Branched polyaromatic piperidine anion exchange membrane, preparation method and application

Abstract

The invention belongs to the technical field of water electrolysis hydrogen production, and discloses a branched polyaromatic piperidine anion exchange membrane, a preparation method and application. The preparation method comprises the following steps: preparing a branched polymer precursor, preparing a quaternized branched polymer, and preparing the branched anion exchange membrane: dissolving the quaternized branched polymer in a third solvent, and drying in a vacuum drying oven to obtain the branched anion exchange membrane in the form of iodide ions, and soaking the branched anion-exchange membrane in the form of iodide ions in a NaOH solution for ion exchange, so that the branched anion-exchange membrane in the form of iodide ions is completely converted into a form of hydroxyl ions. According to the invention, ether-free skeleton polyaromatic hydrocarbon is selected as a main chain and has the characteristic of strong alkali-resistant stability, six-membered nitrogen heterocyclic ions are adopted as functional groups, and a large steric hindrance structure can hinder nucleophilic substitution and elimination reaction, so that the alkali-resistant stability of the anion exchange membrane is improved, and the service life of the anion exchange membrane is prolonged.

Description

Technical Field

[0001] This invention belongs to the field of water electrolysis for hydrogen production technology, and particularly relates to a branched polyaromatic piperidine anion exchange membrane, its preparation method, and its application. Background Technology

[0002] The fossil fuel crisis and environmental pollution are severely restricting the development of human society, while hydrogen energy, with its advantages of being green, clean, and having high energy density, holds the promise of being a key to breaking this deadlock. In particular, through water electrolysis technology, hydrogen energy can achieve efficient conversion between hydrogen and electricity, making it a promising energy storage medium for wind and solar power generation. Anion exchange membrane (EEM) water electrolysis for hydrogen production offers advantages such as high current density, high energy conversion efficiency, and adaptability to the volatility of renewable energy sources. It also overcomes the high cost associated with proton exchange membrane (PEM) water electrolysis using precious metal catalysts, thus making it a promising technology for large-scale application in the future. The anion exchange membrane, as one of the core components of anion exchange membrane water electrolysis technology, primarily functions to isolate the gases in the anode and cathode chambers and to transfer hydroxide ions, directly affecting the efficiency and stability of the electrolyzer.

[0003] Previous studies, based on the microstructure of anion exchange membranes, have proposed strategies to effectively improve ionic conductivity by controlling the separation of hydrophilic / hydrophobic phases within the membrane and constructing ion transport channels. However, increasing ionic conductivity inevitably increases the membrane's water absorption and swelling rate, thereby reducing its dimensional stability. Some studies have found that constructing cross-linked structures within the membrane can improve its mechanical strength and dimensional stability; however, this cross-linking sacrifices ionic conductivity. Therefore, how to improve membrane conductivity while reducing water absorption and swelling rate remains a technical challenge.

[0004] In addition, the poor chemical stability of the cationic groups and the polymer backbone affects the membrane lifetime. Quaternary ammonium cations are susceptible to hydroxyl attack during hydroxide ion transport, undergoing SN2 substitution and Hoffmann degradation reactions, leading to a significant decrease in membrane ionic conductivity and severely impacting membrane performance. Polymer backbones such as polyetheretherketone, polysulfone, and polyphenylene ether are widely used due to their good film-forming properties and flexibility; however, electron-withdrawing groups in these polymers easily activate the positive charge of adjacent carbon atoms on the benzene ring, making them vulnerable to OH groups. - The attack accelerates the main chain breakage, leading to a significant decrease in the mechanical properties of the membrane and triggering a series of chemical and physical degradations that shorten the membrane's service life.

[0005] In summary, how to prepare anion exchange membranes with excellent ionic conductivity, good alkalinity and dimensional stability, and use them in electrolyzers to achieve efficient and stable hydrogen production is a technical problem that urgently needs to be solved. Summary of the Invention

[0006] To overcome the problems existing in related technologies, this invention discloses a branched polyaromatic piperidine anion exchange membrane, its preparation method, and its application. The purpose of this invention is to introduce a basic and stable piperidine cation combined with a branching agent into the ether-free aromatic polymer backbone, thereby avoiding the presence of benzylammonium groups and strong electron-withdrawing groups in the backbone, ensuring the membrane has excellent mechanical properties and alkali resistance stability; simultaneously, by constructing a branched structure and changing the proportion of the branching agent, the hydrophilic / hydrophobic phase separation structure is controlled, thereby improving ion conductivity while limiting membrane swelling.

[0007] The technical solution is as follows: A branched anion exchange membrane, which contains a branched polymer and has the following structure:

[0008]

[0009] Wherein, R is a branched structural unit, A is a phenyl structural unit; a is the molar percentage of the branched structural unit in the polymer, %; b is the molar percentage of the phenyl structural unit in the polymer, %; and a+b=100%.

[0010] Furthermore, the branched structural unit R includes at least one of the following: triphenylmethane, tetraphenylmethane, triphenylbenzene, and triphenylene oxide.

[0011] The phenyl structural unit A includes at least one of biphenyl, p-terphenyl, tetraphenyl, m-terphenyl, diphenylethane, and trans-1,2-stilbene.

