JP2002083612A - Electrolyte film and its manufacturing method, and fuel cell and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a new electrolyte film, in which permeation of methanol (cross-over) is restrained as much as possible and which is also durable under an environment of higher temperature (not lower than about 130 deg.C), and a fuel cell using the electrolyte film, especially methanol direct type solid polymer fuel cell, as well as to provide its manufacturing method. SOLUTION: This electrolyte film, in which the first and the second polymers having a protonic conductivity are filled in fine pores of porous base material, which substantially does not swell with respect to methanol and water, and the electrolyte film where one end of the first polymer is made to be bonded to an inner surface of fine pores of the base material is used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention generally relates to an electrolyte membrane, and more particularly, to an electrolyte membrane for a fuel cell, and more particularly to an electrolyte membrane for a direct methanol solid polymer fuel cell. Further, the present invention relates to a fuel cell having the electrolyte membrane and a method for manufacturing the same.

[0002]

2. Description of the Related Art As global environmental protection activities have become more active, there has been a strong demand for prevention of so-called greenhouse gases and NOx emissions. In order to reduce the total emission of these gases, it is considered that the practical application of a fuel cell system for an automobile is very effective.

[0003] Solid polymer fuel cells (PEFC, Polyme
r Electrolyte Fuel Cell) has the excellent features of low temperature operation, high power density, and the ability to generate only water due to the power generation reaction. In particular, methanol fueled PEFCs
Since it can be supplied as a liquid fuel like gasoline, it is considered to be promising as power for electric vehicles.

[0004] Solid polymer fuel cells include a reforming type in which methanol is converted into a gas containing hydrogen as a main component using a reformer, and a direct type (DM) in which methanol is directly used without using a reformer.
FC and Direct Methanol Polymer Fuel Cell). The direct fuel cell does not require a reformer, so it can be reduced in weight, can withstand frequent start / stop, can greatly improve load fluctuation response, and does not pose a problem with catalyst poisoning. There is a great advantage, and its practical use is expected.

[0005]

SUMMARY OF THE INVENTION However, DMF
Several problems have been pointed out in practical use of C. For example, DMFC uses a solid polymer electrolyte as an electrolyte. However, when a conventional electrolyte membrane for PEFC, for example, a Nafion (registered trademark) membrane of Du Pont, a Dow membrane of Dow Chemical, etc., methanol is used. Are permeated through the membrane, so that the catalyst is depolarized and the electromotive force is reduced, and when the temperature is increased to increase the catalytic activity, melting (creeping) occurs at around 130 ° C. Two problems occur. There is no electrolyte membrane that solves these problems at the same time, but if this problem is solved, there is a possibility that the application to electric vehicles will progress at a stretch.

Accordingly, an object of the present invention is to realize a novel electrolyte membrane which suppresses the permeation (crossover) of methanol as much as possible and which can withstand use in a high-temperature (about 130 ° C. or higher) environment. The object of the present invention is
An object of the present invention is to provide a method for manufacturing the electrolyte membrane. A further object of the present invention is to realize a novel methanol direct type solid polymer fuel cell using the above-mentioned electrolyte membrane.

[0007]

Means for Solving the Problems In order to solve the above problems, the present inventors have made intensive studies and have obtained the following findings. In other words, in general, the polymer softens at high temperature, but pays attention to the property of maintaining its performance up to the temperature at which the polymer decomposes. It has been found that the skeleton of the base material maintains the structure of the film even below.

Further, the present inventors have stated that if the second polymer is filled in addition to the first polymer, the proton conductivity can be increased while suppressing the permeation (crossover) of methanol. Obtained knowledge. Furthermore, it has been found that proton conductivity is ensured by a polymer embedded in pores, and that shape maintenance, swelling suppression and heat resistance at high temperatures can be achieved by a matrix of a porous substrate.

From these findings, the present inventors have found the following invention. <1> a step of forming a first polymer such that one end thereof is bonded to an inner surface of a pore of a porous substrate having swelling resistance to an organic solvent and water, and even if it is the same as the first polymer, A method for producing an electrolyte membrane comprising a step of filling a second polymer, which may be different, into pores of the base material, wherein the first and second polymers have proton conductivity. Method.

<2> In the above item <1>, the first polymer is derived from a first monomer, and the second polymer is derived from a second monomer which may be the same as or different from the first monomer. There should be. <3> In the above item <1> or <2>, the step of forming the first polymer includes a step of irradiating the base material with energy and a step of bringing the first monomer into contact with the base material. The first polymer is preferably formed such that one end of the first polymer is bonded to the inner surface of the pores of the substrate by contacting the monomer.

<4> In the above item <3>, the energy source of energy is selected from the group consisting of plasma, ultraviolet rays, electron beams, and gamma rays, and the energy source excites the base material to form at least pores of the base material. It is preferred that a first polymer is formed so as to bond to the substrate at the reaction start point by generating a reaction start point on the inner surface and bringing the first monomer into contact with the reaction start point. <5> In the above item <1> or <2>, in the step of forming the first polymer, one end of the first polymer may be bonded to the base material by a coupling agent.

