Bipolar membrane and preparation method thereof
By introducing porous structures and metal oxide catalysts into bipolar films, nanoscale continuous pores are formed, solving the problems of insufficient mass transfer capacity and interface stratification, and achieving low water dissociation voltage and improved stability.
Patent Information
- Application Number
- CN202511999167.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-26
- Publication Date
- 2026-02-13
AI Technical Summary
Existing bipolar membranes have insufficient mass transfer capacity, and interfacial delamination caused by water bubbles or air bubbles between membrane layers leads to performance degradation. In addition, they have high water dissociation voltage and poor interfacial stability.
By employing porous cation exchange layers and anion exchange layers, combined with metal or metal oxide water dissociation catalysts, uniform and continuous nano-sized pores are formed, thus optimizing the structural design of the bipolar membrane.
It significantly improves the mass transfer capability of bipolar membranes, reduces water dissociation voltage, enhances interfacial stability, and accelerates the discharge rate of water or gas.
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Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the technical field of bipolar membrane preparation, and particularly relates to a bipolar membrane and a preparation method thereof. BACKGROUND
[0002] The bipolar membrane is composed of a positive membrane layer (a cation exchange layer), a negative membrane layer (an anion exchange layer) and an interface catalytic layer between the two membrane layers. The water dissociation ability of the interface layer produces acid (H + ) and base (OH ‒ ), which makes the bipolar membrane have a wide application market in many fields, such as acid-base preparation, resource recovery, food processing, energy storage and conversion, etc. However, the current bipolar membrane is limited by slow mass transfer rate of the membrane layer, interface delamination caused by water bubble or gas bubble formed between the layers, etc., which leads to the decline of the performance of the bipolar membrane.
[0003] According to the direction of the electric field applied to the two sides of the bipolar membrane, the bipolar membrane has two working modes. Under the positive bias, the negative and positive membrane layers of the bipolar membrane face the cathode and the anode, respectively. At this time, the cations (such as H + ) and anions (such as OH ‒ ) in the electrolyte solutions on both sides of the membrane are transported to the interface through the negative and positive membrane layers, respectively, and water is generated by the neutralization reaction at the interface. Under the reverse bias, the water molecules at the interface can dissociate to produce H + and OH ‒ under the effect of the field intensity and the catalyst, and the generated ions migrate through the membrane layers to the two sides under the action of the electric field. Therefore, the mass transfer ability of the bipolar membrane layer has an important influence on the overall efficiency of the bipolar membrane. In addition, the substances generated by the reaction at the interface of the bipolar membrane layer will damage the interface, and also need to be quickly discharged.
[0004] In order to improve the mass transfer ability of the bipolar membrane and accelerate the rapid discharge of water, gas and other substances at the interface of the bipolar membrane, the molecular structure of the membrane layer can be designed and the geometric structure can be optimized. Therefore, it is of great significance to research and develop a bipolar membrane with a new structure. SUMMARY
[0005] Therefore, the present application aims to solve the technical problem of providing a bipolar membrane and a preparation method thereof. The bipolar membrane has a lower water dissociation voltage.
[0006] In order to achieve the above purpose, the technical scheme adopted by the present application is as follows:
[0007] The present application provides a bipolar membrane, which comprises a cation exchange layer, a catalytic layer and an anion exchange layer connected in sequence.
[0008] The cation exchange layer or the anion exchange layer is a porous structure.
[0009] The porous structure is a nano-sized uniform continuous pore.
[0010] The catalytic layer comprises a metal or metal oxide hydrolysis catalyst.
[0011] The size of the nanometer-sized uniform continuous pores is preferably 2-500 nm; more preferably 10-200 nm.
[0012] The porous structure can significantly improve the mass transfer capacity of the bipolar membrane, accelerate the discharge of water or gas generated at the interface of the bipolar membrane, and effectively solve the problems of high water dissociation voltage and poor interface stability of the bipolar membrane.
[0013] The water dissociation voltage of the bipolar membrane is 0.3-1.2 V; more preferably 0.3-1.0 V; and further preferably 0.4-0.8 V, at a current density of 0-100 mA / cm 2
[0014] Preferably, when the cation exchange layer is porous, the cation exchange layer is prepared by coating a cation membrane solution containing a water-soluble oligomer onto the surface of the catalytic layer and then water etching.
