Preparation method and application of branched polyarylate indigo ion exchange membrane

Abstract

The application discloses a preparation method and application of a branched polyarylide ion exchange membrane, and comprises the following steps: preparing a branched polyarylide high polymer by using p-terphenyl, diphenylethane, triphenylmethane and indigo; preparing 6-bromoalkyl-1-methylpiperidine monomers by using 1,3-dibromopropane and N-methylpiperidine; after reaction of the branched polyarylide high polymer, the 6-bromoalkyl-1-methylpiperidine monomers and K2CO3, pouring into ethyl acetate, filtering and drying, piperidine functionalized branched polyarylide high polymer is obtained; after dissolving the piperidine functionalized high polymer in N-methylpyrrolidone, casting on a glass plate, drying into a film, soaking in a KOH solution, a branched polyarylide ion exchange membrane is obtained. − The branched polyarylide ion exchange membrane has excellent OH conductivity, and meets the application requirement of anion exchange membrane electrolysis water.

Description

Technical Field

[0001] This invention belongs to the technical field of anion exchange membranes for organic synthesis and water electrolysis. More specifically, this invention relates to a method for preparing and applying a branched polyaryl indigo ion exchange membrane. Background Technology

[0002] With the rapid depletion of global fossil fuels, the greenhouse effect and environmental pollution are becoming increasingly serious, making the reduction of dependence on carbon-based fossil fuels an unprecedentedly urgent task. Hydrogen, with its advantages of high energy density, zero carbon emissions, and non-toxicity, is an ideal energy carrier for building a global renewable energy system. However, over 95% of the world's H2 comes from high-temperature reforming of natural gas, a non-renewable, high-carbon-emission process that produces 7.0 kg of CO2 for every 1.0 kg of H2 produced. Hydrogen production through water electrolysis not only addresses the intermittency of solar and wind power but also improves the utilization rate of renewable energy, making it one of the most promising solutions currently available.

[0003] Based on the operating environment of the electrolyzer and the type of membrane, water electrolysis can be classified into alkaline water electrolysis (AWE), cation exchange membrane water electrolysis (PEMWE), and anion exchange membrane water electrolysis (AEMWE). AWE technology has a lower hydrogen production rate, with a current density typically less than 200 mA cm⁻¹ at 1.8 V. -2 Furthermore, PEMWE technology boasts an energy efficiency of 75%. It utilizes perfluorosulfonic acid proton exchange membranes (such as Nafion membranes) as the separator, reducing ion conduction resistance and improving electrolysis efficiency. PEMWE also exhibits rapid dynamic response and high compatibility with renewable energy sources. However, the use of platinum group metal catalysts results in high costs for PEMWE technology. AEMWE, combining high efficiency and low cost, is considered a promising system for overcoming the shortcomings of both AWE and PEMWE. AEMWE uses an anion exchange membrane as the separator, achieving high operating current density and electrolysis efficiency (>90%), along with rapid response capabilities. Simultaneously, this technology can operate in weakly alkaline environments and can use low-cost, abundant metals such as nickel as electrocatalysts, significantly reducing the cost of hydrogen electrolysis. These characteristics of AEMWE demonstrate its great application potential in large-scale sustainable hydrogen production, attracting the attention and investment of numerous scholars and entrepreneurs.

[0004] Anion exchange membranes (AEMs) are polymer electrolyte membranes that selectively permeate anions. In AEMs, they play a role in transporting OH-. − It isolates the gas generated at the anode and cathode. As one of the core components of the electrolyzer, the AEM directly affects the hydrogen production efficiency and durability of the AEMWE. An ideal AEM not only needs to ensure OH −Rapid transport also requires long-term stability under working conditions. The main challenges currently facing AEMWE technology are the weak stability of anion exchange membranes and low ion conductivity in alkaline environments. Therefore, how to develop high-performance anion exchange membranes is crucial for effectively improving the application of AEMWE technology in large-scale, safe, efficient, and green hydrogen production. An ideal anion exchange membrane must have the following properties: (1) High ion conductivity: AEMWE’s high ion conductivity is beneficial for OH − Transmission, thereby increasing the current density of the membrane electrode reactor. (2) Good alkali resistance and thermal stability: AEM is in a high-temperature and high-alkali working environment for a long time, OH − Attacks and high-temperature thermal degradation can easily damage its chemical structure, thus negatively affecting its performance. (3) Excellent mechanical properties and dimensional stability: AEM should have appropriate tensile strength and elongation at break to avoid mechanical damage during device operation, short circuits or gas crossover, which would damage the performance and safety of AEMWE. In addition, changes in temperature and humidity in the electrolytic cell can cause partial swelling of the membrane, resulting in catalyst stripping and shedding, which affects the electrolytic efficiency of the electrolytic cell. Therefore, by using strategies such as molecular structure design and modification, the polyarylene indigo membrane is optimized to improve its ionic conductivity and stability, thereby further improving the efficiency of AEMWE. Summary of the Invention

[0005] One object of the present invention is to solve at least the above-mentioned problems and / or defects, and to provide at least the advantages described below.

[0006] To achieve these objectives and other advantages according to the present invention, a branched polyaryl indigo ion exchange membrane is provided, the structural formula of which is: Where m:n = 1~4:1.

