JP2008091303A - Membrane electrode assembly for fuel cell and direct methanol type fuel cell using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a membrane electrode assembly having superior power generation characteristics and practical durability, when used for a fuel cell represented by a direct methanol type fuel cell, and to provide a typical utilization method therefor. <P>SOLUTION: The membrane electrode assembly 16 for a fuel cell comprises at least an electrolyte membrane, and a pair of an anode catalyst layer and a cathode catalyst layer sandwiching the electrolyte membrane, wherein the electrolyte membrane contains a hydrocarbon-based electrolyte; the anode catalyst layer contains a hydrocarbon-based electrolyte; and the methanol permeability coefficient of the hydrocarbon-based electrolyte, contained in the anode catalyst layer, is set larger than that of the electrolyte membrane. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a membrane electrode assembly for a fuel cell and a direct methanol fuel cell using the same.

  In recent years, development of highly efficient and clean energy sources has been demanded from the viewpoint of environmental problems such as global warming. Fuel cells are attracting attention as one candidate for this. A fuel cell directly supplies power by supplying a fuel such as hydrogen gas or methanol and an oxidant such as oxygen to electrodes separated by an electrolyte, while oxidizing the fuel on the one hand and reducing the oxidant on the other. is there.

  Among the fuel cell materials described above, one of the most important members is an electrolyte. Various electrolytes have been developed so far to separate such a fuel and an oxidant, and in recent years, an electrolyte composed of a polymer compound containing a proton conductive functional group such as a sulfonic acid group in particular. Development is thriving. In addition to solid polymer fuel cells, direct liquid fuel cells, and direct methanol fuel cells, these electrolytes are also used as raw materials for electrochemical devices such as humidity sensors, gas sensors, and electrochromic display devices. The

  Among these electrolyte utilization methods, solid polymer fuel cells, direct liquid fuel cells, and direct methanol fuel cells are particularly expected as one of the pillars of new energy technology. For example, a polymer electrolyte fuel cell using an electrolyte membrane made of a polymer compound having a proton-conducting functional group has features such as operation at a low temperature and reduction in size and weight. Application to consumer cogeneration systems and consumer small portable devices is under consideration. Direct liquid fuel cells, especially direct methanol fuel cells that use methanol directly as fuel, have features such as a simple structure, ease of fuel supply and maintenance, and high energy density. As an alternative to lithium-ion secondary batteries, it is expected to be applied to small consumer portable devices such as mobile phones and laptop computers.

  Here, as the electrolyte membrane used in the polymer electrolyte fuel cell, there is a styrene-based cation exchange membrane developed in the 1950s, but it has poor stability in the fuel cell operating environment and has a sufficient life. No fuel cell has been produced.

  On the other hand, as an electrolyte membrane having practical stability, a perfluorocarbon sulfonic acid membrane represented by Nafion (registered trademark) has been widely studied. Perfluorocarbon sulfonic acid membranes are said to have high proton conductivity and excellent chemical stability such as acid resistance and oxidation resistance.

  However, since Nafion (registered trademark) is a fluorine-based electrolyte membrane, the raw material used is high, and a complicated manufacturing process is required, so that it is very expensive. In addition, it has been pointed out that Nafion (registered trademark) is deteriorated by hydrogen peroxide generated by an electrode reaction or by a hydroxy radical as a by-product thereof. Further, the permeation (also referred to as crossover) of a hydrogen-containing liquid such as methanol which is a raw material of a direct liquid fuel cell is large, and so-called chemical short reaction occurs. As a result, cathode potential, fuel efficiency, cell characteristics and the like are lowered, and it is difficult to use as an electrolyte membrane of a direct liquid fuel cell such as a direct methanol fuel cell. In addition, Nafion (registered trademark) has a large change in the shape of the film itself, that is, a large swelling. Therefore, mechanical stress is applied to the film itself, which may damage the film. Furthermore, since Nafion (registered trademark) has a high permeability such as a hydrogen-containing liquid, there is a concern that fuel may be lost due to crossover even when power is not generated.

  In order to solve the above problems, various electrolyte membranes have been proposed. For example, Patent Document 1 proposes a sulfonic acid group-containing polyphenylene sulfide that is soluble in an aprotic polar solvent. It is disclosed that by introducing a sulfonic acid group into polyphenylene sulfide under a homogeneous solution of polyphenylene sulfide in chlorosulfonic acid, solubility in an aprotic polar solvent can be imparted and it can be easily processed into a film. However, in the method disclosed here, there is a possibility that solubility in methanol, which is being studied as a fuel for fuel cells, may be imparted to the electrolyte membrane at the same time, and the use range of the electrolyte membrane is significantly restricted. There is a point. In addition, the pertinent effect (also referred to as crossover) of the hydrogen-containing liquid (such as methanol) of the electrolyte membrane described in Patent Document 1 is not mentioned in the patent document, and is described in the patent document. In fact, the electrolyte membrane has a large swellability with respect to a hydrogen-containing liquid such as methanol which is a raw material of a direct liquid fuel cell, and has the same problem as that of Nafion (registered trademark).

  Patent Document 2 discloses a method of filling a polymer porous support with an electrolyte monomer to increase the molecular weight of the monomer, and an electrolyte membrane obtained by the method. Patent Document 3 discloses a method of introducing a sulfonic acid group into a polymer porous support that has been filled with an electrolyte monomer to increase the molecular weight, and an electrolyte membrane obtained by the method. . Since these electrolyte membranes suppress the swelling with respect to methanol and water used as fuel by a porous support, it is said that permeation (crossover) thereof is suppressed. However, since the manufacturing process is complicated, the techniques disclosed in Patent Documents 2 and 3 have problems in terms of manufacturing cost and productivity. In addition, in order to develop sufficient proton conductivity in the electrolyte membrane, it is necessary to increase the content of the proton conductive group in the electrolyte portion. The durability of this portion and the durability of the interface between the electrolyte and the support are required. I am concerned about sex.

Non-patent document 1 reports that Nafion (registered trademark) of DuPont, which is widely used as an electrolyte for a catalyst layer, dissolves in an aqueous methanol solution used directly as a fuel for a methanol fuel cell. Yes. That is, Nafion (registered trademark) is particularly concerned about the durability of the anode catalyst layer that is highly likely to come into contact with a highly concentrated aqueous methanol solution as an electrolyte.
Japanese National Patent Publication No. 11-510198 (Publication date: September 7, 1999) International Publication No. 00/54351 Pamphlet (International Publication Date: September 14, 2000) Japanese Patent Laying-Open No. 2005-5171 (Publication date: January 6, 2005) Shiroma, Fujiwara, Hyakuzo, Yasuda, Miyazaki, The 70th Annual Meeting of the Electrochemical Society of Japan, p. 289, (2003).

  As described above, the structure of a membrane electrode assembly (MEA) used in a solid polymer fuel cell, particularly a direct methanol fuel cell, is sufficient to ensure proton conductivity and hydrogen such as methanol. There is currently a strong demand for the development of an electrolyte membrane that suppresses permeation of contained liquid and the like, and an electrolyte for forming a catalyst layer that does not impede the durability and catalytic reaction of the assumed fuel.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a fuel cell membrane electrode assembly having excellent power generation characteristics and practical durability and a typical application example thereof. .

  MEANS TO SOLVE THE PROBLEM As a result of earnest examination to solve the above-mentioned problems, the inventors of the present invention have at least an electrolyte membrane and a membrane electrode for a fuel cell comprising a pair of an anode catalyst layer and a cathode catalyst layer sandwiching the electrolyte membrane. In the joined body, the electrolyte membrane includes a hydrocarbon-based electrolyte, the anode catalyst layer includes a hydrocarbon-based electrolyte, and the methanol permeability coefficient of the hydrocarbon-based electrolyte included in the anode catalyst layer is determined by the methanol permeation of the electrolyte membrane. The present invention finds that by obtaining a fuel cell membrane electrode assembly having a coefficient greater than the coefficient, the electrolyte membrane can suppress methanol crossover while ensuring high fuel diffusibility in the anode catalyst layer. It came to complete. The present invention has been completed based on such novel findings, and includes the following inventions.

