JP2008177057A - Electrode for solid polymer fuel cell, its manufacturing method, and solid polymer fuel cell equipped with it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of an electrode for a solid polymer fuel cell capable of reducing carrying amount of a metal catalyst and capable of suppressing voltage drop in a large current region. <P>SOLUTION: This is the manufacturing method of an electrode for solid polymer fuel cell equipped with a conductive porous substrate, carbon fiber arranged on the conductive porous substrate, and a metal catalyst carried on the carbon fiber, and comprises (i) a process to apply a water repellency treatment on one of the surfaces of the conductive porous substrate, (ii) a process to produce a fibril-like polymer by electrolytic oxidation polymerization of a compound having an aromatic ring on the other surface of the conductive porous substrate, (iii) a process to produce carbon fiber on the conductive porous substrate by calcining the fibril-like polymer, and (iv) a process to have the metal catalyst carried on the carbon fiber. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a polymer electrolyte fuel cell electrode, a method for producing the same, and a polymer electrolyte fuel cell including the polymer electrolyte fuel cell electrode. Particularly, the gas permeability is good and flooding occurs. The present invention relates to a method for producing a difficult polymer electrolyte fuel cell electrode.

  In recent years, fuel cells have attracted attention as a battery with high power generation efficiency and a low environmental load, and extensive research and development has been conducted. Among fuel cells, polymer electrolyte fuel cells with high output density and low operating temperature are easier to reduce in size and cost than other types of fuel cells. It is expected to spread widely as a household cogeneration system.

  In general, in a polymer electrolyte fuel cell, a pair of electrodes are arranged with a polymer electrolyte membrane sandwiched between them, a fuel gas such as hydrogen is brought into contact with the surface of one electrode, and oxygen is applied to the surface of the other electrode. The contained gas is brought into contact, and electric energy is taken out from between the electrodes by utilizing an electrochemical reaction that occurs at this time (see Non-Patent Documents 1 and 2). A catalyst layer is disposed on the electrode in contact with the polymer electrolyte membrane, and an electrochemical reaction occurs at the three-phase interface between the polymer electrolyte membrane, the catalyst layer, and the gas. Therefore, in order to improve the power generation efficiency of the polymer electrolyte fuel cell, it is necessary to increase the reaction field of the electrochemical reaction.

  In the polymer electrolyte fuel cell, in order to facilitate transmission of protons generated in the catalyst layer on the fuel electrode side to the air electrode (oxygen electrode) side through the polymer electrolyte membrane, the catalyst layer It is also necessary to contain a polymer electrolyte. Therefore, in order to increase the reaction field of the electrochemical reaction and to ensure a sufficient proton conduction path, the catalyst layer has conventionally been prepared by supporting a noble metal catalyst such as platinum on granular carbon such as carbon black. It has been formed by applying a paste or slurry obtained by mixing a powder and a polymer electrolyte onto a conductive porous support such as carbon paper. However, the polymer electrolyte fuel cell including the catalyst layer formed by this method has low power generation efficiency.

  On the other hand, the present inventors prepared carbon fibers by a specific method on a conductive porous support such as carbon paper, and carried a noble metal on the carbon fibers by electroplating. It has been found that the power generation efficiency of a solid polymer fuel cell is improved by using an electrode produced by impregnating a polymer electrolyte in the polymer electrolyte fuel cell (see Patent Document 1).

The Chemical Society of Japan, “Chemical Review No. 49, Material Chemistry of New Batteries”, Academic Publishing Center, 2001, p. 180-182 “Polymer fuel cell <2001 edition>”, Technical Information Association, 2001, p. 14-15 International Publication No. 2004/063438 Pamphlet

  However, as a result of further studies by the present inventors, it has been found that the electrode described in Patent Document 1 has room for improvement in gas permeability from the viewpoint of preventing flooding.

  Accordingly, an object of the present invention is to provide an electrode for a polymer electrolyte fuel cell that solves the above-described problems of the prior art, has good gas permeability, and can suppress flooding, and a method for manufacturing the same. is there. Another object of the present invention is to provide a polymer electrolyte fuel cell comprising such a polymer electrolyte fuel cell electrode, which is less prone to flooding.

