JP2018174158A - Polymer electrolyte composition, and polymer electrolyte membrane, electrode catalyst layer, membrane electrode assembly, and solid polymer fuel cell each using the polymer electrolyte composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polymer electrolyte composition capable of providing a polymer electrolyte membrane, an electrode catalyst layer, a membrane electrode assembly, and a solid polymer fuel cell each being highly durable, and to provide a polymer electrolyte membrane, an electrode catalyst layer, a membrane electrode assembly, and a solid polymer fuel cell each using the polymer electrolyte composition and being highly durable.SOLUTION: The polymer electrolyte composition is provided that contains a polymer electrolyte (a) containing a fluorine element in the molecule and a compound (b) having a metal ion-capturing capability.SELECTED DRAWING: None

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 electrolyte 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 a lower temperature than others.

  Such a solid 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 the above-described high-temperature and low-humidification operation is performed, 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). ) In the polymer electrolyte membrane, it acts as a reducing agent at a potential lower than the oxidation-reduction potential of the hydroxy radical, and also acts as an oxidizing agent at a potential higher than the oxidation-reduction potential at which hydrogen peroxide acts as a reducing agent. A method of blending a compound having a redox cycle (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, Patent Document 3) and the like are disclosed. In addition, metal cations, transition metal complex cations, or quaternary ammonium cations are introduced into the solid electrolyte material for the purpose of trapping metal ions that cause peroxide radicals. A method of capturing and containing a superoxide (O ₂ ⁻ ) exhibiting conductivity and increasing the ionic conductivity of the electrolyte (see, for example, Patent Document 4), an ion comprising an aromatic anion group in the polymer electrolyte material A method of including a complex, capturing and removing a cation (H + ion) by an anion group of the ionic complex, and increasing ion conductivity as a result of anion formation (for example, see Patent Document 5), a method of blending a metal chelating agent (For example, refer to Patent Document 6).

JP 2001-118591 A JP 2006-49263 A JP 2000-223135 A Japanese Patent Publication No. 8-30276 JP 10-510090 Gazette Japanese Patent Laid-Open No. 2001-2223015

  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. In the methods disclosed in Patent Document 4 and Patent Document 5, either an ion or a cation is captured by ion exchange, and the effect is insufficient. Further, the method disclosed in Patent Document 6 uses a hydrocarbon type polymer electrolyte for the proton exchange membrane, and has a problem in chemical durability.

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

  As a result of intensive studies to solve the above problems, the present inventors have found that the above problems can be solved by inactivating the metal ions that are the source of radical species that cause the proton exchange membrane to decompose. It came to the headline and this invention.

That is, the present invention is as follows.
[1]
A polymer electrolyte composition comprising a polymer electrolyte (a) containing a fluorine element in a molecule and a compound (b) having a metal ion scavenging ability.
[2]
The polymer electrolyte composition according to [1], wherein the compound (b) is at least one selected from the group consisting of a phosphoric acid compound, a silicic acid compound, and a compound having a carboxyl group.
[3]
The polymer electrolyte composition according to [1] and [2], wherein the compound (b) has a functional group that forms an ionic bond with the polymer electrolyte (a).
[4]
The polymer electrolyte composition according to [3], wherein the functional group that forms an ionic bond with the polymer electrolyte (a) is a functional group having a nitrogen atom.
[5]
The polymer electrolyte composition according to [2] above, wherein the phosphate compound contains at least one phosphate compound selected from the group consisting of pyrophosphate, pyrophosphate, phytic acid, and phytate.
[6]
The polymer electrolyte composition according to any one of [2] to [5], wherein the silicate compound includes a silicate.
[7]
The polymer electrolyte composition according to any one of [2] to [6], wherein the compound having a carboxyl group includes a perfluorocarbon carboxylic acid compound.
[8]
The polymer electrolyte composition according to any one of [1] to [7], further containing a radical scavenger (c).
[9]
A polymer electrolyte membrane comprising the polymer electrolyte composition according to any one of [1] to [8] above.
[10]
An electrode catalyst layer comprising the polymer electrolyte composition according to any one of [1] to [8] above.
[11]
A membrane electrode assembly comprising the polymer electrolyte membrane according to [9] above and the electrode catalyst layer according to [10] above.
[12]
A polymer electrolyte fuel cell comprising the membrane electrode assembly according to [11] above.

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

  DESCRIPTION OF EMBODIMENTS 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 is
It contains a polymer electrolyte (a) containing fluorine element in the molecule and a compound (b) having a metal ion scavenging ability. As a result, the generation of radical species can be suppressed by inactivating the metal ions that promote the decomposition of hydrogen peroxide, and the durability is excellent even under operating conditions where high temperature and low humidification and 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)]
The polymer electrolyte composition according to this embodiment includes a polymer electrolyte (a) containing a fluorine element in the molecule. The polymer electrolyte (a) is not particularly limited, but for example, a polymer compound having an ion exchange group 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 equivalent 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 tends to be further reduced. is there. 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. In addition, ion exchange capacity can be calculated | required by the method as described in an Example.

  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 perfluorocarbon high molecular compound, 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, 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 It 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 having 1 to 10 carbon atoms or a fluorochloroalkyl group. 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 Is. Also R ^3, R ^4, R ⁵ and R ⁶ is an alkyl or arene group.)

Among these, a perfluorocarbon sulfonic acid resin represented by the following formula [2] or formula [3] or a metal salt thereof is 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 performed by reacting a vinyl fluoride compound and a fluorinated olefin gas in a state where the polymerization solvent is filled and dissolved. 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 fluorinated olefin gas 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 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.

