Intermediate layer modified bipolar membrane and preparation method thereof

Abstract

The preparation method comprises the following steps: firstly, soaking a sulfonic acid type cation exchange membrane in an acid solution, and converting Na < + > in the sulfonic acid type cation exchange membrane into H < + >; the cation exchange membrane is soaked in an aniline solution, so that protonated aniline is electrostatically adsorbed on the cation exchange membrane, and an intermediate catalyst layer is obtained after polymerization reaction and covalent bond binding reaction; and finally, casting an anion exchange membrane liquid composed of quaternized polyphenyl ether, methanol and dimethylformamide on the middle catalyst layer, and heating and drying to obtain the bipolar membrane. The bipolar membrane can effectively reduce the water dissociation voltage and energy consumption, improves the acid and alkali production efficiency and is long in service life.

Description

Technical Field

[0001] The invention belongs to the technical field of bipolar membrane synthesis and preparation, and particularly relates to a bipolar membrane with modified intermediate layer and a preparation method thereof. Background Art

[0002] Bipolar membrane is a new type of ion exchange composite membrane, which is usually composed of a cation exchange layer, an intermediate layer and an anion exchange layer. The intermediate layer is usually a few nanometers thick, electrically neutral and contains a catalyst. Under the action of a DC electric field, the intermediate layer of the bipolar membrane can dissociate water to produce H + and OH - Subsequently, the generated H + and OH - Driven by the potential difference between the cathode and anode, the bipolar membrane migrates toward the cathode and anode, respectively. At the same time, water in the solution on both sides of the bipolar membrane enters the IL layer through the AEL and CEL to replenish the water consumption.

[0003] In practical applications, the bipolar membrane is the core component of a bipolar membrane electrodialysis device, and its performance has a decisive influence on the bipolar membrane electrodialysis process. An ideal bipolar membrane should have high selectivity, reduced voltage, low energy consumption, stable mechanical properties, and a long service life.

[0004] The modification of bipolar membranes can be divided into modification of bipolar membrane materials and modification of the intermediate layer. Regardless of the modification method adopted, improving the water dissociation efficiency of the intermediate layer and reducing the water dissociation voltage and energy consumption of the bipolar membrane are the key to the current research and development of bipolar membranes. Summary of the Invention

[0005] The present invention is proposed to solve the problems existing in the prior art, and its purpose is to provide a bipolar membrane with a modified intermediate layer and a preparation method thereof.

[0006] The present invention is achieved through the following technical solutions:

[0007] A method for preparing a bipolar membrane with a modified intermediate layer comprises the following steps:

[0008] (I) soaking the sulfonic acid type cation exchange membrane in an acidic solution to obtain a base membrane;

[0009] The sulfonic acid cation exchange membrane is immersed in the acidic solution for 1 to 3 days;

[0010] The acidic solution is HCl solution;

[0011] The acidic solution contains H + The concentration is 1 mol / L;

[0012] The sulfonic acid cation exchange membrane is immersed in an acidic solution to remove the Na+ Converted to H + ;

[0013] In addition to hydrochloric acid, other strong acids (such as sulfuric acid) can also be used for protonation treatment. However, attention should be paid to the effect of anions on the membrane structure: if acid ions (such as sulfate) may undergo irreversible adsorption or side reactions with the membrane material, they should be avoided; if sulfuric acid is used instead of hydrochloric acid, it is necessary to thoroughly wash and remove residual sulfate ions to prevent them from interfering with ion migration during the electrolysis process; the acid used in the subsequent application is hydrochloric acid, so hydrochloric acid is preferred to avoid residual impurity ions;

[0014] The concentration of the acidic solution is 0.5M to 2M to ensure sufficient H+ concentration to drive the protonation reaction. Too low a concentration will lead to incomplete protonation and decreased membrane conductivity; too high a concentration may accelerate the swelling of the membrane material or destroy the structure;

[0015] (II) soaking one side of the sulfonic acid cation exchange membrane treated in step (I) in an aniline solution to allow protonated aniline to be electrostatically adsorbed on the cation exchange membrane; after soaking for a certain period of time, adding an oxidant to the aniline solution, continuing soaking, and performing a polymerization reaction on the soaked side of the sulfonic acid cation exchange membrane; after the polymerization reaction, adding graphene oxide powder to the aniline solution, and performing a covalent bond reaction on the soaked side of the sulfonic acid cation exchange membrane; and obtaining an intermediate catalytic layer after the reaction;

[0016] The aniline solution is an aqueous solution of aniline in hydrochloric acid, which is obtained by dissolving 0.2 mol of aniline in 1 L of hydrochloric acid with a concentration of 1 mol / L; the concentration of aniline in the aniline solution is 0.2 mol / L, and the concentration of hydrochloric acid is 1 mol / L;

[0017] The immersion time of one side of the sulfonic acid cation exchange membrane in the aniline solution is 15 hours to 24 hours;

