JP2009226311A - Catalyst, its manufacturing method and its application - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a catalyst which does not corrode in an acidic electrolyte or at high electric potentials and has excellent durability and a high oxygen-reducing ability. <P>SOLUTION: The catalyst is an oxygen occlusion compound containing one or a mixture of transition metals of the groups 4, 5 and 6 and preferably has a composition of MCxNyOz (wherein, M is a transition metal (described as metal M as well) of the group 4, 5 or 6; C is carbon; N is nitrogen; O is oxygen; x, y and z are atomic ratios of C, N and O, respectively, with the atomic ratio of the metal M taken as 1; 0.3≤x≤0.7; 0.3≤y≤0.7; and 0.4≤z≤3.0). <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a catalyst, a method for producing the same, and uses thereof.

  Fuel cells are classified into various types depending on the type of electrolyte and the type of electrode, and representative types include alkali type, phosphoric acid type, molten carbonate type, solid electrolyte type, and solid polymer type. Among them, a polymer electrolyte fuel cell that can operate at a low temperature (about −40 ° C.) to about 120 ° C. attracts attention, and in recent years, development and practical application as a low-pollution power source for automobiles is progressing. As a use of the polymer electrolyte fuel cell, a vehicle driving source and a stationary power source are being studied. However, in order to be applied to these uses, durability over a long period of time is required.

  In this polymer solid fuel cell, a polymer solid electrolyte is sandwiched between an anode and a cathode, fuel is supplied to the anode, oxygen or air is supplied to the cathode, and oxygen is reduced at the cathode to extract electricity. is there. Hydrogen or methanol is mainly used as the fuel.

  Conventionally, in order to increase the reaction speed of the fuel cell and increase the energy conversion efficiency of the fuel cell, a layer containing a catalyst (hereinafter referred to as “for fuel cell”) is provided on the cathode (air electrode) surface or anode (fuel electrode) surface of the fuel cell. Also referred to as “catalyst layer”).

  As this catalyst, a noble metal is generally used, and platinum which is stable at a high potential and has a high activity among noble metals has been mainly used. However, since platinum is expensive and has limited resources, the development of an alternative catalyst has been sought.

  In addition, the noble metal used on the cathode surface may be dissolved in an acidic atmosphere, and there is a problem that the noble metal is not suitable for applications that require long-term durability. Therefore, there has been a strong demand for the development of a catalyst that does not corrode in an acidic atmosphere, has excellent durability, and has high oxygen reducing ability.

  In recent years, materials containing non-metals such as carbon, nitrogen, and boron have attracted attention as catalysts instead of platinum. These non-metal-containing materials are cheaper and have abundant resources than precious metals such as platinum.

  Non-Patent Document 1 reports that a ZrOxN compound based on zirconium exhibits oxygen reducing ability. Patent Document 1 discloses an oxygen reduction electrode material containing one or more nitrides selected from the group of elements of Group 4, Group 5 and Group 14 of the long periodic table as a platinum substitute material. Patent Document 2 discloses that a partially oxidized compound of any one of titanium, lanthanum, tantalum, niobium, and zirconium and any of nitrogen, boron, carbon, or sulfur is used as an electrode catalyst for a fuel cell. ing. Furthermore, Patent Document 3 discloses that titanium carbonitride powder is used as an oxygen electrode catalyst for a polymer electrolyte fuel cell.

  However, these non-metal-containing materials are unstable in an acidic solution or do not have sufficient oxygen reducing ability for practical use as a catalyst, and are not sufficiently active for actual use as a fuel cell. It is.

Non-Patent Document 2 describes partially oxidized TaCN. However, this document describes that TaCN is gradually oxidized to produce an appropriate amount of Ta ₂ O _5. The optimum amount of Ta ₂ O _{5 is} determined from 0.3 to 0 based on DOO (degree of oxidation). The range of .97 is good. That is, it is shown here that a considerable amount of an appropriate by-product Ta ₂ O ₅ is required.

However, the present inventors have found out that what is clearly different from the structure shown in this document is that it exhibits catalytic activity, and has reached the present invention. That is, the active structure maintains the cubic crystal of the original metal compound, and has a large amount of oxygen stored in the structure. Conversely, Ta ₂ O ₅ as described in Non-Patent Document 2 has no activity, and if this substance is contained in a large amount, the catalytic activity is lowered. To the last, Ta ₂ O ₅ is a by-product, and in order to maintain a high degree of catalytic activity, it is important that the amount is 5% by mass or less.

  Here, the amount of the inactive oxide transition metal indicates a case where the height of the oxide peak value is 1/20 or less with respect to the maximum peak value having a rock salt structure in the X-ray diffraction pattern. Overall, it can be judged from the values of XRD and elemental analysis.

  In the case where the activity is a cubic metal compound, for example, a Ta compound obtained by oxidizing TaCN, the catalyst is in TaCNO that stores oxygen.

  As an excellent method for producing an oxygen storage metal compound without producing a large amount of inert metal oxides as by-products, a metal carbonitride is heat-treated in an inert gas containing oxygen and a reducing gas. It can be obtained by doing.

Although platinum is useful not only as a catalyst for the fuel cell, but also as an exhaust gas treatment catalyst or an organic synthesis catalyst, platinum is expensive and has limited resources. There has been a demand for the development of a catalyst that can be used in various applications.

S. Doi, A. Ishihara, S. Mitsushima, N. kamiya, and K. Ota, Journal of The Electrochemical Society, 154 (3) B362-B369 (2007) Akimitsu Ishihara, Kenichiro Ota, Electrochemistry and Industrial Physical Chemistry, 76, N0.1, 59-64 JP 2007-31781 A JP 2006-198570 A JP 2007-257888 A Japanese Patent Laid-Open No. 2003-342058

  An object of the present invention is to solve such problems in the prior art, and an object of the present invention is to provide a catalyst that does not corrode in an acidic electrolyte or at a high potential, has excellent durability, and has a high oxygen reduction ability. There is.

  As a result of intensive studies to solve the problems of the prior art, the present inventors have found that a catalyst comprising a specific oxygen storage compound does not corrode in an acidic electrolyte or at a high potential, has excellent durability, and high oxygen reduction. It was found to have the ability.

  Furthermore, the present inventors have found that a higher performance catalyst can be obtained by controlling the ratio of the number of atoms in the oxygen storage compound constituting the catalyst, and have completed the present invention.

  The present invention relates to the following (1) to (18), for example.

(1)
A catalyst comprising an oxygen storage compound containing a Group 4, 5 or 6 transition metal.

