JP4424491B2 - Catalyst paste for polymer electrolyte fuel cell - Google Patents

Description

  The present invention relates to a solid polymer fuel cell catalyst paste.

  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, and an electrode / membrane assembly (hereinafter simply referred to as a joined body) is formed.

  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 the direct methanol fuel cell using methanol as fuel, Nafion has a large methanol permeability, so that there is a problem that the output is reduced due to the crossover of methanol. In order to reduce 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), hydrocarbons Non-Patent Document 2: B. Yang and A. Manthiram, Electrochemical and Solid-State Letters, 6 (11), A229, 2003) or a film obtained by radiation grafting of styrene to a fluororesin film (for example, non-patent document 2) Patent 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, after the membrane / electrode assembly is used, there is a problem in the bonding property between the membrane and the electrode. Taking as an example a membrane obtained by grafting styrene to a fluororesin film as an electrolyte membrane, Non-Patent Document 6: T.A. Hatanaka et al. , Fuel 81 (17), 2173, 2002, there is a problem that the film and the electrode peel off during or after the 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 a methanol aqueous solution and left to stand, the membrane swells with water or methanol water. 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. T. 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. T. T. Hatanaka et al. , Fuel 81 (17), 2173, 2002

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a catalyst paste for a polymer electrolyte fuel cell that solves the above problems and has excellent bonding properties in a bonded body of a membrane and an electrode substrate. And

  As a result of intensive studies to achieve the above object, the present inventors have found that (1) catalyst particles and (2) at least one in one molecule, instead of a catalyst paste composed of a conventional catalyst and Nafion. A monomer having an ethylenically unsaturated group and at least one ion-conducting group or a precursor group capable of imparting an ion-conducting group using a chemical reaction, and (3) using a catalyst paste containing a solvent, It has been found that by forming a catalyst layer from a catalyst paste, it is possible to obtain a membrane / electrode assembly excellent in bondability, and the present invention has been made.

Accordingly, the present invention provides the following polymer polymer fuel cell catalyst paste.
[Claim 1]
(1) catalyst particles, (2) at least one ethylenically unsaturated group and at least one ion-conducting group or precursor group capable of imparting an ion-conducting group using a chemical reaction in one molecule; (3) Solvent , (4) Oligomer having at least two reactive groups copolymerizable with the ethylenically unsaturated group of component (2) above, and having a number average molecular weight of 400 or more A catalyst paste for a polymer electrolyte fuel cell, comprising:
[Claim 2]
2. The solid polymer fuel cell catalyst paste according to claim 1, wherein the ion conductive group of the component (2) is a sulfonic acid group.
[Claim 3 ]
The catalyst paste for a polymer electrolyte fuel cell according to claim 1 or 2, further comprising a fluororesin.
[Claim 4]
The oligomer (4) has a number average molecular weight of 400 to 10,000 obtained by urethanization reaction of (a) a polyol component, (b) a polyisocyanate component, and (c) a (meth) acrylate compound having a hydroxyl group. The catalyst paste for a polymer electrolyte fuel cell according to any one of claims 1 to 3.

  By using the catalyst paste for a polymer electrolyte fuel cell of the present invention, a hydrocarbon electrolyte in which the bonding property between the electrolyte membrane and the electrode substrate, particularly methanol permeability is smaller than that of a perfluorosulfonic acid membrane such as Nafion Bondability to the film can be improved. Therefore, by using the membrane-electrode assembly using the catalyst paste of the present invention, a direct methanol fuel cell with low methanol permeability and high reliability can be produced.

The present invention is described in detail below.
The catalyst paste of the present invention comprises (1) catalyst particles, (2) at least one ethylenically unsaturated group and at least one ion-conducting group or chemical reaction in one molecule. A monomer having an assignable precursor group, and (3) a solvent.

  Examples of the component (1) catalyst particles include platinum and platinum alloys. 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.

  (2) As a monomer having at least one ethylenically unsaturated group and at least one ion conductive group or a precursor group capable of imparting an ion conductive group using a chemical reaction, for example, Carboxylic acid group-containing monomers such as (meth) acrylic acid, acrylamide sulfonic acid, styrene sulfonic acid, allylbenzene sulfonic acid, allyloxybenzene sulfonic acid, vinyl sulfonic acid, allyl sulfonic acid, fluorovinyl sulfonic acid, perfluorovinyl ether sulfonic acid Phosphonic acid group-containing monomers such as sulfonic acid group and its alkali metal salts, phosphate group-containing monomers such as methacryloxyethyl phosphate, and compounds that do not have ion-conducting functional groups (use chemical reactions to improve ion conductivity) Glycidyl (meth) acrylic compound Such Tomonoma are exemplified monomers having a molecular weight of less than 1,000 is preferable in order to increase the ionic conductivity of the catalyst layer.

