A bipolar membrane based on charged nanosheet catalytic layer, its preparation method and its application in seawater dissociation

Abstract

This invention provides a method for preparing a bipolar membrane based on a charged nanosheet catalytic layer, its preparation method, and its application in seawater dissociation. The method includes: A) coating a cation (anion) exchange membrane solution onto a smooth substrate and drying it to obtain a cation (anion) exchange membrane layer; dissolving modified charged nanosheets to obtain a modified charged nanosheet solution; B) ultrasonically spraying the modified charged nanosheet solution onto the cation (anion) exchange membrane layer and drying it to obtain a bipolar membrane interlayer; C) ultrasonically spraying anion (cation) exchange membrane solution onto the bipolar membrane interlayer and drying it to obtain the bipolar membrane. This invention adopts the concept of introducing confined mass transfer into the bipolar membrane interlayer. Charged nanosheets are stacked through ultrasonic spraying, and the spacing of the modified charged nanosheets is controlled to construct the bipolar membrane interlayer, which has sub-nanometer or nanometer-level charged channels, exhibiting low common ion leakage and excellent water dissociation performance.

Description

Technical Field

[0001] This invention belongs to the field of materials technology, and particularly relates to a bipolar membrane based on a charged nanosheet catalytic layer, its preparation method, and its application in seawater dissociation. Background Technology

[0002] A bipolar membrane (BPM) is composed of a polymer cation exchange layer (CEL) that selectively conducts cations, an anion exchange layer (AEL) that selectively conducts anions, and an intermediate catalyst layer. When a reverse voltage is applied, i.e., the polymer cation exchange layer faces the cathode and the polymer anion exchange layer faces the anode, water in the intermediate catalyst layer dissociates into H+. + and OH - The ions diffuse across the membrane, converting electrical energy into chemical energy in the form of a proton chemical potential difference (i.e., pH gradient). An ideal bipolar membrane prevents ions from crossing the entire membrane layer, ensuring that the two sides of the membrane are in different environments. Therefore, BPM is used today for energy conversion, resource recovery, and food processing.

[0003] Imperfections in the membrane layer mean that ions on both sides of the membrane migrate and diffuse primarily through the uncharged inter-cluster space, leading to low current efficiency in practical applications. Furthermore, in traditional bipolar membranes, water dissociates into H+. + and OH - The process requires a high transmembrane voltage, and introducing an excellent water dissociation catalyst to regulate the bipolar membrane interlayer can effectively reduce the transmembrane voltage. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide a bipolar membrane based on a charged nanosheet catalytic layer and a method for preparing the same. The intermediate layer of the bipolar membrane prepared by this method utilizes sub-nanometer or nano-scale charged channels formed by stacking nanosheets. Under the action of an electric field, it can achieve efficient catalytic water dissociation while restricting the leakage of common ions.

[0005] This invention provides a method for preparing a bipolar film based on a charged nanosheet catalytic layer, comprising the following steps:

[0006] A) The cation (anion) exchange membrane solution is coated onto a smooth substrate and dried to obtain the cation (anion) exchange membrane layer;

[0007] The modified charged nanosheets were dissolved to obtain a modified charged nanosheet solution;

[0008] B) The modified charged nanosheet solution is ultrasonically sprayed onto the cation (anion) exchange membrane layer and dried to obtain the bipolar membrane intermediate layer;

[0009] C) Spray anion (cation) exchange membrane solution onto the intermediate layer of the bipolar membrane, and dry it to obtain the bipolar membrane.

[0010] Preferably, the surface-modifying groups of the modified charged nanosheets are one or more of ions, ionic groups, colloidal molecules and polymer molecules with a size of 0.1 to 20 nm;

[0011] The modified charged nanosheets are boron nitride nanosheets, MXene nanosheets, graphene family nanosheets, hydrotalcite nanosheets, disulfide nanosheets, zeolite nanosheets, MOF nanosheets, or TiO2 nanosheets.

[0012] Preferably, the mass concentration of the cation (anion) exchange membrane solution is 1-10%;

[0013] The solvent in the cation (anion) exchange membrane solution is one or more of water, methanol, ethanol, N,N-dimethylformamide, and dimethyl sulfoxide.

