JP2007035611A - Electrolyte composition for fuel cell and fuel cell - Google Patents

Abstract

（式（１）中、ＢＰはフッ素を含まず且つ炭素系骨格を有する重合体から構成される基材を意味する。；Ｒ¹及びＲ²はそれぞれ独立して構造が決定される水素又はアルキル基；Ｒ³は炭素数がｍである直鎖状又は分枝状のアルキレン基；ｐは０以上の整数；ｍ、ｎ及びｑはそれぞれ正の整数から選択される。；スルホン化工程により導入されたスルホ基を有しない。）
【選択図】なしA fuel cell electrolyte composition having high oxidation resistance and low water absorption is provided.
A fuel cell electrolyte composition comprising a polymer electrolyte material having a structure represented by the following general formula (1).

(In the formula (1), BP means a base material composed of a polymer containing no fluorine and having a carbon-based skeleton. R ¹ and R ² are each independently hydrogen or alkyl whose structure is determined. A group; R ³ is a linear or branched alkylene group having m carbon atoms; p is an integer of 0 or more; m, n and q are each selected from positive integers; Does not have a sulfo group formed.)
[Selection figure] None

Description

  The present invention relates to an electrolyte composition for a fuel cell, a method for producing the same, and a fuel cell using them.

  As an electrolyte membrane for a fuel cell, an electrolyte membrane (trade name: Nafion, Aciplex, etc.) composed of a perfluorocarbon polymer having a sulfo group is used, and good power generation performance and durability have been confirmed. However, for the practical application of fuel cells, the development of inexpensive and high hydrogen ion conductive electrolyte materials is expected, and hydrocarbon electrolyte materials are attracting attention.

  As a prior art, a hydrocarbon-based electrolyte membrane that can be obtained by polymerizing a general-purpose monomer such as styrene using a graft reaction on a substrate film and then sulfonating is disclosed (Patent Document 1). In this specification, “hydrocarbon-based material” means a material in which the basic skeleton constituting the material is formed only of carbon and hydrogen (such as polyolefin), and a certain proportion of hydrogen is substituted with halogen such as fluorine. However, it is a concept that includes a part of hydrogen atoms remaining. In other words, in the present specification, the term “hydrocarbon-based material” includes those in which all hydrogen is replaced with fluorine. Since a material in which hydrogen is not completely substituted with fluorine is simplified, the cost can be reduced as compared with a material in which all hydrogen is completely substituted with fluorine.

  However, there is a known problem that the molecular structure of a hydrocarbon-based electrolyte deteriorates when applied to a fuel cell (Non-Patent Document 1). Further, it is known that oxygen radicals (active oxygen) are generated as an intermediate of the oxygen reduction reaction at the cathode of the fuel cell (Non-patent Document 2).

Thus, for the purpose of improving the durability of the hydrocarbon electrolyte, an electrolyte using an aromatic hydrocarbon polymer having a sulfoalkyl group in the side chain is disclosed (Patent Document 2).
JP 9-l02322 A JP 2002-110174 A Journal of Power Sources 127 (2004) 325-330 Phys.Chem.Chem.Phys., 2004,6,2891-2894

  However, the electrolyte described in Patent Document 2 requires a large number of steps to be formed into a film, which raises the problem of cost increase. If the introduction amount and form of the sulfo group are not precisely controlled, the solubility in water is poor. As a whole, it becomes high and sufficient ionic conductivity cannot be obtained, and sufficient battery performance may not be exhibited.

  By the way, in the prior art, in order to introduce a sulfo group, it is necessary to perform a sulfonation step which is a treatment with a compound having strong reactivity such as concentrated sulfuric acid, chlorosulfonic acid, fuming sulfuric acid and the like. Here, when the sulfonation process is applied to a hydrocarbon-based material that does not contain fluorine, the hydrocarbon-based material may be oxidized and the characteristics such as mechanical strength may change. It is desirable to avoid such a characteristic change because it leads to a narrow selection of materials.

  The present invention has been made in view of the above circumstances, and is composed of a hydrocarbon-based material and has excellent durability, a fuel cell electrolyte composition, a method for producing the same, and a fuel cell using these fuel cell electrolyte compositions Providing is a problem to be solved.

  The electrolyte composition for a fuel cell of the present invention that solves the above-mentioned problems is characterized by containing a polymer electrolyte material having a chemical structure represented by the following general formula (1).

