C / sic composite particles, method for manufacturing the same, electrode catalyst comprising the same, and polymer electrolyte fuel cell

Abstract

The C / SiC composite particle contains a porous carbon particle and SiC particles distributed on the inner wall surface of the pores of the porous carbon particle. Such a C / SiC composite particle can be obtained by: producing a silica / carbon composite A by causing carbon to be deposited within the pores of a porous silica particle; producing a silica / carbon composite B by removing a portion of the silica from the silica / carbon composite A; heat-treating the silica / carbon composite B to graphitize the carbon; and simultaneously generating SiC. The electrode catalyst contains C / SiC composite particles and catalyst particles supported on the surface of the C / SiC composite particles. Furthermore, a polymer electrolyte fuel cell contains such an electrode catalyst as a cathode catalyst or an anode catalyst.

Description

Technical Field

[0001] This invention relates to: C / SiC composite particles, methods for manufacturing said C / SiC composite particles, electrode catalysts, and polymer electrolyte fuel cells; more specifically, it relates to C / SiC composite particles in which SiC particles are distributed on the inner wall surface of porous carbon particles, and electrode catalysts and polymer electrolyte fuel cells comprising said C / SiC composite particles as catalyst supports. Background Technology

[0002] Polymer electrolyte fuel cells have a membrane electrode assembly (MEA), in which electrodes containing a catalyst (catalyst layer) are bonded to both sides of an electrolyte membrane. A gas diffusion layer is typically disposed outside the catalyst layer. Furthermore, a current collector (septum) with a gas flow path is disposed outside the gas diffusion layer. Polymer electrolyte fuel cells typically have a structure in which multiple unit cells are stacked (fuel cell stack), each unit cell containing such an MEA, gas diffusion layer, and current collector.

[0003] It is known that during the operation of a polymer electrolyte fuel cell, hydrogen peroxide is generated in the cathode or anode catalyst layer. This hydrogen peroxide is converted into OH radicals via the Fenton reaction, and these OH radicals degrade the electrolyte in the MEA. Electrolyte degradation leads to a decline in the durability or power generation performance of the fuel cell. Various solutions have been proposed to address this problem.

[0004] For example, Patent Document 1 discloses a membrane electrode assembly obtained by means of:

[0005] (a) Manufacturing a cathode transfer electrode containing NbC powder with an average particle size of 1 to 3 micrometers and an anode transfer electrode without NbC powder;

[0006] (b) Manufacturing an electrolyte membrane containing SiC powder with an average particle size of 50 nm; and

[0007] (c) Transfer the cathode transfer electrode and the anode transfer electrode to both sides of the electrolyte membrane.

[0008] The document describes:

[0009] (A) Certain carbides, borides, and silicides are relatively stable in high-temperature, low-pH water and possess relatively high peroxide decomposition capabilities; and

[0010] (B) Electrolyte degradation caused by peroxide free radicals can be suppressed by fixing it to the electrolyte membrane and / or electrode.

[0011] As described in Patent Document 1, by adding carbides, borides or silicides with peroxide decomposition function to the electrolyte membrane and / or catalyst layer, electrolyte degradation caused by peroxide free radicals can be suppressed to a certain extent.

[0012] However, peroxides are mainly generated on the surface of catalyst particles. Therefore, by adding fine particles to the electrolyte membrane or catalyst layer, sometimes the generated hydrogen peroxide may not be efficiently decomposed, and the effect of inhibiting electrolyte degradation may be insufficient.

[0013] [List of Citations]

[0014] [Patent Literature]

[0015] Patent Document 1: Japanese Patent Application Publication No. 2006-107967 Summary of the Invention

[0016] Technical issues

[0017] The problem to be solved by the present invention is to provide C / SiC composite particles and a method for manufacturing said C / SiC composite particles, which, when used as a catalyst support for a fuel cell, can suppress electrolyte degradation caused by peroxide free radicals.

[0018] Another problem to be solved by the present invention is to provide an electrode catalyst and a polymer electrolyte fuel cell containing such C / SiC composite particles.

[0019] Technical solution

[0020] To address the above problems, the C / SiC composite particles according to the present invention comprise:

[0021] Porous carbon particles; and

[0022] SiC particles distributed on the inner wall surface of the pores of the porous carbon particles.

[0023] The method for manufacturing C / SiC composite particles according to the present invention includes:

[0024] The first step is to prepare porous silica particles as templates.

[0025] The second step involves precipitating carbon within the pores of the porous silica particles to obtain silica / carbon composite A.

[0026] A third step involves removing a portion of the silicon dioxide from the silicon dioxide / carbon composite A to obtain silicon dioxide / carbon composite B; and

[0027] The fourth step of obtaining C / SiC composite particles according to the present invention involves heat-treating the silicon dioxide / carbon composite B to graphitize the carbon, while simultaneously reacting the silicon dioxide with a portion of the carbon to generate SiC.

[0028] The electrode catalyst according to the present invention comprises:

[0029] C / SiC composite particles according to the present invention; and

[0030] Catalyst particles loaded on the surface of the C / SiC composite particles.

[0031] Furthermore, the polymer electrolyte fuel cell according to the present invention comprises the electrode catalyst according to the present invention as a cathode catalyst or an anode catalyst.

[0032] Beneficial effects

[0033] When a portion of the silica is removed from the silica / carbon composite and the composite is heat-treated at a relatively high temperature, the carbon is graphitized, while the silica reacts with the carbon to form SiC. As a result, a C / SiC composite is obtained in which SiC particles are distributed on the inner wall surfaces of the pores of the porous carbon particles.

[0034] SiC particles have the ability to decompose hydrogen peroxide into harmless water and oxygen. Therefore, when catalyst particles are loaded onto the surface of C / SiC composite particles (e.g., the inner wall of the pores), even if hydrogen peroxide is generated on the surface of the catalyst particles, the SiC particles present in the pores will rapidly decompose the hydrogen peroxide. As a result, electrolyte degradation caused by peroxide free radicals can be suppressed.

[0035] Furthermore, decomposition products generated by electrolyte degradation (e.g., sulfonic acid anions) can be a poisoning source for catalyst particles. In contrast, when catalyst particles are loaded within the pores of C / SiC composite particles, catalyst particle poisoning caused by these poisoning sources can be suppressed. Attached Figure Description

[0036] [ Figure 1 ] Figure 1 The pore diameter distribution of the C / SiC composite particles obtained in Examples 1 and 2 and Comparative Example 1 is shown.

[0037] [ Figure 2 ] Figure 2 This is a graph showing the relationship between the Si mass ratio (Si mass per unit surface area of ​​C / SiC composite particles) and the specific surface area of ​​C / SiC composite particles.

