JPH0620710A - Manufacture of gas diffusion electrode for fuel cell - Google Patents

Abstract

PURPOSE:To efficiently make a gas diffusion electrode by junctioning a specified anode ion exchange film with carbon cloth covered with electrode catalyst, using the anode ion exchange film which has a specified thickness and specified ion exchange capacity. CONSTITUTION:A parfluosulfonic acid copolymer anode ion exchange film 1 has the structure shown by formulae I and II. But, X is H, Na or K, k is 2.1-7.6, m is 3.8-9.3, and l and n are positive numbers. This has a specified thickness at room temperature, and the surface of the film has specified ion exchange capacity. On one side of the exchange film, an electrode catalyst layer 3 is made to serve as an anode by covering the surface of conductive and gas transmitting carbon cloth with a mixture consisting of carbon particles bearing electrode catalysts and polytetrafluoroethylene dispersed liquid, and compression-bonding them. A water-repellent layer is provided similarly to serve as a cathode by covering the opposite side of the carbon cloth 4 provided with an electrode catalyst layer 2 with a mixture consisting of carbon particles and polytetrafluoroethylene dispersed liquid, and compression-bonding them.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a proton transfer type fuel cell (PEMFC, Proton Excha) which uses a hydrogen-containing gas, an oxygen-containing gas and a cation exchange membrane as an electrolyte.
nge Membrane Fuel Cell).

[0002]

2. Description of the Related Art Solid polymer electrolyte fuel cells using a cation exchange membrane as an electrolyte are next to phosphoric acid fuel cells, molten carbonate fuel cells, and solid electrolyte fuel cells. Although it was developed as a fourth type of fuel cell, it has the characteristics that it has a higher output than the fuel cells that have been developed up to that point, and because of its compactness, there is high expectation for practical use, and it is now diligently improved. Is being considered.

This type of fuel cell is a PEMFC (PrFC
Oton Exchange Membrane Fuel Cell) and generally has a structure as shown in the attached FIG. This PEMFC
As the cation exchange membrane, which is the solid polymer electrolyte that forms the heart of the product, a perfluorosulfonic acid type cation exchange membrane is preferred because of its durability, chemical resistance, resistance to oxidative deterioration, and heat stability. However, in order to fully demonstrate the performance of the PEMFC, a combination of the physical properties of the cation exchange membrane and the electrode catalyst layers for the anode and the cathode that are bonded to the membrane surface provide a balanced performance. It is important to get.

As a conventional cation exchange membrane for PEMFC, a commercially available perfluorosulfonic acid type cation exchange membrane is a Nafion membrane manufactured by DuPont, USA, such as Naf.
ion117 (has a hydrogen ion as an ion exchange group (H
Shape), ion exchange capacity 0.909 meq / g dry resin, film thickness about 178 μm) are mainly used, but PEMF
When used for C, there is a problem that the cell voltage becomes low due to high membrane resistance due to low ion exchange capacity and too thick film thickness. Especially, air is used for the cathode of PEMFC. In that case, a sufficient cell voltage cannot be obtained, which is a practical problem.

On the other hand, as shown in FIG. 1, the PEMFC has an electrode catalyst layer for the anode and the cathode and a conductive carbon cloth or carbon paper on the surface of the cation exchange membrane. The performance of the electrocatalyst layer for the cathode is effectively exhibited, resulting in PEMF
In order for the performance of C to be fully exhibited, it is necessary that the cation exchange membrane and the carbon cloth or carbon paper having the anode and cathode electrode catalyst layers are sufficiently integrated. , Therefore a cation exchange membrane,
The method of joining the electrode catalyst layers for the anode and cathode and the carbon cloth or carbon paper is also important. Conventionally, as a method of joining the cation exchange membrane and the electrode catalyst layers for the anode and the cathode, a mixture of an electrode catalyst, particulate carbon and a polytetrafluoroethylene dispersion liquid as a binder of a hydrophobic resin has been prepared in a sheet form in advance. Apply it evenly on a substrate (for example, aluminum foil, polyester film, plastic film such as polyolefin film) and dry it to create a separate electrode catalyst layer on the thin film, and transfer it onto the cation exchange membrane to make it hot. A method of press-bonding with a press or a method of directly applying the mixture onto a cation exchange membrane, drying it, and then press-bonding with a hot press is known. However, in these methods, the softening temperature of polytetrafluoroethylene used as the binder of the hydrophobic resin is considerably higher than that of the cation exchange membrane, and the polytetrafluoroethylene used as the binder of the electrode catalyst, the particulate carbon and the hydrophobic resin is polytetrafluoroethylene. Since it is necessary to raise the temperature used for hot pressing depending on the mixing ratio with the fluoroethylene emulsion, it is difficult to set conditions for hot pressing for pressure bonding, and it is difficult to obtain sufficient bonding. However, there is a problem that the PEMFC is expensive because the number of steps for manufacturing the gas diffusion electrode increases and the cost of the PEMFC increases.

