JP2003346815A - Membrane electrode joint body and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a membrane electrode joint body in which the internal structure of a catalyst layer is stably kept even when it is used for a long time in a high-moisture condition or a high-temperature condition, and a high output is obtained even when it is used under a high-temperature and in a low-moisture condition, and a method for manufacturing the membrane electrode joint body. <P>SOLUTION: The membrane electrode joint body comprises a solid polymer electrolytic membrane and electrodes joined with both sides of the solid polymer electrolytic membrane. At least one of the electrodes has a catalyst layer containing an electrolyte in the catalyst layer formed of a solid polymer compound crosslinked via at least one crosslinked group selected from a bis-sulfonyl- imide group, sulfonyl-carbonylimide group, and a bis-carbonyl-imide group. This membrane electrode joint body is obtained by reacting a catalyst layer containing a solid polymer compound having a functional group A with a crosslinking agent having a functional group B or a crosslinking agent capable of introducing the functional group B in the solid polymer compound. <P>COPYRIGHT: (C)2004,JPO

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a membrane electrode assembly and a method for producing the same, and more particularly, to a fuel cell, a water electrolysis apparatus, a hydrohalic acid electrolysis apparatus, a salt electrolysis apparatus,
The present invention relates to a membrane electrode assembly used for various electrochemical devices such as a hydrogen and / or oxygen concentrator, a humidity sensor, a gas sensor, and the like, and a method for manufacturing the same.

[0002]

2. Description of the Related Art A solid polymer electrolyte is a solid polymer material having an electrolyte group such as a sulfonic acid group in a polymer chain.
Since it has the property of firmly binding to specific ions and selectively permeating cations or anions, it is formed into particles, fibers, or films and used for various purposes.

For example, a polymer electrolyte fuel cell is a battery in which chemical energy generated when a continuously supplied fuel is oxidized is directly extracted as electric energy.
As the electrolyte membrane, a solid polymer electrolyte membrane having proton conductivity is used.

The SPE electrolysis method is a method for producing hydrogen and oxygen by electrolyzing water. A solid polymer electrolyte membrane having proton conductivity is used as an electrolyte instead of a conventional alkaline aqueous solution. Have been.

[0005] As solid polymer electrolytes used in such applications, for example, non-crosslinked perfluoro-based electrolytes represented by Nafion (registered trademark, manufactured by DuPont) and various hydrocarbon-based electrolytes are known. I have. In particular, perfluoro-based electrolytes, which have extremely high chemical stability, have been awarded as electrolyte membranes for various electrochemical devices used under severe conditions such as fuel cells and SPE electrolyzers. It is.

In polymer electrolyte fuel cells, SPE electrolyzers, and the like, the polymer electrolyte is formed into an extremely thin film, and a membrane electrode assembly (ME) having electrodes bonded to both surfaces thereof.
Used as A). The electrode of the MEA generally includes a catalyst layer containing carbon carrying a catalyst and an electrolyte in a catalyst layer covering the periphery thereof. In some cases, the electrode has a two-layer structure of a catalyst layer and a porous diffusion layer formed of carbon cloth, carbon paper, or the like formed outside the catalyst layer. Such MEA usually forms a catalyst layer by applying a mixture of carbon carrying a catalyst and an electrolyte in the catalyst layer on the surface of a base material such as tetrafluoroethylene or a diffusion layer, and forms the catalyst layer with a solid. It is manufactured by hot pressing a polymer electrolyte membrane.

In a polymer electrolyte fuel cell, a three-phase interface in which a catalyst, an electrolyte in a catalyst layer, and a reaction gas coexist must be formed in the catalyst layer in order for the cell reaction to proceed efficiently. Further, in order to maintain high performance for a long period of time, the internal structure of such a catalyst layer needs to be stable.

However, in the case of a polymer electrolyte fuel cell, water is generated on the cathode side by a cell reaction. Further, when protons move from the anode side to the cathode side, water also diffuses to the cathode side. Therefore, when the fuel cell is operated for a long period of time particularly at a low operating temperature and a high gas utilization rate, the electrolyte in the catalyst layer on the cathode side swells or dissolves in water, and the internal structure of the catalyst layer becomes unstable. There is.

In order to solve this problem, a method has been proposed in which a crosslinked electrolyte is used as the electrolyte in the catalyst layer. For example, JP-A-2001-176524 discloses that a compound having two double bonds having different reactivities is used as a comonomer, and a copolymer is first synthesized by using a highly reactive first double bond. Then, an ion exchange resin obtained by crosslinking between copolymers using a second double bond having low reactivity is disclosed.

For example, Japanese Patent Application Laid-Open No. 11-7969 discloses a polymer having at least one imidic acid group selected from sulfonylimidic acid, carbonylimidic acid and sulfonylcarbonylimidic acid in a molecule, and magnesium acetate. A cross-linked polymer obtained by reacting is described.

[0011]

Problems to be Solved by the Invention
The publication describes that when a part of the hydrogen of the imidic acid group is substituted with a divalent or higher valent metal ion such as Mg ²⁺ , the polymer is crosslinked. However, when the crosslinked electrolyte obtained by this method is used for a long time in an environment where water coexists, there is a problem that metal ions flow out from the crosslink point and the crosslinked structure disappears. When the crosslinked structure disappears, the electrolyte easily dissolves or swells in water in the catalyst layer, and the internal structure of the catalyst layer becomes unstable. Further, in this method, since the imido acid group is consumed for crosslinking, a crosslinked electrolyte exhibiting high ionic conductivity cannot be obtained.

On the other hand, the crosslinked electrolyte obtained by the method disclosed in JP-A-2001-176524 is
Since the copolymers are cross-linked by a double bond, the internal structure of the catalyst layer is less likely to be destabilized by water in the catalyst layer. However, this method has a problem that a heat treatment at 220 ° C. is required to form a crosslink. When heating at a temperature exceeding 200 ° C. during the production of the MEA, most of the three-phase interface in the catalyst layer is crushed, so that high fuel cell performance cannot be obtained.

In a polymer electrolyte fuel cell,
In order to reduce the size of the system, it is desired to operate it under high temperature and low humidification conditions. However,
MEA provided with catalyst layer containing non-crosslinked type electrolyte in catalyst layer
In the case of, when used at a high temperature, the internal structure of the catalyst layer becomes unstable. In addition, conventional cross-linked electrolytes do not exhibit high ionic conductivity under high temperature and low humidification conditions because of low water retention. Therefore, even if this is used as the electrolyte in the catalyst layer, high fuel cell performance cannot be obtained. Further, the catalyst layer and the electrolyte membrane are usually joined by hot pressing. However, if joining failure occurs during joining or during use, the output is reduced.

An object of the present invention is to provide a membrane / electrode assembly in which the internal structure of a catalyst layer is stably maintained even when used under a high humidity or high temperature condition for a long period of time. It is to provide a manufacturing method. Another object of the present invention is to provide a membrane / electrode assembly capable of obtaining a high output even when used under conditions of high temperature and low humidity, and a method of manufacturing the same. Still another object of the present invention is to provide a membrane / electrode assembly having excellent performance and durability and a method for manufacturing the same.

[0015]

Means for Solving the Problems To solve the above problems, a membrane electrode assembly according to the present invention comprises a solid polymer electrolyte membrane, and electrodes joined to both sides of the solid polymer electrolyte membrane, At least one of the electrodes is a catalyst layer containing an electrolyte in a catalyst layer made of a solid polymer compound crosslinked via at least one crosslinking group selected from a bissulfonylimide group, a sulfonylcarbonylimide group, and a biscarbonylimide group. The gist is that it is provided.

