Preparation method of imidazole anion exchange membrane for electrochemical carbon dioxide reduction

Abstract

The invention relates to a preparation method of an imidazole type anion exchange membrane for electrochemical carbon dioxide reduction, which comprises the following steps: introducing imidazole functional groups with different structures into a polymer skeleton by adopting a one-step simple affinity substitution reaction, and preparing the anion exchange membrane by adopting a tape casting method. The prepared anion exchange membrane shows high ionic conductivity in the electrochemical reduction process of carbon dioxide, and in addition, the anion exchange membrane has excellent selectivity on electrochemical reduction of carbon dioxide and mainly depends on the special affinity effect of imidazole functional groups on carbon dioxide molecules. The preparation method of the anion exchange membrane is simple to operate, and the obtained anion exchange membrane is excellent in performance and has wide application prospects in the fields of alkaline fuel cells, carbon dioxide electrocatalytic reduction reaction (CO2RR), electrolytic water hydrogen evolution reaction (HER), electrocatalytic oxygen reduction (ORR) and the like.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of anion exchange membranes, and particularly relates to a preparation method of an imidazole type anion exchange membrane for electrochemical carbon dioxide reduction. BACKGROUND

[0002] With the rapid development of industrialization, the concentration of carbon dioxide (CO2) in the atmosphere continues to rise, causing global warming, ocean acidification and other serious environmental problems. Traditional carbon capture and storage (CCS) technology is high in cost and difficult to realize resource utilization, while electrochemical CO2 reduction (CO2RR) technology can convert CO2 into high-value chemicals (such as CO, formic acid, ethylene, etc.). Among them, the membrane electrode (MEA) electrolytic cell has become a research hotspot for CO2RR due to its high reaction efficiency, low energy consumption and easy scaling, etc. In the MEA system, the anion exchange membrane (AEM) is a key component, which can significantly inhibit the hydrogen evolution and other side reactions in the CO2RR process by efficiently conducting OH-.

[0003] Currently, the ions of common anion exchange membranes are mainly based on ionic polymers of quaternary ammonium, quaternary phosphonium, piperidine, pyridine, guanidine, terpyridine ruthenium and imidazole functional groups. However, most of them exhibit insufficient electrochemical activity and selectivity in electrochemical carbon dioxide reaction. In recent years, imidazole compounds have attracted widespread attention in the field of carbon capture and storage due to their unique affinity for carbon dioxide. In addition, imidazole type anion exchange membranes are not prone to Hofmann elimination reaction similar to quaternary ammonium type AEM, and thus have excellent alkali resistance and can be operated for a long time under strong alkaline conditions. The high ionic conductivity of imidazole group can effectively promote the transmission of OH-, reduce the internal resistance of the electrolytic cell and improve the current density.

[0004] More importantly, the imidazole structure can interact with metal catalysts (such as Cu, Ag) to optimize the CO2 adsorption and activation process, thereby improving the selectivity of C2+ products. Therefore, imidazole type AEM not only solves the stability bottleneck of traditional AEM, but also enhances the CO2RR performance through catalytic synergy, which is a necessary material to promote the practical application of the technology.

[0005] The present patent aims to further improve the efficiency and stability of electrochemical reduction of CO2 by innovating the design and preparation of imidazole type AEM. SUMMARY

[0006] To overcome the shortcomings of the aforementioned prior art, the present invention provides a method for preparing an imidazole-based anion exchange membrane for electrochemical carbon dioxide reduction. This method utilizes imidazole functional groups introduced into the polymer backbone to enhance the selectivity of the anion exchange membrane for electrocatalytic carbon dioxide reduction products. Furthermore, the chemical stability of the anion exchange membrane is improved by designing a backbone free of ether bonds. Furthermore, the imidazole-based anion exchange membrane is prepared using common steps including free radical polymerization, nucleophilic substitution reaction, flat sheet casting, and ion exchange. This simple preparation method is suitable for large-scale production and can meet the practical application requirements of membrane electrode electrochemical carbon dioxide reduction. It also addresses the issues of insufficient selectivity, ionic conductivity, and stability of existing anion exchange membranes in the carbon dioxide reduction process.

