JP2014234445A - Polymer electrolyte composition, as well as polymer electrolyte membrane, electrode catalyst layer, membrane electrode assembly, and solid polymer fuel cell using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polymer electrolyte composition with which a highly durable polymer electrolyte membrane, an electrode catalyst layer, a membrane electrode assembly, and a solid polymer fuel cell are obtained, and to provide the highly durable polymer electrolyte membrane, the electrode catalyst layer, the membrane electrode assembly, and the solid polymer fuel cell using the same.SOLUTION: A polymer electrolyte composition contains a polymer electrolyte (a), and a compound (b) containing at least one metal element selected from a group consisting of tantalum and niobium.

Description

  The present invention relates to a polymer electrolyte composition, and a polymer electrolyte membrane, an electrode catalyst layer, a membrane electrode assembly, and a solid polymer fuel cell using the same.

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

  Such a polymer electrolyte fuel cell includes at least a membrane electrode assembly in which a gas diffusion electrode in which an electrode catalyst layer and a gas diffusion layer are laminated is bonded to both surfaces of a proton exchange membrane. The proton exchange membrane here is a membrane made of a composition having a strongly acidic group such as a sulfonic acid group or a carboxylic acid group in the polymer chain and a property of selectively transmitting protons. As a composition used for such a proton exchange membrane, a proton exchange membrane using a perfluoro proton composition typified by Nafion (registered trademark, manufactured by DuPont) having high chemical stability is preferably used. It is done.

  During operation of the fuel cell, fuel (for example, hydrogen) is supplied to the gas diffusion electrode on the anode side, and oxidant (for example, oxygen or air) is supplied to the gas diffusion electrode on the cathode side. By being connected, the operation of the fuel cell is realized. Specifically, when hydrogen is used as fuel, hydrogen is oxidized on the anode catalyst to generate protons. After passing through the proton conductive polymer in the anode catalyst layer, the protons move in the proton exchange membrane and reach the cathode catalyst through the proton conductive polymer in the cathode catalyst layer. On the other hand, electrons generated simultaneously with protons by oxidation of hydrogen reach the cathode side gas diffusion electrode through an external circuit. On the cathode catalyst, the protons react with oxygen in the oxidant to generate hydrogen. At this time, electric energy is extracted.

  At this time, the proton exchange membrane must also serve as a gas barrier partition. When the gas permeability of the proton exchange membrane is high, leakage of anode-side hydrogen to the cathode and leakage of cathode-side oxygen to the anode, that is, cross-leakage occurs. When a cross leak occurs, a so-called chemical short circuit occurs and a good voltage cannot be taken out, and hydrogen on the anode side reacts with oxygen on the cathode side. This hydrogen peroxide is decomposed by a trace amount of metal (ions such as Fe, Cr, Ni, etc.) contained in the supply pipe of the humidified gas supplied to the battery to generate hydroxy radicals and peroxide radicals. These radicals cause a problem that the deterioration of the proton exchange membrane is promoted.

  In particular, in the case of fuel cell vehicles, from the viewpoint of reducing vehicle costs, high temperature operation exceeding 80 ° C., low humidification operation such as humidity of 30% RH or less by reducing humidifiers, and use of metal bipolar plates are expected. . When performing the above-described high-temperature and low-humidification operation, there is a problem that the deterioration of the membrane is accelerated even if a perfluoro proton exchange membrane, which is said to be excellent in durability, is used for the diaphragm. When a metal bipolar plate is used, the metal (Fe, Cr, Ni, etc.) gradually dissolves during operation, and the dissolved metal ions promote the decomposition of hydrogen peroxide, generating radical species. There is a risk of accelerating the deterioration of the proton exchange membrane.

  As a method for suppressing the deterioration of the proton exchange membrane due to the radical species as described above, a method in which a metal oxide (eg, manganese oxide, cobalt oxide, etc.) is dispersed and blended in the polymer electrolyte membrane (see, for example, Patent Document 1). ), A redox cycle in the polymer electrolyte membrane that acts as a reducing agent at a potential lower than the redox potential of the hydroxy radical, and that acts as an oxidizing agent at a potential higher than the redox potential at which hydrogen peroxide acts as a reducing agent. A method of blending a compound having a compound (N-hydroxyphthalimide) (for example, see Patent Document 2) or a method of blending a radical trapping agent (compound having a phenolic hydroxyl group) in a polymer electrolyte membrane (for example, see Patent Document 3) Etc.) are disclosed.

JP 2001-118591 A JP 2006-49263 A JP 2000-223135 A

  However, in the methods described in Patent Document 1 and Patent Document 2, there is still room for improvement from the viewpoint of sustainability of hydrogen peroxide resolution because the hydrogen peroxide-decomposing substance has insufficient acidity and heat resistance. . In the method disclosed in Patent Document 3, since the radical scavenger does not regenerate after scavenging the radicals, there is still room for improvement from the viewpoint of the sustainability and addition amount of the hydrogen peroxide trap. These patent documents all capture the generated radical species and do not suppress the decomposition of hydrogen peroxide, which is a radical generation source.

  Accordingly, the present invention has been made in view of the above problems, and a polymer that can provide a highly durable polymer electrolyte membrane, electrode catalyst layer, membrane electrode assembly, and solid polymer fuel cell. It is an object of the present invention to provide an electrolyte composition, and a highly durable polymer electrolyte membrane, electrode catalyst layer, membrane electrode assembly, and polymer electrolyte fuel cell using the electrolyte composition.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors can solve the above-mentioned problems if the decomposition of hydrogen peroxide, which is a source of radical species that cause the polymer electrolyte membrane to decompose, can be suppressed. The inventors have found that the problem can be solved and have come to the present invention.

That is, the present invention is as follows.
[1]
A polymer electrolyte (a);
A compound (b) containing at least one metal element selected from the group consisting of tantalum and niobium,
Polymer electrolyte composition.
[2]
The polymer electrolyte composition according to [1], wherein the compound (b) is at least one selected from the group consisting of sulfates, carbonates, phosphates, and carboxylates.
[3]
The polymer electrolyte composition according to [1] or [2] above, further containing a radical scavenger (c).
[4]
The polymer electrolyte composition according to any one of [1] to [3], wherein the polymer electrolyte (a) is represented by the following formula [1].
_{^{- [CF 2 CX 1 X 2}} ] a - [CF 2 -CF (-O- (CF 2 -CF (CF 2 X 3)) b -O c - (CFR 1) d - (CFR 2) e - ( ^{_{CF 2) f -X 4)]}} g - [1]
(In the 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, a + g = 1,
b is an integer of 0 or more and 8 or less. c is 0 or 1,
d and e are each independently an integer of 0 or more and 6 or less, and 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 or a fluorochloroalkyl group having 1 to 10 carbon atoms,
X ⁴ is COOZ, SO ₃ Z, PO ₃ Z ₂ or PO ₃ HZ, where Z is a hydrogen atom, an alkali metal atom, an alkaline earth metal atom or an amine (NH ₄ , NH ₃ R ³ , NH ₂ R ³ R ⁴ , NHR ³ R ⁴ R ⁵ , NR ³ R ⁴ R ⁵ R ⁶ ), and 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] above.
[6]
An electrode catalyst layer comprising the polymer electrolyte composition according to any one of [1] to [4] above.
[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.

  According to the present invention, a highly durable polymer electrolyte membrane, an electrode catalyst layer, a membrane electrode assembly, and a polymer electrolyte composition capable of obtaining a solid polymer fuel cell, and using the same, A highly durable polymer electrolyte membrane, electrode catalyst layer, membrane electrode assembly, and polymer electrolyte fuel cell can be provided.

  Hereinafter, a mode for carrying out the present invention (hereinafter referred to as “the present embodiment”) will be described in detail. In addition, this invention is not limited to the following embodiment, It can implement by changing variously within the range of the summary.

[Polymer electrolyte composition]
The polymer electrolyte composition according to this embodiment contains a polymer electrolyte (a) and a compound (b) containing at least one metal element selected from the group consisting of tantalum and niobium. As a result, it is possible to suppress the decomposition of hydrogen peroxide, which is a source of radical species that cause decomposition of the polymer electrolyte, and it is excellent in durability under high temperature and low humidity and operating conditions where a large amount of metal ions are generated. . In addition, a polymer electrolyte membrane, an electrode catalyst layer, a membrane electrode assembly, and a solid polymer fuel cell containing such a polymer electrolyte composition are also excellent in durability.

