Manufacturing method for membrane electrode assembly, membrane electrode assembly, and fuel cell

Abstract

To provide a fuel cell that is low-cost and has sufficient performance for practical use.SOLUTION: In a manufacturing method for a membrane electrode assembly 1 using an ink containing a complex 3, the complex 3 is a composite of a polymer 7 polymerized using a compound A having a polymerizable group, an ionic monomer, a compound B having multiple polymerizable groups, and an initiator, and a conductor 11 carrying a metal catalyst 9. The ink containing the complex 3 is applied to an electrolyte membrane 15 after plasma treatment.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a method for manufacturing a membrane electrode assembly, a membrane electrode assembly, and a fuel cell.

Background Art

[0002] Perfluoroalkylsulfonic acid-based polymers (Nafion (registered trademark)) are known as ionomers (polymer electrolytes) for fuel cells (proton exchange membrane fuel cells). Nafion has high synthesis raw material costs and undergoes complex manufacturing processes. Therefore, Nafion has the problem of being very expensive. Therefore, various new polymer electrolytes have been studied so far. For example, in Patent Document 1, a hydrocarbon-based polymer electrolyte having a polyphenylene ether main chain has been proposed.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the conventional technology, it has been difficult to obtain a fuel cell with low cost and practically sufficient performance. An object of the present disclosure is to provide a fuel cell with low cost and practically sufficient performance.

Means for Solving the Problems

[0005] The means of the present disclosure are shown below. A method for manufacturing a membrane electrode assembly using an ink containing a composite, wherein the composite is a composite of a polymer polymerized using a compound A having a polymerizable group, an ionic monomer, a compound B having a plurality of polymerizable groups, and an initiator, and a conductor supporting a metal catalyst. A method for manufacturing a membrane electrode assembly, comprising applying the ink containing the composite to an electrolyte membrane after plasma treatment.

Effects of the Invention

[0006] According to the present disclosure, a fuel cell having low cost and practically sufficient performance can be provided.

Brief Description of the Drawings

[0007]

Figure 1

Figure 2

Figure 3

Figure 4

Modes for Carrying Out the Invention

[0008] Here, another example of the present disclosure is shown. [1] A method for manufacturing a membrane electrode assembly using an ink containing a composite, comprising the composite being a composite of a polymer polymerized using a compound A having a polymerizable group, an ionic monomer, a compound B having a plurality of polymerizable groups, and an initiator, and a conductor supporting a metal catalyst, and applying the ink containing the composite to an electrolyte membrane after plasma treatment. [2] An electrolyte membrane, and a catalyst layer formed on the electrolyte membrane, the membrane electrode assembly comprising the catalyst layer containing a composite, the composite being a composite of a polymer polymerized using a compound A having a polymerizable group, an ionic monomer, a compound B having a plurality of polymerizable groups, and an initiator, and a conductor supporting a metal catalyst. [3] A fuel cell comprising the membrane electrode assembly described in [2].

[0009] Hereinafter, the present disclosure will be described in detail. In this specification, for a description using "-" for a numerical range, unless otherwise specified, it is assumed to include the lower limit value and the upper limit value. For example, in the description "10-20", both the lower limit value "10" and the upper limit value "20" are included. That is, "10-20" has the same meaning as "10 or more and 20 or less". Also, in this specification, the upper limit value and the lower limit value of each numerical range can be arbitrarily combined.

[0010] 1. Method for manufacturing the membrane electrode assembly 1 and the membrane electrode assembly 1 (1) Method for manufacturing the membrane electrode assembly 1 The method for manufacturing the membrane electrode assembly 1 of the present disclosure uses an ink containing the composite 3. The composite 3 is a composite of a polymer 7 described later and a conductor 11 supporting a metal catalyst 9. The polymer 7 is polymerized using a compound A having a polymerizable group, an ionic monomer, a compound B having a plurality of polymerizable groups, and an initiator. In the method for manufacturing the membrane electrode assembly 1 of the present disclosure, the ink containing the composite 3 is applied to the electrolyte membrane 15. The manufacturing method of the present disclosure is particularly effective when forming the cathode catalyst layer 17B having excellent characteristics. However, the manufacturing method of the present disclosure can also be used when forming the anode catalyst layer 17A.

[0011] (2) Membrane electrode assembly 1 The membrane electrode assembly 1 includes an electrolyte membrane 15 and a catalyst layer 17 formed on the electrolyte membrane 15. The catalyst layer 17 contains the composite 3. The composite 3 is a composite of a polymer 7 polymerized using a compound A having a polymerizable group, an ionic monomer, a compound B having a plurality of polymerizable groups, and an initiator, and a conductor 11 supporting a metal catalyst 9. The membrane electrode assembly 1 usually includes an anode catalyst layer 17A formed on one surface of the electrolyte membrane 15 and a cathode catalyst layer 17B formed on the other surface of the electrolyte membrane 15. The membrane electrode assembly 1 is referred to as an MEA (Membrane Electrode Assembly).

