JP2004253399A - Fuel cell and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To increase close adhesion at the interface of an electrode surface and a solid polyelectrolyte film, and improve a battery property and reliability. <P>SOLUTION: An adhesion layer 161 is provided between a solid polyelectrolyte film 114 and a fuel electrode 102. The solid polyelectrolyte film 114 and the adhesion layer 161 are constructed of identical solid polyelectrolytes. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

The present invention relates to a fuel cell and a method for manufacturing the same .

  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 oxidant electrode joined to both sides of this membrane. This is a device that supplies oxygen and generates power by an electrochemical reaction.

The following electrochemical reaction occurs in each electrode.
The fuel ^{_{electrode: H 2 → 2H + + 2e}} -
Oxidant electrode: 1 / 2O ₂ + 2H ⁺ + 2e ⁻ → H ₂ O

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.

  The fuel electrode and the oxidizer electrode are provided with a mixture of carbon particles carrying a catalyst metal and a solid polymer electrolyte. In general, the mixture is applied to an electrode substrate such as carbon paper which becomes a fuel gas diffusion layer. A fuel cell is formed by sandwiching the 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 led to an 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, hydrogen ions generated at the fuel electrode reach the oxidizer electrode through the solid polymer electrolyte in the fuel electrode and the solid polymer electrolyte membrane disposed between the two electrodes, and the oxygen supplied to the oxidizer electrode becomes It 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 flow from the fuel electrode to the oxidant electrode, and power is extracted.

  In order to improve the characteristics of the fuel cell configured as described above, it is important that the adhesion between the electrode and the solid polymer electrolyte membrane be good. That is, it is required that the conductivity of hydrogen ions generated by the electrode reaction is high at the interface between the two. If the adhesion at the interface is poor, the conductivity of hydrogen ions is reduced, the electrical resistance is increased, and the battery efficiency is reduced.

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

  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. A fuel supply system directly to the fuel electrode is known.

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

  Generally, in a fuel cell using an organic liquid fuel, a solid polymer electrolyte membrane made of a solid polymer ion exchange resin is used as an electrolyte. Here, in order for the fuel cell to function, it is necessary for hydrogen ions to move through the membrane from the fuel electrode to the oxidizer electrode. It is known that the movement of the hydrogen ions is accompanied by the movement of water. It is necessary that the film contains 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 a decrease in voltage and output and a decrease in fuel efficiency because the organic liquid fuel that should originally provide electrons at the fuel electrode is oxidized on the oxidant electrode side and is not effectively used as fuel.

  From the viewpoint of solving such a crossover problem, it is desired to select a polymer having a low water content as a material for the solid polymer electrolyte membrane and to suppress the diffusion of an 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, as the polymer constituting the catalyst layer on the electrode surface, a polymer having a high water content and a property of high permeability of organic liquid fuel is used, and the polymer constituting the solid polymer electrolyte membrane is used. It is considered preferable to use a material having a low water content and a property of low permeability of organic liquid fuel.

Patent Literature 1 discloses a technique relating to an ion-conductive film that makes it possible to suppress methanol crossover while maintaining ionic conductivity. Here, the surface layer of the 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. I have.
JP 2001-167775 A

  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, generally, sufficient adhesion cannot be obtained, and the interface between the electrode surface and the solid polymer electrolyte membrane is generally not obtained. May cause peeling. When such peeling occurs, the electric resistance at the interface increases, which causes a decrease in the reliability of the battery performance. Further, as described in Patent Document 1, even when the surface layer of the ion conductive film is modified, the surface strength of the ion conductive film at the time of swelling increases, and the adhesion to the electrode surface catalyst layer deteriorates. Had the problem of doing so.

  In view of the above circumstances, an object of the present invention is to improve the adhesion at the interface between the electrode surface and the solid polymer electrolyte membrane to improve 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 the permeability of the organic liquid fuel on the electrode surface.

  In general, a solid polymer electrolyte having high hydrogen ion conductivity represented by Nafion (registered trademark) or the like is used as a solid polymer electrolyte of a fuel cell. The high proton conductivity of such a solid polymer electrolyte is manifested when the polymer electrolyte contains a large amount of water. On the other hand, the large amount of water contained causes an organic liquid fuel such as methanol to become watery. To facilitate the occurrence of crossover.

  In order to suppress crossover, the present inventor used a polymer material having a lower organic liquid fuel permeability than Nafion or the like as a fuel electrode, an oxidizer electrode, or a solid polymer electrolyte constituting a solid polymer electrolyte membrane. A direct methanol fuel cell was fabricated using the same and evaluated. However, the cell characteristics of this fuel cell were lower than those of a conventional cell using Nafion. This is considered to be due to the decrease in methanol permeability and hydrogen ion conductivity at the fuel electrode. The fuel electrode of the fuel cell has a structure including a catalyst layer in which carbon particles carrying a catalyst and a solid polymer electrolyte as a binder are mixed, and a structure in which the solid polymer electrolyte is interposed between the catalysts. It has become. 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 liquid fuel permeability such as methanol and excellent hydrogen ion conductivity. It is necessary to be. It is probable that in the battery having the above structure, the solid polymer electrolyte did not sufficiently satisfy these performances, so that good battery characteristics could not be obtained.

  Next, the present inventors use Nafion as a solid polymer electrolyte on the electrode surface to improve the efficiency of the catalytic reaction at the fuel electrode, and as a solid polymer electrolyte membrane, have a lower organic liquid fuel permeability than Nafion or the like. When an attempt was made to produce a direct methanol fuel cell using a polymer material, 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 by effectively utilizing a plurality of types of solid polymer electrolytes, the adhesion at the interface between the electrode surface and the solid polymer electrolyte membrane is improved. It has been found that the properties can be effectively improved, and the present invention has been completed.

According to the present invention, a first solid polymer electrolyte made of a polymer containing fluorine and a catalyst electrode containing a catalyst substance, a solid polymer electrolyte membrane made of a polymer containing no fluorine, a catalyst electrode and a solid polymer is provided between the polymer electrolyte membrane, an adhesive layer comprising a second solid polymer electrolyte composed of a polymer containing no fluorine, Ru is provided a fuel cell characterized by having a.

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 oxidant electrode. The first solid polymer electrolyte on the catalyst electrode surface has a 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. In addition, hydrogen ion conductivity and water mobility are required, and further, permeability of an organic liquid fuel such as methanol is required at a fuel electrode, and oxygen permeability is required at an oxidant electrode. 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.

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

  As described above, since the fuel electrode, the oxidizer electrode, and the solid polymer electrolyte membrane have different properties required from each other, it is desirable that they are formed of different materials. However, it is generally difficult to ensure sufficient adhesion at the interface between such different materials. Therefore, the present invention provides an adhesive layer between the catalyst electrode and the solid polymer electrolyte membrane, thereby ensuring sufficient adhesion between the electrodes and the solid polymer electrolyte membrane even when a material suitable for the electrode and the solid polymer electrolyte membrane is selected. be able to.

  That is, the catalyst electrode according to the present invention has a configuration in which the electrode surface contains the first solid polymer electrolyte, the adhesive layer contains the second solid polymer electrolyte, and the first solid polymer electrolyte allows hydrogen to be applied to the electrode surface. The smooth movement of ions and liquid fuel is ensured, and the interface between the catalyst electrode and the solid polymer electrolyte membrane is firmly adhered by the second solid polymer electrolyte. According to the present invention, by adopting such a configuration, good battery efficiency is stably realized over a long period of time while suppressing an increase in electric resistance at the interface between the catalyst electrode and the solid polymer electrolyte membrane. be able to.

