JP2023084553A - Method for producing templated carbon material, method for producing catalyst, method for producing catalyst layer for polymer electrolyte fuel cell, and method for producing fuel cell - Google Patents

Abstract

To provide a method for producing templated carbon material with high carbon yields and good yields, a method for producing a catalyst using the same, a method for producing a catalyst layer for a polymer electrolyte fuel cell, and a method for producing a fuel cell.SOLUTION: The present invention provides a method for producing templated carbon material using a carbon source satisfying the following requirement (A) and a template source satisfying the following requirement (B). The (A) carbon source comprises an aromatic compound that comprises two or more oxygen-containing functional groups and/or two or more nitrogen-containing functional groups, wherein, in a thermogravimetric analysis in an inert atmosphere, it reaches a 5 mass% loss at a temperature T0.05 of 200°C or lower. The (B) template source is at least one selected from oxide, carbonate, sulfate, and hydroxide of magnesium, alkaline-earth metal and aluminum.SELECTED DRAWING: None

Description

The present disclosure relates to a method for producing a template carbon material, a method for producing a catalyst, a method for producing a catalyst layer for a polymer electrolyte fuel cell, and a method for producing a fuel cell.

A template carbon material is a carbon material whose shape is characterized by inverting the shape of a template by coating the surface of a template compound with carbon and then removing template components.
A method for producing a template carbon material includes, for example, using a general-purpose resin typified by polyvinyl alcohol as a carbon source, using an alkaline earth metal compound typified by magnesium oxide as a template source, thoroughly mixing each of them, and producing a non-oxidizing It is a process of carbonizing the carbon source and removing the template source by some method such as dissolving and removing the template source with an acid after heat treatment at 600° C. to 1500° C. in an atmosphere.
Since magnesium oxide and calcium oxide can be easily dissolved in hydrochloric acid, sulfuric acid, etc., template carbon materials using these compounds as template sources are often studied.

In addition, in the process of carbon coating, heat treatment is usually performed at a temperature of 600 ° C. or higher and 1500 ° C., so compounds that chemically change to magnesium oxide or calcium oxide in the heat treatment process (for example, carbonates, hydroxides, etc.) , sulfates, etc.) can also be used as a template source.

The temperature of the heat treatment for carbon coating is selected according to the purpose. For example, 600° C. to 900° C. is selected if a highly amorphous porous carbon material containing a large amount of functional groups is to be prepared. If a porous carbon material with high crystallinity is to be obtained, it is prepared above 1000°C.
However, it is necessary to avoid high-temperature treatment that involves formation of carbides such as calcium carbide or metal acetylides. In practice, the limit of the heat treatment temperature for carbon coating is about 1800.degree.

A template carbon material is classified as one of porous carbon materials corresponding to porous carbon materials (activated carbon, etc.) produced by a so-called activation method.
Structural characteristics of the template carbon material are that the porous carbon material produced by the activation method grows pores from the outside to the inside due to oxidative consumption, whereas the outermost surface of the template carbon material is affected by the manufacturing method, etc. However, the pore structure inside the material is in principle homogeneous, and the pores are generally isotropically connected. This is particularly the structural feature of the template carbon material, which is contrasted with the pore structure of the porous carbon material produced by the activation method.

A template carbon material having isotropic pore connections is sometimes referred to as a communicating pore in the field of polymer electrolyte fuel cells, and has good gas flowability (fast diffusion) inside the material. , is believed to improve power generation performance when used as a catalyst carrier, and is considered a promising material.
Further, in the template carbon material, in principle, the pores are obtained by copying the template and reversing the template, so it is possible to obtain a highly uniform pore structure in the range of several tens of nanometers from micropores. This is in contrast to the fact that the pores formed by the activation method must be widely distributed from micropores to mesopores.

Since the thickness of the carbon layer in the template carbon material can be freely controlled by changing the mixing ratio of the template source and the carbon source, the degree of freedom of the specific surface area per mass is high.

Since the template carbon material is a porous carbon material, it can be used in fields where carbon materials called activated carbon are applied (e.g., selective adsorption of specific gases, selection of molecules with specific structures in the liquid phase, etc.). It is applied to the field of adsorbents such as organic adsorption), the field of solid polymer type fuel cell catalyst carriers to which Ketjenblack is applied, the field of supercapacitor electrodes, and the like.
A field that seems to be peculiar to template carbon materials is how to utilize the high diffusivity inside the material by utilizing the connection of isotropic pores.

For example, with a porous carbon material consisting of only micropores with zeolite as a template, by selecting the type of template and optimizing the conditions for carbon coating in the pores by CVD using propylene gas as a raw material, porous It has been reported that the surface area of quality carbon reaches an astounding 4000 m ² /g. (Non-Patent Document 1)
The pore diameter is 0.00, which is the atomic level. Since it is on the order of several nanometers, the covering carbon wall is formed by a monoatomic layer and by pore walls containing 5-membered rings, 7-membered rings, etc. in order to maintain the curvature.
Therefore, as described above, the pore volume and pore surface area per mass are large, but on the other hand, the carbon structure with curvature tends to be inferior to the aromatic structure in terms of mechanical strength and chemical stability.

On the other hand, magnesium citrate is heat-treated at 900°C for 1 hour in a nitrogen atmosphere, the resulting MgO powder and polyvinyl alcohol powder are mixed, and then treated at 900°C for 1 hour in a nitrogen atmosphere. A manufacturing method is also known (Non-Patent Document 2).

There is also known a method for producing activated carbon, which is characterized by using an organic acid Mg having a C number of 6 or more as a raw material, heating it to 300° C. or more in an inert atmosphere, and then cooling and acid washing ( Patent document 1). In this method for producing activated carbon, citric acid and polyvinyl alcohol (PVA) are used as carbon sources.

Alternatively, the organic resin is mixed with at least one alkaline earth metal compound selected from the group consisting of alkaline earth metal oxides, hydroxides, carbonates and organic acid salts, and heated in a non-oxidizing atmosphere. There is also known a method for producing activated carbon that includes a calcination step, in which the pore size of the activated carbon is adjusted by the crystallite size of the alkaline earth metal oxide produced after calcination ( Patent document 2). In this method for producing activated carbon, resin materials such as polyvinyl alcohol (PVA), polyethylene terephthalate (PET), and hydroxypropyl cellulose (HPC) are used as carbon sources.

