Preparation and application of polybenzimidazole anion exchange membrane capable of regulating hydrophilic and hydrophobic side chains

Abstract

The invention discloses preparation and application of a polybenzimidazole anion exchange membrane capable of regulating and controlling hydrophilic and hydrophobic side chains. Comprising the following steps: synthesizing an ammonium bromide-containing monomer by using dibromohexane, a tertiary ammonium group-containing reagent and ethyl acetate; the preparation method comprises the following steps: synthesizing an ammonium chloride-containing monomer by using 1, 2-di-(2-chloroethoxy) ethane, a tertiary ammonium group-containing reagent, potassium carbonate and acetonitrile; the preparation method comprises the following steps: adding poly (4, 4 '-diphenyl ether-5, 5'-bisbenzimidazole), potassium carbonate and N-methyl pyrrolidone into a reactor, stirring and dissolving, dissolving an ammonium bromide-containing monomer and an ammonium chloride-containing monomer with dimethyl sulfoxide, and adding into the reactor to obtain the polybenzimidazole polymer capable of regulating and controlling hydrophilic and hydrophobic side chains. And dissolving the polybenzimidazole polymer with the adjustable hydrophilic and hydrophobic side chains by using dimethyl sulfoxide, casting to form a membrane, and drying to obtain the polybenzimidazole anion exchange membrane with the adjustable hydrophilic and hydrophobic side chains and high ionic conductivity. The anion exchange membrane constructed by the invention is applied to electrocatalytic CO2 reduction, and the current density and CO Faraday efficiency can be remarkably improved.

Description

Technical Field

[0001] The invention belongs to the field of electrocatalytic CO2 reduction anion exchange membranes, and relates to the preparation and application of a polybenzimidazole anion exchange membrane with adjustable hydrophilic and hydrophobic side chains. Background Art

[0002] With the continuous development of the global economy, CO2 emissions have increased dramatically. Since the Industrial Revolution, the concentration of CO2 in the atmosphere has soared from the initial 280ppm to 400ppm, causing global warming and triggering extreme climate. In this context, converting CO2 into high-value-added chemical products, such as carbon monoxide, methanol, ethanol, dimethyl ether, etc., has become an important path to achieve carbon cycle and high-value utilization. The conversion and utilization methods of CO2 are mainly divided into biological methods, photocatalysis and electrocatalysis. The biological method converts CO2 into organic matter through plant photosynthesis, which is an important mechanism for self-repair in nature. Photocatalytic technology uses photocatalysts to catalyze the reduction reaction of CO2 under light conditions to produce a variety of high-value-added products. In contrast, electrocatalytic CO2 reduction shows higher efficiency and environmental friendliness. Electrocatalytic CO2 reduction technology can be carried out at room temperature and normal pressure. Not only is the reaction condition mild, but it also consumes only CO2 and electricity.

[0003] The key to electrocatalytic CO2 reduction is to select appropriate materials and optimize the reactor to achieve efficient conversion of CO2. Among them, the "zero-gap" membrane electrode reactor, as an electrocatalytic CO2 reduction device, has a sandwich structure consisting of cathode, membrane, and anode that can greatly shorten the distance between the two electrodes, and the cathode does not need to use electrolyte, which not only eliminates the problem of low solubility of CO2 in the electrolyte, but also reduces the system ohmic loss caused by the electrolyte, thereby effectively improving the CO2 reduction efficiency. It is also considered to be the electrocatalytic CO2 reduction reactor with the greatest potential for industrial application.

[0004] In a membrane electrode device, the functions of the diaphragm are mainly the following two aspects: first, it separates the cathode and the anode to prevent the secondary oxidation of the cathode products by the oxygen produced by the anode; second, it allows ions with balanced charges, such as protons or hydroxides, to pass through and build a complete pathway. At present, anion exchange membranes that can promote the transmission of anions from the cathode to the anode, maintain the pH value of the cathode, and inhibit hydrogen evolution during the electrocatalytic CO2 reduction process have received more attention and research. An ideal anion exchange membrane should have excellent hydroxide conductivity, mechanical properties, dimensional stability, and chemical stability. In addition, anion exchange membranes can selectively transfer hydroxide, thereby reducing the hydroxide concentration at the cathode, inhibiting the hydrogen evolution reaction at the cathode, and improving the Faraday efficiency of electrocatalytic CO2 reduction. At the same time, it can effectively avoid the negative impact of the generated hydroxide on the cathode catalyst and cause the loss of CO2; currently, the Sustainion X37-50 anion exchange membrane produced by Dioxide Materials in the United States, the PiperION anion exchange membrane produced by Versogen in the United States, and the FAA-3-PK-130 anion exchange membrane produced by Fumasep in Germany are often used in electrocatalytic CO2 reduction membrane electrode reactors. However, commercial membranes have problems such as low hydroxide conductivity, weak hydroxide selectivity, and insufficient mechanical strength, which are not conducive to improving the efficiency of CO2 reduction. In addition, the price of imported commercial membranes is extremely expensive, and there is a potential "bottleneck" problem. Therefore, it is urgent to develop high-performance new anion exchange membrane materials for electrocatalytic CO2 reduction applications. Summary of the invention

[0005] An object of the present invention is to solve at least the above problems and / or disadvantages and to provide at least the advantages which will be described hereinafter.

[0006] In order to achieve these purposes and other advantages according to the present invention, a polybenzimidazole anion exchange membrane with adjustable hydrophilic and hydrophobic side chains is provided, and the structural formula of the polybenzimidazole anion exchange membrane with adjustable hydrophilic and hydrophobic side chains is:

[0007]

[0008] Among them, the molar ratio of x:y is 1-4:1-4; Q is any one of a 1-methylpiperidine group, a 1,4-dimethylpiperazine group, a 1-methylpyrrole group, a 1-methylimidazole group, a 1-methylpyrrolidine group, a 1-methylpyrazole group, an imidazolium group, a trimethylamine group, a triethylamine group, and a tripropylamine group.

