JP5607435B2 - Electrolyte membrane and method for producing the same, electrode catalyst layer and method for producing the same, membrane electrode assembly, and solid polymer electrolyte fuel cell - Google Patents

Description

The present invention relates to an electrolyte membrane and a production method thereof, an electrode catalyst layer and a production method thereof, a membrane electrode assembly, and a solid polymer electrolyte fuel cell.

A fuel cell is one that converts the chemical energy of fuel directly into electrical energy by electrochemically oxidizing hydrogen, methanol, etc. in the battery, and is attracting attention as a clean electrical energy supply source. ing. In particular, solid polymer electrolyte fuel cells are expected to be used as alternative power sources for automobiles, home cogeneration systems, portable generators, and the like because they operate at a lower temperature than others.

Such a solid polymer electrolyte fuel cell includes at least a membrane electrode assembly in which a gas diffusion electrode in which an electrode catalyst layer and a gas diffusion layer are laminated is bonded to both surfaces of an electrolyte membrane. The electrolyte membrane here is a material having a strongly acidic group such as a sulfonic acid group or a carboxylic acid group in the polymer chain and a property of selectively transmitting protons. As a material for an electrolyte membrane used in such a solid polymer electrolyte fuel cell, a copolymer of tetrafluoroethylene and a monomer having a sulfonic acid group is known, but vinylidene fluoride and sulfonic acid are used. A copolymer with a monomer having a group is not known.

By the way, as a polymer electrolyte of a lithium battery, Patent Document 1 discloses a copolymer composed of a polymerization unit based on vinylidene fluoride and a polymerization unit having a side chain containing —CF ₂ COOLi or —CF ₂ SO ₃ Li. A polymer electrolyte containing a matrix and an organic solvent is disclosed. Patent Document 2 discloses an invention relating to an ionomer comprising a polyethylene main chain having a pendant group of fluoroalkoxysulfonic acid and a metal salt thereof.

Japanese Patent Laid-Open No. 10-284128 JP-T-2002-503734

A copolymer of tetrafluoroethylene and a monomer having a sulfonic acid group, which has been known as a material for an electrolyte membrane, has room for improvement in terms of mechanical strength.

The present invention provides an electrolyte membrane and an electrode catalyst layer that are excellent in battery characteristics and mechanical strength.

The present invention relates to an electrolyte membrane for a solid polymer electrolyte fuel cell comprising a fluorine-containing copolymer, wherein the fluorine-containing copolymer comprises a polymer unit (A) based on vinylidene fluoride and a —SO ₃ X group. And —SO ₃ X group has —SO ₃ H, —SO ₃ NR ¹ R ² R ³ R ⁴ , and —SO ₃ M ¹ _{1 / L} (provided that , R ¹ , R ² , R ³ and R ⁴ are the same or different and each represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms; M ¹ is the same or different and represents an L-valent metal; The valent metal is selected from the group consisting of metals belonging to Group 1, Group 2, Group 4, Group 8, Group 11, Group 12, Group 13 or Group 13 of the periodic table (excluding Li). It is an electrolyte membrane characterized by being at least one functional group.

The present invention is an electrode catalyst layer for a solid polymer electrolyte fuel cell comprising a fluorine-containing copolymer and a fuel cell catalyst, the fluorine-containing copolymer comprising a polymerized unit (A) based on vinylidene fluoride, And a polymer unit (B) having a —SO ₃ X group in the side chain, and the —SO ₃ X group includes —SO ₃ H, —SO ₃ NR ¹ R ² R ³ R ⁴ , and —SO ₃ M ^1. _{1 / L} (wherein R ¹ , R ² , R ³ and R ⁴ are the same or different and each represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms; M ¹ is the same or different and represents an L-valent metal; The L-valent metal is a metal belonging to Group 1, Group 2, Group 4, Group 8, Group 11, Group 12 or Group 13 of the periodic table (excluding Li). It is also an electrocatalyst layer characterized by being at least one functional group selected from the group.

The present invention is also a membrane electrode assembly comprising the electrolyte membrane or the electrode catalyst layer.

The present invention also provides a solid polymer electrolyte fuel cell comprising the membrane electrode assembly.

The present invention is a method for producing the above electrolyte membrane, wherein an electrolyte emulsion containing a fluorine-containing copolymer is obtained by radical polymerization of vinylidene fluoride and a comonomer having a —SO ₃ X group in an aqueous medium. A polymerization step, an organic solvent added to the obtained electrolyte emulsion to obtain an electrolyte solution in which the fluoropolymer is dissolved, a step of applying the electrolyte solution to the substrate, and an electrolyte solution applied to the substrate. A step of obtaining an electrolyte membrane by drying, wherein the —SO ₃ X group is —SO ₃ H, —SO ₃ NR ¹ R ² R ³ R ⁴ , and —SO ₃ M ¹ _{1 / L} (where R ¹ , R ² , R ³ and R ⁴ are the same or different and each represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms; M ¹ is the same or different and represents an L-valent metal; The metals are group 1, group 2, group 4, 8 of the periodic table. A method for producing an electrolyte membrane, comprising at least one functional group selected from the group consisting of metals belonging to Group 11, Group 12, Group 12 or Group 13 (excluding Li). But there is.

The present invention is a method for producing the above electrode catalyst layer, which is an electrolyte emulsion containing a fluorine-containing copolymer obtained by radical polymerization of vinylidene fluoride and a comonomer having a —SO ₃ X group in an aqueous medium. A step of obtaining an electrolyte solution in which an organic solvent is added to the obtained electrolyte emulsion to dissolve the fluorine-containing copolymer;
A step of dispersing a fuel cell catalyst in an electrolyte solution to prepare a catalyst composition;
Applying the catalyst composition to the substrate;
A step of drying the catalyst composition applied to the substrate to obtain an electrode catalyst layer, wherein the —SO ₃ X group is —SO ₃ H, —SO ₃ NR ¹ R ² R ³ R ⁴ , and —SO ³ ₃ M ¹ _{1 / L} (wherein R ¹ , R ² , R ³ and R ⁴ are the same or different and each represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms; M ¹ is the same or different; The L-valent metal represents a metal belonging to Group 1, Group 2, Group 4, Group 8, Group 11, Group 12, or Group 13 of the periodic table (excluding Li). It is also a method for producing an electrode catalyst layer, which is at least one functional group selected from the group consisting of:

The electrolyte membrane and the electrode catalyst layer of the present invention are excellent in battery characteristics such as proton conductivity and mechanical strength due to the above structure. The method for producing an electrolyte membrane and an electrode catalyst layer of the present invention can produce an electrolyte membrane and an electrode catalyst layer that are excellent in battery characteristics and mechanical strength.

The electrolyte membrane of the present invention is made of a fluorine-containing copolymer.

The electrode catalyst layer of the present invention comprises a fluorine-containing copolymer and a fuel cell catalyst.

In the electrolyte membrane and electrode catalyst layer of the present invention, the fluorine-containing copolymer comprises a polymerized unit (A) based on vinylidene fluoride and a polymerized unit (B) having a —SO ₃ X group in the side chain. Is.

The polymerization unit (A) based on vinylidene fluoride has the following formula (1):
—CF ₂ —CH ₂ — (1)
It is a polymerization unit represented by. Since the fluorinated copolymer of the present invention comprises polymerized units (A) based on vinylidene fluoride, the electrolyte membrane and electrode catalyst layer obtained from the fluorinated copolymer are electrochemically stable and ion-conductive. It can be excellent in properties. Moreover, the mechanical strength of the electrolyte membrane and electrode catalyst layer obtained from the fluorine-containing copolymer can be made excellent. Furthermore, gas barrier properties are improved, and output characteristics are improved when used as a fuel cell. And since it is soluble in a general-purpose organic solvent and is excellent in moldability, the manufacturing cost can be reduced.

In the fluorine-containing polymer, -SO ₃ X ^{_{groups, -SO 3 H, -SO 3 NR}} 1 R 2 R 3 R 4 and _-SO 3 ^M _{1 1 / L} ^{(where, R 1, R 2, R} 3 And R ⁴ are the same or different and each represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, M ¹ is the same or different and represents an L-valent metal, and the L-valent metal is represented by 1 in the periodic table. It is at least one functional group selected from the group consisting of metals belonging to Group 2, Group 4, Group 8, Group 8, Group 11, Group 12 or Group 13 (excluding Li). As —SO ₃ NR ¹ R ² R ³ R ⁴ , —SO ₃ NH ₄ is preferable. As the L-valent metal, Na or K is preferable. The —SO ₃ X group is more preferably —SO ₃ H.

The polymerization unit (B) having a —SO ₃ X group in the side chain has a vinyl group capable of radical polymerization and a —SO ₃ X group, and is a comonomer (hereinafter referred to as copolymerizable with vinylidene fluoride). , Also referred to as “comonomer (b)”).

The comonomer (b) has the following general formula (II) because it has good copolymerizability with a fluorine-containing ethylenic monomer and can be easily synthesized industrially:
^{_{CF 2 = CF-O- (CF}} 2 CFY 1 -O) n - (CFY 2) m -SO 3 X 1 (II)
(Wherein, X ¹ represents H, Na, K or NH ₄ , Y ¹ represents F, Cl or CF ₃ , Y ² represents F or Cl, and n and m are integers of 0 to 2) The vinyl ether represented by this is preferred. X ¹ is more preferably H. n is preferably 0. m is preferably 1 or 2.

The polymer unit (B) is preferably a polymer unit based on the vinyl ether represented by the above formula (II). That is, the polymerization unit (B) has the following general formula (2):
^{_{-CF 2 -C (-O- (CF 2}} CFY 1 -O) n - (CFY 2) m -SO 3 X 1) F- (2)
(Wherein, X ¹ represents H, Na, K or NH ₄ , Y ¹ represents F, Cl or CF ₃ , Y ² represents F or Cl, and n and m are integers of 0 to 2) It is preferable that it is a polymerization unit represented by. More preferably, X is H. n is preferably 0. m is preferably 1 or 2.

In the fluorinated copolymer, the polymerization unit (B) is preferably 3 to 50 mol% with respect to the total polymerization units. More preferably, it is 10-40 mol%.

