JP2000106193A - Solid high polymer film electrolyte fuel cell and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solid high polymer film electrolyte fuel cell, capable of improving the durability to an impure material gas, capable of restricting voltage lowering even when loading in a high current density area, and capable of preventing the deterioration of battery characteristics in longtime operation, and having superior economical efficiency and reliability. SOLUTION: An anode 12 of a solid high polymer film electrolyte fuel cell is formed of a gas diffused part 18, anode catalyst 19 and a carbon part 20. The anode catalyst 19 is obtained by carrying platinum or ruthenium metal on carbon and formed of alloy parts 19a, in which platinum and ruthenium are alloyed, and unalloyed parts 19b, in which platinum and ruthenium are not alloyed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel cell having a solid polymer membrane having ion conductivity, and more particularly to a solid polymer electrolyte fuel cell having an improved catalyst for a fuel electrode and a method of manufacturing the same. Things.

[0002]

2. Description of the Related Art In recent years, fuel cells have attracted attention as highly efficient and clean energy conversion devices. Above all, a solid polymer electrolyte fuel cell using a solid polymer membrane as an electrolyte membrane can operate at a relatively low temperature (80 to 100 ° C).
There are advantages such as high output density and compact configuration. Therefore, it is expected to be used in various fields such as a mobile power supply and a stationary power supply.

The operating principle of a solid polymer electrolyte fuel cell is basically the same as that of a phosphoric acid electrolyte fuel cell, except that the solid polymer membrane, which is an electrolyte membrane, has good ion conductivity in a wet state. Therefore, the operating temperature is around 100 ° C. due to the heat resistance of the film. The structure of the cell body is the same as that of the phosphoric acid electrolyte fuel cell. That is, a solid polymer membrane is sandwiched between a pair of porous electrodes including a fuel electrode (hereinafter, referred to as an anode) and an oxidant electrode (hereinafter, referred to as a cathode), and a fuel gas and an oxidized gas are respectively applied to the anode and the cathode. The agent gas is circulated. The anode and the cathode are usually made of a carbon material, and the anode catalyst and the cathode catalyst are formed as catalyst layers on the surfaces in contact with the solid polymer membrane, respectively. The oxidizing gas is air sent from a compressor, and the fuel gas is a hydrogen-rich gas obtained by reforming natural gas or a hydrogen-rich gas obtained by reforming methanol or the like.

In the above-described fuel cell, since power is obtained by an electrochemical reaction occurring on the surface of the catalyst in contact with the electrolyte membrane, the output and life of the fuel cell greatly depend on the characteristics of the catalyst. Examples of the catalyst include platinum (Pt), palladium (Pd), rhodium (Rh), ruthenium (Ru),
Iridium (Ir), osmium (Os), silver (A
g), a material in which a noble metal component such as gold (Au) is carried on a conductive powder carrier such as carbon black is used. According to such a catalyst, sintering can be suppressed and the amount of noble metal used can be reduced, which is advantageous in increasing the economic efficiency of the fuel cell.

[0005] The fuel gas supplied to the anode contains various impurity gases such as CO, H2S, and NH3. It is well known that when these impurity gases are adsorbed on the surface of the anode catalyst, they become so-called catalyst poisons and the catalytic activity is greatly reduced. In addition, since the adsorption of the gas causes an exothermic reaction on the surface of the electrode catalyst, it has a great effect in a solid polymer electrolyte fuel cell operated at a low temperature and must be removed under severe conditions. Therefore,
The CO having the highest concentration among these impurity gases is reduced to about 50 ppm before entering the anode by incorporating a reformer or a shifter into the fuel gas supply system, and then the fuel gas is supplied to the anode. It has become.

