WO2009098982A1 - 膜-電極接合体及び固体高分子型燃料電池 - Google Patents
膜-電極接合体及び固体高分子型燃料電池 Download PDFInfo
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- WO2009098982A1 WO2009098982A1 PCT/JP2009/051355 JP2009051355W WO2009098982A1 WO 2009098982 A1 WO2009098982 A1 WO 2009098982A1 JP 2009051355 W JP2009051355 W JP 2009051355W WO 2009098982 A1 WO2009098982 A1 WO 2009098982A1
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M8/00—Fuel cells; Manufacture thereof
- H01M8/10—Fuel cells with solid electrolytes
- H01M8/1004—Fuel cells with solid electrolytes characterised by membrane-electrode assemblies [MEA]
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M8/00—Fuel cells; Manufacture thereof
- H01M8/02—Details
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M8/00—Fuel cells; Manufacture thereof
- H01M8/10—Fuel cells with solid electrolytes
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M8/00—Fuel cells; Manufacture thereof
- H01M8/10—Fuel cells with solid electrolytes
- H01M8/1016—Fuel cells with solid electrolytes characterised by the electrolyte material
- H01M8/1018—Polymeric electrolyte materials
- H01M8/102—Polymeric electrolyte materials characterised by the chemical structure of the main chain of the ion-conducting polymer
- H01M8/1023—Polymeric electrolyte materials characterised by the chemical structure of the main chain of the ion-conducting polymer having only carbon, e.g. polyarylenes, polystyrenes or polybutadiene-styrenes
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M8/00—Fuel cells; Manufacture thereof
- H01M8/10—Fuel cells with solid electrolytes
- H01M8/1016—Fuel cells with solid electrolytes characterised by the electrolyte material
- H01M8/1018—Polymeric electrolyte materials
- H01M8/1041—Polymer electrolyte composites, mixtures or blends
- H01M8/1053—Polymer electrolyte composites, mixtures or blends consisting of layers of polymers with at least one layer being ionically conductive
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M8/00—Fuel cells; Manufacture thereof
- H01M8/10—Fuel cells with solid electrolytes
- H01M2008/1095—Fuel cells with polymeric electrolytes
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M2300/00—Electrolytes
- H01M2300/0017—Non-aqueous electrolytes
- H01M2300/0065—Solid electrolytes
- H01M2300/0082—Organic polymers
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/30—Hydrogen technology
- Y02E60/50—Fuel cells
Definitions
- the present invention relates to a membrane-electrode assembly and a polymer electrolyte fuel cell.
- Fuel cells have attracted attention as a clean power generation system that is friendly to the global environment.
- Fuel cells are classified into phosphoric acid type, molten carbonate type, solid oxide type, solid polymer type, etc., depending on the type of electrolyte.
- polymer electrolyte fuel cells are applicable to electric vehicle power supplies, portable equipment power supplies, and household cogeneration systems that use both electricity and heat from the viewpoints of low-temperature operability, small size, and light weight. It is being considered.
- a polymer electrolyte fuel cell is generally configured as follows. First, electrode catalyst layers containing carbon powder carrying a platinum group metal catalyst and an ion conductive binder made of a polymer electrolyte are formed on both sides of a polymer electrolyte membrane having ion conductivity (ion is usually proton). Is done. A gas diffusion layer, which is a porous material through which fuel gas and oxidant gas are passed, is formed outside each electrode catalyst layer. Carbon paper, carbon cloth, or the like is used as the gas diffusion layer. A structure in which an electrode catalyst layer and a gas diffusion layer are integrated is called a gas diffusion electrode.
- a structure in which a pair of gas diffusion electrodes is bonded to an electrolyte membrane so that the electrode catalyst layer faces the electrolyte membrane is a membrane-electrode junction. It is called the body (MEA; Membrane Electrode Assembly).
- MEA Membrane Electrode Assembly
- separators having conductivity and airtightness are disposed on both sides of the membrane-electrode assembly.
- a gas flow path for supplying fuel gas or oxidant gas (for example, air) to the electrode surface is formed in the contact portion of the membrane-electrode assembly and the separator or in the separator. Electric power is generated by supplying a fuel gas such as hydrogen or methanol to one electrode (fuel electrode) and an oxidant gas containing oxygen such as air to the other electrode (oxygen electrode).
- the fuel is ionized to produce protons and electrons
- the protons pass through the electrolyte membrane
- the electrons travel through an external electric circuit formed by connecting both electrodes, and are sent to the oxygen electrode
- Water is produced by the reaction.
- the chemical energy of the fuel can be directly converted into electric energy and taken out.
- anion exchange type fuel cells using an anion conductive membrane and an anion conductive binder have been studied for such proton exchange type fuel cells.
- the structure of the polymer electrolyte fuel cell in this case is basically the same as that of the proton exchange type fuel cell except that an anion conductive membrane and an anion conductive binder are used instead of the proton conductive membrane and the proton conductive binder.
- the mechanism of electric energy generation is that oxygen, water, and electrons react at the oxygen electrode to generate hydroxide ions, and the hydroxide ions react with hydrogen at the fuel electrode through the anion conductive membrane.
- the electrode reaction takes place at the three-phase interface formed by the gas phase as the fuel or oxidant supply path, the liquid phase as the ion path, and the solid phase as the electron path.
- the ion conductive binder binds the catalyst and is used for the purpose of increasing the utilization efficiency of the catalyst through the transfer of protons or hydroxide ions from the electrode catalyst layer to the electrolyte membrane. Therefore, a catalyst that does not come into contact with the ion path formed by the ion conductive binder cannot form a three-phase interface, so it is difficult to contribute to the reaction, and in order to obtain high efficiency, a fuel gas or an oxidant gas is required.
- the fine structure design of the electrode catalyst layer is important, such as the pore structure for diffusing the catalyst and the dispersed state of the catalyst.
- the catalyst surface is covered with water contained in the reaction gas, or water generated at the oxygen electrode or the fuel electrode, and the fuel gas or oxidant gas cannot contact the catalyst surface and power generation stops.
- the electrode reaction may be stopped by hindering the supply or discharge of the fuel gas or the oxidant gas. Therefore, water repellency is required for the gas diffusion electrode part.
- a gas diffusion electrode produced by applying and drying a catalyst slurry in which an electrode catalyst and a polymer electrolyte are mixed and dispersed in a solvent on a gas diffusion substrate, and a polymer electrolyte membrane Is known in the order of gas diffusion electrode / polymer electrolyte membrane / gas diffusion electrode, and this is joined by hot pressing or the like.
- Nafion registered trademark of Nafion, DuPont
- Nafion membrane has a structure in which spherical clusters of several nm are connected by narrow channels of about 1 nm due to the strong hydrophobicity of the main chain and the hydrophilicity of the sulfonic acid group. Is expressed. Nafion is also used to form a three-phase interface serving as an electrode reaction site in the electrode catalyst layer.
- Nafion is also used as an electrolyte in the polymer electrolyte membrane and the electrode catalyst layer, that is, since an electrolyte having the same composition is used, good bonding strength and electrical bonding state can be obtained. Is relatively easy. However, even when Nafion is used for both the polymer electrolyte membrane and the electrolyte in the electrode catalyst layer, there is an interfacial resistance between the membrane and the electrode, resulting in a battery internal loss due to the interfacial resistance, resulting in a decrease in power generation efficiency. It has been pointed out.
- the electrode catalyst layer has a porous structure
- the surface of the electrode catalyst layer has a concavo-convex structure, and there is a problem that the reaction area of the electrode catalyst layer is reduced because the electrolyte membrane does not follow the concavo-convex structure.
- an electrolyte other than Nafion such as a hydrocarbon-based electrolyte
- Patent Document 1 As a technique for improving the bondability between the electrolyte membrane and the electrode, for example, it is studied to provide an ion conductor intermediate layer having proton conductivity between the electrolyte membrane and the electrode (Patent Document 1). By using an ionic conductor intermediate layer that is softer than the electrolyte membrane and the electrode, the ionic conductor bites into the irregularities on the surface of the electrode, and the bondability is improved. As another example, a method has been proposed in which the interfacial resistance is reduced by allowing electronic conductive particles to exist between the electrolyte membrane and the electrode (Patent Document 2).
- the surface area of the bonding interface is increased and the interface resistance is reduced by forming a concavo-convex structure at the interface portion between the electrolyte membrane and the electrode.
- Both the method of Patent Document 1 and the method of Patent Document 2 try to increase the power generation efficiency by providing an intermediate layer between the electrolyte membrane and the electrode to substantially increase the junction area between the electrolyte membrane and the electrode. It is. Regarding the method of Patent Document 3, the intermediate layer is not intended to improve the interface resistance between the electrolyte membrane and the electrode, but to improve the mechanical bondability. In the present invention, an intermediate layer is provided between the electrolyte membrane and the electrode, but the interface resistance is reduced by designing the portion responsible for ion conduction in the intermediate layer to efficiently contact the electrolyte membrane and the electrode. It is intended to increase the power generation efficiency, and the point of view and the method are completely different from those of Patent Documents 1 to 3. An object of the present invention is to provide a membrane-electrode assembly and a polymer electrolyte fuel cell that are economical, environmentally friendly, have good moldability, have low membrane-electrode interface resistance, and have excellent power generation efficiency.
- each gas diffusion electrode is composed of an electrode catalyst layer and a gas diffusion layer, and has an intermediate layer made of an ionic conductor between at least one of the electrode catalyst layer and the polymer electrolyte membrane.
- A) comprising a polymer block (A) in which A) forms a continuous phase and the junction between the intermediate layer and the polymer electrolyte membrane and the junction between the intermediate layer and the electrode catalyst layer have an ion conductive group Regarding electrode assemblies .
- the intermediate layer having such a structure since the polymer block (A) having an ion conductive group of the block copolymer forms a continuous phase, the ion conductivity inside the intermediate layer is good, and the intermediate layer and the electrolyte Since the junction between the membrane and the junction between the intermediate layer and the electrode catalyst layer are made of the polymer block (A) having an ion conductive group, an ion path can be efficiently formed.
