JP2022190524A - Polymer electrolyte composition, polymer electrolyte membrane, electrode catalyst layer, membrane electrode assembly, and solid polymer fuel cell - Google Patents

Abstract

To provide a highly durable polymer electrolyte composition that can give a polymer electrolyte membrane, an electrode catalyst layer, a membrane electrode assembly, and a solid polymer fuel cell.SOLUTION: A polymer electrolyte composition contains a polymer electrolyte (a), and niobium oxide (b) having an average particle size of more than 0.050 μm to 5.0 μm or less as determined by laser diffraction particle size distribution measurement.SELECTED DRAWING: None

Description

TECHNICAL FIELD The present invention relates to a polymer electrolyte composition, a polymer electrolyte membrane, an electrode catalyst layer, a membrane electrode assembly, and a polymer electrolyte fuel cell.

A fuel cell directly converts the chemical energy of fuel into electrical energy by electrochemically oxidizing hydrogen, methanol, etc. within the cell, and is attracting attention as a clean source of electrical energy. ing. In particular, solid polymer electrolyte fuel cells are expected to be used as alternative power sources for automobiles, home cogeneration systems, portable power generators, etc., because they operate at lower temperatures than other fuel cells.

Such a solid polymer electrolyte fuel cell comprises a membrane electrode assembly in which electrode catalyst layers respectively constituting a negative electrode and a positive electrode are bonded to both sides of a proton exchange membrane mainly composed of a polymer electrolyte membrane, at least equipped.
A structure in which a gas diffusion electrode having a structure in which an electrode catalyst layer and a gas diffusion layer are laminated is joined to both sides of a proton exchange membrane mainly composed of a polymer electrolyte membrane is referred to as a membrane electrode assembly. There is also
The proton exchange membrane is a membrane made of a composition having a strong acid group such as a sulfonic acid group or a carboxylic acid group in the polymer chain and having a property of selectively permeating protons. Compositions used for such proton exchange membranes include perfluoro-based proton compositions typified by Nafion (registered trademark, manufactured by DuPont), which has high chemical stability.

During operation of the fuel cell, a fuel (e.g., hydrogen) is supplied to the gas diffusion electrode on the anode side, and an oxidant (e.g., oxygen or air) is supplied to the gas diffusion electrode on the cathode side. , the operation of the fuel cell is realized.
Specifically, when hydrogen is used as fuel, hydrogen is oxidized on the electrode catalyst on the anode side to generate protons. After passing through the proton-conducting polymer in the electrode catalyst layer on the anode side, the protons move through the proton exchange membrane, pass through the proton-conducting polymer in the electrode catalyst layer on the cathode side, and onto the electrode catalyst on the cathode side. reach.
On the other hand, electrons generated simultaneously with protons by oxidation of hydrogen pass through an external circuit and reach the gas diffusion electrode on the cathode side. On the electrode catalyst on the cathode side, the protons and oxygen in the oxidant react to produce water. At this time, electrical energy is extracted.

At this time, the proton exchange membrane must also serve as a gas barrier partition. If the gas permeability of the proton exchange membrane is high, hydrogen supplied from the anode side may leak to the cathode side and oxygen supplied from the cathode side may leak to the anode side, that is, cross-leakage may occur. .
When cross-leakage occurs, a so-called chemical short circuit occurs, making it impossible to extract the desired electrical energy, and the hydrogen supplied from the anode side reacts with the oxygen supplied from the cathode side to generate hydrogen peroxide. . This hydrogen peroxide is decomposed by a trace amount of metals (ions such as Fe, Cr, Ni, etc.) contained in the humidified gas supply pipe or the like supplied to the battery to generate hydroxyl radicals and peroxide radicals. A problem arises in that these radicals accelerate deterioration of the proton exchange membrane.

In particular, when a fuel cell is installed in an automobile, the fuel cell must be operated under high-temperature conditions exceeding 80°C or under low-humidity conditions such as 30% RH or less due to reduced use of humidifiers. can be considered.
Further, as the bipolar plates for sandwiching the membrane electrode assembly of the fuel cell, the use of metallic bipolar plates is expected.
When operating under high-temperature conditions and/or low-humidity conditions as described above, a proton exchange membrane made of a perfluoro-based proton composition, which is said to have excellent durability, is used as a fuel cell membrane. Even if there is, there arises a problem that deterioration of the proton exchange membrane is accelerated.
When a metal bipolar plate is used, the metal (Fe, Cr, Ni, etc.) gradually dissolves during operation, and the dissolved metal ions decompose hydrogen peroxide as described above, resulting in radical species. is generated, which may promote deterioration of the proton exchange membrane.

As a method for suppressing deterioration of the proton exchange membrane due to radical species as described above, cerium ions or cerium oxide are contained in the proton exchange membrane, and part of the sulfonic acid groups of the polymer electrolyte membrane constituting the proton exchange membrane is That is, a technique is disclosed in which some of the protons in a plurality of sulfonic acid groups are replaced with cerium ions, and the cerium ions capture radical species to suppress deterioration of the polymer electrolyte membrane (for example, , see Patent Documents 1 and 2).

Japanese Patent No. 3915846 Japanese Patent No. 5176664

However, in the techniques described in Patent Documents 1 and 2, segregation of cerium ions may occur in the polymer electrolyte membrane, and especially under acidic conditions, cerium caused by segregation may desorb. There is a problem that the radical species causes deterioration of the polymer electrolyte membrane, resulting in a decrease in durability.

Therefore, in the present invention, in view of the above-described problems of the prior art, a polymer capable of obtaining a highly durable polymer electrolyte membrane, an electrode catalyst layer, a membrane electrode assembly, and a polymer electrolyte fuel cell An object of the present invention is to provide an electrolyte composition.

The present inventors have made intensive studies to solve the above-described problems, and found that a polymer electrolyte composition constituting a polymer electrolyte membrane comprises a polymer electrolyte and fine particles of niobium oxide having a predetermined average particle size. The inventors have found that the above-described problems of the prior art can be solved by specifying the content, and have completed the present invention.
That is, the present invention is as follows.

[1]
a polymer electrolyte (a);
Niobium oxide (b) having an average particle size of more than 0.050 μm and 5.0 μm or less as measured by laser diffraction particle size distribution measurement;
A polymer electrolyte composition containing
[2]
The niobium oxide (b) is
The polymer electrolyte composition according to [1] above, which is at least one niobium oxide selected from the group consisting of niobium dioxide and niobium pentoxide.
[3]
[ 1] or the polymer electrolyte composition according to [2].
[4]
The polymer electrolyte (a) is
represented by the following general formula (1),
The polymer electrolyte composition according to any one of [1] to [3].
-[ _CF2CX1X2 ] _{a- [CF2-CF(-O-(CF2-CF(CF2X3))b} ^{- Oc-} _{( CFR1 )} ^{d- (} _CFR2 ⁾ _e- (CF ₂ ) _f -X ⁴ )] _g- (1)
(In general formula (1), X ¹ , X ² and X ³ are each independently a halogen element or a perfluoroalkyl group having 1 to 3 carbon atoms.
a and g are 0≦a<1, 0<g≦1, and a+g=1.
b is an integer of 0 to 8; c is 0 or 1;
d and e are each independently an integer of 0 to 6;
f is an integer of 0 or more and 10 or less.
However, d+e+f is not equal to 0.
R ¹ and R ² are each independently a halogen element, a perfluoroalkyl group having 1 to 10 carbon atoms, or a fluorochloroalkyl group.
X4 is ^COOZ , _{SO3Z , PO3Z2} , or _PO3HZ . Z is a hydrogen atom, an alkali metal atom, an alkaline earth metal ^atom , or an ^{amine ( NH4} _{, NH3R3} ^{, NH2R3R4 ,} _NHR3R4R5 ^{, NR3R4R5R 6} ). R ³ , R ⁴ , R ⁵ and R ⁶ are alkyl groups or arene groups. )
[5]
A polymer electrolyte membrane comprising the polymer electrolyte composition according to any one of [1] to [4].
[6]
An electrode catalyst layer comprising the polymer electrolyte composition according to any one of [1] to [4].
[7]
A membrane electrode assembly comprising the polymer electrolyte membrane according to [5] above and/or the electrode catalyst layer according to [6] above.
[8]
A polymer electrolyte fuel cell comprising the membrane electrode assembly according to [7] above.

ADVANTAGE OF THE INVENTION According to this invention, the polymer electrolyte composition with which a highly durable polymer electrolyte membrane, an electrode catalyst layer, a membrane electrode assembly, and a polymer electrolyte fuel cell can be obtained is obtained.

EMBODIMENT OF THE INVENTION Hereinafter, the form (henceforth "this embodiment") for implementing this invention is demonstrated in detail.
The following embodiments are examples for explaining the present invention, and are not intended to limit the present invention to the following contents. The present invention can be implemented with various modifications within the scope of its gist.

[Polymer electrolyte composition]
The polymer electrolyte composition of the present embodiment is
a polymer electrolyte (a);
Niobium oxide (b) having an average particle size of more than 0.050 μm and 5.0 μm or less as measured by laser diffraction particle size distribution measurement;
contains the
When the polymer electrolyte composition of the present embodiment has the above configuration, a highly durable polymer electrolyte membrane, electrode catalyst layer, membrane electrode assembly, and polymer electrolyte fuel cell can be obtained.

(Polymer electrolyte (a))
The polymer electrolyte (a) used in the present embodiment is preferably a polymer compound having ion-exchange groups with an ion-exchange equivalent of 0.5 to 3.0 meq/g.
By setting the ion exchange equivalent of the polymer electrolyte (a) to 3.0 meq/g or less, when it is used as a polymer electrolyte membrane, the polymer electrolyte membrane can withstand high temperature and high humidity conditions during fuel cell operation. Below, swelling is reduced. By reducing the swelling, the decrease in strength of the polymer electrolyte membrane can be suppressed, and problems such as electrode separation due to wrinkles can be prevented from occurring, and furthermore, the problem of decreased gas barrier properties. can be reduced.
On the other hand, by setting the ion exchange equivalent of the polymer electrolyte (a) to 0.5 meq/g or more, the power generation capacity of the fuel cell provided with the polymer electrolyte membrane containing the polymer electrolyte composition of the present embodiment is increased. can be maintained well.
From the viewpoint described above, the ion exchange equivalent of the polymer electrolyte (a) is preferably 0.65 to 2.0 meq/g, more preferably 0.8 to 1.5 meq/g.

