Polysulfonated dopamine modification-based electrospun composite proton exchange membrane and preparation method thereof

Abstract

The invention relates to the field of fuel cells and technologies, in particular to an electrospun composite proton exchange membrane based on polysulfonated dopamine modification and a preparation method thereof. The composite proton exchange membrane comprises a porous electrospinning fiber substrate which is coated and modified by self-polymerization of a sulfonated dopamine monomer, wherein the sulfonated dopamine monomer is any one of aromatic ring sulfonated dopamine, terminal sulfonated dopamine and amino sulfonylated dopamine; the porous electrospinning fiber substrate is filled with the trivalent cerium salt and the sulfonated polymer. By introducing the poly-sulfonated dopamine coating, the wettability and binding force of the sulfonated polymer can be remarkably improved, and uniform dispersion and fixation of Ce < 3 + > are promoted, so that the proton conductivity and chemical stability of the membrane are improved. The preparation method of the composite proton exchange membrane is simple and convenient, the composite proton exchange membrane has good interface compatibility, free radical degradation resistance and long-term operation stability, and the composite proton exchange membrane has good application prospects in proton exchange membrane fuel cells and water electrolysis devices.

Description

Technical Field

[0001] This invention relates to the field of fuel cells and related technologies, specifically to an electrospun composite proton exchange membrane based on polysulfonated dopamine modification and its preparation method. Background Technology

[0002] Proton exchange membrane fuel cells (PEMFCs) and direct methanol fuel cells (DMFCs) have become important research directions in the field of new energy due to their high energy conversion efficiency and environmental friendliness. As a core component, the performance of the proton exchange membrane directly determines the conductivity, stability, and service life of the fuel cell.

[0003] Currently, widely used proton exchange membranes are represented by perfluorosulfonic acid resins (PFSA, such as Nafion), which have high proton conductivity. However, their conductivity decreases rapidly under high temperature and low humidity conditions, and they are also expensive. To address this, researchers have proposed a method to introduce polymer electrolytes into porous polymer substrates to prepare composite proton exchange membranes, thereby achieving a balance between mechanical strength and conductivity.

[0004] Previous studies have utilized polydopamine (PDA) coatings formed by the self-polymerization of dopamine (DA) to improve the bonding between the substrate and the polymer. For example, Yoon Wo et al. reported a PDA-coated PTFE substrate composite film that promotes the wetting, filling, and bonding of Nafion, while the PDA layer can reduce Ce. 3+ And fix CeO x Nanoparticles enhance the free radical oxidation resistance of membranes (Advanced Functional Materials, 2019, 29, 1806929). However, this method relies on the physical adhesion of ordinary PDAs, lacks additional proton-conducting groups, and is mainly limited to the PTFE + Nafion system, thus limiting its application scope.

[0005] Furthermore, patent application CN117659462A discloses a sulfonated polyether ether ketone (SPEEK)-based composite film, which improves mechanical properties and ion selectivity to some extent by modifying it with ordinary dopamine (DA) and further introducing polytetrafluoroethylene (PTFE) nanoparticles. However, in this technical solution, DA also lacks proton conduction function and its contribution to proton conductivity is limited. 3+ The problems of fixation and distribution have not been effectively solved, and the system is mainly limited to the combination of SPEEK and PTFE.

[0006] In summary, while existing technologies can improve the wettability, mechanical stability, or free radical oxidation resistance of composite membranes, they still have the following shortcomings: (1) the interfacial compatibility between ordinary PDA and sulfonated polymers is limited, and strong ionic interactions are lacking; (2) PDA itself does not contain proton-conducting groups and cannot provide additional proton conduction channels; (3) Ce 3+ The distribution and long-term stability of the membrane are insufficient; (4) its applicability to substrate materials is still limited. Therefore, a new composite membrane design scheme is urgently needed to combine high proton conductivity, chemical stability and wide applicability. Summary of the Invention

[0007] The purpose of this invention is to overcome the following shortcomings of existing proton exchange membranes: 1. Limited interfacial compatibility: Ordinary dopamine (PDA) can form hydrogen bonds and π–π interactions with sulfonated polymers such as SPEEK, but due to the lack of strong ionic groups, the overall interfacial binding force and proton conduction enhancement effect are limited; 2. Insufficient proton conductivity: PDA itself does not contain proton-conducting groups and cannot provide additional proton channels for the membrane; 3. Insufficient chemical stability: Ce 3+ Uneven distribution in PDA coatings makes them prone to migration during long-term use, leading to a decrease in free radical scavenging ability; 4. Poor substrate adaptability: Traditional substrates such as PTFE are highly hydrophobic, making them difficult to process and unsuitable for large-scale preparation.

[0008] To address the aforementioned problems, the present invention aims to provide a novel composite proton exchange membrane with high interfacial compatibility, high proton conductivity, and excellent chemical stability, as well as a method for its preparation.

