An ultra-low surface resistivity composite membrane for alkaline water electrolysis based on titanium dioxide and its preparation method.

Abstract

This invention discloses a method for preparing an ultra-low surface resistivity composite membrane for alkaline water electrolysis based on titanium dioxide, belonging to the field of water electrolysis for hydrogen production technology. The invention involves mixing N-methylpyrrolidone and polysulfone to form a uniform, transparent, viscous liquid; then preparing a mixture using N-methylpyrrolidone, carboxymethyl cellulose, and polyethylene glycol; and finally adding inorganic particles to obtain a casting solution. The casting solution is then used to create a membrane on polyphenylene sulfide (PPS) fibers, followed by phase inversion to obtain the ultra-low surface resistivity composite membrane for alkaline water electrolysis based on titanium dioxide. This invention uses titanium dioxide as the inorganic particle, adds carboxymethyl cellulose to fix the particles and enhance toughness, and uses polyethylene glycol as a pore-forming agent to form a microporous structure and fix the particles; the combination of these two improves tensile strength. This method has advantages such as simple operation, low cost, and high yield, and the membrane exhibits low surface resistivity and high airtightness.

Description

Technical Field

[0001] This invention relates to the field of water electrolysis for hydrogen production technology, and more specifically to an ultra-low surface resistance composite membrane for alkaline water electrolysis based on titanium dioxide and its preparation method. Background Technology

[0002] Hydrogen energy, as a zero-carbon emission secondary energy source, can be utilized in various forms (fuel, chemical feedstock, energy storage medium). "Green hydrogen" produced by renewable energy electrolysis of water can achieve zero carbon emissions throughout its entire life cycle, making it a key driver of energy transition. Alkaline water electrolysis (AWE), currently the most mature and commercially viable electrolysis route for hydrogen production, offers significant cost advantages compared to proton exchange membrane (PEM), solid oxide electrolysis (SOEC), and anion exchange membrane (AEM) electrolysis technologies.

[0003] my country holds a leading position globally in the field of alkaline electrolysis equipment, and this technology has been established as the mainstream solution for future green hydrogen production. Against this backdrop, the performance improvement of the alkaline water electrolysis membrane, as a core component of the electrolyzer, is crucial for hydrogen production efficiency. Current technological advancements require membranes to balance high porosity and high gas barrier properties, achieve a balance between thickness reduction and mechanical strength, and possess excellent resistance to alkali corrosion. The porous structure can serve as an ion transport channel, but it must isolate gases to prevent cross-contamination. Membrane materials have undergone a series of technological evolutions. The first-generation asbestos membrane (i.e., asbestos fiber) had good gas barrier properties but was carcinogenic, prone to swelling under high pressure, and had high electrical resistance, thus it was gradually phased out. Currently, the mainstream is the PPS membrane (PPS matrix), which has advantages such as high temperature resistance, alkali corrosion resistance, and high mechanical strength. However, its natural hydrophobicity leads to high internal resistance, and the gas barrier properties under the network structure are insufficient, posing an explosion hazard when the anode and cathode gases mix. Composite membranes represent a third-generation emerging direction. They consist of a PPS substrate combined with an inorganic ceramic coating or an organic polymer (such as sulfonated tetrafluoroethylene) to form a "sandwich" structure. This combines the hydrophilicity and gas barrier properties of the materials, thereby reducing the membrane's surface resistivity and improving its performance.

[0004] For composite membranes, preventing coating peeling and enhancing their mechanical properties and durability while combining the advantages of different materials are bottlenecks in formulation and industrialization. Among mainstream membrane synthesis methods, the phase inversion method can control the formation of micropore morphology and structure by influencing the temperature, humidity, and rate of phase inversion. Its equipment is simple, the process is mature, suitable for large-scale production, and its low-temperature operation is energy-saving and safe, making it the preferred process for preparing composite membranes.