[0038] [ Figure 3 ] Figure 3 A represents the IV characteristics of the cell obtained in Example 3 before and after the durability test. Figure 3 B represents the IV characteristics of the cell obtained in Example 4 before and after the durability test. Figure 3 C represents the IV characteristics of the cell obtained in Comparative Example 2 before and after the durability test.

[0039] [ Figure 4 ] Figure 4 This is a graph showing the relationship between the Si mass ratio (Si mass per unit surface area of ​​C / SiC composite particles) and the activity retention rate.

[0040] [ Figure 5 ] Figure 5 A is the CV of the cell obtained in Example 3 during the durability test. Figure 5 B is the CV of the cell obtained in Example 4 during the durability test. Figure 5 C is the CV of the cell obtained in Comparative Example 2 during the durability test. Detailed Implementation

[0041] One embodiment of the present invention is described in detail below.

[0042] (1.C / SiC composite particles)

[0043] The C / SiC composite particles according to the present invention comprise:

[0044] Porous carbon particles; and

[0045] SiC particles distributed on the inner wall surface of the pores of the porous carbon particles.

[0046] (1.1. Structure)

[0047] The C / SiC composite particles according to the present invention can be obtained by the following means:

[0048] (a) Manufacturing porous silica particles;

[0049] (b) A silica / carbon composite A is manufactured by introducing a carbon source into the pores of the porous silica particles and carbonizing the carbon source;

[0050] (c) Removing a portion of the silicon dioxide from the silicon dioxide / carbon composite A; and

[0051] (d) The silica / carbon composite B formed by removing a portion of the silica is calcined at a high temperature.

[0052] The C / SiC composite particles obtained in this manner have a structure in which SiC particles are distributed on the inner wall surface of the pores of porous carbon particles.

[0053] In this case, the external shape of the porous carbon particles is almost equal to the external shape of the porous silica particles used as templates. For example, when spherical porous silica particles are used as templates, spherical porous carbon particles are obtained.

[0054] Alternatively, porous carbon particles with said beaded structure are obtained when porous silica particles having a structure in which multiple primary particles are connected in a bead-like manner (hereinafter also referred to as "beaded structure") are used as templates. In this case, the primary particles may be spherical particles or particles with a twisted shape having an aspect ratio of about 1.1 to 3.

[0055] SiC particles are formed by the reaction of residual SiO2 within the pores of porous carbon particles with the carbon constituting the pore walls of the porous carbon particles. Therefore, when the amount of carbon reacting with SiO2 is relatively small, the pore structure of the porous carbon particles becomes a structure that almost corresponds to the pore wall structure of the template (porous silica particles). On the other hand, when the amount of carbon reacting with SiO2 is relatively large, the pore structure of the porous carbon particles will disintegrate, and sometimes may become a structure different from the pore wall structure of the template.

[0056] (1.2. Surface functional groups)

[0057] C / SiC composite particles may also contain -OH groups and / or -COOH groups introduced on the surface of porous carbon particles.

[0058] The term "surface of porous carbon particles" as used herein refers to the outer surface of the porous carbon particles and / or the inner surface of the pores.

[0059] When catalyst particles are supported on the surface of C / SiC composite particles, if -OH and / or -COOH groups are present on the surface of the porous carbon particles, the fine catalyst particles can be supported on the surface of the porous carbon particles. There is no particular limitation on the concentration of such functional groups on the surface of the porous carbon particles, and the optimal concentration can be selected according to the purpose.

[0060] (1.3. Physical property values)

[0061] (1.3.1. The mode diameter of the hole)

[0062] "Mode diameter of the pore" refers to the pore diameter (the most frequently occurring peak) at the point of maximum pore volume when analyzing the nitrogen adsorption isotherm data of porous carbon particles (i.e., C / SiC composite particles) in which SiC particles are dispersed on the inner wall of the pore using the BJH method.

[0063] If the mode diameter of the pores in porous carbon particles is too small, it will be difficult for the catalyst particles to be loaded within the pores. Therefore, the ideal mode diameter of the pores is 1.5 nm or larger. An even more ideal mode diameter is 2.0 nm or larger.

[0064] On the other hand, if the mode diameter of the pores is too large, toxic substances can easily penetrate into the pores, and the activity of the catalyst particles loaded within the pores may sometimes deteriorate. Therefore, the ideal mode diameter of the pores is below 5.0 nm. An even more ideal mode diameter is below 4.0 nm.

[0065] (1.3.2. Average primary particle diameter of SiC particles)

[0066] As described above, SiC particles are formed by the reaction of SiO2 remaining within the pores of porous carbon particles with carbon constituting the pore walls of the porous carbon particles. Therefore, the average primary particle diameter of SiC particles is typically no larger than the mode diameter of the pores of the porous carbon particles. By optimizing the manufacturing conditions, the average primary particle diameter of SiC particles can be made smaller than the mode diameter of the pores of the porous carbon particles.

[0067] (1.3.3. Si mass ratio)

[0068] "Si mass ratio" refers to the ratio of the mass of Si per unit surface area of ​​porous carbon particles (i.e., C / SiC composite particles) in which SiC particles are distributed on the inner wall of the pores.

[0069] In C / SiC composite particles, most of the Si exists in the form of SiC particles. A high Si mass ratio means a large amount of SiC particles distributed on the inner wall of the pores. Since SiC particles have the ability to decompose hydrogen peroxide, the hydrogen peroxide decomposition ability of C / SiC composite particles increases with increasing Si mass ratio. To achieve this effect, the Si mass ratio must exceed 0 mg / m³. 2 The ideal Si mass ratio is 0.4 mg / m³. 2 The above, ideally 1.0 mg / m², is preferred. 2 above.

[0070] On the other hand, a high Si mass ratio means consuming more carbon to form SiC. Therefore, if the Si mass ratio is too high, the pores in the porous carbon particles may sometimes disappear. Thus, the ideal Si mass ratio is 6.8 mg / m³. 2 The following is a suggested Si mass ratio: 3.3 mg / m³. 2 The ideal value is 1.6 mg / m². 2 the following.

[0071] (1.3.4. Average primary particle diameter)

[0072] The "average primary particle diameter" of C / SiC composite particles refers to the average size of the primary particles of C / SiC composite particles, and also refers to the average length along the minor axis of 100 particles randomly extracted from the SEM image.

[0073] If the average primary particle diameter of the C / SiC composite particles is too small, the gaps between the primary particles are small, and the resistance to the transfer of reactant gases (hydrogen and oxygen) can sometimes be large. Furthermore, the removal of water generated by the reaction becomes worse, thus potentially degrading battery performance. Therefore, the ideal average primary particle diameter is 50 nm or greater. Even more ideal is 75 nm or greater.

