JP6295450B2 - Catalyst ink and method for producing catalyst layer - Google Patents

Description

The present invention relates to a process for preparing a catalyst ink and catalytic layer, particularly, a catalyst ink for use in the production of the catalyst layer of the fuel cell, and a method for producing a catalyst layer using a catalytic ink.

  As a fuel cell having a polymer electrolyte membrane, a fuel cell in which a hydrophilic layer is formed between a polymer electrolyte and catalyst-supporting carbon has been proposed (see, for example, Patent Document 1). In this fuel cell, by having a hydrophilic layer between the polymer electrolyte and the catalyst-supporting carbon, water and protons can be easily transferred and the drainage of the generated water can be improved. The performance of the fuel cell can be improved.

  Also, a catalyst layer is formed using a catalyst paste obtained by mixing and stirring a pre-paste obtained by mixing a catalyst and water and an electrolyte solution obtained by dissolving a polymer electrolyte in a secondary alcohol or a tertiary alcohol. Thus, a method of manufacturing a catalyst layer in which a hydrophilic layer is formed between a polymer electrolyte and catalyst-supported carbon has also been proposed (see, for example, Patent Document 2). In this method, catalyst metal particles of a catalyst are modified with a modifying group such as a nitrate group, amino group, or sulfonic acid group, and a catalyst having catalyst metal particles modified with the modifying group is mixed with water. The paste is adjusted.

JP 2006-140061 A JP 2011-228267 A

  However, in the method using a catalyst having catalytic metal particles modified with the above-described modifying group, careful attention is required when the pre-paste and the electrolyte solution are mixed and stirred. If the stirring is insufficient, the pre-paste and the electrolyte solution are not sufficiently mixed, and the catalyst is partially solidified, thereby degrading the performance of the catalyst layer. On the other hand, if the stirring is excessive, the polymer electrolyte facing the catalyst is detached from the catalyst, and at this time, the formation of a hydrophilic layer between the polymer electrolyte and the catalyst is hindered in order to take away water on the catalyst surface. .

The catalyst ink of the present invention is an ink for easily producing a catalyst layer in which a hydrophilic layer in which acidic functional groups such as sulfonic acid groups of the polymer electrolyte are oriented on the catalyst side is formed between the polymer electrolyte and the catalyst. The main purpose is to provide . The method for producing a catalyst layer according to the present invention is a method for producing a catalyst layer in which a hydrophilic layer in which acidic functional groups such as sulfonic acid groups of the polymer electrolyte are oriented on the catalyst side is formed between the polymer electrolyte and the catalyst. The main purpose is to provide.

  The catalyst ink of the present invention, the method for producing the same, and the method for producing the catalyst layer employ the following means in order to achieve the respective main objects described above.

The catalyst ink of the present invention is
A catalyst ink mainly composed of a polymer electrolyte having a hydrophilic group in a side chain, a hydrophobic solvent, a catalyst, and water, and used for manufacturing a catalyst layer of a fuel cell,
An emulsion of catalyst reverse micelles having a reverse micelle structure by wrapping the mixture of the catalyst and water as a nucleus with the polymer electrolyte with the hydrophilic group facing inward,
It is characterized by that.

  The catalyst ink according to the present invention has a reverse micelle structure in which a hydrophobic main chain skeleton is directed to the hydrophobic solvent side, and a mixture of the catalyst and water is encapsulated by a polymer electrolyte with a hydrophilic group facing inward. It has a micelle and is an emulsion of this catalytic reverse micelle. When this catalyst ink is applied to the diffusion layer or printed, and the solvent is dried to form the catalyst layer, the structure of the catalyst reverse micelle remains in the catalyst layer as it is, so a hydrophilic layer is formed between the polymer electrolyte and the catalyst. The catalyst layer is formed. When a fuel cell is configured using this catalyst layer, water and protons necessary for the cell reaction can be favorably transferred by the hydrophilic layer of the catalyst layer, and the drainage of water generated by the fuel cell is improved. be able to. Furthermore, since the polymer electrolyte facing the pores of the catalyst layer is formed with a main chain skeleton having high water repellency, water retention is unlikely to occur and gas diffusion is not easily inhibited. As a result, the performance of the fuel cell can be improved. Here, in this specification, “micelle” means a molecule or ion such as a surfactant having a hydrophilic group and a hydrophobic group, which is gathered in a spherical shape with the hydrophilic group facing outward and the hydrophobic group facing inward. The structure of such micelles is called “micelle structure”, and the structure in which the hydrophobic groups are gathered in a spherical shape with the hydrophilic groups facing inward is called “reverse micelle structure”. “Emulsion” means a dispersion solution in which both the dispersoid and the dispersion medium are liquid, that is, an emulsion.

