Conjugated branched anion exchange membrane, preparation method and application

Abstract

The application relates to the technical field of alkaline water electrolysis cells, and particularly discloses a conjugated branched anion exchange membrane, a preparation method and application. A series of conjugated branched anionic polymers are prepared by changing the types and proportions of monomers, solvents and catalysts, and the conjugated branched anionic polymers are used as core components of anion exchange membranes for alkaline electrolysis cells. The synthesis strategy is simple and effective, the preparation cost is low, the performance is excellent, the strategy is highly universal, the industrial production is facilitated, and the application potential is large.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of alkaline water electrolysis cell, and particularly relates to a conjugated branched anion exchange membrane, a preparation method and application. BACKGROUND

[0002] Developing green hydrogen energy is crucial for optimizing the current energy structure and realizing human sustainable growth. Electrolytic water hydrogen production technology combined with renewable energy will be the main way to produce green hydrogen energy and will also occupy most of the hydrogen energy production market in the future. Alkaline water hydrogen production electrolysis cell does not use noble metal resources in the manufacturing process, has low cost, and also has the advantage of long service life, which makes alkaline water hydrogen production become the main technical route of the current electrolytic water hydrogen production market. As a key component of alkaline electrolytic water device, the diaphragm plays a role in isolating hydrogen and oxygen and transferring ions in the electrolysis cell. An ideal diaphragm should have high gas tightness, high electrical conductivity, and excellent dimensional stability and alkali resistance. The diaphragm on the market at present is mainly Zirfon series membrane developed by Agfa Company in Belgium and PPS cloth of Toray. However, these two kinds of membranes themselves have very high surface resistance, which makes the energy consumption of electrolytic water hydrogen production too high, thereby causing the problem of high hydrogen production cost, which limits the further promotion of alkaline electrolytic water technology.

[0003] Anion exchange membrane electrolysis cell (AEMWE) is a new electrolytic water technology. Among them, the anion exchange membrane (AEM) used is a kind of polymer membrane containing basic active groups and having selective permeability to anions. The dense homogeneous membrane can effectively prevent the mutual penetration of hydrogen and oxygen at both poles, and the excellent ion conduction performance gives AEMWE a high current density. For example, AEMWE based on polyaryl piperidine AEM has a current density of up to 1600 mA cm -2 (Lee, Y. M. Energy Environ. Sci., 2021, 14, 6338-6348), showing good application prospect. After years of effort, researchers have gradually developed a series of AEMs with excellent comprehensive performance, but most of the AEMs reported in the literature often need to use expensive transition metal catalysts or high-cost highly corrosive superacid catalysts in the preparation of polymer monomers, polymerization reaction or polymer post-functionalization process, which inevitably causes the increase of the preparation cost of anion exchange membrane, greatly limiting the further promotion and application of AEMWE. Therefore, developing simple and effective synthesis strategies to prepare low-cost anion exchange membrane materials with excellent performance is still the focus and difficulty of current research. SUMMARY

[0004] In view of the deficiencies of the prior art, the purpose of the present application is to provide a conjugated branched anion exchange membrane, a preparation method and application, and an electrolytic cell constructed by the membrane exhibits excellent water electrolysis performance.

[0005] To achieve this purpose, the present application adopts the following technical solutions:

[0006] A conjugated branched polymer, the general structure is as follows:

[0007]

[0008] Wherein x is the branching degree (%), x is in the range of 1-20; R is one or more of the following structures:

[0009]

[0010] M structure is one or more of the following:

[0011] Q=F, Cl, Br, I

[0012]

[0013] A preparation method of a conjugated branched anion exchange membrane, characterized in that it comprises the following steps:

[0014] (1) Polymer preparation: under the inert gas atmosphere, -10-20 DEG C, the catalyst is placed in the organic solvent a and stirred for 10-120 min, then the polymer monomer mixture is added dropwise to start the reaction. After 24-144 h of reaction, the polymer precursor is obtained by extraction with alkaline solution. The polymer precursor is dissolved in organic solvent b, and amine solution is added under inert atmosphere, and the polymer is precipitated under organic solvent after 24-72 h of reaction at 20-80 DEG C. After water washing 2-8 times, the pure polymer product is obtained by vacuum drying.

