WO2017159820A1

WO2017159820A1 - Paste for forming electrode catalyst layer and method for manufacturing same, and methods for manufacturing membrane-electrode catalyst layer assembly, gas diffusion electrode, solid polymer fuel cell and solid polymer water electrolysis cell

Info

Publication number: WO2017159820A1
Application number: PCT/JP2017/010784
Authority: WO
Inventors: 博敏古屋; 伸渡辺
Original assignee: 株式会社トクヤマ
Priority date: 2016-03-17
Filing date: 2017-03-16
Publication date: 2017-09-21
Also published as: JP2019083085A

Abstract

[Problem] The purpose of the present invention is to attain an electrode catalyst layer having no cracks or peeling in a solid polymer fuel cell or a solid polymer water electrolysis cell in a simple manner, without controlling the temperature or humidity during printing or drying and without adding a plurality of solvents that complicate the composition. [Solution] An electrode catalyst layer for a solid polymer fuel cell or a solid polymer water electrolysis cell is formed using a paste for forming an electrode catalyst layer, the paste comprising a catalyst-carrying carbon powder on which a catalyst is carried, water, a hydrophilic organic solvent, and a solid polymer electrolyte, wherein the water content is 8-20 mass%, the hydrophilic organic solvent content is 60-82 mass%, and the total content of the water and the hydrophilic organic solvent is 78-90 mass%.

Description

Electrode catalyst layer forming paste and method for producing the same, and membrane-electrode catalyst layer assembly, gas diffusion electrode, polymer electrolyte fuel cell, and polymer electrolyte water electrolysis cell

The present invention relates to an electrode catalyst layer forming paste for an electrode catalyst layer of a polymer electrolyte fuel cell or a polymer electrolyte water electrolysis cell, a method for producing the same, a membrane-electrode catalyst layer assembly, a gas diffusion electrode, a solid polymer The present invention relates to a method for manufacturing a fuel cell and a polymer electrolyte water electrolysis cell.

The solid polymer fuel cell is a fuel cell using a solid polymer such as an ion exchange resin as an electrolyte. The basic structure of the polymer electrolyte fuel cell is shown in FIG. In the figure, (1) is a battery partition, (2) is a fuel gas flow hole, (3) is an oxidant gas flow hole, (4) is a fuel chamber side gas diffusion electrode layer, and (5) is an oxidant chamber side gas. A diffusion electrode layer (6) represents a solid polymer electrolyte membrane. In a polymer electrolyte fuel cell using a cation exchange membrane as a solid polymer electrolyte membrane, protons (hydrogen ions) and electrons are generated from the supplied hydrogen gas in the fuel chamber (7), and these protons are solid. It conducts in the polymer electrolyte membrane (6), moves to the other oxidant chamber (8), and reacts with oxygen in air or oxygen gas to generate water. At this time, the electrons generated in the fuel chamber side gas diffusion electrode (4) move to the oxidant chamber side gas diffusion electrode (5) through the external load circuit to obtain electric energy.

The solid polymer type water electrolysis cell is a cell for electrolyzing water to obtain hydrogen and oxygen, using a solid polymer such as an ion exchange resin as an electrolyte. A cell having the same configuration as that of the polymer electrolyte fuel cell shown in FIG. 1 is used. When a cation exchange membrane is used as the solid polymer electrolyte membrane, water is supplied to the oxidant chamber of FIG. A voltage is applied so that the side gas diffusion layer has a high potential. In the oxidizer chamber, water is oxidized and protons and oxygen are generated. The protons move through the solid polymer electrolyte membrane (6), receive electrons at the fuel chamber side gas diffusion electrode layer, and become hydrogen. In this way, hydrogen and oxygen can be obtained from water.

A cation exchange membrane is generally used for the solid polymer electrolyte membrane. Among cation exchange membranes, proton conductive electrolyte membranes are often used. As the proton conductive electrolyte membrane, a perfluorocarbon sulfonic acid resin membrane is mainly used because of its excellent chemical stability.

When a proton conductive electrolyte membrane is used as the solid polymer electrolyte membrane, the reaction field becomes acidic and it is necessary to use an expensive noble metal as a catalyst. On the other hand, the use of an anion exchange membrane as a solid polymer electrolyte membrane has been studied in that the reaction field becomes alkaline and an inexpensive metal other than a noble metal can be used as a catalyst. In this case, by supplying hydrogen or alcohol or the like to the fuel chamber and supplying oxygen and water to the oxidant chamber, the catalyst contained in the electrode and the oxygen and water in the oxidant chamber side gas diffusion electrode layer In contact, hydroxide ions are produced. The hydroxide ions are conducted through the anion exchange membrane and move to the fuel chamber, and react with the fuel at the fuel chamber side gas diffusion electrode to generate water. At this time, the electrons generated by the fuel chamber side gas diffusion electrode move to the oxidant chamber side gas diffusion electrode through the external load circuit, thereby obtaining electric energy.

As in the case of solid polymer fuel cells, the use of an anion exchange membrane as a solid polymer electrolyte membrane has also been studied in solid polymer water electrolysis cells because inexpensive precious metals can be used for the catalyst. Yes. In this case, water is supplied to the fuel chamber, and a voltage is applied between the oxidant chamber side gas diffusion layer and the fuel chamber side gas diffusion layer so that the oxidant chamber side gas diffusion layer has a high potential. On the fuel chamber side, water is reduced and hydrogen and hydroxide ions are generated. Hydroxide ions move through the solid polymer electrolyte membrane and are oxidized in the oxidant-side gas diffusion layer to generate oxygen and water.

The gas diffusion electrode layer is formed by laminating an electrode catalyst layer and a gas diffusion layer (Gas Diffusion Layer, GDL). A membrane-electrode assembly (Membrane-Electrode Assembly, MEA) in which a gas diffusion electrode layer is bonded on both sides of a solid polymer electrolyte membrane is called a membrane-electrode assembly (MEA).

There is still another method for constructing the membrane-electrode assembly. This is as follows. Electrocatalyst layers are laminated on both sides of the solid polymer electrolyte to produce a membrane-electrode catalyst layer assembly (Catalyst Coated Membrane, CCM). By laminating gas diffusion layers on both surfaces of the membrane-electrode catalyst layer assembly, a membrane-electrode assembly can be obtained.