  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 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 alone or in admixture of two or more.

  (3) The solvent of the component is preferably a solvent that uniformly dissolves the ion conductive monomer. For example, alcohols such as methanol, ethanol, n-propanol, isopropanol, n-butanol, ethylene glycol, and glycerol, acetone, and methyl ethyl ketone Such as ketones, esters such as ethyl acetate and butyl acetate, ethers such as tetrahydrofuran and dioxane, aromatic hydrocarbons such as benzene and toluene, aliphatic or alicyclic such as n-heptane, n-hexane and cyclohexane Examples thereof include polar solvents such as hydrocarbon, water, dimethyl sulfoxide, N, N-dimethylformamide, N, N-dimethylacetamide, formamide, N-methylformamide, N-methylpyrrolidone, ethylene carbonate, and propylene carbonate. These can be used alone or in admixture of two or more. Among these, polar solvents are more preferable.

  The catalyst paste of the present invention comprises (1) catalyst particles, (2) at least one ethylenically unsaturated group and at least one ion-conducting group or chemical reaction in one molecule. A monomer having an assignable precursor group and (3) a solvent are contained, but other components can be introduced to improve the performance of the catalyst layer.

  For example, for the purpose of making the catalyst layer flexible and adjusting the EW value (exchange capacity weight), as the component (4), one reactive group copolymerizable with the ethylenically unsaturated group of the component (2) is used. It is also possible to add oligomers having at least two in the molecule. Such oligomers include polyethylene glycol di (meth) acrylate, di (meth) acrylate having a perfluoroalkyl ether structure, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, polybutylene glycol, fluoroethylene glycol, perfluoroalkyl ether structure. Examples include polyether polyacrylates such as diurethane (meth) acrylates of diols having polyesters, polyester polyacrylates, (meth) acryloxy group-containing organopolysiloxanes, vinyl group-containing organopolysiloxanes, alkoxy group-containing organopolysiloxanes, and the like. The number average molecular weight of the oligomer is preferably 400 or more in order to improve the curability.

  Here, examples of the reactive group include an ethylenically unsaturated group, which radically polymerizes with the ethylenically unsaturated group of component (2) to increase the molecular weight and increase the EW value. It is.

  The method for producing the oligomer of component (4) is not particularly limited. However, in the case of a polyurethane (meth) acrylate oligomer such as diurethane (meth) acrylate, the polyol and diisocyanate are reacted at OH / NCO <1, and the remaining isocyanate group is further reacted. It is preferable that a functional group (for example, a hydroxyl group) that reacts with a compound having an acrylic group is reacted.

  The polyurethane (meth) acrylate oligomer will be described in more detail. This can be obtained by a urethanization reaction of (a) a polyol component, (b) a polyisocyanate component, and (c) a (meth) acrylate compound having a hydroxyl group. The number average molecular weight of the polyurethane (meth) acrylate oligomer can be selected, for example, from the range of about 400 to 10,000, preferably about 400 to 5,000.

(A) Polyol component Examples of the polyol component include polyether polyols, polyester polyols, polycarbonate polyols, alkyl diols, etc., and fluorinated ones are also effectively used.
(Polyether polyol)
Examples of the polyether polyol include homopolymers or copolymers of alkylene oxides (for example, C _2-5 alkylene oxides such as ethylene oxide, propylene oxide, butylene oxide, tetrahydrofuran, and 3-methyl-tetrahydrofuran), and aliphatic C _{12. -40} polyols (for example, 1,2-hydroxystearyl alcohol, hydrogenated dimer diol, etc.) and the above alkylene oxide homopolymers or copolymers, alkylene oxides of bisphenol A (for example, propylene oxide, butylene oxide, Tetrahydrofuran, etc.) adducts, and hydrogenated bisphenol A alkylene oxide (eg, propylene oxide, butylene oxide, tetrahydrofuran, etc.) adducts. These fluorinated compounds are also preferably used. These polyether polyols can be used alone or in combination of two or more.