  In the present embodiment, a 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) having metal ion scavenging ability]
The polymer electrolyte composition according to this embodiment contains a compound (b) having a metal ion scavenging ability. “Metal ion scavenging ability” refers to an action of inactivating metal ions that promote the decomposition of hydrogen peroxide. Here, the metal ion that promotes decomposition of hydrogen peroxide is not particularly limited, and examples thereof include Fe, Cr, Ni, and the like. The compound (b) having such a metal ion scavenging ability is not particularly limited, but for example, at least one selected from the group consisting of a phosphoric acid compound, a silicic acid compound, and a compound having a carboxyl group is preferable. .

(Phosphate compound)
Although it does not specifically limit as said phosphate compound, For example, the following compound is mentioned. The phosphoric acid compound includes a salt of the phosphoric acid compound.

(1) Phosphate esters The phosphate esters are not particularly limited, and examples thereof include esters such as phosphate esters, phosphonate esters, phosphinate esters, and phosphite esters. More specifically, trimethyl phosphate, triethyl phosphate, tributyl phosphate, trioctyl phosphate, riboflavin phosphate, phospholipid (such as reticin), starch phosphate ester, vitamin C phosphate, phytic acid (IP6: inositol six Phosphoric acid), dimethyl 4-aminobenzylphosphonate, diethyl 4-aminobenzylphosphonate, dipropyl 4-aminobenzylphosphonate, dimethyl 2-aminomethylphosphonate, diethyl 2-aminomethylphosphonate, dipropyl 2-aminomethylphosphonate, phthalimide Dimethyl methylphosphonate, diethyl phthalimidomethylphosphonate, dipropyl phthalimidomethylphosphonate, 1-hydroxymethane-1, dimethyl 1-diphosphonate, 1-hydroxyethane-1, 1-diphosphonate diethyl, -, and the like dipropyl-hydroxy-1,1-diphosphonic acid. These esters form a sparingly soluble salt with Fe ions or the like by hydrolysis, or generate an anion having a chelating ability. Of these, phytic acid and phytate are preferable. Phytic acid and its salts are accepted as food additives and tend to be superior from the viewpoint of toxicity and environmental load of the polymer electrolyte composition.

(2) Compound having a phosphoric acid group The compound having a phosphoric acid group is not particularly limited, and examples thereof include orthophosphoric acid, phosphonic acid, phosphinic acid, pyrophosphoric acid, metaphosphoric acid, tripolyphosphoric acid, hexametaphosphoric acid, and polyphosphoric acid. A compound having a phosphate group or a salt thereof may be mentioned. Phosphoric acid groups (for example, orthophosphate ion PO ₄ ³⁻ , pyrophosphate ion P ₂ O ₇ ⁴⁻ ) form poorly soluble salts or chelates with Fe ions and the like, so that the Fenton activity can be significantly reduced. .

In addition, phosphonate ion PO3 ³⁻ , phosphinate ion PO2 ³⁻ and polyphosphate ion which is a polymer of phosphoric acid are coordinated to Fe ion to form a soluble chelate, and the concentration of free Fe ion (Activity) can be significantly reduced. From this viewpoint, among the compounds having a phosphate group, pyrophosphate and pyrophosphate are preferable.

  Specific compounds having the above functional groups are not particularly limited, and examples thereof include adenosine monophosphate, adenosine diphosphate, adenosine triphosphate, guanosine monophosphate, guanosine diphosphate, guanosine triphosphate, 4-aminobenzylphosphonic acid, dimethyl-4-aminomethylphosphonic acid, 2-aminomethylphosphonic acid, nitrilotris (methylenephosphonic acid), phthalimidomethylphosphonic acid, 4-amino-1-hydroxybutane-1,1-diphosphonic acid, N , N, N ', N'-ethylenediaminetetrakis (methylenephosphonic acid) and the like, and salts of these compounds.

(3) The phosphorus oxides phosphorus oxide is not particularly limited, examples thereof include P ₂ O _5. These yield PO ₄ ³⁻ and P ₂ O ₇ ²⁻ by hydrolysis. Among these, the use of phosphorous oxides capable of generating PO ₄ ^3- ion and P ₂ O ₇ ^{4 -} ion which are permitted as food additives is used from the viewpoint of toxicity and environmental load of the polymer electrolyte composition. preferable.

(Silicic acid compound)
The silicic acid compound is not particularly limited. For example, silicic acid or a heteropoly acid containing the silicic acid (for example, silicomolybdic acid or silicotungstic acid) or a salt thereof, zeolite (sodium aluminum silicate, aluminosilicate) Acid salt). Among these, silicate is preferable. Fe ions generate precipitates or chelates with silicate ions or heteropolyacid ions containing silicon, making it difficult for the Fenton reaction to occur. In addition, in the zeolite, Fe ions are exchanged with metals (for example, sodium and potassium) contained in the zeolite to be taken into the zeolite and tend not to cause the Fenton reaction.

  Although it does not specifically limit as said silicic acid compound, For example, the compound which has a functional group which makes an ionic bond with the proton conductive group of a polymer electrolyte so that it may mention later is preferable. Specifically, N-2- (aminoethyl) -3-aminopropylmethyldimethoxysilane, N-2- (aminoethyl) -3-aminopropyltrimethoxysilane, N-2- (aminoethyl) -3- Aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-triethoxysilyl-N- (1,3-dimethyl-butylidene) propylamine, N-phenyl-3-aminopropyl Examples include trimethoxysilane and 3-ureidopropyltriethoxysilane. In these compounds, amino groups and urea groups form an ionic bond with the proton conducting group of the polymer electrolyte to be immobilized, and the alkoxy group is hydrolyzed to generate silicic acid. The silicate ions tend to cause Fe ions to form precipitates or chelates and make the Fenton reaction difficult.

