Carrier material and preparation method thereof

Abstract

The present application discloses a carrier material and a preparation method thereof. The preparation method comprises the following steps: dispersing a template in a metal salt mixed solution to obtain a first product of a specific concentration; performing low-temperature vacuum drying on the first product to obtain a second product; mixing an organic carbon source with the second product to obtain a third product; performing a first heat treatment on the third product under vacuum or inert gas conditions to obtain a fourth product; washing and drying the fourth product in an acid wash solution to obtain a fifth product; performing a second heat treatment on the fifth product to obtain a carrier material; wherein the pore characteristic value of the carrier material is less than the cavity characteristic value of the carrier material. The beneficial effect of the present application is that it provides a carrier material and a preparation method thereof that improves the mass transfer resistance of a membrane electrode composed of a carrier material by controlling the pore characteristic value and the cavity characteristic value.

Description

Technical Field

[0001] The present application relates to the technical field of fuel cells, and in particular to a carrier material and a preparation method thereof. Background Art

[0002] The membrane electrode is the core component of the fuel cell. The catalyst in the membrane electrode can convert chemical energy into electrical energy. The three components of gas, electrons and protons undergo electrochemical reactions on the catalyst surface to generate water and supply energy to the connected load device. The membrane electrode is provided with a carrier material that carries the catalyst. While carrying the catalyst, it also provides a continuous transmission channel for protons, reaction gases and water for the electrochemical reaction.

[0003] The microscopic particles of the support material are often constructed into a porous structure so that the support material has a larger specific surface area, which will provide more attachment points for the precious metal particles in the catalyst and provide a reaction site for the catalytic reaction.

[0004] However, experiments have found that even when the carrier materials have similar specific surface areas, there will be large differences in the mass transfer capacity of the membrane electrode. The mass transfer resistance of the membrane electrode composed of some carrier materials is relatively large. Summary of the invention

[0005] In view of this, the present application provides a carrier material and a preparation method thereof, aiming to improve the problem of high mass transfer resistance of existing membrane electrodes.

[0006] The embodiment of the present application is implemented as follows: a method for preparing a carrier material comprises the following steps:

[0007] Dispersing the template in the metal salt mixed solution to obtain a first product of a specific concentration;

[0008] performing low-temperature vacuum drying on the first product to obtain a second product;

[0009] mixing an organic carbon source with the second product to obtain a third product;

[0010] performing a first heat treatment on the third product under vacuum or inert gas conditions to obtain a fourth product;

[0011] washing the fourth product in an acid wash solution and drying it to obtain a fifth product;

[0012] subjecting the fifth product to a second heat treatment to obtain a support material;

[0013] wherein the microscopic particles of the carrier material are configured to have a plurality of pores and a plurality of cavities, wherein the pores are connected to the exterior of the microscopic particles and the cavities are isolated from the exterior of the microscopic particles;

[0014] The ratio of the mass of the carrier material to the total volume of the pores is defined as the pore characteristic value; the ratio of the mass of the carrier material to the total volume of the cavity is defined as the cavity characteristic value; the pore characteristic value of the carrier material is smaller than the cavity characteristic value of the carrier material.

[0015] Optionally, in some embodiments of the present application, the pore characteristic value of the carrier material ranges from 0.250 g / cm 3 Up to 0.450g / cm 3 ; and / or the range of the cavity characteristic value of the carrier material includes 10.00g / cm 3 Up to 50.00g / cm 3 .

[0016] Optionally, in some embodiments of the present application, the template includes one or more of carbon quantum dots, nano-aluminum oxide, nano-silicon oxide, nano-magnesium oxide, nano-calcium oxide, and nano-calcium carbonate;

[0017] The metal salt in the metal salt mixed solution includes one or more of ferric nitrate, chromium nitrate, cobalt nitrate, nickel nitrate, zinc nitrate, magnesium nitrate, ferric chloride, cobalt chloride, nickel chloride, zinc chloride, magnesium chloride, ferric sulfate, ferric sulfate, ferric sulfate, zinc sulfate, and magnesium sulfate;

[0018] The mixed solvent in the metal salt mixed solution includes a mixture of one or more of isopropanol, ethylene glycol, n-butanol, N-methylpyrrolidone, ethanol and distilled water;

[0019] The concentration of the metal salt mixed solution ranges from 10 mg / mL to 100 mg / mL, and the concentration of the first product of the specific concentration ranges from 10 wt.% to 50 wt.%.

[0020] Optionally, in some embodiments of the present application, the organic carbon source includes one or more of asphalt, sugar, heavy oil, fatty acid, polyvinyl alcohol, polyamide, epoxy resin, phenolic resin, organic salt and derivatives thereof;

[0021] In mixing the organic carbon source with the second product to obtain the third product, the mass ratio of the organic carbon source to the second product ranges from 0.1 to 3.

[0022] Optionally, in some embodiments of the present application, the third product is subjected to a first heat treatment under vacuum or inert gas conditions to obtain a fourth product, and the heating rate of the first heat treatment ranges from 1°C / min to 20°C / min, and the heat treatment temperature ranges from 200°C to 1000°C.

[0023] Optionally, in some embodiments of the present application, the pickling solution includes one or more of hydrochloric acid, nitric acid, perchloric acid, sulfuric acid, acetic acid, and hydrofluoric acid.

[0024] The molar concentration of the pickling solution ranges from 0.2 mol / L to 5 mol / L.

[0025] Optionally, in some embodiments of the present application, the fifth product is subjected to a second heat treatment to obtain a carrier material, comprising the following steps:

[0026] subjecting the fifth product to high temperature heat treatment under an inert atmosphere to obtain an intermediate product;

[0027] Cooling the intermediate product;

[0028] The intermediate product after cooling is subjected to medium-temperature heat treatment in an oxidative atmosphere to obtain a carrier material;

[0029] Among them, the heating rate range of high-temperature heat treatment includes 1℃ / min to 15℃ / min, and the heat treatment temperature range includes 1000℃ to 3000℃; the heating rate range of medium-temperature heat treatment includes 1℃ / min to 15℃ / min, and the heat treatment temperature range includes 100℃ to 600℃.

