Gas diffusion layer and preparation method and application thereof

Abstract

The invention relates to the technical field of proton exchange membrane fuel cells, in particular to a gas diffusion layer and a preparation method and application thereof. The preparation method comprises the following steps: soaking untreated carbon paper in a hydrophobic agent emulsion, and drying to obtain a hydrophobic substrate layer; the hydrophobic substrate layer is coated with microporous layer slurry of a fluorine-containing polymer through a silk-screen printing technology, then drying and shaping are conducted at the temperature of 20-60 DEG C to remove a solvent, vacuum drying is conducted at the temperature of 80-150 DEG C to form a microporous structure, finally heat treatment is conducted to melt the fluorine-containing polymer and form a continuous hydrophobic phase, and the gas diffusion layer is obtained after cooling. By improving the hydrophobic uniformity of the gas diffusion layer and increasing the pore volume of the small-aperture pores, the drainage capacity of the gas diffusion layer can be effectively improved, so that the transmission efficiency of reaction gas is remarkably improved, and finally, the performance optimization of the battery under high current density is realized.

Description

Technical Field

[0001] This invention relates to the field of proton exchange membrane fuel cell (PEMFC) technology, and particularly to a gas diffusion layer, its preparation method, and its application. Background Technology

[0002] With the acceleration of global industrialization, energy demand and environmental issues are becoming increasingly prominent. Developing efficient and clean energy conversion technologies has become a top priority. Proton exchange membrane fuel cells, as a device that directly converts chemical energy into electrical energy, have advantages such as high energy conversion efficiency, fast start-up speed, and low operating temperature, demonstrating enormous application potential in portable power supplies, distributed power generation, and electric vehicles.

[0003] However, the actual commercialization of proton exchange membrane fuel cells is still hampered by water management failures under high power output conditions. Under high current density conditions, the cathode oxygen reduction reaction (ORR) produces a large amount of liquid water (according to Faraday's law, 0.5 mol of water is generated for every 1 mol of electrons transferred). If the drainage capacity of the gas diffusion layer (GDL) is insufficient, excess water will rapidly accumulate in the microporous layer, leading to the following chain of failures: 1. Gas transport obstruction: Liquid water blocks the pores of carbon paper, hindering the diffusion of oxygen to the catalyst layer and causing mass transfer polarization; 2. Risk of local gas shortage: In the flooded area, the active sites of the catalyst layer are submerged, and the efficiency of electrochemical reaction drops sharply; 3. Significantly shortened lifespan: Repeated flooding-drying cycles accelerate the deterioration of the carbon paper structure and the agglomeration of the platinum catalyst, resulting in a battery degradation rate increase of more than 30%. Summary of the Invention

[0004] To address the technical shortcomings of existing gas diffusion layers that suffer from severe mass transfer polarization and a sharp drop in electrochemical reaction efficiency due to insufficient drainage capacity under high current density conditions, this invention provides a gas diffusion layer with high drainage capacity, its preparation method, and its application.

[0005] The technical solution provided by this invention is as follows: In a first aspect, the present invention provides a method for preparing a gas diffusion layer, comprising the following steps: Untreated carbon paper was impregnated with a hydrophobic emulsion and then dried to obtain a hydrophobic substrate layer; The microporous layer slurry containing fluoropolymer is coated onto the hydrophobic substrate by screen printing. Then, it is dried and shaped at 20~60℃ to remove the solvent, and then vacuum dried at 80~150℃ to form a microporous structure. Finally, heat treatment is performed to melt the fluoropolymer and form a continuous hydrophobic phase. After cooling, a gas diffusion layer is obtained.

[0006] In conjunction with the first aspect of the present invention, in some embodiments: the concentration of the hydrophobic agent emulsion is 8wt% to 12wt%; and / or, the hydrophobic agent emulsion is a fluoropolymer emulsion.

[0007] In conjunction with the first aspect of the present invention, in some embodiments: the mass ratio of carbon powder, deionized water, alcohol solvent, nonionic surfactant, and fluoropolymer in the microporous layer slurry is 1:10~30:1~10:0.1~1:0.1~0.8.

