A method for preparing a dual-functional montmorillonite sulfonated polyetheretherketone composite membrane

Abstract

The present invention relates to the field of fuel cell technology, and specifically discloses a method for preparing a dual-functionalized montmorillonite sulfonated polyetheretherketone composite membrane. The method of the present invention comprises the following steps: (1) coating the montmorillonite surface with dopamine; (2) grafting organic sulfonic acid groups on the surface of the dopamine-coated montmorillonite by reacting with 1,3-propane sultone to obtain a dual-functionalized montmorillonite with sulfonic acid groups grafted on the surface; (3) mixing the dual-functionalized montmorillonite with sulfonic acid groups grafted on the surface with a sulfonated polyetheretherketone solution to obtain a casting mixture, and casting the film. The obtained composite membrane has high proton conductivity and good mechanical properties.

Description

Technical Field

[0001] The invention relates to the technical field of fuel cells, and in particular to a method for preparing a dual-functional montmorillonite sulfonated polyetheretherketone composite membrane. Background Art

[0002] Fuel cells (FCs) are a new type of energy conversion device with the characteristics of high energy conversion rate, environmental friendliness, simple structure, and easy operation. The research and development and application of fuel cells are effective means to deal with current energy problems. Generally, according to the different types of fuel cell electrolytes, fuel cells can be divided into five categories: proton exchange membrane fuel cells, alkaline fuel cells, solid oxide fuel cells, phosphoric acid fuel cells, and molten carbonate fuel cells. Among them, proton exchange membrane fuel cells (PEMFCs) have the advantages of low operating temperature, fast start-up speed at room temperature, simple structure, no electrolyte loss, high specific power and specific energy, easy operation, and long service life. They are ideal power sources for decentralized power stations, mobile power supplies, electric vehicles, mobile communications and other equipment. Therefore, proton exchange membrane fuel cells have become the focus of fuel cell research and are currently the most promising type of fuel cell to achieve commercialization. As a core component of proton exchange membrane fuel cells, proton exchange membranes (PEMs) play a dual role of separating the cathode and anode of the battery and transferring protons, and play a decisive role in the performance of proton exchange membrane fuel cells.

[0003] Non-fluorinated proton exchange membrane materials have the advantages of wide sources, relatively low prices, and relatively little environmental pollution. In recent years, they have become a hot spot in the research of proton exchange membrane materials. Among them, polyaromatic polymers such as polyetheretherketone (PEEK) have good thermal and chemical stability, good mechanical properties, excellent high temperature resistance and long service life, and low cost, and have received very wide attention in recent years. According to the structural characteristics of polyetheretherketone, in order to improve the proton conductivity, direct sulfonation of its skeleton structure is a common method to introduce sulfonic acid groups to obtain higher proton conductivity. However, while a high degree of sulfonation improves proton conductivity, it is accompanied by a sharp decrease in membrane size and chemical stability. Therefore, the key to the research of polyetheretherketone proton exchange membrane is how to accurately control the sulfonation degree of its reaction, and how to balance the contradictions between its proton conductivity, mechanical properties, dimensional stability, etc. At the same time, direct sulfonation reaction will use a large amount of concentrated sulfuric acid, and it is difficult to accurately control the degree of sulfonation.