Therefore, there is a need for improvement in the method of joining a carbon cloth or carbon paper coated with a cation exchange membrane, an anode and a cathode electrode catalyst.

[0007]

From the above viewpoints, the present inventor has found that the properties of the cation exchange membrane itself and the carbon cloth or carbon paper coated with the cation exchange membrane, the electrode catalysts for the anode and the cathode are used. As a result of extensive studies on the bonding method, a cation-exchange membrane having a specific thickness and a specific ion-exchange capacity was used, and a carbon cloth coated with a specific cation-exchange membrane and an electrocatalyst for anode and cathode, or PE capable of producing PEMFC having high molar voltage by joining carbon paper
The present invention has been accomplished by finding that the gas diffusion electrode for MFC can be manufactured extremely efficiently.

The present invention is a method for producing a gas diffusion electrode for a solid polymer electrolyte fuel cell having an anode and cathode electrode catalyst layers and a carbon cloth or carbon paper in this order on both sides of a cation exchange membrane. Then, the surface of a carbon cloth or carbon paper having electrical conductivity and gas permeability for the anode is coated with a mixture of carbon particles supporting an electrode catalyst and a polytetrafluoroethylene dispersion, and pressure-bonded to the electrode. In addition to providing the catalyst layer, a carbon cloth or carbon paper on which the electrode catalyst layer is provided separately for the cathode in the same manner as for the anode is provided with carbon particles and polytetrafluorocarbon on the surface opposite to the electrode catalyst layer. A water-repellent layer was formed by coating a mixture consisting of ethylene dispersion and pressure bonding, and Following structural formula consisting perfluorovinyl ether units to ethylene units and a side chain having a sulfonic acid group (1) or (2)

[Chemical 2] (X represents H, Na or K, k is about 2.1 to about 7.6, m is about 3.8 to 9.3, and 1 and n are positive numbers). And has a film thickness of 50-150μ when dried at room temperature.
m, an cation exchange membrane surface having an ion exchange capacity of 0.83 to 1.43 meq / g (dry resin), an electrode catalyst layer provided on the surface of the carbon cloth or carbon paper for the anode and the cathode is A cation exchange membrane and an electrode catalyst layer, which are pressure-bonded together with a carbon cloth or carbon paper so as to be in contact with the cation exchange membrane, and the electrode catalyst layer and the cation exchange membrane are pressure-bonded. A solution of a perfluorosulfonic acid-based copolymer having the above structural formula (1) or (2) on one or both surfaces of the above and having X as an element of the same kind as X of the copolymer of the cation exchange membrane to be used, or A cation exchange membrane is placed by placing a carbon cloth or carbon paper on which the dispersion liquid is covered and the electrode catalyst layers are provided so that the respective joint surfaces are aligned with each other and the cation exchange membrane. A method for producing a solid polymer electrolyte fuel cell gas diffusion electrode and performing the whole was hot pressed at a temperature lower 10 ° C. or higher than the softening temperature of the copolymer.

As the carbon cloth or carbon paper having conductivity and gas permeability used in the present invention, those conventionally used for the production of gas diffusion electrodes for PEMFC can be used, and various carbon fibers can be used. A plain woven fabric of carbon fibers, a non-woven fabric, and a carbon paper made from carbon fibers are produced by the woven fabric method of.
These carbon cloths or carbon papers have 0.2 ~
Those having a thickness of about 0.5 mm and a weight of about 100 to 400 g / m ² can be preferably used.

