JP2011159624A - Device for manufacturing catalyst layer of fuel cell, method for manufacturing catalyst layer of fuel cell, polymer electrolytic solution, and method for manufacturing polymer electrolytic solution - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a catalyst layer which smoothly advances electrochemical reaction of a fuel cell, a polymer electrolytic solution, and a method for manufacturing a polymer electrolytic solution. <P>SOLUTION: A cathode catalyst layer and an anode catalyst layer are formed with a catalyst paste 42. In manufacturing of the catalyst paste 42, concentration of water in the DE2020 is set up to be 5% by heating 10 g of the DE2020 (product made from Du pont) as a pre-solution in a water bath in a water removing process. Then, 32 g of isopropyl alcohol is mixed, and polymer electrolytic solution 41 can be achieved by churning with a spinning and revolution type centrifugal stirrer 35. Finally, the catalyst paste 42 is achieved by mixing the polymer electrolytic solution 41 and a pre-paste 40 in a churning process. The cathode catalyst layer and the anode catalyst layer which are catalyst layers of a fuel cell are manufactured by applying the catalyst paste 42 to a base material. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a fuel cell catalyst layer manufacturing apparatus, a fuel cell catalyst layer manufacturing method, a polymer electrolyte solution, and a polymer electrolyte solution manufacturing method.

  Conventionally, a fuel cell system using a membrane electrode assembly (MEA) 90 as shown in Patent Document 1 is known. As shown in FIG. 4, the MEA 90 is joined to an electrolyte membrane 91 made of a solid polymer membrane such as Nafion (registered trademark, Nafion (manufactured by DuPont)) and one surface of the electrolyte membrane 91 to supply air. Cathode electrode 93 and an anode electrode 92 joined to the other surface of the electrolyte membrane 91 and supplied with fuel such as hydrogen.

  The cathode electrode 93 includes a gas permeable base material 93b such as carbon cloth, carbon paper, or carbon felt, and a cathode catalyst layer 93a formed on one surface of the base material 93b. The portion other than the cathode catalyst layer 93a in the cathode electrode 93 is a base material 93b, which is a cathode diffusion layer that diffuses air to the cathode catalyst layer 93a on the non-electrolyte side.

  The anode 92 also includes the base material 92b as described above and an anode catalyst layer 92a formed on one surface of the base material. The portion other than the anode catalyst layer 92a in the anode electrode 92 is also a base material 92b, which is an anode diffusion layer that diffuses fuel into the anode catalyst layer 92a on the non-electrolyte side.

  As shown in FIG. 5, the cathode catalyst layer 93 a and the anode catalyst layer 92 a are composed of a myriad of catalysts 81 in which catalyst metal fine particles 81 b such as platinum (Pt) are supported on a carrier 81 a made of carbon black, and each catalyst 81. And a polymer electrolyte 82 bonded to a base material (not shown). As the polymer electrolyte 82, the same one as the electrolyte membrane 91 is used.

  The MEA 90 is sandwiched between unillustrated separators to form a fuel cell, which is the minimum power generation unit, and a number of these cells are stacked to form a fuel cell stack. Air is supplied to the cathode catalyst layer 93a by air supply means, and hydrogen or the like is supplied to the anode catalyst layer 92a by hydrogen supply means or the like. Thus, the fuel cell system is configured.

In the MEA 90, hydrogen ions (H ⁺ ; protons) and electrons are generated from the fuel by an electrochemical reaction in the anode catalyst layer 92a. Protons move in the electrolyte membrane 91 toward the cathode catalyst layer 93a in the form of H ₃ O ⁺ accompanied by water molecules. The electrons flow through the load connected to the fuel cell system and flow into the cathode catalyst layer 93a. On the other hand, in the cathode catalyst layer 93a, water is generated from oxygen, protons and electrons contained in the air. The fuel cell system can continuously generate an electromotive force by continuously performing such an electrochemical reaction.

JP 2009-104905 A

  However, the above-described conventional MEA 90 has a reduced performance due to drying of the polymer electrolyte in the electrolyte membrane and each catalyst layer in the low humidified state, and in the excessively humidified state, the performance deterioration caused by gas supply inhibition (flooding) due to water retention. Arise. For this reason, in the fuel cell provided with this MEA 90, there is a problem that the power generation capacity is lowered under each of the above environments.

