Asymmetric-structure nano-film for fuel cell humidification and preparation method and application of asymmetric-structure nano-film

Abstract

The invention discloses an asymmetric-structure nano-film for humidifying a fuel cell as well as a preparation method and application of the asymmetric-structure nano-film, and belongs to the technical field of gas separation films. Wherein the mass ratio of sulfonated polyethylene sulfone to phenolphthalein-based polyether sulfone or polyvinylidene fluoride is (0.02-1): 1; the membrane is composed of a nanoscale water vapor transfer layer and a porous supporting layer, the pore diameter of the nanoscale water vapor transfer layer is 1-50 nm, the thickness of the nanoscale water vapor transfer layer is 0.05-10 micrometers, the porous supporting layer is of a communicated finger-shaped pore structure, the pore diameter of the porous supporting layer is 1-30 micrometers, the thickness of the porous supporting layer is 50-500 micrometers, and the content of sulfonated polyphenyl sulfone in the nanoscale water vapor transfer layer is 6-60%; and the content of sulfonated polyphenyl sulfone in the porous support layer is 1.5-50%. The nano film with the asymmetric structure has relatively high water vapor permeability and water vapor / air (O2 and N2) selectivity. The water management system is applied to humidification of the fuel cell, and the water management problem existing in PEMFC application is effectively solved.

Description

Technical Field

[0001] The present invention relates to the technical field of gas separation membranes, and specifically relates to an asymmetric nanostructure membrane for fuel cell humidification, a preparation method thereof, and an application thereof. Background Art

[0002] In recent years, the hydrogen energy industry has been accelerating its rise globally. In China, with the implementation of "carbon peak and carbon neutrality", hydrogen energy has received increasing attention. Among them, proton exchange membrane fuel cells (PEMFCs) are a key technology for reducing greenhouse gas emissions due to their advantages of low noise, low operating temperature, and high power density, and are also regarded as the most promising alternative power source for automobiles. Currently, the main problems in fuel cell applications are still deficiencies in technologies such as water management, which hinder the performance improvement and commercialization of fuel cells. How to solve the fuel cell humidification problem has attracted wide attention.

[0003] The membrane humidification method has advantages such as controllable volume and high efficiency compared to traditional humidification technologies such as bubble humidification method and direct water injection method. Currently, polymer membranes are the main materials in the field of humidification membranes, but it is difficult to simultaneously obtain high water vapor permeability and high water vapor / air (O 2 , N 2 ) selectivity for polymer membranes. Currently, commonly used polymer membranes for membrane humidification include polyimide, polyacrylonitrile, polypropylene, etc.

[0004] Sulfonated polysulfone (SPPSU) in the present invention is a type of polysulfone containing hydrophilic sulfonic acid groups (-SO 3 H) after sulfonation. Its sulfonic acid groups can effectively enhance the affinity of the membrane for water molecules, which is beneficial to the dissolution of water molecules on the membrane surface and the transport within the membrane. At the same time, after blending sulfonated polysulfone with high molecular polymers, the pore size of the membrane will be reduced, strengthening the surface diffusion process and capillary condensation mechanism of water molecules in the membrane pores, so that the asymmetric nanostructure membrane regulated by sulfonated polysulfone has a high water vapor permeability coefficient and water vapor / air (O 2 , N 2 ) selectivity.

[0005] Therefore, how to provide an asymmetric nanostructure membrane for fuel cell humidification and a preparation method thereof to promote the application of polymer membranes in proton exchange membrane fuel cell humidification is an urgent problem to be solved by those skilled in the art. Summary of the Invention

[0006] In view of this, the present invention provides an asymmetric nanostructure membrane for fuel cell humidification, a preparation method thereof, and an application thereof.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] An asymmetric nanostructured membrane for fuel cell humidification, composed of phenolphthalein polyethersulfone or polyvinylidene fluoride and sulfonated polyphenylsulfone, wherein the mass ratio of the sulfonated polyphenylsulfone to the phenolphthalein polyethersulfone or polyvinylidene fluoride is (0.02 - 1):1;

