JP2008140703A - Composition material for battery, and film containing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrode which is capable of effectively restraining or preventing elution of Pt and is excellent in electrode catalyst activity. <P>SOLUTION: A composition material for a battery includes a compound containing nitrogen-containing six-membered ring and a nonelectrolyte material, wherein the compound containing nitrogen-containing six-membered ring is coordinated with at least one metal formed of a group consisting of platinum, nickel, cobalt, palladium, and iridium. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a battery composition used for a battery, and more particularly to a battery composition used for a polymer electrolyte fuel cell and a membrane containing the same.

  In recent years, fuel cells, which are clean power generation technologies that have high energy conversion efficiency and do not generate NOx, SOx, and the like, have attracted particular attention in recent years when they have been inspired by the ecology boom. On the other hand, there are various problems to be overcome for practical use and spread of fuel cells. In particular, the current PEFC uses a platinum-based catalyst with excellent activity as an electrode catalyst. However, if mass production is premised, there is a problem in the supply of platinum resources. Is needed. In addition, materials that are normally considered chemically stable, such as precious metals, carbon, and fluorine resins used as catalysts, cause chemical changes over a long period of time, resulting in performance degradation. Actual degradation is influenced by degradation factors in a complex manner, and great efforts are made in the analysis. For example, the following conventional methods exist for solving such problems.

Patent Document 1 describes an electrode catalyst using a platinum alloy including platinum-nickel-cobalt ternary alloy particles having a regular structure by heating at a temperature of 600 ° C. or higher and lower than 800 ° C. Further, the regular structure is confirmed by the fact that the peaks of (100) or (001) and (110) or (100) appear on the lower diffraction angle 2θ side than the main diffraction peak of (111) or (101) ( Patent Document 1 Table 1, FIG. 1), the platinum alloy having a face-centered cubic ordered structure or a face-centered tetragonal ordered structure has little performance deterioration even when used at a relatively high temperature for a long period of time. It also describes that high activity can be maintained.
JP-A-6-176766

  However, when the alloy catalyst of the above-mentioned Patent Document 1 is actually used, even if the alloy catalyst is made into a regular alloy, a large amount of the metal component below the second component elutes, and the catalyst metal composition changes significantly over time. In addition, high elution resistance cannot be maintained for a long time, and the elution metal tends to promote deterioration of the electrolyte and the carbon support.

  Further, it has been found that elution of Pt can be significantly suppressed by preliminarily adsorbing bipyridine (bpy) on a part of the cathode catalyst, particularly the Pt surface. It was found that the bpy oxidation degradation at the time or bpy gradually desorbs from the Pt surface with time and is discharged out of the fuel cell system together with the produced water, so that the Pt elution suppression effect by bpy cannot be obtained.

  Therefore, the present invention has been made in view of the above circumstances, and an object of the present invention is to provide an electrode body that can effectively suppress and prevent elution of Pt and is excellent in electrocatalytic activity.

  According to the present invention, since it is a battery composition that coordinates with a catalyst component, it is likely to coordinate preferentially to a highly active and easily oxidized site on the surface of the catalyst component, thereby suppressing Pt oxidant formation. In addition, elution of Pt can be suppressed / prevented.

  Further, by disposing the battery composition of the present invention between the gas diffusion layer or the electrode catalyst layer and the gas diffusion layer, the liquid water of the electrode catalyst layer intermittently contains a nitrogen-containing 6-membered ring. The compound can be released to the catalyst layer, and further has the function of enhancing the retention of the compound containing a nitrogen-containing 6-membered ring in the catalyst layer. Therefore, it is possible to provide an electrode catalyst with high elution resistance of the catalyst component.

  That is, the object includes a compound containing a nitrogen-containing 6-membered ring and a non-electrolytic material, and the compound containing the nitrogen-containing 6-membered ring is formed from the group consisting of platinum, nickel, cobalt, palladium, and iridium. This is accomplished by providing a battery composition that coordinates with at least one metal.

  The first of the present invention includes a compound containing a nitrogen-containing 6-membered ring and a non-electrolyte material, and the compound containing the nitrogen-containing 6-membered ring is formed from the group consisting of platinum, nickel, cobalt, palladium, and iridium. In addition, a battery composition coordinated with at least one metal.

  When these battery compositions are used, for example, in fuel cells, the battery composition has a particularly highly active site on the surface of a catalyst component such as Pt that is easily oxidized (edge portion of catalyst component, corner portion). ) Can be preferentially coordinated, so that oxidant formation of Pt can be suppressed and elution of Pt can be suppressed.

  More specifically, in general, particles of Pt, which is a typical catalyst component, have a polyhedral structure such as a tetrahedral structure, and the edges and corners of the polyhedron have oxygen reduction activity. Although hardly shown, it is considered that the surface free energy of the Pt atoms at the edges and corners is larger than that of the atoms on the surface, so that it is easily oxidized and tends to be the starting point of elution.

  Therefore, by arranging the battery composition having a compound containing a nitrogen-containing 6-membered ring according to the present invention in advance in a fuel cell, for example, a Pt edge having a polyhedral structure, a nitrogen-containing 6-membered ring at the corner A compound containing can be coordinated. And the presence of this ligand can protect the Pt atoms at the edges and corners that are likely to be the starting point of elution from chemical reactions such as oxidation, and can suppress and prevent elution of Pt. it is conceivable that.

  In the fuel cell, an anode electrode catalyst layer is disposed on one surface of the polymer electrolyte membrane, a cathode electrode catalyst layer is disposed on the other surface, and further on at least one surface of the anode electrode catalyst layer or the cathode deelectrode catalyst layer. The gas-diffusion layer includes a membrane-electrode assembly formed by laminating at least one film formed using the battery composition of the present invention.

Moreover, although the Pt elution suppression mechanism has not been clarified in detail, it is considered that the Pt elution is caused by the generation of Pt oxide species accompanying the generation or reduction of Pt oxide species.
Hereinafter, although the mechanism of Pt elution is shown, even if the mechanism of Pt elution is wrong, since the mechanism of Pt elution is not clear at present, it does not disturb the scope of rights of the present invention.

  The compound containing a nitrogen-containing 6-membered ring according to the present invention is a compound containing a nitrogen-containing 6-membered ring structure which does not show a catalytic effect on the electrode reaction and has a metal coordination ability when the compound is used in a battery. Any known one can be preferably used. More specifically, the compound containing a nitrogen-containing 6-membered ring according to the present invention is preferably a pyridine derivative. The pyridine derivative is preferably at least one selected from the group consisting of bipyridines, terpyridines, and phenanthrolines.

  This is because the bridge structure formed by a compound having a polycyclic structure (especially a polycyclic aromatic compound) secures a catalytic function site of a metal such as platinum and the above-described dissolution mechanism of platinum. It can be assumed that elution can be suppressed. Furthermore, the steric effect resulting from the structure of the polycyclic aromatic compound, that is, the atoms at the edges and corners of the catalyst component such as Pt having a polyhedral structure have a greater degree of freedom than the atoms on the surface. Because there are few steric hindrances when a relatively large polycyclic aromatic compound approaches the catalyst component, it is easy to selectively coordinate to the edge portion and corner portion of the catalyst component preferentially. It is considered that the ligand is stable.