[0014] Preferably, the drying temperature in step A) is 50–90°C, and the drying time is 1–48 h; the thickness of the cation (anion) exchange membrane layer is 1–40 μm.

[0015] In step C), the drying temperature is 50–90°C and the time is 1–48 h; the thickness of the anion (cation) exchange membrane layer is 1–40 μm.

[0016] Preferably, the solvent used to dissolve the modified charged nanosheets is selected from one or more of water, methanol, ethanol, N,N-dimethylformamide and dimethyl sulfoxide;

[0017] The mass-to-volume ratio of the modified charged nanosheets to the solvent is (0.1–1) g:(200–1000) mL.

[0018] Preferably, the thickness of the bipolar film interlayer in step B) is 4–400 nm;

[0019] The loading capacity of modified charged nanosheets on cation (anion) exchange membranes ranges from 1 to 1000 μg / cm. -2 .

[0020] Preferably, the drying temperature in step B) is 50–90°C.

[0021] Preferably, the mass concentration of the anion (cation) exchange membrane solution in step C) is 1-10%;

[0022] The solvent in the anion (cation) exchange membrane solution is selected from one or more of water, methanol, ethanol, N,N-dimethylformamide and dimethyl sulfoxide.

[0023] Preferably, the spraying height used in steps B) and C) is 1 to 10 cm;

[0024] The solution spray rate is set to 0.05–0.8 mL / min. -1 The feed rate is 5–40 mm / s. -1 .

[0025] This invention provides a bipolar membrane based on a charged nanosheet catalytic layer, which is prepared by the method described in the above technical solution.

[0026] This invention provides a method for preparing a bipolar membrane based on a charged nanosheet catalytic layer, comprising the following steps: A) coating a cation (anion) exchange membrane solution onto a smooth substrate and drying it to obtain a cation (anion) exchange membrane layer; dissolving modified charged nanosheets to obtain a modified charged nanosheet solution; B) ultrasonically spraying the modified charged nanosheet solution onto the cation (anion) exchange membrane layer and drying it to obtain a bipolar membrane interlayer; C) ultrasonically spraying anion (cation) exchange membrane solution onto the bipolar membrane interlayer and drying it to obtain a bipolar membrane. This invention employs the concept of introducing confined mass transfer into the bipolar membrane interlayer. Positively (negatively) charged nanosheets are stacked using ultrasonic spraying, and the spacing of the positively (negatively) charged nanosheets is controlled by modifying the spacing to construct the bipolar membrane interlayer, thus preparing a bipolar membrane with low common ion leakage and excellent water dissociation performance. The sub-nanometer or nanometer-level charged channels formed by the stacked modified charged nanosheets in the bipolar membrane interlayer restrict common ion leakage. Experimental results show that: by controlling the spacing between charged nanosheets to construct an intermediate bipolar film, the interlayer can withstand 100 mA cm⁻¹. -2 At this voltage, the water dissociation voltage is only 0.77V, and the first limiting current density is as low as 1.5mA cm⁻¹. -2 . Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the process for preparing a bipolar film based on a charged nanosheet catalytic layer according to the present invention;

[0028] Figure 2 This is a scanning electron microscope image of the cross-section of the bipolar film based on the charged nanosheet catalytic layer prepared in Example 1 of the present invention, magnified 1000 times.

[0029] Figure 3 This is a high-magnification (10000x) scanning electron microscope image of the cross-section of the bipolar film based on the charged nanosheet catalytic layer prepared in Example 1 of the present invention.

[0030] Figure 4 The current-voltage curve of the bipolar film based on the charged nanosheet catalytic layer prepared in Example 1 of this invention is shown.