The electrode catalyst layer includes a catalyst-supported carbon powder such as carbon black on which metal particles such as platinum as a catalyst are supported, and a solid polymer electrolyte. The electrode catalyst layer is generally formed by applying an electrode catalyst layer forming paste on the surface of the solid polymer electrolyte membrane. The electrode catalyst layer forming paste is generally composed of a mixture containing a catalyst-supporting carbon powder and a solid polymer electrolyte.

In the electrode catalyst layer forming paste, the solid polymer electrolyte is generally used by being dissolved or dispersed in an organic solvent so as to be uniformly mixed with the catalyst-supporting carbon powder. In addition to the supported carbon powder and the solid polymer electrolyte, it contains a solvent. The solid polymer electrolyte used in the electrode catalyst layer forming paste is composed of the adhesion between the catalyst-supported carbon powders in the formed electrode catalyst layer, the bonding between the electrode catalyst layer and the solid polymer electrolyte membrane, and the solid catalyst electrolyte from the electrode catalyst layer. Contained for ionic conduction to the molecular electrolyte membrane. As the solid polymer electrolyte used for the electrode catalyst layer forming paste, a polymer compound having a functional group having a sulfonic acid group or a tetraalkylammonium structure is used.

A method for obtaining a membrane-electrode catalyst layer assembly using these solid polymer electrolyte membranes and an electrode catalyst layer forming paste containing the solid polymer electrolyte is as follows. The electrode catalyst layer forming paste is prepared, and is a screen printing method in which printing is directly performed on the solid polymer electrolyte membrane, and a method in which the paste is applied to the solid polymer electrolyte membrane using a sprayer.

As the electrode catalyst layer forming paste, pastes of various compositions have already been proposed (eg, Patent Document 1). In Patent Document 1, 2.6 mg of a perfluorinated sulfonic acid NAFION® solution (NAFION® polymer 5% by weight, isopropyl alcohol 50%, methanol 25% and water 20%), 390 mg A paste consisting of 487.9 mg of catalyst with 20% platinum on 1-methoxy 2-propanol, 2 ml isopropanol, VULCAN® carbon support is described.

When this electrode catalyst layer forming paste is used, the organic solvent often causes an oxidation reaction on the catalyst surface when the catalyst is dispersed, resulting in heat generation and catalyst sintering. For this reason, workability and mass productivity of paste adjustment are lowered, and performance of the electrode catalyst is lowered.

Further, the solid polymer electrolyte membrane and the solid polymer electrolyte in the electrode catalyst layer forming paste may have different swelling rates due to the solvent. For this reason, after printing the electrode catalyst layer forming paste on the solid polymer electrolyte membrane, there is a problem that large cracks and peeling occur in the formed electrode catalyst layer due to different drying shrinkage rates. As a result, it is difficult to form a uniform electrode catalyst layer.

In order to solve the above problems, in Patent Document 2, at least (1) the film thickness of the electrode catalyst layer, (2) the kind of carbon carrying the noble metal catalyst, (3) the drying rate of the solvent of the paste, A method of controlling the crack occupying area of the electrode catalyst layer to 25% or less has been proposed. However, deterioration such as cracks cannot be completely suppressed.

In Patent Document 3, the boiling point is higher than that of water, and an azeotropic solvent that is azeotropic at a predetermined temperature or lower when added to water is added together with water. An electrode catalyst layer forming paste is proposed. However, processes such as addition of an azeotropic solvent and viscosity adjustment are increasing, and workability is reduced.

Japanese National Patent Publication No. 9-501535 International Publication No. 2003/077336 Pamphlet JP 2001-266901 A

The methods described in Patent Document 1, Patent Document 2 and Patent Document 3 did not completely solve problems related to cracking, peeling, and workability. Therefore, an object of the present invention is to provide an electrode that is not cracked or peeled by a simple method without controlling the temperature and humidity during printing and drying, and without adding a plurality of solvents that complicate the composition. It is to obtain a catalyst layer.

The inventors of the present invention have intensively studied to solve the problem. As a result, it was found that by preparing and using an electrode catalyst layer forming paste in which the contents of water and hydrophilic organic solvent were controlled, an electrode catalyst layer free from cracks and peeling could be formed, and the present invention was completed. It came.

That is, the first aspect of the present invention is an electrode catalyst layer forming paste comprising a catalyst-supported carbon powder supporting a catalyst, water, a hydrophilic organic solvent, and a solid polymer electrolyte used for forming an electrode catalyst layer, An electrode catalyst layer forming paste characterized by comprising 8 to 20% by mass, hydrophilic organic solvent 60 to 82% by mass, and a total content of water and hydrophilic organic solvent of 78 to 90% by mass.

The solid polymer electrolyte is preferably hydrocarbon-based because it can be produced at low cost and there is no fear of adverse environmental effects due to elution of fluorine ions when decomposed. More preferably, it is an ion exchange resin.

Also, the electrode catalyst layer forming paste of the first aspect of the present invention can be used for forming any electrode catalyst layer of a solid polymer fuel cell and a solid polymer water electrolysis cell.

The second invention is characterized in that a membrane-electrode catalyst layer assembly is formed by applying the electrode catalyst layer forming paste of the first invention on a solid polymer electrolyte membrane. It is a manufacturing method of an electrode catalyst layer assembly.

The solid polymer electrolyte membrane is preferably a hydrocarbon-based material, more preferably a hydrocarbon-based anion exchange resin, like the solid polymer electrolyte.

According to a third aspect of the present invention, a membrane-electrode catalyst layer assembly is produced by the method for producing a membrane-electrode catalyst layer assembly of the second invention, and then a solid polymer is produced using the membrane-electrode catalyst layer assembly. It is a manufacturing method of a polymer electrolyte fuel cell which manufactures a type fuel cell.

According to a fourth aspect of the present invention, a membrane-electrode catalyst layer assembly is produced by the method for producing a membrane-electrode catalyst layer assembly of the second invention, and then a solid polymer is produced using the membrane-electrode catalyst layer assembly. It is a manufacturing method of a solid polymer type water electrolysis cell which manufactures a type water electrolysis cell.

