Method for preparing microporous layer, microporous layer, gas diffusion layer, and fuel cell

Abstract

A method for preparing a microporous layer. The method comprises the following steps: dissolving a nonionic surfactant and an alcohol solvent in water, so as to obtain a pre-prepared solution; uniformly dispersing carbon powder in the pre-prepared solution, so as to obtain a carbon powder dispersion liquid; uniformly dispersing an ionic polymer in which the main chain thereof is bonded to fluorine atoms into the carbon powder dispersion liquid, so as to obtain a microporous layer slurry; and disposing the microporous layer slurry on the surface of a microporous layer carrier to form a slurry layer, drying the slurry layer, and then roasting same at a predetermined temperature, so as to obtain a microporous layer. In the method, the ionic polymer containing fluorine atoms is used as a hydrophobic agent; the ionic polymer itself has hydrophilicity, can be dissolved in an aqueous ethanol solution, and thus can eliminate the phenomenon of demulsification; and the ionic polymer is uniformly dispersed in the microporous layer slurry, and is then roasted to remove hydrophilic side chains or side groups, so as to form hydrophobic macromolecules uniformly distributed in the microporous layer, thereby allowing the microporous layer to have relatively uniform hydrophobicity.

Description

Preparation method of microporous layer, microporous layer, gas diffusion layer, and fuel cell Technical Field

[0001] The present application relates to the field of proton exchange membrane fuel cells, and in particular to a gas diffusion layer. Background Art

[0002] Proton exchange membrane fuel cells (PEMFCs) are an important part of the development of hydrogen energy and fuel cell technology. They have the advantages of being environmentally friendly, pollution-free, and having high specific power. In recent years, as a power source for vehicles, various domestic and foreign automakers have carried out strategic layouts for fuel cells, and they are widely used in passenger cars and commercial vehicles. The core component of the proton exchange membrane fuel cell is the membrane electrode (MEA), which is the place where the electrochemical reaction of the fuel cell occurs. Its performance directly determines whether the fuel cell can be used. It is usually composed of a gas diffusion layer (GDL), a catalyst layer, and a proton exchange membrane. At present, automotive proton exchange membrane fuel cells are being developed in the direction of high power, mainly for commercial vehicles and heavy trucks. High-power stacks usually require higher power output, and the stacks need to work at high current density (>1500mA / cm 2 ), under this operating condition, a large amount of liquid water is produced inside the battery due to the reaction, which will cause water flooding inside the membrane electrode, thereby causing the performance and durability of the membrane electrode to decline.

[0003] Therefore, the gas diffusion layer in the membrane electrode needs to be treated with hydrophobicity to enable rapid liquid water transport during battery operation and prevent a decrease in gas transmission efficiency. The traditional method is to add polytetrafluoroethylene (PTFE) or polyvinylidene fluoride (PVDF) to the carbon paper substrate and microporous layer (MPL) for hydrophobic treatment, which is also the mainstream hydrophobic method for commercial carbon paper. The method of adding polytetrafluoroethylene or polyvinylidene fluoride to the carbon paper substrate is relatively simple. It only requires dipping the carbon paper substrate in a suitable polytetrafluoroethylene or polyvinylidene fluoride emulsion and then undergoing a high-temperature sintering process to make it hydrophobic. However, making the microporous layer hydrophobic is more complicated. The microporous layer slurry only contains carbon powder and polytetrafluoroethylene or polyvinylidene fluoride. When preparing the microporous layer slurry, the polytetrafluoroethylene or polyvinylidene fluoride emulsion is prone to demulsification in the carbon powder solution, causing the slurry to agglomerate or unevenly disperse. Ultimately, the wettability of the coated microporous layer is greatly varied. The hydrophilic area will cause liquid water to accumulate, affecting the gas transmission of the battery. In addition, the uneven dispersion of the microporous layer slurry also causes a large roughness on the surface of the microporous layer, increasing the ohmic polarization of the battery and also reducing the battery performance.

