JP2016124769A - Nitrogen-containing porous carbon and catalyst - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nitrogen-containing porous carbon which can balance high catalytic activity and life extension when used as a carrier of a catalyst.SOLUTION: A nitrogen-containing porous carbon that total specific surface area of pores which pore size is 5-260 nm is more than 100 m/g, a content of carbon atom is more than 80 mass%, and an atom ratio of nitrogen atom and carbon atom (N/C) is 0.005-0.18.SELECTED DRAWING: None

Description

  The present invention relates to a catalyst contained in, for example, an electrode of a polymer electrolyte fuel cell, and nitrogen-containing porous carbon useful as a support used in the catalyst.

  In recent years, solid polymer fuel cells have attracted attention as one of clean energy sources that do not generate carbon dioxide in order to solve the problems of global warming and environmental pollution. The polymer electrolyte fuel cell includes two electrodes (a fuel electrode (negative electrode) that supplies fuel such as hydrogen and an oxygen electrode (positive electrode) that supplies oxygen), and a polymer electrolyte membrane sandwiched between the electrodes. In a polymer electrolyte fuel cell using hydrogen as a fuel, in the negative electrode, the supplied hydrogen is decomposed into protons and electrons, the protons pass through the polymer electrolyte membrane and move to the positive electrode, and the electrons pass through the conductor. Move to the positive electrode. In the positive electrode, protons and electrons moving from the negative electrode react with the supplied oxygen to generate water.

  An electrode used in a polymer electrolyte fuel cell is usually formed by coating a catalyst in which a metal such as platinum (hereinafter referred to as “catalytic metal”) is supported on a carrier such as carbon black with a binder made of a polymer electrolyte. . The protons that have moved to the positive electrode described above move to the surface of the catalyst metal via the binder. On the other hand, the electrons that have moved to the positive electrode move to the surface of the catalytic metal via the carrier. Furthermore, the catalytic reaction proceeds by supplying oxygen to the interface (three-phase interface) where the binder, the carrier and the catalytic metal come into contact. In the catalyst used for such an electrode, it is desired to further increase the catalytic activity in order to reduce the amount of expensive catalytic metal used.

  As a method for enhancing the catalytic activity, a method of supporting a catalyst metal having a small particle diameter on a carrier is known. In this method, carbon black having fine pores (for example, an average pore diameter of 2 nm or less) is used as a support in order to prevent the catalyst metal from agglomerating and expanding the particle size when supported on the support. However, in such a method, it is difficult to uniformly coat the catalyst with a binder, and there are places where a three-phase interface cannot be formed, and it has been pointed out that the catalytic activity cannot be sufficiently increased (Non-patent Document 1). .

  Another problem with the catalyst is extending its life. It is known that the catalytic activity decreases due to the aggregation of the catalytic metal accompanying the starting and stopping of the polymer electrolyte fuel cell. Non-patent document 2 reports that platinum aggregation can be suppressed in a catalyst using a carbon nanotube (N-CNT) having a nitrogen-doped carbon coating as a carrier. As a hypothesis that the N-CNT suppresses the aggregation of platinum, in Non-Patent Document 2, page 1, right column, lines 1 to 6, hetero atoms such as nitrogen atoms enhance the adsorption of platinum on the carbon material surface. Is described. From this, it is considered that the catalyst obtained by the method described in Non-Patent Document 2 contributes to extending the life, but it has been difficult to achieve high catalytic activity.

Crushing magazine No.56 2013, pp. 3-11 (published by Hosokawa Micron Corporation) Physical Chemistry Chemical Physics, 2012, 14, pp. 6444-6447

  The present invention has been made in view of the above-described problems of the prior art, and has high catalytic activity and long life when used as a support for a catalyst (particularly, a catalyst used in an electrode of a solid polymer fuel cell). An object of the present invention is to provide a nitrogen-containing porous carbon that can be made compatible. Another object of the present invention is to provide a catalyst that can achieve both high catalytic activity and long life.

In order to achieve the above object, the present invention provides:
[1] The total specific surface area of pores having a pore diameter in the range of 5 to 260 nm is 100 m ² / g or more, the carbon atom content is 80 mass% or more, and the atomic ratio of nitrogen atoms to carbon atoms ( N / C) nitrogen-containing porous carbon having 0.005 to 0.18;
[2] The nitrogen-containing porous carbon of [1], wherein the atomic ratio (H / C) of hydrogen atoms to carbon atoms is 0.1 or less;
[3] A catalyst obtained by supporting a catalyst metal on the nitrogen-containing porous carbon of [1] or [2]; and [4] The catalyst of [3], wherein the catalyst metal is a platinum group element;
I will provide a.

  When the nitrogen-containing porous carbon of the present invention is used as a carrier for a catalyst contained in an electrode of a polymer electrolyte fuel cell, both high catalyst activity and long life can be achieved.

2 is a pore distribution curve of nitrogen-containing porous carbon obtained in Example 1. FIG. 2 is a scanning electron micrograph of nitrogen-containing porous carbon obtained in Example 1. FIG.

Hereinafter, the present invention will be described in detail.
(Nitrogen-containing porous carbon)
The nitrogen-containing porous carbon of the present invention has a total specific surface area of pores having a pore diameter in the range of 5 to 260 nm of 100 m ² / g or more, preferably 200 m ² / g or more. The ratio is not particularly limited to the upper limit of the surface area, but preferably at 1000 m ² / g or less, more preferably 800 m ² / g or less.

In the nitrogen-containing porous carbon of the present invention, since pores having a pore diameter of less than 5 nm are difficult to uniformly coat with a binder, the efficiency of supplying protons to the surface of the catalytic metal is lowered, and the catalytic activity is lowered. It becomes a trend. In addition, pores having a pore diameter of more than 260 nm tend to agglomerate when a catalytic metal is supported in the pores, so that the catalytic activity tends to decrease. From such a viewpoint, the peak (maximum peak) indicating the maximum height in the pore distribution curve (differential pore volume distribution curve) is preferably in the range of 5 to 260 nm, and the height of the maximum peak (maximum intensity). ) Is more preferably 1.3 times or more, and even more preferably 1.5 times or more of the height of all other peaks.
In addition, it is preferable that the pore distribution is uniform in order to suppress the aggregation of the catalyst metal due to the uneven loading of the catalyst metal, and from this viewpoint, the half-width of the maximum peak is more preferably 30 nm or less. More preferably, it is 20 nm or less. The half-value width can be calculated from the difference in pore diameter at two points indicating the height of half of the maximum intensity at the maximum peak of the pore distribution curve.

  The pore distribution curve indicates that the nitrogen-containing porous carbon to be measured is cooled to liquid nitrogen temperature (−196 ° C.), gradually pressurized with nitrogen gas, and the adsorption amount of nitrogen gas with respect to the equilibrium pressure of nitrogen gas by the constant volume method. Can be created by the BJH method from the nitrogen adsorption isotherm obtained by plotting. Further, the total specific surface area of the pores in which the pore diameter of the nitrogen-containing porous carbon is in the range of 5 to 260 nm is also calculated from the BJH method. The BJH method is calculated by using cylindrical pores that are not connected to other pores as a model, and is a method for obtaining pore distribution from capillary condensation of nitrogen gas and multi-layer adsorption. The details are described in “Shimadzu review” (Vol. 48, No. 1, pp. 35-44, published in 1991).

  The content of carbon atoms in the nitrogen-containing porous carbon of the present invention is preferably 80% by mass or more, and more preferably 82% by mass or more. When the carbon atom content is 80 mass% or more, the conductivity of the nitrogen-containing porous carbon is increased. By using the nitrogen-containing porous carbon of the present invention having high conductivity as a carrier, the movement of electrons moving through the carrier is improved and the catalytic activity is enhanced. Further, from the viewpoint of securing the content of nitrogen atoms for suppressing the aggregation of the catalyst metal, the content of carbon atoms is preferably 99.4% by mass or less, more preferably 99% by mass or less. preferable.

  The nitrogen atom content in the nitrogen-containing porous carbon of the present invention is preferably 0.6% by mass or more, and more preferably 1% by mass or more. Aggregation of the catalyst metal can be effectively suppressed when the nitrogen atom content is 0.6% by mass or more. Further, from the viewpoint of securing the carbon atom content that improves the conductivity of the nitrogen-containing porous carbon, the nitrogen atom content is preferably 17% by mass or less, and more preferably 10% by mass or less. preferable.

  In the nitrogen-containing porous carbon of the present invention, nitrogen atoms are introduced into the carbon skeleton. The atomic ratio of nitrogen atoms to carbon atoms (N / C (that is, the number of nitrogen atoms / the number of carbon atoms)) in the nitrogen-containing porous carbon is 0.005 to 0.18, and 0.01 to 0.00. 10 is preferable. When (N / C) is 0.005 or more, the nitrogen atoms can enhance the adsorption of the catalytic metal to the carbon surface and suppress the aggregation of the catalytic metal. On the other hand, when (N / C) is 0.18 or less, the conductivity of the carrier is increased, the movement of electrons moving through the carrier is improved, and the catalytic activity is enhanced.

  The atomic ratio of hydrogen atoms to carbon atoms (H / C (that is, the number of hydrogen atoms / number of carbon atoms)) in the nitrogen-containing porous carbon of the present invention is the carbon in the case where a carbon material is obtained by heating an organic compound. It is an index of conversion. Such (H / C) is preferably 0.1 or less, and more preferably 0.05 or less. When (H / C) is 0.1 or less, the conductivity of the carrier is increased, and the movement of electrons moving through the carrier is improved, so that the catalytic activity can be enhanced. (H / C) is preferably as small as possible, and the lower limit is not particularly limited.

  The above-described carbon atom and nitrogen atom contents, and (N / C) and (H / C) can be determined by CHN elemental analysis.

