JPH09245801A - Polymer solid oxide fuel cell electrode and method for producing the same - Google Patents

Abstract

(57) [Summary] [Objective] To provide a fuel cell having a higher catalyst utilization rate than a conventional fuel cell. [Structure] A fuel cell electrode 5 in which an intermediate layer 4 is provided between a gas diffusion layer 1 and a catalyst layer 2. If the intermediate layer is not present, a part of the catalyst layer enters the pores of the gas diffusion layer, a part of the catalyst is not used for the desired reaction, and further the gas diffusing ability is hindered to lower the reaction efficiency. The presence of the intermediate layer prevents the catalyst layer from entering the gas diffusion layer and improves the catalyst utilization rate. Further, the same effect can be obtained by reducing the porosity of the portion of the gas diffusion layer close to the catalyst layer instead of the intermediate layer. Further, in the catalyst layer, for example, a first catalyst metal having a function of promoting a fuel cell reaction and a second catalyst metal for adsorbing and removing CO in the fuel are present in different types in the thickness direction of the catalyst layer. Also, a fuel cell electrode having both functions can be provided. In order to manufacture this electrode, each suspension of the constituent raw materials can be obtained by coating and firing in a plurality of times.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polymer solid oxide fuel cell electrode and a method for producing the same, and more particularly to the use of the catalyst in the catalyst layer in a fuel cell electrode comprising a catalyst layer and a gas diffusion layer. The present invention relates to the fuel cell electrode with improved efficiency and a method for manufacturing the same.

[0002]

2. Description of the Related Art Fuel cells are high efficiency, pollution-free power generators that use hydrogen and various fossil fuels, and are therefore "post-nuclear" power generators that can deal with energy problems and global pollution problems. , There are great expectations in society. Various fuel cells have been developed for different purposes, such as thermal power alternative power generation, on-site power generation for buildings and factories, or for space. In recent years, the greenhouse effect centered on carbon dioxide and the acid rain caused by NOx, SOx and the like have been recognized as serious pollution threatening the future of the earth. Since one of the major emission sources of these pollutant gases is an internal combustion engine of an automobile or the like, there is a rapid increase in the motivation to use the fuel cell as a motor power source that operates instead of the vehicle-mounted internal combustion engine. In this case, it is desirable that the battery be as small as possible, as is the case with many incidental facilities, and for that purpose, it is essential that the output density and output current density of the battery body be high. Polymer solid oxide fuel cells (hereinafter referred to as PEMFC) using an ion exchange membrane have been attracting attention as promising fuel cell candidates that satisfy this condition.

As shown in FIG. 3, an electrode 3 of a fuel cell comprises a gas diffusion layer (electrode substrate) 1 made of, for example, a carbonaceous material, and a carrier made of carbon black or carbon fiber carrying a catalyst, water or an organic solvent. It is manufactured by applying a suspended paste to a catalyst layer (reaction layer, electrode catalyst layer) 2. Since the reaction of the fuel cell occurs on the catalyst, how to effectively utilize the catalyst is the most important factor that determines the amount of energy obtained by the fuel cell. However, the conventional fuel cells have a drawback in that the utilization rate of the catalyst cannot be maximized for various reasons, and an expensive catalyst, particularly a platinum group metal catalyst, cannot be effectively utilized. As a result of careful consideration of the reason why the catalyst existing in the catalyst layer of the fuel cell cannot be effectively utilized, the present inventors have concluded that the following three points are the main reasons.

The first reason is that the conventional gas diffusion layer has a high porosity of about 60 to 80%, so that the catalyst layer containing the catalyst existing in the portion facing or close to the gas diffusion layer of the catalyst layer is This is because the catalyst permeates or penetrates into the gas diffusion layer at the time of forming the electrode, and a part of the catalyst is substantially present in the gas diffusion layer. This catalyst makes it difficult for the conduction of protons, resulting in the catalyst Cannot contribute to the reaction, and the utilization rate of the catalyst decreases. The second reason is that there is only one type of catalyst in the catalyst layer. For example, PEMFC has a problem that the catalyst of the anode electrode is easily poisoned by CO in the fuel due to its low-temperature operability, and various alloy catalysts have been proposed in the past, which have been proposed as fuel cell catalysts having CO poisoning resistance. Practical applications have been tried, but none of them are sufficient.

