In-situ ATRP initiated organic / inorganic hybrid anion exchange membranes and methods of making the same

Abstract

This invention belongs to the field of new materials and polymer materials, and relates to an in-situ ATRP-initiated organic / inorganic hybrid anion exchange membrane and its preparation method. The specific steps are as follows: using brominated carbon nanotubes as an initiator, the atom transfer radical polymerization of N,N-dimethylaminomethyl methacrylate is initiated; further, a quaternary ammonium functional ion is added through a Mensutkin reaction with a methylating agent, thereby obtaining an organic / inorganic hybrid anion exchange membrane material initiated by in-situ atom transfer radical polymerization (ATRP). The anion exchange membrane material prepared by this invention possesses both ionic conductivity and dimensional stability, exhibiting excellent performance in alkaline water electrolysis and fuel cells, and can also be used in anion dialysis, etc. This invention is simple and easy to implement, the raw materials can be industrially produced, and it has broad application prospects.

Description

Technical Field

[0001] This invention belongs to the field of new materials and polymer materials, specifically relating to an in-situ ATRP-induced organic / inorganic hybrid anion exchange membrane and its preparation method. Background Technology

[0002] Currently, alkaline water electrolysis for hydrogen production has attracted widespread attention. It utilizes electricity generated from renewable energy sources such as wind and solar power to separate water into high-purity hydrogen and oxygen, making it a crucial technology for a hydrogen energy society. Among these technologies, alkaline anion exchange membrane (AEM) water electrolysis for hydrogen production uses a polymer as the solid electrolyte, combining the advantages of proton exchange membrane (PEM) water electrolysis and liquid KOH water electrolysis, resulting in significant advantages. Under alkaline conditions, inexpensive, platinum group metal-free catalysts can be used for anion exchange membrane water electrolysis. Furthermore, replacing the liquid alkaline electrolyte (35 wt% KOH) with a solid anion exchange membrane reduces corrosivity while improving the electrolyzer's tolerance to CO2 and pressure differentials.

[0003] However, the development of anion exchange membrane (AEM) water electrolysis for hydrogen production is still in its early stages, and its performance and durability are limited by the ionic conductivity and stability of its core component—the AEM. Increasing the ion exchange capacity (IEC) of the AEM can improve its conductivity, effectively reducing the ohmic resistance of the electrolyzer and thus improving the performance of the AEM electrolyzer. Currently, accurate control of ion exchange capacity and molecular weight can be achieved through living atom transfer radical polymerization (ATRP). This method can precisely control the number and distribution of ion exchange groups on the side chains, as well as the side chain length, to balance stability and conductivity. Zhu et al. prepared cross-linked naphthyl block anion exchange membranes using ATRP, which exhibited high alkalinity stability, low expansion rate, and high ionic conductivity (Zhu ZY, Gou WW, Chen JH, et al. Journal of Membrane Science, 2021, 636: 119569.). Atom transfer radical polymerization has been widely used to synthesize copolymers with controllable structures.

[0004] While introducing more cationic groups to increase ion exchange capacity can improve ionic conductivity, it may also lead to high hydration and swelling of the membrane material, resulting in a loss of chemical and dimensional stability. On the one hand, the dimensional stability of anion exchange membranes (AEMs) can be effectively improved by restricting molecular chain movement through chemical crosslinking, especially for polymer molecules with high IEC (intercalation efficiency). On the other hand, inorganic doping, such as introducing inorganic fillers of different scales (zero-dimensional, one-dimensional, and two-dimensional), can also increase the dimensional stability of the membrane. Currently, graphene oxide, metal-organic frameworks (MOFs), and layered hydrogen hydroxides (LDHs) have been reported to enhance swelling resistance and conductivity in composite AEMs. Patent application CN104231294B discloses a graphene oxide composite polyphenylene ether as an organic component for preparing a nanocomposite anion exchange membrane, whose addition can significantly improve the mechanical properties of the anion exchange membrane. However, preparing reliable composite anion exchange membranes with high organic / inorganic compatibility remains a challenge. Summary of the Invention

[0005] To address the aforementioned problems, this invention discloses an in-situ ATRP-induced organic / inorganic hybrid anion exchange membrane and its preparation.

