Catalyst layer preparation method, catalyst layer and fuel cell

Abstract

A catalyst layer preparation method, the method comprising the following steps: providing a supporting layer, and soaking the supporting layer in methanol; dissolving dimethylimidazole and zinc nitrate in the methanol in which the supporting layer is soaked so as to obtain a prefabricated liquid, the surface of the supporting layer reacting to form a metal organic framework, such that a prefabricated layer is obtained; cleaning and drying the prefabricated layer, and then soaking same in a mixed solution, the solvent of the mixed solution being at least one of an alcohol solvent and water, and the solute thereof comprising transition metal ions and chloroplatinic acid; and drying the soaked prefabricated layer, and then performing heat treatment on same in a reducing atmosphere at a preset temperature to carbonize the metal organic framework, thereby obtaining a catalyst layer. The metal organic framework material is carbonized to form the catalyst layer, and the in-situ synthesis of the metal organic framework allows for homogeneity and may form catalyst layers having relatively high uniformity.

Description

Preparation method of catalytic layer, catalytic layer, and fuel cell Technical Field

[0001] The present application relates to the field of fuel cells, and in particular to a fuel cell catalyst layer. Background Art

[0002] Proton exchange membrane fuel cells (PEMFCs) are a class of highly efficient energy conversion devices that primarily use hydrogen as a fuel. They offer advantages such as being green, pollution-free, and readily available. The membrane electrode (MEA), the core reaction site in PEMFCs, determines the upper limit of fuel cell performance and is crucial for reducing fuel cell costs. Currently, MEA fabrication primarily utilizes the second-generation catalyst-coated membrane (CCM) process, in which a catalyst slurry is sprayed onto the proton exchange membrane using various coating techniques. However, the preparation of the catalytic layer involves a series of processes, including catalyst preparation, slurry preparation, slurry spraying, and catalyst layer drying, which can affect the consistency of the catalytic layer preparation. Furthermore, the catalytic layer of MEAs prepared using the CCM process often lacks a well-defined microstructure and numerous nanoscale porous transport channels. This can hinder water vapor transport in the catalytic layer and even the MEA, ultimately leading to MEA failure, particularly performance degradation at high current densities.

[0003] Summary of the Invention

[0004] The embodiments of the present application provide a method for preparing a catalytic layer, a catalytic layer, and a fuel cell to solve the technical problems of poor consistency and water vapor transmission barriers in MEA prepared by the CCM process.

[0005] In a first aspect, an embodiment of the present application provides a method for preparing a catalytic layer, the method comprising the following steps:

[0006] providing a support layer, and soaking the support layer in methanol;

[0007] dissolving dimethylimidazole and zinc nitrate in methanol soaked with the support layer to obtain a prefabricated solution, and reacting on the surface of the support layer to form a metal organic framework to obtain a prefabricated layer;

[0008] After washing and drying the prefabricated layer, the prefabricated layer is immersed in a mixed solution, wherein the solvent of the mixed solution is at least one of an alcohol solvent and water, and the solute includes transition metal ions and chloroplatinic acid;

[0009] The soaked prefabricated layer is dried and then heat-treated at a predetermined temperature in a reducing atmosphere to carbonize the metal organic framework to obtain the catalytic layer.

[0010] In some embodiments of the present application, the support layer is a gas diffusion layer, and the step of immersing the support layer in methanol comprises the following steps:

[0011] The gas diffusion layer is immersed in methanol, with the microporous layer of the gas diffusion layer facing upward.

[0012] In some embodiments of the present application, the transition metal includes at least one of Co, Cu, Fe, and Ni.

[0013] In some embodiments of the present application, the solvent of the mixed solution is a mixed solvent of methanol and water, and the mass ratio of methanol to water is 1:(0.3-3); and / or,

[0014] In the mixed solution, the concentration of chloroplatinic acid is 0.005-0.05 mol / L, and the concentration of transition metal ions is 0.02-0.2 mol / L.

[0015] In some embodiments of the present application, the predetermined temperature is 600-800°C.

[0016] In some embodiments of the present application, the reducing atmosphere is provided by hydrogen and argon, wherein the volume ratio of hydrogen is 5%-20%.

[0017] In some embodiments of the present application, after carbonization, the metal-organic framework is further soaked in an acid solution, and then washed and dried.

