JP4537337B2 - Hydrogen generating material, method for producing hydrogen generating material, method for producing hydrogen, hydrogen producing apparatus and fuel cell - Google Patents

Description

  The present invention relates to a hydrogen generating material capable of generating hydrogen by reaction with water, a method for producing the same, a method for producing hydrogen using the hydrogen generating material, an apparatus therefor, and a fuel cell including the hydrogen producing apparatus. Is.

  In recent years, with the widespread use of cordless devices such as personal computers and mobile phones, secondary batteries as the power source are increasingly required to be smaller and have higher capacities. Currently, lithium ion secondary batteries have been put into practical use as secondary batteries that have high energy density and can be reduced in size and weight, and demand for portable power sources is increasing. However, depending on the type of cordless device used, this lithium secondary battery has not yet reached a level that guarantees sufficient continuous use time.

  In such a situation, a polymer electrolyte fuel cell can be cited as an example of a battery that can meet the above demand. A polymer electrolyte fuel cell that uses a solid polymer electrolyte as an electrolyte, oxygen in the air as a positive electrode active material, and fuel (hydrogen, methanol) as a negative electrode active material can be expected to have a higher energy density than a lithium ion battery. Attention has been paid. The fuel cell can be used continuously as long as fuel and oxygen are supplied.

  As for fuel cells, some candidates for the fuel to be used are listed, but each has various problems, and a final decision has not yet been made.

  As a fuel cell using hydrogen as a fuel, for example, a method of supplying hydrogen stored in a high-pressure tank or a hydrogen storage alloy tank has been put into practical use in part, but the volume and weight increase and the energy density decreases. However, it has a drawback that it is not suitable for portable power supply applications.

  Also, there is a method of using hydrocarbon-based fuel as fuel cell fuel and reforming it to take out hydrogen, but it requires a reformer and has problems such as heat supply and heat insulation to the reformer Therefore, it is still unsuitable for portable power supply applications. In addition, there is a direct methanol fuel cell that uses methanol as a fuel and reacts with methanol directly as a fuel. This is easy to downsize and is expected as a portable power source in the future. There are problems of voltage drop and energy density reduction.

On the other hand, there is also known a method in which hydrogen generated by a chemical reaction at a low temperature of 100 ° C. or less is used as fuel for a fuel cell (Patent Documents 1 to 5). In these methods, for example, a metal that generates hydrogen by reacting with water, such as aluminum, magnesium, silicon, or zinc, is used as a hydrogen source.
US Pat. No. 6,506,360 Japanese Patent No. 2566248 JP 2004-231466 A JP 2001-31401 A US Pat. No. 6,582,676

  The above Patent Documents 1 to 3 disclose techniques for reacting aluminum with an alkali or an acid. According to these techniques, hydrogen is easily generated chemically, but an equivalent amount of alkali or aluminum suitable for aluminum is disclosed. An acid needs to be added, resulting in a problem of a decrease in energy density due to an increase in the ratio of materials other than the hydrogen source. In addition, the reaction product oxide or hydroxide forms a film on the surface of the aluminum, making it impossible for the aluminum inside the film to come into contact with water, and the oxidation reaction stops only on the surface of the aluminum. Prone to occur.

  On the other hand, in the technique disclosed in Patent Document 4 which attempts to avoid this problem by mechanically removing the surface film, there is a problem that the apparatus becomes large, such as requiring mechanical equipment for removing the surface film. .

  In the technique disclosed in Patent Document 5, alumina is added as a catalyst for making it difficult to form the hydroxide film, and hydrogen is generated at a low temperature. However, hydrogen alone is not generated by a metal such as aluminum, and a catalyst is added, so that there is a problem that the content of metal such as aluminum as a hydrogen source is reduced and the hydrogen generation amount is reduced.

  The present invention has been made in view of the above circumstances, and provides a hydrogen generating material capable of easily and efficiently generating hydrogen and a method for producing the same, and further producing hydrogen using the hydrogen generating material. It is intended to realize miniaturization and efficiency improvement of the fuel cell by using it as fuel for the fuel cell.

  The hydrogen generating material of the present invention capable of achieving the above object contains at least one metal material selected from aluminum and aluminum alloys, and the metal material contains a metal-state aluminum on its surface. It has a surface film containing a phase and an inert phase containing an oxide or hydroxide of aluminum.

The present invention also provides an aluminum or aluminum alloy as a raw material in a processing solvent containing water and an organic solvent in producing a hydrogen generating material containing at least one metal material selected from aluminum and an aluminum alloy. Is made into a metal material having a surface film including a metal phase containing aluminum in a metallic state and an inert phase containing an oxide or hydroxide of aluminum .

  The present invention also provides a method for producing hydrogen, characterized in that hydrogen is produced by reacting the hydrogen generating material with water.

  Furthermore, the present invention includes a container containing the hydrogen generating material, and the container has a lead-out port through which the hydrogen generated by the reaction of the hydrogen generating material and water can be taken out from the container. An apparatus for producing hydrogen and a fuel cell equipped with the same as a hydrogen generation source are provided.

  ADVANTAGE OF THE INVENTION According to this invention, the hydrogen generating material which can generate | occur | produce hydrogen simply and efficiently, and the manufacturing method of hydrogen which uses the said hydrogen generating material as a hydrogen source can be provided. By using the hydrogen generating material of the present invention as a hydrogen source, it is possible to reduce the size and efficiency of the hydrogen generator and the fuel cell.

  The hydrogen generating material of the present invention contains at least one metal material selected from the group consisting of aluminum and aluminum alloys. The metal material is mainly composed of particles inside aluminum metal or aluminum alloy and a surface film covering the inside of the particles. The surface film is made of aluminum in a metal state (aluminum metal or aluminum alloy). And an inert phase containing aluminum oxide or aluminum hydroxide. The hydrogen generating material of the present invention can generate hydrogen quickly and efficiently by including the metal material having the above-described form.