However, if the inlet gas concentration of the impurity gas rises due to the deterioration of the reformer catalyst over time, the sudden failure of the operating mechanism, or the emergence of diversified fuels such as gasoline, poisoning of the anode catalyst is expected. Is done. Therefore, conventionally, a large number of anode catalysts having high resistance to impurity gases (mainly CO) have been developed. For example, it has been proposed to use a carbon-supported platinum-ruthenium alloy catalyst or a catalyst obtained by adding a third additive element such as Sn thereto and alloying it as an anode catalyst.

More specifically, the following prior art is known. In the conventional example described in Japanese Patent Application Laid-Open No. 9-35723, a platinum-ruthenium alloy catalyst is used only on the gas outlet side in the electrode surface, and the atomic ratio of platinum: ruthenium is 8
5:15 to 55:45, which aims to reduce the cost of the platinum-ruthenium alloy catalyst.
Further, instead of alloying platinum and ruthenium, a composite catalyst molded body having platinum and ruthenium is disclosed in
There is a conventional example described in JP-A-153366. In this example, first, a platinum compound is applied to a conductive molded body, this is reduced to deposit platinum on the molded body, and then a ruthenium compound is applied to the molded body, and this is reduced. Two metals can be carried on the compact. When a CO poisoning test is performed using these anode catalysts, it has been proved that the resistance is certainly high. Further, as a conventional example of an anode catalyst, a catalyst having a feature of depositing a hydrogen storage alloy on platinum or a platinum alloy has been proposed (Japanese Patent Application Laid-Open No. HEI 1-1990).
0-74523). According to this anode catalyst,
By the function of the hydrogen storage alloy, the oxidation reaction of hydrogen on platinum or a platinum alloy can be promoted, which can contribute to high activity and long life.

[0008]

However, in the prior art, when the load current of the fuel cell is increased to a high current density region, the voltage decreases and the current tends to reach a limit current. there were. In addition, when the fuel cell has been operated for a long period of time, the polarization of the anode has increased, causing a problem that the cell characteristics gradually deteriorate.
Furthermore, cost is also considered important for fuel cells expected to be used in various applications.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object the purpose of further increasing the resistance to impurity gases, suppressing the voltage drop even when the load is taken up to a high current density region, and providing a long-term operation. It is an object of the present invention to provide a polymer electrolyte membrane fuel cell which can prevent deterioration of battery characteristics at the time of manufacture and which is excellent in economic efficiency and reliability, and a method of manufacturing the same.

[0010]

In order to achieve the above object, the invention according to claim 1 comprises a solid polymer membrane having ion conductivity as an electrolyte membrane, and a fuel electrode and a fuel electrode sandwiching the solid polymer membrane. An oxidant electrode is arranged, and a catalyst in which platinum and ruthenium are supported on carbon is provided in these fuel electrode and oxidant electrode, and a fuel gas is provided on the fuel electrode side, and an oxidant gas is provided on the oxidant side. In the solid polymer electrolyte fuel cell that has been circulated, the catalyst of the fuel electrode is characterized in that it is composed of a part where platinum and ruthenium are alloyed and a part where platinum and ruthenium are non-alloyed. .

In the first aspect of the present invention, the alloy of platinum and ruthenium and the non-alloyed portion of platinum and ruthenium are mixed in the catalyst of the fuel electrode. for that reason,
Agglomeration of metals supported on carbon, that is, platinum and ruthenium, is smaller than that of a platinum-ruthenium alloy catalyst in which both are completely alloyed. Therefore, the electrochemical metal surface area of the anode catalyst is:
Significantly higher values can be taken than for platinum-ruthenium alloy catalysts.

By using such a catalyst for the fuel electrode, it exhibits the electronic properties as an alloy, and at the same time does not poison even when various impurity gases such as high-concentration CO are mixed in the fuel electrode. The proportion of platinum is higher than before. That is, by increasing the surface area of the catalyst, the resistance to a high concentration of impurity gas can be increased. This makes it possible to suppress a voltage drop even when the load current increases. Further, since the initial metal surface area is large, even when the battery is operated for a long time, the reduction rate of the metal surface area can be suppressed. Therefore, the polarization of the fuel electrode does not suddenly increase, and a decrease in cell characteristics can be prevented.