  A preferred method for producing the nitrogen-containing porous carbon of the present invention will be described below. However, the method for producing the nitrogen-containing porous carbon of the present invention is not limited to the following method.

A preferred method for producing nitrogen-containing porous carbon is:
A polar block (S) having a structural unit derived from an aromatic vinyl compound and having a polar group selected from the group consisting of a hydroxy group, an acidic group and a basic group, and a structure derived from an unsaturated aliphatic hydrocarbon In an aqueous dispersion containing a block copolymer (Z) having a non-polar block (T) having units and an N-methylol compound represented by the following formula (1): A first step of polymerizing an N-methylol compound to obtain a mixture;
A second step of removing water from the obtained mixture to obtain a polymer composition and a third step of heating the obtained polymer composition are included.

(In the formula, X represents a hydrogen atom, a hydrocarbon group or an amino group represented by —NR ⁴ R ⁵ , and R ^{1 to} R ⁵ are independently of each other a hydrogen atom, an alkyl group, a hydroxyalkyl group or an alkoxyalkyl group. Represents a group.)

  Hereinafter, the N-methylol compound represented by the formula (1) is simply referred to as “N-methylol compound (1)”. In addition, a polar group selected from the group consisting of a hydroxy group, an acidic group and a basic group is simply referred to as “polar group”. Moreover, it has a structural unit derived from an aromatic vinyl compound, and a polar block (S) having a polar group is simply a “polar block (S)” and a structural unit derived from an unsaturated aliphatic hydrocarbon. The nonpolar block (T) which is amorphous and is simply referred to as “nonpolar block (T)”. Further, the block copolymer (Z) having the polar block (S) and the nonpolar block (T) is simply referred to as “block copolymer (Z)”.

Hereafter, the said manufacturing method is demonstrated in detail.
[First step]
In the first step, the N-methylol compound (1) contained in the aqueous dispersion is polymerized in an aqueous dispersion containing the block copolymer (Z) and the N-methylol compound (1). This is a step of obtaining a mixture containing a polymer of the methylol compound (1), the block copolymer (Z) and water. Here, the aqueous dispersion means a dispersion using water as a dispersion medium.

<Block copolymer (Z)>
The block copolymer (Z) has one or more polar blocks (S) and nonpolar blocks (T). When the block copolymer (Z) has a plurality of polar blocks (S), their structures (for example, the types of structural units, the degree of polymerization, the types of polar groups, the introduction ratio, etc.) may be the same as each other. , May be different. When the block copolymer (Z) has a plurality of nonpolar blocks (T), their structures (for example, the types of structural units, the degree of polymerization, etc.) may be the same or different from each other. Good.

  Examples of the block copolymer (Z) include an ST diblock copolymer, an STS type triblock copolymer, a TST type triblock copolymer, and a mixture thereof (for example, S-T-S type triblock copolymer and S-T type diblock copolymer mixture) and the like (the S and T are the polar block (S) and nonpolar block (T), respectively). Represent). A block copolymer (Z) may be used individually by 1 type, and may use 2 or more types together.

  The block copolymer (Z) is considered to form micelles (hereinafter referred to as “micelles”) with the polar block (S) on the outside and the nonpolar block (T) on the inside in the aqueous dispersion.

The polar block (S) is selected from the group consisting of a hydroxy group, an acidic group (for example, a sulfo group, a phosphonic acid group (—P (O) (OH) ₂ ), a carboxy group, etc.) and a basic group (for example, an amino group). Having polar groups. The polar group is preferably an acidic group, and more preferably a sulfo group. Both acidic groups and basic groups may exist as salt forms.

  The content of the polar group per 1 g of the block copolymer (Z) is preferably 0.2 to 3 mmol / g, more preferably 0.5 to 2 mmol / g, and more preferably 0.7 to 1 from the viewpoint of micelle stability. More preferably, it is 0.5 mmol / g.

When the polar group is a hydroxy group, the content of the polar group can be calculated by ¹ H-NMR measurement. ¹ H-NMR measurement may be performed after a protective group (for example, a trimethylsilyl group) is introduced into the hydroxy group as necessary.

  When the polar group is an acidic group or a basic group, the content of the polar group can be calculated by neutralization titration. The content of a polar group in the case of an acidic group or basic group in the form of a salt can be calculated by neutralizing titration after converting the polar group into an acidic group or basic group in a free form.

The block copolymer (Z) has a structural unit derived from, for example, an aromatic vinyl compound and has no polar group (S ₀ ) (hereinafter referred to as “block (S ₀ )”) and nonpolar A block copolymer (Z ₀ ) having a block (T) (hereinafter referred to as “block copolymer (Z ₀ )”) is produced, and then the block (S ₀ ) of the obtained block copolymer (Z ₀ ) ) By introducing a polar group by a known method.

The number average molecular weight (Mn) of the block copolymer (Z ₀ ) is preferably from 5,000 to 200,000, more preferably from 30,000 to 150,000, and even more preferably from 50,000 to 130,000. By using a block copolymer (Z) obtained from a block copolymer (Z ₀ ) having an Mn of 5,000 to 200,000, a pore diameter of 5 to 260 nm can be obtained in the production of nitrogen-containing porous carbon. It becomes easy to manufacture the nitrogen-containing porous carbon which has. In the present specification, Mn is a value measured by gel permeation chromatography (GPC) method (standard polystyrene conversion).

The content of the block copolymer block in _{(Z 0) (S 0)} is preferably in the range of 10 to 80 wt%, 20 to 70 mass from the viewpoint of pore distribution obtain a uniform nitrogen-containing porous carbon % Is more preferable. In addition, the content of the nonpolar block (T) in the block copolymer (Z ₀ ) is preferably in the range of 20 to 90% by mass, from the viewpoint of obtaining nitrogen-containing porous carbon having a small variation in pore diameter. More preferably, it is in the range of ˜80 mass%. These contents are determined based on the integrated values of the block (S ₀ ) and nonpolar block (T) observed by ¹ H-NMR.

The block (S ₀ ) can be formed by polymerizing an aromatic vinyl compound as a monomer. Examples of the aromatic vinyl compound include styrene, 2-methylstyrene, 3-methylstyrene, 4-methylstyrene, 4-ethylstyrene, 2,4-dimethylstyrene, 2,5-dimethylstyrene, 3,5-dimethyl. Examples thereof include styrene, 2-methoxystyrene, 3-methoxystyrene, 4-methoxystyrene, vinyl biphenyl, vinyl terphenyl, vinyl naphthalene, vinyl anthracene, and 4-phenoxy styrene. These aromatic vinyl compounds may be used individually by 1 type, and may use 2 or more types together.

  Of the hydrogen atoms on the vinyl group of the aromatic vinyl compound, the hydrogen atom bonded to the α-position carbon (α-carbon) of the aromatic ring may be substituted with another substituent. Examples of the substituent include an alkyl group having 1 to 4 carbon atoms (for example, methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, tert-butyl group, etc.). And a halogenated alkyl group having 1 to 4 carbon atoms (for example, a chloromethyl group, a 2-chloroethyl group, a 3-chloroethyl group) and an aryl group (for example, a phenyl group). Examples of the aromatic vinyl compound having a substituted vinyl group include α-methylstyrene, α-methyl-4-methylstyrene, α-methyl-4-ethylstyrene, 1,1-diphenylethylene, and the like.

  Among these aromatic vinyl compounds, styrene, 2-methylstyrene, 3-methylstyrene, 4-methylstyrene, 4-ethylstyrene, 2,4-dimethylstyrene are used from the viewpoint of easy introduction of polar groups (especially sulfo groups). 2,5-dimethylstyrene, 3,5-dimethylstyrene, 2-methoxystyrene, 3-methoxystyrene, 4-methoxystyrene, vinylbiphenyl, vinylterphenyl, vinylnaphthalene, vinylanthracene, 4-phenoxystyrene, α- Methyl styrene, α-methyl-4-methyl styrene, α-methyl-4-ethyl styrene and 1,1-diphenylethylene are preferred, and styrene, 2-methyl styrene, 3-methyl styrene, 4-methyl styrene, 4-ethyl Styrene, 2,4-dimethylstyrene, 2,5-dimethyl Tylene, 3,5-dimethylstyrene, vinylbiphenyl and α-methylstyrene are more preferred, styrene, 4-methylstyrene, 4-ethylstyrene, vinylbiphenyl and α-methylstyrene are more preferred, and styrene and α-methylstyrene are preferred. Particularly preferred.

The block (S ₀ ) and the polar block (S) derived therefrom are monomers other than the aromatic vinyl compound (hereinafter referred to as “other monomers (a)”) as long as the effects of the present invention are not impaired. The structural unit derived from may be included. Examples of the other monomer (a) include conjugated dienes having 4 to 8 carbon atoms (for example, butadiene, 1,3-pentadiene, isoprene, 1,3-hexadiene, 2,4-hexadiene, 2,3-dimethyl- 1,3-butadiene, 2-ethyl-1,3-butadiene, 1,3-heptadiene, etc.), alkenes having 2 to 8 carbon atoms (for example, ethylene, propylene, 1-butene, 2-butene, isobutene, 1-pentene) 2-pentene, 1-hexene, 2-hexene, 1-heptene, 2-heptene, 1-octene, 2-octene, etc.), (meth) acrylic acid esters (for example, methyl (meth) acrylate, (meth) acrylic) Ethyl acetate, butyl (meth) acrylate, etc.), vinyl esters (eg vinyl acetate, vinyl propionate, vinyl butyrate, vinyl pivalate, etc.) Vinyl ether (e.g. methyl vinyl ether, isobutyl vinyl ether) and the like. As the other monomer (a), one type may be used alone, or two or more types may be used in combination.