(2)
The oxygen storage compound has a composition formula MCxNyOz (M is a transition metal of Group 4, 5 or 6 (hereinafter also referred to as “metal M”), C is carbon, N is nitrogen, and O is oxygen. X, y , Z represents the atomic ratio of each of C, N, and O when the atomic ratio of the metal M is 1, and 0.3 ≦ x ≦ 0.7, 0.3 ≦ y ≦ 0.7, and 0 4 ≦ z ≦ 3.0.) The catalyst according to (1).

(3)
When the metal M is a group 4 element, the composition of x, y, z is 3 ≦ 4x + 3y + 2z ≦ 4 when the atomic ratio of the metal M is 1, and when the metal M is a group 5 element, the atoms of the metal M When the ratio is 1, the composition of x, y, z is 4 ≦ 4x + 3y + 2z ≦ 5, and when the metal M is a group 6 element, the composition of x, y, z when the atomic ratio of the metal M is 1 Is 4 ≦ 4x + 3y + 2z ≦ 6, The catalyst according to (1) or (2),

(4)
When the metal M is an alloy or a mixture of transition metals (alloys), the composition ratio of x, y, and z is allocated at a ratio corresponding to the composition ratio of the alloy or transition metal mixture (alloys). (1) or (2) the catalyst characterized by these.

(5)
The catalyst according to any one of (1) to (4), wherein the oxygen storage compound has a rock salt structure (NaCl type structure).

(6)
The catalyst according to any one of (1) to (5), wherein the inactive transition metal oxide is 5% by mass or less.

(7)
Furthermore, platinum is 1.0 mass% or less, The catalyst in any one of (1)-(6) characterized by the above-mentioned.

(8)
(1) The catalyst for fuel cells in any one of (7).

(9)
In the catalyst according to any one of (1) to (8), a carbide, a nitride, or a carbonitride of a group 4, 5 or 6 transition metal in an inert gas containing oxygen and a reducing gas The manufacturing method of the catalyst characterized by including the process heat-processed by.

(10)
The method for producing a catalyst according to (9), wherein the carbide, nitride or carbonitride of the transition metal of Group 4, 5 or 6 has a rock salt structure (NaCl type structure).

(11)
The method for producing a catalyst according to (9) or (10), wherein the reducing gas is hydrogen.

(12)
The method for producing a catalyst according to any one of (9) to (11), wherein the inert gas is nitrogen or argon.

(13)
A catalyst layer for a fuel cell comprising the catalyst according to any one of (1) to (8).

(14)
The catalyst layer for a fuel cell according to (13), further comprising electron conductive particles.

(15)
An electrode having a fuel cell catalyst layer and a porous support layer, wherein the fuel cell catalyst layer is the fuel cell catalyst layer according to (14) or (15).

(16)
A membrane electrode assembly having a cathode, an anode, and an electrolyte membrane disposed between the cathode and the anode, wherein the cathode and / or the anode is an electrode according to (15) Membrane electrode assembly.

(17)
A fuel cell comprising the membrane electrode assembly according to (16).

(18)
A polymer electrolyte fuel cell comprising the membrane electrode assembly according to (16).

  The catalyst of the present invention does not corrode in an acidic electrolyte or at a high potential, is stable, has a high oxygen reducing ability, and is inexpensive compared with platinum. Therefore, the fuel cell including the catalyst is relatively inexpensive and has excellent performance.

<Catalyst>
The catalyst of the present invention is an oxygen storage compound containing a group 4, 5 or 6 transition metal, and preferably has a composition formula MCxNyOz (M is a group 4, 5 or 6 transition metal (hereinafter referred to as "metal M"). And C represents carbon, N represents nitrogen, and O represents oxygen. X, y, and z represent the atomic ratios of C, N, and O, respectively, when the atomic ratio of metal M is 1. 0.3 ≦ x ≦ 0.7, 0.3 ≦ y ≦ 0.7, and 0.4 ≦ z ≦ 3.0.

  In the above composition formula, when the metal M is a group 4 element, the composition of x, y, z is 3 ≦ 4x + 3y + 2z ≦ 4 when the atomic ratio of the metal M is 1, and the metal M is a group 5 element When the atomic ratio of the metal M is 1, the composition of x, y, z is 4 ≦ 4x + 3y + 2z ≦ 5, and when the metal M is a group 6 element, the atomic ratio of the metal M is 1; The composition of y and z is 4 ≦ 4x + 3y + 2z ≦ 6.

  Further, when the metal M is an alloy or a transition metal mixture (alloys), the composition ratio of x, y, and z is allocated at a ratio corresponding to the composition ratio of the alloy or the transition metal mixture (alloys). It is preferable that

  Here, “the composition ratio of x, y, z is allocated at a ratio corresponding to the composition ratio” means that, for example, in the case of alloys of Group 4 and Group 5, Group 4 elements are divided into A group and Group 5 by atomic ratio. When the element is (1-A) percent, it means that 3 × A / 10 + 4 × (1-A) ≦ 4x + 3y + 2Z ≦ 4 × A / 10 + 5 × (1-A).

  The oxygen storage compound and the transition metal carbide, nitride, or carbonitride used as a raw material thereof preferably have a rock salt structure (NaCl-type structure).

  The rock salt structure here refers to a face-centered cubic lattice structure.

  Therefore, the oxygen storage compound used in the present invention is presumed to be a cubic crystal having a distorted shape, and further contains a very large amount of oxygen.

Originally, when a transition metal compound is oxidized, there are many oxide structures of the metal and the crystal structure also changes. For example, in the case of Ta, the rock salt structure changes to form orthorhombic Ta ₂ O ₅ .

In the case of Nb, orthorhombic Nb ₂ O ₅ is also formed. In the case of Zr, monoclinic ZrO ₂ is formed. In the case of Mo, orthorhombic MoO ₃ is easily formed. However, when the transition metal compound is slowly oxidized, the oxide is not easily generated, and a structure in which oxygen is occluded can be obtained while maintaining the rock salt structure. Furthermore, in order to produce an inorganic compound that occludes oxygen efficiently by controlling oxidation conditions, it is preferable to oxidize while introducing a reducing gas. As the reducing gas, ammonia or hydrogen can be recommended. This is because these are easy to obtain, easy to handle and easy to control the concentration. In particular, when hydrogen is used, oxidation can be performed mildly, and oxygen can be occluded inside the entire inorganic compound while maintaining the rock salt structure.
The oxygen storage amount in this case also varies depending on the type of transition metal. The transition metal carbide or nitride or carbonitride of the precursor has a rock salt structure, but in the case of carbide, the transition metal is tetravalent, the nitride is trivalent, and the carbonitride is intermediate 3.5 It is estimated that Since the transition metal is oxidized while oxygen enters, oxygen is occluded according to the valence that the transition metal can stably take.

