JP2008226831A - Manufacturing method of membrane electrode assembly - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a membrane electrode assembly which comprises an aromatic hydrocarbon group polymer electrolyte membrane immediately after production, an anode and a cathode, or a membrane electrode assembly which can attain output power that is proper to a membrane electrode assembly from the beginning, when the membrane electrode assembly is used, after being left standing unused for a long time and which has superior durability. <P>SOLUTION: The manufacturing method of a membrane electrode assembly is constituted of an aromatic hydrocarbon group polymer electrolyte membrane, and anode and a cathode includes a process in which the anode and/or the cathode are made to contact with a solution containing an organic solvent, with a boiling point 70°C or higher under atmospheric pressure, and an acid in a temperature 70°C or higher and lower than the boiling point of the organic solvent. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for producing a membrane electrode assembly.

  A fuel cell is a power generation device with low emissions, high energy efficiency, and low burden on the environment. For this reason, it is in the spotlight again in recent years to the protection of the global environment. Compared to conventional large-scale power generation facilities, this is a power generation device expected in the future as a relatively small-scale distributed power generation facility, and as a power generation device for mobile objects such as automobiles and ships. It is also attracting attention as a power source for small mobile devices and portable devices, as an alternative to secondary batteries such as nickel metal hydride batteries and lithium ion batteries, as a charger for secondary batteries, or in combination with secondary batteries. (Hybrid) is expected to be installed in mobile devices such as mobile phones and personal computers.

  In polymer electrolyte fuel cells (hereinafter sometimes referred to as PEFC), direct fuel cells that supply fuel such as methanol directly in addition to conventional PEFCs that use hydrogen gas as fuel are also available. Attention has been paid. The direct fuel cell has a lower output than the conventional PEFC, but the fuel is liquid and does not use a reformer, so the energy density is high and the usage time of the portable device per filling is long. There is an advantage.

  In PEFC, an anode electrode and a cathode electrode in which a reaction responsible for power generation occurs, and a polymer electrolyte membrane serving as a proton conductor between the anode and the cathode are a membrane electrode composite (hereinafter sometimes referred to as MEA). A cell in which this MEA is sandwiched between separators is configured as a unit. Here, the electrode is composed of an electrode base material (also referred to as a gas diffusion electrode or a current collector) that promotes gas diffusion and collects (supply) electricity, and a catalyst layer that actually becomes an electrochemical reaction field. Yes. For example, in the anode electrode of PEFC, a fuel such as hydrogen gas reacts in the catalyst layer of the anode electrode to generate protons and electrons, and the electrons are conducted to the electrode substrate, and the protons are conducted to the polymer electrolyte membrane. For this reason, the anode electrode is required to have good gas diffusivity, electron conductivity, and proton conductivity. On the other hand, in the cathode electrode, an oxidizing gas such as oxygen or air is reacted with protons conducted from the polymer electrolyte membrane and electrons conducted from the electrode base material in the catalyst layer of the cathode electrode to produce water. For this reason, in the cathode electrode, it is effective to efficiently discharge the generated water in addition to gas diffusibility, electron conductivity, and proton conductivity.

  Among PEFCs, a direct fuel cell using methanol or the like as a fuel requires performance different from that of a conventional PEFC using hydrogen gas as a fuel. That is, in a direct type fuel cell, a fuel such as a methanol aqueous solution reacts with the catalyst layer of the anode electrode to produce protons, electrons, and carbon dioxide at the anode electrode, and the electrons are conducted to the electrode substrate, and the protons are polymer electrolyte. The carbon dioxide passes through the electrode substrate and is released out of the system. For this reason, in addition to the required characteristics of the anode electrode of the conventional PEFC, fuel permeability such as aqueous methanol solution and carbon dioxide emission are also required. Further, in the cathode electrode of the direct type fuel cell, in addition to the reaction similar to that of the conventional PEFC, fuel such as methanol that has permeated through the electrolyte membrane and oxidizing gas such as oxygen or air are mixed with carbon dioxide in the catalyst layer of the cathode electrode. Reactions that produce water also occur. For this reason, since produced water becomes more than conventional PEFC, it is preferable to discharge water more efficiently.

  In such a full-scale spread of fuel cells, it is important to improve performance and improve infrastructure as well as reduce manufacturing costs. In terms of manufacturing costs, in addition to cost reduction of materials and processes, it is also important to make it possible to draw out the original performance as soon as it is assembled as a fuel cell using a membrane electrode assembly left immediately after production or for a long time, for example. is there. If a long-time aging process or the like must be performed in order to obtain the original battery performance, it causes a cost increase.

  Conventionally, as described in Patent Document 1, a polymer electrolyte fuel cell using a perfluorocarbon-based electrolyte membrane is boiled with deionized water or weakly acidic water, or hot water is introduced into a gas supply path Or after introducing an alcohol into the gas supply path of the polymer electrolyte fuel cell and washing with deionized water or weakly acidic water, or generating a low power by using the polymer electrolyte fuel cell with a high oxygen utilization rate. A method has been proposed in which the battery output inherently possessed by the battery is drawn out in a short time by holding it at a potential.

Patent Document 2 and the like describe an example in which the electrolyte membrane is treated with a dilute sulfuric acid solution that boils the perfluorocarbon-based electrolyte membrane.
JP 2000-3718 JP 2006-16294 A

  However, although the method of Patent Document 1 is effective for an electrode composite using a flexible perfluorocarbon-based electrolyte membrane having a relatively high water content, the electrode composite using a rigid aromatic hydrocarbon-based electrolyte membrane is effective. Then the effect is insufficient.

  In Patent Document 2, since the treatment is performed only on the perfluorocarbon-based electrolyte membrane, the treatment of the catalyst layer is insufficient, and a high effect as a membrane electrode assembly cannot be obtained.

  In view of such background art, the present invention uses a membrane electrode composite using an aromatic hydrocarbon electrolyte membrane, or a membrane electrode composite immediately after production or a membrane electrode composite left unused for a long time. Furthermore, the present invention is intended to provide a method for producing a membrane electrode composite that can obtain the original battery output of the membrane electrode composite from the first time and has excellent durability.

  In order to achieve the above object, the present invention employs the following means.

  The method for producing a membrane electrode composite of the present invention is a method for producing a membrane electrode composite comprising an aromatic hydrocarbon polymer electrolyte membrane, an anode and a cathode, wherein the anode and / or the cathode has a boiling point at atmospheric pressure. It has an activation treatment step of contacting a solution containing an organic solvent at 70 ° C. or higher and an acid at a temperature of 70 ° C. or higher and lower than the boiling point of the organic solvent.

