Ultrathin organic-inorganic composite diaphragm for alkaline water electrolyser as well as preparation method and application of ultrathin organic-inorganic composite diaphragm

Abstract

The invention relates to an ultrathin organic-inorganic composite diaphragm for an alkaline water electrolytic bath and a preparation method and application thereof.The organic-inorganic composite diaphragm is of a metal net substrate / insulating ceramic coating / organic-inorganic coating composite structure and comprises a metal net substrate, the insulating ceramic coatings are arranged on the two sides of the metal net substrate, and the organic-inorganic coatings are arranged on the metal net substrate. And an organic-inorganic coating is arranged on the outer surface of the insulating ceramic coating. The preparation method comprises the following steps: carrying out roughening treatment on the metal net substrate; insulating ceramic coatings are prepared on the two sides of the roughened metal net substrate; preparing an organic-inorganic coating on the outer surface of the insulating ceramic coating; and carrying out phase inversion treatment to obtain the organic-inorganic composite diaphragm. And storing in deionized water after cleaning treatment. Compared with the prior art, the organic-inorganic composite diaphragm prepared by the preparation method disclosed by the invention has good surface resistance, mechanical strength and stability at the same time under the condition of relatively thin thickness.

Description

Technical Field

[0001] The present invention relates to the technical field of alkaline water electrolysis hydrogen production diaphragms, and particularly relates to an ultra-thin organic-inorganic composite diaphragm for an alkaline water electrolyzer, a preparation method thereof, and an application thereof. Background Art

[0002] With the continuous growth of the global demand for renewable energy and clean energy, hydrogen energy, as a green energy source with broad prospects, has received extensive attention. Hydrogen energy has characteristics such as cleanness and high efficiency, and is considered to be one of the keys to addressing the global energy crisis and environmental pollution problems. When hydrogen is used as a fuel, only water vapor is produced after combustion, and no harmful gases are emitted, so it has significant environmental protection advantages. In order to achieve the wide application of hydrogen energy, it has become particularly important to develop efficient and low-cost hydrogen production technologies. The electrolytic water hydrogen production technology is one of the most promising hydrogen production methods at present, especially when combined with renewable energy, it is of great significance. This technology uses renewable energy, such as solar energy or wind energy, to provide electric energy and decompose water into hydrogen and oxygen. Electrolytic water hydrogen production not only has a clean process, but also can effectively utilize abundant natural resources to realize the production of green hydrogen energy. Compared with traditional fossil energy hydrogen production methods, the electrolytic water hydrogen production technology greatly reduces carbon dioxide emissions, helps reduce the accumulation of greenhouse gases, and promotes the transformation of the global energy structure towards low-carbon and sustainable development. Therefore, the electrolytic water hydrogen production technology is not only an important technology for realizing the rapid development of hydrogen energy, but also of great strategic significance for promoting the green transformation of the global energy system and addressing climate change. With the continuous progress of technology and the gradual reduction of costs, hydrogen energy will play an increasingly important role in the future energy system.

[0003] Alkaline water electrolysis hydrogen production has become a common electrolytic water hydrogen production technology due to its simple structure, low cost, etc., and has made progress in large-scale commercial applications. In alkaline water electrolysis hydrogen production, an organic-inorganic composite diaphragm is mainly used to separate the anode and cathode regions in the electrolyzer to prevent the mixing of hydrogen and oxygen, thereby improving the system safety and efficiency. In addition to airtightness, the surface resistance of the organic-inorganic composite diaphragm is also an important index of its performance, which reflects the resistance of OH - transmission and directly affects the energy consumption of alkaline water electrolysis hydrogen production. The smaller the surface resistance, the stronger the conduction ability of OH - and the lower the voltage required for electrolyzing water and the lower the energy consumption.

[0004] Therefore, an organic-inorganic composite separator with a smaller surface resistance is crucial for reducing the cost of hydrogen production. The simplest way to achieve this goal is to reduce the thickness of the separator. Lee et al. demonstrated in "Advanced Zirfon-type porous separator for a high-rate alkaline electrolyser operating in a dynamic mode" that when the thickness of the organic-inorganic composite separator was reduced from 500 μm to 300 μm, the surface resistance of the separator decreased from 0.2 Ω·cm 2 to 0.1 Ω·cm 2 .