  The adhesive layer in the present invention does not need to be formed over the entire surface between the solid polymer electrolyte membrane and the catalyst electrode, but may be formed at least partially between them. Further, the adhesive layer can include the first solid polymer electrolyte. In this case, the content of the first solid polymer electrolyte in the adhesive layer may have a distribution along the direction from the catalyst electrode to the solid polymer electrolyte membrane. For example, a configuration in which the adhesive layer includes the first solid polymer electrolyte on the side in contact with the catalyst electrode and does not include the first solid polymer electrolyte on the side in contact with the solid polymer electrolyte membrane. At this time, the adhesive layer may be configured not to include the second solid polymer electrolyte on the side in contact with the catalyst electrode but to include the second solid polymer electrolyte on the side in contact with the solid polymer electrolyte membrane. This can improve the adhesion between the adhesive layer and the catalyst electrode, and between the adhesive layer and the solid polymer electrolyte membrane.

  Further, the adhesive layer may include a catalytic substance. In this case, the content of the catalyst substance in the adhesive layer may have a distribution along the direction from the catalyst electrode to the solid polymer electrolyte membrane. For example, it is possible to adopt a configuration in which the adhesive layer contains a catalytic substance on the side in contact with the catalyst electrode and does not contain a catalytic substance on the side in contact with the solid polymer electrolyte membrane. When the adhesive layer includes a catalyst substance, the electron conductivity can be improved even in the adhesive layer.

  Here, the second solid polymer electrolyte can have higher adhesion to the solid polymer electrolyte membrane than the first solid polymer electrolyte. Further, the second solid polymer electrolyte can be made of a solid polymer electrolyte constituting the solid polymer electrolyte membrane or a derivative thereof. By doing so, good adhesion is developed between the first solid polymer electrolyte and the solid polymer electrolyte membrane via the second solid polymer electrolyte constituting the adhesive layer.

  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. The direct type fuel cell has advantages such as high cell efficiency and space saving because no reformer is required, but crossover of an organic liquid fuel such as methanol becomes a problem. According to the present invention, while suppressing such a crossover problem, an increase in electric resistance at the interface between the catalyst electrode and the solid polymer electrolyte membrane is suppressed, and good battery efficiency is stably realized over a long period of time. be able to.

  Further, according to the present invention, it is characterized by having an electrode layer containing a catalyst substance and a first solid polymer electrolyte, and an adhesive layer containing a second solid polymer electrolyte formed on the electrode layer. An electrode for a fuel cell is provided.

  According to the present invention, while improving hydrogen ion conductivity and liquid fuel permeability on the surface of the catalyst electrode by the first solid polymer electrolyte, the catalyst electrode and the solid polymer electrolyte membrane are formed by the second solid polymer electrolyte. Can be firmly joined. In the conventional catalyst electrode, the solid electrolyte constituting the electrode surface had to simultaneously satisfy both the electrode performance and the interfacial adhesion, but in the present invention, since the adhesive layer is provided, the first solid polymer The electrolyte may improve the electrode performance, and the second solid polymer electrolyte may function to improve the interfacial adhesion. Therefore, it is possible to stably realize both electrode performance and interfacial adhesion, which are difficult to achieve with a single type of solid polymer electrolyte.

Furthermore, according to the present invention, there is provided a method for producing an electrode for a fuel cell, in which a catalyst layer and an adhesive layer are formed on a substrate in this order, comprising: conductive particles carrying a catalyst metal; and a first solid polymer electrolyte . contains a second solid polymer electrolyte composed of different polymer bets and forming the catalyst layer of the first coating liquid was coated on a substrate containing, as the first solid polymer electrolyte Applying the second coating solution to the catalyst layer to form the adhesive layer.

According to this production method, a first coating solution containing a first solid polymer electrolyte is applied to a substrate to form a catalyst layer, and then a catalyst different from the first solid polymer electrolyte is used. The second coating solution containing the second solid polymer electrolyte is applied on the catalyst layer to form an adhesive layer. For this reason, the second solid polymer electrolyte layer is formed on the first solid polymer electrolyte layer, and excellent adhesion between the two is exhibited. Although the reason why good adhesion is obtained by adopting such a method is not necessarily clear, since the catalyst layer is constituted by a layer of particles, moderate irregularities are generated on the surface thereof, and a gap between the catalyst layer and the adhesive layer is generated. This is presumed to be due to the fact that the contact area increases and adsorption or binding easily occurs. Here, if the solid polymer electrolyte membrane is configured to include the second solid polymer electrolyte, the adhesion between the adhesive layer and the solid polymer electrolyte membrane can also be improved.

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

  Further, according to the present invention, after the fuel cell electrode is obtained by the above-described method for producing a fuel cell electrode, the fuel cell electrode and the solid polymer electrolyte are brought into contact with the adhesive 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 production method, the adhesive layer can be stably formed in a simple step, and a fuel cell having good adhesion between the catalyst electrode and the solid polymer electrolyte membrane can be stably obtained.

According to the present invention, there is provided a method for manufacturing a fuel cell comprising a solid polymer electrolyte membrane, and a pair of electrodes sandwiching the solid polymer electrolyte membrane and having a catalyst layer formed on a substrate, comprising: When the second of different polymer forming a catalyst layer a first coating solution containing a first solid polymer electrolyte is coated on a substrate, a first solid polymer electrolyte Applying a second coating solution containing the solid polymer electrolyte to the solid polymer electrolyte membrane to form an adhesive layer, and contacting the catalyst layer and the adhesive layer with the electrode and the solid polymer electrolyte. And a step of thermocompression bonding the membrane and the fuel cell.

In the present invention, it is preferable that the second solid polymer electrolyte has lower permeability to the organic liquid fuel than the first solid polymer electrolyte. By doing so, it becomes possible to obtain the adhesion to the solid polymer electrolyte membrane while securing the organic liquid fuel permeability and the hydrogen ion conductivity in the catalyst electrode. In order to realize this, for example, the following configuration may be used.
(I) The second solid polymer electrolyte has a lower moisture 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 includes the first solid polymer electrolyte; The density of the proton acid groups is lower than that of the electrolyte. Here, the proton acid group is, for example, one or more polar groups selected from the group consisting of a sulfone group, a carboxyl group, a phosphate group, a phosphonate group, and a phosphinate group.

Further, in the present invention, the first solid polymer electrolyte may be constituted by a polymer containing fluorine. Further, in the present invention, the second solid polymer electrolyte may be formed of a polymer containing no 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 a method such as performing secondary ion mass spectrometry (SIMS) while performing sputtering from the surface of the layer structure to be measured. it can.

  As described above, according to the present invention, since the adhesive layer is provided between the catalyst electrode and the solid polymer electrolyte membrane, good adhesion between the solid polymer electrolyte membrane and the electrode can be obtained. For this reason, the adhesion at the interface between the electrode surface and the solid polymer electrolyte membrane can be increased, and the battery characteristics and the battery reliability can be improved. Further, the crossover of the organic liquid fuel can be suppressed while maintaining the hydrogen ion conductivity and the permeability of the organic liquid fuel on the electrode surface in good condition.

In the fuel cell of the present invention, an adhesive layer containing a second solid polymer electrolyte is provided between a catalyst electrode containing a first solid polymer electrolyte and a catalyst substance, and a solid polymer electrolyte membrane. In the manufacturing process, the adhesive layer may be formed on the surface of the catalyst electrode or the solid polymer electrolyte membrane and then joined to the catalyst electrode and the solid polymer electrolyte membrane, or the catalyst electrode and the solid polymer electrolyte membrane may be used. In a state in which a sheet made of the second solid polymer electrolyte is arranged between the two, these may be joined by thermocompression bonding or the like.

  The catalyst electrode in the present invention contains a catalyst substance and a first solid polymer electrolyte. Specifically, for example, it is possible to adopt a configuration in which a catalyst layer containing a catalyst substance and a first solid polymer electrolyte is formed on a substrate such as carbon paper. Here, the catalyst material includes a catalyst metal and conductive particles carrying the catalyst metal. Here, carbon particles or the like are used as the conductive particles. The first solid polymer electrolyte has a role of immobilizing the conductive particles on the base and electrically connecting the conductive particles to the solid polymer electrolyte membrane.