[0009] To achieve the objective of this invention, this invention provides an electrospun composite proton exchange membrane based on polysulfonated dopamine modification. The electrospun composite proton exchange membrane based on polysulfonated dopamine modification comprises: a porous electrospun fiber substrate formed by the self-polymerization of sulfonated dopamine monomers to form polysulfonated dopamine-coated modified substrate, and a mixture of sulfonated polymer and trivalent cerium salt filled in the porous electrospun fiber substrate. The sulfonated dopamine monomer is any one of terminal sulfonated dopamine, aromatic ring sulfonated dopamine, and aminosulfonated dopamine; The porous electrospun fiber substrate is made of one of the following materials: polyvinylidene fluoride (PVDF), polyimide (PI), and polyacrylonitrile (PAN). The sulfonated polymer is one or more of sulfonated polyether ether ketone SPEEK, sulfonated polyether ketone SPEK, sulfonated polyether sulfone SPES, sulfonated polyphenylene ether SPPO, sulfonated polybenzimidazole SPBI, and sulfonated polystyrene SPPS; The terminally sulfonated dopamine is named 4-(2-aminoethyl)-2-(3-sulfopropyl)benzene-1,2-diol, and its structural formula is: ; The aromatic ring sulfonated dopamine is named 3,4-dihydroxy-5-sulfonic acid phenylethylamine, and its structural formula is: ; The aminosulfonated dopamine is named 4-(2-(sulfonylamino)ethyl)benzene-1,2-diol, and its structural formula is: .

[0010] Furthermore, the porous electrospun fiber substrate has an average fiber diameter of 50-1000 nm (preferably 500 nm) and a porosity of 70-95% (preferably 90%).

[0011] Furthermore, the coating amount of the polysulfonated dopamine is 5wt%-20wt% (preferably 10wt%) of the porous electrospun fiber substrate.

[0012] Furthermore, the degree of sulfonation of the sulfonated polymer is 20-80% (preferably 60-70%).

[0013] Further, the trivalent cerium salt is one or more of cerium nitrate, cerium chloride, and cerium sulfate; the mass ratio of the trivalent cerium salt to the sulfonated polymer is 1:50-1:500 (preferably 1:200).

[0014] Furthermore, the electrospun composite proton exchange membrane based on polysulfonated dopamine modification has a proton conductivity greater than 0.05 S / cm at 80°C and 50% relative humidity.

[0015] Furthermore, the mass loss rate of the electrospun composite proton exchange membrane based on polysulfonated dopamine after immersion in an aqueous solution of 3wt% H2O2 containing 2ppm FeSO4 at 80 °C for 1 h is less than 10%.

[0016] The present invention also provides a method for preparing the above-mentioned electrospun composite proton exchange membrane based on polysulfonated dopamine modification, comprising the following steps: (1) Polysulfonated dopamine coating modification: Sulfonated dopamine monomer is dissolved in alkaline buffer solution to form sulfonated dopamine monomer solution. Porous electrospun fiber substrate is immersed in sulfonated dopamine monomer solution and reacted at a certain temperature to form polysulfonated dopamine coating on the surface of porous electrospun fiber substrate. It is rinsed with deionized water and vacuum dried to obtain polysulfonated dopamine coated and modified porous electrospun fiber substrate. (2) Filling with trivalent cerium salt and sulfonated polymer: Prepare sulfonated polymer solution; add trivalent cerium salt and stir evenly to obtain homogeneous mixed solution; immerse the polysulfonated dopamine-coated modified porous electrospun fiber substrate in the homogeneous mixed solution so that the homogeneous mixed solution impregnates and fills the pores of the porous electrospun fiber substrate. (3) The electrospun composite proton exchange membrane based on polysulfonated dopamine is obtained by vacuum drying.

[0017] Furthermore, the method for preparing the porous electrospun fiber substrate is as follows: take one of polyvinylidene fluoride (PVDF), polyimide (PI), and polyacrylonitrile (PAN) and prepare an electrospun precursor solution; use electrospinning to spin the fiber, and vacuum dry the resulting electrospun fiber membrane to obtain the porous electrospun fiber substrate. The concentration of the electrospinning precursor solution is 8-15 wt% (preferably 10%); the electrospinning conditions are as follows: spinning is performed at a voltage of 10-20 kV, a spray rate of 0.3-0.8 mL / h, and a collection distance of 10-20 cm (preferably 15 kV, 0.5 mL / h, and 15 cm); the vacuum drying conditions are 50-80 °C for 8-24 h (preferably 60 °C for 12 h); the porous electrospinned fiber substrate has an average fiber diameter of 50-1000 nm, a porosity of 70%-95%, and a thickness of 30-80 μm (preferably an average fiber diameter of 500 nm, a porosity of 90%, and a thickness of 50 μm); and / or In step (1): the pH of the alkaline buffer solution is 8-10 (preferably 8.5); the concentration of the sulfonated dopamine monomer solution is 0.5-2.0 mg / mL (preferably 1.0 mg / mL); the reaction conditions are 20-30 °C for 6-24 h (preferably 25 °C for 24 h); the vacuum drying conditions are 50-80 °C for 8-24 h (preferably 60 °C for 12 h); and / or In step (2): the concentration of the sulfonated polymer solution is 5-15 wt% (preferably 10 wt%); the solvent for the sulfonated polymer solution is one or more of N,N-dimethylformamide, acetone, N,N-dimethylacetamide, and N-methylpyrrolidone (preferably N,N-dimethylformamide); and / or In step (3), the vacuum drying conditions are 60-90 ℃ vacuum drying for 8-24 h (preferably 80 ℃ vacuum drying for 12 h).

