A gas diffusion layer having hydrophilic and hydrophobic transport channels and a method of making the same

Abstract

The application provides a gas diffusion layer with hydrophilic and hydrophobic transmission channels and a preparation method thereof, and belongs to the technical field of hydrogen energy and hydrogen-rich fuel conversion. The preparation method comprises the following steps: mixing a first carbon nanomaterial, a hydrophilic modified first carbon nanomaterial, a second carbon nanomaterial and a hydrophobic modified second carbon nanomaterial to form a carbon material mixture; the particle size of the first carbon nanomaterial is larger than that of the second carbon nanomaterial; mixing the carbon material mixture, a solvent and a hydrophobic agent to form a slurry; forming a coating layer on a substrate by using the slurry, and drying and sintering. The preparation method can improve the performance of the gas diffusion layer.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of hydrogen energy and hydrogen-rich fuel conversion. BACKGROUND

[0002] Hydrogen energy is a clean and renewable form of energy that is widely used in transportation, power generation, and industrial fields. The application of hydrogen-rich fuel through electrochemical methods to produce green hydrogen is an important way to achieve carbon peak and carbon neutrality, and has great significance for leading global climate governance.

[0003] The gas diffusion layer (GDL) is a core component of hydrogen-rich fuel conversion, hydrogen purification, and efficient hydrogen energy application, playing an important role in rapid water and gas transport, electron conduction, and mechanical application dispersion. The material and structural properties of the GDL, such as porosity, electrical conductivity, and corrosion resistance, directly affect the performance and efficiency of electrochemical devices, so the structural design and optimization of the GDL are crucial.

[0004] The gas diffusion layer is mainly composed of a microporous layer (MPL) formed by stacking carbon particles and a substrate layer composed of carbon fibers or carbon cloth. The conventional preparation method of the existing MPL is wet coating. First, water or a mixture of water and alcohol is used as a solvent to uniformly mix carbon powder and polytetrafluoroethylene (PTFE) emulsion in a certain proportion to form a slurry with a certain viscosity. Then, it is coated on the surface of the carbon substrate layer, and finally, it is treated by high-temperature sintering.

[0005] With the optimization of key component materials and structures, electrochemical devices tend to operate at higher current densities, which also means that the water produced by electrochemical reactions is at a higher rate, posing new challenges for water management in batteries. Water management is one of the key factors limiting further performance improvement. The current commercial gas diffusion layer (GDL) preparation method cannot meet the functional requirements of the material in the application scenario. Although some new experimental preparation methods can improve some performance, the preparation process is complex, the processing and assembly precision requirements are high, and the device cannot work at ultra-high working points, thereby improving the efficiency of the electrochemical device.

[0006] It should be noted that the information disclosed in the above background section is only used to strengthen the understanding of the background of the present disclosure, and therefore can include information that does not constitute prior art known to those of ordinary skill in the art. SUMMARY

[0007] Therefore, the present application provides a gas diffusion layer with hydrophilic and hydrophobic transport channels and a preparation method thereof, which can improve the water management capability of the gas diffusion layer at high current density and improve the performance of the gas diffusion layer.

[0008] The technical solution of the present application is as follows:

[0009] The application provides a preparation method of a gas diffusion layer, comprising:

[0010] In step S1, a first carbon nanomaterial, a hydrophilic modified first carbon nanomaterial, a second carbon nanomaterial and a hydrophobic modified second carbon nanomaterial are mixed to form a carbon material mixture; the particle size of the first carbon nanomaterial is larger than that of the second carbon nanomaterial;

[0011] In step S2, the carbon material mixture, a solvent and a hydrophobic agent are mixed to form a slurry;

[0012] In step S3, a coating layer is formed on a substrate by using the slurry, and then dried and sintered.

[0013] Preferably, the particle size of the first carbon nanomaterial is 30-50 nm, and the particle size of the second carbon nanomaterial is 20-40 nm.

