JP2006202598A - Fuel cell electrode and fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell electrode excellent in durability against fuel and industrial productivity, and to provide a fuel cell using the same. <P>SOLUTION: The fuel cell electrode comprises a catalyst layer composed of metal particles and/or metal carrying particles and a binder, and the binder contains alkylcellulose having an ionic group. The fuel cell using the fuel cell electrode is provided. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an electrode for a fuel cell which is excellent in durability against fuel and excellent in industrial productivity, and a fuel cell using the electrode.

  A fuel cell is a power generation device with low emissions, high energy efficiency, and low burden on the environment. For this reason, it is in the spotlight again in recent years to the protection of the global environment. Compared to conventional large-scale power generation facilities, this is a power generation device expected in the future as a relatively small-scale distributed power generation facility, and as a power generation device for mobile objects such as automobiles and ships. It is also attracting attention as a power source for small mobile devices and portable devices, as an alternative to secondary batteries such as nickel metal hydride batteries and lithium ion batteries, as a charger for secondary batteries, or in combination with secondary batteries. (Hybrid) is expected to be installed in mobile devices such as mobile phones and personal computers.

  In polymer electrolyte fuel cells, in addition to conventional polymer electrolyte fuel cells using hydrogen gas as fuel (hereinafter sometimes referred to as PEFC), fuel such as methanol is directly used. Direct fuel cells to be supplied are also attracting attention. The direct fuel cell has a lower output than the conventional PEFC, but the fuel is liquid and does not use a reformer, so the energy density is high and the usage time of the portable device per filling is long. There is an advantage.

  In a polymer electrolyte fuel cell, an anode electrode and a cathode electrode in which a reaction responsible for power generation occurs, and a polymer electrolyte membrane serving as a proton conductor between the anode and the cathode constitute a membrane electrode assembly (MEA). A cell in which the MEA is sandwiched between separators is configured as a unit. Here, the electrode is composed of an electrode base material (also referred to as a gas diffusion electrode or a current collector) that promotes gas diffusion and collects (supply) electricity, and a catalyst layer that actually becomes an electrochemical reaction field. Yes. For example, in the anode electrode of PEFC, a fuel such as hydrogen gas reacts in the catalyst layer of the anode electrode to generate protons and electrons, and the electrons are conducted to the electrode substrate, and the protons are conducted to the polymer electrolyte membrane. For this reason, the anode electrode is required to have good gas diffusivity, electron conductivity, and proton conductivity. On the other hand, in the cathode electrode, an oxidizing gas such as oxygen or air is reacted with protons conducted from the polymer electrolyte membrane and electrons conducted from the electrode base material in the catalyst layer of the cathode electrode to produce water. For this reason, in the cathode electrode, it is necessary to efficiently discharge the generated water in addition to gas diffusibility, electron conductivity, and proton conductivity.

  Among PEFCs, a direct fuel cell using methanol or the like as a fuel requires performance different from that of a conventional PEFC using hydrogen gas as a fuel. That is, in a direct type fuel cell, a fuel such as a methanol aqueous solution reacts with the catalyst layer of the anode electrode to produce protons, electrons, and carbon dioxide at the anode electrode, and the electrons are conducted to the electrode substrate, and the protons are polymer electrolyte. The carbon dioxide passes through the electrode substrate and is released out of the system. For this reason, in addition to the required characteristics of the anode electrode of the conventional PEFC, fuel permeability such as aqueous methanol solution and carbon dioxide emission are also required. Further, in the cathode electrode of the direct type fuel cell, in addition to the reaction similar to that of the conventional PEFC, fuel such as methanol that has permeated through the electrolyte membrane and oxidizing gas such as oxygen or air are mixed with carbon dioxide in the catalyst layer of the cathode electrode. Reactions that produce water also occur. For this reason, since generated water becomes more than conventional PEFC, it is necessary to discharge water more efficiently.

  Conventionally, a perfluoro proton conductive polymer represented by “Nafion” (R) (manufactured by DuPont) has been used as a binder for catalyst particles (Patent Document 1). However, when these perfluoro proton conducting polymers are used, in the direct liquid fuel supply type fuel cell using methanol aqueous solution as the fuel, if the concentration of methanol in the fuel becomes high, the perfluoro proton conducting property is increased. There was a problem that the polymer swelled excessively, causing the catalyst to fall off or flow out, adversely affecting battery output and durability. Furthermore, perfluoro proton conductive polymers are very expensive in that they use fluorine. The document also describes binders other than perfluoro proton conductive polymers such as alkoxycellulose, but both of them show the durability of the catalyst layer and the battery output (insufficient ion conductivity of the binder). ) Was not compatible.

