Carbon support, catalyst for fuel cells, catalyst layer for fuel cells, and method for producing the carbon support

Abstract

The present invention provides a carbon carrier for a fuel cell catalyst, a catalyst for a fuel cell, a catalyst layer for a fuel cell, and a method for manufacturing a carbon carrier that can improve the power generation performance of a fuel cell. A carbon carrier for a fuel cell catalyst, wherein the thickness of the carbon wall of the carbon carrier derived from the three-dimensional pore structure of the silica mold obtained by measuring the pore volume of the silica mold by the nitrogen adsorption analysis method is 3.3 nm or more and 11.2 nm or less, and the carbon wall content is greater than 60.3 ml / g and less than 190.8 ml / g.

Description

Technology Field

[0001] The present disclosure relates to a carbon carrier, a catalyst for a fuel cell, a catalyst layer for a fuel cell, and a method for manufacturing a carbon carrier. Background Technology

[0002] Various studies are being conducted on fuel cells.

[0003] For example, Patent Document 1 discloses a mesoporous carbon that is low-chargeable and also low-cost, a method for manufacturing the same, and a solid polymer fuel cell using the same.

[0004] Patent Document 2 discloses a monodisperse spherical carbon porous body having a diameter, pore diameter, and specific surface area within a specific range and suitable as a catalyst support for the catalyst layer on the air electrode side of a solid polymer fuel cell, and a solid polymer fuel cell using the same.

[0005] Patent document 3 discloses spherical mesoporous carbon having a central pore diameter exceeding 2 nm and a method for manufacturing the same.

[0006] Patent document 4 discloses a catalyst layer that has high water retention and obtains high battery performance even under low humidity environments, and a solid polymer fuel cell using the same. Prior art literature

[0007] Japanese Patent Publication No. 2021-084852 Japanese Patent Publication No. 2019-169317 Japanese Patent Publication No. 2010-265125 Japanese Patent Publication No. 2007-220414 The problem to be solved

[0008] In order to achieve high power generation performance (efficiency point performance) in the low current density region, the carbon carrier needs to have a three-dimensional pore structure.

[0009] In conventional technology, specifications regarding the average primary particle size, average pore diameter, and pore volume of carbon are established, but specifications regarding the carbon wall content due to nitrogen adsorption, the carbon carrier ratio due to 3D-TEM, and the average diameter of the constriction within the pore are not established, so in conventional technology, the power generation performance of the fuel cell may be insufficient.

[0010] The present disclosure is made in consideration of the above circumstances and aims primarily to provide a carbon carrier for a fuel cell catalyst, a catalyst for a fuel cell, a catalyst layer for a fuel cell, and a method for manufacturing a carbon carrier that can improve the power generation performance of a fuel cell. means of solving the problem

[0011] The carbon carrier of the present disclosure is a carbon carrier having pores, and

[0012] The carbon carrier is a carbon carrier for a fuel cell catalyst, wherein the thickness of the carbon wall of the carbon carrier derived from the three-dimensional pore structure of the silica mold obtained by measuring the pore volume of the silica mold by the nitrogen adsorption analysis method is 3.3 nm or more and 11.2 nm or less, and the carbon wall content is greater than 60.3 ml / g and less than 190.8 ml / g.

[0013] In the carbon carrier of the present disclosure, the carbon carrier ratio calculated by 3D-TEM observation may be greater than 36% and less than 67%.

[0014] In the carbon carrier of the present disclosure, the carbon carrier has at least one constriction within the pore,

[0015] The average diameter of the constriction of the above pores calculated by 3D-TEM observation may be 1.9 nm or more and less than 2.5 nm.

[0016] In the carbon carrier of the present disclosure, the carbon wall content is 61.5 ml / g or more and 168.4 ml / g or less, and

[0017] The above carbon carrier ratio is 46% or more and 57% or less, and

[0018] The average diameter of the constriction of the above pore may be 1.9 nm or more and 2.0 nm or less.

[0019] The fuel cell catalyst of the present disclosure is a fuel cell catalyst comprising a carbon support supporting a metal catalyst, and

[0020] The above carbon carrier is the carbon carrier described above.

[0021] The catalyst layer for a fuel cell of the present disclosure comprises the fuel cell catalyst described above.

