JP2006100056A - Fuel cell electrode and solid polymer fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell electrode having a catalyst layer with low gas permeability on anode or cathode. <P>SOLUTION: The fuel cell electrode 100 has a carbonaceous porous material layer 20 formed by baking a mixture of 50g of phenol novolac resin and 30g of polymethyl methacrylate resin (PMMA) after extracting PMMA therefrom, laminated on porous conductive supporting member 10 like carbon paper, having through holes having diameter of 5 nm to 500 nm; and a catalyst metal plated layer 30 formed by an electric plating method carried out in continuous gas bubble phase of nickel plating solution. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a fuel cell electrode and the like, and more particularly to a fuel cell electrode suitable for a polymer electrolyte fuel cell.

Among fuel cells that have been attracting attention in recent years, solid polymer fuel cells that use a solid polymer membrane as an electrolyte membrane have advantages such as operating at a low temperature of 100 ° C. or lower, and are therefore used in various fields. Is expected.
The polymer electrolyte fuel cell operates in such a manner that an ion-conducting solid polymer membrane is sandwiched between a pair of electrodes consisting of a fuel electrode (anode) and an air electrode (cathode), and hydrogen gas is applied to the anode and cathode, respectively. In addition, electric power is obtained by an electrochemical reaction that occurs at the contact surface between the catalyst layer and the solid polymer film formed on the surfaces of the anode and the cathode, respectively (see Patent Document 1 and Patent Document 2). ).
In addition, a supported catalyst in which a noble metal component such as platinum (Pt) or palladium (Pd) is supported on a conductive powder carrier such as carbon black is used for the catalyst layer on the surfaces of the anode and the cathode. However, a method for supporting the catalyst on the support by electroless plating has also been reported in order to solve the problems such as precipitation of heavy metal components that occur in the production process of the supported catalyst (see Patent Document 3).

JP 2000-106193 A Japanese Patent Laid-Open No. 2002-237306 Japanese Patent Laid-Open No. 08-141400

By the way, in the polymer electrolyte fuel cell, it is known that the gas permeability of the catalyst layer on the anode and cathode surfaces in contact with the ion conductive solid polymer membrane affects the performance of the fuel cell. That is, when the gas permeability of the catalyst layer is high, a gas such as hydrogen supplied to the anode and the cathode tends to diffuse through the solid polymer membrane, and as a result, the performance of the fuel cell tends to be lowered. From this point, as described above, it can be considered that the method such as electroless plating improves the uniformity of the catalyst layer on the surfaces of the anode and the cathode and lowers the gas permeability to some extent.
However, since a gas permeable porous material such as carbon paper is usually used for the anode and the cathode, plating is performed on a support substrate having such a high gas permeability, and the gas permeation of the catalyst layer is performed. In order to reduce the property, it is necessary to perform plating to such an extent that the pores of the porous material are blocked. As a result, the thickness of the catalyst layer increases, which may contribute to a decrease in fuel cell efficiency.
In addition, it is known that the metal particles forming the plating film usually have a particle diameter of 20 nm or more, and that many pinholes having a hole diameter of 1 μm or more are generated. This effectively reduces the gas permeability of the catalyst layer formed by noble metal components such as platinum (Pt) and palladium (Pd), and reduces the diffusion of gases such as hydrogen supplied to the anode and cathode. There are limits.

The present invention has been made to meet the demands that arise in developing such a polymer electrolyte fuel cell. That is, an object of the present invention is to provide a fuel cell electrode in which a low gas permeability catalyst layer is formed on the surface of an anode or a cathode.
Another object of the present invention is to provide a fuel cell in which an ion conductive solid polymer membrane is sandwiched between a pair of electrodes on which a low gas permeable catalyst layer is formed.

In order to meet such a demand, in the present invention, as a fuel cell electrode, a porous material layer having a communication hole with a narrow pore diameter is provided on a support member made of a porous material such as carbon paper. The structure which forms the metal catalyst layer which consists of a metal particle of a small particle diameter is employ | adopted.
That is, according to the present invention, a porous conductive support member that diffuses reactive gas, has gas permeability and conductivity, and is laminated on the porous conductive support member, and has a communication hole having a pore diameter of 10 nm to 500 nm. There is provided a fuel cell electrode comprising a porous material layer having a catalyst metal plating layer formed on the surface of the porous material layer and made of a catalyst for electrochemical reaction.

  A porous material layer in a fuel cell electrode to which the present invention is applied cures a thermosetting resin in a uniform mixture of thermosetting resin / thermoplastic resin of 90/10 to 20/80 (weight% ratio). It is preferably formed by causing the phase separation to occur and then removing the thermoplastic resin and carbonizing the cured thermosetting resin. In such a porous material layer, a communicating pore structure in which the pore diameter is controlled in the range of 10 nm to 500 nm is formed, and a carbonaceous porous material layer having excellent heat resistance is obtained. As a result, it is possible to form a uniform catalyst layer on the porous material layer composed of such a carbonaceous material having a small pore diameter.