[0005] Typical formulations for composite membranes typically include the following components: polymer matrix material, hydrophilic inorganic particles, hydrophilic modifier, binder, pore-forming agent, and PPS reinforcing mesh. Their preparation primarily relies on phase inversion to control the porous structure, while the core objective of formulation optimization is to synergistically improve the overall performance of the membrane, including reducing sheet resistivity, increasing bubble point pressure, and extending service life. Loading inorganic particles such as zirconium dioxide and titanium dioxide can effectively reduce sheet resistivity. However, in current formulations, titanium dioxide, due to its high hydrophilicity, while significantly reducing sheet resistivity, can easily agglomerate if the proportion is too high, thus reducing mechanical strength and gas barrier properties, accelerating polymer aging, and leading to dissolution and loss. Zirconia, on the other hand, enhances mechanical properties and has stronger corrosion resistance, but its electrical conductivity is lower than that of titanium dioxide. Pore-forming agents such as PVP particles can easily cause the loss of inorganic particles during phase inversion. Binders such as polyacrylamide require high temperatures to dissolve, and subsequent precipitation can affect membrane smoothness, thus impacting performance.

[0006] Patent CN120291366A discloses an ultrathin alkaline water electrolysis composite membrane modified with sodium carboxymethyl cellulose, its preparation method, and its application. It discloses a scheme using sodium carboxymethyl cellulose as a hydrophilic modifier. However, the sodium carboxylate groups of sodium carboxymethyl cellulose are highly polar, and although easily dispersed, they are prone to causing membrane swelling. Patent CN116024825A discloses a method for preparing a novel microporous membrane for alkaline water electrolysis, the resulting product, and its application. It uses polyethylene glycol as a raw material to prepare a composite membrane, but the composite membrane obtained from polyethylene glycol alone lacks sufficient hydrophilicity.

[0007] Therefore, improving the composite membrane formulation to achieve a balance between low surface resistivity and high tensile strength, and further improving the membrane performance, is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0008] In view of this, the present invention uses titanium dioxide as inorganic particles, composite zirconium dioxide, and carboxymethyl cellulose to fix the particles and enhance toughness, and polyethylene glycol as a pore-forming agent to form a microporous structure and fix the particles. The combination of the two improves tensile strength, thereby preparing an ultra-low surface resistivity composite membrane for alkaline water electrolysis based on titanium dioxide. The method of the present invention has the advantages of simple operation, low cost, and high yield, and the membrane has the characteristics of low surface resistivity and high airtightness.

[0009] To achieve the above objectives, the present invention adopts the following technical solution:

[0010] A method for preparing an ultra-low surface resistivity composite membrane for alkaline water electrolysis based on titanium dioxide includes the following steps:

[0011] (1) Preparation of casting solution

[0012] 1) Add N-methylpyrrolidone to a container and stir, then add polysulfone particles at a uniform speed and stir until a uniform, transparent, viscous liquid is formed;

[0013] 2) Add N-methylpyrrolidone, carboxymethyl cellulose, polyethylene glycol and magnetic flux to the sample vial, and stir at a constant speed to obtain a mixture;

[0014] 3) Add the uniform, transparent, viscous liquid from step 1) to the mixture from step 2), then add inorganic particles and stir to obtain a milky white, viscous casting solution;

[0015] (2) Film scraping and phase transformation

[0016] Cut the PPS mesh, and use a scraper to coat a uniform thin layer of casting solution to a glass plate with a thickness of 150 μm. Then fix the PPS mesh and immerse it in the coated area. Add casting solution to cover the surface of the mesh with a layer of casting solution. Use a scraper to coat a second uniform thin layer with a thickness of 200-400 μm. Let it stand, and then put the glass plate into water for phase inversion. After 10 minutes, a uniform white composite membrane can be observed floating on the water surface. The resulting composite membrane is then soaked in water again to remove excess casting solution from the surface, and then dried and stored.

[0017] Furthermore, in step 1), the volume ratio of N-methylpyrrolidone to polysulfone is (30-70) ml:(8-12) g;

[0018] The addition rate of the polysulfone particles is 0.5-2 g / s;

[0019] The stirring rate is 100-300 r / min, and the stirring time is 4-10 h.

[0020] The beneficial effect of adopting the above-mentioned further solution is that the above-mentioned solution of this application helps polysulfone particles to dissolve uniformly and quickly in NMP solution, reducing agglomeration.

[0021] Furthermore, in step 2), the ratio of N-methylpyrrolidone, carboxymethyl cellulose, and polyethylene glycol is (3-8) ml:(1-5) g:(1-3) ml;

[0022] The mass ratio of the carboxymethyl cellulose to the polysulfone in step 1) is 1-5:8-12;

[0023] The stirring rate is 100-300 r / min, the stirring temperature is 40-80℃, and the stirring time is 8-24 h.

[0024] The beneficial effect of adopting the above-mentioned further scheme is that: in this application, carboxymethyl cellulose and polyethylene glycol are dissolved in a small amount of NMP solution before heating and dissolving, which is conducive to the uniform dissolution of hydrophilic agent and binder and enhances their interaction.

