Preparation method and device of composite diaphragm for hydrogen production by alkaline electrolysis of water

Abstract

This invention provides a method and apparatus for preparing a composite membrane for alkaline water electrolysis to produce hydrogen, belonging to the field of alkaline water electrolysis technology. The preparation method includes the following steps: (1) mixing polymer, solvent and particulate filler evenly to obtain a membrane slurry; (2) subjecting a porous grid to plasma treatment to obtain a porous grid with a root mean square roughness of not less than 200 nm; (3) simultaneously and uniformly coating both sides of the porous grid obtained in step (2) with the vacuum-degassed membrane slurry, with the porous grid placed vertically during coating, and obtaining a nascent membrane after coating; (4) introducing the nascent membrane obtained in step (3) into a gel bath in a direction perpendicular to the gel bath surface for phase transformation, solidifying into a film, and then washing and winding it to obtain a composite membrane for alkaline water electrolysis to produce hydrogen. The composite membrane obtained by this invention has high compressive strength, high adhesion, and low mass wear loss rate, and is particularly suitable for pressurized electrolyzers.

Description

Technical Field

[0001] This invention belongs to the field of alkaline water electrolysis technology, specifically relating to a method and apparatus for preparing a composite membrane for hydrogen production via alkaline water electrolysis. Background Technology

[0002] Currently, polyphenylene sulfide (PPS) mesh is the most commonly used diaphragm in industrial alkaline water electrolysis devices. However, PPS mesh has relatively weak gas barrier properties, which is not conducive to improving hydrogen purity. Compared with PPS mesh, composite diaphragms have better gas barrier properties, lower surface resistivity, and lower energy consumption, making them a potential alternative. However, due to the compression of the sealing gasket, the edges of the composite diaphragm undergo compression deformation, causing the structure of the functional layer composed of polymer / granular filler to crumble. Under high-temperature and concentrated alkaline operating conditions, mechanical friction can also cause the polymer / granular filler functional layer of the composite diaphragm to crack, crumble, and detach, thus affecting the performance and safety of the water electrolysis device and hindering the industrial application of composite diaphragms.

[0003] In existing technologies, composite membranes used for hydrogen production via water electrolysis are mostly manufactured by coating both sides of a support layer with a casting solution whose main components are polymers and particulate fillers. The bonding force between the polymer and the support layer is relatively weak. Furthermore, the support layer is usually horizontal during coating, making the preparation process of composite membranes for hydrogen production via water electrolysis very complex, generally requiring two coatings (one on each side) to obtain the composite membrane. This method makes it difficult to ensure that the support layer is centered within the composite membrane, affecting its performance.

[0004] In view of this, the present invention is hereby proposed. Summary of the Invention

[0005] To address the shortcomings and defects of existing technologies, this invention aims to provide a method and apparatus for preparing a composite membrane for alkaline water electrolysis hydrogen production. The method / apparatus involves two aspects: first, increasing the roughness of the porous mesh through plasma treatment to enhance the bonding force between the polymer and the support layer; and second, controlling the vertical placement of the porous mesh during coating to ensure that both sides of the mesh, i.e., the two symmetrical surfaces, are simultaneously and uniformly coated with the membrane-forming slurry, guaranteeing that the support layer is located at the center of the composite membrane. This is of great significance for improving the mechanical strength (compressive strength, adhesion, and mass abrasion loss rate) of the composite membrane and promoting the upgrading of alkaline water electrolysis hydrogen production technology.

[0006] To achieve the above objectives, the following technical solution is adopted: In a first aspect, a method for preparing a composite membrane for alkaline water electrolysis to produce hydrogen includes the following steps: (1) Mix the polymer, solvent and particulate filler evenly to obtain a film-forming slurry; (2) The porous grid is subjected to plasma treatment to obtain a porous grid with a root mean square roughness of not less than 200 nm. (3) The vacuum degassing slurry is uniformly applied to both sides of the porous grid obtained in step (2) simultaneously and in equal amounts. The porous grid is placed vertically during the application, and a primary diaphragm is obtained after the application. (4) The nascent membrane obtained in step (3) is introduced into the gel bath in a direction perpendicular to the surface of the gel bath for phase transformation, solidified into a film, and then washed with water and wound up to obtain a composite membrane for alkaline water electrolysis to produce hydrogen.

[0007] Furthermore, the difference in solubility parameters between the polymer in step (1) and the porous mesh in step (2) is not higher than 10.0 MPa. 0.5 .

[0008] Furthermore, the difference in solubility parameters between the polymer described in step (1) and the porous mesh described in step (2) is no higher than 4.0 MPa. 0.5 .

[0009] Further, in step (1), the mass ratio of polymer, solvent and particulate filler in the film-forming slurry is 9~21:32~70:10~60, totaling 100; And / or, the polymer comprises one or more of polysulfone, polyethersulfone, diazonyl biphenyl coethersulfone ketone containing a diazonyl biphenyl structure, and diazonyl biphenyl coethersulfone; And / or, the particulate filler includes one or more of oxide particles, nitride particles and carbide particles; And / or, the solvent is one or more of N-methylpyrrolidone, N,N-dimethylacetamide, N,N-dimethylformamide and dimethyl sulfoxide.

[0010] Furthermore, in step (2), the power of the plasma treatment is 0.5~10kVA.

[0011] Furthermore, in step (4), the nascent diaphragm is pre-evaporated before being immersed in the gel bath.

[0012] Furthermore, the temperature of the pre-evaporation treatment is 20~80°C, and / or the relative humidity of the pre-evaporation treatment is 10~90%.

[0013] Furthermore, the temperature of the pre-evaporation treatment is 35~70℃, and / or the relative humidity of the pre-evaporation treatment is 10~35%.

[0014] Furthermore, in step (4), the phase transformation temperature is 15~70℃; And / or, the temperature of the water wash is 15~70℃; And / or, the winding linear speed is 0.1 to 20 meters per minute.

[0015] In a second aspect, a preparation apparatus for implementing the preparation method described in the first aspect includes a film-forming slurry preparation unit, a slurry conveying and filtering unit, an unwinding unit, a plasma treatment unit, a slit extrusion unit, a constant temperature and humidity evaporation chamber, a gel tank, a cleaning tank, and a composite diaphragm winding unit. The film-forming slurry preparation unit is used for preparing the film-forming slurry and vacuum degassing; The slurry conveying and filtering unit is used to filter and convey the film-forming slurry; The unwinding unit and the composite diaphragm winding unit are used for unwinding the porous grid and winding the composite diaphragm, respectively. The plasma processing unit is used for plasma processing of porous grids; The slit extrusion unit includes symmetrically arranged slit coating dies for double-sided coating of the porous grid, that is, coating the porous grid with equal amounts on both sides simultaneously. The constant temperature and humidity evaporation chamber is used for the pre-evaporation of the film-forming slurry on the porous grid. The gel tank is used for the solidification and molding of the film-forming slurry on the porous grid. The cleaning tank is used for cleaning the composite diaphragm; After passing through the unwinding unit and the composite diaphragm winding unit, the porous mesh is first conveyed to the plasma treatment unit for plasma treatment, and then vertically conveyed to the slit extrusion unit. The slit coating dies located on both sides of the porous mesh and the film-forming slurry conveyed by the slurry conveying and filtering unit are simultaneously coated on the symmetrical surface of the porous mesh. After coating, the nascent diaphragm passes through a constant temperature and humidity evaporation chamber and then enters the gelation tank in a direction perpendicular to the gel bath liquid surface, or directly enters the gelation tank in a direction perpendicular to the gel bath liquid surface without passing through the constant temperature and humidity evaporation chamber, so that the film-forming slurry undergoes phase separation and solidifies into a film. Then it enters the cleaning tank to remove residual solvent by water replacement, and finally the finished composite diaphragm is obtained at the composite diaphragm winding unit.

