Proton exchange membrane as well as preparation method and application thereof

Abstract

The invention discloses a proton exchange membrane as well as a preparation method and application thereof. The preparation method of the proton exchange membrane comprises the following steps: providing aramid fibers, an acid solvent and a substrate; mixing the aramid fiber and the acid solvent, and heating to obtain a fiber dispersion liquid; dispersing the fiber dispersion liquid on the surface of the substrate to form a fiber layer; soaking the fiber layer in a phosphoric acid solution to obtain a phosphoric acid doped fiber layer; and drying the phosphoric acid doped fiber layer. The proton exchange membrane prepared in the invention is stable in a high-temperature environment, has good proton conduction performance, and can be applied to high-temperature fuel cells.

Description

Technical Field

[0001] This application relates to the field of proton exchange membrane materials technology, and in particular to a proton exchange membrane, its preparation method and application. Background Technology

[0002] Proton exchange membrane fuel cells (PEMFCs) have broad development prospects in the field of clean energy. Among them, the proton exchange membrane is a key component affecting the performance, high-temperature resistance, and long-term stability of fuel cells. Traditional PEMFCs limit the stable operation of fuel cells at higher operating temperatures due to factors such as a significant decrease in proton conductivity under high-temperature conditions. Summary of the Invention

[0003] In view of this, this application provides a proton exchange membrane with good proton conduction performance under high temperature environment, its preparation method and application.

[0004] The first aspect of this application provides a method for preparing a proton exchange membrane, comprising the following steps: Provides aramid fibers, acid solvents, and substrates; The aramid fiber and the acid solvent are mixed and heated to obtain a fiber dispersion. The fiber dispersion is dispersed on the surface of the substrate to form a fiber layer; The fiber layer was immersed in a phosphoric acid solution to obtain a phosphoric acid-doped fiber layer. The phosphate-doped fiber layer is dried.

[0005] In some embodiments, the aramid fiber comprises para-aramid and / or meta-aramid.

[0006] In some embodiments, the acid solvent includes one or more of sulfuric acid, methanesulfonic acid, or trifluoromethanesulfonic acid.

[0007] In some embodiments, the heating temperature is 50°C to 120°C.

[0008] In some embodiments, the aramid fiber content in the fiber dispersion is 0.5 wt% to 5 wt%, based on the total mass of the fiber dispersion.

[0009] In some embodiments, the concentration of the phosphoric acid solution is 5 wt% to 20 wt%, and the soaking time is 12 h to 24 h.

[0010] In some embodiments, the fiber dispersion is dispersed on the substrate surface by one or more of casting, spin coating, or blade coating.

[0011] In some embodiments, the phosphate-doped fiber layer is dried in a vacuum environment.

[0012] A second aspect of this application provides a proton exchange membrane, which is prepared according to the preparation method described above.

[0013] The third aspect of this application provides the application of the aforementioned proton exchange membrane in fuel cells.

[0014] This application involves mixing and heating aramid fibers with an acid solvent to obtain a fiber dispersion. The fiber dispersion is then dispersed on a substrate surface to form a fiber layer. Next, the fiber layer is immersed in a phosphoric acid solution to obtain a phosphoric acid-doped fiber layer. After drying, a proton exchange membrane uniformly doped with phosphoric acid is obtained. The proton exchange membrane prepared in this application is stable at high temperatures and exhibits excellent proton conductivity, making it particularly suitable for high-temperature fuel cells. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the preparation method of a proton exchange membrane provided in one embodiment of this application.

[0016] Figure 2 A physical image of a proton exchange membrane provided in one embodiment of this application.

[0017] Figure 3 An optical microscope image of a proton exchange membrane provided in one embodiment of this application.

[0018] Figure 4 A transmission electron microscope image of a proton exchange membrane provided in one embodiment of this application.

[0019] Figure 5 X-ray photoelectron spectrum of a proton exchange membrane provided in one embodiment of this application.

[0020] The following detailed description, in conjunction with the accompanying drawings, will further illustrate this application. Detailed Implementation

[0021] The embodiments of this application are described in detail below. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this application, and should not be construed as limiting this application. The reagents and materials described in the following embodiments are all commercially available.