[0008] In conjunction with the first aspect of the present invention, some embodiments include: the carbon powder being one or more of solid carbon, porous carbon, graphite, conductive carbon black, and carbon nanotubes; and / or, the alcohol solvent being one or more of n-propanol, isopropanol, and ethanol; and / or, the nonionic surfactant being polyethylene glycol octylphenyl ether; and / or, the fluoropolymer being one or more of polytetrafluoroethylene (PTFE), perfluoropolyether (PFPE), and polyvinylidene fluoride (PVDF).

[0009] In conjunction with the first aspect of the present invention, in some embodiments: the drying and shaping time at 20~60°C is 5~10 minutes; and / or, the vacuum drying time is 30~120 minutes; and / or, the heat treatment temperature is 400~470°C; and / or, the heat treatment time is 1~5 hours; and / or, the heating rate of the heat treatment is 2~5°C / minute.

[0010] In conjunction with the first aspect of the present invention, in some embodiments: the method for preparing the gas diffusion layer further includes a step of preparing a microporous layer slurry, the step of preparing the microporous layer slurry including: (1) Dissolve the nonionic surfactant in deionized water and stir to form a surfactant solution; (2) Add alcohol solvent and deionized water to obtain a pre-prepared solution; (3) Add carbon powder to the pre-prepared solution and treat it with ultrasound to obtain a carbon powder dispersion; (4) Add fluoropolymer emulsion to carbon powder dispersion and mechanically stir to obtain the microporous layer slurry.

[0011] In conjunction with the first aspect of the present invention, in some embodiments: coating the microporous layer slurry containing fluoropolymers onto the hydrophobic substrate layer by screen printing includes: coating the microporous layer slurry containing fluoropolymers onto the hydrophobic substrate layer by screen printing includes: pouring the microporous layer slurry onto one end of a screen, uniformly scraping it across the surface of the screen with a squeegee, and extruding the microporous layer slurry onto the hydrophobic substrate layer through the screen.

[0012] In a second aspect, the present invention provides a gas diffusion layer, wherein the gas diffusion layer is prepared by the above-mentioned gas diffusion layer preparation method, and in the microporous layer of the gas diffusion layer, the cumulative pore volume in the pore size range of 20~100nm accounts for ≥90% of the total pore volume of the microporous layer.

[0013] Thirdly, the present invention provides a proton exchange membrane fuel cell, the proton exchange membrane fuel cell including the above-mentioned gas diffusion layer, and the gas diffusion layer being disposed on the cathode side of the proton exchange membrane fuel cell.

[0014] Fourthly, the present invention provides a vehicle comprising the above-described proton exchange membrane fuel cell as a power source.

[0015] Compared with the prior art, the present invention has at least the following beneficial effects: (1) This invention optimizes the pore size distribution of the microporous layer through a vacuum drying process at 80~150℃, increasing the cumulative pore volume ratio of 20~100 nm pores to over 90%, significantly increasing the gas transport channels. Figure 1 This significantly improves the transport efficiency of the reactant gas, ultimately enabling the battery to operate at high current densities (2000 mA / cm²). 2 Performance optimization under ( ).

[0016] (2) The present invention controls the uniform distribution of polytetrafluoroethylene through a heat treatment process of 400~470℃, thereby improving the hydrophobic properties of the microporous layer. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of the gas diffusion layer before and after the improvement of the present invention.

[0019] Figure 2 This is a comparison diagram of the aperture distribution of the embodiments and comparative examples of the present invention.

[0020] Figure 3 This is a performance comparison diagram of the membrane electrodes composed of gas diffusion layers in the embodiments and comparative examples of the present invention. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0022] For simplicity, this paper only discloses some explicitly defined numerical ranges. However, any lower limit can be combined with any upper limit to form an undefined range; and any lower limit can be combined with other lower limits to form an undefined range. Similarly, any upper limit can be combined with any other upper limit to form an undefined range. Furthermore, although not explicitly stated, every point or individual value between the endpoints of a range is included within that range. Therefore, each point or individual value can be used as its own lower or upper limit, combined with any other point or individual value, or combined with other lower or upper limits to form an undefined range.

[0023] It should be noted that, in this description, unless otherwise stated, "above" and "below" include the number itself, and "multiple" in "one or more" means two or more. Relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0024] In the description of this specification, the references to terms such as "any embodiment / mode," "one embodiment / mode," "some embodiments / modes," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment / mode or example is included in at least one embodiment / mode or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment / mode or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments / modes or examples. Furthermore, without contradiction, those skilled in the art can combine and integrate the different embodiments / modes or examples described in this specification, as well as the features of different embodiments / modes or examples.

