Alkaline hydrogen production composite diaphragm and preparation method thereof

Abstract

The invention relates to an alkaline hydrogen production composite diaphragm and a preparation method thereof.The alkaline hydrogen production composite diaphragm comprises a base material, an inner layer and an outer skin layer, the inner layer and the outer skin layer are sequentially constructed on the left side and the right side of the base material from inside to outside with the base material as the center, and the thickness of the inner layer is at least 20 times or above that of the outer skin layer; a membrane casting solution for constructing the inner layer comprises 10%-30% of an unsulfonated organic high-molecular polymer, 30%-50% of hydrophilic inorganic nanoparticles, 1%-10% of a pore-foaming agent and 25%-45% of an organic solvent; a membrane casting solution for constructing the outer skin layer comprises the following components in percentage by weight: 5-35% of sulfonated organic high-molecular polymer, 0-10% of unsulfonated organic high-molecular polymer, 0-30% of hydrophilic inorganic nanoparticles, 0.1-2% of a pore-foaming agent and 50-75% of an organic solvent. The composite membrane has the advantages of low membrane surface resistance, high ionic conductivity, strong gas barrier property, high mechanical strength and long service life.

Description

Technical Field

[0001] The present invention belongs to the technical field of hydrogen production by electrolysis of water, and in particular relates to an alkaline hydrogen production composite diaphragm and a preparation method thereof. Background Art

[0002] As the global demand for clean energy continues to increase, hydrogen, as an efficient and clean energy carrier, has received widespread attention. Hydrogen production by water electrolysis is currently one of the most mainstream methods of hydrogen production, among which alkaline water electrolysis hydrogen production technology is widely used due to its high maturity and low cost. However, this technology still faces several challenges, including high electrolysis energy consumption, low gas production purity, and dependence on imported core components such as diaphragms. In order to achieve large-scale production and reduce energy consumption and costs, the key lies in technological innovation of these core components and seeking domestic alternatives. As a key material in alkaline water electrolysis hydrogen production technology, the performance of the diaphragm directly affects the energy consumption, hydrogen production purity and safety of the electrolyzer under the same catalytic electrode conditions. Therefore, the quality of the diaphragm is crucial to the entire electrolysis process.

[0003] Early asbestos cloth separators suffered from high electrical resistance, high energy consumption, rapid dissolution at high temperatures, and carcinogenicity. Subsequent adoption of polyphenylene sulfide (PPS) separators, while somewhat improving these issues, still suffered from poor hydrophilicity, insufficient electrolyte wetting, high electrical resistance, and high energy consumption. To overcome these shortcomings, researchers developed organic / inorganic composite separators, which enhance the separator's hydrophilicity, ionic conductivity, and mechanical strength by adding inorganic nanoparticles (such as zirconium oxide and titanium dioxide) to a polymer matrix.

[0004] Despite this, existing composite diaphragms still have a significant technical problem, namely the shedding of inorganic nanoparticles. Due to the weak bonding between inorganic nanoparticles and the organic polymer matrix, the particles are easily shed during preparation, transportation, and use. This shedding phenomenon not only increases the resistance of the diaphragm and reduces the electrolysis efficiency, but may also cause hydrogen and oxygen to mix, increasing safety risks and even causing the electrolyzer to explode. In addition, the shed particles may also block the channels of the electrolyzer, further affecting the stability of the electrolysis process. In addition, improving the membrane surface resistance, hydrophilicity, ionic conductivity, mechanical properties, etc. remains a pursuit in this technical field. Summary of the Invention

[0005] The purpose of the present invention is to provide an alkaline hydrogen production composite diaphragm with low membrane surface resistance, high ion conductivity, strong gas barrier property, high mechanical strength and good durability.

[0006] Another object of the present invention is to provide a method for preparing the alkaline hydrogen production composite membrane.

[0007] In order to achieve the above object, the technical solution adopted by the present invention is:

[0008] On the one hand, the present invention provides an alkaline hydrogen production composite membrane, which includes a substrate, and an inner layer and an outer skin layer constructed in sequence from the inside to the outside on the left and right sides of the substrate with the substrate as the center, and the thickness of the inner layer is at least 20 times the thickness of the outer skin layer.

[0009] The present invention effectively solves the problem of powder shedding of the composite membrane by constructing an inner layer with large pore size and high porosity, and an outer layer with small pore size and better hydrophilicity and thin skin. At the same time, the prepared composite membrane also has the advantages of low membrane surface resistance, high ionic conductivity, strong gas barrier properties and high mechanical strength.