[0022] To better understand the above-mentioned objectives, features, and advantages of the embodiments of this application, the application will be described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that, unless otherwise specified, the features in the embodiments of this application can be combined with each other.

[0023] The following description sets forth numerous specific details to provide a thorough understanding of the embodiments of this application. The described implementations are only a portion, not all, of the embodiments described herein. All other implementations obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of the embodiments of this application.

[0024] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which embodiments of this application belong. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the embodiments of this application.

[0025] Proton exchange membrane fuel cells (PEMFCs) have broad development prospects in the field of clean energy. Among them, the proton exchange membrane is a key component affecting the performance, temperature resistance, and long-term stability of fuel cells. Traditional commercial PEMFCs mostly rely on fluoropolymer materials, whose proton conductivity decreases significantly under high temperature and without additional humidification conditions, limiting the stable operation of fuel cells at higher operating temperatures.

[0026] Aramid fibers, also known as aromatic polyamide fibers, possess excellent thermal stability, mechanical strength, and chemical resistance, making them a potential substrate for high-temperature proton exchange membranes. However, aramid fibers themselves lack sufficient proton conduction channels, necessitating further doping with proton carriers to improve their conductivity under high-temperature conditions. Phosphoric acid, a commonly used proton carrier, offers advantages such as non-volatility at high temperatures and strong proton migration capabilities; however, achieving uniform incorporation of phosphoric acid into the aramid matrix while maintaining the structural stability of the film requires extensive research. Existing methods generally suffer from uneven phosphoric acid doping; therefore, developing a simple, uniformly doped, and structurally stable method for preparing aramid proton exchange membranes is of great significance.

[0027] Based on this, please refer to Figure 1 This application provides a method for preparing a proton exchange membrane, comprising the following steps: S1: Provides aramid fibers, acid solvents, and a substrate; S2: Aramid fibers and acid solvent are mixed and heated to obtain a fiber dispersion; S3: Disperse the fiber dispersion on the substrate surface to form a fiber layer; S4: Immerse the fiber layer in a phosphoric acid solution to obtain a phosphoric acid-doped fiber layer; S5: Dry phosphoric acid-doped fiber layer.

[0028] In this application, aramid fibers are first dispersed in an acidic solvent, which swells and disperses the aramid fibers into nanoscale aramid fibers, thus dissociating the aggregated aramid fibers into a nanoscale dispersed state. These nanoscale aramid fibers are then dispersed on a substrate surface to form a fiber layer. Next, the fiber layer is immersed in a phosphoric acid solution to obtain a phosphoric acid-doped fiber layer. After drying, a phosphoric acid-doped proton exchange membrane is obtained. This method allows phosphoric acid molecules to be uniformly distributed among the nanoscale aramid fibers, endowing the fiber layer with excellent proton conductivity at high temperatures. The phosphoric acid-doped fiber layer can be peeled off the substrate as a whole to form a self-supporting structure while maintaining good flexibility and mechanical strength.

[0029] In some embodiments, the aramid fibers in step S1 include para-aramid and / or meta-aramid. For example, the aramid fibers may be selected from para-aramid, meta-aramid, or a mixture of para-aramid and meta-aramid.

[0030] In some embodiments, the acid solvent in step S1 includes one or more of sulfuric acid, methanesulfonic acid, or trifluoromethanesulfonic acid. Choosing sulfuric acid, methanesulfonic acid, or trifluoromethanesulfonic acid facilitates better swelling of the aramid fibers and dispersion at the nanoscale, resulting in uniform dispersion of the aramid fibers and improving uniformity during subsequent phosphoric acid doping.

[0031] In some embodiments, the substrate in step S1 includes materials with supporting functions such as glass, silicon wafers, and polyimide.

[0032] In some embodiments, the heating temperature in step S2 is 50°C to 120°C. For example, the heating temperature can be 50°C, 60°C, 70°C, 80°C, 90°C, 100°C, 110°C, 120°C, or any value within the range of any two of the above values. Using heating and controlling the heating temperature within the above range is beneficial for the aramid fibers to swell and disperse into nanoscale fibers.

[0033] In some embodiments, mechanical stirring, high-speed shearing, and ultrasonic waves can be combined to further promote the uniform dispersion of aramid fibers in acid solvents.