<6> In any one of the above items <1> to <5>, the step of filling the second polymer may include filling the second monomer into the pores of the substrate, and filling the second monomer with the second monomer. Is polymerized in the pores to obtain a second polymer, which is preferably filled in the pores. <7> In any one of the above items <1> to <6>, the porous substrate may be made of an inorganic material or a heat-resistant polymer. <8> In the above item <7>, the inorganic material may be any one of ceramic, glass, and alumina, or a composite material thereof.

<9> In the above item <7>, the heat-resistant polymer may be polytetrafluoroethylene or polyimide. <10> In any one of the above items <1> to <9>, the electrolyte membrane may be a fuel cell electrolyte membrane. <11> In any one of the above items <1> to <9>, the electrolyte membrane may be an electrolyte membrane for a direct methanol solid polymer fuel cell.

<12> An electrolyte membrane, wherein pores of a porous base material that does not substantially swell with methanol and water are filled with a polymer having proton conductivity, wherein the polymer is a first polymer. Wherein the first polymer is a polymer having one end bonded to the inner surface of the pores of the base material, and the second polymer is the first polymer. An electrolyte membrane that is a polymer that may be the same as or different from the polymer.

<13> In the above item <12>, the first polymer may be derived from the first monomer, and the second polymer may be the same as or different from the first monomer.
It is good to be derived from the monomer of. <14> In the above item <12> or <13>, the first polymer may be obtained by irradiating the base material with energy and then contacting the base material with the first monomer.

<15> In the above item <14>, the energy source of energy is selected from the group consisting of plasma, ultraviolet light, electron beam, and gamma ray, and the energy source excites the substrate to form at least pores of the substrate. Preferably, a first polymer is obtained so as to bond to the substrate at the reaction start point by generating a reaction start point on the inner surface and contacting the first monomer with the reaction start point. <16> In the above item <12> or <13>, one end of the first polymer may be bonded to the substrate by a coupling agent.

<17> In any one of the above items <12> to <16>, the second polymer may fill the second monomer into the pores of the substrate, and may fill the second monomer with the pores. It is good to be obtained by polymerizing inside.

<18> In any one of the above items <12> to <17>, the porous substrate may be composed of an inorganic material or a heat-resistant polymer. <19> In the above item <18>, the inorganic material may be any one of ceramic, glass, and alumina, or a composite material thereof.

<20> In the above item <18>, the heat-resistant polymer may be polytetrafluoroethylene or polyimide. <21> In any one of the above items <12> to <20>, the electrolyte membrane may be a fuel cell electrolyte membrane. <22> In any one of the above items <12> to <20>, the electrolyte membrane may be an electrolyte membrane for a direct methanol solid polymer fuel cell.

<23> A fuel cell in which an electrolyte membrane is formed on a cathode electrode or a catalyst layer of a cathode electrode, wherein the electrolyte membrane is any one of the above-mentioned <12> to <22>. battery.

<24> A fuel cell comprising a cathode electrode, an anode electrode, and an electrolyte sandwiched between the two electrodes, wherein the electrolyte is a porous base material that does not substantially swell in methanol and water. An electrolyte characterized in that pores are filled with a polymer having proton conductivity, wherein the polymer has a first proton conductive polymer and a second proton conductive polymer, and the first polymer is A polymer having one end bonded to the inner surface of the pores of the substrate,
Wherein the polymer of is a polymer that may be the same as or different from the first polymer.

<25> In the above item <24>, the first polymer may be derived from the first monomer, and the second polymer may be the same as or different from the first monomer.
It is good to be derived from the monomer of. <26> In the above item <24> or <25>, the first polymer may be obtained by irradiating the substrate with energy and then bringing the first monomer into contact with the substrate.

<27> In the above item <26>, the energy source of energy is selected from the group consisting of plasma, ultraviolet rays, electron beams and gamma rays, and the energy source excites the base material to form at least pores in the base material. Preferably, a first polymer is obtained so as to bond to the substrate at the reaction start point by generating a reaction start point on the inner surface and contacting the first monomer with the reaction start point. <28> In the above item <24> or <25>, it is preferable that one end of the first polymer is bonded to the base material by a coupling agent.

<29> In any one of the above items <24> to <28>, the second polymer may fill the second monomer into the pores of the substrate, and may fill the second monomer with the pores. It is good to be obtained by polymerizing inside. <30> In any one of the above items <24> to <29>, the porous substrate may be made of an inorganic material or a heat-resistant polymer.

<31> In the above item <30>, the inorganic material may be any one of ceramic, glass and alumina, or a composite material thereof. <32> In the above item <30>, the heat-resistant polymer may be polytetrafluoroethylene or polyimide. <33> In any one of the above items <24> to <32>, the fuel cell may be a direct methanol solid polymer fuel cell.

