Abstract:
A system of two fuel ampoules that can deliver a reactant by diffusion through one of the ampoule walls to the other, such that when said reactant enters the second ampoule, it reacts with another reactant in said second ampoule, making hydrogen gas as a product. Both ampoules are stored in a fuel impermeable container. These ampoules used with small low power fuel cells which need a steady controlled uniform delivery of vaporous fuel such hydrogen and alcohols. This fueling system provides a simple safe fuel interactive system for small hydrogen fuel cells that prevents inadvertent hydrogen production by any single ampoule being exposed to water or typical consumer environments.

Description:
BACKGROUND OF THE INVENTION 
     Fuel cells directly transform chemical energy to electrical energy by reacting electrochemically gas or liquids in the presence of an electrolyte, electrodes and a catalyst. Our previous U.S. Pat. No. 4,673,624 “Fuel Cell”, U.S. Pat. No. 5,631,099 “Surface Replica Fuel Cell, and U.S. Pat. No. 5,759,712 “Surface Replica Fuel Cell for Micro Fuel Cell Electrical Power Pack” described a method of forming a fuel cell that efficiently utilizes expensive catalysts, is easily mass produced, and can be packaged for portable electronics. 
     A variety of methods for production and/or delivery of hydrogen gas into fuel cells are known. Some of them include pressurized hydrogen storage in cylinders and storage into metal hydride alloys, such as those used in Ni—MH rechargeable batteries. 
     Needs exist to provide safe and convenient sources of hydrogen fuel for fuel cells at a low cost, especially in portable power applications. 
     A different way of creating and delivering this hydrogen is to use chemical hydride compounds that absorb water or other liquids or gases which react with the chemical hydride to form hydrogen. The hydrogen then diffuses out and is delivered to the fuel cell or hydrogen consuming device. 
     There are a variety of chemical hydrides which release hydrogen when combined with water. Their reaction with water can be described by the following general equation: 
      MH x   +x H 2 O→M(OH) x   +x H 2   
     where M is a metal of valence x. Examples of these chemical hydrides include LiH, LiAlH 4 , LiBH 4 , NaH, NaAlH 4 , NaBH 4 , MgH 2 , Mg(BH 4 ) 2 , KH, KBH 4 , CaH 2  and Ca(BH 4 ) 2  (Kong et. al). Kong et al. showed that LiH, LiAlH 4 , LiBH 4 , NaH, NaBH 4  and CaH 2  all deliver a large fraction of their hydrogen capacity upon reaction with water vapor. Conversely, LiBH 4  and NaBH 4  were observed not to react with water vapor and there was no reaction with water until the powders were effectively dissolved. The U.S. Army Mobility Equipment Research and Development Command developed a system in which liquid water flows from a reservoir into a chamber where it contacts a porous hydrophobic membrane. In this system, water vapor diffuses through the membrane and spontaneously reacts with the hydride to release hydrogen, which then flows out of the reaction chamber to the anode of the fuel cell. Hydrogen production is controlled by virtue of water being forced back into the water reservoir during periods of no load, when the hydrogen is not being consumed. 
     As another example, Millennium Cell has developed a chemical hydrogen generator based on basic solutions of sodium borohydride (Amendola et al.). The generation of hydrogen is based on the reaction: 
     
       
         NaBH 4 +2H 2 O→NaBO 2 +4H 2   (1) 
       
     
     Basic solutions of sodium borohydride were shown to be stable. A catalyst (Ru) releases hydrogen when in contact with the solution and therefore requires mechanical means to bring the solution into contact with the catalyst. This adds complexity to the system. 
     This last case is a particular example of the more general case where NaBH 4  and water are chosen from a larger class of compounds A and B, respectively. 
     This new invention addresses the pre-existing problems. 
     SUMMARY OF THE INVENTION 
     A subject of this invention is to advance fueling systems such as described in our U.S. Pat. No. 5,759,712 that has the fuel ampoules sealed in gas tight packages. An advance is to arrange a system of two ampoules or components (A and B) such that when placed together produce hydrogen and when separated do not. Diffusion regulation mechanisms are used to regulate the production rates, as well as the choice of both A and B components. An objective is to make hydrogen fueling system safer for hydrogen consuming systems such as fuel cells. In products, an A ampoule and a B ampoule are placed in a cavity and sealed together. Reactants diffuse through the walls of one of the ampoules into the other ampoule through the walls of the second ampoule. The reaction then produces hydrogen gas which diffuses out of the second ampoule. 
     Obvious applications of a small fuel cell are in those that are currently powered by batteries, especially rechargeable batteries. By safely encapsulating intrinsically energetic fuels with an interactive hydrogen release reaction, the fuel cells can have higher energy per unit mass, higher energy per unit volume, and be more convenient for the energy user. 
     Our invention provides a safe, convenient, inexpensive and portable hydrogen generator which can be used to fuel a PEM fuel cell. Component A is chosen from chemical hydrides such as LiH, NaH, NaBH 4  CaH 2  and LiAlH 4 , among others. Component B may include, but is not limited to, substances such as water, alcohols, organic and inorganic acids (e.g. acetic acid, sulfuric acid), aldehydes, ketones, esters, nitrites and superacids (e.g. polyoxotungstates), and combinations thereof. Depending on the choice of component B, an appropriate selectively permeable membrane should be selected (e.g. silicone rubber for methanol). 
