A porous polyether sulfone / lamellar double hydroxide nanosheet composite anion exchange membrane, a preparation method and application thereof

Abstract

The application discloses a porous polyether sulfone / layered double hydroxide nanosheet composite anion exchange membrane and a preparation method and application thereof. The method is as follows: AlOOH is prepared from an aluminum isopropyl alcohol solution and nitric acid; AlOOH is taken out of deionized water to obtain an AlOOH solution, nitric acid is added into the AlOOH solution, and AlOOH sol is obtained through stirring and reflux; the AlOOH sol is wrapped on a PES porous substrate, the PES porous substrate wrapped with the AlOOH sol is placed in a mixed solution of a magnesium salt and hexamethylenetetramine for sealing treatment, and a porous polyether sulfone / layered double hydroxide nanosheet composite membrane is obtained. The in-situ growth of the oligolayer LDH nanosheet can improve the tensile property and alkali doping amount of the PES porous substrate-oligolayer LDH nanosheet composite membrane, meanwhile, the high affinity of the oligolayer LDH nanosheet to alkali and the partial filling of the oligolayer LDH nanosheet to the pores of the porous substrate can greatly slow down the loss of alkali metal, so that the fuel cell performance and service life of the PES porous substrate-oligolayer LDH nanosheet composite membrane are improved.

Description

Technical Field

[0001] This invention belongs to the technical field, specifically relating to a porous polyethersulfone / layered double hydroxide nanosheet composite anion exchange membrane and its preparation method. Background Technology

[0002] The energy crisis and environmental problems caused by the overuse of fossil fuels have become major global issues. Therefore, the development and utilization of new clean energy sources have become the focus of attention for countries around the world. Hydrogen energy, due to its high calorific value and pollution-free characteristics, is one of the most competitive representatives of new clean energy. Hydrogen fuel cells, as efficient application devices of hydrogen energy, have received widespread attention from researchers worldwide. Among them, proton exchange membrane fuel cells are an important type of hydrogen fuel cells. After decades of research and development, proton exchange membrane fuel cells have become relatively mature, but they still face the following problems: (1) high cost in the preparation process of proton exchange membranes, (2) limited reserves and high prices of precious metal catalysts, (3) the need to use high-purity hydrogen to avoid efficiency reduction caused by catalyst poisoning, and (4) the need to use corrosion-resistant components due to the high corrosivity of acidic working environments. In contrast, the faster electrode redox reaction kinetics and low corrosivity of anion exchange membrane fuel cells in alkaline working environments allow the use of non-precious metal catalysts, expanding the selectivity of component materials. This is expected to reduce the cost of catalyst materials and hydrogen, thereby significantly reducing the cost of fuel cell use.

[0003] As a core component of fuel cells, anion exchange membranes, characterized by high ion conductivity, stability, reliability, and low cost, have long been a target of researchers. However, due to the higher molecular weight and lower mobility of OH-, the conductivity of anion exchange membranes is often lower than that of proton exchange membranes. Currently, there are two main methods to improve the ion conductivity of anion exchange membranes: one is modification with cationic functional groups, such as quaternary ammonium groups, imidazolium groups, and guanidine groups; the other is alkali-doped anion exchange membranes, which utilize stable organic polymer materials doped with alkali metal solutions to achieve high ion conductivity, such as polybenzimidazole membranes doped with KOH.

[0004] Currently, cation functional group modification is the mainstream method for preparing anion exchange membranes. However, cation-functional group modified anion exchange membranes often have the following drawbacks: complex modification and poisoning steps lead to unstable performance and insufficient durability of the cation functional groups. Due to these problems, there are still no mature commercially available fuel cell anion exchange membranes. While alkali-doped anion exchange membranes do not require complex cation functional group modification and have better structural stability, this method relies entirely on the alkali metal doped in the membrane, which is unsustainable. Water generation during the electrode reaction causes rapid loss of alkali metal from the membrane electrode, making long-term stable operation impossible. Performance degradation due to alkali metal loss is a common problem with current alkali-doped anion exchange membranes, and solving this problem has become crucial for the development of alkali-doped anion exchange membranes. Summary of the Invention

[0005] This invention provides a porous polyethersulfone / layered double hydroxide nanosheet composite anion exchange membrane, its preparation method, and its application, in order to solve the problem of poor performance and short test life of alkali-doped anion exchange membranes caused by the loss of alkali metals.

