Mesoporous carbon, electrode catalyst for fuel cell, catalyst layer, fuel cell, and method for producing mesoporous carbon

Abstract

The present invention relates to mesoporous carbon, an electrode catalyst for a fuel cell, a catalyst layer, a fuel cell, and a method for producing the mesoporous carbon. The mesoporous carbon has a structure connected by primary particles, wherein the primary particles are composed of carbon particles having primary pores with a primary pore diameter of less than 20 nm. The mesoporous carbon has a secondary pore diameter within the range of 20 to 100 nm and a pore volume of 0.42 cm 3 / g~1.34cm 3 / g. Furthermore, the linearity of the mesoporous carbon is 2.2 to 2.6. The fuel cell electrode catalyst comprises mesoporous carbon and catalyst particles supported within the primary pores of the mesoporous carbon. Furthermore, the catalyst layer comprises a fuel cell electrode catalyst and a catalyst layer ionomer.

Description

Technical Field

[0001] The present invention relates to mesoporous carbon, an electrode catalyst for a fuel cell, a catalyst layer, a fuel cell and a method for producing the mesoporous carbon. Background Art

[0002] A polymer electrolyte fuel cell comprises a membrane electrode assembly (MEA) in which electrodes (catalyst layers) containing a catalyst are bonded to both sides of an electrolyte membrane. A gas diffusion layer is typically disposed on the outside of the catalyst layer. Furthermore, a current collector (separator) having a gas flow path is disposed on the outside of the gas diffusion layer. A polymer electrolyte fuel cell typically comprises a structure (fuel cell stack) in which a plurality of single cells composed of such an MEA, a gas diffusion layer, and a current collector are stacked.

[0003] In polymer electrolyte fuel cells, the catalyst layer typically consists of a mixture of an electrode catalyst and a catalyst layer ionomer, with fine particles of a catalytic metal such as platinum supported on the surface of a support. Carbon materials such as carbon black and acetylene black are commonly used as catalyst supports. Furthermore, the pore diameter and specific surface area of ​​the carbon materials used in catalyst supports are known to affect the performance of the fuel cell. Therefore, various proposals have been made for carbon materials with controlled pore diameters and specific surface areas.

[0004] For example, International Publication No. 2016 / 152447 discloses a method for producing a carrier carbon material.

[0005] (a) preparing an alumina-carbon composite by calcining a mixture of γ-alumina particles and polyvinyl alcohol in an inert gas atmosphere,

[0006] (b) dissolving and removing the aluminum oxide in the aluminum oxide-carbon composite using sodium hydroxide to prepare a carbon material,

[0007] (c) The obtained carbon material is pulverized and the pulverized carbon material is activated.

[0008] International Publication No. 2016 / 152447 describes the following aspects:

[0009] (A) The support carbon material thus obtained contains mesopores (catalyst-supporting pores) with a radius of 2 nm to 5 nm and mesopores (gas diffusion pores) with a radius of 5 nm to 25 nm that communicate with the catalyst-supporting pores.

[0010] (B) When catalytic metal fine particles with a radius of 1 to 3 nm are supported on such a support carbon material, the catalytic metal fine particles are supported in the catalyst-supporting pores.

[0011] (C) When a support carbon material having catalytic metal fine particles supported in catalyst-supporting pores is used as an air electrode catalyst for a fuel cell, water molecules generated on the catalytic metal fine particles diffuse from the catalyst-supporting pores through the gas diffusion pores to the outside of the support carbon material, and

[0012] (D) This can suppress flooding that occurs inside the support carbon material.

[0013] In polymer electrolyte fuel cells, if the voids in the catalyst layer become too few, overflow is likely to occur, and depending on the operating conditions, sufficient IV performance may not be achieved. In addition, if the electronic conductivity of the catalyst layer decreases, overvoltage is generated when the electrons required for the reaction are supplied. Therefore, the catalyst carrier used in the catalyst layer is required to have low filling properties and high electronic conductivity to ensure appropriate voids in the catalyst layer. Furthermore, in order to reduce the cost of polymer electrolyte fuel cells, it is also required to reduce the manufacturing cost of such catalyst carriers.

[0014] International Publication No. 2016 / 152447 states that using a support carbon material having catalyst-supporting pores with a radius of 2 to 5 nm and gas diffusion pores with a radius of 5 to 25 nm can suppress overflow within the support carbon material. However, it is believed that the support carbon material described in International Publication No. 2016 / 152447 has difficulty in forming an appropriate catalyst layer structure (a composite structure comprising an appropriate catalyst layer thickness and an appropriate void structure) that is less susceptible to overflow in high current density regions. Summary of the Invention

[0015] One embodiment of the present invention provides a mesoporous carbon having excellent resistance to overflow in a high current density region. In addition, one embodiment of the present invention provides a mesoporous carbon having excellent resistance to overflow and a small voltage drop due to overvoltage. In addition, another embodiment of the present invention provides a fuel cell electrode catalyst using such mesoporous carbon as a catalyst carrier. Furthermore, another embodiment of the present invention provides a catalyst layer, a fuel cell, and a method for manufacturing mesoporous carbon having such a fuel cell electrode catalyst.

[0016] The mesoporous carbon according to one embodiment of the present invention has a connected structure in which primary particles are connected, and the primary particles are composed of carbon particles having primary pores with a primary pore diameter of less than 20 nm.

[0017] The pore volume of the secondary pores of the mesoporous carbon having a secondary pore diameter within the range of 20 to 100 nm as measured by mercury intrusion porosimetry was 0.42 cm 3 / g~1.34cm 3 / g. The linearity of the above mesoporous carbon is 2.2 to 2.6.

[0018] In the above embodiment, the average particle size of the primary particles may be 30 nm to 300 nm.

[0019] In the above method, the pore volume of the secondary pores can be 0.42 cm 3 / g~1.00cm 3 / g.

[0020] A fuel cell electrode catalyst according to another embodiment of the present invention comprises:

[0021] Mesoporous carbon according to one embodiment of the present invention, and

[0022] Catalyst particles supported in the primary pores of the mesoporous carbon.

[0023] Furthermore, a catalyst layer according to another embodiment of the present invention includes:

[0024] Another embodiment of the present invention is an electrode catalyst for a fuel cell, and

[0025] Catalyst layer ionomer.

[0026] In the above embodiment, the catalyst layer may be an air electrode catalyst layer of the fuel cell.

[0027] Furthermore, a fuel cell includes a catalyst layer according to another embodiment of the present invention.

[0028] Another aspect of the present invention provides a method for producing mesoporous carbon comprising:

[0029] The first step is to prepare mesoporous silica as a template.

[0030] a second step of precipitating carbon in the mesopores of the mesoporous silica to produce a mesoporous silica / carbon composite, and

[0031] The third step is to remove the mesoporous silica from the composite.

