JP2003178770A - Film-electrode junction, its manufacturing method, and polymer electrolyte type or direct methanol type fuel cell using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a film-electrode junction, which has high heat resistance and chemical resistance, and moreover functions steady also at high temperature, and its manufacturing method and to provide a solid polymer electrolyte type fuel cell, which is enabled to correspond to high temperature operation by using this, especially a direct methanol type fuel cell. <P>SOLUTION: It is the film-electrode junction, in which the electrode layers have been formed on both sides of a proton conductive film. And the film- electrode junction, which has this electrode layer that consists of a three- dimensional bridge construction structure body containing silane and carbon particles containing a precious-metal catalyst, and its manufacturing method, are provided. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a bonded body of a proton conductive membrane and a gas diffusion electrode in a polymer electrolyte fuel cell (hereinafter simply referred to as “membrane-electrode assembly”), a method for producing the same, and a method for manufacturing the same. Regarding a solid polymer electrolyte type or direct methanol type fuel cell using the same, more specifically, a membrane-electrode assembly having high heat resistance and chemical resistance, and stably functioning even at high temperature, a method for producing the same, and the same. The present invention relates to a solid polymer electrolyte type or direct methanol type fuel cell which can be used at high temperatures.

[0002]

2. Description of the Related Art At present, environmental problems and energy problems have become major problems on a global scale, and fuel cells have been attracting attention as a next-generation promising power generator that can contribute to solving them. This is because the fuel cell has an extremely high power generation efficiency as compared with thermal power generation using fossil fuel, does not emit air pollutants, and is environmentally friendly.

A fuel cell is classified into a phosphoric acid type, a molten carbonate type, a solid oxide type, a solid polymer electrolyte type, etc., depending on the type of electrolyte constituting the fuel cell. Among them, a solid polymer electrolyte type fuel cell is used. Compared with other methods, the device has a smaller size and higher output, and as a fuel cell for small-scale on-site power generation, mobile power sources such as vehicle power sources, or mobile devices, will be the mainstay of the next generation. It is positioned as a responsible system.

The basic structure of a fuel cell is a structure (joint body) in which electrodes carrying a catalyst are arranged on both sides of a proton (hydrogen ion) conducting membrane, and this is used as a unit cell, and fuel and oxygen are provided outside the unit cell. By installing a pair of separators that serve as the passages and connecting a plurality of adjacent cells to each other, a desired power can be taken out. When hydrogen, for example, is supplied as fuel from one side of such a joined body, H ₂ → 2H ⁺ + 2e is produced by the catalyst on the fuel electrode side.
^- the following reaction occurs, protons and electrons are generated.

Here, the protons are supplied to the oxygen electrode side through the proton conductive membrane in contact with the electrodes. The electrons are collected by the electrodes, used as electricity, and then supplied to the oxygen electrode side. On the other hand, at the oxygen electrode, the supplied oxygen, the protons that have passed through the proton conductive membrane,
Receives electrons used as electricity and catalyzes 1
The reaction of / 2O ₂ + 2H ⁺ + 2e ⁻ → H ₂ O occurs.

As described above, since the chemical reaction due to the operation of the fuel cell occurs at the interface between the proton conductive membrane and the catalyst-supporting electrode, the interface structure between the membrane, the electrode and the catalyst greatly affects the performance such as power generation efficiency. To do.

The assembly of the membrane, the catalyst and the electrode is generally a membrane-
It is called an electrode assembly (MEA) and is one of the major technological development fields of fuel cells. In MEA, the membrane,
The catalyst and electrode must be mixed with a proper interface. That is, taking the fuel electrode side as an example, it is necessary that hydrogen, which is a fuel, can contact the surface of the catalyst, and the protons and electrons generated from the hydrogen are efficiently transferred to the membrane and the electrode, respectively.

At present, the most standardly used proton conductive membrane for fuel cells is a sulfonated fluororesin having a thermoplastic property (typical example: DuPo).
nt, product name "Nafion"). In the case of such a thermoplastic film, a method of joining electrodes supporting a catalyst by hot pressing is generally used.

However, in the hot pressing method, there is a problem that the gas diffusion pores of the electrode are deformed or clogged, and the fuel supply capacity is lowered, and because the membrane is strongly heated even for a short time, Causes structural changes in the resin that makes up the film,
It may also reduce the proton conductivity of the membrane.

Therefore, instead of the hot pressing method, a method has been proposed in which a sulfonated fluororesin or the like is dissolved in a suitable solvent and the mixture is used as an adhesive to bond the membrane and the electrode. For example, a method of using an adhesive obtained by dissolving an ion exchange resin composed of a perfluorocarbon polymer in a solvent composed of a hydrocarbon alcohol system, a fluorine-containing hydrocarbon system, or a mixture thereof is disclosed (Patent Document 1
reference. ), In such a method, an appropriate mixed state and interface structure of the proton conductive resin, the catalyst and the electrode can be generated in advance. In addition, a method of forming an interface using an adhesive and then hot pressing has been proposed (see Patent Document 2). This is a method in which a proton conductive polymer dissolved in a solvent is applied onto a catalyst layer, dried to form a proton conductive polymer layer, and then bonded to a solid polymer electrolyte membrane under heating and pressure.