[0018] The oxidant is a hydrochloric acid solution of FeCl3, the concentration of FeCl3 in the oxidant is 0.2 mol / L, and the concentration of hydrochloric acid is 1 mol / L;

[0019] The molar ratio of FeCl3 to aniline in the oxidant is 1:1;

[0020] The polymerization reaction time is 2h to 10h;

[0021] The dosage of graphene oxide is related to the membrane area, specifically 0.016 mg to 0.08 mg / cm 2 ;

[0022] The duration of the covalent bonding reaction is 2h to 6h;

[0023] (III) adding polyphenylene ether and chlorobenzene to a reaction vessel, mixing the polyphenylene ether and chlorobenzene, and then adding azobisisobutyronitrile and N-bromosuccinimide to carry out a synthesis reaction. After the reaction is completed, the product is washed with ethanol or acetone solution to obtain brominated polyphenylene ether;

[0024] The dosage ratio of the polyphenylene ether to chlorobenzene is (1-2) g: (10-20) mL;

[0025] The synthesis reaction of the brominated polyphenylene ether is carried out under nitrogen protection, the temperature of the synthesis reaction of the brominated polyphenylene ether is 135° C., and the reaction time is 4 to 8 hours;

[0026] The degree of bromination of the brominated polyphenylene ether is 25% to 30%;

[0027] (IV) dissolving the brominated polyphenylene ether in N-methylpyrrolidone, adding trimethylamine, reacting at a constant temperature, and vacuum drying after the reaction to obtain a quaternized polyphenylene ether;

[0028] The molar ratio of the brominated polyphenylene ether to trimethylamine is 1:0.6;

[0029] The temperature of the constant temperature reaction is 50°C to 80°C, and the reaction time is 10h to 18h.

[0030] The temperature of vacuum drying is 40℃;

[0031] (V) adding the quaternized polyphenylene ether to a mixed solution of methanol and dimethylformamide to obtain an anion exchange membrane solution;

[0032] The molar ratio of the quaternized polyphenylene ether, methanol and dimethylformamide is 1:8:1;

[0033] (VI) Casting the anion exchange membrane solution prepared in step (V) on the middle catalyst layer of the sulfonic acid type cation exchange membrane, and then heating and drying it on an electric heating plate to obtain a bipolar membrane.

[0034] The drying temperature is 30°C to 60°C.

[0035] The amount of anion exchange membrane solution added was 0.12 g / cm 2 .

[0036] A bipolar membrane with modified intermediate layer is prepared by the above method. The bipolar membrane comprises a cation exchange membrane layer, an intermediate catalytic layer and an anion exchange membrane layer. The intermediate catalytic layer is composed of a polyaniline-graphene oxide composite.

[0037] The beneficial effects of the present invention are:

[0038] The present invention provides a bipolar membrane with modified intermediate layer and a preparation method thereof, which can effectively reduce the water dissociation voltage and energy consumption, improve the acid and alkali production efficiency and have a long service life. The cation exchange membrane used in the present invention has a dense and uniform structure and good hydrophilicity; protonated aniline is loaded onto the surface of the cation exchange membrane by in-situ polymerization of electrostatic adsorption to form polyaniline, and graphene oxide is loaded onto the surface of the cation exchange membrane by reacting with polyaniline to form π-π covalent bonds, so that the bond between the intermediate layer and the two membrane layers of the anion and cation exchange membranes is stronger, stratification is avoided, and the service life is extended; the polyaniline and graphene oxide composite is used as the intermediate layer to effectively improve the water dissociation catalytic effect of the intermediate layer, thereby reducing the water dissociation voltage and energy consumption and improving the acid and alkali production efficiency. Experimental results show that when 50m A / cm is applied 2 At a current density of 1.5 volts, the voltage required for water dissociation by the bipolar membrane was only 1.03 V. Electrochemical impedance spectroscopy was used to test the bipolar membrane, and the results showed that its water dissociation resistance was only 1.16 Ω. After 3 hours of electrodialysis, the concentration of acid and alkali produced by the bipolar membrane reached 0.15 mol / L. In the 8-hour stability test of the bipolar membrane, the constant current (50 mA / cm 2 ), the water dissociation voltage was stable between 1.0 and 1.07 V. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 is a scanning electron microscope image of the bipolar membrane intermediate layer of Example 1 of the present invention;

[0040] Figure 2 is the bipolar membrane current-voltage curve of Example 1 of the present invention;

[0041] Figure 3 This is a diagram showing the acid-base generation effect of the bipolar membrane of Example 1 of the present invention;

[0042] Figure 4 1 is a schematic diagram of electrochemical impedance spectroscopy according to Example 1 of the present invention;

[0043] Figure 5 3 is a schematic diagram of the water dissociation stability test performance under constant current density of Example 1 of the present invention.