In addition, a method for producing a porous carbon material is also known in which alumina nanoparticles (crystallite size is 10 nm on average, commercially available product) are subjected to a thermal CVD treatment using methane as a carbon source gas (Patent Document 3). In this method for producing a porous carbon material, by sufficiently optimizing experimental conditions such as heat treatment temperature, gas concentration, and treatment time, alumina nanoparticles coated with a carbon film with a carbon layer controlled to two layers or less are produced. After obtaining, alumina is dissolved in a hydrofluoric acid solution, diluted with distilled water, filtered, dispersed again with distilled water, filtered, and the powder is vacuum-dried to obtain porous carbon. It has gained.

Furthermore, a method for producing a template carbon material using an alkaline earth metal salt of benzenedicarboxylic acid as a template source is known (Patent Document 4). This template carbon production method is a method for obtaining a template carbon material having mesopores and having high oxidation resistance and electrical conductivity.

JP 2008-013394 A Patent No. 4955952 JP 2015-164889 A Japanese Patent Application Laid-Open No. 2021-034128

Formation of new type of porous carbon by carbonization in zeolite nanochannels, Chemistry of materials, 2, 609-615(1997) A review of the controle of pore structure in MgO-templated nanoporous carbons, Carbon, 48, 2690-2707(2010))

In the above example, for example, in the carbon material using zeolite as a template, the zeolite used as a template itself has a molecular sieve function, that is, the pore diameter is on the order of several Å. However, since one atomic layer itself is 1 nm or less, there is no choice but to use a synthesis method using a vapor phase method such as CVD (Chemical Vapor Deposition). In that case, the material is unsuitable for mass production on an industrial scale.
On the other hand, the method for producing a template carbon material using MgO or the like as a template source as exemplified in Patent Documents 1 to 3 is a simple production method, so it is suitable for industrial materials in terms of production process and production scale. However, as a result of intensive studies by the present inventors, there is a problem that the yield of carbon constituting the template carbon remains at most 10% or more with respect to the weight of the resin used as the carbon source.

Here, in general, activated porous carbon materials such as activated carbon and Ketjenblack have their pore volume and specific surface area significantly reduced by heat treatment in a non-oxidizing atmosphere at 1500° C. or higher. . In order to ensure the chemical stability of carbon materials and control the strength, heat treatment in a non-oxidizing atmosphere is a common processing method. . From this point of view, the template carbon material is a preferable material.

Therefore, at present, there is a demand for a method for producing a template carbon material with a high carbon yield and a good yield.
In addition, in the method for producing a template carbon material exemplified in Patent Document 4, it is described that a template carbon material having excellent oxidation resistance is obtained, but the pore structure can be freely controlled, and , the fact that a template carbon material with a high carbon yield and a good yield is obtained is not described. In particular, in order to improve both the carbon yield and the resistance to oxidation consumption, it is necessary to increase the average thickness of the carbon walls that form the pores, that is, to increase the number of layers of the aromatic network planes of carbon. It is as important as or more important than raising kinship. Since the complex-based raw material described in Patent Document 4 cannot increase the number of carbon atoms with respect to the metal atom, it has a theoretical problem in improving carbon yield and oxidation resistance.

Accordingly, an object of the present invention is to provide a method for producing a template carbon material with a high carbon yield and a good yield, a method for producing a catalyst, a method for producing a catalyst layer for a polymer electrolyte fuel cell, and a fuel cell using the same. is to provide a manufacturing method of

Means for solving the problems include the following aspects.
<1>
A method for producing a template carbon material using, as raw materials, a carbon source satisfying the following requirement (A) and a template source satisfying the following requirement (B).
(A) The temperature T at which the carbon source has at least one of two or more oxygen-containing functional groups and two or more nitrogen-containing functional groups and reaches a weight loss of 5% by mass in thermogravimetric analysis under an inert atmosphere. _0.05 includes aromatics below 200°C.
(B) The template source is at least one selected from oxides, carbonates, sulfates and hydroxides of magnesium, alkaline earth metals and aluminum.
<2>
In the carbon source, the aromatic compound is a compound in which two or more carbon atoms are interposed between at least two oxygen-containing functional groups among the two or more oxygen-containing functional groups <1> The method for producing the template carbon material according to .
<3>
In the carbon source, the aromatic compound is at least one selected from monocyclic aromatic compounds and bicyclic aromatic compounds, the oxygen-containing functional group is a carboxyl group, and the nitrogen-containing functional group is The method for producing a template carbon material according to <1> or <2>, which is an amino group.
<4>
The method for producing a template carbon material according to <3>, wherein the bicyclic aromatic compound is a compound having a naphthalene skeleton.
<5>
<1> or <2>, wherein in the carbon source, the aromatic compound is an aromatic compound having three or more rings, the oxygen-containing functional group is a carboxyl group or a hydroxyl group, and the nitrogen-containing functional group is an amino group; A method for producing the described template carbon material.
<6>
The method for producing a template carbon material according to <5>, wherein the aromatic compound having a condensed ring structure of three or more rings is at least one selected from compounds having an anthraquinone skeleton and compounds having an anthracene skeleton.
<7>
The template carbon material according to any one of <1> to <6>, wherein the template source is at least one selected from oxides, carbonates, sulfates, and hydroxides of magnesium and calcium. manufacturing method.
<8>
The method for producing a template carbon material according to any one of <1> to <7>, wherein the template source is at least one selected from magnesium carbonate and magnesium sulfate.
<9>
A method for producing a catalyst, wherein the carbon material obtained by the method for producing a template carbon material according to any one of <1> to <8> is used as a carrier, and a catalyst component is supported on the surface of the carrier.
<10>
A method for producing a polymer electrolyte fuel cell catalyst layer using the catalyst obtained by the method for producing a catalyst according to <9>.
<11>
A method for producing a fuel cell using the catalyst layer obtained by the method for producing a polymer electrolyte fuel cell catalyst layer according to <10>.
<12>
The method for producing a fuel cell according to <11>, wherein the polymer electrolyte fuel cell catalyst layer is a cathode-side catalyst layer.

