JP2010062062A - Method of manufacturing membrane electrode assembly, membrane electrode assembly, and polymer electrolyte fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a membrane electrode assembly with high efficiency of production. <P>SOLUTION: The method of manufacturing the membrane electrode assembly having either face of a solid polymer electrolyte film pinched with electrocatalyst layers comprises a step of forming a coated film by coating a first catalyst ink containing catalyst-carrying particles, polymer electrolyte and a solvent on a base material, a step of removing the solvent in the formed coated film and forming a first electrocatalyst layer, a step of coating electrolyte ink containing polymer electrolyte and a solvent on the first electrocatalyst layer to form a coated film, a step of removing the solvent in the coated film formed and forming a polymer electrolyte film, a step of coating catalyst ink containing the catalyst-carrying particles, polymer electrolyte, and a solvent on the polymer electrolyte film to form a coated film, and a step of removing the solvent in the coated film formed to form a second electrocatalyst layer. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a membrane electrode assembly, a production method thereof, and a polymer electrolyte fuel cell including the membrane electrode assembly.

  A fuel cell is a power generation system that generates electricity simultaneously with heat by causing a hydrogen gas-containing fuel gas and an oxygen-containing oxidant gas to undergo reverse reaction of water electrolysis at an electrode including a catalyst. This power generation system has features such as high efficiency, low environmental load, and low noise as compared with conventional power generation systems, and is attracting attention as a clean energy source in the future. There are several types depending on the type of ion conductor used, and those using an ion conductive polymer membrane are called solid polymer fuel cells.

  Among fuel cells, polymer electrolyte fuel cells can be used near room temperature, so they are considered promising for use in on-vehicle sources and household stationary power sources. In recent years, various research and development have been conducted. Yes. A polymer electrolyte fuel cell is a fuel gas containing hydrogen on one of the electrodes, which is a membrane electrode assembly (Membrance and Electrolyte Assembly) in which a pair of electrode catalyst layers are disposed on both sides of a polymer electrolyte. And is sandwiched between a pair of separators having a gas flow path for supplying an oxidant gas containing oxygen to the other of the electrodes. Here, the electrode for supplying the fuel gas is called a fuel electrode, and the electrode for supplying the oxidant is called an air electrode. These electrodes are composed of an electrode catalyst layer formed by laminating carbon particles carrying a catalyst substance such as a platinum-based noble metal and a polymer electrolyte, and a gas diffusion layer having both gas permeability and electron conductivity.

  In order to improve the performance of such a polymer electrolyte fuel cell, various methods for producing a membrane electrode assembly have been studied. For example, an electrode catalyst layer is formed on a base film, and then 1 A method of forming a membrane electrode assembly by transferring electrode catalyst layers from a substrate onto a polymer electrolyte membrane by placing a pair of electrode catalyst layers on both sides of the polymer electrolyte membrane and hot pressing, or on a gas diffusion film Then, the electrode catalyst layer is formed on the both sides of the polymer electrolyte membrane and hot-pressed to transfer the electrode catalyst layer from the substrate onto the polymer electrolyte membrane. A method of forming a joined body is known.

JP 2004-0476489 A JP-A-2005-294123

  However, in the manufacturing method in which the electrode catalyst layer is joined to the polymer electrolyte membrane by thermocompression bonding such as hot pressing, the hot pressing step becomes a bottleneck, resulting in a longer tact time, resulting in lower production efficiency. There was a problem of letting it go.

  Then, in this invention, let it be a subject to provide the manufacturing method of a membrane electrode assembly with high production efficiency.

  In order to solve the above-mentioned problems, the invention according to claim 1 is a method for producing a membrane electrode assembly in which both surfaces of a polymer electrolyte membrane are sandwiched between electrode catalyst layers. A step of applying a first catalyst ink containing a polymer electrolyte and a solvent to form a coating film; a step of removing the solvent in the formed coating film to form a first electrode catalyst layer; and A step of applying an electrolyte ink containing a polymer electrolyte and a solvent on the electrode catalyst layer to form a coating film; a step of removing the solvent in the formed coating film to form a polymer electrolyte membrane; and A step of applying a catalyst ink containing catalyst-supporting particles, a polymer electrolyte and a solvent on the polymer electrolyte membrane to form a coating film, and removing the solvent in the formed coating film to form a second electrode catalyst layer And a process for producing a membrane electrode assembly.

  According to a second aspect of the invention, the first electrode catalyst layer before applying the electrolyte membrane ink is 10 wt% or less with respect to the total mass of the solvent contained in the applied first catalyst ink. The method for producing a membrane / electrode assembly according to claim 1, wherein the solvent is removed up to.

  According to a third aspect of the present invention, the polymer electrolyte membrane before applying the second catalyst ink is a solvent up to 5 wt% or less with respect to the total mass of the solvent contained in the applied electrolyte ink. The method for producing a membrane / electrode assembly according to claim 1 or 2, wherein is removed.

  According to a fourth aspect of the invention, the polymer electrolyte contained in the first catalyst ink, the polymer electrolyte contained in the electrolyte ink, and the polymer electrolyte contained in the second catalyst ink are the same. The method for producing a membrane / electrode assembly according to claim 1, wherein the material comprises:

  The invention according to claim 5 is a membrane electrode assembly manufactured by the manufacturing method according to any one of claims 1 to 4.

  According to a sixth aspect of the present invention, the membrane electrode assembly according to the fifth aspect is sandwiched between a pair of gas diffusion layers, and the membrane electrode assembly sandwiched between the gas diffusion layers is a pair of separators. The polymer electrolyte fuel cell is characterized in that it is held between the two.