[0025] The above description of the invention is not intended to describe every disclosed embodiment or implementation. Instead, exemplary embodiments are described in more detail below. These embodiments can be used in various combinations. The examples listed are representative only and should not be construed as exhaustive.

[0026] As described in the background section, if the gas diffusion layer has insufficient drainage capacity, liquid water will accumulate in the microporous layer under high current density conditions, leading to severe mass transfer polarization and a sharp drop in electrochemical reaction efficiency. To solve this problem, the present invention provides a gas diffusion layer with high drainage capacity, its preparation method, and its application.

[0027] The structure of a proton exchange membrane fuel cell is as follows: hydrogen inlet → anode flow field → anode catalyst layer (Pt / C) → proton exchange membrane → cathode catalyst layer (Pt / C) → cathode GDL → cathode flow field → water / oxygen outlet. The gas diffusion layer consists of a microporous layer and a hydrophobic substrate layer. The hydrophobic substrate layer is hydrophobic after being treated with a polytetrafluoroethylene emulsion. The cathode catalyst layer is hydrophilic, while the GDL is hydrophobic. Therefore, when liquid water migrates from the cathode catalyst layer to the GDL, it must overcome the capillary force corresponding to the pore size. (θ represents the contact angle, σ represents the surface tension of water): The smaller the pore size (r), the greater the capillary force (P) c The larger the pore size, the more difficult it is for water to enter the pores. Therefore, at the interface between the cathode catalyst layer and the microporous layer, liquid water preferentially exits through the macropores of the microporous layer to the hydrophobic substrate layer, and finally exits the battery through the flow channel.

[0028] This invention optimizes the pores in the microporous layer through two paths to improve drainage capacity: (1) Regulating pore size distribution: Vacuum drying at 80~150℃ is used to directionally form a 20~100 nm main drainage channel (cumulative pore volume ratio ≥90%), making this pore size range a high-efficiency water transport channel; (2) Improving the uniformity of polytetrafluoroethylene coating: Heat treatment at 400~470℃ is used to make the fluoropolymer melt and uniformly penetrate into the pores, reducing the area of ​​uncoated polytetrafluoroethylene and eliminating local water accumulation points.

[0029] Specifically, the method for preparing the gas diffusion layer provided by the present invention includes the following steps: impregnating untreated carbon paper with a hydrophobic agent emulsion and then drying it to obtain a hydrophobic substrate layer; coating the hydrophobic substrate layer with a microporous layer slurry containing a fluoropolymer by screen printing; then drying and shaping it at 20~60℃ to remove the solvent; then vacuum drying it at 80~150℃ to form a microporous structure; finally heat-treating it to melt the fluoropolymer and form a continuous hydrophobic phase; and finally cooling it to obtain the gas diffusion layer.

[0030] This invention uses a vacuum drying process at 80~150℃ to directionally construct pores of 20~100nm (more than 90% of the volume) in a microporous layer, making this pore size range the main drainage channel; at the same time, through heat treatment, the fluoropolymer is melted to form a continuous hydrophobic phase, thereby improving the hydrophobicity of the microporous layer.

[0031] In some embodiments of the present invention, the concentration of the hydrophobic agent emulsion is 8 wt% to 12 wt%; the concentration of the hydrophobic agent emulsion directly affects the uniformity of the molten hydrophobic agent distribution. When the concentration of the hydrophobic agent emulsion is 8 wt% to 12 wt%, the hydrophobic agent is uniformly dispersed in the slurry, and can fully penetrate into the pores of the carbon paper during impregnation to form a continuous hydrophobic film, while avoiding clogging the microporous structure of the carbon paper. When the concentration of the hydrophobic agent emulsion is >12 wt%, the tendency for particle agglomeration is enhanced, resulting in uneven distribution of the hydrophobic agent; when the concentration of the hydrophobic agent emulsion is <8 wt%, the hydrophobic agent dosage is insufficient, and a continuous and effective hydrophobic film cannot be formed. In some embodiments, the hydrophobic agent emulsion is a fluoropolymer emulsion, and the fluoropolymer is one or more of polytetrafluoroethylene, perfluoropolyether, and polyvinylidene fluoride, and the solvent of the hydrophobic agent emulsion is water.