[0009] The membrane consists of a water vapor transmission layer with nano-scale pores and a porous support layer. The pore size of the nano-scale water vapor transmission layer is 1 - 50 nm, and the thickness is 0.05 - 10 microns. The porous support layer has a connected finger-like pore structure, with a pore size of 1 - 30 microns and a thickness of 50 - 500 microns;

[0010] In the nano-scale water vapor transmission layer, the content of sulfonated polyphenylsulfone is 6 - 60%, and the balance is phenolphthalein polyethersulfone or polyvinylidene fluoride;

[0011] In the porous support layer, the content of sulfonated polyphenylsulfone is 1.5 - 50%, and the balance is phenolphthalein polyethersulfone or polyvinylidene fluoride.

[0012] The beneficial effects of the present invention: The nano-scale water vapor transmission layer can rapidly and selectively conduct water vapor molecules, while air molecules cannot penetrate. The sulfonic acid groups in the sulfonated polyphenylsulfone are enriched and distributed in the transmission layer, enhancing the hydrophilicity of the membrane, which is beneficial to the adsorption and dissolution of water molecules on the membrane surface; and due to the adsorption of water molecules by the sulfonic acid groups on the pore walls of the membrane, the surface diffusion process and capillary condensation mechanism of water molecules in the membrane pores can be strengthened, which is beneficial to the transmission of water vapor in the membrane and can hinder and isolate the diffusion process of nitrogen and oxygen molecules in the air in the membrane pores, thereby enhancing the water vapor / air (O 2 、N 2 ) selectivity. At the same time, the nano-scale pore structure formed after blending sulfonated polyphenylsulfone with the polymer promotes the surface diffusion process and capillary condensation mechanism of water molecules in the membrane pores, making the asymmetric nanostructured membrane regulated by sulfonated polyphenylsulfone have a high water vapor permeability coefficient and water vapor / air (O 2 、N 2 ) selectivity. The selectivity of the asymmetric nanostructured membrane containing sulfonated polyphenylsulfone is higher than that of the asymmetric nanostructured membrane without sulfonated polyphenylsulfone. The asymmetric nanostructured membrane of the present invention can be applied to fuel cell humidification to effectively solve the water management problem existing in PEMFC applications.

[0013] Furthermore, the above-mentioned asymmetric nanostructured membrane for fuel cell humidification is a flat membrane or a hollow fiber membrane.

[0014] Preferably, the pore size of the above-mentioned nano-scale water vapor transmission layer is 1 - 20 nm, and the thickness is 0.1 - 5 microns.

[0015] Advantages of adopting the above further technical solution: The water vapor transmission layer at the nanoscale can rapidly and selectively conduct water vapor molecules, while air molecules cannot pass through.

[0016] The content of sulfonated polysulfone in the water vapor transmission layer at the nanoscale is 2 - 5 times its bulk content. Due to the high hydrophilicity of sulfonated polysulfone, water vapor molecules can be rapidly transmitted.

[0017] Preferably, the above-mentioned porous support layer has a connected finger-like pore structure with a pore diameter of 1 - 10 μm.

[0018] The present invention also provides a method for preparing the asymmetric structure nanomembrane for fuel cell humidification as described above, including the following steps:

[0019] (1) Dissolve phenolphthalein polyether sulfone or polyvinylidene fluoride in a solvent to obtain a phenolphthalein polyether sulfone solution or a polyvinylidene fluoride solution. Add the obtained phenolphthalein polyether sulfone solution or polyvinylidene fluoride solution to sulfonated polysulfone, heat and stir evenly, and place it in a vacuum drying oven or let it stand indoors to remove the bubbles in the casting solution by static defoaming, so as to obtain a casting solution;

[0020] (2) Uniformly scrape the obtained casting solution on a glass plate. After standing and evaporating in the air, immerse the glass plate in deionized water for phase inversion to form a membrane. After the membrane is completely separated from the glass plate, take out the membrane and immerse it in fresh deionized water. Replace the deionized water during the immersion period. Finally, immerse the membrane in absolute ethanol and dry it in a vacuum drying oven or dry it naturally indoors to obtain the asymmetric structure nanomembrane for fuel cell humidification as described above. The prepared asymmetric structure nanomembrane is a flat membrane or a hollow fiber membrane.