[0010] Preferably, the thickness of the inner layer is 30 to 50 times the thickness of the outer layer, such as 30 times, 35 times, 40 times, 45 times, 50 times or a value between any two of the above values.

[0011] Preferably, taking the total mass of the casting liquid constituting the inner layer as 100%, the inner layer casting liquid comprises:

[0012] Unsulfonated organic polymer 10% to 30%,

[0013] Hydrophilic inorganic nanoparticles 30% to 50%,

[0014] Porogen 1% to 10%,

[0015] Organic solvent 25%~45%.

[0016] Further preferably, based on the total mass of the casting liquid constituting the inner layer being 100%, the inner layer casting liquid comprises:

[0017] Unsulfonated organic polymer 15% to 25%,

[0018] Hydrophilic inorganic nanoparticles 35% to 45%,

[0019] Porogen 3% to 8%,

[0020] Organic solvent 30%~40%.

[0021] More preferably, based on the total mass of the casting liquid constituting the inner layer being 100%, the inner layer casting liquid comprises:

[0022] Unsulfonated organic polymer 18% to 22%,

[0023] Hydrophilic inorganic nanoparticles 38% to 42%,

[0024] Porogen 4% to 6%,

[0025] Organic solvent 33%~38%.

[0026] Preferably, based on the total mass of the casting solution for constructing the outer skin layer being 100%, the outer skin layer casting solution comprises:

[0027] Sulfonated organic polymer 5% to 35%,

[0028] Unsulfonated organic polymer 0-10%,

[0029] Hydrophilic inorganic nanoparticles 0-30%,

[0030] Porogen 0.1%~2%,

[0031] Organic solvent 50%~75%.

[0032] In some embodiments, based on the total mass of the casting solution for constituting the outer skin layer being 100%, the outer skin layer casting solution comprises:

[0033] Sulfonated organic polymer 25% to 35%,

[0034] Porogen 0.1%~2%,

[0035] Organic solvent 65%~74%.

[0036] Furthermore, taking the total mass of the casting solution for constituting the outer skin layer as 100%, the casting solution for the outer skin layer comprises:

[0037] Sulfonated organic polymer 28% to 32%,

[0038] Porogen 0.5% to 1.5%,

[0039] Organic solvent 67%~70%.

[0040] In some embodiments, based on the total mass of the casting solution for constituting the outer skin layer being 100%, the outer skin layer casting solution comprises:

[0041] Sulfonated organic polymer 20% to 30%,

[0042] Unsulfonated organic polymer 3-10%,

[0043] Porogen 0.1%~2%,

[0044] Organic solvent 60%~75%.

[0045] Furthermore, taking the total mass of the casting solution for constructing the outer skin layer as 100%, the outer skin layer casting solution comprises:

[0046] Sulfonated organic polymer 23% to 28%,

[0047] Unsulfonated organic polymer 3-8%,

[0048] Porogen 0.5% to 1.5%,

[0049] Organic solvent 65%~73%.

[0050] In some embodiments, based on the total mass of the casting solution for constituting the outer skin layer being 100%, the outer skin layer casting solution comprises:

[0051] Sulfonated organic polymer 5% to 10%,

[0052] Unsulfonated organic polymer 3% to 10%,

[0053] Hydrophilic inorganic nanoparticles 15% to 25%,

[0054] Porogen 0.1%~2%,

[0055] Organic solvent 55%~75%.

[0056] Furthermore, taking the total mass of the casting solution for constructing the outer skin layer as 100%, the outer skin layer casting solution comprises:

[0057] Sulfonated organic polymer 5% to 8%,

[0058] Unsulfonated organic polymer 4% to 6%,

[0059] Hydrophilic inorganic nanoparticles 18% to 23%,

[0060] Porogen 0.5% to 1.5%,

[0061] Organic solvent 65%~70%.

[0062] Preferably, the unsulfonated organic high molecular polymer in the inner layer casting solution and the outer skin layer casting solution is one or more of polysulfone, polyphenylsulfone and polyethersulfone.

[0063] Preferably, the hydrophilic inorganic nanoparticles in the inner layer casting solution and the outer layer casting solution are independently selected from one or more of zirconium dioxide, cerium dioxide, calcium carbonate and barium sulfate.

[0064] More preferably, the diameter of the hydrophilic inorganic nanoparticles in the inner layer casting solution and the outer skin layer casting solution is 10 nm to 50 nm.

[0065] Preferably, the porogens in the inner layer casting solution and the outer layer casting solution are independently selected from one or more of polyvinyl pyrrolidone, glycerol, polyethylene glycol, and ethylene glycol.

