JP4955198B2 - Membrane-electrode structure for polymer electrolyte fuel cell - Google Patents

Description

  The present invention relates to a membrane-electrode structure for a polymer electrolyte fuel cell comprising a pair of electrode catalyst layers and a polymer electrolyte membrane sandwiched between both electrode catalyst layers, and more specifically, a sulfone comprising a specific repeating unit. The present invention relates to a membrane-electrode structure for a polymer electrolyte fuel cell comprising an electrode catalyst layer containing polyarylene having an acid group and a polymer electrolyte membrane sandwiched between both electrode catalyst layers.

  The polymer electrolyte fuel cell has a high output density and can be operated at low temperatures, so it can be reduced in size and weight, and has attracted attention as a power source for automobiles, a stationary power source, a power source for portable devices, etc. Development is underway energetically.

  A polymer electrolyte fuel cell has a pair of electrodes on both sides of a proton conductive solid polymer electrolyte membrane, supplies pure hydrogen or reformed hydrogen gas as a fuel gas to one electrode (fuel electrode), and oxygen gas Alternatively, air is supplied as an oxidizing agent to different electrodes (air electrodes) to obtain an electromotive force.

  Conventionally, in a polymer electrolyte fuel cell, a perfluoroalkylenesulfonic acid polymer compound typified by Nafion (trademark) manufactured by DuPont is widely used as an ion conductive polymer binder for an electrode catalyst layer. The perfluoroalkylene sulfonic acid polymer compound has excellent proton conductivity, but is very expensive and contains a large amount of fluorine atoms in the molecule. There is a problem that makes it difficult to recover expensive precious metals.

  In order to solve the above-mentioned problems, the present inventors have intensively studied an inexpensive ion conductive material that replaces a perfluoroalkylene sulfonic acid polymer compound. It was found that it has excellent covering properties and exhibits excellent power generation performance. Furthermore, this sulfonic acid group-containing polyarylene does not contain a halogen atom such as a fluorine atom in the molecular structure, or the content thereof is greatly reduced, and the above-mentioned problems for recovery of the catalyst metal can be solved. Is possible.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a membrane-electrode structure that solves the above-described problems with the recovery of catalytic metals and that provides a polymer electrolyte fuel cell with excellent power generation performance.

According to this invention, the said objective of this invention is achieved by using the polyarylene which has the following sulfonic acid group for the binder of an electrode catalyst layer.
(1) In a membrane-electrode structure for a polymer electrolyte fuel cell comprising a pair of electrode catalyst layers and a polymer electrolyte membrane sandwiched between both electrode catalyst layers,
The electrode catalyst layer comprises at least one monomer represented by the following formulas (A-1) to (A-6) and at least one oligomer represented by the following formulas (B-1) to (B-2). A membrane-electrode structure for a polymer electrolyte fuel cell, comprising a polyarylene having a sulfonic acid group obtained by hydrolyzing a polyarylene having a sulfonic acid ester group produced by copolymerization .

（上記式（Ａ−１)および（Ａ−５）中のn-C₄ H ₉は、ノルマルブチル基を示す。）

(NC ₄ H ₉ in the above formulas (A-1) and (A-5) represents a normal butyl group.)

(In the above formula, n represents an integer of 2 or more.)

( 2) The solid polymer as described in (1) above, wherein the polyarylene having a sulfonic acid group is a polyarylene containing a sulfonic acid group in a range of 0.3 to 5.0 meq / g. Type fuel cell membrane-electrode structure.

  ADVANTAGE OF THE INVENTION According to this invention, the electrode for fuel cells which shows the outstanding electric power generation performance can be provided. Furthermore, the polyarylene having a sulfonic acid group does not contain a halogen atom such as a fluorine atom in the molecular structure, or the content thereof is greatly reduced, and the recovery of the catalyst metal is easy.

Hereinafter, the membrane-electrode structure for a polymer electrolyte fuel cell according to the present invention will be described in detail.
First, the polyarylene having a sulfonic acid group used in the membrane-electrode structure of the polymer electrolyte fuel cell according to the present invention will be specifically described.
(Polyarylene having a sulfonic acid group)
The polyarylene having a sulfonic acid group used in the membrane-electrode structure includes a repeating structural unit represented by the following general formula (A) and a repeating structural unit represented by the following general formula (B). Yes.

In formula (A), Y represents a single bond, an electron-withdrawing group or an electron-donating group. Specifically, —CO—, —SO ₂ —, —SO—, —CONH—, —COO—, — ( CF ₂ ) _p — (where p is an integer of 1 to 10), electron withdrawing groups such as —C (CF ₃ ) ₂ —, — (CH ₂ ) —, —C
Examples thereof include electron donating groups such as (CH ₃ ) ₂ —, —O—, and —S—.

The electron-withdrawing group refers to a group having a value of 0.06 or more when the Hammett substituent constant is m-position of the phenyl group and 0.01 or more when p-position.
In the formula (A), Ar represents a mononuclear or polynuclear aromatic group, and specific examples include a phenyl group, a naphthyl group, an anthracenyl group, and a phenanthyl group.

m represents an integer of 0 to 10, preferably 0 to 8, and more preferably 0 to 5. When m is 1 to 10, Ys may be the same as or different from each other.
In the formula (A), k represents an integer of 0 to 5, l represents an integer of 0 to 4, and k + l ≧ 1.

In the formula (B), R ^{1 to} R ⁸ may be the same or different from each other, and are at least one selected from the group consisting of a hydrogen atom, a fluorine atom, an alkyl group, a fluorine-substituted alkyl group, an allyl group, and an aryl group. An atom or group of

Examples of the alkyl group include a methyl group, an ethyl group, a propyl group, a butyl group, an amyl group, and a hexyl group, and a methyl group and an ethyl group are preferable.
Examples of the fluorine-substituted alkyl group include trifluoromethyl group, perfluoroethyl group, perfluoropropyl group, perfluorobutyl group, perfluoropentyl group, perfluorohexyl group, trifluoromethyl group, pentafluoroethyl group, and the like. Etc. are preferable.