[0015] Preferably, when the anion exchange layer is porous, the anion exchange layer is prepared by coating an anion membrane solution containing a water-soluble oligomer onto the surface of the catalytic layer and then water etching.
[0016] The water etching is specifically achieved by partially dissolving the water-soluble oligomer through water immersion.
[0017] Preferably, the water-soluble oligomer is selected from one or more of polyethylene glycol, polyvinyl alcohol, polyacrylic acid, and polyvinyl imine; more preferably polyethylene glycol or polyvinyl imine; and further preferably polyvinyl imine.
[0018] The average molecular weight of the polyvinyl imine is not particularly limited.
[0019] In some specific embodiments of the present application, the average molecular weight is preferably 1800 or 5000 or 1000.
[0020] Preferably, the concentration of the water-soluble oligomer in the cation membrane solution or the anion membrane solution is 0.01-1000 mg / mL; more preferably 0.1-20 mg / mL.
[0021] Preferably, when the cation exchange layer is porous, the thickness of the cation exchange layer is 20-100 μm; more preferably 20-50 μm; and further preferably 20 μm or 40 μm.
[0022] Preferably, the thickness of the porous cation exchange layer is 20-100 μm; more preferably 20-50 μm; and even more preferably 20 μm or 40 μm.
[0023] Preferably, the mass fraction of the ion exchange polymer in the cationic membrane solution or the anionic membrane solution is 1wt%-30wt%; more preferably 5wt%-15wt%.
[0024] The ion exchange polymer includes cation exchange polymer and anion exchange polymer.
[0025] The cation exchange polymer includes, but is not limited to, perfluorosulfonic acid cation exchange resin, sulfonated polyphenylene ether, or sulfonated polyether sulfone, etc.
[0026] The anion exchange polymer includes, but is not limited to, quaternary aminated polyphenylene ether, quaternary aminated polyether sulfone, quaternary aminated polystyrene-based copolymer, etc.
[0027] Preferably, the metal hydrolysis catalyst is selected from platinum nanoparticles, iridium nanoparticles, or tin nanoparticles.
[0028] Preferably, the metal oxide hydrolysis catalyst is selected from tin dioxide, titanium dioxide, or hydroxyl ferric oxide.
[0029] The present application also provides a preparation method of the bipolar membrane, comprising the following steps:
[0030] (1) coating a metal or metal oxide hydrolysis catalyst solution on the surface of the cation exchange membrane to obtain a cation exchange layer with a catalytic layer after drying;
[0031] (2) coating an anionic membrane solution containing water-soluble oligomers on the surface of the catalytic layer of the cation exchange layer obtained in step (1), and sequentially drying and water etching to obtain the bipolar membrane.
[0032] Alternatively, the preparation method comprises the following steps:
[0033] (1) coating a metal or metal oxide hydrolysis catalyst solution on the surface of the anion exchange membrane to obtain an anion exchange layer with a catalytic layer after drying;
[0034] (2) coating a cationic membrane solution containing water-soluble oligomers on the surface of the catalytic layer of the anion exchange layer obtained in step (1), and sequentially drying and water etching to obtain the bipolar membrane.
[0035] The catalytic layer component of the cation exchange layer or the anion exchange layer is a metal or metal oxide hydrolysis catalyst.
[0036] Preferably, the concentration of the hydrolysis catalyst in the metal or metal oxide hydrolysis catalyst solution is 0.1-1000 mg / mL; more preferably, 0.1-20 mg / mL; and further preferably, 1 mg / mL.
[0037] Preferably, the loading of the surface hydrolysis catalyst on the cation exchange layer or the anion exchange layer is 0.05-0.1 mg / cm 2 ; further preferably, 0.05 mg / cm 2 , 0.08 mg / cm 2 , or 1 mg / cm 2
[0038] The coating method is not particularly limited in the present application, and can be any coating method known to those skilled in the art.
[0039] In some embodiments of the present application, the coating is preferably spraying or casting. The drying temperature in steps (1) and (2) of the preparation method of the present application is preferably 50°C-100°C.