[0007] A method for preparing a branched polyaryl indigo ion exchange membrane includes the following steps: Step 1: After adding terphenyl, diphenyl ethane, triphenylmethane, and indigo to the reaction vessel, add dichloromethane. Stir in an ice bath and slowly add trifluoroacetic acid (TFA) and trifluoromethanesulfonic acid (TFSA) dropwise to the mixture until the reaction is complete and a brownish-red viscous solution is formed. Immediately pour the solution into a precipitating agent to precipitate the product. Filter and dry to obtain the branched polyaryl indigo polymer. Step 2: Add 1,6-dibromohexane and N-methylpiperidine to ethyl acetate (EA), heat the mixture to react and obtain a white solid precipitate. After the reaction is complete, allow the solution to cool to room temperature, filter and purify repeatedly with EA, and dry under vacuum to obtain 6-bromoalkyl-1-methylpiperidine monomer. Step 3: Completely dissolve the branched polyaryl indigo polymer in N-methylpyrrolidone (NMP), then add 6-bromoalkyl-1-methylpiperidine and K2CO3. After the reaction is complete, slowly pour the reaction solution into ethyl acetate, wash repeatedly with deionized water and dry to obtain piperidine-functionalized branched polyaryl indigo polymer. Step 4: Dissolve piperidine-functionalized branched polyaryl indigo polymer in N-methylpyrrolidone to prepare a 3-8 wt% solution; after thorough stirring, cast the solution onto a glass plate and dry it to form a film. Step 5: Immerse the membrane in KOH solution for 18-30 h for ion exchange to obtain the branched polyaryl indigo ion exchange membrane.

[0008] Preferably, in step one, the molar ratio of terphenyl, diphenylethane, triphenylmethane, and indigo is 1:0.2~0.5:0.02~0.25:1.2~1.8; the molar ratio of terphenyl to dichloromethane is 1 g:3~8 mL; the ice bath stirring temperature is -3~0 ℃; the reaction time is 0.5~1 h; the volume ratio of dichloromethane to trifluoroacetic acid and trifluoromethanesulfonic acid is 3~8 mL:0.3~1.0 mL:5~12 mL; after adding trifluoroacetic acid and trifluoromethanesulfonic acid, the reaction is stirred at -3~5 ℃ for 6~12 h; and the mixture is dried at 50~70 ℃ for 12~36 h; the precipitant is one or more of anhydrous ethanol, deionized water, and NaOH aqueous solution.

[0009] Preferably, in step two, the molar ratio of 1,6-dibromohexane to N-methylpiperidine is 2~3:1, the molar ratio of 1,6-dibromohexane to ethyl acetate is 1 mmol:10~20 mL, the heating reaction temperature is 40~60 ℃, the reaction time is 24~48 h, the vacuum drying temperature is 50~70 ℃, and the drying time is 24~36 h.

[0010] Preferably, in step three, the molar ratio of branched polyaryl indigo polymer to 6-bromoalkyl-1-methylpiperidine is 1:1~1.5, the molar ratio of branched polyaryl indigo polymer to N-methylpyrrolidone is 0.4~0.5 g:10~15 mL, the molar ratio of branched polyaryl indigo polymer to K2CO3 is 1 g:1~3 g, the reaction temperature is 60~90 ℃, the stirring time is 12~36 h, the drying temperature is 60~100 ℃, and the drying time is 6~24 h.

[0011] Preferably, the piperidine-functionalized branched polyaryl indigo polymer obtained in step three is modified by the following method: S31. Dissolve nickel nitrate hexahydrate and ferric nitrate nonahydrate in anhydrous ethanol, then add tartaric acid, heat and stir to react, and obtain a gel-like mixture. Then calcine it at high temperature and grind it to obtain nickel-iron oxide powder. S32. Disperse nickel-iron oxide powder into methanesulfonic acid solution, heat and stir to react, then wash with deionized water and dry to obtain modified powder; S33. The piperidine-functionalized branched polyaryl indigo polymer is dissolved in N-methylpyrrolidone to prepare a 3-8 wt% solution. Then, the modified powder is added, and after ultrasonic dispersion, a modified casting solution is obtained. Then, the solution is cast on a glass plate and dried to form a film.

[0012] Preferably, in step S31, the ratio of nickel nitrate hexahydrate, ferric nitrate nonahydrate, anhydrous ethanol, and tartaric acid is 2.9~5.8 g:4.0~8.0 g:200~400 mL:4.5~9.0 g, the reaction is carried out at 60~80℃ for 2~4 h, and the calcination temperature is 600~800℃ for 1~2 h.

[0013] Preferably, in step S32, the ratio of nickel-iron oxide powder to methanesulfonic acid solution is 2-4 g:100 mL, and the concentration of methanesulfonic acid solution is 0.1-0.2 mol / L. -1 The reaction is carried out at 30-50 °C for 1-2 h.

[0014] Preferably, in step S33, the amount of modified powder added is 2-5 wt% of piperidine-functionalized branched polyaryl indigo polymer, the ultrasonic dispersion frequency is 20-40 kHz, and the dispersion time is 10-20 min.

[0015] An application of a branched polyaryl indigo ion exchange membrane, wherein the branched polyaryl indigo ion exchange membrane is prepared by the above-described preparation method, and the branched polyaryl indigo ion exchange membrane is used as the membrane electrode in anion exchange membrane electrolysis of water.

[0016] An application of the branched polyaryl indigo ion exchange membrane as described above, specifically the method for applying the branched polyaryl indigo ion exchange membrane to the membrane electrode in anion exchange membrane electrolysis of water, includes: adding IrO2 to isopropanol and FAA solution, ultrasonicating to obtain catalyst ink, then uniformly spraying it onto nickel foam and drying it at 50-70 °C to obtain the anode; then adding Pt / C to isopropanol and FAA solution, ultrasonicating, uniformly spraying the resulting solution onto carbon paper, and drying it at 50-70 °C to obtain the cathode; finally, assembling the anode, branched polyaryl indigo ion exchange membrane, and cathode to obtain the membrane electrode; using 1 mol L... -1KOH is used as the electrolyte, and a peristaltic pump delivers the electrolyte to the anode for flow. Pure water is used as the electrolyte, and a peristaltic pump delivers the electrolyte to the cathode for flow. Then, a voltage is applied to the anode and cathode to induce an electrolysis reaction in the water. The peristaltic pump rotates at a speed of 20-80 rpm. The branched polyaryl indigo ion exchange membrane has a thickness of 10-50 μm.