In the fluorinated copolymer, the polymerized units based on vinylidene fluoride are preferably 25 mol% or more, more preferably 40 mol% or more, and more preferably 50 mol% or more based on all polymerized units. More preferably. It is also one of the preferable forms that it is 60 mol% or more. Moreover, 97 mol% or less is preferable with respect to all the polymerization units, and, as for the polymerized unit based on vinylidene fluoride, 90 mol% or less is more preferable. If there are too many polymerized units based on vinylidene fluoride, the crystallinity becomes high, the flexibility is lowered and the molding processability may be lowered, and the electrical conductivity of the electrolyte membrane and the electrode catalyst layer may be lowered. . Moreover, when there are too few polymer units based on a vinylidene fluoride, a softness | flexibility will become high too much and there exists a possibility that intensity | strength may fall.

Particularly in the case of the fluorine-containing copolymer constituting the electrolyte membrane, the polymerization unit based on vinylidene fluoride is preferably 40 mol% or more, more preferably 50 mol% or more, and 60 mol% or more. More preferably. Moreover, 97 mol% or less is preferable and 90 mol% or less is more preferable.

Particularly in the case of the fluorine-containing copolymer constituting the electrode catalyst layer, the polymerization unit based on vinylidene fluoride is preferably 25 mol% or more, more preferably 50 mol% or more, and 60 mol%. More preferably, the above is true. Moreover, 97 mol% or less is preferable and 90 mol% or less is more preferable.

It is also a preferred embodiment that the fluorine-containing copolymer of the present invention further comprises polymerized units based on a fluorine-containing ethylenic monomer (excluding vinylidene fluoride).

According to the knowledge of the present inventors, a copolymer containing a polymer unit based on vinylidene fluoride may undergo a deHF reaction when it comes in contact with a strongly basic active substance, and the electrode paste may gel. The fluorine-containing copolymer of the present invention further comprises a polymerized unit based on a fluorine-containing ethylenic monomer (excluding vinylidene fluoride), so that the chain of vinylidene fluoride is shortened and produced. It has been found by the present inventors that the time deHF reaction is mitigated. Note that if the ratio of the fluorine-containing ethylenic monomer (excluding vinylidene fluoride) is too large, the ionic conductivity may deteriorate, so the fluorine-containing ethylenic monomer (excluding vinylidene fluoride). It is preferable to appropriately adjust the ratio.

Examples of the fluorine-containing ethylenic monomer (excluding vinylidene fluoride) include, for example, tetrafluoroethylene, trifluoroethylene, vinyl fluoride, hexafluoropropylene, perfluoro (methyl vinyl ether), and perfluoro (propyl vinyl ether). At least one monomer selected from the group consisting of

From the group consisting of tetrafluoroethylene and hexafluoropropylene, the fluorine-containing ethylenic monomer (excluding vinylidene fluoride) is particularly easy to copolymerize and stable in the battery system. At least one monomer selected is preferred. That is, the fluorine-containing copolymer of the present invention is at least selected from the group consisting of polymerized units (A), polymerized units (B), polymerized units based on tetrafluoroethylene, and polymerized units based on hexafluoropropylene. It is preferable that it consists of 1 type of polymerization unit (C). The fluorine-containing copolymer of the present invention is more preferably composed of a polymer unit (A), a polymer unit (B), and a polymer unit based on tetrafluoroethylene.

When the fluorinated copolymer is composed of polymerized units based on a fluorinated ethylenic monomer (excluding vinylidene fluoride), a polymerized unit (A) based on vinylidene fluoride and a fluorinated ethylenic monomer ( However, the molar ratio of the total of the polymerized units based on the polymerized units (B) based on (excluding vinylidene fluoride) is preferably 50/50 to 97/3. More preferably, it is 60 / 40-90 / 10.

When the fluorinated copolymer is composed of polymer units (C), the molar ratio of the polymer units (A) and polymer units (C) to the polymer units (B) is 50/50 to 97. / 3 is preferred.

The molar ratio A / (A + C) of the polymerization unit (A) to the polymerization unit (C) is preferably 0.50 to 0.95. More preferably, it is 0.60-0.90.

Particularly in the case of the fluorine-containing copolymer constituting the electrolyte membrane, the fluorine-containing copolymer has a molar ratio A / (A + C) of the polymerization unit (A) to the polymerization unit (C) of 0.80 to 0. .95 is preferred. More preferably, it is 0.82-0.90. In the case of the electrolyte membrane, it is preferable that the ratio of the polymerization units (A) is high from the viewpoint of increasing the strength.

Particularly in the case of the fluorine-containing copolymer constituting the electrode catalyst layer, the fluorine-containing copolymer has a molar ratio A / (A + C) of the polymerization unit (A) to the polymerization unit (C) of 0.50 to 0.50. It is preferably 0.90. More preferably, it is 0.55-0.85, More preferably, it is 0.60-0.80. In the case of the electrode catalyst layer, it is preferable that the ratio of the polymerization units (B) is relatively high from the viewpoint of gas permeability.

The fluorine-containing copolymer of the present invention contains more than 20 mol% of polymerized units based on vinylidene fluoride and the above-mentioned comonomer (b) and other monomers capable of forming a copolymer with respect to the total polymerized units. It may be a copolymer appropriately contained within a range. When the fluorinated copolymer of the present invention is composed of polymerized units based on a fluorinated ethylenic monomer (excluding vinylidene fluoride), the other monomer is a fluorinated ethylenic monomer (provided that , Except vinylidene fluoride) must be able to form a copolymer.

Other monomers are monomers other than vinylidene fluoride, fluorine-containing ethylenic monomer (excluding vinylidene fluoride) and comonomer (b), such as ethylene, propylene, isobutylene, At least one selected from the group consisting of ethyl vinyl ether, vinyl acetate, vinyl benzoate, ethyl allyl ether, cyclohexyl allyl ether, norbornadiene, crotonic acid and its ester, acrylic acid and its alkyl ester, methacrylic acid and its alkyl ester A monomer is preferred.

The fluorine-containing copolymer preferably has a number average molecular weight of 1 to 2 million. When the number average molecular weight exceeds 2 million, the melt viscosity is remarkably increased, so that the workability is deteriorated and the electric conductivity of the electrolyte membrane is lowered. On the other hand, if it is less than 10,000, the mechanical strength of the electrolyte membrane is remarkably lowered, which is not preferable. The number average molecular weight is more preferably 3 to 1,000,000.

The number average molecular weight is a value measured by a GPC (gel permeation chromatograph) method. For example, the number average molecular weight can be calculated based on standard polystyrene by the following method.
TOSOH HLC-8020 is used, and the column is three polystyrene gel MIX columns (Tosoh GMH series, 30 cm size), 40 ° C., NMP (containing 5 mmol / L LiBr) solvent, flow rate 0.7 mL / min. Can do. The sample concentration can be 0.1 wt% and the implantation amount can be 500 μL. The number average molecular weight in terms of polystyrene is about 100,000 to 800,000, preferably about 130,000 to 700,000, and more preferably about 160,000 to 600,000.

The fluorine-containing copolymer has an equivalent weight (EW), that is, a dry weight per equivalent of ion exchange groups of 250 or more and 2000 or less. When EW exceeds 2000, the film forming property may be inferior. The upper limit of EW is preferably 850. More preferably, it is 700, More preferably, it is 650, Especially preferably, it is 600. The lower limit of EW is preferably 300, more preferably 350, and even more preferably 390. The smaller the EW, the higher the conductivity and the better. On the other hand, there is a case where the solubility in hot water is increased. Therefore, the electrolyte membrane of the solid polymer electrolyte fuel cell can be obtained within the appropriate range as described above. Can be suitably used.

Since the electrolyte membrane and the electrode catalyst layer of the present invention are made of the above-mentioned fluorine-containing copolymer, they are excellent in battery characteristics, mechanical strength, and stability. Therefore, it can be suitably used for a solid molecular fuel cell.

The electrolyte membrane of the present invention is an electrolyte membrane for a solid polymer electrolyte fuel cell. It may consist essentially of only the above-mentioned fluorine-containing copolymer, or may contain, for example, a porous support. When the electrolyte membrane includes a porous support, for example, the electrolyte membrane preferably has a layer made of a fluorine-containing copolymer on the surface of the porous support, and such an electrolyte membrane is the above-mentioned fluorine-containing copolymer. Can be obtained by impregnating the porous support with a dispersion in which is dispersed in a liquid medium or a solution in which the above-mentioned fluorine-containing copolymer is dissolved in a liquid medium, and then removing the liquid medium. The porous support is not particularly limited as long as it has a porous structure, and may be any organic or inorganic material such as glass wool, ceramic, alumina, polytetrafluoroethylene [PTFE] porous film, carbon, Nonwoven fabrics, those made of various polymers and the like can be mentioned. Examples of the porous support include a porous membrane obtained by stretching a PTFE membrane as described in JP-A-8-162132, and JP-A-53-149881 and JP-B-63-61337. Fibrillated fibers and the like. In addition, the electrolyte membrane of the present invention preferably does not contain a fuel cell catalyst.

The electrolyte membrane of the present invention preferably has a thickness of 1 μm to 500 μm, more preferably 2 μm to 100 μm, and still more preferably 5 μm to 50 μm. If the film thickness is thin, the direct current resistance during power generation can be reduced, while the gas permeation amount may be increased. Therefore, the appropriate range as described above is desirable. When the electrolyte membrane is a layer made of a fluorine-containing copolymer formed on the surface of the porous support, the thickness of the layer made of the fluorine-containing copolymer is preferably 5 μm or more and 50 μm or less. When the thickness is less than 5 μm, the mechanical strength of the layer made of the fluorinated copolymer is insufficient. When the thickness exceeds 50 μm, for example, when used in a solid polymer electrolyte fuel cell described later, the performance as a fuel cell is high. Since it may decrease, it is not preferable.

The electrode catalyst layer of the present invention comprises a fluorine-containing copolymer and a fuel cell catalyst. The electrode catalyst layer is for a solid polymer electrolyte fuel cell. Electrode catalyst layer, the supported amount of the fluorine-containing copolymer to the electrode area is preferably 0.001 to 10 mg / cm ^2, more preferably 0.01 to 5 mg / cm ^2, more preferably 0.1 to 1 mg / cm ² .

The fuel cell catalyst is not particularly limited as long as it has activity in the electrode catalyst layer, and is appropriately selected according to the intended use of the fuel cell in which the electrode catalyst layer of the present invention is used. The fuel cell catalyst is preferably a catalytic metal.

The catalyst metal may be any metal that promotes the oxidation reaction of hydrogen and the reduction reaction of oxygen. Platinum, gold, silver, palladium, iridium, rhodium, ruthenium, iron, cobalt, nickel, chromium, tungsten, manganese, Vanadium and at least one metal selected from the group consisting of these alloys are preferred. Of these, platinum is preferable. The particle diameter of the catalyst metal is not limited, but is preferably 10 to 1000 angstrom, more preferably 10 to 500 angstrom, and most preferably 15 to 100 angstrom.

