JP2013077436A - Separator and fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a separator contributing to long term stabilization of a solid polymer fuel cell due to suppression of elution of a metal ion even if the solid polymer fuel cell is operated in a state exposed under a strong acid condition.SOLUTION: The separator includes: a substrate formed of metallic material; and a thin film layer consisting of a conductive metal oxide formed on the substrate. The conductive metal oxide preferably includes one or more element selected from a group consisting of tin, tantalum, niobium, titanium, tungsten, and zirconium.

Description

  The present invention relates to a separator and a fuel cell.

  A polymer electrolyte fuel cell (hereinafter referred to as a fuel cell) is a gas diffusion layer that efficiently diffuses reaction gas over the entire electrode on both sides of a membrane electrode assembly (hereinafter also referred to as “MEA”). And a cell sandwiched between a pair of separators provided with a flow path for supplying a reaction gas (fuel gas, oxidant gas) from the outside of the gas diffusion layer (hereinafter sometimes referred to as “fuel cell”) Is the basic configuration. Here, the membrane electrode assembly refers to the oxidation of hydrogen and oxygen, which are power generation fuels, on both sides of a polymer electrolyte membrane containing a polymer having ion conductivity (hereinafter sometimes referred to as “polymer electrolyte”). An electrode called a catalyst layer containing a catalyst for promoting a reduction reaction is formed.

  Of the pair of separators, hydrogen or hydrogen-containing gas is circulated in the flow path of one separator, whereby hydrogen as a fuel is supplied to the fuel cell, and oxygen or oxygen is supplied to the flow path of the other separator. By flowing a gas containing, for example, air, oxygen as fuel is supplied to the fuel cell. In the fuel cell, a direct current is generated by an electrochemical reaction of these gases.

  Such separator forming materials are roughly classified into metal materials and carbon materials. Compared with carbon-based materials that require cutting, stainless steel and other metal-based materials can reduce the thickness of the separator due to the workability unique to the metal. Have advantages.

  However, when a fuel cell is operated, an environment with acidic conditions is created inside the cell. Therefore, separators made of metal-based materials (hereinafter sometimes referred to as “metal separators”) are subject to corrosion under acidic conditions. There is a possibility that metal ions are eluted and the eluted metal ions flow into the polymer electrolyte membrane. The inflowing metal ions react with a peroxide (for example, hydrogen peroxide) generated inside the fuel cell to generate radicals, and the radicals react with the polymer electrolyte membrane. Deterioration of the polymer electrolyte membrane is promoted.

  As one of the methods for solving such problems, the surface of the separator in contact with the electrode is covered with a laminated film of a passive film (oxide film) and a nonmetallic conductive layer, and a conductive material penetrating the laminated film. Therefore, a configuration that ensures electrical continuity has been proposed (see, for example, Patent Document 1).

JP 2010-140886 A

  However, also in the above method, metal ions are eluted from the metal separator due to corrosion, and the eluted metal ions flow into the electrolyte membrane. This inflowing metal ion reacts with a peroxide (for example, hydrogen peroxide) generated inside the fuel cell, thereby generating a radical (for example, a hydroxy radical when it reacts with hydrogen peroxide). Such radicals damage the electrolyte membrane, and consequently promote the deterioration of the electrolyte membrane, so there is still room for improvement.

  This invention is made | formed in view of such a situation, Comprising: It aims at providing the separator by which elution of the metal ion was suppressed. Furthermore, another object is to provide a fuel cell having the above-described separator and having excellent long-term stability.

  In order to solve the above problems, the present invention provides a separator having a base material formed of a metal material and a thin film layer made of a conductive metal oxide formed on the surface of the base material.

  In the present invention, the conductive metal oxide preferably contains one or more elements selected from the group consisting of tin, tantalum, niobium, titanium, tungsten, and zirconium.

  In the present invention, it is desirable that the conductive metal oxide contains tin.

  The present invention is a fuel cell comprising a membrane electrode assembly having a polymer electrolyte membrane and a catalyst layer sandwiching the polymer electrolyte membrane, and a pair of separators sandwiching the membrane electrode assembly, At least one of the pair of separators is the above-described separator, and the fuel cell is characterized in that the thin film layer is disposed on the membrane electrode assembly side.

  According to the present invention, a separator in which elution of metal ions is suppressed can be provided. Moreover, by having such a separator, a fuel cell excellent in long-term stability can be provided.

It is a longitudinal cross-sectional view about the cell of the fuel cell of preferable one Embodiment of this invention.

<Fuel cell>
FIG. 1 is a longitudinal sectional view of a cell of a fuel cell according to a preferred embodiment of the present invention. The fuel cell 10 shown in the figure includes a membrane electrode assembly (MEA) 20 composed of a polymer electrolyte membrane 12 and a pair of catalyst layers 14a and 14b sandwiching the polymer electrolyte membrane 12.

Further, the fuel cell 10 includes a gas diffusion layer 16a and a gas diffusion layer 16b on both sides of the membrane electrode assembly 20, and separators 18a and 18b (separator 18a according to a preferred embodiment of the present invention). On the catalyst layer 14a side, the separator 18b is sequentially provided with a groove (not shown) that forms a flow path for fuel gas or the like on the catalyst layer 14b side. Note that the structure composed of the membrane electrode assembly 20, the gas diffusion layer 16a, and the gas diffusion layer 16b may be generally referred to as a membrane electrode-gas diffusion layer assembly (MEGA).
Hereafter, each structure is demonstrated in order.

<Polymer electrolyte>
As the polymer electrolyte constituting the base material of the polymer electrolyte membrane 12, examples of the polymer electrolyte membrane 12 include a hydrocarbon polymer electrolyte and a fluorine polymer electrolyte as described below. The polymer electrolyte may contain a combination of a fluorine-based polymer electrolyte and a hydrocarbon-based polymer electrolyte. In this case, the hydrocarbon-based polymer electrolyte is based on the total amount (100% by mass) of the polymer electrolyte. Is preferably 51% by mass or more, more preferably 70% by mass or more, still more preferably 85% by mass or more, still more preferably 90% by mass or more. Moreover, as components other than the polymer electrolyte which comprises the base material 12X, additives, such as a plasticizer used for a normal polymer, a stabilizer, a mold release agent, and a water retention agent, are mentioned.

(Hydrocarbon polymer electrolyte)
First, the hydrocarbon polymer electrolyte that can be used for the polymer electrolyte membrane of the present embodiment will be described.

  Here, the hydrocarbon-based polymer electrolyte means a polymer electrolyte having a halogen atom content of 15% by mass or less in terms of a mass content ratio of elements constituting the polymer electrolyte. Such hydrocarbon polymer electrolytes have the advantage of being inexpensive compared to the fluorine polymer electrolytes described above, and therefore more preferred, particularly preferred hydrocarbon polymer electrolytes substantially contain halogen atoms. Such a hydrocarbon-based polymer electrolyte does not generate hydrogen halide during the operation of the fuel cell and does not corrode other members.

  The hydrocarbon-based polymer electrolyte is preferably a polymer having an ion exchange group. The reason is that, when a polymer electrolyte membrane for a fuel cell is obtained using a polymer electrolyte having an ion exchange group as described above, the ion conductivity of the polymer electrolyte membrane is improved.