Preferred polyether polyols are C _2-4 alkylene oxides, in particular homopolymers or copolymers of C _3-4 alkylene oxides (propylene oxide and tetrahydrofuran) (polyoxypropylene glycol, polytetramethylene ether glycol, propylene oxide and tetrahydrofuran). And a copolymer thereof. These fluorinated compounds are also preferred. The number average molecular weight of the polyether polyol can be selected from the range of about 200 to 10,000, for example.

  As these commercially available products, for example, (1) polyethylene glycol, “PEG600”, “PEG1000”, “PEG2000” manufactured by Sanyo Chemical Industries, Ltd. (2) polyoxypropylene glycol, Takeda Pharmaceutical Co., Ltd. ) “Takelac P-21”, “Takelac P-22”, “Takelac P-23”, (3) “PTG650”, “PTG850” manufactured by Hodogaya Chemical Co., Ltd. as polytetramethylene ether glycol , "PTG1000", "PTG2000", "PTG4000", (4) "ED-28" manufactured by Mitsui Toatsu Chemical Co., Ltd. as a copolymer of propylene oxide and ethylene oxide, "Exenol 510" manufactured by Asahi Glass Co., Ltd. (5) As a copolymer of tetrahydrofuran and propylene oxide, Hodogaya "PPTG1000", "PPTG2000", "PPTG4000" manufactured by Kogyo Co., Ltd. (6) "Unisafe DC-1100", "Unisafe DC-1800" manufactured by NOF Corporation as a copolymer of tetrahydrofuran and ethylene oxide (7) As an adduct of ethylene oxide of bisphenol A, “Uniol DA-400” and “Uniol DA-700” manufactured by Nippon Oil & Fats Co., Ltd. (8) As an adduct of propylene oxide of bisphenol A, Japan “Uniol DB-400” manufactured by Yushi Co., Ltd. (9) As perfluoropolyether polyol, “Perfluorotriethylene glycol”, “Perfluorotetraethylene glycol” manufactured by Exfloor, “Fomblin Z DOL” manufactured by Ausimont ” Door can be.

(Polyester polyol)
Examples of the polyester polyol include ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, 1,5-pentaglycol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, and neopentyl glycol. Adducts of diol compounds with ε-caprolactam or β-methyl-δ-valerolactone; reaction products of the diol compounds with dibasic acids such as succinic acid, adipic acid, phthalic acid, hexahydrophthalic acid and tetrahydrophthalic acid A ternary reaction product of the diol compound, the dibasic acid, and ε-caprolactam or β-methyl-δ-valerolactone.

(Polycarbonate polyol)
Examples of the polycarbonate polyol include 1,6-hexanediol, 3-methyl-1,5-pentanediol, neopentyl glycol, 1,4-butanediol, 1,5-octanediol, 1,4-bis- ( Hydroxymethyl) cyclohexane, 2-methylpropanediol, dipropylene glycol, dibutylene glycol, diol compounds such as bisphenol A or short chain chains of these diol compounds and 2 to 6 mol addition products of ethylene oxide, dimethyl carbonate, diethyl carbonate, etc. The polycarbonate polyol which consists of a reaction product with a dialkyl carbonate is mentioned.
Furthermore, the polyester diol etc. which are ethylene oxide, propylene oxide, (epsilon) -caprolactam, or (beta) -methyl-delta-valerolactone addition reaction product of these polycarbonate polyols can also be used.
Examples of commercially available polycarbonate polyols include “Desmophen 2020E” manufactured by Sumitomo Bayer, “DN-980”, “DN-981”, “DN-982”, “DN-983” manufactured by Nippon Polyurethane. .

(Alkyl diol)
Examples of the alkyl diol include 1,6-hexanediol, 3-methyl-1,5-pentanediol, neopentyl glycol, 1,4-butanediol, 1,5-octanediol, 1,4-dihydroxycyclohexane, 1,4-bis- (hydroxymethyl) cyclohexane, 2-methylpropanediol, tricyclodecane dimethanol, 1,4-bis- (hydroxymethyl) benzene, bisphenol A, and perfluoroalkyldiol having 6 to 12 carbon atoms Etc.
Among these polyols, polyether polyols and alkyl diols are preferable from the viewpoint of balance of physical properties and durability of the resin of the present invention.

