JP2003203648A - Solid polymer electrolyte compound membrane, membrane /electrode joint body, solid polymer fuel cell using the sam - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a solid polymer electrolyte compound membrane that has superior ion conductivity and mechanical property. <P>SOLUTION: This is a solid polymer electrolyte compound membrane that has reinforced to the inside the ion conductive polymer electrolyte with a sulfonized ion conductive polymer porous body. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a solid polymer electrolyte composite membrane, a membrane / electrode assembly, and a solid polymer fuel cell (hereinafter abbreviated as PEFC) using the same.

[0002]

2. Description of the Related Art In recent years, fuel cells have been attracting attention due to their characteristics of low pollution and high efficiency. The fuel cell is a cell in which a fuel such as hydrogen, propane, natural gas, or methanol is electrochemically oxidized by using oxygen or air to convert the chemical energy of the fuel into electric energy and take it out. Such fuel cells are classified into a phosphoric acid type, a molten carbonate type, a solid oxide type, a solid polymer electrolyte type, etc., depending on the type of electrolyte used. this house,
PEFCs that use ion exchange membranes as electrolyte membranes have recently received special attention because they operate at low temperatures, have high output density, and can be miniaturized. They are household distributed power sources, commercial distributed power sources, and mobile power sources for automobiles. Development is proceeding at a rapid pace to be applied to the above.

Polyperfluorocarbon sulfonic acid electrolyte membranes are commercially available as electrolyte membranes for polymer electrolyte fuel cells, and typical examples thereof include Nafion (registered trademark: manufactured by Dupont, USA) and Aciplex (registered trademark: Asahi Kasei Corporation). Manufactured by Asahi Glass Co., Ltd., and the like.

In order to spread PEFC in earnest,
Significant performance improvement, long life, and cost reduction are essential. The polyperfluorocarbon sulfonic acid electrolyte membrane requires a fluorine chemical process and is a superfine chemical material whose use is limited to salt electrolysis and fuel cell applications, so that it is difficult to significantly reduce the cost.

A partially fluorinated film (US Pat. No. 4,012,303, US Pat. No. 4,605,68) for the purpose of cost reduction.
5, JP-A-9-102322, JP-A-9-10
2322), sulfonated polyether ether ketone (JP-A-6-93114), sulfonated polyether sulfone (JP-A-9-245818, JP-A-11-111116679), sulfonated polysulfide (Special Table). No. 11-510198),
Sulfonated polyphenylene (Special table 11-515550
A general-purpose engineered plastic electrolyte membrane such as that disclosed in Japanese Patent No. 40) has been proposed.

In order to improve the performance of PEFC by increasing the efficiency and the output density, it is necessary to reduce the ionic conductivity resistance of the solid polymer electrolyte membrane and improve the ionic conductivity.

There are two methods for reducing the ionic conductivity resistance of the solid polymer electrolyte membrane: improving the ionic conductivity by increasing the concentration of sulfonic acid groups and reducing the film thickness. When the concentration of the sulfonic acid group is increased, the toughness of the film is lowered, and in addition, it becomes soluble in water, which causes problems.

On the other hand, reducing the film thickness lowers the mechanical strength of the film,
This causes problems such as reduced workability and handleability.

In order to solve the above problems, various attempts have been made to reinforce the electrolyte membrane with a reinforcing material. For example, a reinforcing method using a polymeric porous material such as a woven cloth or a non-woven cloth made of a fluoropolymer such as polytetrafluoroethylene (PTFE) (JP-A-53-56192 and JP-A-58).
-37186, JP-A-58-37187,
JP-A-6-231779, etc.), after impregnating a porous film with a solution of a fluoropolymer having a functional group,
Reinforcing method of drying and heat treatment (JP-A-6-342666), reinforcement method of mixing PTFE fibrils with a fluorine-containing cation exchange resin having a sulfonic acid group or a carboxylic acid group (JP-A-53-14988). JP-A-5
4-1283, JP-A-54-107479, JP-A-54-157777, and JP-A-2001-2001.
No. 35508) has been tried.

Attempts to mechanically mix a fluoropolymer having a sulfonic acid group or its precursor with a carboxylic acid group or its precursor (Japanese Patent Publication No. 62-7217, Japanese Patent Publication No. 60-17034, Kaisho 62-53341
Japanese Patent Publication No. 59-15934).

Strengthening the adhesion between the reinforcing material and the solid polymer electrolyte having a sulfonic acid group or a carboxylic acid group,
Treatment of the reinforcing material with a surfactant for the purpose of improving mechanical strength (JP-A-6-231779), modification of the surface of the reinforcing material by radiation, discharge, chemicals or graft polymerization method (JP-A-2000-231928). ) Is being tried.

The reinforcement of the reinforcing material improves the mechanical strength of the electrolyte membrane. However, since the reinforcing material itself has a low ionic conductivity, the reinforced electrolyte membrane has a low ionic conductivity, and the effect of reducing the ionic conduction resistance due to the reduction in the film thickness is small. Therefore, the advent of a reinforcing method that reduces the decrease in ionic conductivity has been strongly desired.

Further, a reinforcing method for forming a microphase-separated structure by compatibilizing two or more kinds of fluoropolymers having an acidic functional group or the precursor in a molten state and lowering the temperature (JP-A-2000-222938). Japanese Patent Laid-Open No. 2000-
No. 294034) has been studied. However, this method does not sufficiently improve the mechanical strength, and a means for simultaneously achieving the strength improvement and the retention or reduction of the ionic conduction resistance has been desired.

[0014]

DISCLOSURE OF THE INVENTION An object of the present invention is to provide a solid polymer electrolyte composite membrane which is a high-strength thin film and has a low ionic conduction resistance, the membrane / electrode assembly, and a long-term output using the same It is to provide a polymer electrolyte fuel cell having a high density.

[0015]

In view of the above situation, the present inventors have made the present invention as a result of investigating that the reinforcing material is provided with ion conductivity to the inside.

The present invention is a thin film reinforced with a polymeric porous material such as woven cloth, nonwoven cloth, fibril, porous film, sponge-like, granular, whisker-like, etc., which has been imparted with ion conductivity. It was possible to obtain a solid polymer electrolyte composite membrane having a low conduction resistance, the membrane / electrode assembly, and a solid polymer fuel cell using the same and having a high output density for a long period of time.

In the present invention, the polymeric porous material used as a reinforcing material is not particularly limited as long as it is a polymeric porous material that reinforces the electrolyte membrane, has ion conductivity, and has a melting point higher than the operating temperature of the fuel cell. There is no.

As the material for such a polymer porous material, polyfluorocarbon, polyethylene, polypropylene, polyisobutylene, polyalicyclic olefin, polyoxymethylene, polysulfone, polyether sulfone, polyether ether sulfone, polyphenylene sulfide,
Polyetheretherketone, polyparaphenylenebenzbisthiazole, polyparaphenylenebenzbisoxazole, polybenzimidazole, polyparaamide,
There are materials obtained by imparting ionic conductivity to polymers such as polymethamide and phenol resin. Examples of the polymer having ionic conductivity added to polyfluorocarbon include tetrafluoroethylene, hexafluoropropylene, chlorotrifluoroethylene, and perfluoroolefin homopolymers such as perfluoroalkoxy vinyl ether, and sulfonates of copolymers. .

Specific examples thereof include polytetrafluoroethylene (PTFE), polytetrafluoroethylene-hexafluoropropylene (FEP), polytetrafluoroethylene-perfluoropropyl vinyl ether (PFA), polychlorotrifluoroethylene and polytetrafluoroethylene. Examples thereof include sulfonated products such as ethylene-perfluoro-2,2-dimethyl-1,3-dioxole and polyperfluorobutenyl vinyl ether.

The sulfonic acid equivalent of the sulfonated polymer, that is, the ion exchange capacity is 0.2 to 1.5 meq / g dry resin, and further 0.5 to 1.2 meq / g.
A range of g dry resin is preferred.

When the sulfonic acid equivalent is lower than this range, the ionic conduction resistance becomes large, and when it is high, it is easily dissolved in water, which is not preferable.

It is preferable that the electrolyte material and the reinforcing material are materials of the same system, from the viewpoint of compatibility such as adhesiveness between the two and life. That is, a sulfonated product of a perfluorocarbon polymer such as PTFE, FEP or PFA is preferable for the polyperfluorocarbon sulfonic acid electrolyte in terms of characteristics. For aromatic hydrocarbon electrolyte membranes, polysulfone, polyether sulfone, polyether ether sulfone, polyphenylene sulfide, polyether ether ketone, polyparaphenylene benzbis thiazole, polyparaphenylene benzbisoxazole, polybenzimidazole Sulfonates are preferable in terms of properties.

The polymer porous body made of such a material is not particularly limited as long as it has a shape capable of being combined with an electrolyte material. Examples of such shapes include a film shape, a fibril shape, a woven cloth shape, a non-woven cloth shape, a sponge shape, a granular shape, and a whisker shape.

As a method for compositing the polymer porous material and the electrolyte material, a casting method of impregnating the polymer porous material with a solution or dispersion of an electrolyte membrane material, followed by drying and film formation, or a method of forming an electrolyte membrane A method of molding a polymer porous body by heat melting, specifically, a continuous method such as a batch method such as a flat plate press or a vacuum press or a continuous roll pressing method, an electrolyte membrane material forming a cation exchange membrane, and a polymer porous body. After mixing
Examples include a method of extrusion film formation.

The method for imparting ionic conductivity to the reinforcing material is sulfuric anhydride, fuming sulfuric acid, fuming sulfuric acid / triethyl phosphate complex,
A method of treating with chlorosulfuric acid, sulfuric acid, etc. may be mentioned. It may be heated to impart ionic conductivity to the inside of the reinforcing material.

If the reinforcing material in the portion adjacent to the electrolyte solution has high ionic conductivity, that portion is likely to dissolve in water, which is not preferable. It is important to make the ionic conductivity of the part of the reinforcing material adjacent to the electrolyte solution and the part far from the electrolyte solution as uniform as possible.

There are a method of imparting ion conductivity to the reinforcing material before forming the shape of the porous polymer body and a method of imparting ion conductivity to the reinforcing material after forming the shape of the porous polymer body.
The latter is more cost effective because a general-purpose polymer porous material can be used.

The electrolyte membrane material used in the present invention is not particularly limited as long as it is an electrolyte having ion conductivity. Examples of such a material include a fluorine-based electrolyte membrane material, a partial fluorine-based electrolyte membrane material, and a hydrocarbon-based electrolyte membrane material.

As the fluorine-based electrolyte membrane material used in the present invention, conventionally known polymers are widely adopted. Formula _{CF 2 = CF- (OCF 2 CFX} ) m -O q - (CF 2) n -
A (in the formula, m = 0 to 3, n = 0 to 12, q = 0 or 1, X
= F or CF ₃ , A = sulfonic acid type functional group), and a copolymer of a fluorovinyl compound represented by the formula: tetrafluoroethylene, hexafluoropropylene, chlorotrifluoroethylene, or perfluorolefin such as perfluoroalkoxy vinyl ether. To be

Preferred examples of the fluorovinyl compound include the following. [Chemical Formula 1] CF ₂ ═CFO (CF ₂ ) _a SO ₂ F CF ₂ ═CFOCF ₂ CF (CF ₃ ) O (CF ₂ ) _a SO ₂ F CF ₂ ═CF (CF ₂ ) _b SO ₂ F CF ₂ ═ _{CF (OCF 2 CF (CF 3} )) cO (CF 2) 2 SO 2
F (however, a shows 1-8, b shows 0-8, c shows the integer of 1-5).