[Polymer electrolyte (a)]
Although it does not specifically limit as a polymer electrolyte (a), For example, the polymer electrolyte which contains a fluorine element and / or an ion exchange group in a molecule | numerator is preferable. The ion exchange capacity of the polymer electrolyte (a) is preferably 0.5 to 3.0 meq / g, more preferably 0.65 to 2.0 meq / g, and 0.8 to 1.5 meq / g. / G is more preferable. When the ion exchange capacity is 3.0 meq / g or less, when used as a polymer electrolyte membrane, swelling of the polymer electrolyte membrane under high temperature and high humidity during fuel cell operation is reduced. Tend to be. By reducing the swelling in this way, there is a tendency to reduce the problems such as a decrease in the strength of the polymer electrolyte membrane, wrinkles and peeling from the electrode, and further a problem that the gas barrier property is lowered. It is in. Further, when the ion exchange capacity is 0.5 meq / g or more, the power generation capacity of the fuel cell including the obtained polymer electrolyte membrane tends to be further improved. The ion exchange capacity can be determined by the method described in the examples.

  The polymer electrolyte (a) containing elemental fluorine is not particularly limited. For example, a perfluorocarbon polymer compound having an ion exchange group, or a partially fluorinated carbonization having an aromatic ring in the molecule. A compound obtained by introducing an ion exchange group into a hydrogen polymer compound is preferable. Among these, a perfluorocarbon polymer compound having an ion exchange group is more preferable from the viewpoint of chemical stability.

  Here, the partially fluorinated hydrocarbon polymer compound having an aromatic ring in the molecule is not particularly limited. For example, polyphenylene sulfide, polyphenylene ether, polysulfone, polyether sulfone, polyether ether sulfone. , Polyetherketone, polyetheretherketone, polythioetherethersulfone, polythioetherketone, polythioetheretherketone, polybenzimidazole, polybenzoxazole, polyoxadiazole, polybenzoxazinone, polyxylylene, polyphenylene, polythiophene, polypyrrole, Polyaniline, polyacene, polycyanogen, polynaphthyridine, polyphenylene sulfide sulfone, polyphenylene sulfone, polyimide, polyether De, polyesterimide, polyamideimide, polyarylate, aromatic polyamide, polystyrene, polyester, a portion in the molecule of the polycarbonate, and the like are fluorinated polymer compound.

  Among these, the partially fluorinated hydrocarbon polymer compound having an aromatic ring in the molecule is not particularly limited, but from the viewpoint of heat resistance, oxidation resistance, and hydrolysis resistance, 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, polyphenyle Sulfone, a polyimide, polyether imide, a polymer compound in which a part of the molecule has been fluorinated polyester imide are preferable.

  In addition, although it does not specifically limit as an ion exchange group introduce | transduced into these, For example, a sulfonic acid group, a sulfonimide group, a sulfonamide group, a carboxylic acid group, a phosphoric acid group etc. are preferable. Among these, a sulfonic acid group is particularly preferable.

  Further, the perfluorocarbon polymer compound having an ion exchange group is not particularly limited. For example, perfluorocarbon sulfonic acid resin, perfluorocarbon carboxylic acid resin, perfluorocarbon sulfonimide resin, perfluorocarbon sulfonamide resin, perfluorocarbon phosphoric acid. Examples of the resin include amine salts and metal salts of these resins.

Although it does not specifically limit as a polymer electrolyte (a), More specifically, the polymer represented by following formula [1] is mentioned.
_{^{- [CF 2 CX 1 X 2}} ] a - [CF 2 -CF (-O- (CF 2 -CF (CF 2 X 3)) b -O c - (CFR 1) d - (CFR 2) e - ( ^{_{CF 2) f -X 4)]}} g - [1]
(In the 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, 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 to 10,
However, d + e + f is not equal to 0,
R ¹ and R ² are each independently a halogen element, a perfluoroalkyl group or a fluorochloroalkyl group having 1 to 10 carbon atoms,
X ⁴ is COOZ, SO ₃ Z, PO ₃ Z ₂ or PO ₃ HZ, where Z is a hydrogen atom, an alkali metal atom, an alkaline earth metal atom or an amine (NH ₄ , NH ₃ R ³ , NH ₂ R ³ R ⁴ , NHR ³ R ⁴ R ⁵ , NR ³ R ⁴ R ⁵ R ⁶ ), and R ³ , R ⁴ , R ⁵ and R ⁶ are alkyl groups or arene groups. )

Among these, a perfluorocarbon sulfonic acid resin represented by the following formula [2] or formula [3] or a metal salt thereof is more preferable.
_{- [CF 2 CF 2] a} - [CF 2 -CF (-O- (CF 2 -CF (CF 3)) b -O- (CF 2) c -SO 3 X)] d - [2]
(In the formula, a and d are 0 ≦ a <1, 0 ≦ d <1, and a + d = 1. B is an integer of 1 to 8. c is an integer of 0 to 10. X Is a hydrogen atom or an alkali metal atom.)
_{- [CF 2 CF 2] e} - [CF 2 -CF (-O- (CF 2) f -SO 3 Y)] g - [3]
(In the formula, e and g are 0 ≦ e <1, 0 ≦ g <1, and 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.)

The perfluorocarbon polymer compound having an ion exchange group that can be used in the present embodiment is not particularly limited. For example, after polymerizing a precursor polymer represented by the following formula [4], alkali hydrolysis, acid treatment, and the like are performed. Can be made.
_{^{- [CF 2 CX 1 X 2}} ] a - [CF 2 -CF (-O- (CF 2 -CF (CF 2 X 3)) b -O c - (CFR 1) d - (CFR 2) e - ( ^{_{CF 2) f -X 5)]}} g - [4]
(Wherein 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 independently an integer of 0 to 6, and f is 0. It is an integer of 10 or less, where 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. 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.

  Although the said precursor polymer is not specifically limited, For example, it can manufacture by copolymerizing a fluorinated olefin compound and a vinyl fluoride compound.

Here, although it does not specifically limit as a fluorinated olefin compound, For example, the following compound etc. are mentioned.
CF ₂ = CFZ
(In the formula, Z represents H, Cl, F, a perfluoroalkyl group having 1 to 3 carbon atoms, or a cyclic perfluoroalkyl group that may contain oxygen.)

Moreover, it does not specifically limit as a vinyl fluoride compound, For example, the following compound etc. are mentioned.
_{CF 2 = CFO (CF 2)} z -SO 2 F,
_{CF 2 = CFOCF 2 CF (CF} 3) O (CF 2) z -SO 2 F,
_{CF 2 = CF (CF 2)} z -SO 2 F,
_{CF 2 = CF (OCF 2 CF} (CF 3)) z - (CF 2) z-1 -SO 2 F,
_{CF 2 = CFO (CF 2)} z -CO 2 R,
_{CF 2 = CFOCF 2 CF (CF} 3) O (CF 2) z -CO 2 R,
_{CF 2 = CF (CF 2)} z -CO 2 R,
_{CF 2 = CF (OCF 2 CF} (CF 3)) z - (CF 2) 2 -CO 2 R
(In the formula, Z represents an integer of 1 to 8, and R represents a hydrocarbon alkyl group having 1 to 3 carbon atoms.)

  Although it does not specifically limit as a copolymerization method of a fluorinated olefin compound and a vinyl fluoride compound, For example, the following methods can be mentioned.

(I) Solution polymerization:
A method in which a polymerization solvent such as a fluorinated hydrocarbon is used, and polymerization is carried out by reacting a vinyl fluoride compound and a gas of a fluorinated olefin compound in a state of being charged and dissolved in the polymerization solvent. Although it does not specifically limit as said fluorine-containing hydrocarbon, For example, trichlorotrifluoroethane, 1,1,1,2,3,4,4,5,5,5-decafluoropentane etc. are named generically as "Freon". The compound group which can be used can be used conveniently.