[0006] This invention precisely controls the ion exchange capacity (1.85 mmol / g dry membrane) and molecular weight (Mw = 9320) of anion exchange membrane through atom transfer radical polymerization. Based on this, inorganic doping enhances the dimensional stability, thermal stability, and mechanical properties of the anion exchange membrane, promoting overall performance improvement. In-situ polymerization of polymer monomers is initiated by brominated inorganic fillers, improving the interfacial compatibility of the organic / inorganic hybrid. We report an organic / inorganic hybrid anion exchange membrane supported on carbon nanotubes, exhibiting high ion exchange capacity and high hydroxide conductivity at 80°C. Furthermore, this membrane demonstrates significant high alkalinity stability and mechanical properties, contributing to increased power density and good durability in water electrolysis hydrogen production and fuel cells. This functionalized high-performance composite membrane will open new avenues for the structural design of key materials for alkaline water electrolysis hydrogen production and fuel cells, promoting the reliable application and sustainable development of hydrogen energy technology.

[0007] This invention proposes an in-situ ATRP-initiated organic / inorganic hybrid anion exchange membrane, characterized by using brominated carbon nanotubes (CNTs) simultaneously as initiators and inorganic fillers to initiate the polymerization of monomer N,N-diethylaminoethyl methacrylate, yielding a polymer backbone. The ends of the molecular side chains undergo a Menshoutkin reaction with a methylating agent to obtain quaternary ammonium ions as anion exchange sites. Its structural formula is shown below.

[0008]

[0009] The present invention proposes an in-situ ATRP-initiated method for preparing an organic / inorganic hybrid anion exchange membrane, the specific steps of which are as follows:

[0010] (1) Hydroxylated carbon nanotubes were dispersed in solvent A, and the mixture was sonicated for 10 to 60 minutes. Then, silane coupling agent [4-(bromomethyl)phenyl]-trimethoxysilane was added, and the suspension was refluxed under nitrogen for 12 to 48 hours to obtain the product brominated carbon nanotubes Br@CNTs. After centrifugation and washing with ethanol, the product was vacuum dried at 40 to 60 °C.

[0011] (2) Dissolve Br@CNTs and monomer N,N-diethylaminoethyl methacrylate in anhydrous dimethylformamide, purge with nitrogen and stir until homogeneous. Add catalyst B and ligand N,N,N',N,'N”-pentamethyldiethylenetriamine to the mixture and seal the reaction tube. Degas the reaction flask through three freeze-pump-thaw cycles and react at 60-120°C for 24-48 hours. After terminating the reaction, dilute the mixture with tetrahydrofuran and pass it through a neutral alumina column to remove the catalyst. Obtain the eluent, then concentrate by rotary evaporation, precipitate with precipitant C to obtain the product, and dry under vacuum.

[0012] (3) Dissolve the product obtained in step (2) in tetrahydrofuran, add methylating agent D, react at 40-60°C for 24-72 hours, precipitate and wash with precipitant C to obtain the product and vacuum dry;

[0013] (4) Dissolve the product obtained in step (3) in solvent E to prepare a membrane solution with a concentration of 5wt% to 20wt%, filter it, cast the membrane, and dry it at 50 to 70°C for 5 to 24 hours to obtain an anion exchange membrane.

[0014] In this invention, solvent A is one or more of toluene, methanol, dichloromethane, tetrahydrofuran, N,N-dimethylformamide, N,N-diethylformamide, N,N-dimethylacetamide, or dimethyl sulfoxide; catalyst B is cuprous bromide / bipyridine, cuprous chloride / bipyridine, cuprous bromide / pentamethyldivinyltriamine, cuprous chloride / pentamethyldivinyltriamine, cuprous bromide / tris(2-methylaminoethyl)amine, cuprous chloride / tris(2-methylaminoethyl)amine, cuprous bromide / hexamethyltriethylenetetramine, cuprous chloride / hexamethyl The precipitant C is one or more of triethylenetetramine, cuprous bromide / 2-pyridinecarboxaldehyde propylamine, or cuprous chloride / 2-pyridinecarboxaldehyde propylamine; the precipitant C is one or more of ethyl acetate, diethyl ether, xylene, cyclohexane, or n-hexane; the methylating agent is iodomethane, bromomethane, trifluoroiodomethane, trifluoroiodoethane, iodoethane, or 1-fluoro-2-iodoethane; the solvent E is one or more of dimethyl sulfoxide, dimethylformamide, methylpyrrolidone, or dimethylacetamide; and the carbon nanotubes have a mass percentage of 5 wt% to 20 wt%.

