JP2008091264A - Cathode for fuel cell and solid polymer electrolyte fuel cell equipped with this - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cathode with excellent electrode characteristics against oxygen reduction reaction and a solid polymer fuel cell equipped with it capable of obtaining a high battery output. <P>SOLUTION: Of the solid polymer fuel cell provided with an anode, a cathode, and a polymer electrolyte film arranged between the anode and the cathode, the cathode is provided with a catalyst layer consisting of a catalyst-carrying conductor and polymer electrolyte, and the catalyst-carrying conductor further carries an oxygen-absorbing and -discharging body made of pyrochlore type Ce<SB>2</SB>Zr<SB>2</SB>O<SB>7</SB>. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a cathode for a fuel cell and a polymer electrolyte fuel cell including the same.

  Since a polymer electrolyte fuel cell having a polymer electrolyte membrane is easily reduced in size and weight, it is expected to be put to practical use as a mobile vehicle such as an electric vehicle or a power source for a small cogeneration system. However, since solid polymer fuel cells have a relatively low operating temperature and their exhaust heat is difficult to use effectively for auxiliary power, etc., the utilization rate of the anode reaction gas (pure hydrogen, etc.) and the cathode for practical use. There is a demand for performance capable of obtaining high power generation efficiency and high power density under operating conditions with a high utilization rate of reaction gas (such as air).

  The electrode reaction in each catalyst layer of the anode and cathode of the polymer electrolyte fuel cell is a three-phase interface (hereinafter referred to as reaction site) in which each reaction gas, catalyst, and fluorine-containing ion exchange resin (electrolyte) are present simultaneously. ). Therefore, in a polymer electrolyte fuel cell, a catalyst such as a metal catalyst or a metal-supported catalyst (for example, a metal-supported carbon in which a metal catalyst such as platinum is supported on a carbon black support having a large specific surface area) is used as a polymer. Using the same or different type of fluorine-containing ion exchange resin as the electrolyte membrane and using it as a constituent material of the catalyst layer, the reaction sites in the catalyst layer are three-dimensionalized to increase the reaction sites. Yes.

  The fluorine-containing ion exchange resin that coats the above catalyst has a high ionic conductivity as represented by “Nafion” manufactured by DuPont and the like, and has a sulfonic acid group that is chemically stable in an oxidizing and reducing atmosphere. A perfluorocarbon polymer (hereinafter referred to as sulfonic acid type perfluorocarbon polymer) is used.

  However, while the conventional fluorine-containing ion exchange resin contained in the catalyst layer of the cathode is excellent in ion conductivity and chemical stability, the oxygen gas permeability in the resin is insufficient. As a result, the oxygen permeability of the cathode becomes insufficient, the overvoltage of the oxygen reduction reaction at the cathode increases, and it is difficult to obtain high electrode characteristics.

  On the other hand, in Patent Document 1 below, the cathode overvoltage is reduced by increasing the oxygen permeability in the cathode catalyst layer by mixing a fluorine-containing ether compound with the fluorine-containing ion exchange resin coating the catalyst. A proposed polymer electrolyte fuel cell has been proposed.

  However, even in the polymer electrolyte fuel cell described in Patent Document 1, the oxygen permeability in the catalyst layer of the cathode is insufficient, and the cathode overvoltage cannot be sufficiently reduced. There is a problem that the durability of the catalyst layer is insufficient and the battery life is short. This is because the preferred fluorine-containing ether compound is an oily low molecular weight compound, so that it gradually dissolves in the reaction product water during power generation, or is accompanied by it and desorbed from the fluorine-containing ion exchange resin. It is thought that it is because it is discharged from the catalyst layer together with the produced water.

  Therefore, Patent Document 2 below improves the electrode characteristics particularly in the cathode by including a polymer compound having high oxygen permeability and substantially having no ion exchange group in the electrode catalyst layer of the fuel cell. It is disclosed.

  On the other hand, in Patent Document 3 below, a solution of an oxygen transport carrier containing a metal complex that specifically and reversibly binds to oxygen, imitating hemoglobin contained in blood, is hydrophobic and dissolves carbon dioxide. Diffusion electrode using oxygen as active material along the air intake hole in the battery container having the air intake hole communicating with the outside air by forming the dispersion liquid dispersed in the slow medium into a membrane to form an oxygen selective permeable membrane And a battery in which the oxygen selective permeable membrane is interposed between the gas diffusion electrode and the air intake hole.