[0005] In addition to being limited by the doctor blade size during preparation, the thickness of the organic-inorganic composite separator mainly depends on the thickness of the supporting mesh substrate that provides mechanical strength. That is, preparing a thinner organic-inorganic composite separator requires a thinner supporting mesh substrate. However, to ensure a certain mechanical strength, the mesh number of the traditional polyphenylene sulfide woven mesh increases as the thickness decreases, and the contact area of the coatings on both sides decreases, resulting in poor stability of the organic-inorganic composite separator. Specifically, when the thickness of the polyphenylene sulfide woven mesh is less than 100 μm or the mesh number exceeds 150 mesh, large-area peeling of the single-sided coating often occurs on the organic-inorganic composite separator. Summary of the Invention

[0006] The object of the present invention is to provide an ultra-thin organic-inorganic composite separator for an alkaline electrolyzer, its preparation method and application. The prepared organic-inorganic composite separator has good surface resistance, mechanical strength and stability at a relatively thin thickness.

[0007] The object of the present invention can be achieved by the following technical solutions:

[0008] The present invention provides an ultra-thin organic-inorganic composite separator for an alkaline electrolyzer. The organic-inorganic composite separator includes a metal mesh substrate / insulating ceramic coating / organic-inorganic coating composite structure, including a metal mesh substrate. Insulating ceramic coatings are provided on both sides of the metal mesh substrate, and an organic-inorganic coating is provided on the outer surface of the insulating ceramic coating.

[0009] Preferably, the metal mesh substrate includes any one of 304 stainless steel woven mesh, nickel mesh, and titanium mesh, and the mesh number is 5 - 120 mesh.

[0010] Preferably, the insulating ceramic coating includes one or more of zirconia, silicon carbide, boron nitride, or titanium nitride, and the particle size is 10 - 500 nm.

[0011] Preferably, the organic-inorganic coating is a mixture of a thermoplastic resin and hydrophilic inorganic nanoparticles.

[0012] Preferably, the thermoplastic resin includes one or more of polysulfone, polyethersulfone, polyphenylene sulfide, polypropylene, polyetheretherketone, polyimide, and polyetherimide.

[0013] Preferably, the hydrophilic inorganic nanoparticles include one or more of zirconia, ceria, titania, and barium sulfate, and have a particle size of 10 - 300 nm.

[0014] Preferably, the metal mesh substrate has a thickness of 50 - 200 μm, the insulating ceramic coating has a thickness of 1 - 50 μm, the organic - inorganic coating has a thickness of 10 - 100 μm, and the total thickness of the organic - inorganic composite diaphragm is 100 - 250 μm.

[0015] The present invention also provides a method for preparing the ultra - thin organic - inorganic composite diaphragm for an alkaline water electrolyzer, comprising the following steps:

[0016] S1: Roughen the metal mesh substrate;

[0017] S2: Prepare insulating ceramic coatings on both sides of the roughened metal mesh substrate;

[0018] S3: Prepare an organic - inorganic coating on the outer surface of the insulating ceramic coating;

[0019] S4: Perform phase inversion treatment to obtain the organic - inorganic composite diaphragm;

[0020] S5: After cleaning treatment, store it in deionized water.

[0021] Preferably, step S1 includes the following steps: Clean the metal mesh substrate with absolute ethanol, and dry it after cleaning; Immerse the cleaned and dried metal mesh substrate in a 10 - 35 wt% nitric acid solution for 1 - 10 minutes for chemical etching; Immerse the chemically etched metal mesh substrate in deionized water for ultrasonic cleaning.

[0022] Further preferably, in step S1, the ultrasonic cleaning means immersing the chemically etched metal mesh substrate in deionized water for ultrasonic treatment and replacing the deionized water every 45 - 75 seconds until the deionized water is neutral.

[0023] In the present invention, the chemical etching is used to increase the roughness of the metal mesh, and the ultrasonic cleaning is used to wash away the excess nitric acid used for etching.

[0024] Preferably, step S2 includes the following steps: Prepare an insulating ceramic suspension; Preheat the metal mesh substrate to 250 - 450 °C; Prepare the insulating ceramic coating by a liquid - phase plasma spraying process.

[0025] Further preferably, in step S2, the solid content of the insulating ceramic suspension is 5-40 vol%.

[0026] Further preferably, in step S2, the solvent of the insulating ceramic suspension includes any one of deionized water and absolute ethanol.

[0027] Further preferably, in step S2, the insulating ceramic suspension further includes 0.5-1.5 wt% of a dispersant.

[0028] Even more preferably, in step S2, the dispersant includes any one of sodium polyacrylate and polyethylene glycol.

[0029] Further preferably, after the insulating ceramic suspension is prepared in step S2, it needs to be ultrasonically treated and then filtered and stored.

[0030] Further preferably, in step S2, the filtration means using a filter screen to remove aggregates or contaminants larger than 65-85 μm.

[0031] Further preferably, in step S2, the parameters of the liquid-phase plasma spraying process are as follows: argon 30-40 SLM, hydrogen 2-10 SLM, current 500-900 A, spray gun moving rate 0.5-1.5 m / s, suspension feeding rate 20-200 mL / min, and spraying distance 20-80 mm.