     Our recently issued patent U.S. Pat. No. 6,194,095 describes how the non-bipolar fuel cells can be packaged to form larger power supplies. Our pending patent no. U.S. Ser. No. 09/821,053 describes an ampoule of fuel that can be delivered at a controlled and constant rate by using the selective permeability of the fuel tank. In some fuel cells a controlled release of hydrogen or other gas is also needed. 
     This patent describes a recipe where the choice of A and B influences the rate of hydrogen gas generation. More importantly, this patent discloses a method for combining both chemicals without the aid of any mechanical means, thus resulting in a chemical hydrogen generator which is safe, portable and inexpensive. 
     In our patent application No. U.S. Ser. No. 09/821,053, a liquid hydride solution is immobilized and its contact is controlled with capillary wicking material. It does not have the feature of two components in diffusion contact, instead describing physical contact of a single fuel with a catalyst. Capillary wicking can be used to immobilize any liquid reactants in a two component diffusion delivery system. 
     In our patent U.S. Pat. No. 5,759,712, a vapor phase transport to a hydrophilic outer surface of a gas manifold is described. Selectively permeable membranes in proximity to the fuel cell are described for delivering reactants and products. Fueling is done by breaching a fuel tank and wicking fuel, which is then transported to the fuel cells in the vapor phase. Breaching this fuel tank can lead to spilling of fuel while liquid contact needs to be maintained with the fuel in the fuel tank. Thus, as the fuel tank runs low on fuel some of the fuel may not be in liquid contact and will be unused. To achieve wicking fuel delivery, the fuel needs to be fluid and mobile thus increasing the possibilities of leakage from the fuel ampoule. Gravity can affect the delivery of a liquid fuel. Achieving a good liquid seal on methanol fuel can lead to complex and costly sealing mechanisms for the fueling system and the fuel cell system. Small leaks of liquid fuel compared to vapor loss through the same hole can have a far greater detrimental effect on the air electrode and total fuel loss. 
     In our U.S. Pat. No. 6,326,097 the fuel cell and fueling ampoules are shown being placed in proximity to each other with a diffusion mat. The fuel tanks are described as a liquid wick or fluid motion fueling. Fuel diffusion from the fuel tanks is not described. Plastic blister packaging of the fuel tanks does not indicate the sealing properties of the package, nor individual sealing. Porous fillers are described as being in the fuel tanks, but not as diffusion delivery means. 
     Hydrogen Gas Generation 
     Chemical hydrides are known to react with water and give off hydrogen gas as a product. Reaction (1) shown above serves as an example. In general, hydrogen generation occurs when the hydride ion reacts with a proton from another source. Water is the most common source of protons used, and hence its reactions with chemical hydrides have been extensively studied and are well documented. Additives which reduce the pH of the aqueous solution result in a higher rate of hydrogen generation. Conversely, raising the pH to an appropriate level can stabilize sodium borohydride solutions, effectively lowering the reaction rate to the point where almost no hydrogen evolves. 
     Other reactants may be used instead of water. For example: 
     
       
         NaBH 4 +4CH 3 OH→Na[B(OCH 3 ) 4 ]+4H 2   (2) 
       
     
     We have carried out this reaction in our laboratories and found that the rate of hydrogen generation in the methanolysis reaction is considerably higher than in the hydrolysis reaction. As an example, the powder form of NaBH 4  can be mixed as a slurry in a silicone rubber mix to be encapsulated. Water or methanol diffuse through the silicone rubber to the NaBH 4  and the generated hydrogen can diffuse out. An encapsulated cylinder with water or methanol and a separate encapsulated NaBH 4  cylinder could be placed together in the fuel manifold of a fuel cell to generate hydrogen. We have found this vapor delivery system at room temperature and conditions to be very slow and unsteady with water as the reactant. However with methanol vapor it is immediate and steady. We have tested the produced gas in a residual gas analyzer and confirmed that the product gas is hydrogen, as expected from reaction (2). 
     This reaction system allows us to package the reactants as an AB system of two ampoules which separately do not make hydrogen at a significant rate. We have also found that ethanol and isopropanol do not significantly react with NaBH 4 . 
     Our pending patent application U.S. Ser. No. 09/821,053, the disclosure of which is incorporated herein by reference, discloses a method of using a selectively permeable membrane to diffuse selected chemical species (e.g. methanol through silicone rubber) to provide fuel for a fuel cell. That invention is herein expanded by including a separate component, namely a chemical hydride contained in an ampoule, which reacts which said diffused species producing hydrogen gas which can then be used to fuel a PEM fuel cell. 
     Other reactions may be used to generate hydrogen. Alkaline, alkaline earth metals and metals from Groups IIIA and IVA may react with water, alcohol or dilute acids to liberate hydrogen. The metals may be encapsulated in a matrix and the reactant (water, methanol, dilute acid) allowed to diffuse in through a selectively permeable membrane. 
