JP2004296435A - Electrode catalyst layer, its manufacturing method, and solid polymer type fuel cell using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrode catalyst layer excellent in liquid permeability, gas diffusibility, electronic conductivity, and proton conductivity. <P>SOLUTION: A catalyst-polymer compound material containing a catalyst carrier carbon particle and a polymer has a 3D mesh porous structure. Because the manufacturing method of the electrode catalyst layer uses a wet solidifying method to produce a catalyst-polymer solution composition, the produced electrode catalyst layer is high in void content, and excellent in liquid permeability and gas permeability. An electrode and a membrane electrode assembly (MEA) using the electrode catalyst layer are thus excellent in output property, because the electrode catalyst has the above mentioned properties. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an electrode catalyst layer used for a polymer electrolyte fuel cell using a liquid fuel, an electrode using the same, and a method for producing the same.

  A fuel cell is a power generation device that emits little, has high energy efficiency, and has a low burden on the environment. For this reason, they have been spotlighted again in recent years as global environmental protection has increased. Compared with the conventional large-scale power generation facilities, the power generation apparatus is expected to be a relatively small-scale distributed power generation facility and a power generation apparatus for mobile objects such as automobiles and ships in the future. In addition, it is attracting attention as a power source for small mobile devices and portable devices, and is expected to be mounted on mobile phones and personal computers instead of secondary batteries such as nickel-metal hydride batteries and lithium ion batteries.

  In a polymer electrolyte fuel cell, in addition to a conventional polymer electrolyte fuel cell (hereinafter referred to as PEFC) using hydrogen gas as a fuel, a direct methanol fuel cell (a direct methanol solution of a liquid fuel) is directly supplied. DMFC) is also attracting attention. DMFC has a lower output than conventional PEFC, but has the advantage of higher energy density and longer usage time of portable equipment per charge because the fuel is liquid and no reformer is used. is there.

  In a fuel cell, an anode and a cathode, in which a reaction responsible for power generation takes place, and an electrolyte membrane serving as an ion conductor between the anode and the cathode constitute a membrane-electrode assembly (MEA). The sandwiched cell is configured as a unit. Here, the electrode is an electrode base material (also referred to as a gas diffusion electrode or a current collector) for supplying a fuel liquid or a gas, discharging a product, and collecting (supplying) electricity, and is actually an electrochemical reaction field. And an electrode catalyst layer.

For example, at the anode electrode of a polymer electrolyte fuel cell, a fuel such as an aqueous methanol solution reacts in the catalyst layer of the anode electrode to generate protons, electrons and carbon dioxide, and the electrons are transferred to the electrode substrate and the protons are transferred to the polymer solid electrolyte. And carbon dioxide is discharged out of the system. Therefore, the anode electrode is required to have good penetration of liquid fuel, good gas diffusivity, good electron conductivity, and good ionic conductivity.
The protons conducted from the solid electrolyte and the electrons conducted from the electrode substrate react with each other to generate water. For this reason, in the cathode electrode, it is necessary to efficiently discharge generated water in addition to gas diffusion, electron conductivity, and ion conductivity. Particularly in a DMFC, a reaction in which methanol and oxygen or an oxidizing gas such as air permeating the electrolyte membrane is generated in the catalyst layer of the cathode electrode to generate carbon dioxide and water. For this reason, the amount of generated water is larger than that of the conventional PEFC, and it is necessary to discharge water more efficiently.

  In order to satisfy such requirements, various studies have been made on the electrode catalyst layer. Examples of improving gas diffusivity (Patent Documents 1 to 3) and examples of improving proton conductivity (Patent Documents 4 to 6) have been reported so far.

  In these documents, a catalyst-supporting carbon or polymer (proton exchange resin is used for improving proton conductivity, and discharge of generated water is improved for forming a porous catalyst layer for the purpose of improving gas diffusivity) For example, PTFE (polytetrafluoroethylene) is used as the particle size, or a catalyst layer is prepared by mixing a catalyst-supporting carbon and a proton exchange resin for the purpose of improving proton conductivity. An example in which an exchange resin is applied and then joined to a proton exchange membrane is known.

Further, an electrode catalyst layer having a three-dimensional network microporous structure has been reported (Patent Document 7).
JP-A-8-88007 JP-A-7-183035 JP-A-6-203852 JP-A-4-329264 JP-A-7-296818, JP-A-7-254420 JP 2000-353528 A

  As described above, both the electrode catalyst layer and the electrode substrate (current collector) have the following problems in the fuel cell electrode.

  The electrode catalyst layer is required to have good liquid permeability, gas permeability, electron conductivity, and proton conductivity. In order to improve the liquid permeability and gas diffusivity, it is necessary to increase the gap, that is, to have a rough structure. On the other hand, in order to improve the electron conductivity, it is necessary to reduce the contact resistance between the conductive carbon in the catalyst layer, that is, to have a dense structure. As for the proton conductivity, a structure in which the proton conductive material (proton exchange resin) added to the catalyst layer is continuously connected, that is, a dense structure is required.

  Thus, the structure required for the electrode catalyst layer is a trade-off between liquid permeability and gas diffusion, which require a coarse structure, and electron conductivity and proton conductivity, which require a dense structure. . For this reason, in the conventional catalyst layer, compatibility between liquid permeation or gas diffusion and electron conduction or proton conduction was not sufficient.

  In addition, the adhesiveness at the interface between the electrolyte membrane surface and the electrode catalyst layer is presumed to affect the output, but sufficient adhesiveness could not be obtained with the conventional electrode catalyst layer structure.

  An object of the present invention is to solve the above problems and provide a high-performance electrode catalyst layer, a method for producing the same, and an electrode catalyst layer.