(Ii) Bulk polymerization:
A method of polymerizing a fluorinated olefin compound and a vinyl fluoride compound using a vinyl fluoride compound itself as a polymerization solvent without using a solvent such as a fluorinated hydrocarbon.

(Iii) Emulsion polymerization:
A method in which an aqueous solution of a surfactant is used as a polymerization solvent, and polymerization is carried out by reacting a vinyl fluoride compound and a fluorinated olefin gas in a state of being charged and dissolved in the polymerization solvent.

(Iv) Mini emulsion polymerization, micro emulsion polymerization:
A method in which an aqueous solution of a surfactant and an auxiliary emulsifier such as alcohol is used, and polymerization is performed by reacting a vinyl fluoride compound and a gas of a fluorinated olefin compound in a state where the aqueous solution is filled and emulsified.

(V) Suspension polymerization:
A method in which an aqueous solution of a suspension stabilizer is used, and polymerization is performed by reacting a vinyl fluoride compound and a gas of a fluorinated olefin compound in a state of being filled and suspended in the aqueous solution.

  In the present embodiment, melt mass flow rate (hereinafter abbreviated as “MFR”) can be used as an index of the polymerization degree of the precursor polymer. In the present embodiment, the MFR of the precursor polymer is preferably 0.01 g / 10 min or more, more preferably 0.1 g / 10 min or more, and further preferably 0.3 g / 10 min or more. Although the upper limit of MFR is not limited, 100 g / 10min or less is preferable and 10 g / 10min or less is more preferable. By setting the MFR to 0.01 g / 10 min or more and 100 g / 10 min or less, molding processability such as film formation of the polymer electrolyte composition tends to be more excellent. 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, sufficiently washed with warm water and acid-treated. By this acid treatment, the perfluorocarbon sulfonic acid resin precursor is protonated to form an SO ₃ H form.

[Compound (b)]
The compound (b) used in the present embodiment is a compound containing at least one metal element selected from the group consisting of tantalum and niobium. Compound (b) has an action of suppressing the decomposition of hydrogen peroxide. Thus, the polymer electrolyte composition according to the present embodiment is more excellent in durability because the decomposition reaction in which hydroxy radicals or peroxide radicals are generated from hydrogen peroxide can be suppressed.

  Although it does not specifically limit as a compound (b), For example, Halide; Oxygen compounds, such as a hydroxide and an oxide; Inorganic compounds, such as a sulfate, nitrate, borate, phosphate, carbonate; Examples thereof include organic compounds containing a carboxylic acid group such as oxalate, citric acid, and perfluorocarboxylic acid. By using the compound (b) having such a form, it tends to be more excellent in the action of suppressing the decomposition of the generated hydrogen peroxide. Among these, at least one selected from the group consisting of sulfate, carbonate, phosphate, and carboxylate is preferable. By using such a compound (b), elution of the compound (b) from the polymer electrolyte membrane or the electrode catalyst layer tends to be further suppressed.

  In order to contain the compound (b) in the polymer electrolyte composition, for example, it is preferably added as a halide, and fluoride and chloride are preferred from the viewpoint of solubility. Fluoride, chloride, and the like become the oxygen compound, the inorganic compound, the organic compound, and the like in the polymer electrolyte composition according to the components of the polymer electrolyte composition.

  The content of the compound (b) is preferably 0.0001 to 10.0000% by mass, and more preferably 0.0003 to 100% by mass of the total of the polymer electrolyte (a) and the compound (b). When the total content of the compound (b) which is 5.0000% by mass, more preferably 0.0005 to 5.0000% by mass is within the above range (0.0001 to 10.0000% by mass), good protons are obtained. While maintaining the conductivity, decomposition of hydrogen peroxide is suppressed, and a polymer electrolyte membrane and an electrode catalyst layer having high durability tend to be obtained.

[Radical scavenger (c)]
The polymer electrolyte composition according to the present embodiment can further contain a radical scavenger (c). As described above, the polymer electrolyte composition according to this embodiment can efficiently suppress the generation of radical species. In addition to this, by including the radical scavenger (c), even if a radical species is generated, the radical scavenger (c) can capture it. Thereby, it exists in the tendency which can improve the durability of a fuel cell drastically also on the high temperature low humidification conditions requested | required with a fuel cell vehicle.

  Although it does not specifically limit as a radical scavenger (c) which can be used for this embodiment, Specifically, the compound which has a functional group which enables the mechanism proposed by well-known antioxidant is mentioned. . Such a functional group is not particularly limited, and examples thereof include a functional group having a radical chain inhibiting function, a functional group having a function of decomposing radicals, and a functional group having a function of inhibiting chain initiation. Although it does not specifically limit as a functional group which has a radical chain prohibition function, For example, a phenolic hydroxyl group, a primary amine, a secondary amine etc. can be mentioned. In addition, the functional group having a function of decomposing radicals is not particularly limited, and examples thereof include a mercapto group containing sulfur, phosphorus and the like, a thioether group, a disulphide group, and a phosphite group. Furthermore, the functional group having a function of inhibiting chain initiation is not particularly limited, and examples thereof include hydrazine, amide and the like (“Antioxidant Handbook” (published by Taiseisha 1978)).

  Further, examples of the radical scavenger (c) include compounds having a structure in which atoms are easily extracted by radicals, for example, hydrogen bonded to a tertiary carbon or a carbon-halogen bond.

  In addition, the radical scavenger (c) that can be used in the present embodiment can also have a functional group that forms an ionic bond with the polymer electrolyte (a). Such a radical scavenger (c) is not particularly limited. For example, the compound (c-1) having at least one of a primary amine and a secondary amine in the same molecule and / or the same molecule Selected from the group consisting of sulfur, phosphorus, hydrazine, amide, phenolic hydroxyl group, primary amine, secondary amine, hydrogen bonded to tertiary carbon, and halogen bonded to carbon. And a compound (c-2) having at least one or more thereof.

  Here, the functional group that forms an ionic bond with the polymer electrolyte (a) in the compound (c-1) and the compound (c-2) is not particularly limited. For example, ions in the polymer electrolyte (a) When the exchange group is a sulfonic acid group, it represents a basic functional group, and specifically includes nitrogen-containing functional groups such as primary amine, secondary amine, and tertiary amine. Therefore, if it has a primary amine and a secondary amine, it has an interaction with the ion exchange group of the polymer electrolyte (a) and also has a radical scavenging function (compound (c-1)). Equivalent). On the other hand, when the part that interacts with the ion exchange group of the polymer electrolyte (a) is a tertiary amine, the functional group that forms an ionic bond with the polymer electrolyte (a) is a part having a radical scavenging function. In addition, it is preferably contained in the same molecule, and such a functional group is not particularly limited, and examples thereof include a phenol hydroxyl group and a 1,2 secondary amine (corresponding to the compound (c-2)).

  More specific examples of the compound (c-1) and the compound (c-2) that can be used in the present embodiment are as follows.

  Although it does not specifically limit as a compound (c-1), For example, the aromatic compound partially substituted by said functional group like polyaniline, polybenzimidazole, polybenzoxazole, polybenzothiazole, polybenzoxazi Examples thereof include unsaturated heterocyclic compounds such as azole, phenylated polyquinoxaline, and phenylated polyquinoline.

  Although it does not specifically limit as a compound (c-2), For example, it has the tertiary nitrogen heterocyclic ring which has a sulfonic acid and an acid-base bond in a side chain, and has the hydrogen of the benzyl position which is easy to be extracted with a radical in a principal chain. Examples of the compound include polyvinyl pyridine, polyvinyl carbazole, polystyrene in which an aromatic ring is introduced with a secondary amine or a group containing a tertiary amine.

  The compound (c-1) and the compound (c-2) are a copolymer of a unit having an interaction with the polymer electrolyte (a) having an ion exchange group and a unit having a radical scavenging function. May be. By having a portion having an interaction with the polymer electrolyte (a), the compatibility with the polymer electrolyte (a) tends to be further improved. Moreover, there exists a tendency for chemical durability to improve more by having a radical capture | acquisition function.

