WO2003088386A1

WO2003088386A1 - Fuel cell, electrode for fuel cell, and method for manufacturing them

Info

Publication number: WO2003088386A1
Application number: PCT/JP2003/004853
Authority: WO
Inventors: Shin Nakamura; Yoshimi Kubo; Tsutomu Yoshitake; Yuichi Shimakawa; Takashi Manako; Takeshi Obata; Hidekazu Kimura; Hideto Imai; Sadanori Kuroshima
Original assignee: Nec Corporation
Priority date: 2002-04-17
Filing date: 2003-04-16
Publication date: 2003-10-23

Abstract

The adhesion at the interface between the surface of an electrode and the solid polyelectrolyte membrane is enhanced, and the cell characteristics and the reliability of the cell are improved. A fuel cell comprising a solid polyelectrolyte membrane (114), a fuel electrode (102) provided on the electrolyte membrane, and an oxidizer electrode (108) also provided on the electrolyte membrane, wherein the fuel electrode (102) has a catalyst layer containing carbon particles (140) carrying a catalyst, a first solid polyelectrolyte (150), and a second polyelectrolyte (160) having a stronger adhesion to the solid polyelectrolyte membrane (114) than the first solid polyelectrolyte (150).

Description

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TECHNICAL FIELD The present invention relates to a fuel cell, an electrode for a fuel cell, and a method for producing the same.

The present invention relates to a fuel cell, an electrode for a fuel cell, and a method for producing the same. Conventional technology

A polymer electrolyte fuel cell is composed of a solid polymer electrolyte membrane such as a perfluorosulfonic acid membrane as an electrolyte, and a fuel electrode and an oxidizer electrode bonded to both sides of the membrane. This is a device that supplies oxygen to the agent electrode and generates power by an electrochemical reaction.

The following electrochemical reaction occurs in each electrode.

Fuel electrode: H ₂ → 2 H ++ 2 e-Oxidizer electrode: l Z2〇 ₂ + 2 H ++ 2 e— → H ₂ 〇

By this reaction, the polymer electrolyte fuel cell can obtain a high output of 1 A / cm ² or more at normal temperature and normal pressure.

Each of the fuel electrode and the oxidizer electrode is provided with a mixture of carbon particles carrying a catalytic substance and a solid polymer electrolyte. In general, this mixture is applied to an electrode substrate such as a carbon paper which serves as a fuel gas diffusion layer. A fuel cell is constructed by sandwiching a solid polymer electrolyte membrane between these two electrodes and thermocompression bonding.

In the fuel cell having this configuration, the hydrogen gas supplied to the fuel electrode passes through the pores in the electrode and reaches the catalyst, and emits electrons to become hydrogen ions. The emitted electrons are guided to the external circuit through the carbon particles and the solid electrolyte in the fuel electrode, and flow into the oxidant electrode from the external circuit.

On the other hand, the hydrogen ions generated at the fuel electrode reached the oxidizer electrode through the solid polymer electrolyte in the fuel electrode and the solid polymer electrolyte membrane disposed between both electrodes, and were supplied to the oxidizer electrode. The oxygen reacts with the electrons flowing from the external circuit to produce water as shown in the above reaction formula. As a result, in the external circuit, electrons travel from the fuel electrode to the oxidizer electrode. JP03 / 04853

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Flow, and power is extracted.

In order to improve the characteristics of the fuel cell having the above structure, it is important that the interface between the electrode and the solid polymer electrolyte membrane has good adhesion. That is, it is required that the conductivity of the hydrogen ions generated by the electrode reaction be high at the interface between the two. Poor interfacial adhesion reduces the conductivity of hydrogen ions and increases the electrical resistance, which causes a reduction in battery efficiency.

The fuel cell using hydrogen as a fuel has been described above. In recent years, research and development of a fuel cell using an organic liquid fuel such as methanol has been actively conducted.

Fuel cells that use organic liquid fuel include those that reform organic liquid fuel into hydrogen gas and use it as fuel, and those that do not reform organic liquid fuel, such as direct methanol fuel cells. There is known a fuel cell that supplies fuel directly to a fuel electrode.

Above all, a fuel cell that supplies organic liquid fuel directly to the anode without reforming it does not require a device such as a reformer because it has a structure that supplies organic liquid fuel directly to the anode. Therefore, there is an advantage that the configuration of the battery can be simplified, and the entire device can be reduced in size. In addition, organic liquid fuels can be easily and safely transported compared to gaseous fuels such as hydrogen gas and hydrocarbon gas.

Generally, in a fuel cell using an organic liquid fuel, a solid polymer electrolyte membrane made of a solid high molecular ion exchange resin is used as an electrolyte. Here, in order for the fuel cell to function, hydrogen ions need to move through the membrane from the fuel electrode to the oxidizer electrode, but this movement of hydrogen ions may involve the movement of water. Known, it is necessary that the membrane contain a certain amount of moisture.

However, when an organic liquid fuel such as methanol having a high affinity for water is used, the organic liquid fuel diffuses into the solid polymer electrolyte membrane containing water and further reaches the oxidant electrode (crossover). ). '' This crossover causes the voltage, output, and fuel efficiency to drop because the organic liquid fuel, which should originally provide electrons at the fuel electrode, is oxidized at the oxidant electrode and is not used effectively as fuel. .

From the viewpoint of solving such a crossover problem, the solid polymer electrolyte membrane 03 04853

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It is desirable to select a polymer with a low water content as the material and to suppress the diffusion of organic liquid fuel such as methanol with water. However, for the catalyst layer on the electrode surface in contact with the electrolyte membrane, it is important to efficiently move the organic liquid fuel as fuel from the electrode layer and supply a large amount of hydrogen ions. That is, it is desirable that the catalyst layer on the electrode surface is permeable to the organic liquid fuel and the electrolyte membrane is permeable to the organic liquid fuel. In order to achieve this, the polymer constituting the catalyst layer on the electrode surface should be a polymer having a high water content and high permeability to organic liquid fuel, and the polymer constituting the solid polymer electrolyte membrane should be used. It is considered preferable to use a material having a low water content and a property of low permeability for organic liquid fuel.

Japanese Patent Application Laid-Open Publication No. 2001-167775 discloses a technology relating to an ion conductive film which enables to suppress crossover of methanol while maintaining ion conductivity. . Here, the surface layer of an ion conductive film having a basic structure of a fluororesin such as Nafion (registered trademark) is modified by electron beam irradiation or the like so that the conductivity becomes lower than the internal conductivity. ing. Problems to be solved by the invention

However, when the material of the electrode surface catalyst layer and the material of the solid polymer electrolyte membrane are different from each other as described above, in general, sufficient adhesion cannot be obtained, and the gap between the electrode surface and the solid polymer electrolyte membrane is generally low. Peeling may occur at the interface. When such peeling occurs, the electrical resistance at the interface increases, which causes a decrease in the reliability of the battery performance. Also, as described in the above-mentioned patent document, when the surface layer of the ion-conductive film is modified, the surface strength of the ion-conductive film at the time of swelling is increased, and the adhesion to the electrode surface catalyst layer is deteriorated. There was a problem that.

In view of the above circumstances, an object of the present invention is to increase the adhesion at the interface between the surface of the catalyst electrode and the solid polymer electrolyte membrane, thereby improving battery characteristics and battery reliability.