  The present invention has been made in view of the above-described conventional situation, and an object to be solved is to obtain a fuel cell catalyst layer that allows an electrochemical reaction to proceed smoothly. Moreover, it is set as the problem which should be solved to provide a polymer electrolyte solution and the manufacturing method of this polymer electrolyte solution.

The fuel cell catalyst layer production apparatus of the present invention is a fuel cell catalyst layer production apparatus that forms a catalyst layer with a catalyst paste.
Water removing means for reducing the concentration of water in the pre-solution in which the polymer electrolyte having a side chain having a hydrophilic functional group is dissolved in a solvent to a predetermined value or less, and obtaining a polymer electrolyte solution;
A pre-paste obtained by mixing a catalyst and the water and a stirring means for mixing the polymer electrolyte solution to obtain the catalyst paste are provided (claim 1).

  According to the inventor's knowledge, in the cathode catalyst layer 93a and the anode catalyst layer 92a, a hydrophilic layer formed by a hydrophilic functional group at the end of the side chain 101 of the polymer electrolyte 82 is provided between the catalyst 81 and the polymer electrolyte 82 layer. It is speculated that the formation of 83 facilitates the movement of protons and entrained water, and the reverse diffusion and discharge of produced water. In the catalyst layer in which the hydrophilic layer 83 is aligned in one direction and is formed without any spots in a continuous state, the generated water generated in the cathode electrode 93 is held in the hydrophilic layer 83 even in a low humidified state, and the anode electrode 92 is retained. Can be despread. Therefore, it is possible to prevent the electrolyte membrane 11 and the polymer electrolyte 82 of each catalyst layer from being dried and maintain high performance. Further, even in an excessively humidified state, the generated water can be similarly discharged through the hydrophilic layer 83 to prevent performance degradation.

Therefore, the inventor has found the following knowledge by paying attention to the solid content of the polymer electrolyte 82 in the polymer electrolyte solution so that the hydrophilic layer 83 is formed without unevenness. That is, as shown in FIGS. 8A and 8B, the solid content of the polymer electrolyte 82 has a hydrophobic main chain 100 and a side chain 101 having a hydrophilic functional group. The hydrophilic functional group is composed of, for example, a sulfone group (SO ₃ ⁻ ). Then, by mixing the paste (pre-paste) in which the catalyst 81 and water are mixed with the polymer electrolyte solution, the hydrophilic functional groups are attracted to the water adsorbed on the catalyst 81, and the cathode catalyst layer 93a and the anode catalyst layer 92a. A hydrophilic layer 83 is formed.

  When the inventor reduces the concentration of water in the polymer electrolyte solution, the viscosity of the polymer electrolyte solution increases even when the solid concentration of the polymer electrolyte 82 in the polymer electrolyte solution is the same. It has been found that the viscosity of the polymer electrolyte solution decreases when the water concentration is increased. Accordingly, when the concentration of water in the polymer electrolyte solution is high, the inventor adsorbs water on the side chain 101 of the polymer electrolyte 82, and as shown in FIG. It was inferred that the solid content of the molecular electrolyte 82 was agglomerated and the viscosity of the polymer electrolyte solution was lowered. Further, when the water concentration of the polymer electrolyte solution becomes slightly low, the polymer electrolyte in the polymer electrolyte solution is caused by the action of the organic solvent contained in the polymer electrolyte solution, as shown in FIG. It was estimated that the solid content of 82 was released and the viscosity of the polymer electrolyte solution increased.

  When, for example, the cathode catalyst layer 93a is manufactured by mixing the polymer electrolyte solution containing the solid content of the polymer electrolyte 82 in which aggregation has progressed, the cathode catalyst layer 93a is in the state shown in FIG. it is conceivable that. That is, in this cathode catalyst layer 93a, since the solid content of the polymer electrolyte 82 is aggregated, the side chain 101 extends in multiple directions. Then, the side chains 101 and the water in the cathode catalyst layer 93a are adsorbed, whereby the hydrophilic layer 83 is dispersed and formed in the cathode catalyst layer 93a. For this reason, in the cathode catalyst layer 93a, protons and water hardly move in the cathode catalyst layer 93a due to the ionic resistance in the cathode catalyst layer 93a at the location where the solid content of the polymer electrolyte 82 is aggregated. For this reason, in the low humidification state, the performance degradation due to drying of the electrolyte membrane 11 and the polymer electrolyte 82 in each catalyst layer is caused. In the excessive humidification state, the performance degradation due to flooding is caused.