[0074] On the other hand, if the average primary particle diameter of the C / SiC composite particles is too large, the movement distance of protons and reactant gases (hydrogen and oxygen) within the primary particles increases, and transfer resistance may sometimes increase. Furthermore, the removal of water generated by the reaction deteriorates, thus potentially degrading battery performance. Therefore, the ideal average primary particle diameter is below 200 nm. More ideally, it is below 150 nm, and even more ideally, below 125 nm.

[0075] (1.3.5. Pore Volume)

[0076] "Pore volume" refers to the value calculated from the amount of nitrogen adsorbed at P / P0 = 0 to 0.95 in the nitrogen adsorption isotherm of C / SiC composite particles.

[0077] If the pore volume of the C / SiC composite particles is too small, the catalyst particles will be difficult to load within the pores. Therefore, the ideal pore volume is above 0.5 cc / g.

[0078] On the other hand, if the pore volume is too large, the proportion of the pore wall volume to the C / SiC composite particle volume is small, resulting in a deterioration in the strength of the pore structure and potentially causing durability issues. Therefore, the ideal pore volume is below 2.0 cc / g.

[0079] (2. Electrode catalyst)

[0080] The electrode catalyst according to the present invention comprises:

[0081] C / SiC composite particles according to the present invention; and

[0082] Catalyst particles loaded on the surface of the C / SiC composite particles.

[0083] (2.1.C / SiC composite particles)

[0084] In the electrode catalyst according to the invention, the C / SiC composite particles according to the invention are used as the catalyst support. Details of the C / SiC composite particles are as described above, and therefore omitted.

[0085] (2.2. Catalyst particles)

[0086] Catalyst particles are supported on the surface of C / SiC composite particles.

[0087] Here, the “surface” of the C / SiC composite particles supporting the catalyst particles refers to the outer surface of the porous carbon particles and / or the inner surface of the pores. To reduce catalyst poisoning, it is preferable to load the catalyst particles within the pores of the porous carbon particles.

[0088] In this invention, there are no particular limitations on the materials used for catalyst particles, as long as the material exhibits oxygen reduction reaction activity or hydrogen oxidation reaction activity. Examples of materials used for catalyst particles include:

[0089] (a) Precious metals (Pt, Au, Ag, Pd, Rh, Ir, Ru, Os);

[0090] (b) An alloy containing two or more precious metal elements;

[0091] (c) An alloy containing one or more noble metal elements and one or more base metal elements (e.g., Fe, Co, Ni, Cr, V, Ti, etc.);

[0092] (d) Metal nitrogen oxides; and

[0093] (e) Carbon alloys.

[0094] (3. Polymer electrolyte fuel cells)

[0095] Polymer electrolyte fuel cells include a membrane electrode assembly (MEA), in which a cathode catalyst layer is bonded to one surface of an electrolyte membrane and an anode catalyst layer is bonded to the other surface of an electrolyte membrane.

[0096] The cathode catalyst layer comprises a composite of a cathode catalyst and a catalyst layer ionomer. The anode catalyst layer comprises a composite of an anode catalyst and a catalyst layer ionomer.

[0097] The polymer electrolyte fuel cell according to the invention comprises an electrode catalyst according to the invention for use as a cathode catalyst or anode catalyst. The polymer electrolyte fuel cell according to the invention may also comprise an electrode catalyst according to the invention for use as both a cathode catalyst and anode catalyst.

[0098] The details of the electrode catalyst are as described above, therefore explanation is omitted.

[0099] (4. Method for manufacturing porous silica particles (templates))

[0100] The C / SiC composite particles according to the present invention are manufactured using porous silica particles as a template. The method for manufacturing porous silica particles according to the present invention includes:

[0101] The polymerization process of obtaining precursor particles by polycondensing silica source in a reaction solution containing silica source, surfactant and catalyst;

[0102] The drying process of separating the precursor particles from the reaction solution and drying the precursor particles; and

[0103] The calcination process involves calcining the precursor particles to obtain mesoporous silica.

[0104] The method for manufacturing porous silica particles according to the present invention may further include a diameter expansion step of applying a diameter expansion treatment to the dried precursor particles.

[0105] (4.1. Polymerization process)

[0106] First, precursor particles are obtained by polycondensing the silica source in a reaction solution containing a silica source, a surfactant, and a catalyst (polymerization step).

[0107] (4.1.1. Silica source)

[0108] In this invention, the type of silicon dioxide source is not particularly limited. Examples of silicon dioxide sources include:

[0109] (a) Tetraalkoxysilanes, such as tetramethoxysilane, tetraethoxysilane, tetraisopropoxysilane, tetrabutoxysilane, dimethoxydiethoxysilane, and tetraethylene glycoxysilane;

[0110] (b) Trialkoxysilanes, such as 3-mercaptopropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, and 3-(2-aminoethyl)aminopropyltrimethoxysilane; and

[0111] (c) Silicates, such as sodium silicate and kanemite.

[0112] As a source of silica, any one of them can be used, or a combination of two or more of them can be used.

[0113] (4.1.2. Surfactants)

[0114] When a silica source is polymerized in a reaction solution, the addition of a surfactant to the reaction solution causes the surfactant to form micelles. The silica source is adsorbed onto the surface of the micelles due to the aggregation of hydrophilic groups around the micelles. Furthermore, the micelles adsorbing the silica source self-organize in the reaction solution, and the silica source is polymerized. As a result, mesopores (including micropores with a diameter of less than 2 nm) caused by the micelles are formed within the primary particles. The size of the mesopores can be controlled primarily by the molecular length of the surfactant (1 to 50 nm).

[0115] In this invention, the type of surfactant is not particularly limited, but alkyl quaternary ammonium salts are preferably used as surfactants. The alkyl quaternary ammonium salt is a chemical compound represented by the following formula:

[0116] CH3-(CH2) n -N + (R1)(R2)(R3)X - ...(a).

[0117] In formula (a), R1, R2, and R3 each represent an alkyl group having 1 to 3 carbon atoms. R1, R2, and R3 may be the same as or different from each other. To promote the aggregation of alkyl quaternary ammonium salts (formation of micelles), it is desirable that R1, R2, and R3 are all the same. Furthermore, it is desirable that at least one of R1, R2, and R3 is a methyl group, and more preferably that all of R1, R2, and R3 are methyl groups.

[0118] In equation (a), X represents a halogen atom. There are no particular restrictions on the type of halogen atom, but for reasons of availability, it is desirable that X is Cl or Br.