Another object of the present invention is to suppress the crossover of the organic liquid fuel while maintaining good hydrogen ion conductivity and permeability of the organic liquid fuel in the catalyst electrode. Disclosure of the invention

As a solid polymer electrolyte of a fuel cell, a solid polymer electrolyte having high hydrogen ion conductivity represented by Nafion (registered trademark) or the like is generally used. The high proton conductivity of the solid polymer electrolyte is manifested by the polymer electrolyte containing a large amount of water.On the other hand, the large amount of water causes the organic liquid fuel such as methanol to be produced. It will easily dissolve in water to promote mouth mouthover.

In order to suppress crossover, the present inventor has sought to use a polymer material having lower organic liquid fuel permeability than naphion or the like as the fuel electrode, oxidizer electrode, or solid polymer electrolyte constituting the solid polymer electrolyte membrane. A direct methanol fuel cell was fabricated using this and evaluated. However, the characteristics of this fuel cell were lower than those of a conventional cell using naphion. This is thought to be due to the decrease in methanol permeability and hydrogen ion conductivity at the fuel electrode. The fuel electrode of the fuel cell includes a catalyst layer in which carbon particles carrying a catalyst and a solid polymer electrolyte as a binder are mixed, and the solid polymer electrolyte is interposed between the catalysts. Structure. For this reason, in order for methanol, hydrogen, and electrons to move smoothly on the electrode surface, the solid polymer electrolyte serving as these transmission paths has high permeability to liquid fuel such as methanol and excellent hydrogen ion conductivity. It is necessary to be. It is probable that in the battery with the above structure, good performance was not obtained because the solid polymer electrolyte did not sufficiently satisfy these performances.

Next, in order to improve the efficiency of the catalytic reaction at the fuel electrode, the present inventors used Nafion as the solid polymer electrolyte on the electrode surface, and used the solid polymer electrolyte membrane as an organic liquid fuel permeability rather than Nafion or the like. An attempt was made to fabricate a direct methanol fuel cell using a polymer material with a low molecular weight. However, the bonding between the fuel electrode and the solid polymer electrolyte membrane was insufficient, and a battery that could withstand the evaluation could not be obtained.

Based on the results of the preliminary experiments described above, as a result of further studies, the present inventors have found that the electrode surface is composed of a plurality of types of solid polymer electrolytes, so that the distance between the electrode surface and the solid polymer electrolyte membrane can be improved. It has been found that the adhesion at the interface can be improved, and the present invention has been completed. According to the present invention, there is provided a solid polymer electrolyte membrane, and a catalyst electrode provided on the solid polymer electrolyte membrane, wherein the catalyst electrode comprises: a catalyst substance; a first solid polymer electrolyte; There is provided a fuel cell including a catalyst layer including a second solid polymer electrolyte having higher adhesion to the solid polymer electrolyte membrane than the first solid polymer electrolyte.

Further, according to the present invention, the solid polymer electrolyte membrane includes: a catalyst electrode disposed on the solid polymer electrolyte membrane; the catalyst electrode includes a catalyst substance, a first solid polymer electrolyte, A fuel layer comprising a polymer different from the one solid polymer electrolyte; and a second solid polymer electrolyte comprising a polymer constituting the solid polymer electrolyte membrane or a derivative thereof. A battery is provided.

In the above fuel cell, the catalyst layer and the solid polymer electrolyte membrane may be in contact with or separated from each other. If a configuration in which these are in contact with each other is adopted, the adhesion at the interface between the catalyst electrode and the solid polymer electrolyte membrane can be reliably improved.

The “catalyst electrode” in the present invention is an electrode containing a catalyst, and is used as a general term including a fuel electrode and an oxidizer electrode. The solid polymer electrolyte that constitutes the catalyst layer of the catalyst electrode has the role of electrically connecting the catalyst-supporting carbon particles and the solid polymer electrolyte membrane on the electrode surface and allowing the organic liquid fuel to reach the catalyst surface. Therefore, hydrogen ion conductivity and water mobility are required. Further, the fuel electrode is required to be permeable to organic liquid fuel such as methanol, and the oxidizer electrode is required to be permeable to oxygen.

The solid polymer electrolyte constituting the catalyst layer in the present invention includes the first solid polymer electrolyte and the second solid polymer electrolyte. Among them, the first solid polymer electrolyte has the above-mentioned role. Fulfill. As a material constituting the first solid polymer electrolyte, a material excellent in hydrogen ion conductivity and organic liquid fuel permeability such as methanol is preferably used.

On the other hand, the solid polymer electrolyte membrane separates the fuel electrode and the oxidizer electrode, and has a role to transfer hydrogen ions between the two.In addition, the liquid fuel moves from the fuel electrode to the oxidizer electrode, that is, It is desirable to have the property of suppressing the crossover of organic liquid fuel. T / JP03 / 04853

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As described above, since the properties required for the fuel electrode, the oxidizer electrode, and the solid electrolyte membrane are different from each other, it is preferable that the fuel electrode and the oxidant electrode be formed of different materials. However, in such a case, it is generally difficult to ensure sufficient adhesion between the two. Therefore, the present invention provides a solid polymer electrolyte on the electrode surface with a plurality of types having different functions to improve the adhesion between the electrodes and the solid polymer electrolyte membrane while selecting a suitable material.

That is, the catalyst electrode according to the present invention is configured to include the first and second solid polymer electrolytes, and the first solid polymer electrolyte allows the hydrogen ion liquid fuel to move smoothly on the electrode surface. In addition to ensuring security, the interface between the catalyst electrode and the solid polymer electrolyte membrane is firmly adhered to by the second solid polymer electrolyte. According to the present invention, by adopting such a configuration, it is possible to suppress a rise in electric resistance at the interface between the catalyst electrode and the solid polymer electrolyte membrane, and to maintain good battery efficiency over a long period of time. Can be realized.

The reason why the interface between the catalyst electrode and the solid polymer electrolyte membrane is firmly adhered by the second solid polymer electrolyte is presumed as follows. First, the particles can be made of a material having excellent adhesion to the solid polymer electrolyte membrane, for example, a high molecule constituting the solid polymer electrolyte membrane or a derivative thereof. Further, the particles of the second solid polymer electrolyte can be made of a material having similar physical properties such as polarity, wettability and SP value to the material constituting the solid polymer electrolyte membrane. Thereby, the adhesion of the second solid polymer electrolyte to the solid polymer electrolyte membrane can be higher than that of the first solid polymer electrolyte. For this reason, good adhesion is developed between the first solid polymer electrolyte and the solid polymer electrolyte membrane. On the other hand, since the first solid polymer electrolyte and the second solid polymer electrolyte are in a form in which both are mixed to form a layer, the adhesion between the two is sufficiently good. From the above, the second solid polymer electrolyte shows good adhesion to both the solid polymer electrolyte membrane and the first solid polymer electrolyte, and as a result, the catalyst electrode and the solid polymer electrolyte membrane Are firmly joined.