  For example, in the case of a Group 4 transition element, oxygen can be occluded until the transition element becomes tetravalent. In the case of Group 5 transition elements, there is room for oxygen to enter until pentavalent. In the case of a group 6 element, oxygen can enter until it becomes hexavalent. However, since the amount of oxygen atoms that can enter is determined by the size of the structural vacancies and oxygen atoms and the bond energy between the crystal lattices, it is not always necessary to use a transition gold element of group 6. In terms of stability, transition element compounds of Group 4, Group 5 are more stable than Group 6.

  Therefore, the amount of oxygen stored stably is not determined solely by the valence of the transition metal. As a result of examination by the present inventors, when the metal M is a group 4 element, the composition ratio of x, y, z is 3 ≦ 4x + 3y + 2z ≦ 4 when the metal M of MC × NyOz is 1, and the metal M is a group 5 element In the case where the composition ratio of the metal M is 1, the composition ratio of x, y, z is 4 ≦ 4x + 3y + 2z ≦ 5, and when the metal M is a group 6 element, the composition ratio of the metal M is 1. When the composition ratio of x, y, z is 4 ≦ 4x + 3y + 2z ≦ 6, and the metal M is an alloy or a mixture of transition metals, the composition ratio of x, y, z is allocated within the range of the composition ratio of the metal. It turned out to be desirable.

  In addition, the inorganic compound of the present invention in which a large amount of oxygen is occluded has a cubic shape with a very distorted shape. It is considered that the oxygen storage capacity is increased and the oxygen reducing ability is increased.

The oxygen reduction initiation potential of the catalyst used in the present invention, which is measured according to the following measurement method (A), is preferably 0.7 V (vs. NHE) or more based on the reversible hydrogen electrode.
[Measurement method (A):
The catalyst and carbon are placed in a solvent so that the amount of the catalyst dispersed in the carbon that is the electron conductive particles is 1% by mass, and the mixture is stirred with ultrasonic waves to obtain a suspension. As the carbon, carbon black (specific surface area: 100 to 300 m ² / g) (for example, XC-72 manufactured by Cabot Corporation) is used, and the catalyst and carbon are dispersed so that the mass ratio is 95: 5. As the solvent, isopropyl alcohol: water (mass ratio) = 2: 1 is used.

  30 μl of the suspension is collected while applying ultrasonic waves, and is quickly dropped on a glassy carbon electrode (diameter: 5.2 mm) and dried at 120 ° C. for 1 hour. By drying, a catalyst layer for a fuel cell containing the catalyst is formed on the glassy carbon electrode.

  Next, 10 μl of Nafion (DuPont 5% Nafion solution (DE521)) diluted 10-fold with pure water is further dropped onto the fuel cell catalyst layer. This is dried at 120 ° C. for 1 hour.

Thus, using the obtained electrode, refer to a reversible hydrogen electrode in a sulfuric acid solution of the same concentration at a temperature of 30 ° C. in a 0.5 mol / dm ³ sulfuric acid solution in an oxygen atmosphere and a nitrogen atmosphere. When a current-potential curve was measured by polarizing the electrode at a potential scanning speed of 5 mV / sec, there was a difference of 0.2 μA / cm ² or more between the reduction current in the oxygen atmosphere and the reduction current in the nitrogen atmosphere. The potential that starts to appear is defined as the oxygen reduction start potential. ]
When the oxygen reduction starting potential is less than 0.7 V (vs. NHE), hydrogen peroxide may be generated when the catalyst is used as a catalyst for a cathode of a fuel cell. Further, the oxygen reduction starting potential is preferably 0.85 V (vs. NHE) or more in order to suitably reduce oxygen. Further, the oxygen reduction starting potential is preferably as high as possible. Although there is no particular upper limit, the theoretical value is 1.23 V (vs. NHE).

  The fuel cell catalyst layer of the present invention formed using the above catalyst is preferably used at a potential of 0.4 V (vs. NHE) or more in the acidic electrolyte, and the upper limit of the potential depends on the stability of the electrode. It can be used up to approximately 1.53 (vs. NHE) of the potential at which oxygen is generated.

  When this potential is less than 0.4 V (vs. NHE), there is no problem at all from the viewpoint of the stability of the oxygen storage compound, but oxygen cannot be reduced suitably, and the membrane electrode assembly contained in the fuel cell Is not useful as a catalyst layer for fuel cells.

The current flow when using the catalyst of the present invention is evaluated by the oxygen reduction current density (mA / cm ² ) when the potential measured according to the measurement method (A) is 0.7 V. Can do. The oxygen reduction current density is preferably 0.1 (mA / cm ² ) or more, and more preferably 0.5 (mA / cm ² ) or more. When the oxygen reduction current density is less than 0.1 (mA / cm ² ), the current does not flow so much and its usefulness as a fuel cell catalyst layer is poor.

<Method for producing catalyst>
Although the manufacturing method of the said catalyst is not specifically limited, For example, the manufacturing method including the process of obtaining an oxygen storage compound by heat-processing a transition metal carbonitride in the inert gas containing hydrogen and oxygen is mentioned.

  As a method of obtaining the transition metal carbonitride used in the above step, a method (I) for producing a transition metal carbonitride by heat-treating a mixture of a transition metal oxide and carbon in a nitrogen atmosphere, A method (II) for producing a transition metal carbonitride by heat-treating a mixture of a transition metal carbide, oxide and nitride in a nitrogen atmosphere or the like.

Other, Journal of Solid State Chemistry, 142,
100-107 (1999) (Hak Soo Kim, Guy Bugli, and Gerald Djega-Mariadassou).

[Production Method (I)]
The production method (I) is a method for producing a precursor transition metal carbonitride by heat-treating a mixture of transition metal oxide and carbon in a nitrogen atmosphere.

  The temperature of the heat treatment for producing the carbonitride varies depending on the type of transition metal, but is preferably in the range of 600 ° C to 2000 ° C, more preferably in the range of 900 to 1800 ° C. When the heat treatment temperature is within the above range, it is preferable in terms of good crystallinity and uniformity. If the heat treatment temperature is less than 600 ° C., the crystallinity tends to be poor and the uniformity tends to be poor, and if it is 2000 ° C. or more, sintering tends to occur or sublimation or evaporation may occur depending on the case.

  The raw material oxide is not particularly limited. A catalyst made of a transition metal carbonitride obtained by heat-treating a precursor carbonitride obtained from the oxide in an inert gas containing hydrogen and oxygen has a high oxygen reduction starting potential and is active. There is.