[0018] In a second aspect, an embodiment of the present application provides a catalytic layer, which is prepared by the preparation method of the catalytic layer described in any embodiment of the first aspect.

[0019] In a third aspect, an embodiment of the present application provides a fuel cell, comprising the catalytic layer described in any embodiment of the second aspect.

[0020] The above technical solution provided by the embodiment of the present application has the following advantages compared with the prior art:

[0021] The preparation method of the catalytic layer provided in the embodiment of the present application is to form a catalytic layer by carbonizing the metal organic framework material. It is completely different from the existing CCM process, and there are no operations such as pulping, coating and hot pressing, which avoids the catalyst consistency problem caused by multiple processes. The present application synthesizes the metal organic framework in situ, and the properties are uniform, and a catalytic layer with strong consistency can be formed. In addition, the catalytic layer obtained in the present application is obtained by carbonizing the metal organic framework, which has a rich porous nanostructure and can form a large number of nanoscale porous transmission channels, which is beneficial to improving the operating efficiency of the fuel cell, and is particularly beneficial to the operation of the fuel cell under high current density. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0023] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0024] FIG1 is a SEM image of the catalyst layer obtained in Example 1 of the present application;

[0025] FIG2 is a polarization curve diagram of the membrane electrode obtained in Example 1 of the present application and the comparative example. DETAILED DESCRIPTION

[0026] To make the purpose, technical solutions, and advantages of the embodiments of this application more clear, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the drawings in the embodiments of this application. Obviously, the described embodiments are part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0027] Unless otherwise specified, the terms used herein should be understood as having the same meaning as commonly used in the art. Therefore, unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application belongs. In the event of any conflict, the present specification shall take precedence.

[0028] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this application can be purchased from the market or prepared by existing methods.

[0029] The MEA prepared by the CCM process of proton exchange membrane fuel cell membrane electrode has technical problems such as poor consistency and water vapor transmission barriers.

[0030] The technical solutions provided in the embodiments of this application are intended to solve the above technical problems, and the overall idea is as follows:

[0031] In a first aspect, an embodiment of the present application provides a method for preparing a catalytic layer, the method comprising the following steps:

[0032] S1: providing a support layer, and soaking the support layer in methanol;

[0033] S2: dissolving dimethylimidazole and zinc nitrate in methanol soaked with the support layer to obtain a prefabricated solution, and reacting on the surface of the support layer to form a metal organic framework to obtain a prefabricated layer;

[0034] S3: washing and drying the prefabricated layer, and then immersing the prefabricated layer in a mixed solution, wherein the solvent of the mixed solution is at least one of an alcohol solvent and water, and the solute includes transition metal ions and chloroplatinic acid;

[0035] S4: drying the soaked prefabricated layer and then heat-treating it at a predetermined temperature in a reducing atmosphere to carbonize the metal organic framework to obtain the catalytic layer.

[0036] It should be noted that the support layer described in this application is a material used to provide a support interface for the formation of the catalyst layer. As a preferred embodiment, the support layer can be a gas diffusion layer.

[0037] Those skilled in the art will appreciate that in order to uniformly grow the MOF on the support layer, it is necessary to ensure that the dimethylimidazole and zinc nitrate are fully dissolved. As an example, a methanol solution of dimethylimidazole and a methanol solution of zinc nitrate can be prepared first, and then these two solutions can be added to the methanol in which the support layer is soaked.

[0038] Those skilled in the art will appreciate that preparing a metal organic framework by using dimethylimidazole and zinc nitrate is a conventional method in the art.

[0039] The prefabricated layer is immersed in the mixed solution, where it can adsorb chloroplatinic acid and transition metal ions. The transition metal ions also coordinate with the coordinating functional groups on the dimethylimidazole. This can also cause the transition metal ions to replace zinc ions.

[0040] Those skilled in the art will appreciate that, as a preferred embodiment, the filtered metal ions are dissolved in the mixed solution in the form of nitrates. This is because nitrates are easily decomposed during the subsequent heat treatment, allowing the transition metal ions to easily form oxides and then be reduced, and residual nitrates are therefore easily removed.

[0041] After being soaked, the prefabricated layer is heat-treated in a reducing atmosphere, and the metal organic framework is carbonized to form a porous carbon layer; at the same time, the transition metal ions in the metal organic framework are also reduced to metals to form alloy nanoparticles with metal platinum.

