JP2007026708A - Electrode catalyst layer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrode catalyst layer for a polymer electrolyte fuel cell that can produce a higher output from the same catalytic metal amount. <P>SOLUTION: The electrode catalyst layer for a solid polymer membrane-electrode assembly includes: a sulfonated polyarylene including a structural unit represented by formula (A) and a structural unit represented by formula (B); and a carbon material supporting metal. At least part of the carbon material is at least one kind selected from carbon nanofibers, carbon nanotubes, and fullerenes. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

The present invention relates to an electrode catalyst layer of a solid polymer membrane-electrode assembly used for a polymer electrolyte fuel cell or the like.

  In recent years, fuel cells have attracted particular attention as clean power generators that generate little noise and have low pollution and high efficiency. In particular, since a fuel cell called a solid polymer type is small and capable of high output, research for practical use such as in-vehicle use, stationary use, and portable device use is actively conducted.

  In order to obtain the power generation performance that can withstand the practical use of the fuel cell, it is necessary to use a noble metal as an electrode catalyst. The low utilization efficiency of this precious metal catalyst is one of the major issues in the spread of fuel cells due to the high cost of precious metals, and the amount of catalyst used can be reduced by increasing the utilization efficiency of the catalyst. Is required. In practical use, higher output can be obtained by using at a higher temperature, and the amount of catalyst used can be reduced.

Development of catalytic metal support materials with high utilization efficiency of noble metal catalysts has been actively conducted. For example, Patent Document 1 proposes a technique for increasing the utilization efficiency of a catalyst by using carbon nanofibers as a catalyst metal-supporting material. However, Nafion (trade name, manufactured by DuPont) is used as a binder in the electrode catalyst layer, and power generation at high temperatures is difficult due to low heat resistance.
JP 2002-83604 A

  The problem of the present invention was made against the background of the problems in the prior art as described above. By increasing the utilization efficiency of the electrode catalyst metal and using it at a high temperature, the same catalyst metal amount can be obtained. An object of the present invention is to provide an electrode catalyst layer for a polymer electrolyte fuel cell capable of obtaining a higher output.

  The present inventors diligently examined the power generation output density under conditions of high temperature and high humidity, and found that at least one of the anode electrode catalyst layer and the cathode electrode catalyst layer had an ion conductive component-containing fragrance comprising a polyarylene having a sulfonic acid group. Power generation performance at high temperatures is greatly improved by using a group-based polymer as a binder, and the use efficiency of the catalyst is greatly improved by using a nanocarbon material as a catalyst metal support material in this electrode catalyst layer. As a result, the present invention has been completed.

According to the present invention, the following electrode catalyst layer is provided to achieve the object of the present invention.
(1) A solid comprising a polyarylene having a sulfonic acid group containing a structural unit represented by the following general formula (A) and a structural unit represented by the following general formula (B), and a carbon material supporting a catalyst metal An electrode catalyst layer of a polymer membrane-electrode assembly, wherein at least a part of the carbon material supporting the catalyst metal is at least one kind selected from the group consisting of carbon nanofibers, carbon nanotubes, and fullerenes An electrode catalyst layer, which is a catalytic metal-supported nanocarbon material in which a catalytic metal is supported on a carbon material;

Wherein Y is —CO—, —SO ₂ —, —SO—, —CONH—, —COO—, — (CF ₂ ) ₁ — (l is an integer of 1 to 10) and —C (CF ₃ ) represents at least one structure selected from the group consisting of ₂ —, Z is a direct bond, or — (CH ₂ ) ₁ — (l is an integer of 1 to 10), —C (CH ₃ ) ₂ represents at least one structure selected from the group consisting of —, —O— and —S—, and Ar represents —SO ₃ H, —O (CH ₂ ) _p SO ₃ H or —O (CF ₂ ) _p SO ₃ H
The aromatic group which has a substituent represented by this is shown, m shows the integer of 0-10, n shows the integer of 0-10, k shows the integer of 1-4. )

(In the formula, A and D are independently a direct bond, or —CO—, —SO ₂ —, —SO—, —CONH.
-, - COO -, - ( CF 2) l - (l is an integer of 1 to _{10), - (CH 2) l} - (l is an integer of 1 to 10), - CR _'2 - ( R ′ represents an aliphatic hydrocarbon group, an aromatic hydrocarbon group and a halogenated hydrocarbon group), a cyclohexylidene group, a fluorenylidene group, —O— and —S—. Represents a structure, B is independently an oxygen atom or a sulfur atom, R ^{1 to} R ¹⁶ may be the same as or different from each other, a hydrogen atom,
A fluorine atom, an alkyl group, at least one atom or group selected from the group consisting of a halogenated alkyl group, allyl group, aryl group, nitro group and nitrile group partially or wholly halogenated; t represents an integer of 0 to 4, and r represents 0 or an integer of 1 or more. ).

  (2) The electrode catalyst layer according to (1), wherein the metal-supported nanocarbon material is contained in an amount of 20 to 70% by weight in the catalyst layer.

According to the present invention, an electrode catalyst layer with high catalyst utilization efficiency can be formed, and a fuel cell using a solid polymer membrane-electrode assembly having this electrode catalyst layer has a high initial voltage and excellent durability. Yes.

Hereinafter, the electrode catalyst layer according to the present invention will be described in more detail.
The electrode catalyst layer according to the present invention is an electrode catalyst layer of a solid polymer membrane-electrode assembly, and is an electrode catalyst layer containing an ion-conducting component-containing aromatic polymer and a carbon material supporting a catalyst metal. Thus, at least a part of the carbon material is a nanocarbon material. This nanocarbon material is at least one selected from the group of nanocarbon materials consisting of carbon nanofibers, carbon nanotubes, and fullerenes.

Each component contained in the electrode catalyst layer according to the present invention will be described.
(I) Carbon material carrying a catalyst metal As the catalyst metal used in the present invention, a noble metal catalyst such as platinum, palladium, gold, ruthenium, iridium is preferably used. The noble metal catalyst may contain two or more kinds of elements such as alloys and mixtures.