The content of the structural unit derived from the other monomer (a) in the block (S ₀ ) is preferably 10% by mass or less, more preferably 5% by mass or less. Most preferably, the structural unit derived from (a) is not included. Further, the content of the structural unit derived from the aromatic vinyl compound in the block (S ₀ ) is preferably 90% by mass or more, more preferably 95% by mass or more, and 100% by mass. Most preferred.

The Mn per block (S ₀ ) is preferably from 1,000 to 80,000, more preferably from 3,000 to 70,000, and even more preferably from 5,000 to 50,000. By using the block copolymer (Z) obtained from the block copolymer (Z ₀ ) having an Mn per block (S ₀ ) of 1,000 to 80,000, the uniformity of the pores is improved. High nitrogen-containing porous carbon can be produced.

  The nonpolar block (T) is a block that has a structural unit derived from an unsaturated aliphatic hydrocarbon and is amorphous. It is confirmed that the nonpolar block (T) is amorphous by measuring the dynamic viscoelasticity of the block copolymer (Z) and not having a change in the storage elastic modulus derived from the crystalline olefin polymer. it can.

  The nonpolar block (T) can be formed by polymerizing an unsaturated aliphatic hydrocarbon as a monomer. Examples of the unsaturated aliphatic hydrocarbon include olefins having 2 to 8 carbon atoms (for example, ethylene, propylene, 1-butene, 2-butene, isobutene, 1-pentene, 2-pentene, 1-hexene, 2-hexene, 1 -Heptene, 2-heptene, 1-octene, 2-octene, etc.), conjugated dienes having 4 to 8 carbon atoms (for example, butadiene, 1,3-pentadiene, isoprene, 1,3-hexadiene, 2,4-hexadiene, 2 , 3-dimethyl-1,3-butadiene, 2-ethyl-1,3-butadiene, 1,3-heptadiene, etc.). These unsaturated aliphatic hydrocarbons may be used alone or in combination of two or more. When a conjugated diene is used as the unsaturated aliphatic hydrocarbon, the polymerization (bonding) may be a 1,2-bond, a 1,4-bond, or a mixture thereof.

  Such unsaturated aliphatic hydrocarbons include ethylene, propylene, 1-butene, 2-butene, isobutene, 1-pentene, 2-pentene, 1-hexene, 2-hexene, 1-heptene, 2-heptene, 1- Octene, 2-octene, butadiene, 1,3-pentadiene, isoprene, 1,3-hexadiene, 2,4-hexadiene, 2,3-dimethyl-1,3-butadiene, 2-ethyl-1,3-butadiene and 1,3-heptadiene is preferred, butadiene, isobutene, 1,3-pentadiene, isoprene, 1,3-hexadiene, 2,4-hexadiene, 2,3-dimethyl-1,3-butadiene, 2-ethyl-1, More preferred are 3-butadiene and 1,3-heptadiene, butadiene, isobutene, isoprene, 2,3-dimethyl. 1,3-butadiene and 2-ethyl-1,3-butadiene is more preferable, isobutene, butadiene and isoprene are particularly preferred.

  The nonpolar block (T) includes a structural unit derived from a monomer other than the unsaturated aliphatic hydrocarbon (hereinafter referred to as “other monomer (b)”) as long as the effects of the present invention are not impaired. You may go out. Examples of the other monomer (b) include aromatic vinyl compounds (such as styrene and vinyl naphthalene), halogen-containing vinyl compounds (such as vinyl chloride), vinyl esters (such as vinyl acetate, vinyl propionate, vinyl butyrate, Vinyl pivalate, etc.), vinyl ethers (eg, methyl vinyl ether, isobutyl vinyl ether, etc.). As the other monomer (b), one type may be used alone, or two or more types may be used in combination.

  The content of the structural unit derived from the other monomer (b) in the nonpolar block (T) is preferably 10% by mass or less, and more preferably 5% by mass or less. Further, the content of the structural unit derived from the unsaturated aliphatic hydrocarbon in the nonpolar block (T) is preferably 90% by mass or more, more preferably 95% by mass or more, and 100% by mass. Most preferably.

  The Mn per nonpolar block (T) is preferably 3,000 to 150,000, more preferably 10,000 to 120,000, and even more preferably 20,000 to 100,000. The block copolymer (Z) having a Mn per nonpolar block (T) of 3,000 to 150,000 has good dispersibility in water and easily forms micelles, and has a pore diameter of 5 to 260 nm. It becomes easy to produce nitrogen-containing porous carbon having the following.

As a polymerization method of the monomer for producing the block copolymer (Z ₀ ), a radical polymerization method, an anionic polymerization method, a cationic polymerization method, a coordination polymerization method and the like can be appropriately selected. Among these, the radical polymerization method, the anion polymerization method and the cationic polymerization method are preferable from the viewpoint of industrial ease, and the living radical polymerization method, the living anion polymerization method and the living cationic polymerization method from the viewpoint of controlling the molecular weight and molecular weight distribution. Is more preferable.

As an example of a method for producing a block copolymer (Z ₀ ) by living anionic polymerization, a conjugated diene is used as an unsaturated aliphatic hydrocarbon.
(1) An aromatic vinyl compound, a conjugated diene, and an aromatic vinyl compound are sequentially polymerized in a nonpolar solvent such as cyclohexane in the presence of an anionic polymerization initiator at a temperature of 20 to 100 ° C., and S ₀ − A method for obtaining a T-S ₀ type triblock copolymer (Z ₀ ) (wherein S ₀ and T represent a block (S ₀ ) and a nonpolar block (T), respectively, the same shall apply hereinafter);
(2) A coupling agent such as phenyl benzoate after sequential polymerization of an aromatic vinyl compound and a conjugated diene in a non-polar solvent such as cyclohexane in the presence of an anionic polymerization initiator at a temperature of 20 to 100 ° C. To obtain a S ₀ -T-S ₀ type triblock copolymer (Z ₀ );
(3) In a nonpolar solvent such as cyclohexane, in the presence of an organic lithium compound as an anionic polymerization initiator and a polar compound (for example, ether, amine, etc.) that is an activator of a polymerization terminal anion, -30 ° C to 30 ° C At a temperature, an aromatic vinyl compound is polymerized, a conjugated diene is polymerized to the resulting living polymer, a coupling agent such as phenyl benzoate is added, and an S ₀ -TS ₀ type block copolymer A method of obtaining (Z ₀ );
(4) In the presence of an anionic polymerization initiator in a nonpolar solvent such as cyclohexane, t-butylstyrene, styrene, and conjugated diene are sequentially added one or more times in the desired order under a temperature condition of 20 to 100 ° C. Examples thereof include a method for obtaining a block copolymer (Z ₀ ) comprising three or more types of blocks.

As an example of a method for producing a block copolymer (Z ₀ ) by living cationic polymerization, when isobutene is used as an unsaturated aliphatic hydrocarbon, in a mixed solvent of halogenated hydrocarbon and hydrocarbon at −78 ° C. A bifunctional halogenated initiator is used to cationically polymerize isobutene in the presence of a Lewis acid, and then an aromatic vinyl compound such as styrene is polymerized to produce an S ₀ -TS ₀ type triblock copolymer. (Z ₀ ) (for example, the method described in Makromol. Chem., Macromol. Symp., 32, pp. 119-129 (1990)).

When an unsaturated aliphatic hydrocarbon having a plurality of carbon-carbon double bonds is used as the monomer for producing the block copolymer (Z ₀ ), the carbon-carbon double is usually added to the obtained polymer. Bonds remain. In this case, hydrogenation (hydrogenation) may be performed by a known hydrogenation reaction (hydrogenation reaction), and some or all of the carbon-carbon double bonds remaining after polymerization may be converted into saturated bonds. The hydrogenation rate (hydrogenation rate) of the carbon-carbon double bond is preferably 50 mol% or more, and more preferably 80 mol% or more. The hydrogenation rate can be calculated by ¹ H-NMR measurement.

The block copolymer (Z) can be produced by introducing a polar group into the block copolymer (Z ₀ ) produced as described above by a known method.

Examples of the method for introducing a sulfo group into the block copolymer (Z ₀ ) include known sulfonation reactions. For example, a sulfonating agent described later is added to a solution or suspension of the block copolymer (Z ₀ ). And a method of directly adding a gaseous sulfonating agent to the block copolymer (Z ₀ ).

  Sulfonating agents include sulfuric acid, a mixture of sulfuric acid and aliphatic acid anhydride, chlorosulfonic acid, a mixture of chlorosulfonic acid and trimethylsilyl chloride, sulfur trioxide, a mixture of sulfur trioxide and triethyl phosphate, 2, 4 An aromatic sulfonic acid such as 1,6-trimethylbenzenesulfonic acid is exemplified.

  Examples of the solvent used in the sulfonation reaction include halogenated hydrocarbons such as methylene chloride, chain aliphatic hydrocarbons such as hexane, cycloaliphatic hydrocarbons such as cyclohexane, and mixed solvents thereof.

Further, for example, as a method of introducing a block copolymer phosphonic acid to _{(Z 0) (-P (O} ) (OH) 2) , the block copolymer solution or suspension of _{(Z 0)} was prepared In the presence of anhydrous aluminum chloride, the block copolymer (Z ₀ ) is reacted with chloromethyl ether and the like, and after introducing a halomethyl group into the aromatic ring, phosphorus trichloride and anhydrous aluminum chloride are added thereto and reacted. And a method of introducing a phosphonic acid group by further performing a hydrolysis reaction. Further, phosphorus trichloride and anhydrous aluminum chloride are added to the block copolymer (Z ₀ ) for reaction, and after introducing a phosphinic acid group (—PH (O) (OH)) into an aromatic ring, the phosphinic acid is added with nitric acid. The method of oxidizing a group and converting it into a phosphonic acid group is mentioned.

Further, for example, a method for introducing an amino group into the block copolymer (Z ₀ ) includes a method in which the block copolymer (Z ₀ ) is chloromethylated and then reacted with an amine or the like.