(Compound having a carboxyl group)
Although it does not specifically limit as a compound which has the said carboxyl group, For example, the following compounds are mentioned. In addition, the salt of the compound which has a carboxyl group is also contained in the compound which has a carboxyl group.

(1) Polyaminocarboxylic acid Although it does not specifically limit as polyaminocarboxylic acid, For example, EDTA (ethylenediaminetetraacetic acid), DTPA (diethylenetriaminepentaacetic acid), TTHA (triethylenetetraaminehexaacetic acid), HIDA (hydroxyethyliminodiacetic acid) ) And the like or salts thereof. Polyaminocarboxylic acids can be used as chelating agents.

(2) COO ^- compound COO having ion ^- Examples of the compound having an ion is not particularly limited, for example, oxalic acid (oxalic anhydride, oxalic acid dihydrate), gallate, or salts thereof . COO ⁻ ion as an anion (especially, oxalate ion of (COO ⁻ ) ₂ ) is a preferable anion because it easily forms a sparingly soluble salt with Fe. When these anions form a sparingly soluble salt with Fe, the Fenton reaction can be suppressed. In particular, gallic acid ions that are acceptable as food additives are preferred from the viewpoints of toxicity and environmental burden.

(3) Carboxylic acid ester compound Although it does not specifically limit as a carboxylic acid ester compound, For example, oxalic acid ester (For example, dimethyl oxalate, diethyl oxalate, dipropyl oxalate etc.) etc. are mentioned. Carboxylic acid ester compounds form a sparingly soluble salt with Fe ions by hydrolysis, or generate an anion having a chelating ability.

(4) Polymeric carboxylic acid Although it does not specifically limit as polymeric carboxylic acid, For example, polymeric carboxylic acids, such as humic acid and tannic acid, or its salt is mentioned. Polymeric carboxylic acids also form sparingly soluble salts with Fe.

(5) Perfluorocarboxylic acid Although it does not specifically limit as perfluorocarboxylic acid, For example, perfluorocarboxylic acid or its salt, a perfluorocarbon carboxylic acid compound is mentioned. Perfluorocarboxylic acid also forms a sparingly soluble salt with Fe. Further, since it is a fluorine compound, it has a high resistance to radicals generated during battery operation, and tends to be able to exhibit functions for a long time.

Among these, a perfluorocarbon carboxylic acid resin represented by the following formula [5] or [6] or a metal salt thereof is particularly preferable.
_{- [CF 2 CF 2] a} - [CF 2 -CF (-O- (CF 2 -CF (CF 3)) b -O- (CF 2) c -CO 2 X)] d - [5]
(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 -CO 2 Y)] g - [6]
(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.)

(Functional groups that form ionic bonds)
The compound (b) is preferably a compound having a functional group that forms an ionic bond with the polymer electrolyte (a). When the compound (b) forms an ionic bond with the proton conductive group of the polymer electrolyte (a), the compound (b) can be immobilized in the polymer electrolyte, and elution of these can be prevented.

  Although it does not specifically limit as a functional group which forms an ionic bond with the proton conductive group of a polymer electrolyte (a), For example, the functional group which has a nitrogen atom is preferable. The functional group having a nitrogen element is not particularly limited, and specific examples include amino groups, imide groups, urea groups, urethane groups, amide groups, imidazole groups, diazole groups, triazole groups, thiazole groups, triazine groups, ureas. Groups and the like. Of these, an amino group is preferable. The proton conductive group is not particularly limited, but is an acidic group such as sulfonic acid or phosphoric acid. Since the functional group having a nitrogen atom tends to be basic, the functional group having a nitrogen atom tends to form an ionic bond well with the proton conducting group.

  The content of the compound (b) is preferably 0.001 to 50000 mass%, more preferably 0.005 to 100 mass% of the total of the polymer electrolyte (a) and the compound (b). It is 20.000 mass%, More preferably, it is 0.010-10.000 mass%, More preferably, it is 0.100-5.000 mass%, More preferably, it is 0.100-2.000 mass%. When the content of the compound (b) is in the above range (0.001 to 50.000% by mass), metal ions are effectively captured while maintaining good proton conductivity, and high durability is achieved. It tends to be possible to obtain a polymer electrolyte membrane and an electrode catalyst layer.

〔solvent〕
The polymer electrolyte composition according to this embodiment may contain a solvent. Although it does not specifically limit as a solvent used, For example, what contained at least 1 or more types in water, an organic solvent, a liquid resin monomer, and a liquid resin oligomer is mentioned.

  Although it does not specifically limit as said organic solvent, For example, alcohols, such as methanol, ethanol, 2-propanol, butanol, octanol; Ethyl acetate, butyl acetate, ethyl lactate, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether Esters such as 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 monoethyl ether, etc. Ethers; acetone, methyl ethyl ketone, methyl isobutyl ketone, acetyl acetone, Ketones such as Rohekisanon, benzene, toluene, xylene, ethylbenzene and the like; dimethylformamide, N, N- dimethyl acetoacetamide, amides such as N- methyl pyrrolidone is preferably used. In addition, these solvents may be used individually by 1 type, or may use 2 or more types together.

  50 mass%-98 mass% are preferable with respect to 100 mass% of polymer electrolyte compositions, and, as for content of a solvent, 60 mass%-95 mass% are more preferable. When the content of the solvent is 50% by mass to 98% by mass, a polymer electrolyte composition in which various materials without precipitates are uniformly dispersed tends 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.

