JP3097258B2 - Method for producing electrode for ion exchange membrane fuel cell - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel cell using a reducing agent such as pure hydrogen or reformed hydrogen from methanol and fossil fuel as fuel and using air or oxygen as an oxidizing agent. The present invention relates to a method for manufacturing an electrode for an exchange membrane fuel cell.

[0002]

2. Description of the Related Art One of the most important factors influencing the discharge performance of an ion exchange membrane fuel cell is a pore serving as a supply path of a reaction gas and a proton conductor near an interface between the ion exchange membrane and an electrode. This is the width of the three-phase interface formed by the ion exchange resin and the electrode material that is an electronic conductor. Therefore, conventionally, in order to increase the three-phase interface, an attempt has been made to provide a layer in which an electrode material and an ion exchange membrane resin are mixed at the interface between the membrane and the porous electrode. For example,
61118 and JP-B-62-61119, a method of applying a mixture of a solution of an ion-exchange membrane resin and a catalyst compound on an ion-exchange membrane, hot-pressing the electrode material and reducing the catalyst compound, or applying a coating after reduction. Then, a hot press method was used. In Japanese Patent Publication No. 2-48632, a method is used in which a porous electrode is molded, a solution of an ion exchange membrane resin is sprayed on the electrode, and the electrode and the ion exchange membrane are hot pressed.

[0003]

However, in the above-mentioned conventional method, the solution of the ion-exchange membrane resin applied on the ion-exchange membrane and the electrode substrate is dried in a state where the permeation into the inside of the electrode is insufficient. The electrode and the ion exchange membrane were not sufficiently bonded, and a wide three-phase interface was not obtained.

SUMMARY OF THE INVENTION The present invention solves the above-mentioned conventional problems. An ion-exchange membrane fuel cell having a higher performance by sufficiently applying an ion-exchange membrane resin inside an electrode to increase a three-phase interface. It is an object of the present invention to provide an electrode manufacturing method for realizing the above.

[0005]

In order to achieve this object, an electrode for an ion exchange membrane fuel cell according to the present invention comprises a carbon fine powder having an ion exchange membrane resin and a noble metal catalyst supported in an aqueous solution of a lower saturated monohydric alcohol. A step of forming a dispersion of the ion exchange membrane resin and the carbon fine powder catalyst by adding the powder, and a step of filtering, drying, and grinding the dispersion of the ion exchange membrane resin and the carbon fine powder. a catalyst for batteries provided with ion exchange membranes resin powder carbon fines were, mixed with carbon fine powder which has been water-repellent treated with a fluorine resin, by using a method of pressure molding it into-conductive electrode substrate electrode And then ion exchange
A method of bonding with a film was used . Further, the electrode for an ion exchange membrane fuel cell of the present invention is obtained by adding a carbon fine powder carrying an ion exchange membrane resin and a noble metal catalyst and a carbon fine powder water-repellent to a fluororesin to an aqueous solution of a lower saturated monohydric alcohol. Forming a dispersion of the ion-exchange membrane resin, the carbon fine powder catalyst, and the water-repellent carbon fine powder; and a dispersion of the ion-exchange membrane resin, the carbon fine powder catalyst, and the water-repellent carbon fine powder. Was pressed onto a porous conductive electrode substrate from below the electrode substrate, and the electrode obtained from the step of applying was pressed and molded. Further, the electrode for an ion-exchange membrane fuel cell of the present invention is obtained by mixing a carbon fine powder carrying a noble metal catalyst and a carbon fine powder subjected to a water-repellent treatment with a fluororesin, and placing the mixed powder on a porous conductive electrode substrate. A method was used in which a dispersion of an aqueous solution of a lower saturated monohydric alcohol and an ion-exchange membrane resin was applied onto the pressure-molded electrode molded body while sucking the dispersion from below the electrode substrate.