INDUSTRIAL APPLICABILITY According to the present invention, a method for producing a template carbon material with a high carbon yield and a good yield, a method for producing a catalyst, a method for producing a catalyst layer for polymer electrolyte fuel cells, and a fuel cell using the same can provide a method.

1 is a schematic diagram showing a schematic configuration of a fuel cell according to an embodiment; FIG.

The present invention will be described below.
In this specification, a numerical range represented by "-" means a range including the numerical values before and after "-" as lower and upper limits.
In the numerical ranges described stepwise, the upper limit value or lower limit value described in a certain numerical range may be replaced with the upper limit value or lower limit value of another numerical range described stepwise.
In numerical ranges, the upper limit or lower limit described in a certain numerical range may be replaced with the values shown in the examples.
The term "process" is included in this term not only as an independent process, but also as long as the intended purpose of the process is achieved even if it cannot be clearly distinguished from other processes.
A "combination of preferred aspects" is a more preferred aspect.

The method for producing a template carbon material of the present invention is a production method that uses, as raw materials, a carbon source that satisfies the following requirement (A) and a template source that satisfies the following requirement (B).
(A) The temperature T ₀ at which the carbon source has at least one of two or more oxygen-containing functional groups and two or more nitrogen functional groups and reaches a weight loss of 5% by mass in thermogravimetric analysis under an inert atmosphere. _.05 contains aromatics below 200°C.
(B) The template source is at least one selected from oxides, carbonates, sulfates and hydroxides of magnesium, alkaline earth metals and aluminum.

INDUSTRIAL APPLICABILITY The method for producing a template carbon material of the present invention is a method for producing a template carbon material with a high carbon yield and a good yield. The method for producing a template carbon material of the present invention was found from the following findings.

First, in a conventional method for producing a template carbon material, ceramics (MgO, CaO, alumina, etc.) are generally used as a template source and a resin as a carbon source. The carbon film formed on the surface of the ceramics by the gaseous component generated by the thermal decomposition of the resin is the reason for using the resin exclusively as a carbon source. I think that the. On the other hand, carbon coating on ceramics by thermal CVD using propylene gas is also well known as a general technique, and these two phenomena are essentially pyrolyzed gaseous small molecules It became an opportunity to think that it was fundamentally important.
Most resins used contain oxygen in their monomer structures, and a typical example is polyvinyl alcohol represented by the formula (--(CH ₂ --CHOH) _n --).
These resins are thermally decomposed simply by heat treatment above 600° C. in a non-oxidizing atmosphere, leaving no solids behind. However, when it coexists with ceramics such as MgO, CaO and alumina, the differentiated gaseous compounds are adsorbed on the ceramics and remain as a carbon film. This phenomenon has been considered to be a phenomenon peculiar to radical compounds because it has been regarded as similar to thermal CVD.

On the other hand, the present inventors investigated the mechanism at the atomic level of what kind of elementary process the material used as the carbon source undergoes to be carbonized and deposited on the surface of the template source. As a result, the following findings were obtained.
First, it is not necessary to decompose resin as a carbon source. By using a low-molecular-weight compound with multiple oxygen-containing functional groups or nitrogen-containing functional groups instead of resin, a much higher carbon yield than resin can be obtained. It is possible to obtain When at least one selected from oxides, carbonates, sulfates, and hydroxides of magnesium, alkaline earth metals, and aluminum is used as a template source, carbon yield is achieved by the mechanism described below. This is because the rate increases.

Oxygen-containing functional group or nitrogen-containing functional group in template source (template source is at least one selected from oxides, carbonates, sulfates, and hydroxides of magnesium, alkaline earth metals and aluminum) In contrast, it has a strong affinity for the template source. Therefore, when an aromatic compound having a molecular structure in which two or more oxygen-containing functional groups or nitrogen-containing functional groups having an affinity for the template source are present is used as the carbon source and heated in a non-oxidizing atmosphere with the template source, Higher carbon yield.
Although the elementary process of the carbon fixation reaction of the carbon source at the atomic level is not clear, at least two or more oxygen-containing functional groups in the molecular structure of the carbon source fix the carbon source to the surface of the template source, and heat is generated. It is presumed that the molecular structure between the two oxygen-containing functional groups is fixed when oxygen is released in the form of carbonic acid in the mechanical process. Similarly, with two or more nitrogen-containing functional groups, it is presumed that the molecular structure between the two nitrogen-containing functional groups is fixed when the nitrogen is released during the thermal process.

Even when a typical resin material such as polyvinyl alcohol represented by the formula (-(CH ₂ -CHOH) _n -) is used as the carbon source, a gaseous compound generated by thermal decomposition is always present in the structure. Since it contains oxygen atoms, only compounds containing multiple oxygen-containing functional groups or multiple nitrogen-containing functional groups have a high carbon yield, but it is speculated that the overall carbon yield is low because the probability is low. be done.

From the above findings, it was found that the method for producing a template carbon material of the present invention is a method for producing a template carbon material with a high carbon yield and a good yield.

The details of the method for producing the template carbon material of the present invention will be described below.

The method for producing a template carbon material of the present invention includes, for example, a mixing step of mixing a carbon source and a template source, a first heating step, a template source removing step, and a second heating step. Each step will be described in detail below.

(Mixing process)
In this step, the carbon source and the template source are mixed.

-Carbon source-
The carbon source has at least one of two or more oxygen-containing functional groups and two or more nitrogen-containing functional groups, and in thermogravimetric analysis under an inert atmosphere, the temperature T _0.05 at which a 5% weight loss is reached is At least aromatic compounds below 200°C are applied.

In the aromatic compound, the number of oxygen-containing functional groups and nitrogen functional groups is 2 or more, preferably 2 to 6, more preferably 2 to 6, from the viewpoint of improving the carbon yield.
A carboxyl group, a hydroxyl group, etc. are mentioned as an oxygen-containing functional group. An amino group etc. are mentioned as a nitrogen functional group.