[0042] Those skilled in the art can prepare a reducing gas to form the reducing atmosphere based on existing knowledge in the field, such as ammonia, hydrogen, and mixtures thereof with inert gases. Those skilled in the art will understand that carbon monoxide is not suitable for use in the reducing atmosphere of this application due to its strong coordination ability. In other words, the reducing atmosphere referred to in this application does not include carbon monoxide.

[0043] The present application forms a catalytic layer after carbonizing the metal organic framework material, which is completely different from the existing CCM process. There are no operations such as pulping, coating and hot pressing, which avoids the catalyst consistency problem caused by multiple processes. The present application synthesizes the metal organic framework in situ, and the properties are uniform, and a catalytic layer with strong consistency can be formed. In addition, the catalytic layer obtained in the present application is obtained by carbonizing the metal organic framework, which has a rich porous nanostructure and can form a large number of nanoscale porous transmission channels, which is beneficial to improving the operating efficiency of the fuel cell, especially beneficial to the operation of the fuel cell under high current density.

[0044] In some embodiments of the present application, the support layer is a gas diffusion layer, and the step of immersing the support layer in methanol comprises the following steps:

[0045] S11: immersing the gas diffusion layer in methanol, and keeping the microporous layer of the gas diffusion layer facing upward.

[0046] Those skilled in the art will understand that a gas diffusion layer typically comprises carbon paper and a microporous layer disposed on the carbon paper. Those skilled in the art will also understand that when the gas diffusion layer is immersed in methanol, it will sink to the bottom of the container containing the methanol. However, this application requires in-situ preparation of an organic metal framework on the microporous layer. If the microporous layer faces downward, it will stick to the bottom of the container, hindering the formation of the organic metal framework. Therefore, the microporous layer needs to face upward.

[0047] The concentrations of zinc nitrate and dimethylimidazole in methanol in the preformed solution affect the rate of metal-organic framework formation. Excessively high concentrations of zinc nitrate and dimethylimidazole lead to overly rapid metal-organic framework formation, resulting in poor uniformity of the metal-organic framework formed by the surface reaction of the support layer. Excessively low concentrations of zinc nitrate and dimethylimidazole result in a slow rate of metal-organic framework formation.

[0048] In some embodiments of the present application, the transition metal includes at least one of Co, Cu, Fe, and Ni.

[0049] Nitrates of Co, Cu, Fe, and Ni are all common industrial raw materials. The alloys formed by Co, Cu, Fe, Ni and platinum have good catalytic activity for oxygen reduction reaction and hydrogen oxidation reaction in proton exchange membrane fuel cells.

[0050] In some embodiments of the present application, the solvent of the mixed solution is a mixed solvent of methanol and water, and the mass ratio of methanol to water is 1:(0.3-3); and / or,

[0051] In the mixed solution, the concentration of chloroplatinic acid is 0.005-0.05 mol / L, and the concentration of transition metal ions is 0.02-0.2 mol / L.

[0052] The beneficial effect of using a methanol-water mixture as the solvent for the mixed solution is that it optimizes the distribution of organic molecules such as dimethylimidazole, facilitating its uniform dispersion. A methanol-water mass ratio of 1:0.3-3 is beneficial for fine-tuning the solvent's solubility, regulating the coordination rate between organic molecules and zinc ions and the spatial structure of the coordinated molecules.

[0053] The beneficial effect of controlling the concentrations of chloroplatinic acid and transition metal ions within the above range is that a large number of alloy nanoparticles with catalytic activity can be generated without causing the alloy nanoparticles to have too large a particle size, thereby reducing the catalytic activity or even causing agglomeration.

[0054] In some embodiments of the present application, the predetermined temperature is 600-800°C.

[0055] The beneficial effect of controlling the predetermined temperature within the above range is that the metal organic framework can be fully carbonized without causing excessive growth of alloy nanoparticles, excessive particle size, or even agglomeration.

[0056] In some embodiments of the present application, the reducing atmosphere is provided by a mixture of hydrogen and argon, wherein the volume ratio of hydrogen is 5%-20%.

[0057] Controlling the volume ratio of hydrogen to the above range can provide a mild environment for the reduction of valuable metal elements, thereby controlling the growth rate of alloy nanoparticles.

[0058] In some embodiments of the present application, after carbonization, the metal-organic framework is further soaked in an acid solution, and then washed and dried.