[0007] In order to achieve the above object, the technical solution adopted by the present invention is:

[0008] An imidazole anion exchange membrane for electrochemical carbon dioxide reduction has the chemical formula:

[0009]

[0010] in:

[0011] R1=-H,-CH3,-C2H5,-C6H5;

[0012] R2=-CH3,-C2H5,-C3H7,-CHCH2,-C6H5;

[0013] R3=-CH3,-C6H5.

[0014] The preparation formula of an imidazole anion exchange membrane for electrochemical carbon dioxide reduction is:

[0015]

[0016] A method for preparing an imidazole-type anion exchange membrane for electrochemical carbon dioxide reduction comprises the following steps:

[0017] S1. Styrene and p-chloromethylstyrene are mixed in a mass ratio of 1:(0.01-0.65), and the mixture is then mixed with a chlorobenzene solvent in a mass ratio of 1:(0.5-20), an initiator having a monomer mass fraction of 0.5-3.0% is added, nitrogen is introduced for deoxygenation for at least 30 minutes, and then a tube is sealed and heated with stirring. After the reaction is completed, the product is poured into a precipitant for precipitation, and the product is filtered, washed, and dried to obtain a styrene-co-p-chloromethylstyrene copolymer;

[0018] S2, dissolving the styrene-co-p-chloromethylstyrene copolymer obtained in step S1 in an organic solvent at a mass concentration of 0.1-60% to prepare a polymer solution, adding an imidazole compound at a mass ratio of styrene-co-p-chloromethylstyrene copolymer to imidazole compound of 1:(0.01-0.6), heating at 70-130° C. to react for 2-72 hours, and after the reaction is completed, pouring the product into ethyl acetate for precipitation, filtering, washing and drying the product to obtain an imidazole-type anion exchange resin;

[0019] S3. The imidazole anion exchange resin solution obtained in step S2 is dissolved in an organic solvent at a mass concentration of 10-30%, and then the casting solution is coated on a glass plate by a flat plate casting method and dried at a temperature of 40-100° C. to form a film after 0.3-1.5 hours; the membrane is immersed in a sodium hydroxide solution at room temperature for 24 hours to perform an ion exchange reaction, so that the anions are converted into hydroxides, thereby obtaining an imidazole anion exchange membrane for electrochemical carbon dioxide reduction.

[0020] The initiator is one of azobisisobutyronitrile, azobisbenzoyl peroxide and the like.

[0021] The precipitant is at least one of methanol, tetrahydrofuran and ethanol.

[0022] The organic solvent in step S2 and step S3 is at least one of N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone.

[0023] The imidazole compound comprises one of the following substances:

[0024]

[0025]

[0026] The beneficial effects of the present invention are:

[0027] The imidazole anion exchange membrane provided by the present invention has the advantages that the introduction of imidazole groups can effectively improve the selectivity of electrocatalytic carbon dioxide production (the highest Faraday efficiency of CO production using Ag-based catalysts reaches 94%, and the highest Faraday efficiency of CO production using Cu-based catalysts reaches 94%). 2+ The Faradaic efficiency of the product reached 73%. In addition, due to its high swelling rate, a higher ionic conductivity (>125mS·cm) was obtained. -1 , 80 ° C). At room temperature, the bismuth-based catalyst was used to electrocatalyze the reduction of carbon dioxide to produce formic acid at a voltage of 2.0 to 3.2 V with a flow rate greater than 500 mA cm -2 high current density.