[0015] (2) The polymer obtained in step (1) is dissolved in organic solvent b. After filtration and degassing, the film is poured to obtain the conjugated branched anion exchange membrane.

[0016] The inert atmosphere is nitrogen or argon;

[0017] The catalyst is one or more of the following: transition metals and their corresponding oxides, halides; further preferably copper, zinc, copper-zinc alloy, magnesium, zinc-silver alloy, titanium trichloride, titanium tetrachloride, etc.

[0018] The polymerization monomer mixture is selected from a mixture of di-, tri-functional acyl chloride monomers, wherein the di-functional acyl chloride monomers include, but are not limited to, terephthaloyl dichloride, diphenyl dicarboxylic acid dichloride, and the tri-functional acyl chloride monomers include, but are not limited to, trimesoyl chloride, 1,3,5-tris(p-formylchloride) benzene, 3,4',5-triacid chloride-1,1-biphenyl, tris(4-formylchloride phenyl) phosphine. The addition of the tri-functional acyl chloride monomers significantly improves the electrochemical performance of the membrane material.

[0019] The polymerization monomer mixture accounts for 0.1-15% of the molar ratio of the entire system; if the molar ratio is too high, it will cause gelation and cannot obtain a soluble polymer.

[0020] The basic solution in step (1) is one or more aqueous solutions of potassium hydroxide, sodium hydroxide, sodium carbonate, and potassium carbonate.

[0021] The organic solvent a in step (1) is one or more mixtures of methanol, ethanol, N,N'-dimethylformamide, dimethyl sulfoxide, diethyl ether, acetone, tetrahydrofuran, ethyl acetate, dichloromethane, chloroform, carbon tetrachloride, and petroleum ether.

[0022] The amine solution in step (1) includes, but is not limited to, aqueous trimethylamine.

[0023] The organic solvent b in steps (1) and (2) is one or more solvents of N-methylpyrrolidone, N,N'-dimethylformamide, N,N'-dimethylacetamide, and dimethyl sulfoxide mixed in any ratio.

[0024] The application also proposes the application of the anion exchange membrane in an alkaline electrolytic water device, including the following steps:

[0025] (1) Membrane electrode preparation: dissolving the conjugated branched anion exchange membrane in a polar organic solvent to obtain an ionomer solution; uniformly dispersing the catalyst Pt / C and IrO2 in a dispersant to prepare a catalyst solution; taking the ionomer solution and the catalyst solution respectively, mixing them uniformly, and uniformly spraying them on both sides of the conjugated branched anion exchange membrane to prepare a membrane electrode; and then performing ion exchange in an alkaline solution.

[0026] (2) Assembling the electrolytic water device: clamping the membrane electrode between the cathode and the anode to assemble the electrolytic water device.

[0027] The polar organic solvent includes NMP, DMF, DMSO, DMAc, etc.

[0028] As preferred, the application of the anion exchange membrane in the alkaline electrolytic water device includes the following steps:

[0029] (1) Membrane electrode preparation: The anion exchange membrane described above was dissolved in DMSO (4 wt%) as an ionomer solution. Then a certain amount of Pt / C and IrO2 catalyst (2 mg cm -2 ) was weighed and a catalyst solution was prepared by adding water and isopropanol solution as a dispersant, and it was uniformly dispersed by magnetic stirring and ultrasonic crushing. Finally, the ionomer solution was added and ultrasonically treated again to make it uniform, and it was uniformly sprayed on both sides of the conjugated branched anion exchange membrane to prepare a membrane electrode. After the solvent evaporated, it was immersed in 1M KOH solution for ion exchange for 48h;

[0030] (2) Assembly of water electrolysis device: the membrane electrode was clamped between the anode and cathode to assemble the water electrolysis device;

[0031] (3) Water electrolysis performance test: electrochemical test was carried out by immersing in 1M KOH solution at the anode and cathode, and the temperature was kept at 80℃. The polarization curve was obtained by measuring the cell voltage under different current densities.

