JP2007207625A - Solid polymer electrolyte and solid polymer fuel cell using this - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize a solid polymer electrolyte superior in thermal resistance, proton conductivity, mechanical strength, and water retention. <P>SOLUTION: The solid polymer electrolyte is compounded of an organic metal compound as shown by a formula and an organic polymer having proton conductivity. In the formula, X<SB>1</SB>-X<SB>3</SB>express each independently hydrogen atom, hydrocarbon group which may have a substituent, or alkoxyl group, X<SB>4</SB>expresses hydrogen atom, or a hydrocarbon group which may have a substituent, M is at least one kind of metal atom selected from a group of Si, Ti, Al, Zr, and Ge, and n is an integer of 1-100. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a solid polymer electrolyte having proton conductivity.

  A polymer electrolyte fuel cell generally includes a laminate in which a membrane electrode assembly (MEA) is sandwiched between separators. The MEA has a solid polymer electrolyte membrane sandwiched between a pair of electrode catalyst layers and further sandwiched between a pair of gas diffusion layers from the outside.

  The electrode catalyst layer is a porous layer formed by a mixture of a solid polymer electrolyte and an electrode catalyst in which catalyst particles are supported on a conductive carrier. In addition, a gas diffusion layer is used in which a carbon water repellent layer composed of carbon particles, a water repellent and the like is formed on the surface of a gas diffusion base material such as carbon cloth.

  Examples of solid polymer electrolyte membranes used in polymer electrolyte fuel cells include polystyrene-based cation exchange membranes having sulfonic acid groups, mixed membranes of fluorocarbon sulfonic acid and polyvinylidene fluoride, and trifluoroethylene as a fluorocarbon matrix. Grafted membranes, perfluorocarbon sulfonic acid membranes and the like are used.

  The solid polymer electrolytes constituting these membranes have a glass transition temperature (Tg) around 130 ° C., and when reaching a temperature region higher than that, the ion channel structure contributing to proton conduction is destroyed. End up. For this reason, when using a polymer electrolyte fuel cell including the above-described polymer electrolyte membrane, the battery is usually operated in a relatively low temperature range from room temperature to about 80 ° C.

  In addition, the output of the fuel cell can be increased by improving the solid polymer electrolyte membrane.

  Therefore, the conventional solid polymer electrolyte membrane is used to reduce the internal resistance of the battery and increase the battery output, thereby reducing the thickness of the solid polymer electrolyte membrane or improving the proton conductivity of the solid polymer electrolyte membrane. Attempts have been made to increase the sulfonic acid group concentration of the solid polymer electrolyte constituting the membrane. However, the reduction in the thickness of the solid polymer electrolyte membrane decreases the mechanical strength of the solid polymer electrolyte membrane itself, and causes pinholes during the production of the solid polymer electrolyte membrane or during long-term operation. sell. In addition, a significant increase in the sulfonic acid group concentration leads to a decrease in the mechanical strength of the solid polymer electrolyte membrane due to swelling, and on the contrary, the battery performance may be deteriorated.

In addition, the proton conductivity of the solid polymer electrolyte membrane depends on the water content of the solid polymer electrolyte membrane. If the water content is low, the proton conductivity of the solid polymer electrolyte membrane decreases. Thus, Patent Document 1 discloses a solid polymer electrolyte membrane containing fine particles of silica and / or fibrous silica fibers.
Japanese Patent Laid-Open No. 06-1111827

  When the operating temperature of the fuel cell is low, not only the power generation efficiency is lowered, but also the catalyst may be poisoned by carbon monoxide depending on the type of catalyst used. Therefore, realization of a solid polymer electrolyte membrane excellent in heat resistance that does not deteriorate even when used at a high temperature of 100 ° C. or higher for a long time is desired.

  Further, as described above, it is desired that the solid polymer electrolyte membrane is excellent in proton conductivity and mechanical strength. However, there is a trade-off relationship between proton conductivity and mechanical strength in a solid polymer electrolyte membrane, and it is difficult to obtain a solid polymer electrolyte membrane with high proton conductivity and excellent mechanical strength. It was.

  Furthermore, as described in Patent Document 1, when an additive such as fine particle silica or fibrous silica fiber is used for the solid polymer electrolyte membrane, the additive aggregates depending on pH during film formation, and the additive As a result, the particle size and dispersibility of the polymer particles varied, and the resulting solid polymer electrolyte membrane had non-uniform water retention.

  Then, an object of this invention is to provide the solid polymer electrolyte excellent in heat resistance, proton conductivity, mechanical strength, and water retention.

  The present invention solves the above problems by a solid polymer electrolyte obtained by combining an organometallic compound represented by the following chemical formula 1 and an organic polymer having proton conductivity.

