Preparation method and application of composite ion exchange membrane

Abstract

The invention particularly discloses a preparation method and application of a composite ion exchange membrane. The composite ion exchange membrane is prepared from the following components in parts by weight: 95 to 110 parts of perfluorinated sulfonic acid resin, 5 to 8 parts of functionalized multi-walled carbon nanotubes, 10 to 15 parts of phosphotungstic acid, 1 to 1.8 parts of cerium-tannin complex, 12 to 20 parts of polyphenylene sulfide enhanced net, 30 to 40 parts of sulfonated polyether ether ketone solution, 3 to 5 parts of MXene-silicotungstic acid compound and 1 to 3 parts of polyethyleneimine cross-linking agent. The preparation method comprises the following steps: preparing the functionalized multi-walled carbon nanotube and the cerium-tannin complex; blending the perfluorinated sulfonic acid resin and the functional filler to prepare a membrane casting solution, and coating to form a membrane; a PPS reinforced net and an SPEEK solution are subjected to composite reinforcement, the PPS reinforced net and the SPEEK solution are subjected to PEI crosslinking and then superposed with the membrane, an MXene-silicotungstic acid compound is sprayed on the surface, and the composite ion exchange membrane is obtained through hot pressing and acid activation, has high proton conductivity and excellent mechanical strength and chemical stability and can be applied to a proton exchange membrane electrolytic cell and an all-vanadium redox flow battery.

Description

Technical Field

[0001] This invention relates to the field of water electrolysis for hydrogen production technology, specifically to a method for preparing and applying a composite ion exchange membrane. Background Technology

[0002] In today's era of rapid technological advancement, the energy and chemical industries face numerous challenges. Ion exchange membranes, as key materials, directly impact the development and application of many related technologies, especially in fields like water electrolysis and battery separators, where the demand for high-performance ion exchange membranes is extremely urgent. From the perspective of water electrolysis for hydrogen production, this clean and efficient method is gradually becoming a focus of research in the energy sector. However, in practical applications, it faces many challenging problems. Traditional ion exchange membranes lack durability in water electrolysis environments and are easily corroded by strong alkaline or acidic electrolytes, leading to structural damage and affecting their ion conductivity. Furthermore, the membrane's high resistance results in high energy consumption during water electrolysis, significantly limiting the large-scale commercial application of this technology. For example, in some industrial-scale water electrolysis plants, frequent replacement of damaged ion exchange membranes not only increases production costs but also reduces production efficiency. Simultaneously, due to the limited selective separation capability of the membrane for gases, hydrogen and oxygen mix during electrolysis, reducing hydrogen purity and posing serious safety hazards. In the field of battery separators, numerous challenges remain to be solved. Taking common flow batteries as an example, ion exchange membranes need to possess excellent ion conductivity to ensure efficient charging and discharging. However, existing ion exchange membranes, while conducting ions, often struggle to effectively prevent the interpenetration of active materials between the positive and negative electrodes. Once this occurs, it exacerbates self-discharge, significantly reducing battery capacity and lifespan. Furthermore, traditional ion exchange membranes have poor mechanical properties; during charging and discharging, they are prone to rupture or deformation due to electrolyte swelling and mechanical stress, further impacting battery stability and reliability. In addition, existing methods for preparing ion exchange membranes also have significant shortcomings. Some processes are complex and require expensive equipment and specialized raw materials, greatly increasing production costs and keeping ion exchange membranes expensive, thus limiting their wider application. Moreover, these complex processes are often difficult to scale up for industrial production, resulting in low efficiency. Simultaneously, the manufacturing process causes significant environmental pollution, contradicting current green and environmentally friendly development principles. Furthermore, ion exchange membranes operate in diverse environments, with frequent changes in temperature, humidity, and pH levels. Existing ion exchange membranes, in terms of both material properties and structural design, struggle to adapt to these complex and variable environments. When ambient temperature rises, the membrane's ion conductivity may change uncontrollably, potentially leading to softening or deformation and a sharp decline in performance. In high-humidity environments, the membrane readily absorbs moisture, affecting its ion exchange capacity and mechanical properties.This poor environmental adaptability severely restricts the application of ion exchange membranes in more practical scenarios and limits the further development and innovation of related technologies.

[0003] In conclusion, developing a novel method for preparing and applying composite ion exchange membranes has significant practical and strategic value. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing and applying a composite ion exchange membrane, in order to solve the problems of insufficient durability, high membrane resistance, poor selective separation ability of gas or active substances, unstable ion conductivity of the membrane, and easy softening and water absorption deformation in the existing composite ion exchange membrane.

