JP2016035890A - Oxygen reduction catalyst - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an oxygen reduction catalyst capable of achieving an improvement in durability of a fuel cell.SOLUTION: An oxygen reduction catalyst is used for a cathode electrode 3 of an anion-exchange polymer electrolyte fuel cell. The oxygen reduction catalyst contains a first composition having oxygen reduction activity and a second component having peroxide decomposition activity, the second component being selected from at least one of manganese, a manganese-containing alloy, cerium, a cerium-containing alloy and an oxide thereof.SELECTED DRAWING: None

Description

  The present invention relates to an oxygen reduction catalyst, and more particularly to an oxygen reduction catalyst used for an oxygen side electrode of a fuel cell such as a solid polymer fuel cell.

  Conventionally, various fuel cells such as alkaline type (AFC), solid polymer type (PEFC), phosphoric acid type (PAFC), molten carbonate type (MCFC), and solid electrolyte type (SOFC) are known as fuel cells. Yes. These fuel cells are being studied for use in various applications such as automobile applications.

  For example, a polymer electrolyte fuel cell includes an electrolyte membrane made of a solid polymer membrane, a fuel side electrode (anode) formed on one side of the electrolyte membrane, and an oxygen side electrode (anode) formed on the other side of the electrolyte membrane ( A membrane electrode assembly integrally having a cathode). In such a fuel cell, fuel is supplied to the anode and air is supplied to the cathode, so that an electromotive force is generated between the anode and the cathode to generate electric power.

  As a cathode used in such a polymer electrolyte fuel cell, for example, an oxygen reduction catalyst obtained by firing a transition metal complex in which a ligand such as sarcomin is coordinated to a transition metal such as cobalt is known. (For example, refer to Patent Document 1).

JP 2012-157811 A

  However, in the fuel cell described in Patent Document 1 described above, further improvement in durability has been studied.

  Therefore, an object of the present invention is to provide an oxygen reduction catalyst capable of improving the durability of a fuel cell.

  The oxygen reduction catalyst of the present invention is an oxygen reduction catalyst used for a cathode electrode of an anion exchange type solid polymer fuel cell, and includes a first component having oxygen reduction activity and a second component having peroxide decomposition activity. And the second component is selected from at least one of manganese, an alloy containing manganese, cerium, an alloy containing cerium, and an oxide thereof.

  In the oxygen reduction catalyst of the present invention, it is preferable that the first component is a fired body of an iron complex in which an organic compound is coordinated to iron.

  In the oxygen reduction catalyst of the present invention, it is preferable that the content ratio of the second component in the oxygen reduction catalyst is 20% by mass or more and 60% by mass or less.

  According to the oxygen reduction catalyst of the present invention, in addition to the first component having oxygen reduction activity, manganese, an alloy containing manganese, cerium, an alloy containing cerium, and oxides thereof as the second component At least one of them is contained.

  Therefore, the peroxide generated by the side reaction in the oxygen reduction reaction can be decomposed.

  As a result, the deterioration of the fuel cell, in particular, the membrane electrode assembly of the fuel cell, can be suppressed.

  Thereby, when the oxygen reduction catalyst of the present invention is used for a fuel cell, the durability of the fuel cell can be improved.

FIG. 1 is a schematic configuration diagram of a fuel cell in which the oxygen reduction catalyst of the present invention is used. FIG. 2 is a correlation diagram showing the relationship between the half-wave potential (V vs Hg / HgO) and the peroxide generation rate of a three-electrode cell produced using an oxygen reduction catalyst. FIG. 3 is a correlation diagram showing the relationship between the half-wave potential (V vs RHE) and the peroxide generation rate of a three-electrode cell produced using an oxygen reduction catalyst.

1. Fuel Cell FIG. 1 is a schematic configuration diagram of a fuel cell in which the oxygen reduction catalyst of the present invention is used.

  The fuel cell 1 is a polymer electrolyte fuel cell, and includes a plurality of fuel cells S, and is formed as a stack structure in which these fuel cells S are stacked. In FIG. 1, only one fuel cell S is shown for easy illustration.

  The fuel cell S includes an electrolyte layer 4, an anode electrode 2 (anode), a cathode electrode 3 (cathode), a fuel supply member 5, and an oxygen supply member 6.