[0014] Preferably, the mass percentage of the hydrophilic modified first carbon nanomaterial in the carbon material mixture is 15-30%, and the mass percentage of the hydrophobic modified second carbon nanomaterial in the carbon material mixture is 5-10%. Preferably, the hydrophilic modified first carbon nanomaterial is prepared by the following method:

[0015] In step S101, the first carbon nanomaterial is dispersed in deionized water to obtain a first carbon nanomaterial dispersion liquid;

[0016] In step S102, p-phenylenediamine or p-aminobenzenesulfonic acid and nitric acid are added to the first carbon nanomaterial dispersion liquid, and then ultrasonic treatment and stirring are performed for 1-3 hours to obtain a first carbon nanomaterial pretreatment liquid;

[0017] In step S103, a nitrate salt is added to the first carbon nanomaterial pretreatment liquid, and then reaction is performed for 1-24 hours, and then filtration, washing and drying are performed to obtain the hydrophilic modified first carbon nanomaterial.

[0018] Preferably, in step S102, the mass ratio of p-phenylenediamine to the first carbon nanomaterial is (0.5-1):1000.

[0019] In step S103, a sodium nitrate aqueous solution is added dropwise to the first carbon nanomaterial pretreatment liquid, and then reaction is performed at 50-80 ℃ for 10-14 hours.

[0020] Preferably, the hydrophobic modified second carbon nanomaterial is prepared by the following method:

[0021] Step S201, dispersing the second carbon nanomaterial in a mixed solution of pentafluoroaniline and acetonitrile to obtain a second carbon nanomaterial dispersion;

[0022] Step S202, adding nitrous acid ester to the second carbon nanomaterial dispersion, reacting for 1-24 hours, filtering, washing and drying to obtain a hydrophobically modified second carbon nanomaterial.

[0023] On the basis of the above technical solutions, preferably, in step S201, the second carbon nanomaterial is dispersed in a mixed solution of pentafluoroaniline and acetonitrile, and stirred under ultrasonic conditions for 1-3 hours to obtain a second carbon nanomaterial dispersion; wherein the mass of the second carbon nanomaterial: the mass of pentafluoroaniline = 1:(3-5).

[0024] In step S202, pentyl nitrite is added to the second carbon nanomaterial dispersion, and then reacted under reflux conditions for 8-12 hours; wherein the working concentration of the pentyl nitrite is 0.5-5 mol / L.

[0025] On the basis of the above technical solutions, preferably, the first carbon nanomaterial is selected from carbon powder, carbon black powder, acetylene black powder, ketchen black powder, and graphene powder; and the second carbon nanomaterial is selected from carbon powder, carbon black powder, acetylene black powder, ketchen black powder, and graphene powder.

[0026] On the basis of the above technical solutions, preferably, in step S2, the solvent is a mixed solvent of water and alcohol; and the hydrophobic agent is at least one of polytetrafluoroethylene, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, polychlorotrifluoroethylene, tetrafluoroethylene-ethylene copolymer, and polyvinylidene fluoride.

[0027] The application also provides a gas diffusion layer prepared by the above preparation method.

[0028] The gas diffusion layer and the preparation method thereof have the following beneficial effects over the prior art:

[0029] The present application is based on the surface hydrophilicity and hydrophobicity regulation and size effect of carbon materials, and proposes a gas diffusion layer with hydrophilic and hydrophobic transmission channels. In the preparation process of the microporous layer, the pores formed by large particle carbon nanoparticles are larger, and the pores formed by small particle stacking are smaller. Based on this principle and the high water drainage requirement of the gas diffusion layer, hydrophilic modification is performed on the large particle carbon material, and hydrophobic modification is performed on the small particle carbon surface, thereby forming a gas diffusion layer with hydrophilic and hydrophobic transmission channels. The performance of the batteries assembled by the examples and the comparative examples is tested, and in the higher current density area, the output performance of the examples is improved by 20% compared with the comparative examples. 2 The output performance of the examples is improved by 20% compared with the comparative examples.

