Preparation method of efficient monolithic bipolar membrane

Abstract

The invention relates to the technical field of bipolar membranes, in particular to a preparation method of an efficient monolithic bipolar membrane, which comprises the following steps: preparing a co-support basement membrane; functionalizing the cation exchange layer; preparing and coating a modified bentonite-based catalyst layer; functionalizing the anion exchange layer; compounding and curing; according to the technical scheme, leap-type improvement of the comprehensive performance of the bipolar membrane is achieved, and the bipolar membrane has remarkable practical application value. Through the optimization and synergistic effect of the technical scheme, the cation transference number of the prepared bipolar membrane is higher than 0.96, the water dissociation voltage is lower than 0.85 V, the tensile strength exceeds 28 MPa, and the core problems that an existing bipolar membrane is poor in ion selectivity, large in energy loss and insufficient in mechanical stability are synchronously solved. Compared with a traditional preparation method, the technology does not need complex equipment, parameters of all steps are controllable, and the method is suitable for large-scale production; and meanwhile, the stable structure of the catalyst layer is firmly combined with the membrane layer, so that the service life of the bipolar membrane is prolonged.

Description

Technical Field

[0001] This invention relates to the field of bipolar membrane technology, specifically to a method for preparing a high-efficiency monolithic bipolar membrane. Background Technology

[0002] Bipolar membranes, as a special type of ion exchange composite membrane, play an irreplaceable role in fields such as electrodialysis for acid and alkali production, wastewater treatment and resource recovery, and energy storage. Their core advantage lies in their ability to efficiently dissociate water molecules under an electric field, generating hydrogen ions and hydroxide ions, thus achieving the conversion of salts into acids and alkalis or the deep treatment of pollutants. Therefore, they have become a key material in the fields of green chemistry and environmental protection.

[0003] However, current bipolar membrane fabrication technologies still face numerous practical application challenges, limiting their large-scale promotion and performance improvement. Firstly, traditional substrate membranes are mostly prepared using conventional polymer materials, which are prone to swelling and cracking during long-term electrolysis, resulting in insufficient mechanical stability and shortened membrane lifespan. Some composite substrate membranes, due to poor component compatibility, also introduce new problems such as increased ion transport resistance. Secondly, the performance of the water dissociation catalyst layer is crucial to the efficiency of the bipolar membrane, but existing catalyst layers often suffer from uneven dispersion of active components and low loading. Conventional metal oxide catalysts are prone to agglomeration, ultimately leading to a high water dissociation voltage and significant energy loss. Furthermore, insufficient bonding strength between membrane layers is a common problem. Whether using adhesive bonding or conventional hot pressing methods, the cation exchange layer, catalyst layer, and anion exchange layer are prone to peeling, leading to catalyst loss and rapid performance degradation. These problems make it difficult for existing bipolar membranes to simultaneously achieve high ion selectivity, low water dissociation voltage, and excellent mechanical stability, thus limiting their application in industrial scenarios.

[0004] To overcome the aforementioned technical bottlenecks, developing a bipolar membrane preparation method that can simultaneously optimize the substrate membrane support performance, catalytic layer activity, and membrane layer bonding stability has become an important research direction in this field. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and propose a method for preparing a highly efficient monolithic bipolar film.

[0006] The specific technical solution is as follows: A method for preparing a high-efficiency monolithic bipolar film, comprising the following steps:

[0007] Preparation of co-supported basement membrane: Dissolve amino-sulfonated polyether ether ketone in N-methylpyrrolidone, add 10-20 wt% of polyvinylidene fluoride of the total mass of the basement membrane raw material, ultrasonically disperse for 30-60 min, cast into a film, and vacuum dry at 80-100℃ for 12-18 h to obtain a homogeneous basement membrane.

[0008] Cation exchange layer functionalization: One side of the base membrane is immersed in 0.5-1.0 mol / L of 1,3-propanesulfonic acid lactone / ethanol sulfonation reagent and reacted at 60-80℃ for 4-8 hours. After hydrolysis with NaOH solution and washing with deionized water until neutral, the cation exchange layer is formed after drying.

[0009] Preparation and coating of modified bentonite-based catalyst layer: ZnO-ZrO2-supported modified bentonite and SPEEK binder were mixed at a mass ratio of 7:3, N-methylpyrrolidone was added and ultrasonically dispersed for 2-3 hours to form a catalyst slurry, which was then coated on the surface of the cation exchange layer. The coating thickness was controlled at 5-10 μm and pre-dried at 60℃ for 3 hours.

[0010] Functionalization of the anion exchange layer: A solution of anion exchange resin of brominated 1-vinyl-3-methylimidazolium modified SPEEK is cast onto the surface of the catalyst layer and dried at 40-50℃ for 6-8 hours to form an anion exchange layer.

[0011] Composite curing: The membrane material, in which the cation exchange layer, catalyst layer and anion exchange layer are formed in sequence, is hot-pressed at 120-140℃ and 0.5-1.0MPa for 30-60 minutes and then naturally cooled to room temperature to obtain a high-efficiency monolithic bipolar membrane.