[0006] This invention provides a method for preparing a porous polyethersulfone / layered double hydroxide nanosheet composite anion exchange membrane, comprising:

[0007] Nitric acid was added to aluminum isopropoxide solution to obtain a first solution. The first solution was kept at a preset pH value. The solvent of the first solution was evaporated to obtain AlOOH.

[0008] AlOOH was added to deionizer to obtain AlOOH solution. Nitric acid was added to AlOOH solution to obtain a second solution. The second solution was stirred and refluxed to obtain AlOOH sol.

[0009] AlOOH sol was coated onto PES filter fibers to obtain a PES porous substrate coated with AlOOH sol.

[0010] The PES porous substrate coated with AlOOH sol was placed in a mixed solution of magnesium salt and hexamethylenetetramine for sealing treatment. After sealing treatment, it was heated to obtain a porous polyethersulfone / layered double hydroxide nanosheet composite film.

[0011] The preset pH value of the first solution is between 3 and 4.

[0012] The concentration of the nitric acid is 0.5~2 M.

[0013] The pH of the second solution is less than 4.

[0014] The magnesium salt is one of magnesium nitrate hexahydrate and magnesium chloride, and the molar ratio of magnesium salt to hexamethylenetetramine in the mixed solution of magnesium salt and hexamethylenetetramine is 1:1 to 1:1.5.

[0015] The molar concentration of the AlOOH sol is 0.5~1.5 mol L. -1 .

[0016] The process of coating AlOOH sol onto PES filter fibers to obtain an AlOOH sol-coated porous PES substrate is specifically as follows:

[0017] The AlOOH sol was ultrasonically treated for 30-60 minutes, and then the AlOOH sol was uniformly coated onto the PES filter fibers by immersion and vacuum filtration to obtain a PES porous substrate coated with AlOOH sol.

[0018] The heating conditions after sealing are heating at 80~90℃ for 20~24 hours.

[0019] The present invention also provides a porous polyethersulfone / layered double hydroxide nanosheet composite anion exchange membrane prepared by the above preparation method.

[0020] The present invention also provides the application of the above-mentioned porous polyethersulfone / layered double hydroxide nanosheet composite anion exchange membrane in hydrogen fuel cells.

[0021] Compared with the prior art, the present invention has at least the following beneficial effects:

[0022] The preparation method provided by this invention enables in-situ growth of oligolayer LDH nanosheets in a PES porous substrate, while ensuring the non-directional growth state of the oligolayer LDH nanosheets, which helps overcome the anisotropy of two-dimensional nanosheets. The in-situ growth of oligolayer LDH nanosheets protects the PES porous substrate, reducing the swelling ratio of the PES porous substrate-oligolayer LDH nanosheet composite membrane and improving its tensile strength. The in-situ growth of oligolayer LDH nanosheets significantly increases the specific surface area of ​​the PES porous substrate-LDH nanosheets, providing more adsorption sites for alkali adsorption and resulting in a substantial increase in alkali doping. Simultaneously, the high affinity of the oligolayer LDH nanosheets for alkali and their partial filling of the pores in the porous substrate greatly slows down the loss of alkali metals, thereby improving the fuel cell performance and lifespan of the PES porous substrate-oligolayer LDH nanosheet composite membrane. The preparation method provided by this invention is simple and does not involve complex chemical reaction processes. The in-situ growth process of LDH nanosheets is simple and does not involve complex chemical reaction processes. Furthermore, it does not involve modification of cationic functional groups and does not require the participation of poisoning reagents.