  Examples of the carbon material that supports the catalyst include carbon black such as oil furnace black, channel black, lamp black, thermal black, and acetylene black, carbon nanofibers, carbon nanotubes, and fullerenes.

  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 Corporation # 3150. , # 3250, and the like, and examples of acetylene black include those marketed under trademarks such as Denka Black manufactured by Denki Kagaku Kogyo.

  Carbon nanofibers having various diameters can be used, and those having a diameter in the range of 50 to 500 nm can be mentioned. The carbon nanotubes may be used synonymously with carbon nanofibers in a broad sense, but usually the diameter is generally several nanometers or less, mainly about 1 to 2 nm. C60 is generally used as the fullerene, but C70 or the like having a large number of carbon atoms such as C70 can also be used, and a structure having an open end as a part of the structure can also be mentioned.

  Further, as the carbon material used in the present invention, artificial graphite or carbon obtained from an organic compound such as natural graphite, pitch, coke, polyacrylonitrile, phenol resin, furan resin, or the like can also be used.

  The supported amount of the metal catalyst supported on the carbon material supporting the catalyst metal used in the present invention is not particularly limited as long as it is an amount that can effectively exhibit catalytic activity. It is desirable to be in the range of 0.1 to 9.0 g-metal / g-carbon, preferably 0.15 to 2.4 g-metal / g-carbon based on weight.

(Ii) Aromatic polymer containing ion-conducting component The aromatic polymer containing ion-conducting component serves as a binder component that binds the carbon material carrying the catalyst, and at the fuel electrode, ions generated by a reaction on the catalyst. It is possible to efficiently supply ions to the ion conductive membrane, and it is possible to efficiently supply ions supplied from the ion conductive membrane to the catalyst at the air electrode.

  In the ion-conducting component-containing aromatic polymer used in the present invention, a polymer segment (A) having an ion-conducting component composed of a sulfonic acid group and a polymer segment (B) having no proton-conducting component are covalently bonded. It is a block copolymer. More preferably, the main chain skeleton forming the copolymer is a polyarylene having a structure in which an aromatic ring is covalently bonded with a linking group, and particularly preferably a structural unit represented by the following general formula (A): And a polyarylene having a sulfonic acid group represented by the following general formula (C) including a structural unit represented by the following general formula (B). When such polyarylene is used, an electrode catalyst layer having higher heat resistance and higher mechanical strength can be formed.

  The polyarylene having a sulfonic acid group used in the present invention has a structural unit having a sulfonic acid group represented by the following general formula (A) and a sulfonic acid group represented by the following general formula (B). And a polymer represented by the following general formula (C).

  <Structural unit having sulfonic acid group>

In the general formula (A), Y represents —CO—, —SO ₂ —, —SO—, —CONH—, —CO.
It represents at least one structure selected from the group consisting of O—, — (CF ₂ ) ₁ — (wherein 1 is an integer of 1 to 10) and —C (CF ₃ ) ₂ —. Of these, —CO— and —SO ₂ — are preferable.

Z is a direct bond or at least one selected from the group consisting of — (CH ₂ ) ₁ — (wherein 1 is an integer of 1 to 10), —C (CH ₃ ) ₂ —, —O— and —S—. The structure of the species is shown. Among these, a direct bond and -O- are preferable.

Ar is an aromatic group having a substituent represented by —SO ₃ H, —O (CH ₂ ) _p SO ₃ H or —O (CF ₂ ) _p SO ₃ H (p represents an integer of 1 to 12). Indicates.
Specific examples of the aromatic group include a phenyl group, a naphthyl group, an anthryl group, and a phenanthryl group. Of these groups, a phenyl group and a naphthyl group are preferable. -SO ₃
The substituent represented by H, —O (CH ₂ ) _p SO ₃ H or —O (CF ₂ ) _p SO ₃ H (p represents an integer of 1 to 12) is substituted with at least one aromatic group. When the aromatic group is a naphthyl group, it is preferable that two or more are substituted.

m is an integer of 0 to 10, preferably 0 to 2, n is an integer of 0 to 10, preferably 0 to 2, and k is an integer of 1 to 4.
As a preferable combination of the values of m and n and the structures of Y, Z and Ar,
(1) a structure in which m = 0, n = 0, Y is —CO—, and Ar is a phenyl group having —SO ₃ H as a substituent;
(2) a structure in which m = 1, n = 0, Y is —CO—, Z is —O—, and Ar is a phenyl group having —SO ₃ H as a substituent;
(3) a structure in which m = 1, n = 1, k = 1, Y is —CO—, Z is —O—, and Ar is a phenyl group having —SO ₃ H as a substituent;
(4) a m = 1, n = 0, Y is -CO-, 2 pieces of -SO ₃ as Ar is a substituted group
A structure which is a naphthyl group having H,
(5) m = 1, n = 0, Y is —CO—, Z is —O—, and Ar is a phenyl group having —O (CH ₂ ) ₄ SO ₃ H as a substituent. Examples include structures.

  <Structural unit without sulfonic acid group>

In the general formula (B), A and D are independently a direct bond or —CO—, —SO ₂ —, —S.
O -, - CONH -, - COO -, - (CF 2) l - (l is an integer of 1 to 10), - (
CH _{2) l} - _(l is an integer of 1 to _{10), - CR '2 - (} R' represents an aliphatic hydrocarbon group, aromatic hydrocarbon group or a halogenated hydrocarbon group), cyclohexylidene And at least one structure selected from the group consisting of a group, a fluorenylidene group, -O- and -S-. Here, specific examples of the structure represented by —CR ′ ₂ — include methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, t-butyl group, propyl group, octyl group, decyl group. Group, octadecyl group, phenyl group, trifluoromethyl group and the like.

Among these, a direct bond, —CO—, —SO ₂ —, —CR ′ ₂ — (R ′ represents an aliphatic hydrocarbon group, an aromatic hydrocarbon group or a halogenated hydrocarbon group), cyclohexylidene Group, fluorenylidene group and -O- are preferred.