  According to the present invention, even when a membrane electrode composite immediately after production or a membrane electrode composite left unused for a long time is used, the membrane electrode composite capable of obtaining the original battery output from the first time is used. A manufacturing method can be provided.

  Hereinafter, preferred embodiments of the present invention will be described.

  The present invention relates to a method for producing a membrane electrode composite comprising an aromatic hydrocarbon polymer electrolyte membrane, an anode and a cathode, and comprising a membrane electrode composite comprising an aromatic hydrocarbon polymer electrolyte membrane, an anode and a cathode. An activation treatment step, wherein the anode and / or the cathode is brought into contact with a solution containing an organic solvent having an atmospheric pressure boiling point of 70 ° C. or higher and an acid at a temperature of 70 ° C. or higher and lower than the boiling point of the organic solvent. It is a manufacturing method of the membrane electrode composite characterized by having.

  In the present invention, it is essential to use a solution containing an organic solvent and an acid having a boiling point of 70 ° C. or higher (hereinafter sometimes abbreviated as “treatment liquid”). explain.

  First, the electrolyte membrane of the present invention is an aromatic hydrocarbon-based electrolyte membrane (hereinafter sometimes abbreviated as “electrolyte membrane”), as will be described in detail later.

  An organic solvent having an atmospheric pressure boiling point of 70 ° C. or higher (hereinafter may be abbreviated as “organic solvent”) is necessary to rapidly absorb or infiltrate the treatment liquid throughout the electrode. . In addition, it is essential that the atmospheric pressure has a boiling point of 70 ° C. or higher because it is necessary to bring the treatment liquid into contact with the anode and / or cathode at a temperature of 70 ° C. or higher and lower than the boiling point of the organic solvent. If the boiling point is 70 ° C. or higher, a stable activation treatment with a small amount of volatilization of the organic solvent is possible. By setting the treatment liquid to 70 ° C. or higher, sufficient activation treatment can be performed even with a membrane electrode assembly using an aromatic hydrocarbon electrolyte membrane having poor water absorption.

  The solution containing an organic solvent having an atmospheric pressure boiling point of 70 ° C. or higher and an acid is preferably an aqueous solution.

  The boiling point of the organic solvent at atmospheric pressure is preferably 80 ° C. or higher, and more preferably 90 ° C. or higher, for increasing the speed of the activation treatment. Moreover, when it is set as aqueous solution, 100 degrees C or less is preferable for the reason which suppresses volatilization of water. It is also a preferable means to increase the treatment temperature by pressurizing with an autoclave or the like.

  Next, a part of the ionic group of the anode and / or cathode electrolyte is in a metal salt state due to, for example, contamination of impurity ions in the manufacturing process, or decomposition of the ionic group in the manufacturing process, For the purpose of preventing corrosion, even when the metal salt is formed as it is, the proton exchange is possible with the acid contained in the treatment liquid, the ionic conductivity can be improved, and the oxide on the catalyst surface. In some cases, the catalytic activity can be improved.

  The contact time with the treatment liquid is preferably as short as possible from the viewpoint of reducing the production cost, and it is preferable that the activation treatment effect is obtained by treatment within 2 hours, preferably within 1 hour, and more preferably within 30 minutes.

  In the present invention, the organic solvent having an atmospheric pressure boiling point of 70 ° C. or higher is not particularly limited as long as it does not adversely affect the performance of the electrolyte membrane, the catalyst, and the membrane electrode assembly, but is water-soluble from the viewpoint of working environment and safety. Compounds are preferred. For example, ethanol (boiling point 78 ° C.), isopropyl alcohol (boiling point 83 ° C.), 1-butanol (boiling point 118 ° C.), 2-methyl-1-propanol (boiling point 108 ° C.), 2-butanol (boiling point 100 ° C.), 2- Alcohols such as methyl-2-propanol (boiling point 83 ° C), benzyl alcohol (boiling point 205 ° C), ethylene glycol (boiling point 198 ° C), propylene glycol (boiling point 187 ° C), trimethylene glycol (boiling point 208 ° C), 1 1,2-butylene glycol (decomposition temperature 191 ° C), 1,3-butylene glycol (decomposition temperature 208 ° C), 1,4-butylene glycol (decomposition temperature 229 ° C), 2,3-butylene glycol (decomposition temperature 182 ° C) Glycerin (boiling point 290 ° C., decomposition temperature 171 ° C.), polyhydric alcohols such as pentaerythritol, diethyl carbonate (boiling point 127 ° C.) Esters such as propylene carbonate (boiling point 242 ° C.), ethylene carbonate (boiling point 238 ° C.), γ-butyllactone (boiling point 204 ° C.), N-methyl-2-pyrrolidone (boiling point 202 ° C.), 1.3-dimethyl-2- Examples include imidazolidinone (boiling point 225 ° C.), pyrrole (boiling point 130 ° C.), heterocyclic compounds such as thiophene (boiling point 84 ° C.), ionic liquids, and the like, and these can be used alone or in admixture of two or more. Among them, from the viewpoint of low volatility and safety, polyhydric alcohols such as glycerin and ethylene glycol, esters such as γ-butyllactone and propylene carbonate, and heterocyclic compounds such as N-methyl-2-pyrrolidone can be preferably used. .

  These organic solvents are preferably used after being diluted with water or the like from the viewpoint of workability, and are preferably used by adjusting them to be 0.05 mol / L to 10 mol / L.

The acid used in the present invention may be an inorganic acid or an organic acid.
Specific examples include hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, formic acid, acetic acid, citric acid, malic acid, and the like, and these can be used alone or in combination. In particular, when an electrolyte membrane having a sulfonic acid group is used, sulfuric acid is preferable.

  These acid concentrations are not particularly limited and can be appropriately determined experimentally. From the viewpoint of workability, it is preferable to dilute with water so that the concentration is 0.05 mol / L to 6.0 mol / L.

  In the method for producing a membrane electrode composite of the present invention, at least one of the anode and the cathode needs to be brought into contact with the above-described treatment liquid. However, the method is not particularly limited, and the treatment liquid is immersed in the membrane electrode composite. It can be put in a container, and the membrane electrode assembly can be immersed or continuously fed by a roll, or sprayed by a shower or the like. In addition, it is possible to sequentially bring the processing liquids having different concentrations and types into contact with the preparation of a plurality of tanks. Further, after the contacting step, it is also effective to perform washing with water or alcohol water in order to prevent acid or the like from being brought into the next step.