Examples of the ion exchange group include an acidic ion exchange group (cation exchange group) or a basic ion exchange group (anion exchange group). From the viewpoint of obtaining high proton conductivity, the ion exchange group is preferably a cation exchange group. By using a polymer electrolyte having a cation exchange group, a fuel cell having further excellent power generation performance can be obtained. Examples of the cation exchange group include a sulfo group (—SO ₃ H), a carboxyl group (—COOH), a phosphone group (—PO ₃ H ₂ ), a sulfonylimide group (—SO ₂ NHSO ₂ —), a phenolic hydroxyl group, and the like. Can be given. Among these, as the cation exchange group, a sulfo group or a phosphone group is more preferable, and a sulfo group is particularly preferable. These ion exchange groups may be partially or wholly exchanged with metal ions or quaternary ammonium ions to form a salt, but when used as a fuel cell member, It is preferred that substantially all are in the free acid form. When the ion exchange group is in the form of a free acid, there is an advantage that the polymer electrolyte solution can be more easily prepared in the production of the laminated film described later.

  These ion exchange groups may be introduced into one or both of the main chain and the side chain of the polymer electrolyte, preferably those introduced into the main chain.

  When the polymer electrolyte has an ion exchange group, the introduction amount of the ion exchange group can be represented by an ion exchange group capacity which is the number of ion exchange groups per unit mass of the polymer electrolyte.

  Here, the “ion exchange group capacity” is a value [milli equivalent / g dry resin] defined by the number of equivalents of ion exchange groups contained in 1 g of dry resin in the polymer electrolyte constituting the polymer electrolyte membrane. Hereinafter, meq / g).

  In addition, “dry resin” refers to a resin in which the polymer electrolyte is maintained at a temperature equal to or higher than the boiling point of water, the mass decrease hardly occurs, and the change in mass with time converges to a substantially constant value.

  In the polymer electrolyte used in the present embodiment, the amount of ion exchange groups introduced is preferably 1.0 meq / g or more and 6.0 meq / g or less in terms of ion exchange capacity, and 2.0 meq / g or more and 5.5 meq. / G or less is more preferable, and 2.7 meq / g or more and 5.0 meq / g or less is most preferable. When the ion exchange capacity is within this range, the polymer electrolyte membrane to be obtained has better proton conductivity and water resistance, both of which are excellent because the function as a polymer electrolyte membrane used in a fuel cell is excellent.

Hereinafter, a polymer electrolyte having a suitable ion exchange group will be described in detail. Specific examples of such a polymer electrolyte include polymer electrolytes represented by the following (A) to (F).
(A) a polymer electrolyte in which an ion exchange group is introduced into a polymer whose main chain is an aliphatic hydrocarbon;
(B) a polymer electrolyte in which an ion exchange group is introduced into a polymer in which the main chain is composed of an aliphatic hydrocarbon and a part of the hydrogen atoms of the main chain is substituted with fluorine atoms;
(C) a polymer electrolyte in which an ion exchange group is introduced into a polymer having a main chain having an aromatic ring;
(D) a polymer electrolyte in which an ion exchange group is introduced into a polymer whose main chain has an inorganic unit structure such as a siloxane group or a phosphazene group;
(E) A polymer electrolyte in which two or more structural units constituting the main chain of the polymer used in (A) to (D) are selected, and an ion exchange group is introduced into a copolymer obtained by combining them;
(F) A polymer electrolyte in which an acidic compound such as sulfuric acid or phosphoric acid is introduced into a hydrocarbon polymer containing a nitrogen atom in the main chain or side chain by ionic bond

  In the following examples, the case where the ion exchange group is a sulfo group is mainly exemplified, but this ion exchange group may be replaced with another ion exchange group.

  Examples of the polymer electrolyte (A) include polyvinyl sulfonic acid, polystyrene sulfonic acid, poly (α-methylstyrene) sulfonic acid, and the like.

  As the polymer electrolyte (B), a polymer produced by copolymerization of a fluorocarbon vinyl monomer and a hydrocarbon vinyl monomer described in JP-A-9-102322 has a main chain, and a sulfo group. And a sulfonic acid type polystyrene-graft-ethylene-tetrafluoroethylene copolymer (ETFE) having a side chain as a hydrocarbon chain and having a copolymerization mode of graft polymerization. In addition, a copolymer of a fluorocarbon vinyl monomer and a hydrocarbon vinyl monomer obtained by the method described in U.S. Pat. No. 4,012,303 or U.S. Pat. No. 4,605,685, α Further, sulfonic acid type poly (trifluorostyrene) -graft-ETFE obtained by graft polymerization of .beta.,. Beta.-trifluorostyrene and introducing a sulfo group therein to form a solid polymer electrolyte can also be mentioned.

  The polymer electrolyte (C) may contain a hetero atom such as an oxygen atom in the main chain. Examples of such a polymer electrolyte include polyether ketone, polyether ether ketone, polysulfone, polyether sulfone, polyether ether sulfone, poly (arylene ether), polyimide, poly ((4-phenoxybenzoyl) -1, 4-phenylene), polyphenylquinoxalene and the like each having a sulfo group introduced therein. Specific examples include sulfoarylated polybenzimidazoles and sulfoalkylated polybenzimidazoles (for example, see JP-A-9-110882). A compound in which the main chain is interrupted by a hetero atom such as an oxygen atom may be used. For example, polyether ether ketone, polysulfone, polyether sulfone, poly (arylene ether), polyimide, poly ((4-phenoxybenzoyl) -1,4-phenylene), polyphenylene sulfide, polyphenylquinoxalen, sulfoarylated polybenzimidazole, sulfoalkylated polybenzimidazole, phosphoalkylated polybenzimidazole, phosphonated poly (phenylene ether). Such a polymer electrolyte is disclosed in JP-A-9-110882 and J.A. Appl. Polym. Sci. 18, 1969 (1974).

  Examples of the polymer electrolyte (D) include those in which a sulfo group is introduced into polyphosphazene. These can be found in Polymer Prep. , 41, no. It can be easily produced according to 1,70 (2000).

  The polymer electrolyte of (E) is either a random copolymer having a sulfo group introduced therein, an alternating copolymer having a sulfo group introduced therein, or a block copolymer having a sulfo group introduced therein. There may be.

  Examples of the polymer electrolyte (F) include polybenzimidazole containing phosphoric acid as described in JP-T-11-503262.

  Furthermore, the polymer electrolyte used in the polymer electrolyte membrane of the present embodiment is preferably a copolymer composed of a structural unit having an ion exchange group and a structural unit having no ion exchange group. When such a copolymer is used, the polymer electrolyte membrane prepared by the method described later using the resulting polymer electrolyte exhibits good proton conductivity and water resistance, and is advantageous for fuel cells. There is an advantage. In addition, regarding such a copolymer, the copolymerization mode of the two structural units may be any of random copolymerization, block copolymerization, graft copolymerization or alternating copolymerization, and these copolymerization modes are combined. May be good.

  In order to obtain a polymer electrolyte membrane having good heat resistance for a fuel cell, among the hydrocarbon polymer electrolytes, those having an aromatic ring in the main chain (above (C)) are preferable, and moreover, A hydrocarbon-based polyelectrolyte having an aromatic ring constituting a chain and having an ion exchange group directly bonded to the aromatic ring or indirectly bonded through another atom or atomic group is preferable. In particular, it may have aromatics constituting the main chain, and may further have side chains having aromatic rings, and directly bonded to either the aromatic ring constituting the main chain or the aromatic ring of the side chain. An aromatic polymer electrolyte having an ion exchange group is preferred.