Preferred commercially available carbon cloths and carbon papers are trading card fabrics (plain woven fabrics) and carbon papers manufactured by Toray Industries, Inc.
6344B (thickness 0.38 mm, 320 g / m ² ), trading card # 6343 (thickness 0.
27 mm, 200 g / m ² ) etc. plain weave carbon fiber cloth, trading card TGP-120
Includes carbon fiber paper (thickness 0.37 mm, 170 g / m ² ). Further, as will be described later, such carbon cloth or carbon paper provided with an electrode catalyst layer is also commercially available.

The electrode catalyst used in the electrode catalyst layer may be one conventionally used in a solid polymer electrolyte fuel cell, and Pt, Rh, Ir, Ru, etc. can be used, but platinum is usually used. For example, fine carbon particles (platinum content is generally about 10 to 20% by weight) coated with a platinum catalyst having a particle size of about 15 to 30 angstroms and having a particle size of about 50 to 100 angstroms are used. Examples of such fine carbon particles coated with a platinum catalyst include Platinum on Vulcan XC-72 or Platinum on Vulca from E-TEK.
As n XC-72R, a catalyst substance supporting 5 to 30% by weight of platinum with respect to carbon particles (diameter of carbon particles is about 100 angstrom, surface area is 100 to 200 g / m ² , platinum particle diameter is about 20 angstrom) is produced, It is sold.

The electrode catalyst layer is in the form of a paste obtained by uniformly mixing the above-mentioned catalyst substance and a dispersion liquid of polytetrafluoroethylene as a binder of the hydrophobic resin or a dispersion liquid of partially reduced polytetrafluoroethylene. It is provided by coating the carbon cloth or carbon paper with the mixture and hot pressing. As a result, the electrode catalyst layer is formed in such a manner that it is embedded in the openings of the carbon cloth or carbon paper. In the case of platinum, the catalyst coating amount is preferably about 0.04 to 0.5 mg / cm ² .

The paste containing the hydrophobic resin is coated as uniformly as possible (the coating amount is 60 to 70 gr paste / m ² (carbon cloth or carbon paper)), and is naturally dried at room temperature to some extent, or immediately under reduced pressure. The thickness of the electrode catalyst layer is related to the amount of platinum catalyst deposited on the carbon cloth or carbon paper, but is usually about 50 to 100 μm.

Polytetrafluoroethylene is usually used as the binder of the hydrophobic resin. The paste-like mixture containing the electrode catalyst and the binder of the hydrophobic resin can be prepared by uniformly mixing the carbon particles supporting the electrode catalyst and the polytetrafluoroethylene dispersion liquid. Usually, the content of polytetrafluoroethylene in a paste composed of carbon particles supporting an electrode catalyst and a polytetrafluoroethylene dispersion is adjusted to about 50% by weight. The hot press conditions can be arbitrarily selected, but usually a temperature of about 290 to 350 ℃, 80 to 15
It can be performed at a pressure of 0 kg / cm ² for about 3 to 60 minutes. The polytetrafluoroethylene dispersion used above can be prepared using water as a dispersion medium and a surfactant as a dispersant, but various polytetrafluoroethylene dispersions are commercially available, and the like. Can be preferably used. These dispersions contain colloidal polytetrafluoroethylene.

Carbon cloth or carbon cloth as described above
Shape the electrocatalyst layer so that it is embedded in the entire
The product is commercially available from E-TEK.
Medium layer thickness of several tens of μm to 100 μm, platinum catalyst adhered
Amount 0.04mg / cm²~ About 0.5mg / cm ² Something is available
is there.

Regarding the carbon cloth or carbon paper used on the cathode side of the PEMFC, in order to prevent water generated on the cathode side from entering the electrode catalyst layer, the carbon cloth or carbon paper is repelled on the surface opposite to the surface on which the electrode catalyst layer is provided. It is necessary to impart water-based property. To impart water repellency, a dispersion of carbon particles (similar to those used to form the electrode catalyst layer but not supporting a catalyst) and polytetrafluoroethylene as a binder for the hydrophobic resin is used. Then prepare a paste-like mixture and coat it on the side opposite to the side where the electrode catalyst layer of carbon cloth or carbon paper is provided,
It can be performed by hot pressing. The hot press conditions may be the same as those for forming the electrode catalyst layer, but the amount of paste may be such that the conductivity and gas permeability are not impaired, and the paste is embedded in the openings of carbon cloth or carbon paper. The amount is sufficient. The electrode catalyst layer formed on the above carbon cloth or carbon paper is pressure-bonded to the following cation exchange membrane.