  The adhesive layer in the present invention contains the second solid polymer electrolyte. As a component other than the second solid polymer electrolyte, conductive particles such as a catalyst metal and carbon particles carrying the catalyst metal may be included. Since the adhesive layer contains the catalytic metal and the conductive particles as described above, the organic liquid fuel is consumed in the adhesive layer, and an electrode reaction occurs, so that the electron conductivity of the adhesive layer can be improved. Note that the adhesive layer in the present invention may include a solid polymer electrolyte other than the second solid polymer electrolyte, such as the first solid polymer electrolyte.

(First embodiment)
Hereinafter, the first 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 includes a base 104 and a catalyst layer 106. The oxidant electrode 108 includes a base 110 and a catalyst layer 112. Adhesion layers 161 are provided between the solid polymer electrolyte membrane 114 and the fuel electrode 102 and between the solid polymer electrolyte membrane 114 and the oxidant electrode 108, respectively. The plurality of electrode-electrolyte assemblies 101 are electrically connected via the fuel electrode side separator 120 and the oxidant electrode side separator 122 to manufacture the fuel cell 100.

  The fuel electrode 102 and the oxidizer electrode 108 are configured to include a catalyst layer 106 and a catalyst layer 112 containing a catalyst and a first solid polymer electrolyte, respectively. The solid polymer electrolyte membrane 114 is made of a second solid polymer electrolyte. The adhesive layer 161 contains a second solid polymer electrolyte. Specific materials constituting the first and second solid polymer electrolytes will be described later.

  In the fuel cell 100 configured as described above, the fuel 124 is supplied to the fuel electrode 102 of each electrode-electrolyte assembly 101 via the fuel electrode side separator 120. Further, an oxidant 126 such as air or oxygen is supplied to the oxidant electrode 108 of each electrode-electrolyte assembly 101 via an oxidant electrode side separator 122.

The solid polymer electrolyte membrane 114 has a role of separating the fuel electrode 102 and the oxidizer electrode 108 and moving hydrogen ions and water molecules between the two. For this reason, the solid polymer electrolyte membrane 114 is preferably a membrane having high conductivity of hydrogen ions. Further, it is preferable that the material is chemically stable and has high mechanical strength. As a material constituting the solid polymer electrolyte membrane 114,
Organic polymers 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 carboxyl group are preferably used. As such organic polymers,
Aromatic-containing polymers such as sulfonated poly (4-phenoxybenzoyl-1,4-phenylene) and alkylsulfonated polybenzimidazole;
Copolymers such as a polystyrene sulfonic acid copolymer, a polyvinyl sulfonic acid copolymer, a cross-linked alkyl sulfonic acid derivative, a fluorine-containing polymer composed of a fluororesin skeleton and sulfonic acid;
A copolymer obtained by copolymerizing acrylamides such as acrylamide-2-methylpropanesulfonic acid and acrylates such as n-butyl methacrylate;
Sulfone group-containing perfluorocarbon (Nafion (registered trademark, manufactured by DuPont), Aciplex (manufactured by Asahi Kasei Corporation));
Carboxyl group-containing perfluorocarbon (Flemion (registered trademark) S membrane (manufactured by Asahi Glass Co., Ltd.));
And the like. Of these, when aromatic-containing polymers such as sulfonated poly (4-phenoxybenzoyl-1,4-phenylene) and alkylsulfonated polybenzimidazole are selected, permeation of organic liquid fuel can be suppressed, and the battery by crossover can be suppressed. A decrease in efficiency can be suppressed.

  In addition, a crosslinkable substituent, such as a vinyl group, an epoxy group, an acryl group, a methacryl group, a cinnamoyl group, a methylol group, an azide group, and a naphthoquinonediazide group, are appropriately introduced into the polymer described above. A polymer cross-linked by irradiating the polymer with radiation in a molten state can also be used.

FIG. 2 is a cross-sectional view schematically showing the structures of the fuel electrode 102, the oxidizer electrode 108, the solid polymer electrolyte membrane 114, and the adhesive layer 161. As shown, the fuel electrode 102 and oxidizing electrode 108 in this embodiment, the catalyst layer 106 is a layer containing a catalyst was supported carbon particles and solid polymer electrolyte, a catalyst layer 112 The substrate 104, the substrate 110 It has the configuration formed above. The substrate surface may be subjected to a water repellent treatment.

  As the bases 104 and 110, a porous base such as carbon paper, a carbon molded body, a carbon sintered body, a sintered metal, or a foamed metal can be used. Further, a water repellent such as polytetrafluoroethylene can be used for the water repellent treatment of the substrate.

  Examples of the catalyst for the fuel electrode 102 include platinum, alloys of platinum with ruthenium, gold, rhenium, and the like, rhodium, palladium, iridium, osmium, ruthenium, rhenium, gold, silver, nickel, cobalt, lithium, lanthanum, strontium, and yttrium. And the like. 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-described exemplary substances can be used. The catalysts of the fuel electrode 102 and the oxidant electrode 108 may be the same or different.

  Examples of the carbon particles supporting the catalyst include acetylene black (Denka Black (registered trademark, manufactured by Denki Kagaku Kogyo Co., Ltd.), XC72 (manufactured by Vulcan), etc.), Ketjen Black, carbon nanotubes, carbon nanohorns, and the like. . The particle size of the carbon particles is, for example, 0.001 to 0.1 μm, preferably 0.02 to 0.06 μm.

  The solid polymer electrolyte constituting the fuel electrode 102 or the oxidizer electrode 108 is configured to include at least the first solid polymer electrolyte. Further, the solid polymer electrolyte constituting the fuel electrode 102 or the oxidizer electrode 108 may include a second solid polymer electrolyte. Here, both the fuel electrode 102 and the oxidant electrode 108 may be configured to include the first and second solid polymer electrolytes. It may be configured to include the second solid polymer electrolyte.

The first solid polymer electrolyte constituting the fuel electrode 102 and the oxidizer electrode 108 has a role of electrically connecting the carbon particles carrying the catalyst and the solid polymer electrolyte membrane 114 on the electrode surface, Good hydrogen ion conductivity and good water mobility are required. Further, the fuel electrode 102 is required to have an organic liquid fuel permeability such as methanol, and the oxidant electrode 108 is required to have an oxygen permeability. 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. As such organic polymers,
Sulfone group-containing perfluorocarbon (Nafion (registered trademark, manufactured by DuPont), Aciplex (manufactured by Asahi Kasei Corporation), etc.);
Carboxyl group-containing perfluorocarbon (such as Flemion (registered trademark) S film (manufactured by Asahi Glass Co., Ltd.));
Copolymers such as a polystyrene sulfonic acid copolymer, a polyvinyl sulfonic acid copolymer, a cross-linked alkyl sulfonic acid derivative, a fluorine-containing polymer composed of a fluororesin skeleton and sulfonic acid;
A copolymer obtained by copolymerizing acrylamides such as acrylamide-2-methylpropanesulfonic acid and acrylates such as n-butyl methacrylate;
And the like.
In addition, as a polymer to be bonded to a polar group,
Resins having nitrogen or hydroxyl groups such as polybenzimidazole derivatives, polybenzoxazole derivatives, crosslinked polyethyleneimine, polysilamine derivatives, amine-substituted polystyrene such as polydiethylaminoethyl polystyrene, nitrogen-substituted polyacrylate such as diethylaminoethyl polymethacrylate;
Hydroxyl-containing polyacrylic resin represented by silanol-containing polysiloxane and hydroxyethyl polymethyl acrylate;
Hydroxyl-containing polystyrene resin represented by parahydroxy polystyrene;
Etc. can also be used.
Among these, from the viewpoint of ion conductivity and the like, sulfone group-containing perfluorocarbons (such as Nafion (registered trademark, manufactured by DuPont) and Aciplex (made by Asahi Kasei Corporation)) and carboxyl group-containing perfluorocarbons (Flemion (registered trademark)) S film (manufactured by Asahi Glass Co., Ltd.) or the like is preferably used.