[0030] Correspondingly, an embodiment of the present application further provides a carrier material, which is prepared by the above-mentioned method for preparing the carrier material.

[0031] Accordingly, an embodiment of the present application further provides a carrier material, wherein microscopic particles of the carrier material are configured to have a plurality of holes and a plurality of cavities, wherein the holes are connected to the outside of the microscopic particles, and the cavities are isolated from the outside of the microscopic particles;

[0032] The ratio of the mass of the support material to the total volume of the pores is defined as the pore characteristic value;

[0033] The ratio of the mass of the carrier material to the total volume of the cavity is defined as the cavity characteristic value;

[0034] Therein, the hole characteristic value of the carrier material is smaller than the cavity characteristic value of the carrier material.

[0035] Optionally, in some embodiments of the present application, the pore characteristic value of the carrier material ranges from 0.250 g / cm 3 Up to 0.450g / cm 3 ; and / or the range of the cavity characteristic value of the carrier material includes 10.00g / cm 3 Up to 50.00g / cm 3 .

[0036] Optionally, in some embodiments of the present application, the specific surface area of ​​the carrier material ranges from 400 m 2 / g to 1500m 2 / g; and / or the particle size of the carrier material ranges from 100nm to 2μm; and / or the compacted density of the carrier material ranges from 0.05g / mL to 0.80g / mL; and / or the electrical conductivity of the carrier material ranges from 6.4S / cm to 26.5S / cm; and / or the fixed carbon content of the carrier material ranges from 84.5% to 97.2%.

[0037] Correspondingly, an embodiment of the present application also provides a membrane electrode for a fuel cell, comprising the aforementioned carrier material.

[0038] The beneficial effect of the present application is that it provides a carrier material and a preparation method thereof for improving the mass transfer resistance of a membrane electrode composed of the carrier material by controlling the pore characteristic value and the cavity characteristic value. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For those skilled in the art, other drawings can be obtained based on these drawings without paying any creative work.

[0040] Figure 1 It is a schematic diagram of the structure of a fuel cell provided in an embodiment of the present application;

[0041] Figure 2 This is a schematic diagram of the main steps of a method for preparing a carrier material provided in an embodiment of the present application;

[0042] Figure 3 is a schematic diagram of the microstructure of a catalytic layer provided in an embodiment of the present application;

[0043] Figure 4 This is a schematic diagram of the structure of a carrier material and catalyst particles combined in an embodiment of the present application;

[0044] Figure 5 It is a schematic diagram of the main steps of a method for preparing a catalytic layer provided in an embodiment of the present application;

[0045] Figure 6 It is a structural diagram of the equivalent circuit of the EIS test;

[0046] Figure 7 This is a schematic diagram of the law of pore characteristic value and mass transfer impedance of a carrier material provided in an embodiment of the present application;

[0047] Figure 8 It is a schematic diagram of the law of cavity characteristic value and ECSA retention rate of a carrier material provided in an embodiment of the present application.

[0048] Meaning of the reference symbols:

[0049] 100, plate;

[0050] 200, diffusion layer;

[0051] 300, proton membrane;

[0052] 400, catalytic layer; 410, carrier material; 420, catalyst particles. DETAILED DESCRIPTION

[0053] The technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without making creative work belong to the scope of protection of the present application. In addition, it should be understood that the specific implementation methods described herein are only used to illustrate and explain the present application, and are not used to limit the present application.

[0054] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by those skilled in the art of the present invention. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0055] In this application, unless otherwise stated, directional words such as "upper" and "lower" generally refer to the upper and lower parts of the device in actual use or working state, specifically the drawing direction in the accompanying drawings; while "inner" and "outer" refer to the outline of the device. In addition, in the description of this application, the term "including" means "including but not limited to". The terms first, second, third, etc. are used only as labels and do not impose numerical requirements or establish an order.

[0056] In this application, "and / or" describes the association relationship of associated objects, indicating that there may be three relationships. For example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone. A and B can be singular or plural.

[0057] In the present application, "at least one" means one or more, and "plurality" means two or more. "One or more", "at least one of the following" or similar expressions refer to any combination of these items, including any combination of single items or plural items. For example, "at least one of a, b, or c", or "at least one of a, b, and c" can all mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or multiple, respectively.

[0058] Various embodiments of the present application may be presented in the form of a range; it should be understood that the description in the form of a range is only for convenience and brevity, and should not be understood as a rigid limitation on the scope of the present application; therefore, the range description should be considered to have specifically disclosed all possible sub-ranges and single numerical values ​​within the range. For example, the range description from 1 to 6 should be considered to have specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as single numbers within the range, such as 1, 2, 3, 4, 5 and 6, which apply regardless of the range. In addition, whenever a numerical range is indicated herein, it is meant to include any cited number (fractional or integer) within the indicated range.

[0059] Reference Figure 1 As shown, the fuel cell of the present application includes: a membrane electrode with two plates 100 disposed therebetween. The membrane electrode includes: a proton membrane 300, a catalyst layer 400 and a diffusion layer 200. The functions, structures and preparation methods of each part of the fuel cell of the present application except the catalyst layer 400 are conventional solutions well known to those skilled in the art, and are not the focus of improvement of the present application, and will not be elaborated here.

[0060] The technical solution of this application is as follows:

[0061] First, refer to Figure 2 As shown, the present application embodiment provides a method for preparing a carrier material, comprising the following main steps:

[0062] S110: dispersing the template in the metal salt mixed solution to obtain a first product of a specific concentration.

[0063] Specifically, the template includes one or a mixture of two or more of carbon quantum dots, nano-aluminum oxide, nano-silicon oxide, nano-magnesium oxide, nano-calcium oxide, and nano-calcium carbonate.