The third reason is that the catalyst concentration in the catalyst layer is uniform. Conventionally, the catalyst layer of the polymer solid oxide fuel cell electrode has a catalyst and an ion exchange resin,
Alternatively, it is manufactured by applying a suspension of a catalyst, an ion exchange resin, and a water-repellent resin suspended in a mixed liquid of an organic solvent and water onto an electrode substrate at once, followed by drying and baking. In this method, since the coating is performed at once, the mixed raw material of the catalyst layer cannot be changed in the thickness direction of the catalyst layer, and the optimum catalyst layer cannot be obtained in the thickness direction of the catalyst layer. Most of the reaction of the fuel cell occurs at the interface between the gas diffusion layer and the catalyst layer, and in the catalyst layer of the fuel cell in which the catalyst in the conventional catalyst layer is uniformly dispersed, most of the catalyst located far from the gas diffusion layer undergoes the above reaction. However, the catalyst utilization rate is decreasing. Further, in this method, since the suspension is applied onto the electrode substrate at a time, the catalyst layer becomes thick and a large crack may occur during the drying process.

[0006]

SUMMARY OF THE INVENTION Accordingly, the present invention provides
Further, there is provided an electrode for a polymer solid oxide fuel cell in which the catalyst in the catalyst layer does not enter the gas diffusion layer and loses its catalytic activity. Secondly, the present invention provides an electrode for a polymer electrolyte fuel cell, which has CO poisoning resistance and is active also for the reaction of the fuel cell. Thirdly, the present invention provides an electrode for a polymer electrolyte fuel cell, which has an activity depending on the thickness direction of the catalyst layer.

[0007]

A first aspect of the present invention for solving the above-mentioned problems is to provide a catalyst layer comprising a catalyst and an ion exchange resin, or a catalyst layer comprising a catalyst, an ion exchange resin and a water repellent resin,
In a polymer solid oxide fuel cell electrode formed on a gas diffusion layer, an intermediate layer is provided between the catalyst layer and the gas diffusion layer so that the catalyst layer does not soak into or enter the gas diffusion layer. The polymer solid oxide fuel cell electrode is characterized by being provided with. According to a second aspect of the present invention, in a similar polymer solid oxide fuel cell electrode, the porosity of the gas diffusion layer in the portion where the catalyst layer is close is set to 10 to 50%. It is an electrode for a molecular solid oxide fuel cell.

In a third aspect of the present invention, in the same polymer solid oxide fuel cell electrode, two or more kinds of noble metals or noble metal alloys used as catalysts are different in the thickness direction of the electrode. A polymer solid oxide fuel cell electrode, in particular, an anode electrode, which is characterized by being arranged differently. A fourth aspect of the present invention is the same polymer solid oxide fuel cell electrode, wherein a catalyst and an ion exchange resin, or a catalyst, an ion exchange resin and a water repellent resin are mixed with an organic solvent and water. This is a method for producing an electrode for a polymer electrolyte fuel cell, in which an electrode catalyst layer is formed by repeating a process in which a suspension liquid suspended in a liquid is applied onto an electrode substrate, dried and fired a plurality of times.

Hereinafter, the present invention will be described in detail. Both the first aspect and the second aspect are intended to prevent the catalyst in the catalyst layer from entering the gas diffusion layer and losing the catalytic activity. As described above, the catalyst in the catalyst layer produces a catalytic effect that accelerates the fuel cell reaction only when it is present in the catalyst layer. When it is present in the gas diffusion layer, it inhibits gas diffusion and reacts to the catalyst layer. It has only the function of hindering the supply of gas and the discharge of produced gas. Therefore, if the catalyst existing in the catalyst layer or the catalyst layer itself can be prevented from entering the gas diffusion layer, the utilization rate of the catalyst is surely improved. Therefore, in the present invention, the porosity of the gas diffusion layer in contact with the catalyst layer is suppressed to suppress the invasion of the catalyst, or the catalyst layer and the catalyst layer so as not to soak into or enter the gas diffusion layer. An intermediate layer is formed between the gas diffusion layer and the gas diffusion layer.

