Preparation method of functional composite diaphragm

Abstract

The application discloses a preparation method of a functional composite diaphragm and relates to the technical field of hydrogen production by water electrolysis. The preparation method comprises the following steps: preparing a casting solution: mixing a polymer with a solvent, heating and dispersing to prepare a uniform polymer solution; mixing zirconium oxide and a coupling agent with the solvent, ultrasonic dispersion to obtain an inorganic material dispersion liquid containing the coupling agent; under stirring, adding the dispersion liquid into the polymer solution, continuously stirring to obtain a uniform casting solution; forming a base film: coating the casting solution on a polyphenylene sulfide support net, placing in an oven after standing at room temperature to dry, and obtaining a composite base film; surface modification: sequentially immersing the composite base film in a first organic alkali solution and a second organic alkali solution, washing with a solvent after each immersion, and obtaining the functional composite diaphragm after washing.

Description

Technical Field

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

[0002] As the global energy structure shifts towards a green and low-carbon model, water electrolysis for hydrogen production, as a key link between renewable energy and clean fuels, is receiving unprecedented attention. Among the core components of the electrolyzer, the performance of the membrane is crucial, requiring both high-efficiency ion conduction and excellent gas barrier properties. To overcome the limitations of traditional single-material membranes, organic-inorganic composite membranes have emerged. These materials, through ingenious structural design, successfully combine the excellent film-forming properties and flexibility of polymers with the inherent high hydrophilicity, thermal stability, and chemical inertness of inorganic materials, demonstrating enormous application potential.

[0003] However, current composite membranes face two main limitations in practical applications: First, their operating temperature range is clearly limited. Commercial composite membranes typically require operating temperatures below 110°C to avoid exacerbating the attack of hydroxyl groups on the polymer backbone under high temperatures, which could trigger degradation reactions and lead to membrane peeling and a significant decrease in membrane life. This characteristic places extremely high demands on the temperature field uniformity management and system design of industrial-grade large-scale electrolyzers. Second, the sheet resistivity of these membranes is currently high, with a sheet resistivity of approximately 0.3 Ω·cm² measured at room temperature based on a 500 μm thick membrane. When used in combination with conventional electrodes, at a current density of 4000 A·m... -2 Under these conditions, the energy consumption of the electrolysis system is between 3.9 and 4.5 kWh·Nm³. -3 This is not conducive to reducing the cost of hydrogen production.

[0004] Therefore, current organic-inorganic composite ion exchange membranes still need improvement in terms of high-temperature stability and ion conduction performance. Summary of the Invention

[0005] In view of this, the present invention provides a method for preparing a functional composite membrane. The functional composite membrane of this application exhibits significant advantages in preparation process, interface design, and functional durability, providing an innovative solution for advancing high-performance, long-life alkaline water electrolysis hydrogen production technology. Through an organic base functionalization strategy, the problem of insufficient durability in traditional modification methods is successfully solved, while the unique interface design effectively prevents polymer aging and the shedding of inorganic fillers, providing a reliable material basis for the commercial application of alkaline water electrolysis hydrogen production technology.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: A method for preparing a functional composite membrane includes the following steps: S1. Preparation of casting solution: The polymer and solvent are mixed and dispersed by heating to prepare a homogeneous polymer solution; Zirconia (ZrO2) and coupling agent are mixed with solvent and dispersed by ultrasonication to obtain an inorganic material dispersion containing coupling agent; Under stirring conditions, the dispersion is added to the polymer solution and stirred continuously to obtain a uniform casting solution. S2. Base film forming: The casting solution is coated onto the polyphenylene sulfide (PPS) support mesh, left to stand at room temperature, and then dried in an oven to obtain the composite base film; S3. Surface modification: The composite base membrane is sequentially immersed in a first organic alkali solution and a second organic alkali solution. After each immersion, it is rinsed with solvent. After rinsing, the functional composite membrane is obtained.

[0007] Preferably, the polymer in step S1 is one or a mixture of polysulfone (PSF), polyethersulfone (PES), sulfonated polysulfone (SPSF), and sulfonated polyethersulfone (SPES), and the polymer accounts for 10-30% of the mass of the casting solution.

[0008] Preferably, the solvent in step S1 includes any one of N-methylpyrrolidone (NMP), dimethyl sulfoxide (DMSO), N,N-dimethylformamide (DMF), and N,N-dimethylacetamide (DMAc), and the solvent accounts for 20-80% of the mass of the casting solution.

[0009] Preferably, the coupling agent in step S1 includes any one of diethanolamine phosphate (DEA-P), hexadecyltrimethylammonium bromide phosphate (CTAB-P), and triethylenetetramine phosphate (TETA-P), and the coupling agent accounts for 0.1-3% of the casting solution by mass, while zirconium oxide accounts for 10-50% of the casting solution by mass.