The ion exchange capacity of the polymer electrolyte (a) can be measured as follows.
First, the membrane composed of the polymer electrolyte (a) in which the counter ions of the ion-exchange groups are in the proton state is immersed in a saturated NaCl aqueous solution at 25° C., and the aqueous solution is stirred for a sufficient time. Then, the protons in the saturated NaCl aqueous solution are neutralized and titrated with 0.01N sodium hydroxide aqueous solution. A membrane composed of the polymer electrolyte (a) in which the counter ions of the ion-exchange groups are in the state of sodium ions obtained by filtration after neutralization is rinsed with pure water, vacuum-dried, and then weighed. Let M (mmol) be the amount of sodium hydroxide required for neutralization, W (mg) be the mass of the polymer electrolyte membrane whose ion-exchange group counterions are sodium ions, and the equivalent mass EW ( g/equivalent).
EW=(W/M)-22
Furthermore, by taking the reciprocal of the obtained EW value and multiplying it by 1000, the ion exchange equivalent (millieq/g) can be calculated.

The material constituting the polymer electrolyte (a) is not limited to the following, but for example, a fluorine polymer electrolyte, a hydrocarbon polymer compound having an aromatic ring in the molecule, and Preferred are fluorinated hydrocarbon-based polymer compounds and hydrocarbon-based polymer compounds into which ion-exchange groups have been introduced. A perfluorocarbon polymer compound having an exchange group is more preferred.
The polymer electrolyte composition of the present embodiment is not limited to fuel cell applications, and the polymer electrolyte used in the polymer electrolyte composition can be similarly applied to applications other than fuel cells. For example, it can be used for PEM type water electrolysis, RF battery, alkaline water electrolysis, and the like.

The hydrocarbon-based polymer compound having an aromatic ring in the molecule, which is a partially fluorinated hydrocarbon-based polymer compound, which is the polymer electrolyte (a), is not limited to the following. , for example, polyphenylene sulfide, polyphenylene ether, polysulfone, polyethersulfone, polyetherethersulfone, polyetherketone, polyetheretherketone, polythioetherethersulfone, polythioetherketone, polythioetheretherketone, polybenzimidazole, polybenzoxazole , polyoxadiazole, polybenzoxazinone, polyxylylene, polyphenylene, polythiophene, polypyrrole, polyaniline, polyacene, polycyanogen, polynaphthyridine, polyphenylene sulfide sulfone, polyphenylene sulfone, polyimide, polyetherimide, polyesterimide, polyamideimide, polyarylate, Partially fluorinated polymer compounds such as aromatic polyamides, polystyrenes, polyesters, and polycarbonates can be mentioned.

From the viewpoint of heat resistance, oxidation resistance, and hydrolysis resistance, particularly , polyphenylene sulfide, polyphenylene ether, polysulfone, polyethersulfone, polyetherethersulfone, polyetherketone, polyetheretherketone, polythioetherethersulfone, polythioetherketone, polythioetheretherketone, polybenzimidazole, polybenzoxazole, poly Oxadiazole, polybenzoxazinone, polyxylylene, polyphenylene, polythiophene, polypyrrole, polyaniline, polyacene, polycyanogen, polynaphthyridine, polyphenylene sulfide sulfone, polyphenylene sulfone, polyimide, polyetherimide, and polyesterimide are partially fluorinated. polymer compounds are preferred.

The ion exchange groups to be introduced into the various polymer compounds described above are not limited to the following, but examples include sulfonic acid groups, sulfonimide groups, sulfonamide groups, carboxylic acid groups, phosphoric acid groups, and the like. is preferred, and a sulfonic acid group is more preferred.

In addition, the perfluorocarbon polymer compound having an ion exchange group is not limited to the following, but for example, perfluorocarbon sulfonic acid resin, perfluorocarbon carboxylic acid resin, perfluorocarbon sulfonimide resin, perfluorocarbon sulfonamide resin , perfluorocarbon phosphoric acid resins, and amine salts and metal salts of these resins.

<Preferred Form of Polymer Electrolyte (a)>
The perfluorocarbon polymer compound, which is a fluorine-based polymer electrolyte constituting the polymer electrolyte (a), is not limited to the following, but a polymer represented by the following general formula (1) is preferable. mentioned.
-[ _CF2CX1X2 ] _a- [CF2 ^- CF(-O-(CF2 ^- CF _{( CF2X3} )) _b ^- _Oc- ( _CFR1 ) _d- ^{( CFR2} ) _e- ( CF ₂ ) _f -X ⁴ )] _g -- (1)
(In general formula (1), X ¹ , X ² and X ³ are each independently a halogen element or a perfluoroalkyl group having 1 to 3 carbon atoms.
a and g are 0≦a<1, 0<g≦1, and a+g=1.
b is an integer of 0 to 8; c is 0 or 1;
d and e are each independently an integer of 0 to 6;
f is an integer of 0 or more and 10 or less.
However, d+e+f is not equal to 0.
R ¹ and R ² are each independently a halogen element, a perfluoroalkyl group having 1 to 10 carbon atoms, or a fluorochloroalkyl group.
X4 is ^COOZ , _{SO3Z , PO3Z2} , or _PO3HZ .
Here, Z is a hydrogen atom, an alkali metal atom, an alkaline earth metal atom, or an ^{amine ( NH4} _{, NH3R3} ^{, NH2R3R4 ,} _NHR3R4R5 ^{, NR3R4R 5R6 )} . R ³ , R ⁴ , R ⁵ and R ⁶ are alkyl groups or arene groups. )

As the perfluorocarbon polymer compound which is a fluorine-based polymer electrolyte constituting the polymer electrolyte (a), in particular, a perfluorocarbon sulfonic acid resin represented by the following general formula (2) or general formula (3) or a metal thereof Salt is preferred.
-[ _CF2CF2 ] _a- [CF2 _- CF(-O-(CF2-CF( _CF3 )) _{b -} O-(CF2) _{c - SO3X} )] _d -...( ₂ )
(In the general formula (2), a and d are 0 ≤ a < 1, 0 ≤ d < 1, a + d = 1. b is an integer of 1 or more and 8 or less. c is an integer of 0 or more and 10 or less. and X is a hydrogen atom or an alkali metal atom.)
-[ _CF2CF2 ] _e- [CF2 _- CF ₍ -O-(CF2) _{f -} SO3Y)] _g -...( ₃ )
(In the general formula (3), e and g are 0 ≤ e < 1, 0 ≤ g < 1, e + g = 1. f is an integer of 0 or more and 10 or less. Y is a hydrogen atom or an alkali metal atom is.)

The perfluorocarbon polymer compound having an ion exchange group, which can be used as the polymer electrolyte (a), is not limited to the following, but for example, a precursor polymer represented by the following general formula (4) is polymerized. After that, it can be produced by performing alkali hydrolysis, acid treatment, or the like.
-[ _CF2CX1X2 ] _a- [CF2 ^- CF(-O-(CF2 ^- CF _{( CF2X3} )) _b ^- _Oc- ( _CFR1 ) _d- ^{( CFR2} ) _e- ( CF ₂ ) _f −X ⁵ )] _g (4)
(In the general formula (4), X ¹ , X ² and X ³ are each independently a halogen element or a perfluoroalkyl group having 1 to 3 carbon atoms. a and g are 0 ≤ a < 1 , 0 < g ≤ 1, a + g = 1. b is an integer of 0 to 8. c is 0 or 1. d and e are each independently an integer of 0 to 6. f is an integer of 0 or more and 10 or less, provided that d + e + f is not equal to 0. R ¹ and R ² are each independently a halogen element, a perfluoroalkyl group having 1 or more and 10 or less carbon atoms, or a fluorochloro an alkyl group, X ⁵ is COOR ⁷ , COR ⁸ or SO ₂ R ⁸ , where R ⁷ is a hydrocarbon alkyl group having 1 to 3 carbon atoms, and R ⁸ is a halogen element.)

As the polymer electrolyte (a), for example, it is also possible to use a polymer electrolyte having a polymer compound disclosed in WO 2017/033685.
That is, the polymer electrolyte (a) is, for example, a precursor polymer formed from a polymer compound having a cyclic structure having no ion-exchange groups in the polymer main chain and a polymer compound having an ion-exchange group, Alternatively, after polymerizing a precursor polymer formed by a polymer compound having two ion exchange groups on the side chains of the perfluorocarbon polymer compound represented by the above general formula (2) or general formula (3), respectively , alkali hydrolysis, acid treatment, and the like.

Each of the above precursor polymers is not limited to the following, but can be produced, for example, by copolymerizing a fluorinated olefin compound and a fluorinated vinyl compound.

Examples of the fluoroolefin compound include, but are not limited to, compounds represented by the following general formula (5).
CF2 ₌ CFZ (5)
(In general formula (5), Z represents H, Cl, F, a perfluoroalkyl group having 1 to 3 carbon atoms, or a cyclic perfluoroalkyl group which may contain oxygen.)

In addition, the vinyl fluoride compound is not limited to the following, but includes, for example, the following compounds.
CF2 ₌ CFO(CF2) _{z - SO2F}
CF2 ₌ CFOCF2CF _{( CF3} )O(CF2) _{z - SO2F}
CF2 ₌ CF ₍ CF2) _{z -} SO2F
CF2 ₌ CF(OCF2CF _{( CF3} )) _z- (CF2)z _{- 1- SO2F}
CF2 ₌ CFO(CF2) _{z - CO2R}
CF2 ₌ CFOCF2CF _{( CF3} )O(CF2) _{z - CO2R}
CF2=CF ₍ CF2) _{z - CO2R}
CF2=CF( _{OCF2CF ( CF3} )) _z- (CF2) _{2 - CO2R}
(In each formula, Z represents an integer of 1 to 8, and R represents a hydrocarbon-based alkyl group having 1 to 3 carbon atoms.)