According to a second aspect of the present invention, there is provided the solid polymer electrolyte fuel cell according to the first aspect, wherein the starting material is a platinum catalyst or ruthenium catalyst carrying carbon, and the starting material is a platinum catalyst carrying carbon. A ruthenium compound is added here, and when the starting material is a ruthenium catalyst carrying carbon, a platinum compound is added here,
A catalyst heat-treated in a reducing gas or inert gas atmosphere is used as a catalyst for a fuel electrode.

According to a third aspect of the present invention, in the polymer electrolyte membrane fuel cell according to the first aspect, a platinum compound and a ruthenium compound are simultaneously mixed with carbon and then heat-treated in a reducing gas or inert gas atmosphere. The catalyst is used as a fuel electrode catalyst.

According to a fourth aspect of the present invention, there is provided a solid polymer electrolyte fuel cell according to the first aspect, wherein a platinum catalyst carrying carbon and a ruthenium catalyst carrying carbon are mixed and then mixed in a reducing gas or inert gas atmosphere. Characterized in that the catalyst heat-treated in the above was used as the catalyst for the fuel electrode.

According to the second, third and fourth aspects of the present invention, a catalyst in which an alloy portion and a non-alloy portion of platinum and ruthenium are mixed can be obtained by performing a heat treatment in a reducing gas or an inert gas atmosphere. . In addition, the degree of alloying in the catalyst can be adjusted by the heat treatment conditions such as temperature and time, or the amount of the platinum or ruthenium catalyst or compound to be mixed. At this time, the degree of alloying was determined by the diffraction angle 2θ of platinum in the X-ray diffraction pattern = 39.
It can be estimated by examining how much it has shifted from 7 ° to the higher angle side.

Specifically, the degree of alloying is adjusted as follows. For example, the amount of the ruthenium compound is made smaller (or the amount of the platinum compound is larger) than the stoichiometric amount at which platinum and ruthenium are completely alloyed, and the platinum metal component is added in excess of the ruthenium metal component. Suppose you did. An excessively added platinum component is deposited on carbon as it is without alloying. As a result, a catalyst in a mixed state of an alloy and a non-alloy can be obtained. Further, the amount of the added metal may be set to a stoichiometric composition or less. In this case, the insufficient metal is supported on the carbon without being alloyed, and as in the case where the excess amount is set, a part of the object of the present invention is alloyed, and the other part is unalloyed. A catalyst can be made.

According to a fifth aspect of the present invention, in the solid polymer electrolyte fuel cell according to the fourth aspect, of the specific surface areas of the platinum catalyst and the carbon support of the ruthenium catalyst, the specific surface area of the carbon support of the platinum catalyst is reduced. Is larger than the specific surface area of the carbon support of the ruthenium catalyst.

According to the fifth aspect of the present invention, since the specific surface area of the carbon support in the platinum catalyst before mixing is made larger than the specific surface area of the carbon support in the ruthenium catalyst, the dispersibility of the carbon-supported platinum catalyst is improved. ,
Its surface area is greater than the surface area of the ruthenium catalyst. By using such a catalyst as a catalyst for the fuel electrode, excellent resistance can be exhibited even when a high concentration of impurity gas is mixed, and a decrease in battery voltage up to a high load can be prevented. Furthermore, even if the battery is operated for a long period of time, since the initial surface area of platinum is large, the reduction rate can be small,
It is possible to suppress a decrease in battery characteristics due to a sudden increase in anodic polarization.

The invention according to claim 6 is the invention according to claims 1, 2, 3, and 4.
Or in the solid polymer electrolyte fuel cell according to 5, wherein the carbon is heat-treated at least 50 m 2.
/ G is used as a catalyst for the fuel electrode. Generally, the surface area of carbon and the catalyst surface area (metal surface area) are in a proportional relationship. That is, in the invention of claim 6, since the carbon has a specific surface area of at least 50 m 2 / g in a heat-treated state, it is possible to secure a catalyst surface area that can withstand a high load operation from the beginning of the battery operation. .