(B) Polyisocyanate component Examples of the polyisocyanate component include 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, m-phenylene diisocyanate, p-phenylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate, transcyclohexane-1, 4-diisocyanate, lysine diisocyanate, tetramethylxylene diisocyanate, l, 4-cyclohe San diisocyanate, 1,3-cyclohexane diisocyanate, 1,4-bis [isocyanate methyl] cyclohexane, methyl-2,4-cyclohexane diisocyanate, methyl-2,6-cyclohexane diisocyanate, norbornene diisocyanate (1,3-cyclopentene diisocyanate), etc. Diisocyanate, lysine ester triisocyanate, 1,6,11-undecane triisocyanate, 1,8-diisocyanate-4-isocyanate methyloctane, 1,3,6-hexamethylene triisocyanate, bicycloheptane triisocyanate, trimethylhexamethylene diisocyanate 1,3,5-triisocyanatecyclohexane, 1,3,5-trimethylisocyanatecyclohexane, 2 [3-isocyanatopropyl] -2,5-di [isocyanatomethyl] -bicyclo [2,2,1] heptane, 2- [3-isocyanatopropyl] -2,6-di [isocyanatomethyl] -bicyclo [2, 2,1] heptane, 3- [3-isocyanatopropyl] -2,5-di [isocyanatomethyl] -bicyclo [2,2,1] heptane, 5- [2-isocyanatoethyl] -2-isocyanatomethyl- 3- [3-Isocyanatopropyl] -bicyclo [2,2,1] heptane, 6- [2-isocyanatoethyl] -2-isocyanatomethyl-3- [3-isocyanatopropyl] -bicyclo [2,2,1] Heptane, 5- [2-isocyanatoethyl] -2-isocyanatomethyl-2- [3-isocyanatopropyl] -bicycl (B) Polyisocyanates such as [2,2,1] heptane, 6- [2-isocyanatoethyl] -2-isocyanatomethyl-2- [3-isocyanatopropyl] -bicyclo [2,2,1] heptane are used. The These diisocyanates may be used alone or in combination of two or more.
Among these, 2,4-tolylene diisocyanate and isophorone diisocyanate are preferable from the viewpoint of the ease of the synthesis reaction and the cured film characteristics.

(C) (Meth) acrylate compound having a hydroxyl group Examples of the (meth) acrylate having a hydroxyl group include hydroxyalkyl (meth) acrylate [for example, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, pentanediol mono (meth) acrylate, hexanediol mono (meth) acrylate, neopentyl glycol mono (meth) hydroxy -C _2-10 alkyl, such as acrylates (meth) acrylate, etc.], 2-hydroxy-3-phenyloxypropyl (meth) acrylate, 2-hydroxyalkyl (meth) acryloyl phosphate Fe 4-hydroxycyclohexyl (meth) acrylate, cyclohexane-1,4-dimethanol mono (meth) acrylate, trimethylolpropane di (meth) acrylate, pentaerythritol tri (meth) acrylate, and the like, and glycidyl group or The compound produced | generated by the addition reaction of an epoxy group containing compound (For example, alkyl glycidyl ether, allyl glycidyl ether, glycidyl (meth) acrylate, etc.) and (meth) acrylic acid is also mentioned. These hydroxyl group-containing (meth) acrylates can be used alone or in combination of two or more. Preferred hydroxyl group-containing (meth) acrylates are hydroxy C _2-4 alkyl (meth) acrylates, particularly 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate and the like.

  The polyurethane (meth) acrylate oligomer can be prepared by reacting the above components, and the ratio of each component constituting the polyurethane (meth) acrylate oligomer is, for example, with respect to 1 mol of the isocyanate group of the polyisocyanate. 0.1 to 0.8 mol of a hydroxyl group of the polyol component, preferably 0.2 to 0.7 mol, particularly about 0.2 to 0.5 mol, and 0.2 to 0.9 mol of a hydroxyl group-containing (meth) acrylate. , Preferably 0.3 to 0.8 mol, particularly about 0.5 to 0.8 mol.

  Moreover, the reaction method of the said component is not specifically limited, Each component may be mixed and made to react, and polyisocyanate will react with any one component among a polyol component and a hydroxyl-containing (meth) acrylate. Then, the other component may be reacted.

