JPH07134994A - Fuel cell electrode and manufacture thereof - Google Patents

Abstract

PURPOSE:To provide a fuel cell electrode capable of maintaining stable performance over a long period of time by enhancing gas seal capability at the end of a ribbed electrode, and provide the manufacturing method of the electrode. CONSTITUTION:A unit cell is formed by arranging a pair of porous ribbed electrodes 1 in which a liquid fuel passing groove 2 and a liquid oxidizing agent passing groove 2 are formed, on both sides of an electrolyte-containing matrix. One end 3 or both ends 3 of the ribbed electrode is or are constituted so that the pore volume of pores having a pore radius of 10mum or more becomes 30% or less. The gas seal structure is obtained by filling a filler 4 in the end 3 of the electrode 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel cell electrode for converting chemical energy of a fuel into electric energy and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, a fuel cell has been known as a device for directly converting the energy of fuel into electric energy. This fuel cell system is usually a reformer that produces hydrogen from fuel, a cell body that directly reacts hydrogen with oxygen in the air to directly convert it into electrical energy, and an orthogonal transformation that converts the generated DC output into AC. It consists of equipment, control equipment that controls the entire system, and other auxiliary equipment.

In a battery body in which hydrogen and oxygen are reacted to directly convert them into electric energy, a single cell consisting of an anode electrode and a cathode electrode is interposed with a separator, and a cooling plate is arranged every several cells to laminate a large number. Composed.

The unit cells are classified into a rib type electrode and a bipolar type.

FIG. 5 is a perspective view schematically showing a unit cell of a fuel cell, which is generally called a ribbed electrode. A pair of porous ribbed electrodes, anode 11 and cathode 12
Is a matrix layer 13 impregnated with an electrolyte such as phosphoric acid
It is placed across. In this case, the fuel flow path 14 and the oxidant flow path 15 are provided on the back surfaces of the anode 11 and the cathode 12.
Are formed respectively. The end portions 3 located outside the flow path through which the fluid of the pair of porous ribbed electrodes passes are
It is wet-sealed by impregnating it with a filler to increase its density and further impregnating it with an electrolyte. Further, the anode 11 and the cathode 12 are arranged such that the fuel flow passage 14 and the oxidant flow passage 15 thereof are orthogonal to each other. On the other hand, a catalyst layer 16 made of platinum or the like is formed on the surface of the anode 11 and the cathode 12 facing the matrix layer 13, so that the electrochemical reaction as described above is promoted.

Next, FIG. 6 schematically shows a unit cell of a fuel cell called a bipolar type. An anode 11 and a cathode 12, which are a pair of porous flat plate electrodes, are arranged with a matrix layer 13 impregnated with an electrolyte such as phosphoric acid interposed therebetween. Further, a unit cell is formed by arranging a porous electrolyte reservoir plate 17 for accumulating the electrolyte in which the fuel flow path 14 and the oxidant flow path 15 are formed, outside the pair of flat plate-shaped electrodes. The ends 3 of the pair of porous flat plate electrodes and the ends 3 of the electrolyte reservoir plate 17 located outside the flow path through which the fluid passes are impregnated with a filler to increase the density, and further impregnated with the electrolyte. It is wet-sealed by. Further, the anode 11 and the cathode 12 are
The fuel flow path 14 and the oxidant flow path 15 are arranged so as to be orthogonal to each other. On the other hand, a catalyst layer 16 made of platinum or the like is formed on the surfaces of the anode 11 and the cathode 12 facing the matrix layer 13, so that the electrochemical reaction is promoted.

The fuel cell is constructed by stacking a plurality of unit cells having such a structure with a separator interposed therebetween. Further, such a fuel cell is usually operated under a high pressure of about 200 ° C., and it is desired to maintain stable performance for a long time.

[0008]

However, in the conventional fuel cell, because of its electrode structure, in particular, the end of the ribbed electrode, or in the bipolar type, the end of the flat plate-shaped electrode and the end of the electrolyte reservoir plate are used. Has a problem that a sufficient gas sealing property cannot be obtained. That is, the end portions located outside the flow path through which these gas fluids are formed are each made of a porous member having a pore distribution of several hundredths to several tens of μm, and In order to prevent gas leakage, the gap between the ends is filled with a filler, the atmospheric pore size is changed to micropores, and the micropores are impregnated with an electrolyte such as phosphoric acid, and the surface tension of this phosphoric acid causes The gas is sealed. However, when the fuel cell is operated for a long time, gas gradually leaks from the end of the ribbed electrode, or in the bipolar type, the end of the flat plate-shaped electrode and the end of the electrolyte reservoir plate. There is a possibility that the oxidizer may generate heat or burn due to the mixing, and eventually it becomes impossible to operate.

