CN103897335A - Modified silicon nano-tube hybrid membrane as well as preparation process and application thereof - Google Patents

Abstract

The invention relates to a hybrid membrane, in particular to a sulfonated polyether ether ketone/polyvinyl phosphoric acid functionalized silicon nanotube hybrid membrane and a preparation method and application thereof, which belong to the field of fuel cell proton exchange membranes. The preparation process includes: using carbon-carbon double bond-modified silica/alumina nanorods as templates, in-situ polymerizing polyvinyl phosphate to obtain polyvinyl phosphate functionalized silicon nanotubes; combining the prepared nanotubes with sulfonic acid Polyetheretherketone is blended to obtain a casting solution, cast, and heat-treated to form a film. The invention has the advantages of providing a method for preparing inorganic/organic double-layered nanotubes, which is simple in preparation and controllable in structure. The polyvinyl phosphate functionalized silicon nanotubes can build fast proton transfer channels in the membrane, significantly increase the proton conductivity of sulfonated polyether ether ketone; and can enhance the alcohol resistance and mechanical strength of the membrane. The prepared hybrid membrane is expected to be used in proton exchange membrane fuel cells.

Description

Modified silicon nanotube hybrid film and its preparation method and application

technical field

The present invention relates to a modified silicon nanotube hybrid membrane and its preparation method and application, in particular to a sulfonated polyether ether ketone/polyvinyl phosphoric acid modified silicon nanotube hybrid membrane and its preparation method and application. The invention belongs to the technical field of fuel cell proton exchange membrane.

Background technique

Proton exchange membrane fuel cell is a representative of new energy. It directly converts the chemical energy of fuel into electrical energy. It has the advantages of green, high efficiency and portability, and has been widely studied. The proton exchange membrane is the core component of the fuel cell, and strengthening the proton conductivity of the membrane is the key to improving the overall performance of the battery. Sulfonated polyether ether ketone has become one of the most concerned proton exchange membrane materials because of its low cost, good thermal stability, mechanical properties and alcohol resistance. However, the low proton conductivity of the membrane is still a bottleneck restricting the application. Constructing a continuous proton transfer channel in the membrane is an effective way to improve its proton conductivity. Nanotubes have a one-dimensional continuous feature, and the nanotubes themselves can be loaded with high-density proton-conducting carriers to build efficient and continuous proton transfer channels in the membrane, thereby enhancing the proton conductivity. In addition, the nanotubes in the membrane can bend the diffusion path of fuel molecules and enhance the alcohol resistance of the membrane; the nanotubes can also transfer the stress load to itself to enhance the mechanical properties of the membrane.

Contents of the invention

The object of the present invention is to provide a sulfonated polyether ether ketone/polyvinyl phosphoric acid modified silicon nanotube hybrid membrane and its preparation method, as well as its application in fuel cells. The hybrid membrane is used in a proton exchange membrane fuel cell, and has better proton conductivity, higher alcohol resistance performance and good mechanical stability.

The sulfonated polyether ether ketone/polyvinyl phosphoric acid modified silicon nanotube hybrid membrane of the present invention is prepared by physically blending polyvinyl phosphoric acid modified silicon nanotubes and polymer sulfonated polyether ether ketone. Polyvinylphosphoric acid modified silicon nanotubes are synthesized with alumina nanorods as a one-dimensional template, and 3-(trimethoxysilyl)propyl-2-methyl-2-acrylate is used in the nanotubes Carbon-carbon double bonds were introduced on the surface to provide active sites for phosphoric acid modification, and then silicon nanotubes were modified with phosphoric acid using vinyl dimethyl phosphate as a phosphoric acid modifier. Finally, aluminum oxide nanorods were etched with hydrochloric acid, and phosphoric acid The esters are converted to phosphate groups, forming hollow polyvinyl phosphate-modified silicon nanotubes. The preparation method of hybrid film comprises the following steps:

1. Preparation of polyvinyl phosphoric acid modified silicon nanotubes

1) Preparation of alumina nanorods. Slowly add ammonia solution dropwise to the _AlCl solution at room temperature to produce a white precipitate, which is centrifuged and washed to obtain a white precipitate of aluminum hydroxide. Add deionized water to the white precipitate, add 0-0.032 M dilute H ₂ SO ₄ solution at a mass ratio of 1:5-1:20 between the white precipitate and dilute sulfuric acid and stir, then pour the mixture into polytetrafluoroethylene container, placed in a muffle furnace. After rising from room temperature to 200 ^oC , the temperature was kept constant for 24 hours at a rate of 5 ^o C/min. After the hydrothermal reaction, the reaction product was centrifuged and washed until the pH of the solution was close to neutral, and then freeze-dried to obtain alumina nanorods. By adjusting the concentration of sulfuric acid, the structure and morphology of nanorods can be controlled, and the morphology of silicon nanotubes can be further adjusted.

2) Preparation and surface modification of silicon nanotubes. Weigh 0.15 g of alumina nanorods prepared in step 1) and ultrasonically disperse them in a mixed solution of 200 mL of ethanol, 12 mL of water, 1.2 mL of ammonia water, and 0.3 mL of tetraethylorthosilicate, stir at 30 ^o C for 24 h, and A silica layer is introduced on the surface of the nanorods to form silica nanotubes. Add 0.2 mL of 3-(trimethoxysilyl)propyl-2-methyl-2-acrylate and continue stirring for 24 h to form carbon-carbon double bonds on the surface of silicon nanotubes, providing active sites for phosphorylation reactions . After centrifugation and washing, they were vacuum-dried at 60 ^oC for more than 24 h to obtain carbon-carbon double bond-modified silicon nanotubes.

3) Phosphoric acid modification of silicon nanotubes. Disperse 0.05 g of carbon-carbon double bond-modified silicon nanotubes prepared in step 2) in 80 mL of acetonitrile, add 0.6 mL of vinyl phosphate phosphoric acid modifier, 0.4 mL of divinylbenzene crosslinking agent, 0.02 g 2,2'-Azobisisobutyronitrile, reacted in boiling state for 80 min, separated the product, washed it with ethanol, dispersed it in 10 M hydrochloric acid solution, refluxed it at 100 ^oC for 24 h, and distilled phosphoric acid Methyl esters were converted into phosphoric acid groups, and alumina nanorods were etched away to obtain hollow silica tubular structures, which were washed by centrifugation until neutral, and finally dried in a vacuum oven at 60 ^oC for more than 24 h to obtain polyvinyl phosphoric acid-modified silicon nanotubes.

2. Preparation of sulfonated polyether ether ketone/polyvinyl phosphoric acid modified silicon nanotube hybrid membrane

Polyvinylphosphoric acid-modified silicon nanotubes were ultrasonically dispersed in nitrogen-nitrogen-dimethylformamide solution, and sulfonated polyetheretherketone was added into the nitrogen-nitrogen-dimethylformamide solution and stirred for 24 h to dissolve. The above two solutions were mixed and stirred for 2 h to obtain a casting solution, wherein the mass ratio of nanotubes to sulfonated polyether ether ketone was 1:100-1:10. After standing for defoaming, the casting solution was poured on a clean glass plate, heat treated at 60 ^o C for 12 h, and then at 80 ^o C for 12 h. After cooling to room temperature, the film was peeled off from the glass plate, then acidified in 2 M sulfuric acid solution for 48 h, washed with deionized water until neutral, and then dried in a vacuum oven at 60 ^°C for more than 24 h. A sulfonated polyether ether ketone/polyvinyl phosphoric acid modified silicon nanotube hybrid membrane was obtained.