According to a seventh aspect of the present invention, there is provided the first, second, third and fourth aspects.
Or a method for producing a solid polymer electrolyte membrane fuel cell according to 5, which comprises a heat treatment step of heat-treating the catalyst at the fuel electrode in a reducing gas or inert gas atmosphere. As the active gas, hydrogen, carbon monoxide, nitrogen, argon, helium, or a mixed gas thereof is used. According to the invention of claim 7, by performing the heat treatment in the gas atmosphere, it is possible to obtain a fuel electrode catalyst in which a part is alloyed and the other part is non-alloyed.

The invention of claim 8 is the first, second, third and fourth invention.
Or a method for producing a solid polymer electrolyte fuel cell according to 5, which comprises a heat treatment step of heat-treating the catalyst of the fuel electrode in a reducing gas or inert gas atmosphere, wherein the heat treatment time in this heat treatment step is reduced. It is characterized in that it took about 30 minutes. In the present invention, only a part of the catalyst of the fuel electrode needs to be alloyed, so that the heat treatment time required for the catalyst production is about 1 hour in the conventional case.
It can be as short as about 30 minutes, which is half of that, which can contribute to reduction of manufacturing cost.

The ninth aspect of the present invention is the first aspect of the present invention.
Or a method for producing a solid polymer electrolyte fuel cell according to 5, comprising a heat treatment step of heat-treating the catalyst of the fuel electrode in a reducing gas or inert gas atmosphere, wherein the heat treatment temperature in this heat treatment step is 300 ~
The temperature is set to 2000 ° C. As described in the preceding paragraph, in the present invention, only a part of the catalyst of the fuel electrode needs to be alloyed, so that the heat treatment temperature required for the production of the catalyst may be low. The catalyst intended for the invention can be obtained. More specifically, the value of the surface area of the carbon support used before the heat treatment is 10
1000 m 2 / g or more, 1000-2000 ° C., 10
If it is less than 00 m 2 / g, a treatment temperature of 300 to 1000 ° C. is a guide. However, it should be noted that the value of the surface area of the catalyst obtained varies depending not only on the heat treatment temperature but also on the heat treatment time.

According to a tenth aspect of the present invention, in the method for manufacturing a solid polymer electrolyte membrane fuel cell according to the ninth aspect, the heat treatment step includes a first step using a reducing gas at 300 to 600 ° C .; A second step using an inert gas at a temperature of 300 ° C. and a third step using a reducing gas at a temperature of 300 to 600 ° C. are performed.

According to the tenth aspect of the present invention, when performing the heat treatment step of the catalyst, first, a reduction reaction having a chemical bond interaction between the surface metal and the carrier carbon in a reducing gas atmosphere at 300 to 600 ° C. I do. Then 600
Alloying is performed by heat reduction in an inert gas at 2000 ° C. At the same time, reduction products such as CO can be formed around the metal fine particles. Therefore, aggregation of the metal fine particles can be suppressed by the reduction product. As a result, the electrochemical metal surface area of the catalyst can be increased, and the resistance to a high concentration of impurity gas can be increased. However, when the surface area of the carrier carbon is not so large, the degree of alloying tends to be too high when the above-described three-stage heat treatment is performed. In this case, only the first stage is performed. Obtain the anode catalyst.

[0026]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (1) This Embodiment [Configuration] An example of an embodiment of the present invention will be specifically described below with reference to the drawings. This embodiment includes claims 1, 2, 6, 7 and 8.

First, the fuel cell power generation system to which the present embodiment is applied will be described with reference to FIG. As shown in FIG. 2, the fuel cell system is provided with a pipe 2 for supplying natural gas as a raw fuel and a water supply pipe 3. A reformer 4 for producing a hydrogen-rich reformed gas is connected to these pipes 2 and 3, and the reformer 4 further converts carbon monoxide gas and the like in the reformed gas into hydrogen. And a transformer 5 for producing a fuel gas.