Examples of allyl groups include propenyl groups,
Examples of the aryl group include a phenyl group and a pentafluorophenyl group.
W represents a single bond or a divalent electron withdrawing group, T represents a single bond, a divalent electron withdrawing group, a divalent electron donating group, represented by the following general formula (C-1) or (C-2) And at least one bond or group selected from the divalent groups represented.
Examples of the divalent electron withdrawing group include the same groups as the electron withdrawing group and the electron donating group represented by Y described above.

In the formulas (C-1) and (C-2), R ^{9 to} R ²⁰ may be the same as or different from each other, and are composed of a hydrogen atom, a fluorine atom, an alkyl group, a fluorine-substituted alkyl group, an allyl group, and an aryl group. Represents an atom or group selected from the group, specifically, R ¹ to R in formula (B)
The same atom or group as R < ⁸ > is mentioned.

  In formulas (C-1) and (C-2), Q represents a single bond or a divalent electron donating group, and examples of the divalent electron donating group include -O-, -S-, -CH =. CH—, —C≡C— and the like can be mentioned.

In the formula (C-2), J represents a single bond, an alkylene group, a fluorine-substituted alkylene group, an aryl-substituted alkylene group, an alkenylene group, an alkynylene group, an arylene group, a fluorenylidene group, -O-, -S-, -CO-, -CONH -, - COO -, - SO- and -SO ₂
One type of bond, atom or group selected from the group consisting of-is shown.

Specific examples of the alkylene group, fluorine-substituted alkylene group, aryl-substituted alkylene group, alkenylene group, alkynylene group, arylene group, and fluorenylidene group include, for example, —C (CH ₃ ) ₂ —, —CH═CH—, —CH═. CH—CH ₂ —, —C≡C—, — (CF ₂ ) _p —
(Here, p is an integer of 1 to _{10), - C (CF 3)} 2 -, the following formula

Group represented by these.
In the formula (B), n is an integer of 2 or more, and the upper limit is usually 100, preferably 10-80. When n is less than 2, durability during power generation as an electrolyte in the electrode may not be obtained, and n is preferably 10 or more in order to maintain durability with no practical problem. On the other hand, when n exceeds 100, the viscosity of the resulting sulfonated polyarylene copolymer may be too high, and the function as a binder for electrodes may not be sufficiently exhibited.

  The polyarylene having a sulfonic acid group used in the present invention has a repeating structural unit represented by the formula (A) in a proportion of 0.05 to 99.95 mol%, preferably 10 to 99.5 mol%. The repeating structural unit represented by (B) is contained in a proportion of 99.95 to 0.05 mol%, preferably 90 to 0.5 mol%.

(Method for producing polyarylene having a sulfonic acid group)
The polyarylene having a sulfonic acid group includes a monomer having a sulfonic acid ester group that can be a structural unit represented by the general formula (A) and an oligomer that can be a structural unit represented by the general formula (B). It can be synthesized by polymerizing to produce a polyarylene having a sulfonic acid ester group, hydrolyzing the polyarylene having a sulfonic acid ester group, and converting the sulfonic acid ester group into a sulfonic acid group.

  The polymer having a sulfonic acid group includes a structural unit having a skeleton represented by the general formula (A) and having no sulfonic acid group or sulfonic acid ester group, and a structural unit of the general formula (B). It can also be synthesized by previously synthesizing polyarylene having sulphonate and sulfonating the polymer.

  A monomer that can be a structural unit of the general formula (A) (for example, a monomer represented by the following general formula (D), also referred to as monomer (D)) and an oligomer that can be a structural unit of the general formula (B) (for example, In the case of synthesizing a polyarylene having a sulfonate group by copolymerizing with an oligomer represented by the following general formula (E) or oligomer (E), examples of the monomer (D) include: A sulfonic acid ester represented by the formula (D) is used.

In the formula (D), X represents a halogen atom other than fluorine (chlorine, bromine, iodine), —OSO ₂ Z (
Here, Z represents an alkyl group, a fluorine-substituted alkyl group or an aryl group. An atom or group selected from
In the formula (D), Y, Ar, m, k and l are respectively synonymous with Y, Ar, m, k and l in the general formula (A). When m is 1 to 10, Y is They may be the same as or different from each other, and k + l ≧ 1.

In the formula (D), R represents a hydrocarbon group having 4 to 20 carbon atoms, specifically, tert-butyl group, iso-butyl group, n-butyl group, sec-butyl group, neopentyl group, cyclopentyl. Group, hexyl group, cyclohexyl group, cyclopentylmethyl group, cyclohexylmethyl group, adamantyl group, adamantanemethyl group, 2-ethylhexyl group, bicyclo [2.2.1] heptyl group, bicyclo [2.2.1] heptylmethyl A linear hydrocarbon group such as a group, a branched hydrocarbon group, an alicyclic hydrocarbon group, or the like is used. Of these ester groups, bulky substituents such as branched and alicyclic structures derived from primary alcohols are preferred from the viewpoint of stability during the polymerization process.

  Specific examples of the sulfonic acid ester represented by the formula (D) include the following compounds.

  Specific examples of the compound having the same skeleton as the monomer (D) represented by the general formula (D) and having no sulfonic acid group or sulfonic acid ester group include the following compounds.

  As the oligomer (E), for example, a compound represented by the following general formula (E) is used.