Patent Documents 2 and 3 describe examples in which an ammonium salt of carboxymethylcellulose resin or methylcellulose is used as a binder for electrodes. The field of electric double layer capacitors uses a non-aqueous electrolyte. It is not described at all that it can be used for a fuel cell. This is because, in the electric double layer capacitor, the required conditions are a binding force with a carbon material such as activated carbon and an adhesive property with a current collector metal, and a fuel containing water (humidity) required for fuel cell applications. This is because the product is different from the durability of the product, the discharge of the product accompanying the power generation (influence on the output), etc., and the ammonium salt of carboxymethyl cellulose resin with poor water resistance is usually applied to the electrode supplied with water or fuel containing moisture It is not generally considered to use it as a binder.
No. 10-507872 specification Japanese Patent Publication No.59-42448 JP-A-11-102844

  In view of the background of the prior art, the present invention intends to provide a fuel cell electrode excellent in durability against fuel and excellent in industrial productivity, and a fuel cell using the electrode.

  The present invention employs the following means in order to solve such problems. That is, the fuel cell electrode of the present invention has a catalyst layer composed of metal particles and / or metal carrier particles and a binder, and contains an alkyl cellulose having an ionic group as the binder. The fuel cell is characterized by using the fuel cell electrode.

  ADVANTAGE OF THE INVENTION According to this invention, it is possible to provide a fuel cell electrode that is excellent in durability against fuel and excellent in industrial productivity. By using such a fuel cell electrode, a fuel cell having high durability and excellent durability. Can be provided. In particular, it is suitable for a fuel cell of a type that supplies liquid fuel containing water to the anode.

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

  The fuel cell electrode of the present invention has a catalyst layer composed of metal particles and / or metal support particles and a binder, and needs to contain an alkyl cellulose having an ionic group as the binder. It is.

  The inventors unexpectedly have superior durability to fuels of alkyl cellulose having an ionic group as an inexpensive material to replace the expensive perfluoro proton conductive polymer conventionally used as a binder. As a result, the present inventors have found that a high output density can be obtained when combined with an electrolyte membrane described later without adversely affecting the output as a fuel cell. In addition, the catalyst paste containing the binder precursor (alkyl cellulose salt having an ionic group) has a thickening effect only by containing a small amount of an alkyl cellulose salt having an ionic group, and is very coatable. In addition, an aqueous paste having excellent storage stability can be obtained.

  That is, the binding property of these particles and the stability of the paste coating liquid can be obtained by adding a small amount of an alkyl cellulose salt having an ionic group to the metal particles and / or metal carrier particles.

As the ionic group of the alkyl cellulose having an ionic group, a sulfonic acid group (—SO ₂ (OH)), a sulfuric acid group (—OSO ₂ (OH)), a sulfonimide group (—SO ₂ NHSO ₂ R (R is Represents an organic group.)), Phosphonic acid group (—PO (OH) ₂ ), phosphoric acid group (—OPO (OH) ₂ ), carboxylic acid group (—CO (OH) 2), hydroxyl group (—OH) and these And the like. Further, two or more kinds of these ionic groups can be contained in the polymer material. The combination is appropriately determined depending on the structure of the polymer. Among these ionic groups, a carboxylic acid group is preferable from the viewpoint of fuel resistance, and examples of the alkyl cellulose having an ionic group include carboxymethyl cellulose and hydroxypropyl cellulose. These Na salts, Mg salts, and Ca salts , Ammonium salts and the like may be included.
The amount of the binder contained in the catalyst layer is not particularly limited, but is preferably in the range of 0.1% to 50% by weight, and more preferably in the range of 1% to 30%. If it is 0.1% or more, the metal particles can be prevented from sliding off, and if it is less than 50%, the permeation of fuel and gas permeability is not inhibited, and the adverse effect on the performance as a fuel cell is small.

  In addition, in the fuel cell electrode of the present invention, a polymer other than the alkyl cellulose having the ionic group can be used as a binder. In particular, for the purpose of improving ionic conductivity, a polymer material having an ionic group can be used to the extent that the durability of the catalyst is not impaired. From the viewpoint of durability and cost, the content of the alkyl cellulose having an ionic group in the binder is preferably 30% or more and 100% or less, and more preferably 50% or more.

  As specific examples of the polymer material having an ionic group, a polymer electrolyte material having an aromatic ring in the main chain is preferable from the viewpoints of ionic conductivity, fuel durability, and the like. Group-containing polyetherketone, ionic group-containing polyetheretherketone, ionic group-containing polyethersulfone, ionic group-containing polyetherethersulfone, ionic group-containing polyetherphosphine oxide, ionic group-containing polyetheretherphosphine oxide , Ionic group-containing polyphenylene sulfide, ionic group-containing polyamide, ionic group-containing polyimide, ionic group-containing polyetherimide, ionic group-containing polyimidazole, ionic group-containing polyoxazole, ionic group-containing polyphenylene, Ionic group Aromatic hydrocarbon-based polymer and the like. Depending on the type of fuel and the fuel concentration, an ionic group-containing polyolefin or an ionic group-containing perfluoropolymer can be used in combination.

