A bipolar membrane comprising a middle catalytic layer containing a MOF, a method of preparation and use

Abstract

The application discloses a bipolar membrane containing a MOF intermediate catalytic layer, a preparation method and application, and relates to the technical field of bipolar membranes, and specifically discloses a bipolar membrane containing a MOF intermediate catalytic layer, which comprises a base film, an anode film, a MOF-containing intermediate catalytic layer and a cathode film; wherein the MOF-containing intermediate catalytic layer is a carbon-coated oxygen evolution catalyst / hydrogen evolution catalyst / MOF catalyst; the preparation raw material of the anode film is composed of strong acid type sulfonic acid group cation exchange resin, carboxyl cation exchange resin and phosphonic acid group cation exchange resin with a mass ratio of (40-55):(20-30):(25-35); and the preparation raw material of the cathode film is composed of strong alkaline quaternary ammonium type II anion exchange resin, strong alkaline quaternary ammonium type I anion exchange resin and chloro type anion exchange resin with a mass ratio of (50-60):(15-25):(20-30). The bipolar membrane has the characteristics of high ion selectivity, high acid-base separation efficiency and superior ion interception rate.

Description

Technical Field

[0001] The present invention relates to the technical field of bipolar membranes, and in particular to a bipolar membrane containing an intermediate catalytic layer of MOF, a preparation method and applications thereof. Background Art

[0002] Metal-organic frameworks (MOFs) were first proposed in the 1990s. These porous crystalline materials, composed of metal ions or metal clusters coordinated with organic ligands, exhibit ultra-low mass density, large pore volumes, and a well-defined pore size distribution. They are widely used in gas adsorption and storage, catalysis, sensors, drug release, biomass separation and storage, and capacitors. In recent years, researchers have widely applied MOFs as catalysts in various battery applications, including bipolar membrane electrodialysis, fuel cells, and electrolyzers.

[0003] The bipolar membrane is composed of an anode membrane, an intermediate layer and a cathode membrane. It is a special ion exchange membrane. It has anion and cation selectivity. Under the action of the DC electric field, the H2O between the bipolar membranes is dissociated into H + and OH - . H + Through the cation membrane, as H + Ion source; OH - Through the anorectal membrane, as OH - Ion source. + and OH - The membrane is replenished in time mainly through the dissociation of water in the transition zone, and the consumed water is compensated by the water in the surrounding solution penetrating into the middle of the membrane.

[0004] The bipolar membranes in the prior art have problems such as poor performance stability, reduced ion selectivity, low acid-base separation efficiency, and poor interception rate.

[0005] The development of bipolar membranes with high acid-base separation efficiency and good interception effect is urgent and of great significance. Summary of the Invention

[0006] To address the above technical issues, the present invention provides a bipolar membrane containing a MOF intermediate catalytic layer, a preparation method, and applications. This bipolar membrane exhibits high ion selectivity, excellent acid-base separation efficiency, and superior interception rate, and is widely applicable in electrolytic cells, fuel cells, and bipolar membrane electrodialysis.

[0007] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0008] In a first aspect, the present invention provides a bipolar membrane containing an intermediate catalytic layer of MOF, the bipolar membrane comprising: a base membrane, an anode membrane, an intermediate catalytic layer containing MOF, and a cathode membrane;

[0009] Wherein, the intermediate catalytic layer containing MOF is: carbon-coated oxygen evolution catalyst / hydrogen evolution catalyst / MOF catalyst;

[0010] The raw materials for preparing the anode membrane are composed of a strong acid type sulfonic acid group cation exchange resin, a carboxyl group cation exchange resin and a phosphonic acid group cation exchange resin in a mass ratio of (40-55): (20-30): (25-35);

[0011] The raw materials for preparing the cathode membrane consist of strongly alkaline quaternary ammonium type II anion exchange resin, strongly alkaline quaternary ammonium type I anion exchange resin and chloride type anion exchange resin in a mass ratio of (50-60):(15-25):(20-30).

[0012] Under the joint action of the anode membrane, the intermediate catalytic layer containing MOF and the cathode membrane, the bipolar membrane of the present invention obtains a bipolar membrane with high ion selectivity, high acid-base separation efficiency and excellent ion interception rate, which can be used for a long time in electrolytic cells, fuel cells and electrodialysis.

[0013] The anode membrane of the present invention is made of the above-mentioned strong acid type sulfonic acid cation exchange resin, carboxyl cation exchange resin and phosphonic acid cation exchange resin. It can dissociate H + The anodic membrane of the present invention mainly utilizes the sulfonic acid group of the strong acid sulfonic acid cation exchange resin to dissociate H + , the ion exchange capacity is large, and it can intercept cations (Ca 2+ Mg 2+ ); while cooperating with carboxyl cation exchange resin and phosphonic acid cation exchange resin to selectively adsorb and separate high-valent, large-diameter cations (such as Fe 3+ 、Al 3+ Cr 6+ 、Mn 4+ heavy metal ions, and rare earth metal ions, etc.), thereby efficiently intercepting cations in the solution and having good ion selectivity.