[0006]

According to this manufacturing method, it is possible to disperse the ion exchange membrane resin in a deep portion inside the catalyst layer of the electrode. With this catalyst layer configuration, a gas channel formed by a water-repellent carbon fine powder serving as a supply path for a fuel gas such as hydrogen or an oxidizing gas such as oxygen, a proton conductive channel formed by an ion exchange membrane resin, The three phases of the electron conducting channel formed by the powder material are formed very close within the same catalyst layer.

Therefore, at the hydrogen electrode,

[0008]

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In the above reaction, and at the oxygen electrode,

[0010]

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In the above reaction, the supply of hydrogen and oxygen gas and the transfer of protons and electrons are performed smoothly and widely, and the reaction rate and reaction area are increased.
It is possible to realize an ion exchange membrane fuel cell exhibiting higher discharge performance.

[0012]

Embodiments of the present invention will be described below with reference to the drawings.

Embodiment 1 FIG. 1 shows the steps of a method for manufacturing an electrode for an ion exchange membrane fuel cell according to Embodiment 1 of the present invention. First, as an ion exchange membrane resin, Nafion (registered trademark ) manufactured by DuPont, USA
With 5 wt% solution of US Aldrich Chemical Co. ion exchange membranes resin powder using a recording trademark), the ion-exchange membrane resin solution 1ml per isopropyl alcohol 4
mix with water and 250 ml of water. This was dispersed for about 5 minutes using an ultrasonic homogenizer. Next, carbon fine powder carrying 10 to 25% by weight of a catalyst was added to the dispersion. Here, the addition amount of the ion exchange resin is 10 to 30 by weight ratio to the carbon fine powder supporting the noble metal catalyst.
%. Subsequently, a dispersion treatment was performed for about 10 minutes using an ultrasonic homogenizer. The dispersion is filtered and
After drying at 10 ° C. and removing the solvent, the mixture was pulverized to prepare a fine catalyst-supporting carbon powder with an ion-exchange membrane resin. The catalyst-carrying carbon fine powder with the ion-exchange membrane resin was prepared by mixing polytetrafluoroethylene (hereinafter referred to as PTFE) with 25 to 7 particles.
The powder was mixed with the water-repellent fine carbon powder by adding 0% by weight. The mixed powder for the catalyst layer is coated on an electrode substrate, which is a conductive sheet made of a fine carbon powder to which 50 to 70% by weight of PTFE is added, or a mixture of ethylene tetrafluoride and propylene hexafluoride. It was sprayed on an electrode substrate which is a porous carbon fired plate to which a fluororesin composed of a polymer was added in a weight ratio of 20 to 40%, and was preformed using the fluororesin as a binder. This molded body was hot-pressed at a temperature of 340 to 380 ° C. and a pressure of 5 to ²⁰ kg / cm ² to produce an electrode for an ion exchange membrane fuel cell of Example 1 of the present invention.

Example 2 FIG. 2 shows steps of a method for manufacturing an electrode for an ion exchange membrane fuel cell according to Example 2 of the present invention. First, as an ion exchange membrane resin, Nafion (registered trademark ) manufactured by DuPont, USA
With 5 wt% solution of US Aldrich Chemical Co. ion exchange membranes resin powder using a recording trademark), the ion-exchange membrane resin solution per 1g, isopropyl alcohol 10
of water, 10 ml of water, 10 to 25% by weight of a predetermined amount of catalyst supported on carbon, and carbon fine powder treated with water repellency by adding 25 to 70% by weight of PTFE. The dispersion treatment was performed for about 5 minutes using a homogenizer. This dispersion is made up of 50-70% by weight of PTFE.
20 to 4 parts by weight of a fluororesin made of a copolymer of ethylene tetrafluoride and propylene hexafluoride on an electrode substrate which is a conductive sheet made of added carbon fine powder, or
It was applied to a 0% -added porous carbon fired plate as an electrode substrate while being sucked by a pump from below the electrode substrate. After sucking the solvent of this dispersion liquid to such an extent that the dispersion liquid did not flow down, it was heated in a vacuum at 70 ° C. using a vacuum dryer to remove alcohol and water. This electrode is 340
An electrode for an ion-exchange membrane fuel cell of Example 2 of the present invention was prepared by hot pressing at a temperature of 380 ° C. and a pressure of 5-20 kg / cm ² .