[0064] The metal salt in the metal salt mixed solution includes one or more of ferric nitrate, chromium nitrate, cobalt nitrate, nickel nitrate, zinc nitrate, magnesium nitrate, ferric chloride, cobalt chloride, nickel chloride, zinc chloride, magnesium chloride, ferric sulfate, ferric sulfate, ferric sulfate, zinc sulfate, and magnesium sulfate.

[0065] The mixed solvent in the metal salt mixed solution includes a mixture of one or more of isopropanol, ethylene glycol, n-butanol, N-methylpyrrolidone, ethanol and distilled water.

[0066] More specifically, the volume ratio of distilled water to the organic solvent in the mixed solvent ranges from 1 to 20.

[0067] The mixed solution of the template and the metal salt is sealed and stirred evenly at room temperature to obtain a first product. The purpose of step S110 is to obtain a template with a specific arrangement and to make the metal salt evenly attached to the template.

[0068] The concentration of the metal salt mixed solution in step S110 ranges from 10 mg / mL to 100 mg / mL, and a further optional concentration range includes 20 mg / mL to 50 mg / mL.

[0069] The specific concentration range of the first product in step S110 includes 10 wt.% to 50 wt.%, and a further optional concentration range includes 20 wt.% to 40 wt.%.

[0070] S120: performing low-temperature vacuum drying on the first product to obtain a second product.

[0071] Specifically, the second product is a template metal salt mixture.

[0072] The temperature range of low-temperature vacuum drying includes -40°C to 10°C, and a further optional temperature range includes -30°C to -10°C.

[0073] S130: Mixing the organic carbon source with the second product to obtain a third product.

[0074] Specifically, the organic carbon source includes one or more substances such as asphalt, sugar, heavy oil, fatty acid, polyvinyl alcohol, polyamide, epoxy resin, phenolic resin, organic salt and their derivatives.

[0075] More specifically, the mass ratio of the organic carbon source to the second product is 0.1 to 3.

[0076] The purpose of step S130 is to mix with the organic carbon source without destroying the arrangement of the template.

[0077] S140: performing a first heat treatment on the third product in a vacuum or inert gas condition to obtain a fourth product.

[0078] Specifically, the first heat treatment in step S140 is performed under vacuum or inert gas conditions, and the inert gas includes one or both of argon and nitrogen.

[0079] More specifically, the temperature rise rate of the first heat treatment in step S140 ranges from 1°C / min to 20°C / min, and the heat treatment temperature ranges from 200°C to 1000°C.

[0080] Further optionally, the temperature rise rate of the first heat treatment ranges from 5°C / min to 10°C / min, and the heat treatment temperature ranges from 500°C to 700°C.

[0081] The function of step S140 is to carbonize the organic carbon source to obtain a specific pore or cavity structure, wherein the source of the pores includes the pore-forming effect of the template and the pore-forming catalysis of the metal salt, and the carbon source itself generates pores or cavities during the shrinkage and carbonization process. The fourth product is a carbon powder with a specific pore or cavity structure.

[0082] The function of step S140 is to make the template and the metal salt work together to form a product with a certain pore and cavity structure.

[0083] S150: The fourth product is washed in an acid washing solution and dried to obtain a fifth product.

[0084] Specifically, the pickling solution includes one or more of hydrochloric acid, nitric acid, perchloric acid, sulfuric acid, acetic acid, and hydrofluoric acid.

[0085] The molar concentration of the pickling solution ranges from 0.2 mol / L to 5 mol / L. Further optionally, the molar concentration of the pickling solution ranges from 0.5 mol / L to 2 mol / L.

[0086] The purpose of step S150 is to remove most of the metal salt and the template.

[0087] S160: The fifth product is subjected to a second heat treatment to obtain a carrier material.

[0088] The purpose of S160 is that some pores will be closed to form cavities during the graphitization process, and the metal salts remaining in some cavities will react with carbon to form a pore structure. At the same time, the metal will undergo catalytic graphitization to varying degrees, increasing the degree of graphitization of the material.

[0089] Specifically, step S160 mainly includes the following steps:

[0090] S161: subjecting the fifth product to high-temperature heat treatment under an inert atmosphere to obtain an intermediate product.

[0091] Specifically, the inert atmosphere gas includes one or both of argon and nitrogen.

[0092] The temperature rise rate of the high temperature heat treatment in step S161 ranges from 1°C / min to 20°C / min, and the heat treatment temperature ranges from 1000°C to 2600°C.

[0093] Further optionally, the range of the heating rate of the high temperature heat treatment includes 5°C / min to 10°C / min, and the range of the heat treatment temperature includes 1400°C to 1900°C.

[0094] S162: Cooling the intermediate product.

[0095] Specifically, the cooling process adopts a method of natural cooling to room temperature.

[0096] S163: The intermediate product after cooling is subjected to medium-temperature heat treatment in an oxidizing atmosphere, and the carrier material is obtained after cooling.

[0097] Specifically, the oxidizing atmosphere gas includes one or more of carbon dioxide, oxygen-containing oxidizing atmosphere (air, water vapor, oxygen, ozone, etc.), and ammonia.

[0098] The temperature rise rate of the medium-temperature heat treatment in step S163 ranges from 1°C / min to 20°C / min, and the heat treatment temperature ranges from 150°C to 500°C.

[0099] Further optionally, the range of the heating rate of the medium-temperature heat treatment includes 1°C / min to 15°C / min, and the range of the heat treatment temperature includes 200°C to 400°C.

[0100] The heat treatment scheme of step S160 is adopted to control the hole characteristic value and cavity characteristic value of the carrier material 410 .

[0101] Among them, high-temperature heat treatment increases the crystallinity of carbon materials. The higher the crystallinity, the stronger the corrosion resistance and the lower the specific surface area. The carbon materials will undergo structural reorganization under high temperature conditions. The surface graphite micro-chip layer will polymerize and rearrange in this process. The pore structure (pore size, pore volume, etc.) will change in the process, and some of the pores will become cavities. At the same time, high temperature will also cause some metal salts to escape, forming new pore and cavity structures.

