JP4889006B2 - Catalyst electrode, membrane electrode assembly, and polymer electrolyte fuel cell - Google Patents

Description

  The present invention relates to a catalyst electrode, a membrane electrode assembly, and a polymer electrolyte fuel cell using a novel sulfonated aromatic polyimide having a siloxane bond.

In recent years, portable electronic devices such as mobile phones, personal digital assistants, laptop computers, etc., have increased power consumption with the increase in functionality, and the output density of batteries used in portable electronic devices has increased. There is a strong demand for higher energy density. In the notebook personal computer and the portable information terminal, the currently installed battery has a short drive time per charge and takes a long time to charge.
Currently, the most common driving power source mounted on the portable electronic device is a lithium ion secondary battery. However, it is expected that the energy density required for portable electronic devices whose functions will continue to increase in the future will be several times the current level. In the lithium ion secondary battery, as a drive power source for portable electronic devices, It is in a situation where it is becoming impossible to fully satisfy the requirements.

Under such circumstances, development of a new energy device to replace the lithium ion secondary battery is expected, and a fuel cell is attracting attention as one of them. In the fuel cell, by supplying fuel to the negative electrode, electrons and protons are generated, and by reacting the protons with oxygen supplied to the positive electrode, power generation is enabled.
Since the theoretical energy density of the fuel cell itself is several times higher than that of a lithium ion secondary battery, the fuel cell can be made to react efficiently by reducing the power generation part of the fuel cell compared to the fuel. There is a possibility that energy density far exceeding that of the secondary battery can be achieved. From such a background, a fuel cell is attracting attention as a power source replacing a lithium ion secondary battery.

The fuel cell mounted on the portable electronic device is required to have a structure that is small and light, has good handleability, is easy to start and stop, and is strong against shock and vibration. In this respect, the all-solid-state polymer electrolyte fuel cell having a simple structure, capable of operating even at low temperatures, and fast starting and stopping operations and having a polymer membrane as an electrolyte is the portable electronic device. Suitable for equipment. In particular, a small portable electronic device has a simple battery structure, and since methanol has a high energy density and is easy to store, a direct methanol fuel cell (DMFC) using methanol as a fuel is used. It has been adopted.
The direct methanol fuel cell (DMFC) generally includes at least a solid electrolyte membrane having proton conductivity and two electrodes, a fuel electrode and an air electrode, which sandwich the solid electrolyte membrane.
In the DMFC, when an aqueous methanol solution as a fuel is supplied to the fuel electrode side, water is generated by the following mechanisms (1) to (3) along with the power generation reaction of methanol. First, methanol (fuel) reacts with water (power generation reaction) as in the following formula: CH ₃ OH (fuel) + H ₂ O → CO ₂ (discharged from the fuel electrode) + 6H ⁺ + 6e ⁻ . Thus, carbon dioxide and H ⁺ (proton) are generated. Next, (2) H ⁺ (proton) moves (proton conduction) from the fuel electrode to the air electrode in the solid electrolyte membrane, and an internal current is generated in the fuel cell. Next, protons are oxidized at the air electrode as in (3) following formula: 6H ⁺ + 3 / 2O ₂ + 6e ⁻ → 3H ₂ O to generate water. At this time, electric power can be taken out by connecting the fuel electrode and the air electrode to an external circuit, and the generated water is discharged out of the system from the air electrode.

In the fuel cell, for example, an organic polymer material having a sulfonic acid group, a carboxylic acid group, a phosphoric acid group, or the like is used as a solid electrolyte membrane that is an important component. As the organic polymer material, for example, perfluorosulfonic acid conventionally used for membranes represented by Nafion (trade name) membrane (manufactured by Du Pont), Dow membrane (manufactured by Dow Chemical), and the like. Based polymers are known.
However, although the perfluorosulfonic acid polymer is excellent in proton conductivity and functions well as a membrane for a fuel cell using hydrogen as a fuel, when used as a solid electrolyte membrane in the DMFC, There is a problem that methanol having high affinity tends to permeate (crossover) from the anode side to the cathode side.
When the crossover occurs, the supplied fuel (methanol) and the oxidant (cathode oxygen) directly react with each other, resulting in a decrease in utilization efficiency and cell voltage. For this reason, the concentration of the methanol aqueous solution filled in the fuel electrode cannot be sufficiently increased, and there is a limit to improvement in output. On the other hand, if the methanol concentration can be increased, the driving time of the portable device can be extended. Therefore, development of a novel solid electrolyte membrane material capable of realizing methanol crossover resistance is desired.

Materials that can suppress methanol crossover include sulfonated polyphenylene ether, polyetherketone, and polyetheretherketone as materials with excellent chemical and thermal stability such as heat-resistant polymers and engineering plastics. , Polyphenylene, polyethersulfone, polybenzimidazole, polybenzoxazole, polybenzothiazole, polyimide, and the like have attracted attention (see Patent Document 1). The Nafion or the like is referred to as a fluorine-based electrolyte (membrane), whereas these are referred to as a hydrocarbon-based electrolyte (membrane).
Among the hydrocarbon electrolytes, a sulfonic acid group-containing polyimide (sulfonic acid group-containing polyimide) is excellent in mechanical strength, heat resistance, solvent resistance, tough thin film forming ability, and the like. Although it has been proposed to use the membrane as a solid electrolyte membrane (see Patent Documents 2 to 3 and Non-Patent Documents 1 and 2). In order to improve the hydrolyzability of the imide ring for the purpose of improving high temperature water resistance, 1,4,5,8-tetracarboxynaphthalene dianhydride (NTDA) or the like is used as the tetracarboxylic dianhydride. The polyimide used has been proposed (see Patent Document 4 and Non-Patent Documents 3 to 6), but these polymers do not contain sulfonic acid groups in their constituent monomers, and are heat resistant high strength polymers. The application as the solid electrolyte membrane is not disclosed at all.

By the way, the sulfonated polyimide electrolyte membrane containing the sulfonic acid group-containing polyimide is not only used as a solid electrolyte membrane for the DMFC, but also an H ₂ / O ₂ solid polymer fuel cell (hereinafter simply referred to as “PEFC”). It is also useful as a solid electrolyte membrane.
In the fuel cell, whether it is the DMFC or the PEFC, the presence of a catalyst together with the solid electrolyte membrane is important. The catalyst is a powder of nickel, palladium, platinum, and oxides thereof, or an alloy obtained by adding a small amount of other metals to these (hereinafter sometimes referred to as “platinum-based catalyst”), for example, Examples include those supported on carbon powder. The catalyst layer as the fuel electrode and the air electrode contains these catalysts, the solid-liquid-gas three phases must contact each other on the surface and participate in the reaction, and proton conduction is easy. Need to be done. For this reason, the catalyst layer is porous, has proton conductivity, and needs to maintain its shape, and is formed using a polymer electrolyte (ionomer) together with the catalyst.
In order to reduce electric resistance, it is preferable that the fuel electrode and the air electrode are as close as possible with the solid electrolyte membrane interposed therebetween. Usually, these electrodes are on the surface of the solid electrolyte membrane. It is used as a membrane electrode assembly (MEA (Membrane Electrode Assembly)) that is applied and integrated on the substrate. In the fuel cell having such a structure (solid polymer fuel cell), the polymer electrolyte is used as an electrolyte membrane material that conducts protons and blocks the permeation of fuel and oxidant, and the matrix of the catalyst layer. It is an important element as the ionomer that forms a three-phase interface and transports protons.

In the polymer electrolyte fuel cell, as a method of forming the catalyst layer as the fuel electrode and the air electrode, for example, a mixture of a carbon powder supporting the platinum-based catalyst and an ionomer in a solvent state After that, a method of forming a thin coating on a porous carbon support, a carbon powder carrying the platinum catalyst, an ionomer solution in which an ionomer is dispersed or dissolved in ethanol and alcohol such as propanol and water A catalyst paste is prepared by mixing the catalyst paste, and the catalyst paste is applied to the solid electrolyte membrane using a doctor blade method, a roll coater method, a spray method, a screen printing method, or the like. In the former, a membrane / electrode assembly is formed by adhering the obtained catalyst layer to a solid electrolyte membrane. In these cases, as the polymer electrolyte (ionomer), a perfluorosulfonic acid polymer represented by Nafion (manufactured by Du Pont, “Nafion (registered trademark)”) is generally used.
In the case of an electrode formed using a perfluorosulfonic acid polymer as the ionomer, when a Nafion membrane is used as the solid electrolyte membrane, Nafion is the same material as the ionomer in the catalyst layer. There is no problem in the bonding property between the solid electrolyte membrane and the catalyst layer in the electrode assembly. However, in the above-described DMFC using methanol as a fuel, in the membrane electrode assembly using a Nafion membrane, as described above, the phenomenon of methanol crossover accompanying an increase in methanol concentration becomes remarkable, and it is used for portable devices using high-concentration methanol. There is a problem that it is difficult to increase the output of the fuel cell.

  As a method for solving such a problem, it is conceivable to produce a membrane electrode assembly using a sulfonated aromatic hydrocarbon solid electrolyte membrane having a methanol crossover smaller than that of a Nafion membrane. However, the ionomer currently used for the catalyst layer of the membrane electrode assembly having a sulfonated aromatic hydrocarbon-based solid electrolyte membrane is generally Nafion. If the material of the solid electrolyte membrane is different from the material of the ionomer in the catalyst layer, the coefficient of thermal expansion, the swelling rate with respect to the methanol aqueous solution, etc. will differ. It is difficult to secure the sex. This situation is the same in the PEFC.

JP 2002-201269 A JP 2003-64181 A JP 2003-234014 A JP 2004-83864 A J. Fang et al., “Macromolecules”, Vol. 35, 2002, p. 9022-9028 X. Guo et al., “Macromolecules”, Vol. 35, 2002, p. 6707-6713 “Macro Molecules”, Vol. 16, p. 522-526 (1983) Acta Polymerica, Vol. 39, p. 460-464 (1988) “Journal Polymer Science Polymer Chemistry”, Vol. 35, p. 539-545 (1997) “Polymer”, Vol. 33, p. 190-193 (1992)

An object of the present invention is to solve the conventional problems and achieve the following objects. That is, an object of the present invention is to provide a catalyst electrode excellent in proton conductivity and durability.
An object of the present invention is to provide a membrane electrode assembly having the catalyst electrode of the present invention, having good bonding properties with an electrolyte membrane, and excellent in proton conductivity and durability.
The present invention has the membrane electrode assembly of the present invention, is excellent in proton conductivity and durability, suppresses the crossover of fuel (for example, methanol or hydrogen), improves the utilization efficiency, and decreases the cell voltage. An object of the present invention is to provide a high-performance and highly reliable polymer electrolyte fuel cell in which the above is suppressed.