  In the present invention, the object to be treated in the step of contacting with the treatment liquid (activation treatment step) may be in the form of a membrane electrode composite comprising an electrolyte membrane, an anode and a cathode, or the anode electrode before producing the membrane electrode composite. The cathode and the cathode may be treated independently, or either an anode or a cathode may be formed on the electrolyte membrane. Here, the activation treatment step is preferably after the step of producing an anode and / or a cathode on the aromatic hydrocarbon polymer electrolyte membrane. It is possible to treat not only the anode and cathode, but also the electrolyte membrane and electrode / electrolyte membrane interface at the same time, preventing reduction of treatment effect in the joining process with the electrolyte membrane after activating the anode and / or cathode. Because it can.

  Next, a specific example of the aromatic hydrocarbon polymer electrolyte membrane will be described. As a basic skeleton, from the viewpoint of mechanical strength, fuel durability, heat resistance, etc., polyphenylene oxide, polyether ketone, polyether ether ketone, polyether sulfone, polyether ether sulfone, polyether phosphine oxide, polyether ether phosphine oxide , Polyphenylene sulfide, polyamide, polyimide, polyetherimide, polyimidazole, polyoxazole, polyphenylene and the like. It may be a copolymer or a mixture of two or more tumors. In particular, from the viewpoint of heat resistance and mechanical strength, the aromatic hydrocarbon is preferably polyether ketone, polyether sulfone, or polyimide.

  In order to make an electrolyte membrane, it is necessary to introduce an ionic group into a part of these polymers. For the method of introducing an ionic group into these polymer materials, an ionic group is introduced into the polymer. Alternatively, a monomer having an ionic group may be polymerized. Two or more kinds of these ionic groups can be contained in the basic skeleton, and there are cases where it is preferable to combine them. The combination is appropriately determined depending on the structure of the polymer. Among them, it is more preferable to have at least one of a sulfonic acid group, a sulfonimide group, and a sulfuric acid group from the viewpoint of high proton conductivity, and most preferable to have at least a sulfonic acid group from the viewpoint of hydrolysis resistance. In the case of having a sulfonic acid group, the density of the sulfonic acid group is preferably 0.1 to 5.0 mmol / g, more preferably 0.5 to 3.5 mmol / g, still more preferably from the viewpoint of proton conductivity and water resistance. Is 1.0 to 3.5 mmol / g. By setting the sulfonic acid group density to 0.1 mmol / g or more, a high-power fuel cell can be obtained, and by setting it to 5.0 mmol / g or less, for example, a liquid fuel such as a direct methanol fuel cell can be obtained. When used in a fuel cell that is in direct contact, it is possible to prevent the electrolyte membrane from being excessively swollen by the fuel and eluting or flowing out.

  Here, the sulfonic acid group density is the molar amount of the sulfonic acid group introduced per unit dry weight of the polymer material, and the larger the value, the higher the degree of sulfonation. The sulfonic acid group density of the polymer material to be used can be measured by elemental analysis, neutralization titration, nuclear magnetic resonance spectroscopy or the like. Elemental analysis is preferable from the viewpoint of ease of measurement of sulfonic acid group density and accuracy, and analysis is usually performed by this method. However, the neutralization titration method is used when it is difficult to accurately calculate the sulfonic acid group density by the elemental analysis method such as when a sulfur source is included in addition to the sulfonic acid group. Furthermore, when it is difficult to determine the sulfonic acid group density by these methods, it is possible to use a nuclear magnetic resonance spectrum method.

  An ionic group can be introduced into the polymer having the basic skeleton by a method described in “Polymer Preprints, Japan”, 51, 750 (2002). Introduction of a phosphate group into the polymer is possible by, for example, phosphate esterification of a polymer having a hydroxyl group. Introduction of a carboxylic acid group into the polymer is possible by, for example, oxidizing a polymer having an alkyl group or a hydroxyalkyl group. Introduction of a sulfonimide group into the polymer is possible, for example, by treating a polymer having a sulfonic acid group with an alkylsulfonamide. The introduction of sulfate groups into the polymer is possible, for example, by sulfate esterification of a polymer having hydroxyl groups. The introduction of the sulfonic acid group into the polymer can be performed, for example, by a method in which the polymer is reacted with chlorosulfonic acid, concentrated sulfuric acid, or fuming sulfuric acid. These ionic group introduction methods can be controlled to a desired ionic group density by appropriately selecting conditions such as treatment time, concentration, and temperature.

  Further, as a method for polymerizing a monomer having an ionic group, for example, a method described in “Polymer Preprints”, 41 (1) (2000) 237. When a polymer is obtained by this method, the degree of introduction of ionic groups is most preferable because it can be easily controlled by the charge ratio of monomers having ionic acid groups.

  When the aromatic hydrocarbon electrolyte membrane used has a non-crosslinked structure, the weight average molecular weight is preferably 10,000 to 5,000,000, more preferably 30,000 to 1,000,000. By setting the weight average molecular weight to 10,000 or more, it is possible to obtain mechanical strength that can be practically used. The weight average molecular weight can be measured by GPC method.

In particular, as the ionic group, an aromatic hydrocarbon electrolyte membrane having a sulfonic acid group is most preferable as described above. However, as an example of using an aromatic hydrocarbon electrolyte membrane having a sulfonic acid group, —SO ₃ M Examples include a method in which a polymer containing a group (M is a metal) is formed from a solution state, and then heat-treated at a high temperature to remove the solvent, followed by proton substitution to obtain an aromatic hydrocarbon electrolyte membrane. The metal M may be any salt as long as it can form a salt with sulfonic acid, but Li, Na, K, Rb, Cs, Mg, Ca, Sr, Ba, Ti, V, Mn, Fe, Co, Ni, Cu, Zn, Zr, Mo, W, and the like are preferable. Among these, Li, Na, K, Ca, Sr, and Ba are more preferable, and Li, Na, and K are more preferable. By forming a film in the state of these metal salts, heat treatment at a high temperature is possible, and this method is suitable for an aromatic hydrocarbon electrolyte membrane that can obtain a high glass transition point and a low water absorption.