<34> a step of applying a sol to the first electrode, a step of forming the applied sol into a porous thin film layer, and filling a pore of the obtained porous thin film layer with a proton-conductive polymer to form a first thin film. Forming an electrolyte membrane on the electrode, a method for manufacturing a fuel cell having a step of adhering a second pole on the electrolyte membrane, wherein the step of forming the electrolyte membrane,
Forming the first polymer such that the proton conductive polymer has first and second proton conductive polymers, and one end of the first polymer is bonded to the surface of the pore; A method for manufacturing a fuel cell, comprising a step of filling a second polymer after forming one polymer.

<35> In the above item <34>, the first polymer and the second polymer may be the same or different. <36> In the above item <34> or <35>, the first polymer may be derived from the first monomer, and the second polymer may be the same as or different from the first monomer.
It is good to be derived from the monomer of.

<37> In any one of the above items <34> to <36>, the step of forming the first polymer may comprise irradiating the substrate with energy and then bringing the first monomer into contact with the substrate. Good to be done.

<38> In the above item <37>, the energy source of energy is selected from the group consisting of plasma, ultraviolet rays, electron beams and gamma rays, and the energy source excites the base material so that at least the pores of the base material are excited. Preferably, a first polymer is obtained so as to bond to the substrate at the reaction start point by generating a reaction start point on the inner surface and contacting the first monomer with the reaction start point. <39> In any one of the above items <34> to <36>, in the step of forming the first polymer, one end of the first polymer may be bonded to the substrate by a coupling agent.

<40> In any one of the above items <34> to <39>, the second polymer may fill the second monomer into the pores of the substrate, and may fill the second monomer into the pores. It is good to be obtained by polymerizing inside. <41> In any one of the above items <34> to <40>, the porous substrate may be composed of an inorganic material or a heat-resistant polymer.

<42> In the above item <41>, the inorganic material may be any one of ceramic, glass and alumina, or a composite material thereof. <43> In the above item <41>, the heat-resistant polymer may be polytetrafluoroethylene or polyimide.

<44> In any one of the above items <34> to <43>, the first electrode may include a first support layer and a first catalyst layer. It is preferably applied to the catalyst layer. <45> In any one of the above items <34> to <44>, the second electrode may include a second support layer and a second catalyst layer, and in the step of adhering the second electrode, It is preferable that the electrolyte membrane and the second catalyst layer be in close contact with each other.

<46> In any one of the above items <34> to <45>, the fuel cell may be a direct methanol solid polymer fuel cell.

[0034]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
The electrolyte membrane of the present invention uses a porous material having heat resistance and substantially not swelling in an organic solvent such as methanol and water. Examples of materials having such properties include glass, ceramics such as alumina and silica as inorganic materials. Other materials include polytetrafluoroethylene (for example, Teflon (registered trademark)), polyimide, and the like. These materials are
A single material may be used, or two or more materials may be used as a composite material. When used as a composite material, the form may be a laminate of two or more layers.

The porosity of the substrate that can be used in the present invention is preferably 10% to 95%. Further, the average pore diameter is desirably in the range of 0.001 μm to 100 μm. Further, the thickness of the substrate is 100 μm or less, and preferably on the order of several μm.

The electrolyte membrane of the present invention is obtained by bonding a first polymer, particularly a graft polymer, to the surface of a substrate made of a porous material, particularly to the inner surface of pores. The first polymer is derived from a first monomer, and the first monomer and the first polymer have ion exchange groups. The first polymer, especially the graft polymer, first fills the pores of the substrate. Since the first polymer is formed so that one end thereof is bonded to the inner surface of the pore, the first polymer formed in the pore does not easily flow out or elute.

[0037] In this specification, the term "ion exchange groups", for example, -SO ₃ H group derived from -SO ₃ ^-, etc.,
A group that retains a proton and is easily released. When these are present in the first polymer in a pendant manner and the polymer fills the pores, proton conductivity occurs.

To form the first polymer so that one end thereof is bonded to the inner surface of the pore, there are the following methods. For example, exciting a substrate with plasma, ultraviolet rays, electron beams, gamma rays, or the like, generating a reaction initiation point on at least the inner surface of the pores of the substrate, and bringing the first monomer into contact with the reaction initiation point. Is a method for obtaining a first polymer by Further, the first polymer can be bonded to the inner surface of the pore by a chemical method such as a silane coupler.
Further, a first monomer is filled in the pores, and a polymerization reaction is performed therein to use a general polymerization method of obtaining a first polymer. Then, the obtained first polymer is used as a base material. For example, the chemical bonding can be performed using a coupling agent containing the above-mentioned silane coupler or the like.

In the present invention, it is preferable to use the plasma graft polymerization method described below. That is, it is preferable that the first monomer is subjected to a plasma graft polymerization reaction to obtain a first polymer having one end bonded to the surface of the pore. The plasma graft polymerization can be performed using a liquid phase method described below and a well-known gas phase polymerization method.

