JP2003272672A - Electrolyte membrane electrode jointed body and its manufacturing method and fuel cell using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrolyte membrane electrode jointed body that secures adhesion when a plurality of different materials are compounded to an electrolyte membrane or a polymer electrolyte and used for the electrolyte membrane electrode jointed body in accordance with the usage and function of a fuel cell. <P>SOLUTION: In this electrolyte membrane electrode jointed body, the electrolyte membrane and the electrode are jointed in a state of being dipped in or exposed to, beforehand, a substance that exists in the environment where they are actually used. It is desirable that the ion conductive substance contained in the electrolyte membrane electrode joint body is made of substances of two or more kinds. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an electrolyte membrane electrode assembly, a method for producing the same, and a fuel cell using the same,
More specifically, the present invention relates to an electrolyte membrane electrode assembly applicable to a fuel cell using hydrogen, water, alcohol, etc. as a fuel.

[0002]

2. Description of the Related Art In recent years, new energy storage or power generation elements have been strongly demanded in society from the viewpoint of environmental problems.
Fuel cells are also attracting attention as one of them, and are the most promising power generation elements because of their characteristics of low pollution and high efficiency. A fuel cell is a cell in which a fuel such as hydrogen or methanol is electrochemically oxidized using oxygen or air to convert the chemical energy of the fuel into electric energy and to extract it.

Such fuel cells are classified into phosphoric acid type, molten carbonate type, solid oxide type and polymer electrolyte type depending on the type of electrolyte used. Phosphoric acid fuel cells have already been put to practical use for electric power. However, the phosphoric acid fuel cell needs to be operated at a high temperature (around 200 ° C.), so that the startup time is long, it is difficult to downsize the system, and the proton conductivity of phosphoric acid is low. It has a drawback that it cannot take out an electric current.

On the other hand, the operating temperature of the polymer fuel cell is about 80 to 100 ° C. at the maximum. Further, since the internal resistance in the fuel cell can be reduced by thinning the electrolyte membrane used, it is possible to operate at a high current, and therefore the size can be reduced. Due to these advantages, research on polymer fuel cells has been actively conducted.

In the electrolyte membrane electrode assembly used in this polymer electrolyte fuel cell, electrodes in which a catalyst such as platinum is fixed to carbon paper with an ion conductive binder are joined to both surfaces of the electrolyte membrane. The joined product is sandwiched between separators to form a fuel cell. This bonded body needs an adhesive strength such that the bonded portion does not peel off in the actually used power generation state.
If the adhesive strength is weak, sufficient output may not be obtained.
When a composite of a plurality of different materials is used for the electrolyte membrane and the binder depending on the application and function of the fuel cell, there is a problem that the adhesive force cannot be secured and peeling occurs.

[0006]

SUMMARY OF THE INVENTION The present invention is intended to solve the problems of the prior art. That is, the purpose is to ensure this adhesive force when a plurality of different materials are mixed into the electrolyte membrane and the polymer electrolyte and used for the electrolyte membrane electrode assembly according to the application and function of the fuel cell.

[0007]

Means for Solving the Problems As a result of intensive studies to achieve the above object, the present inventors have found that the electrolyte membrane electrode assembly has a fuel existing in the environment in which it is actually used. A substance such as a reaction product or a reaction product causes stress due to expansion or contraction when permeating the ion conductive substance contained in the bonded body, and the stress causes the electrolyte membrane electrode assembly to be separated from the electrolyte membrane and the electrode. I found it. Therefore, the electrolyte membrane and the electrode are joined by being immersed in or exposed to a substance existing in the environment in which they are actually used, to reduce the stress generated during actual use and to improve the adhesive strength. The inventors have found an electrode assembly and completed the present invention.

The electrolyte membrane electrode assembly of the present invention is characterized in that the electrolyte membrane and the electrode are joined in a state of being immersed or exposed in advance to a substance existing in the environment in which they are actually used.

In a preferred aspect of the present invention, the ion conductive material contained in the electrolyte membrane electrode assembly is preferably an electrolyte membrane electrode assembly composed of two or more kinds of substances.

Further, in a preferred aspect of the present invention, it is preferable that at least one kind of the ion conductive material is a perfluorosulfonic acid resin.