The method for copolymerizing the fluorinated olefin compound and the fluorinated vinyl compound is not limited to the following, but includes, for example, the method described later.

(i) Solution polymerization method The solution polymerization method uses a polymerization solvent such as a fluorine-containing hydrocarbon, and the vinyl fluoride compound and the fluorinated olefin gas are allowed to react with each other in a state of filling and dissolving in the polymerization solvent to carry out polymerization. is the way to do it.
Examples of the fluorine-containing hydrocarbon used as the polymerization solvent include, but are not limited to, trichlorotrifluoroethane, 1,1,1,2,3,4,4,5,5,5-decaflo A group of compounds collectively referred to as "freons" can be used, such as oropentane.

(ii) Bulk polymerization method In the bulk polymerization method, a fluorinated olefin compound and a vinyl fluoride compound are polymerized using a vinyl fluoride compound itself as a polymerization solvent without using a polymerization solvent such as a fluorine-containing hydrocarbon. The method.

(iii) Emulsion polymerization method Emulsion polymerization method is a method in which an aqueous solution of a surfactant is used as a polymerization solvent, and a vinyl fluoride compound and a fluorinated olefin gas are reacted in a state of filling and dissolving in the polymerization solvent to perform polymerization. is.

(iv) Mini-emulsion polymerization or micro-emulsion polymerization method Emulsion polymerization involves using an aqueous solution of a surfactant and a co-emulsifier such as alcohol, filling the aqueous solution with a vinyl fluoride compound and a fluorinated olefin gas in an emulsified state. It is a method of polymerizing by reacting.

(v) Suspension polymerization method In the suspension polymerization method, an aqueous solution of a suspension stabilizer is used, and polymerization is carried out by reacting a vinyl fluoride compound and a fluorinated olefin gas in a state of being filled and suspended in the aqueous solution. The method.

Melt mass flow rate (hereinafter abbreviated as "MFR") can be used as an index of the degree of polymerization of the precursor polymer used in the polymer electrolyte (a) constituting the polymer electrolyte composition of the present embodiment. .
The MFR of the precursor polymer is preferably 0.01 g/10 minutes or more, more preferably 0.1 g/10 minutes or more, and even more preferably 0.3 g/10 minutes or more. Although the upper limit of MFR is not limited, it is preferably 100 g/10 minutes or less, more preferably 10 g/10 minutes or less.
By setting the MFR to 0.01 g/10 min or more and 100 g/10 min or less, there is a tendency that molding workability such as formation of a polymer electrolyte membrane is more excellent.
The MFR can be measured at 270° C., a load of 2.16 kgf, and an orifice inner diameter of 2.09 mm based on JIS K-7210.

The precursor polymer produced as described above is hydrolyzed in a basic reaction liquid, thoroughly washed with warm water or the like, and acid-treated, and the perfluorocarbon sulfonic acid resin precursor is protonated by the acid treatment. to form the SO ₃ H form.

(niobium oxide (b))
The polymer electrolyte composition of the present embodiment contains niobium oxide (b).
By containing niobium oxide (b), in the polymer electrolyte membrane, the electrode catalyst layer, and the membrane electrode assembly using the polymer electrolyte composition of the present embodiment, it can flow out for a long time even under acidic conditions. , excellent radical trapping ability is exhibited, and stable operation is possible.
Niobium oxide (b) has an average particle size of more than 0.05 μm and not more than 5.0 μm as measured by laser diffraction particle size distribution measurement.
Since the average particle size is more than 0.05 μm, when combined with polyphenylene sulfide as the polymer electrolyte (a) described above, a uniform polymer electrolyte membrane with excellent dispersion stability can be obtained.
Further, since the average particle size is 5 μm or less, the niobium oxide (b) has a sufficiently large specific surface area, exhibits excellent radical trapping ability, and provides a highly durable polymer electrolyte membrane.
The average particle size of niobium oxide (b) is preferably 0.05 μm to 5.0 μm, more preferably 0.10 μm to 1.0 μm.
The average particle size of niobium oxide (b) can be measured by analyzing laser scattered light according to the Microtrac method using a laser diffraction/scattering particle size analyzer. Specifically, it can be measured by the method described in the examples below.
In niobium oxide (b), methods for controlling the average particle size to be more than 0.05 μm and 5.0 μm or less include, but are not limited to, high impact/shear energy such as jet milling and ball milling. Examples thereof include a method of pulverizing and pulverizing by giving, a method of filtering a solution before preparation of the polymer electrolyte composition to remove coarse particles, and the like.

Niobium oxide (b) is preferably at least one niobium oxide selected from the group consisting of niobium dioxide and niobium pentoxide.
By using niobium dioxide and/or niobium pentoxide as the niobium oxide (b), the types of radicals to be trapped are increased, and the effect of increasing the overall radical trapping ability is obtained.

The content of niobium oxide (b) in the polymer electrolyte composition of the present embodiment is preferably 0.1 to 5.0% by mass, more preferably 0.1 to 3.0% by mass. , more preferably 0.5 to 3.0% by mass.
The content of niobium oxide (b) is 0.1 to 5.0% by mass, so that the decomposition of hydrogen peroxide is suppressed while maintaining good proton conductivity, and the polymer electrolyte has high durability. It tends to be possible to obtain membranes, electrode catalyst layers, membrane electrode assemblies, and solid polymer fuel cells.

In the polymer electrolyte composition of the present embodiment, the passage integral value based on the volume-based particle size distribution obtained by laser diffraction particle size distribution measurement of the niobium oxide (b) is, from the viewpoint of the balance between dispersion stability and radical quenching ability, It is preferable that the area having a particle size of more than 0.05 μm and 5.0 μm or less accounts for 30% or more of the whole.
The passage integral value based on the volume-based particle size distribution is more preferably 30% or more, more preferably 40% or more, in the region where the particle diameter is more than 0.05 μm and 5.0 μm or less.
The pass-integrated value based on the volume-based particle size distribution can be obtained by the method described in the examples below.
By controlling the processing time in the particle pulverization step, the passage integral value based on the volume-based particle size distribution can be controlled to 30% or more of the entire particle size range of more than 0.05 μm and 5.0 μm or less.

In the polymer electrolyte composition of the present embodiment, the niobium oxide (b) is preferably dispersed in the polymer electrolyte (a) described above.
Here, the term “dispersion” means that when TEM observation is performed without dyeing, the phase containing niobium oxide (b) is dispersed in the form of particles in the polymer electrolyte (component a) phase. It means a state in which the That is, it means that the component (a) constitutes the sea portion and the component (b) constitutes the island portion, thus having a sea-island structure. Dispersing in such a state means that the portion mainly composed of niobium oxide (b) is uniformly and finely dispersed in the portion mainly composed of the polymer electrolyte (a), and the durability is improved. preferred from

(Radical scavenger (c))
The polymer electrolyte composition of this embodiment can further contain a radical scavenger (c).
The polymer electrolyte composition of the present embodiment can efficiently suppress the generation of radical species and exhibits high durability. Even if it does, it can be captured by the radical scavenger (c). As a result, in a fuel cell vehicle using a polymer electrolyte membrane using the polymer electrolyte composition of the present embodiment, the durability of the fuel cell can be dramatically improved even under high temperature and low humidity conditions. There is a tendency.

Examples of radical scavengers (c) include, but are not limited to, compounds having functional groups that enable mechanisms proposed in known antioxidants.
Examples of such functional groups include, but are not limited to, a functional group having a radical chain terminating function, a functional group having a function of decomposing radicals, and a functional group having a function of inhibiting chain initiation. is mentioned.
Examples of functional groups having a radical chain-blocking function include, but are not limited to, phenolic hydroxyl groups, primary amines, secondary amines, and the like.
In addition, the functional group having a function of decomposing radicals is not limited to the following, and examples thereof include a mercapto group containing sulfur, phosphorus, etc., a thioether group, a disulfide group, a phosphite group, and the like.
Further, functional groups having a function of inhibiting chain initiation include, but are not limited to, hydrazine, amide, and the like ("Antioxidant Handbook" (Taiseisha, 1978)).

Radical scavengers (c) also include compounds whose atoms are easily abstracted by radicals, such as compounds having hydrogen bonded to tertiary carbons or carbon-halogen bonds in their structures.

Moreover, the radical scavenger (c) may have a functional group that forms an ionic bond with the polymer electrolyte (a). Examples of such a radical scavenger (c) include, but are not limited to, a compound (c-1) having at least one of primary amine and secondary amine in the same molecule. and/or having a tertiary amine in the same molecule and hydrogen bonded to sulfur, phosphorus, hydrazine, amide, phenolic hydroxyl group, primary amine, secondary amine, or tertiary amine, and halogen bonded to carbon A compound (c-2) having at least one selected from the group consisting of

Here, the functional group forming an ionic bond with the polymer electrolyte (a) in the compound (c-1) and the compound (c-2) is not limited to the following, for example, the polymer electrolyte ( When the ion exchange group in a) is a sulfonic acid group, it is a basic functional group, and specific examples include nitrogen-containing functional groups such as primary amine, secondary amine, and tertiary amine. Therefore, if it has a primary amine or a secondary amine, it will interact with the ion exchange groups of the polymer electrolyte (a) and also have a radical scavenging function (compound (c-1) equivalent).
On the other hand, when the portion interacting with the ion exchange group of the polymer electrolyte (a) is a tertiary amine, the functional group forming an ionic bond with the polymer electrolyte (a) is a portion having a radical scavenging function. is preferably contained in the same molecule, and examples of such functional groups include, but are not limited to, phenolic hydroxyl groups, primary and secondary amines (corresponding to compound (c-2)).

More specific examples of the compound (c-1) and compound (c-2), which are radical scavengers (c), are as follows.