The electrode catalyst layer of the present invention is preferably composed of a fluorine-containing copolymer, a catalyst metal and a conductive agent. For example, the electrode catalyst layer of the present invention comprises a fluorine-containing copolymer, catalyst metal fine particles (catalyst metal particles), and composite particles (for example, Pt-supported carbon) made of a conductive agent supporting the catalyst metal particles. It is also a preferred form. In this case, the fluorine-containing copolymer also functions as a binder. The electrode catalyst layer of the present invention may contain a water repellent as necessary.

The conductive agent is not limited as long as it is conductive particles (conductive particles). For example, carbon black such as furnace black, channel black, and acetylene black, activated carbon, graphite, and various metals (excluding catalytic metals). It is preferably at least one type of conductive particles selected from the group consisting of: The particle diameter of these conductive agents is preferably 10 Å to 10 μm, more preferably 50 Å to 1 μm, and most preferably 100 to 5000 Å.

The composite particles are preferably 1 to 99% by mass, more preferably 10 to 90% by mass, and most preferably 30 to 70% by mass of the catalyst metal particles with respect to the conductive particles. Specifically, Pt catalyst supporting carbon such as TEC10E40E manufactured by Tanaka Kikinzoku Kogyo Co., Ltd. can be mentioned as a suitable example.

The content of the composite particles is preferably 20 to 95% by mass, more preferably 40 to 90% by mass, still more preferably 50 to 85% by mass, and particularly preferably 60 to 90% by mass with respect to the total mass of the electrode catalyst layer. 80% by mass. When the electrode catalyst layer is used as an electrode catalyst layer of a solid polymer electrolyte fuel cell, the amount of catalyst metal supported with respect to the electrode area is preferably 0.001 to 10 mg / cm ² in the state where the electrode catalyst layer is formed. More preferably, it is 0.01-5 mg / cm < ² >, More preferably, it is 0.1-1 mg / cm < ² >. The thickness of the electrode catalyst layer is preferably 0.01 to 200 μm, more preferably 0.1 to 100 μm, and most preferably 1 to 50 μm.

The electrode catalyst layer of the present invention may further contain polytetrafluoroethylene (hereinafter referred to as PTFE) in order to improve water repellency. In this case, the shape of PTFE is not particularly limited, but may be any shape as long as it is regular, preferably in the form of particles or fibers, and these may be used alone or in combination. . When the electrode catalyst layer contains PTFE, the content of PTFE is preferably 0.001 to 20% by mass, more preferably 0.01 to 10% by mass, most preferably relative to the total mass of the electrode catalyst layer. It is 0.1-5 mass%.

The electrode catalyst layer of the present invention may further contain a metal oxide for improving hydrophilicity. In this case, the metal oxide is not particularly limited, but Al ₂ O ₃ , B ₂ O ₃ , MgO, SiO ₂ , SnO ₂ , TiO ₂ , V ₂ O ₅ , WO ₃ , Y ₂ O ₃ , ZrO ₂ It is preferably at least one metal oxide selected from the group consisting of Zr ₂ O ₃ and ZrSiO ₄ . Among these, at least one metal oxide selected from the group consisting of Al ₂ O ₃ , SiO ₂ , TiO ₂ and ZrO ₂ is preferable, and SiO ₂ is particularly preferable. When the electrode catalyst layer of the present invention contains a metal oxide, the metal oxide content is preferably 0.001 to 20 mass%, more preferably 0.01 to the total mass of the electrode catalyst layer. 10% by mass, most preferably 0.1 to 5% by mass. The metal oxide may be in the form of particles or fibers, but it is particularly desirable that the metal oxide be amorphous. The term “amorphous” as used herein means that no particulate or fibrous metal oxide is observed even when observed with an optical microscope or an electron microscope. In particular, even when the electrode catalyst layer is magnified up to several hundred thousand times using a scanning electron microscope (SEM), no particulate or fibrous metal oxide is observed. In addition, even when the electrode catalyst layer is observed by magnifying it to several hundred thousand to several million times using a transmission electron microscope (TEM), it is possible to clearly observe a particulate or fibrous metal oxide. Can not. Thus, within the scope of the current microscopic technique, it means that the particle shape or fiber shape of the metal oxide cannot be confirmed.

Although it does not specifically limit as a porosity of an electrode catalyst layer, Preferably it is 10-90 volume%, More preferably, it is 20-80 volume%, Most preferably, it is 30-60 volume%.

The present invention is also a membrane / electrode assembly (hereinafter also referred to as “MEA”) including at least one of the electrolyte membrane and the electrode catalyst layer. Since the membrane / electrode assembly of the present invention comprises at least one of the electrolyte membrane and the electrode catalyst layer, it has excellent battery characteristics and mechanical strength, and is excellent in stability.

A unit in which two types of electrode catalyst layers of an anode and a cathode are bonded to both surfaces of an electrolyte membrane is called a membrane electrode assembly (hereinafter also referred to as “MEA”). A material in which a pair of gas diffusion layers are bonded to the outer side of the electrode catalyst layer so as to face each other is sometimes referred to as MEA. The electrode catalyst layer needs to have proton conductivity.

The electrode catalyst layer as an anode includes a catalyst that easily oxidizes fuel (for example, hydrogen) to easily generate protons, and the electrode catalyst layer as a cathode reacts protons and electrons with an oxidizing agent (for example, oxygen or air). And a catalyst that produces water. For both the anode and the cathode, the catalyst metal described above can be suitably used as the catalyst.

As the gas diffusion layer, commercially available carbon cloth or carbon paper can be used. Representative examples of the former include carbon cloth E-tek and B-1 manufactured by DE NORA NORTH AMERICA, USA. Representative examples of the latter include CARBEL (registered trademark, Japan Gore-Tex, Japan), Japan. Examples include TGP-H manufactured by Kunito Toray Industries, Inc., and carbon paper 2050 manufactured by SPECTRACORP USA.

A structure in which the electrode catalyst layer and the gas diffusion layer are integrated is called a “gas diffusion electrode”. MEA can also be obtained by bonding the gas diffusion electrode to the electrolyte membrane. A typical example of a commercially available gas diffusion electrode is a gas diffusion electrode ELAT (registered trademark) manufactured by DE NORA NORTH AMERICA (using carbon cloth as a gas diffusion layer).

The MEA can be produced, for example, by sandwiching an electrolyte membrane between electrode catalyst layers and joining them by hot pressing. More specifically, a commercially available platinum-supporting carbon (for example, TEC10E40E manufactured by Kunitaka Tanaka Kikinzoku Co., Ltd.) is dispersed as a catalyst in a dispersion or solution of the fluoropolymer in a mixed solution of alcohol and water. And paste it. A certain amount of this is applied to one side of each of the two PTFE sheets and dried to form an electrode catalyst layer. Next, the application surfaces of the PTFE sheets face each other, an electrolyte membrane is sandwiched between them, and after transfer joining by hot pressing at 100 to 200 ° C., the MEA can be obtained by removing the PTFE sheet. A person skilled in the art knows how to make MEAs. The method for producing MEA is described in, for example, JOURNAL OF APPLIED ELECTROCHEMISTRY, 22 (1992) p. 1-7.

The MEA (including an MEA having a structure in which a pair of gas diffusion electrodes are opposed to each other) is further combined with components used in a general solid polymer electrolyte fuel cell such as a bipolar plate or a backing plate, A molecular electrolyte fuel cell is constructed.
The present invention is also a solid polymer electrolyte fuel cell having the membrane electrode assembly. The solid polymer electrolyte fuel cell of the present invention is not particularly limited as long as it has the above membrane electrode assembly, and usually contains constituent components such as gas constituting the solid polymer electrolyte fuel cell. It's okay. Since the solid polymer electrolyte fuel cell of the present invention comprises a membrane electrode assembly having at least one of the electrolyte membrane and the electrode catalyst layer, it has excellent cell characteristics and mechanical strength, and is excellent in stability.

The bipolar plate means a composite material of graphite and resin having a groove for flowing a gas such as fuel or oxidant on its surface, or a metal plate. In addition to the function of transmitting electrons to an external load circuit, the bipolar plate has a function of a flow path for supplying fuel and oxidant to the vicinity of the electrode catalyst. A fuel cell is manufactured by inserting and stacking a plurality of MEAs between such bipolar plates.

The present invention is a method for producing the above electrolyte membrane, wherein an electrolyte emulsion containing a fluorine-containing copolymer is obtained by radical polymerization of vinylidene fluoride and a comonomer having a —SO ₃ X group in an aqueous medium. A polymerization step, a step of applying the obtained electrolyte emulsion to a substrate, and a step of drying the electrolyte emulsion applied to the substrate to obtain an electrolyte membrane, wherein the —SO ₃ X group is —SO ₃ H, —SO ₃ NR ¹ R ² R ³ R ⁴ , and —SO ₃ M ¹ _{1 / L} (provided that R ¹ , R ² , R ³ and R ⁴ are the same or different and have a hydrogen atom or a carbon number of 1 to 4 represents an alkyl group, M ¹ is the same or different and represents an L-valent metal, and the L-valent metal is represented by Group 1, Group 2, Group 4, Group 8, Group 12, Group 12 of the Periodic Table. Alternatively, it represents a metal belonging to Group 13 (excluding Li). It is also a method for producing an electrolyte membrane, which is at least one functional group selected from the group consisting of:

The above method of manufacturing the electrolyte membrane, in obtaining the fluorine-containing copolymer comprising a polymerized units having polymerized units and -SO 3 _X groups based on vinylidene fluoride in the side chain, the co-monomer having a -SO 3 _X group There is a feature in using the body. This feature eliminates the need for a step of bringing into contact with a strongly alkaline solution having a pH of more than 8, so that the fluorine-containing copolymer obtained by the polymerization step is also high when used in a solid polymer electrolyte fuel cell. Shows stability.
For example, in JP-A-10-284128, after a copolymer is obtained using a monomer having —CF ₂ COOCH ₃ or —CF ₂ SO ₂ F, a strongly alkaline compound such as LiOH is used. how to convert -CF 2 _sO 3 _Li is taken Te, but the thus obtained polymer electrolyte, HF elimination reaction of vinylidene fluoride progresses, unstable double bonds in the main chain As a result, there is a problem of poor stability. In the above Japanese translation of PCT publication No. 2002-503734, a method of converting —CF ₂ SO ₂ F into —CF ₂ SO ₃ Li using lithium carbonate is employed. Lithium carbonate is a strong basic compound with an aqueous solution having a pH of about 11, and was insufficient to prevent the deHF reaction of vinylidene fluoride.

