JP2008186767A - Catalyst ink, catalyst electrode and method for producing the same, adhesive, membrane electrode assembly (MEA) and method for producing the same - Google Patents

Abstract

The present invention provides a catalyst electrode with high air permeability and an MEA having a high effective utilization rate of a noble metal catalyst using the catalyst electrode.
As a material for a catalyst layer of a catalyst electrode, a catalyst-supporting conductive particle, a proton conductive substance, and a polyion complex composed of a polymer having an acidic group and a polymer having a basic group are insoluble in water. Use a catalyst ink dissolved in an organic solvent.
As a method for producing a catalyst electrode, a first step for forming a catalyst ink layer by applying a catalyst ink;
A second step for arranging micro water droplets in the catalyst ink layer by bringing high-humidity air into contact with the catalyst ink layer;
A method for producing a catalyst electrode having a third step for forming a catalyst layer by drying and removing the fine water droplets is used.
[Selection] Figure 1

Description

The present invention relates to a catalyst electrode that is used in a fuel cell and has high utilization efficiency of a platinum catalyst, an MEA that is excellent in output characteristics using the same, a catalyst ink that is used to produce a catalyst electrode, and an adhesive that is used to produce MEA It is about.

In the present specification, “MEA” is an abbreviation for “membrane electrode assembly”, and “PEFC” is an abbreviation for “solid polymer fuel cell”.

Fuel cells that use hydrogen and oxygen (which are not potentially depleted) are depleted of resources (crude oil availability; approximately 30 years, natural gas availability; approximately 40 years, uranium availability; approximately 45 It is attracting attention as a power generation system that does not require the use of fossil fuels that are feared.

Fuel cells are roughly classified into PAFC (phosphoric acid type), PEFC (solid polymer type), SOFC (solid oxide type), and MCFC (molten carbonate type) depending on the type of electrolyte used.

Among the above fuel cells, unlike other fuel cells, PEFC has low operating temperature, high output density, and easy miniaturization, so it is expected to be used for in-vehicle power supplies and household stationary power supplies. Has been.

The PEFC is configured by stacking a large number of single cells.
As shown in FIG. 5, the single cell is configured by laminating an anode side separator 10, an anode side catalyst electrode 20, a solid polymer electrolyte membrane 30, a cathode side catalyst electrode 40, and a cathode side separator 50 in this order. .

The anode separator 10 is provided with a fuel gas passage 10a, which supplies hydrogen to the MEA.
The cathode side separator 50 is provided with an oxidant gas flow path 50a to supply oxygen to the MEA.

The anode side catalyst electrode 20 includes an anode side electrode base material 21 and an anode side catalyst layer 22 laminated on the surface thereof, and the cathode side catalyst electrode 40 is laminated on the surface of the cathode side electrode base material 41. And the cathode side catalyst layer 42.

The anode side electrode base material 21 and the cathode side electrode base material 41 are both made of a material having gas diffusibility and conductivity, and for example, carbon paper or carbon cloth is used.

In each of the anode side catalyst layer 22 and the cathode side catalyst layer 42, particles obtained by supporting catalyst particles on conductive particles are applied to the anode side electrode base material 21 and the cathode side electrode base material 41 using a proton conductive material. It is configured by fixing.

As the catalyst particles, precious metals such as platinum ruthenium, platinum iron, platinum, palladium, ruthenium, rhodium, cobalt and molybdenum are widely used.

As a power generation method of PEFC, hydrogen (included in the fuel gas) and oxygen (included in the oxidant gas) are passed through the solid polymer electrolyte membrane 30 (on the anode side catalyst layer 22 or the cathode side catalyst layer 42). A method of causing an electrochemical reaction of the following formulas (a) and (b) on the surface of the catalyst particles (included) is used.

Anode; H ₂ → 2H ⁺ + 2e ⁻ (A)
Cathode; 4H ⁺ + 4e ⁻ + O ₂ → 2H ₂ O (A)

A method for producing the anode side catalyst electrode 20 and the cathode side catalyst electrode 40 includes a step of placing a particle comprising noble metal catalyst particles supported on the surface of a conductive particle, a paste made of a proton conductive substance and a solvent on a conductive porous body. There has been proposed a method in which a film is formed and then heated and dried. (For example, see Non-Patent Document 1)

However, in the MEA using the catalyst electrode produced by such a manufacturing method, the effective utilization rate of the noble metal catalyst (the value obtained by dividing the electrochemical hydrogen adsorption amount on the surface of the noble metal catalyst by the surface area of the noble metal catalyst) is 10 When all the current automobiles are replaced from gasoline cars to fuel cell cars with the precious metal catalyst effective utilization rate, the amount of noble metals required exceeds the precious metal reserves on the entire earth.

The reason why the effective utilization rate of the noble metal catalyst is low is considered to be that the gas permeability of the reaction gas (oxidant gas and fuel gas) in the catalyst layer is poor, so that the reaction gas is difficult to be supplied to the surface of the noble metal catalyst. .

As a method for improving the gas permeability of the reaction gas (oxidant gas and fuel gas) in the catalyst layer, a powder such as a metal or its oxide is previously mixed in the catalyst layer as a pore forming agent to form a catalyst electrode. A method for producing an electrode having pores inside a catalyst layer by being immersed in an acidic solution has been proposed. (For example, see Patent Document 1)

In addition, when forming a catalyst layer on a solid polymer electrolyte membrane, both catalyst salt and polymer particles are adsorbed by a chemical plating method, and then the polymer particles are removed with an acidic solution to form a porous catalyst. A method of forming a layer has been proposed. (For example, see Patent Document 2)

In addition, a conductive polymer carrying a noble metal catalyst, a proton conductive material, and an alcohol solvent are mixed with a sublimable pore-forming agent such as camphor to form an ink, and this ink is converted into a solid polymer by screen printing. A method of forming a catalyst layer having a plurality of pores by sublimating camphor after forming a catalyst layer by coating on an electrolyte membrane has been proposed. (For example, see Patent Document 3)

Edson A. Ticianelli, J .; Electroanal. Chem. 251, 275 (1988) JP-A-6-36771 JP-A-8-138715 JP-A-9-199138

However, when using a method in which a powder of a metal or its oxide is previously mixed in the catalyst layer as a pore-forming agent, radicals may be generated due to residual metal or metal ions in the catalyst layer. It has a problem of inducing deterioration of the polymer electrolyte membrane and the catalyst layer.

