JPH11354129A - Electrode catalyst coating agent for fuel cell and membrane/electrode joint body using same coating agent - Google Patents

Abstract

PROBLEM TO BE SOLVED: To lower an oxygen-concentration overvoltage when normal-pressure air is supplied and provide a high output voltage, by using a composition comprising a perfluorosulfonic-acid polymer and a fluorine-containing ether compound as an electrode-catalyst coating agent used for a gas diffusion electrode. SOLUTION: A membrane/electrode joint body for a solid high-polymer type fuel cell comprises an ion-exchange membrane serving as an electrolyte and a gas diffusion electrode jointed to the ion-exchange membrane. An electrode- catalyst coating agent used for the gas diffusion electrode contains a perfluorosulfonic-acid polymer of 30 to 95 wt.% expressed by an expression I and a fluorine-containing ether compound of 5 to 70 wt.% expressed by an expression II. In the expression I, x=0 to 2, y=2 to 3, and n/m=1 to 10. In the expression II, Rf is a perfluoroalkylene group having the C number of 1 to 3, x and y are perfluoroalkyl groups having the C number of 1 to 5, and k is 1 to 100. The gas diffusion electrode using the electrode-catalyst coating agent is used at least on the side of a cathode.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrode catalyst coating material used for a gas diffusion electrode constituting a polymer electrolyte fuel cell, and to a polymer electrolyte fuel having a gas diffusion electrode using the electrode catalyst coating material. The present invention relates to a membrane / electrode assembly for a battery.

[0002]

2. Description of the Related Art Fuel cells convert fuel chemical energy directly into electric energy by electrochemically oxidizing a fuel such as hydrogen or methanol in the cell and take out the fuel. It is drawing attention as an energy source. Particularly, a polymer electrolyte fuel cell using an ion exchange membrane as an electrolyte has a high output density,
Since it can be operated at low temperatures, it is expected as a power source for electric vehicles.

[0003] The basic structure of such a polymer electrolyte fuel cell is composed of an ion exchange membrane as a solid electrolyte and a pair of gas diffusion electrodes joined to both surfaces thereof. A catalyst is supported on the membrane side. Then, hydrogen as a fuel is supplied to one of the gas diffusion electrodes, and oxygen or air as an oxidant is supplied to the other gas diffusion electrode, and an external load circuit is connected between the two gas diffusion electrodes. Works as a battery. That is, in the former gas diffusion electrode (anode), protons and electrons are generated by the oxidation of the fuel, and the protons travel through the electrolyte to move to the latter gas diffusion electrode (cathode), where the protons and the oxidized gas are oxidized. The oxygen in the agent reacts to produce water. At this time, electric energy is obtained by the electrons generated at the anode moving through the external load circuit and moving to the cathode.

In such a polymer electrolyte fuel cell, a proton-conducting polymer electrolyte is used for the purpose of mediating proton transfer onto a catalyst carried on a gas diffusion electrode and increasing the utilization efficiency of the catalyst. It is used as an electrode catalyst coating. At present, proton conductive polymer electrolytes mainly used in polymer electrolyte fuel cells include "Nafion (registered trademark)" manufactured by DuPont and "Aciplex-S (registered trademark)" manufactured by Asahi Kasei Corporation. )) And the like.
Since these polymers have strong acidic groups and high chemical stability, they are used as ion exchange membranes as electrolytes, and their solutions are used as electrocatalyst coating materials for the catalyst layer of gas diffusion electrodes. (For example, Japanese Patent Publication No. 2-7398, Japanese Unexamined Patent Publication No. Hei 3-20826).
No. 0).

However, the conventionally used electrode catalyst coating material has a disadvantage that the oxygen concentration overvoltage is high due to insufficient oxygen supply capability to the catalyst layer through the coating material. Therefore, when trying to obtain a high output voltage,
Means such as pressurizing oxygen or supplying oxygen at a higher concentration were required, and for that purpose, an expensive system was required for the whole battery. For this reason, there has been a demand for an electrode catalyst coating agent having a low oxygen concentration overvoltage, which can obtain a high output voltage even when air is supplied at normal pressure.