[0032] In the above embodiment, the method for producing mesoporous carbon further comprises: after the third step, a fourth step of heat-treating the mesoporous carbon at a temperature higher than 1500°C.

[0033] In the above method, the first step may include:

[0034] a polymerization step of polycondensing the silica source in a reaction solution containing the silica source, a surfactant, and a catalyst to obtain precursor particles;

[0035] a drying step of separating the precursor particles from the reaction solution and drying them, and

[0036] A calcination step is performed to calcine the precursor particles to obtain mesoporous silica.

[0037] In the above embodiment, the first step further includes a diameter expansion step of expanding the diameter of the dried precursor particles.

[0038] When an electrode catalyst is made using the mesoporous carbon of one embodiment of the present invention as a catalyst carrier, and a solid polymer fuel cell is made using the electrode catalyst as an air electrode catalyst, especially in the high current density region, an IV performance equal to or higher than that in the past can be obtained. It is believed that this is because by using a mesoporous carbon having a connection structure and optimized pore size, pore capacity and linearity as a catalyst carrier, an air electrode catalyst layer having a moderate thickness and an appropriate amount of voids can be obtained, thereby suppressing overflow. Furthermore, if the mesoporous carbon is heat-treated at a temperature exceeding 1500°C, the IV performance of the fuel cell using the mesoporous carbon pores is further improved. It is believed that this is because the mesoporous carbon is graphitized by a heat treatment exceeding 1500°C, and the electronic conductivity of the mesoporous carbon is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Hereinafter, features, advantages, and technical and industrial significance of exemplary embodiments of the present invention will be described with reference to the accompanying drawings, wherein like symbols represent like elements, and wherein:

[0040] Figure 1A This is a schematic diagram of mesoporous carbon according to one embodiment of the present invention.

[0041] Figure 1B This is a diagram used to explain the definition of linearity.

[0042] Figure 2A is a SEM image of the mesoporous carbon of Example 1.

[0043] Figure 2B is a schematic diagram of the mesoporous carbon of Example 1.

[0044] Figure 3A This is a SEM image of the hollow carbon of Comparative Example 2.

[0045] Figure 3B This is a schematic diagram of the hollow carbon of Comparative Example 2.

[0046] Figure 4A This is a schematic cross-sectional view of the air electrode catalyst layer of the fuel cell obtained in Example 1.

[0047] Figure 4B This is a schematic cross-sectional view of the air electrode catalyst layer of the fuel cell obtained in Comparative Example 2.

[0048] Figure 5This is the output point performance @ high humidification of the fuel cells obtained in Examples 1 to 4 and Comparative Examples 1 to 3. DETAILED DESCRIPTION

[0049] Hereinafter, one embodiment of the present invention will be described in detail.

[0050] 1. Mesoporous carbon

[0051] Figure 1A A schematic diagram showing a mesoporous carbon according to one embodiment of the present invention. Figure 1A In the figure, the mesoporous carbon 10 has a structure in which primary particles 12 composed of carbon particles having primary pores (not shown) are connected. Therefore, the mesoporous carbon 10 has a distorted shape rather than a spherical particle. The degree of deviation of the shape of the mesoporous carbon 10 from the spherical shape can be represented by linearity. The details of linearity will be described later. When such mesoporous carbon 10 is stacked in layers, secondary pores 14 having a specified secondary pore diameter are formed between adjacent mesoporous carbons 10, 10.

[0052] 1.1. Connection structure

[0053] As described later, mesoporous carbon 10 is manufactured using mesoporous silica as a template. Mesoporous silica can generally be synthesized by polycondensing a silica source in a reaction solution comprising a silica source, a surfactant, and a catalyst. At this time, if the type of solvent, the concentration of the surfactant in the reaction solution, and / or the concentration of the silica source are optimized, a mesoporous silica having a connection structure and a pore size, a pore volume, and a linearity within a specific range can be obtained. Furthermore, if such mesoporous silica is used as a template, a mesoporous carbon 10 having a connection structure and a pore size, a pore volume, and a linearity within a specific range can be obtained.

[0054] Here, the term "connected structure" refers to a structure in which primary particles 12 composed of carbon particles are connected in a bead-like manner. Each primary particle 12 that constitutes the connected structure has a primary pore (not shown) within it. The primary pores within the primary particles 12 are the cavities remaining after removing the pore walls of the mesoporous silica used in the template. Figure 1A 、 1B In FIG, each primary particle 12 is depicted as a spherical particle, but this is merely an illustration. The primary particle 12 is usually not a completely spherical particle, but rather has a distorted shape with an aspect ratio of about 1.1 to 3.

[0055] 1.2. Primary particles

[0056] The primary particles 12 are composed of carbon particles having primary pores with a primary pore diameter of less than 20 nm. Since the mesoporous carbon 10 is produced using a method described below, the primary particles 12 constituting the mesoporous carbon 10 have the following characteristics.

[0057] 1.2.1. Average particle size of primary particles

[0058] The "average particle size of the primary particles 12" refers to the average value of the lengths in the minor axis direction of the primary particles 12. The "length in the minor axis direction" refers to the length in the direction perpendicular to the longest direction (major axis direction) of the primary particles 12. The average particle size of the primary particles 12 is obtained by measuring the lengths in the minor axis direction of at least 100 randomly selected primary particles 12 using a microscope and calculating the average value.

[0059] Generally, if the average particle size of the primary particles 12 is too small, the catalyst particles are not easily supported in the primary pores. Therefore, the average particle size of the primary particles 12 is preferably 30 nm or larger. The average particle size is preferably 40 nm or larger, and more preferably 50 nm or larger.

[0060] On the other hand, if the average particle size of the primary particles 12 is too large, it becomes difficult to supply the reaction gas and protons to the catalyst particles supported within the primary pores, and it becomes difficult to discharge the water generated by the reaction. Therefore, the average particle size is preferably 300 nm or less. The average particle size is preferably 250 nm or less, and more preferably 150 nm or less.

[0061] 1.2.2. Primary pore diameter

[0062] The "primary pore diameter" refers to the average diameter of the primary pores contained in the primary particles 12, and does not include the size of the voids (secondary pores 14) between the primary particles 12. The primary pore diameter is obtained by analyzing the adsorption side data of the nitrogen adsorption isotherm of the mesoporous carbon 10 using the BJH method and determining the pore diameter (most frequent peak) at which the pore volume reaches a maximum.