[0119] In equation (a), n represents an integer from 7 to 21. Generally, the smaller n is, the smaller the mesopore diameter of the resulting spherical mesoporous material. On the other hand, the larger n is, the larger the central pore diameter. However, if n is too large, the hydrophobic interactions of the alkyl quaternary ammonium salt become excessive. As a result, layered compounds are formed, and mesoporous materials are not obtained. Ideally, n is 9 to 17, and more ideally, 13 to 17.

[0120] Among the surfactants represented by formula (a), alkyltrimethylammonium halides are ideal. Examples of alkyltrimethylammonium halides include hexadecyltrimethylammonium halide, octadecyltrimethylammonium halide, nonyltrimethylammonium halide, decyltrimethylammonium halide, undecyltrimethylammonium halide, dodecyltrimethylammonium halide, and tetradecylammonium halide.

[0121] Among them, alkyltrimethylammonium bromide or alkyltrimethylammonium chloride are particularly ideal.

[0122] In the synthesis of porous silica particles, one or more alkyl quaternary ammonium salts can be used. However, since the alkyl quaternary ammonium salt serves as a template for forming mesopores in the primary particles, its type greatly influences the shape of the mesopores. To synthesize porous silica particles with more uniform mesopores, the use of an alkyl quaternary ammonium salt is required.

[0123] (4.1.3. Catalyst)

[0124] When silica sources undergo polycondensation, a catalyst is typically added to the reaction solution. In the synthesis of porous silica particles, bases such as sodium hydroxide or ammonia, or acids such as hydrochloric acid, can be used as catalysts.

[0125] (4.1.4. Solvent)

[0126] As a solvent, water, organic solvents such as alcohol, and mixed solvents of water and organic solvents are used.

[0127] As an alcohol, any of the following may be acceptable:

[0128] (1) Monohydric alcohols, such as methanol, ethanol, and propanol.

[0129] (2) Diols, such as ethylene glycol, and

[0130] (3) Triols, such as glycerol.

[0131] (4.1.5. Composition of the reaction solution)

[0132] The composition of the reaction solution affects the external shape and pore structure of the synthesized porous silica particles. In particular, the concentrations of the surfactant and the silica source in the reaction solution significantly influence the average particle size, pore diameter, pore volume, and linearity of the primary particles in the porous silica particles.

[0133] (A. Concentration of surfactant)

[0134] If the surfactant concentration is too low, there will be insufficient surfactant to form the porous structure, and the shape and size of the primary particles may sometimes become uneven. Therefore, the surfactant concentration is ideally above 0.003 mol / L. More ideally, the surfactant concentration is above 0.0035 mol / L, and even more ideally, above 0.004 mol / L.

[0135] On the other hand, if the surfactant concentration is too high, the primary particle diameter may sometimes become too large. Therefore, the surfactant concentration is ideally below 1.0 mol / L. More ideally, the surfactant concentration is below 0.95 mol / L, and even more ideally, below 0.90 mol / L.

[0136] (B. Concentration of silica source)

[0137] If the concentration of the silica source is too low, the surfactant will be excessive, and the primary particles may sometimes become too large. Therefore, the concentration of the silica source is ideally above 0.05 mol / L. More ideally, it is above 0.06 mol / L, and even more ideally, above 0.07 mol / L.

[0138] On the other hand, if the concentration of the silica source is too high, it may sometimes result in sheet-like particles instead of particles with a small aspect ratio. Therefore, the concentration of the silica source is ideally below 1.0 mol / L. More ideally, the concentration is below 0.95 mol / L, and even more ideally, below 0.9 mol / L.

[0139] (C. Catalyst concentration)

[0140] In this invention, the concentration of the catalyst is not particularly limited. Generally, if the catalyst concentration is too low, the particle precipitation rate will decrease. On the other hand, if the catalyst concentration is too high, the particle precipitation rate will increase. Preferably, the optimal catalyst concentration is selected based on the type of silica source, the type of surfactant, the target physical property values, etc.

[0141] For example, when an acid is used as a catalyst, it is preferable to adjust the concentration of the catalyst so that the pH of the reaction solution is below 9. More ideally, the pH of the reaction solution is below 8.5, and even more ideally, it is less than 5.

[0142] On the other hand, when the base is used as a catalyst, it is preferable to adjust the concentration of the catalyst so that the pH of the reaction solution can exceed 7.

[0143] (4.1.6. Reaction conditions)

[0144] Hydrolysis and polycondensation were performed by adding a silica source to a solvent containing a predetermined amount of surfactant. Thus, the surfactant served as a template, and precursor particles containing silica and surfactant were obtained.

[0145] The optimal reaction conditions are selected based on the type of silica source and the particle size of the precursor particles. Typically, the ideal reaction temperature is -20°C to 100°C. More ideally, the reaction temperature is 0°C to 100°C, even more ideally 0°C to 90°C, even more ideally 10°C to 80°C, and even more ideally 35°C to 80°C.

[0146] (4.2. Drying process)

[0147] The precursor particles are then separated from the reaction solution and dried (drying process).

[0148] Drying is applied to remove residual solvent from the precursor particles. There are no particular restrictions on drying conditions, as long as the solvent is removed.

[0149] (4.3. Diameter Enlargement Treatment)

[0150] Next, if necessary, a diameter expansion process (diameter expansion step) can be applied to the dried precursor particles. "Diameter expansion process" refers to the process of increasing the diameter of the mesopores in the primary particles.

[0151] Specifically, the diameter expansion treatment is applied by hydrothermally treating the synthesized precursor particles (particles without surfactant removal) in a solution containing a diameter expander. This treatment can increase the pore diameter of the precursor particles.

[0152] Examples of diameter expanders include:

[0153] (a) Hydrocarbons, such as trimethylbenzene, triethylbenzene, benzene, cyclohexane, triisopropylbenzene, naphthalene, hexane, heptane, octane, nonane, decane, undecane, and dodecane; and

[0154] (b) Acids, such as hydrochloric acid, sulfuric acid and nitric acid.

[0155] The pore diameter is enlarged by hydrothermal treatment in the presence of hydrocarbons. This may be because silica rearrangement occurs when the diameter expander is introduced from the solvent into the pores of more hydrophobic precursor particles.

[0156] Furthermore, hydrothermal treatment in the presence of acids such as hydrochloric acid increased the pore diameter. This is likely because the dissolution / re-precipitation of silica occurs within the primary particles. When manufacturing conditions are optimized, radial pores are formed within the silica. When hydrothermal treatment is applied in the presence of acids, the silica dissolves / re-precipitates, and the radial pores transform into interconnected pores.