Examples of the compound (c-1) include, but are not limited to, aromatic compounds partially substituted with the above functional groups such as polyaniline, polybenzimidazole, polybenzoxazole, and polybenzothiazole. , polybenzoxadiazole, phenylated polyquinoxaline, and unsaturated heterocyclic compounds such as phenylated polyquinoline.

Examples of the compound (c-2) include, but are not limited to, benzyl, which has a tertiary nitrogen heterocycle having a sulfonic acid and an acid-base bond in the side chain and is easily abstracted by a radical in the main chain. Specific examples include polyvinylpyridine, polyvinylcarbazole, polystyrene in which a group containing a secondary amine or a tertiary amine is introduced into an aromatic ring, and the like.

The compound (c-1) and the compound (c-2) are copolymers or the like of a unit having an ion-exchange group-having interaction with the polymer electrolyte (a) and a unit having a radical scavenging function. may By having a portion that interacts with the polymer electrolyte (a) having ion exchange groups, the compatibility with the polymer electrolyte (a) tends to be further improved. In addition, chemical durability tends to be further improved by having a portion having a radical scavenging function.

The content of compound (c-1) and compound (c-2) in the polymer electrolyte composition of the present embodiment is preferably 0.001 to 50.000% by mass in the polymer electrolyte composition, and more Preferably 0.005 to 20.000% by mass, more preferably 0.010 to 10.000% by mass, still more preferably 0.100 to 5.000% by mass, still more preferably 0.100 to 2.000% by mass % by mass.
In the polymer electrolyte composition of the present embodiment, by setting the total content of the compound (c-1) and the compound (c-2) within the above range (0.001 to 50.000% by mass), good There is a tendency to obtain a polymer electrolyte membrane, an electrode catalyst layer, a membrane electrode assembly, and a polymer electrolyte fuel cell having high durability while maintaining high proton conductivity.

(Thioether compound (d))
The polymer electrolyte composition of the present embodiment includes the above-described polymer electrolyte (a), niobium oxide having an average particle size of more than 0.050 μm and 5.0 μm or less (b), a radical scavenger (c), and a thioether. It may contain a compound (d).

The thioether compound (d) is not particularly limited, but for example, a chemical structure of —(R—S) _n — (S is a sulfur atom, R is a hydrocarbon group, and n is an integer of 1 or more). Specific examples include dialkylthioethers such as dimethylthioether, diethylthioether, dipropylthioether, methylethylthioether and methylbutylthioether; cyclic thioethers such as tetrahydrothiophene and tetrahydroapiran; methylphenyl sulfide; Aromatic thioethers such as ethylphenylsulfide, diphenylsulfide and dibenzylsulfide are included.
They may be used in monomeric form or in polymeric form, for example polyphenylene sulfide (PPS).

From the viewpoint of durability, the thioether compound (d) is a compound containing a chemical structure of -(R-S) _n- (S is a sulfur atom, R is a hydrocarbon group, and n is an integer of 1 or more), wherein n≥ It is preferably a polymer of 10 (oligomer, polymer), more preferably a polymer of n≧1,000. A more preferred thioether compound (d) is polyphenylene sulfide (PPS).

Polyphenylene sulfides that can be used as the thioether compound (d) are described below.
The polyphenylene sulfide that can be used as the component (d) is a polyphenylene sulfide having a paraphenylene sulfide skeleton of preferably 70 mol% or more, more preferably 90 mol% or more.

The method for producing the polyphenylene sulfide is not limited to the following, but for example, a method of polymerizing a halogen-substituted aromatic compound (such as p-dichlorobenzene) in the presence of sulfur and sodium carbonate; Method of polymerizing a halogen-substituted aromatic compound in the presence of sodium sulfide or sodium hydrogen sulfide and sodium hydroxide; polymerizing a halogen-substituted aromatic compound in the presence of hydrogen sulfide and sodium hydroxide or sodium aminoalkanoate in a polar solvent and a method of self-condensation of p-chlorothiophenol. Specifically, a method of reacting sodium sulfide and p-dichlorobenzene in an amide solvent such as N-methylpyrrolidone or dimethylacetamide or a sulfone solvent such as sulfolane is preferably used.

In addition, the content of -SX groups (S is a sulfur atom and X is an alkali metal or a hydrogen atom) possessed by the polyphenylene sulfide which is the component (d) is the total of the polymer electrolyte (a) and the polyphenylene sulfide (d). The amount is generally 10 μmol/g or more and 10,000 μmol/g or less, preferably 15 μmol/g or more and 10,000 μmol/g or less, more preferably 20 μmol/g or more and 10,000 μmol/g or less.
When the -SX group concentration is within the above range, the number of reactive sites tends to increase. By using polyphenylene sulfide whose -SX group concentration satisfies the above range, miscibility with the polymer electrolyte (a) is improved, dispersibility is improved, and higher durability is obtained under high temperature and low humidity conditions. .

As the thioether compound (d), a compound having an acidic functional group introduced at the end thereof can also be preferably used. Examples of the acidic functional group to be introduced include, but are not limited to, sulfonic acid group, phosphoric acid group, carboxylic acid group, maleic acid group, maleic anhydride group, fumaric acid group, itaconic acid group, acrylic Acid groups and methacrylic acid groups are preferred. Among these, a sulfonic acid group is more preferable.

The method for introducing the acidic functional group in the thioether compound (d) is not particularly limited, and a general method can be used.
For example, introduction of a sulfonic acid group can be carried out under known conditions using a sulfonating agent such as sulfuric anhydride and fuming sulfuric acid. Such introduction methods are not limited to the following; , Journal of Polymer Science: Part A: Polymer Chemistry, Vol.27, 3043-3051 (1989).

Moreover, as the thioether compound (d), those in which the introduced acidic functional group is substituted with a metal salt or an amine salt are also preferably used. Examples of metal salts include, but are not limited to, alkali metal salts such as sodium salts and potassium salts; and alkaline earth metal salts such as calcium salts.

Furthermore, when the thioether compound (d) is used in powder form when producing the polymer electrolyte composition of the present embodiment, the median diameter of the thioether compound (d) is 0.01 to 0.01 when dispersed in water. 2.0 μm is preferred, 0.01 to 1.0 μm is more preferred, 0.01 to 0.5 μm is even more preferred, and 0.01 to 0.1 μm is even more preferred. When the median diameter is within the above range, dispersibility in the polymer electrolyte (a) is further improved, and effects such as durability and longevity tend to be more excellent. In addition, the median diameter of the thioether compound (d) is not limited to the following, but can be determined, for example, by observation using a particle size distribution meter or scanning electron microscope (SEM).

The method for finely dispersing the thioether compound (d) in the polymer electrolyte (a) is not limited to the following. After obtaining a mixed solution of the polymer electrolyte (a) and the thioether compound (d), the mixed solution is filtered to remove coarse thioether compound (d) particles, and the filtered solution and the like.

When dispersing the thioether compound (d) in the polymer electrolyte (a) by melt kneading, when polyphenylene sulfide, which is suitable as the component (d), is used, the melt viscosity of the polyphenylene sulfide (using a flow tester , 300 ° C., load 196 N, L / D (L: orifice length, D: orifice inner diameter) = 10/1 value held for 6 minutes) is preferably 1 to 10,000 poise from the viewpoint of moldability. Yes, more preferably 100 to 10,000 poise.

The mass ratio (a/d) of the polymer electrolyte (a) and the thioether compound (d) in the polymer electrolyte composition of the present embodiment is (a/d) = 60/40 to 99.99/0.01. Preferably, (a/d) = 70/30 to 99.95/0.05, more preferably (a/d) = 80/20 to 99.9/0.1, (a /d)=90/10 to 99.5/0.5 is even more preferred.
By setting the mass ratio of the polymer electrolyte (a) to 60 or more, there is a tendency that good ion conductivity can be achieved and good battery characteristics can be achieved. On the other hand, by setting the mass ratio of the thioether compound (d) to 40 or less, the durability in battery operation under high temperature and low humidity conditions tends to be further improved.

Further, by blending the thioether compound (d) together with the radical scavenger (c) described above, a polymer electrolyte membrane, an electrode catalyst layer, and a membrane electrode assembly using the polymer electrolyte composition of the present embodiment tend to be able to exhibit extremely high durability even under high temperature and low humidity conditions.

The mass ratio (c/d) of the radical scavenger (c) and the thioether compound (d) is preferably (c/d) = 1/99 to 99/1, (c/d) = 5/95 to 95. /5 is more preferred, (c/d) = 10/90 to 90/10 is more preferred, and (c/d) = 20/80 to 80/20 is even more preferred.
When the mass ratio (c/d) is within the above range, the balance between chemical stability and durability (dispersibility) tends to be excellent.

Furthermore, the content of the total mass of the radical scavenger (c) and the thioether compound (d) in the polymer electrolyte composition is preferably 0.01 to 50% by mass, more preferably 0.05 to 45% by mass. , more preferably 0.1 to 40% by mass, even more preferably 0.2 to 35% by mass, and even more preferably 0.3 to 30% by mass. When the total content of the component (c) and the component (d) is within the above range, the balance between ionic conductivity and durability (dispersibility) tends to be excellent.

In one preferred embodiment, the polymer electrolyte composition of the present embodiment is a polymer electrolyte solution containing predetermined components including the above-described polymer electrolyte (a) and niobium oxide (b) as essential components. be. The polymer electrolyte composition having such a form can be processed into the form of the polymer electrolyte membrane and the electrode catalyst layer of the present embodiment.

(polymer electrolyte solution)
The polymer electrolyte membrane of the present embodiment is formed from the polymer electrolyte composition of the present embodiment containing polymer electrolyte (a) and niobium oxide (b) as essential components.
The polymer electrolyte composition may be used as a polymer electrolyte solution by dissolving or dispersing each component in a predetermined solvent simultaneously or separately and then mixing.

The polymer electrolyte solution can be used as a material for polymer electrolyte membranes, electrode catalyst layers, etc., as it is, or after undergoing steps such as filtration and concentration, either alone or mixed with other electrolyte solutions.

