An ultrathin organic-inorganic composite membrane for alkaline water electrolyzer, its preparation method and application

Abstract

This invention relates to an ultrathin organic-inorganic composite membrane for alkaline water electrolyzers, its preparation method, and its application. The organic-inorganic composite membrane is a composite structure of a metal mesh substrate / insulating ceramic coating / organic-inorganic coating, including a metal mesh substrate, insulating ceramic coatings on both sides of the metal mesh substrate, and an organic-inorganic coating on the outer surface of the insulating ceramic coating. The preparation method includes the following steps: roughening the metal mesh substrate; preparing insulating ceramic coatings on both sides of the roughened metal mesh substrate; preparing an organic-inorganic coating on the outer surface of the insulating ceramic coating; phase inversion treatment to obtain the organic-inorganic composite membrane; and cleaning and storing in deionized water. Compared with the prior art, the organic-inorganic composite membrane prepared by this invention exhibits good sheet resistivity, mechanical strength, and stability at a relatively thin thickness.

Description

Technical Field

[0001] This invention relates to the field of membrane technology for alkaline water electrolysis hydrogen production, and in particular to an ultrathin organic-inorganic composite membrane for alkaline water electrolyzers, its preparation method, and its application. Background Technology

[0002] With the ever-increasing global demand for renewable and clean energy, hydrogen energy, as a promising green energy source, has received widespread attention. Hydrogen energy is clean and efficient, and is considered one of the keys to addressing the global energy crisis and environmental pollution. When used as fuel, hydrogen combustion produces only water vapor and does not emit harmful gases, thus offering significant environmental advantages. To achieve widespread application of hydrogen energy, developing efficient and low-cost hydrogen production technologies is crucial. Water electrolysis is currently the most promising hydrogen production method, especially when combined with renewable energy sources. This technology utilizes renewable energy, such as solar or wind power, to generate electricity and decompose water into hydrogen and oxygen. Water electrolysis is not only a clean process but also effectively utilizes abundant natural resources to achieve green hydrogen production. Compared to traditional fossil fuel-based hydrogen production methods, water electrolysis significantly reduces carbon dioxide emissions, helping to reduce greenhouse gas accumulation and promoting the global energy structure towards a low-carbon, sustainable development model. Therefore, water electrolysis is not only an important technology for the rapid development of hydrogen energy but also has significant strategic importance for promoting the green transformation of the global energy system and addressing climate change. With continuous technological advancements and gradual cost reductions, hydrogen energy will play an increasingly important role in the future energy system.

[0003] Alkaline water electrolysis for hydrogen production has become a common technology due to its simple structure and low cost, and has made progress in large-scale commercial applications. In alkaline water electrolysis, organic-inorganic composite membranes are mainly used to separate the anode and cathode regions of the electrolyzer, preventing hydrogen and oxygen from mixing, thereby improving system safety and efficiency. Besides airtightness, the sheet resistivity of the organic-inorganic composite membrane is also an important performance indicator, reflecting the properties of OH... - The resistance to transmission directly affects the energy consumption of hydrogen production through alkaline water electrolysis. The lower the surface resistivity, the lower the energy consumption of OH-. - The stronger the conductivity, the lower the voltage required for water electrolysis and the lower the energy consumption.

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

[0005] The thickness of organic-inorganic composite membranes is limited not only by the coating size during preparation but also primarily by the thickness of the supporting mesh substrate that provides mechanical strength; that is, thinner organic-inorganic composite membranes require thinner supporting mesh substrates. However, to ensure a certain level of mechanical strength, the mesh count of traditional polyphenylene sulfide (PPS) woven mesh increases as the thickness decreases, reducing the contact area between the coatings on both sides and resulting in poor stability of the organic-inorganic composite membrane. Specifically, when the PPS woven mesh thickness is less than 100 μm or the mesh count exceeds 150 mesh, large-area coating peeling off from one side is a common phenomenon in organic-inorganic composite membranes. Summary of the Invention

[0006] The purpose of this invention is to provide an ultrathin organic-inorganic composite membrane for alkaline water electrolyzers, its preparation method and application. The prepared organic-inorganic composite membrane has good sheet resistance, mechanical strength and stability at a relatively thin thickness.

