JP2003331850A - Electrode and fuel cell using it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrode capable of moderately retaining water in a catalyst layer and to provide a fuel cell using the electrode. <P>SOLUTION: An electrode-membrane assembly 50 is arranged so that a solid polymer electrolyte membrane 1 is interposed between a fuel electrode catalyst layer 2 and an air electrode catalyst layer 3, a gas diffusion layer 4 is closely in contact with the fuel electrode catalyst layer 2, and a gas diffusion layer 6 is closely contacted with the air electrode catalyst layer 3. The gas diffusion layer 6 is comprised of first and second gas diffusion layers 6a, 6b having different water repellency, and the first and second gas diffusion layers 6a, 6b are laminated so that the first gas diffusion layer 6a with higher water repellency is closely contacted with the air electrode catalyst layer 3. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrode applied to a fuel cell or various electrochemical devices that generate electricity by utilizing an electrochemical reaction.

[0002]

2. Description of the Related Art A fuel cell comprises a unit cell in which a pair of electrodes are arranged so as to face each other with an electrolyte in between. A fuel is supplied to one electrode and an oxidant is supplied to the other electrode to form a fuel. It is a device for directly converting chemical energy into electric energy by electrochemically reacting the oxidation of the above in a battery cell. BACKGROUND ART Fuel cells are classified into various types depending on the type of electrolyte, and in recent years, solid polymer fuel cells using a solid polymer electrolyte membrane as an electrolyte have been attracting attention as fuel cells capable of obtaining high output.

FIG. 12 is a sectional view for explaining the structure of an electrode / membrane assembly in a conventional polymer electrolyte fuel cell. In FIG. 12, the solid polymer electrolyte membrane 1 is made of, for example, a perfluorosulfonic acid polymer. And
The fuel electrode catalyst layer 2 is formed on one surface of the solid polymer electrolyte membrane 1, and the air electrode catalyst layer 2 is formed on the other surface of the solid polymer electrolyte membrane 1. Further, the gas diffusion layers 4 and 5 having conductivity and gas permeability are arranged so as to sandwich the solid polymer electrolyte membrane 1 on which the fuel electrode catalyst layer 2 and the air electrode catalyst layer 3 are formed. There is. A conventional solid polymer electrolyte fuel cell is an electrode / membrane formed by laminating the solid polymer electrolyte membrane 1, the fuel electrode catalyst layer 2, the air electrode catalyst layer 3 and the gas diffusion layers 4 and 5 configured as described above. It is configured by stacking a plurality of bonded bodies with a separator having a gas channel formed therebetween.

In the conventional polymer electrolyte fuel cell having such a structure, hydrogen gas (fuel) is used as the gas diffusion layer 4
The oxygen gas (oxidant) is supplied to the fuel electrode catalyst layer 2 via the gas diffusion layer 5 and to the air electrode catalyst layer 3 via the gas diffusion layer 5. Note that oxygen gas is generally supplied as air.
Then, in the fuel electrode catalyst layer 2, hydrogen is oxidized by the following anode reaction to generate protons (hydrogen ions) and electrons. Further, in the air electrode catalyst layer 3, protons that have moved through the fixed polymer electrolyte membrane 1 and reached the air electrode catalyst layer 3, and oxygen gas supplied to the air electrode catalyst layer 3 via the gas diffusion layer 5. , The air electrode catalyst layer 3 through the external circuit
The electrons supplied to the above react with the following cathode reaction to generate water. Then, the electrons generated by this chemical reaction are taken out as a current by an external circuit.

[0005] anode ^{_{reaction: H 2 → 2H + + 2e}} - cathodic ^{reaction: 2H + + 2e - + (} 1/2) O2 → H 2
O

Here, in order for the protons to move (conduct) in the solid polymer electrolyte membrane 1, it is necessary to sufficiently humidify the solid polymer electrolyte membrane 1. The reason for this is that the protons of the sulfonic acid groups present in the solid polymer electrolyte membrane 1 dissociate due to the presence of water and act as good conductors of the protons generated in the fuel electrode catalyst layer 2. To supply water to the solid polymer electrolyte membrane 1, the supply gas is humidified or the water generated in the air electrode catalyst layer 3 is directly used. However, in order to humidify the supply gas, a humidifier such as a bubbler is required outside the battery. Therefore, it is desirable to efficiently humidify the solid polymer electrolyte membrane 1 with the water generated in the air electrode catalyst layer 3. . If the solid polymer electrolyte membrane 1 can be sufficiently humidified only with the water generated in the air electrode catalyst layer 3, an external humidifier will be unnecessary.

In order to efficiently humidify the fixed polymer electrolyte membrane 1 using the water generated in the air electrode catalyst layer 3, a part of the generated water is removed from the air so as not to be released to the outside. It is necessary that the solid polymer electrolyte membrane 1 be retained in the electrode catalyst layer 3 and that the retained water keep the humidity of the solid polymer electrolyte membrane 1 moderate. However, if excessive water stays in the air electrode catalyst layer 3, the diffusion of oxygen supplied through the gas diffusion layer 5 into the air electrode catalyst layer 3 is hindered, and the battery performance deteriorates. Therefore, in order to operate the fuel cell with less humidification from the outside, an appropriate amount of water is retained in the air electrode catalyst layer 3 to such an extent that the diffusion of oxygen into the air electrode catalyst layer 3 is not hindered. Is required.

In the conventional polymer electrolyte fuel cell,
As the gas diffusion layer 5, a water repellent treatment of porous carbon such as carbon paper with PTFE (polytetrafluoroethylene) has been used. However, the water generated in the air electrode catalyst layer 3 is more likely to stay in the air electrode catalyst layer 3 having a lower water repellency than the gas diffusion layer 5 configured in this way, and oxygen diffuses into the air electrode catalyst layer 3. There was a problem that it hindered. Further, a technique has been proposed in which the gas diffusion layer 5 treated with a hydrophilic substance such as silica is used to promptly discharge the water generated in the air electrode catalyst layer 3.
This technique has a problem that the gas diffusion layer 5 is likely to be flooded under a high humidification condition of the reaction gas, while the air electrode catalyst layer 3 is easily dried under a low humidification condition.

[0009]

Since the conventional solid polymer electrolyte fuel cell is constructed as described above, the solid polymer electrolyte membrane 1 is humidified when it is operated under operating conditions where the humidification conditions are not constant. There is a problem that it is difficult to adjust appropriately and the battery performance greatly changes depending on operating conditions. In particular, under low humidification conditions, the internal resistance increases as the fixed polymer electrolyte membrane 1 dries,
Battery performance will drop significantly. Therefore, there is a problem that a humidifier must be provided outside.

The present invention has been made in order to solve the above-mentioned problems, and constitutes a gas diffusion layer by laminating at least two or more divided gas diffusion layers having different contact angles of water, and forming a plurality of gas diffusion layers. The divided gas diffusion layer is laminated on the catalyst layer so that the contact angle of the water becomes gradually smaller in the direction away from the catalyst layer to obtain an electrode capable of appropriately retaining water in the catalyst layer. The purpose is to Further, at least two or more divided gas diffusion layers having different contact angles of water are laminated to form a gas diffusion layer, and the plurality of divided gas diffusion layers are arranged in a direction in which the contact angles of water are separated from the catalyst layer. Using an electrode formed by laminating on the catalyst layer so as to be gradually smaller, while appropriately humidifying the solid polymer electrolyte membrane by efficiently utilizing the water generated in the air electrode catalyst layer under low humidification conditions, An object of the present invention is to obtain a high-performance fuel cell by preventing excessive retention of water in the air electrode catalyst layer under high humidification conditions to prevent gas diffusion to the catalyst.