[0015] Compared with existing technologies, the advantages of this invention are as follows: The preparation method provided by this invention uses widely available raw materials, including carbon nanotubes, diethylaminoethyl N,N-methacrylate, methylating agents, catalysts, and solvents, all of which can be industrially produced. The synthesis method is simple and easy to implement. The synthesized atom-transfer radical polymerization-induced organic / inorganic hybrid anion exchange membrane exhibits precisely controlled ion exchange capacity, and with the support of inorganic dopants, it is dimensionally stable, resistant to swelling, and possesses excellent thermal properties, thus achieving reliable anion exchange membrane preparation. The resulting in-situ atom-transfer radical polymerization-induced organic / inorganic hybrid anion exchange membrane will have wide applications in alkaline water electrolysis for hydrogen production, alkaline fuel cells, and anion dialysis. Attached image description:

[0016] Figure 1 Example 1: A schematic diagram of the structure of an in-situ ATRP-induced organic / inorganic hybrid anion exchange membrane.

[0017] Figure 2 Example 1: Ionic conductivity-temperature bar chart of an in-situ ATRP-induced organic / inorganic hybrid anion exchange membrane prepared.

[0018] Figure 3 Example 1: Gel permeation chromatography (GPC) results of an in-situ ATRP-initiated organic / inorganic hybrid anion exchange membrane prepared in Example 1. Detailed Implementation

[0019] The following embodiments are further illustrations of the present invention, but are not intended to limit the scope of the invention.

[0020] Example 1:

[0021] (1) Weigh 1.0g of hydroxylated carbon nanotubes and disperse them in 20ml of solvent toluene. The mixture is ultrasonically treated for 10 minutes. Then, 2ml of silane coupling agent [4-(bromomethyl)phenyl]-trimethoxysilane is added, and the suspension is refluxed for 12 hours under nitrogen atmosphere to obtain the product brominated carbon nanotubes Br@CNTs. After centrifugation and washing with ethanol, the product is vacuum dried at 40℃.

[0022] (2) Weigh 0.5g Br@CNTs and 2.0g monomer N,N-methacrylate diethylaminoethyl ester and dissolve them in 20ml of anhydrous dimethylformamide. Purge with nitrogen and stir until homogeneous. Add 0.05g catalyst cuprous bromide / bipyridine and 0.62g complexing agent N,N,N',N,'N”-pentamethyldiethylenetriamine to the mixture and seal the reaction tube. Degas the reaction flask through three freeze-pump-thaw cycles and react at 60℃ for 24 hours. After terminating the reaction, dilute the mixture with tetrahydrofuran and pass it through a neutral alumina column to remove the catalyst. Obtain the eluent, then concentrate it by rotary evaporation. Precipitate the product with diethyl ether and dry it under vacuum.

[0023] (3) Dissolve the product obtained in step (2) in 10 ml of tetrahydrofuran, add 10 ml of methylating agent iodomethane, react at 40 °C for 24 hours, precipitate and wash with precipitant diethyl ether to obtain the product and dry under vacuum.

[0024] (4) Weigh the product obtained in step (3) and dissolve it in dimethyl sulfoxide to prepare a membrane solution with a concentration of 5 wt%. After filtration, cast the membrane and dry it at 50°C for 5 h to obtain anion exchange membrane. The final structure of an in-situ ATRP-initiated organic / inorganic hybrid anion exchange membrane is as follows: Figure 1 As shown, its ionic conductivity-temperature relationship is as follows: Figure 2 As shown.