  Further, in order to further improve the fuel durability, those not containing an ionic group of the polymer group can be used in combination. Further, a polymer containing a fluorine atom such as polyvinyl fluoride, polyvinylidene fluoride, polyhexafluoropropylene, polytetrafluoroethylene, polyperfluoroalkyl vinyl ether, or the like can be added. Furthermore, if necessary, a crosslinked structure may be introduced using radiation, metal alkoxide, or the like, or a network of crosslinked bodies may be formed with a polyfunctional monomer or the like.

  In addition, water-soluble polymers such as polyvinyl alcohol and polyvinyl pyrrolidone can be used from the viewpoint of work environment, productivity, cost, etc., and water resistance is increased by crosslinking with metal coupling agents, epoxy resins, urethane resins, formaldehyde, etc. Also good.

  As the metal particles and / or metal carrier particles, generally known particles can be used. For example, noble metals such as platinum, palladium, ruthenium, rhodium, iridium and gold are preferably used as the metal particles. One of these may be used alone, or two or more of them, such as alloys and mixtures, may be used in combination.

In addition, the use of the metal-supported particles may improve the utilization efficiency of the metal catalyst, and may contribute to improvement of battery performance and cost reduction. As the support, a carbon material, SiO ₂ , TiO ₂ , ZrO ₂ , RuO ₂ , zeolite, or the like can be used, but a carbon material from the viewpoint of electron conductivity is preferable.

  Examples of the carbon material include amorphous and crystalline carbon materials. For example, carbon black such as channel black, thermal black, furnace black, and acetylene black is preferably used because of its electron conductivity and specific surface area. Furnace Black includes “Vulcan XC-72” (R), “Vulcan P” (R), “Black Pearls 880” (R), “Black Pearls 1100” (R), “Black Pearls 1300” R), "Black Pearls 2000" (R), "Legal 400" (R), "Ketjen Black" EC (R), EC600JD, Mitsubishi Chemical Corporation # 3150, # 3250, etc. Examples of acetylene black include “DENKA BLACK” (R) manufactured by Denki Kagaku Kogyo Co., Ltd. In addition to carbon black, artificial graphite or carbon obtained from organic compounds such as natural graphite, pitch, coke, polyacrylonitrile, phenol resin, and furan resin can also be used. As the form of these carbon materials, in addition to irregular particles, fibers, scales, tubes, cones, and megaphones can also be used. Moreover, you may use what post-processed these carbon materials. These may be used as the metal carrier, or may be used alone as an electron conductivity improver for the catalyst layer.

  As a method for producing the fuel cell electrode of the present invention, a generally known method can be applied. For example, after dissolving the binder in a solvent, add metal particles and / or metal support particles, and knead and knead to prepare a catalyst paste, which is applied to the electrode substrate or electrolyte membrane, dried, and if necessary Can be produced by pressing.

  The present invention includes an alkyl cellulose having an ionic group, but the catalyst paste is preferably used in the form of a metal salt of an alkyl cellulose having an ionic group or an ammonium salt. These can be proton-substituted with an acid such as hydrochloric acid or sulfuric acid after coating. Furthermore, ammonium salts are particularly preferable from the viewpoint of productivity because they can be removed by heating.

  Although there is no restriction | limiting in particular as a solvent which can be used for melt | dissolution of a binder, Water is preferable when using the derivative | guide_body of the alkyl cellulose which has an ionic group. Further, depending on the polymer used in combination, it can be used in a mixed system of water and an organic solvent or an emulsion of water and an organic solvent. Examples of organic solvents include, for example, N, N-dimethylacetamide, N, N-dimethylformamide, N-methyl-2-pyrrolidone, dimethyl sulfoxide, sulfolane, 1,3-dimethyl-2-imidazolidinone, hexamethylphosphone. Aprotic polar solvents such as triamide, ester solvents such as γ-butyrolactone and butyl acetate, carbonate solvents such as ethylene carbonate and propylene carbonate, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, propylene glycol monomethyl ether, propylene Alkylene glycol monoalkyl ethers such as glycol monoethyl ether, alcohol solvents such as isopropanol, n-propanol, ethanol, methanol, , And the like aromatic solvents xylene.

  As a method for applying the catalyst paste, generally known methods can be used, and techniques such as spray coating, brush coating, dip coating, slit die coating, curtain coating, flow coating, spin coating, and screen printing can be applied.

  In addition, when the fuel is a liquid or gas, the fuel cell electrode of the present invention preferably has a structure through which the liquid or gas easily permeates, and promotes the discharge of by-products due to the electrode reaction. A structure is preferred. An example thereof is a method of forming a catalyst layer on an electrode substrate.