[0004] In comparison, the organic-inorganic composite modification strategy is more favored by researchers because it has the advantages of simple modification process, more selectivity of modified materials, and can effectively combine the excellent properties of materials with different properties. In order to effectively improve the specific properties of composite membranes, the properties of inorganic materials (fillers) are crucial to the performance. At present, such as titanium oxide (TiO 2 ), silicon oxide (SiO 2 ), zirconium oxide (ZrO 2 ), cerium oxide (CeO 2 ) and other metal oxide nanoparticles with good hydrophilicity can effectively improve the water retention performance of the composite membrane and balance the hydrophilicity and hydrophobicity of the membrane. They are commonly used fillers for organic-inorganic composite modification. In addition, such as phosphotungstic acid (PWA), boron phosphate (BPO 4 ), phosphomolybdic acid (PMA), silicotungstic acid (SWA) and other heteropoly acids are excellent inorganic proton conductors. In addition to having excellent hydrophilicity, they can also transport protons through their own ionization and are also used in composite modification research. In recent years, clay materials have attracted widespread attention in the field of organic-inorganic composite modification as a green, low-cost inorganic nanomaterial with obvious performance advantages. The structure of clay materials contains rich hydroxyl structures and crystal water, with excellent hydrophilic and water-retaining properties, and the unique two-dimensional and three-dimensional structural characteristics can not only effectively improve the thermal and mechanical stability, but also effectively improve the fuel barrier properties of the composite film. Montmorillonite, as a type of clay material, is a type of clay mineral with a special microcrystalline structure. It has a unique layered two-dimensional structure and a large specific surface area. It is not easy to slide between layers and has strong rigidity and adsorption. Mochammad et al. added montmorillonite to a matrix such as chitosan, and found that its rigidity would help improve the mechanical properties of the composite, while its layered structure would help build an orderly proton transport channel, showing great application potential in the field of proton exchange membrane composite modification. [RSCAdv., 2016, 6, 2314–2322] However, how to improve the compatibility between inorganic montmorillonite and the organic polymer matrix is ​​the key to exerting its performance advantages. Summary of the invention

[0005] The purpose of the present invention is to provide a dual-functional montmorillonite material for use in the modification research of sulfonated polyetheretherketone, and specifically proposes a method for preparing a dual-functional montmorillonite sulfonated polyetheretherketone composite membrane. The composite membrane prepared by the present invention has high proton conductivity and good mechanical properties.

[0006] The technical concept of the present invention is as follows: first, dopamine-coated montmorillonite is prepared, then organic sulfonic acid groups are grafted on the surface of the montmorillonite, and finally a dual-functional montmorillonite sulfonated polyetheretherketone composite membrane is prepared.

[0007] In order to achieve the above object, the present invention adopts the following technical scheme:

[0008] The invention provides a dual-functional montmorillonite sulfonated polyetheretherketone composite membrane. First, the montmorillonite is surface-coated with dopamine to improve the compatibility between the montmorillonite and the sulfonated polyetheretherketone, thereby achieving good dispersion of the montmorillonite in a polymer matrix; then, organic sulfonic acid groups are grafted onto the surface of the dopamine-coated montmorillonite by reacting with 1,3-propane sultone to provide more proton action sites, thereby ensuring that the proton conduction performance is improved under the condition of a lower sulfonation degree; finally, the montmorillonite is doped with the sulfonated polyetheretherketone to prepare a composite proton exchange membrane.

[0009] A method for preparing a dual-functional montmorillonite sulfonated polyetheretherketone composite membrane, which specifically comprises the following steps:

[0010] (1) placing montmorillonite in a tris(hydroxymethyl)aminomethane hydrochloride solution, then adding dopamine thereto, ultrasonicating for 20 to 30 minutes to make it uniformly dispersed, and then stirring at room temperature for 20 to 24 hours. After the reaction is completed, the reaction solution is centrifuged, the solid is washed with anhydrous ethanol, and then dried at 80° C. for 24 hours to obtain dopamine-coated montmorillonite;

[0011] The mass ratio of the montmorillonite to dopamine is 1.0-1.2:1.5-2.0; the mass volume ratio of the montmorillonite to tris(hydroxymethyl)aminomethane hydrochloride solution is 1.0-1.2:100, g / mL;

[0012] The surface area of ​​the montmorillonite is 250 m 2 / g or more;

[0013] (2) adding the dopamine-coated montmorillonite obtained in step (1) into dichloromethane, subjecting it to ultrasonic treatment for 30 to 40 minutes to achieve uniform dispersion, then adding 1,3-propane sultone, stirring and reacting at room temperature for 36 to 48 hours. After the reaction is completed, centrifuging the reaction solution, washing the solid with dichloromethane and anhydrous ethanol, respectively, and then drying it at 60° C. for 24 hours to obtain a dual-functionalized montmorillonite with sulfonic acid groups grafted onto its surface;

[0014] The mass ratio of the dopamine-coated montmorillonite to 1,3-propane sultone is 1.0-1.2:2.0-2.5; the mass volume ratio of the dopamine-coated montmorillonite to dichloromethane is 1.0-1.2:100, g / mL;