[0022] The method for manufacturing a carbon carrier of the present disclosure is a method for manufacturing a carbon carrier described above, wherein a porous silica is used as a mold. Effects of the invention

[0023] According to the present disclosure, the power generation performance of a fuel cell can be improved. Brief explanation of the drawing

[0024] Figure 1a is a planar TEM image of the carbon carrier of Example 1. Figure 1b is a three-dimensional reconstruction of Figure 1a. Figure 2a is a planar TEM image of the carbon carrier of Comparative Example 1. Figure 2b is a three-dimensional reconstruction of Figure 2a. Specific details for implementing the invention

[0025] Embodiments according to the present disclosure are described below. Furthermore, regarding matters other than those specifically mentioned in this specification, matters necessary for the implementation of the present disclosure (e.g., general configurations and manufacturing processes of carbon carriers, etc., that do not characterize the present disclosure) may be understood as design matters by those skilled in the art based on prior art in the relevant field. The present disclosure may be implemented based on the contents disclosed in this specification and common technical knowledge in the relevant field.

[0026] In addition, dimensional relationships (length, width, thickness, etc.) in drawings do not reflect actual dimensional relationships.

[0027] In this specification, the term "to" indicating a numerical range is used to mean including the values ​​described before and after it as lower and upper limits.

[0028] In addition, any combination of upper and lower limits can be adopted for the numerical range.

[0029] 1. Carbon carrier

[0030] The carbon carrier of the present disclosure is a carbon carrier having pores, and

[0031] The carbon carrier is a carbon carrier for a fuel cell catalyst, wherein the thickness of the carbon wall of the carbon carrier derived from the three-dimensional pore structure of the silica mold obtained by measuring the pore volume of the silica mold by the nitrogen adsorption analysis method is 3.3 nm or more and 11.2 nm or less, and the carbon wall content is greater than 60.3 ml / g and less than 190.8 ml / g.

[0032] According to the present disclosure, a carbon carrier is obtained in which the thickness of the carbon wall and the carbon wall content are controlled by using silica having a three-dimensional pore structure as a mold.

[0033] The carbon carrier of the present disclosure has a carbon wall with a predetermined thickness and a three-dimensional pore structure containing a predetermined amount of carbon wall, thereby making it possible to uniformly support a metal catalyst within the pores of the carbon carrier. By using the carbon carrier with the uniformly supported metal catalyst as a catalyst for a fuel cell, the power generation performance of the fuel cell can be improved, and in particular, the efficiency point performance (power generation performance in the low current density region) can be improved.

[0034] The carbon carrier of the present disclosure may have pores and be a porous body.

[0035] The pores may be mesoporous. The carbon carrier may be mesoporous carbon.

[0036] The average pore diameter of the mesopore may be 2 nm to 50 nm. The average pore diameter is obtained by measuring the pore diameters of a plurality of randomly selected pores and calculating the average value thereof. The average pore diameter can be measured using a 3D-TEM (transmission electron microscope), etc.

[0037] In the carbon carrier of the present disclosure, the thickness of the carbon wall of the carbon carrier derived from the three-dimensional pore structure of the silica mold obtained by measuring the pore volume of the silica mold by the nitrogen adsorption analysis method is 3.3 nm or more and 11.2 nm or less, and the carbon wall content is greater than 60.3 ml / g and less than 190.8 ml / g. The carbon wall content may be 61.5 ml / g or more and 168.4 ml / g or less from the viewpoint of further improving the power generation performance of the fuel cell.

[0038] The carbon carrier of the present disclosure is obtained by using silica having a three-dimensional pore structure as a template, introducing a carbon source into the pores of the silica to obtain a silica-carbon composite, carbonizing the carbon source in the silica-carbon composite to remove the silica in the silica-carbon composite. Therefore, the structure of the silica is transferred to the carbon carrier of the present disclosure.

[0039] Accordingly, the thickness of the carbon wall of the carbon carrier can be derived by measuring the pore diameter of the three-dimensional pore structure of the silica mold, which is obtained by measuring the pore volume of the silica mold by the nitrogen adsorption analysis method. The thickness of the carbon wall can be derived by measuring the pore diameters of a plurality of randomly selected pores of the three-dimensional pore structure of the silica mold and calculating the average value thereof.

[0040] In addition, in the present disclosure, the term "carbon wall" is synonymous with the so-called porous wall and refers to a carbon porous wall.

[0041] In addition, the carbon wall content can be derived by measuring the pore volume of the three-dimensional pore structure of the silica mold obtained by measuring the pore volume of the silica mold by the nitrogen adsorption analysis method. The pore volume of the three-dimensional pore structure of the silica mold may be calculated, for example, from the difference between the adsorption amount when the relative nitrogen adsorption pressure of the silica pores is 0.8 and the adsorption amount when it is 0.4.