The electrolyte layer 4 is formed from an anion exchange membrane. The anion exchange membrane is not particularly limited as long as it is a medium capable of moving hydroxide ions (OH ⁻ ) as anion components generated at the cathode electrode 3 from the cathode electrode 3 to the anode electrode 2. Examples thereof include a solid polymer membrane (anion exchange resin) having an anion exchange group such as a quaternary ammonium group and a pyridinium group.

  The anode electrode 2 is formed on one surface of the electrolyte layer 4 by an electrode material such as a catalyst carrier carrying a catalyst. Further, without using the catalyst carrier, catalyst particles may be used as the electrode material, and the catalyst particles may be directly formed as the anode electrode 2.

  The catalyst is not particularly limited, and examples thereof include platinum group elements (ruthenium (Ru), rhodium (Rh), palladium (Pd), osmium (Os), iridium (Ir), platinum (Pt)), iron group elements ( According to a periodic table such as iron (Fe), cobalt (Co), nickel (Ni)) (IUPAC Periodic Table of the Elements (version date 22 June 2007), the same applies hereinafter) Group 8 to 10 (VIII) elements, For example, periodic table 11th group (IB) elements, such as copper (Cu), silver (Ag), and gold (Au), and simple metals such as zinc (Zn), and alloys thereof may be used.

  These can be used alone or in combination of two or more.

  Examples of the catalyst carrier include porous substances such as carbon. The amount of the catalyst supported on the catalyst carrier is not particularly limited, and is appropriately set according to the purpose and application.

  The thickness of the anode electrode 2 is, for example, 10 μm or more, preferably 20 μm or more, and for example, 200 μm or less, preferably 100 μm or less.

  The cathode electrode 3 is formed by the method described later on the other surface of the electrolyte layer 4 (the surface opposite to the surface on which the anode electrode 2 is formed) using an oxygen reduction catalyst described later instead of the above-described catalyst. Has been.

  The thickness of the cathode electrode 3 is, for example, 0.1 μm or more, preferably 1 μm or more, and for example, 100 μm or less, preferably 10 μm or less.

  The fuel supply member 5 is made of a gas-impermeable conductive member, and one surface thereof is opposed to the anode electrode 2. In the fuel supply member 5, a fuel-side flow path 7 for bringing fuel into contact with the entire anode electrode 2 is formed as a distorted groove that is recessed from one surface. In addition, the fuel supply member 5 has a supply port 8 and a discharge port 9 communicating with the fuel-side flow path 7 at its upstream end and downstream end.

  Similar to the fuel supply member 5, the oxygen supply member 6 is made of a gas-impermeable conductive member, and one surface thereof is in contact with the cathode electrode 3. In the oxygen supply member 6, an oxygen-side flow path 10 for bringing oxygen (air) into contact with the entire cathode electrode 3 is formed as a twisted groove recessed from one surface. The oxygen supply member 6 has a supply port 11 and a discharge port 12 communicating with the oxygen-side flow path 10 at the upstream end portion and the downstream end portion thereof.

  In this fuel cell 1, fuel (preferably liquid fuel) containing a fuel compound is supplied to the fuel-side flow path 7 through the supply port 8 of the fuel supply member 5, and oxygen (air) is supplied to the oxygen supply. It is supplied to the oxygen side flow path 10 through the supply port 11 of the member 6.

  Examples of the fuel compound include alcohols such as methanol, ethers having an alkyl group such as dimethyl ether, hydrazines, and the like, preferably alcohols and hydrazines, and more preferably hydrazines. It is done.

Examples of hydrazines include hydrazine (NH ₂ NH ₂ ), hydrated hydrazine (NH ₂ NH ₂ .H ₂ O), hydrazine carbonate ((NH ₂ NH ₂ ) ₂ CO ₂ ), and hydrazine hydrochloride (NH ₂ NH _2). HCl), hydrazine sulfate (NH ₂ NH ₂ .H ₂ SO ₄ ), monomethyl hydrazine (CH ₃ NHNH ₂ ), dimethyl hydrazine ((CH ₃ ) ₂ NNH ₂ , CH ₃ NHNHCH ₃ ), carboxylic hydrazide ((NHNH ₂ ) ₂ CO).