[0032] In the present invention, through the liquid-phase plasma spraying process, a layer of heat-resistant and alkali-resistant insulating ceramic coating is wrapped on the surface of the metal mesh substrate.

[0033] Preferably, step S3 includes the following steps: dissolving a thermoplastic resin and a hydrophilic inorganic nanoparticle in an organic solvent, mixing them evenly to obtain a casting solution; coating the casting solution on the outer surfaces of the insulating ceramic coatings on both sides of the metal mesh substrate prepared in step S2 at 15-35 °C and a relative humidity of 30-70%.

[0034] Further preferably, in step S3, the mass ratio of the thermoplastic resin to the organic solvent is 1:9-1:1, and the mass ratio of the thermoplastic resin to the hydrophilic inorganic nanoparticle is 1:10-10:3.

[0035] Further preferably, in step S3, the organic solvent includes one or more of N-methyl-2-pyrrolidone, dimethyl sulfoxide, N,N-dimethylformamide, formamide, and N,N-dimethylacetamide.

[0036] Further preferably, in step S3, it is mixed evenly by dispersion methods such as mechanical stirring and planetary ball milling.

[0037] Further preferably, in step S3, the casting solution is coated on both sides of the anion exchange membrane by a doctor blade or a coating head.

[0038] Preferably, step S4 includes the following steps: The metal mesh substrate prepared with the insulating ceramic coating and the organic-inorganic coating is successively immersed in non-solvents at low temperature, room temperature, and high temperature, and the immersion time each time is not less than 30 minutes, and it is taken out after the organic solvent is completely replaced.

[0039] Further preferably, in step S4, the non-solvent includes one or more of deionized water, n-propanol, isopropanol, and ethanol.

[0040] Further preferably, in step S4, the low temperature is -15 - 15°C, the room temperature is 15 - 40°C, and the high temperature is 40 - 100°C.

[0041] Further preferably, in step S4, when the non-solvent is deionized water, the lowest temperature of the deionized water is 0°C, and if further cooling is required, other non-solvents such as ethanol can be added.

[0042] Further preferably, in step S4, the non-solvent at high temperature is usually deionized water.

[0043] Further preferably, in step S4, the immersion time each time is 1 hour.

[0044] Preferably, step S5 includes the following steps: The organic-inorganic composite separator is cleaned with deionized water, cut to a suitable size, and stored in deionized water.

[0045] Further preferably, in step S5, the deionized water for cleaning and storage is at room temperature.

[0046] Further preferably, the method for preparing the ultra-thin organic-inorganic composite separator for the alkaline water electrolyzer includes the following steps:

[0047] S1: Select a flat metal mesh and clean it with absolute ethanol to ensure the cleanliness of the metal mesh. Immerse the dried metal mesh in a 15wt% nitric acid solution for 10 minutes to chemically etch the metal mesh and increase the roughness of the metal mesh. Immerse the etched metal mesh in deionized water and ultrasonically clean it, and replace the deionized water every 1 minute until the deionized water is neutral.

[0048] S2: Adopt the liquid-phase plasma spraying process to coat a layer of high-temperature and alkali-resistant insulating ceramic coating on the surface of the metal mesh. First, prepare an insulating ceramic suspension with a solid content of 10 - 20 vol%, filter it after ultrasonic treatment and store it; preheat the metal mesh to 300 - 350 °C to enhance the adhesion of the coating; carry out liquid-phase plasma spraying, and the spraying process parameters are: argon 37 SLM, hydrogen 8 SLM, current 700 A, spray gun moving rate 1 m / s, suspension feeding rate 27 mL / min.

[0049] S3: Dissolve the thermoplastic resin in an organic solvent through mechanical stirring, and then add hydrophilic inorganic nanoparticles to the polymer solution. Mix evenly through dispersion methods such as mechanical stirring and planetary ball milling to obtain a casting solution. At 25 °C and 60% relative humidity, fix the dried and clean metal mesh with a fixture, and coat the casting solution on both the left and right sides of the metal mesh with a scraper or coater head.

[0050] S4: Immerse the coated metal mesh in non-solvents at low temperature, normal temperature, and high temperature in sequence, with each immersion time being 1 hour, and take out the organic-inorganic composite diaphragm after the organic solvent is completely replaced.

[0051] S5: Wash the organic-inorganic composite diaphragm with deionized water, cut it to a suitable size, and store it in deionized water.

[0052] The present invention also provides an application of the ultra-thin organic-inorganic composite diaphragm for an alkaline water electrolyzer in alkaline water electrolysis for hydrogen production.