  The inventor has intensively studied to solve the above problems, and has invented the battery catalyst layer production apparatus of the present invention. That is, in the polymer electrolyte solution obtained by the water removing means provided in the manufacturing apparatus, the concentration of water is not more than a predetermined value, so that the viscosity is high and the polymer electrolyte 82 of the polymer electrolyte 82 is contained in the polymer electrolyte solution. The side chain 101 is difficult to adsorb with water. Therefore, it is considered that the polymer electrolyte solution is in a state as shown in FIG. 1, that is, in a state where the solid content of the polymer electrolyte 82 is released in the polymer electrolyte solution. For this reason, in the catalyst paste obtained by mixing with the pre-paste by the stirring means, that is, the catalyst layer for the fuel cell, the hydrophilic functional group of the polymer electrolyte 82, that is, the sulfone group is adsorbed with water in the pre-paste. It becomes. For this reason, as shown in FIG. 6, in this fuel cell catalyst layer, a hydrophilic layer 83 of the polymer electrolyte 82 is formed in a state of being oriented on the surface of the catalyst 81. Then, as described above, the sulfone group is adsorbed with the water in the pre-paste, so that in the fuel cell catalyst layer, as shown in FIG. It is considered that the hydrophilic functional group of the side chain 101 of the electrolyte 82 is oriented to the catalyst 81 side (PFF structure). For this reason, in the fuel cell catalyst layer obtained by this production apparatus, as shown in FIG. 5, protons and water easily move, and the electrochemical reaction proceeds smoothly. For this reason, in the MEA 90 having this fuel cell catalyst layer, it is possible to increase the power generation capacity in both the low humidification state and the excessive humidification state.

  Therefore, according to the fuel cell catalyst layer manufacturing apparatus of the present invention, it is possible to obtain a fuel cell catalyst layer in which an electrochemical reaction is smoothly performed.

  In the apparatus for producing a fuel cell catalyst layer according to the present invention, the water removing means is preferably a hot water bath (claim 2). In this case, the concentration of water in the pre-solution can be easily reduced to a predetermined value or less, and a polymer electrolyte solution can be easily obtained.

  The polymer electrolyte solution of the present invention is characterized in that a polymer electrolyte having a side chain having a hydrophilic functional group is dissolved in a solvent, and the concentration of water is 10% or less (claim 3).

  Since the concentration of water is as low as 10% or less, the polymer electrolyte solution of the present invention has a state as shown in FIG. 1, that is, a state in which the solid content of the polymer electrolyte 82 is released in the polymer electrolyte solution. It is thought that it has become. The main chain 100 extends in one direction in the polymer electrolyte 82 in a state of being unraveled in this way. Therefore, in the fuel cell catalyst layer mixed with the polymer electrolyte solution, the hydrophilic functional group and water are adsorbed in one direction, and the hydrophilic layer 83 is aligned in one direction in the fuel cell catalyst layer, and It is considered to be a continuous state. For this reason, in such a fuel cell catalyst layer, protons and water easily move, and the electrochemical reaction proceeds smoothly.

  Therefore, the polymer electrolyte solution of the present invention is suitable as a polymer electrolyte solution constituting the fuel cell catalyst layer.

  According to the inventor's test results, the polymer electrolyte solution preferably has a water concentration of 5% or less (claim 4). In this case, since the concentration of water in the polymer electrolyte solution becomes lower, the polymer electrolyte 82 in the polymer electrolyte solution becomes more undissolved and tends to be in the state shown in FIG.