  In addition, a crosslinkable substituent, for example, a vinyl group, an epoxy group, an acryl 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. .

  The second solid polymer electrolyte constituting the adhesive layer 161 in FIG. 1 plays a role in improving the adhesion between the electrode surface and the solid polymer electrolyte membrane 114, and the adhesion to the solid polymer electrolyte membrane 114. It is preferable to use a material having good 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 or physical properties such as polarity, wettability, and SP value are used. By selecting polymers having similar values, 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. In addition, the adhesive layer 161 may be formed of a material cross-linked by irradiating radiation in a state in which a polymer having a crosslinkable substituent introduced therein is melted.

  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 alkylsulfonated polybenzimidazole. The solid polymer electrolyte membrane 114 and the second solid polymer electrolyte may have a swelling property of, for example, 50% or less, more preferably 20% or less (swelling property in a 70 vol% MeOH aqueous solution) with methanol. By doing so, particularly good interfacial adhesion and proton conductivity are obtained.

  The first solid polymer electrolyte in the fuel electrode 102 and the oxidant electrode 108 may be the same or different.

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

  The method for producing the electrode-electrolyte joined body 101 in the present embodiment is not particularly limited, but can be produced, for example, as follows.

First, a catalyst is supported on carbon particles. This step can be performed by a commonly used impregnation method. Then the catalyst carbon particles supporting the above-described first solid polymer electrolyte is dispersed in a solvent and, after a paste, the paste is applied to the substrate, the catalyst layer 106 or the catalyst layer 112 by dry form The fuel electrode 102 and the oxidizer electrode 108 thus manufactured can be manufactured. Here, the particle size of the carbon particles is, for example, 0.001 to 0.1 μm. The particle size of the catalyst particles, for example, shall be the 0.1 nm to 100 nm. The coal particles and solid polymer electrolyte, for example, a weight ratio of 1: 5-40: As used 1. The weight ratio between water and solute in the paste is, for example, about 1: 2 to 10: 1. There is no particular limitation on the method of applying the paste to the substrate. For example, methods such as brush coating, spray coating, and screen printing can be used. The paste is applied with a thickness of about 1 μm to 2 mm. After applying the paste, the paste is heated and dried at a heating temperature and a heating time according to the first solid polymer electrolyte to be used. The heating temperature and the heating time are appropriately selected depending on the material to be used. For example, the heating temperature may be 100 ° C. to 250 ° C., and the heating time may be 30 seconds to 30 minutes.

  The solid polymer electrolyte membrane 114 according to the present invention can be manufactured by employing an appropriate method depending on a material to be used. For example, it can be obtained by casting a liquid obtained by dissolving or dispersing an organic polymer material in a solvent on a releasable sheet of polytetrafluoroethylene or the like and drying it.

  Next, an adhesive layer 161 is formed. The adhesive layer 161 is formed by applying and drying a coating solution in which the second solid polymer electrolyte is dissolved or dispersed on the catalyst layer 106 or the catalyst layer 112 and / or the surface of the solid polymer electrolyte membrane 114. can do. When the application liquid is applied on the solid polymer electrolyte membrane 114, this step is performed on both the front and back surfaces of the solid polymer electrolyte membrane 114. In this case, for example, after applying the coating solution on one surface of the solid polymer electrolyte membrane 114, the surface is covered with a peelable sheet such as polytetrafluoroethylene, and the other surface of the solid polymer electrolyte membrane 114 is covered. The method of applying the above-mentioned coating solution to the above can be adopted. Thereby, the solid polymer electrolyte membrane 114 having the adhesive layers 161 formed on both surfaces can be obtained.

  In the present embodiment, the adhesive layer 161 is provided in both regions between the solid polymer electrolyte membrane 114 and the fuel electrode 102 and between the solid polymer electrolyte membrane 114 and the oxidant electrode 108. Alternatively, it may be provided on one side. In addition, the adhesive layer 161 does not need to be formed over the entire surface in these regions, but may be formed only partially in the above regions. For example, the adhesive layer 161 may be formed in an island shape. The thickness of the adhesive layer 161 is appropriately selected, for example, from the range of 0.1 μm to 20 μm.

The solid polymer electrolyte membrane 114 manufactured as described above is sandwiched between the fuel electrode 102 and the oxidant electrode 108 and hot pressed to obtain the electrode-electrolyte assembly 101. At this time, the surfaces of both electrodes where the catalyst is provided and the solid polymer electrolyte membrane 114 are opposed to each other with the adhesive layer 161 interposed therebetween. The conditions of the hot pressing are selected according to the material, and are set, for example, to a temperature exceeding the softening temperature or the glass transition temperature of the first solid polymer electrolyte or the second solid polymer electrolyte. Specifically, for example, the temperature is 100 to 250 ° C., the pressure is 5 to 100 kgf / cm ² , and the time is 10 seconds to 300 seconds.

  In FIG. 2, since the second solid polymer electrolyte constituting the adhesive layer 161 is common or similar to the material of the solid polymer electrolyte membrane 114, the interface between the electrode and the solid polymer electrolyte membrane 114 is firmly adhered. . As a result, it is possible to prevent the transfer of hydrogen ions from being hindered due to the separation of the interface and to suppress the deterioration of the battery performance. In addition, the physical strength of the battery is increased and the durability is improved.

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

From the viewpoint of effectively suppressing crossover, it is effective to select the first and second solid polymer electrolytes as follows.
(I) A material having a lower methanol permeability than the first solid polymer electrolyte is selected as the second solid polymer electrolyte.
(Ii) As the second solid polymer electrolyte, a material having a lower water content than the first solid polymer electrolyte is selected.
(Iii) A material having a lower polar group content density than the first solid polymer electrolyte is selected as the second solid polymer electrolyte.
(Iv) As 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 it is possible to suppress a decrease in battery performance due to crossover. Hereinafter, methods for measuring the physical properties shown in the above (i) to (iv) will be described.

Methanol permeability can be measured as follows. Into a liquid container separated by an electrolyte membrane to be measured (thickness: 50 μm, area: 1 cm ² ), inject 50 cc of 99.5% methanol on one side and 50 cc of pure water on the other side, and seal each liquid not to evaporate. I do. The change over time of the concentration of methanol permeating the measured electrolyte membrane into pure water is measured by gas chromatography to determine the amount of methanol permeated. In the case of adopting the configuration of the above (i), the second solid polymer electrolyte should have a permeation amount of methanol of 300 μmol / cm ² / h or less per unit area and per unit time when the membrane has a thickness of 50 μm. Is preferred. By selecting such a material, methanol can be prevented from reaching the oxidizing agent, and the above-described problem of crossover can be overcome.

  The water content is a value represented by (B−A) / A, 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 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, after the sulfone group is converted into a sulfate ion by an oxygen combustion flask method or the like, it can be determined by ion chromatography or titration. Titration is performed using carboxyarsenazo as an indicator, and titration is performed with 0.01 M barium perchlorate to determine a color change point from blue to purple.

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

(Second embodiment)
The present embodiment is different from the first embodiment in that the adhesive layer 161 also contains a catalyst and carbon particles carrying the catalyst.

  The method for producing the electrode-electrolyte assembly 101 in the present embodiment is not particularly limited, but can be produced, for example, as follows.