[0011]

The electrode according to the present invention comprises:
The catalyst layer, and a gas diffusion layer having conductivity, and a plurality of divided gas diffusion layers having different water contact angles, the plurality of divided gas diffusion layers, the contact angle of water is The catalyst layer is laminated so as to be smaller in the direction away from the catalyst layer and is integrally laminated on the catalyst layer.

Further, the plurality of divided gas diffusion layers are configured to have different water repellency, and are stacked so that the water repellency becomes lower in the direction of separating from the catalyst layer and laminated and integrated on the catalyst layer. It is what

The plurality of divided gas diffusion layers have different average pore diameters, and are stacked so that the average pore diameters become larger in the direction away from the catalyst layer. It has been made into.

The plurality of divided gas diffusion layers are made of a carbon material.

Further, the plurality of divided gas diffusion layers in which layers of conductive fine particles are laminated are interposed between adjacent layers.

Further, at least one of a substance having water repellency and a substance having hydrophilicity is mixed in the layer made of the conductive fine particles.

Further, the layer made of the conductive fine particles is divided into a plurality of sections in the surface direction, and the adjacent divided gas diffusion layers are in contact with each other between the sections of the layer made of the conductive fine particles. .

Further, in the fuel cell according to the present invention, the fuel electrode catalyst layer and the air electrode catalyst layer are arranged so as to sandwich the solid polymer electrolyte membrane, and the fuel electrode side gas diffusion layer is in close contact with the fuel electrode catalyst layer. In a fuel cell in which a plurality of single cells constituted by stacking the air electrode side gas diffusion layers in intimate contact with the air electrode catalyst layer are stacked via a separator having a gas flow path, At least one of a laminated body of the fuel electrode side gas diffusion layer and the fuel electrode catalyst layer, and a laminated body of the air electrode side gas diffusion layer and the air electrode catalyst layer is at least one of claims 1 to 7. It is configured by the electrode described in any one of the items.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. Embodiment 1. 1 is a sectional view showing an electrode / membrane assembly of a polymer electrolyte fuel cell according to Embodiment 1 of the present invention. In FIG. 1, the same or corresponding parts as those of the electrode / membrane assembly of the conventional polymer electrolyte fuel cell shown in FIG. 12 are designated by the same reference numerals, and the description thereof will be omitted.

In FIG. 1, in the electrode / membrane assembly 50, the fuel electrode catalyst layer 2 is integrally formed on one surface of the solid polymer electrolyte membrane 1, and the air electrode catalyst layer 3 is formed on the other surface of the solid polymer electrolyte membrane 1. The gas diffusion layers 4 and 6 which are formed integrally with each other and have conductivity and gas permeability are joined and integrated with the solid polymer electrolyte membrane 1 interposed therebetween. And the gas diffusion layer 6
Are the first and second gas diffusion layers 6a, 6 having different water repellency.
b (divided gas diffusion layer) is laminated. Here, the water repellency of the first gas diffusion layer 6a in contact with the air electrode catalyst layer 3 is formed to be higher than that of the second gas diffusion layer 6b and the air electrode catalyst layer 3. That is, the contact angle of water of the first gas diffusion layer 6a is formed larger than that of the second gas diffusion layer 6b and the air electrode catalyst layer 3. This polymer electrolyte fuel cell is configured by stacking a plurality of the electrode / membrane assembly 50 thus configured with a separator having a gas channel formed therebetween.

Next, a method of manufacturing the electrode / membrane assembly 50 will be described. First, an electrode catalyst in which fine particles of noble metal are attached to the surface of carbon black and a solution of a perfluorosulfonic acid-based solid polymer electrolyte (here, a Nafion solution manufactured by Aldrich is used) are mixed to form a catalyst. Make layer ink. Platinum-supporting carbon black (platinum: 50% by weight) was used as the electrode catalyst on the air electrode side, and platinum-ruthenium-supporting carbon black (platinum-ruthenium: 50% by weight) was used as the electrode catalyst on the fuel electrode side.

Then, the aqueous polytetrafluoroethylene dispersion was mixed with carbon paper (here, TGP manufactured by Toray).
(H-120) was soaked, dried, and then baked at 360 ° C. to form the gas diffusion layer 4 that has been subjected to the water repellent treatment. In addition, 100% in aqueous polytetrafluoroethylene dispersion
μm thick carbon paper (here, Toray TGP-
(H-030) was soaked, dried and then baked at 360 ° C. to prepare the first gas diffusion layer 6a which has been subjected to the water repellent treatment.
Similarly, in an aqueous polytetrafluoroethylene dispersion, 2
00μm thick carbon paper (here, Toray TG
(P-H-060 was used) is soaked, dried and baked at 360 ° C. to form the second gas diffusion layer 6b that has been subjected to the water repellent treatment. Here, the water-repellent treatment ratio of the first gas diffusion layer 6a is 3
The proportion of the water repellent treatment of the second gas diffusion layer 6b is 0% by weight and 5% by weight.

Next, the catalyst electrode ink for the fuel electrode is applied to the surface of the gas diffusion layer 4 and the catalyst layer ink for the air electrode is applied to the surface of the first gas diffusion layer 6a by screen printing. Then, the gas diffusion layer 4 and the first gas diffusion layer 6a are heated to dry the catalyst layer ink, and the fuel electrode catalyst layer 2 and the air electrode catalyst layer 3 are respectively formed on the surfaces of the gas diffusion layer 4 and the first gas diffusion layer 6a. To make. Then, the gas diffusion layer 4 and the first gas diffusion layer 4 are arranged so that the fuel electrode catalyst layer 2 and the air electrode catalyst layer 3 are in contact with both surfaces of the polymer electrolyte membrane 1 (here, Nafion 112 membrane manufactured by DuPont is used). 6a are superposed and hot pressed at a temperature near the glass transition point of the solid polymer electrolyte membrane 1 to heat-bond the fuel electrode catalyst layer 2 and the air electrode catalyst layer 3 to the solid polymer electrolyte membrane 1. Then, the second gas diffusion layer 6b is replaced with the first gas diffusion layer 6a.
The electrode / membrane assembly 50 is manufactured by sticking it to the back surface of the electrode.

Next, a single cell prepared to evaluate the performance of the electrode / membrane assembly 50 will be described with reference to FIGS.
Will be described with reference to. Frame-shaped PTFE gaskets 10 and 11 are attached to the outside of the gas diffusion layer 4 and the first and second gas diffusion layers 6a and 6b of the electrode / membrane assembly 50, respectively. The carbon-made separator 12 having the fuel flow path 14 and the carbon-made separator 13 having the air flow path 15 both sides of the electrode / membrane structure 50 integrated with the gaskets 10, 11. The evaluation unit cells 70 are arranged so as to be sandwiched between them. As shown in FIG. 4, the single cell 70 thus configured is connected to the external load 30 and constitutes an evaluation circuit.