JP 11-354129 A JP 2002-252001 A JP-A-8-173775 JP 2005-100780 A

  If the oxygen-permeable resin is mixed with the catalyst-supporting carbon and the electrolyte when the catalyst is prepared as in Patent Document 2, the oxygen-permeable resin is dispersed in the electrode. Is difficult to be performed. That is, it is a problem that the drainage path of the generated water and the oxygen diffusion path are in the same place. Inside the electrode, the electrode reaction proceeds at a site called a three-phase interface where the reaction gas, catalyst, and electrolyte meet. The supply of oxygen to the three-phase interface is an important topic. In Patent Document 2, the efficiency of the reaction is increased by physically mixing a polymer having a high oxygen permeability coefficient, an electrolyte, and a catalyst. However, oxygen actually requires a three-phase interface, In physical mixing, a high oxygen-permeable polymer cannot be concentrated in the vicinity of the three-phase interface. Therefore, even if a high oxygen permeable material is used, the ability cannot be fully exhibited. After all, it can be said that the approach to the idea that the electrode reaction takes place at the three-phase interface is not sufficient.

  In addition, as in Patent Document 3, a battery in which an oxygen selective permeable membrane is simply interposed between the gas diffusion electrode and the air intake hole does not directly diffuse oxygen into the catalyst, and its catalytic activity is sufficient. I could not increase it.

Therefore, Patent Document 4 discloses a cathode for a fuel cell having a catalyst layer composed of a catalyst-carrying conductor and a polymer electrolyte, and the catalyst-carrying conductor further carries an oxygen storage / release body. An invention of a cathode for a fuel cell is disclosed. By carrying a catalyst and an oxygen storage / release body on a conductor, a cathode having excellent electrode characteristics for an oxygen reduction reaction, and a solid polymer fuel cell capable of obtaining a high battery output including the cathode have been obtained. . Patent Document 4 discloses Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Nb, Mo, Ta, W, Ce, Pr, and Nd metals, or oxides thereof as oxygen storage / release bodies. Are specifically disclosed, and oxides of Mn, Fe, Co, and Ni are more preferable. Further, oxides of Zr, Y, alkali metals, or alkaline earth metals are specifically disclosed, and CeO ₂ and CeO ₂ —ZrO ₂ compounds are more preferable.

  Patent Document 4 discloses a cathode having excellent electrode characteristics for an oxygen reduction reaction by supporting a catalyst and an oxygen storage / release body on a conductor, and a solid polymer capable of obtaining a high battery output equipped with the cathode Type fuel cells have been obtained.

  The present invention is a further improvement of the invention disclosed in Patent Document 4, and includes a cathode having further excellent electrode characteristics for an oxygen reduction reaction, and a solid polymer type having a high battery output equipped with the cathode. An object is to provide a fuel cell.

  The present inventor has found that the above problems can be solved by securing a path through which oxygen molecules can diffuse on carbon using a specific oxygen storage / release material, and has reached the present invention.

That is, first, the present invention is an invention of a cathode for a fuel cell having a catalyst layer comprising a catalyst-carrying conductor and a polymer electrolyte, and the catalyst-carrying conductor has a pyrochlore type Ce ₂ Zr ₂ O. Further, an oxygen storage / release body consisting of ₇ is further supported.

In the cathode of the present invention, the catalyst is supported on the conductor, and at the same time, the oxygen absorption / release body composed of pyrochlore-type Ce ₂ Zr ₂ O ₇ is further supported. Since it is ensured by the pyrochlore type Ce ₂ Zr ₂ O ₇ located in the vicinity of the catalyst, the concentration of the reaction gas in the vicinity of the reaction site in the catalyst layer is made higher than in the case of using a conventional CeO ₂ or CeO ₂ —ZrO ₂ compound. It is possible. As a result, the exchange current density in the electrode reaction can be increased, and the oxygen overvoltage can be reduced. That is, high electrode characteristics can be obtained. In particular, when used as a cathode of a polymer electrolyte fuel cell, the overvoltage of the oxygen reduction reaction at the cathode can be effectively reduced, so that the electrode characteristics of the cathode can be improved. Although the shortage of oxygen gas occurs particularly during operation of the fuel cell, the present invention makes it possible to maintain high electrode characteristics even during long-time operation.