The monomers usable as the first monomer of the present invention are preferably sodium acrylsulfonate (SAS), sodium methallylsulfonate (SM)
S), sodium p-styrenesulfonate (SSS), acrylic acid (AA) and the like. However, monomers that can be used in the present invention are not limited to the above, and include allylamine, allylsulfonic acid, allylphosphonic acid, methallylsulfonic acid, methallylphosphonic acid, vinylsulfonic acid, vinylphosphonic acid, and styrene sulfone. Acids, styrene phosphonic acid, sulfonic acid or phosphonic acid derivatives of acrylamide, ethyleneimine, methacrylic acid, etc., vinyl group and sulfonic acid, strong acid groups such as phosphonic acid, weak acid groups such as carboxyl group, primary, secondary
It may be a derivative having a strong base such as a tertiary, tertiary or quaternary amine, a monomer having a weak base, or an ester thereof. When a salt type such as a sodium salt is used as the monomer, it is preferable to convert the salt into a proton type after forming the polymer.

Further, only one of these monomers may be used to form a homopolymer, or two or more of these monomers may be used to form a copolymer. That is, the first polymer having one end bonded to the surface in the pores of the substrate may be a homopolymer or a copolymer.

The proton conductivity of the electrolyte membrane changes depending on the type of the first monomer used and / or the type of the second monomer described later. Therefore, it is desirable to use a monomer material having high proton conductivity. The proton conductivity of the electrolyte also depends on the degree of polymerization of the polymer filling the pores.

In the present invention, proton conductivity is imparted by forming and / or filling the pores with the first polymer and a second polymer described later.
Therefore, it is preferable that both the first polymer and the second polymer have a high degree of polymerization, or one of them has a high degree of polymerization. In particular, in terms of manufacturing efficiency,
It is preferred that the second polymer has a high degree of polymerization. Or, both do not have a relatively high degree of polymerization,
It is preferable that each of them has a degree of polymerization that has a high proton conductivity by combining both.

In the plasma graft polymerization method which can be used for producing the electrolyte membrane of the present invention, after the substrate is irradiated with plasma to generate a reaction initiation point on the surface of the substrate and the inner surface of the pores, preferably, The first monomer is brought into contact with a well-known liquid phase polymerization method, and the first monomer is graft-polymerized on the surface of the base material and inside the pores.

Next, the plasma graft polymerization method usable in the present invention will be described in detail with reference to the drawings. For more information on plasma graft polymerization,
Prior application by the inventors of the present invention, Japanese Patent Application Laid-Open No. 3-9863.
2, JP-A-4-334431, JP-A-5-31343
The details are also described in JP-A-5-237352 and JP-A-6-246141.

FIG. 1 is a partial cross-sectional perspective view showing a porous substrate 1 usable for the electrolyte membrane of the present invention. The porous substrate 1 has many pores 2 penetrating the substrate.

The porous substrate 1 is usually subjected to a frequency of 10 to 50 MHz and an output of 1 to 100 in the presence of a gas such as argon, nitrogen, or air having a pressure range of 1 mPa to 120 kPa.
Plasma treatment is performed at 0 W for about 1 to 1000 seconds. At this time, a reaction start point (not shown) is generated on the surface (including the inner surface of the pores) of the substrate 1 exposed to the plasma.

Next, the first monomer having an ion exchange group is dissolved in water to prepare a uniform solution of the first monomer. The concentration of the aqueous solution of the first monomer is desirably 0.1 to 80% by weight, preferably 1 to 10% by weight. Note that the homogeneous solution of the first monomer may have a surfactant such as dodecylbenzenesulfonic acid so that the solution can easily enter the pores. In the case where the second monomer solution is used, the surfactant may be the second monomer solution.
May be contained in the monomer solution.

The substrate 1 after the plasma treatment is preferably treated with the aqueous solution of the first monomer as follows. That is,
In an argon gas atmosphere, the first monomer aqueous solution is brought into direct contact with the first monomer aqueous solution. Alternatively, the substrate 1 is once taken out into the air, reacted with oxygen, and the point activated by the plasma is converted into a peroxide group. Thereafter, the substrate 1 having a peroxide group is brought into contact with the first aqueous monomer solution. More specifically, the contact is performed by immersing the porous substrate 1 in which the reaction starting point has occurred in the aqueous solution. In addition, when this process is directly performed in an argon gas atmosphere, it is preferable to perform the process at a temperature of 20 ° C to 100 ° C, preferably 30 ° C to 60 ° C.
It is good to carry out at 60 ° C to 150 ° C, preferably at 80 ° C to 120 ° C. The immersion is preferably performed while bubbling with an inert gas such as nitrogen gas. The time for immersion is about 1 minute to about 1 day, preferably 1 hour to 24 hours.

Next, the porous substrate 1 after a predetermined time has elapsed is taken out of the aqueous solution, washed with an organic solvent such as toluene or xylene, and dried. This is because the homopolymer and the like formed as a by-product during the polymerization are completely washed away with an organic solvent so that the graft polymer is left only on the surface and inside of the pores of the base material.

FIG. 2 is a perspective view conceptually showing a state in which a monomer is graft-polymerized on the substrate 1. It can be seen that the graft-polymerized first polymer 3 is formed not only on the surface of the base material but also inside the pores 2.

In this way, a substrate having the first polymer formed such that one end thereof is bonded to the surface of the pores of the porous substrate is obtained. Next, in the present invention, the second polymer is filled in the pores of the obtained base material. The second polymer is preferably a polymer having proton conductivity.
That is, similar to the first polymer described above, any polymer having an ion exchange group may be the same as or different from the first polymer.