[0009] The present invention also provides a method for preparing the polybenzimidazole anion exchange membrane with adjustable hydrophilic and hydrophobic side chains as described above, comprising the following steps:

[0010] Step 1: Under a nitrogen atmosphere, add a tertiary ammonium group-containing reagent, dibromohexane and ethyl acetate into a reactor, stir and dissolve, and after the reaction is completed, a white solid is generated, which is filtered, repeatedly washed with ethyl acetate, and vacuum dried to obtain an ammonium bromide-containing monomer;

[0011] Step 2: Under a nitrogen atmosphere, a tertiary ammonium group-containing reagent, 1,2-di-(2-chloroethoxy)ethane, potassium carbonate and acetonitrile are added to a reactor, condensed and refluxed, and after the reaction is completed, the acetonitrile is removed by rotary evaporation, and the remaining solution is poured into ethyl acetate for precipitation, and the light yellow precipitate is collected, washed with ether for multiple times, filtered and vacuum dried to obtain an ammonium chloride-containing monomer;

[0012] Step 3: under a nitrogen atmosphere, poly(4,4'-diphenylether-5,5'-bisbenzimidazole), potassium carbonate and N-methylpyrrolidone are added to a reactor, stirred and dissolved, and then the ammonium bromide-containing monomer obtained in the above step 1 and the ammonium chloride-containing monomer obtained in step 2 are first dissolved in dimethyl sulfoxide and then added to the reactor. After the reaction is completed, the reaction solution is poured into a precipitant, filtered, and a yellow fibrous solid is collected and dried to obtain a polybenzimidazole polymer with adjustable hydrophilic and hydrophobic side chains;

[0013] Step 4: Add the polybenzimidazole polymer with adjustable hydrophilic and hydrophobic side chains obtained in step 3 and dimethyl sulfoxide into a reactor, stir and dissolve to obtain a bright yellow casting solution, pour the casting solution onto a clean glass plate to form a film, and after drying, soak the film in ethanol to remove the residual solvent, and wash with deionized water;

[0014] Step 5: soak the membrane obtained in step 4 in a KOH solution for ion exchange, thereby obtaining a polybenzimidazole anion exchange membrane with adjustable hydrophilic and hydrophobic side chains.

[0015] Preferably, in the step 1, the molar ratio of the reagent containing a tertiary ammonium group to dibromohexane is 1:2-10; the molar volume ratio of the reagent containing a tertiary ammonium group to ethyl acetate is 10-30 mmol:20-50 mL, the reaction temperature is 20-50° C., and the reaction time is 24-48 h; the vacuum drying temperature is 40-60° C., and the drying time is 12-36 h; the reagent containing a tertiary ammonium group is any one of 1-methylpiperidine, 1,4-dimethylpiperazine, 1-methylpyrrole, 1-methylimidazole, 1-methylpyrrolidine, 1-methylpyrazole, imidazolium, trimethylamine, triethylamine, and tripropylamine.

[0016] Preferably, in the step 2, the molar ratio of the reagent containing a tertiary ammonium group, 1,2-di-(2-chloroethoxy)ethane and potassium carbonate is 1:1-5:5-20; the molar volume ratio of the reagent containing a tertiary ammonium group and acetonitrile is 10-30mmol:20-100mL; the reaction temperature is 40-70°C, and the reaction time is 24-48h; the vacuum drying temperature is 40-60°C, and the drying time is 12-36h; the tertiary ammonium group-containing reagent is any one of 1-methylpiperidine, 1,4-dimethylpiperazine, 1-methylpyrrole, 1-methylimidazole, 1-methylpyrrolidine, 1-methylpyrazole, imidazolium, trimethylamine, triethylamine, and tripropylamine.

[0017] Preferably, in the step three, the molar volume ratio of poly(4,4'-diphenyl ether-5,5'-bisbenzimidazole), potassium carbonate and N-methylpyrrolidone is 1mmol:1-3mmol:5-15mL; the molar volume ratio of ammonium bromide monomer, ammonium chloride monomer and dimethyl sulfoxide is 0-4mmol:0-4mmol:5-10mL; the reaction temperature is 80-110°C, and the reaction time is 24-72h; the precipitant is one or more of anhydrous ethanol, ethyl acetate and deionized water.

[0018] Preferably, in the step 4, the stirring and dissolving temperature is 60-80°C, and the stirring time is 6-24h; the casting solution drying temperature is 60-100°C, and the drying time is 12-24h; the mass volume ratio of the polybenzimidazole polymer with adjustable hydrophilic and hydrophobic side chains and dimethyl sulfoxide is 0.3-0.8g:10mL; in the step 5, the concentration of the KOH solution is 0.5-4mol·L-1, and the immersion time is 24-72h.

[0019] The present invention also provides an application of a polybenzimidazole anion exchange membrane with adjustable hydrophilic and hydrophobic side chains prepared by the preparation method as described above in electrocatalytic CO2 reduction, wherein the polybenzimidazole anion exchange membrane with adjustable hydrophilic and hydrophobic side chains is used as a diaphragm in an electrocatalytic CO2 reduction membrane electrode.

[0020] Preferably, the preparation method of the membrane electrode comprises: adding nano silver powder to deionized water, anhydrous ethanol, and FAA solution, ultrasonicating to obtain cathode catalyst ink, and then using a spray gun to evenly spray it onto hydrophobic carbon paper, and drying it at 50 to 70°C to obtain a cathode; adding iridium oxide to deionized water, anhydrous ethanol, and FAA solution, ultrasonicating to obtain anode catalyst ink, and then using a spray gun to evenly spray it onto hydrophobic carbon paper, and drying it at 50 to 70°C to obtain an anode; finally, assembling the cathode, a polybenzimidazole anion exchange membrane with adjustable hydrophilic and hydrophobic side chains, and an anode to obtain a membrane electrode.

