Bipolar membrane containing middle catalyst layer of MOF (Metal Organic Framework) as well as preparation method and application of bipolar membrane

Abstract

The invention discloses a bipolar membrane with an MOF-containing middle catalyst layer, a preparation method and application. The bipolar membrane comprises a base membrane, an anode membrane, the MOF-containing middle catalyst layer and a cathode membrane, wherein the middle catalyst layer containing the MOF is a carbon-coated oxygen evolution catalyst / hydrogen evolution catalyst / MOF catalyst; the anode film is prepared from the following raw materials: strong acid type sulfonic cation exchange resin, carboxyl cation exchange resin and phosphonic cation exchange resin in a mass ratio of (40-55): (20-30): (25-35); the cathode membrane is prepared from the following raw materials: strongly alkaline quaternary ammonium II type anion exchange resin, strongly alkaline quaternary ammonium I type anion exchange resin and chlorine type anion exchange resin in 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 excellent ion interception rate.

Description

Technical Field

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

[0002] Metal-organic frameworks (MOFs) materials were first proposed in the 1990s. It is a porous crystalline material formed by the coordination of metal ions or metal clusters with organic ligands, with ultra-low mass density, large pore volume and clear pore size distribution, and is widely used in gas adsorption and storage, catalysis, sensors, drug release, biomass separation and storage, capacitors and other fields. In recent years, researchers have widely applied MoFs as catalysts in battery fields such as bipolar membrane electrodialysis, fuel cells, and electrolytic cells.

[0003] A bipolar membrane is composed of an anode membrane, an intermediate layer and a cathode membrane, and is a special ion exchange membrane. It has anion and cation selectivity. Under the action of a direct current electric field, H 2 O between the bipolar membranes is dissociated into H + and OH - . H + passes through the anode membrane and serves as an H + ion source; OH - passes through the cathode membrane and serves as an OH - ion source. H + and OH - are mainly replenished in a timely manner through the dissociation of water in the transition region, and the consumed water is compensated by the penetration of water in the surrounding solution into the middle of the membrane.

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

[0005] There is an urgent need to develop a bipolar membrane with high acid-base separation efficiency and good interception effect, and it is of great significance. Summary of the Invention

[0006] In view of the above technical problems, the present invention provides a bipolar membrane containing an intermediate catalytic layer of MOF, a preparation method and an application thereof. This bipolar membrane has high ion selectivity, good acid-base separation efficiency, excellent interception rate, and can be widely used in the fields of electrolytic cells, fuel cells and bipolar membrane electrodialysis.

[0007] To solve the above technical problems, the present invention adopts the following technical solutions:

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

[0009] Among them, 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 strongly acidic sulfonic 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);

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

[0012] Under the combined action of the anode membrane, the intermediate catalytic layer containing MOF and the cathode membrane of the bipolar membrane of the present invention, a bipolar membrane with high ion selectivity, high acid-base separation efficiency and excellent ion interception rate is obtained, and it 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 strongly acidic sulfonic group cation exchange resin, carboxyl cation exchange resin and phosphonic acid group cation exchange resin with the above-mentioned ratio. It can dissociate H + , has a high ion exchange capacity, can synergistically and efficiently intercept cations in the solution, and at the same time has high chemical stability and thermal stability. The anode membrane of the present invention mainly utilizes the sulfonic acid group of the strongly acidic sulfonic group cation exchange resin to dissociate H + , has a large ion exchange capacity, and can intercept cations (Ca 2+ , Mg 2+ ) in the solution; at the same time, it synergistically combines with the carboxyl cation exchange resin and the phosphonic acid group cation exchange resin to selectively adsorb and separate high-valent and large-diameter cations (such as Fe 3+ , Al 3+ , Cr 6+ , Mn 4+ and other heavy metal ions, and rare earth metal ions, etc.) in the solution, so as to efficiently intercept cations in the solution and have good ion selectivity.