[0030] The hydrophilic modified first carbon nanomaterials can form hydrophilic channels after sintering, which is conducive to improving the water drainage capacity of the gas diffusion layer and reducing the waterlogging risk of the catalyst layer. The hydrophobic modified second carbon nanomaterials can form hydrophobic channels after sintering, which is conducive to oxygen transmission and improves the efficiency.

[0031] In addition, the particle size of the first carbon nanomaterials is larger than that of the second carbon nanomaterials, which makes the size of the hydrophilic channels formed by the hydrophilic modified first carbon nanomaterials after sintering larger than the size of the hydrophobic channels formed by the hydrophobic modified second carbon nanomaterials after sintering, so that the water drainage capacity and oxygen transmission capacity of the gas diffusion layer are generally balanced, and the performance of the gas diffusion layer is better. BRIEF DESCRIPTION OF DRAWINGS

[0032] In order to more clearly illustrate the technical solutions of the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0033] Figure 1 The S2p spectrum of the XPS analysis of the hydrophilic modified first carbon nanomaterials.

[0034] Figure 2 The contact angle analysis diagram of the hydrophilic modified first carbon nanomaterials.

[0035] Figure 3 The F1s spectrum of the XPS analysis of the hydrophobic modified second carbon nanomaterials.

[0036] Figure 4 The contact angle analysis diagram of the hydrophobic modified second carbon nanomaterials.

[0037] Figure 5 The polarization curve test result diagram. DETAILED DESCRIPTION

[0038] The technical solutions in the embodiments of the present application will be described clearly and completely below in combination with the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0039] In the prior art, the gas diffusion layer (GDL) is formed by directly mixing and coating a hydrophobic agent, a solvent and carbon powder. Currently, the optimization of the structure and performance of the GDL mainly includes the porosity design of the microporous layer, the hierarchical porosity of the microporous layer, the perforated structure of the microporous layer, the resin binder with different hydrophilic and hydrophobic degrees, and the composite gas diffusion layer prepared by different carbon powders. However, the above improvement schemes do not fully consider the demand for fast water and gas transmission of the electrode under high current density, so that the device is prone to flooding under high working points and high humidity conditions, and the performance is reduced. Based on this, the present application provides a preparation method of a gas diffusion layer, comprising:

[0040] Step S1, mixing a first carbon nanomaterial, a hydrophilically modified first carbon nanomaterial, a second carbon nanomaterial and a hydrophobically modified second carbon nanomaterial to form a carbon material mixture; the particle size of the first carbon nanomaterial is larger than the particle size of the second carbon nanomaterial;

[0041] Step S2, mixing the carbon material mixture, a solvent and a hydrophobic agent to form a slurry;

[0042] Step S3, forming a coating layer on the substrate with the slurry, drying and sintering.

[0043] The slurry used in the gas diffusion layer provided by the application contains a plurality of carbon nanomaterials. The hydrophilically modified first carbon nanomaterial can form a hydrophilic channel after sintering, thereby improving the water drainage capacity of the gas diffusion layer and reducing the risk of waterlogging of the catalyst layer. The hydrophobically modified second carbon nanomaterial can form a hydrophobic channel after sintering, thereby facilitating oxygen transmission and improving efficiency. In addition, the particle size of the first carbon nanomaterial is larger than that of the second carbon nanomaterial, which makes the size of the hydrophilic channel formed by the hydrophilically modified first carbon nanomaterial after sintering larger than that of the hydrophobic channel formed by the hydrophobically modified second carbon nanomaterial after sintering, so that the water drainage capacity and oxygen transmission capacity of the gas diffusion layer are balanced, and the performance of the gas diffusion layer is better. In other words, by optimizing the types, sizes and performances of the carbon nanomaterials in the slurry, the gas diffusion layer can maintain high oxygen transmission capacity under the premise of high hydrophobic capacity, thereby improving the performance. In this way, the present disclosure provides a preparation method of a gas diffusion layer with hydrophilic and hydrophobic transmission channels based on the surface hydrophilicity and hydrophobicity regulation and size effect of carbon materials, which can ensure fast gas diffusion while building hydrophilic channels. This method effectively improves the water drainage management capacity of the gas diffusion layer, reduces the risk of electrode waterlogging failure, and improves the performance and stability of the electrochemical device under high current density and high power output.