  The solvent preferably contains at least one of a secondary alcohol and a tertiary alcohol (Claim 5). According to the inventor's test, if the solvent contains a primary alcohol such as methanol or ethanol, the viscosity of the polymer electrolyte solution does not increase even if the water concentration is reduced. If the solvent included a secondary alcohol such as isopropyl alcohol (IPA) or a tertiary alcohol such as tertiary butyl alcohol (TBA), the solid content of the polymer electrolyte 82 in the polymer electrolyte solution was further solved. It becomes a state. Further, according to the inventors' test, when the solvent includes secondary alcohol and tertiary alcohol, the solid content of the polymer electrolyte 82 in the polymer electrolyte solution is further unraveled.

The method for producing a polymer electrolyte solution of the present invention comprises a pre-solution preparation step of preparing a pre-solution in which a polymer electrolyte having a side chain having a hydrophilic functional group is dissolved in a solvent;
It comprises a solution preparation step in which at least water is reduced to a concentration of 10% or less from the pre-solution to obtain a polymer electrolyte solution (claim 6).

  According to the method for producing a polymer electrolyte solution of the present invention, a polymer electrolyte solution having the above characteristics can be produced stably.

The method for producing a catalyst layer for a fuel cell according to the present invention is a method for producing a catalyst layer for a fuel cell in which the catalyst layer is formed with a catalyst paste.
A water removal step of reducing the concentration of water in the pre-solution in which the polymer electrolyte having a side chain having a hydrophilic functional group is dissolved in a solvent to 10% or less to obtain a polymer electrolyte solution;
A pre-paste preparation step of mixing the catalyst and the water to produce a pre-paste;
And a stirring step of mixing the polymer electrolyte solution with the pre-paste to obtain a catalyst paste (Claim 7).

  According to the production method of the present invention, the concentration of water in the polymer electrolyte solution is 10% or less in the water removal step. For this reason, this polymer electrolyte solution has the characteristics as described above. For this reason, the catalyst layer for fuel cells formed by the catalyst paste obtained through the stirring step has the above characteristics.

  Therefore, according to the method for producing a fuel cell catalyst layer of the present invention, it is possible to obtain a fuel cell catalyst layer in which an electrochemical reaction is smoothly performed.

It is a schematic diagram which shows the state of the solid content of the polymer electrolyte in the polymer electrolyte solution with a low water concentration. 6 is a schematic diagram showing a process for producing a polymer electrolyte solution of Experimental Example 1. FIG. It is a schematic diagram which shows the manufacturing process of the catalyst paste in an Example. It is a model structure figure which shows MEA of the past and the Example. It is a model expanded sectional view of MEA of the former and an example. It is a model expanded sectional view of VI part in MEA of an Example. It is a graph which shows the change of the voltage of a cell and current density in example 2 of an experiment. It is a schematic diagram which shows the state of the solid content of the polymer electrolyte in the conventional polymer electrolyte solution. It is a model expanded sectional view which shows the conventional cathode catalyst layer.

  Hereinafter, examples and experimental examples 1 and 2 embodying the present invention will be described with reference to the drawings.

(Experimental example 1)
In manufacturing the MEA 90 having the cathode catalyst layer 93a and the anode catalyst layer 92a of the embodiment shown in FIG. 4 and the catalyst layers 93a and 92a, first, the following experiment was performed. In Experimental Example 1, six types of polymer electrolyte solutions having different configurations and manufacturing processes were prepared, and the viscosity of each polymer electrolyte solution was measured. In addition, all the polymer electrolyte solutions used in Examples and Experimental Examples 1 are ionomer solutions.

(Production of sample A)
In producing the polymer electrolyte solution of Sample A, first, DE2020 (manufactured by DuPont) was prepared as a pre-solution. Then, 10 g of DE2020 was placed in a container and boiled at 85 ° C. as shown in FIG. 2A to evaporate water and normal propyl alcohol (NPA), which are solvents in DE2020. With this hot water bath, the content of water and NPA in DE2020 was reduced to 2 g. Thereby, the content of water and NPA in DE 2020 is equivalent to 5% in terms of the concentration in the polymer electrolyte solution of sample A.

  Next, 6.8 g of water was mixed with DE 2020 after the hot water bath (see FIG. 2B), and stirred for 3 minutes by the rotation / revolution centrifugal stirrer 35 (see FIG. 2C). . Note that “Hybrid Mixer HM-500” manufactured by Keyence Corporation was adopted as the rotation / revolution centrifugal stirrer 35.