  As a result of intensive studies by the present inventors to solve the above problems, the use of a novel sulfonated aromatic polyimide having a siloxane bond as a polymer electrolyte (ionomer) makes it possible to achieve proton conductivity and water resistance. It has been found that a catalyst electrode that is excellent and has good bondability to a solid electrolyte can be obtained. Further, a membrane electrode assembly (MEA (Membrane Electrode Assembly)) in which the catalyst electrode and the solid electrolyte membrane are joined together is excellent in proton conductivity and water resistance, and is a fuel (for example, methanol or hydrogen). It was found that crossover can be suppressed, and it has high strength and high durability. Furthermore, it has been found that when the membrane electrode assembly is used, improvement in utilization efficiency and suppression of cell voltage reduction can be realized, and a high-performance and highly reliable polymer electrolyte fuel cell can be obtained. It came to complete.

The present invention is based on the above findings by the present inventors, and means for solving the above problems are as described in the following supplementary notes. That is,
The catalyst electrode of the present invention comprises at least a catalyst and a polymer electrolyte, and the polymer electrolyte is a sulfonated aromatic polyimide having a siloxane bond.
In the catalyst electrode, the polymer electrolyte used as a matrix material for the catalyst (hereinafter sometimes referred to as “ionomer”) is the sulfonated aromatic polyimide having the siloxane bond, Aromatic polyimide has a flexible and highly hydrophobic siloxane unit having a siloxane bond and a hydrophilic sulfonated aromatic unit, so it is easy to take a microphase-separated structure, and the balance between hydrophilicity and hydrophobicity is achieved. Good, excellent in proton conductivity and water resistance. For this reason, the said catalyst electrode is excellent in proton conductivity and durability, and its joining property with a solid electrolyte is favorable.
The catalyst electrode of the present invention can be suitably used for a membrane electrode assembly in a polymer electrolyte fuel cell, and can be particularly suitably used for the following membrane electrode assembly and polymer electrolyte fuel cell of the present invention. is there.

The membrane electrode assembly of the present invention comprises at least an electrolyte membrane and the catalyst electrode of the present invention bonded to the surface of the electrolyte membrane.
Since the membrane electrode assembly (hereinafter sometimes referred to as “MEA (Membrane Electrode Assembly)”) has the catalyst electrode of the present invention, it has good bondability with the electrolyte membrane. In particular, when a sulfonated aromatic hydrocarbon-based solid electrolyte membrane is used as the electrolyte membrane, the polymer electrolyte in the catalyst electrode and the material of the electrolyte membrane are the same material, so that the bonding strength In addition to being excellent in durability, crossover of fuel (for example, methanol) can be suppressed.
Further, when the catalyst electrode and the electrolyte membrane are bonded using an electrolyte binder, and the electrolyte binder is a sulfonated aromatic polyimide having the siloxane bond, the bonding strength is further improved. .
The membrane electrode assembly of the present invention can be suitably used for a polymer electrolyte fuel cell, and can be particularly suitably used for the following polymer electrolyte fuel cell of the present invention.

The polymer electrolyte fuel cell of the present invention has at least the membrane electrode assembly of the present invention.
Since the polymer electrolyte fuel cell has the membrane electrode assembly of the present invention, it is excellent in proton conductivity and durability, can suppress crossover of fuel (for example, methanol or hydrogen), and can be used. Improvement in efficiency and suppression of cell voltage reduction can be realized, and high performance and high reliability are achieved. For this reason, it is particularly suitable for direct methanol fuel cells and hydrogen fuel cells.

According to the present invention, the conventional problems can be solved, and a catalyst electrode excellent in proton conductivity and durability can be provided.
According to the present invention, it is possible to provide a membrane electrode assembly that has the catalyst electrode of the present invention, has good bondability with an electrolyte membrane, and is excellent in proton conductivity and durability.
According to the present invention, the membrane electrode assembly according to the present invention has excellent proton conductivity and durability, suppresses crossover of fuel (for example, methanol or hydrogen), improves utilization efficiency, and increases cell voltage. It is possible to provide a high-performance and highly reliable polymer electrolyte fuel cell in which the decrease is suppressed.

(Catalyst electrode)
The catalyst electrode of the present invention includes at least a catalyst and a polymer electrolyte, and further includes other components as necessary, and the polymer electrolyte is a sulfonated aromatic polyimide having a siloxane bond.
There is no restriction | limiting in particular as a use of the catalyst electrode of this invention, Although it can select suitably according to the objective, It is especially suitable for the catalyst electrode for fuel cells.

-Polymer electrolyte-
The polymer electrolyte (hereinafter sometimes referred to as “polymer electrolyte” or “ionomer”) disperses the catalyst (particles) and is integrated with the catalyst to form the catalyst electrode (catalyst layer). And function as a matrix.
The polymer electrolyte needs to be a sulfonated aromatic polyimide having the siloxane bond, and as such a sulfonated aromatic polyimide, a structural unit represented by the following general formula (1) and the following general formula Suitable examples include those having at least a structural unit represented by the formula (2), preferably further having a structural unit represented by the following general formula (3).

ただし、前記一般式（１）及び一般式（２）中、Ａｒは、下記構造式（１）から（５）で表される置換基から選択される少なくとも１種を表す。Ｒ^１は、スルホン酸基を有する２価の芳香族基を表す。Ｒ^２は、下記構造式（６）で表される基を表す。

ただし、前記構造式（６）中、Ｘ^１及びＸ^２は、互いに同一であってもよいし、異なっていてもよく、アルキル基及びフェニル基のいずれかを表す。Ａは、下記構造式（７）から（９）で表される置換基から選択される少なくとも１種を表す。ｍは、１〜１３０の整数を表し、ｎは、１〜４の整数を表す。

However, in said general formula (1) and general formula (2), Ar represents at least 1 sort (s) selected from the substituent represented by following Structural formula (1) to (5). R ¹ represents a divalent aromatic group having a sulfonic acid group. R ² represents a group represented by the following structural formula (6).

However, in the structural formula (6), X ¹ and X ² may be the same as or different from each other, and represent either an alkyl group or a phenyl group. A represents at least one selected from substituents represented by the following structural formulas (7) to (9). m represents an integer of 1 to 130, and n represents an integer of 1 to 4.

ただし、前記一般式（３）中、Ａｒは、前記一般式（１）及び一般式（２）におけるＡｒと同様であり、前記構造式（１）から（５）で表される置換基から選択される少なくとも１種を表す。Ｒ^３は、スルホン酸基を有しない２価の芳香族基を表す。

However, in the general formula (3), Ar is the same as Ar in the general formula (1) and the general formula (2), and is selected from the substituents represented by the structural formulas (1) to (5). Represents at least one kind. R ³ represents a divalent aromatic group having no sulfonic acid group.

-Structural unit represented by general formula (1)-
The structural unit represented by the general formula (1) (hereinafter sometimes referred to as “sulfonated aromatic unit”) includes an aromatic tetracarboxylic acid anhydride represented by the following structural formula (10): It is obtained by reacting with an aromatic diamine having a sulfonic acid group, and has a polyimide skeleton.

ただし、前記構造式（１０）中、Ａｒは、下記構造式（１）から（５）で表される置換基から選択される少なくとも１種である。

However, in the structural formula (10), Ar is at least one selected from substituents represented by the following structural formulas (1) to (5).

  Since the substituents represented by the structural formulas (1) to (5) contain a naphthalene ring, the water resistance of the polyimide can be improved. Among the substituents represented by the structural formulas (1) to (5), the substituents represented by the structural formulas (3) to (5) are preferable in view of excellent solubility in a solvent. ) To (5) are more preferred. When an electron-withdrawing group such as a carbonyl group or a phthaloyl group is present, the sulfonated aromatic group is highly reactive with the aromatic diamine having the sulfonic acid group, easily forms a higher molecular weight polyimide, and has excellent high-temperature water resistance. A group polyimide is obtained.

  There is no restriction | limiting in particular as aromatic diamine which has the said sulfonic acid group, According to the objective, it can select suitably, For example, what is represented by following Structural formula (11) to (14) is mentioned.

ただし、前記構造式（１１）から（１４）中、Ｙは、酸素原子（−Ｏ−）、硫黄原子（−Ｓ−）、メチレン基（−ＣＨ_２−）、イソプロピリデン基（−Ｃ（ＣＨ_３）_２−）、及びジ（トリフルオロメチル）メチレン基（−Ｃ（ＣＦ_３）_２−）から選択される少なくとも１種であるのが好ましい。

In Structural Formulas (11) to (14), Y represents an oxygen atom (—O—), a sulfur atom (—S—), a methylene group (—CH ₂ —), an isopropylidene group (—C (CH ₃ ) _2- ) and at least one selected from a di (trifluoromethyl) methylene group (—C (CF ₃ ) ₂ —) are preferred.

ただし、前記構造式（１５）から（１８）中、Ｙは、酸素原子（−Ｏ−）、硫黄原子（−Ｓ−）、メチレン基（−ＣＨ_２−）、イソプロピリデン基（−Ｃ（ＣＨ_３））_２−）、及びジ（トリフルオロメチル）メチレン基（−Ｃ（ＣＦ_３）_２−）から選択される少なくとも１種であるのが好ましい。この場合、より柔軟性が高く、かつ高分子量のスルホン化芳香族ポリイミドが得られる。
また、高温耐水性に優れたスルホン化芳香族ポリイミドが得られる点で、前記スルホン酸基は、側鎖の芳香族核に結合しているのが好ましい。 The divalent aromatic group having a sulfonic acid group represented by R ¹ is not particularly limited and may be appropriately selected depending on the intended purpose. For example, the following structural formulas (15) to (18) The thing represented by is mentioned.

In Structural Formulas (15) to (18), Y represents an oxygen atom (—O—), a sulfur atom (—S—), a methylene group (—CH ₂ —), an isopropylidene group (—C (CH ₃₎₎ 2 -), and di (trifluoromethyl) methylene group (-C _{(CF 3) 2} -) preferably it is at least one selected from the. In this case, a sulfonated aromatic polyimide having higher flexibility and higher molecular weight can be obtained.
Moreover, it is preferable that the said sulfonic acid group is couple | bonded with the aromatic nucleus of a side chain at the point from which the sulfonated aromatic polyimide excellent in high temperature water resistance is obtained.

-Structural unit represented by general formula (2)-
The structural unit represented by the general formula (2) (hereinafter sometimes referred to as “siloxane unit”) includes the aromatic tetracarboxylic acid anhydride represented by the structural formula (10) and the following structural formula. (19), which is obtained by reacting an aromatic diamine having a siloxane bond in the main chain, and has a siloxane bond and a polyimide skeleton.

ただし、前記構造式（１９）中、Ｘ^１及びＸ^２は、互いに同一であってもよいし、異なっていてもよく、メチル基、エチル基、プロピル基、ブチル基等のアルキル基及びフェニル基のいずれかを表し、一般的には、メチル基、フェニル基の順に好ましい。Ａは、下記構造式（７）から（９）で表される置換基から選択される少なくとも１種を表す。ｍは、１〜３０の整数を表し、５〜３０が好ましく、ｎは、１〜４の整数を表し、２〜３が好ましい。この場合、高分子骨格がフレキシブルで、高分子樹脂がミクロ相分離し、親水性−疎水性のバランスの取れたポリイミドを合成することができる。

ただし、構造式（７）から（９）において、−（ＣＨ_２）_ｎ−側が、前記シロキサン鎖と結合する。

However, in the structural formula (19), X ¹ and X ² may be the same as or different from each other, an alkyl group such as a methyl group, an ethyl group, a propyl group, or a butyl group, and a phenyl group. In general, a methyl group and a phenyl group are preferable in this order. A represents at least one selected from substituents represented by the following structural formulas (7) to (9). m represents an integer of 1 to 30, preferably 5 to 30, and n represents an integer of 1 to 4, and preferably 2 to 3. In this case, the polymer skeleton is flexible, the polymer resin undergoes microphase separation, and a hydrophilic-hydrophobic balanced polyimide can be synthesized.