[0028] The imidazole anion exchange membrane provided by the present invention is prepared through the steps of free radical polymerization, affinity substitution reaction, flat plate casting, ion exchange, etc. Its preparation process is simple, suitable for large-scale production, and can meet the practical application requirements of carbon dioxide electrochemical reduction. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a sample image of the imidazole anion exchange membrane prepared in Example 1 of the present invention;

[0030] Figure 2 This is a graph of the ion conductivity of the imidazole-type anion exchange membrane prepared in Example 1 of the present invention. Figure 3 This is a stability test chart of the imidazole anion exchange membrane prepared in Example 2 of the present invention. Figure 4 This is a Faraday efficiency diagram of the imidazole anion exchange membrane prepared in Example 3 of the present invention for the electrochemical reduction of carbon dioxide to CO using an Ag catalyst.

[0031] Figure 5 The imidazole anion exchange membrane prepared in Example 4 of the present invention is used for the electrochemical reduction of carbon dioxide to C using a Cu2O-based catalyst. 2+ Faradaic efficiency diagram of the products.

[0032] Figure 6 This is a Faraday efficiency diagram of the imidazole anion exchange membrane prepared in Example 4 of the present invention for the electrochemical reduction of carbon dioxide into Cl and H2 products using a Cu2O-based catalyst.

[0033] Figure 7 This is a gas chromatogram of the imidazole anion exchange membrane prepared in Example 4 of the present invention used for the electrochemical reduction of carbon dioxide using a Cu2O-based catalyst.

[0034] Figure 8 This is the hydrogen nuclear magnetic resonance spectrum of the imidazole-type anion exchange membrane prepared in Example 4 of the present invention used for the electrochemical reduction of carbon dioxide using a Cu2O-based catalyst.

[0035] Figure 9 This is a product Faraday efficiency distribution diagram of the imidazole anion exchange membrane prepared in Example 5 of the present invention used for the electrochemical reduction of carbon dioxide using a Bi catalyst.

[0036] Figure 10 This is a relationship diagram between current density and voltage when the imidazole anion exchange membrane prepared in Example 5 of the present invention is used for electrochemical reduction of carbon dioxide using Bi catalyst.

[0037] Figure 11 This is the hydrogen nuclear magnetic resonance spectrum of the imidazole-type anion exchange membrane prepared in Example 5 of the present invention used for the electrochemical reduction of carbon dioxide using Bi catalyst. DETAILED DESCRIPTION

[0038] The present invention is further described below with reference to the following examples, but the present invention is not limited to the following examples.

[0039] Example 1:

[0040] The method for preparing an imidazole-type anion exchange membrane for electrochemical carbon dioxide reduction in this embodiment comprises the following steps:

[0041] S1. Styrene (10.00 g), p-chloromethylstyrene (5.60 g) and chlorobenzene (15.0 mL) were mixed, 0.16 g of azobisisobutyronitrile (AIBN) as an initiator was added, nitrogen was introduced for deoxygenation for 30 minutes, and then the tube was sealed and stirred and heated (75°C). After reacting for 10 hours, the product was poured into 100 mL of anhydrous methanol, filtered, and washed three times with methanol, and then dried at 60°C for 24 hours to obtain a styrene-co-p-chloromethylstyrene copolymer;

[0042] S2, dissolving the styrene-co-p-chloromethylstyrene copolymer (10.0 g) obtained in step S1 in 30.0 mL of N,N-dimethylformamide to prepare a polymer solution, adding 2.68 g of N-methylimidazole, and heating to 120° C. to react for 12 h, pouring the reaction solution into 100.0 mL of ethyl acetate to precipitate the product, filtering, and washing with ethyl acetate three times, drying the product at 60° C., and applying imidazole anion exchange resin;

[0043] S3, dissolving the imidazole anion exchange resin obtained in step S2 in 30.0 mL of N,N-dimethylformamide, then coating the casting solution on a glass plate using a flat plate casting method, and drying at 60°C for 1 hour to form a film; soaking the membrane in a 1 mol·L-1 potassium hydroxide solution at room temperature for 24 hours to convert anions into hydroxide, to obtain an imidazole anion exchange membrane for electrochemical carbon dioxide reduction. Figure 1 shown.