In the fuel cell according to the present invention, an organic liquid fuel may be supplied to the catalyst electrode. That is, a so-called direct type fuel cell can be obtained. Here, the organic liquid fuel can be, for example, methanol. Direct fuel cells have the advantages of high cell efficiency, space savings because a reformer is not required, and the like, but have the problem of crossover of organic liquid fuels such as methanol. Become. According to the present invention, it is possible to eliminate the problem of crossover while suppressing an increase in electric resistance at the interface between the catalyst electrode and the solid polymer electrolyte membrane, and stably maintain good battery efficiency over a long period of time. Can be realized. In the present invention, the catalyst electrode can include a porous substrate, and the catalyst layer can be provided in contact with the porous substrate. The content of the catalyst substance in the catalyst layer may have a distribution along the direction from the porous substrate to the solid polymer electrolyte membrane. For example, a configuration in which the catalyst layer contains a catalyst substance on the side in contact with the porous substrate and does not contain a catalyst substance on the side in contact with the solid polymer electrolyte membrane can be employed.

Further, the content of the first solid polymer electrolyte in the catalyst layer may have a distribution along a direction from the porous substrate to the solid polymer electrolyte membrane. For example, a configuration can be adopted in which the adhesive layer includes the first solid polymer electrolyte on the side in contact with the porous substrate, and does not include the first solid polymer electrolyte on the side in contact with the solid polymer electrolyte membrane. At the same time, the adhesive layer may not include the second solid polymer electrolyte on the side in contact with the porous base material, and may include the second solid polymer electrolyte on the side in contact with the solid polymer electrolyte membrane. it can. By doing so, the adhesion between the catalyst layer and the solid polymer electrolyte membrane can be improved.

Further, according to the present invention, there is provided a catalyst layer including a catalyst substance, a first solid polymer electrolyte, and a second solid polymer electrolyte made of a polymer different from the first solid polymer electrolyte. An electrode for a fuel cell is provided.

In the present invention, the solid polymer electrolyte on the electrode surface is composed of a plurality of types having different functions. For this reason, it is possible to stably realize performance that is difficult to achieve with a single type of solid polymer electrolyte.

For example, as in the description of the fuel cell according to the present invention, the smooth movement of hydrogen ions and liquid fuel on the electrode surface is ensured by the first solid polymer electrolyte, and the catalyst is formed by the second solid polymer electrolyte. The interface between the electrode and the solid polymer electrolyte membrane is firmly adhered to, and the increase in electrical resistance at the interface between the catalyst electrode and the solid polymer electrolyte membrane is suppressed, and good battery efficiency is maintained over a long period of time. Achieving stability for the whole time Can be.

Also, of the first and second solid polymer electrolytes, a material having excellent hydrogen ion conductivity and liquid fuel permeability is selected as the first solid polymer electrolyte. As an electrolyte, it is inferior in terms of hydrogen ion conductivity or liquid fuel permeability compared to the first solid polymer electrolyte, but is a low-cost material, or contributes to improvement in manufacturing stability such as film forming properties. Material can be selected. By doing so, it is possible to stably realize excellent electrode performance while realizing inexpensive cost or good manufacturing stability.

Furthermore, according to the present invention, there is provided a method for producing an electrode for a fuel cell in which a catalyst layer is provided on a substrate, comprising: conductive particles carrying a catalyst substance; a first solid polymer electrolyte; A step of applying a coating solution containing a second solid polymer electrolyte composed of a polymer different from the solid polymer electrolyte onto a substrate to form the catalyst layer, A manufacturing method is provided.

According to this production method, the coating solution containing the first and second solid polymer electrolytes is applied to the base to form the catalyst layer, and thus the first and second solid polymer electrolytes are formed in the catalyst layer. Are mixed well. For this reason, the respective characteristics of both are effectively exhibited, and both the performance of the catalyst electrode and the adhesion between the catalyst electrode and the solid polymer electrolyte membrane are improved.

The coating liquid may have a structure in which particles containing the first solid polymer electrolyte and particles containing the second solid polymer electrolyte are dispersed in the coating liquid. By doing so, workability during coating and production stability can be improved.

The catalyst electrode obtained by the above manufacturing method comprises a plurality of types of solid polymer electrolytes having different functions on the electrode surface. For this reason, it is possible to stably realize performance that is difficult to achieve with a single type of solid polymer electrolyte.

Further, according to the present invention, after the catalyst electrode is obtained by the above-described method for producing an electrode for a fuel cell, the catalyst electrode and the solid polymer electrolyte are contacted with the catalyst layer and the solid polymer electrolyte membrane in contact with each other. A method for manufacturing a fuel cell, comprising a step of thermocompression bonding with a membrane is provided. According to this manufacturing method, the adhesive layer can be stably formed in a simple process, and a fuel cell having good adhesion between the catalyst electrode and the solid polymer electrolyte membrane can be obtained. It can be obtained stably.

In the present invention, the second solid polymer electrolyte preferably has a lower permeability of the organic liquid fuel than the first solid polymer electrolyte. By doing so, it becomes possible to obtain the adhesion with the solid polymer electrolyte membrane while securing the organic liquid fuel permeability and the hydrogen ion conductivity in the catalyst electrode. To achieve this, for example, the following configuration may be used.

(i) The second solid polymer electrolyte has a lower water content than the first solid polymer electrolyte.

(ii) the first solid polymer electrolyte and the second solid polymer electrolyte each include a protonic acid group; and the second solid polymer electrolyte comprises the first solid polymer electrolyte. The density of the protonic acid groups is lower than that of the molecular electrolyte. Here, the protonic acid group is, for example, one or more polar groups selected from the group consisting of a sulfone group, a carboxyl group, a phosphoric acid group, a phosphonic acid group and a phosphinic acid group. -In the present invention, the first solid polymer electrolyte may be constituted by a fluorine-containing high molecule.

Further, in the present invention, the second solid polymer electrolyte may be constituted by a high molecule not containing fluorine.

Further, in the present invention, the second solid polymer electrolyte may be constituted by a polymer containing an aromatic.

The measurement of the resin content and the catalyst content in the present invention can be performed by, for example, a method such as performing secondary ion mass spectrometry (SIMS) while sputtering the layer structure to be measured from the surface. it can. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a sectional view schematically showing the structure of an example of the fuel cell of the present invention. FIG. 2 is a cross-sectional view schematically showing a fuel electrode, an oxidizer electrode, and a solid polymer electrolyte membrane in an example of the fuel cell of the present invention.

FIG. 3 shows the fuel electrode and the solid polymer electrolyte membrane in the fuel cell according to the embodiment of the present invention. It is the figure which showed typically.

FIG. 4 is a diagram schematically showing a fuel electrode and a solid polymer electrolyte membrane in the fuel cell of Comparative Example 1. ,

Reference numeral 100 denotes a fuel cell. Reference numeral 101 denotes an electrode-electrolyte assembly. Reference numeral 102 is a fuel electrode. Reference numeral 104 denotes a substrate. Reference numeral 106 denotes a catalyst layer. Reference numeral 108 denotes an oxidizer electrode. Reference numeral 110 denotes a substrate. Reference numerals 1 and 12 are catalyst layers. Reference numeral 114 denotes a solid polymer electrolyte membrane. Reference numeral 120 is a fuel electrode side separator. Reference numeral 122 denotes an oxidizer electrode side separator. Reference numeral 124 is fuel. Reference numeral 126 is an oxidizing agent. Reference numeral 140 is a carbon particle carrying a catalyst. Reference numeral 150 is a first solid polymer electrolyte. Reference numeral 160 is a second solid polymer electrolyte. Reference numeral 301 denotes a fuel electrode. BEST MODE FOR CARRYING OUT THE INVENTION

