Composite separator, and preparation method therefor and use thereof

Abstract

A composite separator and a preparation method therefor. The composite separator comprises a main film and an anti-contamination layer, which is arranged on one or both surfaces of the main film, wherein the anti-contamination layer comprises a first polymer, a charge agent and / or an anti-fouling agent. The composite separator can be applied to alkaline water electrolysis for hydrogen production and other electrolysis industries, and the anti-contamination layer of the composite separator can effectively prevent impurity species, especially metal ions fallen from a cathode catalyst, from being attached to the surface, which causes the sheet resistance to increase, thereby increasing the electrolytic energy consumption.

Description

Composite diaphragm and its preparation method and application Technical Field

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

[0002] In current industrial hydrogen production, alkaline water electrolysis offers advantages in technological maturity and low equipment costs, making it suitable for large-scale hydrogen production. The diaphragm, a key material in alkaline electrolyzers, serves the dual function of separating the gases generated in the positive and negative electrode chambers while also providing a pathway for ions in the electrolyte to migrate across the membrane.

[0003] Composite membranes are a typical example of alkaline water hydrogen production membranes. They use oxide ceramic powders with hydrophilic properties. At the same time, the nanoporous structure can be regulated by controlling the film-forming process, which can effectively promote electrolyte diffusion. Compared with other hydrogen production membranes, they have obvious advantages in gas barrier properties and reduced ion transport resistance, making them a hot topic of research. Patent CN110869538A discloses an asymmetric composite membrane. By changing the solidification temperature and humidity conditions, asymmetric channels on both sides of the membrane are obtained to avoid "bubble traps", prevent gas cross-contamination, and ensure OH - Effective ion transport; a study (Russian Journal of Applied Chemistry, 2016, 89, 618-621) also reported that adding polyvinylpyrrolidone to the casting solution significantly improved the porosity and hydrophilicity of polysulfone membranes. Therefore, current research focuses on improving the membrane's hydrophilicity and gas barrier properties, with considerable success. However, impurity contamination of electrolytic membranes is a common problem in the industry and urgently needs to be addressed. Impurities can clog membrane pores and coat the membrane surface, significantly reducing electrolysis efficiency. These impurities often originate from catalytic electrode detachment or corrosion, corrosion of system process piping and tanks, and the introduction of electrolyte or water impurities. They exist in the electrolyte as particulate matter or metal ions and are difficult to remove using traditional physical filtration methods. As electrolysis proceeds, they gradually accumulate on the membrane surface or internal pores, increasing the electrolyte ion migration resistance, significantly increasing the electrolysis chamber voltage, and shortening the membrane's service life.

[0004] Therefore, in order to improve the above problems encountered in the actual use of the diaphragm, it is necessary to develop a composite diaphragm for electrolysis that is efficient in electrolysis and resistant to impurity pollution. In view of this, the present disclosure is specially proposed.

[0005] Summary of the Invention

[0006] The present disclosure provides an anti-pollution electrolytic composite diaphragm and a preparation method thereof.

[0007] The present disclosure provides a composite membrane, comprising a main membrane and an anti-fouling layer disposed on one or both surfaces of the main membrane, wherein the anti-fouling layer comprises a first polymer, a charging agent and / or an anti-fouling agent.

[0008] According to one embodiment of the present disclosure, the antifouling agent is one or more of graphene, graphene oxide, and MXene; the charging agent is one or more of aromatic polyamide, polypiperazineamide, polyamide, cellulose acetate, polyetherimide, polyimide, polyaniline, and chitosan.

[0009] According to another embodiment of the present disclosure, the anti-fouling layer has a thickness of 2-100 μm; preferably, the weight ratio of the first polymer, the charging agent and the anti-fouling agent is (5-30): (0-40): (0-30).

[0010] According to another embodiment of the present disclosure, the first polymer is one or more of polyarylsulfone, polyethersulfone, polyphenylenesulfone, bisphenol A type polysulfone, and polyetheretherketone.

[0011] According to another embodiment of the present disclosure, the main membrane includes a hydrophilic inorganic substance, a second polymer and a pore aid, the mass ratio of the second polymer to the hydrophilic inorganic substance is 1:1-1:8, and the mass ratio of the pore aid to the second polymer is 1:10-2:1; preferably, the thickness of the main membrane is 100-700 μm.

[0012] According to another embodiment of the present disclosure, the second polymer is one or more of polyarylsulfone, polyethersulfone, polyphenylenesulfone, bisphenol A polysulfone, and polyetheretherketone; the pore-aiding agent is one or more of polyvinylpyrrolidone, polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer, polypropylene glycol and ethylene oxide addition polymer, polyethyleneimine, and polyacrylonitrile; the hydrophilic inorganic substance is one or more of titanium dioxide, zirconium dioxide, cerium oxide, barium sulfate, calcium sulfate, barium titanate, and calcium titanate. Preferably, the particle size of the hydrophilic inorganic substance is 5 nm-3 μm.

[0013] According to another embodiment of the present disclosure, the main membrane further comprises a support mesh or a support cloth, and preferably the thickness of the support mesh or the support cloth is 50-500 μm.