Among such hydrazines, preferably, hydrazines containing no carbon, that is, hydrazine, hydrated hydrazine, hydrazine sulfate, and the like. Hydrazine, hydrated hydrazine, hydrazine sulfate, etc. do not generate CO and CO ₂ and do not cause poisoning of the catalyst. Therefore, durability can be improved and substantially zero emission can be realized. it can.

  Such fuel components can be used alone or in combination of two or more.

  As the fuel, the fuel compound exemplified above may be used as it is, but the fuel compound exemplified above is used as a solution such as water and / or alcohol (for example, lower alcohol such as methanol, ethanol, propanol, isopropanol). Can be used.

For example, when the electrolyte membrane 4 is an anion exchange type solid polymer membrane and the fuel compound is hydrazine, an electrochemical reaction of the following formulas (1) to (3) occurs and an electromotive force is generated. .
(1) N ₂ H ₄ + 4OH ⁻ → N ₂ + 4H ₂ O + 4e ⁻ (reaction at anode electrode 2)
(2) O ₂ + 2H ₂ O + 4e ⁻ → 4OH ⁻ (reaction at cathode electrode 3)
(3) N ₂ H ₄ + O ₂ → N ₂ + 2H ₂ O (reaction in the entire fuel cell 1)
That is, in the anode electrode 2, hydrazine (N ₂ H ₄ ) reacts with hydroxide ions (OH ⁻ ) generated by the reaction at the cathode electrode 3 to react with nitrogen (N ₂ ) and water (H ₂ O). Are generated and electrons (e ⁻ ) are generated (see the above formula (1)).

On the other hand, at the cathode electrode 3, electrons (e ⁻ ), water (H ₂ O) generated by reaction from the outside or the fuel cell 1, and oxygen (O ₂ ) react to generate hydroxide. Ion (OH ⁻ ) is generated (see the above formula (2)). The generated hydroxide ions (OH ⁻ ) pass through the electrolyte membrane 4 and are supplied to the anode electrode 2.

  When such an electrochemical reaction occurs continuously, the reaction represented by the above formula (3) occurs in the fuel cell 1 as a whole, and an electromotive force is generated.

2. Oxygen reduction catalyst Hereinafter, the oxygen reduction catalyst used for the cathode electrode 3 will be described.

  The oxygen reduction catalyst contains a first component having oxygen reduction activity and a second component having peroxide decomposition activity.

  Examples of the first component include a fired body of a transition metal complex in which an organic compound is coordinated to a transition metal, and a composite in which a transition metal is supported on a carbon composite composed of a conductive polymer and carbon.

  Examples of the transition metal include scandium (Sc), titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu ), Yttrium (Y), zirconium (Zr), niobium (Nb), molybdenum (Mo), technetium (Tc), ruthenium (Ru), rhodium (Rh), palladium (Pd), silver (Ag), lanthanum (La) ), Hafnium (Hf), tantalum (Ta), tungsten (W), rhenium (Re), osmium (Os), iridium (Ir), platinum (Pt), gold (Au), and the like.

  Examples of the organic compound coordinated to the transition metal include pyrrole, porphyrin, tetramethoxyphenylporphyrin, dibenzotetraazaannulene, phthalocyanine, choline, chlorin, phenanthroline, salcomine, nicarbazine, and polymers thereof.

  As the conductive polymer, there is a compound overlapping with the above organic compound, for example, polyaniline, polypyrrole, polythiophene, polyacetylene, polyvinylcarbazole, polytriphenylamine, polypyridine, polypyrimidine, polyquinoxaline, polyphenylquinoxaline, polyphenyl Examples include isothianaphthene, polypyridinediyl, polythienylene, polyparaphenylene, polyflurane, polyacene, polyfuran, polyazulene, polyindole, and polydiaminoanthraquinone.

  The first component is preferably a fired body of an iron complex in which an organic compound is coordinated to iron. The first component can be used alone or in combination of two or more.

  In the oxygen reduction catalyst, the first component is, for example, 25% by mass or more, preferably 40% by mass or more, more preferably 50% by mass or more, and further preferably 60% by mass or more, for example, 99% by mass or less. Preferably, it is 90 mass% or less, More preferably, it is 80 mass% or less, More preferably, it is 70 mass% or less.