[0102] The medium temperature heat treatment is used to oxidize and modify the material. This process will reduce the fixed carbon content of the material, increase the content of oxygen, hydrogen, and nitrogen (depending on the synthesis conditions), and increase the content of corresponding groups to facilitate the attachment of precious metal particles. It will also improve the connectivity of the pore structure, and some cavity structures will be converted into pore structures.

[0103] Second, refer to Figure 3 and Figure 4As shown, an embodiment of the present application provides a carrier material 410, which mainly provides a carrier for catalyst particles 420 (precious metal particles, such as Pt nanoparticles) in the catalytic layer 400, and the carrier material 410 is a powder material.

[0104] Specifically, the microscopic particles of the carrier material 410 of the present application are constructed to have multiple pores and multiple cavities, wherein the pores are connected to the outside of the microscopic particles, and the cavities are isolated from the outside of the microscopic particles; the ratio of the mass of the carrier material 410 to the total volume of the pores is defined as the pore characteristic value; the ratio of the mass of the carrier material 410 to the total volume of the cavities is defined as the cavity characteristic value; wherein the pore characteristic value of the carrier material 410 is less than the cavity characteristic value of the carrier material 410.

[0105] As an option, the carrier material 410 consists at least of a carbon material.

[0106] The mass transfer capacity of carbon materials is related to the size and type of pores. Usually, when the pore diameter is 2nm or above, the space that can be connected to the outside world during the mass transfer process is more likely to react continuously and stably and can promptly discharge the generated water to ensure the continuous reaction. These spaces are called pores, including cross-linked pores, through holes and blind holes. The surface area of ​​these pores can be detected and analyzed by gas adsorption method.

[0107] In addition to these pores, there may be some closed spaces in the microscopic particles of the carrier material 410. The pore diameters of these pores are small (≤2nm) or they are not connected to the outer surface, so the fluid cannot penetrate. These spaces cannot be effectively measured by gas adsorption method, mercury injection method and other measurement methods. Under working conditions, it is difficult to use them as the place where sustained and stable electrochemical reactions occur.

[0108] Therefore, when the pores in the microscopic particles of the carrier material of the present application have a pore size of 2 nm or less, it is difficult for the fluid to enter. Therefore, the pores with a pore size of 2 nm or less can also be classified as the cavities defined in the present application. That is, the "isolation from the outside of the microscopic particles of the carrier material 410" referred to in the present application is based on the inability of the fluid to effectively flow into. That is, the "cavity" referred to in the present application as "isolation from the outside of the microscopic particles of the carrier material 410" includes both closed spaces that are completely not connected to the outside of the microscopic particles of the carrier material 410, and those pores (non-closed spaces) that are connected to the outside of the microscopic particles of the carrier material 410 but have a pore size of 2 nm or less.

[0109] Carbon materials with larger pore characteristic values ​​can greatly improve mass transfer capacity and reduce mass transfer resistance under high current density conditions. Suitable pore structures can delay catalyst flooding and gas diffusion channel blockage. In addition, carrier materials 410 with high cavity characteristic values ​​can show higher durability under start-stop and other operating conditions.

[0110] This porous carbon material with optimized pores and cavities may also be used in other fields involving mass transfer and charge transfer processes, such as lithium batteries, sodium ion batteries, drug delivery, etc.

[0111] In some embodiments, the ratio of the pore characteristic value to the cavity characteristic value of the carrier material 410 ranges from 0.005 to 0.045.

[0112] In some embodiments, the ratio of the pore characteristic value to the cavity characteristic value of the carrier material 410 ranges from 0.0102 to 0.0163, more specifically from 0.014 to 0.015, or from 0.0145 to 0.0148.

[0113] In some embodiments, the ratio of the pore characteristic value to the cavity characteristic value of the carrier material 410 ranges from 0.0232 to 0.0384, more specifically, from 0.020 to 0.030, or from 0.025 to 0.028.

[0114] In some embodiments, the ratio of the pore characteristic value to the cavity characteristic value of the carrier material 410 ranges from 0.0090 to 0.0180, more specifically, from 0.012 to 0.013, or from 0.0125 to 0.0129.

[0115] In some embodiments, the pore characteristic value of the carrier material 410 may range from 0.250 g / cm 3 Up to 0.450g / cm 3 .

[0116] In some embodiments, the pore characteristic value of the carrier material 410 may range from 0.260 g / cm 3 Up to 0.350g / cm 3 .

[0117] In some embodiments, the cavity characteristic value of the carrier material 410 may range from 10.00 g / cm 3 Up to 50.00g / cm 3 .

[0118] In some embodiments, the cavity characteristic value of the carrier material 410 may range from 20.00 g / cm 3 Up to 40.00g / cm 3 .

[0119] In some embodiments, the pore characteristic value of the carrier material 410 may range from 0.256 g / cm 3 Up to 0.298g / cm 3 At the same time, the cavity characteristic value of the carrier material 410 can range from 18.306 g / cm 3Up to 24.902g / cm 3 .

[0120] In some embodiments, the pore characteristic value of the carrier material 410 may range from 0.375 g / cm 3 Up to 0.418g / cm 3 At the same time, the cavity characteristic value of the carrier material 410 can range from 10.897 g / cm 3 Up to 16.105g / cm 3 .

[0121] In some embodiments, the pore characteristic value of the carrier material 410 may range from 0.260 g / cm 3 Up to 0.350g / cm 3 At the same time, the cavity characteristic value of the carrier material 410 can range from 19.306 g / cm 3 Up to 30.026g / cm 3 .

[0122] In some embodiments, the pore characteristic value of the carrier material 410 may be 0.284, 0.319, or 0.399.

[0123] In some embodiments, the cavity characteristic value of the carrier material 410 may be 14.298, 19.306, or 24.902.

[0124] In some embodiments, the specific surface area of ​​the carrier material 410 may range from 400 m 2 / g to 1500m 2 As a further option, the specific surface area of ​​the carrier material 410 may range from 500 m 2 / g to 1100m 2 / g.

[0125] In some embodiments, the particle size of the carrier material 410 may range from 100 nm to 2 μm. As a further option, the particle size of the carrier material 410 may range from 200 nm to 800 nm.