[0023] The PES porous substrate-oligolayer LDH nanosheet composite membrane provided by this invention, when applied in hydrogen fuel cells, improves the stability of hydrogen fuel cells, with a maximum operating temperature of 110℃ and a working temperature of 0.1 A cm⁻¹. -2 During constant current discharge, the voltage decay rate is only about 16% after 100 hours, and its performance can be restored by secondary alkali doping, showing good recyclability. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the following description of the relative embodiments will be briefly introduced. Obviously, the 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.

[0025] Figure 1 This is a flowchart of the preparation method of the porous polyethersulfone / layered double hydroxide nanosheet composite anion exchange membrane of the present invention;

[0026] Figure 2 The X-ray diffraction pattern of AlOOH synthesized during the preparation process;

[0027] Figure 3 Electron microscope image of an existing PES porous substrate;

[0028] Figure 4 Electron microscope cross-sectional view of an existing PES porous substrate;

[0029] Figure 5 The electron microscope image shows the surface of the PES porous substrate-oligolayer LDH nanosheet composite film prepared in Example 1.

[0030] Figure 6 This is an electron microscope cross-sectional image of the PES porous substrate-oligolayer LDH nanosheet composite film prepared in Example 1;

[0031] Figure 7 This is an electron microscope magnified image of the oligolayer LDH nanosheets on the PES porous substrate-oligolayer LDH nanosheet composite membrane prepared in Example 1.

[0032] Figure 8 (1) shows the surface of the PES porous substrate-single-layer LDH nanosheet composite film and its EDS elemental analysis; (2) shows the cross-sectional view of the PES porous substrate-single-layer LDH nanosheet and its EDS elemental analysis.

[0033] Figure 9(1) shows the Nyquist curves and fitting curves of AC impedance after doping with alkali on PES porous substrate at different temperatures; (2) shows the Nyquist curves and fitting curves of AC impedance after doping with alkali on PES porous substrate-oligolayer LDH nanosheet composite film at different temperatures.

[0034] Figure 10 The conductivity of PES porous substrate and PES porous substrate-oligolayer LDH nanosheet composite film at different temperatures;

[0035] Figure 11 (1) is a test graph of the power density of the PES porous substrate membrane fuel cell; (2) is a test graph of the durability of the PES porous substrate membrane; (3) is a test graph of the power density of the PES porous substrate-oligolayer LDH nanosheet composite membrane fuel cell prepared in Example 1; (4) is a test graph of the durability of the PES porous substrate-oligolayer LDH nanosheet composite membrane prepared in Example 1. Detailed Implementation

[0036] The technical solution of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0037] Unless otherwise specified, all embodiments and preferred embodiments mentioned herein can be combined to form new technical solutions.

[0038] Unless otherwise specified, all the technical features and preferred features mentioned herein can be combined to form new technical solutions.

[0039] In this invention, unless otherwise specified, percentage (%) or parts refer to weight percentage or parts relative to the composition.

[0040] Unless otherwise specified, the components or preferred components involved in this invention can be combined with each other to form new technical solutions.

[0041] In this invention, unless otherwise specified, the numerical range "a~b" represents an abbreviation of any combination of real numbers between a and b, where a and b are both real numbers. For example, the numerical range "6~22" means that all real numbers between "6~22" have been listed in this document, and "6~22" is simply an abbreviation of these numerical combinations.

[0042] The "scope" disclosed in this invention can be in the form of a lower limit and an upper limit, and can be one or more lower limits and one or more upper limits, respectively.

[0043] In this invention, the term "and / or" as used herein refers to any combination of one or more of the associated listed items, as well as all possible combinations, and includes such combinations.

[0044] In this invention, unless otherwise stated, the various reactions or operation steps may be performed sequentially or in a particular order. Preferably, the reaction methods described herein are performed sequentially.