In Chemical Formula 1, X _{1 to} X ₃ are each independently a hydrogen atom, a hydrocarbon group that may have a substituent, or an alkoxyl group, and X ₄ has a hydrogen atom or a substituent. And M is at least one metal atom selected from the group consisting of Si, Ti, Al, Zr and Ge, and n is an integer of 1 to 100.

  According to the present invention, a solid polymer electrolyte excellent in heat resistance, proton conductivity, mechanical strength, and water retention can be obtained.

  The first of the present invention is a solid polymer electrolyte obtained by combining an organometallic compound represented by Chemical Formula 1 and an organic polymer having proton conductivity.

Chemical formula 1, X _{1 to} X ₃ are each independently a hydrogen atom, a hydrocarbon group which may have a substituent, or an alkoxyl group, and X ₄ has a hydrogen atom or a substituent. And M is at least one metal atom selected from the group consisting of Si, Ti, Al, Zr and Ge, and n is an integer of 1 to 100.

  Since the organometallic compound is excellent in heat resistance, by using a composite of the organic polymer having proton conductivity and the organometallic compound, cutting of the organic polymer due to heat is suppressed, and the solid high in heat resistance is excellent. A molecular electrolyte can be obtained. Furthermore, the organic polymer and the organometallic compound can be combined in a state where both components are highly dispersed. As a result, while maintaining the proton conductivity and flexibility of the organic polymer, the organometallic compound can suppress the thermal decomposition of the organic polymer, and the solid polymer electrolyte has excellent proton conductivity, mechanical strength, and heat resistance. Is obtained.

  Furthermore, the water retention of the obtained solid polymer electrolyte is improved by the interaction between the organometallic compound and the electrolyte component.

  Therefore, according to the present invention, a solid polymer electrolyte excellent in heat resistance, proton conductivity, mechanical strength, and water retention can be obtained.

  Hereinafter, the organometallic compound, the organic polymer, and the solid polymer electrolyte, which are constituent elements of the solid polymer electrolyte of the present invention, will be described in detail.

[Organic metal compound]
The organometallic compound used in the solid polymer electrolyte of the present invention is represented by the following chemical formula 1.

In the chemical formula 1, X _{1 to} X ₃ are each independently a hydrogen atom, a hydrocarbon group which may have a substituent, or an alkoxyl group.

  As said hydrocarbon group, Preferably it is a C1-C10 hydrocarbon group, More preferably, a 2-4 hydrocarbon group is mentioned. The hydrocarbon group may be linear, branched or cyclic, but is preferably linear or branched. Specifically, methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, tert-butyl group, n-pentyl group, n-hexyl group, cyclohexyl group, Examples thereof include a phenyl group, a benzyl group, a vinyl group, an allyl group, an ethynyl group, and a propargyl group.

  The hydrocarbon group may have a substituent, and examples of the substituent include a halogen atom, an alkoxyl group, an alkylthio group, an ester group, and an acyl group.

  As said alkoxyl group, Preferably a C1-C10 alkoxyl group, More preferably, a C2-C4 alkoxyl group is mentioned. Specifically, methoxy group, ethoxy group, n-propyloxy group, isopropyloxy group, n-butyloxy group, sec-butyloxy group, tert-butyloxy group, isobutyloxy group, n-pentyloxy group, 2,2- Examples thereof include a dimethylpropyloxy group, a cyclopentyloxy group, an n-hexyloxy group, a cyclohexyloxy group, a 2-methylpentyloxy group, and a 2-ethylhexyloxy group.

  The alkoxyl group may have a substituent, and examples of the substituent include the same as those described above for the hydrocarbon group.

X _{1 to} X ₃ are preferably an alkoxyl group and an alkyl group in consideration of reactivity with an organic polymer and dispersibility, and particularly preferably a methoxy group, an ethoxy group, an isopropyloxy group, a butoxy group, and the like.

In Formula 1, X ₄ is a hydrogen atom or a hydrocarbon group that may have a substituent. Note that the hydrocarbon group which may have a substituent group, is the same as X ₁ to X ₃ as described above.

X ₄ is preferably an alkyl group in consideration of reactivity with organic polymers and dispersibility, and particularly preferably a methyl group, an ethyl group, an isopropyl group, a butyl group, or the like.

In the chemical formula 1, when n is 2 or more, X ₁ and X ₂ in each repeating unit may be the same or different.

  In Formula 1, M is at least one metal atom selected from the group consisting of Si, Ti, Al, Zr, and Ge. When n is 2 or more, M may be the same or different. Among these, M is preferably Si or Ti in consideration of reactivity and affinity with organic substances and water.