A fuel gas supply pipe 6 is attached to the transformer 5, and the solid polymer membrane electrolyte type fuel cell stack 1 is connected via the fuel gas supply pipe 6. The fuel cell stack 1 is formed by stacking a plurality of unit cells,
An air supply pipe 9 for supplying air as an oxidizing gas is attached, and a compressor 8 is connected through the supply pipe 9. Further, the fuel cell stack 1 has a fuel gas exhaust pipe 7 for sending fuel gas and air to the outside and an air exhaust pipe 1.
0 is attached.

Next, the unit cells constituting the fuel cell stack 1 will be described with reference to FIG. The unit cell of the fuel cell stack 1 is provided with a solid polymer membrane 11 which is an electrolyte membrane. The solid polymer membrane 11 is an ion-exchange membrane formed of a polymer material and a fluorine-based resin, and has good ion conductivity in a wet state. An anode 12 and a cathode 13, which are gas diffusion electrodes, are arranged so as to sandwich the electrolyte membrane 11 from above and below. Separators 14 and 15 forming flow paths for the fuel gas and the oxidizing gas are disposed on the back of the anode 12 and the cathode 13, and current collectors 16 and 17 serving as current collectors of the anode 12 and the cathode 13 are disposed outside the separators 14 and 15. Is arranged.

Next, the anode 12 will be described with reference to FIG. That is, the anode 12 is configured by laminating the gas diffusion section 18, the anode catalyst 19, and the carbon section 20.
The gas diffusion portion 18 is formed of a porous carbon paper having gas permeability and electron conductivity. An anode catalyst 19 is applied to the surface of the gas diffusion section 18 on the side of the solid polymer film 11. Further, the carbon part 20 is located in the middle between the gas diffusion layer 18 and the catalyst layer 19, and is for improving the bonding between them.

Configuration of Anode Catalyst The feature of the present embodiment lies in the anode catalyst 19. That is, the anode catalyst 19 is a catalyst in which platinum and ruthenium metal are supported on carbon, and as shown in FIG.
An alloy portion 19a in which platinum and ruthenium are alloyed and a non-alloy portion 19b in which platinum and ruthenium are non-alloyed are mixed.

Manufacturing Process of the Present Embodiment The anode catalyst 19 in such a state is manufactured by the following method. First, ruthenium chloride and ion-exchanged water are added to a platinum catalyst carrying carbon, and a reducing agent such as sodium formate is added thereto to precipitate ruthenium on carbon. In this case, the liquid phase reducing agent need not always be added. The starting materials of platinum and ruthenium supported on carbon are not limited to the above-mentioned chlorides, but may be hydroxides,
Sulfides or complexes of these metals may be used.
As the liquid phase reducing agent, any reducing agent usable in the liquid phase such as sodium thiosulfate, formaldehyde, methanol, hydrazine and the like may be used.

Next, this solution is subjected to suction filtration and then repeatedly washed with ion-exchanged water to remove chlorine ions or other anions, and then dried at 60 ° C. Next, the catalyst is reduced by heating at 800 ° C. for 30 minutes in a hydrogen stream to obtain a catalyst for an anode. Such a heat treatment of the catalyst is a heat treatment step according to claim 7. When the carbon is heat-treated, the catalyst has a specific surface area of 80 m2 / g.

The anode catalyst 1 of the present embodiment up to this point
Table 1 below summarizes the results of comparing the heat treatment temperature and time, the physical properties, and the production cost at the time of preparation with those of the conventional product.