  In such a catalyst ink of the present invention, a reverse micelle of water having a reverse micelle structure in which a hydrophobic main chain skeleton is directed to the hydrophobic solvent side and water is encapsulated by the polymer electrolyte with a hydrophilic group facing inward. The catalyst reverse micelle emulsion may be used. When the catalyst layer is formed using this catalyst ink, the structure of the reverse micelle of water remains in the catalyst layer as it is, so that the structure of the reverse micelle of water is combined with the structure of the reverse micelle of water, and there is a hydrophilic portion having a widened portion. A layer is formed. For this reason, the movement of water and protons can be further improved.

The method for producing the catalyst ink of the present invention comprises:
A method for producing a catalyst ink used for producing a catalyst layer of a fuel cell, comprising:
An electrolyte solution in which a polymer electrolyte having a hydrophilic group in the side chain is dissolved in a hydrophobic solvent and a catalyst paste in which water is mixed with the catalyst to form a paste, the hydrophobic solvent with respect to the sum of the hydrophobic solvent and water A step of mixing and stirring so that the ratio of hydrophobic solvent, which is a ratio, is within a predetermined range to be an emulsion of a reverse micelle structure,
It is characterized by providing.

  In the method for producing the catalyst ink of the present invention, the electrolyte solution and the catalyst paste are mixed and stirred so that the hydrophobic solvent ratio is within a predetermined range to be an emulsion having a reverse micelle structure. Catalytic reverse micelles with a mixture of catalyst and water as a nucleus by a polymer electrolyte directed to reverse micelle structure or water with a polymer electrolyte with a hydrophilic group facing inward as a nucleus to form a reverse micelle structure A catalyst ink of reverse micelle emulsion can be produced. Here, the “predetermined range” may be in a range of a ratio that can constitute a reverse micelle structure, but in particular, in the range of 0.45 to 0.60, stable catalyst reverse micelle or reverse micelle of water. It can be an emulsion.

The method for producing the catalyst layer of the present invention comprises:
A method for producing a catalyst layer of a fuel cell, comprising:
Applying or printing the catalyst ink of the present invention of any of the above-described aspects onto a gas diffusion layer having conductivity and gas permeability, and drying the solvent to form a catalyst layer.
It is characterized by that.

  According to the method for producing a catalyst layer of the present invention, a catalyst layer is formed using a catalyst ink having catalyst reverse micelles or water reverse micelles, and therefore a catalyst in which a hydrophilic layer is formed between a polymer electrolyte and a catalyst. Layers can be manufactured. Therefore, if a fuel cell is constituted using the catalyst layer produced by the method for producing a catalyst layer of the present invention, water and protons necessary for the cell reaction can be favorably transferred to the hydrophilic layer of the catalyst layer. At the same time, it is possible to improve the drainage of water generated by the fuel cell. Furthermore, since the polymer electrolyte facing the pores of the catalyst layer is formed with a main chain skeleton having high water repellency, water retention is unlikely to occur and gas diffusion is not easily inhibited. As a result, the performance of the fuel cell can be improved.