The present invention has the following configuration in order to solve the above-mentioned problems.
"An electrode catalyst layer for a polymer electrolyte fuel cell using a liquid fuel, wherein at least a catalyst-polymer composite containing catalyst-carrying carbon particles and at least one polymer is a three-dimensional network-like microporous material. An electrode catalyst layer characterized by having a porous structure. "
That is, the electrode catalyst layer of the present invention is characterized in that the catalyst-polymer composite containing at least the catalyst-supporting carbon particles and at least one polymer has a three-dimensional network microporous structure.

  In addition, the method for producing an electrode catalyst layer of the present invention includes, after applying a catalyst-polymer solution composition comprising a polymer solution containing at least uniformly dispersed catalyst particles to a substrate, coating the coating layer with a coagulating solvent for the polymer. The method is characterized in that coagulation of the catalyst-polymer solution composition and solvent extraction are simultaneously performed by contacting.

  Further, the electrode of the present invention is characterized in that the catalyst-polymer composite containing at least the catalyst-supporting carbon particles and at least one polymer has a three-dimensionally network-like microporous structure. Characterized by comprising the above electrode catalyst layer and an electrode substrate.

  Further, a fuel cell using a liquid fuel according to the present invention is characterized in that the above-mentioned electrode catalyst layer is applied.

  Further, the moving object of the present invention is characterized in that the fuel cell serves as a power supply source.

  The present invention provides a polymer electrolyte fuel cell using a liquid fuel, in which at least a catalyst-polymer composite containing catalyst-supporting carbon particles and at least one polymer has a three-dimensional network-like microporous structure. The electrode catalyst layer is characterized in that it has a microporous structure while maintaining proton conductivity and electron conductivity in the catalyst layer, thereby enhancing the movement of fuel and reaction products. Performance.

  Hereinafter, preferred embodiments of the present invention will be described.

  In the electrode catalyst layer of the present invention, a catalyst-polymer composite containing at least catalyst-supporting carbon particles and one or more polymers has a network-like microporous structure in a three-dimensional direction (hereinafter simply referred to as a three-dimensional network microporous structure). Structure). Hereinafter, the contents will be described in detail.

  Conventionally, there is an example in which only a polymer is wet-coagulated, but as a result of intensive studies, the inventors have obtained a catalyst-polymer composite obtained by wet-coagulating a polymer solution composition in which catalyst particles such as catalyst-supporting carbon are dispersed. Has been found to be an electrode catalyst layer exhibiting excellent fuel cell performance. That is, the catalyst-polymer composite of the present invention is a polymer composite containing catalyst particles, and is characterized in that the composite has a three-dimensional network microporous structure. The “three-dimensional network microporous structure” refers to a state in which the catalyst-polymer composite has a three-dimensional network structure three-dimensionally connected.

  It has been found that the electrode catalyst layer having a three-dimensional network microporous structure in the present invention exerts its effect in a polymer electrolyte fuel cell using a liquid such as methanol as a fuel rather than a gas such as hydrogen as a fuel. This is also a point of the present invention. For example, in the above-mentioned DMFC, the anode electrode needs to supply a methanol aqueous solution of fuel and discharge carbon dioxide as a reaction product, so that a more sufficient gap is required than the PEFC of hydrogen fuel. In a DMFC, methanol crossover (MCO) occurs in which methanol as fuel permeates through the electrolyte membrane from the anode to the cathode. For this reason, the permeated methanol reacts with the air to generate water at the cathode, so that more sufficient voids are required for discharging a large amount of water as compared with the hydrogen fuel PEFC.

  It is a preferred embodiment that the electrode catalyst layer having a three-dimensional network microporous structure in the present invention has a thickness of 10 μm or more and 200 μm or less. When the thickness of the electrode catalyst layer is less than 10 μm or more than 200 μm, there is a possibility that the effect of the microporous structure on the mass transfer of a liquid or gas in the catalyst layer may not be obtained.

In an embodiment, the electrode catalyst layer having a three-dimensional network microporous structure in the present invention preferably has a catalyst metal weight of 1 mg / cm ² or more and 7 mg / cm ² or less. The amount of catalyst metal can be analyzed by X-ray fluorescence analysis or ICP emission analysis.For example, after scraping the electrode catalyst layer from MEA and dissolving the contained polymer with a solvent, the remaining catalyst metal and carbon emit fluorescent X-ray. It is possible to determine the amount of catalytic metal by line analysis or the like. If the weight of the catalyst metal is less than 1 mg / cm ² , the power generation performance may be reduced. On the other hand, if the amount of the catalyst metal exceeds 7 mg / cm ² , the electrode catalyst layer becomes too thick, which may lower the performance or increase the cost.

It is a preferred embodiment that the electrode catalyst layer having a three-dimensional network microporous structure in the present invention has a carbon weight of 0.2 mg / cm ² or more and 4 mg / cm ² or less. The amount of carbon in the electrode catalyst layer can be determined, for example, by scraping the electrode catalyst layer from MEA, dissolving the contained polymer with a solvent, and then subtracting the catalyst metal from the remaining catalyst metal and carbon. If the carbon weight is less than 0.2 mg / cm ² or more than 4 mg / cm ² , the effect of the microporous structure on the mass transfer of liquids and gases in the catalyst layer may not be obtained.

In an embodiment, the electrode catalyst layer having a three-dimensional network microporous structure in the present invention preferably has an electrolyte polymer weight of 0.2 mg / cm ² or more and 5 mg / cm ² or less. The amount of the electrolyte polymer in the electrode catalyst layer can be determined, for example, by scraping the electrode catalyst layer from MEA, dissolving the contained polymer with a solvent, and evaluating the weight of the dissolved electrolyte polymer. If the weight of the electrolyte polymer is less than 0.2 mg / cm ² , power generation performance may not be obtained. On the other hand, if it exceeds 5 mg / cm ² , the effect of the microporous structure on mass transfer of liquids and gases in the catalyst layer may not be obtained.