[0014] The MOF-containing intermediate catalytic layer of the present invention is first prepared by mixing an oxygen evolution catalyst, a hydrogen evolution catalyst and a MOF catalyst with excellent redox reaction (ORR) catalytic activity to form a composite catalyst with strong conductivity and multiple active sites. The composite catalyst is then carbon-coated to protect the composite catalyst from harsh environments such as oxidation, reduction or corrosion, thereby improving the stability and durability of the catalyst, and the mass and heat transfer efficiency, thereby increasing the catalytic reaction rate and yield. The carbon-coated oxygen evolution catalyst / hydrogen evolution catalyst / MOF catalyst has the characteristics of high stability, strong conductivity, multiple active sites and excellent catalytic performance, greatly improving the acid-base separation efficiency of the bipolar membrane.

[0015] The cathode membrane of the present invention is made of the above-mentioned ratio of strong alkaline quaternary ammonium type II anion exchange resin, strong alkaline quaternary ammonium type I anion exchange resin and chloride type anion exchange resin. It can dissociate OH- in water, has high ion exchange capacity, and can synergistically and efficiently intercept anions (SO4 2 -、PO43-、SiO32-、N 3- ), etc., which greatly accelerates the water dissociation rate of the bipolar membrane and improves the acid-base separation efficiency; at the same time, it has high chemical stability and thermal stability.

[0016] The present invention utilizes a strong alkaline quaternary ammonium type II anion exchange resin (its alkalinity is equivalent to that of a strong base) having the characteristics of strong alkali resistance, high ion exchange capacity, good mechanical strength, and excellent heat resistance. At the same time, a strong alkaline quaternary ammonium type I anion exchange resin having large exchange capacity, fast ion diffusion exchange characteristics, and a macroporous structure and a chloride type anion exchange resin are synergistically used to prepare a cathode membrane, so that the cathode membrane can adsorb anions with larger molecular sizes. Under the synergistic effect of the three anion exchange resins, OH- can be dissociated in water, the ion exchange capacity is high, and anions (SO42-, PO43-, SiO32-, N 3- ), etc., with high ion selectivity and high acid-base separation efficiency.

[0017] Preferably, the carbon-coated oxygen evolution catalyst / hydrogen evolution catalyst / MOF catalyst is prepared by mixing a carbon-coated material, an oxygen evolution catalyst, a hydrogen evolution catalyst and a MOF catalyst, and subjecting the mixture to heat treatment.

[0018] The carbon-coated composite catalyst (oxygen evolution catalyst, hydrogen evolution catalyst and MOF catalyst) of the present invention can improve the stability, durability, mass transfer and heat transfer efficiency of the catalyst in the intermediate catalytic layer, improve the catalytic reaction rate and yield of the intermediate catalytic layer, effectively avoid the catalyst in the intermediate catalytic layer from being affected by harsh environments such as oxidation, reduction or corrosion, and cause catalyst leakage accidents, thereby extending the service life of the catalyst.

[0019] Preferably, the mass ratio of the carbon-coated material, the oxygen evolution catalyst, the hydrogen evolution catalyst and the MOF catalyst is (10-15):(30-35):(30-35):(70-80).

[0020] The carbon-coated material, oxygen evolution catalyst, hydrogen evolution catalyst, and MOF catalyst in the aforementioned mass ratios of the present invention can uniformly coat the carbon-coated material on the surface of the composite catalyst, enhancing the catalyst's stability and conductivity. The oxygen evolution catalyst, hydrogen evolution catalyst, and MOF catalyst exhibit a synergistic effect, providing abundant active sites and superior catalytic performance, thereby accelerating the water dissociation reaction rate and yield of the bipolar membrane, thereby improving the bipolar membrane's ion selectivity and acid-base separation efficiency.

[0021] Preferably, the heat treatment is: heat preservation treatment at 400-600° C. for 8-10 hours. The carbon coating material includes any one of graphite, carbon black and graphene.

[0022] This temperature allows the carbon coating material to be evenly coated on the surface of the complex catalyst, forming a uniform shell without destroying the structure and composition of the organic matter in the MOF catalyst, allowing the MOF catalyst to maintain its activity. Temperatures below 400°C are not conducive to the coating of the carbon coating material; temperatures above 600°C are likely to cause changes in the organic structure of the MOF catalyst, resulting in a reduction in the number of active sites in the MOF catalyst.

[0023] The oxygen evolution catalyst includes any one of NiFeLDH, CoFeLDH and β-FeOOH; the hydrogen evolution catalyst includes a Pt / C catalyst or an AEM cathode catalyst;

[0024] The MOF catalyst includes: Ni-CO-Fe-MOF or Cu-MOF.

[0025] In a second aspect, the present invention further provides a method for preparing the above-mentioned bipolar membrane, comprising the following steps:

[0026] S1. Add the raw materials for preparing the anode membrane, the raw materials for preparing the cathode membrane, and the raw materials for preparing the intermediate catalyst layer containing MOF into the polyurethane adhesive solution, respectively, and stir them evenly at 20-30° C. and 300-400 r / min to obtain a cationic casting solution, an anionic casting solution, and an intermediate catalyst layer solution containing MOF, respectively;

[0027] S2, uniformly coating the cationic casting solution on the base membrane, and drying it to obtain a cationic exchange membrane layer;

[0028] S3, uniformly coating the intermediate catalytic layer solution containing MOF on the cation exchange membrane layer, and drying to obtain a cation exchange membrane layer / intermediate catalytic layer containing MOF;

[0029] S4. Evenly coating anion casting solution on one side of the cation exchange membrane layer / MOF-containing intermediate catalytic layer, and drying to obtain a bipolar membrane.