  In the chemical formula 1, n is an integer of 1 to 100. When n is 100 or less, the dispersibility is excellent. In addition, n is an integer of 1 to 100, so that the organic polymer and the organometallic compound are more uniformly dispersed and combined, and heat resistance, proton conductivity, mechanical strength, water retention, etc. Uniform solid polymer electrolyte is obtained.

  When n is 1 in the chemical formula 1, tetraethyl orthosilicate, tetramethyl orthosilicate and the like can be mentioned. In addition, as the organometallic compound in which n is 2 to 10 in the chemical formula 1, methyl silicate manufactured by Fuso Chemical Industry Co., Ltd., MKC silicate manufactured by Mitsubishi Chemical Co., Ltd., ethyl silicate manufactured by Colcoat Co., Ltd., Toray Dow Corning Co., Ltd. Silicone resin manufactured by Toshiba Silicone Co., Ltd. Silicone resin manufactured by Shin-Etsu Chemical Co., Ltd., Polydimethylsiloxane containing hydroxyl group manufactured by Dow Corning-Asia Co., Ltd., Silicon oligomer manufactured by Nihon Unica Co., Ltd., etc. It is done.

  The organometallic compound is preferably one that is soluble in an organic solvent used when preparing a solid polymer electrolyte. Thereby, the dispersibility of the organometallic compound in the solid polymer electrolyte is improved, and a solid polymer electrolyte having uniform heat resistance, proton conductivity, mechanical strength, water retention and the like is obtained. Specifically, being soluble in an organic solvent is a state in which the viscosity of the organometallic compound is reduced without becoming cloudy in the organic solvent. The specific types of the organic solvent will be described later.

  In the solid polymer electrolyte of the present invention, it is desirable that the organometallic compound is further subjected to condensation polymerization to obtain a polymer compound, and the polymer compound and the organic polymer are combined. The polymer compound can be obtained by using an organometallic compound having two or more hydroxyl groups or alkoxyl groups as monomers or oligomers and subjecting these to condensation polymerization. According to the polymer compound, the effect of suppressing the cutting of the organic polymer due to heat is high, and the heat resistance of the solid polymer electrolyte can be further improved.

  The polymer compound is particularly preferably a compound obtained by further condensing an oligomer having two or more hydroxyl groups, alkoxyl groups, etc. as the organometallic compound. According to the oligomer, the condensation reaction proceeds more slowly than the monomer even under a low pH condition. Therefore, when preparing the solid polymer electrolyte, after the oligomer and the organic polymer are sufficiently mixed, the oligomer can be condensed to form a polymer compound, and the oligomer condensation reaction together with the production of the solid polymer electrolyte. Thus, the manufacturing process can be simplified in material synthesis. Furthermore, the solid polymer electrolyte in which the organic polymer and the polymer compound are uniformly dispersed in the obtained solid polymer electrolyte, has excellent proton conductivity, mechanical strength, water retention, heat resistance, etc., and has uniform characteristics as a whole. Is obtained.

  The polymer compound preferably has an average degree of polymerization of 100 to 10,000 in consideration of mechanical strength, heat resistance, and the like of the obtained solid polymer electrolyte.

  In the solid polymer electrolyte of the present invention, the organometallic compound and / or the polymer compound described above may be used singly or in combination of two or more.

[Organic polymer]
The organic polymer used in the solid polymer electrolyte of the present invention has proton conductivity, and any conventionally known one can be used without particular limitation.

  Specific examples of the organic polymer include a fluorinated polymer having an ion exchange group and all or part of the polymer skeleton being fluorinated, or a hydrocarbon polymer having an ion exchange group and containing no fluorine in the polymer skeleton. , Etc.

Examples of the ion-exchange group is not particularly _{limited, -SO 3 H, -COOH, -PO} (OH) 2, -POH (OH), - SO 2 NHSO 2 -, - Ph (OH) (Ph represents a phenyl group A cation exchange group such as —NH ₂ , —NHR, —NRR ′, —NRR′R ″ ⁺ , —NH ₃ ^{+ and the} like (R, R ′, R ″ represent an alkyl group, cycloalkyl Anion exchange groups such as a group, an aryl group, and the like.

  Specific examples of the fluorine-based polymer having an ion exchange group include Nafion (registered trademark, manufactured by DuPont), Aciplex (registered trademark, manufactured by Asahi Kasei Co., Ltd.), Flemion (registered trademark, manufactured by Asahi Glass Co., Ltd.), and the like. Perfluorocarbon sulfonic acid polymer, polytrifluorostyrene sulfonic acid polymer, perfluorocarbon phosphonic acid polymer, trifluorostyrene sulfonic acid polymer, ethylene tetrafluoroethylene-g-styrene sulfonic acid polymer, ethylene-tetrafluoroethylene Preferred examples include a copolymer, polytetrafluoroethylene-g-polystyrene sulfonic acid polymer, and polyvinylidene fluoride-g-polystyrene sulfonic acid polymer.