[0016] Compared with the prior art, the technical solution of the present invention has at least the following technical effects: 1. The preparation method of this invention involves two aspects: First, a plasma treatment process is used to ensure that the surface roughness of the porous mesh wires is not less than 200 nm, thereby strengthening the bonding force between the polymers in the porous mesh (support layer) and the functional layer (composed of polymers and fillers), thus enhancing the mechanical properties of the composite membrane. Second, during coating, the porous mesh is controlled to be placed vertically so that both sides of the porous mesh, i.e., the two mutually symmetrical surfaces, can be coated with equal amounts of membrane-forming slurry simultaneously and uniformly. This avoids the situation where, when the porous mesh is placed horizontally, the upper surface can be coated first, followed by the lower surface, to prevent the slurry from falling off when the lower surface is coated along with the upper surface. This not only simplifies the preparation steps of the composite membrane for hydrogen production by water electrolysis but also ensures that the support layer is located at the center of the composite membrane.

[0017] The composite diaphragm prepared by this invention exhibits enhanced mechanical strength, high compressive strength, high adhesion, and low mass wear loss rate. It also features low sheet resistivity (high hydroxide conductivity) and high bubble point pressure (low hydrogen permeability), making it suitable for alkaline water electrolysis hydrogen production, particularly in pressurized electrolyzers. Currently, commercially available water electrolysis diaphragms have poor compressive strength and are prone to cracking during use. The composite diaphragm obtained by this invention, while maintaining superior sheet resistivity and bubble point pressure compared to commercially available products, significantly improves the diaphragm's mechanical properties, increasing compressive strength by 3-4 times and wear resistance by orders of magnitude. Therefore, it is particularly suitable for pressurized alkaline water electrolysis hydrogen production electrolyzers.

[0018] 2. The preparation device of the present invention allows the porous mesh to be in continuous motion during the preparation process by being wound up, and then undergoing plasma treatment, coating and molding in sequence. This not only improves production efficiency, but also ensures that the prepared composite membrane structure is stable and has excellent performance. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the composite membrane preparation apparatus of the present invention; wherein, reference numerals are as follows: 1-8: guide rollers; 100: membrane slurry preparation unit; 101: slurry conveying and filtering unit; 102: unwinding unit; 103: plasma treatment unit; 104: slot extrusion unit; 105: constant temperature and humidity evaporation chamber; 106: gel tank; 107: cleaning tank; 108: composite membrane winding unit; 300: support layer; 201a and 201b: slot coating dies; Figure 2 This is a cross-sectional schematic diagram of the composite membrane of the present invention along the thickness direction; wherein, reference numerals: 1: support layer; 2: functional layer composed of polymer and particulate filler; Figure 3 An atomic force microscope image of the PPS porous grid used in Comparative Example 1 of this invention; Figure 4 An atomic force microscope image of the plasma-treated PPS porous grid from Example 1. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions in the embodiments of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. Those skilled in the art should understand that the embodiments described are merely illustrative of the invention and should not be considered as specific limitations thereof. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention. Process parameters not specifically specified in the following embodiments are generally performed under conventional conditions.

[0021] In the description of this invention, the terms "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," and "bottom," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and do not require the invention to be constructed and operated in a specific orientation; therefore, they should not be construed as limitations on the invention. The terms "connected," "linked," and "set up" used in this invention should be interpreted broadly. For example, they can refer to a fixed connection or a detachable connection; a direct connection or an indirect connection through intermediate components; a wired connection, a radio connection, or a wireless communication signal connection. Those skilled in the art can understand the specific meaning of the above terms according to the specific circumstances.

[0022] The endpoints and any values ​​of the ranges disclosed in this invention are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this invention.

[0023] In a first aspect, this invention provides a method for preparing a composite membrane for alkaline water electrolysis to produce hydrogen, comprising the following steps: (1) Mix the polymer, solvent and particulate filler evenly to obtain a film-forming slurry; (2) The porous grid is subjected to plasma treatment to obtain a porous grid with a root mean square roughness of not less than 200 nm. (3) The vacuum degassing slurry is uniformly applied to both sides of the porous grid obtained in step (2) simultaneously and in equal amounts. The porous grid is placed vertically during the application, and a primary diaphragm is obtained after the application. (4) The nascent membrane obtained in step (3) is introduced into the gel bath in a direction perpendicular to the surface of the gel bath for phase transformation, solidified into a film, and then washed with water and wound up to obtain a composite membrane for alkaline water electrolysis to produce hydrogen.

[0024] The preparation method of this invention involves two aspects. First, a plasma treatment process is used to ensure that the surface roughness of the porous mesh wires is not less than 200 nm (e.g., 200 nm, 210 nm, 220 nm, 230 nm, 240 nm, 250 nm, 260 nm, 270 nm, 280 nm, 290 nm, 300 nm, 320 nm, 350 nm, etc.), thereby strengthening the bonding force between the porous mesh (support layer) and the polymer in the functional layer (composed of polymer and filler), thus enhancing the mechanical properties of the composite membrane. Second, during coating, the porous mesh is placed vertically to ensure that both sides of the porous mesh, i.e., the two mutually symmetrical surfaces, are simultaneously coated with an equal amount of membrane-forming slurry evenly. This avoids the situation where, when the porous mesh is placed horizontally, the upper surface can be coated first, followed by the lower surface, to prevent the slurry from falling off when the lower surface is coated along with the upper surface. This not only simplifies the preparation steps of the composite membrane for hydrogen production by water electrolysis but also ensures that the support layer is located at the center of the composite membrane.

[0025] The composite diaphragm prepared by the method of this invention has low sheet resistance (high hydroxide conductivity), high bubble point pressure (low hydrogen permeability), and excellent mechanical properties (high compressive strength, high adhesion, and low mass wear loss rate). It is suitable for alkaline water electrolysis hydrogen production, especially for pressurized electrolyzers. Currently, commercially available water electrolysis diaphragms have poor compressive strength and are easily cracked during use. However, the composite diaphragm obtained by this invention, while ensuring that the sheet resistance and bubble point pressure are superior to those of commercially available products, significantly improves the mechanical properties of the diaphragm, increasing the compressive strength by 3-4 times and the wear resistance by orders of magnitude. Therefore, it is particularly suitable for pressurized alkaline water electrolysis hydrogen production electrolyzers.

[0026] The composite membrane of this invention comprises only three substances: a polymer, particulate filler, and a porous mesh. The porous mesh serves as a support layer, supporting a functional layer composed of the polymer and particulate filler to form the composite membrane for alkaline water electrolysis to produce hydrogen. In this composite membrane, the mixture of polymer and particulate filler is filled within the pores of the porous mesh and also supported on the mesh lines. The mixture within the pores connects the mixtures on both sides of the mesh lines into a unified whole, forming the functional layer composed of polymer and filler particles, which encapsulates the porous mesh.

[0027] In this invention, low-temperature plasma treatment is selected, such as atmospheric pressure dielectric barrier discharge plasma or radio frequency (RF) low-temperature plasma. The main process parameters affecting surface roughness in plasma treatment are power and treatment time. The treatment time is affected by the winding speed. A faster winding speed results in a shorter treatment time. Increasing power and extending the treatment time can both increase surface roughness.

[0028] As an optional embodiment of the preparation method of the present invention, the power of the plasma treatment is 0.5~10kVA (e.g., 0.6kVA, 1kVA, 2kVA, 3kVA, 4kVA, 5kVA, 6kVA, 7kVA, 8kVA, 9kVA, 9.5kVA, etc.). By controlling the magnitude of the plasma treatment power, the surface roughness of the porous mesh wires can be controlled; the higher the power of the plasma treatment per unit time, the rougher the mesh wires.