[0012] As a further technical solution, in the 1,3-propanesulfonic acid lactone / ethanol sulfonating reagent in step S2, the volume ratio of 1,3-propanesulfonic acid lactone to ethanol is 1:3-5.

[0013] As a further technical solution, the preparation steps of the ZnO-ZrO2-supported modified bentonite in step S3 include:

[0014] Acid-base activation: Crush natural bentonite through a 200-mesh sieve, add 5-10wt% hydrochloric acid solution, reflux and stir at 80℃ for 4-6 hours, filter and wash until neutral; then add 5-8wt% sodium hydroxide solution, stir at 60℃ for 2-3 hours, filter and wash until neutral, and dry at 105℃ for 8 hours to obtain activated bentonite.

[0015] Ion intercalation: The activated bentonite is added to deionized water and ultrasonically dispersed to form a 5-10 wt% suspension. Then, 15-25% (by weight of the activated bentonite) of hexadecyltrimethylammonium bromide is added. The mixture is stirred at 70-80°C for 3-5 hours, centrifuged, and washed until Cl-free. - The organic-intercalated bentonite was obtained by vacuum drying at 60℃ for 6 hours.

[0016] Active component loading: The organic intercalated bentonite was added to a mixed solution of zinc nitrate and zirconium chloride, the pH was adjusted to 8-9, stirred at 50℃ for 4-6h, allowed to stand and precipitate, filtered, washed until no nitrate ions were detected, and calcined at 450-550℃ for 2-3h to obtain the active component.

[0017] As a further technical solution, in the mixed solution of zinc nitrate and zirconium chloride, the molar ratio of zinc nitrate to zirconium chloride is 1:1, and the total concentration is 0.2-0.5 mol / L.

[0018] As a further technical solution, hexadecyltrimethylammonium bromide is added by dropping, with a dropping rate of 1-2 mL / min.

[0019] As a further technical solution, in step S3, the loading amount of ZnO-ZrO2 on the modified bentonite is 25-35% of the mass of the modified bentonite, and the particle size of ZnO-ZrO2 is 20-50nm.

[0020] As a further technical solution, the sulfonation degree of the SPEEK adhesive in step S3 is 50-70%.

[0021] As a further technical solution, in step S3, the viscosity of the catalytic slurry at 25°C is 500-1500 mPa·s, and the shear rate is 100 s⁻¹. -1 .

[0022] As a further technical solution, the concentration of the anion exchange resin solution in step S4 is 15-25 wt%.

[0023] As a further technical solution, nitrogen gas is introduced for protection during the hot pressing process in step S5.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] First, the optimization of each core component and step has led to performance improvements. The introduction of polyvinylidene fluoride (PVDF) into the base membrane forms an interpenetrating network structure with amino-sulfonated polyether ether ketone (PEEK), not only filling the internal pores of the single base membrane but also significantly improving the compactness and tensile strength of the base membrane by utilizing PVDF's excellent mechanical strength and chemical stability. This solves the problems of swelling and cracking common in traditional base membranes, providing stable support for the subsequent construction of functional layers. Simultaneously, PVDF and PEEK exhibit good compatibility and do not increase ion transport resistance. Through ion intercalation of bentonite, the gradual introduction of hexadecyltrimethylammonium bromide expands the interlayer spacing of the bentonite, improving its surface hydrophilicity and hydrophobicity. This provides a uniformly dispersed carrier space for the ZnO-ZrO2 active components, thereby increasing the ZnO-ZrO2 loading to 25-35% and controlling the particle size to 20-50 nm. This effectively avoids the aggregation of active components, maximizes the exposure of catalytic sites, and lowers the energy barrier for the water dissociation reaction. The hot pressing process under nitrogen protection can isolate oxygen from the oxidative erosion of organic components, protect the internal chemical bonds and interfacial bonding of the film, and solve the problem of film performance degradation caused by conventional hot pressing.

[0026] Secondly, the synergistic effect of each step constructs a highly efficient and stable overall system. The reinforced support of the base membrane provides a solid foundation for the adhesion of the catalyst layer and the ion exchange layer, enabling the catalyst slurry to be uniformly coated and not easily detached. At the same time, the dense base membrane structure reduces the penetration of non-target ions and improves ion selectivity. The high catalytic activity of ZnO-ZrO2 in the catalyst layer synergizes with the efficient ion transport capabilities of the cation exchange layer and the anion exchange layer. Hydrogen ions and hydroxide ions can quickly migrate from the catalytic sites to both sides of the membrane, further reducing the water dissociation voltage and improving the current efficiency. The SPEEK anion exchange resin modified with 1-vinyl-3-methylimidazolium bromide forms a matching ion transport channel with the cation exchange layer. Combined with the thickness control of the catalyst layer, it ensures the ion transport rate and avoids the superposition of resistance between membrane layers.