  To prepare the first component, for example, when the first component is a fired product of a transition metal complex, a salt of a transition metal (for example, an inorganic salt such as sulfate, nitrate, chloride, phosphate, An organic acid salt such as acetate and oxalate) and an organic compound in a known solvent such as water, alcohol, aliphatic hydrocarbon, aromatic hydrocarbon, halogenated hydrocarbon, and nitrile. By mixing, a transition metal complex can be produced.

  The solution or dispersion of the transition metal complex thus prepared is dried if necessary and then calcined.

  In the firing, for example, heating is performed in an atmosphere of an inert gas (for example, nitrogen gas, argon gas, or the like) or a reducing gas (for example, a mixed gas of nitrogen gas and hydrogen gas).

  Moreover, a calcination temperature is 850 degreeC or more, for example, Preferably, it is 900 degreeC or more, for example, is 1500 degrees C or less. The firing time is, for example, 1 hour or longer, and for example, 10 hours or shorter, preferably 5 hours or shorter.

  The transition metal complex can be fired in one step or in multiple steps.

  When drying, the drying temperature is, for example, −25 ° C. or more, preferably 15 ° C. or more, and for example, 80 ° C. or less, preferably 50 ° C. or less. The drying time is, for example, 12 to 48 hours.

  Thereby, the sintered body of the transition metal complex can be obtained as the first component.

  The second component is selected from at least one of manganese, an alloy containing manganese, cerium, an alloy containing cerium, and an oxide thereof.

Specifically, as the second component, for example, manganese, for example, manganese dioxide (MnO ₂ ), manganese oxide such as manganese oxide (MnO, Mn ₂ O ₃ , Mn ₃ O ₄ ), for example, AlMn, CrMn, Alloys containing manganese such as FeMn, CoMn, NiMn, and CuMn, for example, manganese such as Fe ₂ MnO ₄ , FeMn ₂ O ₄ , La ₂ MnO ₄ , LaMn ₂ O ₄ , Sr ₂ MnO ₄ , and SrMn ₂ O ₄ are used. oxides of alloys containing, for example, cerium, e.g., cerium dioxide _(CeO 2), oxides of cerium, such as cerium oxide _(Ce 2 _{O 3),} for _{example, CeAl 2, CeCu 2, CePd} 3, cerium such CeSe Containing alloys such as CeCoO ₃ , CeFeO ₃ , CeZnO ₃ , CeYO _And oxides of alloys containing cerium such as ₃ .

  The second component is preferably manganese, manganese oxide, cerium, cerium oxide, more preferably manganese oxide, cerium oxide, and still more preferably manganese oxide.

  In the oxygen reduction catalyst, the second component is, for example, 1% by mass or more, preferably 10% by mass or more, more preferably 20% by mass or more, and further preferably 30% by mass or more, for example, 75% by mass or less. Preferably, it is 60 mass% or less, More preferably, it is 50 mass% or less, More preferably, it is 40 mass% or less.

  By setting the content ratio of the second component in the above range, it is possible to decompose the peroxide generated by the side reaction in the oxygen reduction reaction and improve the oxygen reduction activity.

  The second component is, for example, 1 part by mass or more, preferably 11 parts by mass or more, more preferably 30 parts by mass or more, for example, 200 parts by mass or less, preferably 100 parts by mass with respect to the first component. 100 parts by mass or less, more preferably 80 parts by mass or less, and still more preferably 43 parts by mass or less.

  The oxidation-reduction catalyst is obtained, for example, by blending and mixing the first component and the second component at the blending ratio described above.

  In order to produce the cathode electrode 3 using an oxygen reduction catalyst, for example, first, an oxygen reduction catalyst and an ionomer are dispersed in an organic solvent to prepare a dispersion. Next, the dispersion is applied to the other surface of the electrolyte layer 4 (the surface opposite to the surface on which the anode electrode 2 is formed) and dried to obtain the cathode electrode 3.

  Examples of the ionomer include an anion exchange resin having an anion exchange group. Anion exchange resins are commercially available, and specific examples include Nafion (registered trademark).

  Examples of the organic solvent include known solvents such as lower alcohols such as methanol, ethanol, 1-propanol, and 2-propanol, ethers such as tetrahydrofuran, and water. These solvents can be used alone or in combination of two or more.

  The oxygen reduction catalyst is contained in the cathode electrode 3 by, for example, 50% by mass or more, preferably 70% by mass or more, for example, 90% by mass or less, preferably 80% by mass or less.