[0042] In addition, in the present disclosure, carbon wall content refers to the volume of carbon walls per 1g of carbon carrier (unit: ml / g).

[0043] In the carbon carrier of the present disclosure, the carbon carrier ratio calculated by 3D-TEM observation may be greater than 36% and less than 67%, and may be greater than 46% and less than 57% from the view of further improving the power generation performance of the fuel cell.

[0044] In addition, in the present disclosure, the carbon carrier ratio refers to the ratio of the area occupied by carbon when the entire area occupied by the carbon carrier is considered to be 100%, and the area other than the area occupied by carbon is occupied by voids.

[0045] The porosity of the carbon carrier may be, for example, 33% to 64%.

[0046] The carbon carrier may have at least one constriction within the pore.

[0047] The diameter of the constriction is smaller than the diameter of the workpiece.

[0048] In the carbon carrier of the present disclosure, the average diameter of the constriction portion of the pores calculated by 3D-TEM observation may be 1.9 nm or more and less than 2.5 nm, and may be 1.9 nm or more and less than 2.0 nm from the viewpoint of further improving the power generation performance of the fuel cell. The average diameter of the constriction portion is an average value obtained by measuring the diameters of a plurality of randomly selected constriction portions.

[0049] The carbon carrier may be a carbon carrier particle with a particulate shape.

[0050] The particle size of the carbon carrier particles is not particularly limited as long as it is larger than the pore diameter, and for example, it may be 4 nm or larger and 100 nm or smaller.

[0051] The particle size of carbon carrier particles can be measured using 3D-TEM, etc.

[0052] 2. Method for manufacturing a carbon carrier

[0053] The method for manufacturing a carbon carrier of the present disclosure involves producing a pore-forming silica as a mold.

[0054] The method for manufacturing a carbon carrier of the present disclosure may include: (1) a step of preparing silica having pores as a mold; (2) a step of precipitating carbon within the pores of the silica to obtain a silica-carbon composite; and (3) a step of removing silica from the silica-carbon composite to obtain a carbon carrier.

[0055] (1) Process for preparing silica

[0056] The silica being prepared has pores and also has a three-dimensional pore structure. The silica may be a porous material or a mesoporous silica.

[0057] The three-dimensional processing structure may be a performance structure (random structure) described later, etc.

[0058] For silica, commercially available silica may be used, or synthetic silica may be used.

[0059] A method for manufacturing silica comprises a polymerization process in which a silica source is polycondensed to obtain precursor particles in a reaction solution containing a silica source, a surfactant, and a catalyst, a drying process in which the precursor particles are separated from the reaction solution and dried, and a calcination process in which the precursor particles are calcined to obtain silica particles having pores. When manufacturing silica, if the concentration of the surfactant and the concentration of the silica source in the reaction solution are each limited to a specific range, mesoporous silica having a continuous structure and having pore diameters, pore volumes, etc., within a specific range is obtained. Furthermore, if such mesoporous silica having a continuous structure is used in a mold, mesoporous carbon having a continuous structure is obtained. Here, "continuous structure" refers to a structure in which primary particles are connected in a string-bead pattern. The primary particles constituting the continuous structure have pores within them. In the continuous structure, since primary particles having pores are connected, interconnected pores may be formed in which the pores of the primary particles are connected. The shape of the primary particle is usually not perfectly spherical, but has a distorted shape with an aspect ratio of about 1.1 to 3, and in the continuous structure, one or more constrictions having a diameter smaller than the diameter of the pore may be formed within the connected pore.

[0060] (1-1) Polymerization Process

[0061] First, precursor particles are obtained by condensing the silica source in a reaction solution containing a silica source, a surfactant, and a catalyst.

[0062] The type of silica source is not particularly limited. As for silica sources, for example

[0063] (a) Tetraalkoxysilanes such as tetramethoxysilane, tetraethoxysilane, tetraisopropoxysilane, tetrabutoxysilane, dimethoxydiethoxysilane, tetraethyleneglycoxysilane, etc.

[0064] (b) Trialkoxysilanes such as 3-mercaptopropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-(2-aminoethyl)aminopropyltrimethoxysilane, etc.

[0065] There are others.

[0066] As for the silica source, any one of these may be used, or two or more may be used in combination.

[0067] If the concentration of the silica source is too low, the precipitation rate of the precursor particles slows down, and a structure in which the primary particles are connected is not obtained. Therefore, the concentration of the silica source may be 0.05 mol / L or higher.

[0068] Meanwhile, if the concentration of the silica source is too high, the precipitation rate of the precursor particles becomes too fast, and the primary particle size easily exceeds 300 nm. Therefore, the concentration of the silica source may be 1.0 mol / L or less.