  Particularly preferred aromatic polymer electrolytes include polymer electrolytes having a structural unit having an ion exchange group in the molecular structure and a structural unit having substantially no ion exchange group.

  Examples of the structural unit having an ion exchange group described above include structures represented by the following formulas (11a) to (14a).

（式中、Ａｒ¹〜Ａｒ⁹は、それぞれ同一または相異なり、主鎖に芳香族環を有し、さらに芳香族環を有する側鎖を有してもよい２価の芳香族基を表す。該主鎖の芳香族環か側鎖の芳香族環の少なくとも１つが該芳香族環に直接結合したイオン交換基を有する。
Ｚ、Ｚ’はそれぞれ同一または相異なり−ＣＯ−で示される基、−ＳＯ₂−で示される基のいずれかを表し、Ｘ、Ｘ’、Ｘ”はそれぞれ同一または相異なり−Ｏ−で示される基、−Ｓ−で示される基のいずれかを表す。Ｙは直接結合もしくは下記一般式（１５）で表される基を表す。ｐは０、１又は２を表し、ｑ、ｒはそれぞれ同一または相異なり１、２又は３を表す。）

(In formula, Ar < ¹ > -Ar < ⁹ > is the same or different, respectively, represents the bivalent aromatic group which may have a side chain which has an aromatic ring in a principal chain, and also has an aromatic ring. At least one of the aromatic ring of the main chain or the aromatic ring of the side chain has an ion exchange group directly bonded to the aromatic ring.
Z and Z ′ are the same or different and each represents a group represented by —CO— or a group represented by —SO ₂ —, and X, X ′, and X ″ are each the same or different and represented by —O—. Y represents a direct bond or a group represented by the following general formula (15), p represents 0, 1 or 2, and q and r each represents a group represented by -S-. (The same or different represents 1, 2 or 3.)

  Moreover, as a structural unit which does not have the above-mentioned ion exchange group, the structure shown by following formula (11b)-(14b) can be illustrated.

（式中、Ａｒ¹¹〜Ａｒ¹⁹は、それぞれ同一または相異なり側鎖としての置換基を有していてもよい２価の芳香族炭素基を表す。Ｚ、Ｚ’はそれぞれ同一または相異なり−ＣＯ−で示される基、−ＳＯ₂−で示される基のいずれかを表し、Ｘ、Ｘ’、Ｘ”はそれぞれ同一または相異なり−Ｏ−で示される基、−Ｓ−で示される基のいずれかを表す。Ｙは直接もしくは下記一般式（１５）で表される基を表す。ｐ’は０、１又は２を表し、ｑ’、ｒ’はそれぞれ同一または相異なり１、２又は３を表す。）

(In the formula, Ar ^{11 to} Ar ¹⁹ are the same or different and each represents a divalent aromatic carbon group which may have a substituent as a side chain. Z and Z ′ are the same or different; Represents a group represented by CO— or a group represented by —SO ₂ —, wherein X, X ′, and X ″ are the same or different from each other, a group represented by —O—, and a group represented by —S—. Y represents a group represented directly or by the following general formula (15), p ′ represents 0, 1 or 2, and q ′ and r ′ are the same or different and are 1, 2 or 3 respectively. Represents.)

（式中、Ｒ¹及びＲ²はそれぞれ同一または相異なり、水素原子、置換基を有していてもよい炭素数１〜２０のアルキル基、置換基を有していてもよい炭素数１〜２０のアルコキシ基、置換基を有していてもよい炭素数６〜２０のアリール基、置換基を有していてもよい炭素数６〜２０のアリールオキシ基又は置換基を有していてもよい炭素数２〜２１のアシル基を表し、Ｒ¹とＲ²とが連結して環を形成していてもよい。Ｒ¹とＲ²とが連結して形成される環を有する式（１５）の基としては、シクロヘキシリデン基などの炭素数５〜２０の２価の環状炭化水素基があげられる。）

(In formula, R < ¹ > and R < ² > are the same or different, respectively, a hydrogen atom, the C1-C20 alkyl group which may have a substituent, and C1-C1 which may have a substituent. It may have an alkoxy group having 20 carbon atoms, an aryl group having 6 to 20 carbon atoms which may have a substituent, an aryloxy group having 6 to 20 carbon atoms which may have a substituent, or a substituent. Represents a good acyl group having 2 to 21 carbon atoms, and R ¹ and R ² may be linked to form a ring, wherein R ¹ and R ² are linked to form a ring (15 ) Is a divalent cyclic hydrocarbon group having 5 to 20 carbon atoms such as a cyclohexylidene group.

In the formulas (11a) to (14a) showing the structural unit having an ion exchange group, Ar ^{1 to} Ar ⁹ represent a divalent aromatic group. Examples of the divalent aromatic group include bivalent monocyclic aromatic groups such as 1,3-phenylene group and 1,4-phenylene group, 1,3-naphthalenediyl group, and 1,4-naphthalenediyl group. Divalent condensed aromatics such as 1,5-naphthalenediyl group, 1,6-naphthalenediyl group, 1,7-naphthalenediyl group, 2,6-naphthalenediyl group, 2,7-naphthalenediyl group, etc. Group, pyrrole, 2H-pyrrole, imidazole, pyrazole, isoxazole, pyridine, pyrazine, pyrimidine, pyridazine, indolizine, isoindole, 3H-indole, indole, 1H-indazole, purine, 4H-quinolidine, quinoline, isoquinoline, Phthalazine, naphthyridine, quinoxaline, quinazoline, cinnoline, pteridine, carbazole, carboline, Enanthridine, acridine, perimidine, phenanthroline, phenazine, furazane, phenoxazine, pyrrolidine, pyrroline, imidazoline, imidazolidine, pyrazolidine, pyrazoline, piperidine, piperazine, indoline, isoindoline, quinuclidine, oxazole, benzoxazole, 1,3,5- A heteroaromatic group obtained by removing two hydrogen atoms on an aromatic ring from one selected from the group consisting of triazine, brine, tetrazole, tetrazine, triazole, phenalsazine, benzimidazole, and benzotriazole, or the following formula (N-01 ) To (N-07), and a heteroaromatic group containing at least one structure selected from the group consisting of structures represented by (N-07).

Ar ^{1 to} Ar ⁹ in the formulas (11a) to (14a) are preferably divalent monocyclic aromatic groups such as 1,3-phenylene group and 1,4-phenylene group, 1,3-naphthalene. Diyl group, 1,4-naphthalenediyl group, 1,5-naphthalenediyl group, 1,6-naphthalenediyl group, 1,7-naphthalenediyl group, 2,6-naphthalenediyl group, 2,7-naphthalenediyl group And the like, more preferably a divalent monocyclic aromatic group.

Moreover, Ar < ¹ > -Ar < ⁹ > in Formula (11a)-(14a) is the C1-C20 alkyl group which may have a substituent, and the C1-C20 which may have a substituent. An alkoxy group having 6 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms which may have a substituent, an aryloxy group having 6 to 20 carbon atoms which may have a substituent, or a substituent. It may be substituted with an acyl group having 2 to 21 carbon atoms.