[0032] In some embodiments of the present invention, the mass ratio of toner, deionized water, alcohol solvent, nonionic surfactant, and fluoropolymer in the microporous slurry is 1:10~30:1~10:0.1~1:0.1~0.8. This ratio ensures good dispersibility of the toner and fluoropolymer, good flowability of the slurry, and facilitates solvent evaporation.

[0033] In some embodiments of the present invention, the toner is one or more of solid carbon, porous carbon, graphite, conductive carbon black, and carbon nanotubes; and / or, the alcohol solvent is one or more of n-propanol, isopropanol, and ethanol; and / or, the nonionic surfactant is polyethylene glycol octylphenyl ether; and / or, the fluoropolymer is one or more of polytetrafluoroethylene, perfluoropolyether, and polyvinylidene fluoride. Preferably, the toner is solid carbon, the alcohol solvent is isopropanol, and the fluoropolymer is polytetrafluoroethylene.

[0034] In some embodiments of the present invention, the drying and setting time at 20-60°C is 5-10 minutes. The drying and setting temperature of 20-60°C and the time limit of 5-10 minutes ensure that the microporous slurry slowly dehydrates at 20-60°C, forming a uniform preliminary gel structure, laying the foundation for the subsequent directional generation of 20-100 nm main drainage channels during vacuum drying at 80-150°C. If the drying and setting time is less than 5 minutes, the solvent will not evaporate completely, and sudden evaporation during the vacuum drying stage may lead to pore collapse; if the drying and setting time is more than 10 minutes, the microporous slurry may become pulverized due to excessive dehydration.

[0035] In some embodiments of the present invention, the vacuum drying time is 30 to 120 minutes, which can ensure that the solvent evaporates at a controllable rate in a vacuum environment of 80 to 150°C, forming a 20 to 100 nm main drainage channel and a continuous hydrophobic phase of fluoropolymer.

[0036] In some embodiments of the present invention, the heat treatment time is 1 to 5 hours, which ensures that polytetrafluoroethylene (PTFE) completely melts and penetrates into the pores of the microporous layer at 400 to 470°C, forming a continuous hydrophobic phase. When the time is less than 1 hour, insufficient melting of PTFE leads to an increase in the uncoated area and a decrease in the penetration rate; when the heat treatment lasts for 5 hours, PTFE can completely coat the microporous layer, and the heat treatment can be stopped.

[0037] In some embodiments of the present invention, the method for preparing the gas diffusion layer further includes a step of preparing a microporous layer slurry, wherein the step of preparing the microporous layer slurry includes: (1) Dissolve the nonionic surfactant in deionized water and stir to form a surfactant solution; (2) Add alcohol solvent and deionized water to obtain a pre-prepared solution; (3) Add carbon powder to the pre-prepared solution and treat it with ultrasound to obtain a carbon powder dispersion; (4) Add fluoropolymer emulsion to carbon powder dispersion and mechanically stir to obtain the microporous layer slurry.

[0038] In some embodiments of the present invention, coating the microporous layer slurry containing fluoropolymer onto the hydrophobic substrate by screen printing includes: pouring the microporous layer slurry onto one end of a screen printing plate, uniformly scraping the surface of the screen printing plate with a squeegee, and extruding the microporous layer slurry onto the hydrophobic substrate through the screen printing plate.

[0039] In some embodiments of the present invention, the heating rate of the heat treatment is 2~5°C / min, which ensures that the polytetrafluoroethylene melts uniformly and penetrates into the pores of the microporous layer to form a continuous hydrophobic phase. A heating rate lower than 2°C / min is too inefficient; a rate higher than 5°C / min will result in uneven melting of the polytetrafluoroethylene.

[0040] like Figure 1 As shown, in the microporous layer of the gas diffusion layer prepared by the above preparation method, the cumulative pore volume in the pore size range of 20~100nm accounts for ≥90% of the total pore volume of the microporous layer.

[0041] The present invention also provides a proton exchange membrane fuel cell, wherein the proton exchange membrane fuel cell includes the aforementioned gas diffusion layer, and the gas diffusion layer is disposed on the cathode side of the fuel cell. Due to the good drainage capacity of the gas diffusion layer, the transport efficiency of the reactant gas in the proton exchange membrane fuel cell is high, ultimately enabling the battery to operate at high current densities (2000 mA / cm²). 2 It exhibits good performance under these conditions.