It is the structure schematic diagram which showed the structure of the catalyst ink 20 of embodiment typically. 4 is a partially enlarged view showing a part of the catalyst reverse micelle 40 in an enlarged manner. FIG. It is a flowchart which shows an example of the manufacturing method of the catalyst ink 20 of embodiment. It is a block diagram which shows an example of a structure of MEA50. It is explanatory drawing which shows an example of the relationship between the solid-liquid ratio of catalyst ink 20, and a hydrophobic solvent ratio. It is explanatory drawing explaining the function of the cathode catalyst layer 54b formed using the catalyst ink 20 of embodiment. It is explanatory drawing which expands and shows typically a part of catalyst layer formed with the catalyst ink made into the emulsion by the catalyst reverse micelle 40 and the reverse micelle 42 of water. It is explanatory drawing which shows the current voltage performance evaluation result in case the temperature of MEA of Example 1 and Comparative Example 1 is 50 ° C. and the humidity is 100% RH. It is explanatory drawing which shows the current voltage performance evaluation result in case the temperature of MEA of Example 1 and Comparative Example 1 is 80 ° C. and the humidity is 40% RH. It is explanatory drawing explaining the comparison of the catalyst layer proton resistance when the MEA of Examples 1 and 2 and the MEA of Comparative Example 2 are operated at a temperature of 50 ° C. and a humidity of 100% RH. It is explanatory drawing explaining the comparison of the performance when the MEA of Examples 1 and 2 and the MEA of Comparative Example 2 are operated by changing the temperature and humidity at a constant current density. It is explanatory drawing explaining the performance when the MEA of Examples 3-6 is drive | operated on the conditions whose temperature is 60 degreeC and humidity is 62% RH. It is explanatory drawing explaining the performance when the MEA of Examples 3-6 is drive | operated on the conditions whose temperature is 90 degreeC and humidity is 18% RH.

(Catalyst ink)
FIG. 1 is a structural schematic view schematically showing the structure of the catalyst ink 20 of the embodiment, and FIG. 2 is a partially enlarged view showing a part of the catalyst reverse micelle 40 included in the catalyst ink 20 in an enlarged manner. . As illustrated, the catalyst ink 20 of the embodiment is configured as an emulsion in which a large number of catalyst reverse micelles 40 and water reverse micelles 42 are emulsified in a hydrophobic solvent 38. The catalyst reverse micelle 40 has a plurality of high nuclei made of a catalyst 22 having catalyst metal particles 26 supported on a carrier 24 and a nucleus made of water 28 so that a sulfonic acid group 34 which is a hydrophilic group of the polymer electrolyte 32 is located inside. The reverse micelle structure is formed by enclosing with a molecular electrolyte 32 and having the main chain skeleton directed toward the hydrophobic solvent, and the reverse micelle 42 of water is reversely encased in a plurality of polymer electrolytes 32 in the same manner. It has a micelle structure.

  Here, as the carrier 24, conductive particles such as carbon particles can be used. As the catalyst metal particles 26, metal particles such as platinum or a platinum alloy can be used. As the polymer electrolyte 32, a fluorine-based polymer having a sulfonic acid group can be used. As the hydrophobic solvent 38, any hydrophobic liquid material may be used. For example, hexane, benzene, toluene, diethyl ether, ethyl acetate, 1-butanol, isobutyl alcohol, sec-butyl alcohol, 1-pentanol. 2-pentanol, 3-pentanol, 3-methyl-1-butanol, 3-methyl-3-buten-1-ol and the like are preferable, and these can be used alone or as a mixture. Of these, 1-butanol is particularly preferable. Further, a plurality of hydrophobic solvents or an amphiphilic solvent such as ethanol or 1-propanol may be added for the boiling point operation or the improvement of the solubility of the polymer electrolyte. However, when a large amount of an amphiphilic solvent is added, the solubility in water is increased and an emulsion is not formed. Therefore, the composition ratio is preferably set so as to phase separate from water.