  Also, there is no particular problem even if it is combined with fine particles, fibers, porous substrates, etc. made of polymer materials, inorganic materials or their hybrids that do not contain ionic groups, depending on the harsh conditions of use such as automotive fuel cells. May be preferable from the viewpoint of heat resistance, water resistance, and dimensional change resistance.

  As an example of the configuration of the anode and cathode of the present invention, a non-woven fabric made of conductive fibers such as carbon fibers and metal fibers, papermaking, fabrics, and conductive gas diffusers such as porous carbon sheets and porous metal sheets; A catalyst layer is mentioned. Further, there may be a porous layer made of a carbon material and a binder between them.

  In addition, the electrode of the membrane electrode composite in the present invention has at least a catalyst layer that performs an electrochemical reaction, and the conductive gas diffuser, the carbon material, and the binder during the manufacturing process of the membrane electrode composite of the present invention. The presence or absence of a porous layer made of In other words, at least the membrane electrode assembly of the present invention has a catalyst layer laminated so as to sandwich the electrolyte membrane, and the conductive gas diffuser and the conductive gas diffuser with a porous layer made of a carbon material and a binder. May be provided on the catalyst layer before the production process of the present invention, or may be joined on the catalyst layer by a press after the production process, or may be simply laminated on the catalyst layer when assembling the cells. It is not necessary to use it. Therefore, the step of producing an anode (cathode) on the electrolyte membrane is applicable as long as at least a catalyst layer is formed.

  In addition, the catalyst layer can be formed on the electrolyte membrane by a generally known method, such as a flat or roll press method, a printing method such as ink jet printing, gravure printing, or screen printing, or a coating method using a spray, die coater, or knife coater. , Electrophoresis method, plating method, etc. can be selected according to the purpose as appropriate. When applying a flat or roll press method, when using a rigid aromatic hydrocarbon electrolyte membrane, it is also preferable to use an ion conductive adhesive layer between the catalyst layer and the electrolyte membrane.

  The catalyst in the electrode of the present invention preferably contains metal particles and / or metal carrier particles, and generally known ones can be used. For example, noble metals such as platinum, palladium, ruthenium, rhodium, iridium and gold are preferably used as the metal particles. One of these may be used alone, or two or more of them, such as alloys and mixtures, may be used in combination. Depending on the type of fuel in the fuel cell, the above-mentioned metal species and adhesion amount can be determined experimentally as appropriate, and a pair of electrodes using the same type of metal may be used for the anode and cathode, and the anode and cathode may differ. An electrode using metal may be used. For example, a fuel cell using hydrogen for the anode and air or oxygen for the cathode preferably uses Pt as the metal for both electrodes. In the case of a fuel cell using methanol water for the anode and air or oxygen for the cathode, the anode is PtRu, It is preferable to use Pt for the cathode.

In addition, the use of the metal-supported particles may improve the utilization efficiency of the metal catalyst, and may contribute to improvement of battery performance and cost reduction. As the support, a carbon material, SiO ₂ , TiO ₂ , ZrO ₂ , RuO ₂ , zeolite, or the like can be used, but a carbon material from the viewpoint of electron conductivity is preferable.

  In particular, the method for producing a membrane electrode assembly of the present invention is highly effective when the anode contains a metal catalyst containing Ru. When a PtRu alloy is used for the anode, if a Ru compound such as oxidized Ru is mixed, Ru will elute during the operation of the fuel cell, reducing the ionic conductivity of the electrolyte membrane, or coming into contact with hydrogen peroxide generated by power generation. It may promote chemical degradation. Therefore, according to the present invention, removing the soluble Ru compound before power generation can improve the durability of the membrane electrode assembly. Examples of the carbon material include amorphous and crystalline carbon materials. For example, carbon black such as channel black, thermal black, furnace black, and acetylene black is preferably used because of its electron conductivity and specific surface area. Furnace Black includes “Vulcan (registered trademark) XC-72”, “Vulcan (registered trademark) P”, “Black Pearls (registered trademark) 880”, “Black Pearls (registered trademark) 1100”, “Black” manufactured by Cabot Corporation. "Pearls (registered trademark) 1300", "Black Pearls (registered trademark) 2000", "Regal (registered trademark) 400", "Ketjen Black (registered trademark) EC" manufactured by Ketjenblack International, EC600JD, Mitsubishi Chemical Corporation Examples of the acetylene black include “Denka Black (registered trademark)” manufactured by Denki Kagaku Kogyo Co., Ltd. In addition to carbon black, artificial graphite or carbon obtained from organic compounds such as natural graphite, pitch, coke, polyacrylonitrile, phenol resin, and furan resin can also be used. As the form of these carbon materials, in addition to irregular particles, fibers, scales, tubes, cones, and megaphones can also be used. Moreover, you may use what post-processed these carbon materials. These may be used as the metal carrier, or may be used alone as an electron conductivity improver for the catalyst layer.

In the electrode of the present invention, a binder may be used to improve the adhesion between the catalyst particles in contact with the gas diffusion layer such as an electrolyte membrane and the catalyst particles so that the catalyst particles do not slide down. preferable. The binder is not particularly limited, and commonly known materials can be used. In particular, when a liquid fuel is used, a polymer material is preferable from the viewpoint of fuel resistance and productivity, and can be appropriately selected depending on the fuel to be used, and may include a material containing or not containing an ionic group. Examples of the ionic group include a sulfonic acid group (—SO ₂ (OH) ₂ ), a sulfuric acid group (—OSO ₂ (OH) ₂ ), and a sulfonimide group (—SO ₂ NHSO ₂ R (R represents an organic group)). Phosphonic acid group (—PO (OH) ₂ ), phosphoric acid group (—OPO (OH) ₂ ), carboxylic acid group (—CO (OH) 2), hydroxyl group (—OH), and salts thereof. Further, two or more kinds of these ionic groups can be contained in the hydrocarbon-based electrolyte. The combination is appropriately determined depending on the structure of the polymer. Among these ionic groups, phosphonic acid groups and sulfonic acid groups are preferable from the viewpoints of proton conductivity and productivity, and these Na salts, Mg salts, Ca salts, ammonium salts, and the like may be included.