[0042] The present invention also provides a vehicle, the vehicle including the above-described proton exchange membrane fuel cell as a power source.

[0043] The technical solution of the present invention will be described in detail below through examples and comparative examples. Unless otherwise specified, the reagents and instruments used in the present invention are common reagents and instruments that are commonly used and readily available in the art.

[0044] The hydrophobic carbon paper used in the following examples and comparative examples was prepared by the following method: the purchased bare carbon paper (JZ13, Shanghai Jiazi) was immersed in polytetrafluoroethylene emulsion (10wt%) for 30 seconds, then removed and dried. After the surface was free of impregnation solution, it was placed in a vacuum drying oven at 60°C for 30 minutes and dried for later use.

[0045] Example 1: The method for preparing the gas diffusion layer provided in this embodiment includes the following steps: (1) Polyethylene glycol octylphenyl ether (Triton X-100) was added to deionized water and mechanically stirred to obtain a surfactant solution; wherein the stirring rate was 1500 r / min and the stirring time was 20 min.

[0046] (2) Isopropanol and deionized water are added to the surfactant solution and mechanically stirred to obtain a pre-prepared solution; wherein the stirring rate is 1000 r / min and the stirring time is 10 min.

[0047] (3) Add solid carbon (XC-72) to the pre-prepared solution and sonicate to obtain carbon powder dispersion.

[0048] (4) Add polytetrafluoroethylene emulsion (10 wt% by mass, water as solvent) to the toner dispersion and mechanically stir to obtain a microporous slurry; wherein the stirring rate is 500 r / min and the stirring time is 5 min. In the microporous slurry, the mass ratio of toner, water, isopropanol, polyethylene glycol octylphenyl ether and polytetrafluoroethylene is 1:20:2:0.1:0.8.

[0049] (5) Pour the prepared microporous layer slurry onto one end of the screen printing plate, and use a scraper to evenly scrape it across the surface of the screen printing plate to extrude the microporous layer slurry onto the substrate surface through the screen, thus completing the coating of the gas diffusion layer. Dry at 25°C for 2 hours to obtain the gas diffusion layer precursor.

[0050] (6) The gas diffusion layer precursor is placed in a vacuum oven for drying; the drying temperature is 100℃ and the drying time is 60 minutes.

[0051] (7) After drying the gas diffusion layer precursor, heat it at 450°C for 1 hour to obtain the gas diffusion layer.

[0052] Tests showed that the thickness of the bare carbon paper was approximately 160 micrometers, the coated microporous layer was approximately 20 micrometers, and the final gas diffusion layer was approximately 180 micrometers thick.

[0053] Example 2: This embodiment provides a gas diffusion layer, which is prepared in the following manner: (1) Polyethylene glycol octylphenyl ether (Triton X-100) was added to deionized water and mechanically stirred to obtain a surfactant solution; wherein the stirring rate was 1500 r / min and the stirring time was 20 min.

[0054] (2) Isopropanol and deionized water are added to the surfactant solution and mechanically stirred to obtain a pre-prepared solution; wherein the stirring rate is 1000 r / min and the stirring time is 10 min.

[0055] (3) Add solid carbon (XC-72) to the pre-prepared solution and sonicate to obtain carbon powder dispersion.

[0056] (4) Add polytetrafluoroethylene emulsion (10 wt% by mass, water as solvent) to the toner dispersion and mechanically stir to obtain a microporous slurry; wherein the stirring rate is 500 r / min and the stirring time is 5 min; in the microporous slurry, the mass ratio of toner, water, isopropanol, polyethylene glycol octylphenyl ether and polytetrafluoroethylene is 1:20:2:0.1:0.8.

[0057] (5) Pour the prepared microporous layer slurry onto one end of the screen printing plate, and use a scraper to evenly scrape it across the surface of the screen printing plate to extrude the microporous layer slurry onto the substrate surface through the screen, thus completing the coating of the gas diffusion layer. Dry at 25°C for 2 hours to obtain the gas diffusion layer precursor.

[0058] (6) Place the gas diffusion layer precursor into a vacuum oven for drying; the drying temperature is 150℃ and the drying time is 120 minutes.

[0059] (7) After drying the gas diffusion layer precursor, heat it at 400°C for 1 hour to obtain the gas diffusion layer.