     The reaction of the hydrides with water produces basic solutions and compounds. When the product is a strong base this can be neutralized with carbon dioxide to form a carbonate and water. Other alternatives are the reactions with acids. This makes available more water for the reaction with the hydride and neutralizes the caustic base. The carbon dioxide could come from the direct methanol or hydrocarbon utilizing fuel cell. In some cases by making water available from the reaction this would be a net gain in the energy per unit mass for the system. An ideal combination might be a hydrocarbon which results in hydrogen gas and a carbonate product when combined with the chemical hydride. A fueling system is made up of two diffusion ampoules which slowly diffuse into the other to produce hydrogen gas and solid encapsulated carbonate products when placed within an enclosure. As an example, consider the reaction of water with lithium hydride: 
     
       
         LiH+H 2 →LiOH+H 2   (3) 
       
     
     A subsequent reaction takes place between LIOH and CO 2 : 
     
       
         LiOH+CO 2 →Li 2 CO 3 +H 2 O  (4) 
       
     
     The water resulting from (4) can react with unreacted LiH as shown in reaction (3) to further produce hydrogen gas. At the same time, a more benign end product (lithium carbonate) is produced. 
     In our previous patents U.S. Pat. No. 5,631,099 and U.S. Pat. No. 5,759,712, the carbon dioxide exhaust can diffuse out through a selectively permeable membrane or the fuel tank itself. This feature can control reaction (4). We have found that a simple gaseous diffusion route such as a capillary tube can effectively exhaust product gases and maintain gas pressure equilibrium across the fuel cells. The capillary tube can also function as a controlled leak for the beneficial in-leakage of oxygen to the fuel electrode. 
     The production of fuel such as hydrogen from a chemical hydride can be regulated by delivery of moisture or acid. A valve or pump can used to regulate moisture from a tank containing the moisture to the second tank containing the hydride. This is an AB system where the two tanks work together. The moisture can be also very useful to maintain the humidity for the fuel cells. Thus all the separate parts can form an interacting system. The moisture valve can be a membrane with small controllable apertures, or a gap between the tanks that is increased to decrease the delivery of reactants and is decreased to increase the delivery of reactants. 
     Hydrogen ion-drag pumping through a membrane can be used to drag water and solvents from one ampoule to the other. This can act as a solid state pumping system to move reactants. The amount of reactant moved across the membrane is proportional to the electrical current going through the membrane. Thus, the production of hydrogen can be controlled through the electrical current through the separating membrane. Examples of a suitable membrane are Nafion with platinum-catalyzed electrode on either side. 
     Another feature is to add a separate catalyst mixed with the hydride to increase the hydrogen production rate. Noble metal catalysts (e.g. Pt, Ru) and transition metals in general are particularly suitable to perform this function. Other suitable catalysts are substances such as Co 2 B, CoCl 2 , CuCl 2 , NiCl 2 , Fe 2  when mixed with NaBH 4  powder. 
     Selectively Permeable Membranes 
     By having a selectively permeable fuel tank wall, the fuel delivery can have the advantageous effect of delivering fuel at a constant rate throughout its life cycle. Component B may be made up of two or more chemicals, one or more of which may react with the chemical hydride. If the membrane had similar permeability to the main chemical in component B (i.e. the fuel) compared to a minority chemical in component B, the latter would diffuse in while the former diffused out. The presence of this minor chemical would drop the fuel vapor pressure and reduce the rate at which fuel can diffuse out. Thus, the rate of fuel delivery would gradually drop. As an example, our measurements on silicone rubber membranes show a molecular diffusion rate difference for methanol over water of 20 to 36 times. In performance tests with a small ampoule containing 95% methanol and 5% water with a silicone rubber membrane, the fuel delivery system is effective in delivering fuel with only a small fraction of the original fuel volume left as water in the fuel container. 
     Mixed fuels in component B made up of chemicals such as methanol, formaldehyde, formic acid and water could be used in the fuel ampoule. If these additives are permeable through the fuel ampoule they will also be delivered according to their respective rates and concentration gradients. The fuel ampoule material could also be chosen or designed by a mixture of materials to have a permeability that allows the fuel to be delivered at the rate ratio matching that of the fuel. An example is an ampoule wall material that has a 1:1 diffusion rate for methanol over water. Thus, if fueled by a 1:1 fuel mixture and assuming a low exterior concentration of both, the diffusion delivery system would deliver fuel at a 1:1 concentration. 
     The process of enhancing the selective vaporization of fuel from a membrane is called per-evaporation. It essentially increases the evaporation of that fuel. The ampoule membrane may use this effect when the fuel concentration is low. It can keep the fuel concentration higher at the fuel cell than it would be without the fuel ampoule selectively permeable membrane. 
     The tank walls can be made of composite materials. Examples are fiberglass cloth and silicone rubber, where the fiberglass cloth gives mechanical strength and the silicone rubber has high diffusion rate properties. The mechanical and diffusion properties of the fuel tanks can be adjusted to reflect the blend of materials and components making up the fuel system. The tanks may also be made in layers. One option is to make the outer layer have the highest diffusion resistance and have a single fuel such as methanol, with the interior having rapid diffusion. This would give the fuel delivery a flat output with time, matching the vapor pressure of the fuel liquid, and then a steep decline as the remaining vapor diffuses out of the interior materials and voids. 
     Incorporating electrical and mechanical diffusion control into the fuel ampoule or between the fuel ampoule and the fuel cell allows the membrane diffusion to have a feedback mechanism to adjust to consumption demands by the fuel cell, or to different environmental conditions around the system. Possible mechanisms are drawing fuel using ionic drag through a membrane, piezoelectric operating of micro apertures in the membrane, or impermeable membranes that act as apertures which can be adjusted to a specific opening path between the fuel ampoule and the fuel cell, or alternatively a fan. 