The fifth aspect of the present invention is a method for producing a gas diffusion electrode, wherein the gas diffusion electrode is formed by applying the electrode catalyst layer forming paste of the first aspect of the present invention onto the gas diffusion layer. .

According to a sixth aspect of the present invention, there is provided a polymer electrolyte fuel, wherein a gas diffusion electrode is manufactured by the gas diffusion electrode manufacturing method according to the fifth aspect of the invention, and then a polymer electrolyte fuel cell is manufactured using the gas diffusion electrode. It is a manufacturing method of a battery.

The seventh aspect of the present invention is a solid polymer type wherein a gas diffusion electrode is produced by the method for producing a gas diffusion electrode of the fifth aspect of the invention, and then a solid polymer type water electrolysis cell is produced using the gas diffusion electrode. It is a water electrolysis cell.

The eighth invention is a method for producing the electrode catalyst layer forming paste of the first invention,
(I) Step of dispersing catalyst-supported carbon powder supporting catalyst in water (II) Step of dissolving solid polymer electrolyte in hydrophilic organic solvent (III) Water in which catalyst-supported carbon powder is dispersed and solid polymer electrolyte Step of mixing the dissolved hydrophilic organic solvent (IV) The content of water and the hydrophilic organic solvent is 8-20% by mass of water, 60-82% by mass of the hydrophilic organic solvent, water and the hydrophilic organic solvent. A step of adjusting the total content to 78 to 90% by mass;
It is a manufacturing method of the paste for electrode catalyst layer formation characterized by including.

By using the electrode catalyst layer forming paste of the present invention, a uniform and good electrode catalyst layer free from cracking and peeling can be formed without controlling temperature, humidity, drying speed, etc. in the atmosphere. For this reason, the performance variation of the polymer electrolyte fuel cell and the polymer electrolyte water electrolysis cell using the membrane-electrode catalyst layer assembly and the gas diffusion electrode manufactured using the electrode catalyst layer forming paste of the present invention is reduced. It can be made extremely small. Further, since the electrode catalyst layer is not easily deformed or dropped off by the fuel or water generated or supplied, it is possible to prevent the performance degradation of the polymer electrolyte fuel cell and the polymer electrolyte water electrolysis cell.

Also, since the composition of the solvent does not become complicated, it can be prepared by a simple process. Furthermore, by using the electrode catalyst layer forming paste of the present invention, workability is improved and the efficiency of the electrode catalyst layer forming step is improved. Therefore, when the electrode catalyst layer forming paste of the present invention is used, a membrane-electrode catalyst layer assembly, a gas diffusion electrode, a solid polymer fuel cell, and a solid polymer water electrolysis cell can be efficiently produced.

This figure is a conceptual diagram showing the basic structure of a polymer electrolyte fuel cell. This drawing is a drawing-substituting photograph showing the state of the electrode catalyst layer produced in Example 1. FIG. This figure is a drawing-substituting photograph showing the state of the electrode catalyst layer produced in Comparative Example 4.

(Electrode catalyst layer forming paste)
The electrode catalyst layer forming paste of the present invention is used for forming an electrode catalyst layer used for a polymer electrolyte fuel cell or a polymer electrolyte water electrolysis cell. Here, the electrode catalyst layer means both an anode that reacts with a fuel gas such as hydrogen and a cathode that reacts with an oxidant gas such as oxygen and air, and its use is particularly limited to one electrode. is not. The electrode catalyst layer forming paste of the present invention can be suitably used for the production of both the anode and cathode electrode catalyst layers.

The electrode catalyst layer forming paste of the present invention comprises catalyst-carrying carbon powder carrying a catalyst, water, a hydrophilic organic solvent, and a solid polymer electrolyte.

(Catalyst-supported carbon powder supporting catalyst)
The catalyst-carrying carbon powder carrying the catalyst used in the present invention is obtained by carrying a catalyst on carbon for carrying a catalyst. A catalyst described later is used as the catalyst, and a fuel cell fuel such as hydrogen or alcohol and hydroxide ions or oxygen and water react on the surface to generate electrons, water, hydroxide ions, and the like. In order to take out the generated electrons as an electric current, a catalyst is supported on a carbon powder having electron conductivity, and used as a catalyst-supported carbon powder supporting the catalyst.

(catalyst)
As the catalyst, those used in known fuel cells or water electrolysis cells can be used without any limitation, and promote the oxidation reaction of fuel such as hydrogen, the reduction reaction of oxygen, or the reaction related to the electrolysis of water. If it is a metal particle, it will not restrict | limit in particular. For example, platinum, gold, silver, palladium, iridium, rhodium, ruthenium, tin, iron, cobalt, nickel, molybdenum, tungsten, vanadium, or an alloy thereof can be given. Of these catalysts, platinum is preferred because of its excellent catalytic activity against hydrogen and oxygen. In addition, when an anion exchange resin is used as the solid polymer electrolyte, transition metals such as iron, cobalt, and nickel are not dissolved by the hydroxide ions generated by the oxygen reduction reaction or water reduction reaction, or very little. Therefore, it is preferable that the performance is not deteriorated.

The particle size of the metal particles used for the catalyst is usually 0.1 to 100 nm, more preferably 0.5 to 10 nm. In general, the smaller the particle size, the higher the catalyst performance. However, a particle size of 0.5 nm or more is preferable because of its ease of preparation, and a sufficiently large catalyst performance can be obtained by increasing the specific surface area. A diameter is preferred.

The catalyst content is usually 1 to 30% by mass, preferably 2 to 15% by mass, more preferably 3 to 10% by mass in the paste. By keeping the content in this range, a suitable amount of catalyst can be contained in the electrode catalyst layer after coating. Considering that a suitable amount of catalyst in the electrocatalyst layer can sufficiently promote a reaction involving fuel oxidation, oxygen reduction or water electrolysis, usually 0.01 to 10 mg / cm ^2. More preferably, it is 0.1 to 6.0 mg / cm ² . More preferably, 0.2 mg / cm ² or more is preferable, and a catalyst content of 5.0 mg / cm ² or less that does not saturate the fuel cell output performance is suitable.