  The metal material is made of aluminum (pure aluminum) or an aluminum alloy. As an aluminum alloy, aluminum should just be a main structural element and it does not specifically limit about the composition of an alloy. Examples of the alloy elements include silicon, iron, copper, manganese, magnesium, zinc, nickel, titanium, lead, tin, and chromium. From the viewpoint of increasing the amount of hydrogen generated by increasing the content ratio of aluminum in the metal material, the content of aluminum in the aluminum alloy is preferably 80% by mass or more.

  In general, aluminum has a surface film (oxide film) formed of a dense, poorly water-soluble inert phase composed of aluminum oxide or aluminum hydroxide on the surface inside particles of aluminum metal. In the reaction between aluminum and water, when water penetrates the surface film and reaches the aluminum metal inside the particles, hydrogen is generated. Therefore, in a normal hydrogen generating material using aluminum as a hydrogen generation source, a certain period of time is required until hydrogen generation starts.

  As a result of intensive studies by the present inventors, when hydrogen is produced using aluminum, there is a large difference in the time until the hydrogen generation rate and the time until the hydrogen generation rate is maximized depending on the surface state of the aluminum particles. It became clear. Specifically, when a metal phase containing aluminum in a metallic state exists in at least a part of the surface coating of the aluminum particles, the surface of the aluminum particles is composed of aluminum oxide or aluminum hydroxide. It has been found that the time until the start of hydrogen generation and the time until the hydrogen generation rate reaches the maximum can be shortened as compared with the case where only a dense film exists.

  This is because at least part of the surface film has a metal phase containing aluminum in a metallic state, so that water penetrates into the surface film and before the water reaches the aluminum metal inside the particles. The above metal phase present in the water reacts with water to start the reaction, and the reaction between the inside of the particle and water is promoted, so the time to start hydrogen generation and the time to maximum hydrogen generation speed are shortened. It is thought that it is done.

  The form of the metal phase and the inert phase in the surface coating is not particularly limited, but at least a part of the metal phase and the inert phase each form a layer, and the surface coating is the metal When the layer composed of the phase and the layer composed of the inert phase are included so as to be laminated with each other, it is expected that the reaction between the metal phase and water continuously occurs and the reactivity increases. . Moreover, the form which the metal phase of a fine particle size disperse | distributed inside the inert phase may be sufficient.

  As described above, the metal material contained in the hydrogen generating material of the present invention is a metal material composed of a conventional aluminum or aluminum alloy (a metal on which only a dense oxide film is formed on the surface). Compared to (material), the time until the start of hydrogen generation and the time until the hydrogen generation rate is maximized are shortened, and hydrogen can be produced easily and efficiently.

  In the metal material, when there are pores in the surface film (the inside of the laminated part or the interface between the laminated part and the inside of the particle), water is contained in the laminated part and the inside of the particle. This is preferable because it easily penetrates and the metal phase contained in the laminated portion or the inside of the particles easily reacts with water.

  The observation result by the electron microscope of the cross section of a normal aluminum powder is shown to Fig.1 (a)-(c). Moreover, the observation result by the electron microscope of the cross section of the metal material used for FIG.2 (a)-(c) for the hydrogen generating material of Example 1 of this invention is shown. 1 (a) and 2 (a) show images of the above-mentioned cross section with a scanning electron microscope (SEM), and FIGS. 1 (b) and 2 (b) show the above-mentioned cross-sectional scanning transmission electron microscope (STEM). FIGS. 1 (c) and 2 (c) show elemental mapping by an energy dispersive X-ray microanalyzer (EDX) in the field of view of FIGS. 1 (b) and 2 (b), respectively. .

  As is clear from FIG. 1A, in a normal aluminum powder, a dense surface film having a thickness of about 5 nm is present on the outer surface of the particles. Looking at the elemental mapping in FIG. 1 (c), oxygen is distributed almost only on the surface of the aluminum powder, so the surface film is considered to be an oxide or hydroxide of aluminum. Moreover, since the element distributed inside the particles is almost only aluminum, the inside is considered to be composed of aluminum metal.

  The “protective film” shown in FIGS. 1 (a), 1 (b) and 2 (a), 2 (b) is used for analysis that is attached to the particle surface for the purpose of protecting the particles during observation with an electron microscope. The film present on the outermost surface of the aluminum powder is actually the portion represented by the “surface film”.

  On the other hand, in the metal material shown to Fig.2 (a)-(c), particle | grains are comprised by the inner surface comprised with the aluminum metal, and the surface membrane | film | coat of about 1 micrometer or less which exists in the outer surface. When this surface film is seen by element mapping in FIG. 2 (c), a layer in which oxygen is mainly distributed (that is, aluminum oxide or aluminum hydroxide) is contained from the outermost surface side (inside the protective film). A layer composed of an inert phase) and a layer in which aluminum is mainly distributed (that is, a layer composed of a metal phase containing aluminum in a metallic state) are alternately laminated to form a laminated portion. It can be seen that there are two or more layers in each layer (see FIG. 2B). Moreover, it turns out that the void | hole is formed in the said surface film from Fig.2 (a).

  The surface film in the hydrogen generating material only needs to have the laminated portion in at least a part thereof, and the whole may be constituted by the laminated portion. For example, the surface film is formed on a part of the surface film. A laminated part may be formed, and the other part may be composed of only an inert phase. Specifically, the ratio of the laminated portion in the surface film can be, for example, 25 area% or more in the total surface area of the hydrogen generating material, and may be the total quantity, that is, 100 area%.

  Further, the laminated portion in the surface film may have a structure in which a layer made of a metal phase and a layer made of an inert phase are laminated one by one, for example, as shown in FIG. As described above, the metal phase layer and the inert phase layer may have a structure in which two or more layers are stacked on each other. Although the upper limit of the total number of laminated parts is not specifically limited, For example, each layer can be 4-5 layers.

  If the thickness of the laminated portion in the surface coating is too thick, the proportion of aluminum oxide and aluminum hydroxide that do not participate in the hydrogen generation reaction increases. From the viewpoint of hydrogen generation efficiency, for example, it is 2 μm or less. Is preferred. Moreover, the minimum of the thickness of the said laminated part can be 10 nm, for example.

  The metal material preferably contains 60% by mass or more, and more preferably 70% by mass or more, of aluminum in a metal state. When the aluminum content in the metal state in the metal material is lowered, the hydrogen generation amount may be lowered.