[0060] Example 3: This embodiment provides a gas diffusion layer, which is prepared in the following manner: (1) Polyethylene glycol octylphenyl ether (Triton X-100) was added to deionized water and mechanically stirred to obtain a surfactant solution; wherein the stirring rate was 1500 r / min and the stirring time was 20 min.

[0061] (2) Isopropanol and deionized water are added to the surfactant solution and mechanically stirred to obtain a pre-prepared solution; wherein the stirring rate is 1000 r / min and the stirring time is 10 min.

[0062] (3) Add solid carbon (XC-72) to the pre-prepared solution and sonicate to obtain carbon powder dispersion.

[0063] (4) Add polytetrafluoroethylene emulsion (10 wt% by mass, water as solvent) to the toner dispersion and mechanically stir to obtain a microporous slurry; wherein the stirring rate is 500 r / min and the stirring time is 5 min. In the microporous slurry, the mass ratio of toner, water, isopropanol, polyethylene glycol octylphenyl ether and polytetrafluoroethylene is 1:20:2:0.1:0.8.

[0064] (5) Pour the prepared microporous layer slurry onto one end of the screen printing plate, and use a scraper to evenly scrape it across the surface of the screen printing plate to extrude the microporous layer slurry onto the substrate surface through the screen, thus completing the coating of the gas diffusion layer. Dry at 25°C for 2 hours to obtain the gas diffusion layer precursor.

[0065] (6) Place the gas diffusion layer precursor into a vacuum oven for drying; the drying temperature is 120℃ and the drying time is 120 minutes.

[0066] (7) After drying the gas diffusion layer precursor, heat it at 420°C for 1 hour to obtain the gas diffusion layer.

[0067] Example 4: The method for preparing the gas diffusion layer provided in this embodiment includes the following steps: (1) Polyethylene glycol octylphenyl ether (Triton X-100) was added to deionized water and mechanically stirred to obtain a surfactant solution; wherein the stirring rate was 1500 r / min and the stirring time was 20 min.

[0068] (2) Isopropanol and deionized water are added to the surfactant solution and mechanically stirred to obtain a pre-prepared solution; wherein the stirring rate is 1000 r / min and the stirring time is 10 min.

[0069] (3) Add solid carbon (XC-72) to the pre-prepared solution and sonicate to obtain carbon powder dispersion.

[0070] (4) Add polytetrafluoroethylene emulsion (10 wt% by mass, water as solvent) to the toner dispersion and mechanically stir to obtain a microporous slurry; wherein the stirring rate is 500 r / min and the stirring time is 5 min. In the microporous slurry, the mass ratio of toner, water, isopropanol, polyethylene glycol octylphenyl ether and polytetrafluoroethylene is 1:20:2:0.1:0.8.

[0071] (5) Pour the prepared microporous layer slurry onto one end of the screen printing plate, and use a scraper to evenly scrape it across the surface of the screen printing plate to extrude the microporous layer slurry onto the substrate surface through the screen, thus completing the coating of the gas diffusion layer. Dry at 25°C for 2 hours to obtain the gas diffusion layer precursor.

[0072] (6) The gas diffusion layer precursor is placed in a vacuum oven for drying; the drying temperature is 100℃ and the drying time is 60 minutes.

[0073] (7) After drying the gas diffusion layer precursor, heat it at 420°C for 1 hour to obtain the gas diffusion layer.

[0074] Comparative Example 1: The method for preparing the gas diffusion layer provided in this comparative example includes the following steps: (1) Polyethylene glycol octylphenyl ether (Triton X-100) was added to deionized water and mechanically stirred to obtain a surfactant solution; wherein the stirring rate was 1500 r / min and the stirring time was 20 min.

[0075] (2) Isopropanol and deionized water are added to the surfactant solution and mechanically stirred to obtain a pre-prepared solution; wherein the stirring rate is 1000 r / min and the stirring time is 10 min.

[0076] (3) Add solid carbon (XC-72) to the pre-prepared solution and sonicate to obtain carbon powder dispersion.

[0077] (4) Add polytetrafluoroethylene emulsion (10 wt% by mass, water as solvent) to the toner dispersion and mechanically stir to obtain a microporous slurry; wherein the stirring rate is 500 r / min and the stirring time is 5 min. In the microporous slurry, the mass ratio of toner, water, isopropanol, polyethylene glycol octylphenyl ether and polytetrafluoroethylene is 1:20:2:0.1:0.8.