  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 phenol 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 is a primary amine or a secondary amine, it will interact with the ion exchange group of the polymer electrolyte (a) and also has a radical scavenging function (corresponding to the compound (c-1)). ). 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 that has a radical scavenging function. In addition, there may be mentioned phenolic hydroxyl groups, primary and secondary amines, etc., which are contained in the same molecule (corresponding to 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) may be a copolymer of a unit having an interaction with a polymer substance having an ion exchange group and a unit having a radical scavenging function. By having a portion having an interaction with the polymer solid electrolyte, the compatibility with the polymer electrolyte tends to be further improved. Moreover, there exists a tendency for chemical durability to improve more by having a radical capture | acquisition function.

  Content of the compound (c-1) and the compound (c-2) in the polymer electrolyte membrane of this embodiment is 100 in total of the polymer electrolyte (a), the compound (c-1), and the compound (c-2). Preferably it is 0.001-50000 mass% with respect to mass%, More preferably, it is 0.005-20.000 mass%, More preferably, it is 0.010-10.000 mass%, Still more preferably, it is 0.100-5.000 mass%, More preferably, it is 0.100-2.000 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%). The polymer electrolyte membrane having higher durability tends to be obtained.

〔Additive〕
In addition to the polymer electrolyte (a), the compound (b), and the radical scavenger (c), the following compounds can be blended in the polymer electrolyte composition according to this embodiment. The additives described below can be blended alone or in combination of two or more.

(Metal oxide (d))
Although it does not specifically limit as a metal oxide, For example, the metal oxide which has hydrogen peroxide resolution and a primary particle diameter is 1 nm-50 nm is mentioned. Here, the “primary particle size” of the metal oxide (d) means that the dispersion is adjusted so that the content of the metal oxide (d) in the solvent is 1% by mass, and the dynamic light scattering particle size is adjusted. The average particle size measured using a distribution meter (manufactured by Otsuka Electronics). The “hydrogen peroxide resolution” means that the metal oxide (d) decomposes into water and oxygen when it comes into contact with hydrogen peroxide.

The metal oxides having a hydrogen peroxide resolution is not particularly limited, for example, zirconia (ZrO _2), titania (TiO _2), silica (SiO _2), alumina (Al ₂ O3), iron oxide (Fe ₂ O _{3, FeO, Fe 3 O 4} ), copper oxide (CuO, Cu ₂ O), zinc oxide (ZnO), yttrium oxide (Y ₂ O _3), niobium oxide (Nb ₂ O5), molybdenum oxide (MoO _3), Indium oxide (In ₂ O ₃ , In ₂ O), tin oxide (SnO ₂ ), tantalum oxide (Ta ₂ O ₅ ), tungsten oxide (WO ₃ , W ₂ O ₅ ), lead oxide (PbO, PbO ₂ ), Bismuth oxide (Bi ₂ O ₃ ), cerium oxide (CeO ₂ , Ce ₂ O ₃ ), antimony oxide (Sb ₂ O ₃ , Sb ₂ O ₅ ), germanium oxide (GeO ₂ , GeO), lanthanum oxide (La ₂ O) _3), Ruthenium (RuO _2), and the like. These metal oxides may be used alone or as a mixture. For example, tin-added indium oxide (ITO), antimony-added tin oxide (ATO), aluminum zinc oxide (ZnO.Al ₂ O ₃ ), etc. The composite oxides listed in (1) may be used.

The metal oxide (d) used in the present embodiment prevents elution due to ionization of the metal oxide (due to heat, acid, alkali, etc.) during operation of the fuel cell, and maintains the hydrogen peroxide resolution. Zirconia (ZrO ₂ ), titania (TiO ₂ ), and yttrium oxide (Y ₂ O ₃ ) are preferable. The surface of the metal oxide (d) used in the present embodiment is preferably modified with a surface modifier having at least one reactive functional group from the viewpoint of dispersibility.

  The surface modifier of the metal oxide (d) preferably has one or more reactive functional groups. Although it does not specifically limit as this reactive functional group, For example, it is preferable to have a carbon-carbon double bond or a silicon-hydrogen bond, and an alkoxyl group, a hydroxyl group, a vinyl group, a styryl group, an acryl group, a methacryl group, One or more reactive functional groups selected from the group of acryloyl group and epoxy group are preferred. Particularly preferred in this embodiment is one or more selected from the group consisting of a silane coupling agent, a modified silicone, and a surfactant among those having a carbon-carbon double bond or silicon-hydrogen bond. .