  In the heated state, a part of the surface reacts with water to generate hydrogen, so that aluminum forms a stable oxide film on the surface, so that a so-called bulk such as a plate, a block, or a particle of 1 mm or more is formed. In this state, the reaction with water does not proceed, and the amount of hydrogen generated at room temperature is 5 ml or less per 1 g of the metal material.

  Therefore, the metal material used for the hydrogen generating material of the present invention desirably contains fine particles at a certain ratio or more, and the ratio of particles having a particle diameter of 60 μm or less is preferably 80% by volume or more, and 90% by volume. More preferably. Further, the average particle size of the metal material is preferably 30 μm or less, and more preferably 20 μm or less. However, the form of the metal material is not limited to the particulate form, and may be a shape like a metal foil.

It is considered that the reaction in which aluminum generates hydrogen and an oxidation product proceeds according to one of the following formulas.
2Al + 6H ₂ O → Al ₂ O ₃ .3H ₂ O + 3H ₂ (1)
2Al + 4H ₂ O → Al ₂ O ₃ .H ₂ O + 3H ₂ (2)
2Al + 3H ₂ O → Al ₂ O ₃ + 3H ₂ (3)

  As described above, when aluminum is in a bulk state, these reactions stabilize the formation of an oxide film on the surface. However, by reducing the particle size, the reaction between aluminum and water inside the particles is less likely to be inhibited by the oxide film, and the hydrogen generation reaction occurs continuously. That is, when the metal material has the above particle size distribution and average particle size, the action of suppressing the reaction with water due to the formation of the oxide film can be reduced, and hydrogen can be generated efficiently.

  On the other hand, if the particle size of the metal material is too small, the hydrogen generation rate increases, but the flammability increases and handling in the air becomes difficult. Furthermore, since the bulk density is reduced, the filling density of the hydrogen generating material in the hydrogen generator is lowered, and the energy density is likely to be lowered. For this reason, the average particle size of the metal material in the hydrogen generating material is preferably 0.1 μm or more.

  The average particle diameter of the metal material as used in this specification means the value of 50% diameter in the volume-based integrated fraction. Further, the particle size distribution and average particle size of the metal material referred to in the present specification are values measured by a laser diffraction / scattering method. Specifically, this method is a particle size distribution measurement method using a scattering intensity distribution detected by irradiating a measurement target substance dispersed in a liquid phase such as water with laser light. As a particle size distribution measuring apparatus by the laser diffraction / scattering method, for example, “Microtrack HRA” manufactured by Nikkiso Co., Ltd. can be used.

  The metal material having a surface film including the laminated portion is obtained by pulverizing aluminum or an aluminum alloy in a treatment solvent containing water and an organic solvent, and performing surface modification of the metal material, and then removing the treatment solvent. Can be obtained.

  Aluminum or an alloy thereof used as a hydrogen generation source is pulverized to increase its surface area and improve the hydrogen generation rate. Here, when aluminum is pulverized by a general mechanical pulverization method such as a stamp mill method, a ball mill method, or a vibration mill method, aluminum is a highly malleable metal. A powder.

On the other hand, when aluminum or an aluminum alloy is mechanically pulverized in a processing solvent containing water and an organic solvent, a black granular fine powder is obtained, and aluminum produced by the general mechanical pulverization method as described above. It becomes a metal material that can react with water more quickly and efficiently generate hydrogen than the pulverized product. As described above, by adopting the above-described manufacturing method, the surface of the metal material includes a metal phase containing aluminum in a metal state and an inert phase containing aluminum oxide or aluminum hydroxide. This is considered to be due to the formation of a surface film containing Further, by adopting the above-described manufacturing method, at least a part of the metal phase and at least a part of the inert phase are respectively formed in layers, and the surface film includes the layer made of the metal phase and the inert phase. A layer composed of a phase has a laminated portion laminated with each other. Furthermore, by adopting the above production method, pores are formed in the surface film formed on the particle surface. As described above, the hydrogen generating material of the present invention is obtained by using aluminum or an aluminum alloy as a raw material, It can be obtained by using a metal material formed by pulverization in a processing solvent containing water and an organic solvent. If the liquid used for pulverization does not contain water and is composed of only an organic solvent, part or all of the metal material after pulverization becomes scale-like particles with metallic luster, resulting in reduced hydrogen generation efficiency. In addition, since the pulverized material easily adheres to the inner wall surface of the powder adoption pot or the like of the pulverizer, the target metal material cannot be produced efficiently.

  In addition, when the processing solvent used for pulverizing aluminum or aluminum alloy does not contain an organic solvent and is composed only of water, the oxidation of the surface of the metal material proceeds excessively during the pulverization process. A large amount of product or hydroxide is formed. For this reason, content of the aluminum which exists in a metal state in a metal material falls, and the amount of hydrogen generation will reduce.

  On the other hand, when the treatment solvent contains an organic solvent, the oxidation reaction during the pulverization of aluminum or the aluminum alloy can be controlled to adjust the thickness of the laminated portion in the surface film. In addition, the thickness of the laminated portion can be adjusted by controlling the pulverization time.

  The treatment solvent used for pulverizing aluminum or aluminum alloy has an amount of water of 0.02 parts by mass or more with respect to 1 part by mass of aluminum or aluminum alloy to be pulverized in order to form the surface film structure described above. The ratio is desirably adjusted so that the amount of water is 0.1 mass parts or more. On the other hand, in order to suppress the progress of oxidation during the pulverization of aluminum or aluminum alloy, the amount of water is preferably 2 parts by mass or less, more preferably 1 part by mass or less, and 0.4 parts by mass or less. It is most desirable to do. If the amount of water relative to the raw material aluminum or aluminum alloy is too small, the surface modification of the metal material becomes insufficient, and it becomes easy to obtain a scaly powder having a metallic luster, and the hydrogen generation efficiency of the metal material is low. May be. On the other hand, if the amount of water is too large, the content of metal aluminum in the metal material may be reduced, causing a decrease in the amount of hydrogen generated.