     The permeability of the fuel ampoule can vary with temperature. This property can be used to match the fuel cell consumption rate as the temperature increases. The permeability rate can also be chosen to not rise as much as the fuel cell consumption rate to keep the fuel cell at higher temperatures using more fuel than necessary. This could be the case in power applications where the power delivery is constant regardless of the temperature environment. 
     Molecular filtration can be used to keep impurities that can be dissolved in the fuel or come with the fuel to be left in the fuel ampoule. This feature can be used to allow a fuel of low purity. The fuel cell may also be protected by using the same principle. The hydrogen gas generated inside the ampoule with the chemical hydride may be filtered using a selectively permeable membrane made of palladium or an alloy thereof before the hydrogen fed to the PEM fuel cell. This keeps impurities from affecting fuel cell performance. 
     The vapor fuel delivery and selective permeability of the ampoule also have the effect of filtering the fuel. Additives such as dyes, flame colorizers and bitterants can be added to the fuel to make the fuel safer and possibly aesthetically pleasing to consumers. Adding water absorbing chemicals can be added to the fuel to maintain the vapor pressure of the fuel. The interior of the tank could have a filler, such as cellulose sponge, that has a higher diffusion rate to fuel than the walls but would keep liquid fuel from being accessible even if the fuel tank is ruptured or crushed. 
     By simply being able to remove the fuel tank from a sealed container and sliding it into a chamber without alignment necessities, a system with large dimensional tolerances where the user can close the cover is very simple and makes it convenient and low error prone. 
     The fuel tank as it uses fuel, if it has selective fuel delivery, will mechanically collapse. This fuel tank collapse can be used to form a mechanical fuel status indicator. A color stripe could be used that moves by a viewing window the fuel ampoule could be used. The fuel tank itself can be tinted to give a visual indication of fuel level. The fuel can have colored dyes so that as the fuel is used it will give a color change indication of fuel status since the remaining fuel will be darker. The fuel ampoule can also have materials, such as salts, that produce an opaque interior or color change in the fuel ampoule as the fuel is used. 
     Safety 
     An important feature of our invention is that the chemical hydrides, traditionally thought of as dangerous can be safely immobilized in a number of ways. 
     The first is to contain the reactants inside a porous bag or material. The powdered hydrides are contained within a hydrophobic porous plastic such as microporous polypropylene. In the event that the bag is dropped in water, only vapor contact with the hydride is made. The liquid fuel can be held in a container that has porous walls that will gradually wick the fuel to the surface of the container. 
     The second is to employ a container which can be a wicking sponge material such that the chemical hydride or fuel are distributed through it. 
     Another way is to employ a container which can have a pore free material that surrounds the liquid or solid fuel. Delivery of reactants would be by diffusion through this material and may be selective, e.g. such as the preferential permeability of silicone rubber to methanol over water. 
     Yet another method employs an ion-exchange membrane. The fuels could be reacted with an ion exchange material making them chemically attached to a surface or polymer. Both A and B fuels could be held by the ion exchange materials. 
     Packaging 
     The next challenge is to package the diffusion system to work with fuel cells or other devices and maintain the desired flow rate. A potential problem is that the delivery rate of component B to the ampoule which contains component A will be uneven depending on where the individual particles of the latter are within their ampoule. Molecules of component B will react first with those particles in the adjacent ampoule closest to the selective membrane. This may have the effect that the rate of hydrogen production decrease with time. To compensate for this, the diffusion wall encapsulated materials or homogenous material composites can be perforated with small channels. The diffusion walls can also have their highest resistance concentrated at the surface. We have found in experiments that the encapsulation can gradually break apart as the reaction proceeds opening up further in diffusion routes. A fan or pump system that forces moist gas or fluid through the material can be used to increase the interaction of the water and the hydrides. With a feedback loop to this fan the output of the generator can adjust the production rate to match the consumption rate. The small perforation hydrophobic pores in silicone rubber keep liquid water from being able to penetrate and increase the production rate. The encapsulation can also be designed to have an outer skin that is the predominant rate limiting diffusion barrier and where the interior of the encapsulation has a relatively high diffusion rate. 
     An unusual design of a reactor that mixes various features of the above description and our previous patent No. U.S. Ser. No. 09/821,053 is to encapsulate the dry reactant in the form of a long capillary tube or tube bundle and a liquid filled capillary tube or tube bundle. Each of these capillary tubes can form a separate ampoule. When the two ampoules are pressed together contact is made with a liquid filled capillary tube and the dry reactant ampoule. Diffusion of liquid and direct liquid contact is forced into the dry hydrophobic reactant tubes by static pressure on the back of the liquid reactant tubes. The liquid reactant will diffuse into the walls of the tube and produce hydrogen which can diffuse back out through the walls of the tube. Bubbles will form and grow in the liquid and reactants and drive a water droplet through the long capillary tube until the droplet is broken. The flow of produced hydrogen will continue to push forward the liquid reactant vapor. A small pump or static pressure against the gas pressure in the back of the liquid capillary tube can control the reactant delivery. When the evolved gas pressure is high, it will force the liquid back out of the dry reactant capillary tubes to the source tube. This design does not have the capability to fully shut off the reaction due to the diffusion though the capillary tubes, but if either reactor has a long diffusion length of non reactant between each other this can be effective in reducing the reaction to a low rate. 