The basis weight of the cathode electrode 3 (the amount of the cathode electrode 3 attached to the electrolyte layer 4) is, for example, 0.01 mg / cm ² or more, for example, 10 mg / cm ² or less.

  The oxidation-reduction catalyst is prepared by mixing the first component and the second component in the ionomer and the organic solvent when the cathode electrode 3 is produced without previously mixing the first component and the second component. A dispersion can also be prepared.

In the power generation in the fuel cell 1 described above, since the electrolyte membrane 4 is made of an anion exchange membrane, the electrochemical reaction (reaction of the above formula (2)) at the cathode electrode 3 proceeds in an alkaline environment. In this case, HO ₂ ⁻ (peroxide) may be generated as a side reaction product.

  However, according to this oxygen reduction catalyst, in addition to the first component having oxygen reduction activity, as the second component, manganese, an alloy containing manganese, cerium, an alloy containing cerium, and oxides thereof At least one of them is contained.

Therefore, peroxide (HO ₂ ⁻ ) generated by a side reaction in the oxygen reduction reaction can be decomposed.

The oxidation reaction (decomposition reaction) of this peroxide (HO ₂ ⁻ ) is represented by the following formula (4).
(4) HO ₂ ⁻ + H ₂ O + 2e ⁻ → 3OH ⁻ +0.87 V (vs. SHE)
As a result, it is possible to suppress the deterioration of the fuel cell 1, particularly the membrane electrode assembly of the fuel cell 1, due to the peroxide (HO ₂ ⁻ ).

  Thereby, when the oxygen reduction catalyst of this invention is used for the fuel cell 1, the improvement of durability of the fuel cell 1 can be aimed at.

  Moreover, the oxygen reduction catalyst of the present invention has improved oxygen reduction activity. Therefore, when the oxygen reduction catalyst of the present invention is used for the fuel cell 1, the output of the fuel cell 1 can be improved.

3. Modified Example of Production Method of Oxygen Reduction Catalyst (1) When the above transition metal complex is calcined, the calcined body of the transition metal complex aggregates and grows, and its effective surface area is reduced. May decrease.

  Therefore, in order to ensure a sufficient effective surface area, it is preferable to form pores in the granular material in which the transition metal complex is aggregated and grown to form a porous fired body.

It does not restrict | limit especially as a method of forming a porous baked body, A well-known method is mentioned.
For example, first, a method of firing a particle mixture of a transition metal complex and soluble particles to produce a composite containing the transition metal complex and soluble particles at random, and then removing the soluble particles in the composite. Can be mentioned.

  Although it does not restrict | limit especially as a soluble particle, For example, at the time of mixing a complex mixture and a soluble particle, it can disperse | distribute uniformly to a complex mixture, and it distributes uniformly to a composite, without melt | dissolving by said baking, Examples of the particles that are dissolved and removed by firing with an acid or alkali after firing are exemplified.

  Examples of such soluble particles include amorphous silica such as fumed silica and colloidal silica, polymer particles such as polystyrene and polyimide, and fired bodies thereof.

  These soluble particles can be used alone or in combination of two or more, preferably amorphous silica, more preferably fumed silica.

  In this method, for example, first, the transition metal complex and the soluble particles are mixed before the firing.

  In order to mix the transition metal complex and the soluble particles, for example, first, the transition metal complex is dissolved or dispersed in a solvent.

  Although it does not restrict | limit especially as a solvent, For example, water, for example, protic polar solvent (For example, alcohol, such as methanol, ethanol, isopropanol, glycol, etc.), aprotic polar solvent (for example, acetone, N, N-dimethyl). Formamide (DMF), N, N-dimethylacetamide (DMAC), dimethyl sulfoxide (DMSO), N-methylpyrrolidone (NMP), acetonitrile, piperidine, etc.), amines (eg, ammonia, eg, triethylamine, pyridine, etc.), Ethers (for example, dioxane, tetrahydrofuran (THF), etc.), aromatic hydrocarbons (for example, benzene, toluene, xylene, etc.) and the like can be mentioned.

  These solvents can be used alone or in combination of two or more, and preferably include tetrahydrofuran, acetone and the like.