The sulfonated polyether ether ketone/polyvinyl phosphoric acid modified silicon nanotube hybrid membrane prepared by the above method is used as a proton exchange membrane fuel cell. Polyvinyl phosphoric acid modified silicon nanotubes can effectively enhance the proton conductivity, alcohol resistance and mechanical strength of the hybrid membrane.

The invention has the advantages of providing a sulfonated polyether ether ketone/polyvinyl phosphoric acid modified silicon nanotube hybrid membrane with a simple preparation method. The polyvinyl phosphate-modified silicon nanotubes can build fast proton transfer channels in the membrane, significantly increase the proton conductivity of sulfonated polyether ether ketone; and can enhance the alcohol resistance and mechanical strength of the membrane. The prepared hybrid membrane is expected to be used in proton exchange membrane fuel cells.

Description of drawings

Fig. 1 is a high-magnification cross-sectional scanning electron microscope photo of the pure sulfonated polyether ether ketone membrane prepared in the comparative example.

FIG. 2 is a high-magnification cross-sectional scanning electron micrograph of the hybrid membrane 3 in the embodiment.

Detailed ways

Example 1

1. Preparation of polyvinyl phosphoric acid modified silicon nanotubes

Weigh 5.4 g AlCl ₃ ·6H ₂ O and dissolve in 22.5 mL of water, take 5.2 mL of ammonia solution and add it to 22.5 mL of water for dilution. Ammonia solution was slowly added dropwise to the _AlCl solution at room temperature to produce a white precipitate, which was washed by centrifugation. Add a certain amount of deionized water to the white precipitate, and slowly add 0.032 M dilute H ₂ SO ₄ solution to it and stir. The mass ratio of white precipitate to dilute sulfuric acid is 1:10, and then pour the mixture into poly Vinyl fluoride container, put into the muffle furnace. After rising from room temperature to 200 ^oC , the temperature was kept constant for 24 h at a rate of 5 ^oC /min. After the hydrothermal reaction, the reaction product was centrifuged and washed until the pH of the solution was close to neutral, and then freeze-dried to obtain alumina nanorods.

Weigh 0.15 g alumina nanorods and ultrasonically disperse them in a mixed solution of 200 mL ethanol, 12 mL water, 1.2 mL ammonia water, and 0.3 mL ethyl orthosilicate, stir at 30 ^°C for 24 h, then add 0.2 mL 3-(trimethoxy Silyl)propyl-2-methyl-2-acrylate was stirred for 24 h. After centrifugation and washing, vacuum-dry at 60 ^oC for more than 24 h to obtain silicon nanotubes modified with carbon-carbon double bonds.

Disperse 0.05 g carbon-carbon double bond modified nanotubes in 80 mL acetonitrile, add 0.6 mL vinyl phosphate dimethyl ester, 0.4 mL divinylbenzene, 0.02 g 2,2'-azobisisobutyronitrile, in React in boiling state for 80 min, separate the product, wash with ethanol, disperse into 10 M hydrochloric acid solution, reflux and hydrolyze at 100 ^oC for 24 h, centrifuge and wash until neutral, and finally dry in a vacuum oven at 60 ^oC for 24 h h or more to obtain polyvinyl phosphoric acid modified silicon nanotubes.

The obtained nanotube has a length of 1240 nm, a diameter of 27 nm, a wall thickness of 9 nm, and an aspect ratio of 45.9.

2. Preparation of sulfonated polyether ether ketone/polyvinyl phosphoric acid modified silicon nanotube hybrid membrane

A certain amount of silicon nanotubes was dispersed in 3 mL of nitrogen-nitrogen dimethylformamide solution and ultrasonicated for 12 h. Weigh 0.7 g of sulfonated polyether ether ketone and dissolve it in 4 mL of azide-nitrogen dimethylformamide solution, and stir for 24 h. The above two solutions were mixed and stirred for 2 h to obtain the casting solution. After standing for defoaming, the casting solution was poured on a clean glass plate, heat treated at 60 ^°C for 12 h, and then at 80 ^°C for 12 h. After cooling to room temperature, the film was peeled off from the glass plate, then acidified in 2 M sulfuric acid solution for 48 h, washed with deionized water until neutral, and then dried in a vacuum oven at 60 ^°C for more than 24 h. A sulfonated polyether ether ketone/polyvinyl phosphoric acid modified silicon nanotube hybrid membrane was obtained. Four films were prepared by changing the amount of nanotubes, numbered respectively as film 1, film 2, film 3, and film 4. The contents of nanotubes in the hybrid films were 2.5 wt%, 5 wt%, 7.5 wt%, and 10 wt%, respectively.