[0069] In the case of polycondensing silica source in a reaction solution, if a surfactant is added to the reaction solution, the surfactant forms micelles in the reaction solution. Since hydrophilic groups are clustered around the micelles, silica source is adsorbed onto the surface of the micelles. Furthermore, the micelles with adsorbed silica source self-organize in the reaction solution, and the silica source undergoes polycondensation. As a result, pores attributable to the micelles are formed inside the primary particles. The size of the pores can be controlled, for example, from 1 to 50 nm, mainly depending on the molecular length of the surfactant.

[0070] Examples of surfactants include hexadecyltrimethylammonium halide, octadecyltrimethylammonium halide, nonyltrimethylammonium halide, decyltrimethylammonium halide, undecyltrimethylammonium halide, and dodecyltrimethylammonium halide.

[0071] When synthesizing porous silica, one type of surfactant may be used, or two or more types may be used. However, since the surfactant serves as a template for forming pores within the primary particles, its type has a significant effect on the shape of the pores. From the perspective of synthesizing silica particles with more uniform pores, one type of surfactant may be used.

[0072] If the concentration of the surfactant is too low, the precipitation rate of the precursor particles slows down, and a structure in which the primary particles are connected is not obtained. Therefore, the concentration of the surfactant may be 0.03 mol / L or higher.

[0073] On the other hand, if the concentration of the surfactant is too high, the precipitation rate of the precursor particles becomes too fast, and the primary particle size easily exceeds 300 nm. Therefore, the concentration of the surfactant may be 1.0 mol / L or less.

[0074] When polycondensing silica sources, a catalyst is typically added to the reaction solution. Examples of catalysts include alkalis such as sodium hydroxide and ammonia water.

[0075] The catalyst concentration is not specifically limited. Generally, if the catalyst concentration is too low, the precipitation rate of precursor particles slows down. On the other hand, if the catalyst concentration is too high, the precipitation rate of precursor particles accelerates. The optimal catalyst concentration may be selected based on the type of silica source, the type of surfactant, and the target physical properties.

[0076] As solvents, water, organic solvents, and mixed solvents of water and organic solvents are used.

[0077] Examples of organic solvents include monohydric alcohols such as methanol, ethanol, and propanol, dihydric alcohols such as ethylene glycol, and trihydric alcohols such as glycerin.

[0078] When using a mixed solvent of water and an organic solvent, the content of the organic solvent in the mixed solvent can be arbitrarily selected depending on the purpose. Generally, adding an appropriate amount of organic solvent to the solvent facilitates the control of the particle size and particle size distribution of silica particles.

[0079] A silica source is added to a solvent containing a predetermined amount of surfactant to perform hydrolysis and polycondensation. Accordingly, the surfactant functions as a template to obtain precursor particles containing silica and surfactant.

[0080] The reaction conditions are selected based on the type of silica source and the particle size of the precursor particles, etc. Generally, the reaction temperature may be between -20℃ and 100℃.

[0081] (1-2) Drying process

[0082] Next, the precursor particles are separated from the reaction solution and dried.

[0083] Drying is performed to remove the solvent remaining within the precursor particles. The drying conditions are not particularly limited, as long as the solvent can be removed.

[0084] (1-3) Diameter enlargement process

[0085] Next, if necessary, a diameter enlargement treatment may be performed on the dried precursor particles. "Diameter enlargement treatment" refers to a treatment that enlarges the pore diameter within the primary particles.

[0086] Specifically, the diameter enlargement treatment is performed by hydrothermally treating synthesized precursor particles (without surfactant removed) in a solution containing a diameter enlarger. Through this treatment, the pore diameter of the precursor particles can be enlarged.

[0087] Examples of diameter-enhancing agents include (a) hydrocarbons such as trimethylbenzene, triethylbenzene, benzene, cyclohexane, triisopropylbenzene, naphthalene, hexane, heptane, octane, nonane, decane, undecane, and dodecane, and (b) acids such as hydrochloric acid, sulfuric acid, and nitric acid.

[0088] The expansion of pore diameter by hydrothermal treatment in the presence of hydrocarbons is thought to be due to the rearrangement of silica when a diameter expanding agent is introduced from the solvent into the pores of the more hydrophobic precursor particles.

[0089] In addition, it is thought that the expansion of pore diameter by hydrothermal treatment in the presence of an acid such as hydrochloric acid is due to the dissolution and reprecipitation of silica within the primary particles. When manufacturing conditions are optimized, radial pores are formed within the silica. When this is hydrothermally treated in the presence of an acid, dissolution and reprecipitation of silica occur, and the radial pores are converted into interconnected pores.