  The mixing ratio of the transition metal complex and the solvent is such that the solvent is, for example, 1 part by mass or more, preferably 10 parts by mass or more, for example, 100000 parts by mass or less, with respect to 100 parts by mass of the transition metal complex. Preferably, it is 50000 parts by mass or less.

  Next, the obtained transition metal complex solution or dispersion and the soluble particles are mixed by a known method such as wet mixing.

  The blending ratio of the transition metal complex solution or dispersion and the soluble particles is, for example, that the soluble particles contain, for example, 100 parts by mass of the transition metal complex (solid content) in the transition metal complex solution or dispersion, for example, It is 10 parts by mass or more, preferably 50 parts by mass or more, and for example, 500 parts by mass or less, preferably 200 parts by mass or less.

  Thereby, a solution or dispersion of the transition metal complex and soluble particles is obtained.

  Then, in this method, the obtained transition metal complex and soluble particle solution or dispersion are dried.

  As drying conditions, the drying temperature is, for example, −25 ° C. or higher, preferably 15 ° C. or higher, and for example, 80 ° C. or lower, preferably 50 ° C. or lower. The drying time is, for example, 12 to 48 hours.

  Next, under the above firing conditions, the mixture of the transition metal complex and the soluble particles is fired to obtain a composite containing the transition metal complex and the soluble particles at random.

  The method then removes the soluble particles in the composite.

  For example, when amorphous silica is used as the soluble particles, the amorphous silica may be crystallized by firing to form silica (fired body). In such a case, in order to remove the silica, for example, the composite is treated with an alkali.

  As the alkali treatment, the composite is impregnated with an alkaline solution such as potassium hydroxide or sodium hydroxide. Thereby, the soluble particles in the composite are dissolved to form pores, and as a result, a porous fired body is obtained.

  According to such a porous fired body, even when the transition metal complex aggregates and grows by firing, the effective surface area of the transition metal complex is sufficiently secured by the pores. Can be maintained.

The method for removing the soluble particles is not limited to the above, and can be appropriately selected according to the type of the soluble particles, such as a method of immersing in water or an acid treatment method.
(2) The first component or the second component described above can be carried on a carrier such as carbon particles.

  In order to support the first component or the second component on the support, for example, the support is mixed with the solution or dispersion of the first component or the second component described above, and then fired. The mixing ratio of the carrier is, for example, 10 parts by mass or more, preferably 50 parts by mass or more, and for example, 500 parts by mass or less, preferably 100 parts by mass of the first component or the second component. It is 200 parts by mass or less.

  Next, although this invention is demonstrated based on an Example and a comparative example, this invention is not limited by the following Example. The numerical values in the following examples can be substituted for the numerical values (that is, the upper limit value or the lower limit value) described in the above embodiment.

1) Preparation of measurement electrode Example Nicarbazin Fe complex (NPC-2000, manufactured by Pajarito) as the first component and manganese oxide-supported carbon as the second component (supporting manganese oxide on a support made of carbon particles) Ink (dispersed liquid) prepared by dispersing an ionomer and an ionomer in an organic solvent was dropped onto glassy carbon to form a measurement electrode (supported amount 0.51 μg / mm ² ).

  The ink was prepared by mixing 8 mg of nicarbazine Fe complex, 2 mg of manganese oxide-supporting carbon, 0.8 mL of ultrapure water, and 0.2 mL of 2-propanol (organic solvent) to obtain a primary ink. Ink 0.1 mL, ultrapure water 0.75 mL, 2-propanol (organic solvent) 0.1 mL, and 5 w% Nafion (registered trademark) solution (Ionomer, trade name: Nafion 5 wt.% Dispersion 70160 (product number), Aldrich Prepared) and mixed with 0.05 mL of a 10-fold diluted solution.

Example 2
A measurement electrode was prepared in the same manner as in the above example except that the content ratio of the nicarbazine Fe complex was 7 mg and the content ratio of the manganese oxide-supporting carbon was 3 mg.

Example 3
A measurement electrode was produced in the same manner as in the above-described example except that the content ratio of the nicarbazine Fe complex was 6 mg and the content ratio of the manganese oxide-supported carbon was 4 mg.

Example 4
A measurement electrode was produced in the same manner as in the above example except that the content ratio of the nicarbazine Fe complex was 4 mg and the content ratio of the manganese oxide-supporting carbon was 6 mg.