[0045] Unless otherwise stated, the technical and scientific terms used herein have the same meanings as those familiar to those skilled in the art. Furthermore, any methods or materials similar to or equivalent to those described herein may also be used in this invention.

[0046] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0047] Please see Figure 1 The present invention provides a method for preparing a porous polyethersulfone / layered double hydroxide nanosheet composite anion exchange membrane, comprising the preparation of boehmite (AlOOH) sol; coating the boehmite sol onto a PES porous substrate; and in-situ growth of oligolayer LDH nanosheets, specifically:

[0048] Nitric acid was added to aluminum isopropoxide solution to obtain the first solution. The pH of the first solution was maintained between 3 and 4. After cooling to room temperature, the first solution was treated by solvent evaporation to obtain AlOOH.

[0049] Add AlOOH to deionized water and stir at 80~90℃ for 1h to completely dissolve AlOOH to obtain AlOOH solution. Add nitric acid to AlOOH solution to obtain second solution. The pH of the second solution is less than 4. Stir and reflux the second solution for 6~8h to obtain AlOOH sol.

[0050] The AlOOH sol was ultrasonically treated for 30-60 min, and then the AlOOH sol was uniformly coated on the filter fibers of the PES porous substrate by soaking and vacuum filtration to obtain the PES porous substrate coated with AlOOH sol.

[0051] The porous PES substrate coated with AlOOH sol was placed in a mixed solution of magnesium nitrate hexahydrate and hexamethylenetetramine, sealed, and then heated at 80~90℃ for 20~24h to obtain a porous polyethersulfone (PES) / layered double hydroxide (LDH) nanosheet composite anion exchange membrane (PES porous substrate-oligolayer LDH nanosheet composite membrane).

[0052] In some embodiments, the concentration of nitric acid is 0.5~2M. In preparing the first solution, the role of nitric acid is to provide an acidic environment to induce the hydrolysis of aluminum isopropoxide. In preparing the second solution, it is used to obtain a stable AlOOH sol, as the sol system is most stable when the pH of the solution is <4. The main function of nitric acid is to adjust the pH of the solution to 4 or below. Different concentrations of nitric acid can be selected according to the required final solution concentration.

[0053] In some embodiments, magnesium salts such as magnesium nitrate hexahydrate and magnesium chloride are used as magnesium sources, and reagents such as hexamethylenetetramine or urea, which are hydrolyzed into alkaline forms at high temperatures, provide the alkaline environment required for the reaction. In this case, the reagent selected is magnesium nitrate hexahydrate and hexamethylenetetramine. The molar ratio of magnesium salt to hexamethylenetetramine in the mixed solution of magnesium salt and hexamethylenetetramine is between 1:1 and 1:1.5.

[0054] In some embodiments, the molar concentration of AlOOH sol is 0.5~1.5 mol L. -1 The specific concentration of the sol can be selected according to the pore size of the selected porous substrate. High concentrations of AlOOH sol may cause pore blockage of the porous substrate during soaking and filtration, making it impossible to complete the process of AlOOH coating the PES substrate. Therefore, the concentration should be selected according to the pore size of the porous substrate.

[0055] This method enables in-situ growth of oligolayer LDH nanosheets in a porous substrate while ensuring the non-directional growth of the nanosheets, which helps overcome the anisotropy of two-dimensional nanosheets. The preparation process is simple, involves no toxic reagents, and does not involve complex chemical reactions. The prepared PES porous substrate-oligolayer LDH nanosheet composite membrane exhibits a wide operating temperature range and good durability and recyclability. The in-situ growth of oligolayer LDH nanosheets protects the original porous substrate, reducing the swelling ratio of the PES porous substrate-oligolayer LDH nanosheet composite membrane and improving its tensile strength. In previous tests of alkali-doped anion exchange membranes, such as polybenzimidazole-doped KOH anion exchange membranes, the low alkali doping level and the rapid loss of KOH due to water molecule generation and flow during testing significantly reduced the fuel cell power density and test life. The porous substrate provides more space for KOH doping, and the in-situ growth of oligolayer LDH nanosheets greatly increases the specific surface area of ​​the PES porous substrate-LDH nanosheets, providing more adsorption sites for KOH adsorption and resulting in a significant increase in the amount of KOH doped. At the same time, the high affinity of oligolayer LDH nanosheets for KOH and the partial filling of the pores of the porous substrate greatly slow down the loss of KOH, thereby improving the fuel cell performance and service life of the PES porous substrate-oligolayer LDH nanosheet composite membrane.