  As a result of intensive studies to achieve the above object, the present inventors have produced a fibril polymer on one surface of a conductive porous substrate, and calcined the fibril polymer to form a three-dimensional continuous carbon. Conductive material that is not subjected to water repellent treatment after being subjected to water repellent treatment on the other surface of the conductive porous substrate on which the carbon fiber is supported and the carbon catalyst is not disposed. By impregnating a carbon electrolyte located on the surface of the porous porous substrate with a polymer electrolyte, an electrode for a polymer electrolyte fuel cell having good gas permeability can be obtained. It has been found that flooding is less likely to occur in the fuel cell by incorporating it into the battery, and the present invention has been completed.

That is, the method for producing an electrode for a polymer electrolyte fuel cell of the present invention comprises a conductive porous substrate, a carbon fiber disposed on the conductive porous substrate, and a metal supported on the carbon fiber. A method for producing a polymer electrolyte fuel cell electrode comprising a catalyst and a polymer electrolyte impregnated in the carbon fiber,
(i) on one surface of the conductive porous substrate, a step of electrolytically oxidatively polymerizing a compound having an aromatic ring to produce a fibrillated polymer;
(ii) firing the fibrillated polymer to form carbon fibers on the conductive porous substrate;
(iii) supporting a metal catalyst on the carbon fiber;
(iv) performing a water repellent treatment on the other surface of the conductive porous substrate on which the carbon fiber supporting the metal catalyst is not disposed;
(v) a step of impregnating a polymer electrolyte into a carbon fiber disposed on one surface of the conductive porous substrate not subjected to the water repellent treatment and carrying a metal catalyst. And

  In a preferred example of the method for producing an electrode for a polymer electrolyte fuel cell of the present invention, the conductive porous substrate is carbon paper.

  In another preferred embodiment of the method for producing a polymer electrolyte fuel cell electrode of the present invention, the compound having an aromatic ring is at least one selected from the group consisting of aniline, pyrrole, thiophene and derivatives thereof. .

  In another preferred embodiment of the method for producing an electrode for a polymer electrolyte fuel cell of the present invention, the firing is performed in a non-oxidizing atmosphere.

  In another preferred embodiment of the method for producing an electrode for a polymer electrolyte fuel cell of the present invention, the metal catalyst contains at least Pt.

  In another preferred embodiment of the method for producing a polymer electrolyte fuel cell electrode of the present invention, the water repellent treatment is performed with a fluorine-based water repellent.

  In another preferred embodiment of the method for producing a polymer electrolyte fuel cell electrode of the present invention, the polymer electrolyte is at least one selected from the group consisting of sulfonic acid, carboxylic acid, phosphonic acid and phosphonous acid. It is an ion conductive polymer having an ion exchange group.

  In addition, the polymer electrolyte fuel cell electrode of the present invention is manufactured by the above-described method, and the polymer electrolyte fuel cell of the present invention includes the electrode.

  ADVANTAGE OF THE INVENTION According to this invention, the gas permeability is favorable and the electrode for solid polymer type fuel cells which can suppress flooding, and its manufacturing method can be provided. In addition, it is possible to provide a polymer electrolyte fuel cell that includes such an electrode and is less likely to flood.

<Electrode for polymer electrolyte fuel cell and method for producing the same>
Below, the electrode for solid polymer type fuel cells of the present invention and its manufacturing method are explained in detail. The method for producing an electrode for a polymer electrolyte fuel cell according to the present invention includes (i) a step of producing a fibril polymer by electrolytic oxidation polymerization of a compound having an aromatic ring on one surface of a conductive porous substrate. (Ii) firing the fibrillated polymer to form carbon fibers on a conductive porous substrate; (iii) supporting a metal catalyst on the carbon fibers; and (iv) A step of performing water repellent treatment on the other surface of the conductive porous substrate on which the supported carbon fibers are not disposed, and (v) one surface of the conductive porous substrate not subjected to the water repellent treatment. And impregnating a polymer fiber in a carbon fiber on which a metal catalyst is supported. According to the method, the conductive porous substrate and the conductive porous substrate A carbon fiber disposed on the metal fiber, a metal catalyst supported on the carbon fiber, and An electrode for a polymer electrolyte fuel cell comprising a polymer electrolyte impregnated in carbon fiber can be produced.

