JP2002334702A - Gas diffusion electrode for solid polymer electrolyte membrane type fuel cell and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrode for solid polymer electrolyte membrane type fuel cells capable of enhancing the characteristics of the electrode by securing continuous proton conduction paths while securing more triphasic interfaces serving as electrode reaction sites, and resultantly capable of economically enhancing the output performance of a fuel cell incorporating this electrode. SOLUTION: This gas diffusion electrode equipped with catalyst layers for sandwiching between them a solid polymer electrolyte membrane of the solid polymer electrolyte membrane type fuel cell is characterized in that the catalyst layers contain a compound made by introducing a proton-conductive functional group into a hydrocarbon resin.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an electrode for a solid polymer electrolyte membrane fuel cell and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, a solid polymer which is clean, has a high energy density and does not require a charging time in order to cope with global environmental and resource problems such as CO2 emission regulations for preventing air pollution and depletion of petroleum resources. Electrolyte-type fuel cells are the hottest spotlight, and research and development is being carried out at a rapid pace in Japan and other countries around the world.

A polymer electrolyte fuel cell is characterized by having a proton conductive solid polymer electrolyte membrane as a component thereof, and by electrochemically reacting a fuel gas such as hydrogen with an oxidizing gas. This is a device for obtaining the electromotive force generated at that time.

A fuel cell uses hydrogen gas as a fuel gas,
In the electrode reaction when oxygen is used as the oxidizing gas, a reaction represented by 2H2 → 4H ++ 4e− reaction formula 1 occurs on the anode electrode side, and the generated proton passes through the solid electrolyte membrane, and 4H + + O2 + 4e- → 2H2O Reaction 2 occurs, and an electromotive force is generated between the two electrodes.

[0005] By the way, at this stage, there are still some problems to be overcome for practical use of fuel cells.

As shown in US Pat. No. 4,876,115 or JP-A-3-208260, the current composition of the electrode catalyst layer is a material in which platinum as a catalyst is supported on carbon black, a perfluorocarbon sulfonic acid-based material. A gas diffusion electrode is formed by applying a catalyst composition made of a proton conductive material and kneading them to a base material such as carbon paper.

Further, in Electrochemistry, 53, No. 10, p8
12-817 (1985) "Solid polymer electrolyte (Naf
The addition of an ion exchange resin to the oxygen electrode to be bonded to the ion-ion) and its electrode characteristics include “a styrene divinylbenzene sulfonic acid resin as a solid polymer electrolyte membrane, a carbon powder carrying a catalytic metal, and a proton conductor. It is disclosed that the gas diffusion electrode is formed from a mixture of styrene divinylbenzene sulfonic acid resin powder and a polystyrene binder as a catalyst layer.

[0008]

However, US Pat. No. 4,876,115 or JP-A-3-20826.
In Publication No. 0, the proton conductive material in the gas diffusion electrode of the fuel cell must be insoluble in water,
If there are many proton conductive functional groups, it becomes water-soluble, and therefore, the perfluorocarbon sulfonic acid-based proton conductive material cannot increase the ion exchange capacity. High current cannot be extracted.

Further, in Electrochemistry, 53, No. 10, p8
Regarding 12 to 817 (1985), the ion exchange capacity can be made larger than that of the perfluorocarbon sulfonic acid-based proton conductive material. However, since the proton conductor is a powder, poor contact of the powder particles due to defects of the powder particles and the like is caused. Occurs, and the function cannot be sufficiently exerted. Therefore, the movement of protons is rate-determining, the protons do not reach the solid polymer electrolyte membrane, and a sufficient current cannot be taken out.

As described above, according to the conventional technique, since the proton conductor in the catalyst layer is in the form of a powder or does not have a large ion exchange capacity, the three-phase interface (hydrogen gas phase, catalyst phase, The rate at which the protons generated in the active substance phase) move through the proton conductor to the solid polymer electrolyte membrane is rate-determining, and as a result, a sufficient current cannot be taken out. Therefore, in order to improve the output performance of the fuel cell, it is necessary to improve the characteristics of the proton conductor.

A platinum catalyst and a perfluorocarbon sulfonic acid-based proton conductive material are used in the catalyst layer having the basic composition, which causes high cost. The possibility of cost reduction remains.

[0012] However, the proton conductive material is produced by using a very expensive perfluorocarbon sulfonic acid resin as a raw material and by dissolving it. The cost is a material as expensive as platinum, and is currently used as a mainstream material by many manufacturers of fuel cell stacks and gas diffusion electrodes, and it is difficult to reduce the cost of the fuel cell as it is. Therefore, it is necessary to reduce the cost of the proton conductor.