FIG. 7 is a characteristic diagram showing the pore distribution at the electrode end of the conventional ribbed electrode and the cumulative pore volume with respect to the total pore volume. As shown in FIG. 7, the conventional pore distribution at the electrode end has a large peak at a pore radius of 10 μm or more. That is, the gas leak has a pore radius of 10 μm.
It was found that a large number of large pores of m or more remained, and the seal broke from that portion and leaked.

The present invention has been proposed in order to solve the above problems of the prior art, and its purpose is to:
A highly reliable fuel cell electrode that can maintain stable performance for a long time by improving the gas sealability between the end of the ribbed electrode or the end of the plate electrode and the end of the electrolyte reservoir plate in the bipolar type. And a method for manufacturing the same.

[0011]

According to a first aspect of the present invention, a matrix containing an electrolyte is formed by forming a catalyst layer on a pair of porous ribbed electrodes in which liquid fuel and liquid oxidizer flow channels are formed. In the electrodes of the fuel cell in which the unit cells are formed by sandwiching the electrodes, the ends of the ribbed electrodes located outside the groove through which the fluid passes are wet-sealed by the electrolyte,
And, the pores of 10 μm or more in that part should be 3 of the total pore volume.
It is characterized by being 0% or less.

According to a second aspect of the present invention, a catalyst layer is formed on a pair of porous flat plate electrodes, the pair of porous flat plate electrodes are formed with a matrix interposed therebetween, and the pair of porous flat plate electrodes are formed. In the electrode of a fuel cell in which a unit cell is formed by arranging a porous electrolyte reservoir plate for accumulating an electrolyte in which liquid fuel and liquid oxidant flow channels are formed outside a flexible flat electrode The end portion of the electrode substrate and the end portion of the electrolyte reservoir plate located outside the groove through which the fluid passes are wet-sealed by the electrolyte, and the pores of 10 μm or more in that portion are set to 30% or less of the total pore volume. Characterize.

According to a third aspect of the present invention, the end portion of the ribbed electrode located outside the groove through which the fluid passes, is a solution in which a filler having a predetermined concentration is dispersed in a solvent. 10
The method is characterized in that pores having a size of μm or more are impregnated so as to be 30% or less of the total pore volume, and only the solvent in the solution is removed after impregnation.

According to a fourth aspect of the present invention, the end portion of the flat electrode substrate and the end portion of the electrolyte reservoir plate located outside the groove through which the fluid passes, are a solution in which a filler having a predetermined concentration is dispersed in a solvent, 10 at the edge of the electrolyte reservoir plate
It is characterized in that the impregnation is carried out so as to be 30% or less of the total pore volume of the pores of μm or more, and only the solvent in the solution is removed after the impregnation.

According to a fifth aspect of the present invention, the filler for filling the end of the ribbed electrode, the end of the plate electrode substrate, and the end of the electrolyte reservoir plate is carbon, graphite, fluororesin, metal oxide, or metal. It is characterized by being carbide particles.

[0016]

According to the present invention having the above-mentioned structure, the end portion of the ribbed electrode, or in the bipolar type, the end portion of the flat plate-shaped electrode and the end portion of the electrolyte reservoir plate are entirely formed. Pore radius to pore volume 10μ
By configuring the pore volume ratio of the pores of m or more to be 30% or less, it is possible to reduce the proportion of the large pores that greatly affects the gas leak, and thus it is possible to improve the gas sealing property at the end portion.

If the wettability with phosphoric acid is sufficient, the capillary pressure representing the sealing property is substantially inversely proportional to the pore radius. Therefore, the micropores having a pore radius of less than 10 μm have a high capillary pressure and sufficient phosphoric acid is present due to the capillary phenomenon, so that a sufficient sealing property can be obtained. On the other hand, a large pore with a pore radius of 10 μm or more has a pore radius of 1
Compared with the micropores of less than 0 μm, the capillary pressure is low and the presence of phosphoric acid is insufficient, so the sealing property is insufficient.