[0063] Generally speaking, if the primary pore diameter is too small, it is difficult to supply reaction gases and protons to the catalyst particles carried in the primary pores, or it is difficult to discharge water produced by the reaction. Therefore, the primary pore diameter is preferably 2 nm or larger. The primary pore diameter is preferably 2.5 nm or larger. On the other hand, if the primary pore diameter is too large, ionomers easily invade the primary pores. As a result, the catalyst particles are poisoned by the ionomers, and their activity decreases. Therefore, the primary pore diameter needs to be less than 20 nm. The primary pore diameter is preferably 10 nm or smaller, more preferably 7 nm or smaller, and even more preferably 5 nm or smaller.

[0064] 1.2.3. Average thickness of pore walls

[0065] The “average pore wall thickness” refers to the average thickness of the pore walls of the primary pores contained in the primary particles 12. The average pore wall thickness is obtained by measuring the thickness of pore walls at 100 or more randomly selected locations using a microscope and calculating the average value.

[0066] If the average thickness of the pore walls is too thin, carbon is easily oxidized, which may reduce durability. Therefore, the average thickness of the pore walls is preferably 3 nm or greater. The average thickness is preferably 3.5 nm or greater, and more preferably 4 nm or greater. On the other hand, if the average thickness of the pore walls is too thick, the pore volume of the primary particles 12 decreases, making it difficult to support catalyst particles. Therefore, the average thickness of the pore walls is preferably 15 nm or less. The average thickness is preferably 12 nm or less, and more preferably 10 nm or less.

[0067] 1.2.4. Pore capacity of primary pores

[0068] The "pore volume of primary pores" refers to the volume of the primary pores contained in the primary particles 12, excluding the volume of the voids (secondary pores 14) between the primary particles 12. The pore volume of primary pores is calculated by analyzing the adsorption data of the nitrogen adsorption isotherm of the mesoporous carbon 10 using the BJH method and using a value of P / P0 = 0.03 to 0.99.

[0069] Generally speaking, if the pore capacity of a primary pore is too small, it is not easy to carry catalyst particles. Therefore, the pore capacity of a primary pore is preferably more than 0.2mL / g. The pore capacity of a primary pore is preferably more than 0.5mL / g, more preferably more than 1.0mL / g. On the other hand, if the pore capacity of a primary pore is too large, the proportion of the volume of the pore wall in the volume of the primary particle 12 becomes smaller, and sometimes the electronic conductivity becomes lower. In addition, the amount of ionomer intrusion becomes more, and sometimes the activity decreases due to catalyst poisoning. Therefore, the pore capacity of a primary pore is preferably less than 3.0mL / g. The pore capacity of a primary pore is preferably less than 2.5mL / g, more preferably less than 2.0mL / g.

[0070] 1.3. Pore capacity of secondary pores

[0071] "Secondary pores" refer to pores between adjacent mesoporous carbons 10 when the mesoporous carbons 10 are stacked in layers. "Secondary pore diameter" refers to the diameter of the secondary pores 14 measured by mercury intrusion porosimetry. "Secondary pore volume" refers to the volume of the secondary pores 14 measured by mercury intrusion porosimetry.

[0072] When measuring the pore volume of mesoporous carbon 10 by mercury intrusion porosimetry, secondary pores 14 with a secondary pore diameter exceeding 100 nm are sometimes detected. However, the secondary pores 14 with a secondary pore diameter in the range of 20 to 100 nm are the main factors affecting flooding in the high current density region.

[0073] If the pore volume of the secondary pores 14 in the range of 20 to 100 nm (hereinafter referred to as "pore volume @ 20 to 100 nm") is reduced, the flooding resistance in the high current density region is reduced. Therefore, the pore volume @ 20 to 100 nm needs to be 0.42 cm 3 / g or more. Pore capacity @20-100nm is preferably 0.50cm 3 / g or more, more preferably 0.70cm 3 On the other hand, if the pore volume @20-100 nm is too large, the catalyst layer thickness becomes thicker and the proton transport resistance may become higher. Therefore, the pore volume @20-100 nm needs to be 1.34 cm 3 / g or less. Pore capacity @20-100nm is preferably 1.32cm 3 / g or less, more preferably 1.30cm 3 / g or less, more preferably 1.00cm 3 / g or less.

[0074] 1.4. Linearity

[0075] Figure 1B A schematic diagram for explaining the definition of linearity is shown. "Linearity" refers to a value represented by the following formula (1).

[0076] Linearity = (L max 2 / S)×(π / 4)…(1)

[0077] Among them, L max is the length of the particle in the direction where its length reaches its maximum (the length in the major axis direction), and S is the area of ​​the particle's projection surface.

[0078] Linearity indicates the degree to which a particle's shape deviates from a spherical shape. The closer the particle's projected shape is to a circle, the closer the value is to 1. The linearity of the mesoporous carbon 10 affects the secondary pore diameter and pore volume of the secondary pores 14. Generally, if the linearity is too low, the secondary pore diameter and / or pore volume of the secondary pores 14 become too small, reducing flooding resistance in high current density regions. Therefore, the linearity needs to be 2.2 or higher.

[0079] On the other hand, in order to obtain high output in a solid polymer fuel cell, it is necessary to make the catalyst unit area weight (the amount of catalyst particles per unit area) be above a certain threshold value. Then, when the linearity of the mesoporous carbon 10 is too large, in order to make the catalyst unit area weight be above the threshold value, it is necessary to thicken the thickness of the catalyst layer. As a result, the proton conductivity of the catalyst layer is sometimes reduced. Therefore, the linearity needs to be below 2.6. The linearity is preferably below 2.5, more preferably below 2.4.

[0080] 1.5. Graphitization degree

[0081] Mesoporous carbon is produced by filling the pores of mesoporous silica with a carbon source and carbonizing the carbon source. However, to suppress the reaction between mesoporous silica and carbon, the carbonization temperature of the carbon source must be relatively low. Therefore, the carbonized carbon source tends to form a turbostratic structure. Compared to graphite-like mesoporous carbon, turbostratic mesoporous carbon has lower electronic conductivity.

[0082] In contrast, if turbostratic mesoporous carbon is graphitized at a temperature exceeding 1500° C., the turbostratic mesoporous carbon gradually changes into a graphite structure. Generally speaking, the higher the graphitization temperature, the higher the degree of graphitization.

[0083] 2. Electrode catalysts for fuel cells

[0084] A fuel cell electrode catalyst according to another embodiment of the present invention comprises:

[0085] Mesoporous carbon, and

[0086] Catalyst particles supported within the primary pores of mesoporous carbon.

[0087] Mesoporous carbon

[0088] In fuel cell electrode catalysts, mesoporous carbon is a catalyst carrier for supporting catalyst particles. The catalyst particles are mainly supported within the primary pores of the primary particles 12 constituting the mesoporous carbon. The details of the mesoporous carbon are as described above, so their description is omitted.