In the aromatic compound, among the two or more oxygen-containing functional groups or nitrogen functional groups, the number of carbon atoms interposed between at least two oxygen-containing functional groups or nitrogen functional groups is determined from the viewpoint of improving the carbon yield. , preferably 2 or more, more preferably 2 or more and 5 or less, and preferably 2 or more and 4 or less.
Here, the number of carbon atoms interposed between two oxygen-containing functional groups or nitrogen functional groups does not include the carbon atoms of the oxygen-containing functional groups or nitrogen functional groups (e.g., the carbon atoms of the carboxyl group). It is the number of carbon atoms connected in a straight chain between each oxygen-containing functional group or nitrogen functional group. That is, when the carbon atom intervening between two oxygen-containing functional groups or nitrogen functional groups has a substituent (for example, an alkyl group, etc.), the carbon intervening between the two oxygen-containing functional groups or nitrogen functional groups The number of atoms does not include the number of carbon atoms in the substituents.
Also, the number of carbon atoms intervening between two oxygen-containing functional groups or nitrogen functional groups is the number of carbon atoms intervening between the nearest oxygen-containing functional groups or nitrogen functional groups.

The functional group in the aromatic compound strongly adsorbs to the template source magnesium, alkaline earth metal oxide, carbonate, sulfate, or hydroxide. The inorganic compound and the oxygen- or nitrogen-containing functional group are strongly bonded to each other, and function to suppress the disappearance of the decomposition product of the carbon source in the gas phase. Therefore, in the first place, it is assumed that the carbon source is thermally decomposed in the carbonization process. That is, the aromatic compound needs to satisfy the temperature T _0.05 at which the weight loss reaches 5% in the thermogravimetric analysis under an inert atmosphere at 200° C. or less.
In this regard, anthraquinone and phenanthrenequinone, for example, have two quinone-type oxygen-containing functional groups, but do not correspond to aromatic compounds having a temperature T _0.05 of 200° C. or less. This is because the quinone-type functional group has very high stability and does not thermally decompose in the carbonization process, but sublimes and the carbonization yield becomes substantially zero.
In the thermogravimetric analysis under an inert atmosphere, the method for measuring the temperature _T0.05 at which the weight loss of 5% by mass is reached is as described in Examples below.

Here, the aromatic compound includes monocyclic aromatic compounds and aromatic compounds with two or more rings (condensed polycyclic aromatic compounds with two or more rings, non-condensed polycyclic aromatic compounds with two or more rings). The report group compounds also include aromatic heterocyclic compounds.
Monocyclic aromatic compounds include compounds having a benzene skeleton, heterocyclic rings (compounds having a pyridine skeleton, compounds having a pyrimidine skeleton, compounds having a triazine skeleton, compounds having a pyrrole skeleton, compounds having a furan skeleton, compounds having a triazine skeleton, and the like).
A condensed polycyclic aromatic compound having two or more rings is a compound in which two or more aromatic rings are condensed, and includes a compound having a naphthalene skeleton, a compound having an anthracene skeleton, a compound having an anthraquinone skeleton, a compound having a phenanthrenequinone skeleton, compounds having a three-ring skeleton containing nitrogen (e.g., 1-azaphenanthrene, 4-azaphenanthrene, 9-azaphenanthrene, 1,10-phenanthroline, 9-azaanthracene, 9,10-diazaanthracene, etc.), pyrene skeleton , a compound having a perylene skeleton, a compound having a phenanthrene skeleton, a compound having a pentacene skeleton, a compound having a coronene skeleton, and the like.
A non-condensed polycyclic aromatic compound having two or more rings is a compound in which two or more aromatic rings are connected to each other directly or via a bridging member (aliphatic hydrocarbon group, nitrogen atom, sulfur atom, etc.), and has a biphenyl skeleton. , a compound having a terphenyl skeleton, a compound having a triphenylmethane skeleton, and the like.

The aromatic compound is at least one selected from monocyclic aromatic compounds and bicyclic aromatic compounds (preferably bicyclic condensed polycyclic aromatic compounds) from the viewpoint of improving the carbon yield. A compound in which the oxygen-containing functional group is a carboxyl group and the nitrogen-containing functional group is an amino group is preferred.
As the bicyclic aromatic compound, a bicyclic condensed polycyclic aromatic compound is preferable, and naphthalene is preferable.

From the viewpoint of improving the carbon yield, the aromatic compound is preferably an aromatic compound having three or more rings, the oxygen-containing functional group is a carboxyl group or a hydroxyl group, and the nitrogen-containing functional group is an amino group.
The aromatic compound having three or more rings is preferably a condensed polycyclic aromatic compound having three or more rings, and is preferably at least one selected from compounds having an anthraquinone skeleton and compounds having an anthracene skeleton.

Here, from the viewpoint of improving the carbon yield, the total oxygen number of all oxygen-containing functional groups in the aromatic compound is preferably 4 or more, and preferably 4 or more and 8 or less. Moreover, the total nitrogen number of all nitrogen-containing groups is preferably 2 or more, and preferably 2 or more and 4 or less.
Two or more carboxyl groups may form an anhydride. Two or more carboxyl groups may form an alkyl metal salt. That is, for example, an aromatic compound having one carboxylic anhydride group corresponds to an aromatic compound having two carboxyl groups.
Further, the amino group includes a primary amino group, a secondary amino group and a tertiary amino group. Secondary amino groups include —NR ¹ H (R ¹¹ is an alkyl group having 1 to 6 carbon atoms). Tertiary amino groups include -NR ² R ³ (R ² and R ³ are each independently an alkyl group having 1 to 6 carbon atoms). Among these, the amino group is preferably a primary amino group.

The number of carbon atoms in the aromatic compound is preferably 6 to 30, more preferably 6 to 24, even more preferably 10 to 20, from the viewpoint of improving the carbon yield.
Here, the number of carbon atoms in the aromatic compound is the number of carbon atoms including the carbon atoms of the oxygen-containing functional group and the nitrogen-containing functional group.

Among aromatic compounds, monocyclic or bicyclic aromatic compounds having two or more carboxyl groups include benzenedicarboxylic acid, naphthalenedicarboxylic acid, benzenetetracarboxylic anhydride, naphthalenetetracarboxylic anhydride, and the like. is mentioned. Also included are dicarboxylic acids of nitrogen-containing heterocyclic rings of benzene, dicarboxylic acids of nitrogen-containing heterocyclic rings of naphthalene, and anhydrides thereof.

Polycarboxylic acids such as phenanthrene, anthracene, pyrene, and coronene are exemplified as aromatic compounds having two or more carboxyl groups and having three or more rings. Nitrogen-containing heterocyclic rings of aromatic compounds having three or more rings are also included.