The catalyst electrode in the present invention contains a catalyst substance and first and second solid polymer electrolytes. Specifically, for example, a structure in which a catalyst layer containing conductive particles carrying a catalyst and first and second solid polymer electrolytes is formed on a substrate such as carbon paper or the like. it can. Here, carbon particles and the like are used as the conductive particles. The first and second solid polymer electrolytes serve to immobilize the conductive particles on the substrate and to electrically connect between the conductive particles and the solid polymer electrolyte membrane. In the catalyst layer, the first and second solid polymer electrolytes may be distributed uniformly or non-uniformly. Here, the content of the second solid polymer electrolyte on the surface of the catalyst layer opposite to the substrate (hereinafter, referred to as the first surface), that is, the surface in contact with the solid polymer electrolyte membrane, is defined as If the content of the second solid polymer electrolyte in the surface of the layer on the substrate side (hereinafter referred to as the second surface) is higher, the adhesion between the solid polymer electrolyte membrane and the catalyst electrode becomes better. . For example, if the first surface is mainly composed of the second solid polymer electrolyte and the second surface is mainly composed of the first solid polymer electrolyte, the transfer of hydrogen ions and organic liquid fuel on the electrode surface The adhesion between the catalyst electrode and the solid polymer electrolyte membrane can be improved while maintaining good properties. Hereinafter, an embodiment of the present invention will be described in detail.

FIG. 1 is a sectional view schematically showing the structure of the fuel cell according to the present embodiment. The electrode-electrolyte assembly 101 includes a fuel electrode 102, an oxidant electrode 108, and a solid polymer electrolyte membrane 114. The fuel electrode 102 is composed of a substrate 104 and a catalyst layer 106. The oxidant electrode 108 is composed of a base 110 and a catalyst layer 112. The plurality of electrode-electrolyte assemblies 101 are electrically connected via the fuel electrode side separator 120 and the oxidizing agent electrode side separator 122 to produce the fuel cell 100. .

In the fuel cell 100 configured as described above, the fuel electrode 102 of each electrode-electrolyte assembly 101 is supplied with the fuel 124 via the fuel electrode side separator 120. . In addition, an oxidizer 126 such as air or oxygen is supplied to the oxidizer electrode 108 of each electrode-electrolyte assembly 101 via an oxidizer electrode side separator 122. The solid polymer electrolyte membrane 114 has a role of separating the fuel electrode 102 from the oxidant electrode 108 and has a role of transferring hydrogen ions and water molecules between the two. For this reason, it is preferable that the solid polymer electrolyte membrane 114 has high conductivity for hydrogen ions. It is also preferable that the material is chemically stable and has high mechanical strength. Examples of the material constituting the solid polymer electrolyte membrane 114 include an organic polymer having a polar group such as a strong acid group such as a sulfone group, a phosphate group, a phosphone group, or a phosphine group, or a weak acid group such as a lipoxyl group. Is preferably used. Examples of such organic polymers include aromatic-containing polymers such as sulfonated poly (4-phenoxybenzoyl-1,4-phenylene) and alkylsulfonated polybenzoimidazole; polystyrene sulfonic acid copolymer, polyvinyl Copolymers such as sulfonic acid copolymers, cross-linked alkylsulfonic acid derivatives, fluororesin skeletons, and fluorine-containing polymers composed of sulfonic acid; acrylamides such as acrylamide-12-methylpropanesulfonic acid And copolymers obtained by copolymerizing acrylates such as n_butyl methacrylate; sulfonate-containing perfluorocarbons (Naphion (registered trademark, manufactured by DuPont), a complex (manufactured by Asahi Kasei Corporation) ); Carboxyl group-containing perfluorocarbon (Flemion (registered trademark) S film (Asahi Glass) Company, Ltd.)); and the like are exemplified. Of these, sulfonated poly (4-phenoxybenzoyl-1,4-phenylene), alkyl sulf When an aromatic-containing polymer such as polybenzoimidazole is selected, permeation of an organic liquid fuel can be suppressed, and a decrease in cell efficiency due to crossover can be suppressed.

FIG. 2 is a cross-sectional view schematically showing the fuel electrode 102, the oxidizer electrode 108, and the solid polymer electrolyte membrane 114. As shown in the figure, the fuel electrode 102 and the oxidizer electrode 108 are, for example, a catalyst layer 106 and a catalyst layer 1, each of which is a film containing carbon particles carrying a catalyst and fine particles of a solid polymer electrolyte. A configuration in which the substrate 12 is formed on the substrate 104 and the substrate 110 can be employed. The substrate surface may be subjected to a water-repellent treatment.

In addition, a crosslinkable substituent, for example, a vinyl group, an epoxy group, an acrylic group, a methacryl group, a cinnamoyl group, a methylol group, an azide group, or a naphthoquinonediazide group is appropriately introduced into the above-described polymer. A polymer crosslinked by irradiating the polymer with a radiation in a molten state can also be used.

For the base material 104 and the base material 110, both the fuel electrode 102 and the oxidizer electrode 108 are formed of carbon paper, carbon compact, sintered carbon, sintered metal, foamed metal, etc. Can be used. In addition, a water repellent such as polytetrafluoroethylene can be used for the water repellent treatment of the substrate.

Examples of the catalyst for the anode 102 include platinum, alloys of platinum and ruthenium, gold, rhenium, etc., rhodium, palladium, iridium, osmium, ruthenium, rhenium, gold, silver, nickel, cobalt, lithium. , Lanthanum, strontium, and lithium. On the other hand, as the catalyst for the oxidant electrode 108, the same catalyst as the catalyst for the fuel electrode 102 can be used, and the above-mentioned exemplified substances can be used. The catalyst of the fuel electrode 102 and the catalyst of the oxidation electrode 108 may be the same or different.

The carbon particles supporting the catalyst include acetylene black (Denka Black (registered trademark, manufactured by Denki Kagaku Kogyo), XC72 (Vu1can), etc.), ketjen black, carbon nanotubes, carbon nanohorns and the like. And the like. The particle size of the carbon particles is, for example, 0.01 to 1 m, preferably 0.02 to 0.06 m.

Here, the catalyst layer 106 and the catalyst layer 112 are made of a porous substrate 104 and a substrate. JP03 / 04853

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Each of the bases 104 and 110 may have a configuration in which it is formed to be exposed to the surface of the base 104 and the base 110. A configuration formed from the inside to the surface of 110 can also be adopted.

In the present invention, the fine particles of the solid polymer electrolyte constituting the fuel electrode 102 or the oxidizer electrode 108 have a constitution including at least a first solid polymer electrolyte and a second solid polymer electrolyte. I do. Here, both the fuel electrode 102 and the oxidizer electrode 108 may be configured to include the first and second solid polymer electrolytes, or the fuel electrode 102 and the oxidizer electrode 108 One of them may be configured to include the first and second solid polymer electrolytes.