The cation exchange membrane used in the present invention has a tetrafluoroethylene unit represented by the above structural formula (1) or (2) and a side chain of -SO ₃ H, -SO ₃ K or -SO ₃ Na. It consists of a copolymer composed of perfluorovinyl ether units having groups. This copolymer (K-type and Na-type) film having -SO ₃ K or -SO ₃ Na group in the side chain is tetrafluoroethylene and perfluoro having a sulfonyl fluoride (-SO ₂ F) group at the end of the side chain. It is obtained by treating a membrane of the copolymer obtained by copolymerization of vinyl ether with a mixed solution consisting of an aqueous solution of KOH or NaOH and / or an alcohol solution and / or dimethylsulfoxide. The copolymer (H-type) film having —SO ₃ H in the side chain is obtained by immersing the K-type and Na-type copolymer films in a dilute sulfuric acid aqueous solution.

The ion exchange capacity of the cation exchange membrane obtained above is determined by using tetrafluoroethylene used as a comonomer and a sulfonyl fluoride group (-SO
_It can be changed by changing the copolymerization ratio with the perfluorovinyl ether-based monomer having ₂ F) to carry out polymerization, and modifying the -SO ₂ F group of the side chain of the synthesized copolymer to a sulfonic acid group. Yes, but 0.83-1.43 meq / g
(Dry resin), preferably 0.91 to 1.25 meq / g (dry resin) is used. A sufficiently large ion exchange capacity not only lowers the membrane resistance but also PEMFC
At the same time, the ability of the anode catalyst to move protons to the cathode is improved, the equilibrium water content of the membrane is increased, and the water generated at the cathode is easily back-diffused to the anode side, so that the drying of the membrane during operation of the PEMFC is suppressed. It also has a function and is also effective in improving the conductivity of the film. However, if the ion exchange capacity is too large, the membrane strength will be reduced, and the water content in the membrane will be too large, which is not preferable.

The dry thickness of the cation exchange membrane is 50 to 150 μm.
m, preferably 70-140 μm. The thickness of the cation exchange membrane is an important factor in transferring the water generated on the cathode side to the anode side, and in order to maintain the optimum balanced performance of the PEMFC, it is necessary to select the ion exchange capacity. It is important to select the optimum film thickness.

The carbon cloth or paper provided with the above-mentioned anode and cathode electrode catalyst layers is pressure-bonded to both surfaces of the cation exchange membrane so that the electrode catalyst layers are in contact with the surface of the cation exchange membrane. On the cathode side, a water repellent layer was provided by coating a mixture of carbon particles and a polytetrafluoroethylene dispersion liquid on the surface opposite to the surface coated with an electrode catalyst layer of carbon cloth or carbon paper by pressure bonding and bonding. Use one. The cation exchange membrane and the electrode catalyst layer coated with carbon cloth or carbon paper for the anode and the cathode are bonded to each other by using the above formula (1) on the bonding surface of either or both of the cation exchange membrane and the electrode catalyst layer. Or a solution or dispersion of the perfluorosulfonic acid copolymer having the structure of (2) or (2) is coated, the joint surfaces of both are aligned, and the whole is hot pressed.

At this time, X contained in the perfluorosulfonic acid copolymer having the structure of the above formula (1) or (2) in the solution or dispersion liquid coated on the surface of the electrode catalyst layer.
Is the same element as X contained in the perfluorosulfonic acid copolymer having the structure of the above formula (1) or (2) which constitutes the cation exchange membrane. That is, when X of the sulfonic acid group of the cation exchange membrane is H, H (H type),
If Na is Na (Na type), if K is K (K type)
A solution or dispersion containing the perfluorosulfonic acid copolymer having X as a binder is used. The perfluorosulfonic acid copolymer in the solution or the dispersion may be one in which the kind of the element X matches the kind of the element X of the cation exchange membrane, and the structure thereof is one of the above formulas (1) and (2). One can also be used and need not be consistent with the structure of the cation exchange membrane copolymer. The concentration of the copolymer in the solution or dispersion is preferably about 1 to 5% by weight.