[0004] Summary of the Invention

[0005] The embodiments of the present application provide a method for preparing a microporous layer, a microporous layer, and a gas diffusion layer to solve the technical problem of uneven slurry dispersion when preparing microporous layer slurry.

[0006] In a first aspect, an embodiment of the present application provides a method for preparing a microporous layer, the method comprising the following steps:

[0007] Dissolving a nonionic surfactant and an alcohol solvent in water to obtain a prefabricated solution;

[0008] Evenly dispersing carbon powder into the prefabricated solution to obtain a carbon powder dispersion;

[0009] uniformly dispersing an ionic polymer having fluorine atoms connected to its main chain into the carbon powder dispersion to obtain a microporous layer slurry;

[0010] The microporous layer slurry is placed on the surface of a microporous layer support to form a slurry layer, and the slurry layer is dried and then calcined at a predetermined temperature to obtain the microporous layer.

[0011] In some embodiments of the present application, the nonionic surfactant is Triton X100; and / or,

[0012] The alcohol solvent is at least one of isopropyl alcohol, ethanol and glycerol; and / or,

[0013] The carbon powder is at least one of solid carbon, porous carbon, graphite, conductive carbon black, and carbon nanotubes; and / or,

[0014] The ionic polymer is at least one of perfluorosulfonic acid resin, perfluorocarboxylic acid resin, ionic polyvinylidene fluoride, and ionic polyperfluoroethylene propylene.

[0015] In some embodiments of the present application, the carbon powder is uniformly dispersed in the prefabricated solution by at least one of mechanical stirring, ball milling, or ultrasonic shearing; and / or,

[0016] The ionic polymer is uniformly dispersed in the carbon powder dispersion by at least one of mechanical stirring, ball milling or ultrasonic shearing.

[0017] In some embodiments of the present application, in the microporous layer slurry, the mass ratio of carbon powder, water, alcohol, nonionic surfactant, and ionic polymer is 1:(10-30):(1-10):(0.1-1):(0.1-0.8).

[0018] In some embodiments of the present application, the predetermined temperature is 350-380°C.

[0019] In some embodiments of the present application, the microporous layer carrier is carbon paper.

[0020] In some embodiments of the present application, the carbon paper is bare carbon paper that has undergone hydrophobic treatment.

[0021] In a second aspect, an embodiment of the present application provides a microporous layer, which is a microporous layer prepared by any embodiment of the first aspect.

[0022] In a third aspect, an embodiment of the present application provides a gas diffusion layer, which includes the microporous layer described in any embodiment of the second aspect.

[0023] In a fourth aspect, an embodiment of the present application provides a fuel cell, which includes the gas diffusion layer described in the third aspect.

[0024] The above technical solution provided by the embodiment of the present application has the following advantages compared with the prior art:

[0025] The method for preparing a microporous layer provided in the embodiments of the present application utilizes a fluorine-containing ionic polymer instead of conventional polytetrafluoroethylene or polyvinylidene fluoride as a hydrophobic agent. The ionic polymer is inherently hydrophilic and soluble in aqueous-alcoholic solutions, eliminating demulsification. It is uniformly dispersed in the microporous layer slurry. The hydrophilic side chains or groups are then removed by calcination, resulting in a hydrophobic polymer uniformly distributed throughout the microporous layer, imparting relatively uniform hydrophobicity to the microporous layer. Furthermore, due to the relatively uniform dispersion of the components within the microporous layer slurry, the resulting microporous layer has low surface roughness, which reduces the contact resistance between the microporous layer and the catalytic layer, thereby improving battery performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] 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.

[0027] 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.

[0028] FIG1 is a schematic flow chart of a method for preparing a microporous layer provided in an embodiment of the present application. DETAILED DESCRIPTION

[0029] 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.

[0030] 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.

[0031] 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.