When the pore volume of the large pores having a pore radius of 10 μm or more with insufficient sealing property is 30% or less of the total pore volume, the large pores are relatively dispersed. Therefore, even if the wet seal due to phosphoric acid breaks in some of these large pores, the breaking of the wet seal stops only in that part, and it does not lead to a large gas leak, and the sealability is affected. Considered to be few. On the other hand, when the ratio of the pore volume of large pores having a pore radius of 10 μm or more to the total pore volume exceeds about 30%, the large pores are relatively densely present, and thus the large pores are large. It is considered that the mutual connection is likely to occur, the breakage of the wet seal is expanded, and the gas leak is rapidly increased.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Prior to the description of the embodiments of the present invention, the concept of the present invention will be described.

As described above, the wet seal at the end portion changes the atmospheric pore diameter to a fine pore diameter by filling the porous carbon plate serving as the electrode substrate with the filler, and the phosphoric acid is added to the portion having the fine pore diameter. The gas is sealed by the surface tension of the phosphoric acid after being impregnated with an electrolyte such as. However, it was found that the conventional end portion had a large number of large pores remaining, and the seal broke and leaked from that portion. From this, in order to more specifically show the effect of the pore volume with a large pore radius on the total pore volume at the end, the relationship between the ratio of the pore volume with a pore radius of 10 μm or more to the total pore volume at the end and the gas leak amount was investigated. As a result, it was found that when the ratio of the pore volume of pores having a pore radius of 10 μm or more to the total pore volume was 30% or less, sufficient sealing property was obtained and the battery performance was also improved.

An embodiment of the fuel cell according to the present invention will be specifically described below with reference to FIGS.

(1) Structure of the Embodiment (1-a) Structure of Rib Electrode First, FIG. 1 is a perspective view schematically showing a part of the rib electrode. As shown in FIG. 1, the ribbed electrode 1 is composed of a porous member having a pore distribution of several hundredths to several tens of μm, and a flow path 2 through which a fluid of the rib electrode 1 passes. In order to prevent gas leakage from the end portion, the end portion 3 located on the outer side is filled with the filler 4 to change the large pores into minute pores, and phosphoric acid (not shown) or the like is added to the portion of the minute pores. The electrolyte is impregnated, and the gas is wet-sealed by the surface tension of the phosphoric acid. In this case, as the filler 4, for example, carbon, graphite, S
Fluorine resins such as iC and PTFE, heat-resistant and phosphoric acid-resistant fine powders such as metal oxides and metal carbides are used. The end portion 3 is filled with the filling material 4 as described above.
Is configured so that the atmospheric pore diameter is changed to a minute pore diameter, and the ratio of the pore volume of pores having a pore radius of 10 μm or more to the total pore volume is 30% or less.

Then, using the pair of ribbed electrodes 1 having such a structure, a unit cell as shown in FIG. 5 is constituted, and further a fuel cell is constituted.

Similarly, in the bipolar type, the end of the plate electrode and the end of the electrolyte reservoir plate are also several hundredths.
It is composed of a porous member having a pore distribution of tens of μm, and is configured to be wet-sealed by filling the end portion with a filler like the ribbed electrode. In this case, the unit cell shown in FIG. 6 is formed, and further the fuel cell is formed.

(1-b) Method for producing ribbed electrode As an electrode member of a fuel cell, electrical conductivity, thermal conductivity,
Mechanical strength, heat resistance and chemical resistance are required. In order to satisfy these characteristics, a resin is added to carbon fiber, graphite or carbonaceous powder, which is then molded and fired to form a porous ribbed electrode, a bipolar flat plate electrode, or an electrolyte reservoir plate. Is obtained. Therefore, depending on the particle size distribution of the carbon fiber, or the graphite or carbonaceous powder itself, the mixing ratio of these with the resin, the mixed dispersion state of the resin and the carbon fiber, or the graphite or the carbonaceous powder, several hundreds to several tens to several tens are obtained. A porous substrate with a pore distribution of μm is obtained.