The fine particles of the solid polymer electrolyte have a role of electrically connecting the catalyst-supporting carbon particles to the solid polymer electrolyte membrane 114 on the electrode surface and allowing the organic liquid fuel to reach the catalyst surface. Hydrogen ion conductivity and water mobility are required.Furthermore, the fuel electrode 10 is required to have organic liquid fuel permeability such as methanol, and the oxidizing agent electrode 108 is required to have oxygen permeability. Desired. The first solid polymer electrolyte satisfies these requirements, and a material having excellent hydrogen ion conductivity and organic liquid fuel permeability such as methanol is preferably used. Specifically, an organic polymer having a polar group such as a strong acid group such as a sulfone group or a phosphate group or a weak acid group such as a carboxyl group is preferably used. Examples of such organic polymers include sulfone-group-containing perfluorocarbons (Naphion (registered trademark, manufactured by DuPont), acyplex (manufactured by Asahi Kasei Corporation), etc.); carboxyl-group-containing perfluorocarbon (Flemion (registered trademark) S film) (Made by Asahi Glass Co., Ltd.); Copolymers such as polystyrene sulfonic acid copolymer, polyvinyl sulfonic acid copolymer, cross-linked alkylsulfonic acid derivative, fluororesin skeleton and fluorine-containing polymer composed of sulfonic acid; acrylic Copolymers obtained by copolymerizing acrylamides such as amide 2-methylpropanesulfonic acid and atalylates such as n-butyl methacrylate; and the like.

Examples of the polymer to which the polar group is bonded include a polybenzimidazole derivative, a polybenzoxazole derivative, a polyethyleneimine cross-linked product, a polysilamine derivative, and a polyethylaminoethyl polystyrene. Amine-substituted polystyrene Nitrogen or hydroxyl-containing resins such as nitrogen-substituted polyacrylates such as len and acetylaminoethyl polymethacrylate; hydroxyl-containing polyacrylic resins typified by silanol-containing polysiloxane and hydroxyethyl polymethyl acrylate; parahydroxy polystyrene Typical examples include a hydroxyl group-containing polystyrene resin; and the like.

In addition, a crosslinkable substituent, for example, a vinyl group, an epoxy group, an acrylic group, a methacryl group, a cinnamoyl group, a methylol group, an azide group, or a naphthoquinonediazide group may be appropriately introduced into the above-described polymer. Good.

The second solid polymer electrolyte plays a role in improving the adhesion between the electrode surface and the solid polymer electrolyte membrane 114, and a material having good adhesion to the solid polymer electrolyte membrane 114 is used. Preferably, it is used. For example, when the solid polymer electrolyte membrane 114 is composed of an organic polymer, as the second solid polymer electrolyte, a polymer having a structure similar to the organic polymer, polarity, wettability, SP value, etc. By selecting a polymer having similar physical properties, the adhesion between the electrode and the solid polymer electrolyte membrane 114 can be improved. For example, when a polymer containing no fluorine is used as the material of the solid polymer electrolyte membrane 114, it is preferable to select a polymer containing no fluorine as the second solid polymer electrolyte. When an aromatic polymer is used as the material of the solid polymer electrolyte membrane 114, it is preferable to select an aromatic polymer as the second solid polymer electrolyte.

Here, from the viewpoint of suppressing crossover, it is preferable that both the solid polymer electrolyte membrane 114 and the second solid polymer electrolyte are made of a material having low permeability to organic liquid fuel. For example, it is preferable to use an aromatic condensed polymer such as sulfonated poly (4-phenoxybenzoyl 1,4-phenylene) and alkyl sulfonidyl polybenzoimidazole.

The first solid polymer electrolyte in the fuel electrode 102 and the oxidant electrode 108 may be the same or different. Similarly, the second solid polymer electrolytes in the fuel electrode 102 and the oxidizer electrode 108 may be the same or different.

As the fuel for the fuel cell according to the present invention, a liquid organic fuel or a hydrogen-containing gas is used. be able to. Among them, when the liquid organic fuel is used, the cell efficiency can be improved while suppressing the crossover of the organic liquid fuel, and the effect of the present invention is more remarkably exhibited.

The method for producing the fuel electrode 102 and the oxidant electrode 108 in the present invention is not particularly limited, but can be produced, for example, as follows.

First, the fuel electrode 102 and the oxidant electrode 108 can be supported on the carbon particles by the catalyst by a commonly used impregnation method. Next, the catalyst-supported carbon particles and the first and second solid polymer electrolyte particles are dispersed in a solvent to form a paste, which is then applied to a substrate and dried to form the catalyst layer 106 and The fuel electrode 102 and the oxidant electrode 108 each having the catalyst layer 112 formed thereon can be produced. Here, the particle size of the carbon particles is, for example, 0.01 to 1 m. The particle size of the catalyst particles is, for example, 0.1 nm to 100 nm. The particle size of the first and second solid polymer electrolyte particles is, for example, 0.05 to 100 m. The carbon particles and the solid polymer electrolyte particles are used, for example, in a weight ratio of 1: 5 to 40: 1. The weight ratio between water and solute in the paste is, for example, about 1: 2 to 10: 1. The weight ratio of the second solid polymer electrolyte Z in the paste to the first solid polymer electrolyte can be preferably 10/1 to 1/10, and more preferably 4/1 to 1Z4. The method for applying the paste to the substrate is not particularly limited, and for example, methods such as brush coating, spray coating, and screen printing can be used. The paste is applied to a thickness of about 1 μm to 2 mm.後 After applying the strike, heating is performed at a heating temperature and a heating time according to the first and second solid polymer electrolyte particles to be used, and a fuel electrode 102 or an oxidizer electrode 108 is produced. The heating temperature and the heating time are appropriately selected depending on the material used. For example, the heating temperature can be 100 ° C. to 250 ° C., and the heating time can be 30 seconds to 30 minutes.

The solid polymer electrolyte membrane 114 in the present invention can be produced by employing an appropriate method according to the material to be used. For example, when the solid polymer electrolyte membrane 114 is composed of an organic polymer material, a liquid in which the organic polymer material is dissolved or dispersed in a solvent is cast on a peelable sheet such as polytetrafluoroethylene. Let it dry Can be obtained.

The solid polymer electrolyte membrane 114 produced as described above is sandwiched between the fuel electrode 102 and the oxidant electrode 108 and hot pressed to obtain an electrode-electrolyte assembly. At this time, the surfaces of both electrodes where the catalyst is provided are in contact with the solid polymer electrolyte membrane 114. The hot pressing conditions are selected according to the material, but when the solid polymer electrolyte membrane 114 and the electrolyte membrane on the electrode surface are composed of organic polymers, the temperature exceeds the softening temperature or glass transition temperature of these polymers. It can be. Specifically, for example, the temperature is 100 to 250 ° C., the pressure is 1 to 100 kgfZcm ² , and the time is 10 seconds to 300 seconds.

In the present invention, since the second solid polymer electrolyte constituting the fuel electrode 102 or the oxygen electrode 108 is common to the material of the solid polymer electrolyte membrane 114, an electrode containing the second solid polymer electrolyte is used. The interface between the polymer electrolyte membrane 114 and the solid polymer electrolyte membrane 114 is firmly adhered. As a result, it is possible to suppress deterioration of battery performance due to hindrance of movement of hydrogen ions due to separation of the interface, as well as to increase physical strength and durability of the battery.

Next, preferred embodiments of the first and second solid polymer electrolytes in the present invention will be described.

In the present invention, from the viewpoint of effectively suppressing crossover, it is effective to select the constituent materials of the first and second solid polymer electrolytes and the solid polymer electrolyte membrane 114 as follows.

(i) A material having a lower methanol permeability than the first solid polymer electrolyte is selected as the solid polymer electrolyte membrane 114 and the second solid polymer electrolyte.

(ii) As the solid polymer electrolyte membrane 114 and the second solid polymer electrolyte, a material having a lower moisture content than the first solid polymer electrolyte is selected.