[0012] Another object of the present invention is to provide a method for preparing a branched anion exchange membrane, which is used for preparing the branched anion exchange membrane, the method comprising:

[0013] S1, Preparation of branched polymer precursor: Dissolve branched structural unit R, phenyl structural unit A and N-methyl-4-piperidinone in a first solvent, add a first catalyst, react, precipitate the product with a second solvent, wash with a first alkaline solution and dry, and collect the branched polymer precursor.

[0014] S2, Preparation of quaternized branched polymer: The branched polymer precursor is dissolved in a third solvent, iodomethane is added, and after a reaction in the dark, ethyl acetate is added to precipitate the polymer. After washing with water, filtering and drying, the quaternized branched polymer is collected.

[0015] S3, Preparation of branched anion exchange membrane: The quaternized branched polymer is dissolved in a third solvent and dried in a vacuum drying oven to obtain a branched anion exchange membrane in the form of iodide ions. The branched anion exchange membrane in the form of iodide ions is then immersed in NaOH solution for ion exchange, so that the branched anion exchange membrane in the form of iodide ions is completely converted into the form of hydroxide ions.

[0016] Further, in step S1, the molar ratio of the branched structural unit R to the aromatic monomer A is 0-99:100; the molar ratio of the sum of the amounts of the branched structural unit R and the phenyl structural unit A to the amount of the N-methyl-4-piperidinone added is 1:1.1-1.3.

[0017] In step S1, the molar ratio of N-methyl-4-piperidinone to trifluoroacetic acid is 1:1.0-1.2; the molar ratio of N-methyl-4-piperidinone to trifluoromethanesulfonic acid is 1:8-12.

[0018] In step S1, the first solvent includes at least one of dichloromethane, chloroform, or tetrahydrofuran.

[0019] In step S1, the second solvent includes at least one of ethyl acetate, methanol, or anhydrous ethanol.

[0020] In step S1, the first catalyst includes at least one of trifluoroacetic acid and trifluoromethanesulfonic acid.

[0021] In step S1, the first alkaline solution includes one of K2CO3, NaOH, or KOH, with a concentration of 0.5-2.0M.

[0022] The reaction time for preparing branched polymer precursors is 6-24 h.

[0023] In step S2, the third solvent includes at least one of methyl sulfoxide, N-methylpyrrolidone, or N,N-dimethylformamide; the quaternization reaction is carried out at a temperature of 40-60°C for 24-48 hours.

[0024] In step S3, the drying temperature is 60-80℃.

[0025] Another object of the present invention is to provide a branched polyaromatic piperidine anion exchange membrane comprising a copolymer of the following repeating structural units:

[0026]

[0027] Where: x = 0.005 to 0.02.

[0028] Another object of the present invention is to provide a method for preparing a branched polyarylene piperidine anion exchange membrane, the method comprising:

[0029] 1) Synthesis of polymers with branched structures: Under ice bath conditions, p-terphenyl and triphenylmethane were first dissolved in dichloromethane. Then, N-methyl-4-piperidinone was added to the dichloromethane solution, and after stirring for 10 min, trifluoroacetic acid and trifluoromethanesulfonic acid were added dropwise to initiate polymerization. After reacting for 12 h, the solution became viscous. The solution was poured into solvent T to precipitate a blocky solid, which was then cut into small pieces and 1 mol·L⁻¹ was added. -1 Soak in potassium carbonate solution for 6-12 hours to remove excess acid from the solution; wash repeatedly until neutral, and dry in a vacuum drying oven at 80-100℃ for 24 hours to obtain polyaromatic piperidine polymer;

[0030] 2) Preparation of quaternized polymer: The dried polyaromatic piperidine polymer from step 1) is dissolved in solvent U, iodomethane is added rapidly, and the reaction is carried out in the dark for 6-48 hours. After the reaction is completed, the solution is precipitated in solvent V, the precipitate is washed several times and dried in a vacuum drying oven at 80-100℃ for 24 hours to obtain quaternized polyaromatic piperidine.

[0031] 3) Dissolve the polymer obtained in step 2) in solvent W, sonicate to dissolve, filter impurities to obtain casting solution with a concentration of 3-10 wt%, cast directly onto a glass plate or ultra-flat culture dish, and dry at 60-100℃ for 24-48 h to form a film, thus obtaining a branched polyaromatic piperidine anion exchange membrane.

[0032] Furthermore, in step 1), the molar ratio of p-terphenyl:triphenylmethane:N-methyl-4-piperidinone is 1-0.85:0-0.02:1.1;

[0033] The molar ratio of p-terphenyl to trifluoroacetic acid is 1:1 to 1.1;

[0034] The molar ratio of trifluoroacetic acid to trifluoromethanesulfonic acid is 1:8-10;

[0035] The solid content of the solution system is 12-18 wt%.