In addition, in a fuel cell using air as an oxidant, the presence of nitrogen can cause an electrode reaction suppression. In the present invention, by using pyrochlore type Ce ₂ Zr ₂ O ₇ supported in the vicinity of the catalyst, diffusion of nitrogen gas is suppressed, a high oxygen concentration in the vicinity of the electrode is realized, and higher power generation performance is obtained. Can do.

The pyrochlore-type Ce ₂ Zr ₂ O ₇ used in the present invention is a kind of oxygen storage / release body having a function capable of reversibly repeating absorption and release of oxygen due to fluctuations in the oxygen concentration in the vicinity. It is a complex metal oxide having a crystal structure. That is, a relatively O ₂ concentration absorbs oxygen under high oxidizing atmosphere, a relatively O ₂ concentration can this be releasing oxygen under low reducing atmosphere. Specifically, it is an oxidation number variable composite metal oxide that absorbs and releases oxygen by changing the oxidation number.

Pyrochlore-type Ce ₂ Zr ₂ O ₇ used in the present invention is substantially insoluble in aqueous solvents such as water and alcohol, and therefore is detached from the conductor surface during a long-term operation and is discharged from the catalyst layer. Such a problem can be sufficiently prevented. As a result, the gas diffusion electrode of the present invention can stably obtain high electrode characteristics over a long period of time.

In the present invention, the conductor on which the catalyst and pyrochlore Ce ₂ Zr ₂ O ₇ are supported on the surface is preferably carbon powder or a fibrous carbon material.

Second, the present invention is an invention of a polymer electrolyte fuel cell having an anode, a cathode, and a polymer electrolyte membrane disposed between the anode and the cathode, wherein the cathode And a catalyst layer comprising a catalyst-carrying conductor and a polymer electrolyte, wherein the catalyst-carrying conductor further carries an oxygen storage / release body comprising a pyrochlore type Ce ₂ Zr ₂ O _7. To do.

  Thus, by providing the cathode of the present invention having excellent electrode characteristics with respect to the oxygen reduction reaction described above, it becomes possible to configure a polymer electrolyte fuel cell having a high cell output. In addition, as described above, the cathode of the present invention can sufficiently prevent the occurrence of flooding and is excellent in durability. Therefore, the polymer electrolyte fuel cell of the present invention including the cathode has a high cell output. Can be obtained stably over a long period of time.

According to the present invention, the pyrochlore-type Ce ₂ Zr ₂ O ₇ that is an oxygen storage / release body is present in the catalyst layer of the fuel cell cathode, so that it is not affected by gas diffusion in the catalyst layer and in the vicinity of the electrode. Higher oxygen concentration was achieved, and higher power generation performance was obtained.

  Hereinafter, preferred embodiments of the cathode of the present invention and a polymer electrolyte fuel cell including the cathode will be described in detail.

FIG. 1 shows a conceptual diagram of a catalytic electrode reaction at a conventional cathode. FIG. 1 (a) shows the time when the reaction starts or when the output is low. Since oxygen is not required much, the supply of oxygen is maintained in the vicinity of the catalyst by normal diffusion. In other words, oxygen molecules that have diffused near the catalyst generate water molecules by reacting protons and electrons with the following chemical formula.
O ₂ + 4H ⁺ + 4e ^{− −−} →→ 2H ₂ O

  FIG.1 (b) is a time when an output becomes large and consumes a lot of oxygen. Therefore, the oxygen partial pressure near the catalyst is extremely reduced. In order to carry out the reaction, there is no choice but to wait for the next oxygen to diffuse, leading to a reduction in power generation characteristics.

FIG. 2 shows a conceptual diagram of the catalytic electrode reaction at the cathode of the present invention. In the vicinity of the conductive carbon on which the catalyst is supported, pyrochlore-type Ce ₂ Zr ₂ O ₇ is also supported on the conductive carbon as an oxygen storage / release body. When the fuel cell is operated in the low output region, the oxygen consumption in the catalyst is small and the oxygen concentration in the vicinity of the oxygen storage / release body is high, so that excess oxygen is stored in the oxygen storage / release body. On the other hand, when the fuel cell is operated at a high output, the amount of oxygen consumed by the catalyst is large and the oxygen concentration in the vicinity of the oxygen storage / release body is reduced, so that oxygen is released from the oxygen storage / release body. The released oxygen is reduced on the catalyst, thereby further improving the fuel cell performance. In this way, since oxygen is released from the vicinity of the Pt electrode catalyst, oxygen is supplied to the Pt catalyst without being affected by gas diffusion in the catalyst layer, so that the output of the fuel cell is improved.