[0157] There are no particular restrictions on the conditions for the diameter expansion treatment, as long as the target pore diameter is obtained. Generally, it is preferable to add about 0.05 mol / L to 10 mol / L of diameter expander to the reaction solution and apply hydrothermal treatment at 60°C to 150°C.

[0158] (4.4. Calcination)

[0159] Next, after applying a diameter expansion treatment as needed, the precursor particles are calcined (calcination process). Thus, porous silica particles according to the present invention are obtained.

[0160] Calcination is performed to dehydrate / polymerize the precursor particles containing residual OH groups and to thermally decompose the surfactants remaining in the mesopores. There are no particular restrictions on the calcination conditions, as long as they allow for the dehydration / crystallization and thermal decomposition of the surfactants. Typically, calcination is performed by heating the precursor particles in air at 400°C to 800°C for 1 to 10 hours.

[0161] (5. Method for manufacturing C / SiC composite particles)

[0162] The method for manufacturing C / SiC composite particles according to the present invention includes:

[0163] The first step is to prepare porous silica particles as templates.

[0164] The second step involves precipitating carbon within the pores of the porous silica particles to obtain silica / carbon composite A.

[0165] A third step involves removing a portion of the silicon dioxide from the silicon dioxide / carbon composite A to obtain silicon dioxide / carbon composite B; and

[0166] The fourth step of obtaining C / SiC composite particles according to the present invention involves heat-treating the silicon dioxide / carbon composite B to graphitize the carbon, while simultaneously reacting the silicon dioxide with a portion of the carbon to generate SiC.

[0167] The method for manufacturing C / SiC composite particles according to the present invention may further include, after the fourth step, a fifth step of activation treatment to introduce -OH groups and / or -COOH groups onto the surface of the porous carbon particles.

[0168] (5.1. First Process (Made Template))

[0169] First, porous silica particles are prepared as templates (first step). The details of the method for manufacturing porous silica particles are as described above, and therefore will not be explained.

[0170] (5.2. Second step (carbon precipitation into the pores))

[0171] Next, carbon is precipitated within the pores of the porous silica particles to obtain silica / carbon composite A (second step).

[0172] Specifically, carbon is deposited within the pores in the following manner:

[0173] (a) Introducing the carbon precursor into the pores; and

[0174] (b) The carbon precursor is polymerized and carbonized within the pore.

[0175] (5.2.1. Introduction of carbon precursors)

[0176] "Carbon precursors" refer to substances that can produce carbon through thermal decomposition. Specific examples of such carbon precursors include:

[0177] (1) Thermally polymerizable polymer precursors that are liquid at room temperature (e.g., furfuryl alcohol, aniline, etc.);

[0178] (2) A mixture of aqueous solutions of carbohydrates and acids (e.g., a mixture of monosaccharides, disaccharides, or polysaccharides such as sucrose, xylose, or glucose with acids such as sulfuric acid, hydrochloric acid, nitric acid, or phosphoric acid); and

[0179] (3) A mixture of two curable polymer precursors (e.g., phenol and formalin).

[0180] The polymer precursor can be filled into the pores without solvent dilution, thus generating a relatively large amount of carbon within the pores with a relatively small number of filling operations. Furthermore, it has the advantages of not requiring a polymerization initiator and being easy to handle.

[0181] When using liquid or solution carbon precursors, the larger the amount of liquid or solution adsorbed at one time, the better, and preferably the amount of liquid or solution that fills the entire pore.

[0182] Furthermore, when using a mixture of an aqueous solution of carbohydrates and an acid as a carbon precursor, the amount of acid is preferably the minimum amount that enables the organic matter to polymerize.

[0183] Furthermore, when using a mixture of two-component curable polymer precursors as a carbon precursor, the optimal ratio should be selected based on the type of polymer precursor.

[0184] (5.2.2. Polymerization and carbonization of carbon precursors)

[0185] Next, the polymerized carbon precursor is carbonized within the pores.

[0186] Carbonization of the carbon precursor is achieved by heating porous silica particles containing the carbon precursor to a predetermined temperature in a non-oxidizing atmosphere (e.g., in an inert atmosphere or in a vacuum). Specifically, the ideal heating temperature is above 500°C but below 1200°C. If the heating temperature is below 500°C, the carbonization of the carbon precursor is insufficient. On the other hand, if the heating temperature exceeds 1200°C, the silica and carbon will undesirably react. The optimal heating time is selected based on the heating temperature.

[0187] Here, the amount of carbon generated within the pores can be any amount, as long as it is not less than the amount that allows the carbon particles to retain their shape when a portion of the silica is removed. Therefore, when the amount of carbon generated through a single filling, polymerization, and carbonization is relatively small, it is preferable to repeat these processes multiple times. In this case, the conditions for repeating the processes can be the same or different.

[0188] Furthermore, when the filling, polymerization, and carbonization processes are repeated multiple times, the carbonization process can be carried out at a relatively low temperature, and then, after the final carbonization process, a second carbonization process can be applied at a higher temperature. When the temperature of the final carbonization process is higher than that of the previous carbonization processes, the carbon introduced into the pores in multiple stages is more easily integrated.

[0189] (5.3. Third step (partial removal of template))

[0190] Next, a portion of the silica is removed from silica / carbon composite A (third step). Therefore, silica / carbon composite B with a silica content less than that of silica / carbon composite A is obtained.

[0191] A specific example of a method for removing a portion of silica is:

[0192] (1) A method for heating silica / carbon complex A in an alkaline aqueous solution such as sodium hydroxide; and

[0193] (2) A method for etching silicon dioxide / carbon composite A in hydrofluoric acid aqueous solution.

[0194] In this case, by optimizing the composition and temperature of the aqueous solution, the processing time, etc., a silica / carbon composite B was obtained, in which a portion of the silica remained in the pores of the porous carbon particles.

[0195] The amount of silica remaining in the pores affects the properties of the C / SiC composite particles. Generally, if the amount of residual silica is too small, the amount of SiC particles generated within the pores of the porous carbon particles will be insufficient. On the other hand, if the amount of residual silica is too large, a large amount of carbon will be consumed to generate SiC particles, and this may sometimes damage the pore structure of the porous carbon particles. Therefore, in the third step, it is preferable to remove a portion of the silica / carbon composite A, such that the Si mass ratio of the C / SiC composite particles can exceed 0 mg / m³. 2 Up to 6.8 mg / m³ 2 .

[0196] (5.4. Fourth step (generating SiC particles))

[0197] Next, SiC is generated by heat-treating the silicon dioxide / carbon composite B, graphitizing the carbon, and simultaneously reacting a portion of the silicon dioxide with the carbon (fourth step). Thus, C / SiC composite particles according to the present invention are obtained.