[0036] The solvent T is methanol, ethanol, water, or 1 mol·L⁻¹. -1 One or more of the following in KOH solution;

[0037] In step 2), the ratio of the polymer to iodomethane is 1g: 1-1.5mL;

[0038] The reaction temperature is 20–50°C;

[0039] The solvent U is one or more selected from dimethyl sulfoxide, N-methylpyrrolidone, N,N-dimethylformamide, and N,N-dimethylacetamide;

[0040] The solvent V is one or more selected from diethyl ether, ethyl acetate, and acetone;

[0041] In step 3), the solvent W is one or more of dimethyl sulfoxide, N-methylpyrrolidone, N,N-dimethylformamide, and N,N-dimethylacetamide.

[0042] Another objective of this invention is to provide an application of a branched anion exchange membrane in alkaline water electrolysis for hydrogen production, wherein the branched anion exchange membrane is used to prepare membrane electrodes and to assemble an electrolytic cell for durability testing.

[0043] Combining all the above technical solutions, the beneficial effects of this invention are as follows:

[0044] The rigid main-chain polyaromatic hydrocarbon selected in this invention can ensure the mechanical strength of the anion exchange membrane, while the branched structure further enhances the toughness of the anion exchange membrane. The branched network formed can reduce the swelling of the anion exchange membrane, thereby improving the mechanical properties and dimensional stability.

[0045] Anion exchange membranes with different degrees of branching were prepared by adjusting the proportion of branching agents, which induced the formation of hydrophilic / hydrophobic microphase separation structures in the membrane, improved the hydroxide ion transport rate, and further enhanced the ionic conductivity of the anion exchange membrane.

[0046] This invention uses ether-free polyaromatic hydrocarbons as the main chain, which have strong alkali resistance and stability. It employs six-membered nitrogen heterocyclic ions as functional groups, whose large steric hindrance structure can hinder nucleophilic substitution and elimination reactions, thereby improving the alkali resistance and extending the lifespan of the anion exchange membrane. Attached Figure Description

[0047] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this disclosure and, together with the description, serve to explain the principles of this disclosure;

[0048] Figure 1 These are diagrams illustrating the branched anion exchange membrane, its preparation method, and its applications provided in embodiments of the present invention.

[0049] Figure 2 This is a comparison of the NMR spectra of the branched polyarylene piperidine anion exchange membranes prepared in Examples 5-7 of this invention and the quaternized polyarylene piperidine anion exchange membranes prepared in the comparative example.

[0050] Figure 3A comparison of the ionic conductivity curves of the branched polyarylene piperidine anion exchange membranes prepared in Examples 5-7 and the quaternized polyarylene piperidine anion exchange membranes prepared in the comparative example at different temperatures.

[0051] Figure 4 A comparison of the tensile strength and elongation at break curves of the branched polyarylene piperidine anion exchange membranes prepared in each embodiment and the quaternized polyarylene piperidine anion exchange membranes prepared in the comparative example.

[0052] Figure 5 Thermogravimetric curves of the branched polyarylene piperidine anion exchange membranes prepared in Examples 5-7 are compared with those of the quaternized polyarylene piperidine anion exchange membranes prepared in the comparative examples.

[0053] Figure 6 A comparison of the polarization curves of the branched polyarylene piperidine anion exchange membranes prepared in Examples 5-7 and the quaternized polyarylene piperidine anion exchange membranes prepared in the comparative example at 80°C in a water electrolysis cell.

[0054] Figure 7 The branched polyarylpiperidine anion exchange membranes prepared in Examples 5-7 and the quaternized polyarylpiperidine anion exchange membranes prepared in the comparative example were tested in a water electrolysis cell at 80°C with a flow rate of 1 A / cm. 2 Comparison of alkali resistance stability test curves. Detailed Implementation

[0055] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of the present invention. However, the present invention can be practiced in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0056] The innovative aspects of the branched anion exchange membrane, its preparation method, and its application provided in this invention are: selecting a main chain structure without ether oxygen bonds, combining it with a basic and stable piperidine cation to improve the basic stability of the anion exchange membrane; and introducing a branched structure with large steric hindrance into the main chain structure to improve the membrane's dimensional stability and ionic conductivity.

[0057] Example 1: To address the issue of synergistic improvement in ionic conductivity and swelling ratio, the branched anion exchange membrane provided in this embodiment of the invention contains a branched polymer and has the following structure:

[0058]

[0059] Wherein, R is a branched structural unit, A is a phenyl structural unit; a is the molar percentage of the branched structural unit in the polymer, %; b is the molar percentage of the phenyl structural unit in the polymer, %; and a+b=100%.

[0060] Preferably, the R comprises at least one of the following structural monomers:

[0061]

[0062] Wherein, (a) is triphenylmethane, (b) is tetraphenylmethane, (c) is triphenylbenzene, and (d) is triphenylene.

[0063] Preferably, A comprises at least one of the following structural monomers:

[0064]

[0065] Wherein, (a) is biphenyl, (b) is p-terphenyl, (c) is tetraphenyl, (d) is m-terphenyl, (e) is diphenylethane, and (f) is trans-1,2-stilbene.

[0066] For example, the present invention provides a method for preparing the branched polymer, comprising the following steps: according to the selected structure of the branched polymer, taking branched monomer R, phenyl structural unit A and N-methyl-4-piperidinone and adding them to a first solvent for mixing; preparing a polymer precursor in the presence of a first catalyst; precipitating and collecting the precipitated precursor in a second solvent; purifying the precursor with a first alkaline solution; dissolving the washed and dried precursor in a third solvent; adding iodomethane to carry out a second quaternization reaction; adding ethyl acetate to collect the precipitated branched polymer; and washing and drying the polymer.