（式（１）中、ＢＰはフッ素を含まず且つ炭素系骨格を有する重合体から構成される基材を意味する。；Ｒ¹及びＲ²はそれぞれ独立して構造が決定される水素又はアルキル基；Ｒ³は炭素数がｍである直鎖状又は分枝状のアルキレン基；ｐは０以上の整数；ｍ、ｎ及びｑはそれぞれ正の整数から選択される。；ｍ、ｎ、ｐ及びｑは部位毎に独立して選択できる。；スルホン化工程により導入されたスルホ基を有しない。）

(In the formula (1), BP means a base material composed of a polymer containing no fluorine and having a carbon-based skeleton. R ¹ and R ² are each independently hydrogen or alkyl whose structure is determined. A group; R ³ is a linear or branched alkylene group having m carbon atoms; p is an integer of 0 or more; m, n, and q are each selected from positive integers; And q can be selected independently for each site; it does not have a sulfo group introduced by the sulfonation step.)

  Here, the “sulfonation step” in the present specification is a step of introducing a sulfo group by contacting with a strong acid of concentrated sulfuric acid, chlorosulfonic acid and fuming sulfuric acid.

  Moreover, the fuel cell electrolyte composition of the present invention that solves the above-mentioned problems is characterized by containing a polymer electrolyte material having a chemical structure represented by the following general formula (2).

（式（２）中、ＢＰは炭素系骨格を有する重合体から構成される基材を意味する。；Ｒ¹及びＲ²はそれぞれ独立して構造が決定される水素又はアルキル基；Ｒ³は炭素数がｍである直鎖状又は分枝状のアルキレン基；ｐ及びｐ１は０以上の整数；ｍ、ｎ１、ｎ２、ｎ３、ｎ４及びｑはそれぞれ正の整数から選択される。；Ｒ¹〜Ｒ³、ｍ、ｎ１、ｎ２、ｎ３、ｎ４、ｐ及びｑは部位毎に独立して選択できる。；（Ｌ）で表されるベンゼン環にはスルホ基を有しない。）

(In formula (2), BP means a base material composed of a polymer having a carbon-based skeleton; R ¹ and R ² are each independently a hydrogen or alkyl group whose structure is determined; R ³ is carbon atoms straight-chain or branched alkylene group is m; p and p1 is an integer of 0 or more; m, n1, n2, n3 , n4 and q are selected from positive integers, respectively;. R ¹ no (L) sulfo group to the benzene ring represented ^{by); ~R 3, m, n1} , n2, n3, n4, p and q can be selected independently for each site..

Furthermore, the fuel cell electrolyte composition of the present invention that solves the above-described problems contains a polymer electrolyte material that can be produced by the following production method (i) and / or (ii). .
(I) forming a graft initiation point on a film-like substrate composed of a polymer containing no fluorine and having a carbon-based skeleton;
A step of polymerizing styrene or a styrene derivative partially substituted with an alkyl group from the graft start point to obtain a grafted substrate;
Reacting the benzene ring derived from styrene or a derivative thereof with a sultone constituting a ring composed of m elements (m is 1 or more), oxygen element and sulfur element, and sulfonation A manufacturing method that does not have a process.
(Ii) forming a graft initiation point on a film-like substrate composed of a polymer not containing fluorine and having a carbon-based skeleton;
A step of polymerizing a vinyl derivative described in the following general formula (a) and / or (b) based on the graft initiation point to obtain a grafted substrate;
The manufacturing method which does not have a sulfonation process. In the step of polymerizing the vinyl derivative in this production method, it is desirable to contain divinylbenzene. When divinylbenzene is contained, a material containing fluorine can be employed as the polymer constituting the substrate.

（一般式（ａ）中、Ｒ²は水素又はアルキル基；Ｙは−Ｏ−（ＣＨ₂）_m−、−Ｓ−（ＣＨ₂）_m−又は−（ＣＨ₂）_m−；ｐは正の整数である。一般式（ａ）及び（ｂ）中、Ｒ¹は水素又はアルキル基；Ｘは水素又は炭素数１〜３のアルキル基；一般式（ａ）中のｍは０以上の整数である；一般式（ｂ）中のｍは１以上の整数である）

(In General Formula (a), R ² is hydrogen or an alkyl group; Y is —O— (CH ₂ ) _m —, —S— (CH ₂ ) _m — or — (CH ₂ ) _m —; In general formulas (a) and (b), R ¹ is hydrogen or an alkyl group, X is hydrogen or an alkyl group having 1 to 3 carbon atoms, and m in general formula (a) is an integer of 0 or more. Yes; m in the general formula (b) is an integer of 1 or more)

  That is, in introducing the sulfo group, since the sulfonation step is not employed, it is not necessary to consider the deterioration of the base material, and the range of material selection is widened.