As the hydrocarbon-based electrolyte membrane material used in the present invention, sulfone such as sulfonated polyether ether ketone, sulfonated polyether sulfone, sulfonated polyether polyether sulfone, sulfonated polysulfone, sulfonated polysulfide, sulfonated polyphenylene, etc. Engineered sulfoalkylated plastic electrolyte membrane, sulfoalkylated polyetheretherketone, sulfoalkylated polyethersulfone, sulfoalkylated polyetherethersulfone, sulfoalkylated polysulfone, sulfoalkylated polysulfide, sulfoalkylated polyphenylene, etc. Examples include plastic electrolyte membranes.

The sulfonic acid equivalent of the electrolyte membrane material is 0.5 to 2.0 meq / g dry resin, and further 0.7.
A range of up to 1.6 meq / g dry resin is preferred. When the sulfonic acid equivalent is lower than this range, the ionic conduction resistance of the membrane becomes large, and when it is high, it is easily dissolved in water, which is not preferable.

The gas diffusion electrode used in the membrane / electrode assembly when used as a fuel cell is composed of a conductive material carrying fine particles of a catalytic metal and, if necessary, a water repellent or a binder. A binder may be included.

Further, a layer composed of a conductive material which does not carry a catalyst and a water repellent or a binder which is contained as necessary may be formed outside the catalyst layer. The catalyst metal used for this gas diffusion electrode may be any metal as long as it 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,
Examples thereof include tungsten, manganese, vanadium, and alloys of these.

Of these catalysts, platinum is often used. The particle size of the catalyst metal is usually 10
~ 300 Angstroms. It is more cost effective to attach these catalysts to a carrier such as carbon because the amount of the catalyst used is small. The supported amount of the catalyst is preferably 0.01 to 10 mg / cm ² when the electrode is molded.

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, graphite and the like, and these can be used alone or in combination.

As the water repellent, for example, fluorinated carbon can be used, and as the binder, it is preferable to use the solution of the electrolyte composite membrane of the present invention as it is from the viewpoint of adhesiveness, but various other resins are used. It doesn't matter.

Further, a fluorine-containing resin having water repellency, for example, polytetrafluoroethylene, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, or
A tetrafluoroethylene-hexafluoropropylene copolymer may be added.

There is no particular limitation on the method of joining the electrolyte composite membrane and the electrode when it is used as a fuel cell, and known methods can be applied.

As a method for producing the membrane / electrode assembly, for example, Pt catalyst powder supported on carbon is mixed with a polytetrafluoroethylene suspension, coated on carbon paper and heat-treated to form a catalyst layer. Then, there is a method in which the same electrolyte solution as that of the electrolyte composite membrane is applied to the catalyst layer and the electrolyte membrane is integrated with the hot press. In addition, a method of coating the same electrolyte solution as the electrolyte composite membrane on Pt catalyst powder in advance, a method of applying a catalyst paste to the electrolyte composite membrane,
There are a method of electroless plating an electrode on an electrolyte composite membrane, a method of adsorbing a platinum group metal complex ion on the electrolyte composite membrane, and then reducing it.

A solid polymer electrolyte fuel cell is a current collector with a groove for forming a fuel flow path and an oxidant flow path, which is provided outside a joined body of an electrolyte composite membrane formed as described above and a gas diffusion electrode. The fuel distribution plate (separator) as a body and the oxidant distribution plate (separator) are arranged to form a single cell, and a plurality of the single cells are laminated via a cooling plate or the like.

It is better to operate the fuel cell at high temperature.
It is desirable because the catalytic activity of the electrode increases and the electrode overvoltage decreases, but since the electrolyte composite membrane does not function without water,
It must be operated at a temperature that allows water management. The preferable operating temperature range of the fuel cell is room temperature to 100 ° C.

[0043]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described based on examples. The measurement conditions for each physical property are as follows.

(1) Sulfonic Acid Equivalent The sulfonated sample was precisely weighed (a: gram) in a glass container capable of being sealed, an excess amount of calcium chloride aqueous solution was added thereto, and the mixture was stirred overnight. Hydrogen chloride generated in the system was adjusted to 0.1N sodium hydroxide standard aqueous solution (f: titer f)
Then, titrate with phenolphthalein as an indicator (b:
ml). The sulfonic acid equivalent (equivalent / g) was calculated from the formula [1]. [Equation 1] Sulfonic acid equivalent = (0.1 × b × f) / a ... [1] (2) Tensile strength An electrolyte membrane or an electrolyte composite membrane is cut into a strip shape with a width of 10 mm, and is cut into 3% hydrogen peroxide solution. Boil for 1 hour, in distilled water for 1 hour, and then in a 1 molar aqueous solution of sulfuric acid for 1 hour,
A pretreatment of boiling for 1 hour was performed in distilled water. According to JIS K7127, the tensile strength was measured using an autograph with a chuck-to-chuck distance of 50 mm in conformity with JIS K7127 in the water-containing state.

Evaluation test piece Stress S acting on the film (kg / m
m ² ) was obtained from the following equation [2], where W (kg) is the applied load and A ₀ (mm ² ) is the cross-sectional area before applying the applied load. [Equation 2] S (kg / mm ² ) = W / A ₀ (2) (3) Dimensionally stable electrolyte membrane or electrolyte composite membrane was pretreated in the same manner as (2) above. 10 cm of this electrolyte membrane or electrolyte composite membrane
A test piece was cut into a corner. This sample piece at 25 ℃, 50
After being kept under the condition of% RH for 24 hours, the film size (L ₀ ) at a predetermined position was measured.

Next, this sample piece was immersed in ion-exchanged water at 80 ° C. for 24 hours, the membrane size (L ₁ ) at the same position as above was measured, and the dimensional change rate (ΔL) was calculated by the following formula [3]. did. [Equation 3] ΔL (%) = (L ₁ −L ₀ ) / L ₁ × 100 (3) (4) Creep characteristics The electrolyte membrane or the electrolyte composite membrane was pretreated in the same manner as in the above (2). Width of this electrolyte membrane or electrolyte composite membrane is 10 m
was cut into m strip, distance between chucks 50mm using the creep tensile tester conforming to JIS K 7115, with a load 0.5 kg / mm ² and 0.21 kg / mm ^2, the amount of displacement of the aging Was measured continuously. In addition, the operation state of the fuel cell was simulated, and the experiment was performed under the conditions of 80 ° C. and 95% RH.

(5) Evaluation of Fuel Cell Single Cell Output Performance An electrolyte composite membrane having electrodes bonded thereto was incorporated into an evaluation cell to evaluate the fuel cell output performance. Hydrogen / oxygen was used as a reaction gas, and both were pressurized at a pressure of 1 atm through a water bubbler at 23 ° C and then supplied to an evaluation cell. Gas flow rate is hydrogen 6
0 ml / min, oxygen 40 ml / min, cell temperature is 7
It was set to 0 ° C. The battery output performance was evaluated by a H201B charging / discharging device (manufactured by Hokuto Denko KK).

Example 1 (1) Preparation of Electrolyte Composite Membrane A porous polytetrafluoroethylene film having a thickness of 20 μm and a porosity of 95% was kept in 100% anhydrous sulfuric acid gas at 100 ° C. for 24 hours to perform sulfone. Turned into The obtained film was washed 3 times with boiling distilled water, and then the sulfonic acid equivalent was measured. As a result, the sulfonic acid equivalent is 0.7 meq / g
Met. ESCA (Electron Spectroscopy for C
When the sulfur atom S in the thickness direction was measured by a sputtering method by chemical analysis, absorption of the sulfur atom was recognized up to the central portion.

On the sulfonated polytetrafluoroethylene porous film, an aqueous solution of 5 wt% perfluorocarbon sulfonic acid (sulfonic acid equivalent 0.9 meq / g) in isopropyl alcohol (manufactured by Aldrich Chemical Co.)
Was impregnated and dried at 60 ° C. Then 5 at 140 ℃
The film was heat treated for minutes. This was repeated until the pinholes disappeared, that is, impregnation, drying and heat treatment were repeated 6 times.

Then, it was immersed in 1N sulfuric acid at 60 to 70 ° C. for 1 hour and in pure water at 60 to 70 ° C. for 1 hour to convert the terminal groups of the side chains of the electrolyte into —SO ₃ H. The obtained electrolyte composite membrane I had an ionic conductivity of 0.15 S / cm and a tensile strength of 3.5 kg / mm ² .

The ionic conductivity and the tensile strength of the electrolyte composite membrane I of this example are the same as those of the electrolyte composite membrane I'of Comparative Example 1 reinforced by a polytetrafluoroethylene porous film which is not subjected to the sulfonation treatment described later. Significantly superior to no electrolyte membrane.

The periphery of the electrolyte composite membrane I was fixed with a SUS metal frame and kept at 80 ° C. and 95% RH for 1.5 hours.
An environmental cycle simulating a fuel cell environment in a high temperature wet condition and a room temperature dry condition, which was maintained at 50 ° C and 50% RH for 1.5 hours, was added 500 times. Electrolyte composite membrane I after environmental testing cycle I
The tensile strength of was the same as the initial one.

On the other hand, as described below, the electrolyte composite membrane I'of Comparative Example 1 reinforced with the polytetrafluoroethylene porous film which was not subjected to the sulfonation treatment and the electrolyte membrane which was not reinforced were each at the initial 1 after the environmental test cycle. / 3, 1 /
It had dropped to 10. From this, it is clear that the electrolyte composite membrane I is superior to the electrolyte composite membrane I ′ of Comparative Example 1 and the electrolyte membrane without reinforcement.

When the electrolyte composite membrane I kept at 25 ° C. and 50% RH for 24 hours was immersed in ion exchange water at 80 ° C. for 24 hours, the dimensional change rate in the plane direction was 1.5%. On the other hand, as described later, the dimensional change rate of the electrolyte composite membrane I ′ of Comparative Example 1 reinforced with the non-sulfonation-treated polytetrafluoroethylene film was 2.0%, and the dimensional change rate of the non-reinforced electrolyte membrane was 14%. there were. From this, it is clear that the electrolyte composite membrane I is superior to the electrolyte composite membrane I ′ of Comparative Example 1 and the electrolyte membrane that is not reinforced.

In addition, the fuel cell operating state is simulated to 80
The creep strain when a load of 0.5 kg / mm ² was applied for 50 hours under the conditions of ℃ and 95% RH was 15%, and 1 of Comparative Example 1 reinforced with a non-sulfonation-treated polytetrafluoroethylene film described later. / 2, which is as small as 1/12 of the unreinforced electrolyte membrane, which is excellent.

From the above, it is clear that when the electrolyte membrane is reinforced with a non-sulfonated polymer porous body, the tensile strength, the dimensional change rate and the creep resistance are improved, but the ionic conductivity is lowered. A major issue is to achieve both good characteristics and ionic conductivity.

When reinforced to the inside with a sulfonated polymer porous material, mechanical properties such as mechanical strength, dimensional stability, and creep resistance, which cannot be achieved with a non-sulfonated polymer porous material, and ionic conductivity. It is clear that both are compatible.

(2) Preparation of membrane / electrode assembly 40% by weight of platinum-supported carbon was dispersed in an isopropanol solution, and then 5% by weight of perfluorocarbon sulfonic acid (sulfonic acid equivalent: 0.9 meq / g) isopropyl. Alcohol aqueous solution (Aldrich Chemical Co.)
Was added so that the weight ratio of the platinum catalyst and the polymer electrolyte was 2: 1 and was uniformly dispersed by ultrasonic waves to prepare a paste (electrode catalyst coating solution). After applying this electrode catalyst coating solution on both sides of the electrolyte composite membrane I obtained in (1) above,
After drying, a membrane / electrode assembly I having a platinum loading of 0.25 mg / cm ² was prepared.

The periphery of the membrane / electrode assembly I was fixed with a SUS metal frame and kept at 80 ° C. and 95% RH for 1.5 hours.
An environmental cycle of a high temperature wet state and a room temperature dry state, in which the temperature was kept at 50% RH for 1.5 hours, was added 500 times. No peeling was observed in the membrane / electrode assembly I after the environmental test cycle as in the initial stage.