[0067] For example, the first solvent includes at least one of dichloromethane, chloroform, or tetrahydrofuran; and / or,

[0068] The second solvent includes at least one of ethyl acetate, methanol, or anhydrous ethanol; and / or,

[0069] The third solvent includes at least one of dimethyl sulfoxide, N-methylpyrrolidone, or N,N-dimethylformamide; and / or,

[0070] The first catalyst comprises at least one of trifluoroacetic acid and trifluoromethanesulfonic acid; and / or,

[0071] The first alkaline solution comprises one of K₂CO₃, NaOH, or KOH, preferably with a concentration of 0.5-2.0 M; and / or,

[0072] The reaction time for the first step of preparing the precursor is 6-24 hours;

[0073] The second step of the quaternization reaction is carried out at a temperature of 40-60℃ for a reaction time of 24-48 hours.

[0074] The drying step includes a vacuum drying process at 60-80°C.

[0075] Example 2: This embodiment of the invention provides a branched anion exchange membrane, wherein the branched anion exchange membrane contains a branched polymer, and its structural formula is as follows:

[0076]

[0077] For example, R can be one or more of the following structures:

[0078]

[0079] For example, A can be one or more of the following structures:

[0080]

[0081] For example, such as Figure 1 As shown, the present invention provides a method for preparing a branched anion exchange membrane, comprising the following steps:

[0082] S1, Preparation of branched polymer precursor: Dissolve branched structural unit R, phenyl structural unit A and N-methyl-4-piperidinone in a first solvent, add a first catalyst, react, precipitate the product with a second solvent, wash with a first alkaline solution and dry, and collect the branched polymer precursor.

[0083] S2, Preparation of quaternized branched polymer: The branched polymer precursor is dissolved in a third solvent, iodomethane is added, and after a reaction in the dark, ethyl acetate is added to precipitate the polymer. After washing with water, filtering and drying, the quaternized branched polymer is collected.

[0084] S3, Preparation of branched anion exchange membrane: The quaternized branched polymer is dissolved in a third solvent and dried in a vacuum drying oven at 80°C for 24 hours to obtain a branched anion exchange membrane in the form of iodide ions. The branched anion exchange membrane in the form of iodide ions is then immersed in a 1M NaOH solution for 24-48 hours to perform ion exchange, ensuring that the branched anion exchange membrane in the form of iodide ions is completely converted to hydroxide ions (OH-). - form.

[0085] For example, in step S1, the molar ratio of the branched structural unit R to the aromatic monomer A is 0-99:100; and / or, the molar ratio of the sum of the amounts of the branched structural unit R and the phenyl structural unit A to the amount of the N-methyl-4-piperidinone added is 1:1.1-1.3.

[0086] For example, in step S1, the molar ratio of N-methyl-4-piperidinone to trifluoroacetic acid is 1:1.0-1.2; and / or, the molar ratio of N-methyl-4-piperidinone to trifluoromethanesulfonic acid is 1:8-12.

[0087] For example, in step S1, the first solvent includes at least one of dichloromethane, chloroform, or tetrahydrofuran.

[0088] For example, in step S1, the second solvent includes at least one of ethyl acetate, methanol, or anhydrous ethanol.

[0089] For example, in step S1, the first catalyst includes at least one of trifluoroacetic acid and trifluoromethanesulfonic acid.

[0090] For example, in step S1, the first alkaline solution includes one of K2CO3, NaOH or KOH, preferably with a concentration of 0.5-2.0M.

[0091] For example, in step S2, the third solvent includes at least one of methyl sulfoxide, N-methylpyrrolidone, or N,N-dimethylformamide.

[0092] As demonstrated by the above embodiments, the anion exchange membrane prepared by this invention enables stable and efficient operation of the electrolytic cell, and eliminates the need for precious metal catalysts, significantly reducing the operating cost of the electrolytic cell. This invention solves the challenge of synergistically improving the ionic conductivity and stability of anion exchange membranes.

[0093] This invention overcomes the technical bias of previous methods for preparing membranes that improve ionic conductivity but reduce dimensional stability.

[0094] Example 3, another exemplary embodiment, provides an application of a branched anion exchange membrane in alkaline water electrolysis for hydrogen production.

[0095] For example, the application of the branched anion exchange membrane in alkaline water electrolysis for hydrogen production includes the following steps:

[0096] (1) Membrane electrode preparation: Ni(NO3)2·6H2O was dissolved in isopropanol, and then FeSO4 solution was added dropwise. After stirring at 400 rpm for 24-48 h, the anode catalyst solution became clear. The nickel felt washed with hydrochloric acid was immersed in the clear anode catalyst solution for 24 h, and then dried at 25 °C for 24 h to obtain the anode catalyst sheet. The cathode catalyst Pt / C was dissolved in a mixed solution of water and isopropanol, and an appropriate amount of FAA ionomer was added. The solution was ultrasonicated for 40 min to prepare a uniform anode and cathode catalyst solution. The cathode catalyst solution was sprayed onto carbon paper at 60 °C to obtain the cathode catalyst sheet. The membrane was sandwiched between the anode and cathode catalyst sheets to obtain the membrane electrode.