In the formula (E), R ′ and R ″ may be the same as or different from each other, and a halogen atom or —OSO ₂ Z excluding a fluorine atom (where Z is an alkyl group, a fluorine-substituted alkyl group or an aryl group) The group represented by this is shown. Examples of the alkyl group represented by Z include a methyl group and an ethyl group, examples of the fluorine-substituted alkyl group include a trifluoromethyl group, and examples of the aryl group include a phenyl group and a p-tolyl group.

In formula (E), R ^{1 to} R ⁸ may be the same as or different from each other, and represent the same atom or group as R ^{1 to} R ⁸ in formula (B), and n is an integer of 2 or more. The upper limit is usually 100, preferably 10-80.

  Examples of such a compound represented by the formula (E) include a compound represented by the following formula.

The oligomer (E) as described above can be synthesized, for example, by the method shown below.
First, in order to convert bisphenol to the corresponding alkali metal salt of bisphenol, lithium is used in a polar solvent having a high dielectric constant, such as N-methyl-2-pyrrolidone, N, N-dimethylacetamide, sulfolane, diphenylsulfone, and dimethylsulfoxide. Add alkali metals such as sodium and potassium, alkali metal hydrides, alkali metal hydroxides, alkali metal carbonates and the like. Specific examples of bisphenol include 2,2-bis (4-hydroxyphenyl) -1,1,1,3,3,3-hexafluoropropane, 2,2-bis (4-hydroxyphenyl) ketone, 2, 2-bis (4-hydroxyphenyl) sulfone, 9,9-bis (4-hydroxyphenyl) fluorene, 9,9-bis (4-hydroxy-3-phenylphenyl) fluorene, 9,9-bis (4-hydroxy) -3,5-diphenylphenyl) fluorene, 4,4'-bis (4-hydroxyphenyl) diphenylmethane, 4,4'-bis (4-hydroxy-3-phenylphenyl) diphenylmethane, 4,4'-bis (4 -Hydroxy-3,5-diphenylphenyl) diphenylmethane, 2-phenylhydroquinone and the like.

Usually, the alkali metal is reacted in excess with respect to the hydroxyl group of phenol, and usually 1.1 to 2 times equivalent is used. Preferably, 1.2 to 1.5 times equivalent is used. In this case, fluorine, chlorine, etc. activated with an electron-withdrawing group in the presence of water and an azeotropic solvent such as benzene, toluene, xylene, hexane, cyclohexane, octane, chlorobenzene, dioxane, tetrahydrofuran, anisole, and phenetole Aromatic halogen-substituted aromatic dihalide compounds such as 4,4′-difluorobenzophenone, 4,4′-dichlorobenzophenone, 4,4′-chlorofluorobenzophenone, bis (4-chlorophenyl) sulfone, bis (4 -Fluorophenyl) sulfone, 4-fluorophenyl-4'-chlorophenylsulfone, bis (3-nitro-4-chlorophenyl) sulfone, 2,6-dichlorobenzonitrile, 2,6-difluorobenzonitrile, hexafluorobenzene, deca Fluorobiphenyl, , 5-difluorobenzophenone, 1,3-bis (4-chlorobenzoyl) reacting benzene. In terms of reactivity, a fluorine compound is preferable, but in consideration of the following aromatic coupling reaction, it is necessary to assemble an aromatic nucleophilic substitution reaction so that the terminal is a chlorine atom. For example, an active aromatic halogen compound such as 4,4′-dichlorobenzophenone or bis (4-chlorophenyl) sulfone, or a substitution reaction using 4,4′-difluorobenzophenone and 4,4′-chlorofluorobenzophenone in combination. The desired compound is obtained.

The amount of the active aromatic dihalide used can be changed according to the molecular weight of the target oligomer.
Prior to the aromatic nucleophilic substitution reaction, an alkali metal salt of bisphenol may be used. The reaction temperature is 60 ° C to 300 ° C, preferably 80 ° C to 250 ° C. The reaction time ranges from 15 minutes to 100 hours, preferably from 1 hour to 24 hours.

  The polyarylene having a sulfonate group is synthesized by reacting the monomer (D) and the oligomer (E) in the presence of a catalyst. The catalyst used in this case is a catalyst system containing a transition metal compound. The catalyst system includes (1) a transition metal salt and a compound to be a ligand (hereinafter referred to as “ligand component”), or a transition metal complex in which a ligand is coordinated (including a copper salt). ), And (2) a reducing agent as an essential component, and in order to further increase the polymerization rate, a “salt” may be added.

  Here, as the transition metal salt, nickel compounds such as nickel chloride, nickel bromide, nickel iodide, nickel acetylacetonate; palladium compounds such as palladium chloride, palladium bromide, palladium iodide; iron chloride, iron bromide And iron compounds such as iron iodide; cobalt compounds such as cobalt chloride, cobalt bromide, and cobalt iodide. Of these, nickel chloride, nickel bromide and the like are particularly preferable.

As the ligand component, triphenylphosphine, 2,2′-bipyridine, 1,5-
Examples include cyclooctadiene and 1,3-bis (diphenylphosphino) propane. Of these, triphenylphosphine and 2,2′-bipyridine are preferred. The compound which is the said ligand component can be used individually by 1 type or in combination of 2 or more types.

Furthermore, as the transition metal complex in which the ligand is coordinated, for example, nickel chloride bis (triphenylphosphine), nickel bromide bis (triphenylphosphine), nickel iodide bis (triphenylphosphine), nickel nitrate bis (Triphenylphosphine), nickel chloride (2,2'-bipyridine), nickel bromide (2,2'-bipyridine), nickel iodide (2,2'-bipyridine), nickel nitrate (2,2'-bipyridine) ), Bis (1,5-cyclooctadiene) nickel, tetrakis (triphenylphosphine) nickel, tetrakis (triphenylphosphite) nickel, tetrakis (triphenylphosphine) palladium and the like. Of these, nickel chloride bis (triphenylphosphine) and nickel chloride (2,2′-bipyridine) are preferred.