  In the method for producing an electrode for a polymer electrolyte fuel cell of the present invention, after forming carbon fibers on one surface of the conductive porous substrate in the steps (i) and (ii), the carbon is added in the step (iii). A metal catalyst is supported on the fiber, and further, in step (iv), the other surface of the conductive porous substrate is subjected to water repellency treatment, so that the surface subjected to water repellency treatment in step (v) It is possible to prevent the polymer electrolyte from adhering. Therefore, in the step (v), the polymer electrolyte is impregnated only in the carbon fibers carrying the metal catalyst located on the surface of the conductive porous substrate that has not been subjected to the water repellent treatment. As a result, the surface of the conductive porous substrate that has been subjected to the water repellent treatment does not have a polymer electrolyte attached thereto, and therefore has high gas permeability and is unlikely to flood.

  In the method for producing a polymer electrolyte fuel cell electrode of the present invention, in step (i), a compound having an aromatic ring is electrolytically oxidatively polymerized on one surface of the conductive porous substrate to produce a fibril polymer. Let Here, the conductive porous substrate to be used may be any porous and conductive material, and specifically includes carbon paper, porous carbon cloth, etc. Among these, carbon Paper is preferred.

  Examples of the compound having an aromatic ring include a compound having a benzene ring and a compound having an aromatic heterocyclic ring. Here, as the compound having a benzene ring, aniline and aniline derivatives are preferable, and as the compound having an aromatic heterocyclic ring, pyrrole, thiophene and derivatives thereof are preferable. These compounds having an aromatic ring may be used singly or as a mixture of two or more.

In the electrolytic oxidation polymerization, it is preferable to mix an acid together with a raw material compound having an aromatic ring. In this case, the negative ion of the acid is taken into the fibril polymer synthesized as a dopant to obtain a fibril polymer excellent in conductivity. By using this fibril polymer, the conductivity of the carbon fiber is finally improved. Further improvement can be achieved. Here, examples of the acid mixed in the electrolytic oxidation polymerization include HBF ₄ , H ₂ SO ₄ , HCl, HClO _{4 and the} like. The acid concentration is preferably in the range of 0.1 to 3 mol / L, more preferably in the range of 0.5 to 2.5 mol / L.

In the step (i), the conductive porous substrate is immersed as a working electrode in a solution containing a compound having an aromatic ring, and the counter electrode is further immersed. It is only necessary to apply a voltage or to pass a current under such a condition that a voltage sufficient to polymerize the compound having an aromatic ring can be ensured, whereby a fibril-like structure is formed on the conductive porous substrate (working electrode). A polymer is formed. Here, as the counter electrode, a plate made of a highly conductive material such as stainless steel, platinum, or carbon, a porous support, or the like can be used. An example of a method for synthesizing a fibril-like polymer by this electrolytic oxidation polymerization method is as follows. A working electrode composed of a conductive porous substrate in an electrolytic solution containing a compound having an acid and an aromatic ring, such as H ₂ SO ₄ and HBF ₄ , and A method of polymerizing and depositing a fibrillated polymer on the working electrode side made of a conductive porous substrate by immersing the counter electrode and passing a current of 0.1 to 1000 mA / cm ² , preferably 0.2 to 100 mA / cm ² between both electrodes Is exemplified. The fibril polymer is mainly generated on the surface facing the counter electrode of the working electrode made of a conductive porous substrate. Here, the concentration of the compound having an aromatic ring in the electrolytic solution is preferably 0.05 to 3 mol / L, and more preferably 0.25 to 1.5 mol / L. Moreover, in addition to the said component, you may add a soluble salt etc. to an electrolyte solution suitably in order to adjust pH.

  The fibril-like polymer obtained by electrolytic oxidation polymerization of the compound having an aromatic ring usually has a three-dimensional continuous structure, has a diameter of 30 to several hundred nm, preferably 40 to 500 nm, and has a length of 0.5. It is μm to 100 mm, preferably 1 μm to 10 mm.