[0031] Figure 5 This is a first limiting current density diagram of the bipolar film based on a charged nanosheet catalytic layer prepared in Example 1 of the present invention;

[0032] Figure 6 This is the first limiting current density diagram of the bipolar film based on the charged nanosheet catalytic layer prepared in Example 2 of the present invention. Detailed Implementation

[0033] This invention provides a method for preparing a bipolar film based on a charged nanosheet catalytic layer, comprising the following steps:

[0034] A) The cation (anion) exchange membrane solution is coated onto a smooth substrate and dried to obtain the cation (anion) exchange membrane layer;

[0035] The modified charged nanosheets were dissolved to obtain a modified charged nanosheet solution;

[0036] B) The modified charged nanosheet solution is ultrasonically sprayed onto the cation (anion) exchange membrane layer and dried to obtain the bipolar membrane intermediate layer;

[0037] C) Anion (cation) exchange membrane solution is ultrasonically sprayed onto the intermediate layer of the bipolar membrane and dried to obtain the bipolar membrane.

[0038] The method provided by this invention introduces the concept of confined mass transfer into the intermediate catalytic layer. Modified charged nanosheets are stacked using ultrasonic spraying, and the spacing between the modified charged nanosheets is controlled to construct a bipolar membrane intermediate layer, thus preparing a bipolar membrane with low common ion leakage and excellent water dissociation performance. The sub-nanometer or nanometer-scale charged channels formed by the stacked modified charged nanosheets in the bipolar membrane intermediate layer restrict common ion leakage.

[0039] This invention involves coating a cation (anion) exchange membrane solution onto a smooth substrate and drying it to obtain a cation (anion) exchange membrane layer. The cation (anion) exchange membrane solution is prepared by uniformly mixing sulfonic acid-type polyphenylsulfone powder particles with an organic solvent; the mass concentration of the cation (anion) exchange membrane solution is 1-10%; the solvent in the cation (anion) exchange membrane solution is selected from one or more of water, methanol, ethanol, N,N-dimethylformamide, and dimethyl sulfoxide. The drying process uses a heating temperature of 50-90℃, preferably 55-70℃, and a drying time of 1-48 hours, preferably 4-20 hours. The thickness of the cation (anion) exchange membrane layer is 1-40 μm.

[0040] Specifically, the cation exchange membrane liquid in this invention is a sulfonic acid type polyphenylsulfone membrane liquid; the smooth substrate is a smooth glass plate; the heating temperature is 60°C and the heating time is 5 hours; the thickness of the cation (anion) exchange membrane layer is 6.5 μm.

[0041] This invention dissolves modified charged nanosheets to obtain a modified charged nanosheet solution. The invention modifies the surface of charged nanosheets through electrostatic attraction and chemical modification. The surface modification groups of the modified charged nanosheets are selected from one or more of ions, ionic groups, colloidal molecules, and polymer molecules with a size of 0.1–20 nm. The modified charged nanosheets are boron nitride nanosheets, MXene nanosheets (negatively charged), graphene family nanosheets, hydrotalcite nanosheets (positively charged), disulfide nanosheets, zeolite nanosheets (negatively charged), MOF nanosheets, or TiO2 nanosheets. Boron nitride nanosheets, disulfide nanosheets, MOF nanosheets, or TiO2 nanosheets are inherently uncharged but can be made charged through modification; or they may be nanosheets from the above categories that are inherently uncharged but become charged through modification. Graphene nanosheets are not inherently charged, but their surface charge state can be changed through chemical modification or material treatment, such as graphene oxide becoming negatively charged.

[0042] The present invention involves ultrasonically spraying the modified charged nanosheet solution onto the cation (anion) exchange membrane layer, followed by drying, to obtain a bipolar membrane intermediate layer.

[0043] It should be noted that if the modification or alteration of charged nanosheets is carried out in solution, there is no need to dissolve them in a solvent. In this invention, the modified charged nanosheets are positively (negatively) charged nanosheets.

[0044] This invention can use unmodified or unaltered ordinary (uncharged) nanosheets, modifying them to become charged nanosheets; the charged nanosheets can be further modified to increase the spacing between the nanosheets. If the charged nanosheets are already charged, they can be used directly without modification.

[0045] Specifically, in this invention, negatively charged MXene nanosheets are dissolved in water at a mass concentration of 0.25 mg / ml. -1 Add Fe(OH)3 colloidal solution and stir for 30 min to obtain the modified negatively charged MXene nanosheet solution.