As such a manufacturing method, for example, a porous carbon base material having a small pore distribution is used.
This can be obtained by using carbon fibers having a particle diameter as uniform as possible, or graphite or carbonaceous powder, and mixing them with a resin so as to be as uniform as possible.

On the other hand, as the filler, there may be mentioned a method of using fine particles having a uniform particle diameter as much as possible and decreasing the viscosity of the dispersed filler to uniformly fill the filler. An even easier method is to increase the concentration of the filler in the solution in which the filler is dispersed. The most reliable method is to fill a solution having different filler concentrations in several times. For example, when carbon is used as the filler, a solution having a relatively low concentration (about 5 to 40% by weight) is first filled and dried. Next, high concentration (about 40-70% by weight)
The above solution is filled. It is also possible to reverse the filler concentration.

As the filler to be filled in the end portion, in principle, any powder can be used as long as it is heat resistant and phosphoric acid resistant powder, but carbon, graphite and Si are preferable.
Examples thereof include fluororesins such as C and PTFE, metal oxides and metal carbides. It is desirable that the particle diameter of the powder is small, and at least several microns or less is preferable. It is also possible to mix and use several kinds of powders having different particle sizes. The shape of the particles is preferably as spherical as possible. If the particles have the same particle size, the closer they are spherical, the lower the viscosity of the solution, the better the fluidity, and the more uniform the filling.

The ratio of the total pore volume of the large pores to the ribbed electrode portion, or to the end portion of the plate electrode and the end portion of the electrolyte reservoir plate in the ribbed electrode portion, or the bipolar type electrode It is filled so that the gas sealing property is maintained or less. That is, pore radius 10
It is filled so that the ratio of the pore volume of pores of μm or more is 30% or less. This filling method can be any method,
Generally, a method of applying pressure to a solution in which a filler is dispersed in a solvent and filling the end portion of the ribbed electrode is used. Alternatively,
It is also possible to immerse the electrode end portion in a solution in which a filler is dispersed in a solvent to fill it.

After the filling with the filler, it is heated and dried to remove only the solvent. In the case of heat drying, the whole is uniformly heated and gradually heated to dry. In this case, the drying temperature is not lower than the boiling point of the solvent. In addition, in this heating and drying, when heating is performed from only one direction, the filler is unevenly distributed toward the heating surface side as the solvent evaporates, and thus it is desirable to heat from a plurality of directions. Furthermore, when heated and dried rapidly, the filler-containing solution bumps and the filler scatters,
Further, since there is a possibility that air bubbles may remain inside the electrode end portion, it is desirable to perform heat drying so that the temperature rising rate is as low as possible.

(2) Operation of the Embodiment (2-a) Outline of Operation The operation of the ribbed electrode, or the flat plate type electrode of the bipolar type, and the electrolyte reservoir plate configured as described above is as follows. is there. That is, the gas sealability at the electrode end is related to the pore distribution of the ribbed electrode end rather than the average pore diameter. And this gas sealing property is
In particular, it relates to the volume of large pores having a pore radius of 10 μm or more, and when the pore volume having a pore radius of 10 μm or more exceeds 30%, the amount of gas leak increases rapidly. Therefore, the end 3
In the present embodiment in which the ratio of the pore volume having a pore radius of 10 μm or more to the total pore volume is 30% or less, the gas leak amount at the end portion 3 can be suppressed to be low.

(2-b) Comparison of Pore Distribution and Gas Leakage in Example and Conventional Example The operation of the present example as described above will be described in detail with reference to FIG. Here, FIG. 2 is a characteristic diagram showing the pore distribution of the electrode end A of the ribbed electrode of the present embodiment (FIG. 1) and the cumulative pore volume with respect to the total pore volume.

FIG. 2 of the electrode end A of this embodiment and
Compared with FIG. 7 showing the pore distribution of the conventional electrode end B described above, the pore distribution of the conventional electrode end B has a large peak of 10 μm or more with a large pore radius, resulting in a total pore volume. The ratio of the volume of pores having a pore radius of 10 μm or more with respect to is over 30%. On the other hand, the pore distribution of the electrode end portion A in this embodiment is 10 μm with a large pore radius.
The above peaks are extremely small, and as a result, the ratio of the pore volume with a pore radius of 10 μm or more to the total pore volume is 10%.
It is less than that. Also, the electrode ends A, B
The average pore radius of (the average of the integrated values of the pore distribution curve) is
The conventional electrode end B is about twice as large.