[0097] (2) Assemble the electrolytic cell for durability testing: Assemble the membrane electrode in the cell with a torque of 5-7 N·m and conduct a durability test at a constant current density of 1 A / cm2.

[0098] Example 4, as another embodiment of the present invention, provides a branched polyaromatic piperidine anion exchange membrane comprising a copolymer of the following repeating structural units:

[0099]

[0100] Where: x = 0.005 to 0.02. Specifically, it is 0.005, 0.01 or 0.02, and preferably, x is 0.01.

[0101] As can be seen from the above embodiments, the present invention introduces a branched structure of triphenylmethane. The slightly branched network increases the free volume of the membrane, increases the number of ion channels, and improves ionic conductivity. Moreover, the rigid branched structure restricts the movement of the membrane backbone, thus improving dimensional stability.

[0102] An exemplary method for preparing a branched polyarylene piperidine anion exchange membrane includes the following steps:

[0103] 1) Synthesis of polymers with branched structures: Under ice bath conditions, p-terphenyl and triphenylmethane were first dissolved in dichloromethane. Then, N-methyl-4-piperidinone was added to the dichloromethane solution, and after stirring for 10 min, trifluoroacetic acid and trifluoromethanesulfonic acid were added dropwise to initiate polymerization. After reacting for 12 h, the solution became viscous. The solution was then poured into solvent T to precipitate a blocky solid, which was then cut into small pieces and 1 mol·L⁻¹ added. -1 Soak in potassium carbonate solution for 6-12 hours to remove excess acid from the solution; wash repeatedly until neutral, and dry in a vacuum drying oven at 80-100℃ for 24 hours to obtain polyaromatic piperidine polymer;

[0104] The molar ratio of p-terphenyl:triphenylmethane:N-methyl-4-piperidinone is 1-0.85:0-0.02:1.1;

[0105] The molar ratio of p-terphenyl to trifluoroacetic acid is 1:1 to 1.1;

[0106] The molar ratio of trifluoroacetic acid to trifluoromethanesulfonic acid is 1:8-10;

[0107] The solid content of the solution system is 12-18 wt%.

[0108] The solvent T is methanol, ethanol, water, or 1 mol·L⁻¹. -1 One or more of the following: KOH solution.

[0109] 2) Preparation of quaternized polymer: Dissolve the dried polyaromatic piperidine polymer in step (1) in solvent U, add iodomethane quickly, and react in the dark for 6-48 hours. After the reaction is completed, precipitate the solution in solvent V, wash the precipitate several times, and dry it in a vacuum drying oven at 80-100℃ for 24 hours to obtain quaternized polyaromatic piperidine.

[0110] The ratio of the polymer to iodomethane is 1g: 1-1.5mL;

[0111] The reaction temperature is 20–50°C;

[0112] The solvent U is one or more selected from dimethyl sulfoxide, N-methylpyrrolidone, N,N-dimethylformamide, and N,N-dimethylacetamide;

[0113] The solvent V is one or more of diethyl ether, ethyl acetate, and acetone.

[0114] 3) Dissolve the polymer obtained in step 2) in solvent W, sonicate to dissolve, filter impurities to obtain casting solution with a concentration of 3-10 wt%, cast directly onto a glass plate or ultra-flat culture dish, and dry at 60-100℃ for 24-48 h to form a film, thus obtaining a branched polyaromatic piperidine anion exchange membrane.

[0115] The solvent W is one or more of dimethyl sulfoxide, N-methylpyrrolidone, N,N-dimethylformamide, and N,N-dimethylacetamide.

[0116] For example, the reaction formula for the preparation method of branched polyarylene piperidine anion exchange membrane is as follows:

[0117]

[0118] Example 5, this embodiment of the invention provides a method for preparing a branched polyarylpiperidine anion exchange membrane, comprising:

[0119] (1) Under ice bath conditions, 2.303 g of p-terphenyl and 0.012 g of triphenylmethane were first dissolved in 7 mL of dichloromethane. Then, 1.24 mL of N-methyl-4-piperidinone was added to the mixed solution. After stirring for 10 min, 0.820 mL of trifluoroacetic acid and 9.8 mL of trifluoromethanesulfonic acid were added dropwise to initiate polymerization. After reacting for 12 h, the viscous solution was poured into ethanol to precipitate a blocky solid. After cutting it into small pieces, 1 mol·L⁻¹ was added to the precipitate. -1 The polymer was soaked in potassium carbonate solution for 12 hours to remove excess acid; it was washed several times until neutral, and then dried in a vacuum drying oven at 80°C for 24 hours to obtain the unquaternized polymer.

[0120] (2) Weigh 1g of the dried polyarylene piperidine polymer in step (1) and dissolve it in 20mL of dimethyl sulfoxide. Quickly add 1mL of iodomethane and react at 40℃ in the dark for 24h. After the reaction is complete, precipitate the solution in ethyl acetate and wash the precipitate with deionized water several times until it is neutral. Then dry the precipitate in a vacuum drying oven at 80℃ for 24h to obtain the quaternized polymer.

