JP2003173785A - Forming method and device of catalyst layer for solid polymer fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a forming method of a catalyst layer for a solid polymer fuel cell with a fine structure having a good ion conductivity, gas permeability and electron conductivity. <P>SOLUTION: With the forming method of a catalyst layer for a solid polymer fuel cell in which a catalyst layer is formed by applying mixture liquid containing catalyst-supporting carbon powder and a proton conductive polymer on a base material, two or more kinds of liquid drops with different composition are formed from two or more kinds of mixture liquid with different composition to apply on the base material. With this, a catalyst layer can be made in a fine structure having a good ion conductivity, gas permeability and electron conductivity, so that a fuel cell equipped with it can improve power generation. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for forming a catalyst layer for a polymer electrolyte fuel cell and an apparatus for forming the same.

[0002]

2. Description of the Related Art A fuel cell is highly efficient because it electrochemically oxidizes a fuel such as hydrogen or methanol and directly extracts the chemical energy of the fuel as electrical energy.
Since the reaction product is only water in principle, it is attracting attention as a clean power generation system. Depending on the type of electrolyte used, there are phosphoric acid type, molten carbonate type, solid polymer type, etc. in this fuel cell. Among them, the solid high type which is advantageous in that it operates at low temperature and can be downsized Research and development of molecular fuel cells are being actively pursued.

The basic structure of a solid polymer electrolyte fuel cell is such that a catalyst layer is formed on both sides of a solid polymer electrolyte membrane, and a fuel gas supply layer and an air supply layer made of a conductive porous membrane sandwich the catalyst layer. It is laminated. One of the most important factors affecting the power generation capacity of this fuel cell is the catalyst layer, which is a porous body composed of carbon powder carrying a catalyst and a proton conductive polymer. Reaction gas, generated water, protons through the proton-conducting polymer containing water, and electrons through the carbon powder, respectively, are supplied or taken out through the pores in the catalyst layer, which often form a fine structure capable of efficient mass transfer. It is important for realizing the power generation capacity. The optimization of the fine structure of the catalyst layer has great significance in that the catalyst is effectively used. Usually, a noble metal such as platinum is used as the catalyst, and it is very preferable in terms of cost to reduce the amount used. It is necessary to realize a method of forming a catalyst layer that can apply this catalyst without waste to form a catalyst layer and make it function with high efficiency.

The catalyst layer is generally formed by preparing a mixed solution in which a carbon powder carrying a catalyst, a proton conductive polymer and the like are dispersed, and then directly coating it on the ion exchange membrane or on the gas supply layer. Target. Many attempts have been made to obtain the desired fine structure of the catalyst layer by devising the coating conditions and composition of the mixed solution.
As disclosed in JP-A-2000-260435, a pore-forming agent may be added to the mixed solution, or JP-A-2001-11
As disclosed in Japanese Patent No. 0430, there is a method of forming a fine structure capable of efficient mass transfer by adding a gas generating agent to a mixed solution to make the catalyst layer porous.

With respect to the porous structure of the catalyst layer thus formed, various measures have been taken so that mass transfer can be more favorably carried out. A method of forming a proton conductive polymer layer on a catalyst layer as disclosed in JP-A-11-40172, and a method of adding a water repellent agent as disclosed in JP-A-2001-76734. There is a method of allowing the reaction product water to be discharged well.

However, in the method of adding the additive for porosity to the mixed solution described in the above-mentioned documents, etc., the usable solvent is limited, the stability of the mixed solution becomes low, and stable production can be performed. In addition to the difficulty, there is a problem that extra steps such as cleaning are often required. Further, the method of forming the catalyst layer in multiple layers has a drawback that the process becomes complicated.

[0007]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a method for forming a catalyst layer for a polymer electrolyte fuel cell having a fine structure having good ionic conductivity, gas permeability and electron conductivity. Is to provide.

[0008]

The present invention provides a mixed solution containing a catalyst-supporting carbon powder and a proton conductive polymer,
A method for forming a catalyst layer for a polymer electrolyte fuel cell, which comprises applying the catalyst layer on a substrate to form two or more kinds of droplets having different compositions from a mixed solution of two or more kinds having different compositions. The method for forming a catalyst layer is characterized by being applied on a substrate. Furthermore, the present invention is a polymer electrolyte fuel cell comprising a catalyst layer formed by the above method.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The catalyst-supporting carbon powder according to the present invention may be any carbon powder on which a catalyst for promoting hydrogen oxidation reaction and oxygen reduction reaction is supported. The catalyst here promotes the oxidation reaction of hydrogen and the reduction reaction of oxygen, and any material can be used as long as it is in the form of fine powder and insoluble in water, but platinum, palladium, ruthenium, iridium, rhodium can be used. , Osmium platinum group elements, iron, lead,
Metals such as copper, chromium, cobalt, nickel, manganese, vanadium, molybdenum, gallium, and aluminum, alloys thereof, oxides, double oxides, and the like can be used. The particle size of these catalysts is preferably 5 to 500 angstroms, more preferably 10 to 150 angstroms. If the particle size is too small, the catalyst may lack stability, and if the particle size is too large, the catalyst activity may be poor. The carbon powder carrying these catalysts may be in the form of a fine powder having conductivity, so long as it is not violated by the catalyst,
Carbon black, graphite, graphite, activated carbon, aggregates of fullerenes and carbon nanotubes, and various fine metal powders can also be used. Particle size is 5-5000 nm
Is preferable, and 10-500 nm is more preferable. If the particle size is too small, sufficient conductivity may not be obtained when the catalyst layer is formed. If the particle size is too large, it may be difficult to form a mixed liquid containing the same into fine liquid droplets, which is not preferable. The amount of the catalyst supported on the carbon powder largely depends on the shape of the carbon powder, but is 5 to 70% by mass, preferably 10 to 60% by mass of the mass of the carbon powder. If the amount of the catalyst is too small, the power generation efficiency when forming the fuel cell will not be sufficient, and if it is too large, the reaction efficiency will not improve as much as it is added and the cost will be wasted, which is not preferable.