The method using such an adhesive is excellent in that a proper mixed state of a proton conductive resin, a catalyst and an electrode and an interfacial structure can be produced in advance, but a sulfonated fluororesin is used as a binder of the adhesive. When used, there is a problem of insufficient heat resistance. Nafion
In sulfonated fluororesins such as (registered trademark), ion channels are formed due to aggregation of sulfone groups, and this exhibits proton conductivity.

However, since the sulfonated fluororesin has thermoplasticity, it plastically deforms above a specific temperature,
The ion channel structure is destroyed. For example, Na
The glass transition temperature (Tg) of fion (registered trademark) is 1
It is 30 ℃, and above this temperature in a short time, 100
Even at ˜130 ° C., plastic deformation gradually occurs, resulting in extremely low ionic conductivity. From this, Nafion
The stable usable temperature of (registered trademark) is limited to 80 ° C.

In the current solid polymer electrolyte fuel cell,
In most cases, since a sulfonated fluororesin such as Nafion (registered trademark) is used as the electrolyte membrane, the operating temperature is limited to a relatively low temperature range from room temperature to about 80 ° C. However, if the operating temperature is lowered as described above, the power generation efficiency of the fuel cell is lowered. In addition, when hydrogen, which is the fuel, contains impurities such as carbon monoxide, there are disadvantages such as significant catalyst poisoning.In addition, in order to keep the operating temperature low, it is constantly cooled. Since water or the like must be supplied, it is an obstacle to higher efficiency, downsizing, and cost reduction of the device.

By the way, if the operating temperature of the apparatus can be raised to 100 ° C. or higher, the power generation efficiency is improved, and at the same time, exhaust heat can be utilized, so that the energy can be utilized more efficiently. In particular, if the operating temperature can be increased to 140 ° C., not only the efficiency improvement and utilization of exhaust heat but also the range of selection of the catalyst material is widened and an inexpensive fuel cell can be realized.

From this point of view, research and development of a film that can withstand higher temperatures is being promoted. For example, Ogata et al. Manufacture a heat resistant film using a heat resistant aromatic polymer compound (see Non-Patent Document 1). Further, the present applicants have already proposed a membrane material that shows stable proton conductivity even at high temperature by producing an organic-inorganic composite membrane based on a completely new idea (see Patent Document 3). .).

However, even if such a film having heat resistance is obtained, if a fluororesin is used as an adhesive agent in the membrane-electrode assembly as in the above-mentioned Patent Document 1 and Patent Document 2, the film is Although it can withstand high temperatures, the membrane-electrode assembly does not have heat resistance, which means that the fuel cell cannot operate at high temperatures. Further, if a thermoplastic material other than a fluorine-based resin is used for the adhesive, the creep property thereof causes the performance to vary.

On the other hand, in the current fuel cell, hydrogen is extracted as a fuel by treating methanol with a reformer, and the hydrogen is used as a fuel. In recent years, a direct methanol fuel in which methanol is directly introduced into the fuel cell is used. Batteries are also being actively studied. In the case of a direct methanol fuel cell, not only heat resistance but also methanol resistance is required for the membrane.

For example, the present applicants have disclosed a membrane that can also be used in a direct methanol fuel cell (see Patent Document 4).
However, also in this case, in order to form a membrane-electrode assembly, if a thermoplastic material such as a fluorine-based resin is used as an adhesive, not only heat resistance becomes a problem, but also due to extreme swelling and dissolution, There is a risk that the pores of the gas diffusion electrode will be blocked or the catalyst will be liberated.

Further, when the fluororesin is present at the catalyst interface, a special treatment is required also when recovering the catalyst, and from this aspect, the advent of a non-halogen resin material is desired.

[0020]

[Patent Document 1] Japanese Patent Laid-Open No. 11-339824

[Patent Document 2] Japanese Patent Laid-Open No. 11-40172

[Patent Document 3] Japanese Patent Application No. 2000-38727

[Patent Document 4] Japanese Patent Application No. 11-264066

[Non-Patent Document 1] "Solid State Ioni
cs ", No. 106 (1998), p. 219

[0021]

In view of the above-mentioned problems of the prior art, an object of the present invention is to provide a membrane-electrode assembly which has high heat resistance and chemical resistance and which functions stably even at high temperatures.
It is an object of the present invention to provide a method for producing the same, and a solid polymer electrolyte fuel cell, particularly a direct methanol fuel cell, which can be used for high temperature operation by using the method.