  Specific examples of the bipyridines, terpyridines, and phenanthrolines according to the present invention include 2,2′-bipyridine, 2,6-di (2-pyridyl) pyridine, 1,10-phenanthroline, 4,7-biphenyl- 1,10-phenanthroline, 1,7-phenanthroline, bathocuproin, bathocuproin sulfonic acid and the like are mentioned. Among them, the compound containing a nitrogen-containing 6-membered ring according to the present invention is particularly 2,2′-bipyridine. preferable.

  In addition, the compound containing a nitrogen-containing 6-membered ring according to the present invention is preferably added in an amount of 0.001 to 50% by mass, more preferably 0.01 to 20% by mass, particularly preferably based on the mass of the non-electrolyte. Is 0.1 to 10% by mass. When the amount is less than 0.001% by mass, the amount of the compound containing a nitrogen-containing 6-membered ring cannot be obtained for a long time because the amount of the compound containing the nitrogen-containing 6-membered ring is small. In addition to the decrease in the electron conductivity of the gas diffusion layer due to the excessive amount, the pores are filled, so that the gas diffusibility is also reduced and the power generation performance is significantly reduced.

  The compound containing a nitrogen-containing 6-membered ring according to the present invention coexists on the catalyst surface via a nitrogen atom having a metal coordination ability, thereby suppressing / preventing Pt elution to suppress Pt oxidation. it is conceivable that. Assuming that Pt elution starts from the formation of Pt oxide species that occurs at this highly active site, these aromatic compounds selectively adsorb to the highly active site to suppress platinum oxidant formation, As a result, it is thought that the elution of platinum is suppressed.

  Furthermore, when the battery composition according to the present invention is used for a conventional membrane-electrode assembly, it can be applied as it is without changing the form of the conventional membrane-electrode assembly. The amount of Pt elution can be suppressed with an effective and inexpensive countermeasure. Moreover, since the effect can be exhibited with a very small amount of adsorption, it is possible to suppress a decrease in catalyst performance accompanying adsorption of the adsorbent to the catalyst metal.

  And since organic substances are coordinated to the electrode catalyst, it is recognized that the initial catalytic electrode characteristics are slightly lower than those of the untreated ones, but the durability is improved and the battery life can be extended. it can.

  Moreover, the adsorption rate with respect to the catalyst component of the compound containing a nitrogen-containing 6-membered ring according to the present invention is preferably 20 to 70, more preferably 30 to 60, per 100 atoms of the catalyst component.

  Examples of the non-electrolyte material according to the present invention include carbon paper, non-woven fabric, carbon woven fabric, paper-like paper body, felt and the like.

  The battery composition according to the present invention includes the above non-electrolyte material and the above compound containing a nitrogen-containing 6-membered ring, and, if necessary, additives, alcohols (methanol, ethanol, Propanol, butanol, etc.), water, water repellent, binder, and the like. For example, the water repellent material includes polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polyhexafluoropropylene, tetrafluoroethylene. -Fluororesin such as hexafluoropropylene copolymer (FEP), polypropylene, polyethylene and the like. Of these, fluororesins are preferred because they are excellent in water repellency and corrosion resistance during electrode reaction.

  Incidentally, the “binder” refers to a substance having a role of adhesion, and in the examples according to the present invention, a fluororesin having both a role of a binder and a role of water repellency is used, but it is not necessarily limited thereto. Alternatively, the binder and the water repellent material may be mixed and used as independent substances.

  As the additive, for example, when a fluorine-based resin is used as a binder, the water repellency may be too high, and a hydrophilic substance may be mixed as an additive in order to appropriately adjust this. As such an additive, any hydrophilic substance having durability in a use environment can be used, and examples thereof include fine metal oxide powders such as tin oxide, alumina, and silica.

  In the battery composition according to the present invention, the amounts of additives, alcohols (methanol, ethanol, propanol, butanol, etc.), water, water repellent, and binder used as necessary are appropriately selected according to various conditions. However, 0.01 to 30% by mass is preferable with respect to the total mass of the battery composition.

  The compound containing a nitrogen-containing 6-membered ring and a non-electrolyte material according to the present invention, and the compound containing the nitrogen-containing 6-membered ring are at least one formed from the group consisting of platinum, nickel, cobalt, palladium, and iridium. A battery composition coordinated with two metals (hereinafter also simply referred to as a battery composition) can be used in a battery (particularly a fuel cell) by making it granular, rod-like, film-like, or plate-like. It is particularly preferable to use the battery composition as a film. In addition, when using the particle | grains, stick | rod, film | membrane, or plate-like body containing the composition for batteries concerning this invention for a battery (especially fuel cell), it is preferable to be provided adjacent to an electrode (catalyst) layer, Furthermore, It is preferable to provide particles, rods, membranes or plates containing the battery composition according to the present invention between the electrode (catalyst) layer and the gas diffusion layer. Alternatively, the film itself containing the battery composition according to the present invention is preferably provided as a gas diffusion layer adjacent to the electrode (catalyst) layer.

  The film containing the battery composition according to the present invention contains a non-electrolyte material and a compound containing a nitrogen-containing 6-membered ring, but does not contain an electrolyte (or also referred to as an ion conductive substance), and an electrode ( Since it is preferably provided adjacent to the (catalyst) layer, for example, when used in a fuel cell, the present invention is a non-electrolyte even if the region where the electrolyte exists is increased in potential (potential exceeding 1.2 V). The film itself containing the battery composition according to the above does not increase in potential. Therefore, the deterioration of the oxidation of the compound containing a nitrogen-containing 6-membered ring according to the present invention due to the increase in potential is small.

  Furthermore, since the membrane containing the battery composition according to the present invention is preferably provided adjacent to the electrode (catalyst) layer or used as a gas diffusion layer, liquid water in the electrode catalyst layer (especially the cathode electrode) The compound containing a nitrogen-containing 6-membered ring is released from the film containing the battery composition according to the present invention using the generated water on the side as a bridge. Further, in the fuel cell, water and the like generated on the cathode electrode side is discharged to the outside through the gas diffusion layer and the like. At this time, on the surface of the membrane containing the battery composition according to the present invention, The adsorbing part of the compound containing a nitrogen-containing 6-membered ring captures the compound containing the nitrogen-containing 6-membered ring that is about to flow out, suppresses the outflow of the compound containing the nitrogen-containing 6-membered ring, and catalyst components such as platinum It is thought that elution of can be suppressed and prevented over a long period of time.

  Moreover, when using the film | membrane, particle | grains, stick | rod or plate-like body containing the composition for batteries which concerns on this invention for a battery (especially fuel cell), it provides in the outer side of at least one electrode side of a cathode electrode side or an anode electrode side. It is preferable that it is provided on the cathode electrode side, and may be provided on both sides.

  The thickness of the film containing the battery composition according to the present invention (when used separately from the gas diffusion layer) is preferably 1 to 100 μm, and more preferably 5 to 50 μm.

  Moreover, when the film | membrane containing the composition for batteries concerning this invention is used as a gas diffusion layer, 0.05-1 mm is preferable and 0.1-0.5 mm is more preferable.

  The material used for the gas diffusion layer (hereinafter referred to as GDL) according to the present invention is preferably the same material as the above non-electrolyte, such as carbon paper, non-woven fabric, carbon woven fabric, paper-like paper body, felt. A sheet-like material composed of such materials has been proposed. When GDL has excellent electron conductivity, efficient transport of electrons generated by a power generation reaction is achieved, and the performance of the fuel cell is improved. Further, if the GDL has an excellent water repellency, the generated water is efficiently discharged.