[0017] Preferably, the mass-to-volume ratio of IrO2, isopropanol, and FAA solution per unit area is 1-3 mg: 100-300 μL: 20-60 μL; the mass-to-volume ratio of Pt / C, isopropanol, and FAA solution per unit area is 1-3 mg: 100-300 μL: 5-20 μL; and the size of the branched polyaryl indigo ion exchange membrane is 2.3 × 2.3 cm. 2 .

[0018] The present invention has at least the following beneficial effects: (1) The present invention uses a branched polyarylene indigo ion exchange membrane prepared from terphenyl, diphenyl ethane, triphenylmethane and indigo, which can increase the membrane free volume, thereby optimizing the ion conduction capacity of the branched polyarylene indigo ion exchange membrane and further improving the water electrolysis efficiency of the ion exchange membrane. (2) In this invention, 1,6-dibromohexane is used as a cationic functional group and grafted with branched polyarylene indigo to obtain a branched polyarylene indigo ion exchange membrane, which can improve the alkali resistance stability of the ion exchange membrane. (3) The present invention also increases the surface area and the number of active sites by doping modified nickel-iron oxide powder into the branched polyaryl indigo polymer casting solution and etching the nickel-iron oxide powder with methanesulfonic acid. When the ion exchange membrane is used as a membrane electrode assembly for water electrolysis, it has better electrochemical performance and can significantly increase the rate of hydrogen electrolysis reaction.

[0019] Other advantages, objectives and features of the present invention will become apparent in part from the following description, and in part from those skilled in the art through study and practice of the invention. Attached Figure Description

[0020] Figure 1 Synthetic route diagram of the 6-bromoalkyl-1-methylpiperidine monomer in this invention; Figure 2 This is a synthetic route diagram of the branched polyaryl indigo ion exchange membrane in this invention; Figure 3 The 6-bromoalkyl-1-methylpiperidine monomer of this invention 1 H-NMR spectrum Figure 4 The branched polyaryl indigo ion exchange membrane of the present invention 1H-NMR spectrum; Figure 5 ATR-FTIR spectra of the branched polyaryl indigo polymers prepared in Examples 1-3, the polyaryl indigo polymer in Comparative Example 1, and the branched polyaryl indigo ions in Example 2; Figure 6 The mechanical strength and elongation at break of the ion exchange membranes of Examples 1-3 and Comparative Examples 1-2 are measured. Figure 7 Polarization curves of the branched polyaryl indigo ion exchange membranes prepared in Examples 1-3 and the ion exchange membranes prepared in Comparative Examples 1-2; Figure 8 This is a schematic diagram of a membrane electrode structure assembled using a branched polyaryl indigo ion exchange membrane. Detailed Implementation

[0021] The present invention will now be described in further detail with reference to the accompanying drawings, so that those skilled in the art can implement it based on the description.

[0022] It should be understood that terms such as “having,” “comprising,” and “including” as used herein do not exclude the presence or addition of one or more other elements or combinations thereof.

[0023] Example 1 This embodiment provides a method for preparing a branched polyaryl indigo ion exchange membrane, the synthetic route of which is as follows: Figure 2 As shown, the specific steps include: Step 1: Dissolve 1.10 g indigo, 1.16 g p-terphenyl, 0.29 g diphenylethane and 0.08 g triphenylmethane in 5.0 mL dichloromethane and stir for 0.5 h. Slowly add 0.3 mL TFA to the mixture at 0 °C, then add 8.00 mL TFSA and react at 0 °C until viscous, resulting in a viscous reddish-brown liquid. Pour the viscous solution into an ethanol / water mixed solvent for precipitation to obtain a yellow fibrous solid. Wash the solid product repeatedly with deionized water until neutral, and finally dry it in a 60 °C oven to obtain a branched polyaryl indigo polymer, denoted as bPIT-5. Step 2: 7.0 g of 1,6-dibromohexane and 1.3 g of N-methylpiperidine were added to a round-bottom flask containing 30.0 mL of EA. The mixture was reacted continuously at 40 °C for 48 h to obtain a white solid precipitate. After the reaction was completed, the solution was cooled to room temperature, filtered, and repeatedly purified with EA to remove excess reactants. The precipitate was then dried in a vacuum oven at 60 °C for 24 h to obtain the 6-bromoalkyl-1-methylpiperidine monomer (synthetic route as follows). Figure 1 (as shown) Step 3: Weigh 0.5 g of bPIT-5 polymer and dissolve it in 15 mL of NMP solution. Then, at 80 °C, add 1.2 g of K2CO3 and 0.70 g of 6-bromoalkyl-1-methylpiperidine monomer. After reacting for 24 h, pour the solution into EA to precipitate the product. Wash it repeatedly with deionized water to remove residual K2CO3 and 6-bromoalkyl-1-methylpiperidine. After drying at 100 °C for 24 h, a white solid product is obtained, namely the piperidine-functionalized branched polyaryl indigo polymer. Step 4: Dissolve piperidine-functionalized branched polyaryl indigo polymer in N-methylpyrrolidone to prepare a 5wt% solution; after thorough stirring, cast the solution onto a glass plate and dry it to form a film; Step 5: Immerse the membrane in KOH solution for 24 h for ion exchange to obtain the branched polyaryl indigo ion exchange membrane, denoted as bPIT-5-PiP.

