydrogen, molecular hydrogen, atomic hydrogen, deuterium, tritium, any combinations thereof, or the like. Other gases that may be stored in gas storage system 8 comprise Carbon Monoxide, Oxygen, Carbon Dioxide, Nitrogen, Methane, and oxides of nitrogen and sulphur and combinations thereof or any gas that is polar or capable of polarization.

In one embodiment, the gas storage material 14 comprises a dielectric. If the gas storage material 14 is a dielectric material, the at least one field 10 typically comprises an electric field (as depicted in FIGS 1-3), a stress field, a strain field, or combinations thereof. The gas storage system 8 typically comprises additional features such as temperature control mean and pressure control means. In some embodiments, the dielectric material comprises at least one of a piezoelectric, a ferroelectric, a ceramic, a non-metal, an organic material, or a semiconductor material. In the case of a piezoelectric storage material, one embodiment comprises barium titanate. In the case of ceramics, one embodiment comprises V₂O₅. In the case of organic materials, one embodiment comprises polyvinylidene fluoride, (PVDF) or a microporous metal-organic framework.

In another embodiment, the gas storage material 14 comprises a magnetic material, for example a ferromagnetic, a paramagnetic, a diamagnetic, or a ferrimagnetic material. If the gas storage material 14 is a magnetic material, then at least one field 10 typically comprises a magnetic field, possibly in combination with other fields, for example, stress, strain, or electric fields and combinations thereof. In one embodiment, the ferromagnetic material comprises at least one of iron, cobalt, manganese, nickel and combinations, alloys and compounds thereof.

This invention typically relates to gas storage materials comprising a high density of useable hydrogen or other gas storage sites, both per unit mass and per unit volume of storage material. While many of these gas storage sites may comprise low energy lattice or defect sites that exist naturally, or that are created via chemical changes to the crystallographic structure, the gas storage sites are created via field-induced changes to the crystallographic structure of the material. Such changes yield gas storage materials having increased gas mobility and solubility, as well as a gating mechanism for controlling the charging of gas to and the releasing of gas from the crystallographic structure. Additionally, these materials are durable, thermally and chemically stable, and can be made for relatively low cost. As used herein, the term solubility means "the capacity to store a quantity of gas in the bulk of a material, on the surface of a material, or combinations thereof."

The solubility of gas in gas storage materials may be increased by the creation of bonding sites that result from dipoles being created in the crystallographic structures of the gas storage materials. Dipoles may be created or enhanced in such materials by altering the stoichiometry of the base compound. Such alterations may be achieved in numerous ways, such as, for example, by chemically substituting aliovalent cations and anions. In accordance with the instant invention, dipoles may also be created or enhanced in materials via fields (i.e., via stress field, strain fields, and/or via electric and/or magnetic fields). The solubility of a gas in gas storage materials may be enhanced by creating crystallographic defects in the structure of the materials so that interstitials and vacancies exist in the sublattices of the materials. Selective alteration of the crystal structure of a material may also provide easier diffusion paths for the gas. The changes to the structure of some base compounds give rise to local electronic or magnetic dipoles that provide attachment sites for gas. The field- induced and field-enhanced dipoles polarize the gas atom, which gas atom orients itself with respect to the dipole so as to reduce the total free energy of the system. These dipoles attract and hold gas atoms while a field is being applied during charging, and then removal of the field lowers the effective solubility of the gas in the material by eliminating the dipole, thereby causing the gas to be released. Reversal of the field can be employed to drive off residual gases that may be retained by permanent dipoles or that require additional activation for release. Controlling the application of the field serves as a switching or gating mechanism that allows the uptake of gas during charging, and the release of gas during a demand cycle, to be controlled.

While metals and metal hydrides have long been used as hydrogen storage materials, the materials of this invention may prove to be more preferable hydrogen or other gas storage materials. The materials of this invention provide enhanced gas mobility and solubility when used as gas storage materials. For example, most ceramics comprise mainly ionic bonds having centers of positive and negative charge within their structures, but some ceramics (i.e., Al₂O₃, SiC) may also have a substantial amount of covalent bonds that are directional bonds. Metals, on the other hand, comprise metallic bonds (i.e., basically a sea of electrons), while metal hydrides comprise mainly covalent bonds, with some metallic and ionic bonds. Materials that have predominantly ionic or covalent bonds (i.e., ceramics) react to electric fields, and to other ions that are put into the materials, by rearranging their structure, thereby changing the shape, physical structure or electronic structure of the material, without causing the material to become conductive. Materials that have unpaired electrons, particularly certain d- or f- series elements (i.e., Fe, Co, Nd, Sm), will align internal magnetic dipoles in response to a magnetic field. This response will be observed in materials having metallic, ionic or covalent bonding.