  The silane coupling agent is not particularly limited. For example, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltrichlorosilane, vinyltophenoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltri Ethoxysilane, 3-glycidoxypropyltrichlorosilane, 3-glycidoxypropyltriphenoxysilane, p-styryltrimethoxysilane, p-styryltriethoxysilane, p-styryltrichlorosilane, p-styryltriphenoxysilane, 3-acryloxypropyltrimethoxysilane, 3-acryloxypropyltriethoxysilane, 3-acryloxypropyltrichlorosilane, 3-acryloxypropyltriphenoxysilane, 3-methacryloxypropiyl Trimethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-methacryloxypropyltrichlorosilane, 3-methacryloxypropyltriphenoxysilane, allyltrimethoxysilane, allyltriethoxysilane, allyltrichlorosilane, allyltriphenoxysilane, Vinylethyldimethoxysilane, vinylethyldiethoxysilane, vinylethyldichlorosilane, vinylethyldiphenoxysilane, 3-glycidoxypropylethyldimethoxysilane, 3-glycidoxypropyltriethyldiethoxysilane, 3-glycidoxypropyl Ethyldichlorosilane, 3-glycidoxypropylethyldiphenoxysilane, p-styrylethyldimethoxysilane, p-styrylethyldiethoxysilane, p-styryl Liethyldichlorosilane, p-styrylethyldiphenoxysilane, 3-acryloxypropylethyldimethoxysilane, 3-acryloxypropylethyldiethoxysilane, 3-acryloxypropylethyldichlorosilane, 3-acryloxypropylethyldi Phenoxysilane, 3-methacryloxypropylethyldimethoxysilane, 3-methacryloxypropylethyldiethoxysilane, 3-methacryloxypropylethyldichlorosilane, 3-methacryloxypropylethyldiphenoxysilane, allylethyldimethoxysilane, allylethyldi Ethoxysilane, allylethyldichlorosilane, allylethyldiphenoxysilane, vinyldiethylmethoxysilane, vinyldiethylethoxysilane, vinyldiethylchlorosilane, Vinyldiethylphenoxysilane, 3-glycidoxypropyldiethylmethoxysilane, 3-glycidoxypropyldiethylethoxysilane, 3-glycidoxypropyldiethylchlorosilane, 3-glycidoxypropyldiethylphenoxysilane, p-styryldiethylmethoxy Silane, p-styryldiethylethoxysilane, p-styryldiethylchlorosilane, p-styryldiethylphenoxysilane, 3-acryloxypropyldiethylmethoxysilane, 3-acryloxypropyldiethylethoxysilane, 3-acryloxypropyldiethylchlorosilane 3-acryloxypropyldiethylphenoxysilane, 3-methacryloxypropyldiethylmethoxysilane, 3-methacryloxypropyldiethylethoxysilane, 3- Taku Lilo propyl diethyl dichlorosilane, 3-methacryloxypropyl diethyl phenoxy silane, allyl diethyl silane, allyl diethyl silane, allyl diethyl chloro silane, may also be mentioned allyl diethyl phenoxy silane.

  The modified silicone is not particularly limited, and examples thereof include epoxy-modified silicone, epoxy-polyether-modified silicone, methacryl-modified silicone, phenol-modified silicone, methylstyryl-modified silicone, acrylic-modified silicone, alkoxy-modified silicone, and methylhydrogen silicone. Can be mentioned.

  Although it does not specifically limit as surfactant, For example, a nonionic surfactant is used suitably. The nonionic surfactant is not particularly limited, and examples thereof include unsaturated fatty acids such as acrylic acid, crotonic acid, oleic acid, linoleic acid, and linolenic acid.

  Examples of the method for modifying the surface of the metal oxide (d) using the surface modifier include a wet method and a dry method.

  The wet method is a method of modifying the surface of the metal oxide (d) by adding a surface modifier and the metal oxide (d) to a solvent and mixing them.

  The dry method is a method of modifying the surface of the metal oxide (d) by putting the surface modifier and the dried metal oxide (d) into a dry mixer such as a mixer and mixing them.

  The mass ratio of the modified portion of the metal oxide (d) whose surface has been modified is 5% with respect to 100% by mass of the total amount of the metal oxide (d) from the viewpoint of miscibility with the polymer electrolyte (a). It is preferable that they are mass%-200 mass%, More preferably, they are 10 mass%-100 mass%, More preferably, they are 20 mass%-100 mass%.

  The primary particle diameter of the metal oxide (d) used in the present embodiment is preferably in the range of 1 nm to 50 nm from the balance of hydrogen peroxide resolution and dispersibility. When the primary particle diameter of the metal oxide (d) is 50 nm or less, the dispersibility of the metal oxide (d) in the polymer electrolyte composition tends to be improved. Further, when the primary particle diameter of the metal oxide (d) is 1 nm or more, the crystallinity is improved and the hydrogen peroxide resolution tends to be good. Therefore, the more preferable range of the primary particle diameter of the metal oxide (d) is 1 nm to 30 nm, and particularly preferably 2 nm to 20 nm.

  The mass ratio (a / d) between the polymer electrolyte (a) and the metal oxide (d) is (a / d) = 50/50 to 99.99 / 0.00 from the viewpoint of the balance between durability and conductivity. 01 is preferable, (a / d) = 70/30 to 99.99 / 0.01 is more preferable, (a / d) = 80/20 to 99.9 / 0.1 is further preferable, and (a / d) ) = 95/5 to 99.5 / 0.5 is even more preferable.

  Moreover, when mixing and dispersing the metal oxide (d), it is preferable to use it dispersed in a solvent from the viewpoint of suppressing aggregation.

  The content of the metal oxide (d) in the dispersion is preferably 1% by mass to 70% by mass, more preferably 1% by mass to 50% by mass, and still more preferably 5% by mass to 30% by mass. By setting the content of the metal oxide (d) in the dispersion to 1 mass% to 70 mass%, the metal oxide (d) maintains a good dispersion state without causing gel or precipitation in the solvent. Tend to be able to.

(Thioether compound (e))
The thioether compound (e) 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, and n is an integer of 1 or more). 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 (e) 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 particularly preferred thioether compound (e) 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.

  Further, as the thioether compound (e), those having an acidic functional group introduced at the terminal can 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. Although it does not specifically limit as a metal salt, For example, alkaline-earth metal salts, such as alkali metal salts, such as sodium salt and potassium salt, and calcium salt, are preferable.

  Furthermore, when the thioether compound (e) is used in a powder form, the average particle diameter of the thioether compound (e) can be effectively achieved by improving the dispersibility in the polymer electrolyte (a), thereby improving the service life. From the viewpoint of making it, 0.01 to 2.0 μm is preferable, 0.01 to 1.0 μm is more preferable, 0.01 to 0.5 μm is further preferable, and 0.01 to 0.1 μm is still more preferable. .