The proton-conducting polymer in the present invention is not particularly limited as long as it is a polymer that conducts protons, but a fluorinated polymer such as Nafion (manufactured by DuPont) is used as a skeleton. It has at least a proton exchange group such as a sulfonic acid group, a carboxylic acid group, a phosphonic acid group, and a phosphoric acid group. Also,
Those having a hydrocarbon skeleton such as polyolefin and those having an aromatic skeleton such as polyphenyl ether can also be used.

The above-mentioned proton-conducting polymer or the like can be used as the substrate in the present invention, and it may consist of a single proton-conducting polymer or a mixture of two or more kinds of proton-conducting polymers. May be In particular, it is preferable to use a solid polymer electrolyte membrane having a film thickness of 20 to 300 μm, preferably 40 to 200 μm, which is formed by extruding a proton conductive polymer as a substrate. Further, a Teflon (registered trademark) film or the like capable of transferring the catalyst layer onto the solid polymer electrolyte membrane can also be used as the substrate.

Furthermore, by adding a water repellent to the catalyst layer,
The water generated by power generation can be efficiently removed, power generation efficiency can be improved, and the life of the catalyst layer can be extended. In particular, the effect is great when a water repellent is added to the positive electrode side catalyst layer. As a method of addition, a method of mixing a water-repellent substance such as a fluororesin typified by polytetrafluoroethylene or fine particles that have been water-repellent by a surface treatment such as fluorination, a non-aqueous resin such as polyvinylidene fluoride in a liquid is added. And a method of adding a chemical agent that causes a hydrophobizing reaction such as hexamethyldisilazane, various silane coupling agents, titanium coupling agents, and aluminum coupling agents.

Further, a hydrophilic agent can be mixed. Hydrophilic agents include fine particles of hydrophilic compounds such as oxides and nitrides of metals such as alumina, silica, titanium oxide, and cerium oxide, homopolymers or copolymers of acrylic acid or methacrylic acid, polyvinyl alcohol, polyvinylpyrrolidone, and polyacrylamide. Fine particles in which a hydrophilic polymer represented by a homopolymer or a copolymer is insoluble in water due to crosslinking can be used.

The mixed liquid in the present invention is only required to be in a state of high fluidity by dissolving or dispersing the proton conductive polymer in the form of a fine gel. The content of the constituent components of this mixed solution varies greatly depending on the difference in the types of the proton conductive polymer and the solvent, but the catalyst-supporting carbon powder is preferably 1 to 70% by mass, more preferably 3 to 50% by mass. The proton conductive polymer is 0.01
-50 mass% is preferred, and 0.1-20 mass% is more preferred. Within these ranges, the formed catalyst layer can have a desired fine structure. If the amount of the catalyst-supporting carbon powder is too small, the conductivity of the catalyst layer will be insufficient and the reaction efficiency of redox will be reduced. When the amount is too large, the reaction efficiency is not improved as much as it is added, and the cost is wasted, which is not preferable. If the amount of the proton conductive polymer is too small, the proton conductivity of the catalyst layer will be insufficient. If the amount is too large, not only the viscosity of the mixed solution becomes high and coating becomes difficult, but also the gas diffusion of the formed catalyst layer tends to be insufficient.

This mixed solution may contain a solvent and is not particularly limited, but methanol, ethanol, 1
-Propanol, 2-propanol, 1-butanol,
Alcohols such as 2-butanol, isobutyl alcohol, tert-butyl alcohol, pentanol, etc., esters such as lactic acid, formic acid, acetic acid, propionic acid and the like, and esters in the form of dehydration condensation of an alcohol having 1 to 5 carbon atoms, acetone, methyl ethyl ketone , Pentanone, methyl isobutyl ketone,
Heptanone, cyclohexanone, methylcyclohexanone, acetonylacetone, ketone type solvents such as diisobutyl ketone, tetrahydrofuran, dioxane, diethylene glycol dimethyl ether, anisole, methoxytoluene, ether type such as dibutyl ether, etc.
A polar solvent such as ethylene glycol, diethylene glycol, diacetone alcohol, 1-methoxy-2-propanol, dimethylformamide, N-methylpyrrolidone or dimethylacetamide, and a mixture of two or more kinds selected from the above solvent group can be used. is there. Furthermore, it is also possible to add hydrocarbons and water to the above solvent group to the extent that the proton-conducting polymer does not separate and cause white turbidity or gelation.