[0018] The present invention also provides the application of the above-mentioned electrospun composite proton exchange membrane based on polysulfonated dopamine modification in proton exchange membrane fuel cells or water electrolysis devices.

[0019] Compared with the prior art, the present invention has the following advantages and beneficial effects: 1. Improved interfacial compatibility: Sulfonated dopamine introduces –SO3H groups, which form stronger hydrogen bonds and ionic interactions with sulfonated polymers (such as SPEEK), improving the distribution and binding force of the polymer in the electrospun fiber substrate; 2. Enhanced proton conductivity: The –SO3H group of SDA itself acts as an additional proton channel, combined with the ion network of SPEEK, making the proton conductivity of the membrane greater than 0.05 S / cm at 80 ℃ and 50%RH; 3. Excellent chemical stability: The catechol groups have a high affinity for Ce. 3+ It has an anchoring effect, making Ce 3+ It is uniformly distributed in the membrane to prevent migration and loss, enhances free radical scavenging ability, and has a mass loss rate of less than 10% under Fenton test conditions; 4. Wide applicability: Electrospun substrates can be PVDF, PI, or PAN, all of which are easy to process, have simple processes, and are easy to prepare on a large scale.

[0020] To further illustrate, the "sulfonated dopamine monomer" of the present invention is not limited to a specific sulfonation site, but includes the following three types (structures are attached). Figure 1 As shown): 1) Terminal sulfonated dopamine: –SO3H is introduced at the end of the ethylamine side chain of the dopamine molecule, for example, 4-(2-aminoethyl)-2-(3-sulfopropyl)benzene-1,2-diol. This type of structure increases the overall hydrophilicity and proton conductivity of the molecule while undergoing self-polymerization, which is beneficial for improving the water content of the membrane and the continuity of ion channels.

[0021] 2) Aromatic ring sulfonated dopamine: –SO3H is introduced onto the benzene ring of dopamine, for example, 3,4-dihydroxy-5-sulfonic acid phenylethylamine. This type of structure retains the self-polymerization ability of the catechol group while directly providing a strong acidic group on the aromatic ring, significantly enhancing proton conductivity.

[0022] 3) Aminosulfonated dopamine: –SO2–NH2 or its derivatives, such as 4-(2-(sulfonamide)ethyl)benzene-1,2-diol, are introduced into the amino site of dopamine. This type of structure can enhance the interfacial bonding with polymers through hydrogen bonding, thereby improving the mechanical strength and durability of the film.

[0023] In summary, this invention solves the problem of limited compatibility between PDA and sulfonated polymers such as SPEEK by using polysulfonated dopamine modification, and achieves a composite proton exchange membrane design with high conductivity, high stability and wide applicability. Attached Figure Description

[0024] Figure 1 The chemical structures of aromatic ring sulfonated dopamine, terminal sulfonated dopamine, and aminosulfonated dopamine are shown. Figure 2 The image shows the SEM image and elemental distribution diagram of the poly(T-SDA) modified PVDF membrane prepared in step (2) of Example 4. Detailed Implementation

[0025] The applicant will now provide a more detailed description of the technical solution of the present invention in conjunction with specific embodiments, with the aim of enabling those skilled in the art to have a clearer understanding and knowledge of the present application.

[0026] The following specific embodiments should not be construed or interpreted in any way as limiting the scope of protection claimed in this application.

[0027] The polyvinylidene fluoride (HSV900) used in the following examples was purchased from Arcamar, France; polyetheretherketone (PEEK) (021P) was from Jilin University; and polyimide (PI) (Ultem) was used. ® 1000 was purchased from SABIC, polyethersulfone (PES, brand name Ultrason E6020) was purchased from BASF, Germany, and polybenzimidazole (PBI, SJ-10) was purchased from Shanghai Shengjun Plastics Technology Co., Ltd. Other reagents and raw materials were commercially available.

[0028] The sulfonated polyether ether ketone (SPEEK) used was prepared as follows: 200 mL of concentrated sulfuric acid (98 wt%) was heated to 50 °C. 10 g of PEEK was added uniformly to the concentrated sulfuric acid over 1 minute, and the mixture was stirred with a mechanical stirrer. The reaction was carried out at 50 °C for 5 hours. After the reaction was complete, the resulting mixture was slowly poured into ice water with continuous stirring. The precipitate was then washed with deionized water until the pH of the filtrate reached 7.0. Finally, the sample was vacuum dried at 60 °C for 24 hours to obtain the sulfonated polyether ether ketone. The degree of sulfonation was calculated to be 65% by 1H NMR spectroscopy.

[0029] The sulfonated polyether sulfone (SPES) used was prepared as follows: PES (2 g) was dissolved in 20 mL of dry dichloromethane, and 20 mL of concentrated sulfuric acid (98%) was cooled to 0-5 °C in an ice-water bath; the dissolved PES solution was slowly added dropwise with stirring, and the addition rate was controlled to avoid the temperature from exceeding 20 °C; after the addition was completed, the temperature was raised to room temperature and then stirred at 50 °C for 5 hours. After the reaction was completed, the resulting mixture was slowly poured into ice water with continuous stirring. The precipitate was then washed with deionized water until the pH of the filtrate was 7.0. Finally, the sample was vacuum dried at 80 °C for 24 h to obtain sulfonated polyether sulfone. The degree of sulfonation was calculated to be 60% by 1H NMR spectroscopy.