Ar ^{1 to} Ar ⁹ in formulas (11a) to (14a) have at least one ion exchange group in the aromatic ring. Specific examples and preferred examples of the ion exchange group are the same as those described above. These ion exchange groups may be introduced into either or both of the main chain and the side chain of the polymer electrolyte, but those introduced into the aromatic ring of the main chain are preferred. As the ion exchange group, an acidic ion exchange group is preferable as described above, and among the acidic ion exchange groups, a sulfo group or a phosphone group is more preferable, and a sulfo group is particularly preferable.

  Moreover, the following formula (14a-1) can be given as one example of the structural unit having an ion exchange group represented by the formula (14a).

(上記式１４ａ−１中、Ａｒ^１１０、Ａｒ^１２０、Ａｒ^１３０は、それぞれ独立に、２価の芳香族基を示し、該芳香環上の水素原子はフッ素原子で置換されていてもよい。Ｙは、−ＣＯ−、−ＳＯ_２−、−ＳＯ−、−ＣＯＮＨ−，−ＣＯＯ−、−（ＣＦ_２）_ｕ０００−（ｕ０００は１〜１０の整数である）、−Ｃ（ＣＦ_３）_２−または直接結合を示す。Ｚ^０００は、−Ｏ−、−Ｓ−、直接結合、−ＣＯ−、−ＳＯ_２−、−ＳＯ−、−（ＣＨ_２）_l０００−（ｌ０００は１〜１０の整数である）または−Ｃ（ＣＨ_３）_２−を示す。Ｒ^１１０は、直接結合、−Ｏ（ＣＨ_２）_ｐ０００−、−Ｏ（ＣＦ_２）_ｐ０００−、−（ＣＨ_２）_ｐ０００−または−（ＣＦ_２）_ｐ０００−を示す（ｐ０００は、１〜１２の整数を示す）。Ｒ^１２０、Ｒ^１３０は、それぞれ独立に、水素原子、アルカリ金属原子または炭化水素基を示す。ただし、上記式中に含まれる全てのＲ^１２０およびＲ^１３０のうち少なくとも１個は水素原子である。ｘ１００は、０〜４の整数。ｘ２００は、１〜５の整数。a０００は、０〜１の整数。ｂ０００は、０〜３の整数を示す。）

(In the formula 14a-1, Ar ¹¹⁰ , Ar ¹²⁰ , and Ar ¹³⁰ each independently represent a divalent aromatic group, and a hydrogen atom on the aromatic ring may be substituted with a fluorine atom. Y _Are —CO—, —SO ₂ —, _{—SO—, —CONH—, —COO—} , — (CF ₂ ) _u000 — (u000 is an integer of 1 to 10), —C (CF ₃ ) ₂ —. Or Z ⁰⁰⁰ represents —O—, —S—, direct bond, —CO—, —SO ₂ —, _—SO— , — (CH ₂ ) 1 ₀₀₀ — (1000 is an integer of 1 to 10). there) or -C _{(CH 3) 2} - are shown ^{.R 110} is a direct _{bond, -O (CH 2) p000 -} , - O (CF 2) p000 -, - (CH 2) p000 - or - (CF _{2) p000} - shows a (p000 shows an integer of 1 to 12) R ^{120, R 130} are each independently a hydrogen atom, an alkali metal atom or a hydrocarbon group. Provided that at least one of all ^{R 120} and ^{R 130} contained in the formula is a hydrogen atom. x100 is an integer of 0 to 4. x200 is an integer of 1 to 5. a000 is an integer of 0 to 1. b000 represents an integer of 0 to 3.)

Ar ¹¹⁰ , Ar ¹²⁰ and Ar ¹³⁰ in the formula (14a-1) represent a divalent aromatic group. Examples of the divalent aromatic group include those similar to Ar ^{1 to} Ar ⁹ in formulas (11a) to (14a).

R ¹²⁰ and R ¹³⁰ each independently represent a hydrogen atom, an alkali metal atom or a hydrocarbon group. Examples of the alkali metal atom include lithium, sodium, potassium, rubidium, cesium, and rubidium. Examples of the hydrocarbon group include a methyl group, an ethyl group, an n-propyl group, an iso-propyl group, and a tert-butyl group. 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 group, tetrahydrofurfuryl group, 2-methylbutyl group, 3,3-dimethyl-2,4-dioxolanemethyl group, cyclohexylmethyl group , Adamantylmethyl group, bicyclo [2.2.1] hep Examples thereof include a linear hydrocarbon group such as a tilmethyl group, a branched hydrocarbon group, an alicyclic hydrocarbon group, and a hydrocarbon group having a heterocyclic ring. Of these, n-butyl group, neopentyl group, tetrahydrofurfuryl group, cyclopentyl group, cyclohexyl group, cyclohexylmethyl group, adamantylmethyl group, and bicyclo [2.2.1] heptylmethyl group are preferable, and neopentyl group is more preferable. . R ¹²⁰ and R ¹³⁰ are preferably hydrogen atoms.

  The structural unit represented by the above formula (14a-1) is preferably represented by the following formula (14a-2).

（式(１４ａ-２)中、Ｙ^００１は−ＣＯ−、−ＳＯ_２−、−ＳＯ−、−ＣＯＮＨ−、−ＣＯＯ−、−（ＣＦ_２）_ｌ−（ここでのｌは１〜１０の整数である）、−Ｃ（ＣＦ_３）_２−からなる群より選ばれた少なくとも１種の構造を示し、Ｚ^００１は直接結合または、−（ＣＨ_２）_ｌ−（ここでのｌは１〜１０の整数である）、−Ｃ（ＣＨ_３）_２−、−Ｏ−、−Ｓ−、−ＣＯ−、−ＳＯ_２−からなる群より選ばれた少なくとも１種の構造を示し、Ａｒ^００１は−ＳＯ3Ｈまたは−Ｏ（ＣＨ_２）_ｐＳＯ_３Ｈまたは−Ｏ（ＣＦ_２）_ｐＳＯ_３Ｈで表される置換基を有する芳香族基を示す。ｐは１〜１２の整数を示し、ｍは０〜１０の整数を示し、ｎは０〜１０の整数を示し、ｋは１〜４の整数を示す。）

(In the formula (14a-2), Y ⁰⁰¹ is —CO—, —SO ₂ —, —SO—, —CONH—, —COO—, — (CF ₂ ) ₁ — (where l is 1 to 10 Is an integer), and represents at least one structure selected from the group consisting of —C (CF ₃ ) ₂ —, wherein Z ⁰⁰¹ is a direct bond or — (CH ₂ ) ₁ — (where l is 1 to 1) 10 is an integer _{of), - C (CH 3)} 2 -, - O -, - S -, - CO -, - SO 2 - represents at least one structure selected from the group consisting ^{of, Ar 001} is —SO ₃ H or —O (CH ₂ ) _p SO ₃ H or —O (CF ₂ ) _p represents an aromatic group having a substituent represented by _p SO ₃ H. _p represents an integer of 1 to 12, m represents An integer of 0 to 10 is shown, n is an integer of 0 to 10, and k is an integer of 1 to 4.

  Specific examples of the structural unit having an ion exchange group represented by the above formula (14a-2) include the following formulas (4a-13) to (4a-20).

