JP2006032181A - Film/electrode structure for polymer electrolyte fuel cell, and polymer electrolyte fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a film/electrode structure for a polymer electrolyte fuel cell which has high proton conductivity even under low humidification condition and low temperature condition, and which is provided with a superior power generating performance, and provide the polymer electrolyte fuel cell. <P>SOLUTION: In the film/electrode structure for the polymer electrolyte fuel cell in which a polymer electrolyte film 2 is pinched by a pair of electrodes 1 containing a catalyst, the polymer electrolyte film 2 is composed of an ionic liquid, and a polyarylene based copolymer having a sulfonic acid group. The ionic liquid contains a proton donor, and the proton donor is chosen from a group composed of trifluoromethane sulfonic acid, bis (trifluoromethylsufonyl) imide acid, and tris (fluoromethylsulfonyl) methide acid. The ionic liquid is contained within a range of 0.5 to 200 pts. wt. to 100 pts. wt. of the polyarylene based copolymer. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a membrane / electrode structure for a polymer electrolyte fuel cell and a polymer electrolyte fuel cell comprising the membrane / electrode structure.

  While petroleum resources are depleted, environmental problems such as global warming due to the consumption of fossil fuels have become serious, and fuel cells have been widely developed as a clean power source for motors without carbon dioxide generation. At the same time, some have begun to be put into practical use. When the fuel cell is mounted on an automobile or the like, a solid polymer fuel cell using a polymer electrolyte membrane is preferably used because a high voltage and a large current can be easily obtained.

  As an electrode structure used in the polymer electrolyte fuel cell, a pair of electrode catalysts formed by a catalyst such as platinum being supported on a catalyst carrier such as carbon black and integrated with an ion conductive polymer binder There is known a structure in which a polymer electrolyte membrane capable of ion conduction is sandwiched between both electrode catalyst layers, and a diffusion layer is laminated on each electrode catalyst layer. The electrode structure further forms a polymer electrolyte fuel cell by laminating a separator also serving as a gas passage on each electrode catalyst layer.

  In the polymer electrolyte fuel cell, a reducing gas such as hydrogen or methanol is introduced through the diffusion layer using one electrode catalyst layer as a fuel electrode, and the diffusion layer is formed using the other electrode catalyst layer as an oxygen electrode. An oxidizing gas such as air or oxygen is introduced. In this way, on the fuel electrode side, protons and electrons are generated from the reducing gas by the action of the catalyst contained in the electrode catalyst layer, and the protons pass through the polymer electrolyte membrane to the oxygen electrode side. To the electrode catalyst layer. The protons react with the oxidizing gas and electrons introduced into the oxygen electrode by the action of the catalyst contained in the electrode catalyst layer in the electrode catalyst layer on the oxygen electrode side to generate water. Therefore, by connecting the fuel electrode and the oxygen electrode with a conducting wire, a circuit for sending electrons generated at the fuel electrode to the oxygen electrode is formed, and a current can be taken out.

  In the electrode structure, a perfluoroalkyl typified by a polymer belonging to a so-called cation exchange resin as the polymer electrolyte membrane, for example, a sulfonated product of vinyl polymer such as polystyrene sulfonic acid, Nafion (trade name, manufactured by DuPont). An organic polymer such as a polymer in which a sulfonic acid group or a phosphoric acid group is introduced into a heat-resistant polymer such as a sulfonic acid polymer, a perfluoroalkylcarboxylic acid polymer, polybenzimidazole, or polyether ether ketone is preferably used.

  On the other hand, solid polymer electrolytes made of sulfonated rigid polyphenylene are known (see, for example, Patent Document 1). The rigid polyphenylene is mainly composed of a polymer obtained by polymerizing an aromatic compound comprising a phenylene chain, and this is reacted with a sulfonating agent to introduce a sulfonic acid group.

However, since polymer electrolyte membranes suitably used for these solid polymer fuel cells all have proton conductivity that depends on the water content of the membrane, in order to achieve high power generation performance as a fuel cell, a high humidity Conditions have to be maintained, and there is a disadvantage that the load on the humidifier becomes large. In addition, the polymer electrolyte membrane has a disadvantage that, under freezing, water in the polymer electrolyte membrane involved in proton conduction freezes, so that proton conductivity is greatly reduced and power generation cannot be performed.
US Pat. No. 5,403,675 JP-A-2-159 Japanese Patent Laid-Open No. 7-220741 Polymer Preprints, Japan, Vol.42, No.3, p.730 (1993) Polymer Preprints, Japan, Vol.43, No.3, p.736 (1994) Polymer Preprints, Japan, Vol.42, No.7, p.2490-2492 (1993)

  The present invention provides a membrane / electrode structure for a polymer electrolyte fuel cell that eliminates such inconvenience, has high proton conductivity even under low humidification conditions and low temperature conditions, and has excellent power generation performance. For the purpose.

  Another object of the present invention is to provide a polymer electrolyte fuel cell comprising the membrane / electrode structure and having excellent power generation performance even under low humidification conditions and low temperature conditions.

  In order to achieve such an object, the membrane / electrode structure for a polymer electrolyte fuel cell of the present invention comprises a membrane for a polymer electrolyte fuel cell in which a polymer electrolyte membrane is sandwiched between a pair of electrodes containing a catalyst. In the electrode structure, the polymer electrolyte membrane includes an ionic liquid and a polyarylene copolymer having a sulfonic acid group.

  In the membrane / electrode structure of the present invention, since the polymer electrolyte membrane is composed of an ionic liquid and a polyarylene copolymer having a sulfonic acid group, the polyarylene copolymer can be coated with the ionic liquid. A proton conduction mechanism independent of the water contained in the coalescence is constructed. Therefore, in the membrane / electrode structure of the present invention, proton conduction is performed by the ionic liquid under low humidification conditions or low temperature conditions in which water freezes, and excellent power generation performance can be obtained. it can.

  The ionic liquid preferably contains a proton donor in order to satisfactorily conduct protons even under low humidification conditions or low temperature conditions. Examples of the proton donor include at least one compound selected from the group consisting of trifluoromethanesulfonic acid, bis (trifluoromethylsulfonyl) imidic acid, and tris (trifluoromethylsulfonyl) methideic acid. .

  The ionic liquid is used in an amount of 0.5 to 200 with respect to 100 parts by weight of the polyarylene copolymer having a sulfonic acid group in order to conduct protons well even under low humidification conditions or low temperature conditions. It is preferably contained in the range of parts by weight.

  When the content of the ionic liquid is less than 0.5 parts by weight based on 100 parts by weight of the polyarylene copolymer, sufficient proton conductivity can be obtained under low humidification conditions or low temperature conditions. There may not be. In addition, if the content of the ionic liquid exceeds 200 parts by weight with respect to 100 parts by weight of the polyarylene copolymer, the proton conductivity of the polyarylene copolymer is inhibited, and therefore, under low humidification conditions, In addition, sufficient proton conductivity may not be obtained under conditions other than low temperature conditions.

