JP4632053B2 - Curable composition for fuel cell catalyst layer and catalyst layer - Google Patents

Description

  The present invention relates to a curable composition for a fuel cell catalyst layer and a catalyst layer.

The polymer electrolyte fuel cell has a structure in which a catalyst layer is disposed on both sides of a proton conductive polymer electrolyte membrane, and a porous electrode substrate such as carbon paper or carbon cloth is disposed on both sides. These are integrated to form an electrode / membrane assembly.
Conventionally, as a proton conductive polymer electrolyte membrane, a fluororesin-based perfluorosulfonic acid membrane “Nafion (registered trademark of DuPont)” or the like has been generally used. However, in a direct methanol fuel cell using methanol as fuel, Nafion has a large methanol permeability, so that there is a problem that output is reduced due to methanol crossover. In order to reduce the methanol permeability of the electrolyte membrane, modification of the Nafion membrane (for example, Non-Patent Document 1: LJ Hobson et al., Journal of Material Chemistry 12 (6), 1650, 2002), hydrocarbon type Materials (for example, Non-Patent Document 2: B. Yang and A. Manthiram, Electrochemical and Solid-State Letters, 6 (11), A229, 2003), a film obtained by radiation-grafting styrene on a fluororesin film (for example, Non-Patent Document) Document 3: T. Hatanaka et al., Fuel 81 (17), 2173, 2002) and other electrolyte membranes other than perfluorosulfonic acid are being studied.

  In the membrane-electrode assembly, the catalyst layer that contacts the electrolyte membrane is generally composed of catalyst particles and Nafion. As a method of forming the catalyst layer, catalyst particles and a Nafion solution are dispersed in a solvent to prepare a catalyst paste, and this is applied directly to an electrolyte membrane, or a catalyst paste is applied on a substrate such as polytetrafluoroethylene, A method of transferring this to a film by a hot press method, or applying a catalyst paste on an electrode substrate to form a catalyst layer is used (for example, Non-Patent Document 4: MS Wilson and S. et al.). Gottsfeld, Journal of Applied Electrochemistry 22 (2), 1, 1992, Non-Patent Document 5: M. Uchida et al., Journal of Electrochemical Society 142 (2), 463, 195, etc.

  As described above, in order to reduce methanol permeability, a hydrocarbon film or a film obtained by radiation-grafting styrene on a fluorine resin film has been studied. However, these have a problem in the bonding property between the membrane and the electrode after the membrane / electrode assembly is formed. Taking as an example a membrane obtained by grafting styrene to a fluororesin film as the electrolyte membrane, Non-Patent Document 3: T.A. Hatanaka et al. , Fuel 81 (17), 2173, 2002, there is a problem that the membrane and the electrode peel off during or after operation as a fuel cell. When peeling occurs, it means that the contact resistance increases and the performance of the fuel cell decreases.

  As a result of studies by the present inventors, if a membrane / electrode assembly in which an electrode is joined to a radiation graft membrane by a hot press method is immersed in water or an aqueous methanol solution, the membrane is swollen by water or an aqueous methanol solution. It was confirmed that the film and the electrode were peeled off. This is because the radiation graft membrane swells in the methanol aqueous solution, which is a fuel, and stress is generated at the joint surface between the membrane and the electrode, but peeling occurs because the joint force is not sufficient to withstand the stress change. It seems to be. Further, since the portion in contact with the membrane is the catalyst layer, it is considered that peeling occurs because the bonding force between the membrane and the catalyst layer is weak.

L. J. et al. Hobson et al. , Journal of Material Chemistry 12 (6), 1650, 2002. B. Yang and A.M. Manthiram, Electrochemical and Solid-State Letters, 6 (11), A229, 2003 T.A. Hatanaka et al. , Fuel 81 (17), 2173, 2002 M.M. S. Wilson and S.W. Gottesfeld, Journal of Applied Electrochemistry 22 (2), 1, 1992 M.M. Uchida et al. , Journal of Electrochemical Society 142 (2), 463, 1995.

  The present invention has been made in view of the above circumstances, and provides a curable composition for a fuel cell catalyst layer and a fuel cell catalyst layer, which solves the above problems and has excellent bondability in a joined body of a membrane and an electrode substrate. The purpose is to provide.