[0012] (3) Electrolyte membrane 15 The electrolyte membrane 15 is not particularly limited. The electrolyte constituting the electrolyte membrane 15 is preferably an ion-conductive polymer electrolyte. The electrolyte preferably contains, for example, one or more selected from the group consisting of fluorine-based polymer electrolytes and hydrocarbon-based polymer electrolytes, and more preferably contains a fluorine-based polymer electrolyte. The resin constituting the fluorine-based polymer electrolyte is, for example, perfluorocarbon sulfonic acid-based polymers such as Nafion (registered trademark, manufactured by DuPont), Aciplex (registered trademark, manufactured by Asahi Kasei Corporation), Flemion (registered trademark, manufactured by Asahi Glass Co., Ltd.), perfluorocarbon phosphonic acid-based polymers, trifluorostyrene sulfonic acid-based polymers, ethylene tetrafluoroethylene-g-styrene sulfonic acid-based polymers, ethylene-tetrafluoroethylene copolymers, polyvinylidene fluoride-perfluorocarbon sulfonic acid-based polymers, and the like. The fluorine-based polymer electrolyte is particularly preferably a fluorine-based polymer electrolyte composed of a perfluorocarbon sulfonic acid-based polymer.

[0013] Examples of the hydrocarbon-based electrolyte include sulfonated polyethersulfone (S-PES), sulfonated polyaryl ether ketone, sulfonated polybenzimidazole alkyl, phosphonated polybenzimidazole alkyl, sulfonated polystyrene, sulfonated polyether ether ketone (SPEEK), sulfonated polyphenylene (S-PP), and the like.

[0014] (4) Composite 3 The composite 3 is formed by the composite of a polymer 7 described later and a conductor 11 supporting a metal catalyst 9. (4.1) Polymer 7 The polymer 7 is polymerized using a compound A having a polymerizable group, an ionic monomer, a compound B having a plurality of polymerizable groups, and an initiator. The polymer 7 is an electrolyte having proton conductivity. The polymer constituting the polymer 7 is not particularly limited. Polymer 7 contains a repeating unit derived from compound A having a polymerizable group, a repeating unit derived from an ionic monomer, and a repeating unit derived from compound B having a plurality of polymerizable groups. In this specification, the "compound A having a polymerizable group" refers to a compound having a single polymerizable group, and is a concept excluding the "compound B having a plurality of polymerizable groups (crosslinkable monomer)" described later. Examples of the compound A having a polymerizable group include styrene, t-butylstyrene, α-methylstyrene, β-methylstyrene, p-methylstyrene, N,N-dimethyl-p-aminoethylstyrene, N,N-diethyl-p-aminoethylstyrene, methyl acrylate, methyl methacrylate, etc. From the viewpoint of cost, styrene is preferred. The compound A having a polymerizable group may be used alone or in combination of two or more. Examples of the ionic monomer include vinyl monomers having a sodium sulfonate group, vinyl monomers having an amino group, etc. Examples of the vinyl monomer having a sodium sulfonate group include sodium 4-styrenesulfonate, sodium 2-sulfoethyl methacrylate, sodium β-styrenesulfonate, etc. From the viewpoint of cost, sodium 4-styrenesulfonate is preferred. The ionic monomer may be used alone or in combination of two or more. The compound B having a plurality of polymerizable groups functions as a crosslinkable monomer. Examples of the compound B having a plurality of polymerizable groups include divinylbenzene, ethylene glycol dimethacrylate, 1,3-butylene glycol dimethacrylate, trimethylolpropane trimethacrylate, allyl methacrylate, etc. From the viewpoint of cost, divinylbenzene is preferred. The compound B having a plurality of polymerizable groups may be used alone or in combination of two or more. The content ratio of each repeating unit contained in the polymer 7 is not particularly limited. In addition, although the mass ratio of the compound A having a polymerizable group and the compound B having a plurality of polymerizable groups is not particularly limited, the following ratio is preferred when the total of the compound A and the compound B is 100 parts by mass. Compound A: 10 parts by mass or more and 100 parts by mass or less Compound B: 0 parts by mass or more and 90 parts by mass or less

[0015] (4.2) Metal catalyst 9 As the metal catalyst 9 (catalyst particles), in addition to platinum group elements such as platinum, palladium, ruthenium, iridium, rhodium, and osmium, metals such as iron, lead, gold, silver, silicon, germanium, tin, indium, cadmium, zinc, tungsten, tantalum, copper, cobalt, nickel, chromium, iron, vanadium, manganese, yttrium, technetium, gallium, niobium, molybdenum, zirconium, rhenium, aluminum, titanium, etc., or alloys thereof can be used. The particle size of the catalyst is not particularly limited. From the viewpoints of improving the activity of the catalyst and the stability of the catalyst, the particle size of the catalyst is preferably 0.3 nm or more and 30 nm or less, and more preferably 0.5 nm or more and 10 nm or less. When the catalyst contains at least one noble metal selected from the group consisting of platinum (Pt), palladium (Pd), rhodium (Rh), gold (Au), silver (Ag), iridium (Ir), and ruthenium (Ru), it has excellent electrode reactivity and can perform the electrode reaction efficiently and stably. The particle size of the catalyst can be determined, for example, by the following method. Observe the catalyst with a transmission electron microscope (TEM). Print out the TEM photograph on paper, regard the catalyst (black circular image) as a sphere, regard the distance from end to end of the catalyst as the diameter, and randomly measure a total of 300 particles from the images of several fields of view (3 to 5 fields of view). The average of the 300 counted diameters is taken as the particle size.