[0022]

In order to solve the above-mentioned problems, the inventors of the present invention have conducted extensive studies on various membrane-electrode bonding methods, and as a result, have found that a three-dimensional crosslinked structure containing silane in the electrode portion. By using a body-based one, a structural change does not occur even at high temperature and a suitable interface structure can be maintained, so that a membrane-electrode assembly that exhibits stable performance even at a high temperature of 100 ° C. or higher. It was found that the body can be obtained. The present invention has been completed based on these findings.

That is, according to the first aspect of the present invention,
A membrane-electrode assembly in which electrode layers are formed on both sides of a proton conductive membrane, wherein the electrode layer comprises a three-dimensional crosslinked structure containing silane and carbon fine particles carrying a noble metal catalyst. A membrane-electrode assembly is provided.

According to the second aspect of the present invention, the first aspect
In the invention described above, the monomer before the polymerization of the three-dimensional crosslinked structure is a polar compound represented by the following chemical formula (1), a non-polar compound represented by the following chemical formula (2), or a mixture thereof. A membrane-electrode assembly is provided.

[0025]

[Chemical 3]

(In the formula, R ¹ represents an alkyl group having 4 or less carbon atoms, R ² represents any organic group containing a polar group, m,
Each of n is an integer of 1 to 3. However, m + n =
When R is 4 and m is 2 or 3, R ² may be a mixture of different organic groups. )

[0027]

[Chemical 4]

(Wherein R ¹ and R ³ represent an alkyl group having 4 or less carbon atoms, R ⁴ represents a hydrocarbon group having 20 or less carbon atoms, x is 1 to 3 and y is an integer of 0 to 2). Where x
When + y = 3 and y is 2, R ³ may be a mixture of different alkyl groups. )

According to the third aspect of the present invention, the first aspect
In the invention of 1, the membrane-electrode assembly is provided, wherein the electrode layer contains an inorganic acid.

Furthermore, according to the fourth aspect of the present invention, in the third aspect, the inorganic acid is at least one compound selected from phosphotungstic acid, silicotungstic acid, and phosphomolybdic acid. A membrane-electrode assembly is provided.

According to the fifth aspect of the present invention, the second aspect
In the invention of 1, the polar group in R ² represented by the chemical formula (1) is a sulfonic acid group or a phosphoric acid group, and a membrane-electrode assembly is provided.

On the other hand, according to the sixth aspect of the present invention, a liquid containing a silane-containing three-dimensional crosslinkable monomer, carbon fine particles carrying a noble metal catalyst, and a water-soluble material on both sides of the proton conductive membrane. A first step of applying a product, a second step of curing the liquid material, and a third step of eluting a water-soluble material from the cured product to make the cured product porous, A method for producing a membrane-electrode assembly according to any one of the inventions 1 to 5 is provided.

According to the seventh aspect of the present invention, a liquid material containing a three-dimensional crosslinkable monomer containing silane, carbon fine particles, and a water-soluble material is applied to both surfaces of the proton conductive membrane. One step, a second step of hardening the liquid material, a third step of eluting a water-soluble material from the hardened material to make the hardened material porous, and a solution containing a precious metal in the porous hardened material. The method for producing a membrane-electrode assembly according to any one of the first to fifth inventions, characterized in that the method further comprises a fourth step of fixing the noble metal in the cured product which has been made porous by reduction. To be done.

Further, according to an eighth aspect of the present invention, there is provided a solid polymer electrolyte fuel cell comprising the membrane-electrode assembly according to any one of the first to fifth aspects.

According to a ninth aspect of the present invention, the first aspect
A direct methanol fuel cell using the membrane-electrode assembly according to any one of the first to fifth inventions is provided.

[0036]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below for each item.

1. Membrane-Electrode Assembly The membrane-electrode assembly of the present invention is one in which an electrode layer is formed on both surfaces of a proton conductive membrane, and the electrode layer comprises a three-dimensional crosslinked structure containing silane and a noble metal catalyst. It is characterized in that it is composed of supported carbon fine particles.

The three-dimensional crosslinked structure containing the above-mentioned silane takes into consideration the stability against an acid (proton) and the heat resistance, so that hydrolysis of a metal alkoxide or a metal halide,
A so-called sol-gel that forms a three-dimensional crosslinked structure by a silicon-oxygen bond by a condensation reaction
Reactive materials can be used with particular preference.

The sol-gel reaction for forming a three-dimensional crosslinked structure by a silicon-oxygen bond is a hydrolysis or condensation reaction of a silicon compound (precursor) having an alkoxy group or a halogen. The silicon compound used here is, for example, alkoxysilanes such as tetraethoxysilane, tetramethoxysilane, tetraisopropoxysilane, tetra n-propoxysilane, tetra n-butoxysilane, and halogenated silanes such as tetrachlorosilane. However, the reaction material is not particularly limited to these, and is not particularly limited as long as it is a reaction material that forms a three-dimensional crosslinked structure by a silicon-oxygen bond by hydrolysis and condensation reaction.