[0032] The beneficial results of the present application are:

[0033] (1) The conjugated branched polymer-based anion exchange membrane of the present application adds trifunctional reactants to the polymerization monomers, significantly improves the electrochemical performance of the membrane, has good adaptability to industrial alkaline electrolytic cells, and also has good dimensional stability; The polymer prepared by the present application has good solubility and can be dissolved in polar organic solvents such as NMP, DMF, DMSO, DMAc, etc. at room temperature.

[0034] (2) The present application has the characteristics of strong universality, and can realize the preparation of high-performance conjugated branched polymers under the condition of reasonable regulation and control of the types and ratio of di- and tri-functional reactants.

[0035] (3) The present application reduces the preparation cost of anion exchange membrane, and the synthesis strategy is simple and effective, which is more conducive to industrialization promotion and use. BRIEF DESCRIPTION OF DRAWINGS

[0036] Figure 1 Polarization curves on alkaline water electrolysis devices equipped with polymer membranes of Examples 1-5 and Comparative Example 1. DETAILED DESCRIPTION

[0037] The present application is further described in conjunction with examples and drawings, and the examples are only used to explain the present application, and the present application is not limited to only the examples. Therefore, according to the claims of the present application, simple modifications and changes of the examples or related types of conjugated branched polymers are within the scope of the technical solutions of the present application.

[0038] Example 1

[0039] A method for preparing a conjugated branched anion exchange membrane, comprising the following steps:

[0040] (1) 24 g of zinc copper alloy was dispersed in 140 mL of tetrahydrofuran at 0°C, 15 mL of titanium tetrachloride was slowly added dropwise, after mixing evenly, terephthaloyl chloride (5 g) and trimesoyl chloride (0.3 g) were added, and the reaction was carried out for 120 h, then the reaction was quenched with 10% potassium carbonate aqueous solution, after filtration and extraction, the solvent was evaporated to obtain a polymer precursor. The polymer precursor was dissolved in NMP (10 wt%) and 2M trimethylamine THF solution was added under nitrogen atmosphere, and the reaction was carried out at room temperature for 72 h, the polymer was precipitated with ethyl acetate, and after water washing for 8 times, vacuum drying was carried out to obtain a conjugated branched anion polymer.

[0041] (2) The dried polymer was dissolved in DMAc solution (solid content: 6%) to prepare a film-forming solution, which was filtered and degassed, then poured on a glass plate and leveled with a scraper. After drying at 80°C for 6 h, the film was taken off to obtain a conjugated branched anion exchange membrane with a thickness of about 60 μm.

[0042] Example 2

[0043] A method for preparing a conjugated branched anion exchange membrane, comprising the following steps:

[0044] (1) 24 g of zinc was dispersed in 120 mL of tetrahydrofuran at -10°C, 15 mL of titanium tetrachloride was slowly added dropwise, after mixing evenly, terephthaloyl chloride (5 g) and tris(4-formylchlorobenzyl) phosphine (0.5 g) were added, and the reaction was carried out for 100 h, then the reaction was quenched with 10% potassium carbonate aqueous solution, after filtration and extraction, the solvent was evaporated to obtain a polymer precursor. The polymer precursor was dissolved in NMP (10 wt%), and trimethylamine was added under nitrogen atmosphere, and the reaction was carried out at room temperature for 72 h, the polymer was precipitated with ethyl acetate, and after water washing for 8 times, vacuum drying was carried out to obtain a conjugated branched anion polymer.

[0045] (2) The dried polymer was dissolved in DMAc solution (solid content: 4%) to prepare a film-forming solution, which was filtered and degassed, then poured on a glass plate and leveled with a scraper. After drying at 60°C for 6 h, vacuum drying was carried out at 80°C for 3 h, the film was taken off to obtain a conjugated branched anion exchange membrane with a thickness of about 63 μm.