[0025] The above technical solution allows for the controlled synthesis of the membrane's molecular weight and ion exchange capacity through atom transfer radical polymerization; it also enhances the membrane's resistance to swelling and dimensional stability through inorganic composites; and the in-situ initiation of subsequent monomer atom radical polymerization by the inorganic material increases the compatibility and reliability of the organic / inorganic composite membrane.

[0026] Specifically, this invention precisely controls the ion exchange capacity (1.85 mmol / g dry membrane, tested by acid-base titration) and molecular weight (Mw = 9320, see appendix) of the anion exchange membrane through atom transfer radical polymerization. Figure 3Furthermore, based on this, inorganic doping enhances the dimensional stability, thermal stability, and mechanical properties of the anion exchange membrane, promoting a comprehensive improvement in its performance. In-situ polymerization of polymer monomers is initiated using brominated inorganic fillers, improving the interfacial compatibility of the organic / inorganic hybrid. The organic / inorganic hybrid anion exchange membrane supported by carbon nanotubes exhibits high ion exchange capacity and high hydroxide conductivity at 80°C. In addition, this membrane demonstrates significant high alkalinity stability and mechanical properties, contributing to increased power density and good durability in water electrolysis for hydrogen production and fuel cells.

[0027] Example 2:

[0028] (1) Weigh 1.2g of hydroxylated carbon nanotubes and disperse them in 20ml of methanol. The mixture is ultrasonically treated for 20 minutes. Then, 2.5ml of silane coupling agent [4-(bromomethyl)phenyl]-trimethoxysilane is added, and the suspension is refluxed for 16 hours under nitrogen atmosphere to obtain the product brominated carbon nanotubes Br@CNTs. After centrifugation and washing with ethanol, the product is vacuum dried at 45℃.

[0029] (2) Weigh 0.55g Br@CNTs and 2.1g monomer N,N-methacrylate diethylaminoethyl ester and dissolve them in 20ml of anhydrous dimethylformamide. Purge with nitrogen and stir until homogeneous. Add 0.06g catalyst cuprous chloride / bipyridine and 0.64g complexing agent N,N,N',N,'N”-pentamethyldiethylenetriamine to the mixture and seal the reaction tube. Degas the reaction flask through three freeze-pump-thaw cycles and react at 70℃ for 30 hours. After terminating the reaction, dilute the mixture with tetrahydrofuran and pass it through a neutral alumina column to remove the catalyst. Obtain the eluent, then concentrate it by rotary evaporation. Precipitate the product with ethyl acetate and dry it under vacuum.

[0030] (3) Dissolve the product obtained in step (2) in 10 ml tetrahydrofuran, add 10 ml methylation reagent iodoethane, react at 45 °C for 30 hours, precipitate and wash with ethyl acetate to obtain the product and dry under vacuum.

[0031] (4) Weigh the product obtained in step (3) and dissolve it in the solvent dimethyl sulfoxide to prepare a membrane solution with a concentration of 10 wt%. After filtration, cast the membrane and dry it at 55°C for 8 hours to obtain an anion exchange membrane.

[0032] Example 3:

[0033] (1) Weigh 1.5g of hydroxylated carbon nanotubes and disperse them in 20ml of dichloromethane solvent. The mixture is ultrasonically treated for 30 minutes. Then, 2.8ml of silane coupling agent [4-(bromomethyl)phenyl]-trimethoxysilane is added, and the suspension is refluxed under nitrogen for 20 hours to obtain the product brominated carbon nanotubes Br@CNTs. After centrifugation and washing with ethanol, the product is vacuum dried at 50℃.

[0034] (2) Weigh 0.68g Br@CNTs and 2.4g monomer N,N-methacrylate diethylaminoethyl ester and dissolve them in 20ml of anhydrous dimethylformamide. Purge with nitrogen and stir until homogeneous. Add 0.07g catalyst cuprous bromide / bipyridine and 0.72g complexing agent N,N,N',N,'N”-pentamethyldiethylenetriamine to the mixture and seal the reaction tube. Degas the reaction flask through three freeze-pump-thaw cycles and react at 80℃ for 35 hours. After terminating the reaction, dilute the mixture with tetrahydrofuran and pass it through a neutral alumina column to remove the catalyst. Obtain the eluent, then concentrate it by rotary evaporation. Precipitate the product with cyclohexane and dry it under vacuum.