  The organic solvent for constituting the treatment solvent is not particularly limited as long as it is a solvent that does not easily react with aluminum or an aluminum alloy, and may be one that does not mix with water. Specific examples include aromatic hydrocarbons such as toluene, aliphatic hydrocarbons such as hexane and cyclohexane, ketones such as acetone, ethers, N, N-dimethylformamide, and the like. Among the organic solvents, those that become an azeotropic mixture with water (for example, toluene, cyclohexane, etc.) are more preferably used because they facilitate removal of the treatment solvent from the pulverized product. Only 1 type may be used for the said organic solvent, and 2 or more types may be used for it. Moreover, alcohol can also be used, and low molecular weight (for example, carbon number 10 or less) alcohol like methanol and ethanol is a solvent with high reactivity with aluminum compared with the organic solvent of the said illustration, and it depends on conditions. May react with aluminum to produce an alkoxide, but its reactivity is considerably low in comparison with water. Therefore, instead of the organic solvent exemplified above or together with the organic solvent exemplified above It is possible to use.

  In the processing solvent used for pulverization of aluminum or aluminum alloy, the ratio of water and organic solvent used is not necessarily limited. However, in order to moderately suppress the progress of oxidation of the metal material, for example, water 1 The amount of the organic solvent is preferably 5 parts by mass or more with respect to part by mass, and on the other hand, the amount of the organic solvent is preferably 300 parts by mass or less in order to enhance the effect of surface modification. .

  The method for pulverizing aluminum or aluminum alloy in the treatment solvent is not particularly limited, and for example, a mechanical pulverization method using a ball mill, a sand mill, a vibration mill, a jet mill or the like can be employed. In addition, when manufacturing the metal material used for the hydrogen generating material of the present invention, since hydrogen is generated during pulverization, it is desirable to provide a mechanism for escaping such hydrogen in the pulverizing apparatus as described above.

  The hydrogen generating material of the present invention is produced using a metal material obtained through such a process. As described above, the metal material preferably contains 60% by mass or more of aluminum in a metal state, and 70 It is more preferable to contain it by mass% or more. When the content of metallic aluminum in the metal material is reduced, the hydrogen generation amount may be reduced. In the present invention, since pulverization is performed in a processing solvent containing water, it is difficult for all of the aluminum elements contained in the metal material to exist in a metal state. However, as described above, the oxidation of aluminum or aluminum alloy during pulverization can be controlled by adding an organic solvent to the treatment solvent used for pulverization and limiting the content of water in the treatment solvent. Therefore, in the present invention, the hydrogen generating material can be configured using a metal material that contains a large amount of aluminum in a metal state and can efficiently generate hydrogen.

  In the present specification, the content of metallic aluminum in the metal material is measured as follows. When the metal material is analyzed by an X-ray diffractometer, aluminum or an aluminum alloy and aluminum hydroxide are observed. Therefore, the contents of aluminum and oxygen in the metal material are measured by fluorescent X-ray analysis (XRF), the aluminum hydroxide content is determined from the oxygen content, and the remainder is used as the aluminum content in the metallic state.

  When aluminum or an aluminum alloy is pulverized in the processing solvent, a substantially spherical or irregularly-shaped metal material is obtained. Such a metal material may be used as it is, or may be used after further processing, such as rolling into a scale shape.

  The hydrogen generating material of the present invention is constituted by mixing the metal material with a heat generating material, an additive and the like described later. However, since the metal material has good reactivity with water, the content of heat generating materials and additives can be reduced or the addition can be omitted. Therefore, the energy density can be improved.

  Moreover, there is no restriction | limiting in particular as a form of the said hydrogen generating material, For example, although it may remain with the powder form (particulate form) which has the same shape as said metal material, it is shape | molded by the pellet form or the granule form. It is more preferable. When the powdered hydrogen generating material is compression-molded into a pellet, the packing density is improved and the volume is reduced, so that the energy density is improved. In the case of granules, the hydrogen generation rate can be increased by granulating the hydrogen generating material into, for example, millimeter-sized granules.

  As will be described in detail later, the hydrogen generating material of the present invention is preferably heated at the start of the reaction with water. In addition to external heating, the hydrogen generating material is a heat generating material that generates heat by reacting with water. By making other materials coexist at the time of the reaction between the hydrogen generating material and water, the heat generated by the reaction of the heat generating material with water can be used. Therefore, it is also preferable that the hydrogen generating material contains a heat generating material that generates heat by reacting with water. Examples of such heat generating materials include calcium oxide, magnesium oxide, calcium chloride, magnesium chloride, calcium sulfate and the like, alkali metals or alkaline earths that generate heat by reacting with water or generate heat by hydration. Examples thereof include materials such as metal oxides. Moreover, metal powder which reacts with oxygen and generates heat, such as iron powder, can also be used as a heat generating material.

  When the hydrogen generating material contains the exothermic material, the content of the exothermic material is preferably, for example, 1% by mass or more in the total amount of the hydrogen generating material from the viewpoint of increasing the hydrogen generation rate. It is more preferable to be at least mass%. Further, from the viewpoint of the total amount of hydrogen generation, for example, it is preferably 15% by mass or less, and more preferably 10% by mass or less.

  When the heat generating material is contained in the hydrogen generating material, it is preferable to form the heat generating material including the heat generating material into pellets or granules.

  Further, the hydrogen generating material of the present invention can contain various additives according to various purposes.

  For example, a hydrophilic material (alumina, silica, magnesia, zinc oxide, etc.), carbon, a water-absorbing polymer (carboxymethylcellulose, polyvinyl alcohol, polyethylene glycol, etc.), etc. are included in the hydrogen generating material as the additive. Thus, hydrogen can be generated more efficiently. These additives may be used alone or in combination of two or more. Although the action of these additives is unclear, the contact between the metal material and water is improved by the additive, and the reaction product produced by the reaction of the metal material with water condenses the unreacted metal material. It is considered that there is an effect such that water penetrates into the inside of the pellet when the above is prevented or the pellet is formed as described later.

  In the case of using the above-mentioned various additives, the content thereof is, for example, preferably 1% by mass or more, more preferably 10% by mass or more in the hydrogen generating material from the viewpoint of hydrogen generation efficiency. Also, from the viewpoint of the total amount of hydrogen generation, for example, it is preferably 30% by mass or less, and more preferably 20% by mass or less.