[0021] Preferably, the mass volume ratio of nano silver powder, anhydrous ethanol, deionized water, and FAA solution in the cathode is: 1-3 mg: 100-300 μL: 20-100 μL: 5-20 μL; the mass volume ratio of iridium oxide, anhydrous ethanol, deionized water, and FAA solution in the anode is: 1-3 mg: 100-300 μL: 20-100 μL: 5-20 μL.

[0022] Preferably, 0.1 to 1 mol·L -1 KHCO3 is used as the anode electrolyte, and the electrolyte is transported to the anode through a peristaltic pump for flow, and the dry CO2 is humidified by a gas humidifier and transported to the cathode for flow, and then a constant current is applied for electrolysis to promote electrocatalytic reduction of CO2; the rotation speed of the peristaltic pump is 20 to 80 rpm; the flow rate of the CO2 is 10 to 40 mL min -1 ; The thickness of the adjustable hydrophilic and hydrophobic side chain polybenzimidazole anion exchange membrane is 10 to 50 μm.

[0023] The present invention has at least the following beneficial effects:

[0024] (1) The present invention uses polybenzimidazole as the polymer main chain, which can improve the alkaline stability and mechanical properties of the anion exchange membrane;

[0025] (2) The present invention can significantly improve the ion conductivity of the anion exchange membrane by regulating the ratio of the hydrophilic side chain containing ammonium chloride and the hydrophobic side chain containing ammonium bromide, thereby improving the current density and CO Faraday efficiency of the membrane electrode, and overcoming the disadvantage of the polybenzimidazole polymer membrane having too large surface resistance during use;

[0026] (3) Through molecular structure design by hydrophilic and hydrophobic side chains, side chains carrying different functional groups are grafted onto polybenzimidazole, and the cationic groups are regulated to give it better hydroxide conductivity and electrochemical stability, so that it can meet the application requirements of electrocatalytic CO2 reduction.

[0027] Other advantages, objectives and features of the present invention will be embodied in part through the following description, and in part will be understood by those skilled in the art through study and practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 The synthetic route of the polybenzimidazole anion exchange membrane with adjustable hydrophilic and hydrophobic side chains in Example 1;

[0029] Figure 2 The synthetic route of the polybenzimidazole anion exchange membrane with adjustable hydrophilic and hydrophobic side chains in Example 2;

[0030] Figure 3The synthetic route of the polybenzimidazole anion exchange membrane with adjustable hydrophilic and hydrophobic side chains in Example 3;

[0031] Figure 4 It is a schematic diagram of the structure of membrane electrode;

[0032] Figure 5 This is a current density diagram of a membrane electrode assembled using the polybenzimidazole anion exchange membrane with adjustable hydrophilic and hydrophobic side chains according to Example 3 of the present invention;

[0033] Figure 6 This is a diagram of the CO Faraday efficiency of a membrane electrode assembled using the polybenzimidazole anion exchange membrane with adjustable hydrophilic and hydrophobic side chains according to Example 3 of the present invention; DETAILED DESCRIPTION

[0034] The present invention is further described in detail below in conjunction with the accompanying drawings so that those skilled in the art can implement the invention with reference to the description.

[0035] It should be understood that terms such as “having”, “including” and “comprising” used herein do not specify the existence or addition of one or more other elements or combinations thereof.

[0036] Embodiment 1:

[0037] like Figure 1 As shown, this embodiment provides a method for preparing a polybenzimidazole anion exchange membrane with adjustable hydrophilic and hydrophobic side chains, comprising the following steps:

[0038] Step 1, under a nitrogen atmosphere, add 5 mL of 30 wt% trimethylamine ethanol solution, 7.32 g of dibromohexane and 30 mL of ethyl acetate into a reactor, stir and dissolve at 40°C, react for 48 hours to generate a white solid, filter, wash repeatedly with ethyl acetate, filter and vacuum dry to obtain 1-(6-bromohexyl)trimethylammonium bromide monomer;

[0039] Step 2, under a nitrogen atmosphere, 5 mL of 30 wt% trimethylamine ethanol solution, 18.33 g of 1,2-di-(2-chloroethoxy)ethane, 2.00 g of potassium carbonate and 50 mL of acetonitrile were added to the reactor, and condensed and refluxed at 60°C; after the reaction was completed, the acetonitrile was removed by rotary evaporation, and the remaining solution was poured into ethyl acetate for precipitation, and the light yellow precipitate was collected, washed with ether several times, filtered and vacuum dried to obtain 1-(2-(2-(2-chloroethoxy)ethoxy)-ethoxy)trimethylammonium chloride monomer;

[0040] Step 3: Under a nitrogen atmosphere, 0.30 g of poly(4,4'-diphenyl ether-5,5'-bisbenzimidazole), 0.10 g of potassium carbonate and 10 mL of N-methylpyrrolidone were added to the reactor, stirred and dissolved at 80°C, and then 0.30 g of 1-(6-bromohexyl)trimethylammonium bromide monomer obtained in the above step 1 and 0.11 g of 1-(2-(2-chloroethoxy)ethoxy)-ethoxy)trimethylammonium chloride monomer obtained in step 2 were first dissolved with 5 mL of dimethyl sulfoxide, and then added to the reactor, and reacted at 110°C for 72 hours. After the reaction was completed, the reaction solution was poured into a precipitant, filtered, the yellow fibrous solid was collected, and dried to obtain a polybenzimidazole polymer with adjustable hydrophilic and hydrophobic side chains;

[0041] Step 4: Add 0.50 g of the polybenzimidazole polymer with adjustable hydrophilic and hydrophobic side chains obtained in step 3 and 10 mL of dimethyl sulfoxide into a reactor, stir and dissolve at 80° C. to obtain a bright yellow casting solution, pour the casting solution onto a clean glass plate to form a film, dry at 80° C., soak the film in ethanol to remove residual solvent, and wash with deionized water;

[0042] Step 5: Place the film obtained in step 4 in a 1.0 mol·L -1 The membrane was immersed in KOH solution for 24 hours for ion exchange, thereby obtaining a polybenzimidazole anion exchange membrane with adjustable hydrophilic and hydrophobic side chains.