The porosity of the gas diffusion layer of a normal fuel cell is about
Although it is 60 to 80%, in the present invention, by lowering the porosity to 10 to 50%, the pore diameter formed in the gas diffusion layer is reduced to prevent the catalyst layer from entering. Porosity 10 ~
The reason for setting it to 50% is that if it is less than 10%, the gas diffusion function, which is the original function of the gas diffusion layer, is impaired, and the supply of reaction gas and the discharge of generated gas cannot be performed smoothly. If it exceeds 50%, the porosity of the ordinary gas diffusion layer becomes almost the same, and the effect of improving the invasion of the catalyst is small. It is sufficient to prevent the invasion of the catalyst only in the portion of the gas diffusion layer which is in contact with the catalyst layer and has a relatively small thickness. For example, the porosity of the gas diffusion layer is made smaller toward the catalyst layer side. It is preferable that the gas diffusion ability of the gas diffusion layer is not impaired.

The size of the porosity can be adjusted by the conditions of hot pressing during the production of the gas diffusion layer, etc. In order to produce the gas diffusion layer having a small porosity, the pressure of the hot press may be increased. . In order to manufacture a gas diffusion layer having a smaller porosity toward the catalyst layer, for example, a plurality of thin gas diffusion layers having different porosities may be prepared and bonded to each other. Next, to provide the above-mentioned intermediate layer,
This is because the intermediate layer has the same function as at least a portion of the gas diffusion layer having a reduced porosity, which is close to the catalyst layer. It is desirable to reduce the porosity so that the catalyst layer does not enter the intermediate layer, but even if a part of the intermediate layer enters the intermediate layer, the reaction does not deteriorate so much, and the intermediate layer directly contacts the catalyst layer and the gas diffusion layer. If this can be prevented, the function can be achieved, and the porosity of the intermediate layer can be set in a wide range of about 10 to 80%, preferably about 20 to 60%. Even if the porosity of the intermediate layer is 80%, the catalyst layer does not directly enter the gas diffusion layer, so that the presence of the intermediate layer greatly reduces the proportion of the catalyst layer that enters the gas diffusion layer. Contribute to improving the rate.

The material of the intermediate layer may be the same as the material of the gas diffusion layer, or may be another material having similar properties.
It is preferably composed of carbon and ion exchange resin or carbon and ion exchange resin and water repellent resin. According to the first and second aspects of the present invention, the catalyst in the catalyst layer of the fuel cell hardly enters the gas diffusion layer and the substantial amount of the catalyst does not decrease, and the effective use thereof can be achieved. The third aspect of the present invention is intended to improve the catalyst utilization rate by maximizing the performance of the catalyst of the catalyst layer by using two or more kinds of noble metals or alloys thereof constituting the catalyst layer. There is. Even the catalysts existing in the same catalyst layer may have different functions depending on their existing positions. In an electrode of a fuel cell, particularly in the anode, the electrode catalyst has a function of promoting the reaction of the fuel cell, and adsorbs CO that is mixed with fuel and supplied to the catalyst to poison the anode and reduce the reaction activity of the anode. Has the function of removing it from the fuel.

For example, a platinum alloy is preferable as the catalyst for the fuel cell reaction, and a platinum catalyst or a ruthenium catalyst is preferable for the CO adsorption. Only one kind of noble metal or its alloy is almost uniformly dispersed in the catalyst layer of the conventional fuel cell electrode, which is effective for the fuel cell reaction and also effective for CO adsorption and removal.
Although various kinds of precious metal alloy catalysts have been explored, no precious metal alloy catalyst satisfying both functions has been found. In the third aspect of the present invention, a plurality of optimum noble metal or noble metal alloy catalysts for each function are used in combination, apart from the conventional basic idea of achieving two or more kinds of functions with this one kind of noble metal or noble metal alloy catalyst. By doing so, a fuel cell catalyst, especially an anode catalyst, which can satisfy all the functions is provided.