  The three-dimensional network microporous structure of the catalyst-polymer composite in the present invention preferably has a microporous diameter of 0.05 to 5 μm. More preferably, it is 0.1 to 1 μm. The microporous diameter can be determined from an average of 20 or more, preferably 100 or more from a photograph of the surface taken with a scanning electron microscope (SEM) or the like, and is usually measured with 100. Since the catalyst layer having a microporous structure of the present invention when produced by a wet coagulation method has a wide distribution of microporous diameters, it is preferable to average as many pore diameters as possible.

  The porosity of the three-dimensional network microporous structure is preferably from 10 to 95%. More preferably, it is 50 to 90%. The porosity is a percentage (%) obtained by subtracting the volume occupied by the catalyst-polymer composite from the total volume of the catalyst layer and dividing by the total volume of the catalyst layer. The catalyst layer is wet-solidified after being applied to the electrode substrate, the proton exchange membrane, and other substrates.If it is difficult to determine the porosity of the catalyst layer alone, the electrode substrate, the proton It is also possible to previously determine the porosity of the exchange membrane and the other substrates, determine the porosity including these substrates and the catalyst layer, and then determine the porosity of the catalyst layer alone. .

  The electrode catalyst layer has a high porosity, good gas diffusibility and good discharge of generated water, and good electron conductivity and proton conductivity. In the conventional porous method, the catalyst particle diameter and the particle diameter of the added polymer are increased, and pores are formed using a pore-forming agent. And the contact resistance between the proton exchange resins becomes larger than that of the electrode catalyst layer. In contrast, in the three-dimensional network microporous structure formed by the wet coagulation method of the present invention, since the polymer composite containing the catalyst-supporting carbon has a three-dimensional network, electrons and protons conduct through the polymer composite. In addition, the gas diffusion property and the discharge of generated water are excellent because of the microporous structure.

  The catalyst contained in the catalyst-supporting carbon of the catalyst-polymer composite is not particularly limited, but a noble metal catalyst such as platinum, gold, palladium, ruthenium, and iridium is preferably used from the viewpoint of the efficiency of the protonation reaction. Further, two or more elements such as alloys and mixtures of these noble metal catalysts may be contained. It is also a preferred embodiment to include fine particles of only the above-mentioned catalytic metal. In this case, the weight of the catalyst metal fine particles may be greater than the weight of the catalyst metal-supporting carbon.

  The carbon contained in the catalyst-supporting carbon of the catalyst-polymer composite is not particularly limited, but carbon blacks such as channel black, thermal black, and furnace black are preferred from the viewpoint of electron conductivity and the specific surface area. is there. Examples of the oil furnace black include Vulcan XC-72, Vulcan P, Black Pearls 880, Black Pearls 1100, Black Pearls 1300, Black Pearls 2000, Regal 400, Ketchen Black EC manufactured by Lion Corporation, Ketjen Black EC manufactured by Mitsubishi Chemical Corporation, and # 3150 manufactured by Mitsubishi Chemical Corporation. , # 3250, and the like, and acetylene black includes Denka Black manufactured by Denki Kagaku Kogyo KK. Particularly, Vulcan XC-72R manufactured by Cabot Corporation is preferably used.

  The polymer used in the catalyst-polymer composite is not particularly limited, but is preferably a polymer that disperses catalyst particles well and does not deteriorate in an oxidation-reduction atmosphere in a fuel cell. Examples of such a polymer include a polymer containing a fluorine atom, and are not particularly limited. For example, polyvinyl fluoride (PVF), polyvinylidene fluoride (PVDF), polyhexafluoropropylene (FEP), Tetrafluoroethylene, polyperfluoroalkyl vinyl ether (PFA) or the like, a copolymer thereof, a copolymer of these monomer units with another monomer such as ethylene or styrene, or a blend can also be used. Further, heat-resistant and oxidation-resistant polymers are also preferable. Examples of such a polymer include polyimide (PI), polyphenylene sulfide (PPSS), polysulfone (PSF), polyphenylene sulfide (PPS), polyphenylene oxide (PPO), polyether ketone (PEK), and polyether ether ketone (PEEK ), Polyethersulfone (PES), polyetherethersulfone (PEES), polybenzimidazole (PBI) and the like. Further, those having polyphosphazene (PPho) or the like as a main skeleton are also preferably used.

  Among them, polyvinylidene fluoride (PVDF) and hexafluoropropylene-vinylidene fluoride copolymer are obtained by a wet coagulation method using an aprotic polar solvent and a protic polar solvent as a coagulating solvent, by the three-dimensional method of the present invention. It is a particularly preferred polymer in that a catalyst-polymer composite having a network microporous structure can be obtained. Examples of solvents for these polymers include N-methylpyrrolidone (NMP), dimethylformamide (DMF), dimethylacetamide (DMAC), propylene carbonate (PC), dimethylimidazolidinone (DMI), and the like. In addition to lower alcohols such as methanol, ethanol, and isopropanol, esters such as ethyl acetate and butyl acetate, and various aromatic or halogen-based organic solvents are used.

  As the polymer of the catalyst-polymer composite of the present invention, a polymer having a proton exchange group for improving proton conductivity in the catalyst layer is also preferable. Examples of the proton exchange group contained in such a polymer include a sulfonic acid group, a carboxylic acid group, and a phosphoric acid group, but are not particularly limited. Further, such a polymer having a proton exchange group is also selected without particular limitation, but a polymer having a proton exchange group composed of a fluoroalkyl ether side chain and a fluoroalkyl main chain is preferably used. For example, Nafion manufactured by DuPont (a trademark of DuPont; the same applies hereinafter) and the like are also preferable. Further, a polymer containing the above-described fluorine atom having a proton exchange group, another polymer such as ethylene or styrene, a copolymer or a blend thereof may be used.