[0126] In some embodiments, the compacted density of the carrier material 410 may range from 0.05 g / mL to 0.80 g / mL. As a further option, the compacted density of the carrier material 410 may range from 0.10 g / mL to 0.50 g / mL.

[0127] In order to quantitatively represent the structural characteristics of the pores in the carbon material that are conducive to mass transfer reactions, the present application sets the pore characteristic value ρ AAs a characteristic value that can represent the content of pores in the carrier material where mass transfer reactions can occur stably, the cavity characteristic value ρ is set Ir As a characteristic value that can represent the content of the reaction chamber in which stable mass transfer occurs in the carrier material, its derivation formula is as follows:

[0128]

[0129] In formula 1: Id Refers to the theoretical true density of ideal single crystal graphite (2.266 g / cm 3 ), m refers to the mass of ideal single crystal graphite, V Id Refers to the volume of an ideal single crystal graphite with mass m.

[0130] In formula 2: T refers to the true density of the carrier material, m refers to the mass of the carrier material, V Id Refers to the volume of an ideal single crystal graphite with a mass of m, V Ir Refers to the cavity volume with a mass of m carrier material.

[0131] In formula 3: C refers to the compacted density of the carrier material, m refers to the mass of the carrier material, V Id Refers to the volume of an ideal single crystal graphite with a mass of m, V A refers to the pore volume of the carrier material with a mass m, v Ir Refers to the cavity volume with a mass of m carrier material.

[0132] The carrier materials with specific pore structures are shown in Formulas 4 and 5.

[0133]

[0134] Then the hole characteristic value ρ A , cavity characteristic value ρ Ir The eigenvalues ​​are shown in formulas 6 and 7.

[0135]

[0136] The above describes the calculation formulas for the pore characteristic value and cavity characteristic value in this application, so the true density ρ of the carrier material is T , refers to the compaction density of the carrier material ρ C and the theoretical true density ρ of ideal single crystal graphite Id That is, the hole characteristic value and cavity characteristic value in this application can be calculated.

[0137] Thirdly, refer to Figure 5 As shown, the present embodiment provides a method for preparing a catalytic layer using the above-mentioned carrier material, comprising the following steps:

[0138] S210: Take a certain amount of precious metal precursor and dissolve it in an organic solvent, add a certain amount of carrier material 410 under vigorous stirring, seal and stir evenly, and then dry to obtain the sixth product.

[0139] Specifically, the organic solvent in S210 includes one or more of ethanol, isopropanol, ethylene glycol, and n-butanol.

[0140] In step S210, the noble metal precursor includes one or more of chloroplatinic acid, potassium chloroplatinate, potassium chloroplatinite, platinum dichloride, platinum tetrachloride, tetraammine dichloroplatinum, and platinum di(acetylacetonate).

[0141] The molar concentration of the noble metal precursor in step S210 ranges from 0.1 mol / L to 5 mol / L, and further optionally ranges from 1 mol / L to 2 mol / L.

[0142] The rotation speed of the vigorous stirring in S210 is 300-1000 rpm / min.

[0143] S220: Take the sixth product and heat and reduce it in a mixed gas atmosphere of H2 and inert gas at a specific concentration to obtain carbon powder (seventh product) with a specific precious metal content.

[0144] Specifically, the specific concentration of H2 in S220 can be a mixed gas of any ratio of H2 and Ar or H2 and N2.

[0145] The range of the heating rate for heating reduction in step S220 includes 1°C / min to 20°C / min, and a further optional range of 5°C / min to 10°C / min; the temperature range for heating reduction is 200°C to 900°C, and a further optional range of 300°C to 400°C.

[0146] S230: taking a quantitative amount of the seventh product, washing it with an acid wash solution, and drying it to obtain a platinum-containing catalyst.

[0147] Specifically, the pickling solution in S230 includes one or more of nitric acid, perchloric acid, and acetic acid.

[0148] The molar concentration of the pickling solution in S230 ranges from 0.2 mol / L to 5 mol / L, and a further optional range includes 0.5 mol / L to 2 mol / L.

[0149] It is understandable that the mass transfer capacity of the fuel cell catalyst layer 400 is related to the size and type of the carbon material pores. During the mass transfer process, the cavities and pores connected to the outside world react continuously and stably, and the generated water can be discharged in time to ensure the continuous progress of the reaction. The organic biomass precursor treated at high temperature is decomposed and carbonized by heat, and the corresponding pore structure is generated under the action of the template agent. Under the catalysis of the metal salt, the molecules of the surface graphite micro-chip layer are polymerized and rearranged, and the regularity and order are continuously improved and tend to graphitization, and finally a porous carbon structure with a certain degree of graphitization is formed.

[0150] Specifically, the hole characteristic value ρ A As a characteristic value that can represent the content of pores in the carrier material where mass transfer reactions can occur stably, the pore characteristic value ρ A The smaller it is, the stronger the ability of the carrier material to stably carry out mass transfer reactions, and the water produced by the reaction of the catalytic layer 400 is easier to discharge, thereby reducing the risk of the reaction site being flooded and inhibiting the entry of oxygen.

[0151] In addition to these holes, there are some cavities in the carrier material 410 that are not connected to the outer surface and cannot be penetrated by fluid. These cavities do not directly affect the performance of the catalytic layer 400 in the early stage of the electrochemical reaction, and cannot be detected and analyzed by gas adsorption method. However, under high potential conditions such as starting and stopping, the existence of these cavities will aggravate the corrosion of the carrier material.

[0152] Specifically, the cavity characteristic value ρ Ir As a characteristic parameter that can represent the structure, it is used to evaluate the condition of the cavity that is not connected to the outer surface and cannot be penetrated by fluid. The cavity characteristic value ρ Ir The larger it is, the fewer the cavity structures are, and the more corresponding corrosion-resistant high-graphitized components are. The carrier material has stronger corrosion resistance under high-potential conditions such as starting and stopping.