  Examples of the polyarylene-based copolymer having a sulfonic acid group include those containing a structural unit represented by the following general formula (1) and a structural unit represented by the general formula (2). Can do.

  Further, the solid polymer fuel cell of the present invention is a solid in which a polymer electrolyte membrane comprising the ionic liquid and a polyarylene copolymer having a sulfonic acid group is sandwiched between a pair of electrodes including a catalyst. A membrane / electrode structure for a polymer fuel cell is provided.

  Since the polymer electrolyte fuel cell of the present invention includes the membrane / electrode structure, excellent power generation performance can be obtained even under low humidification conditions or low temperature conditions.

  Next, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is an explanatory sectional view showing the configuration of the membrane / electrode structure of the present embodiment.

  As shown in FIG. 1, the membrane / electrode structure of this embodiment includes a pair of electrode catalyst layers 1, 1, a polymer electrolyte membrane 2 sandwiched between both electrode catalyst layers 1, 1, and each electrode catalyst layer. 1, gas diffusion layers 3 and 3 stacked on top of each other.

  The electrode catalyst layer 1 is composed of a catalyst and an ion conductive polymer electrolyte.

  The catalyst is preferably a supported catalyst in which platinum or a platinum alloy is supported on a carbon material having developed pores. As the carbon material having developed pores, carbon black, activated carbon, or the like can be preferably used. Examples of the carbon black include channel black, furnace black, thermal black, acetylene black and the like, and the activated carbon includes those obtained by carbonizing and activating various carbon atom-containing materials. Can be mentioned. Moreover, you may use what carbonitized these carbon materials.

  The catalyst may be one in which platinum is supported on a carbon support, but by using a platinum alloy, stability and activity as an electrode catalyst can be further imparted. Examples of the platinum alloy include platinum group metals other than platinum such as ruthenium, rhodium, palladium, osmium, iridium, iron, titanium, gold, silver, chromium, manganese, molybdenum, tungsten, aluminum, silicon, rhenium, zinc, and tin. An alloy of one or more metals selected from the group consisting of and platinum is preferred. The platinum alloy may contain an intermetallic compound with a metal alloyed with platinum.

  The supported rate of platinum or platinum alloy (ratio of the mass of platinum or platinum alloy to the total mass of the supported catalyst) may be in the range of 20 to 80% by mass, particularly 30 to 55% by mass in order to obtain high output. preferable. If the loading rate is less than 20% by mass, sufficient output may not be obtained. If the loading rate exceeds 80% by mass, platinum or platinum alloy particles may not be supported on the carbon material serving as a carrier with good dispersibility.

Further, the primary particle diameter of platinum or platinum alloy is preferably 1 to 20 nm in order to obtain a highly active gas diffusion electrode, and in particular, a large surface area of platinum or platinum alloy can be ensured in terms of reaction activity. 5 nm is preferable. Moreover, it is preferable that platinum or a platinum alloy is contained in the range of 0.1-1.0 mg / cm < ² > in a catalyst particle.

The electrode catalyst layer 1 includes an ion conductive polymer electrolyte having a sulfonic acid group in addition to the supported catalyst. Usually, the supported catalyst is covered with the polymer electrolyte, and protons (H ⁺ ) move through a path where the polymer electrolyte is connected.

  Examples of the ion conductive polymer electrolyte having a sulfonic acid group are represented by Nafion (trade name) manufactured by DuPont, Flemion (trade name) manufactured by Asahi Glass Co., Ltd., and Aciplex (trade name) manufactured by Asahi Kasei Corporation. A perfluoroalkylenesulfonic acid polymer compound is preferably used. In addition to the perfluoroalkylene sulfonic acid polymer compound, an ion conductive polymer electrolyte mainly composed of an aromatic hydrocarbon compound such as a sulfonated polyarylene copolymer described in the present specification may be used. .

  The polymer electrolyte membrane 2 is composed of an ionic liquid and a polyarylene copolymer having a sulfonic acid group.

  The ionic liquid is composed of a cation component and an anion component, and has a melting point of 100 ° C. or lower, preferably 80 ° C. or lower, more preferably 50 ° C. or lower.

  Examples of the cationic component include imidazolium, pyridinium, ammonium, pyrrolidinium, lutidinium, triazolium, indolium, pyrazolium, and carbazolium compounds. Specific examples of the cation component include 1,3-dimethylimidazolium cation, 1,3-diethylimidazolium cation, 1,2-dimethylimidazolium cation, 1,2-diethylimidazolium cation, 1-ethyl- 3-methylimidazolium cation, 1-methyl-3-propylimidazolium cation, 2-ethyl-1-methylimidazolium cation, 1-ethyl-2-methylimidazolium cation, 1,2,3-trimethylimidazolium cation 1,2-dimethyl-3-propylimidazolium cation, 1-methylimidazolium cation, 2-methylimidazolium cation, 1-ethylimidazolium cation, 2-ethylimidazolium cation, 1-vinylimidazolium cation, 1 -Methylpyrrolidi Cation, 2,4-lutidinium cation, 1-butyl-3-methylimidazolium cation, 1,2-dimethyl-1,2,4-triazolium cation, 1-butylpyridinium cation, 2-methyl-1 -Pyrrolium cation, 1-ethyl-2-phenylindolium cation, 1,2-dimethylindolium cation, 1-ethylcarbazolium cation, 1-methylpyrazolium cation and the like.

Examples of the anionic component include carboxylic acid, sulfonic acid, sulfonic acid compound, inorganic acid, and the like. Specifically, CH ₃ CO ₂ ⁻ , CF ₃ CO ₂ ⁻ , C ₃ F ₇ CO ₂ ⁻ , CF ₃ SO ₃ ⁻ , (CF ₃ SO ₂ ) ₃ C ⁻ , C ₄ F ₉ SO ₃ ⁻ , (CF ₃ SO ₂ ) ₂ N ⁻ , BF ₄ ⁻ , PF ₆ ⁻ , ClO ₄ ⁻ , NO ₃ ⁻ , NO ^{_{2 -, AlCl 4 -, Al}} 3 Cl 8 -, Al 2 Cl 2 - and the like.

  Specific examples of the compound composed of the cation component and the anion component include N-ethylimidazole bis (trifluoromethylsulfonylimide).

  A zwitterion type ionic liquid having both a cation component and an anion component in the molecule can also be used. Examples of the zwitterionic ionic liquid include the following compounds.