Further, in a preferred aspect of the present invention, at least one of the ion conductive materials is a sulfonated polyether ketone resin, a sulfonated polyether sulfone resin, a sulfonated polyphenylene sulfide resin, a sulfonated polyimide resin, Sulfonated polyamide resin,
It is preferably either a sulfonated epoxy resin or a sulfonated polyolefin resin.

In the present invention, the substance used at the time of immersion or exposure is preferably pure water, methanol or a mixed solution thereof.

Further, in the present invention, it is preferable that the electrolyte membrane and the electrode are joined by an electrolyte membrane electrode assembly which is formed by pressing.

According to the present invention, there is provided a fuel cell characterized by using the electrolyte membrane electrode assembly.

The method for producing an electrolyte membrane-electrode assembly according to the present invention comprises preliminarily immersing or exposing the electrolyte membrane and the electrode in a substance existing in the environment in which they are actually used,
It is characterized by being joined by a press.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION The electrolyte membrane electrode assembly according to the present invention will be specifically described below. The electrolyte membrane electrode assembly according to the present invention is composed of an electrolyte membrane having ion conductivity, and a positive electrode and a negative electrode arranged in contact with both sides of the electrolyte membrane. Fuels such as hydrogen and methanol are electrochemically oxidized at the negative electrode to generate protons and electrons. This proton moves through the electrolyte membrane to the positive electrode to which oxygen is supplied. On the other hand, the electrons generated in the negative electrode flow to the positive electrode through the load connected to the battery, and the proton, oxygen and electrons react in the positive electrode to generate water.

The electrolyte membrane forming the electrolyte membrane electrode assembly is made of a substance having ion conductivity. Examples of these are fluororesins, polyetherketone resins,
Examples of the resin include polyether sulfone resin, polyphenylene sulfide resin, polyimide resin, polyamide resin, epoxy resin, polyolefin resin and the like to which a protonic acid group is added. Examples of the protonic acid group include a sulfonic acid group, a carboxylic acid group, a phosphoric acid group, and a sulfonimide group. Of these, a sulfonic acid group is desirable, and a perfluorosulfonic acid resin is preferably used.

Further, at least one of the ion conductive materials
It is desirable to use a sulfonated polyether ketone resin, a sulfonated polyether sulfone resin, a sulfonated polyphenylene sulfide resin, a sulfonated polyimide resin, a sulfonated polyamide resin, a sulfonated epoxy resin, or a sulfonated polyolefin resin as the seed. Particularly, it is desirable to use a perfluorosulfonic acid resin or a sulfonated polyetherketone resin.

The electrolyte membrane may use an inorganic ion conductive material such as silica. Further, these may be used alone or in combination of plural kinds. It is also possible to use a blend of a plurality of types or a composite of fibers.

The electrodes constituting the electrolyte membrane electrode assembly are composed of a conductive material, an ion conductive binder and a catalyst. As the conductive material, any material may be used as long as it is an electrically conductive material, and various metals, carbon materials and the like can be mentioned. For example, carbon black such as acetylene black,
Activated carbon, graphite, etc. are mentioned, and these are used individually or in mixture.

As the ion conductive binder, it is preferable to use the same resins as those for the above-mentioned electrolyte membrane, especially those obtained by diluting a perfluorosulfonic acid resin or a sulfonated polyetherketone resin with a solvent. Not limited to this, other various resins can be used. The catalyst metal is not particularly limited as long as it is a metal that promotes the oxidation reaction of hydrogen and the reduction reaction of oxygen, and for example, lead, iron, manganese, cobalt, chromium, gallium, vanadium, tungsten,
Examples include ruthenium, iridium, palladium, platinum, rhodium or alloys thereof. Of these, platinum, ruthenium, or alloys thereof are preferable.

Before the joining of the electrolyte membrane electrode assembly according to the present invention, the substances to be used for dipping or exposing in advance include substances existing in the fuel cell in the environment of actual use, such as fuel and reaction products. A solution or gas can be used. Usually, it is preferable to use pure water, methanol, or a mixed solution thereof. In particular, it is preferable to use pure water when the joined body is used for a fuel cell using hydrogen as a fuel, and to use a mixed solution of methanol and pure water for a direct methanol fuel cell that uses methanol as a fuel. The mixing ratio of methanol and pure water is not particularly limited, but a ratio corresponding to the concentration of the solution used as the fuel is preferable, and among them, the methanol concentration is 0.01% by weight or more and 50% or more.
It is particularly preferable that the content is less than or equal to wt%.