  In order to ensure high water repellency, a technique for water repellency treatment of a material constituting the GDL has also been proposed. For example, a solution containing a fluorine-based resin such as polytetrafluoroethylene (PTFE) is impregnated with a material constituting GDL such as carbon paper, and dried in the air or an inert gas such as nitrogen. Depending on the case, the hydrophilization treatment may be performed on the material constituting the GDL.

  In addition, carbon particles and a binder may be disposed on a sheet-like GDL made of carbon paper, non-woven fabric, carbon woven fabric, paper-like paper body, felt, etc., and both may be used as a gas diffusion layer. You may use the film itself which consists of particle | grains and a binder as a gas diffusion layer. As a result, since the water repellent material and the carbon particles are uniformly formed on the film itself, the water repellent efficiency is increased as compared with the above application.

  Examples of the water repellent material include fluorine resins such as polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polyhexafluoropropylene, and tetrafluoroethylene-hexafluoropropylene copolymer (FEP), polypropylene, polyethylene, and the like. Is mentioned. Of these, fluororesins are preferred because they are excellent in water repellency and corrosion resistance during electrode reaction.

  Incidentally, the “binder” refers to a substance having a role of adhesion, and in the examples according to the present invention, a fluororesin having both a role of a binder and a role of water repellency is used, but it is not necessarily limited thereto. Alternatively, the binder and the water repellent material may be mixed and used as independent substances.

Incidentally, the water-repellent material, for the compound containing a nitrogen-containing 6-membered ring of the present invention, it is sufficient 1 to 1 × 10 ⁴ times by mass.

The film containing the composition for a battery according to the present invention does not contain an ion conductive substance, and contains 0.1 nmol / cm ² to 10 μmol of a compound containing the nitrogen-containing 6-membered ring coordinated with the metal per unit area. / Cm ² is preferable.

  The amount of the compound containing a nitrogen-containing 6-membered ring having a metal coordination ability is preferably applied within a range that does not significantly affect the electrode performance of the membrane-electrode assembly (MEA). The applied state is 20% to 70%, more preferably 30% to 60%, based on the platinum electrode area, and is adsorbed by the compound containing the nitrogen-containing 6-membered ring structure for the reasons described above. Can be effective.

The amount of the compound containing a nitrogen-containing 6-membered ring according to the present invention is preferably applied in the range of 0.1 nmol / cm ² to 10 μmol / cm ² per unit area of the gas diffusion layer. It is preferably 1 nmol / cm ² to 1 μmol / cm ² , particularly preferably 10 nmol / cm ² to 0.1 μmol / cm ² .

0.1 nmol / cm prolonged catalyst dissolution preventing effect for a small amount of storage compound comprising a less than ² a nitrogen-containing 6-membered ring can not be obtained, including 10 [mu] mol / cm ² than it and a nitrogen-containing 6-membered ring Since the amount of the compound is too large and the electron conductivity of the gas diffusion layer is lowered, the pores are filled and the gas diffusibility is also lowered, so that the power generation performance is significantly lowered.

  When the membrane containing the battery composition according to the present invention is used in, for example, a fuel cell, a sufficient amount of the above compound containing a nitrogen-containing 6-membered ring can be stored in the membrane-electrode assembly, so that high electrode performance is maintained for a long time. A possible membrane-electrode assembly can be obtained.

  The method for producing a film containing the battery composition according to the present invention comprises a non-electrolyte material according to the present invention in a solution obtained by dissolving or dispersing a compound containing a nitrogen-containing 6-membered ring according to the present invention in a known solvent. , A method of spraying a solution obtained by dissolving or dispersing a compound containing a nitrogen-containing 6-membered ring according to the present invention in a known solvent onto a non-electrolyte material, a nitrogen-containing composition according to the present invention in a known solvent Examples thereof include a method in which a solution in which a compound containing a 6-membered ring is dissolved or dispersed is directly applied to a non-electrolyte material.

  The above-mentioned known solvents are mainly alcohols (methanol, ethanol, propanol, butanol, etc.), but acetone, water, pyridine, etc. for the purpose of easily dissolving or dispersing the compound containing a nitrogen-containing 6-membered ring. Other organic solvents such as hexane may be included. The concentration of the above solution is preferably 0.001 to 10% by mass and more preferably 0.01 to 1% by mass with respect to the solvent.

  A method of directly applying a solution obtained by dissolving or dispersing a compound containing a nitrogen-containing 6-membered ring according to the present invention in the above-mentioned known solvent to a non-electrolyte material may be applied a plurality of times. Then, the step of applying again may be performed a plurality of times. Further, when the solution is directly applied to the non-electrolyte material, it may be applied on one side or on both sides.

  In the case of forming a film containing the battery composition according to the present invention, the impregnation time when employing the above impregnation method is not particularly limited, and is appropriately selected according to the size of the non-electrolyte material. However, for example, the solution may be impregnated for about 4 to 48 hours under conditions of 0 ° C to 50 ° C.

  Further, after the above impregnation method or spraying method, drying, re-impregnation, or re-spraying may be performed as necessary.

  In the membrane-electrode assembly according to the present invention, an anode electrode catalyst layer is disposed on one surface of a polymer electrolyte membrane, a cathode electrode catalyst layer is disposed on the other surface, and the anode electrode catalyst layer or the cathode electrode catalyst layer is further disposed. In the membrane-electrode assembly in which at least one gas diffusion layer according to the present invention is laminated on at least one side of the first gas diffusion layer, the first gas diffusion layer in contact with the electrode catalyst layer has opposite hydrophilicity on the surface in contact with the electrode catalyst layer. It is preferable that it is equal or higher than the surface.

  The compound containing a nitrogen-containing 6-membered ring of the present invention is slightly water-soluble, and the supply from the gas diffusion layer to the electrode catalyst layer is supplied as a bridge with liquid water staying at the boundary between the electrode catalyst layer and the gas diffusion layer. The The compound containing the nitrogen-containing 6-membered ring of the present invention may be contained in the electrode catalyst layer, or may not be contained in advance. In either case, the anode electrode catalyst layer or the cathode electrode catalyst Since the compound is supplied from the gas diffusion layer in contact with the layer, the Pt elution suppression effect is obtained.

  In addition, although the compound containing the nitrogen-containing 6-membered ring of this invention may be added to an electrode catalyst layer, it is more preferable not to add. Moreover, since at least one gas diffusion layer according to the present invention may be laminated, it may be a single layer or a plurality of layers.

  Moreover, since the compound containing a nitrogen-containing 6-membered ring according to the present invention can be supplied from the gas diffusion layer to the electrode catalyst layer, the membrane capable of largely suppressing elution of the electrode catalyst material and maintaining high electrode performance for a long period of time -An electrode assembly can be obtained.

  In addition, as a manufacturing method of the first gas diffusion layer in which the hydrophilicity of the surface in contact with the electrode catalyst layer is equal to or higher than that of the opposite surface, for example, in the same manner as described above, the nitrogen-containing 6-membered material according to the present invention is used in a known solvent A method in which a solution containing a ring-containing compound is dissolved or dispersed is directly applied to one side of the gas diffusion layer, a method of applying the water repellent material described in the above gas diffusion layer to one side of the gas diffusion layer, etc. Can be mentioned.