On the other hand, in the formulas (11b) to (14b) indicating the structural units having no ion exchange group, Ar ^{11 to} Ar ¹⁹ represent divalent aromatic groups independent of each other. Examples of the divalent aromatic group include bivalent monocyclic aromatic groups such as 1,3-phenylene group and 1,4-phenylene group, 1,3-naphthalenediyl group, and 1,4-naphthalenediyl group. Divalent condensed aromatics such as 1,5-naphthalenediyl group, 1,6-naphthalenediyl group, 1,7-naphthalenediyl group, 2,6-naphthalenediyl group, 2,7-naphthalenediyl group, etc. Group, pyrrole, 2H-pyrrole, imidazole, pyrazole, isoxazole, pyridine, pyrazine, pyrimidine, pyridazine, indolizine, isoindole, 3H-indole, indole, 1H-indazole, purine, 4H-quinolidine, quinoline, isoquinoline, Phthalazine, naphthyridine, quinoxaline, quinazoline, cinnoline, pteridine, carbazole, carboline, Enanthridine, acridine, perimidine, phenanthroline, phenazine, furazane, phenoxazine, pyrrolidine, pyrroline, imidazoline, imidazolidine, pyrazolidine, pyrazoline, piperidine, piperazine, indoline, isoindoline, quinuclidine, oxazole, benzoxazole, 1,3,5- A heteroaromatic group obtained by removing two hydrogen atoms on an aromatic ring from one selected from the group consisting of triazine, brine, tetrazole, tetrazine, triazole, phenalsazine, benzimidazole, and benzotriazole, or the following formula (N- And a heteroaromatic group containing at least one structure selected from the group consisting of structures represented by (01) to (N-07).

Ar ^{11 to} Ar ¹⁹ in the formulas (11b) to (14b) are preferably a bivalent monocyclic aromatic group such as a 1,3-phenylene group or a 1,4-phenylene group, or 1,3-naphthalene. Diyl group, 1,4-naphthalenediyl group, 1,5-naphthalenediyl group, 1,6-naphthalenediyl group, 1,7-naphthalenediyl group, 2,6-naphthalenediyl group, 2,7-naphthalenediyl group And the like, more preferably a divalent monocyclic aromatic group.

Ar ^{11 to} Ar ¹⁹ are each a fluorine atom, a formyl group, a cyano group, an optionally substituted alkyl group having 1 to 20 carbon atoms, or an optionally substituted carbon atom having 1 to 20 carbon atoms. An alkoxy group having 6 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms which may have a substituent, an aryloxy group having 6 to 20 carbon atoms which may have a substituent, or a substituent. It may be substituted with an acyl group having 2 to 21 carbon atoms. The “optionally substituted” substituent here does not include an ion exchange group.

Here, the substituents of the aforementioned divalent aromatic groups (Ar ^{1 to} Ar ⁹ in formulas (11a) to (14a) and Ar ^{11 to} Ar ¹⁹ in formulas (11b) to (14b)) are exemplified. .

  Examples of the alkyl group having 1 to 20 carbon atoms which may have a substituent include, for example, methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, sec-butyl group, isobutyl group, n -Pentyl group, 2,2-dimethylpropyl group, cyclopentyl group, n-hexyl group, cyclohexyl group, 2-methylpentyl group, 2-ethylhexyl group, nonyl group, dodecyl group, hexadecyl group, octadecyl group, icosyl group, etc. Alkyl groups having 1 to 20 carbon atoms, and these groups include fluorine atom, hydroxyl group, nitrile group, amino group, methoxy group, ethoxy group, isopropyloxy group, phenyl group, naphthyl group, phenoxy group, naphthyloxy group, etc. Examples thereof include an alkyl group which is substituted and has a total carbon number of 20 or less.

  Examples of the alkoxy group having 1 to 20 carbon atoms which may have a substituent include a methoxy group, an ethoxy group, an n-propyloxy group, an isopropyloxy group, an n-butyloxy group, a sec-butyloxy group, and a tert- Butyloxy group, isobutyloxy group, n-pentyloxy group, 2,2-dimethylpropyloxy group, cyclopentyloxy group, n-hexyloxy group, cyclohexyloxy group, 2-methylpentyloxy group, 2-ethylhexyloxy group, dodecyl C1-C20 alkoxy groups such as oxy group, hexadecyloxy group, icosyloxy group, etc., and fluorine atom, hydroxyl group, nitrile group, amino group, methoxy group, ethoxy group, isopropyloxy group, phenyl group for these groups , Naphthyl group, phenoxy group, naphthyloxy group There is substituted, the total carbon number and an alkoxy group having 20 or less.

  Examples of the aryl group having 6 to 20 carbon atoms which may have a substituent include aryl groups such as a phenyl group, a naphthyl group, a phenanthrenyl group, and an anthracenyl group, and these groups include a fluorine atom, a hydroxyl group, and a nitrile. Group, amino group, methoxy group, ethoxy group, isopropyloxy group, phenyl group, naphthyl group, phenoxy group, naphthyloxy group and the like are substituted, and aryl groups having a total carbon number of 20 or less can be mentioned.

Examples of the aryloxy group having 6 to 20 carbon atoms that may have a substituent include aryloxy groups such as a phenoxy group, a naphthyloxy group, a phenanthrenyloxy group, and an anthracenyloxy group, and the like. Are substituted with fluorine atom, hydroxyl group, nitrile group, amino group, methoxy group, ethoxy group, isopropyloxy group, phenyl group, naphthyl group, phenoxy group, naphthyloxy group, etc. A certain aryloxy group is mentioned.

  Examples of the optionally substituted acyl group having 2 to 21 carbon atoms include acetyl group, propionyl group, butyryl group, isobutyryl group, pivaloyl group, benzoyl group, 1-naphthoyl group, and 2-naphthoyl group. Acyl groups having 2 to 20 carbon atoms, and fluorine, hydroxyl, nitrile, amino, methoxy, ethoxy, isopropyloxy, phenyl, naphthyl, phenoxy, naphthyloxy, etc. And an acyl group having a total carbon number of 21 or less.

  Among these aromatic ring substituents, aryl groups such as phenyl group, naphthyl group, phenanthrenyl group, anthracenyl group, aryloxy groups such as phenoxy group, naphthyloxy group, phenanthrenyloxy group, anthracenyloxy group, An acyl group having an aromatic ring such as a benzoyl group, a 1-naphthoyl group, or a 2-naphthoyl group is preferable because the heat resistance of the polymer tends to be good and a more practical fuel cell member can be obtained.

In a polymer electrolyte including a polymer having an acyl group having an aromatic ring as an aromatic ring substituent, two structural units having the acyl group are adjacent to each other, and the acyl groups in the two structural units are bonded to each other. In some cases, the structure is changed by causing a rearrangement reaction after the acyl groups are bonded to each other. Whether such a structural change has occurred can be confirmed by measuring, for example, a ¹³ C-nuclear magnetic resonance spectrum.

  In addition, as one of the preferable elements of the hydrocarbon-based polymer electrolyte in the present invention, it is a polymer electrolyte having a halogen atom content of 15% by mass or less in terms of a mass content ratio of elements constituting the polymer electrolyte. can give. Such hydrocarbon polymer electrolytes have the advantage of being inexpensive compared to the fluorine polymer electrolytes described above, and therefore more preferred, particularly preferred hydrocarbon polymer electrolytes substantially contain halogen atoms. Such a hydrocarbon-based polymer electrolyte does not generate hydrogen halide during the operation of the fuel cell and does not corrode other members.

  The hydrocarbon-based polymer electrolyte includes a structural unit having an ion exchange group and a structural unit having no ion exchange group, and a dense phase of the structural unit having an ion exchange group is a continuous phase in the film thickness direction. Can be formed, because there is an advantage that a polymer electrolyte membrane having more excellent proton conductivity can be obtained.