[0030] The present invention adds raw materials for preparing an anode membrane, raw materials for preparing a cathode membrane and raw materials for preparing an intermediate catalytic layer containing MOF into a polyurethane molten solution with strong adhesion, and heats and melts them at 20-30°C to obtain a cationic casting liquid, an intermediate catalytic layer solution containing MOF and an anionic casting liquid with uniform composition; then, the cationic casting liquid, the intermediate catalytic layer solution containing MOF and the anionic casting liquid are sequentially coated on a base membrane to obtain a bipolar membrane, and the membrane is dried, so that the three membrane layers are tightly bonded, have strong adhesion, are not easily separated or peeled off, and the obtained bipolar membrane has good quality and a long service life.

[0031] Preferably, the polyurethane adhesive solution is formed by stirring and melting polyurethane resin at 80-150° C. and 50-70 r / min.

[0032] The present invention eliminates the need for adding an organic solvent to dissolve the polyurethane resin. Instead, the polyurethane is melted into a solution that can remain stable in a liquid state at room temperature and serve as a binder. The polyurethane molten solution is then stirred at room temperature (20-30°C) with raw materials for the anode membrane, cathode membrane, and intermediate catalyst layer containing MOF to form a solution with strong adhesion and uniform composition. This solution remains stable at room temperature and does not solidify. The room temperature ensures uniform distribution of the cathode and anode resins within the polyurethane binder while preserving their inherent properties without disrupting their structures. The polyurethane resin and anionic and cationic resins are prepared in two steps, maintaining the structural integrity of the cathode and anode resins.

[0033] Preferably, the polyurethane resin is any one of PU-6045, PU-2050 and PU-5800. The polyurethane resin of the present invention is a polymer material with high strength, tear resistance, wear resistance and other characteristics. After melting, it has strong adhesion and is suitable as a binder for bipolar membranes and is not easy to separate or peel off.

[0034] Preferably, the base film includes: a polyurethane film or a polymethacrylate film.

[0035] The polyurethane membrane of the present invention, as the base membrane material of the bipolar membrane, has excellent elasticity, wear resistance and chemical stability and is durable. The polymethacrylate membrane, as the base membrane of the bipolar membrane, has wear resistance and chemical stability.

[0036] The mass concentration of the raw materials for preparing the anode film in the polyurethane bonding solution is 10%-20%;

[0037] The mass concentration of the raw materials for preparing the cathode membrane in the polyurethane bonding solution is 10%-20%;

[0038] The raw materials for preparing the intermediate catalytic layer containing MOF account for 1%-5% of the mass concentration of the polyurethane bonding solution.

[0039] Preferably, the thickness of the cation exchange membrane layer is 70-120 μm; the thickness of the intermediate catalytic layer containing MOF is 10-30 nm (0.01-0.02 μm); and the thickness of the bipolar membrane is 90-180 μm.

[0040] Preferably, the drying temperature is 50-80° C. This drying temperature can volatilize the polyurethane adhesive solution as a solvent faster, thereby obtaining a uniform film surface.

[0041] In a third aspect, the present invention further provides applications of the bipolar membrane or the bipolar membrane obtained by the method for preparing the bipolar membrane in electrolytic cells, fuel cells, and bipolar membrane electrodialysis.

[0042] The bipolar membrane of the present invention is universally applicable in the fields of electrolytic cells, fuel cells, and bipolar membrane electrodialysis, and can be widely selected and used in the market. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 Schematic diagram of the bipolar membrane structure of the present invention.

[0044] In the figure: 1. Base membrane; 2. Anode membrane; 3. Intermediate catalytic layer containing MOF; 4. Cathode membrane.

[0045] Figure 2 Graph showing the current-voltage test results of the bipolar membranes prepared in Example 1 and Comparative Examples 1-5;

[0046] Figure 3 Graph showing the current-voltage test results of the bipolar membranes prepared in Examples 1-3;

[0047] Figure 4 This is a diagram showing the stability test results of the bipolar membrane prepared in Example 1. DETAILED DESCRIPTION

[0048] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention is further described in detail below with reference to specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. The specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. The "upper", "lower", "left" and "right" defined in the present invention are limited to the views shown in the drawings of the present invention specification. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0049] The present invention provides a bipolar membrane containing an intermediate catalytic layer of MOF, the structural diagram of which is shown as follows: Figure 1 shown.

[0050] from Figure 1 It can be seen that the intermediate catalytic layer containing MOF and the bipolar membrane of the present invention are composed of a base membrane 1, an anode membrane 2, an intermediate catalytic layer containing MOF 3 and a cathode membrane 4 from left to right.

[0051] 1. The strongly acidic sulfonic acid cation exchange resin (001×7 strongly acidic cation exchange resin), carboxyl cation exchange resin (D113 macroporous weakly acidic cation exchange resin), phosphonic acid cation exchange resin (D418 cation resin, which is a styrene-divinylbenzene copolymer with a special macroporous structure and a weakly acidic aminophosphonic acid group -CH2NHCH2PO3-), strongly basic quaternary ammonium type II anion exchange resin (D202 macroporous strong base type II styrene anion exchange resin), strongly basic quaternary ammonium type I anion exchange resin (D-201 high-grade macroporous strong base type I anion exchange resin) and chloride-type anion exchange resin (D301 macroporous weakly basic anion exchange resin) used in the present invention can all be purchased commercially.