[0029] As an optional embodiment of the preparation method of the present invention, the difference in solubility parameters between the polymer in step (1) and the porous grid in step (2) is not higher than 10.0 MPa. 0.5 Furthermore, the difference in solubility parameters between the polymer in step (1) and the porous mesh in step (2) is not higher than 4.0 MPa. 0.5 Furthermore, the difference in solubility parameters between the polymer described in step (1) and the porous mesh described in step (2) is no higher than 3.0 MPa. 0.5 Solubility parameter difference Ra Typically, but not exclusively, it can be selected as 10.0 MPa. 0.5 9.0 MPa 0.5 8.0 MPa 0.5 7.0 MPa 0.5 6.0 MPa 0.5 5.0 MPa 0.5 4.0MPa 0.5 3.0 MPa 0.5 2.0 MPa 0.5 1.0 MPa 0.5 0.5 MPa 0.5 0.1 MPa 0.5 The smaller the difference in solubility parameters, the better the compatibility and the stronger the binding force. By matching the polymer and the porous mesh, the difference in solubility parameters between the polymer and the mesh can be reduced. Ra This enhances the thermodynamic compatibility between the two, thereby further improving the mechanical strength of the composite diaphragm, such as adhesion, compressive strength, and mass wear loss rate.

[0030] Optionally, the polymer includes one or more of polysulfone (PSU), polyethersulfone (PES), diazonyl biphenyl coethersulfone ketone (PPBESK) containing a diazonyl biphenyl structure, and diazonyl biphenyl coethersulfone (PPBES); preferably, the polymer includes at least one of diazonyl biphenyl coethersulfone ketone and diazonyl biphenyl coethersulfone. Polysulfone and polyethersulfone are both conventional membrane-forming polymers, and when the root mean square roughness of the porous mesh surface... Rq At a wavelength of at least 200 nm, even these conventional membrane-forming polymers can bond well with the porous grid, improving the mechanical strength of the membrane. PPBESK and PPBES contain diazanaphthone structures (naphthyl biphenyl), which have good solubility and good compatibility with the porous grid, thus improving the bonding force and enhancing the mechanical strength of the membrane.

[0031] Optionally, the porous mesh is a polyphenylene sulfide (PPS) mesh or a polypropylene (PP) mesh. In particular, the PPS mesh, compared to the PP mesh, has a lower solubility parameter difference with the polymer. Ra Lower, such as the difference in solubility parameters between PSU and PPS. Ra 3.9 MPa 0.5 The difference in solubility parameters between PSU and PP Ra 9.4 MPa 0.5 More specifically, the difference in solubility parameters between PPBES and PPS, and between PPBESK and PPS. Ra Not exceeding 1.0 MPa 0.5 Even after doping PSU with an equal mass in PPBES and PES with an equal mass in PPBES, the difference in solubility parameter between them remains the same. Ra It does not exceed 3.0 MPa 0.5 .

[0032] In this invention, the thickness and mesh count of the porous mesh material are not particularly limited and can be specifically selected as needed. For example, the thickness can be 240~270 micrometers, specifically 245 micrometers, 250 micrometers, 255 micrometers, 260 micrometers, 265 micrometers, etc., and the mesh count can be 30~60 mesh, specifically 32 mesh, 35 mesh, 38 mesh, 40 mesh, 45 mesh, 47 mesh, 50 mesh, 55 mesh, 57 mesh, etc.

[0033] Furthermore, there are no particular limitations on the particle fillers and their particle size in the membrane slurry. Commonly used oxide, nitride, and carbide particle fillers in the membrane field can all be used, such as zirconium oxide particles, titanium oxide particles, and cerium oxide particles. The particle size of the particle fillers is 30~200 nanometers, specifically 35 nanometers, 40 nanometers, 50 nanometers, 60 nanometers, 70 nanometers, 80 nanometers, 90 nanometers, 100 nanometers, 110 nanometers, 120 nanometers, 130 nanometers, 140 nanometers, 150 nanometers, 160 nanometers, 170 nanometers, 180 nanometers, and 190 nanometers.

[0034] As an optional embodiment of the preparation method of the present invention, in step (1), the mass ratio of polymer, solvent and particulate filler in the film-forming slurry is 9~21:32~70:10~60 (such as 9:32:59, 11:39:50, 13:45:42, 15:50:35, 17:63:20, 19:66:15, 21:69:10, etc.), totaling 100; And / or, the polymer comprises one or more of polysulfone, polyethersulfone, diazonyl biphenyl coethersulfone ketone containing a diazonyl biphenyl structure, and diazonyl biphenyl coethersulfone; And / or, the particulate filler includes one or more of oxide particles, nitride particles and carbide particles, and further includes one or more of zirconium oxide particles, titanium oxide particles and cerium oxide particles; And / or, the solvent is one or more of N-methylpyrrolidone, N,N-dimethylacetamide, N,N-dimethylformamide and dimethyl sulfoxide.

[0035] As an optional embodiment of the preparation method of the present invention, in step (4), the nascent diaphragm is pre-evaporated before being immersed in the gel bath. Further, the temperature of the pre-evaporation treatment is 20~80℃ (e.g., 30℃, 40℃, 50℃, 60℃, 70℃, etc.), more specifically 35~70℃, and / or the relative humidity of the pre-evaporation treatment is 10~90% (e.g., 15%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, etc.), more specifically 10~35%.

[0036] As an optional embodiment of the preparation method of the present invention, in step (4), the phase transformation temperature is 15~70℃ (such as 20℃, 25℃, 30℃, 40℃, 50℃, 60℃, 65℃, etc.). And / or, the temperature of the water washing is 15~70℃ (e.g., 20℃, 25℃, 30℃, 40℃, 50℃, 60℃, 65℃, etc.).

[0037] As an optional embodiment of the preparation method of the present invention, in step (4), the winding linear speed is 0.1~20 m / min (e.g., 0.2 m / min, 0.3 m / min, 0.5 m / min, 1 m / min, 1.5 m / min, 2 m / min, 2.5 m / min, 3 m / min, 5 m / min, 7 m / min, 9 m / min, 11 m / min, 13 m / min, 15 m / min, 17 m / min, 19 m / min, etc.). Controlling the winding speed within the aforementioned range can yield a composite diaphragm with stable structural performance. Within the aforementioned range, the faster the winding linear speed, the higher the production efficiency. Furthermore, the winding linear speed is related to the plasma treatment time; a faster winding speed corresponds to a shorter plasma treatment time. The roughness of the porous grid is controlled by the plasma treatment power and treatment time. Increasing the power and extending the time can both increase the roughness.

[0038] In a second aspect, the present invention provides a preparation apparatus capable of realizing the composite membrane preparation method for alkaline water electrolysis to produce hydrogen in the first aspect, specifically as follows: Figure 1 As shown, the system includes a slurry preparation unit 100, a slurry conveying and filtering unit 101, an unwinding unit 102, a plasma treatment unit 103, a slot extrusion unit 104, a constant temperature and humidity evaporation chamber 105, a gelation tank 106, a cleaning tank 107, a composite diaphragm winding unit 108, and guide rollers 1-8 for a guide support layer 300 (such as a porous grid) and the composite diaphragm; wherein, The film-forming slurry preparation unit 100 is used for preparing the film-forming slurry and vacuum degassing; The slurry conveying and filtering unit 101 is used to filter and convey the film-forming slurry; The unwinding unit 102 and the composite diaphragm winding unit 108 are respectively used for unwinding the support layer 300 and winding the composite diaphragm. The plasma processing unit 103 is used for plasma processing of the support layer 300; The slit extrusion unit 104 includes symmetrically arranged slit coating dies 201a and 201b, which are used to coat the support layer 300 on both sides, i.e., to coat the support layer 300 with equal amounts on both sides, i.e., on the symmetrical surfaces. The constant temperature and humidity evaporation chamber 105 is used for the pre-evaporation of the film-forming slurry on the support layer 300; The gel groove 106 is used for the curing and molding of the film-forming slurry on the support layer 300; The cleaning tank 107 is used for cleaning the composite diaphragm.

[0039] When the above-mentioned device is used, the unwinding unit 102 conveys the support layer 300 to the plasma processing unit 103, and then vertically conveys it to the slit extrusion unit 104. The slit coating dies 201a and 201b located on both sides of the support layer simultaneously coat the film-forming slurry (casting liquid) delivered by the film-forming slurry delivery and filtration unit 101 onto the two sides of the support layer, i.e., the symmetrical surface. The coated nascent (composite) membrane enters the gel tank 106 through the constant temperature and humidity evaporation chamber 105 (or directly enters the gel tank 106 without going through the constant temperature and humidity evaporation chamber 105). Specifically, it enters the gel tank 106 in a direction perpendicular to the gel bath liquid surface, causing phase separation of the casting liquid and solidification into a film. Then, it enters the cleaning tank 107 to remove residual solvent by water replacement. The finished composite membrane is obtained at the composite membrane winding unit 108.