  Examples of catalysts for these urethanization reactions include organometallic urethanization catalysts such as stannous octoate, dibutyltin diacetate, dibutyltin dilaurate, cobalt naphthenate, lead naphthenate, and the like, for example, triethylamine, triethylenediamine, diaza An amine-based catalyst such as bicycloundecene can be used, but other known urethanization catalysts can also be used.

  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 as the component (5). 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), trifluoroethylene-ethylene copolymer (ECTFE), and the like can be used alone or in combination of two or more. it can. In addition, as these fluororesins, the commercial item about number average molecular weight 100,000-600,000 can be used.

  In the present invention, the number average molecular weight of the component (5) is more preferably 400 to 2,000, and still more preferably 800 to 1,000. In this case, this number average molecular weight is a polystyrene conversion value by gel permeation chromatography.

  The proportions of the above-mentioned (1) to (3) and (4) component oligomers and (5) component fluororesin component contained in the catalyst paste of the present invention are not limited and are appropriately selected within a wide range. The component (2) is 5 to 500 parts by mass, particularly 5 to 200 parts by mass, and the component (3) is the component excluding the component (3) with respect to 100 parts by mass of the component (1). 0 to 10,000 parts by mass, particularly 5 to 5,000 parts by mass, and (4) component is 10 to 400 parts by mass, particularly 20 to 100 parts by mass with respect to 100 parts by mass of component (100). It is preferable that a mass part and (5) component shall be the usage-amount of 10-400 mass parts with respect to 100 mass parts of (2) component, especially 40-130 mass parts.

  In order to form a catalyst layer from the catalyst paste of the present invention, when the catalyst paste is applied on an electrolyte membrane or a porous electrode substrate, and the component (1) and (4) in the paste are added (1 ) Component and (4) component are cured, and then the solvent of component (3) is removed.

  As a method for applying the catalyst paste 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.

As a curing method after applying the catalyst paste, it can be performed by heating, irradiation with ultraviolet rays or electron beams.
In the curing by heating, the catalyst paste applied is heated to 80 ° C. or higher, preferably 100 ° C. or higher. In this case, the upper limit of the temperature is appropriately selected, but from the viewpoint of heat resistance of the curable resin, 200 ° C. or less, particularly 180 ° C. or less is preferable. If the temperature is lower than 80 ° C, curing may be insufficient, and if it exceeds 200 ° C, the ion conductive group may be decomposed. The heating time varies depending on the heating temperature, but is usually 1 minute to 2 hours, particularly 3 minutes to 30 minutes. In order to accelerate curing, a thermal polymerization initiator such as azobisisobutyronitrile, benzoyl peroxide, or ammonium persulfate may be added to the catalyst paste.

Curing by ultraviolet rays, may be irradiated with 10 mJ / cm ² or more radiation dose, preferably 10~1,000mJ / cm ^2, the irradiation dose more desirable is 50~1,000mJ / cm ^2. If it is less than 10 mJ / cm ² , the curing of the curable resin may be insufficient, and if it exceeds 1,000 mJ / cm ² , energy is wasted and production efficiency is reduced, which is not economical. As in the case of heat curing, a photopolymerization initiator such as benzophenone may be used in combination in order to accelerate curing.

  Curing with an electron beam may be performed so that the absorbed dose is 5 kGy or more, preferably 5 to 1,000 kGy, and more preferably 10 to 500 kGy. If it is less than 5 kGy, curing may be insufficient, and if it exceeds 1,000 kGy, the curable resin may be decomposed.

  The temperature at the time of irradiation with ultraviolet rays or an electron beam may be around room temperature, but in order to adjust the viscosity of the catalyst paste so that it can be easily applied, or to make the coating thickness and the state of the coating surface constant, It is better to adjust the temperature of the irradiation atmosphere to be constant. In this case, the temperature of the paste or irradiation atmosphere is 25 to 60 ° C., and a constant temperature is desirable.

  Since the catalyst paste contains platinum or platinum alloy fine particles and / or a catalyst in which the catalyst paste is supported on carbon black, it is difficult to transmit ultraviolet rays. If an attempt is made to load a desired amount of catalyst, the coating thickness of the catalyst paste becomes thick, and there is a possibility that ultraviolet rays do not reach the inside sufficiently. Therefore, as a curing method, curing by heating or curing by an electron beam is preferable.