  Examples of the reducing agent that can be used in the catalyst system include iron, zinc, manganese, aluminum, magnesium, sodium, calcium, and the like. Of these, zinc, magnesium and manganese are preferred. These reducing agents can be used after being more activated by bringing them into contact with an acid such as an organic acid.

  Examples of the “salt” that can be used in the above catalyst system include sodium compounds such as sodium fluoride, sodium chloride, sodium bromide, sodium iodide, sodium sulfate, potassium fluoride, potassium chloride, potassium bromide, Examples include potassium compounds such as potassium iodide and potassium sulfate; ammonium compounds such as tetraethylammonium fluoride, tetraethylammonium chloride, tetraethylammonium bromide, tetraethylammonium iodide, and tetraethylammonium sulfate. Of these, sodium bromide, sodium iodide, potassium bromide, tetraethylammonium bromide, and tetraethylammonium iodide are preferred.

  The proportion of each component used is usually 0.0001 to 10 moles, preferably 0.001 moles per mole of transition metal salt or transition metal complex ((D) + (E), hereinafter the same). 01-0.5 mol. When the amount is less than 0.0001 mol, the polymerization reaction may not proceed sufficiently. On the other hand, when the amount exceeds 10 mol, the molecular weight may decrease.

  When a transition metal salt and a ligand component are used in the catalyst system, the ratio of the ligand component used is usually 0.1 to 100 mol, preferably 1 to 10 mol, per 1 mol of the transition metal salt. is there. When the amount is less than 0.1 mol, the catalytic activity may be insufficient. On the other hand, when the amount exceeds 100 mol, the molecular weight may decrease.

  Moreover, the usage-amount of a reducing agent is 0.1-100 mol normally with respect to the total of 1 mol of the said monomer, Preferably it is 1-10 mol. If the amount is less than 0.1 mol, polymerization may not proceed sufficiently. If the amount exceeds 100 mol, purification of the resulting polymer may be difficult.

  Furthermore, when using "salt", the usage-ratio is 0.001-100 mol normally with respect to the total of 1 mol of the said monomer, Preferably it is 0.01-1 mol. If it is less than 0.001 mol, the effect of increasing the polymerization rate may be insufficient, and if it exceeds 100 mol, purification of the resulting polymer may be difficult.

Examples of the polymerization solvent that can be used when the monomer (D) and the oligomer (E) are reacted include tetrahydrofuran, cyclohexanone, dimethyl sulfoxide, N,
N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone, γ-butyrolactone, N, N′-dimethylimidazolidinone and the like can be mentioned. Of these, tetrahydrofuran, N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone, and N, N′-dimethylimidazolidinone are preferable. These polymerization solvents are preferably used after sufficiently dried.

The total concentration of the monomers in the polymerization solvent is usually 1 to 90% by weight, preferably 5 to 40% by weight.
Moreover, the superposition | polymerization temperature at the time of superposing | polymerizing is 0-200 degreeC normally, Preferably it is 50-120 degreeC. The polymerization time is usually 0.5 to 100 hours, preferably 1 to 40 hours.

  The polyarylene having a sulfonic acid ester group obtained using the monomer (D) can be converted into a polyarylene having a sulfonic acid group by hydrolyzing the sulfonic acid ester group and converting it to a sulfonic acid group. .

Hydrolysis is
(1) A method in which polyarylene having the sulfonic acid ester group is added to an excess amount of water or alcohol containing a small amount of hydrochloric acid and stirred for 5 minutes or longer. (2) The sulfonic acid ester group is contained in trifluoroacetic acid. Method of reacting polyarylene for about 5 to 10 hours at a temperature of about 80 to 120 ° C. (3) 1 to 3 mol per mol of sulfonic acid ester group (—SO ₃ R) in polyarylene having a sulfonic acid ester group Examples include a method of reacting the polyarylene in a solution containing double moles of lithium bromide, such as N-methylpyrrolidone, at a temperature of about 80 to 150 ° C. for about 3 to 10 hours, and then adding hydrochloric acid. Can do.

  The polyarylene having a sulfonic acid group is synthesized in advance using a monomer having a skeleton similar to the monomer (D) represented by the general formula (D) and having no sulfonic acid ester group. It can also be synthesized by sulfonating polyarylene. In this case, after producing a polyarylene by copolymerizing a monomer having no sulfonic acid group and an oligomer (E) by a method according to the above synthesis method, a polyarylene having no sulfonic acid group is prepared using a sulfonating agent. A polyarylene having a sulfonic acid group can be obtained by introducing a sulfonic acid group into.

  The sulfonation reaction conditions can be obtained by introducing a sulfonic acid group into a polyarylene having no sulfonic acid group by a conventional method using a sulfonating agent in the absence of a solvent or in the presence of a solvent. .

  As a method for introducing a sulfonic acid group, for example, the polyarylene having no sulfonic acid group is known by using a known sulfonating agent such as sulfuric anhydride, fuming sulfuric acid, chlorosulfonic acid, sulfuric acid, sodium hydrogen sulfite and the like. [Polymer Preprints, Japan, Vol. 42, No. 3, p. 730 (1993); Polymer Preprints, Japan, Vol. 43, No. 3, p. 736 (1994); Polymer Preprints, Japan, Vol. 42, No. 7, p. 2490-2492 (1993)].

  That is, as the reaction conditions for the sulfonation, the polyarylene having no sulfonic acid group is reacted with the sulfonating agent in the absence of a solvent or in the presence of a solvent. Examples of the solvent include hydrocarbon solvents such as n-hexane, ether solvents such as tetrahydrofuran and dioxane, aprotic polar solvents such as dimethylacetamide, dimethylformamide, and dimethylsulfoxide, tetrachloroethane, dichloroethane, chloroform, and chloride. And halogenated hydrocarbons such as methylene. The reaction temperature is not particularly limited, but is usually −50 to 200 ° C., preferably −10 to 100 ° C. Moreover, reaction time is 0.5 to 1,000 hours normally, Preferably it is 1 to 200 hours.