(Carbon powder for catalyst support)
The carbon powder for supporting the catalyst supports the catalyst and also serves as a conductive agent. Therefore, as long as it is an electron conductive carbon, those used in known fuel cells or water electrolysis cells can be used without any limitation, and are not particularly limited. For example, carbon black such as furnace black and acetylene black, activated carbon, graphite and the like are generally used alone or in combination. The shape is irregular, but an average particle diameter (equivalent circle diameter) of 1 to 1000 nm, preferably 5 to 100 nm, more preferably 10 to 50 nm is used. By using carbon having a preferable particle size, good electron conductivity can be obtained while supporting a large number of catalyst particles.

The amount of the catalyst supported on the carbon powder is 10% by mass to 90% by mass, preferably 20% by mass to 80% by mass with respect to the total mass of the catalyst-supported carbon powder (total mass of the catalyst and carbon). Is preferred. If a more preferable range is shown, the amount is preferably 30% by mass or more at which the catalyst activity is sufficient, and 70% by mass or less is preferable because the catalyst is saved and the electroconductivity of the electrode catalyst layer is sufficiently performed.

The content of the catalyst-carrying carbon powder carrying the catalyst in the paste greatly affects the viscosity of the paste. By keeping the viscosity of the paste in an appropriate range, a suitable electrode catalyst layer can be obtained without uneven coating or bleeding after coating. The preferred range is 2 to 35% by mass in the paste, more preferably 2 to 20% by mass, still more preferably 3 to 20% by mass, and particularly preferably 5 to 15% by mass.

(water)
In the electrode catalyst layer forming paste of the present invention, water is added in a certain range together with the hydrophilic organic solvent in order to prevent cracking and peeling of the electrode catalyst layer when the membrane-electrode catalyst layer assembly is produced. Is done. There is also a secondary effect of preventing ignition when the catalyst is brought into contact with a hydrophilic organic solvent.

The water used in the present invention is not particularly limited as long as the ions that interfere with the ionic conduction of the solid polymer electrolyte are removed, and are not limited. Ion exchange water (IEW), ultrapure water, distilled water, deionized water, and the like. A single solution or a mixed solution such as ionic water (DIW) can be used. When ions are included as impurities, there is a possibility of affecting fuel cell characteristics or water electrolysis cell characteristics. Therefore, water (such as well water) having an electric conductivity of 0.1 S / m or more can be used. Can not. Therefore, in the present invention, water having an electric conductivity of less than 0.1 S / m is used.

The water contained in the paste is used in the range of 8 to 20% by mass in the paste, preferably 8 to 18% by mass, more preferably 11 to 18% by mass, particularly preferably. Is 12 to 18% by mass. The By keeping the amount of water in this range, cracking and peeling can be prevented.

The mechanism is not clear, but is estimated as follows. After the paste is applied to the solid polymer electrolyte membrane, the organic solvent is dried. However, since water remains in the solid polymer electrolyte in the paste, rapid shrinkage does not occur. Therefore, the solid polymer electrolyte membrane and the solid polymer electrolyte in the paste are dried over time while dispersing the stress. Therefore, there is no great difference between the shrinkage rates of the two, and cracking and peeling can be prevented.

When there is a lot of water, since the solid polymer electrolyte starts to be deposited with the drying of the organic solvent, a uniform electrode catalyst layer cannot be formed. Moreover, when there is little water, since said prevention effect is not expressed, it is unpreferable.

(Hydrophilic organic solvent)
The hydrophilic organic solvent used in the electrode catalyst layer forming paste of the present invention is an organic solvent that dissolves in water at an arbitrary ratio at the temperature at which the electrode catalyst layer is formed, and is a known fuel cell or solid polymer. What is used by the paste for electrode catalyst layer formation of a type | mold water electrolysis cell can be used without a restriction | limiting. Since it is a hydrophilic organic solvent, the surface of the electrode catalyst layer becomes hydrophilic after the electrode catalyst layer is formed, and the water generated or supplied during the operation of the fuel cell or the polymer electrolyte water electrolysis cell can move smoothly. In addition, the hydrophilic organic solvent preferably has a boiling point lower than that of water because the drying speed is sufficiently high and there is no possibility of causing problems such as the paste after printing flowing out. As a preferred hydrophilic organic solvent, for example, tetrahydrofuran, methanol, ethanol, 1-propanol, acetone and the like can be used alone or in combination. Of these, tetrahydrofuran and 1-propanol are preferably used because of their high solubility and rapid drying.

The content of the hydrophilic organic solvent in the paste has a suitable range for keeping the solid polymer electrolyte in a stable dissolved state, and is in the range of 60 to 82% by mass in the paste, preferably 62. Is 80 to 80% by mass, more preferably 65 to 75% by mass, and particularly preferably 68 to 73% by mass. If the content is small, the solid polymer electrolyte cannot be dissolved. Moreover, when there is much content, since the quantity of water becomes relatively small, a crack and peeling arise. Therefore, the amount of the hydrophilic organic solvent needs to be in a favorable range together with the water content.

If the preferred range is indicated by mass% of water and hydrophilic organic solvent, the paste contains 8 to 20 mass% of water, 60 to 82 mass% of hydrophilic organic solvent, and the total of water and hydrophilic organic solvent. The amount is 78 to 90% by mass. If a preferable range is shown, 8 to 18% by mass of water, 62 to 80% by mass of the hydrophilic organic solvent, and 70 to 88% by mass of the total content of water and the hydrophilic organic solvent in the paste. More preferably, the paste contains 11 to 18% by mass of water, 65 to 75% by mass of the hydrophilic organic solvent, and 76 to 93% by mass of the total amount of water and the hydrophilic organic solvent. A particularly preferable range is 12 to 18% by mass of water, 68 to 73% by mass of the hydrophilic organic solvent, and 80 to 91% by mass of the total content of water and the hydrophilic organic solvent in the paste.