[0035]

[Table 1] The catalyst thus obtained is dispersed in ion-exchanged water, a predetermined amount of a dispersion of Teflon (polytetrafluoroethylene) is mixed therein, and this mixture is sprayed onto the gas diffusion layer 18 as a substrate. The solid polymer film 11 and the gas diffusion layer 18 are integrated with each other by hot pressing, so that the solid polymer film 11 and the anode 12 are joined together.
The catalyst layer 19 is formed. In addition, instead of hot pressing,
A configuration in which the solid polymer membrane 11 and the anode 12 are joined using a hydrogen ion conductive solid polymer solution may be employed.
In the above embodiment, the loading amount of the metal catalyst is 0.5 mg per cm 2 of the anode. Further, the composition ratio of platinum and ruthenium is 10 to 70 wt% as ruthenium content.
Is fine.

[Operation and Effect] The operation and effect of the present embodiment having the above configuration are as follows. That is, since the alloyed portion of platinum and ruthenium and the non-alloyed portion of platinum and ruthenium are mixed in the anode catalyst 19, the platinum supported on carbon is more compared with the catalyst layer in which both are completely alloyed. And the agglomeration of ruthenium is reduced. Therefore, the electrochemical metal surface area (particularly platinum) of the catalyst can be much larger than that of the platinum-ruthenium alloy catalyst. That is, the anode catalyst 19 has electronic properties as an alloy, and at the same time, the ratio of non-poisoned platinum is increased, and the resistance to various impurity gases including high-concentration CO can be increased.

FIG. 4 shows IV characteristics of the solid polymer electrolyte fuel cell having the anode catalyst 19 and the conventional solid polymer electrolyte fuel cell having the anode catalyst. The solid line is the present embodiment, and the broken line is the conventional example. It is assumed that the fuel gas contains 50 ppm of CO in the natural gas reformed gas. As is clear from this graph, according to the present embodiment, a high-performance battery in which a limit current does not appear even at a high load current density can be obtained.

FIG. 5 is a graph showing the change over time of the cell voltage when the solid polymer electrolyte fuel cell having the anode catalyst 19 and the conventional solid polymer electrolyte fuel cell having the anode catalyst are operated at a constant load current. Show. In this graph, as in the graph of FIG. 4, the solid line is the present embodiment and the broken line is the conventional example. It is assumed that the natural gas reformed gas contains 50 ppm CO in the fuel gas. As can be seen from this graph, in the present embodiment, even when the battery is operated for a long period of time, the polarization of the anode 12 does not rapidly advance, and the deterioration of the battery characteristics can be suppressed. This is because the initial value of the metal surface area is large and the reduction rate of the metal surface area is small.

Moreover, in the present embodiment, since the carbon has a specific surface area of 80 m 2 / g in a heat-treated state,
A catalyst surface area that can withstand a high-load operation from the beginning of the battery operation can be secured. Further, in the present embodiment, since only a part of the anode catalyst 19 needs to be alloyed, as shown in Table 1 above, the heat treatment temperature of the catalyst 19 is lower than that of the conventional catalyst.
The temperature can be reduced from 100 ° C. to 800 ° C., and the heat treatment time can be reduced from the conventional one hour to 30 minutes.
As a result, the manufacturing cost can be reduced to 3/4 of the conventional cost.

In the present embodiment, the amount can be adjusted based on the amount of the platinum catalyst carrying carbon and the amount of ruthenium chloride, which is a ruthenium compound. In other words, if the amount of added metal is set to an excess or stoichiometric composition of the target composition or less, the excess or deficient metal will be supported on carbon without alloying, and the object of the present invention will be described. The catalyst can be produced in a state where a part of the catalyst is alloyed and the other part is non-alloyed. Although the composition of the alloy is not specified here, from the viewpoint of increasing the platinum surface area, the amount of the ruthenium compound is smaller than the stoichiometric amount at which platinum and ruthenium are completely alloyed (or the platinum compound Is more desirable).