In other words, materials having predominantly ionic character (i.e., ceramics) show or have the potential for Van der Waals bonding (i.e., dipole-dipole interactions). Applying electric fields external to such predominantly ionic character materials, this invention enhances the electric dipoles in the material, and encourages Van der Waals-like bonding with a gas, such as hydrogen. The gas responds by polarizing (i.e., shifting the electron orbit), to counter the field-induced dipole, thereby lowering the free energy of the system. In contrast, materials having metal-like conductivity dissipate the applied electric field by the motion of their unbound electrons, thereby precluding electric dipole formation, and making such materials unsuitable for use with an applied electric field.

In other embodiments of this invention, application of a magnetic field, instead of an electric field, may be more desirable to enhance the gas solubility or mobility. For example, when a magnetic field is applied to materials having a significant amount of magnetic character, the permanent magnetic dipoles therein are aligned, thereby increasing the solubility and mobility of the gas that may be stored therein. Hydrogen, having a single, unpaired electron and a single proton, is ideally suited to respond to magnetic fields.

Using fields, for example electric, magnetic, stress and strain fields, to control the uptake and release of gas in the gas storage materials of this invention allows for much quicker response times to be realized than currently possible with typical pressure-activated or temperature-activated gas storage materials. The typical pressure-activated or temperature-activated gas storage materials experience a lag in the response time from when the pressure or temperature is applied. Additionally, the high temperature (>100°C) required for most metal hydrides to discharge the gases stored therein is a problem. In contrast, the gas storage materials of this invention have an essentially instantaneous response time to a field at any temperature, making them ideal for a wide variety of applications, such as for example, vehicular fuel cell applications. The fields herein are potentially used to: (1) increase the solubility of the gas in the gas storage materials, (2) take advantage of the quick response time of the material instead of relying on the thermal diffusivity of the material, (3) throttle the release of gas in proportion to field strength, and (4) allow low temperature desorption of the gas.

Silicate materials, such as micas, zeolites, and vermiculites, are comprised of open channels and layered structures, which allow rapid access of hydrogen or other gas to their interiors along those easy diffusion paths. In materials such as zeolite, the gas is trapped at storage sites within cage-like crystallographic structures defined by polyhedra comprising Si^", Al^", Mg, Na, O^" and F^", for example. Most gas adsorption in zeolites is strongly controlled by internal electric fields such as those described above. These internal electric fields and the structures that support them may be modified by chemically tailoring the crystallographic structure. Additionally, crystal chemical manipulation can alter the size of the gas diffusion paths, alter the size of the storage cages, or alter the electronic state of the storage cages, so the material accepts and holds more gas, even in the absence of an applied field, and allows it to diffuse therethrough more rapidly. Additionally, a field, such as an electric or magnetic field, may be applied to such structures to enhance the gas storage capacity and release capability thereof.

Ferroelectric materials, ferromagnetic materials, piezoelectric materials and dielectric materials in particular, are ideal materials for modifying, either chemically or via application of a field, to enhance the gas storage capacity/solubility and gas mobility thereof, and are also ideal for using a field to control the uptake and release of gas. Piezoelectrics are one type of ceramic material wherein an applied field (i.e., stress, strain or electric field) can induce a large internal dipole. Stress or strain on a piezoelectric material results in a separation of the centers of positive and negative charges leading to a field-induced dipole. This field-induced dipole serves to attract a gas such as hydrogen, which polarizes and arranges itself to form a Van der Waals- like bond, thereby reducing the free energy of the system and counteracting the field- induced dipole. The net effect thereof is an increase of hydrogen solubility in the piezoelectric storage material. Removal, reversal, or decrease of the stress or strain changes the dipole strength and alters, in the desired manner, the hydrogen solubility of the piezoelectric storage material, thereby establishing a gating mechanism for controlling the uptake and release of hydrogen.

The reverse piezoelectric effect may also be used to create a field-induced dipole. In this case, the field may be an electric field, instead of a stress or strain field, which may be more conveniently applied to the piezoelectric material via electrodes attached to the piezoelectric material. Electric fields also produce displacements in the piezoelectric material, along with an attendant induced dipole. Hydrogen in its atomic or protonic form may have higher mobility in certain materials than molecular hydrogen. Therefore, in order to take advantage of this phenomenon, known catalytic materials (i.e., Pd and Pt) for the separation of molecular hydrogen into atomic hydrogen may be employed as the electrodes during application of the electric field. When the electric field is applied, molecular hydrogen is dissociated into atomic hydrogen by the catalytic electrodes, dissolved therein, and transported therethrough to the storage material. Such catalysts may be used, even in the absence of an applied electric field, to transform molecular hydrogen into a more mobile form for transport through the material.