The solvent that can be used in the present invention has a wide range of compositions as described above, but the viscosity of the mixed liquid is preferably 300 cp or less, and more preferably 100 cp or less in order to form a droplet. If the viscosity is too high, the droplet diameter becomes too large to form a thin catalyst layer, and the nozzle is likely to be clogged, which causes problems. In addition, the final viscosity of the mixed liquid may vary greatly depending on the mixing conditions of the constituent materials. Although not particularly limited, the viscosity of the liquid may be reduced by adding a dispersant to reduce the liquid viscosity, vigorously stirring by using an ultrasonic homogenizer or the like, or slowly stirring on a rotary rack after mixing. Adjustment is also effective.

The droplets are preferably formed by a piezo type or thermal type ink jet nozzle. The droplet diameter is preferably 3 to 300 μm, and 10 to 200 μm.
m is more preferred. If the particle size is too small, the amount of evaporation will be too large, and it will be difficult to apply the composition on a substrate. If the particle size is too large, it becomes difficult to give the catalyst layer a good fine structure.

(Preparation of mixed liquid having different composition and application of droplets thereof) I. Catalyst-supporting powder A method for preparing a mixed solution of two or more catalyst-supporting carbon powders having different types includes different types of supported catalysts, different types of carbon powders supporting catalysts, or different amounts of supported catalysts. There is a method using a catalyst-supporting carbon powder.
There is also a method of preparing a mixed solution of two or more kinds by changing the addition amount of the catalyst-supporting carbon powder. In these methods, it is necessary that the supported catalyst amounts differ by at least 10%, more preferably by 20% or more. If the difference in the amount of catalyst is too small, the effect of using a mixed solution of two or more kinds cannot be sufficiently exerted. Various methods can be used in the method for forming the catalyst layer in which two or more kinds of liquid droplets are respectively formed from a mixed liquid of two or more kinds having different kinds and / or amounts of the above-mentioned catalyst-supporting carbon powder, and applied on the substrate Thus, the catalyst utilization efficiency can be improved. Below, those methods are illustrated.

Droplets are formed from separate nozzles from a mixture of two or more kinds of catalyst-supporting carbon powders having different addition amounts, and the droplets are applied onto a substrate, preferably a solid polymer electrolyte membrane, or a solid polymer electrolyte. There is a method of applying it on a Teflon (registered trademark) film or the like which can transfer a catalyst layer onto the film. By applying droplets having different compositions to each other and applying them on a substrate (solid polymer electrolyte membrane, Teflon (registered trademark) membrane, etc.), a fine structure with different carbon powder content concentration is formed in the catalyst layer. it can. Thereby, the electron conductivity of the catalyst layer can be efficiently increased, and the catalyst layer having high catalyst utilization efficiency can be obtained. The fine structure in this case is effective when the droplets are mixed and randomly applied on the base material so as to have a submicron to several hundreds of micron level structure. Further, like the image formation by an ink jet printer, by controlling the liquid droplets and forming a catalyst layer pattern such as a linear or mesh structure in the plane direction of the catalyst layer, the catalyst utilization efficiency can be further optimized. It can be carried out.

Droplets are formed from a separate nozzle from a mixture of two or more kinds of catalyst-supporting carbon powders having different supported catalyst amounts, and the droplets are applied onto a substrate, preferably a solid polymer electrolyte membrane. Alternatively, there is a method of applying it on a Teflon (registered trademark) membrane or the like which can transfer a catalyst layer onto a solid polymer electrolyte membrane. By sequentially applying droplets having different compositions onto the substrate, a catalyst layer pattern having a catalyst concentration distribution in the thickness direction of the catalyst layer can be formed. For example, the catalyst utilization efficiency can be optimized by a method such as increasing the catalyst concentration closer to the solid polymer electrolyte membrane. Further, as in the case of image formation by an inkjet printer, a droplet is controlled to form a catalyst layer pattern having a concentration distribution in the plane direction of the catalyst layer in the plane direction of the catalyst layer, a gas flow path, and a fuel flowing therethrough. By the method corresponding to the oxygen concentration
The catalyst utilization efficiency can be optimized.

Droplets are formed from separate nozzles from a mixture of two or more kinds of catalyst-supporting carbon powders having different supported catalyst species and applied onto a substrate, preferably a solid polymer electrolyte membrane. Alternatively, there is a method of applying it on a Teflon (registered trademark) membrane or the like which can transfer a catalyst layer onto a solid polymer electrolyte membrane. By sequentially applying droplets having different compositions onto the base material, a catalyst layer pattern having a distribution of catalyst species in the thickness direction of the catalyst layer can be formed. For example, the catalyst utilization efficiency can be optimized by disposing a catalyst that is less susceptible to poisoning by carbon monoxide or the like near the gas diffusion layer.