  Specific examples of the hydrocarbon polymer having an ion exchange group include a polysulfone sulfonic acid polymer, a polyether ether ketone sulfonic acid polymer, a polybenzimidazole alkyl sulfonic acid polymer, and a polybenzimidazole alkylphosphonic acid polymer. Suitable examples include cross-linked polystyrene sulfonic acid polymers, polyether sulfone sulfonic acid polymers, and the like.

  The weight average molecular weight of the organic polymer is preferably 10,000 to 1,000,000, more preferably 300,000 to 1,000,000.

  The organic polymer preferably has at least one reactive group that can interact with or react with an organometallic compound and / or a polymer compound. As a result, the organic polymer and the organometallic compound and / or the polymer compound can be combined at the molecular level, and the properties of the solid polymer electrolyte such as proton conductivity, mechanical strength, water retention and heat resistance are stabilized. Can be demonstrated. Examples of the reactive group include at least one selected from the group consisting of a hydroxyl group, a sulfonic acid group, a phosphonic acid group, a sulfonamide group, a sulfonimide group, and derivatives thereof. Of these, sulfonic acid groups and phosphonic acid groups are preferred.

  The reactive group can be introduced into the organic polymer by using a known method such as using concentrated sulfuric acid.

[Composite of organometallic compound and organic polymer]
The solid polymer electrolyte of the present invention is a composite of an organic metal compound and an organic polymer. Here, “composite” means that the organic metal compound and the organic polymer are covalently bonded, hydrogen bond, ionic bond, interaction between polar groups, etc., in addition to those in which the organic metal compound and the organic polymer are simply mixed. Including those chemically bound or adsorbed by.

  The solid polymer electrolyte is preferably one in which an organometallic compound and an organic polymer are chemically bonded or adsorbed by a covalent bond, a hydrogen bond, an interaction between polar groups, or the like. This makes it possible to stably exhibit the properties of the solid polymer electrolyte such as proton conductivity, mechanical strength, water retention, and heat resistance.

  In the solid polymer electrolyte of the present invention, the mixing ratio of the organometallic compound and the organic polymer is not particularly limited, but is preferably from 1:20 to 1: 2, more preferably from 1:10 to 1: 5 by mass ratio. It is good to do.

  The same applies when the solid polymer electrolyte contains a polymer compound obtained by condensation polymerization of an organometallic compound.

  If the amount of the organic metal compound or polymer compound added is too small, the heat resistance of the obtained solid polymer electrolyte may not be sufficiently improved. If the amount of the organic polymer added is too small, the flexibility of the solid polymer electrolyte will be reduced. There is a fear. Therefore, it is desirable that the mixing ratio is within the above range.

[Composite of organometallic compound and organic polymer]
The composite of the organometallic compound and the organic polymer can be performed according to a known method. The organic metal compound and the organic polymer are obtained by a method of dissolving or suspending an organic solvent in an organic solvent to prepare a slurry and removing the organic solvent. As a result, a solid polymer electrolyte in which an organic metal compound and an organic polymer are mixed and combined is obtained.

  Examples of the organic solvent include alcohol solvents such as methanol, ethanol and 1-propanol (NPA), ether solvents such as tetrahydrofuran, tetrahydropyran, monoglyme and diglyme, alcohols such as methoxyethanol, ethoxyethanol, cyclohexanol and benzyl alcohol. Solvent, cyclopentanone, cyclohexanone and other ketone solvents, chloroform and other halogen solvents, N, N-dimethylacetamide, N, N-dimethylformamide, dimethyl sulfoxide, N-methyl-2-pyrrolidone and other aprotic polar solvents And so on. A solvent can be used individually by 1 type, or if possible, can use 2 or more types together.

  In order to improve the dispersibility and reactivity of the organometallic compound and the organic polymer, the slurry is generally used in a conventional manner such as a stirring bar, a stirring blade, a mechanical stirring means by a homogenizer, a stirring means by a jet, etc., ultrasonic treatment, etc. It is advisable to apply appropriate mixing means.

  Further, by adding water and, if necessary, an acid catalyst to the slurry, hydrolysis and polycondensation reaction of the organometallic compound, so-called sol-gel reaction, the solid polymer compound of the organic polymer and the polymer compound is obtained. A molecular electrolyte is obtained. If necessary, it may be heated during the hydrolysis and polycondensation reaction.

  The acid catalyst is for the organic metal compound to promote hydrolysis and polycondensation reaction, and is preferably an inorganic protonic acid or an organic protonic acid.