  The Nafion polymer solution may be obtained by dissolving a commercially available Nafion membrane in an aprotic polar solvent, or a Nafion solution of Aldrich water-methanol-isopropanol mixed solvent or a solvent obtained by replacing the Nafion solution with a solvent. . In this case, the coagulation solvent for wet coagulation should be appropriately determined depending on the solvent of the Nafion solution.However, when the solvent of the Nafion solution is an aprotic polar solvent, water or alcohols may be used as the coagulation solvent. And esters, and various organic solvents are preferred. In the case of a mixed solvent of water, methanol and isopropanol, esters such as butyl acetate and various organic solvents are preferably used.

  As the polymer used in the catalyst-polymer composite, it is also preferable to use a polymer containing a fluorine atom or a polymer containing a proton exchange membrane by copolymerization or blending. In particular, blending polyvinylidene fluoride, poly (hexafluoropropylene-vinylidene fluoride) copolymer, and a polymer such as Nafion, which has a fluoroalkyl ether side chain and a fluoroalkyl main chain in the proton exchange group, can improve electrode performance. It is preferable from the viewpoint.

  The main components of the catalyst-polymer composite are a catalyst-supporting carbon and a polymer, and the ratio thereof is to be appropriately determined according to the required electrode characteristics, and is not particularly limited. Is preferably used in a weight ratio of 5/95 to 95/5. In particular, when used as an electrode catalyst layer for a polymer electrolyte fuel cell, the weight ratio of the catalyst-supporting carbon / polymer is preferably 40/60 to 85/15.

  It is also a preferred embodiment to add various conductive agents to the catalyst-polymer composite in addition to the above-described carbon supported on the catalyst-supporting carbon in order to improve electron conductivity. Examples of such a conductive agent include, in addition to carbon black of the same type as the carbon used for the above-mentioned catalyst-supporting carbon, various graphitic and carbonaceous carbon materials, or metals and metalloids, but are particularly limited. Not something. Examples of such carbon materials include artificial graphite and carbon obtained from organic compounds such as natural graphite, pitch, coke, polyacrylonitrile, phenol resin, and furan resin, in addition to the above-described carbon black. As a form of these carbon materials, a fibrous material can be used in addition to a particle shape. It is also possible to use carbon materials obtained by post-processing these carbon materials. The amount of the conductive material to be added is preferably 1 to 80%, more preferably 5 to 50% as a weight ratio to the catalyst-polymer composite.

  As a method for producing a catalyst-polymer composite having a three-dimensional network microporous structure, a method using a wet coagulation method, a stretching method, or an extraction method is preferable. In the wet coagulation method, after the catalyst-polymer solution composition is applied, the coating layer is brought into contact with a coagulation solvent for the polymer, and coagulation precipitation of the catalyst-polymer solution composition and solvent extraction are simultaneously performed. In the stretching method, a catalyst-polymer composite sheet is prepared in advance and stretched to make it microporous. The extraction method is a method in which a catalyst-polymer composite sheet containing a compound to be a pore-forming agent is prepared in advance, and the sheet is immersed in a solvent to extract the pore-forming agent, thereby making the pore-forming agent fine.

  This catalyst-polymer solution composition is obtained by uniformly dispersing the catalyst-supporting carbon in the polymer solution. The above-mentioned catalyst-supporting carbon and polymer are preferably used. The solvent for dissolving the polymer should be appropriately determined according to the polymer used, and is not particularly limited. It is important that the polymer solution disperse the catalyst-supporting carbon well. If the dispersion state is poor, the catalyst-carrying carbon and the polymer cannot form a complex during wet coagulation, and only the polymer will have a three-dimensional network microporous structure, and the present invention The embodiment will be different from the feature.

  With respect to the coating method, a coating method is selected according to the viscosity and solid content of the catalyst-polymer solution composition, and it is not particularly limited, but a knife coater, a bar coater, a spray, a dip coater, a spin coater, A general coating method such as a roll coater, a die coater, and a curtain coater is used.

  On the other hand, the coagulation solvent for wet coagulation of the polymer is not particularly limited, but a solvent which is easy to coagulate and precipitate the polymer to be used and which is compatible with the solvent of the polymer solution is preferable. The method of contact with the coagulation solvent in which wet coagulation is actually performed is also not particularly limited, but the base material is immersed in the coagulation solvent, only the coating layer is brought into contact with the liquid surface of the coagulation solvent, There is no particular limitation such as showering or spraying the coating layer.

  The substrate on which the catalyst-polymer solution composition is applied can be applied to any of the electrode substrate and the solid electrolyte, and thereafter can be subjected to wet coagulation. In addition, after applying to a substrate other than the electrode substrate and the solid electrolyte, and then performing wet solidification to produce a three-dimensional network microporous structure, the catalyst layer is transferred or sandwiched to the electrode substrate or the solid electrolyte. You may let it. As the substrate in this case, a polytetrafluoroethylene (PTFE) sheet, a glass plate or a metal plate whose surface is treated with a fluorine or silicone release agent, or the like is used.

  As the electrode substrate on which the catalyst-polymer composite is formed, an electrode substrate generally used for a fuel cell is used without any particular limitation. For example, a porous conductive sheet having a conductive inorganic material as a main constituent material may be mentioned. Examples of the conductive inorganic material include fired bodies from polyacrylonitrile, fired bodies from pitch, and carbon materials such as graphite and expanded graphite. , Stainless steel, molybdenum, titanium and the like. The form of the conductive inorganic material is not particularly limited, such as fibrous or particulate. Of these, carbon paper TGP series manufactured by Toray, SO series, carbon cloth manufactured by E-TEK, etc. are preferably used.

  It is also a preferable embodiment that the electrode catalyst layer of the present invention is formed into a membrane-electrode assembly (MEA: Membrane Electrode Assembly) by combining the above-mentioned electrode substrate and the polymer solid electrolyte membrane.