(2) Other Embodiments The present invention is not limited to the above embodiments, but also includes the following other embodiments. That is, the catalyst may be synthesized by adding a platinum compound to a ruthenium catalyst supported on carbon as a starting material in the catalyst synthesis and then heat-treating in a reducing gas or inert gas atmosphere. Correspondence). Alternatively, a catalyst synthesized by simultaneously mixing a platinum compound and a ruthenium compound with carbon and then performing a heat treatment in a reducing gas or inert gas atmosphere may be used (corresponding to claim 3).

Further, a pre-synthesized carbon-supported platinum catalyst and a carbon-supported ruthenium catalyst may be mixed and then partially alloyed by heat treatment reduction (corresponding to claim 4). At this time, if the carrier surface area of the carbon-supported platinum catalyst to be mixed is larger than the carrier surface area of the carbon-supported ruthenium catalyst, the dispersibility of platinum is kept high, and ruthenium is supported and alloyed here. This is desirable because a catalyst having a large platinum surface area is synthesized (corresponding to claim 5).

In the production method according to the present invention, not only the above-mentioned hydrogen but also carbon monoxide, nitrogen, argon, helium or a mixed gas thereof is used as the reducing gas and the inert gas for heat treatment and reduction. (Corresponding to claim 7). The heat treatment temperature is preferably from 1000 to 2000 ° C. if the surface area of the carbon support before the heat treatment is not less than 1000 m 2 / g, and from 300 to 1000 ° C. if it is not more than 1000 m 2 / g. 9).

Further, mixing of a reducing gas and an inert gas,
Alternatively, it is also possible to perform multi-stage reduction using a combination of a reducing gas and an inert gas (corresponding to claim 10).
That is, reduction is performed in a reducing gas atmosphere at 300 to 600 ° C. with a chemical bond interaction between the surface metal and the carrier carbon. Next, alloying is performed by heat reduction in an inert gas at 600 to 2000 ° C. At this time, reduction products such as CO can be formed around the metal fine particles. Therefore, aggregation of the metal fine particles can be suppressed by the reduction product. As a result, the electrochemical metal surface area of the catalyst can be increased, and the resistance to a high concentration of impurity gas can be increased. However, when the surface area of the carrier carbon is not very large, the degree of alloying becomes too high when the heat treatment is performed in three stages, so that the state where the alloy portion and the non-alloy portion intended by the present invention are mixed cannot be achieved. In such a case, a catalyst of a desired fuel electrode can be obtained by performing only the first step.

[0045]

As is apparent from the above description, according to the present invention, in the catalyst of the anode supporting platinum and ruthenium metal, a part is alloyed and the other part is non-alloyed. With a simple structure, a large metal surface area can be ensured, so that resistance to impurity gases is increased, and at the same time, voltage drop is small even under high load, and characteristics are stable over time. A manufacturing method could be provided.

[Brief description of the drawings]

FIG. 1 is a schematic view showing a structure of an anode in a solid polymer electrolyte fuel cell according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram of a solid polymer electrolyte fuel cell system.

FIG. 3 is a structural diagram of a unit cell in a solid polymer electrolyte fuel cell;

FIG. 4 is a graph showing IV characteristics of a solid polymer electrolyte fuel cell according to the present embodiment and a conventional example.

FIG. 5 is a graph showing the change over time in cell voltage when the solid polymer electrolyte fuel cells according to the present embodiment and the conventional example are operated at a constant load current.

FIG. 6 is a graph showing a relationship between a carrier surface area and a catalyst surface area (metal surface area).