[0056] In the following embodiments, unless otherwise specified, all materials used can be obtained through ordinary channels; the testing methods used are conventional methods in the art.

[0057] Example 1

[0058] Dissolve 11.3g of aluminum isopropoxide in 100ml of deionized water and stir at 85℃ for 20min to ensure complete dissolution of aluminum isopropoxide and obtain aluminum isopropoxide solution.

[0059] The aluminum isopropoxide solution was continuously stirred for 2 hours. During the stirring process, 1 M HNO3 was slowly added dropwise to the aluminum isopropoxide solution to maintain the pH of the aluminum isopropoxide solution between 3 and 4. After cooling to room temperature, the aluminum isopropoxide solution was treated by solvent evaporation to obtain AlOOH.

[0060] Weigh 6g of AlOOH and dissolve it in 100mL of deionized water. Stir at 85℃ for 1h to completely dissolve AlOOH to obtain an AlOOH solution. Then slowly add HNO3 (1 M, 9.5mL) dropwise to the AlOOH solution and stir under reflux for 6h to obtain AlOOH sol.

[0061] A molar concentration of 1 mol L -1The AlOOH sol was ultrasonically treated for 30 minutes to avoid possible particle aggregation; a combination of soaking and vacuum filtration was used to ensure that the AlOOH sol was uniformly coated on the PES filter fibers.

[0062] The PES porous substrate coated with AlOOH sol was placed in an 80 ml mixed solution of 2.56 g magnesium nitrate hexahydrate (purity >99%) and 1.82 g hexamethylenetetramine (purity >99%) for sealing treatment. The molar ratio of magnesium nitrate hexahydrate to hexamethylenetetramine was 1:1.3. After sealing treatment, the substrate was heated at 85℃ for 24 h to obtain the PES porous substrate-oligolayer LDH nanosheet composite membrane.

[0063] Example 2

[0064] Dissolve 11.3g of aluminum isopropoxide in 100ml of deionized water and stir at 85℃ for 20min to ensure complete dissolution of aluminum isopropoxide and obtain aluminum isopropoxide solution.

[0065] The aluminum isopropoxide solution was continuously stirred for 2 hours. During the stirring process, 0.5 M HNO3 was slowly added dropwise to the aluminum isopropoxide solution to maintain the pH of the aluminum isopropoxide solution between 3 and 4. After cooling to room temperature, the aluminum isopropoxide solution was treated by solvent evaporation to obtain AlOOH.

[0066] Weigh 6g of AlOOH and dissolve it in 100mL of deionized water. Stir at 85℃ for 1h to completely dissolve AlOOH to obtain an AlOOH solution. Then slowly add HNO3 (0.5 M, 19mL) dropwise to the AlOOH solution and stir and reflux for 8h to obtain AlOOH sol.

[0067] A molar concentration of 1 mol L -1 The AlOOH sol was ultrasonically treated for 30 minutes to avoid possible particle aggregation; a combination of soaking and vacuum filtration was used to ensure that the AlOOH sol was uniformly coated on the PES filter fibers.

[0068] The PES porous substrate coated with AlOOH sol was sealed in an 80 ml mixed solution of magnesium nitrate hexahydrate and hexamethylenetetramine with a molar ratio of 1:1.5. After sealing, the substrate was heated at 80 °C for 24 h to obtain the PES porous substrate-oligolayer LDH nanosheet composite membrane.