  The polymer solid electrolyte membrane is not particularly limited as long as it is an electrolyte used in a normal fuel cell, but a proton exchange membrane is preferably used for exhibiting the fuel cell performance of the present invention. The proton exchange group of the proton exchange membrane is not particularly limited, such as a sulfonic acid group, a carboxylic acid group, and a phosphoric acid group.

  This proton exchange membrane is roughly classified into a hydrocarbon system such as a styrene-divinylbenzene copolymer and a perfluoro system of a copolymer composed of a fluoroalkyl ether side chain and a fluoroalkyl main chain. It should be appropriately selected according to the intended use and environment. Further, a partial fluorine film partially substituted with fluorine atoms is also preferably used. Examples of perfluoro membranes include DuPont's Nafion, Asahi Kasei's Aciplex, and Asahi Glass's Flemion.Examples of partial fluorine membranes include polymers of trifluorostyrene sulfonic acid and those obtained by introducing sulfonic acid groups to polyvinylidene fluoride. .

  The proton exchange membrane is not only one kind of polymer, but also a copolymer or blend polymer of two or more kinds of polymers, a composite membrane in which two or more kinds of membranes are bonded together, or a membrane in which the proton exchange membrane is reinforced with a nonwoven fabric or a porous film. Etc. can also be used.

  The anionic group-containing polymer constituting the polymer solid electrolyte membrane of the present invention is not particularly limited, and a polymer having an anionic group such as a sulfonic acid group, a phosphonic acid group, a phosphoric acid group, and a carboxylic acid group. Is used. For example, a sulfonyl group (-SO2-), an oxy group (-O-), a thio group (-S-), a carbonyl group (-CO-), an ester group (-COO-), an amide group (- Polymers containing NRCO-), imide groups and the like are preferably used. Specifically, polyphenylene sulfide sulfone, polyphenylene sulfide, polyphosphazene, polyimide, and polysulfone (PSF), polyphenylene oxide (PPO), polyether ketone (PEK), polyether ether ketone (PEEK), polybenzimidazole (PBI) ), Heat-resistant and oxidation-resistant polymers such as polyethersulfone (PES) are preferably used. Among them, polyphenylene sulfide sulfone, polyphenylene sulfide, polyphosphazene, polyimide, polybenzimidazole, and polysulfone are preferably used because water coordinates to the main chain. Further, two or more of these polymers can be used in combination.

  The polymer constituting the polymer solid electrolyte membrane of the present invention is also preferably one in which the polymer molecular chains are constrained, and the method is not particularly limited, and may be a method by cross-linking or internal penetration polymer network or the like. Is mentioned. The stronger the constraint of the molecular chain, the more the uptake of free water can be suppressed, but the ion conductivity may be reduced. For this reason, the degree of restriction of the molecular chain needs to be appropriately selected according to the required characteristics. Specific methods for constraining the molecular chains include introducing a crosslinkable functional group into the polymer and causing the molecules to crosslink with each other, or using another crosslinkable polymer to form an internal penetrating polymer network (IPN) structure. is there. Other methods of forming an IPN structure using a crosslinkable polymer include a method of forming a three-dimensional cross-linked body of carbon such as divinylbenzene and diacrylate, and a method of forming a three-dimensional cross-linked body using elements other than carbon such as siloxane as cross-linking points. Body and the like.

  When the polymer solid electrolyte membrane of the present invention has an IPN structure, in the method for producing a three-dimensional crosslinked body having an element other than carbon as a crosslinking point, a crosslinked body is produced using an alkoxide compound composed of an element other than carbon. Is also a preferred embodiment. The alkoxide compound is preferably hydrolyzable, and when a solution containing the hydrolyzable compound and / or a hydrolyzate thereof and a polymer having an anionic group is used, an internal penetrating polymer network structure is formed. This is preferable because it is easy to perform. In particular, it is also a preferable manufacturing method to manufacture an IPN structure using a condensation reaction of an alkoxide compound. When the fine particles to be mixed have a surface functional group, the crosslinked product and the fine particles have a chemical bond and are integrated by the condensation reaction of the alkoxide compound, and the effect of reducing the MCO and improving the proton conductivity increases. It will be.

  In the present invention, the solid polymer electrolyte membrane can be formed by filling a porous film with an electrolyte polymer, and the solid polymer electrolyte thus obtained is preferable because deformation due to swelling is suppressed. . The porous film is not particularly limited, such as a three-dimensional mesh microporous hole opened in a random direction and a through hole opened in a film thickness direction.

  As a preferable production method of the porous film used for the polymer solid electrolyte of the present invention, for example, a processing method such as photolithography, laser perforation, needle punching, wet coagulation or a method of forming a microporous film by stretching and extraction is applied. can do.

  The method for filling the porous film with the proton conductor is not particularly limited. For example, by filling or immersing a polymer having an anionic group in a solution as a solution onto a porous film, it becomes possible to fill the void. It is also preferable to use ultrasonic waves or to reduce the pressure in order to facilitate the filling into the voids, and it is preferable to use them at the time of coating or immersion because the filling efficiency is further improved. Further, a method may be employed in which a monomer, which is a precursor of a polymer having an anionic group, is filled in the gap and then polymerized in the gap, or plasma polymerization is performed by vaporizing the monomer.

  The method for producing the membrane-electrode composite is not particularly limited. When an electrode catalyst layer made of a catalyst-polymer composite is formed on an electrode substrate, the electrode substrate with a catalyst layer is bonded to an electrolyte such as a proton exchange membrane. Alternatively, it should be appropriately determined according to the characteristics of the electrochemical device. When the electrode catalyst layer comprising the catalyst-polymer composite is formed on a solid electrolyte such as a proton exchange membrane, the solid electrolyte with the catalyst layer is bonded to the electrode substrate. It should be appropriately determined according to the characteristics of the layer or the electrochemical device.