[0090] The conditions for the diameter enlargement treatment are not particularly limited as long as the desired pore diameter is obtained. Typically, a diameter enlarger of 0.05 mol / L to 10 mol / L is added to the reaction solution, and hydrothermal treatment is performed at 60°C to 150°C. The pore diameter obtained may be controlled by controlling the hydrothermal temperature.

[0091] (1-4) Sintering process

[0092] Next, the precursor particles are calcined after performing a diameter enlargement treatment as needed. Accordingly, pore-forming silica particles are obtained.

[0093] Calcination is performed to dehydrate and crystallize precursor particles containing residual OH groups and to thermally decompose surfactants remaining in the pores. The calcination conditions are not particularly limited as long as dehydration, crystallization, and thermal decomposition of surfactants are possible. Calcination is typically performed by heating in an atmosphere at 400°C to 700°C for 1 to 10 hours.

[0094] (2) Process for obtaining a silica-carbon composite

[0095] The method of obtaining a silica-carbon composite by precipitating carbon within the pores of silica is not particularly limited, and conventionally known methods may be appropriately employed.

[0096] Specifically, the precipitation of carbon into the pores is carried out by introducing a carbon precursor into the pores and polymerizing and carbonizing the carbon precursor within the pores.

[0097] "Carbon precursor" refers to a substance capable of generating carbon through thermal decomposition. Specifically, examples of such carbon precursors include polymer precursors that are liquid at room temperature and are also thermally polymerizable (e.g., furfuryl alcohol and aniline), a mixture of an aqueous solution of a carbohydrate and an acid (e.g., a mixture of a carbohydrate such as monosaccharides, disaccharides, and polysaccharides such as sucrose, xylose, and glucose, and an acid such as sulfuric acid, hydrochloric acid, nitric acid, and phosphoric acid), and a mixture of two-component curing polymer precursors (e.g., phenol and formalin).

[0098] When using a carbon precursor in liquid or solution form, the amount of liquid or solution adsorbed per cycle should be as large as possible, and it may be an amount that fills the entire pore with liquid or solution.

[0099] In addition, when using a mixture of an aqueous solution of carbohydrate and an acid as a carbon precursor, the amount of acid may be the minimum amount necessary to polymerize the organic material.

[0100] In addition, when using a mixture of two-component curing polymer precursors as a carbon precursor, the ratio is selected to be optimal depending on the type of polymer precursor.

[0101] Next, the polymerized carbon precursor is carbonized within the pores.

[0102] Carbonization of the carbon precursor is carried out by heating silica containing the carbon precursor to a predetermined temperature in a non-oxidizing atmosphere (e.g., in an inert atmosphere and vacuum). Specifically, the heating temperature may be 500°C or higher and 1200°C or lower. If the heating temperature is less than 500°C, the carbonization of the carbon precursor becomes insufficient. On the other hand, if the heating temperature exceeds 1200°C, the silica reacts with the carbon. The heating time is selected as an optimal time depending on the heating temperature.

[0103] (3) Silica removal process

[0104] Next, the silica template is removed from the silica-carbon composite. Accordingly, a porous carbon carrier is obtained.

[0105] The method for removing silica from a silica-carbon composite is not particularly limited, and conventionally known methods may be appropriately employed. Examples of methods for removing silica from a silica-carbon composite include heating the silica-carbon composite in an alkaline aqueous solution such as sodium hydroxide to dissolve and remove the silica, and etching the silica in the silica-carbon composite with an aqueous hydrofluoric acid solution.

[0106] (4) Graphitization process

[0107] Next, if necessary, the carbon carrier is heat-treated at a temperature higher than 1500°C. When carbonizing a carbon source within the pores of silica, the heat treatment temperature must be kept low to suppress the reaction between silica and carbon. Consequently, the degree of graphitization of the carbon carrier after carbonization treatment is low. To obtain a high degree of graphitization, it is desirable to heat-treat the carbon carrier at a high temperature after removing the mold.

[0108] If the heat treatment temperature is too low, graphitization becomes insufficient. Therefore, the heat treatment temperature may exceed 1500℃.

[0109] Meanwhile, even if the heat treatment temperature is raised higher than necessary, there is no difference in effect and no benefit. Therefore, the heat treatment temperature may be 2300℃ or lower.