  Next, as shown in FIG. 2D, 7.2 g of NPA was mixed with the mixture of DE2020 and water. Then, it stirred with the autorotation / revolution type centrifugal stirrer 35 (refer (E) of FIG. 2). As shown in FIG. 2F, 20 g of IPA as an organic solvent was mixed with the mixture of DE2020 thus obtained and water and NPA. And it stirred with the autorotation / revolution type | formula centrifugal stirrer 35 (refer (G) of FIG. 2), and obtained the polymer electrolyte solution of the sample A (refer (H) of FIG. 2).

(Production of sample B)
In the production of the polyelectrolyte solution of sample B, 10 g of DE2020 was boiled at 85 ° C. as in the production of the polyelectrolyte solution of sample A, and the content of water and NPA in DE2020 was 2 g. Reduced to. Thereby, the content of water and NPA in DE2020 is equivalent to 5% in terms of the concentration in the polymer electrolyte solution of sample B.

  Next, 20 g of IPA was mixed with DE 2020 after the hot water bath, and the mixture was stirred for 3 minutes by the rotation / revolution centrifugal stirrer 35. To this mixture of DE2020 and IPA, 7.2 g of NPA was mixed and stirred by a rotation / revolution centrifugal stirrer 35. 6.8 g of water was mixed with the mixture of DE2020, IPA and NPA thus obtained. And it stirred with the autorotation / revolution type centrifugal stirrer 35, and the polymer electrolyte solution of the sample B was obtained.

(Production of sample C)
In the production of the polymer electrolyte solution of Sample C, 10 g of DE2020 was mixed with 20 g of IPA, and the mixture was stirred for 3 minutes by the rotation / revolution centrifugal stirrer 35. Thereafter, 4.7 g of NPA was mixed with the mixture of DE2020 and IPA, and the mixture was stirred by a rotating / revolving centrifugal stirrer 35. 5.3 g of water was mixed with the mixture of DE2020, IPA and NPA thus obtained. And it stirred with the autorotation / revolution type centrifugal stirrer 35, and the polymer electrolyte solution of the sample C was obtained. In the production of the polymer electrolyte solution of sample C, since no hot water bathing is performed, the content of water in DE2020 is an amount equivalent to about 9% in terms of the concentration in the polymer electrolyte solution of sample C. Become. In addition, the content of NPA in DE2020 is equivalent to about 11% in terms of the concentration in the polymer electrolyte solution of Sample C.

(Production of sample D)
Also in the production of the polymer electrolyte solution of Sample D, 10 g of DE2020 was boiled at 85 ° C., and the contents of water and NPA in DE2020 were both reduced to 2 g. Thereby, the content of water and NPA in DE2020 is equivalent to 5% in terms of the concentration in the polymer electrolyte solution of sample D. Next, 34 g of NPA was mixed with this DE2020, and stirred for 3 minutes by a rotation / revolution centrifugal stirrer 35. In this way, a polymer electrolyte solution of Sample D was obtained.

(Manufacture of sample E)
Also in the production of the polymer electrolyte solution of Sample E, 10 g of DE2020 was boiled at 85 ° C., and the contents of water and NPA in DE2020 were both reduced to 2 g. Thereby, the content of water and NPA in DE2020 is an amount corresponding to 5% in terms of the concentration in the polymer electrolyte solution of sample E. Next, 34 g of IPA was mixed with DE2020, and the mixture was stirred for 3 minutes by a rotation / revolution centrifugal stirrer 35. In this way, a polymer electrolyte solution of Sample E was obtained.

(Manufacture of sample F)
Also in the production of the polymer electrolyte solution of Sample F, 10 g of DE2020 was boiled at 85 ° C., and the contents of water and NPA in DE2020 were both reduced to 2 g. Thereby, the content of water and NPA in DE2020 is an amount corresponding to 5% in terms of the concentration in the polymer electrolyte solution of sample E. Next, 34 g of IPA: TBA = 1: 1 solution was mixed with this DE2020, and the mixture was stirred for 3 minutes by the rotation / revolution centrifugal stirrer 35. Thus, a polymer electrolyte solution of Sample F was obtained.