  Moreover, as an electrode base material, an electrical resistance is low and what can collect or supply electric power can be used. Further, when the catalyst layer is used also as a current collector, it is not necessary to use an electrode substrate. Examples of the constituent material of the electrode base material include carbonaceous and conductive inorganic substances. For example, a fired body from polyacrylonitrile, a fired body from pitch, a carbon material such as graphite and expanded graphite, stainless steel, molybdenum And titanium. These forms are not particularly limited, and are used, for example, in the form of fibers or particles. From the viewpoint of fuel permeability, fibrous conductive materials (conductive fibers) such as carbon fibers are preferable. As an electrode base material using conductive fibers, either a woven fabric or a non-woven fabric structure can be used. For example, carbon paper TGP series, SO series manufactured by Toray Industries, Inc., carbon cloth manufactured by E-TEK, etc. are used. Examples of the woven fabric include plain weave, oblique weaving, satin weaving, crest weaving, binding weaving, and the like. Moreover, as a nonwoven fabric, it does not specifically limit, such as a paper making method, a needle punch method, a spun bond method, a water jet punch method, and a melt blow method. It may also be a knitted fabric. In these fabrics, especially when carbon fibers are used, a plain fabric using flame-resistant spun yarn is carbonized or graphitized woven fabric, and the flame-resistant yarn is carbonized after being processed into a nonwoven fabric by the needle punch method or water jet punch method. Alternatively, a graphitized nonwoven fabric, a flameproof yarn, a carbonized yarn, or a mat nonwoven fabric by a paper making method using a graphitized yarn is preferably used. In particular, it is preferable to use a nonwoven fabric or cloth from the viewpoint of obtaining a thin and strong fabric.

    Examples of the carbon fiber used for the electrode substrate include polyacrylonitrile (PAN) carbon fiber, phenolic carbon fiber, pitch carbon fiber, and rayon carbon fiber.

  In addition, the electrode base material has a water repellent treatment for preventing gas diffusion / permeability deterioration due to water retention, a partial water repellent treatment for forming a water discharge path, a hydrophilic treatment, and a resistance reduction. For example, carbon powder can be added. Further, a conductive intermediate layer containing at least an inorganic conductive substance and a hydrophobic polymer can be provided between the electrode substrate and the catalyst layer. In particular, when the electrode base material is a carbon fiber woven fabric or a nonwoven fabric having a large porosity, by providing the conductive intermediate layer, it is possible to suppress performance degradation due to the catalyst layer soaking into the electrode base material.

  Further, even when a catalyst layer is formed on the electrolyte membrane, there is no particular problem if the electrode base material is used in an overlapping manner on the catalyst layer to improve the current collection efficiency and the diffusibility of fuel and by-products.

  Next, a fuel cell using the fuel cell electrode of the present invention will be described. As the fuel cell, the fuel cell electrode of the present invention is used in at least one of an anode and a cathode, and is used in a membrane electrode assembly (MEA) in a state of sandwiching an electrolyte membrane. Depending on the type of fuel in the fuel cell, the above-mentioned metal species and adhesion amount can be determined experimentally as appropriate, and a pair of electrodes using the same type of metal may be used for the anode and cathode, and the anode and cathode may differ. An electrode using metal may be used. For example, a fuel cell using hydrogen for the anode and air or oxygen for the cathode preferably uses Pt as the metal for both electrodes. In the case of a fuel cell using methanol water for the anode and air or oxygen for the cathode, the anode is PtRu, It is preferable to use Pt for the cathode.

  The electrode for a fuel cell of the present invention is particularly suitable for a liquid fuel supply type fuel cell because of its good durability against liquid fuel containing water and good liquid fuel retention, and is preferably used at least for the anode.

  Next, an electrolyte membrane used as a fuel cell will be described. As the electrolyte membrane, a perfluoro electrolyte membrane represented by “Nafion” (R) (manufactured by DuPont) or a hydrocarbon electrolyte membrane can be used without particular limitation.

In particular, it is preferable to use an electrolyte membrane having a high heat resistance, a high strength, a high tensile elastic modulus, and a low water content in a fuel cell that supplies a liquid fuel such as methanol water to the anode. The reason for this is that in a perfluoro-based electrolyte membrane, when the concentration of methanol increases, the amount of methanol permeating the electrolyte membrane increases (fuel crossover phenomenon), and the performance of the fuel cell is reduced. Further, even in a type in which hydrogen gas is supplied to the anode, the perfluoro-based electrolyte membrane generates hydrofluoric acid due to fluorine ions, which causes deterioration of the fuel cell. Specific examples of the electrolyte membrane to be used include membranes having a glass transition temperature of 130 ° C. or higher, a tensile elastic modulus of 100 MPa or higher, and a moisture content of 40 wt% or lower. Ionic group-containing polyphenylene oxide, ionic group-containing polyether Ketone, ionic group-containing polyether ether ketone, ionic group-containing polyether sulfone, ionic group-containing polyether ether sulfone, ionic group-containing polyether phosphine oxide, ionic group-containing polyether ether phosphine oxide, ionic group Containing polyphenylene sulfide, ionic group containing polyamide, ionic group containing polyimide, ionic group containing polyetherimide, ionic group containing polyimidazole, ionic group containing polyoxazole, ionic group containing polyphenylene, ionic group containing poly Aromatic compounds having ionic groups such as azomethine, ionic group-containing polyimide azomethine, ionic group-containing polystyrene and ionic group-containing polyolefin polymers such as styrene-maleimide cross-linked copolymers and cross-linked products thereof A hydrocarbon polymer is mentioned. In particular, in a fuel cell that supplies a liquid such as an aqueous methanol solution, from the viewpoint of methanol resistance, a component derived from 9,9-bis (4-hydroxyphenyl) fluorene and / or 4,4′-dihydroxytetraphenylmethane is used. A membrane made of a sulfonic acid group-containing aromatic hydrocarbon polymer containing a component derived therefrom is suitable.
These polymer materials can be used alone or in combination of two or more, and can be used as a polymer blend, a polymer alloy, or a laminated film of two or more layers.