[0044] For ordinary technicians in this field, other relevant drawings can be obtained based on the above drawings without any creative work. DETAILED DESCRIPTION

[0045] In order to enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be further described below with reference to the accompanying drawings and through specific implementation methods.

[0046] Example 1

[0047] A method for preparing a bipolar membrane with a modified intermediate layer comprises the following steps:

[0048] (I) soaking the sulfonic acid cation exchange membrane in a 1 mol / L hydrochloric acid solution for 1 day, and converting the sulfonic acid cation exchange membrane into a hydrogen cation exchange membrane after the soaking, and using the hydrogen cation exchange membrane as a base membrane;

[0049] The sulfonic acid type cation exchange membrane is a cation exchange membrane manufactured by Fuji, Japan;

[0050] (II) Immerse one side of the hydrogen-type cation exchange membrane in 120 mL of a 0.2 mol / L protonated aniline acidic mixed solution at a low temperature of 10°C for 24 h to allow the protonated aniline to be electrostatically adsorbed on the cation exchange membrane;

[0051] The protonated aniline acidic mixed solution is prepared by adding 18.626 g of aniline to 1 L of 1 mol / L hydrochloric acid to prepare an aniline-hydrochloric acid solution with an aniline concentration of 0.2 mol / L, and stirring the aniline-hydrochloric acid solution at a low temperature of 10° C. for 24 hours to completely protonate the aniline and convert it into a protonated aniline-hydrochloric acid solution.

[0052] (III) taking out 60 mL of a 0.2 mol / L protonated aniline-hydrochloric acid solution and adding 60 mL of a 0.2 mol / L ferric chloride-hydrochloric acid solution to obtain a polymerization solution, immersing the side of the cation exchange membrane adsorbing the protonated aniline in the polymerization solution, and performing an in-situ polymerization reaction for 5 hours; after the polymerization reaction is completed, adding 2 mg of graphene oxide powder to the polymerization solution at a low temperature of 10°C, stirring thoroughly, and reacting for 4 hours, so that the hydroxyl groups on the graphene oxide combine with the polyaniline to form π-π covalent bonds, thereby forming an intermediate layer containing a polyaniline-graphene oxide composite;

[0053] The ferric chloride-hydrochloric acid solution is prepared by weighing 32.44 g of anhydrous ferric chloride, adding it to 1 L of 1 mol / L hydrochloric acid to prepare a ferric chloride-hydrochloric acid solution with a ferric chloride concentration of 0.2 mol / L, and storing it at a low temperature of 10° C.

[0054] (IV) In a three-necked round-bottom flask, 6 g of polyphenylene ether and 60 mL of chlorobenzene solution were added to completely dissolve the polyphenylene ether at room temperature. 0.25 g of azobisisobutyronitrile and 9.8 g of N-bromosuccinimide were then added. The mixed solution was heated to 135° C. under a nitrogen atmosphere for 6 h of condensation and reflux. After the reaction, the mixture was poured into an ethanol solvent and washed three times. The product precipitated in the solvent. The dried product was redissolved in a chloroform solvent to remove insoluble impurities. The product was again precipitated with an ethanol solvent, washed three times, and dried to obtain brominated polyphenylene ether with a degree of bromination of 25-30%.

[0055] (V) 0.3 g of brominated polyphenylene ether was dissolved in N-methylpyrrolidone solution, and trimethylamine was added. The mixture was reacted at a constant temperature of 60° C. for 12 h, and then dried in a vacuum oven at 40° C. to obtain quaternized polyphenylene ether with a quaternization degree of 30-35%.

[0056] The molar ratio of brominated polyphenylene ether to trimethylamine is 1:0.6;

[0057] (VI) adding 1 g of quaternized polyphenylene ether to a mixed solution of methanol and dimethylformamide to prepare a quaternized polyphenylene ether-methanol / dimethylformamide solution, which is an anion exchange membrane solution;

[0058] The molar ratio of the quaternized polyphenylene ether, methanol and dimethylformamide is 1:8:1;

[0059] (VII) Place a hydrogen-type cation exchange membrane on a glass plate with the side having the intermediate layer facing upward, cast an anion exchange membrane liquid on the hydrogen-type cation exchange membrane having the intermediate catalytic layer, heat the glass plate on a heating plate at 60°C, and scrape the membrane with a scraper.

[0060] The experimental results show that applying 50mA / cm 2 At a current density of 1.5 volts, the voltage required for water dissociation by the bipolar membrane was only 1.03 V. Electrochemical impedance spectroscopy was used to test the bipolar membrane, and the results showed that its water dissociation resistance was only 1.16 Ω. After 3 hours of electrodialysis, the concentration of acid and alkali produced by the bipolar membrane reached 0.15 mol / L. In the 8-hour stability test of the bipolar membrane, the constant current (50 mA / cm 2 ), the water dissociation voltage was stable between 1.0-1.07V.