II. Proton-Conducting Polymer As a method for preparing a mixed solution of two or more kinds having different kinds of proton-conducting polymers, there is a method in which the proton-conducting polymers have different ionic conductivity and molecular weight. There is also a method of preparing a mixed solution of two or more kinds by changing the addition amount of the proton conductive polymer. The added amount should be different by at least 10%, more preferably by 20% or more. If the difference in the added amount is too small, the effect of using a mixed solution of two or more kinds cannot be sufficiently exerted. Various methods can be used in the method for forming the catalyst layer in which two or more kinds of liquid droplets are respectively formed from a mixed liquid of two or more kinds having different kinds and / or amounts of the above-mentioned proton-conducting polymer and applied on the substrate. Thus, the power generation efficiency of the catalyst layer can be improved. Below, those methods are illustrated.

A droplet is formed from a mixed liquid of two or more kinds having different amounts of addition of the proton conductive polymer from separate nozzles and applied onto a substrate, preferably a solid polymer electrolyte membrane, or a solid polymer electrolyte. There is a method of applying it on a Teflon (registered trademark) film or the like which can transfer a catalyst layer onto the film. By applying the droplets having different compositions to each other by mixing them on the substrate, it is possible to form a fine structure having a different concentration of the proton conductive polymer in the catalyst layer. Thereby, the ion conductivity of the catalyst layer can be efficiently increased, and the catalyst layer having high power generation efficiency can be obtained. The fine structure in this case is effective when the droplets are mixed and randomly applied on the base material so as to have a submicron to several hundreds of micron level structure. Furthermore,
Like image formation with an inkjet printer, by controlling droplets to form a catalyst layer pattern such as a linear or mesh structure in the plane direction of the catalyst layer, it is possible to optimize power generation efficiency to a higher degree. it can.

In addition to the above, a droplet is formed from a mixed liquid of two or more kinds having different addition amounts of the proton conductive polymer from separate nozzles, and the droplets are successively applied onto the substrate to obtain the thickness of the catalyst layer. There is also a method of providing a concentration distribution of the proton conductive polymer in the direction. For example, the power generation efficiency can be optimized by, for example, increasing the concentration of the proton conductive polymer closer to the solid polymer electrolyte membrane.

III. Water repellent When a water repellent is added, the amount of the water repellent is 0.
The range of 2 to 20% is preferable. If the amount added is too small, the water produced during power generation clogs the fine pores of the catalyst layer, and gas supply cannot be performed well, which is not preferable. If the amount added is too large, the water content of the proton-conductive polymer in the catalyst layer decreases, so that the ionic conductivity decreases and good power generation cannot be performed. A larger effect can be obtained by adding the water repellent to the catalyst layer on the positive electrode side.

As a method for preparing a mixed liquid of two or more kinds having different water repellents, in addition to the method of changing the amount of the water repellent to be added,
There is a method of using different water repellent species. The added amount should be different by at least 20%, more preferably by 40% or more. If the difference is too small, the effect of using a mixed solution of two or more kinds cannot be sufficiently exerted.

In the method for forming the catalyst layer, in which two or more kinds of liquid droplets are respectively formed from a mixed liquid of two or more kinds having different kinds and / or amounts of the above-mentioned water repellents, and applied on the substrate, various methods are used. The power generation efficiency of the catalyst layer can be improved by this method.
Below, those methods are illustrated.

A droplet is formed from a mixed liquid of two or more kinds having different addition amounts of a water repellent from separate nozzles and applied onto a substrate, preferably a solid polymer electrolyte membrane, or a solid polymer electrolyte membrane. There is a method of applying it on a Teflon (registered trademark) film or the like on which a catalyst layer can be transferred. By mixing the droplets having different compositions and applying the droplets onto the base material, it is possible to form a fine structure having a different water repellent content concentration in the catalyst layer. The microstructure in this case is a submicron to several hundreds of micron level structure formed by mixing droplets and randomly applying it on the substrate, so that the water content of the proton conductive polymer in the catalyst layer is increased. While maintaining the rate
Since the generated water can be easily removed from the pores by the minute water-repellent portion, high power generation efficiency can be achieved. Further, as in the case of image formation by an inkjet printer, by controlling droplets to form a catalyst layer pattern such as a linear or mesh structure in the plane direction of the catalyst layer, the power generation efficiency is optimized to a higher degree. be able to.

In addition to this, droplets are formed from separate nozzles from a mixed liquid of two or more kinds having different amounts of water repellents, and the droplets are sequentially applied onto the base material so that the thickness direction of the catalyst layer is increased. There is also a method of giving the water repellent concentration distribution. For example, the generated water can be easily removed from the pores while maintaining the water content of the proton-conducting polymer in the catalyst layer by a method such as increasing the hydrophobicity near the gas diffusion layer. Can achieve efficiency.