[0015] (3) After the sulfonated polyetheretherketone is fully dissolved in a solvent, the dual-functionalized montmorillonite with sulfonic acid groups grafted on the surface obtained in step (2) is added, and after ultrasonic treatment for 30 to 40 minutes, stirring at room temperature for 3 to 4 hours to obtain a uniformly dispersed solution, which is then evenly distributed on a clean glass plate for film casting, and dried at 60° C. for 24 hours to obtain a dual-functionalized montmorillonite sulfonated polyetheretherketone composite membrane;

[0016] The mass ratio of the dual-functionalized montmorillonite with sulfonic acid groups grafted on the surface to the sulfonated polyetheretherketone is 2 / 100 to 10 / 100;

[0017] The sulfonation degree of the sulfonated polyetheretherketone is 40% to 45%;

[0018] The solvent may be N,N-dimethylformamide.

[0019] The technical solution of the present invention mainly solves the following problems:

[0020] 1. The surface of montmorillonite is coated with dopamine to improve the compatibility between montmorillonite and sulfonated polyetheretherketone, enhance the dispersibility in the organic polymer matrix, and enhance the mechanical properties.

[0021] 2. By grafting sulfonic acid groups on the surface, the conductive performance is effectively improved while ensuring the low sulfonation degree and dimensional stability of sulfonated polyetheretherketone. DETAILED DESCRIPTION

[0022] The applicant will further explain the technical solution of the present invention in detail below in conjunction with specific embodiments, with the aim of enabling those skilled in the art to have a clearer understanding and recognition of the present application.

[0023] The following specific embodiments should not be understood or interpreted in any degree as limiting the scope of protection requested by the claims of this application.

[0024] The preparation method of the sulfonated polyetheretherketone used in the following examples is as follows: 5.0 g of polyetheretherketone is slowly added to 30 mL of 98 wt% sulfuric acid, reacted at 40° C. for 2 h, then the reactant is poured into a beaker filled with 200 mL of cold water, the obtained solid is washed with a large amount of deionized water, and then dried at 60° C. to obtain the sulfonated polyetheretherketone. The sulfonation degree is measured to be 43% by H NMR spectrum analysis.

[0025] The polyetheretherketone (021P) was purchased from Changchun Jida Special Plastic Engineering Research Co., Ltd.

[0026] Example 1

[0027] A method for preparing a dual-functional montmorillonite sulfonated polyetheretherketone composite membrane, the steps are as follows:

[0028] (1) In a dry and clean beaker, first add 2.0 g of montmorillonite and 200 mL of tris(hydroxymethyl)aminomethane hydrochloride solution (1×TBE), then add 3.0 g of dopamine, ultrasonicate for 30 min to make it evenly dispersed, and then stir at room temperature for 24 h. After the reaction is completed, the reaction solution is centrifuged, the solid is washed with anhydrous ethanol, and then dried at 80°C for 24 h to obtain dopamine-coated montmorillonite.

[0029] The dopamine, tris(hydroxymethyl)aminomethane hydrochloride, and anhydrous ethanol were all analytically pure (purchased from Sinopharm Group); the surface area of ​​the montmorillonite was 250m 2 / g (purchased from Sigma).

[0030] (2) Weigh 1.0 g of the dopamine-coated montmorillonite sample obtained in step (1) into a single-mouth round-bottom flask, then add 100 mL of dichloromethane, ultrasonicate for 40 min to make it uniformly dispersed, then add 2.5 g of 1,3-propane sultone, and react at room temperature for 48 h. After the reaction is completed, the reaction solution is centrifuged, the solid is washed with dichloromethane and anhydrous ethanol, and then dried at 60° C. for 24 h to obtain a dual-functional montmorillonite with sulfonic acid groups grafted on the surface.

[0031] The dichloromethane and anhydrous ethanol were both analytically pure (purchased from Sinopharm Group), and the 1,3-propane sultone had a purity of 99% (purchased from Aladdin Chemical Reagent Co., Ltd.).

[0032] (3) After 1.0 g of sulfonated polyetheretherketone was fully dissolved in 30 mL of N,N-dimethylformamide, 0.02 g of the dual-functionalized montmorillonite sample with surface grafted sulfonic acid groups obtained in step (2) was added, and after ultrasonic treatment for 30 min, the solution was stirred at room temperature for 4 h to obtain a uniformly dispersed solution, which was then evenly distributed on a clean glass plate for film casting, and dried at 60°C for 24 h to obtain a dual-functionalized montmorillonite sulfonated polyetheretherketone composite membrane.