[0014] The intermediate catalytic layer containing MOF of the present invention is first made of an oxygen evolution catalyst, a hydrogen evolution catalyst, and an MOF catalyst with excellent catalytic activity for the oxygen reduction reaction (ORR) to form a composite catalyst with strong conductivity and many active sites. Then, by carbon coating the composite catalyst, it can avoid the influence of harsh environments such as oxidation, reduction, or corrosion on the composite catalyst, improve the stability, durability, mass transfer, and heat transfer efficiency of the catalyst, thereby increasing the catalytic reaction rate and yield, making the carbon-coated oxygen evolution catalyst / hydrogen evolution catalyst / MOF catalyst have the characteristics of high stability, strong conductivity, many active sites, and excellent catalytic performance, and greatly improving the acid-base separation efficiency of the bipolar membrane.

[0015] The cathode membrane of the present invention is made of strongly basic quaternary ammonium type II anion exchange resin, strongly basic quaternary ammonium type I anion exchange resin, and chloride form anion exchange resin in the above-mentioned ratio. It can dissociate OH- in water, has a high ion exchange capacity, and can cooperate to efficiently intercept anions (SO4 2 -, PO43-, SiO 3 2-, N 3- ) etc. in the solution, greatly accelerating the hydrolysis dissociation rate of the bipolar membrane and improving the acid-base separation efficiency; at the same time, it has high chemical stability and thermal stability.

[0016] The present invention utilizes a strongly basic quaternary ammonium type II anion exchange resin with strong alkali resistance, high ion exchange capacity, good mechanical strength, and excellent heat resistance (its alkalinity is equivalent to that of a strong base). At the same time, it cooperates with a strongly basic quaternary ammonium type I anion exchange resin with a large exchange capacity, fast ion diffusion and exchange characteristics, and a macroporous structure, and a chloride form anion exchange resin to prepare a cathode membrane, enabling the cathode membrane to adsorb anions with larger molecular sizes. Under the synergistic action of these three anion exchange resins, it can dissociate OH- in water, has a high ion exchange capacity, and can efficiently intercept anions (SO42-, PO43-, SiO 3 2-, N 3- ) etc. in the solution, with high ion selectivity and high acid-base separation efficiency.

[0017] Preferably, the preparation method of the carbon-coated oxygen evolution catalyst / hydrogen evolution catalyst / MOF catalyst is: mixing a carbon coating material, an oxygen evolution catalyst, a hydrogen evolution catalyst, and an MOF catalyst, and heat-treating them.

[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, increase the catalytic reaction rate and yield of the intermediate catalytic layer, effectively avoid the leakage accident of the catalyst caused by the influence of harsh environments such as oxidation, reduction, or corrosion on the catalyst in the intermediate catalytic layer, and extend the service life of the catalyst.

[0019] Preferably, the mass ratio of the carbon-coated material, oxygen evolution catalyst, hydrogen evolution catalyst, and 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 with the above mass ratio in the present invention can uniformly coat the carbon-coated material on the surface of the composite catalyst, enhancing the stability and conductivity of the catalyst. Among them, the oxygen evolution catalyst, hydrogen evolution catalyst, and MOF catalyst have a synergistic effect, which can provide abundant active sites and excellent catalytic performance, thereby accelerating the dissociation reaction rate and yield of water in the bipolar membrane, and further improving the ion selectivity and acid-base separation efficiency of the bipolar membrane.

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

[0022] This temperature can uniformly coat the carbon-coated material on the surface of the composite catalyst, forming a uniform outer shell without destroying the structure and composition of the organic matter in the MOF catalyst, enabling the MOF catalyst to maintain its own activity. When the temperature is lower than 400 °C, it is not conducive to the coating of the carbon-coated material; when the temperature is higher than 600 °C, it is easy to cause changes in the organic structure in the MOF catalyst, resulting in a decrease in the number of active sites of 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 also provides a method for preparing the above bipolar membrane, including 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 catalytic layer containing MOF into the polyurethane adhesive solution respectively, and stir evenly at 20 - 30 °C and 300 - 400 r / min to obtain a cationic casting solution, an anionic casting solution, and an intermediate catalytic layer solution containing MOF respectively;

[0027] S2. Uniformly coat the cationic casting solution on the base membrane and dry it to obtain a cation exchange membrane layer;

[0028] S3. Uniformly coat the cation exchange membrane layer with an intermediate catalytic layer solution containing MOF, and after drying, obtain a cation exchange membrane layer / intermediate catalytic layer containing MOF;

[0029] S4. Uniformly coat the side of the intermediate catalytic layer containing MOF in the cation exchange membrane layer / intermediate catalytic layer containing MOF with an anion casting solution, and after drying, obtain a bipolar membrane.