[0030] The sulfonated polybenzimidazole SPBI used was prepared as follows: 1 g of polybenzimidazole powder was dissolved in 40 mL of dimethyl sulfoxide at 80 °C. Then, 0.64 g of sodium hydride was added under nitrogen protection, and the reaction was carried out at 40 °C for 3 h. After the reaction was complete, 0.3 g of 1,3-propanesulfonate lactone was added, and the reaction was carried out at 40 °C for 14 h. After the reaction was completed, the clear mixed solution was poured into excess acetone to precipitate the precipitate. The precipitate was collected by filtration, washed with 1 M Na₂CO₃ aqueous solution, and then washed with deionized water until neutral. The precipitate was collected by centrifugation and dried at 80 °C for 12 h to obtain sulfonated polybenzimidazole. The degree of sulfonation was calculated to be 70% by 1H NMR spectroscopy.

[0031] Example 1: Preparation of terminally sulfonated dopamine (T-SDA) (1) Raw materials: dopamine hydrochloride, 1,3-propanesulfonyl lactone, ammonia (25% by mass), sodium carbonate, anhydrous ethanol, deionized water.

[0032] (2) Procedure: 1.0 g of dopamine hydrochloride was dissolved in 30 mL of anhydrous ethanol / water (volume ratio of anhydrous ethanol / water was 4:1). Sodium carbonate (molar ratio of dopamine hydrochloride to sodium carbonate was 1:2) was added to neutralize the hydrochloric acid and release free dopamine. 1,3-propanesulfonyl lactone (molar ratio of dopamine hydrochloride to 1,3-propanesulfonyl lactone was 1:1.2) was slowly added under ice bath conditions of 0-5 °C. Then a small amount of ammonia water (approximately 1% of the volume of the anhydrous ethanol / water mixed solvent, as a catalyst) was added, and the temperature was gradually increased to 50 °C for 12 h. After the reaction was completed, the mixture was cooled to room temperature, the organic solvent was removed by rotary evaporation, the mixture was reconstituted with deionized water, and the pH was adjusted to neutral with 0.1 M dilute hydrochloric acid. Inorganic salt impurities were removed by dialysis, and the mixture was freeze-dried to obtain a light brown solid, which was terminal sulfonated dopamine (T-SDA).

[0033] (3) Explanation: This method is a typical amino alkylation and sulfonyl lactone ring-opening reaction, that is, by attacking 1,3-propane sulfonyl lactone with the amino group in the dopamine molecule, a –(CH2)3–SO3H group is introduced at the end of the ethylamine side chain.

[0034] Example 2 Preparation of Aromatic Ring Sulfonated Dopamine (R-SDA) (1) Raw materials: dopamine hydrochloride, fuming sulfuric acid (containing 20% ​​SO3), ice water, deionized water.

[0035] (2) Steps: Dissolve 1.0 g of dopamine hydrochloride in 20 mL of deionized water, cool to 0-5 °C, slowly add 5 mL of fuming sulfuric acid, control the reaction temperature to not exceed 10 °C, and stir the reaction for 3 h; after the reaction, slowly pour the mixture into a large amount of ice water to dilute, adjust the pH to 7.0 (using NaOH aqueous solution), filter and wash with deionized water, and vacuum dry at 60 °C to obtain 3,4-dihydroxy-5-sulfonic acid phenylethylamine (R-SDA).

[0036] (3) Explanation: This reaction is a direct sulfonation of the benzene ring, introducing a –SO3H group at the 5 position of the catechol; the temperature should be controlled to avoid the dopamine skeleton being oxidized and decomposed.

[0037] Example 3 Preparation of aminosulfonated dopamine (N-SDA) (1) Raw materials: dopamine hydrochloride, chlorosulfonic acid, triethylamine, anhydrous dichloromethane, deionized water.

[0038] (2) Procedure: Dissolve 1.0 g of dopamine hydrochloride in 30 mL of anhydrous dichloromethane and cool in an ice bath to 0-5 °C. Under nitrogen protection, slowly add a certain amount of chlorosulfonic acid (molar ratio of dopamine hydrochloride to chlorosulfonic acid is 1:1.2), and simultaneously add triethylamine (molar ratio of dopamine hydrochloride to triethylamine is 1:2) to neutralize the byproduct HCl, controlling the pH of the reaction system to 7-8. After stirring in an ice bath at 0-5 °C for 1 h, the reaction is brought to room temperature and stirred for another 5 h. After the reaction is complete, wash the organic phase with deionized water, separate the phases, and remove the solvent by rotary evaporation under reduced pressure to obtain a brown solid. This solid, after vacuum drying at 60 °C for 12 h, becomes aminosulfonated dopamine (N-SDA), which can be directly used for subsequent self-polymerization coating.

[0039] (3) Explanation: This reaction is a typical aminosulfonation reaction, that is, the introduction of the –SO2- group on the amino group of the dopamine molecule; air oxidation should be avoided during operation, and it can be carried out under nitrogen protection.