  In addition, by using an alkylene group between a styrene-derived benzene ring (or carbonyl group: hereinafter referred to as “benzene ring”) and a sulfo group, the influence of the sulfo group on the benzene ring or the like is reduced. it can. Specifically, the hydrophilization of the benzene ring portion derived from the direct bonding of a sulfo group or the like to the benzene ring can be suppressed. The active oxygen generated in the fuel cell is presumed to be particularly aggressive against the benzene ring in the structure of the present invention. Moreover, oxidation resistance can be improved by employ | adopting a carbon-carbon bond as a chemical structure of the part inserted between parts, such as a benzene ring, and a sulfo group.

  When the benzene ring or the like is hydrophilized, the active oxygen generated in the fuel cell is likely to approach and the chance of attack increases. Therefore, by suppressing the hydrophilization of the benzene ring or the like, the active oxygen can be prevented from approaching the benzene ring or the like, the stability of the benzene ring part or the like is improved, and the deterioration of the molecular structure due to the active oxygen can be suppressed. I can guess it. A sulfo group, which is a site that exhibits ionic conductivity, is bonded to the benzene ring, etc., so if the benzene ring etc. deteriorates, the elimination of the sulfo group proceeds and the ionic conductivity of the electrolyte material decreases. it is conceivable that.

  Here, in the production method (i), a base material (BP) that is composed of a polymer having a carbon-based skeleton and is generally insoluble in water has a benzene ring into which a sulfo group is introduced for the purpose of improving ion conductivity. Therefore, the electrolyte material as a whole can be expected to be insoluble in water without precisely controlling the amount of sulfo group introduced.

In addition, in the production method (ii), the amount of the sulfo group introduced can be controlled more precisely because the monomer having the sulfo group previously introduced is grafted. Here, m is preferably 3 from the viewpoint of ease of synthesis. Also, divinylbenzene that can be added for crosslinking in the production method (ii) does not employ a sulfonation step, so that a sulfo group is not introduced, the hydrophilicity of the crosslinked portion is not increased, and durability is improved. In this case, fluorine-containing hydrocarbon-based materials that can be used as a base material include at least part of the hydrogen in the polyolefin (polyolefin (a hydrocarbon polymer containing a double bond in the main chain)) is replaced with a fluorine atom. Examples thereof include fluorinated polyolefins and fluorinated polyolefins. In this case, those in which the introduction of fluorine atoms such as fluorination of polyolefin is not regular are included. And what substituted all the hydrogen of polyolefin with fluorine is also included as a desirable form. Furthermore, CH ₂ CHR; (R is hydrogen or an alkyl group having 1 to 3 carbon atoms (preferably 1 carbon atom)) and CF ₂ CFR; (R is fluorine or 1 to 3 carbon atoms (preferably having a carbon number) A copolymer of 1) with a perfluoroalkyl group) can be preferably used. In particular, a copolymer of ethylene and tetrafluoroethylene (ETFE) is preferable. In ETFE, a part of hydrogen atoms is mainly replaced with the aforementioned side chain portion.

  The electrolyte composition for a fuel cell of the present invention is a polymer obtained by copolymerizing at least one of the monomers having the chemical structure represented by the general formulas (a) and (b) and divinylbenzene. It contains an electrolyte material. A sulfo group is not introduced into the benzene ring derived from divinylbenzene in the syntax electrolyte material.

  Therefore, the hydrophilicity of divinylbenzene does not decrease and is hardly oxidized. Therefore, the effect as a crosslinking agent can be maintained for a long time.

  Furthermore, the fuel cell of the present invention that solves the above-described problems has the above-described electrolyte composition for fuel cells of the present invention as an electrolyte. A fuel cell that employs the fuel cell electrolyte composition of the present invention as an electrolyte can exhibit high performance.

  Since the fuel cell electrolyte composition and the production method of the present invention have the above-described configuration, introduction of a sulfo group can be realized without adopting a sulfonation step. Therefore, a molecule derived from a hydrocarbon-based material when introducing a sulfo group. The influence on the structure can be minimized. Further, since it has the above chemical structure, it is less susceptible to the influence of active oxygen generated when used in a fuel cell, and the molecular structure is less likely to deteriorate. Moreover, even if the introduction amount of the sulfo group is increased for the purpose of improving the ion conductivity, the possibility of water solubility is reduced. Therefore, the fuel cell employing the fuel cell electrolyte composition of the present invention is excellent in durability.

  Hereinafter, the electrolyte composition for fuel cell and the fuel cell of the present invention will be described in more detail based on embodiments.

[Electrolyte composition for fuel cell]
-The fuel cell electrolyte composition of this embodiment contains the polymer electrolyte material mentioned later. Furthermore, other polymer electrolyte materials (such as Nafion (trademark)) and fillers can also be contained.