For example, promotion of fuel cell reaction and CO in fuel
In the case of an anode for a fuel cell intended to achieve both functions of adsorption removal of CO, a platinum catalyst or a ruthenium catalyst is used on the side of the catalyst layer close to the gas diffusion layer to mainly remove CO in the adsorbed fuel in this catalyst layer. Adsorption and removal is carried out, and a platinum alloy catalyst is used on the side of the catalyst layer close to the membrane to promote the fuel cell reaction in this catalyst layer. That is, the fuel is supplied to the catalyst layer through the gas diffusion layer of the anode, an oxidation reaction of hydrogen gas occurs in the vicinity of the film on the side opposite to the gas diffusion layer of the catalyst layer, and even in the same catalyst layer, the portion near the gas diffusion layer is the film. It does not contribute so much to the oxidation reaction of hydrogen gas that occurs in the vicinity. Therefore, the catalyst metal in the portion of the catalyst layer close to the gas diffusion layer is not so effective for hydrogen gas oxidation but is effective for CO adsorption and removal. For example, when platinum or ruthenium described above is carried, the catalytic effect of the entire anode is obtained. The synergistic effect is that CO in the fuel supplied to the anode can be removed with almost no reduction in CO2. That is, the CO supplied to the anode electrode along with the fuel is first easily adsorbed on the platinum catalyst or the ruthenium catalyst, and therefore is adsorbed on this. When the adsorption equilibrium is reached here, the adsorption progresses to the platinum alloy catalyst, but the CO that reaches the catalyst near the platinum alloy alloy membrane decreases due to the filter effect in the platinum catalyst or ruthenium catalyst region. , CO poisoning rate is reduced. Therefore, the electrode has excellent CO resistance without deteriorating the performance of the catalyst that promotes the fuel cell reaction on the side closer to the membrane.

The type of the noble metal or the noble metal alloy used is not limited to two or more types, but is usually two types, and the cathode may be similarly configured in addition to the anode. The two or more precious metals or precious metal alloys are layered,
That is, the catalyst layers are arranged so that a plurality of noble metals or noble metal alloys exist in the thickness direction. The intermetallic interface does not have to be strictly partitioned, and two or more kinds of noble metals or noble metal alloys may be mixed near the interface. The catalyst layer containing two or more kinds of noble metals or noble metal alloys is prepared by preparing a plurality of catalyst layer precursors containing one kind of noble metal or noble metal alloy and bonding them, or by using only the noble metal or noble metal alloy prepared in advance. It can be produced by applying a suspension containing another noble metal or a noble metal alloy to the surface of the first catalyst precursor containing it and firing it to form a second catalyst precursor.

A fourth aspect of the present invention relates to a method for producing an electrode for a polymer electrolyte fuel cell, in which a catalyst layer without large cracks or a noble metal or its alloy forming the catalyst layer is formed in the layer thickness direction. It is suitable for producing a catalyst layer in which two or more kinds are used or the concentration of one kind of noble metal or noble metal alloy in the thickness direction is changed. A catalyst layer of a conventional fuel cell is produced by coating a suspension supporting a catalyst and a fluororesin on a gas diffusion layer at one time and baking the suspension. The amount of suspension liquid applied at one time on the top increases, distortion due to shrinkage during firing and drying increases, large cracks are likely to occur, and liquid leakage and gas leakage during use as a fuel cell are likely to occur. On the other hand, when the suspension is applied in a plurality of times and baked as in the present invention, the amount of the suspension applied at one time becomes small and the film thickness becomes thin. A catalyst layer that is small and therefore is not prone to large cracks, and that is uniform and has no distortion can be produced.

Further, by applying the suspension liquid using different mixing ratios (compositions) or raw materials a plurality of times, various functions required in the thickness direction of the obtained electrode catalyst layer can be provided. For example, many catalysts can be arranged on the membrane side, or many ion exchange resins can be arranged,
As a result, the effective use of the catalyst, the conduction of protons and the gas diffusion function are improved, and the electrode characteristics are excellent. Further, it is useful, for example, in the production of a catalyst layer having a plurality of noble metals or noble metal alloys, which is the above-mentioned third aspect of the present invention. It is desirable that the number of times of application is 2 to 6 times, and if it exceeds 6 times, the above effect cannot be expected, but the workability is poor and the cost is high.

[0018]

EXAMPLES Examples of the polymer solid oxide fuel cell electrode and the method for producing the same of the present invention will be described together with comparative examples, but these do not limit the present invention.