In the present invention, the alkoxysilanes more preferably used include those represented by the following chemical formula (1).

[0041]

[Chemical 5]

(In the formula, R ¹ represents an alkyl group having 4 or less carbon atoms, R ² represents any organic group including a polar group, m,
Each of n is an integer of 1 to 3. However, m + n =
When R is 4 and m is 2 or 3, R ² may be a mixture of different organic groups. )

Specific examples of R ¹ include a methyl group, an ethyl group, a propyl group and a butyl group. Also,
Examples of the polar group contained in R ² include a hydroxyl group, a sulfonic acid group, a phosphoric acid group, a cyano group, an amino group, and a nitro group. Of these, a sulfonic acid group and a sulfonic acid group are preferred because of their particularly high affinity for protons. Phosphate groups are particularly preferred.

The electrode has a channel through which electrons generated by the reaction or necessary for the reaction can move, a channel through which oxygen or hydrogen necessary for the reaction passes, and a channel through which the proton generated or necessary by the reaction can move. It is necessary that a total of three channels (1) and (2) be present in the vicinity of the noble metal catalyst in a dense and intricate form.

The silane compound (alkoxysilanes) represented by the chemical formula (1) plays a role of giving a polar group having a high affinity to protons (water containing protons) in order to mainly secure a channel through which protons can move. Fulfill In the present invention, when this silane compound is not used,
It is necessary to add a proton conductivity imparting agent separately.

As the proton conductivity imparting agent, an inorganic acid can be preferably used. An example of an inorganic acid is heteropoly acid. Heteropolyacids have a large molecular size and are physically confined within the crosslinked structure to prevent acid dissipation from the electrode. Further, in the case where the electrode has silica fine particles or an alkoxysilyl group, the dissipation is further prevented by the ionic interaction with these. Examples of heteropolyacids include, but are not particularly limited to, those having a Keggin structure, a Dawson structure, and strong acidity, but from the viewpoint of stability, phosphotungstic acid,
Examples thereof include silicotungstic acid and phosphomolybdic acid.

Next, the silane compound represented by the chemical formula (2) has a low affinity for protons (water containing protons), in other words, in order to secure a channel through which gases such as oxygen and hydrogen can move. Hydrocarbons are the main constituents for high water repellency.

[0048]

[Chemical 6]

(Wherein R ¹ and R ³ represent an alkyl group having 4 or less carbon atoms, R ⁴ represents a hydrocarbon group having 20 or less carbon atoms, x is 1 to 3 and y is an integer of 0 to 2). Where x
When + y = 3 and y is 2, R ³ may be a mixture of different alkyl groups. )

Specific examples of the silane compound represented by the chemical formula (2) include bis (triethoxysilyl) ethane, bis (triethoxysilyl) butane, bis (triethoxysilyl) hexane, bis (triethoxysilyl) octane, Bis (triethoxysilyl) nonane, bis (triethoxysilyl) decane, bis (triethoxysilyl) dodecane, bis (triethoxysilyl) tetradodecane,
Examples thereof include bis (triethoxysilylethyl) benzene and methoxy and propoxy forms thereof. These materials are commercially available from Gelest and the like, and are easily available, and hydrosilylation reaction using a chloroplatinic acid catalyst or the like from an organic raw material having a corresponding skeleton and having unsaturated bonds at both ends. Can be obtained by using.

Since the silane compounds represented by the chemical formulas (1) and (2) both have a three-dimensional crosslinked structure after the condensation of silanol groups, they are essentially porous. In addition, since the crosslink density is high, as described above, it is possible to form an electrode having a solid porous structure, and to maintain a suitable interfacial structure without causing structural changes even at high temperatures, 100 ° C or higher. It is possible to obtain a membrane-electrode assembly that exhibits stable performance even at high temperatures.

In the present invention, as described above, the electrode layer is composed of a carbon fine particle carrying a three-dimensional crosslinked structure containing silane and a noble metal catalyst. Is preferably carbon black. The types of carbon black include both difficult-to-graft carbon black and easy-to-graft carbon black, and both can be used. The surface area of carbon black is preferably 50 m ² / g or more from the viewpoint of easy loading of the catalyst. Also,
The particle size of 100 to 400 angstrom is preferably used. Further, as the noble metal catalyst, platinum, palladium, ruthenium or the like can be used.