[0059] As an example, the acid solution may be at least one of sulfuric acid, nitric acid, and hydrochloric acid solutions, preferably hydrochloric acid or nitric acid solutions, because any residual hydrochloric acid or nitric acid is likely to volatilize during subsequent high-temperature treatment.

[0060] As an example, the hydrogen ion concentration in the acid solution may be 0.2-2 mol / L, and the soaking time in the acid solution may be 8-24 hours.

[0061] In a second aspect, embodiments of the present application provide a catalytic layer, which is prepared by the method for preparing a catalytic layer described in any embodiment of the first aspect. The catalytic layer is implemented based on the method for preparing a catalytic layer described in the first aspect. The specific implementation of the catalytic layer can refer to the embodiments of the first aspect. Since the catalytic layer adopts all the technical solutions of the embodiments of the first aspect, it has at least all the beneficial effects brought about by the technical solutions of the embodiments of the first aspect, and will not be detailed here.

[0062] In a third aspect, embodiments of the present application provide a fuel cell, comprising the catalytic layer described in any embodiment of the second aspect. The fuel cell is implemented based on the catalytic layer described in the second aspect. The specific implementation of the fuel cell can refer to the embodiments of the second aspect and common knowledge in the field of fuel cells. Because the fuel cell utilizes all of the technical solutions of the embodiments of the second aspect, it at least has all of the beneficial effects brought about by the technical solutions of the embodiments of the second aspect, and no further details will be given here.

[0063] The present application will be further described below in conjunction with specific examples. It should be understood that these examples are intended to illustrate the present application only and are not intended to limit the scope of the present application. The experimental methods in the following examples where specific conditions are not specified are generally measured in accordance with national standards. If there are no corresponding national standards, then the methods are carried out in accordance with general international standards, conventional conditions, or the conditions recommended by the manufacturer.

[0064] Example 1

[0065] This embodiment provides a catalytic layer, which is prepared by the following steps in sequence:

[0066] Providing a gas diffusion layer, immersing the gas diffusion layer in 60 mL of anhydrous methanol, with the microporous layer of the gas diffusion layer facing upward, the gas diffusion layer and the anhydrous methanol used for immersion together forming a pre-reaction system A;

[0067] Add 500 mg of dimethylimidazole to 50 mL of anhydrous methanol and stir at 500 r / min for 30 min to obtain solution B;

[0068] 300 mg of zinc nitrate hexahydrate was added to 50 mL of anhydrous methanol and stirred at 500 r / min for 30 min to obtain solution C;

[0069] Solution B and solution C were added to the pre-reaction system A to obtain a reaction system D, which was stirred at 500 r / min for 40 min to obtain a composite layer having a metal organic framework and a gas diffusion layer. The composite layer was washed and dried at 60°C for 12 h.

[0070] Providing 30 mL of a mixed solvent E formed by mixing anhydrous methanol and water in a mass ratio of 1:1, immersing the composite layer therein, and adding dropwise a solution F into the mixed solvent E, wherein the solution F is a mixed solution of cobalt nitrate and chloroplatinic acid, wherein the concentration of cobalt ions is 0.1 mol / L, the concentration of chloroplatinic acid is 0.05 mol / L, and the volume of the solution F is 3-20 mL;

[0071] The soaked composite layer was dried at 60°C for 12 hours, then placed in a quartz sintering boat, transferred to a tube furnace, and treated at 700°C for 3 hours in a reducing atmosphere, wherein the reducing atmosphere is a mixture of hydrogen and argon, wherein the volume ratio of hydrogen is 10%;

[0072] After the composite layer is cooled, it is soaked in 1 mol / L hydrochloric acid for 20 minutes, the composite layer is taken out, washed, and then dried at 60° C. for 12 hours to obtain the catalytic layer.

[0073] This embodiment also provides a fuel cell, which is prepared by the following method:

[0074] Providing proton exchange membranes;

[0075] The catalyst layer obtained in this embodiment is attached to the gas diffusion layer, and the catalyst is attached to both sides of the proton exchange membrane to obtain a membrane electrode.

[0076] The obtained membrane electrode is assembled with the gas exchange layer and the outer shell component of the fuel cell to obtain the fuel cell.