[0121] (3) Weigh 0.5g of the dried polymer from step (2), dissolve it in 8mL of dimethyl sulfoxide, sonicate for 1h, filter out impurities to obtain casting solution, directly cast the casting solution into an ultra-flat petri dish, dry at 80℃ for 24h to form a film, and immerse the polymer film in 1mol·L⁻¹ solution at 80℃. -1 Ion exchange was performed in KOH for 48 hours to obtain a branched polyarylpiperidine anion exchange membrane in the form of hydroxide ions (PTP-TPM-0.5%).

[0122] Example 6, this embodiment of the invention provides a method for preparing a branched polyarylpiperidine anion exchange membrane, comprising:

[0123] (1) Under ice bath conditions, 2.303 g of p-terphenyl and 0.024 g of triphenylmethane were first dissolved in 7 mL of dichloromethane. Then, 1.24 mL of N-methyl-4-piperidinone was added to the mixed solution. After stirring for 10 min, 0.820 mL of trifluoroacetic acid and 9.8 mL of trifluoromethanesulfonic acid were added dropwise to initiate polymerization. After reacting for 12 h, the viscous solution was poured into ethanol to precipitate a blocky solid. After cutting it into small pieces, 1 mol·L⁻¹ was added to the precipitate. -1 The polymer was soaked in potassium carbonate solution for 12 hours to remove excess acid; it was washed several times until neutral, and then dried in a vacuum drying oven at 80°C for 24 hours to obtain the unquaternized polymer.

[0124] (2) Weigh 1g of the dried polyarylene piperidine polymer in step (1) and dissolve it in 20mL of dimethyl sulfoxide. Quickly add 1mL of iodomethane and react at 40℃ in the dark for 24h. After the reaction is complete, precipitate the solution in ethyl acetate and wash the precipitate with deionized water several times until it is neutral. Then dry the precipitate in a vacuum drying oven at 80℃ for 24h to obtain the quaternized polymer.

[0125] (3) Weigh 0.5g of the dried polymer from step (2), dissolve it in 8mL of dimethyl sulfoxide, sonicate for 1h, filter out impurities to obtain casting solution, directly cast the casting solution into an ultra-flat petri dish, dry at 80℃ for 24h to form a film, and immerse the polymer film in 1mol·L⁻¹ solution at 80℃. -1 Ion exchange was performed in KOH for 48 hours to obtain a branched polyarylpiperidine anion exchange membrane in the form of hydroxide ions (PTP-TPM-1%).

[0126] Example 7, this embodiment of the invention provides a method for preparing a branched polyarylpiperidine anion exchange membrane, comprising:

[0127] (1) Under ice bath conditions, 2.303 g of p-terphenyl and 0.048 g of triphenylmethane were first dissolved in 7 mL of dichloromethane. Then, 1.24 mL of N-methyl-4-piperidinone was added to the mixed solution. After stirring for 10 min, 0.820 mL of trifluoroacetic acid and 9.8 mL of trifluoromethanesulfonic acid were added dropwise to initiate polymerization. After reacting for 12 h, the viscous solution was poured into ethanol to precipitate a blocky solid. After cutting it into small pieces, 1 mol·L⁻¹ was added to the precipitate. -1 The polymer was soaked in potassium carbonate solution for 12 hours to remove excess acid; it was washed several times until neutral, and then dried in a vacuum drying oven at 80°C for 24 hours to obtain the unquaternized polymer.

[0128] (2) Weigh 1g of the dried polyarylene piperidine polymer in step (1) and dissolve it in 20mL of dimethyl sulfoxide. Quickly add 1mL of iodomethane and react at 40℃ in the dark for 24h. After the reaction is complete, precipitate the solution in ethyl acetate and wash the precipitate with deionized water several times until it is neutral. Then dry the precipitate in a vacuum drying oven at 80℃ for 24h to obtain the quaternized polymer.

[0129] (3) Weigh 0.5g of the dried polymer from step (2), dissolve it in 8mL of dimethyl sulfoxide, sonicate for 1h, filter out impurities to obtain casting solution, directly cast the casting solution into an ultra-flat petri dish, dry at 80℃ for 24h to form a film, and immerse the polymer film in 1mol·L⁻¹ solution at 80℃. -1 Ion exchange was performed in KOH for 48 hours to obtain a branched polyarylpiperidine anion exchange membrane in the form of hydroxide ions (PTP-TPM-2%).

[0130] Comparative example:

[0131] (1) Under ice bath conditions, 1.152 g of p-terphenyl was first dissolved in 5 mL of dichloromethane. Then, 0.625 mL of N-methyl-4-piperidinone was added to the dichloromethane solution. After stirring for 10 min, 0.370 mL of trifluoroacetic acid and 4 mL of trifluoromethanesulfonic acid were added dropwise to initiate polymerization. After reacting for 12 h, the viscous solution was poured into ethanol to precipitate a blocky solid. After cutting it into small pieces, 1 mol·L⁻¹ was added to the precipitate. -1 The solution was soaked in potassium carbonate solution for 12 hours to remove excess acid; after washing several times until neutral, it was dried in a vacuum drying oven at 80°C for 24 hours to obtain polyaromatic piperidine polymer.