[0053] Aiming at the problem that the thickness of the existing organic-inorganic composite diaphragm is limited by the substrate, the present invention proposes an ultra-thin organic-inorganic composite diaphragm for an alkaline water electrolyzer, its preparation method and application. By using a metal mesh with alkali resistance and good mechanical properties to replace the traditional polyphenylene sulfide woven mesh, under the same mechanical strength, the mesh number is decreased by dozens of times, providing sufficient contact area for the coatings on both sides to improve the stability of the organic-inorganic composite diaphragm. In addition, to solve the conductivity of the metal mesh, the present invention proposes an insulation treatment for the metal mesh to prevent short-circuit accidents during the operation of the electrolyzer.

[0054] The ultra-thin organic-inorganic composite diaphragm proposed by the present invention has excellent stability mainly due to two points. One is that the mesh number is reduced, the aperture of the metal mesh becomes larger, and the contact area of the coatings on both sides increases, avoiding the overall peeling of the single-sided coating. The other is that the insulating ceramic coating increases the wire diameter and roughness of the metal mesh, increasing the contact area between the coating and the substrate.

[0055] Compared with the prior art, the present invention has the following beneficial effects:

[0056] (1) The present invention provides an ultra-thin organic-inorganic composite diaphragm for an alkaline water electrolyzer. The organic-inorganic composite diaphragm has a composite structure of a metal mesh substrate / insulating ceramic coating / organic-inorganic coating. At a relatively thin thickness, it can achieve fewer mesh numbers, and at the same time has good surface resistance, mechanical strength and stability.

[0057] (2) By using a metal mesh as the support substrate of the organic-inorganic composite diaphragm, the present invention prepares an ultra-thin and stable organic-inorganic composite diaphragm. Compared with a mesh woven from organic materials, at a relatively thin thickness, the metal mesh substrate can achieve fewer mesh numbers, increase the contact area of the coatings on both sides of the substrate, and ensure that the stability of the organic-inorganic composite diaphragm does not deteriorate as the thickness decreases.

[0058] (3) In the present invention, the surface of the metal mesh is covered with a double coating, providing double protection for the safe operation of the electrolyzer. In the present invention, the organic-inorganic coating not only plays a role in isolating gases, but also can serve as the outermost insulating coating of the metal mesh. After the organic-inorganic coating is damaged, the surface of the metal mesh is still covered with an insulating ceramic coating, greatly avoiding short-circuit accidents in the electrolyzer.

[0059] (4) The rough outer surface and internal stacking pores of the insulating ceramic coating on both sides of the metal mesh substrate in the present invention increase the total surface area of the metal mesh substrate, provide a larger contact area for the organic-inorganic coating and the metal mesh substrate, and improve the stability of the organic-inorganic composite diaphragm.

[0060] (5) The organic-inorganic coating in the present invention includes hydrophilic zirconia, silicon carbide, etc., which can enhance the hydrophilicity of the organic-inorganic composite diaphragm and play a positive role in reducing the surface resistance of the organic-inorganic composite diaphragm.

[0061] (6) The organic-inorganic composite diaphragm prepared by the present invention has good electrochemical performance. As the thickness decreases, the electrochemical performance of the diaphragm is significantly improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0062] Figure 1 is a flowchart of the preparation method of the present invention;

[0063] Figure 2 is a schematic structural diagram of the present invention; (in the figure: 1 - metal mesh substrate; 2 - insulating ceramic coating; 3 - organic-inorganic coating). DETAILED DESCRIPTION OF THE EMBODIMENTS

[0064] The present invention will be described in detail below with reference to the drawings and specific embodiments. This embodiment is implemented on the premise of the technical solution of the present invention, and gives detailed implementation manners and specific operation processes, but the protection scope of the present invention is not limited to the following embodiments.

[0065] Unless otherwise specified, the reagents, methods, instruments, and equipment used in the present invention are conventional reagents, methods, instruments, and equipment in the art. Unless otherwise specified, the reagents and materials used in the following examples are commercially available.

[0066] An ultra-thin organic-inorganic composite diaphragm for an alkaline water electrolyzer, the structural schematic diagram is as Figure 2 shown. The organic-inorganic composite diaphragm is a metal mesh substrate / insulating ceramic coating / organic-inorganic coating composite structure, including a metal mesh substrate 1, insulating ceramic coatings 2 are provided on both sides of the metal mesh substrate 1, and an organic-inorganic coating 3 is provided on the outer surface of the insulating ceramic coating 2.