B is independently an oxygen atom or a sulfur atom, preferably an oxygen atom.
R ^{1 to} R ¹⁶ may be the same as or different from each other, and are a hydrogen atom, a fluorine atom, an alkyl group, a halogenated alkyl group in which a part or all of them are halogenated, an allyl group, an aryl group, a nitro group, a nitrile group. At least one atom or group selected from the group consisting of

  Examples of the alkyl group include a methyl group, an ethyl group, a propyl group, a butyl group, an amyl group, a hexyl group, a cyclohexyl group, and an octyl group. Examples of the halogenated alkyl group include a trifluoromethyl group, a pentafluoroethyl group, a perfluoropropyl group, a perfluorobutyl group, a perfluoropentyl group, and a perfluorohexyl group. Examples of the allyl group include a propenyl group, and examples of the aryl group include a phenyl group and a pentafluorophenyl group.

s and t represent an integer of 0 to 4. r shows 0 or an integer greater than or equal to 1, and an upper limit is 100 normally, Preferably it is 1-80.
Preferred combinations of the values of s and t and the structures of A, B, D, and R ^{1 to} R ¹⁶ are as follows:
(1) s = 1, t = 1, and A is —CR ′ ₂ — (R ′ represents an aliphatic hydrocarbon group, an aromatic hydrocarbon group and a halogenated hydrocarbon group), a cyclohexylidene group or A structure which is a fluorenylidene group, B is an oxygen atom, D is —CO— or —SO ₂ —, and R ^{1 to} R ¹⁶ are a hydrogen atom or a fluorine atom,
(2) a structure in which s = 1, t = 0, B is an oxygen atom, D is —CO— or —SO ₂ —, and R ^{1 to} R ¹⁶ are hydrogen atoms or fluorine atoms,
(3) s = 0, t = 1, and A is —CR ′ ₂ — (R ′ represents an aliphatic hydrocarbon group, an aromatic hydrocarbon group and a halogenated hydrocarbon group), a cyclohexylidene group or Examples include a fluorenylidene group, B is an oxygen atom, and R ^{1 to} R ¹⁶ are a hydrogen atom, a fluorine atom, or a nitrile group.

  <Polymer structure>

In the general formula (C), A, B, D, Y, Z, Ar, k, m, n, r, s, t, and R ^{1 to} R ¹⁶ are respectively in the general formulas (A) and (B). A, B, D, Y, Z, Ar, k
, M, n, r, s, t, and R ^{1 to} R ¹⁶ . x and y represent molar ratios when x + y = 100 mol%.

  In the polyarylene having a sulfonic acid group used in the present invention, the structural unit represented by the formula (A), that is, the unit of x is 0.5 to 100 mol%, preferably 10 to 99.999 mol%, The structural unit represented by the formula (B), that is, the unit of y is contained in a ratio of 99.5 to 0 mol%, preferably 90 to 0.001 mol%.

<Method for producing polymer>
For the production of a polyarylene having a sulfonic acid group, for example, the following methods A, B, C and the like can be used.

(Method A)
For example, in the method described in JP-A No. 2004-137444, a monomer having a sulfonate group that can be a structural unit represented by the general formula (A), and a structural unit represented by the general formula (B) A polyarylene having a sulfonic acid ester group is produced by copolymerization with a monomer or oligomer that can be synthesized, and the sulfonic acid ester group is deesterified, and then the sulfonic acid ester group is converted into a sulfonic acid group. be able to.

(Method B)
For example, in the method described in JP-A No. 2001-342241, a monomer having a skeleton represented by the general formula (A) and having no sulfonic acid group or sulfonic acid ester group, and the general formula (B) It can also be synthesized by copolymerizing a monomer or oligomer that can be a structural unit represented, and sulfonating the polymer using a sulfonating agent.

(Method C)
In the general formula (A), when Ar is an aromatic group having a substituent represented by —O (CH ₂ ) _p SO ₃ H or —O (CF ₂ ) _p SO ₃ H, for example, A precursor monomer that can be a structural unit represented by the general formula (A) and a monomer or oligomer that can be a structural unit represented by the general formula (B) by the method described in Japanese Unexamined Patent Application Publication No. 2005-60625 Can be synthesized by a method in which an alkylsulfonic acid or a fluorine-substituted alkylsulfonic acid is introduced.

Specific examples of the monomer having a sulfonate group that can be used in (Method A) and can be the structural unit represented by the above general formula (A) are disclosed in JP-A Nos. 2004-137444 and 2004-2004. Examples thereof include sulfonic acid esters described in Japanese Patent Nos. 3459997 and 2004-346163.

  As a specific example of a monomer having no sulfonic acid group or sulfonic acid ester group that can be a structural unit represented by the above general formula (A) that can be used in (Method B), JP-A-2001-342241 Examples thereof include dihalides described in Japanese Patent Laid-Open No. 2002-293889.

  Specific examples of precursor monomers that can be used in (Method C) and can be structural units represented by the above general formula (A) include dihalides described in JP-A-2005-36125. Can be mentioned.

In addition, as a specific example of a monomer or oligomer that can be a structural unit represented by the general formula (B) used in any method,
When r = 0, for example, 4,4′-dichlorobenzophenone, 4,4′-dichlorobenzanilide, 2,2-bis (4-chlorophenyl) difluoromethane, 2,2-bis (4-chlorophenyl) -1, 1,1,3,3,3-hexafluoropropane, 4-chlorobenzoic acid-4-
Examples include chlorophenyl ester, bis (4-chlorophenyl) sulfoxide, bis (4-chlorophenyl) sulfone, and 2,6-dichlorobenzonitrile. In these compounds, a compound in which a chlorine atom is replaced with a bromine atom or an iodine atom is exemplified.

In the case of r = 1, for example, compounds described in JP-A-2003-113136 can be exemplified.
In the case of r ≧ 2, for example, compounds described in JP-A Nos. 2004-137444, 2004-244517, and 2005-112985 can be exemplified.