That is, the membrane electrode assembly for a fuel cell according to the present invention is
In a membrane electrode assembly for a fuel cell, comprising at least an electrolyte membrane and a pair of an anode catalyst layer and a cathode catalyst layer sandwiching the electrolyte membrane, the electrolyte membrane includes a hydrocarbon-based electrolyte, and the anode catalyst layer Is a membrane electrode assembly for a fuel cell, comprising a hydrocarbon electrolyte, wherein the methanol permeability coefficient of the hydrocarbon electrolyte contained in the anode catalyst layer is larger than the methanol permeability coefficient of the electrolyte membrane.

  In the membrane electrode assembly for a fuel cell according to the present invention, the electrolyte membrane has a proton conductive group in a polymer film containing a polymer compound having an aromatic unit and a polymer compound not having an aromatic unit. An introduced electrolyte membrane may be used.

  The membrane electrode assembly for a fuel cell according to the present invention includes a porous support in which the electrolyte membrane has at least continuous pores, and a hydrocarbon system filled in the pores of the porous support. It may be an electrolyte membrane containing an electrolyte.

  In the fuel cell membrane electrode assembly according to the present invention, the hydrocarbon electrolyte contained in the anode catalyst layer is a hydrocarbon system in which a proton conductive group is introduced into at least a polymer compound having an aromatic unit. It may be an electrolyte.

  The proton conductive group may contain a sulfonic acid group.

  By using the fuel cell membrane electrode assembly according to the present invention, as described later, while maintaining the electrochemical reactivity in the anode catalyst layer and having sufficient proton conductivity, methanol crossover It becomes possible to obtain a membrane electrode assembly for a fuel cell capable of suppressing the above.

  In the membrane electrode assembly for a fuel cell according to the present invention, the hydrocarbon electrolyte contained in the anode catalyst layer is a reaction product of a hydrocarbon electrolyte and a crosslinking agent capable of crosslinking reaction with the hydrocarbon electrolyte. It is preferable that a thing is included.

In the membrane electrode assembly for a fuel cell according to the present invention, the hydrocarbon electrolyte contained in the anode catalyst layer preferably has a weight reduction rate of 8% or less after being immersed in methanol at 60 ° C. for 50 hours.
The said aspect can enjoy the effect that the chemical deterioration by methanol can be suppressed, maintaining the diffusibility of methanol in an anode catalyst layer.

The membrane electrode assembly for a fuel cell according to the present invention may include a diffusion layer on the outside of the anode catalyst layer and on the outside of the cathode catalyst layer.
According to the above aspect, it is possible to uniformly supply the fuel to the anode catalyst layer and the oxidant to the cathode catalyst layer, and enjoy the effect that the reactant can be efficiently supplied onto the catalyst surface in the catalyst layer. it can.

  A direct methanol fuel cell according to the present invention uses the fuel cell membrane electrode assembly according to the present invention. Therefore, the fuel cell according to the present invention can suppress the crossover of methanol while having sufficient proton conductivity while ensuring excellent fuel diffusibility to the anode catalyst layer, and has excellent power generation characteristics. Can be expressed.

  According to the present invention, in a membrane electrode assembly for a fuel cell comprising at least an electrolyte membrane and a pair of anode catalyst layer and cathode catalyst layer sandwiching the electrolyte membrane, the electrolyte membrane comprises a hydrocarbon-based electrolyte. The anode catalyst layer contains a hydrocarbon-based electrolyte, and the methanol permeability coefficient of the hydrocarbon-based electrolyte contained in the anode catalyst layer is larger than the methanol permeability coefficient of the electrolyte membrane. It is possible to obtain a fuel cell membrane electrode assembly capable of suppressing methanol crossover while maintaining electrochemical reactivity and having sufficient proton conductivity.

  Therefore, the present invention can be used in the field of fuel cells, and can be preferably used particularly for direct methanol fuel cells.

  Note that, in a membrane electrode assembly for a fuel cell including at least an electrolyte membrane and a pair of anode catalyst layer and cathode catalyst layer sandwiching the electrolyte membrane, the electrolyte membrane includes a hydrocarbon-based electrolyte, and the anode In the fuel cell membrane electrode assembly in which the catalyst layer includes a hydrocarbon electrolyte, and the methanol permeability coefficient of the hydrocarbon electrolyte contained in the anode catalyst layer is the methanol permeability coefficient of the electrolyte membrane is “below”, As a result of the difficulty in permeating methanol in the anode catalyst layer, for example, the rate of methanol permeation in the anode catalyst layer is limited, the electrochemical reactivity in the anode catalyst layer is impaired, and the original reactivity of the anode catalyst can be exhibited. It may disappear. Therefore, as in the present invention, the fuel cell membrane electrode assembly in which the methanol permeability coefficient of the hydrocarbon-based electrolyte contained in the anode catalyst layer is “greater than” the methanol permeability coefficient of the electrolyte membrane is a direct methanol fuel. It is preferably used as a battery.

  An embodiment of the present invention will be described as follows. It should be noted that the present invention is not limited to the following description.

<1. Fuel Cell Membrane Electrode Assembly According to the Present Invention>
That is, a fuel cell membrane electrode assembly according to the present invention (hereinafter referred to as “membrane electrode assembly of the present invention”) includes at least an electrolyte membrane, a pair of anode catalyst layer and cathode catalyst layer sandwiching the electrolyte membrane, In the membrane electrode assembly for a fuel cell, the electrolyte membrane contains a hydrocarbon electrolyte, the anode catalyst layer contains a hydrocarbon electrolyte, and the methanol permeability coefficient of the hydrocarbon electrolyte contained in the anode catalyst layer However, the specific structure such as other production conditions, components, materials, and blending ratios is not particularly limited as long as it is larger than the methanol permeability coefficient of the electrolyte membrane.

  That is, the membrane electrode assembly of the present invention comprises a membrane electrode assembly (three-layer membrane electrode) comprising at least “an electrolyte membrane containing a hydrocarbon-based electrolyte”, “an anode catalyst layer containing a hydrocarbon-based electrolyte” and “a cathode catalyst layer”. In some cases, it is expressed as a joined body, a three-layer MEA, a CCM, or the like. Furthermore, it is a membrane / electrode assembly including “diffusion layers” on the outside of the anode and cathode catalyst layers (sometimes referred to as a 5-layer membrane / electrode assembly, 5-layer MEA, etc.). Further, the present invention may be expressed as a membrane electrode assembly (a seven-layer membrane electrode assembly, a seven-layer MEA, etc.) in which a “gasket” is disposed in a portion in contact with the electrolyte membrane in the peripheral portion of the catalyst layer. .) Is also included in the category. Hereinafter, each component will be explained.

(1-1) Electrolyte Membrane Containing Hydrocarbon Electrolyte First, the hydrocarbon electrolyte contained in the electrolyte membrane in the membrane electrode assembly will be specifically described. Such a hydrocarbon electrolyte is literally a hydrocarbon electrolyte known to those skilled in the art, and has a methanol permeability coefficient smaller than that of the hydrocarbon electrolyte contained in the anode catalyst layer of the present invention. Other specific configurations are not particularly limited. For example, a hydrocarbon electrolyte in which a proton conductive group is introduced into a polymer compound having an aromatic unit can be exemplified. The polymer compound having an aromatic unit is literally a polymer compound having a conventionally known aromatic unit for those skilled in the art, and other specific configurations are not particularly limited. Examples of the polymer compound having an aromatic unit include polyaryl ether sulfone, polyether ether sulfone, polyether ketone, polyether ketone ketone, polysulfone, polyparaphenylene, polyphenylene sulfide, polyphenylene ether, polyphenylene sulfoxide, polyphenylene sulfide. Sulfone, polyphenylenesulfone, polybenzimidazole, polybenzoxazole, polybenzothiazole, polystyrene, syndiotactic polystyrene, polyethersulfone, styrene- (ethylene-butylene) styrene copolymer, styrene- (polyisobutylene) -styrene copolymer Union, poly 1,4-biphenylene ether ether sulfone, polyarylene ether sulfone, polyimide, polyether Imide, cyanate ester resin, polyether ether ketone, polyethylene-polystyrene graft copolymer, polyethylene-polystyrene block copolymer, polypropylene-polystyrene graft copolymer, (ethylene-glycidyl methacrylate) -polystyrene graft copolymer, Ethylene-ethyl acrylate) -polystyrene graft copolymer, polypropylene- (acrylonitrile-styrene) graft copolymer, polycarbonate-polystyrene graft copolymer, polycarbonate- (acrylonitrile-styrene) graft copolymer, vinyl acetate resin-polystyrene block Copolymer, acrylic resin-polystyrene block copolymer, Modiper series (manufactured by NOF Corporation, registered trademark), Epofriendcy (Manufactured by Daicel Chemical Co., Ltd.), and the like. In particular, chemical stability and thermal stability, ease of introduction of proton-conductive substituents, proton conductivity of the resulting proton-conductive polymer electrolyte, and methanol of the resulting proton-conductive polymer electrolyte membrane In consideration of blocking properties, the polymer compound having an aromatic unit is preferably one polymer selected from the following (i) to (iii), or a mixture of these polymers.
(I) at least one polymer selected from the group of polymers consisting of polystyrene, syndiotactic polystyrene, polyphenylene ether, modified polyphenylene ether, polysulfone, polyethersulfone, polyetheretherketone, and polyphenylene sulfide;
(Ii) a copolymer comprising the polymer described in (i) above;
(Iii) Derivatives of the polymers described in (i) and (ii) above.