[0032] The existing proton exchange membrane fuel cell manufacturing process has a technical problem of uneven slurry dispersion when preparing the microporous layer slurry.

[0033] 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:

[0034] In a first aspect, an embodiment of the present application provides a method for preparing a microporous layer. Referring to FIG1 , the method comprises the following steps:

[0035] S1: dissolving a nonionic surfactant and an alcohol solvent in water to obtain a prefabricated solution;

[0036] S2: evenly dispersing the carbon powder into the prefabricated solution to obtain a carbon powder dispersion;

[0037] S3: uniformly dispersing an ionic polymer having fluorine atoms connected to its main chain into the carbon powder dispersion to obtain a microporous layer slurry;

[0038] S4: placing the microporous layer slurry on the surface of the microporous layer support to form a slurry layer, drying the slurry layer, and then calcining it at a predetermined temperature to obtain the microporous layer.

[0039] Those skilled in the art will understand that non-ionic surfactants refer to surfactants that are not ionized in aqueous solution, and their hydrophilic groups are mainly composed of a certain number of oxygen-containing groups (such as ether groups and hydroxyl groups), and their lipophilic groups can generally be high-carbon fatty alcohols, alkylphenols, fatty acids, fatty amines and oils.

[0040] Those skilled in the art will understand that the purpose of adding an alcohol solvent is to adjust the polarity of the prefabricated solution.

[0041] Those skilled in the art will understand that alcohol solvents refer to alcohol reagents that can be used as solvents, such as methanol, ethanol, propanol, isopropanol, glycerol, etc.

[0042] Those skilled in the art can uniformly disperse the carbon powder into the prefabricated solution by conventional means in the art, such as stirring, grinding, shaking, ultrasonic treatment, etc.

[0043] Those skilled in the art can uniformly disperse the ionic polymer having fluorine atoms connected to the main chain into the carbon powder dispersion by conventional means in the art, such as stirring, grinding, shaking, ultrasonic treatment, etc.

[0044] Those skilled in the art will appreciate that the microporous layer generally exists as part of the gas diffusion layer in a proton exchange membrane fuel cell. In practical applications, the microporous layer support described herein is typically carbon paper. However, it should be noted that the microporous layer support described herein is not limited to carbon paper and can include any layered support that can be used to form a gas diffusion layer.

[0045] In step S4, during the calcination process, the hydrophilic side chains or side groups of the ionic polymer will be oxidized or decomposed, thereby increasing the hydrophobicity of the ionic polymer to form a hydrophobic polymer. Those skilled in the art can reasonably select the predetermined temperature value based on the above technical principles.

[0046] As a specific implementation, step S1 can be performed as follows:

[0047] S11: adding the nonionic surfactant to deionized water and performing a first mechanical stirring to obtain a surfactant solution, wherein the stirring rate of the first stirring is 100-500 r / min and the stirring time is 1-10 min;

[0048] S12: adding the alcohol solvent to the surfactant solution and performing a second mechanical stirring to obtain a prefabricated solution, wherein the stirring rate of the second stirring is 100-500 r / min and the stirring time is 0.5-3 min.

[0049] This application replaces traditional polytetrafluoroethylene or polyvinylidene fluoride with a fluorine-containing ionic polymer as a hydrophobic agent. The ionic polymer is inherently hydrophilic and soluble in aqueous alcohol solutions, eliminating demulsification. It is evenly dispersed in the microporous layer slurry. The hydrophilic side chains or groups are then removed by calcination, forming a hydrophobic polymer evenly distributed in the microporous layer, resulting in a relatively uniform hydrophobicity of the microporous layer. Furthermore, because the components in the microporous layer slurry are more uniformly dispersed, the resulting microporous layer has a low surface roughness, which can reduce the contact resistance between the microporous layer and the catalytic layer, thereby improving battery performance.