[0034] In some embodiments, the content of aramid fiber in the fiber dispersion is 0.5 wt% to 5 wt%, based on the total mass of the fiber dispersion. For example, the content of aramid fiber in the fiber dispersion can be 0.5 wt%, 1 wt%, 1.5 wt%, 2 wt%, 2.5 wt%, 3 wt%, 3.5 wt%, 4 wt%, 4.5 wt%, 5 wt%, or any value within the range of any two of the above values. Controlling the content of aramid fiber in the fiber dispersion within the above range helps to ensure uniform dispersion of the aramid fiber in the acid solution, providing a basis for subsequent uniform doping with phosphoric acid.

[0035] In some embodiments, step S3, dispersing the fiber dispersion on the substrate surface, can be done in various ways, including casting, spin coating, or blade coating. This is just an example; this application does not specifically limit the method of dispersing the fiber dispersion on the substrate surface. Alternatively, the fiber dispersion can be dispersed on the substrate surface under heating conditions, with the heating temperature ranging from 50°C to 120°C, allowing the fiber dispersion to spread into a continuous thin layer under heating conditions. The thickness can be precisely adjusted by controlling the casting speed, coating thickness, solid content, etc.

[0036] In some embodiments, the concentration of the phosphoric acid solution in step S4 is 5 wt% to 20 wt%, and the soaking time is 12 h to 24 h. For example, the concentration of the phosphoric acid solution can be 5 wt%, 8 wt%, 10 wt%, 13 wt%, 15 wt%, 18 wt%, 20 wt%, or any value within the range of any two of the above values. The soaking time can be 12 h, 14 h, 16 h, 18 h, 20 h, 22 h, 24 h, or any value within the range of any two of the above values. In this step, phosphoric acid molecules spontaneously enter the network structure formed by the aramid fibers and are fixed in the fiber interstices through hydrogen bonding, electrostatic adsorption, and spatial confinement effects, resulting in uniform and stable doping. Controlling the concentration of the phosphoric acid solution and the soaking time within the above range helps to further promote the smooth entry of phosphoric acid into the network structure of the aramid fibers and uniform doping.

[0037] In some embodiments, the phosphoric acid-doped fiber layer obtained in step S4 can be directly peeled off from the substrate to form a flexible, self-supporting film with a certain mechanical strength.

[0038] In some embodiments, step S5, drying the phosphoric acid-doped fiber layer, can be performed in various ways, including natural placement, stretch drying, and confined drying, to obtain a dense, stable, and self-supporting phosphoric acid-doped proton exchange membrane. The drying temperature can be between 25°C and 120°C, for example, 25°C, 40°C, 50°C, 80°C, 100°C, 120°C, or any value within the range of any two of these values. Controlling the drying temperature within this range balances drying efficiency with protecting the fiber layer from damage caused by extremely high temperatures.

[0039] In some embodiments, the phosphoric acid-doped fiber layer is dried in a vacuum environment. The vacuum environment helps reduce phosphoric acid volatilization or structural damage at high temperatures, resulting in a proton exchange membrane with a dense structure and excellent thermal stability and proton conductivity.

[0040] A second aspect of this application provides a proton exchange membrane prepared according to the above-described preparation method. The proton exchange membrane prepared according to the method provided in this application has a uniform and dense structure.

[0041] The third aspect of this application provides the application of the above-mentioned proton exchange membrane in fuel cells. The proton exchange membrane of this application is stable in high-temperature environments and has good proton conduction performance, making it suitable for use in high-temperature fuel cells.

[0042] The present application will be further illustrated below with reference to specific embodiments.

[0043] Example 1 S1: Provides para-aramid chopped fibers as raw material, 98% concentrated sulfuric acid as acid solvent, and glass as substrate.

[0044] S2: Under magnetic stirring, 1g of para-aramid short-cut fibers were added to 100g of concentrated sulfuric acid. The mixture was heated at 80℃ and stirred for 24h to obtain a fiber dispersion with a solid content of 1 wt%.

[0045] S3: By casting, the fiber dispersion is uniformly coated onto a glass substrate at 80°C to form a thin layer. After the thin layer is cooled to room temperature, a uniform and dense fiber layer is obtained.