  The polymer electrolyte material has a chemical structure represented by the above general formula (1), that is, a structure in which several side chains are bonded to the base material BP. The same applies to the compound represented by the general formula (2). The base material BP has q side chain moieties bonded to one molecule. The value of q is determined in relation to the number of sulfo groups provided in the side chain portion, and is determined so that sufficient ion conductivity (ion exchange capacity) can be obtained. The bond between the base material BP and the side chain portion is bonded by a covalent bond. In the general formulas (1) and (2), m, n, n1, n2, n3, n4, p, and q are integers in individual portions, but the polymer electrolyte material in the present embodiment has the general formula ( 1) When it is difficult to adjust the values of m, n, n1, n2, n3, n4, p, and q in the same way in all parts. There is. Therefore, when considering the polymer electrolyte material as a whole, the values of m, n, n1, n2, n3, n4, p, and q may be expressed as average values and may not be integers.

  (A) The base material BP is a water-insoluble polymer, and is composed of a polymer having a carbon-based skeleton that does not contain fluorine. The degree of polymerization (molecular weight) of the polymer may be not less than the limit that makes it insoluble in water. Here, having a carbon-based skeleton is not limited as long as the main chain contains carbon atoms, and even a single chain polymer (carbon-chain polymer) or a hetero-chain polymer [(oxygen, carbon) -chain polymer, ( Oxygen, carbon, silicon) -chain polymer, (carbon, silicon) -chain polymer, etc.]. The single chain polymer includes polyalkylene, polycycloalkylene, polyarylene and the like, and does not include a structure substituted with a fluorine atom.

  Preferable basic structure of the main chain portion includes polyolefin (polyolefin (a hydrocarbon polymer containing a double bond in the main chain) is also possible).

  (B) The side chain portion has a polymer composed of styrene and / or a derivative thereof as a basic skeleton, and a sulfo group is bonded to a benzene ring derived from styrene via an alkylene group. Moreover, like the compound of General formula (2), divinylbenzene or its derivative (s) can be added and a crosslinked structure can also be implement | achieved.

In formula (1), R ¹ and R ² are each independently hydrogen or an alkyl group whose structure is determined. R ¹ and R ² are each preferably hydrogen. When selecting an alkyl group, it is preferable to select one having about 1 to 3 carbon atoms. For example, a methyl group, an ethyl group, an n-propyl group, and an iso-propyl group are preferable. R ¹ and R ² may all be unified as the whole polymer electrolyte material, or may not be unified. Moreover, it does not need to be unified in one side chain part.

Since the sulfo group has an alkylene group (R ³ ) having a carbon number of m between the benzene ring portion and the benzene ring portion, an increase in hydrophilicity of the benzene ring can be suppressed. As for carbon number m of an alkylene group, about 1-6 are preferable. The value of m is particularly preferably 3 because the effect is saturated even if it is too large and the synthesis is easy. This alkylene group may be branched.

  The values of n, n1, n2, n3, and n4 that determine the degree of polymerization of a polymer comprising styrene and / or a derivative thereof are not particularly limited. Further, p, which is the number of sulfo groups introduced for each monomer that becomes a polymer group constituting the side chain portion, can be different for each benzene ring portion. Considering the whole polymer electrolyte material, the value of p is the ratio of the number of introduced sulfo groups to the number of benzene rings contained in the polymer electrolyte material {(number of introduced sulfo groups) / (polymer electrolyte material The number of benzene rings contained in the In this case, it can be expressed as a real number exceeding 0.

  -The polymer electrolyte material which the electrolyte composition for fuel cells of this embodiment contains can be manufactured with the following method.

  (Part 1): (i) a step of forming a graft initiation point on a film-like substrate composed of a polymer having a carbon-based skeleton, (ii) styrene or a part thereof based on the graft initiation point A step of polymerizing a styrene derivative in which hydrogen is substituted with an alkyl group (hereinafter referred to as “grafting monomer”) to obtain a grafted substrate; (iii) a carbon atom on a benzene ring derived from the styrene or derivative thereof; A step of reacting sultone constituting a ring composed of m elements, oxygen element and sulfur element.

  (i) As the polymer having a carbon-based skeleton, a material having a structure corresponding to the base material BP is selected. That is, it is a hydrocarbon-based material that does not contain fluorine. For example, polyolefin. The substrate is in the form of a film.

  Although the method of specifically forming the graft initiation point for the polymer constituting the substrate is not particularly limited, it is preferable to generate a radical in the polymer and use the radical as the graft initiation point. The method for generating radicals is not particularly limited, such as a physical method, a chemical method, and a mechanical method. For example, a method of irradiating radiation (such as gamma rays) with an appropriate amount of energy, a method using low-temperature plasma irradiation, a method of extracting a hydrogen atom of a polymer material by a chemical reaction, or a mechanochemical reaction is advanced by pulling / grinding / grinding. There are methods. In particular, the method by irradiation is preferable because it is easy to uniformly generate radicals not only on the surface of the polymer but also inside. Increasing the amount of the graft initiation point increases the number of side chain moieties introduced (that is, the value of q in the general formula (1)).