[0052] 2. The catalysts used in the present invention are all prepared by existing technologies.

[0053] The preparation method of NiFeLDH is:

[0054] The nickel foam (2cm 2 ) were ultrasonically treated with hydrochloric acid solution, anhydrous ethanol and deionized water for 15 minutes, respectively, and dried at 50°C for 6 hours; 1 mmol of Ni(NO3)2·9H2O, 1 mmol of Fe(NO)·9HO and 5 mmol of urea were weighed and dissolved together in 30 ml of ethylene / deionized water (volume ratio of 1:1) to obtain a mixed solution; the mixed solution was transferred to a 50 ml polytetrafluoroethylene reactor, and a piece of treated foamed nickel was added. The reaction was carried out at 120°C for 12 hours, cooled to room temperature, and the foamed nickel was removed. The mixture was washed several times with deionized water and anhydrous ethanol, respectively, and then dried at 50°C for 5 hours to obtain NiFeLDH.

[0055] The preparation method of CoFeLDH is:

[0056] 1) Boil deionized water and maintain constant boiling for 5 minutes, then cool to room temperature and set aside. Using an electronic balance, weigh 0.7138 g of CoCl2·6H2O, 0.2982 g of FeCl2·4H2O, 0.3963 g of ascorbic acid, and 3.7851 g of hexamethylenetetramine.

[0057] 2) The weighed CoCl2·6H2O and FeCl2·4H2O were dissolved in 100 mL of reserved water at room temperature to obtain a mixed solution; under the same conditions, ascorbic acid and hexamethylenetetramine were dissolved in 50 mL of reserved water to obtain their respective aqueous solutions.

[0058] 3) The mixed solution, ascorbic acid, and an aqueous solution of hexamethylenetetramine were sequentially mixed in a three-necked flask, with the latter slowly added to the former in each step. Finally, the mixture was reacted in an oil bath at 110°C for 4 hours. The reaction system was exposed to air and cooled to 25°C. The mixture was then washed with deionized water, centrifuged, and vacuum-dried.

[0059] The preparation method of β-FeOOH is:

[0060] Transfer 50 ml of 0.1 mol FeCl3 aqueous solution into the reactor and react at 140 °C for 2 h. After washing, high-speed centrifuge and vacuum drying, β-FeOOH was obtained.

[0061] MOF catalysts: Ni-Co-Fe-MOF and Cu-MOF are prepared using existing technology.

[0062] The preparation method of Ni-Co-Fe-MOF is:

[0063] Pretreatment of nickel foam: Put nickel foam (2cm 2 ) were ultrasonically washed with dilute hydrochloric acid, ethanol, and deionized water for 15 minutes, respectively, and dried for later use. 11 mg of ferric nitrate and 24 mg of cobalt nitrate were dissolved in 3 mL of deionized water and stirred evenly. The pretreated nickel foam was then added and allowed to stand at room temperature for 1 hour to obtain a NiCoFe-LDH mixture. 30 mg of dipotassium 2,6-naphthalenedicarboxylate was added to the mixture and shaken until completely dissolved. The mixture was then transferred to an oven at 60°C and reacted for 20 hours to obtain the product, which was then washed with ethanol and deionized water and dried to obtain Ni-Co-Fe-MOF.

[0064] The preparation method of Cu-MOF catalyst is as follows:

[0065] 1. Weigh 0.0051 mol of Zn(NO3)2·6H2O, 1.62×10 -41 mol of Cu(NO₃)₂·3H₂O was added to 50 mL of DMF and mixed thoroughly. At room temperature, 0.0038 mol of terephthalic acid was added to the mixture and stirred until the solid was completely dissolved. 2.75 mL of triethylamine was then added and stirred for 2 hours to obtain a white solid. The product was filtered and washed four times with DMF during filtration to remove impurities. The resulting product was then dried in a 65°C oven for 5 hours and then ground to obtain MOF-5(Cu), which contained 3% Cu by mass.

[0066] 2. MOF-5(Cu)3%Cu was placed in a tube furnace, heated to 600°C at a heating rate of 10°C / min under air atmosphere, and calcined at a constant temperature for 2h to obtain a Cu-MOF catalyst.

[0067] The hydrogen evolution catalyst was purchased from a commercial source, including Pt / C catalyst, CAS number: 7440-06-4, and AEM cathode catalyst, model: FAHC-S1.

[0068] The present invention will be further described in detail below with reference to specific embodiments.

[0069] Example 1

[0070] Step 1: A method for preparing a carbon-coated oxygen evolution catalyst / hydrogen evolution catalyst / MOF catalyst, comprising:

[0071] A carbon-coated material (graphite), an oxygen evolution catalyst (NiFeLDH), a hydrogen evolution catalyst (Pt / C catalyst, CAS No. 7440-06-4), and a MOF catalyst (Ni-Co-Fe-MOF) were mixed in a mass ratio of 10:30:30:70 and ground for 48 hours to obtain a mixture. The mixture was then placed in a furnace and heat treated at 400°C for 8 hours before cooling to room temperature to obtain a carbon-coated oxygen evolution catalyst / hydrogen evolution catalyst / MOF catalyst.