[0089] 2.2. Catalyst particles

[0090] In the present invention, the material of the catalyst particles is not particularly limited as long as it exhibits oxygen reduction reaction activity or hydrogen oxidation reaction activity. Examples of the material of the catalyst particles include:

[0091] (a) Noble metals (Pt, Au, Ag, Pd, Rh, Ir, Ru, Os),

[0092] (b) alloys containing two or more noble metal elements,

[0093] (c) alloys containing one or more noble metal elements and one or more base metal elements (e.g., Fe, Co, Ni, Cr, V, Ti, etc.),

[0094] (d) metal oxynitrides,

[0095] (e) Carbon alloys, etc.

[0096] 3. Catalyst layer

[0097] A catalyst layer according to another embodiment of the present invention comprises:

[0098] Electrode catalysts for fuel cells, and

[0099] Catalyst layer ionomer.

[0100] The catalyst layer is particularly suitable as a catalyst layer on the air electrode side, but can also be used as a catalyst layer on the fuel electrode side.

[0101] 3.1. Electrode catalysts for fuel cells

[0102] The catalyst layer includes a fuel cell electrode catalyst. The details of the fuel cell electrode catalyst are as described above, and therefore, description thereof will be omitted.

[0103] 3.2. Catalyst layer ionomer

[0104] In the catalyst layer, the material of the catalyst layer ionomer is not particularly limited. Examples of catalyst layer ionomers include perfluorocarbon sulfonic acid polymers and highly oxygen permeable ionomers. The ionomer may be composed of any one of these, or a combination of two or more thereof.

[0105] "Perfluorocarbon sulfonic acid polymer" refers to a fluorinated ion exchange resin containing repeating units based on a fluorinated sulfonyl vinyl ether monomer. Examples of perfluorocarbon sulfonic acid polymers include Nafion (registered trademark), Flemion (registered trademark), Aquivion (registered trademark), and Aciplex (registered trademark).

[0106] A "highly oxygen-permeable ionomer" refers to a polymer compound containing an acid group and a cyclic structure within its molecular structure. Because a highly oxygen-permeable ionomer contains a cyclic structure within its molecular structure, it has a high oxygen permeability coefficient. Therefore, when used as an ionomer, the oxygen transfer resistance at the interface with the catalyst is relatively low. In other words, a "highly oxygen-permeable ionomer" refers to an ionomer with an oxygen permeability coefficient higher than that of perfluorocarbon sulfonic acid polymers such as Nafion (registered trademark).

[0107] Examples of highly oxygen permeable ionomers include:

[0108] (a) an electrolyte polymer comprising a perfluorocarbon unit having an aliphatic ring structure and an acid group unit having a perfluorosulfonic acid in a side chain,

[0109] (b) an electrolyte polymer comprising a perfluorocarbon unit having an aliphatic ring structure and an acid group unit having a perfluoroimide group in a side chain,

[0110] (c) Electrolyte polymers including a unit in which perfluorosulfonic acid is directly bonded to perfluorocarbon having an aliphatic ring structure (see Japanese Patent Application Laid-Open No. 2003-036856, International Publication No. 2012 / 088166, Japanese Patent Application Laid-Open No. 2013-216811, and Japanese Patent Application Laid-Open No. 2006-152249).

[0111] 4. Method for manufacturing mesoporous silica (template)

[0112] The mesoporous carbon of one embodiment of the present invention is produced using mesoporous silica as a template. The method for producing mesoporous silica comprises:

[0113] a polymerization step of polycondensing the silica source in a reaction solution containing the silica source, a surfactant, and a catalyst to obtain precursor particles;

[0114] a drying step of separating the precursor particles from the reaction solution and drying them, and

[0115] A calcination step is performed to calcine the precursor particles to obtain mesoporous silica.

[0116] The method for producing mesoporous silica may further include a diameter expansion step of expanding the diameter of the dried precursor particles.

[0117] 4.1. Polymerization process

[0118] First, in a reaction solution containing a silica source, a surfactant, and a catalyst, the silica source is polycondensed to obtain precursor particles (polymerization step).

[0119] Silica source

[0120] In the present invention, the type of silica source is not particularly limited. Examples of silica sources include: (a) tetraalkoxysilanes such as tetramethoxysilane, tetraethoxysilane, tetraisopropoxysilane, tetrabutoxysilane, dimethoxydiethoxysilane, and tetraethyleneglycoxysilane;

[0121] (b) trialkoxysilanes such as 3-mercaptopropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, and 3-(2-aminoethyl)aminopropyltrimethoxysilane,

[0122] (c) Silicates such as sodium silicate and layered silicate (Kanemite), etc. As the silica source, any one of these may be used, or two or more of them may be used in combination.

[0123] 4.1.2. Surfactants

[0124] When a silica source is polycondensed in a reaction solution, if a surfactant is added to the reaction solution, the surfactant forms micelles in the reaction solution. Since hydrophilic groups gather around the micelles, the silica source is adsorbed on the surface of the micelles. Furthermore, the micelles adsorbed with the silica source self-organize in the reaction solution, and the silica source undergoes polycondensation. As a result, mesopores (including micropores with a diameter of 2 nm or less, the same applies hereinafter) originating from the micelles are formed within the primary particles. The size of the mesopores can be primarily controlled by the molecular length of the surfactant (1 to 50 nm).

[0125] In the present invention, the type of surfactant is not particularly limited, but an alkyl quaternary ammonium salt is preferably used as the surfactant. The alkyl quaternary ammonium salt refers to a compound represented by the following formula (a).

[0126] CH3-(CH2) n -N + (R1)(R2)(R3)X - ···(a)

[0127] In the formula (a), R1, R2, and R3 each independently represent an alkyl group having 1 to 3 carbon atoms. R1, R2, and R3 may be the same as or different from each other. In order to facilitate the aggregation (micelle formation) of the alkyl quaternary ammonium salts, R1, R2, and R3 are preferably the same. Furthermore, at least one of R1, R2, and R3 is preferably a methyl group, and preferably all of them are methyl groups. In the formula (a), X represents a halogen atom. The type of halogen atom is not particularly limited, and from the perspective of ease of availability, X is preferably Cl or Br.

[0128] In formula (a), n represents an integer from 7 to 21. Generally speaking, the smaller n is, the smaller the central pore diameter of the mesopores is, and the spherical mesoporous body is obtained. On the other hand, the larger n is, the larger the central pore diameter is. However, if n is too large, the hydrophobic interaction of the alkyl quaternary ammonium salt is excessive. As a result, a layered compound is produced, and the mesoporous body cannot be obtained. n is preferably from 9 to 17, and more preferably from 13 to 17.