In the membrane-electrode assembly of the present invention, as the proton-conducting membrane to be used, a sulfonated fluororesin having a general thermoplasticity (for example, a product name "Nafion" manufactured by DuPont) is used. Can be used. However, as mentioned above, the higher temperature a fuel cell can operate, the more energy efficient it becomes. In order to realize such a fuel cell capable of operating at high temperatures, the membrane and the electrode portion are required to have heat resistance. Therefore, in order to obtain heat resistance of the membrane, it is more preferable to use a proton conductive membrane mainly composed of the above-mentioned three-dimensional crosslinked structure containing silane.

Further, in a direct methanol fuel cell which is included in the solid polymer electrolyte fuel cell according to the present invention and which is used as a fuel without reforming methanol, for example, a sulfonated fluororesin is pressed or The membrane-electrode assembly used as an adhesive is most commonly used, but when this is operated at high temperature, the sulfonated fluororesin swells or dissolves due to high temperature methanol, and the performance deteriorates. Not only that, but it may lead to failure of the fuel cell. On the other hand, the film of the present invention
In the electrode assembly, the membrane is preferably a proton conductive membrane mainly composed of the above-mentioned three-dimensional crosslinked structure containing silane, and the electrode part is mainly composed of the three-dimensional crosslinked structure containing silane. By using one, the resin swells relatively little and does not dissolve in methanol, so that it can be suitably used for a direct methanol fuel cell.

2. Method for Producing Membrane-Electrode Assembly Next, the method for producing the membrane-electrode assembly of the present invention will be described.

First, in the method for producing a membrane-electrode assembly according to the present invention, the first step is to coat both surfaces of the proton conductive membrane with
This is a step of applying a liquid material for forming electrodes. The liquid substance is a solution prepared by dissolving the silane compound represented by the chemical formulas (1) and (2) in an organic solvent, and further dispersing the carbon fine particles and the water-soluble material described later. To use. The organic solvent used at this time is not particularly limited as long as it can dissolve the silane compound, but alcohols such as methyl alcohol, ethyl alcohol, isopropyl alcohol and butyl alcohol are usually used.

As the carbon fine particles, those carrying the above-mentioned noble metal catalyst in advance may be used, but in order to reduce the amount of the noble metal catalyst used, the noble metal catalyst is used in the final step as described later. May be added.

As the water-soluble material, a solid acid such as the above-mentioned heteropoly acid can be used, but it is not particularly required to dissolve it in the alcohol as long as it can be sufficiently dispersed in the alcohol. However, it is desirable that the dispersed particles have a diameter of 10 μm or less. Examples of such water-soluble materials include various salts, carbohydrates, water-soluble resins, and the like, and specifically, lactose, glucose, mannitol, sugars such as D-sorbit, sodium glutamate, glycine, glutamic acid, Amino acids such as alanine and aspartic acid, or salts thereof, water-soluble resins such as polyvinylpyrrolidone, polyvinyl alcohol and polyacrylic acid, carboxylates, sulfonates, sulfates, phosphates, aliphatic amines, poly Examples include various surfactants such as oxyethylene alkyl ether and p polyethylene glycol fatty acid ester, and inorganic salts such as ammonium phosphate, sodium sulfite, ammonium sulfate, and sodium chloride.

In the first step, the above-mentioned liquid material is applied to the proton conductive membrane, and a known method can be used as the applying method, such as a bar coating method, a doctor blade method, a spray coating method and a curtain. A coating method, a gravure printing method, an electrodeposition coating method, a dipping method, a spin coating method, or the like, which is suitable for the electrolyte membrane or the like, can be appropriately selected.

Next, the second step is a step of curing the liquid material applied to the proton conductive membrane. If the silane compound has water necessary for hydrolysis, the reaction proceeds even at room temperature, but in order to accelerate the reaction, it is usually 50 to 50%.
It is preferable to heat in the range of 100 ° C. If it is lower than 50 ° C., the promoting effect is small, and if it exceeds 100 ° C., excessive bubbles are likely to enter the cured product. Time is preferably 10 minutes to 2 hours. If the time is less than 10 minutes, the silanol groups of the unreacted substances are likely to remain, while heating for more than 2 hours has a disadvantage that the process is unnecessarily lengthened.

Further, the third step is a step in which the water-soluble material inside is eluted by bringing the cured product obtained in the second step into contact with water. Also in this case, it is usually preferable to heat in the range of 50 to 100 ° C. in order to promote the elution. If it is less than 50 ° C, the promoting effect is small, while on the other hand, 10
If the temperature exceeds 0 ° C, there is a problem that excessive bubbles are likely to enter the cured product. In terms of time, if it is less than 10 minutes, there is a problem that elution is insufficient, and 10 minutes or more is preferable.

The cured product produced through these steps is
It becomes a porous body containing many voids. As described above, the electrode has a channel through which electrons generated by the reaction or necessary for the reaction can move, a channel through which oxygen or hydrogen necessary for the reaction passes, and a proton through which the reaction or the necessary moves. It is necessary that a total of three channels including the formed channel are present in the vicinity of the noble metal catalyst in a dense and intricate form. The large number of voids formed in the above-mentioned cured product effectively act as a channel through which oxygen or hydrogen necessary for the reaction passes.