[0021] Advantages of the present invention: An asymmetric structure nanomembrane for fuel cell humidification composed of phenolphthalein polyether sulfone or polyvinylidene fluoride and sulfonated polysulfone is prepared by the phase inversion method. The membrane is composed of a water vapor transmission layer with a pore diameter at the nanoscale and a porous support layer. The pore diameter of the above-mentioned water vapor transmission layer at the nanoscale is 1 - 50 nm, and the thickness is 0.05 - 10 μm. The above-mentioned porous support layer has a connected finger-like pore structure with a pore diameter of 1 - 30 μm and a thickness of 50 - 500 μm. The water vapor transmission layer at the nanoscale is mainly composed of sulfonated polysulfone material enriched in the transmission layer during the film-making process, and the content of sulfonated polysulfone is 6 - 60%. Due to the high hydrophilicity of sulfonated polysulfone, water vapor molecules can be rapidly transmitted. The water vapor transmission layer at the nanoscale can rapidly and selectively conduct water vapor molecules, while air molecules cannot pass through.

[0022] Furthermore, in step (1), the sulfonation degree of the above-mentioned sulfonated polysulfone is 10%, 20%, 30% or 50%.

[0023] Further, in step (1), the concentration of the above-mentioned phenolphthalein-based polyethersulfone solution or polyvinylidene fluoride solution is 10 wt% - 30 wt%, and the mass ratio of the above-mentioned sulfonated polysulfone to phenolphthalein-based polyethersulfone or polyvinylidene fluoride is (0.02 - 1):1.

[0024] Further, in step (1), the above-mentioned solvent is any one or a mixture of two of tetrahydrofuran, N,N-dimethylacetamide or N-methylpyrrolidone.

[0025] Further, in step (1), the temperature of the heating and stirring is 50 - 90 °C, the time of heating and stirring is 4 - 8 h, the rotation speed of heating and stirring is 30 - 150 revolutions per minute, the temperature in the vacuum drying oven is 50 - 80 °C, the time of vacuum degassing is 4 - 8 hours, and the time of static degassing indoors is 24 - 48 hours.

[0026] Further, in step (2), the obtained casting solution is evenly blade-coated on a glass plate, and the blade-coating thickness is 50 - 500 μm.

[0027] Further, in step (2), it is left to stand and evaporate in the air for 10 - 120 s.

[0028] Further, in step (2), the membrane is taken out and immersed in fresh deionized water for 48 - 64 h, and the deionized water is changed every 24 h. Finally, the membrane is immersed in absolute ethanol for 24 - 64 h. The drying temperature in the vacuum drying oven is 30 - 60 °C, the drying time is 4 - 8 hours, and the natural drying time indoors is 24 - 72 h.

[0029] The present invention also provides an application of the above-mentioned asymmetric structure nanofilm or the asymmetric structure nanofilm prepared by the above-mentioned method in the field of fuel cell humidification. Description of the Drawings

[0030] Figure 1 It is the cross-sectional SEM image of the asymmetric structure nanofilm prepared in Example 1.

[0031] Figure 2 It is the high-magnification cross-sectional SEM image of the asymmetric structure nanofilm prepared in Example 2.

[0032] Figure 3 It is the cross-sectional SEM image of the film prepared in Example 3.