[0007] The objective of this invention can be achieved through the following technical solutions:

[0008] This invention provides an ultrathin organic-inorganic composite membrane for alkaline water electrolyzers. The organic-inorganic composite membrane comprises a composite structure of a metal mesh substrate, an insulating ceramic coating, and an organic-inorganic coating. The metal mesh substrate has insulating ceramic coatings on both sides, and an organic-inorganic coating is disposed 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, with a mesh count of 5-120 mesh.

[0010] Preferably, the insulating ceramic coating comprises one or more of zirconium dioxide, silicon carbide, boron nitride, or titanium nitride, with a particle size of 10-500 nm.

[0011] Preferably, the organic-inorganic coating is a mixture of 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 zirconium dioxide, cerium dioxide, titanium dioxide, and barium sulfate, with a particle size of 10-300 nm.

[0014] Preferably, 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.

[0015] This invention also provides a method for preparing the ultrathin organic-inorganic composite membrane for alkaline water electrolyzer, comprising the following steps:

[0016] S1: Roughening treatment of 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 an insulating ceramic coating;

[0019] S4: Phase inversion treatment to obtain the organic-inorganic composite membrane;

[0020] S5: Store in deionized water after cleaning.

[0021] Preferably, 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.

[0022] More preferably, in step S1, the ultrasonic cleaning refers to immersing the chemically etched metal mesh substrate in deionized water and ultrasonically cleaning it, replacing the deionized water every 45 to 75 seconds until the deionized water is neutral.

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

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

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

[0026] More preferably, in step S2, the solvent of the insulating ceramic suspension includes either deionized water or anhydrous ethanol.

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

[0028] More preferably, in step S2, the dispersant includes either sodium polyacrylate or polyethylene glycol.

[0029] More preferably, in step S2, the insulating ceramic suspension is further prepared by ultrasonication and then filtered and stored.

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

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

[0032] In this invention, a high-temperature resistant and alkali-resistant insulating ceramic coating is applied to the surface of a metal mesh substrate using a liquid-phase plasma spraying process.

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

[0034] More 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 nanoparticles is 1:10-10:3.

[0035] More 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] More preferably, in step S3, the mixture is homogeneously mixed by means of mechanical stirring, planetary ball milling, or other dispersion methods.

[0037] More preferably, in step S3, a casting solution is applied to both sides of the anion exchange membrane using a scraper or a coating head.

[0038] Preferably, step S4 includes the following steps: immersing the metal mesh substrate with the prepared insulating ceramic coating and organic-inorganic coating sequentially in non-solvent solutions at low temperature, room temperature, and high temperature, with each immersion time not less than 30 minutes, and removing it after the organic solvent has been completely replaced.

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

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

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

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

[0043] More preferably, in step S4, the soaking time is 1 hour each time.

[0044] Preferably, step S5 includes the following steps: washing the organic-inorganic composite membrane with deionized water, cutting it to a suitable size, and storing it in deionized water.

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

[0046] More preferably, the preparation method of the ultrathin organic-inorganic composite membrane for the alkaline water electrolyzer includes the following steps:

[0047] S1: Select a straight metal mesh and clean it with anhydrous ethanol to ensure cleanliness. Immerse the dried metal mesh in a 15wt% nitric acid solution for 10 minutes to chemically etch the mesh, increasing its roughness. Immerse the etched metal mesh in deionized water and sonicate it, changing the deionized water every minute until the deionized water is neutral.

[0048] S2: A high-temperature and alkali-resistant insulating ceramic coating is applied to the surface of a metal mesh using liquid-phase plasma spraying. First, an insulating ceramic suspension with a solid content of 10-20 vol% is prepared, ultrasonicated, filtered, and stored. The metal mesh is preheated to 300-350℃ to enhance coating adhesion. Liquid-phase plasma spraying is then performed with the following parameters: argon 37 SLM, hydrogen 8 SLM, current 700 A, spray gun movement speed 1 m / s, and suspension feed rate 27 mL / min.