[0024] Example 2 This embodiment provides a method for preparing a branched polyaryl indigo ion exchange membrane, comprising the following steps: Step 1: Dissolve 1.10 g indigo, 1.06 g p-terphenyl, 0.27 g diphenylethane and 0.16 g triphenylmethane in 5.0 mL dichloromethane and stir for 0.5 h. Slowly add 0.3 mL TFA to the mixture at 0 °C, then add 8.00 mL TFSA and react at 0 °C until viscous, resulting in a viscous reddish-brown liquid. Pour the viscous solution into an ethanol / water mixed solvent for precipitation to obtain a yellow fibrous solid. Wash the solid product repeatedly with deionized water until neutral, and finally dry it in a 60 °C oven to obtain a branched polyaryl indigo polymer, denoted as bPIT-10. Step 2: 7.0 g of 1,6-dibromohexane and 1.3 g of N-methylpiperidine were added to a round-bottom flask containing 30.0 mL of EA. The mixture was reacted continuously at 40 °C for 48 h to obtain a white solid precipitate. After the reaction was completed, the solution was cooled to room temperature, filtered, and repeatedly purified with EA to remove excess reactants. The solution was then dried in a vacuum oven at 60 °C for 24 h to obtain 6-bromoalkyl-1-methylpiperidine monomer. Step 3: Weigh 0.5 g of PIT-10 polymer and dissolve it in 15 mL of NMP solution. Then, at 80 °C, add 1.2 g of K2CO3 and 0.70 g of 6-bromoalkyl-1-methylpiperidine. After reacting for 24 h, pour the solution into EA to precipitate the product. Wash it repeatedly with deionized water to remove residual K2CO3 and 6-bromoalkyl-1-methylpiperidine. After drying at 100 °C for 24 h, a white solid product is obtained, namely the piperidine-functionalized branched polyaryl indigo polymer. Step 4: Dissolve piperidine-functionalized branched polyaryl indigo polymer in N-methylpyrrolidone to prepare a 5wt% solution; after thorough stirring, cast the solution onto a glass plate and dry it to form a film; Step 5: Immerse the membrane in KOH solution for 24 h for ion exchange to obtain the branched polyaryl indigo ion exchange membrane, denoted as bPIT-10-PiP.

[0025] Example 3 This embodiment provides a method for preparing a branched polyaryl indigo ion exchange membrane, comprising the following steps: Step 1: Dissolve 1.10 g indigo, 1.00 g p-terphenyl, 0.26 g diphenylethane and 0.25 g triphenylmethane in 5.0 mL dichloromethane and stir for 0.5 h. Slowly add 0.3 mL TFA to the mixture at 0 °C, then add 8.00 mL TFSA and react at 0 °C until viscous, resulting in a viscous reddish-brown liquid. Pour the viscous solution into an ethanol / water mixed solvent for precipitation to obtain a yellow fibrous solid. Wash the solid product repeatedly with deionized water until neutral, and finally dry it in a 60 °C oven to obtain polyaryl indigo polymer, denoted as bPIT-15. Step 2: 7.0 g of 1,6-dibromohexane and 1.3 g of N-methylpiperidine were added to a round-bottom flask containing 30.0 mL of EA. The mixture was reacted continuously at 40 °C for 48 h to obtain a white solid precipitate. After the reaction was completed, the solution was cooled to room temperature, filtered, and repeatedly purified with EA to remove excess reactants. The solution was then dried in a vacuum oven at 60 °C for 24 h to obtain 6-bromoalkyl-1-methylpiperidine monomer. Step 3: Weigh 0.5 bPIT-15 polymer and dissolve it in 15 mL NMP solution. Then, at 80 °C, add 1.2 g K2CO3 and 0.69 g 6-bromoalkyl-1-methylpiperidine monomer. After reacting for 24 h, pour the solution into EA to precipitate the product. Wash it repeatedly with deionized water to remove residual K2CO3 and 6-bromoalkyl-1-methylpiperidine. After drying at 100 °C for 24 h, a white solid product is obtained, namely piperidine-functionalized branched polyaryl indigo polymer. Step 4: Dissolve piperidine-functionalized branched polyaryl indigo polymer in N-methylpyrrolidone to prepare a 5wt% solution; after thorough stirring, cast the solution onto a glass plate and dry it to form a film; Step 5: Immerse the membrane in KOH solution for 24 h for ion exchange to obtain the branched polyaryl indigo ion exchange membrane, denoted as bPIT-15-PiP.