[0072] Step 2: The embodiment of the present invention provides a bipolar membrane containing an intermediate catalytic layer of MOF, such as Figure 1 As shown, the bipolar membrane consists of a base membrane 1, an anode membrane 2, an intermediate catalyst layer 3 containing MOF, and a cathode membrane 4 from left to right.

[0073] The main raw materials of the intermediate catalytic layer containing MOF are: carbon-coated oxygen evolution catalyst / hydrogen evolution catalyst / MOF catalyst;

[0074] The raw materials for preparing the anodic membrane consist of a strong acid sulfonic acid cation exchange resin (001×7 strong acid cation exchange resin), a carboxyl cation exchange resin (D113 macroporous weak acid cation exchange resin), and a phosphonic acid cation exchange resin (D418 cation exchange resin) in a mass ratio of 55:30:25.

[0075] The raw materials for preparing the cathode membrane are composed of a strong alkaline quaternary ammonium type II anion exchange resin (D202 macroporous strong base type II styrene anion exchange resin), a strong alkaline quaternary ammonium type I anion exchange resin (D-201 high-grade macroporous strong base type I anion exchange resin) and a chloride anion exchange resin (D301 macroporous weakly basic anion exchange resin) in a mass ratio of 60:20:30.

[0076] Step 3: The embodiment of the present invention further provides a method for preparing the above-mentioned bipolar membrane, comprising the following steps:

[0077] S1. Stir and melt the polyurethane resin PU-6045 at 80°C and 50 r / min to form a polyurethane adhesive solution.

[0078] S2. Weigh the raw materials for preparing the anode membrane, the raw materials for preparing the cathode membrane, and the raw materials for preparing the intermediate catalyst layer containing MOF, respectively, add them to the polyurethane adhesive solution, and stir them evenly at 20° C. and 300 r / min to obtain 10% cationic casting solution, 10% anionic casting solution, and 1% intermediate catalyst layer solution containing MOF, respectively;

[0079] S3, evenly coating 10% of the cationic casting solution on the (polyurethane membrane) base film, and drying at 50° C. to obtain a cation exchange membrane layer with a thickness of 85 μm;

[0080] S4. Evenly coating the cation exchange membrane layer with 1% of an intermediate catalytic layer solution containing MOF, and drying at 50° C. to obtain a cation exchange membrane layer / MOF-containing intermediate catalytic layer with a thickness of 85.01 μm.

[0081] S5. Evenly coat 10% anion casting solution on one side of the cation exchange membrane layer / MOF-containing intermediate catalytic layer, and dry at 50° C. to obtain a bipolar membrane with a thickness of 120 μm.

[0082] Example 2

[0083] Step 1: A method for preparing a carbon-coated oxygen evolution catalyst / hydrogen evolution catalyst / MOF catalyst, comprising:

[0084] A carbon-coated material (carbon black), an oxygen evolution catalyst (CoFeLDH), a hydrogen evolution catalyst (AEM cathode catalyst, model: FAHC-S1), and a metal-organic framework (MOF) catalyst (Cu-MOF) were mixed in a mass ratio of 12:33:35:78 and ground for 48 hours. The mixture was then heat-treated in a furnace at 500°C for 9 hours and cooled to room temperature to obtain a carbon-coated oxygen evolution catalyst / hydrogen evolution catalyst / MOF catalyst.

[0085] Step 2: An embodiment of the present invention provides a bipolar membrane containing an intermediate catalytic layer of MOF. The bipolar membrane consists of a base membrane 1, an anode membrane 2, an intermediate catalytic layer 3 containing MOF, and a cathode membrane 4 from left to right.

[0086] The main raw materials of the intermediate catalytic layer containing MOF are: carbon-coated oxygen evolution catalyst / hydrogen evolution catalyst / MOF catalyst;

[0087] The raw materials for the preparation of the anodic membrane consist of a strong acid sulfonic acid cation exchange resin (001×7 strong acid cation exchange resin), a carboxyl cation exchange resin (D113 macroporous weak acid cation exchange resin), and a phosphonic acid cation exchange resin (D418 cation exchange resin) in a mass ratio of 40:20:35.

[0088] The raw materials for preparing the cathode membrane are composed of a strong alkaline quaternary ammonium type II anion exchange resin (D202 macroporous strong base type II styrene anion exchange resin), a strong alkaline quaternary ammonium type II anion exchange resin (D-201 high-grade macroporous strong base type I anion exchange resin) and a chloride anion exchange resin (D301 macroporous weakly basic anion exchange resin) in a mass ratio of 50:15:30.

[0089] Step 3: The embodiment of the present invention also provides a method for preparing a bipolar membrane, comprising the following steps:

[0090] S1. Stir and melt the polyurethane resin PU-2050 at 90°C and 60 r / min to form a polyurethane adhesive solution.