Examples of the raw material carbon include carbon, carbon black, graphite, graphite, activated carbon, carbon nanotube, carbon nanofiber, carbon nanohorn, and fullerene. It is preferable that the particle size of the carbon powder is smaller because the specific surface area is increased and the reaction with the oxide is facilitated. For example, carbon black (specific surface area: 100 to 300 m ² / g, for example, XC-72 manufactured by Cabot Corporation) is preferably used.

A suitable carbonitride can be obtained by controlling the molar ratio of the oxide of transition metal and carbon of the starting material stoichiometrically according to the valence of the transition metal such as trivalent, tetravalent, pentavalent or hexavalent. It is done. For example, when niobium is used as a transition metal, for example, in a divalent niobium oxide, 1 to 3 mol of carbon is preferable with respect to 1 mol of niobium oxide. In the case of tetravalent niobium oxide, 2 to 4 mol of carbon is preferable with respect to 1 mol of niobium oxide. In the pentavalent niobium oxide, 3 to 9 mol of carbon is preferable with respect to 1 mol of niobium oxide. Niobium carbide tends to be formed when the upper limit value of these ranges is exceeded, and niobium nitride is generated when the lower limit value is exceeded. When titanium is used as a transition metal, titanium carbide is 10 to 300 mol and titanium oxide is 0.1 to 10 mol with respect to 1 mol of titanium nitride. When titanium carbonitride obtained at a blending ratio that satisfies the above range is used, titanium carbonitride oxide (TiC _x N _y O _z ) with appropriate atomic ratios (x, y, z) and x + y + z is obtained. Becomes easy. Moreover, when it is desired to synthesize a compound of an alloy as a transition metal, a composition corresponding to the maximum valence number that the alloy can take is required. For example, when it is desired to use a composite compound of niobium and molybdenum as the target oxygen storage compound, 0.1 to 4 mol of molybdenum oxide and 2 to 6 mol of carbon are preferable with respect to 1 mol of niobium oxide. Further, when the target oxygen storage compound is a complex oxide of zirconium and niobium, 0.2 to 5 mol of niobium oxide and 2 to 5 mol of carbon are preferable with respect to 1 mol of zirconium oxide.

[Production Method (II)]
The production method (II) is a method of producing a precursor transition metal carbonitride by heat-treating a mixture of a transition metal carbide, oxide and nitride in a nitrogen atmosphere or the like.

  The temperature of the heat treatment for producing the fiber metal carbonitride is in the range of 600 ° C to 2000 ° C, preferably in the range of 800 to 1600 ° C. When the heat treatment temperature is within the above range, it is preferable in terms of good crystallinity and uniformity. If the heat treatment temperature is less than 600 ° C., the crystallinity tends to be poor and the uniformity tends to deteriorate, and if it is 1800 ° C. or more, it tends to be easy to sinter.

  Thus, the carbonitride obtained by heat-treating the precursor carbonitride in an inert gas containing a reducing gas and oxygen has a large oxygen storage capacity and becomes a catalyst having a high oxygen reduction activity.

(Production process of oxygen storage carbonitride)
Next, a process for obtaining a transition metal carbonitride having a large oxygen storage amount by heat-treating the transition metal carbonitride in an inert gas containing a reducing gas and oxygen will be described.

  Examples of the inert gas include helium gas, neon gas, argon gas, krypton gas, xenon gas, radon gas, and nitrogen gas. Argon gas, helium gas or nitrogen gas is particularly preferable because it is relatively easy to obtain.

  The oxygen concentration in the step depends on the heat treatment time and the heat treatment temperature, but is preferably 0.1 to 5% by volume, particularly preferably 0.5 to 3% by volume. The reducing gas is most preferably hydrogen, and the hydrogen concentration is preferably 0.5 to 5% by volume, particularly preferably 1.0% to 4% by volume. However, when the volume ratio of oxygen and hydrogen is the same or slightly more hydrogen, the oxidation reaction can proceed more gently, and the production of transition metal oxides as side reaction products can be suppressed. Oxidation treatment is performed for several hours in an inert gas atmosphere containing oxygen and hydrogen at this concentration, but the temperature at that time changes depending on the transition metal, but if it is too high, the oxidation may proceed excessively or decomposition may occur. It is not desirable to happen. The recommended temperature is 400 ° C to 1000 ° C. The fine temperature setting is preferably performed in the temperature range of 300 ° C. to 800 ° C. lower than the melting point in light of the melting point of the transition metal oxide. If it is too high, the amount of by-product oxides can be increased, or the grain growth can proceed so much that the catalyst has a small specific surface area. If the temperature is too low, oxidation and oxygen storage will not proceed.

  The oxygen storage compound catalyst prepared in this way may use the transition metal oxynitride obtained by the above-described production method as it is, but further pulverize the obtained transition metal oxynitride to obtain a finer You may use what was made into the powder.

  Examples of the method of pulverizing transition metal carbonitride oxide include a roll rolling mill, a ball mill, a medium stirring mill, an airflow crusher, a mortar, a method using a tank disintegrator, etc. A method using an airflow pulverizer is preferable in that the product can be made finer, and a method using a mortar is preferable in that a small amount of processing is easy.

Furthermore, when platinum is added in an amount of 1.0% by mass or less to the catalyst produced as described above, the catalytic activity can be further enhanced. Oxygen reduction ability can be further enhanced by adding platinum. However, adding too much platinum does not change the effect, and adding 1.0% by mass or more is meaningless. In addition, since platinum is effective, it is important to determine whether or not to add it appropriately in view of applications and effects. In any case, the catalyst of the present invention has sufficient oxygen reducing ability without adding platinum and is excellent in catalytic activity.

<Application>
The catalyst of the present invention can be used as an alternative catalyst for a platinum catalyst.

  For example, it can be used as a catalyst for fuel cells, a catalyst for exhaust gas treatment, or a catalyst for organic synthesis.

  The fuel cell catalyst layer of the present invention is characterized by containing the catalyst.

  The fuel cell catalyst layer includes an anode catalyst layer and a cathode catalyst layer, and the catalyst can be used for both. Since the catalyst is excellent in durability and has a large oxygen reducing ability, it is preferably used in the cathode catalyst layer.

  The catalyst layer for a fuel cell of the present invention preferably further contains electron conductive particles. When the fuel cell catalyst layer containing the catalyst further contains electron conductive particles, the reduction current can be further increased. The electron conductive particles are considered to increase the reduction current because they generate an electrical contact for inducing an electrochemical reaction in the catalyst.