The conditions of immersion or exposure are not particularly limited as long as those substances can sufficiently penetrate, but at room temperature
It is preferable to use a solution under normal pressure or a gas under high temperature and high pressure. It is preferable to use the electrolyte membrane and the electrode in which these substances have sufficiently penetrated without being dried until the next bonding, but they may be dried in a range in which the shape does not change depending on the handling method.

The method for joining the electrolyte membrane and the electrode is not particularly limited as long as it can hold the shape in which the substance has permeated and join, but examples include hot pressing, cold pressing and ultrasonic welding. Especially, it is preferable to use a hot press. When a hot press is used, the permeated substance may evaporate and volatilize during the press, causing shrinkage.
If the electrolyte membrane and the electrode are bonded while maintaining the shape of the immersed and exposed state, there is no particular problem. A fuel cell is formed by sandwiching the electrolyte membrane electrode assembly thus created between separators that have been processed for fuel and oxygen flow paths.

The electrolyte membrane electrode assembly according to the present invention has an adhesive strength that poses no practical problem. In particular, when a fuel cell is formed using the electrolyte membrane electrode assembly according to the present invention, a fuel cell having excellent durability and capable of operating at high current can be obtained.

[0026]

EXAMPLES The present invention will now be described in detail with reference to examples, but the present invention is not limited to these examples. Example 1 Preparation of Electrolyte Membrane A 5-neck reactor equipped with a nitrogen inlet tube, a thermometer, a reflux condenser and a stirrer was charged with 5,5′-carbonylbis (sodium 2-fluorobenzenesulfonate). 22 g
(0.01 mol), 4,4'-difluorobenzophenone 2.18 g (0.01 mol), 2,2-bis (3,5-dimethyl-4-hydroxyphenyl) propane 5.69 g (0.02 mol) and carbonic acid 3.46 g (0.025 mol) of potassium was weighed out. Add 40 ml of dimethyl sulfoxide and 30 ml of toluene to this,
While stirring under a nitrogen atmosphere, the mixture was heated at 130 ° C. for 2 hours to remove produced water out of the system, and then toluene was distilled off. Subsequently, the reaction was carried out at 160 ° C. for 14 hours to obtain a viscous polymer solution. 60 ml of dimethyl sulfoxide was added to the resulting solution to dilute it, and then the solution was filtered. This polymer solution was discharged into 600 ml of acetone, and the precipitated polymer powder was filtered and dried at 160 ° C. for 4 hours to obtain 10.39 g of polymer powder (yield 92%). 0.50 g of the obtained polyetherketone powder was added to dimethyl sulfoxide 10
After dissolving in 0 ml, the logarithmic viscosity measured at 35 ° C. was 0.85 dl / g. Temperature rising rate 10 ° C / min
The glass transition temperature measured by differential scanning calorimetry (DSC, DSC3100 manufactured by Mac Science Co.) is 2
It was 30 ° C. Similarly, the temperature rise rate in air is 10 ° C /
DTA-TG (TG-made by Mac Science Co., Ltd.)
The 5% weight loss temperature measured using DTA2000) was 367 ° C.

The obtained polymer powder was dissolved in dimethylsulfoxide and cast on a glass substrate, and the mixture was heated at 200 ° C. for 4 hours.
After drying for an hour to obtain a polyetherketone film containing Na sulfonate, 600 using a metal halide lamp
Light irradiation of 0 mJ / cm ² was performed to crosslink. Further, after soaking the membrane in 2N-sulfuric acid overnight and then in distilled water overnight,
After drying at 150 ° C. for 4 hours, an electrolyte membrane 1 containing a free protonic acid was obtained. The thickness of the obtained film was 50 μm, which was rich in flexibility and tough.