(Manufacture of catalyst ink)
FIG. 3 is a flowchart illustrating an example of a method for producing the catalyst ink 20 according to the embodiment. In the manufacture of the catalyst ink 20, first, an electrolyte solution 39 in which the polymer electrolyte 32 is dissolved in the hydrophobic solvent 38 and a catalyst paste 29 in which the catalyst 22 is mixed with water 28 to form a paste are prepared (S100). , S110). At this time, the hydrophobic solvent 38 of the electrolyte solution 39 and the water 28 of the catalyst paste 29 are adjusted so that the hydrophobic solvent ratio becomes 0.45 to 0.60 when the electrolyte solution 39 and the catalyst paste 29 are mixed. . Here, the hydrophobic solvent ratio means the weight ratio of the hydrophobic solvent 38 to the total solvent (the hydrophobic solvent 38 and the water 28). Then, the adjusted electrolyte solution 39 and the catalyst paste 29 are mixed and sufficiently stirred (S120) to complete the catalyst ink 20 as an emulsion.

It can be confirmed in the same manner as in the following preliminary experiment that the catalyst ink 20 thus produced is an emulsion of a reverse micelle-structured catalyst reverse micelle or water reverse micelle. In the preliminary experiment, first, 20 g of polymer electrolyte solution SS900 / 10 (manufactured by Asahi Kasei E-Materials) was bathed at 85 ° C. in a container, and 2 g of ethanol or water as a solvent (4 g in total of the polymer electrolyte and the solvent). Evaporate until Then, 36 g of 1-butanol is added to the polymer electrolyte solution after the bathing, and the electrolyte solution 39 is obtained by stirring for 3 minutes with a rotation / revolution centrifugal stirrer (a hybrid mixer HM500 manufactured by Keyence Corporation). . Water and 1-butanol are placed in a glass bottle and shaken to obtain the following samples A, B, and C. Then, a 1-butanol solution of the fat-soluble dye oil red O is added to the samples A, B, and C, and it is confirmed whether or not the whole emulsion is dyed. In this preliminary experiment, it was confirmed that the continuous phase of sample A was not stained, but the continuous phases of samples B and C were stained. This means that sample A is an emulsion with a micelle structure, and samples B and C are emulsions with a reverse micelle structure.
Sample A: 1 g of electrolyte solution, 2 g of water, 0 g of 1-butanol
Sample B: 1 g of electrolyte solution, 1.3 g of water, 0.7 g of 1-butanol
Sample C: 1 g of electrolyte solution, 1 g of water, 1 g of 1-butanol

(Catalyst layer)
The catalyst layer using the catalyst ink 20 of the embodiment is formed by applying or printing the catalyst ink 20 on the gas diffusion layer and drying the solvent. FIG. 4 is a configuration diagram showing an example of a configuration of an MEA (membrane and electrode assembly) 50 as a unit unit of the fuel cell. As shown in the figure, the MEA 50 includes a cathode catalyst layer 54b and an anode catalyst layer by a cathode 54 comprising a cathode gas diffusion layer 54a and a cathode catalyst layer 54b, and an anode 56 comprising an anode gas diffusion layer 56a and an anode catalyst layer 56b. The solid electrolyte membrane 52 is sandwiched so that the solid electrolyte membrane 52 is in close contact with the solid electrolyte membrane 52. The cathode catalyst layer 54b and the anode catalyst layer 56b are formed using the catalyst ink 20 of the embodiment. Here, as the solid electrolyte membrane 52, like the polymer electrolyte 32, a membrane formed of a fluorinated polymer having a sulfonic acid group or the like (for example, Nafion manufactured by DuPont) can be used. As the cathode gas diffusion layer 54a and the anode gas diffusion layer 56a, carbon paper, carbon cloth, carbon felt or the like having conductivity and gas diffusibility can be used.

(Hydrophobic solvent ratio)
The reason why the hydrophobic solvent ratio is preferably 0.45 to 0.60 in the production of the catalyst ink 20 will be described. FIG. 5 is an explanatory diagram showing an example of the relationship between the solid-liquid ratio of the catalyst ink 20 and the hydrophobic solvent ratio. Here, the solid-liquid ratio means the ratio of solid to the sum of solid (catalyst 22 and polymer electrolyte 32) and liquid (water 28 and hydrophobic solvent 38) in the catalyst ink 20. In the figure, a circle indicates when the catalyst layer formed using the catalyst ink functions well, and a cross indicates when the catalyst layer formed using the catalyst ink does not function well. Show. As shown in the figure, the formed catalyst layer functions well when the hydrophobic solvent ratio is 0.45 to 0.60.