  By using the membrane electrode assembly of the present invention, a membrane electrode assembly with high production efficiency could be obtained.

  Below, the membrane electrode assembly (MEA) of this invention, its manufacturing method, and a polymer electrolyte fuel cell are demonstrated. Note that the present invention is not limited to the embodiments described below, and modifications such as design changes can be made based on the knowledge of those skilled in the art, and such modifications are added. The embodiments may be included in the scope of the present invention.

First, the membrane electrode assembly of the present invention will be described.
FIG. 1 shows a schematic cross-sectional view of a membrane electrode assembly (MEA) of the present invention.

  The membrane electrode assembly A of the present invention includes electrode catalyst layers 2 and 3 on both surfaces of the polymer electrolyte membrane 1. The polymer electrolyte membrane 1 has a structure in which the electrode catalyst layers 2 and 3 are sandwiched. The electrode catalyst layers 2 and 3 include catalyst-supporting particles and a polymer electrolyte. The electrode catalyst layers 2 and 3 may be made of the same material or may be made of different materials.

  In the membrane / electrode assembly of the present invention, the electrode catalyst layers 2 and 3 and the polymer electrolyte membrane 1 may have the same size as shown in FIG. As shown in FIG. 5, the size of the polymer electrolyte membrane 1 may be larger than the size of the electrode catalyst layers 2 and 3. In either case, it is necessary to prevent the electrode catalyst layers 2 and 3 from short-circuiting or from leaking.

Below, the manufacturing method of the membrane electrode assembly of this invention is described.
FIG. 2 shows an explanatory view of a method for producing a membrane electrode assembly (MEA) of the present invention.

  In the method for producing a membrane / electrode assembly of the present invention, a first catalyst ink 2 ″ containing catalyst-carrying particles, a polymer electrolyte, and a solvent is prepared, and the first catalyst ink 2 ′ is provided on the support S. 'Is applied to form a coating film 2'. (FIG. 2 (a)). Next, the solvent in the coating film 2 ′ made of the first catalyst ink applied on the support S is removed, and the first electrode catalyst layer 2 is formed on the support S (FIG. 2B). )).

  Next, an electrolyte membrane ink 1 ″ containing a polymer electrolyte and a solvent is prepared, and the electrolyte membrane ink 1 ″ is applied on the first electrode catalyst layer to form a coating film 1 ′ (FIG. 2 ( c)). Next, the solvent in the coating film 1 ′ made of the electrolyte membrane ink applied on the support S is removed, and the polymer electrolyte membrane 1 is formed on the first electrode catalyst layer 2 (FIG. 2D). )).

  Next, a second catalyst ink 3 ″ containing catalyst-carrying particles, a polymer electrolyte, and a solvent is prepared, and the second electrode catalyst ink 3 ″ is applied onto the polymer electrolyte membrane 1, and the coating film 3 ′. Is formed (FIG. 2E). Next, the solvent in the coating film 3 ′ made of the second catalyst ink applied on the polymer electrolyte membrane 1 is removed, and the second electrode catalyst layer 3 is formed on the polymer electrolyte membrane 1 ( FIG. 2 (f)).

  Finally, the membrane electrode assembly A composed of the first electrode catalyst layer 2, the polymer electrolyte membrane 1, and the second electrode catalyst layer 3 is peeled from the support, if necessary, from the support S, and the present invention. The membrane electrode assembly A is manufactured (FIG. 2G). In addition, when the gas diffusion layer and separator which are mentioned later are used as the support S, it is not necessary to peel the membrane electrode assembly A from the support S.

  In the method for producing a membrane electrode assembly of the present invention, the first electrode catalyst layer 2, the polymer electrolyte membrane 1, and the second electrode catalyst layer are sequentially laminated, and the production efficiency can be very high. . Therefore, a membrane electrode assembly can be manufactured at low cost. In the membrane / electrode assembly of the present invention, the polymer electrolyte membrane 1 and the electrode catalyst layers 2 and 3 can be sufficiently joined, and the interface between the polymer electrolyte membrane 1 and the electrode catalyst layers 2 and 3 can be obtained. The ion resistance can be reduced.

  Moreover, in the manufacturing method of the membrane electrode assembly of the present invention, the hot pressing step is omitted as compared with the manufacturing method of the membrane electrode assembly in which the electrode catalyst layer is transferred to both surfaces of the polymer electrolyte membrane by hot pressing. be able to. When the hot pressing step is omitted, it is possible to prevent a decrease in membrane strength and a decrease in ion exchange capacity due to damage to the polymer electrolyte membrane due to heating and pressure during hot pressing.

  Moreover, in the membrane electrode assembly of the present invention, the film thickness of the polymer electrolyte membrane positioned between a pair of electrode catalyst layers can be reduced. In the method of manufacturing a membrane electrode assembly in which the electrode catalyst layer is transferred to both surfaces of the polymer electrolyte membrane by hot pressing, the carbon fibers contained in the gas diffusion layer provided so as to be adjacent to the electrode catalyst layer at the time of hot pressing Since the electrode catalyst layer and the polymer electrolyte membrane are difficult to be inserted, there is a problem that gas leakage occurs and the circuit voltage of the membrane electrode assembly is lowered. In addition, the carbon fiber contained in the gas diffusion layer provided so as to be adjacent to the electrode catalyst layer at the time of hot pressing has a problem that the electrode catalyst layer and the polymer electrolyte membrane are short-circuited when the power is generated. there were. Therefore, in manufacturing a membrane electrode assembly by a method of transferring electrode catalyst layers to both surfaces of a polymer electrolyte membrane by hot pressing, it is necessary to increase the thickness of the polymer electrolyte membrane.