In preparing the above solution or dispersion,
The H-type copolymer solution or dispersion of the perfluorosulfonic acid-based copolymer having the structure of the above formula (1) or (2) is not particularly limited, but is, for example, a solution in a mixed solvent of a lower aliphatic alcohol and water, or It can be prepared as a dispersion, which is about 5% NaOH solution or KO.
Solutions or dispersions of K-type or Na-type perfluorosulphonic acid-based copolymers can be prepared by neutralizing using the stoichiometrically required amount of H solution, respectively. A solution of a perfluorosulfonic acid-based copolymer having the structure of formula (1) or (2) in the H form in a mixed solvent of a lower aliphatic alcohol such as isopropanol and water is commercially available. For example, Aldrich Chemical C
marketed under the name Nafion Solution (mixture of copolymer content 5% by weight in a mixture of 85% by weight lower alcohol and 15% by weight water). Thus, as the binder used when pressure-bonding the electrode catalyst layer to the cation exchange membrane, use a perfluorosulfonic acid-based copolymer solution or dispersion of the same kind as the cation-exchange membrane perfluorosulfonic acid-based copolymer. Can be easily pressure-bonded by hot pressing, and when the copolymer is Na type or K type, the softening temperature of the cation exchange membrane itself can be increased and hot pressing can be performed at high temperature. The adhesiveness and bondability between the exchange membrane surface and the electrode catalyst layer are remarkably improved.

The copolymer solution or dispersion formed as described above is uniformly coated on the surface of the electrode catalyst layer on the carbon cloth or carbon paper to sufficiently remove the solvent in the solution or dispersion. The coating amount of the solution or dispersion is preferably such that the dry film thickness is about 5 to 20 μm. The drying can be carried out under the same conditions as the drying of the electrode catalyst layer, but since the copolymer solution or dispersion is applied thinner than the electrode catalyst layer, there is little risk of swelling and the like and it can be carried out at normal pressure. Then, the coated surface is placed on the surface of the cation exchange membrane, and hot pressing is performed at a temperature lower by 10 ° C. or more than the softening temperature of the cation exchange membrane to obtain an integrated gas diffusion electrode for PEMFC.

As described above, hot pressing is performed from the softening temperature of the copolymer of the cation exchange membrane (measured by the softening temperature test method by thermomechanical analysis of thermoplastic films and sheets specified in JIS K7196-1991). It is carried out at a temperature of at least 10 ° C. or lower, but at a temperature higher than this, water in the copolymer membrane is rapidly vaporized, which is not preferable because sufficient adhesion between the cation exchange membrane and the electrode catalyst layer is ensured. .

The softening temperature of the cation exchange membrane depends on the average molecular weight and the ion exchange capacity of the copolymer constituting the membrane, the equilibrium water content in the membrane, and the like. In the case of the sulfonic acid membrane of the copolymer (2), it is generally in the range of about 100 to 150 ° C. Therefore, in this case, the temperature during hot pressing is at least 140 ° C or lower, preferably 130 ° C or lower. The softening temperature of the K-type or Na-type cation exchange membrane depends on the average molecular weight and ion exchange capacity of the copolymer constituting the membrane and the equilibrium water content in the membrane. Since the sulfonic acid membrane of the copolymer of the above formula (1) or (2) is considered to form an ionic cross-linking type structure, it has a higher softening temperature than that of the H-form, and is generally about 2
It is in the range of 00 to 260 ℃. Therefore, the temperature during hot pressing is at least 250 ° C or lower, preferably 200 ° C or lower.

In the case of the sulfonic acid membrane of the copolymer of the above formula (1) or (2) which is H type, the pressure during hot pressing is
It is at least 80 kg / cm ² or more, preferably 120 kg / cm ² or more, and in the case of K type or Na type, it is at least 120 kg / cm ² or more, preferably 140 kg / cm ² or more. The hot pressing time may vary depending on the pressure, temperature, etc., but is usually several minutes to
It is several tens of minutes, for example, 5 to 60 minutes.

The average molecular weight of the cation exchange membrane used in the present invention is preferably 300,000 to 2.4 million, more preferably 900,000 to 1.2 million, from the viewpoints of mechanical strength and film forming property of the membrane. It is not limited to. The copolymer average molecular weight of the copolymer solution or dispersion is slightly lower or comparable to that of the membrane. Integrated P after hot pressing
The gas diffusion electrode for EMFC can be changed to H type by immersing it in a 5 wt% sulfuric acid aqueous solution at room temperature for about 16 hours when the copolymer film used is K type or Na type.