Examples of the inorganic protonic acid include hydrochloric acid, sulfuric acid, phosphoric acids (such as H ₃ PO ₄ , H ₃ PO ₃ , H ₄ P ₂ O ₇ , H ₅ P ₃ O ₁₀ , metaphosphoric acid, or hexafluorophosphoric acid), boric acid, Examples thereof include nitric acid, perchloric acid, tetrafluoroboric acid, hexafluoroarsenic acid, hydrobromic acid, solid acid (tungstophosphoric acid, tungsten peroxo complex, etc.) and the like.

  Examples of organic protonic acids include phosphoric acid esters (for example, phosphoric acid esters having 1 to 30 carbon atoms, phosphoric acid methyl ester, phosphoric acid propyl ester, phosphoric acid dodecyl ester, phosphoric acid phenyl ester, phosphoric acid dimethyl ester, Or phosphorous acid dododecyl ester, etc.), phosphorous acid esters (for example, phosphorous acid esters having 1 to 30 carbon atoms, phosphorous acid methyl ester, phosphorous acid dodecyl ester, phosphorous acid diethyl ester, phosphorous acid) Diisopropyl or phosphorous acid dododecyl ester), sulfonic acids (for example, sulfonic acids having 1 to 15 carbon atoms, such as benzenesulfonic acid, toluenesulfonic acid, hexafluorobenzenesulfonic acid, trifluoromethanesulfonic acid, or dodecylsulfone) Acid), carboxylic acids (for example, carbon number 1) 15 carboxylic acids such as acetic acid, trifluoroacetic acid, benzoic acid, or substituted benzoic acid), imides (bis (trifluoromethanesulfonyl) imidic acid, trifluoromethanesulfonyl trifluoroacetamide, etc.), phosphonic acids (for example, carbon number) 1 to 30 phosphonic acids, such as methylphosphonic acid, ethylphosphonic acid, phenylphosphonic acid, diphenylphosphonic acid, or 1,5-naphthalene bisphosphonic acid) or the like, or represented by Nafion (registered trademark) Perfluorocarbon sulfonic acid polymer, poly (meth) acrylate having a phosphate group in the side chain (Japanese Patent Laid-Open No. 2001-14834), sulfonated polyether ether ketone (Japanese Patent Laid-Open No. 6-93111), sulfonated polyether sulfone (Japanese Patent Laid-Open No. Hei 10 45913 JP), a polymer compound having a proton acid site of sulfonated such heat aromatic polymers such as sulfonated polysulfone (JP-A-9-245818) and the like. Two or more acid catalysts can be used in combination.

  The reaction temperature for the sol-gel reaction of the organometallic compound is related to the reaction rate, and can be selected according to the reactivity of the organometallic compound and the type and amount of the acid catalyst. Preferably it is 0-200 degreeC, More preferably, it is 30-120 degreeC. The reaction time may be about 1 to 72 hours.

  Examples of the acid catalyst acid include hydrochloric acid, nitric acid, sulfuric acid, and acetic acid, but are not limited thereto.

  The addition amount of the acid for the acid catalyst is 0.005 to 100 mol, preferably 0.01 to 20 mol, per 1 mol of the organometallic compound. When the amount of catalyst acid added is 100 mol or less, the hydrolysis reaction rate is adjusted (controlled) so that it does not become too fast, so it is excellent in that the surface property of the film can be maintained well. ing. In addition, when the addition amount of the acid for the catalyst is 0.005 mol or more, since the reaction rate is adjusted (controlled) so as not to be too slow, it is economical without taking too long a film formation time. .

  The addition amount of the acid catalyst is 0.005 to 100 mol, preferably 0.01 to 20 mol, per 1 mol of the organometallic compound in the slurry. When the addition amount of the acid catalyst is 0.005 mol or more, the progress of the reaction does not become too slow, and the reaction can proceed favorably. It is excellent in that the reaction can be controlled well when it is 100 mol or less.

  The method for adding the acid catalyst is not particularly limited, but the dropping rate is 0.001 to 10 ml / min, preferably 0.01 to 0.5 ml / min with respect to 10 ml of the slurry. It is desirable to drop slowly. The slow addition with stirring is because it is desirable from the viewpoint of preventing the electrolyte from precipitating. If added at a stretch, precipitation of the electrolyte may occur, and there is a possibility that the film forming performance may be affected, for example, the film thickness may not be well controlled as described above. That is, it is excellent in that the reaction can be controlled satisfactorily when the dropping rate of the catalyst is 10 ml / min or less. Therefore, the electrolyte can be uniformly dropped without precipitation. As a result, it is possible to control the film forming performance satisfactorily, for example, the film thickness can be well controlled as described above. On the other hand, when the dropping speed is 0.001 ml / min or more, it can be dropped uniformly without causing precipitation.