[0049] S3: The thermoplastic resin is dissolved in an organic solvent by mechanical stirring. Then, hydrophilic inorganic nanoparticles are added to the polymer solution and mixed evenly by mechanical stirring, planetary ball milling, etc., to obtain the casting solution. At 25℃ and 60% relative humidity, a dry and clean metal mesh is fixed with a clamp, and the casting solution is applied to both sides of the metal mesh by a doctor blade or coating head.

[0050] S4: Immerse the coated metal mesh in non-solvent solutions at low temperature, room temperature, and high temperature in sequence, with each immersion time being 1 hour. After the organic solvent is completely replaced, remove the organic-inorganic composite membrane.

[0051] S5: Clean the organic-inorganic composite membrane with deionized water, cut it to the appropriate size, and store it in deionized water.

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

[0053] This invention addresses the limitation of existing organic-inorganic composite membrane thickness caused by the substrate, proposing an ultrathin organic-inorganic composite membrane for alkaline water electrolyzers, its preparation method, and its application. This invention replaces the traditional polyphenylene sulfide woven mesh with an alkali-resistant and mechanically sound metal mesh, achieving a reduction in mesh count by tens of times while maintaining the same mechanical strength. This provides sufficient contact area for the coatings on both sides, thereby improving the stability of the organic-inorganic composite membrane. Furthermore, to address the conductivity issue of the metal mesh, this invention incorporates insulation treatment to prevent short circuits during electrolyzer operation.

[0054] The ultrathin organic-inorganic composite diaphragm proposed in this invention has excellent stability mainly due to two factors: first, the reduced mesh size and larger metal mesh aperture increase the contact area between the coatings on both sides, preventing the overall peeling off of the coating on one side; second, the insulating ceramic coating increases the diameter and roughness of the metal mesh wires, thereby 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 alkaline water electrolysis cell. The organic-inorganic composite diaphragm is a composite structure of metal mesh substrate / insulating ceramic coating / organic-inorganic coating. With a thinner thickness, it can achieve a smaller mesh count, while having good sheet resistance, mechanical strength and stability.

[0057] (2) This invention uses a metal mesh as the supporting substrate for the organic-inorganic composite membrane to prepare an ultrathin and stable organic-inorganic composite membrane. Compared with organic material woven mesh, the metal mesh substrate can achieve a smaller mesh count at a thinner thickness, increasing the contact area of ​​the coatings on both sides of the substrate and ensuring that the stability of the organic-inorganic composite membrane does not deteriorate as the thickness decreases.

[0058] (3) In this invention, the metal mesh surface is covered with a double coating, providing double protection for the safe operation of the electrolytic cell. In this invention, the organic-inorganic coating not only isolates the gas but also serves as the outermost insulating coating of the metal mesh. Even after the organic-inorganic coating is damaged, the surface of the metal mesh is still covered with an insulating ceramic coating, which greatly avoids short circuit accidents in the electrolytic cell.

[0059] (4) The rough outer surface and internal accumulation holes of the insulating ceramic coating on both sides of the metal mesh substrate in this invention increase the total surface area of ​​the metal mesh substrate, providing a larger contact area between the organic-inorganic coating and the metal mesh substrate, and improving the stability of the organic-inorganic composite membrane.

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

[0061] (6) The organic-inorganic composite membrane prepared by the present invention has good electrochemical performance. As the thickness decreases, the electrochemical performance of the membrane is significantly improved. Attached Figure Description

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

[0063] Figure 2 This is a schematic diagram of the structure of the present invention; (in the figure: 1-metal mesh substrate; 2-insulating ceramic coating; 3-organic-inorganic coating). Detailed Implementation

[0064] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

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

[0066] A schematic diagram of an ultrathin organic-inorganic composite membrane for an alkaline water electrolyzer is shown below. Figure 2 As shown, the organic-inorganic composite membrane is a composite structure of metal mesh substrate / insulating ceramic coating / organic-inorganic coating, including metal mesh substrate 1, insulating ceramic coating 2 on both sides of metal mesh substrate 1, and organic-inorganic coating 3 on the outer surface of insulating ceramic coating 2.