Preparation of electrodes Tanaka Kikinzoku's 30 wt% Pt-supported catalyst (product number: TEC
10 V30E) 0.5 g and a 5 wt% solution of a perfluorosulfonic acid polymer (Nafion (registered trademark)) manufactured by Aldrich Co., Ltd. as a binder (product number: 27,470-4) 10
g was mixed, ultrasonic waves were applied and then stirred to obtain a catalyst paste. Toray carbon paper (Part number: TGP-H-0
60) was coated with a catalyst paste using an applicator, dried in vacuum at 70 ° C. for 12 hours, and then cut into 5 cm ² to obtain an electrode 2. Catalyst coating amount is 2 mg / cm 2 in Pt amount
² Further, on the electrode 2, a perfluorosulfonic acid polymer (Nafion (registered trademark)) 5 manufactured by Aldrich
spray coating a wt% solution (product number: 27,470-4),
Then, it was dried in normal temperature air overnight. The coating amount of the perfluorosulfonic acid polymer was 1 mg / cm ^{2 in} dry weight.

Preparation of bonded body The two electrodes prepared above and the sulfonated polyetherketone electrolyte membrane prepared in the above were immersed in pure water at room temperature for 2 hours. The electrolyte membrane and the electrode after the immersion were sufficiently swollen by absorbing pure water. These were laminated in a predetermined order in a water-absorbed state, introduced into a hot press preheated to 80 ° C., and pressed at a pressure of 0.4 MPa only on the electrode surface. Then, the temperature was raised from 80 ° C. to 130 ° C. in the pressurized state. The hot press used took 15 minutes. The electrolyte membrane electrode assembly after bonding was almost dry, but the electrodes were not peeled off.

Power Generation Test The electrolyte membrane electrode assembly prepared above was electrified.
fuel cell test cell manufactured by Ochem (product number: EFC-0
5-REF), and the fuel cell of FIG. 1 was assembled. After assembling the cell, a fuel cell evaluation device as shown in FIG. 2 (where humidified hydrogen and air are flown into the fuel cell to measure the cell characteristics using an electronic load) is used to measure the cell characteristics using hydrogen as a fuel. After that, about 0.19 W / cm ²
Got the output of. FIG. 4 shows the cell characteristics of the fabricated fuel cell (the voltage of the fuel cell was measured while increasing the current with an electronic load). Table 1 shows the measurement conditions of the discharge characteristics.

[0031]

[Table 1]

(Comparative Example 1) A bonded body was prepared in the same manner as in Example 1 except that the bonded body of Example 1 was bonded in a dry state without immersion in pure water at room temperature. It was The produced bonded body had low adhesive strength, and the electrolyte membrane and the electrode were peeled off when taken out from the hot press, and the output could not be taken out as a fuel cell.

Example 2 Preparation of Electrolyte Membrane An electrolyte membrane 1 was prepared in the same manner as in Example 1. Preparation of electrodes Tanaka Kikinzoku's 33wt% PtRu supported catalyst (product number: T
EC61V33) 0.5g and Aldric as a binder
h company perfluorosulfonic acid polymer (Nafion
(Registered trademark)) 5 wt% solution (product number: 27,470-4)
10 g was mixed, ultrasonic waves were applied and then stirred to obtain a catalyst paste. Toray carbon paper (product number: TGP-H
-060) was coated with a catalyst paste using an applicator, dried in vacuum at 70 ° C for 12 hours, and then cut into 5 cm ² to obtain an electrode 2 '. Catalyst coating amount is PtRu 2
It was set to mg / cm ² . Further on the electrode 2 ', Aldrich
Perfluorosulfonic acid polymer (Nafion
(Registered trademark)) 5 wt% solution (product number: 27,470-4)
Was spray coated and then dried overnight in normal temperature air. Perfluorosulfonic acid polymer coating amount is 1m dry weight
It was set to g / cm ² .

Preparation of bonded body One piece of each of the electrode 2'made of the sulfonated polyetherketone electrolyte membrane prepared above and the electrode 2 prepared in 2 was placed in a 1M aqueous methanol solution at room temperature.
Soak for hours. The electrolyte membrane and the electrode after the immersion were swollen by sufficiently absorbing the aqueous methanol solution. These were laminated in a predetermined order in the state of absorbing them, introduced into a hot press preheated to 80 ° C., and pressed only on the electrode surface with a pressure of 0.4 MPa. Then, the temperature was raised from 80 ° C. to 130 ° C. in the pressurized state. 15 in the heat press used
It took a minute. The electrolyte membrane electrode assembly after bonding was almost dry, but the electrodes were not peeled off.