[0014] The present disclosure also provides a method for preparing a composite membrane, including: S1, using a first liquid pore-forming agent, the first polymer, the charging agent and / or the anti-fouling agent to prepare an anti-fouling layer slurry; S2, coating the casting liquid for forming the main membrane on the surface of the substrate, and coating the anti-fouling layer slurry on its surface, after pre-curing in the air, placing it in a coagulation bath and curing it until the liquid pore-forming agent is precipitated to obtain a composite membrane.

[0015] According to one embodiment of the present disclosure, the casting liquid includes a second liquid pore-forming agent, and the addition amount of the second liquid pore-forming agent accounts for 30% to 70% of the total mass of the casting liquid; the addition amount of the first liquid pore-forming agent accounts for 30% to 70% of the total mass of the anti-pollution layer slurry.

[0016] According to another embodiment of the present disclosure, in step S2, the pre-curing time in the air is 3-120s, the temperature of the coagulation bath is 5-80 degrees, the coagulation bath time is 10min-2h, and the solvent in the coagulation bath is deionized water or a mixed solvent of deionized water and one of dimethyl sulfoxide, 1-methyl-2-pyrrolidone, N,N-dimethylformamide, and N,N-dimethylacetamide.

[0017] The present disclosure also provides application of the composite diaphragm in electrolysis, preferably application in hydrogen production by alkaline water electrolysis.

[0018] The composite diaphragm disclosed in the present invention can be applied to alkaline water electrolysis for hydrogen production and other electrolysis industries, and its anti-pollution layer can effectively prevent impurity species, especially metal ions shed from cathode catalysts from adhering to the surface, resulting in an increase in surface resistance, thereby increasing electrolysis energy consumption. The anti-pollution layer contains a charging agent and / or an anti-fouling agent, and the charging agent carries a positive charge, so that the anti-pollution layer forms an electrostatic repulsion effect with the positive charge of the metal ions of the impurities, blocking them from covering or passing into the diaphragm, thereby enhancing the anti-fouling effect of the anti-pollution layer; the anti-fouling agent in the anti-pollution layer can provide a lower friction coefficient, which is beneficial for flushing away impurities on the surface of the diaphragm during the circulation of the electrolyte, thereby achieving the purpose of self-cleaning, and at the same time, the conductive layer can have a good charge transfer capability, effectively promoting electron and ion conduction, thereby improving the electrolysis efficiency and the service life and stability of the diaphragm, which is beneficial to the promotion and application of the composite diaphragm in the electrolytic hydrogen production industry. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] FIG1 is a schematic flow diagram of the composite membrane preparation method disclosed herein.

[0020] FIG2 is a schematic cross-sectional view of the composite diaphragm of the present disclosure.

[0021] FIG3 is an electron microscope image of the surface of the composite diaphragm prepared in Example 1.

[0022] FIG4 is an electron microscope image of a cross section of the composite diaphragm prepared in Example 1.

[0023] FIG5 is an electron microscope image of the surface of the composite diaphragm prepared in Example 2.

[0024] FIG6 is an electron microscope image of the cross section of the composite diaphragm prepared in Example 2.

[0025] FIG7 is a contact angle test diagram of the composite diaphragm prepared in Example 1.

[0026] FIG8 is a contact angle test diagram of the composite diaphragm prepared in Example 2.

[0027] FIG9 is a graph showing the electrolysis evaluation performance of Example 1.

[0028] FIG10 is a graph showing the electrolysis evaluation performance of Example 2.

[0029] FIG. 11 is a graph showing the electrolysis evaluation performance of Example 3.

[0030] FIG12 is a graph showing the electrolysis evaluation performance of Example 4.

[0031] FIG13 is a graph showing the electrolysis evaluation performance of Example 5.

[0032] FIG14 is a graph showing the electrolysis evaluation performance of Example 6.

[0033] FIG15 is a graph showing the electrolysis evaluation performance of Example 7.

[0034] FIG16 is a graph showing the electrolysis evaluation performance of Example 8.

[0035] FIG. 17 is a graph showing the electrolysis evaluation performance of Example 9.

[0036] FIG18 is a graph showing the electrolysis evaluation performance of Example 10.

[0037] FIG19 is a graph showing the electrolysis evaluation performance of Comparative Example 1. DETAILED DESCRIPTION

[0038] The present disclosure is described in detail below in conjunction with specific implementation methods.

[0039] The composite membrane disclosed in the present invention includes a main membrane and an anti-pollution layer provided on one or both surfaces of the main membrane, wherein the anti-pollution layer includes a first polymer, a charging agent and / or an anti-fouling agent. The positive charge of the charging agent in the composite membrane causes the anti-pollution layer to form an electrostatic repulsion with the positive charge of the metal ions of the impurities, preventing them from covering or transmitting into the membrane, thereby enhancing the anti-fouling effect of the anti-pollution layer. The anti-fouling agent in the anti-pollution layer can provide a lower friction coefficient, which is beneficial for flushing away impurities on the surface of the membrane during the circulation of the electrolyte, thereby achieving the purpose of self-cleaning; at the same time, the conductive layer can have a good charge transfer capability, effectively promoting the conduction of electrons and ions, thereby improving the electrolysis efficiency and the service life and stability of the membrane, which is beneficial to the promotion and application of the composite membrane in the electrolytic hydrogen production industry.