  The electron conductive particles are usually used as a catalyst carrier.

  Examples of the electron conductive particles include carbon, conductive polymers, conductive ceramics, metals, and conductive inorganic oxides such as tungsten oxide or iridium oxide, and these can be used alone or in combination. In particular, since carbon has a large specific surface area, carbon alone or a mixture of carbon and other electron conductive particles is preferable. That is, the fuel cell catalyst layer preferably contains the catalyst and carbon.

  As carbon, carbon black, graphite, graphite, activated carbon, carbon nanotube, carbon nanofiber, carbon nanohorn, fullerene and the like can be used. If the particle size of the carbon is too small, it becomes difficult to form an electron conduction path, and if it is too large, the gas diffusibility of the catalyst layer for fuel cells tends to decrease or the utilization factor of the catalyst tends to decrease. A range of 1000 nm is preferable, and a range of 10 to 100 nm is more preferable.

  When the electron conductive particles are carbon, the mass ratio of the catalyst to carbon (catalyst: electron conductive particles) is preferably 4: 1 to 1000: 1.

  The conductive polymer is not particularly limited. For example, polyacetylene, poly-p-phenylene, polyaniline, polyalkylaniline, polypyrrole, polythiophene, polyindole, poly-1,5-diaminoanthraquinone, polyaminodiphenyl, poly (o- Phenylenediamine), poly (quinolinium) salts, polypyridine, polyquinoxaline, polyphenylquinoxaline and the like. Among these, polypyrrole, polyaniline, and polythiophene are preferable, and polypyrrole is more preferable.

  The polymer electrolyte is not particularly limited as long as it is generally used in a fuel cell catalyst layer. Specifically, a perfluorocarbon polymer having a sulfonic acid group (for example, Nafion (DuPont 5% Nafion solution (DE521), etc.), a hydrocarbon polymer compound having a sulfonic acid group, and an inorganic acid such as phosphoric acid are used. Examples thereof include doped polymer compounds, organic / inorganic hybrid polymers partially substituted with proton-conductive functional groups, and proton conductors in which a polymer matrix is impregnated with a phosphoric acid solution or a sulfuric acid solution. Of these, Nafion (DuPont 5% Nafion solution (DE521)) is preferably used.

  The catalyst layer for a fuel cell of the present invention includes a catalyst layer (catalyst catalyst for cathode) provided on the cathode of a fuel cell because it contains a catalyst having high oxygen reducing ability and hardly corroded even in a high potential in an acidic electrolyte. Layer). In particular, it is suitably used for a catalyst layer provided on the cathode of a membrane electrode assembly provided in a polymer electrolyte fuel cell.

  Examples of the method for dispersing the catalyst on the electron conductive particles as a support include air flow dispersion and dispersion in liquid. Dispersion in liquid is preferable because a catalyst and electron conductive particles dispersed in a solvent can be used in the fuel cell catalyst layer forming step. Examples of the dispersion in the liquid include a method using an orifice contraction flow, a method using a rotating shear flow, and a method using an ultrasonic wave. The solvent used for dispersion in the liquid is not particularly limited as long as it does not erode the catalyst or electron conductive particles and can be dispersed, but a volatile liquid organic solvent or water is generally used. The

  Further, when the catalyst is dispersed on the electron conductive particles, the electrolyte and the dispersing agent may be further dispersed at the same time.

  The method for forming the catalyst layer for the fuel cell is not particularly limited. For example, a method of applying a suspension containing the catalyst, the electron conductive particles, and the electrolyte to the electrolyte membrane or the gas diffusion layer to be described later. It is done. Examples of the application method include a dipping method, a screen printing method, a roll coating method, and a spray method. In addition, after forming a catalyst layer for a fuel cell on a base material by a coating method or a filtration method using a suspension containing the catalyst, electron conductive particles, and an electrolyte, the catalyst layer for a fuel cell is formed on the electrolyte membrane by a transfer method. The method of forming is mentioned.

  The electrode of the present invention can be used as either a cathode or an anode. Since the electrode of the present invention is excellent in durability and has a large catalytic ability, it is more effective when used for a cathode.

  In general, a fuel cell is formed by providing a gas diffusion layer between a current collector outside an anode and a cathode electrode sandwiched between solid electrolytes (membrane electrode assembly) and an electrode catalyst. In addition, a device for improving the efficiency of the fuel cell by increasing the diffusibility of the oxidizing gas is devised. For the gas diffusion layer, a carbon-based porous material such as carbon paper or carbon cloth, or an aluminum foil coated with stainless steel or corrosion-resistant material for weight reduction is generally used.

  The membrane electrode assembly of the present invention is a membrane electrode assembly including a cathode, an anode, and an electrolyte membrane disposed between the cathode and the anode, wherein the cathode is the electrode. .

  As the electrolyte membrane, for example, an electrolyte membrane using a perfluorosulfonic acid system or a hydrocarbon electrolyte membrane is generally used. However, a membrane or porous body in which a polymer microporous membrane is impregnated with a liquid electrolyte is used. A membrane filled with a polymer electrolyte may be used.

  The fuel cell according to the present invention includes the membrane electrode assembly.

  Fuel cell electrode reactions occur at the so-called three-phase interface (electrolyte-electrode catalyst-reaction gas). Fuel cells are classified into several types depending on the electrolyte used, etc., and include molten carbonate type (MCFC), phosphoric acid type (PAFC), solid oxide type (SOFC), and solid polymer type (PEFC). . Since the catalyst of the present invention can be used as an alternative to platinum, it can be used regardless of the type of fuel cell, but among these, the effect is even greater when used in a polymer electrolyte fuel cell.

  EXAMPLES The present invention will be described below in more detail with reference to examples, but the present invention is not limited to these examples.

  In addition, various measurements in Examples and Comparative Examples were performed by the following methods.

[Elemental analysis]
Carbon: About 0.1 g of a sample was weighed and measured with Horiba EMIA-110.

  Nitrogen / oxygen: About 0.1 g of a sample was weighed and sealed in Ni-Cup, and then measured with an ON analyzer.

  Titanium: About 0.1 g of a sample was weighed on a platinum dish, and nitric acid-hydrofluoric acid was added for thermal decomposition. This heat-decomposed product was diluted, diluted, and quantified by ICP-MS.

[Example 1]
1. Catalyst preparation 1.93 g (10 mmol) of tantalum carbide (TaC), 0.66 g (1.5 mmol) of tantalum oxide (Ta ₂ O ₅ ), 0.16 g (0.8 mmol) of tantalum nitride (TaN) were mixed well. By heating in a nitrogen atmosphere at 1800 ° C. for 3 hours, 2.75 g of tantalum carbonitride was obtained. Since it became a sintered body, it was pulverized in an automatic mortar.