     The storage container of the permeable fuel container needs to be impermeable to the fuel. This container could be a disposable bag with metal coatings or coatings such as Aclar® (Honeywell Specialty Films, PO Box 1039, 101 Columbia Road, Morristown, N.J. 07962) PVDF polyvinylidene fluoride plastic. This tank could also be made of composite materials, such as PET plastic polyethylene terephthalate with an Aclar coating. The storage container could be a heat sealed bag with a tear point to allow the consumer to easily open. The essential parallel is that of packages for foods and ink jet cartridges. 
     These and further and other objects and features of the invention are apparent in the disclosure, which includes the above and ongoing written specification, with the claims and the drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 schematically shows the basic diffusion reaction system. 
     FIG. 2 schematically shows two encapsulated diffusion ampoule system. 
     FIG. 3 schematically shows a water-ion drag for diffusion regulation. 
     FIG. 4 schematically shows a diaphragm valve diffusion regulated system. 
     FIG. 5 schematically shows a micro-valve regulated diffusion system. 
     FIG. 6 schematically shows a diaphragm pumped system. 
     FIG. 7 schematically shows a gas pumped circulation system. 
     FIG. 8 schematically shows an elastic wall diffusion regulator. 
     FIG. 9 schematically shows details of open elastic valve. 
     FIG. 10 schematically shows details of closed elastic valve. 
     FIG. 11 schematically shows the gas pumped circulation system. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The construction of a two ampoule fueling system is shown in FIG.  1 . The volatile reactant ampoule  1  can be made of a polyvinyl alcohol sponge (PVA Sponge; Shima American Corporation, 171 Internationale Blvd., Glendale Heights, Ill. 60139) or cellulose sponge, soaked with methanol and water. Within the ampoule container  7  a solid reactant such as sodium borohydride is mixed within a material that is highly permeable to methanol such as a silicone rubber compound (AB mix GE silicones: RTV6166A silicone polymer and 6166B curing agent GE Silicones GE Company, Waterford, N.Y. 12188). This ampoule can be formed by mixing the sodium borohydride powder with this two component silicone and curing the mixture at 60° C. in an oven. The silicone rubber material AB mix GE silicones were chosen because they did not have water in the cure, and the silicone rubber is approximately 40 times more permeable to methanol compared to water. The hydrophobic nature of the silicone rubber also prevents liquid water from penetrating or wicking into the ampoule  3 . Thus the embalmed sodium borohydride ampoule  3  has very low reactivity to liquid water if accidentally immersed in water. The two ampoules  1 ,  3  are separated by a selectively permeable membrane  2 . This membrane  2  can be constructed of a fiberglass mat such as Freudenburg Eglass mat T-1785 (Freudenburg Non-Wovens Ltd., 221 Jackson St., Lowell, Mass. 01852) impregnated with silicone rubber adhesive (GE silicones RTV 118) and compressed between low density polyethylene sheets. This results in strong silicone rubber membranes that are 25 to 200 microns thick. The membrane is held in a gas tight frame of the container  7  separating the two reactant ampoules  1  and  3 . At the gas exit of the container  7  a filter  5  covers the exit port  4  to filter the gas of particulate or unreacted materials. This filter  5  could be made of a porous polyethylene (0.03 micron pore; Mobil Chemical Company, Films Division, 729 Pittsford-Palmyra Rd., Macedon, N.Y. 14502) with sub micron pores. The filter  5  could also have selective permeability properties such as a thin palladium metal foil or a pore-free transition metal film supported on a substrate to filter the hydrogen  21  from the volatile reactants  6 . In operation this system is expected to have container  7  open; then the two ampoules  1 ,  3  are inserted, and the container  7 , is resealed. Methanol and water will diffuse from the volatile ampoule  1  through the separating membrane  2  and into the solid reactant ampoule  3 . Hydrogen gas  21  is produced in the solid reactant ampoule  3  and it diffuses out of the ampoule, through the exit filter  5  and out the exit port  4 . 
     In FIG. 2 a similar system as the membrane separated system is shown as in FIG. 1, except that there is no separating membrane  2 . The two ampoule walls  8  and  12 , are now the selective diffusion mechanism. The ampoules  8 ,  12  can be made out of silicone rubber enclosing a reactant filled sponge. In the volatile reactant ampoule  8  methanol fuel fills a sponge material such as PVA or cellulose. In the dry reactant ampoule  12  sodium borohydride powder  11  is packed into an open cell urethane foam or embalmed in silicone rubber. In operation the two ampoules  8 ,  12  are placed together inside the fuel container  7 , and the container is sealed. The volatile reactant  8  diffuses into the powder ampoule  12 . The volatile reactant reacts with the chemical hydride powder  11  in the powder ampoule  12 , and hydrogen gas is produced. The hydrogen gas diffuses out of the powder ampoule  12  into the interior  10  of the container  7 , and the hydrogen gas  21  goes through the exit filter  14  and out of an exit port  13 . The exit filter can be a porous membrane such as porous polyethylene (Mobil Chemical Company, Films Division, 729 Pittsford-Palmyra Rd., Macedon, N.Y. 14502) or expanded PTFE (Corning Costar, One Alewife Center, Cambridge, Mass. 02140). Products of water vapor and carbon dioxide from the fuel cell or consuming device  90  diffuse back up the outlet tube  13  and through the exit filter  14 . These products react with the chemical hydride in ampoule  11 ,  12  to produce more hydrogen. The hydrogen production of this device could be regulated through changing the gas separation gap  10  between the ampoules  8 ,  12 , and the diffusion length through the exit filter  14  and exit tube  13  for the product  91  interactions with the fuel cell  90 . The gas separation gap  10  is a diffusion limiting point in the system such that, if the container walls  7  are flexible and the ampoules  8 ,  12  are attached to the walls, the ampoules will move apart when the internal pressure increases, subsequently increasing the diffusion path  10  between the ampoules and reducing the hydrogen production rate. 