However, in Structural Formulas (7) to (9), the — (CH ₂ ) _n — side is bonded to the siloxane chain.

-Structural unit represented by general formula (3)-
The structural unit represented by the general formula (3) (hereinafter sometimes referred to as “non-sulfonated aromatic unit”) includes the aromatic tetracarboxylic acid anhydride represented by the structural formula (10) and It is obtained by reacting with an aromatic diamine having no sulfonic acid group and has an imide group.
The aromatic diamine having no sulfonic acid group is not particularly limited and may be appropriately selected depending on the intended purpose. For example, compounds represented by the following structural formulas (20) to (23) are preferred. Can be mentioned.

ただし、前記構造式（２３）中、ｎは、１〜２０の整数を表し、高分子骨格がフレキシブルで、分子量の高いポリイミドを合成することができる点で、６〜１２が好ましい。

However, in said Structural Formula (23), n represents the integer of 1-20, 6-12 are preferable at the point which can synthesize | combine a high molecular weight polyimide with flexible polymer frame | skeleton.

In the structural unit represented by the general formula (3), the divalent aromatic group having no sulfonic acid group represented by R ³ is a trivalent aromatic group having no sulfonic acid group. Is preferably substituted with. In this case, durability is improved by forming a branched structure in the sulfonated aromatic polyimide.
The trivalent aromatic group having no sulfonic acid group is not particularly limited and may be appropriately selected depending on the intended purpose. For example, the trivalent aromatic group is formed from a triamine represented by the following structural formula (24). A group is preferably mentioned.

There is no restriction | limiting in particular as molar ratio of substitution by the trivalent aromatic group which does not have the said sulfonic acid group, Although it can select suitably according to the objective, The structural unit represented by the said General formula (3) The amount is preferably 10 mol% or less, and more preferably 5 mol% or less.
When the molar ratio exceeds 10 mol%, the polymer solution of the sulfonated polyimide is easily insolubilized and may be gelled.

  In the sulfonated aromatic polyimide of the present invention, the molar ratio (x / mol) of the structural unit (z mol) represented by the general formula (2) to the structural unit (x mol) represented by the general formula (1). z) is not particularly limited and may be appropriately selected depending on the intended purpose, but is preferably 99/1 to 10/90. When the molar ratio is within the above numerical range, desired proton conductivity can be obtained.

  Further, by replacing a part of the structural unit represented by the general formula (2) with the structural unit represented by the general formula (3), the structural unit represented by the general formula (3) is changed. Furthermore, the sulfonated aromatic polyimide which has is obtained. In this case, the membrane strength (durability) of the electrolyte membrane using the sulfonated aromatic polyimide obtained can be increased, and the ion exchange group concentration can be adjusted.

The sulfonated aromatic polyimide may be a random copolymer obtained by randomly copolymerizing the structural units represented by the general formulas (1) to (3), or a plurality of the structural units may be connected to each other. Then, it may be a block copolymer (hereinafter also referred to as “sequence copolymer”) copolymerized as a block (hereinafter also referred to as “sequence block”).
However, when the ratio of the siloxane unit represented by the general formula (2) in the sulfonated aromatic polyimide is high, for example, 20% by mass or more, the sulfone represented by the general formula (1) The sulfonated aromatic unit is preferably copolymerized as a sequence block. When the non-sulfonated aromatic unit represented by the general formula (3) is used, the sulfonated aromatic unit may be random and sequenced. Any may be used for copolymerization.
In addition, when the block chain of the sulfonated aromatic unit is long, for example, when it is 8 or more, a part of R ^{1 in} the structural unit represented by the general formula (1) is caused by triamine, tetramine, or the like. A branched structure may be formed.

  There is no restriction | limiting in particular as the synthesis | combining method of the said sulfonated aromatic polyimide, According to the objective, it can select suitably, For example, the synthesis method of a general polyimide can be used as it is.

  The method for confirming the presence of the polyimide skeleton, sulfonic acid group and siloxane chain in the sulfonated aromatic polyimide is not particularly limited and may be appropriately selected depending on the intended purpose. For example, a nuclear magnetic resonance analyzer ( A method for analyzing these structures by measuring absorption peaks using (NMR).

  Since the sulfonated aromatic polyimide has a flexible and highly hydrophobic siloxane chain in the main chain, it is easy to adopt a microphase-separated structure and has a good balance between hydrophobicity and hydrophilicity. Excellent water resistance. The sulfonated aromatic polyimide has a large molecular weight, high heat resistance and durability. Furthermore, the sulfonated aromatic polyimide is soluble in a solvent such as dimethyl sulfoxide (DMSO), dimethylacetamide (DMAc), N-methylpyrrolidone (NMP), dimethylformamide (DMF), and has good film formability. In addition, the flexible main chain structure enables thin film formation. For this reason, it is suitable for the polymer electrolyte (ionomer), an electrolyte binder described later, and the like.

-Catalyst-
There is no restriction | limiting in particular as said catalyst, Although it can select suitably according to the objective, For example, platinum, ruthenium, etc. are mentioned suitably.
The catalyst is preferably supported on carbon powder. The carbon powder is preferably conductive and has a high structure and a large specific surface area produced by the Ketjen method, the acetylene method or the like.
Specific examples of the use of the catalyst include, for example, carbon powder supporting platinum, carbon powder supporting platinum-ruthenium, and the like in the catalyst electrode on the anode side. In this case, the amount of the catalyst supported on the carbon powder is preferably, for example, 10 to 60% by mass.
Further, for example, carbon powder carrying platinum can be used for the catalyst electrode on the cathode side. In this case, the amount of the catalyst supported on the carbon powder is preferably 10 to 80% by mass, for example.

  There is no restriction | limiting in particular as a preparation method of the said catalyst electrode (catalyst layer), According to the objective, it can select suitably, For example, the sulfonated aromatic polyimide which has the said siloxane bond as the said polymer electrolyte (ionomer), The obtained catalyst paste is applied to the surface of the electrolyte membrane or the surface of the porous carbon to be the diffusion layer by mixing the carbon powder carrying the catalyst and the solvent. And a drying step. By these steps, a porous catalyst layer is formed.

There is no restriction | limiting in particular as a solvent used for preparation of the said catalyst paste, Although it can select suitably according to the objective, A polar solvent with a low melting point is preferable, Specifically, melting | fusing point is 20 degrees C or less polar A solvent is preferred. As such a polar solvent, for example, N-methylpyrrolidone, N, N-dimethylacetamide, N, N-dimethylformamide, dimethyl sulfoxide and the like are preferably exemplified. These may be used individually by 1 type and may use 2 or more types together.
In addition, when the polar solvent to be used is water-soluble, you may use the mixed solution mixed with water in the range which does not impair the solubility of the said sulfonated aromatic polyimide.

The catalyst paste can be produced by stirring and mixing using a stirrer, and the stirrer is not particularly limited and can be appropriately selected as long as it is a stirrer and mixer having a mechanically pulverizing effect. . Examples of the stirring device include a homogenizer, a ball mill, a planetary ball mill, and the like.
In order to perform the stirring and mixing efficiently, the stirring and mixing time is preferably 30 to 300 minutes at room temperature.
If the stirring and mixing time is less than 30 minutes, the mixing of the carbon powder supporting the catalyst and the polymer electrolyte may be insufficient, and even if the mixing time exceeds 300 minutes, a suitable mixing effect is obtained. It may not be possible.

  In the formed porous catalyst layer, the carbon powder supporting the catalyst is covered with a sulfonated aromatic polyimide having a hydrophobic block structure portion and a hydrophilic block structure portion. Thus, since the polymer electrolyte covering the carbon powder has a hydrophobic block structure portion, the outermost surface layer of the carbon powder exhibits hydrophobicity, is formed of the carbon powder, and has a gas diffusion path and The part of the void | hole which becomes shows hydrophobicity. As a result, the retention of the reaction gas, generated water and the like inside the catalyst layer is suppressed, gas diffusion is facilitated, and the battery reaction is stably performed for a long time.

(Membrane electrode assembly)
The membrane electrode assembly of the present invention (hereinafter sometimes referred to as “MEA (Membrane Electrode Assembly)”) includes at least an electrolyte membrane and the catalyst electrode of the present invention joined to the surface of the electrolyte membrane. And, if necessary, other members appropriately selected.
The details of the catalyst electrode of the present invention are as described above.

The electrolyte membrane is not particularly limited and can be appropriately selected according to the purpose, and a known solid electrolyte can be used. However, a sulfonated aromatic hydrocarbon polymer electrolyte membrane is preferable, and a sulfonated aroma is used. A group polyimide film is more preferred.
In the membrane electrode assembly, since the electrolyte membrane is joined to the catalyst electrode of the present invention containing the sulfonated aromatic polyimide having the siloxane bond (the polymer electrolyte), the sulfonated aromatic hydrocarbon polymer. By using the electrolyte membrane, these bonding strengths can be improved, and by using an electrolyte membrane made of the same type of material as the polymer electrolyte, the bonding strength can be further improved.

There is no restriction | limiting in particular as thickness of the said electrolyte membrane, Although it can select suitably according to the objective, 20-200 micrometers is preferable and 30-150 micrometers is more preferable.
When the thickness is less than 20 μm, the strength of the electrolyte membrane is low and the influence of fuel crossover is likely to occur. When the thickness exceeds 200 μm, the resistance of the electrolyte membrane becomes too large during fuel cell operation. There is.

The joining of the electrolyte membrane and the catalyst electrode is preferably performed using an electrolyte binder.
The electrolyte binder has a function as an adhesive for fixing the catalyst electrode to the surface of the electrolyte membrane. The electrolyte binder is preferably a sulfonated aromatic polyimide having a siloxane bond. In this case, since the material is the same system as the polymer electrolyte (ionomer) in the catalyst electrode, the bondability with the catalyst electrode is improved, and the electrolyte membrane is the same as a sulfonated hydrocarbon polymer solid electrolyte. When formed of a system material, the bonding strength can be further improved, which is advantageous in that a membrane electrode assembly having extremely excellent durability can be obtained.
In addition, about the detail of the sulfonated aromatic polyimide which has the said siloxane bond, it is as having mentioned above in the said polymer electrolyte in the said catalyst electrode of this invention.