In addition, when a method of adsorbing both catalyst salt and polymer particles by chemical plating is used, it takes a long time to remove the polymer particles by pickling, and thus has a problem of poor productivity. Yes.

In addition, when using a method in which a conductive particle carrying a noble metal catalyst, a proton conductive material, and an alcohol solvent are mixed with a sublimable pore-forming agent such as camphor to form an ink, the solvent residue or There is a problem that parts, piping, and the like constituting the fuel cell are deteriorated due to the altered residue.

An object of the present invention is to provide a catalyst electrode having high air permeability and an MEA having a high effective utilization rate of a noble metal catalyst using the catalyst electrode.

The invention according to claim 1 is a solution in which a catalyst-carrying conductive particle, a proton conductive material, and a polyion complex comprising a polymer having an acidic group and a polymer having a basic group are dissolved in a water-insoluble organic solvent. A catalyst ink.

The catalyst portion of the catalyst-carrying conductive particles has a role of causing the reaction of the above formulas (a) and (b).
In addition, the conductive particle portion of the catalyst-carrying conductive particles has a role as a transmission path for electrons generated on the catalyst particle surface and electrons used on the catalyst particle surface.

The proton conductive material has a role as a transmission path of protons generated on the surface of the catalyst particles and protons used on the surface of the catalyst particles.

The polyion complex is a substance having an interfacial activity that forms a stable monomolecular film at the gas-liquid interface, and has a role of preventing the water droplets formed on the liquid film of the catalyst ink layer from aggregating.

The water-insoluble organic solvent has a role of forming minute water droplet particles in the liquid film of the catalyst ink layer.

The invention according to claim 2 is the catalyst ink according to claim 1, wherein the proton conductive material has a structure represented by the following formula (1).
(In formula 1, d represents an integer, e represents an integer of 1 to 5, a represents an integer of 5 to 150, and b represents an integer of 0 to 1100.)
It is.

The proton conductive material having this structure is a material having high proton conductivity, excellent chemical resistance, heat resistance, electrochemical stability, and mechanical stability.

Invention of Claim 3 has the structure where the polymer which has the said acidic group is represented by following formula (2) or following formula (3),
The catalyst ink according to claim 1 or 2, wherein the polymer having a basic group has a structure represented by the following formula (4).
(In Formula 2, R represents —SO ₃ —, and f represents an integer.)
(In formula 4, g represents an integer of 12 or more.)
It is.

A polyion complex having such a polymer structure having an acidic group has a high degree of crosslinking.

A polyion complex having such a polymer structure having a basic group has high surface activity and solubility.

The invention according to claim 4 is a first step for forming a catalyst ink layer by applying the catalyst ink according to any one of claims 1 to 3 on the electrode substrate;
A second step for arranging micro water droplets in the catalyst ink layer by bringing high-humidity air into contact with the catalyst ink layer;
A method for producing a catalyst electrode, comprising: a third step for forming a catalyst layer by drying and removing the fine water droplets.

When a catalyst ink layer is formed by applying a catalyst ink on an electrode substrate and high-humidity air is applied to the catalyst ink layer, water molecules in the high-humidity air are caused by latent heat when the solvent in the catalyst ink layer evaporates. Condensates and a large number of minute water droplets are deposited on the catalyst ink layer.

The minute water droplets start to move due to convection generated in the catalyst ink layer by the latent heat and capillary action on the surface of the catalyst ink layer.

Since the size of the minute water droplets is substantially uniform, as the solvent in the catalyst ink layer volatilizes, the minute water droplets are regularly arranged on the surface of the catalyst ink layer and fixed on the surface of the catalyst ink layer by a polyion complex.

By evaporating the fine water droplets regularly arranged on the surface of the catalyst ink layer, air holes (evaporation traces of the fine water droplets) are formed.

The invention according to claim 5 is a catalyst electrode formed by using the method for producing a catalyst electrode according to claim 4.

The catalyst electrode produced in this way has better air permeability than conventional catalyst electrodes.

The invention according to claim 6 is an adhesive for joining the catalyst layer of the catalyst electrode and the solid polymer electrolyte membrane,
An adhesive having a structure represented by the following formula (5):
(In formula 5, k represents an integer of 3 to 8, i represents an integer of 5 to 150, and j represents an integer of 0 to 1100.)
It is.

The adhesive having such a structure includes a proton conductive material having a structure represented by the formula (1), which is a main component of the catalyst layer, and a solid polymer electrolyte membrane (for example, DuPont) that is widely used. Adhesiveness with Nafion (registered trademark) manufactured by Asahi Kasei Corporation, Aciplex (registered trademark) manufactured by Asahi Kasei Co., Ltd., Flemion (registered trademark) manufactured by Asahi Glass Co., Ltd., and Gore (registered trademark) manufactured by Japan Goattex Co., Ltd.) is good.

The invention according to claim 7 is a coating process for forming an adhesive layer by coating the adhesive on a solid polymer electrolyte membrane;
It is a manufacturing method of a membrane electrode assembly (MEA) which has a crimping | compression-bonding process which crimps | bonds the said contact bonding layer with the catalyst layer of the catalyst electrode of Claim 5.

When the adhesive is coated not on the catalyst layer of the catalyst electrode but on the solid polymer electrolyte membrane, the air holes formed in the catalyst layer are not buried with the adhesive.

When the catalyst layer of the catalyst electrode and the solid polymer electrolyte membrane are pressure-bonded rather than thermally bonded, the air holes formed in the catalyst layer are not buried by the hot melt of the catalyst layer and the solid polymer electrolyte membrane during MEA production.

The invention according to claim 8 is a membrane electrode assembly (MEA) formed by using the method for producing a membrane electrode assembly (MEA) according to claim 7.

The adhesive serves to bond the catalyst layer of the catalyst electrode and the solid polymer electrolyte membrane without heat melting.