  On the other hand, in the membrane electrode assembly of the present invention, the hot pressing step can be omitted, and the thickness of the formed polymer electrolyte membrane can be reduced. Specifically, the thickness of the polymer electrolyte membrane can be 20 μm or less. And in the membrane electrode assembly with a small film thickness of the polymer electrolyte membrane, the power generation characteristics can be improved by lowering the membrane resistance.

  Moreover, in the manufacturing method of the membrane electrode assembly of this invention, the 1st electrode catalyst layer 2 before apply | coating electrolyte membrane ink is with respect to the total mass of the solvent contained in the said 1st catalyst ink. It is preferable that the solvent is removed to 10 wt% or less. By sufficiently removing the solvent in the coating film made of the first catalyst ink and applying the electrolyte membrane ink to the sufficiently dried first electrode catalyst layer, the first electrode catalyst layer and It is possible to prevent the electrolyte membrane ink from being mixed.

  In the method for producing a membrane / electrode assembly according to the present invention, the polymer electrolyte membrane before applying the second catalyst ink is 5 wt% or less with respect to the total mass of the solvent contained in the electrolyte ink. It is preferred that the solvent has been removed. The polymer electrolyte membrane and the second catalyst are removed by sufficiently removing the solvent in the coating film made of the electrolyte membrane ink and applying the second catalyst ink to the sufficiently dried polymer electrolyte membrane. Ink can be prevented from mixing.

  In the method for producing a membrane electrode assembly of the present invention, the polymer electrolyte contained in the first catalyst ink, the polymer electrolyte contained in the electrolyte ink, and the polymer contained in the second catalyst ink The electrolytes preferably include the same material. When each ink contains the same polymer electrolyte, the junction between the polymer electrolyte membrane and the two electrode catalyst layers can be improved, and the ionic resistance at the interface between the polymer electrolyte membrane and the electrode catalyst layer can be reduced. it can.

  In the membrane electrode assembly formed by the production method of the present invention, the production efficiency is high, the polymer electrolyte membrane and the electrode catalyst layer are sufficiently joined, and ions at the interface between the polymer electrolyte membrane and the electrode catalyst layer are A membrane electrode assembly having low resistance, low cost and sufficient power generation performance can be obtained.

The solid polymer fuel cell of the present invention will be described below.
FIG. 3 shows an exploded schematic view of the polymer electrolyte fuel cell of the present invention.

  In the polymer electrolyte fuel cell of the present invention, the air electrode side gas diffusion layer 4 and the fuel electrode side gas diffusion layer 5 are opposed to the electrode catalyst layer 2 and the electrode catalyst layer 3 of the membrane electrode assembly A. Be placed. Thereby, the air electrode 6 and the fuel electrode 7 are comprised, respectively. A set of separators 10 made of a conductive and impermeable material is provided, which includes a gas flow path 8 for gas flow and a cooling water flow path 9 for cooling water flow on the opposing main surface. For example, hydrogen gas is supplied as a fuel gas from the gas flow path 8 of the separator 10 on the fuel electrode 7 side. On the other hand, a gas containing oxygen, for example, is supplied as an oxidant gas from the gas flow path 8 of the separator 10 on the air electrode 6 side. An electromotive force can be generated between the fuel electrode and the air electrode by causing an electrode reaction between hydrogen and oxygen gas of the fuel gas in the presence of the catalyst.

  In FIG. 3, the polymer electrolyte fuel cell has the first electrode catalyst layer 2 disposed on the air electrode 6 side and the second electrode catalyst layer 3 disposed on the fuel electrode 7 side. However, in the membrane electrode assembly of the present invention, the solid polymer fuel in which the first electrode catalyst layer 2 is disposed on the fuel electrode 7 side and the second electrode catalyst layer 3 is disposed on the air electrode 6 side. It does not matter as a battery.

  The solid polymer type fuel cell shown in FIG. 3 has a so-called single cell structure with a solid polymer electrolyte membrane 1, electrode catalyst layers 2, 3, and gas diffusion layers 4, 5 sandwiched between a pair of separators. Although it is a molecular type fuel cell, in the present invention, a plurality of cells can be stacked via the separator 10 to form a fuel cell.

  Next, the membrane electrode assembly (MEA) of the present invention, the production method thereof, and the polymer electrolyte fuel cell of the present invention will be described in more detail.

  As the support S to which the first catalyst ink of the present invention is applied, a polymer film, a sheet or a glass plate can be used. At this time, as the polymer film and sheet, polyimide, polyethylene terephthalate (PET), polyparvanic acid aramid, polyamide (nylon), polysulfone, polyethersulfone, polyethersulfone, polyphenylene sulfide, polyetheretherketone, poly Examples thereof include polymer films and sheets such as etherimide, polyacrylate, and polyethylene naphthalate.

  In addition, heat resistance of polyethylene tetrafluoroethylene copolymer (ETFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroperfluoroalkyl vinyl ether copolymer (PFA), polytetrafluoroethylene (PTFE), etc. Fluororesin can also be used as a polymer film and sheet.

  Further, as the support S, a gas diffusion layer or a separator can be used. When a gas diffusion layer or a separator is used as the support S, the formed membrane electrode assembly A and the support S do not have to be peeled off after the membrane electrode assembly is formed on the support S.

  The support S preferably has a small arithmetic average roughness Ra on the surface on which the first catalyst ink is applied, specifically 5 μm or less, and more preferably 1 μm or less. preferable. If a support having a large arithmetic average roughness Ra on the surface on which the first catalyst ink is applied is used, the first catalyst ink cannot be stably applied in a uniform manner.

  As the support S, it is preferable to use a film or sheet. By using a film-like or sheet-like material as a support, it is possible to continuously produce a membrane electrode assembly by a roll-to-roll method, and to produce a membrane electrode assembly at a low cost. Can do.