[0016] (4.3) Conductor 11 The conductor 11 is an electronically conductive substance (catalyst-supporting particles) that supports the metal catalyst 9. The conductor 11 is not particularly limited. As the conductor 11, carbon particles are preferably used. The type of carbon particles is not limited. As the carbon particles, carbon black, graphene, graphite, graphite, activated carbon, carbon fiber, carbon nanotube, fullerene, etc. are preferably used. The particle size of the carbon particles is not particularly limited. From the viewpoint of forming a good electron conduction path and ensuring the gas diffusibility of the catalyst layer, the particle size of the carbon particles is preferably 10 nm or more and 1000 nm or less, and more preferably 10 nm or more and 100 nm or less. The particle size of the conductor 11 can be determined, for example, by the following method. Observe the conductor 11 with a transmission electron microscope (TEM). Print out the TEM photograph on paper, regard the conductor 11 as spherical, regard the distance from end to end of the conductor 11 as the diameter, and randomly measure a total of 300 particles from the images of several fields of view (3 to 5 fields of view). The average of the 300 counted diameters is taken as the particle size.

[0017] (4.4) Structure of the composite 3 The structure of the composite 3 is not particularly limited. In the composite 3, it is preferable that there are a coated portion 21 coated with the polymer 7 and an uncoated portion 23 not coated with the polymer 7 in the conductor 11 supporting the metal catalyst 9. In the coated portion 21, the metal catalyst 9 is covered with the polymer 7. On the other hand, in the uncoated portion 23, the metal catalyst 9 is not covered with the polymer 7. In the uncoated portion 23, since the metal catalyst 9 is not covered with the polymer 7, the gas diffusion is good. Also, in the uncoated portion 23, since the metal catalyst 9 is not covered with the polymer 7, the catalyst poisoning is small.

[0018] (4.5) Manufacturing method of the composite 3 The manufacturing method of the composite 3 is not particularly limited. Hereinafter, a preferable manufacturing method will be described. By using this manufacturing method, a high-performance composite 3 can be obtained. In the preferable manufacturing method, a polymerization reaction is started in a solvent using a monomer group containing a compound A having a polymerizable group, an ionic monomer, and a compound B having a plurality of polymerizable groups, and an initiator. After the start of the polymerization reaction, a conductor 11 carrying a metal catalyst 9 is introduced into a solvent in which at least one of the monomer groups remains, and the polymerization reaction is further advanced. By this production method, a coated portion 21 coated with the polymer 7 and an uncoated portion 23 not coated with the polymer 7 can be formed on the conductor 11 carrying the metal catalyst 9.

[0019] (4.5.1) Monomer group The monomer group includes a compound A having a polymerizable group, an ionic monomer, and a compound B having a plurality of polymerizable groups. For the "compound A having a polymerizable group", "ionic monomer", and "compound B having a plurality of polymerizable groups", the descriptions in the column of "(4.1) Polymer 7" are applied as they are, and the description is omitted. That is, the "compound A having a polymerizable group", "ionic monomer", and "compound B having a plurality of polymerizable groups" described in the item of "(4.1) Polymer 7" are applied as they are. The usage amount of each monomer (compound A having a polymerizable group, ionic monomer, compound B having a plurality of polymerizable groups) may be appropriately set according to polymerization conditions such as the type of monomer used, the type of initiator used, the amount of initiator, polymerization temperature, polymerization concentration, etc., and is not particularly limited.

[0020] (4.5.2) Initiator (polymerization initiator) The initiator is not particularly limited as long as it can initiate polymerization by generating radicals, anions, or cations. As the initiator, for example, peroxides and azo compounds are preferably exemplified. The initiator can be appropriately selected according to the polymerization temperature, solvent, type of monomer, etc. Examples of the peroxide among the initiators include potassium persulfate, t-butyl hydroperoxide, cumene hydroperoxide, t-butyl peroxyacetate, t-butyl peroxybenzoate, t-butyl peroxyoctanoate, t-butyl peroxypivalate, t-butyl peroxyneodecanoate, t-butyl peroxyisobutyrate, lauroyl peroxide, t-amyl peroxypivalate, t-butyl peroxypivalate, dicumyl peroxide, benzoyl peroxide, ammonium persulfate, etc.

[0021] Examples of azo compounds include oil-soluble azo compounds such as 2,2'-azobis(isobutyronitrile), 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), dimethyl 2,2'-azobis(2-methylpropionate), 2,2'-azobis(2-methylbutyronitrile), 1,1'-azobis(cyclohexanecarbonitrile), 2,2'-azobis[N-(2-propenyl)-2-methylpropionamide], 2,2'-azobis[N-butyl-2-methylpropionamide]; water-soluble azo compounds such as 2,2'-azobis[2-(2-imidazolin-2-yl)propane] dihydrochloride, 2,2'-azobis[2-(2-imidazolin-2-yl)propane] disulfate dihydrate, 2,2'-azobis(2-methylpropionamide) dihydrate, 2,2'-azobis[N-(2-carboxyethyl)-2-methylpropionamide] tetrahydrate, 2,2'-azobis[2-(2-imidazolin-2-yl)propane], 2,2'-azobis[2-methyl-N-(2-hydroxyethyl)propionamide], 2,2'-azobis[1-imino-1-pyrrolidino-2-methylpropane] dihydrochloride, etc. The initiator may be used alone or in combination of two or more.

[0022] The amount of the initiator used may be appropriately set according to polymerization conditions such as the type of monomer used, the amount of monomer, the type of initiator used, the polymerization temperature, the polymerization concentration, etc., and is not particularly limited.