The catalyst layer 106 or the catalyst layer 112 can be manufactured in the same manner as in the first embodiment. The adhesive layer 161 is formed by dispersing a second solid polymer electrolyte and a carbon particle supporting a catalyst in a solvent, and forming a paste-like coating solution on the catalyst layer 106 or the catalyst layer 112 and / or the solid polymer electrolyte. It can be formed by applying and drying the surface of the film 114. The carbon particles and the solid polymer electrolyte in the coating liquid, for example, a weight ratio of 1: 5-40: As used 1. Thereby, the adhesive layer 161 including the carbon particles supporting the catalyst can be manufactured. Further, in the adhesive layer 161, the content of the carbon particles supporting the catalyst has a distribution along the direction from the surface in contact with the catalyst layer 106 or the catalyst layer 112 to the surface in contact with the solid polymer electrolyte membrane 114. Is also good. For example, the surface of the adhesive layer 161 that contacts the catalyst layer 106 or the catalyst layer 112 may include carbon particles, and the surface that contacts the solid polymer electrolyte membrane 114 may not include the carbon particles.

  In this embodiment, since the adhesive layer 161 also contains the carbon particles carrying the catalyst, the electron conductivity of the adhesive layer can be improved.

(Third embodiment)
This embodiment is different from the first and second embodiments in that the adhesive layer 161 includes the first solid polymer electrolyte in addition to the second solid polymer electrolyte. By doing so, the adhesion between the adhesive layer 161 and the catalyst layer 106 or the catalyst layer 112 is more significantly improved. In this case, the weight ratio of the second solid polymer electrolyte to the first solid polymer electrolyte in the adhesive layer 161 is preferably 10/1 to 1/10, more preferably 4/1 to 1/4. be able to. Also, in the present embodiment, similarly to the second embodiment, the adhesive layer 161 may include carbon particles supporting a catalyst.

  In the adhesive layer 161, the first and second solid polymer electrolytes may be uniformly or non-uniformly distributed. When the first and second solid polymer electrolytes are unevenly distributed, the content of the first solid polymer electrolyte on the surface of the adhesive layer 161 in contact with the catalyst layer 106 or the catalyst layer 112 is determined by the solid content of the adhesive layer 161. It can be configured to be higher than the content of the second solid polymer electrolyte on the surface in contact with the polymer electrolyte membrane 114. In this embodiment, the adhesive layer 161 and the catalyst layer 106 contain the first solid polymer electrolyte, and the solid polymer electrolyte membrane 114 contains the second solid polymer electrolyte. The adhesiveness between the adhesive layer 161 and the catalyst layer 106 or the catalyst layer 112 can be improved, and the adhesiveness between the adhesive layer 161 and the solid polymer electrolyte membrane 114 can also be increased. Also in the present embodiment, the adhesive layer 161 can be made of a material cross-linked by irradiating radiation in a state in which a polymer having a crosslinkable substituent introduced therein is melted.

  FIG. 4 is a cross-sectional view illustrating an example of the adhesive layer 161 in the present embodiment in detail. Here, the adhesive layer 161 can be composed of a plurality of adhesive layers 161a, 161b, 161c, 161d, and 161e. The adhesive layer 161a is a layer in contact with the catalyst layer 106 or the catalyst layer 112, and the adhesive layer 161e is a layer in contact with the solid polymer electrolyte membrane 114. In such a configuration, each of the adhesive layers 161a to 161e includes both or at least one of the first solid polymer electrolyte and the second solid polymer electrolyte. In the adhesive layers 161a to 161e, the content ratio of the second solid polymer electrolyte to the first solid polymer electrolyte is higher in the order of the adhesive layer 161e, the adhesive layer 161d, the adhesive layer 161c, the adhesive layer 161b, and the adhesive layer 161a. It is configured to be. The adhesive layer 161a may be configured not to include the second solid polymer electrolyte. Further, the adhesive layer 161e may be configured not to include the first solid polymer electrolyte.

The method for producing the electrode-electrolyte assembly 101 in the present embodiment is not particularly limited, but can be produced, for example, as follows.
The catalyst layer 106 or the catalyst layer 112 can be manufactured in the same manner as in the first embodiment. When the first and second solid polymer electrolytes are uniformly distributed in the adhesive layer 161, the first and second solid polymer electrolytes are dispersed in a solvent, and the paste-like coating liquid is applied to the catalyst layer 106 or the catalyst. The adhesive layer 161 can be formed by applying and drying the layer 112 and / or the surface of the polymer electrolyte membrane 114. The coating liquid may include carbon particles supporting a catalyst.

  As described with reference to FIG. 4, when the content of the first solid polymer electrolyte in the second solid polymer electrolyte is changed in the adhesive layer 161, the adhesive layer 161 is formed as follows. can do. Hereinafter, description will be made with reference to FIG.

When the application liquid is applied onto the solid polymer electrolyte membrane 114 , an application liquid e containing at least a second solid polymer electrolyte is applied onto the solid polymer electrolyte membrane 114 and dried to form an adhesive layer 161e. Subsequently, the first and second solid polymer electrolytes are dispersed in a solvent so that the content of the first solid polymer electrolyte is higher than that of the coating liquid e, and the paste-like coating liquid d is formed into an adhesive layer. The adhesive layer 161d is formed by coating and drying on the 161e. By repeating the process of applying and drying a coating solution in which the content of the first solid polymer electrolyte is gradually increased, the content of the first solid polymer electrolyte is increased in a region farther from the solid polymer electrolyte membrane 114. An adhesive layer 161 configured to have a high rate can be formed. The thus-formed solid polymer electrolyte membrane 114 including the adhesive layer 161 is sandwiched between the fuel electrode 102 and the oxidant electrode 108 and hot-pressed, whereby the electrode-electrolyte assembly 101 can be obtained.

When the coating solution is applied on the catalyst layer 106 or the catalyst layer 112, a coating solution a containing at least the first solid polymer electrolyte is applied on the catalyst layer 106 or the catalyst layer 112 and dried to form an adhesive layer 161a. To form Subsequently, the first and second solid polymer electrolytes are dispersed in a solvent so that the content of the second solid polymer electrolyte is higher than that of the coating solution a, and the paste-like coating solution b is formed into an adhesive layer. The adhesive layer 161b is formed by applying and drying on the 161a. By repeating the step of applying and drying the coating liquid in which the content of the second solid polymer electrolyte is gradually increased, the area of the second solid polymer electrolyte becomes more distant from the catalyst layer 106 or the catalyst layer 112. An adhesive layer 161 configured to have a high content can be formed. The electrode-electrolyte assembly 101 can be obtained by sandwiching the solid polymer electrolyte membrane 114 between the fuel electrode 102 and the oxidant electrode 108 including the adhesive layer 161 thus formed, and hot pressing.

  After the adhesive layer 161 is formed on the solid polymer electrolyte membrane 114 and the catalyst layer 106 or the catalyst layer 112 as described above, the solid polymer electrolyte membrane 114 is sandwiched between the fuel electrode 102 and the oxidant electrode 108. By hot pressing, the electrode-electrolyte assembly 101 can also be obtained.

  The object to which the coating solution is applied may be the solid polymer electrolyte membrane 114 and / or the catalyst layer 106 or the catalyst layer 112, but the coating solution may be the first and second solid polymer electrolytes. If it is included, it is preferable to apply it to the solid polymer electrolyte membrane 114. A substrate such as carbon paper has an uneven surface, whereas the solid polymer electrolyte membrane 114 has a relatively flat surface. Is improved.

  Hereinafter, the electrode for a polymer electrolyte fuel cell of the present invention and a 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 example, Nafion was used as the first solid polymer electrolyte, and sulfonated poly (4-phenoxybenzoyl-1,4-phenylene) (hereinafter referred to as PPBP) was used as the second solid polymer electrolyte. . The first solid polymer electrolyte forms part of the catalyst layer on the electrode surface, and the second solid polymer electrolyte forms part of the catalyst layer on the electrode surface and the solid polymer electrolyte membrane. In this embodiment, platinum was used as a noble metal catalyst for both the fuel electrode and the oxidant electrode.

  A method for manufacturing the fuel cell according to this embodiment will be described with reference to FIGS.