Examples of aromatic compounds having two or more hydroxyl groups and three or more rings include anthraquinone, phenanthrenequinone, dihydroxyanthraquinone, tetrahydroxyanthraquinone, and dihydroxyanthracene.

Examples of monocyclic or bicyclic aromatic compounds having two or more amino groups include diaminobenzene, diaminonaphthalene, diamines having a nitrogen-containing benzene ring, and diamines having a nitrogen-containing naphthalene ring.

Diaminoanthraquinone, diaminoanthracene, diaminophenanthrene, triaminoanthraquinone, etc. are mentioned as an aromatic compound with two or more amino groups and two or more rings.

As the carbon source, a resin may be used in combination with the above aromatic compound. However, the blending amount of the aromatic compound is, for example, 30% by mass or more (preferably 40% by mass or more) relative to the total carbon source.
Resins as carbon sources include well-known resins used as carbon sources, such as polyvinyl alcohol, polyethylene glycol, and polyacrylic acid.

-Mold source-
As the template source, at least one selected from oxides, carbonates, sulfates and hydroxides of magnesium, alkaline earth metals and aluminum is applied. Here, alkaline earth metals include calcium, barium, strontium, and the like.

Mg and alkaline earth metal oxides include magnesium oxide (MgO), calcium oxide, barium oxide, strontium oxide, and the like.
Mg and alkaline earth metal carbonates include magnesium carbonate, calcium carbonate, barium carbonate, strontium carbonate, and the like.
Sulfates of Mg and alkaline earth metals include magnesium sulfate, calcium sulfate, barium sulfate, strontium sulfate, and the like.
Mg and alkaline earth metal hydroxides include magnesium hydroxide, calcium hydroxide, barium hydroxide, strontium hydroxide, and the like.

Among these, from the viewpoint of improving the carbon yield, the carbon source is preferably at least one selected from oxides, carbonates, sulfates, and hydroxides of magnesium, alkaline earth metals and aluminum, At least one selected from oxides, carbonates and oxides of magnesium and calcium is more preferred, and at least one selected from magnesium carbonate and magnesium sulfate is more preferred.
Among oxides, carbonates, sulfates, and hydroxides of aluminum, aluminum oxide is preferred.

-Mixing ratio of carbon source and template source-
The mixing ratio of the carbon source and the template source (template source/carbon source) is preferably 0.1 to 15.0, more preferably 0.5 to 10.0, as the molar ratio of carbon C in the template source and the carbon source. more preferred. Thereby, a template carbon material (that is, a porous carbon material) having the desired BET specific surface area and pore distribution is obtained.

(First heating step)
In the first heating step, for example, a mixture of the carbon source and the template source is heated to 800 to 1100° C. at a temperature elevation rate of 5 to 30° C./min under an inert gas atmosphere. Hold for ~200 minutes.
This heat treatment thermally decomposes and oxidizes the template source in parallel with the carbonization of the carbon source to obtain a composite of carbon and the template (ie oxide of magnesium, alkaline earth metal or aluminum).

(Template source removal step)
In the template source removal step, the template is dissolved in the pickling solution by pickling a composite of carbon and the template (that is, magnesium, alkaline earth metal or aluminum oxide). This removes the template from the carbon-template complex. Thereby, a porous carbon material intermediate is obtained.
The acid used for pickling may be any acid as long as the template is soluble, and a preferred example thereof is sulfuric acid. After pickling, the carbon material is washed with water and dried.

(Second heating step)
In the second heating step, for example, the obtained intermediate of the template carbon material is held at 2300 to 2600° C. for 0.5 to 3.0 hours in an inert gas atmosphere.
This heat treatment enhances the crystallinity of the template carbon material and improves the durability at high temperatures (oxidative consumption resistance).
After the second heating step, the intermediate of the template carbon material may be graphitized at 2400° C. or higher.

Through the above steps, the desired template carbon material (that is, the porous carbon material) is obtained.

The method for producing a template carbon material of the present invention is applicable to fields where a carbon material called activated carbon is applied (for example, selective adsorption of specific gases, selective adsorption of molecules with specific structures in the liquid phase, etc.). agent), as a catalyst carrier for solid polymer fuel cells to which Ketjenblack is applied, and in the field of supercapacitor electrodes.

<Method for producing catalyst>
The method for producing a template carbon material of the present invention can be applied to a method for producing a catalyst. The method for producing a catalyst of the present invention is a method for producing a catalyst in which a catalyst component is supported on the surface of the carbon material obtained by the method for producing a template carbon material of the present invention as a carrier.
As the catalyst component, solid polymer fuel catalysts are typical catalysts. Examples of catalyst components include platinum, platinum alloys, and the like. Alloy components of platinum alloys include gold, silver, chromium, iron, titanium, manganese, cobalt, nickel, molybdenum, tungsten, aluminum, silicon, zinc, tin, ruthenium, rhodium, palladium, osmium, and iridium.
In addition, as a catalyst component, a polymer electrolyte fuel catalyst is mentioned as a typical catalyst. Examples of catalyst components include platinum, platinum alloys, and the like. Alloy components of platinum alloys include Au, Ag, Cr, Fe, Ti, Mn, Co, Ni, Mo, W, Al, Si, Zn, Sn, Ru, Rh, Pd, Os, and Ir.

The method for producing a catalyst of the present invention provides a large reaction surface area for a polymer electrolyte fuel cell catalyst layer, a metal-air battery cathode represented by a Li-air battery, a redox flow battery electrode, and the like, and , can be applied to the production of electrodes that require high chemical and electrochemical stability.

<Method for Producing Polymer Electrolyte Fuel Cell>
The method for producing a template carbon material of the present invention can be applied to a method for producing a polymer electrolyte fuel cell (or its catalyst layer).
An example of the polymer electrolyte fuel cell to be manufactured is the polymer electrolyte fuel cell 100 shown in FIG. The polymer electrolyte fuel cell 100 includes separators 110 and 120, gas diffusion layers 130 and 140, catalyst layers 150 and 160, and an electrolyte membrane 170, for example.