[0061] Example 2

[0062] A method for preparing a bipolar membrane with a modified intermediate layer comprises the following steps:

[0063] (I) soaking the sulfonic acid cation exchange membrane in a 1 mol / L hydrochloric acid solution for 2 days, converting the sulfonic acid cation exchange membrane into a hydrogen cation exchange membrane, and using the hydrogen cation exchange membrane as a base membrane;

[0064] The sulfonic acid type cation exchange membrane is a cation exchange membrane manufactured by Fuji, Japan;

[0065] (II) Immerse one side of the hydrogen-type cation exchange membrane in 120 mL of a 0.2 mol / L protonated aniline acidic mixed solution at a low temperature of 10°C for 24 h to allow the protonated aniline to be electrostatically adsorbed on the cation exchange membrane;

[0066] The protonated aniline acidic mixed solution is prepared by adding 18.626 g of aniline to 1 L of 1 mol / L hydrochloric acid to prepare an aniline-hydrochloric acid solution with an aniline concentration of 0.2 mol / L, and stirring the aniline-hydrochloric acid solution at a low temperature of 10° C. for 24 hours to completely protonate the aniline and convert it into a protonated aniline-hydrochloric acid solution.

[0067] (III) taking out 60 mL of a 0.2 mol / L protonated aniline-hydrochloric acid solution and adding 60 mL of a 0.2 mol / L ferric chloride-hydrochloric acid solution to obtain a polymerization solution, immersing the side of the cation exchange membrane adsorbing the protonated aniline in the polymerization solution, and performing an in-situ polymerization reaction for 5 hours; after the polymerization reaction, adding 0.5 mg of graphene oxide powder to the polymerization solution at a low temperature of 10°C, stirring thoroughly, and reacting for 4 hours, wherein the hydroxyl groups on the graphene oxide combine with the polyaniline to form π-π covalent bonds, thereby forming an intermediate layer containing a polyaniline-graphene oxide composite;

[0068] The ferric chloride-hydrochloric acid solution is prepared by weighing 32.44 g of anhydrous ferric chloride, adding it to 1 L of 1 mol / L hydrochloric acid to prepare a ferric chloride-hydrochloric acid solution with a ferric chloride concentration of 0.2 mol / L, and storing it at a low temperature of 10° C.

[0069] (IV) In a three-necked round-bottom flask, 6 g of polyphenylene ether and 60 mL of chlorobenzene solution were added to completely dissolve the polyphenylene ether at room temperature. 0.25 g of azobisisobutyronitrile and 9.8 g of N-bromosuccinimide were then added. The mixed solution was heated to 135° C. under a nitrogen atmosphere for condensation and reflux, and reacted for 6 h. After the reaction, the mixture was poured into an ethanol solvent and washed three times. The product precipitated in the solvent. The dried product was redissolved in a chloroform solvent to remove insoluble impurities. The product was again precipitated with an ethanol solvent, washed three times, and dried to obtain brominated polyphenylene ether with a degree of bromination of 30%.

[0070] (V) 0.3 g of brominated polyphenylene ether was dissolved in N-methylpyrrolidone solution, and trimethylamine was added. The mixture was reacted at a constant temperature of 60° C. for 12 h, and then dried in a vacuum oven at 40° C. to obtain quaternized polyphenylene ether with a quaternization degree of 30%.

[0071] The molar ratio of brominated polyphenylene ether to trimethylamine is 1:0.6;

[0072] (VI) adding 1 g of quaternized polyphenylene ether to a mixed solution of methanol and dimethylformamide to prepare a quaternized polyphenylene ether-methanol / dimethylformamide solution, which is an anion exchange membrane solution;

[0073] The molar ratio of the quaternized polyphenylene ether, methanol and dimethylformamide is 1:8:1;

[0074] (VII) Place a hydrogen-type cation exchange membrane on a glass plate with the side having the intermediate layer facing upward, cast an anion exchange membrane liquid on the hydrogen-type cation exchange membrane having the intermediate catalytic layer, heat the glass plate on a heating plate at 60°C, and scrape the membrane with a scraper.

[0075] The experimental results show that applying 50mA / cm 2 At a current density of 1.5 volts, the voltage required for water dissociation by the bipolar membrane was only 1.35 V. Electrochemical impedance spectroscopy was used to test the bipolar membrane, and the results showed that its water dissociation resistance was only 1.86 Ω. After 3 hours of electrodialysis, the concentration of acid and alkali produced by the bipolar membrane reached 0.12 mol / L. In the stability test of the bipolar membrane for 8 hours, the constant current (50 mA / cm 2 ), the water dissociation voltage was stable between 1.31-1.42V.