(Solid polymer electrolyte)
The solid polymer electrolyte of the present invention is a solid substance that conducts ions from the catalyst surface to the solid polymer electrolyte membrane in the electrode catalyst layers of the fuel chamber side gas diffusion electrode layer and the oxidant chamber side gas diffusion electrode layer. is there.

As the solid polymer electrolyte, any known polymer can be used as long as it exhibits ionic conductivity of protons or hydroxide ions. However, cation exchange resins and anion exchange resins give good performance. Therefore, it is preferably used.

(Cation exchange resin)
The cation exchange resin is a resin having a cation exchange group and is not particularly limited as long as protons can be conducted in the resin. Examples of the cation exchange group include a sulfonic acid group, a carboxylic acid group, and a phosphonic acid group. Of these, a sulfonic acid group that is a strongly acidic group excellent in proton conductivity is particularly desirable.

The content of the cation exchange group is such that the cation exchange capacity is 0.1 to 5.0 mmol / g, preferably 0.5 to 3.0 mmol, from the viewpoint of imparting good ion conductivity to the electrode catalyst layer. / G is preferred. In the case where the proton conductive resin is non-crosslinkable, it is 0.5 to 1.5 mmol / g because it becomes soluble in water and may be deformed if the cation exchange capacity is high. Is preferred.

As the cation exchange resin, a known cation exchange resin can be used without limitation. Typical examples include hydrocarbon cation exchange resins and fluorine cation exchange resins. As an example of the hydrocarbon-based cation exchange resin, a cation-exchange group is introduced into the following hydrocarbon-based resin. That is, examples of hydrocarbon resins include styrene resins such as polystyrene and poly-α-methylstyrene, polyether ether ketone, polysulfone, polyether sulfone, polybenzimidazole, polyoxazole, polyphenylene oxide, and polysulfide engineering plastics. Examples include styrene resins.

In addition, fluorine-based cation exchange resins include perfluorinated cation exchange resins in which all hydrogen atoms in the polymer are replaced with fluorine atoms and partially fluorinated cations in which hydrogen atoms are partially replaced with fluorine atoms. There is an exchange resin. Examples of commercially available fluorine-based cation exchange resins include Nafion (manufactured by DuPont) whose cation exchange group is sulfonic acid, Flemion (manufactured by Asahi Glass Co., Ltd.), and Aciplex (manufactured by Asahi Kasei Chemicals).

In recent years, hydrocarbon cation exchange resins having no fluorine atoms have been developed and used in place of fluorine cation exchange resins. The hydrocarbon-based cation exchange resin can be produced at low cost because the raw materials are inexpensive, and it does not adversely affect the environment by generating fluorine ions during decomposition, which is a disadvantage of the fluorine-based cation exchange resin. Has merit.

(Anion exchange resin)
The anion exchange resin is a resin having an anion exchange group and is not particularly limited as long as it conducts hydroxide ions. An example that can be preferably used is disclosed in Japanese Patent Application Laid-Open No. 2002-367626. For example, there are hydrocarbon-based or fluorine-based anion exchange resins. Examples of hydrocarbon resins include styrene resins and acrylic resins, and examples of fluorine resins include perfluorocarbon resins.

Examples of the anion exchange group include a primary to tertiary amino group, a quaternary ammonium group, a pyridyl group, an imidazole group, a phosphonium group, and a quaternary pyridinium group. Ammonium groups and quaternary pyridinium groups are preferred.

If the range of the anion exchange capacity of the anion exchange resin is suitably used, it is 0.3 to 10 mmol / g, preferably 1.0 to 5.0 mmol / g, and 1.2 to 4. Particularly preferred is 0 mmol / g.

The counter ion of the anion exchange group of the anion exchange resin is any one of OH ⁻ , HCO ₃ ⁻ , CO ₃ ²⁻ , or a mixed system thereof. Since it can raise, it is suitable. HCO ₃ ⁻ and CO ₃ ²⁻ are most preferable as the counter ion from the viewpoint of enhancing the safety of the operation for converting the counter ion to the ionic form and the chemical stability of the obtained anion exchange resin.

As the anion exchange resin, those having a moisture content of 1 to 90% at a temperature of 40 ° C. and a humidity of 90% RH are generally used from the viewpoint of exhibiting excellent durability and bonding properties.

As the anion exchange resin used for the electrode catalyst layer forming paste of the present invention, those used in known fuel cells or water electrolysis cells can be used without any limitation. In general, hydrocarbon-based anion exchange resins are preferably used because of their availability and low manufacturing costs.

The content of the solid polymer electrolyte in the paste is generally used in the range of 1 to 20% by mass in order to prevent the reaction of the catalyst surface from being hindered by the coating and to keep the ionic conduction good. The preferable range is 2 to 10% by mass, and the more preferable range is 3 to 5% by mass.

(Other ingredients)
In addition to the above-described components, the electrode catalyst layer forming paste includes a non-hydrophilic organic solvent for increasing the solubility of the solid polymer electrolyte of the present invention and facilitating preparation of the paste. Carbon powder or the like on which a catalyst is not supported may be included in order to increase the electron conductivity when formed. Non-hydrophilic organic solvents include chloroform, dichloromethane, toluene, benzene, ethyl acetate and the like. In general, a non-hydrophilic organic solvent alone often does not dissolve a solid polymer electrolyte, but its solubility may be increased by mixing with a hydrophilic organic solvent. When a non-hydrophilic organic solvent is used, the non-hydrophilic organic solvent and the hydrophilic solvent can be mixed in advance, and then mixed and dissolved with the solid polymer electrolyte. These other components may be contained in a proportion of less than 10% by mass with respect to the total amount of the electrode catalyst layer forming paste.

(Method for producing electrode catalyst layer forming paste)
The manufacturing method of the electrode catalyst layer forming paste is not particularly limited, and a known method can be used. Examples are as follows.