The method for producing an electrolyte membrane of the present invention includes a polymerization step of obtaining an electrolyte emulsion containing a fluorine-containing copolymer by radical polymerization of vinylidene fluoride and a comonomer having a —SO ₃ X group in an aqueous medium. .

It is also one of preferable embodiments that the polymerization step further includes radical polymerization of at least one monomer selected from the group consisting of tetrafluoroethylene and hexafluoropropylene in an aqueous medium.

In the radical polymerization, a comonomer having a —SO ₃ X group (for example, the above-mentioned comonomer (b)) is dissolved in an aqueous medium, and vinylidene fluoride and the comonomer are radically polymerized. It is preferable.

The aqueous medium is not particularly limited as long as it is liquid and contains water. By being an aqueous medium, it is excellent in environmental load and cost. Also, the dispersion stability is improved. The content of water in the aqueous medium is preferably 10% by mass or more, more preferably 30% by mass or more, further preferably 50% by mass or more, and 90% by mass or more. Particularly preferred. Most preferably, the aqueous medium consists essentially of water.

The aqueous medium may contain, together with water, a fluorine-free organic solvent such as alcohol, ether or ketone, a fluorine-containing organic solvent having a boiling point of 40 ° C. or lower, and the like.

The above radical polymerization may be carried out in the presence of a surfactant. However, since the present invention polymerizes a comonomer having a —SO ₃ X group, the surfactant is not necessarily required. Rather, radical polymerization without using a surfactant is preferred in that a polymer with few impurities can be obtained.

The radical polymerization is preferably performed by adding a polymerization initiator. The polymerization initiator is not particularly limited as long as it can generate radicals at the polymerization temperature, and known oil-soluble and / or water-soluble polymerization initiators can be used. A redox initiator may also be used. The concentration of the polymerization initiator is appropriately determined depending on the molecular weight and reaction rate of the target fluorine-containing copolymer.

Examples of the polymerization initiator include persulfates such as ammonium persulfate and potassium persulfate, and organic peroxides such as disuccinic acid peroxide, diglutaric acid peroxide, and tert-butyl hydroperoxide. As the above redox initiator, a combination of a persulfate or an organic peroxide and a reducing agent such as sodium sulfite, a bisulfite such as sodium hydrogen sulfite, a bromate, diimine, or oxalic acid. Is mentioned.

The radical polymerization can be performed under a pressure of 0.05 to 5.0 MPa. A preferable pressure range is 1.5 to 3.0 MPa. Moreover, radical polymerization can be performed at the temperature of 10-100 degreeC. A preferred temperature range is 50-90 ° C. In radical polymerization, a known stabilizer, chain transfer agent, or the like may be added depending on the purpose.

When producing an electrolyte membrane comprising a fluorine-containing copolymer comprising polymer units (A) based on vinylidene fluoride and polymer units having —SO ₃ H groups in the side chain, the polymerization step is obtained by radical polymerization. A step of converting the —SO ₃ X group (excluding the —SO ₃ H group) of the fluoropolymer into an —SO ₃ H group may be included. For example, the polymerization step includes radical polymerization of a vinylidene fluoride and a comonomer having —SO ₃ X group (excluding —SO ₃ H group) in an aqueous medium to form —SO ₃ X group ( However, the step of obtaining a precursor emulsion containing a fluorine-containing copolymer having -SO ₃ H group in the side chain and -SO ₃ X group (however, -SO ₃ H group is excluded)- And a step of obtaining an electrolyte emulsion containing a fluorine-containing copolymer having —SO ₃ H in the side chain by conversion to an SO ₃ H group. The method for converting —SO ₃ X group (excluding —SO ₃ H group) to —SO ₃ H group is not particularly limited, but for example, —SO ₃ X group (provided —SO ₃ H group) And a fluorine-containing copolymer having a side chain in contact with an ion exchange resin converted into an acid form (for example, Amberlite IR120B manufactured by Rohm & Haas). More specifically, after the ion exchange resin is converted into an acid type using sulfuric acid, the precursor emulsion is washed with pure water and filled with the ion exchange resin converted into the acid type and contains the above fluoropolymer. The method of letting pass is mentioned.

The method for producing an electrolyte membrane of the present invention may include a step of obtaining a comonomer having a —SO ₃ X group in the side chain before the polymerization step. In the step of obtaining a comonomer having a —SO ₃ X group in the side chain, a comonomer having an ionic dissociable sulfonic acid derivative is brought into contact with a solution having a pH of 8 or less or a solution having a pH exceeding 8 —SO ₃ X It may be a step of obtaining a comonomer having a group in the side chain.
Here, the ion dissociable sulfonic acid derivative is a functional group that can be converted into a —SO ₃ X group. Sulfonic acid derivatives of ion dissociation ^{_{property, -SO 3 H, -SO 3 NR}} 1 R 2 R 3 R 4, -SO 2 NR 5 R 6 and _-SO 3 ^M _{1 1 / L} ^{(where, R 1,} R ² , R ³ and R ⁴ are the same or different and each represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, R ⁵ represents a hydrogen atom or M ² _{1 / L} , and R ⁶ represents a hydrogen atom or 1 to C carbon atoms. 4 represents an alkyl group or a sulfonyl-containing group, M ¹ and M ² are the same or different and represent an L-valent metal, and the L-valent metal is represented by Group 1, Group 2, Group 4, 8 of the Periodic Table. It is preferably at least one functional group selected from the group consisting of metals belonging to Group 11, Group 12, Group 12 or Group 13).

The comonomer having the —SO ₃ X group is the comonomer (b) described above, and is preferably a vinyl ether represented by the general formula (II) described above. In the vinyl ether represented by the general formula (II), the —SO ₃ X group is the same as described above.

The method for producing an electrolyte membrane of the present invention includes a step of applying the electrolyte emulsion obtained by the polymerization step to a substrate, and a step of obtaining an electrolyte membrane by drying the electrolyte emulsion applied to the substrate. The manufacturing method of the electrolyte membrane of this invention may have a process of peeling the electrolyte membrane obtained by drying the electrolyte emulsion apply | coated to the base material from a base material as needed. When the electrolyte membrane of the present invention includes a porous support, it is preferable to use a porous support as the substrate. In this case, the process of peeling the electrolyte membrane obtained by drying the electrolyte emulsion applied to the substrate from the substrate is not required.
The electrolyte emulsion is obtained by dispersing the fluorine-containing copolymer in an aqueous medium.

The manufacturing method of the electrolyte membrane may be performed by a so-called cast film forming method. For example, after the polymer electrolyte-containing solution is developed in a container such as a petri dish and heated in an oven as necessary, the aqueous medium is at least partially distilled off, and then peeled off from the container, etc. Can be obtained. Further, by using a device such as a blade coater, a gravure coater or a comma coater having a mechanism such as a blade, an air knife or a reverse roll so that the dispersion containing the above-mentioned fluorine-containing copolymer is uniform on a glass plate or film. A cast film can be formed by controlling the film thickness to form a single wafer. Further, it can be continuously cast to form a continuous film to form a long film-like film.

The film is not particularly limited, but includes polyethylene terephthalate (PET), polyethylene butaleate (PBT), polyethylene naphthalate (PEN) and polyesters including liquid crystal polyesters, triacetyl cellulose (TAC), polyarylate, polyether, Polycarbonate (PC), polysulfone, polyethersulfone, cellophane, aromatic polyamide, polyvinyl alcohol, polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC), polystyrene (PS), acrylonitrile-butadiene-styrene copolymer ( ABS), polymethyl methacrylate (PMMA), polyamide, polyacetal (POM), polyphenylene terephthalate (PPE), polybutylene terephthalate (PBT), polyphenylene sulfide (PPS), polyamideimide (PAI), polyetheramide (PEI), polyetheretherketone (PEEK), polyimide (PI), polymethylpentene (PMP), polytetrafluoroethylene, (PTFE) ), Fluorinated ethylene-propylene (FEP), tetrafluoroethylene-ethylene (ETFE) copolymer, polyvinylidene fluoride (PVDF), rebenzazole (PBZ), polybenzoxazole (PBO), polybenzothiazole (PBT), polybenzimidazole (PBI) and polyparaphenylene terephthalimide (PPTA) can be selected and used.

When the electrolyte membrane of the present invention includes a porous support, it is preferable that the step of applying the electrolyte emulsion obtained by the polymerization step on the base material impregnates the porous support with the electrolyte emulsion.

The method for producing an electrolyte membrane of the present invention is also a method for producing the above electrolyte membrane, wherein the fluorine-containing copolymer is obtained by radical polymerization of vinylidene fluoride and a comonomer having a —SO ₃ X group in an aqueous medium. A polymerization process for obtaining an electrolyte emulsion containing a polymer, a process for obtaining an electrolyte solution in which a fluoropolymer is dissolved by adding an organic solvent to the electrolyte emulsion obtained by the polymerization process, and applying the electrolyte solution to a substrate And a step of drying the electrolyte solution applied to the substrate to obtain an electrolyte membrane, wherein the —SO ₃ X group is —SO ₃ H, —SO ₃ NR ¹ R ² R ³ R ⁴ , and — SO ₃ M ¹ _{1 / L} (wherein R ¹ , R ² , R ³ and R ⁴ are the same or different and each represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and M ¹ is the same or different, Represents an L-valent metal, The L-valent metal is selected from the group consisting of metals belonging to Group 1, Group 2, Group 4, Group 8, Group 11, Group 12, Group 13 or Group 13 of the periodic table (excluding Li). It is also a method for producing an electrolyte membrane, characterized in that it is at least one kind of functional group. As described above, this feature does not require a step of contacting with a strongly alkaline solution having a pH of more than 8, so that the fluorine-containing copolymer obtained by the polymerization step is used for a solid polymer electrolyte fuel cell. High stability is also exhibited. The method for producing an electrolyte membrane may include a step of peeling the electrolyte membrane obtained by drying the electrolyte emulsion applied to the substrate from the substrate, if necessary.