Here, a single cell 6 prepared for comparison
0 will be described with reference to FIGS. 5 and 6. First, carbon paper (here, TGP-H-120 manufactured by Toray) was dipped in an aqueous polytetrafluoroethylene dispersion, dried, and baked at 360 ° C. to obtain a water-repellent gas diffusion layer. Make 4 and 5. Then, the catalyst layer inks for the fuel electrode and the air electrode, which are produced in the same manner as the electrode / membrane structure 50 described above, are applied to the surfaces of the gas diffusion layers 4 and 5 by screen printing. Next, the gas diffusion layers 4 and 5 are heated to dry the catalyst layer ink, and the fuel electrode catalyst layer 2 and the air electrode catalyst layer 3 are formed on the surfaces of the gas diffusion layers 4 and 5, respectively. Then, the gas diffusion layers 4 and 5 are superposed so that the fuel electrode catalyst layer 2 and the air electrode catalyst layer 3 are in contact with both surfaces of the polymer electrolyte membrane 1 (here, Nafion 112 membrane manufactured by DuPont was used), The electrode / membrane assembly 61 is hot-pressed at a temperature near the glass transition point of the solid polymer electrolyte membrane 1 to thermally fuse the fuel electrode catalyst layer 2 and the air electrode catalyst layer 3 to the solid polymer electrolyte membrane 1. Is created.

Next, frame-shaped PTFE gaskets 10 and 11 are attached to the outsides of the gas diffusion layers 4 and 5 of the electrode / membrane assembly 61, respectively. Then, the fuel flow path 14
An electrode / membrane structure 61 in which the carbon-made separator 12 in which the gas is formed and the carbon-made separator 13 in which the air flow path 15 is formed are integrated with the gaskets 10 and 11.
Are arranged so as to be sandwiched from both sides, and a single cell 60 for comparison is configured. Single cell 6 configured in this way
As shown in FIG. 6, 0 is connected to the external load 30 and constitutes an evaluation circuit.

In the evaluation circuit thus constructed, the unit cells 70, 60 are kept warm at 80 ° C.
Hydrogen and air humidified by a bubbler (not shown) kept at 75 ° C. were supplied to the air flow path 15 and the air flow path 15, respectively, and the power generation characteristics were measured under normal pressure. The current density was 0.5 A / cm.
^In No. ² , in the single cell 70 according to the present application, a cell voltage of 0.63V was obtained, and in the single cell 60 for comparison, a cell voltage of 0.62V was obtained. In addition, the unit cells 70 and 60 are at 80 °
To keep the temperature of the fuel flow path 14 and the air flow path 15 6
Hydrogen and air humidified by a bubbler kept at 0 ° C. were supplied, and the power generation characteristics were measured at normal pressure.
At 5 A / cm ² , in the single cell 70 according to the present application, it is 0.
A cell voltage of 55 V was obtained, and a cell voltage of 0.52 V was obtained in the single cell 60 for comparison.

As described above, the single cell 70 using the present electrode / membrane assembly 50 has higher battery performance than the comparative single cell 60 using the conventional electrode / membrane assembly 61.
In particular, under low humidification conditions, the difference in battery performance between the single cell 70 and the single cell 60 becomes significant. In this, drainage of water generated in the air electrode catalyst layer 3 to the second gas diffusion layer 6b side through the first gas diffusion layer 6a is blocked by the water repellent action of the first gas diffusion layer 6a. As a result, the water generated in the air electrode catalyst layer 3 stays in the air electrode catalyst layer 3 and the solid electrolyte membrane 1
It is presumed that this is to prevent the dryness of. Further, even in a highly humidified state, high battery performance is maintained because water overflowing from the first gas diffusion layer 6a having high water repellency is smoothly discharged to the second gas diffusion layer 6b having low water repellency. It is presumed that excessive water does not stay in the air electrode catalyst layer 3 and oxygen diffusion into the air electrode catalyst layer 3 is not hindered.

The electrode on the air electrode side according to the first embodiment is formed by laminating the air electrode catalyst layer 3, the first gas diffusion layer 6a, and the second gas diffusion layer 6b. The water repellency of the first gas diffusion layer 6a is higher than that of the second gas diffusion layer 6b and the air electrode catalyst layer 3. Therefore, when the water is appropriately retained in the air electrode catalyst layer 3, the movement of the water moving from the air electrode catalyst layer 3 to the second gas diffusion layer 6b via the first gas diffusion layer 6a is water repellent. It is blocked by the high first gas diffusion layer 6a, and the depletion of water in the air electrode catalyst layer 3, that is, the drying of the air electrode catalyst layer 3 is prevented. On the other hand, when water is excessively retained in the air electrode catalyst layer 3,
Excessive water moves from the air electrode catalyst layer 3 to the first gas diffusion layer 6a. Then, the water retained in the first gas diffusion layer 6a quickly moves to the second gas diffusion layer 6b having low water repellency, and is drained to the outside. Thereby, excessive retention of water in the air electrode catalyst layer 3 is suppressed. That is, the electrode on the air electrode side according to the first embodiment can appropriately retain water in the air electrode catalyst layer 3.

Further, a plurality of electrode / membrane assemblies 50 using the electrodes on the side of the air electrode thus constructed are laminated via the separators 12 and 13 in which the fuel channel 14 and the air channel 15 are formed. In the solid polymer electrolyte fuel cell thus configured, under low humidification conditions, the water produced in the air electrode catalyst layer 3 becomes difficult to be discharged to the second gas diffusion layer 6b, and the air electrode catalyst layer 3 can be prevented from drying. The first gas diffusion layer 6 under high humidification conditions
Excessive water overflowing from a promptly becomes the second gas insulating layer 6b.
And is excessively retained in the air electrode catalyst layer 3. As a result, the decrease in battery performance due to the increase in internal resistance due to the drying of the solid polymer electrolyte membrane 1 is suppressed, and the excessive retention of water in the air electrode catalyst layer 3 prevents the oxygen in the air electrode catalyst layer 3 from being accumulated. A decrease in cell performance due to a decrease in diffusion is suppressed, and a polymer electrolyte fuel cell having high cell performance can be obtained. Furthermore, since the air electrode catalyst layer 3 is prevented from drying under low humidification conditions, a polymer electrolyte fuel cell in which the external humidifier can be made small can be obtained. Finally, it is possible to realize a polymer electrolyte fuel cell that can operate without a humidifier.

In the first embodiment described above, the first and second gas diffusion layers 6a and 6b are treated to be water repellent, but the first gas diffusion layer adjacent to the air electrode catalyst layer 3 is described. It suffices that the contact angle of water of 6a is larger than that of the second gas diffusion layer 6b which is separated from the air electrode catalyst layer 3. For example, the first gas diffusion layer is subjected to water repellent treatment and the second gas diffusion layer is subjected to hydrophilic treatment. May be given. Then, as the hydrophilic treatment, an oxide such as silica is suitable.

Embodiment 2. FIG. 7 is a sectional view showing an electrode / membrane assembly of a polymer electrolyte fuel cell according to Embodiment 2 of the present invention. In FIG. 7, the electrode / membrane assembly 51
The fuel electrode catalyst layer 2 is integrally formed on one surface of the solid polymer electrolyte membrane 1, and the air electrode catalyst layer 3 is formed on the solid polymer electrolyte membrane 1.
The gas diffusion layers 6 and 7 which are integrally formed on the other surface and have conductivity and gas permeability are joined and integrated with the solid polymer electrolyte membrane 1 interposed therebetween. The gas diffusion layer 6 is composed of the first and second gas diffusion layers 6 having different water repellency.
The gas diffusion layer 7 is formed by laminating first and second gas diffusion layers 7a and 7b (divided gas diffusion layers) having different water repellency. Here, the water repellency of the first gas diffusion layer 6a in contact with the air electrode catalyst layer 3 is higher than that of the second gas diffusion layer 6b and the air electrode catalyst layer 3,
The water repellency of the first gas diffusion layer 7a in contact with the fuel electrode catalyst layer 2 is higher than that of the second gas diffusion layer 7b and the fuel electrode catalyst layer 2. The second embodiment is similar to the first embodiment except that the gas diffusion layer 7 on the fuel electrode side is formed by stacking the first and second gas diffusion layers 7a and 7b. It is configured.