In particular, as the ionic group, a polymer material having a sulfonic acid group is most preferable as described above. However, as an example of using a polymer material having a sulfonic acid group, a —SO ₃ M group (M is a metal) -containing material is used. Examples include a method in which a polymer is formed into a film from a solution state, and then heat-treated at a high temperature to remove the solvent and replace with protons to form a film. The metal M may be any salt as long as it can form a salt with sulfonic acid, but Li, Na, K, Rb, Cs, Mg, Ca, Sr, Ba, Ti, V, Mn, Fe, Co, Ni, Cu, Zn, Zr, Mo, W, and the like are preferable. Among these, Li, Na, K, Ca, Sr, and Ba are more preferable, and Li, Na, and K are more preferable. Film formation in the state of these metal salts enables heat treatment at a high temperature, and this method is suitable for a polymer material system that can obtain a high glass transition point and a low water absorption rate.

  The temperature of the heat treatment is preferably 100 to 500 ° C., more preferably 200 to 450 ° C., and further preferably 250 to 400 ° C. in terms of water absorption of the obtained film. A temperature of 100 ° C. or higher is preferable for obtaining a low water absorption rate. On the other hand, by setting the temperature to 500 ° C. or lower, the polymer material can be prevented from being decomposed.

  As the thickness of the electrolyte membrane to be used, a membrane having a thickness of 3 to 2000 μm is usually preferably used. A thickness of more than 3 μm is preferable to obtain a membrane strength that can withstand practical use, and a thickness of less than 2000 μm is preferable in order to reduce membrane resistance, that is, improve power generation performance. A more preferable range of the film thickness is 5 to 1000 μm, and a more preferable range is 10 to 500 μm.

  The film thickness can be controlled by various methods. For example, when forming a film by the solvent casting method, it can be controlled by the solution concentration or the coating thickness on the substrate. For example, when forming the film by the cast polymerization method, it is prepared by the spacer thickness between the plates. You can also.

  In addition, the electrolyte membrane of the present invention can be crosslinked in whole or in part by a means such as radiation irradiation as necessary. By crosslinking, an effect of further suppressing fuel crossover and swelling with respect to fuel can be expected, and mechanical strength is improved, which may be more preferable. Examples of radiation irradiation include electron beam irradiation and γ-ray irradiation. By having a cross-linked structure, it is possible to suppress the spread between polymer chains with respect to moisture and fuel intrusion. Since the amount of water absorption can be kept low and the swelling with respect to the fuel can also be suppressed, the fuel crossover can be reduced as a result. Moreover, since a polymer chain can be restrained, heat resistance and rigidity can be imparted. The crosslinking here may be chemical crosslinking or physical crosslinking. This crosslinked structure can be formed by a generally known method, for example, by copolymerization of a polyfunctional monomer or electron beam irradiation. In particular, crosslinking with a polyfunctional monomer is preferable from an economical viewpoint, and a copolymer of a monofunctional vinyl monomer and a polyfunctional monomer or a polymer having a vinyl group or an allyl group is crosslinked with a polyfunctional monomer. Things. The cross-linked structure here means a state where there is substantially no fluidity to heat or a state where it is substantially insoluble in a solvent.

  In the electrolyte membrane of the present invention, the purpose of improving the mechanical strength, improving the thermal stability of the ionic group, improving the workability, etc. within a range that does not impair the ionic conductivity and the suppression effect of the fuel crossover. Therefore, a filler or inorganic fine particles may be contained, a network or fine particles made of a polymer or metal oxide may be formed, or a film impregnated in a support may be used.

  The fuel of the fuel cell of the present invention includes oxygen, hydrogen and methane, ethane, propane, butanemethanol, isopropyl alcohol, acetone, glycerin, ethylene glycol, formic acid, acetic acid, dimethyl ether, hydroquinone, cyclohexane and the like having 1 to 6 carbon atoms. Examples thereof include organic compounds and mixtures of these with water, and one or a mixture of two or more may be used. In particular, a fuel containing hydrogen and an organic compound having 1 to 6 carbon atoms is preferably used from the viewpoint of power generation efficiency and simplification of the entire battery system, and hydrogen and aqueous methanol are particularly preferable in terms of power generation efficiency.