[0198] A heat treatment temperature higher than or equal to the temperature at which SiC particles are formed is acceptable. Generally, if the heat treatment temperature is too low, SiC will not form within a practical processing time. Therefore, the ideal heat treatment temperature is above 1,300°C, and more ideally above 1,400°C.

[0199] On the other hand, if the heat treatment temperature is too high, SiC may sometimes decompose. Therefore, the ideal heat treatment temperature is below 2,300°C, and more ideally below 2,000°C.

[0200] The preferred fourth step is to heat-treat the silicon dioxide / carbon composite B in an inert gas atmosphere or in a vacuum.

[0201] When heat treatment is applied in an inert gas atmosphere, reactions mainly represented by the following equations (1) and (2) are expected to occur. In this case, if more carbon is consumed to generate SiC, the pore structure is more easily destroyed:

[0202] SiO2 + C → SiO + CO . . . (1),

[0203] SiO + 2C → SiC + CO . . . (2).

[0204] On the other hand, when heat treatment is applied in a vacuum, the SiO generated by the reaction in equation (1) is vaporized, and the reaction in equation (2) is less likely to occur. As a result, carbon consumption is reduced, and the amount of SiC generated is also reduced.

[0205] Therefore, it is preferable to select the optimal temperature and atmosphere during heat treatment, taking these factors into account. Particularly preferably, the temperature and atmosphere during heat treatment are selected such that the Si mass ratio of the C / SiC composite particles can exceed 0 mg / m³. 2 Up to 6.8 mg / m³ 2 .

[0206] (5.5. Fifth step (activation treatment))

[0207] Next, an activation treatment (fifth step) is applied, which introduces -OH groups and / or -COOH groups onto the surface of the porous carbon particles, as needed.

[0208] When activation treatment is applied, the surfaces of porous carbon particles (outer surface and inner surface within the pores) become hydrophilic. As a result, it becomes easier to load fine catalyst particles within the pores.

[0209] There are no particular limitations to the activation treatment, as long as it introduces -OH and / or -COOH groups onto the surface of porous carbon particles. An example of an activation treatment method is the oxidation of the carbon particle surface using an oxidizing agent. Examples of oxidizing agents include air, oxygen, ozone, hydrogen peroxide, and nitric acid.

[0210] (6. Effect)

[0211] When a portion of the silica is removed from the silica / carbon composite and the composite is heat-treated at a relatively high temperature, the carbon is graphitized, while the silica reacts with the carbon to form SiC. As a result, a C / SiC composite is obtained in which SiC particles are dispersed on the inner wall surfaces of the pores of porous carbon particles.

[0212] SiC particles have the ability to decompose hydrogen peroxide into harmless water and oxygen. Therefore, when catalyst particles are loaded onto the surface of C / SiC composite particles (e.g., the inner wall of the pores), even if hydrogen peroxide is generated on the surface of the catalyst particles, the SiC particles present in the pores will rapidly decompose the hydrogen peroxide. As a result, electrolyte degradation caused by peroxide free radicals can be suppressed.

[0213] Furthermore, decomposition products generated by electrolyte degradation (e.g., sulfonic acid anions) can be a poisoning source for catalyst particles. In contrast, when catalyst particles are loaded within the pores of C / SiC composite particles, catalyst particle poisoning caused by these poisoning sources can be suppressed.

[0214] When an electrode catalyst in which the catalyst particles are supported in the pores of C / SiC composite particles is used as a cathode catalyst or anode catalyst in a polymer electrolyte fuel cell, the contact between the catalyst particles in the pores and the ionomers in the catalyst layer is avoided, thus resulting in high catalyst activity.

[0215] Furthermore, hydrogen peroxide generated during open circuit and power generation is one of the causes of electrolyte membrane degradation. In the C / SiC composite particles according to the present invention, SiC particles acting as a catalyst for hydrogen peroxide decomposition are distributed on the inner surface of the pores of the porous carbon particles, thus suppressing electrolyte membrane degradation caused by hydrogen peroxide. In addition, the generation of free sulfonic acid anions due to electrolyte degradation is reduced, and catalyst particle poisoning caused by sulfonic acid anions is also reduced. Therefore, the degradation of catalyst activity over time can be suppressed.

[0216] [Example]

[0217] (Examples 1 to 4, Comparative Example 1)

[0218] (1. Manufacturing C / SiC composite particles)

[0219] (1.1.1. Synthesis of template silica)

[0220] Table 1 shows the raw material composition used to synthesize template silica. The template silica was synthesized according to the following procedure.

[0221] [Table 1]

[0222]

[0223]

[0224] First, a 30% by mass aqueous solution of hexadecyltrimethylammonium chloride was used as the surfactant. Predetermined amounts of water, methanol, and ethylene glycol (hereinafter also referred to as "EG") were added to the predetermined amount of the surfactant aqueous solution and stirred. A predetermined amount of 1N sodium hydroxide aqueous solution was added to the mixture as a silica-based hydrolysis catalyst to obtain solution A.

[0225] In addition, a predetermined amount of tetraethoxysilane (hereinafter also referred to as "TEOS") was dispersed as a silica source in a predetermined amount of a mixed solvent of methanol and EG to obtain solution B.

[0226] Solution B was added to solution A and stirred at room temperature for 6 hours. After standing overnight, the solution was filtered by suction. The filter residue was dispersed in distilled water and washed by ultrasonic treatment. The filter residue was further recovered by suction filtration and dried overnight in a desiccator at 45°C.

[0227] Next, to adjust the pore diameter, the dried silica precursor was dispersed in 1N sulfuric acid. The solution was then placed in a pressure vessel and hydrothermally treated at 120°C for 68 hours. Subsequently, after filtration and washing similarly to the above, the silica precursor was calcined in atmospheric atmosphere by heating from room temperature to 550°C for two hours and holding at 550°C for six hours to obtain template silica.

[0228] (1.1.2. Carbon precipitation)

[0229] Weigh template silica into a PFA container, add an amount of furfuryl alcohol (hereinafter also referred to as "F-AL") equivalent to the pore volume obtained by measuring nitrogen adsorption, and seal the container. After filling the pores in the template silica with F-AL by shaking the container, polymerize the F-AL by heating the template silica in an oven at 150°C for 18 hours. Furthermore, carbonize the F-AL using a tube furnace by heating from room temperature to 500°C over two hours at a nitrogen flow rate (1 L / min) and holding at 500°C for six hours.

[0230] After the first carbonization, a similar treatment was performed again with half the amount of F-AL. However, the heat treatment was carried out by heating at 500°C for six hours, followed by a further heating to 900°C for two hours and holding at 900°C for six hours.