About the polymer electrolyte solution of each of these samples A to F, the viscosity at 20 ° C. was measured. The measurement results are shown in Table 1. In Table 1, the viscosity ratio of each of the samples B to F with respect to the sample A is represented on the basis of the viscosity of the sample A. In Table 1, the solid content of the polymer electrolyte, the composition ratio of IPA, NPA, H ₂ O, and TBA in the polymer electrolyte solution of each sample A to F, and the order of addition of the solvent are also described. Yes.

  As shown in Table 1, the polymer electrolyte solutions of Samples A to C had different viscosities despite the same composition ratio. Thus, it was found that the order of the solvent mixed with DE2020 is related to the change in viscosity. More specifically, a comparison between the polymer electrolyte solution of sample A and the polymer electrolyte solutions of samples B and C revealed that the viscosity is lowered by first mixing water with DE2020. Further, by comparing the polymer electrolyte solution of sample B and the polymer electrolyte solution of sample C, before the IPA is mixed, that is, as the proportion of water and NPA in the pre-solution DE2020 is larger, the polymer electrolyte solution It became clear that the viscosity decreased.

  Furthermore, from the measurement results of the polymer electrolyte solution of sample D, it was found that when only NPA was mixed with DE2020, the viscosity decreased. On the other hand, from the measurement results of the polymer electrolyte solutions of Sample E and Sample F, it has been found that the viscosity increases when IPA is mixed with DE2020 and when IPA and TBA are mixed. Since the ratio of water in the polymer electrolyte solution, that is, the lower the water concentration, the higher the viscosity, the polymer electrolyte 82 in the polymer electrolyte solutions of Sample E and Sample F has a main structure as shown in FIG. It is considered that the chain 100 and the side chain 101 are in a disconnected state. That is, IPA, IPA, and TBA have an effect of solving the solid content of the polymer electrolyte 82 in the polymer electrolyte solution, and conversely, water and NPA are used for the polymer electrolyte 82 in the polymer electrolyte solution. It can be inferred that it has the effect of aggregating solids. It can be assumed that NPA has a high effect of aggregating the solid content of the polymer electrolyte 82 in the polymer electrolyte solution.

  Thus, primary alcohols such as NPA and ethanol and water have the effect of aggregating the polymer electrolyte, and secondary alcohols such as IPA and tertiary alcohols such as TBA are effective for polymer electrolytes. It can be inferred that there is an effect to understand. The effects of the secondary alcohol and the tertiary alcohol are considered to be derived from the dielectric constant, and it can be inferred that a solvent having a dielectric constant of 20 or less has a high effect of deaggregating the polymer electrolyte.

(Example)
<Manufacture of cathode catalyst layer 93a and anode catalyst layer 92a>
Based on the above experimental results, the MEA 90 of the example shown in FIG. 4 was manufactured. As described above, the cathode electrode 93 of the MEA 90 includes the cathode catalyst layer 93a as a fuel cell catalyst layer and the cathode diffusion layer 93b formed of a gas diffusion layer base material.

  First, the catalyst paste 42 constituting the cathode catalyst layer 93a is manufactured. In the production of the catalyst paste 42, first, a catalyst 81 in which Pt fine particles as catalyst metal fine particles 82 were supported at a support density of 50 wt% on a carbon support 81a was prepared. Then, the catalyst 81 and water were mixed in an amount of 5 g with respect to 1 g of the catalyst 81, and stirred by the hybrid mixer 35 to obtain a pre-paste 40 (see FIG. 3A).

  Next, a polymer electrolyte solution 41 to be mixed with the pre-paste 40 was prepared. The configuration of the polymer electrolyte solution 41 is the same as that of the polymer electrolyte solution manufactured as Sample E in Experimental Example 1 described above. That is, the concentration of water in this polymer electrolyte solution 41 is 5%. In addition, the hot water bath performed in obtaining this polymer electrolyte solution 41, that is, the hot water bath in the production of the polymer electrolyte solution of sample E is the water removing means in the fuel cell catalyst layer manufacturing apparatus of the present invention and the present invention. This corresponds to the water removal step in the method for producing a fuel cell catalyst layer.