  The first catalyst ink 2 ″ of the present invention includes at least catalyst-supporting particles, a polymer electrolyte, and a solvent.

  The catalyst-carrying particles used in the first catalyst ink 2 ″ of the present invention are those in which a catalytic substance is carried on the particles, and as the catalytic substance, platinum group elements such as platinum, palladium, ruthenium, iridium, rhodium and osmium are used. In addition, metals such as iron, lead, copper, chromium, cobalt, nickel, manganese, vanadium, molybdenum, gallium, and aluminum, alloys thereof, oxides, double oxides, and the like can be used. Moreover, since the activity of a catalyst will fall when the particle size of these catalysts is too large, and stability of a catalyst will fall when too small, 0.5-20 nm is preferable. More preferably, 1-5 nm is good.

  Carbon particles can be used as the particles for supporting the catalyst. Any carbon particles can be used as long as they are in the form of fine particles, have conductivity and are not affected by the catalyst, but carbon black, graphite, graphite, activated carbon, carbon fiber, carbon nanotube, and fullerene are used. it can. If the particle size of the carbon particles is too small, it becomes difficult to form an electron conduction path. If the particle size is too large, the gas diffusibility of the electrode catalyst layer is reduced or the utilization rate of the catalyst is reduced. Is preferred. More preferably, 10-100 nm is good.

  As the polymer electrolyte used in the first catalyst ink 2 ″ of the present invention, a polymer electrolyte exhibiting proton conductivity can be used. In particular, perfluorosulfonic acid-based polymer electrolytes can be suitably used, and product names such as Nafion (Nafion, a registered trademark of DuPont), Flemion (registered trademark of Asahi Glass Co., Ltd.), Aciplex (Asahi Kasei Corporation) A film such as a registered trademark can be used. Also, hydrocarbon polymer electrolytes such as sulfonated PEEK (polyether ether ketone), PES (polyether sulfone), and PI (polyimide) can be used.

  The polymer electrolyte contained in the first catalyst ink and the polymer electrolyte contained in the electrolyte ink are preferably the same material. By using the same material for the polymer electrolyte contained in the first catalyst ink and the polymer electrolyte contained in the electrolyte ink, the bonding between the formed first electrode catalyst layer and the polymer electrolyte membrane can be improved. And the ionic resistance at the interface can be further reduced.

  As the solvent 2 ″ used for the first catalyst ink of the present invention 2 ″, the polymer electrolyte dissolves or forms a fine gel in a highly fluid state without corroding the catalyst-supporting particles and the polymer electrolyte. There are no particular restrictions on what can be dispersed.

  Among them, it is desirable that the solvent contains at least an organic solvent, and is not particularly limited, but examples of the organic solvent include methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, isobutyl alcohol, alcohols such as tert-butyl alcohol, pentanol, 2-heptanol, benzyl alcohol, acetone, methyl ethyl ketone, methyl propyl ketone, methyl butyl ketone, methyl isobutyl ketone, methyl amyl ketone, pentanone, heptanone, cyclohexanone, methylcyclohexanone, Ketones such as acetonyl acetone, diethyl ketone, dipropyl ketone, diisobutyl ketone, tetrahydrofuran, tetrahydropyran, dioxane, diethylene glycol dimethyl Ethers such as ether, anisole, methoxytoluene, diethyl ether, dipropyl ether, dibutyl ether, amines such as isopropylamine, butylamine, isobutylamine, cyclohexylamine, diethylamine, aniline, propyl formate, isobutyl formate, amyl formate, acetic acid Esters such as methyl, ethyl acetate, propyl acetate, butyl acetate, isobutyl acetate, pentyl acetate, isopentyl acetate, methyl propionate, ethyl propionate, butyl propionate, other acetic acid, propionic acid, dimethylformamide, dimethylacetamide, N- Methyl pyrrolidone, ethylene glycol, diethylene glycol, propylene glycol, ethylene glycol monomethyl ether, ethylene glycol dimethyl ether Le, ethylene glycol diethyl ether, diacetone alcohol, 1-methoxy-2-propanol or the like is used. Moreover, water can also be used as a solvent. Moreover, what mixed 2 or more types of these solvents can also be used.

  In addition, those using lower alcohol as the solvent have a high risk of ignition, and when using such a solvent, it is preferable to use a mixed solvent with water. The amount of water added is not particularly limited as long as the polymer electrolyte is not separated to cause white turbidity or gelation. In consideration of the temperature of the drying step, the solvent used for the first catalyst ink preferably has a boiling point in the range of 60 to 120 ° C.

  The first catalyst ink 2 ″ contains these catalyst-supporting particles, polymer electrolyte, and solvent, but may contain other components. For example, a pore-forming agent may be included, and pores can be formed by removing the pore-forming agent after the formation of the electrode catalyst layer. Examples include substances that are soluble in acids, alkalis, and water, substances that sublime such as camphor, and substances that thermally decompose. In addition, if the substance is soluble in hot water, it may be removed with water generated during power generation.

  The first catalyst ink 2 ″ of the present invention can be obtained by mixing these catalyst-supporting particles, polymer electrolyte, and solvent. When adjusting the first catalyst ink, a dispersion process can be performed. Various treatment methods can be used for the dispersion treatment, and for example, treatment can be performed using a ball mill, a roll mill, a shear mill, a wet mill, an ultrasonic dispersion treatment, or a homogenizer.

  The adjusted first catalyst ink 2 ″ is applied on the support S. As a method for applying the first catalyst ink at this time, a screen printing method, a die coating method, a slit coating method, or an applicator method can be suitably used.