(iii) As the solid polymer electrolyte membrane 114 and the second solid polymer electrolyte, a material having a lower polar group content density than the first solid polymer electrolyte is selected.

(iV) As the solid polymer electrolyte membrane 114 and the second solid polymer electrolyte, a material having a lower fluorine content than the first solid polymer electrolyte is selected.

By adopting such a method, it is possible to suppress the permeation of the organic liquid fuel in the solid polymer electrolyte membrane 114 and to suppress the deterioration of the battery performance due to the crossover. Wear. Hereinafter, methods for measuring the physical properties shown in the above (i) to (iv) will be described. Methanol permeability can be measured as follows. 50 cc of 99.5% methanol on one side and 50 cc of pure water on the other side in a liquid container separated by the electrolyte membrane to be measured (membrane thickness 50 i / m, area 1 cm ² ) Inject and seal each liquid so that it does not evaporate. The time change of the concentration of methanol permeating the electrolyte membrane into pure water is measured by gas chromatography to determine the amount of methanol permeated. When the above (U configuration is adopted, the second solid polymer electrolyte has a unit area and a methanol permeation amount of 300 mo 1 / cm per unit time when a membrane having a thickness of 50 ^ m is used. it is preferable that the ² / h or less. by selecting such a material, it is possible to suppress the methanol reaches the oxidizing agent, it can be overcome the problem of the crossover.

The moisture content is expressed as (B-A) ZA, where A is the weight of the test material dried at 100 ° C for 2 hours, and B is the weight of the test material after immersion in pure water for 24 hours. It is the value represented.

The content density of the polar group can be measured using a predetermined method according to the type of the functional group. In the case of a sulfone group, for example, the sulfonate group can be quantified by ion chromatography or titration after converting the sulfonate group into a sulfate ion by an oxygen combustion flask method or the like. Titration is performed using carboxyl senazo as an indicator and titration with 0.1 M barium perchlorate to determine the color change point from blue to purple.

The fluorine content can be quantified by X-ray fluorescence analysis or the like.

In the catalyst layer 106 and the catalyst layer 112, the first and second solid polymer electrolyte particles may be distributed uniformly or non-uniformly. For example, the catalyst layer 106 or the catalyst layer 112 contains the first solid polymer electrolyte particles on the side in contact with the substrate 104 or the substrate 110, and the catalyst layer 106 or the catalyst layer 111 On the side where 2 is in contact with the solid polymer electrolyte membrane 114, it is possible to adopt a configuration that does not include the first solid polymer electrolyte particles. At this time, the catalyst layer 106 or the catalyst layer 112 does not include the second solid polymer electrolyte particles on the side where the catalyst layer 106 or the catalyst layer 112 contacts the substrate 104 or the substrate 110, and the catalyst layer 106 or the catalyst layer 11 A configuration in which 2 includes second solid polymer electrolyte particles on the side in contact with the solid polymer electrolyte membrane 114 may be employed. in this way, T JP03 / 04853

18

The content of the first solid polymer electrolyte particles is increased in the region near the substrate 104 or the substrate 110, and the content of the second solid polymer electrolyte particles is increased in the region near the solid polymer electrolyte membrane 114. By increasing the content, the adhesion to the solid electrolyte membrane 114 is increased while the content of the first solid polymer electrolyte particles in the catalyst layer 106 and the catalyst layer 112 is maintained to some extent. be able to. The first solid polymer electrolyte has a higher water content than the second solid polymer electrolyte and has a property of high organic liquid fuel and oxygen permeability, so that the organic liquid fuel can be efficiently moved and many hydrogen ions are removed. It can be supplied.

In this case, the catalyst layer 106 and the catalyst layer 112 can be formed as follows. First, the first solid polymer electrolyte particles and the carbon particles carrying the catalyst are dispersed in a solvent on the substrate 104, and a paste-like coating liquid a is applied. Subsequently, the first and second solid polymer electrolytes and the carbon particles carrying the catalyst are dispersed in a solvent on the applied coating liquid a, and a coating liquid b in the form of a paste is applied. Similarly, while gradually increasing the content of the second solid polymer electrolyte particles, the first and second solid polymer electrolytes and the carbon particles carrying the catalyst are dispersed in a solvent, and the paste is formed. The coating liquids described above are sequentially applied to form a catalyst layer 106 or 112 composed of a plurality of layers. This makes it possible to form the catalyst layer 106 or 112 configured to increase the content of the second solid polymer electrolyte particles in the substrate 104 or in a region far from the substrate 110. it can. The solid electrolyte membrane 114 is sandwiched between the fuel electrode 102 and the oxidant electrode 108 containing the catalyst layer 106 and the catalyst layer 112 formed in this manner, and the electrode is formed by hot pressing. (I) An electrolyte conjugate can be obtained. The above steps may include a step of drying after applying each layer.

(Example)

Hereinafter, the electrode for a polymer electrolyte fuel cell of the present invention and the fuel cell using the same will be specifically described with reference to Examples, but the present invention is not limited thereto.

(Example 1)

In this embodiment, naphion is used as the first solid polymer electrolyte, and sulfonated poly (4-phenoxybenzoyl-1,4-) is used as the second solid polymer electrolyte. An example using phenylene) (hereinafter referred to as PPBP) will be described. In this example, platinum was used as a noble metal catalyst for both the fuel electrode and the oxidant electrode. A method for manufacturing a fuel cell according to this example will be described with reference to FIG.

First, acetylene black 1 Og (Denki Black (registered trademark); manufactured by Denki Kagaku Kogyo Co., Ltd.) is mixed with 500 g of dinitrodiamine platinum nitrate solution containing 3% of platinum serving as a catalyst at the fuel electrode 102 and the oxidizer electrode 108, followed by stirring. Thereafter, 60 ml of 98% ethanol was added as a reducing agent. This solution was stirred and mixed at about 95 ° C. for 8 hours, and the catalyst substance and the platinum fine particles were supported on the acetylene black particles. Then, this solution was filtered and dried to obtain catalyst-carrying carbon particles. The supported amount of platinum was about 50% based on the weight of the acetylene black.

Next, 20 Omg of the catalyst-supporting carbon particles and 3.5 ml of a 5% naphion solution (alcohol solution, manufactured by Aldrich Chemical Co., Ltd.) were mixed and stirred to adsorb the nafion on the surfaces of the catalyst and the carbon particles. The dispersion thus obtained was dispersed in an ultrasonic disperser at 50 ° C. for 3 hours to obtain a paste, and paste A was obtained.

Next, 10 g of finely powdered poly (4-phenoxybenzoyl-1,4-phenylene) was suspended in 95% sulfuric acid (10 Om1) and stirred for 200 hours to perform sulfonation treatment. went. The PPBP thus obtained was washed with sufficient distilled water, dried and pulverized, and dissolved in a dimethylformamide solution. A solid polymer electrolyte membrane 114 having a size of 10 cm × 10 cm and a thickness of 30 m was obtained by a casting method. In addition, 0.15 ml of the dimethylformamide solution of the above-obtained PP BP in the form of fine particles was mixed with paste A to obtain paste B. This paste B is applied to the bases 104 and 110 which are carbon paper (manufactured by Toray Co., Ltd .: TGP-H-120) by a screen printing method, and then heated and dried at 100 ° C. to form the fuel electrodes 102 andぴ Oxidant electrode 108 was obtained. The amount of platinum on the obtained electrode surface was 0.1 to 0.4 mg Zcm ² .