<N-methylol compound (1)>
The N-methylol compound (1) is represented by the following formula (1).

(In the formula, X represents a hydrogen atom, a hydrocarbon group or an amino group represented by —NR ⁴ R ⁵ , and R ^{1 to} R ⁵ are independently of each other a hydrogen atom, an alkyl group, a hydroxyalkyl group or an alkoxyalkyl group. Represents a group.)

  Examples of the hydrocarbon group represented by X in the formula (1) include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, a pentyl group, and an isopentyl group. Alkyl groups such as a group, neopentyl group, 1-ethylpropyl group, hexyl group, isohexyl group, 1,1-dimethylbutyl group, 2,2-dimethylbutyl group, 3,3-dimethylbutyl group, 2-ethylbutyl group; Aryl groups such as phenyl and tolyl groups; aralkyl groups such as benzyl and the like.

Examples of the alkyl group represented by R ^{1 to} R ⁵ in the formula (1) include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, and pentyl. Group, isopentyl group, neopentyl group, 1-ethylpropyl group, hexyl group, isohexyl group, 1,1-dimethylbutyl group, 2,2-dimethylbutyl group, 3,3-dimethylbutyl group, 2-ethylbutyl group, etc. Among these, an alkyl group having 1 to 5 carbon atoms is preferable, an alkyl group having 1 to 3 carbon atoms is more preferable, and an alkyl group having 1 to 2 carbon atoms is more preferable.

In the hydroxyalkyl group represented by R ^{1 to} R ⁵ in formula (1), at least one (preferably 1 to 3, most preferably 1) of the above alkyl groups is substituted with a hydroxy group. Means what was done. As such a hydroxyalkyl group, a hydroxymethyl group, a 2-hydroxyethyl group and a 3-hydroxypropyl group are preferable, and a hydroxymethyl group is most preferable.

In the alkoxyalkyl group represented by R ^{1 to} R ⁵ in the formula (1), at least one (preferably 1 to 3, most preferably 1) hydrogen atom of the above alkyl group is substituted with an alkoxy group. Means a functional group formed. Specific examples of such alkoxy groups include, for example, methoxy group, ethoxy group, propoxy group, isopropoxy group, butoxy group, isobutoxy group, sec-butoxy group, tert-butoxy group, pentyloxy group, hexyloxy group and the like. The alkoxyalkyl group is preferably a methoxymethyl group, a 2-methoxyethyl group or a 3-methoxypropyl group, more preferably a methoxymethyl group or a 2-methoxyethyl group.

From the viewpoint of promoting polymerization in the first step, as the N-methylol compound (1), a compound in which X is —NR ⁴ R ⁵ and R ^{1 to} R ⁵ are each independently a hydrogen atom or a hydroxymethyl group Is preferred. N-methylol compound (1) may be used individually by 1 type, and may use 2 or more types together. In addition, when manufacturing N-methylol compound (1) with the method mentioned later, it becomes a mixture of a several N-methylol compound (1) normally. Average number of hydroxymethyl groups _(-CH 2 OH) is preferably 1 to 4 in the N- methylol compounds (1), 1.5 to 3 is more preferable.

  Among the N-methylol compounds (1), from the viewpoint of increasing the amount of nitrogen introduced into the obtained nitrogen-containing porous carbon, a compound represented by the following formula (2) (that is, methylol melamine having at least one hydroxymethyl group, Hereinafter, referred to as “N-methylol compound (2)”).

(In the formula, R ^{1 to} R ⁵ each independently represent a hydrogen atom, an alkyl group, a hydroxyalkyl group or an alkoxyalkyl group.)

The explanation of R ^{1 to} R ⁵ in the formula (2) is the same as that explained in the formula (1). As the N-methylol compound (2), a compound in which R ^{1 to} R ⁵ are each independently a hydrogen atom or a hydroxymethyl group is preferable. N-methylol compound (2) may be used individually by 1 type, and may use 2 or more types together. Average number of hydroxymethyl groups _(-CH 2 OH) is preferably 1 to 4 in the N- methylol compounds (2), 1.5 to 3 is more preferable.

  The N-methylol compound (1) reacts with formaldehyde or paraformaldehyde (hereinafter referred to as “formaldehydes”) and an amine represented by the following formula (3) (hereinafter referred to as “amine (3)”) (N-methylol). It is obtained by carrying out the reaction.

(In the formula, X represents a hydrogen atom, a hydrocarbon group or —NR ⁴ R ⁵ , and R ^{1 to} R ⁵ each independently represent a hydrogen atom, an alkyl group, a hydroxyalkyl group or an alkoxyalkyl group.)

Specific examples of amine (3) include melamine (R ¹ = R ² = R ³ = H, X = NR ⁴ R ⁵ and R ⁴ = R ⁵ = H), benzoguanamine (R ¹ = R ² = R). ³ = H, X = phenyl group), acetoguanamine (R ¹ = R ² = R ³ = H, X = methyl group) and the like, from the viewpoint of increasing the amount of nitrogen introduced into the resulting nitrogen-containing porous carbon Melamine is preferred.

  Formaldehyde is preferred as the formaldehyde, and such formaldehyde is preferably used as a formaldehyde solution. Examples of the solvent for the formaldehyde solution include water, polar organic solvents, and mixed solvents thereof, and water is preferable. Examples of the polar organic solvent include alcohols such as methanol, ethanol, n-propanol, 2-propanol and 2-methyl-1-propanol; ethers such as tetrahydrofuran; ketones such as acetone and cyclohexanone. A polar organic solvent may be used individually by 1 type, and may use 2 or more types together. The formaldehyde concentration in the formaldehyde solution is preferably 5 to 80% by mass, and more preferably 10 to 50% by mass.

  The amount of formaldehyde used in the N-methylolation reaction is preferably 1 to 6 mol times, 1.5 to 3 mol times in terms of HCHO, relative to the partial structure represented by -NH- in amine (3). More preferred. The progress of the reaction is promoted when the amount is 1 mol or more, and the production cost is increased when the amount is 6 mol or less, thereby increasing industrial productivity.

  The N-methylolation reaction is generally performed in a solvent. Examples of such a solvent include water and a mixed solvent thereof, and water is preferable. Examples of the polar organic solvent include alcohols such as methanol, ethanol, n-propanol, 2-propanol and 2-methyl-1-propanol; ethers such as tetrahydrofuran; ketones such as acetone and cyclohexanone. A polar organic solvent may be used individually by 1 type, and may use 2 or more types together. The amount of the solvent used in the N-methylolation reaction is preferably 0.5 mass times or more of the amine (3) from the viewpoint of the solubility of the N-methylol compound (1) to be produced.

  From the viewpoint of promoting the N-methylolation reaction, a base other than amine (3) may be added to the reaction system. As the base, ammonia and trialkylamine (trimethylamine, triethylamine, triisopropylamine, etc.) are preferable from the viewpoint of easiness of removal, and ammonia is more preferable. The base may be distilled off after the first step or may be subjected to the second step while remaining in the N-methylol compound (1).

  The N-methylolation reaction may be performed in an inert gas atmosphere such as nitrogen or argon, but is usually performed in the air. 50-100 degreeC is preferable and the reaction temperature of N-methylolation reaction has more preferable 60-80 degreeC. The reaction time of the N-methylolation reaction varies depending on the heating temperature, the amount of formaldehyde used, the amount of amine (3) used, etc., but is generally 1 minute to 1 hour.

The N-methylolation reaction is usually performed by adding amine (3) to the aqueous formaldehyde solution. The amine (3) is usually dispersed without dissolving in the aqueous formaldehyde solution, but as the N-methylolation reaction proceeds, the dispersed amine (3) disappears and the produced N-methylol compound (1) A uniform aqueous solution is obtained by dissolving in a solvent. It is preferable to carry out the N-methylolation reaction until such a uniform aqueous solution is obtained. The N-methylol compound (1) obtained by the N-methylolation reaction may be used in the first step after being isolated from the aqueous solution by a known method such as recrystallization or may be used as it is. . In addition, the aqueous solution of the N-methylol compound (1) obtained by the N-methylolation reaction usually contains a plurality of N-methylol compounds (1). From the viewpoint of simplifying the operation, it is preferable to use the obtained aqueous solution of the N-methylol compound (1) as it is in the first step. The structure of the N-methylol compound (1) can be specified by ¹ H-NMR measurement after removing the basic substance and the solvent from the solution.

  The aqueous dispersion containing the block copolymer (Z) and the N-methylol compound (1) used in the first step is preferably prepared, for example, as an aqueous dispersion of (i) the block copolymer (Z). (Ii) Separately, the N-methylol compound (1) was produced by the N-methylolation reaction described above, and (iii) the N obtained in (ii) above was added to the aqueous dispersion prepared in (i) above. -It can manufacture by adding a methylol compound (1).

  In the above (iii), the N-methylol compound (1) obtained in the above (ii) may be isolated and added to the aqueous dispersion of the block copolymer (Z) prepared in the above (i). The reaction mixture (usually an aqueous solution) after the N-methylolation reaction performed in (ii) above may be added as it is to the aqueous dispersion of the block copolymer (Z) prepared in (i) above. From the viewpoint of simplifying the operation, it is preferable to add the solution after the N-methylolation reaction as it is to the aqueous dispersion of the block copolymer (Z) prepared in the above (i). There is no restriction | limiting in particular in the addition method of N-methylol compound (1), Any of collective addition, sequential addition, and continuous addition may be sufficient.

  As the method for preparing the aqueous dispersion of the block copolymer (Z) in (i) above, for example, (1) After adding water to the organic solution of the block copolymer (Z) and stirring, the organic solvent is removed. (2) A polar organic solvent such as alcohol is added to the organic solution of the block copolymer (Z) and stirred, and water is added to the original organic solution. And a method of removing the added organic solvent and the added polar organic solvent.