Power Generation Test The electrolyte membrane electrode assembly prepared above was electrified.
fuel cell test cell manufactured by Ochem (product number: EFC-0
5-REF), and the fuel cell of FIG. 1 was assembled. After assembling the cell, a fuel cell evaluation device as shown in FIG. 3 (a methanol aqueous solution and air are flown into the fuel cell to measure the cell characteristics by using an electronic load) is used to measure the cell characteristics using a 1 M aqueous methanol solution as a fuel. When I measured
An output of about 2.5 mW / cm ² was obtained. Here, the PtRu electrode 2'created here was used as a methanol electrode. The cell characteristics of the fabricated fuel cell (the voltage of the fuel cell was measured while increasing the current with an electronic load) are shown in FIG. Table 2 shows the measurement conditions of the discharge characteristics.

[0036]

[Table 2]

(Comparative Example 2) A joined body was prepared in the same manner as in Example 2 except that the joined body of Example 2 was joined in a dry state without immersion in a 1 M aqueous methanol solution at room temperature. I did. The produced bonded body had low adhesive strength, and the electrolyte membrane and the electrode were peeled off when taken out from the hot press, and the output could not be taken out as a fuel cell.

[0038]

EFFECTS OF THE INVENTION According to the present invention, an electrolyte membrane electrode assembly with improved adhesion can be obtained, and when a fuel cell is formed using this, a fuel cell excellent in durability and capable of high current operation can be obtained. it can.

[Brief description of drawings]

FIG. 1 is a cross-sectional structural diagram of a fuel cell used in an example of the present invention.

FIG. 2 is a schematic diagram of a fuel cell evaluation apparatus used in Example 1 and Comparative Example 1 of the present invention.

FIG. 3 is a schematic diagram of a fuel cell evaluation apparatus used in Example 2 and Comparative Example 2 of the present invention.

FIG. 4 is a diagram showing a cell characteristic measurement result of the fuel cell of Example 1.

5 is a diagram showing the results of measuring the cell characteristics of the fuel cell of Example 2. FIG.

[Explanation of symbols]

1 electrolyte membrane 2, 2'catalyst electrode 3 gasket 4 separator 5 pressure plate 6 gas flow paths 7 Tightening bolt 8 Fuel cells 9 Bubbling tank for humidification 10 electronic load 11 Mass flow controller 12 Liquid feed pump

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Claims (9)

[Claims] 1. An electrolyte membrane electrode assembly, wherein an electrolyte membrane and an electrode are joined in a state where they are immersed or exposed in advance to a substance existing in the environment in which they are actually used. 2. The electrolyte membrane electrode assembly, wherein the ion conductive material contained in the electrolyte membrane electrode assembly is composed of two or more kinds of substances. 3. At least one of the ion-conducting substances is
The electrolyte membrane electrode assembly according to claim 2, which is a perfluorosulfonic acid resin. 4. At least one of the ionic conductive materials is
Characterized by being any one of sulfonated polyetherketone resin, sulfonated polyethersulfone resin, sulfonated polyphenylene sulfide resin, sulfonated polyimide resin, sulfonated polyamide resin, sulfonated epoxy resin, and sulfonated polyolefin resin. The electrolyte membrane electrode assembly according to claim 2 or 3. 5. The electrolyte membrane electrode assembly according to claim 1, wherein the substance used during the immersion or exposure is pure water, methanol, or a mixed solution thereof. 6. The electrolyte membrane electrode assembly according to any one of claims 1 to 5, wherein the electrolyte membrane and the electrode are joined by hot pressing. 7. A fuel cell comprising the electrolyte membrane electrode assembly according to any one of claims 1 to 6. 8. A method for producing an electrolyte membrane electrode assembly, which comprises preliminarily immersing or exposing the electrolyte membrane and the electrode in a substance existing in the environment in which they are actually used, and joining them by hot pressing. 9. The method for producing an electrolyte membrane electrode assembly according to claim 8, wherein the substance used at the time of immersion or exposure is pure water, methanol, or a mixed solution thereof.