[0030] In the present invention, the raw materials for preparing the anode membrane, the raw materials for preparing the cathode membrane, and the raw materials for preparing the intermediate catalytic layer containing MOF are respectively added to a polyurethane molten solution with strong adhesion, and heated and melted at 20 - 30 °C to obtain a cation casting solution, an intermediate catalytic layer solution containing MOF, and an anion casting solution with uniform composition; then the cation casting solution, the intermediate catalytic layer solution containing MOF, and the anion casting solution are sequentially coated on the base membrane to obtain a bipolar membrane, and dried, so that the three layers of membranes are tightly combined, have strong adhesion, are not easily separated and peeled off, and the obtained bipolar membrane has good quality and long service life.

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

[0032] In the present invention, it is not necessary to add an organic solvent to dissolve the polyurethane resin, but the polyurethane is melted into a solution, which can stably exist as a liquid at room temperature and be used as an adhesive; then the polyurethane molten solution and the raw materials for preparing the anode membrane, the raw materials for preparing the cathode membrane, and the raw materials for preparing the intermediate catalytic layer containing MOF are stirred at room temperature (20 - 30 °C) to form a solution with strong adhesion and uniform composition among them. This solution can stably exist at room temperature without solidifying, and the temperature at room temperature can ensure the uniform distribution of the cathode resin and the anode resin in the polyurethane adhesive, while not destroying the structure of the cathode and anode resins themselves and maintaining their own characteristics. Preparing the polyurethane resin and the cation and anion resins in two steps can maintain the integrity of the structures 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 characteristics such as high strength, tear resistance, and wear resistance. After melting, it has strong adhesion and is suitable as an adhesive for the bipolar membrane, and is not easily separated and peeled off.

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

[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 membrane in the polyurethane adhesive solution is 10%-20%;

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

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

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

[0040] Preferably, the drying temperature is 50-80 °C. This drying temperature can volatilize the polyurethane adhesive solution used as a solvent faster and obtain a uniform membrane surface.

[0041] In a third aspect, the present invention also provides the application of the above bipolar membrane or the bipolar membrane obtained by the above preparation method of the bipolar membrane in electrolytic cells, fuel cells, and the field of bipolar membrane electrodialysis.

[0042] The bipolar membrane of the present invention is universal 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 It is a schematic diagram of the structure of the bipolar membrane 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 It is a current-voltage test result diagram of the bipolar membranes prepared in Example 1 and Comparative Examples 1-5;

[0046] Figure 3 It is a current-voltage test result diagram of the bipolar membranes prepared in Examples 1-3;

[0047] Figure 4 It is a stability test result diagram of the bipolar membrane prepared in Example 1. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0048] In order to make the objectives, technical solutions and advantages of the present invention more clear and understandable, the present invention will be further described in detail below in conjunction with 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 "upper", "lower", "left" and "right" defined in the present invention are limited to the views shown in the accompanying drawings of the specification of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present invention.

[0049] The present invention provides a bipolar membrane containing a middle catalytic layer of MOF, and its structural schematic diagram is as Figure 1 shown.

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

[0051] I. The strong acid type sulfonic acid group cation exchange resin (001×7 strong acid cation exchange resin), carboxyl cation exchange resin (D113 macroporous weak acid cation resin), phosphonic acid group cation exchange resin (D418 cation resin, which is a styrene-divinylbenzene copolymer with a special macroporous structure and has a weak acid amino phosphonic acid group -CH2NHCH2PO3-), strong base quaternary ammonium type II anion exchange resin (D202 macroporous strong base type II styrene-based anion exchange resin), strong base 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 weak base anion exchange resin) used in the present invention can all be commercially purchased.

[0052] II. The catalysts used in the present invention are all prepared by existing technologies. Among them,

[0053] The preparation method of NiFeLDH is as follows:

[0054] The nickel foam (2 cm 2 ) is ultrasonically treated with hydrochloric acid solution, absolute ethanol and deionized water for 15 min respectively, and dried at 50 °C for 6 h; 1 mmol of Ni(NO 3 ) 2 ·9H 20 mmol of Fe(NO)·9HO and 5 mmol of urea were dissolved in 30 ml of ethylene / deionized water (volume ratio 1:1) to obtain a mixed solution; the mixed solution was transferred to a 50 ml polytetrafluoro reaction kettle, a piece of treated nickel foam was added, and the reaction was carried out at 120 °C for 12 h. After cooling to room temperature, the nickel foam was removed, and it was washed several times with deionized water and absolute ethanol respectively, and then dried at 50 °C for 5 h to obtain NiFeLDH.