[0026] Example 4 This embodiment provides a method for preparing a branched polyaryl indigo ion exchange membrane, comprising the following steps: Step 1: Dissolve 1.10 g indigo, 1.06 g p-terphenyl, 0.27 g diphenylethane and 0.16 g triphenylmethane in 5.0 mL dichloromethane and stir for 0.5 h. Slowly add 0.3 mL TFA to the mixture at 0 °C, then add 8.00 mL TFSA and react at 0 °C until viscous, resulting in a viscous reddish-brown liquid. Pour the viscous solution into an ethanol / water mixed solvent for precipitation to obtain a yellow fibrous solid. Wash the solid product repeatedly with deionized water until neutral, and finally dry it in a 60 °C oven to obtain a branched polyaryl indigo polymer, denoted as bPIT-10. Step 2: 7.0 g of 1,6-dibromohexane and 1.3 g of N-methylpiperidine were added to a round-bottom flask containing 30.0 mL of EA. The mixture was reacted continuously at 40 °C for 48 h to obtain a white solid precipitate. After the reaction was completed, the solution was cooled to room temperature, filtered, and repeatedly purified with EA to remove excess reactants. The solution was then dried in a vacuum oven at 60 °C for 24 h to obtain 6-bromoalkyl-1-methylpiperidine monomer. Step 3: Weigh 0.5 g of bPIT-10 polymer and dissolve it in 15 mL of NMP solution. Then, at 80 °C, add 1.2 g of K₂CO₃ and 0.70 g of 6-bromoalkyl-1-methylpiperidine. After reacting for 24 h, pour the solution into EA to precipitate the product. Wash repeatedly with deionized water to remove residual K₂CO₃ and 6-bromoalkyl-1-methylpiperidine. Dry at 100 °C for 24 h to obtain a white solid product, namely, piperidine-functionalized branched polyaryl indigo polymer. Modify the obtained piperidine-functionalized branched polyaryl indigo polymer as follows: S31. Dissolve 2.9 g of nickel nitrate hexahydrate and 4.0 g of ferric nitrate nonahydrate in 200 mL of anhydrous ethanol, then add 4.5 g of tartaric acid, heat to 80 °C and stir for 2 h to obtain a gel-like mixture, then calcine it at 600 °C for 2 h and grind it to obtain nickel-iron oxide powder. S32. Disperse 2.0 g of nickel-iron oxide powder into 100 mL of a 0.1 mol / L solution. -1 The modified powder was obtained by heating the mixture in a methanesulfonic acid solution to 50 °C and stirring for 1 h, followed by washing and drying with deionized water. S33. Dissolve 5.0 g of piperidine-functionalized branched polyaryl indigo polymer in 100 mL of NMP to prepare a 5 wt% solution, then add 0.1 g of modified powder, and ultrasonically disperse at 20 kHz for 10 min to obtain a modified casting solution, which is then cast on a glass plate and dried to form a film. Step 4: Immerse the membrane in KOH solution for 24 h for ion exchange to obtain the modified branched polyaryl indigo ion exchange membrane, denoted as G-bPIT-10-PiP.

[0027] Example 5 This embodiment provides a method for preparing a branched polyaryl indigo ion exchange membrane, comprising the following steps: Step 1: Dissolve 1.10 g indigo, 1.06 g p-terphenyl, 0.27 g diphenylethane and 0.16 g triphenylmethane in 5.0 mL dichloromethane and stir for 0.5 h. Slowly add 0.3 mL TFA to the mixture at 0 °C, then add 8.00 mL TFSA and react at 0 °C until viscous, resulting in a viscous reddish-brown liquid. Pour the viscous solution into an ethanol / water mixed solvent for precipitation to obtain a yellow fibrous solid. Wash the solid product repeatedly with deionized water until neutral, and finally dry it in a 60 °C oven to obtain a branched polyaryl indigo polymer, denoted as bPIT-10. Step 2: 7.0 g of 1,6-dibromohexane and 1.3 g of N-methylpiperidine were added to a round-bottom flask containing 30.0 mL of EA. The mixture was reacted continuously at 40 °C for 48 h to obtain a white solid precipitate. After the reaction was completed, the solution was cooled to room temperature, filtered, and repeatedly purified with EA to remove excess reactants. The solution was then dried in a vacuum oven at 60 °C for 24 h to obtain 6-bromoalkyl-1-methylpiperidine monomer. Step 3: Weigh 0.5 g of bPIT-10 polymer and dissolve it in 15 mL of NMP solution. Then, at 80 °C, add 1.2 g of K2CO3 and 0.70 g of 6-bromoalkyl-1-methylpiperidine. After reacting for 24 h, pour the solution into EA to precipitate the product. Wash repeatedly with deionized water to remove residual K2CO3 and 6-bromoalkyl-1-methylpiperidine. Dry at 100 °C for 24 h to obtain a white solid product, namely, piperidine-functionalized branched polyaryl indigo polymer. Modify the obtained branched polyaryl indigo polymer as follows: S31. Dissolve 2.9 g of nickel nitrate hexahydrate and 4.0 g of ferric nitrate nonahydrate in 200 mL of anhydrous ethanol, then add 4.5 g of tartaric acid, heat to 80 °C and stir for 2 h to obtain a gel-like mixture, then calcine it at 600 °C for 2 h and grind it to obtain nickel-iron oxide powder. S32. Dissolve 5.0 g of piperidine-functionalized branched polyaryl indigo polymer in 100 mL of NMP to prepare a 5 wt% solution. Then add 0.1 g of nickel iron oxide powder and ultrasonically disperse at 20 kHz for 10 min to obtain a modified casting solution. Then cast the solution on a glass plate and dry it to form a film. Step 4: Immerse the membrane in KOH solution for 24 h for ion exchange to obtain the modified branched polyaryl indigo ion exchange membrane, denoted as N-bPIT-10-PiP.