[0023] (4.5.3) Solvent The solvent is not particularly limited. The solvent preferably contains at least a solvent capable of dissolving the monomer. As such a solvent, at least one selected from the group consisting of alcohol, water, ketone, and ether can be preferably used. As the alcohol, an alcohol having 1 to 5 carbon atoms is preferably used. Examples of the alcohol having 1 to 5 carbon atoms include at least one selected from the group consisting of ethanol, methanol, 1-propanol, 2-propanol, isopropyl alcohol, 1-butanol, 2-butanol, t-butyl alcohol, 1-pentanol, and 3-pentanol. Among these, from the viewpoint of reducing the environmental load, it is preferable to use ethanol. Examples of the ketone preferably include acetone, methyl ethyl ketone, pentanone, methyl isobutyl ketone, heptanone, cyclohexanone, methyl cyclohexanone, acetonylacetone, and diisobutyl ketone. Examples of the ether preferably include tetrahydrofuran, dioxane, diethylene glycol dimethyl ether, anisole, methoxytoluene, and dibutyl ether. In addition to those described above, as the solvent, polar solvents such as dimethylformamide, dimethylacetamide, N-methylpyrrolidone, ethylene glycol, diethylene glycol, diacetone alcohol, and 1-methoxy-2-propanol can also be used. The solvent may be used alone or in a mixture of two or more. From the viewpoint of facilitating the distribution control of the polymer electrolyte, a mixed solvent of an organic solvent and water is preferable. When using a mixed solvent of an organic solvent and water, the ratio of the amount of the organic solvent to the amount of water is not particularly limited. The mixing ratio (volume ratio) of the organic solvent to water is preferably 1:1000 - 1000:1, more preferably 1:100 - 100:1, and still more preferably 1:10 - 10:1 in terms of facilitating the distribution control of the polymer electrolyte. The amount of the solvent is not particularly limited. From the viewpoint of facilitating the distribution control of the polymer electrolyte, for example, with respect to 100 parts by mass of the total amount of the monomers, it is preferably 10 parts by mass or more and 5000000 parts by mass or less, more preferably 100 parts by mass or more and 500000 parts by mass or less, and still more preferably 1000 parts by mass or more and 50000 parts by mass or less.

[0024] (4.5.4) Polymerization temperature The polymerization temperature is not particularly limited. The polymerization temperature is appropriately set according to polymerization conditions such as the type of initiator, the type of monomer, the amount of initiator, the amount of monomer, the polymerization concentration, etc. When a peroxide is used as the initiator, for example, a suitable polymerization reaction proceeds at a polymerization temperature of 40°C or higher and 100°C or lower.

[0025] (4.5.5) Conductor 11 supporting metal catalyst 9 Regarding the "conductor 11 supporting the metal catalyst 9", the description in the column of "(4) Composite 3" is directly applied as it is, and the description thereof is omitted. That is, the "(4.2) Metal catalyst 9" and "(4.3) Conductor 11" described in the item of "(4) Composite 3" are directly applied as they are. The amount of the conductor 11 supporting the metal catalyst 9 introduced in the production method of the present disclosure is not particularly limited. From the viewpoint of facilitating the control of the distribution of the polymer 7, the amount of the conductor 11 supporting the metal catalyst 9 is preferably 0.001 part by mass or more and 50000 parts by mass or less, more preferably 0.01 part by mass or more and 5000 parts by mass or less, and still more preferably 0.1 part by mass or more and 500 parts by mass or less, based on 100 parts by mass of the total amount of the monomers.

[0026] (4.5.6) Initiation of polymerization reaction In the reaction vessel, at least one selected from the group of monomers (including compound A having a polymerizable group, an ionic monomer, and compound B having a plurality of polymerizable groups) and an initiator are put in, and polymerization can be started by raising the temperature. The timing of putting the compound A having a polymerizable group, the ionic monomer, and the compound B having a plurality of polymerizable groups into the solvent is not particularly limited. The compound A having a polymerizable group, the ionic monomer, and the compound B having a plurality of polymerizable groups may be added separately, or two of them may be added after adding one of them, or one of them may be added after adding two of them, or the three may be added simultaneously.

[0027] (4.5.7) Introduction of conductor 11 supporting metal catalyst 9 and further polymerization reaction In the method for producing the composite 3 of the present disclosure, after the start of the polymerization reaction, a conductor 11 supporting a metal catalyst 9 is introduced into a solvent in which at least one of the monomer groups remains, and the polymerization reaction is further advanced. Here, at least one of the monomer groups is at least one of a compound A having a polymerizable group, an ionic monomer, and a compound B having a plurality of polymerizable groups. That at least one of the monomer groups remains means, in other words, the middle of the polymerization reaction. During the polymerization reaction, the polymer is considered to be relatively short and not curled. That is, it is presumed to exist in a state like a chain-like oligomer. In this state, when the conductor 11 supporting the metal catalyst 9 is present in the solvent, it is considered that a polymer like a chain-like oligomer adsorbs to the conductor 11 supporting the metal catalyst 9. Then, it is considered that the monomer remaining in the solvent reacts with the polymer like a chain-like oligomer, and the polymer grows to become the polymer 7. According to the production method of the present disclosure, a polymer like the above-described chain-like oligomer adsorbs to the conductor 11 supporting the metal catalyst 9, and through the process of growth of this polymer, it is presumed that a coated portion 21 coated with the polymer 7 and an uncoated portion 23 not coated with the polymer 7 are formed on the conductor 11. The timing for introducing the conductor 11 supporting the metal catalyst 9 into the solvent in which at least one of the monomer groups remains is not particularly limited. For example, this timing can be adopted from 10 seconds to 1 hour after the start of polymerization. The reaction time of the further polymerization reaction after the conductor 11 supporting the metal catalyst 9 is introduced is not particularly limited. The reaction time is, for example, 1 minute or more and 200 hours or less.

