JP2016032799A - Oxygen reduction catalyst - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an oxygen reduction catalyst that has improved oxygen reduction activity and can improve the power generation performance of fuel cells.SOLUTION: A phenanthroline Fe complex in which a phenanthroline ligand is coordinated to iron is fired to obtain a fired body that has, in an X-ray photoelectron spectrum, a higher strength in 401 eV than in 399 eV.SELECTED DRAWING: Figure 2

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 a fuel-side electrode (anode) to which fuel is supplied and an oxygen-side electrode (cathode) to which oxygen is supplied. These electrodes are formed from a solid polymer membrane. Are arranged opposite to each other with an electrolyte layer interposed therebetween. In this 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, thereby generating electric power.

  As a cathode used in such a polymer electrolyte fuel cell, for example, an oxygen reduction catalyst obtained by calcining a phenanthroline iron complex at a high temperature is known (for example, see Non-Patent Document 1). Since this oxygen reduction catalyst has a good oxygen reduction activity, it can activate the chemical reaction of the cathode and improve the power generation performance of the fuel cell.

Michel Lefev et al., "Iron-Based Catalysts with Improved Oxygen Reduction Activity in Polymer Electrolyte Fuel Cells", April 3, 2009, SCIENCE / A32 (71), SCIENCE / A32

  However, in the technical field of fuel cells, it is always expected to improve the power generation performance of the fuel cell, and in recent years, the demand is increasing. Therefore, the development of a high-performance catalytic reduction catalyst that can further improve the power generation performance of the fuel cell as compared with the above-described oxygen reduction catalyst is expected.

  Accordingly, an object of the present invention is to provide an oxygen reduction catalyst that can further improve the oxygen reduction activity ability and improve the power generation performance of the fuel cell.

  The oxygen reduction catalyst of the present invention contains a fired body obtained by firing a phenanthroline Fe complex in which a phenanthroline-based ligand is coordinated to iron, and the fired body has an intensity at 401 eV in an X-ray photoelectron spectrum. Is greater than the intensity at 399 eV.

  According to the oxygen reduction catalyst of the present invention, it contains a fired body having a specific structure in which the intensity at 401 eV is larger than the intensity at 399 eV in the X-ray photoelectron spectrum by firing the phenanthroline Fe complex. ing.

  As a result, the oxygen reduction reaction can be activated, and the oxygen reduction activity can be further improved.

  Thereby, when the oxygen reduction catalyst of the present invention is used for a fuel cell, the power generation performance 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 shows the X-ray photoelectron spectrum of the oxygen reduction catalyst. FIG. 3 is a correlation diagram showing the relationship between the half-wave potential and the reaction initiation potential 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 battery cell S includes an electrolyte layer 4, a fuel side electrode 2 (anode), an oxygen side 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 an anion component generated at the oxygen side electrode 3 from the oxygen side electrode 3 to the fuel side electrode 2. However, for example, a solid polymer membrane (anion exchange resin) having an anion exchange group such as a quaternary ammonium group or a pyridinium group can be mentioned.

  The fuel side 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 fuel side 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 fuel side 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 oxygen side electrode 3 uses the oxygen reduction catalyst described later instead of the above-described catalyst, and uses the above-described fuel on the other surface of the electrolyte layer 4 (the surface opposite to the surface on which the fuel-side electrode 2 is formed). It is formed by the same method as the side electrode 2. The basis weight of the oxygen-side electrode 3 (the amount of oxygen reduction catalyst attached to the electrolyte layer 4) is, for example, 0.01 to 10 mg / cm ² .

  The thickness of the oxygen side 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 in opposed contact with the fuel-side electrode 2. The fuel supply member 5 is formed with a fuel-side flow path 7 for bringing fuel into contact with the entire fuel-side electrode 2 as a distorted groove 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 opposed to the oxygen side electrode 3. In the oxygen supply member 6, an oxygen-side flow path 10 for bringing oxygen (air) into contact with the entire oxygen-side 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 the fuel cell 1, the fuel containing the 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) passes through the supply port 11 of the oxygen supply member 6. To the oxygen-side flow path 10.