[0077] Example 2

[0078] This embodiment provides a catalytic layer, which is prepared by the following steps in sequence:

[0079] Providing a gas diffusion layer, immersing the gas diffusion layer in 60 mL of anhydrous methanol, with the microporous layer of the gas diffusion layer facing upward, the gas diffusion layer and the anhydrous methanol used for immersion together forming a pre-reaction system A;

[0080] Add 2000 mg of dimethylimidazole to 50 mL of anhydrous methanol and stir at 500 r / min for 30 min to obtain solution B;

[0081] 1500 mg of zinc nitrate hexahydrate was added to 50 mL of anhydrous methanol and stirred at 500 r / min for 30 min to obtain solution C;

[0082] Solution B and solution C were added to the pre-reaction system A to obtain a reaction system D, which was stirred at 500 r / min for 40 min to obtain a composite layer having a metal organic framework and a gas diffusion layer. The composite layer was washed and dried at 60°C for 12 h.

[0083] Providing 100 mL of a mixed solvent E formed by mixing anhydrous methanol and water in a mass ratio of 1:1, immersing the composite layer therein, and dropwise adding solution F into the mixed solvent E, wherein solution F is a mixed solution of nickel nitrate and chloroplatinic acid, wherein the concentration of nickel ions is 0.1 mol / L, the concentration of chloroplatinic acid is 0.05 mol / L, and the volume of solution F is 3-20 mL;

[0084] The soaked composite layer was dried at 60°C for 12 hours, then placed in a quartz sintering boat, transferred to a tube furnace, and treated at 700°C for 3 hours in a reducing atmosphere, wherein the reducing atmosphere is a mixture of hydrogen and argon, wherein the volume ratio of hydrogen is 10%;

[0085] After the composite layer is cooled, it is soaked in 1 mol / L hydrochloric acid for 20 minutes, the composite layer is taken out, washed, and then dried at 60° C. for 12 hours to obtain the catalytic layer.

[0086] This embodiment also provides a fuel cell, which is prepared by the following method:

[0087] Providing proton exchange membranes;

[0088] The catalyst layer obtained in this embodiment is attached to the gas diffusion layer, and the catalyst is attached to both sides of the proton exchange membrane to obtain a membrane electrode.

[0089] The obtained membrane electrode is assembled with the gas exchange layer and the outer shell component of the fuel cell to obtain the fuel cell.

[0090] Example 3

[0091] This embodiment provides a catalytic layer, which is prepared by the following steps in sequence:

[0092] Providing a gas diffusion layer, immersing the gas diffusion layer in 60 mL of anhydrous methanol, with the microporous layer of the gas diffusion layer facing upward, the gas diffusion layer and the anhydrous methanol used for immersion together forming a pre-reaction system A;

[0093] Add 1000 mg of dimethylimidazole to 50 mL of anhydrous methanol and stir at 500 r / min for 30 min to obtain solution B;

[0094] 800 mg of zinc nitrate hexahydrate was added to 50 mL of anhydrous methanol and stirred at 500 r / min for 30 min to obtain solution C;

[0095] Solution B and solution C were added to the pre-reaction system A to obtain a reaction system D, which was stirred at 500 r / min for 40 min to obtain a composite layer having a metal organic framework and a gas diffusion layer. The composite layer was washed and dried at 60°C for 12 h.

[0096] Providing 50 mL of a mixed solvent E formed by mixing anhydrous methanol and water in a mass ratio of 1:1, immersing the composite layer therein, and adding dropwise a solution F into the mixed solvent E, wherein the solution F is a mixed solution of copper nitrate, ferric nitrate, and chloroplatinic acid, wherein the concentration of the copper ion is 0.02 mol / L, the concentration of the iron ion is 0.08 mol / L, the concentration of the chloroplatinic acid is 0.05 mol / L, and the volume of the solution F is 3-20 mL;

[0097] The soaked composite layer was dried at 60°C for 12 hours, then placed in a quartz sintering boat, transferred to a tube furnace, and treated at 700°C for 3 hours in a reducing atmosphere, wherein the reducing atmosphere is a mixture of hydrogen and argon, wherein the volume ratio of hydrogen is 10%;

[0098] After the composite layer is cooled, it is soaked in 1 mol / L hydrochloric acid for 20 minutes, the composite layer is taken out, washed, and then dried at 60° C. for 12 hours to obtain the catalytic layer.

[0099] This embodiment also provides a fuel cell, which is prepared by the following method:

[0100] Providing proton exchange membranes;

[0101] The catalyst layer obtained in this embodiment is attached to the gas diffusion layer, and the catalyst is attached to both sides of the proton exchange membrane to obtain a membrane electrode.