[0010] Preferably, the ultrasonic power in step S1 is 50~100W and the stirring speed is 200~600rpm.

[0011] Preferably, the drying temperature in step S2 is 60~120℃ and the time is 0.5~12h.

[0012] Preferably, the first organic base solution in step S3 is one or a mixture of tetrabutylammonium hydroxide, tetrabutylphosphine hydroxide, and tetraphenylphosphine hydroxide.

[0013] Preferably, in step S3, the second organic base solution is one or more of tetramethylammonium hydroxide, tetraethylammonium hydroxide, and choline hydroxide, and the concentrations of both the first and second organic base solutions are 0.1~2.0 mol / L.

[0014] In the preparation method of the functional composite membrane described in this invention, the selected organic base molecule contains specific functional groups (such as quaternary ammonium groups, quaternary phosphorus groups, etc.). These functional groups can dissociate in situ, continuously providing OH-. - An ion source is used to achieve efficient, stable, and sustainable hydroxide ion transport at the molecular scale. Furthermore, by using coupling agents to covalently crosslink organic bases and inorganic materials, the micro-crosslinking structure of the membrane can be optimized, enhancing the intermolecular interactions and thus significantly improving the membrane's chemical stability and structural durability in strongly alkaline environments.

[0015] Preferably, the solvents of both the first organic base solution and the second organic base solution include any one of methanol, ethanol, toluene, chloroform, dichloromethane, and water.

[0016] Preferably, the surface modification steps in step S3 specifically include: First impregnation: The composite base film is impregnated in the first organic alkaline solution and kept at 25~40℃ for 30~120min; First rinse: Remove the composite base membrane from the first organic alkaline solution and rinse or immerse it 1 to 3 times with ethanol or deionized water as the rinsing solvent, each time for 1 to 2 minutes; Second impregnation: The rinsed composite base film is immediately impregnated in the second organic alkaline solution and kept at 25~40℃ for 10~30 min; Second rinse: Remove the diaphragm again and rinse gently with deionized water 2-4 times.

[0017] As can be seen from the above technical solution, compared with the prior art, the present invention has the following beneficial effects: (1) Organic base molecules can spontaneously and completely dissociate in the system, allowing organic base molecules to continuously provide mobile OH groups. - The membrane can still maintain a high intrinsic OH group level inside the membrane body. - The increased ion concentration significantly lowers the energy barrier for ion transport, thereby substantially reducing the sheet resistance of the membrane and improving the energy efficiency of the electrolyzer. Organic base molecules possess extremely strong hydration capabilities, rapidly adsorbing water molecules to form a stable hydration layer around them. This completely alters the wettability of the originally poorly hydrophobic or hydrophilic polymer surface, allowing the electrolyte to fully wet all the pores of the membrane, providing the essential medium environment for ion conduction.

[0018] (2) The phosphate ester group at one end of the coupling agent forms a strong ≡Zr-OP=O covalent bond with the surface of ZrO2 nanoparticles. On the oxygen evolution side, this dense layer works synergistically with the inorganic particles to form the first physical barrier to block the penetration of reactive oxygen free radicals (ROS), delaying the oxidative attack of ROS on the internal polymer matrix and improving the antioxidant properties of the membrane.

[0019] (3) The organic functional groups (such as amino groups and long-chain alkyl groups) at the other end of the coupling agent can be bonded to the polymer matrix through various non-covalent forces such as hydrogen bonds, ion-dipole interactions, hydrophobic effects, and van der Waals forces. These abundant intermolecular forces are indirectly and firmly fixed to the surface of inorganic particles through the "coupling agent bridge", which completely solves the industry problem of easy dissolution and loss of organic base functional layers, and ensures the durability and lifespan of the modification effect. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0021] Figure 1 The image shows a scanning electron microscope (SEM) image of the surface of the composite membrane prepared in Example 1.

[0022] Figure 2 The image shows a cross-sectional scanning electron microscope image of the composite membrane prepared in Example 1. Detailed Implementation

[0023] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some 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.

[0024] Example 1

[0025] 1. Preparation of casting solution: 5g of polysulfone (PSF) was dissolved in 10g of N-methylpyrrolidone (NMP) and stirred in a 70°C water bath for 6h to obtain a homogeneous polymer solution. 8g of nano-zirconia (ZrO2) and 0.15g of diethanolamine phosphate (DEA-P) were added to 10g of NMP and ultrasonically dispersed for 2h to obtain a dispersion. The dispersion was then added to the polymer solution under stirring, and stirring was continued for 12h to obtain a uniform casting solution.