  The coating film 2 ′ made of the applied first catalyst ink is dried to remove the solvent in the coating film, and the first electrode catalyst layer 2 is formed on the support S. As the drying means, drying by heating, drying by blowing, drying by heating, or the like can be used. At this time, it is preferable that the solvent is removed from the first electrode catalyst layer to 10 wt% or less with respect to the total mass of the solvent contained in the first catalyst ink.

  Thus, the first electrode catalyst layer 2 is formed on the support S. Next, the polymer electrolyte membrane 1 is formed on the first electrode catalyst layer 2 using the electrolyte ink 1 ″.

  The electrolyte ink 1 '' includes at least a polymer electrolyte and a solvent. As the polymer electrolyte contained in the electrolyte ink, a polymer electrolyte exhibiting proton conductivity can be used. In particular, perfluorosulfonic acid-based polymer electrolytes can be suitably used, and product names such as Nafion (Nafion, a registered trademark of DuPont), Flemion (registered trademark of Asahi Glass Co., Ltd.), Aciplex (Asahi Kasei Corporation) A film such as a registered trademark can be used. Also, hydrocarbon polymer electrolytes such as sulfonated PEEK (polyether ether ketone), PES (polyether sulfone), and PI (polyimide) can be used.

  Solvents contained in the electrolyte ink 1 ″ are organic solvents such as methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, isobutyl alcohol, tert-butyl alcohol, pentanol, and 2-heptanol. , Alcohols such as benzyl alcohol, acetone, methyl ethyl ketone, methyl propyl ketone, methyl butyl ketone, methyl isobutyl ketone, methyl amyl ketone, pentanone, heptanone, cyclohexanone, methyl cyclohexanone, acetonyl acetone, diethyl ketone, dipropyl ketone, Ketones such as diisobutyl ketone, tetrahydrofuran, tetrahydropyran, dioxane, diethylene glycol dimethyl ether, anisole, methoxytoluene, diethyl ether , Ethers such as dipropyl ether and dibutyl ether, amines such as isopropylamine, butylamine, isobutylamine, cyclohexylamine, diethylamine and aniline, propyl formate, isobutyl formate, amyl formate, methyl acetate, ethyl acetate, propyl acetate, Esters such as butyl acetate, isobutyl acetate, pentyl acetate, isopentyl acetate, methyl propionate, ethyl propionate, butyl propionate, other acetic acid, propionic acid, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, ethylene glycol, diethylene glycol, Propylene glycol, ethylene glycol monomethyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diacetone alcohol Lumpur, 1-methoxy-2-propanol or the like is used. Moreover, water can also be used as a solvent. Moreover, what mixed 2 or more types of these solvents can also be used.

  The electrolyte ink 1 '' of the present invention can be obtained by mixing these polymer electrolytes and a solvent. At this time, the electrolyte ink may contain other components.

  The viscosity of the electrolyte ink 1 ″ is preferably adjusted to a range of 100 cP to 200 cP. When the viscosity of the electrolyte ink is 100 cP or less, the electrolyte ink can easily enter the pores in the first electrode catalyst layer, and the gas diffusibility of the produced membrane electrode assembly may be lowered. On the other hand, when the viscosity of the electrolyte ink is 200 cP or more, it becomes difficult to apply the electrolyte ink, and it may be difficult to form a polymer electrolyte membrane having a uniform film thickness on the first electrode catalyst layer. is there.

  The adjusted electrolyte ink 1 ″ is applied on the support S. As a method for applying the electrolyte ink at this time, a screen printing method, a die coating method, a slit coating method, or an applicator method can be suitably used.

  The coating film 1 ′ made of the applied electrolyte ink is dried to remove the solvent in the coating film, and the polymer electrolyte membrane 1 is formed. As the drying means, drying by heating, drying by blowing, drying by heating, or the like can be used. At this time, it is preferable that the solvent is removed from the polymer electrolyte to 5 wt% or less with respect to the mass of the applied electrolyte ink.

  In the method for producing a membrane electrode assembly of the present invention, the solvent removal step of the coating film made of the electrolyte ink by the drying means by heating, the drying means by blowing, and the drying means by heating and blowing is performed immediately after the application of the electrolyte ink. Is preferred. When it takes time to remove the solvent, the first electrode catalyst layer and the polymer electrolyte membrane component to be formed are mixed, which is not preferable. Specifically, it is preferable that the time from the application of the electrolyte ink to the removal of the solvent up to 5 wt% or less with respect to the mass of the applied electrolyte ink is in the range of 30 seconds to 10 minutes. .

  As a result, the polymer electrolyte membrane 1 is formed on the first electrode catalyst layer 2. Next, the second electrode catalyst layer 3 is formed on the polymer electrolyte membrane 1 using 3 ″ of the second catalyst ink.

  The second catalyst ink 3 ″ of the present invention includes at least catalyst-supporting particles, a polymer electrolyte, and a solvent.

  The catalyst-carrying particles used in the second catalyst ink 3 ″ of the present invention are those in which a catalytic substance is carried on the particles. Examples of the catalytic substance include platinum group elements such as platinum, palladium, ruthenium, iridium, rhodium, and osmium. In addition, metals such as iron, lead, copper, chromium, cobalt, nickel, manganese, vanadium, molybdenum, gallium, and aluminum, alloys thereof, oxides, double oxides, and the like can be used. Moreover, since the activity of a catalyst will fall when the particle size of these catalysts is too large, and stability of a catalyst will fall when too small, 0.5-20 nm is preferable. More preferably, 1-5 nm is good.