  In the method for producing an electrode for a polymer electrolyte fuel cell of the present invention, in the step (ii), the fibrillated polymer is baked and carbonized to generate carbon fibers on the conductive porous substrate. In addition, before the step (ii), it is preferable that the fibrillated polymer is washed with a solvent such as water or an organic solvent and dried. Here, the drying method is not particularly limited, and examples thereof include a method using a fluidized bed drying device, an air dryer, a spray dryer, etc., in addition to air drying and vacuum drying.

  The firing conditions in the above step (ii) are not particularly limited, and may be set as appropriate so as to obtain optimum conductivity. Particularly, when high conductivity is required, the temperature is 500 to 3000 ° C., Preferably, baking is performed at 600 to 2800 ° C. for 0.5 to 6 hours. In the production method of the present invention, the firing step is preferably performed in a non-oxidizing atmosphere, and examples of the non-oxidizing atmosphere include a nitrogen atmosphere, an argon atmosphere, and a helium atmosphere. It can also be.

The carbon fiber usually has a three-dimensional continuous structure, has a diameter of 30 to several hundred nm, preferably 40 to 500 nm, has a length of 0.5 μm to 100 mm, preferably 1 μm to 10 mm, and has a surface resistance. 10 ⁶ to 10 ⁻² Ω, preferably 10 ⁴ to 10 ⁻² Ω. The carbon fiber has a residual carbon ratio of 95 to 30%, preferably 90 to 40%. Since the carbon fiber has a structure in which the entire carbon is three-dimensionally continuous, the carbon fiber has higher conductivity than the granular carbon.

  In the method for producing an electrode for a polymer electrolyte fuel cell of the present invention, a metal catalyst is supported on the carbon fiber in the step (iii). Here, as the metal catalyst supported on the carbon fiber, a noble metal is preferable, and Pt is particularly preferable. In the present invention, Pt may be used alone or as an alloy with another metal such as Ru. By using Pt as the noble metal, hydrogen can be oxidized with high efficiency even at a low temperature of 100 ° C. or lower. In addition, by using an alloy such as Pt and Ru, it is possible to prevent poisoning of Pt by CO and prevent a decrease in the activity of the catalyst. The particle size of the metal catalyst supported on the carbon fiber is preferably in the range of 0.5 to 20 nm, and the support rate of the metal catalyst is preferably in the range of 0.05 to 5 g with respect to 1 g of the carbon fiber. Here, the method for supporting the metal catalyst on the carbon fiber is not particularly limited, and examples thereof include an impregnation method, an electroplating method (electrolytic reduction method), an electroless plating method, and a sputtering method. .

In the method of the present invention, it is preferable to carry the metal catalyst on the carbon fiber by an electroplating method in which a current is applied in a pulsed manner. Here, the current application condition is the following formula (I):
Duty ratio = t ₁ / (t ₁ + t ₂ ) × 100 (I)
It is preferable that the duty ratio represented by [where t ₁ represents current application time (seconds) and t ₂ represents rest time (seconds)] be 2 to 20%. If the duty ratio in the pulse current is less than 2%, it takes a long time to satisfy the predetermined energized charge amount, which is not suitable for practical use, and the effect of improving the surface area of the metal catalyst is insufficient, while the duty ratio is 20 If it exceeds%, the effect of applying current in a pulsed manner is small, and the surface area of the supported metal catalyst cannot be sufficiently improved.

Dwell time in the electroplating (t ₂₎ is preferably set to 0.05 to 0.5 seconds. When the pause time (t ₂ ) is less than 0.05 seconds, the effect of applying the current in a pulsed manner is small, and the surface area of the supported metal catalyst cannot be sufficiently improved, while the pause time (t ₂ ) is 0.5. If it exceeds 2 seconds, it takes a total time to satisfy the predetermined energized charge amount, which is not suitable for practical use, and the effect of improving the surface area of the metal catalyst is insufficient.

