JP2003086193A - Method of manufacturing gas diffusion electrode - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing an ion conductivity imparting agent capable of providing a gas diffusion electrode having a good ion conductivity inside an electrode and therefore stably usable over a long period in a solid polymer fuel cell having a hydrocarbon type negative ion exchange membrane as an electrolyte membrane. SOLUTION: The gas diffusion electrode for a solid polymer fuel cell is manufactured by obtaining a molding made of a composition containing an electrode catalyst and not less than two kinds of organic compounds capable of forming an ion-exchange resin by means of crosslink with each other upon contact, such as in a combination of polychloromethylstyrene and tetramethylhexamethylenediamine, and then by performing heat treatment or the like to crosslink the not less than two kinds of organic compounds contained in the molding.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing a gas diffusion electrode for a polymer electrolyte fuel cell, and a polymer electrolyte fuel in which the gas diffusion electrode produced by the method is joined to a polymer electrolyte membrane. The present invention relates to a cell member and a polymer electrolyte fuel cell including the member.

[0002]

2. Description of the Related Art A polymer electrolyte fuel cell is a fuel cell cell using a solid polymer such as an ion exchange resin as an electrolyte, and has a characteristic that the operating temperature is relatively low. As shown in FIG. 1, the solid polymer electrolyte fuel cell has a solid polymer electrolyte membrane 6 in which a space in a cell partition 1 having a fuel gas passage 2 and an oxidant gas passage 3 respectively communicating with the outside is formed. A fuel chamber 7 communicating with the outside through a fuel gas flow hole 2 and a oxidant gas flow hole 3 which are partitioned by a joined body in which a fuel chamber side gas diffusion electrode 4 and an oxidant chamber side gas diffusion electrode 5 are bonded to both surfaces of Oxidant chamber 8 communicating with outside through
Has a basic structure formed. In the polymer electrolyte fuel cell having such a basic structure, the fuel chamber 7
To the oxidant chamber 8 through the oxidant gas flow hole 3 and oxygen-containing gas such as oxygen or air, and further diffuse both gases. By connecting an external load circuit between the electrodes, electric energy is generated by the following mechanism. That is, in the fuel chamber side gas diffusion electrode 4, protons (hydrogen ions) generated by the contact between the catalyst and the fuel contained in the electrode are conducted in the solid polymer electrolyte membrane 6 and moved to the oxidant chamber 8. Then, the gas diffusion electrode 5 on the oxidant chamber side reacts with oxygen in the oxidant gas to generate water. On the other hand, the electrons generated at the same time as the protons in the fuel chamber side gas diffusion electrode 4 move to the oxidant chamber side gas diffusion electrode 5 through the external load circuit, so that the energy of the above reaction can be used as electric energy.

In the polymer electrolyte fuel cell having the above structure, a perfluorocarbon sulfonic acid resin membrane which is a cation exchange resin membrane is most commonly used as the electrolyte membrane. Further, as a gas diffusion electrode in the case of using such a perfluorocarbon sulfonic acid resin film, an electrode catalyst composed of metal particles such as platinum supported on a conductive agent such as carbon black is formed from a porous material, if necessary. What is supported by the electrode base material is generally used, and the gas diffusion electrode is usually bonded to the perfluorocarbon sulfonic acid resin film by thermocompression bonding. Then, when joining is performed by such a method,
In order to increase the utilization rate of the protons generated on the catalyst inside the gas diffusion electrode (in other words, in order for the protons to efficiently move to the oxidant chamber), ion conductivity is imparted to the joint surface of the gas diffusion electrode. As an agent, an organic solution of a perfluorocarbon sulfonic acid resin is applied, or a perfluorocarbon sulfonic acid resin is blended inside the electrode (JP-A-3-208260 and JP-A-4-329264). . The perfluorocarbon sulfonic acid resin also has a function of improving the bondability between the solid polymer electrolyte membrane and the gas diffusion electrode.

However, in the polymer electrolyte fuel cell using such a perfluorocarbon sulfonic acid resin membrane, the main problems due to the perfluorocarbon sulfonic acid resin membrane are (i) the water retention capacity is not sufficient and Replenishment is required, (ii) it is difficult to reduce the electrical resistance by thinning due to low physical strength, (iii) expensive, (iv) methanol permeability when methanol is used as fuel It has been pointed out that the methanol having reached the oxidant side gas diffusion electrode reacts with oxygen or air on the surface thereof, so that the overvoltage increases and the output voltage decreases. Then, in order to solve such a problem, especially the problem of the above (iv), it has been studied to use a hydrocarbon-based anion exchange membrane in place of the perfluorocarbon sulfonic acid resin membrane, and such a solid polymer type Several fuel cells have been proposed (Japanese Patent Laid-Open Nos. 11-273695, 11-135137, and 2000-3).
No. 31693). The power generation mechanism in polymer electrolyte fuel cells using these hydrocarbon-based anion exchange membranes is basically the same as in the case of using cation exchange membranes, but from the oxidant chamber side to the fuel chamber side during energization. It is said that the migration of methanol is less likely to occur due to migration of anions such as hydroxide ions, and the problem (iv) above can be solved. Further, since the hydrocarbon type ion exchange membrane is used, the problems (i) to (iii) can be solved.