The solid polymer electrolyte membrane serves as a passage for H ⁺ generated at the anode by the oxidation reaction to move to the cathode.
The solid polymer electrolyte membrane serves to separate the anode and the cathode.

The invention according to claim 1 is a solution in which a catalyst-carrying conductive particle, a proton conductive material, and a polyion complex comprising a polymer having an acidic group and a polymer having a basic group are dissolved in a water-insoluble organic solvent. A catalyst ink.

By using such a catalyst ink, a catalyst layer with good air permeability can be formed.

The invention according to claim 2 is the catalyst ink according to claim 1, wherein the proton conductive material has a structure represented by the formula (1).

By using such a catalyst ink, a catalyst layer having high proton conductivity, excellent chemical resistance, heat resistance, electrochemical stability and mechanical stability can be formed.

Invention of Claim 3 has the structure where the polymer | macromolecule which has the said acidic group is represented by Formula (2) or Formula (3),
The catalyst ink according to claim 1 or 2, wherein the polymer having a basic group has a structure represented by the formula (4).

By using such a catalyst ink, the air holes can be regularly arranged in the catalyst layer.

The invention according to claim 4 is a first step for forming a catalyst ink layer by applying the catalyst ink according to any one of claims 1 to 3 on the electrode substrate;
A second step for arranging micro water droplets in the catalyst ink layer by bringing high-humidity air into contact with the catalyst ink layer;
A method for producing a catalyst electrode, comprising: a third step for forming a catalyst layer by drying and removing the fine water droplets.

By using such a manufacturing method, a highly breathable catalyst electrode can be manufactured.

The invention according to claim 5 is a catalyst electrode formed by using the method for producing a catalyst electrode according to claim 4.

By using such a catalyst electrode, an MEA having a high effective utilization rate of a noble metal catalyst can be produced.

The invention according to claim 6 is an adhesive for joining the catalyst layer of the catalyst electrode and the solid polymer electrolyte membrane,
An adhesive having a structure represented by Formula (5).

By using such an adhesive, the catalyst layer of the catalyst electrode and the solid polymer electrolyte membrane can be strongly bonded.

The invention according to claim 7 is a coating process for forming an adhesive layer by coating the adhesive on a solid polymer electrolyte membrane;
It is a manufacturing method of a membrane electrode assembly (MEA) which has a crimping | compression-bonding process which crimps | bonds the said contact bonding layer with the catalyst layer of the catalyst electrode of Claim 5.

By using such a manufacturing method, the catalyst layer of the catalyst electrode and the solid polymer electrolyte membrane can be joined without blocking the vent hole of the catalyst layer.

The invention according to claim 8 is a membrane electrode assembly (MEA) formed by using the method for producing a membrane electrode assembly (MEA) according to claim 7.

Thereby, MEA with a high precious metal catalyst effective utilization rate can be obtained.

Hereinafter, the catalyst electrode-supporting conductive particles, the catalyst electrode, and the MEA manufacturing method of the present invention will be described using the catalyst electrode and MEA manufacturing process explanatory diagram (FIG. 1) of the present invention.

(Production of catalyst-carrying conductive particles)
First, a complex cation having metal particles and a solvent thereof, and conductive particles are dissolved in a reducing agent and stirred to form a dispersion.

The complex cation having metal particles is not particularly limited as long as it is a complex cation having metal particles (catalytically active substance) having a function of separating hydrogen into protons and electrons, and examples thereof include tetraammine platinum dichloride. Metal chlorides and metal nitrates such as dinitrodiammine platinum nitric acid can be used. Among them, dinitrodiammine platinum nitric acid is preferable from the viewpoint of a high reduction rate.

The particle size (measured value by X-ray diffraction method) of the metal particles can be selected from the range of 1 to 5 nm, but preferably 2 to 4 nm.

If it exceeds 4 nm, particularly if it exceeds 5 nm, the surface area of the metal particles per weight of the metal particles is reduced, so that the catalyst efficiency is deteriorated, and if it is less than 2 nm, particularly less than 1 nm, it is difficult to produce metal particles. The cost will increase.

As the conductive particles, for example, acetylene black, ketjen black, carbon nanotube, carbon nanohorn and the like can be used. Among them, acetylene black is preferable from the viewpoint of a large surface area.

The particle diameter of the conductive particles can be selected from the range of 0.01 to 0.07 μm, and preferably 0.03 to 0.05 μm.

When it exceeds 0.05 μm, particularly when it exceeds 0.07 μm, the diffusibility of the conductive particles in the catalyst layer of the catalyst electrode is deteriorated, and is less than 0.03 μm, particularly less than 0.01 μm. There is a concern that sufficient electrical conductivity cannot be obtained in the catalyst layer of the catalyst electrode.

The compounding amount of the complex cation having metal particles and the conductive particles is preferably 3 to 25 parts by weight, more preferably 5 to 20 parts by weight of the conductive particles with respect to 10 parts by weight of the metal particles. .

If the amount of conductive particles is less than 5 parts by weight with respect to 10 parts by weight of metal particles, particularly less than 3 parts by weight, sufficient electrical conductivity cannot be obtained in the catalyst layer of the catalyst electrode, and metal When the conductive particles exceed 20 parts by weight with respect to 10 parts by weight of the particles, particularly when it exceeds 25 parts by weight, sufficient battery performance cannot be obtained.

The reducing agent is preferably a substance having a reducing power and evaporating in the drying and removing step in order to avoid remaining in the complex cation-carrying conductive particles having metal particles. Alcohols such as propanol, acids such as formic acid, acetic acid, lactic acid, and oxalic acid, and alcohol aqueous solutions such as an ethanol aqueous solution can be used.

For example, when a 98 vol% ethanol aqueous solution is used as the reducing agent, the amount of the reducing agent can be selected from a range of 3 to 5 times the total mass of the metal particles to be reacted, but 3.5 to 4.5 times. Is preferred.

When it exceeds 4.5 times, particularly when it exceeds 5 times, the time spent for drying and removing the reducing agent becomes long, and when it is less than 3.5 times, particularly less than 3 times, a complex having metal particles The reducing ability necessary for supporting the cation on the conductive particles cannot be obtained.