[0040] In an optional embodiment, the antifouling agent in the antifouling layer can be one or more of graphene, graphene oxide, and MXene. The charging agent can be one or more of aromatic polyamide, polypiperazineamide, polyamide, cellulose acetate, polyetherimide, polyimide, polyaniline, and chitosan.

[0041] In an optional embodiment, the anti-fouling layer has a thickness of 2-100 μm. The thickness of the anti-fouling layer can be selected according to specific needs, for example, 10 μm, 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm, etc. The weight ratio of the first polymer, the charging agent, and the anti-fouling agent in the anti-fouling layer is (5-30):(0-40):(0-30).

[0042] In an optional embodiment, the primary film layer includes a second polymer, a hydrophilic inorganic material, and a pore-enhancing agent. The mass ratio of the second polymer to the hydrophilic inorganic material is 1:1-1:8, and the mass ratio of the pore-enhancing agent to the second polymer is 1:10-2:1. The primary film layer may have a thickness of 100-700 μm.

[0043] In an optional embodiment, the pore-improving agent may be one or more of polyvinyl pyrrolidone (PVP), polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer, polypropylene glycol and ethylene oxide addition polymer, polyethylene imine, and polyacrylonitrile.

[0044] In an optional embodiment, the hydrophilic inorganic material is one or more of titanium dioxide, zirconium dioxide, cerium dioxide, barium sulfate, calcium sulfate, barium titanate, and calcium titanate. The particle size of the hydrophilic inorganic material is 5 nm-3 μm.

[0045] In an optional embodiment, the primary membrane may further include a support mesh or support cloth to enhance the mechanical properties of the primary membrane. The support mesh or support cloth may be made of one or more of polyphenylene sulfide, polytetrafluoroethylene, polyethylene, polypropylene, nylon, polysulfone, and polyetheretherketone. The thickness of the support mesh or support cloth may be 50-500 μm.

[0046] In an optional embodiment, the first polymer in the anti-fouling layer and the second polymer in the main film may be the same or different, and may be selected from one or more of polyarylsulfone, polyethersulfone, polyphenylenesulfone, bisphenol A polysulfone, and polyetheretherketone.

[0047] As shown in Figure 1, the composite membrane of the present disclosure can be prepared by the following steps: S1, preparing an anti-fouling layer slurry using a first liquid pore-forming agent, a first polymer, a charging agent, and / or an anti-fouling agent; S2, coating the casting solution for forming the main membrane on the surface of a substrate, and then coating the anti-fouling layer slurry on the surface. After pre-curing in air, the slurry is placed in a coagulation bath and cured until the liquid pore-forming agent precipitates to obtain a composite membrane.

[0048] In an optional embodiment, a first liquid pore-forming agent, a first polymer, a charging agent, and / or an antifouling agent can be mixed to form an antifouling layer slurry. The order of adding the first polymer, charging agent, and / or antifouling agent can be arbitrary, as long as a uniform slurry is formed. For example, but not limited to, a certain mass of antifouling agent can be added to the first liquid pore-forming agent, stirred and mixed, and then a certain mass of polymer and charging agent can be added. In the antifouling layer slurry, the first polymer accounts for 5-30% of the total mass of the antifouling layer slurry; the first liquid pore-forming agent accounts for 30-70% of the total mass of the antifouling layer slurry; the charging agent accounts for 0-40% of the total mass of the antifouling layer slurry; and the antifouling agent accounts for 0-30% of the total mass of the antifouling layer slurry. The ultrasonic or stirring time can be 4-72 hours.

[0049] In an alternative embodiment, a second liquid pore-forming agent, a hydrophilic inorganic powder, a second polymer, and a pore-enhancing agent can be mixed to form a casting solution. The order of adding the second liquid pore-forming agent, the hydrophilic inorganic powder, the second polymer, and the pore-enhancing agent can be arbitrary, as long as a uniform casting solution is formed. For example, but not limited to, a certain amount of hydrophilic inorganic powder can be added to the second liquid pore-forming agent, stirred and mixed, and then a certain amount of polymer and pore-enhancing agent are added and stirred to obtain a uniform casting solution. The prepared casting solution can be stirred and mixed for 4-72 hours.

[0050] In an optional embodiment, the amount of the second liquid pore-forming agent added to the casting solution accounts for 30% to 70% of the total mass of the casting solution. The amount of the first liquid pore-forming agent added to the anti-pollution layer slurry accounts for 30% to 70% of the total mass of the anti-pollution layer slurry.

[0051] In an optional embodiment, the first liquid pore-forming agent and the second liquid pore-forming agent may be the same or different and are each selected from one or more of 1-methyl-2-pyrrolidone (NMP), dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide, acetone, and tetrahydrofuran.

[0052] In step S2, the coating method can be any one of spraying, brushing, dipping, blade coating, and roller coating.

[0053] In step S2, the pre-curing time in air is 3-120 seconds, the temperature of the coagulation bath is 5-80 degrees Celsius, and the coagulation bath time is 10 minutes to 2 hours. The solvent in the coagulation bath is deionized water or a mixed solvent of deionized water and dimethyl sulfoxide, 1-methyl-2-pyrrolidone, N,N-dimethylformamide, or N,N-dimethylacetamide.

[0054] The present disclosure is further described below through specific examples. However, these examples are merely exemplary and do not constitute any limitation on the scope of protection of the present disclosure.