[0040] The device of this invention is a preparation device for a composite membrane that enhances the bonding force between the support layer (such as a porous grid) and the functional layer (composed of polymer and particulate filler). By setting up a plasma treatment unit, the surface roughness of the support layer is increased, thereby strengthening the bonding force between the support layer and the functional layer, and achieving the purpose of enhancing the mechanical properties of the composite membrane.

[0041] Meanwhile, the device of this invention features symmetrically arranged slit extrusion dies on both sides of the support layer. The support layer is in a vertical position when the casting solution is applied, allowing the casting solution to be evenly applied to both sides of the support layer simultaneously. This ensures that the support layer is located at the center of the composite membrane, with the functional layers composed of polymer and particulate fillers symmetrically distributed and covering both sides of the support layer. This is of great significance for improving the mechanical strength (compressive strength, adhesion, mass wear loss rate) of the composite membrane and promoting the upgrading of alkaline water electrolysis hydrogen production technology.

[0042] In the apparatus of this invention, the process steps of each unit can be carried out sequentially, that is, the porous mesh is unwound and wound up simultaneously, maintaining a continuous dynamic state during the composite diaphragm preparation process. This ensures both the stability and excellent performance of the prepared composite diaphragm structure and improves production efficiency. The main preparation process parameters for each unit when using this apparatus are as follows: (1) Plasma processing power: 0.5~10kVA (such as 0.6kVA, 1kVA, 2kVA, 3kVA, 4kVA, 5kVA, 6kVA, 7kVA, 8kVA, 9kVA, 9.5kVA, etc.); (2) Winding speed: 0.1-20 m / min (e.g. 0.2 m / min, 0.3 m / min, 0.5 m / min, 1 m / min, 1.5 m / min, 2 m / min, 2.5 m / min, 3 m / min, 5 m / min, 7 m / min, 9 m / min, 11 m / min, 13 m / min, 15 m / min, 17 m / min, 19 m / min, etc.); (3) Evaporator temperature: 20-80℃ (e.g., 30℃, 40℃, 50℃, 60℃, 70℃, etc.); (4) Evaporator relative humidity: 10-90% (e.g., 15%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, etc.); (5) Gel bath water temperature: 15-70℃ (e.g., 20℃, 25℃, 30℃, 40℃, 50℃, 60℃, 65℃, etc.); (6) Water temperature of the cleaning tank: 15-70℃ (such as 20℃, 25℃, 30℃, 40℃, 50℃, 60℃, 65℃, etc.).

[0043] Specifically, in application, the membrane slurry is prepared and defoamed at the membrane slurry preparation unit 100. Larger particles in the membrane slurry are blocked in the slurry conveying and filtering unit 101 to prevent clogging of the die orifice of the slit extrusion unit 104, and the filtered membrane slurry is conveyed to the slit extrusion unit 104. In the slit extrusion unit 104, the membrane slurry is coated on both sides of the porous grid from top to bottom in equal amounts by symmetrically arranged slit coating dies 201a and 201b, realizing double-sided coating of high-viscosity slurry. Because the slurry viscosity of membranes used for alkaline water electrolysis to produce hydrogen is usually very high, and high-viscosity slurries cannot be coated with a scraper, slit extrusion is more suitable. Moreover, if double-sided coating is used, the support layer can only be coated from top to bottom, which is difficult to achieve from bottom to top. Horizontal coating not only requires coating the upper and lower surfaces in stages, but also easily leads to asymmetry on both sides of the composite membrane, affecting the performance of the membrane. The coated nascent composite diaphragm enters the gel bath 106 perpendicular to the gel bath surface (it may or may not pass through a constant temperature and humidity evaporation chamber 105 before entering the gel bath 106), causing phase separation of the casting solution and solidification into a film. It then enters the cleaning tank 107 to remove residual solvent by water replacement. The finished composite diaphragm is obtained at the composite diaphragm winding unit 108. The surface roughness of the porous mesh is controlled by the plasma treatment power and the winding speed. The structure and forming of the composite diaphragm are controlled by the evaporation chamber temperature, relative humidity, gel bath water temperature, cleaning tank water temperature, and winding speed.

[0044] The present invention will now be described in further detail with reference to specific embodiments and comparative examples: Example 1 An apparatus and method for preparing a composite membrane for alkaline water electrolysis to produce hydrogen, the apparatus being as follows: Figure 1 As shown, with the winding speed set to 1 meter / minute, the composite diaphragm is prepared according to the following steps: (1) Preparation of film-forming slurry: In the film-forming slurry preparation unit 100, polysulfone, N-methylpyrrolidone and zirconium oxide particles with a particle size of 100 nanometers are stirred at a temperature of 50 °C to obtain a uniform and degassed film-forming slurry with a composition of 13 wt% polysulfone, 57 wt% N-methylpyrrolidone and 30 wt% zirconium oxide particles. (2) Preparation of the support layer: A 50-mesh polyphenylene sulfide (PPS) porous mesh with a thickness of 256 micrometers (root mean square roughness of 148 nm, as shown in the atomic force microscope image) was selected. Figure 3 (As shown) is the support layer 300. The unwinding unit 102 unfolds the support layer 300, conveys it between the guide roller 1 and the guide roller 2, and then enters the plasma treatment unit 103. (3) Plasma treatment: The power of the atmospheric pressure dielectric barrier discharge plasma was set to 2 kVA. The root mean square roughness of the PPS porous mesh leaving the plasma treatment unit 103 was 220 nm, and its atomic force microscopy image is shown below. Figure 4 As shown; (4) Double-sided coating: The PPS porous grid that leaves the plasma processing unit 103 is vertically conveyed to the slit extrusion unit 104. The slurry conveying and filtering unit 101 conveys the film-forming slurry to two slit coating dies 201a and 201b symmetrically arranged on both sides of the PPS porous grid. The film-forming slurry is uniformly coated on both sides of the PPS porous grid simultaneously and in equal amounts by 201a and 201b. (5) Pre-evaporation: The coated nascent diaphragm enters the constant temperature and humidity evaporation chamber 105, where the air temperature and relative humidity are 50 ℃ and 30%, respectively; (6) Phase transformation and solidification to form a film: The nascent membrane leaving the constant temperature and humidity evaporation chamber 105 enters the gel tank 106 in a direction perpendicular to the surface of the gel bath, and phase separation occurs in the water at 25 °C, which then solidifies into a film. (7) Cleaning: The cured composite diaphragm enters the cleaning tank 107 through the guide roller 5 to remove the residual solvent by water replacement. The water temperature in the cleaning tank is 25 ℃. (8) Collection of finished composite membrane: The composite membrane leaving the washing tank is collected by the composite membrane winding unit 108 to obtain the finished product, namely the composite membrane for alkaline water electrolysis to produce hydrogen. The cross-sectional view of the composite membrane along the thickness direction is shown in the figure. Figure 2 As shown, the thickness of the composite membrane is 460 micrometers.

[0045] Examples 2-11 were prepared using the same apparatus as in Example 1. The specific preparation methods for each example are as follows: Example 2 A method for preparing a composite membrane for alkaline water electrolysis to produce hydrogen includes the following steps: (1) Preparation of film-forming slurry: In the film-forming slurry preparation unit 100, polysulfone, N-methylpyrrolidone and cerium oxide particles with a particle size of 30 nanometers are stirred at a temperature of 60°C to obtain a uniform and defoamed film-forming slurry with a composition of 21 wt% polysulfone, 48 wt% N-methylpyrrolidone and 31 wt% cerium oxide particles.

[0046] (2) Plasma treatment of the support layer: After the 40-mesh polyphenylene sulfide (PPS) porous grid with a thickness of 268 micrometers was treated with plasma with a power of 2 kVA, the root mean square roughness of its surface was 230 nm.