[0033] Figure 4 It is the cross-sectional SEM image of the asymmetric structure nanofilm prepared in Example 5. Detailed Embodiments

[0034] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0035] Example 1

[0036] A preparation method of an asymmetric structure nanofilm for fuel cell humidification includes the following steps:

[0037] (1) Dissolve 12.25 g of phenolphthalein polyethersulfone in a mixed solvent of 37.5 g of tetrahydrofuran and N-methylpyrrolidone, where the mass ratio of tetrahydrofuran to N-methylpyrrolidone is 1:4, to obtain a phenolphthalein polyethersulfone solution with a concentration of 24.5 wt%. Add the obtained phenolphthalein polyethersulfone solution to 0.25 g of sulfonated polysulfone with a sulfonation degree of 20%, heat and stir evenly. The temperature of heating and stirring is 70 °C, the time of heating and stirring is 4 h, the rotation speed of heating and stirring is 150 revolutions per minute, and place it in a vacuum drying oven to remove the bubbles in the casting solution. The defoaming temperature is 60 °C, and the defoaming time is 4 hours to obtain a casting solution;

[0038] (2) Uniformly scrape the obtained casting solution on a glass plate with a scraping thickness of 300 μm. After standing in the air for evaporation for 10 s, immerse the glass plate in deionized water for phase inversion to form a film. After the film is completely separated from the glass plate, take out the film and immerse it in fresh deionized water for 24 h, and replace the deionized water every 24 h. Finally, immerse the film in absolute ethanol for 24 h and dry it naturally indoors for 24 h. Obtain an asymmetric structure nanofilm with a thickness of 200 μm for fuel cell humidification. The prepared asymmetric structure nanofilm is a flat film.

[0039] Among them, the water vapor transmission layer with a pore size at the nanoscale has a pore size of 10 nm, a thickness of 1 μm, and the content of sulfonated polysulfone is 8%; the porous support layer is a connected finger-like pore structure, the thickness of the porous support layer is 199 μm, and the average pore size is 5 μm. In the porous support layer, the content of sulfonated polysulfone is 1.8%.

[0040] Example 2

[0041] The preparation method is the same as that in Example 1, except that: the mass of 20% sulfonation degree sulfonated polysulfone is 0.5 g, and the mass of phenolphthalein polyethersulfone (C-PES) polymer is 12 g. The prepared asymmetric structure nanofilm is a flat film.

[0042] The thickness of the asymmetric structure nanofilm is 300 μm, where the pore size of the water vapor transmission layer is 8 nm, the thickness is 2 μm, and the content of SPPSU is 12%; the thickness of the support layer is 298 μm, and the average pore size is 8 μm. In the porous support layer, the content of sulfonated polysulfone is 3.5%.

[0043] Example 3

[0044] The preparation method is the same as that of Example 1, except that: the mass of sulfonated polysulfone with 20% sulfonation degree is 0.75 g, and the mass of the phenolphthalein polyethersulfone (C-PES) polymer is 11.75 g. The prepared asymmetric structure nanofilm is a flat film.

[0045] The thickness of the asymmetric structure nanofilm is 200 μm, where the pore size of the water vapor transmission layer is 5 nm, the thickness is 3 μm, and the content of SPPSU is 18%; the thickness of the support layer is 197 μm, and the average pore size is 10 μm. In the porous support layer, the content of sulfonated polysulfone is 5.5%.

[0046] Example 4

[0047] The preparation method is the same as that of Example 1, except that: the mass of sulfonated polysulfone with 20% sulfonation degree is 1 g, and the mass of the phenolphthalein polyethersulfone (C-PES) polymer is 11.5 g. The prepared asymmetric structure nanofilm is a flat film.

[0048] The thickness of the asymmetric structure nanofilm is 200 μm, where the pore size of the water vapor transmission layer is 4.5 nm, the thickness is 4 μm, and the content of SPPSU is 20%; the thickness of the support layer is 196 μm, and the average pore size is 15 μm. In the porous support layer, the content of sulfonated polysulfone is 7.5%.