[0028] (4.5.8) Treatment after the polymerization reaction Post-treatment may be performed after the polymerization reaction. For example, the conductor 11 may be washed. For washing, for example, an alcohol having 1 to 5 carbon atoms or water may be used. Regarding the "alcohol having 1 to 5 carbon atoms", the description in the column of "(4) Composite 3" is applied as it is, and the description thereof is omitted. That is, the description of the "alcohol having 1 to 5 carbon atoms" described in the item of "(4) Composite 3" is applied as it is.

[0029] (5) Ink The ink contains the composite 3 and a solvent as a dispersion medium. (5.1) Solvent The solvent is not particularly limited. It is preferable that the boiling point of the solvent is 10°C or higher and 100°C or lower, more preferably 15°C or higher and 100°C or lower, and even more preferably 25°C or higher and 100°C or lower. The solvent preferably contains at least a volatile organic solvent. As the organic solvent, at least one selected from the group consisting of alcohols, ketones, and ethers can be preferably used. From the viewpoint of volatility, alcohols having 1 to 5 carbon atoms are preferably used as the alcohol. As the alcohol having 1 to 5 carbon atoms, at least one selected from the group consisting of ethanol, methanol, 1-propanol, 2-propanol, isopropyl alcohol, 1-butanol, 2-butanol, t-butyl alcohol, 1-pentanol, and 3-pentanol can be preferably used. Among these, from the viewpoint of reducing the environmental load, it is preferable to use ethanol. Examples of the ketone include acetone, methyl ethyl ketone, pentanone, methyl isobutyl ketone, heptanone, cyclohexanone, methyl cyclohexanone, acetonylacetone, and diisobutyl ketone. Examples of the ether include tetrahydrofuran, dioxane, diethylene glycol dimethyl ether, anisole, methoxytoluene, and dibutyl ether. In addition to those described above, polar solvents such as dimethylformamide, dimethylacetamide, N-methylpyrrolidone, ethylene glycol, diethylene glycol, diacetone alcohol, and 1-methoxy-2-propanol can also be used as the solvent. The solvent may be used as a mixture of two or more kinds. The blending amount of the solvent is preferably 80 parts by mass or more and 99.9 parts by mass or less, more preferably 85 parts by mass or more and 99 parts by mass or less, and still more preferably 80 parts by mass or more and 98 parts by mass or less, when the total amount of the ink is 100 parts by mass, from the viewpoint of forming the cathode catalyst layer 17B or the anode catalyst layer 17A that is advantageous for gas supply and discharge of generated water due to the volatilization of the solvent. From the viewpoint of forming the cathode catalyst layer 17B or the anode catalyst layer 17A that is advantageous for gas supply and discharge of generated water due to the volatilization of the solvent, the organic solvent is preferably a mixed solvent mixed with water. When using a mixed solvent of an organic solvent and water as the solvent, the ratio of the amount of the organic solvent to the amount of water is not particularly limited. The mixing ratio (mass ratio) of the organic solvent to water is preferably 20:80 - 80:20, more preferably 30:70 - 70:30, and still more preferably 40:60 - 60:40, in terms of forming the cathode catalyst layer 17B or the anode catalyst layer 17A that is advantageous for gas supply and discharge of generated water due to the volatilization of the solvent.

[0030] (5.2) Other components In order to disperse the composite 3, a dispersant may be contained in the ink. Examples of the dispersant include anionic surfactants, cationic surfactants, amphoteric surfactants, nonionic surfactants, and the like.

[0031] (5.3) Solids concentration of the ink The solids concentration of the ink is not particularly limited. From the viewpoint of suppressing variations in the coating amount, etc., the solids concentration is preferably 0.1% by mass or more and 20% by mass or less, more preferably 1% by mass or more and 15% by mass or less, and still more preferably 2% by mass or more and 10% by mass or less.

[0032] (6) Coating method The coating method is not particularly limited. As the coating method, for example, a spray method, a doctor blade method, a die coating method, a dipping method, a screen printing method, a laminator roll coating method can be used. From the viewpoint of suppressing variations in the coating amount, etc., the spray method is preferred. The coating thickness before drying is not particularly limited. From the viewpoint of suppressing variations in coating amount, the coating thickness is preferably 0.03 μm or more and 600 μm or less, more preferably 0.1 μm or more and 200 μm or less, and still more preferably 0.2 μm or more and 100 μm or less. In addition, from the viewpoint of the affinity between the composite 3 and the electrolyte membrane 15, it is preferable to perform plasma treatment on the electrolyte membrane 15 before coating.

[0033] 2. Fuel cell 30 The fuel cell 30 includes a membrane electrode assembly 1. Examples of the fuel cell 30 include a polymer electrolyte fuel cell (PEFC), a phosphoric acid fuel cell (PAFC), a molten carbonate fuel cell (MCFC), an alkaline electrolyte fuel cell (AFC), and a direct form fuel cell (DFC). In the fuel cell 30 of the present disclosure, the conductor 11 carrying the metal catalyst 9 has a coated portion 21 coated with the polymer 7 and an uncoated portion 23 not coated with the polymer 7, so that gas diffusion is good and the performance is high. A configuration example of the fuel cell 30 will be described. This fuel cell 30 is a polymer electrolyte fuel cell as a preferred example. As shown in FIG. 1, the fuel cell 30 includes an electrolyte membrane 15. The electrolyte membrane 15 (polymer electrolyte membrane) is composed of, for example, a perfluorosulfonic acid resin. Anode catalyst layers 17A and cathode catalyst layers 17B are provided on both sides of the electrolyte membrane 15 so as to sandwich it. The electrolyte membrane 15 and a pair of anode catalyst layers 17A and cathode catalyst layers 17B sandwiching it constitute the membrane electrode assembly 1.