[0006]

DISCLOSURE OF THE INVENTION The present inventors have found that a conventionally used composition comprising a perfluorosulfonic acid polymer and a certain kind of fluorine-containing ether compound has high oxygen permeability, By using it as an electrode catalyst coating agent, it is possible to reduce the oxygen concentration overvoltage when air at normal pressure is supplied, and to obtain a membrane / electrode assembly for a polymer electrolyte fuel cell capable of obtaining a high output voltage. Found and led to the present invention.

[0007]

That is, the present invention is as follows. 1. In a membrane / electrode assembly for a polymer electrolyte fuel cell comprising an ion exchange membrane serving as an electrolyte and a gas diffusion electrode joined to the ion exchange membrane, an electrode catalyst coating agent used for the gas diffusion electrode is used. A composition containing 30 to 95% by weight of a perfluorosulfonic acid polymer represented by the general formula (1) and 5 to 70% by weight of a fluorinated ether compound represented by the general formula (2). An electrode catalyst coating comprising:

[0008]

Embedded image (Where x is an integer of 0 to 2, y is an integer of 2 to 3, n /
m = 1 to 10. )

[0009]

Embedded image (Where Rf is a single or plural kinds of carbon atoms having 1 to 1
Three perfluoroalkylene groups, X and Y each have 1 to 1 carbon atoms
5 perfluoroalkyl groups, which may contain double bonds, wherein each carbon has H, Cl, Br, SO ₃ H, CO
A group selected from an OR group may substitute up to one for each carbon. R is H or an alkyl group. Also, k
= 1 to 100. ) 2. A membrane / electrode assembly for a polymer electrolyte fuel cell, wherein a gas diffusion electrode using the above-mentioned electrode catalyst coating material is used at least on a cathode side.

The components of the electrode catalyst coating composition of the present invention will be described below. First, for a perfluorosulfonic acid polymer having a structure represented by the general formula (1),
First, x = 0 to 2 can be used,
X = 1 is preferred because production and polymerization are easy. Also, n /
Although it can be used in the range of m = 1 to 10, it is easy to obtain a high molecular weight product, and it is easy to dissolve in a solvent.
2-7 are preferred. Therefore, "Nafion" manufactured by DuPont and "Aciplex-S" manufactured by Asahi Kasei Corporation
A conventionally used perfluorosulfonic acid polymer can be used as it is.

Next, the fluorine-containing ether compound represented by the general formula (2) will be described. In the general formula (2), Rf is a single or plural kinds of perfluoroalkylene groups having 1 to 3 carbon atoms. Specifically, -CF _2- ,
_{-CF 2 CF 2 -, - CF} 2 CF 2 CF 2 -, - CF 2
CF (CF ₃ ) — and the like, and two or more kinds may be mixed in the molecule. Among them, -CF ₂ CF (C
Those containing F ₃ ) — are particularly preferred. X and Y are perfluoroalkyl groups having 1 to 5 carbon atoms, and 1 to 5 carbon atoms.
Three are preferred and may contain double bonds.
Each carbon may be substituted with up to one group selected from H, Cl, Br, SO ₃ H, and COOR groups. R is H or an alkyl group, and in the case of an alkyl group, those having 1 to 3 carbon atoms are preferable. X and Y may be the same or different. To give a specific example, CF
_{3 -, CF 3 CF 2 -} , CF 3 CF 2 CF 2 -, CF 3
_{CHF-, CF 2 = CF-, CHF} 2 CHF-, CCl
F ₂ CCIF-, CBrF ₂ CBrF-, HOOCCF
_{2 -, CH 3 OOCCF 2 -} , HOOCCF (CF 3)
—, CH ₃ OOCCF (CF ₃ ) —, HO ₃ SCF ₂ C
_{F 2 -, HO 3 SCF 2} CF 2 CF 2 -, HO 3 S-C
And a group such as F (CF ₃ ) CF ₂ —. Of the compounds consisting of these combinations, since they are easily formed into a solution and easily mixed with a perfluorosulfonic acid polymer, at least one or two COOH groups or / and S
Compounds having an O ₃ H group are preferred. Specifically, the following compounds can be exemplified.

[0012]

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Among these compounds, compounds having no CH bond are more preferable because of excellent stability. The value of k is 1
However, if it is too large, mixing with the perfluorosulfonic acid polymer becomes difficult, or it becomes difficult to achieve compatibility, and therefore, it is preferably 50 or less, more preferably 30 or less. On the other hand, if the value of k is too small, the effect of addition is small. Particularly, in the case of a compound having a carboxylic acid group or a sulfonic acid group, the compound is easily dissolved in water, and thus is preferably 2 or more, more preferably 3 or more. In the case of a compound having a trifluorovinyl group in the molecule, it can be fixed by polymerizing after forming the catalyst layer.