[0033] The N,N-dimethylformamide was analytically pure (purchased from Sinopharm Group), and the sulfonated polyetheretherketone was prepared in the laboratory.

[0034] In the dual-functional montmorillonite sulfonated polyetheretherketone composite membrane, the mass ratio of the dual-functional montmorillonite to the sulfonated polyetheretherketone is 2 / 100.

[0035] Example 2

[0036] A method for preparing a dual-functional montmorillonite sulfonated polyetheretherketone composite membrane, the steps are as follows:

[0037] (1) In a dry and clean beaker, first add 2.0 g of montmorillonite and 200 mL of tris(hydroxymethyl)aminomethane hydrochloride solution (1×TBE), then add 3.0 g of dopamine, ultrasonicate for 30 min to make it evenly dispersed, and then stir at room temperature for 24 h. After the reaction is completed, the reaction solution is centrifuged, the solid is washed with anhydrous ethanol, and then dried at 80°C for 24 h to obtain dopamine-coated montmorillonite.

[0038] The dopamine, tris(hydroxymethyl)aminomethane hydrochloride, and anhydrous ethanol were all analytically pure (purchased from Sinopharm Group); the surface area of ​​the montmorillonite was 250m 2 / g (purchased from Sigma).

[0039] (2) Weigh 1.0 g of the dopamine-coated montmorillonite sample obtained in step (1) into a single-mouth round-bottom flask, then add 100 mL of dichloromethane, ultrasonicate for 40 min to make it uniformly dispersed, then add 2.5 g of 1,3-propane sultone, and react at room temperature for 48 h. After the reaction is completed, the reaction solution is centrifuged, the solid is washed with dichloromethane and anhydrous ethanol, and then dried at 60° C. for 24 h to obtain a dual-functional montmorillonite with sulfonic acid groups grafted on the surface.

[0040] The dichloromethane and anhydrous ethanol were both analytically pure (purchased from Sinopharm Group), and the 1,3-propane sultone had a purity of 99% (purchased from Aladdin Chemical Reagent Co., Ltd.).

[0041] (3) After 1.0 g of sulfonated polyetheretherketone was fully dissolved in 30 mL of N,N-dimethylformamide, 0.04 g of the dual-functionalized montmorillonite sample with surface grafted sulfonic acid groups obtained in step (2) was added, and after ultrasonic treatment for 30 min, the solution was stirred at room temperature for 4 h to obtain a uniformly dispersed solution, which was then evenly distributed on a clean glass plate for film casting, and dried at 60°C for 24 h to obtain a dual-functionalized montmorillonite sulfonated polyetheretherketone composite membrane.

[0042] The N,N-dimethylformamide was analytically pure (purchased from Sinopharm Group), and the sulfonated polyetheretherketone was prepared in the laboratory.

[0043] In the dual-functional montmorillonite sulfonated polyetheretherketone composite membrane, the mass ratio of the dual-functional montmorillonite to the sulfonated polyetheretherketone is 4 / 100.

[0044] Example 3

[0045] A method for preparing a dual-functional montmorillonite sulfonated polyetheretherketone composite membrane, the steps are as follows:

[0046] (1) In a dry and clean beaker, first add 2.0 g of montmorillonite and 200 mL of tris(hydroxymethyl)aminomethane hydrochloride solution (1×TBE), then add 3.0 g of dopamine, ultrasonicate for 30 min to make it evenly dispersed, and then stir at room temperature for 24 h. After the reaction is completed, the reaction solution is centrifuged, the solid is washed with anhydrous ethanol, and then dried at 80°C for 24 h to obtain dopamine-coated montmorillonite.

[0047] The dopamine, tris(hydroxymethyl)aminomethane hydrochloride, and anhydrous ethanol were all analytically pure (purchased from Sinopharm Group); the surface area of ​​the montmorillonite was 250m 2 / g (purchased from Sigma).