  In the polyarylene having a sulfonic acid group produced by the method as described above, the amount of the sulfonic acid group is usually 0.3 to 5 meq / g, preferably 0.5 to 3 meq / g, more preferably 0.8 to 2.8 meq / g. If it is less than 0.3 meq / g, the proton conductivity is low and not practical. On the other hand, if it exceeds 5 meq / g, the water resistance may be significantly lowered, which is not preferable.

The amount of the sulfonic acid group can be adjusted, for example, by changing the type, usage ratio, and combination of the monomer (D) and the oligomer (E).
The molecular weight of the polyarylene having a sulfonic acid group thus obtained is 10,000 to 1,000,000, preferably 20,000 to 800,000 in terms of polystyrene-equivalent weight average molecular weight by gel permeation chromatography (GPC).

  The polyarylene having a sulfonic acid group may contain an anti-aging agent, preferably a hindered phenol compound having a molecular weight of 500 or more, and the anti-aging agent can be used as an electrode electrolyte. Can be further improved.

As a hindered phenol compound having a molecular weight of 500 or more that can be used in the present invention, triethylene glycol-bis [3- (3-t-butyl-5-methyl-4-hydroxyphenyl) proonate] (trade name: IRGANOX 245) 1,6-hexanediol-bis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate] (trade name: IRGANOX 259), 2,4-bis- (n- Octylthio) -6- (4-hydroxy-3,
5-Di-t-butylanilino) -3,5-triazine (trade name: IRGANOX 565), pentaerythrityl-tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate] (product) Name: IRGANOX 1010), 2,2-thio-diethylenebis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate] (trade name: IRGANOX 1035), octadecyl-3- (3, 5-Di-t-butyl-4-hydroxyphenyl) propionate) (trade name: IRGANOX 1076), N, N-hexamethylenebis (3,5-di-t-butyl-4-hydroxy-hydrocinnamamide) (Product name: IRGAONOX 1098) 1,3,5-trimethyl-
2,4,6-tris (3,5-di-t-butyl-4-hydroxybenzyl) benzene (trade name: IRGANOX 1330), tris- (3,5-di-t-butyl-4-hydroxybenzyl) -Isocyanurate (trade name: IRGANOX 3114), 3,9-bis [2- [3- (3-t-butyl-4-hydroxy-5-methylphenyl) propionyloxy] -1,1-dimethylethyl] -2,4,8,10-tetraoxaspiro [5.5] undecane (trade name: Sumilizer GA-80).

  In the present invention, the hindered phenol compound having a molecular weight of 500 or more with respect to 100 parts by weight of the polyarylene having a sulfonic acid group is preferably used in an amount of 0.01 to 10 parts by weight.

  Next, a polymer electrolyte fuel cell according to the present invention will be described with reference to the accompanying drawings. FIG. 1 is an explanatory cross-sectional view showing a configuration example of a membrane-electrode structure used in a polymer electrolyte fuel cell.

  The polymer electrolyte fuel cell includes, for example, a membrane-electrode structure having the configuration shown in FIG. The membrane-electrode structure has a polymer electrolyte membrane 3 between an oxygen electrode 1 and a fuel electrode 2, and the oxygen electrode 1 and the fuel electrode 2 are both a diffusion layer 4 and a diffusion layer 4. The electrode catalyst layer 5 is formed on the electrode catalyst layer 5 and is in contact with the polymer electrolyte membrane 3 on the electrode catalyst layer 5 side. The electrode catalyst layer 5 includes the above-described polyarylene having a sulfonic acid group. The diffusion layer 4 includes a carbon paper 6 and a base layer 7.

  In the membrane-electrode structure, the underlayer 7 is made of, for example, carbon paper 6 and a slurry in which carbon black mixed with a predetermined weight ratio and polytetrafluoroethylene (PTFE) are uniformly dispersed in an organic solvent such as ethylene glycol. It is formed by coating on one side and drying. The carbon paper 6 includes an oxygen passage 1a through which an oxygen-containing gas such as air flows in the oxygen electrode 1 and a fuel passage 2a through which a fuel gas such as hydrogen flows in the fuel electrode 2 on the base layer 7 side. ing. The electrode catalyst layer 5 is formed, for example, by applying and drying a catalyst paste obtained by uniformly mixing a catalyst-carrying carbon black carrying a hydrogen reduction catalyst with an ion conductive binder on the underlayer 7.

Then, the membrane-electrode structure is formed by hot pressing the polymer electrolyte membrane 3 with the electrode catalyst layer 5 of the oxygen electrode 1 and the fuel electrode 2 sandwiched therebetween.
As the polymer electrolyte membrane 3 used in the present invention, a membrane formed from a polyarylene having a sulfonic acid group used for the electrode catalyst layer binder of the present invention can be used, or a perfluoroalkylene sulfonic acid type can be used. It is formed from polymer compounds and sulfonic acid group-containing polymer compounds in which sulfonic acid groups are introduced into engineering plastics such as polyether ether ketone, polyether ketone, polysulfone, polyether sulfone, polyether, polyimide, polyazole, and polyphenylene sulfide. A membrane can be used. Moreover, what impregnated these sulfonic acid group containing high molecular compounds to the porous base material can also be used.

  Here, as the hydrogen reduction catalyst used in the catalyst-supporting carbon black used in the catalyst paste, a noble metal catalyst such as platinum, palladium, gold, ruthenium, iridium is preferably used. Two or more elements such as alloys and mixtures of these noble metal catalysts may be contained.