[0046] In this invention, the modified charged nanosheet solution is ultrasonically sprayed onto the cation (anion) exchange membrane layer, and then dried at a temperature of 50–90°C for 1–48 h; the thickness of the anion (anion) exchange membrane layer is 1–40 μm. The ultrasonic spraying height is 1–10 cm, and the solution spraying rate is set to 0.05–0.8 mL / min. -1 The feed rate is 5–40 mm / s. -1 .

[0047] In this invention, the thickness of the bipolar membrane interlayer is 4–400 nm, and the loading of modified charged nanosheets on the cation (anion) exchange membrane layer is 1–1000 μg / cm³. -2The bipolar membrane interlayer is a layer of modified charged nanosheets stacked together with modified interlayer spacing.

[0048] Specifically, a mass concentration of 0.25 mg / ml was used. -1 Fe(OH)3-modified negatively charged MXene nanosheets were ultrasonically sprayed onto a sulfonic acid-based polyphenylene ether cation exchange membrane layer. The spraying height was 5 cm and the spraying rate was 0.2 ml / min. -1 The feed rate is 25 mm / s. -1 The heating temperature was 80℃, the height of the catalyst layer was approximately 20 nm, and the loading of positively (negatively) charged nanosheets was 12 μg / cm³. -2 Drying yields a controlled-spacing intermediate layer of charged nanosheets.

[0049] The present invention involves ultrasonically spraying anion (cation) exchange membrane solution onto the intermediate layer of the bipolar membrane, followed by drying to obtain the bipolar membrane.

[0050] In this invention, the mass concentration of the anion (cation) exchange membrane solution is 1-10%. The solvent in the anion (cation) exchange membrane solution is selected from one or more of water, methanol, ethanol, N,N-dimethylformamide, and dimethyl sulfoxide. The ultrasonic spraying height of the anion (cation) exchange membrane solution is 1-10 cm; the solution spraying rate is set to 0.05-0.8 mL / min. -1 The feed rate is 5–40 mm / s. -1 The drying temperature is 50–90℃, and the time is 1–48 h; the thickness of the anion (cation) exchange membrane layer is 1–40 μm.

[0051] The anion exchange membrane liquid described in this invention is a poly(terphenyl arylpiperidone) anion exchange membrane liquid. This invention utilizes an ultrasonic spraying method to uniformly spray the poly(terphenyl arylpiperidone) anion exchange membrane liquid onto the intermediate layer, followed by heating and drying to obtain a bipolar membrane constructed by regulating the spacing between charged nanosheets.

[0052] Specifically, a glass slide loaded with an cation exchange membrane layer and an intermediate layer is placed inside a precision ultrasonic spraying instrument. The heating temperature is set to 80℃. A 3.2% (w / w) poly(terphenyl arylpiperidone) anion exchange membrane solution is sprayed onto the catalytic intermediate layer. The solvent for the anion exchange membrane solution is dimethyl sulfoxide. The spraying height is 5 cm, and the solution spraying rate is 0.2 ml / min. -1 The feed rate is 25 mm / s. -1 The heating temperature was 80℃, and the coating was continued to be heated for 5 hours after spraying to obtain a poly(terphenyl arylpiperidone) anion exchange membrane with a thickness of 32.5 μm, and a bipolar membrane based on a charged nanosheet catalyst layer was obtained.

[0053] See Figure 1A method for preparing a bipolar film based on a charged nanosheet catalytic layer includes:

[0054] S100: The cation (anion) exchange membrane solution is coated onto a smooth substrate and dried to obtain the cation (anion) exchange membrane layer.

[0055] S200: Modified nanosheets with positive (negative) charge;

[0056] S300: A modified solution of positively (negatively) charged nanosheets is ultrasonically sprayed onto a cation (anion) exchange membrane layer and dried to obtain a bipolar membrane intermediate layer with layers of positively (negatively) charged nanosheets stacked and the interlayer spacing modified.

[0057] S400: Anion (cation) exchange membrane solution is sprayed onto the intermediate layer of the bipolar membrane and dried to obtain the bipolar membrane.

[0058] The present invention also provides an application of the bipolar membrane based on charged nanosheet catalytic layer described above in seawater dissociation.

[0059] This invention simulates the transmembrane potential difference of a bipolar membrane based on a charged nanosheet catalytic layer in a 0.5 mol / L NaCl solution.