  Further, the timing for adding the acid catalyst to the slurry is not particularly limited. It is desirable to finish dropping the acid catalyst several hours before adding the organometallic compound, preferably 0.1 to 72 hours before. By doing so, the solution becomes uniform and desirable. Therefore, the start timing of adding the acid catalyst can be determined from the addition amount of the catalyst and the dropping rate of the catalyst so as to finish dropping the catalyst several hours before adding the organometallic compound.

  While the slurry has fluidity, the solid polymer electrolyte can be formed by using a known method such as coating on a support or placing it in a petri dish.

  The support on which the slurry is applied is not particularly limited, and examples thereof include a glass substrate, a metal substrate, a polymer film, and a reflection plate. Examples of the polymer film include cellulose polymer films such as TAC (triacetyl cellulose), ester polymer films such as PET (polyethylene terephthalate) and PEN (polyethylene naphthalate), PTFE (polytrifluoroethylene), and the like. And fluorinated polymer films, polyimide films and the like.

  The slurry may be applied by a known method, such as curtain coating, extrusion coating, roll coating, spin coating, dip coating, bar coating, spray coating, slide coating, or print coating. Can be used.

  The slurry may be dried by a known method such as natural drying, heat drying, or pressure drying with an autoclave. Although drying in particular is not restrict | limited, 0 to 350 degreeC is preferable, More preferably, it is 30 to 150 degreeC, Preferably it carries out for 1 to 72 hours.

[Solid polymer electrolyte membrane]
The solid polymer electrolyte of the present invention can be used in the form of particles, fibers, membranes and the like. The solid polymer electrolyte can be applied to various uses such as a fuel cell, water electrolysis, hydrohalic acid electrolysis, salt electrolysis, oxygen concentrator, humidity sensor, and gas sensor. Especially, it is preferable to use as an electrolyte in a membrane electrode assembly for fuel cells, and a fuel cell excellent in power generation efficiency and output voltage can be obtained.

  When the solid polymer electrolyte of the present invention is used for a membrane electrode assembly for a fuel cell, it can be applied to an electrode catalyst layer in a fuel cell. Particularly preferably, the solid polymer electrolyte of the present invention is used as a membrane. The solid polymer electrolyte membrane formed in the above is preferably used for a membrane electrode assembly for a fuel cell. As a result, a fuel cell membrane electrode assembly excellent in power generation efficiency and output voltage can be obtained.

  Although there is no restriction | limiting in particular in the film thickness of a solid polymer electrolyte membrane, Usually, 10-300 micrometers, Preferably it is 30-150 micrometers. If it is in this range, sufficient film strength can be obtained, and the film resistance will be sufficiently low in practical use. If the film thickness is significantly smaller than 10 μm, there is a possibility that the positive electrode fuel and the negative electrode fuel are not sufficiently blocked. If the film thickness greatly exceeds 300 μm, the film resistance becomes too high, which may adversely affect the power generation performance of the fuel cell.

[Membrane electrode assembly for fuel cells]
According to the solid polymer electrolyte and / or the solid polymer electrolyte membrane of the present invention, since it has the above-mentioned various characteristics, it becomes possible to provide a membrane electrode assembly for a fuel cell that is excellent in power generation efficiency and output voltage. .

  The configuration of the fuel cell membrane electrode assembly is not particularly limited as long as it is a conventionally known one. Specifically, as shown in FIG. 1, a fuel electrode side gas diffusion electrode having a fuel electrode side electrode catalyst layer 120a and a fuel electrode side gas diffusion layer 130a on both sides of the solid polymer electrolyte membrane 110, and an air electrode side Examples thereof include a membrane electrode assembly 140 having a configuration in which the electrode electrode layer 120c and the air electrode side gas diffusion electrode having the air electrode side gas diffusion layer 130c are arranged to face each other.

  As described above, the solid polymer electrolyte of the present invention can be applied to a solid polymer electrolyte membrane in addition to the fuel electrode side electrode catalyst layer and the air electrode side catalyst layer in the membrane electrode assembly. The membrane / electrode assembly is not particularly limited except that the solid polymer electrolyte and / or solid polymer electrolyte membrane of the present invention is used, and various conventionally known techniques may be appropriately referred to. Therefore, the detailed description regarding the electrode catalyst layer and the gas diffusion layer in the fuel electrode and the air electrode is omitted here.

  Furthermore, according to the membrane electrode assembly, it is possible to provide a polymer electrolyte fuel cell capable of exhibiting excellent power generation performance over a long period of time. As a result, a highly reliable polymer electrolyte fuel cell can be obtained as a power source for moving bodies and a stationary power source. Among them, since the polymer electrolyte membrane is excellent in proton conductivity, mechanical strength, water retention, heat resistance, etc., the polymer electrolyte fuel cell according to the present invention is used as a power source for moving bodies such as automobiles. It is preferable to use it.