As shown in FIG. 1, a carbon plate (fine carbon powder and polyvinylidene fluoride powder or low molecular weight polytetrafluorocarbon) was formed on the surface of the carbon cloth or carbon paper opposite to the surface on which the electrode catalyst layer was provided. Fluoroethylene powder is dry blended and molded into a plate shape by hot pressing) 7 and 8. The thickness of the carbon plates of both poles is several mm, and the inner surface has a width of about 1.0 to 1.5 mm for supplying fuel gas and a depth of about 1.0 to 1.
The 2 mm grooves are vertically provided at intervals of about 1.0 to 1.5 mm, and the gas is supplied from the lower side to the upper side. The PEMFC using the gas diffusion electrode manufactured by the method of the present invention can be operated by supplying hydrogen / air or oxygen, and can use a natural gas reformed gas (CO having a hydrogen content of 5 PPM or less as the anode side fuel gas). ₂ / CO ₂ gas), methanol / steam reformed gas (H ₂ / CO ₂ gas with CO less than 5 PPM), hydrogen desorbed from hydrogen storage alloy, CNG reformed gas (hydrogen-containing gas with CO less than 5 PPM) Further, it is also possible to operate by using hydrogen or the like, which is a by-product of salt electrolysis. Incidentally, in PEMFC, when protons move from the anode side to the cathode, about 3 to 5 moles of water are entrained with 1 mole of protons, so that it is necessary to prevent dry up on the anode side of the membrane. It is preferable to supply hydrogen that has been previously absorbed.

The terminal terminals of the anode and the cathode may be provided on any of carbon cloth or carbon paper and carbon plate, and direct current can be taken out from these terminals. The PEMFC using the gas diffusion electrode for PEMFC manufactured by the method of the present invention is suitable for automobiles, submarines, space, on-site power generation, and is an alternative to nickel-cadmium secondary batteries, chlor-alkali. The use of by-product hydrogen for electrolysis and the heating of hot water obtained on the cathode side can be expected to be useful.

[0030]

In the method of the present invention, the perfluorosulfone of the cation exchange membrane is used as a binder when bonding the carbon cloth or carbon paper coated with the anode and cathode electrode catalyst layers to the cation exchange membrane. The use of a perfluorosulfonic acid-based copolymer solution or dispersion of the same type as the acid-based copolymer facilitates the setting of hot press conditions. However, when the copolymer is Na-type or K-type, it can be used positively. The softening temperature of the ion exchange membrane itself becomes high and hot pressing can be performed at a high temperature, and the electrical resistance is remarkably improved by improving the adhesion and bonding between the cation exchange membrane surface and the electrode catalyst layer. PEM that generates high cell voltage
A gas diffusion electrode for PEMFC capable of providing FC can be manufactured. Further, since the electrode catalyst layer coated on the carbon cloth or carbon paper can be bonded to both surfaces of the cation exchange membrane by hot pressing once, the gas diffusion electrode for PEMFC can be manufactured very efficiently. .

[0031]

The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples.