By the way, in the gas diffusion electrodes in the polymer electrolyte fuel cells disclosed in the above publications,
For the same reason as adding the perfluorocarbon sulfonic acid resin to the gas diffusion electrode when using the perfluorocarbon sulfonic acid resin film, it is performed to add an anion exchange resin as an ion conductivity imparting agent. As such anion exchange resins, anion exchange resins obtained by aminating a chloromethylated product of a copolymer of aromatic polyether sulfonic acid and aromatic polythioether sulfonic acid (Japanese Patent Laid-Open No. 11-273695 and Japanese Patent Laid-Open No. 11-273695) -135137), or a quaternized polymer of a perfluorocarbon polymer having a sulfonic acid group with a terminal treated with a diamine, or a polymer such as a quaternized product of polychloromethylsultylene, which is preferably solvent-soluble (special (Kai 2000-331693).

[0006]

However, when the inventors of the present invention investigated a polymer electrolyte fuel cell using a hydrocarbon-based anion exchange membrane as an electrolyte membrane, the performance of the polymer electrolyte fuel cell was improved. It depends on the properties of the ion-conductivity imparting agent contained in the gas diffusion electrode, and it has been found that a polymer electrolyte fuel cell with sufficient performance cannot be obtained depending on the properties. That is, when a fluororesin-based anion exchange resin is used as the ion-conductivity imparting agent, the two become unfamiliar at the bonding interface between the hydrocarbon-based anion exchange membrane and the gas diffusion electrode, and even if a binder is added. In some cases, the bonding strength may decrease, and even when a hydrocarbon-based anion exchange resin is used as the ion conductivity-imparting agent, the anion exchange resin is used in order to improve the dispersibility and improve the contact with the electrode catalyst. It has been found that the resin is often non-crosslinkable, and when it is attempted to increase the ion exchange capacity to increase the catalytic activity, the resin becomes soluble in water, and thus the performance may be deteriorated when used for a long period of time.

Therefore, the present invention is a solid polymer type fuel cell using a hydrocarbon type anion exchange membrane as an electrolyte membrane, which has a high initial performance and is hard to deteriorate in the performance even if it is used for a long time. An object of the present invention is to provide a method for manufacturing a gas diffusion electrode for a polymer fuel cell.

[0008]

Means for Solving the Problems The inventors of the present invention have made extensive studies to solve the above problems. As a result, as a method for producing a gas diffusion electrode to be used by bonding it to a hydrocarbon-based anion exchange membrane, after molding a composition containing an organic compound having a crosslinkability and an electrode catalyst, a crosslinking reaction and an ion exchange group are performed. By performing the introduction of at the same time, it is difficult to dissolve in water and methanol, the dispersibility of the electrode catalyst, a good gas diffusion electrode bondability with the ion exchange membrane can be obtained, further with the gas diffusion electrode produced by the above method. The present inventors have found that a fuel cell using a bonded body bonded to a hydrocarbon-based anion exchange membrane is less likely to deteriorate in performance even after long-term use, and have completed the present invention.

That is, according to the first aspect of the present invention, after obtaining a molded article composed of a composition containing two or more kinds of organic compounds capable of cross-linking by contact with each other to form an ion exchange resin, and an electrode catalyst. A method for producing a gas diffusion electrode for a polymer electrolyte fuel cell, which comprises cross-linking the two or more kinds of organic compounds contained in the molded body.

In the above-mentioned production method of the present invention, since an organic compound which can be cross-linked to form an ion exchange resin by contacting with each other is used as a main component, the formed ion exchange resin is a proton or hydroxide. It functions as an ionic conductor of ions and can increase the effective utilization rate of the catalyst in the gas diffusion electrode. Moreover, unlike the case of using a pre-crosslinked ion exchange resin, the above organic compound before crosslinking is well kneaded with the electrode catalyst and uniformly mixed, so that not only the paste properties are good, but also it is formed after the crosslinking reaction. The contact between the ion exchange resin and the electrode catalyst is also very good. Therefore, a gas diffusion electrode having good catalyst dispersibility and ion conductivity can be formed, and high electrode activity can be obtained. In addition, when a compound that gives a hydrocarbon-based anion exchange resin is used as the organic compound, it also functions as a binder when used for a gas diffusion electrode bonded to a hydrocarbon-based anion exchange membrane. Therefore, the hydrocarbon resin-based solid polymer electrolyte membrane and the gas diffusion electrode can be satisfactorily joined, and high electrode activity can be obtained. Further, the ion exchange resin formed has a cross-linking structure and thus is poorly soluble in water and methanol, and when a fuel cell using a gas diffusion electrode formed by using the production method of the present invention is used. In addition to preventing elution in the fuel methanol, water contained in the fuel, or water produced as a by-product during use, it also improves heat resistance and chemical resistance and enhances the durability of the battery itself. Is also possible.

In the above-mentioned production method of the present invention, as a combination of two or more kinds of organic compounds capable of cross-linking to form an ion exchange resin by contacting each other, (1) containing at least one halogen atom at the terminal. Halogen atom organic compound, and (2) Lone electron pair-containing organic compound which has at least one atom having a lone electron pair in the molecule and can bond with the halogen-containing atom organic compound by forming an onium salt at the atom. When a combination of compounds that crosslinks by a bond accompanied by the formation of the onium salt is used and these compounds are crosslinked by heat treatment after molding the composition, the crosslinking reaction proceeds. Easy to do. Further, in this case, a paste-like composition obtained by mixing a solution or suspension of the lone electron pair-containing organic compound and the halogen-containing atom organic compound with an electrode catalyst was molded and then obtained. By heat-treating the molded body, the organic compound can be uniformly dispersed in the gas diffusion electrode, and as a result, a gas diffusion electrode having high electrode reactivity can be provided. Furthermore, without previously mixing the lone electron pair-containing organic compound and the halogen-containing atom organic compound, a paste-like composition containing either one and an electrode catalyst is molded, and then the other is formed on the surface of the obtained molded body. The same effect can be obtained by a simple operation of applying a solution containing an atomic organic compound and heating it. Furthermore, in the ion exchange resin formed in the molded body after the heat treatment, the onium ion formed functions as an anion exchange group, but the halide ion that is the counter anion of the onium ion is the gas diffusion electrode. It is possible to easily substitute the hydroxide ion generally preferred in the above.