[0026] 2. Base film forming: The casting solution is scraped onto the PPS support mesh, left at room temperature for 10 minutes, and then transferred to an 80°C vacuum oven to dry for 8 hours to obtain a composite base film.

[0027] 3. Surface modification: The composite base membrane was immersed in a 0.5 mol / L tetrabutylammonium hydroxide ethanol solution for 60 min (25°C), and then rinsed three times with ethanol. It was then immersed in a 0.1 mol / L tetramethylammonium hydroxide aqueous solution for 30 min (25°C), and then rinsed three times with deionized water to obtain the functional composite membrane.

[0028] Example 2

[0029] 1. Preparation of casting solution: Polyethersulfone was used to replace the polysulfone in Example 1, and the remaining steps were the same as in Example 1.

[0030] 2. Base film forming: Same as in Example 1.

[0031] 3. Surface modification: The composite base membrane was first immersed in a 1.0 mol / L tetrabutylammonium hydroxide methanol solution for 120 min (30°C), and then rinsed twice with ethanol. Next, it was immersed in a 0.5 mol / L choline hydroxide aqueous solution for 20 min (40°C), and then rinsed four times with deionized water to obtain the functional composite membrane.

[0032] Example 3

[0033] 1. Preparation of casting solution: N-methylpyrrolidone in Example 1 was replaced with dimethyl sulfoxide, and the remaining steps were the same as in Example 1.

[0034] 2. Base film forming: Same as in Example 1.

[0035] 3. Surface modification: The composite membrane was first immersed in a 2.0 mol / L tetrabutylammonium hydroxide methanol solution for 100 min (25°C), and then rinsed three times with ethanol. Next, it was immersed in a 0.2 mol / L tetramethylammonium hydroxide aqueous solution for 15 min (40°C), and then rinsed four times with deionized water to obtain the functional composite membrane.

[0036] Example 4

[0037] 1. Preparation of casting solution: Same as in Example 1.

[0038] 2. Base film forming: The casting solution is scraped onto the PPS support mesh, left at room temperature for 10 minutes, and then transferred to a 60°C vacuum oven to dry for 12 hours to obtain a composite base film.

[0039] 3. Surface modification: The composite membrane was first immersed in a 0.8 mol / L tetrabutylphosphonium hydroxide methanol solution for 90 min (25°C), and then rinsed with ethanol. Next, it was immersed in a 0.5 mol / L tetraethylammonium hydroxide aqueous solution for 30 min (40°C), and then rinsed three times with deionized water to obtain the functional composite membrane.

[0040] Example 5

[0041] 1. Preparation of casting solution: Replace DEA-P in Example 1 with 0.15g of triethylenetetramine phosphate (TETA-P), and follow the same steps as in Example 1.

[0042] 2. Base film forming: Same as in Example 1.

[0043] 3. Surface modification: Same as in Example 2.

[0044] Comparative Example

[0045] At room temperature, 5 g of polysulfone (PSF) and 8 g of zirconium oxide nanoparticles were dispersed in 20 g of N-methyl-2-pyrrolidone (NMP) and stirred at high speed using a ball mill to obtain a homogeneous and stable casting solution. The obtained casting solution was coated onto a PPS support mesh and then slowly immersed in deionized water at room temperature to complete the phase inversion. The resulting membrane was then soaked in deionized water for 24 h to thoroughly remove residual solvent, finally preparing a polysulfone-ZrO2 composite membrane.

[0046] Performance testing: The membranes for alkaline water electrolysis hydrogen production prepared in Examples 1-5 and comparative examples were tested according to the following methods.

[0047] 1. Tensile strength: The tensile strength of the diaphragms in the test examples and comparative examples were determined according to GB / T 1040 "Determination of Tensile Properties of Plastics and Composite Materials"; 2. Sheet resistance test: In accordance with the provisions of standard SJ / T-10171-2016 "General Test Method for Basic Performance of Alkaline Battery Separator", the sheet resistance of the separators of the examples and comparative examples was tested by electrochemical workstation. 3. Electrolysis performance: The diaphragms prepared in the examples and comparative examples were assembled into an electrolytic cell (effective area 5 cm²), and a 30 wt% potassium hydroxide aqueous solution was used. The temperature was controlled at 90 °C, and the current density at 2 V was tested. 4. Antioxidant coefficient test: The antioxidant coefficient of the separators in the examples and comparative examples was tested according to the standard NB / T 42080-2023 "General Technical Conditions and Test Methods for Ion Conducting Membranes for Vanadium Redox Flow Batteries". 5. Alkali loss test: The membrane was treated in a hydrothermal reactor in a closed environment at 120 ℃ and 30 wt% KOH solution for 24 h, and the diaphragm mass loss rate after alkali treatment was measured.