[0043] Embodiment 2:

[0044] like Figure 2 As shown, this embodiment provides a method for preparing a polybenzimidazole anion exchange membrane with adjustable hydrophilic and hydrophobic side chains, comprising the following steps:

[0045] Step 1: Under a nitrogen atmosphere, add 2.28 g of 1,4-dimethylpiperazine, 7.32 g of dibromohexane and 30 mL of ethyl acetate into a reactor, stir and dissolve at 40°C, react for 48 hours to generate a white solid, filter, wash repeatedly with ethyl acetate, filter and vacuum dry to obtain 1-(6-bromohexyl)-1,4-dimethylpiperazine ammonium bromide monomer;

[0046] Step 2: Under a nitrogen atmosphere, 1.17 g of 1,4-dimethylpiperazine, 18.33 g of 1,2-di-(2-chloroethoxy)ethane, 2.00 g of potassium carbonate and 50 mL of acetonitrile were added to a reactor and condensed and refluxed at 60° C. After the reaction was completed, the acetonitrile was removed by rotary evaporation, and the remaining solution was poured into ethyl acetate for precipitation. The light yellow precipitate was collected, washed with ether for multiple times, filtered and vacuum dried to obtain 1-(2-(2-(2-chloroethoxy)ethoxy)-ethoxy)-1,4-dimethylpiperazine ammonium chloride monomer;

[0047] Step 3: Under a nitrogen atmosphere, 0.30 g of poly(4,4'-diphenyl ether-5,5'-bisbenzimidazole), 0.10 g of potassium carbonate and 10 mL of N-methylpyrrolidone were added to the reactor, stirred and dissolved at 80°C, and then 0.36 g of 1-(6-bromohexyl)-1,4-dimethylpiperazine ammonium bromide monomer obtained in the above step 1 and 0.14 g of 1-(2-(2-chloroethoxy)ethoxy)-ethoxy)-1,4-dimethylpiperazine ammonium chloride monomer obtained in step 2 were first dissolved with 5 mL of dimethyl sulfoxide, and then added to the reactor, reacted at 110°C for 72 hours, and after the reaction was completed, the reaction solution was poured into a precipitant, filtered, the yellow fibrous solid was collected, and dried to obtain a polybenzimidazole polymer with adjustable hydrophilic and hydrophobic side chains;

[0048] Step 4: Add 0.50 g of the polybenzimidazole polymer with adjustable hydrophilic and hydrophobic side chains obtained in step 3 and 10 mL of dimethyl sulfoxide into the reactor, stir and dissolve at 80°C to obtain a bright yellow casting liquid, pour the casting liquid onto a clean glass plate to cast a film, dry at 80°C, soak the film in ethanol to remove the residual solvent, and wash with deionized water.

[0049] Step 5: Place the film obtained in step 4 in a 1.0 mol·L -1 The membrane was immersed in KOH solution for 24 hours for ion exchange, thereby obtaining a polybenzimidazole anion exchange membrane with adjustable hydrophilic and hydrophobic side chains.

[0050] Embodiment 3:

[0051] like Figure 3 As shown, this embodiment provides a method for preparing a polybenzimidazole anion exchange membrane with adjustable hydrophilic and hydrophobic side chains, comprising the following steps:

[0052] Step 1: Under a nitrogen atmosphere, 1.98 g of 1-methylpiperidine, 7.32 g of dibromohexane and 30 mL of ethyl acetate were added to a reactor, stirred and dissolved at 40° C., and a white solid was generated after reacting for 48 hours. The solid was filtered, repeatedly washed with ethyl acetate, filtered and vacuum dried to obtain 1-(6-bromohexyl)-1-methylpiperidinium bromide monomer;

[0053] Step 2: Under a nitrogen atmosphere, 1.02 g of 1-methylpiperidine, 18.33 g of 1,2-di-(2-chloroethoxy)ethane, 2.00 g of potassium carbonate and 50 mL of acetonitrile were added to a reactor and condensed and refluxed at 60° C. After the reaction was completed, the acetonitrile was removed by rotary evaporation, and the remaining solution was poured into ethyl acetate for precipitation. The light yellow precipitate was collected, washed with ether for multiple times, filtered and vacuum dried to obtain 1-(2-(2-(2-chloroethoxy)ethoxy)-ethoxy)-methylpiperidinium chloride monomer;

[0054] Step 3: Under a nitrogen atmosphere, 0.30 g of poly(4,4'-diphenyl ether-5,5'-bisbenzimidazole), 0.10 g of potassium carbonate and 10 mL of N-methylpyrrolidone were added to the reactor, stirred and dissolved at 80°C, and then 0.35 g of 1-(6-bromohexyl)-1-methylpiperidinium bromide monomer obtained in the above step 1 and 0.13 g of 1-(2-(2-chloroethoxy)ethoxy)-ethoxy)-methylpiperidinium chloride obtained in step 2 were first dissolved with 5 mL of dimethyl sulfoxide, and then added to the reactor, and reacted at 110°C for 72 hours. After the reaction was completed, the reaction solution was poured into a precipitant, filtered, the yellow fibrous solid was collected, and dried to obtain a polybenzimidazole polymer with adjustable hydrophilic and hydrophobic side chains;

[0055] Step 4: Add 0.50 g of the polybenzimidazole polymer with adjustable hydrophilic and hydrophobic side chains obtained in step 3 and 10 mL of dimethyl sulfoxide into a reactor, stir and dissolve at 80° C. to obtain a bright yellow casting solution, pour the casting solution onto a clean glass plate to form a film, dry at 80° C., soak the film in ethanol to remove residual solvent, and wash with deionized water;

[0056] Step 5: Place the film obtained in step 4 in a 1.0 mol·L -1 The membrane was immersed in KOH solution for 24 hours for ion exchange, thereby obtaining a polybenzimidazole anion exchange membrane with adjustable hydrophilic and hydrophobic side chains.