[0060] To further illustrate the present invention, the following detailed description, in conjunction with embodiments, provides a bipolar membrane based on a charged nanosheet catalytic layer, its preparation method, and its application in seawater dissociation. However, these descriptions should not be construed as limiting the scope of protection of the present invention.

[0061] This invention provides a method for preparing a bipolar film based on a charged nanosheet catalytic layer. The technical solutions in the embodiments of this invention will be described in detail below. It should be particularly noted that the specific embodiments described herein are merely some embodiments of this invention, not all embodiments. All similar substitutions and modifications are obvious to those skilled in the art and fall within the scope of protection of this invention. All other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of this invention.

[0062] Furthermore, the technical solutions of the various embodiments can be combined with each other, but only if they are feasible for those skilled in the art. If the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

[0063] This invention provides an embodiment of a method for preparing an intermediate bipolar film by controlling the spacing between charged nanosheets. It should be noted that although the logical order is shown in the flowchart, in some cases, the steps shown or described may be performed in a different order than shown here.

[0064] Example 1

[0065] A 1.6% (w / w) sulfonic acid-type polyphenylsulfone cation exchange membrane solution was coated onto a smooth glass plate, and the glass plate was heated and dried at 60°C for 5 hours to obtain a cation exchange membrane layer with a thickness of 6.5 μm.

[0066] Add Fe(OH)3 colloidal solution to 0.25 mg / ml -1 A Fe(OH)3-modified MXene nanosheet solution (MXene@Fe(OH)3) was obtained by stirring in a negatively charged aqueous solution of MXene for 30 min. The Fe(OH)3-modified MXene nanosheet solution was then ultrasonically sprayed onto a cation exchange membrane at a height of 5 cm and a spray rate of 0.2 ml / min. -1 The feed rate is 25 mm / s. -1 The heating temperature was 80℃, the catalyst layer height was approximately 20nm, and the loading of (MXene@Fe(OH)3) was 12μg / cm³. -2 Drying yields a controlled-spacing intermediate layer of charged nanosheets;

[0067] The glass slide loaded with the cation exchange membrane layer and the intermediate layer was placed in a precision ultrasonic spraying instrument. The heating temperature was set to 80°C. A 3.2% (w / w) poly(terphenyl arylpiperidone) anion exchange membrane solution was ultrasonically sprayed onto the catalytic intermediate layer. The solvent for the anion exchange membrane solution was dimethyl sulfoxide. The spraying height was 5 cm, and the solution spraying rate was 0.2 ml / min. -1 The feed rate is 25 mm / s. -1 The heating temperature was 80℃, and the coating was continued to be heated for 5 hours after spraying to obtain a poly(terphenyl arylpiperidone) anion exchange membrane with a thickness of 32.5 μm, and a bipolar membrane based on a charged nanosheet catalyst layer was obtained.

[0068] The present invention performs cross-sectional scanning electron microscopy analysis on the bipolar film based on the charged nanosheet catalytic layer prepared in Example 1. The specific process is as follows:

[0069] A glass plate loaded with a bipolar film based on a charged nanosheet catalytic layer was placed in deionized water, allowing the bipolar film to detach automatically from the smooth glass plate. The bipolar film was then removed from the deionized water and dried using a hot plate and vacuum suction in a precision ultrasonic spraying device. A suitable size of the bipolar film was cut and immersed in liquid nitrogen for a few seconds, then removed and subjected to low-temperature brittle fracture treatment. The resulting bipolar film cross-sectional sample was attached to a sample stage with conductive adhesive and sputtered with gold. It was then transferred to a scanning electron microscope sample chamber for testing and observation, obtaining cross-sectional morphology images of the bipolar film based on the charged nanosheet catalytic layer, as shown below. Figure 2 As shown. The cross-section was photographed at high magnification to observe the catalyst layer, as shown. Figure 3 As shown.

[0070] Reference Figure 2 , Figure 2 The prepared bipolar membranes based on charged nanosheet catalyst layers exhibit uniform membrane thickness, with the cation exchange membrane having a thickness of 6.5 μm and the anion exchange membrane having a thickness of 36.5 μm. A catalyst layer exists between the two membrane layers. See also Figure 3 As can be seen, the catalyst layer is uniformly dispersed between the anion and cation film layers, and the thickness of the catalyst layer is about 20 nm.