[0027] Third, the technical solution of this invention achieves a significant leap in the overall performance of bipolar membranes, possessing substantial practical application value. Through the optimization and synergistic effect of the technical solution, the bipolar membranes prepared by this invention exhibit cation mobility numbers higher than 0.96, water dissociation voltages lower than 0.85V, and tensile strengths exceeding 28MPa, simultaneously solving the core problems of poor ion selectivity, high energy loss, and insufficient mechanical stability in existing bipolar membranes. Compared with traditional preparation methods, the process of this invention requires no complex equipment, and the parameters of each step are controllable, making it suitable for large-scale production. Furthermore, the stable structure of the catalyst layer and the strong bonding between membrane layers extend the service life of the bipolar membrane and reduce industrial application costs. It can be widely applied to scenarios such as high-purity acid and alkali preparation, industrial wastewater treatment, and lithium salt refining. Attached Figure Description

[0028] Figure 1 This is a flowchart of a method for preparing a high-efficiency monolithic bipolar film. Detailed Implementation

[0029] 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.

[0030] This invention provides a method for preparing a high-efficiency monolithic bipolar membrane. This method, through multi-step synergistic optimization, achieves simultaneous improvement in the ion selectivity, water dissociation efficiency, and mechanical stability of the bipolar membrane. Specifically, it includes the following steps:

[0031] (a) Preparation of co-supported basement membrane:

[0032] Commercially available amino-sulfonated polyether ether ketone (PEEK) was selected as the core substrate and dissolved in N-methylpyrrolidone solvent. 10-20 wt% (preferably 12-18 wt%) of polyvinylidene fluoride (PVDF) was added to this substrate film. The components were uniformly mixed by ultrasonic dispersion for 30-60 min, preferably 35-55 min. The film was then cast using a casting method. The cast film was placed in a vacuum drying oven and dried at 80-100℃ for 12-18 h, preferably 85-95℃, for 14-16 h, ultimately obtaining a homogeneous substrate film.

[0033] (ii) Functionalization of cation exchange layers:

[0034] Prepare a sulfonating agent of 0.5-1.0 mol / L 1,3-propanesulfonate lactone / ethanol, wherein the volume ratio of 1,3-propanesulfonate lactone to ethanol is 1:3-5, preferably 1:3.5-4.5. Immerse one side of the homogeneous substrate membrane in the sulfonating agent and react at 60-80℃ for 4-8 hours, preferably at 65-75℃, for 5-7 hours. After the reaction, hydrolyze the membrane in NaOH solution, then wash repeatedly with deionized water until the washing solution is neutral, and dry to form a cation exchange layer.

[0035] (III) Preparation and coating of modified bentonite-based catalyst layer:

[0036] 1. Preparation of ZnO-ZrO2-supported modified bentonite:

[0037] Acid-base activation: After crushing natural bentonite and passing it through a 200-mesh sieve, add 5-10wt% hydrochloric acid solution, preferably 6-9wt% hydrochloric acid concentration, reflux and stir at 80℃ for 4-6 hours, preferably 4.5-5.5 hours, filter and wash until neutral; then add 5-8wt% sodium hydroxide solution, preferably 6-7wt% sodium hydroxide concentration, stir at 60℃ for 2-3 hours, preferably 2.2-2.8 hours, filter and wash until neutral, and dry at 105℃ for 8 hours to obtain activated bentonite.

[0038] Ion intercalation: Activated bentonite is added to deionized water and ultrasonically dispersed to form a 5-10 wt% suspension, preferably 6-9 wt%. 15-25% (by weight of the activated bentonite) of hexadecyltrimethylammonium bromide is added, preferably 18-22%, by dropwise addition at a rate of 1-2 mL / min, preferably 1.2-1.8 mL / min. The mixture is stirred at 70-80℃ for 3-5 h, preferably 72-78℃, for 3.5-4.5 h. After centrifugation, the mixture is washed until Cl-free. - The organic-intercalated bentonite was obtained by vacuum drying at 60℃ for 6 hours.

[0039] Active component loading: Organically intercalated bentonite was added to a mixed solution of zinc nitrate and zirconium chloride, with a molar ratio of zinc nitrate to zirconium chloride of 1:1 and a total concentration of 0.2-0.5 mol / L, preferably 0.3-0.4 mol / L. The pH of the system was adjusted to 8-9, preferably 8.2-8.8. The mixture was stirred at 50℃ for 4-6 h, preferably for 4.5-5.5 h. After settling, the mixture was filtered and washed until no nitrate was detected. The mixture was then calcined at 450-550℃ for 2-3 h, preferably at 480-520℃, for 2.2-2.8 h, to obtain ZnO-ZrO2-loaded modified bentonite. The loading amount of ZnO-ZrO2 on the modified bentonite was 25-35% of the modified bentonite mass, preferably 28-32%, and the particle size of ZnO-ZrO2 was 20-50 nm, preferably 25-45 nm.

[0040] 2. Catalytic slurry preparation and coating:

[0041] The ZnO-ZrO2-supported modified bentonite was mixed with SPEEK binder at a mass ratio of 7:3. The degree of sulfonation of the SPEEK binder was 50-70%, preferably 55-65%. N-methylpyrrolidone was added and ultrasonically dispersed for 2-3 hours to form a catalytic slurry. The viscosity of this catalytic slurry at 25°C was 500-1500 mPa·s, preferably 600-1400 mPa·s, and the shear rate was 100 s⁻¹. -1 The catalytic slurry is coated onto the surface of the cation exchange layer, with the coating thickness controlled at 5-10 μm, preferably 6-9 μm. After coating, it is pre-dried at 60°C for 3 hours.