When the gas leak amount of these electrode end portions A and B was examined, the gas leak amount of the conventional electrode end portion B was about 130 times that of the electrode end portion A of this embodiment. Also reached. As is clear from a comparison between FIG. 2 and FIG. 7, such a large difference in gas leak amount is not the average pore diameter of the electrode ends A and B, but rather the pore distribution, that is, the pore radius with respect to the total pore volume. Large pore volume has a large effect.

(2-c) Experiment on Relation between Pore Distribution and Gas Leakage In order to more specifically show the influence of the pore volume having a large pore radius on the total pore volume of the electrode end as described above, The relationship between the ratio of the pore volume having a pore radius of 10 μm or more to the total pore volume of No. 3 and the gas leak amount was examined as follows.

That is, first, by using a ribbed electrode having a porosity of about 70%, the voids at the ends of the ribbed electrode are filled with solutions having different filling concentrations, so that the pore volume with a pore radius of 10 μm or more with respect to the total pore volume. Was changed. In this case, carbon powder having a particle diameter of 2 microns or less was used as the filler. Then, a solution in which this carbon was dispersed using water and a small amount of a dispersant was filled in the end portion of the electrode with ribs, dried, and allowed to stand in 200 ° C. phosphoric acid for a whole day and night to be impregnated with phosphoric acid. I checked. At this point, it was confirmed that the pores were impregnated with 60% or more of phosphoric acid. At the same time, the pore distribution was measured with a mercury porosimeter.

From the above experiment, the results shown in FIG. 3 were obtained. Here, FIG. 3 is a graph showing the relationship between the gas leak amount and the ratio of the pore volume having a pore radius of 10 μm or more to the total pore volume of the electrode end of the ribbed electrode. As shown in FIG. 3, when the ratio of the pore volume of the pore radius of 10 μm or more to the total pore volume of the electrode end portion is about 30% or less, the gas leak amount is small, but when it exceeds 30%, the gas leak amount is rapidly increased. There is a tendency to increase.

(2-d) Interpretation of Experimental Results Further, the above experimental results, that is, the relationship between the ratio of the pore volume of large pores having a pore radius of 10 μm or more to the total pore volume at the electrode end and the gas leak amount is as follows. It can be interpreted as follows.

First, in the wet seal of the end portion 3, as described above, the porous carbon plate serving as the electrode substrate is filled with the filler to change the atmospheric pore diameter to the minute pore diameter, and the portion having the minute pore diameter. An electrolyte, such as phosphoric acid, is impregnated in and the gas is sealed by the surface tension of the phosphoric acid.
The sealability of the wet seal having such a principle is
The smaller the pore size at the electrode end, and the better the compatibility between phosphoric acid and the filler, or phosphoric acid and the porous carbon plate that is the electrode substrate, the better. Therefore, ideally, it is desirable to have a uniform micropore diameter.

However, the electrode substrate made of a porous carbon plate or the like actually has a distribution of several hundredths to several tens of μm. On the other hand, if the wettability with phosphoric acid is sufficient, the capillary pressure representing the sealing property is almost inversely proportional to the pore radius. Therefore, the micropores having a pore radius of less than 10 μm have a high capillary pressure and sufficient phosphoric acid is present due to the capillary phenomenon, so that a sufficient sealing property can be obtained. On the other hand, large pores having a pore radius of 10 μm or more have lower capillary pressure and insufficient presence of phosphoric acid as compared with micropores having a pore radius of less than 10 μm, and therefore their sealing properties are insufficient.

When the ratio of the pore volume of large pores having a pore radius of 10 μm or more with insufficient sealing property to the total pore volume is about 30% or less, the large pores are relatively large. Even if the wet seal due to phosphoric acid breaks in some of these large pores because they exist in a dispersed state, the break in the wet seal stops only in that part, and it does not lead to a large gas leak, affecting the sealing performance. Is considered to be small. On the other hand, when the ratio of the pore volume of the large pores having a pore radius of 10 μm or more to the total pore volume exceeds about 30%, the large pores are relatively densely present,
It is considered that if the wet seal due to phosphoric acid breaks in some of these large pores, the connection of the large pores is likely to occur, the breakage of the wet seal expands, and the amount of gas leak increases rapidly.