  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 the fuel side electrode 2)
(2) O ₂ + 2H ₂ O + 4e ⁻ → 4OH ⁻ (reaction at oxygen side 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 fuel side electrode 2, hydrazine (N ₂ H ₄ ) reacts with hydroxide ions (OH ⁻ ) generated by the reaction at the oxygen side electrode 3 to react with nitrogen (N ₂ ) and water (H ₂ ). O) is generated and electrons (e ⁻ ) are generated (see the above formula (1)).

On the other hand, in the oxygen side electrode 3, electrons (e ⁻ ), water (H ₂ O) generated by reaction from the outside or the reaction in the fuel cell 1, and oxygen (O ₂ ) react to generate hydroxyl. Product ions (OH ⁻ ) are generated (see the above formula (2)). The generated hydroxide ions (OH ⁻ ) pass through the electrolyte membrane 4 and are supplied to the fuel side 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. Hereinafter, the oxygen reduction catalyst used for the oxygen side electrode 3 will be described.

  The oxygen reduction catalyst contains, as an essential component, a fired body of a phenanthroline Fe complex, and preferably comprises a fired body of a phenanthroline Fe complex.

  The phenanthroline Fe complex is a transition metal complex in which a phenanthroline-based ligand is coordinated to iron.

  The phenanthroline-based ligand is phenanthroline or a derivative thereof, and preferably 1,10-phenanthroline or a derivative thereof. More specifically, the phenanthroline type compound mentioned by General formula (1) is mentioned.

  m is 0 or an integer of 1 to 3, preferably 0 or 1, and more preferably 0.

  n is 0 or an integer of 1 to 3, preferably 0 or 1, and more preferably 0.

  k is 0 or an integer of 1 to 2, preferably 0 or 1, and more preferably 0.

R ¹ , alone or independently of each other, represents, for example, an alkyl group, an alkoxy group, an aryl group, a carboxyl group (—COOH), a sulfo group (—SO ₃ H), or the like.

The alkyl group represented by R ¹ is preferably an alkyl group having 1 to 6 carbon atoms. Specifically, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert Examples thereof include linear, branched or cyclic alkyl groups having 1 to 6 carbon atoms such as butyl, pentyl, isopentyl, sec-pentyl, neopentyl, cyclopentyl, n-hexyl, isohexyl, and cyclohexyl.

The alkoxy group represented by R ¹ is preferably an alkoxy group having 1 to 6 carbon atoms, specifically, methoxy, ethoxy, propoxy, isopropoxy, butoxy, isobutoxy, sec-butoxy, tert-butoxy, pentyl. C1-C6 linear or branched alkoxy groups, such as oxy, isopentyloxy, neopentyloxy, n-hexyloxy, isohexyloxy, are mentioned.

Examples of the aryl group represented by R ¹ include aryl groups such as phenyl, tolyl, xylyl, biphenyl, naphthyl, phenylnaphthyl, anthryl, phenanthryl, and azulenyl.

When R ¹ is a carboxyl group (—COOH) or a sulfo group (—SO ₃ H), these may form a metal salt. Examples of the metal that forms the metal salt include sodium and potassium.

R ² represents an alkyl group, an alkoxy group, an aryl group, a carboxyl group, a sulfo group, or the like, alone or independently of each other.

Alkyl group represented by R ^2, an alkoxy group, an aryl group, a carboxyl group, etc. sulfo group include the same as R ^1.

R ³ singly or independently represents an alkyl group, an alkoxy group, an aryl group, a carboxyl group, a sulfo group, or the like.

Alkyl group represented by R ^3, an alkoxy group, an aryl group, a carboxyl group, etc. sulfo group include the same as R ^1.

  Specific examples of the phenanthroline ligand include 1,10-phenanthroline.

  The phenanthroline-based ligand is available as a commercial product, and specifically includes 1,10-phenanthroline monohydrate (manufactured by Tokyo Chemical Industry Co., Ltd., manufactured by Kishida Chemical Co., Ltd.).

  In the phenanthroline Fe complex, the phenanthroline-based ligand is coordinated with, for example, three molecules of iron as a bidentate ligand.