[0050] In some embodiments of the present application, the nonionic surfactant is Triton X100; and / or,

[0051] The alcohol solvent is at least one of isopropyl alcohol, ethanol and glycerol; and / or,

[0052] The carbon powder is at least one of solid carbon, porous carbon, graphite, conductive carbon black, and carbon nanotubes; and / or,

[0053] The ionic polymer is at least one of perfluorosulfonic acid resin, perfluorocarboxylic acid resin, ionic polyvinylidene fluoride, and ionic polyperfluoroethylene propylene.

[0054] The beneficial effect of selecting at least one of isopropyl alcohol, ethanol and glycerol as the alcohol solvent is that isopropyl alcohol, ethanol and glycerol are commonly used alcohol solvents, have good miscibility with water and are easy to adjust the polarity of the solution.

[0055] The carbon powder is selected from at least one of solid carbon, porous carbon, graphite, conductive carbon black, and carbon nanotubes. The beneficial effect is that the above raw materials have a wide range of access routes, are easy to form a porous structure, and have good dispersibility.

[0056] The ionic polymer is selected from at least one of perfluorosulfonic acid resin, perfluorocarboxylic acid resin, ionic polyvinylidene fluoride, and ionic polyperfluoroethylene propylene. The beneficial effects are that the above raw materials are relatively common, mature products are available on the market, the properties are stable, and it is easy to disperse in the aqueous solution; and after calcination to remove the hydrophilic side chains or side groups, it can show excellent hydrophobicity.

[0057] In some embodiments of the present application, the carbon powder is uniformly dispersed in the prefabricated solution by at least one of mechanical stirring, ball milling, or ultrasonic shearing; and / or,

[0058] The ionic polymer is uniformly dispersed in the carbon powder dispersion by at least one of mechanical stirring, ball milling or ultrasonic shearing.

[0059] In some embodiments of the present application, in the microporous layer slurry, the mass ratio of carbon powder, water, alcohol, nonionic surfactant, and ionic polymer is 1:(10-30):(1-10):(0.1-1):(0.1-0.8).

[0060] In some embodiments of the present application, the predetermined temperature is 350-380°C.

[0061] The beneficial effect of limiting the predetermined temperature to the above range is that the hydrophilic side chains or side groups of the ionic polymer can be effectively removed without destroying the overall structure of the ionic polymer.

[0062] In some embodiments of the present application, the calcination time is 0.5-1.5 h.

[0063] In some embodiments of the present application, the microporous layer carrier is carbon paper.

[0064] In some embodiments of the present application, the carbon paper is bare carbon paper that has undergone hydrophobic treatment.

[0065] In a second aspect, embodiments of the present application provide a microporous layer, which is a microporous layer prepared according to any embodiment of the first aspect. The microporous layer is produced using the method for producing a microporous layer according to the first aspect. The specific steps of the method for producing the microporous layer can be referred to the embodiments of the first aspect. Since the microporous layer utilizes all the technical solutions of the embodiments of the first aspect, it at least has all the beneficial effects brought about by the technical solutions of the aforementioned embodiments, and no further description is given here.

[0066] In a third aspect, embodiments of the present application provide a gas diffusion layer, comprising the microporous layer described in any embodiment of the second aspect. The gas diffusion layer is implemented based on the microporous layer described in the second aspect. The specific implementation of the microporous layer can refer to the embodiments of the second aspect. Because the gas diffusion layer utilizes all of the technical solutions of the embodiments of the second aspect, it at least possesses all of the beneficial effects of the technical solutions of the aforementioned embodiments, and therefore will not be further elaborated here.

[0067] In a fourth aspect, embodiments of the present application provide a fuel cell comprising the gas diffusion layer described in the third aspect. The fuel cell is implemented based on the gas diffusion layer described in the second aspect. The specific implementation of the gas diffusion layer can be found in the embodiments of the second aspect. Since 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 aforementioned embodiments, and no further details are given here.

[0068] 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.