Example 1 H-type membrane of perfluorosulfonic acid type copolymer having the structure of the above formula (1) (dry film thickness 125 μm, ion exchange capacity 1.12 meq / g (dry resin), softening Temperature about 1
40 ° C, average molecular weight about 1 million) was used. On the other hand, 9.9% by weight of a platinum catalyst having a particle size of 5 to 20 angstroms was supported on the surface of carbon particles (Vulcan XC-72 manufactured by E-TEK) having a surface area of about 200 m ² / g and an average particle size of about 100 angstrom. Prepare a paste-like mixture that is a mixture of an electrode catalyst and about 50% by weight polytetrafluoroethylene dispersion and is uniformly mixed so that the polytetrafluoroethylene content is about 50% by weight. Cloth (Toray
Plain woven carbon fiber cloth trading card # 6644B, thickness 0.38 mm, 32
(0 g / m ² ) on the surface with a thickness of about 100 μm, dried, and then hot-pressed at 340 ° C for about 30 minutes to obtain a platinum coverage of about 0.
A carbon cloth (I) coated with an electrode catalyst layer for an anode of 5 mg / cm ² (electrode area) was formed. Separately, on the surface of the carbon cloth (I) coated with the electrode catalyst layer formed in the same manner as above, on the side opposite to the electrode catalyst layer, the carbon particles Vulcan XC-72 not supporting the platinum catalyst and the polytetrafluoroethylene emulsion were formed. A paste-like mixture prepared by uniformly mixing in the same manner as above was applied uniformly to a thickness of about 50 μm, dried, and then hot pressed at 340 ° C. for about 25 minutes to impart water repellency to the surface. A carbon cloth (II) coated with the cathode electrode catalyst layer was obtained. Next, H-form perfluorosulfonic acid copolymer having a structure in which X is H in the above formula (1) in a mixed solvent mainly composed of lower alcohol (ion exchange capacity of about 0.91 meq / g (dry resin), average) Nafion Solution (Al, which is a 5 wt% solution with a molecular weight of about 900,000)
drich Chemical Co.) on the surface of the electrode catalyst layers of the carbon cloths (I) and (II) in a dry film thickness of about 5-10.
It was applied so as to have a thickness of μm and dried. These carbon cloths (I) and (II) and the cation exchange membrane are placed so that the coated surfaces of the carbon cloths (I) and (II) with Nafion Solution are in contact with both surfaces of the cation exchange membrane. 130 ° C, approx. 140
Carbon cloth (I) and hot-pressed for about 60 minutes at kg / cm ²
A gas diffusion electrode for PEMFC was prepared by integrating (II) and a cation exchange membrane. Integrated PEM obtained above
Carbon plates for the anode and cathode are provided on the carbon cloth on both sides of the FC gas diffusion electrode (grooves with a width of 1.2 mm and a depth of 1.2 mm are provided at a distance of 1.2 mm in the vertical direction on the inner surface, and in the vicinity of the grooves. PEMFC (effective electrode area) was obtained by crimping each of the back inside with a passage for supplying cooling water through a gasket made of heat resistant silicone rubber.
12.5cm x 12.5cm). Hydrogen and oxygen were supplied to the PEMFC at 3 atm and 5 atm, respectively, and the PEMFC was operated at 80 ° C. As a result, the following performances were obtained. Cell current density (A / cm ² ) 1.0 2.0 3.0 Cell voltage (Volt) 0.71 0.62 0.51

Example 2 A cation exchange membrane (H type, dry film thickness 125 μm, ion exchange capacity, comprising a copolymer having the structure of the above structural formula (2))
Using 1.33 meq / g (dry resin), softening temperature of about 130 ° C, average molecular weight of about 900,000, a hot press for integrating the carbon cloth coated with the electrode catalyst layer and the cation exchange membrane was performed at a temperature of about 120. An electrode for PEMFC was prepared in the same manner as in Example 1 except that the treatment was carried out at a temperature of about 140 kg / cm ² for about 60 minutes. Further, as a result of forming and operating a PEMFC in the same manner as in Example 1, the following performance was obtained. Cell current density (A / cm ² ) 1.0 2.0 3.0 Cell voltage (Volt) 0.78 0.68 0.58

Example 3 A cation exchange membrane (H type, dry film thickness: 76 μm, ion exchange capacity: 1.) comprising a copolymer having the structure of the above structural formula (1).
Using 12 meq / g (dry resin), softening temperature of about 135 ° C, average molecular weight of about 900,000), a hot press for integrating the carbon cloth coated with the electrode catalyst layer and the cation exchange membrane was performed at a temperature of about 125. A gas diffusion electrode for PEMFC was prepared in the same manner as in Example 1 except that the treatment was carried out at a temperature of about 130 kg / cm ² for about 60 minutes. Further, a PEMFC is formed in the same manner as in Example 1,
As a result of operating in the same manner as in Example 1 except that air was supplied instead of oxygen, the following performance was obtained. Cell current density (A / cm ² ) 1.0 2.0 3.0 Cell voltage (Volt) 0.73 0.63 0.53