  Specific examples of the phenanthroline Fe complex include tris (phenanthroline) iron (II) complex.

  The preparation of the phenanthroline Fe complex is not particularly limited, and a known method can be employed.

  For example, an iron salt (for example, an inorganic salt such as sulfate, nitrate, chloride, or phosphate, for example, an organic acid salt such as acetate or oxalate) and a phenanthroline ligand may be used. A phenanthroline Fe complex can be produced by mixing in a known solvent such as water, alcohol, aliphatic hydrocarbon, aromatic hydrocarbon, halogenated hydrocarbon, or nitrile.

  The solution or / dispersion of the phenanthroline Fe complex thus prepared is dried if necessary and then calcined.

  In the firing, for example, the complex mixture is heated in an atmosphere of an inert gas (for example, nitrogen gas, argon gas, etc.) or a reducing gas (for example, a mixed gas of nitrogen gas and hydrogen gas).

  The flow rate of the inert gas at the time of firing is, for example, 10 mL / min · g or more, preferably 15 mL / min · g or more, for example, 40 mL / min · g or less.

  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 phenanthroline Fe 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 a phenanthroline Fe complex can be obtained.

  The X-ray photoelectron spectrum of the obtained fired body has peaks at 399 eV and 401 eV, and the intensity at 401 eV is higher than the intensity at 399 eV.

  In the X-ray photoelectron spectrum, the 399 eV peak is derived from a six-membered ring structure containing a nitrogen atom, and the 401 eV peak is derived from a five-membered ring structure containing a nitrogen atom.

  According to this oxygen reduction catalyst, the fired phenanthroline Fe complex contains a fired body having a specific structure such that the intensity at 401 eV is greater than the intensity at 399 eV in the X-ray photoelectron spectrum. .

  As a result, the oxygen reduction reaction can be activated, and the oxygen reduction activity can be further improved.

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

3. Modified Example (1) of Oxygen Reduction Catalyst Production Method The oxygen reduction activity of the oxygen reduction catalyst can be further improved by treating the above-mentioned calcined phenanthroline Fe complex with ammonia.

In the ammonia treatment, the fired body obtained as described above is fired (secondary firing), for example, in an ammonia atmosphere (100% ammonia gas). As firing conditions in the ammonia treatment, the firing temperature is, for example, 400 ° C. or more, preferably 600 ° C. or more, and, for example, 1000 ° C. or less. The firing time is, for example, 0.5 hours or more, and for example, 10 hours or less, preferably 5 hours or less.
(2) When the above-described phenanthroline Fe complex is fired, the fired body of the phenanthroline Fe complex aggregates and grows, and its effective surface area decreases, and as a result, the catalytic activity 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, a method of first firing a particle mixture of a phenanthroline Fe complex and soluble particles to produce a composite containing phenanthroline Fe 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 phenanthroline Fe complex and the soluble particles are mixed before the firing.

  In order to mix the phenanthroline Fe complex and the soluble particles, for example, first, the phenanthroline Fe complex is dissolved and / 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 phenanthroline Fe 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, and, for example, 100000 parts by mass or less, relative to 100 parts by mass of the phenanthroline Fe complex. Preferably, it is 50000 parts by mass or less.

  Next, the obtained solution and / or dispersion liquid of the phenanthroline Fe complex and the soluble particles are mixed by a known method such as wet mixing.

  The mixing ratio of the solution and / or dispersion of the phenanthroline Fe complex and the soluble particles is, for example, soluble with respect to 100 parts by mass of the total amount of the phenanthroline Fe complex (solid content) in the solution and / or dispersion of the phenanthroline Fe complex. The particles are, 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 200 parts by mass or less.

  This gives a solution and / or dispersion of the phenanthroline Fe complex and soluble particles.

  Then, in this method, the obtained phenanthroline Fe complex and soluble particle solution and / or dispersion liquid 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, the mixture of the phenanthroline Fe complex and the soluble particles is fired under the above firing conditions to obtain a composite containing the phenanthroline Fe 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 if the phenanthroline Fe complex aggregates and grows by firing, the effective surface area of the phenanthroline Fe 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.
(3) The oxygen reduction catalyst of this invention can also contain arbitrary components other than an above-described sintered body. Examples of such an optional component include a carrier.