[0129] Among the compounds represented by formula (a), alkyl trimethylammonium halides are preferred. Examples of alkyl trimethylammonium halides include hexadecyl trimethylammonium halide, octadecyl trimethylammonium halide, nonyl trimethylammonium halide, decyl trimethylammonium halide, undecyl trimethylammonium halide, dodecyl trimethylammonium halide, and tetradecyl trimethylammonium halide. Among these, alkyl trimethylammonium bromide or alkyl trimethylammonium chloride is particularly preferred.

[0130] In the case of synthetic mesoporous silica, one alkyl quaternary ammonium salt can be used, or two or more can be used. However, since the alkyl quaternary ammonium salt becomes a template for forming mesopores in primary particles, its kind has a great impact on the shape of the mesopores. In order to synthesize silica particles with more uniform mesopores, one alkyl quaternary ammonium salt is preferably used.

[0131] Catalyst

[0132] When polycondensing the silica source, a catalyst is usually added to the reaction solution. When synthesizing particulate mesoporous silica, the catalyst may be an alkali such as sodium hydroxide or ammonia water, or an acid such as hydrochloric acid.

[0133] 4.1.4. Solvent

[0134] The solvent used is water, an organic solvent such as alcohol, a mixed solvent of water and an organic solvent, etc. The alcohol may be any of the following alcohols:

[0135] (1) Monohydric alcohols such as methanol, ethanol, and propanol,

[0136] (2) diols such as ethylene glycol,

[0137] (3) Triols such as glycerol.

[0138] When using a mixed solvent of water and an organic solvent, the content of the organic solvent in the mixed solvent can be selected arbitrarily according to purpose. Generally speaking, if an amount of organic solvent is added in a solvent, the control of particle diameter, size distribution becomes easy. And then, when using a mixed solvent of water and an organic solvent, if the content of the organic solvent is a mixed solvent of below 5 quality %, the mesoporous silica for manufacturing the excellent mesoporous carbon of anti-overflow can be manufactured at low cost.

[0139] 4.1.5. Composition of reaction solution

[0140] The composition of the reaction solution affects the shape and pore structure of the synthesized mesoporous silica. In particular, the concentration of the surfactant and silica source in the reaction solution significantly influences the average primary particle size, pore diameter, pore volume, and linearity of the mesoporous silica particles.

[0141] A. Surfactant concentration

[0142] If the concentration of the surfactant is too low, the precipitation rate of the particles slows down and a structure connected by primary particles cannot be obtained. Therefore, the concentration of the surfactant needs to be 0.03 mol / L or more. The concentration of the surfactant is preferably 0.035 mol / L or more, more preferably 0.04 mol / L or more.

[0143] On the other hand, if the concentration of the surfactant is too high, the precipitation rate of the particles becomes faster and the primary particle size easily exceeds 300nm. Therefore, the concentration of the surfactant needs to be 1.0mol / L or less. The concentration of the surfactant is preferably 0.95mol / L or less, more preferably 0.90mol / L or less.

[0144] B. Concentration of silica source

[0145] If the concentration of the silica source is too low, the precipitation rate of the particles slows down, and a structure formed by connecting primary particles cannot be obtained. Alternatively, if the surfactant is excessive, uniform mesopores may not be obtained. Therefore, the concentration of the silica source needs to be 0.05 mol / L or more. The concentration of the silica source is preferably 0.06 mol / L or more, and more preferably 0.07 mol / L or more.

[0146] On the other hand, if the concentration of the silica source is too high, the particle precipitation rate becomes too fast, and the primary particle size tends to exceed 300 nm. Alternatively, flaky particles may be obtained instead of spherical particles. Therefore, the concentration of the silica source needs to be 1.0 mol / L or less. The concentration of the silica source is preferably 0.95 mol / L or less, and more preferably 0.9 mol / L or less.

[0147] C. Catalyst concentration

[0148] In the present invention, the concentration of the catalyst is not particularly limited. Generally speaking, if the concentration of the catalyst is too low, the precipitation rate of the particles slows down. On the other hand, if the concentration of the catalyst is too high, the precipitation rate of the particles accelerates. The optimal concentration of the catalyst is preferably selected according to the type of silica source, the type of surfactant, the physical property value of the target, etc. For example, when an acid is used as a catalyst, the concentration of the catalyst is preferably adjusted in such a way that the pH of the reaction solution becomes 9 or less. The pH of the reaction solution is preferably 8.5 or less, and more preferably less than 5. On the other hand, when an alkali is used as a catalyst, the concentration of the catalyst is preferably adjusted in such a way that the pH of the reaction solution exceeds 7.

[0149] 4.1.6 Reaction conditions

[0150] A silica source is added to a solvent containing a predetermined amount of a surfactant, and hydrolysis and polycondensation are carried out. The surfactant thus acts as a template, yielding precursor particles comprising silica and the surfactant. The optimal reaction conditions are selected based on factors such as the type of silica source and the particle size of the precursor particles. Generally, the reaction temperature is preferably between -20°C and 100°C. The reaction temperature is preferably between 0°C and 100°C, more preferably between 0°C and 90°C, even more preferably between 10°C and 80°C, and even more preferably between 35°C and 80°C.

[0151] 4.2. Drying process

[0152] Next, the precursor particles are separated from the reaction solution and dried (drying step). Drying is performed to remove the solvent remaining in the precursor particles. The drying conditions are not particularly limited as long as the solvent can be removed.

[0153] 4.3. Diameter expansion

[0154] Then, the dried precursor particles can be subjected to a diameter expansion process (diameter expansion process) as needed." diameter expansion process" refers to the process of expanding the diameter of the mesopores in the primary particle. Diameter expansion process is specifically carried out by hydrothermally treating the synthesized precursor particles (particles without removing surfactant) in a solution comprising a diameter expander. By this process, the pore diameter of the precursor particles can be expanded.

[0155] Examples of the diameter-expanding agent include:

[0156] (a) Hydrocarbons such as trimethylbenzene, triethylbenzene, benzene, cyclohexane, triisopropylbenzene, naphthalene, hexane, heptane, octane, nonane, decane, undecane, and dodecane,

[0157] (b) Acids such as hydrochloric acid, sulfuric acid, and nitric acid.

[0158] It is believed that the pore diameter increases with hydrothermal treatment in the presence of hydrocarbons because the silica rearranges when the diameter-expanding agent is introduced from the solvent into the pores of the more hydrophobic precursor particles. Furthermore, it is believed that the pore diameter increases with hydrothermal treatment in the presence of an acid such as hydrochloric acid due to the dissolution and reprecipitation of silica within the primary particles. If the manufacturing conditions are optimized, radial pores are formed within the silica. If hydrothermal treatment is performed in the presence of an acid, the dissolution and reprecipitation of silica occur, converting the radial pores into interconnected pores.

[0159] The conditions for the diameter expansion treatment are not particularly limited as long as the target pore diameter can be obtained. Generally, it is preferred to add about 0.05 mol / L to 10 mol / L of a diameter expansion agent to the reaction solution and perform a hydrothermal treatment at 60 to 150°C.