[0110] 3. Catalysts for Fuel Cells

[0111] The fuel cell catalyst of the present disclosure is a fuel cell catalyst comprising a carbon carrier supporting a metal catalyst, wherein the carbon carrier is the carbon carrier described above.

[0112] A metal catalyst is supported on a carbon carrier of the present disclosure.

[0113] Examples of metal catalysts include platinum and platinum alloys. As a platinum alloy, it may be an alloy comprising one or more metals selected from the group consisting of platinum and cobalt, nickel, iron, manganese, copper, titanium, tungsten, tin, gallium, zirconium, chromium, gadolinium, terbium, ytterbium, hafnium, and osmium. Among these, it may be platinum, platinum-cobalt alloys, platinum-nickel alloys, etc., and in particular, it may be a platinum-cobalt alloy.

[0114] The metal catalyst may be a metal catalyst particle in a particulate form.

[0115] The particle size of the metal catalyst particles is not specifically limited, but may be 1 nm or larger and 10 nm or smaller. The particle size of the metal catalyst particles can be measured using 3D-TEM, etc.

[0116] Metal catalyst particles may be supported on the outer surface of the carbon carrier if their particle size is greater than or equal to the pore diameter of the carbon carrier.

[0117] The metal catalyst particles may be supported in an area further forward than the constriction within the pores of the carbon carrier if the particle size is greater than or equal to the average diameter of the constriction within the pores of the carbon carrier and less than the diameter of the pores of the carbon carrier.

[0118] If the metal catalyst particles have a particle diameter less than the average diameter of the constriction within the pores of the carbon carrier, they may be supported in an area further inward than the constriction within the pores of the carbon carrier.

[0119] 4. Catalyst layer for fuel cell

[0120] The catalyst layer for a fuel cell of the present disclosure comprises the catalyst for a fuel cell described above and typically further comprises an electrolyte.

[0121] As an electrolyte, it may be one that has proton conductivity, or a fluorine-based resin. As a fluorine-based resin, for example, a perfluorosulfonic acid-based resin such as Nafion (registered trademark) may be used.

[0122] The catalyst layer of the present disclosure is for a fuel cell.

[0123] The fuel cell of the present disclosure comprises a catalyst layer of the present disclosure.

[0124] The fuel cell may have only one single cell, or it may be a fuel cell stack in which multiple single cells are stacked.

[0125] The number of stacked cells is not particularly limited and can range from 2 to several hundred.

[0126] A single cell of a fuel cell comprises at least a membrane electrode gas diffusion layer assembly.

[0127] The membrane electrode gas diffusion layer assembly has an anode-side gas diffusion layer, an anode catalyst layer, an electrolyte membrane, a cathode catalyst layer, and a cathode-side gas diffusion layer in this order.

[0128] The cathode (oxidizing electrode) includes a cathode catalyst layer and, if necessary, a cathode-side gas diffusion layer.

[0129] The anode (fuel electrode) includes an anode catalyst layer and, if necessary, an anode-side gas diffusion layer.

[0130] The catalyst layer for a fuel cell disclosed in this disclosure may be used as a cathode catalyst layer, as an anode catalyst layer, or as both a cathode catalyst layer and an anode catalyst layer.

[0131] The cathode catalyst layer and the anode catalyst layer are combined and referred to as the catalyst layer.

[0132] The cathode-side gas diffusion layer and the anode-side gas diffusion layer are combined and referred to as the gas diffusion layer.

[0133] The gas diffusion layer may be a conductive member having gas permeability, etc.

[0134] Examples of conductive materials include carbon porous materials such as carbon cloth and carbon paper, and metal porous materials such as metal mesh and foamed metal.

[0135] The electrolyte membrane may be a solid polymer electrolyte membrane. Examples of solid polymer electrolyte membranes include fluorine-based electrolyte membranes, such as a thin film of perfluorosulfonic acid containing water, and hydrocarbon-based electrolyte membranes. As for the electrolyte membrane, for example, a Nafion membrane (manufactured by DuPont) may be used.

[0136] A single cell may, if necessary, be provided with two separators that support both sides of a membrane electrode gas diffusion layer assembly. Of the two separators, one is an anode-side separator and the other is a cathode-side separator. In this disclosure, the anode-side separator and the cathode-side separator are combined and referred to as a separator.

[0137] The separator may have supply holes and discharge holes for circulating reaction gases and refrigerants in the stacking direction of the single cells. As for the refrigerant, a mixed solution of ethylene glycol and water, for example, may be used to prevent freezing at low temperatures.