  In particular, from the viewpoints of thermal and chemical stability, industrial availability, and proton conductivity of the obtained electrolyte membrane, the polymer compound having the aromatic unit is most preferably polyphenylene sulfide.

  The electrolyte membrane used in the membrane / electrode assembly of the present invention is more preferably composed of a combination of different materials in order to achieve excellent proton conductivity and high methanol barrier properties.

  Specifically, an electrolyte membrane in which a proton conductive group is introduced into a polymer film containing a polymer compound having an aromatic unit and a polymer compound not having an aromatic unit is used as the membrane electrode junction of the present invention. It is preferable to use it for the body. In the electrolyte membrane having this configuration, a proton conductive group such as a sulfonic acid group is introduced into a portion having an aromatic unit, but a proton conductive group such as a sulfonic acid group is introduced into a portion having no aromatic unit. It will not be done. Therefore, the electrolyte membrane obtained from the polymer film has a structure that hardly swells with respect to water or an aqueous methanol solution even though a hydrophilic proton conductive group such as a sulfonic acid group is introduced. An electrolyte membrane having a barrier property can be obtained. Here, the polymer compound having an aromatic unit used in the electrolyte membrane is literally a polymer compound having an aromatic unit conventionally known to those skilled in the art. It is not limited. As the polymer compound having an aromatic unit, for example, those similar to those exemplified for the hydrocarbon electrolyte are preferable.

  The electrolyte membrane preferably has a sea-island structure in which a polymer compound having an aromatic unit is dispersed in a polymer compound not having an aromatic unit, from the viewpoint of further improving methanol barrier properties. Swelling of a polymer compound having an aromatic unit having a sulfonic acid group introduced in an island portion can be suppressed by a polymer compound having no aromatic unit in the sea portion that is difficult to swell with methanol or the like.

  On the other hand, the polymer compound having no aromatic unit (polymer compound having no aromatic unit) applied to the electrolyte membrane used in the membrane electrode assembly of the present invention literally has no aromatic unit in the structure. It means a compound. Whether or not an aromatic unit is contained in the polymer compound can be easily confirmed by a known method such as NMR, so that "polymer compound not having an aromatic unit" and "aromatic unit" Those skilled in the art can easily understand the “polymer compound having”. Examples of the polymer compound having no aromatic unit include ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 3-methyl-1-butene, 4-methyl-1-pentene, and 5-methyl. A homopolymer of α-olefin such as -1-heptene or a polyolefin resin including these copolymers, cyclic polyolefin such as norbornene resin, polyvinyl chloride; vinyl chloride-vinyl acetate copolymer; vinyl chloride-chloride Vinylidene copolymer; vinyl chloride resin including vinyl chloride-olefin copolymer, nylon 6; polyamide resin including nylon 66 and the like; and polytetrafluoroethylene; tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer; Tetrafluoroethylene-exafluoropropylene copolymer Coalescing; tetrafluoroethylene - ethylene copolymer; polychlorotrifluoroethylene; polyvinylidene fluoride; and fluorine-based resins such as polyvinyl fluoride and the like.

  The polymer compound having no aromatic unit is compatible or dispersible with other polymer compound components, processability when producing a polymer film, handling property of the resulting polymer film, and further obtained therefrom. Considering the methanol barrier property, chemical stability, thermal stability, etc. of the electrolyte membrane, one polymer selected from polymer compounds having a repeating unit of the following general formula (1), or a mixture thereof: It is particularly preferred.

-(CX ₁ X ₂ -CX ₃ X ₄ )-(1)
(Wherein, X ₁ ~ ₄ is, H, based on any one of _{CH 3, Cl, F, OCOCH} 3, CN, COOH, COOCH 3, and OC ₄ H _9, is selected from the group consisting of, X ₁ ~ ₄ may be the same or different from each other)
Furthermore, considering the industrial availability, the mechanical properties and handling properties of the resulting polymer film, the proton conductivity, methanol blocking properties, and chemical stability of the resulting electrolyte membrane, the above aromatic units are present. Preferably, the polymer compound that does not include polyethylene and / or polypropylene.

  In particular, from the viewpoint of workability, chemical stability, balance of proton conductivity and methanol blocking property, polyphenylene sulfide, which is a polymer compound having the aromatic unit, and a polymer not having the aromatic unit A combination with the compound polyethylene is most preferred. The weight ratio of polyphenylene sulfide to polyethylene is 5 parts by weight or more of polyethylene with respect to 100 parts by weight of polyphenylene sulfide, from the viewpoint of obtaining an electrolyte membrane having a good appearance and the balance between proton conductivity and methanol blocking property. The amount is preferably 500 parts by weight or less.

  Various additives commonly used in the production of polymer films, such as compatibilizers for improving compatibility, antioxidants for preventing resin deterioration, and antistatics for improving handling in film processing Agents, lubricants and the like can be appropriately used as long as they do not affect the processability and performance of the electrolyte membrane. In particular, when a polymer resin film is produced by combining different materials, it is preferable to use a compatibilizing agent in order to increase the compatibility.

In the membrane electrode assembly for a fuel cell comprising at least the electrolyte membrane of the present invention and a pair of anode catalyst layer and cathode catalyst layer sandwiching the electrolyte membrane,
The “electrolyte membrane includes a hydrocarbon-based electrolyte” and “the anode catalyst layer includes a hydrocarbon-based electrolyte” are preferable from the viewpoint of reducing the solubility in methanol. When the anode catalyst layer does not contain a hydrocarbon-based electrolyte and a conventional perfluorocarbon sulfonic acid-based electrolyte is used, there is a problem that the anode catalyst layer is soluble in a high-concentration methanol aqueous solution or a high-temperature methanol aqueous solution. When the catalyst layer contains a hydrocarbon-based electrolyte, the conventional problem of dissolution in a methanol aqueous solution can be solved.

The electrolyte membrane used in the membrane electrode assembly of the present invention is an electrolyte membrane comprising a porous support having continuous pores and a hydrocarbon-based electrolyte filled in the pores of the porous support. It is preferable that In the electrolyte membrane having this configuration, the hydrocarbon electrolyte is constrained by the pores of the porous support, and therefore, the electrolyte membrane has a configuration that hardly swells with respect to water or an aqueous methanol solution and has a high methanol barrier property. Can be obtained.