  The method for producing the membrane electrode assembly is not particularly limited and may be appropriately selected according to the purpose. For example, the carbon powder supporting the catalyst, the polymer electrolyte (ionomer), and the solvent are mixed with stirring. After the catalyst paste prepared in this manner is applied to the surface of the electrolyte membrane, heat treatment is performed at a temperature of 60 to 250 ° C., and the catalyst electrodes (catalyst layers) are stably thermocompression-bonded on both surfaces of the electrolyte membrane. Examples thereof include a method, a method in which the catalyst paste is applied to a carbon porous support to form a gas diffusion electrode, and this is joined to the electrolyte membrane. In the latter, the electrolyte binder is used as a bonding material as required.

The catalyst paste can be applied to the electrolyte membrane or the carbon porous support with a desired film thickness by, for example, a doctor blade.
The film thickness of the catalyst paste can be changed by adjusting screen printing and the clearance of the doctor blade, and catalyst layers having various thicknesses can be produced. In addition, as a film thickness at the time of application | coating of the said catalyst paste, it is the range of 50-300 micrometers, for example.
The carbon porous support is an electron conductive support, and examples thereof include porous substrates such as carbon paper and carbon cloth.

The catalyst electrode (catalyst layer) and / or the gas diffusion electrode applied and formed on the electrolyte membrane and the electrolyte membrane can be joined by thermocompression bonding (hot pressing). By thermocompression bonding, these are integrated to form a membrane electrode assembly (MEA).
The temperature at the time of joining by thermocompression bonding is preferably 120 to 250 ° C., and the pressure is preferably ²⁰ to 200 kgf / cm ² .
When the temperature is less than 120 ° C. and the pressure is less than 20 kgf / cm ^{2, the} bondability between the electrolyte membrane and the catalyst electrode (catalyst layer) may be deteriorated and peeling may occur. . Further, when the temperature exceeds 250 ° C. and when the pressure exceeds 200 kgf / cm ² , decomposition of the electrolyte portion may occur.
Although the time of the said thermocompression bonding (hot press) changes with joining temperature and pressure, Usually, it is preferable that it is the range for 30 to 600 seconds.
If the thermocompression bonding time is less than 30 seconds, the bonding property between the electrolyte membrane and the catalyst electrode (catalyst layer) may be insufficient, and if it exceeds 600 seconds, decomposition of the electrolyte portion may occur. There is.

Here, an example of the membrane electrode assembly of the present invention will be described below with reference to the drawings.
As shown in FIG. 1, the membrane electrode assembly 10 has a structure in which a fuel electrode catalyst layer (catalyst electrode) 12A, an electrolyte membrane 15, and an air electrode catalyst layer (catalyst electrode) 12B are laminated in this order. And both surfaces of the electrolyte membrane 15, the fuel electrode catalyst layer (catalyst electrode) 12 </ b> A and the air electrode catalyst layer (catalyst electrode) 12 </ b> B are joined by hot pressing or the like via the electrolyte binder 16. Has been. The catalyst electrodes 12A and 12B are formed by dispersing a carbon powder 13B carrying a catalyst 13A in a polymer electrolyte (ionomer) 14.
In the membrane electrode assembly 10, since the polymer electrolyte 14 in the catalyst electrodes 12A and 12B is a sulfonated aromatic polyimide having the siloxane bond, the sulfonated aromatic polyimide having the siloxane bond is used as the electrolyte binder 16. If a sulfonated aromatic hydrocarbon polymer is used as the material for the electrolyte membrane 15, the bonding properties of the catalyst electrodes 12A and 12B and the electrolyte membrane 15 can be significantly improved.

Since the membrane electrode assembly of the present invention has excellent proton conductivity and high durability (bonding strength between the electrolyte membrane and the catalyst electrode), a direct methanol fuel cell (DMFC), a reformed methanol fuel cell, It can be suitably used for a polymer electrolyte fuel cell such as a hydrogen fuel cell, and can be particularly suitably used for the following polymer electrolyte fuel cell of the present invention.
In addition, since the membrane electrode assembly is capable of suppressing methanol crossover, when used in the DMFC, it exhibits excellent proton conductivity and suppresses methanol permeation, improving utilization efficiency and cell voltage. Can be suppressed.

(Solid polymer fuel cell)
The polymer electrolyte fuel cell of the present invention comprises at least the membrane electrode assembly of the present invention, and further comprises other members as necessary.
The details of the membrane electrode assembly of the present invention are as described above.

  The aspect of the polymer electrolyte fuel cell is not particularly limited and may be appropriately selected depending on the purpose. Examples thereof include a direct methanol fuel cell (DMFC), a reformed methanol fuel cell, and a hydrogen fuel cell. It is done. Among these, direct methanol fuel cells and hydrogen fuel cells are particularly preferable in that crossover of methanol and hydrogen can be suppressed and power generation characteristics can be effectively improved.

  Since the polymer electrolyte fuel cell of the present invention has the membrane electrode assembly of the present invention, the crossover of fuel (for example, methanol or hydrogen) is suppressed, the utilization efficiency is improved, and the cell voltage is lowered. Can be suppressed. For this reason, it can be suitably used for various electric devices, for example, portable information devices, specifically, mobile phones, personal computers, digital cameras, portable audio, MP3, toys, and the like.

  Examples of the present invention will be described below, but the present invention is not limited to the following examples.

Example 1
-Synthesis of a sulfonated aromatic polyimide having a siloxane bond (sequenced copolymerized sulfonated polyimide KDNTDA-BAPBDS / APPDMS (5/1) -s)-
First, 4,4′-ketone dinaphthalene-1,1 ′, 8,8′-tetracarboxylic dianhydride (KDNTDA) was synthesized based on Synthesis Step 1 below.
4-acetylnaphthene (AAN) was synthesized by reacting acenaphthene with acetyl chloride using aluminum chloride as a catalyst and 1,1,2,2-tetrachloroethane as a solvent, respectively. This was oxidized using NaBrO synthesized by reacting caustic soda water and bromine to produce 4-acenaphthenecarboxylic acid (ANCA). Furthermore, carboxylic acid chloride (ANCC) was produced using thionyl chloride. Subsequently, AAN and ANCC were subjected to Friedel-Craft reaction to synthesize 4,4′-diacenaphthyl ketone (DANK). This is oxidized with potassium dichromate in an acetic acid solution to produce 4,4′-ketone dinaphthalene-1,1 ′, 8,8′-tetracarboxylic acid (KDNTA), and then acetic anhydride. To obtain tetracarboxylic dianhydride (KDNTDA).

As an acid dianhydride, 4,4′-ketone dinaphthalene-1,1 ′, 8,8′-tetracarboxylic dianhydride (KDNTDA) synthesized based on Synthesis Step 1 is used as a sulfonated diamine, 4 , 4′-bis (4-aminophenoxy) biphenyl 3,3′-disulfonic acid (BAPBDS) was used as the siloxane-containing diamine, and α, ω-aminopropyl polydimethylsiloxane oligomer (APPDMS1) was used.
First, in a dry 100 ml four-necked flask, 1.901 g (3.6 mmol) of BAPBDS and 1.2 ml of triethylamine (TEA) were added to 26 ml of m-cresol and dissolved in a nitrogen gas stream. Then, 0.810 g (0.90 mmol) of APPDMS1 was added and dissolved, then 1.899 g (4.5 mmol) of KDNTDA and 0.77 g of benzoic acid were added, and the mixture was heated at 80 ° C. under a nitrogen gas atmosphere. Then, 16 mL of m-cresol and 0.40 g of isoquinoline were added, and the mixture was stirred at 180 ° C. for 20 hours. The obtained polymerization reaction liquid was cooled to room temperature, then poured into a large amount of acetone, and the precipitated solid was separated by filtration. Further, the obtained solid was washed with acetone, extracted with Soxhlet with isopropanol, dried, and a random copolymerized sulfonated polyimide KDNTDA-BAPBDS / APPDMS1 (4/1) -r represented by the following structural formula was obtained. It was. The product obtained had a reduced viscosity η _SP / c (solvent: m-cresol; 0.5 mass%, 35 ° C.) of 3.5 dl / g.

なお、前記構造式中、ｘ／ｚ＝４／1、ｍ＝９．８であり、シロキサンの含有量は、１５．９質量％である。

In the structural formula, x / z = 4/1, m = 9.8, and the siloxane content is 15.9% by mass.

  The obtained sulfonated aromatic polyimide is dissolved in dimethyl sulfoxide (DMSO), cast on a Teflon (registered trademark) plate, dried at 120 ° C. for 10 hours, and a TEA salt-type copolymerized sulfonated polyimide membrane Got. This was immersed in methanol for 2 days, and then immersed in 1M sulfuric acid solution for 3 days to exchange protons. Next, it was immersed in water for 2 days, washed, and then vacuum-dried at 150 ° C. for 1 hour and further at 200 ° C. for 1 hour to obtain proton type sequence copolymerized sulfonated polyimide KDNTDA-BAPBDS / APPDMS (4/1) A -s film was produced.

The ¹ HNMR spectrum in _{DMSO-d 6} obtained sulfonated aromatic polyimide shown in FIG. The spectrum of dimethylsiloxane-containing diamine (APPDMS) is also shown in FIG.
From FIG. 2, when comparing the spectrum of the synthesized sulfonated aromatic polyimide and the spectrum of APPDMS1, in addition to the peak of the sulfonated aromatic polyimide, in the sulfonated aromatic polyimide, It was found that methylene protons in the propylene part were further incorporated. The ion exchange capacity IEC determined from the intensity ratio of the naphthalene ring proton (1,2,5) to the proton of the sulfonic acid diamine residue (6,7,8,9) is 1.65 meq / g. The IEC value calculated from the charged monomer ratio was almost the same.

<Preparation of membrane electrode assembly>
-Fabrication of catalyst electrode-
(1) Preparation of anode side catalyst electrode As the polymer electrolyte (ionomer), synthesized sequence copolymerization sulfonated polyimide KDNTDA-BAPBDS / APPDMS (4/1) -s was used. Pt-Ru supported carbon was added to 20 g of a dimethylacetamide (DMAc) solution of the ionomer (KDNTDA-BAPBDS / APPDMS (4/1) -s, ion exchange capacity 1.7 meq / g, triethylamine salt type, resin component 6% by mass). 2.6 g of particles (manufactured by Tanaka Kikinzoku Kogyo Co., Ltd., “TEC61E54”, 54% by mass of Pt—Ru supported) are added and stirred and mixed (200 rpm, 1 hour) using a planetary ball mill, and the catalyst paste on the anode side Was prepared.
The obtained catalyst paste was applied onto a carbon paper having a thickness of 280 μm (“TGH-H-090” manufactured by Toray Industries, Inc.) using a bar coater and then dried to produce a catalyst electrode (catalyst layer). did. Here, the amount of Pt—Ru in the catalyst layer was set to 2 mg / cm ² .
Next, the obtained catalyst electrode was immersed in a 0.5N sulfuric acid aqueous solution at 25 ° C. for 24 hours to remove the residual solvent in the catalyst layer and to perform proton exchange of the sulfonated aromatic polyimide resin. Further, the catalyst electrode was immersed in ion exchange water at 25 ° C. for 24 hours, and excess sulfuric acid in the catalyst layer was removed by washing.