[0042] (iv) Functionalization of the anion exchange layer:

[0043] Prepare an anion exchange resin solution of SPEEK modified with 1-vinyl-3-methylimidazolium bromide, with a concentration of 15-25 wt%, preferably 18-22 wt%. Cast the resin solution onto the surface of the catalyst layer and dry it at 40-50°C for 6-8 hours, preferably at 42-48°C for 6.5-7.5 hours, to form the anion exchange layer.

[0044] (v) Composite curing:

[0045] The membrane material, in which the cation exchange layer, catalyst layer, and anion exchange layer are sequentially formed, is protected with nitrogen gas and hot-pressed at 120-140℃ and 0.5-1.0MPa for 30-60 minutes. The preferred hot-pressing temperature is 125-135℃, the preferred hot-pressing pressure is 0.6-0.9MPa, and the preferred hot-pressing time is 35-55 minutes. After natural cooling to room temperature, a high-efficiency monolithic bipolar membrane is obtained.

[0046] This invention utilizes an amino-sulfonated polyether ether ketone (PEEK) and polyvinylidene fluoride (PVDF) composite to prepare a co-supported substrate membrane, enhancing the membrane's mechanical stability and structural density. The substrate membrane is functionalized using a specific ratio of sulfonating agents to ensure the ion exchange capacity of the cation exchange layer. A catalytic layer is constructed using ZnO-ZrO2-modified bentonite, and ion intercalation is employed to optimize the dispersion and loading of active components, thereby enhancing water dissociation catalytic efficiency. A SPEEK anion exchange layer modified with brominated 1-vinyl-3-methylimidazolium forms a highly efficient ion transport channel. Finally, hot-pressing under nitrogen protection ensures the bonding strength and structural integrity between membrane layers. The synergistic effect of each step and component results in a bipolar membrane exhibiting high ion selectivity, low water dissociation voltage, and excellent mechanical properties. Furthermore, the preparation process is stable and controllable, making it suitable for large-scale production.

[0047] To further illustrate the present invention, detailed descriptions are provided below through examples, comparative examples, and performance tests. The amino-sulfonated polyetheretherketone, polyvinylidene fluoride, 1,3-propanesulfonate lactone, ethanol, sodium hydroxide, natural bentonite, hexadecyltrimethylammonium bromide, zinc nitrate, zirconium chloride, SPEEK binder, and 1-vinyl-3-methylimidazole bromide used in the examples and comparative examples of the present invention are all commercially available conventional products. The degree of sulfonation of the SPEEK binder was determined by conventional titration, and the ZnO-ZrO2 loading was determined by inductively coupled plasma mass spectrometry.

[0048] Example 1:

[0049] Preparation of co-supported basement membrane: Take amino-sulfonated polyether ether ketone, dissolve it in N-methylpyrrolidone, add 12 wt% of polyvinylidene fluoride of the basement membrane raw material, ultrasonically disperse for 35 min, cast into a film, place the film in a vacuum drying oven, and vacuum dry at 85℃ for 14 h to obtain a homogeneous basement membrane.

[0050] Cation exchange layer functionalization: Prepare a 0.6 mol / L sulfonating reagent of 1,3-propanesulfonate lactone / ethanol, wherein the volume ratio of 1,3-propanesulfonate lactone to ethanol is 1:3.5. Immerse one side of the homogeneous substrate membrane in the sulfonating reagent and react at 65 °C for 5 h. After the reaction, hydrolyze with 0.5 mol / L NaOH solution, wash with deionized water until neutral, and vacuum dry at 60 °C for 4 h to form a cation exchange layer.

[0051] Preparation and coating of modified bentonite-based catalyst layer:

[0052] a. Acid-base activation: Natural bentonite was pulverized and passed through a 200-mesh sieve, then 6wt% hydrochloric acid solution was added, and the mixture was refluxed and stirred at 80℃ for 4.5h. After filtration and washing until neutral, 6wt% sodium hydroxide solution was added, and the mixture was stirred at 60℃ for 2.2h. After filtration and washing until neutral, the mixture was dried at 105℃ for 8h to obtain activated bentonite.

[0053] b. Ion intercalation: Activated bentonite was added to deionized water and ultrasonically dispersed to form a 6wt% suspension. Hexadecyltrimethylammonium bromide was added dropwise at 1.2 mL / min (18% of the activated bentonite mass). The mixture was stirred at 72°C for 3.5 h, centrifuged, and washed until Cl-free. - The organic-intercalated bentonite was obtained by vacuum drying at 60℃ for 6 hours.

[0054] c. Loading of active components: Organically intercalated bentonite was added to a mixed solution of zinc nitrate and zirconium chloride, with a molar ratio of zinc nitrate to zirconium chloride of 1:1 and a total concentration of 0.3 mol / L. The pH was adjusted to 8.2, and the mixture was stirred at 50°C for 4.5 h. After standing and precipitation, the mixture was filtered and washed until no nitrate was detected. The mixture was then calcined at 480°C for 2.2 h to obtain ZnO-ZrO2-loaded modified bentonite, with a loading amount of 28% of the modified bentonite mass and a ZnO-ZrO2 particle size of 25 nm.