  Since the compound containing a nitrogen-containing 6-membered ring according to the present invention is a hydrophobic substance because it is difficult to dissolve in water, the electrode catalyst layer can be obtained by applying the compound containing the nitrogen-containing 6-membered ring to one side of the gas diffusion layer. It is considered that there is a difference in hydrophilicity between the surface in contact with the surface and the opposite surface. The reason for applying the water repellent material is the same reason.

  The above-mentioned known solvents are mainly alcohols (methanol, ethanol, propanol, butanol, etc.), but acetone, water, pyridine, hexane are used for the purpose of easily dissolving or dispersing a compound containing a nitrogen-containing 6-membered ring. Other organic solvents such as may be included. The concentration of the above solution is preferably 0.001 to 10% by mass and more preferably 0.01 to 1% by mass with respect to the solvent.

  A method in which the compound containing the nitrogen-containing 6-membered ring according to the present invention is dissolved or dispersed in the above-mentioned known solvent may be directly applied to one side of the gas diffusion layer. The process of drying and applying again may be performed a plurality of times.

  Moreover, the solution at the time of using it for the method of apply | coating said water repellent material to the single side | surface of a gas diffusion layer should just melt | dissolve or disperse | distribute 1-50 mass% with respect to said well-known solvent.

  In the membrane-electrode assembly according to the present invention, a second gas diffusion layer is further laminated on the first gas diffusion layer, and the second gas diffusion layer in contact with the first gas diffusion layer is more than the first gas diffusion layer. It is preferable to have the same or high hydrophobicity.

  Therefore, in the membrane-electrode assembly according to the present invention, the amount of the compound containing the nitrogen-containing 6-membered ring of the present invention may be adjusted so as to increase outward from the gas diffusion layer. A gas diffusion layer (for example, the second gas diffusion layer) produced with a high concentration of a solution containing a compound containing a nitrogen-containing 6-membered ring and a concentration of the solution containing a compound containing a nitrogen-containing 6-membered ring of the present invention are low. A preferred membrane-electrode assembly according to the present invention can be manufactured by laminating a gas diffusion layer (for example, a first gas diffusion layer) manufactured with a material in the order of a first gas diffusion layer and a second gas diffusion layer. it can.

The electrode catalyst layer according to the present invention includes a conductive material on which a catalyst component is supported and an electrolyte (also referred to as an ionic conductive substance). Hereinafter, after describing the catalyst component, the conductive material, and the ion conductive substance according to the present invention, the polymer electrolyte according to the present invention will be described.
Since the gas diffusion layer according to the present invention has been described above, it is omitted here.

  As the catalyst component used in the electrode catalyst according to the present invention, the cathode catalyst is not particularly limited as long as it has a catalytic action for the oxygen reduction reaction, and a known catalyst can be used in the same manner. The catalyst component used for the anode catalyst is not particularly limited as long as it has a catalytic action for the oxidation reaction of hydrogen, and a known catalyst can be used in the same manner. Specifically, platinum, ruthenium, iridium, rhodium, palladium, osmium, tungsten, lead, iron, chromium, gold (Au), silver (Ag), cobalt, nickel, manganese, vanadium, molybdenum, gallium, aluminum, etc. It is selected from metals and their alloys. Among these, those containing at least platinum are preferably used in order to improve catalyst activity, poisoning resistance to carbon monoxide and the like, heat resistance, and the like.

  Further, Pt, Pd, Ir, Rh, and Au are particularly preferable as the catalyst species that is excellent in the electrocatalytic activity for each electrocatalytic reaction and has an elution suppressing effect by adsorption of a compound containing a nitrogen-containing 6-membered ring. These catalytic metals can be used in the state where a metal alone or an alloy, or other noble metal, base metal, or metal composition is mixed. Like Pt, Pd, Ir, Rh, and Au are considered to be eluted by the generation of dissolved species in their own redox process, and the same elution suppression effect as Pt is obtained.

  In general, an alloy is a generic term for a metal element having one or more metal elements or non-metal elements added and having metallic properties.

  The alloy structure consists of a eutectic alloy, which is a mixture of the component elements as separate crystals, a component element completely melted into a solid solution, and a component element composed of an intermetallic compound or a compound of a metal and a nonmetal. There is what is formed, and any may be used in the present application. At this time, the catalyst component used for the cathode electrode catalyst (layer) and the catalyst component used for the anode electrode catalyst (layer) can be appropriately selected from the above. In the following description, unless otherwise specified, the descriptions of the catalyst components for the cathode electrode catalyst (layer) and the anode electrode catalyst (layer) are the same definitions for both, and are collectively referred to as “catalyst components”. However, the catalyst components for the cathode electrode catalyst (layer) and the anode electrode catalyst (layer) do not have to be the same, and are appropriately selected so as to exhibit the desired action as described above.

  The shape and size of the catalyst component are not particularly limited, and the same shape and size as known catalyst components can be used, but the catalyst component is preferably granular. At this time, the smaller the average particle size of the catalyst component used in the electrode catalyst, the higher the effective electrode area where the electrochemical reaction proceeds, which is preferable because the oxygen reduction activity is also high, but actually the average particle size is too small On the other hand, a phenomenon in which the oxygen reduction activity decreases is observed. Therefore, the average particle diameter of the catalyst component according to the present invention is preferably 1 to 20 nm, more preferably 2 to 15 nm, and further preferably 4 to 10 nm. When the average particle diameter is 1 nm or more, the specific surface area is not too large, high mass activity is obtained, and sufficient Pt elution resistance is obtained. If it is 20 nm or less, it is considered that elution resistance is obtained, and the specific surface area is not too small so that sufficient mass activity can be obtained.

  Examples of the method for measuring the average particle diameter of the catalyst component according to the present invention include a method of measuring the particle diameter of particles observed in several to several tens of fields for a representative sample from a transmission electron microscope image. In this measurement method, there is a significant difference in the average particle diameter depending on the sample to be observed and the visual field. More simply, the crystallite diameter determined from the half width of a specific reflection peak from the X-ray diffraction profile can be used as the average particle diameter of the catalyst component.

  The average particle size of the catalyst component of the present invention was determined by measuring all the particle sizes of the primary particles of the conductive material observed in any 8 fields of the transmission electron microscope image (total N> 120). The test was carried out under the condition that the median was the average particle diameter of the catalyst component.

  The primary particle diameter of the conductive material according to the present invention can be measured by using a known method using an electron microscope such as a scanning type or a transmission type, or an X-ray diffraction method. For example, the ratio of the average particle diameter with the catalyst component to the primary particle diameter of the conductive material calculated from the image taken by TEM is preferably 1 to 50, more preferably 1.5 to 15, and more preferably 2 to 2. 10.

  If the ratio of the average particle size of the primary particle size of the conductive material to the catalyst component is 1 to 50, the catalyst component particles are not too large with respect to the primary particle size of the carrier. Aggregation is difficult to occur, and high dispersion support is easily maintained. For this reason, sufficient electrode performance can be obtained with respect to the amount of Pt used. Further, if the ratio of the average particle size of the primary particle size of the conductive material to the catalyst component is 50, the specific surface area of the carrier does not become too small, and there is a sufficient area for supporting the catalyst component. For this reason, the agglomeration of the supported catalyst component particles hardly occurs as described above, and sufficient electrode performance can be obtained with respect to the used Pt amount.

  In the electrode catalyst in which the catalyst component is supported on the conductive material, the supported amount of the catalyst component is preferably 10 to 80% by mass, more preferably 30 to 60% by mass with respect to the conductive material. . The amount of the catalyst component supported can be examined by inductively coupled plasma emission spectroscopy (ICP).