  In order to obtain a polyarylene having a sulfonic acid group, first, a monomer that can be a structural unit represented by the general formula (A) and a monomer that can be a structural unit represented by the general formula (B), Alternatively, it is necessary to copolymerize with an oligomer to obtain a precursor polyarylene. This copolymerization is carried out in the presence of a catalyst, and the catalyst used in this case is a catalyst system containing a transition metal compound. This catalyst system is (1) a transition metal salt and a ligand. A compound (hereinafter referred to as “ligand component”) or a transition metal complex coordinated with a ligand (including a copper salt) and (2) a reducing agent as essential components, and further increase the polymerization rate. Therefore, “salt” may be added.

  Specific examples of these catalyst components, the use ratio of each component, the polymerization conditions such as the reaction solvent, concentration, temperature, time, etc. include the compounds described in JP-A No. 2001-342241.

  The polyarylene having a sulfonic acid group can be obtained by converting the precursor polyarylene into a polyarylene having a sulfonic acid group. Examples of this method include the following methods A, B, and C.

(Method A)
A method of deesterifying a polyarylene having a sulfonate group of a precursor by a method described in JP-A-2004-137444.

(Method B)
A method of sulfonating a precursor polyarylene by a method described in JP-A No. 2001-342241.

(Method C)
A method of introducing an alkylsulfonic acid group into the precursor polyarylene by the method described in JP-A-2005-60625.

  The ion exchange capacity of the polyarylene having a sulfonic acid group represented by the general formula (C) produced by the method as described above is usually 0.3 to 5 meq / g, preferably 0.5 to 3 meq / g. More preferably, it is 0.8 to 2.8 meq / g. If it is less than 0.3 meq / g, the proton conductivity is low and the power generation performance is low. On the other hand, if it exceeds 5 meq / g, the water resistance may be significantly lowered, which is not preferable.

  The ion exchange capacity is, for example, a precursor monomer that can be a structural unit represented by the general formula (A), a monomer that can be a structural unit represented by the general formula (B), or the kind of oligomer, and the use ratio. It can be adjusted by changing the combination.

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).
(Method for producing electrode catalyst layer)
(Preparation of electrode paste)
The method for producing the electrode catalyst layer according to the present invention is not particularly limited. For example, the electrode catalyst layer is prepared using the carbon material supporting the catalyst metal and the ion-conducting component-containing aromatic polymer. A method for preparing an electrode catalyst layer by applying the electrode paste composition onto an electrode substrate, a transfer substrate, or an ionic conductive film and drying it can be mentioned.

  The method for preparing the electrode paste composition is not particularly limited. For example, the electrode paste composition is prepared by kneading the carbon material supporting the catalyst metal and the ion conductive component-containing aromatic polymer by a conventionally known method. The

  Although the mixing order of each component is not specifically limited, for example, all components are mixed and stirred for a certain period of time, or components other than the dispersant are mixed and stirred for a certain period of time, and then a dispersant is added as necessary. It is preferable to add and to stir for a certain time. Moreover, you may adjust the quantity of an organic solvent and water as needed, and may adjust the viscosity of a composition.

  Examples of the coating method include brush coating, brush coating, bar coater coating, knife coater coating, doctor blade method, screen printing, spray coating, and the like. The catalyst electrode is coated on another substrate (transfer substrate). Once formed, it may be transferred to an electrode substrate or an ion conductive membrane. As the transfer substrate in this case, a polytetrafluoroethylene (PTFE) sheet or a glass plate or a metal plate whose surface is treated with a release agent can be used.

As said electrode base material, the electrode base material generally used for a fuel cell is used without being specifically limited. For example, a porous conductive sheet having a conductive material as a main constituent material can be mentioned. Examples of the conductive material include a fired body from polyacrylonitrile, a fired body from pitch, a carbon material such as graphite and expanded graphite, stainless steel, and the like. 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 substance (inorganic conductive fiber), particularly carbon fiber is preferable. As a porous conductive sheet using inorganic conductive fibers, either a woven fabric or a non-woven fabric structure can be used. As the woven fabric, plain weaving, oblique weaving, satin weaving, crest weaving, binding weaving and the like are not particularly limited. Moreover, as a nonwoven fabric, what was manufactured by methods, such as a papermaking method, a needle punch method, a spun bond method, a water jet punch method, a melt blow method, is used, without being specifically limited. The porous conductive sheet using inorganic conductive fibers may be a knitted fabric.

  In particular, when carbon fibers are used as these fabrics, a woven fabric obtained by carbonizing or graphitizing a plain woven fabric using flame-resistant spun yarn, or carbonizing or non-woven fabric after processing the flame-resistant yarn by a needle punch method or a water jet punch method. A graphitized non-woven fabric, a mat non-woven fabric by a paper making method using a flame-resistant yarn, a carbonized yarn or a graphitized yarn is preferable. For example, Toray carbon paper TGP series, SO series, E-TEK carbon cloth, etc. are preferably used.

It is also a preferred embodiment that conductive particles such as carbon black or conductive fibers such as carbon fibers are added to the porous conductive sheet as an auxiliary agent in order to improve conductivity.
The formation on the proton conductive membrane is not particularly limited as long as it is a known ion conductive membrane, but on the ion conductive membrane made of a polymer having excellent heat resistance such as polyarylene having a sulfonic acid group. It is preferable to form.

The thickness of the applied coating film (i.e., the thickness of the catalyst electrode) is not particularly limited, but the metal supported as a catalyst is 0.05 to 4.0 mg / cm per unit surface area of the coating. ² , preferably in the range of 0.1 to 2.0 mg / cm ² .

Within this range, sufficiently high catalytic activity is exhibited, and protons can be extracted efficiently.
The carbon material carrying the catalyst metal contained in the electrode catalyst layer thus obtained includes a catalyst metal-carrying carbon material in which a catalyst is carried on a carbon material other than the nanocarbon material, a catalyst metal-carrying nanocarbon material, The catalyst metal-supporting nanocarbon material is preferable. The electrode catalyst layer contains 20 to 70% by weight, preferably 30 to 70% by weight of the catalyst metal-supported nanocarbon material.

  When the metal-supported nanocarbon material is contained in the electrode catalyst layer in the above amount, the utilization efficiency of the catalyst is increased and the initial voltage is increased. Moreover, even if it is used for a long time, there is almost no voltage drop and it has excellent durability.