[0055] d. Catalytic slurry preparation and coating: The ZnO-ZrO2-supported modified bentonite and SPEEK binder with 55% sulfonation degree were mixed at a mass ratio of 7:3, and N-methylpyrrolidone was added and ultrasonically dispersed for 2 hours to form a catalytic slurry. The viscosity of the slurry at 25°C was 600 mPa·s, and the shear rate was 100 s⁻¹. -1 It was coated onto the surface of the cation exchange layer, with the coating thickness controlled at 6 μm, and pre-dried at 60℃ for 3 h.

[0056] Functionalization of the anion exchange layer: Prepare an anion exchange resin solution of 18 wt% of 1-vinyl-3-methylimidazolium bromide modified SPEEK, cast it on the surface of the catalyst layer, and dry it at 42°C for 6.5 h to form an anion exchange layer.

[0057] Composite curing: The membrane material, in which the cation exchange layer, catalyst layer and anion exchange layer are formed in sequence, is protected by nitrogen gas and hot-pressed at 125℃ and 0.6MPa for 35 minutes, and then naturally cooled to room temperature to obtain a high-efficiency monolithic bipolar membrane.

[0058] Example 2:

[0059] Preparation of co-supported basement membrane: Take amino-sulfonated polyether ether ketone, dissolve it in N-methylpyrrolidone, add 15 wt% of polyvinylidene fluoride of the total mass of the basement membrane raw material, ultrasonically disperse for 45 min, cast into a film, place the film in a vacuum drying oven, and vacuum dry at 90℃ for 15 h to obtain a homogeneous basement membrane.

[0060] Cation exchange layer functionalization: Prepare a 0.8 mol / L sulfonating reagent of 1,3-propanesulfonate lactone / ethanol, wherein the volume ratio of 1,3-propanesulfonate lactone to ethanol is 1:4. Immerse one side of the homogeneous substrate membrane in the sulfonating reagent and react at 70 °C for 6 h. After the reaction, hydrolyze with 0.5 mol / L NaOH solution, wash with deionized water until neutral, and vacuum dry at 60 °C for 4 h to form a cation exchange layer.

[0061] Preparation and coating of modified bentonite-based catalyst layer:

[0062] a. Acid-base activation: Natural bentonite was pulverized and passed through a 200-mesh sieve, then 7.5wt% hydrochloric acid solution was added, and the mixture was refluxed and stirred at 80℃ for 5 hours. After filtration and washing until neutral, 6.5wt% sodium hydroxide solution was added, and the mixture was stirred at 60℃ for 2.5 hours. After filtration and washing until neutral, the mixture was dried at 105℃ for 8 hours to obtain activated bentonite.

[0063] b. Ion intercalation: Activated bentonite was added to deionized water and ultrasonically dispersed to form a 7.5 wt% suspension. Hexadecyltrimethylammonium bromide was added dropwise at 20% of the activated bentonite mass at a rate of 1.5 mL / min. The mixture was stirred at 75°C for 4 hours, centrifuged, and washed until Cl-free. - The organic-intercalated bentonite was obtained by vacuum drying at 60℃ for 6 hours.

[0064] c. Loading of active components: Organically intercalated bentonite was added to a mixed solution of zinc nitrate and zirconium chloride, with a molar ratio of zinc nitrate to zirconium chloride of 1:1 and a total concentration of 0.35 mol / L. The pH was adjusted to 8.5, and the mixture was stirred at 50°C for 5 h. After settling, the mixture was filtered, washed until no nitrate was detected, and calcined at 500°C for 2.5 h to obtain ZnO-ZrO2-loaded modified bentonite. The loading amount was 30% of the modified bentonite mass, and the particle size of ZnO-ZrO2 was 35 nm. d. Preparation and coating of catalytic slurry: The above-mentioned ZnO-ZrO2-loaded modified bentonite was mixed with SPEEK binder with a sulfonation degree of 60% at a mass ratio of 7:3. N-methylpyrrolidone was added and ultrasonically dispersed for 2.5 h to form a catalytic slurry. The viscosity of the slurry at 25°C was 1000 mPa·s, and the shear rate was 100 s⁻¹. -1 It was coated onto the surface of the cation exchange layer, with the coating thickness controlled at 7.5 μm, and pre-dried at 60℃ for 3 hours.

[0065] Functionalization of the anion exchange layer: Prepare a 20wt% solution of SPEEK modified with 1-vinyl-3-methylimidazolium bromide, cast it on the surface of the catalyst layer, and dry it at 45°C for 7 hours to form an anion exchange layer.

[0066] Composite curing: The membrane material, in which the cation exchange layer, catalyst layer and anion exchange layer are formed in sequence, is protected by nitrogen gas and hot-pressed at 130℃ and 0.75MPa for 45 minutes, and then naturally cooled to room temperature to obtain a high-efficiency monolithic bipolar membrane.