[0025] Furthermore, the mass ratio of the inorganic particles in step 3) to the mass of the polysulfone in step 1) is 1:1;

[0026] The inorganic particles are TiO2 and / or ZrO2.

[0027] The beneficial effects of adopting the above-mentioned further solutions are as follows: the inorganic particles added in this application are beneficial to improving hydrophilicity and can effectively reduce sheet resistivity. Different inorganic particles have different advantages. The addition of titanium dioxide can significantly improve hydrophilicity, while zirconium dioxide has weaker hydrophilicity than titanium dioxide, but can significantly improve the mechanical properties of the membrane.

[0028] Furthermore, the stirring procedure described in step 3) is to stir at a speed of 100-600 r / min for 12-48 hours, and then stir at a low speed of 50-150 r / min for 6-24 hours to defoam.

[0029] Furthermore, the PPS mesh described in step (2) has a specification of (5-20)cm × (5-20)cm.

[0030] Furthermore, the standing time mentioned in step (2) is to stand for 1-10 minutes at 15-40℃ and 20-50%RH humidity.

[0031] The beneficial effects of adopting the above-mentioned further solutions are as follows: In the above-mentioned solutions of this application, high-speed stirring can enable the effective components of the casting solution to interact well and form a uniform slurry. However, as the viscosity of the slurry increases, a large number of bubbles are easily formed during stirring. Low-speed stirring eliminates a large number of bubbles in the casting solution, thereby reducing the impact of uneven pore cavities formed by large bubbles on the mechanical strength of the membrane during subsequent coating. The sheet resistivity of the membrane is less affected after adding the PPS mesh, but its skeleton effectively supports the mechanical strength of the membrane. Furthermore, allowing the membrane to stand in the environment first facilitates the redistribution of the micropores formed in the casting solution, transforming them from finger-like pores to sponge-like pores, thereby improving the membrane performance. Simultaneously, the pre-evaporation of the solvent helps the phase transformation to proceed.

[0032] The beneficial effects of this invention are as follows:

[0033] (1) Improved hydrophilicity: Compared to the single inorganic particle compound carboxymethyl cellulose / polyethylene glycol, the contact angle of the membrane in the composite formulation is reduced to 28.9°. The surface of the titanium dioxide inorganic particles used is hydrophilic and rich in hydroxyl groups. The hydrophilic groups of carboxymethyl cellulose and polyethylene glycol can form a continuous hydration layer, which significantly enhances the hydrophilicity of the membrane. In the process of water electrolysis to produce hydrogen, the hydrophilic membrane can better absorb and retain water. The hydration channels formed can reduce the membrane resistance, thereby reducing the ohmic polarization loss of the electrolyzer. At the same time, it is beneficial to transport water from the flow field or electrode layer to the reaction area (especially the anode catalyst layer), preventing the increase in resistance and the formation of hot spots due to local dehydration, and improving the stability of operation. Renewable energy (such as wind power and solar power) power supply is intermittent and fluctuating. This may lead to frequent start-up and shutdown of the electrolyzer or rapid power changes. The membrane with good hydrophilicity can also respond more quickly to the changes in water demand caused by power changes, maintain a good hydration state, reduce the risk of local drying due to rapid load changes, and improve the robustness of the system under fluctuating conditions.

[0034] (2) Optimization of ion transport channels: Compared with single inorganic particles combined with carboxymethyl cellulose / polyethylene glycol, the carboxyl groups of CMC in the composite formulation synergistically adsorb free H+ with the ether bonds in polyethylene glycol. + / OH － This reduces ion concentration polarization near the electrodes. The flexible side chains of polyethylene glycol optimize charge transport paths and lower migration barriers. The hydrophilicity of the membrane further promotes ion migration, thereby reducing sheet resistance. Oxygen-vacant TiO2 can catalyze water splitting. The unsaturated bonds of titanium atoms on the TiO2 surface readily coordinate with water to form Ti-OH groups (double bond coordination), enabling dynamic regulation of surface charge. A three-dimensional conductive network for electron transfer is formed within the pores, promoting the reaction kinetics of hydrogen production through water electrolysis.