[0132] (2) Weigh 1g of the dried polyaromatic piperidine polymer in step (1) and dissolve it in 20mL of dimethyl sulfoxide. Quickly add 1mL of iodomethane and react at 40℃ in the dark for 24h. After the reaction is complete, precipitate the solution in ethyl acetate, wash the precipitate several times and dry it in a vacuum drying oven at 80℃ for 24h to obtain quaternized polyaromatic piperidine.

[0133] (3) Weigh 0.4g of the quaternized polyarylene piperidine obtained in step (2) and dissolve it in 7.34mL of dimethyl sulfoxide. Dissolve it by sonication, filter out impurities to obtain the casting solution, directly cast the casting solution into an ultra-flat petri dish, dry it at 100℃ for 24h to form a film, and immerse the polymer film in 1mol·L⁻¹ water at 80℃. -1 Ion exchange was performed in KOH for 48 hours to obtain a quaternized polyaromatic piperidine anion exchange membrane in the form of hydroxide ions.

[0134] Performance comparison of the above embodiments and comparative examples of the present invention Figures 2-7 ;in, Figure 2 This is a comparison of the NMR spectra of the branched polyarylene piperidine anion exchange membranes prepared in Examples 5-7 of this invention and the quaternized polyarylene piperidine anion exchange membranes prepared in the comparative example. Figure 3 A comparison of the ionic conductivity curves of the branched polyarylene piperidine anion exchange membranes prepared in Examples 5-7 and the quaternized polyarylene piperidine anion exchange membranes prepared in the comparative example at different temperatures. Figure 4 A comparison of the tensile strength and elongation at break curves of the branched polyarylene piperidine anion exchange membranes prepared in each embodiment and the quaternized polyarylene piperidine anion exchange membranes prepared in the comparative example. Figure 5 Thermogravimetric curves of the branched polyarylene piperidine anion exchange membranes prepared in Examples 5-7 are compared with those of the quaternized polyarylene piperidine anion exchange membranes prepared in the comparative examples. Figure 6 A comparison of the polarization curves of the branched polyarylene piperidine anion exchange membranes prepared in Examples 5-7 and the quaternized polyarylene piperidine anion exchange membranes prepared in the comparative example at 80°C in a water electrolysis cell. Figure 7The branched polyarylpiperidine anion exchange membranes prepared in Examples 5-7 and the quaternized polyarylpiperidine anion exchange membranes prepared in the comparative example were tested in a water electrolysis cell at 80°C with a flow rate of 1 A / cm. 2 Comparison of alkali resistance stability test curves.

[0135] In summary, the branched polyaromatic piperidine anion exchange membrane and its preparation method of this invention select pure carbon chains of polyaromatic hydrocarbons as the polymer backbone and six-membered nitrogen heterocyclic ions with large steric hindrance as functional groups to improve the alkali resistance of the membrane; the branched structure allows the polymer backbone to be connected by covalent bonds, which not only limits the swelling of the anion exchange membrane but also improves the toughness of the membrane; the cross-linked polyaromatic piperidine anion exchange membrane exhibits a controllable microphase separation structure by regulating the monomer feeding, thereby achieving high ion transport efficiency.

[0136] In the above embodiments, the descriptions of each embodiment have different focuses. For parts that are not described in detail or recorded in a certain embodiment, please refer to the relevant descriptions of other embodiments.

[0137] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications, equivalent substitutions and improvements made by those skilled in the art within the scope of the technology disclosed in the present invention and within the spirit and principles of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A branched anion exchange membrane, characterized in that, This exchange membrane contains a branched polymer and has the following structure: Wherein, R is a branched structural unit, A is a phenyl structural unit; a is the molar percentage of the branched structural unit in the polymer, %; b is the molar percentage of the phenyl structural unit in the polymer, %; and a+b=100%.

2. The branched anion exchange membrane according to claim 1, characterized in that, The branched structural unit R includes at least one of the following: triphenylmethane, tetraphenylmethane, triphenylbenzene, and triphenylene oxide.

3. The branched anion exchange membrane according to claim 1, characterized in that, The phenyl structural unit A includes at least one of biphenyl, p-terphenyl, tetraphenyl, m-terphenyl, diphenylethane, and trans-1,2-stilbene.

4. A method for preparing a branched anion exchange membrane, characterized in that, The method for preparing the branched anion exchange membrane according to any one of claims 1 to 3 comprises: S1, Preparation of branched polymer precursor: Dissolve branched structural unit R, phenyl structural unit A and N-methyl-4-piperidinone in a first solvent, add a first catalyst, react, precipitate the product with a second solvent, wash with a first alkaline solution and dry, and collect the branched polymer precursor. S2, Preparation of quaternized branched polymer: The branched polymer precursor is dissolved in a third solvent, iodomethane is added, and after a reaction in the dark, ethyl acetate is added to precipitate the polymer. After washing with water, filtering and drying, the quaternized branched polymer is collected. S3, Preparation of branched anion exchange membrane: The quaternized branched polymer is dissolved in a third solvent and dried in a vacuum drying oven to obtain a branched anion exchange membrane in the form of iodide ions. The branched anion exchange membrane in the form of iodide ions is then immersed in NaOH solution for ion exchange, so that the branched anion exchange membrane in the form of iodide ions is completely converted into the form of hydroxide ions.