  The electrode reaction proceeds at a site called a three-phase interface where reaction gas, catalyst, and electrolyte meet. The supply of oxygen to the three-phase interface is an important topic. When the output of the battery is increased, a large amount of oxygen is required for the reaction, and if there is no oxygen in the vicinity of the catalyst, the power generation characteristics deteriorate rapidly. In the conventional technique, a high concentration oxygen is supplied. However, as shown in FIG. 1, the actual reaction is performed at the three-phase interface (near the catalyst). The ability cannot be fully demonstrated. In particular, when the output is increased, the amount of oxygen consumed on the catalyst surface increases, but the diffusion rate of oxygen from the outside to the catalyst surface hardly changes. Therefore, when the oxygen consumption rate on the catalyst surface above a certain level exceeds the oxygen supply rate on the catalyst surface, the power generation characteristics deteriorate due to lack of oxygen in the vicinity of the catalyst. On the other hand, as shown in FIG. 2, in the present invention, the power supply characteristic is prevented from being deteriorated due to lack of oxygen in the vicinity of the catalyst by increasing the supply rate of oxygen to the catalyst surface.

  The cathode of the polymer electrolyte fuel cell of the present invention comprises a catalyst layer, and preferably comprises a catalyst layer and a gas diffusion layer disposed adjacent to the catalyst layer. As a constituent material of the gas diffusion layer, for example, a porous body having electronic conductivity (for example, carbon cloth or carbon paper) is used.

Pyrochlore-type Ce ₂ Zr ₂ O ₇ is present in the cathode catalyst layer, and the cathode electrode reaction rate is improved by reducing the overvoltage for the oxygen reduction reaction at the cathode.

Further, the content of pyrochlore-type Ce ₂ Zr ₂ O ₇ contained in the catalyst layer is preferably 0.01 to 30% by mass with respect to the total amount of the catalyst-carrying conductor and the polymer electrolyte, More preferably, it is 0.01-20 mass%. Here, when the content of the pyrochlore-type Ce ₂ Zr ₂ O ₇ is less than 0.01% by mass, it tends to be difficult to sufficiently reduce the oxygen overvoltage for the oxygen reduction reaction. On the other hand, when the content of pyrochlore-type Ce ₂ Zr ₂ O ₇ exceeds 30% by mass, the content of the fluorinated ion exchange resin contained in the catalyst layer is relatively lowered, and as a result, it is effective in the catalyst layer. Therefore, it is difficult to obtain high electrode characteristics because the number of reaction sites that function in a reduced manner.

The catalyst contained in the cathode catalyst-carrying conductor of the present invention is not particularly limited, but platinum or a platinum alloy is preferable. Furthermore, the catalyst contained in the catalyst-carrying conductor is preferably carried on an electrically conductive carrier. Although this support | carrier is not specifically limited, The carbon material whose specific surface area is 200 m < ² > / g or more is preferable. For example, carbon black or activated carbon is preferably used.

  The polymer electrolyte contained in the catalyst layer of the present invention is preferably a fluorine-containing ion exchange resin, and particularly preferably a sulfonic acid type perfluorocarbon polymer. The sulfonic acid-type perfluorocarbon polymer enables proton conduction that is chemically stable for a long period of time in the cathode and is prompt.

  The layer thickness of the catalyst layer of the cathode of the present invention may be the same as that of a normal gas diffusion electrode, preferably 1 to 100 μm, more preferably 3 to 50 μm.

  In a polymer electrolyte fuel cell, since the overvoltage of the cathode oxygen reduction reaction is usually very large compared to the overvoltage of the anode hydrogen oxidation reaction, the oxygen in the vicinity of the reaction site in the cathode catalyst layer as described above. Increasing the concentration to effectively use the reaction site and improving the electrode characteristics of the cathode is effective in improving the output characteristics of the battery.

  On the other hand, the configuration of the anode is not particularly limited. For example, the anode may have a configuration of a known gas diffusion electrode.

  In addition, the polymer electrolyte membrane used in the solid polymer fuel cell of the present invention is not particularly limited as long as it is an ion exchange membrane exhibiting good ion conductivity in a wet state. As the solid polymer material constituting the polymer electrolyte membrane, for example, a perfluorocarbon polymer having a sulfonic acid group, a polysulfone resin, a perfluorocarbon polymer having a phosphonic acid group or a carboxylic acid group can be used. Among these, a sulfonic acid type perfluorocarbon polymer is preferable. And this polymer electrolyte membrane may consist of the same resin as the fluorine-containing ion exchange resin contained in a catalyst layer, and may consist of different resin.