  Here, in the polymer electrolyte fuel cell to which the present invention is applied, the porous conductive support member is a uniform mixture of thermosetting resin / thermoplastic resin of 90/10 to 20/80 (weight% ratio). It is formed by curing the thermosetting resin therein, causing phase separation, removing the thermoplastic resin, and further carbonizing the cured thermosetting resin. In this case, the thermoplastic resin Is preferably a thermoplastic resin different from that used when forming the porous material layer.

Further, in the polymer electrolyte fuel cell to which the present invention is applied, the porous conductive support member is 90 / 10-20 / 80 of thermosetting resin / thermoplastic resin applied to the surface of the carbon fiber member. It is formed by curing the thermosetting resin in a uniform mixture (weight% ratio) to cause phase separation, removing the thermoplastic resin, and further carbonizing the cured thermosetting resin. Is preferred. In this case, the porous conductive support member has a surface layer having extremely small holes and a structure having relatively large communication holes formed under the surface layer.
In addition, it is preferable that the thickness of a porous material layer is the range of 10 micrometers-500 micrometers.

The catalytic metal plating layer in the fuel cell electrode to which the present invention is applied is formed by plating the surface of the porous material layer in a continuous cell phase composed of an electrolyte solution containing a catalyst and a surfactant. It is preferred that Thus, by performing the plating process in a continuous bubble phase, pinholes existing on the surface of the catalytic metal plating layer are greatly reduced.
Specifically, the catalyst metal plating layer preferably has a crystal particle diameter of a metal used as a catalyst of 40 nm or less. The thickness of the catalytic metal plating layer is preferably in the range of 0.1 μm to 10 μm.

  Next, according to the present invention, there is provided a solid polymer fuel cell having an ion conductive solid polymer membrane sandwiched between a pair of electrodes, the electrode comprising a porous conductive support member and a porous A porous material layer made of a carbonaceous material having a communication hole with a pore diameter of 5 nm to 1000 nm laminated on a conductive support member, and catalytic metal plating formed on the surface of the porous material layer and in contact with the ion conductive solid polymer film And a polymer electrolyte fuel cell comprising a layer.

  In the solid polymer fuel cell to which the present invention is applied, the ion conductive solid polymer membrane is preferably a perfluorosulfonic acid polymer membrane.

  Thus, according to the present invention, there is provided a fuel cell electrode in which a low gas-permeable catalyst layer is formed on the surface of an anode or a cathode.

Hereinafter, the best mode for carrying out the present invention (hereinafter referred to as an embodiment) will be described in detail with reference to the drawings.
FIG. 1 is a diagram illustrating a fuel cell electrode to which the present embodiment is applied. FIG. 1 shows a fuel cell electrode 100 used in a polymer electrolyte fuel cell. The fuel cell electrode 100 is composed of a porous conductive support member 10 having gas permeability and conductivity, and a carbonaceous material laminated on the porous conductive support member 10 and having communication holes having a pore diameter of 10 nm to 500 nm. It has a porous material layer 20 and a catalytic metal plating layer 30 formed on the surface of the porous material layer 20. As shown in FIG. 1, the surface of the catalytic metal plating layer 30 is in contact with a solid polymer film 40 made of an electrolyte solid polymer material.

  The porous conductive support member 10 usually has pores having a pore diameter of about 0.5 μm to 50 μm, and functions to diffuse a reactive gas such as hydrogen or oxygen into the catalyst metal plating layer 30 which is a catalyst layer. The material constituting the porous conductive support member 10 is not particularly limited. Usually, the material having conductivity is paper using carbon fiber (carbon paper), woven fabric using carbon fiber (carbon). Cross), sintered metal, ceramics and the like.

Next, the porous material layer 20 will be described.
The porous material layer 20 is usually composed of a carbonaceous material having a communication hole having a pore diameter of 5 nm to 1000 nm, preferably 10 nm to 500 nm, and is usually 10 μm to 500 μm in thickness on the porous conductive support member 10. It is formed as a porous layer.
The method for forming the porous material layer 20 is not particularly limited, but usually, after the thermosetting resin and the thermoplastic resin are uniformly mixed, the thermosetting resin is cured to cause phase separation, It is formed by removing the separated thermoplastic resin.