[0102] The obtained membrane electrode is assembled with the gas exchange layer and the outer shell component of the fuel cell to obtain the fuel cell.

[0103] Comparative Example

[0104] The difference between this comparative example and Example 1 is that the catalytic material prepared in this comparative example is exactly the same as that in Example 1, but the catalytic layer is formed by the traditional CCM process. The details are as follows:

[0105] This comparative example first provides a catalytic material, which is prepared by the following method:

[0106] Provide 60 mL of anhydrous methanol as pre-reaction system A;

[0107] Add 500 mg of dimethylimidazole to 50 mL of anhydrous methanol and stir at 500 r / min for 30 min to obtain solution B;

[0108] 300 mg of zinc nitrate hexahydrate was added to 50 mL of anhydrous methanol and stirred at 500 r / min for 30 min to obtain solution C;

[0109] Solution B and solution C were added to the pre-reaction system A to obtain reaction system D, which was stirred at 500 r / min for 40 min to obtain a metal-organic framework. The metal-organic framework was washed and dried at 60°C for 12 h.

[0110] Providing 30 mL of a mixed solvent E formed by mixing anhydrous methanol and water in a mass ratio of 1:1, immersing the metal-organic framework therein, and dropwise adding solution F into the mixed solvent E, wherein solution F is a mixed solution of cobalt nitrate and chloroplatinic acid, wherein the concentration of cobalt ions is 0.1 mol / L, the concentration of chloroplatinic acid is 0.05 mol / L, and the volume of solution F is 3-20 mL;

[0111] The impregnated metal-organic framework was dried at 60°C for 12 hours, then placed in a quartz sintering boat, transferred to a tube furnace, and treated at 700°C for 3 hours in a reducing atmosphere, wherein the reducing atmosphere was a mixture of hydrogen and argon, with a volume ratio of hydrogen of 10%;

[0112] After the metal organic framework is cooled, it is soaked in 1 mol / L hydrochloric acid for 20 minutes. The metal organic framework is taken out, washed, and then dried at 60° C. for 12 hours to obtain the catalytic material.

[0113] This comparative example also provides a fuel cell, which is prepared by the following method:

[0114] Providing proton exchange membranes;

[0115] Preparation of the catalytic layer: The catalytic material provided in this comparative example was moistened with deionized water, and then a 5% by mass Nafion emulsion and isopropanol were added and mixed evenly to obtain a catalyst ink, wherein the solid content of the catalyst ink was controlled to be 2%; the catalyst ink was ultrasonically treated in an ice-water bath for 30 minutes, and then ultrasonically sprayed onto both sides of the proton exchange membrane to form an anode catalyst layer and a cathode catalyst layer, thereby obtaining a membrane electrode.

[0116] The obtained membrane electrode is assembled with the gas exchange layer and the outer shell component of the fuel cell to obtain the fuel cell.

[0117] Related experiments and effect data:

[0118] A scanning electron microscope (SEM) test was performed on Example 1, and the obtained SEM image is shown in FIG1 .

[0119] Figure 1 shows a uniform distribution of carbon nanotubes and stacked pore structures on the surface of the catalyst layer, with the nanostructures measuring tens of nanometers. These complex nanostructures provide numerous channels for water and gas transport, ensuring optimal mass transfer polarization at high current densities.

[0120] Hydrogen-air fuel cell tests were conducted on Example 1 and the comparative example under the following conditions: the membrane electrode was activated and loaded at 0.5 V for 2 hours until the current density reached a steady state. The electrode area was 25 cm², and the test conditions were 80°C, 100% relative humidity, 150 kPa back pressure, 500 cc / min cathode / 210 cc / min anode gas flow rates, and 1.5 / 2.5 excess coefficients. Polarization curves were then run over a range of 0-65 A, with a test point taken every 2.5 A, and a 60-second interval between test points.

[0121] The polarization curves of Example 1 and the comparative example are shown in FIG2 . It can be seen that the membrane electrode of Example 1 has a high polarization current of 2000 mA / cm 2 The voltage reaches 0.580V under high current density, and the corresponding power density reaches 1.16W / cm 2 , showing excellent membrane electrode performance. While the comparative example is at 2000mA / cm 2 The voltage is 0.505V at the current density, and the corresponding power density is 1.01W / cm 2 , and did not exceed the performance of the membrane electrode obtained by the general CMM process. Since the materials of Example 1 and the comparative example are exactly the same, and the only difference is the preparation process of the catalytic layer, the hydrogen-air fuel cell test results can prove that the preparation method used in Example 1 is more superior.