[0028] Comparative Example 1 This embodiment provides a method for preparing a branched polyaryl indigo ion exchange membrane, comprising the following steps: Step 1: Dissolve 1.10 g indigo, 1.17 g p-terphenyl, and 0.31 g diphenyl ethane in 5.0 mL dichloromethane and stir for 0.5 h. Slowly add 0.3 mL TFA to the mixture at 0 °C, then add 8.00 mL TFSA. React at 0 °C until viscous, resulting in a viscous reddish-brown liquid. Pour the viscous solution into an ethanol / water mixture for precipitation, resulting in a yellow fibrous solid. Wash the solid product repeatedly with deionized water until neutral, and finally dry it in a 60 °C oven to obtain polyaryl indigo polymer, denoted as bPIT-0. Step 2: 7.0 g of 1,6-dibromohexane and 1.3 g of N-methylpiperidine were added to a round-bottom flask containing 30.0 mL of EA. The mixture was reacted continuously at 40 °C for 48 h to obtain a white solid precipitate. After the reaction was completed, the solution was cooled to room temperature, filtered, and repeatedly purified with EA to remove excess reactants. The solution was then dried in a vacuum oven at 60 °C for 24 h to obtain 6-bromoalkyl-1-methylpiperidine monomer. Step 3: Weigh 0.5 g of bPIT-0 polymer and dissolve it in 15 mL of NMP solution. Then, at 80 °C, add 1.2 g of K2CO3 and 0.71 g of 6-bromoalkyl-1-methylpiperidine monomer. After reacting for 24 h, pour the solution into EA to precipitate the polymer and wash it repeatedly with deionized water to remove residual K2CO3 and 6-bromoalkyl-1-methylpiperidine. After drying for 24 h, piperidine-functionalized polyaryl indigo polymer is obtained. Step 4: Dissolve piperidine-functionalized polyaryl indigo polymer in NMP to prepare a 5 wt% solution; after thorough stirring, cast the solution onto a glass plate and dry it to form a film; Step 5: Immerse the membrane in KOH solution for 24 h to perform ion exchange, thus obtaining the polyaryl indigo ion exchange membrane, denoted as bPIT-0-PiP.

[0029] Comparative Example 2 This comparative example uses a commercially available FAA-3-PK-75 anion exchange membrane.

[0030] Figure 3 The 6-bromoalkyl-1-methylpiperidine used in Examples 1-3 and Comparative Example 1 1 ¹H-NMR spectra. The triplet at 3.54 ppm (H10) is attributed to the hydrogen atom on the −CH2− atom bonded to the Br phase; the signals at 3.34 ppm (H3, H4) are attributed to the hydrogen atom on the −CH2− atom bonded to N; the peak at 3.01 ppm (H5) originates from −CH3; the peaks at 1.83 ppm (H2) and 1.55 ppm (H1) correspond to the hydrogen atoms on the remaining methylene groups on the piperidine ring; the remaining methylene peaks in the hydrophobic alkyl chain appear at 1.77 ppm (H6), 1.67 ppm (H9), 1.42 ppm (H7), and 1.30 ppm (H8). These results demonstrate the successful preparation of 6-bromoalkyl-1-methylpiperidine.

[0031] Figure 4 The branched polyaryl indigo ion exchange membrane prepared in Example 1 1 ¹H-NMR spectrum. The peak at 6.98–7.87 ppm corresponds to the hydrogen on the benzene ring of the polyaryl indigo polymer backbone; 2.83 ppm corresponds to the hydrogen on the −CH₂− of diphenylethane; 5.58 ppm corresponds to the hydrogen on the methine group of triphenylmethane; the peak at 3.82 ppm is attributed to the hydrogen on the −CH₂− linked to the N group on indigo; the signal at 3.25 ppm is attributed to the hydrogen on the −CH₂− linked to the quaternary ammonium group; 2.94 ppm corresponds to the hydrogen on the methyl group of the side chain; the peak at 1.12–1.82 ppm is attributed to the hydrogen on the remaining −CH₂− on the side chain. This indicates that the branched polyaryl indigo ion exchange membrane was successfully prepared.

[0032] Figure 5 ATR-FTIR spectra of the branched polyaryl indigo polymers prepared in Examples 1-3, the polyaryl indigo polymer in Comparative Example 1, and the branched polyaryl indigo ions in Example 2. 1706 cm⁻¹ -1 The peak corresponds to the C=O stretching vibration of the indigo structural unit in the polymer framework. From Figure 5 As can be seen, compared with the ATR-FTIR spectrum of the branched polyaryl indigo polymer, the ATR-FTIR spectrum of the branched polyaryl indigo ion exchange membrane shows a new absorption peak. A new peak appears at 1360 cm⁻¹. -1 The absorption peak at [location] is attributed to the piperidine cationic group on the side chain. This indicates that 1,6-dibromohexane has been grafted onto the branched polyaryl indigo polymer via the expected reaction, and a branched polyaryl indigo ion exchange membrane has been successfully prepared.

[0033] The mechanical properties of the diaphragm can be tested using an electronic universal testing machine at room temperature, with a tensile rate of 10 mm / min. -1 The membrane was tested at least three times in the experiment, and the average value was taken. The maximum tensile strength of the membrane (…). S ) and elongation at break ( E The calculation formula for ) is as follows: in, S The maximum tensile strength of the membrane (MPa). F The maximum stress (N) at which the membrane breaks. d and L These represent the thickness (μm) and length (mm) at the center of the membrane, respectively. E This indicates the elongation at break of the membrane (%). L 'Indicates the absolute elongation (mm) at which the membrane breaks. The mechanical strength and elongation at break of the anion exchange membranes of Examples 1-3 and Comparative Examples 1-2 were tested, and the results are as follows: Figure 6 As shown. From Figure 6 It can be seen that the tensile strength and elongation at break of bPIT-X-PiP (X=0, 5, 10, 15) are in the range of 40-55 MPa and 16-8.3%, respectively. The tensile strength of the bPIT-X-PiP membrane gradually increases with increasing branching degree, with bPIT-10-PiP exhibiting the highest tensile strength. With further increases in branching degree, the rigidity of the bPIT-X-PiP membrane increases, while the elongation at break decreases.