[0153] Fourthly, the application of the above-mentioned carrier material in the membrane electrode of a fuel cell enables the membrane electrode to have excellent mass transfer capability.

[0154] The technical solution of the present application is further described below in conjunction with specific embodiments.

[0155] Example 1

[0156] (1) Dispersing carbon quantum dots in a 10 mg / mL ferric nitrate-isopropanol mixed solution, sealing and stirring at room temperature, to obtain a 10 wt.% template mixed solution (first product); wherein the volume ratio of water to isopropanol in the ferric nitrate-isopropanol mixed solution is 0.5.

[0157] (2) The first product is taken and vacuum dried at -40°C to obtain a template metal salt mixture (second product).

[0158] (3) adding heavy oil to the second product, and stirring in a sealed state at room temperature to obtain a third product; wherein the mass ratio of the heavy oil to the second product is 0.1.

[0159] (4) The third product was subjected to a first heat treatment in nitrogen using a KSL-1700L box-type furnace from Hefei Kejing. The heating rate for the first heat treatment was 1°C / min and the temperature was 200°C. After cooling and taking out, the fourth product was obtained.

[0160] (5) The fourth product is added to a 0.2 mol / L hydrochloric acid solution for acid washing, purification, filtration and drying to obtain carbon powder (fifth product).

[0161] (6) The fifth product is subjected to a second heat treatment (high temperature heat treatment) in an argon atmosphere. The equipment used is a Vlad graphitization furnace. The heating rate of the high temperature heat treatment is 10°C / min, and the temperature is 1600°C. It is naturally cooled to room temperature. Then, a medium temperature heat treatment is carried out in a carbon dioxide atmosphere. The heating rate of the medium temperature heat treatment is 10°C / min, and the temperature is 200°C. After cooling, a carrier material is obtained. The carrier material of this embodiment is defined as C1.

[0162] (7) The carrier material was added to a 1 mol / L chloroplatinic acid ethanol solution at a rotation speed of 500 rpm / min, sealed, stirred evenly, and dried to obtain the sixth product.

[0163] (8) The sixth product is heated and reduced in a H2 (20% Ar) gas atmosphere to obtain the seventh product. The equipment used is a tubular furnace from Zhengzhou Bona. The heating rate of the heating reduction is 5°C / min and the temperature is 200°C.

[0164] (9) The seventh product is acid-washed in a 1 mol / L hydrochloric acid solution, purified, filtered and dried to obtain a platinum-containing catalyst. The platinum-containing catalyst of this embodiment is defined as C1-cat.

[0165] Embodiment 2-10

[0166] The difference between Example 2-10 and Example 1 is that the mass concentration of the template mixed solution (first product) obtained in (1) is different.

[0167] Table 1 Mass concentration of template mixture (first product) in Examples 2-10

[0168]

[0169]

[0170] Examples 11-19

[0171] The difference between Examples 11-19 and Example 1 is that the concentration of the isopropanol mixed solution of ferric nitrate in (1) is different.

[0172] Table 2 Concentration of isopropanol mixed solution of ferric nitrate

[0173]

[0174] The test method of this application is described below.

[0175] 1) Testing method for specific surface area of ​​carbon materials:

[0176] At constant temperature and low temperature, the ASAP2460 Micrometer tester is used to measure the adsorption amount of gas on the solid surface at different relative pressures. Based on the Brownauer-Etter-Taylor adsorption theory and its formula (BET formula), the monolayer adsorption amount of the sample is obtained, thereby calculating the specific surface area SA of the material.

[0177] 2) Testing methods for hole characteristic values ​​and cavity characteristic values:

[0178] The carrier material was randomly obtained and the ρ was measured by the Pentapyctm5200e true density tester. T , measured by GeoPyc-1365 Micrometer tap density tester C (The pressure is the same as the membrane electrode preparation pressure, 1 MPa). According to formulas 6 and 7 and the theoretical true density ρ of ideal single crystal graphite Id (2.266g / cm 3 ), and obtain the carbon material pore characteristic value ρ A , cavity characteristic value ρ Ir .

[0179] 3) Test method for carrier material particle size:

[0180] The particle size of the carrier material is tested by Malvern 3000 laser particle size analyzer. The intensity distribution of scattered light generated by the particles in all directions depends on the size of the particles. Large particles have small scattering angles, and small particles have large scattering angles. The particle size distribution of the particles can be obtained by using the scattered light intensity distribution of laser diffraction.

[0181] 4) Test method for platinum content of catalyst:

[0182] The quantitative catalyst sample is digested by adding aqua regia, filtered, and fixed to volume, and the element content ICP-Pt is tested by ICP spectrometer.

[0183] 5) Test method for catalyst electrochemical active area and retention rate:

[0184] The performance of the catalyst prepared by the support material was tested by a three-electrode system. A certain amount of catalyst was weighed and 5% Nafion solution, deionized water and isopropanol were added in sequence. Ultrasound was used to mix the slurry evenly. The catalyst loading on the electrode surface was 20ug / cm 2 ~50ug / cm 2 , take the dispersed slurry and add it evenly to the surface of the disk electrode, and use it as the working electrode after drying. The working electrode, reference electrode and counter electrode are placed in the electrolytic cell to form a three-electrode system. Among them, the reference electrode is a RHE reversible hydrogen electrode, the counter electrode is a large-area Pt sheet, and the electrolyte is a saturated 0.1M HClO4 solution.

[0185] Test the cyclic voltammetry curve. First, activate the catalyst at a scanning speed of 20mV / s until the hydrogen desorption peak area no longer increases, and then scan 10 times at a speed of 20mV / s, with a potential scanning range of 1.0V to 1.5VvsRHE. Select the stabilized cyclic voltammetry curve, integrate its hydrogen desorption peak (0.05V to 0.4VvsRHE), and obtain the area S. Calculate the electrochemical active area ECSA according to formula 8:

[0186]

[0187] In formula 8, ECSA refers to the electrochemically active area, which is measured in square meters per gram (m / g), S refers to the integrated area of ​​the hydrogen desorption zone, which is measured in amperes (A*V), and C refers to the adsorption charge constant of hydrogen hydroxide on the smooth Pt surface, which is 0.21 millicoulombs per square centimeter (0.21mC / cm 2 ), V refers to the scanning speed in millivolts per second (mV / s), and M refers to the mass of Pt on the electrode in grams (g).