- the presence of the polymer block (B) having no ion conductive group increases the water resistance of the intermediate layer, and the intermediate layer is formed by moisture contained in the reaction gas during power generation, generated water of the oxygen electrode, or the like. It is possible to prevent the block copolymer that forms a gradual elution from the battery system and the membrane-electrode assembly from deteriorating.
- the repeating unit constituting the polymer block (A) is preferably an aromatic vinyl compound unit
- the polymer block (B) is preferably a rubbery polymer block (B1).
- the rubber-like polymer block has a flexible structure, so that the block copolymer is elastic and flexible as a whole, and it is easy to mold (assemble) the membrane-electrode assembly and the polymer electrolyte fuel cell. , Bondability, tightenability, etc.).
- the polymer block (B) preferably comprises a polymer block (B1) and a structure-retaining polymer block (B2). By adding the polymer block (B2), it is possible to reduce the possibility that the continuity of the ion channel and the durability of the membrane-electrode assembly are impaired due to the change in the phase separation structure.
- the ionic conductor forming the intermediate layer is obtained from a dispersion obtained by dispersing the block copolymer and, if necessary, various additives in an aqueous dispersion medium so that the particle size of the block copolymer is 1 ⁇ m or less. It can be obtained by removing the dispersion medium.
- the particle size of the block copolymer By setting the particle size of the block copolymer to 1 ⁇ m or less, the contact area between the block copolymers can be increased, and the continuity of the polymer block (A) having an ion conductive group is increased. be able to.
- the particle size of the copolymer exceeds 1 ⁇ m, a concavo-convex structure resulting from the particle size of the copolymer is formed at the junction between the intermediate layer and the electrolyte membrane or at the junction between the intermediate layer and the electrode catalyst layer. Therefore, it is difficult to efficiently form an ion path at the junction, and the membrane-electrode interface resistance cannot be reduced. Further, by using an aqueous dispersion medium, that is, water or a solvent mainly composed of water, the copolymer has a polymer block (B) having no ion conductive group as an inner layer and a polymer having an ion conductive group.
- the contact portion between the block copolymers is made of a polymer block (A) having an ion conductive group, and the intermediate layer, the electrolyte membrane, The joining portion of the intermediate layer and the joining portion of the intermediate layer and the electrode catalyst layer are made of the polymer block (A).
- the present invention also relates to a fuel cell using the membrane-electrode assembly.
- the membrane-electrode assembly and solid polymer fuel cell of the present invention are economical, environmentally friendly, have good moldability, have a low membrane-electrode interface resistance, and have excellent power generation efficiency.
- FIG. 1 is a configuration diagram schematically showing the structure of an intermediate layer provided in the membrane-electrode assembly of the present invention.
- the intermediate layer is made of an ionic conductor
- the block copolymer which is a main constituent of the ionic conductor has a polymer block (A) having an ionic conductive group and an ionic conductive group.
- the polymer block (A) having an ion conductive group is phase-separated into a polymer block (B) that does not form a continuous phase, and the junction between the intermediate layer and the electrolyte membrane, and the intermediate layer and the electrode catalyst layer,
- the junction part of the polymer is composed of a polymer block (A) having an ion conductive group.
- the block copolymer used in the present invention comprises a polymer block (A) having an ion conductive group and a polymer block (B) having no ion conductive group, and both blocks are phase-separated from each other. It is.
- a copolymer include the copolymer described in WO 2006/068279 A1, and the block copolymer used in the present invention will be described in detail below.
- the monomer capable of forming the repeating unit of the polymer block (A) is not particularly limited, and examples thereof include aromatic vinyl compounds, conjugated dienes having 4 to 8 carbon atoms (1,3-butadiene, isoprene, etc.) Alkene having 2 to 8 carbon atoms (ethylene, propylene, isobutylene, etc.), (meth) acrylic acid ester (methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, etc.), vinyl ester ( Vinyl acetate (vinyl acetate, vinyl propionate, vinyl butyrate, vinyl pivalate, etc.), vinyl ethers (methyl vinyl ether, isobutyl vinyl ether, etc.) and the like.
- Aromatic vinyl compounds are preferred because of the ease of introduction of ion conductive groups.
- aromatic vinyl compounds include styrene, ⁇ -methylstyrene, alkyl groups having 1 to 3 hydrogen atoms bonded to a benzene ring and having 1 to 4 carbon atoms (methyl group, ethyl group, n-propyl group, Examples thereof include styrene (p-methylstyrene etc.) substituted with isopropyl group, n-butyl group, isobutyl group or tert-butyl group), vinylnaphthalene, vinylanthracene, vinylpyrene, vinylpyridine and the like.
- the aromatic vinyl compound unit is preferably a styrene unit and / or an ⁇ -methylstyrene unit from the viewpoint of easy introduction of an ion conductive group.
- the aromatic vinyl-based compound unit preferably has a structure having no tertiary carbon in order to improve stability from oxidation by hydrogen peroxide or hydrogen peroxide-derived hydroxyl radical generated in the side reaction of the electrode reaction. Specifically, an ⁇ -methylstyrene unit is preferable.
- the polymer block (A) may contain one or more other monomer units.
- other monomer units include conjugated diene units having 4 to 8 carbon atoms (1,3-butadiene units, isoprene units, etc.), (meth) acrylate units (methyl (meth) acrylate units, (Meth) ethyl acrylate units, butyl (meth) acrylate units, etc.), alkene units having 2 to 8 carbon atoms (ethylene units, propylene units, isobutene units, etc.) and the like.
- the ratio of the aromatic vinyl compound unit in the polymer block (A) is preferably 80% by mass or more, and preferably 90% by mass or more. More preferred.
- the copolymerization form of the aromatic vinyl compound and the other monomer is preferably random copolymerization.
- the molecular weight of the polymer block (A) in a state where no ion conductive group is introduced is appropriately selected depending on the properties of the ion conductor, required performance, other polymer components, and the like.
- the molecular weight is usually preferably selected from 100 to 1,000,000, more preferably from 1,000 to 100,000, as the number average molecular weight in terms of polystyrene.
- the block copolymer has a polymer block (B) having no ion conductive group in addition to the polymer block (A). Even if a high content of ionic groups is introduced into the polymer block (A), the polymer block (B) has improved water resistance and can prevent the ionic conductor from flowing out during power generation.
- the polymer block (B) is not particularly limited as long as it is phase-separated from the polymer block (A) and has water resistance, but is preferably a flexible polymer block (B1).
- the flexible polymer block (B1) referred to here is a so-called rubber-like polymer block having a glass transition point or softening point of 50 ° C. or lower, preferably 20 ° C. or lower, more preferably 10 ° C. or lower.
- Examples of the repeating unit constituting the polymer block (B1) include conjugated diene units having 4 to 8 carbon atoms (1,3-butadiene units, isoprene units, etc.), alkene units having 2 to 8 carbon atoms (isobutylene units, etc.), etc. Can be mentioned.
- the monomer which gives these units can be used individually or in combination of 2 or more types.
- the form in the case of copolymerizing two or more types may be random copolymerization, block copolymerization, graft copolymerization, or tapered copolymerization.
- the monomer to be used for (co) polymerization has two carbon-carbon double bonds
- any of them may be used for the polymerization, and in the case of a conjugated diene, it is a 1,2-bond.
- 1,4-bonds may be used, and the ratio of 1,2-bonds to 1,4-bonds is not particularly limited as long as the glass transition point or softening point is 50 ° C. or lower.
- the membrane-electrode junction using the ion conductive binder of the present invention From the viewpoint of improving the power generation performance of the body and heat resistance deterioration, it is preferable that 30 mol% or more of such carbon-carbon double bonds are hydrogenated, and 50 mol% or more is hydrogenated. More preferably, 80 mol% or more is hydrogenated.
- the hydrogenation rate of the carbon-carbon double bond can be calculated by a commonly used method, for example, iodine value measurement method, 1 H-NMR measurement or the like.
- the polymer block (B1) includes the above monomer units (conjugated diene units having 4 to 8 carbon atoms (1,3-butadiene units, isoprene units, etc.), alkene units having 2 to 8 carbon atoms (isobutylene units, etc.). And the like, in addition to other monomer units, for example, aromatic vinyl compounds such as styrene and vinyl naphthalene, as long as the purpose of the polymer block (B1) for imparting elasticity to the block copolymer is not impaired. Monomer units such as halogen-containing vinyl compounds such as vinyl chloride may be included. In this case, the copolymerization form of the monomer unit and other monomer units is preferably random copolymerization.
- the above-mentioned monomers a conjugated diene unit having 4 to 8 carbon atoms (1,3-butadiene unit, isoprene unit, etc.), an alkene unit having 2 to 8 carbon atoms (isobutylene unit, etc.), etc.
- the ratio is preferably 50% by mass or more, more preferably 70% by mass or more, and more preferably 90% by mass or more based on the total of the monomer units and other monomer units. Is even more preferable.
- the polymer block (B1) does not have an ion conductive group means that the polymer block (B1) has substantially no ion conductive group, and a small amount of the ion conductive group is taken into the polymer block (B1) in the process of producing the block copolymer. This is within the scope of the present invention. This also applies to the polymer block (B2) described later.
- the mass ratio of the polymer block (A) to the polymer block (B1) of the copolymer is not particularly limited as long as the water resistance of the ionic conductor is obtained, and is 95: 5 to 5:95. It is preferably 90:10 to 10:90, more preferably 50:50 to 10:90.
- the arrangement of the polymer block (A) and the polymer block (B1) in the block copolymer is not particularly limited, and the block copolymer may be an A-B1 type diblock copolymer, an A-B1-A type triblock.
- These block copolymers may be used alone or in combination of two or more.
- the block copolymer used in the present invention is different from these blocks in addition to the polymer block (A) and the polymer block (B1), and is different from those having no other ion-conducting groups that are phase-separated from these blocks.