[0044] In an embodiment of the present disclosure, the first carbon nanomaterial has a particle size of 30-50 nm; and the second carbon nanomaterial has a particle size of 20-40 nm. As an example, the first carbon nanomaterial has a particle size of 1.2-1.5 times of the particle size of the second carbon nanomaterial.

[0045] For example, the first carbon nanomaterial has an average particle size of 50 nm; and the second carbon nanomaterial has an average particle size of 35 nm.

[0046] In an embodiment of the present disclosure, the hydrophilic-modified first carbon nanomaterial is obtained by hydrophilic modification of the first carbon nanomaterial; and the hydrophobic-modified second carbon nanomaterial is obtained by hydrophilic modification of the second carbon nanomaterial. Further, the modification of the first carbon nanomaterial and the second carbon nanomaterial is performed by inorganic or low-molecular-weight organic modification, for example, surface modification of the carbon nanomaterial by inorganic or small-molecular organic modification. Therefore, the particle size of the hydrophilic-modified first carbon nanomaterial is substantially the same as the particle size of the first carbon nanomaterial; and the particle size of the hydrophobic-modified second carbon nanomaterial is substantially the same as the particle size of the second carbon nanomaterial. Thus, the particle size of the hydrophobic-modified second carbon nanomaterial is smaller than the particle size of the hydrophilic-modified first carbon nanomaterial.

[0047] In an embodiment of the present disclosure, the hydrophilic-modified first carbon nanomaterial is prepared by the following method:

[0048] In step S101, the first carbon nanomaterial is dispersed in deionized water to obtain a first carbon nanomaterial dispersion liquid;

[0049] In step S102, p-phenylenediamine or p-aminobenzenesulfonic acid and nitric acid are added to the first carbon nanomaterial dispersion liquid; and the mixture is ultrasonically treated and stirred for 1-3 hours to obtain a first carbon nanomaterial pretreatment liquid;

[0050] In step S103, a nitrate salt is added to the first carbon nanomaterial pretreatment liquid; and the mixture is reacted for 1-24 hours, filtered, washed and dried to obtain the hydrophilic-modified first carbon nanomaterial.

[0051] Optionally, in step S102, the mass ratio of p-phenylenediamine to the first carbon nanomaterial is (0.5-1) : 1000.

[0052] Optionally, in step S101, before the first carbon nanomaterial is dispersed in deionized water, the first carbon nanomaterial can be dried to accurately determine the amount of the first carbon nanomaterial. In an example, the first carbon nanomaterial is dried at 100°C for 10 hours.

[0053] Optionally, in step S103, the sodium nitrate aqueous solution is added dropwise into the first carbon nanomaterial pretreatment solution, and then reacted at 50-80°C for 10-14 hours.

[0054] Optionally, in step S103, after the reaction is completed, the hydrophilic modified first carbon nanomaterial is dried at 100°C for 10 hours after multiple filtration and washing.

[0055] In an embodiment of the present disclosure, the mass percentage of the hydrophilic modified first carbon nanomaterial in the carbon material mixture is 15%-30%, and the mass percentage of the hydrophobic modified second carbon nanomaterial in the carbon material mixture is 5%-10%. The mass percentage of the first carbon nanomaterial in the carbon material mixture is 20%-35%, and the mass percentage of the second carbon nanomaterial in the carbon material mixture is 40%-45%.

[0056] In an embodiment of the present disclosure, the hydrophobic modified second carbon nanomaterial is prepared by the following method:

[0057] Step S201: dispersing the second carbon nanomaterial in a mixed solution of pentafluoroaniline and acetonitrile to obtain a second carbon nanomaterial dispersion;

[0058] Step S202: adding nitrous acid ester into the second carbon nanomaterial dispersion, reacting for 1-24 hours, filtering, washing, and drying to obtain the hydrophobic modified second carbon nanomaterial.