Moreover, 1-30 mass% is preferable and, as for content of the block copolymer (Z) in the aqueous dispersion of the block copolymer (Z) in said (i), 2-20 mass% is more preferable. The content can be determined as the solid content of the aqueous dispersion. Specifically, the aqueous dispersion is dried at 150 ° C. for 60 minutes with a heat-drying moisture meter (MX-50 manufactured by A & D Co., Ltd.). The solid content can be calculated from the mass of the aqueous dispersion before drying and the mass of the solid material obtained after drying (that is, the block copolymer (Z)) by the following formula.
Content (% by mass) of block copolymer (Z) = 100 × mass of solid matter obtained after drying (g) / mass of aqueous dispersion before drying

  Further, in the aqueous dispersion of the block copolymer (Z), the average dispersed particle size of the block copolymer (Z) forming the micelle is a nitrogen-containing porous carbon having a pore size of 5 to 260 nm. From the viewpoint of making, a range of 5 to 200 nm is preferable, and a range of 10 to 100 nm is more preferable. The average dispersed particle diameter is a value measured by a dynamic light scattering method. In detail, the measurement conditions and apparatus of a dynamic light scattering method are described in the below-mentioned Example.

  The average dispersion particle size of the block copolymer (Z) forming micelles in the aqueous dispersion of the block copolymer (Z) is the Mn of the block copolymer (Z), the block copolymer (Z). It can be adjusted depending on the content of the polar block (S) and nonpolar block (T) to be formed, the type of polar group, the amount of polar group and the like. For example, when the Mn of the block copolymer (Z) is large, the average dispersed particle size tends to increase. Further, when the polarity of the polar group is low, the average dispersed particle size tends to increase. Moreover, when there is little content of the polar group of a block copolymer (Z), there exists a tendency for this average dispersed particle diameter to become large.

  In the first step, the total content of the N-methylol compound (1) and the block copolymer (Z) before polymerization in the aqueous dispersion containing the block copolymer (Z) and the N-methylol compound (1). Is preferably 0.5 to 50% by mass, more preferably 5 to 40% by mass from the viewpoint of productivity.

The amount of the N-methylol compound (1) used relative to the block copolymer (Z) used for the preparation of the aqueous dispersion containing the block copolymer (Z) and the N-methylol compound (1) is the block copolymer ( Z) is preferably 1 to 8 times by mass, more preferably 1.2 to 4 times by mass. By making the usage-amount of N-methylol compound (1) into 8 mass times or less of a block copolymer (Z), the pore diameter in the range whose pore diameter in the nitrogen-containing porous carbon obtained is 5-260 nm. The total specific surface area can be 100 m ² / g or more.

  The polymerization of the N-methylol compound (1) in the first step may be performed in an inert gas atmosphere such as nitrogen or argon, but is usually performed in the air. 20-100 degreeC is preferable and the polymerization temperature which performs this superposition | polymerization has more preferable 50-90 degreeC. The polymerization time is preferably 10 minutes to 10 hours, more preferably 20 minutes to 2 hours, from the viewpoint of enhancing the uniformity of the pores of the obtained nitrogen-containing porous carbon.

  The aqueous dispersion containing the block copolymer (Z) and the N-methylol compound (1) is preferably acidic in order to promote polymerization, and more preferably has a pH of 5 or less. An acid may be contained for the purpose of adjusting the aqueous dispersion to be acidic. Such acids include inorganic acids such as hydrochloric acid, sulfuric acid, nitric acid; organic acids such as acetic acid, oxalic acid, p-toluenesulfonic acid, and mixtures thereof. Inorganic acids and organic acids may be used alone or in combination of two or more. When the polar group of the block copolymer (Z) is an acidic group, it is preferable because the aqueous dispersion can be adjusted to acidic without containing the above-mentioned acid.

[Second step]
The second step is a step of removing the water from the mixture obtained in the first step and obtaining a polymer composition. Such a polymer composition is considered to form a structure in which the particulate block copolymer (Z) is dispersed in the polymer of the N-methylol compound (1).

  The method for removing water is not particularly limited, and known methods such as filtration, natural drying, heating, reduced pressure, and combinations thereof can be appropriately employed. When heating to remove water, the heating temperature is preferably 30 to 150 ° C, more preferably 60 to 120 ° C. When reducing the pressure to remove water, the pressure is preferably 1.3 to 13,000 Pa, and more preferably 13 to 1,300 Pa. The removal of water may be performed in the air or in an inert gas atmosphere such as nitrogen or argon. Further, water contained in the mixture obtained in the first step may be removed while the temperature is raised to the heating temperature in the third step. That is, the removal of water in the second step and the temperature increase for the third step may be performed simultaneously.

[Third step]
The third step is a step of obtaining the nitrogen-containing porous carbon of the present invention by heating the polymer composition obtained in the second step described above in the third step. In the third step, the particulate block copolymer (Z) dispersed in the polymer of the N-methylol compound (1) is removed to form pores, and the N-methylol compound (1) The polymer is converted to nitrogen-containing carbon, and nitrogen-containing porous carbon having pores can be produced.

  The polymer composition used in the third step is preferably pulverized in advance for the purpose of improving the dispersibility of the nitrogen-containing porous carbon when preparing the catalyst ink. The pulverization method is not particularly limited, and examples thereof include a ball mill, a bead mill, and freeze pulverization. Among these, a ball mill is preferable. Although there is no restriction | limiting in particular in the grade of a grinding | pulverization, It is preferable that the particle size of a polymer composition shall be 100 micrometers or less, and it is more preferable to set it as 50 micrometers or less.

  In the third step, heating may be performed in an inert gas atmosphere such as nitrogen or argon, or heating may be performed in a gas atmosphere such as carbon dioxide or water vapor. When heated in a gas atmosphere such as carbon dioxide or water vapor, the total specific surface area of the pores in the pore diameter range of 5 to 260 nm of the obtained nitrogen-containing porous carbon tends to be improved.

From the viewpoint that the content of carbon atoms in the obtained nitrogen-containing porous carbon is 80 mass% or more, and the atomic ratio (N / C) of nitrogen atoms to carbon atoms is in the range of 0.005 to 0.18, The heating temperature is preferably 1000 to 1400 ° C., more preferably 1000 to 1200 ° C. when heating in an inert gas atmosphere such as nitrogen, and preferably when heating in a gas atmosphere such as carbon dioxide and water vapor. It is 800-1400 degreeC, More preferably, it is 800-1200 degreeC. The time for holding at the heating temperature (heating time) is preferably 30 minutes to 12 hours.
On the other hand, from the viewpoint of setting the atomic ratio (H / C) of hydrogen atoms to carbon atoms in the obtained nitrogen-containing porous carbon to 0.1 or less, the heating temperature is an inert gas atmosphere such as nitrogen or argon. In the case of heating at a lower temperature, 1000 ° C. or higher is preferable, and the heating temperature for heating in a gas atmosphere such as carbon dioxide or water vapor is preferably 800 ° C. or higher.
As the heating temperature is increased, the carbon content of the obtained nitrogen-containing porous carbon is improved, and the atomic ratio of nitrogen atoms to carbon atoms (N / C) and the atomic ratio of hydrogen atoms to carbon atoms (H / C) ) Tends to decrease, so the heating temperature is appropriately adjusted according to the desired composition.

  The heating rate up to the heating temperature is preferably 1 to 50 ° C./min, more preferably 2 to 30 ° C./min. The productivity is improved by setting the heating rate to 1 ° C./min or more, and the uniformity of the pores of the nitrogen-containing porous carbon obtained by setting it to 50 ° C./min or less is improved.

  After the third step, the obtained nitrogen-containing porous carbon is usually cooled to room temperature. The cooling rate is preferably 1 to 50 ° C./min, and more preferably 5 to 30 ° C./min. Productivity improves by making a cooling rate into 1 degree-C / min or more. There is no restriction | limiting in particular in the cooling method, You may use a well-known cooling device or may cool naturally.

(catalyst)
The catalyst of the present invention comprises a catalyst metal supported on the nitrogen-containing porous carbon. Only one type of catalyst metal may be used, or two or more types may be used in combination. There is no particular limitation on the catalyst metal, and those usually used for catalysts (particularly, catalysts used for electrodes of solid polymer fuel cells) such as Pt, Pd, Ru, Os, Ir, Rh, Au, Fe, Ni, Cr, Mn, Co, Cu, Ti, Zn and V can be mentioned. Among these, Pt, Pd, Ru, Os, Ir and Rh, which are platinum group elements having high activity, are preferable, and Pt is more preferable.

  The catalyst metal preferably has a particle size of 1 to 10 nm, more preferably 2 to 8 nm. When the particle size of the catalyst metal is 1 nm or more, the durability of the catalyst is improved, and when it is 10 nm or less, the catalyst activity is enhanced. This particle diameter is calculated by measuring the X-ray diffraction of the catalyst and using the Serrer equation from the obtained diffraction peak.

  Moreover, it is preferable that it is 20-70 mass%, and, as for content of the catalyst metal in the catalyst of this invention, it is more preferable that it is 30-60 mass%. When the content is 20% by mass or more, the catalytic activity is increased, and when the content is 70% by mass or less, aggregation of the catalyst metal is suppressed.

  The method for supporting the catalyst metal on the nitrogen-containing porous carbon may be any of the conventionally known support methods. For example, after the catalyst metal precursor solution is immersed in the support, the catalyst metal precursor is A method of reducing or a method of immersing a catalytic metal colloid solution in a carrier is employed. For example, in order to obtain a catalyst in which platinum is supported on nitrogen-containing porous carbon, a dichloromethane solution of platinum (II) acetylacetonate is added to the nitrogen-containing porous carbon of the present invention, and the solvent is distilled off to remove nitrogen-containing porous carbon. It can be produced by a dipping method in which platinum (II) acetylacetonate is adsorbed on carbonaceous material, heated under an inert atmosphere, and reduced.