  (ii) The grafting monomer is selected from styrene and / or a derivative thereof, which is a compound represented by the following general formula (3). Other monomers such as a cross-linking agent (divinylbenzene, etc.), acrylic acid and derivatives thereof can also be mixed. By reacting the crosslinking agent, the water resistance of the resulting film can be improved. When other monomers other than styrene and its derivatives are employed as grafting monomers, those monomers are introduced into the side chain portion. These monomers may be introduced into the side chain portion in the manner of introduction of a general copolymer such as a random copolymer, an alternating copolymer or a block copolymer in relation to the styrene and its derivatives. it can.

（式（３）中のＲ¹及びＲ²は式（１）中のＲ¹及びＲ²と同様の範囲から選択される。すなわち、Ｒ¹及びＲ²はそれぞれ独立して構造が決定される水素又はアルキル基である。）

(R ¹ and R ² in the formula (3) is selected from the same range as R ¹ and R ² in the formula (1). That is, the structure is determined independently R ¹ and R ² are each It is hydrogen or an alkyl group.)

  When a radical is adopted as the graft starting point, the grafted monomer can be grafted to the substrate by immersing the substrate in the grafted monomer and reacting under a predetermined condition. . By this reaction, a side chain portion can be introduced into the substrate. The length of the side chain portion can be controlled by the reaction conditions of the grafting reaction.

  For example, when a radical is used as a graft initiation point and radical polymerization is employed for side chain growth, the length of the side chain portion can be increased by suppressing radical movement. That is, the length of the side chain portion can be controlled by controlling the amount and type of the solvent present in the polymerization reaction or by controlling the reaction temperature.

  When grafting is performed in this step, it is difficult to make the value of n the same in all graft side chain portions. It is considered that the value of n usually varies under normal reaction conditions.

(iii) Sultone is a compound having an alkylene group corresponding to R ³

を選択する。Ｒ³は前述の通り炭素数がｍ個のアルキレン基である。例えば、ｍが３であるプロパンスルトンなどがある。

Select. R ³ is an alkylene group having m carbon atoms as described above. For example, there is propane sultone in which m is 3.

  Introduction of a sulfo group into a benzene ring by sultone can be carried out in the presence of aluminum chloride after dissolving in a solvent such as in nitrobenzene. This reaction is preferably carried out under anhydrous and inert conditions.

  (Part 2): (i) a step of forming a graft initiation point on a film-like substrate composed of a polymer having a carbon-based skeleton, (ii) using the graft initiation point as a base point, the general formula (a ) And / or (b) to polymerize the vinyl derivative (in order to adjust the introduction amount of the sulfo group, an appropriate amount of the aforementioned grafting monomer may be mixed) to polymerize the grafted group. This is a process for obtaining a material. Here, the process (i) is the same as that described in (Part 1), and the description thereof will be omitted.

 As the vinyl derivatives represented by the general formulas (a) and (b) used in (ii), the following structures are preferable. The following vinyl derivatives can be used alone or in combination. It can be used together with styrene or a styrene derivative (such as methylstyrene or α-methylstyrene).

Here, m is preferably 2 to 7. X is preferably a methyl group or an ethyl group. p is preferably 1 or 2, and particularly preferably 1. R ¹ and R ² are preferably hydrogen.

  These vinyl derivatives may be produced in any way, but can be synthesized, for example, by the following method.

First, a vinyl derivative (compound 1: 4- (4-vinylphenyl) in which R ¹ and R ² are hydrogen, p is 1, m is methylene group, m is 4, and X is methyl group in the general formula (a) ) (Butylsulfonic acid methyl ester) will be described below (formula below). For other derivatives, the reaction can be advanced by appropriately adopting R ¹ , R ^2, or compounds having different m, X, and p.

  By reacting 3-chloropropylsulfonyl chloride with dry methanol in the presence of a basic substance such as dried triethylamine, 3-chloropropylsulfonic acid methyl ester (compound 2) is obtained.

  In an inert atmosphere, a dry diethyl ether solution of compound 2 is added dropwise to magnesium powder in dry diethyl ether. Thereafter, 4-chloromethylstyrene is added and stirred to carry out the reaction. Then, 4- (4-vinylphenyl) butylsulfonic acid methyl ester is obtained by performing purification by column chromatography or the like.

As another synthesis method, there is the following method (for compound 5 where m = 3: the following formula).