  Here, the porous support used for the electrolyte membrane may literally be a porous support conventionally known to those skilled in the art, and the other specific configurations are not particularly limited. Examples of the porous support include polyimide, polyetherimide, polysulfone, polyethersulfone, polyarylethersulfone, polyphenylene ether, polyphenylene sulfide, polyetherketone, polyetheretherkenton, polybenzimidazole, polybenzoxazole, Listed are porous supports such as polybenzthiazole, polyquinoxaline, polyphenylquinoxaline, polytetrafluoroethylene, polyethylene, and polypropylene. Moreover, the porous body which consists of an inorganic compound which has porous glass, a silica, and an alumina as a main component can also be used. Among these, polytetrafluoroethylene, polyethylene, polyimide and polytetrafluoroethylene are preferred because of their ease of filling with hydrocarbon electrolytes, heat resistance, chemical stability, resistance to swelling with water and methanol, and industrial availability. It is preferable to include at least one selected from the group consisting of benzoxazole. In order to control the elastic modulus and improve heat resistance and chemical stability, these may be used by introducing or modifying a crosslinked structure.

  The hydrocarbon electrolyte filled in the porous support may literally be a hydrocarbon electrolyte that is conventionally known to those skilled in the art, and the other specific configuration is not particularly limited. For example, as described above, a hydrocarbon-based electrolyte in which a proton conductive group is introduced into a polymer compound having an aromatic unit can be used.

  In addition, as the hydrocarbon electrolyte to be filled in the porous support, a crosslinked electrolyte polymer having 2-methacrylamide-2-methylpropanesulfonic acid or a salt thereof as an essential constituent monomer can be used.

In the membrane electrode assembly of the present invention, examples of proton conductive groups include sulfonic acid groups (—SO ₃ H), carboxyl groups (—COOH), phenolic hydroxyl groups (Ph (OH): Ph represents a phenyl group). _{, -PO (OH) 2, -POH} (OH), - SO 2 NHSO 2 - cation exchange groups such as can be enumerated. Of these, a sulfonic acid group is preferable in view of proton conductivity and ease of introduction thereof.

(1-2) Anode Catalyst Layer Containing Hydrocarbon Electrolyte Next, the anode catalyst layer containing the hydrocarbon electrolyte in the membrane electrode assembly of the present invention will be specifically described. Such an anode catalyst layer is composed of at least a fuel cell anode catalyst and a hydrocarbon-based electrolyte. A non-electrolyte binder, a water repellent, a dispersant, and the like may be included as necessary.

  Such an anode catalyst for a fuel cell is literally a conventionally known anode catalyst for a fuel cell for those skilled in the art. Other specific configurations are not particularly limited. For example, a noble metal such as platinum or ruthenium or an alloy thereof can be exemplified as a catalyst, and these include conductive particles having a high specific surface area such as activated carbon, carbon black, ketjen black, vulcan, carbon nanohorn, fullerene, and carbon nanotube. Used as a carrier. A co-catalyst for promoting catalyst activity or suppressing poisoning by reaction by-products may be added.

  Such a hydrocarbon electrolyte is literally a hydrocarbon electrolyte conventionally known to those skilled in the art, except that the methanol permeability coefficient is larger than the methanol permeability coefficient of the electrolyte membrane used in the membrane electrode assembly of the present invention. The specific configuration of is not particularly limited. For example, a hydrocarbon electrolyte similar to that described in “(1-1) Electrolyte membrane containing hydrocarbon electrolyte” can be used.

  Note that “the methanol permeability coefficient of the hydrocarbon-based electrolyte contained in the anode catalyst layer is larger than the methanol permeability coefficient of the electrolyte membrane” literally means. “The methanol permeability coefficient of the hydrocarbon-based electrolyte contained in the anode catalyst layer” and “the methanol permeability coefficient of the electrolyte membrane” are values that can be measured independently.

  In addition, a copolymer of an unsaturated hydrocarbon monomer and acrylamide containing a proton conductive group can be exemplified. Such an unsaturated hydrocarbon monomer is literally an unsaturated hydrocarbon monomer conventionally known to those skilled in the art, and other specific configurations are not particularly limited. That is, it may be appropriately selected in consideration of the proton conductivity, methanol permeability coefficient, catalyst dispersibility, thermal / chemical stability, catalyst layer formability, etc. of the obtained electrolyte. it can. Acrylamide containing such a proton conductive group is represented by the following general formula (2).

ここで、Ｒ₁に入る基は特に限定されず、水素あるいはアルキル基でも良い。アルキル基は特に限定されず、直鎖である場合には、メチル、エチル、プロピル、ブチル、あるいはペンチルなどで例示され、分岐した場合には、２−メチルプロピル、２−エチルプロピル、２−メチルブチル、３−メチルブチルなどが例示される。これらは、単独、あるいは複数用いても良い。

Here, the group entering R ₁ is not particularly limited, and may be hydrogen or an alkyl group. The alkyl group is not particularly limited, and when it is linear, it is exemplified by methyl, ethyl, propyl, butyl, pentyl, etc., and when branched, 2-methylpropyl, 2-ethylpropyl, 2-methylbutyl , 3-methylbutyl and the like. These may be used alone or in combination.

The alkyl group entering R ₂ is not particularly limited, and when it is linear, it is exemplified by methyl, ethyl, propyl, butyl, pentyl, etc., and when branched, 2-methylpropyl, 2-ethylpropyl , 2-methylbutyl, 3-methylbutyl and the like. These may be used alone or in combination. Such a copolymer is not particularly limited, but a copolymer obtained by block copolymerization, random copolymerization, or graft copolymerization by a known method such as anionic polymerization, cationic polymerization, coordination polymerization, radical polymerization or the like is employed without any particular limitation. .

Examples of proton conductive groups entering P include sulfonic acid groups (—SO ₃ H), carboxyl groups (—COOH), phenolic hydroxyl groups (Ph (OH): Ph represents a phenyl group), —PO (OH) ₂ , cation exchange groups such as —POH (OH) and —SO ₂ NHSO ₂ — can be listed. Of these, a sulfonic acid group is preferred in view of proton conductivity and ease of introduction thereof.

Moreover, in the membrane electrode assembly of the present invention, the hydrocarbon electrolyte contained in the anode catalyst layer may contain a reactive organism of a hydrocarbon electrolyte and a crosslinking agent capable of crosslinking reaction with the hydrocarbon electrolyte. preferable. Such a crosslinking agent is not particularly limited as long as it can undergo a crosslinking reaction with the hydrocarbon-based electrolyte. For example, the hydrocarbon electrolyte is a hydrocarbon system in which a proton conductive group is introduced into a polymer compound having an aromatic unit described in “(1-1) Electrolyte membrane containing a hydrocarbon electrolyte”. In the case of “electrolyte”, “at least one compound X having two or more groups represented by the following general formula (3):
-CH ₂ OR (3)
(In the formula, R represents hydrogen, an alkyl group, or an acyl group, and Rs contained in one kind of compound are each independent and may be the same or different from each other). Can be used.