  The hydrogen generating material of the present invention generates hydrogen when brought into contact with water. However, in order to improve the reactivity and obtain a hydrogen generation rate above a certain level, it is desirable to promote the reaction by heating from the outside. The heating temperature is desirably 40 ° C. or higher, and is desirably 95 ° C. or lower in order to prevent water evaporation. The heating method is not particularly limited as long as it is a method capable of keeping the hydrogen generating material and water within the above temperature range. For example, electric heating by energizing a resistor as a heat source is possible. A method of heating a container containing a hydrogen generating material and water from the outside using a chemical exothermic reaction or the like can be employed.

  Examples of the heat source that generates heat by a chemical reaction include the various compounds exemplified as the heat generating material that generates heat by reacting with water. The exothermic material reacts with water to generate heat, and the heat can be used to heat the reaction vessel containing the hydrogen generating material. However, the exothermic material is contained in the reaction vessel together with the hydrogen generating material, and heat is generated in the reaction vessel to generate hydrogen. The generated material may be heated directly. In this case, it is preferable that the amount of the heat generating material used is approximately equal to the above preferred content when the heat generating material is previously contained in the hydrogen generating material. That is, in the total of the hydrogen generating material and the heat generating material, the amount of the heat generating material is preferably 1% by mass or more, and more preferably 30% by mass or less.

  In addition, since the reaction between aluminum and water is an exothermic reaction, heat generation from the reaction heat is prevented, and if it is used to increase the temperature of the hydrogen generating material and water, hydrogen is continuously generated without the above heat source. It is possible to make it.

  Furthermore, the amount of hydrogen generation can be controlled by controlling the supply of water to be reacted with the hydrogen generating material.

  The hydrogen generating material of the present invention includes a container for storing the hydrogen generating material and water, and in the hydrogen generating apparatus having a mechanism for reacting the hydrogen generating material with water and taking out the generated hydrogen. Can be used as a source. The container in the hydrogen generator may have the above-described heating means for heating the hydrogen generating material and water from the outside, and hydrogen generation can be promoted as necessary. In this case, the amount of generated hydrogen can be controlled by controlling the heating temperature.

  The form and shape of the container in the hydrogen generator is not particularly limited, but it may be provided with a water supply port and a hydrogen discharge port so that the inside can be sealed so that water and hydrogen do not leak to the outside. desirable. The material used for the container is not particularly limited as long as it is difficult to permeate water and hydrogen and does not break even when heated to about 100 ° C. For example, heat resistant glass, metals such as titanium and nickel, and resins such as polyethylene and polypropylene can be used. An example of the hydrogen generator is shown in FIG. This hydrogen generation apparatus supplies water 7 into the reaction vessel 1 through a reaction vessel 1 having a container 2 for containing a hydrogen generating material 6 and a lid 3, and a water supply port 4 provided in the lid 3. The generated hydrogen is composed of the pump 8 and can be taken out through the hydrogen discharge port 5 provided in the lid 3.

  It is preferable to install a filter at the hydrogen outlet 5 of the hydrogen generator so that the contents of the container do not leak out. The filter is not particularly limited as long as it is a structure that allows gas to pass but hardly allows liquid and solids to pass therethrough, and a porous polytetrafluoroethylene gas-liquid separation membrane used in a fuel cell or the like may be used. Moreover, the porous film made from a polypropylene utilized as a separator of a battery can also be used.

  In the hydrogen generator, it is desirable that the flow rate of water to be supplied to the inside of the container can be controlled. As described above, the amount of hydrogen generated can be controlled by controlling the supply of water. .

Hydrogen generated using the hydrogen generating material of the present invention does not contain CO and CO ₂ which are problematic in hydrogen obtained by reforming hydrocarbon-based fuels. Therefore, in the polymer electrolyte fuel cell operating at 100 ° C. or lower, the problem of poisoning due to the gas does not occur, and water is involved in the reaction. It is very useful in a fuel cell using as a fuel.

  Hereinafter, the present invention will be described in detail based on examples. However, the following examples are not intended to limit the present invention, and all modifications made without departing from the spirit of the preceding and following descriptions are included in the technical scope of the present invention.

<Experiment 1 Production of metal material and hydrogen generating material, and hydrogen generation test>
Example 1
Aluminum powder with an average particle size of 55 μm prepared by the atomization method: 5 g, toluene: 15 g, water: 1 g (0.2 parts by mass with respect to 1 part by mass of the aluminum powder) and zirconia beads having a particle size of 2 μm: 85 g was put into a grinding pot of a planetary ball mill, and aluminum powder was crushed at a rotation speed of 200 rpm. Since hydrogen was generated during the pulverization, the rotation was stopped after 10 minutes, and the generated hydrogen was released in the pot and rotated again. This procedure was repeated to rotate the pot for a total of 1 hour. Thereafter, toluene and water were removed by drying under reduced pressure to obtain a metal material for constituting the hydrogen generating material of the present invention. The obtained metal material was black-brown due to loss of surface metallic luster, and became irregularly-shaped particles having an average particle diameter of 12 μm. With respect to this metal material, the content of aluminum in the metal state was measured by the above-mentioned method, and found to be 80% by mass, and in the aluminum powder produced by the atomizing method as the raw material, it was 99% by mass. Further, the particle size distribution of the metal material was measured by the particle size distribution measuring apparatus described above.

  Next, the observation result by the electron microscope of the cross section of the aluminum powder used as a raw material when producing the metal material of Example 1 is shown to Fig.1 (a)-(c). Moreover, the observation result by the electron microscope of the cross section of the metal material produced in Example 1 is shown to Fig.2 (a)-(c). As described above, FIG. 1 (a) and FIG. 2 (a) show images of the above section with a scanning electron microscope (SEM), and FIG. 1 (b) and FIG. FIG. 1 (c) and FIG. 2 (c) are images obtained with an energy dispersive X-ray microanalyzer (EDX) in the fields of FIG. 1 (b) and FIG. 2 (b), respectively. Element mapping is shown.