The separator 110 is an anode-side separator and introduces a fuel gas such as hydrogen into the gas diffusion layer 130 . The separator 120 is a separator on the cathode side, and introduces an oxidizing gas such as oxygen gas or air into the gas diffusion and aggregation phase. The type of the separators 110 and 120 is not particularly limited as long as they are separators used in conventional fuel cells such as polymer electrolyte fuel cells.

The gas diffusion layer 130 is a gas diffusion layer on the anode side, and supplies the catalyst layer 150 after diffusing the fuel gas supplied from the separator 110 . The gas diffusion layer 140 is a cathode-side gas diffusion layer, and after diffusing the oxidizing gas supplied from the separator 120 , supplies the gas to the catalyst layer 160 . The type of gas diffusion layers 130 and 40 is not particularly limited as long as they are gas diffusion layers used in conventional fuel cells, such as polymer electrolyte fuel cells. Examples of the gas diffusion layers 130 and 40 include porous carbon materials (carbon cloth, carbon paper, etc.), porous metal materials (metal mesh, metal wool, etc.), and the like.
As a preferred example of the gas diffusion layers 130 and 140, the separator-side layer of the gas diffusion layer is a gas diffusion fiber layer containing a fibrous carbon material as a main component, and the catalyst layer-side layer contains carbon black as a main component. A gas diffusion layer having a two-layer structure that serves as a microporous layer is exemplified.

The catalyst layer 150 is a so-called anode. An oxidation reaction of the fuel gas occurs in the catalyst layer 150 to generate protons and electrons. For example, when the fuel gas is hydrogen gas, the following oxidation reactions occur.
H ₂ →2H ⁺ +2e ⁻ (E ₀ =0 V)

Protons generated by the oxidation reaction reach catalyst layer 160 through catalyst layer 150 and electrolyte membrane 170 . Electrons generated by the oxidation reaction pass through the catalyst layer 150, the gas diffusion layer 130, and the separator 110 and reach the external circuit. The electrons are introduced into separator 120 after doing work in the external circuit. After that, the electrons reach the catalyst layer 160 through the separator 120 and the gas diffusion layer 140 .

The configuration of the catalyst layer 150 that serves as the anode is not particularly limited. That is, the structure of the catalyst layer 150 may be the same as that of a conventional anode, or the same as that of the catalyst layer 160, or may be more hydrophilic than the catalyst layer 160. may

The catalyst layer 160 is a so-called cathode. A reduction reaction of the oxidizing gas occurs in the catalyst layer 160 to produce water. For example, when the oxidizing gas is oxygen gas or air, the following reduction reactions occur. Water generated by the oxidation reaction is discharged outside the solid polymer fuel cell 100 together with unreacted oxidizing gas.
O ₂ +4H ⁺ +4e ⁻ →2H ₂ O (E ₀ =1.23 V)

In this manner, the polymer electrolyte fuel cell 100 generates electricity using the energy difference (potential difference) between the oxidation reaction and the reduction reaction. In other words, the electrons produced in the oxidation reaction do work in the external circuit.

The catalyst layer 160 contains the template carbon material of the present invention. That is, the catalyst layer 160 includes the template carbon material of the present invention, an electrolyte material, and a fuel cell catalyst. Thereby, the catalyst utilization rate in the catalyst layer 160 can be increased. As a result, the catalyst utilization rate of the polymer electrolyte fuel cell 100 can be increased.

Although the fuel cell catalyst loading rate in the catalyst layer 160 is not particularly limited, it is preferably 30% by mass or more and less than 80% by mass. Here, the fuel cell catalyst support rate is preferably mass % of the fuel cell catalyst with respect to the total mass of the catalyst-supported particles (particles in which the template carbon material supports the fuel cell catalyst). In this case, the catalyst utilization rate is further increased. If the fuel cell catalyst support rate is less than 30% by mass, it may be necessary to increase the thickness of the catalyst layer 160 in order to make the polymer electrolyte fuel cell 100 practically usable. On the other hand, when the fuel cell catalyst support rate is 80% by mass or more, catalyst aggregation tends to occur. Also, the catalyst layer 160 may become too thin, causing flooding.

The mass ratio I/C between the mass I (g) of the electrolyte material and the mass C (g) of the carbon material for catalyst support in the catalyst layer 160 is not particularly limited, but is preferably more than 0.5 and less than 5.0. . In this case, both the pore network and the electrolyte material network can be achieved, and the catalyst utilization rate increases. On the other hand, when the mass ratio I/C is 0.5 or less, the electrolyte material network tends to be poor and the proton conduction resistance tends to be high. If the mass ratio I/C is 5.0 or more, the electrolyte material may disrupt the pore network. In either case, catalyst utilization may decrease.

Moreover, the thickness of the catalyst layer 160 is not particularly limited, but is preferably more than 5 μm and less than 20 μm. In this case, the oxidizing gas easily diffuses into the catalyst layer 160, and flooding is less likely to occur. When the thickness of the catalyst layer 160 is 5 μm or less, flooding is likely to occur. When the thickness of the catalyst layer 160 is 20 μm or more, it becomes difficult for the oxidizing gas to diffuse in the catalyst layer 160, and the fuel cell catalyst in the vicinity of the electrolyte membrane 170 becomes difficult to work. That is, the catalyst utilization rate may decrease.

The electrolyte membrane 170 is made of an electrolyte material having proton conductivity. The electrolyte membrane 170 introduces the protons generated by the oxidation reaction into the catalyst layer 160, which is the cathode. Here, the type of electrolyte material is not particularly limited as long as it is an electrolyte material used in conventional fuel cells such as polymer electrolyte fuel cells. A suitable example is an electrolyte material used in a polymer electrolyte fuel cell, ie, an electrolyte resin. Examples of electrolyte resins include polymers into which phosphoric acid groups, sulfonic acid groups, etc. are introduced (for example, perfluorosulfonic acid polymers or polymers into which benzenesulfonic acid is introduced). Of course, the electrolyte material may be other types of electrolyte materials. Examples of such electrolyte materials include inorganic electrolyte materials, inorganic-organic hybrid electrolyte materials, and the like. The polymer electrolyte fuel cell 100 may be a fuel cell that operates within the range of room temperature to 150.degree.