[0066] Preferably, the organic solvents in the inner layer casting solution and the outer layer casting solution are independently selected from one or more of N-methylpyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide and dimethyl sulfoxide.

[0067] Preferably, the sulfonated organic high molecular polymer is selected from one or more of sulfonated polysulfone, sulfonated polyphenylsulfone, sulfonated polyethersulfone and sulfonated polyetherketone.

[0068] Preferably, the thickness of the inner layer is 50μm to 300μm, more preferably 150μm to 300μm, and even more preferably 220μm to 250μm, such as 220μm, 225μm, 230μm, 235μm, 240μm, 245μm, 250μm or a value between any two of the above values.

[0069] Preferably, the thickness of the outer skin layer is 1 μm to 10 μm, more preferably 3 μm to 8 μm, such as 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm or a value between any two of the above values.

[0070] Preferably, the substrate is polyphenylene sulfide.

[0071] Another aspect of the present invention provides an alkaline hydrogen production composite membrane, which includes a substrate, and an inner layer, an intermediate layer, and an outer skin layer constructed in sequence from the inside to the outside on the left and right sides of the substrate with the substrate as the center, wherein the thickness of the inner layer is 10 μm to 25 μm, the thickness of the intermediate layer is 20 μm to 50 μm, and the thickness of the outer layer is 5 μm to 15 μm. When the amount of hydrophilic inorganic nanoparticles added is high, the flexibility of the membrane decreases and it is easy to crack. By providing a three-layer structure (i.e., an inner layer, an intermediate layer, and an outer skin layer), the flexibility of the membrane can be effectively improved and the cracking problem can be solved.

[0072] Preferably, taking the total mass of the casting liquid constituting the inner layer as 100%, the inner layer casting liquid comprises:

[0073] Sulfonated organic polymer 0% to 10%,

[0074] Unsulfonated organic polymer 3% to 10%,

[0075] Hydrophilic inorganic nanoparticles 0% to 10%,

[0076] Porogen 0.1%~2%,

[0077] Organic solvent 70%~80%.

[0078] Further preferably, based on the total mass of the casting liquid constituting the inner layer being 100%, the inner layer casting liquid comprises:

[0079] Unsulfonated organic polymer 5% to 10%,

[0080] Hydrophilic inorganic nanoparticles 5% to 10%,

[0081] Porogen 0.1%~2%,

[0082] Organic solvent 76%~80%.

[0083] Preferably, based on the total mass of the casting solution constituting the intermediate layer being 100%, the intermediate layer casting solution comprises:

[0084] Sulfonated organic polymer 0% to 10%,

[0085] Unsulfonated organic polymer 3% to 10%,

[0086] Hydrophilic inorganic nanoparticles 40% to 70%,

[0087] Porogen 0.1%~5%,

[0088] Organic solvent 25%~45%.

[0089] Further preferably, based on the total mass of the casting solution constituting the intermediate layer being 100%, the intermediate layer casting solution comprises:

[0090] Sulfonated organic polymer 5% to 10%,

[0091] Unsulfonated organic polymer 3% to 6%,

[0092] Hydrophilic inorganic nanoparticles 40% to 60%,

[0093] Porogen 0.1%~5%,

[0094] Organic solvent 25%~45%.

[0095] Preferably, based on the total mass of the casting solution for constructing the outer skin layer being 100%, the outer skin layer casting solution comprises:

[0096] Sulfonated organic polymer 3% to 10%,

[0097] Unsulfonated organic polymer 0% to 10%,

[0098] Hydrophilic inorganic nanoparticles 0% to 10%,

[0099] Porogen 0.1%~2%,

[0100] Organic solvent 70%~85%.

[0101] Further preferably, based on the total mass of the casting solution constituting the outer skin layer being 100%, the outer skin layer casting solution comprises:

[0102] Sulfonated organic polymer 3% to 10%,

[0103] Hydrophilic inorganic nanoparticles 5% to 10%,

[0104] Porogen 0.5% to 1.5%,

[0105] Organic solvent 78.5%~85%.

[0106] The sulfonated organic high molecular polymer, the unsulfonated organic high molecular polymer, the hydrophilic inorganic nanoparticles, the porogen, and the organic solvent are as described above and will not be described in detail here.

[0107] On the other hand, the present invention also provides a method for preparing the alkaline hydrogen production composite membrane as described above, comprising coating multiple layers of casting liquid on both sides of a substrate from the inside out, then treating the substrate with steam, immersing the substrate in a coagulation bath for phase conversion, and finally washing the substrate to obtain the alkaline hydrogen production composite membrane.