  Then, 10 g of the polymer electrolyte solution 41 was mixed with the pre-paste 40 and stirred by the hybrid mixer 35 as shown in FIG. Thus, the catalyst paste 42 was manufactured (see FIG. 3C). The hybrid mixer 35 corresponds to the stirring means in the fuel cell catalyst layer production apparatus of the present invention. Further, the stirring by the hybrid mixer 35 corresponds to the stirring step in the method for manufacturing the fuel cell catalyst layer of the present invention.

  The catalyst paste 42 was applied to the base material 93b to form the cathode catalyst layer 93a. The base material 93b is obtained by laminating carbon black subjected to water repellent treatment with PTFE and a carbon cloth as a base material having electron conductivity. The base material 93b may be employed by providing a water repellent layer made of a mixture of carbon black and PTFE on carbon paper or the like. Further, as a method of applying the catalyst paste 41 to the base material 93b, means such as screen printing, a spray method, an ink jet method and the like can be employed.

  A cathode electrode 93 is obtained by drying the cathode catalyst layer 93a on the base material 93b. The anode catalyst layer 92a and the anode electrode 92 are also obtained by the same process.

<Manufacture of MEA90>
Then, the anode electrode 92, the electrolyte membrane (Nafion membrane: NR211) 91, and the cathode electrode 93 were laminated in this order, and bonded by hot pressing at 140 ° C. and an applied pressure of 40 kgf / cm ² . In this way, MEA90 was manufactured.

  In this MEA 90, in the production of the catalyst paste 42 constituting the cathode catalyst layer 93a and the anode catalyst layer 92a, the polymer electrolyte solution 41 having a water concentration of 5% in the polymer electrolyte solution 41 and the pre-paste 40 are mixed. ing. As shown in FIG. 3A, in the polymer electrolyte solution 41, it is considered that the solid content of the polymer electrolyte 82 has been released. Further, it is considered that the main chain 100 extends in one direction in the solid content of the polymer electrolyte 82 in such a state of being unraveled. For this reason, as shown to (C) of FIG. 3, a sulfone group will adsorb | suck with the water in the pre paste 40. FIG. Therefore, in the cathode catalyst layer 93a and the anode catalyst layer 92a obtained by this catalyst paste 42, a layer of the polymer electrolyte 82 is formed in a state of being oriented on the surface of the catalyst 81 as shown in FIG. As the sulfone group adsorbs with the water in the pre-paste 40 as described above, a hydrophilic layer 83 is formed on the catalyst 81 in the cathode catalyst layer 93a and the anode catalyst layer 92a as shown in FIG. Thus, it is considered that the hydrophilic functional group of the side chain 101 of the polymer electrolyte 82 is oriented to the catalyst 81 side (PFF structure). For this reason, in the cathode catalyst layer 93a and the anode catalyst layer 92a obtained by this manufacturing method, protons and water easily move as shown in FIG. 5, and the electrochemical reaction proceeds smoothly. For this reason, in the MEA 90 having the cathode catalyst layer 93a and the anode catalyst layer 92a obtained as described above, it is possible to increase the power generation capacity in either the low humidification state or the excessive humidification state.

  Therefore, according to the manufacturing method of this embodiment, it is possible to obtain the cathode catalyst layer 93a and the anode catalyst layer 92a in which the electrochemical reaction is smoothly performed. As a result, the MEA 90 in which the electrochemical reaction is smoothly performed. It is possible to obtain

(Experimental example 2)
Next, in order to grasp the voltage characteristics of the MEA 90 obtained in the example, verification by experiments was performed on a cell including the MEA 90 and a cell including the MEA of Comparative Examples 1 and 2 shown below. The configuration and manufacturing method of the cell are the same as the known configuration and method.

(Comparative Example 1)
The MEA of Comparative Example 1 is composed of the cathode catalyst layer and the anode by the catalyst paste obtained by mixing the pre-paste 40 and the polymer electrolyte solution of Sample A in the above Experimental Example 1 (water concentration is 22%). A catalyst layer is formed. Other configurations and manufacturing methods are the same as those in the example.