A solid polymer electrolyte membrane 114 was sandwiched between these electrodes, and hot-pressed at a temperature of 150 ° C. and a pressure of 10 kgf / cm ^{2 for} 10 seconds to produce an electrode-electrolyte assembly. Further, this electrode-electrolyte assembly was set in an apparatus for measuring a single cell of a fuel cell to produce a single cell. The current-voltage characteristics of the single cell were measured using a 10 wt% methanol aqueous solution and oxygen (1.1 atm, 25 ° C) as fuel. As a result, an open circuit voltage of 0.54 V and a short circuit current of 0.21 A / cm ² were continuously observed.

The fuel electrode 102 and the oxidizer electrode 108 showed good bonding properties to the solid polymer electrolyte membrane 114, and it was confirmed that the fuel electrode 102 and the oxidant electrode 108 function effectively as a direct methanol fuel cell using methanol as a fuel.

FIG. 3 is a diagram schematically showing the fuel electrode 102 and the solid polymer electrolyte membrane 114 of the fuel cell according to the present embodiment. The fuel electrode 102 comprises a catalyst layer formed by mixing a second solid polymer electrolyte 160 made of PP BP, a first solid polymer electrolyte 150 made of naphion, and carbon particles 140 carrying a catalyst. Is provided on the substrate 104. Here, the second solid polymer electrolyte 160 and the solid polymer electrolyte membrane 114 are both made of PPBP. Therefore, of the second solid polymer electrolyte 160, the one in contact with the solid polymer electrolyte membrane 114 serves as a binder at the interface between the solid polymer electrolyte membrane 114 and the fuel electrode 102. Therefore, the bonding property between the solid polymer electrolyte membrane 114 and the fuel electrode 102 is good, and this is considered to contribute to the good operation of the fuel cell in this embodiment.

Here, Table 1 shows the values of methanol permeability and water content of PPBP and naphion.

[table 1]

In the present embodiment, as the solid polymer electrolyte membrane 114 and the second solid polymer electrolyte 160, materials having lower methanol permeability and water content than the first solid polymer electrolyte 150 are selected. However, methanol permeation in the solid polymer electrolyte membrane 114 is suppressed. This suggests that a decrease in cell performance due to crossover was suppressed, and a fuel cell with good cell characteristics was obtained. (Example 2)

Also in this example, naphion was used as the first solid polymer electrolyte, and PP BP was used as the second solid polymer electrolyte. Also in this example, platinum was used as the catalyst for both the fuel electrode and the oxidant electrode.

The fuel electrode 102, the oxidizer electrode 108, and the solid electrolyte membrane 114 were produced in the same manner as in Example 1. 0.1 ml of a dimethylformamide solution of PPBP obtained by the same method as in Example 1 and fine particles of PPBP mixed therein was mixed with the first A of the naphion obtained by the same method as in Example 1 to obtain the first C. Was. Further, 0.15 ml of a dimethylformamide solution prepared by adding PPPP fine particles to paste A was mixed with paste A to obtain paste D.

First, paste C was applied to the substrate 104 and the substrate 110 by a brush coating method, and dried after application. Next, paste D was applied onto paste C by a brush coating method, and after coating, dried. As a result, a catalyst layer 106 and a catalyst layer 112 composed of the paste C and the paste D were formed on the base 104 and the base 110. Using this, hot pressing was performed in the same manner as in Example 1 to produce an electrode-electrolyte assembly. This electrode-electrolyte assembly was set in an apparatus for measuring a single cell of a fuel cell to produce a single cell.

The current-voltage characteristics of the single cell were measured using a 1 Owt% methanol aqueous solution and oxygen (1.1 atm, 25 ° C) as fuel. As a result, an open circuit voltage of 0.54 V and a short circuit current of 0.19 A / cm ² were continuously observed.

(Comparative Example 1)

The solid polymer electrolyte membrane was produced in the same manner as in the above example. The fuel electrode and the oxidizer electrode were prepared by applying paste A in Example 1 on a carbon paper by a screen printing method, and then heating and drying the paste.

The above-mentioned solid polymer electrolyte membrane was sandwiched between these electrodes, and hot-pressed under the conditions of a temperature of 150 ° C. and a pressure of 10 kgf / cm ² 10 seconds, thereby producing an electrode-electrolyte assembly.

Further, these were set in an apparatus for measuring a single cell of a fuel cell to produce a single cell. A discharge test similar to that of the above example was performed, but no discharge could be confirmed. Fig. 4 shows the fuel electrode 301 and the solid polymer electrolyte membrane 1 in the fuel cell of this comparative example. FIG. 14 is a diagram schematically showing a numeral 14. As in the example, there is a carbon particle 140 supporting a catalyst and a first solid polymer electrolyte 150 composed of naphion on a substrate 104. That is, a solid polymer electrolyte made of the same material as the polymer electrolyte membrane 114 does not exist in the fuel electrode 301. Therefore, since there is no solid polymer electrolyte serving as a binder at the interface between the fuel electrode 301 and the solid polymer electrolyte membrane 114, it is not possible to ensure the bondability between the two. Therefore, it is probable that hydrogen ions did not move from the fuel electrode to the oxidizer electrode, and did not function as a battery.

(Comparative Example 2)

In Comparative Example 1, an example was shown in which only naphion was used as the solid polymer electrolyte in the electrode. In this comparative example, only PPPBP was used as the solid polymer electrolyte in the electrode, and the other configurations of the battery were the same as those in the above example and comparative example 1.

The solid polymer electrolyte membrane was produced in the same manner as in the above example.

5 g of a dimethylformamide solution (5 wt% solution) obtained by finely pulverizing PPBP prepared by the method described in the above example was added to 0.5 g of the catalyst-supporting carbon particles prepared by the method described in the above example, and distillation was performed. Colloid was adsorbed on the surface of these carbon particles by adding 0.3 g of water. The dispersion thus obtained was dispersed in an ultrasonic disperser at 50 ° C. for 3 hours to obtain a paste. I got This paste C was applied on a carbon paper by a screen printing method, and then heated and dried to produce a fuel electrode and an oxidizer electrode.

An electrode-electrolyte assembly and a single cell were prepared from the above fuel electrode, oxidizer electrode and solid polymer electrolyte membrane in the same manner as in the above example, and a discharge test was performed. As a result, an open-circuit voltage of 0.58 V and a short-circuit current of 0.16 A / cm ² were observed.

In this comparative example, since the solid polymer electrolyte and the solid polymer electrolyte membrane in the electrode are both made of PPBP, it is considered that the bonding between the electrode and the solid polymer electrolyte membrane is maintained. Nevertheless, good cell characteristics could not be obtained because of insufficient electrode permeability at the fuel electrode due to insufficient methanol permeability and hydrogen ion permeability at the fuel electrode. Then inferred 4853

twenty three

It is.

In the above examples, when a platinum-ruthenium catalyst was used as the noble metal catalyst of the oxidant electrode 108, it was shown that each example had more stable battery characteristics. Industrial applicability

As described above, according to the present invention, by including a solid polymer electrolyte having low organic liquid fuel permeability in a catalyst electrode, a solid polymer electrolyte membrane made of a solid polymer electrolyte having low organic liquid fuel permeability can be obtained. Good bondability with the electrode is obtained. Therefore, improvement in battery characteristics and improvement in battery reliability can be realized. In addition, it is possible to suppress the crossover of the organic liquid fuel while maintaining the hydrogen ion conductivity and the permeability of the organic liquid fuel at the catalyst electrode in a good condition.