The said polymerization process can be performed by the same method as the method mentioned above. For example, when producing an electrolyte membrane comprising a fluorine-containing copolymer comprising a polymer unit (A) based on vinylidene fluoride and a polymer unit having a —SO ₃ H group in the side chain, the fluorine-containing heavy polymer obtained by radical polymerization is used. A step of converting the —SO ₃ X group (excluding the —SO ₃ H group) of the coalescence into a —SO ₃ H group may be included. Specifically, the polymerization step includes radical polymerization of vinylidene fluoride and a comonomer having a —SO ₃ X group (excluding —SO ₃ H group) in an aqueous medium to produce —SO _3. A step of obtaining a precursor emulsion containing a fluorine-containing copolymer having X group (excluding —SO ₃ H group) in the side chain; and —SO ₃ X group (excluding —SO ₃ H group). And a step of obtaining an electrolyte emulsion containing a fluorine-containing copolymer having —SO ₃ H in the side chain by converting it to —SO ₃ H groups. The method for converting the —SO ₃ X group (excluding the —SO ₃ H group) into the —SO ₃ H group includes the same method as described above.

Examples of the organic solvent include protic organic solvents such as methanol, ethanol, n-propanol, isopropyl alcohol, butanol, and glycerin, and aprotic substances such as N, N-dimethylformamide, N, N-dimethylacetamide, and N-methylpyrrolidone. An organic solvent. These can be used alone or in combination of two or more.

The dissolution method is not particularly limited. For example, first, for example, a mixed solvent of water and a protic organic solvent is added to the electrolyte emulsion under such a condition that the total solid concentration is 1 to 50% by mass. Next, the composition is placed in an autoclave having a glass inner cylinder as necessary, and the internal air is replaced with an inert gas such as nitrogen. Heat and stir for 12 hr. Thereby, an electrolyte solution is obtained. The step of obtaining the electrolyte solution is preferably a step of obtaining an electrolyte solution in which the fluoropolymer is dissolved by adding an organic solvent to the obtained electrolyte emulsion and then heating. The higher the total solid content concentration, the better from the viewpoint of yield. However, when the concentration is increased, undissolved material may be formed. Therefore, the amount is preferably 1 to 50% by mass, more preferably 3 to 40% by mass, and still more preferably 5 -30 mass%.
An electrode catalyst layer was prepared as follows.

When a protic organic solvent is used, the composition ratio of water and the protic organic solvent in the obtained electrolyte solution depends on the dissolution method, dissolution conditions, type of polymer electrolyte, total solid content concentration, dissolution temperature, stirring speed, etc. Although it can select suitably, 10-1000 mass parts of protic organic solvents are preferable with respect to 100 mass parts of water, Especially preferably, it is 10-500 mass parts of organic solvents with respect to 100 mass parts of water.

The electrolyte solution includes an emulsion (a liquid particle in which liquid particles are dispersed as colloidal particles or coarser particles to form a milky state), a suspension (solid particles in a liquid are colloidal particles or Such as those dispersed as particles that can be seen with a microscope), colloidal liquid (macromolecules dispersed), micellar liquid (a lyophilic colloidal dispersion system made up of many small molecules associated by intermolecular forces), etc. 1 type (s) or 2 or more types may be contained.

The electrolyte solution can be concentrated. The concentration method is not particularly limited. For example, there are a method of heating and evaporating the solvent, a method of concentrating under reduced pressure, and the like. If the resulting coating solution has a solid content ratio that is too high, the viscosity may increase and it may be difficult to handle, and if it is too low, the productivity may decrease. The fraction is preferably 0.5 to 50% by mass.

The electrolyte solution is more preferably filtered from the viewpoint of removing coarse particle components. The filtration method is not particularly limited, and a general method conventionally performed can be applied. For example, a method of pressure filtration using a filter obtained by processing a filter medium having a normally used rated filtration accuracy is typically mentioned. As for the filter, it is preferable to use a filter medium whose 90% collection particle size is 10 to 100 times the average particle size of the particles. The filter medium may be filter paper or a filter medium such as a sintered metal filter. Particularly in the case of filter paper, the 90% collection particle size is preferably 10 to 50 times the average particle size of the particles. In the case of a sintered metal filter, the 90% collection particle size is preferably 50 to 100 times the average particle size of the particles. Setting the 90% collection particle size to be 10 times or more of the average particle size prevents the pressure necessary for liquid feeding from becoming too high, or the filter is blocked in a short period of time. Can be suppressed. On the other hand, setting it to 100 times or less of the average particle diameter is preferable from the viewpoint of satisfactorily removing particle agglomerates and resin undissolved materials that cause foreign matters in the film.

The electrolyte solution obtained in this manner can be applied to a substrate, and the electrolyte solution applied to the substrate can be dried to obtain an electrolyte membrane. As a method of applying the electrolyte solution to the substrate, it can be performed by cast film formation or the like, similarly to the method of applying the electrolyte emulsion to the substrate.

The present invention is a method for producing the above electrode catalyst layer, which is an electrolyte emulsion containing a fluorine-containing copolymer obtained by radical polymerization of vinylidene fluoride and a comonomer having a —SO ₃ X group in an aqueous medium. A step of preparing a catalyst composition by dispersing a fuel cell catalyst in the obtained electrolyte emulsion, a step of applying the catalyst composition to a substrate, and a drying of the catalyst composition applied to the substrate And a step of obtaining an electrode catalyst layer, wherein the —SO ₃ X group is —SO ₃ H, —SO ₃ NR ¹ R ² R ³ R ⁴ , and —SO ₃ M ¹ _{1 / L} (where R ¹ , R ² , R ³ and R ⁴ are the same or different and each represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms; M ¹ is the same or different and represents an L-valent metal; Metals are Group 1, 2, 4, 8, 11 , A metal belonging to Group 12 or 13 (however, Li is excluded). The method is also a method for producing an electrode catalyst layer, which is at least one functional group selected from the group consisting of. In the polymerization step, it is further preferable that the polymerization step includes radical polymerization of at least one monomer selected from the group consisting of tetrafluoroethylene and hexafluoropropylene in an aqueous medium.

The said polymerization process can be performed by the same method as the method mentioned above. For example, when producing an electrolyte membrane comprising a fluorine-containing copolymer comprising a polymer unit (A) based on vinylidene fluoride and a polymer unit having a —SO ₃ H group in the side chain, the fluorine-containing heavy polymer obtained by radical polymerization is used. A step of converting the —SO ₃ X group (excluding the —SO ₃ H group) of the coalescence into a —SO ₃ H group may be included. Specifically, the polymerization step includes radical polymerization of vinylidene fluoride and a comonomer having a —SO ₃ X group (excluding —SO ₃ H group) in an aqueous medium to produce —SO _3. A step of obtaining a precursor emulsion containing a fluorine-containing copolymer having X group (excluding —SO ₃ H group) in the side chain; and —SO ₃ X group (excluding —SO ₃ H group). And a step of obtaining an electrolyte emulsion containing a fluorine-containing copolymer having —SO ₃ H in the side chain by converting it to —SO ₃ H groups. The method for converting the —SO ₃ X group (excluding the —SO ₃ H group) into the —SO ₃ H group includes the same method as described above.

The method for producing an electrode catalyst layer of the present invention includes a step of dispersing a fuel cell catalyst in the obtained electrolyte emulsion to prepare a catalyst composition, a step of applying the catalyst composition to a substrate, and a step of applying the catalyst composition to the substrate. Drying the catalyst composition to obtain an electrode catalyst layer.

The step of preparing a catalyst composition by dispersing a fuel cell catalyst in the obtained electrolyte emulsion comprises the steps of preparing fine particles of catalyst metal (catalyst metal particles) and composite particles comprising a conductive agent carrying the catalyst particles in the obtained electrolyte emulsion. It is preferable to prepare a dispersed catalyst composition.

The method for producing an electrode catalyst layer of the present invention includes, for example, preparing the electrolyte emulsion, dispersing the fuel cell catalyst in the electrolyte emulsion to prepare a catalyst composition, and preparing this on an electrolyte membrane or a PTFE sheet or the like After coating on another substrate, it can be produced by drying and solidifying. In the present invention, the catalyst composition can be applied by various generally known methods such as a screen printing method and a spray method. The catalyst composition includes a fluoropolymer, a catalytic metal, and an aqueous medium. The method for producing an electrode catalyst layer of the present invention may further include a step of immersing in an inorganic acid such as hydrochloric acid after the electrode catalyst layer is produced. The acid treatment temperature is preferably 5 to 90 ° C, more preferably 10 to 70 ° C, and most preferably 20 to 50 ° C.

The present invention is a method for producing the above electrode catalyst layer, which is an electrolyte emulsion containing a fluorine-containing copolymer obtained by radical polymerization of vinylidene fluoride and a comonomer having a —SO ₃ X group in an aqueous medium. A step of obtaining an electrolyte solution in which a fluorine-containing copolymer is dissolved by adding an organic solvent to the obtained electrolyte emulsion, and preparing a catalyst composition by dispersing a fuel cell catalyst in the electrolyte solution And a step of applying a catalyst composition to a substrate, and a step of drying the catalyst composition applied to the substrate to obtain an electrode catalyst layer, wherein the —SO ₃ X group is —SO ₃ H, —SO ₃ NR ¹ R ² R ³ R ⁴ , and —SO ₃ M ¹ _{1 / L} (provided that R ¹ , R ² , R ³ and R ⁴ are the same or different and have a hydrogen atom or a carbon number of 1 to 4) Represents an alkyl group, and M ¹ is the same or different. The L-valent metal is a metal belonging to Group 1, Group 2, Group 4, Group 8, Group 11, Group 12 or Group 13 of the periodic table (excluding Li). It is also a method for producing an electrode catalyst layer that is at least one functional group selected from the group consisting of: In this case, the fluoropolymer contained in the electrolyte solution is dissolved.

The said polymerization process can be performed by the same method as the method mentioned above. For example, when producing an electrolyte membrane comprising a fluorine-containing copolymer comprising a polymer unit (A) based on vinylidene fluoride and a polymer unit having a —SO ₃ H group in the side chain, the fluorine-containing heavy polymer obtained by radical polymerization is used. A step of converting the —SO ₃ X group (excluding the —SO ₃ H group) of the coalescence into a —SO ₃ H group may be included. Specifically, the polymerization step includes radical polymerization of vinylidene fluoride and a comonomer having a —SO ₃ X group (excluding —SO ₃ H group) in an aqueous medium to produce —SO _3. A step of obtaining a precursor emulsion containing a fluorine-containing copolymer having X group (excluding —SO ₃ H group) in the side chain; and —SO ₃ X group (excluding —SO ₃ H group). And a step of obtaining an electrolyte emulsion containing a fluorine-containing copolymer having —SO ₃ H in the side chain by converting it to —SO ₃ H groups. The method for converting the —SO ₃ X group (excluding the —SO ₃ H group) into the —SO ₃ H group includes the same method as described above.