[0047] (3) Double-sided coating: The membrane slurry is applied evenly and in equal amounts to both sides of the porous grid obtained in step (2). The porous grid is placed vertically during coating, and a primary diaphragm is obtained after coating.

[0048] (4) Molding: The nascent membrane obtained in step (3) is pre-evaporated in a constant temperature and humidity evaporator 105 and then enters the gel tank 106 in a direction perpendicular to the surface of the gel bath. Phase separation occurs in the water, and the membrane is then solidified. The solidified composite membrane enters the cleaning tank 107 to remove residual solvent by water replacement. The membrane is then wound up to obtain a composite membrane for alkaline water electrolysis to produce hydrogen, with a thickness of 500 micrometers. The winding speed is 0.5 m / min, the temperature and relative humidity of the constant temperature and humidity evaporator are 65℃ and 25%, respectively, and the temperature of the gel tank and the cleaning tank are both 25℃.

[0049] Example 3 A method for preparing a composite membrane for alkaline water electrolysis to produce hydrogen includes the following steps: (1) Preparation of film-forming slurry: In the film-forming slurry preparation unit 100, polysulfone, diazonite-containing poly(naphthyl biphenyl) co-ether sulfone ketone (PPBESK), N-methylpyrrolidone, and zirconium oxide particles with a particle size of 100 nanometers are stirred at 50°C to obtain a uniform and deaerated film-forming slurry with the composition of 6.5 wt% polysulfone, 6.5 wt% PPBESK, 57 wt% N-methylpyrrolidone, and 30 wt% zirconium oxide particles.

[0050] (2) Plasma treatment of the support layer: After the 50-mesh polyphenylene sulfide (PPS) porous grid with a thickness of 256 micrometers is treated with plasma with a power of 2 kVA, the root mean square roughness of its surface is 220 nm.

[0051] (3) Double-sided coating: The membrane slurry is applied evenly and in equal amounts to both sides of the porous grid obtained in step (2). The porous grid is placed vertically during coating, and a primary diaphragm is obtained after coating.

[0052] (4) Molding: The nascent diaphragm obtained in step (3) is pre-evaporated in a constant temperature and humidity evaporator 105 and then enters a gel tank 106 in a direction perpendicular to the gel bath surface. Phase separation occurs in the water, and the diaphragm is then solidified into a film. The solidified composite diaphragm enters a cleaning tank 107 to remove residual solvent by water replacement, and is then wound up to obtain a composite diaphragm for alkaline water electrolysis to produce hydrogen, with a thickness of 460 micrometers. The winding speed is 1 meter / minute, the temperature and relative humidity of the constant temperature and humidity evaporator are 50°C and 14%, respectively, and the temperature of both the gel tank and the cleaning tank is 25°C.

[0053] Example 4 A method for preparing a composite membrane for alkaline water electrolysis to produce hydrogen includes the following steps: (1) Preparation of film-forming slurry: In the film-forming slurry preparation unit 100, the diazonaphthone-containing poly(diazonaphthone) co-polyether sulfone ketone (PPBESK), N-methylpyrrolidone, and zirconium oxide particles with a particle size of 100 nanometers are stirred at a temperature of 50°C to obtain a uniform and defoamed film-forming slurry with the composition of 13 wt% PPBESK, 57 wt% N-methylpyrrolidone, and 30 wt% zirconium oxide particles.

[0054] (2) Plasma treatment of the support layer: After the 50-mesh polyphenylene sulfide (PPS) porous grid with a thickness of 256 micrometers is treated with plasma with a power of 2 kVA, the root mean square roughness of its surface is 220 nm.

[0055] (3) Double-sided coating: The membrane slurry is applied evenly and in equal amounts to both sides of the porous grid obtained in step (2). The porous grid is placed vertically during coating, and a primary diaphragm is obtained after coating.

[0056] (4) Molding: The nascent membrane obtained in step (3) is pre-evaporated in a constant temperature and humidity evaporator 105 and then enters the gel tank 106 in a direction perpendicular to the surface of the gel bath. Phase separation occurs in the water, and the membrane is then solidified. The solidified composite membrane enters the cleaning tank 107 to remove residual solvent by water replacement. The membrane is then wound up to obtain a composite membrane for alkaline water electrolysis to produce hydrogen, with a thickness of 460 micrometers. The winding speed is 1 meter / minute. The temperature and relative humidity of the constant temperature and humidity evaporator are 50°C and 30%, respectively. The temperature of both the gel tank and the cleaning tank is 25°C.

[0057] Example 5 A method for preparing a composite membrane for alkaline water electrolysis to produce hydrogen includes the following steps: (1) Preparation of film-forming slurry: In the film-forming slurry preparation unit 100, polysulfone, N-methylpyrrolidone and zirconium oxide particles with a particle size of 80 nanometers are stirred at a temperature of 40°C to obtain a uniform and deaerated film-forming slurry with a composition of 13 wt% polysulfone, 57 wt% N-methylpyrrolidone and 30 wt% zirconium oxide particles.

[0058] (2) Plasma treatment of the support layer: After the 30-mesh polypropylene (PP) porous mesh with a thickness of 245 micrometers was treated with plasma with a power of 3kVA, the root mean square roughness of its surface was 206 nm.

[0059] (3) Double-sided coating: The membrane slurry is applied evenly and in equal amounts to both sides of the porous grid obtained in step (2). The porous grid is placed vertically during coating, and a primary diaphragm is obtained after coating.

[0060] (4) Molding: The nascent membrane obtained in step (3) is pre-evaporated in a constant temperature and humidity evaporator 105 and then enters the gel tank 106 in a direction perpendicular to the surface of the gel bath. Phase separation occurs in the water, and the membrane is then solidified. The solidified composite membrane enters the cleaning tank 107 to remove residual solvent by water replacement. The membrane is then wound up to obtain a composite membrane for alkaline water electrolysis to produce hydrogen, with a thickness of 490 micrometers. The winding speed is 2 meters / minute. The temperature and relative humidity of the constant temperature and humidity evaporator are 35°C and 20%, respectively. The temperature of both the gel tank and the cleaning tank is 24°C.

[0061] Example 6 A method for preparing a composite membrane for alkaline water electrolysis to produce hydrogen includes the following steps: (1) Preparation of film-forming slurry: In the film-forming slurry preparation unit 100, polysulfone, N,N-dimethylacetamide and zirconium oxide particles with a particle size of 80 nanometers are stirred at a temperature of 70°C to obtain a uniform and deaerated film-forming slurry with a composition of 18 wt% polysulfone, 70 wt% N,N-dimethylacetamide and 12 wt% zirconium oxide particles.

[0062] (2) Plasma treatment of the support layer: After the 40-mesh polyphenylene sulfide (PPS) porous grid with a thickness of 268 micrometers was treated with plasma with a power of 8 kVA, the root mean square roughness of its surface was 200 nm.

[0063] (3) Double-sided coating: The membrane slurry is applied evenly and in equal amounts to both sides of the porous grid obtained in step (2). The porous grid is placed vertically during coating, and a primary diaphragm is obtained after coating.

[0064] (4) Molding: The nascent membrane obtained in step (3) is pre-evaporated in a constant temperature and humidity evaporator 105 and then enters the gel tank 106 in a direction perpendicular to the surface of the gel bath. Phase separation occurs in the water, and the membrane is then solidified. The solidified composite membrane enters the cleaning tank 107 to remove residual solvent by water replacement. The membrane is then wound up to obtain a composite membrane for alkaline water electrolysis to produce hydrogen, with a thickness of 440 micrometers. The winding speed is 5 meters / minute, the temperature and relative humidity of the constant temperature and humidity evaporator are 60°C and 15%, respectively, and the temperature of the gel tank and the cleaning tank are both 25°C.

[0065] Example 7 A method for preparing a composite membrane for alkaline water electrolysis to produce hydrogen includes the following steps: (1) Preparation of film-forming slurry: In the film-forming slurry preparation unit 100, polysulfone, dimethyl sulfoxide and zirconium oxide particles with a particle size of 100 nanometers are stirred at a temperature of 60°C to obtain a uniform and defoamed film-forming slurry with a composition of 9 wt% polysulfone, 36 wt% dimethyl sulfoxide and 55 wt% nano-zirconia particles.