Claims

The scope of the claims

1. A solid polymer electrolyte membrane, comprising: a catalyst electrode disposed on the solid polymer electrolyte membrane, wherein the catalyst electrode comprises a catalyst substance, a first solid polymer electrolyte, and the first solid polymer. A fuel cell, comprising: a catalyst layer including a second solid polymer electrolyte having higher adhesion to the solid polymer electrolyte membrane than an electrolyte.

2. A solid polymer electrolyte membrane, and a catalyst electrode disposed on the solid polymer electrolyte membrane, wherein the catalyst electrode comprises a catalyst substance, a first solid polymer electrolyte, and the first solid polymer. A catalyst layer comprising a polymer compound different from an electrolyte, and a second solid polymer electrolyte comprising a polymer compound or a derivative thereof constituting the solid polymer electrolyte membrane; Fuel cell.

3. The fuel cell according to claim 1, wherein the catalyst electrode includes a porous base material, and the catalyst layer is formed in contact with the porous base material. .

4. The fuel cell according to claim 3, wherein a content of the second solid polymer electrolyte in a surface of the catalyst layer in contact with the porous substrate is opposite to a surface in contact with the porous substrate. A fuel cell, wherein the content of the second solid polymer electrolyte is lower than the content of the second solid polymer electrolyte.

5. The fuel cell according to claim 3, wherein a content of the catalyst substance in a surface of the catalyst layer in contact with the porous substrate is the same as that in a surface opposite to a surface in contact with the porous substrate. A fuel cell characterized by having a higher content of a catalytic substance.

6. The fuel cell according to claim 1, wherein the catalyst layer is provided in contact with the solid polymer electrolyte membrane.

7. The fuel cell according to claim 1, wherein an organic liquid fuel is supplied to the catalyst electrode.

8. The fuel cell according to any one of claims 1 to 7, wherein the second solid polymer electrolyte has a lower permeability of the organic liquid fuel than the first solid polymer electrolyte. Fuel cell.

9. The fuel cell according to any one of claims 1 to 8, wherein the second solid polymer electrolyte has a lower moisture content than the first solid polymer electrolyte.

10. The fuel cell according to any one of claims 1 to 9, wherein the first solid polymer electrolyte and the second solid polymer electrolyte each include a proton acid group. battery.

11. The fuel cell according to any one of claims 1 to 10, wherein the first solid polymer electrolyte is made of a polymer containing fluorine.

12. The fuel cell according to claim 1, wherein the second solid polymer electrolyte is made of a polymer containing no fluorine.

13. The fuel cell according to claim 1, wherein the second solid polymer electrolyte is made of an aromatic-containing polymer.

1 4. A catalyst layer comprising a catalyst substance, a first solid polymer electrolyte, and a second solid polymer electrolyte made of a polymer different from the first solid polymer electrolyte. Electrode for a fuel cell.

15. The fuel cell electrode according to claim 14, further comprising a porous substrate, wherein the catalyst layer is formed in contact with the porous substrate.

16. The fuel cell electrode according to claim 15, wherein a content of the second solid polymer electrolyte on a surface of the catalyst layer in contact with the porous substrate is in contact with the porous substrate. An electrode for a fuel cell, wherein the content of the second solid polymer electrolyte is lower than the content of the second solid polymer electrolyte on the surface opposite to the surface.

17.The fuel cell electrode according to claim 15, wherein the content of the catalyst substance on a surface of the catalyst layer in contact with the porous substrate is different from a surface of the catalyst layer in contact with the porous substrate. An electrode for a fuel cell, wherein the content of the catalyst material is higher than the content of the catalyst material on the opposite surface.

1 8. The fuel cell electrode according to any one of claims 14 to 17, wherein the second solid polymer electrolyte has a lower methanol permeability than the first solid polymer electrolyte. Characteristic electrode for fuel cells.

1 9. The fuel cell electrode according to claim 14 or 18 V, wherein the second solid polymer electrolyte has a lower moisture content than the first solid polymer electrolyte. Characteristic electrode for fuel cells.

20. The fuel cell electrode according to any one of claims 14 to 20, wherein the first solid polymer electrolyte and the second solid polymer electrolyte each have a protonic acid group. An electrode for a fuel cell, comprising:

21. The fuel cell electrode according to any one of claims 14 to 21, wherein the first solid polymer electrolyte is made of a polymer containing fluorine. .

2 2. The fuel cell electrode according to any one of claims 14 to 21, wherein the second solid polymer electrolyte is made of a fluorine-free polymer. .

23. The fuel cell electrode according to any one of claims 14 to 22, wherein the second solid polymer electrolyte comprises an aromatic-containing polymer. electrode.

2 4. A method for manufacturing a fuel cell electrode having a catalyst layer provided on a substrate, comprising: conductive particles supporting a catalyst metal; particles including a first solid polymer electrolyte; A step of applying a coating solution containing particles containing a second solid polymer electrolyte made of a polymer different from the molecular electrolyte onto a substrate to form the catalyst layer. Manufacturing method of electrode.

25. The method for producing an electrode for a fuel cell according to claim 24, wherein the step of forming the catalyst layer comprises applying a plurality of coating liquids having different content rates of particles including the second solid polymer electrolyte. A method for producing an electrode for a fuel cell, comprising:

26. In the method for producing an electrode for a fuel cell according to claim 24 or 25, the step of forming the catalyst layer comprises: applying a plurality of coating liquids having different contents of the conductive particles supporting the catalyst metal. A method of manufacturing an electrode for a fuel cell, comprising a step of coating. Law.

27. The method of manufacturing an electrode for a fuel cell according to any one of claims 24 to 26, wherein the second solid polymer electrolyte is more permeable to methanol than the first solid polymer electrolyte. A method for producing an electrode for a fuel cell, wherein the electrode has low performance.

28. The method for producing an electrode for a fuel cell according to any one of claims 24 to 27, wherein the second solid polymer electrolyte has a higher water content than the first solid polymer electrolyte. A method for producing an electrode for a fuel cell, wherein the electrode is low.

29. The method for manufacturing an electrode for a fuel cell according to claim 24, wherein the first solid polymer electrolyte and the second solid polymer electrolyte are each a proton. A method for producing an electrode for a fuel cell, comprising an acid group.

30. The method for producing a fuel cell electrode according to any one of claims 24 to 29, wherein the first solid polymer electrolyte is made of a polymer containing fluorine. A method for manufacturing a battery electrode.

31. The method for producing an electrode for a fuel cell according to any one of claims 24 to 30, wherein the second solid polymer electrolyte is made of a polymer containing no fluorine. A method for manufacturing a battery electrode.

3 2. The method for producing an electrode for a fuel cell according to any one of claims 24 to 31, wherein the second solid polymer electrolyte comprises an aromatic-containing polymer. A method for manufacturing a fuel cell electrode.

3 3. After obtaining a catalyst electrode by the method for producing an electrode for a fuel cell according to any one of claims 24 to 32, the catalyst in a state where the catalyst layer and the solid polymer electrolyte membrane are in contact with each other. A method for producing a fuel cell, comprising a step of thermocompression bonding an electrode and a solid polymer electrolyte membrane.