  Synthesis of Compound 3 (3- (4-hydroxyethylphenyl) propanesulfonic acid): Aluminum chloride is added to 2-phenylethanol, and propane sultone is added therein and heated. After the reaction, the reaction solution is acidified with hydrochloric acid, and then compound 3 is extracted and purified.

  Synthesis of Compound 4 (3- (4-hydroxyethylphenyl) propanesulfonic acid methyl ester): Compound 3 is dissolved in chloroform, and thionyl chloride is added and allowed to react at room temperature overnight. After the reaction, the reaction solution is transferred to a pyridine-methanol solution and stirred. Thereafter, compound 4 is purified.

  Synthesis of compound 5 (3- (4-vinylphenyl) propanesulfonic acid methyl ester): Compound 5 is obtained by heating compound 4 under reflux.

Synthesis of compound 6 (3- (4-vinylphenoxy) propanesulfonic acid methyl ester):

  4-Vinylphenol is dissolved in tetrahydrofuran, sodium hydride is added thereto, and the mixture is heated and stirred. To this reaction solution, a tetrahydrofuran solution of 3-chloropropylsulfonic acid methyl ester is dropped and reacted. After the reaction, the mixture is extracted with water-ethyl acetate and purified.

-Method for producing compound 7 (6- (hex-1-ene-3-one) sulfonic acid methyl ester)

  To a mixture of magnesium powder and dried diethyl ether, a diethyl ether solution of 3-chloropropylsulfonic acid methyl ester is added dropwise under an inert atmosphere. Thereafter, acrylic chloride is added and stirred. Thereafter, purification is performed.

  (Part 3) The polymer electrolyte material may be obtained by polymerizing at least one of the monomers having the chemical structure represented by the general formulas (a) and (b) and divinylbenzene. Since the present polymer electrolyte material does not have the base material BP, the solubility in a solvent can be adjusted appropriately, and it can also be used as an electrode for a fuel cell (so-called membrane liquid). . Other details are the same as described above, and will be omitted.

〔Fuel cell〕
The fuel cell of this embodiment is a solid polymer electrolyte fuel cell. As the fuel cell of this embodiment, a stack in which fuel cells are singly or plurally stacked is formed. The fuel cell has a membrane electrode assembly in which electrode membranes are bonded to both surfaces of an electrolyte membrane obtained by forming the above-described fuel cell electrolyte composition into a membrane, and the membrane electrode assembly is further sandwiched between separators. Yes.

  Gas supply devices for supplying fuel gas and oxidant gas to the electrodes on both sides of the membrane electrode assembly sandwiching the solid polymer electrolyte membrane are connected from the corresponding separators. Hydrogen gas or the like can be used as the fuel gas, and air or the like can be used as the oxidant gas.

  The separator can also use the material and form generally used. The separator is provided with a flow path through which fuel gas or oxidant gas flows, and a gas supply device for supplying the fuel gas is connected to the flow path. A means for removing is connected.

  Examples of the present invention will be described below. In the following examples, either a film made of ETFE (thickness 25 μm) or a film made of polypropylene (thickness 20 μm) was adopted as a polymer constituting the base material BP.

(Example 1)
The polypropylene film was washed with acetone and then irradiated with 20 kGy of gamma rays using cobalt 60 as a radiation source. After putting the obtained film in a glass reaction tube, 4-vinylphenylmethylsulfonic acid methyl ester-divinylbenzene mixture (95: 5) was added and reacted at 60 ° C. for 14 hours. Here, 4-vinylphenylmethylsulfonic acid methyl ester is a compound in which R ¹ and R ² in the general formula (a) are hydrogen, Y is a methylene group, and X is methyl.

  Thereafter, the film was washed three times with methanol and then dried using a dryer. (Mass of 4-vinylphenylmethylsulfonic acid methyl ester-divinylbenzene grafted) / (mass of film before reaction) was 1.9 (grafting ratio 190%).

  200 mg of this dry film was placed in a 1N aqueous sodium hydroxide solution and reacted at 80 ° C. for 15 hours. Further, a membrane obtained by washing with ion exchange water at 90 ° C. after washing with 1N hydrochloric acid overnight was used as a test membrane of Example 1.

Evaluation The obtained test sample was cut into 2 × 3 cm, sufficiently dried with a drier, and then immersed in 3% hydrogen peroxide water containing 2 ppm of divalent iron ions at 90 ° C. for 40 minutes. The change in mass before and after immersion was measured in a dry state. The mass measurement after immersion was performed by washing in order of ethanol, 1N hydrochloric acid and purified water, and then sufficiently drying the membrane with a dry heat dryer. The oxidation resistance was calculated by (mass retention) (%) = (dry mass after immersion in hydrogen peroxide solution) ÷ (dry mass before immersion in hydrogen peroxide solution) × 100. Note that hydrogen peroxide has a high oxidizing power against organic compounds in the presence of divalent iron ions.

