JP2003173786A - 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 having a good ion conductivity, gas permeability and electron conductivity which can avoid such problems as swelling of an electrolyte material and permeation into a gas supply layer and minimize loss of catalyst or the like in manufacturing. <P>SOLUTION: Liquid drops, formed of mixture liquid containing catalyst- supporting carbon powder, a proton conductive polymer and solvent, is applied on an electrolyte material to form a catalyst layer for a solid polymer fuel cell. Here, during the processes of forming liquid drops and application, the amount of evaporation of the solvent from the liquid drops or the amount of moisture absorption by the liquid drops are controlled in the forming method of the catalyst layer. 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 the same can be improved in 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 catalyst layer is formed by preparing a mixed solution in which additives such as carbon powder carrying a catalyst, a proton conductive polymer, and a fluororesin are dispersed, and directly on the solid polymer electrolyte membrane or on the gas supply layer. The application method is generally used. When the mixed solution is applied on the solid polymer electrolyte membrane, the solvent of the mixed solution causes the solid polymer electrolyte membrane to swell, or when applied on the gas diffusion layer, the mixed solution is mixed with the gas diffusion layer. There is a problem that it penetrates into the interior of the catalyst, and avoiding these is a necessary condition for forming a good catalyst layer. Further, when the mixed solution is diluted or when the composition of the mixed solution is not proper, the desired fine structure of the catalyst layer cannot be obtained.

For example, in US Pat. No. 5,211,984, swelling of a solid polymer electrolyte membrane is suppressed by transferring a catalyst layer once formed on a Teflon (registered trademark) membrane. Further, Japanese Patent Laid-Open No. 7-183035 discloses a method of forming a preferable catalyst layer by coating a solid polymer electrolyte in a slurry in a colloidal form to prevent the gas diffusion layer from seeping.

As a coating method, screen printing, roller coating, spray coating and the like are used. A method for applying a catalyst by ink jet is also disclosed in Japanese Patent Publication No. 2001-504755 as a pollutant treatment device. Screen printing and roller coating are commonly used methods because a highly viscous liquid mixture can be easily coated. Both inkjet coating and spray coating have a merit that a minute amount of coating can be easily realized because they are methods of applying slurry in the form of minute droplets. Further, since the solid polymer electrolyte membrane can be easily applied even after being fixed to a frame such as a gas seal, the selectivity of the production method is widened, which is advantageous. Particularly in the case of inkjet coating, there is also an advantage that expensive catalyst layer materials can be coated without waste.

However, the methods such as the transfer of the catalyst layer described in the above documents have a problem that the process is complicated, and the method of forming a good catalyst layer by adjusting the colloidalization of the mixed solution and the like. However, there is a problem that the solvent that can be used is limited and the stability of the mixed solution becomes low, which makes it difficult to perform stable production. Regarding the coating method, in commonly used screen printing or roller coating, although a highly viscous mixed solution such as the colloidal mixed solution can be coated, it is difficult to suppress the coating amount to a very small amount. There is a problem that a different mixed solution is applied. When the coating is diluted to suppress the coating amount, swelling of the solid polymer electrolyte membrane and penetration into the gas supply layer are likely to occur, and there is also a problem that the fine structure of the catalyst layer is not good. is there. Although spray coating and ink jet can reduce the coating amount, there is a restriction that the viscosity of the mixed liquid that can be applied is only low, so if you simply apply a low viscosity mixed liquid, you will end up with screen printing or roller coating. Similar problems will occur.

[0008]

Therefore, the object of the present invention is to avoid the problems such as swelling of the solid polymer electrolyte membrane and soaking into the gas supply layer, the loss of the catalyst, etc. in the production, and the gas permeability. Another object of the present invention is to provide a method for forming a catalyst layer for polymer electrolyte fuel cells, which is excellent in electron conductivity and ionic conductivity.

[0009]

DISCLOSURE OF THE INVENTION The present invention is directed to a catalyst for polymer electrolyte fuel cells by forming droplets from a mixed liquid containing a catalyst-supporting carbon powder, a proton conductive polymer and a solvent and applying the droplets to an electrolyte material. A method for forming a catalyst layer, which comprises controlling the amount of solvent evaporated from the droplets or the amount of moisture absorption of the droplets in the process from the formation of the droplets to the application when forming the layer.