Examples of the compound X include 1,2-bis (hydroxymethyl) benzene, 1,3-bis (hydroxymethyl) benzene, 1,4-bis (hydroxymethyl) benzene, 2,6-bis ( Hydroxymethyl) phenol, 3,5-bis (hydroxymethyl) phenol, 4,6-bis (hydroxymethyl) -o-cresol, 2,6-bis (hydroxymethyl) -p-cresol, 2,6-bis ( Hydroxymethyl) -4-t-butylphenol, 2,2′-bis (hydroxymethyl) diphenyl ether, 4,4′-bis (hydroxymethyl) diphenyl ether, 1,2,4-benzenetrimethanol, 1,3,5- Benzene trimethanol, 4,4′-methylenebis [2,6-di (hydroxymethyl)] phenol, oxybi (3,4-dihydroxymethyl) benzene, 1,2-bis (methoxymethyl) benzene, 1,3-bis (methoxymethyl) benzene, 1,4-bis (methoxymethyl) benzene, 2,6-bis (methoxy) Methyl) -p-cresol, 2,6-bis (methoxymethyl) -4-tert-butylphenol, 2,4,6-tris [bis (methoxymethyl) amino] -1,3,5-triazine, Cymel (registered) Trademarks, manufactured by Nippon Cytec Industries Co., Ltd., DML-PC (manufactured by Honshu Chemical Industry Co., Ltd.), TML-BPA-MF (manufactured by Honshu Chemical Industry Co., Ltd.), TML-BPAF-MF (manufactured by Honshu Chemical Industry Co., Ltd.), DML-OC (made by Honshu Chemical Industry Co., Ltd.), Dimethymethyl p-CR (made by Honshu Chemical Industry Co., Ltd.), DML-MBP (Honshu Chemical Industry Co., Ltd.), DML-BPC (Honshu Chemical Industry Co., Ltd.), TML-BP (Honshu Chemical Industry Co., Ltd.), TMOM-BP (Honshu Chemical Industry Co., Ltd.), DML-PEP (Honshu) Chemical Industry Co., Ltd.), DML-34X (Honshu Chemical Industry Co., Ltd.), DML-PSBP (Honshu Chemical Industry Co., Ltd.), DML-PTBP (Honshu Chemical Industry Co., Ltd.), DML-PCHP (Honshu Chemical Industry Co., Ltd.) Co., Ltd.), DML-POP (Honshu Chemical Industry Co., Ltd.), DML-PFP (Honshu Chemical Industry Co., Ltd.), DML-MBOC (Honshu Chemical Industry Co., Ltd.), HML-TPPHBA (Honshu Chemical Industry Co., Ltd.) ), HMOM-TPPHBA (manufactured by Honshu Chemical Industry Co., Ltd.), 26DMPC (manufactured by Asahi Organic Materials Co., Ltd.), 46DMOC (Asahi Organic Material Industries Co., Ltd.) DM-BIPC-F (Asahi Organic Material Industries Co., Ltd.), DM-BIOC-F (Asahi Organic Material Industries Co., Ltd.), TM-BIP-A (Asahi Organic Material Industries Co., Ltd.), Nikarak (Manufactured by Sanwa Chemical Co., Ltd.) can be exemplified, but is not limited thereto. Furthermore, although partially overlapping with the above, compound X can also be exemplified by compounds represented by the following chemical formula. That is, for example, 44 types of compounds represented by the following structural formulas (4) to (47) (wherein R ^{2 to} R ⁷ each represent hydrogen or a methyl group in the structural formula (33)) can be exemplified. It is not limited only to these.

これらの化合物は１種類であっても複数であってもかまわない。これらのなかで、入手の容易さや前記「芳香族単位を有する高分子化合物にプロトン伝導性基が導入されてなる炭化水素系電解質」との反応性、前記「芳香族単位を有する高分子化合物にプロトン伝導性基が導入されてなる炭化水素系電解質」との反応生成物の耐熱性やメタノールなどの水素含有液体に対する膨潤性・溶解性や透過性の抑制効果などを考慮すると、下記構造式（３８）〜（４７）で示される１０種類の化合物

These compounds may be one kind or plural. Among these, availability and reactivity with the above-mentioned “hydrocarbon electrolyte in which a proton-conducting group is introduced into a polymer compound having an aromatic unit” and the above “polymer compound having an aromatic unit” Considering the heat resistance of the reaction product with the "hydrocarbon electrolyte into which proton-conducting groups are introduced" and the effect of suppressing swelling, solubility, and permeability in hydrogen-containing liquids such as methanol, the following structural formula ( 38)-(47) 10 kinds of compounds

からなる群から選択される少なくとも１種以上であることが特に好ましい。

Particularly preferred is at least one selected from the group consisting of

  Further, in the membrane / electrode assembly of the present invention, it is preferred that the hydrocarbon electrolyte contained in the anode catalyst layer has a weight reduction rate of 8% or less after being immersed in methanol at 60 ° C. for 50 hours. If the weight loss of the hydrocarbon-based electrolyte is larger than the above range, there is a possibility that the proton conductivity is lowered and it is difficult to maintain the shape of the catalyst layer, leading to a decrease in the performance of the membrane electrode assembly.

(1-3) Cathode catalyst layer Next, the cathode catalyst layer containing a hydrocarbon-based electrolyte in the membrane electrode assembly of the present invention will be specifically described. Such a cathode catalyst layer is composed of at least a fuel cell cathode catalyst and an electrolyte. A non-electrolyte binder, a water repellent, a dispersant, and the like may be included as necessary.

  Such a fuel cell cathode catalyst may literally be a fuel cell cathode catalyst conventionally known to those skilled in the art, and the other specific configuration is not particularly limited. For example, a noble metal such as platinum or an alloy thereof can be exemplified as a catalyst, and these are carriers made of conductive particles having a high specific surface area such as activated carbon, carbon black, ketjen black, vulcan, carbon nanohorn, fullerene, and carbon nanotube. It is used when being carried on. A co-catalyst for promoting catalyst activity or suppressing poisoning by reaction by-products may be added.

  Such an electrolyte is literally a conventionally known electrolyte for those skilled in the art, and other specific configurations are not particularly limited. For example, perfluorocarbon sulfonic acid represented by DuPont's Nafion (registered trademark) or a hydrocarbon electrolyte similar to that described in “(1-2) Anode catalyst layer containing hydrocarbon electrolyte” can be used. It is.

When a hydrocarbon electrolyte is used in the cathode catalyst layer, the magnitude relationship between the methanol permeability coefficient of the hydrocarbon electrolyte used in the cathode catalyst layer and the methanol permeability coefficient of the electrolyte membrane is not particularly limited. Membrane electrode assembly of the present invention Preferably, a diffusion layer is provided outside the anode catalyst layer and outside the cathode catalyst layer. Such a diffusion layer may literally be a diffusion layer conventionally known to those skilled in the art, and the other specific configuration is not particularly limited. For example, a porous conductive material such as carbon cloth or carbon paper can be used. In order to promote the diffusibility of the fuel and the oxidant and the discharge of reaction by-products and unreacted substances, it is preferable to use those which are coated with tetrafluoroethylene or the like to impart water repellency. In addition, different types of diffusion layers may be used on the anode side and the cathode side, respectively.

  As described above, as the membrane electrode assembly of the present invention, a three-layer membrane electrode assembly composed of an electrolyte membrane and a pair of anode catalyst layer and cathode catalyst layer sandwiching the electrolyte membrane, and the electrolyte, A five-layer membrane electrode assembly composed of a pair of anode and cathode catalyst layers sandwiching the electrolyte membrane and a pair of diffusion layers disposed outside the catalyst layer has been described.

  Further, a microporous layer that is conventionally known to those skilled in the art and that is composed of at least conductive carbon particles and a water repellent agent is provided between the diffusion layer and the catalyst layer as necessary. It is added that a seven-layer membrane electrode assembly constituted by arranging a pair of gaskets on the electrolyte membrane is also within the scope of the present invention.

<2. Utilization of Membrane / Electrode Assembly According to the Present Invention>
The membrane electrode assembly according to the present invention can be used in various industries, and its use (use) is not particularly limited. For example, a direct methanol type using the membrane electrode assembly is used. Mention may be made of fuel cells. Such a direct methanol fuel cell can be used, for example, as a power source for a small consumer portable device such as a mobile phone or a notebook personal computer, or in a general power generator for leisure or construction.

  That is, the present invention may include a direct methanol fuel cell using the membrane electrode assembly.

  According to the membrane electrode assembly and the direct methanol fuel cell, the electrolyte membrane having both excellent proton conductivity and high methanol barrier property as described above, excellent proton conductivity and high methanol diffusibility, and methanol resistance. Since it is composed of the anode catalyst layer electrolyte provided, it has high power generation characteristics and excellent long-term durability.

  Next, an embodiment of a polymer electrolyte fuel cell using the membrane electrode assembly of the present invention will be described with reference to the drawings. In the present embodiment, a solid polymer fuel cell will be described as an example, but a direct liquid fuel cell and a direct methanol fuel cell can also be implemented in the same manner as a solid polymer fuel cell. .

  FIG. 1 is a diagram schematically showing a cross-sectional structure of a main part of a polymer electrolyte fuel cell using a membrane electrode assembly according to the present embodiment. As shown in the figure, a polymer electrolyte fuel cell 10 according to the present embodiment includes an electrolyte membrane 1, catalyst layers 2 and 2, diffusion layers 3 and 3, and separators 4 and 4.