[0055] In the following examples and comparative examples, all reagents, materials and instruments used are commercially available unless otherwise specified.

[0056] Example 1

[0057] Weigh 83.25g of NMP, add 48.5g of ZrO2 (average particle size 100nm) powder, place in a blender and stir evenly, then add 11.1g of PSF solid and 1.6g of PVP, and continue stirring to obtain a uniform casting solution. Weigh 4g of polyaniline and disperse it in 5g of NMP, add 1g of PSF, and place in a 25°C ultrasonic bath for ultrasonic stirring for 6h to prepare a uniform anti-pollution layer slurry. The casting solution is then symmetrically coated on both sides of a 200μm thick PPS support mesh to form a liquid film with a main film thickness of 300μm. Then, the prepared anti-pollution layer slurry is sprayed on one side to a thickness of 20μm. After pre-curing in air for 30s, it is then immersed in deionized water at 25°C to remove the pore-forming agent, resulting in a composite membrane with the structure shown in Figure 2.

[0058] The composite membrane obtained above was subjected to a scanning electron microscope test to observe its surface morphology. As shown in Figure 3, it can be observed that the surface is relatively dense and smooth, with no obvious macroporous structure, and all are nanopores. Figure 4 is a cross-sectional view of the membrane. The interior of the membrane is a macroporous structure, which provides a channel for ion transmission. The anti-pollution layer is well composited with the main membrane. Figure 7 shows a contact angle test photo. The contact angle is 65.53°, indicating that the surface of the composite membrane has good water wettability and can effectively isolate the adsorption and penetration of gases in the electrolysis of water to produce hydrogen. The test data of the composite membrane surface resistance, tensile strength, peel strength, bubble point, etc. are shown in Table 1. The composite membranes sprayed with the anti-pollution layer all exhibited good gas barrier properties and strong peel strength, indicating that the addition of the anti-pollution layer makes the entire embryo of the composite membrane and the matrix PPS support mesh more bonded, the stability is greatly improved, the surface resistance is low, the surface pore size of the membrane is small, the bubble point pressure is greater than 2Bar, and it exhibits good gas barrier performance.

[0059] The composite membrane was installed in an electrolytic cell for hydrogen production by electrolysis of water for electrolysis performance testing. The cathode of the electrolytic cell used a commercial Raney nickel electrode, the anode was a nickel mesh, the current collector was a nickel plate, and the electrolyte was 30wt% KOH. 0.01M FeCl3 and 0.01M NiCl2 soluble impurities were added to the cathode electrolyte to simulate metal ions caused by catalyst shedding. The geometric area of ​​the working electrode was 25cm 2, control the temperature of the electrolyte and the electrolytic cell to be constant at 85 degrees, control the current of the electrolytic cell to be in the range of 5-15A, and measure the change of the cell voltage. The IV relationship diagram for electrolytic performance evaluation is shown in Figure 9b. The prepared composite diaphragm is then subjected to a long-term test of its anti-pollution performance under constant current. Figure 9a shows the curve of its cell voltage change over time. The test conditions are consistent with the above IV performance test conditions, and the current density is constant at 400mA / cm 2 It can be seen that the presence of metallic impurities in the cathode electrolyte has no effect on the cell voltage, indicating relatively stable operation (Figure 9, Panel a). Furthermore, the surface resistance remains virtually unchanged after operation (Table 1). Furthermore, the IV relationship of the diaphragm after 1000 hours of operation is similar to that before (Figure 9, Panel b), demonstrating that the anti-fouling layer effectively prevents contamination of the diaphragm surface by impure metal ions.

[0060] Example 2

[0061] Weigh 83.25g of NMP, add 48.5g of ZrO2 (average particle size 100nm) powder to it, put it in a blender and stir evenly, then add 11.1g of polyethersulfone solid and 1.6g of PVP, and continue stirring to obtain a casting liquid with a uniform texture. Weigh 3g of graphene and disperse it in 6g of NMP, add 1g of PSF, place it in an ultrasonic bath at 20 degrees and ultrasonically stir for 6h to prepare a uniform anti-pollution layer slurry. Then, the casting liquid is symmetrically coated on both sides of a PPS support mesh with a thickness of 200μm to form a liquid film. The main film thickness is 300μm. The prepared anti-pollution layer slurry is sprayed on one side, and the anti-pollution layer thickness is 40μm. After pre-curing in air for 30s, it is then immersed in deionized water at 25°C to remove the pore-forming agent to obtain a composite diaphragm.

[0062] The resulting composite membrane was tested using a scanning electron microscope to observe its surface morphology. Figure 5 shows its surface structure, Figure 6 shows a cross-sectional view of the membrane, and Figure 8 shows a contact angle measurement photograph of the membrane, which shows a contact angle of 68.68°.