  Carbon particles can be used as the particles for supporting the catalyst. Any carbon particles can be used as long as they are in the form of fine particles, have conductivity and are not affected by the catalyst, but carbon black, graphite, graphite, activated carbon, carbon fiber, carbon nanotube, and fullerene are used. it can. If the particle size of the carbon particles is too small, it becomes difficult to form an electron conduction path. If the particle size is too large, the gas diffusibility of the electrode catalyst layer is reduced or the utilization rate of the catalyst is reduced. Is preferred. More preferably, 10-100 nm is good.

  As the polymer electrolyte used in the second catalyst ink 3 ″ of the present invention, a polymer electrolyte exhibiting proton conductivity can be used. In particular, perfluorosulfonic acid-based polymer electrolytes can be suitably used, and product names such as Nafion (Nafion, a registered trademark of DuPont), Flemion (registered trademark of Asahi Glass Co., Ltd.), Aciplex (Asahi Kasei Corporation) A film such as a registered trademark can be used. Also, hydrocarbon polymer electrolytes such as sulfonated PEEK (polyether ether ketone), PES (polyether sulfone), and PI (polyimide) can be used.

  The polymer electrolyte contained in the second catalyst ink 3 ″ and the polymer electrolyte contained in the electrolyte ink are preferably the same material. By using the same material for the polymer electrolyte contained in the second catalyst ink and the polymer electrolyte contained in the electrolyte ink, the bonding between the formed second electrode catalyst layer and the polymer electrolyte membrane can be improved. And the ionic resistance at the interface can be further reduced.

  As the solvent used in the second catalyst ink 3 '' of the present invention, the polymer electrolyte can be dissolved or dispersed as a fine gel in a highly fluid state without eroding the catalyst-carrying particles and the polymer electrolyte. There are no particular restrictions.

  Among them, it is desirable that the solvent contains at least an organic solvent, and is not particularly limited, but examples of the organic solvent include methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, isobutyl alcohol, alcohols such as tert-butyl alcohol, pentanol, 2-heptanol, benzyl alcohol, acetone, methyl ethyl ketone, methyl propyl ketone, methyl butyl ketone, methyl isobutyl ketone, methyl amyl ketone, pentanone, heptanone, cyclohexanone, methylcyclohexanone, Ketones such as acetonyl acetone, diethyl ketone, dipropyl ketone, diisobutyl ketone, tetrahydrofuran, tetrahydropyran, dioxane, diethylene glycol dimethyl Ethers such as ether, anisole, methoxytoluene, diethyl ether, dipropyl ether, dibutyl ether, amines such as isopropylamine, butylamine, isobutylamine, cyclohexylamine, diethylamine, aniline, propyl formate, isobutyl formate, amyl formate, acetic acid Esters such as methyl, ethyl acetate, propyl acetate, butyl acetate, isobutyl acetate, pentyl acetate, isopentyl acetate, methyl propionate, ethyl propionate, butyl propionate, other acetic acid, propionic acid, dimethylformamide, dimethylacetamide, N- Methyl pyrrolidone, ethylene glycol, diethylene glycol, propylene glycol, ethylene glycol monomethyl ether, ethylene glycol dimethyl ether Le, ethylene glycol diethyl ether, diacetone alcohol, 1-methoxy-2-propanol or the like is used. Moreover, water can also be used as a solvent. Moreover, what mixed 2 or more types of these solvents can also be used.

  In addition, those using lower alcohol as the solvent have a high risk of ignition, and when using such a solvent, it is preferable to use a mixed solvent with water. The amount of water added is not particularly limited as long as the polymer electrolyte is not separated to cause white turbidity or gelation. In consideration of the temperature of the drying step, the solvent used for the first catalyst ink preferably has a boiling point in the range of 60 to 120 ° C.

  The second catalyst ink 3 ″ contains these catalyst-supporting particles, polymer electrolyte, and solvent, but may contain other components. For example, a pore-forming agent may be included, and pores can be formed by removing the pore-forming agent after the formation of the electrode catalyst layer. Examples include substances that are soluble in acids, alkalis, and water, substances that sublime such as camphor, and substances that thermally decompose. If the substance is soluble in hot water, it may be removed with water generated during power generation.

  The second catalyst ink 3 ″ of the present invention can be obtained by mixing these catalyst-supporting particles, polymer electrolyte, and solvent. When adjusting the second catalyst ink, a dispersion process can be performed. The dispersion treatment can be performed using various apparatuses, for example, a ball mill, a roll mill, a shear mill, a wet mill, an ultrasonic dispersion treatment, or a homogenizer.

  The adjusted second catalyst ink 3 ″ is applied on the polymer electrolyte membrane 1. As a method for applying the second catalyst ink at this time, a screen printing method, a die coating method, a slit coating method, and an applicator method can be suitably used.

  The coating film 3 ′ made of the applied second catalyst ink is dried to remove the solvent in the coating film, thereby forming a second electrode catalyst layer. As the drying means, drying by heating, drying by blowing, drying by heating, or the like can be used.

  In the method for producing a membrane electrode assembly of the present invention, the solvent removal step of the coating film composed of the second catalyst ink by the drying means by heating, the drying means by blowing, and the drying means by heating and blowing is performed on the second catalyst ink. It is preferable to carry out immediately after application. When it takes time to remove the solvent, the polymer electrolyte membrane and the component of the second electrode catalyst layer to be formed are mixed, which is not preferable. Specifically, the time until the solvent is removed to 10 wt% or less with respect to the total mass of the solvent contained in the applied electrolyte ink after applying the electrolyte ink is within a range of 30 seconds to 10 minutes. Preferably there is.

  Thus, the second electrode catalyst layer 3 is formed on the polymer electrolyte membrane 1, and the membrane electrode assembly of the present invention is manufactured.