[0034] The branched polyaryl indigo ion exchange membranes prepared in Examples 1-3 and the ion exchange membranes prepared in Comparative Examples 1-2 were tested for anion exchange membrane electrolysis of water.

[0035] Anion exchange membranes are components of the membrane electrode used in anion exchange membrane water electrolysis, and current density is the main parameter for evaluating the membrane's performance. The preparation method of the membrane electrode is as follows: Preparation of cathode catalyst slurry: 7.5 mg Pt / C was mixed with 250 μL deionized water, 750 μL isopropanol, and 70 μL FAA ionomer solution (15 wt%, ethanol as solvent), followed by ultrasonic treatment for 30 min. Preparation of anode catalyst slurry: 10.0 mg IrO2 nanoparticles were mixed with 300 μL deionized water, 900 μL isopropanol, and 100 μL FAA ionomer solution (15 wt%, ethanol as solvent), followed by ultrasonic treatment for 30 min. Cathodes and anodes were prepared by spraying the catalyst slurries onto carbon paper and nickel foam substrates, respectively, with catalyst loadings controlled at 1.5 mg / cm³. -2and 2.0 mgcm -2 The cathode, membrane, and anode are sandwiched together to prepare a membrane electrode assembly, the structural schematic of which is shown in the figure below. Figure 8 As shown.

[0036] The diffusion layer, membrane, and endplate of the supported catalyst were assembled into a water electrolysis cell for electrochemical testing. A 1.0 mol L⁻¹ solution was used. -1 KOH solution was used as the electrolyte, with a flow rate of 20 mL / min. -1 The flow rate was cyclical. Polarization curves were recorded using a DC power supply, with a test voltage range of 1.0 V to 3.0 V.

[0037] The polarization curves of the branched polyaryl indigo ion exchange membranes prepared in Examples 1-3 and the ion exchange membranes of Comparative Examples 1-2 are shown below. Figure 7 As shown in the polarization curve test, the current density of bPIT-X-PiP gradually increased with the increase of branching degree, and was higher than that of the unbranched bPIT-0-PiP film, and superior to the commercial film FAA-3-PK-75. Among them, the film with a branching degree of 10% (bPIT-10-PiP) showed the highest current density, that is, 1.02 A cm⁻¹ at 60 °C and 2.25 V. -2 The results showed that introducing branched structures into the polymer membrane significantly improved its electrochemical performance, which is beneficial to promoting the practical performance of ion exchange membranes in water electrolysis applications. Example 4 also involved doping modified nickel-iron oxide powder into a piperidine-functionalized branched polyaryl indigo polymer casting solution, followed by etching the nickel-iron oxide powder with methanesulfonic acid to increase the surface area and the number of active sites. The resulting ion exchange membrane, when used as a membrane electrode for water electrolysis, exhibited better electrochemical performance, significantly increasing the rate of hydrogen evolution reaction in water electrolysis. The ion exchange membrane showed a current density of 1.35 A cm⁻¹ at 60 °C and 2.25 V. -2 The current density of Example 5 was 1.21 A cm⁻¹, while Example 5 only doped nickel-iron oxide powder without etching. The resulting ion exchange membrane exhibited a current density of 1.21 A cm⁻¹ at 60 °C and 2.25 V. -2 The current density is only slightly improved compared to Example 4.

[0038] The number of devices and processing scale described herein are for the purpose of simplifying the description of the invention. Applications, modifications, and variations of the invention will be readily apparent to those skilled in the art.

[0039] Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and illustrations shown and described herein.

Claims

1. A branched polyaryl indigo ion exchange membrane, characterized in that, The structural formula of the branched polyaryl indigo ion exchange membrane is: Where m:n = 1~4:

1.

2. A method for preparing a branched polyaryl indigo ion exchange membrane as described in claim 1, characterized in that, Includes the following steps: Step 1: After adding terphenyl, diphenyl ethane, triphenylmethane, and indigo to the reaction vessel, add dichloromethane, stir in an ice bath, and slowly add trifluoroacetic acid and trifluoromethanesulfonic acid to the mixture until a brownish-red viscous solution is formed. Immediately pour the solution into a precipitating agent to precipitate the product, filter and dry it to obtain the branched polyaryl indigo polymer. Step 2: Add 1,6-dibromohexane and N-methylpiperidine to ethyl acetate, heat and react to obtain a white solid precipitate. After the reaction is complete, allow the solution to cool to room temperature, filter and purify repeatedly with ethyl acetate, and dry under vacuum to obtain 6-bromoalkyl-1-methylpiperidine monomer. Step 3: Completely dissolve the branched polyaryl indigo polymer in N-methylpyrrolidone, then add 6-bromoalkyl-1-methylpiperidine and K2CO3. After the reaction is complete, slowly pour the reaction solution into ethyl acetate, wash repeatedly with deionized water and dry to obtain piperidine-functionalized branched polyaryl indigo polymer. Step 4: Dissolve piperidine-functionalized branched polyaryl indigo polymer in N-methylpyrrolidone to prepare a 3-8 wt% solution; after thorough stirring, cast the solution onto a glass plate and dry it to form a film. Step 5: Immerse the membrane in KOH solution for 18-30 h for ion exchange to obtain the branched polyaryl indigo ion exchange membrane.