IV. Hydrophilic agent When a hydrophilic agent is added, the optimum addition amount largely varies depending on the hydrophilicity of other components of the catalyst layer, but is preferably in the range of 5 to 40% with respect to the catalyst layer mass. If the addition amount is too small, a sufficient addition effect cannot be obtained. If the addition amount is too large, good power generation cannot be performed due to the influence of the decrease in electron conductivity of the catalyst layer. A larger effect can be obtained by adding the hydrophilic agent to the catalyst layer on the negative electrode side.

As a method for preparing a mixed solution of two or more kinds having different hydrophilic agents, in addition to the method of changing the amount of hydrophilic agent to be added,
There is a method of using different kinds of hydrophilic agents. The addition amount is
It should differ by at least 20%, more preferably by 40% or more. If the difference is too small, the effect of using a mixed solution of two or more kinds cannot be sufficiently exerted.

In the method for forming the catalyst layer, in which two or more kinds of liquid droplets are respectively formed from a mixed liquid of two or more kinds having different kinds and / or amounts of the above-mentioned hydrophilic agents, and applied on the substrate, various methods are used. The method can improve the power generation efficiency of the catalyst layer.
Below, those methods are illustrated.

Droplets are formed from separate nozzles from a mixed liquid of two or more kinds having different amounts of hydrophilic agents added, and applied onto a substrate, preferably a solid polymer electrolyte membrane, or on a solid polymer electrolyte membrane. There is a method of applying the catalyst layer on a Teflon (registered trademark) film or the like which can be transferred. By mixing the droplets having different compositions and applying them on the substrate, it is possible to form a fine structure having different hydrophilic agent content concentrations in the catalyst layer. The fine structure in this case has a submicron to several hundred micron level structure that is formed by mixing droplets and applying them randomly on the substrate, so that the generated water can be removed from the pores, etc. While maintaining the above, the water content of the proton conductive polymer can be kept high by the minute hydrophilic portion, so that high power generation efficiency can be achieved. Furthermore,
Like image formation with an inkjet printer, by controlling droplets to form a catalyst layer pattern such as a linear or mesh structure in the plane direction of the catalyst layer, it is possible to optimize power generation efficiency to a higher degree. it can.

In addition to this, droplets are formed from separate nozzles from two or more kinds of mixed liquids having different amounts of hydrophilic agents, and the droplets are sequentially applied onto the base material, so that the thickness direction of the catalyst layer is increased. There is also a method of providing a concentration distribution of the hydrophilic agent. For example, by increasing the hydrophilicity of the side closer to the fuel gas supply layer,
By efficiently humidifying the proton conductive polymer,
High power generation efficiency can be achieved.

Up to this point, the method for forming the catalyst layer having the composition distribution of the catalyst-supporting carbon powder, the proton conductive polymer, the water repellent and the hydrophilic agent has been described. In addition to these methods, a catalyst layer pattern having a larger scale composition distribution can be formed. Some of these methods are illustrated below.

In the fuel cell, fuel and oxygen gas are supplied to the catalyst layer from the narrow grooves formed in the separator. During power generation, the concentration of fuel and oxygen is high in the upstream portion of the supply gas flow path, the concentration of fuel and oxygen is low in the downstream portion, and the amount of produced water discharged is large. In this method, a catalyst layer pattern corresponding to the difference in gas flow path and gas concentration can be easily formed.

For example, in the upstream portion of the fuel supply path (negative electrode), the amount of supported catalyst is lowered, and on the downstream side, the amount of supported catalyst is increased so that a homogeneous reaction occurs in the whole, thereby improving catalyst utilization efficiency. The method of making local retention of generated water less likely to occur and the discharge of generated water by containing a large amount of a water repellent agent in the catalyst layer at the downstream portion of the oxygen supply path (positive electrode), especially in the surface portion of the catalyst layer. There is a method of making it possible to perform well.

Although carbon paper or carbon cloth, which is a conductive porous material, is sandwiched between the narrow groove of the separator and the catalyst layer, the gas is supplied to the catalyst layer as uniformly as possible. The gas concentrations in the catalyst layer facing the narrow groove and in the catalyst layer distant from the narrow groove are different. In addition, the discharge speed of the generated water is also greatly different, and the retention state of the generated water is also greatly different depending on the position of the catalyst layer.
In this method, a catalyst layer pattern depending on the difference in the gas composition and the diffusion rate of generated water can be easily formed.

For example, a method of suppressing retention of generated water by adding a large amount of a water-repellent agent to a portion not facing the catalyst layer facing the narrow groove of the positive electrode separator, facing the narrow groove of the negative electrode separator. By reducing the content of the supported catalyst in the portion not facing the catalyst layer, the catalyst utilization efficiency is improved, and on the contrary, the content of the supported catalyst in the catalyst layer facing the other is reduced, thereby causing the reaction to occur homogeneously. , There is a method of improving the power generation performance by improving the removability of generated water.