Next, after pressurizing and heating the mixed liquid of the solvent and reducing agent of the complex cation having metal particles to supercritical conditions, reducing the pressure to atmospheric pressure and returning to room temperature, the complex cation having metal particles has The mixed liquid composed of the solvent and the reducing agent is removed by drying to obtain complex cation-carrying conductive particles having metal particles.

As the pressurization and decompression means, a reaction vessel such as a pressure cell or an autoclave can be used.

Finally, the catalyst particle-supporting conductive particles are obtained by reducing the complex cation-supporting conductive particles having metal particles in a reducing atmosphere.

As the reducing gas for producing the reducing atmosphere, for example, hydrogen gas, a mixed gas of hydrogen gas and inert gas, methane gas, a mixed gas of methane gas and inert gas, or the like can be used. Among these, a mixed gas of hydrogen gas and an inert gas is preferable from the viewpoint that the time required for reduction is short and from the viewpoint of work safety.

The blending amount of the hydrogen gas and the inert gas is preferably 85 to 110 mol parts, more preferably 90 to 105 mol parts of the inert gas with respect to 10 mol parts of the hydrogen gas.

If the inert gas is less than 90 mol parts with respect to 10 mol parts of hydrogen gas, especially if it is less than 85 mol parts, there is a concern about explosion or fire during operation, and the conductivity with respect to 10 mol parts of hydrogen gas. When the particle exceeds 105 mol part, particularly when it exceeds 110 mol part, sufficient reducibility cannot be obtained.

The inert gas is not particularly limited as long as it is inert, and for example, nitrogen gas, argon gas, helium gas, or the like can be used.

The temperature of the reducing atmosphere can be selected from the range of 200 to 500 ° C, but preferably 300 to 400 ° C.

Above 400 ° C., especially above 500 ° C., the catalyst particle diameter increases, thus reducing the catalyst particle surface area per catalyst particle weight, resulting in poor catalyst efficiency and less than 300 ° C. In particular, when the temperature is less than 200 ° C., the crystallization of the catalyst particles becomes insufficient, and the catalyst particle diameter tends to increase when used at the catalyst electrode.

(Catalyst ink generation)
Catalyst ink is obtained by dissolving a catalyst-carrying conductive particle, a proton conductive material, and a polyion complex composed of a polymer having an acidic group and a polymer having a basic group in a water-insoluble organic solvent and stirring. Generate.

The proton conductive substance is not particularly limited as long as it is a material having proton conductivity. For example, a polar group (ion exchange group) such as a strong acid group such as a sulfone group or a phosphate group, or a weak acid group such as a carboxyl group. In particular, from the viewpoint of high hydrogen ion conductivity, excellent chemical resistance, heat resistance, electrochemical stability, and mechanical stability, A proton conductive material (shown in the above formula (1)) having an alkylene group as the main skeleton and a sulfonic acid group at the end of the side chain of the perfluorovinyl ether is preferred.

The composition of the catalyst-carrying conductive particles and the proton conductive material can be selected from the range of 2: 5 to 1: 1 by mass ratio, but 3: 5 to 4: 5 is preferable.

When it exceeds 4: 5, particularly when it exceeds 1: 1, the strength of the catalyst layer decreases, and when it is less than 3: 5, particularly less than 2: 5, sufficient electric conductivity is provided in the catalyst layer. In addition, there is a concern that catalyst activity cannot be obtained.

The polymer having an acidic group is not particularly limited as long as it is a polymer having a strong acid group such as a sulfone group or a phosphoric acid group, or a weak acid group such as a carboxyl group, and examples thereof include sulfated polyacrylamide and sulfated cyclodextrin. , Heparan sulfate, chondroitin sulfate, sulfated oligosaccharides, and aromatic polyketone polymers having a sulfonic group introduced therein (shown in the above formula (2)), or containing a styrene sulfonic acid structural unit (the above formula The polymer (shown in (3)) can be used, but in particular, from the viewpoint of a high degree of crosslinking, a product in which a sulfone group is introduced into the aromatic polyketone polymer (shown in the formula (2)) Or, a polymer containing a styrenesulfonic acid structural unit (shown in the above formula (3)) is preferred.

Examples of the polymer having a basic group include polyallylamine, polyethyleneimine, polylysine, 2-diethylaminomethylmethacrylate, N-3-N, N-dimethylaminopropylacrylamide, polyprene, diethylaminoethyldextran, xososan, protamine, In addition, a product having a quaternary ammonium structure having an alkyl chain having 12 or more carbon atoms (shown in [Chemical Formula 4]) or a combination of two or more of these materials can be used. From the viewpoint of good properties, a product having a quaternary ammonium structure having an alkyl chain having 12 or more carbon atoms (shown in the above formula (4)) is preferred.

The mixing ratio of the proton conductive substance and the polyion complex is preferably in the range of 1: 1 to 9: 1 by mass ratio, but more preferably 4: 1 to 6: 1.

If it exceeds 6: 1, especially 9: 1, the air permeability of the catalyst layer is lowered, and if it is less than 4: 1, particularly less than 1: 1, sufficient proton conduction in the catalyst layer is achieved. Sex cannot be obtained.

The water-insoluble organic solvent is not particularly limited as long as it is an inert solvent having no polar group, for example, methyl isobutyl ketone, butyl acetate, benzene, toluene, xylene, ethyl acetate, chloroform, methylene chloride, and A mixed solvent in which these solvents are combined can be used. Among them, methyl isobutyl ketone is preferable from the viewpoint that the catalyst-carrying conductive particles hardly precipitate.

The concentration of the catalyst ink is such that the total amount of catalyst-carrying conductive particles, proton conductive material, and polyion complex composed of a polymer having an acidic group and a polymer having a basic group is in the range of 0.1 to 9% by weight. 1 to 8% by weight is preferable.

If it exceeds 8% by weight, in particular, if it exceeds 9% by weight, the viscosity of the catalyst ink becomes high and it becomes difficult to make the thickness of the catalyst layer uniform, and less than 1% by weight, in particular 0.1% by weight. If it is less than%, the viscosity is too low, so that the catalyst ink layer coating pattern bleeds or economic loss due to overdilution occurs.