3. The method for preparing the branched polyaryl indigo ion exchange membrane as described in claim 2, characterized in that, In step one, the molar ratio of terphenyl, diphenylethane, triphenylmethane, and indigo is 1:0.2~0.5:0.02~0.25:1.2~1.8, the mass-to-volume ratio of terphenyl and dichloromethane is 1 g:3~8 mL, the ice bath stirring temperature is -3~0 ℃, the reaction time is 0.5~1 h, the volume ratio of dichloromethane to trifluoroacetic acid and trifluoromethanesulfonic acid is 3~8 mL:0.3~1.0 mL:5~12 mL, after adding trifluoroacetic acid and trifluoromethanesulfonic acid dropwise, the reaction is stirred at -3~5 ℃ for 6~12 h, and then dried at 50~70 ℃ for 12~36 h; the precipitant is one or more of anhydrous ethanol, deionized water, and NaOH aqueous solution.

4. The method for preparing the branched polyaryl indigo ion exchange membrane as described in claim 2, characterized in that, In step two, the molar ratio of 1,6-dibromohexane to N-methylpiperidine is 2~3:1, the molar ratio of 1,6-dibromohexane to ethyl acetate is 1mmol:10~20mL, the heating reaction temperature is 40~60 ℃, the reaction time is 24~48 h, the vacuum drying temperature is 50~70 ℃, and the drying time is 24~36 h.

5. The method for preparing the branched polyaryl indigo ion exchange membrane as described in claim 2, characterized in that, In step three, the molar ratio of branched polyaryl indigo polymer to 6-bromoalkyl-1-methylpiperidine is 1:1~1.5, the molar ratio of branched polyaryl indigo polymer to N-methylpyrrolidone is 0.4~0.5 g:10~15 mL, the molar ratio of branched polyaryl indigo polymer to potassium carbonate is 1 g:1~3 g, the reaction temperature is 60~90 ℃, the stirring time is 12~36 h, the drying temperature is 60~100 ℃, and the drying time is 6~24 h.

6. The method for preparing the branched polyaryl indigo ion exchange membrane as described in claim 2, characterized in that, The piperidine-functionalized branched polyaryl indigo polymer obtained in step three was modified by the following method: S31. Dissolve nickel nitrate hexahydrate and ferric nitrate nonahydrate in anhydrous ethanol, then add tartaric acid, heat and stir to react, and obtain a gel-like mixture. Then calcine it at high temperature and grind it to obtain nickel-iron oxide powder. S32. Disperse nickel-iron oxide powder into methanesulfonic acid solution, heat and stir to react, then wash with deionized water and dry to obtain modified powder; S33. The piperidine-functionalized branched polyaryl indigo polymer is dissolved in N-methylpyrrolidone to prepare a 3-8 wt% solution. Then, the modified powder is added, and after ultrasonic dispersion, a modified casting solution is obtained. Then, the solution is cast on a glass plate and dried to form a film.

7. The method for preparing the branched polyaryl indigo ion exchange membrane as described in claim 6, characterized in that, In S31, the ratio of nickel nitrate hexahydrate, ferric nitrate nonahydrate, anhydrous ethanol, and tartaric acid is 2.9~5.8 g:4.0~8.0 g:200~400 mL:4.5~9.0 g. The reaction is carried out at 60~80 °C for 2~4 h, and the calcination temperature is 600~800 °C for 1~2 h. In step S32, the ratio of nickel-iron oxide powder to methanesulfonic acid solution is 2-4 g:100 mL, and the concentration of methanesulfonic acid solution is 0.1-0.2 mol / L. -1 The reaction is carried out at 30-50 °C for 1-2 h. In S33, the amount of modified powder added is 2-5 wt% of piperidine-functionalized branched polyaryl indigo polymer, the ultrasonic dispersion frequency is 20-40 kHz, and the dispersion time is 10-20 min.

8. An application of a branched polyaryl indigo ion exchange membrane, wherein the branched polyaryl indigo ion exchange membrane is prepared by the preparation method according to any one of claims 2-7, characterized in that, The branched polyaryl indigo ion exchange membrane is used as the membrane electrode in anion exchange membrane water electrolysis.

9. The application of the branched polyaryl indigo ion exchange membrane as described in claim 8, characterized in that, The specific method for applying the branched polyaryl indigo ion exchange membrane to the anion exchange membrane electrolysis water electrode includes: adding IrO2 to isopropanol, deionized water, and FAA solution, ultrasonicating to obtain catalyst ink, then uniformly spraying it onto nickel foam, and drying it at 50-70℃ to obtain the anode; then adding Pt / C to isopropanol, deionized water, and FAA solution, ultrasonicating, and uniformly spraying the resulting solution onto carbon paper, and drying it at 50-70℃ to obtain the cathode; finally, assembling the anode, branched polyaryl indigo ion exchange membrane, and cathode to obtain the membrane electrode; using 1 mol L -1 KOH is used as the electrolyte, and a peristaltic pump delivers the electrolyte to the anode for flow. Pure water is used as the electrolyte, and a peristaltic pump delivers the electrolyte to the cathode for flow. Then, a voltage is applied to the anode and cathode to induce an electrolysis reaction in the water. The peristaltic pump rotates at a speed of 20-80 rpm. The branched polyaryl indigo ion exchange membrane has a thickness of 10-50 μm.

10. The application of the branched polyaryl indigo ion exchange membrane as described in claim 9, characterized in that, The mass-to-volume ratio of IrO2, deionized water, isopropanol, and FAA solution per unit area is 1~3 mg:30~100 μL:100~300 μL:20~60 μL; the mass-to-volume ratio of Pt / C, deionized water, isopropanol, and FAA solution per unit area is 1~3 mg:30~100 μL:100~300 μL:5~20 μL; the size of the branched polyaryl indigo ion exchange membrane is 2.3 × 2.3 cm. 2 .

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