On the other hand, peeling was observed in the membrane / electrode assembly I'of Comparative Example 1 described later after the environmental test cycle. From this, it is clear that the membrane / electrode assembly I of the present invention is superior to the membrane / electrode assembly I ′ of Comparative Example 1.

(3) Durability Test of Fuel Cell Single Cell The membrane / electrode assembly I was immersed in boiling deionized water for 2 hours to absorb water. The obtained membrane / electrode assembly was incorporated into an evaluation cell and the fuel cell output performance was evaluated.
That is, the support current collector 5 made of a packing material of thin carbon paper is brought into close contact with both electrodes of the membrane / electrode assembly 4 of Example 1 which is composed of the electrolyte membrane 1, the oxygen electrode 2 and the hydrogen electrode 3.
A solid polymer electrolyte fuel cell single cell shown in FIG. 1 was prepared, which was composed of a conductive separator (bipolar plate) 6 that also functions as a gas supply passage to the electrode from both sides of the electrode chamber separation.

A current density of 300 mA was applied to the above fuel cell single cell.
A long-term operation test was performed under the condition of / cm ² . The result is shown in FIG. In addition, 12 in FIG. 2 is the durability test result of the fuel cell single cell using the membrane / electrode assembly I of the present invention, and 13 in FIG. 2 is the fuel cell using the membrane / electrode assembly I. It is a durability test result of a single cell.

The polymer electrolyte fuel cell using the membrane / electrode assembly I of this example is more stable than the polymer electrolyte fuel cell using the membrane / electrode assembly I ′ of Comparative Example 1. There is.

(4) Preparation of Fuel Cell When a solid polymer fuel cell was prepared by stacking 36 layers of the single cell prepared in (3) above, an output of 1 kW was shown.

Comparative Example 1 (1) Preparation of Electrolyte Composite Membrane A polytetrafluoroethylene porous film having a film thickness of 20 μm and a porosity of 95% was formed in the same manner as in Example 1 (1) with 5% by weight of perfluorocarbon. After impregnating with isopropyl alcohol aqueous solution of sulfonic acid (sulfonic acid equivalent 0.9 milliequivalent / g), drying, and heat treatment were repeated, 6% in 1N sulfuric acid
It was immersed at 0 to 70 ° C. for 1 hour and then immersed in pure water at 60 to 70 ° C. for 1 hour to convert the terminal group of the electrolyte side chain into —SO ₃ H.

The obtained electrolyte composite membrane I'has an ionic conductivity of 0.04 S / cm and a tensile strength of 3.0 kg / mm ² . The ionic conductivity and tensile strength of the electrolyte membrane not reinforced with the same thickness and the same sulfonic acid equivalent were 0.12 S / cm and 1.2 kg / mm ² , respectively.

Further, the periphery of the electrolyte composite membrane I'or the non-reinforced electrolyte membrane was fixed with a SUS metal frame,
Hold at 95% RH for 1.5 hours, 25 ℃, 50% RH
An environmental cycle of high temperature wet condition and room temperature dry condition, which was held for 1.5 hours, was added 500 times. The tensile strengths of the electrolyte composite membrane I ′ and the non-reinforced electrolyte membrane after the environmental test cycle were reduced to 1/3 and 1/10 of the initial values, respectively.

The electrolyte composite membrane I'and the non-reinforced electrolyte membrane kept at 25 ° C. and 50% RH for 24 hours were heated to 80 ° C.
The dimensional change rates in the plane direction when immersed in ion exchange water for 24 hours were 2.0% and 14%, respectively.

Simulate the operating state of the fuel cell at 80 ° C., 9
Under the condition of 5% RH, load load 0.5 kg / mm ² 50
The creep strains of the electrolyte composite membrane I ′ and the electrolyte membrane that were not reinforced when added for 30 hours were 30% and 180%, respectively.

From the above, it is clear that when the electrolyte membrane is reinforced with a non-sulfonated polymer porous body, the tensile strength, the dimensional change rate and the creep resistance are improved, but the ionic conductivity is lowered, and It can be seen that compatibility between characteristics and ionic conductivity is a major issue.

(2) Preparation of Electrode Catalyst Coating Solution and Membrane / Electrode Assembly 40% by weight of platinum-supported carbon was dispersed in isopropanol, and then 5% by weight of perfluorocarbon sulfonic acid (sulfonic acid equivalent 0.9 meq / g). In the isopropyl alcohol aqueous solution, the weight ratio of platinum catalyst to polymer electrolyte is 2:
It was added so that it became 1 and was uniformly dispersed by ultrasonic waves to prepare a paste (electrode catalyst coating solution).

This electrode catalyst coating solution was applied to both sides of the electrolyte composite membrane I'obtained in (1) above and dried to obtain a membrane / electrode assembly I'having a platinum loading of 0.25 mg / cm ^2. It was made.

The periphery of the membrane / electrode assembly I'was fixed with a SUS metal frame and kept at 80 ° C and 95% RH for 1.5 hours.
An environmental cycle of a high temperature wet state and a room temperature dry state, in which 5 hours and 50% RH were kept for 1.5 hours, was added 500 times. In the membrane / electrode assembly I ′ after the environmental test cycle, peeling was observed unlike the initial stage.

(3) Durability Test of Fuel Cell Single Cell A thin carbon paper packing material (supporting current collector) is adhered to both sides of the membrane / electrode assembly I ', and polar chamber separation and electrodes are performed from both sides. A polymer electrolyte fuel cell unit cell composed of a conductive separator (bipolar plate) that also serves as a gas supply passage to the
A long-term operation test was performed under the condition of / cm ² . as a result,
As shown in 13 of FIG. 2, the output voltage tended to decrease after 3000 hours of operation.

Example 2 (1) Preparation of Electrolyte Composite Membrane A reinforcing woven fabric in which 200 denier polytetrafluoroethylene multifilaments were woven and entangled in 25 mesh with weft and warp, was dried at 100 ° C. and 100% anhydrous. The fabric was kept in sulfuric acid gas for 24 hours to obtain a sulfonated polytetrafluoroethylene-based reinforcing woven fabric.

After washing this woven fabric three times with boiling distilled water,
The sulfonic acid equivalent was measured. The reinforcing woven fabric of this example had a sulfonic acid equivalent of 0.8 meq / g. ESCA
When the sulfur atom S in the thickness direction was measured by using the sputtering method, absorption of the sulfur atom was recognized up to the central portion.

The sulfonated polytetrafluoroethylene-based reinforcing woven fabric was treated with 5% by weight of perfluorocarbon sulfonic acid (sulfonic acid equivalent: 0.9 meq / g) in isopropyl alcohol as in Example 1 (1). Using, the impregnation, drying and heat treatment were repeated. Then, the terminal group of the electrolyte side chain was converted to —SO ₃ H using 1N sulfuric acid under the same conditions as in Example 1 (1).

The obtained electrolyte composite membrane II had an ionic conductivity of 0.17 S / cm and a tensile strength of 3.5 kg / mm ² . The ionic conductivity and tensile strength of the electrolyte composite membrane II of the present example are the same as those of the electrolyte composite membrane II 'of Comparative Example 2 reinforced by a polytetrafluoroethylene film not subjected to the sulfonation treatment described later.
Or significantly better than the unreinforced electrolyte membrane.

Further, the periphery of the electrolyte composite membrane II was fixed with a SUS metal frame and held at 80 ° C. and 95% RH for 1.5 hours and at 25 ° C. and 50% RH for 1.5 hours. An environmental cycle simulating a fuel cell environment in a high temperature wet state and a room temperature dry state was added 500 times. The tensile strength of the electrolyte composite membrane II after the environmental test cycle was the same as the initial one.

On the other hand, the electrolyte composite membrane II 'of Comparative Example 2 reinforced by the polytetrafluoroethylene film which is not subjected to the sulfonation treatment described later and the electrolyte membrane which is not reinforced are 1/4 and 1 of the initial values after the environmental test cycle, respectively. It had fallen to / 10. From this, too, it is clear that the electrolyte composite membrane II is superior to the electrolyte composite membrane II ′ of Comparative Example 2 and the non-reinforced electrolyte membrane.

When the electrolyte composite membrane II kept at 25 ° C. and 50% RH for 24 hours was immersed in ion-exchanged water at 80 ° C. for 24 hours, the dimensional change rate in the plane direction was 2.0%. On the other hand, the dimensional change rate of the electrolyte composite membrane II ′ of Comparative Example 2 reinforced with the polymer porous body not subjected to sulfonation described later was 2.5%, and the dimensional change rate of the non-reinforced electrolyte membrane was 14%. From this, too, it is clear that the electrolyte composite membrane II is superior to the electrolyte composite membrane II ′ of Comparative Example 2 and the non-reinforced electrolyte membrane.

Further, the operation state of the fuel cell is simulated to 80
Load load 0.5 kg / mm ² under conditions of ℃ and 95% RH
The creep strain when applied for 50 hours is 15%, which is 1/2 of the electrolyte composite membrane II 'reinforced by the polymer porous body not subjected to the sulfonation treatment of Comparative Example 2 described later, and 1 of the non-reinforced electrolyte membrane. It is as small as / 12 and excellent.

From the above, when the inside is reinforced with the sulfonated polymer porous body, the mechanical properties such as mechanical strength, dimensional stability, and creep resistance, which cannot be achieved by the non-sulfonated polymer porous body, It is clearly compatible with ionic conductivity.

(2) Preparation of Membrane / Electrode Assembly 40% by weight of platinum-supported carbon was dispersed in an isopropanol solution, and then 5% by weight of perfluorocarbon sulfonic acid (sulfonic acid equivalent 0.9 meq / g) isopropyl An alcohol aqueous solution was added so that the weight ratio of the platinum catalyst and the polymer electrolyte was 2: 1, and the mixture was ultrasonically dispersed to prepare a paste (electrode catalyst coating solution). This electrode catalyst coating solution is applied to the electrolyte composite membrane obtained in (1) above.
After applying to both sides of II, it is dried and the amount of platinum carried is 0.25m.
A membrane / electrode assembly II of g / cm ² was prepared.

The periphery of the membrane / electrode assembly II was fixed with a SUS metal frame and kept at 80 ° C. and 95% RH for 1.5 hours and 25 hours.
An environmental cycle of a high temperature wet state and a room temperature dry state, in which the temperature was kept at 50% RH for 1.5 hours, was added 500 times. No peeling was observed in the membrane / electrode assembly II after the environmental test cycle as in the initial stage. On the other hand, peeling of the membrane / electrode assembly II of Comparative Example 2 described later was observed after the environmental test cycle. From this, it is clear that the membrane / electrode assembly II of the present invention is superior to the membrane / electrode assembly II ′ of Comparative Example 2.

(3) Durability Test of Fuel Cell Single Cell A thin carbon paper packing material (supporting current collector) is closely adhered to both sides of the membrane / electrode assembly II to separate the polar chamber and the electrode from both sides. A polymer electrolyte fuel cell unit cell composed of a conductive separator (bipolar plate) that also serves as a gas supply passage was manufactured, and the current density was 300 mA / cm.
^A long-term operation test was performed under the condition of ² . The result is shown in FIG.

Reference numeral 14 in FIG. 3 denotes the membrane / electrode assembly of this embodiment.
The result of the durability test of the fuel cell single cell using II, 15 in FIG. 3 is the result of the durability test of the fuel cell single cell using the membrane / electrode assembly II ′.

The polymer electrolyte fuel cell using the membrane / electrode assembly II of this example is more stable than the one using the membrane / electrode assembly II ′ of Comparative Example 2.

(4) Production of Fuel Cell A solid polymer fuel cell was produced by stacking 36 layers of the single cell produced in (3) above, and showed an output of 1 kW.