(Production of catalyst electrode)
First, the catalyst ink layer 2 (or 4) is formed on the electrode substrate 1 (or 5) by applying the catalyst ink onto the electrode substrate 1 (or 5). (See Fig. 1 (a))

The electrode substrate is not particularly limited as long as it has a gas supply / diffusion / discharge function and a current collecting function. For example, carbon cloth, carbon paper, carbon net, mesh-like carbon, etc. A conductive porous material such as a conductive polymer fiber aggregate, a carbon sintered body, a sintered metal, and a foamed metal can be used. Among these, carbon paper is preferable from the viewpoint of mechanical strength.

The thickness of the electrode substrate may be appropriately determined so as to obtain desired battery characteristics, and is not particularly limited.

As a method for applying the catalyst ink onto the electrode substrate 1 (or 5), a bar coating method, a spray method, or a screen printing method can be used. Among these, from the viewpoint of coating thickness accuracy, a screen printing method is preferable. preferable.

Next, the minute water droplets 6 are arranged on the catalyst ink layer 2 (or 4) by contacting the catalyst ink layer 2 (or 4) with high-humidity air. (See Fig. 1 (b))

The relative humidity of the high-humidity air can be selected from the range of 55 to 95% RH, but 60 to 90% RH is preferable.

If it exceeds 90% RH, particularly if it exceeds 95% RH, the minute water droplets 6 will aggregate, and if it is less than 60% RH, particularly less than 55% RH, the catalyst ink layer 2 (or 4). ) The water droplet 6 condensation speed to the) becomes slow.

The temperature of the catalyst ink layer 2 can be selected from a range of 0.1 to 20 ° C, and preferably 1 to 15 ° C.

If it exceeds 15 ° C., in particular, if it exceeds 20 ° C., the condensation rate of the fine water droplets 6 on the catalyst ink layer 2 becomes slow, and if it is less than 1 ° C., particularly less than 0.1 ° C., the fine water droplets 6 are formed. There is a risk of freezing.

The method for bringing the high humidity air into contact with the catalyst ink layer 2 (or 4) is not particularly limited as long as it is a method capable of bringing the high humidity air into contact with the catalyst ink layer 2 (or 4). A method of leaving the layer 2 (or 4) in a high-humidity air atmosphere or a method of spraying high-humidity air on the catalyst ink layer (or 4) can be used, but among them, the viewpoint that the minute water droplets 6 hardly aggregate. Therefore, a method of leaving the catalyst ink layer 2 (or 4) in a high-humidity air atmosphere is preferable.

As a method for producing high-humidity air, a method of passing an air flow through water or a method of applying ultrasonic waves to water can be used. However, water particles in high-humidity air can be made smaller, and the size of the minute water droplet 6 can be reduced. From the viewpoint of easy control of the thickness, a method of applying ultrasonic waves to water is preferable.

Finally, the fine water droplet 6 is removed by drying to form a vent 6 'to obtain the catalyst electrode 7. (See Fig. 1 (c))

The drying method is not particularly limited as long as it does not affect the formation of the vent 6 ', and natural drying method, freeze drying method, reduced pressure drying method, heat drying method and the like can be used. More specifically, as the heat drying method, a ventilation heat drying method, a thermostatic drying method, a pine-fur furnace drying method, a drum heat drying method, or the like can be used.

When using the heat drying method, in order to avoid excessive heating, it is preferable to dry under a condition that the heating temperature is 95 to 100 ° C. and the drying time is 55 to 65 minutes.

The diameter of the air hole (L in FIG. 1C) can be selected from the range of 0.10 to 3.0 μm, and is preferably 1.0 to 2.0 μm.

If it exceeds 2.0 μm, especially if it exceeds 3.0 μm, the mechanical strength of the catalyst layer 2 ″ (or 4 ″) decreases, and it is less than 1.0 μm, particularly less than 0.1 μm. If it is, air permeability will worsen.

(Production of MEA)
First, an adhesive layer 8 a is formed by applying an adhesive on the solid polymer electrolyte membrane 3. (See Fig. 2 (a))

The solid polymer electrolyte membrane 3 is not particularly limited as long as it is a material having proton conductivity. For example, an organic material having a polar group such as a strong acid group such as a sulfone group or a phosphoric acid group or a weak acid group such as a carboxyl group. Polymers can be used.

The thickness of the solid polymer electrolyte membrane 3 can be selected from the range of 30 to 70 μm, and preferably 40 to 60 μm.

If it exceeds 60 μm, in particular, if it exceeds 70 μm, the proton conductivity of the solid polymer electrolyte membrane 3 deteriorates, so that the battery performance decreases, and if it is less than 40 μm, particularly less than 30 μm, it is supplied to the anode. The fuel gas permeates the electrolyte membrane and reaches the cathode side (crossover), and the hydrogen in the fuel gas that has permeated the electrolyte membrane and the oxygen in the oxidant gas cause a direct combustion reaction. As a result, the battery performance decreases.

As the adhesive, a paste obtained by dissolving the resin represented by the formula (5) in a solvent can be used.

As the solvent, alcohol, hydrochlorofluorocarbon, fluorocarbon, fluoroether, and a mixed solvent of alcohol and water can be used. Among them, the viewpoint that the solubility of the substance represented by the formula (5) is good. Therefore, alcohol is preferable.

The alcohol is not particularly limited as long as it has a boiling point of 100 ° C. or less. For example, tert-butyl alcohol, methyl alcohol, ethyl alcohol, n-propyl alcohol, i-propyl alcohol, trifluoroethanol, pentafluoropropanol, Hexafluoroisopropanol or the like can be used.

The blend of the resin represented by the formula (5) and the solvent is preferably in the range of 1:19 to 1: 1 by mass ratio, but more preferably 1:12 to 1: 6.

When it exceeds 1: 6, particularly when it exceeds 1: 1, the wettability of the adhesive onto the solid polymer electrolyte membrane 3 decreases, and it is less than 1:12, particularly less than 1:19. , The viscosity of the adhesive is too low, making uniform application difficult.