[0059] Optionally, in step S201, the second carbon nanomaterial is dispersed in a mixed solution of pentafluoroaniline and acetonitrile, and stirred under ultrasonic conditions for 1-3 hours to obtain a second carbon nanomaterial dispersion; wherein the mass of the second carbon nanomaterial: the mass of pentafluoroaniline = 1:(3-5).

[0060] Optionally, in step S201, the ratio between the second carbon nanomaterial and acetonitrile is between 1g:(100mL-200mL).

[0061] Optionally, in step S201, before dispersing the second carbon nanomaterial in the mixed solution of pentafluoroaniline and acetonitrile, the second carbon nanomaterial can also be dried to accurately determine the amount of the second carbon nanomaterial. In an example, the first carbon nanomaterial is dried at 100°C for 10 hours.

[0062] Optionally, in step S202, nitrous acid ester is added into the second carbon nanomaterial dispersion, and then reacted under reflux conditions for 8-12 hours; wherein the working concentration of the nitrous acid ester is 0.5-5 mol / L.

[0063] Optionally, after the reaction is completed, the hydrophobically modified second carbon nanomaterial is dried at 100°C for 10 hours after multiple filtration and washing.

[0064] In an embodiment of the present disclosure, the first carbon nanomaterial is selected from carbon powder, carbon black powder, acetylene black powder, ketjen black powder, and graphene powder; and the second carbon nanomaterial is selected from carbon powder, carbon black powder, acetylene black powder, ketjen black powder, and graphene powder. The first carbon nanomaterial and the second carbon nanomaterial can be the same material but have different particle sizes. Of course, the first carbon nanomaterial and the second carbon nanomaterial can also be different.

[0065] In an example, the first carbon nanomaterial is selected from acetylene black powder.

[0066] In an example, the second carbon nanomaterial is selected from Vulcan-XC72.

[0067] In an embodiment of the present disclosure, in step S2, the carbon material mixture can be dispersed in a mixed solvent composed of water and alcohol to obtain a carbon material mixture dispersion. For example, the carbon material mixture is dispersed in a mixed solvent composed of water and isopropyl alcohol, and then a slurry is formed after the hydrophobic agent is added to the carbon material mixture dispersion and mixed.

[0068] Further, the mass ratio of the carbon material mixture to the carbon material mixture dispersion is (5-15): 100.

[0069] Optionally, when the carbon material mixture is dispersed in a mixed solvent composed of water and alcohol, the carbon material mixture dispersion can be treated under ultrasonic for 20-40 minutes to ensure that the carbon material mixture is fully dispersed.

[0070] Optionally, when the hydrophobic agent is added to the carbon material mixture dispersion, the hydrophobic agent is at least one of polytetrafluoroethylene, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, polychlorotrifluoroethylene, tetrafluoroethylene-ethylene copolymer, and polyvinylidene fluoride. Further, the mass ratio of the hydrophobic agent to the carbon material mixture is (2-6): 10.

[0071] In an example, PTFE (polytetrafluoroethylene) emulsion can be added to the carbon material mixture dispersion and stirred for 20-40 minutes to achieve sufficient mixing of the carbon material and the hydrophobic agent.

[0072] In an embodiment of the present disclosure, in step S3, a coating layer is formed on the substrate using the slurry, and then dried and sintered.

[0073] In an example, the substrate can be carbon paper. Of course, other substrate materials can also be selected as needed.

[0074] Optionally, a coater can be used to coat the slurry on the substrate to form a coating layer, and the thickness of the coating layer can be between 30-100 microns, for example, 50 microns.

[0075] Optionally, the substrate with the coating layer can be placed in an oven at 90°C for drying for 20-40 minutes, then dried at high temperature (for example, 230-280°C) in a tube furnace for 20-40 minutes, and finally sintered at 350°C in a tube furnace for 20-40 minutes to obtain the required gas diffusion layer.