[0010]

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, fullerenes, aggregates of carbon nanotubes and the like can be used. The particle size is preferably 5 to 5000 nm, 10 to 50
0 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 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 electrolyte material 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 As the electrolyte material, a proton conductive polymer is extruded to form a film, and the film thickness is 20 to 300 μm, preferably 40 to 300 μm.
It is preferable to use a solid polymer electrolyte membrane having a thickness of 200 μm.

The solvent in the present invention is not particularly limited as long as it can dissolve the proton conductive polymer or disperse it as a fine gel in a state of high fluidity, and is not particularly limited, but methanol, ethanol, 1-propanol, 2 −
Alcohols such as propanol, 1-butanol, 2-butanol, isobutyl alcohol, tert-butyl alcohol, pentanol, etc., acids such as lactic acid, formic acid, acetic acid, propionic acid and alcohols having 1 to 5 carbon atoms are dehydrated and condensed. Ketone type solvents such as esters, acetone, methyl ethyl ketone, pentanone, methyl isobutyl ketone, heptanone, cyclohexanone, methyl cyclohexanone, acetonyl acetone, diisobutyl ketone, etc., ether type such as tetrahydrofuran, dioxane, diethylene glycol dimethyl ether, anisole, methoxytoluene, dibutyl ether, etc. , Other, ethylene glycol,
Diethylene glycol, diacetone alcohol, 1-methoxy-2-propanol, dimethylformamide, N
-A polar solvent such as methylpyrrolidone or dimethylacetamide, and a mixture of two or more selected from the above solvent group can be used. 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 content of the constituent components in the mixed solution varies greatly depending on the type of solvent and the difference in the proton conductive polymer, but the catalyst-supporting carbon powder is preferably 1 to 70% by mass, and 3 to 50% by mass. More preferably, the proton conductive polymer is preferably 0.01 to 20% by mass,
0.1 to 10 mass% is more preferable. 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. If too much,
The more it is added, the more the reaction efficiency is not improved 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. In addition to the components shown here, conventionally known polytetrafluoroethylene, tetrafluoroethylene-
A hexafluoropropylene copolymer, a water repellent agent such as polyvinylidene fluoride, and a hydrophilic agent such as alumina, silica, titanium oxide, or cerium oxide can also be mixed.

The mixed solution which can be used in the present invention has a wide range of compositions as described above, but the viscosity of the mixed solution is preferably 300 cp or less, more preferably 100 cp or less in order to form droplets. If the viscosity is too high, the droplet size becomes so large that a catalyst layer having a preferable fine structure cannot be formed, and problems such as nozzle clogging easily occur. Also,
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 formed by an air atomizing spray nozzle or a piezo type or thermal type ink jet nozzle. When using an air atomizing spray nozzle, the particle size of the droplets discharged from the nozzle is preferably 50 to 500 μm, and 100 to 2
00 μm is more preferable. If the particle size is too small, the amount of evaporation becomes too large and it is difficult to apply.
If the particle size is too large, it is difficult to cause sufficient concentration or moisture absorption during application, and it becomes difficult to provide the catalyst layer with a fine structure. When an inkjet nozzle is used, the particle size of the liquid droplets is preferably 3 to 300 μm, more preferably 10 to 200 μm. The only difference from the case of the air atomizing spray is that the nozzle can be brought close to the electrolyte material, and the same problem occurs when the particle size is too large or too small.

Evaporation of the solvent from the droplets or moisture absorption of the droplets changes the dissolution state of the proton conductive polymer in the droplets or the dispersed state of various contained components, resulting in a marked decrease in fluidity. In this case, swelling of the electrolyte material can be greatly suppressed even if the droplet is directly applied onto the electrolyte material. Further, even if the droplets are applied to the gas supply layer side, the permeation of the liquid can be greatly suppressed. A further great advantage is that the catalyst layer formed by applying the droplets becomes porous and a favorable microstructure is obtained.

There are several preferable application conditions for applying the droplets to the electrolyte material as described above, and one of them is a method of applying the droplets to the heated electrolyte material.
The heated electrolyte material can promote solvent evaporation of the applied droplets. By adjusting the temperature, it is possible to control the evaporation amount of the solvent and form the desired catalyst layer. Although the temperature of the electrolyte material depends on the coating solution and coating conditions, it is 10
It is preferable to control in the temperature range of ~ 200 ° C,
-150 degreeC is more preferable. Outside the above temperature range, it becomes difficult to control the evaporation rate, which is not preferable.