[0069] Example 3

[0070] Dissolve 11.3g of aluminum isopropoxide in 100ml of deionized water and stir at 85℃ for 20min to ensure complete dissolution of aluminum isopropoxide and obtain aluminum isopropoxide solution.

[0071] The aluminum isopropoxide solution was continuously stirred for 2 hours. During the stirring process, 1 M HNO3 was slowly added dropwise to the aluminum isopropoxide solution to maintain the pH of the aluminum isopropoxide solution between 3 and 4. After cooling to room temperature, the aluminum isopropoxide solution was treated by solvent evaporation to obtain AlOOH.

[0072] Weigh 6g of AlOOH and dissolve it in 200mL of deionized water. Stir at 90℃ for 1h to completely dissolve AlOOH to obtain an AlOOH solution. Then slowly add HNO3 (1 M, 9.5mL) dropwise to the AlOOH solution and stir under reflux for 7h to obtain AlOOH sol.

[0073] A molar concentration of 0.5 mol L -1 The AlOOH sol was ultrasonically treated for 60 min to avoid possible particle aggregation; a combination of soaking and vacuum filtration was used to ensure that the AlOOH sol was uniformly coated on the PES filter fibers.

[0074] The PES porous substrate coated with AlOOH sol was sealed in an 80 ml mixed solution of magnesium nitrate hexahydrate and hexamethylenetetramine, with a molar ratio of 1:1.4. After sealing, the substrate was heated at 85°C for 20 h to obtain the PES porous substrate-oligolayer LDH nanosheet composite membrane.

[0075] Example 4

[0076] Dissolve 11.3g of aluminum isopropoxide in 100ml of deionized water and stir at 85℃ for 20min to ensure complete dissolution of aluminum isopropoxide and obtain aluminum isopropoxide solution.

[0077] The aluminum isopropoxide solution was continuously stirred for 2 hours. During the stirring process, 2M HNO3 was slowly added dropwise to the aluminum isopropoxide solution to maintain the pH of the aluminum isopropoxide solution between 3 and 4. After cooling to room temperature, the aluminum isopropoxide solution was treated by evaporating the solvent to obtain AlOOH.

[0078] Weigh 9 g of AlOOH and dissolve it in 100 mL of deionized water. Stir at 85 °C for 1 h to completely dissolve AlOOH to obtain an AlOOH solution. Then slowly add HNO3 (2 M, 4.8 mL) dropwise to the AlOOH solution and stir and reflux for 7 h to obtain AlOOH sol.

[0079] A molar concentration of 1.5 mol L -1 The AlOOH sol was ultrasonically treated for 60 minutes to avoid possible particle aggregation; a combination of soaking and vacuum filtration was used to ensure that the AlOOH sol was uniformly coated on the PES filter fibers.

[0080] The PES porous substrate coated with AlOOH sol was placed in an 80 ml mixed solution of magnesium chloride and hexamethylenetetramine for sealing treatment. The molar ratio of magnesium chloride to hexamethylenetetramine was 1:1.3. After sealing treatment, the substrate was heated at 90℃ for 20 h to obtain a PES porous substrate-oligolayer LDH nanosheet composite membrane.

[0081] The application of the PES porous substrate-oligolayer LDH nanosheet composite membrane in Example 1 in hydrogen fuel cells is as follows:

[0082] The PES porous substrate-oligolayer LDH nanosheet composite membrane from Example 1 was immersed in a supersaturated alkaline solution at room temperature. In this case, a 25 M KOH solution was selected and immersed at 80-90°C for 3 hours.