  Further, the electrode catalyst layer of the present invention, and the electrode comprising the electrode catalyst layer and the electrode base material, or the membrane-electrode composite (MEA) comprising the electrode catalyst layer, the electrode base material and the polymer solid electrolyte membrane are prepared by direct methanol It can be applied to the shape fuel cell.

  Further, the use of the fuel cell using the electrode catalyst layer of the present invention can be considered without any particular limitation, and a power supply source of a mobile object or a portable device, which is a useful application in a polymer electrolyte fuel cell, can be used. It is preferred. In particular, mobile devices such as mobile phones, notebook computers, PDAs, digital cameras, and video cameras are preferable, and automobiles such as passenger cars, buses, trucks, ships, and railways are also preferable mobile objects.

  Hereinafter, the details of the present invention will be further described in accordance with each procedure using examples.

Example 1
(1) Production of cathode electrode Preparation of Cathode Catalyst-Polymer Composition
A catalyst-supporting carbon (catalyst; Pt, carbon; VulcanXC-72R, platinum supported amount: 50% by weight) and isopropanol were added to a DuPont Nafion solution, and the mixture was stirred well to prepare a catalyst-polymer composition.

B. Coating of Cathode Catalyst-Polymer Composition and Wet Solidification The above-mentioned (1) was applied to an electrode substrate (carbon paper TGP-H-060 manufactured by Toray) which had been subjected to a water-repellent treatment (impregnated with 20% by weight of PTFE and sintered). The catalyst-polymer composition prepared in the above was applied. Immediately after the application, this was impregnated with butyl acetate together with the substrate, and then dried to prepare a cathode electrode made of a catalyst-polymer composite on an electrode substrate by a wet coagulation method.
(2) Preparation of anode electrode Preparation of Anode Catalyst-Polymer Composition
To a DuPont Nafion solution, a catalyst-supporting carbon (catalyst; Pt-Ru (1: 1), carbon; Cabot's VulcanXC-72R, platinum loading; 30% by weight) and isopropanol were added, and the mixture was stirred well and the catalyst- A polymer composition was prepared.

B. Anode catalyst-coating and wet solidification of polymer composition (1) B. In the same manner as in the above, an anode electrode was produced.
(3) Preparation and evaluation of membrane-electrode composite (MEA) Production of Membrane-Electrode Composite (MEA) An MEA was produced by a hot press method using the electrodes produced in the above (1) and (2) and an electrolyte membrane (Nafion 117 manufactured by DuPont). The electrolyte membrane was swollen in advance, sandwiched between electrodes, and pressed at 90 ° C. for 1 hour at 50 kgf / cm 2.

B. Evaluation of MEA Using the fuel cell evaluation cell, the MEA produced in the above section A was subjected to fuel cell performance evaluation (current-voltage (IV) measurement). The cell temperature was 20 ° C., a 1M aqueous methanol solution was passed through the anode, and air was flowed through the cathode. At a current density of 40 mA / cm ² , a reaction resistance (an arc as an AC component in a Nyquist plot) was determined by an AC impedance method at a current amplitude of 4 mA / cm ² and a measurement frequency of 1 MHz to 100 mHz. The results are shown in Tables 1 and 2.

C. Evaluation of Electrode Catalyst Layer A predetermined area of the electrode catalyst layer was scraped off from each of the anode electrode catalyst layer and the cathode electrode catalyst layer of the MEA prepared in the above section A, and the electrolyte polymer was obtained using N-methyl-2-pyrrolidone (NMP). (Nafion) was dissolved, the amount of catalytic metal was determined from the solid content after filtration by a fluorescent X-ray method, and the amount of carbon was determined by subtracting the amount of catalytic metal from the solid content. Furthermore, the NMP solution in which the electrolyte polymer was dissolved was dried to obtain the amount of the electrolyte polymer. The results are shown in Tables 1 and 2.

  When the catalyst layer was observed by SEM, the catalyst-polymer composite had a three-dimensional network microporous structure, the microporous diameter was 0.5 μm on average, and the porosity was 50%. The thickness of the anode electrode catalyst layer was 50 μm, and the thickness of the cathode electrode catalyst layer was 100 μm. FIG. 1 is an SEM observation photograph of the cross section.

Comparative Example 1
(1) Production of cathode electrode Preparation of Cathode Catalyst-Polymer Composition A cathode electrode catalyst-polymer composition was prepared in the same manner as in Example 1 (1) A.

B. Coating of Cathode Catalyst-Polymer Composition In the same manner as in Example 1 (1) B, the catalyst-polymer composition prepared in (1) was applied to the electrode substrate which had been previously subjected to the water-repellent treatment, and this was immediately applied. The resultant was dried with a heated air dryer to produce a cathode electrode provided with an electrode catalyst layer on an electrode substrate.
(2) Preparation of anode electrode Preparation of Anode Catalyst-Polymer Composition An anode electrode catalyst-polymer composition was prepared in the same manner as in Example 1 (2) A.

B. Application of anode catalyst-polymer composition An anode electrode was produced in the same manner as in Comparative Example 1 (1) B.
(3) Preparation and evaluation of membrane-electrode composite (MEA) Production of Membrane-Electrode Composite (MEA) Using the electrodes produced in Comparative Examples 1 (1) and (2), an MEA was produced in the same manner as in Example 1 (3) A.

B. Evaluation of MEA The MEA produced in Comparative Example 1 (3) A was evaluated in the same manner as in Example 1 (3) B. The results are shown in Tables 1 and 2.

C. Evaluation of Electrode Catalyst Layer The anode electrode catalyst layer and the cathode electrode catalyst layer of the MEA produced in Comparative Example 1 (3) A were evaluated in the same manner as in Example 1 (3) C. The results are shown in Tables 1 and 2.