[0091] S2. Weigh the raw materials for preparing the anode membrane, the raw materials for preparing the cathode membrane, and the raw materials for preparing the intermediate catalyst layer containing MOF, respectively, add them to the polyurethane adhesive solution, and stir them evenly at 25°C and 400 r / min to obtain 15% cationic casting solution, 15% anionic casting solution, and 3% intermediate catalyst layer solution containing MOF, respectively;

[0092] S3, evenly coating 15% of the cationic casting solution on the (polyurethane membrane) base film, and drying at 70° C. to obtain a cation exchange membrane layer with a thickness of 100 μm;

[0093] S4. Evenly coating 1.5% of an intermediate catalyst layer solution containing MOF on the cation exchange membrane layer, and drying the solution to obtain a cation exchange membrane layer / MOF-containing intermediate catalyst layer having a thickness of 100.02 μm.

[0094] S5. Evenly coat the anion casting solution on one side of the cation exchange membrane layer / MOF-containing intermediate catalytic layer, and dry at 70° C. to obtain a bipolar membrane with a thickness of 160 μm.

[0095] Example 3

[0096] Step 1: A method for preparing a carbon-coated oxygen evolution catalyst / hydrogen evolution catalyst / MOF catalyst, comprising:

[0097] A carbon-coated material (graphene), an oxygen evolution catalyst (β-FeOOH), a hydrogen evolution catalyst (Pt / C catalyst), and a MOF catalyst (Ni-Co-Fe-MOF) were mixed in a mass ratio of 15:35:35:80 and ground for 48 hours to obtain a mixture. The mixture was then placed in a furnace and heat treated at 600°C for 10 hours before cooling to room temperature to obtain a carbon-coated oxygen evolution catalyst / hydrogen evolution catalyst / MOF catalyst.

[0098] Step 2: An embodiment of the present invention provides a bipolar membrane containing an intermediate catalytic layer of MOF. The bipolar membrane consists of a base membrane, an anode membrane, an intermediate catalytic layer containing MOF, and a cathode membrane from left to right.

[0099] The main raw materials of the intermediate catalytic layer containing MOF are: carbon-coated oxygen evolution catalyst / hydrogen evolution catalyst / MOF catalyst;

[0100] The raw materials for preparing the anodic membrane consist of a strong acid sulfonic acid cation exchange resin (001×7 strong acid cation exchange resin), a carboxyl cation exchange resin (D113 macroporous weak acid cation exchange resin), and a phosphonic acid cation exchange resin (D418 cation exchange resin) in a mass ratio of 50:25:25.

[0101] The raw materials for preparing the cathode membrane are composed of a strong alkaline quaternary ammonium type II anion exchange resin (D202 macroporous strong base type II styrene anion exchange resin), a strong alkaline quaternary ammonium type I anion exchange resin (D-201 high-grade macroporous strong base type I anion exchange resin) and a chloride anion exchange resin (D301 macroporous weakly basic anion exchange resin) in a mass ratio of 55:20:25.

[0102] An embodiment of the present invention also provides a method for preparing a bipolar membrane, comprising the following steps:

[0103] S1. Stir and melt the polyurethane resin PU-5800 at 100°C and 70 r / min to form a polyurethane adhesive solution.

[0104] S2. Weigh the raw materials for preparing the anode membrane, the raw materials for preparing the cathode membrane, and the raw materials for preparing the intermediate catalyst layer containing MOF respectively, add them to the polyurethane adhesive solution, and stir them evenly at 30° C. and 300 r / min to obtain 20% cationic casting solution, 20% anionic casting solution, and 5% intermediate catalyst layer solution containing MOF respectively;

[0105] S2, evenly coating the cationic casting solution on the (polymethacrylate membrane) base membrane, and drying at 80° C. to obtain a cation exchange membrane layer with a thickness of 120 μm;

[0106] S3. Evenly coating the intermediate catalytic layer solution containing MOF on the cation exchange membrane layer and drying at 80° C. to obtain a cation exchange membrane layer / MOF-containing intermediate catalytic layer with a thickness of 120.03 μm;

[0107] S4. Evenly coat the anion casting solution on one side of the cation exchange membrane layer / MOF-containing intermediate catalytic layer, and dry at 80° C. to obtain a bipolar membrane with a thickness of 180 μm.

[0108] Comparative Example 1

[0109] In this example, the anode membrane was prepared using only acidic sulfonic acid cation exchange resin (001×7 strongly acidic cation exchange resin); the cathode membrane was prepared using only strongly basic quaternary ammonium type II anion exchange resin (D202 macroporous strong base type II styrene anion exchange resin). The remaining components were the same as in Example 1. The bipolar membrane had a 10% cation casting solution concentration, a 10% anion casting solution concentration, and a 1% MOF-containing intermediate catalyst layer solution concentration.

[0110] Comparative Example 2

[0111] The raw materials for preparing the anode membrane of this embodiment are acid-type sulfonic acid cation exchange resin (001×7 strong acid cation exchange resin) and carboxyl cation exchange resin (D113 macroporous weak acid cation exchange resin) in a mass ratio of 55:30; the raw materials for preparing the cathode membrane are: strong alkaline quaternary ammonium type II anion exchange resin (D202 macroporous strong base type II styrene anion exchange resin) and strong alkaline quaternary ammonium type I anion exchange resin (D-201 high-grade macroporous strong base type I anion exchange resin) in a mass ratio of 60:20, and the remaining components are the same as in Example 1.