[0076] The preparation method of the gas diffusion layer of the present application is exemplarily described as follows in combination with a plurality of specific embodiments.

[0077] Example 1

[0078] Step S1:

[0079] Acetylene black is used as the first carbon nanomaterial, and the particle size is 50 nm.

[0080] The acetylene black is dried at 100°C for 10 h; then 4 g of the dried acetylene black, 2.6 mg of p-aminobenzenesulfonic acid and 10 uL of nitric acid are placed in a flask and ultrasonically stirred for 2 h to obtain a first carbon nanomaterial pretreatment solution; 2.4 g of sodium nitrate is dissolved in 10 mL of deionized water, and then added dropwise into the above first carbon nanomaterial pretreatment solution; the reaction is carried out at 70°C for 12 h; after multiple filtration and washing, the product is dried at 100°C for 10 h to obtain a hydrophilic modified first carbon nanomaterial. The S2p spectrum of the hydrophilic modified first carbon nanomaterial is shown in FIG. 1. According to the S2p spectrum, the hydrophilic modified first carbon nanomaterial contains sulfur element, which indicates that it is modified by p-aminobenzenesulfonic acid, and thus has certain hydrophilicity. Figure 1 Figure 1 The contact angle of the hydrophilic modified first carbon nanomaterial is shown in FIG. 2. According to the contact angle, the contact angle of the hydrophilic modified first carbon nanomaterial is 106.5°, which shows that the hydrophobicity of the hydrophilic modified first carbon nanomaterial is obviously weakened through the modification of the first carbon nanomaterial. Figure 2 Figure 2 The second carbon nanomaterial is Vulcan-XC72, and the particle size is 35 nm.

[0081] The second carbon nanomaterial is Vulcan-XC72, and the particle size is 35 nm.

[0082] ​​The second carbon nanomaterial was dried at 100℃ for 10 h. Then, 1 g of Vulcan-XC72, 4 g of pentafluorophenyl, and 150 mL of acetonitrile were added to a flask and mixed and ultrasonically stirred for 2 h under a nitrogen atmosphere to obtain a dispersion of the second carbon nanomaterial. Then, 3.7 mL of amyl nitrite was gradually added, and the mixture was heated under reflux for 10 h. After multiple filtrations and washings, the sample was dried at 100℃ for 10 h to obtain the hydrophobically modified second carbon nanomaterial. XPS (X-ray photoelectron spectroscopy) analysis was performed on the hydrophobically modified second carbon nanomaterial, and its F1s spectrum is shown below. Figure 3 As shown. According to Figure 3 The hydrophobically modified second carbon nanomaterial contains fluorine, suggesting it has been modified with pentafluorophenyl, thus acquiring hydrophobicity. Contact angle analysis was performed on the hydrophobically modified second carbon nanomaterial, and the contact angles are as follows: Figure 4 As shown. According to Figure 4 The contact angle of the hydrophobically modified second carbon nanomaterial is 142.7°, which shows that the hydrophobicity of the second carbon nanomaterial is significantly improved by modifying it.

[0083] A carbon material mixture is formed by mixing a first carbon nanomaterial, a hydrophilically modified first carbon nanomaterial, a second carbon nanomaterial, and a hydrophobically modified second carbon nanomaterial. The hydrophilically modified first carbon nanomaterial comprises 30% by mass, the hydrophobically modified second carbon nanomaterial comprises 5% by mass, the first carbon nanomaterial comprises 20% by mass, and the second carbon nanomaterial comprises 45% by mass.

[0084] Step S2:

[0085] The carbon material mixture was dissolved in a mixed solvent of water and isopropanol and stirred for 30 minutes to obtain a dispersion of the carbon material mixture; the mass of the carbon material mixture / mass of the carbon material mixture dispersion was 8%; the volume ratio of water to isopropanol was 1:3.