  Hereinafter, the present invention will be described in more detail using examples and comparative examples. The present invention is not limited to the following examples.

1. Characteristic evaluation of polymer used in production of nitrogen-containing porous carbon (1) Measurement of number average molecular weight (Mn) Mn of polymer used in production of nitrogen-containing porous carbon is measured according to the following measuring apparatus and conditions. did. In addition, Mn of the polymer was converted using a calibration curve of standard polystyrene.
GPC system: “HLC-8220GPC” manufactured by Tosoh Corporation
Column: TSK guard Column Super MP-M; TSK gel G3000H; and TSKgel Super Multipore HZ-M were connected in series in this order.
RI detector: HLC-8220GPC
Column oven temperature: 40 ° C
Eluent: Tetrahydrofuran Standard sample: Polystyrene

(2) Sulfonation of the block copolymer _{(Z 0)} the content of the block _{(S 0)} in, in a non-polar block (T) 1,4 bond content and hydrogenation ratio as well as block copolymer (Z) Measurement of rate ¹ H-NMR was measured by the following measuring apparatus and conditions, the content of block (S ₀ ) in the block copolymer (Z ₀ ), 1,4-bond in the nonpolar block (T) The amount and the hydrogenation rate, and the sulfonation rate of the block copolymer (Z) (the introduction rate of the sulfo group relative to the structural unit derived from the aromatic vinyl compound in the polar block (S)) were calculated.
¹ H-NMR system: JEOL JNM-ECX400
Solvent: Deuterated chloroform Reference peak: Tetramethylsilane

(3) Measurement of Sulfo Group Content The block copolymer (Z) was weighed (weighed value a (g)) and dissolved in 100 mass times tetrahydrofuran. An excessive amount of saturated aqueous sodium chloride solution ((300 to 500) × a (mL)) was added to the solution, and the mixture was stirred for 12 hours in a closed system. Using phenolphthalein as an indicator, hydrogen chloride generated in water was subjected to neutralization titration (titration b (mL)) with a 0.01 N standard aqueous sodium hydroxide solution (titer f). From the above results, the sulfo group content per 1 g of the block copolymer (Z) was calculated from the following formula.
Content of sulfo group per 1 g of block copolymer (Z) (mmol / g) = (0.01 × b × f) / a

(4) Amorphous Evaluation of Nonpolar Block (T) A toluene / 2-propanol (mass ratio 5/5) solution of a block copolymer (Z) (20% by mass) was prepared, and a release-treated PET film (Mitsubishi Resin “MRV”) is coated at a thickness of about 350 μm, dried in a hot air dryer at 100 ° C. for 4 minutes, and then peeled off from the release-treated PET film at 25 ° C. to a thickness of 30 μm. Film was obtained. The obtained film was -80 ° C. at a temperature rising rate of 3 ° C./min in a tensile mode (frequency: 11 Hz) using a wide-range dynamic viscoelasticity measuring device (“DVE-V4FT Rheospectr” manufactured by Rheology). The temperature was raised to 250 ° C., and the storage elastic modulus (E ′), loss elastic modulus (E ″) and loss tangent (tan δ) were measured. The amorphous nature of the nonpolar block (T) was evaluated from the presence or absence of a change in storage elastic modulus at 80 to 100 ° C. derived from the crystalline olefin polymer. As a result, in all the block copolymers (Z) obtained in the following production examples, there was no change in the storage elastic modulus, and those nonpolar blocks (T) were amorphous.

(5) Measurement of average dispersed particle size of block copolymer (Z) in aqueous dispersion In production example 3 using a particle size measuring device (Otsuka Electronics "FPAR-1000") by a dynamic light scattering method. The average dispersed particle size of the block copolymer (Z) in the aqueous dispersion of the produced block copolymer (Z) was measured. The measurement temperature was 26 ° C., the particle diameter was calculated using the Stokes-Einstein equation, and the average particle diameter was obtained by averaging the obtained particle diameters.

(6) Analysis of N-methylol compound (1) The number of hydroxymethyl groups (—CH ₂ OH) in the N-methylol compound (1) was measured by ¹ H-NMR according to the following measuring apparatus and conditions, Calculated.
¹ H-NMR system: JEOL JNM-ECM400
Solvent: Deuterated dimethyl sulfoxide Reference peak: Tetramethylsilane

2. Production of raw materials used in the production of nitrogen-containing porous carbon [Production Example 1: Production of block copolymer (Z ₀ ) -1]
Each raw material was sufficiently dehydrated in advance. After fully drying the pressure vessel equipped with a stirrer and replacing with nitrogen, 172 g of α-methylstyrene, 251 g of cyclohexane, 47.3 g of methylcyclohexane and 5.9 g of tetrahydrofuran were added with stirring, and then −10 The mixture was cooled to 0 ° C., and 16.8 mL of a sec-butyllithium (1.3 M) cyclohexane solution was added, and stirring was continued for 5 hours to carry out a polymerization reaction. At this time, when the Mn of the polymer (poly (α-methylstyrene)) was confirmed by sampling the polymerization solution, it was 7,100. Next, 35.4 g of butadiene was added, and after stirring for 30 minutes, 1,680 g of cyclohexane was added. From the difference between the Mn of the polymer (poly (α-methylstyrene) -polybutadiene type diblock copolymer) confirmed by sampling the polymerization solution and the Mn of the poly (α-methylstyrene) described above, The Mn was 3,350. Next, 310 g of butadiene was added to the polymerization solution over 1 hour. At the same time as the start of the addition of butadiene, the temperature was raised, and after raising the temperature to 60 ° C. over 30 minutes, the temperature was maintained at 60 ° C. for 30 minutes. After completion of the butadiene addition, polymerization was further performed at 60 ° C. for 1 hour. Thereafter, 21.8 mL of α, α′-dichloro-p-xylene (0.5 M, toluene solution) was added to the polymerization solution, and the mixture was stirred at 60 ° C. for 1 hour to perform a coupling reaction. An α-methylstyrene) -polybutadiene-poly (α-methylstyrene) type triblock copolymer (referred to as “mSEBmS”) was synthesized. The obtained mSEBmS has a Mn of 79,500, the 1,4-bond content in the nonpolar block (T) is 44.0%, and the content of the block (S ₀ ) (that is, α-methylstyrene unit) Content) was 31% by mass.
Next, a cyclohexane solution of mSEBmS was prepared and charged into a pressure-resistant vessel that had been sufficiently purged with nitrogen. Then, a hydrogenation reaction was performed at 80 ° C. for 5 hours in a hydrogen atmosphere using a Ni / Al Ziegler catalyst. Thus, a poly (α-methylstyrene) -hydrogenated polybutadiene-poly (α-methylstyrene) type triblock copolymer (referred to as “block copolymer (Z ₀ ) -1”) was obtained. The resulting block copolymer (Z ₀ ) -1 had a hydrogenation rate of 99.6 mol%, Mn of 79,600, and each poly (α-methylstyrene) block had a Mn of 7, 100, and Mn of the hydrogenated polybutadiene block was 65,400.

[Production Example 2: Production of block copolymer (Z) -1]
100 g of the block copolymer (Z ₀ ) -1 obtained in Production Example 1 was dried in a glass reaction vessel equipped with a stirrer at 40 ° C. and 50 Pa for 6 hours, and then purged with nitrogen. Methylene was added and dissolved by stirring at 35 ° C. for 2 hours. After dissolution, a sulfonating agent obtained by reacting 21.0 mL of acetic anhydride and 9.34 mL of sulfuric acid at 0 ° C. in 41.8 mL of methylene chloride was gradually added dropwise over 20 minutes. After stirring at 25 ° C. for 7 hours, the polymer solution was poured into 2 L of distilled water while stirring to coagulate and precipitate the polymer. The precipitated polymer was washed with distilled water at 90 ° C. for 30 minutes and then filtered. This washing and filtration operation is repeated until there is no change in the pH of the washing water, and the polymer collected by filtration at the end is dried at 20 ° C. and 50 Pa for 12 hours to give a sulfonated product (“block copolymer (Z) -1”). Called). The resulting block copolymer (Z) -1 had a sulfonation rate of 50 mol% and a sulfo group content of 1.06 mmol / g.

[Production Example 3: Production of aqueous dispersion of block copolymer (Z) -1]
30 g of the block copolymer (Z) -1 synthesized in Production Example 2 was dissolved in 270 g of a tetrahydrofuran / 2-methylpropanol mixed solvent (mass ratio 50/50), and the block copolymer (Z) -1 (containing) A 10% by weight) solution was prepared. After adding 300 g of methanol to this solution and adding 600 g of water, the organic solvent was removed with an evaporator. Further, 100 g of water was added and then concentrated again with an evaporator to obtain an aqueous dispersion. The solid content of the aqueous dispersion measured by the method described above was 11.8% by mass. Further, the average dispersed particle size of the block copolymer (Z) -1 in the aqueous dispersion was 32 nm.

[Production Example 4: Production of aqueous methylolmelamine solution]
A 100 mL three-necked flask equipped with a reflux tube and containing a magnetic stirrer was charged with 10 g of formaldehyde aqueous solution (manufactured by Wako Pure Chemical Industries, formaldehyde concentration 37% by mass, formaldehyde amount 3.7 g) and 5 g of 1M ammonia water (Kanto Chemical). And mixed with stirring at room temperature. To the obtained mixture, 8.0 g of melamine (made by Wako Pure Chemical Industries, special grade) was added all at once at room temperature, and then the temperature was raised from room temperature to 80 ° C. over 5 minutes while stirring the mixture in the atmosphere. The mixture was further stirred at 80 ° C. for 40 minutes. With the progress of the N-methylolation reaction, the solid melamine dispersed at the beginning of the addition disappeared, and 23.0 g of a uniform methylolmelamine aqueous solution was obtained.
1 g was collected from the obtained methylolmelamine aqueous solution and dried at 100 ° C. for 60 minutes to obtain 500 mg of a solid. The obtained solid is an average of 2 methylol melamines per molecule from ¹ H-NMR spectrum (that is, methylol melamine having ₂ hydroxymethyl groups (—CH ₂ OH) on average). It was confirmed. In the ¹ H-NMR spectrum, no peak derived from another compound was observed. From this result, the said methylol melamine content in the obtained methylol melamine aqueous solution was determined to be 50 mass%.