The membrane electrode assembly according to the present invention is characterized in that the electrolyte in the catalyst layer is made of a solid polymer compound crosslinked via a crosslinking group comprising a bissulfonylimide group, a sulfonylcarbonylimide group and / or a biscarbonylimide group. Therefore, the internal structure of the catalyst layer is stably maintained even under a high humidity condition or a high temperature condition. Further, since the crosslinking group itself functions as an acid group, the water retention of the catalyst layer is improved.
Therefore, high output can be obtained even under high temperature and low humidity conditions.

Further, according to the method for producing a membrane electrode assembly according to the present invention, a catalyst layer forming step of forming a catalyst layer containing a solid polymer compound having a functional group A; A crosslinking agent having a functional group B capable of forming at least one crosslinking group selected from a sulfonylimide group, a sulfonylcarbonylimide group, and a biscarbonylimide group, or crosslinking capable of introducing the functional group B into the solid polymer compound An agent is introduced into the catalyst layer, and the functional group A
And a crosslinking step of reacting the functional group B, and a protonation step of performing hydrolysis and proton exchange of the catalyst layer,
And a joining step of joining the catalyst layer and the solid polymer electrolyte membrane.

A catalyst layer containing a solid polymer compound having a functional group A is formed, and this is reacted with a crosslinking agent having a functional group B or a crosslinking agent capable of introducing the functional group B into the solid polymer compound. And the solid polymer compound is cross-linked via a cross-linking group comprising a bissulfonylimide group or the like. Next, this catalyst layer is protonated, and this is joined to a solid polymer electrolyte membrane, to obtain a membrane electrode assembly having a catalyst layer having excellent structural stability and water retention.

The second embodiment of the membrane / electrode assembly according to the present invention comprises a solid polymer electrolyte membrane and electrodes bonded to both sides of the solid polymer electrolyte membrane, and at least one of the electrodes is The gist is that at least a part of the electrolyte in the catalyst layer included in the catalyst layer provided in the electrode is covalently bonded to the solid polymer electrolyte membrane. In this case, the covalent bond is preferably at least one selected from a bissulfonylimide bond, a sulfonylcarbonyl bond, and a biscarbonylimide bond.

When the electrolyte in the catalyst layer and the solid polymer electrolyte membrane contained in the electrode are covalently bonded, the bondability between the solid polymer electrolyte membrane and the electrolyte in the catalyst layer is improved, and proton and water between the two are improved. Transfer is performed more smoothly. Therefore, if such a membrane electrode assembly is applied to a fuel cell, a gas sensor, and the like, the performance and durability thereof can be improved.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below in detail. The membrane electrode assembly according to the first embodiment of the present invention includes a solid polymer electrolyte membrane and electrodes joined to both surfaces of the solid polymer electrolyte membrane.

First, the solid polymer electrolyte membrane will be described. The solid polymer electrolyte refers to one in which an electrolyte group is bonded to any of the solid polymer compounds. In the present invention, the material of the solid polymer electrolyte constituting the MEA membrane is not particularly limited, and is a solid polymer electrolyte having various compositions or various molecular structures such as linear or branched. The present invention can be applied to this.

That is, in the solid polymer electrolyte, an electrolyte group is bonded to one of solid polymer compounds having a C—F bond in a polymer chain (hereinafter referred to as “fluorine compound”). (Hereinafter referred to as “fluorinated electrolyte”), or C-
A solid polymer compound containing only H bonds (hereinafter referred to as "hydrocarbon-based compound") having an electrolyte group bonded thereto (hereinafter referred to as "hydrocarbon-based electrolyte"). There may be.

The fluorine-based electrolyte contains C in the polymer chain.
A solid polymer compound having both an —F bond and a C—H bond (hereinafter referred to as “fluorine / hydrocarbon compound”) to which an electrolyte group is bonded (hereinafter referred to as “a fluorine-hydrocarbon compound”); A fluorine-hydrocarbon-based electrolyte ”) or a solid polymer compound containing a C—F bond in a polymer chain and containing no C—H bond (hereinafter referred to as“ perfluoro (Hereinafter referred to as "perfluoro-based electrolyte"). In addition, in addition to a CF bond, a C-Cl bond and other bonds (for example, -O-, -S-, -C (=
O)-, -N (R)-, etc.).

The hydrocarbon electrolyte has an electrolyte group bonded to one of solid polymer compounds having no aromatic ring in the polymer chain (hereinafter referred to as "aliphatic hydrocarbon compounds"). (Hereinafter referred to as “aliphatic hydrocarbon-based electrolyte”) or a solid polymer compound having an aromatic ring in any of the polymer chains (hereinafter referred to as “aromatic”). (Hereinafter referred to as "aromatic hydrocarbon-based electrolyte").

Further, the aromatic hydrocarbon-based electrolyte has an alkylene chain (-(CH ₂ ) _n- , n ≧
1) and branched carbon structure (e.g., -CHCH ₃ -, - C
(CH ₃ ) ₂ -or the like (hereinafter referred to as “partially aromatic hydrocarbon compound”) having an electrolyte group bonded thereto (hereinafter referred to as “partially aromatic hydrocarbon compound”). Or a solid polymer compound containing no alkylene chain or branched carbon structure in the bonding chain (hereinafter referred to as a “whole aromatic hydrocarbon compound”). ) (Hereinafter referred to as a “whole aromatic hydrocarbon-based electrolyte”).

The type of the electrolyte group provided in the solid polymer electrolyte is not particularly limited. Preferred examples of the electrolyte group include a sulfonic acid group, a carboxylic acid group, a phosphonic acid group, and a sulfonimide group. The solid polymer electrolyte may contain only one of these electrolyte groups, or 2
More than one species may be included. Further, these electrolyte groups may be directly bonded to the linear solid polymer compound, or may be bonded to either the main chain or the side chain of the branched solid polymer compound.

Specific examples of the perfluoro-based electrolyte include Nafion (registered trademark) manufactured by DuPont, Aciplex (registered trademark) manufactured by Asahi Kasei Corporation, Flemion (registered trademark) manufactured by Asahi Glass Co., Ltd., and the like. Is a preferred example.

Further, as the fluorine / hydrocarbon electrolyte, specifically, a polystyrene-graft-ethylenetetrafluoroethylene copolymer (hereinafter referred to as a copolymer) having an electrolyte group such as a sulfonic acid group introduced into one of the polymer chains. , Which is referred to as “PS-g-ETFE”), polystyrene-graft-polytetrafluoroethylene, and the like, and derivatives thereof.

Further, as the aliphatic hydrocarbon-based electrolyte,
Specifically, polyamide, polyacetal, polyethylene, polypropylene, acrylic resin, polyester, polysulfone, polyether, etc., in which an electrolyte group such as a sulfonic acid group is introduced into any of the polymer chains, and derivatives thereof are preferable. An example is given.

Specific examples of the partially aromatic hydrocarbon-based electrolyte include polystyrene in which an electrolyte group such as a sulfonic acid group is introduced into one of the polymer chains, polyamide having an aromatic ring, polyamideimide, and polyimide. , Polyester, polysulfone, polyetherimide, polyethersulfone, polycarbonate and the like, and their derivatives are preferred examples.

Examples of the wholly aromatic hydrocarbon electrolyte include polyether ether ketone in which an electrolyte group such as a sulfonic acid group is introduced into one of the polymer chains.
Preferable examples include polyether ketone, polysulfone, polyether sulfone, polyimide, polyether imide, polyphenylene, polyphenylene ether, polycarbonate, polyamide, polyamide imide, polyester, polyphenylene sulfide, and derivatives thereof.