  As described above, in the raw material aluminum powder shown in FIGS. 1A to 1C, aluminum is mainly distributed inside the particles, whereas the outer surface has a width of about 5 nm. Mainly oxygen is distributed. That is, in the raw material aluminum powder, a dense surface film that is considered to be an oxide film exists on the surface of particles that are considered to be composed of aluminum metal.

  In contrast, in the metal material of Example 1 shown in FIGS. 2A to 2C, aluminum is mainly distributed inside the particles, and the inside of the particles is made of aluminum metal. On the outer surface, a layer in which oxygen is mainly distributed (that is, a layer made of an inert phase containing aluminum oxide or aluminum hydroxide) and a layer in which aluminum is mainly distributed (that is, metal) A layer made of a metal phase containing aluminum in a state) is alternately laminated one by one, and there is a surface film having a thickness of about 1 μm or less including a laminated portion having a plurality of layers.

  A hydrogen generation test was performed using the above metal material alone as a hydrogen generation material. The metal material: 1 g and water: 10 g were put in a sample bottle, and a resistor was placed outside the sample bottle. Hydrogen was generated by heating the container to 50 ° C. with a resistor, and the generated hydrogen was collected by a water displacement method and the amount of generation was measured.

(Comparative Example 1)
The aluminum powder used as a raw material in Example 1 was directly used as a hydrogen generating material, and a hydrogen generation test was performed in the same manner as in Example 1 to measure the amount of hydrogen generation.

  For the hydrogen generating materials of Example 1 and Comparative Example 1, the amount of hydrogen collected every 2 minutes was measured, and the time from the start of the hydrogen generation test to the start of hydrogen generation was determined. In addition, the hydrogen production rate was determined from the change in the amount of hydrogen collected over time, and the time until the value reached the maximum value was also determined. The results are shown in Table 1.

  From Table 1, in Example 1, which was prepared by pulverizing aluminum powder in a processing solvent containing water and an organic solvent, compared to the raw material powder used as the hydrogen generating material in Comparative Example 1, the time until the start of hydrogen generation was reached. The time and the time until the hydrogen generation rate was maximized could be greatly reduced. In consideration of the particle cross-sectional images shown in FIGS. 2 (a) to 2 (c), this is because a part of the surface film is composed of a laminated portion of a metal phase and an inert phase, so that the surface film has water. Before the water reaches the aluminum metal inside the particle, the metal phase and water in the layered portion of the surface film reacts to become the starting point of the reaction, and the reaction between the inside of the particle and water is promoted. It is considered that the time until hydrogen is generated and the time until the hydrogen generation rate is maximized are greatly reduced. In addition, the vacancies present in the laminated portion observed in the metal material of Example 1 were also greatly reduced in the time until the start of hydrogen generation and the maximum hydrogen generation rate. This is considered to be one of the factors.

(Example 2)
A metal material was produced in the same manner as in Example 1 except that the amount of water used for pulverizing the aluminum powder was changed to 0.5 g (0.1 part by mass with respect to 1 part by mass of the aluminum powder). A hydrogen generation material was composed of only this metal material, a hydrogen generation test was performed, and a hydrogen generation amount was measured.

(Example 3)
A metal material was produced in the same manner as in Example 1 except that the amount of aluminum powder used for pulverization was changed to 3 g and the amount of water was changed to 3 g (1 part by mass with respect to 1 part by mass of the aluminum powder). A hydrogen generation material was composed of only this metal material, a hydrogen generation test was performed, and a hydrogen generation amount was measured.

Example 4
A metal material was produced in the same manner as in Example 1 except that the amount of aluminum powder used for pulverization was changed to 1 g and the amount of water was changed to 3 g (3 parts by mass with respect to 1 part by mass of the aluminum powder). A hydrogen generation material was composed of only this metal material, a hydrogen generation test was performed, and a hydrogen generation amount was measured.

(Example 5)
A metal material was produced in the same manner as in Example 1 except that the total rotation time of the grinding pot was changed to 10 minutes. A hydrogen generation material was composed of only this metal material, a hydrogen generation test was performed, and a hydrogen generation amount was measured.

(Example 6)
A metal material was produced in the same manner as in Example 1 except that the amount of water used for pulverizing the aluminum powder was 0.05 g (0.01 parts by mass with respect to 1 part by mass of the aluminum powder). A hydrogen generation material was composed of only this metal material, a hydrogen generation test was performed, and a hydrogen generation amount was measured.

(Example 7)
A hydrogen generating material was prepared by mixing 0.9 g of the metal material prepared in Example 1 and 0.1 g of alumina having an average particle diameter of 1 μm in a mortar. Using this hydrogen generating material, a hydrogen generation test was performed in the same manner as in Example 1, and the amount of hydrogen generation was measured.

(Example 8)
A hydrogen generating material was produced by mixing 0.93 g of the metal material produced in Example 1 and 0.07 g of carbon (“Vulcan XC-72R” manufactured by Cabot Corporation). Using this hydrogen generating material, a hydrogen generation test was performed in the same manner as in Example 1, and the amount of hydrogen generation was measured.

Example 9
0.96 g of the metal material produced in Example 1 and 0.04 g of carboxymethyl cellulose (manufactured by Daicel) were mixed to produce a hydrogen generating material. Using this hydrogen generating material, a hydrogen generation test was performed in the same manner as in Example 1, and the amount of hydrogen generation was measured.

(Comparative Example 2)
A metal material was produced in the same manner as in Example 1 except that the processing solvent used for grinding the aluminum powder was only 16 g of water. A hydrogen generation material was composed of only this metal material, a hydrogen generation test was performed, and a hydrogen generation amount was measured.

(Comparative Example 3)
A metal material was produced in the same manner as in Example 1 except that the processing solvent used for pulverizing the aluminum powder was only 15 g of toluene. A hydrogen generation material was composed of only this metal material, a hydrogen generation test was performed, and a hydrogen generation amount was measured.