  In the present invention, suitable polymer electrolytes are represented by the structural units having an ion exchange group, which are composed of the structural units represented by the formulas (11a) to (14a), and the formulas (11b) to (14b). And a structural unit having substantially no ion exchange group. Such a polymer electrolyte can be obtained as a copolymer starting from a monomer or oligomer corresponding to each of a structural unit having an ion exchange group and a structural unit having substantially no ion exchange group. it can. In such a copolymer, suitable combinations of a structural unit having an ion exchange group and a structural unit having substantially no ion exchange group are shown in <a> to <su> in Table 1 below. You can give a combination.

  More preferably, the structure of the polymer electrolyte suitably used in the present invention is <A>, <U>, <D>, <K>, <K>, <K>, <K>, <B> Or <su>, more preferably <ki>, <ku>, <si> or <su>, and particularly preferably <ki>, <ku>, <si>.

  Specific examples of the suitable copolymer include one or more structural units selected from the following structural units having an ion exchange group and the following structural units having no ion exchange group. Examples of the copolymer include one or more structural units. In addition, the ion exchange group in the repeating unit which has an ion exchange group is illustrated by the suitable sulfo group. Of course, any of the above-described ion exchange groups may be employed instead of the sulfo group.

  In addition, these structural units may be directly bonded to each other, or may be connected to each other with an appropriate atom or atomic group. As typical examples of the atoms or atomic groups connecting the structural units here, a divalent aromatic group, an oxygen atom, a sulfur atom, a carbonyl group, a sulfonyl group, or a divalent group formed by combining these is used. I can give you.

(Structural unit having an ion exchange group)

(Structural unit without ion exchange group)

（４ｂ−１５）〜（４ｂ−３２）中、ｒ０００は０または１以上の整数を示す。ｒ０００は、好ましくは１００以下であり、 より好ましくは１以上８０以下である。

In (4b-15) to (4b-32), r000 represents 0 or an integer of 1 or more. r000 is preferably 100 or less, more preferably 1 or more and 80 or less.

  Among the examples described above, structural units having an ion exchange group include (4a-1), (4a-2), (4a-3), (4a-4), (4a-5), and (4a-6). One or more structural units selected from the group consisting of: (4a-7), (4a-8), (4a-9), (4a-10), (4a-11), (4a-12) are preferred. . Similarly, (4a-10), (4a-11), and (4a-12) are more preferable, and (4a-11) and (4a-12) are particularly preferable.

  A polymer electrolyte having a segment containing such a structural unit, particularly a polymer electrolyte having a segment containing such a structural unit as a repeating unit (segment having an ion exchange group) has a polyarylene structure. Therefore, the chemical stability tends to be relatively good.

  Moreover, as a structural unit which does not have an ion exchange group, (4b-1), (4b-2), (4b-3), (4b-4), (4b-5), (4b-6), ( 4b-7), (4b-8), (4b-9), (4b-10), (4b-11), (4b-12), (4b-13), (4b-14) One or more selected structural units are preferred. Similarly, (4b-2), (4b-3), (4b-10), (4b-13), and (4b-14) are more preferable.

  The hydrocarbon-based polymer electrolyte has a structural unit having an ion exchange group and a structural unit not having an ion exchange group. The copolymerization mode of these two structural units is random copolymerization, Any of alternating copolymerization, block copolymerization, and graft copolymerization may be used, or a combination of these copolymerization modes may be used. Random copolymerization, block copolymerization, and graft copolymerization are preferred, random copolymerization and block copolymerization are more preferred, and block copolymerization is particularly preferred.

  As block copolymers, segments mainly composed of structural units having ion-exchange groups (segments having ion-exchange groups) and segments composed mainly of structural units not having ion-exchange groups (substantially having ion-exchange groups). Having no segment) is preferred. Such a block copolymer has an advantage that a polymer electrolyte membrane having more excellent proton conductivity can be obtained by forming a continuous phase in the film thickness direction with a dense phase having segments having ion exchange groups. Moreover, when the combination of the structural unit which comprises the segment which has a suitable ion exchange group, and the structural unit which comprises the segment which does not have an ion exchange group substantially is given, <a>-<su> of following Table 2 The combination of the segment shown can be mention | raise | lifted.

  <I>, <U>, <D>, <K>, <K>, <K>, <K>, <Shi>, or <S>, and more preferably <K>. , <Ku>, <si> or <su>, <ki>, <ku> and <si> are particularly preferred.

  Among the above examples, structural units used for the repeating unit constituting the segment having an ion exchange group include (4a-1), (4a-2), (4a-3), (4a-4), (4a- 5), (4a-6), (4a-7), (4a-8), (4a-9), (4a-10), (4a-11) and (4a-12). One or more structural units are preferable, and one or more structural units selected from the group consisting of (4a-10), (4a-11), and (4a-12) are more preferable, and (4a-11) or (4a -12) is particularly preferred.

  As one of the preferred embodiments of the aromatic polymer electrolyte membrane according to the present invention, a polyarylene having a polyarylene structure in which a main chain of a segment having an ion exchange group is substantially formed by directly connecting a plurality of aromatic rings It is a system block copolymer. As the structural unit of such a segment, the above-mentioned (4a-10), (4a-11), (4a-12), (4a-13), (4a-14), (4a-15), ( 4a-16), (4a-17), (4a-18), (4a-19) and one or more structural units selected from the group consisting of (4a-20) are preferred, (4a-10), ( One or more structural units selected from the group consisting of 4a-11) and (4a-12) are more preferred, and (4a-11) or (4a-12) is particularly preferred.

  A polymer electrolyte having a segment (a segment having an ion exchange group) containing such a structural unit as a repeating unit, in particular, a polymer electrolyte having a segment consisting of such a repeating unit can exhibit excellent ionic conductivity. Therefore, since the segment has a polyarylene structure, the chemical stability tends to be relatively good.

  Here, the “polyarylene structure” is a form in which the aromatic rings constituting the main chain are substantially directly bonded to each other. Specifically, the total number of bonds between the aromatic rings is 100. %, The direct bond ratio is preferably 80% or more, more preferably 90% or more, and even more preferably 95% or more. The bond other than the direct bond is a form in which the aromatic rings are bonded with a divalent atom or a divalent atomic group.

  As the structural unit used for the repeating unit constituting the segment having no ion exchange group, (4b-1), (4b-2), (4b-3), (4b-4), (4b-5), (4b-6), (4b-7), (4b-8), (4b-9), (4b-10), (4b-11), (4b-12), (4b-13) and (4b -14) is preferably one or more structural units selected from the group consisting of (4b-2), (4b-3), (4b-9), (4b-10), (4b-13) and (4b). -14) is more preferably one or more structural units selected from the group consisting of (4b-2), (4b-3), (4b-13) and (4b-14). The above structural units are more preferable, and are the groups consisting of (4b-2), (4b-3) and (4b-14)? One or more structural units selected is particularly preferable.

  In addition, the segment having an ion exchange group and the segment having substantially no ion exchange group may be directly bonded or may be connected by an appropriate atom or atomic group. Typical examples of the atoms or atomic groups connecting the segments here include a divalent aromatic group, an oxygen atom, a sulfur atom, a carbonyl group, a sulfonyl group, or a divalent group formed by combining these. be able to.