  The electrolyte membrane 1 is located at the approximate center of the cell of the polymer electrolyte fuel cell 10. The catalyst layer 2 is provided in contact with the electrolyte membrane 1. The diffusion layer 3 is provided adjacent to the catalyst layer 2, and a separator 4 is disposed on the outer side thereof. The separator 4 is formed with a flow path 5 for feeding fuel gas or liquid (such as aqueous methanol solution) and an oxidant. In other words, these members are configured as cells of the polymer electrolyte fuel cell 10.

  In general, the one in which the catalyst layer 2 is joined to the electrolyte membrane 1 or the one in which the catalyst layer 2 and the diffusion layer 3 are joined to the electrolyte membrane 1 is called a membrane electrode assembly, and is a polymer electrolyte fuel cell (direct liquid Used as a basic member of a fuel cell and a direct methanol fuel cell).

  A method for producing a membrane electrode assembly has been studied in the past by electrolyte membranes made of perfluorocarbon sulfonic acid and other hydrocarbon electrolyte membranes (for example, sulfonated polyetheretherketone, sulfonated polyethersulfone, sulfonated). Polysulfone, sulfonated polyimide, sulfonated polyphenylene sulfide, etc.) can be used.

  An example of a specific method for producing a membrane electrode assembly is shown below, but the present invention is not limited to this.

  One embodiment of the formation of the catalyst layer 2 is to disperse the fuel cell catalyst in an electrolyte solution or dispersion and apply it on a release film such as fluoroethylene by spraying to dry and remove the solvent in the dispersion. The predetermined catalyst layer 2 is formed on the release film. The catalyst layer 2 formed on the release film is disposed on both surfaces of the electrolyte membrane 1 and hot-pressed under predetermined heating and pressurizing conditions to join the polymer electrolyte membrane 1 and the catalyst layer 2 to release the release film. By peeling off, a three-layer membrane electrode assembly in which the catalyst layer 2 is formed on both surfaces of the electrolyte membrane 1 can be produced.

  Also, a catalyst-carrying gas diffusion electrode in which the dispersion solution is coated on the diffusion layer 3 using a coater or the like, the solvent in the dispersion solution is dried and removed, and the catalyst layer 2 is formed on the diffusion layer 3 And the catalyst layer 2 side of the catalyst-carrying gas diffusion electrode is disposed on both sides of the electrolyte membrane 1 and hot-pressed under predetermined heating and pressurizing conditions. A five-layer membrane electrode assembly in which the diffusion layer 3 is formed can be manufactured.

  As the electrolyte solution, an alcohol solution of a perfluorocarbon sulfonic acid polymer compound (such as Nafion (registered trademark) solution manufactured by Aldrich) or an organic solvent solution of a hydrocarbon electrolyte contained in the anode catalyst layer described above can be used. .

  The dispersion solution for forming the catalyst layer may be appropriately diluted with water or an organic solvent in order to adjust the viscosity so that it can be easily applied by spraying or coated by a coater. Moreover, in order to impart water repellency to the catalyst layer 2 as necessary, a fluorine-based compound such as tetrafluoroethylene is mixed, or the hydrocarbon-based electrolyte is improved to improve chemical stability such as methanol resistance. These crosslinking agents may be mixed, or a dispersant for improving the dispersibility by suppressing the aggregation of the fuel cell catalyst may be mixed.

  Further, an adhesive layer made of an electrolyte as described above may be provided between the electrolyte membrane 1 and the catalyst layer 2 as necessary.

  The conditions for hot pressing the electrolyte membrane 1 and the catalyst layer 2 under heating and pressurizing conditions need to be appropriately set according to the type of electrolyte contained in the electrolyte membrane 1 and the catalyst layer 2 to be used. In general, the temperature is lower than the thermal degradation or thermal decomposition temperature of the electrolyte contained in the electrolyte membrane or the catalyst layer, and is higher than the glass transition point or softening point of the electrolyte contained in the electrolyte membrane or the catalyst layer. Or it is preferable to implement on temperature conditions more than the glass transition point and softening point of the electrolyte contained in a catalyst layer.

  As the pressurizing condition, it is preferable that the pressure is in the range of about 0.1 MPa or more and 20 MPa or less because the electrolyte membrane 1 and the catalyst layer 2 are in sufficient contact with each other and there is no deterioration in characteristics due to significant deformation of the materials used. Further, in the case of a three-layer membrane electrode assembly formed only from the electrolyte membrane 1 and the catalyst layer 2, the diffusion layer 3 is disposed outside the catalyst layer 2 and used only by contacting without being joined. It doesn't matter.

  By inserting the membrane electrode assembly obtained by the above method between a pair of separators 4 and the like in which a flow path 5 for feeding fuel gas or liquid and an oxidant is formed, this embodiment The polymer electrolyte fuel cell 10 according to the above is obtained.

  As the separator 4, a conductive material such as carbon graphite or stainless steel can be used. In particular, when a metal material such as stainless steel is used, it is preferable to perform a corrosion resistance treatment.

  For the polymer electrolyte fuel cell 10 described above, a gas containing hydrogen as a main component or a gas or liquid containing methanol as a main component as a fuel gas or liquid, and a gas containing oxygen (oxygen or oxygen) as an oxidant. The solid polymer fuel cell generates electric power by supplying air) to the catalyst layer 2 via the diffusion layer 3 from the respective separate flow paths 5. At this time, for example, when a hydrogen-containing liquid is used as the fuel, a direct liquid fuel cell is obtained, and when methanol is used, a direct methanol fuel cell is obtained. That is, it can be said that the above-described embodiment exemplified for the polymer electrolyte fuel cell 10 can be applied to a direct liquid fuel cell and a direct methanol fuel cell as they are.

  In addition, the polymer electrolyte fuel cell 10 according to the present embodiment can be used alone or in a stacked manner to form a stack, or a fuel cell system incorporating them.

  Next, an embodiment of a direct methanol fuel cell using the membrane electrode assembly of the present invention will be described with reference to the drawings.

  FIG. 2 is a diagram schematically showing a cross-sectional structure of a main part of a direct methanol fuel cell including the membrane electrode assembly according to the present embodiment. As shown in the figure, a direct methanol fuel cell 20 according to the present embodiment includes a membrane electrode assembly 16, a fuel tank 17, and a support 19. The fuel tank 17 includes a fuel (methanol or methanol aqueous solution) filling unit (supply unit) 18, and an oxidant channel 15 is formed in the support 19.

  The required number of membrane electrode assemblies 16 obtained by the above-described method are arranged in a plane on both sides of the fuel tank 17 having the fuel filling portion 18. Further, a support body 19 in which an oxidant channel 15 is formed is disposed on the outside thereof. That is, a cell or stack of the direct methanol fuel cell 20 is configured by being sandwiched between the two supports 19 and 19.

  In addition to the examples described above, the polymer electrolyte membrane according to the present invention is disclosed in JP 2001-313046, JP 2001-313047, JP 2001-93551, and JP 2001-93558. JP-A-2001-93561, JP-A-2001-102069, JP-A-2001-102070, JP-A-2001-283888, JP-A-2000-268835, JP-A-2000-268836, It can be used as an electrolyte membrane of a polymer electrolyte fuel cell or a direct methanol fuel cell, which is publicly known in Japanese Laid-Open Patent Publication No. 2001-283893. Based on these known documents, those skilled in the art can easily construct a polymer electrolyte fuel cell or a direct methanol fuel cell using the membrane electrode assembly of the present invention.

  Hereinafter, examples will be shown and the embodiment of the present invention will be described in more detail. Of course, the present invention is not limited to the following examples, and it goes without saying that various aspects are possible in detail. Further, the present invention is not limited to the above-described embodiments, and various modifications can be made within the scope shown in the claims, and the present invention is also applied to the embodiments obtained by appropriately combining the disclosed technical means. It is included in the technical scope of the invention.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further more concretely, this invention is not limited at all by these Examples, In the range which does not change the summary, it can change suitably.

(Example 1)
<Preparation of electrolyte membrane>
Polyphenylene sulfide (manufactured by Dainippon Ink and Chemicals, LD10p11) as a polymer compound having an aromatic unit, and high-density polyethylene (HI-ZEX 3300F, manufactured by Mitsui Chemicals, Inc.) as a polymer compound having no aromatic unit. used.