  Examples of the support include carbon such as carbon black. When the oxygen reduction catalyst includes a support, the fired body is supported on the support. In order to support the fired body on the support, a known support method can be employed.

  For example, in the impregnation method, the support is mixed with the solution and / or dispersion of the above-described phenanthroline Fe complex, and then fired under the above-described firing conditions. The mixing ratio of the support 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 200 parts by mass with respect to 100 parts by mass of the phenanthroline ligand. 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.

1. Example 1 Preparation of Oxygen Reduction Catalyst
A ligand dispersion was prepared by adding 500 mg of 1,10-phenanthroline (manufactured by Tokyo Chemical Industry Co., Ltd.) as a ligand and dispersing in a mixed solvent of 25 g of ethanol and 10.5 g of water.

  To this prepared ligand dispersion, 32.205 g of iron acetic acid was added and dispersed. Subsequently, 500 mg of carbon black (manufactured by Cabot, BP2000) was added, dispersed, and dried.

  Thereafter, the obtained dried product was fired at a firing temperature of 1000 ° C. for 2 hours in an inert gas atmosphere (inert gas flow rate: 25 mL / min · g). Thereby, an oxygen reduction catalyst was obtained.

Example 2
An oxygen reduction catalyst was obtained in the same manner as in Example 1 except that the calcination temperature was 900 ° C.

Comparative Example 1
An oxygen reduction catalyst was obtained in the same manner as in Example 1 except that the calcination temperature was 800 ° C.

Comparative Example 2
An oxygen reduction catalyst was obtained in the same manner as in Example 2 except that the flow rate of the inert gas was 7 mL / min · g.

Evaluation method 1) Component analysis In order to analyze the composition of the oxygen reduction catalyst obtained in each Example and each Comparative Example, hard X-ray photoelectron spectroscopy (HAXPES) measurement was performed.

  For the photoelectron spectroscopy analyzer, R-4000 manufactured by VG-SCIENTA was used. The pass energy was 200 eV, and the slit size was 0.5 mm. A SPring-8 standard vacuum sealed undulator was used as the light source, and an inclined direct water-cooled two-crystal monochromator using Si111 crystal was used as the monochromator. A channel-cut monochromator (Si111 crystal 444 reflection) was used between the monochromator and the mirror. The beam size was 0.5 mm (H) × 0.5 mm (V). For fixing the sample, a hole having a diameter of 2 mm was formed in a copper plate, and the electrode catalyst powder was pushed into the sample to form a sample. The incident energy was 7940 eV, the photoelectron emission angle was 80 °, and X-ray photoelectron spectra were measured for Fe, N, C, and O, which are main elements in the oxygen reduction catalyst. The results are shown in FIG.

2) Oxygen reduction activity evaluation Oxygen reduction activity was measured using a rotating ring disk electrode (Rotating Ring-Disk Electrode: RRDE).

An ink prepared by dispersing an oxygen reduction catalyst 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 10 mg of an oxygen reduction catalyst, 0.8 mL of ultrapure water and 0.2 mL of 2-propanol to prepare a primary ink, and 0.1 mL of the obtained primary ink and 0.75 mL of ultrapure water. The mixture was prepared by mixing 0.1 mL of 2-propanol and 0.05 mL of 0.5 w% Nafion solution.

  Then, using the obtained measurement electrode, 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 potential at 10 ⁻⁵ A (reaction initiation potential) and the potential at half the maximum current value (half-wave potential) were measured. When the reaction initiation potential and the half-wave potential are high, the oxygen reduction activity is excellent. The results are shown in FIG.

Claims (1)

Containing a fired product obtained by firing a phenanthroline Fe complex in which a phenanthroline-based ligand is coordinated to iron;
An oxygen reduction catalyst characterized in that the fired body has an intensity at 401 eV greater than an intensity at 399 eV in an X-ray photoelectron spectrum.

Images