Here, the first and second gas diffusion layers 7a,
7b is manufactured similarly to the first and second gas diffusion layers 6a and 6b in the first embodiment. Then, a plurality of the electrode / membrane assembly 51 are laminated with a separator having a gas channel formed therebetween to form a polymer electrolyte fuel cell.

The electrode on the fuel electrode side according to the second embodiment is formed by stacking the fuel electrode catalyst layer 2, the first gas diffusion layer 7a and the second gas diffusion layer 7b. The water repellency of the first gas diffusion layer 7a is higher than that of the second gas diffusion layer 7b and the fuel electrode catalyst layer 2. Therefore, when the water is appropriately retained in the fuel electrode catalyst layer 2, the movement of the water moving from the fuel electrode catalyst layer 2 to the second gas diffusion layer 7b via the first gas diffusion layer 7a is water repellent. It is blocked by the high first gas diffusion layer 7a, and the depletion of water in the fuel electrode catalyst layer 2, that is, the drying of the fuel electrode catalyst layer 2 is prevented. On the other hand, when water is excessively retained in the fuel electrode catalyst layer 2,
Excessive water moves from the fuel electrode catalyst layer 2 to the first gas diffusion layer 7a. Then, the water retained in the first gas diffusion layer 7a quickly moves to the second gas diffusion layer 7b having low water repellency, and is drained to the outside. As a result, excessive retention of water in the fuel electrode catalyst layer 2 is suppressed. The electrode on the air electrode side is configured and operates in the same manner as in the first embodiment.

In the polymer electrolyte fuel cell using this electrode-membrane assembly 51, the water produced in the air electrode catalyst layer 3 moves to the fuel electrode catalyst layer 2 through the polymer electrolyte membrane 1. And stays in the fuel electrode catalyst layer 2. Then, the movement of water moving from the fuel electrode catalyst layer 2 to the second gas diffusion layer 7b via the first gas diffusion layer 7a is blocked by the first gas diffusion layer 7a having high water repellency, and the inside of the fuel electrode catalyst layer 2 is blocked. Depletion of water,
That is, the drying of the fuel electrode catalyst layer 2 is prevented. On the other hand, when water is excessively retained in the fuel electrode catalyst layer 2, excessive water moves from the fuel electrode catalyst layer 2 to the first gas diffusion layer 7a. Then, the water retained in the first gas diffusion layer 7a quickly moves to the second gas diffusion layer 7b having low water repellency, and is drained to the outside. As a result, excessive retention of water in the fuel electrode catalyst layer 2 is suppressed, and diffusion of fuel into the fuel electrode catalyst layer 2 is not hindered. It should be noted that on the air electrode side, the same operation as in the first embodiment is performed.

As described above, in the polymer electrolyte fuel cell according to the second embodiment, the gas diffusion layer 6 on the air electrode side is formed.
In addition, the gas diffusion layer 7 on the fuel electrode side is configured by laminating first and second gas diffusion layers 7a and 7b having different water repellencies, and the water repellency of the first gas diffusion layer 7a is the second gas diffusion layer. 7b
Further, since the water repellency of the fuel electrode catalyst layer 2 is higher than that of the fuel electrode catalyst layer 2, water discharge under the low humidification condition is suppressed even on the fuel electrode side, and the solid polymer electrolyte membrane 1 is reliably prevented from drying under the low humidification condition. it can. Further, also in the polymer electrolyte fuel cell according to the second embodiment, as in the first embodiment, excessive retention of water in the fuel electrode catalyst layer 2 and the air electrode catalyst layer 3 under high humidification conditions is suppressed. As a result, deterioration of gas diffusivity in the fuel electrode catalyst layer 2 and the air electrode catalyst layer 3 is suppressed. Further, the fuel electrode side electrode according to the second embodiment is also configured similarly to the air electrode side electrode, and has the same effect.

In the second embodiment, the gas diffusion layers 6 and 7 on the fuel electrode and air electrode sides are formed by laminating the first and second gas diffusion layers 6a, 6b, 7a and 7b having different water repellency. The gas diffusion layer on the air electrode side is 1
The same effect can be obtained even if the gas diffusion layer on the fuel electrode side is constituted by laminating the first and second gas diffusion layers.

Embodiment 3. In the first embodiment, the water repellency of the first and second gas diffusion layers 6a and 6b is made different, and the contact angle of water between the first and second gas diffusion layers 6a and 6b is changed. However, in the third embodiment, as shown in FIG. 8, the first and second gas diffusion layers 8a and 8b (divided gas diffusion layers) are configured to have different average pore diameters, and the first and second gas diffusion layers 8a and 8b are configured to have different average pore diameters. 2 gas diffusion layers 8a, 8
The contact angle of water in b is changed. The larger the average pore diameter, the smaller the contact angle of water. That is, the larger the average pore diameter, the smaller the surface free energy per unit area and the smaller the contact angle of water.

Here, the characteristic part of the method of manufacturing the electrode / membrane assembly 52 according to the third embodiment will be described. Aqueous polytetrafluoroethylene (PTFE) dispersion was added to 100 μm thick carbon paper (here, Toray T
GP-H-030) was soaked, dried and baked at 360 ° C. to prepare a water repellent carbon paper for the first gas diffusion layer 8a. Similarly, 200 μm thick carbon paper (here, TGP-H-060 made by Toray was used) was dipped in an aqueous polytetrafluoroethylene dispersion, dried and baked at 360 ° C. for water repellent treatment. The second gas diffusion layer 8b is prepared. Where the first and second
Both carbon papers forming the gas diffusion layers 8a and 8b have substantially the same average porosity, and the water repellent treatment (PTFE) ratio of both carbon papers is 15% by weight.

Next, an ink prepared by adding a polytetrafluoroethylene dispersion liquid to carbon black powder and kneading is impregnated into the pores of the carbon paper for the first gas diffusion layer 8a, dried at 110 ° C., and then 360. Baked at ° C. As a result, the first gas diffusion layer 8a having an average pore diameter of half or less of the average pore diameter of the second gas diffusion layer 8b was produced.
The water repellent rate of the impregnated carbon black is 15% by weight, which is the same as the rate of the water repellent treatment of carbon paper.

The first gas diffusion layer 8a thus produced
The catalyst electrode ink for the air electrode is applied to and the catalyst layer ink is dried to form the air electrode catalyst layer 3. In addition, the gas diffusion layer 4
The catalyst electrode ink for the fuel electrode is applied to and the catalyst layer ink is dried to prepare the fuel electrode catalyst layer 2. Then, the gas diffusion layer 4 and the first gas diffusion layer 8a are superposed so that the fuel electrode catalyst layer 2 and the air electrode catalyst layer 3 are in contact with both surfaces of the polymer electrolyte membrane 1, respectively, and the glass transition of the solid polymer electrolyte membrane 1 is performed. By hot pressing at a temperature near the point, the fuel electrode catalyst layer 2 and the air electrode catalyst layer 3 and the solid polymer electrolyte membrane 1 are heat-sealed. Further, the second gas diffusion layer 8b is replaced with the first gas diffusion layer 7a.
The electrode / membrane assembly 52 is manufactured by attaching the electrode / membrane assembly 52 to the back surface of the.