[0083] The soaked PES porous substrate-oligolayer LDH nanosheet composite membrane was removed, and a membrane electrode assembly (MEA) was performed using a gas diffusion electrode (Suzhou Shengernuo) for fuel cell performance testing. Fuel cell performance was tested at 40℃, 60℃, 80℃, and 110℃. Furthermore, at an operating temperature of 95℃, the performance was tested at 0.1 A cm⁻¹. -1 The current density was used to test the fuel cell lifespan. During the test, the gas flow rate at both the anode and cathode was 100 cc / min. -1 All tests were conducted under no back pressure conditions. After completing the 100-hour durability test, a second and third durability test were conducted by re-immersing the membrane in KOH. The test results showed that the PES porous substrate-oligolayer LDH nanosheet composite membrane has good recyclability.

[0084] As shown in Table 1, the swelling ratio, tensile strength, and alkali doping amount of the existing PES porous substrate (from Combat) and the PES porous substrate-oligolayer LDH nanosheet composite membrane prepared in Example 1 were tested. The power density and durability performance of the PES porous substrate and the PES-oligolayer LDH nanosheet composite membrane in fuel cells were tested and compared using fuel cell testing equipment. The test results are shown in Table 1 and... Figure 11 As shown.

[0085] Table 1. Performance comparison results of PES porous substrate and PES-oligolayer LDH nanosheet composite membrane

[0086]

[0087] Please see Figure 2-11 As shown, Figure 2 The X-ray diffraction peaks of AlOOH synthesized during the preparation process are consistent with the standard diffraction peaks of AlOOH, confirming the successful synthesis of AlOOH. Figure 3The image shows a scanning electron microscope image of the surface of a PES porous substrate. The pore structure on the surface of the PES porous substrate is approximately uniformly distributed, with varying pore sizes and an average pore size of 220 nm. The surface is smooth and flat. Figure 4 This is a scanning electron microscope image of the cross-section of a PES porous substrate, showing a continuous honeycomb-like internal structure. Figure 5 The image shows a surface scanning electron microscope image of the PES porous substrate-oligolayer LDH nanosheet composite film prepared in Example 1. After the in-situ growth of oligolayer LDH nanosheets, the pore structure of the PES porous substrate can no longer be observed, and its surface is covered by oligolayer LDH nanosheets. Figure 6 The image shows a scanning electron microscope image of the cross-section of the PES porous substrate-oligolayer LDH nanosheet composite film prepared in Example 1. After the growth of the oligolayer LDH nanosheets, it can be clearly observed that the fibers inside the original PES porous substrate are completely covered with oligolayer LDH nanosheets, and the whole structure is approximately honeycomb-like. Figure 7 This is an enlarged image of the oligolayer LDH nanosheets on the PES porous substrate-oligolayer LDH nanosheet composite film prepared in Example 1. The thickness of the nanosheets is between 10 and 15 nm, as measured by scanning electron microscopy. Figure 8 (1) and (2) are EDS elemental analysis images of the surface and cross-section of the PES porous substrate-oligolayer LDH nanosheet composite film prepared in Example 1, respectively, and the LDH component was successfully detected.

[0088] Please see Figure 9 After alkali doping, the AC impedance Nyquist curves of the PES porous substrate and the PES porous substrate-oligolayer LDH nanosheet composite film prepared in Example 1 were tested at different temperatures and fitted using Zview software. The working environment of the fuel cell was provided by a fuel cell workstation (Scribner 850), and the AC impedance Nyquist curves of both were tested using an electrochemical workstation (CHI760E). The perturbation voltage during the test was 5 mV, and the test frequency was 10~10. 6 Hz. After the test, the impedances of both components at different temperatures were obtained through data fitting, and the results were calculated. Figure 10 The conductivity data are shown. At the same temperature, the conductivity of the PES porous substrate-oligolayer LDH nanosheet composite film prepared in Example 1 is superior to that of the existing PES porous substrate. The calculation formula is σ=L / (R∙S), where σ is the conductivity, L is the film thickness, R is the fitted resistance value, and S is the electrode contact area.