[0067] Its preparation method is as Figure 1 shown, and includes the following steps:

[0068] S1: Roughen the metal mesh substrate;

[0069] S2: Prepare insulating ceramic coatings on both sides of the roughened metal mesh substrate;

[0070] S3: Prepare an organic-inorganic coating on the outer surface of the insulating ceramic coating;

[0071] S4: Phase inversion treatment to obtain the organic-inorganic composite diaphragm;

[0072] S5: After cleaning treatment, store it in deionized water.

[0073] Example 1

[0074] An ultra-thin organic-inorganic composite diaphragm for an alkaline water electrolyzer is prepared as follows: Cut a 304 stainless steel woven mesh with a size of 60mm×80mm, a thickness of 80μm, and a mesh size of 40 meshes, soak it in absolute ethanol and ultrasonicate for 10 minutes, and then put the washed stainless steel woven mesh into an 80°C oven and dry it for 10 minutes. Take out the dried stainless steel woven mesh, cool it to room temperature, and soak it in a 15wt% nitric acid solution for 10 minutes. Take out the etched stainless steel woven mesh, put it into deionized water and ultrasonicate, and change the deionized water every 1 minute until the deionized water is neutral. Prepare a 10vol% zirconia suspension (the zirconia is a powder with a particle size of 40nm), which contains 1wt% sodium polyacrylate as a dispersant, and adjust the pH to 6. At 25°C, ultrasonicate the suspension for 20 minutes, and then use a filter screen to remove aggregates or contaminants larger than 75μm. After heating the metal mesh to 300°C in an oven, use a Metco F4MB-XL device for liquid-phase plasma spraying, and the spraying process parameters are: argon 37SLM, hydrogen 8SLM, current 700A, spray gun moving rate 1m / s, suspension feeding rate 27mL / min, spraying distance 40mm, and spraying times 25 times. At 80°C, put 15g of polysulfone into 85g of N-methyl-2-pyrrolidone (NMP) and mechanically stir until the polysulfone is completely dissolved, then add 85g of zirconia with a particle size of 40nm in batches and mechanically stir and disperse at 2000rpm for 3 hours. After standing and degassing, a casting solution is obtained; at 25°C and 60% relative humidity, fix the clean and dry stainless steel woven mesh between two 100μm doctor blades, (fix the clean and dry stainless steel woven mesh between two doctor blades with a length of 110mm, an effective coating area of 80mm, and a coating thickness of 100μm, and the stainless steel woven mesh is within the effective coating area of the doctor blade) feed the material, and evenly scrape the casting solution from bottom to top; soak the entire fixture in deionized water at 5°C, 25°C, and 90°C in turn, and the soaking time for each time is 1 hour; disassemble the entire fixture, take out the organic-inorganic composite diaphragm and rinse the surface with deionized water, cut it to a suitable size and store it in deionized water for convenient subsequent testing and use.

[0075] Example 2

[0076] An ultra-thin organic-inorganic composite diaphragm for an alkaline water electrolyzer is prepared as follows: Cut a 100-μm-thick, 40-mesh 304 stainless steel woven mesh with a size of 60 mm × 80 mm, soak it in absolute ethanol and ultrasonicate for 10 minutes, and then put the washed stainless steel woven mesh into an 80°C oven and dry for 10 minutes. Take out the dried stainless steel woven mesh, cool it to room temperature, and soak it in a 15 wt% nitric acid solution for 10 minutes. Take out the etched stainless steel woven mesh, put it into deionized water and ultrasonicate, and change the deionized water every 1 minute until the deionized water is neutral. Prepare a 10 vol% zirconia suspension (the zirconia is a powder with a particle size of 40 nm), which contains 1 wt% sodium polyacrylate as a dispersant, and adjust the pH to 6. At 25°C, ultrasonicate the suspension for 20 minutes, and then use a filter screen to remove aggregates or contaminants larger than 75 μm. After heating the metal mesh to 300°C in an oven, use a Metco F4MB-XL device for liquid-phase plasma spraying. The spraying process parameters are: argon 37 SLM, hydrogen 8 SLM, current 700 A, spray gun moving rate 1 m / s, suspension feeding rate 27 mL / min, spraying distance 40 mm, and spraying times 25 times. At 80°C, put 15 g of polysulfone into 85 g of N-methyl-2-pyrrolidone (NMP) and mechanically stir until the polysulfone is completely dissolved. Then, add 85 g of zirconia with a particle size of 40 nm in batches and mechanically stir and disperse at 2000 rpm for 3 hours. After standing and defoaming, a casting solution is obtained; at 25°C and 60% relative humidity, fix the clean and dry stainless steel woven mesh between two 125-μm doctor blades, (fix the clean and dry stainless steel woven mesh between two doctor blades with a length of 110 mm, an effective coating area of 80 mm, and a coating thickness of 125 μm, and the stainless steel woven mesh is within the effective coating area of the doctor blade) feed the material, and evenly scrape and coat the casting solution from bottom to top; soak the entire fixture in deionized water at 5°C, 25°C, and 90°C in turn, and the soaking time for each time is 1 hour; disassemble the entire fixture, take out the organic-inorganic composite diaphragm, rinse the surface with deionized water, cut it to a suitable size and store it in deionized water for convenient subsequent testing and use.