  The powder X-ray diffraction spectrum of the obtained tantalum carbonitride is shown in FIG. Table 1 shows the elemental analysis results of the obtained tantalum carbonitride.

  300 mg of the obtained titanium carbonitride was heated at 900 ° C. for 10 hours in a tubular furnace while flowing nitrogen gas containing 1% by volume of oxygen gas and 2% by volume of hydrogen. Hereinafter also referred to as “catalyst (1)”.) 291 mg was obtained.

  The powder X-ray diffraction spectrum of the obtained catalyst (1) is shown in FIG. The elemental analysis values are shown in Table 2.

2. Production of Fuel Cell Electrode The oxygen reducing ability was measured as follows. 95 mg of catalyst (1) and 5 mg of carbon (XC-72 manufactured by Cabot Corporation) were mixed in 10 g of a mixture having a mass ratio of isopropyl alcohol: pure water = 2: 1, and stirred and suspended in an ultrasonic wave. 30 μl of this mixture was applied to a glassy carbon electrode (manufactured by Tokai Carbon Co., Ltd., diameter: 5.2 mm) and dried at 120 ° C. for 1 hour. Further, 10 μl of Nafion (DuPont 5% Nafion solution (DE521)) diluted 10 times with pure water was applied and dried at 120 ° C. for 1 hour to obtain a fuel cell electrode (1).

3. Evaluation of oxygen reducing ability The catalytic ability (oxygen reducing ability) of the thus produced fuel cell electrode (1) was evaluated by the following method.

First, the prepared fuel cell electrode (1) was polarized in an oxygen atmosphere and a nitrogen atmosphere in a 0.5 mol / dm ³ sulfuric acid solution at 30 ° C. and a potential scanning rate of 5 mV / sec, and a current-potential curve was obtained. It was measured. At that time, a reversible hydrogen electrode in a sulfuric acid solution having the same concentration was used as a reference electrode.

From the above measurement results, the potential at which a difference of 0.2 μA / cm ² or more appears between the reduction current in the oxygen atmosphere and the reduction current in the nitrogen atmosphere was defined as the oxygen reduction start potential, and the difference between the ^two was defined as the oxygen reduction current.

  The catalytic ability (oxygen reducing ability) of the fuel cell electrode (1) produced by this oxygen reduction starting potential and oxygen reducing current was evaluated.

  That is, the higher the oxygen reduction start potential and the larger the oxygen reduction current, the higher the catalytic ability (oxygen reducing ability) of the fuel cell electrode.

  The result of examining the oxygen reducing ability of the electrode using the catalyst (1) is shown in FIG. This electrode had an oxygen reduction starting potential of 0.91 V (vs. NHE), and was found to have a high oxygen reduction ability.

[Example 2]
1. Catalyst Preparation 1.55 g (15 mmol) of zirconium carbide (ZrC), 0.31 g (2.5 mmol) of zirconium oxide (ZrO ₂ ), 0.105 g (1.0 mmol) of zirconium nitride (ZrN) were mixed well, and 1800 By heating in a nitrogen atmosphere at 3 ° C. for 3 hours, 2.02 g of zirconium carbonitride was obtained. Since it became a sintered body, it was pulverized in an automatic mortar.

  The powder X-ray diffraction spectrum of the obtained zirconium carbonitride is shown in FIG. Table 1 shows the elemental analysis results of the obtained zirconium carbonitride.

  By heating 300 mg of the obtained zirconium carbonitride in a tubular furnace at 1000 ° C. for 10 hours while flowing nitrogen gas containing 1% by volume oxygen gas and 2% by volume hydrogen, zirconium carbonitride oxide ( Hereinafter also referred to as “catalyst (2)”.) 280 mg was obtained.

  The powder X-ray diffraction spectrum of the resulting catalyst (2) is shown in FIG. The elemental analysis values are shown in Table 2.

2. Production of Fuel Cell Electrode The oxygen reduction ability was measured in the same manner as in Example 1.

3. Evaluation of oxygen reduction ability The catalyst ability (oxygen reduction ability) of the thus produced fuel cell electrode was also carried out in the same manner as in Example 1.

  The results of examining the oxygen reducing ability of the electrode using this catalyst are shown in FIG. This electrode had an oxygen reduction starting potential of 0.94 V (vs. NHE), and was found to have a very high oxygen reducing ability.

[Example 3]
To 2.50 g (20 mmol) of niobium oxide (IV) (NbO ₂ ), 600 mg (50 mmol) of carbon (manufactured by Cabot, Vulcan 72) was sufficiently pulverized and mixed. This mixed powder was heated in a tube furnace at 1600 ° C. for 1.5 hours in a nitrogen atmosphere to obtain 2.35 g of niobium carbonitride. The powder X-ray diffraction spectrum of the obtained niobium carbonitride is shown in FIG. In addition, Table 1 shows the elemental analysis results of the obtained niobium carbonitride.

The obtained niobium carbonitride was heated at 500 ° C. for 1 hour in a tubular furnace while flowing nitrogen gas containing 1% by volume of oxygen gas and 1% by volume of hydrogen gas. 0.98 g of oxide was obtained. Further, FIG. 8 shows a powder X-ray diffraction spectrum of a powder obtained by heating this at 900 ° C. for 3 hours in an argon atmosphere (hereinafter referred to as “catalyst (3)”). Table 2 shows the results of elemental analysis of the catalyst (3). In the obtained niobium carbonitride (NbC _x N _y O _z ), x, y, and z were 0.51, 0.50, and 0.72, respectively, and 4x + 3y + 2z was 4.98.

2. Production of Fuel Cell Electrode The oxygen reduction ability was measured in the same manner as in Example 1.

3. Evaluation of oxygen reduction ability The catalyst ability (oxygen reduction ability) of the thus produced fuel cell electrode was also carried out in the same manner as in Example 1.

  The results of examining the oxygen reducing ability of the electrode using this catalyst are shown in FIG. The oxygen reduction starting potential of this electrode was 0.96 V (vs. NHE), and it was found that the electrode had a very high oxygen reducing ability.

[Example 4]
Niobium carbide 1.150 g (11 mmol), pentavalent niobium oxide 0.175 g (1 mmol), hexavalent molybdenum oxide 0.864 g (6 mmol), niobium nitride 0.11 g (1 mmol) were mixed well, and the mixture was mixed at 1000 ° C. 3 By heating in a nitrogen atmosphere for a period of time, 2.02 g of niobium carbonitride was obtained. FIG. 10 shows a powder X-ray diffraction spectrum of the obtained niobium molybdenum carbonitride. In addition, Table 1 shows the elemental analysis results of the obtained niobium molybdenum carbonitride.