A method for producing a polymer electrolyte solution will be described.
The method for producing the polymer electrolyte solution is not limited to the following, but for example, first, a molded article made of a polymer electrolyte precursor is immersed in a basic reaction liquid and hydrolyzed. This hydrolysis treatment converts the polymer electrolyte precursor into the polymer electrolyte (a). Next, the hydrolyzed molding is thoroughly washed with warm water or the like, and then acid-treated.

The acid used for the acid treatment is not particularly limited, but mineral acids such as hydrochloric acid, sulfuric acid and nitric acid, and organic acids such as oxalic acid, acetic acid, formic acid and trifluoroacetic acid are preferred. By this acid treatment, the polymer electrolyte precursor is protonated into an SO ₃ H body. The molded article (molded article containing the protonated polymer electrolyte (a)) acid-treated as described above is a solvent capable of dissolving and/or suspending the polymer electrolyte (a) (affinity with the resin). are dissolved and/or suspended in a solvent with good properties).
Examples of such solvents include, but are not limited to, water; ethanol, methanol, n-propanol, isopropyl alcohol, butanol, protic organic solvents such as glycerin; N,N-dimethylformamide, N , N-dimethylacetamide, N-methylpyrrolidone and other aprotic solvents. These can be used singly or in combination of two or more. In particular, when using one solvent, water alone is preferred. Moreover, when using 2 or more types together, the mixed solvent of water and a protic organic solvent is preferable.

The method of dissolving and/or suspending is not limited to the following, but for example, it is preferable to dissolve and/or disperse as it is in the various solvents described above, and sealed and pressurized under atmospheric pressure or in an autoclave or the like. Under the conditions, it is more preferable to dissolve and/or disperse in a temperature range of 0 to 250°C. In particular, when using a protic organic solvent as a solvent, the mixing ratio of water and protic organic solvent depends on the dissolution method, dissolution conditions, type of polymer electrolyte (a), total solid concentration, dissolution temperature, stirring speed, etc. It can be selected as appropriate. The mass ratio of the protic organic solvent to water is preferably 0.1 to 10 parts of the protic organic solvent to 1 part of water, more preferably 0.1 to 5 parts of the protic organic solvent to 1 part of water.

The solution/suspension of the polymer electrolyte (a) is not particularly limited. ), suspension (solid particles dispersed as colloidal particles or microscopically visible particles in a liquid), colloidal liquid (a state in which macromolecules are dispersed), micellar liquid (a large number of small molecules are intermolecular lyophilic colloidal dispersion system formed by force association), etc., or two or more.

The polymer electrolyte solution, as described above, can be used to produce the polymer electrolyte membrane of this embodiment and contains niobium oxide (b).
Niobium oxide (b) can be contained in the polymer electrolyte solution, for example, through a step of adding niobium oxide (b) to the solution of the polymer electrolyte (a).

In addition, the polymer electrolyte solution may further contain a solvent depending on the molding method and application. Examples of such a solvent include, but are not limited to, at least one of water, organic solvents, liquid resin monomers, and liquid resin oligomers.

Examples of the organic solvent include, but are not limited to, alcohols such as methanol, ethanol, 2-propanol, butanol, octanol; ethyl acetate, butyl acetate, ethyl lactate, propylene glycol monomethyl ether acetate, propylene Esters such as glycol monoethyl ether acetate and γ-butyrolactone; diethyl ether, ethylene glycol monomethyl ether (methyl cellosolve), ethylene glycol monoethyl ether (ethyl cellosolve), ethylene glycol monobutyl ether (butyl cellosolve), diethylene glycol monomethyl ether, diethylene glycol mono Ethers such as ethyl ether; Ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, acetylacetone, cyclohexanone; Aromatic hydrocarbons such as benzene, toluene, xylene, ethylbenzene; Dimethylformamide, N,N-dimethylacetamide, N-methyl and amides such as pyrrolidone. An organic solvent may be used individually by 1 type, or may use 2 or more types together.

Moreover, the polymer electrolyte solution can be concentrated or filtered depending on the molding method and application.
The concentration method is not limited to the following, but includes, for example, a method of heating to evaporate the solvent, a method of concentrating under reduced pressure, and the like.
When the polymer electrolyte solution is used as the coating solution, the solid content of the polymer electrolyte solution is preferably 0.5 to 50% by mass. When the solid content is 0.5% by mass or more, an increase in viscosity is suppressed, and handleability tends to be excellent. Further, when the solid content is 50% by mass or less, the productivity tends to be improved.

The method of filtration is not limited to the following, but a typical example is a method of pressure filtration using a filter.
As for the filter, it is preferable to use a filter medium whose 90% collection particle size is 10 to 100 times the average particle size of the particles. Examples of this filter medium include those made of paper and those made of metal. Particularly when the filter medium is paper, the 90% collected particle size is preferably 10 to 50 times the average particle size of the particles. When using a metal filter, the 90% collected particle size is preferably 50 to 100 times the average particle size of the particles. By setting the 90% collected particle diameter to 10 times or more of the average particle diameter, it is possible to suppress the pressure required when feeding the liquid from becoming too high and to prevent the filter from clogging in a short period of time. It tends to be controllable. On the other hand, by setting the particle size to 100 times or less of the average particle size, there is a tendency to favorably remove agglomerates of particles and undissolved resin that cause foreign matter in the film.

[Polymer electrolyte membrane]
The polymer electrolyte membrane of the present embodiment contains the polymer electrolyte composition of the present embodiment described above.
The film thickness of the polymer electrolyte membrane of the present embodiment is preferably 1 μm or more and 500 μm or less, more preferably 2 μm or more and 100 μm or less, and still more preferably 5 μm or more and 50 μm or less. When the film thickness is 1 μm or more, it is possible not only to reduce the inconvenience of direct reaction between hydrogen and oxygen, but also to prevent differential pressure, strain, etc. from occurring during handling during fuel cell manufacturing and during fuel cell operation. Also, the polymer electrolyte membrane tends to be less likely to be damaged.
On the other hand, when the film thickness is 500 μm or less, the ion permeability tends to be improved, and the performance as a solid polymer electrolyte membrane tends to be improved.

(Method for producing polymer electrolyte membrane)
The method for producing the polymer electrolyte membrane of the present embodiment is not particularly limited, and the polymer electrolyte solution described above may be used to form a cast membrane, or through processes such as melt extrusion and stretching. It can be molded.
When molding is performed by melt extrusion, from the viewpoint of moldability, a mixture of a polymer electrolyte precursor, niobium oxide (b), optionally a radical scavenger (c), and a thioether compound (d) is melt-kneaded and then extruded. It is preferable to form a film by molding and then immerse it in a basic reaction liquid for hydrolysis. This hydrolysis treatment converts the polymer electrolyte precursor into the polymer electrolyte (a).

Further, after the hydrolysis treatment in the basic reaction liquid as described above, the membrane is sufficiently washed with warm water or the like, and then subjected to an acid treatment.
Acids used for the acid treatment are not limited to the following, but mineral acids such as hydrochloric acid, sulfuric acid and nitric acid, and organic acids such as oxalic acid, acetic acid, formic acid and trifluoroacetic acid are preferred. By this acid treatment, the polymer electrolyte precursor is protonated into an SO ₃ H body.

Further, the polymer electrolyte membrane of the present embodiment includes polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-perfluoro(alkoxyvinyl ether) copolymer (PFA), Porous materials such as polyethylene and polypropylene, porous sheets such as fibers, woven fabrics and non-woven fabrics; may be reinforced with inorganic whiskers such as silica and alumina, polytetrafluoroethylene (PTFE), organic fillers such as polyethylene and polypropylene .

Further, the polymer electrolyte membrane of the present embodiment may be subjected to cross-linking treatment using a cross-linking agent, ultraviolet rays, electron beams, radiation, or the like.

The polymer electrolyte membrane of the present embodiment is preferably subjected to heat treatment after molding. The heat treatment promotes crystallization of the polymer electrolyte and can stabilize the mechanical strength of the polymer electrolyte membrane. In addition, the crystal part of the additive such as the radical scavenger (c) and the thioether compound (d) and the polymer electrolyte part are strongly adhered by the heat treatment, and as a result, the mechanical strength tends to be more stabilized. be.

The heat treatment temperature is preferably 120° C. or higher and 300° C. or lower, more preferably 140° C. or higher and 250° C. or lower, and still more preferably 160° C. or higher and 230° C. or lower. When the heat treatment temperature is 120° C. or higher, the adhesiveness between the crystalline portion and the polymer electrolyte portion tends to be further improved.
On the other hand, when the heat treatment temperature is 300° C. or less, the properties of the polymer electrolyte membrane tend to be further improved.
The heat treatment time is preferably 5 minutes or more and 3 hours or less, more preferably 10 minutes or more and 2 hours or less, although it depends on the heat treatment temperature.

[Membrane electrode assembly]
The membrane electrode assembly of this embodiment has the above-described polymer electrolyte membrane and electrode catalyst layer.
That is, the membrane electrode assembly of this embodiment has the polymer electrolyte membrane of this embodiment and an electrode catalyst layer disposed on the polymer electrolyte membrane.
The polymer electrolyte membrane of this embodiment can be used as a constituent member of a membrane electrode assembly and a solid polymer electrolyte fuel cell.
A unit in which two types of electrode catalyst layers, an anode and a cathode, are bonded to both sides of a polymer electrolyte membrane is called a membrane electrode assembly (hereinafter sometimes abbreviated as "MEA"). A device in which a pair of gas diffusion layers are joined to the outside of the electrode catalyst layer so as to face each other is also sometimes called an MEA.