  50 parts by weight of polyphenylene sulfide pellets and 50 parts by weight of high density polyethylene pellets were dry blended. The dry blended pellet mixture was melt-extruded by a twin screw extruder with a T die set under the conditions of a screw temperature of 290 ° C. and a T die temperature of 290 ° C. to obtain a polymer film (high in the polymer film). 50% by weight density polyethylene).

  In a glass container, 905 g of dichloromethane and 18.0 g of chlorosulfonic acid were weighed to prepare a 2% by weight chlorosulfonic acid solution. 2.1 g of the polymer film was weighed, immersed in the chlorosulfonic acid solution, and left at 25 ° C. for 20 hours. Thereafter, the polymer film was recovered and washed with ion exchange water until neutral.

  The polymer film after washing was dried in a constant temperature and humidity chamber adjusted to 23 ° C. for 30 minutes under humidity control of relative humidity 98%, 80%, 60% and 50%, An electrolyte membrane containing a hydrocarbon electrolyte was obtained.

<Measurement method of ion exchange capacity>
The electrolyte membrane (about 10 mm × 40 mm) was immersed in 20 mL of a saturated aqueous sodium chloride solution at 25 ° C., and subjected to an ion exchange reaction at 60 ° C. for 3 hours in a water bath. Thereafter, it was cooled to 25 ° C., and then the electrolyte membrane was thoroughly washed with ion-exchanged water, and a saturated aqueous sodium chloride solution and washing water were all recovered. To this recovered solution, a phenolphthalein solution was added as an indicator, and neutralization titration was performed with a 0.01N sodium hydroxide aqueous solution to calculate the ion exchange capacity. The results are shown in Table 1.

<Measurement method of proton conductivity>
The electrolyte membrane (about 10 mm × 40 mm) stored in the ion exchange water was taken out, and water on the surface of the electrolyte membrane was wiped off with a filter paper. An electrolyte membrane was placed in a dipolar non-sealed polytetrafluoroethylene cell, and a platinum electrode was placed on the membrane surface (on the same side) so that the distance between the electrodes was 30 mm. The membrane resistance at 23 ° C. was measured by an alternating current impedance method (frequency: 42 Hz to 5 MHz, applied voltage: 0.2 V, Hioki LCR meter 3531Z HITESTER), and proton conductivity was calculated. The results are shown in Table 1.

<Measurement method of methanol barrier properties>
In an environment of 25 ° C., membrane exchange experiment apparatus (KH-5PS) manufactured by Beadrex Co. was used to isolate ion exchange water and 64% by weight methanol aqueous solution with the electrolyte membrane. A solution containing methanol permeated to the ion exchange water side after a predetermined time (2 hours) was collected, and the amount of methanol permeated with a gas chromatograph (Gas Chromatography GC-201 manufactured by Shimadzu Corporation) was quantified. From this quantitative result, the methanol permeation rate was determined, and the methanol permeation coefficient was calculated. The methanol permeability coefficient was calculated according to the following formula 1. The results are shown in Table 1.
[Formula 1]
Methanol permeability coefficient (μmol / (cm · day))
= Methanol permeation amount (μmol) × film thickness (cm) / (membrane area (cm ² ) × permeation time (days))
In addition, the measuring method of "methanol permeability coefficient of hydrocarbon electrolyte contained in anode catalyst layer" uses a membrane permeation experiment apparatus (KH-5PS) manufactured by Beadrex in an environment of 25 ° C,
Instead of the electrolyte membrane,
This is a measurement method using a cast membrane of “hydrocarbon electrolyte contained in the anode catalyst layer”. The method for producing a cast membrane of “hydrocarbon electrolyte contained in the anode catalyst layer” is a flat plate having a smooth surface obtained by dissolving a solution in which “hydrocarbon electrolyte contained in the anode catalyst layer” is dissolved in a soluble solvent. This is a production method in which the solvent is produced by casting it up and removing the solvent by drying. Since the methanol permeability coefficient is normalized by the thickness of the cast film, the thickness of the cast film may be arbitrary. The results are shown in Table 1.

<Preparation of electrolyte for anode catalyst layer>
A sulfonic acid group-containing polyether ether ketone (S-PEEK) was synthesized as a hydrocarbon electrolyte used for the anode catalyst layer.

  First, 552.0 g of sulfuric acid was placed in a reaction vessel equipped with a mechanical stirrer, a reflux pipe, and a calcium chloride pipe, and then 22.2 g of PEEK 450PF (polyether ether ketone manufactured by Victorex MC) was added with stirring. For 3 days. The reaction solution was dropped into ion-exchanged water to precipitate a reaction product, followed by filtration, and washed with ion-exchanged water until the filtrate became neutral. The obtained reaction product was dried at 105 ° C. under vacuum for 8 hours to obtain 26.94 g of a yellow solid (S-PEEK).

  Using S-PEEK (0.300 g), 2,6-bis (hydroxymethyl) -p-cresol (0.060 g) as a crosslinking agent, and methanol (8.640 g) as a solvent, a uniform solution was prepared. Prepared. The obtained solution was put in a petri dish having an inner diameter of 60 mm and dried under vacuum at 25 ° C. for 2 hours, then at 45 ° C. for 2 hours, and at 100 ° C. for 2 hours to obtain a crosslinked S-PEEK film. . Then, it vacuum-dried at 150 degreeC for 1 hour. Table 1 shows the results of evaluating the characteristics of the electrolyte.

＜メタノール浸漬試験＞
電解質膜（約１０ｍｍ×４０ｍｍ）を、約５０ｍＬのメタノール（試薬特級)に浸漬し、６０℃、５時間静置した。所定時間経過後の電解質膜を回収し、１００℃、１０時間真空乾燥した。試験前後の重量から、以下の数式２に従って、重量減少率を算出した。結果を表２に示す。
［数式２］
重量減少率（重量％）＝｛試験前の重量（ｇ）−試験後の重量（ｇ）｝／試験前の重量（ｇ）×１００
＜アノード触媒層の作製＞
アノード触媒層は、次の手順にて作製した。まず、電解質溶液として前記Ｓ−ＰＥＥＫ（０．１７２ｇ）と２，６−ビス（ヒドロキシメチル）−ｐ−クレゾール（０．０３４ｇ）のメタノール溶液（５ｗｔ％、４．１２３ｇ）を調製した。次いで純水（４．６３０ｇ）に白金−ルテニウム担時カーボン触媒粉末（ＴＥＣ６１Ｅ５４、田中貴金属工業株式会社製、０．４６３ｇ）、および前記電解質溶液（５ｗｔ％、４．１２３ｇ）を加えた後に、マグネチックスターラーを用いて３０分撹拌することによってアノード触媒インクを作製した。前記アノード触媒インクをエアブラシで、カーボンペーパー製拡散層（ＳＧＬ２４ＢＡ、ＳＧＬカーボンジャパン株式会社製、５０ｍｍ×５０ｍｍ）に白金担持量１．０ｍｇ／ｃｍ²になるまで吹き付けた。その後、１５０℃、１時間真空乾燥させたのちに、２２ｍｍ×２２ｍｍの大きさに裁断することによって、白金担持量１．０ｍｇ／ｃｍ²のアノード触媒層形成拡散層を得た。

<Methanol immersion test>
The electrolyte membrane (about 10 mm × 40 mm) was immersed in about 50 mL of methanol (special grade reagent) and allowed to stand at 60 ° C. for 5 hours. The electrolyte membrane after the lapse of a predetermined time was recovered and vacuum dried at 100 ° C. for 10 hours. From the weight before and after the test, the weight reduction rate was calculated according to the following formula 2. The results are shown in Table 2.
[Formula 2]
Weight reduction rate (% by weight) = {weight before test (g) −weight after test (g)} / weight before test (g) × 100
<Preparation of anode catalyst layer>
The anode catalyst layer was produced by the following procedure. First, a methanol solution (5 wt%, 4.123 g) of S-PEEK (0.172 g) and 2,6-bis (hydroxymethyl) -p-cresol (0.034 g) was prepared as an electrolyte solution. Next, after adding platinum-ruthenium-supported carbon catalyst powder (TEC61E54, manufactured by Tanaka Kikinzoku Kogyo Co., Ltd., 0.463 g) to the pure water (4.630 g) and the electrolyte solution (5 wt%, 4.123 g), An anode catalyst ink was prepared by stirring for 30 minutes using a tic stirrer. The anode catalyst ink was sprayed onto a carbon paper diffusion layer (SGL24BA, SGL Carbon Japan Co., Ltd., 50 mm × 50 mm) with an air brush until the amount of platinum supported was 1.0 mg / cm ² . Then, after vacuum-drying at 150 ° C. for 1 hour, the resultant was cut into a size of 22 mm × 22 mm to obtain an anode catalyst layer forming diffusion layer having a platinum loading of 1.0 mg / cm ² .