  The method for finely dispersing the thioether compound (e) in the polymer electrolyte (a) is not particularly limited. Examples thereof include a method, a method of obtaining a polymer electrolyte solution, filtering the solution to remove coarse thioether compound (e) 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 / e) between the polymer electrolyte (a) and the thioether compound (e) is preferably (a / e) = 60/40 to 99.99 / 0.01, (a / e) = 70/30 to 99.95 / 0.05 is more preferable, (a / e) = 80/20 to 99.9 / 0.1 is more preferable, and (a / e) = 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 (e) to 40 or less, durability in battery operation under high temperature and low humidification conditions tends to be further improved.

  Moreover, the thioether compound (e) 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 the present embodiment.

  Here, the mass ratio (c / e) of the radical scavenger (c) to the thioether compound (e) is preferably (c / e) = 1/99 to 99/1, and (c / e) = 5/95 to 95/5 is more preferable, (c / e) = 10/90 to 90/10 is more preferable, and (c / e) = 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 (e) 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.

  The polymer electrolyte composition according to this embodiment can be used in the form of a polymer electrolyte solution, a polymer electrolyte membrane, 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. Furthermore, the polymer electrolyte solution can be used as a material such as a polymer electrolyte membrane or an electrode binder as it is or after being subjected to steps such as filtration and concentration, and then 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) treated with an acid as described above has a good solvent (resin affinity) that can dissolve or suspend the polymer electrolyte (a). Or dissolved in a 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 is appropriately determined according to the dissolution method, dissolution conditions, type of polymer electrolyte, total solid content concentration, dissolution temperature, stirring speed, and the like. You can choose. 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.

  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 that the filter is blocked in a short period of time. It tends to be suppressed. On the other hand, by setting it to 100 times or less of the average particle diameter, there is a tendency that agglomerates of particles and undissolved resin that can cause foreign matters in the film can be removed satisfactorily.

[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 can be reduced, and even if differential pressure, strain, etc. occur during handling during fuel cell production or during fuel cell operation, It tends to be difficult to cause damage. 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 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, a mixture of a polymer electrolyte precursor, a radical scavenger (c), and additives (d, e) is melt-kneaded and then extrusion molded to form a film. Thereafter, it is preferably immersed in a basic reaction liquid and hydrolyzed. 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 crystallization of the polymer electrolyte is promoted by the heat treatment, and the mechanical strength of the polymer electrolyte membrane can be stabilized. In addition, the crystal part of the additive such as the radical scavenger (c) and the thioether compound (e) and the polymer solid electrolyte part are firmly bonded by heat treatment, and as a result, the mechanical strength tends to be further stabilized. It is in.

  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 may be called MEA.

  Although it does not specifically limit as a manufacturing method of MEA, For example, the following methods are performed. First, platinum-supported carbon as an electrode material is dispersed in a solution obtained by dissolving an electrode binder ion exchange resin in a mixed solution of alcohol and water to form a paste. 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 polymer electrolyte fuel cell according to the present embodiment includes the membrane electrode assembly (MEA). 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 in general solid polymer electrolyte fuel cells such as a bipolar plate and a backing plate. 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), and the weight of the polymer electrolyte membrane in which the ion-exchange group counter ion is sodium ion is W (mg), and the equivalent weight 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 polymer 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 the solid content (the sum of the electrode catalyst and the perfluorosulfonic acid polymer) was 11 wt%. Ethanol was added so that the electrode catalyst ink was obtained by stirring for 10 minutes at 3,000 rpm with a homogenizer (manufactured by ASONE).

(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 was 0 on the anode side. .2mg / 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 with 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 leak current was 10 mA / cm ² or more, it was judged that the film was broken even if the test time was less than 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.

(Fenton test)
The polymer electrolyte membrane was pretreated in air at 200 ° C. for 2 hours. Next, an aqueous solution containing 2 ppm of iron ions and 1% of hydrogen peroxide was prepared, and the polymer electrolyte membrane after pretreatment was immersed for 1 hour in a place heated to 80 ° C. Then, the fluorine ion contained in the liquid after a test was measured with the ion chromatograph. In addition, it becomes a polymer electrolyte composition which gives a highly durable polymer electrolyte membrane, an electrode catalyst layer, etc., so that there are few fluorine ion amounts (fluorine elution amount).

  The following Examples 1 to 10 and Comparative Examples 1 to 2 are application examples of the polymer electrolyte composition to the polymer electrolyte membrane. Examples 11 to 12 and Comparative Example 3 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 methyl alcohol (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, 0.15 g of phytic acid (manufactured by Kanto Chemical Co., Inc.) was added to 100 g of this solution as the compound (b), and the mixture was adjusted to a / b = 97/3 (mass ratio). Finally, for the purpose of confirming the effect of the compound (b), iron (II) sulfate (manufactured by Kanto Chemical Co., Inc.) is blended so as to be 20 ppm with respect to the perfluorosulfonic acid resin, and includes a polymer electrolyte composition. A polymer electrolyte solution was obtained.

(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 casting 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]
A polymer electrolyte solution and a polymer electrolyte membrane were obtained in the same manner as in Example 1 except that sodium polyphosphate (manufactured by Kanto Chemical Co., Inc.) was used as the compound (b), and (3) a durability test was performed. However, good results were obtained. The results are shown in Table 1.

Example 3
A polymer electrolyte solution and a polymer electrolyte membrane were prepared in the same manner as in Example 1 except that 4-amino-1-hydroxybutane-1,1-diphosphonic acid (manufactured by Kanto Chemical Co., Inc.) was used as the compound (b). As a result, (3) when a durability test was performed, good results were obtained. The results are shown in Table 1.