[0063] The composite membrane was placed in an electrolytic cell for hydrogen production by electrolysis of water for electrolysis performance testing. The test conditions were consistent with those of Example 1, and the IV relationship diagram for electrolysis performance evaluation is shown in Figure 10b. The prepared composite membrane was then subjected to a long-term test of anti-pollution performance under constant current. Figure 10a shows a curve of cell voltage change over time. The test conditions were consistent with the above IV performance test conditions, and the current density was constant at 400mA / cm 2 It can be seen that the presence of metallic impurities in the cathode electrolyte has no effect on the cell voltage, indicating relatively stable operation (Figure 10a). Furthermore, the surface resistance remains virtually unchanged after operation (Table 1). Furthermore, the IV relationship of the diaphragm after 1000 hours of operation is similar to that before (Figure 10b), demonstrating that the anti-fouling layer effectively prevents contamination of the diaphragm surface by impure metal ions.

[0064] Example 3

[0065] Weigh 83.25g of NMP, add 48.5g of ZrO2 (average particle size 100nm) powder, place in a blender and stir evenly, then add 11.1g of PSF solid and 1.6g of F123, and continue stirring to obtain a uniform casting solution. Weigh 1g of polyetherimide and 1g of graphene oxide and disperse them in 7g of NMP, add 1g of PSF, place in a 20°C ultrasonic bath and ultrasonically stir for 6h to prepare a uniform anti-pollution layer slurry. Then, the casting solution is symmetrically coated on both sides of a 200μm thick PPS support mesh to form a liquid film, with a main film thickness of 300μm. The prepared anti-pollution layer slurry is sprayed on one side to a thickness of 60μm. After pre-curing in air for 40s, it is then immersed in deionized water at 25°C to remove the pore-forming agent to obtain a composite diaphragm.

[0066] The composite membrane was placed in an electrolytic cell for hydrogen production by electrolysis of water for electrolysis performance testing. The test conditions were consistent with those in Example 1, and the IV relationship diagram for electrolysis performance evaluation is shown in Figure 11b. The prepared composite membrane was then subjected to a long-term test of anti-pollution performance under constant current. Figure 11a shows a curve of cell voltage change over time. The test conditions were consistent with the above IV performance test conditions, and the current density was constant at 400mA / cm 2 It can be seen that the presence of metallic impurities in the cathode electrolyte has no effect on the cell voltage, indicating relatively stable operation (Figure 11, Panel a). Furthermore, the surface resistance remains virtually unchanged after operation (Table 1). Furthermore, the IV relationship of the diaphragm after 1000 hours of operation is similar to that before (Figure 11, Panel b), demonstrating that the anti-fouling layer effectively prevents contamination of the diaphragm surface by impure metal ions.

[0067] Example 4

[0068] Weigh 83.25g of NMP, add 48.5g of ZrO2 (average particle size 100nm) powder to it, put it in a blender and stir evenly, then add 11.1g of polyethersulfone solid and 1.6g of F123, and continue stirring to obtain a uniform casting liquid. Weigh 2g of polyetherimide and 3g of MXene and disperse them in 4.5g of NMP, add 0.5g of polyarylsulfone, place it in an ultrasonic bath at 25 degrees and stir ultrasonically for 6h to prepare a uniform anti-pollution layer slurry. Then the casting liquid is symmetrically coated on both sides on the surface of a PPS support mesh with a thickness of 300μm to form a liquid film. The main film thickness is 500μm, and the prepared anti-pollution layer slurry is sprayed on one side with a spray thickness of 80μm. After pre-curing in air for 30s, it is then immersed in deionized water at 25°C to remove the pore-forming agent to obtain a composite diaphragm.

[0069] The composite membrane was placed in an electrolytic cell for hydrogen production by electrolysis of water for electrolysis performance testing. The test conditions were consistent with those in Example 1, and the IV relationship diagram for electrolysis performance evaluation is shown in Figure 12b. The prepared composite membrane was then subjected to a long-term test of anti-pollution performance under constant current. Figure 12a shows a curve of cell voltage change over time. The test conditions were consistent with the above IV performance test conditions, and the current density was constant at 400 mA / cm 2 It can be seen that the presence of metallic impurities in the cathode electrolyte has no effect on the cell voltage, indicating relatively stable operation (Figure 12, Panel a). Furthermore, the surface resistance remains virtually unchanged after operation (Table 1). Furthermore, the IV relationship of the diaphragm after 1000 hours of operation is similar to that before (Figure 12, Panel b), demonstrating that the anti-fouling layer effectively prevents contamination of the diaphragm surface by impure metal ions.

[0070] Example 5

[0071] Weigh 83.25g of NMP, add 48.5g of ZrO2 (average particle size 100nm) powder, and stir thoroughly in a blender. Then add 11.1g of polysulfone solid and 1.6g of PVP, and continue stirring to obtain a uniform casting solution. Weigh 3.2g of polyaniline and 3g of molybdenum disulfide, disperse them in 3g of NMP, add 0.8g of polysulfone, and place in an ultrasonic bath at 25°C for 6 hours to prepare a uniform anti-fouling layer slurry. The casting solution is then symmetrically coated on both sides of a 300μm-thick PPS support mesh to form a liquid film, with a main film thickness of 500μm. The prepared anti-fouling layer slurry is sprayed on one side to a thickness of 40μm. After pre-curing in air for 30s, the membrane is immersed in deionized water at 25°C to remove the pore-forming agent, resulting in a composite membrane.