The present invention has solved the above-mentioned problems, and can improve the characteristics of an electrode to secure a continuous proton conduction path while securing more three-phase interfaces as electrode reaction sites. As a result, an object of the present invention is to provide an electrode for a solid polymer electrolyte membrane fuel cell and a fuel cell which can remarkably improve the output performance of a fuel cell combined with this electrode at low cost.

[0014]

SUMMARY OF THE INVENTION In order to solve the above technical problems, the invention of claim 1 is directed to a gas comprising a catalyst layer sandwiching a solid polymer electrolyte membrane of a solid polymer electrolyte membrane fuel cell. In the gas diffusion electrode, the catalyst layer contains a compound in which a proton conductive functional group is introduced into a hydrocarbon resin.

According to the first aspect of the invention, the characteristics of the electrode can be improved to secure a continuous proton conduction path while securing more three-phase interfaces as electrode reaction sites,
As a result, it is possible to provide an electrode for a solid polymer electrolyte membrane fuel cell, which can remarkably improve the output performance of a fuel cell combined with this electrode at low cost.

In order to solve the above technical problems, the invention of claim 2 is directed to a method of manufacturing a gas diffusion electrode for sandwiching a solid polymer electrolyte membrane of a solid polymer electrolyte membrane fuel cell, the method comprising the steps of: Gas diffusion for a solid polymer electrolyte membrane fuel cell, comprising: mixing and dispersing a monomer having a proton-conductive functional group introduced into the catalyst layer in the catalyst layer; and polymerizing the monomer to increase the molecular weight. This is a method for manufacturing an electrode.

According to the second aspect of the present invention, the characteristics of the electrode can be improved to secure a continuous proton conduction path while securing more three-phase interfaces as electrode reaction sites,
As a result, it is possible to provide a method of manufacturing an electrode for a solid polymer electrolyte membrane fuel cell, which can significantly improve the output performance of a fuel cell combined with this electrode at low cost.

In addition, this manufacturing method has an advantage that a continuous proton conduction path can be formed since the liquid is mixed and dispersed in the catalyst layer and then solidified.

The invention according to claim 3, which has been made to solve the above technical problem, relates to a method for manufacturing an electrode sandwiching a solid polymer electrolyte membrane of a solid polymer electrolyte membrane fuel cell,
A solid polymer electrolyte membrane comprising: a step of mixing and dispersing a monomer of a hydrocarbon resin in the catalyst layer; a step of polymerizing the monomer to increase the molecular weight; and a step of introducing a proton conductive functional group into the polymer. 1 is a method for manufacturing a gas diffusion electrode for a fuel cell.

In addition, this manufacturing method has an advantage that a continuous proton conduction path can be formed since the liquid is mixed and dispersed in the catalyst layer and then solidified.

According to a fourth aspect of the present invention, which has been made to solve the above technical problem, the proton conductive functional group is selected from an acid group consisting of sulfonic acid, carboxylic acid, phosphonic acid and phosphoric acid. The gas diffusion electrode for a solid polymer electrolyte membrane fuel cell according to any one of claims 1 to 3, and a method for producing the same.

According to the fourth aspect of the present invention, an effect of exhibiting proton conductivity can be provided.

The invention of claim 5 made in order to solve the above technical problem is characterized in that the hydrocarbon resin is made of polystyrene, ABS resin, SB resin, AS resin, AES resin, styrene divinylbenzene copolymer, polycarbonate ,
Polyethylene terephthalate, polyarylate, polysulfone, polyethersulfone, polyphenylene sulfide, polyamideimide, polyamide, polyimide, polyether, polyetherketone, polyetheretherketone, polybenzimidazole, etc. are polymers composed of at least carbon and hydrogen. The gas diffusion electrode for a solid polymer electrolyte membrane fuel cell according to any one of claims 1 to 3, and a method for producing the same.

According to the fifth aspect of the present invention, it is possible to provide an effect that a polymer can be produced from a monomer and a proton conductive functional group can be introduced.

[0025]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings.

The present invention relates to a catalyst layer of a gas diffusion electrode for a polymer electrolyte fuel cell comprising a catalyst-carrying carbon particle, a proton conductive material or, if necessary, a polytetrafluoroethylene as a water repellent material. After mixing and dispersing in the catalyst layer a monomer of a compound having a proton-conductive functional group introduced into a hydrocarbon-based resin, the polymer is polymerized to have a high molecular weight, thereby producing a three-phase interface as an electrode reaction site. In order to secure a continuous proton conduction path while securing more, the characteristics of the electrode are improved. As a result, the invention is capable of significantly improving the output performance of a fuel cell combined with this electrode.