  As the thermosetting resin, a resin that does not cause phase separation when mixed with a thermoplastic resin and is usually cured at 140 ° C. or higher is preferably used. The weight average molecular weight of the thermosetting resin is usually 10,000 or less, preferably 5,000 or less. Furthermore, what has a benzene ring and a hetero ring in a molecule | numerator, or the thing which produces | generates these rings by heat processing is used preferably.

  Specific examples of the thermosetting resin include phenol resin, epoxy resin, polyimide resin, silicon resin, lignin resin, and the like. Among these, a phenol resin, an epoxy resin, a polyimide resin, and a lignin resin are preferable. Any one of these thermosetting resins may be used alone, or any two or more thereof may be mixed and used in any combination.

Although it does not specifically limit as a thermoplastic resin, The thing decomposed | disassembled at the temperature lower than the decomposition temperature of the thermosetting resin to mix is used, and what decomposes | disassembles normally at the temperature of 500 degrees C or less is preferable.
Specific examples of the thermoplastic resin include, for example, polyacrylate ester, polymethacrylate ester, polyester resin, polyether resin, polyvinyl acetate, polystyrene resin, vinyl alcohol resin, acrylamide resin, vinyl pyrrole resin, acrylonitrile resin, and these. Among these copolymers, those containing at least one kind and oligomers thereof may be mentioned. Among these, polyacrylic acid ester, polymethacrylic acid ester, polyether resin, polyether resin, polyvinyl acetate, and copolymers thereof are preferable.

  Specific examples include polystyrene, polycarbonate, polymethyl methacrylate, polyethyl methacrylate, polyethyl acrylate, polyisopropyl methacrylate, polyvinyl methyl ether, polyethylene oxide, polyvinyl alcohol, polyvinyl pyrrolidone, and polyacrylamide. Among these, polycarbonate, polymethyl methacrylate, polyethyl methacrylate, polyethyl acrylate, polyvinyl methyl ether, and polyethylene oxide are preferable.

  In addition, it is also possible to use derivatives obtained by adding functional groups to these thermoplastic resins. As the types of functional groups, if the thermosetting resin is a phenol resin, a phenolic hydroxyl group and a hydrogen bonding functional group, For example, those having a carboxyl group, nitro group, amino group, amide group, halogen group, sulfonyl group and the like are preferable. Any one of the thermoplastic resins may be used alone, or any two or more may be mixed and used in any combination, but it is usually preferable to use them alone.

  Preferred combinations of thermosetting resin and thermoplastic resin include, for example, phenol novolac / polymethyl methacrylate, phenol novolac / polyethyl methacrylate, phenol novolac / styrene-acrylonitrile copolymer, phenol novolac / polyacrylonitrile, phenol novolac / Polycarbonate, phenol novolac / polyethylene oxide, phenol novolac / polyacrylamide, phenol resole / polymethyl methacrylate, phenol resole / polyethyl methacrylate, phenol resole / styrene-acrylonitrile copolymer, phenol resole / polyacrylonitrile, phenol resole / polycarbonate, phenol Resole / polyethylene oxide, fluorine Nordresol / polyacrylamide, cresol novolak / polymethyl methacrylate, cresol novolak / polyethyl methacrylate, cresol novolak / polybutyl acrylate, cresol novolak / styrene-acrylonitrile copolymer, cresol novolak / polyacrylonitrile, cresol novolak / polycarbonate, cresol novolak / Polyethylene oxide, cresol novolak / polyacrylamide, cresol resol / polymethyl methacrylate, cresol resol / polyethyl methacrylate, cresol resol / polybutyl acrylate, cresol resol / styrene-acrylonitrile copolymer, cresol resol / polyacrylonitrile, cresol resol / Po Carbonate, cresol resol / polyethylene oxide, cresol resol / polyacrylamide and the like.

  Among these, phenol novolak / polymethyl methacrylate, phenol novolak / polyethylene oxide, phenol resole / polymethyl methacrylate, phenol resole / polyethylene oxide, cresol novolak / polymethyl methacrylate, cresol novolak / polyethyl methacrylate, cresol novolak / polybutyl acrylate Cresol novolak / polyethylene oxide, cresol novolak / polyacrylamide, cresol resol / polymethyl methacrylate, cresol resol / polyethyl methacrylate, cresol resol / polyethylene oxide are preferred.

  After preparing a resin mixture in a uniform mixed state by an appropriate combination of a thermosetting resin and a thermoplastic resin, the thermosetting resin component is cured, and a transition from a uniform mixed state to a phase separated state occurs. Then, a state in which the thermoplastic resin component communicates is generated, and from this state, by removing the thermoplastic resin component, a communication hole structure controlled from the mesopore to the macropore region is formed.