As a method of controlling the application conditions, there is also a method of controlling the atmosphere between the nozzle and the electrolyte material. By controlling the temperature and humidity between the nozzle and the electrolyte material, it is possible to control the evaporation rate of the solvent from the droplet and the amount of moisture absorbed by the droplet. Although the temperature depends on the coating solution and coating conditions, it is 10 to 1
It is preferable to control in the temperature range of 50 ° C., 20 to 1
00 ° C. is more preferable. Regarding humidity, relative humidity 1
It is realistic to control at 0 to 95%. Increasing the amount of evaporation or decreasing the amount of moisture absorption has the effect of increasing the temperature or decreasing the humidity, and suppressing the evaporation or increasing the amount of the moisture absorption has the effect of increasing the humidity.

As a method of controlling the application method, there is also a method of controlling the distance between the nozzle and the electrolyte material. Although depending on temperature and humidity, the distance between the nozzle and the electrolyte material is preferably 5 to 150 mm, more preferably 7 to 100 mm when an inkjet nozzle is used. In the case of air atomizing spray, it is preferably 50 to 500 mm, more preferably 70 to 250 mm. If the distance is too small, sufficient effect of solvent evaporation and moisture absorption cannot be obtained. If it is too large, it becomes difficult to control the application position of the droplet, and the application becomes unstable, which is not preferable. In particular, when an air atomizing spray is used, there is a drawback that the application efficiency of droplets becomes low when the distance is large. The larger the distance between the nozzle and the electrolyte material, the larger the amount of solvent evaporation or the amount of moisture absorption. The application state can be easily adjusted by changing this distance.

During the period in which droplets are formed and applied to the electrolyte material to be stabilized, evaporation of the solvent and penetration of water from the air occur. The evaporation of the solvent and the penetration of water from the air occur at the same time, but it can be quantified by using the method described below. First, application is performed with a constant discharge amount. The weight change immediately after the application of the electrolyte material is measured. For this purpose, it is necessary to measure by covering with a film immediately after coating in order to avoid the weight fluctuation after applying the droplet. Further, the weight change of the electrolyte material after drying is determined. The increase in water content of the liquid immediately after being applied to the electrolyte material is measured by the Karl Fischer method. From the above measurement results, it is possible to determine the application efficiency of the droplet to the electrolyte material, the solvent evaporation amount at the time of application, and the moisture absorption amount at the time of application.

As a result of actually measuring the solvent evaporation amount and the droplet moisture absorption amount while applying the above conditions, a simple guideline for forming a good catalyst layer was obtained. In an extremely humid and non-dry environment, both solvent evaporation and moisture absorption occur. However, from the results of various examinations under the above conditions, it is not necessary to monitor both of them, and when the electrolyte material is heated or the solvent evaporation such as low humidity is promoted and adjusted, the solvent evaporation amount is adjusted. It has been found that, in the case of promoting moisture absorption such as high humidity, by adjusting the moisture absorption amount, a good catalyst layer can be formed without any practical problem. That is,
In the actual process from droplet formation to application, either the solvent evaporation amount or the moisture absorption amount may be controlled. When controlling the solvent evaporation amount, 15% to 60%, more preferably the total amount of the droplets, is more preferable. A good catalyst layer can be formed by concentrating in the range of 20% to 50%. The optimum value of these values largely depends on the material forming the droplet. When managing the amount of moisture absorption, the amount of moisture absorption is 20% to 5% of the total amount of liquid droplets.
When it is 0%, more preferably 30% to 45%, a good catalyst layer can be formed. The optimum value of these values is largely dependent on the material forming the droplet. In particular, when the droplet contains a substance having hydrophobicity, it tends to form a good catalyst layer with a small amount of moisture absorption.

The catalyst layer of the present invention comprises (1) a droplet forming device, (2) a temperature between the droplet forming device and the electrolyte material,
It is formed by a catalyst layer forming device including a humidity and distance control device, (3) a device for heating an electrolyte material, and (4) a device for drying a catalyst layer. As a droplet forming device, an air atomizing spray nozzle, or
Any ink jet nozzle of piezo type or thermal type can be used as long as it can form droplets having the above-mentioned preferable droplet diameter. As a device for controlling the temperature, humidity and distance between the droplet forming device and the electrolyte material, a temperature adjusting part by an electric heater or the like, a humidity adjusting part by introducing an inert gas, a droplet forming device and an electrolyte material. Any device may be used as long as it has a drive unit that can adjust the distance between them. The device for heating the electrolyte material is not particularly limited, but an indirect heating device such as a hot plate using an electric heater whose temperature can be easily controlled can be used. As a drying device for the catalyst layer, a container capable of keeping the temperature of the atmosphere at a constant high temperature with an electric heater, an infrared lamp, or the like may be used, and a vacuum drying device that also uses a vacuum pump may be used.