[0072] The composite membrane was placed in an electrolytic cell for hydrogen production by electrolysis of water for electrolysis performance testing. The test conditions were consistent with those in Example 1, and the IV relationship diagram for electrolysis performance evaluation is shown in Figure 13b. The prepared composite membrane was then subjected to a long-term test of anti-pollution performance under constant current. Figure 13a shows a curve of cell voltage change over time. The test conditions were consistent with the above IV performance test conditions, and the current density was constant at 400mA / cm 2 It can be seen that the presence of metallic impurities in the cathode electrolyte has no effect on the cell voltage, indicating relatively stable operation (Figure 13, Panel a). Furthermore, the surface resistance remains virtually unchanged after operation (Table 1). Furthermore, the IV relationship of the diaphragm after 1000 hours of operation is similar to that before (Figure 13, Panel b), demonstrating that the anti-fouling layer effectively prevents contamination of the diaphragm surface by impure metal ions.

[0073] Example 6

[0074] Weigh 83.25g of NMP, add 48.5g of ZrO2 (average particle size 100nm) powder to it, put it in a blender and stir evenly, then add 11.1g of PSF solid and 1.6g of PVP, and continue stirring to obtain a uniform casting liquid. Weigh 2g of chitosan and 2g of graphene and disperse them in 4.4g of NMP, add 1.6g of PSF, place it in an ultrasonic bath at 25 degrees and ultrasonically stir for 3h to prepare a uniform anti-pollution layer slurry. Then, the casting liquid is symmetrically coated on both sides of a PPS support mesh with a thickness of 300μm to form a liquid film. The main film thickness is 400μm, and the prepared anti-pollution layer slurry is sprayed on one side with a spray thickness of 100μm. After pre-curing in air for 30s, it is then immersed in deionized water at 25°C to remove the pore-forming agent to obtain a composite diaphragm.

[0075] The composite membrane was placed in an electrolytic cell for hydrogen production by electrolysis of water for electrolysis performance testing. The test conditions were consistent with those of Example 1, and the IV relationship diagram for electrolysis performance evaluation is shown in Figure 14b. The prepared composite membrane was then subjected to a long-term test of anti-pollution performance under constant current. Figure 14a shows a curve of cell voltage change over time. The test conditions were consistent with the above IV performance test conditions, and the current density was constant at 400 mA / cm 2 It can be seen that the presence of metallic impurities in the cathode electrolyte has no effect on the cell voltage, indicating relatively stable operation (Figure 14a). Furthermore, the surface resistance remains virtually unchanged after operation (Table 1). Furthermore, the IV relationship of the diaphragm after 1000 hours of operation is similar to that before (Figure 14b), demonstrating that the anti-fouling layer effectively prevents contamination of the diaphragm surface by impure metal ions.

[0076] Example 7

[0077] Weigh 83.25g of NMP, add 48.5g of ZrO2 (average particle size 100nm) powder to it, put it in a blender and stir evenly, then add 11.1g of PSF solid and continue stirring to obtain a uniform casting liquid. Weigh 1.5g of polypiperazineamide and 1.5g of graphene and disperse them in 4g of NMP, add 3g of PSF, place it in an ultrasonic bath at 20 degrees and ultrasonically stir for 3h to prepare a uniform anti-fouling layer slurry. Then, the casting liquid is symmetrically coated on both sides of a PPS support mesh with a thickness of 300μm to form a liquid film. The main film thickness is 400μm, and the prepared anti-fouling layer slurry is sprayed on one side with a spraying thickness of 60μm. After pre-curing in air for 30s, it is then immersed in deionized water at 25°C to remove the pore-forming agent to obtain a composite diaphragm.

[0078] The composite membrane was placed in an electrolytic cell for hydrogen production by electrolysis of water for electrolysis performance testing. The test conditions were consistent with those of Example 1, and the IV relationship diagram for electrolysis performance evaluation is shown in Figure 15b. The prepared composite membrane was then subjected to a long-term test of anti-pollution performance under constant current. Figure 15a shows a curve of cell voltage change over time. The test conditions were consistent with the above IV performance test conditions, and the current density was constant at 400mA / cm 2 It can be seen that the presence of metallic impurities in the cathode electrolyte has no effect on the cell voltage, indicating relatively stable operation (Figure 15(a)). Furthermore, the surface resistance remains virtually unchanged after operation (Table 1). Furthermore, the IV relationship of the diaphragm after 1000 hours of operation is similar to that before (Figure 15(b)), demonstrating that the anti-fouling layer effectively prevents contamination of the diaphragm surface by impure metal ions.

[0079] Example 8

[0080] Weigh 67.2g of NMP, add 40g of ZrO2 (average particle size 100nm) powder, place in a blender and stir evenly, then add 7g of PSF solid and 1.6g of PVP, and continue stirring to obtain a uniform casting solution. Weigh 3.5g of polyimide and disperse it in 6g of NMP, add 0.5g of PSF, place in a 20-degree ultrasonic bath and ultrasonically stir for 3 hours to prepare a uniform anti-pollution layer slurry. Then, the casting solution is symmetrically coated on both sides of a 300μm thick PPS support mesh to form a liquid film. The main film thickness is 400μm, and the prepared anti-pollution layer slurry is sprayed on one side with a spray thickness of 20μm. After pre-curing in air for 40s, it is then immersed in deionized water at 25°C to remove the pore-forming agent to obtain a composite diaphragm.