[0005] To solve the above-mentioned technical problems, the present invention specifically provides the following technical solution: A method for preparing a composite ion exchange membrane includes the following steps: S1: Dissolving perfluorosulfonic acid resin in N,N-dimethylformamide, adding functionalized multi-walled carbon nanotubes, phosphotungstic acid and cerium-tannin complex, and heating and stirring to obtain a casting solution; S2: Coat the casting solution onto the polyester release film and dry to obtain the modified polyester release film; S3: The sulfonated polyether ether ketone solution is coated on both sides of the polyphenylene sulfide reinforced mesh, treated with polyethyleneimine crosslinking liquid and cured to obtain a reinforced mixture. The MXene dispersion is mixed with silicotungstic acid, the pH is adjusted, and the mixture is heated and stirred to obtain the MXene-silicotungstic acid composite. S4: The modified polyester release membrane is laminated with the reinforcing mixture, and the surface is sprayed with MXene-silicotungstic acid composite. After hot pressing, acid activation and water washing to neutrality, a composite ion exchange membrane is obtained.

[0006] Furthermore, the sulfonated polyether ether ketone solution is prepared by dissolving sulfonated polyether ether ketone with a sulfonation degree of 20% in N,N-dimethylacetamide, wherein the mass ratio of sulfonated polyether ether ketone to solvent is 7:10.5.

[0007] Furthermore, by weight, the perfluorosulfonic acid resin comprises 95-110 parts, functionalized multi-walled carbon nanotubes comprises 5-8 parts, phosphotungstic acid comprises 10-15 parts, cerium-tannin complex comprises 1-1.8 parts, polyphenylene sulfide reinforced mesh comprises 12-20 parts, sulfonated polyether ether ketone solution comprises 30-40 parts, MXene-silicotungstic acid composite comprises 3-5 parts, and polyethyleneimine crosslinking agent comprises 1-3 parts.

[0008] Furthermore, the dispersant stabilizer comprises 13-16 parts of modified polyetheretherketone and 8-11 parts of PEG-40 hydrogenated castor oil.

[0009] Furthermore, the preparation conditions for the casting solution in step S1 are stirring at 65°C for 6 hours; the drying conditions in step S2 are drying at 75°C for 3 hours.

[0010] Furthermore, the hot-pressing conditions in step S4 are 2 MPa and 120°C for 15 minutes; the acid activation conditions are soaking in 0.5 mol / L H2SO4 for 24 hours.

[0011] Furthermore, the preparation method of the functionalized multi-walled carbon nanotubes includes placing concentrated sulfuric acid in a water bath, adding multi-walled carbon nanotubes, potassium nitrate and potassium permanganate, ultrasonically stirring the reaction, vacuum filtering, dispersing in N,N-dimethylformamide, and ultrasonically vibrating to obtain functionalized multi-walled carbon nanotubes.

[0012] Furthermore, the preparation method of the cerium-tannin complex includes dissolving tannic acid in deionized water to prepare a 5wt% solution, adding CeCl3 solution, mixing and stirring at 60℃ for 2 h, and centrifuging and drying to obtain the cerium-tannin complex.

[0013] The present invention also relates to the application of the composite ion exchange membrane as described above in a proton exchange membrane electrolyzer, wherein the electrolyzer adopts a zero-gap structure, the anode catalyst is IrO2, the cathode catalyst is Pt or C, and the electrolyte is 0.5 mol / L H2SO4.

[0014] This invention also relates to the application of the composite ion exchange membrane as described above in a vanadium redox flow battery, wherein the positive electrode electrolyte is 1.8 mol / L VO₂. 2+ The negative electrode electrolyte is 1.8 mol / L H2SO4 and 3 mol / L H2SO4. 3+ The electrode was made of graphite felt and 3 mol / L H2SO4.

[0015] Compared with existing technologies, this invention has the following advantages: By combining the synergistic effect of polyphenylene sulfide reinforcing mesh and polyethyleneimine crosslinking system, this invention improves the performance of composite ion exchange membranes, resulting in a longer lifespan in Fenton reagents. The cerium-tannin complex effectively delays membrane degradation due to its free radical scavenging ability, exhibiting better performance than traditional Nafion membranes. The channels formed by functionalized MWCNTs and phosphotungstic acid significantly enhance the membrane proton conductivity. The dense layer of the MXene-silicotungstic acid composite effectively blocks ion crosslinking. The synergistic effect of the PPS reinforcing mesh and PEI crosslinking agent results in a smaller membrane swelling rate, which is beneficial for structural stability under high temperature and high pressure. After soaking in 80℃ and 3 mol / L KOH for 14 days, the ion exchange capacity (IEC) retention rate is high. The composite system of SPEEK and perfluorosulfonic acid resin effectively resists acid / alkali / humid heat fluctuations.