[0055] The preparation method of CoFeLDH is as follows:

[0056] 1) Boil deionized water and maintain a constant boil for 5 min, then cool to room temperature for standby; weigh 0.7138 g of CoCl 2 ·6H 2 O, 0.2982 g of FeCl 2 ·4H 2 O, 0.3963 g of ascorbic acid, and 3.7851 g of hexamethylenetetramine with an electronic balance.

[0057] 2) Dissolve the weighed CoCl 2 ·6H 2 O and FeCl 2 ·4H 2 O in 100 mL of standby water at room temperature respectively to obtain a mixed solution; under the same conditions, dissolve ascorbic acid and hexamethylenetetramine in 50 mL of standby water respectively to obtain their respective aqueous solutions.

[0058] 3) Mix the mixed solution, the aqueous solutions of ascorbic acid and hexamethylenetetramine in a three-necked flask in sequence, with the latter added slowly to the former each time. Finally, react in an oil bath at 110 °C for 4 h. The reaction system is in contact with air, and then cool to 25 °C; wash with deionized water, centrifuge, and dry in vacuum.

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

[0060] Take 50 ml of 0.1 mol FeCl 3 aqueous solution and transfer it to a reaction kettle, react at 140 °C for 2 h respectively, and obtain β-FeOOH after washing, high-speed centrifugation, and vacuum drying.

[0061] MOF catalysts: Ni-Co-Fe-MOF and Cu-MOF were prepared by the existing technology.

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

[0063] Pretreatment of nickel foam: Nickel foam (2 cm 2Wash them ultrasonically with dilute hydrochloric acid, ethanol, and deionized water for 15 min respectively, and dry them for later use. Dissolve 11 mg of iron nitrate and 24 mg of cobalt nitrate in 3 mL of deionized water, stir evenly, then add the pretreated nickel foam, and let it stand at room temperature for 1 h to obtain the NiCoFe-LDH mixture. Add 30 mg of dipotassium 2,6-naphthalenedicarboxylate to the mixture, shake until completely dissolved, transfer it to an oven, react at 60 °C for 20 h, obtain the product, wash it with ethanol and deionized water, and dry it to obtain Ni-Co-Fe-MOF.

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

[0065] 1. Weigh 0.0051 mol of Zn(NO 3 ) 2 ·6H 2 O, 1.62×10 -4 mol of Cu(NO 3 ) 2 ·3H 2 O, add them to 50 mL of DMF and mix evenly. At room temperature, add 0.0038 mol of terephthalic acid to the mixed system, stir until the solid is completely dissolved; then add 2.75 mL of triethylamine, stir and react for 2 h to obtain a white solid, obtain the product, filter it by suction, and wash it 4 times with DMF during suction filtration to remove impurities. Then, put the obtained product into an oven at 65 °C and dry it for 5 h, and then grind it to obtain MOF-5(Cu), where MOF-5 contains 3% mass concentration of Cu.

[0066] 2. Place 3% Cu of MOF-5(Cu) in a tubular furnace, and heat it to 600 °C at a heating rate of 10 °C / min in an air atmosphere and calcine it at a constant temperature for 2 h to obtain the Cu-MOF catalyst.

[0067] The hydrogen evolution catalyst is purchased commercially. Among them, the Pt / C catalyst, CAS number: 7440-06-4; the AEM cathode catalyst, model: FAHC-S1.

[0068] Next, the present invention will be further elaborated in detail with specific examples.