Examples of the organic solvent added to the electrolyte emulsion in order to obtain an electrolyte solution include alcohols (ethanol, 2-propanol, ethylene glycol, glycerin, etc.), single solvents such as chlorofluorocarbon, and composite solvents. The amount of the solvent added is preferably 0.1 to 90% by mass, more preferably 1 to 50% by mass, and most preferably 5 to 20% by mass with respect to the total mass of the catalyst composition. desirable.

The step of preparing the catalyst composition by dispersing the fuel cell catalyst in the electrolyte solution can be performed in the same manner as the step of preparing the catalyst composition by dispersing the fuel cell catalyst in the electrolyte emulsion. The step of applying the catalyst composition to the substrate and the step of obtaining the electrode catalyst layer by drying the catalyst composition applied to the substrate can also be performed in the same manner as described above.

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

Evaluation of the electrolyte membrane, the electrode catalyst layer, and the fuel cell was performed by the following method.
(EW measurement)
A polymer electrolyte membrane, approximately ² to 20 cm ^{2, in} which the counter ion of the ion exchange group is in a proton state, was immersed in 30 ml of a saturated NaCl aqueous solution at 25 ° C. and left for 30 minutes with stirring. Next, the protons in the saturated NaCl aqueous solution were subjected to neutralization titration with 0.01N sodium hydroxide aqueous solution using phenolphthalein as an indicator. The polymer electrolyte membrane obtained after neutralization, in which the counter ion of the ion exchange group is in the state of sodium ions, was rinsed with pure water, further vacuum dried and weighed. The amount of sodium hydroxide required for neutralization is M (mmol), and the weight of the polymer electrolyte membrane whose sodium ion is the counter ion of the ion exchange group is W (mg). g / eq).
EW = (W / M) −22 (3)

(Proton conductivity measurement)
The electrolyte membrane sample is cut out in a wet state, and the thickness T is measured. And it attached to the conductivity measuring cell of 2 terminal type which measures the conductivity of the film length direction of width 1cm and length 5cm. This cell was placed in ion exchange water at 80 ° C., and the resistance value R of the real component at a frequency of 10 kHz was measured by an alternating current impedance method, and proton conductivity σ was derived from the following equation.
σ = L / (R × T × W)
σ: proton conductivity (S / cm)
T: Thickness (cm)
R: Resistance value (Ω)
L (= 5): film length (cm)
W (= 1): film width (cm)

(Tensile creep property)
Tensile creep characteristics were examined using a three-creep creep tester (CP3-P-20 manufactured by Orientec Co., Ltd.). First, a membrane sample is cut out in a wet state, and the thickness T is measured. Then, a film having a width of 1 cm and a length of 5 cm was mounted on the chuck with a chuck interval of 2 cm. The test was performed in a constant temperature and humidity chamber and maintained at 80 ° C. and 95% RH. The test load is 20 kg / cm ² , and after 40 hours from the start of the test, the film is taken out from the thermo-hygrostat, and the ratio (%) of the length after the test to the initial length (2 cm) is calculated. The amount of creep was taken.

(Fuel cell evaluation)
The following fuel cell evaluation was carried out in order to examine the initial battery characteristics (hereinafter referred to as initial characteristics) of a membrane electrode assembly (MEA) prepared from the polymer electrolyte membrane and electrode catalyst layer prepared below. .

First, the anode-side gas diffusion layer and the cathode-side gas diffusion layer were faced to each other, and an MEA produced below was sandwiched between them and incorporated in an evaluation cell. As the gas diffusion layer, carbon cloth (ELAT (registered trademark) B-1 manufactured by DE NORA NORTH AMERICA, USA) was set and incorporated in the evaluation cell. This evaluation cell is set in an evaluation apparatus (manufactured by Chino Co., Ltd., Japan) and heated to 80 ° C., then hydrogen gas is supplied to the anode side at 300 cc / min and air gas is supplied to the cathode side at 800 cc / min. The anode and cathode were pressurized at 0.15 MPa (absolute pressure). A water bubbling system was used for gas humidification, and the initial characteristics were examined by measuring a current-voltage curve in a state where the gas was humidified at 85 ° C. and the air gas was humidified at 75 ° C. and supplied to the cell.

[Synthesis Example 1]
Using a stainless steel autoclave with a stirrer with an internal volume of 3 L, 1500 g of ion exchange water and 300 g of CF ₂ = CFOCF ₂ CF ₂ SO ₃ Na were charged. Next, after the autoclave was purged with nitrogen, vinylidene fluoride was introduced, the gauge pressure was increased to 0.2 MPa, and the temperature was increased to 50 ° C. Then, after further introducing vinylidene fluoride to increase the gauge pressure to 0.50 MPa, a solution in which 3 g of ammonium persulfate was dissolved in 20 g of water was charged to initiate polymerization. Since the pressure decreased as the polymerization progressed, additional vinylidene fluoride was supplied so as to maintain a gauge pressure of 0.50 MPa. Six hours later, when 200 g of vinylidene fluoride was charged, the pressure in the autoclave was released to complete the polymerization, and an emulsion was obtained.

After diluting 1.5 kg of the emulsion with 1.5 kg of water, unreacted water-soluble monomers and water-soluble impurities are removed using an ultrafiltration device (Pellicon-2 Cassette Biomax-10) manufactured by Millipore. However, it was purified by adding pure water so that the total amount of the emulsion was 2.0 to 3.0 kg. When the ionic conductivity of the filtrate, which was examined using a handheld ion conductivity meter (compact conductivity meter B-173 type), reached 0 S · cm ⁻¹ , purification was completed, and pure water was added to complete the amount. Was adjusted to 3.0 kg.

Separately, 3 kg of Amberlite IR120B manufactured by Rohm & Haas was converted into an acid form using sulfuric acid, washed thoroughly with pure water, and filled into a glass burette. The emulsion was passed through the burette for 6 hours to obtain an emulsion of a polymer having —SO ₃ H groups in the side chain.

A part of the emulsion was dried at 120 ° C., and the obtained polymer was dissolved in N-methyl-2-pyrrolidinone and analyzed by NMR (Fourker Transform Nuclear Magnetic Resonance Apparatus (FT-NMR) AC300P manufactured by Bruker). When the polymer composition was examined, it was confirmed that the molar ratio of the polymerized units based on vinylidene fluoride and the polymerized units based on CF ₂ = CFOCF ₂ CF ₂ SO ₃ H contained in the polymer was 85/15, respectively. Moreover, from the weight change before and behind drying of an emulsion, solid content of the emulsion was 10.1%.

Moreover, when the N methyl-2-pyrrolidinone (NMP) solution of the said polymer was measured by GPC, the number average molecular weight was 330,000.

[Synthesis Example 2]
Using a stainless steel autoclave with a stirrer with an internal volume of 3 L, 1500 g of ion exchange water and 300 g of CF ₂ = CFOCF ₂ CF ₂ SO ₃ Na were charged. Next, after the autoclave was purged with nitrogen, vinylidene fluoride was introduced, the gauge pressure was increased to 0.2 MPa, and the temperature was increased to 50 ° C. Thereafter, a gas having a composition of 9/1 of vinylidene fluoride and tetrafluoroethylene was further introduced to increase the gauge pressure to 0.45 MPa, and then a solution in which 3 g of ammonium persulfate was dissolved in 20 g of water was charged to initiate polymerization. . Since the pressure decreased as the polymerization progressed, a gas having a composition of vinylidene fluoride / tetrafluoroethylene = 7/3 was additionally supplied so as to maintain a gauge pressure of 0.45 MPa. Six hours later, when 200 g of a gas having a composition of vinylidene fluoride / tetrafluoroethylene = 7/3 was charged, the pressure in the autoclave was released to complete the polymerization, and an emulsion was obtained.

After diluting 1.5 kg of the emulsion with 1.5 kg of water, unreacted water-soluble monomers and water-soluble impurities are removed using an ultrafiltration device (Pellicon-2 Cassette Biomax-10) manufactured by Millipore. However, it was purified by adding pure water so that the total amount of the emulsion was 2.0 to 3.0 kg. When the ionic conductivity of the filtrate, which was examined using a handheld ion conductivity meter (compact conductivity meter B-173 type), reached 0 S · cm ⁻¹ , purification was completed, and pure water was added to complete the amount. Was adjusted to 3.0 kg.

Separately, 3 kg of Amberlite IR120B manufactured by Rohm & Haas was converted into an acid form using sulfuric acid, washed thoroughly with pure water, and filled into a glass burette.
The emulsion was passed through the burette for 6 hours to obtain an emulsion of a polymer having —SO ₃ H groups in the side chain.

The emulsion was dried at 120 ° C., and the polymer obtained was dissolved in N-methyl-2-pyrrolidinone and analyzed by NMR (Fourker Transform Nuclear Magnetic Resonance Device (FT-NMR) AC300P manufactured by Bruker). As a result, the molar ratio of the polymerized unit based on vinylidene fluoride, the polymerized unit based on tetrafluoroethylene, and the polymerized unit based on CF ₂ = CFOCF ₂ CF ₂ SO ₃ H contained in the polymer was 55/27/18, respectively. It was confirmed that.

Moreover, when the NMP solution of the said polymer was measured by GPC, the number average molecular weight was 300,000.

[Synthesis Example 3]
Using a stainless steel autoclave with a stirrer with an internal volume of 3 L, 1500 g of ion exchange water and 300 g of CF ₂ = CFOCF ₂ CF ₂ SO ₃ Na were charged. Next, after the autoclave was purged with nitrogen, vinylidene fluoride was introduced, the gauge pressure was increased to 0.2 MPa, and the temperature was increased to 42 ° C. Thereafter, a gas having a composition of 9/1 of vinylidene fluoride and tetrafluoroethylene was further introduced to raise the gauge pressure to 0.35 MPa, and then a solution in which 3 g of ammonium persulfate was dissolved in 20 g of water was charged to initiate polymerization. . Since the pressure decreased as the polymerization progressed, a gas having a composition of vinylidene fluoride / tetrafluoroethylene = 9/1 was additionally supplied so as to maintain a gauge pressure of 0.35 MPa. Nine hours later, when 200 g of a gas having a composition of vinylidene fluoride / tetrafluoroethylene = 9/1 was charged, the pressure of the autoclave was released to complete the polymerization to obtain an emulsion.