This gas diffusion electrode is a gas diffusion electrode characterized in that a compound obtained by introducing a proton conductive functional group into a hydrocarbon resin is contained in the catalyst layer.

The method for producing a gas diffusion electrode is the same as the method for producing a gas diffusion electrode sandwiching a solid polymer electrolyte membrane of a solid polymer electrolyte membrane fuel cell, except that a proton conductive functional group is introduced into the hydrocarbon resin. The production method includes a step of mixing and dispersing a monomer in the catalyst layer, and a step of polymerizing the monomer to increase the molecular weight.

Further, as another production method, a step of mixing and dispersing a monomer of a hydrocarbon resin in the catalyst layer, a step of polymerizing the monomer and increasing the molecular weight, and introducing a proton conductive functional group into the polymer. Manufacturing process.

Here, an acid group consisting of sulfonic acid, carboxylic acid, phosphonic acid and phosphoric acid is introduced as the proton conductive functional group. Of these, it is preferable to make the sulfonic acid group an essential functional group. Because the proton dissociation constant is high and has the effect of having high proton conductivity, hydrocarbon resins used for the proton conductor include polystyrene, ABS resin, SB resin, AS resin,
AES resin, styrene divinylbenzene copolymer, polycarbonate, polyethylene terephthalate, polyarylate, polysulfone, polyethersulfone, polyphenylene sulfide, polyamide imide, polyamide,
Examples include polymers such as polyimide, polyether, polyether ketone, polyether ether ketone, and polybenzimidazole.

There is no particular limitation on the method for introducing this functional group into the hydrocarbon resin. As shown in the chemical reaction formula in FIG. 4, a monomer having a functional group may be synthesized by polymerizing a monomer to form a polymer resin and then introducing a functional group.
It is preferable to synthesize a polymer resin having a functional group by introducing a functional group into a resin monomer and then polymerizing the resin as shown in the chemical reaction formula in FIG.

The reason is that it is easier to introduce a functional group into a monomer than into a polymer.

The method for forming the proton conductor in the catalyst layer is not particularly limited. After mixing and dispersing the resin monomer in the catalyst layer components such as catalyst-supporting carbon particles, a catalyst layer is formed, and the monomer is polymerized to have a high molecular weight, or the resin monomer is coated on the formed catalyst layer. Alternatively, the monomer may be polymerized to have a high molecular weight.

Example 1 As shown in FIG. 1 (a), the concentration of polyterafluoroethylene (PTFE) particles was 6%.
0% dispersion liquid (Daikin Industries,
POLYFLOND1 grade) with PTFE concentration of 15
It was diluted with water to give a weight%. Thickness 1 in this solution
80 μm carbon paper CP (Toray, Inc., T
GP-060).

Subsequently, the carbon paper CP was taken out of the solution and dried in the air at 80 ° C. (FIG. 1B).
Hold at 90 ° C for 60 minutes to sinter PTFE (Fig. 1
(C)) Water-repellent carbon paper was obtained (FIG. 1 (d)).

As shown in FIG. 2, the platinum concentration was 40% by weight.
Platinum-supported carbon (manufactured by Johnson Matthey, HIS
(PEC4000) 15 g of methanol 115 g, water 11
It was uniformly dispersed in 5 g.

Next, 10 g of sodium styrenesulfonate, 1 g of divinylbenzene (DVB) and 0.1 g of azobisisobutyronitrile (ABIN) were added to the solution, mixed and dispersed to obtain a catalyst paste (FIG. 2). . The above chemical reaction formula is represented by the reaction shown in FIG.

This catalyst paste was applied to water-repellent treated carbon paper by a doctor blade method so that the amount of platinum carried was 0.2 m.
The catalyst layer was formed so as to be g / cm2. Subsequently, after air-drying, the temperature was maintained at 80 ° C. × 8 hours to polymerize the monomer. Next, after washing several times with water, the resultant was immersed in a 0.5 mol / l aqueous solution of sulfuric acid to exchange sulfonic acid groups into H-type, thereby obtaining a gas diffusion electrode (FIG. 1 (e)).

A polymer electrolyte membrane obtained by the following method was sandwiched between the gas diffusion electrodes, and was placed at 150 ° C., 8 MPa,
By hot pressing for 5 minutes, a membrane electrode assembly was produced.