Example 2

The preparation method is consistent with that of Example 1, except that in the preparation process of polyvinyl phosphoric acid modified silicon nanotubes, the concentration of _{dilute H2SO4} used is 0.011 M, and the prepared nanotubes have a length of 675 nm and a diameter of 36nm, the wall thickness is 14nm, and the aspect ratio is 18.7. The dosage of polyvinyl phosphoric acid modified silicon nanotubes is 0.0525 g. The content of nanotubes in the hybrid film was 7.5 wt% (film 5).

Example 3

The preparation method is the same as that in Example 1, except that dilute H ₂ SO ₄ is not used in the preparation process of polyvinylphosphoric acid-modified silicon nanotubes, and the prepared nanotubes have a length of 115 nm, a diameter of 44 nm, and a wall thickness of 10nm, the aspect ratio is 2.6. The dosage of polyvinyl phosphoric acid modified silicon nanotubes is 0.0525 g. The content of nanotubes in the hybrid film was 7.5 wt% (film 6).

comparative example

Weigh 0.7 g of sulfonated polyetheretherketone and dissolve it in 7 mL of nitrogen-nitrogen dimethylformamide solution, and stir for 24 h. After standing for defoaming, the casting solution was poured on a clean glass plate, heat treated at 60 ^°C for 12 h, and then at 80 ^°C for 12 h. After cooling to room temperature, the film was peeled off from the glass plate, then acidified in 2 M sulfuric acid solution for 48 h, washed with deionized water until neutral, and then dried in a vacuum oven at 60 ^°C for more than 24 h. A sulfonated polyether ether ketone comparative membrane (membrane 7) was obtained.

Test Methods

Proton conductivity (horizontal direction): The 1×2 cm hybrid membrane was fully hydrated in deionized water, the membrane was sandwiched between two platinum electrodes with an electrode spacing of 1.2 cm, and placed in a temperature-humidity control device. The impedance was measured with an electrochemical workstation, and the proton conductivity was calculated with the formula σ=l/AR, where l is the electrode spacing, A is the cross-sectional area of the membrane, and R is the impedance value.

Methanol Permeability: Measured using a diaphragm diffusion cell consisting of two glass half-chambers of equal volume. Take a 4 x 4 cm diaphragm and sandwich it tightly between the two glass halves. Add 30 mL of water to the left half chamber, and add 30 mL of methanol solution to the right glass half chamber with a methanol concentration of 2 M. Diffusion under magnetic stirring, take out a certain amount of solution from the left glass half chamber with a micro-syringe every 3 minutes, and use a gas chromatograph to detect the concentration of methanol aqueous solution at this time. The methanol permeability (P) can be derived from Fick's second law.

Mechanical Strength: Tested with an electronic tensile testing machine, the tensile speed is 2 mm min ^-1 , the test diaphragm is 1×4 cm in size, the tensile strength, elastic modulus and elongation at break are measured from the measured strain-stress curve derived from.

Table 1 shows the proton conductivity of the membrane 1 made by the embodiment, the membrane 2, the membrane 3, the membrane 4, the membrane 5, the membrane 6 and the membrane 7 made by the comparative example, methanol permeability, tensile strength, modulus of elasticity and elongation at break.

^a Proton conductivity at 30 ^o C, 100% relative humidity;

^bTested at room temperature.