[0035] (3) Improved tensile strength: Carboxymethyl cellulose forms a cross-linked network with particles through hydrogen bonds, which not only reduces particle dissolution but also significantly improves mechanical strength. At the same time, the plasticizing effect of polyethylene glycol can suppress brittleness, and the spontaneously formed microporous structure can optimize the balance between gas barrier and ion flux without the need for additional pore-forming agents.

[0036] (4) Improved durability: The hydroxyl layer blocks oxygen from contacting the titanium substrate, reducing the interfacial resistance of the water electrolysis membrane by 40% and delaying the degradation of Ti. 4+ →Ti 3+ Passivation. The ether bonds (—O—) in polyethylene glycol are chemically inert, and their flexible chains encapsulate TiO2 particles, preventing direct corrosion of TiO2 by the electrolyte. The membrane is rich in hydrophilic groups, and self-healing is expected to be achieved through hydrogen bond reconnection. Attached Figure Description

[0037] Figure 1This is a scanning electron microscope (SEM) cross-sectional view of the TiO2 and PPS mesh composite membrane in Example 1;

[0038] Figure 2 This is a SEM cross-sectional view of the TiO2 and PPS mesh composite membrane in Example 1;

[0039] Figure 3 This is a magnified SEM cross-sectional view of the TiO2 and PPS mesh composite membrane in Example 1.

[0040] Figure 4 This is a SEM image of the TiO2 and PPS mesh composite membrane in Example 1.

[0041] Figure 5 This is a magnified SEM image of the TiO2 and PPS mesh composite membrane in Example 1.

[0042] Figure 6 This is a stress-strain curve of the TiO2 and PPS mesh composite membrane in Example 1;

[0043] Figure 7 This is a contact angle test diagram of the TiO2 and PPS mesh composite membrane in Example 1;

[0044] Figure 8 This is a blank impedance diagram of the clamp without the TiO2 and PPS mesh composite diaphragm in Example 1;

[0045] Figure 9 The impedance diagram of the TiO2 and PPS mesh composite membrane in Example 1;

[0046] Figure 10 This is a contact angle test diagram of the TiO2 and PPS mesh composite membrane in Example 2;

[0047] Figure 11 This is a blank impedance diagram of the clamp without the TiO2 and PPS mesh composite diaphragm in Example 2;

[0048] Figure 12 The impedance diagram of the TiO2 and PPS mesh composite membrane in Example 2;

[0049] Figure 13 This is a contact angle test diagram of the TiO2 and PPS mesh composite membrane in Example 3;

[0050] Figure 14 This is a blank impedance diagram of the clamp without the TiO2 and PPS mesh composite diaphragm in Example 3;

[0051] Figure 15 The impedance diagram of the TiO2 and PPS mesh composite membrane in Example 3;

[0052] Figure 16 The diagram shows a comparison of the cell voltages of the TiO2 and PPS mesh composite membranes in Examples 1, 2, and 3. Detailed Implementation

[0053] 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.

[0054] Example 1

[0055] (1) Add 50 mL of N-methylpyrrolidone (NMP) to a three-necked flask and plug the left and right openings with glass stoppers. Fix the three-necked flask on a mechanical stirrer, turn it on and adjust the speed to 300 r / min. Slowly and evenly add 10 g of polysulfone to the three-necked flask and stir for 5 h until a uniform, transparent, viscous liquid is formed.

[0056] (2) Add 5 mL of NMP, 4 g of carboxymethyl cellulose, and 2 mL of polyethylene glycol to the sample vial. Stir at 60 °C for 12 h.

[0057] (3) Mix the solution and add 10g TiO2. Stir at 300r / min for 24h and then stir at 60r / min for 12h to defoam, so as to obtain a milky white viscous uniform casting solution.

[0058] (4) Cut a 10cm × 8cm PPS mesh. Using a scraper, apply a uniform thin layer of 150μm thickness to a glass plate at a uniform speed. Fix the PPS mesh and immerse it in the scraped area. Add a small amount of casting solution and use the scraper to apply another uniform thin layer of 200μm thickness. Let it stand for 5 minutes at 25℃ and 40% RH humidity. Then, place it in deionized water for phase inversion to obtain a smooth and uniform white composite membrane. Soak it in a large amount of deionized water until the deionized water is clear to remove excess casting solution from the surface. Then, dry and store it.

[0059] SEM testing was performed to observe the surface and cross-sectional pore structure. A 200μm thick strip of composite diaphragm measuring 0.14cm × 4cm was cut and subjected to tensile strength testing, which yielded a tensile strength of 21.13MPa.