  In order to further suppress the elution of Pt, it is better to set the catalyst component loading in a certain range. If it is 20 mass% or more, the catalyst layer does not become too thick, and high electrode performance can be obtained. On the other hand, if it is 70% by mass or less, the elution of Pt is further suppressed, and the catalyst component becomes highly dispersed, so that the performance obtained with respect to the amount of the catalyst component is sufficient.

  The conductive material according to the present invention is used in the present invention as long as it has a specific surface area for supporting the catalyst component in a desired dispersed state and has sufficient electronic conductivity as a current collector. Preferably, the main component is a conductive material. By using a conductive material for the conductive material according to the present invention, a high-performance anode electrode with little electrical resistance loss and material diffusion loss can be obtained. Specific examples include carbon particles made of carbon black, activated carbon, coke, natural graphite, artificial graphite and the like. Further, as such carbon materials, more specifically, acetylene black, Vulcan, Ketjen black, black pearl, graphitized acetylene black, graphitized Vulcan, graphitized Ketjen black, graphitized carbon, graphitized black pearl , Carbon nanotubes, carbon nanofibers, carbon nanohorns, and carbon fibrils as main components.

  In the present invention, “the main component is carbon” refers to containing a carbon atom as a main component, and is a concept including both a carbon atom only and a substantially carbon atom. In some cases, elements other than carbon atoms may be included in order to improve the characteristics of the fuel cell. In addition, being substantially composed of carbon atoms means that mixing of impurities of about 2 to 3% by mass or less is allowed.

  Further, the size of the conductive material is not particularly limited, but from the viewpoint of controlling the ease of loading, the catalyst utilization, and the thickness of the electrode catalyst (layer) within an appropriate range, the primary particle size is It is good to set it as 2-100 nm, Preferably it is 10-80 nm, More preferably, it is about 20-50 nm.

  If the primary particle diameter of the conductive material according to the present invention is 2 nm or more, it becomes easy to maintain highly dispersed support without being too small with respect to the catalyst component particle diameter. Since the specific surface area is obtained, sufficient electrode performance can be obtained without aggregation of the catalyst components.

  In the present specification, the “primary particle” means that a plurality of conductive materials, for example, carbon materials such as the above-described carbon black are generally aggregated. An individual particle.

  Moreover, 5-80 volume% is preferable and, as for the porosity of the electroconductive material which concerns on this invention, 10-70 volume% is more preferable.

  The primary particle diameter of the conductive material according to the present invention is a method for measuring the primary particle diameter of the conductive material according to the present invention. All the primary particle sizes were measured (total N> 60), and the median value of the particle sizes was set to the primary particle size. However, the primary particle diameter can be calculated not only by this measuring method but also by a known method.

  The conductive material according to the present invention is preferably a powder or a porous structure composed of 85% by mass to 100% by mass of carbon, more preferably 90% by mass to 100% by mass, and 95% by mass to 100% by mass. % Is more preferable.

  When the proportion of carbon in the conductive material is 85% by mass to 100% by mass, it is possible to obtain a high-performance electrode that can achieve both a sufficient specific surface area and electronic conductivity.

  A material composed of carbon carrying the catalyst component has sufficient electronic conductivity, and since it is necessary to easily disperse the catalyst component easily, a carbonaceous material is preferably used. Elements other than carbon include, for example, fluorine and silicon for imparting water repellency, boron for improving the corrosion resistance of conductive materials, hydrogen contained in surface functional groups, oxygen and nitrogen Impure metal content and the like.

  The catalyst component can be supported on the conductive material according to the present invention by a known method. For example, known methods such as impregnation method, liquid phase reduction support method, evaporation to dryness method, colloid adsorption method, spray pyrolysis method, reverse micelle (microemulsion method) can be used.

  For example, in order to support the catalyst component on the surface of the conductive material by an impregnation method, a step of adding the conductive material to a solution containing the catalyst component (hereinafter also referred to as catalyst solution), and the catalyst solution on the surface of the conductive material And a step of supporting the catalyst component on the conductive material by the impregnation step. As a result, the catalyst component can be highly dispersed and supported on the surface of the conductive material, and an electrode catalyst having sufficient initial performance and excellent durability can be obtained.

  The solution containing the catalyst component is a solution containing the element of the catalyst component supported on the conductive material. Since the catalyst component exhibits high catalytic activity, the electrode catalyst according to the present invention described above is used. The same element as the catalyst component used for (layer) is mentioned.

  The ion conductive material that is an electrolyte in the electrode catalyst layer according to the present invention is not particularly limited and a known material can be used, but the same materials as those used for the polymer electrolyte membrane can be used, and at least high Any material having proton conductivity may be used. The cathode catalyst (layer) / anode catalyst (layer) (hereinafter, also simply referred to as “catalyst (layer)”) of the present invention includes a polymer electrolyte in addition to the electrode catalyst. The polymer electrolyte that can be used in this case is roughly classified into a fluorine-based electrolyte containing fluorine atoms in the whole or a part of the polymer skeleton and a hydrocarbon-based electrolyte not containing fluorine atoms in the polymer skeleton.

  Specific examples of the fluorine electrolyte include perfluorocarbon sulfonic acids such as Nafion (registered trademark, manufactured by DuPont), Aciplex (registered trademark, manufactured by Asahi Kasei Co., Ltd.), and Flemion (registered trademark, manufactured by Asahi Glass Co., Ltd.). Polymer, polytrifluorostyrene sulfonic acid polymer, perfluorocarbon phosphonic acid polymer, trifluorostyrene sulfonic acid polymer, ethylene tetrafluoroethylene-g-styrene sulfonic acid polymer, ethylene-tetrafluoroethylene Preferred examples include polymers and polyvinylidene fluoride-perfluorocarbon sulfonic acid polymers.

  Specific examples of the hydrocarbon electrolyte include polysulfone sulfonic acid, polyaryl ether ketone sulfonic acid, polybenzimidazole alkyl sulfonic acid, polybenzimidazole alkyl phosphonic acid, polystyrene sulfonic acid, polyether ether ketone sulfonic acid, polyphenyl. A suitable example is sulfonic acid.

  The polymer electrolyte preferably contains a fluorine atom because of its excellent heat resistance and chemical stability. Among them, Nafion (registered trademark, manufactured by DuPont), Aciplex (registered trademark, manufactured by Asahi Kasei Co., Ltd.) Fluorine electrolytes such as Flemion (registered trademark, manufactured by Asahi Glass Co., Ltd.) are preferred.

  The catalyst component can be supported on the conductive material by a known method. For example, known methods such as impregnation method, liquid phase reduction support method, evaporation to dryness method, colloid adsorption method, spray pyrolysis method, reverse micelle (microemulsion method) can be used.

  In the case where the electrode according to the present invention is used as a membrane-electrode assembly (MEA), the polymer electrolyte used in the polymer electrolyte membrane and the electrode layer may be different, but the contact resistance between the membrane and the electrode, etc. In consideration, it is preferable to use the same one. In addition, when the electrode catalyst according to the present invention is used as a membrane-electrode assembly (MEA), the thickness of the electrode catalyst layer is preferably 1 to 50 μm, more preferably about 5 to 20 μm.