[0086] PTFE (polytetrafluoroethylene) emulsion was added to the above carbon material mixture dispersion and stirred for 30 minutes to obtain a slurry; wherein the mass ratio of PTFE to carbon material mixture was 40%.

[0087] Step S3:

[0088] A coating is obtained by applying a paste to carbon paper using a coating machine to a thickness of 50 micrometers.

[0089] The prepared coating is first dried in an oven at 90°C for 30 min, then dried in a tube furnace at 250°C for 30 min, and finally sintered at 350°C for 30 min to obtain a gas diffusion layer capable of efficient water management, which is designated as gas diffusion layer A1 in this invention.

[0090] Example 2:

[0091] A gas diffusion layer was prepared by substantially the same method as in Example 1; the difference between the preparation process and that of Example 1 is that the mass ratio of the hydrophilically modified first carbon nanomaterial in the carbon material mixture is 15%, and the mass ratio of the hydrophobically modified second carbon nanomaterial in the carbon material mixture is 10%. The mass ratio of the first carbon nanomaterial is 35%, and the mass ratio of the second carbon nanomaterial is 40%.

[0092] The gas diffusion layer obtained in this example is marked as gas diffusion layer A2 in the present application.

[0093] Comparative Example 1:

[0094] A gas diffusion layer was prepared by substantially the same method as in Example 1; the difference between the preparation process and that of Example 1 is that the first carbon nanomaterial is not hydrophilically modified, and the second carbon nanomaterial is not hydrophobically modified. The amount of the first carbon nanomaterial in the slurry of Comparative Example 1 is equal to the total amount of the first carbon nanomaterial and the hydrophilically modified first carbon nanomaterial in the slurry of Example 1. The amount of the second carbon nanomaterial in the slurry of Comparative Example 1 is equal to the total amount of the second carbon nanomaterial and the hydrophobically modified second carbon nanomaterial in the slurry of Example 1.

[0095] The gas diffusion layer obtained in this comparative example is marked as gas diffusion layer B1 in the present application.

[0096] Comparative Example 2:

[0097] A gas diffusion layer was prepared by substantially the same method as in Example 1; the difference between the preparation process and that of Example 1 is that part of the first carbon nanomaterial is hydrophobically modified instead of being hydrophilically modified, and part of the second carbon nanomaterial is hydrophilically modified instead of being hydrophobically modified.

[0098] The carbon material mixture of Comparative Example 2 includes the first carbon nanomaterial, the hydrophobically modified first carbon nanomaterial, the second carbon nanomaterial, and the hydrophilically modified second carbon nanomaterial mixed to form the carbon material mixture. In the carbon material mixture of Comparative Example 2, the mass content of the first carbon nanomaterial is the same as that in the carbon material mixture of Example 1; the mass content of the hydrophobically modified first carbon nanomaterial is the same as that of the hydrophilically modified first carbon nanomaterial in the carbon material mixture of Example 1; the mass content of the second carbon nanomaterial is the same as that in the carbon material mixture of Example 1; and the mass content of the hydrophilically modified second carbon nanomaterial is the same as that of the hydrophobically modified second carbon nanomaterial in the carbon material mixture of Example 1. The gas diffusion layer obtained from the carbon material mixture of Comparative Example 2 is marked as gas diffusion layer B2 in the present application.

[0099] The gas diffusion layers prepared from Example 1, Example 2, Comparative Example 1, and Comparative Example 2 were prepared into membrane electrodes for polarization curve test, and the results are shown in Table 1. Figure 5 Figure 5 At a higher current density (2500 mA / cm 2 ), the cell voltage of the membrane electrode formed by the gas diffusion layer of Example 1 reached 0.543 V, and that of the membrane electrode formed by the gas diffusion layer of Example 2 reached 0.48 V, which were obviously improved by 0.4 V compared with Comparative Examples 1 and 2. This indicates that, by hydrophilically modifying part of the carbon material with larger particle size and hydrophobically modifying part of the carbon material with smaller particle size, the performance of the prepared gas diffusion layer can be obviously improved.​