[0016] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0017] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings: Figure 1 This is a schematic flowchart of a method for preparing a composite ion exchange membrane according to the present invention. Detailed Implementation

[0018] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and 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.

[0019] The concepts involved in this application will first be described with reference to the accompanying drawings. It should be noted that the following descriptions of various concepts are only for the purpose of making the content of this application easier to understand and do not constitute a limitation on the scope of protection of this application; furthermore, the embodiments and features in the embodiments of this application can be combined with each other unless otherwise specified. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0020] The perfluorosulfonic acid resin was purchased from Zhejiang Qianrui New Material Technology Co., Ltd.; the polyester release film was purchased from Huizhou Yingbo New Material Technology Co., Ltd.; the sulfonated polyether ether ketone (SPEEK) solution was obtained by dissolving 7.0g of sulfonated polyether ether ketone (SPEEK) with a sulfonation degree DS=20% in 10.5g of N,N-dimethylacetamide solution (DMAc); the polyphenylene sulfide (PPS) reinforced mesh was purchased from Suzhou Zhongsicheng New Material Co., Ltd. as Celstran PPS-GF40-01; and the polyethyleneimine (PEI) crosslinking agent was Jinke pei-10000.

[0021] Example 1 This invention provides a raw material for preparing a composite ion exchange membrane, comprising, by weight, 100 parts perfluorosulfonic acid resin, 7 parts functionalized multi-walled carbon nanotubes, 13 parts phosphotungstic acid, 1.5 parts cerium-tannin complex, 15 parts polyphenylene sulfide (PPS) reinforcing mesh, 35 parts sulfonated polyether ether ketone (SPEEK) solution, 4 parts MXene-silicotungstic acid composite and 2 parts polyethyleneimine (PEI) crosslinking agent.

[0022] See also Figure 1 A method for preparing a composite ion exchange membrane includes the following steps: S1. Dissolve perfluorosulfonic acid resin in 20 wt% N,N-dimethylformamide (DMF), add functionalized multi-walled carbon nanotubes, phosphotungstic acid and cerium-tannin complex in proportion, and mix and stir at 65℃ for 6 h to obtain casting solution. S2. The casting solution is coated onto the polyester release film, the wet film thickness is 500 μm, and the film is dried at 75℃ for 3 hours to obtain the modified polyester release film. S3. Sulfonated polyether ether ketone (SPEEK) solution was coated on both sides of the PPS reinforced mesh, immersed in PEI crosslinking liquid and reacted for 30 min, and cured at 60℃ to obtain the reinforced mixture; MXene dispersion and silicotungstic acid were mixed at a mass ratio of 1:1, the pH was adjusted to 2.0, and stirred at 70℃ for 1 h to obtain the MXene-silicotungstic acid composite. S4. The modified polyester release membrane is laminated with the reinforcing mixture, and the surface is sprayed with MXene-silicotungstic acid composite. It is hot-pressed at 2MPa and 120℃ for 15 minutes, then immersed in 0.5 mol / L H2SO4 for 24 h for activation, and rinsed with deionized water until neutral to obtain the composite ion exchange membrane.

[0023] The preparation method of the functionalized multi-walled carbon nanotubes includes: placing 450 mL of concentrated sulfuric acid in a 20°C water bath, adding 15 g of multi-walled carbon nanotubes with a radial diameter of 15 nm and an axial diameter of 30 μm and 10 g of potassium nitrate in sequence under stirring, and adding 14 g of potassium permanganate after complete dissolution. The mixture is then ultrasonically stirred in a 20 kHz ultrasonic cell disruptor for 6 hours to generate a turbid mixture. The mixture is then vacuum filtered through a Buchner funnel and repeatedly washed with deionized water until the pH of the filtrate reaches 7 to ensure the removal of residual acid. The washed solid is dispersed in N,N-dimethylformamide (DMF) at a ratio of 1 g solid / 10 mL of DMF and ultrasonically vibrated for 1 hour to obtain functionalized multi-walled carbon nanotubes.

[0024] The preparation method of the cerium-tannin complex includes: dissolving tannic acid in deionized water (concentration 5 wt%), adding CeCl3 solution (0.1 mol / L), stirring at 60℃ for 2 h (speed 500 rpm), and centrifuging and drying to obtain the cerium-tannin complex.