[0078] (5) Pour the prepared microporous layer slurry onto one end of the screen printing plate, and use a scraper to evenly scrape it across the surface of the screen printing plate to extrude the microporous layer slurry onto the substrate surface through the screen, thus completing the coating of the gas diffusion layer. Dry at 25°C for 2 hours to obtain the gas diffusion layer precursor.

[0079] (6) Dry the gas diffusion layer precursor at room temperature for 60 minutes.

[0080] (7) After drying the gas diffusion layer precursor, heat it at 450°C for 1 hour to obtain the gas diffusion layer.

[0081] Comparative Example 2: The method for preparing the gas diffusion layer provided in this comparative example includes the following steps: (1) Polyethylene glycol octylphenyl ether (Triton X-100) was added to deionized water and mechanically stirred to obtain a surfactant solution; wherein the stirring rate was 1500 r / min and the stirring time was 20 min.

[0082] (2) Isopropanol and deionized water are added to the surfactant solution and mechanically stirred to obtain a pre-prepared solution; wherein the stirring rate is 1000 r / min and the stirring time is 10 min.

[0083] (3) Add solid carbon (XC-72) to the pre-prepared solution and sonicate to obtain carbon powder dispersion.

[0084] (4) Add polytetrafluoroethylene emulsion (10 wt% by mass, water as solvent) to the toner dispersion and mechanically stir to obtain a microporous slurry; wherein the stirring rate is 500 r / min and the stirring time is 5 min. In the microporous slurry, the mass ratio of toner, water, isopropanol, polyethylene glycol octylphenyl ether and polytetrafluoroethylene is 1:20:2:0.1:0.8.

[0085] (5) Pour the prepared microporous layer slurry onto one end of the screen printing plate, and use a scraper to evenly scrape it across the surface of the screen printing plate to extrude the microporous layer slurry onto the substrate surface through the screen, thus completing the coating of the gas diffusion layer. Dry at 25°C for 2 hours to obtain the gas diffusion layer precursor.

[0086] (6) The gas diffusion layer precursor is placed in a vacuum oven for drying; the drying temperature is 100℃ and the drying time is 60 minutes.

[0087] (7) After drying the gas diffusion layer precursor, heat it at 350°C for 1 hour to obtain the gas diffusion layer.

[0088] Comparative Example 3: The method for preparing the gas diffusion layer provided in this comparative example includes the following steps: (1) Polyethylene glycol octylphenyl ether (Triton X-100) was added to deionized water and mechanically stirred to obtain a surfactant solution; wherein the stirring rate was 1500 r / min and the stirring time was 20 min.

[0089] (2) Isopropanol and deionized water are added to the surfactant solution and mechanically stirred to obtain a pre-prepared solution; wherein the stirring rate is 1000 r / min and the stirring time is 10 min.

[0090] (3) Add solid carbon (XC-72) to the pre-prepared solution and sonicate to obtain carbon powder dispersion.

[0091] (4) Add polytetrafluoroethylene emulsion (10 wt% by mass, water as solvent) to the toner dispersion and mechanically stir to obtain a microporous slurry; wherein the stirring rate is 500 r / min and the stirring time is 5 min. In the microporous slurry, the mass ratio of toner, water, isopropanol, polyethylene glycol octylphenyl ether and polytetrafluoroethylene is 1:20:2:0.1:0.8.

[0092] (5) Pour the prepared microporous layer slurry onto one end of the screen printing plate, and use a scraper to evenly scrape it across the surface of the screen printing plate to extrude the microporous layer slurry onto the substrate surface through the screen, thus completing the coating of the gas diffusion layer. Dry at 25°C for 2 hours to obtain the gas diffusion layer precursor.

[0093] (6) Dry the gas diffusion layer precursor at room temperature for 60 minutes.

[0094] (7) After drying the gas diffusion layer precursor, heat it at 350°C for 1 hour to obtain the gas diffusion layer.

[0095] After the gas diffusion layer is prepared, it is combined with the prepared CCM to form a film electrode. The Pt loading of the anode and cathode in the CCM is 0.4 mg / cm³, respectively. 2and 0.1 mg / cm 2 Subsequently, the polarization curves of single-cell tests were recorded on the automated HEPHAS (HTS-125) fuel cell test station to evaluate the performance of the membrane electrode assembly. The specific test methods were in accordance with the national standard "Proton Exchange Membrane Fuel Cells Part 5: Membrane Electrode Test Methods" (GB / T 20042.5-2024).