Specifically, polyphenylene oxide, polyether ketone, polyether ether ketone, polyether sulfone, polyether ether sulfone, polyether phosphine oxide, polyether ether phosphine oxide, polyphenylene sulfide, polyamide, polyimide, polyetherimide, polyimidazole , (Meth) acrylic copolymers such as polyoxazole, polyphenylene, polycarbonate, polyarylate, polyethylene, polypropylene, amorphous polyolefin, polystyrene, polystyrene maleimide copolymer, polymethyl acrylate, and polyurethane, and polymer materials such as these And hydrocarbon polymers such as a polymer material into which an ionic group is introduced.
Further, from the viewpoint of the stability of the ionic group, a perfluoro ion conductive polymer composed of a fluoroalkyl ether side chain and a fluoroalkyl main chain can also be used as a binder. For example, “Nafion (registered trademark)” manufactured by DuPont, “Aciplex (registered trademark)” manufactured by Asahi Kasei Corporation, “Flemion (registered trademark)” manufactured by Asahi Glass Co., Ltd., etc. are preferably used.

  Furthermore, depending on the type and concentration of fuel, in order to further improve fuel durability, polyvinyl fluoride, polyvinylidene fluoride, polyhexafluoropropylene, polytetrafluoroethylene, polyperfluoroalkyl vinyl ether, fluorine-based polyacrylate, Polymers containing fluorine atoms such as fluorine-based polymethacrylate can also be used. Particularly, when methanol aqueous solution is used as the fuel, the binder is preferably polyvinylidene fluoride from the viewpoint of fuel resistance and productivity. From the viewpoint of work environment, productivity, cost, etc., it is also preferable to select a hydrophilic polymer such as carboxymethyl cellulose, hydroxypropyl cellulose, polyvinyl alcohol, polyvinyl pyrrolidone, and metal coupling agents, epoxy resins, urethane resins, glutars. Fuel resistance can be improved by crosslinking with aldehyde. In particular, when an aqueous methanol solution is used as a fuel, carboxymethylcellulose is more preferable from the viewpoint of ease of imparting fuel resistance (productivity).

  The binder exemplified above may further introduce a crosslinked structure using radiation, metal alkoxide, or the like, if necessary, or a network of a crosslinked product may be formed with a polyfunctional monomer or the like. . The binder may be used alone or in combination of two or more.

  The amount of the binder contained in the electrode is not particularly limited, but is preferably in the range of 0.1% to 50% by weight, and more preferably in the range of 1% to 30%. . If it is 0.1% or more, it is easy to prevent the metal particles from sliding off, and if it is less than 50%, it is difficult to inhibit the permeation of fuel and gas, and the adverse effect on the performance as a fuel cell is small.

  As a method for producing the electrode of the present invention, a generally known method can be applied. For example, after dissolving the binder in a solvent, metal particles and / or composite particles of a metal carrier and a hydrocarbon-based electrolyte are added, and the mixture is stirred and kneaded to prepare an electrode paste on the electrode substrate or electrolyte membrane. It can be prepared by coating and drying by the method described above, and if necessary, pressing.

  The solvent that can be used is not particularly limited. For example, water, N, N-dimethylacetamide, N, N-dimethylformamide, N-methyl-2-pyrrolidone, dimethyl sulfoxide, sulfolane, 1,3-dimethyl-2- Aprotic polar solvents such as imidazolidinone and hexamethylphosphontriamide, ester solvents such as γ-butyrolactone and butyl acetate, carbonate solvents such as ethylene carbonate and propylene carbonate, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, Alkylene glycol monoalkyl ethers such as propylene glycol monomethyl ether and propylene glycol monoethyl ether, or alcohols such as isopropanol, n-propanol, ethanol and methanol Call solvents, toluene, and aromatic solvents such as xylene and the like.

  For example, when an aromatic hydrocarbon polymer material containing polyvinylidene fluoride or a sulfonic acid group is used as a binder, N-methyl-2-pyrrolidone, 1 from the viewpoint of electrode paste stability and workability, , 3-dimethyl-2-imidazolidinone is preferable, and from the viewpoint of cost and the like, when carboxymethyl cellulose or the like is used as a binder, water or a mixed solution of water and alcohol is preferable. In this case, the electrode paste is preferably used in the form of a metal salt or ammonium salt of carboxymethyl cellulose. After coating and drying, proton substitution can be performed with an acid such as hydrochloric acid or sulfuric acid to improve fuel resistance. Furthermore, the ammonium salt is particularly preferable from the viewpoint of productivity because it can be removed by heating.

  In addition, when the fuel is a liquid or gas as described above, the electrode of the present invention preferably has a structure that allows the liquid or gas to easily permeate, and promotes the discharge of by-products due to the electrode reaction. A structure is preferred.

  In particular, it is preferable to use a substrate that has a low electrical resistance and can collect or supply power. For example, the base material which consists of carbonaceous and a conductive inorganic substance is mentioned. Further, specific examples include a fired body from polyacrylonitrile, a fired body from pitch, carbon materials such as graphite and expanded graphite, stainless steel, molybdenum, titanium, and the like. These forms are not particularly limited, and are used, for example, in the form of fibers or particles. From the viewpoint of fuel permeability, fibrous conductive materials (conductive fibers) such as carbon fibers are preferable. As an electrode base material using conductive fibers, either a woven fabric or a non-woven fabric structure can be used. For example, carbon paper TGP series, SO series manufactured by Toray Industries, Inc., carbon cloth manufactured by E-TEK, etc. are used. Examples of the woven fabric include plain weave, oblique weaving, satin weaving, crest weaving, binding weaving, and the like. Moreover, as a nonwoven fabric, it does not specifically limit, such as a paper making method, a needle punch method, a spun bond method, a water jet punch method, and a melt blow method. It may also be a knitted fabric.

  In these fabrics, especially when carbon fibers are used, a plain fabric using flame-resistant spun yarn is carbonized or graphitized woven fabric, and the flame-resistant yarn is carbonized after being processed into a nonwoven fabric by the needle punch method or water jet punch method. Alternatively, a graphitized nonwoven fabric, a flameproof yarn, a carbonized yarn, or a mat nonwoven fabric by a paper making method using a graphitized yarn is preferably used. In particular, it is preferable to use a nonwoven fabric or cloth from the viewpoint of obtaining a thin and strong fabric.

  Examples of the carbon fiber used for the electrode substrate include polyacrylonitrile (PAN) carbon fiber, phenolic carbon fiber, pitch carbon fiber, and rayon carbon fiber.