  As a result of intensive studies to achieve the above object, the present inventors have found that (1) metal particles, (2) ion-conducting groups or chemical reactions are used instead of catalyst pastes composed of conventional catalysts and Nafion. Use for a fuel cell catalyst layer containing an alkoxysilane having a precursor group capable of imparting an ion-conducting group or hydrolyzate thereof, and (3) a perfluoropolyether having an alkoxysilyl group bonded to both ends of the molecular chain It was found that by using a curable composition and forming a catalyst layer from the curable composition, it was possible to obtain a membrane / electrode assembly excellent in bondability, and the present invention was made. Is.

Accordingly, the present invention provides the following curable composition for a fuel cell catalyst layer and a catalyst layer.
Claim 1:
(1) 100 parts by mass of metal particles, (2) 10 to 130 parts by mass of an alkoxysilane or a hydrolyzate thereof having an ion conductive group or a precursor group capable of imparting an ion conductive group using a chemical reaction, 3) A curable composition for a fuel cell catalyst layer, comprising 10 to 130 parts by mass of perfluoropolyether having alkoxysilyl groups bonded to both ends of the molecular chain.
Claim 2:
2. The curable composition for a fuel cell catalyst layer according to claim 1, wherein the metal particles of the component (1) are selected from platinum, gold, ruthenium, palladium, iron, cobalt, nickel, chromium and alloys thereof. object.
Claim 3:
The curable composition for a fuel cell catalyst layer according to claim 1 or 2, wherein the average particle diameter of the metal particles of the component (1) is 10 nm or less.
Claim 4:
4. The curable composition for a fuel cell catalyst layer according to claim 1, wherein the ion conductive group of the component (2) is a sulfonic acid group.
Claim 5:
The curable composition for a fuel cell catalyst layer according to any one of claims 1 to 4, wherein the number average molecular weight of the component (3) is from 400 to 10,000.
Claim 6:
The curable composition for a fuel cell catalyst layer according to any one of claims 1 to 5, further comprising a solvent.
Claim 7:
A fuel cell catalyst layer, which is formed by applying the curable composition for a fuel cell catalyst layer according to any one of claims 1 to 6 on an electrode substrate, and heating and curing the composition.

  When the curable composition for a fuel cell catalyst layer of the present invention is used for a catalyst layer, the hydrocarbon having a smaller bondability between an electrolyte membrane and an electrode substrate, particularly methanol permeability than a perfluorosulfonic acid-based membrane such as Nafion Bondability of the system to the electrolyte membrane can be improved. Therefore, by using the membrane / electrode assembly using the curable composition for a fuel cell catalyst layer of the present invention, a direct methanol fuel cell having low methanol permeability and high reliability can be produced. it can.

  The curable composition for a fuel cell catalyst layer of the present invention comprises (1) metal particles, (2) an alkoxysilane having a precursor group capable of imparting an ion conductive group using an ion conductive group or a chemical reaction, or The hydrolyzate contains (3) perfluoropolyether having alkoxysilyl groups bonded to both ends of the molecular chain.

  Examples of the component (1) metal particles include platinum, gold, ruthenium, palladium, iron, cobalt, nickel, chromium, and alloys thereof. Examples of platinum alloys include alloys of platinum and at least one metal selected from ruthenium, palladium, rhodium, iridium, osmium, molybdenum, tin, cobalt, nickel, iron, chromium, and the like. In this case, the platinum alloy is preferably one containing 5% by mass or more, particularly 10% by mass or more of platinum.

  The platinum, platinum alloy or the like may be in the form of fine particles, or may be supported on an electrically conductive carrier such as carbon black or carbon nanotube. Alternatively, a supported state and an unsupported state may be mixed.

  The average particle size of the fine particles such as platinum and platinum alloy is preferably 10 nm or less, more preferably 5 nm or less. In this case, the upper limit of the average particle size is usually 1 nm or more, and particularly preferably 2 nm or more. In addition, the measuring method of this average particle diameter is based on TEM observation.