[0044] The test results show that the ionic conductivity of the anion exchange membrane of this embodiment can reach up to 125mS·cm-(1 Figure 2 The swelling ratio is 22.5%. The ion exchange capacity is 2.75 mmol·g-1.

[0045] Example 2;

[0046] The method for preparing an imidazole-type anion exchange membrane for electrochemical carbon dioxide reduction in this embodiment comprises the following steps:

[0047] S1. Styrene (10.00 g), p-chloromethylstyrene (5.60 g) and chlorobenzene (15.0 mL) were mixed, 0.16 g of azobisisobutyronitrile (AIBN) as an initiator was added, nitrogen was introduced for deoxygenation for 30 minutes, and then the tube was sealed and stirred and heated (75°C). After reacting for 10 hours, the product was poured into 100 mL of anhydrous methanol, filtered, and washed three times with methanol, and then dried at 60°C for 24 hours to obtain a styrene-co-p-chloromethylstyrene copolymer;

[0048] S2. The styrene-co-p-chloromethylstyrene copolymer (10.0 g) obtained in step S1 was dissolved in 30.0 mL of N,N-dimethylformamide to prepare a polymer solution, 4.05 g of 1,2,4,5-tetramethylimidazole was added, and the mixture was heated to 120° C. for 12 h. The reaction solution was poured into 100.0 mL of ethyl acetate to precipitate the product, which was filtered and washed with ethyl acetate three times. The product was dried at 60° C. and then added with an imidazole anion exchange resin;

[0049] S3. The imidazole anion exchange resin obtained in step S2 was dissolved in 30.0 mL of N,N-dimethylformamide, and the casting solution was then coated on a glass plate by a flat plate casting method, and dried at 60° C. for 1 hour to form a film; the membrane was immersed in a 1 mol L-1 potassium hydroxide solution at room temperature for 24 hours to convert the anions into hydroxide, thereby obtaining an imidazole anion exchange membrane for electrochemical carbon dioxide reduction.

[0050] The test results show that when the anion exchange membrane of this embodiment is immersed in 80℃, 1mol·L-1KOH solution for 30 days, the ion conductivity only decreases by 13% (such as Figure 3 shown).

[0051] Example 3;

[0052] The method for preparing an imidazole-type anion exchange membrane for electrochemical carbon dioxide reduction in this embodiment comprises the following steps:

[0053] S1. Styrene (10.00 g), p-chloromethylstyrene (5.60 g) and chlorobenzene (15.0 mL) were mixed, 0.16 g of azobisisobutyronitrile (AIBN) as an initiator was added, nitrogen was introduced for deoxygenation for 30 minutes, and then the tube was sealed and stirred and heated (75°C). After reacting for 10 hours, the product was poured into 100 mL of anhydrous methanol, filtered, and washed three times with methanol, and then dried at 60°C for 24 hours to obtain a styrene-co-p-chloromethylstyrene copolymer;

[0054] S2. The styrene-co-p-chloromethylstyrene copolymer (10.0 g) obtained in step S1 was dissolved in 30.0 mL of N,N-dimethylformamide to prepare a polymer solution, 3.13 g of 1,2-dimethylimidazole was added, and the mixture was heated to 120° C. for 12 h. The reaction solution was poured into 100.0 mL of ethyl acetate to precipitate the product, which was filtered and washed with ethyl acetate three times. The product was dried at 60° C. and then added with an imidazole anion exchange resin;

[0055] S3. The imidazole anion exchange resin obtained in step S2 was dissolved in 30.0 mL of N,N-dimethylformamide, and the casting solution was then coated on a glass plate by a flat plate casting method, and dried at 60° C. for 1 hour to form a film; the membrane was immersed in a 1 mol L-1 potassium hydroxide solution at room temperature for 24 hours to convert the anions into hydroxide, thereby obtaining an imidazole anion exchange membrane for electrochemical carbon dioxide reduction.