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

[0068] S1: Roughening treatment of 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 an insulating ceramic coating;

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

[0072] S5: Store in deionized water after cleaning.

[0073] Example 1

[0074] An ultrathin organic-inorganic composite diaphragm for an alkaline water electrolyzer is prepared as follows: A 60mm × 80mm piece of 80μm thick, 40-mesh 304 stainless steel woven mesh is cut, soaked in anhydrous ethanol, and sonicated for 10 minutes. The cleaned stainless steel woven mesh is then dried in an 80℃ oven for 10 minutes. The dried stainless steel woven mesh is removed, cooled to room temperature, and soaked in a 15wt% nitric acid solution for 10 minutes. The etched stainless steel woven mesh is then removed and sonicated in deionized water, with the deionized water replaced every minute until it is neutral. A 10vol% zirconium dioxide suspension (zirconia powder at 40nm) is prepared, containing 1wt% sodium polyacrylate as a dispersant, and the pH is adjusted to 6. The suspension is sonicated at 25℃ for 20 minutes, and then aggregates or contaminants larger than 75μm are removed using a filter. After heating the metal mesh to 300℃ in an oven, liquid phase plasma spraying was performed using a Metco F4MB-XL device. The spraying process parameters were: argon 37 SLM, hydrogen 8 SLM, current 700A, spray gun movement speed 1m / s, suspension feed rate 27mL / min, spraying distance 40mm, and 25 spraying cycles. At 80℃, 15g of polysulfone was added to 85g of N-methyl-2-pyrrolidone (NMP) and mechanically stirred until the polysulfone was completely dissolved. Then, 85g of 40nm zirconium dioxide was added in batches and mechanically stirred at 2000rpm for 3 hours to disperse the solution. After standing to remove bubbles, a casting solution was obtained. At 25℃ and 60% relative humidity, a clean, dry stainless steel woven mesh was fixed between two 100μm scrapers. The casting liquid is fed in the middle of a 10mm scraper with an effective coating area of ​​80mm and a coating thickness of 100μm, with the stainless steel woven mesh within the effective coating area of ​​the scraper. The casting liquid is then evenly scraped from bottom to top. The entire fixture is then sequentially immersed in deionized water at 5℃, 25℃, and 90℃, with each immersion time being 1 hour. The entire fixture is then removed, the organic-inorganic composite diaphragm is taken out, and its surface is rinsed with deionized water. It is then cut to a suitable size and stored in deionized water for convenient subsequent testing and use.

[0075] Example 2

[0076] An ultrathin organic-inorganic composite diaphragm for an alkaline water electrolyzer is prepared as follows: A 100μm thick, 40-mesh 304 stainless steel woven mesh (60mm × 80mm) is cut and immersed in anhydrous ethanol, then sonicated for 10 minutes. The cleaned stainless steel woven mesh is then dried in an 80℃ oven for 10 minutes. The dried stainless steel woven mesh is removed, cooled to room temperature, and immersed in a 15wt% nitric acid solution for 10 minutes. The etched stainless steel woven mesh is then removed and sonicated in deionized water, with the deionized water replaced every minute until it is neutral. A 10vol% zirconium dioxide suspension (zirconia powder at 40nm) is prepared, containing 1wt% sodium polyacrylate as a dispersant, and the pH is adjusted to 6. The suspension is sonicated at 25℃ for 20 minutes, and then aggregates or contaminants larger than 75μm are removed using a filter. After heating the metal mesh to 300℃ in an oven, liquid phase plasma spraying was performed using a Metco F4MB-XL device. The spraying process parameters were: argon 37 SLM, hydrogen 8 SLM, current 700A, spray gun movement speed 1m / s, suspension feed rate 27mL / min, spraying distance 40mm, and 25 spraying cycles. At 80℃, 15g of polysulfone was added to 85g of N-methyl-2-pyrrolidone (NMP) and mechanically stirred until the polysulfone was completely dissolved. Then, 85g of 40nm zirconium dioxide was added in batches and mechanically stirred at 2000rpm for 3 hours to disperse the solution. After standing to remove bubbles, a casting solution was obtained. At 25℃ and 60% relative humidity, a clean, dry stainless steel woven mesh was fixed between two 125μm scrapers. The casting liquid is fed in the middle of a 10mm scraper with an effective coating area of ​​80mm and a coating thickness of 125μm, with the stainless steel woven mesh within the effective coating area of ​​the scraper. The casting liquid is then evenly scraped from bottom to top. The entire fixture is then sequentially immersed in deionized water at 5℃, 25℃, and 90℃, with each immersion time being 1 hour. The entire fixture is then removed, the organic-inorganic composite diaphragm is taken out, and its surface is rinsed with deionized water. It is then cut to a suitable size and stored in deionized water for convenient subsequent testing and use.