  The atmosphere for curing the catalyst paste is preferably an inert gas atmosphere such as nitrogen, helium or argon in order to facilitate radical polymerization, and the oxygen concentration in the gas is preferably 500 ppm or less, and more preferably 200 ppm or less.

  The solvent remains in the cured catalyst paste, particularly in the catalyst paste cured by ultraviolet rays or electron beam irradiation, but this can be removed by annealing. The upper limit of the annealing temperature is appropriately selected depending on the boiling point and vapor pressure of the solvent to be used, but is preferably 200 ° C. or less, particularly 180 ° C. or less from the viewpoint of the heat resistance of the cured resin. The catalyst layer obtained by curing is kept at a high temperature when the electrolyte membrane and the electrode substrate are integrated by a hot press method, or can be washed after integration, so that May not have been completely removed.

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 type and blending ratio of the component (2), oligomer, and fluororesin in the electrolyte membrane or catalyst paste to be used, but the desirable temperature range is 50 to 200 ° C., more desirably 80-180 ° 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 type and blending ratio of component (2), oligomer, and fluororesin in the electrolyte membrane and / or catalyst paste, and the type of porous electrode substrate. ˜100 kgf / cm ² , more desirably 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 an air electrode composed of a porous electrode substrate 2 made of carbon paper, carbon cloth, etc. and a catalyst layer 3, and 4 is a porous electrode substrate 5 made of carbon paper, carbon cloth, etc. A fuel electrode 7 including the catalyst 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.

  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 (made by Saint-Gobain, trademark Norton) having a size of 6 cm × 6 cm and a thickness of 50 μm 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, and 40 parts by mass of hexane. In a 500 cc separable flask charged with 0.01 parts by weight 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] Synthesis of oligomer 100 g of polytetramethylene glycol (manufactured by Hodogaya Chemical Co., Ltd.) having a number average molecular weight of 1,000 and 0.05 g of 2,6-di-tert-butylhydroxytoluene were placed in a reaction vessel, and nitrogen was introduced. Below, 33.7 g of 2,4-tolylene diisocyanate was added dropwise. After dropping, the mixture was further reacted at 70 ° C. for 2 hours, 0.02 g of dibutyltin dilaurate was added to make the atmosphere dry air, and then 22.5 g of 2-hydroxyethyl acrylate was dropped. Furthermore, it was made to react at 70 degreeC for 5 hours, and the polytetramethylene glycol urethane acrylate oligomer (B) whose number average molecular weight is 1,600 was obtained.

[ Reference Example 1]
The cathode electrode paste is composed of a carbon catalyst TEC10E50E (manufactured by Tanaka Kikinzoku) carrying 50% by mass of platinum as component (1), 2-acrylamido-2-methylpropanesulfonic acid (manufactured by Wako Pure Chemical Industries) as component (2), ( 3) N, N-dimethylformamide (hereinafter referred to as DMF) was used as the component. First, a dispersion liquid in which 2 g of TEC10E50E was dispersed in 6 g of DMF was prepared. Separately, a solution in which 1 g of 2-acrylamido-2-methylpropanesulfonic acid was dissolved in 4 g of DMF was prepared, added to the above dispersion, and further mixed to obtain a cathode electrode paste.

  The anode electrode paste includes a carbon catalyst TEC61E54 (manufactured by Tanaka Kikinzoku) carrying 54 mass% platinum + ruthenium in component (1), 2-acrylamido-2-methylpropanesulfonic acid in component (2), and component (3). It was prepared using DMF. A dispersion in which 2 g of TEC61E54 is dispersed in 6 g of DMF is prepared. Separately, a solution in which 1 g of 2-acrylamido-2-methylpropanesulfonic acid is dissolved in 4 g of DMF is prepared, and this is added to the above dispersion and further mixed. As a result, an anode electrode paste was obtained.

The catalyst layer was formed by applying the catalyst paste to the electrode side. Water repellent made of carbon paper TGP-H-060 (manufactured by Toray) as a porous electrode base material, and further comprising tetrafluoroethylene-hexafluoropropylene copolymer (FEP) and carbon black Vulcan-XC-72 (manufactured by Cabot) After applying the paste and forming a water-repellent layer by treating at 340 ° C., each catalyst paste was applied thereon with a bar coater. After coating, the resin component in the catalyst paste was cured by irradiation with an electron beam of 100 kGy at room temperature, and then dried at 100 ° C. for 2 hours. 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.