  In addition, since the solid polymer electrolyte is excellent in heat resistance, the fuel cell can exhibit high power generation performance with less deterioration of the solid polymer electrolyte even under operating conditions at a higher temperature than in the past. Is possible.

  The structure of the fuel cell is not particularly limited, and examples thereof include a structure in which a membrane electrode assembly 140 is sandwiched between separators 150a and 150c as shown in FIG. The separator has a function of separating air and fuel gas, and any conventional separator can be used without particular limitation. Further, gas supply grooves 151a and 151c may be formed in the separators 150a and 150c in order to secure air and fuel gas flow paths.

  Furthermore, a stack in which a plurality of membrane electrode assemblies are stacked via a separator and connected in series may be formed so that the fuel cell can obtain a desired voltage or the like. The shape of the fuel cell is not particularly limited, and may be determined as appropriate so that desired battery characteristics such as voltage can be obtained.

  Hereinafter, the present invention will be specifically described based on examples. In addition, this invention is not limited only to these Examples.

Example 1
15 g of NPA is added to 5 g of a solid polymer electrolyte solution (Nafion DE2029; Nafion 5 wt%, water 47.5 wt%, NPA 47.5 wt%), and stirred for 15 minutes, and methyl silicate 51 (registered trademark, Fuso Chemical Industry Co., Ltd.) is added to this solution. 98 mg) was mixed and stirred while applying ultrasonic waves at 20 ° C. in an air atmosphere for 0.5 hour. The stirred liquid was poured into a square-shaped Teflon container, allowed to stand at room temperature for 24 hours, and further dried at 70 ° C. for 5 hours to obtain a solid polymer electrolyte membrane 1 (thickness 50 μm, size 10 cm × 10 cm) was obtained. The silicate accounts for 10% by mass of the completed electrolyte membrane 1.

  At this time, it was confirmed that the polymerization was progressing by measuring solid Si-NMR.

(Example 2)
51 mg of tetraethyl orthosilicate (manufactured by Wako Pure Chemical Industries, Ltd.) is mixed with 5 g of a solid polymer electrolyte solution (Nafion DE2029; Nafion 5 wt%, water 47.5 wt%, NPA 47.5 wt%), and at 20 ° C. in an air atmosphere. And stirred for 0.5 hour while applying ultrasonic waves. The stirred liquid was poured into a square-shaped Teflon container, allowed to stand at room temperature for 24 hours, and further dried at 70 ° C. for 5 hours to obtain a solid polymer electrolyte membrane 2 (thickness 50 μm, size 10 cm × 10 cm) was obtained. The silicate accounts for 10% by mass of the finished electrolyte membrane 2. Also in this Example 2, it was confirmed that the polymerization was progressing by measuring solid Si-NMR.

(Comparative Example 1)
5 g of solid polymer electrolyte solution (Nafion DE2029; Nafion 5 wt%, water 47.5 wt%, NPA 47.5 wt%) and colloidal silica PL-1 (manufactured by Fuso Chemical, Si 12 wt%, water dispersion, primary particle diameter 15 nm, secondary 42 mg of a particle size of 40 nm, pH 7.0) was mixed and stirred while applying ultrasonic waves at 20 ° C. in an air atmosphere for 0.5 hours. The stirred liquid was poured into a square type Teflon container, allowed to stand at room temperature for 24 hours, and further dried at 70 ° C. for 5 hours, whereby solid polymer electrolyte membrane 3 (thickness 50 μm, size 10 cm × 10 cm) was obtained. In Comparative Example 1, colloidal silica is simply in a mixed state.

(Comparative Example 2)
A solid polymer electrolyte solution (Nafion DE2029; 5% by weight of Nafion, 47.5% by weight of water, 47.5% by weight of NPA) was stirred while applying ultrasonic waves at 20 ° C. in an air atmosphere for 0.5 hours. The stirred liquid was poured into a square-shaped Teflon container, allowed to stand at room temperature for 24 hours, and further dried at 70 ° C. for 5 hours, whereby the solid polymer electrolyte membrane 4 (thickness 50 μm, size 10 cm × 10 cm) was obtained.

(Evaluation)
The solid polymer electrolyte membranes 1 to 4 produced above were evaluated according to the following procedure.

(Cell evaluation)
Using the solid polymer electrolyte membrane, a membrane electrode assembly was produced according to the following procedure.