  The porous material layer 20 in the present embodiment needs to be prepared from a resin mixture in a uniform mixed state of a thermosetting resin and a thermoplastic resin. For example, in the case of a mixture of thermoplastic resins, it is often difficult to remove only one component, and even if it can be successfully removed, the glass transition temperature of the remaining porous film is low, or by high temperature treatment such as baking Problems such as destruction of the porous structure or vaporization due to complete decomposition occur. In addition, when incompatible thermosetting resin and thermoplastic resin are combined as a blend component, both resin components form a sea-island structure and are separated into a matrix and a domain, and the pores communicated with each other are formed. The problem that it cannot be formed arises.

  In addition, the compatibility of the mixture of a thermosetting resin and a thermoplastic resin is judged from the measurement result of a glass transition temperature using a differential scanning calorimeter (Differential Scanning Calorimeter: DSC). When there is compatibility between the thermosetting resin and the thermoplastic resin, the glass transition temperature of the uniform mixture of these resins is the glass transition temperature of the thermosetting resin and the thermoplastic resin as the base material. At different temperatures, in particular when the compatibility is high, only one glass transition temperature is observed.

As a method of mixing the thermosetting resin and the thermoplastic resin, for example, these resins are dissolved in a solvent such as acetone, methanol, tetrahydrofuran, chloroform, water, dimethylformamide and then mixed, And a method of directly mixing these resins by mechanical mixing such as a kneader.
The mixing ratio of the thermosetting resin and the thermoplastic resin is not particularly limited, but usually the ratio of the thermosetting resin / thermoplastic resin is appropriately selected within the range of 90/10 to 20/80 by weight ratio. .

The mixture of the thermosetting resin and the thermoplastic resin is usually 140 ° C. or higher, preferably 160 ° C. or higher, more preferably 180 ° C. or higher, but usually 300 ° C. or lower, preferably 250 ° C. or lower, more preferably 200 ° C. A heat treatment is performed under the condition of 0 ° C. or less, and a curing reaction of the thermosetting resin is performed. Next, the porous body which consists of a thermosetting resin component is obtained by removing a thermoplastic resin component from the mixed resin which hardened the thermosetting resin component.
The method for removing the thermoplastic resin component is not particularly limited, but usually the method of extracting the thermoplastic resin component with acetone, chloroform, water or the like, and the thermosetting resin component is usually cured at a temperature of 500 ° C. or higher. And a method of removing the mixed resin by appropriately firing.

  Moreover, also when carbonizing a thermosetting resin component and making it a carbonaceous porous material, the method by baking can be used. For example, after extracting and removing a thermoplastic resin from a thermosetting resin / thermoplastic resin mixture, the temperature is raised to a target temperature at 2 ° C./min in an inert gas atmosphere, and the target temperature is 1 to 2 hours. After maintaining the degree, the carbonaceous porous material is obtained by cooling to room temperature. In this case, it is preferable that the remaining thermosetting resin component is baked after the thermoplastic resin component is previously removed by a technique such as extraction. Furthermore, when the decomposition temperature of the thermoplastic resin is lower than the decomposition carbonization temperature of the thermosetting resin, the thermosetting resin component can be carbonized simultaneously with the removal of the thermoplastic resin component by baking.

  The porous conductive support member 10 is prepared by preparing a 90 / 10-20 / 80 (weight% ratio) mixture of a thermosetting resin and a thermoplastic resin, and curing the thermosetting resin in the mixture. It can also be formed by removing the thermoplastic resin and carbonizing the cured thermosetting resin after causing phase separation. In this case, the thermoplastic resin used for mixing with the thermosetting resin is preferably another thermoplastic resin different from the thermoplastic resin used when forming the porous material layer 20.

  Furthermore, the porous conductive support member 10 is obtained by applying a solution of a thermosetting resin / thermoplastic resin mixture to the surface of the porous conductive support member 10 made of a carbon fiber member such as carbon paper or carbon cloth. Then, after the thermosetting resin in the mixture is cured to cause phase separation, the thermoplastic resin is removed, and the cured thermosetting resin can be carbonized. In this case, the porous conductive support member 10 has a surface layer having extremely small holes and a structure having relatively large communication holes formed therebelow.

Next, the catalytic metal plating layer 30 will be described.
The catalytic metal plating layer 30 acts as a catalyst for an electrochemical reaction that occurs on the surface in contact with the solid polymer film 40 of the electrolyte. Examples of the catalyst include noble metal components such as platinum (Pt), palladium (Pd), rhodium (Rh), ruthenium (Ru), iridium (Ir), osmium (Os), silver (Ag), and gold (Au). Furthermore, nickel (Ni) etc. are mentioned.
A method for forming the catalytic metal plating layer 30 is not particularly limited, but usually, a surfactant is dispersed in the above-described electrolytic solution containing the catalytic metal, and the resultant is foamed to continuously form fine bubbles. A bubble phase is formed, and an anode and a cathode made of the porous conductive support member 10 on which the porous material layer 20 is formed are provided in the bubble phase, and a plating process is performed on the porous material layer 20. The method of forming by this is preferable.