[0188] The electrode was cycled for 10,000 cycles in the range of 1.0 V to 1.5 V vs RHE, and the electrochemical active area retention rate before and after the cyclic voltammetry test of the working electrode was recorded.

[0189] 6) Test method for mass transfer impedance of catalytic layer:

[0190] The performance of a single cell prepared from carbon materials for the catalyst layer was tested on a battery test bench. The catalyst loading of the membrane electrode anode used was 0.2 mg / cm 2 , cathode catalyst loading 0.4 mg / cm 2 After full activation, the impedance test was carried out under the conditions of battery operating temperature of 80°C, humidity of 100RH%, battery back pressure of 150kPa / 150kPa, and connected to a load so that the current reached 2A / cm 2 ,In the current control mode, a 10% disturbance current is applied with a frequency of 10000Hz~0.5Hz.

[0191] Reference Figure 6 As shown, the Nyquist plot obtained by EIS test is Figure 6 The equivalent circuit shown is fitted to characterize the mass transfer impedance through a finite Warburg impedance element.

[0192] The test results of SA, fixed carbon, conductivity, pore characteristic value, cavity characteristic value, ideal density, true density and compacted density are shown in Table 3.

[0193] The test results of ICP-Pt, ECSA, ECSA retention rate and mass transfer impedance are shown in Table 4.

[0194] Table 3

[0195]

[0196]

[0197] Table 4

[0198]

[0199]

[0200] Combining the test results of Examples 1-19 and Tables 3-4, it can be seen that the sources of the pores of the carrier material include the pores of the template agent and the catalytic pores of the metal salt. The examples of the present application mainly change the mass concentration of the template agent mixed solution and the concentration of the metal salt mixed solution. The two work together to play a role in pore formation / cavity formation. The pore characteristic value of the obtained carrier material is 0.15-0.52g / cm 3 , the cavity characteristic value is about 7-60g / cm 3 The ICP-Pt that can be achieved is 46.2-49.2wt.% and ECSA is 66.7-96.2g / cm 3 , ECSA retention rate is 62.54-83.84%, and mass transfer impedance is 0.553-1.1312A / cm 2 @Ω.cm 2 According to the required ECSA retention rate and mass transfer impedance, the pore characteristic values ​​and cavity characteristic values ​​suitable for this application are screened, so as to realize the use of pore characteristic values ​​and cavity characteristic values ​​to represent the mass transfer capacity of the membrane electrode.

[0201] Combining the test results of Example 6 and Example 9 and Table 4, it can be seen that the specific surface area of ​​Example 6 is 1459.56 m 2 / g, ECSA is 79.1m 2 / g, ECSA retention rate is 62.54%, and mass transfer impedance is 1.131Ω.cm 2 @2A / cm2 ; The specific surface area of ​​Example 9 is 1502.91m 2 / g, ECSA is 89.5m 2 / g, ECSA retention rate is 83.84%, and mass transfer impedance is 0.637Ω.cm 2 @2A / cm 2 ; Example 6 and Example 9 belong to carrier materials with similar specific surface areas, but their ECSA retention rates and mass transfer impedances are significantly different, indicating that the mass transfer of membrane electrodes composed of carrier materials is quite different.

[0202] By changing the concentration of the template mixture under the same metal salt conditions, the prepared carrier material helps to attach more uniform metal salts to the template so that it can fully contact with the carbon source during the first heat treatment process to form certain template-connected or close pores or cavities. If the mass concentration of the template mixture is too high, the metal salt may not be dispersed uniformly on the template, and the above-mentioned pore-forming process cannot be achieved. If the metal salt acts directly on the carbon source without the template, a large number of unconnected micropores and cavities will be generated.

[0203] Under the condition of the same concentration of template agent, by changing the concentration of the metal salt mixed solution, the metal salt can catalyze graphitization during the second heat treatment, which helps to improve the stability of the mass transfer process; in addition, the residual metal salt can also act as a pore-forming agent, opening up some tiny micropores to form holes, reducing the cavity structure ratio, increasing the cavity characteristic value, and facilitating the improvement of the degree of graphitization. When used under high potential conditions such as start-up and shutdown, the carrier material has stronger corrosion resistance.

[0204] Combined with Examples 1-19, Table 4 and Figure 7 The test results show that there is a certain regularity between the pore characteristic value and the mass transfer impedance of the carrier material prepared in the present application. With the increase of the pore characteristic value, the mass transfer impedance increases synchronously in the trend, but there will be a sudden change in the change process. Therefore, the pore characteristic value is further screened, and the pore characteristic value is between 0.25-0.45g / cm 3 Between 0.45g / cm and 0.50g / cm, a carrier material with high mass transfer impedance can be obtained, and the mass transfer capacity of the membrane electrode is good. 3 When the pore characteristic value is less than 0.25g / cm, the mass transfer impedance rises sharply, resulting in a rapid decrease in the current density on the membrane electrode polarization curve, which in turn leads to a decrease in the membrane electrode power density. 3 When , the mass transfer impedance changes are not obvious enough.

[0205] Combined with Examples 1-19, Table 4 and Figure 8The test results show that there is a certain regularity between the cavity characteristic value and the ECSA retention rate of the carrier material prepared in the present application. With the increase of the cavity characteristic value, the ECSA retention rate first increases and then gradually decreases. Therefore, the preferred range of the cavity characteristic value is 10-50 g / cm 3 .

[0206] In summary, the mass transfer capacity of the membrane electrode is related to the size and type of the carbon material pores. During the mass transfer process, the cavities and channels connected to the outside world react continuously and stably, and the generated water can be discharged in time to ensure the continuous progress of the reaction. The organic biomass precursor treated at high temperature is decomposed and carbonized by heat, and the corresponding pore structure is generated under the action of the template agent. Under the catalysis of the metal salt, the surface graphite micro-chip layer molecules are polymerized and rearranged, and the regularity and order are continuously improved and tend to graphitization, and finally a porous carbon structure with a certain degree of graphitization is formed, which makes the mass transfer capacity of the membrane electrode excellent.