Example 5
The same procedure as in Example 1 was performed except that 2 mg of cerium oxide-supported carbon (the one in which cerium oxide was supported on a support made of carbon particles) was added instead of 2 mg of manganese oxide-supported carbon Thus, a measurement electrode was produced.

Comparative Example 1
A measurement electrode was produced in the same manner as in Example 1 except that 2 mg of ketjen black was blended instead of 2 mg of manganese oxide-supporting carbon.

Comparative Example 2
A measurement electrode was produced in the same manner as in Example 1 except that 8 mg of nicarbazine Fe complex and 2 mg of manganese oxide-supporting carbon were mixed with 10 mg of nicarbazine Fe complex.

Comparative Example 3
A measurement electrode was produced in the same manner as in Example 1 except that 8 mg of nicarbazine Fe complex and 2 mg of manganese oxide-supported carbon were added instead of 10 mg of manganese oxide-supported carbon.

Comparative Example 4
A measurement electrode was prepared in the same manner as in Example 1 except that 10 mg of cerium oxide-supporting carbon was added instead of 8 mg of nicarbazine Fe complex and 2 mg of manganese oxide-supporting carbon.

2) Evaluation of peroxide decomposition performance 1
The generation rate of peroxide and the activity of oxygen reduction were measured using a rotating ring disk electrode (Rotating Ring-Disk Electrode: RRDE).

  Using the measurement electrodes obtained in Examples 1 and 5 and Comparative Example 1, a three-electrode cell containing a 1 mol / L potassium hydroxide aqueous solution saturated with oxygen was produced.

  In the three-electrode type cell, a mercury-mercury oxide electrode (Hg / HgO) was used as the reference electrode, and a platinum wire was used as the counter electrode.

  The measurement temperature was 30 ° C., and the rotation speed was 1600 rpm. The scanning speed was 0.01 V / s, and scanning was performed from a high potential toward a low potential.

  The peroxide generation rate was converted from the current value of the ring set to 0.6 V (vs. Hg / HgO). In addition, the potential (half-wave potential) at a current value half that of the maximum current value was measured. The results are shown in FIG.

3) Evaluation of peroxide decomposition performance 2
Using a rotating ring disk electrode, the peroxide generation rate and oxygen reduction activity were measured.

  Using the measurement electrodes obtained in Examples 1 to 5 and Comparative Examples 2 to 4, a three-electrode cell containing a 1 mol / L potassium hydroxide aqueous solution saturated with oxygen was produced.

  In the three-electrode cell, a reversible hydrogen electrode (RHE) was used as the reference electrode, and a platinum wire was used as the counter electrode.

  The measurement temperature was 30 ° C., and the rotation speed was 1600 rpm. The scanning speed was 0.01 V / s, and scanning was performed from a high potential toward a low potential.

  The peroxide generation rate was converted from the current value of the ring set to 0.6 V (vs. RHE). In addition, the potential (half-wave potential) at a current value half that of the maximum current value was measured. The results are shown in FIG.

(Discussion)
As apparent from FIG. 2 and FIG. 3, Examples 1 to 5 have a lower peroxide generation rate than Comparative Examples 1 to 4, and thus the peroxide generated by the side reaction in the oxygen reduction reaction is reduced. You can see that it is disassembled. Therefore, Examples 1-5 can suppress the deterioration by the peroxide of a membrane electrode assembly, and can aim at the improvement of durability of a fuel cell.

  In addition, as is clear from FIG. 3, Examples 1 to 5 have higher half-wave potential than Comparative Example 2 in which only the nicarbazin Fe complex is used as the oxygen reduction catalyst. I understand that Therefore, Examples 1 to 5 can improve the output of the fuel cell.

Claims (3)

An oxygen reduction catalyst used for a cathode electrode of an anion exchange type polymer electrolyte fuel cell,
A first component having oxygen reduction activity;
A second component having peroxide decomposition activity;
The oxygen reduction catalyst, wherein the second component is selected from at least one of manganese, an alloy containing manganese, cerium, an alloy containing cerium, and an oxide thereof.   The oxygen reduction catalyst according to claim 1, wherein the first component is a fired body of an iron complex in which an organic compound is coordinated to iron.   3. The oxygen reduction catalyst according to claim 1, wherein a content ratio of the second component in the oxygen reduction catalyst is 20% by mass or more and 60% by mass or less.

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