[0025] Example 2 This invention provides a raw material for preparing a composite ion exchange membrane, comprising, by weight, 95 parts perfluorosulfonic acid resin, 5 parts functionalized multi-walled carbon nanotubes, 10 parts phosphotungstic acid, 1 part cerium-tannin complex, 12 parts polyphenylene sulfide (PPS) reinforcing mesh, 30 parts sulfonated polyether ether ketone (SPEEK) solution, 3 parts MXene-silicotungstic acid composite and 1 part polyethyleneimine (PEI) crosslinking agent.

[0026] Example 3 This invention provides a raw material for preparing a composite ion exchange membrane, comprising, by weight, 110 parts perfluorosulfonic acid resin, 8 parts functionalized multi-walled carbon nanotubes, 15 parts phosphotungstic acid, 1.8 parts cerium-tannin complex, 20 parts polyphenylene sulfide (PPS) reinforcing mesh, 40 parts sulfonated polyether ether ketone (SPEEK) solution, 5 parts MXene-silicotungstic acid composite and 3 parts polyethyleneimine (PEI) crosslinking agent.

[0027] Application Example 1 The composite ion exchange membrane prepared according to the preparation method in Example 1 was applied in a proton exchange membrane electrolyzer. The electrolyzer adopted a zero-gap electrolyzer structure, and the anode catalyst was IrO2 (2 mg / cm³). 2 The cathode catalyst is Pt / C (0.5 mg / cm³). 2 The composite ion exchange membrane was placed between the anode and cathode. The operating conditions were: temperature 85℃±2℃, electrolyte 0.5 mol / L H2SO4, and flow rate 50 mL / min.

[0028] Application Example 2 The composite ion exchange membrane prepared according to the method in Example 1 was applied in an all-vanadium redox flow battery, with a positive electrode electrolyte of 1.8 mol / L VOC. 2+ The electrolyte concentrations were 3 mol / L H₂SO₄ and 1.8 mol / L V for the negative electrode. 3+ The concentration of H2SO4 was 3 mol / L, and the electrode was graphite felt.

[0029] Comparative Example 1 The difference from Example 1 is that it lacks an equal weight portion of the reinforcing mixture; otherwise, it is the same as Example 1.

[0030] Comparative Example 2 The difference from Example 1 is that functionalized multi-walled carbon nanotubes are replaced with an equal weight of original MWCNTs; otherwise, they are the same as in Example 1.

[0031] Comparative Example 3 The difference from Example 1 is that an equal amount of CeCl3 is used to directly replace the cerium-tannin complex; otherwise, it is the same as Example 1.

[0032] Comparative Example 4 The difference from Example 1 is that it lacks an equal weight of MXene-silicotungstic acid composite, otherwise it is the same as Example 1.

[0033] Performance testing 1. The tensile strength of the products prepared in the examples and comparative examples was tested according to ASTM D882. The testing equipment was a universal testing machine (WDW-100), the tensile rate was 10 mm / min, and the humidity was 60% RH. The samples were immersed in deionized water at 85℃ for 24 h, and the area change rate SR (%) was measured. SR (%) = [(S wet - S dry ) / S dry The wet swelling rate was tested by measuring 100 × 100; the burst strength was tested by using a water pressure burst tester (GTR-704R) at a pressurization rate of 0.1 MPa / min until the membrane ruptured. The test results are shown in Table 1.

[0034] Table 1 The samples prepared in Example 1 and Comparative Example 3 were subjected to durability testing by placing them at 80°C in Fenton's reagent (3% H2O2 + 2×10⁻⁶). -5 mol / L Fe 2+ The samples were immersed in 3 mol / L KOH at 80°C for 14 days to test the lifetime. The membrane mass loss rate and ·OH removal rate were measured every 24 hours. The ion exchange capacity (IEC) retention rate was calculated and the stability was tested. The results are shown in Table 2.

[0035] Table 2 In summary, this invention successfully prepared a composite ion exchange membrane with excellent conductivity, durability, swelling ratio, and stability through the proton conduction network of functionalized MWCNTs, the free radical capture mechanism of cerium-tannin complexes, the ion sieving and layering of MXene-silicotungstic acid complexes, and the PPS / PEI enhancement system. Compared with traditional membranes, its proton conductivity is effectively improved, its chemical lifetime is extended, and its vanadium ion permeability is reduced. It solves the core defects of existing technologies, such as high membrane resistance, poor selectivity, and weak environmental adaptability. The successful application of this membrane in proton exchange membrane electrolyzers and all-vanadium redox flow batteries verifies its industrial value.