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Fuel cell stack 2 ... Natural gas supply pipe 3 ... Water supply pipe 4 ... Reformer 5 ... Transformer 6 ... Fuel gas supply pipe 7 ... Fuel gas discharge pipe 8 ... Compressor 9 ... Air supply pipe 10 ... Air discharge pipe DESCRIPTION OF SYMBOLS 11 ... Solid polymer membrane 12 ... Anode 13 ... Cathode 14, 15 ... Separator 16, 17 ... Current collector 18 ... Gas diffusion part 19 ... Anode catalyst 19a ... Alloy part 19b ... Non-alloy part 20 ... Carbon part

 ──────────────────────────────────────────────────続 き Continued on the front page F-term (reference)

Claims (10)

[Claims] A solid polymer membrane having ion conductivity is provided as an electrolyte membrane, and a fuel electrode and an oxidizer electrode are arranged so as to sandwich the solid polymer membrane. In a solid polymer membrane electrolyte fuel cell in which a catalyst carrying platinum and ruthenium is provided, a fuel gas is passed on the fuel electrode side, and an oxidant gas is passed on the oxidant side, respectively. A solid polymer membrane electrolyte fuel cell, wherein the catalyst comprises an alloy portion in which platinum and ruthenium are alloyed and a non-alloy portion in which platinum and ruthenium are not alloyed. 2. When a starting material is a platinum catalyst supported on carbon or a ruthenium catalyst supported on carbon, and when the starting material is a platinum catalyst supported on carbon, a ruthenium compound is added thereto, and when the starting material is a ruthenium catalyst supported on carbon, 2. The solid polymer membrane electrolyte type according to claim 1, wherein a catalyst added with a platinum compound and then heat-treated in a reducing gas or an inert gas atmosphere is used as a catalyst for the fuel electrode. Fuel cell. 3. The catalyst for a fuel electrode according to claim 1, wherein a catalyst heat-treated in a reducing gas or inert gas atmosphere after simultaneously mixing a platinum compound and a ruthenium compound with carbon is used as the catalyst for the fuel electrode. Solid polymer electrolyte fuel cell. 4. A catalyst obtained by mixing a platinum catalyst supported on carbon and a ruthenium catalyst supported on carbon and then heat-treated in a reducing gas or inert gas atmosphere is used as the catalyst for the fuel electrode. The polymer electrolyte membrane fuel cell according to claim 1. 5. The specific surface area of the carbon support of the platinum catalyst out of the specific surface areas of the carbon support of the platinum catalyst and the ruthenium catalyst is larger than the specific surface area of the carbon support of the ruthenium catalyst. The polymer electrolyte membrane fuel cell according to claim 4. 6. A catalyst having a specific surface area of at least 50 m 2 / g when the carbon is heat-treated, wherein the catalyst is used as a catalyst for the fuel electrode.
6. The solid polymer electrolyte fuel cell according to 2, 3, 4 or 5. 7. The method for producing a solid polymer electrolyte fuel cell according to claim 1, 2, 3, 4, or 5, wherein the catalyst for the fuel electrode is placed in a reducing gas or inert gas atmosphere. A solid polymer membrane electrolyte fuel cell, wherein hydrogen, carbon monoxide, nitrogen, argon, helium or a mixed gas thereof is used as the reducing gas or the inert gas. Manufacturing method. 8. The method for producing a solid polymer electrolyte fuel cell according to claim 1, 2, 3, 4 or 5, wherein the catalyst of the fuel electrode is placed in a reducing gas or inert gas atmosphere. A method of manufacturing a solid polymer electrolyte fuel cell, comprising: a heat treatment step of heat treating the polymer electrolyte membrane, wherein the heat treatment time in the heat treatment step is about 30 minutes. 9. The method for manufacturing a solid polymer electrolyte fuel cell according to claim 1, 2, 3, 4, or 5, wherein the catalyst for the fuel electrode is placed in a reducing gas or inert gas atmosphere. A heat treatment step of heat-treating, wherein the heat treatment temperature in said heat treatment step is 300 to 20
A method for producing a solid polymer electrolyte fuel cell, wherein the temperature is set to 00 ° C. 10. The method according to claim 10, wherein the heat treatment step is performed at 300 to 60.
A first stage with a reducing gas at 0 ° C. and 600-2000
The method according to claim 9, wherein a second step using an inert gas at a temperature of 300 ° C. and a third step using a reducing gas at a temperature of 300 to 600 ° C. are performed.