<Preparation of cathode catalyst layer>
The cathode catalyst layer was prepared by the following procedure. After adding platinum-supported carbon catalyst powder (TEC10E50E, Tanaka Kikinzoku Kogyo Co., Ltd., 0.250 g) to pure water (2.500 g) and Nafion solution (5 wt%, 1.840 g) as an electrolyte solution, magnetic Cathode catalyst ink was prepared by stirring for 30 minutes using a stirrer. The cathode catalyst ink was sprayed onto a carbon paper diffusion layer (SGL24BA, SGL Carbon Japan, 50 mm × 50 mm) with an airbrush until the platinum loading was 1.0 mg / cm ² . Finally, it was dried at 50 ° C. and then cut into a size of 22 mm × 22 mm to obtain a cathode catalyst layer-forming diffusion layer having a platinum loading of 1.0 mg / cm ² .

<Fabrication of membrane electrode assembly for fuel cell>
The membrane electrode assembly of the present invention was produced by the following procedure using a heating and pressure welding machine (manufactured by Tester Sangyo Co., Ltd.). First, a SUS plate, a polytetrafluoroethylene sheet (100 mm × 100 mm × 0.05 mm), the anode catalyst layer forming diffusion layer (22 mm × 22 mm), the electrolyte membrane, the cathode catalyst layer forming diffusion layer (22 mm × 22 mm), A polytetrafluoroethylene sheet (100 mm × 100 mm × 0.05 mm) and a SUS plate were laminated in this order. The laminate was placed on a pressure plate heated to 110 ° C., and then heat-pressed under the conditions of 9.8 MPa and holding for 5 minutes to obtain a membrane electrode assembly of the present invention.

<Power generation test of direct methanol fuel cell>
The fuel cell of the present invention was assembled by installing the membrane electrode assembly in a commercially available single cell for PEFC (manufactured by Electrochem). First, anode side end plate (current collector), gas flow plate (carbon separator), polytetrafluoroethylene gasket (0.2 mm), membrane electrode assembly, polytetrafluoroethylene gasket (0.18 mm), gas flow plate (Carbon separator) and cathode side end plate (current collector) were laminated in this order. Next, the fuel cell of the present invention was obtained by tightening at 2 N · m using M3 bolts. The power generation characteristics of the fuel cell thus prepared were measured by supplying a cell temperature of 60 ° C., supplying a 1 mol / L aqueous methanol solution to the anode side, and non-humidified air to the cathode side. The results are shown in FIG.

(Comparative Example 1)
Nafion was used as the electrolyte for the anode catalyst layer. In order to evaluate various properties, a Nafion (registered trademark) solution (5% by weight) was placed in a petri dish having an inner diameter of 60 mm, and under vacuum, 2 hours at 25 ° C., then 2 hours at 45 ° C., 2 hours at 100 ° C. The film was dried to obtain a cast Nafion (registered trademark) film. Tables 1 and 2 show the evaluation results of the characteristics of the electrolyte.

表１の実施例１と比較例１との比較から、本発明の膜電極接合体の炭化水素系電解質を含む電解質膜は、燃料電池用電解質膜として市販されている比較例１の電解質膜と同等のプロトン伝導性と優れたメタノール遮断性を示すことが明らかとなった。

From the comparison between Example 1 and Comparative Example 1 in Table 1, the electrolyte membrane containing the hydrocarbon-based electrolyte of the membrane electrode assembly of the present invention was compared with the electrolyte membrane of Comparative Example 1 commercially available as an electrolyte membrane for fuel cells. It was revealed that the proton conductivity was equivalent and the methanol barrier property was excellent.

  Moreover, it was confirmed that the methanol permeability coefficient of the hydrocarbon electrolyte used for the anode catalyst layer showed a methanol permeability coefficient larger than that of the electrolyte membrane containing the hydrocarbon electrolyte.

  From comparison between Example 1 and Comparative Example 1 in Table 2, the hydrocarbon electrolyte used in the anode catalyst layer of the membrane electrode assembly of the present invention showed excellent methanol resistance. On the other hand, the non-hydrocarbon (fluorine) electrolyte shown in Comparative Example 1 is soluble in methanol used as a fuel for direct methanol fuel cells, and a membrane electrode assembly having practical durability can be obtained. It became clear that there was no.

  From Example 1 in FIG. 3, it was confirmed that the membrane electrode assembly of the present invention functions as a membrane electrode assembly in a direct methanol fuel cell, and the effectiveness of the present invention was shown.

  The membrane electrode assembly for a fuel cell according to the present invention has various industrial applicability including a fuel cell represented by a direct methanol fuel cell.

FIG. 1 is a diagram schematically showing a cross-sectional structure of a main part of a polymer electrolyte fuel cell using an electrolyte membrane according to the present embodiment. FIG. 2 is a diagram schematically showing a cross-sectional structure of a main part of a direct methanol fuel cell made of the electrolyte membrane according to the present embodiment. FIG. 3 shows the power generation characteristics of a direct methanol fuel cell using the fuel cell membrane electrode assembly of Example 1.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Electrolyte membrane 2 Catalyst layer 3 Diffusion layer 4 Separator 5 Channel 10 Solid polymer fuel cell 15 Oxidant channel 16 Membrane-electrode assembly (MEA)
17 Fuel Tank 18 Fuel Filling Portion 19 Support 20 Direct Methanol Fuel Cell

Claims (9)

  In a membrane electrode assembly for a fuel cell, comprising at least an electrolyte membrane and a pair of an anode catalyst layer and a cathode catalyst layer sandwiching the electrolyte membrane, the electrolyte membrane includes a hydrocarbon-based electrolyte, and the anode catalyst layer A fuel cell membrane electrode assembly, comprising a hydrocarbon electrolyte, wherein the methanol permeability coefficient of the hydrocarbon electrolyte contained in the anode catalyst layer is greater than the methanol permeability coefficient of the electrolyte membrane.   The electrolyte membrane is an electrolyte membrane in which a proton conductive group is introduced into a polymer film containing a polymer compound having an aromatic unit and a polymer compound not having an aromatic unit. The membrane electrode assembly for fuel cells according to claim 1.   2. The electrolyte membrane according to claim 1, wherein the electrolyte membrane includes at least a porous support having continuous pores, and a hydrocarbon-based electrolyte filled in the pores of the porous support. The membrane electrode assembly for fuel cells as described.   The hydrocarbon electrolyte contained in the anode catalyst layer is a hydrocarbon electrolyte obtained by introducing a proton conductive group into at least a polymer compound having an aromatic unit. The membrane electrode assembly for fuel cells according to any one of the above.   The membrane electrode assembly for a fuel cell according to any one of claims 1 to 4, wherein the proton conductive group includes a sulfonic acid group.   The hydrocarbon electrolyte contained in the anode catalyst layer includes a reaction product of a hydrocarbon electrolyte and a crosslinking agent capable of undergoing a crosslinking reaction with the hydrocarbon electrolyte. The membrane electrode assembly for fuel cells according to any one of the above.   The hydrocarbon-based electrolyte contained in the anode catalyst layer has a weight reduction rate of not more than 8% after being immersed in methanol at 60 ° C for 50 hours, according to any one of claims 1 to 6. A fuel cell membrane electrode assembly.   The membrane electrode assembly for a fuel cell according to any one of claims 1 to 7, wherein a diffusion layer is provided outside each of the anode catalyst layer and the cathode catalyst layer.   A direct methanol fuel cell comprising the fuel cell membrane electrode assembly according to any one of claims 1 to 8.

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