[0160] 4.4. Calcination process

[0161] Then, after the diameter expansion treatment is performed as needed, the above-mentioned precursor particles are calcined (calcination step). In this way, mesoporous silica can be obtained. Calcination is carried out to dehydrate and polymerize the precursor particles with residual OH groups and to thermally decompose the surfactant remaining in the mesopores. The calcination conditions are not particularly limited as long as dehydration and crystallization and thermal decomposition of the surfactant can be performed. Calcination is usually carried out by heating at 400°C to 800°C in the atmosphere for 1 hour to 10 hours.

[0162] 5. Method for producing mesoporous carbon

[0163] The method for producing mesoporous carbon according to the sixth aspect of the present invention comprises:

[0164] The first step is to prepare mesoporous silica as a template.

[0165] a second step of precipitating carbon in the mesopores of the mesoporous silica to produce a mesoporous silica / carbon composite, and

[0166] The third step is to remove the mesoporous silica from the composite.

[0167] The method for producing mesoporous carbon may further include a fourth step of heat-treating the mesoporous carbon at a temperature higher than 1500° C. after the third step.

[0168] 5.1. First step (template production)

[0169] First, mesoporous silica is prepared as a template (first step). The details of the method for producing mesoporous silica are as described above, and therefore, description thereof will be omitted.

[0170] 5.2. Second Step (Carbon Precipitation in Mesoporous Pores)

[0171] Next, carbon is precipitated in the mesopores of the mesoporous silica to produce a mesoporous silica / carbon composite (second step).

[0172] Specifically, the precipitation of carbon in the mesopores can be carried out by the following operations:

[0173] (a) introducing carbon precursor into the mesopores,

[0174] (b) Polymerization and carbonization of the carbon precursor within the mesopores.

[0175] 5.2.1. Introduction of carbon precursor

[0176] "Carbon precursor" refers to a substance that can generate carbon by thermal decomposition. Specific examples of such carbon precursors include:

[0177] (1) a polymer precursor that is liquid at room temperature and thermally polymerizable (e.g., furfuryl alcohol, aniline, etc.),

[0178] (2) A mixture of an aqueous solution of carbohydrates and an acid (for example, a mixture of monosaccharides such as sucrose, xylose, and glucose, or a mixture of disaccharides or polysaccharides with an acid such as sulfuric acid, hydrochloric acid, nitric acid, and phosphoric acid),

[0179] (3) A mixture of two-component curing polymer precursors (for example, phenol and formaldehyde).

[0180] Among these, polymer precursors can be impregnated into the mesopores without dilution with a solvent, thus allowing a relatively large amount of carbon to be generated in the mesopores with a relatively small number of impregnations. Furthermore, they do not require a polymerization initiator and are easy to handle.

[0181] In the case of using a liquid or solution carbon precursor, the more the adsorption amount of the liquid or solution each time, the better, preferably the amount in which the mesopore is filled with the liquid or solution as a whole. In addition, when using a mixture of an aqueous solution of a carbohydrate and an acid as a carbon precursor, the amount of the acid is preferably the minimum amount that can polymerize the organic matter. Furthermore, when using a mixture of a two-liquid curing polymer precursor as a carbon precursor, the ratio is selected to be optimal according to the type of the polymer precursor.

[0182] 5.2.2. Polymerization and carbonization of carbon precursors

[0183] Next, the polymerized carbon precursor is carbonized in the mesopores. The carbonization of the carbon precursor is carried out by heating the mesoporous silica containing the carbon precursor to a predetermined temperature in a non-oxidizing atmosphere (e.g., an inert atmosphere, a vacuum, etc.). Specifically, the heating temperature is preferably 500° C. to 1200° C. If the heating temperature is less than 500° C., the carbonization of the carbon precursor is insufficient. On the other hand, if the heating temperature exceeds 1200° C., the silica reacts with the carbon, which is not preferred. The optimal heating time is selected according to the heating temperature.

[0184] It should be noted that the amount of carbon generated in the mesopores is as long as the carbon particles can maintain the shape when removing the mesoporous silica. Therefore, in the case where the amount of carbon generated by a single filling, polymerization and carbonization is relatively small, it is preferred to repeatedly perform these processes. At this time, the conditions of each repeated process can be respectively the same, or they can be different. In addition, in the case of each process of repeated filling, polymerization and carbonization, each carbonization process can be carbonized at a relatively low temperature, and after the last carbonization is completed, it is further carbonized again at a higher temperature than the last carbonization. If the last carbonization is performed at a temperature higher than the previous carbonization, the carbon introduced into the pores is easily integrated.

[0185] 5.3. Third step (removal of template)

[0186] Next, the mesoporous silica serving as a template is removed from the composite (third step), thereby obtaining mesoporous carbon.

[0187] Specific methods for removing mesoporous silica include:

[0188] (1) A method of heating the composite in an alkaline aqueous solution such as sodium hydroxide, (2) A method of etching the composite with an aqueous hydrofluoric acid solution, etc.

[0189] 5.4. The fourth step (graphitization treatment)

[0190] Next, as needed, the mesoporous carbon is heat-treated at a temperature higher than 1500°C (the fourth step). When the carbon source is carbonized in the mesopores of the mesoporous silica, the heat treatment temperature has to be lowered in order to suppress the reaction between the silica and the carbon. Therefore, the carbon after the carbonization treatment has a low degree of graphitization. In order to obtain a high degree of graphitization, it is preferred to remove the template and then heat-treat the mesoporous carbon at a high temperature.

[0191] If the heat treatment temperature is too low, graphitization is insufficient. Therefore, the heat treatment temperature is preferably higher than 1500°C. The heat treatment temperature is preferably higher than 1700°C, and more preferably higher than 1800°C. On the other hand, even if the heat treatment temperature is increased beyond necessity, the effect is not significantly different, and there is no practical benefit. Therefore, the heat treatment temperature is preferably lower than 2300°C. The heat treatment temperature is preferably lower than 2200°C.

[0192] 6. Function

[0193] In polymer electrolyte fuel cells, if the gaps in the catalyst layer are too few, overflow is likely to occur, and depending on the operating conditions, sufficient IV performance may not be achieved. Furthermore, if the electronic conductivity of the catalyst layer decreases, overvoltage is generated when the electrons required for the reaction are supplied. Therefore, the catalyst carrier used in the catalyst layer is required to have a low fillability and high electronic conductivity to ensure appropriate gaps within the catalyst layer. Furthermore, in order to reduce the cost of polymer electrolyte fuel cells, it is also necessary to reduce the manufacturing cost of such catalyst carriers.