After irradiating a 50 μm-thick poly (ethylene-tetrafluoroethylene) film with 20 kGy γ-rays in nitrogen at room temperature, the film was treated with styrene monomer:
By immersing in a mixed solution of divinylbenzene: xylene = 95: 5: 30 (volume part) at 60 ° C. for 2 hours, a styrene chain was grafted on poly (ethylene-tetrafluoroethylene). After drying the film, the film was immersed in a mixture of 30 parts by volume of chlorosulfonic acid and 100 parts by volume of 1,2-dichloroethane at 50 ° C. for 1 hour. The dried membrane was washed with fresh deionized water at 90 ° C. for 2 hours. The chemical formula of the membrane (polystyrene sulfonic acid graft-poly (ethylene-
Tetrofluoroethylene)) is shown in FIG.

Next, this membrane electrode assembly was assembled into a single fuel cell and evaluated for power generation. Evaluation conditions were cell temperature 75 ° C,
Using air as oxidant gas and pure hydrogen as fuel gas,
The utilization rates were 40% and 80%, respectively, and the gas pressure was both supplied at 0.25 MPa. At this time, water vapor was supplied to the oxidizing gas at a molar ratio to the air amount of 0.04 and the fuel gas was supplied to the hydrogen gas at a molar ratio of 0.22 to the hydrogen gas amount for humidification. FIG. 5 shows the evaluation results.

(Example 2) 15 g of platinum-supported carbon same as in Example 1 was mixed with 115 g of isopropyl alcohol and 11 g of water.
The catalyst layer uniformly dispersed in 5 g of the catalyst layer was formed on the same water-repellent carbon paper as in Example 1 by the same method as in Example 1 so as to have the same amount of platinum.

Subsequently, a solution prepared by adding 10 g of sodium styrenesulfonate, 1 g of divinylbenzene, and 0.1 g of azobisisobutyronitrile to 100 g of methanol and mixing and dispersing the mixture was coated on the surface of the catalyst layer formed on the water-repellent carbon paper. Coating and drying were repeated several times. afterwards,
The temperature was maintained at 80 ° C. × 8 hours, and the monomer was polymerized to obtain a gas diffusion electrode.

A membrane / electrode assembly was produced using the same electrolyte membrane and the electrodes as in Example 1 under the same conditions as in Example 1, and the power generation was evaluated under the same evaluation conditions as in Example 1. FIG. 5 shows the evaluation results.

Comparative Example 15 g of platinum-supported carbon and 180 g of a 5% by weight ion-exchange resin solution (SS-1080, manufactured by Asahi Kasei Corporation) as in Example 1 were uniformly dispersed in 24 g of isopropyl alcohol and 24 g of water to form a catalyst paste. I got A catalyst layer was formed on the same water-repellent carbon paper as in Example 1 by the same method as in Example 1 so as to have the same amount of platinum, and a gas diffusion electrode was obtained. The chemical formula of the ion exchange resin is the chemical formula shown in FIG.

The Nafion 112 (Du) was applied to the polymer electrolyte membrane.
(Pont), and hot pressed at 120 ° C., 2 MPa, for 5 minutes to produce a membrane-electrode assembly, and the power generation was evaluated under the same evaluation conditions as in Example 1. FIG. 5 shows the evaluation results.

FIG. 5 is a graph showing the relationship between the output voltage and the current density. As can be seen from this graph, the output voltage of each of Examples 1 and 2 is higher than that of the comparative example. The reason for this is that the characteristics of the electrode can be improved to secure a continuous proton conduction path while securing more three-phase interfaces, which are electrode reaction sites, and as a result, the fuel cost combined with this electrode can be reduced. It is thought that the output performance of the battery is significantly improved.

[0048]

According to a first aspect of the present invention, there is provided a gas diffusion electrode provided with a catalyst layer sandwiching a solid polymer electrolyte membrane of a solid polymer electrolyte membrane fuel cell. Since it is a gas diffusion electrode characterized by containing a compound having introduced a group in the catalyst layer, to ensure a continuous proton conduction path while securing more three-phase interface is an electrode reaction site of the electrode The characteristics can be improved, and as a result, it is possible to provide an electrode for a solid polymer electrolyte membrane fuel cell that can significantly improve the output performance of a fuel cell combined with this electrode at low cost. is there.