  Further, as the carbon black for supporting the hydrogen reduction catalyst, carbon black such as oil furnace black, channel black, lamp black, thermal black, acetylene black is preferable from the viewpoint of electronic conductivity and the specific surface area.

Oil furnace black includes Vulcan XC-72, Vulcan P, Black Pearls 880, Black Pearls 1100, Black Pearls 1300, Black Pearls 2000, Legal 400, Lion Ketjen Black EC, Mitsubishi Chemical # 3150 , # 3250, and the like, and examples of acetylene black include those marketed under trademarks such as Denka Black manufactured by Denki Kagaku Kogyo.

  Further, as the carbon black used in the present invention, artificial graphite or carbon obtained from organic compounds such as natural graphite, pitch, coke, polyacrylonitrile, phenol resin, furan resin and the like can also be used. As the form of these carbon materials, not only particles but also fibers can be used.

The present invention is characterized in that the polyarylene having a sulfonic acid group is used as the ion conductive polymer in the catalyst paste.
The catalyst paste can be produced by mixing catalyst-supported carbon black and polyarylene having a sulfonic acid group with a solvent.

Here, as the solvent, an organic solvent such as an aprotic dipole solvent or a mixture of an organic solvent and water can be used.
In the catalyst paste, the catalyst-supported carbon black / polyarylene having a sulfonic acid group (weight ratio) is 40/60 to 95/5, and preferably 55/45 to 85/15.

  The concentration of the solid content of the catalyst-supporting carbon black and the polyarylene having a sulfonic acid group in the catalyst paste is usually 2 to 40% by weight, preferably 5 to 30% by weight.

  There are brush coating, brush coating, bar coater coating, knife coater coating, screen printing, spray coating, and other methods for applying the catalyst paste to the base layer and other substrates. On other substrates (transfer substrates) The electrode catalyst layer may be formed once by coating on the electrode, and then transferred to the electrode substrate or the proton conducting membrane. As the transfer substrate in this case, a polytetrafluoroethylene (PTFE) sheet, a glass plate or a metal plate whose surface is treated with a release agent can be used.

  As the electrode base material constituting the oxygen electrode and the fuel electrode in the present invention, materials generally used for fuel cells are used without particular limitation. For example, a porous conductive sheet whose main constituent material is a conductive material, and the conductive material includes a fired body from polyacrylonitrile, a fired body from pitch, a carbon material such as graphite and expanded graphite, stainless steel, etc. Examples include steel, molybdenum, and titanium.

  The form of the conductive material is not particularly limited, such as fibrous or particulate, but a fibrous conductive inorganic material (inorganic conductive fiber), particularly carbon fiber is preferable. As the porous conductive sheet using inorganic conductive fibers, either a woven fabric or a non-woven fabric structure can be used. As the woven fabric, a plain weave, a twill weave, a satin weave, a crest weave, a binding weave and the like are used without particular limitation. Moreover, as a nonwoven fabric, it does not specifically limit, such as a papermaking method, a needle punch method, a spun bond method, a water jet punch method, a melt blow method.

It may be a knitted fabric. In these fabrics, particularly when carbon fibers are used, a plain fabric using flame-resistant spun yarn is carbonized or graphitized, and the flame-resistant yarn is processed by nonwoven fabric by the needle punch method or water jet punch method. Carbonized or graphitized nonwoven fabrics, flameproofed yarns, mat nonwoven fabrics made by paper making using carbonized yarns or graphitized yarns, and the like are preferably used. For example, Toray carbon paper TGP series, SO series, E-TEK carbon cloth, etc. are preferably used. The porous conductive sheet in the present invention is not particularly limited, but it is also a preferred embodiment to add conductive particles such as carbon black or conductive fibers such as carbon fiber as an auxiliary agent for improving conductivity. .
[Example]
EXAMPLES Hereinafter, although this invention is demonstrated further more concretely based on an Example, this invention is not limited to these Examples.

In the examples, the sulfonic acid equivalent, molecular weight, and proton conductivity were determined as follows.
1. Sulfonic acid equivalent The polymer having the sulfonic acid group was washed with water until the water was neutral, thoroughly washed with water except for free remaining acid, dried, weighed a predetermined amount, THF / Phenolphthalein dissolved in a mixed solvent of water was used as an indicator, titration was performed using a standard solution of NaOH, and the sulfonic acid equivalent was determined from the neutralization point.
2. Measurement of molecular weight The polyarylene weight average molecular weight having no sulfonic acid group was determined by GPC using tetrahydrofuran (THF) as a solvent, and the molecular weight in terms of polystyrene was obtained. The molecular weight of the polyarylene having a sulfonic acid group was determined by GPC using N-methyl-2-pyrrolidone (NMP) to which lithium bromide and phosphoric acid were added as a solvent as an eluent.
3. Measurement of proton conductivity AC resistance was measured by pressing a platinum wire (f = 0.5 mm) against the surface of a 5 mm wide strip-shaped proton conducting membrane sample, holding the sample in a constant temperature and humidity device, and between the platinum wires It was obtained from AC impedance measurement. That is, the impedance at an alternating current of 10 kHz was measured in an environment of 25 ° C., 60 ° C., and a relative humidity of 80%. A chemical impedance measurement system manufactured by NF Circuit Design Block Co., Ltd. was used as the resistance measurement device, and JW241 manufactured by Yamato Scientific Co., Ltd. was used as the constant temperature and humidity device. Five platinum wires were pressed at intervals of 5 mm, the distance between the wires was changed to 5 to 20 mm, and the AC resistance was measured. The specific resistance of the membrane was calculated from the distance between the lines and the resistance gradient, the alternating current impedance was calculated from the reciprocal of the specific resistance, and the proton conductivity was calculated from this impedance.