  The ionic liquid is usually 0.5 to 200 parts by weight, preferably 5 to 100 parts by weight, more preferably 7 to 80 parts by weight with respect to 100 parts by weight of the polyarylene copolymer having a sulfonic acid group. Used in quantity. When the ionic liquid is contained in the polyarylene-based copolymer within the above range, the proton conductivity of the polymer electrolyte membrane 2 under low humidification conditions and low temperature conditions can be effectively improved. it can.

  As the ionic liquid, an ionic liquid composed of the cation component and the anion component can be used alone, or a combination of the ionic liquid combined with a proton donor may be used. Thus, the proton conductivity of the polymer electrolyte membrane 2 can be further improved by adding a proton donor to the ionic liquid.

  Examples of the proton donor include phosphoric acid, sulfuric acid, sulfonic acid, inorganic solid acid, and derivatives thereof. Specific examples include trifluoromethanesulfonic acid, bis (trifluoromethylsulfonyl) imidic acid, and tris (trifluoromethylsulfonyl) methide acid. Among these, trifluoromethanesulfonic acid, bis (trifluoromethylsulfonyl) imidic acid, and tris (trifluoromethylsulfonyl) methide acid are preferable.

  The mixing ratio of the proton donor to the ionic liquid is not particularly limited, but is usually 0.001 to 1 equivalent, preferably 0.01 to 0.7 equivalent, more preferably 0 to the cation component of the ionic liquid. It is mixed in the range of 0.05 to 0.5 equivalent. If the mixing amount of the proton donor is excessive, the proton conductivity tends to decrease. Conversely, if the mixing amount of the proton donor is too small, the effect of improving the proton conductivity may not be obtained.

  The polyarylene-based copolymer having a sulfonic acid group includes a structural unit represented by the following general formula (1) and a structural unit represented by the general formula (2). ).

In the general formula (1), A represents a divalent electron-withdrawing group, specifically, —CO—, —SO ₂ —, —SO—, —CONH—, —COO—, — (CF ₂ ). _q - (q is an integer of 1 to _{10), - C (CF 3)} 2 - and the like. The electron-withdrawing group refers to a group having a Hammett substituent constant of 0.06 or more when the phenyl group is in the m-position and 0.01 or more when it is in the p-position.

B represents a divalent electron-donating group or a direct bond. Specific examples of the electron-donating group include —CH ₂ —, —C (CH ₃ ) ₂ —, —O—, —S—, —CH═. CH-, -C≡C-,

等を挙げることができる。

Etc.

Ar represents an aromatic group having a substituent represented by —SO ₃ H. Specific examples of the aromatic group include a phenyl group, a naphthyl group, an anthracenyl group, and a phenanthyl group. Of these aromatic groups, a phenyl group and a naphthyl group are preferable.

  m represents an integer of 0 to 10, preferably 0 to 2, n represents an integer of 0 to 10, preferably 0 to 2, and k represents an integer of 1 to 4.

In general formula (2), R ^{1 to} R ⁸ may be the same as or different from each other, and are selected from the group consisting of a hydrogen atom, a fluorine atom, an alkyl group, a fluorine-substituted alkyl group, an allyl group, an aryl group, and a cyano group. At least one atom or group selected.

  Examples of the alkyl group include a methyl group, an ethyl group, a propyl group, a butyl group, an amyl group, and a hexyl group, and a methyl group and an ethyl group are preferable.

  Examples of the fluorine-substituted alkyl group include a trifluoromethyl group, a pentafluoroethyl group, a perfluoroethyl group, a perfluoropropyl group, a perfluorobutyl group, a perfluoropentyl group, and a perfluorohexyl group. A fluoromethyl group and a pentafluoroethyl group are preferred.

  Examples of the allyl group include a propenyl group, and examples of the aryl group include a phenyl group and a pentafluorophenyl group.

  W represents a single bond or a divalent electron-withdrawing group, and T represents a single bond or a divalent organic group. p is 0 or a positive integer, and the upper limit is usually 100, preferably 10-80.

In general formula (3), W, T, A, B, Ar, m, n, k, p and R ^{1 to} R ⁸ are respectively W, T in general formula (1) and general formula (2). , A, B, Ar, m, n, k, p and R ^{1 to} R ⁸ . x and y represent molar ratios when x + y = 100 (mol%).

  The polyarylene copolymer having a sulfonic acid group contains the structural unit represented by the general formula (1) in a proportion of 0.5 to 100 mol%, preferably 10 to 99.999 mol%. The structural unit represented by the formula (2) is contained in a ratio of 99.5 to 0 mol%, preferably 90 to 0.001 mol%.

  The polyarylene-based copolymer having a sulfonic acid group includes, for example, a monomer that can be a structural unit having a sulfonic acid ester group in place of the sulfonic acid group in the general formula (1), and the general formula (2). To produce a polyarylene copolymer having a sulfonic acid ester group and hydrolyzing the polyarylene copolymer having a sulfonic acid ester group to obtain a sulfonic acid. It can be synthesized by converting an ester group to a sulfonic acid group.

  The polyarylene-based copolymer having a sulfonic acid group includes, for example, a structural unit having no sulfonic acid group in the general formula (1) and a structural unit represented by the general formula (2). It is also possible to synthesize a polyarylene-based copolymer in advance and sulphonate the copolymer.

  Examples of the monomer that can be a structural unit having a sulfonic acid ester group in place of the sulfonic acid group in the general formula (1) include a sulfonic acid ester represented by the following general formula (4) (hereinafter, monomer (4)) Can be mentioned).

In the general formula (4), X is an atom selected from halogen atoms other than fluorine (chlorine, bromine, iodine), —OSO ₂ Z (wherein Z represents an alkyl group, a fluorine-substituted alkyl group, or an aryl group) or A, B, m, n and k are the same as A, B, m, n and k in the general formula (1), respectively.

R ^a represents a hydrocarbon group having 1 to 20 carbon atoms, preferably 4 to 20 carbon atoms. Specifically, methyl group, ethyl group, n-propyl group, iso-propyl group, tert-butyl group, iso- Butyl group, n-butyl group, sec-butyl group, neopentyl group, cyclopentyl group, hexyl group, cyclohexyl group, cyclopentylmethyl group, cyclohexylmethyl group, adamantyl group, adamantylmethyl 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, etc. Linear hydrocarbon groups, branched hydrocarbon groups, alicyclic hydrocarbon groups, hydrocarbon groups having a 5-membered heterocyclic ring, etc. wear. Among 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 particularly preferable. preferable.

Ar represents an aromatic group having a substituent represented by _-SO 3 ^{R b.} Specific examples of the aromatic group include a phenyl group, a naphthyl group, an anthracenyl group, and a phenanthyl group. Of these groups, a phenyl group and a naphthyl group are preferable.

Substituents -SO ₃ R ^b is substituted one or two or more aromatic groups, when the substituent -SO ₃ R ^b is substituted two or more, these substituents is each independently But it can be different.