By including such a fluorine-containing ether compound, an effect of increasing oxygen permeability can be obtained.
In addition, such a fluorinated ether compound also has an effect of promptly discharging generated water because it also has an appropriate water repellency, and it is presumed that it also contributes to improvement of performance when used as a fuel cell. . In the electrode catalyst coating material of the present invention, the content of the fluorine-containing ether compound represented by the general formula (2) is used in the range of 5 to 70% by weight. Preferably 10 to 60% by weight, more preferably 20 to 50% by weight.
% By weight. If the content is less than 5% by weight, the effect of addition is poor, and if it exceeds 70% by weight, it becomes too soft to maintain a stable catalyst layer.

As a method of using the composition as an electrode catalyst coating agent for a catalyst layer of a gas diffusion electrode, a solution of the composition is usually prepared by mixing a catalyst powder and a binder or the like added as necessary. And a method of forming a catalyst layer by shaping the mixture, and a method of impregnating a catalyst layer of a gas diffusion electrode formed in advance with a solution of the composition, and the like. Accordingly, the composition will generally be used as a solution. Further, a conventional gas diffusion electrode, that is, a catalyst layer formed using only the perfluorosulfonic acid polymer of the general formula (1) as an electrode catalyst coating agent is impregnated with a solution of a fluorine-containing ether of the general formula (2), A composition may be formed.

When the composition is used as a solution, the solvent may be methanol, ethanol, 1-propanol,
Lower alcohols such as 2-propanol and butanol,
2,2,2-trifluoroethanol, 2,2,3
Fluorinated alcohols such as 3,3-pentafluoropropanol, hexafluoroisopropanol, 2,2,3,3-tetrafluoropropanol, and a mixed solvent of those alcohols are used. Other fluorinated compounds such as hydrofluorocarbons and hydrofluoroethers, ether compounds, ketones, amides, nitrile compounds, dimethyl sulfoxide and the like may be used alone or as a mixed solvent, and furthermore, these alone or mixed solvents and water and May be used. The concentration of the composition solution may be any suitable concentration for forming the catalyst layer, and usually 3 to 20% by weight is used.

Since the electrode catalyst coating material of the present invention has a high oxygen gas permeability, its properties are exhibited when used on the cathode side. Therefore, it is essential to use it on the cathode side, but it may be used on the anode side. In addition, the electrode catalyst coating material as in the present invention is sometimes referred to as an electrode catalyst binder or a bonding material in terms of its function, and there is no clear distinction in the function corresponding to each name. It is included in the invention. That is, the electrode catalyst coating agent may be present only in a part of the catalyst layer, but is preferably present in the entire catalyst layer and also has a function as a binder. Further, when the coating agent is provided in a state of being in contact with the ion exchange membrane when the ion exchange membrane and the gas diffusion electrode are joined, the coating agent acts as a bonding material and joins the ion exchange membrane and the gas diffusion electrode. Power can be increased.

Next, a membrane / electrode assembly using the electrode catalyst coating agent of the present invention will be described. Explaining the constitution, first, as the ion exchange membrane, "Nafion" which is a uniform membrane of perfluorosulfonic acid polymer or "Aciplex-S" manufactured by Asahi Kasei Kogyo Co., Ltd. can be used. As the thickness of the ion exchange membrane, for example, 10 to 300
μm is used. If the ion exchange membrane is thinner than 10 μm, the strength at the time of film formation cannot be maintained, and if it is thicker than 300 μm, the resistance of the ion exchange membrane increases and the output characteristics during operation of the fuel cell deteriorate. The preferred thickness of the ion exchange membrane is 30 to 15
It is about 0 μm. If necessary, the membrane may be provided with a core material for reinforcement. Further, a porous film of polytetrafluoroethylene or the like doped with the above-mentioned perfluorosulfonic acid polymer can also be used.