The content of the compound (c-1) and the compound (c-2) in the polymer electrolyte composition according to this embodiment is the same as that of the polymer electrolyte (a), the compound (c-1), and the compound (c-2). It is 0.001-50.000 mass% with respect to 100 mass% in total, More preferably, it is 0.005-20.000 mass%, More preferably, it is 0.010-10.000 mass%, More preferably, It is 0.100 to 5.000% by mass, and still more preferably 0.100 to 2.000% by mass.
In this embodiment, favorable proton conductivity was maintained by setting the total content of the compound (c-1) and the compound (c-2) in the above range (0.001 to 50.000 mass%). A polymer electrolyte membrane having high durability can be obtained as it is.

[Thioether compound (d)]
The polymer electrolyte composition according to this embodiment may contain a thioether compound (d) in addition to the polymer electrolyte (a), the compound (b), and the radical scavenger (c).

The thioether compound (d) is not particularly limited, and is a compound having a chemical structure of-(R-S) _n- (S is a sulfur atom, R is a hydrocarbon group, n is an integer of 1 or more), for example, Dialkylthioethers such as dimethylthioether, diethylthioether, dipropylthioether, methylethylthioether, methylbutylthioether; cyclic thioethers such as tetrahydrothiophene, tetrahydroapiran; methylphenyl sulfide, ethylphenyl sulfide, diphenyl sulfide, dibenzyl sulfide And aromatic thioethers. These may be used as a monomer or may be used as a polymer such as polyphenylene sulfide (PPS).

  The thioether compound (d) is preferably a polymer of n ≧ 10 (oligomer or polymer) from the viewpoint of durability, and more preferably a polymer of n ≧ 1,000. A more preferred thioether compound (d) is polyphenylene sulfide (PPS).

  Here, polyphenylene sulfide will be described. The polyphenylene sulfide used in the present embodiment 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 particularly limited. For example, a method in which a halogen-substituted aromatic compound (p-dichlorobenzene or the like) is polymerized in the presence of sulfur and sodium carbonate, a halogen-substituted aromatic compound in a polar solvent. Polymerizing in the presence of sodium sulfide or sodium hydrogen sulfide and sodium hydroxide, or polymerizing a halogen-substituted aromatic compound in the presence of hydrogen sulfide and sodium hydroxide or sodium aminoalkanoate in a polar solvent, p. -Self-condensation of chlorothiophenol and the like. In particular, 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 group (S is a sulfur atom, X is an alkali metal or a hydrogen atom) of polyphenylene sulfide is usually 10 μmol / g or more and 10,000 μmol / g or less, preferably 15 μmol / g or more. It is 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 in the above range, the number of reactive sites increases. -Use of polyphenylene sulfide having a SX group concentration satisfying the above range improves dispersibility by improving the miscibility with the polymer electrolyte (a) of the present embodiment, and higher durability under high temperature and low humidification conditions. It is thought that sex is obtained.

  Moreover, as the thioether compound (d), those having an acidic functional group introduced at the terminal can also be suitably used. The acidic functional group to be introduced is not particularly limited. For example, sulfonic acid group, phosphoric acid group, carboxylic acid group, maleic acid group, maleic anhydride group, fumaric acid group, itaconic acid group, acrylic acid group, methacrylic acid Groups are preferred. Among these, a sulfonic acid group is more preferable.

  In addition, the introduction method of an acidic functional group is not specifically limited, It implements using a general method. For example, the introduction of the sulfonic acid group can be carried out under known conditions using a sulfonating agent such as sulfuric anhydride or fuming sulfuric acid. Such an introduction method is not particularly limited. Hu, T .; Xu, W .; Yang, Y. et al. Fu, Journal of Applied Polymer Science, Vol. 91, E.E. Montoneri, Journal of Polymer Science: Part A: Polymer Chemistry, Vol. 27, 3043-3051 (1989).

  Moreover, what substituted the introduce | transduced acidic functional group with the metal salt or amine salt is used suitably. The metal salt is not particularly limited, but for example, alkali metal salts such as sodium salt and potassium salt; alkaline earth metal salts such as calcium salt are preferable.

  Further, when the thioether compound (d) is used in a powder form, the average particle size of the thioether compound (d) is preferably 0.01 to 2.0 μm, more preferably 0.01 to 1.0 μm, and 0 0.01 to 0.5 μm is more preferable, and 0.01 to 0.1 μm is still more preferable. When the average particle diameter is within the above range, the dispersibility in the polymer electrolyte (a) is further improved and tends to be more excellent in effects such as a longer life. In addition, an average particle diameter can be calculated | required by observation using a scanning electron microscope (SEM).

  The method for finely dispersing the thioether compound (d) in the polymer electrolyte (a) is not particularly limited. For example, it is pulverized and finely dispersed by applying high shear during melt kneading with the polymer electrolyte (a). Examples thereof include a method, a method of obtaining a polymer electrolyte solution, filtering the solution to remove coarse thioether compound (d) particles, and using the solution after filtration.

  Melt viscosity of polyphenylene sulfide suitably used for melt kneading (using a flow tester, 300 ° C., load 196 N, L / D (L: orifice length, D: orifice inner diameter) = 10/1, hold for 6 minutes Is preferably 1 to 10,000 poise, more preferably 100 to 10,000 poise from the viewpoint of moldability.

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

  Moreover, the thioether compound (d) tends to be able to exhibit extremely high durability even under conditions of high temperature and low humidity by blending with the radical scavenger (c) according to this embodiment.

  Here, the mass ratio (c / d) of the radical scavenger (c) to the thioether compound (d) is preferably (d / d) = 1/99 to 99/1, and (c / d) = 5/95 to 95/5 is more preferable, (c / d) = 10/90 to 90/10 is more preferable, and (c / d) = 20/80 to 80/20 is still more preferable. When the mass ratio (c / e) 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 membrane is preferably 0.01 to 50% by mass, more preferably 0.05 to 45% by mass, 0.1-40 mass% is further more preferable, 0.2-35 mass% is further more preferable, and 0.3-30 mass% is still more preferable. When the content is in the above range, the balance between ion conductivity and durability (dispersibility) tends to be excellent.

  In addition, the polymer electrolyte composition according to this embodiment can be used in the form of a polymer electrolyte solution, a polymer electrolyte membrane, an electrode catalyst layer, a polymer electrolyte binder, and the like.

[Polymer electrolyte solution]
The polymer electrolyte composition according to this embodiment may be used as a polymer electrolyte solution by dissolving or dispersing the components constituting the composition simultaneously or separately and then mixing them.

  The polymer electrolyte solution can be used as a material such as a polymer electrolyte membrane or a binder for an electrode as it is or after being subjected to steps such as filtration and concentration, either alone or mixed with another electrolyte solution.

  A method for producing the polymer electrolyte solution will be described. The method for producing the polymer electrolyte solution is not particularly limited. For example, first, a molded product made of the polymer electrolyte precursor is immersed in a basic reaction liquid and hydrolyzed. By this hydrolysis treatment, the polymer electrolyte precursor is converted into the polymer electrolyte (a). Next, the hydrolyzed molded product is sufficiently washed with warm water or the like, and then acid-treated.

The acid used for the acid treatment is not particularly limited, but for example, 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 preferable. By this acid treatment, the polymer electrolyte precursor is protonated and becomes SO ₃ H form. The above-mentioned molded product (molded product containing a protonated polymer electrolyte (a)) treated with an acid as described above is a solvent (affinity with resin) that can dissolve or suspend the polymer electrolyte (a). Is dissolved or suspended in a good solvent). Examples of such a solvent include, but are not limited to, water; protic organic solvents such as ethanol, methanol, n-propanol, isopropyl alcohol, butanol, glycerin; N, N-dimethylformamide, N, N-dimethylacetamide And aprotic solvents such as N-methylpyrrolidone. These can be used alone or in combination of two or more. In particular, when one solvent is used, water alone is preferable. Moreover, when using 2 or more types together, the mixed solvent of water and a protic organic solvent is preferable.

  Although the method of dissolving or suspending is not particularly limited, for example, it is preferable to dissolve or disperse as it is in the above-mentioned solvent, and it is 0 to 250 ° C. under the condition of being sealed and pressurized under an atmospheric pressure or an autoclave. It is more preferable to dissolve or disperse in the temperature range. In particular, when a protic organic solvent is used as the solvent, the mixing ratio of water and the protic organic solvent depends on the dissolution method, the dissolution conditions, the type of the polymer electrolyte (a), the total solid content concentration, the dissolution temperature, the stirring speed, and the like. It can be selected as appropriate. The ratio of the mass of the protic organic solvent to water is preferably from 0.1 to 10 protic organic solvents relative to water 1, and more preferably from 0.1 to 5 protic organic solvents relative to water 1.