(Catalyst ink preparation)
<Cathode catalyst ink> Fine particles of Pt-supported carbon (platinum supported amount: 50% by mass) in a commercially available Nafion solution (Aldrich 5% by mass solution), and the mass ratio of carbon to Nafion is carbon: Nafion = 1: 0. After mixing so as to be 0.8, a cathode catalyst ink was produced in a homogenizer (pulverizer) for about 3 hours.

  <Anode catalyst ink> An anode catalyst ink was prepared in the same manner as the cathode catalyst ink.

(Catalyst layer transfer sheet production)
The ink prepared as described above was applied onto a Teflon sheet used as a mount using a screen printer to prepare a catalyst layer transfer sheet for cathode and anode. As the mount, a PET (polyethylene terephthalate) sheet or the like is excellent in addition to the Teflon sheet. Coating and drying were repeated until the Pt carrying amount reached 0.4 mg / cm ² to prepare a catalyst layer transfer sheet having a predetermined platinum amount.

(Catalyst layer transfer)
When the catalyst layer surface of the cathode and anode catalyst layer transfer sheets prepared as described above is sprayed and infiltrated with ethanol, and the catalyst layer surface is dried, the electrolyte membranes prepared with these transfer sheets are sandwiched, 130 Hot pressing was performed at a temperature of 6.5 MPa and a holding time of 10 minutes. The reason for infiltrating with ethanol is to make the catalyst layer and membrane electrolyte flexible and to facilitate the transfer of the catalyst layer.

  After cooling, the mount of the transfer sheet was peeled off to produce a membrane-catalyst layer assembly.

  In this example, a non-fluorine solid polymer electrolyte was used only for the cathode binder, and ordinary Nafion was used for the anode binder. This is because it is more convenient to use Nafion as the anode binder for CV (cyclic voltammetry) measurement. Both binders are made of a non-fluorinated solid polymer electrolyte. Needless to say, there is essentially no change.

(3) Assembly of single cell for evaluation Two commercially available gas diffusion layers each having an electrode catalyst layer formed on one side are stacked on a solid polymer electrolyte membrane so that the electrode catalyst layer forming side faces each other, and 6.5 MPa A membrane / electrode assembly was produced by hot pressing at 130 ° C. for 10 minutes at a pressure of 5 ° C. Further, the membrane electrode assembly was sandwiched between graphite separators and sandwiched between gold-plated stainless steel current collector plates to form a single cell for evaluation.

(4) Power generation evaluation Hydrogen was supplied as a fuel to the anode side of each evaluation single cell, and air was supplied as an oxidant to the cathode side. For both gases, the cell outlet pressure was atmospheric pressure, and the power generation conditions were: cell temperature 70 ° C., relative humidity anode / cathode = 90% R.S. H. / 30% R.V. H. The voltage was measured at a hydrogen utilization rate of 67% and an air utilization rate of 40%.

  The measurement results are shown in FIG. However, the cell of Comparative Example 2 was unable to generate electricity.

  In the sample of the example, the cell voltage is less likely to be lower than that of the comparative example, and power generation is stable. It can be said that the inorganic metal oxide in the film is uniformly dispersed, so that the strength can withstand power generation, and the water retention and power generation performance are improved.

1 is a schematic cross-sectional view of a fuel cell using a solid polymer electrolyte membrane, which is a preferred embodiment of the present invention. The electric power generation result in an Example is shown.

Explanation of symbols

100 fuel cells,
110 solid polymer electrolyte membrane,
120a, 120c electrode catalyst layer,
130a, 130c gas diffusion layers,
140 membrane electrode assembly,
150a, 150c separator,
151a, 151c Gas supply grooves.

Claims (6)

A solid polymer electrolyte obtained by combining an organometallic compound represented by Chemical Formula 1 and an organic polymer having proton conductivity;

In Formula 1,
X _{1 to} X ₃ are each independently a hydrogen atom, an optionally substituted hydrocarbon group, or an alkoxyl group,
X ₄ is a hydrogen atom or an optionally substituted hydrocarbon group,
M is at least one metal atom selected from the group consisting of Si, Ti, Al, Zr, and Ge;
n is an integer of 1-100.   The organic polymer has at least one reactive group selected from the group consisting of a hydroxyl group, a sulfonic acid group, a phosphonic acid group, a sulfonamide group, a sulfonimide group, and derivatives thereof. The solid polymer electrolyte described.   The solid polymer electrolyte according to claim 1 or 2, wherein the organometallic compound is soluble in an organic solvent.   A solid polymer electrolyte membrane comprising the solid polymer electrolyte according to claim 1.   A fuel cell membrane electrode assembly comprising the solid polymer electrolyte according to any one of claims 1 to 3 and / or the solid polymer electrolyte membrane according to claim 4.   A polymer electrolyte fuel cell comprising the fuel cell membrane electrode assembly according to claim 5.

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