[0057] Comparative Example 1:

[0058] This comparative example provides a method for preparing a polybenzimidazole anion exchange membrane with a hydrophilic side chain, comprising the following steps:

[0059] Step 1: Under nitrogen atmosphere, 1.02 g of 1-methylpiperidine, 18.33 g of 1,2-di-(2-chloroethoxy)ethane, 2.00 g of potassium carbonate and 50 mL of acetonitrile were added to the reactor and condensed and refluxed at 60° C. After the reaction was completed, the acetonitrile was removed by rotary evaporation, and the remaining solution was poured into ethyl acetate for precipitation. The light yellow precipitate was collected, washed with ether for multiple times, filtered and vacuum dried to obtain 1-(2-(2-(2-chloroethoxy)ethoxy)-ethoxy)-methylpiperidinium chloride monomer;

[0060] Step 2: Under a nitrogen atmosphere, 0.30 g of poly(4,4'-diphenyl ether-5,5'-bisbenzimidazole), 0.10 g of potassium carbonate and 10 mL of N-methylpyrrolidone were added to a reactor, stirred and dissolved at 80°C, and then 0.38 g of 1-(2-(2-(2-chloroethoxy)ethoxy)-ethoxy)-methylpiperidinium chloride monomer obtained in the above step 1 was first dissolved with 5 mL of dimethyl sulfoxide and then added to the reactor, and reacted at 110°C for 72 hours. After the reaction was completed, the reaction solution was poured into a precipitant, filtered, the yellow fibrous solid was collected, and dried to obtain a polybenzimidazole polymer containing a hydrophilic side chain;

[0061] Step 4: Add 0.50 g of the polybenzimidazole polymer containing hydrophilic side chains obtained in step 3 and 10 mL of dimethyl sulfoxide into the reactor, stir and dissolve at 80°C to obtain a bright yellow casting liquid, pour the casting liquid onto a clean glass plate to cast a film, dry at 80°C, soak the film in ethanol to remove residual solvent, and wash with deionized water.

[0062] Step 5: Place the film obtained in step 4 in a 1.0 mol·L -1 The membrane was immersed in KOH solution for 24 hours for ion exchange to obtain a hydrophilic polybenzimidazole anion exchange membrane.

[0063] Comparative Example 2:

[0064] This comparative example provides a method for preparing a polybenzimidazole anion exchange membrane with a hydrophobic side chain, comprising the following steps:

[0065] Step 1: Under a nitrogen atmosphere, 1.98 g of 1-methylpiperidine, 7.32 g of dibromohexane and 30 mL of ethyl acetate were added to a reactor, stirred and dissolved at 40° C., and a white solid was generated after reacting for 48 hours. The solid was filtered, repeatedly washed with ethyl acetate, filtered and vacuum dried to obtain 1-(6-bromohexyl)-1-methylpiperidinium bromide monomer;

[0066] Step 2: Under a nitrogen atmosphere, 0.30 g of poly (4,4'-diphenyl ether-5,5'-bisbenzimidazole), 0.10 g of potassium carbonate and 10 mL of N-methylpyrrolidone were added to a reactor, stirred and dissolved at 80°C, and then 0.52 g of 1-(6-bromohexyl)-1-methylpiperidinium bromide monomer obtained in the above step 1 was first dissolved with 5 mL of dimethyl sulfoxide and then added to the reactor, and reacted at 110°C for 72 hours. After the reaction was completed, the reaction solution was poured into a precipitant, filtered, and a yellow fibrous solid was collected and dried to obtain a polybenzimidazole polymer containing a hydrophobic side chain;

[0067] Step 4: Add 0.50 g of the polybenzimidazole polymer containing hydrophobic side chains obtained in step 3 and 10 mL of dimethyl sulfoxide into the reactor, stir and dissolve at 80°C to obtain a bright yellow casting solution, pour the casting solution onto a clean glass plate to cast a film, dry at 80°C, soak the film in ethanol to remove residual solvent, and wash with deionized water.

[0068] Step 5: Place the film obtained in step 4 in a 1.0 mol·L -1 The membrane was immersed in KOH solution for 24 hours for ion exchange to obtain a hydrophobic polybenzimidazole anion exchange membrane.

[0069] Comparative Example 3: (Here, the ratio of the grafted hydrophilic side chain to the hydrophobic side chain is different, the molar ratio of the ammonium bromide-containing monomer to the ammonium chloride-containing monomer is 1:1, and the ratio in Example 3 is 1:2)

[0070] This comparative example provides a method for preparing a polybenzimidazole anion exchange membrane with adjustable hydrophilic and hydrophobic side chains, comprising the following steps:

[0071] Step 1: Under a nitrogen atmosphere, 1.98 g of 1-methylpiperidine, 7.32 g of dibromohexane and 30 mL of ethyl acetate were added to a reactor, stirred and dissolved at 40° C., and a white solid was generated after reacting for 48 hours. The solid was filtered, repeatedly washed with ethyl acetate, filtered and vacuum dried to obtain 1-(6-bromohexyl)-1-methylpiperidinium bromide monomer;

[0072] Step 2: Under a nitrogen atmosphere, 1.02 g of 1-methylpiperidine, 18.33 g of 1,2-di-(2-chloroethoxy)ethane, 2.00 g of potassium carbonate and 50 mL of acetonitrile were added to a reactor and condensed and refluxed at 60° C. After the reaction was completed, the acetonitrile was removed by rotary evaporation, and the remaining solution was poured into ethyl acetate for precipitation. The light yellow precipitate was collected, washed with ether for multiple times, filtered and vacuum dried to obtain 1-(2-(2-(2-chloroethoxy)ethoxy)-ethoxy)-methylpiperidinium chloride monomer;