  In addition, the electrode base material has a water repellent treatment for preventing gas diffusion / permeability deterioration due to water retention, a partial water repellent treatment for forming a water discharge path, a hydrophilic treatment, and a resistance reduction. For example, carbon powder can be added. Further, a conductive intermediate layer containing at least an inorganic conductive substance and a hydrophobic polymer can be provided between the electrode substrate and the catalyst layer. In particular, when the electrode base material is a carbon fiber woven fabric or a nonwoven fabric having a large porosity, by providing the conductive intermediate layer, it is possible to suppress performance degradation due to the electrode paste soaking into the electrode base material.

  Further, even when an electrode is formed on the electrolyte membrane, there is no particular problem if the base material is used while being overlapped on the electrode to improve the current collection efficiency and the diffusibility of fuel and by-products. Moreover, it is not necessary to use the said base material.

  As the anode fuel of a fuel cell using the membrane electrode composite obtained by the method for producing a membrane electrode composite of the present invention, hydrogen and methane, ethane, propane, butanemethanol, isopropyl alcohol, acetone, glycerin, ethylene glycol, Examples thereof include organic compounds having 1 to 6 carbon atoms such as formic acid, acetic acid, dimethyl ether, hydroquinone, and cyclohexane, and a mixture of these with water, and may be a single type or a mixture of two or more types. In particular, a fuel containing hydrogen and an organic compound having 1 to 6 carbon atoms is preferably used from the viewpoint of power generation efficiency and simplification of the entire battery system, and hydrogen and aqueous methanol are particularly preferable in terms of power generation efficiency.

  In the case of using an aqueous methanol solution, the concentration of methanol is appropriately selected depending on the fuel cell system to be used, but a concentration as high as possible is preferable from the viewpoint of long-time driving. For example, an active fuel cell having a system for sending a medium necessary for power generation, such as a liquid feed pump or a blower fan, to a membrane electrode assembly, or an auxiliary machine such as a cooling fan, a fuel dilution system, or a product recovery system has a methanol concentration of 30. It is preferable to inject a fuel of 100% or more by a fuel tank or a fuel cassette and dilute it to about 0.5-29% or send it directly to the membrane electrode assembly. A fuel having a methanol concentration in the range of 10 to 100% is preferred.

  The cathode may be air, oxygen, etc., and may be sent by natural suction or by a pump, blower or fan.

  Further, the membrane electrode assembly may be used in the form of a stack of a plurality of sheets or in a state of being arranged. Further, the fuel cell may be built in the device to be used, or may be used as an external unit. From the viewpoint of maintenance, it is also preferable that the membrane electrode assembly is detachable from the fuel cell.

  In addition, a fuel cell for a portable device using a gas such as hydrogen as a fuel preferably has a structure in which those gases do not leak to the outside from the viewpoint of safety and long-time driving, and at least the anode side, which is the hydrogen electrode, is sealed. It is preferable to use it. The cathode preferably has a structure that naturally sucks air for the purpose of reducing peripheral devices and the like. The anode side is preferably a positive pressure, such as a hydrogen generator, a hydrogen cylinder, or a hydrogen storage alloy, and preferably 0.1 MPa to 0.0001 MPa. Preferably, it is 0.05 MPa to 0.001 MPa. Depending on the current to be extracted, power generation by natural convection is also preferable.

  As the use of these fuel cells, a power supply source of a moving body is preferable. Especially mobile devices such as mobile phones, personal computers, PDAs, video cameras (camcorders), digital cameras, surveillance cameras, handy terminals, RFID readers, various displays, home appliances such as electric shavers and vacuum cleaners, electric tools, and household power It is preferably used as a power supply source for mobile bodies such as feeders, passenger cars, automobiles such as buses and trucks, motorcycles, bicycles with electric assistance, electric carts, electric wheelchairs, ships and railways. Especially in portable devices, it is used not only for power supply sources, but also for charging secondary batteries installed in portable devices, and also suitable for use as a hybrid power supply source used in combination with secondary batteries and solar cells. it can.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, these examples are for understanding this invention better, and this invention is not limited to these.

(1) Power generation evaluation method A membrane electrode composite is provided with a gasket around it and incorporated into a single cell “EFC05-01SP” (cell for electrode area 5 cm ² ) manufactured by Electrochem, and a cathode current collector and an anode current collector A lead is attached to the plate, the cell temperature is 60 ° C., a 10% methanol aqueous solution is supplied from the fuel supply port to the anode side at a rate of 0.2 ml / min, and synthetic air is supplied to the cathode side at a rate of 50 ml / min. Using a potentiostat 1470 made by solartron and a frequency response analyzer 1255B made by solartron, current-voltage characteristics (cell current-voltage characteristics) were measured up to a potential difference of 0.05V.

  Table 1 summarizes the voltage values at the current density of 200 mA / cm 2 immediately after the production of the membrane electrode assembly of each example (first time) and the 10th time.

Further, as a durability evaluation, power generation was further repeated 200 times, and a voltage holding ratio at a current density of 200 mA / cm ² was measured.

(2) Production Example of Electrode Pt-Ru supported carbon catalyst “HiSPEC (registered by Johson & Matthey) on a carbon cloth“ TL-1400W ”made by E-TEK (USA) made of carbon fiber fabric. Trademark) "10000", "HiSPEC (registered trademark)" 6000, a 20% "Nafion (registered trademark)" solution manufactured by DuPont and a catalyst comprising N-methyl-2-pyrrolidone The coating liquid was applied and dried to prepare an electrode A. The carbon cloth was coated with a carbon black dispersion liquid, and the catalyst coating liquid was coated on the surface coated with the carbon black dispersion liquid.

  Similarly, a Pt-supported carbon catalyst TEC10V50E manufactured by Tanaka Kikinzoku Kogyo Co., Ltd., a 20% “Nafion (registered trademark)” (“Nafion®”) solution and n A cathode catalyst coating solution made of -propanol was applied and dried to prepare an electrode B.

The catalyst adhesion amount was adjusted so that the electrode A was 2.0 mg / cm ² in terms of platinum weight, and the electrode B was 4.0 mg / cm ^{2 in} terms of platinum weight.

(3) Production Example of Electrode Transfer Sheet On a polyimide film “Kapton (registered trademark)” manufactured by Toray DuPont, Pt-Ru supported carbon catalyst “HiSPEC (registered trademark)” 10000, “Johnson & Matthey” Apply HiSPEC (registered trademark) “6000”, DuPont 20% “Nafion (registered trademark)” (“Nafion (registered trademark)”) solution and N-methyl-2-pyrrolidone catalyst coating solution. The catalyst transfer sheet A was prepared by drying.