It can be seen from the examples that during the preparation of alumina nanorods, as the concentration of sulfuric acid used decreases, the aspect ratio of alumina nanorods decreases, and thus the aspect ratio of the prepared silicon nanotubes decreases.

It can be seen from the table that compared with the pure membrane 7, the proton conduction and alcohol inhibition properties of the hybrid membrane have been significantly improved. Filling 2.5 wt% of modified nanotubes with an aspect ratio of 45.9 (the longest among the three nanotubes), the mechanical properties of the hybrid film are significantly improved, and the mechanical properties decrease when the filling amount continues to increase, indicating that a small amount of filling (<2.5 wt%, good dispersion effect) nanotubes with large aspect ratio (>45.9) are conducive to the improvement of mechanical properties.

The comparison of membranes 3, 5, and 6 with the same filling amount shows that the proton conductivity and mechanical properties of the membrane increase with the increase of the aspect ratio (length/outer diameter) of the filled nanotubes.

Membrane 3 exhibits the best overall performance, and it can be seen that filling 7.5 wt% of polyvinylphosphoric acid-modified silicon nanotubes with an aspect ratio of 45.9 is the optimal process condition. According to the obtained experimental rules, increasing the aspect ratio of the modified nanotubes and adjusting the filling amount between 5-10 wt% can further optimize the comprehensive performance of the membrane.

Claims (6)

1. A sulfonated polyether ether ketone/polyvinyl phosphoric acid modified silicon nanotube hybrid membrane, characterized in that the sulfonated polyether ether ketone is the main polymer matrix, and the polyvinyl phosphoric acid modified silicon nanotube is The filling material, wherein the mass content of polyvinyl phosphoric acid modified silicon nanotubes is 2.5%-10%. 2. a preparation method of sulfonated polyether ether ketone/polyvinyl phosphoric acid modified silicon nanotube hybrid membrane as claimed in claim 1, wherein said polyvinyl phosphoric acid modified silicon nanotube is Alumina nanorods were used as one-dimensional templates to synthesize silicon nanotubes, and 3-(trimethoxysilyl)propyl-2-methyl-2-acrylate was used to introduce carbon-carbon double bonds on the surface of silicon nanotubes to modify phosphoric acid. to provide active sites, and then use vinyl dimethyl phosphate as a phosphoric acid modifier to modify the surface of silicon nanotubes with phosphoric acid, and finally use hydrochloric acid to etch the aluminum oxide nanorods, and convert the phosphate esters into phosphoric acid groups to form Hollow polyvinyl phosphate-modified silicon nanotubes. 3. a kind of preparation method of sulfonated polyether ether ketone/polyvinyl phosphoric acid modified silicon nanotube hybrid film as claimed in claim 2, it is characterized in that described aluminum oxide nanorod is made aluminum hydroxide and dilute H ₂ SO ₄ obtained by hydrothermal reaction. 4. a kind of preparation method of sulfonated polyether ether ketone/polyvinyl phosphoric acid modified silicon nanotube hybrid film as claimed in claim 2, it is characterized in that silicon nanotube is to be template with aluminum oxide nanorod, with Ethanol, water, ammonia and ethyl orthosilicate as raw materials for synthesis. 5. A preparation method of sulfonated polyether ether ketone/polyvinyl phosphoric acid modified silicon nanotube hybrid membrane as claimed in claim 2, wherein the phosphoric acid modification of silicon nanotube is based on acetonitrile, vinyl Dimethyl phosphate, divinylbenzene, and 2,2'-azobisisobutyronitrile are reacted in a boiling state. 6. The sulfonated polyetheretherketone/polyvinylphosphoric acid modified silicon nanotube hybrid membrane as claimed in claim 1 is used as the purposes of methanol fuel cell proton exchange membrane, and the polyvinylphosphoric acid modified silicon nanotube can effectively Enhanced proton conductivity, alcohol resistance and mechanical strength of the hybrid membrane.

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