The second invention is a gas diffusion electrode manufactured by the manufacturing method of the invention. Although the gas diffusion electrode uses an ion exchange resin having a crosslinked structure as an ion conductivity-imparting agent, the ion conductivity-imparting agent is uniformly dispersed and has good adhesion to an electrode catalyst. It has the feature.

The third aspect of the present invention is a solid polymer electrolyte membrane comprising a joined body in which the gas diffusion electrode produced by the production method of the present invention is joined to at least one surface of the solid polymer electrolyte membrane. A fourth aspect of the present invention is a polymer electrolyte fuel cell, which is a member for a molecular fuel cell and which comprises the member as a constituent member.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION According to the production method of the present invention, a molded product comprising a composition containing two or more kinds of organic compounds capable of cross-linking to form an ion exchange resin by contact with each other and a composition containing an electrode catalyst is obtained. 2 contained in the molded body after
A gas diffusion electrode for a polymer electrolyte fuel cell is manufactured by crosslinking one or more organic compounds. As described above, the gas diffusion electrode for polymer electrolyte fuel cells includes, in addition to the electrode catalyst, ions inside or near the surface of the gas diffusion electrode (specifically, an electrode catalyst such as a platinum group catalyst contained in the gas diffusion electrode). It contains an ion-conductivity imparting agent for enhancing the conductivity of the above-generated protons and ions such as hydroxide ions. In the present invention, an ion exchange resin functioning as the ion-conductivity imparting agent is used. Instead of using it as it is, it is added to the gas diffusion electrode forming paste in the form of a raw material to form the paste, and then the raw material is reacted (crosslinked) to be converted into an ion exchange resin. By adopting such a method, it is possible to further improve the contact between the electrode catalyst and the ion exchange resin, as compared with the case where the ion exchange resin having a crosslinked structure is directly added to the paste. In addition, since the ion exchange resin produced by the reaction has crosslinkability, its solubility in water and organic solvents is zero or extremely low and does not elute during use, and it is a noncrosslinkable ion exchange resin that has solubility in solvents. The durability can be improved as compared with the case where a resin is used.

As used in the production method of the present invention, "they can be crosslinked to form an ion exchange resin by contacting each other. 2
The “more than one organic compound” is not particularly limited as long as it crosslinks to form an ion exchange resin by coming into contact with each other, and a conventionally known anion exchange resin having a crosslinked structure and having an ion exchange group or A raw material compound of a cation exchange resin can be used, for example, a compound having a functional group that can be converted into an ion exchange group and one or more functional groups involved in crosslinking, and crosslinking and ion exchange group formation simultaneously proceed during the crosslinking reaction. Examples of the exchange group of the ion exchange resin include known anions such as quaternary ammonium salt group, pyridinium salt group, imidazolium salt group, phosphonium group and sulfonium group. An exchange group can be adopted, and as the cation exchange group, a known cation exchange group such as a sulfonic acid group, a carboxylic acid group or a phosphonic acid group can be used. However, it is preferable to use an organic compound that forms a hydrocarbon-based anion exchange resin, particularly when forming a gas diffusion electrode to be used by bonding to a hydrocarbon-based anion exchange membrane. It is preferable to use an organic compound which gives an anion exchange resin having a strongly basic quaternary ammonium base or pyridinium base capable of imparting good ionic conductivity. This means that 50% or more, preferably 80% or more, of the atoms bonded to carbon atoms present in the molecule are hydrogen atoms.

The content of ion-exchange groups in the obtained ion-exchange resin is not particularly limited, but from the viewpoint that good ion conductivity can be imparted to the gas diffusion electrode, the ion-exchange capacity is 0.1 to 5. 0 mmol / g, preferably
It is preferably 0.5 to 4.0 mmol / g. Further, in order to improve the contact between the formed ion exchange resin and the electrode catalyst, at least the organic compound and the electrode catalyst are well mixed in the molded body made of the composition containing the at least two kinds of organic compounds and the electrode catalyst. It is preferable that the above-mentioned at least 2
It is preferable that the kind of organic compound does not cause a cross-linking reaction merely by contact, and is cross-linked by subjecting to a heat treatment, light irradiation, addition of a cross-linking agent or the like after obtaining a molded body. .

In the production method of the present invention, from the viewpoints that the crosslinking reaction easily proceeds by a simple operation of heating and an ion exchange resin suitable as an ion conductivity-imparting agent can be provided, the above-mentioned two types are used. As the above compounds, as a combination, (1) a halogen-containing organic compound having at least one halogen atom at the terminal, and (2) at least one atom having a lone electron pair in the molecule, In the combination of a lone electron pair-containing organic compound capable of forming an onium salt and forming a bond with the halogen-containing atom organic compound, a combination of compounds crosslinkable by a bond accompanied by the formation of the onium salt is preferable. Is. When the halogen-containing atom organic compound (1) and the lone-electron-pair-containing organic compound (2) are brought into contact with each other and heated, the compound of (1) is added to the atom having a lone electron pair of the compound of (2). A proton or carbocation derived from is coordinated to form an onium ion, and similarly, a halide ion derived from the compound of (1) forms a salt to form a compound of (1) and a compound of (2). Join. Then, this bonding point (onium salt portion) becomes a cross-linking point, and at the same time, it becomes an anion-exchange group to form an anion-exchange resin having a cross-linking structure.