Further, as described above, when the carbon fine particles that do not carry the noble metal catalyst are used in advance, a step of fixing the noble metal in the above-described porous cured product is required as the fourth step. Becomes The step of fixing the noble metal is generally performed by an electroless plating method in which the porous hardened material is dipped in an aqueous solution of the noble metal to perform reduction.
Specifically, the porous cured product, an aqueous solution of a noble metal,
For example, after immersing in a chloroplatinic acid aqueous solution, sufficiently drying, and then heating in an inert atmosphere containing hydrogen to fix platinum, or after immersing, a reducing agent such as sodium thiosulfate or sodium borosulfate is used. Examples include a method of performing reduction using an aqueous solution of hydride, hydrazine hydrate, or the like. Through this step, good performance can be exhibited with a relatively small amount of precious metal catalyst.

3. Solid Polymer Electrolyte Fuel Cell The fuel cell of the present invention is a fuel cell in which the above-mentioned membrane-electrode assembly is incorporated as a unit cell, and this includes a direct methanol fuel cell expressed by the type of fuel. It
As described above, a membrane-electrode assembly, that is, a structure in which electrodes are arranged on both sides of a proton (hydrogen ion) conducting membrane (junction)
As a unit cell, a pair of separators serving as fuel and oxygen passages are installed outside the unit cell, and a plurality of adjoining cells are connected to each other so that desired power can be taken out. In the present invention, since a membrane-electrode assembly having high heat resistance and chemical resistance and stably functioning at high temperature is used, a solid polymer electrolyte fuel cell or direct methanol fuel capable of operating at high temperature is used. Can provide batteries.

[0065]

EXAMPLES The present invention will be described below based on examples.
The present invention is not limited thereby. In addition,
The compounds, solvents, etc. used were commercially available products as they were.
The evaluation method and the production of the proton conductive membrane are as follows.

[Evaluation Method] (1) Evaluation of Power Generation Performance The membrane-electrode assembly sample of the example or the comparative example was sandwiched between two sheets of water-repellent carbon paper (manufactured by E-TEK), and the whole was further assembled. , Single cell for fuel cell
(Chem Co.) as shown in FIG.
A separator 30 and a current collector plate 27 are arranged on both sides of this membrane-electrode assembly 29, and a torque of 15 Kg-
A single-cell fuel cell was produced by tightening at cm. The power generation performance of the fuel cell configured as described above is measured by using an electronic load device (“890B” manufactured by US Scribner Co., Ltd.) and a gas supply device (“FC-GAS-1” manufactured by Toyo Technica Co., Ltd.) as shown in FIG. evaluated. The evaluation cell composed of the anode 17 and the cathode 19 is a high temperature cell that pressurizes the inside of the apparatus at 100 ° C. or higher, and the hydrogen gas 1 and the oxygen gas 3 are
The system can be diluted with nitrogen gas 2 and 4, and the bubblers 13 and 14 and the piping can be arbitrarily changed by a temperature controller, and the gas discharged from the cell is a humidification trap 2.
It was released via 1, 22. Cell temperature from room temperature to 160 ° C
Up to 30 ° C., and the power generation performance of the cell using the membrane-electrode assembly 18 of the present invention was evaluated at each temperature. Evaluation,
Connect the cell and electronic load device 20, gradually apply resistance,
The output (IV characteristic) of the battery itself was measured, and the maximum output density was measured. As a representative value, the measured value at 140 ° C. is shown. At 140 ° C., the measurement tank was pressurized (5 atm) for measurement. The gas flow rate is 500 ml / min for both hydrogen and oxygen.

(2) Evaluation of low temperature proton conductivity The membrane-electrode assembly sample of the example or comparative example was brought into close contact with a platinum plate which is an electrode. On this platinum plate, an electrochemical impedance measuring device (1260 type, manufactured by Soratron)
Was used to measure the impedance in a frequency range of 0.1 Hz to 100 kHz, and the proton conductivity of the ion conductive membrane was evaluated. In the above measurement, the sample was supported in an electrically insulated airtight container, and the temperature of the cell was changed from room temperature to 160 ° C. by a temperature controller in a steam atmosphere (95 to 100% RH). The proton conductivity was measured at. As a typical value,
The evaluation results at 140 ° C are shown. In the measurement at 140 ° C., the measurement tank was pressurized (5 atm).