  In the case of using an aqueous methanol solution, the concentration of methanol is appropriately selected depending on the fuel cell system to be used. A concentration as high as possible is preferable from the viewpoint of long-time driving. For example, an active fuel cell having a system for sending a medium necessary for power generation, such as a liquid feed pump or a blower fan, to a membrane electrode assembly, or an auxiliary machine such as a cooling fan, a fuel dilution system, or a product recovery system has a methanol concentration of 30. It is preferable to inject a fuel of 100% or more by a fuel tank or a fuel cassette and dilute it to about 0.5-29% or send it directly to the membrane electrode assembly. A fuel having a methanol concentration in the range of 10 to 100% is preferred.

  Moreover, the membrane electrode assembly of the present invention may be used in the form of a stack of a plurality of sheets or in a state of being arranged. Further, the fuel cell may be built in the device to be used, or may be used as an external unit. From the viewpoint of maintenance, it is also preferable that the membrane electrode assembly is detachable from the fuel cell.

  As a use of the fuel cell of the present invention, a power supply source of a moving body is preferable. In particular, mobile devices such as mobile phones, personal computers, PDAs, video cameras (camcorders), digital cameras, handy terminals, PFID readers, various displays, home appliances such as electric shavers and vacuum cleaners, electric tools, household power supplies, It is preferably used as a power supply source for mobile bodies such as passenger cars, automobiles such as buses and trucks, motorcycles, bicycles with electric assist, electric carts, electric wheelchairs, ships, and railways. Especially in portable devices, it is used not only for power supply sources, but also for charging secondary batteries installed in portable devices, and also suitable for use as a hybrid power supply source used in combination with secondary batteries and solar cells. it can.

EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, these examples are for understanding this invention better, and this invention is not limited to these.
[Measuring method]
(1) Quantitative determination of metal amount of electrode for fuel cell It was measured using a tabletop fluorescent X-ray analyzer “SEA2120” manufactured by Seiko Instruments Inc.
(2) Fuel immersion evaluation A 60% methanol aqueous solution is heated to 60 ° C, the fuel cell electrode is cut into 4 cm ² squares and immersed for 1 week, and the weight retention is calculated by the following (Equation 1). Good durability. For the drying before and after the test, a value obtained by drying with hot air at 100 ° C. for 8 hours was used.

Weight retention (%) = (W ₂ −W ₀ ) / (W ₁ −W ₀ ) × 100 (Formula 1)
4 cm ² dry weight of substrate only: W ₀ (g)
Dry weight of electrode including base material before test: W ₁ (g)
Dry weight of electrode including substrate after test: W ₂ (g)
(3) Density of sulfonic acid group After stirring and washing in pure water at 25 ° C. for 24 hours or more, vacuum drying was performed at 100 ° C. for 24 hours, and then the purified and dried polymer was measured by elemental analysis. Analysis of C, H, and N was performed by a fully automatic elemental analyzer varioEL, analysis of S was performed by a flask combustion method / barium acetate titration, and analysis of P was performed by a flask combustion method / phosphovanadomolybdic acid colorimetric method. . The sulfonic acid group density per unit gram (mmol / g) was calculated from the composition ratio of each polymer.
(4) Weight average molecular weight The weight average molecular weight of the polymer was measured by GPC. Tosoh's HLC-8022GPC is used as an integrated device of an ultraviolet detector and a differential refractometer, and Tosoh's TSK gel SuperHM-H (inner diameter 6.0 mm, length 15 cm) is used as the GPC column. N-methyl-2 -Measured with a pyrrolidone solvent (N-methyl-2-pyrrolidone solvent containing 10 mmol / L of lithium bromide) at a flow rate of 0.2 mL / min, and the weight average molecular weight was determined in terms of standard polystyrene.
(5) Film thickness It measured using Mitutoyo ID-C112 type | mold set to Mitutoyo granite comparator stand BSG-20.
(6) Tensile modulus Using “Tensilon” manufactured by Orientec Co., Ltd., the tensile modulus of elasticity in the tensile mode was obtained under the conditions of load cell 50N, range 40%, distance between chucks 3 cm, crosshead speed 100 mm / min, n = 5. It was measured.

The test sample was prepared by immersing the polymer formed into a film in water at 25 ° C. for 24 hours, and cutting it into a strip having a length of about 5 cm and a width of 2 mm.
[Reference example]
(1) Synthesis Example of Polymer Material Having Ionic Group 109.1 g of 4,4′-difluorobenzophenone was reacted at 100 ° C. for 10 hours in 150 mL of fuming sulfuric acid (50% SO ₃ ). Thereafter, the mixture was poured little by little into a large amount of water, neutralized with NaOH, and 200 g of sodium chloride was added to precipitate the composite. The resulting precipitate was filtered off and recrystallized with an aqueous ethanol solution to obtain disodium 3,3′-disulfonate-4,4′-difluorobenzophenone. (Yield 181 g, 86% yield).