Add water to the catalyst-supported carbon powder supporting the catalyst and knead. This is mixed with a hydrophilic organic solvent in which a solid polymer electrolyte is dissolved in advance, and is dispersed using an ultrasonic irradiator or the like in order to sufficiently disperse the contents. When the catalyst-carrying carbon powder carrying the catalyst is directly mixed with the hydrophilic organic solvent, an oxidation reaction of the hydrophilic organic solvent occurs suddenly and there is a risk of heat generation and ignition. Therefore, it is desirable that the catalyst-carrying carbon powder carrying the catalyst is first mixed with water. Alternatively, the catalyst-supported carbon powder can be previously placed in an inert gas stream such as nitrogen to make the catalyst surface an inert gas atmosphere, and then directly mixed with the hydrophilic organic solvent in the inert gas.

The paste for forming an electrode catalyst layer of the present invention contains 8 to 20% by mass of water and 60 to 82% by mass of a hydrophilic organic solvent, and the total content of water and the hydrophilic organic solvent is 78 to 90% by mass. It is characterized by being. By having water and a hydrophilic organic solvent in these contents, the catalyst electrode layer can be formed without the solid polymer electrolyte contracting rapidly. Therefore, it is possible to form an electrode catalyst layer that does not crack or peel off. In addition, since the total content of water and the hydrophilic organic solvent is within this range, the electrode catalyst layer forming paste has an appropriate viscosity. And unevenness can be prevented.

The electrode catalyst layer forming paste according to the present invention is prepared by adding a required amount of water as a paste to a catalyst-supporting carbon powder supporting a catalyst, kneading the mixture, and previously mixing the solid polymer in a required amount of a hydrophilic organic solvent as a paste. What is necessary is just to mix and manufacture with the hydrophilic organic solvent which melt | dissolved electrolyte. However, normally, solid polymer electrolytes are not so high in solubility and are often dissolved in more than the required amount of hydrophilic organic solvent. Therefore, water is added to the catalyst-supporting carbon powder and kneaded, and this is mixed with a hydrophilic organic solvent in which the solid polymer electrolyte is dissolved in advance, and then the excess hydrophilic organic solvent is removed. In that case, since water may also decrease with a hydrophilic organic solvent, it is necessary to adjust content of water and a hydrophilic organic solvent.

As a method for adjusting the content of water and the hydrophilic organic solvent in the paste, a known method can be used without any particular limitation. An example of its preferred use is as follows.

When the water content is increased, the paste can be put in a mortar and kneaded while dropping water. In order to reduce the water content, the paste can be placed in a mortar or the like and heated while kneading. It is desirable that the heating temperature does not exceed the boiling point of the hydrophilic organic solvent, and is generally about 40 ° C. In addition, since the content of the hydrophilic organic solvent is reduced by this operation, it is desirable to drop the hydrophilic organic solvent appropriately.

In the case of increasing the content of the hydrophilic organic solvent, it can be similarly carried out by kneading while dropping the hydrophilic organic solvent. Moreover, when reducing content of a hydrophilic organic solvent, it can knead | mix in a mortar etc. at room temperature, or it can carry out by the pressure reduction process.

The content of water and hydrophilic organic solvent in the paste can be measured by a known method such as gas chromatography or 1H NMR measurement.

(Method for forming electrode catalyst layer and membrane-electrode assembly)
In the present invention, the electrode catalyst layer is formed by applying an electrode catalyst layer forming paste to the substrate. Although it does not restrict | limit especially as a base material, For example, the gas diffusion layer which consists of a solid polymer electrolyte membrane or porous carbon paper etc. is mentioned.

The solid polymer electrolyte membrane used as a base material in the present invention is formed in the electrode catalyst layer of the fuel chamber side gas diffusion electrode layer and the oxidant chamber side gas diffusion electrode layer of the solid polymer fuel cell or the solid polymer water electrolysis cell. It is used to conduct protons or hydroxide ions that are produced or consumed in the reaction. It also has the function of separating fuel, water and gas in both chambers.

As such a solid polymer electrolyte membrane, those generally known can be used as long as they exhibit ionic conductivity of protons or hydroxide ions, but cation exchange resins and anion exchange resins are used. It is preferably used to give good performance. As the cation exchange resin and the anion exchange resin, the solid polymer electrolyte of the present invention can be used, and those formed into a film shape are used. As a method of forming these ion exchange resins into a film, known ones can be used without limitation, but examples include the following. Heat is applied to the solid polymer electrolyte to develop flexibility, and pressure is applied to flatten it to form a membrane. After the solid polymer electrolyte is made into a solution, it is cast on a flat surface to volatilize the solvent. A film-like material, impregnating a porous membrane-like substrate with a monomer that is a raw material of a solid polymer electrolyte, and then polymerizing it by heating or the like to obtain a membrane-like material Method, etc. Cation exchange resins and anion exchange resins are often classified into two types, those composed of hydrocarbon polymers and those composed of fluorine polymers. When the cost is important, cation exchange resin and anion exchange resin made of hydrocarbon polymer, and when durability is important, cation exchange resin made of fluorine polymer, An anion exchange resin is applied as a constituent material of the solid polymer electrolyte membrane. Moreover, since the adhesiveness of a solid polymer electrolyte membrane and an electrode catalyst layer becomes favorable, both are selected so that it may become the same material. That is, when the solid polymer electrolyte membrane is composed of a hydrocarbon polymer, a hydrocarbon polymer is used as the solid polymer electrolyte used in the electrode catalyst layer forming paste.

A membrane-electrode catalyst layer assembly is produced by applying an electrode catalyst layer forming paste to the solid polymer electrolyte membrane by screen printing, spraying or the like to form an electrode catalyst layer. A membrane-electrode assembly can be produced by bonding a gas diffusion layer to the electrode catalyst layer of the membrane-electrode catalyst layer assembly.

A gas diffusion layer-electrode catalyst layer assembly (Gas Diffusion Electrode, GDE) in which an electrode catalyst layer is formed by applying screen printing, spray coating, or the like to a gas diffusion layer. As the gas diffusion layer, porous carbon paper or porous carbon cloth is generally used. A membrane-electrode assembly is produced by bonding the gas diffusion layer-electrode catalyst layer assembly to both surfaces of the ion exchange membrane.

The thickness of the electrode catalyst layer is not particularly limited, and may be appropriately determined according to the intended use. In general, the thickness is preferably 0.1 to 500 μm, and more preferably 0.5 to 100 μm.