[0034] A gas diffusion layer 31 is provided outside the anode catalyst layer 17A. The gas diffusion layer 31 is composed of a porous material such as carbon paper, carbon cloth, or a metal porous body, and has a function of uniformly diffusing the gas supplied from the separator 33 side to the anode catalyst layer 17A. Similarly, a gas diffusion layer 35 is provided outside the cathode catalyst layer 17B. The gas diffusion layer 35 has a function of uniformly diffusing the gas supplied from the separator 37 side to the cathode catalyst layer 17B. In this figure, only one set of the membrane electrode assembly 1, gas diffusion layers 31 and 35, and separators 33 and 37 configured as described above is shown, but in an actual fuel cell 30, the membrane electrode assembly 1 and gas diffusion layers 31 and 35 may be stacked in a plurality through the separators 33 and 37 to have a stack structure.

Example

[0035] 1. Preparation of Membrane Electrode Assembly 1 A. Example (1) Formation of Cathode Catalyst Layer 17B (1.1) Preparation of Composite 3 Sodium 4-styrenesulfonate (NaSS, 0.12 g), potassium persulfate (KPS, 1.0 g), ethanol (340.9 mL), and water (Milli-Q water (registered trademark), 92.9 mL) were mixed. This mixture was heated to 70°C. Then, a mixture of styrene and divinylbenzene (DVB) (4.1 mL, 99:1, wt / wt) was added. Two minutes later, an aqueous dispersion of Pt-supported carbon (TEC10V50E, Tanaka Kikinzoku Kogyo K.K.) (62.0 mL, containing 0.15 g of Pt-supported carbon) was further added and reacted at 70°C for another 2 hours. After naturally cooling this solution to room temperature, it was washed with ethanol and water (Milli-Q water (registered trademark)) to obtain Composite 3. When observed with a transmission electron microscope (TEM) of Composite 3, there were a coated portion 21 coated with polymer 7 and an uncoated portion 23 not coated with polymer 7 in Composite 3.

[0036] (1.2) Preparation of Ink for Cathode Catalyst Layer 17B The composite 3 was dispersed in a mixed solvent of ethanol and water (ethanol / water = 1 / 1 (w / w)) to prepare an ink. The solid content concentration of the ink was 6% by mass.

[0037] (1.3) Treatment of the electrolyte membrane 15 As the electrolyte membrane 15, a Nafion membrane (NR-211, The Chemours Company) was used. The surface (one side) of the electrolyte membrane 15 was subjected to plasma treatment under the following apparatus and conditions. <Plasma treatment> Carbon coater with hydrophilic treatment function (CADE-E, Meiwa Fosis Co., Ltd.) For 15 seconds 5×10 0 Pa

[0038] (1.4) Formation of the cathode catalyst layer 17B The ink was spray-coated on the treated surface of one side of the electrolyte membrane 15 after plasma treatment to obtain an electrolyte membrane 15 provided with a cathode catalyst layer 17B. The portion of the cathode catalyst layer 17B was rectangular, and the area of the cathode catalyst layer 17B was 50 mm × 50 mm. In the electrolyte membrane 15 after the formation of the cathode catalyst layer 17B, it was confirmed that there were no defects such as cracks in the cathode catalyst layer 17B and little non-uniformity in thickness. Therefore, it was confirmed that the composite 3 and the electrolyte membrane 15 had high affinity.

[0039] (2) Formation of the anode catalyst layer 17A An anode catalyst layer 17A was formed on the other surface of the electrolyte membrane 15 on which the cathode catalyst layer 17B was formed. The anode catalyst layer 17A was formed as follows. (2.1) Materials · Catalyst (conductor supporting the catalyst): TEC10EA20E manufactured by Tanaka Kikinzoku Kogyo K.K. · Ionomer dispersion (ionic conductor dispersion): 20 mass% Nafion dispersion solution DE2020 CS type manufactured by Fujifilm Wako Pure Chemical Corporation · Ethanol (solvent): Reagent grade ethanol (99.5) manufactured by Fujifilm Wako Pure Chemical Corporation · Water (solvent): Ultrapure water ·Electrolyte membrane (solid polymer electrolyte membrane): Nafion NR-211 (thickness: 25 μm) manufactured by Chemours

[0040] (2.2) Catalyst ink composition ·Solid content (catalyst + ionomer): 7% by mass ·Water:ethanol ratio = 1:1 ·Ionomer / carbon weight ratio (I / C): 0.75 (mass ratio)

[0041] (2.3) Production procedure of catalyst layer transfer sheet (substrate with anode catalyst layer 17A formed) The catalyst, ultrapure water, ionomer dispersion, and ethanol were put into a beaker in this order and stirred with an ultrasonic homogenizer. The stirred solution (anode catalyst ink) was dropped onto a PTFE sheet (substrate) attached to glass. It was spread with an applicator and air-dried. The air conditioner was adjusted so that the room temperature was about 25°C. In this way, a catalyst layer transfer sheet with an anode catalyst layer 17A formed on one side was produced. <Equipment and supplies used> ·Ultrasonic homogenizer: UH-50 manufactured by SMT Co., Ltd. ·Tabletop coater: TC-3 type manufactured by Mitsui Electric Precision Co., Ltd. ·Applicator: YBA-2 type manufactured by Yoshimitsu Seiki Co., Ltd. ·PTFE sheet: MSF-100 manufactured by Chukyo Chemical Industry Co., Ltd.