[0069] Example 1

[0070] This embodiment provides a gas diffusion layer, which is prepared by the following method:

[0071] Sa: adding the nonionic surfactant to deionized water and performing a first mechanical stirring to obtain a surfactant solution, wherein the stirring rate of the first stirring is 200 r / min and the stirring time is 5 min;

[0072] Sb: adding the alcohol solvent to the surfactant solution and performing a second mechanical stirring to obtain a prefabricated solution, wherein the stirring rate of the second stirring is 100 r / min and the stirring time is 2 min;

[0073] Sc: adding carbon powder to the prefabricated solution, ball milling and ultrasonic treatment to obtain a carbon powder dispersion;

[0074] Sd: adding a hydrophobic agent to the carbon powder dispersion, ball milling and ultrasonic treatment to obtain a microporous layer slurry;

[0075] Se: coating the microporous layer slurry onto the surface of hydrophobic carbon paper by screen printing to obtain a gas diffusion layer precursor;

[0076] Sf: The gas diffusion layer precursor is dried and then calcined at 360° C. for 1 hour to obtain the gas diffusion layer.

[0077] Wherein, the nonionic surfactant is Triton X100,

[0078] The alcohol solvent is isopropyl alcohol,

[0079] The carbon powder is VULCAN XC72 conductive carbon black,

[0080] The hydrophobic agent is perfluorosulfonic acid resin,

[0081] In the microporous layer slurry, the mass ratio of carbon powder, water, alcohol, nonionic surfactant and ionic polymer is 1:10:10:0.4:0.5.

[0082] The preparation method of hydrophobic carbon paper is as follows: the purchased bare carbon paper is impregnated in 5% PTFE emulsion for 300s. After the impregnation is completed, it is first dried at room temperature and then placed in an oven to dry to obtain the hydrophobic carbon paper.

[0083] Example 2

[0084] This embodiment provides a gas diffusion layer, which is prepared by the following method:

[0085] Sa: adding the nonionic surfactant to deionized water and performing a first mechanical stirring to obtain a surfactant solution, wherein the stirring rate of the first stirring is 200 r / min and the stirring time is 5 min;

[0086] Sb: adding the alcohol solvent to the surfactant solution and performing a second mechanical stirring to obtain a prefabricated solution, wherein the stirring rate of the second stirring is 100 r / min and the stirring time is 2 min;

[0087] Sc: adding carbon powder to the prefabricated solution, ball milling and ultrasonic treatment to obtain a carbon powder dispersion;

[0088] Sd: adding a hydrophobic agent to the carbon powder dispersion, ball milling and ultrasonic treatment to obtain a microporous layer slurry;

[0089] Se: coating the microporous layer slurry onto the surface of hydrophobic carbon paper by screen printing to obtain a gas diffusion layer precursor;

[0090] Sf: The gas diffusion layer precursor is dried and then calcined at 360° C. for 1 hour to obtain the gas diffusion layer.

[0091] Wherein, the nonionic surfactant is Triton X100,

[0092] The alcohol solvent is ethanol,

[0093] The carbon powder is at least one of solid carbon, porous carbon, graphite, conductive carbon black, and carbon nanotubes.

[0094] The hydrophobic agent is a perfluorocarboxylic acid resin,

[0095] In the microporous layer slurry, the mass ratio of carbon powder, water, alcohol, nonionic surfactant and ionic polymer is 1:30:1:0.1:0.8.

[0096] The preparation method of hydrophobic carbon paper is as follows: the purchased bare carbon paper is impregnated in 5% PTFE emulsion for 300s. After the impregnation is completed, it is first dried at room temperature and then placed in an oven to dry to obtain the hydrophobic carbon paper.