Of these, fluorine-based electrolytes, particularly perfluoro-based electrolytes, have a C—F bond in the polymer chain. An MEA with excellent properties is obtained. Further, aromatic hydrocarbon-based electrolytes, particularly wholly aromatic hydrocarbon-based electrolytes,
Since the introduction of an acid group is relatively easy, application of the present invention to this can provide an MEA exhibiting high electrical conductivity.

Next, the electrodes will be described. The electrode generally includes a catalyst layer including a catalyst carrier supporting a catalyst and an electrolyte in a catalyst layer covering the periphery of the catalyst carrier. In the present invention, the electrode may have only such a catalyst layer, or may have a two-layer structure including a catalyst layer and a diffusion layer formed outside the catalyst layer. May be.

As the catalyst, an optimum catalyst is used according to the purpose of use of the MEA, the use conditions and the like. For example, in the case of a polymer electrolyte fuel cell, platinum, a platinum alloy, palladium, ruthenium, rhodium or the like is used as a catalyst. The optimal amount of the catalyst contained in the catalyst layer is selected according to the use of the MEA, the use conditions, and the like.

The catalyst carrier is for carrying fine particles of the catalyst and for transferring electrons in the catalyst layer. As the catalyst carrier, carbon, activated carbon, fullerene, carbon nanophone, carbon nanotube, and the like are generally used. The amount of the catalyst carried on the surface of the catalyst carrier is:
The optimum amount of the catalyst and the catalyst carrier is selected in accordance with the material of the MEA, the application of the MEA, the conditions of use, and the like.

The electrolyte in the catalyst layer is for transferring protons between the solid polymer electrolyte membrane and the electrode.
In the present invention, a catalyst layer constituting at least one electrode (hereinafter, referred to as a “first catalyst layer”) includes a bissulfonylimide group (—SO 2) as an electrolyte in the catalyst layer.
_{2 -NH-SO 2} -), at least one selected from the sulfonyl carbonyl imide group _(-SO 2 -NH-CO-) and bis-carbonyl imide group (-CO-NH-CO-)
One cross-linking group (hereinafter referred to as “acidic cross-linking group”)
A solid polymer compound cross-linked through is used. In this case, the electrolyte in the catalyst layer may further include an electrolyte group other than an acidic crosslinking group such as a sulfonic acid group, a carboxylic acid group, a phosphonic acid group, and a sulfonimide group.

The solid polymer compound constituting the main part of the electrolyte in the catalyst layer is not particularly limited, and may be any of the above-mentioned fluorine / hydrocarbon compounds, perfluoro compounds, or aliphatic hydrocarbon compounds. Either a partially aromatic hydrocarbon compound or a wholly aromatic hydrocarbon compound may be used.

Of these, fluorine compounds, particularly perfluoro compounds, have a C—F bond in the polymer chain, and thus those obtained by crosslinking them with an acidic crosslinking group are used as the electrolyte in the catalyst layer. If this is the case, a catalyst layer having excellent heat resistance and oxidation resistance can be obtained. In addition, aromatic hydrocarbon compounds, particularly wholly aromatic hydrocarbon compounds, are relatively easy to introduce an electrolyte group. A catalyst layer exhibiting proton conductivity is obtained.

The equivalent weight EW of the entire electrolyte in the catalyst layer is 2
The amount is preferably from 50 g / equivalent to 2000 g / equivalent. When the equivalent weight EW is less than 250 g / equivalent, the electrolyte in the catalyst layer easily dissolves or swells in water, and it becomes difficult to stably maintain the internal structure of the first catalyst layer. On the other hand, the equivalent weight E
If W exceeds 2000 g / equivalent, the water retention of the first catalyst layer is reduced, and high ionic conductivity cannot be obtained, especially under low humidity conditions. The equivalent weight EW of the entire electrolyte in the catalyst layer is more preferably 250 g / equivalent or more and 1000 g / equivalent or less.

The amount of the acidic crosslinking groups contained in the electrolyte in the catalyst layer is preferably at least 0.05% of the total number of the crosslinkable functional groups contained in the electrolyte in the catalyst layer. When the amount of the acidic crosslinking group is less than 0.05%, it is difficult to stably maintain the internal structure of the first catalyst layer at a high temperature, which is not preferable. The amount of the acidic crosslinking group is more preferably 0.1% or more.

The amount of the acidic crosslinking groups contained in the electrolyte in the catalyst layer is preferably 50% or less of the total number of the crosslinkable functional groups contained in the electrolyte in the catalyst layer. If the amount of the acidic cross-linking group exceeds 50%, the electric conductivity is undesirably reduced. The amount of the acidic crosslinking group is more preferably 25% or less.

An electrolyte in the catalyst layer in the first catalyst layer;
The ratio of the catalyst to the catalyst carrier supporting the catalyst is not particularly limited, and an optimum ratio may be selected according to the material of the catalyst, the catalyst carrier and the electrolyte in the catalyst layer, the application of the MEA, the use conditions, and the like.

As for the catalyst layer constituting the other electrode, an electrolyte having the same cross-linking structure as the electrolyte in the catalyst layer contained in the first catalyst layer may be used as the electrolyte in the catalyst layer. Alternatively, a crosslinked electrolyte or a non-crosslinked electrolyte having a crosslinked structure different from the above may be used.

However, in the case of the polymer electrolyte fuel cell, since water is generated on the cathode side, it is preferable to use an electrolyte cross-linked by such an acid cross-linking group at least as an electrolyte in the catalyst layer on the cathode side. Also,
In order to obtain a high output under high temperature and low humidity conditions, it is preferable to use an electrolyte cross-linked by such an acid cross-linking group for the electrolyte in the catalyst layer of both the cathode and the anode.

Next, the operation of the membrane electrode assembly according to this embodiment will be described. An electrolyte crosslinked via a bissulfonylimide group, a sulfonylimide group or a biscarbonylimide group is less likely to be dissolved or swelled in water than a non-crosslinked electrolyte and has excellent heat resistance. These cross-linking groups are all acidic cross-linking groups that function as acids. Further, these cross-linking groups function as strong acid groups when both ends are bonded to a perfluoro skeleton.

Therefore, the MEA using the electrolyte cross-linked by such an acid cross-linking group as the electrolyte in the catalyst layer has a stable internal structure of the catalyst layer even when used under high humidity or high temperature conditions. Will be kept. Further, since the crosslinking group itself functions as an acid group, the water retention of the catalyst layer is improved, and the proton conductivity of the catalyst layer is improved. Therefore, high output can be obtained even when used under high temperature and low humidity conditions.

Next, a method for manufacturing the membrane / electrode assembly according to the present embodiment will be described. The method for producing a membrane electrode assembly according to the present embodiment includes a catalyst layer forming step, a crosslinking step,
The method includes a protonation step and a bonding step.

First, the catalyst layer forming step will be described. The catalyst layer forming step is a step of forming a catalyst layer containing a solid polymer compound having a functional group A.

The solid polymer compound used as a starting material constitutes a main part of the electrolyte in the catalyst layer.
Any of those having the functional group A and those capable of introducing the functional group A by an addition reaction, a substitution reaction, or the like may be used. That is, the catalyst layer may be formed using a solid polymer compound having a functional group A as a starting material, or the functional group A may be introduced into the solid polymer compound after the formation of the catalyst layer.

The structure of the solid polymer compound may be either linear or branched. Further, the solid polymer compound may be any of the above-mentioned fluorine-based compounds or hydrocarbon-based compounds.