  First, 10 g of acetylene black (Denka Black (registered trademark); manufactured by Denki Kagaku Kogyo) is mixed with 500 g of a dinitrodiamine platinum nitrate solution containing 3% of platinum serving as a catalyst in the fuel electrode 102 and the oxidizer electrode 108, and the mixture is stirred. 60 ml of 98% ethanol was added as a reducing agent. This solution was stirred and mixed at about 95 ° C. for 8 hours to support the catalyst 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 acetylene black.

By mixing 200 mg of the above-described catalyst-supporting carbon particles and 3.5 ml of a 5% Nafion solution (alcohol solution, manufactured by Aldrich Chemical Co., Ltd.), Nafion was adsorbed on the surfaces of these catalysts and 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. This paste A was applied to a base made of carbon paper (TGP-H-120, manufactured by Toray Industries, Inc.) by a screen printing method, and then heated and dried at 100 ° C. to obtain a fuel electrode 102 and an oxidizer electrode 108. The platinum amount on the obtained electrode surface was 0.1 to 0.4 mg / cm ² .

  Next, a sulfonation treatment was performed by suspending 10 g of the finely powdered PPBP in 100 ml of 95% sulfuric acid and stirring for 200 hours. The PPBP thus obtained was washed with sufficient distilled water, dried and pulverized, and dissolved in a dimethylformamide solution. This is called solution A.

  The solution A was cast on a Teflon (registered trademark) sheet and then dried to obtain a solid polymer electrolyte membrane 114 having a size of 10 cm × 10 cm and a thickness of 30 μm.

  On the other hand, the solution A was applied to the surfaces of the fuel electrode 102 and the oxidant electrode 108. The coating method was a brush coating method. After the application, the coating was dried to form an adhesive layer 161 on the surface of each electrode.

An electrode-electrolyte assembly was produced by hot-pressing the solid polymer electrolyte membrane 114 between these electrodes under the conditions of a temperature of 150 ° C. and a pressure of 10 kgf / cm ^{2 for} 10 seconds. 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 this 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 0.18 A / cm ² were continuously observed.

  The above-mentioned electrode showed good bonding property to the above-mentioned solid polymer electrolyte membrane, and it was confirmed that the above-mentioned electrode effectively functions as a direct methanol fuel cell using methanol as a fuel.

FIG. 3 is a diagram schematically illustrating the fuel electrode 102 and the solid polymer electrolyte membrane 114 of the fuel cell of the present embodiment, and the adhesive layer 161 interposed therebetween. As shown, the catalyst layer of the fuel electrode 102 of the present embodiment includes a first solid polymer electrolyte 150 made of Nafion and carbon particles 140 carrying a catalyst (not shown). The adhesive layer 161 has a second solid polymer electrolyte 160 made of PPBP as a main component. The solid polymer electrolyte membrane 114 is made of PPBP. Since both the adhesive layer 161 and the solid polymer electrolyte membrane 114 contain PPBP, the adhesion between them is good. On the other hand, since Nafion and PPBP are entangled with each other, adhesion between the adhesive layer 161 and the fuel electrode 102 is also good. From the above, the adhesive layer 161 functions as a binder between the solid polymer electrolyte membrane 114 and the fuel electrode 102, and the bondability between the solid polymer electrolyte membrane 114 and the fuel electrode 102 is improved. It is considered that this contributes to good operation of the fuel cell in the embodiment.

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

  In the present embodiment, a material having a lower methanol permeability and a lower moisture content than the first solid polymer electrolyte 150 is selected as the solid polymer electrolyte membrane 114 and the second solid polymer electrolyte 160. 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 having good cell characteristics was obtained.

(Example 2)
Also in this example, Nafion was used as the first solid polymer electrolyte, and PPBP 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 polymer electrolyte membrane 114 were produced in the same manner as in Example 1. The PPBP and the catalyst-supporting carbon particles obtained in the same manner as in Example 1 were dissolved in a dimethylformamide solution to obtain a paste B. The paste B was applied on the surfaces of the fuel electrode 102 and the oxidant electrode 108 by a brush coating method, and dried after application to form an adhesive layer 161 on the surface of each electrode.

An electrode-electrolyte assembly was produced by hot-pressing the solid polymer electrolyte membrane 114 between these electrodes under the conditions of a temperature of 150 ° C. and a pressure of 10 kgf / cm ^{2 for} 10 seconds. 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 0.19 A / cm ² were continuously observed.

FIG. 5 is a diagram schematically showing the fuel electrode 102 and the solid polymer electrolyte membrane 114 of the fuel cell of the present embodiment, and the adhesive layer 161 interposed therebetween. As shown, the adhesive layer 161 includes PPBP and carbon particles 140. Since both the adhesive layer 161 and the solid polymer electrolyte membrane 114 contain PPBP, the adhesion between them is good. On the other hand, since Nafion and PPBP are entangled with each other, adhesion between the adhesive layer 161 and the fuel electrode 102 is also good. Here, since the conductive carbon particles 140 are also included in the adhesive layer 161, the electron conductivity of the adhesive layer can be improved. From the above, the bonding property between the solid polymer electrolyte membrane 114 and the fuel electrode 102 is improved by the presence of the adhesive layer 161, and the organic liquid fuel can also be consumed in the adhesive layer. Therefore, it is considered that this contributes to good operation of the fuel cell in this embodiment.

(Example 3)
Also in this example, Nafion was used as the first solid polymer electrolyte, and PPBP 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 polymer electrolyte membrane 114 were produced in the same manner as in Example 1. The PPBP solution A obtained by the same method as in Example 1 was mixed with the Nafion paste A obtained by the same method as in Example 1 to obtain a paste C and a paste D. At this time, the weight ratio of Nafion and PPBP in paste C is 1: 1. The weight ratio of Nafion and PPBP in paste D is 4: 1.

  First, paste C was applied on both sides of solid polymer electrolyte membrane 114 by a brush coating method, and dried after application. Next, the paste D was applied on the paste C by a brush coating method, and dried after the application. As a result, an adhesive layer 161 composed of the paste C and the paste D was formed on both surfaces of the solid polymer electrolyte membrane 114. 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 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 0.19 A / cm ² were continuously observed.

  FIG. 6 is a diagram schematically showing the fuel electrode 102 and the solid polymer electrolyte membrane 114 of the fuel cell of the present embodiment, and the adhesive layer 161 interposed therebetween. As illustrated, the adhesive layer 161 has a high content of the second solid polymer electrolyte 160 (PPBP) in a region near the solid polymer electrolyte membrane 114 and a first solid polymer polymer in a region near the catalyst layer 106. It is configured so that the content of the electrolyte 150 (Nafion) is high. Since the PPBP content is high in a region of the adhesive layer 161 near the solid polymer electrolyte membrane 114, the adhesion between the two is good. On the other hand, in a region of the adhesive layer 161 close to the catalyst layer 106, the content of Nafion is high, so that the adhesion between the adhesive layer 161 and the fuel electrode 102 is also good. From the above, it is considered that the presence of the adhesive layer 161 improves the bondability between the solid polymer electrolyte membrane 114 and the fuel electrode 102, and contributes to the good operation of the fuel cell in this embodiment.

(Example 4)
Also in this example, Nafion was used as the first solid polymer electrolyte, and PPBP 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 polymer electrolyte membrane 114 were produced in the same manner as in Example 1. 200 mg of catalyst-carrying carbon particles were added to the same paste C and paste D as in Example 3 to obtain paste E and paste F.

  First, paste E was applied to both surfaces of solid polymer electrolyte membrane 114 by a brush coating method, and dried after application. Next, the paste F was applied on the paste E by a brush coating method, and dried after the application. Thus, an adhesive layer 161 composed of the paste E and the paste F was formed on both surfaces of the solid polymer electrolyte membrane 114. 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 10 wt% methanol aqueous solution and oxygen (1.1 atm, 25 ° C.) as fuel. As a result, an open voltage of 0.54 V and a short circuit current of 0.20 A / cm ² were continuously observed.