[0049] Example 5

[0050] The preparation method is the same as that of Example 1, except that: the phenolphthalein polyethersulfone (C-PES) polymer is replaced by polyvinylidene fluoride. The prepared asymmetric structure nanofilm is a flat film.

[0051] The thickness of the asymmetric structure nanofilm is 200 μm, where the pore size of the water vapor transmission layer is 15 nm, the thickness is 5 μm, and the content of SPPSU is 8%; the thickness of the support layer is 195 μm, and the average pore size is 20 μm. In the porous support layer, the content of sulfonated polysulfone is 1.8%.

[0052] Example 6

[0053] The preparation method is the same as that of Example 1, except that: the sulfonation degree of sulfonated polysulfone is 10%. The prepared asymmetric structure nanofilm is a flat film.

[0054] The thickness of the asymmetric structure nanofilm is 200 μm, where the pore size of the water vapor transmission layer is 20 nm, the thickness is 8 μm, and the SPPSU content is 6%; the thickness of the support layer is 192 μm, and the average pore size is 8 μm. In the porous support layer, the content of sulfonated polysulfone is 1.85%.

[0055] Example 7

[0056] The preparation method is the same as that of Example 1, except that: the sulfonation degree of sulfonated polysulfone is 30%, and the prepared asymmetric structure nanofilm is a flat film.

[0057] The thickness of the asymmetric structure nanofilm is 200 μm, where the pore size of the water vapor transmission layer is 5 nm, the thickness is 2 μm, and the SPPSU content is 7%; the thickness of the support layer is 198 μm, and the average pore size is 5 μm. In the porous support layer, the content of sulfonated polysulfone is 1.75%.

[0058] Example 8

[0059] The preparation method is the same as that of Example 1, except that: the sulfonation degree of sulfonated polysulfone is 50%, and phenolphthalein polyether sulfone is replaced by polyvinylidene fluoride, and the prepared asymmetric structure nanofilm is a flat film.

[0060] The thickness of the asymmetric structure nanofilm is 200 μm, where the pore size of the water vapor transmission layer is 3 nm, the thickness is 5 μm, and the SPPSU content is 8.5%; the thickness of the support layer is 195 μm, and the average pore size is 20 μm. In the porous support layer, the content of sulfonated polysulfone is 1.65%.

[0061] Comparative Example 1

[0062] The preparation method of the phenolphthalein polyether sulfone membrane includes the following steps:

[0063] (1) Dissolve 12.25 g of phenolphthalein polyether sulfone in a mixed solvent of 37.5 g of tetrahydrofuran and N-methylpyrrolidone, heat and stir. The mass ratio of tetrahydrofuran to N-methylpyrrolidone is 1:4, the heating and stirring temperature is 70 °C, the heating and stirring time is 4 h, the heating and stirring speed is 150 revolutions per minute, place it in a vacuum drying oven, the defoaming temperature is 60 °C, and the defoaming time is 4 hours to remove the bubbles in the casting solution to obtain the casting solution;

[0064] (2) Uniformly scrape the obtained casting solution on a glass plate, the scraping thickness is 300 μm, after standing in the air for evaporation for 10 s, immerse the glass plate in deionized water for phase inversion to form a film. After the film is completely separated from the glass plate, take out the film and immerse it in fresh deionized water, the immersion time is 48 h, change the deionized water every 24 h, and finally immerse the film in absolute ethanol for 24 h and dry it naturally indoors for 24 h. Obtain a phenolphthalein polyether sulfone membrane with a thickness of 200 μm.

[0065] The water vapor permeation and selectivity of asymmetric membranes are usually calculated using the following formulas. First, to calculate the water vapor flux, the water vapor flow rates of the feed stream, the retentate stream, and the permeate stream need to be calculated, which can be obtained from the following formulas:

[0066]

[0067] where Q vapor and Q N2 are the water vapor flow rate and nitrogen flow rate on the permeate side, respectively, with the unit of cm 3 / s, γ H2O is the absolute humidity, with the unit of g / m 3 , Vm is the volume of water vapor at standard temperature and standard pressure, with a value of 22.4 L / mol, and M w,H2O is the molecular weight of water, with a value of 18 g / mol.