[0042] (2.4) Transfer of anode catalyst layer 17A The anode catalyst layer 17A of the catalyst layer transfer sheet was joined to the other side of the electrolyte membrane 15 on which the cathode catalyst layer 17B was formed (the side where the cathode catalyst layer 17B was not formed) so that they faced each other. When joining, the substrate was heated. Then, the substrate was peeled off to manufacture the membrane electrode assembly 1 shown in Fig. 1.

[0043] B. Comparative Example 1 An attempt was made to create a catalyst layer transfer sheet provided with a cathode catalyst layer by applying an ink containing the composite 3 onto a substrate (PTFE sheet) that had not been plasma-treated. However, the substrate and the composite 3 had low affinity, and defects such as cracks occurred.

[0044] C. Comparative Example 2 (1) Formation of the cathode catalyst layer 17B The cathode catalyst layer 17B was formed as follows. (1.1) Materials · Catalyst (conductor supporting the catalyst): TEC10V50E manufactured by Tanaka Kikinzoku Kogyo K.K. · Ionomer dispersion (ionic conductor dispersion): 20 mass% Nafion dispersion solution DE2020 CS type manufactured by Fujifilm Wako Pure Chemical Corporation · Ethanol (solvent): Reagent grade ethanol (99.5) manufactured by Fujifilm Wako Pure Chemical Corporation · Water (solvent): Ultrapure water · Electrolyte membrane (solid polymer electrolyte membrane): Nafion NR-211 (thickness: 25 μm) manufactured by Chemours

[0045] (1.2) Catalyst ink composition · Solids content (catalyst + ionomer) 7 mass% · Water:ethanol ratio = 1:1 · Ionomer / carbon weight ratio (I / C) 0.75 (mass ratio)

[0046] (1.3) Production procedure of the catalyst layer transfer sheet (substrate with the cathode catalyst layer 17B formed) Into a beaker, the catalyst, ultrapure water, ionomer dispersion, and ethanol were put in this order and stirred with an ultrasonic homogenizer. The stirred solution (cathode catalyst ink) was dropped onto a PTFE sheet (substrate) pasted on glass. It was spread with an applicator and air-dried. The air conditioner was adjusted so that the room temperature was about 25°C. In this way, a catalyst layer transfer sheet with the cathode catalyst layer 17B formed on one side was produced. <Equipment and supplies used> · Ultrasonic homogenizer: UH-50 manufactured by SMT Co., Ltd. · Desktop coater: TC-3 type manufactured by Mitsui Electric Machine Co., Ltd. · Applicator: YBA-2 type manufactured by Yoshimitsu Seiki Co., Ltd. · PTFE sheet: MSF-100 manufactured by Chukyo Chemical Industry Co., Ltd.

[0047] (1.4) Transfer of the cathode catalyst layer 17B It was joined to the surface (one side) of the electrolyte membrane 15 so that the cathode catalyst layer 17B of the catalyst layer transfer sheet faced it. When joining, the base material was heated. Then, the base material was peeled off to obtain the electrolyte membrane 15 provided with the cathode catalyst layer 17B.

[0048] (2) Formation of the anode catalyst layer 17A The anode catalyst layer 17A was formed on the other surface of the electrolyte membrane 15 on which the cathode catalyst layer 17B was formed. The anode catalyst layer 17A was formed as follows. (2.1) Materials · Catalyst (conductor supporting the catalyst): TEC10EA20E manufactured by Tanaka Precious Metals Industry Co., Ltd. · Ionomer dispersion liquid (ionic conductor dispersion liquid): 20 mass% Nafion dispersion solution DE2020 CS type manufactured by Fujifilm Wako Pure Chemical Corporation · Ethanol (solvent): Reagent special grade ethanol (99.5) manufactured by Fujifilm Wako Pure Chemical Corporation · Water (solvent): Ultrapure water · Electrolyte membrane (solid polymer electrolyte membrane): Nafion NR-211 (thickness: 25 μm) manufactured by Chemours

[0049] (2.2) Catalyst ink composition · Solids content (catalyst + ionomer) 7 mass% · Water:ethanol ratio = 1:1 · Ionomer / carbon weight ratio (I / C) 0.75 (mass ratio)

[0050] (2.3) Production procedure of the catalyst layer transfer sheet (base material on which the anode catalyst layer 17A is formed) A catalyst, ultrapure water, an ionomer dispersion, and ethanol were sequentially added to a beaker and stirred with an ultrasonic homogenizer. The stirred solution (anode catalyst ink) was dropped onto a PTFE sheet (substrate) attached to glass. It was spread with an applicator and air-dried. The air conditioner was adjusted so that the room temperature was about 25°C. In this way, a catalyst layer transfer sheet with an anode catalyst layer 17A formed on one side was produced. <Equipment and Supplies> · Ultrasonic homogenizer: UH-50 manufactured by SMT Co., Ltd. · Tabletop coater: TC-3 type manufactured by Mitsui Electric Precision Co., Ltd. · Applicator: YBA-2 type manufactured by Yoshimitsu Seiki Co., Ltd. · PTFE sheet: MSF-100 manufactured by Chukyo Kasei Kogyo Co., Ltd.