[0035] (3) Dissolve the product obtained in step (2) in 15 ml tetrahydrofuran, add 15 ml methylation reagent bromomethane, react at 50 °C for 35 hours, precipitate and wash with precipitant cyclohexane to obtain the product and vacuum dry.

[0036] (4) Weigh the product obtained in step (3) and dissolve it in the solvent dimethyl sulfoxide to prepare a membrane solution with a concentration of 12 wt%. After filtration, cast the membrane and dry it at 60°C for 12 h to obtain an anion exchange membrane.

[0037] Example 4:

[0038] (1) Weigh 1.6g of hydroxylated carbon nanotubes and disperse them in 20ml of solvent toluene. The mixture is ultrasonically treated for 40 minutes. Then, 2.8ml of silane coupling agent [4-(bromomethyl)phenyl]-trimethoxysilane is added, and the suspension is refluxed for 30 hours under nitrogen atmosphere to obtain the product brominated carbon nanotubes Br@CNTs. After centrifugation and washing with ethanol, the product is vacuum dried at 55℃.

[0039] (2) Weigh 0.71g Br@CNTs and 2.45g monomer N,N-methacrylate diethylaminoethyl ester and dissolve them in 20ml of anhydrous dimethylformamide. Purge with nitrogen and stir until homogeneous. Add 0.08g catalyst cuprous bromide / bipyridine and 0.83g complexing agent N,N,N',N,'N”-pentamethyldiethylenetriamine to the mixture and seal the reaction tube. Degas the reaction flask through three freeze-pump-thaw cycles and react at 90℃ for 36 hours. After terminating the reaction, dilute the mixture with tetrahydrofuran and pass it through a neutral alumina column to remove the catalyst. Obtain the eluent, then concentrate it by rotary evaporation. Precipitate the product with diethyl ether and dry it under vacuum.

[0040] (3) Dissolve the product obtained in step (2) in 15 ml tetrahydrofuran, add 15 ml methylating agent iodomethane, react at 55 °C for 48 hours, precipitate and wash with precipitant diethyl ether to obtain the product and vacuum dry.

[0041] (4) Weigh the product obtained in step (3) and dissolve it in the solvent dimethyl sulfoxide to prepare a membrane solution with a concentration of 15 wt%. After filtration, cast the membrane and dry it at 65°C for 18 h to obtain an anion exchange membrane.

[0042] Example 5:

[0043] (1) Weigh 2.0g of hydroxylated carbon nanotubes and disperse them in 20ml of methanol. The mixture is ultrasonically treated for 60 minutes. Then, 2ml of silane coupling agent [4-(bromomethyl)phenyl]-trimethoxysilane is added, and the suspension is refluxed under nitrogen for 48 hours to obtain the product brominated carbon nanotubes Br@CNTs. After centrifugation and washing with ethanol, the product is vacuum dried at 60℃.

[0044] (2) Weigh 0.75g Br@CNTs and 2.5g monomer N,N-methacrylate diethylaminoethyl ester and dissolve them in 20ml of anhydrous dimethylformamide. Purge with nitrogen and stir until homogeneous. Add 0.082g catalyst cuprous bromide / bipyridine and 0.85g complexing agent N,N,N',N,'N”-pentamethyldiethylenetriamine to the mixture and seal the reaction tube. Degas the reaction flask through three freeze-pump-thaw cycles and react at 120℃ for 48 hours. After terminating the reaction, dilute the mixture with tetrahydrofuran and pass it through a neutral alumina column to remove the catalyst. Obtain the eluent, then concentrate it by rotary evaporation. Precipitate the product with ethyl acetate and dry it under vacuum.

[0045] (3) Dissolve the product obtained in step (2) in 20 ml tetrahydrofuran, add 20 ml methylation reagent bromoethane, react at 60 °C for 72 hours, precipitate and wash with ethyl acetate precipitant to obtain the product and dry under vacuum;

[0046] (4) Weigh the product obtained in step (3) and dissolve it in the solvent dimethyl sulfoxide to prepare a membrane solution with a concentration of 20 wt%. After filtration, cast the membrane and dry it at 70°C for 24 h to obtain an anion exchange membrane.