[0096] Table 1

[0097] Table 1 data shows that: Examples 1-4 at 2000 mA / cm 2 Under rated operating conditions, the voltages of all samples were significantly higher than those of the comparative examples. Among them, the proton exchange membrane fuel cell assembled with the gas diffusion layer obtained in Example 1 (heating at 450°C + vacuum drying at 100°C) exhibited the highest voltage (0.672 V), representing a 7.7% improvement compared to the comparative example. This result directly demonstrates that the synergistic effect of the vacuum drying process and heating temperature effectively improves the drainage efficiency of the microporous layer, reduces mass transfer polarization, and thus enhances the high-power performance of the fuel cell.

[0098] The above description is merely a specific embodiment of the present invention, enabling those skilled in the art to understand or implement the invention. 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 invention. Therefore, the present invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A method for producing a gas diffusion layer, characterized by, The method comprises the following steps: The untreated carbon paper is immersed in a hydrophobic agent emulsion and then dried to obtain a hydrophobic substrate layer; A microporous layer slurry containing fluoropolymers is coated on the hydrophobic substrate layer by a screen printing process, then dried and shaped at 20-60°C to remove the solvent, vacuum dried at 80-150°C to form a microporous structure, and finally heat treated to melt the fluoropolymers and form a continuous hydrophobic phase, thereby obtaining a gas diffusion layer after cooling.

2. The method according to claim 1, wherein: The concentration of the hydrophobic agent emulsion is 8wt%-12wt%; and / or, The hydrophobic agent emulsion is a fluoropolymer emulsion.

3. The method according to claim 1, wherein: The mass ratio of carbon powder, deionized water, alcohol solvent, non-ionic surfactant, and fluoropolymer in the microporous layer slurry is 1:10-30:1-10:0.1-1:0.1-0.

8.

4. The method according to claim 3, wherein: The carbon powder is one or more of solid carbon, porous carbon, graphite, conductive carbon black, and carbon nanotubes; and / or, The alcohol solvent is one or more of n-propanol, isopropanol, and ethanol; and / or, The non-ionic surfactant is polyethylene glycol octylphenyl ether; and / or, The fluoropolymer is one or more of polytetrafluoroethylene, perfluoropolyether, and polyvinylidene fluoride.

5. The method according to claim 1, wherein: The time for drying and shaping at 20-60°C is 5-10 minutes; and / or, The time for vacuum drying is 30-120 minutes; and / or, The temperature for heat treatment is 400-470°C; and / or, The time for heat treatment is 1-5 hours; and / or, The heating rate for heat treatment is 2-5°C / min.

6. The method for producing a gas diffusion layer according to claim 1, characterized by: The method further comprises a step of preparing the microporous layer slurry, which comprises: (1) dissolving the non-ionic surfactant in deionized water to form a surfactant solution; (2) adding the alcohol solvent and deionized water to obtain a pre-prepared solution; (3) adding the carbon powder to the pre-prepared solution and performing ultrasonic treatment to obtain a carbon powder dispersion; (4) adding the fluoropolymer water emulsion to the carbon powder dispersion and mechanically stirring to obtain the microporous layer slurry.

7. The method for producing a gas diffusion layer according to claim 1, characterized by: The step of coating the microporous layer slurry containing fluoropolymers on the hydrophobic substrate layer by a screen printing process comprises pouring the microporous layer slurry into one end of a screen, uniformly scraping the surface of the screen with a doctor blade, and extruding the microporous layer slurry through the screen onto the hydrophobic substrate layer.

8. A gas diffusion layer characterized by: The gas diffusion layer is prepared by the method according to any one of claims 1-7, and in the microporous layer of the gas diffusion layer, the cumulative pore volume in the range of 20-100 nm pore size accounts for ≥90% of the total pore volume of the microporous layer.

9. A proton exchange membrane fuel cell characterized by: The proton exchange membrane fuel cell comprises the gas diffusion layer according to claim 8, and the gas diffusion layer is arranged on the cathode side of the proton exchange membrane fuel cell.

10. A vehicle characterized by: The vehicle includes the proton exchange membrane fuel cell of claim 9 as a power source.

Images