As the above-mentioned joining method, there are known methods such as a method of simply superimposing both and applying a pressure of several MPa or less for several minutes, and a method of applying a pressure of several MPa or less for several minutes at a temperature of about 50 to 200 ° C. The method can be used.

The method for producing the membrane-electrode catalyst layer assembly and the gas diffusion layer-electrode catalyst layer assembly is not particularly limited, and a known method can be used. An example of commonly used screen printing is as follows.

The electrode catalyst layer forming paste prepared by placing a mask with a hole with an arbitrary area and shape on a solid polymer electrolyte membrane (such as an ion exchange membrane) or a gas diffusion layer (such as porous carbon paper) Screen printing with a doctor blade.

By using the electrode catalyst layer forming paste of the present invention, the temperature and humidity during printing are not particularly adjusted, and the general room temperature and humidity, that is, 5 ° C. to 30 ° C., 20% RH to 70% RH. Screen printing, application by spraying, etc. can be performed under the environment. Drying is performed by standing in the atmosphere at room temperature, and air blowing, temperature adjustment, etc. are not performed.

Thus, by using the electrode catalyst layer forming paste of the present invention, a uniform and good electrode catalyst layer free from cracking and peeling can be formed without controlling temperature, humidity, drying speed, etc. in the atmosphere. Can do.

(Solid polymer fuel cell)
A solid polymer membrane-electrode assembly is produced using the membrane-electrode catalyst layer assembly or the gas diffusion layer-electrode catalyst layer assembly. If this is used, for example, a polymer electrolyte fuel cell can be assembled with the configuration shown in FIG.

That is, when the gas diffusion layer-electrode catalyst layer assembly is formed, two of them are used to sandwich the ion exchange membrane with the surface on which the electrode catalyst layer is formed facing the ion exchange membrane. As a result, a state in which 4, 5, and 6 in FIG. 1 are combined can be realized. Alternatively, if a membrane-electrode catalyst layer assembly is formed, use it as it is or by stacking a gas diffusion layer (carbon paper, etc.) on top to improve gas diffusibility. Can do.

In the following, the configuration of FIG. 1 is taken as an example, and the case of hydrogen fuel is taken as an example. Electric power can be generated by supplying humidified hydrogen gas to the fuel chamber side and humidified oxygen gas or air to the oxidant chamber side. Since there is an optimum value for the flow rate of each gas, it is possible to measure the voltage value or the current value when a certain load is applied, and set them so that they become the largest. The humidification of the gas is performed to prevent the ion exchange membrane and the electrode catalyst layer from being dried and the ionic conductivity from being lowered, and this can also be optimized in the same manner. The higher the reaction temperature in the fuel cell, the higher the output can be obtained, but the higher the temperature, the more the deterioration of the ion exchange membrane and the electrode catalyst layer is promoted.

(Solid polymer water electrolysis cell)
The polymer electrolyte water electrolysis cell can also be produced with the same configuration as the polymer electrolyte fuel cell. When an anion exchange membrane is used as the solid polymer electrolyte membrane, water is supplied to the fuel chamber side, and the oxidant side gas diffusion is provided between the fuel chamber side gas diffusion electrode layer and the oxidant side gas diffusion electrode layer. By applying a voltage so that the electrode layer has a high potential, hydrogen can be obtained from the fuel chamber side gas diffusion electrode layer and oxygen can be obtained from the oxidant chamber side gas diffusion electrode layer.

Hereinafter, the present invention will be described in detail using examples, but the present invention is not limited to these examples.

Example 1 (Effect of electrode catalyst layer size and drying rate)
The electrode catalyst layer forming paste was prepared and applied on both sides of the anion exchange membrane using a screen printing method. The produced membrane-electrode catalyst layer assembly was visually confirmed, and the presence or absence of cracks and peeling of the electrode catalyst layer was confirmed.

After weighing 0.5 g of platinum-supported catalyst-supported carbon powder (with high specific surface area carbon particles having a primary particle size of 30 to 50 nm and 50% by mass of platinum particles having a particle size of 2 to 10 nm) in an agate mortar, The amount of ion exchange water shown in Table 1 was dropped and kneaded. 8.2 g of a 3% by mass solid polymer electrolyte solution was weighed into a sample bottle, and the kneaded sample was added to the sample bottle. As the solid polymer electrolyte, an anion exchange resin obtained by chloromethylating a styrene unit of a styrene-ethylenebutylene-styrene triblock copolymer and then quaternizing with trimethylamine was used. The solvent of the solid polymer electrolyte solution is 1-propanol, which is the hydrophilic organic solvent of the present invention. Thereafter, dispersion by ultrasonic irradiation was performed for 30 minutes, and further, stirring was performed for about 12 hours using a stirrer. After stirring, the paste was poured into an agate mortar to volatilize the hydrophilic organic solvent. The paste was kneaded for several minutes to volatilize the hydrophilic organic solvent, thereby adjusting the content thereof to produce an electrode catalyst layer forming paste. The content was adjusted while confirming by measuring the weight of the agate mortar containing the paste about every 1 minute and determining the content of the hydrophilic organic solvent from the change in weight. Table 1 shows water and 1% by weight of 1-propanol which is a hydrophilic organic solvent in the paste. The water content was 8% by mass, the hydrophilic organic solvent content was 82% by mass, and the total content of water and the hydrophilic organic solvent was 90% by mass. The contents of water and the hydrophilic organic solvent were measured by a gas chromatograph using a heat conduction detector (TCD) as a detector.

The electrode catalyst layer forming paste was prepared by using a stainless steel mask having a hole (23 mm × 23 mm) with a size shown in Table 1 and a doctor blade, and an anion exchange membrane (A201 made by Tokuyama Corporation: hydrocarbon, anion Screen-printed on an exchange capacity of 1.8 mmol / g, a moisture content of 33% by mass at 25 ° C., and a dry film thickness of 28 μm. Then, it was made to dry on the conditions (25 degreeC, 0.5 hour) shown in Table 1. The drying speed is a value obtained by measuring a change in weight before and after drying. Further, after standing and drying at room temperature for about 12 hours, the back surface was similarly coated and dried to obtain a membrane-electrode catalyst layer assembly. The surface of the obtained membrane / electrode assembly was visually observed, and the results are shown in Table 1. The notation is as follows.