<Experimental example>
The types and amounts of carbon sources and template sources shown in Tables 1 to 4 were mixed. Particles with as small a particle size as possible will form a uniform fired product in the first heating step, so the carbon source and mold source are pulverized with a mortar, planetary ball mill, etc. before being subjected to the test. and the volume average particle size was adjusted to 1.0 to 10.0 μm. Mixing was carried out using a mortar for at least several minutes.
Here, the compounds used as carbon sources were evaluated by thermogravimetric analysis under an inert atmosphere. For thermogravimetric analysis, TG-DTA8122 manufactured by Rigaku was used, and the temperature was raised from room temperature (25°C) to 500°C at a temperature elevation rate of 10°C/min, and the temperature at which weight loss reached 5% by mass under argon gas flow conditions. T _0.05 was calculated. In Tables 1 to 4, ◯ indicates that T _0.05 satisfies 200° C. or lower, and x indicates that T 0.05 does not satisfy.
Next, the mixture was sintered (first heat treatment) in a horizontal gas-flow tubular electric furnace while argon gas was being passed through to obtain a composite of carbon and template. Specifically, argon is circulated at a linear velocity of 3 cm per minute, heated from room temperature to 900° C. at a temperature increase rate of 20° C. per minute, held at 900° C. for 1 hour, then allowed to cool to 100° C. or less. It was taken out when the temperature reached 100°C, and a complex of carbon and template was obtained.
Next, the composite was lightly pulverized in a mortar, dispersed in a 20% by mass sulfuric acid aqueous solution, stirred at 90° C. for 40 hours, suction filtered with a membrane filter, dispersed again in distilled water and filtered for 2 times. Washed repeatedly. This removed the template.
Next, after removing moisture from the washed product with a hot air dryer at 100° C., it was vacuum-dried at 90° C. for 5 hours to obtain an intermediate of a template carbon material.
Next, in order to increase the crystallinity of the resulting template carbon material, the intermediate of the template carbon material was subjected to a second heat treatment at 1500° C. for 1.0 hour in an inert gas atmosphere. After that, graphitization treatment (heat treatment) was performed on the intermediate of the template carbon material.
A template carbon material (that is, a porous carbon material) was obtained through the above steps.

Benzene-1,4-dicarboxylic acid calcium salt was obtained by reproducing the description of Example 1 of Patent Document 4 (Experimental Example No. Ar1-12). Specifically, 2 L of pure water, 1 mol of calcium hydroxide, and 1 mol of terephthalic acid were placed in a reaction vessel and mixed at 80° C. for 3 hours to prepare calcium terephthalate. The prepared calcium terephthalate was allowed to stand for 24 hours. Thereafter, calcium terephthalate was filtered, dried at 115° C. for 24 hours, and coarsely pulverized. The resulting benzene-1,4-dicarboxylic acid calcium salt was subjected to the same procedure after the above-described first heat treatment to obtain a template carbon material (that is, a porous carbon material).

<Evaluation>
The following evaluation was performed on the resulting template carbon material (that is, porous carbon material).

(carbon yield)
The carbon yield in the manufacturing method of the template carbon material of each example was determined as follows.
The carbon yield was defined as the mass ratio of the mass of carbon after the template source removal step to the mass of the carbon source used as the raw material, and was measured by the following method.
That is, after the first heat treatment at 900° C. for 1 hour, the sample was subjected to a sulfuric acid solution treatment, followed by a washing treatment to remove the template, and further subjected to a vacuum tube treatment to obtain an intermediate of template carbon. was weighed, and the mass was divided by the mass of the carbon source used as the raw material to calculate the carbon yield in %.

(Preparation of catalyst, preparation of catalyst layer, preparation of MEA, assembly of fuel cell, and evaluation of cell performance)
Using the obtained template carbon material, a polymer electrolyte fuel cell catalyst supporting a catalytic metal is prepared as follows, and the obtained catalyst is used to prepare a catalyst layer ink solution. A catalyst layer is formed using this catalyst layer ink solution, a membrane electrode assembly (MEA) is produced using the formed catalyst layer, and the produced MEA is incorporated into a fuel cell, A power generation test was conducted using a fuel cell measuring device. Hereinafter, cell evaluation by preparation of each member and power generation test will be described in detail.

(1) Production of solid polymer fuel cell catalyst (platinum-supporting carbon material) The obtained template carbon material was dispersed in distilled water, formaldehyde was added to the dispersion, and the mixture was placed in a water bath set at 40°C. After the temperature of the dispersion reached 40° C., which was the same as that of the bath, the dinitrodiamine Pt complex nitric acid aqueous solution was slowly poured into the dispersion with stirring. Then, after continuing stirring for about 2 hours, it filtered and the solid substance obtained was washed. The solid thus obtained was vacuum-dried at 90° C., pulverized in a mortar, and then heat-treated at 200° C. for 1 hour in an argon atmosphere containing 5% by volume of hydrogen to produce a carbon material supporting platinum catalyst particles. bottom.
The amount of platinum supported by the platinum-supported carbon material was adjusted to 40% by mass with respect to the total mass of the template carbon material and platinum particles, and was subjected to Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES). - determined and confirmed by Atomic Emission Spectrometry).

(2) Preparation of catalyst layer Using the platinum-supported carbon material (Pt catalyst) prepared as described above, Nafion manufactured by Dupont (registered trademark: Nafion; persulfonic acid-based ion exchange resin) was used as the electrolyte resin. Using these Pt catalysts and Nafion in an Ar atmosphere, the mass of the Nafion solid content is 1.0 times the mass of the platinum catalyst particle-supporting carbon material, and the mass of the non-porous carbon is 0.5 times. After blending and stirring lightly, the Pt catalyst is crushed with ultrasonic waves, and ethanol is added to adjust the total solid content concentration of the Pt catalyst and the electrolyte resin to be 1.0% by mass, A catalyst layer ink liquid in which the Pt catalyst and the electrolyte resin were mixed was prepared.

Ethanol was further added to each catalyst layer ink solution having a solid content concentration of 1.0% by mass thus prepared to prepare a catalyst layer ink solution for spray coating having a platinum concentration of 0.5% by mass. The spray conditions were adjusted so that the mass per unit area of the layer (hereinafter referred to as "platinum coating weight") was 0.2 mg/cm2, and the catalyst layer ink for spray coating was sprayed onto a Teflon (registered trademark) sheet. After that, drying treatment was performed in argon at 120° C. for 60 minutes to prepare a catalyst layer.