Most ceramics are not known for having high hydrogen diffusivity rates. As moving gas into and out of these gas storage materials as quickly as possible is advantageous to the operation of gas storage systems, it would be beneficial to improve the gas diffusivity rates, or to have some other way to get the gas into and out of the gas storage material without having to diffuse it over long distances through the bulk of the material. One way to get gas into and out of the gas storage material quickly is to take advantage of high gas diffusivity paths in the gas storage material. Such paths may exist in the material naturally, or they may be intentionally created. For example, grain boundaries, defect structures and dislocations are naturally occurring high hydrogen diffusivity paths. Engineered porosity or other defects may also be intentionally created within a material so as to provide additional high gas diffusivity paths in a material. Utilizing materials that comprise both field-induced dipoles for increasing the gas solubility therein, and high mobility diffusion paths for increasing the gas mobility therein, would be ideal.

Referring now to Figure 1, there is shown a diagram showing the dissociation of molecular hydrogen and its storage in a hydrogen storage material as atomic hydrogen, as utilized in one exemplary embodiment of this invention. In this embodiment, an electric field 10 is applied to two electrodes 12a, 12b surrounding the gas storage material 14, which in this case is depicted as being a hydrogen storage material. Preferably, the electrodes comprise a material that actively breaks down H₂ (molecular hydrogen) into H (atomic hydrogen), such as for example, platinum or palladium. As shown in the enlarged section of this diagram, once the electric field is applied and the molecular hydrogen is broken down into atomic hydrogen, the atomic hydrogen 16 polarizes and aligns itself with the anions 18 and cations 20 in the storage material. The virtual dipole 22 that is created is the result of the combined effects of the applied field, the composition of the material, and the structure thereof. Therefore, it can be seen that such application of an electric field enhances the hydrogen solubility of this hydrogen storage material, thereby acting as a gating mechanism for controlling the uptake and release of hydrogen.

Referring now to Figure 2, there is shown a diagram showing the dissociation of molecular hydrogen and its storage in a hydrogen storage material as protonic hydrogen, as utilized in one exemplary embodiment of this invention. In this embodiment, an electric field 10 is applied to two electrodes 12a, 12b surrounding the gas storage material 14, which in this case is depicted as being a hydrogen storage material. Preferably, the electrodes comprise a material that actively breaks down H₂ (molecular hydrogen) into HT (protonic hydrogen) with the assistance of an applied electric field, such as for example, Pd or Pt. As shown in the enlarged section of this diagram, once the electric field is applied and the molecular hydrogen is broken down into protonic hydrogen, the protonic hydrogen 17 diffuses into the material along the field gradient, and aligns itself with the anions 18 and cations 20 in the storage material. The virtual dipole 22 that is created is the result of the combined effects of the applied electric field, the composition of the material, and the structure thereof. The electrons can be stored in an external capacitor until the release of hydrogen is required. Therefore, it can be seen that such application of an electric field enhances the hydrogen solubility of this hydrogen storage material, thereby acting as a gating mechanism for controlling the uptake and release of hydrogen.

Referring now to Figure 3, there is shown a diagram showing the storage of molecular hydrogen in a hydrogen storage material, as utilized in one exemplary embodiment of this invention. In this embodiment, an electric field 10 is applied to two electrodes 12a, 12b surrounding the gas storage material 14, which in this case is depicted as being a hydrogen storage material. In this embodiment, the structure of the hydrogen storage material 14 must be open enough to accept H₂ as is. Zeolites may work well for such storage. As shown in the enlarged section of this diagram, once the electric field is applied, the molecular hydrogen diffuses through the open zeolite channels formed by assemblages of cages 16 until it encounters a dipole storage site. The dipole storage site can be native to the base zeolite material, it can be created or enhanced by chemical alterations, or it can be created or enhanced by an applied field. The molecular hydrogen then polarizes in response to the dipole site and aligns itself with the anions and cations in the storage material. Many locations within various specific cages are known to serve as sites for hydrogen storage. Therefore, it can be seen that such application of an electric field enhances the hydrogen solubility of this hydrogen storage material, thereby acting as a gating mechanism for controlling the uptake and release of hydrogen.

While several different manners of storing hydrogen in a hydrogen storage material have just been described, this invention contemplates the storage of any suitable gas in any suitable material. Therefore, all such embodiments are intended to be covered within the spirit and scope of this invention.

As described above, the gas storage materials of this invention allow high performance gas storage materials to be realized for a variety of applications, such as for fuels cells and vehicles comprising the same. Advantageously, the gas storage materials of this invention show tremendous promise for commercial, industrial and consumer uses. These materials may be used for gas phase storage, and are particularly well suited for vehicular fuel cell applications. Many other advantages will also be apparent to those skilled in the relevant art.