  The dissolution / suspension of the polymer electrolyte (a) is not particularly limited. For example, an emulsion (a liquid emulsion in which liquid particles are dispersed as colloidal particles or coarser particles in a liquid is formed. ), Suspensions (solid particles dispersed in a liquid as colloidal particles or microscopic particles), colloidal liquids (macromolecules dispersed), micellar liquids (many small molecules are intermolecular) 1 type or 2 types or more, such as a lyophilic colloidal dispersion system formed by force association.

  In addition, the polymer electrolyte solution may further contain a solvent depending on the molding method and application. Such a solvent is not particularly limited, and examples thereof include those containing at least one of water, an organic solvent, a liquid resin monomer, and a liquid resin oligomer.

  Although it does not specifically limit as said organic solvent, For example, alcohol, such as methanol, ethanol, 2-propanol, butanol, octanol; Ethyl acetate, butyl acetate, ethyl lactate, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate Esters such as γ-butyrolactone; ethers such as 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 monoethyl ether Acetone, methyl ethyl ketone, methyl isobutyl ketone, acetylacetone, siku Ketones such as hexanone; benzene, toluene, xylene, ethylbenzene and the like; dimethylformamide, N, N- dimethylacetamide, amides such as N- methylpyrrolidone. A solvent may be used individually by 1 type or may use 2 or more types together.

  The polymer electrolyte solution can be concentrated or filtered according to the molding method and application. The concentration method is not particularly limited, and examples thereof include a method of evaporating the solvent by heating and a method of concentrating under reduced pressure. When the polymer electrolyte solution is used as a coating solution, the solid content ratio 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 the handling property tends to be excellent. Moreover, it exists in the tendency for productivity to improve because a solid content rate is 50 mass% or less.

  Although it does not specifically limit as a filtration method, For example, the method of carrying out pressure filtration using a filter is mentioned typically. As for the filter, it is preferable to use a filter medium whose 90% collection particle diameter is 10 to 100 times the average particle diameter of the particles. Examples of the filter medium include paper and metal. In particular, when the filter medium is paper, the 90% collection particle size is preferably 10 to 50 times the average particle size of the particles. When using a metal filter, it is preferable that the 90% collection particle diameter is 50 to 100 times the average particle diameter of the particles. By setting the 90% collection particle size to 10 times or more of the average particle size, it is possible to prevent the pressure required for liquid feeding from becoming too high, or the filter may be blocked in a short period of time. There is a tendency to suppress more. On the other hand, by setting the average particle diameter to 100 times or less, there is a tendency that particle aggregates and resin undissolved substances that cause foreign substances in the film can be removed better.

[Polymer electrolyte membrane]
The polymer electrolyte membrane according to the present embodiment includes the polymer electrolyte composition. The thickness of the polymer electrolyte membrane is preferably 1 μm or more and 500 μm or less, more preferably 2 μm or more and 100 μm or less, and further preferably 5 μm or more and 50 μm or less. When the film thickness is 1 μm or more, inconveniences such as direct reaction between hydrogen and oxygen tend to be reduced, even if differential pressure and strain occur during handling during fuel cell production or during fuel cell operation, There is a tendency that the film is not easily damaged. On the other hand, when the film thickness is 500 μm or less, the ion permeability is improved and the performance as a solid polymer electrolyte membrane tends to be further improved.

  A method for forming the polymer electrolyte membrane will be described. The method for forming the polymer electrolyte membrane is not particularly limited, and may be cast using a polymer electrolyte solution, or may be formed through steps such as melt extrusion and stretching. When molding by melt extrusion, from the viewpoint of moldability, the polymer electrolyte precursor and a mixture of the radical scavenger (c) and the thioether compound (d) used as necessary are melt-kneaded and then extrusion molded. It is preferred to form a membrane and then immerse in a basic reaction liquid and hydrolyze. By this hydrolysis treatment, the polymer electrolyte precursor is converted into the polymer electrolyte (a).

Further, the molded product is hydrolyzed in the basic reaction liquid, and then sufficiently washed with warm water, and then acid-treated. The acid used for the acid treatment is not particularly limited, but for example, 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 preferable. By this acid treatment, the polymer electrolyte precursor is protonated and becomes SO ₃ H form.

  Polymer electrolyte membranes include polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-perfluoro (alkoxy vinyl ether) copolymer (PFA), polyethylene, polypropylene, etc. Porous sheets such as porous materials, fibers, woven fabrics, nonwoven fabrics, etc .; inorganic whiskers such as silica and alumina, polytetrafluoroethylene (PTFE), polyethylene, polypropylene organic fillers, and the like may be used.

  Furthermore, the polymer electrolyte membrane can be crosslinked using a crosslinking agent, ultraviolet rays, electron beams, radiation, or the like.

  The polymer electrolyte membrane according to this embodiment is preferably subjected to heat treatment after molding. The heat treatment promotes crystallization of the polymer electrolyte (a), and can stabilize the mechanical strength of the polymer electrolyte membrane. Further, the crystal part of the additive such as the radical scavenger (c) and the thioether compound (d) and the polymer solid electrolyte part are firmly bonded by heat treatment, and as a result, the mechanical strength tends to be further improved. .

  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 further preferably 160 ° C. or higher and 230 ° C. or lower. When the heat treatment temperature is 120 ° C. or higher, the adhesion between the crystal part and the electrolyte composition part tends to be further improved. On the other hand, when the heat treatment temperature is 300 ° C. or lower, the characteristics of the polymer electrolyte membrane tend to be further improved. Although the heat treatment time depends on the heat treatment temperature, it is preferably 5 minutes or more and 3 hours or less, more preferably 10 minutes or more and 2 hours or less.

(Electrocatalyst layer)
The electrode catalyst layer according to the present embodiment includes the polymer electrolyte composition. The electrode catalyst layer is composed of a polymer electrolyte composition, and, if necessary, fine particles of a catalytic metal and a conductive agent carrying the catalyst metal. Moreover, a water repellent is contained as needed. The catalyst used for the electrode is not particularly limited as long as it is a metal that promotes the oxidation reaction of hydrogen and the reduction reaction of oxygen. For example, platinum, gold, silver, palladium, iridium, rhodium, ruthenium, iron, Examples thereof include cobalt, nickel, chromium, tungsten, manganese, vanadium, and alloys thereof. Among these, platinum is mainly used.

[Membrane electrode assembly]
The membrane electrode assembly according to the present embodiment includes the polymer electrolyte membrane and the electrode catalyst layer. The polymer electrolyte membrane according to the present 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 surfaces of a polymer electrolyte membrane is called a membrane electrode assembly (hereinafter sometimes abbreviated as “MEA”). A material in which a pair of gas diffusion layers are bonded to the outer side of the electrode catalyst layer so as to face each other is sometimes referred to as MEA.

  Although it does not specifically limit as a manufacturing method of MEA, For example, the following methods are performed. First, a platinum-supported carbon serving as an electrode material is dispersed into a paste obtained by dissolving an ion exchange resin serving as an electrode binder in a mixed solvent of alcohol and water. A certain amount of this is applied to a PTFE sheet and dried. Next, the application surface of the PTFE sheet is faced to each other, and a polymer electrolyte membrane is sandwiched therebetween, and transfer joining is performed by hot pressing at 100 ° C. to 200 ° C. to obtain an MEA. In general, a binder for an electrode is prepared by dissolving an ion exchange resin in a solvent (alcohol, water, etc.). From the viewpoint of durability during operation of the fuel cell, the polymer electrolyte composition according to this embodiment is used. .

[Solid polymer electrolyte fuel cell]
The solid polymer electrolyte fuel cell according to the present embodiment includes at least one of the polymer electrolyte membrane, the electrode catalyst layer, and the membrane electrode assembly described above. The MEA obtained above, and in some cases, the MEA having a structure in which a pair of gas diffusion electrodes are opposed to each other, are further combined with components used for general solid polymer electrolyte fuel cells such as bipolar plates and backing plates. Thus, a solid polymer electrolyte fuel cell can be configured.