In the electroplating, the current density is preferably in the range of 10 to 500 mA / cm ² , and the energization charge amount is preferably in the range of 0.1 to 5C. The application time (t ₁ ) is preferably selected so that the rest time (t ₂ ) is in the range of 0.05 to 0.5 seconds while the duty ratio is 2 to 20%. Furthermore, the number of pulses (number of cycles) in pulse plating is preferably selected as appropriate so as to be in the above-described range of the preferred energized charge amount.

  In the method for producing a polymer electrolyte fuel cell electrode of the present invention, in step (iv), the water repellent treatment is performed on the other surface of the conductive porous substrate on which the carbon fiber supporting the metal catalyst is not disposed. Apply. The water repellent treatment is preferably carried out with a fluorine-based water repellent mainly composed of a fluorine-based copolymer such as polytetrafluoroethylene or tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer. By applying a surface treatment to the surface of the conductive porous substrate on which the carbon fibers are not disposed with the liquid agent, it is possible to reliably prevent the polymer electrolyte from adhering to the surface in the step (v). The water repellent treatment is carried out, for example, by dissolving a water repellent in a suitable solvent and applying it to the surface of the conductive porous substrate where the carbon fibers are not disposed. The concentration and the like of the water repellent component can be adjusted as appropriate. Further, after the application of the water repellent solution, it is preferable to perform a heat treatment to remove the solvent and fix the water repellent.

In the method for producing an electrode for a polymer electrolyte fuel cell of the present invention, in step (v), the metal catalyst is supported and disposed on one surface of the conductive porous substrate not subjected to the water-repellent treatment. A polymer electrolyte is impregnated into the carbon fiber. Here, the polymer electrolyte is preferably an ion conductive polymer, and examples of the ion conductive polymer include polymers having an ion exchange group such as sulfonic acid, carboxylic acid, phosphonic acid, and phosphonous acid. The polymer may or may not contain fluorine. Examples of the ion conductive polymer include perfluorocarbon sulfonic acid polymers such as Nafion (registered trademark). The impregnation of the polymer electrolyte is performed by, for example, preparing a solution by dissolving the polymer electrolyte in water and / or an organic solvent, and applying the solution of the polymer electrolyte to carbon fibers supporting a metal catalyst. The amount of impregnation can be appropriately adjusted by controlling the amount and concentration of the solution. Impregnated amount of the polymer electrolyte is preferably in the range of ^{0.01mg / cm 2 ~4.0mg / cm 2} , in less than 0.01 mg / cm ² impregnation amount of the polymer electrolyte, proton conductivity is lowered, whereas, If it exceeds 4.0 mg / cm ² , the gas permeability decreases and flooding is likely to occur.

The electrode for a polymer electrolyte fuel cell of the present invention produced by the above-described method comprises a conductive porous substrate, carbon fibers disposed on the conductive porous substrate, and supported on the carbon fibers. The metal catalyst and the polymer electrolyte impregnated in the carbon fiber can be used as a fuel electrode or an air electrode (oxygen electrode). Here, in the polymer electrolyte fuel cell electrode, the carbon fiber supported with the metal catalyst and impregnated with the polymer electrolyte functions as a catalyst layer, and the conductive porous substrate is supplied with hydrogen gas or the like to the catalyst layer. It functions as a gas diffusion layer for supplying an oxygen-containing gas such as oxygen or air, and as a current collector for transferring generated electrons. The thickness of the catalyst layer is not particularly limited, but is preferably in the range of 0.1 to 100 μm. The amount of the metal catalyst supported on the catalyst layer is determined by the loading rate and the thickness of the catalyst layer, and is preferably in the range of 0.001 to 0.8 mg / cm ² .

<Solid polymer fuel cell>
Next, a polymer electrolyte fuel cell using the polymer electrolyte fuel cell electrode of the present invention will be described with reference to FIG. The illustrated polymer electrolyte fuel cell includes a membrane electrode assembly (MEA) 1 and separators 2 located on both sides thereof. The membrane electrode assembly (MEA) 1 includes a solid polymer electrolyte membrane 3, a fuel electrode 4A and an air electrode (oxygen electrode) 4B located on both sides thereof. In the fuel electrode 4A, a reaction represented by 2H ₂ → 4H ⁺ + 4e ⁻ occurs, the generated H ⁺ passes through the solid polymer electrolyte membrane 3 to the air electrode 4B, and the generated e ⁻ is taken out to the outside. Current. On the other hand, in the air electrode 4B, a reaction represented by O ₂ + 4H ⁺ + 4e ⁻ → 2H ₂ O occurs, and water is generated. The fuel electrode 4 </ b> A and the air electrode 4 </ b> B are composed of a catalyst layer 5 and a gas diffusion layer (conductive porous substrate) 6, and are arranged so that the catalyst layer 5 is in contact with the solid polymer electrolyte membrane 3.