Example 4 A cation exchange membrane (Na type, dry film thickness 100 μm, ion exchange capacity) made of a copolymer having the structure of the above structural formula (1).
1.12 meq / g (dry resin), softening temperature about 220 ° C, average molecular weight about 1 million), and the amount of platinum deposited was about 0.2 mg / cm ^2, and Nafion Sol was used instead of Nafion Solution.
Substantially all H of sulfonic acid group contained in ution
Use the one neutralized with 5 wt% NaOH aqueous solution necessary for changing to Na, and use a hot press for integrating the carbon cloth coated with the electrode catalyst layer and the cation exchange membrane at a temperature of about 210 ° C. A diffusion electrode for PEMFC gas was prepared in the same manner as in Example 1 except that the pressure was about 150 kg / cm ² for about 60 minutes. The gas diffusion electrode was immersed in a 5% aqueous solution of sulfuric acid at room temperature for about 16 hours to convert the whole into an H shape. Further Example 1
As a result of operating in the same manner as in Example 1 except that a PEMFC was formed in the same manner as described above and air was supplied instead of oxygen, the following performance was obtained. Cell current density (A / cm ² ) 1.0 2.0 3.0 Cell voltage (Volt) 0.72 0.62 0.52

Example 5 For PEMFC as in Example 1, except that carbon paper (TPG-120 manufactured by Toray Industries, Inc., thickness: 0.37 mm, 170 g / m ² ) was used in place of the carbon cloth trading card # 6644B. The following performance was obtained as a result of making a gas diffusion electrode and forming and operating a PEMFC. Cell current density (A / cm ² ) 1.0 2.0 3.0 Cell voltage (Volt) 0.72 0.62 0.52

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of a proton transfer type solid polymer electrolyte fuel cell using a cation exchange membrane as an electrolyte.

[Explanation of symbols]

1 Perfluorosulfonic Acid Copolymer Cation Exchange Membrane 2 Anode Electrode Catalyst Layer 3 Cathode Electrode Catalyst Layer 4 Anode Carbon Cloth or Paper 5 Cathode Carbon Cloth or Paper 6 Carbon Cloth or Paper Opposite to Electrode Catalyst Layer 7. Water repellent treatment layer coated on 7 Carbon plate with groove for supplying hydrogen-containing gas for anode 8 Carbon plate with groove for supplying oxygen or air for cathode 9 Cooling water supply channel for cathode

Claims (1)

[Claims] 1. A method for producing a gas diffusion electrode for a solid polymer electrolyte fuel cell, comprising an electrode catalyst layer for an anode and a cathode and a carbon cloth or carbon paper on both sides of a cation exchange membrane in this order, Electrode catalyst layer by coating the surface of a carbon cloth or carbon paper having electrical conductivity and gas permeability for an anode with a mixture of carbon particles supporting an electrode catalyst and a polytetrafluoroethylene dispersion and press-bonding the mixture. And for the cathode separately from this,
Similar to the one for the anode, a surface of the carbon cloth or carbon paper opposite to the electrode catalyst layer provided with the electrode catalyst layer is coated with a mixture of carbon particles and a polytetrafluoroethylene dispersion and pressure-bonded. Accordingly, a water repellent layer is provided, and the following structural formula (1) or (2) consisting of a tetrafluoroethylene unit and a perfluorovinyl ether unit having a sulfonic acid group in the side chain is represented by the following formula: (X represents H, Na or K, k is about 2.1 to about 7.6, m is about 3.8 to 9.3, and 1 and n are positive numbers). And has a film thickness of 50-150μ when dried at room temperature.
m, an cation exchange membrane surface having an ion exchange capacity of 0.83 to 1.43 meq / g (dry resin), an electrode catalyst layer provided on the surface of the carbon cloth or carbon paper for the anode and the cathode is A cation exchange membrane and an electrode catalyst layer, which are pressure-bonded together with a carbon cloth or carbon paper so as to be in contact with the cation exchange membrane, and the electrode catalyst layer and the cation exchange membrane are pressure-bonded. A solution of a perfluorosulfonic acid-based copolymer having the above structural formula (1) or (2) on one or both surfaces of the above and having X as an element of the same kind as X of the copolymer of the cation exchange membrane to be used, or A cation exchange membrane is placed by placing a carbon cloth or carbon paper on which the dispersion liquid is covered and the electrode catalyst layers are provided so that the respective joint surfaces are aligned with each other and the cation exchange membrane. The process for producing a solid polyelectrolyte type fuel cell gas diffusion electrode and performing the whole was hot pressed at a temperature lower 10 ° C. or higher than the softening temperature of the copolymer.