The method of filling the second polymer may be a method of directly filling the second polymer into the pores, or a method of filling the second polymer into the pores to form the second polymer by the subsequent treatment. There is a method of performing a polymerization reaction in the pores to obtain a second polymer, and thereby filling the second polymer into the pores.

When a second monomer is used, the second monomer may be the same as or different from the first monomer. That is, one or more selected from the first monomers exemplified above can be used. Suitable second monomers include those described above for the first monomer, and additionally include vinyl sulfonic acid. When one type is selected as the second monomer, the second polymer is a homopolymer, and when two or more types are selected as the second monomer,
The second polymer is a copolymer.

It is preferable that the second polymer is chemically and / or physically bonded to the first polymer. For example, all of the second polymers may be chemically bonded to the first polymer, or all of the second polymers may be physically bonded to the first polymer. Further, a part of the second polymer may be chemically bonded to the first polymer, and another second polymer may be physically bonded to the first polymer. Note that the chemical bond includes a bond between the first polymer and the second polymer. This connection is, for example, the first
The polymer can be formed by holding a reactive group in the polymer and reacting the reactive group with the second polymer and / or the second monomer. The state of physical bonding includes, for example, a state in which the first and second polymers are entangled with each other.

In the present invention, by using the first and second polymers together, the permeation (crossover) of methanol is suppressed, and the entire polymer filled in the pores is eluted or discharged from the pores. And the proton conductivity can be increased. In particular, since the first polymer and the second polymer are chemically and / or physically bonded, the entire polymer filled in the pores does not elute or flow out of the pores. Further, even when the degree of polymerization of the first polymer is low, the proton conductivity of the obtained electrolyte membrane can be increased by the presence of the second polymer, particularly the second polymer having a high degree of polymerization. .

Hereinafter, a method of filling the second polymer will be briefly described with reference to FIG. FIG. 3A is a diagram schematically showing a cross section of the pores of the substrate after the first polymer is formed. In FIG. 3 (a), the same figure numbers as those in FIG. 2 are used, and the pores 2 are provided on the base material 1 so that the first polymer 3 is bonded to the surface of the pores 2 at one end. Is formed.

As described above, the second monomer is filled in the pores of the substrate on which the first polymer is formed, and the polymerization reaction is performed in the pores. FIG. 3B shows that the second polymer 5 obtained by the polymerization reaction fills the pores. As described above, the second polymer 5 is chemically and / or physically bonded to the first polymer 3, and the second polymer 5 also easily flows out of the pores like the first polymer. Or do not elute.

In the electrolyte membrane or the fuel cell of the present invention and the method for producing the same, the third polymer, the fourth polymer,. . . , N-th polymer (ie, n is an integer of 3 or more). The n-th polymer, like the second polymer, may have an effect of increasing proton conductivity. Further, the n-th polymer is configured to have other properties required for a fuel cell even if it has an action of preventing the entire polymer from flowing out or eluting from the pores of the base material. Is also good.

The electrolyte membrane of the present invention is preferably used for a fuel cell, particularly a methanol fuel cell including a direct methanol solid polymer fuel cell or a modified methanol solid polymer fuel cell. The electrolyte membrane of the present invention is particularly preferably used for a direct methanol solid polymer fuel cell.

Here, the configuration of the methanol fuel cell will be briefly described with reference to FIG. FIG. 4 is a schematic diagram showing one embodiment of a methanol fuel cell using the electrolyte membrane of the present invention.

The methanol fuel cell 11 has the cathode 1
3. Anode 15 and electrolyte 17 sandwiched between both electrodes
Having. The methanol fuel cell may be a reformed methanol fuel cell having a reformer (not shown) on the anode electrode side.

The cathode electrode may have a conventionally known structure, and may include, for example, a catalyst layer and a support layer for supporting the catalyst layer in order from the electrolyte side. In addition, the anode electrode can also have a conventionally known configuration, and can have, for example, a catalyst layer and a support layer that supports the catalyst layer in this order from the electrolyte side.

Further, in the methanol fuel cell having the electrolyte of the present invention, after the first electrode and the electrolyte are integrally formed to obtain a molded body, the second electrode different from the first electrode is obtained. The molded body and the second electrode can also be obtained in close contact with each other so that the catalyst layer and the electrolyte side are in close contact with each other.

FIG. 5 shows a case where the first pole is a cathode pole.
This will be described with reference to FIG. FIG. 5 is a schematic view showing one embodiment of a cathode using the electrolyte membrane of the present invention. In FIG. 5, the cathode 13 has a catalyst layer 21 on a support layer 19. The support layer 19 is preferably made of a material having gas permeability, particularly oxygen gas permeability, heat resistance and electron conductivity. For example, porous carbon having electronic conductivity is preferable.