[0047] The above description is merely a description of preferred embodiments of this application and is not intended to limit the scope of this application in any way. Any changes or modifications made by those skilled in the art based on the above-disclosed technical content should be considered as equivalent and valid embodiments and fall within the scope of protection of the technical solution of this application.

Claims

1. An in-situ ATRP-initiated organic / inorganic hybrid anion exchange membrane, characterized in that, Brominated carbon nanotubes (CNT) are used as initiator and inorganic filler to initiate the polymerization of monomer N,N-methyldiethylaminoethyl methacrylate to obtain a polymer skeleton, and the molecular side chain end is reacted with a methylating agent to obtain quaternary ammonium ions as anion exchange sites, and the structural formula is shown as follows, 2. A method for preparing an in-situ ATRP-initiated organic / inorganic hybrid anion exchange membrane, characterized in that, The preparation method comprises the following steps in sequence: (1) Disperse hydroxylated carbon nanotubes in solvent A, and ultrasonically treat the mixture for 10-60 minutes, then add silane coupling agent [4-(bromomethyl)phenyl]-trimethoxysilane, and reflux the suspension under a nitrogen atmosphere for 12-48 hours to obtain product brominated carbon nanotubes Br@CNTs, centrifuge and wash with ethanol, and vacuum dry at 40-60℃; (2) Dissolve Br@CNTs and monomer N,N-methyldiethylaminoethyl methacrylate in solvent anhydrous dimethylformamide, stir uniformly under nitrogen, add catalyst B and complexing agent N,N,N',N',N"-pentamethyldiethylene triamine to the mixture, seal the reaction tube, degas the reaction bottle by three cycles of freezing-pumping-thawing, dilute the mixture with tetrahydrofuran after the reaction is terminated, remove the catalyst by passing through a neutral alumina column to obtain an eluent, then concentrate by rotary evaporation, precipitate the product with precipitant C, and vacuum dry; (3) Dissolve the product obtained in step (2) in tetrahydrofuran, add methylating agent D, and react at 40-60℃ for 24-72 hours, precipitate and wash the product with precipitant C, and vacuum dry; (4) Dissolve the product obtained in step (3) in solvent E, prepare a membrane solution with a concentration of 5wt%-20wt%, filter, and cast a film, and dry at 50-70℃ for 5-24 hours to obtain an anion exchange membrane.

3. The preparation method according to claim 2, wherein the solvent A is one or more of toluene, methanol, dichloromethane, tetrahydrofuran, N,N-dimethylformamide, N,N-diethylformamide, N,N-dimethylacetamide or dimethyl sulfoxide.

4. The preparation method according to claim 2, wherein the catalyst B is one or more of cuprous bromide / dipyridyl, cuprous chloride / dipyridyl, cuprous bromide / pentamethyldiethylene triamine, cuprous chloride / pentamethyldiethylene triamine, cuprous bromide / tris(2-methylaminoethyl)amine, cuprous chloride / tris(2-methylaminoethyl)amine, cuprous bromide / hexamethyltris(ethylene) tetramine, cuprous chloride / hexamethyltris(ethylene) tetramine, cuprous bromide / 2-pyridine formaldehyde n-propylamine or cuprous chloride / 2-pyridine formaldehyde n-propylamine.

5. The preparation method according to claim 2, wherein the precipitant C is one or more of ethyl acetate, diethyl ether, dimethylbenzene, cyclohexane or n-hexane.

6. The preparation method according to claim 2, wherein the methylating agent D is iodomethane, bromomethane, trifluoroiodomethane, trifluoroiodoethane, iodoethane or 1-fluoro-2-iodoethane.

7. The preparation method according to claim 2, wherein ​ ​ ​ ​ The solvent E is one or several of dimethyl sulfoxide, dimethyl formamide, methyl pyrrolidone, dimethyl acetamide; the mass percentage of the carbon nanotube is 5wt%-20wt%.

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