As a coating method, a bar coating method, a spray coating method, a dip coating method, a spin coating method, a doctor blade method, a roll coating method, a brush coating method, or a screen printing method can be used. From this point of view, the screen printing method is preferable.

Next, the adhesive layer 8a and the catalyst layer 1 ″ of the catalyst electrode are pressure-bonded. (See FIG. 2 (b) and (c))

As a method of pressure bonding, a die press method and an isostatic press method can be used, but an isostatic press method is preferable from the viewpoint that pressure can be applied uniformly.

Pressure to crimping, may be selected from the range of 10 to 200 / cm ^2, further preferably if 50~150kg / cm ^2.

When it exceeds 150 kg / cm ² , particularly when it exceeds 200 kg / cm ² , there is a concern that the solid polymer electrolyte membrane 3 and the electrode substrate 1 may be damaged, and thus the fuel gas and the oxidant gas may not be supplied satisfactorily. Further, if it is less than 50 kg / cm ² , particularly less than 10 kg / cm ² , uniform adhesion becomes difficult, and thus the resistance increases and the battery characteristics deteriorate.

Next, the solvent contained in the adhesive is removed by drying.

As a drying method, a hot air drying method, an infrared heater drying method, or the like can be used, but a hot air drying method with a high drying speed is preferable.

The drying temperature is not particularly limited as long as it is higher than the boiling point of the solvent and lower than the glass transition point of the resin represented by the formula (5), preferably 100 to 115 ° C, and 105 to 110 ° C. More preferably.

Next, an adhesive layer 8b is formed by applying an adhesive on the surface of the solid polymer electrolyte membrane 3 opposite to the surface on which the adhesive layer 8a is formed. (See Fig. 3 (d))

As the adhesive, a paste obtained by dissolving the resin represented by the formula (5) in a solvent can be used.

As the solvent, alcohol, hydrochlorofluorocarbon, fluorocarbon, fluoroether, and a mixed solvent of alcohol and water can be used. Among them, the solubility in the substance represented by the formula (5) is good. From the viewpoint, alcohol is preferable.

The alcohol is not particularly limited as long as it has a boiling point of 100 ° C. or lower. For example, butyl alcohol, methyl alcohol, ethyl alcohol, trifluoroethanol, propanol, hexafluoroisopropanol, and a mixed solvent thereof can be used. However, among these, a mixed solvent of 1-propanol and 2-propanol is preferable from the viewpoint of good solubility of the substance represented by the formula (5).

The blend of the resin and the solvent represented by the formula (5) is preferably in the range of 1:19 to 1: 1 by mass ratio, and more preferably 1:12 to 1: 6.

When it exceeds 1: 6, particularly when it exceeds 1: 1, the wettability of the adhesive onto the solid polymer electrolyte membrane 3 decreases, and it is less than 1:12, particularly less than 1:19. , The viscosity of the adhesive is too low, making uniform application difficult.

As a coating method, a bar coating method, a spray coating method, a dip coating method, a spin coating method, a doctor blade method, a roll coating method, a brush coating method, or a screen printing method can be used. From this point of view, the screen printing method is preferable.

Next, the adhesive layer 8b and the catalyst layer 4 ″ of the catalyst electrode are pressure-bonded. (See FIGS. 3 (e) and (f))

As a method for pressure bonding, a die press method and an isostatic press method can be used, but an isostatic press method is preferable from the viewpoint that pressure can be applied uniformly.

Pressure to crimping, may be selected from the range of 10 to 200 / cm ^2, further preferably if 50~150kg / cm ^2.

When it exceeds 150 kg / cm ² , particularly when it exceeds 200 kg / cm ² , there is a concern that the solid polymer electrolyte membrane 3 and the electrode substrate 1 may be damaged, and thus the fuel gas and the oxidant gas may not be supplied satisfactorily. Further, if it is less than 50 kg / cm ² , particularly less than 10 kg / cm ² , uniform adhesion becomes difficult, and thus the resistance increases and the battery characteristics deteriorate.

Finally, by drying, the solvent contained in the adhesive is removed by drying to obtain MEA.

As a drying method, a hot air drying method, an infrared heater drying method, or the like can be used, but a hot air drying method having a high drying speed is preferable.

The drying temperature is not particularly limited as long as it is higher than the boiling point of the solvent and lower than the glass transition point of the resin represented by the formula (5), preferably 100 to 115 ° C, and 105 to 110 ° C. More preferably.

Hereinafter, the present invention will be described with reference to examples and comparative examples, but the present invention is not limited thereto.

Further, the MEA produced in the following examples and comparative examples is effectively utilized (a value obtained by dividing the amount of electrochemical hydrogen adsorption on the surface of the noble metal catalyst by the surface area of the noble metal catalyst), and an output evaluation method. Is as follows.

(Effective utilization rate of MEA precious metal catalyst)
With no current flowing through the MEA, at 80 ° C., 50 mL / min of hydrogen (80 ° C., RH = 100%) was flowed to the anode side, and nitrogen (80 ° C., RH = 100%) 2000 mL / min was flowed to the cathode side. Obtained by scanning the potential in a potential range from 0.14 V to 1.10 V and applying a cyclic voltammogram (cyclic voltammogram) of the MEA (a voltage that increases or decreases at a predetermined rate to the electrode). A graph in which the relationship between current and voltage was plotted as a voltage-current curve was obtained.
From this cyclic voltammogram, the amount of electrochemical hydrogen adsorption (the amount of electricity: unit coulomb) on the surface of the noble metal catalyst was calculated.
The surface area of the noble metal catalyst was determined by measuring the particle diameter of the noble metal by X-ray diffraction and calculating the surface area based on the particle diameter.