3. Production of nitrogen-containing porous carbon or ground ketjen black [Example 1]
A 100 mL three-necked flask equipped with a reflux tube and containing a magnetic stir bar was charged with 12.1 g of an aqueous dispersion of the block copolymer (Z) -1 obtained in Production Example 3 (block copolymer (Z)). −1: 1.43 g) was added, and the aqueous dispersion was heated to 80 ° C. in the atmosphere while stirring, and 4.7 g of methylol melamine aqueous solution obtained in Production Example 4 (methylol melamine: 2. 35 g containing) was added all at once to prepare an aqueous dispersion. The pH of the aqueous dispersion before polymerization was 7.8). The obtained aqueous dispersion was further stirred at 80 ° C. for 30 minutes to polymerize methylolmelamine to obtain a gel-like mixture (first step). The mixture was taken out from the three-necked flask onto a Teflon container and the magnetic stirrer was removed. Then, the temperature was raised to 100 ° C. in the atmosphere, and then the water was removed by heating at 100 ° C. for 1 hour to obtain a polymer composition. 3.4 g of product was obtained (second step). Subsequently, the polymer composition was pulverized at 400 rpm for 2 hours using 5 mmφ beads to obtain a polymer composition having a particle size of 20 μm. 1.0 g of the pulverized polymer composition was heated to 1000 ° C. at a heating rate of 2.7 ° C./min in a nitrogen atmosphere, heated at 1000 ° C. for 1 hour, and then cooled at 7 ° C./min. To 25 ° C. to obtain powdered nitrogen-containing porous carbon (third step). 3.5 g of ethanol was added to the obtained nitrogen-containing porous carbon, and pulverization was performed for 2 hours at 400 rpm using beads of 2 mmφ. The solvent was distilled off by heating at 100 ° C. for 1 hour to obtain 106 mg of nitrogen-containing porous carbon (hereinafter referred to as “support (1)”). The maximum intensity of the pore distribution curve of the carrier (1) was more than twice the height of all the other peaks, and the half width of the maximum peak was 9 nm.

[Example 2]
1.0 g of a polymer composition produced and pulverized in the same manner as in Example 1 was heated to 1000 ° C. at a heating rate of 2.7 ° C./min in a nitrogen atmosphere and heated at 1000 ° C. for 1 hour. Then, it cooled to 25 degreeC with the cooling rate of 7 degreeC / min, and obtained powder (3rd process (1st time)). 3.5 g of ethanol was added to the obtained powder, and 2 mmφ beads were used for grinding for 2 hours at 400 rpm. Then, the solvent was distilled off by heating at 100 ° C. for 1 hour. Next, the temperature was raised to 1200 ° C. at a rate of 10 ° C./min in a nitrogen atmosphere, heated at 1200 ° C. for 1 hour, then cooled to 25 ° C. at a rate of 7 ° C./min, and the nitrogen-containing porous material 85 mg of carbon (hereinafter referred to as “support (2)”) was obtained (third step (second time)). The maximum intensity of the pore distribution curve of the carrier (2) was more than twice the height of all the other peaks, and the half width of the maximum peak was 10 nm.

[Example 3]
The nitrogen-containing porous carbon (hereinafter referred to as “Example 3”) except that the heating temperature in the third step (first time) was changed from 1000 ° C. to 800 ° C. and the heating atmosphere was changed from a nitrogen atmosphere to a carbon dioxide atmosphere. 51 mg) (referred to as “carrier (3)”) was obtained. The maximum intensity of the pore distribution curve of the carrier (3) was at least 1.4 times the height of all other peaks, and the half width of the maximum peak was 13 nm.

[Comparative Example 1]
24.6 g of 0.1M hydrochloric acid (manufactured by Wako Pure Chemical Industries, Ltd.) was added to a 100 mL three-necked flask equipped with a reflux tube and a magnetic stir bar, and the temperature was raised to 80 ° C. in the atmosphere while stirring. Thereto, 9.3 g of the methylolmelamine aqueous solution obtained in Production Example 4 was added all at once, and the mixture was stirred for 50 minutes to synthesize a melamine resin. The melamine resin was taken out from the three-necked flask onto a Teflon container and the magnetic stirrer was removed. Then, the temperature was raised to 100 ° C. in the atmosphere, and the water was removed by heating for 1 hour to obtain 3.9 g of melamine resin. It was. Next, the melamine resin was pulverized at 400 rpm for 2 hours using 5 mmφ beads. 1.5 g of pulverized melamine resin was heated to 1000 ° C. at a heating rate of 2.7 ° C./min in a nitrogen atmosphere, heated at 1000 ° C. for 1 hour, and then cooled at a cooling rate of 7 ° C./min. After cooling to 0 ° C., nitrogen-containing porous carbon was obtained. 3.5 g of ethanol was added to the obtained nitrogen-containing porous carbon, and pulverization was performed for 14 hours at 400 rpm using beads of 2 mmφ. The solvent was distilled off by heating at 100 ° C. for 1 hour to obtain 142 mg of nitrogen-containing porous carbon (hereinafter referred to as “support (4)”).

[Comparative Example 2]
After 2.1 g of pulverized melamine resin obtained in the same manner as in Comparative Example 1 was heated to 1000 ° C. at a heating rate of 2.7 ° C./min in a nitrogen atmosphere and heated at 1000 ° C. for 1 hour. And cooled to 25 ° C. at a cooling rate of 7 ° C./min to obtain a powder. 3.5 g of ethanol was added to the obtained powder, and pulverization was performed at 400 rpm for 14 hours using 2 mmφ beads, and then the solvent was distilled off by heating at 100 ° C. for 1 hour. Next, the temperature was raised to 1200 ° C. at a rate of 10 ° C./min in a nitrogen atmosphere, heated at 1200 ° C. for 1 hour, then cooled to 25 ° C. at a rate of 7 ° C./min, and the nitrogen-containing porous material 109 mg of carbon (hereinafter referred to as “support (5)”) was obtained.

[Comparative Example 3]
125 mg of nitrogen-containing porous carbon (hereinafter referred to as “support (6)”) was obtained in the same manner as in Example 1 except that the heating temperature in the third step was changed from 1000 ° C. to 800 ° C.

[Comparative Example 4]
Ketjen black ("EC300") purchased from Lion Corporation was pulverized in a mortar to obtain pulverized ketjen black (hereinafter referred to as "carrier (7)").

4). Characteristic Evaluation of Carrier (1) Measurement of pore diameter at maximum peak of specific surface area, pore volume and pore distribution curve Carriers (1) to carrier (7) obtained in Examples 1 to 3 and Comparative Examples 1 to 4 Was dried at 100 ° C. for 6 hours at 1 Pa. Subsequently, the nitrogen adsorption and desorption isotherm of the carrier (1) to the carrier (7) after the drying treatment was measured using an automatic specific surface area / pore distribution measuring device (“BELSORP-miniII” manufactured by Nippon Bell). A pore distribution curve is prepared from the obtained nitrogen adsorption isotherm using the BJH method, and pores in the pore diameter range of 5 to 260 nm of the carrier (1) to the carrier (7) after the drying treatment are prepared. The pore diameter at the maximum peak of the total specific surface area, pore volume and pore distribution curve was calculated. The results are shown in Table 1.

(2) Elemental analysis CHN elemental analysis of the carriers (1) to (7) obtained in Examples 1 to 3 and Comparative Examples 1 to 4 was performed using an elemental analyzer ("2400II type" manufactured by Perkin Elmer). The content of carbon atoms, hydrogen atoms, and nitrogen atoms, the atomic ratio of nitrogen atoms to carbon atoms (N / C), and the atomic ratio of hydrogen atoms to carbon atoms (H / C) were calculated. The results are shown in Table 1.

As shown in Table 1, the carriers (1), (2), (3), (6) and (7) have a total specific surface area of 100 m ² / g of pores having a pore diameter in the range of 5 to 260 nm. That was all.

  In the pore distribution curves of the carriers (1), (2), (3) and (6), a sharp maximum peak is observed in the vicinity of 14 to 19 nm, and the uniformity of the pore distribution is high. confirmed. A pore distribution curve of nitrogen-containing porous carbon of the support (1) is shown in FIG. 1, and a scanning electron micrograph is shown in FIG. From this scanning electron micrograph, it was confirmed that the carrier (1) which is the nitrogen-containing porous carbon of the present invention has a large number of pores.

  As shown in Table 1, the content of carbon atoms in the carriers (1), (2), (3), (4), (5) and (7) was 80% by mass or more. ) Content of carbon atoms was less than 80% by mass. As the reason, in Comparative Example 3, since the heating temperature in the third step was as low as 800 ° C. in a nitrogen atmosphere, it is assumed that the progress of carbonization was insufficient. As the heating temperature increases, the proportion of nitrogen atoms introduced into the carbon skeleton tends to decrease, but the carriers (1), (2) and (3) contain 2 to 7% by mass of nitrogen atoms. It was.