(3) Production of MEA Using the catalyst layer produced as described above, an MEA (membrane electrode assembly) was produced by the following method.
A 6 cm square electrolyte membrane was cut from a Nafion membrane (NR211 manufactured by Dupont). Further, each of the catalyst layers of the anode and cathode coated on the Teflon (registered trademark) sheet was cut into a square shape of 2.5 cm on each side with a utility knife.
The electrolyte membrane was sandwiched between the catalyst layers of the anode and the cathode cut out in this way so that the catalyst layers were in contact with each other with the central part of the electrolyte membrane sandwiched therebetween and there was no displacement with each other. /cm2 for 10 minutes, then cooled to room temperature, and then carefully peeled off only the Teflon sheet on both the anode and cathode to prepare a catalyst layer-electrolyte membrane assembly in which each catalyst layer of the anode and cathode was fixed to the electrolyte membrane. .

Next, as gas diffusion layers, carbon paper (35BC manufactured by SGL Carbon Co., Ltd.) was cut into a pair of square-shaped carbon papers with a size of 2.5 cm on each side. The catalyst layer-electrolyte membrane assembly was sandwiched so that there was no deviation, and pressed at 120° C. and 50 kg/cm 2 for 10 minutes to prepare an MEA.
The basis weight of each component of the catalyst metal component, the carbon material, and the electrolyte material in each MEA produced was calculated from the difference between the mass of the Teflon sheet with the catalyst layer before pressing and the mass of the Teflon sheet peeled off after pressing. The mass of the catalyst layer fixed to the membrane (electrolyte membrane) was obtained, and calculated from the mass ratio of the composition of the catalyst layer.

(4) Evaluation of fuel cell power generation characteristics (evaluation of low current characteristics)
Each of the MEAs prepared in each test example and prepared using the prepared porous carbon material for catalyst support is assembled into a cell, set in a fuel cell measurement device, and evaluated for fuel cell performance by the following procedure. did
The reaction gas was air on the cathode side, and pure hydrogen on the anode side, and the pressure was adjusted by a back pressure valve provided downstream of the cell under atmospheric pressure so that the utilization rates were 40% and 70%, respectively. , at a back pressure of 0.04 MPa. The cell temperature was set to 80° C., and both the cathode and the anode were supplied with distilled water kept at 60° C. in a humidifier by bubbling. ℃ humidified gas was supplied and power generation evaluation was performed.

Under the condition that the reactant gas was supplied to the cell under such settings, the load was gradually increased, and the voltage between the cell terminals at a current density of 100 mA/cm ² was recorded as the output voltage to evaluate the performance of the fuel cell. , was evaluated according to the criteria for the following pass rank and fail rank. The results are shown in Tables to Tables 4.
[passing rank]
A: The output voltage at 100 mA/cm ² is 0.880 V or higher.
◯: Output voltage at 100 mA/cm ² is 0.870 V or more.
[Fail rank]
x: The output voltage at 100 mA/cm ² is less than 0.870V.

From the above results, the method for producing the template carbon material of the example of the present invention is a method for producing a template carbon material with a high carbon yield and a good yield equal to or higher than the comparative example in which a resin material is applied as a carbon source. Recognize.

Details of abbreviations and the like in the table are shown below.
ATQ: anthraquinone PVA: polyvinyl alcohol (weight average molecular weight = 10000)
PEG: polyethylene glycol (weight average molecular weight = 600)
PAA: polyacrylic acid (weight average molecular weight = 10000)

100 polymer electrolyte fuel cell 110, 120 separator 130, 140 gas diffusion layer 150, 160 catalyst layer 170 electrolyte membrane

Claims (12)

A method for producing a template carbon material using, as raw materials, a carbon source satisfying the following requirement (A) and a template source satisfying the following requirement (B).
(A) The temperature T at which the carbon source has at least one of two or more oxygen-containing functional groups and two or more nitrogen-containing functional groups and reaches a weight loss of 5% by mass in thermogravimetric analysis under an inert atmosphere. _0.05 includes aromatics below 200°C.
(B) The template source is at least one selected from oxides, carbonates, sulfates and hydroxides of magnesium, alkaline earth metals and aluminum. 2. In the carbon source, the aromatic compound is a compound in which at least two of the two or more oxygen-containing functional groups are interposed between two or more carbon atoms. 3. The method for producing the template carbon material according to . In the carbon source, the aromatic compound is at least one selected from monocyclic aromatic compounds and bicyclic aromatic compounds, the oxygen-containing functional group is a carboxyl group, and the nitrogen-containing functional group is 3. The method for producing a template carbon material according to claim 1 or 2, which is an amino group. 4. The method for producing a template carbon material according to claim 3, wherein the bicyclic aromatic compound is a compound having a naphthalene skeleton. In the carbon source, the aromatic compound is an aromatic compound having three or more rings, the oxygen-containing functional group is a carboxyl group or a hydroxyl group, and the nitrogen-containing functional group is an amino group. A method for producing the described template carbon material. 6. The method for producing a template carbon material according to claim 5, wherein the aromatic compound having a condensed ring structure of three or more rings is at least one selected from compounds having an anthraquinone skeleton and compounds having an anthracene skeleton. The template carbon material according to any one of claims 1 to 6, wherein the template source is at least one selected from oxides, carbonates, sulfates, and hydroxides of magnesium and calcium. manufacturing method. The method for producing a template carbon material according to any one of claims 1 to 7, wherein the template source is at least one selected from magnesium carbonate and magnesium sulfate. A method for producing a catalyst, wherein the carbon material obtained by the method for producing a template carbon material according to any one of claims 1 to 8 is used as a carrier, and a catalyst component is supported on the surface of the carrier. A method for producing a polymer electrolyte fuel cell catalyst layer using the catalyst obtained by the method for producing a catalyst according to claim 9 . 11. A method for producing a fuel cell using the catalyst layer obtained by the method for producing a polymer electrolyte fuel cell catalyst layer according to claim 10. 12. The method of manufacturing a fuel cell according to claim 11, wherein the polymer electrolyte fuel cell catalyst layer is a cathode-side catalyst layer.

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