[0071] The present invention also tested the current-voltage curve of the bipolar film prepared in Example 1, and the specific process is as follows:

[0072] First, the bipolar membrane based on the charged nanosheet catalytic layer to be tested in this invention is immersed in 0.5 mol L... -1 The solution was equilibrated in Na₂SO₄ solution for 24 hours, and then the bipolar membrane was installed in a two-chamber four-electrode apparatus for current-voltage testing. 0.5 mol L⁻¹ was injected into each of the two intermediate chambers. -1 Na2SO4 solution. An Ag / AgCl electrode was used as the inductive electrode and reference electrode, and a platinum electrode was used as the working electrode and counter electrode.

[0073] Under the influence of a reverse DC electric field, i.e., with the cation exchange membrane facing the negative electrode and the anion exchange membrane facing the positive electrode, an electrochemical workstation is used with a current of 2 mAs. -1 Gradually increase the current while recording the transmembrane potential difference. Plot the obtained current versus transmembrane voltage data to obtain the following result: Figure 3 The current-voltage curve of the bipolar membrane is shown.

[0074] like Figure 4 As shown, the voltage across the membrane increases with the applied current. The bipolar membrane based on the charged nanosheet catalytic layer at 100 mA / cm²... -2 The dissociation voltage of the wastewater is only 0.77V.

[0075] Similarly, under the influence of a reverse DC electric field, an electrochemical workstation was used with a current of 0.1 mAs.-1 The current was slowly increased while the bipolar membrane was recorded in simulated seawater (0.5 mol L⁻¹). -1 The transmembrane potential difference in NaCl solution is used to obtain current and transmembrane voltage data, which are then plotted as a current-voltage curve. The current corresponding to the maximum value of the derivative (dU / dI) of the current-voltage curve is the first limiting current density.

[0076] Please see Figure 5 The first limiting current density of the bipolar film based on the MXene@Fe(OH)3 charged nanosheet catalyst layer is 1.7 mAcm. -2 This demonstrates that this type of bipolar membrane has extremely low ion leakage, which lays the foundation for maintaining the pH difference across the bipolar membrane and enabling bipolar membranes to be used in electrodialysis for acid and alkali production and in seawater electrolysis for hydrogen production.

[0077] Example 2

[0078] The difference from Example 1 is that the intermediate layer is different, specifically:

[0079] A mass concentration of 0.25 mg / mL -1 A solution of negatively charged MXene nanosheets was ultrasonically sprayed onto a sulfonic acid-based polyphenylene ether cation exchange membrane layer, with an MXene loading of 12 μg cm⁻¹. -2 24μg cm -2 36μg cm -2 The intermediate layer is constructed by drying the charged nanosheets and regulating their spacing, and finally a bipolar film based on the MXene nanosheet catalytic layer is obtained.

[0080] Under the influence of a reverse DC electric field, an electrochemical workstation was used to apply a 2 mA s -1 Slowly increase the current while recording the bipolar membrane temperature at 0.5 mol / L. -1 The transmembrane potential difference in Na2SO4 solution is used to obtain the current and transmembrane voltage data, which are then plotted as a current-voltage curve. The current corresponding to the maximum value of the derivative (dU / dI) of the current-voltage curve is the first limiting current density.

[0081] Please see Figure 6 The MXene loading was 12 μg cm. -2 24μg cm -2 36μg cm -2 The first limiting current density of the prepared bipolar film based on the MXene charged nanosheet catalytic layer was 2.04 mA cm⁻¹. -2 1.70mA cm -2 and 1.36mA cm -2This demonstrates that the common ion leakage of this type of bipolar membrane is extremely low. At the same time, the higher the MXene loading, that is, the thicker the catalyst layer, the lower the common ion leakage, further illustrating the inhibitory effect of the catalyst layer on common ion leakage.