  In the method for producing a membrane electrode assembly of the present invention, hot pressing may be performed after the membrane electrode assembly is formed using the first catalyst ink, the electrolyte ink, and the second catalyst ink. At this time, pressing time can be shortened compared with the method of manufacturing the membrane electrode assembly which transfers an electrode catalyst layer on both surfaces of a polymer electrolyte membrane by hot pressing. Therefore, even when a hot press process is provided, a production method of a membrane electrode assembly with high production efficiency can be obtained. In addition, the heating and pressurizing conditions during hot pressing may be milder than the method of manufacturing a membrane electrode assembly in which electrode catalyst layers are transferred to both surfaces of a polymer electrolyte membrane by hot pressing. it can.

  The membrane electrode assembly of the present invention is sandwiched between a pair of gas diffusion layers, and further sandwiched by a separator, whereby the polymer electrolyte fuel cell of the present invention can be obtained.

  At this time, as the gas diffusion layer, a material having gas diffusibility and conductivity can be used. Specifically, porous carbon materials such as carbon cloth, carbon paper, and non-woven fabric can be used as the gas diffusion layer. The gas diffusion layer can also be used as a substrate. At this time, it is not necessary to peel off the base material that is the gas diffusion layer after the joining step.

  Moreover, when using a gas diffusion layer as a support body, before applying a catalyst ink, you may form a mesh layer on a gas diffusion layer previously. The mesh layer is a layer that prevents the first catalyst ink from permeating into the gas diffusion layer, and deposits on the mesh layer to form a three-phase interface even when the amount of catalyst ink applied is small. Such a sealing layer can be formed, for example, by dispersing carbon particles in a fluorine resin solution and sintering at a temperature equal to or higher than the melting point of the fluorine resin. As the fluororesin, polytetrafluoroethylene (PTFE) or the like can be used.

  Moreover, as a separator, a carbon type or a metal type can be used. The gas diffusion layer and the separator may be integrated. Further, the gas diffusion layer is a layer for uniformly supplying the gas supplied from the separator side to the electrode catalyst layer in the plane, and when the separator or the electrode catalyst layer serves as a gas diffusion layer, In the polymer electrolyte fuel cell of the present invention, the gas diffusion layer may be omitted.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited to these.

(Adjustment of the first catalyst ink and the second catalyst ink)
A platinum-supported carbon catalyst and a 20% by mass polymer electrolyte solution (Nafion: registered trademark, manufactured by DuPont) were mixed in a solvent and subjected to dispersion treatment with a planetary ball mill. Ball mill pots and balls made of zirconia were used.
The composition ratio of the starting materials is platinum-supported carbon and polymer electrolyte Nafion (registered trademark) (manufactured by DuPont) at a mass ratio of 2: 1 and dispersed in a solvent to form a first catalyst ink and a second catalyst ink. Adjusted. At this time, the solvent was ethanol and methanol at a volume ratio of 1: 1. The solid content was 10% by mass.

(Adjustment of electrolyte ink)
As the electrolyte ink, a 20 wt% Nafion (registered trademark) solution (purchased from Wako Pure Chemical Industries) was used.

(Confirmation of first electrode catalyst layer thickness)
A polymer film (polyethylene tetrafluoroethylene copolymer (ETFE)) is fixed on a glass plate, and a catalyst ink is applied onto the polymer film by a doctor blade in which a gap between the blade and the polymer film is set to 125 μm. A catalyst layer was prepared by drying in an oven set at 70 ° C. for 5 minutes. The amount of platinum supported was adjusted to 0.3 mg / cm ² . When the film thickness of the catalyst layer was measured with a contact-type film thickness meter, it was about 8 μm. The residual solvent at this time was 7.4 wt% of the mass of the applied catalyst ink.

(Confirmation of polymer electrolyte layer thickness)
A polymer film (polyethylenetetrafluoroethylene copolymer (ETFE)) is fixed on a glass plate, and a polymer electrolyte ink is applied onto the polymer film with a doctor blade in which the gap between the blade and the polymer film is set to 287 μm. And it was made to dry for 60 minutes in the vacuum oven set to 80 degreeC, and the polymer electrolyte layer was produced. When the film thickness of the polymer electrolyte layer was measured with a contact-type film thickness meter, it was about 25 μm.

Example 1
(Formation of first electrode catalyst layer)
A polymer film (polyethylenetetrafluoroethylene copolymer (ETFE)) is fixed on a glass plate, and the first catalyst ink is applied onto the polymer film with a doctor blade in which the gap between the blade and the substrate is set to 125 μm. Then, immediately after coating, the first electrode catalyst layer was produced by drying in an oven set at 70 ° C. for 5 minutes. At this time, the residual solvent of the first electrode catalyst layer was 7.4 wt% of the mass of the applied catalyst ink.

(Polymer electrolyte layer formation)
A polymer film having a first electrode catalyst layer formed on a glass plate is fixed, and an electrolyte ink is applied on the first electrode catalyst layer by a doctor blade with a gap of 287 μm between the blade and immediately after application. A polymer electrolyte membrane was prepared by drying in an oven set at 60 ° C. for 5 minutes. At this time, the residual solvent of the electrolyte membrane was 5.4 wt% of the mass of the applied electrolyte ink.

(Formation of second electrode catalyst layer)
A polymer film on which a first electrode catalyst layer and a polymer electrolyte layer are formed on a glass plate is fixed, and a second catalyst ink is applied with a doctor blade with a gap of 287 μm between the blade and immediately after application. The second electrode catalyst layer was prepared by drying in an oven set at 60 ° C. for 5 minutes.