[0040] Example 4: A method for preparing an electrospun composite proton exchange membrane based on polysulfonated dopamine modification, comprising the following steps: (1) Preparation of PVDF electrospun fiber substrate Polyvinylidene fluoride (PVDF) was dissolved in a mixed solvent of N,N-dimethylformamide / acetone (N,N-dimethylformamide / acetone mass ratio 6:4) to obtain a 10 wt% electrospinning precursor solution. Electrospinning was performed at a voltage of 15 kV, a spray rate of 0.5 mL / h, and a collection distance of 15 cm. The resulting electrospun membrane was vacuum dried at 60 °C for 12 h to obtain a porous PVDF electrospun fiber substrate with an average fiber diameter of approximately 500 nm, a porosity of 90%, and a thickness of 50 μm.

[0041] (2) Poly(terminated sulfonated dopamine) coating modification The terminally sulfonated dopamine (T-SDA) monomer prepared in Example 1 was dissolved in a Tris-HCl buffer solution at pH 8.5 (where the Tris concentration was 5 mmol / L, the same below, not repeated) to obtain a solution with a concentration of 1.0 mg / mL. A porous PVDF electrospun fiber substrate was immersed in this solution and reacted at 25 °C for 24 h to allow T-SDA to self-polymerize on the fiber surface to form a coating. Subsequently, it was rinsed with deionized water and vacuum dried at 60 °C for 12 h to obtain a poly-T-SDA-coated modified PVDF electrospun fiber substrate with a poly-T-SDA coating amount of 10 wt% (the coating amount was calculated by dividing the weight difference before and after coating by the weight before coating multiplied by 100%, the same below). Figure 2 Provide its SEM image and elemental distribution diagrams of C, F, O, N, and S elements.

[0042] from Figure 2 As can be seen, the average fiber diameter of the poly(T-SDA) coated and modified PVDF electrospun fiber substrate is approximately 500 nm. The interwoven fibers form pores of varying sizes, which are used for subsequent SPEEK–Ce 3+ Filling; C and F are elements in the PVDF structure, and a clear fiber shape can be seen. After modification with poly-T-SDA, O, N and S elements appear on the fiber surface and are evenly and densely distributed, which confirms the success of poly-T-SDA coating modification of the PVDF fiber surface.

[0043] (3) SPEEK–Ce 3+ Filler composite Sulfonated polyether ether ketone (SPEEK) with a sulfonation degree of 65% was dissolved in N,N-dimethylacetamide to prepare a 10 wt% solution. Cerium nitrate (Ce(NO3)3·6H2O) was added to achieve a Ce(NO3)3·6H2O to SPEEK mass ratio of 1:200, and the mixture was stirred until homogeneous. A poly(T-SDA)-coated modified PVDF electrospun fiber substrate was then immersed in this solution, creating a SPEEK / Ce... 3+ The mixed solution was impregnated into the pores of the fiber substrate and then vacuum dried at 80°C for 12 hours to obtain a poly(terminated dopamine) modified electrospun composite proton exchange membrane.

[0044] (4) Performance testing The prepared poly(terminated dopamine) modified electrospun composite proton exchange membrane had a water content of 40.5%; At room temperature, at a stretching rate of 2 mm·min -1 The tensile strength measured under the specified conditions was 32.5 MPa; The proton conductivity measured by electrochemical impedance spectroscopy (EIS) at 80 °C and 50% relative humidity is 0.073 S / cm. Under Fenton's test conditions (3% H2O2 + 2 ppm Fe), 2+ The mass loss rate was 7% at 80 °C for 1 h, demonstrating excellent proton conductivity and chemical stability.

[0045] Comparative Example 1: Electrospun composite proton exchange membrane based on polynon-sulfonated dopamine (PDA) modification To verify the effect of polysulfonated dopamine modification on membrane performance improvement, a comparative sample was prepared using essentially the same steps as in Example 1, except that the terminal sulfonated dopamine (T-SDA) was replaced with an equal mass of ordinary dopamine (DA). The details are as follows: (1) Preparation of PVDF electrospun fiber substrate Polyvinylidene fluoride (PVDF) was dissolved in a mixed solvent of N,N-dimethylformamide / acetone (N,N-dimethylformamide / acetone mass ratio 6:4) to obtain a 10 wt% electrospinning precursor solution. Electrospinning was performed at a voltage of 15 kV, a spray rate of 0.5 mL / h, and a collection distance of 15 cm. The resulting electrospun membrane was vacuum dried at 60 °C for 12 h to obtain a porous PVDF electrospun fiber substrate with an average fiber diameter of approximately 500 nm, a porosity of 90%, and a thickness of 50 μm.

[0046] (2) Polydopamine (DA) coating modification Dopamine hydrochloride was dissolved in Tris-HCl buffer at pH 8.5 to obtain a solution with a concentration of 1.0 mg / mL. A porous PVDF electrospun fiber substrate was immersed in this solution and reacted at 25 °C for 24 h, allowing dopamine to self-polymerize on the fiber surface to form a polydopamine (PDA) coating. The substrate was then rinsed with deionized water and vacuum dried at 60 °C for 24 h to obtain a PDA-coated modified PVDF electrospun fiber substrate with a PDA coating amount of 10 wt%.