After diluting 1.5 kg of the emulsion with 1.5 kg of water, unreacted water-soluble monomers and water-soluble impurities are removed using an ultrafiltration device (Pellicon-2 Cassette Biomax-10) manufactured by Millipore. However, it was purified by adding pure water so that the total amount of the emulsion was 2.0 to 3.0 kg. When the ionic conductivity of the filtrate, which was examined using a handheld ion conductivity meter (compact conductivity meter B-173 type), reached 0 S · cm ⁻¹ , purification was completed, and pure water was added to complete the amount. Was adjusted to 3.0 kg.

Separately, 200 g of Amberlite IR120B manufactured by Rohm & Haas Co. was converted into an acid form using sulfuric acid, washed thoroughly with pure water, and filled into a glass burette.
200 g of the emulsion was passed through the burette for 1 hour to obtain an emulsion of a polymer having —SO ₃ H groups in the side chain.

The emulsion was dried at 120 ° C., and the polymer obtained was dissolved in N-methyl-2-pyrrolidinone and analyzed by NMR (Fourker Transform Nuclear Magnetic Resonance Device (FT-NMR) AC300P manufactured by Bruker). As a result, the molar ratio of the polymerized units based on vinylidene fluoride, the polymerized units based on tetrafluoroethylene, and the polymerized units based on CF ₂ = CFOCF ₂ CF ₂ SO ₃ H contained in the polymer was 64/7/29, respectively. It was confirmed that.

Moreover, when the NMP solution of the said polymer was measured by GPC, the number average molecular weight was 230,000.

[Synthesis Example 4]
Using a stainless steel autoclave with a stirrer with an internal volume of 3 L, 1500 g of ion exchange water and 300 g of CF ₂ = CFOCF ₂ CF ₂ SO ₃ Na were charged. Next, after the autoclave was purged with nitrogen, vinylidene fluoride was introduced, the gauge pressure was increased to 0.2 MPa, and the temperature was increased to 50 ° C. Thereafter, a gas having a composition of 9/1 of vinylidene fluoride and tetrafluoroethylene was further introduced to increase the gauge pressure to 0.60 MPa, and then a solution in which 3 g of ammonium persulfate was dissolved in 20 g of water was charged to initiate polymerization. . Since the pressure decreased as the polymerization progressed, a gas having a composition of vinylidene fluoride / tetrafluoroethylene = 9/1 was additionally supplied so as to maintain a gauge pressure of 0.60 MPa. Six hours later, when 200 g of a gas having a composition of vinylidene fluoride / tetrafluoroethylene = 9/1 was charged, the pressure of the autoclave was released to complete the polymerization, and an emulsion was obtained.

After diluting 1.5 kg of the emulsion with 1.5 kg of water, unreacted water-soluble monomers and water-soluble impurities are removed using an ultrafiltration device (Pellicon-2 Cassette Biomax-10) manufactured by Millipore. However, it was purified by adding pure water so that the total amount of the emulsion was 2.0 to 3.0 kg. When the ionic conductivity of the filtrate, which was examined using a handheld ion conductivity meter (compact conductivity meter B-173 type), reached 0 S · cm ⁻¹ , purification was completed, and pure water was added to complete the amount. Was adjusted to 3.0 kg.

Separately, 200 g of Amberlite IR120B manufactured by Rohm & Haas Co. was converted into an acid form using sulfuric acid, washed thoroughly with pure water, and filled into a glass burette.
200 g of the emulsion was passed through the burette for 1 hour to obtain an emulsion of a polymer having —SO ₃ H groups in the side chain.

The emulsion was dried at 120 ° C., and the polymer obtained was dissolved in N-methyl-2-pyrrolidinone and analyzed by NMR (Fourker Transform Nuclear Magnetic Resonance Device (FT-NMR) AC300P manufactured by Bruker). As a result, the molar ratio of the polymerized units based on vinylidene fluoride, the polymerized units based on tetrafluoroethylene, and the polymerized units based on CF ₂ = CFOCF ₂ CF ₂ SO ₃ H contained in the polymer was 78/9/13, respectively. It was confirmed that.

Moreover, when the NMP solution of the said polymer was measured by GPC, the number average molecular weight was 600,000.

Example 1
Production of Electrolyte Membrane The emulsion obtained in Synthesis Example 1 was poured into a petri dish having a diameter of 15.4 cm and dried on a hot plate at 60 ° C. for 1 hour and at 80 ° C. for 1 hour to remove the solvent. Next, the petri dish was placed in an oven and heat treated at 160 ° C. for 1 hour. Thereafter, the membrane was taken out from the oven and poured into a cooled petri dish to peel off the membrane, thereby obtaining a polymer electrolyte membrane having a thickness of about 50 μm.

The obtained polymer electrolyte membrane was measured for proton conductivity, EW, and tensile creep characteristics. The results are shown in Table 1 below.

(Example 2)
Production of Electrolyte Membrane The emulsion obtained in Synthesis Example 2 was poured into a petri dish having a diameter of 15.4 cm and dried on a hot plate at 60 ° C. for 1 hour and at 80 ° C. for 1 hour to remove the solvent. Next, the petri dish was placed in an oven and heat treated at 160 ° C. for 1 hour. Thereafter, the membrane was taken out from the oven and poured into a cooled petri dish to peel off the membrane, thereby obtaining a polymer electrolyte membrane having a thickness of about 50 μm.

The obtained polymer electrolyte membrane was measured for proton conductivity, EW, and tensile creep characteristics. The results are shown in Table 1 below.

(Example 3)
Production of electrolyte membrane Ethanol was added to the emulsion obtained in Synthesis Example 1 and diluted to a solid content of 5% by mass (water: ethanol = 50.0: 50.0 (mass ratio)) and placed in a 5 L autoclave. The mixture was sealed, heated to 160 ° C. while stirring with a stirring blade, and held for 5 hours. Thereafter, the autoclave was naturally cooled to obtain a 5% by mass uniform electrolyte polymer solution.

Next, ethylene glycol (EG) was added to this polymer solution, and it concentrated under reduced pressure at 80 degreeC with the evaporator, and produced 20 mass% cast solution.

The cast solution was poured into a petri dish having a diameter of 15.4 cm and dried on a hot plate at 60 ° C. for 1 hour and at 80 ° C. for 1 hour to remove the solvent. Next, the petri dish was placed in an oven and heat treated at 160 ° C. for 1 hour. Thereafter, the membrane was taken out from the oven and poured into a cooled petri dish to peel off the membrane, thereby obtaining a polymer electrolyte membrane having a thickness of about 50 μm.

The obtained polymer electrolyte membrane was measured for proton conductivity, EW, and tensile creep characteristics. The results are shown in Table 1 below.

Example 4
Production of electrolyte membrane Ethanol was added to the emulsion obtained in Synthesis Example 2 and diluted to a solid content of 5% by mass (water: ethanol = 50.0: 50.0 (mass ratio)) and placed in a 5 L autoclave. The mixture was sealed, heated to 160 ° C. while stirring with a stirring blade, and held for 5 hours. Thereafter, the autoclave was naturally cooled to obtain a 5% by mass uniform electrolyte polymer solution.

Next, ethylene glycol (EG) was added to this polymer solution, and it concentrated under reduced pressure at 80 degreeC with the evaporator, and produced 20 mass% cast solution.

The cast solution was poured into a petri dish having a diameter of 15.4 cm and dried on a hot plate at 60 ° C. for 1 hour and at 80 ° C. for 1 hour to remove the solvent. Next, the petri dish was placed in an oven and heat treated at 160 ° C. for 1 hour. Thereafter, the membrane was taken out from the oven and poured into a cooled petri dish to peel off the membrane, thereby obtaining a polymer electrolyte membrane having a thickness of about 50 μm.

The obtained polymer electrolyte membrane was measured for proton conductivity, EW, and tensile creep characteristics. The results are shown in Table 1 below.

(Example 5)
Production of electrolyte membrane Ethanol was added to the emulsion obtained in Synthesis Example 3, diluted to 5% by mass of solid content (water: ethanol = 50.0: 50.0 (mass ratio)), and placed in a 5 L autoclave. The mixture was sealed, heated to 160 ° C. while stirring with a stirring blade, and held for 5 hours. Thereafter, the autoclave was naturally cooled to obtain a 5% by mass uniform electrolyte polymer solution.

Next, ethylene glycol (EG) was added to this polymer solution, and it concentrated under reduced pressure at 80 degreeC with the evaporator, and produced 20 mass% cast solution.

The cast solution was poured into a petri dish having a diameter of 15.4 cm and dried on a hot plate at 60 ° C. for 1 hour and at 80 ° C. for 1 hour to remove the solvent. Next, the petri dish was placed in an oven and heat treated at 160 ° C. for 1 hour. Thereafter, the membrane was taken out from the oven and poured into a cooled petri dish to peel off the membrane, thereby obtaining a polymer electrolyte membrane having a thickness of about 50 μm.

The obtained polymer electrolyte membrane was measured for proton conductivity, EW, and tensile creep characteristics. The results are shown in Table 1 below.

(Comparative Example 1)
Production of Electrolyte Membrane A polymer electrolyte membrane having a thickness of about 50 μm was obtained in the same manner as in Example 1 except that Nafion® DE2020 (manufactured by DuPont) was used as the electrolyte polymer solution.

The obtained polymer electrolyte membrane was measured for proton conductivity, EW, and tensile creep characteristics. The results are shown in Table 1 below.

(Example 6)
Preparation of electrode catalyst layer An electrode catalyst layer was prepared as follows.

Ethanol was added to the polymer emulsion obtained in Synthesis Example 3 to obtain a 5% by mass fluoropolymer emulsion having a solvent composition of ethanol / water = 50/50 (mass ratio). Next, 7.28 g of the above emulsion was added to 1.00 g of Pt-supported carbon (TEC10E40E, Pt 36.4 wt%, manufactured by Nihon Kunidanaka Kikinzoku Co., Ltd.), and 3.24 g of ethanol was further added. The ink was obtained by mixing well.

This electrode ink was applied on a PTFE sheet by a screen printing method. There were two types of coating amounts: a coating amount in which both the Pt loading amount and the polymer loading amount were 0.15 mg / cm ^2, and a coating amount in which both the Pt loading amount and the polymer loading amount were 0.30 mg / cm ² . After coating, the electrode catalyst layer having a thickness of about 10 μm was obtained by drying at room temperature for 1 hour and in air at 120 ° C. for 1 hour.

Of these electrode catalyst layers, those having both Pt loading and polymer loading of 0.15 mg / cm ² are anode catalyst layers, and those having both Pt loading and polymer loading of 0.30 mg / cm ² are cathodes. A catalyst layer was obtained.