[0077] Example 3

[0078] An ultra-thin organic-inorganic composite diaphragm for an alkaline water electrolyzer is prepared as follows: Cut a 304 stainless steel woven mesh with a size of 60 mm × 80 mm, a thickness of 150 μm, and a mesh size of 40 meshes. Immerse it in absolute ethanol and ultrasonicate for 10 minutes, and then put the washed stainless steel woven mesh into an 80°C oven and dry for 10 minutes. Take out the dried stainless steel woven mesh, cool it to room temperature, and immerse it in a 15 wt% nitric acid solution for 10 minutes. Take out the etched stainless steel woven mesh, put it into deionized water and ultrasonicate, and change the deionized water every 1 minute until the deionized water is neutral. Prepare a 10 vol% zirconia suspension (the zirconia is a powder with a particle size of 40 nm), which contains 1 wt% sodium polyacrylate as a dispersant, and adjust the pH to 6. At 25°C, ultrasonicate the suspension for 20 minutes, and then use a filter screen to remove aggregates or contaminants larger than 75 μm. After heating the metal mesh to 300°C in an oven, use a Metco F4MB-XL device for liquid-phase plasma spraying. The spraying process parameters are: argon 37 SLM, hydrogen 8 SLM, current 700 A, spray gun moving rate 1 m / s, suspension feeding rate 27 mL / min, spraying distance 40 mm, and spraying times 25 times. At 80°C, put 15 g of polysulfone into 85 g of N-methyl-2-pyrrolidone (NMP) and mechanically stir until the polysulfone is completely dissolved. Then, add 85 g of zirconia with a particle size of 40 nm in batches and mechanically stir and disperse at 2000 rpm for 3 hours. After standing and degassing, a casting solution is obtained. At 25°C and 60% relative humidity, fix the clean and dry stainless steel woven mesh between two 150-μm doctor blades, (fix the clean and dry stainless steel woven mesh between two doctor blades with a length of 110 mm, an effective coating area of 80 mm, and a coating thickness of 150 μm, and the stainless steel woven mesh is within the effective coating area of the doctor blade), feed the material, and evenly scrape the casting solution from bottom to top. Immerse the whole set of jigs in deionized water at 5°C, 25°C, and 90°C in sequence, and the immersion time for each time is 1 hour. Remove the whole set of jigs, take out the organic-inorganic composite diaphragm, rinse the surface with deionized water, cut it to a suitable size, and store it in deionized water for convenient subsequent testing and use.

[0079] Example 4

[0080] An ultra-thin organic-inorganic composite diaphragm for an alkaline water electrolyzer is prepared as follows: Cut a 304 stainless steel woven mesh with a size of 60 mm × 80 mm, a thickness of 80 μm, and a mesh size of 40, soak it in absolute ethanol and ultrasonicate for 10 minutes, and then put the washed stainless steel woven mesh into an oven at 80 °C and dry it for 10 minutes. Take out the dried stainless steel woven mesh, cool it to room temperature, and soak it in a 15 wt% nitric acid solution for 10 minutes. Take out the etched stainless steel woven mesh, put it into deionized water and ultrasonicate, and change the deionized water every 1 minute until the deionized water is neutral. Prepare a 10 vol% boron nitride suspension (boron nitride is a powder with a particle size of 40 nm), which contains 1 wt% sodium polyacrylate as a dispersant, and adjust the pH to 6. At 25 °C, ultrasonicate the suspension for 20 minutes, and then use a filter screen to remove aggregates or contaminants larger than 75 μm. After heating the metal mesh to 300 °C in an oven, use a Metco F4MB-XL device for liquid-phase plasma spraying, and the spraying process parameters are: argon 37 SLM, hydrogen 8 SLM, current 700 A, spray gun moving rate 1 m / s, suspension feeding rate 27 mL / min, spraying distance 40 mm, spraying times 25 times. At 80 °C, put 15 g of polysulfone into 85 g of N-methyl-2-pyrrolidone (NMP) and mechanically stir until the polysulfone is completely dissolved, then add 85 g of zirconia with a particle size of 40 nm in batches and mechanically stir and disperse at 2000 rpm for 3 hours. After standing and degassing, a casting solution is obtained; at 25 °C and 60% relative humidity, fix the clean and dry stainless steel woven mesh between two 100-μm doctor blades, (fix the clean and dry stainless steel woven mesh between two doctor blades with a length of 110 mm, an effective coating area of 80 mm, and a coating thickness of 100 μm, and the stainless steel woven mesh is within the effective coating area of the doctor blade) feed the material, and uniformly scrape the casting solution from bottom to top; soak the whole set of jigs in deionized water at 5 °C, 25 °C, and 90 °C in turn, and the soaking time for each time is 1 hour; disassemble the whole set of jigs, take out the organic-inorganic composite diaphragm and rinse the surface with deionized water, cut it to a suitable size and store it in deionized water for convenient subsequent testing and use.