  In the polymer electrolyte fuel cell of the present invention, an ion conductive polymer can be used as the solid polymer electrolyte membrane 3, and the ion conductive polymer includes a carbon fiber carrying the metal catalyst. What was illustrated as a polymer electrolyte which can be impregnated in can be used. Moreover, as the separator 2, the normal separator with which flow paths (not shown), such as fuel, air, and produced | generated water, were formed in the surface can be used.

  In the polymer electrolyte fuel cell of the present invention, the catalyst layer 5 is formed by supporting a metal catalyst on carbon fiber, and further impregnating the carbon fiber with a polymer electrolyte, and the surface area of the supported metal catalyst is very high. Since it is wide, the reaction field of the electrochemical reaction at the three-phase interface between the solid polymer electrolyte membrane 3, the catalyst layer 5, and the gas is very large, and as a result, the power generation efficiency of the solid polymer fuel cell is greatly improved. The In addition, the gas diffusion layer 6 has a very high gas permeability because the polymer electrolyte is not attached to the surface not in contact with the catalyst layer 5. Therefore, in the polymer electrolyte fuel cell of the present invention, flooding is unlikely to occur, and the voltage drop is small even when operated in a high current region.

  Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to the following examples.

(Example 1)
<Production of carbon fiber>
In an acidic aqueous solution containing aniline 0.5 mol / L and borohydrofluoric acid 1.0 mol / L, carbon paper [manufactured by Toray] was installed as a working electrode, and punching metal made of SUS316L was installed as a counter electrode at 15 ° C. Electrolytic oxidation polymerization was carried out at a constant current of 5 mA / cm ² for 700 seconds, and polyaniline was electrodeposited on the working electrode. The obtained polyaniline was immersed in a 1.0 mol / L NaOH aqueous solution for 1 hour, washed thoroughly with pure water, and dried at 100 ° C. under reduced pressure. Further, the obtained polyaniline was heated together with carbon paper to 1200 ° C. in an Ar reduced pressure atmosphere over 2 hours, and held at that temperature for 1 hour for firing treatment. Then, it cooled to room temperature and took out the obtained baked material (carbon fiber).

<Platinum support>
Next, the fired product (carbon fiber) obtained above was placed as a working electrode in an aqueous solution obtained by dissolving 10 g of chloroplatinic acid hexahydrate together with carbon paper in 1 L of pure water, and further, white as a counter electrode. A gold-plated titanium plate was installed. Thereafter, a pulse current of 120 mA / cm ² was passed at room temperature, and platinum was supported on the carbon fiber. The pulse conditions were as follows: application time (on time): 0.005 seconds, rest time (off time): 0.1 seconds, and energization amount: 1.0 C / cm ² . Moreover, after energization was completed, it was sufficiently washed and dried. The platinum loading was calculated from the mass change and found to be 0.27 mg / cm ² .

<Production of MEA>
Next, the carbon paper with platinum-supported carbon fibers obtained as described above was punched out to a size of 50 mm square, and a fluorine-based treatment agent [die-free GA- 6010, manufactured by Daikin Industries, Ltd.] and sprayed at 170 ° C. for 5 minutes. The adhesion amount of the fluorinated treating agent was calculated from the mass change and found to be 0.05 mg / cm ² . Then, apply Nafion (registered trademark) solution [polymer: 5% by mass, isopropyl alcohol: 50% by mass, water: 45% by mass] on the surface of the carbon paper where the platinum-supported carbon fibers are disposed, The solvent was removed by drying. The amount of Nafion was adjusted to 0.4 mg / cm ² . The two Nafion-coated platinum-supported carbon fibers / carbon paper sandwiched the Nafion 112 membrane and integrated by hot pressing to obtain a membrane electrode assembly (MEA).