The gas diffusion electrode used in the membrane / electrode assembly is made of a conductive material carrying fine particles of a catalyst metal, and contains a water repellent and a binder as necessary. Alternatively, a layer composed of a conductive material not carrying a catalyst and a water repellent or a binder contained as necessary may be formed outside the catalyst layer. The catalyst metal used for this gas diffusion electrode may be any metal that promotes the oxidation reaction of hydrogen and the reduction reaction of oxygen, for example, platinum, gold, silver, palladium, iridium, rhodium, ruthenium. , Iron, cobalt, nickel,
Chromium, tungsten, manganese, vanadium, or alloys thereof are mentioned. In such a catalyst,
In particular, platinum is often used. The particle size of the metal serving as a catalyst is usually from 10 to 300 angstroms. The supported amount of the catalyst is, for example, 0.01 in a state where the electrode is formed.
-10 mg / cm ² .

The conductive material may be any material as long as it is an electron conductive material, and examples thereof include various metals and carbon materials. Examples of the carbon material include carbon black such as furnace black, channel black, and acetylene black, activated carbon, and graphite. These may be used alone or in combination. As the water repellent, for example, fluorinated carbon or the like is used. As the binder, the catalyst coating agent of the present invention is preferably used as it is, but other various resins may be used. In that case, a fluorine-containing resin having water repellency is preferable, and those having excellent heat resistance and oxidation resistance are more preferable. For example, polytetrafluoroethylene, tetrafluoroethylene-perfluoroalkylvinyl ether copolymer, and tetrafluoroethylene -Hexafluoropropylene copolymer.

The bonding between the ion exchange membrane and the gas diffusion electrode is as follows:
It is carried out using a device that can be pressurized and heated. Generally, for example, it is performed by a hot press machine, a roll press machine or the like. The pressing temperature at this time may be any temperature as long as it is equal to or higher than the glass transition temperature of the ion exchange membrane.
50 ° C. The pressing pressure depends on the hardness of the gas diffusion electrode used, but is usually 5 to 200 kg / cm ² . If it is less than 5 kg / cm ² , the bonding between the ion exchange membrane and the electrode will be insufficient, and if it exceeds 200 kg / cm ² , the pores of the gas diffusion electrode will be crushed. A preferred range of the pressing pressure is 20 to 100 kg / cm ² .

The joined body of the ion-exchange membrane and the gas diffusion electrode formed as described above is inserted between two graphite flanges provided with a current collector, a gas inlet and a gas outlet, and is provided with a fuel. Assembled as a battery. here,
One gas diffusion electrode contains hydrogen gas as fuel, and the other gas diffusion electrode contains oxygen-containing gas (oxygen or air).
To operate as a fuel cell. It is desirable to operate the fuel cell at a high temperature because it increases the catalytic activity of the electrode and reduces the electrode overvoltage.However, the ion exchange membrane serving as the electrolyte does not function without moisture, so it operates at a temperature that allows moisture management. Need to be done. A preferred range of the operating temperature of the fuel cell is from room temperature to 100 ° C. As described above, the electrode catalyst coating material of the present invention exhibits excellent performance when used for a gas diffusion electrode of a polymer electrolyte fuel cell. It is not always clear whether this performance improvement is due solely to high oxygen gas permeability, but even when air is used as the oxidizing agent, it is industrially preferable because a higher output voltage can be obtained compared to conventional materials. .

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in more detail with reference to the following examples.

EXAMPLES <Example 1> (Synthesis of fluorinated ether compound (3)) A mixture (1 layer separation) of 12.5 g of the following acid fluoride (manufactured by PCR) and 50 ml of ether (separated into two layers) was stirred under ice-cooling. 20ml
Of water was added dropwise. During the dropping, the solution once became a homogeneous solution, and then separated into two layers again.

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After the completion of the dropwise addition, stirring was continued for 3 hours, followed by liquid separation, and the aqueous phase was extracted three times with ether. The ether phase was collected, washed twice with a saturated saline solution, and then the ether was distilled off to obtain 12.6 g of a colorless oil. From NMR and IR spectra, it was confirmed that the compound was a fluorine-containing ether compound containing a carboxylic acid represented by the following formula (3).