5). Catalyst production
[Example 4]
75.8 mg of the carrier (1) obtained in Example 1 was placed in a 100 mL eggplant flask, and 1.57 g of a 10 mass% methylene chloride solution of platinum (II) acetylacetonate (manufactured by Sigma Aldrich) was added thereto (platinum ( II) Acetylacetonate (corresponding to 157 mg) was added, and the mixture was then irradiated with ultrasound until it was dried and free of methylene chloride. The mixture obtained by drying is put into an alumina boat, heated to 210 ° C. at a heating rate of 1 ° C./min in a nitrogen atmosphere, heated at 210 ° C. for 3 hours, and then heated at 1 ° C./min. The temperature was raised to 240 ° C. at a rate, heated at 240 ° C. for 3 hours, and then cooled to 25 ° C. at a cooling rate of 5 ° C./min to obtain 138 mg of a catalyst. The thermogravimetric measurement of the catalyst was performed in the atmosphere, and the platinum content in the catalyst was 39.3% by mass. Further, the X-ray diffraction of the catalyst was measured, and the particle size of platinum was calculated from the (111) diffraction peak of the obtained platinum using the Serrer equation.

[Example 5]
156 mg of catalyst was obtained in the same manner as in Example 4 except that the carrier (2) obtained in Example 2 was used. The thermogravimetric measurement of the catalyst was performed in the atmosphere, and the platinum content in the catalyst was 39.2% by mass. Further, the X-ray diffraction of the catalyst was measured, and the particle diameter of platinum was calculated from the (111) diffraction peak of the obtained platinum using the Serrer equation.

[Example 6]
135 mg of catalyst was obtained in the same manner as in Example 4 except that the carrier (3) obtained in Example 3 was used. The thermogravimetric measurement of the catalyst was performed in the atmosphere, and the platinum content in the catalyst was 38.3 mass%. Further, the X-ray diffraction of the catalyst was measured, and the particle diameter of platinum was calculated from the (111) diffraction peak of the obtained platinum using the Serrer equation.

[Comparative Example 5]
123 mg of catalyst was obtained in the same manner as in Example 4 except that the carrier (4) obtained in Comparative Example 1 was used. The thermogravimetric measurement of the catalyst was performed in the atmosphere, and the platinum content in the catalyst was 35.6% by mass. Further, the X-ray diffraction of the catalyst was measured, and the particle diameter of platinum was calculated from the (111) diffraction peak of the obtained platinum using the Serrer equation.

[Comparative Example 6]
116 mg of catalyst was obtained in the same manner as in Example 4 except that the carrier (5) obtained in Comparative Example 2 was used. The thermogravimetric measurement of the catalyst was performed in the atmosphere, and the platinum content in the catalyst was 33.0% by mass. Further, the X-ray diffraction of the catalyst was measured, and the particle size of platinum was calculated from the (111) diffraction peak of the obtained platinum using the Serrer equation.

[Comparative Example 7]
131 mg of catalyst was obtained in the same manner as in Example 4 except that the carrier (6) obtained in Comparative Example 3 was used. The thermogravimetric measurement of the catalyst was performed in the atmosphere, and the platinum content in the catalyst was 38.5% by mass. Further, the X-ray diffraction of the catalyst was measured, and the particle size of platinum was calculated from the (111) diffraction peak of the obtained platinum using the Serrer equation.

[Comparative Example 8]
149 mg of catalyst was obtained in the same manner as in Example 4 except that the carrier (7) obtained in Comparative Example 4 was used. The thermogravimetric measurement of the catalyst was performed in the atmosphere, and the platinum content in the catalyst was 42.3 mass%. Further, the X-ray diffraction of the catalyst was measured, and the particle size of platinum was calculated from the (111) diffraction peak of the obtained platinum using the Serrer equation, and found to be 2.0 nm.

6). Evaluation of catalyst characteristics Evaluation of catalyst activity and catalyst durability was conducted according to the method proposed by the Council for Promotion of Practical Use of Fuel Cells (Proposal of Solid Polymer Polymer Fuel Cell Targets, R & D Issues, and Evaluation Methods) January 2011 Fuel Cell Commercialization Promotion Council).

(1) Evaluation of catalyst activity (i) Manufacture of catalyst ink A mixture of 1.17 g of 2-propanol (manufactured by Wako Pure Chemical Industries, Ltd.) and 4.75 g of ultrapure water was mixed with 5.56 mg of catalyst to obtain a polymer electrolyte. Then, 30 μL of Nafion dispersion solution (DE520CS type, Nafion concentration: 5% by mass, manufactured by Wako Pure Chemical Industries, Ltd.) was added, followed by ultrasonic treatment (UH-600, manufactured by SMT Co., Ltd.) for 30 minutes to produce a catalyst ink.

(Ii) Manufacture of electrode The catalyst ink is made into a disc-like (diameter 6 mm) glassy carbon (manufactured by Nisatsu Gakko) buffed with 0.05 μm alumina powder so that the platinum content becomes 16 μg / cm ^2. The electrode was manufactured by applying and drying at 60 ° C. under a humidity control condition of 85% RH for 1 hour and then drying at 100 ° C. for 1 hour.

(Iii) Measurement of catalytic activity The catalytic activity was evaluated by the rotating disk electrode method (RDE) using a standard three-electrode electrochemical cell. Specifically, using the above electrode, platinum (manufactured by Nisshin Kogyo) as a counter electrode, and a double junction silver / silver chloride reference electrode (manufactured by ECO CHEMIE) as a reference electrode, a potentiostat (IVIUM) in 0.1 M perchloric acid solution. The catalytic activity was evaluated by COMPACTSTAT (TECHNOLOGIES). The electrodes were scanned in advance for 50 cycles at 25 ° C. in a nitrogen atmosphere at a sweep rate of 50 mV / sec, 0.05 V to 1.2 V (vs RHE). After this pretreatment, linear scanning voltammetry was performed in an oxygen atmosphere at a sweep rate of 10 mV / sec, 0.17 V to 1.21 V (vsRHE, forward sweep), and rotation speeds of 400, 900, 1600, 2500 rpm. Each current value was measured while changing. For correction of oxygen diffusion, a Koutecky-Levic plot was used, and the current value per 1 g of platinum at 0.9 V was determined as the catalyst activity (mass activity). The results are shown in Table 2.

  As shown in Table 2, the catalysts of Examples 4 to 6 and Comparative Example 8 have high catalytic activity (mass activity). In addition, as shown in Tables 1 and 2, when the total specific surface area of the pores in the range of 5 to 260 nm of the nitrogen-containing porous carbon that is the support is increased, a tendency to improve the catalytic activity (mass activity) was confirmed. . On the other hand, the catalysts of Comparative Examples 5 to 7 were inferior in catalytic activity. The reason why the catalytic activities of Comparative Examples 5 and 6 are low is presumed to be that the total specific surface area of the pores in the range of 5 to 260 nm of the nitrogen-containing porous carbon that is the support is small. The reason why the catalytic activity of Comparative Example 7 is low is presumed to be due to the low carbon atom content of the nitrogen-containing porous carbon that is the carrier and the low conductivity.

(2) Evaluation of catalyst durability Evaluation of catalyst durability was performed using a standard three-electrode electrochemical cell. Specifically, an electrode manufactured by the method of (1) above from the catalyst of Example 5 and Comparative Example 8, a platinum electrode (manufactured by Nisatsu Kogyo) as a counter electrode, and a double junction silver / silver chloride reference electrode (manufactured by ECO CHEMIE) as a reference electrode The catalyst durability was evaluated with a potentiostat (COMPACTSTAT manufactured by IVIUM TECHNOLOGIES) in a 0.1 M perchloric acid solution.

The electrodes were scanned in advance for 50 cycles at 25 ° C. in a nitrogen atmosphere at a sweep rate of 50 mV / sec, 0.05 V to 1.2 V (vs RHE). After performing this pretreatment, 3 cycles of cyclic voltammetry were performed under conditions of a sweep rate of 50 mV / sec, 0.05 V to 1.2 V (vs RHE), and a nitrogen atmosphere at 25 ° C. The electrochemical effective surface area (ECSA) of platinum was calculated from the hydrogen adsorption wave.
Thereafter, the ECSA at the 40000th cycle was calculated in the same manner as described above, in which a potential cycle of 0.6V for 3 seconds and 1V for 3 seconds was repeated for a total of 40000 cycles.
From the ECSA at the third cycle and the ECSA at the 40,000 cycle, an ECSA maintenance ratio (%) (= 100 × 40000 cycle ECSA / third cycle ECSA) was calculated as an index of catalyst durability.

  The ECSA maintenance rate of the electrode obtained from the catalyst of Example 5 (support (2): nitrogen-containing porous carbon) was 59%, and was obtained from the catalyst of Comparative Example 8 (support (7): Ketjen Black). The ECSA maintenance rate of the electrode was 49%. The reason why the durability (ECSA maintenance rate) of the catalyst of Example 5 is high is presumed to be that the nitrogen atoms strengthened the adsorption of platinum to the nitrogen-containing porous carbon and suppressed its aggregation.

  As described above, when the nitrogen-containing porous carbon of the present invention is used as a carrier for the catalyst contained in the electrode, both high catalytic activity and long life can be achieved.

  The nitrogen-containing porous carbon of the present invention is useful as a support for a catalyst (particularly, a catalyst used for an electrode of a polymer electrolyte fuel cell).

Claims (4)

The total specific surface area of the pores in the pore diameter range of 5 to 260 nm is 100 m ² / g or more, the carbon atom content is 80 mass% or more, and the atomic ratio of nitrogen atoms to carbon atoms (N / C ) Is 0.005 to 0.18 nitrogen-containing porous carbon.   The nitrogen-containing porous carbon according to claim 1, wherein the atomic ratio (H / C) of hydrogen atoms to carbon atoms is 0.1 or less.   A catalyst comprising a catalyst metal supported on the nitrogen-containing porous carbon according to claim 1.   The catalyst according to claim 3, wherein the catalyst metal is a platinum group element.