[0112] The preparation method of the bipolar membrane of this embodiment is the same as that of embodiment 1, wherein the concentration of the cationic casting solution in the bipolar membrane is 10%, the concentration of the anionic casting solution is 10%, and the concentration of the intermediate catalyst layer solution containing MOF is 1%.

[0113] Comparative Example 3

[0114] In the bipolar membrane of this embodiment, the main raw material of the intermediate catalytic layer containing MOF is not carbon-coated, that is, NiFeLDH, Pt / C catalyst and Ni-CO-Fe-MOF are mixed and ground for 48 hours in a mass ratio of 30:30:70. The remaining components are the same as those in Example 1.

[0115] The preparation method of the bipolar membrane is the same as that of Example 1, wherein the concentration of the cationic casting solution in the bipolar membrane is 10%, the concentration of the anionic casting solution is 10%, and the concentration of the intermediate catalyst layer solution containing MOF is 1%.

[0116] Comparative Example 4

[0117] In the bipolar membrane of this embodiment, the catalyst of the intermediate catalytic layer containing MOF is only Ni-Co-Fe-MOF, and the other components are the same as those in Example 1.

[0118] The preparation method of the bipolar membrane is the same as that of Example 1, wherein the concentration of the cationic casting solution in the bipolar membrane is 10%, the concentration of the anionic casting solution is 10%, and the concentration of the intermediate catalyst layer solution containing MOF is 1%.

[0119] Comparative Example 5

[0120] In the bipolar membrane of this embodiment, the catalyst of the middle catalytic layer is a mixture of an oxygen evolution catalyst (NiFeLDH) and a hydrogen evolution catalyst (Pt / C catalyst, CAS No.: 7440-06-4) in a ratio of 30:30, which is ground for 48 hours. The remaining components are the same as those in Example 1.

[0121] The preparation method of the bipolar membrane is the same as that of Example 1, wherein the concentration of the cationic casting solution in the bipolar membrane is 10%, the concentration of the anionic casting solution is 10%, and the concentration of the intermediate catalyst layer solution is 1%.

[0122] Effect Example 1

[0123] Before testing, the bipolar membrane samples prepared in Example 1 and Comparative Examples 1-5 were immersed in a 0.5 mol / l sodium chloride solution for 24 hours to avoid possible effects of the solution.

[0124] The bipolar membranes prepared in Example 1 and Comparative Examples 1-5 were subjected to current-voltage curve testing (IV). Current-voltage curve testing was performed using a quadrupole system membrane stack (+proton exchange membrane | bipolar membrane | proton exchange membrane | -) connected to an electrochemical workstation. The Linear Sweep Voltammetry Galvanostatic program was selected, and a 1 mol / L sodium sulfate solution was used in both the electrode and acid / base compartments. The current was increased at a rate of 2 mA / s over a current range of 0-0.2 A.

[0125] Figure 2 Graph showing the current-voltage test results of the bipolar membranes prepared in Example 1 and Comparative Examples 1-5.

[0126] from Figure 2 It can be seen that the transmembrane voltage of the bipolar membranes of Example 1 and Comparative Examples 1-5 gradually increases with the increase of current.2 When the transmembrane voltages of Comparative Examples 1-5 were 5.5V, 4.15V, 1.79V, 3.16V, and 3.57V, respectively, and the transmembrane voltage of Example 1 was 0.48V. It can be seen that the transmembrane voltage of the bipolar membrane of Example 1 is significantly lower than that of the bipolar membranes of Comparative Examples 1-5. This shows that the performance of the bipolar membrane of Example 1 of the present invention is better than that of Comparative Examples 1-5. Compared with Comparative Examples 1-5, the bipolar membrane of Example 1 has a higher current density (20mA / cm 2 ), Example 1 had the lowest hydrolysis voltage, indicating that the bipolar membrane of Example 1 of the present invention can effectively reduce the voltage required for water dissociation and has better water dissociation efficiency. However, the water dissociation performance of the bipolar membranes of Comparative Examples 1-5 was inferior to that of Example 1. At the same voltage (0.40 V), the current density of Example 1 was higher than that of Comparative Examples 1-5. Based on the principle that higher current density indicates higher ion selectivity of a bipolar membrane, it can be inferred that the bipolar membrane of Example 1 of the present invention has higher ion selectivity than Comparative Examples 1-5.

[0127] In summary, compared with Comparative Examples 1-5, the formula and composition of each membrane layer of the electrode membrane of Example 1 have the best effect. Comparative Examples 1-5 lack any component or composition, and the performance of the obtained bipolar membrane cannot achieve the effect of Example 1.

[0128] Figure 3 Graph showing the current-voltage test results of the bipolar membranes prepared in Examples 1-3.

[0129] from Figure 3 It can be seen that the performances of the bipolar membranes prepared in Example 1, Example 2 and Example 3 are similar, with little difference.

[0130] Effect Example 2

[0131] 1. Bipolar membrane stability test

[0132] The stability of the bipolar membrane of Example 1 was measured using a quadrupole chamber system membrane stack (+|proton exchange membrane|bipolar membrane|proton exchange membrane|-) connected to an electrochemical workstation, and the Chrono Potentiometry program was selected. 1 mol / L sodium sulfate solution was used in both the electrode chamber and the acid-base chamber. During the test, the current was set to 50 mA / cm 2 , the test duration is 10h.