<Performance evaluation of fuel cell>
The obtained membrane electrode assembly was incorporated into a test cell (EFC25-01SP) manufactured by Electrochemical Co., and a fuel cell was produced. The power generation characteristics of the obtained fuel cell were determined with a fuel gas (hydrogen) flow rate of 0.3 L / min, Measurement was performed under the conditions of a fuel gas humidification temperature of 80 ° C., an oxidizing gas (oxygen) flow rate of 0.3 L / min, an oxidizing gas humidification temperature of 80 ° C., and a cell temperature of 80 ° C. Table 1 shows the voltage at each current.

(Comparative Example 1)
Carbon fibers were produced in the same manner as in Example 1 and supported with platinum. The platinum loading determined from the mass change was 0.27 mg / cm ² . Furthermore, an MEA was prepared in the same manner as in Example 1 except that the water repellent treatment with a fluorine-based treatment agent was not performed before the Nafion liquid was applied, and a fuel cell was assembled to evaluate the power generation performance. Table 2 shows the voltage at each current.

  From Tables 1 and 2, it can be seen that the fuel cell provided with the electrode of Example 1 according to the present invention has a small voltage drop in a high current region in which flooding is generally likely to occur, and the flooding is suppressed. On the other hand, the fuel cell including the electrode of Comparative Example 1 manufactured without performing the water repellent treatment before the application of the Nafion liquid had a large voltage drop particularly in a high current region due to the occurrence of flooding.

It is sectional drawing of an example of the polymer electrolyte fuel cell of this invention.

Explanation of symbols

1 Membrane electrode assembly (MEA)
2 Separator 3 Solid polymer electrolyte membrane 4A Fuel electrode 4B Air electrode (oxygen electrode)
5 Catalyst layer 6 Gas diffusion layer (conductive porous substrate)

Claims (9)

A conductive porous substrate; carbon fibers disposed on the conductive porous substrate; a metal catalyst supported on the carbon fibers; and a polymer electrolyte impregnated in the carbon fibers. A method for producing a polymer electrolyte fuel cell electrode,
(i) on one surface of the conductive porous substrate, a step of electrolytically oxidatively polymerizing a compound having an aromatic ring to produce a fibrillated polymer;
(ii) firing the fibrillated polymer to form carbon fibers on the conductive porous substrate;
(iii) supporting a metal catalyst on the carbon fiber;
(iv) performing a water repellent treatment on the other surface of the conductive porous substrate on which the carbon fiber supporting the metal catalyst is not disposed;
(v) a step of impregnating a polymer electrolyte into a carbon fiber disposed on one surface of the conductive porous substrate not subjected to the water repellent treatment and carrying a metal catalyst. A method for producing an electrode for a polymer electrolyte fuel cell.   The method for producing an electrode for a polymer electrolyte fuel cell according to claim 1, wherein the conductive porous substrate is carbon paper.   2. The method for producing an electrode for a polymer electrolyte fuel cell according to claim 1, wherein the compound having an aromatic ring is at least one selected from the group consisting of aniline, pyrrole, thiophene and derivatives thereof. .   The method for producing an electrode for a polymer electrolyte fuel cell according to claim 1, wherein the firing is performed in a non-oxidizing atmosphere.   The method for producing a polymer electrolyte fuel cell electrode according to claim 1, wherein the metal catalyst contains at least Pt.   The method for producing an electrode for a polymer electrolyte fuel cell according to claim 1, wherein the water repellent treatment is performed with a fluorine-based water repellent.   The polymer electrolyte is an ion conductive polymer having at least one ion exchange group selected from the group consisting of sulfonic acid, carboxylic acid, phosphonic acid and phosphonous acid. A method for producing an electrode for a polymer electrolyte fuel cell.   An electrode for a polymer electrolyte fuel cell produced by the method according to claim 1.   A polymer electrolyte fuel cell comprising the electrode for a polymer electrolyte fuel cell according to claim 8.

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