Here, R ^b represents a hydrocarbon group having 1 to 20 carbon atoms, preferably 4 to 20 carbon atoms, and specific examples thereof include the hydrocarbon groups having 1 to 20 hydrocarbon atoms. Among 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 particularly preferable. preferable.

  Specific examples of the sulfonic acid ester represented by the general formula (4) include the following compounds.

In addition, the sulfonate ester represented by the general formula (4) is a compound in which a chlorine atom is replaced with a bromine atom in the compound of the specific example, a compound in which —CO— is replaced with —SO ₂ — in the compound, or the compound in the chlorine atom is replaced with a bromine atom, and, -CO- is -SO ₂ - also includes compounds such as replacing a.

The R ^b group in the general formula (4) is derived from a primary alcohol, and the β carbon is a tertiary or quaternary carbon, which is excellent in stability during the polymerization process and originates from the formation of sulfonic acid by deesterification. It is preferable in that it does not cause polymerization inhibition or crosslinking, and it is preferable that these ester groups are derived from primary alcohols and the β-position is a quaternary carbon.

  In the general formula (1), specific examples of the compound having no sulfonic acid group include the following compounds.

The compound having no sulfonic acid group in the general formula (1) is a compound in which a chlorine atom is replaced with a bromine atom in the compound of the specific example, a compound in which —CO— is replaced with —SO ₂ — in the compound, or the compound in the chlorine atom is replaced with a bromine atom, and, -CO- is -SO ₂ - also includes compounds such as replacing a.

  Examples of the oligomer that can be a constituent unit of the general formula (2) include an oligomer represented by the following general formula (5) (hereinafter sometimes referred to as “oligomer (5)”).

In the general formula (5), R ′ and R ″ may be the same or different from each other, and are a halogen atom excluding a fluorine atom (chlorine, bromine, iodine), —OSO ₂ Z (where Z is an alkyl group, An atom or group selected from a fluorine-substituted alkyl group or an aryl group. Examples of the alkyl group represented by Z include a methyl group and an ethyl group, examples of the fluorine-substituted alkyl group include a trifluoromethyl group, and examples of the aryl group include a phenyl group and a p-tolyl group. Can be mentioned.

R ^{1 to} R ⁸ may be the same as or different from each other, and at least one atom selected from the group consisting of a hydrogen atom, a fluorine atom, an alkyl group, a fluorine-substituted alkyl group, an allyl group, an aryl group, and a cyano group, or Indicates a group.

  Examples of the alkyl group include a methyl group, an ethyl group, a propyl group, a butyl group, an amyl group, and a hexyl group, and a methyl group and an ethyl group are preferable. Examples of the fluorine-substituted alkyl group include a trifluoromethyl group, a pentafluoroethyl group, a perfluoroethyl group, a perfluoropropyl group, a perfluorobutyl group, a perfluoropentyl group, and a perfluorohexyl group. A methyl group, a pentafluoroethyl group and the like are preferable. Examples of the allyl group include a propenyl group, and examples of the aryl group include a phenyl group and a pentafluorophenyl group.

  W represents a divalent electron-withdrawing group or a single bond, and examples of the electron-withdrawing group include the same groups as those described for the general formula (1). T is a divalent organic group or a single bond, and the organic group may be an electron-withdrawing group or an electron-donating group. Examples of the electron-withdrawing group or the electron-donating group include the same groups as those described for the general formula (1). p is 0 or a positive integer, and the upper limit is usually 100, preferably 10-80.

  Examples of the compound represented by the general formula (5) include 2,2-bis [4- {4- (4-chlorobenzoyl) phenoxy} phenyl] -1,1,1,3,3,3-hexafluoro. In addition to propane and bis [4- {4- (4-chlorobenzoyl) phenoxy} phenyl] sulfone, the following compounds can be exemplified.

  The compound represented by the general formula (5) can be synthesized, for example, by the method shown below.

  First, N-methyl-2-pyrrolidone, N, N-dimethylacetamide, sulfolane, diphenylsulfone, dimethylsulfoxide, etc. are used in order to convert the bisphenol linked with an electron-withdrawing group into the corresponding alkali metal salt of bisphenol. In a polar solvent having a high dielectric constant, an alkali metal such as lithium, sodium or potassium, an alkali metal hydride, an alkali metal hydroxide, an alkali metal carbonate or the like is added. The alkali metal is reacted in excess with respect to the hydroxyl group of phenol, and is usually used in an amount of 1.1 to 2 times equivalent, preferably 1.2 to 1.5 times equivalent.

  At this time, fluorine, chlorine, etc. activated with an electron-withdrawing group in the presence of water and an azeotropic solvent such as benzene, toluene, xylene, hexane, cyclohexane, octane, chlorobenzene, dioxane, tetrahydrofuran, anisole, phenetole, etc. The aromatic dihalide compound substituted with the halogen atom is reacted. Examples of the aromatic dihalide compound include 4,4′-difluorobenzophenone, 4,4′-dichlorobenzophenone, 4,4′-chlorofluorobenzophenone, bis (4-chlorophenyl) sulfone, bis (4-fluorophenyl) sulfone, 4-fluorophenyl-4′-chlorophenylsulfone, bis (3-nitro-4-chlorophenyl) sulfone, 2,6-dichlorobenzonitrile, 2,6-difluorobenzonitrile, hexafluorobenzene, decafluorobiphenyl, 2,5 -Difluorobenzophenone, 1,3-bis (4-chlorobenzoyl) benzene and the like can be mentioned. The aromatic dihalide compound is preferably a fluorine compound from the viewpoint of reactivity. However, in consideration of performing an aromatic coupling reaction, it is possible to assemble an aromatic nucleophilic substitution reaction so that the terminal is a chlorine atom. preferable.

  The aromatic dihalide compound activated with the electron-withdrawing group is used in an amount of 2 to 4 times mol, preferably 2.2 to 2.8 times mol of the bisphenol. Prior to the aromatic nucleophilic substitution reaction, an alkali metal salt of bisphenol may be used. The reaction temperature is in the range of 60 to 300 ° C, preferably 80 to 250 ° C. The reaction time is 15 minutes to 100 hours, preferably 1 to 24 hours.

  The most preferable method is to use a chlorofluoro compound having one halogen atom having a different reactivity as the aromatic dihalide compound activated with the electron-withdrawing group, as shown by the following formula. According to the chlorofluoro product, a nucleophilic substitution reaction occurs preferentially between the fluorine atom and phenoxide, which is convenient for obtaining the desired activated terminal chloro product.

  In formula, W is synonymous with General formula (5).

  Further, a flexible compound having a target electron-withdrawing group and an electron-donating group may be synthesized by combining a nucleophilic substitution reaction and an electrophilic substitution reaction (see, for example, Patent Document 2).