  The polymer electrolyte is preferably coated with an electrode catalyst as a polymer that functions as an adhesive. Thereby, while being able to maintain the structure of an electrode stably, the sufficient three-phase interface where an electrode reaction advances can be ensured, and high catalyst activity can be obtained. Although content of the said ion conductive material contained in an electrode is not specifically limited, It is good to set it as 20-60 mass% with respect to the whole quantity of a catalyst component.

  The polymer electrolyte membrane used for the membrane-electrode assembly of the present invention is not particularly limited, and examples thereof include a membrane made of the same polymer electrolyte as that used for the electrode catalyst layer. In addition, various Nafion (registered trademark of DuPont) manufactured by DuPont and perfluorosulfonic acid membranes represented by Flemion, ion exchange resins manufactured by Dow Chemical, ethylene-tetrafluoroethylene copolymer resin membrane, trifluoro Fluorine polymer electrolytes such as styrene-based polymer membranes, hydrocarbon-based resin membranes with sulfonic acid groups, etc. A membrane impregnated with a liquid electrolyte, a membrane in which a porous body is filled with a polymer electrolyte, or the like may be used. The polymer electrolyte used for the polymer electrolyte membrane and the polymer electrolyte used for each electrode catalyst layer may be the same or different, but the adhesion between each electrode catalyst layer and the polymer electrolyte membrane From the viewpoint of improving the properties, it is preferable to use the same one.

  The thickness of the polymer electrolyte membrane may be appropriately determined in consideration of the characteristics of the obtained membrane / electrode assembly, but is preferably 10 to 75 μm, more preferably 15 to 70 μm, and particularly preferably 20 to 60 μm. . The thickness is preferably 10 μm or more from the viewpoint of strength during film formation and durability during operation of the membrane electrode assembly, and is preferably 75 μm or less from the viewpoint of output characteristics during operation of the membrane electrode assembly.

  The polymer electrolyte membrane includes polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVDF) in addition to the above-described fluorine-based polymer electrolyte and membranes made of hydrocarbon resins having sulfonic acid groups. For example, a porous thin film formed from a material such as phosphoric acid or an ionic liquid impregnated with an electrolyte component may be used.

  In the membrane-electrode assembly according to the present invention, the gas diffusion layer is formed on the cathode electrode catalyst, and the content of the compound having a nitrogen-containing 6-membered ring structure in the vicinity of the gas supply port on the cathode electrode catalyst layer side is: The content is preferably less than the content of the compound having a nitrogen-containing 6-membered ring structure in the vicinity of the gas outlet.

  In the EFC cathode, the gas inlet portion and the gas outlet portion have different degrees of deterioration, and the same applies to Pt elution. At the cathode, the gas outlet side has a higher moisture content in the exhaust gas due to the influence of the produced water, and tends to be excessively humidified. A large amount of water has an effect of promoting Pt elution. In addition, the rate of deterioration at the outlet side suggests that the potential is considerably higher under certain conditions at the outlet side than at the inlet side. It is thought that it is easily oxidized and deteriorated. By adding more aromatic compound to the gas outlet side, the elution suppression effect can be obtained for a longer period.

  In the present specification, the “gas supply port” is an inlet of the reaction gas to the electrode in both the anode and the cathode.

  In the present specification, the “gas supply port portion” includes all points (not necessarily one point) immediately below the gas supply port in the electrode plane, and occupies a region of 25% of the geometric area of the electrode, and The shape is an area of a rectangle (a square if the aspect ratio is 1) that minimizes the aspect ratio.

  Next, a preferred embodiment of the method for producing a membrane electrode assembly of the present invention will be described below, and the above membrane electrode assembly will be described. In addition, the following aspects show the preferable aspect of this invention, and the manufacturing method of the membrane electrode assembly of this invention is not limited to the following method.

  The electrode catalyst of the present invention has been described in detail above. For example, in addition to an aqueous catalyst component ion solution such as platinum, a conductive carrier such as carbon black is dispersed with a homogenizer and then reduced and supported. Next, a conductive material carrying the heated and dried components is obtained and then dried to produce. Thereafter, an electrode catalyst having a catalyst component supported on a conductive carrier and an ion conductive material such as Nafion are added to a solvent such as water or alcohol as necessary to prepare a catalyst slurry.

  The catalyst slurry of the present invention is applied to a transfer mount and dried to form an electrode catalyst layer. In this case, as the transfer mount, a known sheet such as a PTFE (polytetrafluoroethylene) sheet, a PET (polyethylene terephthalate) sheet, or a polyester sheet can be used. The transfer mount is appropriately selected according to the type of catalyst slurry used (particularly, a conductive carrier such as carbon in ink). In the above process, the thickness of the electrode catalyst layer is not particularly limited as long as it can sufficiently exhibit the catalytic action of the hydrogen oxidation reaction (anode side) and the oxygen reduction reaction (cathode side). Thickness can be used. Specifically, the thickness of the electrode catalyst layer is 0.1 to 50 μm, more preferably 1 to 20 μm.

  The catalyst slurry on the transfer mount is not particularly limited, and a known method such as a screen printing method, a deposition method, or a spray method can be similarly applied. The applied electrode catalyst layer drying conditions are not particularly limited as long as the polar solvent can be completely removed from the electrode catalyst layer. Specifically, the coating layer (electrode catalyst layer) of the catalyst slurry is dried at room temperature to 100 ° C., more preferably 50 to 80 ° C. for 30 to 60 minutes in a vacuum dryer. At this time, if the thickness of the catalyst layer is not sufficient, the coating and drying process is repeated until a desired thickness is obtained. Next, the process proceeds to the following steps.

  That is, after sandwiching the solid polymer electrolyte membrane thus produced, hot pressing is performed on the laminate. At this time, the hot press conditions are not particularly limited as long as the electrode catalyst layer and the solid polymer electrolyte membrane can be joined sufficiently closely, but are 110 to 150 ° C., more preferably 120 to 140 ° C., with respect to the electrode surface. The press pressure is preferably 1 to 5 MPa. Thereby, bondability with a solid polymer electrolyte membrane and an electrode catalyst layer can be improved.

  After performing the hot press, the composite of the electrode catalyst layer and the solid polymer electrolyte membrane (so-called CCM) can be obtained by peeling off the transfer mount.

  As will be described below, the method for producing a fuel cell using the membrane-electrode assembly according to the present invention has a six-membered nitrogen-containing composition according to the present invention on both sides of the composite of the electrode catalyst layer and the solid polymer electrolyte membrane. It is necessary to provide a pair of gas diffusion layers containing a compound containing a ring or a film containing the battery composition according to the present invention. In addition, the manufacturing method of the gas diffusion layer which has a film | membrane containing the composition for batteries concerning this invention and a compound containing a nitrogen-containing 6-membered ring is the same as that of the above-mentioned.

  This gas diffusion layer is produced by using a compound containing a nitrogen-containing 6-membered ring, a known solvent such as ethanol, carbon paper or carbon non-woven fabric or carbon cloth, if necessary, such as polytetrafluoroethylene (PTFE). After impregnation in a solution containing a fluorine-based resin and drying in an atmosphere or an inert gas such as nitrogen, a gas diffusion layer is produced.

  The film containing the battery composition according to the present invention is produced by impregnating a carbon paper, a carbon non-woven fabric, or a carbon cloth with a solution containing a compound containing a nitrogen-containing six-membered ring and a known solvent such as ethanol, or After the solution is applied to carbon paper, carbon non-woven fabric, or carbon cloth, and dried in the air or an inert gas such as nitrogen, a film containing the battery composition according to the present invention is produced.