Comparative Example 2 (1) Preparation of Electrolyte Composite Membrane 5% by weight perfluorocarbon sulfonic acid was added to a reinforcing woven fabric in which 200 denier polytetrafluoroethylene multifilaments were woven and woven in 25 mesh as weft and warp. (Sulfonic acid equivalent 0.9 milliequivalent / g) isopropyl alcohol / water solution (manufactured by Aldrich Chemical Co.)
Was impregnated and dried at 60 ° C.

Next, the film was heat-treated at 140 ° C. for 5 minutes. The impregnation, drying, and heat treatment were repeated until pinholes disappeared, that is, five times. Then, 60 ~ in 1N sulfuric acid
It was immersed at 70 ° C. for 1 hour and then immersed in pure water at 60 to 70 ° C. for 1 hour to convert the terminal groups of the electrolyte side chains into —SO ₃ H.
The ionic conductivity of the obtained electrolyte composite membrane II 'was 0.01S.
/ Cm, and the tensile strength was 3.1 kg / mm ² . The ionic conductivity and tensile strength of an unreinforced electrolyte membrane having the same thickness and the same sulfonic acid equivalent were 0.12 S / cm and
It was 1.2 kg / mm ² .

Further, the periphery of the electrolyte composite membrane II 'was fixed with a SUS metal frame and held at 80 ° C. and 95% RH for 1.5 hours and at 25 ° C. and 50% RH for 1.5 hours. An environmental cycle of high temperature wet condition and room temperature dry condition was added 500 times. The tensile strengths of the electrolyte composite membrane II ′ and the non-reinforced electrolyte membrane after the environmental test cycle were 1 / initial
It fell to 4, 1/10.

The electrolyte composite membrane II 'and the non-reinforced electrolyte membrane kept at 25 ° C. and 50% RH for 24 hours were treated at 80 ° C.
The dimensional change rates in the plane direction when immersed in ion-exchanged water for 24 hours were 3.0% and 14%, respectively.

Simulate the operating state of the fuel cell at 80 ° C., 9
Under the condition of 5% RH, load load 0.5 kg / mm ² 50
The creep strains of the electrolyte composite membrane II ′ and the non-reinforced electrolyte membrane when added over time were 33% and 180%, respectively.

From the above, when the electrolyte membrane is reinforced with a non-sulfonated polymer porous material, the tensile strength, the dimensional change rate and the creep resistance are improved, but it is clear that the ionic conductivity is lowered. It can be seen that compatibility of conductivity is a major issue.

(2) Preparation of Membrane / Electrode Assembly 40% by weight of platinum-supported carbon was dispersed in isopropanol, and then 5% by weight of perfluorocarbon sulfonic acid (sulfonic acid equivalent 0.9 meq / g) isopropyl alcohol. The aqueous solution was added so that the weight ratio of the platinum catalyst to the polymer electrolyte was 2: 1, and the mixture was ultrasonically uniformly dispersed to prepare a paste (electrode catalyst coating solution).

This electrode catalyst coating solution was applied to both sides of the electrolyte composite membrane II ′ obtained in (1) above and dried to obtain a membrane / electrode assembly II ′ having a platinum loading of 0.25 mg / cm ^2. It was made.

The periphery of the membrane / electrode assembly II 'was fixed with a SUS metal frame and kept at 80 ° C and 95% RH for 1.5 hours.
An environmental cycle of a high temperature wet state and a room temperature dry state, in which 5 hours and 50% RH were kept for 1.5 hours, was added 500 times. In the membrane / electrode assembly II ′ after the environmental test cycle, peeling was observed unlike the initial stage.

(3) Durability Test of Fuel Cell Single Cell A thin carbon paper packing material (supporting current collector) was adhered to both sides of the membrane / electrode assembly II ', and the polar chamber separation and the electrode were performed from both sides. A polymer electrolyte fuel cell unit cell composed of a conductive separator (bipolar plate) that also serves as a gas supply passage to the
A long-term operation test was performed under the condition of / cm ² . as a result,
As shown at 15 in FIG. 3, the output voltage has an operating time of 3000
A tendency of decreasing after hours was observed.

Example 3 (1) Preparation of Electrolyte Composite Membrane Polytetrafluoroethylene fibrils were heated at 100 ° C. for 1 hour.
The mixture was kept in 00% sulfuric acid gas for 24 hours for sulfonation.

After washing the fibrils 3 times with boiling distilled water, the sulfonic acid equivalent was measured. The value was 0.8 meq / g. When the sulfur atom S in the thickness direction was measured by ESCA using the sputtering method, absorption of the sulfur atom was recognized up to the central portion.

The sulfonated polytetrafluoroethylene fibrils were subjected to the same impregnation, drying and heat treatment as in Example 1 (1) using an aqueous isopropyl alcohol solution containing 5% by weight of perfluorocarbon sulfonic acid. Then, the terminal group of the electrolyte side chain was converted to —SO ₃ H using 1N sulfuric acid under the same conditions as in Example 1 (1).

The electrolyte composite membrane III thus obtained had an ionic conductivity of 0.17 S / cm and a tensile strength of 3.8 kg / mm ² .

The ionic conductivity and the tensile strength of the electrolyte composite membrane III of the present invention are the same as those of the electrolyte composite membrane III 'of Comparative Example 3 reinforced with polytetrafluoroethylene fibril which is not subjected to the sulfonation treatment described later and the electrolyte membrane which is not reinforced. Significantly better than

Further, the periphery of the electrolyte composite membrane III was fixed with a SUS metal frame and held at 80 ° C. and 95% RH for 1.5 hours and at 25 ° C. and 50% RH for 1.5 hours. An environmental cycle simulating a fuel cell environment in a high temperature wet state and a room temperature dry state was added 500 times. The tensile strength of the electrolyte composite membrane III after the environmental test cycle was the same as the initial one.

On the other hand, the electrolyte composite membrane III 'of Comparative Example 3 reinforced with polytetrafluoroethylene fibril which is not subjected to the sulfonation treatment described later and the electrolyte membrane which is not reinforced are respectively 2/5, 1 of the initial stage after the environmental test cycle. It had fallen to / 10. From this, it is clear that the electrolyte composite membrane III is superior to the electrolyte membrane not reinforced and the electrolyte composite membrane III ′ of Comparative Example 3.

When the electrolyte composite membrane III kept at 25 ° C. and 50% RH for 24 hours was immersed in ion-exchanged water at 80 ° C. for 24 hours, the dimensional change in the plane direction was 2.5%. On the other hand, the dimensional change rate of the electrolyte composite membrane III 'of Comparative Example 3 reinforced with polytetrafluoroethylene fibril which was not sulfonated as described later was 4.0%, and the dimensional change rate of the non-reinforced electrolyte membrane was 14%. From this, it is clear that the electrolyte composite membrane III is superior to the electrolyte composite membrane III ′ of Comparative Example 3 and the non-reinforced electrolyte membrane.

Moreover, the fuel cell is operated in a simulated state of 80
The creep strain when a load of 0.5 kg / mm ² was applied for 50 hours under the conditions of ° C and 95% RH was 18%, and 1 of Comparative Example 3 reinforced with polytetrafluoroethylene fibrils not subjected to sulfonation treatment described later. / 2, which is as small as 1/10 of the unreinforced electrolyte membrane, which is excellent.

From the above, tensile strength, dimensional change rate and creep resistance are improved when the electrolyte membrane is reinforced with a non-sulfonated polymer porous material, but it is clear that the ionic conductivity is lowered, and the mechanical properties A major issue is to achieve both ionic conductivity and ionic conductivity. When reinforced with a sulfonated polymer porous material, mechanical properties such as mechanical strength, dimensional stability, and creep resistance, which could not be achieved with a non-sulfonated polymer porous material, and ionic conductivity are compatible. Is clear.

(2) Preparation of Membrane / Electrode Assembly 40% by weight of platinum-supported carbon was dispersed in isopropanol, and then 5% by weight of perfluorocarbon sulfonic acid (sulfonic acid equivalent 0.9 meq / g) isopropyl alcohol. The aqueous solution was added so that the weight ratio of the platinum catalyst to the polymer electrolyte was 2: 1, and the mixture was ultrasonically uniformly dispersed to prepare a paste (electrode catalyst coating solution).

This electrode catalyst coating solution was applied to both sides of the electrolyte composite membrane III obtained in the above (1) and dried to prepare a membrane / electrode assembly III having a platinum loading of 0.25 mg / cm ^2. did.

The periphery of the membrane / electrode assembly III was fixed with a SUS metal frame and kept at 80 ° C. and 95% RH for 1.5 hours.
500 cycles of a high temperature wet condition and a room temperature dry condition, which were maintained at 5 ° C. and 50% RH for 1.5 hours, were added. No peeling was observed in the membrane / electrode assembly III after the environmental test cycle as in the initial stage.

On the other hand, the membrane / electrode assembly II of Comparative Example 3 described later.
For I ', peeling was observed after the environmental test cycle. From this, it is clear that the membrane / electrode assembly III of this example is superior to the membrane / electrode assembly III ′ of Comparative Example 3.

(3) Durability Test of Fuel Cell Single Cell A thin carbon paper packing material (supporting current collector) is closely adhered to both sides of the membrane / electrode assembly III, and both sides are separated into polar chambers and electrodes. A polymer electrolyte fuel cell unit cell composed of a conductive separator (bipolar plate) that also serves as a gas supply passage was manufactured, and the current density was 300 mA / c.
A long-term operation test was conducted under the condition of m ² . The result is shown in Figure 4.
Shown in.

16 in FIG. 4 is the membrane / electrode assembly of this embodiment.
It is a durability test result of the fuel cell single cell using III.
Further, 17 in FIG. 4 is a membrane / electrode assembly III ′ of Comparative Example 3.
3 is a result of a durability test of a fuel cell single cell using. film/
The polymer electrolyte fuel cell using the electrode assembly III has a membrane /
It is more stable than the polymer electrolyte fuel cell using the electrode assembly III '.

(4) Production of Fuel Cell A solid polymer electrolyte fuel cell was produced by stacking 36 layers of the single cell produced in (3) above, and showed an output of 1 kW.

Comparative Example 3 (1) Preparation of Electrolyte Composite Membrane Polytetrafluoroethylene fibrils were impregnated with an aqueous isopropyl alcohol solution containing 5% by weight of perfluorocarbon sulfonic acid (sulfonic acid equivalent 0.9 meq / g), 60
It was dried at ° C. The film was then heat treated at 140 ° C. for 5 minutes. The impregnation, drying, and heat treatment were repeated until pinholes disappeared, that is, five times. Then, it is immersed in 1N sulfuric acid at 60 to 70 ° C for 1 hour, and then immersed in pure water at 60 to 70 ° C for 1 hour.
After immersion for a period of time, the end groups of the side chains of the electrolyte were converted to —SO ₃ H. The ionic conductivity of the obtained electrolyte composite membrane III 'was 0.
The tensile strength was 015 S / cm and the tensile strength was 3.5 kg / mm ² .

The ionic conductivity and tensile strength of the unreinforced electrolyte membrane having the same thickness and the same sulfonic acid equivalent were 0.12 S / cm and 1.2 kg / mm ² , respectively.

Further, the periphery of the electrolyte composite membrane III 'or the non-reinforced electrolyte membrane is fixed with a SUS metal frame,
Hold at ℃, 95% RH for 1.5 hours and 25 ℃, 50% R
500 cycles of high temperature wet and room temperature dry environmental cycles of 1.5 hour hold in H were added. The tensile strengths of the electrolyte composite membrane III ′ and the non-reinforced electrolyte membrane after the environmental test cycle were reduced to 2/5 and 1/10 of the initial values, respectively.