- the combined block (B2) may be included. That is, the polymer block (B) may be composed of the polymer block (B1), or may be composed of the polymer block (B1) and the polymer block (B2).
- Specific examples of the repeating unit constituting the polymer block (B2) include the aromatic vinyl compound units described in the explanation of the polymer block (A).
- the block copolymer is composed of the polymer block (A), the polymer block (B1) and the polymer block (B2)
- the arrangement of these polymer blocks is not particularly limited, and A-B1-B2 Type triblock copolymer, A-B1-B2-A type tetrablock copolymer, A-B1-A-B2 type tetrablock copolymer, B1-A-B1-B2 type tetrablock copolymer, A -B1-B2-B1 type tetrablock copolymer, B2-B1-B2-A type tetrablock copolymer, B2-A-B1-AB2 type pentablock copolymer, B2-B1-A-B1 -B2-type pentablock copolymer, A-B2-B1-B2-A-type pentablock copolymer, A-B1-B2-B1-A-type pentablock copolymer, A-B2-B1-A
- a rubbery polymer block (B1) such as A-B2-B1-B2-A is provided.
- the swelling of the ion conductor is suppressed, and the swelling of the ion conductor during power generation may impair the continuity of the ion channel and the durability of the membrane-electrode assembly. Can be reduced. Further, in the step of forming the intermediate layer by removing the aqueous dispersion medium from the aqueous dispersion in which the block copolymer is dispersed by the polymer block (B2), the phase separation of the ionic conductor formed in the dispersion is performed. The possibility that the structure changes can be reduced. *
- the block copolymer used by this invention contains a polymer block (B2)
- the ratio of the polymer block (B2) to a block copolymer is less than 75 mass%, and is less than 70 mass%. More preferably, it is more preferably less than 60% by mass.
- the proportion of the polymer block (B2) in the block copolymer is preferably 10% by mass or more, and 20% by mass or more. More preferably, it is more preferably 25% by mass or more.
- a block copolymer contains a polymer block (B2)
- the mass ratio of the sum of a polymer block (A) and a polymer block (B2) and a polymer block (B1) is required performance, flexibility.
- the ratio is 20:80 to 80:20, and 25:75 to 75:25. More preferably, the ratio is 30:70 to 70:30.
- the number average molecular weight of the block copolymer used in the present invention in a state where no ion conductive group is introduced is not particularly limited, but the number average molecular weight in terms of polystyrene is usually 10,000 to 2,000,000. It is preferably 15,000 to 1,000,000, more preferably 20,000 to 500,000.
- the block copolymer used in the present invention has an ion conductive group in the polymer block (A).
- ion conductivity there are a cation and an anion
- examples of the cation include protons
- examples of the anion include hydroxide ions.
- the ion conductive group may be a cation conductive group or an anion conductive group, but a cation conductive group is preferably used.
- the cation conductive group is not particularly limited as long as the membrane-electrode assembly produced using the ionic conductor can express a sufficient cation conductivity, but is not limited to -SO 3 M or -PO 3.
- a sulfonic acid group, a phosphonic acid group or a salt thereof represented by HM is preferably used.
- M represents a hydrogen atom, an ammonium ion or an alkali metal ion
- alkali metal ion include sodium ion, potassium ion, and lithium ion.
- a carboxyl group or a salt thereof can also be used.
- the anion conductive group is not particularly limited as long as the membrane-electrode assembly produced using the ionic conductor can exhibit sufficient anion conductivity, but examples include the groups shown below. It is done.
- the amount of ion-conducting group introduced is appropriately selected depending on the required performance of the resulting block copolymer, etc., but in order to develop sufficient ion conductivity for use as an intermediate layer, block copolymer is usually used.
- the amount is preferably such that the ion exchange capacity of the coalescence is 0.30 meq / g or more, and more preferably 0.40 meq / g or more.
- the ion exchange capacity of the coalescence is 0.30 meq / g or more, and more preferably 0.40 meq / g or more.
- the ratio of the monomer unit having an ion conductive group in the polymer block (A) is preferably 10 mol% or more, more preferably 30 mol% or more, and 50 mol% or more. Even better.
- the copolymer form of the monomer unit having an ion conductive group and the other monomer unit in the polymer block (A) is random copolymerization so that the polymer block (A) does not undergo phase separation. It is preferable.
- the block copolymer used in the present invention can be produced by the production method described in the above-mentioned WO 2006/068279 A1, or according to this.
- the block copolymer particles are in contact with each other by the polymer block (A) having an ion conductive group, and the intermediate layer, the electrolyte membrane,
- the joining portion of the intermediate layer and the joining portion of the intermediate layer and the electrocatalyst layer are composed of a polymer block (A) having an ion conductive group. It is preferable to take a core-shell structure in which the block (B) is used and the outer layer (shell phase) is the polymer block (A). This core-shell structure is usually spherical.
- the polymer block (A) having an ion conductive group can efficiently form a continuous phase, has excellent ion conductivity inside the intermediate layer, and is a junction between the intermediate layer and the electrolyte membrane.
- an ion path can be easily formed at the junction between the intermediate layer and the electrode catalyst layer.
- the membrane-electrode interface resistance can be reduced and the power generation efficiency can be increased.
- the ionic conductor used in the present invention contains the above block copolymer as a main component.
- the ion conductive material of the present invention is various additives such as a softener, a stabilizer, a light stabilizer, an antistatic agent, a release agent, a flame retardant, a foaming agent, and a pigment.
- Dyes, brighteners, carbon fibers, inorganic fillers and the like may be used alone or in combination of two or more.
- softener examples include petroleum softeners such as paraffinic, naphthenic or aromatic process oils, paraffin, vegetable oil softeners, plasticizers, and the like.
- Stabilizers include phenol-based stabilizers, sulfur-based stabilizers, phosphorus-based stabilizers, and the like.
- the block copolymer and the additive may be mixed in advance, or the block copolymer water, which will be described later, is mainly used. You may add when preparing the dispersion liquid to a dispersion medium.
- the content of the block copolymer in the ionic conductor used in the present invention is preferably 50% by mass or more, more preferably 70% by mass or more, and 90% by mass or more. Is more preferable.
- the block copolymer particles are in contact with each other by the polymer block (A) having an ion conductive group, and the intermediate layer, the electrolyte membrane,
- the junction between the intermediate layer and the electrode catalyst layer comprises a polymer block (A) having an ion conductive group.
- the block copolymer has an ion conductive group.
- the polymer block (B) not to be used has a form (namely, a core-shell structure) in which the polymer block (A) having an ion conductive group on the inside is phase-separated on the outside.
- a method for inducing such a form is not particularly limited. Examples include (1) a method of removing the dispersion medium from a dispersion obtained by dispersing the block copolymer in a dispersion medium mainly composed of water.
- the dispersion in this method is preferably an emulsion or suspension, more preferably an emulsion.
- the particle size of the block copolymer in the dispersion in the method (1) is preferably 1 ⁇ m or less, more preferably 0.5 ⁇ m or less, and more preferably 0.1 ⁇ m or less in order to increase the contact area between the ion conductors. Even more preferred.
- the lower limit of the particle size of the block copolymer in the dispersion is not particularly limited, but the block copolymer is phase-separated into a phase having an ion conductive group and a phase having no ion conductive group. Is preferably 10 nm or more, and more preferably 40 nm or more from the viewpoint of obtaining a particle size necessary for the above.
- the particle size in the dispersion can be measured by a commonly used method such as a dynamic light scattering method.
- a method for obtaining a dispersion of a block copolymer is not particularly limited, and a method for emulsifying the copolymer in an aqueous dispersion medium, a method for obtaining from a liquid phase polymerization such as emulsion polymerization or suspension polymerization.
- the method of emulsifying the copolymer is preferable.
- a direct emulsification method in which a melt of the block copolymer is dispersed in an aqueous dispersion medium at a temperature equal to or higher than the melting point of the block copolymer can be used.
- the aqueous dispersion medium means water or a solvent mainly composed of water.
- a solution inversion emulsification method in which the block copolymer is dissolved in an organic solvent and then this solution is dispersed in an aqueous dispersion medium can be used.
- Examples of the organic solvent used for dissolving the block copolymer and the organic solvent mixed with water used as the dispersion medium include alcohols such as methanol, ethanol, propanol and isopropanol, halogenated hydrocarbons such as methylene chloride, toluene and xylene.
- Aromatic hydrocarbon solvents such as benzene, linear aliphatic hydrocarbons such as hexane and heptane, cycloaliphatic hydrocarbons such as cyclohexane, ethers such as tetrahydrofuran, acetonitrile, nitromethane, dimethyl sulfoxide, Examples thereof include N-methylpyrrolidone, N, N-dimethylformamide, N, N-dimethylacetamide and the like. These solvents can be used alone or in combination of two or more. In addition, when using an organic solvent in dispersion
- the removal of the organic solvent can be carried out using azeotropy with water using, for example, a reaction tank equipped with a stirrer and a condenser, an extruder equipped with a vent, a rotary evaporator, or the like.
- the removal of the organic solvent may be carried out under normal pressure or reduced pressure.
- the dispersion of the copolymer can be carried out using a container equipped with stirring means.
- the stirring means is not particularly limited, but a turbine type stirrer, a colloid mill, a homomixer, and a homogenizer are preferable from the viewpoint of generating a large shearing force.
- the dispersion may be performed using a line mixer equipped with a movable stirring device, a non-movable line mixer (static mixer, trade name, manufactured by Noritake Co., Ltd.), or the like.
- a high-pressure homogenizer Manton Gorin, trade name, manufactured by APV Gorin; Microfluidizer, trade name, manufactured by Mizuho Kogyo Co., Ltd .; Nanomizer, You may perform the fine dispersion process by a brand name, the product made by Yoshida machine industry, etc.).
- a surfactant When dispersing the copolymer in an aqueous dispersion medium, a surfactant may be used as an emulsifying / dispersing agent, and a nonionic surfactant, an anionic surfactant, or the like can be used.