[0068] The water vapor permeability coefficient Pi is calculated by the following formula:

[0069]

[0070] where Pi is the partial pressure difference of water vapor between the feed side and the permeate side of the membrane, A is the membrane area, and the water vapor permeability coefficient is expressed in gas permeation units GPU, 1 GPU = 1×10 -6 ·cm 3 (STP) / (cm 2 ·cmHg·s). The selectivity αi / j of the membrane to water vapor is calculated by the following formula:

[0071]

[0072] where Pi is the water vapor permeability and Pj is the nitrogen permeability. By collecting and weighing the water vapor in the gas at the outlet of the membrane cell using a cold trap device, the water vapor flux of the membrane can be measured; by detecting the N 2 content in the outlet gas using a gas chromatography device, the N 2 permeability coefficient of the membrane can be measured.

[0073] Effect verification

[0074] 1. The cross-sectional SEM image of the asymmetric structure nanofilm prepared in Example 1 is as shown in Figure 1 . It can be seen from Figure 1 that the C-PES / SPPSU asymmetric structure nanofilm has a typical asymmetric structure, including a porous support layer and a thinner upper surface layer.

[0075] 2. The high-magnification cross-sectional SEM image of the asymmetric structure nanofilm prepared in Example 2 is as shown in Figure 2As shown in the figure. As the content of SPPSU (sulfonation degree 20%) increases, the interaction force between the sulfonic acid groups in SPPSU and the molecular chain of C-PES will cause the viscosity of the casting solution to increase, and the transfer layer on the upper surface of the membrane will gradually become thick and dense.

[0076] 3. The cross-sectional SEM image of the membrane prepared in Example 3 is as Figure 3 shown.

[0077] 4. The cross-sectional SEM image of the sulfonated polysulfone-regulated asymmetric structure nanofilm prepared in Example 5 is as Figure 4 shown.

[0078] The humidification performance of Examples 1-8 and Comparative Example 1 was tested, and the performance test results are shown in Table 1.

[0079] Table 1

[0080]

[0081] It can be seen from Table 1 that compared with Comparative Example 1, the water vapor permeability coefficient of the membrane prepared in Example 3 is 3311 GPU, and the water vapor / N 2 selectivity reaches the maximum value of 504.95. The improvement of the water vapor permeability coefficient of the membrane can be attributed to the enrichment distribution of the sulfonic acid groups contained in SPPSU on the surface of the transfer layer membrane, which enhances the hydrophilicity of the membrane and is conducive to the adsorption and dissolution of water molecules on the membrane surface; at the same time, the adsorption of sulfonic acid groups on the pore wall to water molecules can strengthen the surface diffusion process and capillary condensation mechanism of water molecules in the membrane pores, which is conducive to the transmission of water vapor in the membrane and hinders the diffusion process of N 2 in the membrane pores, thus improving the water vapor / N 2 selectivity.

[0082] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to these embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. An asymmetric structure nanomembrane for fuel cell humidification, characterized in that: It is composed of phenolphthalein polyether sulfone or polyvinylidene fluoride and sulfonated polyphenylene sulfone, wherein the mass ratio of the sulfonated polyphenylene sulfone to the phenolphthalein polyether sulfone or polyvinylidene fluoride is (0.02-1):1; The membrane is composed of a water vapor transfer layer with a pore size of nanometer scale and a porous support layer. The pore size of the water vapor transfer layer is 1-50nm and the thickness is 0.05-10 micrometers. The porous support layer is a connected finger-like pore structure with a pore size of 1-30 micrometers and a thickness of 50-500 micrometers. In the nano-scale water vapor transfer layer, the content of sulfonated polyphenylsulfone is 6-60%, and the balance is phenolphthalein-based polyethersulfone or polyvinylidene fluoride; In the porous support layer, the content of sulfonated polyphenylsulfone is 1.5-50%, and the balance is phenolphthalein polyethersulfone or polyvinylidene fluoride.