[0060] Table 1. Tensile strength test parameters and data in Example 1

[0061]

[0062] A contact angle test was conducted, and the result was 28.9°, verifying that the formulation membrane has good hydrophilicity.

[0063] A 3cm × 3cm composite membrane was prepared and tested using a Chenhua electrochemical workstation in a 6M potassium hydroxide solution at 30℃. The effective area was 4cm². 2 First, blank samples were obtained by testing twice under conditions where no alkaline solution was applied to the membrane. Then, the membrane resistance was tested and repeated twice. The results are as follows:

[0064] Table 2. Surface resistance test data in Example 1

[0065]

[0066] The sheet resistivity of the composite diaphragm was measured to be 0.064 Ωcm. －2 This demonstrates that the improved formulation significantly reduced the surface resistivity of the membrane after enhancing its hydrophilicity.

[0067] Determination of alkali absorption rate: Prepare a 30wt% KOH solution, cut a 1cm × 1cm composite diaphragm sample, and weigh it to obtain the sample mass m1. After drying the sample, immerse it in the 30wt% KOH solution. After the sample is immersed in the alkali for 4 hours, use clamps to hold one corner of the sample and remove it from the alkali, suspending it for 30±2s, dripping off the alkali solution, and weigh it on a balance to obtain the mass m2. (Note: If less than 1 drop of alkali solution does not drip, touch the corner of the sample containing the droplet against the wall of the container to make the droplet fall off before weighing.) The alkali absorption rate A of the diaphragm is calculated according to the following formula:

[0068]

[0069] Where: A--diaphragm alkali absorption rate, %; m1--sample mass before alkali immersion, g; m2--sample mass after alkali immersion, g.

[0070] The experiment was repeated three times, and the results are as follows:

[0071] Table 3. Alkali absorption rate test data in Example 1

[0072] <![CDATA[Mass of the sample before alkali dipping m1 (g)]]> <![CDATA[Mass m2 (g) of the specimen after alkali soaking]]> Alkali absorption rate A (%) <![CDATA[Specimen H 1-1 > 0.0181 0.0879 385 <![CDATA[Specimen H 1-2 > 0.0193 0.1030 433 <![CDATA[Specimen H 1-3 > 0.0208 0.1097 427

[0073] Example 2

[0074] The scheme is basically the same as that in Example 1, except that the casting solution formulation is changed. 5 mL of NMP and 4 g of carboxymethyl cellulose are added to the sample bottle, but polyethylene glycol is not added. The test results are as follows: due to the lack of polyethylene glycol in the formulation, the carboxymethyl cellulose in the CMC group composite membrane cannot be well dispersed in the organic substrate material and inorganic particles. The resulting composite membrane has insufficient flatness and uniformity, and its overall performance is slightly worse than that in Example 1.

[0075] Tensile strength was tested under the same conditions as in Example 1, and the result was 13.79 MPa.

[0076] Table 4. Tensile strength test parameters and data in Example 2

[0077]

[0078] The surface resistivity was tested, and the results are as follows.

[0079] Table 5. Surface resistance test data in Example 2

[0080]

[0081] The contact angle test yielded a result of 39.9°.

[0082] The alkali absorption rate was tested, and the results are as follows.

[0083] Table 6. Data on alkali absorption rate test in Example 2

[0084]

[0085] Example 3

[0086] The scheme was basically the same as in Example 1, except that the casting solution formulation was changed. 5 mL of NMP and 2 mL of polyethylene glycol were added to the sample vial, while carboxymethyl cellulose was omitted. The test results are as follows: due to the lack of carboxymethyl cellulose, the cross-linking between the inorganic particles and the organic substrate material of the polyethylene glycol (PEG) composite membrane was weaker, resulting in significantly reduced tensile strength and hydrophilicity. Furthermore, the fixation of the inorganic particles was poor, leading to increased sheet resistance. The overall performance of the composite membrane was inferior to that of Example 1, verifying the effectiveness of the composite carboxymethyl cellulose and polyethylene glycol formulation.

[0087] Tensile strength was tested under the same conditions as in Example 1, and the result was 11.709 MPa.

[0088] Table 7 Tensile strength test parameters and data in Example 3

[0089]

[0090] The surface resistivity test was performed, and the results are as follows:

[0091] Table 8. Surface resistance test parameters and data for Example 3.

[0092]

[0093] The contact angle test yielded a result of 72.9°.

[0094] The alkali absorption rate was tested, and the results are as follows.