(2) Preparation of cathode side catalyst electrode As the polymer electrolyte (ionomer), synthesized sequence copolymerization sulfonated polyimide KDNTDA-BAPBDS / APPDMS (4/1) -s was used. 20 g of a dimethylacetamide (DMAc) solution of this ionomer (KDNTDA-BAPBDS / APPDMS (4/1) -s, ion exchange capacity 1.7 meq / g, triethylamine salt type, resin component 6% by mass) was added to Pt-supported carbon particles ( 4.4 g of “TEC10E50E” manufactured by Tanaka Kikinzoku Kogyo Co., Ltd., Pt loading amount of 46% by mass) was added and stirred and mixed (200 rpm, 1 hour) using a planetary ball mill to prepare a catalyst paste on the cathode side.
The obtained catalyst paste was applied onto a carbon paper having a thickness of 280 μm (“TGH-H-090” manufactured by Toray Industries, Inc.) using a bar coater and then dried to produce a catalyst electrode (catalyst layer). did. Here, the amount of Pt in the catalyst layer was set to 2 mg / cm ² .
Next, the obtained catalyst electrode was immersed in a 0.5N sulfuric acid aqueous solution at 25 ° C. for 24 hours to remove the residual solvent in the catalyst layer and to perform proton exchange of the sulfonated aromatic polyimide resin. Further, the catalyst electrode was immersed in ion exchange water at 25 ° C. for 24 hours, and excess sulfuric acid in the catalyst layer was removed by washing.

-Production of electrolyte membrane-
--Synthesis of sulfonated aromatic polyimide having no siloxane chain (random copolymerized sulfonated polyimide NTDA-BAPBDS / BAPB (2/1) -r)-
1,4,5,8-Naphthalenetetracarboxylic dianhydride (NTDA) 1.609 g (6.0 mmol) as the acid dianhydride and 4,4′-bis (4- Aminophenoxy) biphenyl 3,3′-disulfonic acid (BAPBDS) 2.114 g (4.0 mmol) as a non-sulfonic diamine, 4,4′-bis (4-aminophenoxy) biphenyl (BAPB) 0.737 g (2.0 mmol) was used in the same manner as in Example 3 to obtain a random copolymerized sulfonated polyimide NTDA-BAPBDS / BAPB (2/1) -r represented by the following structural formula. The product obtained had a reduced viscosity η _SP / c (solvent: m-cresol; 0.5 mass%, 35 ° C.) of 2.8 dl / g.

なお、前記構造式中、ｘ／ｙ＝２／1である。

In the structural formula, x / y = 2/1.

  The obtained sulfonated aromatic polyimide having no siloxane chain was dissolved in m-cresol, cast on a glass plate, and dried at 120 ° C. for 10 hours to prepare a TEA salt type copolymer sulfonated polyimide membrane. Obtained. This was immersed in methanol for 2 days, and then immersed in 1M sulfuric acid solution for 3 days to exchange protons. Next, after being immersed in water for 2 days, washed, and then vacuum-dried at 150 ° C. for 1 hour and further at 200 ° C. for 1 hour, proton-type random copolymer sulfonated polyimide NTDA-BAPBDS / BAPB (2/1)- An r film (electrolyte film) was prepared.

Using the catalyst electrode and the electrolyte membrane obtained as described above, a membrane electrode assembly was produced.
Using the synthesized sequence copolymerization sulfonated polyimide KDNTDA-BAPBDS / APPDMS (4/1) -s as the electrolyte binder (bonding binder) on both sides of the prepared electrolyte membrane (thickness 50 μm), dimethyl of the electrolyte binder A sulfoxide (DMSO) solution (ion exchange capacity 1.7 meq / g, proton type, 5% by mass of resin component) was applied and dried at 50 ° C. for 30 minutes. Here, the coating amount of the electrolyte binder was set to 1.5 mg / cm ² .
The prepared anode electrode side catalyst layer is superimposed on one surface of the electrolyte membrane, and the prepared cathode electrode side catalyst layer is superimposed on the other surface, respectively, at 160 ° C. and 50 kgf / cm ² for 120 seconds. Hot pressing was performed to obtain a membrane electrode assembly.
FIG. 3 shows the relationship between the current density and the cell voltage of a direct methanol fuel cell (DMFC) using the obtained membrane electrode assembly.

(Example 2)
A membrane electrode assembly was produced in the same manner as in Example 1 except that the anode side catalyst electrode was produced by the following method in Example 1.

-Production of anode side catalyst electrode-
In the same manner as in Example 1, sequenced copolymerized sulfonated polyimide KDNTDA-BAPBDS / APPDMS (4/1) -s was used as the polymer electrolyte (ionomer). Pt-Ru-supported carbon particles (manufactured by Tanaka Kikinzoku Co., Ltd., "TEC61E54") were added to 20 g of a dimethylacetamide (DMAc) solution of the ionomer (ion exchange capacity 1.7 meq / g, triethylamine salt type, resin component 6% by mass). , Pt-Ru supported amount 54 mass%) was added and stirred and mixed (200 rpm, 1 hour) using a planetary ball mill to prepare a catalyst paste on the anode side.
The obtained catalyst paste was applied onto a carbon paper having a thickness of 280 μm (“TGH-H-090” manufactured by Toray Industries, Inc.) using a bar coater and then dried to produce a catalyst electrode (catalyst layer). did. Here, the amount of Pt—Ru in the catalyst layer was set to 2 mg / cm ² .
Thereafter, in the same manner as in Example 1, an anode side catalyst electrode was produced.

A membrane electrode assembly was produced using the obtained anode side catalyst electrode and the cathode side catalyst electrode and electrolyte membrane produced in Example 1.
A sequence-copolymerized sulfonated polyimide KDNTDA-BAPBDS / APPDMS (4/1) -s is used as the electrolyte binder (bonding binder) on both surfaces of the electrolyte membrane (50 μm), and the dimethylacetamide (DMAc) solution of the electrolyte binder is used. (Ion exchange capacity 1.7 meq / g, triethylamine salt type, resin component 5% by mass) was applied and dried at 50 ° C. for 30 minutes. Here, the coating amount of the electrolyte binder was set to 1.5 mg / cm ² .
The prepared anode electrode side catalyst layer was superimposed on one surface of a 50 μm thick electrolyte membrane, and the cathode electrode side catalyst layer was superimposed on the other surface for 120 seconds at 160 ° C. and 50 kgf / cm ^2. Hot pressing was performed to obtain a membrane electrode assembly.
The obtained membrane / electrode assembly was immersed in a 0.5N aqueous sulfuric acid solution at 25 ° C. for 24 hours, and proton exchange of the sulfonated aromatic polyimide resin as the electrolyte binder was performed. Furthermore, the membrane / electrode assembly was immersed in ion-exchanged water at 25 ° C. for 24 hours, and excess sulfuric acid in the membrane / electrode assembly was removed by washing.
FIG. 3 shows the relationship between the current density and the cell voltage of a direct methanol fuel cell (DMFC) using the obtained membrane electrode assembly.

(Example 3)
In Example 1, sequence copolymerized sulfonated polyimide KDNTDA-BSPOB / APPDMS (5/1) -s was used as the polymer electrolyte (ionomer), the material of the electrolyte membrane, and the electrolyte binder (bonding binder). Except for the above, a membrane / electrode assembly was produced in the same manner as in Example 1.

-Synthesis of sulfonated aromatic polyimide (sequenced copolymerized sulfonated polyimide KDNTDA-BSPOB / APPDMS (5/1) -s)-
First, “Polymer Preprint, Japan”, Volume 54, p. 2,2′-bis (4-sulfophenoxy) benzidine (BSPOB) was synthesized by the method described in 1751-1752 (2005).

As the acid dianhydride, 1.823 g (4.32 mmol) of 4,4′-ketone dinaphthalene-1,1 ′, 8,8′-tetracarboxylic dianhydride (KDNTDA) synthesized in Example 1 As a sulfonated diamine, 1.901 g (3.6 mmol) of synthesized BSPOB, and as a siloxane-containing diamine, 0.648 g (0.72 mmol) of α, ω-aminopropyl polydimethylsiloxane oligomer (APPDMS), The TEA salt type sulfonated polyimide KDNTDA-BSPOB / APPDMS (5/1) -s represented by the following structural formula was synthesized in the same manner as in Example 1. The product obtained had a reduced viscosity η _SP / c (solvent: m-cresol; 0.5 mass%, 35 ° C.) of 2.6 dl / g.

なお、前記構造式中、ｘ／ｚ＝５／1、ｍ＝９．８であり、シロキサンの含有量は、１３．４質量％である。

In the structural formula, x / z = 5/1, m = 9.8, and the siloxane content is 13.4% by mass.

<Preparation of membrane electrode assembly>
-Fabrication of catalyst electrode-
(1) Preparation of anode side catalyst electrode As the polymer electrolyte (ionomer), synthesized sequence copolymerization sulfonated polyimide KDNTDA-BSPOB / APPDMS (5/1) -s was used. To 20 g of a dimethylacetamide (DMAc) solution of the ionomer (ion exchange capacity 1.7 meq / g, triethylamine salt type, resin component 6% by mass), Pt-supported carbon particles (manufactured by Tanaka Kikinzoku Kogyo Co., Ltd., “TEC10E50E”, Pt (Supported amount 46% by mass) 2.2 g was added and stirred and mixed (200 rpm, 1 hour) using a planetary ball mill to prepare a catalyst paste on the anode side.
Using the obtained catalyst paste, a catalyst electrode (catalyst layer) was produced in the same manner as in Example 1. Here, the amount of Pt in the catalyst layer was set to 0.5 mg / cm ² .

(2) Production of cathode-side catalyst electrode In production of the anode-side catalyst electrode, the amount of Pt-supported carbon particles (manufactured by Tanaka Kikinzoku Kogyo Co., Ltd., “TEC10E50E”, 46% by mass of Pt supported) was added to 4.4 g. A cathode side catalyst electrode was produced in the same manner as in the production of the anode side catalyst electrode, except for the change.

-Production of electrolyte membrane-
The synthesized sulfonated aromatic polyimide was dissolved in dimethyl sulfoxide (DMSO) and formed into a film in the same manner as in Example 1, and the proton-type sequence copolymerized sulfonated polyimide KDNTDA-BSPOB / APPPDMS (5/1)- An s film (the electrolyte film) was prepared. The ion exchange capacity is 1.71 meq / g.

Implementation was carried out except that the catalyst electrode and the electrolyte membrane obtained as described above were used, and the sequence copolymerized sulfonated polyimide KDNTDA-BSPOB / APPDMS (5/1) -s was used as the electrolyte binder (bonding binder). A membrane / electrode assembly was prepared in the same manner as in Example 1.
And the current density of the obtained membrane electrode assembly H _{2 /} O ₂ system using the solid polymer electrolyte fuel cell (PEFC), showing the relationship between the cell voltage and power density in FIG.

(Comparative Example 1)
Example 1 is the same as Example 1 except that the polymer electrolyte (ionomer) and the electrolyte binder (bonding binder) are replaced with random copolymerized sulfonated polyimide NTDA-BDSA / mBAPPS (1/1) -r. Thus, a membrane electrode assembly was produced.