[Preparation of Proton-Conductive Membrane] 7 g of 8 bis (triethoxysilyl) octane (manufactured by GELEST) and (trihydroxysilyl) propanesulfonic acid (GEL)
3 g of EST) was dissolved in 15 g of isopropyl alcohol. This solution was poured into a polystyrene petri dish (made by Yamamoto Seisakusho) having an inner diameter of 9 cm. This petri dish
When it was transferred to a container humidified at 60 ° C., water vapor generated at 70 ° C. was introduced, and it was heated for 12 hours, a colorless transparent film was obtained. The membrane is flat and has an average thickness of 20
It was 0 μm. In the following examples, this sample was used as the proton-conductive membrane, and a membrane-electrode assembly sample was prepared.

Example 1 On both sides of the proton conductive membrane,
5 g of carbon black having a specific surface area of 250 m ² / g (Vulcan XC72R, manufactured by Cabot), 8 g of bis (triethoxysilyl) octane (manufactured by GELEST) and (trihydroxysilyl) propanesulfonic acid (GELES)
A solution in which 10 g of ammonium phosphate (Wako Pure Chemical Industries, Ltd.) and 10 g of ammonium phosphate (Wako Pure Chemical Industries) were uniformly dispersed in 15 g of isopropyl alcohol were applied to a thickness of 100 μm. The membrane was heated at 80 ° C. for 30 minutes to highly crosslink the silyl compound. Next, this cured product was heated in a vacuum heating device at 100 ° C. under reduced pressure to further increase the degree of crosslinking. Thereafter, this cured product was immersed in hot water at 80 ° C. for 1 hour to elute the water-soluble ammonium phosphate salt from the cured product. Then, by further drying in a vacuum heating device at 100 ° C. for 1 hour, a three-dimensional crosslinked cured product containing porous silane could be laminated on both surfaces of the proton conductive membrane. Further, the whole is immersed in an ethanol solution (5% by weight solution) of chloroplatinic acid (Wako Pure Chemical Industries, Ltd.) for 1 hour, and then hydrogen 1
150 ° C in a gas mixture of 0% and 90% argon.
Then, reduction treatment was carried out for 2 hours to fix platinum in the porous cured product. The sample (membrane-
The electrode assembly) was evaluated for its power generation performance and proton conductivity by the above-described evaluation method. The results are shown in Table 1.

Example 2 In Example 2, a cured product was prepared by using 5 g of carbon black (TEC10A30E manufactured by Tanaka Kikinzoku Kogyo Co., Ltd.) on which a platinum catalyst was previously loaded, and the final reduction treatment. A sample (membrane-electrode assembly) was prepared in the same manner as in Example 1 except that the above was not performed. The power generation performance and the proton conductivity of the obtained sample (membrane-electrode assembly) were evaluated by the evaluation method described above. The results are shown in Table 1.

Example 3 In Example 3, 10 g of PWA (12-tungstophosphoric acid) (manufactured by Wako Pure Chemical Industries) was used instead of 10 g of ammonium phosphate (manufactured by Wako Pure Chemical Industries) in Example 1. A sample was prepared in the same manner as in Example 1 except that was used. The power generation performance and the proton conductivity of the obtained sample (membrane-electrode assembly) were evaluated by the evaluation method described above. The results are shown in Table 1.

Example 4 Example 4 is the same as Example 1 except that 7 g of 8 bis (triethoxysilyl) octane (manufactured by Azumax) and 3 g of (trihydroxysilyl) propanesulfonic acid (manufactured by GELEST) are mixed silanes. A sample was prepared in the same manner as in Example 1 except that only 10 g of 8bis (triethoxysilyl) octane was used instead of using the compound. Obtained sample (membrane-
The electrode assembly) was evaluated for its power generation performance and proton conductivity by the evaluation method described above. The results are shown in Table 1.

Example 5 Example 5 is the same as Example 1 except that 8 g of bis (triethoxysilyl) octane (manufactured by Azumax) and 3 g of (trihydroxysilyl) propanesulfonic acid (manufactured by GELEST) are mixed silanes. A sample was prepared in the same manner as in Example 1 except that only 10 g of (trihydroxysilyl) propanesulfonic acid was used instead of using the compound. The power generation performance and the proton conductivity of the obtained sample (membrane-electrode assembly) were evaluated by the evaluation method described above. The results are shown in Table 1.

Example 6 Example 6 is the same as Example 1 except that the ammonium phosphate salt was not used.
A sample was prepared in the same manner as in Example 1. The power generation performance and the proton conductivity of the obtained sample (membrane-electrode assembly) were evaluated by the evaluation method described above. The results are shown in Table 1.

Comparative Example 1 In Comparative Example 1, 5 g of carbon black (TEC10A30E made by Tanaka Kikinzoku Co., Ltd.) carrying a platinum catalyst and a commercially available ion exchange resin solution (Nafion perfluoroion exchange resin, product of Aldrich Co.)
10 g was vigorously stirred in isopropanol to prepare a suspension. This suspension was applied to both sides of the proton conductive membrane used in Example 1 and further heated to 80 ° C. to evaporate isopropanol as a solvent to form a membrane.
A sample of the electrode assembly was prepared. The power generation performance and the proton conductivity of the obtained sample (membrane-electrode assembly) were evaluated by the evaluation method described above. The results are shown in Table 1.