[0076] Example 3

[0077] A method for preparing a bipolar membrane with a modified intermediate layer comprises the following steps:

[0078] (I) soaking the sulfonic acid cation exchange membrane in a 1 mol / L hydrochloric acid solution for 3 days, and converting the sulfonic acid cation exchange membrane into a hydrogen cation exchange membrane, which is used as a base membrane;

[0079] The sulfonic acid type cation exchange membrane is a cation exchange membrane manufactured by Fuji, Japan;

[0080] (II) Immerse one side of the hydrogen-type cation exchange membrane in 120 mL of a 0.2 mol / L protonated aniline acidic mixed solution at a low temperature of 10°C for 24 h to allow the protonated aniline to be electrostatically adsorbed on the cation exchange membrane;

[0081] The protonated aniline acidic mixed solution is prepared by adding 18.626 g of aniline to 1 L of 1 mol / L hydrochloric acid to prepare an aniline-hydrochloric acid solution with an aniline concentration of 0.2 mol / L, and stirring the aniline-hydrochloric acid solution at a low temperature of 10° C. for 24 hours to completely protonate the aniline and convert it into a protonated aniline-hydrochloric acid solution.

[0082] (III) taking out 60 mL of a 0.2 mol / L protonated aniline-hydrochloric acid solution and adding 60 mL of a 0.2 mol / L ferric chloride-hydrochloric acid solution to obtain a polymerization solution, immersing the side of the cation exchange membrane adsorbing the protonated aniline in the polymerization solution, and performing an in-situ polymerization reaction for 5 hours; after the polymerization reaction is completed, adding 1 mg of graphene oxide powder to the polymerization solution at a low temperature of 10°C, stirring thoroughly, and reacting for 4 hours, so that the hydroxyl groups on the graphene oxide combine with the polyaniline to form π-π covalent bonds, thereby forming an intermediate layer containing a polyaniline-graphene oxide composite;

[0083] The ferric chloride-hydrochloric acid solution is prepared by weighing 32.44 g of anhydrous ferric chloride, adding it to 1 L of 1 mol / L hydrochloric acid to prepare a ferric chloride-hydrochloric acid solution with a ferric chloride concentration of 0.2 mol / L, and storing it at a low temperature of 10° C.

[0084] (IV) In a three-necked round-bottom flask, 6 g of polyphenylene ether and 60 mL of chlorobenzene solution were added to completely dissolve the polyphenylene ether at room temperature. 0.25 g of azobisisobutyronitrile and 9.8 g of N-bromosuccinimide were then added. The mixed solution was heated to 135° C. under a nitrogen atmosphere for condensation and reflux, and reacted for 6 h. After the reaction, the mixture was poured into an ethanol solvent and washed three times. The product precipitated in the solvent. The dried product was redissolved in a chloroform solvent to remove insoluble impurities. The product was again precipitated with an ethanol solvent, washed three times, and dried to obtain brominated polyphenylene ether with a degree of bromination of 30%.

[0085] (V) 0.3 g of brominated polyphenylene ether was dissolved in N-methylpyrrolidone solution, and trimethylamine was added. The mixture was reacted at a constant temperature of 60° C. for 12 h, and then dried in a vacuum oven at 40° C. to obtain quaternized polyphenylene ether with a quaternization degree of 30%.

[0086] The molar ratio of brominated polyphenylene ether to trimethylamine is 1:0.6;

[0087] (VI) adding 1 g of quaternized polyphenylene ether to a mixed solution of methanol and dimethylformamide to prepare a quaternized polyphenylene ether-methanol / dimethylformamide solution, which is an anion exchange membrane solution;

[0088] The molar ratio of the quaternized polyphenylene ether, methanol and dimethylformamide is 1:8:1;

[0089] (VII) Place a hydrogen-type cation exchange membrane on a glass plate with the side having the intermediate layer facing upward, cast an anion exchange membrane liquid on the hydrogen-type cation exchange membrane having the intermediate catalytic layer, heat the glass plate on a heating plate at 60°C, and scrape the membrane with a scraper.

[0090] The experimental results show that applying 50mA / cm 2At a current density of 1.5 volts, the voltage required for water dissociation by the bipolar membrane was only 1.25 V. Electrochemical impedance spectroscopy was used to test the bipolar membrane, and the results showed that its water dissociation resistance was only 1.61 Ω. After 3 hours of electrodialysis, the concentration of acid and alkali produced by the bipolar membrane reached 0.13 mol / L. In the stability test of the bipolar membrane for 8 hours, the constant current (50 mA / cm 2 ), the water dissociation voltage was stable between 1.2-1.32V.

[0091] Example 4

[0092] A method for preparing a bipolar membrane with a modified intermediate layer comprises the following steps:

[0093] (I) soaking the sulfonic acid cation exchange membrane in a 1 mol / L hydrochloric acid solution for 3 days, and converting the sulfonic acid cation exchange membrane into a hydrogen cation exchange membrane, which is used as a base membrane;

[0094] The sulfonic acid type cation exchange membrane is a cation exchange membrane manufactured by Fuji, Japan;

[0095] (II) Immerse one side of the hydrogen-type cation exchange membrane in 120 mL of a 0.2 mol / L protonated aniline acidic mixed solution at a low temperature of 10°C for 24 h to allow the protonated aniline to be electrostatically adsorbed on the cation exchange membrane;

[0096] The protonated aniline acidic mixed solution is prepared by adding 18.626 g of aniline to 1 L of 1 mol / L hydrochloric acid to prepare an aniline-hydrochloric acid solution with an aniline concentration of 0.2 mol / L, and stirring the aniline-hydrochloric acid solution at a low temperature of 10° C. for 24 hours to completely protonate the aniline and convert it into a protonated aniline-hydrochloric acid solution.