[0133] Figure 4 The bipolar membrane prepared in Example 1 was 2 Figure 2 shows the stability test results at current density of 100 nm.

[0134] like Figure 4As shown in the figure, during the test process of up to 10 hours, the transmembrane voltage of the bipolar membrane prepared in Example 1 changed very little (the transmembrane voltage increased from 0.52V to 0.54V: the actual transmembrane voltage increase rate was 3.8%), and the water dissociation voltage of the bipolar membrane of Example 1 was relatively stable, indicating that the bipolar membrane of the present invention is stable and can operate for a long time.

[0135] In summary, the bipolar membrane of the present invention, through the combined action of the anode membrane, the MOF-containing intermediate catalytic layer, and the cathode membrane, produces a bipolar membrane with high ion selectivity, high acid-base separation efficiency, and excellent ion interception rate. This bipolar membrane also exhibits excellent stability and can be used for long periods of time in electrolytic cells, fuel cells, and electrodialysis.

[0136] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions or improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A bipolar membrane containing an intermediate catalytic layer of MOF, characterized in that include: Base membrane, anode membrane, intermediate catalyst layer containing MOF and cathode membrane; Wherein, the intermediate catalytic layer containing MOF is: carbon-coated oxygen evolution catalyst / hydrogen evolution catalyst / MOF catalyst; The raw materials for preparing the anode membrane are composed of a strong acid type sulfonic acid cation exchange resin, a carboxyl cation exchange resin and a phosphonic acid cation exchange resin in a mass ratio of (40-55): (20-30): (25-35); The raw materials for preparing the cathode membrane are composed of a strongly basic quaternary ammonium type II anion exchange resin, a strongly basic quaternary ammonium type I anion exchange resin and a chloride type anion exchange resin in a mass ratio of (50-60):(15-25):(20-30); Wherein, the carbon coating material includes any one of graphite, carbon black and graphene; The oxygen evolution catalyst comprises any one of NiFeLDH, CoFeLDH and β-FeOOH; The hydrogen evolution catalyst includes: a Pt / C catalyst or an AEM cathode catalyst; The MOF catalyst includes: Ni-Co-Fe-MOF or Cu-MOF.

2. The bipolar membrane according to claim 1, characterized in that The preparation method of the carbon-coated oxygen evolution catalyst / hydrogen evolution catalyst / MOF catalyst is as follows: a carbon-coated material, an oxygen evolution catalyst, a hydrogen evolution catalyst and a MOF catalyst are mixed and heat-treated.

3. The bipolar membrane according to claim 2, characterized in that The mass ratio of the carbon coating material, the oxygen evolution catalyst, the hydrogen evolution catalyst and the MOF catalyst is (10-15):(30-35):(30-35):(70-80).

4. The bipolar membrane according to claim 2, characterized in that The heat treatment is: heat preservation treatment at 400-600°C for 8-10 hours.

5. The method for preparing a bipolar membrane according to any one of claims 1 to 4, wherein: At least the following steps are included: S1. Add the raw materials for preparing the anode membrane, the raw materials for preparing the cathode membrane, and the raw materials for preparing the intermediate catalyst layer containing MOF into the polyurethane adhesive solution, respectively, and stir them uniformly at 20-30° C. and 300-400 r / min to obtain a cationic casting solution, an anionic casting solution, and an intermediate catalyst layer solution containing MOF, respectively; S2, uniformly coating the cationic casting solution on the base membrane, and drying it to obtain a cationic exchange membrane layer; S3, uniformly coating the intermediate catalytic layer solution containing MOF on the cation exchange membrane layer, and drying to obtain a cation exchange membrane layer / intermediate catalytic layer containing MOF; S4. Evenly coating anion casting solution on one side of the cation exchange membrane layer / MOF-containing intermediate catalytic layer, and drying to obtain a bipolar membrane.

6. The method for preparing a bipolar membrane according to claim 5, wherein: The polyurethane adhesive solution is prepared by stirring and melting a polyurethane resin at 80-150° C. and 50-70 r / min; wherein the polyurethane resin is any one of PU-6045, PU-2050 and PU-5800.

7. The method for preparing a bipolar membrane according to claim 5 or 6, characterized in that: The base film comprises: a polyurethane film or a polymethacrylate film; and / or The mass concentration of the raw materials for preparing the anode film in the polyurethane bonding solution is 10%-20%; and / or The mass concentration of the raw materials for preparing the cathode membrane in the polyurethane bonding solution is 10%-20%; and / or The raw materials for preparing the intermediate catalytic layer containing MOF account for 1%-5% of the mass concentration of the polyurethane bonding solution; and / or The thickness of the cation exchange membrane layer is 70-120 μm; and / or The thickness of the intermediate catalytic layer containing MOF is 10-30 nm; and / or The thickness of the bipolar membrane is 90-180um.

8. The method for preparing a bipolar membrane according to claim 5, wherein: The drying temperature is 50-80°C.

9. Use of the bipolar membrane according to any one of claims 1 to 4 or the bipolar membrane prepared by the method for preparing a bipolar membrane according to any one of claims 5 to 8 in the field of water dissociation electrolysis cells.

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