-Synthesis of Random Copolymerized Sulfonated Polyimide NTDA-BDSA / mBAPPS (1/1) -r-
Using 2,2′-benzidinedisulfonic acid (BDSA) as a sulfonic acid diamine and 3,3′-bis (4-aminophenoxy) phenylsulfone (mBAPPS) as a non-sulfonic acid diamine, the above-mentioned Non-Patent Document 1 ( Random copolymerization sulfonation in the same manner as described in J. Fang et al., “MacromoLecules”, Vol. 35, 2002, p. 9022-9028. Polyimide NTDA-BDSA / mBAPPS (1/1) -r was synthesized. The resulting sulfonated polyimide had a reduced viscosity η _SP / c (solvent: m-cresol; 0.5 mass%, 35 ° C.) of 1.8 dl / g, and an ion exchange capacity of 1.60 meq / g. is there.

<Preparation of membrane electrode assembly>
-Fabrication of catalyst electrode-
As the polymer electrolyte (ionomer), a synthesized random copolymer sulfonated polyimide NTDA-BDSA / mBAPPS (1/1) -r was used, and a dimethylacetamide (DMAc) solution of the ionomer (triethylamine type, resin component 6 mass%) Anode-side catalyst in the same manner as in Example 1, except that 2.2 g of Pt—Ru supported carbon particles (manufactured by Tanaka Kikinzoku Kogyo Co., Ltd., “TEC61E54”, Pt—Ru supported amount: 54 mass%) was added to 20 g. An electrode was produced.
Moreover, the synthesized random copolymer sulfonated polyimide NTDA-BDSA / mBAPPS (1/1) -r was used as the polymer electrolyte (ionomer), and a dimethylacetamide (DMAc) solution of the ionomer (triethylamine type, resin component 6 mass). %) A cathode side catalyst electrode was prepared in the same manner as in Example 1 except that 20 g was used.

Using the catalyst electrode obtained above and the electrolyte membrane prepared in Example 1 (random copolymer sulfonated polyimide NTDA-BAPBDS / BAPB (2/1) membrane; thickness 50 μm), the electrolyte binder (bonding binder) ) Was used in the same manner as in Example 1 except that random copolymer sulfonated polyimide NTDA-BDSA / mBAPPS (1/1) -r was used.
FIG. 3 shows the relationship between the current density and the cell voltage of a direct methanol fuel cell (DMFC) using the obtained membrane electrode assembly.

(Comparative Example 2)
-Synthesis of random copolymerized sulfonated polyimide NTDA-BDSA / mBAPPS (2/1) -r-
1,4,5,8-naphthalenetetracarboxylic dianhydride (NTDA), 2,2′-benzidinedisulfonic acid (BDSA), and 3,3′-bis (4-aminophenoxy) phenylsulfone (mBAPPS) Random copolymerized sulfonated polyimide NTDA-BDSA / mBAPPS (2/1) -r was synthesized.

<Preparation of membrane electrode assembly>
-Fabrication of catalyst electrode-
As the polymer electrolyte (ionomer), a random copolymerized sulfonated polyimide NTDA-BDSA / mBAPPS (2/1) -r was used, and a dimethylacetamide (DMAc) solution of the ionomer (ion exchange capacity 2.3 meq / g, Example 1 except that 2.2 g of Pt-Ru supported carbon particles (manufactured by Tanaka Kikinzoku Kogyo Co., Ltd., TEC61E54, Pt-Ru supported amount 54 mass%) was added to 20 g of a triethylamine type, resin component 6 mass%). In the same manner, an anode side catalyst electrode was produced.
Further, as the polymer electrolyte (ionomer), a synthesized random copolymer sulfonated polyimide NTDA-BDSA / mBAPPS (2/1) -r was used, and a dimethylacetamide (DMAc) solution of the ionomer (triethylamine type, resin component 6 mass). %) A cathode side catalyst electrode was prepared in the same manner as in Example 1 except that 20 g was used.

-Production of electrolyte membrane-
Using the synthesized random copolymer sulfonated polyimide NTDA-BAPBDS / BAPB (2/1) -r, a 50 μm-thick random copolymer sulfonated polyimide NTDA-BAPBDS / BAPB (2/1) -r membrane was prepared. .

Using the catalyst electrode and the electrolyte membrane obtained as described above, a membrane electrode assembly was produced.
As the electrolyte binder (bonding binder), an alcohol aqueous solution of Nafion proton conductive polymer electrolyte (manufactured by DuPont, “DE2020”, ion exchange capacity 0.9 meq / g, proton type, resin component 21 mass%), This was applied to both surfaces of the produced electrolyte membrane (thickness 50 μm) and dried at 50 ° C. for 30 minutes. Here, the coating amount of the electrolyte binder was set to 1.5 mg / cm ² .
The prepared anode-side catalyst layer was superimposed on one surface of the 50 μm-thick electrolyte membrane, and the prepared cathode-side catalyst layer was superimposed on the other surface, respectively, at a temperature of 160 ° C. and 50 kgf / cm ² . Hot pressing was performed for 120 seconds to obtain a membrane electrode assembly.
FIG. 3 shows the relationship between the current density and the cell voltage of a direct methanol fuel cell (DMFC) using the obtained membrane electrode assembly.

(Comparative Example 3)
<Preparation of membrane electrode assembly>
-Fabrication of catalyst electrode-
(1) Production of anode-side catalyst electrode As the polymer electrolyte (ionomer), a proton conductive polymer electrolyte Nafion alcohol aqueous solution ("DE2020" manufactured by DuPont, ion exchange capacity 0.9 meq / g, proton type, resin) 16 g of component (21 mass%) was used, and 6 g of n-propanol and 17 g of 2-propanol were added thereto. 15 g of water was added to 5 g of Pt-Ru-supported carbon particles (manufactured by Tanaka Kikinzoku Kogyo Co., Ltd., “TEC61E54”, Pt-Ru supported amount 54 mass%), and these were put into agate and then stirred using a planetary ball mill. Mixing (200 rpm, 1 hour) was performed to prepare a catalyst paste on the anode side.
The obtained catalyst paste was applied on a carbon paper having a thickness of 280 μm (“TGH-H-090” manufactured by Toray Industries, Inc.) using a bar coater, and then dried at 100 ° C. for 1 hour to obtain a catalyst electrode ( Catalyst layer) was prepared. Here, the amount of Pt—Ru in the catalyst layer was set to 2 mg / cm ² .

(2) Production of Cathode Side Catalytic Electrode As the polymer electrolyte (ionomer), a proton conductive polymer electrolyte Nafion alcohol aqueous solution (“DE2020” manufactured by DuPont, ion exchange capacity 0.9 meq / g, proton type, resin 9 g of component (21% by mass) was used, and 6 g of n-propanol and 17 g of 2-propanol were added thereto. 15 g of water was added to 5 g of Pt-Ru-supported carbon particles (manufactured by Tanaka Kikinzoku Kogyo Co., Ltd., “TEC10E50E”, Pt support amount of 46 mass%), and these were put into an agate and then stirred and mixed using a planetary ball mill. (200 rpm, 1 hour) to prepare a cathode side catalyst paste.
The obtained catalyst paste was applied on a carbon paper having a thickness of 280 μm (“TGH-H-090” manufactured by Toray Industries, Inc.) using a bar coater, and then dried at 100 ° C. for 1 hour to obtain a catalyst electrode ( Catalyst layer) was prepared. Here, the amount of Pt in the catalyst layer was set to 2 mg / cm ² .

-Production of electrolyte membrane-
In the same manner as in Example 1, a random copolymer sulfonated polyimide film NTDA-BAPBDS / BAPB (2/1) -r film was produced.

Using the catalyst electrode and the electrolyte membrane obtained as described above, a membrane electrode assembly was produced.
As the electrolyte binder (bonding binder), an alcohol aqueous solution of Nafion proton conductive polymer electrolyte (manufactured by DuPont, “DE2020”, ion exchange capacity 0.9 meq / g, proton type, resin component 21 mass%), This was applied to both surfaces of the produced electrolyte membrane (thickness 50 μm) and dried at 50 ° C. for 30 minutes. Here, the coating amount of the electrolyte binder was set to 1.5 mg / cm ² .
The prepared anode electrode side catalyst layer is superimposed on one surface of the electrolyte membrane, and the prepared cathode electrode side catalyst layer is superimposed on the other surface, respectively, at 160 ° C. and 50 kgf / cm ² for 120 seconds. Hot pressing was performed to obtain a membrane electrode assembly.
FIG. 3 shows the relationship between the current density and the cell voltage of a direct methanol fuel cell (DMFC) using the obtained membrane electrode assembly.

(Comparative Example 4)
Comparative Example 3 except that the electrolyte membrane in Comparative Example 3 was replaced with a Nafion (registered trademark) 112 membrane having a thickness of 50 μm (manufactured by DuPont, perfluorosulfonic acid / polytetrafluoroethylene copolymer, proton type). A membrane electrode assembly was prepared in the same manner as described above.
FIG. 3 shows the relationship between the current density and cell voltage of a direct methanol fuel cell (DMFC) using the obtained membrane electrode assembly, and FIG. 3 shows the H ₂ / O ₂ solid polymer type using the membrane electrode assembly. FIG. 4 shows the relationship between the current density of the fuel cell (PEFC), the cell voltage, and the output density.

(Comparative Example 5)
In Comparative Example 3, a membrane / electrode assembly was produced in the same manner as in Comparative Example 3 except that the catalyst electrode was produced by the following method.

-Fabrication of catalyst electrode-
(1) Production of anode-side catalyst electrode As the polymer electrolyte (ionomer), a proton conductive polymer electrolyte Nafion alcohol aqueous solution ("DE2020" manufactured by DuPont, ion exchange capacity 0.9 meq / g, proton type, resin) 16 g of component (21 mass%) was used, and 6 g of n-propanol and 17 g of 2-propanol were added thereto. 15 g of water was added to 4.3 g of Pt-supported carbon particles (manufactured by Tanaka Kikinzoku Kogyo Co., Ltd., “TEC10E50E”, Pt-supported amount of 46% by mass), and these were put into an agate and then stirred and mixed using a planetary ball mill ( 200 rpm for 1 hour) to prepare a catalyst paste on the anode side.
The obtained catalyst paste was applied on a carbon paper having a thickness of 280 μm (“TGH-H-090” manufactured by Toray Industries, Inc.) using a bar coater, and then dried at 100 ° C. for 1 hour to obtain a catalyst electrode ( Catalyst layer) was prepared. Here, the amount of Pt in the catalyst layer was set to 0.5 mg / cm ² .
(2) Production of Cathode Side Catalytic Electrode As the polymer electrolyte (ionomer), a proton conductive polymer electrolyte Nafion alcohol aqueous solution (“DE2020” manufactured by DuPont, ion exchange capacity 0.9 meq / g, proton type, resin 9 g of component (21% by mass) was used, and 6 g of n-propanol and 17 g of 2-propanol were added thereto. 15 g of water was added to 5 g of Pt-supported carbon particles (Tanaka Kikinzoku Kogyo Co., Ltd., “TEC10E50E”, Pt-supported amount 46% by mass), and these were put into agate, and then stirred and mixed using a planetary ball mill (200 rpm, 1 hour) to prepare a cathode side catalyst paste.
The obtained catalyst paste was applied on a carbon paper having a thickness of 280 μm (“TGH-H-090” manufactured by Toray Industries, Inc.) using a bar coater, and then dried at 100 ° C. for 1 hour to obtain a catalyst electrode ( Catalyst layer) was prepared. Here, the amount of Pt in the catalyst layer was set to 0.5 mg / cm ² .
And the current density of the obtained membrane electrode assembly H _{2 /} O ₂ system using the solid polymer electrolyte fuel cell (PEFC), showing the relationship between the cell voltage and power density in FIG.