The halogen-containing atom-containing organic compound (1) is not particularly limited as long as it is an organic compound having at least one halogen atom at the end of the molecule, and known compounds can be used. Further, its molecular weight is not particularly limited, and a polymer can be used as long as it does not have a crosslinked structure itself. However, from the viewpoint that a high crosslink density can be obtained, it is preferable that the compound has two or more halogen atoms at the terminal. Specific examples of the halogen-containing atom organic compound that can be preferably used in the present invention, as the polymer, polychloromethylstyrene, polybromoethylstyrene, polyvinyl chloride,
Polyepichlorohydrin, polybromohydrin, chloromethylated polysulfone, chloromethylated polyphenylene oxide, chloromethylated polyether ether ketone, etc .; Polymerizable monomer (monomer) such as chloromethylstyrene, bromomethylstyrene; non-polymerizable low Examples of the molecular weight compound include dibromoalkane, dichloroalkane, diiodoalkane and the like. These halogen-containing atom compounds can be used alone or in combination of two or more.

The lone electron pair-containing organic compound (2) above has at least one lone electron atom present in the molecule, such as nitrogen, sulfur, oxygen, phosphorus, selenium, tin, iodine and antimony. The compound is not particularly limited as long as it is a compound in which two organic residues are bound and a cation type atom or atomic group is coordinated to the atom to form a cation (onium ion), and known compounds can be used. The atom having the lone electron pair is preferably nitrogen, phosphorus or sulfur from the viewpoint of usefulness of the ion exchange resin to be formed, and particularly preferably nitrogen. Further, from the viewpoint that a high crosslink density can be obtained, it is preferable to use the lone electron pair-containing organic compound having a plurality of atoms having the lone electron pair in the molecule as described above. Specific examples of the lone electron pair-containing organic compound that can be preferably used in the present invention include polymers such as polyvinylpyridine, polyvinylimidazole, polybenzimidazole, polyvinyloxazoline, polyvinylbenzyldimethylamine, and polydimethylarylamine. Compounds, P-containing compounds such as polystyryldiphenylphosphine, S-containing compounds such as polymethylthiostyrene, polyphenylthiostyrene, etc .; vinyl pyridine, vinyl imidazole, vinyl oxazoline, vinyl benzyl dimethylamine as polymerizable monomers (monomers) Nitrogen-containing monomers such as vinylbenzyldiethylamine, phosphorus-containing monomers such as styryldiphenylphosphine, sulfur-containing monomers such as methylthiostyrene; and non-polymerizable low-molecular weight compounds such as tetramethyl Nitrogen-containing compounds such as hexamethylenediamine, dimethylpiperazine and bipyridyl, phosphorus-containing compounds such as bis (dimethylphosphino) ethane, bis (diphenylphosphino) propane, bis (diphenylphosphino) benzene, bis (methylthio) methane, bis (Phenylthio) methane etc. can be mentioned. These compounds may be used alone or in combination of two or more.

When a monomer is used as the organic compound containing a halogen atom (1) and / or the organic compound containing a lone electron pair (2), crosslinking is carried out in order to obtain an ion exchange resin having good properties. It is preferable to polymerize these monomers before the reaction, at the same time as the crosslinking reaction, or after the crosslinking reaction. In this case, in order to control the properties of the resulting ion exchange resin, other monomers copolymerizable with these monomers may be added in addition to these monomers, if necessary. These other monomers include
For example, vinyl compounds such as ethylene, propylene, butylene, acrylonitrile, vinyl chloride and acrylic acid ester are used. The amount used is not particularly limited and may be appropriately determined according to the properties of the ion exchange resin to be obtained, but usually the total amount of the monomers (1) and (2) is 1
It is in the range of 0 to 100 parts by weight with respect to 00 parts by weight. Further, as the polymerization method using these monomers, known polymerization methods such as radical polymerization, cationic polymerization, and anionic polymerization may be applied depending on the type of the monomer, but when the crosslinking reaction is performed by heating, It is preferable to use a radically polymerizable monomer as the monomer and to carry out radical polymerization because the polymerization can be carried out at the same time and a high molecular weight polymer can be easily obtained. When performing radical polymerization, known radical polymerization initiators can be used without limitation.

In the production method of the present invention, the mixing ratio of the halogen-containing atom organic compound and the lone electron pair-containing organic compound is not particularly limited and may be appropriately determined according to the properties of the ion exchange resin to be obtained. From the viewpoint that the ion exchange resin obtained has good properties, the lone electron pair-containing organic compound of (2) with respect to the total number (A) of halogen atoms in the organic compound of halogen-containing atom of (1) is preferable. Total number of moles of atoms having lone electron pairs in the compound (B)
Expressed by the ratio (B / A) of 0.05 to 20.0, especially 0.
The range of 1 to 10.0 is preferable. Generally, an ion exchange resin suitable as an ion-conductivity imparting agent has the above-mentioned ion exchange capacity and is hardly soluble in water and methanol. Among these, the blending ratio and, if necessary, the blending amount of the above-mentioned other monomer may be appropriately determined. It is to be noted that “poorly soluble in water and methanol” means that the solubility in water or methanol at 20 ° C. (concentration of the ion exchange resin in the saturated solution) is less than 1% by weight, preferably 0.8% by weight or less. If the obtained ion exchange resin is easily dissolved in water or methanol, the elastomer will be eluted from the gas diffusion electrode when the fuel cell is constructed and used, and the cell performance is deteriorated. The amount of these compounds used is not particularly limited, but from the viewpoint of ionic conductivity, 5 to 80% by weight, particularly 20 to 50% by weight, based on 100 parts by weight of a conductive agent carrying an electrode catalyst (metal component) described later. %% by weight is preferred.