  FIG. 2 is a diagram illustrating a method for forming a catalytic metal plating layer. FIG. 2 shows an electroplating apparatus 200 in which plating is performed in a continuous bubble phase composed of minute bubbles of an electrolyte solution. An electroplating apparatus 200 shown in FIG. 2 includes a plating tank 201, a DC power supply 207 that is external electrolysis provided outside the plating tank 201, and an anode 205 that is an electrode material that conducts to the positive electrode side of the DC power supply 207. A negative electrode 206, which is a porous conductive support member 10 (FIG. 1) on which a porous material layer 20 (FIG. 1) is formed, and is connected to the negative electrode side of the DC power source 207. 207 and 209 and a switch 208, respectively. Also, a glass filter 213 provided near the bottom of the plating tank 201 and having pores of a predetermined size, and an air supply pipe 212 inserted into the plating tank 201 from the upper part of the plating tank 201 and communicating with the glass filter 213, And a circulation pipe 215 that communicates the upper and lower portions of the plating tank 201 via a pump 214. Further, an anode 205 which is an electrode material conducting to the positive electrode side of the DC power supply 207 is provided on the upper side of the glass filter 213, and a cathode 206 is attached to the upper part of the plating tank 201. The glass filter 213 may be a stainless steel filter.

A switch 208 provided in a power supply circuit of the DC power supply 207 is joined when electroplating is performed, so that the anode 205 and the cathode 206 can be energized.
The glass filter 213 has predetermined pores, and the pore diameter is not particularly limited, but is usually about 5 μm to 100 μm, preferably about 10 μm to 50 μm. The gas supplied to the glass filter 213 via the air supply pipe 212 is not particularly limited, but usually an inert gas such as air or nitrogen gas is used. The pressure of the gas sent to the glass filter 213 is usually 2 kgf / cm ² or less.

As shown in FIG. 2, a plating solution 203 of an electrolyte solution containing a surfactant previously contained in a plating tank 201 is a glass filter in which nitrogen gas (N ₂ gas) supplied through an air supply pipe 212 is a glass filter. Foaming by discharging from 213 forms a continuous cell phase 211 made of an electrolyte solution containing a surfactant. The formed bubble phase 211 is continuously supplied to the cathode 206 through the surface of the anode 205 provided at the bottom of the plating tank 201 together with the flow of N ₂ gas discharged from the glass filter 213. The bubble phase 211 reaches the upper part of the plating tank 201, breaks the bubbles, and returns to the plating solution 203. The plating solution 203 is supplied again from the bottom of the plating tank 201 into the plating tank 201 by the pump 214 through the circulation pipe 215.

The solvent used in the plating solution 203 is not particularly limited as long as it is a polar solvent, but usually water; alcohols such as methanol and ethanol; cyclic carbonates such as ethylene carbonate and propylene carbonate; dimethyl carbonate, ethyl methyl carbonate, diethyl Examples thereof include linear carbonates such as carbonate, or a mixed solvent thereof.
As described above, the metal in the plating solution 203 includes platinum (Pt), palladium (Pd), rhodium (Rh), ruthenium (Ru), iridium (Ir), osmium (Os), silver (as a catalyst). Ag), noble metal components such as gold (Au). Nickel (Ni) or the like can also be used. Furthermore, as an organic electrolyte, for example, an anionic electrolyte such as polyacrylic acid, a cationic electrolyte such as polyethyleneimine, and the like are appropriately added.

  The plating solution 203 may contain one or more substances for the purpose of stabilizing the solution. Specifically, substances that form complex salts with the ions of the catalyst metal to be deposited, other salts to improve the conductivity of the electrolyte solution, stabilizers for the electrolyte solution, warming materials for the electrolyte solution, and changes the physical properties of the deposited metal Examples thereof include substances, substances that help dissolve the cathode, substances that change the properties of the electrolyte solution or the deposited metal, and stabilizers for mixed solutions containing two or more metals.

As the surfactant contained in the plating solution 203, known anionic, nonionic, cationic and zwitterionic surfactants can be used.
Specifically, examples of the anionic surfactant include soap, α-olefin sulfonate, alkylbenzene sulfonate, alkyl sulfate ester salt, alkyl ether sulfate ester salt, phenyl ether sulfate ester salt, methyl tauric acid. Salt, sulfosuccinate, ether sulfonate, sulfated oil, phosphate ester, perfluoroolefin sulfonate, perfluoroalkylbenzene sulfonate, perfluoroalkyl sulfate, perfluorophenyl ether sulfate, perfluoro Examples include methyl taurate, sulfoperfluorosuccinate, and perfluoroethersulfonate.