Example 4
A polymer electrolyte solution and a polymer electrolyte membrane were obtained in the same manner as in Example 1 except that zeolite (manufactured by Wako Pure Chemical Industries, Ltd.) was used as the compound (b), and (3) a durability test was performed. However, good results were obtained. The results are shown in Table 1.

Example 5
A polymer electrolyte solution and a polymer electrolyte membrane were obtained in the same manner as in Example 1 except that a perfluorocarbon carboxylic acid resin (product name Aciplex, manufactured by Asahi Kasei Chemicals Corporation, EW1100) was used as the compound (b). 3) When a durability test was performed, good results were obtained. The results are shown in Table 1.

Example 6
The polymer electrolyte solution and the polymer electrolyte membrane were the same as in Example 1 except that polyphosphoric acid (manufactured by Kanto Chemical Co., Inc.) was used as the compound (b) and polybenzimidazole was blended as the radical scavenger (c). (3) When a durability test was conducted, good results were obtained. The results are shown in Table 1.

Example 7
As compound (b), a perfluorocarbon carboxylic acid resin (product name Aciplex, manufactured by Asahi Kasei Chemicals Co., Ltd., EW1100) was used, and polybenzoimidazole was further added as a radical scavenger (c) in the same manner as in Example 1. When a polymer electrolyte solution and a polymer electrolyte membrane were obtained and (3) a durability test was performed, good results were obtained. The results are shown in Table 1.

Example 8
Example 1 except that 4-amino-1-hydroxybutane-1,1-diphosphonic acid (manufactured by Kanto Chemical Co., Inc.) was used as the compound (b) and polybenzimidazole was added as the radical scavenger (c). In the same manner as above, a polymer electrolyte solution and a polymer electrolyte membrane were obtained, and (3) a durability test was carried out, and good results were obtained. The results are shown in Table 1.

Example 9
(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) Polyphenylene sulfide (manufactured by Sigma-Aldrich Japan) is added to the pellet as a thioether compound (e) and kneaded using a biaxial compounding tester (product name: ULT15TW nano-15MG-NH (-700) manufactured by Technobel). As a result, a pellet having a mass ratio of perfluorosulfonic acid resin precursor / polyphenylene ether of 94/6 was obtained.

The pellet was contacted in an aqueous solution in which potassium hydroxide (15% by mass) and methyl alcohol (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, 0.15 g of 4-amino-1-hydroxybutane-1,1-diphosphonic acid (manufactured by Kanto Chemical Co., Inc.) as a compound (b) was added to 100 g of this solution, and a / b / e = 91/3 / It adjusted so that it might become 6 (mass ratio). Finally, for the purpose of confirming the effect of the compound (b), iron sulfate (II) (manufactured by Kanto Chemical Co., Inc.) was blended at 20 ppm with respect to the perfluorosulfonic acid resin to obtain a polymer electrolyte solution. .

(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 10
Other than using 4-amino-1-hydroxybutane-1,1-diphosphonic acid (manufactured by Kanto Chemical Co., Inc.) as the compound (b) and further adding cerium oxide (manufactured by Kanto Chemical Co., Ltd.) as the metal oxide (d). Obtained a polymer electrolyte solution and a polymer electrolyte membrane in the same manner as in Example 1, and (3) when a durability test was carried out, 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 hydrogen leakage current exceeded 10 mA / cm ² , the film was judged to be broken and the test was terminated. The results are shown in Table 1.

[Comparative Example 2]
A polymer electrolyte solution and a polymer electrolyte membrane were obtained in the same manner as in Example 1 except that 2-aminoethanesulfonic acid (manufactured by Kanto Chemical Co., Inc.) was used instead of compound (b) in Example 1. (3) When the durability test was carried out, the hydrogen leakage current exceeded 10 mA / cm ² in 300 hours. The results are shown in Table 1.

Example 11
(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 methyl alcohol (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, 0.15 g of polyphosphoric acid (manufactured by Kanto Chemical Co., Inc.) as a compound (b) was added to 100 g of this solution to prepare a / b = 97/3 (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 relative to the perfluorosulfonic acid resin, and the solid content is further 20% by mass. Concentration was performed under reduced pressure to obtain a polymer electrolyte solution containing a polymer electrolyte composition.

(Preparation of electrode catalyst ink)
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). . Finally, ethanol is added so that the solid content (the sum of the electrode catalyst, perfluorosulfonic acid polymer and polyphosphoric acid) is 11 wt%, and the mixture is stirred with a homogenizer (manufactured by ASONE) at a rotation speed of 3,000 rpm for 10 minutes. Thus, an electrode catalyst ink was obtained.

(Production of membrane electrode assembly)
Using the obtained electrode ink with an automatic screen printing machine (product name: LS-150, manufactured by Neurong Precision Industry Co., Ltd.), the amount of platinum on both surfaces of the polymer electrolyte membrane (Nafion 211CS (25 μm), manufactured by DuPont) There anode 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.

(Production of fuel cell single cell)
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 12
A fuel cell single cell was obtained in the same manner as in Example 11 except that 4-amino-1-hydroxybutane-1,1-diphosphonic acid (manufactured by Kanto Chemical Co., Inc.) was blended as the compound (b). ) When a durability test was performed, good results were obtained. The results are shown in Table 2.

[Comparative Example 3]
A fuel cell single cell was obtained in the same manner as in Example 11 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 2} was exceeded, it was judged that the membrane was broken and the test was terminated. The results are shown in Table 2.