Embodiment 3 FIG. 3 shows the steps of a method for manufacturing an electrode for an ion exchange membrane fuel cell according to Embodiment 3 of the present invention. First, the catalyst
0 to 25% by weight of supported carbon fine powder is
It was mixed with the water-repellent fine carbon powder by adding 5 to 70% by weight. The mixed powder for the catalyst layer is
E on an electrode substrate, which is a conductive sheet made of fine carbon powder to which 50 to 70% by weight of E is added, or a fluororesin made of a copolymer of ethylene tetrafluoride and propylene hexafluoride on a weight basis Was sprayed on an electrode substrate which was a porous carbon fired plate to which 20 to 40% was added, and this fluororesin was preformed as a binder. This molded body is heated to 340 to 380 ° C.
At a temperature of 5 to 20 kg / cm ² to produce a gas diffusion electrode. Further, as the ion exchange membrane resin, a 5% by weight solution of ion exchange membrane resin powder manufactured by Aldrich Chemical Co., USA using Nafion (registered trademark) manufactured by DuPont, USA was used. Dispersed in 7 ml of isopropyl alcohol. The dispersion liquid of the ion exchange membrane resin solution was applied onto the gas diffusion electrode in a state where the dispersion liquid was sucked by a pump from below the electrode substrate. After sucking the solvent of the dispersion to such an extent that the dispersion does not flow down, using a vacuum dryer,
An alcohol and water were removed by vacuum heating at 70 ° C. to produce an electrode for an ion exchange membrane fuel cell of Example 3 of the present invention.

(Comparative Example) FIG. 4 shows an example of a method for manufacturing an electrode for an ion exchange membrane fuel cell according to a conventional technique. In the step of applying the dispersion of the ion-exchange membrane resin solution on the gas diffusion electrode of Example 3, except that the application was performed without suction by a pump from below the electrode substrate,
An electrode was manufactured in exactly the same steps as in Example 3 of the present invention.

The electrodes of the examples and comparative examples of the present invention and the ion exchange membrane were heated at a temperature of 120 to 150 ° C.,
Hot pressing was performed at a pressure of 60 kg / cm ² to join the negative electrode, the ion exchange membrane, and the positive electrode. Using this assembly, a single cell of the ion exchange membrane fuel cell shown in FIG. 5 was prepared.
In FIG. 5, reference numeral 10 denotes an ion-exchange membrane, and in this example, a Nafion 117 membrane manufactured by DuPont, USA was used. Reference numerals 11 and 12 indicate a negative electrode and a positive electrode, respectively. On the negative electrode side,
Hydrogen gas humidified at a temperature of 90 ° C.
By supplying oxygen gas humidified at a temperature of 80 ° C.,
A discharge test was performed.

FIG. 6 shows the voltage-current characteristics of the ion exchange membrane fuel cells using the electrodes according to the production methods of Examples 1, 2, 3 and Comparative Example of the present invention. The fuel cells of Examples 1, 2 and 3 of the present invention have a current density of 200 mA / cm ^2.
, The battery voltages 0.65 V, 0.67 V,
0.64V. On the other hand, the fuel cell of the comparative example exhibited a cell voltage of 0.53 V at a current density of 200 mA / cm ² .

FIG. 7 shows the relationship between the amount of ion exchange membrane resin added and the cell voltage at a current density of 200 mA / cm ² in an ion exchange membrane fuel cell using electrodes according to the production method of Example 2 of the present invention. As a result, the maximum value was exhibited when the amount of the ion exchange membrane resin added to the catalyst-supporting carbon fine powder was in the range of about 10 to 30%.