  The hydrogen generation test in Examples 1 to 9 and Comparative Examples 2 and 3 was performed for 20 hours, during which time the amount of hydrogen collected every 2 minutes was measured, and the time and test from the start of the hydrogen generation test to the start of hydrogen generation The total amount of hydrogen generation was determined. In addition, the hydrogen generation rate was determined from the change in the amount of hydrogen collected over time, and the time until the value reached the maximum and the maximum value at that time were determined. These results are shown in Tables 2 and 3.

  Further, for the metal materials in Examples 2 to 9 and Comparative Examples 2 and 3, the average particle diameter and the aluminum content in the metal state were measured in the same manner as in Example 1. These results are also shown in Table 2.

  FIG. 4 is a graph showing the particle size distribution of the metal materials of Examples 1, 2, and 5, with the horizontal axis representing the particle size (μm) and the vertical axis representing the frequency (volume%). As is clear from FIG. 4, each of the metal materials of Examples 1, 2, and 5 contains particles having a particle size of 60 μm or less in a proportion of 80% by mass or more.

  In the hydrogen generating materials of Examples 1 to 9 including the metal material prepared by pulverizing aluminum powder in a processing solvent containing water and an organic solvent, generation of hydrogen starts more than the hydrogen generating material of Comparative Example 1 And the time until the hydrogen production rate reaches the maximum, the hydrogen generation material capable of generating hydrogen by easily reacting with water could be obtained. However, since the particle size distribution and the form of the surface film differ depending on the processing conditions of the metal material, differences were observed in the maximum amount of hydrogen generation and the maximum hydrogen generation rate.

  The hydrogen generation materials of Example 2 and Example 5 had values of lower hydrogen generation amount and production rate than the hydrogen generation material of Example 1. As shown in FIG. 4, it is considered that the particle size of the metal material of Example 2 and Example 5 was larger than the particle size of the metal material of Example 1 and the surface area was reduced. In the hydrogen generating material of Example 3, the hydrogen generation rate increased, but the hydrogen generation amount decreased. The increase in the production rate is thought to be because the particle size of the metal material was reduced and the reaction area was increased. However, the amount of water added during the pulverization treatment increased the oxidation of aluminum and the aluminum in the metallic state decreased. Therefore, it seems that the amount of hydrogen generation decreased. In the hydrogen generating material of Example 4, the ratio of water added at the time of treatment was higher than that of Example 3, so that the oxidation of aluminum further progressed, and the hydrogen generation amount and the generation rate were higher than those of Example 1 hydrogen generating material. It is thought that it fell. Therefore, it is considered that the metal aluminum content can be controlled by changing the ratio of aluminum and water during the treatment, and the hydrogen generation amount and the production rate can be controlled. It was also found that the particle size of the metal material can be controlled by changing the ratio of aluminum and water during the treatment. Further, from Example 5, it was found that the particle size of the metal material can be controlled also by changing the pulverization time. By controlling these grinding conditions, it is considered that the amount of hydrogen generation and the rate of hydrogen generation can be controlled by controlling the particle size of the metal material.

  The metal material used in Example 6 was prepared by reducing the proportion of water in the processing solvent used for pulverizing the aluminum powder, but most of the pulverized metal material adhered to the surface of the pulverizing pot. . Moreover, a part was obtained as scale-like particles having a metallic luster. When a hydrogen generation test was performed using this metal material as a hydrogen generation material, the metal material floated in water and became difficult to react with water. Therefore, the amount of hydrogen generation was lower than that in Example 1. On the other hand, the metal materials used in Examples 1 to 5 and Examples 7 to 9 were submerged in water and had good affinity with water.

  In Example 7, alumina was added as an additive, and the content of the metal material was 90% by mass to constitute the hydrogen generating material. In this example, the content of the metal material was reduced as compared with the hydrogen generating material of Example 1, but the reaction rate of aluminum in the metal material increased due to the fact that alumina as an additive promoted the reaction. As a result, it was possible to obtain a hydrogen generation amount and a hydrogen generation rate equivalent to those in Example 1. This is presumably because the addition of alumina prevented the condensation of the unreacted metal material and the product produced by the reaction of the metal material.

  Similarly to Example 7, also in Example 8 in which carbon was added as an additive to form a hydrogen generating material, and Example 9 in which carboxymethyl cellulose as a water-absorbing polymer was added as an additive to form a hydrogen generating material. Although the content of the metal material is reduced as compared with the hydrogen generating material of Example 1, the hydrogen generation amount and the hydrogen generation rate equal to or higher than those of Example 1 are secured, and the carbon in the hydrogen generating material is It was also found that the water-absorbing polymer has the same action as the alumina according to Example 7.

  On the other hand, in Comparative Example 2 in which the aluminum powder was pulverized using only water, most of the aluminum reacted with water and oxidized during the pulverization treatment, so that almost no metallic aluminum remained. The amount of hydrogen obtained in the hydrogen generation test was very small.

  In Comparative Example 3, the aluminum powder was pulverized using only an organic solvent not containing water. However, the amount of pulverized matter adhering to the surface of the pulverizing pot and the proportion of scale-like particles having a metallic luster were obtained. Compared with Example 6, it further increased. And even if the hydrogen generation test was performed using this pulverized product, the pulverized product floated in water, and the amount of hydrogen generation was extremely reduced. It is considered that the difference in particle shape and surface property between the metal materials produced in Examples 1 to 5 and the pulverized product in Comparative Example 3 affect the difference in hydrogen generation.

  About the metal material produced in Examples 2-6, while observing the cross section with an electron microscope and etching the surface with Ar, the peak derived from the metallic state of aluminum by X-ray photoelectron spectroscopy (XPS) And by analyzing the depth of the 2p peak derived from the oxide (or hydroxide), the surface of each metal material has a laminated portion having a structure as shown in the schematic diagram of FIG. It was confirmed that the surface film had.

(Example 10)
The test was performed in the same manner as in Example 1 except that the heating temperature of the container in the hydrogen generation test was changed to 45 ° C., and the amount of hydrogen generation was measured.

(Example 11)
The test was performed in the same manner as in Example 1 except that the heating temperature of the container in the hydrogen generation test was changed to 40 ° C., and the amount of hydrogen generation was measured.

  Table 4 shows the maximum amount of hydrogen generation and the rate of hydrogen generation for Example 10 and Example 11.