Among them, in order to obtain an electrolyte in the catalyst layer having high proton conductivity, the solid polymer compound is preferably an aromatic hydrocarbon compound, and particularly preferably a wholly aromatic hydrocarbon compound. In addition, in order to obtain an electrolyte in the catalyst layer having excellent heat resistance and oxidation resistance, the solid polymer compound is preferably a fluorine compound, and particularly preferably a perfluoro compound.

The functional group A is a functional group B of a crosslinking agent described later.
Refers to a functional group that can become an acidic crosslinking group by reacting with The functional group A may be directly bonded to a linear solid polymer compound, or may be bonded to an intermediate or terminal of a side chain constituting the solid polymer compound.

The content of the functional group A or the amount of the functional group A introduced is determined by the equivalent weight E of the finally obtained electrolyte in the catalyst layer.
It is preferable to select an optimum amount according to starting materials, production conditions, and the like so that W is 250 g / equivalent or more and 2000 g / equivalent or less.

Examples of the functional group A include a sulfonyl halide group, a sulfonamide group, a sulfonamide metal salt, an N-alkylsilylsulfonamide group, an N-alkylsilylsulfonamide metal salt, a carbonyl halide group, and a carboxylic acid. Preferable examples include ester groups, carbonylamide groups, phosphonyl halide groups, phosphonate ester groups, phosphonylamido groups, sulfonic acid groups, carboxylic acid groups, phosphonic acid groups, and the like, and derivatives thereof.

In particular, even when the sulfonyl halide group and its derivative are not consumed in the reaction with the cross-linking agent, the sulfonyl halide group and the derivative thereof are easily converted into a strong acid group by hydrolysis, and the proton in the catalyst layer has high proton conductivity. Can be provided, and thus, is suitable as the functional group A.

Further, a sulfonamide group obtained by reacting a sulfonyl halide group with ammonia or a primary amine is also particularly suitable as the functional group A. In this case, when ammonia or a primary amine is used as the crosslinking agent, the reaction rate between the sulfonyl halide group and ammonia or the primary amine is preferably 0.01 to 50%. The reaction rate is more preferably 0.1 to 20%, more preferably
0.1 to 10%, particularly preferably 0.1 to 5%. When a cross-linking agent having two or more functional groups B, particularly a cross-linking agent having a sulfonyl halide group, is used as the cross-linking agent, the reaction rate between the sulfonyl halide group and ammonia or a primary amine is preferably 20 to 100%. The reaction rate is more preferably 30 to 100%, further preferably 50 to 100%, particularly preferably 70 to 100%.
%.

Further, the formed catalyst layer may contain a solid polymer compound having one kind of functional group A, or a solid polymer compound having two or more kinds of functional group A. It may be. The catalyst layer may include a single solid polymer compound having one or more functional groups A, or two or more solid polymers having the same or different functional groups A. A polymer compound may be contained.

The catalyst layer can be specifically formed by the following procedure. First, a solid polymer compound having the functional group A or capable of introducing the functional group A is dissolved in an appropriate solvent. Next, a predetermined amount of a catalyst carrier supporting a catalyst is added to this solution. Further, this solution is applied to the surface of a substrate made of tetrafluoroethylene, carbon cloth, carbon paper or the like, and the solvent is removed. Thereby, a catalyst layer having a predetermined thickness and composition is obtained. Also, as a starting material,
When a solid polymer compound containing no functional group A is used, the functional group A may be introduced after forming the catalyst layer.

The type and amount of the solvent in which the solid polymer compound is dissolved are appropriately selected according to the material of the solid polymer compound. For example, when the catalyst layer is formed using a perfluoro-based compound having a sulfonic acid group (for example, Nafion), it is preferable to use water, alcohol, or the like as the solvent.

In this case, sulfo is used as the functional group A.
When using a nylfluoride group, after forming the catalyst layer
Exposing the catalyst layer to a gas containing fluorine gas
Is dimethylaminosulfur trifluoride ((CH₃)
₂NSF₃), Triethylamine trisodium florai
Do ((CH₃CH₂) N-3HF), 1,1,2,2
3,3-hexafluorodiethylaminopropane (CF
₃CHFCF₂N (C₂H ₅)₂) Etc.
What is necessary is just to be immersed in the solution which melts. As a result, the scan in the catalyst layer
It is possible to convert sulfonic acid groups to sulfonyl fluoride groups.
it can.

When a sulfonamide group is used as the functional group A, a catalyst layer is first formed, and then the sulfonic acid group is converted into a sulfonyl fluoride group by the above-mentioned method. A gas or a solution containing an amine compound (preferably ammonia) such as a secondary amine may be brought into contact with the catalyst layer. Thereby, the sulfonic acid group in the catalyst layer can be converted to a sulfonamide group.

When the catalyst layer is formed using a perfluoro compound having a sulfonyl fluoride group (eg, a fluoride of Nafion), it is preferable to use a fluorine-based solvent such as AK225 as the solvent. .

In this case, when a sulfonyl fluoride group is used as the functional group A, the resulting catalyst layer may be directly used in the next step. On the other hand, when a sulfonamide group is used as the functional group A, the sulfonyl fluoride group may be converted into a sulfonamide group according to the above-described procedure. The same applies when other functional groups A are used.

Next, the crosslinking step will be described. The cross-linking step is a step of introducing a cross-linking agent into the catalyst layer obtained in the catalyst layer forming step and causing the functional groups A and B to react. In the present invention, a crosslinking agent having a functional group B (hereinafter, referred to as a “first crosslinking agent”) or a crosslinking agent capable of introducing the functional group B into a solid polymer compound contained in a catalyst layer is used. (Hereinafter, this is referred to as “second crosslinking agent”).

The "functional group B" refers to a compound capable of forming at least one cross-linking group selected from a bissulfonylimide group, a sulfonylcarbonylimide group and a biscarbonylimide group by reacting with the functional group A. .

As the functional group B, specifically, a sulfonyl halide group, a sulfonamide group, a sulfonamide metal salt, an N-alkylsilylsulfonamide group, an N-alkylsilylsulfonamide metal salt, a carbonyl halide group, a carboxylic acid group Suitable examples include ester groups, carbonylamide groups, phosphonyl halide groups, phosphonate ester groups, phosphonylamido groups, sulfonic acid groups, phosphonic acid groups, carboxylic acid groups, and the like, and derivatives thereof.

The type of the functional group B can be appropriately selected according to the type of the functional group A so that the crosslinking point becomes an acidic crosslinking group. Among these, a functional group A consisting of a sulfonamide group and at least one functional group selected from a sulfonyl halide group, a carbonyl halide group, a phosphonyl halide group, a sulfonic ester group, a carboxylic ester group, and a phosphonate ester group Combinations of B are particularly preferred.

When crosslinking is performed using the first crosslinking agent,
A crosslinking agent having at least two functional groups B is used. In this case, the type of each functional group B contained in the first crosslinking agent may be the same or different. The crosslinking reaction may be performed using one kind of first crosslinking agent, or may be performed using two or more kinds of first crosslinking agents having the same or different kinds of functional groups B.