[0122] 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 hard 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 numbers within the range. For example, the description of a range 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 applies 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.

[0123] In this application, unless otherwise indicated, directional terms such as "upper" and "lower" refer specifically to the directions of the drawings in the accompanying drawings. In addition, in the description of this application specification, the terms "include", "comprise", etc. mean "including but not limited to". Moreover, the terms "include", "comprises", or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article, or device comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article, or device. In the absence of further restrictions, the elements defined by the phrase "include..." do not exclude the presence of other identical elements in the process, method, article, or device comprising the elements. In this document, relational terms such as "first" and "second" are merely used to distinguish one entity or operation from another, and do not necessarily require or imply any actual relationship or order between these entities or operations. In this document, "and / or" describes the association relationship between associated objects, indicating that three relationships can exist. For example, A and / or B can mean: A exists alone, A and B exist simultaneously, or B exists alone. For the association relationship of more than three associated objects described with "and / or", it means that any one of these three associated objects can exist alone, or any at least two of them exist at the same time. For example, for A, and / or B, and / or C, it can be represented that any one of A, B, and C exists alone, or any two of them exist at the same time, or three of them exist at the same time. In this article, "at least one" refers to one or more, and "multiple" refers to two or more. "At least one", "the following at least one (individual)" or similar expressions refer to any combination of these items, including any combination of single item (individual) or plural items (individual). For example, "at least one (individual) of a, b, or c", or "at least one (individual) of a, b, and c", can all represent: a, b, c, ab (i.e., a and b), ac, bc or abc, where a, b, c can be single or multiple, respectively.

[0124] The foregoing is merely a list of specific embodiments of the present application, intended to enable those skilled in the art to understand or implement the present application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application is not limited to the embodiments shown herein, but is intended to conform to the broadest scope consistent with the principles and novel features of the present application.

Claims

1. A method for preparing a catalytic layer, characterized in that: The method comprises the following steps: providing a support layer, and immersing the support layer in methanol; Dissolving dimethylimidazole and zinc nitrate into methanol soaked with the support layer to obtain a prefabricated liquid, and reacting on the surface of the support layer to form a metal organic framework to obtain a prefabricated layer; After washing and drying the prefabricated layer, the prefabricated layer is immersed in a mixed solution, wherein the solvent of the mixed solution is at least one of an alcohol solvent and water, and the solute includes transition metal ions and chloroplatinic acid; The soaked prefabricated layer is dried and then heat-treated at a predetermined temperature in a reducing atmosphere to carbonize the metal organic framework to obtain the catalytic layer.

2. The method for preparing a catalytic layer according to claim 1, characterized in that: The supporting layer is a gas diffusion layer, and the step of immersing the supporting layer in methanol comprises the following steps: The gas diffusion layer is immersed in methanol, and the microporous layer of the gas diffusion layer is kept facing upward.

3. The method for preparing a catalyst layer according to claim 1, characterized in that: The transition metal includes at least one of Co, Cu, Fe and Ni.

4. The method for preparing a catalyst layer according to claim 1, characterized in that: The solvent of the mixed solution is a mixed solvent of methanol and water, and the mass ratio of methanol to water is 1:(0.3-3); and / or, In the mixed solution, the concentration of chloroplatinic acid is 0.005-0.05 mol / L, and the concentration of transition metal ions is 0.02-0.2 mol / L.

5. The method for preparing a catalyst layer according to claim 1, characterized in that: The predetermined temperature is 600-800°C.

6. The method for preparing a catalytic layer according to claim 1, characterized in that: The reducing atmosphere is provided by hydrogen and argon, wherein the volume ratio of hydrogen is 5%-20%.

7. The method for preparing a catalyst layer according to claim 1, characterized in that: After carbonization, the metal organic framework is further immersed in an acid solution, and then washed and dried.

8. A catalytic layer, characterized in that: The catalytic layer is prepared by the method for preparing a catalytic layer according to any one of claims 1 to 7.

9. A fuel cell, characterized in that: The fuel cell comprises the catalyst layer according to claim 8.

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