Further, a second invention of the present invention relates to a method for producing a gas diffusion electrode sandwiching a solid polymer electrolyte membrane of a solid polymer electrolyte membrane fuel cell, wherein a proton conductive functional group is introduced into the hydrocarbon resin. Mixed monomer into the catalyst layer
A method for producing a gas diffusion electrode for a solid polymer electrolyte membrane fuel cell, which comprises a step of dispersing and a step of polymerizing the monomer to increase the molecular weight; As a result, the characteristics of the electrode can be improved to secure a continuous proton conduction path while securing a larger amount of fuel, and as a result, the output performance of the fuel cell combined with this electrode can be significantly improved at low cost. It is possible to provide a method for producing an electrode for a solid polymer electrolyte membrane fuel cell that can be used. In addition, this manufacturing method has an advantage that a continuous proton conduction path can be formed since the liquid is mixed and dispersed in the catalyst layer and then solidified.

Further, according to a third aspect of the present invention, there is provided a method for manufacturing an electrode sandwiching a solid polymer electrolyte membrane of a solid polymer electrolyte membrane fuel cell, wherein a monomer of a hydrocarbon resin is mixed and dispersed in a catalyst layer. Producing a gas diffusion electrode for a solid polymer electrolyte membrane fuel cell, comprising: a step of polymerizing the monomer to increase the molecular weight; and a step of introducing a proton conductive functional group into the polymer. Since the method is the same as in the second aspect, the characteristics of the electrode can be improved to secure a continuous proton conduction path while securing more three-phase interfaces that are electrode reaction sites, and as a result, It is possible to provide a method of manufacturing an electrode for a solid polymer electrolyte membrane fuel cell, which can significantly improve the output performance of a fuel cell combined with this electrode at a low cost. In addition, this manufacturing method has an advantage that a continuous proton conduction path can be formed since the liquid is mixed and dispersed in the catalyst layer and then solidified.

[Brief description of the drawings]

FIG. 1 is a process chart of a method for producing an electrode for a solid polymer electrolyte membrane fuel cell according to Example 1 of the present invention.

FIG. 2 is a diagram showing a method for producing a catalyst paste of Example 1 of the present invention.

FIG. 3 is a diagram showing a chemical reaction formula of Example 1 of the present invention.

FIG. 4 is a diagram showing a chemical reaction formula according to another embodiment of the present invention.

FIG. 5 is a graph showing the relationship between the output voltage and the current density in Examples 1 and 2 and Comparative Example of the present invention.

FIG. 6 is a diagram showing a chemical formula of an ion exchange resin of a comparative example.

FIG. 7 is a view showing a chemical formula of a polymer electrolyte membrane of Example 1.

[Explanation of symbols]

 CP carbon paper

Claims (5)

[Claims] In a gas diffusion electrode provided with a catalyst layer sandwiching a solid polymer electrolyte membrane of a solid polymer electrolyte membrane fuel cell, a compound obtained by introducing a proton conductive functional group into a hydrocarbon resin is used as the catalyst layer. A gas diffusion electrode comprising: 2. A method for producing a gas diffusion electrode sandwiching a solid polymer electrolyte membrane of a solid polymer electrolyte membrane fuel cell, wherein a monomer obtained by introducing a proton conductive functional group into a hydrocarbon resin is mixed with the catalyst layer. A method for producing a gas diffusion electrode for a solid polymer electrolyte membrane fuel cell, comprising: a step of dispersing; and a step of polymerizing the monomer to increase the molecular weight. 3. A method for producing an electrode sandwiching a solid polymer electrolyte membrane of a solid polymer electrolyte membrane fuel cell, comprising the steps of: mixing and dispersing a monomer of a hydrocarbon resin in a catalyst layer; and polymerizing the monomer. A method for producing a gas diffusion electrode for a solid polymer electrolyte membrane fuel cell, comprising: a step of increasing the molecular weight; and a step of introducing a proton conductive functional group into the polymer. 4. The solid polymer electrolyte membrane according to claim 1, wherein the proton conductive functional group is selected from an acid group consisting of sulfonic acid, carboxylic acid, phosphonic acid, and phosphoric acid. -Type gas diffusion electrode for fuel cell and method for producing the same. 5. The method according to claim 1, wherein the hydrocarbon resin is polystyrene,
ABS resin, SB resin, AS resin, AES resin, styrene divinylbenzene copolymer, polycarbonate, polyethylene terephthalate, polyarylate, polysulfone, polyether sulfone, polyphenylene sulfide, polyamide imide, polyamide, polyimide, polyether, polyether ketone, 2. A polymer comprising at least carbon and hydrogen, such as polyetheretherketone and polybenzimidazole.
4. The gas diffusion electrode for a solid polymer electrolyte membrane fuel cell according to claim 3, and a method for producing the same.