When the surface of the end portion 3 actually filled with the filling material is observed with a microscope, it is found that pores having a pore radius of 10 μm or more with respect to the total pore volume have a pore volume ratio of about 30% or less. Were dispersed almost uniformly, but in the case of more than 30%, large lumps of pores were observed in some places. The cause of such agglomeration of the pores is that the filling of the filler is not uniform and a sufficient amount of the filler was not supplied to that portion, or the pore distribution itself of the porous carbon plate serving as the electrode substrate was It is considered that this is because of the large deviation of the pores.

(2-e) Comparison of Battery Performance Characteristics between Example and Conventional Example Below, the result of actually manufacturing a unit cell and verifying its gas sealing property will be described. First, as a filler, a solution containing carbon powder having a particle diameter of 2 microns or less is pressurized to fill the voids at the end of the electrode and then dried at a temperature not lower than the boiling point of the solvent to remove the solvent. A ribbed electrode was manufactured. As a result of measuring the pore distribution, the ratio of the pore volume of pores having a pore radius of 10 μm or more to the total pore volume was 3.9% at the anode end and 9.8% at the cathode end. Then, a unit cell was constructed using a pair of electrodes with ribs having such a gas sealing structure.

For comparison, the conventional gas seal structure was used, that is, the ratio of the pore volume of pores having a pore radius of 10 μm or more to the total pore volume was 31% at the anode end and 23% at the cathode end. Other than that, a pair of ribbed electrodes having exactly the same configuration as the ribbed electrode of this example was used to form a unit cell of the same size and shape as the unit cell of this example.

The unit cell according to this embodiment and the unit cell according to the conventional example configured as described above were operated under the same conditions for a long time, and the potential change thereof was investigated. It was confirmed that the voids at the end portions of the ribbed electrodes before the test were filled with phosphoric acid at about 60% or more. Figure 4
It is a figure which shows the electric potential change obtained in this way, and as shown in this FIG. 4, the characteristic curve X1 by a present Example compares with the characteristic curve Y1 of a prior art example, and long-time driving | operation is performed. It can be seen that the battery performance does not deteriorate. This result demonstrates that the gas seal structure of this example is remarkably superior to the conventional example, and since the gas leak amount is small, high battery performance can be maintained for a long time.

(3) Effects of Embodiments As described above, the end of the ribbed electrode having the gas sealing structure according to the present invention, the electrode end of the bipolar plate electrode, or the electrode end of the electrolyte reservoir plate is Since the ratio of the pore volume of pores having a pore radius of 10 μm or more to the total pore volume is 30% or less, the gas sealability can be significantly improved as compared with the conventional one, and as a result, Stable performance can be maintained over time.

It should be noted that the pore radius relative to the total pore volume is 10 μm.
The ratio of the pore volume of pores of m or more is 3 as in this embodiment.
If it is about 0% or less, sufficient sealing property can be obtained, but if further mentioned, 10% or less is more preferable than about 30% or less, and the sealing property becomes more reliable.

(4) Other Examples Although carbon is used as the filler in the above examples, other graphite, fluororesins such as SiC and PTFE, heat resistance and phosphorus resistance such as metal oxides and metal carbides. Needless to say, the same effect can be obtained when an acidic powder is used.

Further, in the above-mentioned embodiment, the method of filling the electrode end portion with the filling material is used.
Any method can be used as long as the ratio of the pore volume of pores having a pore radius of 10 μm or more to the total pore volume is 30% or less, and the same effect as in the case of filling with a filler can be used. Needless to say, can be obtained.

For example, when manufacturing a porous electrode substrate, a large amount of the electrode substrate forming material is previously sprayed on both ends of this electrode substrate and heated under pressure to increase the density of the ends.
Pore radius 1 at the end of the electrode for its total pore volume
It is possible to reduce the proportion of pore volume of pores of 0 μm or more to 30% or less. Further, a carbon plate having a ratio of the pore volume of pores having a pore radius of 10 μm or more to the total pore volume of 30% or less to the end portion of the electrode substrate may be adhered in advance. Alternatively, the ratio of the pore volume of pores with a pore radius of 10 μm or more to the total pore volume is increased by increasing the number of laminated prepregs arranged at both ends of the porous carbon plate from the central portion and heating under pressure to integrate them. It is also possible to configure it to be 30% or less.