[0046] S4: Immerse the fiber layer together with the glass substrate in a 10 wt% aqueous solution of phosphoric acid for 24 hours to obtain a phosphoric acid-doped fiber layer with a self-supporting structure.

[0047] S5: The phosphate-doped fiber layer with a self-supporting structure was dried for 12 hours at 80℃ in a vacuum environment to obtain a phosphate-doped proton exchange membrane with a thickness of about 20μm~40μm and uniform phosphate doping.

[0048] Example 2 S1: Provides meta-aramid short-cut fibers as raw materials, provides methanesulfonic acid with a mass fraction of 98% as an acid solvent, and provides silicon wafers as a substrate.

[0049] S2: Under magnetic stirring, 3g of meta-aramid short-cut fibers were added to 100g of methanesulfonic acid. The mixture was stirred for 24h under heating at 90℃ to obtain a fiber dispersion with a solid content of 3 wt%.

[0050] S3: Using spin coating, the fiber dispersion is evenly spread on the silicon wafer substrate at a speed of 500 rpm to form a thin layer. After the thin layer is cooled to room temperature, the fiber layer is obtained.

[0051] S4: Immerse the fiber layer together with the silicon wafer substrate in a 5 wt% aqueous solution of phosphoric acid for 12 hours to obtain a phosphoric acid-doped fiber layer with a self-supporting structure.

[0052] S5: The phosphoric acid-doped fiber layer with a self-supporting structure was dried for 24 hours at 60°C under vacuum to obtain a phosphoric acid-doped proton exchange membrane. The proton exchange membrane obtained in Example 2 is thinner and more flexible than that in Example 1, and can be used in high-temperature fuel cells where a thinner membrane thickness is required.

[0053] Example 3 S1: A composite fiber consisting of para-aramid chopped fibers and meta-aramid chopped fibers, wherein the mass ratio of para-aramid chopped fibers to meta-aramid chopped fibers is 1:1. Trifluoromethanesulfonic acid (98% by mass) is provided as the acid solvent, and polyimide is provided as the substrate.

[0054] S2: Under ultrasonic conditions, 5g of composite fiber was added to 100g of trifluoromethanesulfonic acid. The two were mixed and stirred for 24h under heating at 100℃ to obtain a fiber dispersion with a solid content of 5wt%.

[0055] S3: The fiber dispersion is evenly spread on the polyimide substrate to form a thin layer by scraping. After the thin layer is cooled to room temperature, the fiber layer is obtained.

[0056] S4: Immerse the fiber layer together with the polyimide substrate in a 20 wt% aqueous solution of phosphoric acid for 20 h to obtain a phosphoric acid-doped fiber layer with a self-supporting structure.

[0057] S5: The phosphate-doped fiber layer with a self-supporting structure was dried for 24 hours at 100°C under vacuum to obtain a phosphate-doped proton exchange membrane. The proton exchange membrane obtained in Example 3 has a relatively higher phosphate doping amount and can still maintain a high proton conductivity at 150°C~200°C.

[0058] Please see Figure 2 , Figure 2 This is a photograph of the proton exchange membrane prepared in Example 3. Figure 2 As can be seen, the proton exchange membrane prepared in this application has a smooth surface and a uniform, continuous structure. Please refer to... Figure 3 and Figure 4 , Figure 3 This is an optical microscope image of the proton exchange membrane prepared in Example 3. Figure 4 This is a transmission electron microscope image of the proton exchange membrane prepared in Example 3. Please refer to... Figure 5 , Figure 5 The image shows the X-ray photoelectron spectrum of the proton exchange membrane prepared in Example 3. Figure 5It can be seen that the proton exchange membrane has elements such as C, O, and P, which indicates that the proton exchange membrane of this application has been successfully doped with phosphoric acid.

[0059] Example 4 S1: Provides meta-aramid chopped fibers as raw material, provides sulfuric acid with a mass fraction of 98% as acid solvent, and provides polyimide as base.

[0060] S2: Under ultrasonic conditions, 0.5g of meta-aramid short-cut fibers were added to 100g of sulfuric acid. The two were mixed and stirred for 24h under heating at 100℃ to obtain a fiber dispersion with a solid content of 0.5 wt%.