[0040]

EXAMPLES The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to the examples.

(Examples 1 and 2) A solvent in which 15 parts by weight of ethyl lactate and 55 parts by weight of ethylene glycol were mixed, an alloy of platinum and ruthenium as a catalyst was supported on carbon black, and the average secondary particle size was 10 μm. Catalyst-supported carbon powder, and polyperfluorosulfonic acid (Nafion)
Proton conductive polymer-containing liquid (resin concentration 10% by mass) dissolved in ethanol was mixed with the composition shown in Table 1 to prepare mixed liquids 1 to 3. Liquid mixture 4 using catalyst-supporting carbon powder with platinum as a catalyst instead of platinum-ruthenium alloy
Was prepared.

[Table 1] Next, a method for manufacturing the electrode membrane assembly (MEA) will be described. A catalyst layer was formed by discharging the mixed liquid of Table 1 from an inkjet nozzle and applying it on the polyperfluorosulfonic acid solid polymer electrolyte membrane (Nafion 115). An inkjet printer hp deskjet 990c (manufactured by Hewlett-Packard Co.) was used as an inkjet nozzle and a drive system, and an apparatus suitable for this prototype was manufactured, and a prototype was made using this apparatus. By adjusting the viscosity according to the mixing conditions of the coating liquid mixture and the coating conditions of the inkjet printer, the total amount of solids deposited after drying was adjusted to about 5 mg / cm ^{2 by} repeating the entire coating three times. One time of entire surface coating was set for the case where each mixed solution was applied alone and the case where two kinds of mixed solutions were mixed and applied. When the two kinds of mixed solutions were mixed and applied, the application was performed so that a line pattern having a width of about 0.14 mm could be formed. The negative electrode catalyst layer was formed as shown in Table 2 by combining the entire surface application of each mixed solution alone and the application of a mixture of two kinds of mixed solutions. After applying the negative electrode catalyst layer, the mixed solution 4 was applied over the entire surface of the positive electrode three times.
After forming the catalyst layer as described above and vacuum drying, a thickness of 25
Sandwiched with 0 μm carbon paper, 160 ℃, 50k
Hot pressing was performed under the condition of gf / cm ² to complete the electrode film assembly. Sandwich this MEA between separator plates,
Hydrogen gas was introduced into the negative electrode side and air was introduced into the positive electrode side into the MEA through the flow path cut in the separator plate, and a power generation test was carried out under normal pressure. The power generation characteristics of the fuel cell were compared by the cell voltage when the output current density was 1.0 A / cm ² . The results are shown in Table 2.

[Table 2]

In Example 1, although the amount of catalyst in the negative electrode catalyst layer was smaller than that in Comparative Example 1, the power generation characteristics were hardly deteriorated. In Example 2, compared with Comparative Example 1, the power generation capacity was improved although the catalyst amount was almost the same. These results show that the structure of the catalyst layer formed according to the present invention improved the catalyst utilization efficiency.

(Examples 3 to 6) A solvent prepared by mixing 15 parts by weight of ethyl lactate and 55 parts by weight of ethylene glycol, an alloy of platinum and ruthenium as a catalyst supported on carbon black and having an average secondary particle diameter of 10 microns. Catalyst supported carbon powder, polyperfluorosulfonic acid (Nafion 115)
Proton conductive polymer-containing liquid (resin concentration 10% by mass) dissolved in ethanol was mixed with alumina as a hydrophilic agent in the composition shown in Table 3 to prepare mixed liquids 5 and 6. Alumina was added after all other ingredients were mixed. Using platinum as a catalyst instead of an alloy of platinum and ruthenium,
Polytetrafluoroethylene fine particles (PTFE) were added as a water repellent in place of alumina to prepare mixed liquids 7 and 8 having the compositions shown in Table 3. PTFE was thoroughly mixed with the catalyst-supporting carbon powder and then mixed with other mixed liquid components to obtain a uniform liquid.

[Table 3] As shown in Table 4, a catalyst layer was formed in the same manner as in Example 1 to prepare an electrode membrane assembly (MEA). Using the produced electrode assembly, the power generation characteristics as a fuel cell were compared with the cell voltage at an output current density of 1.0 A / cm ² as in Example 1. The results are shown in Table 4.

[Table 4]

The power generation characteristics of Examples 3 and 4 are improved as compared with Comparative Example 2. It is considered that this is because Examples 3 and 4 had the preferable fine structure of the catalyst layer, and therefore the hygroscopicity of the catalyst layer by the hydrophilic agent was further improved. In comparison between Examples 3 and 4 in which the amount of alumina added is about the same, a higher voltage is obtained in Example 4 because the catalyst layer obtained by the coating method of Example 4 has a finer structure. It is considered that this has the effect of improving power generation efficiency.