  Examples of the cation of the salt of these anionic anionic surfactants include sodium, potassium, calcium, tetraethylammonium, triethylmethylammonium, diethyldimethylammonium, tetramethylammonium and the like.

  Nonionic surfactants include, for example, C1-C25 alkylphenols, C1-C20 alkanols, polyalkylene glycols, alkylolamides, C1-C22 fatty acid esters, C1-C22 aliphatic amines, alkylamine ethylene oxide additions. , Arylalkylphenol, C1-C25 alkylnaphthol, C1-C25 alkoxylated phosphoric acid (salt), sorbitan ester, styrenated phenol, alkylamine ethylene oxide / propylene oxide adduct, alkylamine oxide, C1-C25 alkoxylated phosphoric acid ( Salt), perfluorononylphenol, perfluoro higher alcohol, perfluoropolyalkylene glycol, perfluoroalkylolamide, perfluoro fatty acid ester , Perfluoroalkyl amine oxide adduct, perfluoroalkyl amine oxide / perfluoro propylene oxide adduct, perfluoroalkyl amine oxide, and the like.

  Examples of the cationic surfactant include lauryl trimethyl ammonium salt, stearyl trimethyl ammonium salt, lauryl dimethyl ethyl ammonium salt, dimethyl benzyl lauryl ammonium salt, cetyl dimethyl benzyl ammonium salt, octadecyl dimethyl benzyl ammonium salt, trimethyl benzyl ammonium salt, Hexadecylpyridinium salt, laurylpyridinium salt, dodecylpicolinium salt, stearylamine acetate, laurylamine acetate, octadecylamine acetate, monoalkylammonium chloride, dialkylammonium chloride, ethylene oxide addition type ammonium chloride, alkylbenzylammonium chloride, tetramethylammonium chloride , Trimethylph Sulfonyl chloride, tetrabutylammonium chloride, acetate monoalkyl ammonium, and the like.

  Furthermore, imidazolinium betaine, alanine, alkylbetaine, monoperfluoroalkylammonium chloride, diperfluoroalkylammonium chloride, perfluoroethylene oxide addition type ammonium chloride, perfluoroalkylbenzylammonium chloride, tetraperfluoromethylammonium chloride , Triperfluoromethylphenylammonium chloride, tetraperfluorobutylammonium chloride, monoperfluoroalkylammonium acetate, perfluoroalkylbetaine and the like.

Examples of the zwitterionic surfactant include a sulfated or sulfonated adduct of a condensation product of betaine, sulfobetaine, aminocarboxylic acid, ethylene oxide and / or propylene oxide and an alkylamine or diamine.
The amount of the surfactant used is not particularly limited, but usually 0.0001% by weight or more, preferably 0.001% by weight or more is used as the concentration in the plating solution 203 which is an electrolyte solution. However, the upper limit of the amount used is 20% by weight or less, preferably 10% by weight.

  The particle diameter of the constituent unit of the continuous bubble phase 211 supplied to the anode 205 and the cathode 206 is not particularly limited, but is usually 0.01 mm or more, preferably 0.1 mm or more. However, the upper limit of the particle diameter of the bubbles of the constituent unit of the bubble phase 211 is usually 20 mm or less, preferably 10 mm or less, and more preferably 5 mm or less.

  The conditions for electroplating are appropriately selected depending on the type of metal to be electroplated, and are not particularly limited. For example, when a watt bath is used for nickel plating, the concentration of the plating solution 203 that is an electrolyte solution to be used is usually 260 g. / L to 490 g / l, preferably 300 g / l to 400 g / l. Moreover, the pH of the plating solution 203 which is an electrolyte solution is 1.5-5.0 normally, Preferably, it is 3.0-4.8. The temperature of electroplating is 40 to 70 degreeC normally, Preferably, it is 45 to 60 degreeC.

The catalytic metal plating layer 30 in the fuel cell electrode 100 to which the present embodiment is applied is electroplated using a porous material layer 20 made of a carbonaceous material having a communicating hole with a pore diameter of 10 nm to 500 nm as an underlayer. As a result, the crystal grains of the metal used as the catalyst are reduced in diameter, and a uniform catalyst layer is formed.
That is, it was difficult to obtain a uniform catalyst layer even when direct plating treatment was performed on a gas-permeable porous material such as carbon paper used for conventional fuel cell electrodes. A porous material layer 20 composed of a carbonaceous material having a small pore diameter is formed on a porous material that is gas permeable, and an electroplating process is performed on the porous material layer 20 to achieve uniform A catalyst layer can be formed.