[0095] Table 9. Data on alkali absorption rate test in Example 3

[0096]

[0097] The small-chamber voltage alkaline water electrolysis experiment was conducted in a single-chamber zero-gap electrolytic cell with an effective electrode area of ​​4 cm². 2 Replace the diaphragm with products 1, 2, or 3 from this example, use 30% KOH as the electrolyte, and control the tank temperature at 60°C. Use a DC power supply with a current density range of 0–10000 A / m³. 2 The step size is 100A / m 2 Up to 1000A / m 2 Record the corresponding voltages to obtain the results for Examples 1, 2, and 3, as shown in the graphs below. Figure 16 It can be seen that the alkaline electrolyzed water membrane (Example 1 PC group) prepared by the composite formula has a better current density under the same voltage than the other two groups, and the performance of the composite formula is significantly better than that of the single-component formula.

[0098] Example 4: An ultra-low surface resistivity composite membrane for alkaline water electrolysis based on titanium dioxide

[0099] (1) Preparation of casting solution

[0100] 1) Add 30ml of N-methylpyrrolidone to a container and stir. Then add 12g of polysulfone particles at a constant rate of 0.5g / s. Stir at 100r / min for 10h to form a uniform, transparent, viscous liquid.

[0101] 2) Add 3ml N-methylpyrrolidone, 5g carboxymethyl cellulose, 3ml polyethylene glycol and a magnetic stir bar to the sample vial, and stir at 300r / min and 40℃ for 24h to obtain a mixture;

[0102] 3) Add the uniform, transparent, viscous liquid from step 1) to the mixture from step 2), then add 12g of inorganic particles (TiO2:ZrO2 = 1:1 in the inorganic particles), stir at 600r / min for 12h, and then stir at 150r / min for 6h to defoam, to obtain a milky white viscous casting solution.

[0103] (2) Film scraping and phase transformation

[0104] Cut a 10cm × 8cm PPS mesh. Apply the casting solution to a glass plate using a scraper to create a uniform thin layer of 150μm thickness. Then, fix the PPS mesh and immerse it in the coated area. Add casting solution to cover the mesh surface with a layer of casting solution. Apply another uniform thin layer of 300μm thickness using a scraper. Let it stand for 1 minute at 15℃ and 50% RH. Then, immerse the glass plate in water for phase inversion. Remove the composite membrane and soak it again in water to remove excess casting solution from the surface until the deionized water is clear and colorless. Dry and store.

[0105] Example 5: An ultra-low surface resistivity composite membrane for alkaline water electrolysis based on titanium dioxide.

[0106] (1) Preparation of casting solution

[0107] 1) Add 70ml of N-methylpyrrolidone to a container and stir. Then add 8g of polysulfone particles at a uniform rate of 2g / s. Stir at 100-300r / min for 4h to form a uniform, transparent, viscous liquid.

[0108] 2) Add 8 ml of N-methylpyrrolidone, 3 g of carboxymethyl cellulose, 1 ml of polyethylene glycol and a magnetic stir bar to the sample vial, and stir at 100 r / min and 80 °C for 8 h to obtain a mixture.

[0109] 3) Add the uniform, transparent, viscous liquid from step 1) to the mixture from step 2), then add 8g of inorganic particles (TiO2:ZrO2 = 1:2 in the inorganic particles), stir at 100r / min for 48h, and then stir at 50r / min for 24h to defoam, to obtain a milky white viscous casting solution.

[0110] (2) Film scraping and phase transformation

[0111] Cut a 10cm × 8cm PPS mesh. Apply the casting solution to a glass plate using a scraper to create a uniform thin layer of 150μm thickness. Then, fix the PPS mesh and immerse it in the coated area. Add casting solution to cover the mesh surface with a layer of casting solution. Apply another uniform thin layer of 400μm thickness using a scraper. Let it stand for 10 minutes at 40℃ and 20% RH. Then, immerse the glass plate in water for phase inversion. Remove the composite membrane and soak it again in water to remove excess casting solution from the surface until the deionized water is clear and colorless. Dry and store.

[0112] Example 6: An ultra-low surface resistivity composite membrane for alkaline water electrolysis based on titanium dioxide.

[0113] (1) Preparation of casting solution

[0114] 1) Add 40ml of N-methylpyrrolidone to a container and stir. Then add 10g of polysulfone particles at a uniform rate of 1.5g / s. Stir at 200r / min for 8h to form a uniform, transparent, viscous liquid.