  (2) An alkoxysilane having an ion conductive group or a precursor group capable of imparting an ion conductive group using a chemical reaction (the number of carbon atoms of the alkoxy group is preferably 1 to 6) or a hydrolyzate thereof Are 3-trimethoxysilylpropanesulfonic acid, 3-trihydroxysilylpropanesulfonic acid, 3-trimethoxysilylpropoxy-2-hydroxy-1-propanesulfonic acid, p- (trimethoxysilylethyl) phenylsulfonic acid, 3 -Trihydroxysilylpropylmethyl phosphate, 2-trimethoxysilylpropoxy-1,1,2,2-tetrafluoroethanesulfonic acid, γ-glycidoxypropyltriethoxysilane, γ-mercaptopropyltrimethoxysilane, 2- (4-Chlorosulfonylphenyl) ethyltrimethoxysila Or the like. Of these, 3-trihydroxysilylpropanesulfonic acid, which is easily available, is desirable.

  The component (2) has a carbon-carbon double bond such as an alkenyl group such as a vinyl group or an allyl group and a precursor group capable of imparting an ion conductive group using an ion conductive group or a chemical reaction. The compound can be obtained by addition reaction with an alkoxysilane having a hydrogen atom bonded to a silicon atom, hydrolyzing an alkoxy group as necessary, or oxidizing the mercapto group of an alkoxysilane having a mercapto group. These reactions can be carried out according to conventional methods.

  Examples of the ion conductive group include a carboxylic acid group, a sulfonic acid group, and a phosphoric acid group. A sulfonic acid group is preferable, and a precursor group that is converted into an ion conductive group by a chemical reaction is used. Includes an acyloxy group, an ester group (—COOR: R is a monovalent hydrocarbon group), an acid imide group, a halogenated sulfonyl group, a halogenated alkyl group, a glycidyl group, and the like. This precursor group is one that chemically reacts with, for example, sodium hydroxide, methanol or sodium sulfite to form a carboxylic acid group or a sulfonic acid group. These compounds can be used individually by 1 type or in mixture of 2 or more types.

  Examples of the compound having a carbon-carbon double bond and an ion conductive group include styrene sulfonic acid, allylbenzene sulfonic acid, allyloxybenzene sulfonic acid, vinyl sulfonic acid, allyl sulfonic acid, and fluorovinyl sulfonic acid. -As a compound having a carbon double bond and a precursor group capable of imparting an ion conductive group using a chemical reaction, p-chlorosulfonyl styrene, allyl glycidyl ether, allyl bromide, 2-allyloxy-1, Examples include 1,2,2-tetrafluoroethanesulfonyl fluoride.

  On the other hand, examples of the alkoxysilane having a hydrogen atom bonded to a silicon atom include trimethoxysilane, triethoxysilane, dimethoxymethylsilane, and diethoxyethylsilane.

  Examples of the alkoxysilane having a mercapto group include γ-mercaptopropyltrimethoxysilane and γ-mercaptopropylmethyldimethoxysilane.

For example, as the component (2), 3-trihydroxysilylpropane sulfonic acid is preferable because it is easily available, and this is obtained by subjecting trimethoxysilane and allyl bromide to an addition reaction, and then Na ₂ SO _3. Can be obtained by sulfonating Br and hydrolyzing the methoxy group.

(3) Perfluoropolyether having alkoxysilyl groups bonded to both ends of the molecular chain of the component has an ether structure such as (CF ₂ O), (CF ₂ CF ₂ O), (CF (CF ₃ ) CF ₂ O) It can be obtained by reacting a part of the diisocyanate with a diol having a reaction with an alkoxysilane having a group capable of reacting with the remaining isocyanate.
Alternatively, a perfluorodiol having an ether structure is reacted with allyl bromide, and both ends are allyl etherified, and then a group capable of reacting with this allyl group (that is, a hydrogen atom bonded to a silicon atom, that is, a SiH group). It can be obtained by reacting an alkoxysilane having it.

  Examples of perfluorodiol having an ether structure include Fomblin Z DOL, Fluorolink D, Fluorolink D10H, and Fluorolink D10. The number average molecular weight is preferably 400 to 2,000.

  Examples of diisocyanates include 2,4-tolylene diisocyanate, 4,4′-diphenylmethane diisocyanate, hydrogenated 4,4′-diphenylmethane diisocyanate, xylylene diisocyanate, hydrogenated xylylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, 1 , 5-naphthalene diisocyanate, tolidine diisocyanate, p-phenylene diisocyanate, transcyclohexane-1,4-diisocyanate, lysine diisocyanate, tetramethylxylene diisocyanate, lysine ester triisocyanate, 1,6,11-undecane triisocyanate, 1,8- Diisocyanate-4-isocyanate methyloctane, 1,3,6-hexamethylene triisocyanate, Cycloheptane triisocyanate, trimethylhexamethylene diisocyanate, and the like. Among these, 2,4-tolylene diisocyanate and isophorone diisocyanate are preferable because of excellent adhesion between the electrolyte membrane and the catalyst layer.