[0097] (III) taking out 60 mL of a 0.2 mol / L protonated aniline-hydrochloric acid solution and adding 60 mL of a 0.2 mol / L ferric chloride-hydrochloric acid solution to obtain a polymerization solution, immersing the side of the cation exchange membrane adsorbing the protonated aniline in the polymerization solution, and performing an in-situ polymerization reaction for 5 hours; after the polymerization reaction is completed, adding 1.5 mg of graphene oxide powder to the polymerization solution at a low temperature of 10°C, stirring thoroughly, and reacting for 4 hours, so that the hydroxyl groups on the graphene oxide combine with the polyaniline to form π-π covalent bonds, thereby forming an intermediate layer containing a polyaniline-graphene oxide composite;

[0098] The ferric chloride-hydrochloric acid solution is prepared by weighing 32.44 g of anhydrous ferric chloride, adding it to 1 L of 1 mol / L hydrochloric acid to prepare a ferric chloride-hydrochloric acid solution with a ferric chloride concentration of 0.2 mol / L, and storing it at a low temperature of 10° C.

[0099] (IV) In a three-necked round-bottom flask, 6 g of polyphenylene ether and 60 mL of chlorobenzene solution were added to completely dissolve the polyphenylene ether at room temperature. 0.25 g of azobisisobutyronitrile and 9.8 g of N-bromosuccinimide were then added. The mixed solution was heated to 135° C. under a nitrogen atmosphere for condensation and reflux, and reacted for 6 h. After the reaction, the mixture was poured into an ethanol solvent and washed three times. The product precipitated in the solvent. The dried product was redissolved in a chloroform solvent to remove insoluble impurities. The product was again precipitated with an ethanol solvent, washed three times, and dried to obtain brominated polyphenylene ether with a degree of bromination of 30%.

[0100] (V) 0.3 g of brominated polyphenylene ether was dissolved in N-methylpyrrolidone solution, and trimethylamine was added. The mixture was reacted at a constant temperature of 60° C. for 12 h, and then dried in a vacuum oven at 40° C. to obtain quaternized polyphenylene ether with a quaternization degree of 30%.

[0101] The molar ratio of brominated polyphenylene ether to trimethylamine is 1:0.6;

[0102] (VI) adding 1 g of quaternized polyphenylene ether to a mixed solution of methanol and dimethylformamide to prepare a quaternized polyphenylene ether-methanol / dimethylformamide solution, which is an anion exchange membrane solution;

[0103] The molar ratio of the quaternized polyphenylene ether, methanol and dimethylformamide is 1:8:1;

[0104] (VII) Place a hydrogen-type cation exchange membrane on a glass plate with the side having the intermediate layer facing upward, cast an anion exchange membrane liquid on the hydrogen-type cation exchange membrane having the intermediate catalytic layer, heat the glass plate on a heating plate at 60°C, and scrape the membrane with a scraper.

[0105] The experimental results show that applying 50mA / cm 2 At a current density of 1.5 volts, the voltage required for water dissociation by the bipolar membrane was only 1.13 V. Electrochemical impedance spectroscopy was used to test the bipolar membrane, and the results showed that its water dissociation resistance was only 1.36 Ω. After 3 hours of electrodialysis, the concentration of acid and alkali produced by the bipolar membrane reached 0.14 mol / L. In the stability test of the bipolar membrane for 8 hours, the constant current (50 mA / cm 2 ), the water dissociation voltage was stable between 1.09-1.18V.

[0106] The products prepared in Examples 1 to 4 were tested:

[0107] 1. Appearance test

[0108] The cation exchange membrane containing the intermediate layer of Example 1 was observed using a scanning electron microscope (Gemini SEM500) from Carl Zeiss, Germany. The specific operation was as follows: the cation exchange membrane containing the intermediate layer was removed from the deionized water, dried, and an appropriate amount of the membrane was cut and pasted on the conductive adhesive for gold spraying and observation. The results are shown in FIG. Figure 1 As shown by Figure 1 The wrinkled structure of graphene oxide and the structure of polyaniline can be seen, proving that graphene oxide and polyaniline are successfully combined and loaded onto one side of the cation exchange membrane.