[0073] Step 3: Under a nitrogen atmosphere, 0.30 g of poly(4,4'-diphenyl ether-5,5'-bisbenzimidazole), 0.10 g of potassium carbonate and 10 mL of N-methylpyrrolidone were added to the reactor, stirred and dissolved at 80°C, and then 0.26 g of 1-(6-bromohexyl)-1-methylpiperidinium bromide monomer obtained in the above step 1 and 0.19 g of 1-(2-(2-chloroethoxy)ethoxy)-ethoxy)-methylpiperidinium chloride obtained in step 2 were first dissolved with 5 mL of dimethyl sulfoxide, and then added to the reactor, and reacted at 110°C for 72 hours. After the reaction was completed, the reaction solution was poured into a precipitant, filtered, the yellow fibrous solid was collected, and dried to obtain a polybenzimidazole polymer with adjustable hydrophilic and hydrophobic side chains;

[0074] Step 4: Add 0.50 g of the polybenzimidazole polymer with adjustable hydrophilic and hydrophobic side chains obtained in step 3 and 10 mL of dimethyl sulfoxide into the reactor, stir and dissolve at 80°C to obtain a bright yellow casting liquid, pour the casting liquid onto a clean glass plate to cast a film, dry at 80°C, soak the film in ethanol to remove the residual solvent, and wash with deionized water.

[0075] Step 5: Place the polybenzimidazole anion exchange membrane with adjustable hydrophilic and hydrophobic side chains in a 1.0 mol·L -1 The membrane was immersed in KOH solution for 24 hours for ion exchange, thereby obtaining a polybenzimidazole anion exchange membrane with adjustable hydrophilic and hydrophobic side chains.

[0076] Comparative Example 4: (Here, the ratio of the grafted hydrophilic side chain to the hydrophobic side chain is different, the molar ratio of the ammonium bromide-containing monomer to the ammonium chloride-containing monomer is 1:3, and the grafting ratio of Example 3 is 1:2)

[0077] This comparative example provides a method for preparing a polybenzimidazole anion exchange membrane with adjustable hydrophilic and hydrophobic side chains, comprising the following steps:

[0078] Step 1: Under a nitrogen atmosphere, 1.98 g of 1-methylpiperidine, 7.32 g of dibromohexane and 30 mL of ethyl acetate were added to a reactor, stirred and dissolved at 40° C., and a white solid was generated after reacting for 48 hours. The solid was filtered, repeatedly washed with ethyl acetate, filtered and vacuum dried to obtain 1-(6-bromohexyl)-1-methylpiperidinium bromide monomer;

[0079] Step 2: Under a nitrogen atmosphere, 1.02 g of 1-methylpiperidine, 18.33 g of 1,2-di-(2-chloroethoxy)ethane, 2.00 g of potassium carbonate and 50 mL of acetonitrile were added to a reactor and condensed and refluxed at 60° C. After the reaction was completed, the acetonitrile was removed by rotary evaporation, and the remaining solution was poured into ethyl acetate for precipitation. The light yellow precipitate was collected, washed with ether for multiple times, filtered and vacuum dried to obtain 1-(2-(2-(2-chloroethoxy)ethoxy)-ethoxy)-methylpiperidinium chloride monomer;

[0080] Step 3: Under a nitrogen atmosphere, 0.30 g of poly(4,4'-diphenyl ether-5,5'-bisbenzimidazole), 0.10 g of potassium carbonate and 10 mL of N-methylpyrrolidone were added to the reactor, stirred and dissolved at 80°C, and then 0.39 g of 1-(6-bromohexyl)-1-methylpiperidinium bromide monomer obtained in the above step 1 and 0.10 g of 1-(2-(2-chloroethoxy)ethoxy)-ethoxy)-methylpiperidinium chloride obtained in step 2 were first dissolved with 5 mL of dimethyl sulfoxide, and then added to the reactor, and reacted at 110°C for 72 hours. After the reaction was completed, the reaction solution was poured into a precipitant, filtered, the yellow fibrous solid was collected, and dried to obtain a polybenzimidazole polymer with adjustable hydrophilic and hydrophobic side chains;

[0081] Step 4: Add 0.50 g of the polybenzimidazole polymer with adjustable hydrophilic and hydrophobic side chains obtained in step 3 and 10 mL of dimethyl sulfoxide into the reactor, stir and dissolve at 80°C to obtain a bright yellow casting liquid, pour the casting liquid onto a clean glass plate to cast a film, dry at 80°C, soak the film in ethanol to remove the residual solvent, and wash with deionized water.

[0082] Step 5: Place the polybenzimidazole anion exchange membrane with adjustable hydrophilic and hydrophobic side chains in a 1.0 mol·L -1 The membrane was immersed in KOH solution for 24 hours for ion exchange, thereby obtaining a polybenzimidazole anion exchange membrane with adjustable hydrophilic and hydrophobic side chains.

[0083] The electrocatalytic CO2 reduction performance test was performed on the polybenzimidazole anion exchange membranes with adjustable hydrophilic and hydrophobic side chains prepared in Examples 1-3 and Comparative Examples 1-4 respectively:

[0084] Anion exchange membrane is used as a membrane electrode assembly in electrocatalytic CO2 reduction. Current density (j) and Faraday efficiency (FE) are the main evaluation indicators of membrane electrode performance. The preparation method of the membrane electrode is as follows: 5 mg of nano silver powder is added to 0.25 mL of deionized water, 0.75 mL of anhydrous ethanol, and 50 μL of FAA solution, and ultrasonicated for 1 h to obtain cathode catalyst ink, and then evenly sprayed on a 2×2 cm 2 39BB hydrophobic carbon paper was prepared and dried at 50-70°C to obtain a cathode. Then 5 mg of iridium oxide was added to 0.25 mL of deionized water, 0.75 mL of anhydrous ethanol, and 50 μL of FAA solution, and ultrasonicated for 1 h to obtain an anode catalyst ink, which was then evenly sprayed on a 2×2 cm 2 39BB hydrophobic carbon paper and dried at 50-70°C to obtain an anode; finally, the cathode, anion exchange membrane and anode are assembled to obtain a membrane electrode (such as Figure 4 As shown in the figure, the gas flow field is outside the cathode, and the electrolyte flow field is outside the anode. -1 KHCO3 was used as the electrolyte, and the electrolyte was transported to the anode by a peristaltic pump for flow. The dry CO2 was humidified by a gas humidifier at a rate of 20 mL min -1 The gas was transported to the cathode at a flow rate of 1000 ℃ and flowed. The electrochemical workstation CHI660E produced by Shanghai Chenhua Instrument Co., Ltd. was used for electrolysis for 1 hour under different current conditions. The gas product was passed into the 9790Plus gas chromatograph produced by Fuzhou Fuli Instrument Co., Ltd. for testing. The CO Faraday efficiency calculation formula is as follows:

[0085]

[0086] Where α is the number of electrons transferred when CO2 is reduced to CO2, n is the molar amount of CO (mol), and F is the Faraday constant (96485 mol·C -1 ), Q is the total coulomb amount transferred to the cathode (C).