  The obtained niobium carbonitride molybdenum (1.10 g) was heated at 800 ° C. for 1 hour in a tubular furnace while flowing nitrogen gas containing 1% by volume of oxygen gas and 1% by volume of hydrogen gas. 1.18 g of nitrided oxide (hereinafter also referred to as “catalyst (4)”) was obtained. The powder X-ray diffraction spectrum of this catalyst (4) is shown in FIG. In addition, Table 2 shows the results of elemental analysis of the catalyst (4).

In the obtained niobium molybdenum carbonitride (NbMoC _x N _y O _z ), x, y, and z were 0.50, 0.48, and 0.85 in this order, and 4x + 3y + 2z was 5.14. .

2. Production of Fuel Cell Electrode A fuel cell electrode (4) was obtained in the same manner as in Example 1 except that the catalyst (4) was used.

3. Evaluation of oxygen reduction ability Catalytic ability (oxygen reduction ability) was evaluated in the same manner as in Example 1 except that the fuel cell electrode (4) was used.

  FIG. 12 shows a current-potential curve obtained by the measurement.

The oxygen reduction starting potential of this electrode is 0.96 V (vs. NHE), the oxygen reduction current density when the potential is 0.7 V is (1.2) (mA / cm ² ), and has a high oxygen reducing ability. It was found to have

[Example 5]
Zirconium nitride (0.24 g, 2.3 mmol), pentavalent niobium oxide (1.03 g, 3.9 mmol), and niobium carbide (1.57 g, 15.0 mmol) were mixed well and mixed at 1100 ° C. for 3 hours in a nitrogen atmosphere. To obtain 2.64 g of niobium carbonitride / zirconium. The powder X-ray diffraction spectrum of the obtained niobium zirconium carbonitride is shown in FIG. Table 1 shows the elemental analysis results of the obtained niobium carbonitride and zirconium carbonitride.

  Niobium carbonitride 1.00 g obtained was heated at 800 ° C. for 1 hour in a tubular furnace while flowing nitrogen gas containing 1 vol% oxygen gas and 1 vol% hydrogen gas. 1.15 g of zirconium oxynitride (hereinafter also referred to as “catalyst (5)”) was obtained. The powder X-ray diffraction spectrum of this catalyst (5) is shown in FIG. In addition, Table 2 shows the results of elemental analysis of the catalyst (4).

In the obtained niobium-zirconium oxycarbonitride (NbMoC _x N _y O _z ), x, y, and z were 0.50, 0.33, and 0.81, respectively, and 4x + 3y + 2z was 4.61. It was.

2. Production of Fuel Cell Electrode A fuel cell electrode (5) was obtained in the same manner as in Example 1 except that the catalyst (5) was used.

3. Evaluation of oxygen reduction ability Catalytic ability (oxygen reduction ability) was evaluated in the same manner as in Example 1 except that the fuel cell electrode (5) was used.

  FIG. 15 shows a current-potential curve obtained by the measurement.

The oxygen reduction starting potential of this electrode is 0.96 V (vs. NHE), the oxygen reduction current density when the potential is 0.7 V is (1.2) (mA / cm ² ), and has a high oxygen reducing ability. It was found to have

[Example 6]
900 mg of catalyst (3) of Example 3 (use pulverized product: particle size 100 nm) was added to 100 ml of distilled water, and the mixture was shaken with an ultrasonic cleaner for 30 minutes. This suspension was placed on a hot plate, and the liquid temperature was maintained at 80 ° C. while stirring. To this suspension was added sodium carbonate (0.172 g).

A solution in which 3.0 mg (0.0058 mmol: 1.1 mg of platinum amount) of chloroplatinic acid (H ₂ PtCl6 · 6H ₂ O) was previously dissolved in 5 ml of distilled water was prepared. This solution was slowly added to the suspension over 30 minutes (the liquid temperature was maintained at 80 ° C.). After completion of dropping, the mixture was stirred at 80 ° C. for 2 hours.

  Next, 1 ml of an aqueous formaldehyde solution (commercial product: 37%) was slowly added to the above suspension. After completing the addition, the mixture was stirred at 80 ° C. for 1 hour.

  After completion of the reaction, the suspension was cooled and filtered. The crystals collected by filtration were heated at 400 ° C. for 2 hours under a nitrogen stream to obtain 820 mg of 0.12% platinum supported (hereinafter referred to as “catalyst (6)”).

  Moreover, Pt was 0.12 wt% from the elemental analysis result of the catalyst (6). Table 2 shows the results of elemental analysis of the catalyst (6).

3. Production of Fuel Cell Electrode The oxygen reducing ability was measured as follows. Catalyst (1) 0.095 g and carbon (Cabot XC-72) 0.005 g were mixed in 10 g of a mixed solution of isopropyl alcohol: pure water = 2: 1, and stirred and suspended with ultrasonic waves. did. 30 μl of this mixture was applied to a glassy carbon electrode (manufactured by Tokai Carbon Co., Ltd., diameter: 5.2 mm) and dried at 120 ° C. for 1 hour. Further, 10 μl of Nafion (DuPont 5% Nafion solution (DE521)) diluted 10-fold with pure water was applied and dried at 120 ° C. for 1 hour to obtain a fuel cell electrode (6).

4). Evaluation of oxygen reducing ability The catalytic ability (oxygen reducing ability) of the thus produced fuel cell electrode (6) was evaluated in the same manner as in Example 3. The current-potential curve is shown in FIG.

  As a result, it was found that the oxygen reduction starting potential was 1.01 V (vs. NHE) and had high oxygen reducing ability.

Comparative Example 1
By heating 1.00 g of tantalum carbonitride obtained in Example 1 at 800 ° C. for 2 hours in a tubular furnace while flowing nitrogen gas containing 1% by volume of oxygen, tantalum carbonitride oxide ( (Hereinafter also referred to as “catalyst (7)”.) 1022 mg was obtained.

  The powder X-ray diffraction spectrum of the resulting catalyst (7) is shown in FIG.

In addition, Table 2 shows the elemental analysis results of the catalyst (7). Peak significant Ta2O5 appears, is estimated to be a mixture of TaCNO and _Ta 2 _{O 5} In the light and elemental analysis, it was found _{that Ta} 2 _{O 5} is contained about 7% by weight.
Further, FIG. 18 shows a current-potential curve obtained by performing electrode evaluation in the same manner as in Example 1. 18 that the oxygen reduction starting potential of the fuel cell electrode produced in Comparative Example 1 was as low as 0.56 V (vs. NHE), indicating that the oxygen reducing ability was low.