[0056] The test results show that: the anion exchange membrane of this embodiment is assembled in a membrane electrode assembly with electrodeposited Ag as cathode and IrO2 as anode, the CO2 flow rate is 40mL·min-1, the electrolyte is 1mol·L-1 KOH, and electrolysis is carried out at room temperature and 80℃. The Faraday efficiency of the product CO and its product chromatogram are as follows: Figure 4 shown.

[0057] Example 4;

[0058] The method for preparing an imidazole-type anion exchange membrane for electrochemical carbon dioxide reduction in this embodiment comprises the following steps:

[0059] S1. Styrene (10.00 g), p-chloromethylstyrene (5.60 g) and chlorobenzene (15.0 mL) were mixed, 0.16 g of azobisisobutyronitrile (AIBN) as an initiator was added, nitrogen was introduced for deoxygenation for 30 minutes, and then the tube was sealed and stirred and heated (75°C). After reacting for 10 hours, the product was poured into 100 mL of anhydrous methanol, filtered, and washed three times with methanol, and then dried at 60°C for 24 hours to obtain a styrene-co-p-chloromethylstyrene copolymer;

[0060] S2. The styrene-co-p-chloromethylstyrene copolymer (10.0 g) obtained in step S1 was dissolved in 30.0 mL of N,N-dimethylformamide to prepare a polymer solution, 8.37 g of 1-butyl-2-(2,6-dimethylphenyl)-4,5-dimethyl-1H-imidazole was added, and the mixture was heated to 120° C. and reacted for 12 h. The reaction solution was poured into 100.0 mL of ethyl acetate to precipitate the product, which was filtered and washed with ethyl acetate three times. The product was dried at 60° C. and then added with an imidazole anion exchange resin;

[0061] S3, the imidazole type anion exchange resin obtained in step S2 was dissolved in 30.0 mL of N,N-dimethylformamide, then the casting solution was coated on a glass flat plate by flat plate casting method, and dried at 60°C for 1 h to form a film; the film was soaked in 1 mol / L potassium hydroxide solution at room temperature for 24 hours to convert the anion into hydroxyl to obtain an imidazole type anion exchange film for electrochemical reduction of carbon dioxide.

[0062] The test results show that when the anion exchange film of the present example is assembled into a membrane electrode assembly with electrodeposited Cu2O as the cathode and IrO2 as the anode, the flow rate of CO2 is 60 mL / min, the electrolyte is 1 mol / L KOH, and electrolysis is carried out at room temperature, the Faraday efficiency of the product is as shown in Figure 5 and Figure 6 The gas chromatogram of the product and the nuclear magnetic resonance hydrogen spectrum are as shown in Figure 7 and Figure 8 .

[0063] Example 5;

[0064] The preparation method of the imidazole type anion exchange film for electrochemical reduction of carbon dioxide of the present example comprises the following steps:

[0065] S1, styrene (10.00 g), p-chloromethylstyrene (5.60 g) and chlorobenzene (15.0 mL) solvent were mixed, 0.16 g of initiator azobisisobutyronitrile (AIBN) was added, nitrogen was introduced to remove oxygen for 30 minutes, then the tube was sealed and heated (75°C) with stirring, after 10 h of reaction, the product was poured into 100 mL of anhydrous methanol, filtered, and washed with methanol three times, then dried at 60°C for 24 h to obtain a styrene-co-p-chloromethylstyrene copolymer;

[0066] S2, the styrene-co-p-chloromethylstyrene copolymer (10.0 g) obtained in step S1 was dissolved in 30.0 mL of N,N-dimethylformamide to obtain a polymer solution, 13.07 g of 2-(2,6-dimethylphenyl)-1,4,5-trimethyl-1H-imidazole was added, and heated to 120°C for 12 h, the reaction solution was poured into 100.0 mL of ethyl acetate to precipitate the product, filtered, and washed with ethyl acetate three times, and the product was dried at 60°C to obtain an imidazole type anion exchange resin;

[0067] S3, the imidazole type anion exchange resin obtained in step S2 was dissolved in 30.0 mL of N,N-dimethylformamide, then the casting solution was coated on a glass flat plate by flat plate casting method, and dried at 60°C for 1 h to form a film; the film was soaked in 1 mol / L potassium hydroxide solution at room temperature for 24 hours to convert the anion into hydroxyl to obtain an imidazole type anion exchange film for electrochemical reduction of carbon dioxide.