As the electrode catalyst used in the production method of the present invention, platinum, gold, which is used as an electrode catalyst in a conventional gas diffusion electrode, for promoting the oxidation reaction of hydrogen and the reduction reaction of oxygen, Metal particles such as silver, palladium, iridium, rhodium, ruthenium, tin, iron, cobalt, nickel, molybdenum, tungsten, vanadium, or alloys thereof can be used without limitation. Among these names, it is preferable to use a platinum catalyst because it has excellent catalytic activity. The particle size of the metal particles used as the catalyst is usually 0.1 to 100 nm, and more preferably 0.5 to 10 nm. The smaller the particle size, the higher the catalytic performance, but if the particle size is less than 0.5 nm, it is difficult to prepare, and if the particle size is greater than 100 nm, it becomes difficult to obtain sufficient catalytic performance. In addition, these catalysts may be used after being supported on a conductive agent in advance. The conductive agent is not particularly limited as long as it is an electronically conductive substance, but, for example, furnace black, carbon black such as acetylene black, activated carbon, graphite or the like is generally used alone or as a mixture. . The content of these catalysts is usually 0.01 to 10 mg / cm ² , more preferably 0.1 to 5.0 mg / cm ² in terms of metal weight per unit area in a state where the electrode catalyst phase is in a sheet form. .

In the production method of the present invention, first, a molded body made of a composition containing the above-mentioned "two or more kinds of organic compounds capable of being crosslinked to form an ion exchange resin by contacting each other" is molded. The molding method of the molded body is not particularly limited, but a paste-like composition obtained by mixing a solution or suspension of the lone electron pair-containing organic compound and the halogen-containing atom organic compound with an electrode catalyst is molded. how to,
Alternatively, a paste-like composition obtained by mixing the solution or suspension of the lone electron pair-containing organic compound or the solution or suspension of the halogen-containing atom organic compound with an electrode catalyst is molded, and then the obtained molded body is obtained. Can be suitably carried out by applying a solution of the organic compound containing a halogen atom or a solution of the organic compound containing a lone electron pair to the surface of the. In the above method, a paste containing an lone electron pair-containing organic compound and a halogen-containing atom organic compound and an electrode catalyst is prepared in advance, and the paste is molded to obtain a molded body composed of a composition containing both compounds. The method of 1. prepares a paste containing either an lone electron pair-containing organic compound or a halogen-containing atom-containing organic compound and an electrode catalyst, and after molding this, a solution of the other compound not contained in the molded body is applied. Finally, a molded product composed of a composition containing both compounds is obtained. Both methods are both simple and practical methods, but it is more preferable to adopt the method because it is easy to disperse the ion-exchange resin as the ion-conductivity imparting agent more uniformly in the entire electrode.

In the above method and / or method, the lone electron pair-containing organic compound and / or the halogen-containing atom organic compound are used in the form of a solution or a suspension. The solvent used to obtain the solution at this time is not particularly limited as long as it dissolves these compounds, but an organic solvent having a low boiling point is preferable because the drying operation is easy. Examples of suitable organic solvents include dichloroethane, chloroform, methanol, ethanol, 1-propanol, 2-
Propanol, methyl ethyl ketone, acetonitrile,
Nitromethane, tetrahydrofuran, dioxane, N,
Examples thereof include N-dimethylformamide and toluene.
The concentration of the compound in the solution is not particularly limited, a combination of the solvent and the previous compound, the amount used for the electrode catalyst,
It may be appropriately determined depending on the viscosity, the permeability at the time of application, etc., but it is expressed by the total weight% of both compounds on the basis of the solution, and is 1 to 2
It is preferably 0% by weight, especially 1 to 15% by weight.
In addition, the dispersion medium in the case of using the halogen-containing atom organic compound and the lone electron pair-containing organic compound as a suspension is not particularly limited, and in addition to those which do not dissolve the above compound in the above organic solvent, water It can be used. Further, the content of the above compound in the suspension is not particularly limited, but it is preferable that the content is approximately the same as the concentration in the solution state.

The preparation of the paste composition in the above or the above method can be carried out by mixing and kneading a predetermined amount of the above solution or suspension and the electrode catalyst. At this time, particularly when using a low molecular weight one as the halogen-containing atom organic compound and the lone electron pair-containing organic compound, in order to secure the viscosity of the paste composition and to form it on the support layer with a constant thickness. It is preferable to add a binder to the. As the binder, various thermoplastic resins are generally used, but examples of thermoplastic resins that can be preferably used include polyvinyl chloride, polytetrafluoroethylene, polyvinylidene fluoride, and tetrafluoroethylene-perfluoroalkyl. Examples thereof include vinyl ether copolymers, polyether ether ketones, polyether sulfones, styrene / isoprene copolymers, hydrogenated acrylonitrile / butadiene copolymers and the like. The content of the binder is preferably 5 to 30 parts by weight with respect to 100 parts by weight of the conductive agent supporting the electrode catalyst (metal component). The binder may be used alone,
You may use it in mixture of 2 or more types. Further, conventionally known ion conductivity-imparting agents and other additives may be added as long as the effects of the present invention are not impaired.

The method of molding the paste composition prepared as described above in the above or the above method is not particularly limited, and for example, roll molding can be performed, but usually, a solid polymer electrolyte membrane, carbon paper or the like is supported. Molded on layer material. Examples of the method of molding on these support layers include a method of printing or coating on a support layer material, a method of coating on a blank and transferring to a solid polymer electrolyte membrane, and the like. In the above method, a solution of the halogen-containing atom organic compound or the lone electron pair-containing organic compound which is not contained in the molded body is applied to the surface of the molded body obtained after molding in this way to obtain a solution. The compound of (1) is permeated into the molded body to finally obtain a molded body made of a composition containing the halogen-containing atom organic compound, the lone electron pair-containing organic compound, and the electrode catalyst. Usually, the paste-like composition containing the electrode contact is filled and adhered in the voids and on the surface of such a support layer material so as to have a thickness of 5 to 50 μm.