(Function of catalyst layer)
Next, the function of the cathode catalyst layer 54b formed using the catalyst ink 20 of the embodiment will be described. FIG. 6 is an explanatory view illustrating the function of the cathode catalyst layer 54b formed using the catalyst ink 20 of the embodiment. The fuel cell is operated with the MEA 50 in a wet state because the movement of protons necessary for the cell reaction is performed with water. As shown in the figure, the cathode catalyst layer 54b is formed by drying the solvent of the catalyst reverse micelle 40 having a reverse micelle structure, and therefore, a plurality of polymers are arranged so that the sulfonic acid group 34 of the polymer electrolyte 32 is on the inside. The structure is such that the catalyst 22 (the carrier 24 and the catalyst metal particles 26) is wrapped by the electrolyte 32. For this reason, a hydrophilic layer 60 is formed between the catalyst 22 and the polymer electrolyte 32. Proton (H ⁺ ) generated in the anode catalyst layer 56 b passes through the solid electrolyte membrane 52 in a hydrated state, moves through the hydrophilic layer 60 of the cathode catalyst layer 56 b, and travels toward the catalyst metal particles 26. Since the polymer electrolyte 32 constituting the catalyst reverse micelle 40 has the sulfonic acid group facing inward, the outer surface is hydrophobic. Therefore, it is difficult for water to stay in the gas diffusion pores, and oxygen (O ₂ ) supplied via the cathode gas diffusion layer 54 a is smoothly introduced into the catalyst metal particles 26. That is, both proton (H ⁺ ) and oxygen (O ₂ ) can move well to the catalyst metal particles 26. For this reason, the cathode reaction (4 protons (H ⁺ ) + oxygen (O ₂ ) → 2 water (H ₂ O) +4 electrons (e ⁻ )) occurs favorably on the surface of the catalytic metal particles 26.

  As described above, in the cathode catalyst layer 54b formed using the catalyst ink 20 of the embodiment, the hydrophilic layer 60 is provided between the catalyst 22 and the polymer electrolyte 32, so that water and protons necessary for the cell reaction can be obtained. As a result, the drainage of water produced by the fuel cell can be improved, and as a result, the performance of the fuel cell can be improved.

Example 1
The catalyst paste of Example 1 uses a catalyst in which platinum catalyst metal particles are supported at a support density of 40 wt% on a carbon particle support as a catalyst, and 4 g of water is added to 0.5 g of catalyst to rotate / revolve. It was prepared by stirring for 3 minutes with a centrifugal stirrer (Hybrid Mixer HM500 manufactured by Keyence Corporation).
The electrolyte solution of Example 1 uses a polymer electrolyte solution SS900 / 10 (manufactured by Asahi Kasei E-Materials) as a polymer electrolyte, and 20 g of the polymer electrolyte solution SS900 / 10 is subjected to a solvent (ethanol and water) by 85 ° C. water bathing. It was made to evaporate until it became 2g (4g in total of a polymer electrolyte and a solvent), 36g of 1-butanol was added to this, and it stirred for 3 minutes with a rotation / revolution type centrifugal stirrer.
The catalyst ink of Example 1 was prepared by mixing 4.5 g of the catalyst paste of Example 1 and 6 g of the electrolyte solution of Example 1 and stirring for 3 minutes with a rotation / revolution centrifugal stirrer. . The catalyst ink of Example 1 is considered to be an emulsion by the catalyst reverse micelle 40.

(Example 2)
The catalyst ink of Example 2 was prepared by mixing 4.5 g of the catalyst paste 29 of Example 1, 6 g of the electrolyte solution 39 of Example 1 and 2 g of the sample C of the preliminary experiment, and rotating / revolving centrifugal. It was created by stirring for 3 minutes with a stirrer. The catalyst ink of Example 2 is considered to be an emulsion composed of reverse catalyst micelles 40 and reverse micelles 42 of water. In the catalyst layer formed by the catalyst ink of Example 2, it is considered that the widened portion 62 is formed in the hydrophilic layer 60 by the reverse micelle 42 of water as illustrated in FIG.