(Comparative Example 2)
The MEA of Comparative Example 2 is composed of the cathode catalyst layer and the anode by the catalyst paste obtained by mixing the pre-paste 40 and the polymer electrolyte solution of Sample B in the above Experimental Example 1 (water concentration is 22%). A catalyst layer is formed. Other configurations and manufacturing methods are the same as those in the example.

  In this Experimental Example 2, the cell temperature of each of the cell equipped with the MEA 1 and the cell equipped with the MEA of Comparative Examples 1 and 2 was set to 50 ° C., and hydrogen was supplied to the anode electrode 92 in a measurement environment where the humidity was 100%. The change in the current and voltage of each cell when air was passed through the cathode electrode 93 was measured. The measurement results are shown in FIG.

In FIG. 7, the horizontal axis represents the cell current density (A / cm ² ), and the vertical axis represents the cell voltage (V). As shown in FIG. 7, the decrease in current density when the voltage decreases is the smallest in the cell including the MEA 90 of the example. That is, it can be said that the MEA 90 of the example has the highest power generation capacity.

  As a result of this experiment, it was found that the higher the viscosity of the polymer electrolyte solution, the higher the power generation capacity of the MEA, that is, the smoother the electrochemical reaction. Further, according to the comparison between Comparative Example 1 and Comparative Example 2, even when the concentration of water in the polymer electrolyte solution is the same, the power generation capacity of the MEA tends to increase as the viscosity of the polymer electrolyte solution increases. There was found. That is, it became clear that the power generation capability of the MEA changes depending on the mixing order of the solvents mixed in the polymer electrolyte solution.

  While the present invention has been described with reference to the embodiments, it is needless to say that the present invention is not limited to the above-described embodiments and can be appropriately modified and applied without departing from the spirit thereof.

  The present invention can be used for a moving power source for an electric vehicle or the like, or a stationary power source.

42 ... Catalyst paste 92a, 93a ... Catalyst layer (92a ... Anode catalyst layer, 93a ... Cathode catalyst layer)
DESCRIPTION OF SYMBOLS 101 ... Side chain 82 ... Polymer electrolyte 41 ... Polymer electrolyte solution 81 ... Catalyst 40 ... Pre paste

Claims (7)

In a fuel cell catalyst layer manufacturing apparatus for forming a catalyst layer with a catalyst paste,
Water removing means for reducing the concentration of water in the pre-solution in which the polymer electrolyte having a side chain having a hydrophilic functional group is dissolved in a solvent to a predetermined value or less, and obtaining a polymer electrolyte solution;
A catalyst layer for a fuel cell, comprising: a pre-paste obtained by mixing a catalyst and water; and a stirring means for mixing the polymer electrolyte solution to obtain the catalyst paste. Manufacturing equipment.   The apparatus for producing a catalyst layer for a fuel cell according to claim 1, wherein the water removing means is a hot water bath.   A polymer electrolyte solution, wherein a polymer electrolyte having a side chain having a hydrophilic functional group is dissolved in a solvent, and the concentration of water is 10% or less.   The polymer electrolyte solution according to claim 3, wherein the concentration of water is 5% or less.   The polymer electrolyte solution according to claim 3 or 4, wherein the solvent contains at least one of a secondary alcohol and a tertiary alcohol. A pre-solution preparation step of preparing a pre-solution in which a polymer electrolyte having a side chain having a hydrophilic functional group is dissolved in a solvent;
A method for producing a polymer electrolyte solution, comprising: a solution preparation step in which at least water is reduced from the pre-solution to a concentration of 10% or less to obtain a polymer electrolyte solution. In the method for producing a catalyst layer for a fuel cell, in which the catalyst layer is formed by a catalyst paste,
A water removal step of reducing the concentration of water in the pre-solution in which the polymer electrolyte having a side chain having a hydrophilic functional group is dissolved in a solvent to 10% or less to obtain a polymer electrolyte solution;
A pre-paste preparation step of mixing the catalyst and the water to produce a pre-paste;
A method for producing a fuel cell catalyst layer, comprising: mixing the polymer electrolyte solution with the pre-paste to obtain a catalyst paste.

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