- the amount of the surfactant used is usually in the range of 0.1 to 40 parts by weight, preferably in the range of 0.1 to 20 parts by weight, based on 100 parts by weight of the block copolymer used. However, it is better to keep it to the minimum necessary.
- nonionic surfactants include polyethylene glycol type nonionic surfactants and polyhydric alcohol type nonionic surfactants.
- examples of the polyethylene glycol type nonionic surfactant include ethylene oxide adducts of higher alcohols, ethylene oxide adducts of alkylphenols, ethylene oxide compounds of fatty acids, ethylene oxide adducts of polyhydric alcohol fatty acid esters, and ethylenes of higher alkylamines. Examples thereof include an oxide adduct, an ethylene oxide adduct of fatty acid amide, an ethylene oxide adduct of fats and oils, and an ethylene oxide adduct of polypropylene glycol.
- polyhydric alcohol type nonionic surfactant examples include fatty acid ester of glycerin, fatty acid ester of pentaerythritol, fatty acid ester of sorbitol, fatty acid ester of sorbitan, fatty acid ester of sucrose, alkyl ether of polyhydric alcohol, alkanolamine And fatty acid amides.
- anionic surfactant examples include primary higher fatty acid salts, secondary higher fatty acid salts, primary higher alcohol sulfates, secondary higher alcohol sulfates, and primary higher alkyl sulfonates.
- These surfactants can be used alone or in combination of two or more.
- the method for forming the intermediate layer from the block copolymer dispersion is not particularly limited, and known methods such as a printing method and a spray method can be applied.
- the membrane-electrode assembly of the present invention There are no particular restrictions on the method for producing the membrane-electrode assembly having the intermediate layer.
- the intermediate layer is formed on the surface of the electrolyte membrane and bonded to the gas diffusion electrode so that the intermediate layer and the electrode catalyst layer are bonded.
- a method a method in which an intermediate layer is formed on the surface of an electrode catalyst layer constituting a gas diffusion electrode, and an intermediate layer is formed on the surface of the electrolyte membrane.
- electrode catalyst layers are later formed on both sides of the electrolyte membrane, and a gas diffusion layer is pressure-bonded to each electrode catalyst layer by hot pressing or the like.
- the method for forming the intermediate layer on the surface of the electrolyte membrane or the electrode catalyst layer is not particularly limited, and can include a method of removing the dispersion medium from the dispersion containing the block copolymer.
- the dispersion is applied to the surface of the electrolyte membrane or the electrode catalyst layer by a printing method or a spray method, and at the same time or later, the dispersion medium is naturally dried, heat-dried, dried under reduced pressure, or dried under an air current.
- the method of evaporating can be mentioned.
- an intermediate layer is formed by applying a dispersion on a base film made of polytetrafluoroethylene (PTFE) and removing the dispersion medium, and then forming the intermediate layer on the base film as an electrolyte membrane or an electrode catalyst.
- PTFE polytetrafluoroethylene
- the intermediate layer may be used for either one or both of the membrane-electrode junctions.
- polymer electrolyte membrane constituting the membrane-electrode assembly examples include existing perfluorosulfones such as “Nafion” (registered trademark, manufactured by DuPont) and “Gore-select” (registered trademark, manufactured by Gore).
- An electrolyte membrane made of an acid polymer, an electrolyte membrane made of sulfonated polyethersulfone or sulfonated polyetherketone, an electrolyte membrane made of polybenzimidazole impregnated with phosphoric acid or sulfuric acid, and the like can be used.
- an electrolyte membrane may be produced from a block copolymer constituting an ionic conductor used as an intermediate layer constituting the membrane-electrode assembly of the present invention.
- an electrolyte membrane formed from the same material as the block copolymer used for the intermediate layer constituting the membrane-electrode assembly of the present invention is used. That is, the polymer used for the polymer electrolyte membrane and the block copolymer used for the intermediate layer may be the same or different, but both are included in the definition of the block copolymer used for the intermediate layer. Preferably there is.
- the block copolymer used for the intermediate layer is used as the polymer electrolyte membrane, and the block copolymer contains a polymer block (B2)
- the block copolymer has a structure retaining property.
- those having the polymer block (B2) at both ends such as B2-A-B1-A-B2, are preferred.
- a catalyst paste containing an ion conductive binder can be produced by a printing method or a spraying method. By applying on the diffusion layer and drying, a joined body of the electrode catalyst layer and the gas diffusion layer can be formed.
- the catalyst paste can be prepared by mixing and dispersing an ion conductive binder and catalyst particles in a solvent such as water or an alcohol solvent.
- a small amount of a water repellent material such as polytetrafluoroethylene, polyhexafluoropropylene, and tetrafluoroethylene-hexafluoropropylene copolymer may be contained as long as the effects of the present invention are not impaired.
- a water repellent material such as polytetrafluoroethylene, polyhexafluoropropylene, and tetrafluoroethylene-hexafluoropropylene copolymer may be contained as long as the effects of the present invention are not impaired.
- the content of the ion conductive binder in the catalyst paste may be appropriately determined so that the obtained electrode catalyst layer has desired characteristics, but it is 0.1 to 3.0 times the mass of the catalyst metal.
- the mass is preferably 0.3 to 2.0 times mass, and more preferably 0.5 to 1.5 times mass.
- the mass is preferably 0.1 times or more from the viewpoint of ion conductivity in the electrode catalyst layer, and is preferably 3.0 times or less from the viewpoint of securing the diffusion path of the reactant in the obtained electrode catalyst layer.
- the solid content concentration of the catalyst particles, the ion conductive binder and the like is preferably about 5 to 50% by mass.
- examples of the cation conductive binder include existing perfluorocarbon sulfonic acid type such as “Nafion” (registered trademark, manufactured by DuPont) and “Gore-select” (registered trademark, manufactured by Gore).
- An ion conductive binder made of a polymer, an ion conductive binder made of sulfonated polyether sulfone or sulfonated polyether ketone, an ion conductive binder made of polybenzimidazole impregnated with phosphoric acid or sulfuric acid, and the like can be used.
- anion conductive binder for example, polychloromethylstyrene can be reacted with a tertiary amine to form a quaternary ammonium salt, which can be used in the form of a hydroxide if necessary.
- a quaternary ammonium salt which can be used in the form of a hydroxide if necessary.
- These ion conductive binders may contain the same amount of the same additive as in the ionic conductor described above.
- an ion conductive binder formed of the same material as the block copolymer used for the intermediate layer constituting the membrane-electrode assembly of the present invention is used.
- the polymer used for the ion conductor and the block copolymer used for the intermediate layer may be the same or different, but both are included in the definition of the block copolymer used for the intermediate layer. Preferably there is.
- the catalyst particles are not particularly limited, and catalyst metal fine particles such as platinum black and catalyst-supported particles in which the catalyst metal is supported on a conductive material can be used.
- the catalyst metal may be any metal that promotes the oxidation reaction of fuel such as hydrogen and methanol and the reduction reaction of oxygen, such as platinum, gold, silver, palladium, iridium, rhodium, ruthenium, iron, Cobalt, nickel, chromium, tungsten, manganese, palladium, etc., or alloys thereof, for example, platinum-ruthenium alloy can be mentioned. Of these, platinum and platinum alloys are often used.
- the particle size of the metal serving as a catalyst is usually 10 to 300 angstroms.
- the carrier material may be any conductive material, for example, a carbon material.
- a carbon material examples include carbon black such as furnace black, channel black, and acetylene black, activated carbon, graphite, and the like. These may be used alone or in combination of two or more.
- the gas diffusion layer of the membrane-electrode assembly is made of a material having conductivity and gas permeability, and examples of such a material include porous materials made of carbon fibers such as carbon paper and carbon cloth. Moreover, in order to improve water repellency, this material may be subjected to water repellency treatment.
- a method for performing the water-repellent treatment for example, a method of performing the water-repellent treatment by immersing the gas diffusion layer in a dispersion of a fluorine-based water-repellent material such as polytetrafluoroethylene and then drying by heating in an oven or the like. Can be mentioned.
- the membrane-electrode assembly of the present invention uses a pure hydrogen type using hydrogen as a fuel gas, a methanol reforming type using hydrogen obtained by reforming methanol, and hydrogen obtained by reforming natural gas.
- a pure hydrogen type using hydrogen as a fuel gas a methanol reforming type using hydrogen obtained by reforming methanol
- hydrogen obtained by reforming natural gas can be used as membrane-electrode assemblies for solid polymer fuel cells, such as natural gas reforming type, gasoline reforming type using hydrogen obtained by reforming gasoline, and direct methanol type using methanol directly It is.
- Reference example 2 Synthesis of Sulfonated mSEBmS Sulfonated mSEBmS Sulfonated mSEBmS was synthesized by a method similar to a previously reported method (Japanese Patent Laid-Open No. 2006-210326). Specifically, first, a sulfonation reagent was prepared by reacting 21.0 ml of acetic anhydride and 9.34 ml of sulfuric acid at 0 ° C. in 41.8 ml of methylene chloride. On the other hand, 100 g of the block copolymer mSEBmS obtained in Reference Example 1 was vacuum-dried in a glass reaction vessel equipped with a stirrer for 1 hour and then purged with nitrogen. Stir to dissolve.
- the sulfonation reagent was gradually added dropwise over 20 minutes. After stirring at 35 ° C. for 1 hour, the polymer solution was poured into 2 L of distilled water while stirring to coagulate and precipitate the polymer. The precipitated solid was washed with distilled water at 90 ° C. for 30 minutes and then filtered. This washing and filtration operation was repeated until there was no change in the pH of the washing water, and the polymer collected at the end was vacuum-dried to obtain sulfonated mSEBmS. The ion exchange capacity of the sulfonated mSEBmS obtained was 0.69 meq / g.