[Comparative Example 1] 2 g of Pt 50% supported catalyst, 20 g of concentrated solution of 5% ion exchange resin (trade name Nafion) and 6 parts of distilled water
The paste obtained by mixing g in a planetary ball mill for 50 minutes was applied to the gas diffusion layer 1 having a porosity of 80% shown in FIG. 3 by a bar coating method, dried at 60 ° C. for 10 minutes, and further dried at 130 ° C. 20 kg
The catalyst layer 2 was formed by firing at / cm ² for 1 minute to obtain an electrode 3.

[0019]

Example 1 In the same electrode as that of Comparative Example 1, which was composed of the catalyst layer 2 and the gas diffusion layer 1, carbon 2g and ions were previously provided between the catalyst layer 2 and the gas diffusion layer 1 as shown in FIG. 15 g of concentrated solution of 5% solution of exchange resin (trade name Nafion) and distilled water
A paste obtained by mixing 10 g with a planetary ball mill for 50 minutes was interposed, in other words, the paste was applied to the gas diffusion layer 1, dried at 60 ° C for 10 minutes, and baked at 130 ° C, 20 kg / cm ² for 1 minute. Then, the intermediate layer 4 was formed, and then the catalyst layer 2 was formed on the intermediate layer 4 to obtain the electrode 5.

Using the electrode of Comparative Example 1 and the electrode of Example 1 manufactured as described above, the voltage and current density were changed under the conditions of a cell temperature of 80 ° C., hydrogen gas of 2 atm and oxygen gas of 3 atm. When the relationship was measured, the results shown in the graph of FIG. 5 were obtained. As can be seen from this graph, the electrode (Ec) of Example 1
Indicates that the electrode characteristics are superior to those of the electrode (Ea) of Comparative Example 1. It can be inferred that this is because the electrode of Example 1 did not permeate the catalyst layer due to the presence of the intermediate layer in the gas diffusion layer, the catalyst amount did not decrease, and the catalyst could be effectively used.

[0021]

[Comparative Example 2] 1.43 g of Pt 30% supported catalyst, 10 g of a concentrated solution of a 5% solution of ion exchange resin (trade name Nafion) and 4 distilled water
The paste obtained by mixing 50 g with a planetary ball mill for 50 minutes was applied to the gas diffusion layer 1 having a porosity of 80% shown in FIG. 4 by a bar coating method, dried at 60 ° C. for 10 minutes, and dried at 130 ° C. 20 kg / cm ²
Then, the catalyst layer 2'was formed by firing for 1 minute to obtain an electrode 3 '.

[0022]

Example 2 The same paste as in Comparative Example 2 was applied to the gas diffusion layer 1'shown in FIG. 2 having a porosity of about 33% by the bar coating method,
After drying at 60 ° C. for 10 minutes and baking at 130 ° C. at 20 kg / cm ² for 1 minute, a catalyst layer 2 ′ was formed to obtain an electrode 6. Using the electrode of Comparative Example 2 and the electrode of Example 2 configured as described above, the relationship between voltage and current density was measured under the conditions of cell temperature of 80 ° C. and hydrogen gas and oxygen gas under normal pressure. The results shown in the graph of FIG. 6 were obtained. As can be seen from this graph, Example 2
It can be seen that the electrode (Ed) of No. 2 has better electrode characteristics than the electrode (Eb) of Comparative Example 2. In the electrode of Example 2, the catalyst layer did not soak into the clogged gas diffusion layer,
It can be inferred that the amount of catalyst did not decrease and the catalyst could be effectively used.

[0023]

[Comparative Example 3] 1.43 g of Pt 30% supported catalyst, 10 g of concentrated solution of 5% ion exchange resin (trade name Nafion), 4 distilled water
g was crushed with a planetary ball mill, stirred and mixed to form a paste, and this paste was applied on an electrode substrate of carbon paper, dried and baked to form a 40 μm catalyst layer, and an anode electrode was obtained. .

[0024]

Comparative Example 4 Pt-Mo 33% supported catalyst 1.5 g, Nafion 5% solution concentrate 10 g, and distilled water 4 cc were crushed with a planetary ball mill, stirred and mixed to form a paste. This paste was used as a carbon paper electrode substrate. Apply on top, dry,
By firing, a catalyst layer of 40 μm was formed to obtain an anode electrode.