[0194] In contrast, if an electrode catalyst is made using the mesoporous carbon of one embodiment of the present invention as a catalyst carrier, and a solid polymer fuel cell is made using the electrode catalyst as an air electrode catalyst, then in particular in the high current density region, IV performance equal to or higher than that of the past can be obtained. This is believed to be because by using mesoporous carbon having a connection structure and optimized pore size, pore capacity and linearity as a catalyst carrier, an air electrode catalyst layer having a moderate thickness and an appropriate amount of voids can be obtained, thereby suppressing overflow. Furthermore, if the mesoporous carbon is heat-treated at a temperature exceeding 1500°C, the IV performance of the fuel cell using it is further improved. This is believed to be because the electronic conductivity of the mesoporous carbon is improved by graphitizing the mesoporous carbon through a heat treatment exceeding 1500°C.

[0195] Examples 1 to 4, Comparative Examples 1 to 3

[0196] 1. Preparation of samples

[0197] 1.1. Preparation of mesoporous silica

[0198] 1.1.1. Examples 1-2

[0199] Hexadecyltrimethylammonium chloride (C 16 H 33 17 g of N(CH₃)₃Cl) and 12 g of ethanol were added to 540 g of a 1.5% by mass aqueous hydrochloric acid solution. The aqueous hydrochloric acid solution was heated to 70°C (Example 1) or 40°C (Example 2), and 67 g of No. 1 sodium silicate (SiO₂ content: 30% by mass, SiO₂ / Na₂O = 2.00) was added while stirring. The solution was maintained in this state for 3 hours to allow for a polycondensation reaction.

[0200] The resulting solid product was temporarily separated by filtration, dispersed in 1000 g of ion-exchanged water, and stirred. This filtration, dispersion, and stirring process was repeated five times to wash the solid product, and then dried at 70°C for 24 hours. The dried solid product was then dispersed in 2N hydrochloric acid and heated in an autoclave at 130°C for 3 days. The autoclaved solid product was filtered, washed, and dried, and then calcined at 550°C in the presence of air for 6 hours to obtain mesoporous silica.

[0201] 1.1.2. Examples 3-4

[0202] A first solution was obtained by adding a predetermined amount of a surfactant and 1 equivalent of sodium hydroxide to a mixed solvent containing predetermined amounts of water, methanol, and ethylene glycol (EG). Separately, a predetermined amount of tetraethoxysilane (TEOS) was added to a mixed solvent containing predetermined amounts of methanol and EG to obtain a second solution. Table 1 shows the solution loading amounts.

[0203] [Table 1]

[0204]

[0205] The second solution was added to the first solution, and after a while, the solution became cloudy, confirming that particles had been synthesized. After stirring at room temperature for 8 hours, the mixture was filtered, and the residue was redispersed in water. After filtering again, the residue was dried in an oven at 45°C. The dried sample was dispersed in 2N sulfuric acid and heated in an autoclave at 120°C for 3 days. The autoclaved sample was filtered and washed, then calcined at 550°C for 6 hours to remove organic components.

[0206] Comparative Example 1

[0207] Hexadecyltrimethylammonium chloride (C 16 H 33 51g of N(CH₃)₃Cl) and 36g of ethanol were added to 1600g of a 1.5% by mass aqueous hydrochloric acid solution. This aqueous hydrochloric acid solution was heated to 40°C, and 201g of No. 1 sodium silicate (SiO₂ content: 30% by mass, SiO₂ / Na₂O = 2.00) was added while stirring. The solution was maintained in this state for 3 hours to allow for a polycondensation reaction.

[0208] The resulting solid product was temporarily separated by filtration, dispersed in 2500 g of ion-exchanged water, and stirred. This filtration, dispersion, and stirring process was repeated five times to wash the solid product, and then dried at 70°C for 24 hours. The dried solid product was then dispersed in 2N hydrochloric acid and heated in an autoclave at 140°C for 3 days. The autoclaved solid product was filtered, washed, and dried, and then calcined at 550°C in the presence of air for 6 hours to obtain mesoporous silica.

[0209] 1.2. Preparation of carbon support

[0210] 1.2.1. Examples 1 to 4, Comparative Example 1

[0211] Mesoporous silica is placed in a PFA container, and only furfuryl alcohol (FA) is added in an amount corresponding to the pore volume to allow it to penetrate into the pores of the silica. FA is polymerized by subjecting it to a heat treatment at 150°C for 18 hours. Furthermore, it is subjected to a heat treatment at 500°C for 6 hours in a nitrogen atmosphere to carbonize FA. This is repeated twice, and then subjected to a heat treatment at 900°C for 6 hours in a nitrogen atmosphere to obtain a mesoporous silica / carbon composite. The composite is immersed in a 12% HF solution for 12 hours to dissolve the silica component. After dissolution, it is filtered and washed repeatedly, and then dried at 45°C to obtain mesoporous carbon. Furthermore, the dried mesoporous carbon is subjected to a treatment (graphitization treatment) by heating it at 1800°C for 1 hour.

[0212] Comparative Examples 2 and 3

[0213] Commercially available hollow (mesoporous) carbon (Comparative Example 2) or solid carbon (Comparative Example 3) was used directly as a carbon support.

[0214] 1.3. Fuel cell fabrication

[0215] Pt was loaded onto the carbon support obtained as described above. The Pt loading was 40% by mass. The air electrode catalyst layer was prepared using this. The Pt unit area weight on the air electrode side was 0.15 mg / cm 2 The I / C of the air electrode catalyst layer was 1.0. The fuel electrode catalyst layer was made of commercially available platinum-supported carbon with a Pt loading of 30% by mass. The Pt unit area weight on the fuel electrode side was 0.1 mg / cm 2 In addition, the I / C of the fuel electrode catalyst layer was 0.75.

[0216] The air electrode catalyst layer and the fuel electrode catalyst layer are transferred to each side of the electrolyte membrane to obtain MEA. The electrolyte membrane uses a fluorine-based solid polymer electrolyte membrane. MEA is assembled on a 1cm 2 A square battery cell. Furthermore, diffusion layers and current collectors are placed on both sides of the MEA. Carbon paper (with a microporous layer) is used as the diffusion layer. A gold-plated copper plate with integrated flow channels (flow channels: linear channels with a 0.4 mm pitch) is used as the current collector.

[0217] 2. Test methods

[0218] SEM observation

[0219] The carbon support was observed under an SEM, and the linearity and the average particle size of the primary particles were measured using the SEM image.

[0220] 2.2. Pore capacity of secondary pores

[0221] The pore volume of the secondary pores of the carbon support (the volume of pores having a pore diameter in the range of 20 to 100 nm) was determined using mercury porosimetry.