(Organic solvent)
The organic solvent used for the preparation of the electrode paste composition is not particularly limited, but preferably has a boiling point (b.p.) in the range of 75 to 250 ° C, and -O-, -OH. , —CO—, —SO—, —SO ₂ —, —COO—, —CONR— (wherein R represents a hydrogen atom or a hydrocarbon group), an organic solvent having at least one group can be used.

  When the boiling point of the organic solvent is less than the above range, productivity of the coating may decrease due to a phenomenon such as fast drying of the electrode paste and easy clogging of the die nozzle. When the boiling point of the solvent exceeds the above range, removal of the solvent becomes difficult, pores in the electrode are blocked, and power generation performance may be reduced.

Specific examples of the organic solvent include ethanol (bp 78.3 ° C), n-propyl alcohol (bp 97 ° C), 2-propanol (bp 82.4 ° C), 2- Methyl-2-propanol (bp 82.5 ° C.), 2-butanol (bp 99.5 ° C.), n-butyl alcohol (bp 117 ° C.), 2-methyl-1-propanol (Bp 108 ° C), 1-pentanol (bp 138 ° C), 2-pentanol (bp 119 ° C), 3-pentanol (bp 115 ° C), 2- Methyl-1-butanol (bp 129 ° C.), 3-methyl-1-butanol (bp 131 ° C.), 2-methyl-2-butanol (bp 102 ° C.)
3-methyl-2-butanol (bp 112 ° C), 2,2-dimethyl 1-propanol (bp 113 ° C), cyclohexanol (bp 161 ° C), 1-hexanol (b .
p.157 ° C.), 2-methyl-1-pentanol (bp 148 ° C.), 2-methyl-2-
Pentanol (bp 121 ° C), 4-methyl-2-pentanol (bp 132 ° C), 2-ethyl-1-butanol (bp 147 ° C), 1-methylcyclohexanol ( b.
156), 2-methylcyclohexanol (bp 168 ° C), 3-methylcyclohexanol (bp 168 ° C), 4-methylcyclohexanol (bp 171 ° C), 1-octanol (Bp. 195 ° C), 2-octanol (bp 180 ° C), 2-ethyl-1-hexanol (bp 184 ° C), dioxane (bp 101 ° C), butyl ether (bp 140 ° C), phenyl ether (bp 187 ° C), isopentyl ether (bp 173 ° C), 1,2-dimethoxyethane (bp 85.2 ° C), diethoxyethane (b p.102 ° C), bis (2-methoxyethyl) ether (bp 160 ° C), bis (2-ethoxyethyl) ether (bp 189 ° C), cineol (bp 176 ° C) , Benzyl ethyl ether (bp 185 ° C.) Anisole (bp 154 ° C), phenetole (bp 170 ° C), acetal (bp 104 ° C), methyl ethyl ketone (bp 79.6 ° C), 2-pentanone (bp 102 ° C), 3-pentanone (bp 102 ° C), cyclopentanone (bp 131 ° C), cyclohexanone (bp 156 ° C), 2-hexanone (bp 128 ° C), 4-methyl-2-pentanone (bp 117 ° C.), 2-heptanone (bp 151 ° C.), 2,4-dimethyl-3-pentanone (bp 125 ° C.),
2-octanone (bp 173 ° C.), γ-butyrolactone (bp 204 ° C.), n-butyl acetate (bp 126 ° C.), isobutyl acetate (bp 126 ° C.), acetic acid sec-butyl (bp 112 ° C), pentyl acetate (bp 150 ° C), isopentyl acetate (bp 142 ° C), 3-methoxybutyl acetate (bp 173 ° C), butyric acid Methyl (bp 102 ° C), ethyl butyrate (bp 121 ° C), methyl lactate (bp 145 ° C), ethyl lactate (bp 155 ° C), butyl lactate (bp 185 ° C), 2-methoxyethanol (bp 125 ° C), 2-ethoxyethanol (bp 136 ° C), 2- (methoxymethoxy) ethanol (bp 168 ° C), 2-isopropoxy Ethanol (bp 142 ° C), 1-methoxy-2-propanol (bp 120 ° C), 1 Ethoxy-2-propanol (bp 132 ° C), dimethyl sulfoxide (bp 189 ° C), N-methylformamide (bp 185 ° C), N, N-dimethylformamide (bp 153) ), N, N-diethylformamide (bp 178 ° C.), N, N-dimethylacetamide (bp 166 ° C.), N-methyl-2-pyrrolidone (bp 202 ° C.), tetra Examples include methylurea (bp 177.5 ° C.), and two or more of these can be used in combination.

The organic solvent is used in an amount of 5% to 95% by weight, preferably 15% to 90% by weight in the electrode paste composition.
When the use ratio of the organic solvent is within the above range, a sufficient pore volume in the electrode necessary for power generation can be secured. Moreover, if it exists in the said range, a composition will become a paste-form and is suitable for handling.

(water)
Water may be added to the electrode paste composition as necessary. Examples of water include distilled water and ion exchange water. The addition of water has the effect of reducing heat generation during electrode paste preparation. The proportion of water used is 0 to 70% by weight, preferably 2 to 30% by weight in the electrode paste composition. When the ratio of water used is within the above range, heat generation during electrode paste production can be efficiently reduced.

The organic solvent and water are removed at a drying temperature of 20 ° C. to 180 ° C., preferably 50 ° C. to 160 ° C., and a drying time of 5 minutes to 600 minutes, preferably 30 minutes to 400 minutes. The organic solvent can be removed by water immersion as necessary. Water immersion temperature 5 ° C to 120 ° C
° C, preferably 15 ° C to 95 ° C, and the water immersion time is 1 minute to 72 hours, preferably 5 minutes to 48 hours.

(Dispersant)
The electrode paste composition for producing an electrode catalyst layer according to the present invention may contain a dispersant as required. When a dispersant is added to the electrode paste composition, the electrode paste is excellent in dispersibility, storage stability and fluidity, and productivity during coating is improved.