[0066] (2) Plasma treatment of the support layer: After the 40-mesh polyphenylene sulfide (PPS) porous grid with a thickness of 268 micrometers was treated with plasma with a power of 2 kVA, the root mean square roughness of its surface was 220 nm.

[0067] (3) Double-sided coating: The membrane slurry is applied evenly and in equal amounts to both sides of the porous grid obtained in step (2). The porous grid is placed vertically during coating, and a primary diaphragm is obtained after coating.

[0068] (4) Molding: The nascent membrane obtained in step (3) is pre-evaporated in a constant temperature and humidity evaporator 105 and then enters the gel tank 106 in a direction perpendicular to the surface of the gel bath. Phase separation occurs in the water, and the membrane is then solidified. The solidified composite membrane enters the cleaning tank 107 to remove residual solvent by water replacement. The membrane is then wound up to obtain a composite membrane for alkaline water electrolysis to produce hydrogen, with a thickness of 470 micrometers. The winding speed is 1 meter / minute. The temperature and relative humidity of the constant temperature and humidity evaporator are 60°C and 30%, respectively. The temperature of both the gel tank and the cleaning tank is 15°C.

[0069] Example 8 A method for preparing a composite membrane for alkaline water electrolysis to produce hydrogen includes the following steps: (1) Preparation of film-forming slurry: In the film-forming slurry preparation unit 100, naphthalene biphenyl coether sulfone ketone (PPBESK), N,N-dimethylacetamide, and titanium dioxide particles with a particle size of 20 nanometers are stirred at a temperature of 60°C to obtain a uniform and deaerated film-forming slurry with the composition of 10 wt% naphthalene biphenyl coether sulfone ketone, 32 wt% N,N-dimethylacetamide, and 58 wt% titanium dioxide particles.

[0070] (2) Plasma treatment of the support layer: After the 50-mesh polyphenylene sulfide (PPS) porous grid with a thickness of 256 micrometers was treated with plasma with a power of 10 kVA, the root mean square roughness of its surface was 296 nm.

[0071] (3) Double-sided coating: The membrane slurry is applied evenly and in equal amounts to both sides of the porous grid obtained in step (2). The porous grid is placed vertically during coating, and a primary diaphragm is obtained after coating.

[0072] (4) Molding: The nascent membrane obtained in step (3) is pre-evaporated in a constant temperature and humidity evaporator 105 and then enters the gel tank 106 in a direction perpendicular to the surface of the gel bath. Phase separation occurs in the water, and the membrane is then solidified. The solidified composite membrane enters the cleaning tank 107 to remove residual solvent by water replacement. The membrane is then wound up to obtain a composite membrane for alkaline water electrolysis to produce hydrogen, with a thickness of 410 micrometers. The winding speed is 2 meters / minute. The temperature and relative humidity of the constant temperature and humidity evaporator are 40°C and 20%, respectively. The temperature of both the gel tank and the cleaning tank is 40°C.

[0073] Example 9 A method for preparing a composite membrane for alkaline water electrolysis to produce hydrogen includes the following steps: (1) Preparation of film-forming slurry: In the film-forming slurry preparation unit 100, naphthalene biphenyl copolyether sulfone (PPBES), N-methylpyrrolidone, and zirconium oxide particles with a particle size of 100 nanometers are stirred at a temperature of 60°C to obtain a uniform and defoamed film-forming slurry with the composition of 10 wt% naphthalene biphenyl copolyether sulfone, 59 wt% N-methylpyrrolidone, and 31 wt% zirconium oxide particles.

[0074] (2) Plasma treatment of the support layer: After plasma treatment with a power of 0.6 kVA, the root mean square roughness of the surface of the 60-mesh polyphenylene sulfide (PPS) porous mesh with a thickness of 256 micrometers is 259 nm.

[0075] (3) Double-sided coating: The membrane slurry is applied evenly and in equal amounts to both sides of the porous grid obtained in step (2). The porous grid is placed vertically during coating, and a primary diaphragm is obtained after coating.

[0076] (4) Molding: The nascent membrane obtained in step (3) is pre-evaporated in a constant temperature and humidity evaporator 105 and then enters the gel tank 106 in a direction perpendicular to the surface of the gel bath. Phase separation occurs in the water, and the membrane is then solidified. The solidified composite membrane enters the cleaning tank 107 to remove residual solvent by water replacement. The membrane is then wound up to obtain a composite membrane for alkaline water electrolysis to produce hydrogen, with a thickness of 495 micrometers. The winding speed is 0.1 m / min, the temperature and relative humidity of the constant temperature and humidity evaporator are 70℃ and 25%, respectively, and the temperature of the gel tank and the cleaning tank are both 15℃.

[0077] Example 10 A method for preparing a composite membrane for alkaline water electrolysis to produce hydrogen includes the following steps: (1) Preparation of film-forming slurry: In the film-forming slurry preparation unit 100, naphthalene biphenyl coether sulfone ketone (PPBESK), N,N-dimethylacetamide, and zirconium oxide particles with a particle size of 200 nanometers are stirred at a temperature of 60°C to obtain a uniform and deaerated film-forming slurry with the composition of 12 wt% naphthalene biphenyl coether sulfone ketone (PPBESK), 39 wt% N,N-dimethylacetamide, and 49 wt% zirconium oxide particles.

[0078] (2) Plasma treatment of the support layer: After the 30-mesh polypropylene (PP) porous mesh with a thickness of 245 micrometers was treated with plasma with a power of 3kVA, the root mean square roughness of its surface was 206 nm.

[0079] (3) Double-sided coating: The membrane slurry is applied evenly and in equal amounts to both sides of the porous grid obtained in step (2). The porous grid is placed vertically during coating, and a primary diaphragm is obtained after coating.

[0080] (4) Molding: The nascent membrane obtained in step (3) is pre-evaporated in a constant temperature and humidity evaporator 105 and then enters the gel tank 106 in a direction perpendicular to the gel bath surface. Phase separation occurs in the water, and the membrane is then solidified. The solidified composite membrane enters the cleaning tank 107 to remove residual solvent by water replacement. The membrane is then wound up to obtain a composite membrane for alkaline water electrolysis to produce hydrogen, with a thickness of 470 micrometers. The winding speed is 2 meters / minute. The temperature and relative humidity of the constant temperature and humidity evaporator are 45°C and 35%, respectively. The temperatures of the gel tank and the cleaning tank are both 18°C.

[0081] Example 11 A method for preparing a composite membrane for alkaline water electrolysis to produce hydrogen includes the following steps: (1) Preparation of film-forming slurry: In the film-forming slurry preparation unit 100, polyethersulfone, diazonyl biphenyl copolyethersulfone (PPBES) containing diazonyl ketone structure, N-methylpyrrolidone, and zirconium oxide particles with a particle size of 100 nanometers are stirred at a temperature of 65°C to obtain a uniform and deaerated film-forming slurry with the composition of 7 wt% polyethersulfone, 7 wt% PPBES, 62 wt% N-methylpyrrolidone, and 24 wt% nano-zirconia particles.

[0082] (2) Plasma treatment of the support layer: After the 40-mesh polyphenylene sulfide (PPS) porous grid with a thickness of 280 micrometers is treated with plasma with a power of 4 kVA, the root mean square roughness of its surface is 250 nm.

[0083] (3) Double-sided coating: The membrane slurry is applied evenly and in equal amounts to both sides of the porous grid obtained in step (2). The porous grid is placed vertically during coating, and a primary diaphragm is obtained after coating.

[0084] (4) Molding: The nascent membrane obtained in step (3) is pre-evaporated in a constant temperature and humidity evaporator 105 and then enters the gel tank 106 in a direction perpendicular to the surface of the gel bath. Phase separation occurs in the water, and the membrane is then solidified. The solidified composite membrane enters the cleaning tank 107 to remove residual solvent by water replacement. The membrane is then wound up to obtain a composite membrane for alkaline water electrolysis to produce hydrogen, with a thickness of 455 micrometers. The winding speed is 1 meter / minute. The temperature and relative humidity of the constant temperature and humidity evaporator are 50°C and 14%, respectively. The temperature of both the gel tank and the cleaning tank is 25°C.