The electrode / membrane assembly 52 thus configured
The single cell manufactured in the same manner as in the first embodiment is connected to the external load 30 using. Then, the single cell is kept warm at 80 ° C., and the fuel flow passage 14 and the air flow passage 15 are each kept at 75 ° C.
Hydrogen and air humidified by a bubbler kept warm were supplied to the reactor, and the power generation characteristics were measured at normal pressure.
A cell voltage of 0.63 V was obtained at A / cm ² . Further, the single cell was kept at 80 ° C., and hydrogen and air humidified by bubblers kept at 60 ° C. were supplied to the fuel flow passage 14 and the air flow passage 15, respectively, and the power generation characteristics were measured at normal pressure. , At a current density of 0.5 A / cm ² , 0.
A cell voltage of 56V was obtained.

As described above, also in the third embodiment, a cell voltage higher than that of the comparative example can be obtained under the low humidification condition and the high humidification condition. The improvement of the battery performance under the low humidification condition is that drainage of water generated in the air electrode catalyst layer 3 to the second gas diffusion layer 8b side through the first gas diffusion layer 8a has a small average pore diameter. It is blocked by the first gas diffusion layer 8a. It is presumed that this causes the water generated in the air electrode catalyst layer 3 to stay in the air electrode catalyst layer 3 and prevent the solid electrolyte membrane 1 from drying. In addition, the battery performance is improved in the high humidification state because water overflowing from the first gas diffusion layer 8a having a small average pore diameter is smoothly discharged to the second gas diffusion layer bb having a large average pore diameter. It is presumed that excessive water does not stay in the electrode catalyst layer 3 and oxygen diffusion into the air electrode catalyst layer 3 is not hindered. Therefore, the third embodiment
Also in the above, the same effect as that of the first embodiment can be obtained.

In the third embodiment, the carbon paper having the same average pore diameter is subjected to the water repellent treatment, and then one carbon paper is subjected to the treatment for reducing the average pore diameter. Carbon paper having different average pore diameters may be used as the carbon paper itself.
In the third embodiment, the water repellent ratios of the first and second gas diffusion layers 8a and 8b are the same, but the water repellent ratio of the first gas diffusion layer 8a is the same as that of the second gas diffusion layer 8.
You may make it higher than the water repellent ratio of b. In this case, in addition to reducing the average pore diameter of the first gas diffusion layer 8a and increasing the water repellency ratio, the water repellency of the first gas diffusion layer 8a becomes even higher (that is, the contact angle of water). Is further increased), the water generated in the air electrode catalyst layer 3 can be reliably blocked, and the applied water can be retained in the air electrode catalyst layer 3. In the third embodiment, the gas diffusion layer 8 on the air electrode side is formed by laminating the first and second gas diffusion layers 8a and 8b having different average pore diameters. Similarly to the above, the gas diffusion layer on the fuel electrode side may be configured by laminating first and second gas diffusion layers having different average pore diameters.

Fourth Embodiment In the electrode / membrane assembly 53 according to the fourth embodiment, as shown in FIG. 9, a binding layer 9a is interposed between the first and second gas diffusion layers 6a and 6b. The other structure is the same as that of the first embodiment.

Now, a method of manufacturing the binding layer, which is a characteristic part of the electrode / membrane assembly 53, will be described. First, a polytetrafluoroethylene dispersion is added to carbon black powder, then dried at 110 ° C. to remove water, and then baked at 360 ° C. Then, the fired body is pulverized into powder. A dispersion in which this powder is dispersed in an organic solvent such as alcohol is applied to the entire one surface of the second gas diffusion layer 6b and dried to form the binding layer 9a.

Then, the gas diffusion layer 4 and the first gas diffusion layer 6a are superposed so that the fuel electrode catalyst layer 2 and the air electrode catalyst layer 3 are in contact with both surfaces of the polymer electrolyte membrane 1, respectively.
Hot pressing is performed at a temperature near the glass transition point of the solid polymer electrolyte membrane 1 to thermally fuse the fuel electrode catalyst layer 2 and the air electrode catalyst layer 3 to the solid polymer electrolyte membrane 1. Further, the first gas diffusion layer 6b is formed so as to sandwich the binding layer 9a.
The electrode / membrane assembly 53 is produced by being attached to the back surface of the gas diffusion layer 7a.

The electrode / membrane assembly 53 thus configured
The single cell manufactured in the same manner as in the first embodiment is connected to the external load 30 using. Then, the single cell is kept warm at 80 ° C., and the fuel flow passage 14 and the air flow passage 15 are each kept at 75 ° C.
Hydrogen and air humidified by a bubbler kept warm were supplied to the reactor, and the power generation characteristics were measured at normal pressure.
A cell voltage of 0.65 V was obtained at A / cm ² . Further, the single cell was kept at 80 ° C., and hydrogen and air humidified by bubblers kept at 60 ° C. were supplied to the fuel flow passage 14 and the air flow passage 15, respectively, and the power generation characteristics were measured at normal pressure. , At a current density of 0.5 A / cm ² , 0.
A cell voltage of 57V was obtained.

As described above, according to the fourth embodiment,
Higher battery performance was obtained as compared with the first embodiment.
This is because the layer of the conductive part particles made of carbon black (the binding layer 9a) is interposed between the first gas diffusion layer 6a and the second gas diffusion layer 6b. It is considered that this is because the contact resistance between the second gas diffusion layer 6b and the second gas diffusion layer 6b was reduced. Furthermore, the average pore diameter of the binding layer 9a is smaller than that of the first and second gas diffusion layers 6a and 6b, and the water repellency is higher than that of the first and second gas diffusion layers 6a and 6b. 2 gas diffusion layer 6
It is presumed that the battery performance is improved, especially under low humidification conditions, because the water that moves to b is strongly blocked.

In the fourth embodiment, the binding layer 9a is interposed between the first and second gas diffusion layers 6a and 6b forming the gas diffusion layer 6 on the air electrode side. As in the second embodiment, the gas diffusion layer on the fuel electrode side may be formed by laminating the first and second gas diffusion layers, and the binding layer 9a may be interposed between the first and second gas diffusion layers. Good.

Embodiment 5. In the fifth embodiment, the binding layer interposed between the first and second gas diffusion layers 6a and 6b has hydrophilicity. The other structure is the same as that of the fourth embodiment.

In the fifth embodiment, a mixed powder of carbon black powder and hydrophilic silica powder is dispersed in an organic solvent such as alcohol, and the dispersion contains the same component solution as the solid polymer electrolyte membrane (for example, Add Aldrich Nafion solution) and mix. The mixed solution is dried at 110 ° C. to remove the solvent component, heat-treated at 130 ° C., and then 36
Bake at 0 ° C. Then, the fired body is pulverized into powder. A dispersion in which this powder is dispersed in an organic solvent such as alcohol is applied to one surface of the second gas diffusion layer 6b and dried to form a hydrophilic bind layer. The solution having the same components as the solid polymer electrolyte membrane functions as a binder for each powder in the binding layer.

Then, the gas diffusion layer 4 and the first gas diffusion layer 6a are superposed so that the fuel electrode catalyst layer 2 and the air electrode catalyst layer 3 are in contact with the both surfaces of the polymer electrolyte membrane 1, respectively.
Hot pressing is performed at a temperature near the glass transition point of the solid polymer electrolyte membrane 1 to thermally fuse the fuel electrode catalyst layer 2 and the air electrode catalyst layer 3 to the solid polymer electrolyte membrane 1. Further, the second gas diffusion layer 6b is attached to the back surface of the first gas diffusion layer 7a so as to sandwich the binding layer, and the electrode / membrane assembly is produced.