Comparative Example 2
By heating 300 mg of zirconium carbonitride prepared in Example 2 in a tubular furnace at 1000 ° C. for 5 hours while flowing argon gas in 1% by volume of oxygen gas, zirconium carbonitride (hereinafter referred to as “catalyst”). (Also described as (8).) 342 mg was obtained.

  FIG. 19 shows a powder X-ray diffraction spectrum of the resulting catalyst (8).

In addition, Table 2 shows the elemental analysis results of the catalyst (8). A prominent ZrO ₂ peak appeared, and it was found that it was a mixture of ZrCNO and ZrO ₂ when compared with elemental analysis and contained about 11% by mass of ZrO ₂ .

Further, FIG. 20 shows a current-potential curve obtained by performing electrode evaluation in the same manner as in Example 2. When FIG. 20 was seen, the oxygen reduction start potential of the electrode for fuel cells produced in Comparative Example 1 was as low as 0.55 V (vs. NHE), and it was found that the oxygen reduction ability was low.

Table 1 Elemental analysis results of each active material (mass% (element ratio relative to metal in parentheses))

表２ 各活物質の元素分析結果（質量％（括弧内は金属に対する元素比））

Table 2 Elemental analysis results of each active material (mass% (element ratio relative to metal in parentheses))

  The catalyst of the present invention does not corrode in an acidic electrolyte or at a high potential, is excellent in durability, and has a high oxygen reducing ability. Therefore, it can be used in a fuel cell catalyst layer, an electrode, an electrode assembly, or a fuel cell.

2 is a powder X-ray diffraction spectrum of tantalum carbonitride of Example 1. FIG. 2 is a powder X-ray diffraction spectrum of the catalyst (1) obtained in Example 1. It is the graph which evaluated the oxygen reduction ability of the electrode using a catalyst (1). 2 is a powder X-ray diffraction spectrum of zirconium carbonitride of Example 2. 2 is a powder X-ray diffraction spectrum of the catalyst (2) obtained in Example 2. It is the graph which evaluated the oxygen reduction ability of the electrode using a catalyst (2). 3 is a powder X-ray diffraction spectrum of niobium carbonitride of Example 3. 3 is a powder X-ray diffraction spectrum of the catalyst (3) obtained in Example 3. It is the graph which evaluated the oxygen reduction ability of the electrode using a catalyst (3). 2 is a powder X-ray diffraction spectrum of niobium molybdenum carbonitride of Example 4. FIG. 4 is a powder X-ray diffraction spectrum of the catalyst (4) obtained in Example 4. It is an electric current-potential curve graph of the electrode using a catalyst (4). 3 is a powder X-ray diffraction spectrum of niobium zirconium carbonitride of Example 5. FIG. 2 is a powder X-ray diffraction spectrum of the catalyst (5) obtained in Example 5. It is an electric current-potential curve graph of the electrode using a catalyst (5). It is an electric current-potential curve graph of the electrode using a catalyst (6). 3 is a powder X-ray diffraction spectrum of a catalyst (7) obtained in Comparative Example 1. It is an electric current-potential curve graph of the electrode using a catalyst (7). 3 is a powder X-ray diffraction spectrum of a catalyst (8) obtained in Comparative Example 2. It is an electric current-potential curve graph of an electrode using a catalyst (8).

Claims (18)

A catalyst comprising an oxygen storage compound containing a Group 4, 5 or 6 transition metal.   The oxygen storage compound has a composition formula MCxNyOz (M is a transition metal of Group 4, 5 or 6 (hereinafter also referred to as “metal M”), C is carbon, N is nitrogen, and O is oxygen. X, y , Z represents the atomic ratio of each of C, N, and O when the atomic ratio of the metal M is 1, and 0.3 ≦ x ≦ 0.7, 0.3 ≦ y ≦ 0.7, and 0 4 ≦ z ≦ 3.0)).   When the metal M is a group 4 element, the composition of x, y, z is 3 ≦ 4x + 3y + 2z ≦ 4 when the atomic ratio of the metal M is 1, and when the metal M is a group 5 element, the atoms of the metal M When the ratio is 1, the composition of x, y, z is 4 ≦ 4x + 3y + 2z ≦ 5, and when the metal M is a group 6 element, the composition of x, y, z when the atomic ratio of the metal M is 1 The catalyst according to claim 1, wherein 4 ≦ 4x + 3y + 2z ≦ 6.   When the metal M is an alloy or a mixture of transition metals (alloys), the composition ratio of x, y, and z is allocated at a ratio corresponding to the composition ratio of the alloy or transition metal mixture (alloys). The catalyst according to claim 1 or 2, wherein:   The catalyst according to any one of claims 1 to 4, wherein the oxygen storage compound has a rock salt structure (NaCl type structure).   The catalyst according to any one of claims 1 to 5, wherein an inert oxide transition metal is 5 mass% or less.   Furthermore, platinum is contained 1.0 mass% or less, The catalyst in any one of Claims 1-6 characterized by the above-mentioned.   The fuel cell catalyst according to any one of claims 1 to 7.   The catalyst according to any one of claims 1 to 8, wherein the carbide, nitride or carbonitride of the transition metal of Group 4, 5 or 6 is heat-treated in an inert gas containing oxygen and a reducing gas. The manufacturing method of the catalyst characterized by including the process to do.   The method for producing a catalyst according to claim 9, wherein the carbide, nitride or carbonitride of the transition metal of Group 4, 5 or 6 has a rock salt structure (NaCl type structure).   The method for producing a catalyst according to claim 9 or 10, wherein the reducing gas is hydrogen.   The method for producing a catalyst according to any one of claims 9 to 11, wherein the inert gas is nitrogen or argon.   A catalyst layer for a fuel cell comprising the catalyst according to claim 1. The catalyst layer for a fuel cell according to claim 13, further comprising electron conductive particles.   An electrode having a fuel cell catalyst layer and a porous support layer, wherein the fuel cell catalyst layer is the fuel cell catalyst layer according to claim 14 or 15.   16. A membrane electrode assembly comprising a cathode, an anode, and an electrolyte membrane disposed between the cathode and the anode, wherein the cathode and / or the anode is an electrode according to claim 15. Membrane electrode assembly.   A fuel cell comprising the membrane electrode assembly according to claim 16.   A polymer electrolyte fuel cell comprising the membrane electrode assembly according to claim 16.

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