  The bipolar plate means a composite material of graphite and resin having a groove for flowing a gas such as fuel or oxidant on its surface, or a metal plate. In addition to the function of transmitting electrons to an external load circuit, the bipolar plate has a function of a flow path for supplying fuel and oxidant to the vicinity of the electrode catalyst. A fuel cell is manufactured by inserting and stacking a plurality of MEAs between such bipolar plates.

  Hereinafter, although an example explains still more concretely, this embodiment is not limited only to these examples. Measurement methods and evaluation methods for various physical properties in Examples and the like are as follows.

(1) Ion exchange capacity A polymer electrolyte membrane in which the counter ion of the ion exchange group is in a proton state, approximately ² to 20 cm ² , was immersed in 30 mL of a saturated NaCl aqueous solution at 25 ° C. and left for 30 minutes with stirring. . Next, the protons in the saturated NaCl aqueous solution were subjected to neutralization titration with 0.01N sodium hydroxide aqueous solution using phenolphthalein as an indicator. The polymer electrolyte membrane obtained after neutralization, in which the counter ion of the ion exchange group is in the form of sodium ions, was rinsed with pure water, further vacuum dried and weighed. The amount of sodium hydroxide required for neutralization is M (mmol), the weight of the polymer electrolyte membrane whose sodium ion is the counter ion of the ion exchange group is W (mg), and the equivalent mass EW (g / eq) according to the following formula: )
EW = (W / M) −22
Furthermore, the ion exchange capacity (milli equivalent / g) was calculated by taking the reciprocal of the obtained EW value and multiplying it by 1000.

(2) Film thickness After the polymer electrolyte membrane was allowed to stand in a constant temperature and humidity room at 23 ° C. and 50% RH for 1 hour or longer, it was measured using a film thickness meter (trade name: B-1 manufactured by Toyo Seiki Seisakusho). Went.

(3) Durability Test: Power Generation / OCV Cycle Test In order to accelerate evaluation of the durability of the polymer electrolyte membrane under high-temperature and low-humidification conditions, an acceleration test by power generation and OCV cycle was performed according to the following procedure. Note that “OCV” means an open circuit voltage.

(3) -1 Preparation of electrode catalyst ink 20% by mass of perfluorosulfonic acid resin solution (SS700C / 20, manufactured by Asahi Kasei, equivalent mass (EW): 740), electrode catalyst (TEC10E40E, manufactured by Tanaka Kikinzoku Co., Ltd., platinum supported) 36.7 wt%) was added so that the platinum / perfluorosulfonic acid polymer was 1 / 1.15 (mass), and then the solid content (the sum of the electrode catalyst and the perfluorosulfonic acid polymer) was 11 wt%. Ethanol was added so as to obtain an electrode catalyst ink by stirring with a homogenizer (manufactured by AS ONE) at a rotational speed of 3,000 rpm for 10 minutes.

(3) -2 Production of MEA Using an automatic screen printing machine (product name: LS-150, manufactured by Neurong Seimitsu Kogyo Co., Ltd.), the electrocatalyst ink was placed on both sides of the polymer electrolyte membrane, and the amount of platinum supported was on the anode side. 0.2 mg / cm ^2, was applied to the cathode side 0.3mg / cm ^2, 140 ℃, to obtain a MEA by drying and solidifying at 5 minutes condition.

(3) -3 Fabrication of a fuel cell unit cell A gas diffusion layer (product name: GDL35BC, manufactured by MFC Technology) is stacked on both poles of the MEA, and then a gasket, bipolar plate, and backing plate are stacked to form a fuel cell unit cell. Obtained.

(3) -4 Power Generation / OCV Cycle Test The fuel cell single cell was set in an evaluation device (Fuel Cell Evaluation System 890CL manufactured by Toyo Technica Co., Ltd.), and a durability test was performed by a cycle of power generation 3 hours and OCV 3 hours.

The test conditions for power generation are a cell temperature of 90 ° C. and a humidifying bottle of 61 ° C. (relative humidity of 30% RH), hydrogen gas on the anode side and air gas on the cathode side, and a gas utilization rate of 0.3 A / cm ² respectively. Supply conditions were set to 75% and 55%. Further, no pressure was applied (atmospheric pressure) on both the anode side and the cathode side.

  The OCV test conditions were the same as the power generation test conditions for the cell temperature, humidified bottle temperature, supply gas, and pressure.

(3) -5 Determination of degradation Hydrogen leak current was measured every 100 hours from 0 hour (L0) of the test time. The deterioration was determined by calculating the difference between the hydrogen leakage current and L0 (L500-L0) 500 hours after the start of the test (L500). It was judged that the smaller L500-L0, the better the durability. When the hydrogen leakage current was 10 mA / cm ² or more, it was judged that the film was broken even if the test time was 500 hours, and the test was stopped.

  The hydrogen leakage current was measured by introducing 200 cc / min of hydrogen gas into the anode and nitrogen gas into the cathode under non-pressurized conditions in the same manner as the power generation test conditions for the cell temperature and humidifying bottle temperature. The measurement was performed by using a potentiogalvanostat (product name: Solartron 1280B, manufactured by Toyo Technica Co., Ltd.), holding 0.4 V for 5 minutes, and dividing the current value after 5 minutes by the electrode area.

  Examples 1 to 5 and Comparative Example 1 below are application examples of the polymer electrolyte composition to the polymer electrolyte membrane. Examples 6 to 7 and Comparative Example 2 below are application examples of the polymer electrolyte composition to the electrode catalyst layer.

[Example 1]
(Preparation of polymer electrolyte composition)
Perfluorosulfonic acid resin precursor obtained from tetrafluoroethylene, which is a precursor of the polymer electrolyte (a), and CF ₂ ═CFO (CF ₂ ) ₂ —SO ₂ F (EW after hydrolysis and acid treatment) : 740) The pellet was brought into contact with an aqueous solution in which potassium hydroxide (15% by mass) and methanol (50% by mass) were dissolved at 80 ° C. for 20 hours for hydrolysis treatment. Then, it was immersed in 60 degreeC water for 5 hours. Next, the treatment of immersing in a 2N hydrochloric acid aqueous solution at 60 ° C. for 1 hour was repeated 5 times each time using a new aqueous hydrochloric acid solution, then washed with ion-exchanged water and dried. Thereby, a pellet of the polymer electrolyte (a) having a sulfonic acid group (SO ₃ H) was obtained.

  The pellet was placed in a 5 L autoclave together with an aqueous ethanol solution (water: ethanol = 66.7: 33.3 (mass ratio)), sealed, heated to 160 ° C. with stirring with a blade, and held for 5 hours. Thereafter, the autoclave was naturally cooled to prepare a 5% by mass uniform perfluorosulfonic acid resin solution.

Next, 15 g of tantalum (1,000 ppm standard stock solution for atomic absorption analysis manufactured by Kanto Chemical Co., Inc.) was added as compound (b) to 100 g of this solution, and a / b = 97/3 (mass ratio) It adjusted so that it might become. Finally, for the purpose of confirming the effect of the compound (b), iron sulfate (II) (manufactured by Kanto Chemical Co., Inc.) is blended so as to be 20 ppm with respect to the perfluorosulfonic acid resin, and the polymer electrolyte composition A polymer electrolyte solution containing the product was obtained. Tantalum formed a sulfonic acid salt (SO ₃ H) and a sulfonate salt of the polymer electrolyte (a). The formation of a sulfonate could be confirmed using a Fourier-Transform Infrared Spectrometer. That is, the formation of a sulfonate was confirmed by observing the change in peak intensity around 1458 cm −1 and 626 cm −1 where the contribution of the sulfonic acid group was large.

(Production of polymer electrolyte membrane)
The obtained polymer electrolyte solution was sufficiently stirred using a stirrer and then concentrated under reduced pressure at 80 ° C. to obtain a cast solution. 21 g of the cast solution was poured into a petri dish having a diameter of 15.4 cm and dried on a hot plate at 60 ° C. for 1 hour and at 80 ° C. for 1 hour to remove the solvent. Next, the petri dish was placed in an oven and heat treated at 160 ° C. for 1 hour. Thereafter, the membrane was removed from the oven and poured into a cooled petri dish to peel off the membrane to obtain a polymer electrolyte membrane having a thickness of about 30 μm. Next, it was immersed in a 2N hydrochloric acid aqueous solution at 60 ° C. for 3 hours, then washed with ion-exchanged water and dried to obtain a polymer electrolyte membrane.