The first crosslinking agent is, specifically, 1,1,2,2
2-tetrafluoroethyl 1,2-di-sulfonyl halide _{(XO 2 S-CF 2 CF} 2 -SO 2 X.X is halide), 1,1,2,2,3,3, - hexafluoro propyl - 1,3-disulfonyl halide (XO ₂ S-C
F ₂ CF ₂ CF ₂ —SO ₂ X), 1,1,2,2,3
3,4,4 octafluorobutyl 1,4-sulfonyl halide _{(XO 2 S-CF 2 CF} 2 CF 2 CF 2 -
SO ₂ X), 1,1,2,2,3,3,4,4,5,5
- perfluoro pentyl-1,5-sulfonyl halide _{(XO 2 S-CF 2 CF} 2 CF 2 CF 2 CF 2 -SO
_{2 X)} fluoric sulfonyl halide such as, and derivatives thereof are preferred.

When a fluorinated sulfonyl halide is used as the first crosslinking agent, the number of carbon atoms between the sulfonyl halide groups is preferably from 1 to 20. The fluorine-based sulfonyl halide may have a straight-chain structure or may have a branched structure. In order to impart high proton conductivity to the electrolyte in the catalyst layer, those having a branched structure and having two or more sulfonyl halide groups are particularly suitable.

In the case of crosslinking using a second crosslinking agent,
As the cross-linking agent, one that can convert a part of the functional group A contained in the solid polymer compound into the functional group B can be used. Further, the second crosslinking agent may be one capable of directly introducing an atomic group containing the functional group B into the solid polymer compound by an addition reaction, a substitution reaction, or the like.

For example, when the functional group A is a sulfonyl halide group and a part of the functional group A is converted to a sulfonamide group, an amine compound such as ammonia or a primary amine (preferably a secondary amine) is used as the second crosslinking agent. , Ammonia). In this case, the amount of conversion to a sulfonamide group can be controlled by optimizing the reaction conditions.

When the functional group B is introduced into the solid polymer compound, 1, 2, 2, 2, 3,
3-hexafluoro-3-iodo-1-sulfonyl fluoride _{(FO 2 S-CF 2 CF} 2 CF 2 -I) or the like can be used.

The crosslinking reaction is preferably carried out by bringing a gas or liquid containing a crosslinking agent into contact with the catalyst layer. The reaction conditions such as the concentration of the cross-linking agent to be brought into contact with the catalyst layer, the reaction temperature, and the reaction time are such that a predetermined equivalent weight EW is obtained and a predetermined amount of the acidic cross-linking group is introduced into the solid polymer compound. The selection is made according to the materials of the solid polymer compound and the cross-linking agent, the application of the MEA, the use conditions, and the like.

When or after contacting the catalyst layer with the crosslinking agent, a treatment may be carried out in which the catalyst layer is contacted with a basic compound such as trimethylamine, triethylamine or tripropylamine. Further, after bringing the catalyst layer into contact with the crosslinking agent or the base compound, a treatment of heating the catalyst layer may be performed. In particular, when a treatment for contacting with a crosslinking agent, a treatment for contacting with a base compound, and a treatment for heating the catalyst layer are performed in this order, an electrolyte in the catalyst layer having heat resistance and high proton conductivity is obtained.

Next, the protonation step will be described.
The protonation step is a step of performing hydrolysis and proton exchange of the catalyst layer after crosslinking. The hydrolysis is performed by immersing the crosslinked catalyst layer in an appropriate alkaline aqueous solution. The proton exchange is performed by immersing the hydrolyzed catalyst layer in a suitable acid aqueous solution. Thereby, the solid polymer compound contained in the catalyst layer becomes an electrolyte in the catalyst layer. The conditions for hydrolysis and proton exchange may be appropriately selected according to the material of the solid polymer compound contained in the catalyst layer, the aqueous alkaline solution, the aqueous acid solution, and the like, and are not particularly limited.

Next, the joining step will be described. The joining step is a step of joining the hydrolyzed catalyst layer and the solid polymer electrolyte membrane. The bonding is usually performed by bringing the catalyst layer formed on the base material into close contact with the solid polymer electrolyte membrane and hot pressing. Hot pressing conditions are
Optimal conditions are selected according to the materials of the solid polymer electrolyte membrane and the electrolyte in the catalyst layer.

For example, when the solid polymer electrolyte membrane and the electrolyte in the catalyst layer are made of a perfluoro-based electrolyte, the hot pressing temperature is preferably from 80 ° C. to 150 ° C. The hot press pressure is preferably 2 MPa or more and 20 MPa or less. If the temperature and / or pressure is too low, a good joined body cannot be obtained. On the other hand, if the temperature and / or pressure is too high, a catalyst layer having a predetermined amount of a three-phase interface cannot be obtained. The hot pressing temperature is more preferably 100 ° C.
It is 140 ° C. or lower. The hot press pressure is
More preferably, it is 2 MPa or more and 10 MPa or less.

Next, the operation of the manufacturing method according to the present embodiment will be described. When a catalyst layer containing a solid polymer compound having a predetermined amount of a functional group A is formed and reacted with a cross-linking agent having a functional group B, the solid polymer compounds are cross-linked by the cross-linking agent, Becomes an acidic crosslinking group. When a crosslinking agent capable of introducing a functional group B is introduced into the catalyst layer, first, the functional group B is introduced into the solid polymer compound, and then the solid polymer compounds are cross-linked by an acidic cross-linking group.
Next, if this catalyst layer is protonated and further joined to a solid polymer electrolyte membrane, an MEA is obtained.

Since the catalyst layer of the MEA thus obtained contains the electrolyte in the catalyst layer cross-linked by the acid cross-linking group, it does not easily swell or solubilize in water, and has low heat resistance. Are better. Therefore, the internal structure of the catalyst layer is stably maintained even when used for a long time under high humidity conditions or high temperature conditions. Further, since the crosslinking group itself functions as an acid group, the water retention of the catalyst layer is improved. Therefore, high output can be obtained even under high temperature and low humidity conditions.

Next, a description is given of a membrane electrode assembly according to a second embodiment of the present invention. The membrane electrode assembly according to the present embodiment includes a solid polymer electrolyte membrane and electrodes bonded to both surfaces thereof.

In the present embodiment, the material of the solid polymer electrolyte membrane is not particularly limited, and may be a non-crosslinked electrolyte comprising the above-mentioned fluorine-based electrolyte or hydrocarbon-based electrolyte, or May be a cross-linked electrolyte in which the polymer chains constituting the electrolyte are cross-linked via various cross-linking groups.

When the solid polymer electrolyte membrane is formed of a cross-linked electrolyte, the structure of the cross-linking group is not particularly limited, but the above-mentioned acidic cross-linking group is preferable. in this case,
The solid polymer electrolyte membrane may contain one kind of acidic cross-linking group, or may contain two or more kinds. Further, the solid polymer electrolyte membrane may further contain an electrolyte other than the acidic crosslinking group.

Among these, a cross-linked electrolyte obtained by cross-linking a fluorine compound, particularly a perfluoro compound, with an acid cross-linking group is excellent in oxidation resistance and heat resistance, and is therefore suitable as a material for the solid polymer electrolyte membrane. It is. In addition, a crosslinked electrolyte in which an aromatic hydrocarbon compound, particularly a wholly aromatic hydrocarbon compound is crosslinked with an acidic crosslinking group, is excellent in heat resistance and electric conductivity, so that it is used as a material for a solid polymer electrolyte membrane. It is suitable.

When a cross-linked electrolyte cross-linked by an acid cross-linking group is used as a solid polymer electrolyte membrane, the suitable equivalent weight EW of the whole membrane and the preferable introduction amount of the acid cross-linking group are as described in the first embodiment. This is the same as the electrolyte in the catalyst layer according to the embodiment. In addition, other points regarding the solid polymer electrolyte membrane are the same as those of the first embodiment, and thus the description is omitted.