[0085] Comparative Example 1 An apparatus and method for preparing a composite membrane for alkaline water electrolysis to produce hydrogen, differing from Example 1 only in that the plasma treatment unit 103 is omitted or not used during preparation. The composite membrane is prepared by setting the winding speed to 1 meter / minute and following these steps: (1) Preparation of film-forming slurry: In the film-forming slurry preparation unit 100, polysulfone, N-methylpyrrolidone and zirconium oxide particles with a particle size of 100 nanometers are stirred at a temperature of 50 °C to obtain a uniform and degassed film-forming slurry with a composition of 13 wt% polysulfone, 57 wt% N-methylpyrrolidone and 30 wt% nano-zirconia particles. (2) Preparation of the support layer: A 50-mesh polyphenylene sulfide (PPS) porous mesh with a thickness of 256 micrometers (root mean square roughness of 148 nm, as shown in the atomic force microscope image) was selected. Figure 3 (As shown) is the support layer 300. The unwinding unit 102 unfolds the support layer 300, conveys it between the guide roller 1 and the guide roller 2, and then enters the plasma treatment unit 103. (3) Plasma treatment: The power of the atmospheric pressure dielectric barrier discharge plasma is set to 0 kVA; (4) Double-sided coating: The PPS porous grid that leaves the plasma processing unit 103 is vertically conveyed to the slit extrusion unit 104. The slurry conveying and filtering unit 101 conveys the film-forming slurry to two slit coating dies 201a and 201b symmetrically arranged on both sides of the PPS porous grid. The casting liquid is uniformly coated on both sides of the PPS porous grid simultaneously and in equal amounts by 201a and 201b. (5) Pre-evaporation: The coated nascent diaphragm enters the constant temperature and humidity evaporation chamber 105, where the air temperature and relative humidity are 50 ℃ and 30%, respectively; (6) Phase transformation and solidification to form a film: The nascent membrane leaving the constant temperature and humidity evaporation chamber 105 enters the gel tank 106 in a direction perpendicular to the surface of the gel bath, and phase separation occurs in the water at 25 °C, which then solidifies into a film. (7) Cleaning: The cured composite diaphragm enters the cleaning tank 107 through the guide roller 5 to remove the residual solvent by water replacement. The water temperature in the cleaning tank is 25 ℃. (8) Collection of finished composite diaphragm: The composite diaphragm leaving the cleaning tank is collected by the composite diaphragm winding unit 108 to obtain the finished composite diaphragm with a thickness of 460 micrometers.

[0086] Comparative Example 2 A method for preparing a composite membrane for alkaline water electrolysis to produce hydrogen differs from Example 5 mainly in that it does not use plasma treatment, and specifically includes the following steps: (1) Preparation of film-forming slurry: In the film-forming slurry preparation unit 100, polysulfone, N-methylpyrrolidone and zirconium oxide particles with a particle size of 80 nanometers are stirred at a temperature of 40°C to obtain a uniform and deaerated film-forming slurry with a composition of 13 wt% polysulfone, 57 wt% N-methylpyrrolidone and 30 wt% zirconium oxide particles.

[0087] (2) Double-sided coating: Select a 30-mesh polypropylene (PP) porous mesh with a root mean square roughness of 129 nm and a thickness of 245 μm. Apply the membrane-forming slurry to both sides of the porous mesh simultaneously and in equal amounts. The porous mesh is placed vertically during coating. After coating, a primary diaphragm is obtained.

[0088] (3) Molding: The nascent membrane obtained in step (2) is pre-evaporated in a constant temperature and humidity evaporator 105 and then enters the gel tank 106 in a direction perpendicular to the gel bath surface. Phase separation occurs in the water, and the membrane is then solidified. The solidified composite membrane enters the cleaning tank 107 to remove residual solvent by water replacement. The membrane is then wound up to obtain a composite membrane for alkaline water electrolysis to produce hydrogen, with a thickness of 490 micrometers. The winding speed is 2 meters / minute. The temperature and relative humidity of the constant temperature and humidity evaporator are 35°C and 20%, respectively. The temperature of both the gel tank and the cleaning tank is 24°C.

[0089] Tests and Results 1. Root mean square roughness of porous mesh surface Rq test The root-mean-square surface roughness of the porous mesh wires was characterized by tapping mode analysis using an XE-200 atomic force microscope. Rq See Table 1 for specific results: Table 1

[0090] 2. Solubility parameter testing The Hansen solubility parameters for polymers (PPS, PSU, PP, PES) are derived from Hansen, Charles M. Hansen solubility parameters: a user's handbook [M]. 2 ndEd. Boca Raton, Fla.: Taylor & Francis, 2007. The Hansen solubility parameters of poly(phenylene oxide) coether sulfone ketone (PPBESK) and poly(phenylene oxide) coether sulfone (PPBES) were estimated using the group contribution method. Specific values ​​are shown in Table 2. Table 2. Hansen solubility parameters of polymers

[0091] Solubility parameter difference R a Calculated using formula (1), (1) In the formula, , , and are the dispersion, polarization, and hydrogen bonding components of the Hansen solubility parameter, respectively, and the subscripts 1 and 2 represent the polymer and porous grid, respectively.

[0092] 3. Thickness test The thickness of the composite diaphragm was measured using a high-precision thickness gauge (thousandths).

[0093] 4. Surface resistance test The sheet resistance of the composite membrane was tested using AC impedance constant potential mode on a CS310M electrochemical workstation. The test temperature was 25℃, and the electrolyte was a 30 wt% potassium hydroxide aqueous solution. Specific results are shown in Table 3.

[0094] 5. Bubble Point Pressure Test Referring to the national standard GB / T 32361-2015, the composite diaphragm was subjected to bubble point pressure testing using Porefil™ impregnation fluid on a Porolux™ 1000 capillary porosimeter. Specific results are shown in Table 3.

[0095] 6. Compression strength test The compression curve of the composite diaphragm was tested using an RH-300 computer compression ratio meter, and the compressive stress at 10% compressive strain was taken as the compressive strength of the composite diaphragm. See Table 3 for specific results.

[0096] 7. Mass wear loss rate test The composite diaphragm was tested using a GT-7012-A type AKRON abrasion tester. The mass wear loss rate of the composite diaphragm was calculated using formula (2) according to national standard GB / T1689-2014. MWL ), (2) In the formula m The quality after wear. m 0 represents the initial mass, in units of: g See Table 3 for specific results.

[0097] 8. Adhesion test The adhesion of the composite membrane, i.e., the bonding force between the functional layers composed of the porous mesh and the polymer / particulate filler, was determined using a BGD 500 / S automatic digital pull-off adhesion tester. The test method followed the national standard GB / T 5210-2006, and the specific results are shown in Table 3.

[0098] 9. Polymer molecular weight characterization The weight-average molecular weight and polydispersity index of the polymers used in the examples and comparative examples were characterized using an Agilent 1260 Infinity II high-temperature gel permeation chromatography instrument equipped with a differential detector. The mobile phase was N-methylpyrrolidone (NMP), and the standard was polystyrene (PS). Specific results are as follows: The weight-average molecular weight and polydispersity index of polysulfone are 67 kDa and 2, respectively.

[0099] The weight-average molecular weight and polydispersity index of polyethersulfone are 71 kDa and 2, respectively.

[0100] The weight-average molecular weight and polydispersity index of the polyether sulfone ketone were 47 kDa and 2, respectively.

[0101] The weight-average molecular weight and polydispersity index of the polyether sulfone were 51 kDa and 2, respectively.