  FIG. 2 shows an SEM observation of this catalyst layer. The catalyst-polymer composite did not have a three-dimensional network microporous structure, and no microporosity was observed.

Example 2
(1) Production of cathode electrode A cathode electrode was produced in the same manner as in Comparative Example 1 (1).
(2) Preparation of anode electrode An anode electrode was prepared in the same manner as in Example 1 (2).
(3) Production and Evaluation of Membrane-Electrode Composite (MEA) An MEA was produced and evaluated in the same manner as in Example 1 (3). The results are shown in Tables 1 and 2.

Example 3
(1) Production of cathode electrode A cathode electrode was produced in the same manner as in Example 1 (1).
(2) Preparation of anode electrode An anode electrode was prepared in the same manner as in Comparative Example 1 (2).
(3) Production and Evaluation of Membrane-Electrode Composite (MEA) An MEA was produced and evaluated in the same manner as in Example 1 (3). The results are shown in Tables 1 and 2.

Example 4
(1) Production of cathode electrode A cathode electrode was produced in the same manner as in Comparative Example 1 (1).
(2) Preparation of anode electrode The anode electrode was prepared in the same manner as in Example 1 (2) except that sulfonated polyetheretherketone was used as the electrolyte polymer contained in the electrode catalyst layer and dioxane was used as the solvent for wet coagulation. Was prepared.
(3) Production and Evaluation of Membrane-Electrode Composite (MEA) An MEA was produced and evaluated in the same manner as in Example 1 (3). The results are shown in Tables 1 and 2.

Example 5
(1) Preparation of cathode electrode A cathode electrode was prepared in the same manner as in Example 1 (1) except that carbon cloth (manufactured by ETEK) was used as the electrode base material.
(2) Preparation of anode electrode An anode electrode was prepared in the same manner as in Example 1 (2) except that carbon cloth (manufactured by ETEK) was used as the electrode substrate.
(3) Production and Evaluation of Membrane-Electrode Composite (MEA) An MEA was produced and evaluated in the same manner as in Example 1 (3). The results are shown in Tables 1 and 2.

Example 6
(1) Production of cathode electrode A cathode electrode was produced in the same manner as in Example 1 (1).
(2) Preparation of anode electrode An anode electrode was prepared in the same manner as in Example 1 (2).
(3) Preparation and Evaluation of Membrane-Electrode Composite (MEA) Example 1 (3) except that a polymer obtained by converting sulfonated polyphenylene oxide into an IPN (inner penetration polymer network) with a silane coupling agent was used for the electrolyte membrane. In the same manner as in (1), MEA was prepared and evaluated. The results are shown in Tables 1 and 2.
Example 7
(1) Preparation of cathode electrode A cathode electrode was prepared in the same manner as in Example 1 (1) except that carbon cloth (manufactured by ETEK) was used as an electrode substrate.
(2) Preparation of anode electrode An anode electrode was prepared in the same manner as in Example 1 (2) except that polyvinylidene fluoride (PVdF) was used as a polymer contained in the electrode catalyst layer and methanol was used as a solvent for wet coagulation. Produced.
(3) Preparation of electrolyte membrane An electrolyte membrane was prepared in the following manner.

(Synthesis of fluorenyl polyether ether ketone)
35 g of potassium carbonate,
14 g of hydroquinone,
39 g of 4,4 ′-(9H-fluorene-9-ylidene) bisphenol,
And 48 g of 4,4'-difluorobenzophenone
Was used to perform polymerization at 170 ° C. in N-methylpyrrolidone (NMP).

  After the polymerization, the polymer was washed with water and purified by reprecipitation with a large amount of methanol to obtain fluorenyl polyether ether ketone (hereinafter abbreviated as FK) quantitatively. Its weight average molecular weight was 110,000.

(Sulfonation of FK)
After dissolving 11 g of the polymer (FK) obtained above in chloroform at room temperature under N2 atmosphere, 16 mL of chlorosulfonic acid was slowly added dropwise with vigorous stirring, and reacted for 10 minutes. The white precipitate was separated by filtration, pulverized, sufficiently washed with water, and dried to obtain a desired sulfonated FK (hereinafter abbreviated as SFK).

  The obtained SFK had a sulfonic acid group density of 2.5 mmol / g.

(Film formation)
The SFK obtained above was cast and applied as a N, N-dimethylacetamide solution on a glass substrate, dried at 100 ° C. for 3 hours, and the solvent was removed to form a film.