[0048] The test results are shown in Table 1: Table 1

[0049] According to the test results shown in Table 1, the composite membrane prepared in the examples exhibits significantly higher tensile strength than the comparative example, indicating that the mechanical properties of the membrane are effectively improved after modification with organic alkali. Under the same test voltage conditions, the electrolyzer assembled using Examples 1-5 shows a higher current density compared to the comparative example, and its sheet resistance is significantly reduced by about 50%, indicating that the organic alkali-modified membrane has superior conductivity, which helps to reduce the energy loss of alkaline electrolyzers and improve the efficiency of hydrogen production from water electrolysis. In the accelerated aging test simulating harsh operating environments, the oxidation resistance coefficient and alkali loss rate are also significantly lower than those of the comparative example, which directly confirms that the functional layer synergistically constructed by organic alkali and coupling agent has exceptional chemical stability and anti-dissolution ability, fundamentally solving the technical pain point of easy degradation of functional layers. The above results show that this study has successfully achieved synergistic optimization of the mechanical strength, conductivity, and stability of the membrane material through innovative interface design and molecular anchoring strategy, providing a reliable solution for cost reduction, efficiency improvement, and large-scale application of water electrolysis for hydrogen production.

[0050] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to the method section.

[0051] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing a functional composite diaphragm, characterized in that, Includes the following steps: S1. Preparation of casting solution: The polymer is mixed with a solvent and heated to disperse, thus preparing a homogeneous polymer solution; zirconium oxide and a coupling agent are mixed with a solvent and ultrasonically dispersed to obtain an inorganic material dispersion containing the coupling agent; under stirring conditions, the dispersion is added to the polymer solution and stirred continuously to obtain a uniform casting solution; the coupling agent is selected from any one of diethanolamine phosphate and triethylenetetramine phosphate, and the coupling agent accounts for 0.1-3% of the mass of the casting solution, while zirconium oxide accounts for 10-50% of the mass of the casting solution; the polymer is one or more of polysulfone, polyethersulfone, sulfonated polysulfone, and sulfonated polyethersulfone. S2. Base film forming: The casting solution is coated onto the polyphenylene sulfide support mesh, left to stand at room temperature, and then dried in an oven to obtain the composite base film. S3. Surface modification: The composite base membrane is sequentially immersed in a first organic alkali solution and a second organic alkali solution, and rinsed with solvent after each immersion. After rinsing, the functional composite membrane is obtained. The first organic alkali solution is one or more of tetrabutylammonium hydroxide, tetrabutylphosphine hydroxide, and tetraphenylphosphine hydroxide. The second organic alkali solution is one or more of tetramethylammonium hydroxide, tetraethylammonium hydroxide, and choline hydroxide. The concentrations of the first and second organic alkali solutions are both 0.1~2.0 mol / L.

2. The method for preparing a functional composite diaphragm according to claim 1, characterized in that, In step S1, the polymer accounts for 10-30% of the mass of the casting solution.

3. The method for preparing a functional composite membrane according to claim 1, characterized in that, The solvent in step S1 is selected from any one of N-methylpyrrolidone, dimethyl sulfoxide, N,N-dimethylformamide, and N,N-dimethylacetamide, and the solvent accounts for 20-80% of the mass of the casting solution.

4. The method for preparing a functional composite diaphragm according to claim 1, characterized in that, The ultrasonic power in step S1 is 50~100W, and the stirring speed is 200~600rpm.

5. The method for preparing a functional composite diaphragm according to claim 1, characterized in that, The drying temperature in step S2 is 60~120℃, and the time is 0.5~12h.

6. The method for preparing a functional composite membrane according to claim 1, characterized in that, The solvents for both the first and second organic base solutions are selected from any one of methanol, ethanol, toluene, chloroform, dichloromethane, and water.

7. The method for preparing a functional composite diaphragm according to claim 1, characterized in that, The specific steps of surface modification described in step S3 include: First impregnation: The composite base film is impregnated in the first organic alkaline solution and kept at 25~40℃ for 30~120min; First rinse: Remove the composite base membrane from the first organic alkaline solution and rinse it 1-3 times with ethanol or deionized water as the rinsing solvent, each time for 1-2 minutes; Second impregnation: The rinsed composite base film is immediately impregnated in the second organic alkaline solution and kept at 25~40℃ for 10~30 min; Second rinse: Take out the composite base membrane again and rinse it gently with deionized water 2-4 times.

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