[0067] Example 3:

[0068] Preparation of co-supported basement membrane: Take amino-sulfonated polyether ether ketone, dissolve it in N-methylpyrrolidone, add 18 wt% of polyvinylidene fluoride of the basement membrane raw material, ultrasonically disperse for 55 min, cast into a film, place the film in a vacuum drying oven, and vacuum dry at 95℃ for 16 h to obtain a homogeneous basement membrane.

[0069] Cation exchange layer functionalization: Prepare a 1.0 mol / L sulfonating reagent of 1,3-propanesulfonate lactone / ethanol, wherein the volume ratio of 1,3-propanesulfonate lactone to ethanol is 1:4.5. Immerse one side of the homogeneous substrate membrane in the sulfonating reagent and react at 75 °C for 7 h. After the reaction, hydrolyze with 0.5 mol / L NaOH solution, wash with deionized water until neutral, and vacuum dry at 60 °C for 4 h to form a cation exchange layer.

[0070] Preparation and coating of modified bentonite-based catalyst layer:

[0071] a. Acid-base activation: Natural bentonite was pulverized and passed through a 200-mesh sieve, then 9wt% hydrochloric acid solution was added, and the mixture was refluxed and stirred at 80℃ for 5.5h. After filtration and washing until neutral, 7wt% sodium hydroxide solution was added, and the mixture was stirred at 60℃ for 2.8h. After filtration and washing until neutral, the mixture was dried at 105℃ for 8h to obtain activated bentonite.

[0072] b. Ion intercalation: Activated bentonite was added to deionized water and ultrasonically dispersed to form a 9 wt% suspension. Hexadecyltrimethylammonium bromide was added dropwise at 22% of the activated bentonite mass at a rate of 1.8 mL / min. The mixture was stirred at 78°C for 4.5 h, centrifuged, and washed until Cl-free. - The organic-intercalated bentonite was obtained by vacuum drying at 60℃ for 6 hours.

[0073] c. Loading of active components: Organically intercalated bentonite was added to a mixed solution of zinc nitrate and zirconium chloride, with a molar ratio of zinc nitrate to zirconium chloride of 1:1 and a total concentration of 0.4 mol / L. The pH was adjusted to 8.8, and the mixture was stirred at 50℃ for 5.5 h. After standing and precipitation, the mixture was filtered and washed until no nitrate ions were detected. The mixture was then calcined at 520℃ for 2.8 h to obtain ZnO-ZrO2-loaded modified bentonite, with a loading amount of 32% of the modified bentonite mass and a ZnO-ZrO2 particle size of 45 nm.

[0074] d. Catalytic slurry preparation and coating: The ZnO-ZrO2-supported modified bentonite and SPEEK binder with 65% sulfonation degree were mixed at a mass ratio of 7:3, and N-methylpyrrolidone was added and ultrasonically dispersed for 3 hours to form a catalytic slurry. The viscosity of the slurry at 25°C was 1400 mPa·s, and the shear rate was 100 s⁻¹. -1 It was coated onto the surface of the cation exchange layer, with the coating thickness controlled at 9 μm, and pre-dried at 60℃ for 3 h.

[0075] Functionalization of the anion exchange layer: Prepare a 22 wt% solution of SPEEK modified with 1-vinyl-3-methylimidazolium bromide, cast it on the surface of the catalyst layer, and dry it at 48°C for 7.5 h to form an anion exchange layer.

[0076] Composite curing: The membrane material, in which the cation exchange layer, catalyst layer and anion exchange layer are formed in sequence, is protected by nitrogen gas and hot-pressed at 135℃ and 0.9MPa for 55 minutes, and then naturally cooled to room temperature to obtain a high-efficiency monolithic bipolar membrane.

[0077] Comparative Example 1:

[0078] Preparation of the base film: Take amino-sulfonated polyether ether ketone, dissolve it in N-methylpyrrolidone, ultrasonically disperse it for 35 min, and then cast it into a film. Place the film in a vacuum drying oven and vacuum dry it at 85℃ for 14 h to obtain the base film (without polyvinylidene fluoride).

[0079] Cation exchange layer functionalization: This is exactly the same as step 2 in Example 1, i.e., preparing a 0.6 mol / L 1,3-propanesulfonic acid lactone / ethanol sulfonating agent (volume ratio 1:3.5), reacting at 65°C for 5 h, hydrolyzing with NaOH solution, washing until neutral, and drying to form a cation exchange layer.

[0080] Preparation and coating of modified bentonite-based catalyst layer: The process is exactly the same as step 3 in Example 1, that is, ZnO-ZrO2-supported modified bentonite is prepared by acid-base activation, ion intercalation, and loading of active components, and then mixed with SPEEK binder to prepare catalyst slurry, which is then coated and pre-dried.

[0081] Functionalization of the anion exchange layer: This is exactly the same as step 4 in Example 1, that is, preparing an 18wt% anion exchange resin solution, casting and drying to form an anion exchange layer.

[0082] Composite curing: exactly the same as step 5 of Example 1, that is, hot pressing at 125°C and 0.6MPa for 35 minutes under nitrogen protection, and then cooling to obtain a bipolar film.