(Comparative Example 1)
The electrolyte solution of Comparative Example 1 was prepared by diluting the polymer electrolyte solution SS900 / 10 twice with a solvent of ethanol: water = 1: 1 to prepare an electrolyte solution.
The catalyst ink of Comparative Example 1 was prepared by mixing 4.5 g of the catalyst paste of Example 1 and 7.7 g of the electrolyte solution of Comparative Example 1 and stirring for 3 minutes with a rotation / revolution centrifugal stirrer. Created.

(Comparative Example 2)
The catalyst paste of Comparative Example 2 uses a catalyst in which platinum catalyst metal particles are supported at a support density of 40 wt% on a carbon particle support as a catalyst, and 10 g of water is added to 0.5 g of catalyst to rotate / revolve. It was prepared by stirring for 3 minutes with a centrifugal stirrer.
The catalyst ink of Comparative Example 2 was prepared by mixing 10.5 g of the catalyst paste of Comparative Example 2 and 6 g of the electrolyte solution of Example 1 and stirring for 3 minutes with a rotation / revolution centrifugal stirrer. . The catalyst ink of Comparative Example 2 is considered to be a micelle emulsion because of the large amount of water in the prepared catalyst paste.

(Evaluation of Examples 1 and 2)
The cathode 54 and the anode 56 obtained by forming the cathode catalyst layer 54b and the anode catalyst layer 56b using the catalyst ink of Example 1 were thermocompression bonded to the solid electrolyte membrane 52 at 140 ° C. at 40 kgf / cm. The MEA was configured. Similarly, the MEA of Example 2 and the MEAs of Comparative Examples 1 and 2 were also configured. FIG. 8 and FIG. 9 show the relationship (current / voltage performance evaluation results) between the current density [A / cm ² ] and the voltage [V] of the MEA of Example 1 and the MEA of Comparative Example 1. FIG. 8 shows the current voltage performance evaluation results when the temperature is 50 ° C. and the humidity is 100% RH, and FIG. 9 shows the current voltage performance evaluation results when the temperature is 80 ° C. and the humidity is 40% RH. As shown in FIG. 8, it can be seen that the MEA of Example 1 has higher power generation performance at low temperature and high humidity than the MEA of Comparative Example 1. As shown in FIG. 9, it can be seen that the MEA of Example 1 has higher power generation performance at high temperature and low humidity than the MEA of Comparative Example 1. From these facts, it can be seen that the MEA of Example 1 has a wide range of temperature conditions and humidity conditions in which power generation is possible and high performance as compared with the MEA of Comparative Example 1.

  FIG. 10 is an explanatory diagram for explaining a comparison of catalyst layer proton resistance when the MEAs of Examples 1 and 2 and the MEA of Comparative Example 2 are operated at a temperature of 50 ° C. and a humidity of 100% RH. The vertical axis represents the resistance ratio when the catalyst layer proton resistance of the MEA of Example 1 is 1.00. The proton resistance of the catalyst layer was measured using the alternating current impedance method shown in “'Electrochemical Impedance Method” (Maruzen Masayuki Itagaki) 8 Electrochemical Impedance Analysis Using Distributed Constant Transmission Circuit (p133-146) ”. As shown in the figure, it can be seen that the MEAs of Examples 1 and 2 have a lower proton resistance of the catalyst layer than the MEA of Comparative Example 2.