In the present embodiment, the electrode may have only a catalyst layer, or may have a two-layer structure of a catalyst layer and a diffusion layer.
Further, the electrolyte in the catalyst layer contained in the catalyst layer may be a crosslinked electrolyte in which the above-mentioned fluorine-based compound or hydrocarbon-based compound is crosslinked with the above-mentioned acidic crosslinking group, or a crosslinking group other than the acidic crosslinking group. The electrolyte may be either a crosslinked electrolyte crosslinked with or a non-crosslinked electrolyte.

Among these, a cross-linked electrolyte obtained by cross-linking a fluorine compound, particularly a perfluoro compound, with an acid cross-linking group is excellent in oxidation resistance and heat resistance, and is therefore particularly suitable as an electrolyte in the catalyst layer. . Further, a crosslinked electrolyte in which an aromatic compound, particularly a wholly aromatic compound is crosslinked with an acidic crosslinking group, is excellent in heat resistance and electric conductivity, and is therefore particularly suitable as an electrolyte in the catalyst layer.

When a cross-linked electrolyte cross-linked by an acidic cross-linking group is used as the electrolyte in the catalyst layer, the suitable equivalent weight EW of the entire electrolyte in the catalyst layer, the preferable introduction amount of the acid cross-linking group, and the like are as described above. The description is omitted because it is the same as that of the first embodiment.

Further, in the present embodiment, at least one of the electrodes is characterized in that at least a part of the electrolyte in the catalyst layer contained in the catalyst layer and the solid polymer electrolyte membrane are covalently bonded. I do.

In this case, the bonding structure of the covalent bond is not particularly limited, but it is preferable that the bonding point functions as an acid (hereinafter, this is referred to as “acidic covalent bond”). As such an acidic covalent bond, specifically, a bissulfonylimide bond (—SO ₂ —NH—SO
₂ -), sulfonyl carbonyl imide bond (-SO ₂ -
NH—CO—) or a biscarbonylimide bond (—C
O-NH-CO-) is a preferred example. The electrolyte in the catalyst layer and the solid polymer electrolyte membrane may be bonded via one of these acidic covalent bonds,
Alternatively, they may be bonded via two or more kinds of acidic covalent bonds.

Such a covalent bond may be formed on at least a part of the interface between the electrolyte in the catalyst layer and the solid polymer electrolyte membrane, but may be formed on the entire surface of the interface. Further, the interface between the non-crosslinked type electrolyte in the catalyst layer and the non-crosslinked type solid molecular electrolyte membrane may be bonded by a covalent bond, or at least one of the electrolyte in the catalyst layer or the solid polymer electrolyte is crosslinked. It may be made of a type electrolyte, and a part or the whole of the interface between them may be bonded by a covalent bond.

Among them, at least one of the electrolyte in the catalyst layer and the solid polymer electrolyte membrane is made of a cross-linked electrolyte cross-linked by the above-mentioned acidic cross-linking group, and part or all of the interface between the two is formed by an acidic covalent bond. Preferably they are combined. In particular, when both the electrolyte in the catalyst layer and the solid polymer electrolyte membrane are made of a cross-linked electrolyte cross-linked with an acid cross-linking group, and part or all of the interface between the two is bonded by an acidic covalent bond, An MEA having excellent durability, heat resistance, and electric conductivity can be obtained.

Next, the operation of the membrane electrode assembly according to the present embodiment will be described. The electrolyte in the catalyst layer functions to exchange protons between the three-phase interface in the catalyst layer and the solid polymer electrolyte membrane. Therefore, in order to transfer protons smoothly, the electrolyte in the catalyst layer and the solid polymer electrolyte membrane need to be in close contact with each other. However, in the method in which the catalyst layer and the solid molecular electrolyte membrane are simply thermocompression-bonded with a press or the like, the interface is partially peeled with repeated use,
The interface resistance may increase.

On the other hand, when at least a part of the interface between the electrolyte in the catalyst layer and the solid polymer electrolyte membrane is covalently bonded, the bondability between the solid polymer electrolyte membrane and the electrolyte in the catalyst layer is improved. In addition, the exchange of protons between the two is performed more smoothly. In particular, when the covalent bond is composed of an acidic covalent bond, the bonding point functions as an acid, so that the water retention and proton conductivity of the entire MEA are improved. Therefore, if such a membrane electrode assembly is applied to a fuel cell, a gas sensor, and the like, the performance and durability thereof can be improved.

Next, a method for manufacturing the membrane electrode assembly according to the present embodiment will be described. MEA according to the present embodiment
Can be produced by various methods. Among them, the MEA in which a part or the whole of the interface between the electrolyte in the catalyst layer and the solid polymer electrolyte is bonded by an acidic covalent bond can be manufactured by the following method.

The first method is a method in which an acidic crosslinking group is introduced into both the electrolyte in the catalyst layer and the solid polymer electrolyte membrane, and an acidic covalent bond is introduced into part or all of the interface between the two. The method includes a layer forming step, a film forming step, a catalyst layer forming step, a bonding step, a crosslinking step, and a protonation step.

The catalyst layer forming step is a step of forming a catalyst layer containing the first solid polymer compound having the first functional group A. Since the catalyst layer forming step according to the first method is the same as the catalyst layer forming step according to the first embodiment, the description is omitted.

The film forming step is a step of forming a film made of the second solid polymer having the second functional group A. The method for forming the film is not particularly limited, but a second solid polymer compound having a second functional group A or capable of introducing the second functional group A by an addition reaction, a substitution reaction, or the like. Is dissolved in a suitable solvent, and then the solution is cast on a suitable substrate and the solvent is removed, or a method in which a solid polymer compound is melted and extruded is suitable.

Incidentally, the second functional group A and the second solid polymer compound may be the same as the first functional group A and the first solid polymer compound used for the catalyst layer, respectively. Alternatively, they may be different. In addition, the other points related to the second functional group A and the second solid polymer compound are the same as those of the first functional group A and the first solid polymer compound, respectively, and thus description thereof is omitted.

The joining step is a step of joining the catalyst layer obtained in the catalyst layer forming step and the film obtained in the film forming step. In the crosslinking step, a crosslinking agent having the functional group B or a crosslinking agent capable of introducing the functional group B is introduced into the joined body obtained in the joining step, and the first functional group A and the second functional group are introduced. In this step, the group A is reacted with the functional group B. further,
The protonation step is a step of performing hydrolysis and proton exchange of the catalyst layer and the membrane after the reaction.

[0102] The joining step, the crosslinking step and the protonation step according to the first method are the same as those of the first method except that after the catalyst layer and the membrane are joined, a reaction between the functional groups A and B is caused in the whole joined body. , Respectively, are the same as the bonding step, the cross-linking step, and the protonation step according to the first embodiment, and thus description thereof will be omitted.

A cross-linking agent having a functional group B or a cross-linking agent capable of introducing a functional group B is introduced into a bonded body comprising a catalyst layer having a first functional group A and a film having a second functional group A. When the first functional group A and the second functional group A are reacted with the functional group B, the first solid polymer compound and the second solid polymer compound are respectively cross-linked by the acid cross-linking group. . At the same time, part or all of the interface between the first solid polymer compound and the second solid polymer compound is bonded by an acidic covalent bond. Further, if the catalyst layer and the membrane are protonated, a desired MEA can be obtained.

The second method is to introduce an acidic crosslinking group and an acidic covalent bond only near the interface between the electrolyte in the catalyst layer and the solid polymer electrolyte membrane. First, in the same manner as in the first method, a catalyst layer containing a first solid polymer compound having a first functional group A is formed (catalyst layer forming step). Is formed (film forming step).