[0048] (2) Weigh 1.0 g of the dopamine-coated montmorillonite sample obtained in step (1) into a single-mouth round-bottom flask, then add 100 mL of dichloromethane, ultrasonicate for 40 min to make it uniformly dispersed, then add 2.5 g of 1,3-propane sultone, and react at room temperature for 48 h. After the reaction is completed, the reaction solution is centrifuged, the solid is washed with dichloromethane and anhydrous ethanol, and then dried at 60° C. for 24 h to obtain a dual-functional montmorillonite with sulfonic acid groups grafted on the surface.

[0049] The dichloromethane and anhydrous ethanol were both analytically pure (purchased from Sinopharm Group), and the 1,3-propane sultone had a purity of 99% (purchased from Aladdin Chemical Reagent Co., Ltd.).

[0050] (3) After 1.0 g of sulfonated polyetheretherketone was fully dissolved in 30 mL of N,N-dimethylformamide, 0.08 g of the dual-functionalized montmorillonite sample with surface grafted sulfonic acid groups obtained in step (2) was added, and after ultrasonic treatment for 30 min, the solution was stirred at room temperature for 4 h to obtain a uniformly dispersed solution, which was then evenly distributed on a clean glass plate for film casting and dried at 60°C for 24 h to obtain a dual-functionalized montmorillonite sulfonated polyetheretherketone composite membrane.

[0051] The N,N-dimethylformamide was analytically pure (purchased from Sinopharm Group), and the sulfonated polyetheretherketone was prepared in the laboratory.

[0052] In the dual-functional montmorillonite sulfonated polyetheretherketone composite membrane, the mass ratio of the dual-functional montmorillonite to the sulfonated polyetheretherketone is 8 / 100.

[0053] Example 4

[0054] A method for preparing a dual-functional montmorillonite sulfonated polyetheretherketone composite membrane, the steps are as follows:

[0055] (1) In a dry and clean beaker, first add 2.0 g of montmorillonite and 200 mL of tris(hydroxymethyl)aminomethane hydrochloride solution (1×TBE), then add 3.0 g of dopamine, ultrasonicate for 30 min to make it evenly dispersed, and then stir at room temperature for 24 h. After the reaction is completed, the reaction solution is centrifuged, the solid is washed with anhydrous ethanol, and then dried at 80°C for 24 h to obtain dopamine-coated montmorillonite.

[0056] The dopamine, tris(hydroxymethyl)aminomethane hydrochloride, and anhydrous ethanol were all analytically pure (purchased from Sinopharm Group); the surface area of ​​the montmorillonite was 250m 2 / g (purchased from Sigma).

[0057] (2) Weigh 1.0 g of the dopamine-coated montmorillonite sample obtained in step (1) into a single-mouth round-bottom flask, then add 100 mL of dichloromethane, ultrasonicate for 40 min to make it uniformly dispersed, then add 2.5 g of 1,3-propane sultone, and react at room temperature for 48 h. After the reaction is completed, the reaction solution is centrifuged, the solid is washed with dichloromethane and anhydrous ethanol, and then dried at 60° C. for 24 h to obtain a dual-functional montmorillonite with sulfonic acid groups grafted on the surface.

[0058] The dichloromethane and anhydrous ethanol were both analytically pure (purchased from Sinopharm Group), and the 1,3-propane sultone had a purity of 99% (purchased from Aladdin Chemical Reagent Co., Ltd.).

[0059] (3) After 1.0 g of sulfonated polyetheretherketone was fully dissolved in 30 mL of N,N-dimethylformamide, 0.1 g of the dual-functionalized montmorillonite sample with surface grafted sulfonic acid groups obtained in step (2) was added, and after ultrasonic treatment for 30 min, the solution was stirred at room temperature for 4 h to obtain a uniformly dispersed solution, which was then evenly distributed on a clean glass plate for film casting, and dried at 60°C for 24 h to obtain a dual-functionalized montmorillonite sulfonated polyetheretherketone composite membrane.

[0060] The N,N-dimethylformamide was analytically pure (purchased from Sinopharm Group), and the sulfonated polyetheretherketone was prepared in the laboratory.

[0061] In the dual-functional montmorillonite sulfonated polyetheretherketone composite membrane, the mass ratio of the dual-functional montmorillonite to the sulfonated polyetheretherketone is 10 / 100.