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[Table 1]

From the above evaluation results, the membrane-electrode assemblies of Examples 1 to 6, especially Examples 1 to 3, had a high maximum output of power generation performance and exhibited excellent performance as compared with Comparative Example 1. I understand that

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INDUSTRIAL APPLICABILITY The present invention makes it possible to obtain a membrane-electrode assembly capable of stably exhibiting a power generation function even at a high temperature of 100 ° C. or higher, and a solid polymer electrolyte fuel cell capable of operating at a high temperature, Alternatively, a direct methanol type fuel cell can be realized, and its industrial value is extremely large.

[Brief description of drawings]

FIG. 1 is a layout view showing an apparatus for evaluating the power generation performance of a membrane-electrode assembly of the present invention.

FIG. 2 is a view in which a membrane-electrode assembly is sandwiched between fuel cell unit cells.

[Explanation of symbols]

1 Hydrogen supply 2 Nitrogen supply 3 oxygen supply 4 Nitrogen supply 5 Hydrogen supply servo valve 6 Nitrogen supply servo valve 7 Oxygen supply servo valve 8 Nitrogen supply servo valve 9 MFC 10 MFC 11 MFC 12 MFC 13 Hydrogen bubbler 14 oxygen bubbler 15 Hydrogen stream 16 oxygen stream 17 Anode 18 Membrane-electrode assembly 19 cathode 20 Electronic load device 21 Humidification trap 22 Humidification trap 23 BPV 24 BPV 25 VENT 26 VENT 27 current collector 28 Clamping bolt 29 Membrane-electrode assembly 30 separator

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 5H018 AA06 AA07 BB00 BB05 BB06                       BB07 BB08 BB16 BB17 DD06                       DD08 EE03 EE05 EE08 EE11                       EE16 EE17 EE18                 5H026 AA06 AA08 BB00 BB03 BB04                       BB10 CC03 CX05 EE02 EE05                       EE11 EE17 EE18

Claims (9)

[Claims] 1. A membrane-electrode assembly in which electrode layers are formed on both sides of a proton conductive membrane, the electrode layer comprising carbon fine particles carrying a three-dimensional crosslinked structure containing silane and a noble metal catalyst. And a membrane-electrode assembly. 2. The monomer before polymerization of the three-dimensional crosslinked structure is a polar compound represented by the following chemical formula (1), a non-polar compound represented by the following chemical formula (2), or a mixture thereof. The membrane-electrode assembly according to claim 1. [Chemical 1] (In the formula, R ¹ represents an alkyl group having 4 or less carbon atoms, R ² represents any organic group including a polar group, and m and n are both integers of 1 to 3, where m + n = And when m is 2 or 3, R ² may be a mixture of different organic groups.) (In the formula, R ¹ and R ³ represent an alkyl group having 4 or less carbon atoms,
R ⁴ represents a hydrocarbon group having 20 or less carbon atoms, and x is 1 to
3, y is an integer of 0-2. However, when x + y = 3 and y is 2, R ³ may be a mixture of different alkyl groups. ) 3. The membrane-electrode assembly according to claim 1, wherein the electrode layer contains an inorganic acid. 4. The membrane-electrode assembly according to claim 3, wherein the inorganic acid is at least one compound selected from phosphotungstic acid, silicotungstic acid, and phosphomolybdic acid. 5. The membrane-electrode assembly according to claim ² , wherein the polar group in R ² shown in the chemical formula (1) is a sulfonic acid group or a phosphoric acid group. 6. A first step of applying a liquid containing a silane-containing three-dimensional crosslinkable monomer, carbon fine particles carrying a noble metal catalyst, and a water-soluble material to both surfaces of the proton conductive membrane, the liquid. The film according to any one of claims 1 to 5, comprising a second step of curing the cured product, and a third step of eluting a water-soluble material from the cured product to make the cured product porous. Method for manufacturing electrode assembly. 7. A first step of applying a liquid material containing a silane-containing three-dimensional crosslinkable monomer, carbon fine particles, and a water-soluble material to both surfaces of the proton conductive membrane, and curing the liquid material. Second step, third step of elution of water-soluble material from the cured product to make the cured product porous, and impregnation of a solution containing a noble metal into the porous cured product, followed by curing to make porous The method for producing a membrane-electrode assembly according to claim 1, further comprising a fourth step of fixing a noble metal in the material. 8. A solid polymer electrolyte fuel cell comprising the membrane-electrode assembly according to claim 1. 9. A direct methanol fuel cell comprising the membrane-electrode assembly according to claim 1.