[0051]

As described above, according to the present invention, the end of the ribbed electrode, or the end of the electrode of the bipolar plate electrode and the end of the electrolyte reservoir plate are set to have a pore radius of 10 μm or more with respect to the total pore volume. By configuring the pore volume ratio of the pores to be 30% or less, the gas sealability at the electrode end can be significantly improved as compared with the conventional one, so that stable performance can be maintained for a long time. It is possible to obtain a highly reliable fuel cell.

[Brief description of drawings]

FIG. 1 is a view showing an embodiment of a fuel cell according to the present invention, and is a perspective view schematically showing a part of an electrode with ribs in particular.

FIG. 2 is a characteristic diagram showing a pore distribution at an electrode end portion A of the ribbed electrode of FIG. 1 and a cumulative pore volume with respect to a total pore volume.

FIG. 3 is a characteristic diagram showing a relationship between a gas leak amount and a ratio of a pore volume of pores having a pore radius of 10 μm or more with respect to a total pore volume of an electrode end portion of a ribbed electrode.

FIG. 4 shows a change in potential of the unit cell X1 according to the present invention manufactured using the ribbed electrode having the gas seal structure of FIG. 1 during long-term operation and the ribbed electrode having no conventional gas seal structure. The characteristic view which shows the electric potential change in the long-term operation of the unit cell Y1 manufactured by.

FIG. 5 is a perspective view schematically showing a unit cell of a fuel cell using a ribbed electrode.

FIG. 6 is a perspective view schematically showing a unit cell of a bipolar fuel cell.

FIG. 7 is a characteristic diagram showing the pore distribution of the electrode end B of the conventional ribbed electrode and the cumulative pore volume with respect to the total pore volume.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Electrode with rib 2 ... Groove 3 ... Electrode end 4 ... Filler 11 ... Anode 12 ... Cathode 13 ... Matrix layer 14 ... Fuel channel 15 ... Oxidant channel 16 ... Catalyst layer 17 ... Electrolyte reservoir plate

Claims (5)

[Claims] 1. A unit cell is formed by forming a catalyst layer on a pair of porous ribbed electrodes in which liquid fuel and liquid oxidizer flow channels are formed and sandwiching a matrix containing an electrolyte therebetween. In the electrode of the fuel cell, the end portion of the ribbed electrode located outside the groove through which the fluid passes is wet-sealed with an electrolyte, and the pores of 10 μm or more in that portion are 30% or less of the total pore volume. An electrode for a fuel cell, which is characterized in that 2. A catalyst layer is formed on a pair of porous flat plate electrodes, the pair of porous flat plate electrodes are formed with a matrix interposed therebetween, and the pair of porous flat plate electrodes are formed. In the electrode of the fuel cell in which a unit cell is formed by arranging a porous electrolyte reservoir plate for accumulating the electrolyte in which the liquid fuel and the liquid oxidant flow grooves are formed outside the end of the flat electrode substrate. And an end portion of the electrolyte reservoir plate located outside the groove through which the fluid passes are wet-sealed by the electrolyte, and the pores of 10 μm or more in the portion are 30% or less of the total pore volume. Battery electrode. 3. The end portion of the ribbed electrode located outside the groove through which the fluid passes has a solution in which a filler having a predetermined concentration is dispersed in a solvent, and has pores of 10 μm or more at the end portion of the ribbed electrode. A method for producing a fuel cell, which comprises impregnating so as to have a total pore volume of 30% or less, and removing only the solvent in the solution after impregnation. 4. The end portion of the flat electrode substrate and the end portion of the electrolyte reservoir plate located outside the groove through which the fluid passes, the end portion of the electrolyte reservoir plate containing a solution of a filler having a predetermined concentration dispersed in a solvent. The method for producing a fuel cell is characterized in that impregnation is performed so as to be 30% or less of the total pore volume of pores of 10 μm or more in the part, and only the solvent in the solution is removed after impregnation. 5. The filler for filling the end of the ribbed electrode, the end of the flat electrode substrate, and the end of the electrolyte reservoir plate is carbon, graphite, fluororesin, metal oxide,
An electrode for a fuel cell, which is particles of a metal carbide.