  6.9 g of potassium carbonate, 14 g of 9,9-bis (4-hydroxyphenyl) fluorene, and 2.6 g of 4,4′-difluorobenzophenone, and the disodium 3,3′-disulfonate-4,4 ′ Polymerization was performed at 190 ° C. in N-methyl-2-pyrrolidone using 12 g of difluorobenzophenone. Purification was performed by reprecipitation with a large amount of water to obtain a polymer (A).

The density of the sulfonic acid group of the proton-substituted membrane of the obtained polymer (A) was 2.4 mmol / g and the weight average molecular weight was 240,000 according to elemental analysis.
(2) Preparation Example of Electrolyte Membrane The polymer (A) was dissolved in N-methyl-2-pyrrolidone to obtain a coating solution having a solid content of 25%. The coating solution was cast on a glass plate and dried at 70 ° C. for 30 minutes and further at 100 ° C. for 1 hour to obtain a 72 μm film. Furthermore, after heat-treating under conditions of heating to 200 to 300 ° C. over 1 hour in a nitrogen gas atmosphere and heating at 300 ° C. for 10 minutes, the mixture was allowed to cool and immersed in 1N hydrochloric acid for 12 hours or more to perform proton substitution. The electrolyte membrane (A) was obtained by immersing it in a large excess of pure water for at least one day and thoroughly washing it. The tensile elastic modulus of the film was 1300 MPa.
(3) Preparation of interfacial resistance reducing paste 10 g of the polymer (A), 60 g of N-methyl-2-pyrrolidone as a plasticizer, and 40 g of glycerin are placed in a container, heated to 80 ° C. and stirred until uniform. A resistance-reducing paste (A) was obtained.
[Example 1]
1.5 g of ammonium salt of carboxymethyl cellulose (“DN-800H” manufactured by Daicel Chemical Industries, Ltd.) was slowly added to 98.5 g of water to obtain an aqueous solution of ammonium salt of carboxymethyl cellulose.

  Next, 1 g each of Pt-Ru-supported carbon catalyst “HiSPEC” (R) 7000 and Pt / Ru black “HiSPEC” (R) 6000 manufactured by Johnson & Matthey was used, and 7 g of an aqueous solution of the ammonium salt of carboxymethylcellulose was measured. In addition, a catalyst paste (A) was produced by kneading in a mortar.

The catalyst paste (A) is applied to an electrode base material (carbon paper TGP-H-060 manufactured by Toray Industries, Inc.) with a knife coater, dried with a hot air dryer at 100 ° C. for 30 minutes, and then heat treated at 130 ° C. for 15 minutes. A fuel cell electrode (A) was prepared using carboxylic acid ammonium salt of carboxymethyl cellulose as carboxylic acid. The amount of Pt deposited per unit area of this electrode was 2.0 mg / cm ² .

When this fuel was evaluated for fuel immersion, the weight retention was 99%, indicating excellent durability.
[Example 2]
2 g of fuel cell catalyst “TEC10V50E” manufactured by Tanaka Kikinzoku Kogyo Co., Ltd., 7 g of an aqueous solution of the ammonium salt of carboxymethylcellulose and 2 g of N-methyl-2-pyrrolidone were added and kneaded in a mortar to prepare catalyst paste (B). .

The catalyst paste (B) was applied to an electrode substrate (carbon cloth “W1400” manufactured by E-TEK, Inc. made of carbon fiber fabric) with a knife coater, and dried with a hot air dryer at 100 ° C. for 30 minutes. Then, heat treatment was performed at 130 ° C. for 15 minutes to produce a fuel cell electrode (B). The amount of Pt deposited per unit area of this electrode was 1.0 mg / cm ² .
When this fuel was evaluated for fuel immersion, the weight retention was 98%, indicating excellent durability.
[Comparative Example 1]
Weigh 1 g each of Pt-Ru supported carbon catalyst “HiSPEC” (R) 7000 and Johnson / Matthey's “HiSPEC” (R) 6000 and 1 “Nafion (R)” solution from Aldrich. 0.1 g was added, and 2 g of isopropyl alcohol was further added and kneaded in a mortar to prepare catalyst paste (C).

The catalyst paste (C) is applied to an electrode base material (carbon paper TGP-H-060 manufactured by Toray Industries, Inc.) with a knife coater, dried with a hot air dryer at 100 ° C. for 30 minutes, and then heat treated at 130 ° C. for 15 minutes. Then, a fuel cell electrode (C) was produced. The amount of Pt deposited per unit area of this electrode was 2.0 mg / cm ² .

When the fuel immersion evaluation was performed on this electrode, the weight retention was 3% and the durability was insufficient.
[Comparative Example 2]
2 g of fuel cell catalyst “TEC10V50E” manufactured by Tanaka Kikinzoku Kogyo Co., Ltd., 1.1 g of “Nafion (R)” solution manufactured by Aldrich, 2 g of N-methyl-2-pyrrolidone, kneaded in a mortar and catalyst paste ( D) was prepared.
The catalyst paste (D) was applied to an electrode substrate (carbon cloth “W1400” manufactured by E-TEK, Inc. made of carbon fiber fabric) with a knife coater, and dried with a hot air dryer at 100 ° C. for 30 minutes. Then, heat treatment was performed at 130 ° C. for 15 minutes to produce a fuel cell electrode (D). The amount of Pt deposited per unit area of this electrode was 4.0 mg / cm ² .