(MEA output evaluation)
MEA is incorporated into an evaluation fuel cell (trade name; FC25-02SP, manufactured by Electrochem Co., Ltd.), and the voltage of the MEA is measured using a fuel cell power generation tester (trade name: GFT-SG1 manufactured by Toyo Corporation). -The current characteristics were evaluated.
The test conditions are as follows.
-Cell temperature: 70 ° C
-Fuel: 5 mol / L aqueous methanol solution (flow rate 1.5 ml / min)
・ Oxidant gas; pure oxygen (flow rate 80ml / min)

<Example 1>
(Preparation of conductive particles carrying catalyst particles)
First, 20 g of acetylene black was mixed with 1000 g of a dinitrodiamine platinum nitric acid solution containing 3 wt% of platinum in a stainless steel autoclave (with an internal volume of 3800 ml) equipped with a valve, a pressure gauge, a thermometer and a stirrer, and then reduced. A dispersion was produced by mixing and stirring 120 ml of a 98 wt% aqueous ethanol solution.

Next, the dispersion was heated at 95 ° C. for 10 hours with stirring, whereby the complex cation having platinum particles was supported on acetylene black.

Next, the dispersion liquid is pressurized and heated to 10 MPa and 325 ° C., and then depressurized to 1.01325 × 10 ⁵ Pa, and the temperature is lowered to 25 ° C., whereby the solvent of the dispersion liquid is removed by drying to have platinum particles. A complex cation-carrying conductive particle was obtained.

Finally, the complex cation-supporting conductive particles having platinum particles are reduced by 10 minutes in a reducing atmosphere having a composition of 100 mol of nitrogen with respect to 10 mol of hydrogen and a temperature of 350 ° C. 49.8 g of conductive particles were obtained.

The amount of platinum particles supported was 50.1% with respect to the weight of acetylene black.

(Catalyst ink generation)
49.8 g of catalyst particle-supporting conductive particles, 70.0 g of the proton conductive material of the structural formula (1), 7.0 g of the polymer having an acidic group of the structural formula (2), and the structural formula ( The catalyst ink was prepared by mixing and stirring 7.0 g of the polymer having a basic group of 2).

(Production of catalyst electrode)
First, carbon paper of 110 μm thickness (manufactured by Toray Industries, Inc. (trade name; TGP-H-030)) was cut into 110 mm squares.

Next, the cut carbon paper was set in a screen printer (manufactured by Tokai Seiki Co., Ltd. (trade name; SSA-PC605IP)).

Next, the prepared catalyst ink was placed on a screen of 250 mesh × wire diameter 0.05 mm.

Next, by screen printing the catalyst ink on the cut carbon paper under the conditions that the squeegee pressure is 5 kgf / cm ² , the squeegee speed is 100 mm / sec, and the clearance between the screen and the cut carbon paper is 2.5 mm, A catalyst ink layer was formed.

Next, in the high-temperature and high-humidity layer, the catalyst ink layer is brought into contact with high humidity air with a relative humidity of 75% RH at 10.0 ± 0.1 ° C., so that small water droplets of 1.5 ± 0.1 μmφ are formed. Arranged on the catalyst ink layer.

Finally, the fine water droplets were removed by drying at 97.5 ± 0.1 ° C. to obtain a catalyst electrode in which a vent hole of 1.5 ± 0.1 μmφ was formed.

(Adhesive adjustment)
An adhesive was prepared by mixing and stirring 90.0 g of an adhesive substance of the following structural formula (5), 90.0 g of 1-propanol, and 90.0 g of 2-propanol.

(Production of MEA)
First, a solid polymer electrolyte membrane (manufactured by DuPont, Nafion 112 (registered trademark)) having a thickness of 50 μm was cut into a 110 mm square.

Next, the adhesive was cut under the conditions that the squeegee pressure was 5 kgf / cm ² , the squeegee speed was 100 mm / second, and the clearance between the screen and the solid polymer electrolyte membrane (DuPont, Nafion 112 (registered trademark)) was 2.5 mm. Screen printing was performed on a solid polymer electrolyte membrane (Nafion 112 (registered trademark) manufactured by DuPont).

Next, the catalyst layer of the catalyst electrode was pressure-bonded onto the adhesive printed surface at a pressure of 200.0 ± 0.1 kg / cm ² .

Next, the solvent in the adhesive was removed by drying by leaving it in an oven at 107.5 ± 0.1 ° C.

Next, under the conditions that the squeegee pressure is 5 kgf / cm ² , the squeegee speed is 100 mm / second, and the clearance between the screen and the surface of the solid polymer electrolyte membrane opposite to the adhesive layer forming surface is 2.5 mm, Screen printing was performed on the surface of the molecular electrolyte membrane opposite to the surface on which the adhesive layer was formed.

Next, the catalyst layer of the catalyst electrode was pressure-bonded onto the adhesive printed surface at a pressure of 200.0 ± 0.1 kg / cm ² .

Next, by leaving it in an oven at 107.5 ± 0.1 ° C., the solvent in the adhesive was removed by drying to obtain MEA.

Table 1 shows the effective utilization rates of MEA precious metal catalysts.

The results of MEA output evaluation are shown in FIG.

<Example 2>
An MEA was produced in the same manner as in Example 1 except that the polymer of the structural formula (3) was used instead of the structural formula (2) as the polymer having an acidic group, and the MEA was effectively used as a noble metal catalyst. The rate and MEA output were evaluated.

Table 1 shows the effective utilization rates of MEA precious metal catalysts.

The results of MEA output evaluation are shown in FIG.

<Comparative Example 1>
An MEA was produced in the same manner as in Example 1 except that the polyion complex was not used, and the precious metal catalyst effective utilization rate of the MEA and the output of the MEA were evaluated.

Table 1 shows the effective utilization rates of MEA precious metal catalysts.

The results of MEA output evaluation are shown in FIG.

<Comparative example 2>
An MEA was produced in the same manner as in Example 1 except that the catalyst layer was not contacted with high-humidity air, and the precious metal catalyst effective utilization rate of the MEA and the output of the MEA were evaluated.

Table 1 shows the effective utilization rates of MEA precious metal catalysts.

The results of MEA output evaluation are shown in FIG.

<Comparative Example 3>
Implemented except that the catalyst layer of the catalyst electrode was placed on both sides of the solid polymer electrolyte membrane and then thermocompression bonded (130 ± 1 ° C., 200.0 ± 0.1 kg / cm ² , 30 minutes) to produce the MEA An MEA was prepared in the same manner as in Example 1, and the precious metal catalyst effective utilization rate of the MEA and the output of the MEA were evaluated.