A single cell manufactured in the same manner as in the first embodiment using the electrode / membrane assembly thus constructed was connected to the external load 30. Then, the unit cell is kept warm at 80 ° C., and hydrogen and air humidified by bubblers kept at 75 ° C. are supplied to the fuel passage 14 and the air passage 15, respectively,
When the power generation characteristics were measured at normal pressure, the current density was 0.5 A /
A cell voltage of 0.65 V was obtained in cm ² . Further, the single cell was kept at 80 ° C., and hydrogen and air humidified by bubblers kept at 60 ° C. were supplied to the fuel flow passage 14 and the air flow passage 15, respectively, and the power generation characteristics were measured at normal pressure. , 0.55 V at a current density of 0.5 A / cm ² .
The cell voltage was obtained.

As described above, according to the fifth embodiment,
Higher battery performance was obtained as compared with the first embodiment.
This is because the layer of the electrically conductive portion particles (binding layer) made of carbon black is interposed between the first gas diffusion layer 6a and the second gas diffusion layer 6b, and thus the first gas diffusion layer 6a is formed. It is considered that the contact resistance with the second gas diffusion layer 6b was reduced. Furthermore, since the binding layer has hydrophilicity, the binding layer can efficiently absorb the water generated in the air electrode catalyst layer 3 and smoothly drain it to the outside. As a result, it is presumed that air was supplied to the air electrode catalyst layer 3 without interruption, and high performance was maintained.

In the above fifth embodiment, the hydrophilic binding layer is interposed between the first and second gas diffusion layers 6a and 6b forming the gas diffusion layer 6 on the air electrode side. Similarly to the second embodiment, the gas diffusion layer on the fuel electrode side is formed by stacking the first and second gas diffusion layers, and the hydrophilic binding layer is interposed between the first and second gas diffusion layers. You may wear it.

Sixth Embodiment In the sixth embodiment, the bind layer interposed between the first and second gas diffusion layers 6a and 6b has both hydrophilicity and water repellency. The rest of the configuration is the same as in the fourth and fifth embodiments.

In the sixth embodiment, a polytetrafluoroethylene dispersion is added to carbon black powder, then dried at 110 ° C. to remove water, and then baked at 360 ° C. The fired body is pulverized to be powdered to prepare a powder having water repellency. Further, a mixed powder of carbon black powder and hydrophilic silica powder is dispersed in an organic solvent such as alcohol, and a solution having the same components as the solid polymer electrolyte membrane (for example, Nafion liquid manufactured by Aldrich) is added to the dispersion. And mix. This mixed solution is dried at 110 ° C. to remove the solvent component, heat-treated at 130 ° C., and then baked at 360 ° C. The fired body is pulverized and powdered to produce a hydrophilic powder. Next, the water-repellent powder and the hydrophilic powder are mixed in the same amount, and a dispersion liquid obtained by dispersing the mixed powder in an organic solvent such as alcohol is applied to one surface of the second gas diffusion layer 6b and dried. Then, a bind layer having water repellency and hydrophilicity is prepared.

Then, the gas diffusion layer 4 and the first gas diffusion layer 6a are superposed on both sides of the polymer electrolyte membrane 1 so that the fuel electrode catalyst layer 2 and the air electrode catalyst layer 3 are in contact with each other,
Hot pressing is performed at a temperature near the glass transition point of the solid polymer electrolyte membrane 1 to thermally fuse the fuel electrode catalyst layer 2 and the air electrode catalyst layer 3 to the solid polymer electrolyte membrane 1. Further, the second gas diffusion layer 6b is attached to the back surface of the first gas diffusion layer 7a so as to sandwich the binding layer, and the electrode / membrane assembly is produced.

A single cell manufactured in the same manner as in Embodiment 1 was connected to the external load 30 using the electrode / membrane assembly thus constructed. Then, the unit cell is kept warm at 80 ° C., and hydrogen and air humidified by bubblers kept at 75 ° C. are supplied to the fuel passage 14 and the air passage 15, respectively,
When the power generation characteristics were measured at normal pressure, the current density was 0.5 A /
A cell voltage of 0.65 V was obtained in cm ² . Further, the single cell was kept at 80 ° C., and hydrogen and air humidified by bubblers kept at 60 ° C. were supplied to the fuel flow passage 14 and the air flow passage 15, respectively, and the power generation characteristics were measured at normal pressure. , 0.56 V at a current density of 0.5 A / cm ² .
The cell voltage was obtained.

Thus, according to the sixth embodiment,
Higher battery performance was obtained as compared with the first embodiment.
This is because the layer of the electrically conductive portion particles (binding layer) made of carbon black is interposed between the first gas diffusion layer 6a and the second gas diffusion layer 6b, and thus the first gas diffusion layer 6a is formed. It is considered that the contact resistance with the second gas diffusion layer 6b was reduced. Further, since the bind layer has hydrophilicity and water repellency, the water repellent portion of the bind layer blocks the water generated in the air electrode catalyst layer 3 and retains the applied water in the air electrode catalyst layer 3. The hydrophilic portion of the binding layer efficiently absorbs the water generated in the air electrode catalyst layer 3 and smoothly drains the water to the outside. Thus, by balancing both functions, it becomes possible to maintain high battery performance in a wide operating range from low humidification conditions to high humidification conditions.

In the sixth embodiment, the binding layer having water repellency and hydrophilicity is used as the gas diffusion layer 6 on the air electrode side.
The first and second gas diffusion layers 6a and 6b constituting the above are interposed, but like the second embodiment,
The gas diffusion layer on the fuel electrode side may be formed by laminating the first and second gas diffusion layers, and the bind layer having water repellency and hydrophilicity may be interposed between the first and second gas diffusion layers. .

Embodiment 7. In Embodiment 7, the binding layer 9b is divided into a plurality of segments (compartments) and interposed between the first and second gas diffusion layers 6a and 6b as shown in FIGS. There is. In addition,
The other structure is similar to that of the fourth embodiment.

In this Embodiment 7, a polytetrafluoroethylene dispersion is added to carbon black powder, and then dried at 110 ° C. to remove water, and then baked at 360 ° C. Then, the fired body is pulverized into powder.
A dispersion liquid obtained by dispersing the powder in an organic solvent such as alcohol is applied to one surface of the second gas diffusion layer 6b in a state of being divided into a plurality of segments, and dried to form a water-repellent bind layer 9b. As shown in FIG. 11, each of the binding layers 9b is formed into a regular hexagon with each side being 2 mm, and the interval between the segments is 0.5 mm.
Has become.

Then, the gas diffusion layer 4 and the first gas diffusion layer 6a are superposed so that the fuel electrode catalyst layer 2 and the air electrode catalyst layer 3 are in contact with both surfaces of the polymer electrolyte membrane 1, respectively.
Hot pressing is performed at a temperature near the glass transition point of the solid polymer electrolyte membrane 1 to thermally fuse the fuel electrode catalyst layer 2 and the air electrode catalyst layer 3 to the solid polymer electrolyte membrane 1. Furthermore, the first gas diffusion layer 6b is formed so as to sandwich the binding layer 9b.
The electrode / membrane assembly 54 shown in FIG. 10 is produced by being attached to the back surface of the gas diffusion layer 7a. Here, the first and second gas diffusion layers 6a and 6b are in contact with each other in the gap between the segments of the binding layer 9b.