[0097] Example 3

[0098] This embodiment provides a gas diffusion layer, which is prepared by the following method:

[0099] Sa: adding the nonionic surfactant to deionized water and performing a first mechanical stirring to obtain a surfactant solution, wherein the stirring rate of the first stirring is 200 r / min and the stirring time is 5 min;

[0100] Sb: adding the alcohol solvent to the surfactant solution and performing a second mechanical stirring to obtain a prefabricated solution, wherein the stirring rate of the second stirring is 100 r / min and the stirring time is 2 min;

[0101] Sc: adding carbon powder to the prefabricated solution, ball milling and ultrasonic treatment to obtain a carbon powder dispersion;

[0102] Sd: adding a hydrophobic agent to the carbon powder dispersion, ball milling and ultrasonic treatment to obtain a microporous layer slurry;

[0103] Se: coating the microporous layer slurry onto the surface of hydrophobic carbon paper by screen printing to obtain a gas diffusion layer precursor;

[0104] Sf: The gas diffusion layer precursor is dried and then calcined at 360° C. for 1 hour to obtain the gas diffusion layer.

[0105] Wherein, the nonionic surfactant is Triton X100,

[0106] The alcohol solvent is glycerol,

[0107] The carbon powder is at least one of solid carbon, porous carbon, graphite, conductive carbon black, and carbon nanotubes.

[0108] The hydrophobic agent is ionic polyvinylidene fluoride,

[0109] In the microporous layer slurry, the mass ratio of carbon powder, water, alcohol, nonionic surfactant and ionic polymer is 1:10:7:1:0.1.

[0110] The preparation method of hydrophobic carbon paper is as follows: the purchased bare carbon paper is impregnated in 5% PTFE emulsion for 300s. After the impregnation is completed, it is first dried at room temperature and then placed in an oven to dry to obtain the hydrophobic carbon paper.

[0111] Example 4

[0112] This embodiment provides a gas diffusion layer, which is prepared by the following method:

[0113] Sa: adding the nonionic surfactant to deionized water and performing a first mechanical stirring to obtain a surfactant solution, wherein the stirring rate of the first stirring is 200 r / min and the stirring time is 5 min;

[0114] Sb: adding the alcohol solvent to the surfactant solution and performing a second mechanical stirring to obtain a prefabricated solution, wherein the stirring rate of the second stirring is 100 r / min and the stirring time is 2 min;

[0115] Sc: adding carbon powder to the prefabricated solution, ball milling and ultrasonic treatment to obtain a carbon powder dispersion;

[0116] Sd: adding a hydrophobic agent to the carbon powder dispersion, ball milling and ultrasonic treatment to obtain a microporous layer slurry;

[0117] Se: coating the microporous layer slurry onto the surface of hydrophobic carbon paper by screen printing to obtain a gas diffusion layer precursor;

[0118] Sf: The gas diffusion layer precursor is dried and then calcined at 360° C. for 1 hour to obtain the gas diffusion layer.

[0119] Wherein, the nonionic surfactant is Triton X100,

[0120] The alcohol solvent is a mixed solvent of isopropyl alcohol and ethanol in a volume ratio of 1:1.

[0121] The carbon powder is at least one of solid carbon, porous carbon, graphite, conductive carbon black, and carbon nanotubes.

[0122] The hydrophobic agent is an ionic poly(perfluoroethylene propylene),

[0123] In the microporous layer slurry, the mass ratio of carbon powder, water, alcohol, nonionic surfactant and ionic polymer is 1:18:7:0.2:0.3.

[0124] The preparation method of hydrophobic carbon paper is as follows: the purchased bare carbon paper is impregnated in 5% PTFE emulsion for 300s. After the impregnation is completed, it is first dried at room temperature and then placed in an oven to dry to obtain the hydrophobic carbon paper.