  Then, a plurality of gas diffusion layers prepared as described above, and a plurality of membranes containing the battery composition according to the present invention, if necessary, are sandwiched between the electrodes containing the electrode catalyst layer and the solid polymer electrolyte membrane, thereby forming a membrane An electrode assembly is prepared.

  In the catalyst slurry of the present invention, the electrode catalyst may be used in any amount as long as it can sufficiently exhibit the desired action, that is, the action of catalyzing the hydrogen oxidation reaction (anode side) and the oxygen reduction reaction (cathode side). , May be used. It is preferable that the electrode catalyst is present in the catalyst slurry in an amount of 5 to 75% by mass, more preferably 10 to 60% by mass.

  The catalyst slurry of the present invention includes a water repellency such as polytetrafluoroethylene, polyhexafluoropropylene, and tetrafluoroethylene-hexafluoropropylene copolymer, if necessary, in addition to the electrode catalyst, the ion conductive polymer, and the solvent. Polymers, thickeners and the like may be included. Thereby, the water repellency of the obtained electrode catalyst layer can be increased, and water generated at the time of power generation can be quickly discharged.

  The use of a thickener is effective when the catalyst slurry or the like cannot be successfully applied onto the transfer mount. The thickener that can be used in this case is not particularly limited, and a known thickener can be used. Examples thereof include glycerin, (EG (ethylene glycol), PVA (polyvinyl alcohol)), and the like. The amount of the thickener added when using the thickener is not particularly limited as long as it does not interfere with the above effect of the present invention, but is preferably 0 to 10 with respect to the total mass of the catalyst slurry. % By mass. Furthermore, the solvent constituting the catalyst slurry used in the present invention is not particularly limited, and ordinary solvents used for forming the catalyst layer can be used in the same manner. Specifically, water, lower alcohols such as cyclohexanol, ethanol and 2-propanol can be used.

  The amount of the solvent used in the present invention is not particularly limited as long as the electrolyte can be completely dissolved, but the electrolyte is preferably 0.1 to 20% by mass, more preferably 0.5 to 10% in the solvent. The amount is such that the concentration becomes mass%. At this time, if the concentration of the electrolyte is 20% by mass or less, it is unlikely that the electrolyte is completely dissolved and colloid is formed. Moreover, since the electric field mass contained in it being 0.1 mass% or more is an appropriate amount, the molecular chains of the electrolyte polymer are entangled well. For this reason, the mechanical strength of the electrode catalyst layer formed is excellent. Moreover, in the catalyst slurry, the concentration of the solid content including the electrode catalyst and the solid polymer electrolyte is preferably 5 to 50% by mass, more preferably about 10 to 40% by mass in the catalyst slurry.

  The catalyst slurry of the present invention may be used for only one or both of the cathode side electrode catalyst layer and the anode side electrode catalyst layer, but the cathode side is particularly affected by changes in the amount of water produced due to output fluctuations. At least the anode-side electrode catalyst layer because there is a high risk that the porous structure of the electrode catalyst layer in the initial state collapses due to changes in dryness and moisture, the porosity decreases, and the amount of reaction gas supplied to the electrode catalyst layer decreases. It is preferable to be used for.

  In the above method, the gas diffusion layer according to the present invention is further separated after bonding the electrode catalyst layer and the solid polymer electrolyte membrane by peeling off the transfer mount and further sandwiching the obtained bonded body with the gas diffusion layer. It is preferable to join the electrode catalyst layer. Alternatively, after an electrode catalyst layer is formed on the surface of the gas diffusion layer in advance to produce an electrode catalyst layer-gas diffusion layer assembly, the electrode catalyst layer-gas diffusion layer assembly is solid as described above. It is also preferable to sandwich and bond the polymer electrolyte membrane by hot pressing.

  In addition to the above hot pressing method, a method of laminating an electrode catalyst layer, a polymer electrolyte membrane, an electrode catalyst layer (a membrane containing the battery composition according to the present invention), and a gas diffusion layer on the gas diffusion layer by sequential coating. May be used.

  A second invention is a polymer electrolyte fuel cell using the membrane-electrode assembly according to the present invention.

  Since the membrane-electrode assembly according to the present invention can prevent elution of the catalyst component such as Pt for a long period of time, the polymer electrolyte fuel cell of the present invention can significantly suppress the elution of Pt. A polymer electrolyte fuel cell capable of maintaining high power generation performance can be obtained.

  The type of the fuel cell is not particularly limited. In the above description, the polymer electrolyte fuel cell has been described as an example, but in addition to this, a representative example is an alkaline fuel cell and a phosphoric acid fuel cell. Examples thereof include an acid electrolyte fuel cell, a direct methanol fuel cell, and a micro fuel cell. Among them, a solid polymer electrolyte fuel cell is preferable because it is small in size and can achieve high density and high output. The fuel cell is useful as a stationary power source in addition to a power source for a moving body such as a vehicle in which a mounting space is limited. However, the fuel cell is particularly useful for an automobile application in which system start / stop and output fluctuation frequently occur. It can be particularly preferably used.

  The polymer electrolyte fuel cell is useful not only as a stationary power source but also as a power source for a moving body such as an automobile having a limited mounting space. In particular, moving bodies such as automobiles that are susceptible to corrosion of the carbon support due to the high output voltage required after a relatively long shutdown, and deterioration of the polymer electrolyte due to the high output voltage being taken out during operation. It is particularly preferred to be used as a power source.

  The configuration of the fuel cell is not particularly limited, and a conventionally known technique may be appropriately used. Generally, the fuel cell has a structure in which a membrane electrode assembly is sandwiched between separators.

  The separator can be used without limitation as long as it is conventionally known, such as those made of carbon such as dense carbon graphite and a carbon plate, and those made of metal such as stainless steel. The separator has a function of separating air and fuel gas, and a channel groove for securing the channel may be formed. The thickness and size of the separator, the shape of the flow channel, and the like are not particularly limited, and may be appropriately determined in consideration of the output characteristics of the obtained fuel cell.

  Further, in order to prevent the gas supplied to each catalyst layer from leaking to the outside, a gas seal portion may be further provided at a portion where the catalyst layer is not formed on the gasket layer. Examples of the material constituting the gas seal portion include rubber materials such as fluoro rubber, silicon rubber, ethylene propylene rubber (EPDM), polyisobutylene rubber, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polyhexafluoro. Fluorine polymer materials such as propylene, tetrafluoroethylene-hexafluoropropylene copolymer (FEP), and thermoplastic resins such as polyolefin and polyester. The thickness of the gas seal portion may be 2 mm to 50 μm, preferably about 1 mm to 100 μm.

  Furthermore, a stack in which a plurality of membrane electrode assemblies are stacked via a separator and connected in series may be formed so that the fuel cell can obtain a desired voltage or the like. The shape of the fuel cell is not particularly limited, and may be determined as appropriate so that desired battery characteristics such as voltage can be obtained.

  Hereinafter, the present invention will be specifically described based on examples. In addition, this invention is not limited only to these Examples. In the examples, “%” represents a mass percentage unless otherwise specified.