[0109] 2. Current-voltage curve test

[0110] A quadrupole system membrane stack (+ proton exchange membrane | bipolar membrane | proton exchange membrane | -) was connected to an electrochemical workstation, and the Linear Sweep Voltammetry Galvanostatic program was selected to test a blank sample (excluding the intermediate layer) and the bipolar membrane of Example 1; wherein, a 1 mol / L sodium sulfate solution was used in the electrode chambers, and a 1 mol / L sodium chloride solution was used in the acid-base chambers. During the test, the current increase rate was 2 mA / s, and the current test range was 0-0.2 A; the results are shown in FIG. Figure 2 As shown in the figure, the transmembrane voltage of the blank sample and the bipolar membrane of Example 1 gradually increases with the increase of current; the bipolar membrane of Example 1 has a high voltage at a current density of 9 mA / cm 2 When the current density is 50mA / cm 2 When the membrane voltage of Example 1 is 1.03 V, the membrane voltage of the blank sample is 2.18 V, which proves that the voltage required for water dissociation can be effectively reduced by using the polyaniline and graphene oxide composite as the intermediate catalytic layer.

[0111] 3. Electrochemical Impedance Test

[0112] A quadrupole system membrane stack (+ proton exchange membrane | bipolar membrane | proton exchange membrane | -) was connected to an electrochemical workstation, and the Galvanostatic FAR impedance program was selected to test the blank sample and the bipolar membrane of Example 1. Among them, 1 mol / L sodium sulfate solution was used in the electrode chamber, and 1 mol / L sodium chloride solution was used in the acid-base chamber. During the test, the current was set to 50 mA / cm 2 , the frequency range is 10 6 -0.1HZ; the result is as follows Figure 3As shown, the Nyquist plots of the blank sample and the bipolar membrane of Example 1 exhibit characteristic semicircular curves of the bipolar membrane, wherein the water dissociation resistance of the blank sample is 3.89Ω, and the water dissociation resistance of Example 1 is 1.16Ω. This further proves that using the polyaniline and graphene oxide composite as the intermediate catalytic layer can effectively reduce the water dissociation resistance, thereby reducing the voltage required for water dissociation and reducing energy consumption.

[0113] 4. Acid and alkali production performance test

[0114] A six-electrode system membrane stack (+ anion exchange membrane | cation exchange membrane | bipolar membrane | anion exchange membrane | cation exchange membrane | -) was used to test the blank sample and the bipolar membrane of Example 1. The electrode chamber, salt chamber, and acid-base chamber all used a 1 mol / L sodium sulfate solution, and the current density during the test was set to 50 mA / cm 2 The running time is 3 hours, and samples are taken every 30 minutes to determine the concentration of the acid-base chamber by acid-base titration. Figure 4 As shown, compared with the blank sample, the acid-base chamber concentration of Example 1 is positively correlated with time and is almost linear, that is, the acid and base production rate does not change significantly during the 3-hour operation. 2 At a current density of , after 3 h, the acid and alkali production concentrations of Example 1 can reach 0.15 mol / L.

[0115] 5. Stability test

[0116] A quadrupole system membrane stack (+ proton exchange membrane | bipolar membrane | proton exchange membrane | -) was connected to an electrochemical workstation, and the Chrono Potentiometry program was selected to test the blank sample and the bipolar membrane of Example 1. 1 mol / L sodium sulfate solution was used in the electrode chambers, and 1 mol / L sodium chloride solution was used in the acid-base chambers. During the test, the current was set to 50 mA / cm 2 The test duration is 10 hours and the time interval is 20 seconds. Figure 5 As shown, during the test process of up to 10 hours, compared with the blank sample, the voltage required for water dissociation of the bipolar membrane of Example 1 was stable between 1.0-1.07V, indicating that the bipolar membrane prepared by the bipolar membrane preparation method of the present invention based on in situ growth of polyaniline and bonding graphene oxide through π-π covalent bonds has good stability, and the interlayer can be tightly combined with the cation exchange membrane layer, thereby improving the stability of the bipolar membrane during operation and avoiding the problem of increased water dissociation voltage caused by catalyst shedding.

[0117] Based on all the above test results, it can be concluded that the bipolar membrane obtained by the bipolar membrane preparation method of the present invention based on in situ growth of polyaniline by electrostatic adsorption and bonding with graphene oxide through π-π covalent bonds can significantly reduce the voltage required for water dissociation, reduce energy consumption and improve acid and alkali production performance.

[0118] Compared with the same current density (50mA / cm 2 ) blank sample, the voltage required for water dissociation was 2.18V, the water dissociation resistance was 3.89Ω, and the acid-base concentration was 0.08mol / L. The voltage required for water dissociation in Example 1 was 1.03V, the water dissociation resistance was 1.16Ω, and the acid-base concentration was 1.5mol / L. Furthermore, during the 10-hour test, the voltage required for water dissociation in the bipolar membrane of Example 1 remained stable between 1.0 and 1.07V, compared to the blank sample.