[0222] 2.3. Output point voltage

[0223] The obtained fuel cell was used to evaluate the output voltage (mV) under high humidity conditions (80% RH, cell temperature 60°C). The power generation conditions were H2 flow rate: 500cc / min, air flow rate: 1000cc / min, back pressure: 1kg / cm 2 .

[0224] 3. Results

[0225] SEM observation

[0226] Figure 2A and Figure 2B An SEM image and a schematic diagram of the mesoporous carbon of Example 1 are shown. Figure 3A and Figure 3B The SEM image and schematic diagram of the hollow carbon of Comparative Example 2 are shown. The hollow carbon 10' of Comparative Example 2 has a structure in which rod-shaped bodies composed of carbon having mesopores (not shown) are tree-branched. Therefore, the hollow carbon 10' of Comparative Example 2 includes a relatively large number of secondary pores 14' having large linearity. In contrast, the mesoporous carbon 10 of Example 1 has a structure in which primary particles 12 having primary pores (not shown) are connected. Therefore, the mesoporous carbon 10 of Example 1 has smaller linearity than the hollow carbon 10' of Comparative Example 2, and the pore capacity of the secondary pores 14 is also smaller.

[0227] Figure 4A A schematic cross-sectional view of the air electrode catalyst layer of the fuel cell obtained in Example 1 is shown. Figure 4B The cross-sectional view of the air electrode catalyst layer of the fuel cell obtained in Comparative Example 2 is shown. The linearity of the hollow carbon 10' of Comparative Example 2 is too large, and the pore volume of the secondary pores 14' is also too large. Therefore, if the catalyst layer 20' is formed using the hollow carbon 10' of Comparative Example 2 so that the Pt unit area weight becomes a predetermined value, then Figure 4B As shown in FIG. 1 , the thickness L' of the catalyst layer 20' becomes too thick. In contrast, the mesoporous carbon 10 of Example 1 has appropriate linearity and appropriate pore volume of the secondary pores 14. Therefore, if the catalyst layer 20 is formed using the mesoporous carbon 10 of Example 1 so that the Pt unit area weight becomes a predetermined value, then Figure 4A As shown, the thickness L of the catalyst layer 20 is appropriately thinned.

[0228] 3.2. Output point voltage

[0229] Table 2 shows the physical properties of the carbon support and the output performance of the fuel cell produced using the carbon support @ high humidification. Figure 5 The output performance of the fuel cells obtained in Examples 1 to 4 and Comparative Examples 1 to 3 is shown. Figure 5 In the table, "output point performance @ high humidification" refers to the ratio of the output voltage (V1) of each fuel cell under high humidification conditions to the output point voltage (V0) of the fuel cell of Comparative Example 2 under high humidification conditions (=V1 / V0). Figure 5 , we can know the following content.

[0230] (1) Comparative Example 1 showed lower output point performance @ high humidification than Comparative Example 2. This is believed to be because the linearity of the carbon support was too low and the pore volume of the secondary pores was also small, resulting in overflow under high humidification conditions.

[0231] (2) Comparative Example 3 showed lower output performance @ high humidification than Comparative Example 2. This is considered to be because the carbon support was solid carbon, and therefore the Pt catalyst was poisoned by the ionomer.

[0232] (3) Examples 1 and 2 showed output point performance @ high humidification that was approximately equivalent to that of Comparative Example 2. Examples 1 and 2 showed inferior output point performance @ high humidification compared to Examples 3 and 4. However, Examples 1 and 2 used a solvent primarily composed of water during the synthesis of mesoporous silica, and therefore were less expensive than Examples 3 and 4 and Comparative Example 2.

[0233] (4) Examples 3 and 4 exhibited higher output performance @ high humidification than Comparative Example 2. This is believed to be because the linearity was moderately low, allowing the catalyst layer thickness L to be appropriately thinner, resulting in a lower proton resistance in the catalyst layer. Furthermore, the relatively large pore volume of the secondary pores suppressed flooding under high humidification conditions.

[0234] [Table 2]

[0235]

[0236] *Pore volume in the range of 20 to 100 nm

[0237] As mentioned above, although embodiment of this invention was demonstrated in detail, this invention is not limited to the said embodiment at all, Various changes are possible within the range which does not deviate from the summary of this invention.

[0238] The mesoporous carbon according to one embodiment of the present invention can be used as a catalyst support for an air electrode catalyst layer or a fuel electrode catalyst layer of a polymer electrolyte fuel cell.

Claims

1. A mesoporous carbon, characterized in that The mesoporous carbon has a connected structure of primary particles, wherein the primary particles are composed of carbon particles having primary pores with a primary pore diameter of less than 20 nm. The pore volume of secondary pores with a secondary pore diameter in the range of 20 to 100 nm measured by mercury intrusion porosimetry is 0.42 cm 3 / g~1.34cm 3 / g, The linearity is 2.2~2.6, Where, linearity = (L max 2 / S)×(π / 4) L max It is the length of the direction where the length of the particle reaches the maximum, that is, the length in the major axis direction, and S is the area of ​​the projection surface of the particle.

2. The mesoporous carbon according to claim 1, characterized in that The average particle size of the primary particles is 30 nm to 300 nm.

3. The mesoporous carbon according to claim 1 or 2, characterized in that The pore capacity of the secondary pores is 0.42 cm 3 / g~1.00cm 3 / g.

4. A fuel cell electrode catalyst, characterized in that Include: The mesoporous carbon according to any one of claims 1 to 3, and Catalyst particles are supported in the primary pores of the mesoporous carbon.

5. A catalyst layer, characterized in that Include: The fuel cell electrode catalyst according to claim 4, and Catalyst layer ionomer. The catalyst layer according to claim 5 , wherein: The catalyst layer is the air electrode catalyst layer of the fuel cell.

7. A fuel cell, characterized in that: Comprising the catalyst layer according to claim 5.

8. A method for producing mesoporous carbon according to claim 1, characterized in that: include: The first step is to prepare mesoporous silica as a template. a second step of precipitating carbon in the mesopores of the mesoporous silica to produce a mesoporous silica / carbon composite; The third step is to remove the mesoporous silica from the composite.

9. The method for producing mesoporous carbon according to claim 8, wherein: Further including: After the third step, a fourth step is performed in which the mesoporous carbon is subjected to a heat treatment at a temperature higher than 1500° C.

10. The method for producing mesoporous carbon according to claim 8, wherein: The first step includes: a polymerization step of polycondensing the silica source in a reaction solution containing a silica source, a surfactant, and a catalyst to obtain precursor particles; a drying step of separating the precursor particles from the reaction solution and drying them, and A calcination step is performed to calcine the precursor particles to obtain mesoporous silica.

11. The method for producing mesoporous carbon according to claim 10, wherein: The first step further includes a diameter expansion step of expanding the diameter of the dried precursor particles.

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