Preparation of MEA The anode catalyst layer and the cathode catalyst layer thus obtained are faced to each other, a polymer electrolyte membrane is sandwiched between them, and hot pressing is performed at 160 ° C. and a surface pressure of 0.1 MPa. The catalyst layer was transferred and joined to a polymer electrolyte membrane (trade name: NRE-212, manufactured by DuPont) to produce an MEA.

As a result of fuel cell evaluation using this MEA, the current density at a voltage of 0.6 V was 1.06 A / cm ² , and the initial characteristics were good.

Peel Test Evaluation Adhesive tape (3M Scotch ™ 898) was adhered to one side of the MEA described above. The end of the MEA and the end of the adhesive tape were set in an autograph (TENSILON), and a 180 degree peel test was performed according to JIS K6854 to measure the peel strength of the electrode catalyst layer. The results are shown in Table 2.

(Example 7)
Preparation of Electrode Catalyst Layer An electrode ink was obtained in the same manner as in Example 6 except that the polymer emulsion obtained in Synthesis Example 4 was used. An electrode catalyst layer and an MEA were produced from this electrode ink in the same manner as in Example 6, and a fuel cell evaluation and a peeling test evaluation were performed. As a result of fuel cell evaluation using this MEA, the current density at a voltage of 0.6 V was 1.00 A / cm ² . The peel test evaluation results are shown in Table 2.

(Example 8)
Preparation of Electrode Catalyst Layer Ethanol was added to the emulsion obtained in Synthesis Example 3 and diluted to a solid content of 5% by mass (water: ethanol = 50.0: 50.0 (mass ratio)) in a 5 L autoclave. The mixture was sealed and heated to 160 ° C. while stirring with a stirring blade, and held for 5 hours. Thereafter, the autoclave was naturally cooled to obtain a 5% by mass uniform electrolyte polymer solution.

Next, this polymer solution was concentrated under reduced pressure at 80 ° C. with an evaporator to prepare an 11 mass% concentrated polymer solution.

Next, 3.31 g of the concentrated polymer solution (ionomer for electrode) was added to 1.00 g of Pt-supported carbon (TEC10E40E, Pt 36.4 wt%, manufactured by Nippon Kuninaka Naka Kikinzoku Co., Ltd.), and further 3.24 g of ethanol. Then, the mixture was mixed well with a homogenizer to obtain an electrode ink.

An electrode catalyst layer and an MEA were produced in the same manner as in Example 6 except that the electrode ink was used, and a fuel cell evaluation and a peel test evaluation were performed. As a result of fuel cell evaluation using this MEA, the current density at a voltage of 0.6 V was 1.06 A / cm ² . The peel test evaluation results are shown in Table 2.

Example 9
Preparation of electrode catalyst layer Ethanol was added to the emulsion obtained in Synthesis Example 4 and diluted to a solid content of 5% by mass (water: ethanol = 50.0: 50.0 (mass ratio)) in a 5 L autoclave. The mixture was sealed and heated to 160 ° C. while stirring with a stirring blade, and held for 5 hours. Thereafter, the autoclave was naturally cooled to obtain a 5% by mass uniform electrolyte polymer solution.

An electrode ink was produced in the same manner as in Example 8 except that the above electrolyte polymer was used. An electrode catalyst layer and an MEA were produced from this electrode ink in the same manner as in Example 6, and a fuel cell evaluation and a peeling test evaluation were performed. As a result of fuel cell evaluation using this MEA, the current density at a voltage of 0.6 V was 1.00 A / cm ² . The peel test evaluation results are shown in Table 2.

(Example 10)
Preparation of electrode catalyst layer Ethanol was added to the emulsion obtained in Synthesis Example 2 and diluted to a solid content of 5% by mass (water: ethanol = 50.0: 50.0 (mass ratio)) in a 5 L autoclave. The mixture was sealed and heated to 160 ° C. while stirring with a stirring blade, and held for 5 hours. Thereafter, the autoclave was naturally cooled to obtain a 5% by mass uniform electrolyte polymer solution.

An electrode ink was produced in the same manner as in Example 8 except that the above electrolyte polymer was used. An electrode catalyst layer and an MEA were produced from this electrode ink in the same manner as in Example 6, and a fuel cell evaluation and a peeling test evaluation were performed. As a result of fuel cell evaluation using this MEA, the current density at a voltage of 0.6 V was 1.03 A / cm ² . The peel test evaluation results are shown in Table 2.

(Example 11)
Preparation of electrode catalyst layer Ethanol was added to the emulsion obtained in Synthesis Example 2 and diluted to a solid content of 5% by mass (water: ethanol = 50.0: 50.0 (mass ratio)) in a 5 L autoclave. The mixture was sealed and heated to 160 ° C. while stirring with a stirring blade, and held for 5 hours. Thereafter, the autoclave was naturally cooled to obtain a 5% by mass uniform electrolyte polymer solution.

An electrode ink was prepared in the same manner as in Example 8 except that the electrolyte polymer was used, and an electrode catalyst layer was prepared in the same manner as in Example 6 except that the electrode ink was used.

Preparation of MEA An electrode catalyst layer and an MEA were prepared in the same manner as in Example 6 except that the polymer electrolyte membrane obtained in Example 5 was used as the electrode catalyst layer and the polymer electrolyte membrane, and fuel cell evaluation was performed. And peel test evaluation. As a result of fuel cell evaluation using this MEA, the current density at a voltage of 0.6 V was 1.10 A / cm ² . The peel test evaluation results are shown in Table 2.

(Comparative Example 2)
An electrode ink was obtained in the same manner as in Example 6 except that Nafion® DE2020 (manufactured by DuPont) was used as the ionomer for the electrode. An electrode catalyst layer and an MEA were produced from this electrode ink in the same manner as in Example 6, and a fuel cell evaluation and a peeling test evaluation were performed. As a result of fuel cell evaluation using this MEA, the current density at a voltage of 0.6 V was 0.7 A / cm ² . The peel test evaluation results are shown in Table 2.

The electrolyte membrane and electrode catalyst layer of the present invention can be suitably used for a solid polymer electrolyte fuel cell.

Claims (9)

An electrolyte membrane for a solid polymer electrolyte fuel cell comprising a fluorine-containing copolymer,
The fluorine-containing copolymer includes a polymer unit (A) based on vinylidene fluoride,
^{_{-CF 2 -C (-O- (CF 2}} CFY 1 -O) n - (CFY 2) m -SO 3 X 1) F- (2)
(Wherein, X ¹ represents H, Na, K or NH ₄ , Y ¹ represents F, Cl or CF ₃ , Y ² represents F or Cl, and n and m are integers of 0 to 2) Represents.)
And at least one polymer unit (C) selected from the group consisting of polymer units based on tetrafluoroethylene and polymer units based on hexafluoropropylene ,
Polymerized units (B) are, Ri 10 to 40 mol% der on the total polymerized units,
The electrolyte membrane , wherein the molar ratio A / (A + C) of the polymerized unit (A) to the polymerized unit (C) is 0.80 to 0.95 . An electrode catalyst layer for a solid polymer electrolyte fuel cell comprising a fluorine-containing copolymer and a fuel cell catalyst,
The fluorine-containing copolymer includes a polymer unit (A) based on vinylidene fluoride,
^{_{-CF 2 -C (-O- (CF 2}} CFY 1 -O) n - (CFY 2) m -SO 3 X 1) F- (2)
(Wherein, X ¹ represents H, Na, K or NH ₄ , Y ¹ represents F, Cl or CF ₃ , Y ² represents F or Cl, and n and m are integers of 0 to 2) Represents.)
And at least one polymer unit (C) selected from the group consisting of polymer units based on tetrafluoroethylene and polymer units based on hexafluoropropylene ,
Polymerized units (B) are, Ri 10 to 40 mol% der on the total polymerized units,
The electrode catalyst layer , wherein the molar ratio A / (A + C) of the polymerized unit (A) to the polymerized unit (C) is 0.50 to 0.90 . The electrode catalyst layer according to claim 2 , wherein the fuel cell catalyst is a catalyst metal. The catalytic metal is at least one metal selected from the group consisting of platinum, gold, silver, palladium, iridium, rhodium, ruthenium, iron, cobalt, nickel, chromium, tungsten, manganese, vanadium, and alloys thereof. Item 4. The electrode catalyst layer according to Item 3 . A membrane electrode assembly comprising the electrolyte membrane according to claim 1 . A membrane electrode assembly comprising the electrode catalyst layer according to claim 2, 3 or 4 . Solid polymer electrolyte fuel cell characterized by comprising the claims 5 or 6, wherein the membrane electrode assembly. A method for producing the electrolyte membrane according to claim 1 , comprising:
Vinylidene fluoride and the following general formula (II)
^{_{CF 2 = CF-O- (CF}} 2 CFY 1 -O) n - (CFY 2) m -SO 3 X 1 (II)
(Wherein, X ¹ represents H, Na, K or NH ₄ , Y ¹ represents F, Cl or CF ₃ , Y ² represents F or Cl, and n and m are integers of 0 to 2) Represents.)
And an at least one monomer selected from the group consisting of tetrafluoroethylene and hexafluoropropylene is radically polymerized in an aqueous medium to obtain an electrolyte emulsion containing a fluorine-containing copolymer. A polymerization process;
Adding an organic solvent to the obtained electrolyte emulsion to obtain an electrolyte solution in which the fluoropolymer is dissolved;
Applying an electrolyte solution to a substrate;
And a step of drying the electrolyte solution applied to the substrate to obtain an electrolyte membrane. A method for producing an electrode catalyst layer according to claim 2, 3 or 4 ,
Vinylidene fluoride and the following general formula (II)
^{_{CF 2 = CF-O- (CF}} 2 CFY 1 -O) n - (CFY 2) m -SO 3 X 1 (II)
(Wherein, X ¹ represents H, Na, K or NH ₄ , Y ¹ represents F, Cl or CF ₃ , Y ² represents F or Cl, and n and m are integers of 0 to 2) Represents.)
And an at least one monomer selected from the group consisting of tetrafluoroethylene and hexafluoropropylene is radically polymerized in an aqueous medium to obtain an electrolyte emulsion containing a fluorine-containing copolymer. A polymerization process;
Adding an organic solvent to the obtained electrolyte emulsion to obtain an electrolyte solution in which the fluorine-containing copolymer is dissolved;
A step of dispersing a fuel cell catalyst in an electrolyte solution to prepare a catalyst composition;
Applying the catalyst composition to the substrate;
And a step of drying the catalyst composition applied to the substrate to obtain an electrode catalyst layer.