[0024]

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 to 3) Ethylene glycol 55
Parts by weight, 25 parts by weight of ethyl lactate, 2 parts by weight of catalyst-supporting carbon powder having an average secondary particle size of 10 μm in which an alloy of platinum and ruthenium is supported on carbon black as a catalyst, polyperfluorosulfonic acid (Nafion, DuPont) Mixed solution (resin concentration 10% by mass) 1 dissolved in ethanol
0 part by weight was mixed and sufficiently stirred to disperse the solid content to prepare a negative electrode mixture liquid. Platinum was used as a catalyst instead of an alloy of platinum and ruthenium, and a positive electrode mixture was prepared in the same manner as the negative electrode mixture. Next, the catalyst liquid was formed by discharging the mixed liquid for the negative electrode and the positive electrode from an inkjet nozzle and applying the mixed liquid on a solid polymer electrolyte material (polyperfluorosulfonic acid / Nafion 115, trade name). An inkjet printer hp deskjet 990c (manufactured by Hewlett-Packard Co.) was used as an inkjet nozzle and a drive system to prepare a device suitable for this example, and coating was performed using this device. By adjusting the viscosity according to the mixing conditions of the mixed liquid and the coating conditions of an inkjet printer, the applied solid amount after coating and drying was set to about 3 mg / cm ^{2 for} both the positive electrode and negative electrode catalyst layers. The distance between the inkjet nozzle and the solid polymer electrolyte membrane was 30 mm, and the coating was performed in a nitrogen atmosphere at a temperature of 24 ° C and a humidity of 25%. (If this coating is performed in air with low humidity, there is a risk of ignition by the catalyst. For safety, it is desirable to perform it under humidified conditions or in an inert gas). The coating speed was about 3 cm ² / sec. After the negative electrode catalyst layer was coated, it was vacuum dried at 60 ° C., and the positive electrode catalyst layer was similarly coated and dried. After drying the prepared catalyst layer under vacuum,
It was sandwiched by 50 μm carbon paper and hot pressed at a temperature of 160 ° C. and a pressure of 50 kgf / cm ² to prepare an electrode membrane assembly (MEA). This MEA was sandwiched between separator plates, hydrogen gas was introduced into the negative electrode side, and air was introduced into the positive electrode side into the MEA via the flow path cut in the separator plate, and a power generation test was carried out under normal pressure. The power generation characteristics were compared with the battery voltage when the output current density was 1.0 A / cm ² .

[Table 1] Examples 1 to 3 in Table 1 are the results of applying the catalyst layer while changing the temperature of the solid polymer electrolyte membrane. The solvent evaporation amount and the moisture absorption amount are measured by the above-mentioned method in the catalyst layer formed on the aluminum foil. In the case of Example 3, the temperature was too high to perform accurate measurement, but it is considered that the solvent evaporation amount is large. Despite the same amount of catalyst, the power generation characteristics are greatly improved in Examples 2 and 3. Since the voltage of this level can be maintained at the current density of 1.0 A / cm ² , it can be seen that a good fine structure is obtained.

(Examples 4 to 6) The atmosphere between the nozzle and the solid polymer electrolyte membrane was changed to form the catalyst layer. An MEA was prepared in the same manner as in Example 1 except that the coating was performed under nitrogen gas in a different humidified state.

[Table 2] Examples 4 to 6 in Table 2 summarize these results. Example 4 is a condition to accelerate moisture absorption, and Examples 5 and 6 are conditions to accelerate solvent evaporation. Compared to Example 1, despite the same amount of catalyst, the power generation characteristics were good in all cases, and the amount of solvent evaporation and moisture absorption were changed by changing the atmosphere between the nozzle and the solid polymer electrolyte membrane. It can be seen that the amount can be controlled and a good microstructure can be obtained.

(Examples 7 to 9) The distance between the ink jet nozzle and the solid polymer electrolyte membrane was made variable, and the temperature of the solid polymer electrolyte membrane was kept at 26 ° C. Other conditions were the same as in Example 1 to produce MEA.