[0062] For comparison, 1.0 g of sulfonated polyetheretherketone was fully dissolved in 30 mL of N,N-dimethylformamide to form a sulfonated polyetheretherketone solution, which was then evenly distributed on a clean glass plate for film casting and dried at 60°C for 24 h to obtain a pure sulfonated polyetheretherketone membrane.

[0063] Table 1 below lists the main performance index data of the dual-functionalized montmorillonite and sulfonated polyetheretherketone composite membranes and pure sulfonated polyetheretherketone membranes prepared in Examples 1 to 4. From the data in Table 1, it can be seen that the dual-functionalized montmorillonite and sulfonated polyetheretherketone composite membranes prepared by the present invention are expected to have broad application prospects in the field of fuel cells.

[0064] Table 1

[0065]

[0066] The test conditions for the membrane performance prepared in each embodiment are as follows:

[0067] (1) Proton conductivity: The resistance of the membrane was tested using the AC impedance method on a frequency response analyzer with a frequency sweep range of 1-10 7 Hz, the AC signal amplitude is 100mV, and the cut membrane (length × width = 3cm × 2cm) is tested by two-electrode AC impedance method. Before the test, the membrane sample is placed in deionized water at room temperature to reach saturation. The proton conductivity σ (S / cm) of the membrane is calculated by the following formula:

[0068]

[0069] Wherein, L and A are the distance between the two electrodes and the effective cross-sectional area of ​​the membrane to be tested between the two electrodes, respectively, and R is the resistance of the membrane, which is calculated from the data obtained from the AC impedance test.

[0070] (2) Tensile strength and elongation at break: The film was cut into rectangular strips with a length of 40 mm and a width of 15 mm and tested on an electronic tensile testing machine at a tensile speed of 3 mm / min.

[0071] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principle of the present invention shall be regarded as equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. Application of dual-functional montmorillonite sulfonated polyetheretherketone composite membrane in fuel cells, It is characterized in that The preparation method of the dual-functional montmorillonite sulfonated polyetheretherketone composite membrane comprises the following steps: (1) placing montmorillonite in a tris(hydroxymethyl)aminomethane hydrochloride solution, then adding dopamine thereto, ultrasonicating for 20 to 30 min to make it evenly dispersed, then stirring at room temperature for 20 to 24 h. After the reaction is completed, the reaction solution is centrifuged, the solid is washed with anhydrous ethanol, and dried to obtain dopamine-coated montmorillonite; (2) The dopamine-coated montmorillonite obtained in step (1) was added to dichloromethane, and ultrasonicated for 30 to 40 minutes to make it uniformly dispersed, and then 1,3-propane sultone was added, and the mixture was stirred at room temperature for 36 to 48 hours. After the reaction was completed, the reaction solution was centrifuged, and the solid was washed with dichloromethane and anhydrous ethanol respectively, and then dried to obtain a dual-functional montmorillonite with sulfonic acid groups grafted on the surface; (3) After the sulfonated polyetheretherketone is fully dissolved in a solvent, the dual-functionalized montmorillonite with sulfonic acid groups grafted on the surface obtained in step (2) is added, and after ultrasonic treatment for 30 to 40 minutes, the solution is stirred at room temperature for 3 to 4 hours to obtain a uniformly dispersed solution, which is then evenly distributed on a clean glass plate for film casting and drying to obtain a dual-functionalized montmorillonite sulfonated polyetheretherketone composite membrane; In step (1), the mass ratio of montmorillonite to dopamine is 1.0-1.2:1.5; In step (2), the mass ratio of the dopamine-coated montmorillonite to 1,3-propane sultone is 1.0-1.2:2.0-2.

5.

2. The use according to claim 1, It is characterized in that In step (3), the mass ratio of the dual-functionalized montmorillonite with sulfonic acid groups grafted on the surface to the sulfonated polyetheretherketone is 2 / 100 to 10 / 100.

3. The use according to claim 1, It is characterized in that In step (1), the mass volume ratio of the montmorillonite to the tris(hydroxymethyl)aminomethane hydrochloride solution is 1.0-1.2:100, g / mL; In step (2), the mass volume ratio of the dopamine-coated montmorillonite to dichloromethane is 1.0-1.2:100, g / mL.

4. The use according to claim 1, It is characterized in that In step (3), the solvent is N,N-dimethylformamide.

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