[0040] In the preparation method, the solvent of the cationic membrane solution or the anionic membrane solution is preferably one or more of dimethyl sulfoxide, N-methyl pyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, methanol, water, ethanol, and acetonitrile; more preferably, one or more of dimethyl sulfoxide, N,N-dimethylformamide, and methanol; and further preferably, dimethyl sulfoxide and methanol.
[0041] In the preparation method, the solvent of the metal or metal oxide hydrolysis catalyst solution is preferably one or more of water, methanol, ethanol, and isopropanol; and more preferably, methanol or ethanol.
[0042] Compared with the prior art, the bipolar membrane provided by the present application comprises a cation exchange layer, a catalytic layer, and an anion exchange layer connected in sequence; the cation exchange layer or the anion exchange layer has a porous structure; the porous structure has uniform and continuous nanoscale pores; and the catalytic layer comprises a metal or metal oxide hydrolysis catalyst. The bipolar membrane has a high mass transfer capacity, and the water or gas generated at the interface of the bipolar membrane is discharged quickly, thereby making the bipolar membrane have a low hydrolysis voltage and a more stable structure. BRIEF DESCRIPTION OF DRAWINGS
[0043] Figure 1 The figure is a schematic diagram of the preparation process of the porous bipolar membrane of the present application;
[0044] Figure 2 The figure is a cross-sectional SEM image of the porous bipolar membrane prepared in Example 1;
[0045] Figure 3A cross-sectional SEM image of the porous bipolar membrane prepared in Example 3, with a scale bar of 1 μm;
[0046] Figure 4 A cross-sectional SEM image of the porous bipolar membrane prepared in Example 3, with a scale bar of 200 nm;
[0047] Figure 5 A hydrolysis polarization curve of the porous bipolar membrane-1, the porous bipolar membrane-2, and the porous bipolar membrane-3 prepared in Examples 1, 4, and 5, respectively;
[0048] Figure 6 A cross-sectional SEM image of the non-porous bipolar membrane prepared in Comparative Example 1;
[0049] Figure 7 A hydrolysis polarization curve of the non-porous bipolar membrane prepared in Comparative Example 1;
[0050] Figure 8 A hydrolysis polarization curve of the few-porous bipolar membrane prepared in Comparative Example 2. DETAILED DESCRIPTION
[0051] In order to further illustrate the present application, the bipolar membrane and the preparation method thereof provided by the present application are described in detail below in conjunction with examples.
[0052] Figure 1 A schematic diagram of the preparation process of the porous bipolar membrane of the present application, the preparation method of the bipolar membrane of the present application comprises the following steps:
[0053] 1) spraying a hydrolysis catalyst to the lower ion exchange layer to form a catalytic layer on the surface of the lower ion exchange layer;
[0054] 2) spraying an upper ion exchange membrane solution containing a water-soluble oligomer on the surface of the catalytic layer obtained in step 1), and then drying and water etching in sequence to obtain the bipolar membrane.
[0055] The upper membrane of the bipolar membrane prepared by the above preparation method has a porous structure, and the porous structure is a continuous nanoscale pore.
[0056] The lower ion exchange layer is a cation exchange layer or an anion exchange layer.
[0057] When the lower ion exchange layer is a cation exchange layer, the upper ion exchange membrane solution is an anion exchange membrane solution, and the upper layer of the prepared bipolar membrane is a porous anion exchange layer; when the lower ion exchange layer is an anion exchange layer, the upper ion exchange membrane solution is a cation exchange membrane solution, and the upper layer of the prepared bipolar membrane is a porous cation exchange layer.
[0058] Example 1
[0059] Step S1, the used anode membrane layer is Nafion 212, the hydrolysis catalyst is a methanol solution of titanium dioxide. The hydrolysis catalyst solution is sprayed evenly on the surface of the Nafion 212 at a spraying flow rate of 0.2 mL / min, and the spraying load is controlled to be 0.05 mg / cm 2 2 , the spraying area is 5 cm 2 , and the drying temperature is 80 °C.