[0046] Example 3

[0047] A method for preparing a conjugated branched anion exchange membrane, comprising the following steps:

[0048] (1) 18 g of magnesium was dispersed in 100 mL of tetrahydrofuran at 0°C, 18 g of titanium trichloride was slowly added dropwise, after the mixture was uniformly mixed, terephthaloyl chloride (5 g) and tris(4-formylchlorophenyl)phosphine (0.3 g) were added, and the reaction was carried out for 100 h, then the reaction was quenched with 10% potassium carbonate aqueous solution, after filtration and extraction, the solvent was evaporated to obtain a polymer precursor. The polymer precursor was dissolved in NMP (10 wt%) and triethylamine was added under nitrogen atmosphere, and the reaction was carried out for 72 h at room temperature, the polymer was precipitated with ethyl acetate, and after being washed with water for 8 times, vacuum drying was carried out to obtain a conjugated branched anion polymer.

[0049] (2) The dried polymer was dissolved in a DMAc solution (solid content: 8%) to prepare a film-forming solution, after filtration and degassing, the solution was cast on a glass plate and leveled with a doctor blade. After drying at 60°C for 3 h, vacuum drying was carried out at 80°C for 3 h, the film was taken off to obtain a conjugated branched anion exchange membrane with a thickness of about 67 μm.

[0050] Example 4

[0051] A method for preparing a conjugated branched anion exchange membrane, comprising the following steps:

[0052] (1) 10 g of zinc was dispersed in 90 mL of tetrahydrofuran at 20°C, 18 g of titanium trichloride was slowly added dropwise, after the mixture was uniformly mixed, diphenyl terephthaloyl chloride (8 g) and 3,4',5-triacetyl chloride-1,1-diphenyl (1 g) were added, and the reaction was carried out for 100 h, then the reaction was quenched with 10% potassium carbonate aqueous solution, after filtration and extraction, the solvent was evaporated to obtain a polymer precursor. The polymer precursor was dissolved in NMP (10 wt%) and triethylamine was added under nitrogen atmosphere, and the reaction was carried out for 48 h at room temperature, the polymer was precipitated with ethyl acetate, and after being washed with water for 8 times, vacuum drying was carried out to obtain a conjugated branched anion polymer.

[0053] (2) The dried polymer was dissolved in a DMAc solution (solid content: 4%) to prepare a film-forming solution, after filtration and degassing, the solution was cast on a glass plate and leveled with a doctor blade. After drying at 60°C for 6 h, vacuum drying was carried out at 80°C for 6 h, the film was taken off to obtain a conjugated branched anion exchange membrane with a thickness of about 58 μm.

[0054] Example 5

[0055] A method for preparing a conjugated branched anion exchange membrane, comprising the following steps:

[0056] (1) 15 g of zinc-silver alloy was dispersed in 150 mL of tetrahydrofuran at 0°C, 15 mL of titanium tetrachloride was slowly added dropwise, after the mixture was uniformly mixed, diphenyl dicarboxylic acid chloride (8 g) and 1,3,5-tris (p-formyl chloride) benzene (0.8 g) were added, and after reacting for 240 h, the reaction was quenched with 10% aqueous potassium carbonate solution, and after filtration and extraction, the solvent was evaporated to obtain a polymer precursor. The polymer precursor was dissolved in NMP (10 wt%), and trimethylamine was added under a nitrogen atmosphere, and reacted at room temperature for 48 h, and the polymer was precipitated with ethyl acetate, washed with water 8 times, and vacuum dried to obtain a conjugated branched anion polymer.

[0057] (2) The dried polymer was dissolved in a DMAc solution (solid content: 6%) to prepare a film-forming solution, which was filtered and degassed, and then cast on a glass plate and leveled with a doctor blade. After drying at 60°C for 6 h and vacuum drying at 80°C for 6 h, the film was removed to obtain a conjugated branched anion exchange membrane with a thickness of about 57 μm.

[0058] Comparative Examples 1 and 2 are FuMA-Tech anion exchange membranes FAA-3-PK-75 and FAM purchased on the market.