  Specifically, examples of the aromatic dihalide compound activated with an electron-withdrawing group include the aforementioned compounds. The phenol compound may be substituted, but an unsubstituted compound is preferable from the viewpoint of heat resistance and flexibility. In addition, it is preferable to set it as an alkali metal salt for the substitution reaction of a phenol, and the said compound can be mentioned as an alkali metal compound which can be used. The amount used is 1.2 to 2 moles per mole of phenol. In the reaction, the polar solvent or an azeotropic solvent with water can be used.

  Chlorobenzoic acid chloride is used in an amount of 2 to 4 times mol, preferably 2.2 to 3 times mol of the bisphenoxy compound. The Friedel-Craft reaction between the bisphenoxy compound and the acylating agent chlorobenzoic acid chloride is preferably performed in the presence of a Friedel-Craft activator such as aluminum chloride, boron trifluoride, or zinc chloride. . The Friedel-Craft activator is used in an amount of 1.1 to 2 times equivalent to 1 mol of an active halide compound such as chlorobenzoic acid as an acylating agent. The reaction time is in the range of 15 minutes to 10 hours, and the reaction temperature is in the range of -20 to 80 ° C. As the solvent, chlorobenzene, nitrobenzene and the like which are inert to Friedel-Craft reaction can be used.

Further, in the general formula (5), the compound in which p is 2 or more is, for example, a bisphenol serving as a source of etheric oxygen that is the electron donating group T in the general formula (5) and an electron withdrawing group W. A compound in combination with at least one group selected from —CO—, —SO ₂ —, and —C (CF ₃ ) ₂ —, specifically 2,2-bis (4-hydroxyphenyl) -1 , 1,1,3,3,3-hexafluoropropane, 2,2-bis (4-hydroxyphenyl) ketone, 2,2-bis (4-hydroxyphenyl) sulfone and other alkali metal salts of bisphenol and excess A substitution reaction with an active aromatic halogen compound such as 4,4-dichlorobenzophenone and bis (4-chlorophenyl) sulfone, N-methyl-2-pyrrolidone, N, N-dimethylacetami , In the presence of a polar solvent such as sulfolane, obtained by sequentially polymerizing the synthesis method of the monomer. Examples of such compounds include the following compounds.

  In the compound, p is 0 or a positive integer, and the upper limit is usually 100, preferably 10-80.

  The polyarylene having a sulfonate group is synthesized by reacting the monomer (4) and the oligomer (5) in the presence of a catalyst.

  The catalyst used in this case is a catalyst system containing a transition metal compound, and as such a catalyst system, (i) a compound that becomes a transition metal salt and a ligand (hereinafter referred to as “ligand component”), Alternatively, a transition metal complex coordinated with a ligand (including a copper salt) and (ii) a reducing agent may be essential components, and a “salt” may be added to increase the polymerization rate.

  Here, examples of the transition metal salt include nickel chloride and nickel bromide.

  Examples of the ligand component include triphenylphosphine and 2,2'-bipyridine. The compound which is the said ligand component may be used individually by 1 type, or may use 2 or more types together.

  Furthermore, examples of the transition metal complex in which a ligand is coordinated include nickel chloride bis (triphenylphosphine) and nickel chloride (2,2'-bipyridine).

  Examples of the reducing agent that can be used in the catalyst system include zinc, magnesium, manganese, and the like. These reducing agents can be used after being more activated by contacting with an acid such as an organic acid.

  Examples of the “salt” used in the catalyst system include sodium bromide, sodium iodide, potassium bromide, tetraethylammonium bromide, tetraethylammonium iodide and the like.

  The proportion of each component used is usually from 0.0001 to 10 mol, preferably from 0.0001 to 10 mol, preferably 1 to 1 mol of the total amount of monomers (total of monomer (4) and oligomer (5)) of the transition metal salt or transition metal complex. 0.01 to 0.5 mol. When the amount is less than 0.0001 mol, the polymerization reaction may not proceed sufficiently. On the other hand, when the amount exceeds 10 mol, the molecular weight of the obtained polyarylene copolymer may be decreased.

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

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

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

  As a polymerization solvent that can be used when the monomer (4) and the oligomer (5) are reacted, tetrahydrofuran, N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone, N N'-dimethylimidazolidinone is preferred. These polymerization solvents are preferably used after sufficiently dried.

  The total concentration of the monomers in the polymerization solvent is usually 1 to 90% by weight, preferably 5 to 40% by weight. The polymerization temperature for the polymerization is usually 0 to 200 ° C, preferably 50 to 120 ° C. The polymerization time is usually 0.5 to 100 hours, preferably 1 to 40 hours.

  The polyarylene-based copolymer having a sulfonic acid ester group obtained by using the monomer (4) is a polyarylene-based copolymer having a sulfonic acid group by hydrolyzing the sulfonic acid ester group and converting it into a sulfonic acid group. It can be a copolymer.

As the hydrolysis method, (i) a method in which the polyarylene copolymer having a sulfonate group is added to an excess amount of water or alcohol containing a small amount of hydrochloric acid and stirred for 5 minutes or more, (ii) A method of reacting the polyarylene copolymer having a sulfonate group in trifluoroacetic acid at a temperature of about 80 to 120 ° C. for about 5 to 10 hours; (iii) a polyarylene copolymer having a sulfonate group. In a solution containing 1 to 3 moles of lithium bromide with respect to 1 mole of the sulfonate group (—SO ₃ R ^b ) in the coalescence, for example, a solution of N-methyl-2-pyrrolidone, the polyarylene-based copolymer A method of adding hydrochloric acid after reacting the coalescence at a temperature of about 80 to 150 ° C. for about 3 to 10 hours can be mentioned.

  The polyarylene-based copolymer having a sulfonic acid group is obtained by copolymerizing the oligomer (5) and a monomer having no sulfonic acid group in the general formula (1) to obtain a polyarylene-based copolymer having no sulfonic acid group. It is also possible to synthesize an arylene copolymer by synthesizing it in advance and sulfonate the polyarylene copolymer. In this case, after producing a polyarylene copolymer having no sulfonic acid group by a method according to the synthesis method, a polyarylene having a sulfonic acid group is introduced by introducing a sulfonic acid group using a sulfonating agent. A system copolymer can be obtained.

  The method for introducing the sulfonic acid group is not particularly limited, and can be performed by a general method. For example, the polyarylene copolymer having no sulfonic acid group is used in the absence of a solvent or in the presence of a solvent using a known sulfonating agent such as sulfuric anhydride, fuming sulfuric acid, chlorosulfonic acid, sulfuric acid, sodium hydrogen sulfite and the like. Examples of sulfonation under known conditions can be given (see Non-Patent Documents 1 to 3).