[0108] Preferably, a coating device is used to coat the substrate, and the coating device includes a feeding unit for storing and conveying the casting liquid, a coating unit connected to the feeding unit and used to coat the casting liquid on the surface of the substrate, and a conveying unit for conveying the substrate to the coating unit. The coating unit includes a slit coating die head, which has two groups symmetrically arranged on the left and right sides of the substrate. Each group of slit coating die heads is provided with a plurality of independently controlled and mutually non-interfering coating heads for achieving simultaneous multi-layer coating. Each coating head distributes and controls the casting liquid through an independent feeding pipe and a sparging trough.

[0109] The coating comprises moving the substrate along a preset path through the conveying unit, controlling the slit coating die heads on the left and right sides of the substrate to operate, and coating multiple layers of casting liquid on both sides of the substrate at the same time.

[0110] Preferably, the substrate coated with the multi-layer casting solution is sent into a steam chamber for the steam treatment.

[0111] More preferably, the temperature of the steam chamber is 20°C to 70°C.

[0112] Preferably, the coagulation bath is water or a mixture of water and a solvent. When the coagulation bath is a mixed solution of water and a solvent, the mass content of the solvent is 10% to 55%. The solvent is a conventional solvent in the art, such as dimethyl sulfoxide or N,N-dimethylformamide.

[0113] Preferably, the temperature of the coagulation bath is 25°C to 50°C.

[0114] Due to the application of the above technical solution, the present invention has the following advantages compared with the prior art:

[0115] The present invention effectively solves the problems of membrane powder loss and poor service life by constructing an inner layer and an outer layer on both sides of the substrate, and by designing the formula and thickness of the inner layer and the outer layer. At the same time, the prepared composite membrane also has the advantages of low membrane surface resistance, high ionic conductivity, strong gas barrier properties and high mechanical strength.

[0116] The preparation method of the present invention can simultaneously realize multi-layer coating and one-time molding, has a simple process, low cost and broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0117] Figure 1 A simplified structural diagram of a coating device provided by the present invention;

[0118] Figure 2 A schematic structural diagram of a second coating device provided by the present invention;

[0119] Figure 3 A schematic structural diagram of a third coating device provided by the present invention;

[0120] Figure 4 A simplified structural diagram of a composite diaphragm provided by the present invention;

[0121] Figure 5 This is an exploded view of the structure of a composite diaphragm provided by the present invention;

[0122] Among them, 1. base material; 2. inner layer; 3. outer layer. DETAILED DESCRIPTION

[0123] The present invention is further described below with reference to the following examples. However, the present invention is not limited to the following examples. The implementation conditions used in the examples may be further adjusted according to the specific requirements of the application. Unspecified implementation conditions are conventional conditions in the industry. The technical features involved in the various embodiments of the present invention may be combined with each other as long as they do not conflict with each other.

[0124] Unless otherwise specified, the coating device used in the present invention includes a feeding unit for storing and conveying the casting liquid, a coating unit connected to the feeding unit and used to evenly coat the casting liquid on the surface of the substrate 1, and a conveying unit for conveying the substrate 1 to the coating unit. The feeding unit includes a dosing tank, a feeding pump and a filter. The dosing tank, the feeding pump and the filter can be respectively provided in one or more groups according to the type of casting liquid or actual needs. The specific structure and connection method of the dosing tank, the feeding pump and the filter refer to the prior art, and the present invention does not make specific limitations. The coating unit includes a slit coating die head, which has two groups symmetrically arranged on the left and right sides. Each group of slit coating dies is provided with a plurality of independently controlled and non-interfering coating heads for realizing multi-layer coating. Each coating head distributes and controls the casting liquid through an independent feed pipe and a material sparging trough to ensure the uniformity and consistency of each layer of coating. For example: when it is necessary to construct two film layers (i.e., inner layer 2 and outer skin layer 3) on both sides of the substrate 1, as Figure 1 、 Figure 2 As shown, two coating heads are set on the left and right sides respectively, and the casting liquid of the inner layer 2 and the outer skin layer 3 is transported to the feeding pipes and the slurry tanks of the two coating heads on both sides through the feeding unit for coating. For another example: when it is necessary to construct three layers of film (i.e., inner layer 2, middle layer and outer skin layer 3) on both sides of the substrate 1, as shown in FIG. Figure 3 As shown, three coating heads are positioned on the left and right sides, respectively. A feeding unit delivers the casting solution for the inner layer 2, the middle film layer, and the outer skin layer 3 to the feed pipes and screed troughs of the three coating heads on either side for coating. The conveying unit includes an unwinding mechanism, guide rollers, and a tension control device, which allows the substrate 1 to move along a predetermined path. The specific structure can be referenced in the prior art and is not specifically limited in the present invention.