[0060] Step S2, the anion exchange membrane solution contains quaternary aminated polyphenyl ether and water-soluble oligomer polyethyleneimine, and the solvent of the membrane solution is a mixed solvent of dimethyl sulfoxide and methanol with a mass ratio of 1:2, wherein the mass fraction of quaternary aminated polyphenyl ether is 5%, and the concentration of polyethyleneimine (average molecular weight is 1800) is 1 mg / mL. The anion exchange membrane solution is sprayed evenly on the surface of the catalyst layer formed in step S1 at a spraying flow rate of 0.2 mL / min, and dried by heating at 80 °C, and the dried thickness of the sprayed anode membrane layer is controlled to be 20 µm.
[0061] Step S3, the prepared bipolar membrane is immersed in water for 3 hours, and after the polyethyleneimine in the anode membrane layer is completely dissolved, a porous bipolar membrane with an anode membrane layer is obtained.
[0062] Figure 2 The cross-sectional SEM image of the porous bipolar membrane prepared in Example 1 shows that the porous structure of the porous bipolar membrane prepared in Example 1 is a continuous nanoscale pore.
[0063] Examples 2-3
[0064] In order to verify the universality of the method provided by the application to different molecular weight water-soluble oligomers, Examples 2 and 3 are carried out.
[0065] The difference between Example 1 and Examples 2 and 3 is that the average molecular weight of the polyethyleneimine used in step S2 of Examples 2 and 3 is 5000 and 1000, respectively.
[0066] Figure 3 and Figure 4 The cross-sectional SEM image of the porous bipolar membrane prepared in Example 3 shows that the porous structure of the porous bipolar membrane prepared in Example 3 is a uniform and continuous nanoscale pore with a pore size of 10-200 nm.
[0067] Examples 4-5
[0068] To verify the universality of the method provided by the present application to different cation exchange membranes, Examples 4 and 5 were carried out. The difference between Examples 4 and 5 and Example 1 is that the cation exchange membranes used in Step S1 of Examples 4 and 5 are sulfonated polyphenylene oxide and sulfonated polyether sulfone respectively, and the rest of the steps are the same as Example 1.
[0069] Figure 5 The hydrolysis polarization curves of the porous bipolar membrane-1, porous bipolar membrane-2, and porous bipolar membrane-3 prepared in Examples 1, 4, and 5 respectively were plotted, and the results showed that, within the current density range of 0-100 mA / cm 2 , the hydrolysis voltages of the porous bipolar membrane-1, porous bipolar membrane-2, and porous bipolar membrane-3 were 0.8 V, 0.6 V, and 0.4 V respectively.
[0070] Examples 6-7
[0071] To verify the universality of the method provided by the present application to various anion exchange membrane materials, Examples 6 and 7 were carried out.
[0072] The porous bipolar membranes were prepared according to the method in Example 1, except that the anion membranes used in Step S2 of Examples 6 and 7 were quaternary aminated polyether sulfone and quaternary aminated poly(styrene-divinylbenzene) respectively, and the rest of the steps were the same as Example 1.
[0073] Examples 8-9
[0074] The difference between Examples 8 and 9 and Example 1 is that the spray loadings of the hydrolysis catalysts used in Step S1 of Examples 8 and 9 are 0.08 mg / cm 2 and 0.10 mg / cm 2 respectively.
[0075] Example 10
[0076] The difference between this example and Example 1 is that the hydrolysis catalyst used in Step S1 is a tin dioxide nanoparticle aqueous solution, and the spray loading is 0.05 mg / cm 2 .
[0077] Example 11
[0078] The difference between this example and Example 1 is that the hydrolysis catalyst used in Step S1 is a ferric oxyhydroxide solution, and the spray loading is 0.1 mg / cm 2 .
[0079] Example 12
[0080] The difference between this example and Example 1 is that the thickness of the anion membrane layer is controlled to be 40 µm in Step S3.
[0081] Comparative Example 1
[0082] This example is to verify the promoting effect of the formation of the porous layer on the hydrolysis performance of the bipolar membrane. The difference between this example and Example 1 is that the cathode solution in the S2 step does not contain water-soluble oligomers.
[0083] Figure 6 The cross-sectional SEM image of the non-porous bipolar membrane prepared in Comparative Example 1. Figure 7 The hydrolysis polarization curve of the non-porous bipolar membrane prepared in Comparative Example 1, and the results show that the hydrolysis voltage of the non-porous bipolar membrane is 3.5 V in the current density range of 0-100 mA / cm 2 .