[0077] Example 3

[0078] An ultrathin organic-inorganic composite diaphragm for an alkaline water electrolyzer is prepared as follows: A 150μm thick, 40-mesh 304 stainless steel woven mesh (60mm × 80mm) is cut and immersed in anhydrous ethanol, then sonicated for 10 minutes. The cleaned stainless steel woven mesh is then dried in an 80℃ oven for 10 minutes. The dried stainless steel woven mesh is removed, cooled to room temperature, and immersed in a 15wt% nitric acid solution for 10 minutes. The etched stainless steel woven mesh is then removed and sonicated in deionized water, with the deionized water replaced every minute until it is neutral. A 10vol% zirconium dioxide suspension (zirconia powder of 40nm) is prepared, containing 1wt% sodium polyacrylate as a dispersant, and the pH is adjusted to 6. The suspension is sonicated at 25℃ for 20 minutes, and then aggregates or contaminants larger than 75μm are removed using a filter. After heating the metal mesh to 300℃ in an oven, liquid phase plasma spraying was performed using a Metco F4MB-XL device. The spraying process parameters were: argon 37 SLM, hydrogen 8 SLM, current 700A, spray gun movement speed 1m / s, suspension feed rate 27mL / min, spraying distance 40mm, and 25 spraying cycles. At 80℃, 15g of polysulfone was added to 85g of N-methyl-2-pyrrolidone (NMP) and mechanically stirred until the polysulfone was completely dissolved. Then, 85g of 40nm zirconium dioxide was added in batches and mechanically stirred at 2000rpm for 3 hours to disperse the solution. After standing to remove bubbles, a casting solution was obtained. At 25℃ and 60% relative humidity, a clean, dry stainless steel woven mesh was fixed between two 150μm scrapers. The casting liquid is fed in the middle of a 10mm scraper with an effective coating area of ​​80mm and a coating thickness of 150μm, with the stainless steel woven mesh within the effective coating area of ​​the scraper. The casting liquid is then evenly scraped from bottom to top. The entire fixture is then sequentially immersed in deionized water at 5℃, 25℃, and 90℃ for 1 hour each time. The entire fixture is then removed, the organic-inorganic composite diaphragm is taken out, and its surface is rinsed with deionized water. It is then cut to a suitable size and stored in deionized water for easy subsequent testing and use.