[Table 3] Examples 7 to 9 in Table 3 summarize these results. Solvent evaporation by increasing the nozzle-membrane spacing,
The amount of moisture absorption is also large. Despite the same amount of catalyst, the power generation characteristics in Examples 8 and 9 are good, and the solvent evaporation amount and the moisture absorption amount can be controlled by changing the nozzle-membrane spacing, resulting in a good microstructure. You can see that you can get it.

[0028]

According to the first aspect of the present invention, a solid polymer fuel is produced by forming droplets from a mixed liquid containing a catalyst-supporting carbon powder, a proton conductive polymer and a solvent, and applying the droplets to an electrolyte material. When forming a catalyst layer for a battery, the catalyst layer formed by controlling the amount of solvent evaporation from the droplet or the amount of moisture absorption of the droplet in the process from formation to application of the droplet has good gas permeation. Since it has a fine structure having electrical conductivity and electronic conductivity, a fuel cell provided with it can improve power generation performance.

According to the second aspect of the present invention, the formation of droplets is performed by an air atomizing spray nozzle or a piezo type or thermal type ink jet nozzle, so that the loss of the catalyst in the production is small and the electrolyte material. It is possible to avoid the swelling and the soaking into the gas supply layer.

According to the third aspect of the present invention, the solvent evaporation amount from the droplet or the moisture absorption amount of the droplet is selected from the group consisting of temperature, humidity and distance in the process from formation of the droplet to application. Since the catalyst layer formed by controlling at least one kind has a fine structure having good gas permeability and electron conductivity, the fuel cell provided with the catalyst layer can improve the power generation performance.

According to the fourth aspect of the present invention, since the catalyst layer formed by applying droplets to the heated electrolyte material has a fine structure having good gas permeability and electron conductivity, A fuel cell equipped with it can improve power generation performance.

According to the fifth aspect of the present invention, by using the solid polymer electrolyte membrane as the electrolyte material, it is possible to form a solid polymer electrolyte fuel cell catalyst layer having excellent ion conductivity.

According to the sixth aspect of the present invention, (1) a droplet forming device, (2) a temperature, humidity and distance control device between the droplet forming device and the electrolyte material, (3) A catalyst layer for a polymer electrolyte fuel cell formed by using a catalyst layer forming device including a device for heating an electrolyte material and (4) a device for drying a catalyst layer, swells the electrolyte material, and permeates the gas supply layer. It is possible to avoid such problems as described above, the loss of the catalyst in the production is small, and the gas permeability and the electron conductivity are excellent.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) H01M 8/02 H01M 8/02 P 8/10 8/10 (72) Inventor Hisatoshi Fukumoto Marunouchi, Chiyoda-ku, Tokyo 2-chome 2-3 Sanryo Electric Co., Ltd. (72) Inventor Hideo Maeda 2-3-3 Marunouchi, Chiyoda-ku, Tokyo Sanryo Electric Co., Ltd. F-term (reference) 4D075 AA02 BB24Z CA47 DA04 DA06 DC18 EA10 EB31 EC01 4F041 AA02 AA06 AB02 5H018 AA06 AS01 BB01 BB06 BB08 BB12 EE03 EE04 EE05 EE06 EE07 EE08 EE12 EE13 EE17 EE18 HH03 HH08 5H026 AA06 BB01 BB03 CX05 EE05 EE18 HH03 H08

Claims (6)

[Claims] 1. A liquid when a droplet is formed from a mixed liquid containing a catalyst-supporting carbon powder, a proton conductive polymer and a solvent and applied to an electrolyte material to form a catalyst layer for a polymer electrolyte fuel cell. A method for forming a catalyst layer, which comprises controlling the amount of solvent evaporated from the droplet or the amount of moisture absorbed by the droplet in the process from the formation of the droplet to the application. 2. The method according to claim 1, wherein the droplets are formed by an air atomizing spray nozzle or a piezo type or thermal type ink jet nozzle. 3. The amount of solvent evaporated from a droplet or the amount of moisture absorbed by a droplet is controlled by at least one selected from the group consisting of temperature, humidity and distance in the process from formation to application of the droplet. The method according to claim 1 or 2. 4. The method according to claim 1, wherein the droplets are applied to a heated electrolyte material. 5. The method according to claim 1, wherein the electrolyte material is a solid polymer electrolyte membrane. 6. (1) Droplet forming device, (2) Temperature, humidity and distance control device between the droplet forming device and the electrolyte material, (3) Device for heating the electrolyte material, and ( 4) A catalyst layer forming device used in the method according to any one of claims 1 to 5, which comprises a device for drying the catalyst layer.