[0125] Unless otherwise specified, the raw materials used in the following examples and comparative examples are commercially available or can be prepared by methods known in the art. The polyphenylene sulfide mesh, with a thickness of 100 to 300 μm, was purchased from NBC, Japan, with models PPS-50 and PPS-120; polysulfone was purchased from Solvay, with the designation P-1700NT 11; sulfonated polysulfone was purchased from Tianjin Yanjin Technology Co., Ltd., with the designation SPB1620A; the porogen was polyvinylpyrrolidone, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., with the CAS number 25249-54-1; and zirconium oxide was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., with the CAS number 1314-23-4.

[0126] Example 1

[0127] An alkaline hydrogen production composite membrane, such as Figure 4 、 Figure 5 As shown, with the base material 1 as the center, the inner layer 2 and the outer skin layer 3 are sequentially constructed on the left and right sides of the base material 1 from the inside to the outside.

[0128] The preparation method of the alkaline hydrogen production composite membrane is as follows:

[0129] The casting liquid for constructing the inner layer 2 and the outer skin layer 3 is prepared, which includes mixing the various components of the casting liquid, heating to dissolve, and degassing. The prepared inner layer casting liquid and the outer skin layer casting liquid are transported to the coating unit through the feeding unit, and coated on the surface of the substrate 1 by the coating unit. By setting the outlet flow rate of the inner layer casting liquid and the outer skin layer casting liquid and the moving speed of the substrate 1, a coating with a corresponding thickness is obtained. The specific details can be referred to the existing technology and are not limited here. The coated substrate 1 first passes through a steam chamber (temperature of 30°C to 50°C), and then is immersed in a coagulation bath at 40°C to 80°C for complete phase conversion. After cleaning, an alkaline hydrogen production composite membrane is obtained.

[0130] Substrate 1 is a polyphenylene sulfide mesh. The inner layer casting solution is formulated as follows: 20g polysulfone, 40g zirconium oxide, 5g porogen, and 35g N,N-dimethylacetamide. The outer layer casting solution is formulated as follows: 30g sulfonated polysulfone, 1g porogen, and 69g N,N-dimethylacetamide. The coating thickness of inner layer 2 is 250μm, and that of outer layer 3 is 5μm. The coagulation bath is pure water.

[0131] Example 2

[0132] This embodiment is basically the same as embodiment 1, except that the outer skin layer casting liquid is different.

[0133] In this embodiment, the formula of the outer skin layer casting solution is: 5 g of polysulfone, 25 g of sulfonated polysulfone, 1 g of porogen, and 69 g of N,N-dimethylacetamide.

[0134] Example 3

[0135] This embodiment is basically the same as embodiment 1, except that the outer skin layer casting liquid is different.

[0136] The formula of the outer skin layer casting solution is: 5g polysulfone, 20g zirconium oxide, 5g sulfonated polysulfone, 1g porogen, and 69g N,N-dimethylacetamide.

[0137] Example 4

[0138] This embodiment is substantially the same as embodiment 1, except that the coating thickness of the inner layer is 220 μm.

[0139] Example 5

[0140] An alkaline hydrogen production composite membrane is provided, with a substrate 1 as the center, and an inner layer 2, a middle layer and an outer skin layer 3 are sequentially constructed on the left and right sides of the substrate 1 from the inside to the outside.

[0141] The preparation method of the alkaline hydrogen production composite membrane is as follows:

[0142] The casting liquid for constructing the inner layer 2, the middle layer and the outer skin layer 3 is prepared, which includes mixing the components of the casting liquid, heating to dissolve, and degassing. The prepared inner layer casting liquid, the middle layer casting liquid and the outer skin layer casting liquid are transported to the coating unit through the feeding unit, and are coated on the surface of the substrate 1 by the coating unit. The outlet flow rate of the inner layer casting liquid, the middle layer casting liquid and the outer skin layer casting liquid and the moving speed of the substrate 1 are set to obtain a coating with a corresponding thickness. The coated substrate 1 passes through a steam chamber (temperature of 30°C to 50°C), is immersed in a coagulation bath at 40°C to 80°C for complete phase conversion, and after cleaning, an alkaline hydrogen production composite membrane is obtained.