- TBSSIStBS poly (4-tert-butylstyrene)- b-polystyrene-b-polyisoprene-b-polystyrene-b-poly 4-tert-butylstyrene)
- the number average molecular weight (GPC measurement, polystyrene conversion) of the obtained tBSSIStBS is 94682
- the 1,4-bond content determined from 1 H-NMR measurement is 93.8%
- the content of styrene units is 17.6 mass.
- 4-tert-butylstyrene unit content was 42.9% by mass.
- tBSSEPStBS poly (4-tert-butylstyrene) -b-polystyrene-b-hydrogenated polyisoprene-b-polystyrene-b-poly (4-tert-butylstyrene)
- Reference example 4 Synthesis of sulfonated tBSSEPStBS
- a sulfonation reagent was prepared by reacting 19.2 ml of acetic anhydride and 8.6 ml of sulfuric acid at 0 ° C. in 38.4 ml of methylene chloride.
- 100 g of the block copolymer tBSSEPStBS obtained in Reference Example 3 was vacuum-dried in a glass reaction vessel equipped with a stirrer for 1 hour and then purged with nitrogen.
- sulfonated tBSSEPStBS had an ion exchange capacity of 0.50 meq / g.
- StBSItBSS polystyrene-b- (4-tert-butyl Styrene) -b-polyisoprene-b-poly (4-tert-butyl) Styrene)-b-polystyrene
- the number average molecular weight (GPC measurement, polystyrene conversion) of the obtained StBSItBSS was 167471, the 1,4-bond content determined from 1 H-NMR measurement was 93.5%, and the content of styrene units was 9.6 mass. %, 4-tert-butylstyrene unit content was 62.2% by mass.
- StBSEPtBSS polystyrene-b-poly (4-tert-butylstyrene) -b-hydrogenated polyisoprene-b-poly (4-tert-butylstyrene) -b-polystyrene
- Example 1 (1) Synthesis of sulfonated StBSEPtBSS Sulphonated StBSEPtBSS was synthesized in the same manner as in Reference Example 2. Specifically, first, a sulfonation reagent was prepared by reacting 14.8 ml of acetic anhydride and 6.62 ml of sulfuric acid at 0 ° C. in 29.6 ml of methylene chloride. On the other hand, 20 g of the block copolymer StBSEPtBSS obtained in Reference Example 5 was vacuum-dried in a glass reaction vessel equipped with a stirrer for 1 hour and then purged with nitrogen. Then, 262 ml of methylene chloride was added and stirred at room temperature for 4 hours. And dissolved.
- a sulfonation reagent was prepared by reacting 14.8 ml of acetic anhydride and 6.62 ml of sulfuric acid at 0 ° C. in 29.6 ml of methylene chloride.
- the sulfonation reagent was gradually added dropwise over 20 minutes. After stirring at room temperature for 48 hours, 50 ml of methylene chloride was added to dilute the polymer solution. While stirring, the polymer solution was poured into 2 L of distilled water to coagulate and precipitate the polymer. The precipitated solid was washed with distilled water at 90 ° C. for 30 minutes and then filtered. This washing and filtration operation was repeated until there was no change in the pH of the washing water, and the polymer collected at the end was vacuum dried to obtain sulfonated StBSEPtBSS. The ion exchange capacity of the obtained sulfonated StBSEPtBSS was 0.86 meq / g.
- the ion exchange capacity was measured according to the following procedure.
- the sample for measuring the ion exchange capacity was weighed (a (g)) in a glass container capable of being sealed, and an excess amount of a saturated aqueous sodium chloride solution was added thereto and stirred overnight.
- Hydrogen chloride generated in the system was titrated (b (ml)) with a 0.01N NaOH standard aqueous solution (titer f) using a phenolphthalein solution as an indicator.
- the average particle diameter of the sulfonated StBSEPtBSS in the obtained aqueous dispersion was about 7.0 ⁇ m.
- test membrane A An electrolyte membrane having a thickness of 50 ⁇ m and a size of 9 cm square (hereinafter referred to as test membrane A) was produced from the sulfonated mSEBmS obtained in Reference Example 2 by a known method.
- the gas diffusion electrode was prepared by mixing a dispersion of perfluorocarbon sulfonic acid manufactured by DuPont and a catalyst as an electrolyte to prepare a uniformly dispersed catalyst paste, and then using this paste as a water repellent material. It was prepared by uniformly applying to one side of the treated carbon paper, allowing it to stand at room temperature for several hours, and drying at 115 ° C. for 30 minutes.
- Pt-Ru supported carbon (TEC61E54) manufactured by Tanaka Kikinzoku Kogyo Co., Ltd. was used as the anode catalyst, and Pt supported carbon (TEC10E50E) manufactured by Tanaka Kikinzoku Kogyo Co., Ltd.
- the produced gas diffusion electrodes were anode: Pt 1.00 mg / cm 2 , Ru 0.77 mg / cm 2 , polymer 1.57 mg / cm 2 , cathode: Pt 1.00 mg / cm 2 , polymer 1.20 mg / cm 2. Met.
- Example 1 Preparation of membrane-electrode assembly
- the dispersion obtained in Example 1 (3) was spray-coated on both sides of the test membrane A and dried to form an intermediate layer.
- Example 1 The obtained gas diffusion electrode (5 cm square) was bonded to the test film A on which the intermediate layer was formed to produce a membrane-electrode assembly.
- Example 3 Preparation of Aqueous Dispersion of Sulfonated StBSEPtBSS By treating the aqueous dispersion obtained in Example 1 (2) with a high-pressure homogenizer (Nanomizer mark II manufactured by Yoshida Kikai Kogyo Co., Ltd.), the average particle size is about An aqueous dispersion of sulfonated StBSEPtBSS, 85 nm, was obtained.
- aqueous dispersion of sulfonated StBSEPtBSS 85 nm, was obtained.
- (2) Preparation of membrane-electrode assembly An intermediate layer was formed by spray-coating the dispersion obtained in Example 3 (1) on both sides of the test membrane A, and obtained in Example 1 (5). The membrane-electrode assembly was prepared by bonding the gas diffusion electrode (5 cm square) and the test film A on which the intermediate layer was formed.
- Example 4 Production of membrane-electrode assembly A membrane-electrode assembly was produced in the same manner as in Example 3 (2) except that the test membrane B was used.
- Example 5 Preparation of Aqueous Dispersion of Sulfonated StBSEPtBSS By treating the aqueous dispersion obtained in Example 1 (2) with a high-pressure homogenizer (Nanomizer mark II manufactured by Yoshida Kikai Kogyo Co., Ltd.), the average particle size is about An aqueous dispersion of sulfonated StBSEPtBSS, 117 nm, was obtained.
- (2) Preparation of membrane-electrode assembly An intermediate layer was formed by spray-coating the dispersion obtained in Example 5 (1) on both sides of the test membrane A, and obtained in Example 1 (5). The membrane-electrode assembly was prepared by bonding the gas diffusion electrode (5 cm square) and the test film A on which the intermediate layer was formed.
- Example 6 Production of membrane-electrode assembly A membrane-electrode assembly was produced in the same manner as in Example 5 (2) except that the test membrane B was used.
- Example 7 Preparation of membrane-electrode assembly An intermediate layer was formed by spray-coating the dispersion obtained in Example 5 (1) on the surface of the electrode catalyst layer of the gas diffusion electrode obtained in Example 1 (5). Then, the gas diffusion electrode (5 cm square) on which the intermediate layer was formed was bonded to the test film A to prepare a membrane-electrode assembly.
- Example 8 (1) Production of membrane-electrode assembly A membrane-electrode assembly was produced in the same manner as in Example 7 except that the test membrane B was used.
- Comparative Example 2 Production of membrane-electrode assembly A membrane-electrode assembly was produced in the same manner as in Comparative Example 1 except that the test membrane B was used.
- Comparative Example 4 Production of membrane-electrode assembly A membrane-electrode assembly was produced in the same manner as in Comparative Example 3 except that test membrane B was used.
- Example 5 Preparation of Membrane-Electrode Assembly (Membrane-Electrode Assembly described in Patent Document 1)
- the dispersion of the perfluorocarbon sulfonic acid manufactured by DuPont used in Example 1 (5) was spray-coated on both surfaces of test membrane A. Then, the intermediate layer was formed, and the gas diffusion electrode (5 cm square) obtained in Example 1 (5) and the test film A on which the intermediate layer was formed were hot-pressed (130 ° C., 20 kgf / cm 2, 8 min). A membrane-electrode assembly was produced by bonding.
- Example 6 Production of membrane-electrode assembly (membrane-electrode assembly described in Patent Document 1)
- An intermediate layer was formed by spray-coating a dispersion of perfluorocarbon sulfonic acid, and the gas diffusion electrode (5 cm square) on which the intermediate layer was formed and the test membrane A were hot-pressed (130 ° C., 20 kgf / cm 2). , 8 min) to produce a membrane-electrode assembly.
- Example 8 Preparation of membrane-electrode assembly (membrane-electrode assembly described in Patent Document 2)
- An intermediate layer was obtained by spray-coating a dispersion liquid of perfluorocarbon sulfonic acid produced by the method and carbon black (Valcan XC72) prepared so that the mass ratio of perfluorocarbon sulfonic acid / carbon black was 50/50.
- the gas diffusion electrode (5 cm square) on which the intermediate layer was formed and the test film A were bonded together by hot pressing (130 ° C., 20 kgf / cm 2 , 8 min) to produce a membrane-electrode assembly.
- the outside was sandwiched between two current collector plates and two clamping plates in order to produce a single cell for a polymer electrolyte fuel cell.
- a gasket was disposed between each membrane-electrode assembly and the separator in order to prevent gas leakage from a step corresponding to the thickness of the electrode.
- a 1 mol / L MeOH aqueous solution was used as the fuel, and oxygen wetted with a 40 ° C. bubbler was used as the oxidant.
- test conditions were an anode flow rate: 1 ml / min, a cathode flow rate: 175 ml / min, a cell temperature of 40 ° C., and the electric resistance after carrying out power generation for 2 hours under the conditions of a current value of 50 mA / cm 2 was evaluated.