Specific resistance R (Ω · cm) = 0.5 (cm) × film thickness (cm) × resistance-to-resistance gradient (Ω / cm)
[Synthesis Example 1]
(Preparation of oligomer)
2,2-bis (4-hydroxyphenyl) -1,1,1,3 was added to a 1 L three-necked flask equipped with a stirrer, thermometer, cooling tube, Dean-Stark tube, and three-way cock for introducing nitrogen. , 3,3-hexafluoropropane (bisphenol AF) 67.3 g (0.20 mol), 4,4′-dichlorobenzophenone (4,4′-DCBP) 60.3 g (0.24 mol), potassium carbonate 71 .9 g (0.52 mol), N, N-dimethylacetamide (DMAc) 300 mL, and toluene 150 mL were taken and heated in an oil bath under a nitrogen atmosphere and reacted at 130 ° C. with stirring. When water produced by the reaction was azeotroped with toluene and reacted while being removed from the system with a Dean-Stark tube, almost no water was produced in about 3 hours. The reaction temperature was gradually increased from 130 ° C to 150 ° C. Thereafter, most of the toluene was removed while gradually raising the reaction temperature to 150 ° C., and the reaction was continued at 150 ° C. for 10 hours. Then, 10.0 g (0.040 mol) of 4,4′-DCBP was added, and another 5 Reacted for hours. The resulting reaction solution was allowed to cool, and then the by-product inorganic compound precipitate was removed by filtration, and the filtrate was put into 4 L of methanol. The precipitated product was separated by filtration, collected, dried, and dissolved in 300 mL of tetrahydrofuran. This was reprecipitated in 4 L of methanol to obtain 95 g (yield 85%) of the target compound.

The weight average molecular weight in terms of polystyrene determined by GPC (THF solvent) of the obtained polymer was 11,200. Further, the obtained polymer was soluble in THF, NMP, DMAc, sulfolane and the like, Tg was 110 ° C., and thermal decomposition temperature was 498 ° C.

  The obtained compound was an oligomer represented by the formula (I) (hereinafter referred to as “BCPAF oligomer”).

[Synthesis Example 2]
Preparation of polyarylene copolymer with neopentyl group as protecting group (PolyAB-SO ₃ neo-Pe) 500 mL three-neck equipped with stirrer, thermometer, cooling pipe, Dean-Stark pipe, and nitrogen-introduced three-way cock In a flask, 39.58 g (98.64 mmol) of 4- [4- (2,5-dichlorobenzoyl) phenoxy] benzenesulfonic acid neo-pentyl (A-SO ₃ neo-Pe) and a BCPAF oligomer (Mn = 11200) 15.23 g (0.136 mmol), Ni (PPh ₃ ) ₂ Cl ₂ 1.67 g (0.26 mmol), PPh ₃ 10.49 g (4.00 mmol), NaI 0.45 g (0.30 mmol) ), Zinc powder 15.69 g (24.0 mmol) and dry NMP 129 mL were added under nitrogen. The reaction system is heated with stirring (
The reaction was finally heated to 75 ° C.) and allowed to react for 3 hours. The polymerization reaction liquid was diluted with 250 mL of THF, stirred for 30 minutes, Celite was used as a filter aid, the filter paper and the filtrate were poured into 1500 mL of a large excess of methanol, and solidified. The coagulum was collected by filtration, air-dried, redissolved in THF / NMP (200/300 mL each), and coagulated with 1500 mL of a large excess of methanol. After air drying, 47.0 g (yield 92%) of a copolymer (PolyAB-SO ₃ neo-Pe) composed of a sulfonic acid derivative protected with a target yellow fibrous neopentyl group was obtained by heat drying. The molecular weight by GPC was Mn = 47,600 and Mw = 159,000.

Thus obtained 5.1 g of PolyAB-SO ₃ neo-Pe was dissolved in 60 mL of NMP and heated to 90 ° C. A mixture of 50 mL of methanol and 8 mL of concentrated hydrochloric acid was added to the reaction system at one time. While in suspension, the reaction was allowed to proceed for 10 hours under mild reflux conditions. A distillation apparatus was installed, and excess methanol was distilled off to obtain a light green transparent solution. This solution was poured into a large amount of water / methanol (1: 1 weight ratio) to solidify the polymer, and then the polymer was washed with ion exchange water until the pH of the washing water was 6 or more. From the IR spectrum of the polymer thus obtained and the quantitative analysis of the ion exchange capacity, it was found that the sulfonate group (—SO ₃ R) was quantitatively converted to the sulfonate group (—SO ₃ H).
The obtained polyarylene copolymer having a sulfonic acid group had molecular weights by GPC of Mn = 53,200 and Mw = 185,000, and the sulfonic acid equivalent was 2.2 meq / g.

[Synthesis Example 3]
(Synthesis of polyarylene copolymer)
28.1 g (2.5 mmol) of the oligomer of formula (I) obtained in Synthesis Example 1 above, 2,5-dichloro-4 ′-(4-phenoxy) phenoxybenzophenone (DCPPB) 35.
9 g (82.5 mmol), bis (triphenylphosphine) nickel dichloride
67 g (2.6 mmol), sodium iodide 1.66 g (11.1 mmol), triphenylphosphine 8.92 g (34.0 mmol), zinc dust 13.3 g (204 mm)
ol) in a flask and purged with dry nitrogen. 160 ml of N-methyl-2-pyrrolidone was added, and the mixture was heated to 80 ° C. and stirred for 4 hours to carry out polymerization. The polymerization solution is diluted with THF, coagulated and recovered with hydrochloric acid / methanol, repeatedly washed with methanol, dissolved in THF, purified by reprecipitation into methanol, and the collected polymer is vacuum-dried to obtain 51.0 g of the desired copolymer. (90%) was obtained. The number-average molecular weight in terms of polystyrene determined by GPC (THF) is 38,900,
The weight average molecular weight was 160,000.