Next, a crosslinking agent having a functional group B or a crosslinking agent capable of introducing the functional group B is introduced only into the very surface of the catalyst layer and / or the membrane (crosslinking agent introduction step). Catalyst layer and / or
Alternatively, in order to introduce the crosslinking agent only to the very surface of the membrane, it is only necessary to shorten the contact time between the gas or the solution containing the crosslinking agent and the catalyst layer and / or the membrane.

Next, after joining the catalyst layer and the membrane (joining step), this is brought into contact with the above-mentioned base compound such as trimethylamine (base treatment step). Thereby, only in the vicinity of the interface between the first solid polymer compound and the second solid polymer compound, the first functional group A and / or the second functional group A
And the functional group B progress, and the vicinity of the interface of the catalyst layer and / or the membrane is cross-linked by an acidic cross-linking group, and at the same time, both are bonded by an acidic covalent bond. Furthermore, if hydrolysis and proton exchange are performed on the conjugate after the base treatment, the desired MEA can be obtained.
Is obtained.

The third method is a method in which an acidic crosslinking group is introduced into one of the electrolyte in the catalyst layer and the entire solid polymer electrolyte membrane, and an acidic covalent bond is introduced into the interface between the two. First, in the same manner as in the first method, a catalyst layer containing a first solid polymer compound having a first functional group A is formed (catalyst layer forming step). Is formed (catalyst layer forming step).

Next, a crosslinking agent having a functional group B or a crosslinking agent capable of introducing the functional group B is uniformly introduced into either the catalyst layer or the membrane (crosslinking agent introduction step). Then
After joining the catalyst layer and the membrane (joining step), this is brought into contact with the above-mentioned base compound (base treatment step). Thereby, the first solid polymer compound or the second solid polymer compound is cross-linked by the acid cross-linking group, and at the same time, a part or the whole of the interface between them is bonded by an acidic covalent bond. Further, by subjecting the conjugate after the base treatment to hydrolysis and proton exchange, a desired MEA can be obtained.

In any of the MEAs obtained by the manufacturing method according to the present embodiment, a part or the whole of the interface between the electrolyte in the catalyst layer and the solid polymer electrolyte membrane is bonded by an acidic covalent bond. The bondability with the electrolyte membrane is improved. In addition, since the bonding point functions as an acid, the water retention and proton conductivity of the entire MEA are improved. Therefore, if this is used for a fuel cell, a gas sensor, or the like, its performance and durability can be improved.

[0110]

(Example 1) A mixed aqueous solution of platinum-supported carbon and Nafion (equivalent weight EW: 1000 g / equivalent) (platinum-supported carbon: Nafion = 1: 1) is applied to a tetrafluoroethylene sheet and dried. A sheet having a thickness of 10 μm was formed. This sheet (10cm
× 10 cm) with a 10% fluorine gas (1 kg / cm ² (9.8 × 10 ⁴ Pa)) diluted with argon gas.
The mixture was treated at 25 ° C. for 2 hours to convert a sulfonic acid group into a sulfonyl fluoride group. Further, this was further purified by ammonia gas (1 kg / cm ² (9.8 × 10 ⁴ Pa)).
By treating at 5 ° C. for 2 hours, the sulfonyl fluoride group was almost completely converted into a sulfonamide group.

Next, 5% of 1,1
2,2,3,3, - hexafluoropropane disulfonyl fluoride _{(FO 2 S- (CF 2)} 3 -SO 2 F) solution (solvent: tetrahydrofuran / triethylamine = 10
/ 1) at 50 ° C. for 24 hours to crosslink. Then, at 80 ° C., KOH / water / dimethylsulfoxide (15
(wt% / 50wt% / 35wt%) solution for 2 hours to effect hydrolysis. This is then brought to 50% at 15%
For 30 minutes to perform proton exchange. This was further washed with ion-exchanged water to obtain a catalyst layer. Equivalent weight EW of electrolyte in catalyst layer determined by titration method
Was 790 g / equivalent.

Next, the catalyst layer was disposed on both sides of a Nafion 111 film (25 μm in thickness), and hot pressing was performed to produce an MEA. The hot press was performed at a temperature of 120 ° C. and a pressure of 50 kg / cm ² (4.9 M
Pa).

Example 2 A 10 cm × 10 cm × 10 μm sheet was prepared according to the same procedure as in Example 1. Next, this sheet was immersed in a solution of phosphorus oxychloride and phosphorus pentachloride (7/3 weight ratio) at 90 ° C. for 12 hours, converted into a sulfonyl chloride group, and then converted to 5% dimethylaminosulfur trifluoride ((CH ₃ )). ₂ NSF ₃ ) (solvent:
(Tetrahydrofuran) at 50 ° C. for 24 hours to convert the sulfonic acid group into a sulfonyl fluoride group. Then, according to the same procedure as in Example 1, the sheet was subjected to ammonia treatment, 1,1,2,2,3,3-hexafluoropropanedisulfonyl fluoride treatment, hydrolysis, proton exchange and washing, and the catalyst layer I got The equivalent weight EW of the electrolyte in the catalyst layer was 800 g / equivalent. Further, using the obtained catalyst layer, according to the same procedure as in Example 1,
An MEA was prepared.

Example 3 A 500 ml autoclave was charged with a fluorine solvent (AK225, 100 manufactured by Asahi Glass Co., Ltd.).
g), Nafion monomer (30 g) and an initiator (70% di (ethylhexyl) peroxycarbonate in cyclohexane) (0.07 ml) were charged, cooled to -40 ° C, and hexafluoroethylene (6 g) was sealed. .
After reacting at 50 ° C. for 2 hours, the precipitate was reprecipitated in 200 ml of acetone, filtered and dried. The equivalent weight EW of the obtained Nafion F form was 700 g / equivalent.

Next, a fluorinated solvent (AKA manufactured by Asahi Glass Co., Ltd.)
225), the Nafion F form was dissolved and mixed with platinum-supported carbon. Next, this mixed solution is applied to a tetrafluoroethylene sheet and dried to form a sheet having a thickness of 10%.
A μm sheet was obtained. Further, according to the same procedure as in Example 1, the sheet was treated with ammonia, 1, 1, 2, 2, 3,
3, -Hexafluoropropane disulfonyl fluoride treatment, hydrolysis, proton exchange and washing were performed to obtain a catalyst layer. The equivalent weight EW of the electrolyte in the catalyst layer is 580 g /
Was equivalent. Further, using the obtained catalyst layer, an MEA was manufactured according to the same procedure as in Example 1.

Example 4 Platinum-Supported Carbon and Nafi
ON mixed aqueous solution (Platinum supported carbon: Nafion =
1: 1) on a tetrafluoroethylene sheet and dry
By drying, a sheet having a thickness of 10 μm is formed.
Was. This sheet (10cm × 10cm) is oxychlorinated
Phosphorus (POCl₃), Phosphorus pentachloride (PCl₅) Solution (heavy
7/3) at 90 ° C for 12 hours,
After conversion to a sulfonyl chloride group, 5% of (CH₃)₂
NSF₃For 24 hours at 50 ° C.
Was converted to a sulfonyl fluoride group. This sheet
With ammonia gas (1 kg / cm ²(9.8 × 10⁴P
a)) for 10 minutes at 25 ° C.
Some of the chloride groups were converted to sulfonamide groups.