[0083] Comparative Example 2:

[0084] Preparation of co-supported base membrane: exactly the same as in Example 1, i.e., adding 12wt% polyvinylidene fluoride, ultrasonically dispersing for 35 min, and vacuum drying at 85℃ for 14 h to obtain a homogeneous base membrane.

[0085] Functionalization of the cation exchange layer: exactly the same as in Example 1.

[0086] Catalyst layer preparation and coating: SPEEK binder with 55% sulfonation degree was added and ultrasonically dispersed with N-methylpyrrolidone for 2 hours to form a slurry. The viscosity of the slurry at 25℃ was 600 mPa·s and the shear rate was 100 s⁻¹. -1 It was coated onto the surface of the cation exchange layer, with the coating thickness controlled at 6 μm, and pre-dried at 60℃ for 3 h (without ZnO-ZrO2-loaded modified bentonite).

[0087] Functionalization of the anion exchange layer: exactly the same as in Example 1.

[0088] Composite curing: exactly the same as in Example 1, to obtain a bipolar film.

[0089] Comparative Example 3:

[0090] Preparation of co-supported basement membrane: exactly the same as in Example 1.

[0091] Functionalization of the cation exchange layer: exactly the same as in Example 1.

[0092] Preparation and coating of modified bentonite-based catalyst layer: a. Acid-base activation: exactly the same as in Example 1, i.e., refluxed with 6wt% hydrochloric acid for 4.5 h, stirred with 6wt% sodium hydroxide for 2.2 h, and dried to obtain activated bentonite. b. Loading of active components: the activated bentonite was directly added to a mixed solution of zinc nitrate and zirconium chloride (same as in Example 1: molar ratio 1:1, total concentration 0.3 mol / L, pH 8.2, stirred at 50℃ for 4.5 h), filtered and washed, and then calcined at 480℃ for 2.2 h to obtain ZnO-ZrO2-loaded bentonite, the loading amount of which was 15% of the mass of modified bentonite, and the particle size of ZnO-ZrO2 was 60 nm (ion intercalation step omitted). c. Preparation and coating of catalyst slurry: exactly the same as in Example 1.

[0093] Functionalization of the anion exchange layer: exactly the same as in Example 1.

[0094] Composite curing: exactly the same as in Example 1, to obtain a bipolar film.

[0095] Comparative Example 4:

[0096] Preparation of co-supported basement membrane: exactly the same as in Example 1.

[0097] Functionalization of the cation exchange layer: exactly the same as in Example 1.

[0098] Preparation and coating of modified bentonite-based catalyst layer: exactly the same as in Example 1.

[0099] Functionalization of the anion exchange layer: exactly the same as in Example 1.

[0100] Composite curing: The membrane material, in which the cation exchange layer, catalyst layer and anion exchange layer are formed in sequence, is hot-pressed at 125℃ and 0.6MPa for 35min (without nitrogen protection), and then naturally cooled to room temperature to obtain a bipolar membrane.

[0101] test:

[0102] Key performance tests of high-efficiency monolithic bipolar films;

[0103] The core performance indicators of the bipolar membranes prepared in Examples 1-3 and Comparative Examples 1-4 were tested, including cation transport number, water dissociation voltage, and tensile strength.

[0104] Cation transport number test: The membrane potential method was used. The bipolar membrane was fixed in the middle of a two-chamber electrolytic cell. 0.1 mol / L NaCl solution was added to both sides. Ag / AgCl electrodes were inserted. The potential difference across the membrane was measured using an electrochemical workstation. The cation transport number was calculated according to the Nernst equation. Each sample was tested in parallel 3 times. The average value was taken and the error range was calculated.

[0105] Water dissociation voltage test: A two-chamber electrolytic cell was used. 0.5 mol / L HCl solution was added to the left chamber, and 0.5 mol / L NaOH solution was added to the right chamber. A bipolar membrane was used as the separating medium, and platinum sheets were used as the anode and cathode. A constant current density of 100 mA / cm² was applied. 2 Record the value of the voltage after it stabilizes during the electrolysis process, which is the water dissociation voltage. Each sample is tested in parallel 3 times, and the average value is taken and the error range is calculated.

[0106] Tensile strength test: The bipolar membrane was cut into standard strips of 10mm × 50mm and tested using a universal tensile testing machine. The tensile rate was set to 5mm / min. Five valid strips were tested for each sample, and the average value was taken and the error range was calculated. The results are as follows:

[0107] Table 1

[0108] Sample number Cation transference number Water dissociation voltage (V) Tensile strength (MPa) Example 1 0.96±0.02 0.85±0.03 28.5±1.2 Example 2 0.98±0.01 0.78±0.02 32.3±1.5 Example 3 0.97±0.02 0.81±0.03 30.8±1.3 Comparative Example 1 0.82±0.03 1.52±0.05 15.6±0.8 Comparative Example 2 0.90±0.02 1.85±0.06 25.3±1.1 Comparative Example 3 0.88±0.03 1.63±0.04 24.7±1.0 Comparative Example 4 0.93±0.02 1.05±0.03 22.4±1.0

[0109] As shown in Table 1, the performance advantages of the examples are significant: the bipolar membranes prepared in Examples 1-3 all exhibit excellent comprehensive performance, with cation transference numbers all above 0.96, indicating extremely strong ion selectivity; water dissociation voltages all below 0.85V, demonstrating highly efficient water dissociation catalytic ability; and tensile strengths all exceeding 28MPa, indicating good mechanical stability. Among them, Example 2 has the best comprehensive performance, with a cation transference number reaching 0.98, a water dissociation voltage as low as 0.78V, and a tensile strength as high as 32.3MPa. This is because its preparation parameters are all within the preferred range of this invention, and the amount of polyvinylidene fluoride added, the loading of active components in the catalyst layer, and the hot-pressing process conditions work together to achieve the best balance between the structural integrity of the membrane material, ion transport efficiency, and catalytic activity.