Example 13
A polymer electrolyte membrane having a thickness of 23 μm was prepared in the same manner as in Example 1 except that 4-amino-1-hydroxybutane-1,1-diphosphonic acid was used as the compound (b). Next, the Fenton test was performed by the above method. The results are shown in Table 1.

Example 14
A polymer electrolyte membrane having a thickness of 23 μm was prepared in the same manner as in Example 1 except that N, N, N ′, N′-ethylenediaminetetrakis (methylenephosphonic acid) was used as the compound (b). Subsequently, when the Fenton test was implemented by the same method as Example 13, it turned out that a fluorine elution amount can be reduced compared with the polymer electrolyte membrane which is not mix | blending the compound (b). The results are shown in Table 1.

Example 15
A polymer electrolyte membrane having a thickness of 23 μm was produced in the same manner as in Example 1 except that diethyl 4-aminobenzylphosphonate was used as the compound (b). Subsequently, when the Fenton test was implemented by the same method as Example 13, it turned out that a fluorine elution amount can be reduced compared with the polymer electrolyte membrane which is not mix | blending the compound (b). The results are shown in Table 1.

[Comparative Example 4]
A polymer electrolyte membrane having a thickness of 23 μm was produced in the same manner as in Example 1 except that the compound (b) was not blended. Subsequently, when the Fenton test was implemented by the same method as Example 13, it turned out that a fluorine elution amount becomes larger than the polymer electrolyte membrane which mix | blended the compound (b). The results are shown in Table 1.

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
パーフルオロカーボンカルボン酸樹脂：テトラフルオロエチレン、ＣＦ₂＝ＣＦ−Ｏ−（ＣＦ₂）₂−ＣＯＯＨの共重合体、ＥＷ１１００
フルオロカーボンスルホン酸樹脂：フッ化ビニリデン、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 copolymer of -SO ₃ H, EW740
Perfluorocarbon carboxylic acid resin: _{tetrafluoroethylene, CF 2 = CF-O- (} CF 2) a copolymer of ₂ -COOH, EW1100
Fluorocarbonsulfonic acid resin: vinylidene fluoride, CF ₂ ═CF—O— (CF ₂ ) ₂ —SO ₃ H copolymer, EW740
PBI: Polybenzimidazole PPS: Polyphenylene sulfide

  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.

That is, the present invention is as follows.
[1]
A polymer electrolyte (a) containing fluorine element in the molecule, and a compound (b) having a metal ion scavenging ability,
The compound (b) is at least one selected from the group consisting of a phosphoric acid compound, a silicic acid compound, and a compound having a carboxyl group,
The content of the compound (b) is 0.001 to 50.000% by mass with respect to 100% by mass in total of the polymer electrolyte (a) and the compound (b).
Polymer electrolyte composition.

[2]
The polymer electrolyte composition according to [1], wherein the compound (b) has a functional group that forms an ionic bond with the polymer electrolyte (a).
[3]
The polymer electrolyte composition according to [2], wherein the functional group that forms an ionic bond with the polymer electrolyte (a) is a functional group having a nitrogen atom.
[4]
The phosphoric acid compound according to any one of [1] to [3], including at least one phosphoric acid compound selected from the group consisting of pyrophosphoric acid, pyrophosphate, phytic acid, and phytate. Polymer electrolyte composition.
[5]
The polymer electrolyte composition according to any one of [1] to [4], wherein the silicate compound includes a silicate.
[6]
The polymer electrolyte composition according to any one of [1] to [5], further comprising a radical scavenger (c).
[7]
The polymer electrolyte composition according to any one of [1] to [6], further containing a metal oxide (d).
[8]
The polymer electrolyte composition according to any one of [1] to [7], further comprising a thioether compound (e).
[9]
A polymer electrolyte membrane comprising the polymer electrolyte composition according to any one of [1] to [8].
[10]
An electrode catalyst layer comprising the polymer electrolyte composition according to any one of [1] to [8].
[11]
A membrane electrode assembly comprising the polymer electrolyte membrane according to [9] and the electrode catalyst layer according to [10].
[12]
[11] A polymer electrolyte fuel cell comprising the membrane electrode assembly according to [11].

Claims (12)

  A polymer electrolyte composition comprising a polymer electrolyte (a) containing a fluorine element in a molecule and a compound (b) having a metal ion scavenging ability.   The polymer electrolyte composition according to claim 1, wherein the compound (b) is at least one selected from the group consisting of a phosphoric acid compound, a silicic acid compound, and a compound having a carboxyl group.   The polymer electrolyte composition according to claim 1 or 2, wherein the compound (b) has a functional group that forms an ionic bond with the polymer electrolyte (a).   The polymer electrolyte composition according to claim 3, wherein the functional group that forms an ionic bond with the polymer electrolyte (a) is a functional group having a nitrogen atom.   3. The polymer electrolyte composition according to claim 2, wherein the phosphate compound includes at least one phosphate compound selected from the group consisting of pyrophosphate, pyrophosphate, phytic acid, and phytate.   The polymer electrolyte composition according to any one of claims 2 to 5, wherein the silicate compound includes a silicate.   The polymer electrolyte composition according to any one of claims 2 to 6, wherein the compound having a carboxyl group includes a perfluorocarbon carboxylic acid compound.   The polymer electrolyte composition according to any one of claims 1 to 7, further comprising a radical scavenger (c).   The polymer electrolyte membrane containing the polymer electrolyte composition of any one of Claims 1-8.   The electrode catalyst layer containing the polymer electrolyte composition of any one of Claims 1-8.   A membrane electrode assembly comprising the polymer electrolyte membrane according to claim 9 and the electrode catalyst layer according to claim 10.   A polymer electrolyte fuel cell comprising the membrane electrode assembly according to claim 11.