[0084] Comparative Example 2
[0085] This example is to verify the promoting effect of the formation of the porous layer on the hydrolysis performance of the bipolar membrane. The difference between this example and Example 1 is that the amount of water-soluble oligomers added in the cathode solution in the S2 step is halved, resulting in fewer pore structures formed.
[0086] Figure 8 The hydrolysis polarization curve of the few-porous bipolar membrane prepared in Comparative Example 2, and the results show that the hydrolysis voltage of the few-porous bipolar membrane is 1.9 V in the current density range of 0-100 mA / cm 2 . By comparing the above-mentioned Figure 5 , Figures 7-8 , the results show that the porous bipolar membrane prepared in Example 1 has a lower hydrolysis voltage than the non-porous bipolar membrane prepared in Comparative Example 1 and the few-porous bipolar membrane prepared in Comparative Example 2, which indicates that the formation of the porous layer of the porous bipolar membrane of the present application plays an important role in accelerating the mass transfer of molecules outside the membrane to the interface layer.
[0087] The above examples are only used to help understand the method of the present application and its core idea. It should be noted that for those skilled in the art, without departing from the principles of the present application, the present application can be improved and modified in several ways, and these improvements and modifications also fall within the scope of protection of the claims of the present application.
Claims
1. A bipolar membrane, characterized in that, It includes a cation exchange layer, a catalyst layer, and an anion exchange layer connected in sequence; The cation exchange layer or anion exchange layer has a porous structure; The porous structure consists of uniform, continuous nano-sized pores. The catalyst layer comprises a metal or metal oxide hydrolysis catalyst.
2. The bipolar film according to claim 1, characterized in that, When the cation exchange layer has a porous structure, the cation exchange layer is prepared by coating the surface of the catalyst layer with a cation exchange film containing water-soluble oligomers and then etching it with water. When the anion exchange layer has a porous structure, the anion exchange layer is prepared by coating the surface of the catalyst layer with an anion membrane solution containing water-soluble oligomers and then etching it with water.
3. The bipolar film according to claim 2, characterized in that, The water-soluble oligomer is selected from one or more of polyethylene glycol, polyvinyl alcohol, polyacrylic acid, and polyethyleneimine.
4. The bipolar film according to claim 3, characterized in that, The concentration of water-soluble oligomers in the cation or anion membrane solution is 0.01-1000 mg / mL.
5. The bipolar film according to claim 1, characterized in that, When the cation exchange layer has a porous structure, its thickness is 20-100 μm; When the anion exchange layer has a porous structure, its thickness is 20-100 μm.
6. The bipolar film according to claim 4, characterized in that, The mass fraction of the ion exchange polymer in the cation exchange solution or the anion exchange solution is 1wt%-30wt%.
7. The bipolar film according to claim 1, characterized in that, The metal water dissociation catalyst is selected from platinum nanoparticles, iridium nanoparticles, or tin nanoparticles. The metal oxide hydrolysis catalyst is selected from tin dioxide, titanium dioxide, or iron hydroxyl oxide.
8. The method for preparing the bipolar film according to any one of claims 1 to 7, characterized in that, Includes the following steps: (1) Coating a metal or metal oxide hydrolysis catalyst solution onto the surface of a cation exchange membrane and drying it to obtain a cation exchange layer with a catalyst layer; (2) The anion exchange solution containing water-soluble oligomers is coated onto the surface of the catalyst layer of the cation exchange layer in step (1), and then dried and etched with water to prepare the bipolar membrane. Alternatively, it may include the following preparation steps: (1) Coating the surface of an anion exchange membrane with a metal or metal oxide hydrolysis catalyst solution and drying it to obtain an anion exchange layer with a catalyst layer; (2) The cation exchange liquid containing water-soluble oligomers is coated onto the surface of the catalyst layer of the anion exchange layer in step (1), and then dried and etched with water to prepare the bipolar membrane.
9. The preparation method according to claim 8, characterized in that, The concentration of the hydrolysis catalyst in the metal or metal oxide hydrolysis catalyst solution is 0.1-1000 mg / mL.
10. The preparation method according to claim 8, characterized in that, The loading of the water dissociation catalyst on the surface of the cation exchange layer or anion exchange layer is 0.05-0.1 mg / cm³. 2 .