  Examples of alkoxysilanes having groups capable of reacting with isocyanate include alkoxysilanes having amino groups, in particular γ-aminopropylmethyldiethoxysilane, γ-aminopropyltriethoxysilane, N-β (aminoethyl) γ. -Aminopropylmethyldimethoxysilane, N-β (aminoethyl) γ-aminopropyltrimethoxysilane. γ-Aminopropylmethyldiethoxysilane is preferable because the catalyst layer can be made flexible.

  The method for producing a perfluoropolyether in which an alkoxysilyl group is bonded to both ends of the molecular chain of the component (3) via a bond selected from an amide bond, a urethane bond, and a urea bond is not particularly limited. It is desirable that diol and diisocyanate be reacted at a molar ratio of OH / NCO <1, and further reacted with an alkoxysilane having a functional group (for example, amino group) that reacts with the remaining isocyanate group.

  That is, a perfluoropolyether having an alkoxysilyl group bonded to both ends of the molecular chain via a bond selected from an amide bond, a urethane bond, and a urea bond can be prepared by reacting the above components. Is, for example, 0.1 to 0.8 mol, preferably 0.2 to 0.7 mol, particularly 0.2 to 0 mol of the hydroxyl group of the perfluoropolyether component with respect to 1 mol of the isocyanate group of the polyisocyanate. About 0.5 mol, amino group-containing alkoxysilane 0.2-0.9 mol, preferably 0.3-0.8 mol, especially about 0.5-0.8 mol.

  Moreover, the reaction method of the said component is not specifically limited, Each component may be mixed and made to react, Polyisocyanate, any one component among a perfluoropolyether component and an amino group containing alkoxysilane, After reacting, the other component may be reacted.

  These amidation, urethanization, and ureaation reactions proceed without using a catalyst, but as necessary, for example, stannous octoate, dibutyltin diacetate, dibutyltin dilaurate, cobalt naphthenate, lead naphthenate An organometallic catalyst such as can be used.

  The production method of the perfluoropolyether having an alkoxysilyl group at both ends of the molecular chain not via a bond selected from an amide bond, a urethane bond, and a urea bond is not particularly limited, but sodium hydroxide and perfluoropolyetherdiol are used. It can be obtained by reacting, then reacting with allyl halide such as allyl bromide to make all ends of perfluoropolyether allyl ether, and then adding it with an alkoxysilane having a hydrogen atom bonded to a silicon atom. .

  The number average molecular weight of the component (3) is preferably 400 to 10,000, particularly 400 to 2,000. In addition, this number average molecular weight is a polystyrene conversion value by GPC.

  The curable composition for a fuel cell catalyst layer of the present invention comprises (1) metal particles, (2) an alkoxysilane having a precursor group capable of imparting an ion conductive group using an ion conductive group or a chemical reaction, or The hydrolyzate contains (3) perfluoropolyether with alkoxysilyl groups bonded to both ends of the molecular chain, but other components can be introduced to improve the formability and performance of the catalyst layer. It is.

  In this case, it is also possible to use a solvent for the purpose of improving the coatability. The solvent is preferably an alkoxysilane having an ion conductive group or a hydrolyzate thereof, and a solvent that uniformly dissolves a polyether having alkoxysilyl groups bonded to both ends of the molecular chain. For example, methyl alcohol, ethyl alcohol, n- Alcohols such as propyl alcohol, isopropyl alcohol, n-butyl alcohol, ethylene glycol and glycerol, ketones such as acetone and methyl ethyl ketone, esters such as ethyl acetate and butyl acetate, ethers such as tetrahydrofuran and dioxane, benzene and toluene Aromatic hydrocarbons such as n-heptane, n-hexane, cyclohexane and the like, water, dimethyl sulfoxide, N, N-dimethylformamide, N, N-dimethylacetamide, formamide, N Methylformamide, N- methylpyrrolidone, ethylene carbonate, polar solvents such as propylene carbonate, and a fluorine-based solvents such as hexafluoro-xylene. These can be used individually by 1 type or in mixture of 2 or more types. Among these, polar solvents such as N, N-dimethylformamide and fluorine-based solvents are desirable.