  Further, as described above, the catalyst metal plating layer 30 formed by the electroplating method performed in the continuous bubble phase 211 of the electrolyte solution containing the catalyst metal has a small particle diameter of the deposited metal crystal particles. Become. Specifically, the particle diameter of the precipitated crystal particles is reduced to at least 80% or less as compared with a plating process that is conventionally performed. That is, the size of one crystal grain of a metal used as a catalyst is usually 40 nm or less, preferably 20 nm or less, more preferably 15 nm or less.

  Moreover, in addition to the reduction in the diameter of the crystal particles on the surface of the catalytic metal plating layer 30, the number of pinholes existing on the surface of the catalytic metal plating layer 30 is greatly reduced. For this reason, even when the thickness of the plating film is small, the performance of the fuel cell can be improved. The thickness of the catalytic metal plating layer 30 is usually 0.1 μm to 10 μm.

Next, the polymer electrolyte fuel cell will be described.
FIG. 3 is a diagram illustrating a polymer electrolyte fuel cell. A solid polymer fuel cell 300 shown in FIG. 3 includes a solid polymer film 40 that is an electrolyte membrane, a fuel electrode 301 and an air electrode 302 that are disposed so as to sandwich the solid polymer film 40 from above and below, and a fuel electrode. 301 and separators 303 and 304 which are disposed on the back surfaces of the air electrode 302 and form a flow path for the fuel gas and the oxidant gas, and further on the outside thereof, a current collecting plate 305 which serves as a collecting electrode for the fuel electrode 301 and the air electrode 302. , 306 are arranged.

  The solid polymer membrane 40 is an ion exchange membrane formed from a polymer material, and exhibits good ion conductivity in a wet state. Although it does not specifically limit as a polymeric material which comprises the solid polymer film 40, For example, sulfonated thing of fluororesins, such as a perfluorosulfonic acid polymer; Sulfonated polyetheretherketone, sulfonated polyethersulfone, sulfonated polysulfone Sulfonated products of heat-resistant aromatic polymer compounds such as sulfonated polyphenylene sulfide and sulfonated polyimide; sulfonated products of aromatic hydrocarbon block copolymers such as styrene- (ethylene-butylene) -styrene. Among these, a perfluorosulfonic acid polymer membrane (for example, DuPont's brand name Nafion membrane) is preferable.

  In the polymer electrolyte fuel cell 300, the solid polymer film 40 is sandwiched between a pair of porous electrodes each composed of a fuel electrode 301 and an air electrode 302, and the fuel electrode 301 and the air electrode 302 are respectively reactive. Fuel gas and oxidant gas, which are gases, are circulated. The oxidant gas is oxygen gas or air, and the fuel gas is natural gas or hydrogen-rich gas obtained by reforming methanol or the like.

  As described above, the solid polymer fuel cell 300 shown in FIG. 3 includes the porous conductive support member 10 (as the fuel electrode 301 and the air electrode 302 disposed so as to sandwich the solid polymer film 40 from above and below. By using the fuel cell electrode 100 (FIG. 1) in which the porous material layer 20 (FIG. 1) and the catalyst metal plating layer 30 (FIG. 1) are laminated on the solid polymer membrane 40 and the catalyst. The contact surface with the metal plating layer 30 (FIG. 1) becomes uniform, the gas permeability is reduced, and the hydrogen ion permeability is increased, thereby greatly improving the performance of the fuel cell.

Hereinafter, the present embodiment will be described in more detail based on examples. However, this embodiment is not limited to these examples.
(Example)
A solution prepared by dissolving 50 g of phenol novolac resin and 30 g of polymethyl methacrylate resin (PMMA) and 7.5 g of hexamethylenetetramine in 200 g of a mixed solvent of methanol / acetone = 1/1 is poured into a polytetrafluoroethylene dish, and the solvent is added. After removal, the obtained solid sample was molded by a press molding machine at a molding pressure of 10 kgf / cm ² and a temperature of 180 ° C. for 10 minutes. Next, the molded sample was immersed in acetone to remove the PMMA component, and then fired at 500 ° C. at a temperature rising rate of 2 ° C./min under a nitrogen flow to produce a porous material. The produced porous material has a network structure made of a phenol novolac resin, and communication holes having a pore diameter in the range of 5 nm to 500 nm are formed.

Next, the produced porous material is placed on a conductive ceramic plate, pressed at a pressure of 10 kgf / cm ² and a temperature of 180 ° C., and a porous material layer is formed on the porous conductive support member of the conductive ceramic plate. A test piece in which was stacked was formed.