[0036] This document uses specific examples to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the methods and core ideas of this application. The above descriptions are only preferred embodiments of this application. It should be noted that due to the limitations of written expression, while there are objectively infinite specific structures, those skilled in the art can make several improvements, modifications, or changes without departing from the principles of this application, and can also combine the above technical features in an appropriate manner. These improvements, modifications, changes, or combinations, or the direct application of the inventive concept and technical solution to other situations without modification, should all be considered within the scope of protection of this application.

Claims

1. A method for preparing a composite ion exchange membrane, characterized in that, Includes the following steps: S1: Dissolve perfluorosulfonic acid resin in N,N-dimethylformamide, add functionalized multi-walled carbon nanotubes, phosphotungstic acid and cerium-tannin complex, and heat and stir to obtain casting solution; S2: Coat the casting solution onto the polyester release film and dry to obtain the modified polyester release film; S3: The sulfonated polyether ether ketone solution is coated on both sides of the polyphenylene sulfide reinforced mesh, treated with polyethyleneimine crosslinking liquid and cured to obtain a reinforced mixture. The MXene dispersion is mixed with silicotungstic acid, the pH is adjusted, and the mixture is heated and stirred to obtain the MXene-silicotungstic acid composite. S4: The modified polyester release membrane is laminated with the reinforcing mixture, and the surface is sprayed with MXene-silicotungstic acid composite. After hot pressing, acid activation and water washing to neutrality, a composite ion exchange membrane is obtained.

2. The method for preparing the composite ion exchange membrane according to claim 1, characterized in that, The sulfonated polyether ether ketone solution is prepared by dissolving sulfonated polyether ether ketone with a sulfonation degree of 20% in N,N-dimethylacetamide, wherein the mass ratio of sulfonated polyether ether ketone to solvent is 7:10.

5.

3. The method for preparing the composite ion exchange membrane according to claim 1, characterized in that, The perfluorosulfonic acid resin comprises 95-110 parts by weight, functionalized multi-walled carbon nanotubes comprises 5-8 parts, phosphotungstic acid comprises 10-15 parts, cerium-tannin complex comprises 1-1.8 parts, polyphenylene sulfide reinforced mesh comprises 12-20 parts, sulfonated polyether ether ketone solution comprises 30-40 parts, MXene-silicotungstic acid composite comprises 3-5 parts, and polyethyleneimine crosslinking agent comprises 1-3 parts.

4. The method for preparing the composite ion exchange membrane according to claim 1, characterized in that, The dispersant stabilizer comprises 13-16 parts of modified polyetheretherketone and 8-11 parts of PEG-40 hydrogenated castor oil.

5. The method for preparing the composite ion exchange membrane according to claim 1, characterized in that, The preparation conditions for the casting solution in step S1 are stirring at 65°C for 6 hours; the drying conditions in step S2 are drying at 75°C for 3 hours.

6. The method for preparing the composite ion exchange membrane according to claim 1, characterized in that, The hot-pressing conditions in step S4 are 2 MPa and 120°C for 15 minutes; the acid activation conditions are soaking in 0.5 mol / L H2SO4 for 24 hours.

7. The method for preparing the composite ion exchange membrane according to claim 1 or 3, characterized in that, The method for preparing the functionalized multi-walled carbon nanotubes includes placing concentrated sulfuric acid in a water bath, adding multi-walled carbon nanotubes, potassium nitrate and potassium permanganate, stirring the mixture with ultrasonic waves, vacuum filtering, dispersing the mixture in N,N-dimethylformamide, and then ultrasonically vibrating it to obtain the functionalized multi-walled carbon nanotubes.

8. The method for preparing the composite ion exchange membrane according to claim 1 or 3, characterized in that, The preparation method of the cerium-tannin complex includes dissolving tannic acid in deionized water to prepare a 5 wt% solution, adding CeCl3 solution, mixing and stirring at 60°C for 2 h, and centrifuging and drying to obtain the cerium-tannin complex.

9. The application of the composite ion exchange membrane as described in any one of claims 1-8 in a proton exchange membrane electrolyzer, characterized in that, The electrolytic cell adopts a zero-gap structure, the anode catalyst is IrO2, the cathode catalyst is Pt or C, and the electrolyte is 0.5 mol / L H2SO4.

10. The application of the composite ion exchange membrane as described in any one of claims 1-8 in an all-vanadium redox flow battery, characterized in that, The positive electrode electrolyte is 1.8 mol / L VO 2+ The negative electrode electrolyte is 1.8 mol / L H2SO4 and 3 mol / L H2SO4. 3+ The electrolyte is 3 mol / L H2SO4, and the electrode is graphite felt.

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