The catalyst layer 21 is a layer for supporting a conventionally known catalyst desired on the cathode. On this catalyst layer 21, a porous thin film 23 having pores 2 is formed as shown in FIG. For forming the porous thin film, for example, various glass or ceramic sols such as various silicon alkoxides, various aluminum alkoxides, various titanium alkoxides, or various zirconium alkoxides are prepared, and the sol is prepared. Apply to catalyst layer. As a coating method, a conventionally known method such as dip coating, spin coating, and spray coating can be used. The sol applied in this manner is dried and optionally heated to obtain a porous thin film. The obtained porous thin film is preferably a thin film of silica, alumina (eg, γ-alumina), titania or zirconia, or a mixture or composite thereof.

One end of the first polymer is bonded to the inner surface of the pore by the above-mentioned first polymer, for example, a graft polymerization method or a method using a coupling agent, in the pore of the obtained porous thin film. To form a first polymer. Next, the second polymer is filled in the pores by the method described above. Thus, the cathode and the electrolyte can be integrally formed. The use of such an integrally molded body facilitates handling of the thinned electrolyte membrane.

The molded body and the anode can be closely molded so that the catalyst layer side of the anode and the electrolyte side of the molded body adhere to each other to form a methanol fuel cell. In the above description, the method of integrally forming the cathode and the electrolyte has been described. However, the person of ordinary skill in the art can easily come up with the method of integrally forming the anode and the electrolyte.

[0069]

EXAMPLES The present invention will be described in more detail based on examples, but the present invention is not limited to these examples. (Example 1) A porous PTFE membrane (trade name: Teflon, manufactured by Nitto Denko, flat membrane, thickness 70 μm, pore diameter 50 n) as a substrate
m) was used. The substrate was washed and plasma-irradiated under the following conditions.

High frequency output: 30 W; plasma irradiation time: 60 seconds; atmosphere: argon gas; pressure: 10 Pa.

The substrate after the plasma irradiation was immersed in the first monomer solution which had been deaerated by freezing to perform graft polymerization. The graft polymerization conditions are shown below.

Monomer: acrylic acid (AA); monomer concentration: 10% by weight; solvent: water; temperature: about 60 ° C .; time: 10 to 24 hours; and additives: surfactant (sodium dodecylbenzenesulfonate).

The porous substrate was taken out of the solution, washed in water, and then dried to form the first polymer-formed film A-
1 was obtained. After drying, the mass of the film A-1 was measured, and the graft polymerization amount was calculated in comparison with the mass before the polymerization. The amount of graft polymerization was 0.7 mg / cm ² . Incidentally, the film pressure after the polymerization was about 90 μm.

The thus obtained film A-1 was subjected to FT-IR
(Mapping method) When measured, 17
It was confirmed that a peak at 40 cm ^-1 was also present inside the film, and it was found that a polymer was also formed inside the film.

<Filling the Second Polymer> Next, the second polymer was filled. Acrylic acid (AA) was used as the second monomer similarly to the first polymer. A second monomer solution was prepared comprising 98.9 parts by weight of the second monomer, 0.1 part by weight of divinylbenzene as a crosslinking agent, and 1.0 part by weight of a water-soluble azo-based polymerization initiator. This second
Was immersed in the polymer solution of above.

After immersion, visible light was irradiated for 6 minutes to cause a thermal polymerization reaction inside the pores. Thereafter, the obtained film was washed with water in an ultrasonic wave and dried to obtain a film A-2 filled with the first and second polymers. From the difference in weight before and after the filling of the second polymer, it was found that the polymerization amount was 7.0 mg / cm ² .

Example 2 The procedure was carried out except that a mixture of acrylic acid (AA): vinylsulfonic acid = 2: 1 was used as the second monomer and a small amount of water was used to dissolve the vinylsulfonic acid. In the same manner as in Example 1, the film A-3 was prepared.
I got

Reference Example 1 A film A-4 filled with only the first polymer was obtained in the same manner as the film A-1 of Example 1. However, the polymerization amount of the film A-4 was 3.0 mg / cm ² .

<Measurement of proton conductivity> Obtained membrane A-2
About ~ A-4, the proton conductivity was measured. At the time of measurement, first, the membrane was swollen in water, and then a sample for proton conductivity measurement was prepared by sandwiching the membrane between stainless steel foil electrodes. The impedance of these samples was measured using Hewlett-Packard HP4192A. The results obtained are shown below.

Film A-4 (Reference Example 1): 0.04 × 10
^-2 S / cm; Film A-2 (Example 1): 0.10 × 10 ⁻² S / cm;
And Film A-3 (Example 2): 0.62 × 10 ⁻² S / cm.

Thus, high proton conductivity was obtained by filling the second polymer. In addition, each of the films A-2 and A-3 had desired heat resistance and methanol stopping performance. That is, it was found that the electrolyte membranes A-2 and A-3 of this example had low methanol permeability, heat resistance, and high proton conductivity.

[0082]

According to the present invention, permeation (crossover) of methanol is suppressed as much as possible, and high temperature (about 130
A novel electrolyte membrane that can withstand use in an environment can be provided. Further, according to the present invention, it is possible to provide a method for producing the above-mentioned electrolyte membrane in addition to or in addition to the above effects. Further, according to the present invention, in addition to the above effects or in addition to the above effects, a novel methanol direct type solid polymer fuel cell using the above electrolyte membrane can be provided.