Examples of the dispersant include oleic acid / N-methyltaurine, potassium oleate / diethanolamine salt, alkyl ether sulfate / triethanolamine salt, polyoxyethylene alkyl ether sulfate / triethanolamine salt, amine of special modified polyether ester acid Salts, amine salts of higher fatty acid derivatives, amine salts of specially modified polyester acids, amine salts of high molecular weight polyetherester acids, amine salts of specially modified phosphoric acid esters, high molecular weight polyester acid amidoamine salts, amidoamine salts of special fatty acid derivatives, higher Fatty acid alkylamine salts, high molecular weight polycarboxylic acid amidoamine salts, sodium laurate, sodium stearate, sodium oleate sodium lauryl sulfate, sodium cetyl sulfate Salt, sodium stearyl sulfate, sodium oleyl sulfate, lauryl ether sulfate, sodium alkylbenzene sulfonate, oil-soluble alkylbenzene sulfonate, α-olefin sulfonate, higher alcohol phosphate monoester disodium salt, higher Anionic surfactants such as alcohol sodium diester disodium salt and zinc dialkyldithiophosphate; benzyldimethyl {2- [2- (p-1,1,3,3-tetramethylbutylphenoxy) ethoxy] ethyl}
Ammonium chloride, octadecylamine acetate, tetradecylamine acetate, octadecyltrimethylammonium chloride, tallow trimethylammonium chloride, dodecyltrimethylammonium chloride, coconut trimethylammonium chloride, hexadecyltrimethylammonium chloride, behenyltrimethylammonium chloride, coconut dimethylbenzylammonium chloride Tetradecyldimethylbenzylammonium chloride, octadecyldimethylbenzylammonium chloride, dioleyldimethylammonium chloride, 1-hydroxyethyl-2-tallow imidazoline quaternary salt, 2-heptadecenyl-hydroxyethylimidazoline, stearamide ethyl diethylamine acetate, stearer Doethyldiethylamine hydrochloride, triethanolamine monostearate formate, alkyl pyridium salt, higher alkyl amine ethylene oxide adduct, polyacrylamide amine salt, modified polyacrylamide amine salt, perfluoroalkyl quaternary ammonium iodide, etc. Cationic surfactants: dimethyl coconut betaine, dimethyl lauryl betaine, sodium laurylaminoethylglycine, sodium laurylaminopropionate, stearyl dimethyl betaine, lauryl dihydroxyethyl betaine, amide betaine, imidazolinium betaine, lecithin, 3- [ω-fluoro Accanoyl-N-ethylamino] -1-propanesulfonate sodium, N- [3- (perfluorooctanesulfonamido) propyl] -N, N-dimethyl -Amphoteric surfactants such as N-carboxymethylene ammonium betaine; and coconut fatty acid diethanolamide (1: 2 type), coconut fatty acid diethanolamide (1: 1 type), bovine fatty acid diethanolamide (1: 2 type), bovine fatty acid Diethanolamide (1: 1 type), oleic acid diethanolamide (1: 1 type), hydroxyethyl lauryl amine, polyethylene glycol lauryl amine, polyethylene glycol palm amine, polyethylene glycol stearyl amine, polyethylene glycol beef tallow amine, polyethylene glycol beef tallow propylene diamine , Polyethylene glycol dioleylamine, dimethyl lauryl amine oxide, dimethyl stearyl amine oxide, dihydroxyethyl lauryl amine oxide, perfluoro Alkylamine oxide, polyvinylpyrrolidone, higher alcohol ethylene oxide adduct, alkylphenol ethylene oxide adduct, fatty acid ethylene oxide adduct, polypropylene glycol ethylene oxide adduct, fatty acid ester of glycerin, fatty acid ester of pentaerythrit, fatty acid ester of sorbit, Nonionic surfactants such as fatty acid esters of sorbitan, fatty acid esters of sugar, etc. can be mentioned, and these can be used in combination of two or more, preferably surfactants having a basic group, and more An anionic or cationic surfactant is preferable, and a surfactant having a molecular weight of 5,000 to 30,000 is more preferable.

The use ratio of the dispersant is 0 to 10% by weight, preferably 0 to 2% by weight in the electrode paste composition.
When the use ratio of the dispersant is within the above range, an electrode paste excellent in dispersibility, storage stability and fluidity can be obtained.

(Carbon fiber)
Carbon fiber can be added to the electrode paste composition as necessary. Examples of the carbon fiber used in the present invention include rayon-based carbon fiber, PAN-based carbon fiber, lignin pover-based carbon fiber, pitch-based carbon fiber, and vapor-grown carbon fiber, and preferably vapor-grown carbon fiber. It is. When carbon fiber is added to the electrode paste composition, the pore volume in the electrode is increased, the gas diffusibility is improved, and the flooding phenomenon due to the generated water can be improved, and the power generation performance is improved.

In the electrode paste composition, the ion conductive component-containing aromatic polymer is desirably 0.5 to 50% by weight, preferably 1 to 40% by weight.
When the proportion of the ion-conducting component-containing aromatic polymer is less than the above range, it cannot function as a binder and a catalyst electrode cannot be formed. On the other hand, if it is larger than the above range, the pore volume in the catalyst electrode decreases, and sufficient power generation performance cannot be obtained.

[Example]
EXAMPLES Hereinafter, although this invention is demonstrated further more concretely based on an Example, this invention is not limited to these Examples. The measurement of sulfonic acid equivalent, molecular weight, preparation of fuel cell and evaluation of performance were obtained 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 molecular weight of polyarylene having no sulfonic acid group was determined by GPC using polystyrene (THF) as a solvent and the molecular weight in terms of polystyrene. The molecular weight of polyarylene having a sulfonic acid group was determined by GPC using polystyrene as a molecular weight using N-methyl-2-pyrrolidone (NMP) to which lithium bromide and phosphoric acid were added as a solvent.
3. Preparation of fuel cell and evaluation of performance A single 50 μm-thick film made of the polymer of Synthesis Example 1 described later is prepared, sandwiched between two electrode catalyst layers formed on two water-repellent carbon papers, and a pressure of 50 kg / 160 cm ² below
The electrode assembly was manufactured by hot press molding under the condition of ° C. × 10 min. Next, sandwiching the electrode membrane assembly was prepared made of two titanium collectors, the heater disposed outside, assembled fuel cell having an effective area of 25 cm ² further.