[0068] The test results show that: the anion exchange membrane of this embodiment is assembled in a membrane electrode assembly with carbon-supported metal bismuth nanoparticles as cathode and IrO2 as anode, the CO2 flow rate is 60mL·min-1, the electrolyte is 1mol·L-1 KOH, and electrolysis is carried out at room temperature. The Faraday efficiency, current-voltage relationship and nuclear magnetic resonance hydrogen spectrum of the product are as follows: Figure 9 、 10 and 11.

Claims

1. An imidazole anion exchange membrane for electrochemical carbon dioxide reduction, characterized in that: Its chemical structural formula is: in: R1=-H,-CH3,-C2H5,-C6H5; R2=-CH3,-C2H5,-C3H7,-CHCH2,-C6H5; R3=-CH3,-C6H5.

2. The imidazole anion exchange membrane for electrochemical carbon dioxide reduction according to claim 1, characterized in that: The preparation formula is:

3. A method for preparing an imidazole-type anion exchange membrane for electrochemical carbon dioxide reduction, characterized in that: The following steps are involved: S1. Styrene and p-chloromethylstyrene are mixed in a mass ratio of 1:(0.01-0.65), and the mixture is then mixed with a chlorobenzene solvent in a mass ratio of 1:(0.5-20), an initiator having a monomer mass fraction of 0.5-3.0% is added, nitrogen is introduced for deoxygenation for at least 30 minutes, and then a tube is sealed and heated with stirring. After the reaction is completed, the product is poured into a precipitant for precipitation, and the product is filtered, washed, and dried to obtain a styrene-co-p-chloromethylstyrene copolymer; S2, dissolving the styrene-co-p-chloromethylstyrene copolymer obtained in step S1 in an organic solvent at a mass concentration of 0.1-60% to prepare a polymer solution, adding an imidazole compound at a mass ratio of styrene-co-p-chloromethylstyrene copolymer to imidazole compound of 1:(0.01-0.6), heating at 70-130° C. to react for 2-72 hours, and after the reaction is completed, pouring the product into ethyl acetate for precipitation, filtering, washing and drying the product to obtain an imidazole-type anion exchange resin; S3. The imidazole anion exchange resin solution obtained in step S2 is dissolved in an organic solvent at a mass concentration of 10-30%, and then the casting solution is coated on a glass plate by a flat plate casting method and dried at a temperature of 40-100° C. to form a film after 0.3-1.5 hours; the membrane is immersed in a sodium hydroxide solution at room temperature for 24 hours to perform an ion exchange reaction, so that the anions are converted into hydroxides, thereby obtaining an imidazole anion exchange membrane for electrochemical carbon dioxide reduction.

4. The method for preparing an imidazole-type anion exchange membrane for electrochemical carbon dioxide reduction according to claim 3, characterized in that: The initiator is one of azobisisobutyronitrile, azobisbenzoyl peroxide and the like.

5. The method for preparing an imidazole-type anion exchange membrane for electrochemical carbon dioxide reduction according to claim 3, characterized in that: The precipitant is at least one of methanol, tetrahydrofuran and ethanol.

6. The method for preparing an imidazole-type anion exchange membrane for electrochemical carbon dioxide reduction according to claim 3, characterized in that: The organic solvent in step S2 and step S3 is at least one of N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone.

7. The method for preparing an imidazole-type anion exchange membrane for electrochemical carbon dioxide reduction according to claim 3, characterized in that: The imidazole compound comprises one of the following substances:

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