  Moreover, in order to increase the porosity in the catalyst layer and facilitate the movement of water, it is also possible to add a fluororesin. Examples of fluororesins include polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), polychlorotrifluoroethylene (PCTFE), ethylene-tetra Fluoroethylene copolymer (ETFE), polyvinylidene fluoride (PVDF), polyvinyl fluoride (PVF), ethylene trifluoride-ethylene copolymer (ECTFE), etc. are mentioned, and these may be used alone or in combination of two or more. Can be used. In addition, as these fluororesins, the commercial item about the polystyrene conversion number average molecular weight 100,000-600,000 by GPC can be used.

  The proportions of the components (1) to (3), the solvent, and the fluororesin component contained in the curable composition for a fuel cell catalyst layer of the present invention are not limited and may be appropriately selected within a wide range. The component (2) is 10 to 130 parts by weight, particularly 10 to 80 parts by weight, and the component (3) is 10 to 130 parts by weight, particularly 10 to 80 parts by weight, based on 100 parts by weight of the component (1). The solvent is used in an amount of 0 to 2,000 parts by mass, particularly 100 to 1,000 parts by mass, and the fluororesin component is preferably used in an amount of 10 to 400 parts by mass, particularly 40 to 130 parts by mass.

  In order to form a catalyst layer from the curable composition for a fuel cell catalyst layer of the present invention, the curable composition is applied onto an electrolyte membrane or a porous electrode substrate, and the components (2) and (3) Heat to cure. When a solvent is added to the curable composition, the solvent is removed and at the same time the components (2) and (3) are cured.

  In this case, as a method for applying the curable composition of the present invention, known methods such as an applicator, a bar coater, a spin coater, a knife coater, a dip coater, and a spray can be used.

  The thickness of the catalyst layer of the present invention can be variously selected, but it is preferably 10 to 100 μm, particularly preferably 20 to 50 μm.

  Moreover, hardening after catalyst paste (curable composition) application | coating can be performed by leaving at room temperature for 1 day, or heating at 50-120 degreeC for about 3 to 30 minutes. In order to accelerate curing, an organic tin compound such as dibutyltin diacetate may be added to the catalyst paste.

The catalyst layer is formed on at least one of the electrolyte membrane and the electrode substrate, and the membrane / electrode assembly can be obtained by sandwiching both surfaces of the electrolyte membrane with the electrode substrate and hot pressing. The temperature at the time of hot pressing is appropriately selected depending on the electrolyte membrane to be used or the components (2) and (3) in the curable composition, the type and blending ratio of the fluororesin, but the desirable temperature range is 50 to 200 ° C. More desirably, the temperature is 80 to 180 ° C. If it is less than 50 ° C, bonding may be insufficient, and if it exceeds 200 ° C, the resin component in the electrolyte membrane or the catalyst layer may be deteriorated. The pressure level is appropriately selected depending on the components (2) and (3) in the electrolyte membrane and / or catalyst paste, the type and blending ratio of the fluororesin, and the type of the porous electrode substrate, but the desired pressure range. Is 1 to 100 kgf / cm ² , more preferably 10 to 100 kgf / cm ² . If it is less than 1 kgf / cm ² , the bonding may be insufficient, and if it exceeds 100 kgf / cm ² , the porosity of the catalyst layer and the electrode substrate may decrease, and the performance may deteriorate.

  In this way, an electrode / membrane assembly as shown in FIG. 1 is obtained. Here, in FIG. 1, 1 is a cathode composed of a porous electrode substrate 2 made of carbon paper, carbon cloth or the like and a catalyst layer 3, and 4 is a porous electrode substrate 5 made of carbon paper, carbon cloth or the like, and a catalyst. An anode 7 composed of the layer 6 is a proton conductive polymer electrolyte membrane. In this case, a water repellent layer can be interposed between the catalyst layer 3 and the porous electrode substrate 2 and between the catalyst layer 6 and the porous electrode substrate 5, respectively.

  In this case, various proton conductive polymer electrolyte membranes are selected and used. In particular, when a direct methanol fuel cell is used, a fluorine-based film such as ethylene-tetrafluoroethylene copolymer (ETFE), polytetrafluoroethylene is used. Films obtained by radiation grafting of styrene to ethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-perfluorovinyl ether copolymer (PFA), polyetherketone, polyetheretherketone Hydrocarbon films such as polybenzimidazole and polybenzoxazole are preferably used.

  EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated concretely, this invention is not restrict | limited to the following Example.

[Synthesis Example 1] Synthesis of Electrolyte Membrane As an electrolyte membrane to be used, a sulfonated membrane was produced by radiation-grafting styrene on an ethylene-tetrafluoroethylene copolymer (ETFE) film.
An ETFE film having a size of 6 cm × 6 cm and a thickness of 50 μm (manufactured by Saint-Gobain, Norton (registered trademark)) was irradiated with an electron beam at 25 ° C. so that the absorbed dose was 5 kGy, and 40 parts by mass of styrene, 2 parts by mass of divinylbenzene, The mixture was placed in a 500 cc separable flask charged with 40 parts by mass of hexane and 0.01 parts by mass of azobisisobutylnitrile, and heated at 60 ° C. for 16 hours in a nitrogen atmosphere to perform graft polymerization. The grafted amount was calculated as a graft ratio from the following formula.
Graft ratio = {(film mass after grafting−mass before grafting) / mass before grafting}
× 100 (%)
The graft rate at the absorbed dose was 45% by mass.
The grafted film is immersed in a mixed solution of 30 parts by mass of chlorosulfonic acid and 70 parts by mass of 1,2-dichloroethane, heated at 50 ° C. for 1 hour, and then immersed in a 1N caustic potash aqueous solution at 90 ° C. for 1 hour. After decomposing and subsequently immersed in 2N hydrochloric acid at 90 ° C. for 1 hour, it was washed 3 times with pure water to obtain a solid polymer electrolyte membrane (A) containing sulfonic acid groups.
The produced electrolyte membrane (A) had an ionic conductivity of 0.12 S / cm at room temperature, and a membrane having a ionic conductivity greater than about 0.08 S / cm of a commercially available Nafion membrane was obtained.

[Synthesis Example 2]
4.02 g of 2,4-tolylene diisocyanate was added dropwise to 11.56 g of perfluoropolyether glycol (Fluolink D10) having a number average molecular weight of 1,000 under nitrogen flow. After the dropping, the mixture was further reacted at 70 ° C. for 2 hours, and 4.42 g of γ-aminopropylmethyldiethoxysilane was added dropwise. The reaction was further carried out at 70 ° C. for 5 hours to obtain a perfluoropolyether (B) in which an alkoxysilyl group was bonded to both ends of a molecular chain having a number average molecular weight of 1,730 via a urethane bond and a urea bond.

[Example 1]
As the cathode electrode catalyst paste, 10.0 g of carbon catalyst TEC10E50E (manufactured by Tanaka Kikinzoku Co., Ltd.) supporting 50 mass% platinum was dispersed in 20.0 g of isopropyl alcohol and 20.0 g of ion-exchanged water. To this, 10.0 g of 33% aqueous solution of 3-trihydroxysilylpropane sulfonic acid (manufactured by Gelest) and 2.4 g of (B) synthesized in Synthesis Example 2 were dissolved in 22.5 g of isopropyl alcohol and mixed. As a result, a catalyst paste for a cathode electrode was obtained.
As the anode electrode catalyst paste, a carbon catalyst TEC61E54 (manufactured by Tanaka Kikinzoku Co., Ltd.) 10 supporting 54 mass% (platinum + ruthenium) was used instead of the carbon catalyst TEC10E50E supporting 50 mass% platinum used in the cathode electrode catalyst paste. An anode electrode catalyst paste was obtained in the same manner as the cathode electrode catalyst paste except that 0.0 g was used.
The catalyst layer was formed by applying the catalyst paste to the electrode side. Carbon paper TGP-H-060 (manufactured by Toray Industries, Inc.) is used as a porous electrode substrate, and it is made of tetrafluoroethylene-hexafluoropropylene copolymer (FEP) and carbon black Vulcan-XC-72 (manufactured by Cabot). A water repellent paste was applied and treated at 340 ° C. to form a water repellent layer, and then each catalyst paste was applied thereon with a bar coater. After coating, the catalyst paste was cured by heating at 100 ° C. for 20 minutes, and at the same time, isopropyl alcohol and water were removed. The above operation was repeated until a desired catalyst loading was obtained, and an electrode having a Pt loading of 1 mg / cm ^{2 as} a cathode and a PtRu loading of 1 mg / cm ² as an anode was produced.
After each electrode is 5 cm ^{2 in} size, the electrolyte membrane (A) produced in Synthesis Example 1 is sandwiched between the anode electrode and the cathode electrode so that the catalyst layer is in contact with the electrolyte membrane, and this is 10 ° C. at 130 ° C. and 50 kgf / cm ² . A membrane-electrode assembly was obtained by hot pressing for a minute.