[0061] S3: The fiber dispersion is evenly spread on the polyimide substrate by spin coating at 5000 rpm to form a thin layer. After the thin layer is cooled to room temperature, the fiber layer is obtained.

[0062] S4: Immerse the fiber layer together with the polyimide substrate in a 15 wt% aqueous solution of phosphoric acid for 20 h to obtain a phosphoric acid-doped fiber layer with a self-supporting structure.

[0063] S5: The phosphate-doped fiber layer with a self-supporting structure was dried for 24 hours at 30℃ in a vacuum environment to obtain a phosphate-doped proton exchange membrane.

[0064] Comparative Example 1 The only difference between Comparative Example 1 and Example 2 is that the methanesulfonic acid in Comparative Example 1 was replaced with a DMSO solution containing KOH, wherein the concentration of KOH was 0.003 g / ml, and the other steps were the same as in Example 2.

[0065] Performance Testing (1) Phosphoric acid doping amount: weighing and titration methods were used.

[0066] (2) High-temperature proton conductivity: The test was conducted at 150℃ according to the test method of proton conductivity in Section 5 of GB / T 20042.3-2022.

[0067] (3) Tensile strength: The tensile strength of the film was tested using the Instron 68SC-5 universal material testing system according to the method in Section 8, Tensile Properties Test, of GB / T 20042.3-2022.

[0068] The proton exchange membranes of Examples 1-4 and Comparative Example 1 were subjected to the above tests, and the test results are shown in Table 1.

[0069] Table 1 As can be seen from Table 1, this application uses an acid solvent to pre-disperse aramid fibers to achieve uniform doping of phosphoric acid on aramid fibers, which greatly improves the proton conduction performance of the proton exchange membrane under high temperature conditions, while maintaining good mechanical stability and chemical resistance, making it suitable for use in high-temperature fuel cells.

[0070] As can be seen from the comparison between Example 2 and Comparative Example 1, the acid solvent used in Example 2 can make the aramid fibers disperse more evenly, which is more conducive to the uniform doping of phosphoric acid, thereby improving the proton conduction performance of the proton exchange membrane under high temperature conditions, while maintaining good mechanical stability.

[0071] The above embodiments are only used to illustrate the technical solutions of this application and are not intended to limit it. Although this application has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions to the technical solutions of this application should not depart from the spirit and scope of the technical solutions of this application.

Claims

1. A method for preparing a proton exchange membrane, characterized in that, Includes the following steps: Provides aramid fibers, acid solvents, and substrates; The aramid fiber and the acid solvent are mixed and heated to obtain a fiber dispersion. The fiber dispersion is dispersed on the surface of the substrate to form a fiber layer; The fiber layer was immersed in a phosphoric acid solution to obtain a phosphoric acid-doped fiber layer; The phosphate-doped fiber layer is dried.

2. The method for preparing the proton exchange membrane as described in claim 1, characterized in that, The aramid fibers include para-aramid and / or meta-aramid.

3. The method for preparing the proton exchange membrane as described in claim 1, characterized in that, The acid solvent includes one or more of sulfuric acid, methanesulfonic acid, or trifluoromethanesulfonic acid.

4. The method for preparing the proton exchange membrane as described in claim 1, characterized in that, The heating temperature is 50℃~120℃.

5. The method for preparing the proton exchange membrane as described in claim 1, characterized in that, Based on the total mass of the fiber dispersion, the content of the aramid fiber in the fiber dispersion is 0.5 wt% to 5 wt%.

6. The method for preparing the proton exchange membrane as described in claim 1, characterized in that, The concentration of the phosphoric acid solution is 5wt%~20wt%, and the soaking time is 12h~24h.

7. The method for preparing a proton exchange membrane as described in claim 1, characterized in that, The fiber dispersion is dispersed on the substrate surface by one or more of the following methods: casting, spin coating, or blade coating.

8. The method for preparing a proton exchange membrane as described in claim 1, characterized in that, The phosphate-doped fiber layer is dried in a vacuum environment.

9. A proton exchange membrane, characterized in that, The proton exchange membrane is prepared according to any one of claims 1-8.

10. The application of the proton exchange membrane as described in claim 9 in a fuel cell.

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