[Brief description of the drawings]

FIG. 1 is a schematic view of a porous substrate used in the present invention.

FIG. 2 is a schematic diagram showing that a first monomer is formed in pores of a porous substrate used in the present invention.

FIG. 3 is a schematic view of filling a second polymer of the present invention.

FIG. 4 is a schematic view showing one embodiment of a methanol fuel cell using the electrolyte membrane of the present invention.

FIG. 5 is a schematic view showing one embodiment of a cathode electrode using the electrolyte membrane of the present invention.

[Explanation of symbols]

1 porous substrate, 2 pores, 3rd polymer, 5
2nd polymer, 11 methanol fuel cell, 13 cathode electrode, 15 anode electrode, 17 electrolyte, 19 support layer, 21 catalyst layer, 23 porous thin film

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C08L 79:08 C08L 79:08 (72) Inventor Shinichi Nakao 3-25-5 Akatsuka Shinmachi, Itabashi-ku, Tokyo 303 F term (reference) 4F074 AA39 AA74 CD11 CE13 CE15 CE56 CE84 DA49 5H026 AA06 AA08 BB00 BB04 CX05 EE11 EE18

Claims (46)

[Claims] 1. A step of forming a first polymer such that one end thereof is bonded to an inner surface of a pore of a porous substrate having swelling resistance to an organic solvent and water, and the same as the first polymer. A method for producing an electrolyte membrane comprising a step of filling a second polymer, which may or may not be different, into pores of the base material, wherein the first and second polymers have proton conductivity. Manufacturing method. 2. The method of claim 1, wherein the first polymer is derived from a first monomer and the second polymer is derived from a second monomer that may be the same as or different from the first monomer. . 3. The step of forming a first polymer includes the step of irradiating the substrate with energy and the step of contacting the substrate with a first monomer, and by contacting the first monomer with the substrate. The method of claim 1 or claim 2, wherein the first polymer is formed such that one end thereof is bonded to an inner surface of the pore of the substrate. 4. An energy source for the energy is selected from the group consisting of plasma, ultraviolet rays, electron beams, and gamma rays, and the energy source excites the base material to initiate a reaction on at least the inner surface of the pores of the base material. 4. The method of claim 3, wherein a point is formed and a first polymer is formed to bond to the substrate at the reaction initiation point by contacting a first monomer with the reaction initiation point. 5. The method according to claim 1, wherein the step of forming the first polymer couples one end of the first polymer to the substrate by a coupling agent. 6. The step of filling the second polymer, wherein the second monomer is filled in pores of the base material, and the filled second monomer is polymerized in the pores to form a second polymer.
The method according to any one of claims 2 to 5, which comprises obtaining a polymer of the formula (1) and filling the pores with the polymer. 7. The method according to claim 1, wherein the porous substrate is made of an inorganic material or a heat-resistant polymer. 8. The method according to claim 7, wherein the inorganic material is any one of ceramic, glass, and alumina, or a composite material thereof. 9. The method according to claim 7, wherein said heat-resistant polymer is polytetrafluoroethylene or polyimide. 10. The method according to claim 1, wherein the electrolyte membrane is an electrolyte membrane for a fuel cell. 11. The method according to claim 1, wherein the electrolyte membrane is an electrolyte membrane for a direct methanol solid polymer fuel cell. 12. An electrolyte membrane, wherein pores of a porous substrate that does not substantially swell in methanol and water are filled with a polymer having proton conductivity, wherein the polymer is a first polymer. A first polymer having a proton conductive polymer and a second proton conductive polymer, the first polymer having one end bonded to the pore inner surface of the base material, and the second polymer being a first polymer An electrolyte membrane which is a polymer which may be the same or different. 13. The method of claim 1, wherein the first polymer is derived from a first monomer and the second polymer is derived from a second monomer that may be the same as or different from the first monomer.
3. The electrolyte membrane according to 2. 14. The electrolyte membrane according to claim 12, wherein the first polymer is obtained by irradiating the substrate with energy and then contacting the substrate with a first monomer. 15. The energy source of the energy is selected from the group consisting of plasma, ultraviolet rays, electron beams, and gamma rays, and the energy source excites the base material to initiate a reaction on at least the inner surface of the pores of the base material. 15. The electrolyte membrane according to claim 14, wherein a point is formed and a first monomer is brought into contact with the base material at the reaction start point by contacting a first monomer with the reaction start point. 16. The method according to claim 12, wherein the first polymer has one end bonded to the substrate by a coupling agent. 17. The method according to claim 13, wherein the second polymer is obtained by filling the second monomer into pores of the base material and polymerizing the filled second monomer in the pores. The electrolyte membrane according to claim 16. 18. The electrolyte membrane according to claim 12, wherein the porous substrate is made of an inorganic material or a heat-resistant polymer. 19. The electrolyte membrane according to claim 18, wherein the inorganic material is any one of ceramic, glass, and alumina, or a composite material thereof. 20. The electrolyte membrane according to claim 18, wherein the heat-resistant polymer is polytetrafluoroethylene or polyimide. 21. The electrolyte membrane according to claim 12, wherein the electrolyte membrane is an electrolyte membrane for a fuel cell. 22. The electrolyte membrane according to claim 12, wherein the electrolyte membrane is an electrolyte membrane for a direct methanol solid polymer fuel cell.