[0051] (2.4) Transfer of Anode Catalyst Layer 17A The anode catalyst layer 17A of the catalyst layer transfer sheet is joined to the other side of the electrolyte membrane 15 on which the cathode catalyst layer 17B is formed (the side on which the cathode catalyst layer 17B is not formed) so that they face each other. When joining, the substrate was heated. Then, the substrate was peeled off to manufacture the membrane electrode assembly 1 shown in Fig. 1.

[0052] 2. Evaluation of Power Generation Performance After manufacturing the membrane electrode assembly 1, carbon papers as gas diffusion layers 31 and 35 were pasted on both sides of the membrane electrode assembly 1 and installed in the power generation evaluation cell. Using a fuel cell measurement device, current-voltage measurement was performed at a cell temperature of 80°C. Hydrogen was used as the fuel gas and air was used as the oxidant gas, and flow control was performed with a constant utilization rate. Note that the back pressure was 1×10 2 kPa.

[0053] The results are shown in Table 1 and Fig. 4.

[0054]

Table 1

[0055] (3) Discussion and Effects of Examples The membrane electrode assembly 1 of the example had power generation performance equivalent to that of Comparative Example 2, which was a conventional example. The performance of the membrane electrode assembly 1 of the example exhibited good performance at the time of filing of the present application. In the composite 3 in the cathode catalyst layer 17B of the example, there are a coated portion 21 coated with the polymer 7 and an uncoated portion 23 not coated with the polymer 7, and it is presumed that the mass activity and the area specific activity are high. The polymer 7 in the composite 3 of the example is cheaper in raw materials and can be prepared by a simple production method compared to Nafion. Further, in the conventional example, Nafion covers the surface of the conductor 11, but in the example, since the polymer 7 does not cover a part of the conductor 11, the amount of the polymer 7 used can be reduced. Therefore, the polymer 7 in the cathode catalyst layer 17B of the example costs, for example, 1 / 1000 or less compared to Nafion. Accordingly, the membrane electrode assembly 1 of the example can be manufactured at low cost. Moreover, since the membrane electrode assembly 1 of the example exhibits the same level of performance as the conventional membrane electrode assembly 1 using an expensive polymer 7 such as Nafion, the amount of precious metal used can also be reduced, and cost reduction can be expected from this viewpoint as well. In addition, since the composite 3 in the membrane electrode assembly 1 of the example does not use an organic solvent such as dichloromethane, the environmental load is small. Further, conventionally, after the synthesis of the polymer 7, a mixing step of mixing the polymer 7 and the conductor 11 is provided to manufacture the composite 3, but in the manufacturing method of the present disclosure, the mixing step becomes unnecessary, which is advantageous in terms of cost and the like. Further, in the conventional mixing step, the distribution state of the polymer 7 in the conductor 11 cannot be controlled. In the manufacturing method of the present disclosure, the distribution state of the polymer 7 in the conductor 11 is controlled to form a coated portion 21 coated with the polymer 7 and an uncoated portion 23 not coated with the polymer 7. In the composite 3, in the coated portion 21 coated with the polymer 7, the mobility of protons (H + ) is ensured, and in the uncoated portion 23 not coated with the polymer 7, the diffusibility of gas to the metal catalyst 9 is ensured. Therefore, a high-performance fuel cell 30 can be provided by using the membrane electrode assembly 1 manufactured by this manufacturing method. In addition, since the membrane electrode assembly 1 of the present disclosure is equivalent to a conventional membrane electrode assembly 1 using Nafion or the like, as a result, the amount of precious metal used can also be reduced, and cost reduction can be expected from this perspective as well.

[0056] The above examples are for illustrative purposes only and should not be construed as limiting the present disclosure. Although the present disclosure has been described by way of examples of typical embodiments, it is understood that the language used in the description and illustration of the present disclosure is not limiting but explanatory and exemplary. As detailed herein, changes can be made within the scope of the appended claims without departing from the scope or essence of the present disclosure in its form. Here, specific structures, materials, and examples have been referred to in the detailed description of the present disclosure, but it is not intended to limit the present disclosure to the disclosed matters herein. Rather, the present disclosure is intended to cover all functionally equivalent structures, methods, and uses within the scope of the appended claims.

[0057] The present disclosure is not limited to the embodiments detailed above, and various modifications or changes are possible within the scope indicated in the claims.

Description of Reference Numerals

[0058] 1... Membrane electrode assembly 3... Composite 7... Polymer 9... Metal catalyst 11... Conductor 15... Electrolyte membrane 17... Catalyst layer 17A... Anode catalyst layer 17B... Cathode catalyst layer 21... Coating portion 23... Uncoated portion 30... Fuel cell 31... Gas diffusion layer 33... Separator 35... Gas diffusion layer 37... Separator

Claims

1. A method for manufacturing a membrane electrode assembly using an ink containing a composite, comprising: The composite is a composite of a polymer polymerized using a compound A having a polymerizable group, an ionic monomer, a compound B having a plurality of polymerizable groups, and an initiator, and a conductor supporting a metal catalyst; A method for manufacturing a membrane electrode assembly, wherein the ink containing the composite is applied to an electrolyte membrane after plasma treatment.

2. An electrolyte membrane; A membrane electrode assembly comprising a catalyst layer formed on the electrolyte membrane, wherein: The catalyst layer contains a composite; The composite is a composite of a polymer polymerized using a compound A having a polymerizable group, an ionic monomer, a compound B having a plurality of polymerizable groups, and an initiator, and a conductor supporting a metal catalyst.

3. A fuel cell comprising the membrane electrode assembly according to Claim 2.

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