  Moreover, the elution of the component was investigated when the test sample was immersed in hot water at 90 ° C. for 24 hours or more. Whether or not the component was eluted was judged from the change in dry mass before and after the immersion. In addition, saturation water content, ion exchange capacity and ion conductivity were measured.

(Example 2)
The ETFE film was washed with acetone, and then irradiated with 10 kGy of gamma rays using cobalt 60 as a radiation source. After putting the obtained film in a glass reaction tube, 4-vinylphenylmethylsulfonic acid methyl ester-divinylbenzene mixture (95: 5) was added and reacted at 60 ° C. for 12 hours.

  Thereafter, the film was washed three times with methanol and then dried using a dryer. (Mass of 4-vinylphenylmethylsulfonic acid methyl ester-divinylbenzene grafted) / (mass of film before reaction) was 1.1 (grafting rate 110%).

  200 mg of this dried film was placed in a 1N aqueous sodium hydroxide solution and reacted at 80 ° C. for 10 hours. Further, a membrane obtained by washing with ion exchange water at 90 ° C. after washing with 1N hydrochloric acid overnight was used as a test membrane of Example 2.

(Comparative Example 1)
The ETFE film was washed with acetone, and then irradiated with 10 kGy of gamma rays using cobalt 60 as a radiation source. After putting the obtained film into a glass reaction tube, a styrene-divinylbenzene mixture (95: 5) was added to the reaction tube, and the inside of the reaction tube was sufficiently replaced with nitrogen.

  Then, this reaction tube was immersed in a 60 degreeC thermostat for 2 hours. Thereafter, the film was washed three times with methanol and then dried using a dryer. The mass grafted by the styrene-divinylbenzene mixture was 40% with respect to the ETFE film before the reaction.

  200 mg (0.55 mmol of styrene moles) of this dry film was placed in 30 mL of a 1% sulfonic acid-dichloroethane solution. The reaction was carried out at 60 ° C. for 1.5 hours. After the reaction, a membrane immersed in ion exchange water at 90 ° C. for 24 hours was used as a test membrane of this comparative example.

(result)
The physical properties of the test membrane of Example 1 were an ion exchange capacity of 2.7 meq / g and an ion conductivity of 0.07 S / cm (AC impedance method; measurement conditions: 90 ° C. saturated water-containing state, room temperature). The saturated water content was 56%. The mass retention after immersion in hydrogen peroxide was 90%.

  The physical properties of the test membrane of Example 2 were an ion exchange capacity of 2.0 meq / g and an ion conductivity of 0.08 S / cm (AC impedance method; measurement conditions: 90 ° C. saturated water-containing state, room temperature). The saturated water content was 60%. The mass retention after immersion in hydrogen peroxide was 92%.

  The physical properties of the test membrane of Comparative Example 1 were an ion exchange capacity of 2.0 meq / g and an ion conductivity of 0.09 S / cm (AC impedance method; measurement conditions: 90 ° C. saturated water-containing state, room temperature). The saturated water content was 46.5%. The mass retention after immersion in hydrogen peroxide was 60%.

  From the above results, the test membranes of Examples 1 and 2 have superior oxidation resistance (that is, durability) while having almost the same performance as the ion exchange membrane as compared with the test membrane of Comparative Example 1. I understood. Specifically, in the test film of the comparative example, as a result of the oxidation resistance evaluation test, the grafted styrene is almost lost as the mass retention ratio is 60%, whereas the test films of Examples 1 and 2 retain the mass. The rate was also large and it became clear that it was excellent in oxidation resistance. Since Example 1 does not employ a sulfonation step, it is considered that the substrate was not oxidized and high durability was realized. Further, in Example 2, since the sulfonation step is not adopted, it is considered that a sulfo group is not introduced into the benzene ring of divinylbenzene added and reacted as a crosslinking agent. That is, since the sulfo group is not introduced into the crosslinked structure, it is considered that the hydrophilicity of the crosslinked structure is kept low and the oxidation resistance is improved.