FIG. 11 explains the comparison of performance when the MEAs of Examples 1 and 2 and the MEA of Comparative Example 2 are operated at a constant current density (1.6 [A / cm ² ]) while changing the temperature and humidity. FIG. The vertical axis represents the voltage ratio when the voltage when the temperature of the MEA of Example 1 is 60 ° C. and the humidity is 100% RH is 1.00. In the figure, the left end shows the voltage ratio when the temperature is 60 ° C. and the humidity is 100% RH, the center shows the voltage ratio when the temperature is 90 ° C. and the humidity is 28% RH, and the right end shows the temperature is 95 ° C. The voltage ratio when the humidity is 24% RH is shown. As shown, the MEA of Example 2 is better than the MEA of Example 1 even under conditions of high temperature and low humidity. This is because the effect of forming the catalyst layer using the catalyst ink containing the reverse micelle 42 of water, that is, because the widened portion 62 is generated in the hydrophilic layer 60, the water retainability is maintained even at low humidity. It is thought that the effect is due to the high. In addition, it can be seen that the MEA of Example 1 is also good under conditions of high temperature and low humidity as compared with the MEA of Comparative Example 2.

(Example 3)
The catalyst paste of Example 3 uses a catalyst in which carbon catalyst particles 24 are supported on a carbon particle support 24 at a support density of 50 wt% as a catalyst, and 2.57 g of water 28 is added to 0.5 g of the catalyst. It was prepared by stirring for 3 minutes with a rotation / revolution centrifugal stirrer.
The catalyst ink of Example 3 was prepared by mixing 3.07 g of the catalyst paste of Example 3 and 3.75 g of the electrolyte solution of Example 1 and stirring for 3 minutes with a rotating / revolving centrifugal stirrer. Created. The hydrophobic solvent ratio of the catalyst ink of Example 3 is 0.55.

Example 4
The catalyst paste of Example 4 was prepared by adding 3.19 g of water to 0.5 g of the catalyst of Example 3 and stirring for 3 minutes with a rotation / revolution centrifugal stirrer.
The catalyst ink of Example 4 was prepared by mixing 3.69 g of the catalyst paste of Example 4 and 3.75 g of the electrolyte solution of Example 1 and stirring for 3 minutes with a rotation / revolution centrifugal stirrer. Created. The hydrophobic solvent ratio of the catalyst ink of Example 4 is 0.50.

(Example 5)
The catalyst paste of Example 5 was prepared by adding 2.16 g of water to 0.5 g of the catalyst of Example 3 and stirring for 3 minutes with a rotation / revolution centrifugal stirrer.
The catalyst ink of Example 5 was prepared by mixing 2.66 g of the catalyst paste of Example 5 and 3.75 g of the electrolyte solution of Example 1 and stirring for 3 minutes with a rotating / revolving centrifugal stirrer. Created. The hydrophobic solvent ratio of the catalyst ink of Example 5 is 0.59.

(Example 6)
The catalyst paste of Example 6 was prepared by adding 2.42 g of water to 0.5 g of the catalyst of Example 3 and stirring for 3 minutes with a rotation / revolution centrifugal stirrer.
The electrolyte solution of Example 6 was obtained by evaporating 20 g of the polymer electrolyte solution SS900 / 10 in a hot water bath at 85 ° C. until the solvent (ethanol and water) became 8 g (10 g in total of the polymer electrolyte and the solvent). 36 g of 1-butanol was added, and the mixture was stirred for 3 minutes with a rotation / revolution centrifugal stirrer.
The catalyst ink of Example 6 was prepared by mixing 2.42 g of the catalyst paste of Example 6 and 3.75 g of the electrolyte solution of Example 6 and stirring for 3 minutes with a rotation / revolution centrifugal stirrer. Created. The hydrophobic solvent ratio of the catalyst ink of Example 6 is 0.47.

(Evaluation of Examples 3-6)
Similar to the MEA of Example 1, the MEAs of Examples 3 to 6 were configured, and the MEA of Examples 3 to 6 was at a temperature of 60 ° C. and a humidity of 62% RH, and at a temperature of 90 ° C. and a humidity. Was evaluated under the condition of 18% RH. FIG. 12 illustrates performance (voltage) with respect to a constant current density (1.6 [A / cm ² ]) when the MEAs of Examples 3 to 6 are operated under the conditions of a temperature of 60 ° C. and a humidity of 62% RH. FIG. 13 is a graph illustrating a constant current density (1.6 [A / cm ² ]) when the MEAs of Examples 3 to 6 are operated at a temperature of 90 ° C. and a humidity of 18% RH. It is explanatory drawing explaining performance (voltage). As shown in the figure, it can be seen that when the hydrophobic solvent ratio is 0.55 to 0.59, it has high performance even at high temperature and low humidity.