(Synthesis of polyarylene having a sulfonic acid group)
50 g of the copolymer was placed in a 1000 ml separable flask equipped with a stirrer and a thermometer, 500 ml of sulfuric acid having a concentration of 98% was added, and the mixture was stirred for 24 hours under a nitrogen stream while maintaining the internal temperature at 25 ° C. The obtained solution was poured into a large amount of ion exchange water to precipitate a polymer. The washing of the polymer was repeated until the washing water had a pH of 5. By drying, 56 g (95%) of a sulfonic acid group-containing polymer was obtained. The number average molecular weight in terms of polystyrene determined by GPC (NMP) of the sulfonic acid group-containing polymer was 45,500, and the weight average molecular weight was 176,000. The sulfonic acid equivalent of this sulfonic acid group-containing polymer was 2.1 meq / g.

First, polyarylene having a sulfonic acid group synthesized in Synthesis Example 2 was dissolved in N-methyl-2-pyrrolidone, and a polymer electrolyte membrane having a dry film thickness of 40 μm was prepared by a casting method.
Next, carbon black and polytetrafluoroethylene (PTFE) are mixed at a weight ratio of carbon black: PTFE = 2: 3 to prepare a slurry uniformly dispersed in ethylene glycol, and the slurry is applied to one side of the carbon paper. The base layer was formed by coating and drying, and a diffusion layer composed of carbon paper and the base layer was formed. One diffusion layer was prepared on the oxygen electrode side and one on the fuel electrode side with the same configuration.

Next, catalyst particles in which platinum is supported on a furnace black having a specific surface area of 800 m ² / g or more in a weight ratio of furnace black: platinum = 1: 1, polyarylene having a sulfonic acid group synthesized in Synthesis Example 2 is added to N. -A catalyst paste was prepared by uniformly mixing an ion conductive polymer binder dissolved in methyl-2-pyrrolidone and catalyst particles: binder = 1: 1.25 in a weight ratio. Next, the catalyst paste is screen-printed on the underlayer so as to have a platinum amount of 0.5 mg / cm ² , dried at 60 ° C. for 10 minutes, and then dried at 120 ° C. under reduced pressure to provide an electrode having a catalyst layer Formed.

  Next, the polymer electrolyte membrane is hot-pressed for 4 minutes under the conditions of 160 ° C. and 4 MPa while being sandwiched between the electrode catalyst layers of the oxygen electrode and the fuel electrode, whereby a membrane-electrode structure for a solid polymer fuel cell Formed body.

Using the power generation performance of the membrane-electrode structure for the polymer electrolyte fuel cell as the power generation performance, the change in voltage (V) with respect to the current density (A / cm ² ) in an environment of 80 ° C. and 90% relative humidity was measured. . The results are shown in FIG.

  Membrane-electrode structure for polymer electrolyte fuel cell as in Example 1 except that polyarylene having a sulfonic acid group synthesized in Synthesis Example 3 was used as the polymer electrolyte membrane and the ion conductive polymer binder. Formed body.

Using the power generation performance of the membrane-electrode structure for the polymer electrolyte fuel cell as the power generation performance, the change in voltage (V) with respect to the current density (A / cm ² ) in an environment of 80 ° C. and 90% relative humidity was measured. . The results are shown in FIG.

[Comparative Example 1]
As the polymer electrolyte membrane, a film made of a perfluoroalkylene sulfonic acid polymer compound (Nafion (trademark) manufactured by DuPont) is used, and the perfluoroalkylene sulfonic acid polymer compound is an isopropanol / n-propanol solution of an ion conductive binder. A membrane-electrode structure for a polymer electrolyte fuel cell was formed in the same manner as in Example 1 except that the catalyst particles were uniformly mixed with each other to prepare a catalyst paste.

Using the power generation performance of the membrane-electrode structure for the polymer electrolyte fuel cell as the power generation performance, the change in voltage (V) with respect to the current density (A / cm ² ) in an environment of 80 ° C. and 90% relative humidity was measured. . The results are shown in FIG.

It is explanatory sectional drawing which shows the example of 1 structure of the electrode structure used for the polymer electrolyte fuel cell of this invention. Measurement of change in voltage (V) with respect to current density (A / cm ² ) in an environment of 80 ° C. and relative humidity 90% of membrane-electrode structures for polymer electrolyte fuel cells produced in Examples and Comparative Examples It is a figure which shows the result.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Oxygen electrode 2 ... Fuel electrode 3 ... Polymer electrolyte membrane 4 ... Diffusion layer 5 ... Electrode catalyst layer 6 ... Carbon paper 7 ... Underlayer

Claims (3)

In a membrane-electrode structure for a polymer electrolyte fuel cell comprising a pair of electrode catalyst layers and a polymer electrolyte membrane sandwiched between both electrode catalyst layers,
The electrode catalyst layer comprises at least one monomer represented by the following formulas (A-1) to (A-6) and at least one oligomer represented by the following formulas (B-1) to (B-2). A membrane-electrode structure for a polymer electrolyte fuel cell, comprising a polyarylene having a sulfonic acid group obtained by hydrolyzing a polyarylene having a sulfonic acid ester group produced by copolymerization;

(NC ₄ H ₉ in the above formulas (A-1) and (A-5) represents a normal butyl group.)

(In the above formula, n represents an integer of 2 or more.)   2. The polymer electrolyte fuel cell according to claim 1, wherein the polyarylene having a sulfonic acid group is a polyarylene containing a sulfonic acid group in a range of 0.3 to 5.0 meq / g. Membrane-electrode structure. 2. The membrane-electrode structure for a polymer electrolyte fuel cell according to claim 1, wherein the electrode catalyst layer further contains carbon black carrying a hydrogen reduction catalyst .

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