[0047] (3) SPEEK–Ce 3+ Filler composite Sulfonated polyether ether ketone (SPEEK) with a sulfonation degree of approximately 65% ​​was dissolved in N,N-dimethylacetamide to prepare a 10 wt% solution. Cerium nitrate (Ce(NO3)3·6H2O) was added to achieve a Ce(NO3)3·6H2O to SPEEK mass ratio of 1:200, and the mixture was stirred until homogeneous. A PDA-coated modified PVDF electrospun fiber substrate was then immersed in this solution, creating a SPEEK / Ce... 3+The mixed solution was impregnated into the pores of the fiber substrate and then vacuum dried at 80°C for 12 hours to obtain a PDA-modified electrospun composite proton exchange membrane.

[0048] (4) Performance testing The prepared PDA-modified electrospun composite proton exchange membrane has a water content of 25.6%.

[0049] At room temperature, at a stretching rate of 2 mm·min -1 The tensile strength measured under the specified conditions was 22.0 MPa; The proton conductivity measured by electrochemical impedance spectroscopy (EIS) at 80 °C and 50% relative humidity is 0.030 S / cm. Under Fenton's test conditions (3% H2O2 + 2 ppm Fe), 2+ The mass loss rate was 17% at 80 °C for 1 h.

[0050] (5) Effect comparison Compared with Example 4, the moisture content and proton conductivity of this comparative sample were significantly reduced, and the strength and oxidation resistance were significantly worse, indicating that polysulfonated dopamine modification can effectively improve the proton conductivity and chemical stability of the composite proton exchange membrane.

[0051] Example 5: PI / SPES electrospun composite proton exchange membrane based on poly(arylcyclosulfonated dopamine) modification (1) Preparation of PI electrospun fiber substrate Polyimide (PI) was dissolved in a mixed solvent of N,N-dimethylacetamide / N-methylpyrrolidone (N,N-dimethylacetamide / N-methylpyrrolidone mass ratio 6:4) to obtain an electrospinning precursor solution with a concentration of 15 wt%. Electrospinning was performed at a voltage of 20 kV, a spray rate of 0.8 mL / h, and a collection distance of 20 cm. The resulting electrospun membrane was vacuum dried at 80 °C for 8 h to obtain a porous PI electrospun fiber substrate with an average fiber diameter of approximately 1000 nm, a porosity of 70%, and a thickness of 60 μm.

[0052] (2) Poly(arylcyclosulfonated dopamine) coating modification The aromatic ring sulfonated dopamine (R-SDA) prepared in Example 2 was dissolved in Tris-HCl buffer at pH 8.0 to obtain a solution with a concentration of 2.0 mg / mL. A porous PI electrospun fiber substrate was immersed in this solution and reacted at 25°C for 24 h to allow R-SDA to self-polymerize on the fiber surface to form a coating. The substrate was then rinsed with deionized water and vacuum dried at 80°C for 8 h to obtain a polyR-SDA-coated modified PI electrospun fiber substrate with a polyR-SDA coating amount of 20 wt%.

[0053] (3) SPES–Ce 3+ Filler composite A 5 wt% solution of sulfonated polyethersulfone (SPES) with a sulfonation degree of 60% was prepared by dissolving it in N,N-dimethylacetamide. Ce₂(SO₄)₃·7H₂O was added to achieve a Ce₂(SO₄)₃·7H₂O to SPES mass ratio of 1:150, and the mixture was stirred until homogeneous. A poly(R-SDA)-coated modified PI electrospun fiber substrate was then immersed in this solution, creating a SPES / Ce₂ / Ce₂ / SEE mixture. 3+ The mixed solution was impregnated into the pores of the fiber substrate and then vacuum dried at 60°C for 24 h to obtain a poly-R-SDA modified electrospun composite proton exchange membrane.

[0054] (4) Performance testing The water content of the prepared poly(R-SDA) modified electrospun composite proton exchange membrane was 36.5%.

[0055] At room temperature, at a stretching rate of 2 mm·min -1 The tensile strength measured under the specified conditions was 30.0 MPa; The proton conductivity measured by electrochemical impedance spectroscopy (EIS) at 80 °C and 50% relative humidity is 0.080 S / cm. Under Fenton's test conditions (3% H2O2 + 2 ppm Fe), 2+ The mass loss rate at 80 °C for 1 h is approximately 7%.

[0056] Example 6: Electrospun Proton Exchange Membrane Based on Poly(Aminosulfonated Dopamine) Modified PAN / SPBI (1) Preparation of PAN electrospun fiber substrate Polyacrylonitrile (PAN) was dissolved in N,N-dimethylformamide (DMF) to obtain an 8 wt% electrospinning precursor solution. Electrospinning was performed at a voltage of 10 kV, a spray rate of 0.3 mL / h, and a collection distance of 10 cm. The resulting electrospun membrane was vacuum dried at 50 °C for 24 h to obtain a porous PAN electrospun fiber substrate with an average fiber diameter of approximately 50 nm, a porosity of 95%, and a thickness of 30 μm.