  Examples of the solvent used in the sulfonation include hydrocarbon solvents such as n-hexane, ether solvents such as tetrahydrofuran and dioxane, aprotic polar solvents such as dimethylacetamide, dimethylformamide and dimethylsulfoxide, and tetrachloroethane. And halogenated hydrocarbon solvents such as dichloroethane, chloroform and methylene chloride. Although reaction temperature is not specifically limited, Usually, -50-200 degreeC, Preferably it is -10-100 degreeC. Moreover, reaction time is 0.5 to 1,000 hours normally, Preferably it is 1 to 200 hours.

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

  The amount of the sulfonic acid group can be adjusted, for example, by changing the type, use ratio, and combination of the monomer (4) or oligomer (5).

  The molecular weight of the polyarylene copolymer 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). It is. When the molecular weight is less than 10,000, the polyarylene copolymer having a sulfonic acid group has insufficient coating properties such as cracking in the formed film, and has a problem in strength properties. On the other hand, if it exceeds 1,000,000, the solubility becomes insufficient, and the solution viscosity becomes high, so that the processability is deteriorated.

  The solid polymer electrolyte membrane 2 is manufactured by forming into a film using a polymer electrolyte composed of the ionic liquid and a polyarylene copolymer having a sulfonic acid group.

Examples of a method for producing a film using the polymer electrolyte include a casting method in which a film is cast on a substrate by casting and formed into a film shape.
In the casting method, the solvent that dissolves the polymer electrolyte is not particularly limited, and examples thereof include aprotic systems such as γ-butyrolactone, dimethylacetamide, dimethylformamide, N-methyl-2-pyrrolidone, dimethylsulfoxide, and dimethylurea. A polar solvent etc. can be mentioned. These solvents may be further mixed with alcohol solvents such as methanol, ethanol, N-propyl alcohol, iso-propyl alcohol, 1-methoxy-2-propanol.

  The concentration of the polymer electrolyte in this case is usually 5 to 40% by weight, preferably 7 to 25% by weight, although it depends on the molecular weight of the polyarylene copolymer having a sulfonic acid group. If it is less than 5% by weight, it is difficult to increase the film thickness, and pinholes are likely to occur. On the other hand, if it exceeds 40% by weight, the solution viscosity is so high that it is difficult to form a film, and surface smoothness may be lacking.

  The solution viscosity of the polymer electrolyte is usually 2,000 to 100,000 mPa · s, preferably 3,000, although it depends on the molecular weight and solid content concentration of the polyarylene copolymer having a sulfonic acid group. It is the range of -50,000 mPa * s. If it is less than 2,000 Pa · s, the retentivity of the solution during processing is poor and it may flow from the substrate. On the other hand, if it exceeds 100,000 mPa · s, the viscosity is too high to be extruded from the die, and it may be difficult to form a film by a casting method.

  The substrate is not particularly limited as long as it is a substrate used in an ordinary solution casting method. For example, a substrate made of plastic or metal can be used, and preferably a thermoplastic such as a polyethylene terephthalate (PET) film. A substrate made of a resin can be used.

  After film formation by the casting method, the film can be obtained by drying the undried film at 30 to 160 ° C., preferably 50 to 150 ° C. for 3 to 180 minutes, preferably 5 to 120 minutes. The dry film thickness of the film obtained by the method as described above is usually 10 to 100 μm, preferably 20 to 80 μm.

  The solid polymer electrolyte membrane 2 may contain an anti-aging agent, preferably a hindered phenol compound having a molecular weight of 500 or more. By containing the anti-aging agent, the durability of the solid polymer electrolyte membrane 2 can be improved. It can be improved further.

  As a hindered phenol compound that can be used for the solid polymer electrolyte membrane 2, pentaerythrityl-tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate] (Ciba Specialty)・ IRGANOX 1010 (trade name) manufactured by Chemicals Co., Ltd.), N, N-hexamethylenebis (3,5-di-t-butyl-4-hydroxy-hydrocinnamamide) (IRGANOX manufactured by Ciba Specialty Chemicals Co., Ltd.) 1098 (trade name)), 1,3,5-trimethyl-2,4,6-tris (3,5-di-tert-butyl-4-hydroxybenzyl) benzene (IRGANOX 1330, manufactured by Ciba Specialty Chemicals Co., Ltd.) (Product name)).

  The hindered phenol compound having a molecular weight of 500 or more is preferably used in an amount of 0.01 to 10 parts by weight based on 100 parts by weight of the polyarylene copolymer having a sulfonic acid group.

  In the present embodiment, the membrane / electrode structure is composed of only the anode and cathode electrode catalyst layers 1 and 1 and the solid polymer electrolyte membrane (proton conducting membrane) 2 sandwiched between the electrode catalyst layers 1 and 1. However, it is more preferable that the gas diffusion layer 3 made of a conductive porous substrate such as carbon paper or carbon cloth is disposed outside the electrode catalyst layer 1 for both the anode and the cathode. In addition, this conductive porous substrate may be subjected to a water repellent treatment. Furthermore, a base layer imparted with water repellency may be formed on the gas diffusion layer 3 by applying a slurry in which carbon black and polytetrafluoroethylene (PTFE) particles are mixed. Since the gas diffusion layer 3 also functions as a current collector, in this specification, when the gas diffusion layer 3 is provided, the gas diffusion layer 3 and the electrode catalyst layer 1 are collectively referred to as an electrode.

  In the polymer electrolyte fuel cell having the membrane / electrode structure shown in FIG. 1, a gas containing oxygen is supplied to the cathode, and a gas containing hydrogen is supplied to the anode. Specifically, for example, a separator in which a groove to be a gas flow path is formed is disposed outside both electrodes (gas diffusion layer 3) of the membrane / electrode structure, and the gas is allowed to flow through the gas flow path. To supply gas as fuel to the membrane / electrode structure.

  As a method for producing the membrane / electrode structure shown in FIG. 1, a method in which the electrode catalyst layer 1 is directly formed on the solid polymer electrolyte membrane 2 and sandwiched between the gas diffusion layers 3 as necessary, or gas diffusion such as carbon paper A method of forming the electrode catalyst layer 1 on the base material to be the layer 3 and bonding it to the solid polymer electrolyte membrane 2, and after forming the electrode catalyst layer 1 on a flat plate and transferring it to the solid polymer electrolyte membrane 2 Various methods such as a method of peeling the flat plate and sandwiching it with the gas diffusion layer 3 as required can be employed.

  The electrode catalyst layer 1 is formed by using a dispersion in which a supported catalyst and a perfluoroalkylenesulfonic acid polymer compound having a sulfonic acid group are dispersed in a dispersion medium (if necessary, a water repellent, a pore-forming agent). A known method can be employed in which a solid agent electrolyte membrane 2, a gas diffusion layer 3 or a flat plate is formed by spraying, coating, filtration or the like. When the electrode catalyst layer 1 is not directly formed on the solid polymer electrolyte membrane 2, the electrode catalyst layer 3 and the solid polymer electrolyte membrane 2 are preferably joined by a hot press method, an adhesion method, or the like (for example, Patent Documents). 3).