- the electrical resistance was measured by the current interruption method under the condition that the current value was 50 mA / cm 2 .
- the membrane-electrode assembly obtained in Example 3 was observed for a phase separation structure by selectively staining sulfonic acid groups of the electrolyte material constituting the membrane-electrode assembly using lead acetate.
- the block copolymer in the intermediate layer forms a core-shell structure in which a phase having an ion conductive group is a shell phase and a phase having no ion conductive group is a core phase.
- FIG. 4 shows an electron micrograph of the cross section of the membrane-electrode assembly obtained in Comparative Example 5, which was stained in the same manner as described above. No phase separation of the intermediate layer is observed.
- the ionic conductivities of the test films A and B used in Examples 1 to 8 and Comparative Examples 1 to 6 were 0.024 S / cm and 0.017 S / cm, respectively.
- Table 1 shows the results of measuring the electrical resistance of the single cells at 50 mA / cm 2 for Examples 1 to 8 and Comparative Examples 1 to 6.
- membrane-electrode assemblies having an ion channel controlled core-shell ion conductor as an intermediate layer and membrane-electrode assemblies having sulfonated mSEBmS as an intermediate layer introduce Nafion into the membrane-electrode junction.
- the open circuit voltage was almost equal or higher.
- the membrane-electrode assembly of the present invention was excellent in bonding strength without any peeling or the like even after the power generation test.
- FIG. 3 is a configuration diagram schematically showing the structure of an intermediate layer provided in the membrane-electrode assembly of the present invention.
- 4 is an electron micrograph of a cross section of a membrane-electrode assembly for a polymer electrolyte fuel cell obtained in Example 3.
- FIG. 4 is an electron micrograph of a cross section of a membrane-electrode assembly for a polymer electrolyte fuel cell obtained in Example 3.
- FIG. 6 is an electron micrograph of a cross section of a membrane-electrode assembly for a polymer electrolyte fuel cell obtained in Comparative Example 5.
- FIG. 4 is an electron micrograph of a cross section of a membrane-electrode assembly for a polymer electrolyte fuel cell obtained in Example 3.
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Abstract
Description
合性を改良する手法が提案されている(特許文献3)。
本発明は、経済的で、環境に優しく、成形性が良く、膜-電極界面抵抗が小さく発電効率に優れる膜-電極接合体及び固体高分子型燃料電池を提供することを目的とする。
本発明のイオンチャンネル構造が制御された中間層を適用することにより、膜-電極間の接合状態が改善され、膜-電極間の界面抵抗が低減して、膜-電極接合体の電気抵抗が低減し、出力が向上するなど発電効率が向上する。
このような構造を有する中間層は、ブロック共重合体のイオン伝導性基を有する重合体ブロック(A)が連続相をなすため、中間層内部のイオン伝導性が良く、また、中間層と電解質膜との接合部分及び中間層と電極触媒層との接合部分がイオン伝導性基を有する重合体ブロック(A)からなるために、効率良くイオン経路を形成することができる。また、イオン伝導性基を有さない重合体ブロック(B)があることで、中間層の耐水性が高まり、発電中の反応ガスに含まれる湿分や酸素極の生成水等により、中間層を形成するブロック共重合体が電池系外に徐々に溶出し、膜-電極接合体が劣化することを防止することができる。
重合体ブロック(B)は、また、重合体ブロック(B1)と構造保持性重合体ブロック(B2)からなるのが好ましい。重合体ブロック(B2)を加えることにより、相分離構造の変化によって、イオンチャンネルの連続性、さらには膜-電極接合体の耐久性が損われる可能性を低減することができる。
上記式において多価の基はブロック共重合体間又はブロック共重合体内で重合体ブロック(A)同士を結合する。
イオン伝導性基は、芳香族ビニル重合体ブロック(A)の側鎖または自由末端側に存在しているのが好ましい。
本発明のイオン伝導性体は、本発明の効果を損わない限り、各種添加剤、例えば、軟化剤、安定剤、光安定剤、帯電防止剤、離型剤、難燃剤、発泡剤、顔料、染料、増白剤、カーボン繊維、無機充填剤等を各単独で又は2種以上組み合わせて含有していてもよい。
安定剤は、フェノール系安定剤、イオウ系安定剤、リン系安定剤等を包含し、具体例としては、2,6-ジ-t-ブチル-p-クレゾール、ペンタエリスチリル-テトラキス[3-(3,5-ジ-t-ブチル-4-ヒドロキシフェニル)プロピオネート]、1,3,5-トリメチル-2,4,6-トリス(3,5-ジ-t-ブチル-4-ヒドロキシベンジル)ベンゼン、オクタデシル-3-(3,5-ジ-t-ブチル-4-ヒドロキシフェニル)プロピオネート、トリエチレングリコール-ビス[3-(3-t-ブチル-5-メチル-4-ヒドロキシフェニル)プロピオネート]、2,4-ビス-(n-オクチルチオ)-6-(4-ヒドロキシ-3,5-ジ-t-ブチルアニリノ)-1,3,5-トリアジン、2,2,-チオ-ジエチレンビス[3-(3,5-ジ-t-ブチル-4-ヒドロキシフェニル)プロピオネート]、N,N’-ヘキサメチレンビス(3,5-ジ-t-ブチル-4-ヒドロキシ-ヒドロジナマミド)、3,5-ジ-t-ブチル-4-ヒドロキシ-ベンジルホスホネート-ジエチルエステル、トリス-(3,5-ジ-t-ブチル-4-ヒドロキシベンジル)-イソシアヌレート、3,9-ビス{2-[3-(3-t-ブチル-4-ヒドロキシ-5-メチルフェニル)プロピオニルオキシ]-1,1-ジメチルエチル}-2,4,8,10-テトラオキサスピロ[5,5]ウンデカン等のフェノール系安定剤;ペンタエリスリチルテトラキス(3-ラウリルチオプロピオネート)、ジステアリル3,3’-チオジプロピオネート、ジラウリル3,3’-チオジプロピオネート、ジミリスチル3,3’-チオジプロピオネート等のイオウ系安定剤;トリスノニルフェニルホスファイト、トリス(2,4-ジ-t-ブチルフェニル)ホスファイト、ジアステリルペンタエリスリトールジホスファイト、ビス(2,6-ジ-t-ブチル-4-メチルフェニル)ペンタエリスリトールジホスファイト等のリン系安定剤等が挙げられる。
無機充填剤の具体例としては、タルク、炭酸カルシウム、シリカ、ガラス繊維、マイカ、カオリン、酸化チタン、モンモリロナイト、アルミナ等が挙げられる。
これらの界面活性剤は単独でもしくは2種以上組み合わせて用いることができる。
ポリα-メチルスチレンと水添ポリブタジエンとからなるブロック共重合体の製造
既報の方法(WO 02/40611)と同様の方法で、ポリα-メチルスチレン-b-ポリブタジエン-b-ポリα-メチルスチレン型トリブロック共重合体(以下mSBmSと略記する)を合成した。得られたmSBmSの数平均分子量(GPC測定、ポリスチレン換算)は76000であり、1H-NMR測定から求めた1,4-結合量は55%、α-メチルスチレン単位の含有量は30.0質量%であった。また、ポリブタジエンブロック中には、α-メチルスチレンが実質的に共重合されていないことが、1H-NMRスペクトル測定による組成分析により判明した。
合成したmSBmSのシクロヘキサン溶液を調製し、十分に窒素置換を行った耐圧容器に仕込んだ後、Ni/Al系のZiegler系水素添加触媒を用いて、水素雰囲気下において80℃で5時間水素添加反応を行い、ポリα-メチルスチレン-b-水添ポリブタジエン-b-ポリα-メチルスチレン型トリブロック共重合体(以下mSEBmSと略記する)を得た。得られたmSEBmSの水素添加率を1H-NMRスペクトル測定により算出したところ、99.6%であった。