     In FIG. 3 a system that uses a ion-drag cell to move water and methanol from the volatile ampoule to the chemical hydride ampoule is shown. The volatile ampoule is constructed as a silicone rubber walled ampoule  15 . It is filled with a sponge material such a PVA foam saturated with water and methanol  16 . This ampoule is placed in the fuel system container  26 . The second ampoule is a silicone rubber walled ampoule  19 , filled with sodium borohydride powder and silicone rubber compound (AB mix GE silicones: RTV6166A silicone polymer and 6166B curing agent)  18 . The membrane electrode assembly  23 ,  17 ,  25  separating the two ampoules  15 ,  19  is made up of a Nafion membrane  17  with sputter deposited electrodes  23  and  25  on either side of the membrane  17 . The flow of hydrogen ions from the electrode  25  through the electrolyte  17  to  23  is regulated by the electrical current flow through the membrane  17 . Hydrogen gas is converted to hydrogen ions on the catalytic electrode  17 . These ions travel through the Nafion electrolyte  17  carrying with them 5 to 7 water or methanol molecules with each ion. When the hydrogen ions reach the other side of the membrane  17 , two protons and two electrons make one hydrogen molecule on the catalytic electrode  23 , and water and methanol evaporate from the electrode. The voltage and subsequent current on the electrodes  23 ,  25  comes from an external electrical feedback loop with the fuel cell or device that needs hydrogen on demand. Typically the current though the ion-drag cell would be proportional but smaller than the current output of the fuel cell. The wires  38  and  39  are attached to the catalytic electrodes  23 ,  25 . Water, methanol and hydrogen from the surface of the cathode electrode  23  will diffuse through the ampoule wall  19  to the sodium borohydride powder a silicone rubber compound  18  in ampoule  19  and create hydrogen by hydrolysis. The hydrogen created then diffuses though the porous material and flows through the exit filter  22  or recycles through a long diffusion path  24 . The recycled hydrogen will go through the ion-drag cell  23 ,  17 ,  25 . The exit filter  22  can be formed out of porous membranes such as expanded PTFE (Filinert, Corning CoStar) or a selectively hydrogen permeable membrane formed by films of platinum on palladium silver alloy and platinum on a etched nuclear particle track membrane (Nuclepore, Corning Corstar). The membrane is embalmed in silicone rubber film and is sealed to the exit of the container  26 . The filtered hydrogen  21  exits the container  26  through a vent hose  20  to a fuel cell or device needing hydrogen gas. 
     In FIG. 4 a binary chemical reaction system is shown with a diaphragm valve regulating the reaction diffusion between the two reactant ampoules. An ampoule of the volatile reactant  28  is placed in the container  27 . This ampoule  28  is a PVA sponge saturated with methanol and water. A pore free diffusion membrane  29  and a porous membrane  35  are placed between the ampoule  28  and valve aperture  34 . This drawing shows a single aperture  34  for simplicity in the drawings, but in actual devices an array of apertures spaced out over the separating wall  58  would be expected. On the other side of the separating wall  58  a selectively permeable membrane to methanol and water over hydrogen  30  is placed. This selectively permeable membrane  30  made of silicone rubber is 100 microns thick and is sealed to the container walls  27 . The selectively permeable membrane  30  and has a small sealing disk  37  made with Viton rubber to seal with the valve aperture  34 . The Viton rubber has low permeability to methanol and water. A second ampoule is formed by a mixture of sodium borohydride powder and silicone rubber compound  31  (AB mix GE silicones: RTV6166A silicone polymer and 6166B curing agent). A gas exit filter  33  can be formed out of porous membranes such as expanded PTFE (Filinert, Corning CoStar) or a selectively hydrogen permeable membrane formed by films of platinum on palladium silver alloy and platinum on a etched nuclear particle track membrane (Nuclepore, Corning Corstar). The membrane is embalmed in silicone rubber film and is sealed to the exit of the container  27 . The filtered hydrogen  21  exits the container  27  through a vent hose  32  to a fuel cell or device needing hydrogen gas. A long diffusion vent gas line  36  is placed through the container wall  27 , venting gas from the porous membrane  35 . This vents to the atmosphere to let the selective permeable membrane  30  expand and contract with the pressure and gas generated by the sodium borohydride ampoule  31 . When the hydrogen pressure from the sodium borohydride ampoule  31  is high the selective permeable membrane  30  will expand and press the sealing disk  37  against the sealing aperture  34 . This will seal off the diffusion of methanol and water from the volatile source ampoule  28  to stop further reaction with sodium borohydride ampoule  31  and the production of hydrogen. When the hydrogen pressure drops the selective permeable membrane  30  will move away from the sealing aperture  34 , and methanol and water can diffuse through the membrane and react with the sodium borohydride ampoule  31 . This then leads to hydrogen production and the pressure rising. Thus a pressure regulated hydrogen production operates. 