[0057] (2) Poly(aminosulfonated dopamine) coating modification The aminosulfonated (N-SDA) prepared in Example 3 was dissolved in Tris-HCl buffer at pH 8.5 to obtain a solution with a concentration of 0.5 mg / mL. A porous PAN electrospun fiber substrate was immersed in this solution and reacted at 25°C for 24 h to allow N-SDA to self-polymerize on the fiber surface to form a coating. The substrate was then rinsed with deionized water and vacuum dried at 50°C for 24 h to obtain a poly-N-SDA-coated modified PAN electrospun fiber substrate with a poly-N-SDA coating amount of 5 wt%.

[0058] (3) SPBI–Ce 3+ Filler composite Sulfonated polybenzimidazole (SPBI) with a sulfonation degree of 70% was dissolved in N,N-acetamide to prepare a 15 wt% solution. CeCl3·7H2O was added to make the mass ratio of CeCl3·7H2O to SPBI 1:300, and the mixture was stirred until homogeneous. A poly(N-SDA)-coated modified PAN electrospun fiber substrate was then immersed in this solution, forming a SPBI / CeCl3 / 7H2O mixture. 3+ The mixed solution was impregnated into the pores of the fiber substrate and then vacuum dried at 90 °C for 8 h to obtain a poly-N-SDA modified electrospun composite proton exchange membrane.

[0059] (4) Performance testing The prepared poly-N-SDA modified electrospun composite proton exchange membrane has a water content of 33.6%.

[0060] At room temperature, at a stretching rate of 2 mm·min -1 The tensile strength measured under the specified conditions was 34.0 MPa; The proton conductivity measured by electrochemical impedance spectroscopy (EIS) at 80 °C and 50% relative humidity is 0.075 S / cm. Under Fenton's test conditions (3% H2O2 + 2 ppm Fe), 2+ The mass loss rate at 80 °C for 1 h is approximately 5%.

[0061] Membrane performance testing methods: (1) Porosity: The porosity of the electrospun fiber substrate was determined by gravimetric method. A dried electrospun fiber substrate sample was immersed in n-butanol at room temperature for 2 hours. The sample was then removed, the surface liquid was quickly wiped off with filter paper, and the sample was weighed. The porosity was calculated using the following formula: Among them, V 吸收 V is the volume of n-butanol absorbed by the wet sample. 总 m is the volume of the dry sample. 湿 and m干 These represent the mass of the wet sample and the mass of the dry sample, respectively; ρ 正丁醇 and ρ 膜 The values ​​are the density of n-butanol and the density of the dry sample, respectively.

[0062] (2) Moisture content: The moisture content of the membrane was tested using the wet-dry weight method. The membrane was vacuum dried at 100℃ for 24 hours, and the weight was measured to obtain W. dry Then, the membrane was soaked in distilled water at room temperature for 24 hours, the water on the membrane surface was wiped off with filter paper, and the membrane was quickly weighed to obtain W. wet Moisture content (W) water The following formula is used for calculation: (3) Tensile strength: The stress-strain curve of the membrane was determined using a Shimadzu (Japan) AG-IG 5KN universal tensile testing machine. The sample size was 1 cm × 4 cm. The thickness of the sample was measured using a thickness gauge, and the width and effective length of the sample were measured using vernier calipers. The tensile rate was 2 mm·min. -1 Temperature 20℃, relative humidity 50%.

[0063] (4) Proton conductivity: The resistance of the membrane was tested on a frequency response analyzer with a frequency scan range of 1-10. 6 The AC signal amplitude was 50mV at Hz. A pre-cut electrospun composite proton exchange membrane (length × width = 3cm × 2cm) was tested using the two-electrode AC impedance method. Before testing, the membrane sample was saturated in deionized water at room temperature. The proton conductivity of the membrane was... (S / cm) is calculated using the following formula: In the formula, L and A are the distance between the two electrodes and the effective cross-sectional area of ​​the membrane under test between the two electrodes, respectively, and R is the resistance of the membrane, which is obtained by the Nyquist plot obtained by AC impedance testing.

[0064] (5) Oxidative stability: The oxidative stability was characterized by simulating the working environment of a fuel cell using Fenton's reagent (a 3wt% H2O2 aqueous solution containing 2ppm FeSO4). Electrospun composite proton exchange membranes were cut to the same size (1.5cm × 4cm). The samples were then immersed in Fenton's reagent at 80℃, and the mass loss rate of the electrospun composite proton exchange membrane was recorded after one hour. The measurements were repeated three times or more, and the average value was calculated.

Claims

1. An electrospun composite proton exchange membrane based on poly-sulfonated polydopamine modification, characterized in that, The poly-sulfonated dopamine modified electrospun composite proton exchange membrane comprises: a porous electrospun fiber substrate modified by self-polymerization of sulfonated dopamine monomers to form poly-sulfonated dopamine, and a mixture of sulfonated polymers and trivalent cerium salt filled in the porous electrospun fiber substrate; The sulfonated dopamine monomer is any one of aromatic ring sulfonated dopamine, terminal sulfonated dopamine and aminosulfonylated dopamine; The material of the porous electrospun fiber substrate is one of polyvinylidene fluoride PVDF, polyimide PI and polyacrylonitrile PAN; The sulfonated polymer is one or more of sulfonated polyether ether ketone SPEEK, sulfonated polyether ketone SPEK, sulfonated polyether sulfone SPES, sulfonated polyphenyl ether SPPO, sulfonated polybenzimidazole SPBI and sulfonated polystyrene SPPS; The name of the end-sulfonated dopamine is 4-(2-aminoethyl)-2-(3-sulfopropyl)benzene-1,2-diol, and the structural formula is: ; The name of the aromatic ring sulfonated dopamine is 3,4-dihydroxy-5-sulfonic acid phenethylamine, and the structural formula is: ; The aminosulfonylated dopamine has the name 4-(2-(sulfonamido)ethyl)benzene-1,2-diol and the structural formula: .