5. The method for preparing the branched anion exchange membrane according to claim 4, characterized in that, In step S1, the molar ratio of the branched structural unit R to the aromatic monomer A is 0-99:100; the molar ratio of the sum of the amounts of the branched structural unit R and the phenyl structural unit A to the amount of the N-methyl-4-piperidinone added is 1:1.1-1.

3. In step S1, the molar ratio of N-methyl-4-piperidinone to trifluoroacetic acid is 1:1.0-1.2; the molar ratio of N-methyl-4-piperidinone to trifluoromethanesulfonic acid is 1:8-12. In step S1, the first solvent includes at least one of dichloromethane, chloroform, or tetrahydrofuran. In step S1, the second solvent includes at least one of ethyl acetate, methanol, or anhydrous ethanol. In step S1, the first catalyst includes at least one of trifluoroacetic acid and trifluoromethanesulfonic acid. In step S1, the first alkaline solution includes one of K2CO3, NaOH, or KOH, with a concentration of 0.5-2.0M. The reaction time for preparing branched polymer precursors is 6-24 h.

6. The method for preparing the branched anion exchange membrane according to claim 4, characterized in that, In step S2, the third solvent includes at least one of methyl sulfoxide, N-methylpyrrolidone, or N,N-dimethylformamide; the quaternization reaction is carried out at a temperature of 40-60°C for 24-48 hours. In step S3, the drying temperature is 60-80℃.

7. A branched polyaromatic piperidine anion exchange membrane, characterized in that, The branched polymer contained in the branched anion exchange membrane of claim 1, wherein the exchange membrane comprises a copolymer of the following repeating structural units: Where: x = 0.005~0.

02.

8. A method for preparing a branched polyarylene piperidine anion exchange membrane, characterized in that, The preparation method for the branched polyaromatic piperidine anion exchange membrane according to claim 7 includes: 1) Synthesis of polymers with branched structures: Under ice bath conditions, p-terphenyl and triphenylmethane were first dissolved in dichloromethane. Then, N-methyl-4-piperidinone was added to the dichloromethane solution, and after stirring for 10 min, trifluoroacetic acid and trifluoromethanesulfonic acid were added dropwise to initiate polymerization. After reacting for 12 h, the solution became viscous. The solution was poured into solvent T to precipitate a blocky solid, which was then cut into small pieces and 1 mol·L⁻¹ was added. -1 Soak in potassium carbonate solution for 6-12 hours to remove excess acid from the solution; wash repeatedly until neutral, and dry in a vacuum drying oven at 80-100℃ for 24 hours to obtain polyaromatic piperidine polymer; 2) Preparation of quaternized polymer: The dried polyaromatic piperidine polymer from step 1) is dissolved in solvent U, iodomethane is added rapidly, and the reaction is carried out in the dark for 6-48 hours. After the reaction is completed, the solution is precipitated in solvent V, the precipitate is washed several times and dried in a vacuum drying oven at 80-100℃ for 24 hours to obtain quaternized polyaromatic piperidine. 3) Dissolve the polymer obtained in step 2) in solvent W, sonicate to dissolve, filter impurities to obtain casting solution with a concentration of 3-10 wt%, cast directly onto a glass plate or ultra-flat culture dish, and dry at 60-100℃ for 24-48 h to form a film, thus obtaining a branched polyaromatic piperidine anion exchange membrane.

9. The method for preparing the branched polyaromatic piperidine anion exchange membrane according to claim 8, characterized in that, In step 1), the molar ratio of p-terphenyl:triphenylmethane:N-methyl-4-piperidinone is 1-0.85:0-0.02:1.1; The molar ratio of p-terphenyl to trifluoroacetic acid is 1:1 to 1.1; The molar ratio of trifluoroacetic acid to trifluoromethanesulfonic acid is 1:8-10; The solid content of the solution system is 12-18 wt%. The solvent T is methanol, ethanol, water, or 1 mol·L⁻¹. -1 One or more of the following in KOH solution; In step 2), the ratio of the polymer to iodomethane is 1g: 1-1.5mL; The reaction temperature is 20–50°C; The solvent U is one or more selected from dimethyl sulfoxide, N-methylpyrrolidone, N,N-dimethylformamide, and N,N-dimethylacetamide; The solvent V is one or more selected from diethyl ether, ethyl acetate, and acetone; In step 3), the solvent W is one or more of dimethyl sulfoxide, N-methylpyrrolidone, N,N-dimethylformamide, and N,N-dimethylacetamide.

10. The application of a branched anion exchange membrane in alkaline water electrolysis for hydrogen production, characterized in that, The branched anion exchange membrane described in any one of claims 1 to 3 is used to prepare membrane electrodes and to assemble an electrolytic cell for durability testing.

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