  The catalyst layer of the cathode of the present invention can be prepared in advance using a coating material in which a catalyst and an oxygen storage / release body are supported on a conductor and a polymer electrolyte dissolved or dispersed in a solvent or dispersion medium. . Alternatively, it can be prepared using a coating liquid in which a catalyst-carrying conductor, a polymer electrolyte, and an oxygen storage / release body are dissolved or dispersed in a solvent or dispersion medium. As the solvent or dispersion medium used here, for example, alcohol, fluorine-containing alcohol, fluorine-containing ether and the like can be used. And a catalyst layer is formed by apply | coating a coating liquid to the carbon cloth etc. which become an ion exchange membrane or a gas diffusion layer. Alternatively, the catalyst layer can be formed on the ion exchange membrane by coating the coating solution on a separately prepared substrate to form a coating layer and transferring the coating layer onto the ion exchange membrane.

  Here, when the catalyst layer is formed on the gas diffusion layer, it is preferable to join the catalyst layer and the ion exchange membrane by an adhesion method, a hot press method, or the like. Further, when the catalyst layer is formed on the ion exchange membrane, the cathode may be constituted only by the catalyst layer, but a gas diffusion layer may be further arranged adjacent to the catalyst layer to serve as the cathode.

  A separator having a normal gas flow path is disposed outside the cathode, and a gas containing hydrogen is supplied to the anode, and a gas containing oxygen is supplied to the cathode. Composed.

  Hereinafter, the cathode and the polymer electrolyte fuel cell of the present invention will be described in detail with reference to Examples and Comparative Examples.

[Sample preparation]
Usually, a Pt / C catalyst is used as the electrode catalyst for the cathode (Comparative Example 1). An experiment was conducted by adding CeO ₂ which is a normal oxygen storage / release body (Comparative Example 2). In this experiment, pyrochlore-type Ce ₂ Zr ₂ O ₇ was added to the test (Example).

(Example)
A PtFe (60 wt%) / C + Pt (5 wt%) / pyrochlore type Ce ₂ Zr ₂ O ₇ (20 wt%) mixture was prepared by the following procedure, an MEA was prepared, the MEA was assembled in a cell, and the performance was evaluated.
(1) A predetermined amount of cerium nitrate cerium nitrate and zirconium oxynitrate was dissolved in pure water and stirred for 2 hours.
(2) Water was evaporated to some extent at 120 ° C. and then vacuum-dried.
(3) Firing was performed at 350 ° C. for 5 hours in an atmospheric firing furnace.
(4) The temperature was maintained at 900 ° C. for 2 hours in a reducing gas (H ₂ , CO, etc.) atmosphere, and then the temperature was gradually lowered by switching to an inert gas (N 2, Ar, He, etc.).
(5) After pulverizing the obtained powder in a mortar, the powder was immersed and stirred in a dinitrodiamine Pt complex aqueous solution, and evaporated and dried at 120 ° C. (including Pt 5 wt% with respect to the powder).
(6) After pulverizing in a mortar, it was baked at 500 ° C. for 2 hours in an atmospheric baking furnace. Again pulverized in a mortar.
(7) Predetermined amounts of Pt (5 wt%) / pyrochlore-type Ce ₂ Zr ₂ O ₇ and PtFe (60 wt%) / C catalyst thus obtained in ion-exchanged water, electrolyte solution (Nafion), ethanol, and polyethylene glycol Mixing (Nafion / Carbon = 1.0 wt%, Pt (5 wt%) / pyrochlore type Ce ₂ Zr ₂ O ₇ ) was 20 wt% with respect to PtFe (60 wt%) / C) to prepare a catalyst ink.
(8) The catalyst ink was cast on a Teflon resin film (film thickness: 6 mil), dried, and cut into 13 (cm 2).
(9) Create MEA by thermocompression bonding to electrolyte membrane.
(10) MEA was assembled into a cell and performance was evaluated.

(Comparative Example 1)
In the examples, steps (1) to (6) are not performed, steps (7) to (10) are performed in the same manner, PtFe 60 wt% / C is prepared, MEA is created, MEA is assembled to the cell, and performance evaluation is performed. did.