2. The electrospun composite proton exchange membrane based on poly-sulfonated polydopamine modification according to claim 1, characterized in that, The average diameter of the fibers of the porous electrospun fiber substrate is 50-1000 nm, and the porosity is 70%-95%.

3. The electrospun composite proton exchange membrane based on poly-sulfonated polydopamine modification according to claim 1, characterized in that, The coating amount of the poly-sulfonated dopamine is 5wt%-20wt% of the porous electrospun fiber substrate.

4. The electrospun composite proton exchange membrane based on poly-sulfonated polydopamine modification according to claim 1, characterized in that, The sulfonation degree of the sulfonated polymer is 20-80%.

5. The electrospun composite proton exchange membrane based on poly-sulfonated polydopamine modification according to claim 1, characterized in that, The trivalent cerium salt is one or more of cerium nitrate, cerium chloride and cerium sulfate; the mass ratio of the trivalent cerium salt to the sulfonated polymer is 1:50-1:

500.

6. The electrospun composite proton exchange membrane based on poly-sulfonated polydopamine modification according to claim 1, characterized in that, The proton conductivity of the poly-sulfonated dopamine modified electrospun composite proton exchange membrane is greater than 0.05 S / cm at 80℃ and a relative humidity of 50%.

7. The electrospun composite proton exchange membrane based on poly-sulfonated polydopamine modification according to claim 1, characterized in that, The mass loss rate of the poly-sulfonated dopamine modified electrospun composite proton exchange membrane is less than 10% after being immersed in a 3wt% H2O2 aqueous solution containing 2ppm FeSO4 at 80℃ for 1h.

8. A method for the preparation of the electrospun composite proton exchange membrane based on poly-sulfonated polydopamine modification according to any one of claims 1-7, characterized in that, The method comprises the following steps: (1) poly-sulfonated dopamine coating modification: dissolving sulfonated dopamine monomers in an alkaline buffer to form a sulfonated dopamine monomer solution, immersing a porous electrospun fiber substrate in the sulfonated dopamine monomer solution, and reacting at a certain temperature to form a poly-sulfonated dopamine coating on the surface of the porous electrospun fiber substrate; rinsing with deionized water and vacuum drying to obtain a poly-sulfonated dopamine coated porous electrospun fiber substrate; (2) filling trivalent cerium salt and sulfonated polymer: preparing a sulfonated polymer solution; adding trivalent cerium salt and stirring uniformly to obtain a homogeneous mixed solution; immersing the poly-sulfonated dopamine coated porous electrospun fiber substrate in the homogeneous mixed solution, so that the homogeneous mixed solution is impregnated and filled into the pores of the porous electrospun fiber substrate; (3) vacuum drying to form a film to obtain the poly-sulfonated dopamine modified electrospun composite proton exchange membrane.

9. The preparation method of claim 8, wherein the porous electrospun fiber substrate is prepared by: taking one of polyvinylidene fluoride PVDF, polyimide PI and polyacrylonitrile PAN, and preparing an electrospun precursor solution; performing spinning by electrospinning, and vacuum drying the obtained electrospun fiber membrane to obtain the porous electrospun fiber substrate. ​ The concentration of the electrospinning precursor solution is 8-15 wt%; the electrospinning is performed under the following conditions: voltage 10-20 kV, liquid injection rate 0.3-0.8 mL / h, and collection distance 10-20 cm; the vacuum drying is performed under the following conditions: 50-80 ℃ for 8-24 h; the average diameter of the fibers of the porous electrospinning fiber substrate obtained is 50-1000 nm, the porosity is 70%-95%, and the thickness is 30-80 μm; and / or In the step (1), the pH of the alkaline buffer is 8-10; the concentration of the sulfonated dopamine monomer solution is 0.5-2.0 mg / mL; the reaction is performed at 20-30 ℃ for 6-24 h; the vacuum drying is performed under the following conditions: 50-80 ℃ for 8-24 h; and / or In the step (2), the concentration of the sulfonated polymer solution is 5-15 wt%; the solvent of the sulfonated polymer solution is one or more of N,N-dimethylformamide, acetone, N,N-dimethylacetamide, and N-methylpyrrolidone; and / or In the step (3), the vacuum drying is performed under the following conditions: 60-90 ℃ for 8-24 h.

10. Use of the poly-sulfonated dopamine modified electrospun composite proton exchange membrane according to any one of claims 1-7 or prepared according to the method of claim 8 or 9 in a proton exchange membrane fuel cell or a water electrolysis device.

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