(electrode catalyst layer)
The electrode catalyst layer of this embodiment constitutes the membrane electrode assembly. As the electrode catalyst layer, a known electrode catalyst layer used for MEA can be applied.
The electrode catalyst layer preferably contains the polymer electrolyte composition of the present embodiment described above. That is, in the membrane electrode assembly of the present embodiment, the electrode catalyst layer contains a polymer electrolyte (a) and niobium oxide (b) having an average particle size of more than 0.050 μm and 5.0 μm or less. is preferred.
The electrode catalyst layer of the present embodiment may contain a polymer electrolyte composition, and, if necessary, fine particles of a catalyst metal and a conductive agent supporting the fine particles of the catalyst metal. Moreover, a water-repellent agent may be included as necessary. The catalyst metal used in the electrode catalyst layer is not particularly limited as long as it is a metal that promotes the oxidation reaction of hydrogen and the reduction reaction of oxygen, and is not limited to the following. , silver, palladium, iridium, rhodium, ruthenium, iron, cobalt, nickel, chromium, tungsten, manganese, vanadium, and alloys thereof. Among these, platinum is mainly preferably used.

The method for manufacturing the membrane electrode assembly (MEA) of this embodiment is not particularly limited, but for example, the following method is performed.
First, a binder ion-exchange resin for an electrode catalyst layer is dissolved in a mixed solution of alcohol and water, and platinum-carrying carbon, which is a catalyst metal, is dispersed to form a paste. A certain amount of this is applied to a PTFE sheet and dried. Next, with the coating surfaces of the PTFE sheets facing each other, the polymer electrolyte membrane described above is sandwiched between them, and the sheets are transferred and joined by hot pressing at 100° C. to 200° C. to obtain a membrane electrode assembly (MEA). can be done.
As the binder ion-exchange resin for the electrode catalyst layer, an ion-exchange resin dissolved in a solvent (alcohol, water, etc.) is generally used. From the viewpoint of durability during battery operation, a polymer electrolyte composition containing the polymer electrolyte (a) and niobium oxide (b) described above, which can be used in the production of the polymer electrolyte membrane of the present embodiment, is used. .

[Polymer electrolyte fuel cell]
The solid polymer electrolyte fuel cell of this embodiment includes the membrane electrode assembly (MEA) of this embodiment described above.
The MEA described above, and the MEA having a structure in which a pair of gas diffusion electrodes are arranged to face the MEA, can also be used as a structural member such as a bipolar plate or a backing plate, which is generally used in solid polymer electrolyte fuel cells. They can be combined to form a solid polymer electrolyte fuel cell.

A bipolar plate means a composite material of graphite and resin, a metal plate, or the like, on the surface of which grooves are formed for allowing gases such as fuel and oxidant to flow. The bipolar plate has a function of transmitting electrons to an external load circuit and also a function of a flow path for supplying fuel and oxidant to the vicinity of the electrode catalyst. By inserting the MEA of this embodiment between these bipolar plates and stacking a plurality of them, the solid polymer electrolyte fuel cell of this embodiment can be manufactured.

Hereinafter, the present invention will be described in detail with reference to specific examples and comparative examples, but the present embodiment is not limited to the examples described later.
Methods for measuring various physical properties and evaluating properties in Examples and Comparative Examples are as follows.

[Measurement method of physical properties]
(Measurement of average particle size and cumulative transit integral value)
The volume average particle size of the fine particles of the metal compound in the polymer electrolyte composition was measured using a laser diffraction/scattering particle size analyzer LA-950 manufactured by Horiba, Ltd.
As a pretreatment, the particle dispersion was subjected to ultrasonic treatment at 600 W for 1 minute for measurement.
The volume average particle size obtained by analyzing the scattered light of the laser by the microtrack method was used as the average particle size of the fine particles of the metal compound.
Similarly, the cumulative pass integral value obtained by analyzing the scattered light of the laser by the microtrack method was used as the cumulative pass integral value of the fine particles of the metal compound. As a result, the ratio (%) of the passing integral value in the region with a particle diameter of more than 0.05 μm and 5.0 μm or less to the whole was calculated.

(Durability test: power generation/OCV cycle test)
In order to accelerate the evaluation of the durability of the polymer electrolyte membrane under high-temperature and low-humidity conditions, an accelerated test by power generation and OCV cycle was performed in the following procedure.
In addition, "OCV" means an open circuit voltage (Open Circuit Voltage).
A fuel cell single cell fabricated as described below was set in an evaluation device (Toyo Technica fuel cell evaluation system 890CL), and a durability test was conducted with a cycle of 3 hours of power generation and 3 hours of OCV.

The test conditions for power generation were a cell temperature of 90° ^C and a humidification bottle of 61°C (relative humidity of 30% RH). The supply conditions were set to 75% and 55%. Moreover, both the anode side and the cathode side were set to no pressure (atmospheric pressure).

Regarding the OCV test conditions, the cell temperature, humidification bottle temperature, supply gas, and pressure were the same as those for the power generation test conditions.

<Deterioration judgment>
The leakage current of hydrogen was measured every 100 hours from the test time 0 hour (L0). Degradation was determined by calculating the difference (L500-L0) between the hydrogen leak current and L0 after 500 hours (L500) from the start of the test.
It was judged that the smaller the L500-L0, the better the durability.
When the hydrogen leakage current was 10 mA/cm ² or more, the test was stopped, even if the test time was less than 500 hours, as it was judged to be membrane rupture.

Hydrogen leak current was measured by introducing 200 cc/min of hydrogen gas into the anode and nitrogen gas into the cathode under no pressure conditions, with the same cell temperature and humidifying bottle temperature as the test conditions for power generation.
A potentiogalvanostat (product name: Solartron 1280B, manufactured by Toyo Technica Co., Ltd.) was used for the measurement, 0.4 V was maintained for 5 minutes, and the current value after 5 minutes was calculated by dividing by the electrode area.

<Elution of catalyst>
Elution of the catalyst was determined by measuring the metal ion concentration in the waste liquid generated during power generation by ICP-AES under the following conditions, and comparing the ion concentration immediately after the start of operation and at the end of operation to determine the presence or absence of outflow.

[Elution test of niobium oxide and niobium fluoride]
The presence or absence of elution of niobium oxide or niobium fluoride from the polymer electrolyte membranes of Examples and Comparative Examples containing niobium oxide or niobium fluoride was measured using a high frequency inductively coupled plasma atomic emission spectrometer (ICP-AES device) ( Using SII (SII) SPS3520UV-DD), evaluation was made by quantifying the amount of Nb contained in the waste liquid immediately after the start of the power generation operation and after the end.
Add 1% nitric acid aqueous solution containing hydrofluoric acid to the niobium standard solution for ICP emission spectrometry (1000 mg/L) to prepare samples for creating calibration curves of 0 mg/L, 1 mg/L, 10 mg/L, and 50 mg/L. Then, by ICP-AES, the amount of Nb was measured under the following conditions to create a calibration curve.
A measurement sample was prepared by adding 45 mL of a 1% nitric acid aqueous solution to 5 mL of the waste liquid.
The measurement sample was also measured by ICP-AES under the same conditions, and Nb in the waste liquid was calculated from the calibration curve.
When the amount of Nb was not detected or was 1 ppm by mass or less, it was determined that there was no elution of the catalyst, and when it was over 1 ppm by mass, it was determined that the catalyst was outflowing.
(conditions)
RF power: 1.2kW
Plasma gas (Ar) flow rate: 16 L/min
Auxiliary gas (Ar) flow rate: 0.5 L/mn
Carrier gas (Ar) pressure 0.24 Mpa
Carrier gas (Ar) flow rate: 0.3/min
Photometric height: 12mm
Nb measurement wavelength: 316.431 nm, R spectrometer

[Elution test of cerium oxide and cerium nitrate]
In the same manner as the niobium oxide and niobium fluoride elution tests described above, the presence or absence of cerium oxide or cerium nitrate elution from the polymer electrolyte membrane of the comparative example containing cerium oxide or cerium nitrate was evaluated.
A 1% nitric acid aqueous solution was added to the cerium standard solution for ICP emission spectrometry (1000 mg/L) to prepare 0 mg/L, 1 mg/L, 10 mg/L, and 50 mg/L samples for creating a calibration curve, and ICP - The amount of Ce was measured by AES under the following conditions to create a calibration curve.
Measurement samples were prepared by adding 45 mL of a 1% nitric acid aqueous solution to 5 mL of the waste liquid immediately after the start of the power generation operation and after the end of the power generation operation.
The measurement sample was also measured by ICP-AES under the same conditions, and the amount of Ce in the waste liquid was calculated from the calibration curve.
When the amount of Ce was not detected or was 1 mass ppm or less, it was determined that the catalyst was not eluted, and when it exceeded 1 mass ppm, it was determined that the catalyst had flowed out.
(conditions)
RF power: 1.2kW
Plasma gas (Ar) flow rate: 16 L/min
Auxiliary gas (Ar) flow rate 0.5 L/mn
Carrier gas (Ar) pressure 0.24 MPa
Carrier gas (Ar) flow rate: 0.3 L/min
Photometric height: 12mm
Ce measurement wavelength: 413.765 nm, L spectrometer

<Additional catalyst aggregation>
Aggregation of the added catalyst was judged to be aggregation when the passage integral of particles with a diameter of 5.0 μm or more increased in the particle size distribution of each particle dispersion and polymer electrolyte solution.

[Example 1]
(Preparation of polymer electrolyte composition)
PFSA (perfluorosulfonic acid resin) dispersion solution in a plastic container (Aquivion dispersion solution, manufactured by Sigma-Aldrich; PFSA content: 25% by mass, water content: 75% by mass) A1: 100 g is stirred with a magnetic stirrer. 40 g of 1-propanol was added while stirring, and after stirring until uniform, the mixture was stirred at 23° C. for 24 hours to obtain a transparent and transparent polymer electrolyte solution B1.

A niobium dioxide coarse particle liquid G1 was prepared by adding 900 g of ion-exchanged water to 100 g of niobium dioxide (manufactured by Kojundo Chemical Laboratory) in a predetermined plastic container. The volume average particle size of the niobium dioxide coarse particles was 17.23 μm.

The niobium dioxide coarse particle liquid G1 was treated with 0.5 mm partially stabilized zirconia beads in a bead mill (Labostar LMZ06, manufactured by Ashizawa Fine Tech Co., Ltd.) for 60 minutes to obtain a niobium dioxide particle dispersion liquid H1. The volume average particle diameter of the niobium dioxide fine particles in the obtained niobium dioxide particle dispersion H1 was 3.13 μm.