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(Measurement of oxygen gas permeability) Exchange capacity 950
g / equivalent of perfluorosulfonic acid polymer (Aciplex-S, manufactured by Asahi Kasei Kogyo Co., Ltd.) at a concentration of 5% by weight in a mixed solvent of n-propanol and 2,2,3,3,3-pentafluoropropanol (A weight ratio of 1: 1), a fluorine-containing ether compound of the above formula (3)
It was added so that the weight ratio of the polymer and the ether compound was 8: 2 to obtain a uniform solution. This solution was spread on a Petri dish, air-dried, and then vacuum-dried at 80 ° C. to a film thickness of 42 μm.
Was produced. After immersing this film in water, the water on the surface was wiped off, and the oxygen gas transmission rate was measured using a flow type gas transmission rate measuring system (GTR-100FA manufactured by YANACO). As a result, when the test gas was humidified air and the cell temperature was 40 ° C., the oxygen gas permeability coefficient was 5.0 × 10 ⁻⁹ cc · cm / cm ² · sec · cmHg. For comparison, the measured value of a film made of only the perfluorosulfonic acid polymer prepared without adding the above-mentioned fluorine-containing ether compound was 2.5 × 10 ⁻⁹ cc · cm / cm ² · sec.
-It was cmHg.

(Preparation of Membrane / Electrode Assembly) The above solution was mixed with 40% by weight of a platinum catalyst-supporting carbon (manufactured by E-TEK, USA) at a weight ratio of a platinum catalyst, a polymer and a fluorine-containing ether compound of 2: 1 to obtain a paste. This paste was applied on a Teflon sheet using a 200-mesh screen so as to have a catalyst area of 2 cm × 2 cm.
Dry and fix at 00 ° C, platinum loading 0.25mg / c
m ² of catalyst sheet was obtained. The catalyst layers of the two catalyst sheets face each other, and a perfluorosulfonic acid polymer membrane (Aciplex-S1004, manufactured by Asahi Kasei Kogyo Co., Ltd.) having an exchange capacity of 950 g / equivalent, a thickness of 100 μm, and a membrane area of 3 cm × 3 cm is placed therebetween. Scissors, 150 ° C, pressure 50kg /
After hot pressing in cm ² , the Teflon sheets on both sides were peeled off to produce a membrane / electrode assembly.

As a catalyst layer support, a carbon cloth (manufactured by E-TEK) having a thickness of about 400 μm was used, immersed in a Teflon dispersion (60% by weight), and then sintered at 340 ° C. to form a carbon cloth. On the other hand, it was impregnated with 40% by weight. The porosity was 50%. The membrane / electrode assembly and the catalyst layer support are laminated and incorporated into a fuel cell single cell evaluation apparatus. A single cell characteristic test is performed at normal pressure and a cell temperature of 80 ° C. using hydrogen gas as fuel and air as oxidant. went. The hydrogen gas was humidified at 90 ° C., and the air was supplied to the cell without humidification. As a result, the cell output voltages at the current densities of 0.5 and 1.0 A / cm ² were 0.65 V, respectively.
It was 0.50V.

<Example 2> A mixed solution of a perfluorosulfonic acid polymer and a fluorine-containing ether compound of the above formula (3) was prepared in the same manner as in Example 1 except that the weight ratio of the polymer to the ether compound was 6: 4. When a film was prepared similarly and the oxygen gas permeability was measured, the oxygen gas permeability coefficient was 6.5 × 10 ⁻⁹ cc · cm / cm ² · sec · cmHg.
Further, a membrane / electrode assembly was prepared using the solution of the composition, and a single cell characteristic test was performed.
The cell output voltage at a current density of / cm ² was 0.66 V and 0.57 V, respectively.

Example 3 (Synthesis of Fluorinated Ether Compound (5)) After mixing sulfuric anhydride (SO ₃ ) and tetrafluoroethylene in a pressure vessel, the product was distilled (boiling point: 42 ° C.). 2-hydroxytetrafluoroethanesulfonic acid sultone was obtained. A small amount of triethylamine was added to the 2-hydroxytetrafluoroethanesulfonic acid sultone in an ice-cooled state to open the ring, thereby synthesizing fluorosulfonyldifluoroacetyl fluoride (FOCCF ₂ SO ₂ F). Next, 50 g of fluorosulfonyldifluoroacetyl fluoride, 6.0 g of dry cesium fluoride, and 50 ml of dry diglyme were put into a pressure-resistant container, and about 380 g of hexafluoropropylene oxide was injected several times while cooling with ice. Reaction at 0 ° C. for 8 hours, boiling point to 100 ° C.
32 g of a / 3 mmHg component was obtained. NMR of methyl ester obtained by reacting a part of the product with methanol,
From the IR spectrum, it was confirmed that the compound was the compound of the following formula (4).