[0087] j CO =FEco×j total

[0088] Among them, j CO is the current density of CO, j total is the total cathode current density (mA·cm -2 ), FE CO is the Faradaic efficiency of CO (%).

[0089] CO Faraday efficiency (FE) of anion exchange membranes prepared in Example 1, Example 2, Example 3 and Comparative Example 1, Comparative Example 2, Comparative Example 3 and Comparative Example 4 CO ) and the current density of CO (j CO ) are shown in the following table:

[0090]

[0091] As can be seen from the above table, compared with Comparative Examples 1 and 2, Example 3 can make the polybenzimidazole anion exchange membrane prepared by regulating the content of hydrophilic and hydrophobic side chains enable the membrane electrode reactor to have higher current density and CO Faraday efficiency. This is because the hydrophilic alkoxy side chains can form a hydrogen bond network with water, effectively improving the hydration environment of the ion transmission channel and promoting the transmission of hydroxide; on the other hand, the hydrophilic alkoxy side chains interact with the hydrophobic long side chains to promote the formation of microphase separation in the membrane, so that the membrane has excellent performance. Compared with Comparative Examples 3 and 4, the hydrophilic and hydrophobic side chain ratio of Example 3 has obvious advantages, and the current density and CO Faraday efficiency are significantly higher, indicating that too many hydrophilic side chains will enhance the swelling of the membrane, which is not conducive to the ion conduction and selectivity of the membrane.

[0092] Figure 5 The current density diagram of the membrane electrode assembled using the polybenzimidazole anion exchange membrane with adjustable hydrophilic and hydrophobic side chains of Example 3 of the present invention. It can be seen from the figure that compared with Comparative Examples 1 and 2, the CO current density of Example 3 after adjusting the ratio of hydrophilic and hydrophobic side chains is significantly improved.

[0093] Figure 6 The CO Faraday efficiency diagram of the membrane electrode assembled using the polybenzimidazole anion exchange membrane with adjustable hydrophilic and hydrophobic side chains of Example 3 of the present invention. It can be seen from the figure that the current density is 140 mA cm -1The corresponding CO Faradaic efficiency is 90.2%, indicating that the membrane has significant advantages in electrocatalytic CO2 reduction applications.

[0094] The number of devices and processing scales described here are used to simplify the description of the present invention. Applications, modifications and variations of the present invention will be obvious to those skilled in the art.

[0095] Although the embodiments of the present invention have been disclosed as above, they are not limited to the applications listed in the specification and the implementation modes, and they can be fully applied to various fields suitable for the present invention. For those familiar with the art, additional modifications can be easily implemented. Therefore, without departing from the general concept defined by the claims and the scope of equivalents, the present invention is not limited to the specific details and the illustrations shown and described herein.

Claims

1. A polybenzimidazole anion exchange membrane with adjustable hydrophilic and hydrophobic side chains, characterized in that: The structural formula of the polybenzimidazole anion exchange membrane with adjustable hydrophilic and hydrophobic side chains is: Among them, the molar ratio of x:y is 1-4:1-4; Q is any one of a 1-methylpiperidine group, a 1,4-dimethylpiperazine group, a 1-methylpyrrole group, a 1-methylimidazole group, a 1-methylpyrrolidine group, a 1-methylpyrazole group, an imidazolium group, a trimethylamine group, a triethylamine group, and a tripropylamine group.

2. A method for preparing a polybenzimidazole anion exchange membrane with adjustable hydrophilic and hydrophobic side chains as claimed in claim 1, characterized in that: The following steps are involved: Step 1: Under a nitrogen atmosphere, add a tertiary ammonium group-containing reagent, dibromohexane and ethyl acetate into a reactor, stir and dissolve, and after the reaction is completed, a white solid is generated, which is filtered, repeatedly washed with ethyl acetate, and vacuum dried to obtain an ammonium bromide-containing monomer; Step 2: Under a nitrogen atmosphere, a tertiary ammonium group-containing reagent, 1,2-di-(2-chloroethoxy)ethane, potassium carbonate and acetonitrile are added to a reactor, condensed and refluxed, and after the reaction is completed, the acetonitrile is removed by rotary evaporation, and the remaining solution is poured into ethyl acetate for precipitation, and the light yellow precipitate is collected, washed with ether for multiple times, filtered and vacuum dried to obtain an ammonium chloride-containing monomer; Step 3: under a nitrogen atmosphere, poly(4,4'-diphenylether-5,5'-bisbenzimidazole), potassium carbonate and N-methylpyrrolidone are added to a reactor, stirred and dissolved, and then the ammonium bromide-containing monomer obtained in the above step 1 and the ammonium chloride-containing monomer obtained in step 2 are first dissolved with dimethyl sulfoxide and then added to the reactor. After the reaction is completed, the reaction solution is poured into a precipitant, filtered, and a yellow fibrous solid is collected and dried to obtain a polybenzimidazole polymer with adjustable hydrophilic and hydrophobic side chains; Step 4: Add the polybenzimidazole polymer with adjustable hydrophilic and hydrophobic side chains obtained in step 3 and dimethyl sulfoxide into a reactor, stir and dissolve to obtain a bright yellow casting solution, pour the casting solution onto a clean glass plate to form a film, and after drying, soak the film in ethanol to remove the residual solvent, and wash with deionized water; Step 5: soak the membrane obtained in step 4 in a KOH solution for ion exchange, thereby obtaining a polybenzimidazole anion exchange membrane with adjustable hydrophilic and hydrophobic side chains.