[0125] Example 5

[0126] This embodiment provides a gas diffusion layer, which is prepared by the following method:

[0127] Sa: adding the nonionic surfactant to deionized water and performing a first mechanical stirring to obtain a surfactant solution, wherein the stirring rate of the first stirring is 200 r / min and the stirring time is 5 min;

[0128] Sb: adding the alcohol solvent to the surfactant solution and performing a second mechanical stirring to obtain a prefabricated solution, wherein the stirring rate of the second stirring is 100 r / min and the stirring time is 2 min;

[0129] Sc: adding carbon powder to the prefabricated solution, ball milling and ultrasonic treatment to obtain a carbon powder dispersion;

[0130] Sd: adding a hydrophobic agent to the carbon powder dispersion, ball milling and ultrasonic treatment to obtain a microporous layer slurry;

[0131] Se: coating the microporous layer slurry onto the surface of hydrophobic carbon paper by screen printing to obtain a gas diffusion layer precursor;

[0132] Sf: The gas diffusion layer precursor is dried and then calcined at 360° C. for 1 hour to obtain the gas diffusion layer.

[0133] Wherein, the nonionic surfactant is Triton X100,

[0134] The alcohol solvent is isopropyl alcohol,

[0135] The carbon powder is at least one of solid carbon, porous carbon, graphite, conductive carbon black, and carbon nanotubes.

[0136] The hydrophobic agent is perfluorosulfonic acid resin,

[0137] In the microporous layer slurry, the mass ratio of carbon powder, water, alcohol, nonionic surfactant and ionic polymer is 1:25:5:0.8:0.6.

[0138] The preparation method of hydrophobic carbon paper is as follows: the purchased bare carbon paper is impregnated in 5% PTFE emulsion for 300s. After the impregnation is completed, it is first dried at room temperature and then placed in an oven to dry to obtain the hydrophobic carbon paper.

[0139] Comparative Example 1

[0140] The difference between this comparative example and Example 1 is only that:

[0141] In step Sd, the hydrophobic agent is selected from 10% polytetrafluoroethylene emulsion.

[0142] Comparative Example 2

[0143] The difference between this comparative example and Example 2 is only that:

[0144] In step Sd, the hydrophobic agent is selected from 10% polytetrafluoroethylene emulsion.

[0145] Comparative Example 3

[0146] The difference between this comparative example and Example 3 is only that:

[0147] In step Sd, the hydrophobic agent is selected from 10% polytetrafluoroethylene emulsion.

[0148] Comparative Example 4

[0149] The difference between this comparative example and Example 4 is only that:

[0150] In step Sd, the hydrophobic agent is selected from 10% polytetrafluoroethylene emulsion.

[0151] Comparative Example 5

[0152] The difference between this comparative example and Example 5 is only that:

[0153] In step Sd, the hydrophobic agent is selected from 10% polytetrafluoroethylene emulsion.

[0154] Related experiments and effect data:

[0155] In the comparative example, the addition of a polytetrafluoroethylene solution can cause carbon particles to aggregate and settle, separating from the liquid water due to the colloidal state of the polytetrafluoroethylene particles in the solvent. Alternatively, the slurry viscosity may drop sharply, making subsequent coating processes impossible. However, the addition of a fluorinated ionomer allows it to dissolve evenly in the solvent, ensuring the uniformity of the hydrophobic agent and preventing carbon particles from agglomerating. The resulting dispersion of carbon particles in the slurry is superior to that of the polytetrafluoroethylene slurry. Furthermore, during the subsequent microporous layer coating process, the microporous layer surface is uniform and has low roughness.

[0156] The experimental phenomena during the implementation of Examples 1-5 and Comparative Examples 1-5 were observed and summarized in Table 1:

[0157] Table 1. Statistics of experimental phenomena of Examples and Comparative Examples

[0158] As shown in Table 1, when only the hydrophobic agent was replaced in Comparative Examples 1-5 relative to Examples 1-5, none of Examples 1-5 experienced sedimentation, while three of Comparative Examples 1-5 experienced sedimentation. This indicates that the hydrophobic agent selected in Examples 1-5 can be uniformly dissolved in the solvent.