[0119] The bipolar membrane modified by the intermediate layer disclosed in the present invention comprises: a first membrane layer, a cation exchange membrane layer, which is composed of a sulfonic acid type cation exchange membrane; a second membrane layer, an intermediate layer, which is first loaded onto the cation exchange membrane by electrostatic adsorption of protonated aniline and then subjected to Fe 3+ The bipolar membrane prepared by the present invention tightly combines the intermediate layer with the cation exchange membrane layer through electrostatic adsorption, in-situ growth and covalent bonding, making it difficult to delaminate. This improves the hydrophilicity of the intermediate layer, significantly reduces the water dissociation voltage, and significantly improves the acid-base production performance.

[0120] The applicant declares that the above is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the scope of protection and disclosure of the present invention.

Claims

1. A method for preparing a bipolar membrane with a modified intermediate layer, characterized in that: The following steps are involved: (I) soaking the sulfonic acid type cation exchange membrane in an acidic solution to obtain a base membrane; (II) soaking one side of the sulfonic acid cation exchange membrane treated in step (I) in an aniline solution, adding an oxidant to the aniline solution after soaking for a certain period of time, continuing soaking, and performing a polymerization reaction on the soaked side of the sulfonic acid cation exchange membrane. After the polymerization reaction, adding graphene oxide powder to the aniline solution, and performing a covalent bond reaction on the soaked side of the sulfonic acid cation exchange membrane. After the reaction, an intermediate catalytic layer is obtained; (III) adding polyphenylene ether and chlorobenzene to a reaction vessel, mixing the polyphenylene ether and chlorobenzene, and then adding azobisisobutyronitrile and N-bromosuccinimide to carry out a synthesis reaction. After the reaction is completed, the product is washed with ethanol or acetone solution to obtain brominated polyphenylene ether; (IV) dissolving the brominated polyphenylene ether in N-methylpyrrolidone, adding trimethylamine, reacting at a constant temperature, and vacuum drying after the reaction to obtain a quaternized polyphenylene ether; (V) adding the quaternized polyphenylene ether to a mixed solution of methanol and dimethylformamide to obtain an anion exchange membrane solution; (VI) Casting the anion exchange membrane solution prepared in step (V) on the middle catalyst layer of the sulfonic acid type cation exchange membrane, and then heating and drying it on an electric heating plate to obtain a bipolar membrane.

2. The method for preparing a bipolar membrane with modified intermediate layer according to claim 1, wherein: In the step (I), the sulfonic acid cation exchange membrane is immersed in the acidic solution for 1 to 3 days.

3. The method for preparing a bipolar membrane with modified intermediate layer according to claim 1, wherein: The aniline solution in step (II) is an aqueous solution of aniline and hydrochloric acid; the concentration of aniline in the aniline solution is 0.2 mol / L, and the concentration of hydrochloric acid is 1 mol / L; In step (II), the immersion time of one side of the sulfonic acid cation exchange membrane in the aniline solution is 15 hours to 24 hours; The oxidant is a hydrochloric acid solution of FeCl3, the concentration of FeCl3 in the oxidant is 0.2 mol / L, and the concentration of hydrochloric acid is 1 mol / L; The molar ratio of FeCl3 to aniline in the oxidant is 1:1; The polymerization reaction time in step (II) is 2h to 10h; The amount of graphene oxide added in step (II) is related to the area of the sulfonic acid cation exchange membrane, specifically 0.016 mg to 0.08 mg / cm 2 ; The duration of the covalent bonding reaction in step (II) is 2 h to 6 h.

4. The method for preparing a bipolar membrane with modified intermediate layer according to claim 1, wherein: In the step (III), the addition ratio of polyphenylene ether to chlorobenzene is (1-2) g: (10-20) mL; The synthesis reaction of the brominated polyphenylene ether in step (III) is carried out under nitrogen protection, the temperature of the synthesis reaction of the brominated polyphenylene ether is 135° C., and the reaction time is 4 to 8 hours; The bromination degree of the brominated polyphenylene ether in the step (III) is 25% to 30%.

5. The method for preparing a bipolar membrane with modified intermediate layer according to claim 1, wherein: In the step (IV), the molar ratio of brominated polyphenylene ether to trimethylamine is 1:0.6; The temperature of the isothermal reaction in step (IV) is 50°C to 80°C, and the reaction time is 10h to 18h. The temperature of the vacuum drying in the step (IV) is 40°C.

6. The method for preparing a bipolar membrane with modified intermediate layer according to claim 1, characterized in that: In the step (V), the molar ratio of quaternized polyphenylene ether, methanol and dimethylformamide is 1:8:

1.

7. The method for preparing a bipolar membrane with modified intermediate layer according to claim 1, wherein: The drying temperature in step (VI) is 30° C. to 60° C.; The amount of anion exchange membrane solution added in step (VI) is 0.12 g / cm 2 .

8. A bipolar membrane with modified intermediate layer, characterized in that: Prepared by the method according to any one of claims 1 to 7.

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