[0081] Comparative Example 1

[0082] A commercial product of an organic-inorganic composite diaphragm, model Zirfon PERL UTP 500.

[0083] Comparative Example 2

[0084] An organic-inorganic composite diaphragm, different from Example 1, in this comparative example, a polyphenylene sulfide mesh with a thickness of 100 μm and a mesh size of 150 is used as the substrate, and an insulating ceramic coating and an organic-inorganic coating are prepared on it, and the preparation method is the same as that of Example 1. Among them, the model of the polyphenylene sulfide mesh is PPS-150 of Shanghai Haifan Filter Material Co., Ltd.

[0085] Table 1 Performance Parameters of Comparative Examples 1-2 and Examples 1-4

[0086]

[0087] Table 1 shows the performance parameters of Comparative Example 1, Comparative Example 2, and Examples 1-4. From the analysis of tensile strength, the tensile strength of the organic-inorganic composite diaphragm with a metal mesh as the substrate has been significantly improved; from the analysis of surface resistance, as the thickness of the organic-inorganic composite diaphragm decreases, the surface resistance decreases, proving that reducing the thickness of the organic-inorganic composite diaphragm is an effective solution to reduce the surface resistance. Comparing Example 1 and Example 4, it is verified that good hydrophilicity of the insulating coating is also beneficial to reducing the surface resistance of the organic-inorganic composite diaphragm; from the analysis of bubble point pressure, due to the same coating preparation process, there is no difference in each organic-inorganic composite diaphragm; from the analysis of ultrasonic powder shedding rate, the powder shedding rates of Examples 1-4 are all lower than those of Zirfon UTP 500 and PPS-150. Among them, the powder shedding rate of PPS-150 is 100% because the overall unilateral coating has fallen off.

[0088] Table 2 Electrochemical Performance of Comparative Examples 1-2 and Examples 1-4 in Alkaline Water Electrolyzers

[0089]

[0090] The test conditions for the upper cell are as follows: the temperature of the electrolyzer is 90 °C, both the anode and cathode are ordinary nickel meshes, the electrolyte is 30 wt% KOH solution, the flow rate is 500 ml / min, and the liquid is fed from both sides.

[0091] Table 2 shows the actual on-cell test electrochemical performance of Comparative Examples 1-2 and Examples 1-4. It can be seen that as the thickness decreases, the electrochemical performance of the diaphragm is significantly improved, proving the importance of the diaphragm thickness for the performance of alkaline water electrolyzers. At the same time, no short-circuit accidents occurred during the on-cell test, indicating that the insulating performance of the ultra-thin organic-inorganic composite diaphragm proposed in the present invention is also excellent and is not affected by the metal substrate.

[0092] In summary, the present invention provides an ultra-thin organic-inorganic composite diaphragm for alkaline water electrolyzers. By using a metal mesh (such as a stainless steel woven mesh) with alkali resistance and good mechanical properties to replace the traditional polyphenylene sulfide woven mesh, and by preparing an insulating ceramic coating and an organic-inorganic coating, a composite structure of metal mesh substrate / insulating ceramic coating / organic-inorganic coating is obtained. The prepared organic-inorganic composite diaphragm can achieve fewer mesh numbers at a relatively thin thickness, and at the same time has good surface resistance, mechanical strength, and stability.

[0093] The above description of the embodiments is to enable those of ordinary skill in the art to understand and use the invention. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative efforts. Therefore, the present invention is not limited to the above embodiments, and all improvements and modifications made by those skilled in the art without departing from the scope of the present invention according to the disclosure of the present invention should be within the protection scope of the present invention.

Claims

1. An ultra-thin organic-inorganic composite diaphragm for an alkaline water electrolyzer, characterized in that: The organic-inorganic composite membrane comprises a metal mesh substrate / insulating ceramic coating / organic-inorganic coating composite structure, including a metal mesh substrate, insulating ceramic coatings are arranged on both sides of the metal mesh substrate, and the outer surface of the insulating ceramic coating is provided with an organic-inorganic coating.