[0138] In the present disclosure, the fuel gas and the oxidizer gas are collectively referred to as the reaction gas. The reaction gas supplied to the anode is the fuel gas, and the reaction gas supplied to the cathode is the oxidizer gas. The fuel gas is a gas containing mainly hydrogen, and may be hydrogen. The oxidizer gas may be oxygen, air, dry air, etc.

[0139] The separator may have a reaction gas flow path on the surface in contact with the gas diffusion layer. Additionally, the separator may have a refrigerant flow path on the surface opposite to the surface in contact with the gas diffusion layer to maintain a constant temperature of the fuel cell.

[0140] The separator may be a gas-impermeable conductive member, etc. As a conductive member, it may be, for example, dense carbon made gas-impermeable by compressing carbon, or a press-formed metal plate (e.g., iron, aluminum, stainless steel, etc.). In addition, the separator may be equipped with a current collection function.

[0141] [Example]

[0142] The present disclosure is described in more detail below using examples and comparative examples, but the technical scope of the present disclosure is not limited thereto. Furthermore, examples and comparative examples are not distinguished based on whether they are included in the claims. In particular, an embodiment in which a particularly good result was obtained is designated as an example, and other embodiments are designated as comparative examples.

[0143] (Example 1)

[0144] Mesoporous silica was prepared, and a carbon carrier was manufactured using the said mesoporous silica as a template.

[0145] Mesoporous silica was used as a template in which the thickness of the carbon wall of the resulting carbon carrier was within the range of 3.3 nm to 11.2 nm and the carbon wall content was 168.4 ml / g. The pore volume of the three-dimensional pore structure in the silica was calculated from the difference between the adsorption amount when the relative nitrogen adsorption pressure of the silica pores was 0.8 and the adsorption amount when it was 0.4, and the carbon wall content of the carbon carrier was derived from the said pore volume.

[0146] (Example 2)

[0147] The carbon carrier of Example 2 was obtained in the same manner as in Example 1, except that mesoporous silica with a carbon wall thickness of 3.3 nm or more and 11.2 nm or less was used as a mold and a carbon wall content of 166.6 ml / g was used.

[0148] (Example 3)

[0149] The carbon carrier of Example 3 was obtained in the same manner as in Example 1, except that mesoporous silica with a carbon wall thickness of 3.3 nm or more and 11.2 nm or less and a carbon wall content of 61.5 ml / g was used as a template.

[0150] (Comparative Example 1)

[0151] The carbon carrier of Comparative Example 1 was obtained in the same manner as in Example 1, except that mesoporous silica with a carbon wall thickness of 3.3 nm or more and 11.2 nm or less and a carbon wall content of 42.5 ml / g was used as a mold.

[0152] (Comparative Example 2)

[0153] A carbon carrier of Comparative Example 2 was obtained in the same manner as in Example 1, except that mesoporous silica with a carbon wall thickness of 3.3 nm or more and 11.2 nm or less and a carbon wall content of 40.6 ml / g was used as a mold.

[0154] (Comparative Example 3)

[0155] The carbon carrier of Comparative Example 3 was obtained in the same manner as in Example 1, except that mesoporous silica with a carbon wall thickness of 3.3 nm or more and 11.2 nm or less was used as a mold and a carbon wall content of 190.8 ml / g was used.

[0156] (Comparative Example 4)

[0157] The carbon carrier of Comparative Example 4 was obtained in the same manner as in Example 1, except that mesoporous silica with a carbon wall thickness of 3.3 nm or more and 11.2 nm or less was used as a mold and a carbon wall content of 60.3 ml / g was used.

[0158] [3D-TEM Observation]

[0159] For each of the obtained carbon carriers of Examples 1 to 3 and Comparative Examples 1 to 4, observation was performed by 3D-TEM, and the carbon carrier ratio (%) and the average diameter (nm) of the constrictions within the pores of each carbon carrier were measured. These measurement results are shown in Table 1.

[0160] FIG. 1a is a planar TEM image of the carbon carrier of Example 1. FIG. 1b is a three-dimensional reconstruction image of FIG. 1a.

[0161] FIG. 2a is a planar TEM image of the carbon carrier of Comparative Example 1. FIG. 2b is a three-dimensional reconstruction image of FIG. 2a.

[0162] As shown in FIG. 1a and FIG. 1b and Table 1, the carbon carrier of Example 1 has a suitable carbon wall content, a suitable carbon carrier ratio, and a suitable average diameter of the constriction within the pores of the carbon carrier.

[0163] As shown in FIGS. 2a and 2b and Table 1, the carbon carrier of Comparative Example 1 has a low carbon wall content, a low carbon carrier ratio, and an average diameter of the constriction within the pores of the carbon carrier that is too large.