[0079] Example 4

[0080] An ultrathin organic-inorganic composite diaphragm for an alkaline water electrolyzer is prepared as follows: A 60mm × 80mm piece of 80μm thick, 40-mesh 304 stainless steel woven mesh is cut, immersed in anhydrous ethanol, and sonicated for 10 minutes. The cleaned stainless steel woven mesh is then dried in an 80℃ oven for 10 minutes. The dried stainless steel woven mesh is removed, cooled to room temperature, and immersed in a 15wt% nitric acid solution for 10 minutes. The etched stainless steel woven mesh is then removed and sonicated in deionized water, with the deionized water changed every minute until the deionized water is neutral. A 10vol% boron nitride suspension (boron nitride powder at 40nm) is prepared, containing 1wt% sodium polyacrylate as a dispersant, and the pH is adjusted to 6. The suspension is sonicated at 25℃ for 20 minutes, and then aggregates or contaminants larger than 75μm are removed using a filter. After heating the metal mesh to 300℃ in an oven, liquid phase plasma spraying was performed using a Metco F4MB-XL device. The spraying process parameters were: argon 37 SLM, hydrogen 8 SLM, current 700A, spray gun movement speed 1m / s, suspension feed rate 27mL / min, spraying distance 40mm, and 25 spraying cycles. At 80℃, 15g of polysulfone was added to 85g of N-methyl-2-pyrrolidone (NMP) and mechanically stirred until the polysulfone was completely dissolved. Then, 85g of 40nm zirconium dioxide was added in batches and mechanically stirred at 2000rpm for 3 hours to disperse the solution. After standing to remove bubbles, a casting solution was obtained. At 25℃ and 60% relative humidity, a clean, dry stainless steel woven mesh was fixed between two 100μm scrapers. The casting liquid is fed in the middle of a 10mm scraper with an effective coating area of ​​80mm and a coating thickness of 100μm, with the stainless steel woven mesh within the effective coating area of ​​the scraper. The casting liquid is then evenly scraped from bottom to top. The entire fixture is then sequentially immersed in deionized water at 5℃, 25℃, and 90℃, with each immersion time being 1 hour. The entire fixture is then removed, the organic-inorganic composite diaphragm is taken out, and its surface is rinsed with deionized water. It is then cut to a suitable size and stored in deionized water for convenient subsequent testing and use.

[0081] Comparative Example 1

[0082] A commercially available organic-inorganic composite membrane product, model number Zirfon PERL UTP 500.

[0083] Comparative Example 2

[0084] An organic-inorganic composite membrane, unlike Example 1, uses a 100μm thick, 150-mesh polyphenylene sulfide mesh as a substrate, on which an insulating ceramic coating and an organic-inorganic coating are prepared. The preparation method is the same as in Example 1. The polyphenylene sulfide mesh is of model PPS-150, manufactured by 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 tensile strength analysis, the tensile strength of the organic-inorganic composite membrane using a metal mesh substrate is significantly improved. From the sheet resistance analysis, the sheet resistance of the organic-inorganic composite membrane decreases with decreasing thickness, proving that reducing the thickness of the organic-inorganic composite membrane is an effective way to reduce sheet resistance. Furthermore, comparing Examples 1 and 4 verifies that the good hydrophilicity of the insulating coating also helps to reduce the sheet resistance of the organic-inorganic composite membrane. From the bubble point pressure analysis, since the coating preparation process is the same, there is no difference among the various organic-inorganic composite membranes. From the ultrasonic powder shedding rate analysis, the powder shedding rate of Examples 1-4 is lower than that of Zirfon UTP 500 and PPS-150, with PPS-150 having a 100% powder shedding rate due to the overall peeling off of the coating on one side.

[0088] Table 2. Electrochemical performance of Comparative Examples 1-2 and Examples 1-4 in alkaline water electrolyzers

[0089]

[0090] The conditions for the upper tank test were as follows: the electrolytic cell temperature was 90℃, both the anode and cathode were ordinary nickel mesh, the electrolyte was 30wt% KOH solution, the flow rate was 500ml / min, and the electrolyte was introduced from both sides.

[0091] Table 2 shows the electrochemical performance of Comparative Examples 1-2 and Examples 1-4 in actual cell tests. It can be seen that the electrochemical performance of the diaphragm is significantly improved as the thickness decreases, demonstrating the importance of diaphragm thickness to the performance of the alkaline water electrolyzer. Furthermore, no short circuits or other accidents occurred during the cell tests, indicating that the ultrathin organic-inorganic composite diaphragm proposed in this invention also exhibits excellent insulation properties and is not affected by the metal substrate.

[0092] In summary, this invention provides an ultrathin organic-inorganic composite diaphragm for alkaline water electrolyzers. This invention replaces traditional polyphenylene sulfide woven mesh with an alkali-resistant and mechanically sound metal mesh (e.g., stainless steel woven mesh), and obtains a composite structure of metal mesh substrate / insulating ceramic coating / organic-inorganic coating by preparing an insulating ceramic coating and an organic-inorganic coating. The prepared organic-inorganic composite diaphragm achieves a lower mesh count at a thinner thickness, while also exhibiting good sheet resistance, mechanical strength, and stability.