2. The ultra-thin organic-inorganic composite diaphragm for an alkaline water electrolyzer according to claim 1, characterized in that: The metal mesh substrate includes any one of 304 stainless steel woven mesh, nickel mesh, and titanium mesh, with a mesh size of 5-120 meshes; the insulating ceramic coating includes one or more of zirconium dioxide, silicon carbide, boron nitride, or titanium nitride, with a particle size of 10-500nm; the organic-inorganic coating is a mixture of thermoplastic resin and hydrophilic inorganic nanoparticles.

3. The ultra-thin organic-inorganic composite diaphragm for an alkaline water electrolyzer according to claim 2, characterized in that: The thermoplastic resin includes one or more of polysulfone, polyethersulfone, polyphenylene sulfide, polypropylene, polyetheretherketone, polyimide, and polyetherimide; the hydrophilic inorganic nanoparticles include one or more of zirconium dioxide, cerium dioxide, titanium dioxide, and barium sulfate, and the particle size is 10-300nm.

4. The ultra-thin organic-inorganic composite diaphragm for an alkaline water electrolyzer according to claim 1, characterized in that: The thickness of the metal mesh substrate is 50-200 μm, the thickness of the insulating ceramic coating is 1-50 μm, the thickness of the organic-inorganic coating is 10-100 μm, and the total thickness of the organic-inorganic composite membrane is 100-250 μm.

5. A method for preparing an ultra-thin organic-inorganic composite diaphragm for an alkaline water electrolyzer according to any one of claims 1 to 4, characterized in that: The following steps are involved: S1: roughening the metal mesh substrate; S2: preparing an insulating ceramic coating on both sides of the roughened metal mesh substrate; S3: preparing an organic-inorganic coating on the outer surface of the insulating ceramic coating; S4: phase inversion treatment to obtain the organic-inorganic composite membrane; S5: After cleaning, store in deionized water.

6. The method for preparing an ultra-thin organic-inorganic composite diaphragm for an alkaline water electrolyzer according to claim 5, characterized in that: Step S1 includes the following steps: cleaning the metal mesh substrate with anhydrous ethanol and drying it after cleaning; immersing the cleaned and dried metal mesh substrate in a 10-35wt% nitric acid solution for 1-10 minutes for chemical etching; and immersing the chemically etched metal mesh substrate in deionized water for ultrasonic cleaning.

7. The method for preparing an ultra-thin organic-inorganic composite diaphragm for an alkaline water electrolyzer according to claim 5, characterized in that: Step S2 includes the following steps: preparing an insulating ceramic suspension; preheating the metal mesh substrate to 250-450° C.; preparing an insulating ceramic coating by a liquid plasma spraying process; The solid content of the insulating ceramic suspension is 5-40 vol%; The parameters of the liquid phase plasma spraying process are: argon 30-40 SLM, hydrogen 2-10 SLM, current 500-900 A, spray gun moving speed 0.5-1.5 m / s, suspension feeding rate 20-200 mL / min, and spraying distance 20-80 mm.

8. The method for preparing an ultra-thin organic-inorganic composite diaphragm for an alkaline water electrolyzer according to claim 5, characterized in that: Step S3 comprises the following steps: dissolving the thermoplastic resin and the hydrophilic inorganic nanoparticles in an organic solvent, mixing them evenly to obtain a casting solution; coating the casting solution on the outer surfaces of the insulating ceramic coating on both sides of the metal mesh substrate prepared in step S2 at 15-35° C. and 30-70% relative humidity; The mass ratio of the thermoplastic resin to the organic solvent is 1:9-1:1, and the mass ratio of the thermoplastic resin to the hydrophilic inorganic nanoparticles is 1:10-10:3; The organic solvent includes one or more of N-methyl-2-pyrrolidone, dimethyl sulfoxide, N,N-dimethylformamide, formamide, and N,N-dimethylacetamide.

9. The method for preparing an ultra-thin organic-inorganic composite diaphragm for an alkaline water electrolyzer according to claim 5, characterized in that: Step S4 comprises the following steps: immersing the metal mesh substrate prepared with the insulating ceramic coating and the organic-inorganic coating in low temperature, normal temperature and high temperature non-solvents in sequence, with each immersion time being not less than 30 minutes, and taking it out after the organic solvent is completely replaced; The non-solvent includes one or more of deionized water, n-propanol, isopropanol, and ethanol; The low temperature is -15-15°C, the normal temperature is 15-40°C, and the high temperature is 40-100°C.

10. Use of the ultra-thin organic-inorganic composite diaphragm for alkaline water electrolysis cell according to any one of claims 1 to 4 in hydrogen production by alkaline water electrolysis.

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