[0231] Finally, to partially remove the template silica, a predetermined concentration of hydrofluoric acid (HF) or sodium hydroxide (NaOH) is added to the carbonized sample, and the mixture is stirred for three hours. Here, to produce carbons with different residual Si contents, the template silica is partially removed while varying the processing conditions (HF or NaOH concentration in the processing solution and / or the temperature of the processing solution).

[0232] After partial removal of the template silica, the filter residue was recovered by suction filtration. Additionally, the filter residue was washed with water by ultrasonic treatment, recovered again by suction filtration, and dried overnight in a dryer at 45°C. Table 2 shows the residual Si content (X-ray fluorescence analysis values) after partial removal of the template silica.

[0233] [Table 2]

[0234]

[0235] (1.1.3. Graphitization of carbon)

[0236] The obtained silica / carbon composite was subjected to graphitization treatment to obtain C / SiC composite particles. The graphitization treatment temperature was set to 1,900°C. Furthermore, the atmosphere during the graphitization treatment was either an Ar atmosphere (Examples 1 to 3 and Comparative Example 1) or a vacuum (Example 4).

[0237] (2. Testing Method)

[0238] (2.1. Nitrogen adsorption isotherm)

[0239] To investigate the differences in pore structure after graphitization relative to the amount of residual Si, nitrogen adsorption isotherms of C / SiC composite particles were measured and pore distribution was obtained by BJH analysis.

[0240] (2.2. Si mass ratio)

[0241] X-ray fluorescence analysis (XRF) was applied to C / SiC composite particles and the Si mass ratio was calculated.

[0242] (3. Results)

[0243] (3.1. Nitrogen adsorption isotherm)

[0244] Figure 1 The pore diameter distribution of the C / SiC composite particles obtained in Examples 1 and 2, and Comparative Example 1, is shown. In Examples 1 and 2, pores with diameters of 3 nm to 4 nm remained. On the other hand, in Comparative Example 1, pores with diameters of 3 nm to 4 nm disappeared. This may be because the pore walls of the porous carbon particles reacted with a large amount of residual silica, disrupting the pore structure.

[0245] (3.2. Si mass ratio)

[0246] Figure 2 The relationship between the Si mass ratio (Si mass per unit surface area of ​​the C / SiC composite particle) and the specific surface area is shown. From... Figure 2 It was found that the specific surface area of ​​the C / SiC composite particles decreased with increasing Si mass ratio. Furthermore, it was discovered that to obtain the required 800m² catalyst support... 2 For a specific surface area of ​​ / g or higher, the Si mass ratio should be 6.8 mg / m². 2 the following.

[0247] (Examples 3 and 4, Comparative Example 2)

[0248] (1. Prototype manufacturing)

[0249] (1.1. Manufacturing electrode catalysts)

[0250] As catalyst supports, those prepared by air activation of the C / SiC composite particles obtained in Examples 3 and 4 were used. The air activation conditions were 480°C for 1 hour. Furthermore, for comparison, commercially available porous carbon was used directly as the catalyst support (Comparative Example 2).

[0251] Electrode catalysts are obtained by loading catalyst particles onto the surface of a catalyst support. Platinum alloy catalysts are used as the catalyst particles. The amount of each loaded catalyst is set to 40% by mass.

[0252] (1.2. Manufacturing the catalyst layer)

[0253] The obtained electrode catalyst and ionomer were each dispersed in a solvent to prepare catalyst ink. The catalyst ink was then coated onto a polytetrafluoroethylene sheet using a coating device and dried in the atmosphere to obtain a catalyst layer.

[0254] (1.3. Manufacturing MEA)

[0255] MEA was manufactured by hot pressing the cathode catalyst layer and the anode catalyst layer onto the electrolyte membrane.

[0256] Here, a fluorinated polymer membrane (NR 211) is used as the electrolyte membrane. The catalyst layer manufactured in (1.2.) is used as the cathode catalyst layer. Furthermore, a catalyst layer manufactured using a commercially available Pt / C catalyst and an ionomer is used as the anode catalyst layer.

[0257] (2. Testing Method)

[0258] (2.1. Si mass ratio)

[0259] X-ray fluorescence analysis (XRF) was applied to the C / SiC composite particles after catalyst loading, and the Si mass ratio was calculated.

[0260] (2.2. Battery Evaluation)

[0261] Cell units were fabricated using the obtained MEA. After conditioning the cell units, the initial IV characteristics and electrode characteristics (cyclic voltammograms) were evaluated. Next, durability testing was applied, and the performance after durability testing was evaluated. Evaluation details are as follows.

[0262] (2.2.1. Unit cell)

[0263] Cell units are manufactured by arranging diffusion layers and current collectors on both sides of the MEA. Details of the cell unit are as follows:

[0264] Battery: for 1cm 2 Square batteries,

[0265] Diffusion layer: carbon paper (with a multi-microporous layer),

[0266] Current collector: A gold-plated copper plate with an integrated flow path.

[0267] (2.2.2. Conditioning Procedure)

[0268] Conditioning of the cell unit is performed via voltage scanning. The conditions are as follows:

[0269] Battery temperature / relative humidity (both electrodes): 60℃ / 80% RH

[0270] Air electrode gas: air, 1,000 mL / min, atmospheric pressure.

[0271] Fuel electrode gas: H2, 500 mL / min, atmospheric pressure.

[0272] Voltage scan: Apply a scan at 50mV / second from open circuit voltage to -0.1V and repeat until the IV curve no longer changes.

[0273] (2.2.3. Power generation performance evaluation)

[0274] The IV curve was determined by voltage scanning. The measurement conditions were as follows:

[0275] Battery temperature / relative humidity (both electrodes): 60℃ / 80% RH

[0276] Air electrode gas: air, 1,000 mL / min, atmospheric pressure.

[0277] Fuel electrode gas: H2, 500 mL / min, atmospheric pressure.

[0278] Voltage scan: Apply three scans at 10mV / sec from open circuit voltage to -0.1V (use the data from the third scan).

[0279] (2.2.4. Cyclic voltammogram (CV) measurement)

[0280] CV was measured under the following conditions:

[0281] Battery temperature / relative humidity (both electrodes): 60℃ / 80% RH

[0282] Air electrode gas: N2, 1,000 mL / min

[0283] Fuel electrode gas: H2, 500 mL / min

[0284] Voltage range: 115mV to 1,000mV

[0285] Scanning speed: 50mV / second

[0286] Number of loops: 10.