  In this example, first, an oligomer represented by the general formula (5) was prepared as follows.

  First, 2,2-bis (4-hydroxyphenyl) -1,1,1,3,3,3-into a 1 L three-necked flask equipped with a stirrer, thermometer, Dean-stark tube and nitrogen-introduced three-way cock. Hexafluoropropane (bisphenol AF) 67.3 g (0.20 mol), 4,4′-dichlorobenzophenone (4,4′-DCBP) 60.3 g (0.24 mol), potassium carbonate 71.9 g (0. 52 mol), 300 ml of N, N-dimethylacetamide (DMAc) and 150 ml of toluene were taken and heated in an oil bath in a nitrogen atmosphere and reacted at 130 ° C. with stirring. When water produced by the reaction was azeotroped with toluene and reacted while being removed from the system with a Dean-stark tube, almost no water was produced in about 3 hours. Thereafter, most of the toluene was removed while gradually raising the reaction temperature from 130 ° C. to 150 ° C., and the reaction was continued at 150 ° C. for 10 hours, and then 10.0 g (0.040 mol) of 4,4′-DCBP was added. The mixture was further reacted for 5 hours. The resulting reaction solution was allowed to cool, and then the by-product inorganic compound precipitate was removed by filtration, and the filtrate was put into 4 L of methanol. The precipitated product was separated by filtration, collected, dried, and dissolved in 300 ml of tetrahydrofuran. This was put into 4 L of methanol and reprecipitated to obtain 95 g (yield 85%) of the target compound.

  About the obtained compound, the number average molecular weight (Mn) in terms of polystyrene determined by GPC using THF as a solvent was 11,200. The obtained compound is soluble in THF, NMP, DMAc, sulfolane and the like, has a Tg (glass transition temperature) of 110 ° C. and a thermal decomposition temperature of 498 ° C., and is represented by the following chemical formula (6). It was an oligomer (hereinafter referred to as a BCPAF oligomer).

  Next, a polyarylene copolymer having a sulfonic acid group was prepared as follows.

First, 4- [4- (2,5-dichlorobenzoyl) phenoxy] benzenesulfonic acid neo- was added to a 1 L three-necked flask equipped with a stirrer, a thermometer, a condenser tube, a Dean-stark tube, and a nitrogen-introduced three-way cock. Pentyl (hereinafter referred to as A-SO ₃ neo-Pe) 39.58 g (98.64 mmol), BCPAF oligomer (Mn = 11,200) obtained in this example 15.23 g (1.36 mmol), Ni (PPh ₃ ) ₂ Cl ₂ 1.67 g (2.55 mmol), PPh ₃ 10.49 g (40 mmol), NaI 0.45 g (3 mmol), zinc dust 15.69 g (240 mmol), dry NMP 390 ml under nitrogen Added in. The reaction system was heated with stirring (finally heated to 75 ° C.) and allowed to react for 3 hours. The polymerization reaction solution was diluted with 250 ml of THF, stirred for 30 minutes, filtered using Celite as a filter aid, and the filtrate was poured into a large excess of methanol (1500 ml) to coagulate. The solidified product was collected by filtration, air-dried, redissolved in a mixed solvent of 200 ml of THF and 300 ml of NMP, and solidified and precipitated with a large excess of methanol (1500 ml). After air drying, 47.0 g (yield 99%) of a copolymer (hereinafter referred to as PolyAB-SO ₃ neo-Pe) comprising a sulfonic acid derivative protected with a target yellow fibrous neopentyl group was obtained by heat drying. . Regarding the molecular weight by GPC, the number average molecular weight (Mn) was 47,600, and the weight average molecular weight (Mw) was 159,000.

5.1 g of the obtained PolyAB-SO ₃ neo-Pe was dissolved in 60 ml of NMP and heated to 90 ° C. To the reaction system, a mixture of 50 ml of methanol and 8 ml of concentrated hydrochloric acid was added at a time to form a suspended state and reacted for 10 hours under mild reflux conditions. Next, a distillation apparatus was installed, and excess methanol was distilled off to obtain a light green transparent liquid. This solution is poured into a large amount of water / methanol mixture (water: methanol = 1: 1 (weight ratio)) to solidify the copolymer, and then ion exchange until the pH of the washing water becomes 6 or more. The copolymer was washed with water. From the quantitative analysis of the IR spectrum and ion exchange capacity of the copolymer thus obtained, it was confirmed that the sulfonic acid ester group (—SO ₃ R ^a ) was quantitatively converted to the sulfonic acid group (—SO ₃ H). all right.

  Elution of N-methyl-2-pyrrolidone (NMP) to which lithium bromide and phosphoric acid were added as a solvent from the resulting polyarylene copolymer having a sulfonic acid group (hereinafter sometimes referred to as a sulfonated polymer) The number average molecular weight (Mn) was 53,200, and the weight average molecular weight (Mw) was 185,000.

  Further, the obtained sulfonated polymer is washed until the washing water has a pH of 4 to 6, the remaining free acid is sufficiently removed and dried, and a predetermined amount is weighed to mix THF / water. The sample was dissolved in a solvent, titrated with a standard solution of NaOH using phenolphthalein as an indicator, and the ion exchange capacity was determined from the neutralization point. The sulfonated polymer obtained had an ion exchange capacity (sulfonic acid equivalent) of 1.9 meq / g.

  Next, 10 g of the sulfonated polymer obtained in this example and 1 g of N-ethylimidazole bis (trifluoromethylsulfonylimide) as an ionic liquid were dissolved in 100 ml of N-methyl-2-pyrrolidone. This solution was cast on a glass plate and dried at 80 ° C. for 1 hour and then at 140 ° C. for 60 minutes to obtain a uniform film having a thickness of 40 μm.

  Next, using the membrane, a membrane / electrode structure was produced as follows.

  First, platinum particles were supported on carbon black (furnace black) having an average diameter of 50 nm at a weight ratio of carbon black: platinum = 1: 1 to prepare catalyst particles. Next, the catalyst particles are placed in a perfluoroalkylenesulfonic acid polymer compound solution (Nafion (trade name) manufactured by DuPont) as an ion conductive binder at a weight ratio of ion conductive binder: catalyst particles = 8: 5. A catalyst paste was prepared by uniformly dispersing.

  Next, carbon black and polytetrafluoroethylene (PTFE) particles are mixed at a weight ratio of carbon black: PTFE particles = 4: 6, and a slurry in which the resulting mixture is uniformly dispersed in ethylene glycol is mixed with carbon paper. The base layer was coated and dried on one side, and two gas diffusion layers 3 composed of the base layer and carbon paper were produced.