スルホン化mSEBmSの合成
既報の方法(特開2006-210326号公報)と同様の方法で、スルホン化mSEBmSを合成した。具体的には先ず、塩化メチレン41.8ml中、0℃にて無水酢酸21.0mlと硫酸9.34mlとを反応させてスルホン化試薬を調製した。一方、参考例1で得られたブロック共重合体mSEBmS100gを、攪拌機付きのガラス製反応容器中にて1時間真空乾燥し、ついで窒素置換した後、塩化メチレン1000mlを加え、35℃にて4時間攪拌して溶解させた。溶解後、スルホン化試薬を、20分かけて徐々に滴下した。35℃にて1時間攪拌後、2Lの蒸留水の中に攪拌しながら重合体溶液を注ぎ、重合体を凝固析出させた。析出した固形分を90℃の蒸留水で30分間洗浄し、ついでろ過した。この洗浄及びろ過の操作を洗浄水のpHに変化がなくなるまで繰り返し、最後にろ集した重合体を真空乾燥してスルホン化mSEBmSを得た。得られたスルホン化mSEBmSのイオン交換容量は0.69meq/gであった。
ポリスチレン(重合体ブロック(A))、水添ポリイソプレン(重合体ブロック(B1))及びポリ(4-tert-ブチルスチレン)(重合体ブロック(B2))からなるブロック共重合体の製造
既報の方法(特開2007-258162号公報)と同様の方法で、1000mLナスフラスコに、脱水シクロヘキサン576ml及びsec-ブチルリチウム(1.3M-シクロヘキサン溶液)1.78mlを仕込んだ後、4-tert-ブチルスチレン32.1ml、スチレン13.5ml、イソプレン81.6ml、スチレン13.3ml及び4-tert-ブチルスチレン31.5mlを逐次添加し、30℃で重合させ、ポリ(4-tert-ブチルスチレン)-b-ポリスチレン-b-ポリイソプレン-b-ポリスチレン-b-ポリ(4-tert-ブチルスチレン)(以下、tBSSIStBSと略記する)を合成した。得られたtBSSIStBSの数平均分子量(GPC測定、ポリスチレン換算)は94682であり、1H-NMR測定から求めた1,4-結合量は93.8%、スチレン単位の含有量は17.6質量%、4-tert-ブチルスチレン単位の含有量は42.9質量%であった。
合成したtBSSIStBSのシクロヘキサン溶液を調製し、十分に窒素置換を行った耐圧容器に仕込んだ後、Ni/Al系のZiegler系水素添加触媒を用いて、水素雰囲気下において50℃で12時間水素添加反応を行い、ポリ(4-tert-ブチルスチレン)-b-ポリスチレン-b-水添ポリイソプレン-b-ポリスチレン-b-ポリ(4-tert-ブチルスチレン)(以下、tBSSEPStBSと略記する)を得た。得られたtBSSEPStBSの水素添加率を1H-NMRスペクトル測定により算出したところ、99.9%であった。
スルホン化tBSSEPStBSの合成
参考例2と同様の方法で、スルホン化tBSSEPStBSを合成した。具体的には先ず、塩化メチレン38.4ml中、0℃にて無水酢酸19.2mlと硫酸8.6mlとを反応させてスルホン化試薬を調製した。一方、参考例3で得られたブロック共重合体tBSSEPStBS100gを、攪拌機付きのガラス製反応容器中にて1時間真空乾燥し、ついで窒素置換した後、塩化メチレン840mlを加え、35℃にて4時間攪拌して溶解させた。溶解後、スルホン化試薬を、20分かけて徐々に滴下した。35℃にて1時間攪拌後、2Lの蒸留水の中に攪拌しながら重合体溶液を注ぎ、重合体を凝固析出させた。析出した固形分を90℃の蒸留水で30分間洗浄し、ついでろ過した。この洗浄及びろ過の操作を洗浄水のpHに変化がなくなるまで繰り返し、最後にろ集した重合体を真空乾燥してスルホン化tBSSEPStBSを得た。得られたスルホン化tBSSEPStBSのイオン交換容量は0.50meq/gであった。
ポリスチレン(重合体ブロック(A))、水添ポリイソプレン(重合体ブロック(B1))及びポリ(4-tert-ブチルスチレン)(重合体ブロック(B2))からなるブロック共重合体の製造
既報の方法(特開2007-258162号公報)と同様の方法で、1000mLナスフラスコに、脱水シクロヘキサン568ml及びsec-ブチルリチウム(1.3M-シクロヘキサン溶液)1.14mlを仕込んだ後、スチレン4.27ml、4-tert-ブチルスチレン53.3ml、イソプレン66.4ml、4-tert-ブチルスチレン52.6ml及びスチレン9.30mlを逐次添加し、60℃で重合させ、ポリスチレン-b-(4-tert-ブチルスチレン)-b-ポリイソプレン-b-ポリ(4-tert-ブチルスチレン)-b-ポリスチレン(以下、StBSItBSSと略記する)を合成した。得られたStBSItBSSの数平均分子量(GPC測定、ポリスチレン換算)は167471であり、1H-NMR測定から求めた1,4-結合量は93.5%、スチレン単位の含有量は9.6質量%、4-tert-ブチルスチレン単位の含有量は62.2質量%であった。
合成したStBSItBSSのシクロヘキサン溶液を調製し、十分に窒素置換を行った耐圧容器に仕込んだ後、Ni/Al系のZiegler系水素添加触媒を用いて、水素雰囲気下において50℃で12時間水素添加反応を行い、ポリスチレン-b-ポリ(4-tert-ブチルスチレン)-b-水添ポリイソプレン-b-ポリ(4-tert-ブチルスチレン)-b-ポリスチレン(以下、StBSEPtBSSと略記する)を得た。得られたStBSEPtBSSの水素添加率を1H-NMRスペクトル測定により算出したところ、99.9%であった。
(1)スルホン化StBSEPtBSSの合成
参考例2と同様の方法で、スルホン化StBSEPtBSSを合成した。具体的には先ず、塩化メチレン29.6ml中、0℃にて無水酢酸14.8mlと硫酸6.62mlとを反応させてスルホン化試薬を調製した。一方、参考例5で得られたブロック共重合体StBSEPtBSS20gを、攪拌機付きのガラス製反応容器中にて1時間真空乾燥し、ついで窒素置換した後、塩化メチレン262mlを加え、常温にて4時間攪拌して溶解させた。溶解後、スルホン化試薬を、20分かけて徐々に滴下した。常温にて48時間攪拌後、塩化メチレン50mlを加えて重合体溶液を希釈した。2Lの蒸留水の中に攪拌しながら重合体溶液を注ぎ、重合体を凝固析出させた。析出した固形分を90℃の蒸留水で30分間洗浄し、ついでろ過した。この洗浄及びろ過の操作を洗浄水のpHに変化がなくなるまで繰り返し、最後にろ集した重合体を真空乾燥してスルホン化StBSEPtBSSを得た。得られたスルホン化StBSEPtBSSのイオン交換容量は0.86meq/gであった。イオン交換容量の測定は以下の手順により行った。
イオン交換容量の測定
試料を密閉できるガラス容器中に秤量(a(g))し、そこに過剰量の塩化ナトリウム飽和水溶液を添加して一晩攪拌した。系内に発生した塩化水素を、フェノールフタレイン液を指示薬とし、0.01NのNaOH標準水溶液(力価f)にて滴定(b(ml))した。イオン交換容量は、次式により求めた。イオン交換容量=(0.01×b×f)/a
5質量%のスルホン化StBSEPtBSS溶液(トルエン/イソブチルアルコール=8/2)を調製し、次いで、薄膜旋回型高速ホモジナイザー(プライミクス社製 フィルミックス)に周速30m/sで攪拌しながらポリマー溶液を70ml/min、水を80ml/minの速度で添加し、転相乳化させた。エバポレーターを用いて溶剤を除去し、5質量%の水分散液を得た。得られた水分散液中のスルホン化StBSEPtBSSの平均粒径は約7.0μmであった。
(3)(2)で得られた水分散液を高圧ホモジナイザー(吉田機械興業株式会社製Nanomizer mark II)で処理することで、平均粒径が約59nmである、スルホン化StBSEPtBSSの水分散液を得た。
参考例2で得られたスルホン化mSEBmSから公知の方法で厚さ50μm、サイズ9cm角の電解質膜(以下、試験膜Aと呼ぶ)を作製した。
ガス拡散電極は、電解質としてデュポン社製のパーフルオロカーボンスルホン酸の分散液と触媒とを混合し、均一に分散された触媒ペーストを調製し、次いでこのペーストを撥水処理したカーボンペーパーの片面に均一に塗布し、常温で数時間放置した後、115℃で30分乾燥させることで作製した。アノード用触媒には田中貴金属工業社製のPt-Ru担持カーボン(TEC61E54)を使用し、カソード用触媒には田中貴金属工業社製のPt担持カーボン(TEC10E50E)を使用した。作製したガス拡散電極は、アノード:Pt 1.00mg/cm2、Ru 0.77mg/cm2、ポリマー 1.57mg/cm2、カソード:Pt 1.00mg/cm2、ポリマー 1.20mg/cm2であった。
試験膜Aの両面に実施例1(3)で得られた分散液をスプレ-塗布し乾燥することで中間層を形成し、実施例1(5)で得られたガス拡散電極(5cm角)と中間層を形成させた試験膜Aとを貼り合わせることで膜-電極接合体を作製した。
(1)電解質膜の作製
参考例4で得られたスルホン化tBSSEPStBSを公知の方法で厚さ50μm、サイズ9cm角の電解質膜(以下、試験膜Bと呼ぶ)を作製した。
(2)膜-電極接合体の作製
試験膜Bを用いる以外は実施例1(6)と同様にして膜-電極接合体を作製した。
(1)スルホン化StBSEPtBSSの水分散液の調製
実施例1(2)で得られた水分散液を高圧ホモジナイザー(吉田機械興業株式会社製Nanomizer mark II)で処理することで、平均粒径が約85nmである、スルホン化StBSEPtBSSの水分散液を得た。
(2)膜-電極接合体の作製
試験膜Aの両面に実施例3(1)で得られた分散液をスプレ-塗布することで中間層を形成し、実施例1(5)で得られたガス拡散電極(5cm角)と中間層を形成させた試験膜Aとを貼り合わせることで膜-電極接合体を作製した。
膜-電極接合体の作製
試験膜Bを用いる以外は実施例3(2)と同様にして膜-電極接合体を作製した。
(1)スルホン化StBSEPtBSSの水分散液の調製
実施例1(2)で得られた水分散液を高圧ホモジナイザー(吉田機械興業株式会社製Nanomizer mark II)で処理することで、平均粒径が約117nmである、スルホン化StBSEPtBSSの水分散液を得た。
(2)膜-電極接合体の作製
試験膜Aの両面に実施例5(1)で得られた分散液をスプレ-塗布することで中間層を形成し、実施例1(5)で得られたガス拡散電極(5cm角)と中間層を形成させた試験膜Aとを貼り合わせることで膜-電極接合体を作製した。
膜-電極接合体の作製
試験膜Bを用いる以外は実施例5(2)と同様にして膜-電極接合体を作製した。
膜-電極接合体の作製
実施例1(5)で得られたガス拡散電極の電極触媒層表面に実施例5(1)で得られた分散液をスプレ-塗布することで中間層を形成し、中間層を形成させたガス拡散電極(5cm角)と試験膜Aとを貼り合わせることで膜-電極接合体を作製した。