  Specifically, when a suitable block copolymer is mentioned, a segment (segment having an ion exchange group) containing one or more structural units selected from the structural units having an ion exchange group shown above, and the above And a block copolymer comprising one or more structural units selected from structural units having no ion exchange groups (segments substantially having no ion exchange groups). .

  Here, the “segment having an ion exchange group” means that the ion exchange group is a segment containing an average of 0.5 or more per structural unit constituting the segment. It is more preferable that an average of 1.0 or more per one is included.

  On the other hand, “a segment having substantially no ion exchange group” means that the ion exchange group is a segment having an average of less than 0.5 per structural unit constituting the segment, The average per unit is preferably 0.1 or less, and more preferably 0.05 or less on average.

  Typically, a block copolymer in a form in which a segment having an ion exchange group and a segment having substantially no ion exchange group are bonded by a direct bond or bonded by an appropriate atom or atomic group. is there.

  The degree of polymerization of the segment composed of the structural unit selected from the above formulas (11a) to (14a) is 2 or more, preferably 3 or more, more preferably 5 or more, and still more preferably 10 or more. Further, the polymerization degree of the segment is preferably 1000 or less, and preferably 500 or less. If the degree of polymerization is 2 or more, preferably 5 or more, sufficient proton conductivity is expressed as a polymer electrolyte for a fuel cell, and if the degree of polymerization is 1000 or less, the advantage is that manufacture is easier. There is.

  Moreover, the polymerization degree of the segment which consists of a structural unit chosen from Formula (11b)-(14b) is 1 or more, 2 or more are preferable and 3 or more are more preferable. Further, the polymerization degree of the segment is preferably 100 or less, more preferably 90 or less, and still more preferably 80 or less. Within such a range, the polymer electrolyte for a fuel cell is preferable because it has sufficient mechanical strength and is easy to produce.

  Moreover, the molecular weight of the hydrocarbon-based polymer electrolyte used in the present invention is preferably 5,000 to 1,000,000, more preferably 10,000 to 800,000, and more preferably 10,000 to 600,000 in terms of polystyrene-reduced number average molecular weight. More preferably, it is more preferably 15,000 to 400,000. By using a polymer electrolyte having a molecular weight in such a range, a polymer electrolyte membrane prepared by a method described later tends to stably maintain the shape of the membrane. The number average molecular weight is measured by gel permeation chromatography (GPC).

(Fluoropolymer electrolyte)
Moreover, what is generally known can be illustrated as a fluorine-type polymer electrolyte which can be used for the polymer electrolyte membrane of this embodiment. For example, what substituted the hydrogen atom which the above-mentioned hydrocarbon type polymer electrolyte has as a substituent with the fluorine atom can be used. Specifically, a perfluoroalkyl sulfonic acid polymer and a perfluorocarboxylic acid polymer are exemplified. In addition, fluorine polymer electrolytes such as Nafion (registered trademark of DuPont), Aciplex (Asahi Kasei registered trademark) manufactured by Asahi Kasei, and Flemion (registered trademark of Asahi Glass) manufactured by Asahi Glass, and the above-mentioned JP-A-2006-32157 The described fluorine-based polymer electrolytes can also be used.
In addition, a fluorine-type polymer electrolyte means the polymer electrolyte in which a fluorine atom exceeds 15 mass% when represented with the element mass content ratio which comprises the said polymer electrolyte.

<Catalyst layer>
The catalyst layer 14 a and the catalyst layer 14 b are layers that function as electrode layers in the fuel cell 10. The catalyst layer 14a and the catalyst layer 14b include an electrode catalyst (hereinafter also referred to as a catalyst) and an electrolyte having proton conductivity such as a perfluoroalkylsulfonic acid resin.

  Here, the catalyst used for the catalyst layer 14a and the catalyst layer 14b is not particularly limited as long as it can activate the oxidation-reduction reaction with hydrogen or oxygen, and a known one can be used. It is preferable to use platinum alloy fine particles as a catalyst. The fine particles of platinum or platinum-based alloys are often used by being supported on particulate or fibrous carbon such as activated carbon or graphite.

  A known material can be used for the conductive material as the current collector, but porous carbon woven fabric, carbon non-woven fabric, or carbon paper is preferable in order to efficiently transport the raw material gas to the catalyst.

<Gas diffusion layer>
The gas diffusion layer 16a and the gas diffusion layer 16b are layers having a function of promoting the diffusion of the raw material gas into the catalyst layer 14a and the catalyst layer 14b. The gas diffusion layer 16a and the gas diffusion layer 16b are preferably made of a porous material having electron conductivity. The porous material is preferably a porous carbon non-woven fabric or carbon paper because the source gas can be efficiently transported to the catalyst layer 14a and the catalyst layer 14b.

<Separator>
The separator 18a and the separator 18b have a laminated structure of a base material made of a metal material having electronic conductivity and a thin film layer made of an acid-resistant conductive metal oxide formed on the surface of the base material. doing. The thin film layer is formed on at least the surface on the catalyst layer side of the separator 18a and the separator 18b. Specifically, the portion facing the gas diffusion layer in the surface of the separator on the catalyst layer side is under strongly acidic conditions under the operating condition of the fuel cell, so that at least the portion facing the gas diffusion layer has a thin film layer. Is formed. When a groove serving as a flow path for fuel gas or the like is formed on the catalyst layer 14a side of the separator 18a and the catalyst layer 14b side of the separator 18b, a thin film layer is formed to cover the surface of the groove. Of course, the thin film layer may be formed on the entire surface on the catalyst layer side, or may be formed on both surfaces of the substrate.

  In such a separator 18a and separator 18b, since the thin film layer formed on the surface of the substrate has acid resistance, the separator does not dissolve even under the operating condition of the fuel cell, and metal ions are eluted from the separator. There is no.

  Further, the separator needs to have a function of conducting electricity (electrons) in contact with the catalyst layer, but in the separator 18a and the separator 18b of the present embodiment, the thin film layer is formed of a conductive metal oxide. The conductivity required for the separator is not impaired.

  As the material for forming the base material, a single metal or an alloy is used, and examples thereof include titanium and stainless steel. Stainless steel is preferable as the material of the base material because it is easy to process and hardly corrodes even under acidic conditions.

  As a material for forming the thin film layer, various materials can be used as long as they are conductive and have acid corrosion resistance as long as they are metal oxides (conductive metal oxides). Among these, a metal oxide containing at least one element selected from the group consisting of tin, tantalum, niobium, titanium, tungsten, and zirconium is preferable, and a metal oxide containing tin is more preferable. As the metal oxide containing tin, zinc tin oxide (ZTO) can be suitably used.

  When zinc tin oxide is used as the material for forming the thin film layer, it is preferable to contain more tin from the viewpoint of chemical durability, and a predetermined amount of zinc is preferably contained from the viewpoint of conductivity. In the zinc tin oxide as the forming material, the molar ratio of Sn to the sum of tin (Sn) and zinc (Zn) (Sn / (Sn + Zn)) is preferably in the range of 0.7 to 0.9. . When the molar ratio is less than 0.7, the thin film layer is less likely to have conductivity, and the conductivity of the entire separator having the thin film layer formed on the surface is difficult to obtain. Moreover, since the acid resistance of a separator will fall when the said molar ratio becomes larger than 0.9, it becomes difficult to suppress elution of a metal ion.

  Moreover, it is preferable that ratio ((Sn + Zn) / ZTO) of the sum of tin and zinc with respect to the whole zinc tin oxide (ZTO) is the range of 0.7-0.8.