The electrolyte composite membrane III ′ and the non-reinforced electrolyte membrane, which were kept at 25 ° C. and 50% RH for 24 hours, were
The dimensional change rates in the plane direction when immersed in ion-exchanged water at ℃ for 24 hours were 4.0% and 14%, respectively.

Simulate the operating state of the fuel cell at 80 ° C., 9
Under the condition of 5% RH, load load 0.5 kg / mm ² 50
The creep strains of the electrolyte composite membrane III ′ and the non-reinforced electrolyte membrane when added for time are 35% and 180%, respectively.
Met.

From the above, it is clear that reinforcing the electrolyte membrane with a non-sulfonated polymer porous body improves the tensile strength, dimensional change rate and creep resistance, but decreases the ionic conductivity, and It turns out that compatibility of ionic conductivity is a major issue.

(2) Preparation of Membrane / Electrode Assembly 40% by weight of platinum-supported carbon was dispersed in isopropanol, and then 5% by weight of perfluorocarbon sulfonic acid (sulfonic acid equivalent 0.9 meq / g) isopropyl alcohol. The aqueous solution was added so that the weight ratio of the platinum catalyst to the polymer electrolyte was 2: 1, and the mixture was ultrasonically uniformly dispersed to prepare a paste (electrode catalyst coating solution). This electrode catalyst coating solution was applied to the electrolyte composite membrane II obtained in (1) above.
After being applied to both sides of I ', it is dried and the amount of platinum carried is 0.25m.
A membrane / electrode assembly III ′ of g / cm ² was prepared.

The periphery of the membrane / electrode assembly III 'was fixed with a SUS metal frame and kept at 80 ° C. and 95% RH for 1.5 hours.
An environmental cycle of a high temperature wet condition and a room temperature dry condition of keeping at 25 ° C. and 50% RH for 1.5 hours was added 500 times. After the environmental test cycle, the membrane / electrode assembly III ′ was peeled off after the environmental test cycle, unlike the initial stage.

(3) Durability Test of Fuel Cell Single Cell A thin carbon paper packing material (supporting current collector) was adhered to both sides of the membrane / electrode assembly III ', and the polar chamber separation and the electrode were performed from both sides. A polymer electrolyte fuel cell unit cell composed of a conductive separator (bipolar plate) that also serves as a gas supply passage to the
A long-term operation test was performed under the condition of A / cm ² . As a result, as shown in 17 of FIG.
A tendency to decrease after 00 hours was recognized.

Example 4 (1) Preparation of Electrolyte Composite Membrane A polytetrafluoroethylene non-woven fabric having a thickness of 20 μm and a porosity of 95% was dried in 100% anhydrous sulfuric acid gas at 2 ° C.
After holding for 4 hours, a sulfonated polytetrafluoroethylene nonwoven fabric was obtained. This non-woven fabric was washed three times with boiling distilled water, and the sulfonic acid equivalent was measured. The value is 0.7 meq / g
Met. When the sulfur atom S in the thickness direction was measured by ESCA using the sputtering method, absorption of the sulfur atom was recognized up to the central portion.

The sulfonated polytetrafluoroethylene nonwoven fabric was impregnated with an aqueous isopropyl alcohol solution containing 5% by weight of perfluorocarbon sulfonic acid (sulfonic acid equivalent: 0.9 meq / g) and dried at 60 ° C. Then 14
The film was heat treated at 0 ° C. for 5 minutes. The impregnation, drying, and heat treatment were repeated until pinholes disappeared, that is, five times.
Then, it was immersed in 1N sulfuric acid at 60 to 70 ° C. for 1 hour and in pure water at 60 to 70 ° C. for 1 hour to convert the terminal groups of the side chains of the electrolyte into —SO ₃ H. The ionic conductivity and tensile strength of this electrolyte composite membrane IV are 0.16 S / cm and 4.1 k, respectively.
It was g / mm ² .

The ionic conductivity and tensile strength of the electrolyte composite membrane IV of this example are as follows: the electrolyte composite membrane IV 'of Comparative Example 4 reinforced with a non-sulfonation-treated polytetrafluoroethylene non-woven fabric and the non-reinforced electrolyte membrane. Significantly better than

Further, the periphery of the electrolyte composite membrane IV was fixed with a SUS metal frame and kept at 80 ° C. and 95% RH for 1.5 hours and at 25 ° C. and 50% RH for 1.5 hours. An environmental cycle simulating the fuel cell environment was applied 500 times in a wet state and a room temperature dry state. The tensile strength of the electrolyte composite membrane IV after the environmental test cycle was unchanged from the initial value.

On the other hand, the electrolyte composite membrane IV 'of Comparative Example 4 reinforced with a non-sulfonation-treated polytetrafluoroethylene non-woven fabric and the non-reinforced electrolyte membrane were each 1/4, 1 of the initial after the environmental test cycle. It had fallen to / 10. From this, it is clear that the electrolyte composite membrane IV is superior to the electrolyte composite membrane IV of Comparative Example 4 and the non-reinforced electrolyte membrane.

When the electrolyte composite membrane IV kept at 25 ° C. and 50% RH for 24 hours was immersed in ion-exchanged water at 80 ° C. for 24 hours, the dimensional change rate in the plane direction was 1.5%.

On the other hand, the dimensional change rate of the electrolyte composite membrane IV ′ of Comparative Example 4 reinforced with the non-sulfonation-treated polytetrafluoroethylene film was 2.0%, and the dimensional change rate of the non-reinforced electrolyte membrane was 14%. . Electrolyte composite membrane
It is clear that IV is superior to electrolyte composite membrane IV 'and unreinforced electrolyte membrane.

Also, the fuel cell operating condition is simulated to 80
Load load 0.5 kg / mm under conditions of ℃ and 95% RH
The creep strain when ² was applied for 50 hours was 15%, which was as small as 1/2 of Comparative Example 4 reinforced with a non-sulfonation-treated polytetrafluoroethylene non-woven fabric and 1/12 of the unreinforced electrolyte membrane, which were small and excellent. There is.

From the above, when the electrolyte membrane is reinforced with a non-sulfonated polymer porous material, the tensile strength, the dimensional change rate and the creep resistance are improved, but it is clear that the ionic conductivity is lowered, and the mechanical properties and ionic Compatibility of conductivity is a major issue.

When reinforced with a sulfonated polymer porous body, mechanical strength, dimensional stability, creep resistance, and other mechanical properties unattainable with a non-sulfonated polymer porous body, and ionic conductivity It is clear that and are compatible.

(2) Preparation of Membrane / Electrode Assembly 40% by weight of platinum-supported carbon was dispersed in isopropanol, and then 5% by weight of perfluorocarbon sulfonic acid (sulfonic acid equivalent 0.9 meq / g) isopropyl alcohol. The aqueous solution was added so that the weight ratio of the platinum catalyst to the polymer electrolyte was 2: 1, and the mixture was ultrasonically uniformly dispersed to prepare a paste (electrode catalyst coating solution). This solution of the electrode catalyst coating was applied to the electrolyte composite membrane I obtained in (1) above.
After coating on both sides of V, it is dried and the amount of platinum carried is 0.25m
A membrane / electrode assembly IV of g / cm ² was prepared.

The periphery of the membrane / electrode assembly IV was fixed with a SUS metal frame and kept at 80 ° C. and 95% RH for 1.5 hours.
500 cycles of high temperature wet condition and room temperature dry condition environmental cycles of 5 ° C. and 50% RH for 1.5 hours were added. No peeling was observed in the membrane / electrode assembly IV after the environmental test cycle as in the initial stage.

On the other hand, the membrane / electrode assembly I of Comparative Example 4 described later
Peeling of V'was observed after the environmental test cycle. From this as well, it is clear that the membrane / electrode assembly IV of this example is superior to the membrane / electrode assembly IV ′ of Comparative Example 4.

(3) Durability test of fuel cell single cell A thin carbon paper packing material (supporting current collector) is adhered on both sides of the membrane / electrode assembly IV, and the polar chamber separation and the gas to the electrode from both sides. A polymer electrolyte fuel cell unit cell composed of a conductive separator (bipolar plate) that also serves as a supply passage was manufactured, and the current density was 300 mA / cm ^2.
A long-term operation test was carried out under the conditions. The result is shown in FIG.

18 in FIG. 5 is the membrane / electrode assembly of this embodiment.
It is a durability test result of the fuel cell single cell using IV.
Reference numeral 19 in FIG. 5 is the result of the durability test of the fuel cell single cell using the membrane / electrode assembly IV ′. The polymer electrolyte fuel cell using the membrane / electrode assembly IV of this example is more stable than the polymer electrolyte fuel cell using the membrane / electrode assembly IV 'of Comparative Example 4.

(4) Production of Fuel Cell A solid polymer electrolyte fuel cell was produced by stacking 36 layers of the single cell produced in (3) above, and showed an output of 1 kW.

Comparative Example 4 (1) Preparation of Electrolyte Composite Membrane 5% by weight perfluorocarbon sulfonic acid (sulfonic acid equivalent 0.9 meq / It was impregnated with the isopropyl alcohol aqueous solution of g) and dried at 60 ° C. The film was then heat treated at 140 ° C. for 5 minutes. The impregnation, drying, and heat treatment were repeated until pinholes disappeared, that is, five times. Then, it was immersed in 1N sulfuric acid at 60 to 70 ° C. for 1 hour and in pure water at 60 to 70 ° C. for 1 hour to convert the terminal groups of the side chains of the electrolyte into —SO ₃ H. This electrolyte composite membrane I
The ionic conductivity of V'was 0.03 S / cm. The tensile strength was 3.2 kg / cm. In addition, the ionic conductivity and tensile strength of an unreinforced electrolyte membrane having the same thickness and the same sulfonic acid equivalent are 0.12 S / cm and 1.2 kg, respectively.
/ Mm ² .

The periphery of the electrolyte composite membrane IV 'or the non-reinforced electrolyte membrane was fixed with a SUS metal frame, and the temperature was 80 ° C. and 95%.
Hold at RH for 1.5 hours and at 25 ° C, 50% RH for 1.
An environmental cycle of a high temperature wet state and a room temperature dry state, which was maintained for 5 hours, was added 500 times. The tensile strengths of the electrolyte composite membrane IV ′ and the non-reinforced electrolyte membrane after the environmental test cycle were reduced to 1/4 and 1/10 of the initial values, respectively.

The electrolyte composite membrane IV ′ and the non-reinforced electrolyte membrane, which were kept at 25 ° C. and 50% RH for 24 hours, were
The dimensional change rates in the plane direction when immersed in ion-exchanged water at ℃ for 24 hours were 2.0% and 14%, respectively.

Simulate the operating state of the fuel cell at 80 ° C., 9
The creep strains of the electrolyte composite membrane IV ′ and the non-reinforced electrolyte membrane when a load of 0.5 kg / mm ² was applied for 50 hours under the condition of 5% RH were 30% and 180%, respectively.

From the above, it is clear that when the electrolyte membrane is reinforced with a non-sulfonated polymer porous body, the tensile strength, the dimensional change rate and the creep resistance are improved, but the ionic conductivity is lowered, and the mechanical properties and ionic It can be seen that compatibility of conductivity is a major issue.

(2) Preparation of Membrane / Electrode Assembly 40% by weight of platinum-supported carbon was dispersed in isopropanol, and then 5% by weight of perfluorocarbon sulfonic acid (sulfonic acid equivalent 0.9 meq / g) isopropyl alcohol. The aqueous solution was added so that the weight ratio of the platinum catalyst to the polymer electrolyte was 2: 1, and the mixture was ultrasonically uniformly dispersed to prepare a paste (electrode catalyst coating solution). This solution of the electrode catalyst coating was applied to the electrolyte composite membrane I obtained in (1) above.
After coating on both sides of V ', it is dried and the amount of platinum carried is 0.25.
A mg / cm ² membrane / electrode assembly IV ′ was prepared.