2. A method for preparing the asymmetric structure nanomembrane for fuel cell humidification according to claim 1, characterized in that: The following steps are involved: (1) dissolving phenolphthalein polyether sulfone or polyvinylidene fluoride in a solvent to obtain a phenolphthalein polyether sulfone solution or a polyvinylidene fluoride solution, adding the obtained phenolphthalein polyether sulfone solution or the polyvinylidene fluoride solution to sulfonated polyphenyl sulfone, heating and stirring the solution, placing the solution in a vacuum drying oven or indoors to allow the solution to stand for degassing and remove bubbles in the casting solution, and obtaining a casting solution; (2) The obtained casting liquid is evenly scraped onto a glass plate, and after standing in the air for evaporation, the glass plate is immersed in deionized water for phase transformation into a membrane. After the membrane is completely separated from the glass plate, the membrane is taken out and immersed in new deionized water. The deionized water is replaced during the immersion period. Finally, the membrane is immersed in anhydrous ethanol and placed in a vacuum drying oven for drying or dried naturally indoors to obtain the asymmetric structure nanomembrane for fuel cell humidification. The prepared asymmetric structure nanomembrane is a flat membrane or a hollow fiber membrane.

3. The method for preparing an asymmetric structure nanomembrane for fuel cell humidification according to claim 2, characterized in that: In step (1), the sulfonation degree of the sulfonated polyphenylene sulfone is 10%, 20%, 30% or 50%.

4. The method for preparing an asymmetric structure nanomembrane for fuel cell humidification according to claim 2, characterized in that: In step (1), the concentration of the phenolphthalein polyethersulfone solution or the polyvinylidene fluoride solution is 10wt%-30wt%, and the mass ratio of the sulfonated polyphenylsulfone to the phenolphthalein polyethersulfone or the polyvinylidene fluoride is (0.02-1):

1.

5. The method for preparing an asymmetric structure nanomembrane for fuel cell humidification according to claim 2, characterized in that: In step (1), the solvent is any one of tetrahydrofuran, N,N-dimethylacetamide or N-methylpyrrolidone or a mixture of two thereof.

6. The method for preparing an asymmetric structure nanomembrane for fuel cell humidification according to claim 2, characterized in that: In step (1), the heating and stirring temperature is 50-90°C, the heating and stirring time is 4-8h, the heating and stirring speed is 30-150 rpm, the temperature in the vacuum drying oven is 50-80°C, the vacuum degassing time is 4-8 hours, and the indoor standing degassing time is 24-48 hours.

7. The method for preparing an asymmetric structure nanomembrane for fuel cell humidification according to claim 2, characterized in that: In step (2), the obtained casting solution is evenly scraped onto a glass plate with a scraping thickness of 50-500 μm.

8. The method for preparing an asymmetric structure nanomembrane for fuel cell humidification according to claim 2, characterized in that: In step (2), the mixture is allowed to evaporate in air for 10-120 seconds.

9. The method for preparing an asymmetric structure nanomembrane for fuel cell humidification according to claim 2, characterized in that: In step (2), the membrane is taken out and immersed in new deionized water for 48-64 hours, and the deionized water is replaced every 24 hours. Finally, the membrane is immersed in anhydrous ethanol for 24-64 hours, and the drying temperature in a vacuum drying oven is 30-60°C, the drying time is 4-8 hours, and the natural drying time indoors is 24-72 hours.

10. Use of the asymmetric structure nanomembrane according to claim 1 or the asymmetric structure nanomembrane prepared by the method according to any one of claims 2 to 9 in the field of fuel cell humidification.

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