S: A membrane / electrode assembly having extremely high surface smoothness without cracking and peeling was obtained.
A: Although neither crack nor peeling was seen, the surface was slightly uneven.
B: Either cracking or peeling was observed.
C: Both cracking and peeling were recognized.

An image showing the state of the catalyst electrode layer obtained in Example 1 is shown in FIG.

Examples 2 to 10 (Effect of electrode catalyst layer size and drying rate)
An electrode catalyst layer was prepared in the same manner as in Example 1 except that the conditions shown in Table 1 were used, and a membrane-electrode catalyst layer assembly was obtained.

In any printing area, drying condition, and content of water and hydrophilic organic solvent (1-propanol), the electrode catalyst layer is cracked by using the electrode catalyst layer forming paste and the production method of the present invention. Neither peeling occurred.

Examples 11 to 15 (Influence of the kind of hydrophilic organic solvent)
A membrane-electrode catalyst layer assembly was prepared by preparing an electrode catalyst layer in the same manner as in Example 1, except that the hydrophilic organic solvent shown in Table 2 was used and the conditions were changed as shown in Table 2. Got. The thickness of the mask was 100 μm.

Examples 16 to 19 (Influence of concentration of solid polymer electrolyte solution)
The same operation as in Example 1 was performed except that the thickness of the mask was 100 μm and the concentration and conditions of the solid polymer electrolyte solution were changed to the values shown in Table 3.

From the results of Examples 1 to 19, it was shown that an electrode catalyst layer free from peeling or cracking can be produced by using the electrode catalyst layer forming pace of the present invention regardless of the concentration of the solid polymer electrolyte.

Comparative Examples 1-7
The same operation as in Example 1 was performed using the conditions shown in Table 4. When the mass% of water, the mass% of 1-propanol, or the sum of the mass% of water and 1-propanol deviated from the range of the present invention, the generation of cracks and the occurrence of peeling were observed.

FIG. 3 shows an image showing the state of the electrode catalyst layer produced in Comparative Example 4.

From the results of Examples 1 to 19 and Comparative Examples 1 to 7, it was shown that the electrode catalyst layer forming paste and the production method of the present invention can produce a good catalyst electrode layer without cracking and peeling.

1: Battery partition wall 2: Fuel gas flow hole 3: Oxidant gas flow hole 4: Fuel chamber side gas diffusion electrode layer 5: Oxidant chamber side gas diffusion electrode layer 6: Solid polymer electrolyte membrane (anion exchange membrane)
7: Fuel chamber 8: Oxidant chamber

Claims

An electrode catalyst layer forming paste comprising a catalyst-carrying carbon powder carrying a catalyst, water, a hydrophilic organic solvent, and a solid polymer electrolyte, comprising 8 to 20% by mass of water, 60 to 82% by mass of a hydrophilic organic solvent, water An electrode catalyst layer forming paste, the total content of which is 78 to 90% by mass of the organic solvent and the hydrophilic organic solvent.
The electrode catalyst layer forming paste according to claim 1, wherein the solid polymer electrolyte is a hydrocarbon-based material.
The electrode catalyst layer forming paste according to claim 2, wherein the solid polymer electrolyte is a hydrocarbon-based anion exchange resin.
4. The electrode catalyst layer forming paste according to claim 1, which is used for an electrode catalyst layer of a polymer electrolyte fuel cell.
4. The electrode catalyst layer forming paste according to claim 1, which is used for an electrode catalyst layer of a solid polymer type water electrolysis cell.
Production of a membrane-electrode catalyst layer assembly, wherein the electrode-catalyst layer formation paste according to any one of claims 1 to 3 is applied onto a solid polymer electrolyte membrane to form a membrane-electrode catalyst layer assembly. Method.
The method for producing a membrane-electrode catalyst layer assembly according to claim 6, wherein the solid polymer electrolyte membrane is hydrocarbon-based.
The method for producing a membrane-electrode catalyst layer assembly according to claim 7, wherein the solid polymer electrolyte membrane is a hydrocarbon-based anion exchange resin.
A membrane-electrode catalyst layer assembly is produced by the method for producing a membrane-electrode catalyst layer assembly according to any one of claims 6 to 8, and then a polymer electrolyte fuel is produced using the membrane-electrode catalyst layer assembly. A method for producing a polymer electrolyte fuel cell for producing a battery.
A membrane-electrode catalyst layer assembly is produced by the method for producing a membrane-electrode catalyst layer assembly according to any one of claims 6 to 8, and then a solid polymer type water is produced using the membrane-electrode catalyst layer assembly. A method for producing a polymer electrolyte water electrolysis cell, which produces an electrolysis cell.
A method for producing a gas diffusion electrode, wherein the gas diffusion electrode is formed by applying the electrode catalyst layer forming paste according to any one of claims 1 to 3 on the gas diffusion layer.
A method for producing a solid polymer fuel cell, comprising producing a gas diffusion electrode by the gas diffusion electrode production method according to claim 11 and then producing a solid polymer fuel cell using the gas diffusion electrode.
A method for producing a solid polymer type water electrolysis cell, comprising producing a gas diffusion electrode by the method for producing a gas diffusion electrode according to claim 11 and then producing a solid polymer type water electrolysis cell using the gas diffusion electrode.
A method for producing an electrode catalyst layer forming paste according to any one of claims 1 to 3,
(I) Step of dispersing catalyst-supported carbon powder supporting catalyst in water (II) Step of dissolving solid polymer electrolyte in hydrophilic organic solvent (III) Water in which catalyst-supported carbon powder is dispersed and solid polymer electrolyte Step (IV) of mixing water and hydrophilic organic solvent in which water is dissolved The content of water and hydrophilic organic solvent is 8 to 20% by mass of water, 60 to 82% by mass of hydrophilic organic solvent, water and hydrophilic organic solvent A process for producing an electrode catalyst layer forming paste, comprising a step of adjusting the total content of to 78 to 90% by mass.