[0025]

Example 3 Pt 30% supported catalyst 1.43 g, ion exchange resin (trade name Nafion) 5% solution concentrate 10 g, distilled water 4
The first paste is made by crushing g in a planetary ball mill, stirring, and mixing to make 1.5 g of Pt-Mo 33% supported catalyst, ion exchange resin (trade name Nafion) 5% solution concentrate 10
g, 4 cc of distilled water in a planetary ball mill, agitate and mix to make a second paste, and apply the first paste onto the electrode of carbon paper, dry and fire to 10 μm
To form a first catalyst layer, and then apply a second paste on it, dry and fire to form a 30 μm second catalyst layer,
An anode electrode was obtained.

Voltages and currents were supplied to the anode electrodes of Comparative Examples 3 and 4 and Example 3 at a cell temperature of 80 ° C. and a hydrogen gas containing 100 ppm of CO and an oxygen gas at 1 liter / min each at atmospheric pressure. When the relationship with the density was measured, FIG.
The results are shown in the graph. As can be seen from the graph of FIG. 7, the anode electrode of Example 3 is superior to the anode electrodes of Comparative Examples 3 and 4 in electrode characteristics. This is because the anode electrode of Example 3 is an electrode excellent in CO resistance because CO is adsorbed in the first catalyst layer, CO reaching the second catalyst layer is reduced, and the proportion of CO poisoning is reduced. It can be guessed that it is because of it.

[0027]

[Comparative Example 5] 1.43 g of Pt 30% supported catalyst and 10 g of concentrated solution of 5% ion exchange resin (trade name Nafion) and distilled water 4
g is stirred and mixed in a planetary ball mill for 50 minutes to form a paste, and this paste is printed on a carbon paper electrode substrate so that the Pt carrying amount is 1 mg / cm ² at a time, dried, and baked. Thus, an electrode for polymer solid oxide fuel cell was obtained.

[0028]

Example 4 The same paste as in Comparative Example 5 was prepared, and this paste was printed on a carbon paper electrode substrate in three portions, dried and fired to form a catalyst layer having a Pt loading of 1 mg / cm ^2. A solid polymer electrolyte fuel cell electrode was formed.

[0029]

Example 5 1.43 g of Pt 30% supported catalyst, 6 g of a concentrated solution of a 5% solution of ion exchange resin (trade name Nafion) and distilled water 7
g in a planetary ball mill for 50 minutes with stirring to make a first paste, and the same paste as in Comparative Example 5 was made as a second paste, and the first paste and the second paste were put on a carbon paper electrode substrate. Print 4 times each,
A catalyst layer was formed by drying and firing to obtain a polymer solid oxide fuel cell electrode.

When these electrodes for polymer solid oxide fuel cells were inspected, Comparative Example 5 had partial peeling, but Examples 4 and 5 had no peeling and no large cracks. There wasn't. The relationship between the voltage and the current density of these polymer solid oxide fuel cell electrodes was measured under the conditions of a cell temperature of 80 ° C., hydrogen gas and oxygen gas of 1 liter / min, and normal pressure. Nothing was measurable at all, and those of Examples 4 and 5 gave the results shown in the graph of FIG. Embodiment 5 As can be seen from the graph of FIG.
It can be seen that the electrode for polymer solid oxide fuel cell of No. 2 as well as Example 4 has excellent electrode characteristics.

[0031]

The first aspect of the present invention is a solid polymer electrolyte fuel cell in which a catalyst layer comprising a catalyst and an ion exchange resin or a catalyst, an ion exchange resin and a water repellent resin is formed on a gas diffusion layer. An electrode for a solid polymer electrolyte fuel cell (claim 1), characterized in that an intermediate layer is provided between the catalyst layer and the gas diffusion layer. In a similar embodiment of the solid polymer electrolyte fuel cell electrode, the solid polymer electrolyte fuel cell has a porosity of 10 to 50% in the gas diffusion layer in the portion where the catalyst layer is adjacent. Electrode (claim 3).