[0081] The composite membrane was placed in an electrolytic cell for hydrogen production by electrolysis of water for electrolysis performance testing. The test conditions were consistent with those of Example 1, and the IV relationship diagram for electrolysis performance evaluation is shown in Figure 16b. The prepared composite membrane was then subjected to a long-term test of anti-pollution performance under constant current. Figure 16a shows a curve of cell voltage change over time. The test conditions were consistent with the above IV performance test conditions, and the current density was constant at 400 mA / cm 2 It can be seen that the presence of metallic impurities in the cathode electrolyte has no effect on the cell voltage, indicating relatively stable operation (Figure 16, Panel a). Furthermore, the surface resistance remains virtually unchanged after operation (Table 1). Furthermore, the IV relationship of the diaphragm after 1000 hours of operation is similar to that before (Figure 16, Panel b), demonstrating that the anti-fouling layer effectively prevents contamination of the diaphragm surface by impure metal ions.

[0082] Example 9

[0083] Weigh 83.25g of NMP, add 48.5g of ZrO2 (average particle size 100nm) powder to it, put it in a blender and stir evenly, then add 11.1g of PSF solid and 5.56g of PVP, and continue stirring to obtain a casting liquid with a uniform texture. Weigh 2.5g of MXene and disperse it in 7g of NMP, add 0.5g of PSF, place it in an ultrasonic bath at 25 degrees for ultrasonic stirring for 6h, and prepare a uniform anti-pollution layer slurry. Then the casting liquid is symmetrically coated on both sides on the surface of a PPS support mesh with a thickness of 300μm to form a liquid film. The main film thickness is 400μm, and the prepared anti-pollution layer slurry is sprayed on one side with a spraying thickness of 40μm. After pre-curing in air for 30s, it is then immersed in deionized water at 25°C to remove the pore-forming agent to obtain a composite diaphragm.

[0084] The composite membrane was placed in an electrolytic cell for hydrogen production by electrolysis of water for electrolysis performance testing. The test conditions were consistent with those in Example 1, and the IV relationship diagram for electrolysis performance evaluation is shown in Figure 17b. The prepared composite membrane was then subjected to a long-term test of anti-pollution performance under constant current. Figure 17a shows a curve of cell voltage change over time. The test conditions were consistent with the above IV performance test conditions, and the current density was constant at 400mA / cm 2 It can be seen that the presence of metallic impurities in the cathode electrolyte has no effect on the cell voltage, indicating relatively stable operation (Figure 17a). Furthermore, the surface resistance remains virtually unchanged after operation (Table 1). Furthermore, the IV relationship of the diaphragm after 1000 hours of operation is similar to that before (Figure 17b), demonstrating that the anti-fouling layer effectively prevents contamination of the diaphragm surface by impure metal ions.

[0085] Example 10

[0086] Weigh 83.25g of NMP, add 48.5g of ZrO2 powder (average particle size 100nm), and stir thoroughly in a blender. Then add 11.1g of PSF solid and 1.6g of PVP, and continue stirring to obtain a uniform casting solution. Weigh 1.5g of graphene and 2g of poly(m-phenylene isophthalamide) fiber and disperse them in 6g of NMP. Add 0.5g of PSF, and ultrasonically stir for 3 hours at 25°C to prepare a uniform anti-pollution layer slurry. The casting solution is then symmetrically coated on both sides of a 300μm-thick PPS support mesh to form a liquid film, with a main film thickness of 400μm. The prepared anti-pollution layer slurry is sprayed on one side to a thickness of 60μm. After pre-curing in air for 30s, the membrane is immersed in deionized water at 25°C to remove the pore-forming agent, resulting in a composite membrane.

[0087] The composite membrane was placed in an electrolytic cell for hydrogen production by electrolysis of water for electrolysis performance testing. The test conditions were consistent with those of Example 1, and the IV relationship diagram for electrolysis performance evaluation is shown in Figure 18b. The prepared composite membrane was then subjected to a long-term test of anti-pollution performance under constant current. Figure 18a shows a curve of cell voltage change over time. The test conditions were consistent with the above IV performance test conditions, and the current density was constant at 400 mA / cm 2 It can be seen that the presence of metallic impurities in the cathode electrolyte has no effect on the cell voltage, indicating relatively stable operation (Figure 18a). Furthermore, the surface resistance remains virtually unchanged after operation (Table 1). Furthermore, the IV relationship of the diaphragm after 1000 hours of operation is similar to that before (Figure 18b), demonstrating that the anti-fouling layer effectively prevents contamination of the diaphragm surface by impure metal ions.

[0088] Comparative Example 1

[0089] 83.25g of NMP was weighed, and 48.5g of ZrO2 powder (average particle size 100nm) was added to it. The mixture was then stirred in a blender. 11.1g of PSF solid and 1.6g of PVP were then added and stirred continuously to obtain a uniform casting solution. The casting solution was then symmetrically coated on both sides of a 300μm-thick PPS support mesh to form a liquid film. After pre-curing in air for 30s, the film was placed in a coagulation bath filled with 25°C deionized water to cure. The pore-forming agent was removed to obtain a composite membrane.