     In FIG. 5 two reacting ampoules are separated by a microvalved separating wall. The volatile ampoule  40  is placed in the container  46 . This ampoule is formed by enclosing a PVA sponge saturated with methanol and water with a silicone rubber container. An ampoule of sodium borohydride powder and silicone rubber compound  42  (AB mix GE silicones  42 : RTV6166A silicone polymer and 6166B curing agent) is placed on the other side of the microvalved  41  separator wall  59 . The micro valves  41  are placed over apertures  45  in the separator wall  59 . The micro valves  41  are actuated by electrical or mechanical feedback system from the fuel cell or device. When the micro valves  41  are opened, the volatile reactants methanol and water diffuse to react with the sodium borohydride ampoule. When the micro valves are closed or partially closed, they stop or throttle down the diffusion of the volatile reactants and thus adjust the production of hydrogen. An exit filter  44  can be formed out of porous membranes such as expanded PTFE (Filinert, Corning CoStar) or a selectively hydrogen permeable membrane formed by films of platinum on palladium silver alloy and platinum on a etched nuclear particle track membrane (Nuclepore, Corning Costar). The membrane is embalmed in silicone rubber film and is sealed to the exit of the container  46 . The filtered hydrogen  21  exits the container  46  through a vent hose  43  to a fuel cell or device needing hydrogen gas. 
     In FIG. 6 a system that uses a diaphragm pump to circulate hydrogen gas saturated with methanol and water vapor is shown. An ampoule  52  is made as a perforated PVA sponge saturated with methanol and water  53 . The sponge  52  has gas channel perforations and is placed inside the container  48 . The second ampoule  49  is formed as a molded ampoule, with gas channel perforations, by mixing sodium borohydride powder  56  and silicone rubber compound (AB mix GE silicones  42 : RTV6166A silicone polymer and 6166B curing agent) and filling and separating from a mold. Between the two ampoules  52 ,  49  a diaphragm pump  50  is placed so that it is sealed against the container walls  48 , forming a diffusion barrier when the pump is not running. The diaphragm pump is run by vibrating the diaphragm wall  50 . When the diaphragm  50  moves away from the second diaphragm wall  72 , hydrogen gas mixed with methanol and water is drawn into the cavity between the diaphragms  73  through the inlet valve  51 . When the diaphragms  73  and  72  move toward each other, the gas flows out of the cavity between the diaphragms  73  and out through the exit valve  55 . The methanol, water and hydrogen gas move through the chemical hydride ampoule  49 . Hydrogen gas is produced, while the water and methanol are removed from the ampoule  49 . The hydrogen gas stream  21  with some methanol vapor flows to the fuel cell  90  though exit tube  74 . Unused hydrogen, carbon dioxide and water vapor from the fuel cell  90  flow through inlet tube  57  and through a long diffusion route  54 . The moisture and carbon dioxide carried by the hydrogen flow  21  back to the ampoule  52 , supplementing the volatile reactants from the volatile ampoule  52 . The hydrogen gas stream then passes through the gas channels of the volatile ampoule  52 , absorbing methanol and water and repeating the process. The diaphragm pump is controlled by a feedback loop to the fuel cell or hydrogen consuming device. The output of hydrogen is proportional to the flow rate of reactants through the pump. When the pump is not operated, methanol vapor diffuses back through the channel  54  to the fuel cell  90  and runs the fuel cell at a lower performance level than with hydrogen gas  21 . Thus, the hydrogen generation can be used during needs of high power, and the low level loads can run on methanol vapor and a small amount of hydrogen produced by diffusion of methanol through the channels  54  and  74 . 
     In FIG. 7 a system that uses a fan  61  to circulate hydrogen gas saturated with methanol and water vapor is shown. An ampoule  70  is formed as a perforated PVA sponge saturated with methanol and water. The sponge  70  has gas channel perforations  71  through the sponge. The sponge  70  is placed inside the container  68 . The second ampoule  65  is formed as a molded ampoule, with gas channel perforations  64 , by mixing sodium borohydride powder and silicone rubber compound (AB mix GE silicones  42 : RTV6166A silicone polymer and 6166B curing agent) and filling and separating from a mold. Between the two ampoules  70 ,  65  a wall  62  and fan  61  are placed so that they are sealed against the container walls  68 , forming a diffusion barrier when the pump is not running. When the fan  61  is run by electrical energy, hydrogen gas mixed with methanol and water is blown through the sodium borohydride ampoule  65  channels  64  and around  66 . Sodium borohydride reacts with the methanol and water and produces hydrogen gas  21 . The hydrogen gas flows though a filter of expanded PTFE  67 . Part of the hydrogen gas  21  flow returns through a long diffusion route  69  to the volatile ampoule  70 , and the rest exits through a tube  68  to the fuel cell or hydrogen consuming device. This system will produce hydrogen gas  21  proportional to the methanol and water flow rate through the fan  61 . Thus, the controlling the fan  61  speed controls the hydrogen  21  production rate. 