Various embodiments of this invention have been described in fulfillment of the various needs that the invention meets. It should be recognized that these embodiments are merely illustrative of the principles of various embodiments of the present invention. Numerous modifications and adaptations thereof will be apparent to those skilled in the art without departing from the spirit and scope of the present invention. This invention comprises gas storage materials for a wide variety of end uses. For example, while hydrogen storage materials for vehicular fuel cell applications has been described, the hydrogen storage materials of this invention could also be used in a variety of other applications, such as for personal power generation. Additionally, while hydrogen has been discussed in many embodiments, any suitable gas could be stored in the gas storage materials of this invention. Furthermore, while ceramics and electric fields, and metals and magnetic fields, have been discussed herein in detail, any suitable material and any type of suitable applied field could be utilized in this invention. Thus, it is intended that the present invention cover all suitable modifications and variations as come within the scope of the appended claims and their equivalents.

Claims

WHAT IS CLAIMED IS:

LA gas storage system comprising:

at least one gas storage material; and

at least one field applied upon said gas storage material to control the gas solubility of said gas storage material.

2.A gas storage system in accordance with claim 1, wherein said gas storage material comprises a dielectric.

3.A gas storage system in accordance with claim 2, wherein said at least one field comprises an electric field.

4.A gas storage system in accordance with claim 1, wherein said gas comprises hydrogen.

5.A gas storage system in accordance with claim 4, wherein hydrogen comprises at least one selected from ionic hydrogen, molecular hydrogen and atomic hydrogen.

6.A gas storage system in accordance with claim 2, wherein said at least one field comprises at least one of a stress field, a strain field, and combinations thereof.

7.A gas storage system in accordance with claim 3, wherein said at least one field further comprises at least one of a stress field, a strain field, and combinations thereof.

8.A gas storage system in accordance with claim 3, and further including means for controlling the temperature of said gas storage system.

9.A gas storage system in accordance with claim 3, and further including means for controlling the pressure of said gas storage system.

10. A gas storage system in accordance with claim 2, wherein said dielectric comprises at least one of a piezoelectric, a ferroelectric, a ceramic, a non-metal, an organic material, or a semiconductor material.

11. A gas storage system in accordance with claim I₅ wherein said gas storage material comprises a magnetic material.

12. A gas storage system in accordance with claim 11, wherein said field comprises a magnetic field.

13. A gas storage system in accordance with claim 12, wherein said at least one field further comprises at least one of a stress, a strain, or an electric field and combinations thereof.

14. A gas storage material having a high gas storage density and high gas mobility, the gas storage material comprising:

a material comprising gas storage space and enough ionic character to sustain an electric dipole during application of an applied field, wherein the application of the applied field does not cause the material to become conductive; and

a gas stored within the gas storage space in the material,

wherein the gas is capable of diffusing through the material and wherein application of the applied field allows at least one of the following to be controlled:

gas solubility of the gas storage material;

gas uptake to the gas storage material;

gas discharge from the gas storage material; and

gas mobility within the gas storage material.

15. The gas storage material of claim 14, wherein the material comprises at least one of: a dielectric material, a piezoelectric material, a ferroelectric material, a ceramic material, a non-metal material, a polymer material, and a semiconductor material.

lό.The gas storage material of claim 14, wherein the gas comprises at least one of: hydrogen, a gas with a permanent dipole, and a polarizable gas capable of molecular or atomic transport through the storage material.

17. The gas storage material of claim 14, wherein the applied field comprises at least one of: an electric field, a stress field, and a strain field.

18. A gas storage material having a high gas storage density and high gas mobility, the gas storage material comprising:

a material comprising gas storage space and enough magnetic character to allow magnetic dipoles therein to be enhanced during application of an applied field; and

a gas stored within the gas storage space in the material,

gas solubility of the gas storage material;

gas uptake to the gas storage material;

gas discharge from the gas storage material; and

gas mobility within the gas storage material.

19.The gas storage material of claim 18, wherein the applied field comprises at least one of: a magnetic field, a stress field, and a strain field.

2O.The gas storage material of claim 18, wherein the gas comprises hydrogen.

2 LA method for controlling the solubility of a gas in a gas storage material, said method comprising:

providing at least one gas storage material; and

applying at least one field to said at least one gas storage material.

22.A method in accordance with claim 21, further comprising providing a gas to said gas storage material for storage thereof.

23.A method in accordance with claim 22, wherein said gas comprises hydrogen.

24.A method in accordance with claim 21, wherein providing at least one gas storage material comprises at least one dielectric material.

25.A method in accordance with claim 21, wherein applying at least one field comprises applying at least one of a stress field, a strain field, an electric field, and combinations thereof.

26.A method in accordance with claim 21, wherein providing at least one gas storage material comprises at least one magnetic material.

27.A method in accordance with claim 26, wherein applying at least one field comprises applying at least one magnetic field.