  Similarly, a Pt-supported carbon catalyst TEC10V50E manufactured by Tanaka Kikinzoku Kogyo Co., Ltd., a 20% “Nafion (registered trademark)” (“Nafion (registered trademark)”) solution manufactured by DuPont and n -Cathode catalyst coating solution composed of propanol was applied and dried to prepare catalyst transfer sheet B.

The amount of catalyst adhered was adjusted so that the electrode transfer sheet A was 2.0 mg / cm ^{2 in} terms of platinum weight and the electrode transfer sheet B was 1.0 mg / cm ^{2 in} terms of platinum weight.

(4) Synthetic Example of Aromatic Hydrocarbon Polymer Electrolyte 109.1 g of 4,4′-difluorobenzophenone was reacted at 100 ° C. for 10 hours in 150 mL of fuming sulfuric acid (50% SO ₃ ). Thereafter, the mixture was poured little by little into a large amount of water, neutralized with NaOH, and 200 g of sodium chloride was added to precipitate the composite. The resulting precipitate was filtered off and recrystallized with an aqueous ethanol solution to obtain disodium 3,3′-disulfonate-4,4′-difluorobenzophenone. (Yield 181 g, 86% yield).

  6.9 g of potassium carbonate, 14 g of 4,4 ′-(9H-fluorene-9-ylidene) bisphenol, 2.6 g of 4,4′-difluorobenzophenone, and the disodium 3,3′-disulfonate-4 Polymerization was carried out at 190 ° C. in N-methyl-2-pyrrolidone using 12 g of 4,4′-difluorobenzophenone. Purification was carried out by reprecipitation with a large amount of water to obtain an aromatic hydrocarbon polymer electrolyte A.

(5) Preparation Example of Aromatic Hydrocarbon Polymer Electrolyte Membrane The above aromatic hydrocarbon polymer electrolyte A was dissolved in N-methyl-2-pyrrolidone to obtain a coating solution having a solid content of 25%. The coating solution was cast on a glass plate and dried at 70 ° C. for 30 minutes and further at 100 ° C. for 1 hour to obtain a 30 μm aromatic hydrocarbon polymer electrolyte membrane A.

Further, the aromatic hydrocarbon polymer electrolyte membrane A was heated to 200 to 300 ° C. over 1 hour in a nitrogen gas atmosphere, heat-treated at 300 ° C. for 10 minutes, allowed to cool, and 1N hydrochloric acid. After 12 hours of immersion in proton substitution, the substrate was immersed in a large excess of pure water for 1 day or more and washed thoroughly to obtain an aromatic hydrocarbon polymer electrolyte membrane B.
(Example 1)
A composition in which the aromatic hydrocarbon polymer electrolyte A, N-methyl-2-pyrrolidone and glycerin were uniformly mixed was provided on the catalyst layer side of the electrodes A and B so as to be ² mg / cm ² .

These electrodes were superposed on the aromatic hydrocarbon polymer electrolyte membrane B so as to face each other, and heated and pressed at 100 ° C. for 1 minute at a pressure of 5 MPa. Next, it was immersed for 1 hour in a treatment solution in which 0.5 mol of glycerin and 3 mol of isopropyl alcohol were added to a 1 mol sulfuric acid aqueous solution heated to 100 ° C., and washed until the washing solution became neutral to obtain a membrane electrode assembly. The power generation evaluation results of this membrane electrode composite are summarized in Table 1.
(Example 2)
A composition obtained by uniformly mixing the aromatic hydrocarbon polymer electrolyte A, N-methyl-2-pyrrolidone, and glycerin was provided at 1 mg / cm ² on the catalyst layer side of the electrode transfer sheets A and B.

These electrode transfer sheets were superposed on the aromatic hydrocarbon polymer electrolyte membrane A so as to face each other, and heated and pressed at 100 ° C. for 1 minute at a pressure of 3 MPa. Next, after removing only the polyimide film “Kapton (registered trademark)” manufactured by Toray DuPont Co., Ltd. as an electrode transfer sheet, it was immersed in a treatment solution in which 1 mol of propylene carbonate was added to 1 mol sulfuric acid aqueous solution heated to 95 ° C. for 1 hour. Then, cleaning is performed until the cleaning solution becomes neutral, and an electrode base material (carbon paper TGP-H-060 manufactured by Toray Industries, Inc.) is superimposed on the electrode, and pressed and integrated at 100 ° C. and 5 MPa for 5 minutes. Got the body. The power generation evaluation results of this membrane electrode composite are summarized in Table 1.
(Example 3)
The treatment solution composition and treatment conditions of Example 1 were the same as Example 1 except that 1 mol dimethylimidazolidinone was added to 1 mol sulfuric acid aqueous solution and the temperature was changed to 90 ° C. The power generation evaluation results of these membrane electrode composites are also summarized in Table 1.
Example 4
The treatment solution composition and treatment conditions of Example 1 were the same as those of Example 1 except that 3 mol isopropyl alcohol was added to 2 mol acetic acid aqueous solution and changed to 70 ° C. The power generation evaluation results of these membrane electrode composites are also summarized in Table 1.
(Example 5)
The treatment solution composition and treatment conditions of Example 2 were the same as Example 2 except that 1 mol n-butanol and 0.5 mol of propylene glycol were added to 1 mol sulfuric acid aqueous solution and changed to 80 ° C. The power generation evaluation results of these membrane electrode composites are also summarized in Table 1.
(Example 6)
The treatment solution composition and treatment conditions of Example 2 were the same as those of Example 2 except that 1 mol glycerol and 0.5 mol N-methyl-2-pyrrolidone were added to 1 mol sulfuric acid aqueous solution and changed to 90 ° C. The power generation evaluation results of these membrane electrode composites are also summarized in Table 1.
(Comparative Example 1)
A membrane electrode assembly was produced in the same manner as in Example 1 except that the treatment liquid was not used in Example 1. The power generation evaluation results of this membrane electrode composite are summarized in Table 1.
(Comparative Example 2)
A membrane electrode assembly was produced in the same manner as in Example 1 except that the treatment liquid temperature was changed to 50 ° C. in Example 1. The power generation evaluation results of this membrane electrode composite are summarized in Table 1.
(Comparative Example 3)
A membrane electrode assembly was produced in the same manner as in Example 2 except that the treatment liquid was not used in Example 2. The power generation evaluation results of this membrane electrode composite are summarized in Table 1.
(Example 7)
Electrodes A and B were immersed in a treatment solution in which 0.5 mol of glycerin and 3 mol of isopropyl alcohol were added to a 1 mol sulfuric acid aqueous solution heated to 95 ° C. for 1 hour, and washed until the washing solution became neutral. Next, a composition in which the aromatic hydrocarbon-based polymer electrolyte A, N-methyl-2-pyrrolidone, and glycerin were uniformly mixed was provided at ² mg / cm ² on the catalyst layer side of each electrode.