[0110] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not describe all details exhaustively, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification.

Claims

1. A method for preparing a high-efficiency monolithic bipolar film, characterized in that, Includes the following steps: Preparation of co-supported basement membrane: Dissolve amino-sulfonated polyether ether ketone in N-methylpyrrolidone, add 10-20 wt% of polyvinylidene fluoride of the total mass of the basement membrane raw material, ultrasonically disperse for 30-60 min, cast into a film, and vacuum dry at 80-100℃ for 12-18 h to obtain a homogeneous basement membrane. Cation exchange layer functionalization: One side of the base membrane is immersed in 0.5-1.0 mol / L of 1,3-propanesulfonic acid lactone / ethanol sulfonation reagent and reacted at 60-80℃ for 4-8 hours. After hydrolysis with NaOH solution and washing with deionized water until neutral, the cation exchange layer is formed after drying. Preparation and coating of modified bentonite-based catalyst layer: ZnO-ZrO2-supported modified bentonite and SPEEK binder were mixed at a mass ratio of 7:3, N-methylpyrrolidone was added and ultrasonically dispersed for 2-3 hours to form a catalyst slurry, which was then coated on the surface of the cation exchange layer. The coating thickness was controlled at 5-10 μm and pre-dried at 60℃ for 3 hours. Functionalization of the anion exchange layer: A solution of anion exchange resin of brominated 1-vinyl-3-methylimidazolium modified SPEEK is cast onto the surface of the catalyst layer and dried at 40-50℃ for 6-8 hours to form an anion exchange layer. Composite curing: The membrane material, in which the cation exchange layer, catalyst layer and anion exchange layer are formed in sequence, is hot-pressed at 120-140℃ and 0.5-1.0MPa for 30-60 minutes and then naturally cooled to room temperature to obtain a high-efficiency monolithic bipolar membrane.

2. The preparation method according to claim 1, characterized in that, In step S2, the volume ratio of 1,3-propanesulfonate lactone to ethanol in the sulfonating reagent is 1:3-5.

3. The preparation method according to claim 1, characterized in that, The preparation steps of the ZnO-ZrO2-supported modified bentonite in step S3 include: Acid-base activation: Crush natural bentonite through a 200-mesh sieve, add 5-10wt% hydrochloric acid solution, reflux and stir at 80℃ for 4-6 hours, filter and wash until neutral; then add 5-8wt% sodium hydroxide solution, stir at 60℃ for 2-3 hours, filter and wash until neutral, and dry at 105℃ for 8 hours to obtain activated bentonite. Ion intercalation: The activated bentonite is added to deionized water and ultrasonically dispersed to form a 5-10 wt% suspension. Then, 15-25% (by weight of the activated bentonite) of hexadecyltrimethylammonium bromide is added. The mixture is stirred at 70-80°C for 3-5 hours, centrifuged, and washed until Cl-free. - The organic-intercalated bentonite was obtained by vacuum drying at 60℃ for 6 hours. Active component loading: The organic intercalated bentonite was added to a mixed solution of zinc nitrate and zirconium chloride, the pH was adjusted to 8-9, stirred at 50℃ for 4-6h, allowed to stand and precipitate, filtered, washed until no nitrate ions were detected, and calcined at 450-550℃ for 2-3h to obtain the active component.

4. The preparation method according to claim 3, characterized in that, In a mixed solution of zinc nitrate and zirconium chloride, the molar ratio of zinc nitrate to zirconium chloride is 1:1, and the total concentration is 0.2-0.5 mol / L.

5. The preparation method according to claim 3, characterized in that, The cetyltrimethylammonium bromide was added dropwise at a rate of 1-2 mL / min.

6. The preparation method according to claim 1, characterized in that, In step S3, the loading amount of ZnO-ZrO2 on the modified bentonite is 25-35% of the mass of the modified bentonite, and the particle size of ZnO-ZrO2 is 20-50 nm.

7. The preparation method according to claim 1, characterized in that, In step S3, the degree of sulfonation of the SPEEK adhesive is 50-70%.

8. The preparation method according to claim 1, characterized in that, In step S3, the viscosity of the catalytic slurry at 25°C is 500-1500 mPa·s, and the shear rate is 100 s⁻¹. -1 .

9. The preparation method according to claim 1, characterized in that, The concentration of the anion exchange resin solution in step S4 is 15-25 wt%.

10. The preparation method according to claim 1, characterized in that, Nitrogen gas is introduced for protection during the hot pressing process in step S5.

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