[0143] Substrate 1 is a polyphenylene sulfide mesh. The inner layer casting solution is formulated as follows: 10g polysulfone, 10g zirconium oxide, 2g porogen, and 78g N,N-dimethylacetamide. The intermediate layer casting solution is formulated as follows: 5g polyethersulfone, 10g sulfonated polyethersulfone, 40g zirconium oxide, 3g porogen, and 42g N,N-dimethylacetamide. The outer layer casting solution is formulated as follows: 10g sulfonated polysulfone, 10g zirconium oxide, 1g porogen, and 79g N,N-dimethylacetamide. The coating thickness of inner layer 2 is 10-25μm, the coating thickness of the intermediate layer is 20-50μm, and the coating thickness of outer layer 3 is 5-15μm. The coagulation bath is pure water.

[0144] Example 6

[0145] This comparative example is substantially the same as Example 1, except that the components of the inner layer casting solution are different: the formula of the inner layer casting solution is: 15 g polysulfone, 30 g zirconium oxide, 4 g porogen, and 51 g N,N-dimethylacetamide.

[0146] Comparative Example 1

[0147] This comparative example is substantially the same as Example 1, except that the outer skin layer 3 is not formed, that is, the alkaline hydrogen production composite membrane consists of a substrate 1 and inner layers 2 located on both sides of the substrate 1 .

[0148] Comparative Example 2

[0149] This comparative example is substantially the same as Example 1, except that the coating thickness of the outer skin layer 3 is 20 μm.

[0150] Comparative Example 3

[0151] This comparative example is basically the same as Example 1, except that the outer skin layer casting solution has different components: the outer skin layer casting solution has the following formula: 10 g sulfonated polysulfone, 20 g polysulfone, 1 g porogen, and 69 g N,N-dimethylacetamide.

[0152] Performance Testing

[0153] (1) Thickness: Measure the thickness of the separator according to the national electronic industry standard SJ-T10171.1-1991 "Alkaline Battery Separator Performance Test Method Determination of Separator Thickness", and take the average value of the measurements of three samples as the measurement result.

[0154] (2) Surface contact angle test: Use a contact angle tester to measure the pure water contact angle on the membrane surface, and take the average value of the measurements of three samples as the measured value. Generally, the smaller the contact angle, the better the wettability of the membrane.

[0155] (3) Bubble point pressure: This refers to the pressure at which gas begins to permeate the membrane at a certain temperature. The test method refers to GB / T32361-2015, "Test Methods for Separation Membrane Pore Size - Bubble Point and Average Flow Method." The average value of the measurements from three samples is used as the measurement result. The higher the bubble point pressure, the greater the pressure resistance of the membrane.

[0156] (4) Gas flux: This refers to the permeability of gases to polymer materials such as thin films, coatings, and fabrics. The volume of gas permeating through the membrane per square centimeter per unit time is measured using a chemical sensor using the isobaric method. The average value of measurements from three samples is taken as the measurement result. The higher the gas flux, the better the membrane's gas permeability and the higher the hydrogen production efficiency.

[0157] (5) Diaphragm surface resistance: The diaphragm surface resistance reflects the conductivity of the diaphragm immersed in the electrolyte. The electrochemical impedance of the diaphragm in alkaline electrolyte is measured using an electrochemical workstation, and the average value of the measurements of three samples is taken as the measured value. The lower the diaphragm surface resistance, the less energy loss during the electrolysis process and the higher the electrolysis efficiency.

[0158] (6)OH - Conductivity: represents the OH transfer rate of the membrane - The ability to measure the electrical conductivity of a sample is calculated by the following formula: σ = l / AR × 1000, where σ represents the ionic conductivity (mS / cm), l represents the thickness of the sample being measured (cm), R represents the resistance being measured (Ω), and A represents the area of the sample (cm 2 ).OH - The higher the conductivity, the higher the hydrogen production efficiency.

[0159] (7) Average pore size: Randomly measure 30 pores on the membrane electron microscope image and take the average value as the average pore size of the membrane. Smaller pore sizes help prevent the mixing of hydrogen and oxygen, improving safety; however, smaller pore sizes lead to decreased ion conductivity. Generally, a pore size between 80 nm and 200 nm is more suitable.

[0160] (8) Porosity: The porosity of the membrane is the percentage of the pore volume of the membrane to the membrane volume. It is measured by weighing, that is, the pore volume V of the membrane is determined based on the weight change before and after the membrane is soaked in pure water. 孔The skeleton volume of the material can be obtained by the raw material density and dry weight V 骨 , then the porosity of the porous material can be calculated using the following formula: P = V 孔 / (V 孔 +V 骨 ), taking the average of the measurements from three samples as the measurement result. A higher porosity helps improve electrolyte wettability and ion conductivity, but excessive porosity may reduce the mechanical strength of the separator. Generally speaking, a porosity between 40% and 80% is suitable.