  In both Example 10 and Example 11 in which the heating temperature during the hydrogen generation test was changed, hydrogen generation was observed. If the hydrogen generating material was heated to 40 ° C. or higher, the amount of hydrogen generation and the rate of hydrogen generation were reduced. A significant increase was confirmed. In Example 1 heated to 50 ° C., the maximum hydrogen generation rate was 14 minutes after the start of heating, and then the generation rate rapidly decreased. In contrast, in Examples 10 and 11 heated at 45 ° C. and 40 ° C., the production rate was lower than in Example 1, but hydrogen could be generated stably over a long period of time. Therefore, it is considered that the hydrogen generation rate can be controlled also by controlling the heating temperature.

<Experiment 2 Hydrogen generation test with hydrogen generator>
(Example 12)
A metal material produced in the same manner as in Example 1 was used as a hydrogen generation material as it was, and a hydrogen generation test was performed using a hydrogen generation apparatus having the configuration shown in FIG. 1 g of the hydrogen generating material was placed in a glass container 2 having an internal volume of 50 ml. The glass container 2 was sealed with a lid 3 having a water supply port 4 and a hydrogen discharge port 5. A resistor was disposed outside the container 2 as a heating means. When the resistor was energized and the container was heated to 50 ° C., water was supplied from the water supply port 4 at a rate of 0.02 ml / min using the pump 8, and hydrogen generation was confirmed as in Example 1. It was done. It was also confirmed that when water supply was stopped, hydrogen generation stopped after a few minutes.

(Example 13)
In Example 12, instead of stopping the supply of water, when heating was stopped and the container was allowed to cool, it was confirmed that hydrogen generation stopped after a few minutes.

<Experiment 3 Production of polymer electrolyte fuel cell>
Hydrogen was generated in the same manner as in Example 1, and the generated hydrogen was supplied to a polymer electrolyte fuel cell to conduct a discharge test. As a result, it was found that a high output of 200 mW / cm ² was obtained at room temperature, and it was effective as a fuel source for a compact and portable fuel cell.

It is a figure which shows the observation result by the electron microscope of the cross section of the aluminum powder used as a raw material in the case of preparation of the metal material of Example 1. FIG. It is a figure which shows the observation result by the electron microscope of the cross section of the metal material used for the hydrogen generating material produced in Example 1. FIG. It is a figure which shows typically the structure of a hydrogen generator. It is a graph which shows the particle size distribution of the metal material used for the hydrogen generating material of Example 1, 2 and 5. It is a figure which shows typically the structure of the surface film | membrane of the metal material used for the hydrogen generating material of Examples 2-6.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Reaction container 2 Storage container 3 Lid 4 Water supply port 5 Hydrogen discharge port 6 Hydrogen generating material 7 Water 8 Pump

Claims (21)

A hydrogen generating material containing at least one metal material selected from aluminum and aluminum alloys and generating hydrogen gas by reaction with water,
The metal material has a surface film including a metal phase containing aluminum in a metal state and an inert phase containing an oxide or hydroxide of aluminum.   2. The hydrogen generating material according to claim 1, wherein the surface film includes a laminated portion in which a layer made of the metal phase and a layer made of the inert phase are laminated with each other.   3. The hydrogen generating material according to claim 2, wherein in the laminated portion, two or more layers each including the metal phase and the inert phase are stacked.   The hydrogen generating material according to claim 2 or 3, wherein the thickness of the laminated portion is 2 µm or less.   The hydrogen generating material according to claim 1, wherein the surface film has pores.   The hydrogen generating material according to claim 1, wherein the metal material contains particles having a particle size of 60 μm or less in a proportion of 80% by volume or more.   The hydrogen generating material according to claim 1, wherein the metal material has an average particle size of 30 μm or less.   The aluminum contained in the metal material is a hydrogen generating material according to any one of claims 1 to 7, wherein 60 mass% or more is present in a metal state.   The heat generating material which generates heat by reacting with water, and further contains a heat generating material other than the metal material.   The hydrogen generating material according to any one of claims 1 to 9, further comprising at least one additive selected from a hydrophilic oxide, carbon, and a water-absorbing polymer. A method for producing a hydrogen generating material containing at least one metal material selected from aluminum and an aluminum alloy and generating hydrogen gas by reaction with water,
By crushing aluminum or an aluminum alloy as a raw material in a processing solvent containing water and an organic solvent, a metal phase containing aluminum in a metal state and an inert phase containing an oxide or hydroxide of aluminum A method for producing a hydrogen generating material , comprising forming a metal material having a surface coating containing
  The method for producing a hydrogen generating material according to claim 11, wherein the treatment solvent contains an aromatic hydrocarbon or an aliphatic hydrocarbon.   The method for producing a hydrogen generating material according to claim 11, wherein the treatment solvent contains an organic solvent that becomes an azeotropic mixture with water.   The method for producing a hydrogen generating material according to claim 13, wherein the treatment solvent contains toluene or cyclohexane.   The method for producing a hydrogen generating material according to any one of claims 11 to 14, wherein the amount of water in the treatment solvent is 0.02 to 2 parts by mass with respect to 1 part by mass of aluminum or aluminum alloy as a raw material.   The method for producing a hydrogen generating material according to claim 15, wherein the amount of water in the treatment solvent is 0.1 to 1 part by mass with respect to 1 part by mass of aluminum or aluminum alloy as a raw material.   The manufacturing method of the hydrogen generating material in any one of Claims 11-16 which makes the quantity of the organic solvent with respect to 1 mass part of water 5 mass parts or more in the said process solvent.   A method for producing hydrogen, wherein the hydrogen generating material according to any one of claims 1 to 10 is reacted with water to produce hydrogen.   19. The method for producing hydrogen according to claim 18, wherein at least one of the hydrogen generating material and water is heated.   11. A lead-out port provided with a container containing the hydrogen generating material according to claim 1 and further capable of taking out hydrogen generated by the reaction of the hydrogen generating material with water from the inside of the container. Is provided in the container. A fuel cell using hydrogen as a fuel, comprising the hydrogen production apparatus according to claim 20 as a hydrogen generation source.

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