Subsequently, this test piece was prepared by previously preparing a plating solution (370 parts of nickel, 370 parts of nickel sulfate, 90 parts of nickel chloride and 50 parts of boric acid, adjusting the pH to 5.0 by adding sulfuric acid, Nickel plating solution prepared by adding 3% activator) Fixed as a cathode in a 200 cc plating tank filled with 40 cc, using a pure nickel plate as the anode, and from a glass filter provided at the bottom of the plating tank The plating solution is foamed with the introduced nitrogen gas to form a continuous bubble phase having a height of about 6 cm consisting of bubbles with a bubble diameter of 0.1 mm to 2 mm, and a voltage is applied between both electrodes at 50 ° C. Electroplating was performed on the surface of the cathode for a predetermined time under a current density of ^2.5 mA / dm ² to form a catalytic metal plating layer on the porous material layer.

When the surface roughness of the surface of the prepared catalytic metal plating layer was measured using an ultradeep shape measuring microscope, a value of the surface roughness of 20 nm was obtained, and the smoothness of the surface of the catalytic metal plating layer was good.
Further, when the surface of the catalytic metal plating layer was observed with an optical microscope (450 times magnification), no pinhole having a diameter of 1 μm or more was formed.

It is a figure explaining the electrode for fuel cells to which this Embodiment is applied. It is a figure explaining the method of forming a catalyst metal plating layer. It is a figure explaining the polymer electrolyte fuel cell to which this Embodiment is applied.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Porous conductive support member, 20 ... Porous material layer, 30 ... Catalyst metal plating layer, 40 ... Solid polymer film, 100 ... Fuel cell electrode, 200 ... Electroplating apparatus, 201 ... Plating tank, 203 ... Plating solution, 205 ... anode, 206 ... cathode, 207 ... DC power supply, 208 ... switch, 209,210 ... conductor, 211 ... bubble phase, 212 ... air pipe, 213 ... glass filter, 214 ... pump, 215 ... circulation piping, 300 ... solid polymer fuel cell, 301 ... fuel electrode, 302 ... air electrode, 303, 304 ... separator, 305, 306 ... current collector plate

Claims (10)

A porous conductive support member that diffuses reactive gas and has gas permeability and conductivity;
A porous material layer laminated on the porous conductive support member and having communication holes with a pore diameter of 5 nm to 1000 nm;
A catalytic metal plating layer formed on the surface of the porous material layer and made of a catalyst for electrochemical reaction;
An electrode for a fuel cell comprising:   The porous material layer is formed by curing the thermosetting resin in a uniform mixture of thermosetting resin / thermoplastic resin 90/10 to 20/80 (weight% ratio) to cause phase separation. The fuel cell electrode according to claim 1, wherein the electrode is formed by removing the thermoplastic resin and carbonizing the cured thermosetting resin.   The porous conductive support member cures the thermosetting resin in a 90/10 to 20/80 (weight% ratio) uniform mixture of thermosetting resin / thermoplastic resin to cause phase separation. Then, the thermoplastic resin is removed and further cured by carbonizing the cured thermosetting resin, and the thermoplastic resin is used when forming the porous material layer. 2. The fuel cell electrode according to claim 1, wherein the two are different thermoplastic resins.   The porous conductive support member comprises the thermosetting resin in a 90/10 to 20/80 (weight% ratio) uniform mixture of a thermosetting resin / thermoplastic resin applied to the surface of a carbon fiber member. 2. The fuel cell electrode according to claim 1, wherein the fuel cell electrode is formed by curing and causing phase separation, removing the thermoplastic resin, and further carbonizing the cured thermosetting resin. 3.   2. The fuel cell electrode according to claim 1, wherein the thickness of the porous material layer is in the range of 10 [mu] m to 500 [mu] m.   The catalyst metal plating layer is formed by performing a plating process on the surface of the porous material layer in a continuous cell phase made of an electrolyte solution containing the catalyst and a surfactant. Item 10. The fuel cell electrode according to Item 1.   2. The electrode for a fuel cell according to claim 1, wherein the catalyst metal plating layer has a crystal particle diameter of one of metals used as the catalyst of 40 nm or less.   2. The fuel cell electrode according to claim 1, wherein the thickness of the catalytic metal plating layer is in the range of 0.1 [mu] m to 10 [mu] m. A solid polymer fuel cell having an ion conductive solid polymer membrane sandwiched between a pair of electrodes,
The electrode comprises a porous conductive support member;
A porous material layer made of carbonaceous material having a communication hole with a pore diameter of 5 nm to 1000 nm, laminated on the porous conductive support member;
A catalytic metal plating layer formed on the surface of the porous material layer and in contact with the ion conductive solid polymer film;
A polymer electrolyte fuel cell comprising:   10. The polymer electrolyte fuel cell according to claim 9, wherein the ion conductive solid polymer membrane is a perfluorosulfonic acid polymer membrane.

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