     FIG. 8 shows a system that controls the production of hydrogen by controlling diffusion of reactants between ampoules with a valve that is closed by the wall tension in the container. The volatile reactant ampoule is formed by enclosing a methanol and water saturated PVA sponge  89  with silicone rubber membrane  88 , 10 to 200 microns thick. The volatile reactant ampoule  88 ,  89  is placed inside the Viton™ rubber enclosure  80 . The second ampoule  82 ,  86  is formed as a molded ampoule by mixing sodium borohydride powder and silicone rubber compound (AB mix GE silicones  42 : RTV6166A silicone polymer and 6166B curing agent) and filling and separating from a mold. A skin of silicone rubber  86  (GE silicones RTV 118) 5 to 200 microns thick covers the second ampoule  82 ,  86 . In operation methanol and water are vaporized from the volatile ampoule  89 ,  88  and diffuse through the open apertures of  79  and  81 . The methanol and water vapors diffuse to the chemical hydride ampoule  86 ,  82  where they diffuse though the silicone rubber skin  86  and react with the sodium borohydride imbedded in the silicone rubber  82 . Hydrogen gas  21  is produced and diffuses into the rubber walled cavity  83 . The hydrogen gas leaves through the exit filter  85  made of expanded PTFE (Corning Costar) or hydrogen selective filter formed by coating an ultra filter (polyestersulfone PES; Pall Corporation, 2200 Northern Boulevard, East Hills, N.Y. 11548) with 5 nm of Pd, 50 nm 77% Pd/23% Ag alloy and a 5 nm film. The hydrogen then exits through the exit hose  84  to the fuel cell or hydrogen consuming device. The internal pressure of the hydrogen if higher than the outside pressure will put the rubber container walls  83  in tension and subsequently pull the diaphragm apertures  79  and  81  closer together. The ring seal  87  will progressively close off the diffusion route from aperture  79  to  81  as the pressure rises. If the pressure is high enough the tension in the wall  83  will cause the ring seal  87  to seal off. Details of this operation of the apertures are shown in FIGS. 9 and 10. In FIG. 9 the inlet aperture  75  is a hole, or holes, in the center area of a entrance wall diaphragm  92 . The exit apertures  78  are arranged along the perimeter of the exit wall diaphragm  93 . When the pressure is low the gas can freely diffuse through the apertures  75 ,  78 . When the pressure is high, as shown in FIG. 10, the tension in the wall  83  pulls the aperture diaphragms  92 ,  93  together and causes the ring seal  77  to make a seal. By sealing or partially sealing the ring seal  77 , the diffusion of reactants through the apertures  75  and the exit apertures  78  is fully or partially reduced. 
     FIG. 11 shows a scheme in which liquid reactants are held in capillary tubes in one ampoule and are forced into contact with a hydrophobic encapsulated chemical hydride ampoule via feedback controlled gas pump. In this particular form an ampoule of one liquid reactant held in capillary wick  102  and a chemical hydride ampoule  98  are both placed and sealed in a reaction chamber  95 . The reaction chamber forms gas tight seals  97  on the ampoules and at the access seal  96 . The chemical hydride ampoule  98  is formed by mixing sodium borohydride powder with silicone rubber (AB mix GE silicones  42 : RTV6166A silicone polymer and 6166B curing agent). This ampoule could be made to have exit and channels  101  interdigitated through the ampoule to form high surface diffusion contact throughout the ampoule and liquid free gas exit routes. The liquid reactant ampoule is formed as a bundle of capillary tubes with apertures smaller than 1 mm in diameter, made of materials such as PVC (polyvinylchloride) or polyethylene and treated to be hydrophilic. The liquid reactants, methanol and water, are wicked into the capillary tubes  103 . These capillary tubes  103  could also consist of one long tube coiled and fused to form a compact ampoule with one opening on the pump side and one on the chemical hydride side. The other component of the system is a pressurizing pump  104 , of the diaphragm or centripetal impeller type, which is electrically driven by the output of the fuel cell. It should be mentioned that an alternative scheme is to locate liquid pump  104  between the ampoules and pump the liquid reactant from the capillary ampoule  102  to the chemical hydride ampoule  101 . Electronic controls can be used to control the output of the pump  104  to control the need for generated hydrogen  21 . A filter  100  such as porous expanded PTFE (Corning Costar) to prevent liquid reactants from flowing into the fuel cell or the hydrogen consuming device is placed to cover the hydrogen exit port  99 . The operation of this system consists of pressurizing gas  94  with the input pump  104 ; the electrical energy to run the pump could come from a capacitor charged by previous operation of the fuel cell. The inlet gas for the pump  104  could be obtained from the atmosphere or from the fuel vent exit of the fuel cell. When the pressure difference occurs across the capillary wick ampoule  102  the liquid in the capillary tubes  103  is pushed toward the chemical hydride ampoule  98 . Vapor diffusion to the chemical hydride ampoule  98  could be sufficient for low hydrogen generation rates. The pressure from the generated hydrogen will push the liquid reactants back into the capillary tubes  103 . For higher generation rates the liquid from the capillary tubes  103  makes contact with the chemical hydride ampoule  98 . The liquid reactants flow into the flow channels  101  of the solid hydride  98 . Once the liquid reactants are in the flow channels  101 , bubbles will form in the liquid reactants and tend to push the liquid reactant through the open channels  103 . With closed end channels the liquid will be bubbled out and will pressurize the area between the ampoules  102  and  98 . Both closed and open flow channels  101  may be needed to achieve smooth and responsive reactions with the chemical hydrides and volatile reactants. The hydrogen  21  produced in the chemical hydride ampoule  98  diffuses and flows out of the channels  101 . The hydrogen gas  21  is filtered of liquid reactants by the exit filter  100 , and hydrogen gas  21  is delivered out of the exit port  99  and to a fuel cell or hydrogen consuming device. 
     While the invention has been described with reference to specific embodiments, modifications and variations of the invention may be constructed without departing from the scope of the invention, which is defined in the following claims.