[0069] Example 1

[0070] Step 1. The preparation method of the carbon-coated oxygen evolution catalyst / hydrogen evolution catalyst / MOF catalyst includes:

[0071] Mix carbon-coated material (graphite), oxygen evolution catalyst (NiFeLDH), hydrogen evolution catalyst (Pt / C catalyst, CAS No.: 7440-06-4), and MOF catalyst (Ni-Co-Fe-MOF) with a mass ratio of 10:30:30:70, and grind for 48 h to obtain a mixture. Then, place the mixture in a muffle furnace, keep it at 400 °C for heat treatment for 8 h, and cool to room temperature to obtain 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, as Figure 1 shown. The bipolar membrane is composed of a base film 1, an anode membrane 2, an intermediate catalytic layer 3 containing MOF, and a cathode membrane 4 from left to right.

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

[0074] The preparation raw materials of the anode membrane are composed of strongly acidic sulfonic group cation exchange resin (001×7 strong acidic cation exchange resin), carboxyl cation exchange resin (D113 macroporous weak acidic cation resin), and phosphonic acid group cation exchange resin (D418 cation resin) with a mass ratio of 55:30:25;

[0075] The preparation raw materials of the cathode membrane are composed of strongly basic quaternary ammonium type II anion exchange resin (D202 macroporous strong base type II styrene-based 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 weak basic anion exchange resin) with a mass ratio of 60:20:30.

[0076] Step 3. The embodiment of the present invention also provides a preparation method of the above bipolar membrane, including the following steps:

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

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

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

[0080] S4. Uniformly coat a 1% solution of the intermediate catalytic layer containing MOF on the cation exchange membrane layer, and dry it at 50 °C to obtain a cation exchange membrane layer / intermediate catalytic layer containing MOF with a thickness of 85.01 μm;

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

[0082] Example 2

[0083] Step 1. A preparation method of a carbon-coated oxygen evolution catalyst / hydrogen evolution catalyst / MOF catalyst, including:

[0084] Mix carbon-coated materials (carbon black), oxygen evolution catalysts (CoFeLDH), hydrogen evolution catalysts (AEM cathode catalyst, model: FAHC-S1), and MOF catalysts (Cu-MOF) with a mass ratio of 12:33:35:78, and grind for 48 h. Put the mixture into a muffle furnace, keep it at 500 °C for heat treatment for 9 h, and cool 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 with MOF. The bipolar membrane is composed of a base film 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 material of the intermediate catalytic layer containing MOF is: carbon-coated oxygen evolution catalyst / hydrogen evolution catalyst / MOF catalyst;

[0087] The preparation raw materials of the anode membrane are composed of a strong acid type sulfonic acid group cation exchange resin (001×7 strong acid cation exchange resin), a carboxyl cation exchange resin (D113 macroporous weak acid cation resin), and a phosphonic acid group cation exchange resin (D418 cation resin) with a mass ratio of 40:20:35;

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

[0089] Step 3. An embodiment of the present invention also provides a preparation method of a bipolar membrane, including 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 the preparation of the anode membrane, the raw materials for the preparation of the cathode membrane, and the raw materials for the preparation of the intermediate catalytic layer containing MOF respectively, and add them to the polyurethane adhesive solution. Stir evenly at 25°C and 400 r / min to obtain a 15% cationic casting solution, a 15% anionic casting solution, and a 3% intermediate catalytic layer solution containing MOF respectively.

[0092] S3. Uniformly coat the 15% cationic casting solution on the (polyurethane membrane) base membrane and dry it at 70°C to obtain a cation exchange membrane layer with a thickness of 100 μm.

[0093] S4. Uniformly coat the 1.5% intermediate catalytic layer solution containing MOF on the cation exchange membrane layer, and after drying, obtain a cation exchange membrane layer / intermediate catalytic layer containing MOF with a thickness of 100.02 μm.

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

[0095] Example 3

[0096] Step 1. The preparation method of the carbon-coated oxygen evolution catalyst / hydrogen evolution catalyst / MOF catalyst includes:

[0097] Mix the carbon-coated material (graphene), oxygen evolution catalyst (β-FeOOH), hydrogen evolution catalyst (Pt / C catalyst), and MOF catalyst (Ni-Co-Fe-MOF) with a mass ratio of 15:35:35:80, grind for 48 h to obtain a mixture. Then put the mixture into a muffle furnace, keep it at 600°C for heat treatment for 10 h, and cool to room temperature to obtain the carbon-coated oxygen evolution catalyst / hydrogen evolution catalyst / MOF catalyst.