[0115] 2) Add 5 ml of N-methylpyrrolidone, 1 g of carboxymethyl cellulose, 2 ml of polyethylene glycol and a magnetic stir bar to the sample vial, and stir at a constant speed of 200 r / min and 60 °C for 12 h to obtain a mixture;

[0116] 3) Add the uniform, transparent, viscous liquid from step 1) to the mixture from step 2), then add 10g of inorganic particles (TiO2), stir at 400r / min for 24h, and then stir at 100r / min for 18h to defoam, to obtain a milky white viscous casting solution.

[0117] (2) Film scraping and phase transformation

[0118] Cut a 10cm × 8cm PPS mesh. Apply the casting solution to a glass plate using a scraper to create a uniform thin layer of 150μm thickness. Then, fix the PPS mesh and immerse it in the coated area. Add casting solution to cover the mesh surface with a layer of casting solution. Apply another uniform thin layer of 200μm thickness using a scraper. Let it stand for 5 minutes at 30℃ and 40% RH. Then, immerse the glass plate in water for phase inversion. Remove the composite membrane and soak it again in water to remove excess casting solution from the surface until the water is clear and colorless. Dry and store.

[0119] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A method for producing a composite separator of ultra-low surface resistance for alkaline electrolyzed water based on titanium dioxide, characterized by, Includes the following steps: (1) Preparation of casting solution 1) Add N-methylpyrrolidone to a container and stir, then add polysulfone particles at a uniform rate and stir until a uniform, transparent, viscous liquid is formed; the volume ratio of N-methylpyrrolidone to polysulfone is (30-70) ml: (8-12) g; the addition rate of the polysulfone particles is 0.5-2 g / s; the stirring rate is 100-300 r / min, and the stirring time is 4-10 h; 2) Add N-methylpyrrolidone, carboxymethyl cellulose, polyethylene glycol and a magnetic stir bar to a sample vial and stir at a constant speed to obtain a mixture; the ratio of N-methylpyrrolidone, carboxymethyl cellulose and polyethylene glycol is (3-8) ml:(1-5) g:(1-3) ml; the mass ratio of carboxymethyl cellulose to polysulfone in step 1) is 1-5:8-12; 3) Add the uniform, transparent, viscous liquid from step 1) to the mixture from step 2), then add inorganic particles and stir to obtain a milky white, viscous casting solution; the mass ratio of the inorganic particles to the polysulfone in step 1) is 1:1; the inorganic particles are TiO2 or a mixture of TiO2 and ZrO2; (2) Film scraping and phase transformation Cut the PPS mesh, and use a scraper to coat a uniform thin layer of casting solution to a glass plate with a thickness of 150 μm. Then fix the PPS mesh and immerse it in the coated area. Add casting solution to cover the surface of the mesh with a layer of casting solution, and use a scraper to coat another uniform thin layer with a thickness of 200-400 μm. Let it stand, and then put the glass plate into water for phase inversion. Take out the composite membrane and soak it in water again to remove excess casting solution from the surface until it is clear and colorless after soaking in deionized water. Dry and store.

2. The method of claim 1, wherein the method of preparing a composite diaphragm for alkaline electrolyzed water based on titanium dioxide having an ultra-low surface resistance is characterized by, The stirring rate in step 2) is 100-300 r / min, the stirring temperature is 40-80 ℃, and the stirring time is 8-24 h.

3. The method of claim 2, wherein the method is characterized by the steps of: The stirring procedure described in step 3) is to stir at a speed of 100-600 r / min for 12-48 h, and then stir at a low speed of 50-150 r / min for 6-24 h to defoam.

4. The method of claim 1, wherein the method is characterized by the steps of: a) mixing the titanium dioxide, the binder, and the electrolyte to form a mixture; b) applying the mixture to a substrate; and c) drying the mixture to form the composite membrane. The PPS mesh described in step (2) has a specification of (5-20) cm × (5-20) cm.

5. The method for preparing an ultra-low surface resistivity composite membrane for alkaline water electrolysis based on titanium dioxide according to claim 1 or 4, characterized in that, The standing time mentioned in step (2) is to stand for 1-10 minutes at 15-40 ℃ and 20-50%RH humidity.

6. A composite membrane with ultra-low surface resistivity for alkaline water electrolysis based on titanium dioxide, characterized in that, It is prepared by the method described in any one of claims 1-5.

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