The electrode / membrane assembly 54 thus configured
The single cell manufactured in the same manner as in the first embodiment is connected to the external load 30 using. Then, the single cell is kept warm at 80 ° C., and the fuel flow passage 14 and the air flow passage 15 are each kept at 75 ° C.
Hydrogen and air humidified by a bubbler kept warm were supplied to the reactor, and the power generation characteristics were measured at normal pressure.
A cell voltage of 0.65 V was obtained at A / cm ² . Further, the single cell was kept at 80 ° C., and hydrogen and air humidified by bubblers kept at 60 ° C. were supplied to the fuel flow passage 14 and the air flow passage 15, respectively, and the power generation characteristics were measured at normal pressure. , At a current density of 0.5 A / cm ² , 0.
A cell voltage of 56V was obtained.

As described above, according to the seventh embodiment,
Higher battery performance was obtained as compared with the first embodiment.
This is because the layer of the conductive part particles made of carbon black (the binding layer 9b) is interposed between the first gas diffusion layer 6a and the second gas diffusion layer 6b. It is considered that this is because the contact resistance between the second gas diffusion layer 6b and the second gas diffusion layer 6b was reduced. Further, since the binding layer 9b has water repellency, the binding layer 9b functions to block the water generated in the air electrode catalyst layer 3 and retain an appropriate amount of water in the air electrode catalyst layer 3. Also, the binding layer 9b
The gap between the segments of the
It is presumed that the gas diffusivity became smoother and the battery performance was improved as compared with the case where there were no gaps.

In the seventh embodiment, the binding layer 9b is composed of a plurality of regular hexagonal segments, but the shape of the segments is not limited to regular hexagons, and may be, for example, a circle, a triangle, or a quadrangle. But it's okay. Further, in the above-described seventh embodiment, the binding layer 9b constitutes the first and second gas diffusion layers 6 constituting the gas diffusion layer 6 on the air electrode side.
It is assumed that the gas diffusion layers are provided between a and 6b, but the gas diffusion layers on the fuel electrode side are formed into the first and second gas diffusion layers as in the second embodiment.
The gas diffusion layers may be laminated and configured so that the binding layer 9b is interposed between the first and second gas diffusion layers.

In each of the above embodiments, the gas diffusion layer on the air electrode side (or the fuel electrode side) is formed by laminating two divided gas diffusion layers having different contact angles of water. The number of divided gas diffusion layers to be laminated is not limited to two, and three or more divided gas diffusion layers may be laminated. In this case, the divided gas diffusion layers to be laminated are laminated so that the contact angle of water becomes gradually smaller from the air electrode catalyst layer 3 side toward the outside. Further, considering the complexity of the manufacturing process and the increase of contact resistance due to stacking, the number of stacked layers is preferably 5 or less, and considering the simplification of the structure, it is preferably 3 or less.

If the thickness of the gas diffusion layers on the fuel electrode side and the air electrode side is less than 0.03 mm, the solid polymer electrolyte membrane 1 may be damaged or the separators 12, 1 may be damaged.
3, the gas diffusivity to the portions of the fuel electrode catalyst layer 2 and the air electrode catalyst layer 3 located in the ridge portions of the fuel flow passage 14 and the air flow passage 15 of No. 3 is hindered, which causes a problem that the cell performance is deteriorated. . On the other hand, when the thickness of the gas diffusion layer on the fuel electrode side and the air electrode side is thicker than 0.7 mm, the electrical resistance of the gas diffusion layer increases and the gas diffusivity decreases, which causes a problem that the cell performance decreases. . Therefore, the thickness (t) of the gas diffusion layers on the fuel electrode side and the air electrode side is 0.03.
mm ≦ t ≦ 0.7 mm, preferably 0.05 mm ≦ t ≦ 0.5 mm. The thickness of the divided gas diffusion layer is set so that the gas diffusion layer on the air electrode side (or the fuel electrode side) has a predetermined thickness.

In each of the above embodiments, carbon paper is used as the gas diffusion layer on the fuel electrode side and the air electrode side. However, the material of the gas diffusion layer is not limited to carbon paper, and for example, Carbon cloth,
Porous materials made of other carbon materials such as carbon felt can be used. Further, in consideration of the problem of corrosion, a carbon material is preferable, but it is also possible to use a porous body having other conductivity such as metal.

In each of the above embodiments, the electrode according to the present invention has been described as being applied to a fuel cell. However, the electrode configured in this way is an element utilizing a fuel cell reaction and a reverse reaction, For example, it can be used as an electrode for a dehumidifier, an ozonizer, or the like. Here, the dehumidifier will be described as an example. The dehumidifying element of a dehumidifier is generally arranged such that an anode catalyst layer (for example, platinum black) and a cathode catalyst layer (for example, platinum-supporting carbon black) sandwich a solid polymer electrolyte membrane, and an anode current collector. The platinum-plated titanium mesh as is closely arranged on the outside of the anode catalyst layer, and the carbon porous body as the current collector of the cathode is closely arranged on the outside of the cathode catalyst layer. Is applied to operate. Then, the water introduced into the anode catalyst layer from the space on the anode side is electrolyzed to generate oxygen, hydrogen ions, and electrons. On the cathode side, the hydrogen ions that have moved from the anode catalyst layer through the solid polymer electrolyte membrane to the cathode catalyst layer, the electrons supplied from the external circuit, and the cathode catalyst layer by diffusing in the carbon porous body from the cathode side space The oxygen that has moved to reacts with water to produce water. As a result, the water in the anode side space moves into the cathode side space, and the inside of the anode side space is dehumidified.

Also in this dehumidifying element, it is necessary for the protons present in the solid polymer electrolyte membrane to dissociate due to the presence of water and to act as a good conductor of the protons produced in the anode catalyst layer. That is, an appropriate amount of water needs to stay in the solid polymer electrolyte membrane. And, if the water is excessively retained in the carbon porous body, the diffusivity of oxygen is reduced, and if the water is excessively drained from the carbon porous body to the outside, it causes the drying of the solid polymer electrolyte membrane and deteriorates the dehumidification performance. become. Therefore, by adopting the present electrode structure for the cathode composed of the cathode catalyst layer and the cathode current collector, that is, the cathode current collector is divided into a plurality of current collectors having different contact angles of water, By constituting the cathode by laminating the current collector so that the contact angle of water becomes smaller from the side of the cathode catalyst layer toward the outside, the function and effect of the electrode configuration of the present application are exerted, and the above-mentioned inconvenience is eliminated. The dehumidification performance can be improved.

[0074]

Since the present invention is constituted as described above, it has the following effects.

According to the present invention, the catalyst layer and the gas diffusion layer composed of a plurality of divided gas diffusion layers having conductivity and different water contact angles are provided, and the plurality of divided gas diffusion layers are provided. The layers are laminated and integrated on the catalyst layer so that the contact angle of the water becomes smaller in the direction away from the catalyst layer, so that water can be retained appropriately in the catalyst layer. The electrode can be obtained.

Further, the plurality of divided gas diffusion layers are configured to have different water repellency, and are stacked so that the water repellency becomes lower in the direction of separating from the catalyst layer and laminated and integrated on the catalyst layer. Therefore, the contact angle of water of the divided gas diffusion layer can be easily changed by the water repellent treatment, and the manufacturability of the divided gas diffusion layer is improved.