Although the cause is not clear, the ion exchange membrane resin itself has almost no electron conductivity. When the addition amount of the ion exchange membrane resin exceeds 30%, the electric resistance of the entire electrode increases. It is considered that when the characteristics are deteriorated and the addition amount of the ion exchange membrane resin is 10% or less, the width of the three-phase interface, that is, the reaction area, which influences the discharge performance, is narrow and limited.

Further, in the manufacturing methods of Examples 1 and 3,
As in the case of Example 2 described above, the maximum value was exhibited when the amount of the ion exchange membrane resin added to the fine carbon powder carrying the catalyst was in the range of about 10 to 30%.

As described above, by configuring a fuel cell using the electrode according to the manufacturing method of the present invention, it has become possible to realize an ion exchange membrane fuel cell exhibiting higher discharge performance.

In the examples, as an ion exchange membrane resin, a typical example of a polymer electrolyte comprising a copolymer of tetrafluoroethylene and perfluorovinyl ether is an ion exchange membrane resin powder manufactured by Aldrich Chemical Co., USA. Although a weight% solution was used, similar results can be obtained by using another polymer electrolyte having a proton exchange group.
For example, a polymer electrolyte made of a copolymer of styrene and vinylbenzene may be used.

Also, a dispersion medium of the ion exchange membrane resin,
Although isopropyl alcohol was used as a representative example of the lower saturated monohydric alcohol, any alcohol having a carbon number of 4 or less such as propyl alcohol, butyl alcohol, isobutyl alcohol, sec-butyl alcohol, and tert-butyl alcohol can be used. The same result can be obtained by using.

In this embodiment, a hydrogen-oxygen fuel cell is taken as an example of the ion exchange membrane fuel cell.
A fuel cell using reformed hydrogen using methanol, natural gas, naphtha or the like as a fuel, or a fuel cell using air as an oxidizing agent can be applied.

[0026]

As described above, the present invention provides a water-repellent treatment for supplying a fuel gas such as hydrogen or an oxidizing gas such as oxygen by sufficiently applying an ion exchange membrane resin to the inside of an electrode. A gas channel formed by carbon fine powder;
A proton conducting channel formed by the ion exchange membrane resin,
The three phases of the electron conduction channel formed by the carbon fine powder material are formed in the immediate vicinity inside the same catalyst layer, increasing the three-layer interface, supplying hydrogen and oxygen gas, and smoothly transferring protons and electrons. The reaction can be performed in a wide range, the reaction rate and the reaction area can be increased, and an ion exchange membrane fuel cell exhibiting higher discharge performance can be realized.

[Brief description of the drawings]

FIG. 1 is a diagram showing a manufacturing process of an electrode for an ion exchange membrane fuel cell in Example 1 of the present invention.

FIG. 2 is a view showing a manufacturing process of an electrode for an ion exchange membrane fuel cell in Example 2 of the present invention.

FIG. 3 is a view showing a manufacturing process of an electrode for an ion exchange membrane fuel cell in Example 3 of the present invention.

FIG. 4 is a diagram showing a manufacturing process of an electrode for an ion exchange membrane fuel cell in a comparative example.

FIG. 5 is a schematic sectional view of a unit cell of an ion exchange membrane fuel cell according to an embodiment of the present invention.

FIG. 6 is a diagram showing voltage-current characteristics of an ion exchange membrane fuel cell.

FIG. 7 is a diagram showing the relationship between the amount of ion exchange membrane resin added and the battery voltage.