The obtained film had a thickness of 220 μm and was a colorless and transparent flexible film.
(4) Preparation and Evaluation of Membrane-Electrode Composite (MEA) The MEA was prepared in the same manner as in Example 1 (3) except that the SFK prepared in the above (3) was used for the electrolyte membrane and the hot pressing time was 10 minutes. Was prepared and evaluated. The results are shown in Tables 1 and 2.
Example 8
(1) Production of cathode electrode A cathode electrode was produced in the same manner as in Example 1 (1).
(2) Preparation of anode electrode Except that carbon cloth (manufactured by ETEK) was used as the electrode base material, polysulfone (PSf) was used as the polymer contained in the electrode catalyst layer, and methanol was used as the solvent for wet coagulation. An anode electrode was produced in the same manner as in Example 1 (2).
(3) Preparation and Evaluation of Membrane-Electrode Composite (MEA) An MEA was prepared and evaluated in the same manner as in Example 1 (3). The results are shown in Tables 1 and 2.
Example 9
(1) Production of cathode electrode A cathode electrode was produced in the same manner as in Example 1 (1).
(2) Preparation of anode electrode An anode electrode was prepared in the same manner as in Example 1 (2), except that the catalyst-polymer composition was applied to an electrolyte membrane and was wet-solidified.
(3) Preparation and Evaluation of Membrane-Electrode Composite (MEA) Example 1 (3) was repeated except that an electrode substrate (TGP-H-060) which had been subjected to a water-repellent treatment was placed on the anode applied to the electrolyte membrane. In the same manner as in (1), MEA was prepared and evaluated. The results are shown in Tables 1 and 2.
Example 10
(1) Preparation of cathode electrode The cathode electrode was prepared in the same manner as in Example 1 (1) except that polyvinylidene fluoride (PVdF) was used as the electrolyte polymer contained in the electrode catalyst layer and methanol was used as the solvent for wet coagulation. Was prepared.
(2) Preparation of Anode Electrode Same as Example 1 (2) except that SFK prepared in Example 7 (3) was used as the electrolyte polymer contained in the electrode catalyst layer and water was used as a solvent for wet coagulation. Next, an anode electrode was produced.
(3) Production and Evaluation of Membrane-Electrode Composite (MEA) An MEA was produced and evaluated in the same manner as in Example 1 (3). The results are shown in Tables 1 and 2.
Example 11
(1) Production of cathode electrode A cathode electrode was produced in the same manner as in Example 1 (1).
(2) Preparation of Anode Electrode An anode electrode was prepared in the same manner as in Example 1 (2) except that the polymer contained in the electrode catalyst layer was composed of 50% by weight of PVdF and 50% by weight of Nafion.
(3) Production and Evaluation of Membrane-Electrode Composite (MEA) An MEA was produced and evaluated in the same manner as in Example 1 (3). The results are shown in Tables 1 and 2.
Example 12
(1) Production of cathode electrode A cathode electrode was produced in the same manner as in Example 1 (1).
(2) Preparation of anode electrode Example 1 was repeated except that the polymer contained in the electrode catalyst layer was composed of 70% by weight of PVdF and 30% by weight of polyphenylene sulfide (PPS), and methanol was used as a solvent for wet coagulation. An anode electrode was produced in the same manner as in (2).
(3) Production and Evaluation of Membrane-Electrode Composite (MEA) An MEA was produced and evaluated in the same manner as in Example 1 (3). The results are shown in Tables 1 and 2.

SEM photograph of the surface of the electrode catalyst layer obtained in Example 1 SEM photograph of the surface of the electrode catalyst layer obtained in Comparative Example 1.

Claims (20)

An electrode catalyst layer for a polymer electrolyte fuel cell using a liquid fuel, wherein a catalyst-polymer composite containing at least catalyst-supported carbon particles and one or more polymers has a three-dimensional network-like microporous structure. An electrode catalyst layer comprising: The electrode catalyst layer according to claim 1, wherein the thickness of the electrode catalyst layer having a three-dimensional network microporous structure is 10 µm or more and 200 µm or less. 3. The electrode catalyst layer according to claim 1, wherein the weight of the catalyst metal contained in the electrode catalyst layer having a three-dimensional network microporous structure is 1 mg / cm ² or more and 7 mg / cm ² or less. The electrode according to any one of claims 1 to 3, wherein the weight of carbon contained in the electrode catalyst layer having a three-dimensional network microporous structure is 0.2 mg / cm ² or more and 4 mg / cm ² or less. Catalyst layer. The electrode according to any one of claims 1 to 4, wherein the weight of the polymer contained in the electrode catalyst layer having a three-dimensional network microporous structure is 0.2 mg / cm ² or more and 5 mg / cm ² or less. Catalyst layer. The electrode catalyst layer according to any one of claims 1 to 5, wherein the inner diameter of the micropores in the three-dimensional network microporous structure is 0.05 to 5 µm. The electrode catalyst layer according to any one of claims 1 to 6, wherein the porosity of the three-dimensional network microporous structure is 10 to 95%. The electrode catalyst layer according to any one of claims 1 to 7, wherein the polymer contained in the catalyst-polymer composite is at least one polymer having a proton exchange group. 9. The electrode catalyst layer according to claim 1, wherein the polymer contained in the catalyst-polymer composite is at least one polymer containing a fluorine atom. The electrode catalyst layer according to any one of claims 1 to 9, wherein the catalyst-supporting carbon contained in the catalyst-polymer composite contains at least one of platinum, gold, palladium, ruthenium, and iridium. . 11. The electrode catalyst layer according to claim 1, wherein the electrode having a three-dimensional network microporous structure is an anode. 12. The electrode catalyst layer according to claim 1, wherein the electrode having a three-dimensional network microporous structure is a cathode. After a catalyst-polymer solution composition comprising a polymer solution containing uniformly dispersed catalyst particles is applied to a substrate, this coating layer is brought into contact with a coagulation solvent for the polymer to solidify the catalyst-polymer solution composition and the solvent. A method for producing an electrode catalyst layer, which comprises simultaneously performing extraction (hereinafter, referred to as wet coagulation method). The method for producing an electrode catalyst layer according to claim 13, wherein wet coagulation is performed after applying the catalyst-polymer solution composition to the electrode substrate. The method for producing an electrode catalyst layer according to claim 13 or 14, wherein a catalyst layer is formed by peeling the composite from the substrate after the catalyst-polymer composite is formed on the substrate. The catalyst-polymer composite comprising at least the catalyst-supporting carbon particles and at least one polymer has a three-dimensionally network-like microporous structure. An electrode comprising the electrode catalyst layer and an electrode substrate according to any one of the above. The catalyst-polymer composite comprising at least the catalyst-supporting carbon particles and one or more polymers has a three-dimensionally network-like microporous structure. A membrane-electrode composite comprising an electrode catalyst layer, an electrode substrate, and a solid polymer electrolyte membrane. A polymer electrolyte fuel cell comprising a liquid fuel and comprising the electrode according to claim 16. A polymer electrolyte fuel cell comprising the membrane-electrode assembly according to claim 17 using a liquid fuel. A portable device or a mobile object driven by the fuel cell according to claim 18.