When this fuel was evaluated for fuel immersion, the weight retention was 5% and the durability was insufficient.
[Example 3]
The interface resistance-reducing paste (A) was applied to the surfaces of the fuel cell electrode (A) and the fuel cell electrode (D) to 3 mg / cm ² and heat-treated at 100 ° C. for 1 minute. These electrodes were cut so as to have an electrode area of 5 cm ² , placed so as to sandwich the electrolyte membrane (A), pressed at 100 ° C. for 5 minutes at 5 MPa, immersed in pure water for 30 minutes, a plasticizer and The remaining solvent was washed to obtain a membrane electrode assembly.

A 30% aqueous methanol solution was supplied to the fuel cell electrode (A) side at 0.5 ml / min, and air was flowed to the fuel cell electrode (D) side at 50 ml / min for power generation evaluation. Moreover, the temperature-controlled water was poured on the back side of the separator, and it adjusted to 50 degreeC. In the evaluation, a constant current was passed through the membrane electrode assembly, and the voltage at that time was measured. The measurement was performed until the current was increased and the voltage was 10 mV or less. The product of the current and voltage at each measurement point is the output. FIG. 1 shows the voltage-current characteristics of this fuel cell. Although the fuel cell electrode (D) was insufficient in durability in the fuel immersion evaluation, the catalyst layer was not collapsed because it was used for an air electrode and an electrolyte membrane with little fuel crossover was used.
[Example 4]
A fuel cell was prepared and evaluated in the same manner as in Example 3 except that the fuel cell electrode of Example 3 was changed to the fuel cell electrode (A) and the fuel cell electrode (B). FIG. 1 shows the voltage-current characteristics of the fuel cell.
[Comparative Example 3]
A fuel cell was prepared and evaluated in the same manner as in Example 3 except that the fuel cell electrode of Example 3 was changed to the fuel cell electrode (C) and the fuel cell electrode (D). FIG. 1 shows the voltage-current characteristics of the fuel cell.

As is clear from FIG. 1, Examples 3 and 4 exhibited better voltage-current characteristics as a fuel cell than Comparative Example 3.
[Example 5]
A fuel cell was produced in the same manner as in Example 3, except that two of the fuel cell electrodes (B) were used as electrodes. When this fuel cell was measured at a cell temperature: 60 ° C., fuel gas: hydrogen, oxidizing gas: air, gas utilization: anode 70% / cathode 40%, the maximum output was It was 400 mW / cm ² .
[Example 6]
The electrolyte membrane (A) was used as a substrate, and the catalyst paste (A) was applied with a slit die coater so as to have an electrode area of 5 cm ² and dried at 100 ° C. to form an electrode (E). Further, the catalyst paste (B) was applied to the other surface of the electrolyte membrane (A) with a slit die coater so as to face the electrode (E) so as to have an electrode area of 5 cm ² and dried at 100 ° C. F) was formed. Next, this was heat-treated at 130 ° C. for 30 minutes to produce a membrane electrode assembly. When the electrode portion of this membrane electrode composite was cut out and evaluated for fuel immersion, the catalyst layer did not collapse and the catalyst particles did not slide off, and excellent durability was exhibited. The weight retention rate was 97%.

  The electrode for a fuel cell of the present invention is suitable for various fuel cells, and particularly suitable for a fuel cell using liquid as fuel.

  Although it does not specifically limit as a use of the fuel cell of this invention, Mobile devices, such as a mobile phone, a personal computer, PDA, a video camera, a digital camera, household appliances, such as a cordless vacuum cleaner, toys, an electric bicycle, a motorcycle, a car, For power supply sources for vehicles such as buses and trucks, ships, and mobiles such as railways, stationary primary generators, such as conventional primary batteries, secondary batteries, or hybrid power sources with these or solar cells, or for charging Preferably used.

These are voltage-current characteristic diagrams of the fuel cells of Examples 3 and 4 and Comparative Example 3 of the present invention.

Claims (5)

  An electrode for a fuel cell having a catalyst layer composed of metal particles and / or metal carrier particles and a binder, and using an alkyl cellulose having an ionic group as the binder.   The fuel cell electrode according to claim 1, wherein the alkyl cellulose having an ionic group is carboxymethyl cellulose.   A fuel cell using the fuel cell electrode according to claim 1 for at least an anode.   It has a membrane made of a sulfonic acid group-containing aromatic hydrocarbon polymer containing a component derived from 9,9-bis (4-hydroxyphenyl) fluorene and / or a component derived from 4,4′-dihydroxytetraphenylmethane. The fuel cell according to claim 3. 5. The fuel cell according to claim 3, wherein a liquid fuel containing water is supplied to the anode.

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