In Examples 5 and 6, the power generation capacity is improved as compared with Comparative Example 3. It is considered that this is because Examples 5 and 6 had a preferable fine structure of the catalyst layer, and thus the water produced by the water repellent agent was removed well from the catalyst layer. Examples 5 and 6 in which the water repellent is added in the same amount.
In Example 6, the higher power generation efficiency is considered to be due to the effect of improving the power generation efficiency because the catalyst layer obtained by the coating method of Example 6 has a more preferable fine structure. Further, in Comparative Examples 2 and 3 in which the hydrophilic agent or the water repellent was added, only the power generation capacity comparable to that of Comparative Example 1 in which no hydrophilic agent was added was obtained. It is considered that this is because the catalyst layer does not have a preferable fine structure, and thus the effect of adding the hydrophilic agent or the water repellent is hardly exhibited.

(Examples 7 and 8) A mixed solution 9 having the same composition as the mixed solution 1 and having a high content of the catalyst-supporting carbon powder was prepared as shown in Table 5.

[Table 5] Mixtures 1, 3 and 9 were separately applied onto one solid polymer electrolyte membrane by the same coating method as in Example 2 to form a catalyst layer pattern. The mixed solutions 1 and 3 were mixed and applied near the upstream side of the negative electrode side gas supply passage, and the mixed solutions 1 and 9 were mixed and applied near the downstream side. The positive electrode catalyst layer was formed by coating the entire surface with the mixed solution 4 three times as in Example 2. The coating conditions and the production of MEA were performed in the same manner as in Example 2. That is, the MEA having a large amount of catalyst could be formed on the downstream side of the gas supply passage as compared with the second embodiment.

In Example 8, an attempt was made to form a negative electrode catalyst layer on the solid polymer electrolyte membrane in the same manner as in Example 7, and to form a catalyst layer pattern on the positive electrode side. Mixtures 4, 7 and 8
Was coated on one solid polymer electrolyte membrane by the same coating method as in Example 6 to form a catalyst layer pattern.
The mixed liquids 4 and 7 were mixed and applied to a position facing the air supply narrow groove of the positive electrode side separator, and the mixed liquids 4 and 8 were mixed and applied to the other portions. That is, as compared with Example 6, the MEA having a large amount of water repellent could be formed in the portion of the positive electrode side separator not facing the air supply narrow groove. Using these prepared electrode assemblies, the cell voltage at an output current density of 1.0 A / cm ² and the utilization efficiency of hydrogen fuel were compared. The results are shown in Table 6.

[Table 6]

In Example 7, a battery voltage similar to that in Example 2 was obtained, and the hydrogen utilization efficiency was improved despite the evaluation under the same gas supply conditions. It is considered that this is because the reaction was promoted in Example 7 because the catalyst amount was increased in the vicinity of the downstream of the gas supply path where hydrogen was consumed and the concentration became low. In the method of the present invention, since the catalyst layer is applied by an inkjet printer,
The catalyst layer as in Example 7 can be easily formed without lowering production efficiency, and power generation efficiency can be improved.

In Example 8, both the battery voltage and the hydrogen utilization efficiency are improved as compared with Example 7 in which the catalyst layer pattern is not formed on the positive electrode side. It is considered that this is because the formation of the catalyst layer pattern allows the generated water to be efficiently removed. In the method of the present invention, since the catalyst layer is applied by the inkjet printer, the catalyst layer having a complicated pattern as in Example 8 can be easily formed without lowering the production efficiency, and the power generation efficiency can be improved.

(Examples 9 and 10) A mixed solution 10 comprising the same composition as the mixed solution 1 and the mixed solution 4 with the addition amount of the proton conductive polymer reduced as shown in Table 7.
And a mixed solution 11 were prepared.

[Table 7]

As shown in Table 8, a catalyst layer was formed in the same manner as in Example 1 to prepare an electrode membrane assembly (MEA). Using the produced electrode assembly, the power generation characteristics as a fuel cell were compared with the cell voltage when the output current density was 1.0 A / cm ² . The results are shown in Table 8.

[Table 8]

In Examples 9 and 10, although the content of the proton-conducting polymer in the catalyst layer was smaller than that of Comparative Example 1, the power generation capacity was kept the same, and in the method of the present invention, Even if the amount of the proton conductive polymer is small, it is possible to form a catalyst layer having a good power generation capacity.

[0053]

According to the first aspect of the present invention, a polymer electrolyte fuel cell in which a mixed liquid containing a catalyst-supporting carbon powder and a proton conductive polymer is applied on a substrate to form a catalyst layer. In the method for forming a catalyst layer for use in a catalyst layer formed by applying two or more kinds of liquid droplets having different compositions to a substrate and applying the same onto a substrate, mass transfer is efficient. Since it has a fine structure that can be improved, a fuel cell equipped with it can improve power generation performance.

According to the second aspect of the present invention, a catalyst layer having a catalyst composition distribution can be formed by using a mixed solution of two or more kinds having different kinds and / or amounts of the catalyst-supporting carbon powder, Utilization efficiency can be improved.