Table 1 shows the effective utilization rates of MEA precious metal catalysts.

The results of MEA output evaluation are shown in FIG.

<Comparative Example 4>
An MEA was prepared in the same manner as in Example 1 except that the polyion complex was not used and the catalyst layer was not contacted with high-humidity air, and the MEA's precious metal catalyst effective utilization rate and the MEA output were evaluated. .

Table 1 shows the effective utilization rates of MEA precious metal catalysts.

The results of MEA output evaluation are shown in FIG.

<Comparative Example 5>
After the catalyst layer is not brought into contact with the high-humidity air and the catalyst layer of the catalyst electrode is disposed on both sides of the solid polymer electrolyte membrane, thermocompression bonding (130 ± 1 ° C., 200.0 ± 0.1 kg / cm ² , The MEA was produced in the same manner as in Example 1 except that the MEA was produced for 30 minutes), and the precious metal catalyst effective utilization rate of the MEA and the output of the MEA were evaluated.

Table 1 shows the effective utilization rates of MEA precious metal catalysts.

The results of MEA output evaluation are shown in FIG.

<Comparative Example 6>
Without using a polyion complex, and after placing the catalyst layer of the catalyst electrode on both sides of the solid polymer electrolyte membrane, thermocompression bonding (130 ± 1 ° C., 200.0 ± 0.1 kg / cm ² , 30 minutes) Except for producing the MEA, an MEA was produced in the same manner as in Example 1, and the precious metal catalyst effective utilization rate of the MEA and the output of the MEA were evaluated.

Table 1 shows the effective utilization rates of MEA precious metal catalysts.

The results of MEA output evaluation are shown in FIG.

<Comparative Example 7>
A polyion complex is not used, the catalyst layer is not brought into contact with high-humidity air, and the catalyst layer of the catalyst electrode is disposed on both sides of the solid polymer electrolyte membrane, and then thermocompression bonding (130 ± 1 ° C., 200.0 The MEA was produced in the same manner as in Example 1 except that the MEA was produced by ± 0.1 kg / cm ² for 30 minutes, and the precious metal catalyst effective utilization rate of the MEA and the output of the MEA were evaluated.

Table 1 shows the effective utilization rates of MEA precious metal catalysts.

The results of MEA output evaluation are shown in FIG.

From Table 1 and FIG. 4, it was confirmed that Example 1 improved the precious metal catalyst effective utilization rate of MEA and the output of MEA compared to the comparative example.
Moreover, the same characteristic improvement was confirmed also about Example 2. FIG.

The catalyst ink, the catalyst electrode and the manufacturing method thereof, the adhesive, the membrane electrode assembly (MEA) and the manufacturing method thereof according to the present invention include a camera, a mobile phone, a laptop computer, a PDA (Personal Digital Assistant), a navigation system, and portable music. It can be used for portable small electric devices such as playback players, and PEFCs used as power sources for electric vehicles, vending machines, underwater robots, submarines, spacecrafts, underwater bases, and the like.

It is manufacturing process explanatory drawing of the catalyst electrode of this invention. It is manufacturing process explanatory drawing of MEA of this invention. It is manufacturing process explanatory drawing of MEA of this invention. It is a figure for demonstrating the voltage-current characteristic of MEA of this invention. It is a figure for demonstrating the structure of the conventional fuel cell.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Electrode base 2 ... Catalyst layer 2 '... Catalyst layer 2 "with minute water droplets attached ... Catalyst layer 3 with vents formed ... Solid Polymer electrolyte membrane 4 ... catalyst layer 4 '... catalyst layer 4 "with minute water droplets attached ... catalyst layer 5 with vents formed ... electrode substrate 6 ... ... Small water droplet 6 '... Air vent 7 ... Catalyst electrode 8a ... Adhesive layer 8b ... Adhesive layer 9 ... MEA
10 .... Anode separator 10a ... Fuel gas flow path 20 .... Anode catalyst electrode 21 ... Anode electrode substrate 22 ... Anode catalyst layer 30 ... Solid Polymer electrolyte membrane 40 ... Cathode side catalyst electrode 41 ... Cathode side electrode base material 42 ... Cathode side catalyst layer 50 ... Cathode side separator 50a ... Oxidant gas flow path

Claims (8)

A catalyst ink comprising a catalyst-carrying conductive particle, a proton conductive material, and a polyion complex comprising a polymer having an acidic group and a polymer having a basic group dissolved in a water-insoluble organic solvent. The catalyst ink according to claim 1, wherein the proton conductive material has a structure represented by the following formula (1).
(In formula 1, d represents an integer, e represents an integer of 1 to 5, a represents an integer of 5 to 150, and b represents an integer of 0 to 1100.) The polymer having an acidic group has a structure represented by the following formula (2) or the following formula (3),
The catalyst ink according to claim 1 or 2, wherein the polymer having a basic group has a structure represented by the following formula (4).
(In Formula 2, R represents —SO ₃ —, and f represents an integer.)
(In formula 4, g represents an integer of 12 or more.) A first step for forming a catalyst ink layer by applying the catalyst ink according to any one of claims 1 to 3 on the electrode substrate;
A second step for arranging micro water droplets in the catalyst ink layer by bringing high-humidity air into contact with the catalyst ink layer;
A method for producing a catalyst electrode, comprising a third step of forming a catalyst layer by drying and removing the fine water droplets. A catalyst electrode comprising the catalyst electrode production method according to claim 4. An adhesive for joining the catalyst layer of the catalyst electrode and the solid polymer electrolyte membrane,
An adhesive having a structure represented by the following formula (5):
(In formula 5, k represents an integer of 3 to 8, i represents an integer of 5 to 150, and j represents an integer of 0 to 1100.) A coating process for forming an adhesive layer by coating the adhesive on the solid polymer electrolyte membrane;
The manufacturing method of a membrane electrode assembly (MEA) which has a crimping | compression-bonding process which crimps | bonds the said contact bonding layer with the catalyst layer of the catalyst electrode of Claim 5. The membrane electrode assembly (MEA) which uses the manufacturing method of the membrane electrode assembly (MEA) of Claim 7.