Embedded image

40% based on 5.0 g of the above compound (4)
5 g of an aqueous NaOH solution was added, and the mixture was stirred at 100 ° C. for 5 hours.
Subsequently, the mixture was stirred at 190 ° C. for 5 hours. After cooling to room temperature,
Acidified with 35% sulfuric acid and extracted with ether. The ether phase was concentrated to obtain 3.2 g of a light brown oil. NMR,
From the IR spectrum, it was confirmed that the compound was a fluorine-containing ether compound represented by the following formula (5). The value of n was confirmed again by NMR.

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(Measurement of Oxygen Gas Permeability and Preparation of Membrane / Electrode Assembly) The above-mentioned formula (5) was used as a fluorine-containing ether compound.
A film was prepared and the oxygen gas permeability was measured in the same manner as in Example 1 except that the compound of the formula (1) was used. The oxygen gas permeability coefficient was 5.7 × 10 ⁻⁹ cc · cm / cm ² · sec · cmHg. there were. Further, a membrane / electrode assembly was prepared using the solution of the composition, and a single cell characteristic test was performed.
The cell output voltage at a current density of A / cm ² was 0.68 V and 0.54 V, respectively.

Example 4 In a mixed solution of a perfluorosulfonic acid polymer and a fluorinated ether compound of the above formula (5), the weight ratio of the polymer to the ether compound was changed to 6: 4. When a film was prepared in the same manner and the oxygen gas permeability was measured, the oxygen gas permeability coefficient was 1.9 × 10 ⁻⁸ cc · cm / cm ² · sec · cmHg. Further, a membrane / electrode assembly is prepared using the solution of the composition,
When a single cell characteristic test was performed, it was found that 0.5, 1.0 A / c
The cell output voltage at a current density of m ² is 0.6
9V and 0.58V.

Example 5 (Synthesis of Fluorinated Ether Compound (6)) 5.0 g of the compound of the above formula (4) synthesized in Example 3 was dissolved in 10 ml of perfluorohexane, and a 40% aqueous NaOH solution was prepared. After adding 5 g and stirring at room temperature for 1 hour, reflux temperature (6.
(5 ° C.) for 5 hours. After cooling to room temperature, a white solid obtained by filtration was dissolved in ethanol, insolubles were removed by filtration, and the filtrate was concentrated to obtain a white powder. The resulting powder was acidified with 35% sulfuric acid, extracted with ether, and the ether phase was concentrated to obtain 2.9 g of a light brown oil. NMR,
From the IR spectrum, it was confirmed that the compound was a fluorine-containing ether compound represented by the following formula (6).

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(Measurement of Oxygen Gas Permeability and Preparation of Membrane / Electrode Assembly) As a fluorine-containing ether compound, the above formula (6)
A film was prepared and oxygen gas permeability was measured in the same manner as in Example 1 except for using the compound of formula (1). The oxygen gas permeability coefficient was 5.8 × 10 ⁻⁹ cc · cm / cm ² · sec · cmHg. there were. Further, a membrane / electrode assembly was prepared using the solution of the composition, and a single cell characteristic test was performed.
The cell output voltage at a current density of A / cm ² was 0.68 V and 0.55 V, respectively.

<Example 6> In the mixed solution of the perfluorosulfonic acid polymer and the fluorinated ether compound of the above formula (6), the weight ratio of the polymer to the ether compound was changed to 6: 4. When a film was prepared similarly and the oxygen gas permeability was measured, the oxygen gas permeability coefficient was 2.7 × 10 ⁻⁸ cc · cm / cm ² · sec · cmHg. Further, a membrane / electrode assembly is prepared using the solution of the composition,
When a single cell characteristic test was performed, it was found that 0.5, 1.0 A / c
The cell output voltage at a current density of m ² is 0.7
0V and 0.59V.