According to the third aspect of the present invention, a catalyst layer having a proton conductive polymer composition distribution is formed by using a mixed solution of two or more kinds having different types and / or amounts of proton conductive polymers. Therefore, the ion conductivity of the catalyst layer can be enhanced.

According to the fourth aspect of the present invention, the mixed solution is
In addition, it contains a water repellent, and its type and / or amount are different 2
By using the mixed liquid of at least one species, the produced water can be easily removed from the pores while maintaining the water content of the proton conductive polymer in the catalyst layer.

According to the fifth aspect of the present invention, the mixed solution is
Further containing a hydrophilic agent, the type and / or amount of which is different 2
By using the mixed liquid of at least one species, it is possible to efficiently humidify the proton conductive polymer in the catalyst layer.

According to the sixth aspect of the present invention, a catalyst layer having a fine structure capable of efficient mass transfer can be obtained by mixing two or more kinds of liquid droplets having different compositions and applying the mixture onto a substrate. The fuel cell can be formed, and the fuel cell having the same can improve the power generation performance.

According to the seventh aspect of the present invention, two or more kinds of droplets having different compositions are successively applied onto the substrate to form a catalyst layer pattern having different compositions in the thickness direction of the catalyst layer. Since the catalyst layer has a layer structure with favorable mass transfer, the fuel cell provided with the catalyst layer can improve power generation performance.

According to the eighth aspect of the present invention, a catalyst layer in which two or more kinds of droplets having different compositions are applied on a substrate to form a catalyst layer pattern having different compositions in the plane direction of the catalyst layer is provided. ,
Since the reaction can occur uniformly in the entire catalyst layer, the fuel cell provided with the catalyst layer can improve power generation efficiency.

According to the ninth aspect of the present invention, the catalyst layer in which the catalyst layer pattern is formed in correspondence with the gas flow path is provided with the catalyst layer pattern because the catalyst layer can react uniformly in the entire catalyst layer. The fuel cell can improve the power generation efficiency.

According to the tenth aspect of the present invention, since the catalyst layer having the catalyst layer pattern having the catalyst layer composition corresponding to the composition of the supply gas can uniformly react in the entire catalyst layer. The fuel cell equipped with it can improve power generation efficiency.

According to the eleventh aspect of the present invention, a solid formed by using a catalyst layer forming device comprising (1) an ink jet nozzle, (2) a nozzle driving device, and (3) a device for drying a catalyst layer. Since the catalyst layer for polymer type fuel cells has a fine structure having good ion conductivity, gas permeability and electron conductivity, the fuel cell provided with the catalyst layer can improve power generation performance. .

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Hisatoshi Fukumoto             2-3 2-3 Marunouchi, Chiyoda-ku, Tokyo             Inside Ryo Electric Co., Ltd. (72) Inventor Hideo Maeda             2-3 2-3 Marunouchi, Chiyoda-ku, Tokyo             Inside Ryo Electric Co., Ltd. F-term (reference) 5H018 AA06 AS01 BB08 EE05 EE17                 5H026 AA06

Claims (11)

[Claims] 1. A method for forming a catalyst layer for a polymer electrolyte fuel cell, which comprises applying a mixed solution containing a catalyst-supporting carbon powder and a proton-conducting polymer onto a substrate to form a catalyst layer having different compositions. A method for forming a catalyst layer, which comprises forming two or more kinds of droplets having different compositions from a mixed solution of two or more kinds and applying the droplets onto a substrate. 2. The method according to claim 1, wherein two or more kinds of mixed liquids having different types and / or amounts of the catalyst-supporting carbon powder are used. 3. The method according to claim 1, wherein a mixed solution of two or more kinds having different kinds and / or amounts of the proton conductive polymer is used. 4. The liquid mixture according to claim 1, wherein the liquid mixture further contains a water repellent, and two or more liquids having different types and / or amounts are used. Method. 5. The mixed solution according to claim 1, wherein the mixed solution further contains a hydrophilic agent, and two or more kinds of mixed solutions having different kinds and / or amounts are used. Method. 6. The method according to claim 1, wherein two or more kinds of droplets having different compositions are mixed and applied on the substrate.
5. The method according to any one of 5 above. 7. Two or more kinds of liquid droplets having different compositions are successively formed,
The method according to any one of claims 1 to 5, wherein the method is applied on a substrate to form a catalyst layer pattern having different compositions in the thickness direction of the catalyst layer. 8. The catalyst layer pattern having different compositions is formed in the plane direction of the catalyst layer by applying two or more kinds of droplets having different compositions on the substrate. The method described in paragraph 1. 9. The method according to claim 7, wherein the catalyst layer pattern is formed corresponding to the gas flow path. 10. The method according to claim 7, wherein a catalyst layer pattern having a catalyst layer composition corresponding to the composition of the supply gas is formed. 11. An ink jet nozzle, (1), and (2).
The catalyst layer forming apparatus used in the method according to claim 1, comprising a nozzle driving device and (3) a device for drying the catalyst layer.