0. The electrolyte membrane according to any one of 0. 23. A fuel cell in which an electrolyte membrane is formed on a cathode electrode or a catalyst layer of a cathode electrode, wherein the electrolyte membrane is the electrolyte membrane according to any one of claims 12 to 22. . 24. A fuel cell comprising a cathode electrode, an anode electrode, and an electrolyte sandwiched between both electrodes, wherein the electrolyte is a thin porous base material that does not substantially swell in methanol and water. An electrolyte characterized in that pores are filled with a polymer having proton conductivity, wherein the polymer has a first proton conductive polymer and a second proton conductive polymer, and wherein the first polymer has the group A fuel cell comprising a polymer having one end bonded to the inner surface of a pore of a material, and the second polymer being a polymer which may be the same as or different from the first polymer. 25. The method according to claim 2, wherein the first polymer is derived from a first monomer and the second polymer is derived from a second monomer which may be the same as or different from the first monomer.
4. The fuel cell according to 4. 26. The fuel cell according to claim 24 or 25, wherein the first polymer is obtained by irradiating the substrate with energy and then contacting the substrate with a first monomer. 27. An energy source of the energy is selected from the group consisting of plasma, ultraviolet rays, electron beams, and gamma rays, and the energy source excites the base material to initiate a reaction on at least the inner surface of the pores of the base material. 26. The fuel cell of claim 25, wherein creating a point and contacting a first monomer with the reaction initiation point results in a first polymer that binds to the substrate at the reaction initiation point. 28. The method of claim 24 or claim 25, wherein the first polymer has one end bonded to the substrate by a coupling agent. 29. The method according to claim 25, wherein the second polymer is obtained by filling the second monomer into pores of the base material and polymerizing the filled second monomer in the pores. The fuel cell according to any one of claims 28 to 28. 30. The fuel cell according to claim 24, wherein the porous substrate is made of an inorganic material or a heat-resistant polymer. 31. The fuel cell according to claim 30, wherein the inorganic material is any one of ceramic, glass, and alumina, or a composite material thereof. 32. The fuel cell according to claim 30, wherein the heat-resistant polymer is polytetrafluoroethylene or polyimide. 33. The fuel cell according to claim 24, wherein the fuel cell is a direct methanol solid polymer fuel cell. 34. A step of applying a sol to the first pole, a step of forming the applied sol into a porous thin film layer, and filling the pores of the obtained porous thin film layer with a proton conductive polymer to form a first thin film. Forming an electrolyte membrane on the electrode; and forming a second electrolyte membrane on the electrolyte membrane.
A method of manufacturing a fuel cell, comprising the steps of: adhering the first and second electrodes, wherein, in the step of forming the electrolyte membrane, the proton conductive polymer has first and second proton conductive polymers; Forming the first polymer such that one end of the polymer is attached to the surface of the pore;
And a step of filling the second polymer after the formation of the first polymer. 35. The method of claim 34, wherein said first polymer and said second polymer can be the same or different. 36. The method according to claim 34, wherein the first polymer is derived from a first monomer and the second polymer is derived from a second monomer which may be the same as or different from the first monomer. Item 36. The method according to Item 35. 37. The method according to claim 34, wherein the step of forming the first polymer is performed by irradiating the substrate with energy and then contacting the substrate with a first monomer. The method of claim 1. 38. The energy source of the energy is selected from the group consisting of plasma, ultraviolet rays, electron beams, and gamma rays, and the energy source excites the base material to initiate a reaction on at least the inner surface of the pores of the base material. 38. The method of claim 37, wherein creating a point and contacting a first monomer with the reaction initiation point results in a first polymer to associate with the substrate at the reaction initiation point. 39. The method according to any one of claims 34 to 36, wherein the step of forming the first polymer couples one end of the first polymer to the substrate with a coupling agent. 40. The second polymer is obtained by filling the second monomer into pores of the base material and polymerizing the filled second monomer in the pores. The method according to any one of claims 36 to 39. 41. The method according to claim 34, wherein the porous substrate is made of an inorganic material or a heat-resistant polymer. 42. The method according to claim 41, wherein the inorganic material is any one of ceramic, glass and alumina or a composite material thereof. 43. The method according to claim 41, wherein said heat-resistant polymer is polytetrafluoroethylene or polyimide. 44. The sol is applied to the catalyst layer in the sol coating step, wherein the first pole has a first support layer and a first catalyst layer. The method according to claim 1. 45. The second pole has a second support layer and a second catalyst layer, and in the step of bringing the second pole into close contact, the electrolyte membrane and the second catalyst layer are in contact with each other. The method according to any one of claims 34 to 44, wherein 46. The method according to claim 34, wherein the fuel cell is a direct methanol solid polymer fuel cell.