  When the above (3) durability test was carried out using this polymer electrolyte membrane, good results were obtained. The results are shown in Table 1.

[Example 2]
The polymer electrolyte solution and the polymer were the same as in Example 1 except that 0.01 g of tantalum (manufactured by Kanto Chemical Co., Inc., using 1,000 ppm standard stock solution for atomic absorption analysis) was used as the compound (b). When an electrolyte membrane was obtained and (3) a durability test was performed, good results were obtained. The results are shown in Table 1. Note that tantalum was confirmed in the same manner as in Example 1 that was formed a sulfonic acid group (SO ₃ H) and sulfonate polyelectrolyte (a).

Example 3
The polymer electrolyte solution and the polymer electrolyte membrane were the same as in Example 1 except that 15 g of niobium (manufactured by Kanto Chemical Co., Inc., using 1,000 ppm standard stock solution for atomic absorption analysis) was used as the compound (b). (3) When a durability test was conducted, good results were obtained. The results are shown in Table 1. It was confirmed by the same method as in Example 1 that niobium formed sulfonic acid groups (SO ₃ H) and sulfonates of the polymer electrolyte (a).

Example 4
A polymer electrolyte solution and a polymer electrolyte membrane were obtained in the same manner as in Example 1 except that polybenzimidazole (manufactured by Sigma Aldrich Japan Co., Ltd.) was used as the radical scavenger (c). (3) Durability When the property test was carried out, good results were obtained. The results are shown in Table 1. Note that tantalum was confirmed in the same manner as in Example 1 that was formed a sulfonic acid group (SO ₃ H) and sulfonate polyelectrolyte (a).

Example 5
(Preparation of polymer electrolyte solution)
Perfluorosulfonic acid resin precursor obtained from tetrafluoroethylene, which is a precursor of the polymer electrolyte (a), and CF ₂ ═CFO (CF ₂ ) ₂ —SO ₂ F (EW after hydrolysis and acid treatment) : 740) Kneading polyphenylene sulfide (manufactured by Sigma Aldrich Japan Co., Ltd.) as a thioether compound (d) into a pellet using a biaxial compounding tester (product name: ULT15TW nano-15MG-NH (-700) manufactured by Technobel) As a result, pellets having a mass ratio of perfluorosulfonic acid resin precursor / polyphenylene sulfide of 94/6 were obtained.

The pellet was contacted in an aqueous solution in which potassium hydroxide (15% by mass) and methanol (50% by mass) were dissolved at 80 ° C. for 20 hours for hydrolysis treatment. Then, it was immersed in 60 degreeC water for 5 hours. Next, the treatment of immersing in a 2N hydrochloric acid aqueous solution at 60 ° C. for 1 hour was repeated 5 times each time using a new aqueous hydrochloric acid solution, then washed with ion-exchanged water and dried. Thereby, a pellet of the polymer electrolyte (a) having a sulfonic acid group (SO ₃ H) was obtained.

  The pellet was placed in a 5 L autoclave together with an aqueous ethanol solution (water: ethanol = 66.7: 33.3 (mass ratio)), sealed, heated to 160 ° C. with stirring with a blade, and held for 5 hours. Thereafter, the autoclave was naturally cooled to prepare a 5% by mass uniform perfluorosulfonic acid resin solution.

Next, 15 g of tantalum (manufactured by Kanto Chemical Co., Inc., using 1,000 ppm standard stock solution for atomic absorption analysis) as a compound (b) was added to 100 g of this solution, and polybenzimidazole (Sigma Aldrich Japan) as a radical scavenger (c). 0.15 g) was prepared so that a / b / c / d = 89/3/3/5 (mass ratio). Finally, for the purpose of confirming the effect of the compound (b), iron sulfate (II) (manufactured by Kanto Chemical Co., Ltd.) is blended so as to be 20 ppm with respect to the perfluorosulfonic acid resin, and a polymer electrolyte solution Got. Note that tantalum was confirmed in the same manner as in Example 1 that was formed a sulfonic acid group (SO ₃ H) and sulfonate polyelectrolyte (a).

(Production of polymer electrolyte membrane)
The obtained polymer electrolyte solution was sufficiently stirred using a stirrer and then concentrated under reduced pressure at 80 ° C. to obtain a cast solution. 21 g of the cast solution was poured into a petri dish having a diameter of 15.4 cm, and dried on a hot plate at 60 ° C. for 1 hour and at 80 ° C. for 1 hour to remove the solvent. Next, the petri dish was placed in an oven and heat treated at 160 ° C. for 1 hour. Thereafter, the membrane was removed from the oven and poured into a cooled petri dish to peel off the membrane to obtain a polymer electrolyte membrane having a thickness of about 30 μm. Next, it was immersed in a 2N hydrochloric acid aqueous solution at 60 ° C. for 3 hours, then washed with ion-exchanged water and dried to obtain a polymer electrolyte membrane. When the above (3) durability test was carried out using this polymer electrolyte membrane, good results were obtained. The results are shown in Table 1.

[Comparative Example 1]
Except that the compound (b) was not added in Example 1, a polymer electrolyte solution and a polymer electrolyte membrane were obtained in the same manner as in Example 1, and (3) a durability test was performed in 200 hours. Since the leakage current of hydrogen exceeded 10 mA / cm ² , it was determined that the film was broken and the test was terminated. The results are shown in Table 1.

Example 6
(Preparation of polymer electrolyte composition)
Perfluorosulfonic acid resin precursor obtained from tetrafluoroethylene, which is a precursor of the polymer electrolyte (a), and CF ₂ ═CFO (CF ₂ ) ₂ —SO ₂ F (EW after hydrolysis and acid treatment) : 740) The pellet was brought into contact with an aqueous solution in which potassium hydroxide (15% by mass) and methanol (50% by mass) were dissolved at 80 ° C. for 20 hours for hydrolysis treatment. Then, it was immersed in 60 degreeC water for 5 hours. Next, the treatment of immersing in a 2N hydrochloric acid aqueous solution at 60 ° C. for 1 hour was repeated 5 times each time using a new aqueous hydrochloric acid solution, then washed with ion-exchanged water and dried. Thereby, a pellet of the polymer electrolyte (a) having a sulfonic acid group (SO ₃ H) was obtained.

  The pellet was placed in a 5 L autoclave together with an aqueous ethanol solution (water: ethanol = 66.7: 33.3 (mass ratio)), sealed, heated to 160 ° C. with stirring with a blade, and held for 5 hours. Thereafter, the autoclave was naturally cooled to prepare a 5% by mass uniform perfluorosulfonic acid resin solution.

Next, 15 g of tantalum (manufactured by Kanto Chemical Co., Inc., using 1,000 ppm standard stock solution for atomic absorption analysis) is added to 100 g of this solution as a compound (b), and a / b = 97/3 (mass ratio) It was prepared as follows. Finally, for the purpose of verifying the effect of the compound (b), iron sulfate (II) (manufactured by Kanto Chemical Co., Inc.) is blended so as to be 20 ppm with respect to the perfluorosulfonic acid resin, and the solid content rate is further increased. The solution was concentrated under reduced pressure until the content became 20% by mass to obtain a polymer electrolyte solution containing the polymer electrolyte composition. Note that tantalum was confirmed in the same manner as in Example 1 that was formed a sulfonic acid group (SO ₃ H) and sulfonate polyelectrolyte (a).

(Production of electrode catalyst layer)
An electrode catalyst (TEC10E40E, manufactured by Tanaka Kikinzoku Seiyaku Co., Ltd., platinum support amount 36.7 wt%) was blended with the obtained polymer electrolyte solution so that the platinum / perfluorosulfonic acid polymer was 1 / 1.15 (weight). .