<Power generation characteristics>
FIG. 3 shows the relationship between the current density and the cell voltage of the direct methanol fuel cell (DMFC) using the membrane electrode assemblies obtained in Examples 1-2 and Comparative Examples 1-4. In the DMFC, a 10 mass% methanol aqueous solution was supplied as fuel to the anode side of the membrane electrode assembly at a flow rate of 2 mL / min, while the cathode side was subjected to natural convection of air. The measurement temperature was 60 ° C.

The structure of each membrane / electrode assembly (polymer electrolyte (ionomer) / electrolyte membrane / electrolyte binder (bonding binder) in the catalyst electrode) is as follows.
Example 1: Sulfonated aromatic polyimide with siloxane bond / sulfonated polyimide membrane without siloxane bond / sulfonated aromatic polyimide with siloxane bond Example 2: Sulfonated aromatic polyimide with siloxane bond / siloxane bond No sulfonated polyimide membrane / sulfonated aromatic polyimide with siloxane bond Comparative Example 1: sulfonated polyimide without siloxane bond / sulfonated polyimide membrane without siloxane bond / sulfonated polyimide without siloxane bond Comparative Example 2 : Sulfonated polyimide having no siloxane bond / sulfonated polyimide film having no siloxane bond / Nafion resin Comparative Example 3: Nafion resin / sulfonated polyimide film having no siloxane bond / Nafion tree Fat Comparative Example 4: Nafion resin / Nafion 112 membrane / Nafion resin

From FIG. 3, in the membrane electrode assemblies obtained in Comparative Examples 1 to 4, in particular, in the membrane electrode assembly of Comparative Example 4, the cell voltage was significantly decreased, whereas the membrane electrode assemblies obtained in Examples 1 and 2 were obtained. In the membrane / electrode assembly, it was found that the cell voltage drop was suppressed and excellent fuel cell power generation characteristics were exhibited. Moreover, it turned out that the membrane electrode assembly of Comparative Example 1 and Comparative Example 2 cannot generate power after one day and has poor durability. On the other hand, the membrane electrode assemblies of Example 1, Example 2, and Comparative Example 3 showed stable power generation performance during a measurement time of 200 hours.
In addition, when the membrane electrode assemblies were visually observed after the power generation test, the membrane electrode assemblies of Example 1 and Example 2 were in close contact with the electrolyte membrane and the catalyst electrode. In the membrane / electrode assembly of Comparative Example 3, the electrolyte membrane and a part of the catalyst electrode were peeled off.
As described above, the catalyst electrode of the present invention and the membrane electrode assembly using the catalyst electrode have high utilization efficiency, excellent adhesion (bonding strength), and high durability in a direct methanol fuel cell (DMFC). I found out.

Next, the unit cells (H _{2 /} O 2 based solid polymer electrolyte fuel cell: PEFC) using a membrane electrode assembly obtained in Example 3 and Comparative Examples 4-5 and the current density of the cell voltage and the output The relationship with density is shown in FIG. The unit cell is heated to 80 ° C., and hydrogen gas humidified at 75 ° C. as fuel is supplied to the anode side of the membrane electrode assembly at a flow rate of 100 mL / min, while air humidified at 75 ° C. is supplied to the membrane electrode. The cathode was supplied to the joined body at a flow rate of 750 mL / min. The total gas pressure at this time was set to 0.2 Pa.

The structure of each membrane / electrode assembly (polymer electrolyte (ionomer) / electrolyte membrane / electrolyte binder (bonding binder) in the catalyst electrode) is as follows.
Example 3: Sulfonated aromatic polyimide having siloxane bond / sulfonated aromatic polyimide film having siloxane bond / sulfonated aromatic polyimide having siloxane bond Comparative Example 4: Nafion resin / Nafion 112 membrane / Nafion resin Comparative Example 5 : Nafion resin / sulfonated aromatic polyimide film having no siloxane bond / Nafion resin

As shown in FIG. 4, when the membrane electrode assembly of Example 3 is used for an H ₂ / O ₂ solid polymer fuel cell (PEFC), the cell voltage is reduced as compared with the conventional one using Nafion. It was suppressed and the output density was found to be high.

ただし、前記一般式（１）及び一般式（２）中、Ａｒは、下記構造式（１）から（５）で表される置換基から選択される少なくとも１種を表す。Ｒ^１は、スルホン酸基を有する２価の芳香族基を表す。Ｒ^２は、下記構造式（６）で表される基を表す。

ただし、前記構造式（６）中、Ｘ^１及びＸ^２は、互いに同一であってもよいし、異なっていてもよく、アルキル基及びフェニル基のいずれかを表す。Ａは、下記構造式（７）から（９）で表される置換基から選択される少なくとも１種を表す。ｍは、１〜１３０の整数を表し、ｎは、１〜４の整数を表す。

（付記４） シロキサン結合を有するスルホン化芳香族ポリイミドにおける、一般式（１）で表される構造単位に対する一般式（２）で表される構造単位のモル比（一般式（１）／（一般式（２））が、９９／１〜１０／９０である付記３に記載の触媒電極。
（付記５） シロキサン結合を有するスルホン化芳香族ポリイミドが、下記一般式（３）で表される構造単位を更に有する付記３から４のいずれかに記載の触媒電極。

ただし、前記一般式（３）中、Ａｒは、下記構造式（１）から（５）で表される置換基から選択される少なくとも１種を表す。Ｒ^３は、スルホン酸基を有しない２価の芳香族基を表す。

（付記６） 一般式（３）で表される構造単位におけるＲ^３が、スルホン酸基を有しない３価の芳香族基で置換された付記５に記載の触媒電極。
（付記７） スルホン酸基を有しない３価の芳香族基が、一般式（３）で表される構造単位に対して１０モル％以下である付記６に記載の触媒電極。
（付記８） シロキサン結合を有するスルホン化芳香族ポリイミドが、一般式（１）から（３）のいずれかで表される構造単位が、ランダム共重合及びブロック共重合のいずれかにより重合してなる付記３から７のいずれかに記載の触媒電極。
（付記９） 燃料電池に用いられる付記１から８のいずれかに記載の触媒電極。
（付記１０） 電解質膜と、該電解質膜の表面に接合された、付記１から９のいずれかに記載の触媒電極とを少なくとも有することを特徴とする膜電極接合体。
（付記１１） 接合が、電解質バインダーを用いて行われ、該電解質バインダーが、シロキサン結合を有するスルホン化芳香族ポリイミドである付記１０に記載の膜電極接合体。
（付記１２） 電解質膜が、スルホン化芳香族炭化水素系ポリマーを少なくとも含む付記１０から１１のいずれかに記載の膜電極接合体。
（付記１３） シロキサン結合を有するスルホン化芳香族ポリイミドが、下記一般式（１）で表される構造単位、及び下記一般式（２）で表される構造単位を少なくとも有する付記１０から１２のいずれかに記載の膜電極接合体。

ただし、前記一般式（１）及び一般式（２）中、Ａｒは、下記構造式（１）から（５）で表される置換基から選択される少なくとも１種を表す。Ｒ^１は、スルホン酸基を有する２価の芳香族基を表す。Ｒ^２は、下記構造式（６）で表される基を表す。

ただし、前記構造式（１）中、Ｘ^１及びＸ^２は、互いに同一であってもよいし、異なっていてもよく、アルキル基及びフェニル基のいずれかを表す。Ａは、下記構造式（７）から（９）で表される置換基から選択される少なくとも１種を表す。ｍは、１〜１３０の整数を表し、ｎは、１〜４の整数を表す。

（付記１４） シロキサン結合を有するスルホン化芳香族ポリイミドにおける、一般式（１）で表される構造単位に対する一般式（２）で表される構造単位のモル比（一般式（１）／（一般式（２））が、９９／１〜１０／９０である付記１３に記載の膜電極接合体。
（付記１５） シロキサン結合を有するスルホン化芳香族ポリイミドが、下記一般式（３）で表される構造単位を更に有する付記１３から１４のいずれかに記載の膜電極接合体。

ただし、前記一般式（３）中、Ａｒは、下記構造式（１）から（５）で表される置換基から選択される少なくとも１種を表す。Ｒ^３は、スルホン酸基を有しない２価の芳香族基を表す。

（付記１６） 一般式（３）で表される構造単位におけるＲ^３が、スルホン酸基を有しない３価の芳香族基で置換された付記１５に記載の膜電極接合体。
（付記１７） スルホン酸基を有しない３価の芳香族基が、一般式（３）で表される構造単位に対して１０モル％以下である付記１６に記載の膜電極接合体。
（付記１８） シロキサン結合を有するスルホン化芳香族ポリイミドが、一般式（１）から（３）のいずれかで表される構造単位が、ランダム共重合及びブロック共重合のいずれかにより重合してなる付記１３から１７のいずれかに記載の膜電極接合体。
（付記１９） 付記１０から１８のいずれかに記載の膜電極接合体を少なくとも有することを特徴とする固体高分子型燃料電池。
（付記２０） 直接メタノール型燃料電池及び水素燃料電池のいずれかである付記１９に記載の固体高分子型燃料電池。 The preferred embodiments of the present invention are as follows.
(Appendix 1) A catalyst electrode comprising at least a catalyst and a polymer electrolyte, wherein the polymer electrolyte is a sulfonated aromatic polyimide having a siloxane bond.
(Additional remark 2) The catalyst electrode of Additional remark 1 with which the catalyst was carry | supported by the carbon powder.
(Supplementary Note 3) Any of Supplementary Notes 1 to 2, wherein the sulfonated aromatic polyimide having a siloxane bond has at least a structural unit represented by the following general formula (1) and a structural unit represented by the following general formula (2). A catalyst electrode according to claim 1.

However, in said general formula (1) and general formula (2), Ar represents at least 1 sort (s) selected from the substituent represented by following Structural formula (1) to (5). R ¹ represents a divalent aromatic group having a sulfonic acid group. R ² represents a group represented by the following structural formula (6).

However, in the structural formula (6), X ¹ and X ² may be the same as or different from each other, and represent either an alkyl group or a phenyl group. A represents at least one selected from substituents represented by the following structural formulas (7) to (9). m represents an integer of 1 to 130, and n represents an integer of 1 to 4.