The periphery of the membrane / electrode assembly IV ′ was fixed with a SUS metal frame and kept at 80 ° C. and 95% RH for 1.5 hours.
500 cycles of high temperature wet and room temperature dry environmental cycles of 25 ° C. and 50% RH hold for 1.5 hours were added. In the membrane / electrode assembly IV 'after the environmental test cycle, peeling was observed after the environmental test cycle, unlike the initial stage.

(3) Durability Test of Fuel Cell Single Cell A thin carbon paper packing material (supporting current collector) was adhered to both sides of the membrane / electrode assembly IV ′, and both sides were connected to the polar chamber and the electrode. A single polymer electrolyte fuel cell unit made of a conductive separator (bipolar plate) that also serves as the gas supply passage of
A long-term operation test was conducted under the condition of cm ² . As a result, as shown by 19 in FIG. 5, the output voltage tended to decrease after 3000 hours of operation.

Example 5 (1) Preparation of Sulfonated Polyethersulfone-based Film-like Porous Membrane A 500 ml four-neck round bottom flask equipped with a stirrer, a thermometer, and a reflux condenser connected to a calcium chloride tube. After purging the inside of the reactor with nitrogen, 25 g of polyether sulfone (PES) and 125 ml of concentrated sulfuric acid were added. A uniform solution was obtained by stirring overnight at room temperature under a nitrogen stream.

To this solution, 48 ml of chlorosulfuric acid was added dropwise from a dropping funnel while stirring under a nitrogen stream. Since chlorosulfuric acid violently reacts with water in concentrated sulfuric acid to foam for a while after the start of dropping, dropping was slowly performed, and the dropping was completed within 5 minutes after the bubbling became moderate. The reaction solution after the dropping was stirred at 25 ° C. for 40 minutes to be sulfonated.

Then, the reaction solution was slowly added dropwise to 15 liters of deionized water to precipitate sulfonated polyether sulfone, which was collected by filtration. The deposited precipitate was washed with deionized water using a mixer and collected by suction filtration.
After repeating until the filtrate became neutral, it was dried under reduced pressure at 80 ° C. overnight. The sulfonic acid equivalent of the obtained sulfonated polyether sulfone electrolyte V was 0.5 meq / g.

An electrolyte solution was prepared by dissolving 7 parts of the sulfonated polyether sulfone electrolyte V in 93 parts of γ-butyrolactone. This solution was cast on a glass plate using a film-making applicator to form a thin film of the electrolyte solution. Then, it was immersed in water at 25 ° C. to solidify the electrolyte solution. The residual solvent was removed by immersing in hot water at 80 ° C., and then dried with hot air at 60 ° C. for 1 hour to obtain a film-like porous film V.

(2) Preparation of Sulfonated Polyethersulfone Electrolyte Composite Membrane A stirrer, a thermometer, and a reflux condenser connected to a calcium chloride tube were attached, and after replacing the inside of a 500 ml four-neck round bottom flask with nitrogen, 25 g Polyether sulfone (PES) and 125 ml of concentrated sulfuric acid were added. A uniform solution was obtained by stirring overnight at room temperature under a nitrogen stream. To this solution, 48 ml of chlorosulfuric acid was added dropwise from a dropping funnel while stirring under a nitrogen stream. Since chlorosulfuric acid violently reacts with water in concentrated sulfuric acid to foam for a while after the start of dropping, dropping was slowly performed, and the dropping was completed within 5 minutes after the bubbling became moderate.
The reaction solution after the dropping was stirred at 25 ° C. for 4 hours to be sulfonated.

Then, the reaction solution was slowly added dropwise to 15 liters of deionized water to precipitate sulfonated polyether sulfone, which was collected by filtration. The deposited precipitate was washed with deionized water using a mixer and collected by suction filtration until the filtrate became neutral, and then dried under reduced pressure at 80 ° C. overnight. The sulfonic acid equivalent of the obtained sulfonated polyether sulfone electrolyte V was 1.25 meq / g.

The electrolyte V is isopropyl alcohol /
An electrolyte solution V having a concentration of 30 wt% was prepared by dissolving in water. The electrolyte solution V was vacuum impregnated into the film-like porous membrane V and vacuum dried to obtain a 25 μm sulfonated polyethersulfone electrolyte composite membrane V. This electrolyte composite membrane V
Has an ionic conductivity of 0.2 S / cm and a tensile strength of 4.6 kg.
/ Mm ² .

The ionic conductivity and tensile strength of the electrolyte composite membrane V of the present example are the same as those of the electrolyte composite membrane V ′ of Comparative Example 5 reinforced with a sulfonated polyethersulfone porous film which is not subjected to the sulfonation treatment described later, and the reinforced. Significantly superior to non-sulfonated polyethersulfone electrolyte membranes.

Further, the periphery of the electrolyte composite membrane V was fixed with a SUS metal frame and held at 80 ° C. and 95% RH for 1.5 hours and at 25 ° C. and 50% RH for 1.5 hours. An environmental cycle simulating a fuel cell environment in a high temperature wet state and a room temperature dry state was added 500 times. The tensile strength of the electrolyte composite membrane V after the environmental test cycle did not change from the initial value.

On the other hand, the electrolyte composite membrane V'of Comparative Example 5 reinforced with the polyethersulfone porous film not subjected to the sulfonation treatment and the electrolyte membrane not reinforced were respectively 1/3 and 1 / the initial values after the environmental test cycle. It had dropped to 12. From this, it is clear that the electrolyte composite membrane V is superior to the electrolyte composite membrane V of Comparative Example 5 and the non-reinforced electrolyte membrane.

When the electrolyte composite membrane V kept at 25 ° C. and 50% RH for 24 hours was immersed in ion-exchanged water at 80 ° C. for 24 hours, the dimensional change rate in the plane direction was 1.8%.

On the other hand, the dimensional change rate of the electrolyte composite membrane V'of Comparative Example 5 reinforced with the non-sulfonation-treated polymer porous body was 3.0%, and the dimensional change rate of the non-reinforced electrolyte membrane was 28%.
Met.

From this also, the electrolyte composite membrane V was compared with Comparative Example 5
It is clearly superior to the electrolyte composite membrane V and the non-reinforced electrolyte membrane.

Further, the operation state of the fuel cell is simulated to 80
Load load 0.5 kg / mm under conditions of ℃ and 95% RH
The creep strain when ² was added for 50 hours was 15%, and Comparative Example 1 reinforced with a porous polymer body not subjected to sulfonation treatment
It is as small as 1 / 2.3, which is 1 / 12.5 that of the unreinforced electrolyte membrane.

From the above, when the electrolyte membrane is reinforced with a non-sulfonated polymer porous body, the tensile strength, the dimensional change rate and the creep resistance are improved, but it is clear that the ionic conductivity is lowered, and the mechanical properties and ionic Compatibility of conductivity is a major issue. When reinforced with a sulfonated polymer porous material, mechanical properties such as mechanical strength, dimensional stability, and creep resistance, which could not be achieved with a non-sulfonated polymer porous material, and ionic conductivity are compatible. Is clear.

(3) Preparation of Membrane / Electrode Assembly 40% by weight of platinum-supported carbon was dispersed in isopropanol, and then 5% by weight of perfluorocarbon sulfonic acid (sulfonic acid equivalent 0.9 meq / g) isopropyl alcohol. The aqueous solution was added so that the weight ratio of the platinum catalyst to the polymer electrolyte was 2: 1, and the mixture was ultrasonically uniformly dispersed to prepare a paste (electrode catalyst coating solution). This electrode catalyst coating solution was applied to the electrolyte composite membrane V obtained in (2) above.
Coated on both sides of the coating and dried to support platinum of 0.25mg / c
An m ² membrane / electrode assembly V-1 was prepared.

After 40% by weight of platinum-supported carbon was dispersed in isopropanol, a 5% by weight solution of sulfonated polyethersulfone electrolyte V in isopropyl alcohol having a sulfonic acid equivalent of 1.25 meq / g was added to a platinum catalyst and a polymer. Add it so that the weight ratio with the electrolyte is 2: 1 and disperse it evenly with ultrasonic waves to paste (electrode catalyst coating solution).
Was prepared. This electrode catalyst coating solution was applied on both sides of the electrolyte composite membrane V obtained in (2) above and dried to prepare a membrane / electrode assembly V-2 having a platinum loading of 0.25 mg / cm ² .

The periphery of the membrane / electrode assembly V-1 or V-2 was fixed with a SUS metal frame, kept at 80 ° C. and 95% RH for 1.5 hours, and kept at 25 ° C. and 50% RH for 1.5 hours. With time retention,
An environmental cycle of high temperature wet condition and room temperature dry condition was added 500 times. No peeling was observed in both the membrane / electrode assemblies V-1 and V-2 after the environmental test cycle as in the initial stage.

On the other hand, peeling of the membrane / electrode assembly V'of Comparative Example 5 was observed after the environmental test cycle. From this, it is clear that both the membrane / electrode assembly V-1 and V-2 of this example are superior to the membrane / electrode assembly V'of Comparative Example 5.

(4) Durability Test of Fuel Cell Single Cell A thin carbon paper packing material (supporting current collector) is adhered to both sides of the membrane / electrode assembly V-1 or V-2, and a pole is applied from both sides. A polymer electrolyte fuel cell unit cell composed of an electrically conductive separator (bipolar plate) that also serves as a chamber separation and a gas supply passage to the electrode was prepared, and a current density of 30
A long-term operation test was performed under the condition of 0 mA / cm ² . The result is shown in FIG.

Reference numerals 20 and 21 in FIG. 6 are the results of the durability test of the fuel cell single cell using the membrane / electrode assembly V-1 or V-2 of this example, respectively. Also, 22 and 2 in FIG.
3 is the durability test result of the fuel cell single cell using the membrane / electrode assembly V′-1 or V′-2, respectively.

Membrane / electrode assembly V-1 or V- of this example
The polymer electrolyte fuel cell using 2 is more stable than the polymer electrolyte fuel cell using the membrane / electrode assemblies V′-1 and V′-2 of Comparative Example 5.

(5) Production of Fuel Cell A solid polymer fuel cell was produced by stacking 36 layers of the single cell produced in (4) above, and showed an output of 1 kW.

Comparative Example 5 (1) Preparation of Electrolyte Composite Membrane A sulfonic acid equivalent of 1.25 mm obtained in (2) of Example 5 was applied to a polyether sulfone film having a thickness of 20 μm and a porosity of 95%. Vacuum impregnation of an equivalent / g sulfonated polyether sulfone electrolyte with an electrolyte solution V having a concentration of 30 wt%,
After vacuum drying, a 25 μm sulfonated polyethersulfone electrolyte composite membrane V ′ was obtained.

The ionic conductivity and tensile strength of this electrolyte composite membrane V ′ were 0.02 S / cm and 3.5 kg / mm ² , respectively.
Met. Further, the ionic conductivity and tensile strength of the unreinforced electrolyte membrane having the same thickness and the same sulfonic acid equivalent were 0.12 S / cm and 1.0 kg / mm ² , respectively.

Further, the periphery of the electrolyte composite membrane V ′ or the non-reinforced electrolyte membrane was fixed with a SUS metal frame, and the temperature was kept at 80 ° C. for 9 minutes.
500 cycles of a high temperature wet condition and a room temperature dry condition, which consisted of 1.5 hours of holding at 5% RH and 1.5 hours of holding at 25 ° C. and 50% RH, were applied. The tensile strengths of the electrolyte composite membrane V ′ and the non-reinforced electrolyte membrane after the environmental test cycle were reduced to 1/3 and 1/10 of the initial values, respectively.

The electrolyte composite membrane V ′ and the non-reinforced electrolyte membrane kept at 25 ° C. and 50% RH for 24 hours were heated to 80 ° C.
The dimensional change rates in the plane direction when immersed in ion exchange water for 24 hours were 2.0% and 14%, respectively.