In both embodiments, the catalyst layer of the fuel cell is prevented from seeping into or entering the gas diffusion layer together with the supported catalyst to reduce the catalytic activity and the gas diffusing ability of the gas diffusion layer. It is intended to maximize the activity. The intermediate layer located between the catalyst layer and the gas diffusion layer and the structure thereof are dense. Both the surface of the gas diffusion layer and the catalyst layer side of which the porosity is 10 to 50% prevent the catalyst layer from entering the gas diffusion layer. This makes it difficult to keep the catalyst in the catalyst layer in the original position where the activity is maintained, and prevents gas diffusion due to clogging of the gas diffusion layer and thus prevents reduction in reaction efficiency. The intermediate layer may be the same as or different from the material of the gas diffusion layer, but is preferably made of carbon and ion exchange resin or carbon, ion exchange resin and water repellent resin (claim 2).

Further, the gas diffusion layer whose surface on the catalyst layer side has a porosity of 10 to 50% has a smaller porosity toward the catalyst layer side, in other words, can have a gradient in porosity. 4) As a result, it is possible to more suitably achieve the securing of the gas diffusing ability and the suppression of the invasion of the gas diffusion layer of the catalyst layer. According to a third aspect of the present invention, in a similar polymer solid oxide fuel cell electrode, two or more kinds of noble metals or noble metal alloys used in the catalyst are arranged so that the kinds are different in the thickness direction of the electrode. (Claim 5). In this aspect, 2 to be used
By individually exhibiting the functions of the noble metals or noble metal alloys of different types, it becomes possible to maximize the performance of the catalyst, which has hitherto been unattainable, and improve the catalyst utilization rate.

For example, this embodiment can be preferably used for an anode of a fuel cell (claim 6), and is arranged so that the concentration of platinum and / or ruthenium catalyst on the gas diffusion layer side of the catalyst layer is high, and The platinum-based alloy catalyst on the film side of the layer is arranged to have a high concentration, and the kind of noble metal or noble metal alloy serving as a catalyst is different in the thickness direction of the catalyst layer. In this electrode, the fuel supplied from the gas diffusion layer side first comes into contact with a platinum and / or ruthenium catalyst having an excellent CO adsorption ability, and thereafter comes into contact with a platinum alloy catalyst that promotes a fuel cell reaction, so that the platinum alloy is used. Since the fuel poisoning the catalyst and having a reduced CO concentration participates in the reaction in the catalyst layer, the poisoning amount of the catalyst is significantly reduced as compared with the conventional case, and an efficient fuel cell reaction can be progressed. The CO
Platinum and / or ruthenium catalysts for adsorption removal are excellent in CO adsorption removal ability and inferior to platinum-based alloy catalysts in terms of the progress of the fuel cell reaction. Even if it exists instead, it is far away from the reaction point, so that the contribution to the reaction is small, and the contribution to the reaction by the CO adsorption removal according to the present invention is much larger.

A fourth aspect of the present invention is the same polymer solid oxide fuel cell electrode, wherein a suspension containing a catalyst and an ion exchange resin, or a catalyst, an ion exchange resin and a water repellent resin, A method for producing an electrode for a polymer electrolyte fuel cell, wherein the electrode catalyst layer is formed by repeating coating, drying and firing a plurality of times on an electrode substrate (claim 7). By applying suspensions having different mixing ratios according to this aspect (claim 8), it is possible to manufacture catalyst layers having different catalyst concentrations or constituent element concentrations in the thickness direction of the catalyst layers. When a suspension composed of different raw materials is applied according to the present method (claim 9), a catalyst layer having different kinds of catalyst metals and the like in the thickness direction of the catalyst layer can be produced, in other words, the catalyst layer. It is possible to form an optimal catalyst layer in accordance with various requirements in the thickness direction, and to obtain an electrode having excellent electrode characteristics. Further, in this aspect, 1
Since the amount of the suspension liquid applied at one time is small and the film thickness thereof is thin, distortion due to shrinkage during drying is small, and therefore a large crack is hard to occur, and a uniform and distortion-free catalyst layer can be manufactured.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an embodiment of a polymer solid oxide fuel cell electrode of the present invention.