[0207] The carrier material and preparation method thereof provided in the embodiments of the present application are introduced in detail above. Specific examples are used herein to illustrate the principles and implementation methods of the present application. The description of the above embodiments is only used to help understand the method of the present application and its core idea. At the same time, for technicians in this field, according to the idea of ​​the present application, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as a limitation on the present application.

Claims

1. A method for preparing a carrier material, characterized in that: The steps include: Dispersing the template in the metal salt mixed solution to obtain a first product of a specific concentration; performing low-temperature vacuum drying on the first product to obtain a second product; mixing an organic carbon source with the second product to obtain a third product; performing a first heat treatment on the third product under vacuum or inert gas conditions to obtain a fourth product; washing the fourth product in an acid wash solution and drying the product to obtain a fifth product; performing a second heat treatment on the fifth product to obtain the support material; wherein the microscopic particles of the carrier material are configured to have a plurality of holes and a plurality of cavities, wherein the holes are connected to the outside of the microscopic particles and the cavities are isolated from the outside of the microscopic particles; The ratio of the mass of the carrier material to the total volume of the pores is defined as a pore characteristic value; the ratio of the mass of the carrier material to the total volume of the cavity is defined as a cavity characteristic value; the pore characteristic value of the carrier material is less than the cavity characteristic value of the carrier material; The pore characteristic value of the carrier material ranges from 0.250 g / cm 3 Up to 0.450g / cm 3 ; and / or the cavity characteristic value of the carrier material is in the range of 10.00 g / cm 3 Up to 50.00g / cm 3 .

2. The method for preparing a carrier material according to claim 1, wherein: The template comprises one or more of carbon quantum dots, nano-aluminum oxide, nano-silicon oxide, nano-magnesium oxide, nano-calcium oxide, and nano-calcium carbonate; The metal salt in the metal salt mixed solution includes one or more of ferric nitrate, chromium nitrate, cobalt nitrate, nickel nitrate, zinc nitrate, magnesium nitrate, ferric chloride, cobalt chloride, nickel chloride, zinc chloride, magnesium chloride, ferric sulfate, ferric sulfate, ferric sulfate, zinc sulfate, and magnesium sulfate; The mixed solvent in the metal salt mixed solution includes a mixture of one or more of isopropanol, ethylene glycol, n-butanol, N-methylpyrrolidone, ethanol and distilled water; The concentration of the metal salt mixed solution ranges from 10 mg / mL to 100 mg / mL, and the concentration of the first product of the specific concentration ranges from 10 wt.% to 50 wt.%.

3. The method for preparing a carrier material according to claim 1, wherein: The organic carbon source includes one or more of asphalt, sugar, heavy oil, fatty acid, polyvinyl alcohol, polyamide, epoxy resin, phenolic resin, organic salt and derivatives thereof; In mixing the organic carbon source with the second product to obtain a third product, a mass ratio of the organic carbon source to the second product ranges from 0.1 to 3.

4. The method for preparing a carrier material according to claim 1, wherein: In the first heat treatment of the third product under vacuum or inert gas conditions to obtain the fourth product, the heating rate of the first heat treatment is in the range of 1°C / min to 20°C / min, and the heat treatment temperature is in the range of 200°C to 1000°C.

5. The method for preparing a carrier material according to claim 1, wherein: The pickling solution includes one or more of hydrochloric acid, nitric acid, perchloric acid, sulfuric acid, acetic acid, and hydrofluoric acid; The molar concentration of the pickling solution ranges from 0.2 mol / L to 5 mol / L.

6. The method for preparing a carrier material according to any one of claims 1 to 5, characterized in that: The fifth product is subjected to a second heat treatment to obtain the carrier material, comprising the following steps: subjecting the fifth product to a high-temperature heat treatment under an inert atmosphere to obtain an intermediate product; Cooling the intermediate product; The intermediate product after cooling is subjected to medium-temperature heat treatment in an oxidative atmosphere to obtain the carrier material; Among them, the heating rate of the high-temperature heat treatment ranges from 1°C / min to 15°C / min, and the heat treatment temperature ranges from 1000°C to 3000°C; the heating rate of the medium-temperature heat treatment ranges from 1°C / min to 15°C / min, and the heat treatment temperature ranges from 100°C to 600°C.

7. A carrier material obtained by the method for preparing a carrier material according to any one of claims 1 to 6, wherein the microscopic particles of the carrier material are constructed to have a plurality of pores and a plurality of cavities, wherein: The hole is in communication with the outside of the microscopic particle, and the cavity is isolated from the outside of the microscopic particle; Features: The ratio of the mass of the support material to the total volume of the pores is defined as a pore characteristic value; The ratio of the mass of the carrier material to the total volume of the cavity is defined as a cavity characteristic value; wherein the pore characteristic value of the carrier material is less than the cavity characteristic value of the carrier material; The pore characteristic value of the carrier material ranges from 0.250 g / cm 3 Up to 0.450g / cm 3 ; and / or the cavity characteristic value of the carrier material is in the range of 10.00 g / cm 3 Up to 50.00g / cm 3 .

8. The carrier material according to claim 7, characterized in that: The specific surface area of ​​the carrier material ranges from 400 m 2 / g to 1500m 2 / g; and / or the particle size of the carrier material ranges from 100 nm to 2 μm; and / or the compacted density of the carrier material ranges from 0.05 g / mL to 0.80 g / mL; The conductivity of the carrier ranges from 6.4 S / cm to 26.5 S / cm; The fixed carbon content of the carrier ranges from 84.5% to 97.2%.

9. A fuel cell comprising the carrier material according to any one of claims 7 to 8.

10. Use of the support material according to any one of claims 7 to 8 in a membrane electrode of a fuel cell.

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