  FIG. 7 is a diagram schematically showing the fuel electrode 102 and the solid polymer electrolyte membrane 114 of the fuel cell of the present embodiment, and the adhesive layer 161 interposed therebetween. As illustrated, the adhesive layer 161 has a high content of the second solid polymer electrolyte 160 (PPBP) in a region near the solid polymer electrolyte membrane 114 and a first solid polymer polymer in a region near the catalyst layer 106. It is configured so that the content of the electrolyte 150 (Nafion) is high. Further, the adhesive layer 161 also includes the carbon particles 140. In the present embodiment, as in the third embodiment, the bonding property between the solid polymer electrolyte membrane 114 and the fuel electrode 102 is improved due to the presence of the adhesive layer 161. In addition, since the adhesive layer 161 also includes the conductive carbon particles 140, the conductivity of the electrons in the adhesive layer can be improved. Thus, it is considered that the fuel cell according to the present embodiment shows a good operation.

(Comparative Example 1)
In this comparative example, the first solid polymer electrolyte constituting the fuel electrode 102 and the oxidizer electrode 108 and the second solid polymer electrolyte constituting the solid polymer electrolyte membrane 114 were both made of Nafion, The structure in which the layer 161 was not provided was adopted. Here, the first solid polymer electrolyte forms a part of the catalyst layer on the electrode surface, and the second solid polymer electrolyte forms a solid polymer electrolyte membrane.

  The solid polymer electrolyte membrane 114 was produced by the same method as in the above-described example except that PPBP was changed to Nafion.

  The fuel electrode 102 and the oxidant electrode 108 were manufactured in the same manner as in Example 1.

Subsequently, the solid polymer electrolyte membrane 114 was sandwiched between the fuel electrode 102 and the oxidizer electrode 108, 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, these were set in an apparatus for measuring a single cell of a fuel cell to produce a single cell.

The current-voltage characteristics of this 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 0.45 V and a short circuit current of 0.09 A / cm ² were observed.

  In this comparative example, it is inferred that the cell efficiency was reduced due to crossover of methanol from the fuel electrode to the oxidant electrode.

(Comparative Example 2)
In this comparative example, PPBP was used as the first solid polymer electrolyte and the second solid polymer electrolyte, and no adhesive layer 161 was provided. Here, the first solid polymer electrolyte forms a part of the catalyst layer on the electrode surface, and the second solid polymer electrolyte forms a solid polymer electrolyte membrane.

  The solid polymer electrolyte membrane 114 was manufactured using PPBP in the same manner as in the above embodiment.

Further, the fuel electrode 102 and the oxidant electrode 108 were produced as follows. First, the catalyst-supporting carbon particles obtained in the same manner as in Example 1 were added to the solution A (containing PPBP) of Example 1 to obtain a dispersion. The dispersion thus obtained was dispersed in an ultrasonic disperser at 50 ° C. for 3 hours to obtain a paste, thereby obtaining a paste B. The paste B is applied to the bases 104 and 110 which are carbon paper (manufactured by Toray Industries, Inc .: TGP-H-120) by a screen printing method, and then heated and dried at 100 ° C. to form the fuel electrode 102 and the oxidizer electrode 108. Got. The platinum amount on the obtained electrode surface was 0.1 to 0.4 mg / cm ² .

Subsequently, the solid polymer electrolyte membrane 114 was sandwiched between the fuel electrode 102 and the oxidizer electrode 108, 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, 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 stable discharge could be confirmed.

  The present comparative example has a configuration in which the first solid polymer electrolyte 150 (Nafion) in FIG. 3 is replaced by the second solid polymer electrolyte 160 (PPBP). As shown in Table 1, the second solid polymer electrolyte 160 (PPBP) is inferior to the first solid polymer electrolyte 150 (Nafion) in methanol permeability and water content. Therefore, it is presumed that the transfer of hydrogen ions from the fuel electrode to the oxidant electrode was insufficient, and the battery did not function stably.

(Comparative Example 3)
In this comparative example, Nafion was used as the first solid polymer electrolyte, PPBP was used as the second solid polymer electrolyte, and no adhesive layer 161 was provided. Here, the first solid polymer electrolyte forms a part of the catalyst layer on the electrode surface, and the second solid polymer electrolyte forms a solid polymer electrolyte membrane.
After the fuel electrode 102, the oxidant electrode 108, and the solid polymer electrolyte membrane 114 were produced in the same manner as in Example 1, the fuel electrode 102, the oxidant electrode 108, and the solid polymer electrolyte membrane 114 were thermocompression-bonded. However, the two were not sufficiently joined, and a fuel cell that could withstand the evaluation could not be obtained.

  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.

FIG. 1 is a cross-sectional view schematically illustrating a structure of an example of a fuel cell according to the present invention. FIG. 2 is a cross-sectional view schematically illustrating a fuel electrode, an oxidizer electrode, and a solid polymer electrolyte membrane in an example of the fuel cell of the present invention. FIG. 2 is a diagram schematically showing a fuel electrode and a solid polymer electrolyte membrane in a fuel cell according to an example of the present invention. It is sectional drawing which shows the adhesion layer in embodiment of this invention in detail. FIG. 2 is a diagram schematically illustrating a fuel electrode and a solid polymer electrolyte membrane of a fuel cell according to an embodiment of the present invention, and an adhesive layer interposed therebetween. FIG. 2 is a diagram schematically illustrating a fuel electrode and a solid polymer electrolyte membrane of a fuel cell according to an embodiment of the present invention, and an adhesive layer interposed therebetween. FIG. 2 is a diagram schematically illustrating a fuel electrode and a solid polymer electrolyte membrane of a fuel cell according to an embodiment of the present invention, and an adhesive layer interposed therebetween.

Explanation of reference numerals

REFERENCE SIGNS LIST 100 fuel cell 101 electrode-electrolyte assembly 102 fuel electrode 104 base 106 catalyst layer 108 oxidizer electrode 110 base 112 catalyst layer 114 solid polymer electrolyte membrane 120 fuel electrode separator 122 oxidizer electrode separator 124 fuel 126 oxidizer 140 carbon Particles 150 First solid polymer electrolyte 160 Second solid polymer electrolyte 161 Adhesive layer 161a, 161b, 161c, 161d, 161e Catalyst layer

Claims (48)