[0102] Table 3

[0103] As can be seen from Table 3, the composite diaphragm of this invention, by controlling the root mean square roughness of the porous mesh surface to be no less than 200 nm, improves its bonding force with the functional layer composed of polymer and filler. This results in enhanced mechanical strength of the diaphragm, exhibiting high compressive strength (no less than 40 MPa), high adhesion (no less than 0.12 MPa), and low mass wear loss rate (no more than 4%), while also possessing low surface resistivity (no more than 0.7 Ω·cm). 2 Its characteristics of high bubble point pressure (not less than 2.7 bar) make it suitable for alkaline water electrolysis hydrogen production. Furthermore, the solubility parameter difference between the polymer and the porous grid is controlled to be no higher than 4.0 MPa. 0.5 The resulting diaphragm exhibits a compressive strength of no less than 50 MPa, an adhesion strength of no less than 0.21 MPa, a mass abrasion loss rate of no more than 1%, and a bubble point pressure of no less than 4.1 bar, making it particularly suitable for pressurized electrolytic cells. Furthermore, the difference in solubility parameters between the polymer and the porous mesh is controlled to be no more than 3.0 MPa. 0.5The resulting composite diaphragm exhibits generally good overall performance, particularly with a compressive strength of no less than 90 MPa, an adhesion strength of no less than 0.31 MPa, a mass abrasion loss rate of no more than 0.9%, a bubble point pressure of no less than 5 bar, and a surface resistivity of no more than 0.3 Ω·cm. 2 .

[0104] Specifically, by comparing Example 1 with Comparative Example 1 and Example 5 with Comparative Example 2, it can be seen that as the surface roughness of the porous mesh wire diameter increases, the compressive strength and adhesion of the composite diaphragm increase, the mass wear loss rate decreases, and the mechanical properties are enhanced. In particular, when the root mean square roughness of the porous mesh wire diameter is greater than 200 nm, the composite diaphragm has excellent mechanical properties, while also having low surface resistivity and high bubble point pressure.

[0105] As can be seen from Examples 3, 4, 8, 9, and 11, the solubility parameter difference Ra between PPBES and PPS (Example 9), and between PPBESK and PPS (Examples 4 and 8), does not exceed 1.0 MPa. 0.5 Even after doping PSU with an equal mass in PPBES (Example 3) and PES with an equal mass in PPBES (Example 11), the difference in solubility parameter Ra between them does not exceed 3.0 MPa. 0.5 The resulting composite diaphragm has a compressive strength of not less than 90 MPa. In other examples or comparative cases, the solubility parameter difference Ra between the polymer and the porous mesh is not less than 3.0 MPa. 0.5 The resulting composite membrane has a compressive strength not exceeding 90 MPa. Furthermore, a comparison of Examples 1, 3, and 4 (where the only difference in the type of polymer in the resulting composite membranes) and Examples 1 and 5 (where the polymers in the resulting composite membranes are the same but the porous grids are different) shows that the smaller the solubility difference between the polymer constituting the functional layer and the porous grid support layer, the stronger their compatibility, resulting in greater compressive strength and adhesion of the composite membrane, and a lower mass wear loss rate. In other words, reducing the solubility difference between the polymer constituting the functional layer and the support layer is beneficial for improving the mechanical strength of the composite membrane.

[0106] In summary, the technical solution disclosed in this invention is of great significance for preventing the composite diaphragm from being damaged under compressive stress, maintaining structural integrity, and ensuring the performance and safety of the water electrolysis device.

[0107] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention shall be within the scope of protection of the pending claims of the present invention.

Claims

1. A method for preparing a composite membrane for alkaline water electrolysis to produce hydrogen, characterized in that, Includes the following steps: (1) Mix the polymer, solvent and particulate filler evenly to obtain a film-forming slurry; (2) The porous grid is subjected to plasma treatment to obtain a porous grid with a root mean square roughness of not less than 200 nm. (3) The vacuum degassing slurry is uniformly applied to both sides of the porous grid obtained in step (2) simultaneously and in equal amounts. The porous grid is placed vertically during the application, and a primary diaphragm is obtained after the application. (4) The nascent membrane obtained in step (3) is introduced into the gel bath in a direction perpendicular to the surface of the gel bath for phase transformation, solidified into a film, and then washed with water and wound up to obtain a composite membrane for alkaline water electrolysis to produce hydrogen.

2. The preparation method according to claim 1, characterized in that, The difference in solubility parameters between the polymer in step (1) and the porous mesh in step (2) shall not exceed 10.0 MPa. 0.5 .

3. The preparation method according to claim 2, characterized in that, The difference in solubility parameters between the polymer in step (1) and the porous mesh in step (2) shall not exceed 4.0 MPa. 0.5 .

4. The preparation method according to claim 1, characterized in that, In step (1), the mass ratio of polymer, solvent and particulate filler in the film-forming slurry is 9~21:32~70:10~60, totaling 100; And / or, the polymer comprises one or more of polysulfone, polyethersulfone, diazonyl biphenyl coethersulfone ketone containing a diazonyl biphenyl structure, and diazonyl biphenyl coethersulfone; And / or, the particulate filler includes one or more of oxide particles, nitride particles and carbide particles; And / or, the solvent is one or more of N-methylpyrrolidone, N,N-dimethylacetamide, N,N-dimethylformamide and dimethyl sulfoxide.

5. The preparation method according to claim 1, characterized in that, In step (2), the power of the plasma treatment is 0.5~10kVA.

6. The preparation method according to claim 1, characterized in that, In step (4), the nascent diaphragm is pre-evaporated before being immersed in the gel bath.

7. The preparation method according to claim 6, characterized in that, The temperature of the pre-evaporation treatment is 20~80℃, and / or the relative humidity of the pre-evaporation treatment is 10~90%.

8. The preparation method according to claim 7, characterized in that, The temperature of the pre-evaporation treatment is 35~70℃, and / or the relative humidity of the pre-evaporation treatment is 10~35%.

9. The preparation method according to claim 1, characterized in that, In step (4), the phase transformation temperature is 15~70℃; And / or, the temperature of the water wash is 15~70℃; And / or, the winding linear speed is 0.1 to 20 meters per minute.

10. A preparation apparatus for implementing the preparation method according to any one of claims 1-9, characterized in that, It includes a film-forming slurry preparation unit (100), a slurry conveying and filtering unit (101), an unwinding unit (102), a plasma treatment unit (103), a slit extrusion unit (104), a constant temperature and humidity evaporation chamber (105), a gel tank (106), a cleaning tank (107), and a composite diaphragm winding unit (108). The film-forming slurry preparation unit (100) is used for preparing the film-forming slurry and vacuum degassing; The slurry conveying and filtering unit (101) is used to filter and convey the film-forming slurry; The unwinding unit (102) and the composite diaphragm winding unit (108) are respectively used for unwinding the porous grid and winding the composite diaphragm; The plasma processing unit (103) is used for plasma processing of porous grids; The slit extrusion unit (104) includes symmetrically arranged slit coating dies (201a) and (201b) for double-sided coating of the porous grid, that is, coating the porous grid with equal amounts on both sides at the same time. The constant temperature and humidity evaporation chamber (105) is used for the pre-evaporation of the film-forming slurry on the porous grid. The gel tank (106) is used for the curing and molding of the film-forming slurry on the porous grid. The cleaning tank (107) is used for cleaning the composite diaphragm; After passing through the unwinding unit (102) and the composite membrane winding unit (108), the porous mesh is first conveyed to the plasma treatment unit (103) for plasma treatment, and then vertically conveyed to the slit extrusion unit (104). The slit coating dies (201a) and (201b) located on both sides of the porous mesh simultaneously coat the membrane slurry conveyed by the slurry conveying and filtering unit (101) onto the symmetrical surface of the porous mesh. After coating, the nascent membrane passes through the constant temperature and humidity evaporation chamber (105) and enters the gel tank (106) in a direction perpendicular to the gel bath liquid surface, or directly enters the gel tank (106) in a direction perpendicular to the gel bath liquid surface without passing through the constant temperature and humidity evaporation chamber (105), so that the membrane slurry undergoes phase separation and solidifies into a membrane. Then it enters the cleaning tank (107) to remove residual solvent by water replacement, and finally the finished composite membrane is obtained at the composite membrane winding unit (108).

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