As the support layer material used at this time, those used in conventional polymer type fuel cells can be used without any limitation. For example, as the solid polymer electrolyte membrane, known cation exchange resin membranes or anion exchange resin membranes known to be usable as solid polymer electrolyte membranes for polymer electrolyte fuel cells can be used without limitation. However, it is preferable to use a hydrocarbon-based anion exchange membrane from the viewpoint that the problems (i) to (iv) described above as the conventional techniques are unlikely to occur. An example of a hydrocarbon-based anion exchange membrane that can be preferably used is a desired anion exchange by treatment of a copolymer such as chloromethylstyrene-divinylbenzene copolymer or vinylpyridine-divinylbenzene with amination or alkylation. A membrane in which a group is introduced can be used. These anion exchange resin membranes are generally woven fabrics, woven fabrics, porous membranes, etc. made of thermoplastic resin supported by a substrate, but they have low gas permeability and can be thinned. Therefore, as the base material, a thermoplastic resin such as a polyolefin resin such as polyethylene, polypropylene or polymethylpentene, or a fluorine resin such as polytetrafluoroethylene, poly (tetrafluoroethylene-hexafluoropropylene) or polyvinylidene fluoride. It is preferable to use a substrate made of a porous film. The thickness of these hydrocarbon-based anion exchange membranes is preferably 5 to 200 μm, more preferably from the viewpoint of suppressing the electrical resistance to a low level and imparting the mechanical strength required for the supporting membrane. Is preferably 20 to 150 μm.
As the other support layer material, a porous membrane such as carbon fiber woven fabric or carbon paper is usually used. The thickness of these support layer materials is preferably 50 to 300 μm,
The porosity is preferably 50 to 90%.

Next, in the production method of the present invention, a composition containing the thus obtained "two or more kinds of organic compounds capable of cross-linking by contact with each other to form an ion exchange resin" and an electrode catalyst. The two or more kinds of organic compounds contained in the "molded product" are crosslinked and converted into an ion exchange resin. The crosslinking method at this time is not particularly limited and may be appropriately determined depending on the types of the above-mentioned two or more types of compounds used. Generally, heat treatment, light irradiation, these treatments by adding a radical polymerization initiator and the like can be mentioned. When a radical polymerization initiator is used, the radical polymerization initiator may be mixed in the paste in advance. When a combination of the organic compound containing a halogen atom and the organic compound containing a lone electron is adopted as the above-mentioned two or more compounds, the crosslinking can be easily carried out by a heat treatment.

In this case, the heating conditions for crosslinking are as follows: the type and composition of the compound used, the type of polymerization initiator used when the monomers are used as compounds, and the type of polymerization initiator used when the polymerization reactions are carried out together, and the supporting layer used. It may be appropriately determined in consideration of the heat resistance of the material, but general heating conditions include a heating temperature of 40 to 200 ° C, preferably 80 ° C to 12 ° C.
The temperature is 0 ° C. and the heating time is about 5 to 120 minutes.

The heat treatment can also be carried out as a thermocompression bonding treatment for producing a solid polymer electrolyte membrane / gas diffusion electrode assembly by thermocompression bonding the gas diffusion electrode to the solid polymer electrolyte membrane. The apparatus used at this time is an apparatus capable of pressurizing and heating, generally, a hot press machine, a roll press machine or the like. The pressing temperature may be higher than the glass transition temperature of the solid polymer electrolyte membrane, and generally 80 ° C to 2 ° C.
The pressure is 00 ° C., and the pressing pressure is usually 0.5 to 20 MPa, although it depends on the thickness and hardness of the gas diffusion electrode used. Further, in producing the solid polymer electrolyte membrane / gas diffusion electrode assembly, the gas diffusion electrode obtained by the production method of the present invention may be applied to at least one surface of the solid polymer electrolyte membrane, and the other It is also possible to apply a gas diffusion electrode manufactured by a conventional method to this surface.

By performing such heat treatment,
A cross-linking reaction occurs by the mechanism as described above, and an ion exchange resin having a cross-linking structure having a portion of the onium salt formed as a (anion) ion exchange group is formed. The ion exchange resin functions as an ion conductivity-imparting agent, and the molded body after the heat treatment consequently functions as a gas diffusion electrode. It is of course possible to use the gas diffusion electrode after the heat treatment as it is, but for the reason that high output characteristics can be obtained, a halide which is a counter anion of the onium ion of the above-mentioned onium salt part which becomes an anion exchange group. It is preferable to use by replacing the ions with hydroxide ions. Such ion exchange can be easily performed by treating with an alkaline aqueous solution.

In the production method of the present invention, not only an anion exchange resin but also a cation exchange resin is selected depending on the type of "two or more kinds of organic compounds capable of cross-linking to form an ion exchange resin by contacting each other". Since a gas diffusion electrode containing a resin can be manufactured, any gas diffusion electrode can be manufactured as long as it is a gas diffusion electrode of a polymer electrolyte fuel. However, its effect when used in the production of a gas diffusion electrode containing an anion exchange resin as an ion conductivity imparting agent for polymer electrolyte fuel cells using a hydrocarbon-based anion exchange membrane as a solid polymer electrolyte membrane It is particularly suitable to use as a method for producing such a gas diffusion electrode, since it exhibits the most.