Simulating the operating state of the fuel cell,
Under the condition of 5% RH, load load 0.5 kg / mm ² 50
The creep strains of the electrolyte composite membrane V and the electrolyte membrane not reinforced when added for a time were 45% and 250%, respectively.

From the above, when the electrolyte membrane is reinforced with a non-sulfonated polymer porous body, the tensile strength, the dimensional change rate and the creep resistance are improved, but it is clear that the ionic conductivity is lowered, and the mechanical properties and ionic It can be seen that compatibility of conductivity is a major issue.

(2) Preparation of Membrane / Electrode Assembly 40% by weight of platinum-supported carbon was dispersed in isopropanol, and then 5% by weight of perfluorocarbon sulfonic acid (sulfonic acid equivalent 0.9 meq / g) isopropyl alcohol. The aqueous solution was added so that the weight ratio of the platinum catalyst to the polymer electrolyte was 2: 1, and the mixture was ultrasonically uniformly dispersed to prepare a paste (electrode catalyst coating solution). This electrode catalyst coating solution was applied to both sides of the electrolyte composite membrane V ′ obtained in (1) above and dried to give a platinum loading of 0.25 mg.
/ Cm ² of membrane / electrode assembly V′-1 was prepared.

After dispersing 40% by weight of platinum-supported carbon in isopropanol, the sulfonic acid equivalent was 1.25.
A 5 wt% isopropyl alcohol 5 wt% solution of sulfonated polyether sulfone electrolyte V in milliequivalent / g was added so that the weight ratio of the platinum catalyst and the polymer electrolyte was 2: 1, and the mixture was uniformly dispersed by ultrasonic waves. A paste (electrode catalyst coating solution) was prepared. This electrode catalyst coating solution was added to the above (1)
Applied on both sides of the electrolyte composite membrane V ′ obtained in
Of membrane / electrode assembly platinum content 0.25 mg / cm ² the V'-
2 was produced.

The periphery of the membrane / electrode assembly V'-1 or V'-2 was fixed with a SUS metal frame, and the temperature was kept at 80 ° C. and 95% RH for 1.5.
50 cycles of high-temperature wet state and room-temperature dry state of time holding and holding at 25 ° C, 50% RH for 1.5 hours
Added 0 times. Membrane / electrode assembly V'after environmental test cycle
In both -1 and V'-2, peeling was recognized unlike the initial stage.

(3) Durability Test of Fuel Cell Single Cell A thin carbon paper packing material (support current collector) was adhered to both sides of the membrane / electrode assembly V'-1 or V'-2,
A polymer electrolyte fuel cell unit cell composed of a conductive separator (bipolar plate) that also functions as a gas supply passage to the electrode and a polar chamber separation from both sides of the cell was prepared, and the current density was 3
A long-term operation test was conducted under the condition of 00 mA / cm ² . As a result, as shown by 22 and 23 in FIG. 6, the output voltage tended to decrease after 3000 hours of operation.

Example 6 (1) Preparation of Electrolyte Composite Membrane Using 10 denier polyethylene fibers obtained by twisting 9 filaments having a diameter of 12 μm, the density of warp and weft was 80
Books / inch woven fabric was woven. The woven fabric was flattened by pressing at 100 ° C. to a thickness of 20 μm.

The above woven fabric was treated with 1% in 30%, 8% fuming sulfuric acid gas.
After holding for a time, a sulfonated polyethylene woven fabric was obtained. This woven fabric was washed three times with boiling distilled water, and then the sulfonic acid equivalent was measured. The value was 1.3 meq / g. ES
When the sulfur atom S in the thickness direction was measured by CA using the sputtering method, absorption of the sulfur atom was recognized up to the central portion.

5% by weight of perfluorocarbon sulfonic acid (sulfonic acid equivalent of 0.
It was impregnated with an aqueous solution of isopropyl alcohol (9 meq / g) and dried at 60 ° C. The film was then heat treated at 140 ° C. for 5 minutes. The impregnation, drying, and heat treatment were repeated until the pinholes disappeared, that is, eight times. afterwards,
Immerse in 1N sulfuric acid at 60 to 70 ° C for 1 hour, and then soak in pure water for 6 hours.
Immerse at 0-70 ° C for 1 hour to remove the end groups of the electrolyte side chain by -S
Converted to O ₃ H. The obtained electrolyte composite membrane VI had an ionic conductivity of 0.3 S / cm and a tensile strength of 3.9 kg / mm ² .

The ionic conductivity and tensile strength of the electrolyte composite membrane VI of the present example were as follows: the electrolyte composite membrane VI of Comparative Example 6 reinforced with a polyethylene woven fabric whose surface was sulfonated only as described below.
Significantly superior to non-reinforced electrolyte membranes.

[0187] Further, the periphery of the electrolyte composite membrane VI was fixed with a SUS metal frame and held at 80 ° C and 95% RH for 1.5 hours and at 25 ° C and 50% RH for 1.5 hours. An environmental cycle simulating a fuel cell environment in a high temperature wet state and a room temperature dry state was added 500 times. The tensile strength of the electrolyte composite membrane VI after the environmental test cycle did not change from the initial value.

On the other hand, the electrolyte composite membrane V of Comparative Example 6 reinforced with a polyethylene woven fabric whose surface is sulfonated only as described below.
After the environmental test cycle, I'and the electrolyte membrane not reinforced were lowered to the initial 3/4 and 1/15, respectively.
From this, it is clear that the electrolyte composite membrane VI is superior to the electrolyte composite membrane VI ′ of Comparative Example 6 and the non-reinforced electrolyte membrane.

When the electrolyte composite membrane VI kept at 25 ° C. and 50% RH for 24 hours was immersed in ion-exchanged water at 80 ° C. for 24 hours, the dimensional change rate in the plane direction was 2.0%.

On the other hand, the dimensional change rate of the electrolyte composite membrane VI ′ of Comparative Example 6 reinforced with the polyethylene woven fabric having only the surface sulfonated was 3.0%, and that of the non-reinforced electrolyte membrane was 14%. .

From this, it is clear that the electrolyte composite membrane VI is superior to the electrolyte composite membrane VI 'of Comparative Example 6 and the non-reinforced electrolyte membrane.

Also, the fuel cell operating state is simulated to 80
Load load 0.5 kg / mm ² under conditions of ℃ and 95% RH
Of which the creep strain when 50 hours was applied for 20 hours was 20% and only the surface was reinforced with the sulfonation-treated polymer porous body, Comparative Example 6
It is as small as 1 / 1.5 of that of the non-reinforced electrolyte membrane and excellent.

From the above, it is clear that when the electrolyte membrane is reinforced with a sulfonation-treated polymer porous body, the tensile strength, dimensional change rate and creep resistance are improved, but the ionic conductivity is reduced. A major issue is to achieve both good characteristics and ionic conductivity. When reinforced with a porous polymer that is sulfonated inside, mechanical properties such as mechanical strength, dimensional stability, and creep resistance, which could not be achieved by a porous polymer with sulfonation only on the surface, are compatible with ionic conductivity. It is clear.

(2) Preparation of Membrane / Electrode Assembly 40% by weight of platinum-supported carbon was dispersed in isopropanol, and then 5% by weight of perfluorocarbon sulfonic acid (sulfonic acid equivalent 0.9 meq / g) isopropyl alcohol. The aqueous solution was added so that the weight ratio of the platinum catalyst to the polymer electrolyte was 2: 1, and the mixture was ultrasonically uniformly dispersed to prepare a paste (electrode catalyst coating solution). This electrode catalyst coating solution was applied to the electrolyte composite membrane V obtained in (1) above.
After being applied to both sides of I, it is dried and the amount of platinum carried is 0.25 mg.
/ Cm ² of membrane / electrode assembly VI was prepared.

The periphery of the membrane / electrode assembly VI was fixed with a SUS metal frame and kept at 80 ° C. and 95% RH for 1.5 hours.
500 cycles of high temperature wet condition and room temperature dry condition environmental cycles of 5 ° C. and 50% RH for 1.5 hours were added. No peeling was observed in the membrane / electrode assembly VI after the environmental test cycle as in the initial stage.

On the other hand, the membrane / electrode assembly VI 'of Comparative Example 6 was peeled off after the environmental test cycle. From this, it is clear that the membrane / electrode assembly VI of this example is superior to the membrane / electrode assembly VI ′ of Comparative Example 6.

Comparative Example 6 (1) Preparation of Electrolyte Composite Membrane The 20 μm-thick polyethylene woven fabric prepared in (1) of Example 6 was immersed in a 10% tetrachloroethane solution of chlorosulfuric acid at 30 ° C. for 1 hour. It was held and only the surface of the polyethylene woven fabric was sulfonated. This woven fabric was washed three times with boiling distilled water, and then the sulfonic acid equivalent was measured. The sulfonic acid equivalent was 0.1 meq / g. When the sulfur atom S in the thickness direction was measured by ESCA using the sputtering method, absorption of the sulfur atom was recognized only on the surface.

[0198] The woven polyethylene cloth having only the surface thereof was impregnated with an aqueous isopropyl alcohol solution containing 5% by weight of perfluorocarbon sulfonic acid (sulfonic acid equivalent: 0.9 meq / g) and dried at 60 ° C. Then
The film was heat treated at 140 ° C. for 5 minutes. The impregnation, drying, and heat treatment were repeated until the pinholes disappeared, that is, eight times. Then, it was immersed in 1N sulfuric acid at 60 to 70 ° C. for 1 hour and then immersed in pure water at 60 to 70 ° C. for 1 hour to convert the terminal groups of the side chains of the electrolyte into —SO ₃ H. This electrolyte composite membrane V
I'has an ionic conductivity of 0.01 S / cm and a tensile strength of 7.
It was 6 kg / cm.

The ionic conductivity and tensile strength of the unreinforced electrolyte membrane having the same thickness and the same sulfonic acid equivalent were 0.12 S / cm and 1.2 kg / mm ² , respectively.

The periphery of the electrolyte composite membrane VI ′ and the non-reinforced electrolyte membrane was fixed with a SUS metal frame, and the temperature was 80 ° C. and 95%.
Hold at RH for 1.5 hours and at 25 ° C, 50% RH for 1.
An environmental cycle of a high temperature wet state and a room temperature dry state, which was maintained for 5 hours, was added 500 times. The tensile strengths of the electrolyte composite membrane VI ′ and the non-reinforced electrolyte membrane after the environmental test cycle were lowered to 3/4 and 1/15 of the initial values, respectively.

The electrolyte composite membrane IV ′ held at 25 ° C. and 50% RH for 24 hours and the unreinforced electrolyte membrane were heated to 80 ° C.
The dimensional change rates in the plane direction when immersed in ion-exchanged water for 24 hours were 3.0% and 14%, respectively.

Simulating the operating condition of the fuel cell,
The creep strains of the electrolyte composite membrane IV ′ and the non-reinforced electrolyte membrane when a load of 0.5 kg / mm ² was applied for 50 hours under the condition of 5% RH were 30% and 180%, respectively.

(2) Preparation of Membrane / Electrode Assembly 40% by weight of platinum-supported carbon was dispersed in isopropanol, and then 5% by weight of perfluorocarbon sulfonic acid (sulfonic acid equivalent: 0.9 meq / g) isopropyl alcohol. The aqueous solution was added so that the weight ratio of the platinum catalyst to the polymer electrolyte was 2: 1, and the mixture was ultrasonically uniformly dispersed to prepare a paste (electrode catalyst coating solution). This electrode catalyst coating solution was applied to the electrolyte composite membrane V obtained in (1) above.
After being applied to both sides of I ', it is dried and the amount of platinum carried is 0.25m.
A membrane / electrode assembly VI ′ of g / cm ² was prepared.