[0093] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. An ultrathin organic-inorganic composite diaphragm for an alkaline water electrolyzer, characterized in that, The organic-inorganic composite membrane is a composite structure of metal mesh substrate / insulating ceramic coating / organic-inorganic coating, including metal mesh substrate, insulating ceramic coating on both sides of metal mesh substrate, and organic-inorganic coating on the outer surface of insulating ceramic coating. The metal mesh substrate is selected from any one of 304 stainless steel woven mesh, nickel mesh, and titanium mesh, with a mesh size of 5-120 mesh; the insulating ceramic coating is selected from one or more of zirconium dioxide, silicon carbide, boron nitride, or titanium nitride, with a particle size of 10-500 nm; the organic-inorganic coating is a mixture of thermoplastic resin and hydrophilic inorganic nanoparticles. The total thickness of the organic-inorganic composite membrane is 100-250 μm.

2. The ultrathin organic-inorganic composite diaphragm for an alkaline water electrolyzer according to claim 1, characterized in that, The thermoplastic resin is selected from one or more of polysulfone, polyethersulfone, polyphenylene sulfide, polypropylene, polyetheretherketone, polyimide, and polyetherimide; the hydrophilic inorganic nanoparticles are selected from one or more of zirconium dioxide, cerium dioxide, titanium dioxide, and barium sulfate, with a particle size of 10-300 nm.

3. The ultrathin 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, and the thickness of the organic-inorganic coating is 10-100 μm.

4. A method for preparing an ultrathin organic-inorganic composite diaphragm for an alkaline water electrolyzer as described in any one of claims 1-3, characterized in that, Includes the following steps: S1: Roughening treatment of the metal mesh substrate; S2: Prepare insulating ceramic coatings on both sides of the roughened metal mesh substrate; S3: Prepare an organic-inorganic coating on the outer surface of an insulating ceramic coating; S4: Phase inversion treatment to obtain the organic-inorganic composite membrane; S5: Store in deionized water after cleaning.

5. The method for preparing an ultrathin organic-inorganic composite diaphragm for an alkaline water electrolyzer according to claim 4, 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.

6. The method for preparing an ultrathin organic-inorganic composite diaphragm for an alkaline water electrolyzer according to claim 4, characterized in that, Step S2 includes the following steps: preparing an insulating ceramic suspension; preheating the metal mesh substrate to 250-450℃; and preparing an insulating ceramic coating using a liquid-phase 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 500-900A, spray gun moving speed 0.5-1.5m / s, suspension feeding rate 20-200mL / min, and spraying distance 20-80mm.

7. The method for preparing an ultrathin organic-inorganic composite diaphragm for an alkaline water electrolyzer according to claim 4, characterized in that, Step S3 includes the following steps: dissolving thermoplastic resin and hydrophilic inorganic nanoparticles in an organic solvent, mixing them evenly to obtain a casting solution; coating the outer surfaces of the insulating ceramic coatings on both sides of the metal mesh substrate prepared in step S2 with the casting solution at 15-35℃ 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 is selected from one or more of N-methyl-2-pyrrolidone, dimethyl sulfoxide, N,N-dimethylformamide, formamide, and N,N-dimethylacetamide.

8. The method for preparing an ultrathin organic-inorganic composite diaphragm for an alkaline water electrolyzer according to claim 4, characterized in that, Step S4 includes the following steps: the metal mesh substrate with the insulating ceramic coating and the organic-inorganic coating is sequentially immersed in non-solvents at low temperature, room temperature and high temperature, with each immersion time not less than 30 minutes, and taken out after the organic solvent is completely replaced; The non-solvent is selected from one or more of deionized water, n-propanol, isopropanol, and ethanol; The low temperature is -15 to 15℃, the normal temperature is 15 to 40℃, and the high temperature is 40 to 100℃.

9. The application of an ultrathin organic-inorganic composite membrane for alkaline water electrolysis as described in any one of claims 1-3 in alkaline water electrolysis for hydrogen production.

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