The gas diffusion electrode and the solid polymer electrolyte membrane / gas diffusion electrode assembly thus prepared using the production method of the present invention are solid polymer having a basic structure as shown in FIG. It is used by being attached to a fuel cell.

[0034]

The present invention will be described below with reference to examples and comparative examples, but the present invention is not limited to these examples. The characteristics shown in Examples and Comparative Examples are values measured by the following methods.

(1) Fuel cell output voltage Anion exchange membrane / gas diffusion electrode assembly is sandwiched by carbon paper electrodes having a thickness of 200 μm and a porosity of 80% from both sides, and the fuel having the structure shown in FIG. Incorporated into a battery cell, pressure of 2 atm, fuel cell temperature 50 ℃, humidification temperature 50 ℃ oxygen and hydrogen 200 (ml / mi) each
n. ), 400 (ml / min.) To perform a power generation test, and current density is 0 (A / cm ² ), 0.3 (A / c).
The terminal voltage of the cell at m ² ), and 1.0 (A / cm ² ) was measured.

(2) Durability evaluation After the output voltage was measured, the cell temperature was 50 ° C. and the current density was 0.
A continuous power generation test was performed under the conditions of 3 A / cm ² and 250
The output voltage after a lapse of time was measured to evaluate the durability of the hydroxide ion conductivity-imparting agent.

(3) Bonding Evaluation After the above durability evaluation, the fuel cell was disassembled, the carbon paper was peeled from the anion exchange membrane / gas diffusion electrode assembly, and the anion exchange membrane side of the oxidant chamber was removed. The amount of platinum-supporting carbon adhering to the surface was visually observed. Bonding strength is good when the platinum-supporting carbon is uniformly attached to the surface of the cation exchange membrane (○), and bonding strength is poor when the platinum-supporting carbon is peeled off and the anion-exchange membrane surface is exposed (x).
It was evaluated.

(4) Water resistance evaluation After the evaluation of the output voltage, the fuel cell was disassembled, and the anion exchange membrane / gas diffusion electrode assembly on the oxidant chamber side was
The presence or absence of a discoloration area (area surrounded by a dotted line in FIG. 2) due to the flow of the ion conductivity imparting agent due to the produced water on the surface of the anion exchange membrane around the gas diffusion electrode was observed to impart the hydroxide ion conductivity. The water resistance of the agent was evaluated.

Examples 1 to 4 First, a porous membrane made of polyethylene was used as a base material, a vinylpyridine-divinylbenzene copolymer was quaternized with methyl iodide and a pyridinium group was introduced, and the anion exchange capacity was 2.4 mmol /. On the anion exchange membrane having a thickness of 30 μm and a thickness of 30 μm, carbon black loaded with 30% by weight of platinum having an average particle size of 2 nm as an electrode catalyst, a halogen-containing organic compound shown in Table 1, and a lone electron pair are contained. The paste-like composition obtained by mixing the organic compound and the organic solvent in the weight ratio shown in Table 1 was applied and heated at 25 ° C. for 6 hours.
Next, the film-like material thus obtained is treated at 100 ° C. and a pressure of 5M.
After thermocompression bonding for 100 seconds under a pressure of Pa, it was left at room temperature for 2 minutes. Then, it was immersed in a 0.1 N aqueous sodium hydroxide solution to replace the halide ion, which is a counter anion, with a hydroxide ion, to prepare an anion exchange membrane / gas diffusion electrode assembly. In the gas diffusion electrode, a conductive agent (carbon black) carrying an electrode catalyst (platinum)
The content of the ion-conductivity imparting agent is 20% by weight, and the content of platinum in the electrocatalyst phase is 1 mg /
cm ² .

[0040]

[Table 1]

The anion exchange membrane / gas diffusion electrode assembly thus obtained was assembled into a fuel cell, and then the fuel cell output voltage, bonding property, water resistance and durability were measured. The results are shown in Table 2.

[0042]

[Table 2]

Examples 5 to 8 As a paste composition, the halogen-containing atom organic compound, lone electron pair-containing organic compound, polymerization initiator and binder shown in Table 3 were used, except that heating was carried out at 80 ° C. for 8 hours. An anion exchange membrane / gas diffusion electrode assembly was prepared in the same manner as in Example 1.

[0044]

[Table 3]

After the obtained anion-exchange membrane / gas diffusion electrode assembly was incorporated in a fuel cell, the fuel cell output voltage, bonding property, water resistance and durability were measured. The results are shown in Table 2.

Comparative Example 1 As the hydroxide ion conductivity-imparting agent, polyvinyl pyridine having an average molecular weight of 100,000 was quaternized with methyl iodide (anion exchange capacity 5.0: 20 ° C., solubility in water: 50% by weight). After preparing an anion exchange membrane / gas diffusion electrode assembly using the 10% aqueous solution of 1) and incorporating it into a fuel cell,
The fuel cell output voltage, bondability, water resistance and durability were measured. The results are shown in Table 2.

In the comparative example, as the ion conductivity imparting agent,
This is an example using a water-soluble hydrocarbon-based anion exchange resin solution, but the water resistance is poor and the fuel cell output is reduced as compared with the results of the examples.

Comparative Example 2 A 5% solution of a perfluorocarbon sulfonic acid resin (cation exchange capacity 0.9) in alcohol and water (manufactured by Aldrich Co.) was dried under reduced pressure, and the resin was taken out and sulfonated with thionyl chloride. The group was converted to a sulfonyl chloride group. Then, it is reacted with N, N, N'-tetramethylethylenediamine to convert it into a sulfonic acid amide group, which is then quaternized with methyl iodide, and this is dispersed in a mixed solution of water and 1-propanol to obtain ionic conductivity. It was used as a solution of the property imparting agent (5% by weight solution). An anion exchange membrane / gas diffusion electrode assembly was prepared using this solution and incorporated into a fuel cell, and then the fuel cell output voltage, bondability, water resistance and durability were measured. The results are shown in Table 2.