The periphery of the membrane / electrode assembly VI ′ was fixed with a SUS metal frame and kept at 80 ° C. and 95% RH for 1.5 hours.
500 cycles of high temperature wet condition and room temperature dry condition environmental cycles of 5 ° C. and 50% RH for 1.5 hours were added. After the environmental test cycle, the membrane / electrode assembly VI ′ was peeled off after the environmental test cycle, unlike the initial stage.

[Examples 7 to 26] (1) Preparation of electrolyte composite membrane Polytetrafluoroethylene porous film, polychlorotrifluoroethylene porous film, polyethylene porous film having a film thickness of about 25 µm and a porosity of 95% , Polypropylene porous film, polyalicyclic olefin porous film, polyetheretherketone porous film,
Polyether ether sulfone porous film, polyether sulfone porous film, polysulfone porous film, polyphenylene sulfide porous film,
The polymer porous body of the polyphenylene porous film is shown in Table 1.
Sulfonating was performed under the sulfonation conditions shown in Tables 1 to 5 using the sulfonating agents described in Nos.

The obtained film was washed 3 times with boiling distilled water, and the sulfonic acid equivalent was measured. The sulfonic acid equivalents are shown in Table 1.
.About.5, and is 0.7 to 1.4. Further, when the sulfur atom S in the thickness direction was measured by ESCA using the sputtering method, absorption of the sulfur atom was recognized up to the central portion in all cases. That is, it is sulfonated to the center. In addition,
When sulfonation was carried out under the same conditions using the same film as the above-mentioned material having a porosity of 0%, absorption of sulfur atoms was recognized up to the central part.

The above sulfonated polymer porous materials are shown in Tables 1-5.
Was impregnated with an electrolyte solution in which an electrolyte having an equivalent sulfonic acid of was dissolved and dried at 60 ° C. The film was then heat treated at 140 ° C. for 5 minutes. The impregnation, drying, and heat treatment were repeated until pinholes disappeared, that is, 5 to 8 times. Then, it was immersed in 1N sulfuric acid at 60 to 70 ° C. for 1 hour and in pure water at 60 to 70 ° C. for 1 hour.

The ionic conductivity and tensile strength of the obtained electrolyte composite membrane are, as shown in Tables 1 to 5, 0.15 to 0.1, respectively.
The values were 7 S / cm and 3.9 to 5.1 kg / mm ² . In both cases, the ionic conductivity and tensile strength were superior to those of the electrolyte composite membrane reinforced with the non-sulfonated polymer porous body prepared for comparison.

[0209] Further, the circumference of the electrolyte composite membranes in Tables 1 to 5 was S
Fix with a US metal frame, and keep the battery conditions of high temperature wet condition and room temperature dry condition of 1.5 hours holding at 80 ° C and 95% RH and 1.5 hours holding at 25 ° C and 50% RH. The simulated environmental cycle was added 500 times. The tensile strength values of the electrolyte composite membrane after the environmental test cycle did not change from the initial values in any cases.

On the other hand, the tensile strength value of the electrolyte composite membrane reinforced by the non-sulfonated polymer porous body prepared and tested for comparison was 1/3 to 1 of the initial value after the environmental test cycle.
It had fallen to / 5. From this, it is apparent that the electrolyte composite membranes of the present invention in Tables 1 to 5 are superior to the electrolyte composite membranes reinforced with the non-sulfonated polymer porous body.

When the electrolyte composite membrane kept at 25 ° C. and 50% RH for 24 hours was immersed in 80 ° C. ion-exchanged water for 24 hours, the dimensional change rate in the plane direction was 1 as shown in Tables 1 to 5. It is 0.1 to 2.0%.

On the other hand, the electrolyte composite membrane reinforced with the non-sulfonated polymer porous body of Comparative Example after being kept at 25 ° C. and 50% RH for 24 hours was immersed in ion-exchanged water at 80 ° C. for 24 hours to obtain a flat surface. Directional dimensional change rate is 3.0 to 5.0
%, 25 ° C., 50% RH for 24 hours, the electrolyte membrane not reinforced with the porous polymer was immersed in 80 ° C. ion-exchanged water for 24 hours.
There was ~ 30%.

The rate of dimensional change is smaller than the rate of dimensional change of the electrolyte composite membrane reinforced by the polymer porous body not subjected to sulfonation treatment or the electrolyte membrane not reinforced, and is excellent.

Further, the operation state of the fuel cell is simulated to 80
Load load 0.5 kg / mm under conditions of ℃ and 95% RH
The creep strains when ² is applied for 50 hours are shown in Tables 1-5. Each of them is 10 to 20%, which is smaller than the dimensional change rate of the electrolyte composite membrane reinforced by the polymer porous body not subjected to the sulfonation treatment or the electrolyte membrane not reinforced, and is excellent.

The electrolyte composite membrane reinforced by the above-mentioned sulfonated polymer porous material is a machine which cannot be achieved by the electrolyte composite membrane reinforced by the non-sulfonated polymer porous material or the electrolyte membrane without reinforcement. Strength, dimensional stability,
It can be seen that mechanical characteristics such as creep resistance and ionic conductivity are compatible.

(2) Preparation of Membrane / Electrode Assembly After 40% by weight of platinum-supported carbon was dispersed in a solution such as isopropanol, an electrolyte solution containing sulfonic acid equivalents in Tables 1 to 5 was dissolved in a platinum catalyst. And a polymer electrolyte were added at a weight ratio of 2: 1 and dispersed uniformly by ultrasonic waves to prepare a paste (electrode catalyst coating solution).
This electrode catalyst coating solution was applied to both sides of the electrolyte composite membrane obtained in (1) above and dried to give a platinum loading of 0.25 mg.
A membrane / electrode assembly of / cm ² was prepared.

(3) Durability Test of Fuel Cell Single Cell The membrane / electrode assembly was immersed in boiling deionized water for 2 hours to absorb water. The obtained membrane / electrode assembly was incorporated into an evaluation cell, and the fuel cell output performance was evaluated.
Table 1 shows the output voltage of the single battery cell at the beginning and after 5000 hours.
5 shows.

[0218]

[Table 1]

[Table 2]

[Table 3]

[Table 4]

[Table 5] A fuel cell using an electrolyte composite membrane having a high ionic conductivity has a higher output voltage and is superior. Although the unit cell using the membrane / electrode assembly reinforced with the non-sulfonated porous film was observed to deteriorate after 5000 hours, the unit cell using the membrane / electrode assembly of the present invention was As shown in Tables 1 to 5, it is excellent in that it hardly deteriorates.

[0219]

EFFECTS OF THE INVENTION According to the present invention, an electrolyte composite membrane reinforced by a polymer porous body having ion conductivity even inside is
Compared with an electrolyte composite membrane reinforced with a porous polymer that does not impart ionic conductivity, it has superior ionic conductivity, tensile strength, dimensional stability, creep resistance, and environmental cycle resistance.

The electrolyte composite membrane, membrane / electrode assembly and fuel cell of the present invention can have practically sufficient cell characteristics and high durability.

[Brief description of drawings]

FIG. 1 is a perspective view showing the structure of a battery cell for polymer electrolyte fuel cells of Example 1. FIG.

FIG. 2 is a graph showing the durability test results of the single cell for polymer electrolyte fuel cell of Example 1.

FIG. 3 is a graph showing the durability test results of the single cell for polymer electrolyte fuel cell of Example 2.

FIG. 4 is a graph of durability test results of a single cell for polymer electrolyte fuel cells of Example 3.

FIG. 5 is a graph showing the durability test results of the single cell for polymer electrolyte fuel cell of Example 4.

FIG. 6 is a graph of the durability test results of the single cell for polymer electrolyte fuel cell of Example 5.

[Explanation of symbols]

1 ... Solid polymer electrolyte composite membrane, 2 ... Air electrode, 3 ... Oxygen electrode, 4 ... Membrane / electrode assembly, 5 ... Support current collector, 6 ... Separator, 7 ... Air, 8 ... Air + water, 9 ... Hydrogen + water, 10 ...
Residual hydrogen, 11 ... Water.

Continued front page    (72) Inventor Toshiyuki Kobayashi             7-1-1, Omika-cho, Hitachi-shi, Ibaraki Prefecture             Inside the Hitachi Research Laboratory, Hitachi Ltd. (72) Inventor Yuichi Kamo             7-1-1, Omika-cho, Hitachi-shi, Ibaraki Prefecture             Inside the Hitachi Research Laboratory, Hitachi Ltd. (72) Inventor Kazutoshi Higashiyama             7-1-1, Omika-cho, Hitachi-shi, Ibaraki Prefecture             Inside the Hitachi Research Laboratory, Hitachi Ltd. F-term (reference) 5H026 AA06 BB03 CX05 EE18 HH00                       HH03

Claims (9)

[Claims] 1. A solid polymer electrolyte composite membrane, wherein the polymer porous body is constituted by using a sulfonated membrane. 2. The solid polymer electrolyte composite membrane according to claim 1, wherein the polymer porous body is a porous engineering plastic. 3. The solid polymer electrolyte composite membrane according to claim 1, wherein the polymer porous body has voids filled with a polymer solid electrolyte. 4. The solid polymer electrolyte composite membrane according to claim 3, wherein the solid polymer electrolyte is a sulfoalkylated aromatic hydrocarbon-based polymer electrolyte. 5. The ionic conductivity is 0.15 to 0.7 S / cm.
And after holding at 25 ° C and 50% RH for 24 hours,
The dimensional change rate in the plane direction when immersed in ion-exchanged water at ℃ for 24 hours is 1.1 to 2.0%, or the tensile strength is 3.5 to 5.2 kg / mm ^2. Solid polymer electrolyte composite membrane. 6. A solid polymer electrolyte membrane and a membrane / electrode assembly for a solid polymer fuel cell having a gas electrode joined to the solid polymer electrolyte membrane, wherein the solid polymer electrolyte membrane is one of claims 1 to 5.
A membrane / electrode assembly for a polymer electrolyte fuel cell, which is the solid polymer electrolyte composite membrane according to any one of items 1 to 5. 7. A solid polymer electrolyte membrane and a membrane / electrode assembly for a solid polymer fuel cell having a gas electrode joined to the solid polymer electrolyte membrane, wherein the solid polymer electrolyte membrane is one of claims 1 to 5.
2. The membrane / electrode assembly for a polymer electrolyte fuel cell, which is the solid polymer electrolyte composite membrane according to any one of claims 1 to 3, wherein the electrode catalyst coating solution is a perfluorocarbon sulfonic acid solution. 8. A solid polymer electrolyte membrane and a pair of gas diffusion electrodes consisting of a cathode electrode and an anode electrode on both sides of the solid polymer electrolyte membrane, and a pair of gas impermeable separators sandwiching the gas diffusion electrodes, In a solid polymer electrolyte fuel cell in which a pair of sealing materials are arranged so as to be sandwiched between a solid polymer electrolyte membrane and the separator, and in contact with an outer peripheral portion of the gas electrode, the solid polymer electrolyte membrane may be formed.
5. A solid polymer electrolyte fuel cell, which is the solid polymer electrolyte composite membrane according to any one of items 1 to 5. 9. A solid polymer electrolyte membrane and a pair of gas diffusion electrodes composed of a cathode electrode and an anode electrode on both sides of the solid polymer electrolyte membrane, and a pair of gas impermeable separators sandwiching the gas diffusion electrodes, In a solid polymer electrolyte fuel cell sandwiched between the solid polymer electrolyte membrane and the separator, and a pair of sealing materials arranged so as to contact the outer peripheral portion of the gas electrode, the solid polymer electrolyte membrane and both sides thereof. A pair of gas diffusion electrodes consisting of a cathode electrode and an anode electrode is the membrane / electrode assembly for a polymer electrolyte fuel cell according to claim 6 or 7, wherein the polymer electrolyte fuel cell is a polymer electrolyte fuel cell.