[0089] Please see Figure 11After alkali doping, the fuel cell performance of the PES porous substrate and the PES porous substrate-oligolayer LDH nanosheet composite membrane prepared in Example 1 were tested at different temperatures. The maximum power density of the PES porous substrate at 40℃ was 209.04 mW cm⁻¹. -2 The maximum power density at 60℃ is 389.16 mW / cm³. -2 At 80℃, the increased temperature accelerates the evaporation of water molecules, leading to gas leakage in the pore structure of the PES porous substrate. As a result, performance drops sharply, with the maximum power density reduced to only 15.58 mW / cm³. -2 The PES porous substrate-oligolayer LDH nanosheet composite membrane can operate at temperatures ranging from room temperature to 110°C, with a maximum power density of 303.23 mW / cm³ at 40°C. -2 The maximum power density at 60℃ is 429.60 mW / cm³. -2 The maximum power density at 80℃ is 562.48 mW / cm³. -2 The maximum power density at 110℃ is 455.63 mW / cm³. -2 . respectively with 0.1 A cm -2 The durability of PES porous substrate and PES porous substrate-oligolayer LDH nanosheet composite film was tested using constant current density. Considering the performance degradation of PES porous substrate with increasing temperature, its durability was tested at 60℃. The test results showed that the voltage of PES porous substrate decreased by more than 50% within 2.5 h. This was mainly due to the generation of a large number of water molecules during the electrode reaction, which caused the doped KOH to be rapidly lost through the pore structure. In contrast, the voltage decay rate of PES porous substrate-oligolayer LDH nanosheet composite film was only about 16% after 100 h due to the high affinity of the oligolayer LDH nanosheets for KOH and their blocking effect on the pores. Moreover, its performance could be restored by secondary alkali doping, showing good recyclability.

[0090] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a porous polyethersulfone / layered double hydroxide nanosheet composite anion exchange membrane, characterized in that, include: Nitric acid was added to aluminum isopropoxide solution to obtain a first solution. The first solution was kept at a preset pH value. The solvent of the first solution was evaporated to obtain AlOOH. AlOOH was added to deionized water to obtain an AlOOH solution. Nitric acid was added to the AlOOH solution to obtain a second solution. The second solution was then refluxed with stirring to obtain an AlOOH sol. The molar concentration of the AlOOH sol was 0.5~1.5 mol L. -1 ; The AlOOH sol was ultrasonically treated for 30-60 minutes, and then the AlOOH sol was uniformly coated onto the PES filter fibers by immersion and vacuum filtration to obtain a PES porous substrate coated with AlOOH sol. The PES porous substrate coated with AlOOH sol was placed in a mixed solution of magnesium salt and hexamethylenetetramine for sealing treatment. After sealing treatment, it was heated to obtain a porous polyethersulfone / layered double hydroxide nanosheet composite film. The magnesium salt is one of magnesium nitrate hexahydrate and magnesium chloride. The molar ratio of magnesium salt to hexamethylenetetramine in the mixed solution of magnesium salt and hexamethylenetetramine is 1:1 to 1:1.

5.

2. The method for preparing the porous polyethersulfone / layered double hydroxide nanosheet composite anion exchange membrane according to claim 1, characterized in that, The preset pH value of the first solution is between 3 and 4.

3. The method for preparing the porous polyethersulfone / layered double hydroxide nanosheet composite anion exchange membrane according to claim 1, characterized in that, The concentration of the nitric acid is 0.5~2 M.

4. The method for preparing the porous polyethersulfone / layered double hydroxide nanosheet composite anion exchange membrane according to claim 1, characterized in that, The pH of the second solution is less than 4.

5. The method for preparing the porous polyethersulfone / layered double hydroxide nanosheet composite anion exchange membrane according to claim 1, characterized in that, The heating conditions after sealing are as follows: heating at 80~90℃ for 20~24 hours.

6. A porous polyethersulfone / layered double hydroxide nanosheet composite anion exchange membrane prepared by the preparation method according to any one of claims 1 to 5.

7. The application of the porous polyethersulfone / layered double hydroxide nanosheet composite anion exchange membrane according to claim 6 in hydrogen fuel cells.

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