  According to the catalyst ink 20 of the embodiment described above, the emulsion of the reverse micelle structure 40 and reverse water micelle 42 of reverse micelle structure is formed. Therefore, the solvent is simply dried by coating or printing on the diffusion layer. A catalyst layer in which the hydrophilic layer 60 is formed between the polymer electrolyte 32 and the catalyst 22 can be easily formed. If a fuel cell is constructed using this catalyst layer, the water and protons necessary for the cell reaction can be transferred better by the hydrophilic layer of the catalyst layer, and the drainage of the water generated by the fuel cell can be reduced. Can be improved. Further, since the polymer electrolyte 32 facing the pores of the catalyst layer is formed with a main chain skeleton having high water repellency, water retention is unlikely to occur and gas diffusion is not easily inhibited. As a result, the performance of the fuel cell can be improved.

  According to the method for producing the catalyst ink 20 of the embodiment, the electrolyte solution 39 in which the polymer electrolyte 32 is dissolved in the hydrophobic solvent 38 and the catalyst paste 29 in which the catalyst 22 is mixed with water 28 to form a paste are obtained. When mixed, the hydrophobic solvent ratio is adjusted to 0.45 to 0.60, and the mixed electrolyte solution 39 and the catalyst paste 29 are mixed and sufficiently stirred, so that the catalyst reverse micelle 40 or A catalyst ink 20 that is an emulsion of water reverse micelles 42 can be produced.

  As mentioned above, although the form for implementing this invention was demonstrated, this invention is not limited to such embodiment at all, and it can implement with a various form in the range which does not deviate from the summary of this invention. Of course.

  The present invention is applicable to the manufacturing industry of catalyst layers for fuel cells.

  20 catalyst ink, 22 catalyst, 24 carrier, 26 catalyst metal particles, 28 water, 29 catalyst paste, 32 polymer electrolyte, 34 sulfonic acid group, 38 hydrophobic solvent, electrolyte solution 39, 40 catalyst reverse micelle, 42 reverse of water Micelle, 50 MEA (membrane / electrode assembly), 52 solid polymer membrane, 54 cathode, 54a cathode gas diffusion layer, 54b cathode catalyst layer, 56 anode, 56a anode gas diffusion layer, 56b anode catalyst layer, 60 hydrophilic layer, 62 Widening part.

Claims (4)

A catalyst ink mainly composed of a polymer electrolyte having a hydrophilic group in a side chain, a hydrophobic solvent, a catalyst, and water, and used for producing a catalyst layer of a fuel cell,
The hydrophobic solvent is a solvent that clearly phase-separates upon mixing with water,
The polymer electrolyte is present at the interface between the hydrophilic phase and the hydrophobic phase,
An emulsion of catalyst reverse micelles having a reverse micelle structure by wrapping the mixture of the catalyst and water as a nucleus with the polymer electrolyte with the hydrophilic group facing inward,
A catalyst ink characterized by that. The catalyst ink according to claim 1,
An emulsion of reverse micelles of water and the reverse micelles of the catalyst, which has a reverse micelle structure in which water is encapsulated by the polymer electrolyte with the hydrophilic group facing inward,
A catalyst ink characterized by that. The catalyst ink according to claim 1 or 2,
The hydrophobic solvent is 1-butanol;
The catalyst ink characterized by the above-mentioned. A method for producing a catalyst layer of a fuel cell, comprising:
The catalyst ink according to any one of claims 1 to 3 is applied or printed on a gas diffusion layer having conductivity and gas permeability, and the solvent is dried to form a catalyst layer. ,
A method for producing a catalyst layer, wherein:

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