3. The method for preparing a polybenzimidazole anion exchange membrane with adjustable hydrophilic and hydrophobic side chains as claimed in claim 2, characterized in that: In the step 1, the molar ratio of the reagent containing a tertiary ammonium group to dibromohexane is 1:2-10; the molar volume ratio of the reagent containing a tertiary ammonium group to ethyl acetate is 10-30 mmol:20-50 mL, the reaction temperature is 20-50° C., and the reaction time is 24-48 h; the vacuum drying temperature is 40-60° C., and the drying time is 12-36 h; the reagent containing a tertiary ammonium group is any one of 1-methylpiperidine, 1,4-dimethylpiperazine, 1-methylpyrrole, 1-methylimidazole, 1-methylpyrrolidine, 1-methylpyrazole, imidazolium, trimethylamine, triethylamine, and tripropylamine.

4. The method for preparing a polybenzimidazole anion exchange membrane with adjustable hydrophilic and hydrophobic side chains as claimed in claim 2, characterized in that: In the step 2, the molar ratio of the reagent containing a tertiary ammonium group, 1,2-di-(2-chloroethoxy)ethane and potassium carbonate is 1:1-5:5-20; the molar volume ratio of the reagent containing a tertiary ammonium group and acetonitrile is 10-30mmol:20-100mL; the reaction temperature is 40-70°C, and the reaction time is 24-48h; the vacuum drying temperature is 40-60°C, and the drying time is 12-36h; the reagent containing a tertiary ammonium group is any one of 1-methylpiperidine, 1,4-dimethylpiperazine, 1-methylpyrrole, 1-methylimidazole, 1-methylpyrrolidine, 1-methylpyrazole, imidazolium, trimethylamine, triethylamine, and tripropylamine.

5. The method for preparing a polybenzimidazole anion exchange membrane with adjustable hydrophilic and hydrophobic side chains as claimed in claim 2, characterized in that: In the step 3, the molar volume ratio of poly(4,4'-diphenyl ether-5,5'-bisbenzimidazole), potassium carbonate and N-methylpyrrolidone is 1mmol:1-3mmol:5-15mL; the molar volume ratio of ammonium bromide monomer, ammonium chloride monomer and dimethyl sulfoxide is 0-4mmol:0-4mmol:5-10mL; the reaction temperature is 80-110°C, and the reaction time is 24-72h; the precipitant is one or more of anhydrous ethanol, ethyl acetate and deionized water.

6. The method for preparing a polybenzimidazole anion exchange membrane with adjustable hydrophilic and hydrophobic side chains as claimed in claim 2, characterized in that: In the step 4, the stirring and dissolving temperature is 60-80° C., and the stirring time is 6-24 h; the drying temperature of the casting solution is 60-100° C., and the drying time is 12-24 h; the mass volume ratio of the polybenzimidazole polymer with adjustable hydrophilic and hydrophobic side chains and dimethyl sulfoxide is 0.3-0.8 g:10 mL; in the step 5, the concentration of the KOH solution is 0.5-4 mol·L-1, and the immersion time is 24-72 h.

7. Use of a polybenzimidazole anion exchange membrane with adjustable hydrophilic and hydrophobic side chains prepared by the preparation method according to any one of claims 2 to 6 in electrocatalytic CO2 reduction, characterized in that: The polybenzimidazole anion exchange membrane with adjustable hydrophilic and hydrophobic side chains is used as a diaphragm in the electrocatalytic CO2 reduction membrane electrode.

8. Use of the polybenzimidazole anion exchange membrane with adjustable hydrophilic and hydrophobic side chains as claimed in claim 7 in electrocatalytic CO2 reduction, characterized in that: The preparation method of the membrane electrode comprises: adding nano silver powder to deionized water, anhydrous ethanol and FAA solution, ultrasonicating to obtain cathode catalyst ink, then using a spray gun to evenly spray it on hydrophobic carbon paper, and drying it at 50-70°C to obtain a cathode; adding iridium oxide to deionized water, anhydrous ethanol and FAA solution, ultrasonicating to obtain anode catalyst ink, then using a spray gun to evenly spray it on hydrophobic carbon paper, and drying it at 50-70°C to obtain an anode; and finally assembling the cathode, a polybenzimidazole anion exchange membrane with adjustable hydrophilic and hydrophobic side chains, and an anode to obtain a membrane electrode.

9. The use of the polybenzimidazole anion exchange membrane with adjustable hydrophilic and hydrophobic side chains as claimed in claim 8, characterized in that: The mass volume ratio of nano silver powder, anhydrous ethanol, deionized water and FAA solution in the cathode is 1-3 mg: 100-300 μL: 20-100 μL: 5-20 μL; the mass volume ratio of iridium oxide, anhydrous ethanol, deionized water and FAA solution in the anode is 1-3 mg: 100-300 μL: 20-100 μL: 5-20 μL.

10. Use of the polybenzimidazole anion exchange membrane with adjustable hydrophilic and hydrophobic side chains as claimed in claim 7 in electrocatalytic CO2 reduction, characterized in that: Use 0.1~1mol·L -1 KHCO3 is used as the anode electrolyte, and the electrolyte is transported to the anode through a peristaltic pump for flow, and the dry CO2 is humidified by a gas humidifier and transported to the cathode for flow, and then a constant current is applied for electrolysis to promote electrocatalytic reduction of CO2; the rotation speed of the peristaltic pump is 20 to 80 rpm; the flow rate of the CO2 is 10 to 40 mL min -1 ; The thickness of the adjustable hydrophilic and hydrophobic side chain polybenzimidazole anion exchange membrane is 10 to 50 μm.

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