Next, the catalyst paste is applied on both sides of the membrane as the solid polymer electrolyte membrane 2 with a bar coater so that the platinum content is 0.5 mg / cm ^2, and dried to form an electrode coating membrane (CCM). ) The drying was performed at 100 ° C. for 15 minutes, followed by secondary drying at 140 ° C. for 10 minutes.

  Next, the CCM was sandwiched between the gas diffusion layers 3 and the base layer side, and hot pressing was performed to obtain the membrane / electrode structure shown in FIG. The hot press was a primary hot press at 80 ° C. and 5 MPa for 2 minutes followed by a secondary hot press at 160 ° C. and 4 MPa for 1 minute.

  The membrane / electrode structure obtained in this example can constitute a solid polymer fuel cell by further laminating a separator that also serves as a gas passage on the gas diffusion layer.

  Next, the proton conductivity of the solid polymer electrolyte membrane 2 obtained in this example and the power generation characteristics of the membrane / electrode structure were evaluated as follows. The results are shown in Table 1.

  The proton conductivity of the solid polymer electrolyte membrane 2 is determined by first using the solid polymer electrolyte membrane 2 as a strip-like sample having a width of 5 mm and pressing a platinum wire (diameter 0.5 mm) on the surface of the sample. The sample was held in a wet device, and the AC resistance was determined from the AC impedance measurement between the platinum wires. A SI1260 impedance analyzer (trade name) manufactured by Solartron was used as the resistance measuring device, and a small environmental tester SH-241 (trade name) manufactured by Espec was used as the constant temperature and humidity device. Five platinum wires were pressed at intervals of 5 mm, and the AC resistance was measured while changing the distance between the wires to 5 to 20 mm. Next, the specific resistance of the solid polymer electrolyte membrane 2 was calculated from the gradient of the distance between the lines and the resistance by the following formula, the AC impedance was calculated from the reciprocal of the specific resistance, and the proton conductivity was calculated from this impedance.

Specific resistance R (Ω · cm) = 0.5 (cm) × film thickness (cm) × resistance-to-resistance gradient (Ω / cm)
The power generation characteristics of the membrane / electrode structure were evaluated as follows. First, pure hydrogen is supplied to the fuel electrode side and air is supplied to the oxygen electrode side under a power generation condition in which the relative humidity between the fuel electrode side and the oxygen electrode side is 20% at a temperature of 90 ° C. By measuring the cell potential at a current density of 1 A / cm ² , the power generation performance in a high temperature and low humidity environment was evaluated.

  Moreover, the low temperature startability was evaluated under the condition of −30 ° C. using the membrane / electrode structure obtained in this example. The result was indicated as “Good” if it could be started within 30 seconds, and “X” as bad if it took 30 seconds or more to start or could not be started.

  10 g of the sulfonated polymer obtained in Example 1, 1 g of N-ethylimidazole bis (trifluoromethylsulfonylimide) as an ionic liquid, and 0.15 g of trifluoromethanesulfonic acid as a proton donor In addition, a uniform film having a film thickness of 40 μm was obtained in the same manner as in Example 1 except that a solution dissolved in 100 ml of N-methyl-2-pyrrolidone was used.

  Next, a membrane / electrode structure shown in FIG. 1 was produced in exactly the same manner as in Example 1 except that the membrane obtained in this example was used as the solid polymer electrolyte membrane 2.

Next, the proton conductivity of the solid polymer electrolyte membrane 2 obtained in this example and the power generation characteristics of the membrane / electrode structure were evaluated in the same manner as in Example 1. The results are shown in Table 1.
[Comparative Example 1]
A uniform film having a thickness of 40 μm was obtained in exactly the same manner as in Example 1, except that a solution obtained by dissolving only 10 g of the sulfonated polymer obtained in Example 1 in 100 ml of N-methyl-2-pyrrolidone was used.

  Next, a membrane / electrode structure shown in FIG. 1 was produced in the same manner as in Example 1 except that the membrane obtained in this comparative example was used as the solid polymer electrolyte membrane 2.

  Next, the proton conductivity of the solid polymer electrolyte membrane 2 obtained in this comparative example and the power generation characteristics of the membrane / electrode structure were evaluated in the same manner as in Example 1. The results are shown in Table 1.

  From Table 1, a solid polymer electrolyte membrane 2 (Example 1) comprising a polyarylene copolymer having a sulfonic acid group and an ionic liquid, a polyarylene copolymer having a sulfonic acid group, and an ionic liquid Furthermore, according to the solid polymer electrolyte membrane 2 (Example 2) containing a proton donor, a proton conduction mechanism that does not depend on the water content of the membrane is provided, so that it can be operated under low humidification conditions. It is apparent that a membrane / electrode structure having good power generation performance can be obtained even in a low temperature region where water freezes.

  On the other hand, in the solid polymer electrolyte membrane 2 (Comparative Example 1) made only of the polyarylene copolymer having a sulfonic acid group, the power generation performance (cell potential) of the membrane / electrode structure is low. It is clear that the low temperature startability is poor.

BRIEF DESCRIPTION OF THE DRAWINGS Explanatory sectional drawing which shows the example of 1 structure of the film | membrane and electrode structure of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Electrode catalyst layer, 2 ... Polymer electrolyte membrane, 3 ... Gas diffusion layer.

Claims (6)

In a membrane / electrode structure for a polymer electrolyte fuel cell in which a polymer electrolyte membrane is sandwiched between a pair of electrodes containing a catalyst,
The polymer electrolyte membrane comprises an ionic liquid and a polyarylene-based copolymer having a sulfonic acid group, and a membrane / electrode structure for a polymer electrolyte fuel cell, characterized in that:   The membrane / electrode structure for a polymer electrolyte fuel cell according to claim 1, wherein the ionic liquid contains a proton donor.   The proton donor is at least one compound selected from the group consisting of trifluoromethanesulfonic acid, bis (trifluoromethylsulfonyl) imidic acid, and tris (trifluoromethylsulfonyl) methideic acid. 2. The membrane / electrode structure for a polymer electrolyte fuel cell according to 2.   The ionic liquid is contained in a range of 0.5 to 200 parts by weight with respect to 100 parts by weight of the polyarylene copolymer having the sulfonic acid group. The membrane / electrode structure for a polymer electrolyte fuel cell according to any one of the above. The polyarylene-based copolymer having a sulfonic acid group includes a structural unit represented by the following general formula (1) and a structural unit represented by the general formula (2). The membrane / electrode structure for a polymer electrolyte fuel cell according to any one of claims 1 to 4.

  A solid polymer fuel cell membrane / electrode structure in which a polymer electrolyte membrane comprising an ionic liquid and a polyarylene copolymer having a sulfonic acid group is sandwiched between a pair of electrodes containing a catalyst is provided. A polymer electrolyte fuel cell characterized by the above.

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