(1)膜-電極接合体の作製
試験膜Bを用いる以外は実施例7と同様にして膜-電極接合体を作製した。
膜-電極接合体の作製
試験膜Aと実施例1(5)で得られたガス拡散電極(5cm角)とを貼り合わせることで膜-電極接合体を作製した
膜-電極接合体の作製
試験膜Bを用いる以外は比較例1と同様にして膜-電極接合体を作製した。
膜-電極接合体の作製
試験膜Aと実施例1(5)で得られたガス拡散電極(5cm角)とを熱プレス(130℃、20kgf/cm2、8min)により貼り合わせることで膜-電極接合体を作製した。
膜-電極接合体の作製
試験膜Bを用いる以外は比較例3と同様にして膜-電極接合体を作製した。
膜-電極接合体(特許文献1記載の膜-電極接合体)の作製
試験膜Aの両面に実施例1(5)で用いたデュポン社製のパーフルオロカーボンスルホン酸の分散液をスプレ-塗布することで中間層を形成し、実施例1(5)で得られたガス拡散電極(5cm角)と中間層を形成させた試験膜Aとを熱プレス(130℃、20kgf/cm2、8min)により貼り合わせることで膜-電極接合体を作製した。
膜-電極接合体(特許文献1記載の膜-電極接合体)の作製
実施例1(5)で得られたガス拡散電極の電極触媒層表面に実施例1(5)で用いたデュポン社製のパーフルオロカーボンスルホン酸の分散液をスプレ-塗布することで中間層を形成し、中間層を形成させたガス拡散電極(5cm角)と試験膜Aとを熱プレス(130℃、20kgf/cm2、8min)により貼り合わせることで膜-電極接合体を作製した。
膜-電極接合体(特許文献1記載の膜-電極接合体)の作製
実施例1(5)で得られたガス拡散電極の電極触媒層表面に、スルホン化mSEBmSのテトラヒドロフラン溶液をスプレ-塗布することで中間層を形成し、中間層を形成させたガス拡散電極(5cm角)と試験膜Aとを貼り合わせることで膜-電極接合体を作製した。
膜-電極接合体(特許文献2記載の膜-電極接合体)の作製
実施例1(5)で得られたガス拡散電極の電極触媒層表面に、実施例1(5)で用いたデュポン社製のパーフルオロカーボンスルホン酸の分散液、及びカーボンブラック(Valcan XC72)を、パーフルオロカーボンスルホン酸/カーボンブラックの質量比が50/50になるように調製した混合液をスプレ-塗布することで中間層を形成し、中間層を形成させたガス拡散電極(5cm角)と試験膜Aとを熱プレス(130℃、20kgf/cm2、8min)により貼り合わせることで膜-電極接合体を作製した。
膜-電極接合体(特許文献2又は3記載の膜-電極接合体)の作製
実施例1(5)で得られたガス拡散電極の電極触媒層表面に、参考例2で得られたスルホン化HmSEBmS、及びカーボンブラック(Valcan XC72)を、スルホン化HmSEBmS/カーボンブラックの質量比が50/50になるように調製した混合液をスプレ-塗布することで中間層を形成し、中間層を形成させたガス拡散電極(5cm角)と試験膜Aとを貼り合わせることで膜-電極接合体を作製した。
1)膜のイオン伝導度の測定
試験膜A及び試験膜Bについて、1cm×4cmのサイズに裁断した膜を4本の白金ワイヤーに挟んで測定セルを作製した。測定セルは、温度40℃の水中に浸漬して、膜面方向の交流4端子法にてイオン伝導度を測定した。
2)燃料電池単セル出力性能評価
実施例1~8及び比較例1~6で作製した膜-電極接合体のそれぞれを、2枚のガス供給流路の役割を兼ねた導電性のセパレータで挟み、さらにその外側を2枚の集電板及び2枚の締付板で順に挟み固体高分子型燃料電池用単セルを作製した。なお、それぞれの膜-電極接合体とセパレータとの間には、電極の厚さ分の段差からのガス漏れを防ぐために、ガスケットを配した。燃料には1mol/LのMeOH水溶液を用い、酸化剤には40℃のバブラにて加湿した酸素を用いた。試験条件は、アノード流量:1ml/min、カソード流量:175ml/min、セル温度40℃とし、電流値が50mA/cm2の条件にて2時間の発電を実施した後の電気抵抗を評価した。なお、電気抵抗は電流値が50mA/cm2の条件下で電流遮断法にて測定した。
実施例3で得られた膜-電極接合体の断面における電子顕微鏡写真を図2及び図3に示す。なお、実施例3で得られた膜-電極接合体は酢酸鉛を用いて膜-電極接合体を構成する電解質材料のスルホン酸基を選択的に染色することで相分離構造を観察した。
中間層中のブロック共重合体はイオン伝導性基を有する相がシェル相であり、イオン伝導性基を有さない相がコア相であるコアシェル構造を形成している。コアシェル構造のシェル相は連続的なイオン経路を形成し、また、中間層と電解質膜との接合部分及び中間層と電極触媒層との接合部分はシェル相から形成されている構造が明確に示された。
比較例5で得られた膜-電極接合体であって上記と同様の染色をしたものの断面における電子顕微鏡写真を図4に示す。中間層の相分離は観察されない。
実施例1~8及び比較例1~6に用いた試験膜A及び試験膜Bのイオン伝導度はそれぞれ0.024S/cm及び0.017S/cmであった。実施例1~8及び比較例1~6について50mA/cm2における単セルの電気抵抗を測定した結果を表1に示す。
2及び4 イオン伝導性基を有さない重合体ブロック(B)
5 電極触媒層
6 中間層
7 電解質膜
Claims (13)
- 高分子電解質膜と、この高分子電解質膜に該膜を挟んで接合されている2つのガス拡散電極とからなる、固体高分子型燃料電池用の膜-電極接合体において、各ガス拡散電極は電極触媒層とガス拡散層から構成され、少なくとも一方の電極触媒層と高分子電解質膜との間に、イオン伝導体からなる中間層を有し、イオン伝導体がイオン伝導性基を有する重合体ブロック(A)とイオン伝導性基を有さない重合体ブロック(B)からなり、両ブロックが互いに相分離するブロック共重合体から主としてなり、重合体ブロック(A)が連続相をなし、かつ、中間層と高分子電解質膜との接合部分及び中間層と電極触媒層との接合部分がイオン伝導性基を有する重合体ブロック(A)からなる該膜-電極接合体。
- 重合体ブロック(A)を構成する繰返し単位が芳香族ビニル系化合物単位である請求項1記載の膜-電極接合体。
- 芳香族ビニル系化合物が、スチレン、α-メチルスチレン及びベンゼン環に結合した水素原子の1~3個が炭素数1~4のアルキル基で置換されたスチレンから選ばれる請求項2記載の膜-電極接合体。
- 重合体ブロック(B)がゴム状重合体ブロック(B1)からなる請求項1~3のいずれか1項に記載の膜-電極接合体。
- 重合体ブロック(B1)が、炭素数2~8のアルケン単位、炭素数4~8の共役ジエン単位、及び炭素-炭素二重結合の一部もしくは全部が水素添加された炭素数4~8の共役ジエン単位から選ばれる少なくとも1種を繰返し単位とする重合体ブロックである請求項4記載の膜-電極接合体。
- 重合体ブロック(B)が、重合体ブロック(B1)、及び重合体ブロック(A)及び重合体ブロック(B1)と相分離する構造保持性重合体ブロック(B2)からなる請求項1~5のいずれか1項に記載の膜-電極接合体。
- 重合体ブロック(B2)を構成する繰返し単位が芳香族ビニル系化合物単位である請求項6記載の膜-電極接合体。
- ブロック共重合体が、両末端に重合体ブロック(A)を配した構造を有する請求項1~7のいずれか1項に記載の膜-電極接合体。
- ブロック共重合体が、ゴム状重合体ブロック(B1)を中心にして、その両側に重合体ブロック(B2)を配し、さらに重合体ブロック(B2)の両外側に重合体ブロック(A)を配した構造を有する請求項6~8のいずれか1項に記載の膜-電極接合体。
- イオン伝導性基が、スルホン酸基及びホスホン酸基並びにそれらのアルカリ金属塩及びアンモニウム塩から選ばれるカチオン伝導性基である請求項1~9のいずれか1項に記載の膜-電極接合体。
- イオン伝導体が、イオン伝導性基を有する重合体ブロック(A)をシェル相とし、イオン伝導性基を有さない重合体ブロック(B)をコア相とする、球状のコアシェル構造である請求項1~10のいずれか1項に記載の膜-電極接合体。
- イオン伝導体が、水系分散媒に該ブロック共重合体及び必要に応じ各種添加剤を該ブロック共重合体の粒径サイズが1μm以下になるように分散させた分散液から水系分散媒を除去することにより得られたものである請求項1~11のいずれか1項に記載の膜-電極接合体。
- 請求項1~12のいずれか1項に記載の膜-電極接合体を使用した固体高分子型燃料電池。
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CN2009801043711A CN101939870B (zh) | 2008-02-06 | 2009-01-28 | 膜-电极组件和聚合物电解质燃料电池 |
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JP2017509770A (ja) * | 2014-04-02 | 2017-04-06 | クレイトン・ポリマーズ・ユー・エス・エル・エル・シー | 中間ブロックスルホン化ブロックコポリマーの水性エマルジョンの調製方法 |
JP2017509769A (ja) * | 2014-04-02 | 2017-04-06 | クレイトン・ポリマーズ・ユー・エス・エル・エル・シー | 中間ブロックスルホン化ブロックコポリマーの水性エマルジョンの調製方法 |
US10017611B2 (en) | 2014-04-02 | 2018-07-10 | Kraton Polymers U.S. Llc | Process for the preparation of an aqueous emulsion of a midblock sulfonated block copolymer |
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CN101939870B (zh) | 2013-11-13 |
EP2242137A1 (en) | 2010-10-20 |
CN101939870A (zh) | 2011-01-05 |
JPWO2009098982A1 (ja) | 2011-05-26 |
EP2242137A4 (en) | 2012-01-25 |
US20100310965A1 (en) | 2010-12-09 |
JP5501771B2 (ja) | 2014-05-28 |
EP2242137B1 (en) | 2014-12-03 |
KR101556425B1 (ko) | 2015-10-01 |
KR20100103889A (ko) | 2010-09-28 |
US8263286B2 (en) | 2012-09-11 |
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