  Furthermore, it is preferable that the ratio (Sn / ZTO) of tin with respect to the whole zinc tin oxide which comprises a thin film layer is the range of 0.6-0.8. The tin concentration may be uniform in the layer thickness direction of the thin film layer or may vary in the layer thickness direction.

  Moreover, it is preferable that the thin film layer is formed in the film thickness of 1 micrometer or less on the surface of a base material.

  The thin film layer can be formed by forming a film on the surface of the base material using a physical vapor deposition method or a chemical vapor deposition method using the above-described conductive metal oxide as a forming material. Examples of physical vapor deposition include sputtering, ion plating, and chemical vapor deposition include chemical vapor deposition.

  In addition, it is produced by applying the above-mentioned conductive metal oxide dispersion on the substrate surface. The particle size of the conductive metal oxide dispersed in the dispersion is, for example, 10 nm or more and 1000 nm or less. Examples of the solvent used in the solution or the dispersion medium used in the dispersion include water; alcohols such as methanol, ethanol, and propanol; ethers such as diethyl ether, dimethyl ether, and tetrahydrofuran; acetone, methyl ethyl ketone (MEK), and the like. Ketones; aliphatic hydrocarbons such as pentane and hexane.

  Such a fuel cell 10 is the minimum unit of a polymer electrolyte fuel cell, but the output of a single fuel cell 10 (cell) is limited. Therefore, it is preferable to use a fuel cell stack by connecting a plurality of fuel cells 10 in series so as to obtain a required output. Separator 18a and separator 18b have a function of dividing a plurality of fuel cells in a fuel cell stack in which a plurality of fuel cells are integrated.

  Such a fuel cell 10 can be operated as a solid polymer fuel cell when the fuel is hydrogen, and as a direct methanol fuel cell when the fuel is methanol.

  According to the separator configured as described above, elution of metal ions can be suppressed. Moreover, the fuel cell having the above-described configuration has excellent long-term stability by including the above-described separator.

  EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited to these examples.

(Preparation of catalyst ink)
Platinum-supported carbon in which platinum is supported on 6.30 g of commercially available 5% by weight Nafion (registered trademark) solution (manufactured by Aldrich, solvent: mixture of water and lower alcohol) (manufactured by N.E. Chemcat Co., Ltd.) 5.00 g of SA50BK (platinum content 50% by weight) was added, and 43.45 g of ethanol and 6.43 g of water were further added. The obtained mixture was subjected to ultrasonic treatment for 1 hour and then stirred with a stirrer for 5 hours to obtain a catalyst ink.

(Production of membrane-electrode assembly)
The catalyst ink described above was applied by spraying to a 5 cm × 5 cm region in the center of one side of a commercially available Nafion XL (Du Pont, 25 μm). At this time, the distance from the discharge port to the film was set to 6 cm, and the stage temperature was set to 75 ° C. After overcoating in the same manner, the solvent was removed to form an anode catalyst layer. As an anode catalyst layer, 6.6 mg of solid content (platinum weight: 0.1 mg / cm ² ) was applied. Subsequently, a catalyst ink was similarly applied to the other surface to form a cathode catalyst layer to obtain an MEA. As a cathode catalyst layer, 13.2 mg of solid content (platinum weight: 0.2 mg / cm ² ) was applied.

(Production of metal separator)
A metal separator having a thickness of 5 mm using SUS316L as stainless steel was produced. The gas flow path shape and electrode area were the same as those of the JARI cell separator.

(Vapor deposition of zinc-tin oxide on metal separator)
Zinc oxide powder (ZnO, manufactured by Koyo Chemical Co., Ltd., purity 99.99%) and tin oxide powder (SnO ₂ , manufactured by Koyo Chemical Co., Ltd., purity 99.99%) were used as Zn: Sn at 20:80. And were mixed by a dry ball mill using zirconia balls having a diameter of 5 mm. The obtained mixed powder was put in an alumina crucible and calcined at 900 ° C. for 5 hours in an air atmosphere, and then pulverized by a dry ball mill using zirconia balls having a diameter of 5 mm. The obtained powder was molded into a disk shape by a uniaxial press using a mold at a pressure of 500 kgf / cm ² . Further, the compact was pressed at a pressure of 2000 kgf / cm ² using a cold isostatic press (CIP), and then held at 1200 ° C. for 5 hours in an oxygen atmosphere and fired to obtain a sintered body. It was.

  The sintered body is crushed and used as a 2-5 mm ion plating target, installed in a pressure gradient ion plating apparatus, a metal separator is used as a support, and the metal separator is used as a pressure gradient ion plate. Installed in the ting apparatus. Tin-zinc oxidation formed on a metal separator by forming a film in an argon-oxygen mixed gas (oxygen concentration: 6.2% by volume) atmosphere under a pressure of 0.06 Pa, a metal separator temperature of 200 ° C., and a power of 5 kW. A thin film was obtained. The thickness of the zinc-tin oxide was about 100 nm as measured with a stylus film thickness meter (DEKTAK8 manufactured by ULVAC).

(Production of cell)
The zinc-tin oxide thin film obtained by cutting carbon paper (GDS2120, Ballard Co., Ltd.) as a gas diffusion layer on both outer sides of the MEA obtained above using a commercially available JARI standard cell and a gas passage groove. A fuel cell having an effective electrode area of 25 cm ² was assembled by disposing a metal separator deposited with, arranging a current collector and an end plate in order on the outside, and fastening them with bolts.

(Metal separator corrosion test)
The corrosion test of the metal separator is performed by an open circuit holding test. Test conditions are: fuel cell temperature 100 ° C., hydrogen electrode gas inlet dew point 90 ° C., air electrode gas inlet dew point 90 ° C., hydrogen gas flow rate 50 mL / min, air flow rate 100 mL / min, hydrogen electrode gas outlet The back pressure is 0.1 MPaG, and the air electrode gas outlet back pressure is 0.1 MPaG.

  Even if the appearance of the surface of the metal separator after the open circuit holding test is visually confirmed, no corrosion is confirmed.

(Comparative example)
Except for using a metal separator on which no zinc-tin oxide thin film was deposited, the corrosion test of the metal separator was conducted in the same manner as in the examples, and visually confirmed the progress of corrosion on the surface of the metal separator after the test. Is done.

DESCRIPTION OF SYMBOLS 10 ... Fuel cell, 12 ... Polymer electrolyte membrane, 13a, 13b ... Metal layer, 14a ... Anode catalyst layer, 14b ... Cathode catalyst layer, 16a, 16b ... Gas diffusion layer, 18a, 18b ... Separator, 20 ... Membrane electrode joining Body (MEA)

Claims (4)

A substrate formed of a metal material;
And a thin film layer made of a conductive metal oxide formed on the surface of the substrate.   The separator according to claim 1, wherein the conductive metal oxide contains one or more elements selected from the group consisting of tin, tantalum, niobium, titanium, tungsten, and zirconium.   The separator according to claim 2, wherein the conductive metal oxide contains tin. A membrane electrode assembly having a polymer electrolyte membrane and a catalyst layer sandwiching the polymer electrolyte membrane;
A fuel cell having a pair of separators sandwiching the membrane electrode assembly,
4. The fuel cell according to claim 1, wherein at least one of the pair of separators is the separator according to claim 1, and the thin film layer is disposed on the membrane electrode assembly side.

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