(Supplementary Note 4) The molar ratio of the structural unit represented by the general formula (2) to the structural unit represented by the general formula (1) in the sulfonated aromatic polyimide having a siloxane bond (general formula (1) / (general The catalyst electrode according to supplementary note 3, wherein the formula (2) is 99/1 to 10/90.
(Appendix 5) The catalyst electrode according to any one of appendices 3 to 4, wherein the sulfonated aromatic polyimide having a siloxane bond further has a structural unit represented by the following general formula (3).

In the general formula (3), Ar represents at least one selected from substituents represented by the following structural formulas (1) to (5). R ³ represents a divalent aromatic group having no sulfonic acid group.

(Supplementary note 6) The catalyst electrode according to supplementary note 5, wherein R ³ in the structural unit represented by the general formula (3) is substituted with a trivalent aromatic group having no sulfonic acid group.
(Additional remark 7) The catalyst electrode of Additional remark 6 whose trivalent aromatic group which does not have a sulfonic acid group is 10 mol% or less with respect to the structural unit represented by General formula (3).
(Appendix 8) A sulfonated aromatic polyimide having a siloxane bond is obtained by polymerizing a structural unit represented by any one of the general formulas (1) to (3) by either random copolymerization or block copolymerization. The catalyst electrode according to any one of appendices 3 to 7.
(Additional remark 9) The catalyst electrode in any one of additional remarks 1-8 used for a fuel cell.
(Additional remark 10) It has an electrolyte membrane and the catalyst electrode in any one of Additional remark 1 to 9 joined to the surface of this electrolyte membrane, The membrane electrode assembly characterized by the above-mentioned.
(Supplementary note 11) The membrane / electrode assembly according to supplementary note 10, wherein the joining is performed using an electrolyte binder, and the electrolyte binder is a sulfonated aromatic polyimide having a siloxane bond.
(Supplementary note 12) The membrane electrode assembly according to any one of Supplementary notes 10 to 11, wherein the electrolyte membrane includes at least a sulfonated aromatic hydrocarbon polymer.
(Supplementary note 13) Any of Supplementary notes 10 to 12, wherein the sulfonated aromatic polyimide having a siloxane bond has at least a structural unit represented by the following general formula (1) and a structural unit represented by the following general formula (2). A membrane electrode assembly according to any one of the above.

However, in said general formula (1) and general formula (2), Ar represents at least 1 sort (s) selected from the substituent represented by following Structural formula (1) to (5). R ¹ represents a divalent aromatic group having a sulfonic acid group. R ² represents a group represented by the following structural formula (6).

However, in the structural formula (1), X ¹ and X ² may be the same as or different from each other, and represent either an alkyl group or a phenyl group. A represents at least one selected from substituents represented by the following structural formulas (7) to (9). m represents an integer of 1 to 130, and n represents an integer of 1 to 4.

(Supplementary Note 14) The molar ratio of the structural unit represented by the general formula (2) to the structural unit represented by the general formula (1) in the sulfonated aromatic polyimide having a siloxane bond (general formula (1) / (general The membrane electrode assembly according to supplementary note 13, wherein the formula (2) is 99/1 to 10/90.
(Supplementary note 15) The membrane electrode assembly according to any one of supplementary notes 13 to 14, wherein the sulfonated aromatic polyimide having a siloxane bond further has a structural unit represented by the following general formula (3).

In the general formula (3), Ar represents at least one selected from substituents represented by the following structural formulas (1) to (5). R ³ represents a divalent aromatic group having no sulfonic acid group.

(Supplementary note 16) The membrane / electrode assembly according to supplementary note 15, wherein R ³ in the structural unit represented by the general formula (3) is substituted with a trivalent aromatic group having no sulfonic acid group.
(Additional remark 17) The membrane electrode assembly of Additional remark 16 whose trivalent aromatic group which does not have a sulfonic acid group is 10 mol% or less with respect to the structural unit represented by General formula (3).
(Supplementary Note 18) A sulfonated aromatic polyimide having a siloxane bond is obtained by polymerizing a structural unit represented by any one of the general formulas (1) to (3) by either random copolymerization or block copolymerization. The membrane electrode assembly according to any one of appendices 13 to 17.
(Appendix 19) A polymer electrolyte fuel cell comprising at least the membrane electrode assembly according to any one of Appendices 10 to 18.
(Supplementary note 20) The polymer electrolyte fuel cell according to supplementary note 19, which is either a direct methanol fuel cell or a hydrogen fuel cell.

The catalyst electrode of the present invention is excellent in proton conductivity and durability, and can be suitably used for a membrane electrode assembly (MEA).
The membrane / electrode assembly of the present invention has good bondability between the catalyst electrode and the electrolyte membrane, is excellent in durability, can suppress crossover of fuel (for example, methanol or hydrogen), and is a solid polymer type It can be suitably used for a fuel cell.
The solid polymer fuel cell of the present invention realizes improvement in utilization efficiency and suppression of cell voltage decrease, can suppress crossover of methanol and hydrogen, and is suitable for direct methanol fuel cell and hydrogen fuel cell, It is particularly suitable for a direct methanol fuel cell. The polymer electrolyte fuel cell can be suitably used for various electric devices, for example, portable information devices, specifically, mobile phones, personal computers, digital cameras, portable audio devices, MP3s, toys and the like.

FIG. 1 is a schematic cross-sectional view showing an example of the membrane electrode assembly of the present invention. FIG. 2 is a graph showing the analysis result of ¹ HNMR spectrum of the sulfonated aromatic polyimide having a siloxane bond synthesized in Example 1. FIG. 3 is a graph showing the relationship between the current density and cell voltage of a direct methanol fuel cell (DMFC) using the membrane electrode assemblies obtained in Examples 1-2 and Comparative Examples 1-4. 4, the current density and the cell voltage and power density of the Example 3 and using the resulting membrane electrode assembly in Comparative Example 4~5, H _{2 /} O 2 based solid polymer electrolyte fuel cell (PEFC) It is a graph which shows the relationship.

Explanation of symbols

10 Membrane electrode assembly (present invention)
12A Fuel electrode catalyst layer (catalyst electrode of the present invention)
12B Air electrode catalyst layer (catalyst electrode of the present invention)
13A catalyst 13B carbon powder 14 polymer electrolyte (ionomer)
15 Electrolyte membrane 16 Electrolyte binder

Claims (20)

  A catalyst electrode comprising at least a catalyst and a polymer electrolyte, wherein the polymer electrolyte is a sulfonated aromatic polyimide having a siloxane bond.   The catalyst electrode according to claim 1, wherein the catalyst is supported on carbon powder. The sulfonated aromatic polyimide having a siloxane bond has at least a structural unit represented by the following general formula (1) and a structural unit represented by the following general formula (2). Catalyst electrode.

However, in said general formula (1) and general formula (2), Ar represents at least 1 sort (s) selected from the substituent represented by following Structural formula (1) to (5). R ¹ represents a divalent aromatic group having a sulfonic acid group. R ² represents a group represented by the following structural formula (6).

However, in the structural formula (6), X ¹ and X ² may be the same as or different from each other, and represent either an alkyl group or a phenyl group. A represents at least one selected from substituents represented by the following structural formulas (7) to (9). m represents an integer of 1 to 130, and n represents an integer of 1 to 4.

  In the sulfonated aromatic polyimide having a siloxane bond, the molar ratio of the structural unit represented by the general formula (2) to the structural unit represented by the general formula (1) (general formula (1) / (general formula (2) ) Is 99/1 to 10/90, the catalyst electrode according to claim 3. The catalyst electrode according to any one of claims 3 to 4, wherein the sulfonated aromatic polyimide having a siloxane bond further has a structural unit represented by the following general formula (3).

In the general formula (3), Ar represents at least one selected from substituents represented by the following structural formulas (1) to (5). R ³ represents a divalent aromatic group having no sulfonic acid group.

The catalyst electrode according to claim 5, wherein R ³ in the structural unit represented by the general formula (3) is substituted with a trivalent aromatic group having no sulfonic acid group.   The catalyst electrode according to claim 6, wherein the trivalent aromatic group having no sulfonic acid group is 10 mol% or less with respect to the structural unit represented by the general formula (3).   The sulfonated aromatic polyimide having a siloxane bond is obtained by polymerizing the structural unit represented by any one of the general formulas (1) to (3) by either random copolymerization or block copolymerization. 8. The catalyst electrode according to any one of 7 above.   The catalyst electrode according to any one of claims 1 to 8, which is used in a fuel cell.   A membrane electrode assembly comprising at least an electrolyte membrane and the catalyst electrode according to any one of claims 1 to 9 bonded to the surface of the electrolyte membrane.   The membrane electrode assembly according to claim 10, wherein the bonding is performed using an electrolyte binder, and the electrolyte binder is a sulfonated aromatic polyimide having a siloxane bond.   The membrane electrode assembly according to any one of claims 10 to 11, wherein the electrolyte membrane contains at least a sulfonated aromatic hydrocarbon polymer. Sulfonated aromatic polyimide having a siloxane bond is the electrolyte binder, claim 11 having the structural unit represented by the following general formula (1), and a structural unit represented by the following general formula (2) at least 12 The membrane electrode assembly according to any one of the above.

However, in said general formula (1) and general formula (2), Ar represents at least 1 sort (s) selected from the substituent represented by following Structural formula (1) to (5). R ¹ represents a divalent aromatic group having a sulfonic acid group. R ² represents a group represented by the following structural formula (6).

However, in the structural formula (1), X ¹ and X ² may be the same as or different from each other, and represent either an alkyl group or a phenyl group. A represents at least one selected from substituents represented by the following structural formulas (7) to (9). m represents an integer of 1 to 130, and n represents an integer of 1 to 4.

In the sulfonated aromatic polyimide having a siloxane bond as the electrolyte binder, the molar ratio of the structural unit represented by the general formula (2) to the structural unit represented by the general formula (1) (general formula (1) / ( The membrane electrode assembly according to claim 13, wherein the general formula (2) is 99/1 to 10/90. The membrane electrode assembly according to any one of claims 13 to 14, wherein the sulfonated aromatic polyimide having a siloxane bond as the electrolyte binder further has a structural unit represented by the following general formula (3).

In the general formula (3), Ar represents at least one selected from substituents represented by the following structural formulas (1) to (5). R ³ represents a divalent aromatic group having no sulfonic acid group.

The membrane electrode assembly according to claim 15, wherein R ³ in the structural unit represented by the general formula (3) is substituted with a trivalent aromatic group having no sulfonic acid group.   The membrane electrode assembly according to claim 16, wherein the trivalent aromatic group having no sulfonic acid group is 10 mol% or less with respect to the structural unit represented by the general formula (3). In the sulfonated aromatic polyimide having a siloxane bond as the electrolyte binder, the structural unit represented by any one of the general formulas (1) to (3) is polymerized by either random copolymerization or block copolymerization. The membrane electrode assembly according to any one of claims 13 to 17.   A polymer electrolyte fuel cell comprising at least the membrane electrode assembly according to any one of claims 10 to 18. 20. The polymer electrolyte fuel cell according to claim 19, which is either a direct methanol fuel cell or a hydrogen fuel cell.

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