[0090] The composite membrane was placed in an electrolytic cell for hydrogen production by electrolysis of water for electrolysis performance testing. The test conditions were consistent with those of Example 1, and the IV relationship for electrolysis performance evaluation was shown in Figure 19b. The prepared composite membrane was subjected to a long-term anti-pollution performance test under constant current. Figure 19a shows a curve of its cell voltage changing with time. The test conditions were consistent with the above-mentioned IV performance test conditions, wherein 0.01M FeCl3 and 0.01M NiCl2 soluble impurities were added to the cathode electrolyte to simulate the metal ions caused by catalyst shedding. It was found that the comparative example 1 had an anti-pollution performance of 400mA / cm 2 At this current density, metallic impurity ions in the cathode electrolyte significantly impacted the cell voltage (Figure 19a), and the surface resistance also increased after operation (Table 1). Furthermore, the IV relationship of the diaphragm was measured after 1000 hours of operation (Figure 19b), revealing that metallic impurity ions significantly impacted the electrical properties of the diaphragm, causing the cell voltage to rise and significantly increasing electrolysis energy consumption.

[0091] Table 1 shows the test results of the composite membranes prepared in Examples 1-10 and Comparative Example 1. Sheet resistance was tested on an electrochemical workstation in accordance with SJT10171.5-1991. Tensile strength and peel strength were tested using a universal tensile testing machine in accordance with GBT3923.1. The average pore size and bubble point pressure were measured using a bubble point pore size analyzer in accordance with GB / T32361-2015.

[0092] Table 1

[0093] The preferred embodiments of the present disclosure disclosed above are intended only to help illustrate the present disclosure. The preferred embodiments do not describe all details in detail, nor do they limit the present disclosure to the specific embodiments described. Obviously, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present disclosure, thereby enabling those skilled in the art to better understand and utilize the present disclosure. The present disclosure is limited only by the claims and their full scope and equivalents.

Claims

1. A composite diaphragm, characterized in that: The invention comprises a main membrane and an anti-fouling layer arranged on one or both surfaces of the main membrane, wherein the anti-fouling layer comprises a first polymer, a charging agent and / or an anti-fouling agent.

2. The composite diaphragm according to claim 1, characterized in that: The antifouling agent is one or more of graphene, graphene oxide, and MXene; the charging agent is one or more of aromatic polyamide, polypiperazineamide, polyamide, cellulose acetate, polyimide, polyetherimide, polyaniline, and chitosan.

3. The composite diaphragm according to claim 1, characterized in that: The thickness of the anti-fouling layer is 2-100 μm; preferably, the weight ratio of the first polymer, the charging agent and the anti-fouling agent is (5-30): (0-40): (0-30).

4. The composite diaphragm according to claim 1, characterized in that: The first polymer is one or more of polyaryl sulfone, polyether sulfone, polyphenylene sulfone, bisphenol A type polysulfone and polyether ether ketone.

5. The composite diaphragm according to claim 1, characterized in that: The main film comprises a hydrophilic inorganic substance, a second polymer and a pore-aiding agent, wherein the mass ratio of the second polymer to the hydrophilic inorganic substance is 1:1-1:8, and the mass ratio of the pore-aiding agent to the second polymer is 1:10-2:1; preferably, the thickness of the main film is 100-700 μm.

6. The composite diaphragm according to claim 5, characterized in that: The second polymer is one or more of polyaryl sulfone, polyether sulfone, polyphenylene sulfone, bisphenol A type polysulfone, and polyether ether ketone; the pore-aiding agent is one or more of polyvinyl pyrrolidone, polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer, polypropylene glycol and ethylene oxide addition polymer, polyethyleneimine, and polyacrylonitrile; the hydrophilic inorganic substance is one or more of titanium dioxide, zirconium dioxide, cerium oxide, barium sulfate, calcium sulfate, barium titanate, and calcium titanate. Preferably, the particle size of the hydrophilic inorganic substance is 5nm-3μm.

7. The composite diaphragm according to claim 1, characterized in that: The main film further comprises a support net or a support cloth, and preferably the thickness of the support net or the support cloth is 50-500 μm.

8. A method for preparing the composite diaphragm according to any one of claims 1 to 7, characterized in that: include: S1, preparing an anti-fouling layer slurry by using a first liquid pore-forming agent, the first polymer, the charging agent and / or the anti-fouling agent; S2, coating the casting liquid for forming the main membrane on the surface of the substrate, and coating the anti-pollution layer slurry on the surface thereof, pre-curing in air, and then curing in a coagulation bath until the liquid pore-forming agent is precipitated to obtain a composite diaphragm.

9. The preparation method according to claim 8, characterized in that: The casting liquid includes a second liquid pore-forming agent, and the addition amount of the second liquid pore-forming agent accounts for 30% to 70% of the total mass of the casting liquid; the addition amount of the first liquid pore-forming agent accounts for 30% to 70% of the total mass of the anti-pollution layer slurry; preferably, in step S2, the pre-curing time in the air is 3-120s, the temperature of the coagulation bath is 5-80 degrees, the coagulation bath time is 10min-2h, and the solvent in the coagulation bath is deionized water or a mixed solvent of deionized water and one of dimethyl sulfoxide, 1-methyl-2-pyrrolidone, N,N-dimethylformamide, and N,N-dimethylacetamide.

10. Use of the composite diaphragm according to any one of claims 1 to 7 in electrolysis, preferably in hydrogen production by alkaline water electrolysis.

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