[0059] Example 6

[0060] The conjugated branched anion exchange membranes prepared in Examples 1-5 and the FuMA-Tech anion exchange membranes FAA-3-PK-75 and FAM of Comparative Examples 1 and 2 were tested for ion exchange capacity (IEC), swelling rate, water absorption rate, and ionic conductivity. The ion exchange capacity (IEC) was calculated by precipitation titration to obtain the anion content in a certain mass of anion polymer membrane, thereby obtaining the IEC of the anion polymer membrane. The water absorption and swelling were tested by immersing the membrane in water for 24 h, and then testing the percentage difference in mass and size from the initial state. The ionic conductivity was measured using a Shanghai Chenhua electrochemical test system, using a two-electrode alternating current impedance method to measure the ionic conductivity of the anion polymer membrane in a fully wet state. The specific results are shown in Table 1.

[0061] Table 1. IEC, conductivity, water absorption rate, and swelling rate of Examples 1-5, Comparative Examples 1 and 2 (all measured at 80°C)

[0062] IEC (mmol / g) Swelling ratio (%) Water absorption ratio (%) Conductivity (mS cm -1 )]]> Example 1 2.05 7 39 125 Example 2 2.08 7 43 130 Example 3 2.08 8 42 128 Example 4 2.1 11 45 131 Example 5 2.03 6 38 119 Comparative Example 1 1.24 16.7 33 93 Comparative Example 2 1.37 21 37 109

[0063] Table 1 shows that the conjugated branched anion exchange membranes prepared in the present application have better dimensional stability and higher conductivity than commercially available products, meeting the needs of alkaline water electrolysis.

[0064] Example 7

[0065] The conjugated branched anion exchange membranes obtained in Examples 1-5 and the FuMA-Tech anion exchange membrane FAA-3-PK-75 of Comparative Example 1 were used in an alkaline water electrolysis tank. The specific steps are as follows:

[0066] (1) Preparation of membrane electrode assembly for water electrolysis device:

[0067] Anion exchange membrane was dissolved in DMSO (4 wt%) to prepare an ionomer solution. Then, a certain amount of Pt / C and IrO2 catalyst (2 mg cm⁻¹) was weighed out. -2 A catalyst ink was prepared by adding water and isopropanol solution as dispersants, and then dispersing it uniformly by magnetic stirring and ultrasonic crushing. Finally, an ionomer solution was added and ultrasonically treated again to ensure uniformity. This mixture was then uniformly sprayed onto both sides of a conjugated branched anion exchange membrane to form a membrane electrode. After the solvent evaporated, the electrode was immersed in a 1M KOH solution for ion exchange for 48 hours.

[0068] (2) Water electrolysis performance test: The water electrolysis device was assembled by clamping the membrane electrode between the anode and cathode. Electrochemical tests were conducted by immersing the anode and cathode in a 1M KOH solution at a temperature maintained at 80℃. Polarization curves were obtained by measuring the battery voltage at different current densities.

[0069] Appendix Figure 1 The figures show the polarization curves of the conjugated branched anion exchange membranes prepared in Examples 1-5 and the FuMA-Tech anion exchange membrane FAA-3-PK-75 of Comparative Example 1 in an alkaline water electrolysis device. It can be seen that the electrolyzers assembled with the membranes prepared in Examples 1-5 exhibit significantly improved water electrolysis performance at 500 mA / cm². -2 Its voltage is as low as 1.53V, which is significantly better than the level of commercially available products.

[0070] While the foregoing examples partially illustrate the content of this invention, the invention is not limited to the monomers described in the examples; that is, the description of the foregoing examples is not intended to limit the invention. Those skilled in the art should understand that improvements to this invention, equivalent substitutions of the raw materials used in the product of this invention, the addition of auxiliary components, or direct or indirect applications in other related technical fields should all be included within the scope of protection of this invention.