[0164] [Manufacture of catalysts for fuel cells]

[0165] A platinum-cobalt alloy was supported as a metal catalyst on each of the carbon carriers of Examples 1 to 3 and Comparative Examples 1 to 4 obtained, and a platinum-cobalt alloy supported carbon carrier was obtained as a catalyst for a fuel cell.

[0166] [Mass Activity of Fuel Cell Catalysts]

[0167] For each fuel cell catalyst of Examples 1 to 3 and Comparative Examples 1 to 4, the mass activity per 1 g of platinum (A / g-Pt) was evaluated by the rotating disc electrode (RDE) method.

[0168] Specifically, a catalyst ink was prepared by dispersing a fuel cell catalyst in a mixed solvent containing ultrapure water, alcohol, and Nafion (registered trademark). This catalyst ink was applied onto a glassy carbon (GC) electrode and dried to obtain an evaluation electrode. The cell for the RDE method was a triode type, and a 0.1 M aqueous perchloric acid solution was used as the electrolyte. A reversible hydrogen electrode (RHE) was used as the reference electrode, and a Pt black mesh was used as the counter electrode. The mass activity (MA) of the oxygen reduction reaction (ORR) was determined from the measurement results of the linear shift voltage curve (LSV). These measurement results are shown in Table 1.

[0169] Manufacture of Dancells

[0170] Each fuel cell catalyst of Examples 1 to 3 and Comparative Examples 1 to 4 was dispersed in an organic solvent. The resulting dispersion was applied to a Teflon (registered trademark) sheet to form an electrode. Two electrodes were formed, an electrolyte membrane was sandwiched and supported between the two electrodes, and a bonded membrane electrode assembly was obtained by hot pressing. A single cell was obtained by sandwiching and supporting the membrane electrode assembly between two diffusion layers.

[0171] <Evaluation of Efficiency Point Performance>

[0172] The temperature of each single cell in Examples 1 to 3 and Comparative Examples 1 to 4 was set to 80°C, the relative humidity of the two electrodes of each single cell was set to 85%, and IV measurements of each single cell were performed using a small single cell evaluation device system (manufactured by Toyo Technica Co., Ltd.).

[0173] For IV measurement, 0.01A / cm 2 Up to 4.0 A / cm 2 The current was controlled arbitrarily within the range of 0.2A / cm 2 The voltage value at the time was defined as the efficiency point voltage and measured. The measurement results are shown in Table 1.

[0174]

[0175] The fuel cell catalyst using the carbon support of Examples 1 to 3 has higher mass activity than the fuel cell catalyst using the carbon support of Comparative Examples 1 to 4.

[0176] A single cell using a fuel cell catalyst with a carbon carrier of Examples 1 to 3 has a higher efficiency point voltage than a single cell using a fuel cell catalyst with a carbon carrier of Comparative Examples 1 to 4.

[0177] This is because, by using the carbon support of Examples 1 to 3, the metal catalyst can be uniformly supported, and accordingly, power generation performance, particularly efficiency point performance, is improved.

Claims

Claim 1 A carbon carrier having pores, wherein the thickness of the carbon wall of the carbon carrier is 3.3 nm or more and 11.2 nm or less, derived from the three-dimensional pore structure of the silica mold obtained by measuring the pore volume of the silica mold by nitrogen adsorption analysis and also confirmed by 3D-TEM observation, and the carbon wall content is greater than 60.3 ml / g and less than 190.8 ml / g. Claim 2 A carbon carrier according to claim 1, wherein the carbon carrier ratio calculated by 3D-TEM observation is greater than 36% and less than 67%. Claim 3 In paragraph 2, the carbon carrier has at least one constriction within the pore, and the average diameter of the constriction of the pore calculated by 3D-TEM observation is 1.9 nm or more and less than 2.5 nm. Claim 4 A carbon carrier according to claim 3, wherein the carbon wall content is 61.5 ml / g or more and 168.4 ml / g or less, the carbon carrier ratio is 46% or more and 57% or less, and the average diameter of the constriction portion of the pore is 1.9 nm or more and 2.0 nm or less. Claim 5 A catalyst for a fuel cell comprising a carbon carrier supporting a metal catalyst, wherein the carbon carrier is a carbon carrier described in any one of claims 1 to 4. Claim 6 A catalyst layer for a fuel cell comprising the catalyst for a fuel cell described in paragraph 5. Claim 7 A method for manufacturing a carbon carrier as described in any one of claims 1 to 4, wherein a pore-forming silica is used as a mold.

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