[0098] Step 2. The present invention provides a bipolar membrane with an intermediate catalytic layer containing 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 material of the intermediate catalytic layer containing MOF is: carbon-coated oxygen evolution catalyst / hydrogen evolution catalyst / MOF catalyst;

[0100] The raw materials for preparing the anode membrane are composed of strongly acidic sulfonic group cation exchange resin (001×7 strongly acidic cation exchange resin), carboxyl cation exchange resin (D113 macroporous weakly acidic cation resin), and phosphonic acid group cation exchange resin (D418 cation resin) with a mass ratio of 50:25:25;

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

[0102] The embodiment of the present invention also provides a method for preparing a bipolar membrane, including 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 catalytic layer containing MOF respectively, add them to the polyurethane adhesive solution, and stir evenly at 30 °C and 300 r / min to obtain 20% cationic casting solution, 20% anionic casting solution, and 5% intermediate catalytic layer solution containing MOF respectively;

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

[0106] S3. Uniformly coat the intermediate catalytic layer solution containing MOF on the cation exchange membrane layer and dry it at 80 °C to obtain a cation exchange membrane layer / intermediate catalytic layer containing MOF with a thickness of 120.03 μm;

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

[0108] Comparative Example 1

[0109] In the bipolar membrane of this example, the raw materials for preparing the anode membrane are only acid-type sulfonic acid group cation exchange resin (001×7 strong acid cation exchange resin); the raw materials for preparing the cathode membrane are only strong base quaternary ammonium type II anion exchange resin (D202 macroporous strong base type II styrene-based anion exchange resin), and the other components are the same as those in Example 1. Among them, in the bipolar membrane, the concentration of the cation casting solution is 10%, the concentration of the anion casting solution is 10%, and the concentration of the intermediate catalytic layer solution containing MOF is 1%.

[0110] Comparative Example 2

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

[0112] The preparation method of the bipolar membrane in this example is the same as that in Example 1. Among them, in the bipolar membrane, the concentration of the cation casting solution is 10%, the concentration of the anion casting solution is 10%, and the concentration of the intermediate catalytic layer solution containing MOF is 1%.

[0113] Comparative Example 3

[0114] In the bipolar membrane of this example, the main raw material of the intermediate catalytic layer containing MOF is not carbon-coated, that is, it is formed by mixing and grinding NiFeLDH, Pt / C catalyst and Ni-CO-Fe-MOF with a mass ratio of 30:30:70 for 48 h, and the other components are the same as those in Example 1.

[0115] The preparation method of the bipolar membrane is the same as that in Example 1. Among them, in the bipolar membrane, the concentration of the cation casting solution is 10%, the concentration of the anion casting solution is 10%, and the concentration of the intermediate catalytic layer solution containing MOF is 1%.

[0116] Comparative Example 4

[0117] In the bipolar membrane of this example, 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 in Example 1. Among them, in the bipolar membrane, the concentration of the cation casting solution is 10%, the concentration of the anion casting solution is 10%, and the concentration of the intermediate catalytic layer solution containing MOF is 1%.

[0119] Comparative Example 5

[0120] In the bipolar membrane of this embodiment, the catalyst in the intermediate catalytic layer is a mixture of an oxygen evolution catalyst (NiFeLDH) and a hydrogen evolution catalyst (Pt / C catalyst, CAS number: 7440-06-4) at a ratio of 30:30, which is ground for 48 hours to obtain. The other components are the same as those in Embodiment 1.

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

[0122] Effect Example 1

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

[0124] The bipolar membranes prepared in Embodiment 1 and Comparative Examples 1-5 are subjected to current-voltage curve testing (I-V): Current-voltage curve testing: A four-chamber system membrane stack (+ proton exchange membrane | bipolar membrane | proton exchange membrane | -) is connected to an electrochemical workstation. The Linear Sweep Voltammetry Galvanostatic program is selected, and a 1 mol / L sodium sulfate solution is used in both the electrode chamber and the acid-base chamber. During the test, the current increase rate is 2 mA / s, and the current test range is 0-0.2 A.

[0125] Figure 2 It is a graph of the current-voltage test results of the bipolar membranes prepared in Embodiment 1 and Comparative Examples 1-5.