[0287] (2.2.5. Durability Test)

[0288] Apply open-circuit testing and wet / dry testing alternately under the following conditions:

[0289] (A. Open-circuit test conditions)

[0290] Battery temperature / relative humidity (both electrodes): 82℃ / 30% RH

[0291] Air electrode gas: air, 400 mL / min

[0292] Fuel electrode gas: H2, 100 mL / min

[0293] (B. Dry and wet test)

[0294] Battery temperature / relative humidity (both electrodes): Cycle between 60°C / 80% RH humidification and 60°C / no humidification for 1 minute.

[0295] Air electrode gas: N2, 500 mL / min

[0296] Fuel electrode gas: N2, 500 mL / min.

[0297] (3. Results)

[0298] (3.1.IV Characteristics)

[0299] Figure 3 A, Figure 3 B and Figure 3 C shows the IV characteristics of the cell cells obtained in Examples 3 and 4 and Comparative Example 2 before and after the durability test. Figure 4 The relationship between the Si mass ratio (the mass of Si per unit surface area of ​​the C / SiC composite particles) and the activity retention rate is shown. "Activity retention rate" refers to the ratio of the mass activity after the durability test (the value obtained by dividing the current value at 0.9V in the IV characteristic by the mass of Pt) to the mass activity before the durability test.

[0300] Furthermore, Table 3 shows the Si mass ratio of the C / SiC composite particles containing catalyst particles obtained in Examples 3 and 4. Figure 3 and Figure 4 As shown in Table 3, the decrease in activity after durability testing decreased with increasing Si mass ratio. This may be because the SiC present within the pores of the porous carbon particles decomposes hydrogen peroxide and contributes to improved durability.

[0301] [Table 3]

[0302] Example 3 Example 4 Si mass ratio <![CDATA[1.19mg / m 2 ]]> <![CDATA[0.17mg / m 2 ]]>

[0303] (3.2.CV)

[0304] Figure 5 A, Figure 5 B and Figure 5 C shows the CVs of the cell cells obtained in Examples 3 and 4, and Comparative Example 2, respectively, during the durability test. Figure 5 The table shows the CV (described as "after 27 hours") for accumulated OC time of 19 to 27 hours and the CV (described as "after 69 hours") for accumulated OC time of 63 to 69 hours. Figure 5 Discover:

[0305] (a) Compared to when the cumulative OC time was 19 to 27 hours, when the cumulative OC time was 63 to 69 hours, the increase in Pt oxidation current above 0.7V of CV shifted to a higher potential side; and

[0306] (b) As the Si mass ratio decreases, the offset increases.

[0307] The reason for the oxidation current shift is believed to be the adsorption of free sulfonic acid anions generated during electrolyte degradation in durability testing onto the Pt surface. This suggests that a lower Si mass ratio makes electrolyte degradation more likely.

[0308] The results show that as the Si mass ratio increases, catalyst poisoning caused by electrolyte degradation is suppressed to a greater extent.

[0309] The embodiments of the present invention have been described in detail above, but the present invention is not limited to the embodiments described above, and various modifications can be made without departing from the spirit of the present invention.

[0310] [Industrial Applicability]

[0311] The C / SiC composite particles according to the present invention can be used as catalyst supports for air electrode catalyst layers or fuel electrode catalyst layers in polymer electrolyte fuel cells.

Claims

1. A C / SiC composite particle, said C / SiC composite particle comprising: Porous carbon particles; and SiC particles distributed on the inner wall surface of the pores of the porous carbon particles. The Si mass ratio is greater than 0 mg / m 2 Up to 6.8 mg / m³ 2 The "Si mass ratio" refers to the ratio of the mass of Si per unit surface area of ​​the C / SiC composite particles. The C / SiC composite particles are prepared by a method comprising the following steps: The first step is to prepare porous silica particles as templates. The second step involves precipitating carbon within the pores of the porous silica particles to obtain silica / carbon composite A. A third step involves removing a portion of the silicon dioxide from the silicon dioxide / carbon composite A to obtain silicon dioxide / carbon composite B; and The fourth step involves heat-treating the silicon dioxide / carbon composite B to graphitize the carbon and simultaneously reacting the silicon dioxide with a portion of the carbon to generate SiC, thereby obtaining the C / SiC composite particles.

2. The C / SiC composite particles according to claim 1, wherein the modal diameter of the pores of the porous carbon particles is between 1.5 nm and 5.0 nm.

3. The C / SiC composite particles according to claim 1, wherein the average primary particle diameter of the SiC particles is less than or equal to the modal diameter of the pores of the porous carbon particles.

4. The C / SiC composite particles according to claim 1, wherein the average primary particle diameter is 50 nm or more and less than 200 nm.

5. The C / SiC composite particles according to claim 1, wherein the pore volume is 0.5 cc / g or more to 2.0 cc / g or less.

6. The C / SiC composite particles according to claim 1, wherein the C / SiC composite particles further comprise -OH groups and / or -COOH groups introduced on the surface of the porous carbon particles.

7. A method for manufacturing C / SiC composite particles, the method comprising: The first step is to prepare porous silica particles as templates. The second step involves precipitating carbon within the pores of the porous silica particles to obtain silica / carbon composite A. A third step involves removing a portion of the silicon dioxide from the silicon dioxide / carbon composite A to obtain silicon dioxide / carbon composite B; and The fourth step involves heat-treating the silicon dioxide / carbon composite B to graphitize the carbon and simultaneously reacting the silicon dioxide with a portion of the carbon to generate SiC, thereby obtaining the C / SiC composite particles according to claim 1.

8. The method for manufacturing a C / SiC composite according to claim 7, wherein the third step comprises removing a portion of the silicon dioxide from the silicon dioxide / carbon composite A such that the Si mass ratio of the C / SiC composite particles is greater than 0 mg / m³. 2 Up to 6.8 mg / m³ 2 The process.

9. The method for manufacturing C / SiC composite particles according to claim 7, wherein the fourth step includes a step of heat-treating the silicon dioxide / carbon composite B at a temperature above 1,300°C to below 2,300°C.

10. The method for manufacturing C / SiC composite particles according to claim 7, wherein the fourth step includes a step of heat-treating the silicon dioxide / carbon composite B under an inert gas atmosphere or under vacuum.

11. The method for manufacturing C / SiC composite particles according to claim 7, wherein the method further comprises a fifth step after the fourth step, the fifth step being an activation treatment that introduces -OH groups and / or -COOH groups onto the surface of the porous carbon particles.

12. An electrode catalyst, said electrode catalyst comprising: The C / SiC composite particles according to claim 1; and Catalyst particles loaded on the surface of the C / SiC composite particles.

13. A polymer electrolyte fuel cell, the polymer electrolyte fuel cell comprising the electrode catalyst according to claim 12 as a cathode catalyst or an anode catalyst.

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