These electrodes were superposed on the aromatic hydrocarbon polymer electrolyte membrane B so as to face each other, and heated and pressed at 100 ° C. for 1 minute at a pressure of 5 MPa to obtain a membrane electrode composite.
The power generation evaluation results of this membrane electrode composite are summarized in Table 1.
(Example 8)
The electrode transfer sheets A and B were immersed in a 0.3 mol chlorosulfuric acid and 1,2-dichloroethane solution heated to 70 ° C. for 3 minutes and washed until the cleaning solution became neutral. Next, a composition obtained by uniformly mixing the aromatic hydrocarbon polymer electrolyte A, N-methyl-2-pyrrolidone, and glycerin was provided on the catalyst layer side so as to be 1 mg / cm ² .

  These electrode transfer sheets were superposed on the aromatic hydrocarbon polymer electrolyte membrane A so as to face each other, and heated and pressed at 100 ° C. for 1 minute at a pressure of 3 MPa. Next, after peeling off only the polyimide film “Kapton (registered trademark)” manufactured by Toray DuPont Co., Ltd. as an electrode transfer sheet, it was immersed in a treatment solution in which 1 mol of propylene carbonate was added to 1 mol sulfuric acid aqueous solution heated to 95 ° C. for 30 minutes. Then, cleaning is performed until the cleaning solution becomes neutral, and an electrode base material (carbon paper TGP-H-060 manufactured by Toray Industries, Inc.) is superimposed on the electrode, and pressed and integrated at 100 ° C. and 5 MPa for 5 minutes. Got the body. The power generation evaluation results of this membrane electrode composite are summarized in Table 1.

As is clear from Table 1, Examples 1 to 8 have a small difference in voltage between the first power generation and the tenth time, and the original performance of the membrane electrode assembly is obtained from the first time. On the other hand, in Comparative Examples 1 to 3, the difference between the first time and the 10th time is large, and it is necessary to repeat power generation in order to obtain the original performance of the membrane electrode assembly.
Example 9
The electrode transfer sheet B was provided on the two catalyst layers so that the composition obtained by uniformly mixing the aromatic hydrocarbon polymer electrolyte A, N-methyl-2-pyrrolidone, and glycerin was 1 mg / cm ² . These electrode transfer sheets were superposed on the aromatic hydrocarbon polymer electrolyte membrane B so as to face each other, and heated and pressed at 100 ° C. for 1 minute at a pressure of 3 MPa. Next, after removing only the polyimide film “Kapton (registered trademark)” manufactured by Toray DuPont Co., Ltd. as an electrode transfer sheet, 0.5 mol glycerin and 1 mol ethanol were added to a 1 mol sulfuric acid aqueous solution heated to 70 ° C. Immerse in the treatment liquid for 1 hour, wash until the cleaning liquid becomes neutral, overlay an electrode substrate (carbon paper TGP-H-060 manufactured by Toray Industries, Inc.) on the anode side electrode, and US Tech on the cathode side electrode. Carbon cloth “TL-1400W” manufactured by (E-TEK) was superposed, pressed at 100 ° C. and 5 MPa for 5 minutes, and integrated to obtain a membrane electrode composite. This membrane electrode assembly is set in a JARI standard cell “Ex-1” manufactured by Eiwa Co., Ltd., at a cell temperature of 80 ° C., fuel gas: hydrogen, oxidizing gas: air, gas utilization rate: 70% anode / 40% cathode. When current-voltage (IV) measurement was performed, the initial maximum output was 500 mW / cm ² .
(Comparative Example 4)
A membrane electrode assembly was prepared and evaluated in the same manner as in Example 9 except that the treatment liquid was not used in Example 9. As a result, the initial maximum output was 300 mW / cm ² .
(Example 10)
The processing solution of the membrane electrode assembly of Example 1 was analyzed by SII / Nanotechnology's sequential ICP emission spectroscopic analyzer SPS400. As a result, Ru element could be confirmed, and at least a part of the soluble Ru component could be removed before power generation. It was. The voltage holding ratio of this membrane electrode composite was 98%, indicating excellent durability.
(Comparative Example 5)
The voltage holding ratio of the membrane electrode assembly of Comparative Example 1 was 80%, indicating durability inferior to that of Example 10. The cathode electrode catalyst layer of the membrane electrode composite after this durability evaluation was sampled, heated to ash, thermally decomposed with sulfuric acid, nitric acid and perchloric acid, and then heated and dissolved in dilute aqua, sequentially from SII Nanotechnology. The presence of the Ru element was confirmed by analysis using a type ICP emission spectroscopic analyzer SPS400, and it was confirmed that a part of the Ru of the anode was dissolved during power generation and transmitted to the counter electrode.

  The method for producing a membrane electrode assembly of the present invention is applicable to the production of a membrane electrode assembly used for a fuel cell or the like.

Claims (6)

  A method for producing a membrane electrode assembly comprising an aromatic hydrocarbon polymer electrolyte membrane, an anode and a cathode, wherein the anode and / or the cathode is made into a solution containing an organic solvent having an atmospheric pressure boiling point of 70 ° C. or higher and an acid. A method for producing a membrane electrode assembly comprising an activation treatment step of contacting at a temperature not lower than 70 ° C. and not higher than the boiling point of the organic solvent.   2. The method for producing a membrane electrode assembly according to claim 1, wherein the activation treatment step is after the step of producing an anode and / or a cathode on the aromatic hydrocarbon polymer electrolyte membrane.   The method for producing a membrane electrode assembly according to claim 1 or 2, wherein the organic solvent having a boiling point of 70 ° C or higher is an alcohol and / or a polyhydric alcohol.   The method for producing a membrane electrode assembly according to claim 1 or 2, wherein the organic solvent having a boiling point of 70 ° C or higher at atmospheric pressure is a heterocyclic compound.   The method for producing a membrane electrode assembly according to any one of claims 1 to 4, wherein the acid is sulfuric acid.   A process for producing a membrane electrode assembly, wherein the anode contains Ru.