The plurality of divided gas diffusion layers are constructed so that the average pore diameters are different from each other, and the divided gas diffusion layers are stacked so that the average pore diameters become larger in the direction away from the catalyst layer, and are laminated and integrated on the catalyst layer. As a result, the contact angle of water in the divided gas diffusion layer can be easily changed depending on the average pore diameter, and the manufacturability of the divided gas diffusion layer is improved.

Further, since the plurality of divided gas diffusion layers are made of a carbon material, a stable electrode having excellent corrosion resistance can be obtained.

Further, since the layers composed of the conductive fine particles are interposed between adjacent layers of the plurality of divided gas diffusion layers, the contact resistance between the divided gas diffusion layers is reduced.

Since at least one of the substance having water repellency and the substance having hydrophilicity is mixed in the layer made of the conductive fine particles, the function of blocking or discharging water in the layer made of the conductive fine particles. Can be imparted and water can be appropriately retained in the catalyst layer.

Since the layer composed of the conductive fine particles is divided into a plurality of compartments in the surface direction, and the adjacent divided gas diffusion layers are in contact with each other between the compartments of the layer composed of the conductive fine particles, The layer of water-soluble fine particles has a function of blocking water and a function of discharging water, and water can be appropriately retained in the catalyst layer in a wide range from low humidification to high humidification.

Further, according to the present invention, the fuel electrode catalyst layer and the air electrode catalyst layer are arranged so as to sandwich the solid polymer electrolyte membrane, and the fuel electrode side gas diffusion layer is in close contact with the fuel electrode catalyst layer. A fuel cell comprising a plurality of single cells, which are laminated and in which the air electrode side gas diffusion layer is intimately laminated to the air electrode catalyst layer, are laminated with a separator having a gas flow path interposed therebetween. At least one of a laminated body of the electrode side gas diffusion layer and the fuel electrode catalyst layer and a laminated body of the air electrode side gas diffusion layer and the air electrode catalyst layer is at least one of claims 1 to 7. Since it is constituted by the electrode described in the item 1, the solid polymer electrolyte membrane is appropriately humidified by efficiently utilizing the water generated in the air electrode catalyst layer under the low humidification condition, Excessive retention in the cathode catalyst layer Suppressing the door to prevent the inhibition of gas diffusion into the catalyst, it is possible to obtain a fuel cell performance.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a structure of an electrode / membrane assembly in a polymer electrolyte fuel cell according to Embodiment 1 of the present invention.

FIG. 2 is a plan view illustrating the configuration of a single cell using the electrode / membrane assembly in the polymer electrolyte fuel cell according to Embodiment 1 of the present invention.

FIG. 3 is a cross-sectional view illustrating the configuration of a single cell using an electrode / membrane assembly in the polymer electrolyte fuel cell according to Embodiment 1 of the present invention.

FIG. 4 is an evaluation circuit diagram for evaluating cell characteristics of a single cell using the electrode / membrane assembly in the polymer electrolyte fuel cell according to Embodiment 1 of the present invention.

FIG. 5 is a cross-sectional view illustrating a configuration of a unit cell of a comparative example.

FIG. 6 is an evaluation circuit diagram for evaluating battery characteristics of a single cell of a comparative example.

FIG. 7 is a sectional view showing a structure of an electrode / membrane assembly in a polymer electrolyte fuel cell according to Embodiment 2 of the present invention.

FIG. 8 is a sectional view showing a structure of an electrode / membrane assembly in a polymer electrolyte fuel cell according to a third embodiment of the present invention.

FIG. 9 is a cross-sectional view showing a structure of an electrode / membrane assembly in a polymer electrolyte fuel cell according to a fourth embodiment of the present invention.

FIG. 10 is a sectional view showing a structure of an electrode / membrane assembly in a polymer electrolyte fuel cell according to a seventh embodiment of the present invention.

FIG. 11 is a plan view showing a main part of an electrode / membrane assembly in a polymer electrolyte fuel cell according to a seventh embodiment of the present invention.

FIG. 12 is a cross-sectional view illustrating the structure of an electrode / membrane assembly in a conventional polymer electrolyte fuel cell.

[Explanation of symbols]

1 solid polymer electrolyte membrane, 2 fuel electrode catalyst layer (electrode),
3 air electrode catalyst layer (electrode), 4 gas diffusion layer (electrode),
6 gas diffusion layers (electrodes), 6a first gas diffusion layers (divided gas diffusion layers), 6b second gas diffusion layers (divided gas diffusion layers), 7 gas diffusion layers (electrodes), 7a first gas diffusion layers (division) Gas diffusion layer), 7b second gas diffusion layer (split gas diffusion layer), 8 gas diffusion layer (electrode), 8a first gas diffusion layer (split gas diffusion layer), 8b second gas diffusion layer (split gas diffusion layer) ), 9a, 9b Bind layer (layer made of conductive fine particles), 50, 51, 52, 53, 54 Electrode
Membrane assembly, 70 single cells.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Norio Mitsuda             2-3 2-3 Marunouchi, Chiyoda-ku, Tokyo             Inside Ryo Electric Co., Ltd. (72) Inventor Hideo Maeda             2-3 2-3 Marunouchi, Chiyoda-ku, Tokyo             Inside Ryo Electric Co., Ltd. F-term (reference) 5H018 AA06 AS02 AS03 CC06 DD10                       EE05 HH00 HH04                 5H026 AA06 CC10 EE05 HH04

Claims (8)

[Claims] 1. A catalyst layer and a gas diffusion layer which is composed of a plurality of divided gas diffusion layers having conductivity and different water contact angles, wherein the plurality of divided gas diffusion layers are An electrode which is laminated and integrated on the catalyst layer so that the contact angle of water becomes smaller in the direction away from the catalyst layer. 2. The plurality of divided gas diffusion layers are configured so as to have different water repellency, and are stacked so that the water repellency becomes lower in a direction of separating from the catalyst layer and laminated and integrated on the catalyst layer. The electrode according to claim 1, wherein 3. The plurality of divided gas diffusion layers are configured to have different average pore diameters, and are stacked so that the average pore diameters become larger in the direction away from the catalyst layer and laminated integrally on the catalyst layer. Claim 1 characterized by being made into
Alternatively, the electrode according to claim 2. 4. The electrode according to any one of claims 1 to 3, wherein the plurality of divided gas diffusion layers are made of a carbon material. 5. The method according to claim 1, wherein a layer of conductive fine particles is interposed between adjacent layers of the plurality of divided gas diffusion layers.
The electrode according to the item. 6. The electrode according to claim 5, wherein at least one of a water-repellent substance and a hydrophilic substance is mixed in the layer made of the conductive fine particles. 7. The layer composed of the conductive fine particles is divided into a plurality of compartments in the plane direction, and adjacent divided gas diffusion layers are in contact with each other between the compartments of the layer composed of the conductive fine particles. The electrode according to claim 5 or claim 6. 8. A fuel electrode catalyst layer and an air electrode catalyst layer are arranged so as to sandwich a solid polymer electrolyte membrane, a fuel electrode side gas diffusion layer is laminated in close contact with the fuel electrode catalyst layer, and air In a fuel cell in which a plurality of single cells, each of which is formed by closely stacking an electrode side gas diffusion layer on the air electrode catalyst layer, are stacked via a separator having a gas flow path, At least one of a laminated body with the fuel electrode catalyst layer and a laminated body with the air electrode side gas diffusion layer and the air electrode catalyst layer is described in any one of claims 1 to 7. A fuel cell comprising electrodes.