[0161] (9) Tensile strength: Tested using a tensile testing machine, referencing the standard GBT3923.1-2013 Textile fabrics - Tensile properties - Part 1: Determination of breaking strength and elongation at break (strip method), and taking the average value of the measurements of three specimens as the measurement result. The greater the tensile strength, the better the ability of the diaphragm to resist external damage during use.

[0162] The performance tests of the above embodiments and comparative examples are shown in Table 1.

[0163] Table 1

[0164]

[0165] As shown in Table 1, compared to the alkaline hydrogen production composite membrane of Comparative Example 1, the present invention solves the problems of high membrane resistance, low airtightness, and membrane powder shedding by constructing a small, hydrophilic outer skin layer 3 on the outermost side. This results in a composite membrane with advantages such as an asymmetric stepped structure, low membrane surface resistance, high ionic conductivity, strong gas barrier properties, good durability, and high mechanical strength, making it suitable for alkaline water electrolysis for hydrogen production. The present invention further optimizes the formulation and thickness of the inner and outer skin layers to achieve even better performance.

[0166] The above detailed description of the present invention is intended to enable persons familiar with the art to understand the contents of the present invention and implement them. It does not limit the scope of protection of the present invention. Any equivalent changes or modifications made based on the spirit of the present invention should be included in the scope of protection of the present invention.

Claims

1. An alkaline hydrogen production composite membrane, characterized in that: The alkaline hydrogen production composite membrane includes a substrate, and an inner layer and an outer skin layer respectively constructed on the left and right sides of the substrate from the inside to the outside, with the thickness of the inner layer being at least 20 times the thickness of the outer skin layer. Taking the total mass of the casting liquid constituting the inner layer as 100%, the inner layer casting liquid comprises: Unsulfonated organic polymer 10% to 30%, Hydrophilic inorganic nanoparticles 30% to 50%, Porogen 1% to 10%, Organic solvent 25% to 45%, Taking the total mass of the casting solution for forming the outer skin layer as 100%, the outer skin layer casting solution comprises: Sulfonated organic polymer 5% to 35%, Unsulfonated organic polymer 0-10%, Hydrophilic inorganic nanoparticles 0-30%, Porogen 0.1%~2%, Organic solvent 50%~75%.

2. The alkaline hydrogen production composite membrane according to claim 1, characterized in that: Taking the total mass of the casting solution for forming the outer skin layer as 100%, the outer skin layer casting solution comprises: Sulfonated organic polymer 25% to 35%, Porogen 0.1%~2%, Organic solvent 65%~74%.

3. The alkaline hydrogen production composite membrane according to claim 1, characterized in that: Taking the total mass of the casting solution for forming the outer skin layer as 100%, the outer skin layer casting solution comprises: Sulfonated organic polymer 20% to 30%, Unsulfonated organic polymer 3-10%, Porogen 0.1%~2%, Organic solvent 60%~75%.

4. The alkaline hydrogen production composite membrane according to claim 1, characterized in that: Taking the total mass of the casting solution for forming the outer skin layer as 100%, the outer skin layer casting solution comprises: Sulfonated organic polymer 5% to 10%, Unsulfonated organic polymer 3% to 10%, Hydrophilic inorganic nanoparticles 15% to 25%, Porogen 0.1%~2%, Organic solvent 55%~75%.

5. The alkaline hydrogen production composite membrane according to any one of claims 1 to 4, characterized in that: The unsulfonated organic high molecular polymer in the inner layer casting solution and the outer skin layer casting solution is one or more of polysulfone, polyphenylsulfone and polyethersulfone; and / or, The hydrophilic inorganic nanoparticles in the inner layer casting solution and the outer layer casting solution are independently selected from one or more of zirconium dioxide, cerium dioxide, calcium carbonate, and barium sulfate; and / or, The porogens in the inner layer casting solution and the outer layer casting solution are independently selected from one or more of polyvinyl pyrrolidone, glycerol, polyethylene glycol, and ethylene glycol; and / or, The organic solvents in the inner layer casting solution and the outer layer casting solution are independently selected from one or more of N-methylpyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, and dimethyl sulfoxide; and / or, The sulfonated organic high molecular polymer is selected from one or more of sulfonated polysulfone, sulfonated polyphenylsulfone, sulfonated polyethersulfone and sulfonated polyetherketone.

6. The alkaline hydrogen production composite membrane according to claim 1, characterized in that: The thickness of the inner layer is 50 μm to 300 μm; and / or, The thickness of the outer skin layer is 1 μm to 10 μm.