When the temperature of the fuel cell is kept at 80 ° C., hydrogen and oxygen are supplied at a humidity of 100% RH at a back pressure of 0.02 MPa, and the current density is constant at 1.0 A / cm ^{2 with} respect to the area of the electrode catalyst layer. The initial value of the cell voltage, the value after 100 hours, was measured.

[Synthesis Example 1]
(1) Synthesis of polyarylene 90.3 g of neopentyl 3- (2,5-dichlorobenzoyl) benzenesulfonate (225 mmo) was added to a 1000 mL three-necked flask equipped with a stirring blade, a thermometer, and a nitrogen introduction tube.
L) 2,5-dichlorobenzophenone 69.1 g (275 mmol), 4-chlorobenzophenone 1.08 g (5 mmol), bis (triphenylphosphine) nickel dichloride 9.81 g (15 mmol), sodium iodide 2.25 g (15 mmol) ), 52.5 g (200 mmol) of triphenylphosphine, and 78.4 g (1200 mmol) of zinc. After the inside of the flask was vacuum-dried for 2 hours, 373 mL of dimethylacetamide (DMAc) that had been purged with dry nitrogen and dehydrated was added to initiate polymerization.

The polymerization was continued for 3 hours while controlling the reaction temperature not to exceed 90 ° C. Next, 1400 mL of DMAc was added to dilute the polymerization solution, and the insoluble part was filtered. The filtrate was poured into 10 L of methanol to solidify the polymer. The precipitated polymer was vacuum dried to obtain 120 g of polyarylene. The number average molecular weight of the product determined by GPC was 39000, and the weight average molecular weight was 153000.
(2) Synthesis of polyarylene having a sulfonic acid group To a 300 mL three-necked flask equipped with a stirring blade, a thermometer, and a nitrogen introduction tube, 120 g of polyarylene, 970 mL of DMAc, and 29.3 g (338 mmol) of lithium bromide were added, at 120 ° C. Stir for 7 hours. The reaction solution was poured into 5 L of acetone to solidify the polymer. The obtained solid was treated twice with distilled water / concentrated hydrochloric acid solution (3.0 L / 0.37 L), and then washed with distilled water until the pH became neutral. It dried at 70 degreeC for 12 hours, and obtained 100 g of polyarylenes which have a sulfonic acid group. The ion exchange capacity of this polymer was 2.0 meq / g. The weight average molecular weight was 116000.

[Synthesis Example 2]
193.5 g (540 mmol) of 2,5-dichloro-4′-phenoxybenzophenone
4,4′-dichlorobenzophenone 15.1 g (60 mmol), sodium iodide 11.7 g (78 mmol), bis (triphenylphosphine) nickel dichloride 11.8 g (18 mmol), triphenylphosphine 63.0 g (240 mmol), Place 94.1 g (1.44 mol) of zinc in a three-necked flask equipped with a condenser and a three-way cock, put it in a 70 ° C. oil bath, replace with nitrogen, add 1000 mL of N-methyl-2-pyrrolidone under a nitrogen atmosphere, and react. Started. After the reaction for 20 hours, the reaction mixture was diluted with 500 mL of N-methyl-2-pyrrolidone, poured into a 1:10 hydrochloric acid / methanol solution, the polymer was precipitated, washed, filtered, and vacuum dried to obtain a white powder. . Yield was 153 g. The weight average molecular weight was 159000. To 150 g of this polymer, 1500 mL of concentrated sulfuric acid was added and stirred at room temperature for 24 hours to carry out a sulfonation reaction. After the reaction, it was poured into a large amount of pure water to precipitate a sulfonated polymer. The polymer was washed with pure water until the pH reached 7, and after filtration, the sulfonated polymer was recovered and dried in vacuum at 90 ° C. The yield of sulfonated polymer was 179 g. The ion exchange capacity of this polymer was 2.3 meq / g, and the weight average molecular weight was 183,000.

[Example 1]
[Synthesis of catalytic metal-supported carbon nanofibers]
Ni oxide and Cu oxide were mixed and reduced in hydrogen gas at a temperature of 500 ° C. to obtain a Cu—Ni alloy (Cu / Ni = 1/1). A gas of ethylene / hydrogen = 1/4 was brought into contact with the Cu—Ni alloy obtained above, and carbon nanofibers were obtained by a thermal CVD method at 500 ° C.

  The surface of the obtained carbon nanofiber was washed with dilute nitric acid, washed with water, and then dried at 100 ° C. for 1 hour to remove the Cu—Ni alloy on the surface. From the SEM observation of the obtained carbon nanofiber, the average fiber diameter was 200 nm.

  A suspension was prepared by dispersing 1 g of carbon nanofibers in 100 mL of water in a flask equipped with a reflux condenser. Thereafter, 8 mL of a chloroplatinic acid aqueous solution (Pt: 40 mg / mL) was added, and a 2.5 wt% aqueous solution of sodium bicarbonate was gradually added dropwise over 30 minutes. A magnetic stirrer was placed in the flask and stirred.

  After refluxing for 1 hour, the mixture in the flask was filtered, and the resulting precipitate was washed with ion-exchanged water. The washing operation was performed using 100 times the amount of water with respect to the weight of the precipitate, and the water was changed five times. The resulting precipitate was dried at 100 ° C. for 1 hour.

The precipitate was placed in a furnace at 200 ° C. and subjected to reduction treatment for 10 hours in a hydrogen / nitrogen mixed gas. The weight of the obtained platinum-supported carbon nanofibers was 1.20 g.
[Preparation of electrode paste A]
Put 50 g of zirconia balls (trade name: YTZ ball, manufactured by Nikkato Co., Ltd.) 25 g in a 50 mL glass bottle, 1.50 g of platinum-supported carbon nanofibers obtained above, 0.88 g of distilled water, and sulfone of Synthesis Example 1 A mixture of a 20 wt% N-methyl-2-pyrrolidone solution of polyarylene having an acid group and 12.47 g of N-methyl-2-pyrrolidone was stirred for 10 minutes with a wave blower, and then a dispersant (trade name: DA234 (manufactured by Enomoto Kasei Co., Ltd.) (0.028 g) was added, and the mixture was further stirred for 30 minutes with a wafer blower to obtain electrode paste A.