(Comparative Example 2)
In the example (1), the amount of dissolution of both reagents was adjusted to be Ce _0.5 Zr _0.5 O ₂ in step (4). A PtFe (60 wt%) / C + Pt (5 wt%) / Ce _0.5 Zr _0.5 O ₂ (20 wt%) mixture was prepared, an MEA was prepared, the MEA was assembled into a cell, and the performance was evaluated.
[Catalyst activity evaluation]
The following power generation evaluation test was conducted in a single cell having an electrode area of 12.96 cm ² .
“Gas flow rate” Anode: H ₂ 500 cc / min
Cathode: Air 1000cc / min
"Humidification temperature" Anode bubbling: 75 ° C
Cathode bubbling: 60 ° C
“Pressure” Anode: 0.2 MPa
Cathode: 0.2 MPa
“Cell temperature” 80 ℃

FIG. 3 shows the evaluation results. From the result of FIG. 3, the fuel cell using the electrode carrying the pyrochlore-type Ce ₂ Zr ₂ O _{7 of the} present invention has a higher power generation performance than the comparative example 1 using the electrode not carrying the oxygen storage / release body. It turns out that it is excellent. Similarly, the fuel cell using the electrode carrying the pyrochlore-type Ce ₂ Zr ₂ O ₇ of the present invention has the power generation performance even when compared with the comparative example 2 using the electrode carrying the usual oxygen storage / release body. It can be seen that it is excellent.

[Oxygen absorption and release performance and power generation performance]
FIG. 4 shows the relationship between the oxygen storage / release performance of the oxygen storage / release body further supported by the catalyst-supported conductor and the battery performance. As an evaluation method of oxygen absorption / release performance, the CO ₂ production peak at the time of O ₂ saturated adsorption → CO introduction was measured by MASS (@ 80 ° C.) in the pelletized additive. The peak area value at this time was defined as the CO ₂ production amount (au), which was considered to reflect the oxygen absorption / release amount (oxygen absorption / release performance).

The power generation conditions are
(Cathode) Habra 48 ° C, Air stoichiometric ratio 1.5, 0.1 MPa
(Anode) Habra 58 ° C., H ₂ stoichiometric ratio 5.5, 0.1 MPa
Met.

From the results of FIG. 4, the amount of CO ₂ produced (in order of Pt / Al ₂ O ₃ , Pt / CeO ₂ , Pt / Ce _0.5 Zr _0.5 O ₂ , Pt / Ce ₂ Zr ₂ O ₇ ). It can be seen that u.) increases, that is, the oxygen absorption / release amount (oxygen absorption / release performance) increases. Thus, by mixing pyrochlore-type Ce ₂ Zr ₂ O ₇ with high oxygen absorption / release performance into the electrode, the conventional oxygen absorption / release body (such as Ce _0.5 Zr _0.5 O ₂ ) is mixed with the electrode. Furthermore, it turns out that the battery performance (power generation efficiency) of the low current density side improves.

By analogy with the above results, pyrochlore-type Ce ₂ Zr ₂ O ₇ exists in the vicinity of Pt, and conventional oxygen once strongly adsorbs to pyrochlore-type Ce ₂ Zr ₂ O _7, and the oxygen concentration in the vicinity of the catalyst It is possible that it will be released with a decline.

The conceptual diagram of the catalyst electrode reaction in the conventional cathode is shown. FIG. 1 (a) is when the reaction starts or when the output is low, and FIG. 1 (b) is when the output becomes large. The conceptual diagram of the catalyst electrode reaction in the cathode of this invention is shown. The current density-cell voltage curve of an Example and a comparative example is shown. The relationship between the oxygen storage / release performance of the oxygen storage / release body further supported on the catalyst-supported conductor and the battery performance is shown.

Claims (2)

A cathode for a fuel cell having a catalyst layer made of a catalyst-carrying conductor and a polymer electrolyte, wherein the catalyst-carrying conductor further carries an oxygen storage / release body made of pyrochlore-type Ce ₂ Zr ₂ O _7. A cathode for a fuel cell. A solid polymer fuel cell having an anode, a cathode, and a polymer electrolyte membrane disposed between the anode and the cathode, the cathode comprising a catalyst-supporting conductor and a polymer electrolyte A solid polymer fuel cell, characterized in that an oxygen storage / release body made of pyrochlore-type Ce ₂ Zr ₂ O ₇ is further supported on the catalyst-supporting conductor.

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