Example 7 (Synthesis of Fluorine-Containing Ether Compound (7)) 10 g of the compound of the above formula (4) synthesized in Example 3 was immediately heated to 180 ° C.
After dropping into 10 g of potassium carbonate vacuum-dried with
Heated at 0 ° C. for 2 hours and further heated at 190 ° C. for 2 hours. After cooling to room temperature, water was added, and the mixture was extracted with ether. After the ether was distilled off, the obtained oil was dissolved in 20 ml of perfluorohexane, 10 g of a 40% aqueous NaOH solution was added, and the mixture was stirred at room temperature for 1 hour. After that, the mixture was stirred at a reflux temperature (65 ° C.) for 5 hours. After cooling to room temperature, a white solid obtained by filtration was dissolved in ethanol, insolubles were removed by filtration, and the filtrate was concentrated to obtain a white powder. The resulting powder was acidified with 35% sulfuric acid and extracted with ether, and the ether phase was concentrated to obtain 4.5 g of a light brown oil. NM
From the R and IR spectra, it was confirmed that the compound was a fluorine-containing ether compound represented by the following formula (7).

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(Measurement of Oxygen Gas Permeability and Preparation of Membrane / Electrode Assembly) As a fluorine-containing ether compound, the above formula (7)
A film was prepared and the oxygen gas permeability was measured in the same manner as in Example 2 except that the compound of the formula (1) was used. The oxygen gas permeability coefficient was 1.2 × 10 ⁻⁸ cc · cm / cm ² · sec · cmHg. there were. Further, a membrane / electrode assembly was prepared using the solution of the composition, and a single cell characteristic test was performed.
The cell output voltage at a current density of A / cm ² was 0.68 V and 0.57 V, respectively.

Example 8 (Synthesis of Fluorinated Ether Compound (8)) 2.0 g of the compound of the above formula (7) synthesized in Example 7 was dissolved in 10 ml of carbon tetrachloride, and chlorine gas was added at room temperature. Was infused.
After the reaction, the solvent was distilled off to obtain 2.2 g of a light brown oily substance. From NMR and IR spectra, it was confirmed that the compound was a fluorine-containing ether compound represented by the following formula (8).

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(Measurement of Oxygen Gas Permeability and Preparation of Membrane / Electrode Assembly) As a fluorine-containing ether compound, the above formula (8)
A film was prepared and the oxygen gas permeability was measured in the same manner as in Example 2 except that the compound of the formula (1) was used. The oxygen gas permeability coefficient was 1.7 × 10 ⁻⁸ cc · cm / cm ² · sec · cmHg. there were. Further, a membrane / electrode assembly was prepared using the solution of the composition, and a single cell characteristic test was performed.
The cell output voltage at a current density of A / cm ² was 0.69 V and 0.58 V, respectively.

Comparative Example 1 A membrane / electrode assembly was prepared in the same manner as in Example 1 except that the fluorine-containing ether compound was not added, and a single cell characteristic test was performed. As a result, 0.5, 1.
The cell output voltages at a current density of 0 A / cm ² were 0.60 V and 0.44 V, respectively.

[0041]

When the electrode catalyst coating material of the present invention is used for a gas diffusion electrode of a polymer electrolyte fuel cell, a higher output voltage can be obtained when air is used as an oxidizing agent than conventional materials. Therefore, the membrane using the electrode catalyst coating agent of the present invention /
The electrode assembly is also superior to the conventional one.

Claims (2)

[Claims] 1. A membrane / electrode assembly for a polymer electrolyte fuel cell, comprising an ion exchange membrane serving as an electrolyte and a gas diffusion electrode joined to the ion exchange membrane, used for the gas diffusion electrode. A perfluorosulfonic acid polymer represented by the general formula (1)
An electrode catalyst coating comprising a composition containing 0 to 95% by weight and a fluorine-containing ether compound represented by the general formula (2) in a range of 5 to 70% by weight. Embedded image (Where x is an integer of 0 to 2, y is an integer of 2 to 3, n /
m = 1 to 10. ) (Where Rf is a single or plural kinds of carbon atoms having 1 to 1
Three perfluoroalkylene groups, X and Y each have 1 to 1 carbon atoms
5 perfluoroalkyl groups, which may contain double bonds, wherein each carbon has H, Cl, Br, SO ₃ H, CO
A group selected from an OR group may substitute up to one for each carbon. R is H or an alkyl group. Also, k
= 1 to 100. ) 2. A membrane / electrode assembly for a polymer electrolyte fuel cell, wherein a gas diffusion electrode using the electrode catalyst coating agent according to claim 1 is used at least on a cathode side.