(Production of electrode catalyst layer)
The production of the electrode catalyst layer was performed as follows.
After adding 5 times the amount of purified water to the weight of the Pt-supported carbon powder (Tanaka Kikinzoku: TEC10E50E), 0.5 times the amount of isopropyl alcohol is added, and the weight of Nafion is 0.8 times the amount. A Nafion solution (containing 5 wt.% Nafion manufactured by Aldrich) was added. The mixed slurry was well dispersed with an ultrasonic homogenizer, followed by addition of a vacuum degassing operation to prepare a catalyst ink. A predetermined amount of catalyst ink was printed by screen printing on one side of bpy-supported carbon paper (Example) and non-bpy-supported carbon paper (Comparative Example), and dried at 60 ° C. for 24 hours to prepare an electrode layer. .

(Preparation of bpy-containing electrode catalyst layer)
An electrode catalyst layer was produced by a production method similar to that described above except that bpy was previously dissolved in isopropyl alcohol added during ink production. The bpy contained in the electrode catalyst layer was 0.8 nmol / cm ² -Pt per actual area of platinum.

(Preparation of bpy supported gas diffusion layer)
The bpy carrying gas diffusion layer was produced as follows.
Carbon paper (TGP-H-060 manufactured by Toray Industries, Inc.) is immersed in an ethanol solution (0.1 M / L) of 2,2′-bipyridine (also referred to as “bpy”) and stirred at room temperature for 24 hours. After removing the carbon paper, the carbon paper carrying bpy was prepared by volatilizing the solvent with a vacuum dryer. As a result of quantitative analysis, this bpy-supported carbon paper had a bpy content of 0.05 μmol / cm ² .

(Production of MEA)
For the production of MEA (membrane-electrode assembly), MEA was produced by performing hot pressing at 120 ° C. and 1.2 MPa for 10 minutes with the surface coated with the catalyst aligned with the electrolyte membrane. In all cases, the catalyst of Comparative Example 1 was used as the anode catalyst. The MEA used in both the comparative example and the example was 0.3 mg for the anode and 0.5 mg for the cathode per 1 cm ^{2 of the} apparent electrode area, and the electrode area was 25 cm ² . In addition, Nafion 112 (thickness: about 50 μm) was used as the electrolyte membrane.

Example 1 (MEA configuration)
Electrocatalyst layer: Without bpy Carbon paper: With bpy

Example 2 (MEA configuration)
Electrocatalyst layer: with bpy Carbon paper: with bpy

Comparative Example 1 (MEA configuration)
Electrocatalyst layer: no bpy carbon paper: no bpy

Comparative Example 2 (MEA configuration)
Electrocatalyst layer: With bpy Carbon paper: Without bpy

(Single cell evaluation)
A fuel cell single cell was constructed using the produced MEA, and a potential cycle application test simulating power generation load fluctuation was performed by the following method.
Hydrogen was supplied to the anode side of the single fuel cell and nitrogen was supplied to the cathode side. The supply pressure for both gases was atmospheric pressure, the temperature of the fuel cell body was set to 70 ° C., and both gases were humidified to a dew point of 70 ° C., the hydrogen flow rate was 500 ml / min, and the nitrogen flow rate was 100 ml / min. . In this state, a rectangular wave with a potential range of 0.95 V to 0.60 V was applied at intervals of 10 seconds per cycle, and the electrochemical effective surface area (ECA) of Pt before and after 5000 cycles was compared. The Pt average particle size increases as the number of applied potential cycles increases due to repeated elution and reprecipitation of Pt by applying potential cycles. From this, it can be said that the larger the Pt ECA reduction rate, the lower the resistance to Pt elution and the faster the deterioration rate of the electrode performance. The ECA of the cathode was estimated from the hydrogen adsorption wave area by cyclic voltammetry.

  FIG. 1 is a graph showing the results. At the beginning of the experiment, although the example and comparative example cells used the same electrode catalyst, the ECA value of the cell containing bpy contained no bpy at all. It can be seen that the value is about 20 to 30% lower than that of the cell (Comparative Example 1) which is not performed. This shows that bpy in the electrode catalyst layer or bpy in the carbon paper reaches the catalyst layer even in a cell not previously containing bpy in the electrode catalyst layer, and that bpy is adsorbed on a part of the surface of Pt. It can be said that.

  By applying the potential cycle, it can be seen that the ECA reduction rate is smaller in the example than in the comparative example, and that the active reaction site of Pt can be maintained for a long time by using the catalyst of the example. This indicates that the adsorption of bpy can be maintained for a long period of time, so that the Pt elution resistance can be remarkably improved, and the electrode performance can be maintained for a long time. Although the Pt elution suppression effect was also observed in Comparative Example 1 cell containing bpy, it was found that the effect was difficult to obtain in a long time compared to the Example cell. Although the details of this reason are unknown, for some reason, the adsorption bpy is discharged out of the system together with the liquid water in the cell, and the Pt elution suppression effect is gradually lost, whereas bpy is stored in the carbon paper. If it is, it is estimated that there is an effect to compensate for the loss.

It is a figure which shows the cycle number dependence of the ECA value in the electric potential cycle test with respect to a comparative example and an Example cell.

Claims (12)

  The compound containing a nitrogen-containing 6-membered ring and the non-electrolyte material, and the compound containing the nitrogen-containing 6-membered ring are combined with at least one metal formed from the group consisting of platinum, nickel, cobalt, palladium, and iridium. Battery composition.   The battery composition according to claim 1, wherein the compound containing a nitrogen-containing 6-membered ring is a pyridine derivative.   The battery composition according to claim 2, wherein the pyridine derivative is at least one selected from the group consisting of bipyridines, terpyridines, and phenanthrolines.   The battery composition according to claim 3, wherein the bipyridine is 2,2′-bipyridine.   The film | membrane formed using the composition of Claims 1-4.   The film according to claim 5 is a gas diffusion layer. The film according to claim 5 or 6 does not contain an ion conductive substance and contains a compound containing the nitrogen-containing 6-membered ring coordinated with the metal in a range of 0.1 nmol / cm ² to 10 μmol / cm. The film according to claim 5, wherein ^{2 is} contained. The anode electrode catalyst layer is disposed on one surface of the polymer electrolyte membrane, the cathode electrode catalyst layer is disposed on the other surface, and further, the gas diffusion layer is formed on at least one surface of the anode electrode catalyst layer or the cathode electrode catalyst layer. In the membrane-electrode assembly formed by laminating at least one membrane of any one of -7
The membrane-electrode assembly is characterized in that the first gas diffusion layer in contact with the electrode catalyst layer has a hydrophilic property equal to or higher than that of the opposite surface in contact with the electrode catalyst layer.   A second gas diffusion layer is further laminated on the first gas diffusion layer, and the second gas diffusion layer in contact with the first gas diffusion layer has the same or higher hydrophobicity than the first gas diffusion layer. The membrane-electrode assembly according to claim 8.   The gas diffusion layer is formed on the cathode electrode catalyst, and the content of the compound having a nitrogen-containing six-membered ring structure at the gas supply port portion on the cathode electrode catalyst layer side is the nitrogen-containing six-membered ring structure at the gas discharge port portion. The membrane-electrode assembly according to any one of claims 8 to 10, wherein the content of the compound is less than the content of the compound having the following.   The catalyst component contained in the electrode catalyst layer includes at least one selected from the group consisting of Pt, Pd, Ir, Rh, and Au, according to any one of claims 8 to 10, The membrane-electrode assembly as described.   A polymer electrolyte fuel cell comprising the membrane-electrode assembly according to claim 8.

Images