The comparative example is an example in which a perfluorocarbon resin-based anion exchange resin was dispersed in a solvent as an ion conductivity-imparting agent, but the bonding strength was poor and the fuel cell output was reduced as compared with the results of the examples. ing.

Comparative Example 3 Quaternary ammonium salt type styrene-divinylbenzene copolymer (divinylbenzene content 8% by weight: anion exchange capacity 3.7, solubility in water and methanol 0.01% by weight or less) (organo) (Product name: Amber Light)
Was crushed and dispersed in 1-propanol to obtain an ion conductivity imparting agent solution (10% by weight solution). An anion exchange membrane / gas diffusion electrode assembly was prepared using this solution, and after being assembled in a fuel cell, the fuel cell output voltage,
The bondability, water resistance and durability were measured. The results are shown in Table 2.

The comparative example is an example in which a hydrocarbon type anion exchange resin was dispersed in a solvent as an ion-conductivity imparting agent, but the bonding property was poor and the fuel cell output decreased as compared with the results of the examples. There is.

[0052]

EFFECTS OF THE INVENTION According to the production method of the present invention, it is expected as a solid electrolyte membrane / gas diffusion electrode assembly for a fuel cell which can stably maintain a high output voltage even when methanol is used as a fuel. The gas diffusion electrode suitable for the existing hydrocarbon-based anion exchange membrane / gas diffusion electrode composite can be easily manufactured. And, although the gas diffusion electrode of the present invention produced by the production method of the present invention uses an ion exchange resin having a crosslinked structure as the ion conductivity imparting agent, the ion conductivity imparting agent is uniformly dispersed. However, the adhesion with the electrode catalyst is good, and the effective utilization rate of the electrode catalyst can be increased. Further, since the above ion exchange resin has a crosslinked structure, it is not easily affected by fuel, water present in fuel or water produced as a by-product, and the gas diffusion electrode of the present invention has excellent heat resistance and chemical resistance. As a result, an electrolyte fuel cell using the gas diffusion electrode of the present invention, particularly an electrolyte fuel cell using a hydrocarbon-based anion exchange membrane,
Not only the output characteristics are excellent, but also the effect is high and the fuel cell has high durability.

[Brief description of drawings]

FIG. 1 is a conceptual diagram showing a basic structure of a polymer electrolyte fuel cell.

FIG. 2 is an anion exchange membrane / when an outflow of an ion conductivity-imparting agent occurs after evaluation of an output voltage.
It is a figure which shows the oxidizing agent chamber side surface of a gas diffusion electrode assembly.

[Explanation of symbols]

1; Battery partition 2; Fuel gas flow hole 3; Oxidant gas flow hole 4; Fuel chamber side gas diffusion electrode 5: Gas diffusion electrode on the oxidant chamber side 6; Solid polymer electrolyte (anion exchange membrane) 7; Fuel chamber 8; Oxidizer chamber 9: Discoloration area due to outflow of hydroxide ion conductivity-imparting agent

Continued front page    F-term (reference) 5H018 AA06 AS02 AS03 BB01 BB12                       BB16 EE03 EE16                 5H026 AA06 BB01 BB10 EE02 EE17

Claims (8)

[Claims] 1. A molded body comprising a composition containing two or more kinds of organic compounds capable of cross-linking to form an ion exchange resin by contacting each other and an electrode catalyst, and thereafter contained in the molded body. A method for producing a gas diffusion electrode for a polymer electrolyte fuel cell, which comprises cross-linking the two or more kinds of organic compounds. 2. As two or more kinds of organic compounds capable of forming an ion exchange resin by being cross-linked by coming into contact with each other,
(1) A halogen-containing organic compound having at least one halogen atom at the terminal, and (2) At least one atom having a lone electron pair in the molecule, and the halogen-containing organic compound and onium at the atom. A combination of lone pair-containing organic compounds capable of forming a salt and binding, wherein a combination of compounds that crosslinks by a bond accompanied by the formation of the onium salt is used, and the composition is heat-treated after molding. The method according to claim 1, wherein the compound is crosslinked. 3. A solution or suspension of the lone electron pair-containing organic compound and the halogen-containing atom organic compound,
Mold the paste composition obtained by mixing with the electrode catalyst,
Next, the obtained molded body is heat-treated, and the manufacturing method according to claim 2. 4. A paste-like composition obtained by mixing a solution or suspension of the lone electron pair-containing organic compound or a solution or suspension of the halogen-containing atom-containing organic compound with an electrode catalyst is molded and then obtained. The manufacturing method according to claim 2, wherein a heat treatment is performed after applying the solution of the halogen-containing atom organic compound or the solution of the lone electron pair-containing organic compound on the surface of the formed body. 5. The method according to claim 2, wherein a halide ion, which is a counter anion of the onium ion in the ion exchange resin formed in the molded body after the heat treatment, is converted into a hydroxide ion. A manufacturing method characterized by replacement. 6. A gas diffusion electrode manufactured by the method according to claim 1. 7. A solid polymer comprising a bonded body in which the gas diffusion electrode manufactured by the method according to any one of claims 1 to 5 is bonded to at least one surface of the solid polymer electrolyte membrane. Type fuel cell member. 8. A polymer electrolyte fuel cell comprising the member according to claim 7 as a constituent member.