[0126] From Figure 2 it can be seen that for the bipolar membranes of Embodiment 1 and Comparative Examples 1-5, as the current increases, the transmembrane voltage also gradually increases. When the current density is 50 mA / cm 2 , the transmembrane voltages of Comparative Examples 1-5 are 5.5 V, 4.15 V, 1.79 V, 3.16 V, and 3.57 V respectively, and the transmembrane voltage of Embodiment 1 is 0.48 V. It can be seen that the transmembrane voltage of the bipolar membrane of Embodiment 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 Embodiment 1 of the present invention is superior to that of Comparative Examples 1-5. Compared with Comparative Examples 1-5, the bipolar membrane of Embodiment 1 has a lower transmembrane voltage at the same current density (20 mA / cm 2) In Example 1, the hydrolysis voltage is the smallest, indicating that the bipolar membrane in Example 1 of the present invention can effectively reduce the voltage required for hydrolysis dissociation, has better hydrolysis dissociation efficiency, and the hydrolysis dissociation performance of the bipolar membranes in Comparative Examples 1-5 is inferior to that of Example 1. At the same voltage (0.40V), the current density of Example 1 is higher than that of Comparative Examples 1-5. According to the principle that the higher the current density, the higher the ion selectivity of the bipolar membrane, it can be inferred that the ion selectivity of the bipolar membrane in Example 1 of the present invention is higher than that of Comparative Examples 1-5.

[0127] In summary, compared with Comparative Examples 1-5, the formulation and composition of each film layer of the electrode membrane in Example 1 have the best effect. The absence of any component or composition in Comparative Examples 1-5 results in the performance of the obtained bipolar membrane not reaching the effect of Example 1.

[0128] Figure 3 It is a current-voltage test result graph 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 close and the differences are not significant.

[0130] Effect Example 2

[0131] 1. Bipolar membrane stability test

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

[0133] Figure 4 It is a stability test result graph of the bipolar membrane prepared in Example 1 at a current density of 100mA / cm 2 .

[0134] As Figure 4 shown, during the 10h-long test process, the transmembrane voltage of the bipolar membrane prepared in Example 1 changes very little (the transmembrane voltage rises from 0.52V to 0.54V: the actual transmembrane voltage rise rate is 3.8%). The hydrolysis dissociation voltage of the bipolar membrane in Example 1 is relatively stable, indicating the stability of the bipolar membrane of the present invention and its ability to operate for a long time.

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

[0136] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, or improvements made within the spirit and principles of the present invention shall be included within the protection scope 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 strongly alkaline quaternary ammonium type II anion exchange resin, strongly alkaline quaternary ammonium type I anion exchange resin and chlorine type anion exchange resin in a mass ratio of (50-60):(15-25):(20-30).

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: mixing a carbon-coated material, an oxygen evolution catalyst, a hydrogen evolution catalyst and a MOF catalyst, and heat-treating the mixture.

3. The bipolar membrane according to claim 2, characterized in that 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).

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

5. The bipolar membrane according to any one of claims 2 to 4, characterized in that The carbon coating material includes any one of graphite, carbon black and graphene; and / or The oxygen evolution catalyst comprises: any one of NiFeLDH, CoFeLDH and β-FeOOH; and / or The hydrogen evolution catalyst comprises: a Pt / C catalyst or an AEM cathode catalyst; and / or The MOF catalyst includes: Ni-Co-Fe-MOF or Cu-MOF.

6. The method for preparing a bipolar membrane according to any one of claims 1 to 5, characterized in that: 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 bonding 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; S2, uniformly coating the cationic membrane 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, uniformly coating anion casting solution on one side of the cation exchange membrane layer / MOF-containing intermediate catalyst layer, and drying to obtain a bipolar membrane.

7. The method for preparing a bipolar membrane according to claim 6, characterized in that: 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.

8. The method for preparing a bipolar membrane according to claim 6 or 7, 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 material for preparing the intermediate catalytic layer containing MOF accounts 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 um; 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.

9. The method for preparing a bipolar membrane according to claim 6, characterized in that: The drying temperature is 50-80°C.

10. Use of the bipolar membrane according to any one of claims 1 to 5 or the bipolar membrane prepared by the method for preparing a bipolar membrane according to any one of claims 6 to 9 in the fields of electrolytic cells, fuel cells, and bipolar membrane electrodialysis.

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