[Comparative Example 1]
As a comparative example, a membrane / electrode assembly in which the catalyst layer was composed of conventional catalyst particles and Nafion was produced.
In the cathode electrode catalyst paste, 10.0 g of catalyst particles TEC10E50E were dispersed in 20.0 g of isopropyl alcohol and 20.0 g of ion-exchanged water. A mixed solution of 25.0 g of a 20% by mass Nafion solution and 10.0 g of isopropyl alcohol was added thereto and further mixed to obtain a cathode electrode catalyst paste. The catalyst paste for the anode electrode was obtained by using TEC61E54 as the catalyst particles in the same amount and procedure as the cathode paste preparation.
The electrode was formed by applying a water repellent paste composed of FEP and carbon black Vulcan-XC-72 on carbon paper TGP-H-060 and treating it at 340 ° C. The paste was applied with a bar coater and dried at 60 ° C. to prepare a cathode electrode and an anode electrode.
After each electrode was made 5 cm ^{2 in} size, the electrolyte membrane (A) produced in Synthesis Example 1 was sandwiched and held at 130 ° C. and 50 kgf / cm ² for 10 minutes to obtain a membrane / electrode assembly.

The bondability between Example 1 and Comparative Example 1 was confirmed by immersing the prepared membrane / electrode assembly in a 1M aqueous methanol solution at room temperature for 24 hours to determine whether the electrode was peeled off from the electrolyte membrane. As a result, in the membrane / electrode assembly produced in Example 1, separation between the membrane and the electrode was not observed for both the cathode electrode and the anode electrode, whereas the membrane / electrode assembly produced in Comparative Example 1 was The membrane was peeled off and separated from both the cathode electrode and the anode electrode.
When the electrolyte membrane is immersed in a 1M aqueous methanol solution, it swells and tends to expand in size, and stress is generated at the interface between the membrane and the electrode. In the membrane / electrode assembly produced in Comparative Example 1, -It seems to have peeled off due to weak bonding force at the electrode interface. Since the difference between the membrane / electrode assembly produced in Example 1 and Comparative Example 1 is only the composition of the catalyst layer, it is confirmed that the joining force is improved by using the catalyst paste of the present invention. It was.

It is sectional drawing which shows an example of an electrode and membrane assembly.

Explanation of symbols

1 Cathode 2 Porous Electrode Base 3 Catalyst Layer 4 Anode 5 Porous Electrode Base 6 Catalyst Layer 7 Proton Conducting Polymer Electrolyte Membrane

Claims (7)

  (1) 100 parts by mass of metal particles, (2) 10 to 130 parts by mass of an alkoxysilane or a hydrolyzate thereof having an ion conductive group or a precursor group capable of imparting an ion conductive group using a chemical reaction, 3) A curable composition for a fuel cell catalyst layer, comprising 10 to 130 parts by mass of perfluoropolyether having alkoxysilyl groups bonded to both ends of the molecular chain.   2. The curable composition for a fuel cell catalyst layer according to claim 1, wherein the metal particles of the component (1) are selected from platinum, gold, ruthenium, palladium, iron, cobalt, nickel, chromium and alloys thereof. object.   The curable composition for a fuel cell catalyst layer according to claim 1 or 2, wherein the average particle diameter of the metal particles of the component (1) is 10 nm or less.   4. The curable composition for a fuel cell catalyst layer according to claim 1, wherein the ion conductive group of the component (2) is a sulfonic acid group.   The curable composition for a fuel cell catalyst layer according to any one of claims 1 to 4, wherein the number average molecular weight of the component (3) is from 400 to 10,000.   The curable composition for a fuel cell catalyst layer according to any one of claims 1 to 5, further comprising a solvent. A fuel cell catalyst layer, which is formed by applying the curable composition for a fuel cell catalyst layer according to any one of claims 1 to 6 on an electrode substrate, and heating and curing the composition.

Images