The niobium dioxide coarse particle liquid H1 was treated with 0.1 mm partially stabilized zirconia beads in a bead mill (Labostar LMZ06, manufactured by Ashizawa Fine Tech Co., Ltd.) for 60 minutes to obtain a niobium dioxide particle dispersion liquid I1. The volume average particle diameter of the niobium dioxide fine particles in the obtained niobium dioxide particle dispersion H1 was 0.13 μm.

The niobium dioxide particle dispersion liquid I1 obtained above was added to 100 g of the polymer electrolyte solution B1 in a 500 mL plastic container so that PFSA/niobium dioxide fine particles = 99/1 (mass ratio). After the mixture was added while stirring with a stirrer, it was stirred until uniform to obtain a solution J1 of a polymer electrolyte composition containing niobium dioxide particles.

(Preparation of polymer electrolyte membrane)
Solution J1 of the polymer electrolyte composition was coated with a Kapton (registered trademark) film (250 mm × 600 mm) (application area: about 200 mm wide x about 500 mm long), and dried in an oven at 120°C for 30 minutes.
The membrane thus obtained was further heat-treated in an oven at 200° C. for 30 minutes to obtain a polymer electrolyte membrane C1 with a thickness of about 25 μm.

(Preparation of electrode catalyst ink)
25% by mass PFSA dispersion solution (Aquivion dispersion solution, manufactured by Sigma-Aldrich, mass equivalent (EW) 720; PFSA content: 25% by mass, water content: 75% by mass), electrode catalyst (TEC10E40E, Tanaka Kikinzoku Sales 36.7% by mass of platinum supported) was blended so that the ratio of platinum/perfluorosulfonic acid polymer was 1/1.15 (by mass). Next, ethanol was added so that the solid content (the sum of the electrode catalyst and the perfluorosulfonic acid polymer) was 11% by mass, and the mixture was stirred with a homogenizer (manufactured by AS ONE) at 3,000 rpm for 10 minutes. An electrode catalyst ink D was obtained.

(Production of membrane electrode assembly (MEA))
Using an automatic screen printer (product name: LS-150, manufactured by Newlong Seimitsu Kogyo Co., Ltd.), the electrode catalyst ink D is applied to both surfaces of the polymer electrolyte membrane C1 produced as described above so that the platinum amount is on the anode side. It was applied so as to be 0.2 mg/cm ² and 0.3 mg/cm ² on the cathode side, dried and solidified at 140° C. for 5 minutes to obtain a membrane electrode assembly (MEA) E1.

(Production of single fuel cell)
A gas diffusion layer (product name: GDL35BC, manufactured by MFC Technology) was layered on both electrodes of the MEA, and then a gasket, a bipolar plate, and a backing plate were layered to obtain a single fuel cell F1.

Table 1 shows the results of various evaluations for polymer electrolyte membrane: C1, MEA: E1, and fuel cell: F1.

[Example 2]
Solution J2 of a polymer electrolyte composition was prepared from polymer electrolyte solution B1 and niobium dioxide fine particle dispersion liquid I1 so that PFSA/niobium dioxide fine particles=98/2 (mass ratio).
Other conditions were the same as in Example 1 to obtain polymer electrolyte membrane: C2, MEA: E2, and fuel cell: F2. Table 1 shows the results of various evaluations.

[Example 3]
900 g of deionized water was added to 100 g of niobium pentoxide (manufactured by Kojundo Chemical Laboratory) in a plastic container to prepare niobium pentoxide coarse particle liquid G2.
The volume average particle size of the niobium pentoxide coarse particles was 5.17 μm.
The niobium pentoxide coarse particle liquid G2 was treated with 0.5 mm partially stabilized zirconia beads in a bead mill (Labostar LMZ06, manufactured by Ashizawa Fine Tech Co., Ltd.) for 60 minutes to obtain a niobium pentoxide particle dispersion liquid H2. . The volume average particle size of the niobium pentoxide fine particles in the obtained niobium pentoxide particle dispersion H2 was 3.22 μm.
The niobium dioxide dispersion H2 was similarly treated with 0.1 mm partially stabilized zirconia beads in a bead mill for 60 minutes to obtain a niobium pentoxide particle dispersion I2. The volume average particle diameter of the niobium pentoxide particles in the obtained niobium pentoxide particle dispersion liquid I2 was 0.15 μm.
The niobium pentoxide fine particle dispersion I2 obtained above was added to 100 g of PFSA dispersion B1 in a 500 mL plastic container with a magnetic stirrer so that PFSA/niobium pentoxide fine particles = 99/1 (mass ratio). After the ingredients were added while stirring, they were stirred until uniform, to prepare a solution J3 of a polymer electrolyte composition containing niobium pentoxide microparticles.
Furthermore, polymer electrolyte membrane: C3, MEA: E3, and fuel cell: F3 were obtained according to the above method. Table 1 shows the results of various evaluations.

[Example 4]
Solution J4 of a polymer electrolyte composition was prepared from polymer electrolyte solution B1 and niobium pentoxide particle dispersion liquid I2 so that PFSA/niobium pentoxide fine particles=98/2 (mass ratio).
Other conditions were the same as in Example 3 to obtain polymer electrolyte membrane: C4, MEA: E4, and fuel cell: F4. Table 1 shows the results of various evaluations.

[Example 5]
From polymer electrolyte solution B1, niobium dioxide fine particles I1, and niobium pentoxide particle dispersion I2, so that PFSA/niobium dioxide fine particles/niobium pentoxide fine particles=99/0.5/0.5 (mass ratio), A solution J5 of a polyelectrolyte composition was prepared.
Other conditions were the same as in Example 1 to obtain polymer electrolyte membrane: C5, MEA: E5, and fuel cell: F5. Table 1 shows the results of various evaluations.

[Example 6]
Polymer electrolyte solution B1, niobium dioxide particle dispersion I1, and niobium pentoxide particle dispersion I2 were added so that PFSA/niobium dioxide fine particles/niobium pentoxide fine particles=98/1/1 (mass ratio). A solution J6 of electrolyte composition was prepared.
Other conditions were the same as in Example 3 to obtain polymer electrolyte membrane: C6, MEA: E6, and fuel cell: F6. Table 1 shows the results of various evaluations.

[Example 7]
Solution J7 of a polymer electrolyte composition was prepared from polymer electrolyte solution B1 and niobium dioxide particle dispersion H1 so that PFSA/niobium dioxide fine particles=99/1 (mass ratio).
Other conditions were the same as in Example 1 to obtain polymer electrolyte membrane: C7, MEA: E7, and fuel cell: F7. Table 2 shows the results of various evaluations.

[Example 8]
Solution J8 of a polymer electrolyte composition was prepared from polymer electrolyte solution B1 and niobium pentoxide particle dispersion liquid H2 so that PFSA/niobium pentoxide particles=99/1 (mass ratio).
Other conditions were the same as in Example 3 to obtain polymer electrolyte membrane: C8, MEA: E8, and fuel cell: F8. Table 2 shows the results of various evaluations.

[Example 9]
As the polymer electrolyte solution, Nafion dispersion (manufactured by Sigma-Aldrich, mass equivalent (EW) 950; PFSA content: 20% by mass, water content: 36% by mass, 1-propanol content: 44% by mass) B2 was used.
Other conditions were the same as in Example 1 to obtain polymer electrolyte membrane: C9, MEA: E9, and fuel cell: F9. Table 2 shows the results of various evaluations.

[Example 10]
B2 was used as the polymer electrolyte solution.
Other conditions were the same as in Example 2 to obtain polymer electrolyte membrane: C10, MEA: E10, and fuel cell: F10. Table 2 shows the results of various evaluations.

[Example 11]
B2 was used as the polymer electrolyte solution.
Other conditions were the same as in Example 3 to obtain polymer electrolyte membrane: C11, MEA: E11, and fuel cell: F11. Table 2 shows the results of various evaluations.

[Example 12]
B2 was used as the polymer electrolyte solution.
Other conditions were the same as in Example 4 to obtain polymer electrolyte membrane: C12, MEA: E12, and fuel cell: F12. Table 2 shows the results of various evaluations.

[Example 13]
B2 was used as the polymer electrolyte solution.
Other conditions were the same as in Example 5 to obtain polymer electrolyte membrane: C13, MEA: E13, and fuel cell: F13. Table 3 shows the results of various evaluations.

[Example 14]
B2 was used as the polymer electrolyte solution.
Other conditions were the same as in Example 6 to obtain polymer electrolyte membrane: C14, MEA: E14, and fuel cell: F14. Table 3 shows the results of various evaluations.

[Example 15]
B2 was used as the polymer electrolyte solution.
Other conditions were the same as in Example 7 to obtain polymer electrolyte membrane: C15, MEA: E15, and fuel cell: F15. Table 3 shows the results of various evaluations.

[Example 16]
B2 was used as the polymer electrolyte solution.
Other conditions were the same as in Example 6 to obtain polymer electrolyte membrane: C16, MEA: E16, and fuel cell: F16. Table 3 shows the results of various evaluations.

[Comparative Example 1]
Using B1 as the polymer electrolyte solution, a polymer electrolyte membrane C17 was produced according to the above procedure to obtain MEA: E17 and fuel cell: F17. Table 4 shows the results of various evaluations.

[Comparative Example 2]
The niobium dioxide coarse particle liquid G1 was treated with 0.5 mm partially stabilized zirconia beads in a bead mill (Labostar LMZ06, manufactured by Ashizawa Fine Tech Co., Ltd.) for 30 minutes to obtain a niobium dioxide particle dispersion liquid H18. The volume average particle diameter of the niobium dioxide fine particles in the obtained H18 was 5.12 μm.
The niobium dioxide fine particle dispersion H18 obtained above was added to 100 g of PFSA dispersion B1 in a 500 mL plastic container and stirred with a magnetic stirrer so that PFSA/niobium dioxide fine particles = 99/1 (mass ratio). Then, the mixture was stirred until uniform to obtain a solution J18 of a polymer electrolyte composition containing niobium dioxide fine particles.
Polymer electrolyte membrane: C18, MEA: E18, and fuel cell: F18 were obtained according to the above method. Table 4 shows the results of various evaluations.