Claims

1. A conjugated branched anion exchange membrane, characterized in that, A conjugated branched polymer is dissolved in an organic solvent, filtered, degassed, and then cast. The resulting membrane is dried at 80°C for 6 hours to form a film, or first dried at 60°C for 6 hours and then vacuum-dried at 80°C for 3 hours to form a film, or first dried at 60°C for 3 hours and then vacuum-dried at 80°C for 3 hours to form a film, thus obtaining the conjugated branched anion exchange membrane. The structural formula of the conjugated branched polymer is as follows: Where x ranges from 1 to 20; R is one or both of the following: M is Where Q = Cl.

2. A method for preparing the conjugated branched anion exchange membrane according to claim 1, characterized in that, Includes the following steps: Under an inert atmosphere and at -10 to -20°C, the catalyst is placed in organic solvent a and stirred for 10 to 120 minutes, and then the mixture of polymerizable monomers is added dropwise to start the reaction. The reaction was quenched with an alkaline solution after 24-144 hours, followed by extraction to obtain the polymer precursor. The polymer precursor was dissolved in organic solvent b, and an amine solution was added under an inert atmosphere. The reaction was carried out at 20-80°C for 24-72 hours. The polymer was precipitated out by the organic solvent, washed with water 2-8 times, and then vacuum dried to obtain the polymer. The polymer is dissolved in organic solvent b, filtered, degassed, and then cast into a membrane to obtain the conjugated branched anion exchange membrane.

3. The method for preparing the conjugated branched anion exchange membrane according to claim 2, characterized in that, The inert atmosphere is nitrogen or argon.

4. The method for preparing the conjugated branched anion exchange membrane according to claim 2, characterized in that, The catalyst is titanium trichloride or titanium tetrachloride.

5. The method for preparing the conjugated branched anion exchange membrane according to claim 2, characterized in that, The organic solvent a is one or more of methanol, ethanol, N,N'-dimethylformamide, dimethyl sulfoxide, diethyl ether, acetone, tetrahydrofuran, ethyl acetate, dichloromethane, chloroform, carbon tetrachloride, and petroleum ether; the organic solvent b is one or more of N-methylpyrrolidone, N,N'-dimethylformamide, N,N'-dimethylacetamide, and dimethyl sulfoxide mixed in any proportion.

6. The method for preparing the conjugated branched anion exchange membrane according to claim 2, characterized in that, The monomer mixture is a mixture of di- and tri-functional acyl chloride monomers.

7. The method for preparing the conjugated branched anion exchange membrane according to claim 6, characterized in that, The difunctional acyl chloride monomer is terephthaloyl chloride; the trifunctional acyl chloride monomer is selected from one or two of pyromellitic tricarboxylic acid chloride and tris(4-carboxyphenyl)phosphine.

8. The method for preparing the conjugated branched anion exchange membrane according to claim 2, characterized in that, The alkaline solution is an aqueous solution of one or more of potassium hydroxide, sodium hydroxide, sodium carbonate, and potassium carbonate; the amine solution is an aqueous solution of trimethylamine.

9. An application of a conjugated branched anion exchange membrane, characterized in that, The conjugated branched anion exchange membrane is the conjugated branched anion exchange membrane of claim 1, or the conjugated branched anion exchange membrane prepared by the preparation method of any one of claims 2-8. The conjugated branched anion exchange membrane is used for alkaline water electrolysis to produce hydrogen.

10. The application of the anion exchange membrane according to claim 9, characterized in that, The application of the conjugated branched anion exchange membrane in alkaline water electrolysis for hydrogen production includes the following steps: (1) Membrane electrode preparation: The conjugated branched anion exchange membrane was dissolved in a polar organic solvent to obtain an ionomer solution; the catalysts Pt / C and IrO2 were uniformly dispersed in a dispersant to prepare a catalyst solution; the ionomer solution and the catalyst solution were taken separately, mixed evenly, and then uniformly sprayed onto both sides of the conjugated branched anion exchange membrane to prepare a membrane electrode; then ion exchange was carried out in an alkaline solution. (2) Assemble the water electrolysis device: The membrane electrode is sandwiched between the anode and cathode to assemble the water electrolysis device.

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