(Example 2)
(Formation of first electrode catalyst layer)
A polymer film (polyethylenetetrafluoroethylene copolymer (ETFE)) is fixed on a glass plate, and the first catalyst ink is applied onto the glass substrate by a doctor blade in which the gap between the blade and the polymer film is set to 125 μm. The first electrode catalyst layer was prepared by applying and drying in an oven set at 70 ° C. for 5 minutes. At this time, the residual solvent of the first electrode catalyst layer was 7.4 wt% of the applied first catalyst ink.

(Polymer electrolyte layer formation)
A polymer film having a first electrode catalyst layer formed on a glass plate is fixed, electrolyte ink is applied by a doctor blade with a gap between the blades set to 287 μm, and a dryer set at a vacuum of 80 ° C. The polymer electrolyte layer was produced by drying for 10 minutes. The residual solvent of the polymer electrolyte membrane at this time was 3.7 wt% of the applied electrolyte ink.

(Formation of second electrode catalyst layer)
A polymer film having a first electrode catalyst layer and a polymer electrolyte layer formed on a glass plate is fixed, and a second catalyst ink is applied with a doctor blade with a gap of 287 μm between the blade and immediately after application. The second electrode catalyst layer was prepared by drying in an oven set at 60 ° C. for 5 minutes.

(Cross-sectional comparison between Example 1 and Example 2)
In FIG. 4, the scanning electron microscope (SEM) photograph of the cross section of MEA produced by the sequential lamination shown in Example 1 was shown. In FIG. 5, the scanning electron microscope (SEM) photograph of the cross section of MEA produced by the sequential lamination shown in Example 2 was shown.

  From the above results, in the MEA produced by the sequential lamination shown in (Example 1), the polymer electrolyte layer is as thin as 5 μm. That is, it can be confirmed that the polymer electrolyte membrane and the second electrode catalyst layer are mixed. On the other hand, the MEA produced by sequential lamination shown in (Example 2) has a polymer electrolyte layer of 27 μm (confirmation of the film thickness of the polymer electrolyte membrane), which is almost the same as the polymer electrolyte layer. It can be confirmed that the degree of mixing between the electrolyte membrane and the second electrode catalyst layer is small.

  By using the method for producing a membrane electrode assembly of the present invention, the membrane electrode can be formed in a shorter time compared with the case where the electrode catalyst layer is produced on both surfaces of the membrane electrode assembly by a conventionally used hot press method. A joined body can be manufactured, and a membrane electrode assembly can be provided at low cost in mass production of a membrane electrode assembly. Therefore, it can be said that it is a manufacturing method with extremely high industrial applicability. Moreover, mixing of the polymer electrolyte layer and the second electrode catalyst layer can be prevented by sufficiently drying the first electrode catalyst layer and the polymer electrolyte layer.

FIG. 1 is a schematic sectional view of a membrane electrode assembly (MEA) of the present invention. FIG. 2 is an explanatory view of a method for producing a membrane electrode assembly (MEA) of the present invention. FIG. 3 is an exploded schematic view of the polymer electrolyte fuel cell of the present invention. FIG. 4 is a scanning electron microscope (SEM) photograph of the cross section of the MEA produced by the sequential lamination shown in (Example 1). FIG. 5 is a scanning electron microscope (SEM) photograph of a cross section of the MEA produced by the sequential lamination shown in (Example 2).

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Polymer electrolyte membrane 1 '' Electrolyte ink 1 'Coating film 2 1st electrode catalyst layer 2 "1st catalyst ink 2' Coating film which consists of 1st catalyst ink 3 2nd electrode catalyst layer 3" Second catalyst ink 3 ′ Coating film made of second catalyst ink A Membrane electrode assembly S Support 4 Gas diffusion layer 5 Gas diffusion layer 6 Air electrode 7 Fuel electrode 8 Gas flow channel 9 Cooling water flow channel 10 Separator

Claims (6)

A method for producing a membrane electrode assembly in which both sides of a polymer electrolyte membrane are sandwiched between electrode catalyst layers,
Applying a first catalyst ink containing catalyst-carrying particles, a polymer electrolyte, and a solvent on a substrate to form a coating film;
Removing the solvent in the formed coating film to form a first electrode catalyst layer;
Applying a polymer electrolyte and an electrolyte ink containing a solvent on the first electrode catalyst layer to form a coating film;
Removing the solvent in the formed coating film to form a polymer electrolyte membrane;
Applying a catalyst ink containing catalyst-carrying particles, a polymer electrolyte, and a solvent on the polymer electrolyte membrane to form a coating film;
Removing the solvent in the formed coating film, and forming a second electrode catalyst layer. A method for producing a membrane electrode assembly, comprising:   The first electrode catalyst layer before applying the electrolyte membrane ink is characterized in that the solvent is removed to 10 wt% or less with respect to the total mass of the solvent contained in the applied first catalyst ink. The method for producing a membrane electrode assembly according to claim 1.   The polymer electrolyte membrane before applying the second catalyst ink has the solvent removed to 5 wt% or less with respect to the total mass of the solvent contained in the applied electrolyte ink. The manufacturing method of the membrane electrode assembly of Claim 1 or Claim 2.   The polymer electrolyte contained in the first catalyst ink, the polymer electrolyte contained in the electrolyte ink, and the polymer electrolyte contained in the second catalyst ink contain the same material. The manufacturing method of the membrane electrode assembly in any one of 1 thru | or 3.   A membrane / electrode assembly produced by the production method according to claim 1.   The membrane electrode assembly according to claim 5 is sandwiched between a pair of gas diffusion layers, and the membrane electrode assembly sandwiched between the gas diffusion layers is sandwiched between a pair of separators. Solid polymer fuel cell.