Next, ethanol is added so that the solid content (total weight of the electrode catalyst, perfluorosulfonic acid polymer, and tantalum) is 11 wt%, and the mixture is stirred for 10 minutes with a homogenizer (manufactured by ASONE) at a rotation speed of 3,000 rpm. The electrode catalyst ink was obtained. The obtained electrode ink was supported on platinum on both sides of a polymer electrolyte membrane (Nafion 211CS (25 μm), manufactured by DuPont) using an automatic screen printer (product name: LS-150, manufactured by Neurong Precision Industry Co., Ltd.). anode 0.2 mg / cm ² amounts, was coated such that the cathode side 0.3mg / cm ^2, 140 ℃, membrane electrode assembly having an electrode catalyst layer by drying and solidifying at 5 minutes conditions ( MEA) was obtained.

  A gas diffusion layer (product name: GDL35BC, manufactured by MFC Technology) was stacked on both electrodes of the obtained MEA, and then a gasket, a bipolar plate, and a backing plate were stacked to obtain a fuel cell single cell. When the obtained fuel cell single cell was used to perform the above (3) durability test, good results were obtained. The results are shown in Table 2.

Example 7
A fuel cell single cell was obtained in the same manner as in Example 6 except that 15 g of niobium (manufactured by Kanto Chemical Co., Inc., 1,000 ppm standard stock solution for atomic absorption analysis) was used as the compound (b). ) When a durability test was performed, good results were obtained. The results are shown in Table 2. It was confirmed by the same method as in Example 1 that niobium formed sulfonic acid groups (SO ₃ H) and sulfonates of the polymer electrolyte (a).

Example 8
(Preparation of perfluorosulfonic acid resin / polybenzimidazole solution)
0.32 g of polybenzimidazole (manufactured by Sigma Aldrich Japan Co., Ltd.) as a radical scavenger (c), a mixed solution of 1.39 g of a 16% by mass sodium hydroxide aqueous solution (manufactured by Wako Pure Chemical Industries, Ltd.) and 100 g of ethanol And stirred at 80 ° C. for 1 hour. After the polybenzimidazole was completely dissolved, 53.50 g of ethanol was blended to obtain a reddish brown polybenzimidazole solution.

  Next, 123.12 g of the 5% by mass uniform perfluorosulfonic acid resin solution obtained in Example 6 was blended with the polybenzimidazole solution, and the mixture was stirred at room temperature for 1 hour. A sulfonic acid resin / polybenzimidazole solution-1 was obtained.

  Next, 100 g of the perfluorosulfonic acid resin / polybenzimidazole solution is mixed with 10 g of an ion exchange resin (product name: Diaion SK1B-H manufactured by Mitsubishi Chemical Corporation) and stirred under conditions of room temperature for 30 minutes. Then, a light yellow perfluorosulfonic acid resin / polybenzimidazole solution-2 was obtained by removing the ion exchange resin.

(Preparation of polymer electrolyte solution)
To 100 g of the 5% by mass uniform perfluorosulfonic acid resin solution obtained in Example 6, tantalum (manufactured by Kanto Chemical Co., Inc., using 1,000 ppm standard stock solution for atomic absorption analysis) as a compound (b), The perfluorosulfonic acid resin / polybenzimidazole solution-2 was prepared so that a / b / c = 94/3/3 (mass ratio).

Finally, for the purpose of verifying the effect of the compound (b), iron sulfate (II) (manufactured by Kanto Chemical Co., Inc.) is blended so as to be 20 ppm with respect to the perfluorosulfonic acid resin, and the solid content rate is further increased. The solution was concentrated under reduced pressure until the content became 20% by mass to obtain a polymer electrolyte solution containing the polymer electrolyte composition. Note that tantalum was confirmed in the same manner as in Example 1 that was formed a sulfonic acid group (SO ₃ H) and sulfonate polyelectrolyte (a).

(Production of electrode catalyst layer)
An electrode catalyst (TEC10E40E, manufactured by Tanaka Kikinzoku Seiyaku Co., Ltd., platinum support amount 36.7 wt%) was blended with the obtained polymer electrolyte solution so that the platinum / perfluorosulfonic acid polymer was 1 / 1.15 (weight). .

Next, ethanol is added so that the solid content (total weight of the electrode catalyst, perfluorosulfonic acid polymer, and tantalum) is 11 wt%, and the mixture is stirred for 10 minutes with a homogenizer (manufactured by ASONE) at a rotation speed of 3,000 rpm. The electrode catalyst ink was obtained. The obtained electrode ink was supported on platinum on both sides of a polymer electrolyte membrane (Nafion 211CS (25 μm), manufactured by DuPont) using an automatic screen printer (product name: LS-150, manufactured by Neurong Precision Industry Co., Ltd.). anode 0.2 mg / cm ² amounts, was coated such that the cathode side 0.3mg / cm ^2, 140 ℃, membrane electrode assembly having an electrode catalyst layer by drying and solidifying at 5 minutes conditions ( MEA) was obtained.

  A gas diffusion layer (product name: GDL35BC, manufactured by MFC Technology) was stacked on both electrodes of the obtained MEA, and then a gasket, a bipolar plate, and a backing plate were stacked to obtain a fuel cell single cell. When the durability test of the above (3) was performed using the obtained fuel cell single cell, good results were obtained. The results are shown in Table 2.

[Comparative Example 2]
A fuel cell single cell was obtained in the same manner as in Example 6 except that the compound (b) was not blended, and the above (3) durability test was conducted. As a result, the hydrogen leakage current was 10 mA / cm in 100 hours. ^Since it exceeded ² , it was judged as a ruptured film and the test was terminated. The results are shown in Table 2.

パーフルオロカーボンスルホン酸樹脂：テトラフルオロエチレン、ＣＦ₂＝ＣＦ−Ｏ−（ＣＦ₂）₂−ＳＯ₃Ｈの共重合体。ＥＷ７４０
ＰＢＩ：ポリベンゾイミダゾール
ＰＰＳ：ポリフェニレンスルフィド

Perfluorocarbon sulfonic acid resin: tetrafluoroethylene, CF ₂ ═CF—O— (CF ₂ ) ₂ —SO ₃ H copolymer. EW740
PBI: Polybenzimidazole PPS: Polyphenylene sulfide

パーフルオロカーボンスルホン酸樹脂：テトラフルオロエチレン、ＣＦ₂＝ＣＦ−Ｏ−（ＣＦ₂）₂−ＳＯ₃Ｈの共重合体。ＥＷ７４０

Perfluorocarbon sulfonic acid resin: tetrafluoroethylene, CF ₂ ═CF—O— (CF ₂ ) ₂ —SO ₃ H copolymer. EW740

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

Claims (8)

A polymer electrolyte (a);
A compound (b) containing at least one metal element selected from the group consisting of tantalum and niobium,
Polymer electrolyte composition.   The polymer electrolyte composition according to claim 1, wherein the compound (b) is at least one selected from the group consisting of sulfates, carbonates, phosphates, and carboxylates.   The polymer electrolyte composition according to claim 1 or 2, further comprising a radical scavenger (c). The polymer electrolyte composition according to any one of claims 1 to 3, wherein the polymer electrolyte (a) is represented by the following formula [1].
_{^{- [CF 2 CX 1 X 2}} ] a - [CF 2 -CF (-O- (CF 2 -CF (CF 2 X 3)) b -O c - (CFR 1) d - (CFR 2) e - ( ^{_{CF 2) f -X 4)]}} g - [1]
(In the 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, a + g = 1,
b is an integer of 0 or more and 8 or less. c is 0 or 1,
d and e are each independently an integer of 0 or more and 6 or less, and 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 or a fluorochloroalkyl group having 1 to 10 carbon atoms,
X ⁴ is COOZ, SO ₃ Z, PO ₃ Z ₂ or PO ₃ HZ, where Z is a hydrogen atom, an alkali metal atom, an alkaline earth metal atom or an amine (NH ₄ , NH ₃ R ³ , NH ₂ R ³ R ⁴ , NHR ³ R ⁴ R ⁵ , NR ³ R ⁴ R ⁵ R ⁶ ), and R ³ , R ⁴ , R ⁵ and R ⁶ are alkyl groups or arene groups. )   The polymer electrolyte membrane containing the polymer electrolyte composition of any one of Claims 1-4.   The electrode catalyst layer containing the polymer electrolyte composition of any one of Claims 1-4.   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.