Claims

1. A method of producing a gas diffusion layer having a hydrophilic-hydrophobic transport channel, characterized by, The application relates to a carbon material coating method and a carbon material coating. The method comprises the following steps: S1, mixing a first carbon nanomaterial, a hydrophilic modified first carbon nanomaterial, a second carbon nanomaterial and a hydrophobic modified second carbon nanomaterial to form a carbon material mixture; the particle size of the first carbon nanomaterial is larger than that of the second carbon nanomaterial; S2, mixing the carbon material mixture, a solvent and a hydrophobic agent to form a slurry; S3, forming a coating on a substrate by using the slurry, drying and sintering; The hydrophilic modified first carbon nanomaterial is prepared by the following method: S101, dispersing the first carbon nanomaterial in deionized water to obtain a first carbon nanomaterial dispersion liquid; S102, adding p-phenylenediamine or p-aminobenzenesulfonic acid and nitric acid into the first carbon nanomaterial dispersion liquid, ultrasonicating and stirring for 1-3 hours to obtain a first carbon nanomaterial pretreatment liquid; 2. The method for producing a gas diffusion layer according to claim 1, characterized by, S103, adding a nitrate into the first carbon nanomaterial pretreatment liquid, reacting for 1-24 hours, filtering, washing and drying to obtain the hydrophilic modified first carbon nanomaterial.

3. The method for producing a gas diffusion layer according to claim 1, wherein The particle size of the first carbon nanomaterial is 30-50 nm; the particle size of the second carbon nanomaterial is 20-40 nm.

4. The method for producing a gas diffusion layer according to claim 1, wherein The mass percentage of the hydrophilic modified first carbon nanomaterial in the carbon material mixture is 15%-30%, and the mass percentage of the hydrophobic modified second carbon nanomaterial in the carbon material mixture is 5%-10%. In step S102, the mass ratio of p-phenylenediamine to the first carbon nanomaterial is (0.5-1):1000; 5. The method for producing a gas diffusion layer according to claim 1, wherein In step S103, the sodium nitrate aqueous solution is added dropwise into the first carbon nanomaterial pretreatment liquid, and then the reaction is carried out at 50-80 DEG C for 10-14 hours. The hydrophobic modified second carbon nanomaterial is prepared by the following method: S201, dispersing the second carbon nanomaterial in a mixed solution of pentafluoroaniline and acetonitrile to obtain a second carbon nanomaterial dispersion liquid; 6. The method for producing a gas diffusion layer according to claim 5, wherein S202, adding nitrous acid ester into the second carbon nanomaterial dispersion liquid, reacting for 1-24 hours, filtering, washing and drying to obtain the hydrophobic modified second carbon nanomaterial. In step S201, the second carbon nanomaterial is dispersed in a mixed solution of pentafluoroaniline and acetonitrile, and is stirred under ultrasonic condition for 1-3 hours to obtain the second carbon nanomaterial dispersion liquid; wherein the mass ratio of the second carbon nanomaterial to pentafluoroaniline is 1:(3-5); 7. The method for producing a gas diffusion layer according to claim 1, wherein In step S202, nitrous acid ester is added into the second carbon nanomaterial dispersion liquid, and then the reaction is carried out under reflux condition for 8-12 hours; wherein the working concentration of the nitrous acid ester is 0.5-5 mol / L. The first carbon nanomaterial is selected from carbon powder, carbon black powder, acetylene black powder, ketjen black powder and graphene powder; and the second carbon nanomaterial is selected from carbon powder, carbon black powder, acetylene black powder, ketjen black powder and graphene powder.

8. The method for producing a gas diffusion layer according to claim 1, wherein In step S2, the solvent is a mixed solvent of water and alcohol; the hydrophobic agent is at least one of polytetrafluoroethylene, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, polychlorotrifluoroethylene, tetrafluoroethylene-ethylene copolymer, and polyvinylidene fluoride.

9. A gas diffusion layer, characterized by, The gas diffusion layer is prepared by the preparation method in any one of claims 1-8.

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