[Example 1 ]
For the cathode electrode paste, a dispersion was prepared by dispersing 2 g of TEC10E50E in 6 g of DMF. Separately, 0.8 g of 2-acrylamido-2-methylpropanesulfonic acid and 1.2 g of oligomer (B) were added to 8 g of DMF. A dissolved solution was prepared, and this was added to the catalyst dispersion and further mixed.

  The anode paste was prepared by dispersing 2 g of TEC61E54 in 6 g of DMF. Separately, 0.8 g of 2-acrylamido-2-methylpropanesulfonic acid and 1.2 g of oligomer (B) were dissolved in 8 g of DMF. An anode electrode paste was obtained by preparing a solution, adding this to the catalyst dispersion, and further mixing.

Formation of the catalyst layer were performed in the same manner as in Reference Example 1, loadings of Pt as the cathode 1 mg / cm ^2, loadings of PtRu as anode to produce an electrode which is 1 mg / cm ^2.

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.

[ Reference Example 2 ]
A catalyst paste using a fluororesin was prepared.
The cathode electrode paste was prepared by dispersing 2 g of TEC10E50E in 6 g of DMF. Separately, 0.8 g of 2-acrylamido-2-methylpropanesulfonic acid and polyvinylidene fluoride (PVDF) powder (Aldrich) were prepared. (Manufactured) A solution in which 1.2 g was dissolved in 8 g of DMF was prepared, added to the catalyst dispersion, and further mixed.

  For the anode electrode paste, a dispersion was prepared by dispersing 2 g of TEC61E54 in 6 g of DMF. Separately, 0.8 g of 2-acrylamido-2-methylpropanesulfonic acid and 1.2 g of PVDF powder were dissolved in 8 g of DMF. A solution was prepared, added to the catalyst dispersion, and further mixed to obtain an anode electrode paste.

Formation of the catalyst layer was performed in the same manner as in Reference Example 1 to produce an electrode having a Pt loading amount of 1 mg / cm ^{2 as} a cathode and a PtRu loading amount of 1 mg / cm ² as an anode.

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.
The cathode paste was obtained by mixing 4 g of catalyst particles TEC10E50E with 16 ml of water, adding 10 g of 20% by mass Nafion solution and 20 cc of isopropanol, and mixing. The anode paste was obtained by using TEC61E54 as catalyst particles in the same amount and procedure as in 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.

Confirmation of bondability is confirmed by immersing the membrane / electrode assembly produced in Example 1 , Reference Examples 1 and 2 and Comparative Example 1 in a 1M aqueous methanol solution at room temperature for 24 hours, and checking whether the electrode is peeled off from the electrolyte membrane. did. As a result, the membrane / electrode assembly produced in Example 1 and Reference Examples 1 and 2 showed no separation between the membrane and the electrode, whereas the membrane / electrode assembly produced in Comparative Example 1 The membrane and the electrode peeled off and separated.

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. Example 1, since the difference in the membrane electrode assembly prepared in Reference Example 1 and Comparative Example 1 is only the composition of the catalyst layer, by using a catalyst paste of the present invention, the bonding strength is improved I was confirmed.

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

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Air electrode 2 Porous electrode base material 3 Catalyst layer 4 Fuel electrode 5 Porous electrode base material 6 Catalyst layer 7 Proton conductive polymer electrolyte membrane

Claims (4)

(1) catalyst particles, (2) at least one ethylenically unsaturated group and at least one ion-conducting group or precursor group capable of imparting an ion-conducting group using a chemical reaction in one molecule; (3) Solvent , (4) Oligomer having at least two reactive groups copolymerizable with the ethylenically unsaturated group of component (2) above, and having a number average molecular weight of 400 or more A catalyst paste for a polymer electrolyte fuel cell, comprising:   2. The solid polymer fuel cell catalyst paste according to claim 1, wherein the ion conductive group of the component (2) is a sulfonic acid group. The catalyst paste for a polymer electrolyte fuel cell according to claim 1 or 2, further comprising a fluororesin. The oligomer (4) has a number average molecular weight of 400 to 10,000 obtained by urethanization reaction of (a) a polyol component, (b) a polyisocyanate component, and (c) a (meth) acrylate compound having a hydroxyl group. The catalyst paste for a polymer electrolyte fuel cell according to any one of claims 1 to 3.

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