7. The alkaline hydrogen production composite membrane according to claim 1, characterized in that: The substrate is polyphenylene sulfide.

8. An alkaline hydrogen production composite membrane, characterized by: The alkaline hydrogen production composite membrane includes a substrate, and an inner layer, an intermediate layer, and an outer layer, which are sequentially constructed on the left and right sides of the substrate from the inside to the outside. The thickness of the inner layer is 10 μm to 25 μm, the thickness of the intermediate layer is 20 μm to 50 μm, and the thickness of the outer layer is 5 μm to 15 μm. Taking the total mass of the casting liquid constituting the inner layer as 100%, the inner layer casting liquid comprises: Sulfonated organic polymer 0% to 10%, Unsulfonated organic polymer 3% to 10%, Hydrophilic inorganic nanoparticles 0% to 10%, Porogen 0.1%~2%, Organic solvent 70% to 80%; Taking the total mass of the casting solution constituting the intermediate layer as 100%, the intermediate layer casting solution comprises: Sulfonated organic polymer 0% to 10%, Unsulfonated organic polymer 3% to 10%, Hydrophilic inorganic nanoparticles 40% to 70%, Porogen 0.1%~5%, Organic solvent 25% to 45%; Taking the total mass of the casting solution for forming the outer skin layer as 100%, the outer skin layer casting solution comprises: Sulfonated organic polymer 3% to 10%, Unsulfonated organic polymer 0% to 10%, Hydrophilic inorganic nanoparticles 0% to 10%, Porogen 0.1%~2%, Organic solvent 70%~85%.

9. The alkaline hydrogen production composite membrane according to claim 8, characterized in that: The unsulfonated organic high molecular polymer in the inner layer casting solution, the middle layer casting solution, and the outer layer casting solution is one or more of polysulfone, polyphenylsulfone, and polyethersulfone; and / or, The hydrophilic inorganic nanoparticles in the inner layer casting solution, the middle layer casting solution, and the outer layer casting solution are independently selected from one or more of zirconium dioxide, cerium dioxide, calcium carbonate, and barium sulfate; and / or, The porogens in the inner layer casting solution, the middle layer casting solution, and the outer layer casting solution are independently selected from one or more of polyvinyl pyrrolidone, glycerol, polyethylene glycol, and ethylene glycol; and / or, The organic solvents in the inner layer casting solution, the intermediate layer casting solution, and the outer layer casting solution are independently selected from one or more of N-methylpyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, and dimethyl sulfoxide; and / or, The sulfonated organic high molecular polymer in the inner layer casting solution, the middle layer casting solution, and the outer layer casting solution is selected from one or more of sulfonated polysulfone, sulfonated polyphenylsulfone, sulfonated polyethersulfone, and sulfonated polyetherketone; and / or, The substrate is polyphenylene sulfide.

10. The method for preparing the alkaline hydrogen production composite membrane according to any one of claims 1 to 9, characterized in that: Multilayer casting liquid is coated on both sides of the substrate from the inside out, and then treated with steam, immersed in a coagulation bath for phase conversion, and finally cleaned to obtain the alkaline hydrogen production composite membrane.

11. The method for preparing the alkaline hydrogen production composite membrane according to claim 10, characterized in that: The substrate is coated with a coating device, which includes a feeding unit for storing and conveying the casting liquid, a coating unit connected to the feeding unit and used to coat the casting liquid on the surface of the substrate, and a conveying unit for conveying the substrate to the coating unit. The coating unit includes a slit coating die head, which has two groups symmetrically arranged on the left and right sides of the substrate. Each group of slit coating die heads is equipped with multiple independently controlled and non-interfering coating heads for achieving simultaneous multi-layer coating. Each coating head distributes and controls the casting liquid through an independent feeding pipe and a sparging trough. The coating comprises moving the substrate along a preset path through the conveying unit, controlling the slit coating die heads on the left and right sides of the substrate to operate, and coating multiple layers of casting liquid on both sides of the substrate at the same time.

12. The method for preparing the alkaline hydrogen production composite membrane according to claim 10, characterized in that: The substrate coated with the multi-layer casting solution is sent into a steam chamber for the steam treatment, and the temperature of the steam chamber is 20°C to 70°C.

13. The method for preparing the alkaline hydrogen production composite membrane according to claim 10, characterized in that: The coagulation bath is water or a mixture of water and a solvent. When the coagulation bath is a mixed solution of water and a solvent, the mass content of the solvent is 10% to 55%, and / or, The temperature of the coagulation bath is 25°C to 50°C.

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