Claims (11)

A fuel cell electrolyte composition comprising a polymer electrolyte material having a chemical structure represented by the following general formula (1):

(In the formula (1), BP means a base material composed of a polymer containing no fluorine and having a carbon-based skeleton. R ¹ and R ² are each independently hydrogen or alkyl whose structure is determined. A group; R ³ is a linear or branched alkylene group having m carbon atoms; p is an integer of 0 or more; m, n, and q are each selected from positive integers; And q can be selected independently for each site; it does not have a sulfo group introduced by the sulfonation step.) A fuel cell electrolyte composition comprising a polymer electrolyte material having a chemical structure represented by the following general formula (2):

(In formula (2), BP means a base material composed of a polymer having a carbon-based skeleton; R ¹ and R ² are each independently a hydrogen or alkyl group whose structure is determined; R ³ is alkylene group having a straight-chain or branched are m carbon; m, p and p1 is an integer of 0 or more; n1, n2, n3, n4 and q are selected from positive integers, respectively;. R ¹ no (L) sulfo group to the benzene ring represented ^{by); ~R 3, m, n1} , n2, n3, n4, p and q can be selected independently for each site.. Forming a graft initiation point for a film-like substrate composed of a polymer not containing fluorine and having a carbon-based skeleton;
A step of polymerizing styrene or a styrene derivative partially substituted with an alkyl group from the graft start point to obtain a grafted substrate;
Reacting the benzene ring derived from styrene or a derivative thereof with a sultone constituting a ring composed of m elements (m is 1 or more), oxygen element and sulfur element, and sulfonation A fuel cell electrolyte composition comprising a polymer electrolyte material that can be produced by a production method having no steps. Forming a graft initiation point for a film-like substrate composed of a polymer not containing fluorine and having a carbon-based skeleton;
From the graft initiation point as a base point, a step of polymerizing a vinyl derivative described in the following general formula (a) and / or (b) to obtain a grafted substrate;
And a polymer electrolyte material that can be produced by a production method that does not have a sulfonation step.

(In General Formula (a), R ² is hydrogen or an alkyl group; Y is —O— (CH ₂ ) _m —, —S— (CH ₂ ) _m — or — (CH ₂ ) _m —; In general formulas (a) and (b), R ¹ is hydrogen or an alkyl group, X is hydrogen or an alkyl group having 1 to 3 carbon atoms, and m in general formula (a) is an integer of 0 or more. Yes; m in the general formula (b) is an integer of 1 or more) The base material is a hydrocarbon material that may contain fluorine instead of the hydrocarbon material that does not contain fluorine,
5. The fuel cell electrolyte composition according to claim 4, wherein divinylbenzene is contained in the step of polymerizing the vinyl derivative.   6. The fuel cell electrolyte composition according to claim 1, wherein m is 3. 6. Forming a graft initiation point for a film-like substrate composed of a polymer not containing fluorine and having a carbon-based skeleton;
A step of polymerizing styrene or a styrene derivative partially substituted with an alkyl group from the graft start point to obtain a grafted substrate;
Reacting a benzene ring derived from styrene or a derivative thereof with a sultone constituting a ring composed of m elements (m is 1 or more), oxygen element and sulfur element, and sulfonation The manufacturing method of the electrolyte composition for fuel cells characterized by not having a process. Forming a graft initiation point for a film-like substrate composed of a polymer not containing fluorine and having a carbon-based skeleton;
From the graft initiation point as a base point, a step of polymerizing a vinyl derivative described in the following general formula (a) and / or (b) to obtain a grafted substrate;
And having no sulfonation step, a method for producing an electrolyte composition for a fuel cell.

(In General Formula (a), R ² is hydrogen or an alkyl group; Y is —O— (CH ₂ ) _m —, —S— (CH ₂ ) _m — or — (CH ₂ ) _m —; In general formulas (a) and (b), R ¹ is hydrogen or an alkyl group, X is hydrogen or an alkyl group having 1 to 3 carbon atoms, and m in general formula (a) is an integer of 0 or more. Yes; m in the general formula (b) is an integer of 1 or more) The base material is a hydrocarbon material that may contain fluorine instead of the hydrocarbon material that does not contain fluorine,
The method for producing an electrolyte composition for a fuel cell according to claim 8, wherein divinylbenzene is contained in the step of polymerizing the vinyl derivative. A fuel cell electrolyte comprising a polymer electrolyte material obtained by copolymerizing at least one of monomers having a chemical structure represented by the following general formulas (a) and (b) and divinylbenzene Composition.

(In General Formula (a), R ² is hydrogen or an alkyl group; Y is —O— (CH ₂ ) _m —, —S— (CH ₂ ) _m — or — (CH ₂ ) _m —; In general formulas (a) and (b), R ¹ is hydrogen or an alkyl group, X is hydrogen or an alkyl group having 1 to 3 carbon atoms, and m in general formula (a) is an integer of 0 or more. Yes; m in the general formula (b) is an integer of 1 or more)   It has the electrolyte composition for fuel cells in any one of Claims 1-6 and 10, and / or the electrolyte composition for fuel cells manufactured by the manufacturing method in any one of Claims 7-9. A fuel cell.