[Production of Electrode Catalyst Layer A]
Electrode paste A is applied to one side of carbon paper (Toray) treated with water repellency using a doctor blade, and dried at 120 ° C. for 60 minutes to give a platinum coating amount of 0.5 mg / cm ² . Electrode catalyst layer A was formed. The evaluation results of the fuel cell performance using the electrode catalyst layer A are shown in Table 1.

[Example 2]
[Preparation of electrode paste B]
Into a 50 mL glass bottle, 25 g of a zirconia ball having a diameter of 5 mm (trade name: YTZ ball, manufactured by Nikkato Co., Ltd.) was added, 1.50 g of platinum-supported carbon nanofibers obtained in Example 1, 0.88 g of distilled water, A mixture of a polyarylene having a sulfonic acid group, 3.23 g of a 20% by weight N-methyl-2-pyrrolidone solution and 12.47 g of N-methyl-2-pyrrolidone was stirred for 10 minutes with a wave blower, and then a dispersant (trade name) : DA234, manufactured by Enomoto Kasei Co., Ltd.) 0.028 g was added, and the mixture was further stirred for 30 minutes with a wafer blower to obtain electrode paste B.

[Production of Electrode Catalyst Layer B]
Electrode paste B is applied to one side of a water-repellent carbon paper (manufactured by Toray Industries, Inc.) using a doctor blade and dried at 120 ° C. for 60 minutes to give a platinum coating amount of 0.5 mg / cm ² . Electrode catalyst layer B was formed. Table 1 shows the evaluation results of the fuel cell performance using the electrode catalyst layer B.

[Example 3]
[Synthesis of catalytic metal-supported carbon nanotubes]
As a carbon nanotube, what was obtained by processing high purity graphite by a laser ablation method was used. The tube diameter was about 2 nm.

The treatment was performed in the same manner as in Example 1 except that carbon nanotubes were used in place of the carbon nanofibers to obtain platinum-supported carbon nanotubes.
[Preparation of electrode paste C]
An electrode paste C was obtained in the same manner as in the electrode paste A of Example 1 except that carbon nanotubes were used instead of the carbon nanofibers.

[Production of electrode catalyst layer C]
Electrode paste C is applied to one side of carbon paper (Toray) treated with water repellency using a doctor blade and dried at 120 ° C. for 60 minutes, so that the platinum coating amount becomes 0.5 mg / cm ² . Electrode catalyst layer C was formed. The evaluation results of the fuel cell performance using the electrode catalyst layer C are shown in Table 1.

[Comparative Example 1]
[Synthesis of catalytic metal-supported carbon black]
Except for using carbon black instead of carbon nanofibers, treatment was performed in the same manner as in Example 1 to obtain platinum-supported carbon black.

[Preparation of electrode paste D]
An electrode paste D was obtained in the same manner as the electrode paste A of Example 1 except that the platinum-supported carbon black was used instead of the carbon nanofibers.

[Production of Electrode Catalyst Layer D]
An electrode catalyst layer D was prepared in the same manner as in Example 1 except that the electrode paste D was used in place of the electrode paste A. Table 1 shows the evaluation results of the fuel cell performance using the electrode catalyst layer D.

In Examples 1 to 3 using platinum-supported carbon nanofibers and platinum-supported carbon nanotubes, compared to Comparative Example 1, the initial voltage is higher and the utilization efficiency of the catalyst is increased. Further, even during 100 hours of operation, almost no voltage drop is observed, and it is considered that the durability is sufficient.

Claims (2)

A solid polymer film comprising a polyarylene having a sulfonic acid group containing a structural unit represented by the following general formula (A) and a structural unit represented by the following general formula (B), and a carbon material supporting a catalyst metal The electrode catalyst layer of the electrode assembly, wherein at least a part of the carbon material supporting the catalyst metal is at least one nanocarbon material selected from the group consisting of carbon nanofibers, carbon nanotubes, and fullerenes An electrode catalyst layer, which is a catalyst metal-supported nanocarbon material on which a catalyst metal is supported;

Wherein Y is —CO—, —SO ₂ —, —SO—, —CONH—, —COO—, — (CF ₂ ) ₁ — (l is an integer of 1 to 10) and —C (CF ₃ ) represents at least one structure selected from the group consisting of ₂ —, Z is a direct bond, or — (CH ₂ ) ₁ — (l is an integer of 1 to 10), —C (CH ₃ ) ₂ -, - O-and represents at least one structure selected from the group consisting of -S-, Ar is _{-SO 3 H, -O (CH 2} ) p SO 3 H or -O (CF _{2) p} SO ₃ H
The aromatic group which has a substituent represented by this is shown, m shows the integer of 0-10, n shows the integer of 0-10, k shows the integer of 1-4. )

(In the formula, A and D are independently a direct bond, or —CO—, —SO ₂ —, —SO—, —CONH.
-, - COO -, - ( CF 2) l - (l is an integer of 1 to _{10), - (CH 2) l} - (l is an integer of 1 to 10), - CR _'2 - ( R ′ represents an aliphatic hydrocarbon group, an aromatic hydrocarbon group and a halogenated hydrocarbon group), a cyclohexylidene group, a fluorenylidene group, —O— and —S—. Represents a structure, B is independently an oxygen atom or a sulfur atom, R ^{1 to} R ¹⁶ may be the same as or different from each other, a hydrogen atom,
A fluorine atom, an alkyl group, at least one atom or group selected from the group consisting of a halogenated alkyl group, allyl group, aryl group, nitro group and nitrile group partially or wholly halogenated; t represents an integer of 0 to 4, and r represents 0 or an integer of 1 or more. ). 2. The electrode catalyst layer according to claim 1, wherein the catalyst metal-supporting nanocarbon material is contained in an amount of 20 to 70 wt% in the catalyst layer.