[0082] As can be seen from the above embodiments, the present invention provides a method for preparing a bipolar membrane based on a charged nanosheet catalytic layer, comprising the following steps: A) coating a cation (anion) exchange membrane solution onto a smooth substrate and drying it to obtain a cation (anion) exchange membrane layer; dissolving modified charged nanosheets to obtain a modified charged nanosheet solution; B) ultrasonically spraying the modified charged nanosheet solution onto the cation (anion) exchange membrane layer and drying it to obtain a bipolar membrane interlayer; C) ultrasonically spraying anion (cation) exchange membrane solution onto the bipolar membrane interlayer and drying it to obtain a bipolar membrane. The present invention adopts the idea of ​​introducing confined mass transfer into the bipolar membrane interlayer. Positively (negatively) charged nanosheets are stacked by ultrasonic spraying, and the spacing of the positively (negatively) charged nanosheets is controlled by modifying the spacing to construct the bipolar membrane interlayer, thus preparing a bipolar membrane with low common ion leakage and excellent water dissociation performance. The sub-nanometer or nanometer-level charged channels formed by the stacking of positively (negatively) charged nanosheets in the bipolar membrane interlayer restrict common ion leakage. Experimental results show that: by controlling the spacing between charged nanosheets to construct an intermediate bipolar film, the interlayer can withstand 100 mA cm⁻¹. -2 At this voltage, the water dissociation voltage is only 0.7–2V, and the first limiting current density is as low as 1–5 mA cm⁻¹. -2 .

[0083] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a bipolar film based on a charged nanosheet catalytic layer, comprising the following steps: A) Apply cation exchange membrane solution or anion exchange membrane solution to a smooth substrate and dry it to obtain a cation exchange membrane layer or anion exchange membrane layer. The modified charged nanosheets were dissolved to obtain a modified charged nanosheet solution; the modified charged nanosheets were selected from negatively charged MXene nanosheets modified with Fe(OH)3 colloid. B) The modified charged nanosheet solution is ultrasonically sprayed onto the cation exchange membrane layer or anion exchange membrane layer and dried to obtain a bipolar membrane intermediate layer; the thickness of the bipolar membrane intermediate layer is 4~400 nm; the loading of the modified charged nanosheets on the cation exchange membrane layer or anion exchange membrane layer is 1~1000 μg / cm³. 2 ; C) Ultrasonically spray anion exchange membrane solution or cation exchange membrane solution onto the intermediate layer of the bipolar membrane, and dry it to obtain a bipolar membrane; The spraying height used in steps B) and C) is 1~10cm; The solution spray rate is set to 0.05~0.8 mL / min. -1 The feed rate is 5~40 mm / s. -1 .

2. The preparation method according to claim 1, characterized in that, The mass concentration of the cation exchange membrane solution or the anion exchange membrane solution is 1-10%; The solvent in the cation exchange membrane solution or anion exchange membrane solution is selected from one or more of water, methanol, ethanol, N,N-dimethylformamide and dimethyl sulfoxide.

3. The preparation method according to claim 1, characterized in that, In step A), the drying temperature is 50~90℃ and the time is 1~48h; the thickness of the cation exchange membrane layer or anion exchange membrane layer is 1~40μm. The drying temperature in step B) is 50~90℃; In step C), the drying temperature is 50~90℃ and the time is 1~48h; the thickness of the anion exchange membrane layer or the cation exchange membrane layer is 1~40 μm.

4. The preparation method according to claim 1, characterized in that, The solvent used to dissolve the modified charged nanosheets is selected from one or more of water, methanol, ethanol, N,N-dimethylformamide and dimethyl sulfoxide; The mass-to-volume ratio of the modified charged nanosheets to the solvent is (0.1~1) g: (200~1000) mL.

5. The preparation method according to claim 1, characterized in that, In step C), the mass concentration of the anion exchange membrane solution or the cation exchange membrane solution is 1-10%. The solvent in the anion exchange membrane solution or cation exchange membrane solution is selected from one or more of water, methanol, ethanol, N,N-dimethylformamide and dimethyl sulfoxide.

6. A bipolar membrane based on a charged nanosheet catalytic layer, prepared by the method described in any one of claims 1 to 5.

7. The application of a bipolar membrane prepared by the preparation method according to any one of claims 1 to 5 in seawater dissociation.

Images