A catalyst electrode comprising a first solid polymer electrolyte and a catalyst material,
A solid polymer electrolyte membrane,
An adhesive layer provided between the catalyst electrode and the solid polymer electrolyte membrane, and including a second polymer electrolyte,
A fuel cell comprising:   2. The fuel cell according to claim 1, wherein the adhesive layer is in contact with the solid polymer electrolyte membrane.   3. The fuel cell according to claim 1, wherein the adhesive layer is in contact with the catalyst electrode.   The fuel cell according to any one of claims 1 to 3, wherein the second solid polymer electrolyte has higher adhesion to the solid polymer electrolyte membrane than the first solid polymer electrolyte. Fuel cell.   The fuel cell according to any one of claims 1 to 4, wherein the second solid polymer electrolyte comprises a solid polymer electrolyte constituting the solid polymer electrolyte membrane or a derivative thereof.   The fuel cell according to any one of claims 1 to 5, wherein an organic liquid fuel is supplied to the catalyst electrode.   7. The fuel cell according to claim 6, wherein the organic liquid fuel is methanol.   The fuel cell according to any one of claims 1 to 7, wherein the second solid polymer electrolyte has lower permeability of the organic liquid fuel than the first solid polymer electrolyte. .   9. The fuel cell according to claim 1, wherein the second solid polymer electrolyte has a lower moisture content than the first solid polymer electrolyte. 9.   10. The fuel cell according to claim 1, wherein each of the first solid polymer electrolyte and the second solid polymer electrolyte includes a proton acid group.   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.   The fuel cell according to any one of claims 1 to 11, 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. The fuel cell according to any one of claims 1 to 13,
The fuel cell according to claim 1, wherein the adhesive layer is composed mainly of the second polymer electrolyte. The fuel cell according to any one of claims 1 to 14,
The fuel cell according to claim 1, wherein the adhesive layer further includes the first polymer electrolyte. The fuel cell according to any one of claims 1 to 15,
The adhesive layer is provided in contact with the catalyst electrode and the solid polymer electrolyte membrane,
The content of the second solid polymer electrolyte on the surface of the adhesive layer in contact with the catalyst electrode is higher than the content of the second solid polymer on the surface of the adhesive layer in contact with the solid polymer electrolyte membrane. A fuel cell characterized by being low. The fuel cell according to any one of claims 1 to 16,
The fuel cell according to claim 1, wherein the adhesive layer includes a catalyst material. The fuel cell according to claim 17,
The adhesive layer is provided in contact with the catalyst electrode and the solid polymer electrolyte membrane,
A fuel cell, wherein a content of the catalyst substance on a surface of the adhesive layer in contact with the catalyst electrode is higher than a content of the catalyst substance on a surface of the adhesive layer in contact with the solid polymer electrolyte membrane. The fuel cell according to any one of claims 1 to 18,
The fuel cell according to claim 1, wherein the catalyst material includes a catalyst metal and conductive particles supporting the catalyst metal.   An electrode for a fuel cell, comprising: an electrode layer containing a catalyst substance and a first solid polymer electrolyte; and an adhesive layer formed on the electrode layer and containing a second solid polymer electrolyte.   21. The fuel cell electrode according to claim 20, wherein the second solid polymer electrolyte has a lower methanol permeability than the first solid polymer electrolyte.   22. The fuel cell electrode according to claim 20, wherein the second solid polymer electrolyte has a lower moisture content than the first solid polymer electrolyte.   23. The fuel cell electrode according to claim 20, wherein each of the first solid polymer electrolyte and the second solid polymer electrolyte includes a proton acid group. Electrodes.   24. The electrode for a fuel cell according to claim 20, wherein the first solid polymer electrolyte is made of a polymer containing fluorine.   25. The fuel cell electrode according to claim 20, wherein the second solid polymer electrolyte is made of a polymer containing no fluorine.   26. The fuel cell electrode according to claim 20, wherein the second solid polymer electrolyte is made of a polymer containing an aromatic compound. The fuel cell electrode according to any one of claims 20 to 26,
The electrode for a fuel cell, wherein the electrode layer includes the first solid polymer electrolyte. The fuel cell electrode according to any one of claims 20 to 27,
The adhesive layer is provided in contact with the electrode layer,
The content of the second solid polymer electrolyte in the surface of the adhesive layer in contact with the electrode layer is lower than the content of the second solid polymer electrolyte in the surface opposite to the surface in contact with the electrode layer. An electrode for a fuel cell, comprising: The fuel cell electrode according to any one of claims 20 to 28,
The electrode for a fuel cell, wherein the adhesive layer includes a catalyst material. The fuel cell electrode according to claim 29,
The adhesive layer is provided in contact with the electrode layer,
An electrode for a fuel cell, wherein a content of the catalyst substance in a surface of the adhesive layer in contact with the electrode layer is higher than a content of the catalyst substance in a surface opposite to a surface in contact with the electrode layer. The fuel cell electrode according to any one of claims 20 to 30,
The electrode for a fuel cell, wherein the catalyst material includes a catalyst metal and conductive particles supporting the catalyst metal. A method for producing a fuel cell electrode in which a catalyst layer and an adhesive layer are formed in this order on a substrate,
A step of forming a catalyst layer by applying a first coating solution containing conductive particles carrying a catalyst metal and particles containing a first solid polymer electrolyte onto a substrate,
Forming a second coating solution containing particles containing a second solid polymer electrolyte composed of a polymer different from the first solid polymer electrolyte on the catalyst layer to form the adhesive layer; ,
A method for producing an electrode for a fuel cell, comprising: The method for producing a fuel cell electrode according to claim 32,
The method for producing an electrode for a fuel cell, wherein the second solid polymer electrolyte has a lower methanol permeability than the first solid polymer electrolyte. The method for producing a fuel cell electrode according to claim 32 or 33,
The method for producing an electrode for a fuel cell, wherein the second solid polymer electrolyte has a lower water content than the first solid polymer electrolyte. The method for producing a fuel cell electrode according to any one of claims 32 to 34,
The method for producing an electrode for a fuel cell, wherein the first solid polymer electrolyte and the second solid polymer electrolyte each include a proton acid group. The method for producing a fuel cell electrode according to any one of claims 32 to 35,
The method for producing an electrode for a fuel cell, wherein the first solid polymer electrolyte is made of a polymer containing fluorine. The method for producing a fuel cell electrode according to any one of claims 32 to 36,
The method for manufacturing a fuel cell electrode, wherein the second solid polymer electrolyte is made of a polymer containing no fluorine. The method for producing a fuel cell electrode according to any one of claims 32 to 37,
The method for producing an electrode for a fuel cell, wherein the second solid polymer electrolyte is made of a polymer containing an aromatic. The method for producing a fuel cell electrode according to any one of claims 32 to 38,
The method for producing an electrode for a fuel cell, wherein the second coating liquid contains particles containing the first solid polymer electrolyte. The method for producing a fuel cell electrode according to claim 39,
The method for producing a fuel cell electrode, wherein the step of forming the adhesive layer includes a step of applying a plurality of coating solutions having different content rates of particles including the first solid polymer electrolyte. The method for producing a fuel cell electrode according to any one of claims 32 to 40,
The method for producing an electrode for a fuel cell, wherein the second coating liquid contains conductive particles carrying a catalyst metal. The method for producing a fuel cell electrode according to claim 41,
The method for producing an electrode for a fuel cell, wherein the step of forming the adhesive layer includes a step of applying a plurality of coating solutions having different contents of the conductive particles supporting the catalyst metal.   A fuel cell electrode is obtained by the method for producing a fuel cell electrode according to any one of claims 32 to 42, and the fuel cell electrode and the solid polymer electrolyte membrane are in contact with each other. A method for manufacturing a fuel cell, comprising a step of thermocompression bonding with a solid polymer electrolyte membrane. A method for manufacturing a fuel cell, comprising a solid polymer electrolyte membrane and a pair of electrodes having a catalyst layer formed on a substrate, sandwiching the solid polymer electrolyte membrane,
A step of forming a catalyst layer by applying a first coating solution containing a catalyst substance and particles containing a first solid polymer electrolyte to a substrate,
A step of applying a second coating solution containing particles containing a second solid polymer electrolyte composed of a polymer different from the first solid polymer electrolyte to the solid polymer electrolyte membrane to form an adhesive layer When,
A step of thermocompression bonding the electrode and the solid polymer electrolyte membrane in a state where the catalyst layer and the adhesive layer are in contact with each other;
A method for manufacturing a fuel cell, comprising: The method for producing a fuel cell according to claim 44,
The method for producing a fuel cell, wherein the second coating liquid contains particles containing the first solid polymer electrolyte. The method for manufacturing a fuel cell according to claim 45,
The method of manufacturing a fuel cell, wherein the step of forming the adhesive layer includes a step of applying a plurality of coating solutions having different content rates of particles including the first solid polymer electrolyte. The method for manufacturing a fuel cell according to any one of claims 44 to 46,
The method for producing a fuel cell, wherein the second coating liquid contains conductive particles carrying a catalyst metal. The method for manufacturing a fuel cell according to claim 47,
The method of manufacturing a fuel cell, wherein the step of forming the adhesive layer includes a step of applying a plurality of coating solutions having different contents of the conductive particles carrying the catalyst metal.

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