FIG. 2 is a cross-sectional view showing another embodiment of the polymer solid oxide fuel cell electrode of the present invention.

FIG. 3 is a cross-sectional view showing an example of a conventional polymer solid oxide fuel cell electrode.

FIG. 4 is a cross-sectional view showing another example of a conventional polymer solid oxide fuel cell electrode.

FIG. 5 is a graph obtained by measuring the relationship between the voltage and current density of the electrodes of Example 1 and Comparative Example 1.

FIG. 6 is a graph showing the relationship between the voltage and current density of the electrodes of Example 2 and Comparative Example 2.

FIG. 7 is a graph showing the relationship between the voltage and current density of the electrodes of Example 3, Comparative Example 3 and Comparative Example 4.

FIG. 8 is a graph showing the relationship between the voltage and current density of the electrodes of Examples 4 and 5.

[Explanation of symbols]

1, 1 '... Gas diffusion layer 2, 2' ... Catalyst layer 4
... Intermediate layers 5, 6 ... Electrodes

Front Page Continuation (71) Applicant 391016716 Stonhart Associates Incorporated STONEHART ASSOCIATES S INCORPORATED United States 06443 Connecticut, Madison, Cottage Road 17, P-O Box 1220 (72) Inventor Tada Tomoyuki Hiratsuka, Kanagawa Prefecture 2-73 Shinmachi Tanaka Kikinzoku Kogyo Co., Ltd. Technology Development Center (72) Inventor Yumi Yamamoto 2-73 Shinmachi, Hiratsuka-shi, Kanagawa Tanaka Kikinzoku Kogyo Co., Ltd. Technology Development Center

Claims (9)

[Claims] 1. An electrode for a polymer electrolyte fuel cell in which a catalyst layer comprising a catalyst and an ion exchange resin, or a catalyst layer comprising a catalyst, an ion exchange resin and a water repellent resin is formed on a gas diffusion layer. An electrode for a polymer electrolyte fuel cell, wherein an intermediate layer is provided between the gas diffusion layer and the gas diffusion layer. 2. The electrode for a polymer electrolyte fuel cell according to claim 1, wherein the intermediate layer comprises carbon and an ion exchange resin or carbon, an ion exchange resin and a water repellent resin. 3. A solid polymer electrolyte fuel cell electrode comprising a catalyst and an ion exchange resin, or a catalyst layer comprising the catalyst, an ion exchange resin and a water repellent resin formed on a gas diffusion layer. The porosity of the gas diffusion layer near the
A solid polymer electrolyte fuel cell electrode characterized by being 10 to 50%. 4. The solid polymer electrolyte fuel cell electrode according to claim 3, wherein the porosity of the gas diffusion layer is reduced toward the catalyst layer side. 5. In a polymer solid oxide fuel cell electrode composed of a catalyst and an ion exchange resin, or a catalyst, an ion exchange resin and a water repellent resin, two or more kinds of noble metals or noble metal alloys used for the catalyst are used. An electrode for a polymer electrolyte fuel cell, wherein the catalyst layers are arranged so that the types thereof are different in the thickness direction. 6. The platinum and / or ruthenium catalyst is arranged on the gas diffusion layer side of the catalyst layer, and the platinum alloy catalyst is arranged on the membrane side of the catalyst layer for use as an anode. The polymer solid oxide fuel cell electrode according to item 4. 7. A method for producing a polymer solid electrolyte fuel cell electrode comprising a catalyst and an ion exchange resin, or a catalyst, an ion exchange resin and a water repellent resin, wherein the catalyst and the ion exchange resin, or the catalyst and the ion exchange resin. An electrode for a polymer electrolyte fuel cell, characterized in that a suspension containing a resin and a water-repellent resin is applied onto a gas diffusion layer, dried and fired a plurality of times to form a catalyst layer. Manufacturing method. 8. The solid polymer electrolyte type product according to claim 7, wherein at least one of the suspensions repeatedly applied to the gas diffusion layer is a suspension having different mixing ratios. Manufacturing method of fuel cell electrode. 9. The polymer solid electrolyte type according to claim 7, wherein at least one of the suspensions repeatedly applied to the electrode substrate is a suspension composed of different raw materials. Manufacturing method of fuel cell electrode.