[Comparative Example 3]
As the particle dispersion liquid, G2 was used instead of I1.
Other conditions were the same as in Example 1 to obtain polymer electrolyte membrane: C19, MEA: E19, and fuel cell: F19. Table 4 shows the results of various evaluations.

[Comparative Example 4]
The niobium dioxide dispersion H1 was similarly treated with 0.1 mm partially stabilized zirconia beads in a bead mill for 120 minutes to obtain a niobium dioxide particle dispersion I20. The volume average particle diameter of the niobium dioxide particles in the obtained niobium dioxide particle dispersion liquid I20 was 0.038 μm.
The niobium dioxide particle dispersion I20 obtained above was added to 100 g of PFSA dispersion B1 in a 500 mL plastic container with a magnetic stirrer so that PFSA/niobium dioxide fine particles=99/1 (mass ratio). As a result, aggregation occurred in the mixed solution, and a uniform polymer electrolyte composition could not be obtained.

[Comparative Example 5]
Similarly, the niobium pentoxide particle dispersion H2 was treated with 0.1 mm partially stabilized zirconia beads in a bead mill for 60 minutes to obtain a niobium pentoxide particle dispersion I21. The volume average particle size of the niobium pentoxide particles in the obtained niobium pentoxide particle dispersion liquid I21 was 0.041 μm.
The niobium pentoxide particle dispersion I21 obtained above was added to PFSA dispersion B1: 100 g in a 500 mL plastic container with a magnetic stirrer so that PFSA/niobium pentoxide fine particles = 99/1 (mass ratio). When the mixture was added while stirring, aggregation occurred in the mixed solution, and a uniform polymer electrolyte composition could not be obtained.

[Comparative Example 6]
A cerium dioxide particle liquid G22 was prepared by adding 900 g of ion-exchanged water to 100 g of cerium dioxide (manufactured by Kojundo Chemical Laboratory) in a plastic container. The volume average particle diameter of the cerium dioxide particles was 13.49 μm.
The cerium dioxide particle liquid G22 was treated with 0.5 mm partially stabilized zirconia beads in a bead mill for 60 minutes to obtain a cerium dioxide particle dispersion liquid H22. The volume average particle diameter of the cerium dioxide fine particles in the obtained cerium dioxide particle liquid H22 was 2.29 μm.
The cerium dioxide dispersion H22 was similarly treated with 0.1 mm partially stabilized zirconia beads in a bead mill for 60 minutes to obtain a cerium dioxide particle dispersion I22. The volume average particle size of the cerium dioxide particles in the obtained cerium dioxide dispersion I22 was 0.12 μm.
The cerium dioxide dispersion I22 obtained above was added to 100 g of PFSA dispersion B1 in a 500 mL plastic container while stirring with a magnetic stirrer so that PFSA/cerium dioxide microparticles = 99/1 (mass ratio). After charging, some coagulation sedimentation occurred. This precipitate was removed using a PTFE membrane filter with a pore size of 1.0 μm (manufactured by Advantec Toyo Co., Ltd.) to obtain a uniform solution J22 of a polymer electrolyte composition containing cerium dioxide microparticles. Furthermore, polymer electrolyte membrane: C22, MEA: E22, and fuel cell: F22 were obtained according to the above method. Table 4 shows the results of various evaluations.

[Comparative Example 7]
Cerium nitrate hexahydrate (manufactured by Kojundo Chemical Laboratory) is added to PFSA dispersion solution B1: 100 g in a 500 mL plastic container with a magnetic stirrer so that PFSA / cerium nitrate = 99/1 (mass ratio). After charging while stirring, the mixture was stirred until uniform to obtain a solution J23 of a polymer electrolyte composition containing cerium nitrate. Furthermore, polymer electrolyte membrane: C23, MEA: E23, and fuel cell: F23 were obtained according to the above method. Table 5 shows the results of various evaluations.

[Comparative Example 8]
Niobium pentafluoride (manufactured by Kojundo Chemical Laboratory) is added to PFSA dispersion solution B1: 100 g in a 500 mL plastic container with a magnetic stirrer so that PFSA / niobium pentafluoride = 99/1 (mass ratio). After charging while stirring, the mixture was stirred until uniform to obtain a solution J24 of a polymer electrolyte composition containing niobium pentafluoride. Furthermore, polymer electrolyte membrane: C24, MEA: E24, and fuel cell: F24 were obtained according to the above method. Table 5 shows the results of various evaluations.

[Comparative Example 9]
Using B2 as the polymer electrolyte solution, a polymer electrolyte membrane C25 was produced according to the above procedure to obtain MEA: E25 and fuel cell: F25. Table 5 shows the results of various evaluations.

[Comparative Example 10]
B2 was used as the polymer electrolyte solution.
Other conditions were the same as in Comparative Example 2 to obtain polymer electrolyte membrane: C26, MEA: E26, and fuel cell: F26. Table 5 shows the results of various evaluations.

[Comparative Example 11]
B2 was used as the polymer electrolyte solution.
Other conditions were the same as in Comparative Example 3 to obtain polymer electrolyte membrane: C27, MEA: E27, and fuel cell: F27. Table 5 shows the results of various evaluations.

[Comparative Example 12]
B2 was used as the polymer electrolyte solution.
Other conditions were the same as in Comparative Example 4 to obtain polymer electrolyte membrane: C28, MEA: E28, and fuel cell: F28. Table 5 shows the results of various evaluations.

[Comparative Example 13]
B2 was used as the polymer electrolyte solution.
Other conditions were the same as in Comparative Example 5 to obtain polymer electrolyte membrane: C29, MEA: E29, and fuel cell: F29. Table 6 shows the results of various evaluations.

[Comparative Example 14]
The cerium dioxide particle dispersion I18 obtained in Comparative Example 2 was added to 100 g of PFSA dispersion B2 in a 500 mL plastic container with a magnetic stirrer so that PFSA/cerium dioxide fine particles = 99/1 (mass ratio). When the solution was added while stirring at , some coagulation sedimentation occurred. This precipitate was removed using a PTFE membrane filter with a pore size of 1.0 μm (manufactured by Advantech Toyo Co., Ltd.) to obtain a uniform solution J30 of a polymer electrolyte composition containing cerium dioxide microparticles. Furthermore, polymer electrolyte membrane: C30, MEA: E30, and fuel cell: F30 were obtained according to the above method. Table 6 shows the results of various evaluations.

[Comparative Example 15]
B2 was used as the polymer electrolyte solution.
Other conditions were the same as in Comparative Example 7 to obtain polymer electrolyte membrane: C31, MEA: E31, and fuel cell: F31. Table 6 shows the results of various evaluations.

[Comparative Example 16]
B2 was used as the polymer electrolyte solution.
Other conditions were the same as in Comparative Example 8 to obtain polymer electrolyte membrane: C32, MEA: E32, and fuel cell: F32. Table 6 shows the results of various evaluations.

As shown in Tables 1 to 6, when the polymer electrolyte membranes of Examples 1 to 16 to which niobium oxide fine particles were added were used, practically good results were obtained in the durability test described above.

The polymer electrolyte composition of the present invention has industrial applicability in the fields of polymer electrolyte membranes, electrode catalyst layers, membrane electrode assemblies, and polymer electrolyte fuel cells.

Claims (8)

a polymer electrolyte (a);
Niobium oxide (b) having an average particle size of more than 0.050 μm and 5.0 μm or less as measured by laser diffraction particle size distribution measurement;
A polymer electrolyte composition containing The niobium oxide (b) is
at least one niobium oxide selected from the group consisting of niobium dioxide and niobium pentoxide;
The polymer electrolyte composition according to claim 1. The passage integral value of the volume-based particle size distribution obtained by the laser diffraction particle size distribution measurement of the niobium oxide (b) is 30% or more of the total in the region where the particle size is more than 0.050 μm and 5.0 μm or less.
The polymer electrolyte composition according to claim 1 or 2. The polymer electrolyte (a) is
represented by the following general formula (1),
The polymer electrolyte composition according to any one of claims 1 to 3.
-[ _CF2CX1X2 ] _{a- [CF2-CF(-O-(CF2-CF(CF2X3))b} ^{- Oc-} _{( CFR1 )} ^{d- (} _CFR2 ⁾ _e- (CF ₂ ) _f -X ⁴ )] _g- (1)
(In general formula (1), X ¹ , X ² and X ³ are each independently a halogen element or a perfluoroalkyl group having 1 to 3 carbon atoms.
a and g are 0≦a<1, 0<g≦1, and a+g=1.
b is an integer of 0 to 8; c is 0 or 1;
d and e are each independently an integer of 0 to 6;
f is an integer of 0 or more and 10 or less.
However, d+e+f is not equal to 0.
R ¹ and R ² are each independently a halogen element, a perfluoroalkyl group having 1 to 10 carbon atoms, or a fluorochloroalkyl group.
X4 is ^COOZ , _{SO3Z , PO3Z2} , or _PO3HZ . Z is a hydrogen atom, an alkali metal atom, an alkaline earth metal ^atom , or an ^{amine ( NH4} _{, NH3R3} ^{, NH2R3R4 ,} _NHR3R4R5 ^{, NR3R4R5R 6} ). R ³ , R ⁴ , R ⁵ and R ⁶ are alkyl groups or arene groups. ) A polymer electrolyte membrane comprising the polymer electrolyte composition according to any one of claims 1 to 4. An electrode catalyst layer comprising the polymer electrolyte composition according to any one of claims 1 to 4. A membrane electrode assembly comprising the polymer electrolyte membrane according to claim 5 and/or the electrode catalyst layer according to claim 6. A polymer electrolyte fuel cell comprising the membrane electrode assembly according to claim 7 .