Next, this sheet was treated with trimethylamine gas (1 kg / cm ² (9.8 × 10 ⁴ Pa)) for 8 hours.
Treated at 0 ° C. for 1 hour. Then, at 80 ° C., KOH / water /
Dimethyl sulfoxide (15 wt% / 50 wt% / 35
(% by weight) for 2 hours to perform hydrolysis. Next, this was immersed in a 15% nitric acid aqueous solution at 50 ° C. for 30 minutes to perform proton exchange. This was further washed with ion-exchanged water to obtain a catalyst layer. The equivalent weight EW of the electrolyte in the catalyst layer was 950 g / equivalent. Further, using the obtained catalyst layer, an MEA was manufactured according to the same procedure as in Example 1.

Example 5 According to the same procedure as in Example 3, a 10 μm-thick sheet containing a Nafion F body was obtained. The sheet was bonded to both sides of the F film (sulfonyl fluoride body) of Nafion 111 by hot pressing at 120 ° C. to obtain a bonded body. Next, this bonded body was treated with ammonia gas (1 kg / cm ² (9.8 × 10 ⁴ Pa)) at 25 ° C. for 2 hours to almost completely convert the sulfonyl fluoride groups in the sheet and the F film to sulfonamide groups. Was converted to

Further, this conjugate was subjected to 1,1,2,2,3,3-hexafluoropropanedisulfonyl fluoride treatment, hydrolysis, proton exchange and washing according to the same procedure as in Example 1. An MEA was obtained. Average equivalent weight EW of both the electrolyte in the catalyst layer and the electrolyte membrane
Was 800 g / equivalent.

Example 6 According to the same procedure as in Example 3, a sheet having a thickness of 10 μm containing a Nafion F body was obtained. This sheet was bonded to both sides of the F film (sulfonyl fluoride body) of Nafion 111 by hot pressing at 120 ° C. to obtain a bonded body. Next, this bonded body was subjected to ammonia gas (1 kg / cm ² (9.8 × 10 ⁴ Pa)) for 2 hours.
By treating at 5 ° C. for 10 minutes, a part of the sulfonyl fluoride groups in the sheet and the F film were converted into sulfonamide groups.

Next, the joined body was treated with trimethylamine gas (1 kg / cm ² (9.8 × 10 ⁴ Pa)) for 80 minutes.
Treated at ℃ for 3 hours. Further, the conjugate was subjected to hydrolysis, proton exchange, and washing according to the same procedure as in Example 1 to obtain an MEA. The equivalent weight EW of the electrolyte in the catalyst layer and the electrolyte membrane was 1150 g / equivalent.

(Comparative Example 1) A mixed aqueous solution of platinum-supported carbon and Nafion (platinum-supported carbon: Nafion = 1:
1) was applied to a tetrafluoroethylene sheet and dried to form a catalyst layer having a thickness of 10 μm. The equivalent weight EW of the electrolyte in the catalyst layer was 1000 g / equivalent. Using this catalyst layer, an MEA was manufactured according to the same procedure as in Example 1.

The MEs obtained in Examples 1 to 6 and Comparative Example 1
For A, steady operation (current density 0.5 A / cm ² ) was performed under the conditions shown in Table 1, and the output voltage at that time was evaluated. Table 2 shows the results.

[0124]

[Table 1]

[0125]

[Table 2]

In the case of the MEA of Comparative Example 1, the cell temperature was 100
Under the condition of ° C., an output voltage of 0.53 V was obtained. However, assuming a cell temperature of 110 ° C., the output voltage dropped to 0.39V.

On the other hand, in the case of the MEAs of Examples 1 to 4, under the condition of the cell temperature of 100.degree.
55 to 0.66 V, all of which were improved from Comparative Example 1. Further, even when the cell temperature is 110 ° C., the output voltage is
0.45 to 0.58 V, all of which were higher than Comparative Example 1. This is because the stability, water retention and heat resistance of the internal structure of the catalyst layer were improved because the electrolyte in the catalyst layer was cross-linked by the acid cross-linking group.

Further, in the case of Examples 5 and 6, the output voltage showed higher values than those of Examples 3 and 4, respectively, under both conditions of the cell temperature of 100 ° C. and 110 ° C.
This is because the electrolyte membrane and the electrolyte in the catalyst layer are cross-linked by the acid cross-linking group, and the covalent bond is formed between the catalyst layer and the electrolyte membrane, so that the bonding between them and the overall MEA are improved. This is because the water retention was improved.

Although the embodiments of the present invention have been described in detail, the present invention is not limited to the above-described embodiments, and various modifications are possible without departing from the gist of the present invention. is there.

For example, in the above embodiment, an example was described in which the MEA according to the present invention was applied to a polymer electrolyte fuel cell. However, the application of the present invention is not limited to this. The present invention can also be applied to a device, a hydrogen and / or oxygen concentrator, or various sensors.

[0131]

The MEA according to the present invention comprises a catalyst layer containing an electrolyte in the catalyst layer crosslinked via at least one crosslinking group selected from bissulfonylimide groups, sulfonylcarbonylimide groups and biscarbonylimide groups. Therefore, there is an effect that the internal structure of the catalyst layer is stably maintained even under a high humidity condition or a high temperature condition.
Further, since the crosslinking group itself functions as an acid group, the water retention of the catalyst layer is improved, and there is an effect that a high output can be obtained even under high temperature and low humidity conditions.

The method of manufacturing an MEA according to the present invention
Since the solid polymer compound having the functional group A is reacted with the cross-linking agent having the functional group B or the cross-linking agent capable of introducing the functional group B into the solid polymer compound, the stability of the internal structure and the water retention There is an effect that an MEA having a catalyst layer excellent in heat resistance and heat resistance can be easily manufactured.

Further, the second of the MEAs according to the present invention is:
Since the electrolyte in the catalyst layer and the solid polymer electrolyte membrane are covalently bonded, there is an effect that their performance and durability are further improved.

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Claims (5)

[Claims] 1. A solid polymer electrolyte membrane, comprising electrodes joined to both surfaces of the solid polymer electrolyte membrane, wherein at least one of the electrodes has a bissulfonylimide group,
A membrane electrode assembly comprising a catalyst layer including an electrolyte in a catalyst layer comprising a solid polymer compound crosslinked via at least one crosslinking group selected from a sulfonylcarbonylimide group and a biscarbonylimide group. 2. The equivalent weight EW of the electrolyte in the catalyst layer is:
The polymer electrolyte fuel cell according to claim 1, wherein the amount is from 250 g / equivalent to 2000 g / equivalent. 3. A catalyst layer forming step of forming a catalyst layer containing a solid polymer compound having a functional group A, and a bissulfonylimide group, a sulfonylcarbonylimide group and a biscarbonylimide group by reacting with the functional group A. A cross-linking agent having a functional group B capable of forming at least one cross-linking group selected from the group consisting of: a cross-linking agent capable of introducing the functional group B into the solid polymer compound is introduced into the catalyst layer; A membrane electrode comprising: a crosslinking step of reacting the catalyst layer with the functional group B; a protonation step of performing hydrolysis and proton exchange of the catalyst layer; and a joining step of joining the catalyst layer and the solid polymer electrolyte membrane. Manufacturing method of joined body. 4. A solid polymer electrolyte membrane, and electrodes joined to both surfaces of the solid polymer electrolyte membrane, wherein at least one of the electrodes is an electrolyte in a catalyst layer contained in a catalyst layer provided in the electrode. Is a membrane electrode assembly wherein at least a part of the membrane electrode assembly is covalently bonded to the solid polymer electrolyte membrane. 5. The covalent bond is at least one selected from a bissulfonylimide bond, a sulfonylcarbonyl bond, and a biscarbonylimide bond.
3. The membrane electrode assembly according to item 1.