[0159] The roughness of Examples 1-5 and Comparative Example 1 was tested using a 3D optical profilometer to test the three-dimensional morphology and roughness of the microporous layer surface. Specific test data are shown in Table 2:

[0160] Table 2. Statistics of roughness values ​​of Examples 1-5 and Comparative Example 1

[0161] It can be seen from Table 2 that the roughness of the microporous layer of the five examples is all below 5 μm, while the roughness of the microporous layer of Comparative Example 1 is 7.34 μm. Therefore, by adding the fluorine-containing ionic polymer, the uniformity of the microporous layer slurry and the dispersion of the carbon particles can be improved, and the roughness of the surface of the microporous layer can be reduced.

[0162] At the same time, the contact resistance test of Examples 1-5 and Comparative Example 1 was carried out. First, the contact resistance between the two ends of the electrode and the carbon paper substrate was measured using a four-probe resistivity tester and recorded as R1. Then, the contact resistance R2 of the finished gas diffusion layer coated with the microporous layer was measured. The contact resistance of the microporous layer was R MPL , the above test pressure is carried out at 1.2MPa: R MPL =(R1-R2) / 2

[0163] Specific test data are shown in Table 3:

[0164] Table 3. Statistics of contact resistance values ​​of Examples 1-5 and Comparative Example 1

[0165] As can be seen from Table 2, the contact resistance of the five examples is lower than that of Comparative Example 1, indicating that the surface uniformity of the microporous layer after drying is better and the roughness is reduced, so the contact resistance also decreases accordingly.

[0166] 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.

[0167] 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.

[0168] 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 microporous layer, characterized in that: The method comprises the following steps: Dissolving a nonionic surfactant and an alcohol solvent in water to obtain a prefabricated solution; Evenly dispersing carbon powder into the prefabricated solution to obtain a carbon powder dispersion; Evenly dispersing an ionic polymer having fluorine atoms connected to the main chain into the carbon powder dispersion to obtain a microporous layer slurry; The microporous layer slurry is disposed on the surface of the microporous layer support to form a slurry layer, and the slurry layer is dried and then calcined at a predetermined temperature to obtain the microporous layer.

2. The method for preparing a microporous layer according to claim 1, characterized in that: The nonionic surfactant is Triton X100; and / or, The alcohol solvent is at least one of isopropanol, ethanol and glycerol; and / or, The carbon powder is at least one of solid carbon, porous carbon, graphite, conductive carbon black, and carbon nanotubes; and / or, The ionic polymer is at least one of perfluorosulfonic acid resin, perfluorocarboxylic acid resin, ionic polyvinylidene fluoride and ionic polyperfluoroethylene propylene.

3. The method for preparing a microporous layer according to claim 1, characterized in that: The carbon powder is uniformly dispersed in the prefabricated solution, and the uniform dispersion method is at least one of mechanical stirring, ball milling or ultrasonic shearing; and / or, The ionic polymer is uniformly dispersed in the carbon powder dispersion, and the uniform dispersion method is at least one of mechanical stirring, ball milling or ultrasonic shearing.

4. The method for preparing a microporous layer according to claim 1, characterized in that: In the microporous layer slurry, the mass ratio of carbon powder, water, alcohol, nonionic surfactant and ionic polymer is 1:(10-30):(1-10):(0.1-1):(0.1-0.8).

5. The method for preparing a microporous layer according to claim 1, characterized in that: The predetermined temperature is 350-380°C.

6. The method for preparing a microporous layer according to claim 1, characterized in that: The microporous layer carrier is carbon paper.

7. The method for preparing a microporous layer according to claim 6, characterized in that: The carbon paper is bare carbon paper that has been subjected to hydrophobic treatment.

8. A microporous layer, characterized in that The microporous layer is a microporous layer prepared according to the preparation method according to any one of claims 1 to 7.

9. A gas diffusion layer, characterized in that: The gas diffusion layer comprises the microporous layer according to claim 8.

10. A fuel cell, characterized in that: The fuel cell comprises the gas diffusion layer according to claim 9.

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