[Explanation of symbols]

 Reference Signs List 10 ion exchange membrane 11 negative electrode 12 positive electrode

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-4-305249 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01M 4/88 H01M 8/02 H01M 8 / 10 B01J 31/28

Claims (12)

(57) [Claims] A step of adding a carbon fine powder carrying a noble metal catalyst and an ion exchange membrane resin to an aqueous solution of a lower saturated monohydric alcohol to form a dispersion of the ion exchange membrane resin and the carbon fine powder catalyst; This dispersion is filtered, dried, and then pulverized. A battery catalyst obtained by applying an ion-exchange membrane resin to fine carbon powder obtained from a step of pulverization is mixed with a carbon powder water-repellent treated with a fluororesin. pressure molding and electrode heat electrode substrate
And then joining the ion-exchange membrane to an ion-exchange membrane fuel electrode. 2. The amount of the ion-exchange membrane resin added is 10 to 30 in weight ratio to the carbon fine powder supporting the noble metal catalyst.
The method for producing an electrode for ion exchange membrane fuel cell according to claim 1, wherein 3. The production of an electrode for an ion exchange membrane fuel cell according to claim 1, wherein a polymer electrolyte comprising a copolymer of tetrafluoroethylene and perfluorovinyl ether is used as said ion exchange membrane resin. Method. 4. The lower saturated monohydric alcohol is at least one of alcohols having 4 or less carbon atoms, such as propyl alcohol, isopropyl alcohol, butyl alcohol, isobutyl alcohol, sec-butyl alcohol and tert-butyl alcohol. The method for producing an ion exchange membrane fuel electrode according to claim 1. 5. An ion-exchange membrane resin and carbon fine powder, which are added to an aqueous solution of a lower saturated monohydric alcohol, and a carbon fine powder carrying an ion-exchange membrane resin and a noble metal catalyst and a carbon fine powder water-repellent with a fluororesin are added. An electrode obtained from a step of forming a dispersion of a fine powder catalyst and a water-repellent carbon fine powder, and a step of applying the dispersion onto a porous conductive electrode substrate while sucking the dispersion from below the electrode substrate. A method for producing an electrode for an ion-exchange membrane fuel cell, wherein the electrode is molded under pressure. 6. The amount of the ion-exchange membrane resin to be added is 10 to 30 in weight ratio to the fine carbon powder supporting the noble metal catalyst.
The method for producing an electrode for an ion exchange membrane fuel cell according to claim 5, wherein 7. The production of an electrode for an ion exchange membrane fuel cell according to claim 5, wherein a polymer electrolyte comprising a copolymer of tetrafluoroethylene and perfluorovinyl ether is used as said ion exchange membrane resin. Method. 8. As the lower saturated monohydric alcohol, at least one of alcohols having 4 or less carbon atoms, such as propyl alcohol, isopropyl alcohol, butyl alcohol, isobutyl alcohol, sec-butyl alcohol and tert-butyl alcohol is used. The method for producing an electrode for an ion exchange membrane fuel cell according to claim 5. 9. A fine carbon powder supporting a noble metal catalyst and a fine carbon powder treated with water repellency with a fluororesin are mixed, and the mixed powder is formed on a porous conductive electrode substrate by pressure molding on an electrode molded body. A method for producing an electrode for an ion-exchange membrane fuel cell, comprising applying a dispersion obtained by adding an ion-exchange membrane resin to an aqueous solution of a lower saturated monohydric alcohol and sucking the dispersion from below the electrode substrate. 10. The addition amount of the ion exchange membrane resin is 10 to 3 in weight ratio to the carbon fine powder supporting the noble metal catalyst.
The method for producing an electrode for an ion exchange membrane fuel cell according to claim 9, which is 0%. 11. The electrode for an ion exchange membrane fuel cell according to claim 9, wherein a polymer electrolyte comprising a copolymer of tetrafluoroethylene and perfluorovinyl ether is used as said ion exchange membrane resin. Production method. 12. The lower saturated monohydric alcohol having 4 carbon atoms comprising propyl alcohol, isopropyl alcohol, butyl alcohol, isobutyl alcohol, sec-butyl alcohol and tert-butyl alcohol.
The method for producing an electrode for an ion exchange membrane fuel cell according to claim 9, wherein at least one of the following alcohols is used.