Sulfonated PEEK film for hydrogen fuel cell and preparation method of sulfonated PEEK film

Abstract

The invention discloses a sulfonated PEEK thin film for a hydrogen fuel cell and a preparation method of the sulfonated PEEK thin film, and belongs to the field of thin film materials for cells. The sulfonated PEEK film for the hydrogen fuel cell is prepared from the following raw materials in parts by mass: 100 parts of sulfonated PEEK; 3-7 parts of a PEI grafted silicon dioxide filler; the PEI grafted silicon dioxide filler is formed by reacting PEI and sulfonated silicon dioxide under the crosslinking action of aliphatic diamine, and the mass ratio of the PEI to the sulfonated silicon dioxide to the aliphatic diamine is 1: (1.1-1.5): (0.3-0.5). The sulfonated PEEK has the effect of improving the stability of the sulfonated PEEK.

Description

Technical Field

[0001] The present application relates to the field of thin film materials for batteries, and particularly to a sulfonated PEEK thin film for hydrogen fuel cells and a preparation method thereof. Background Art

[0002] Sulfonated PEEK, namely sulfonated polyetheretherketone, is a special engineering plastic obtained by sulfonation modification of polyetheretherketone, and can be used as a proton exchange membrane for hydrogen fuel cells.

[0003] Hydrogen fuel cells require an efficient proton conduction membrane to achieve proton conduction, thereby promoting the electrochemical reaction of the battery. Sulfonated PEEK has good proton conduction performance, and its sulfonic acid groups can provide proton conduction channels, which can effectively improve the output power and efficiency of fuel cells. Moreover, compared with traditional perfluorosulfonic acid proton exchange membranes, sulfonated PEEK has a relatively low price and good chemical stability.

[0004] Since the proton exchange membrane is in long-term contact with the electrolyte solution in the battery, it is necessary to ensure high stability. However, the current sulfonated PEEK is prone to swelling in the solution and difficult to meet this stability requirement. Summary of the Invention

[0005] In order to improve the stability of sulfonated PEEK, the present application provides a sulfonated PEEK thin film for hydrogen fuel cells and a preparation method thereof.

[0006] In a first aspect, the sulfonated PEEK thin film for hydrogen fuel cells provided by the present application adopts the following technical solution: A sulfonated PEEK thin film for hydrogen fuel cells is prepared from raw materials comprising the following parts by mass: 100 parts of sulfonated PEEK; 3 - 7 parts of PEI-grafted silica filler; The PEI-grafted silica filler is formed by reacting PEI with sulfonated silica under the crosslinking action of aliphatic diamine, and the mass ratio of PEI, sulfonated silica to aliphatic diamine is 1:(1.1 - 1.5):(0.3 - 0.5).

[0007] By adopting the above technical solution, silica plays a role in filling and reinforcing the internal structure of sulfonated PEEK, improving the mechanical properties of sulfonated PEEK and reducing the swelling property, thereby improving the stability of the sulfonated PEEK thin film in the solution.

[0008] Since silica and sulfonated PEEK are inorganic and organic phases respectively, the interfacial bonding force is weak, which affects the dispersion of silica. Therefore, silica is grafted with PEI (i.e., polyetherimide), and the interfacial compatibility between polyetherimide and sulfonated PEEK is good, thus reducing the agglomeration of silica and enhancing the structure of silica and sulfonated PEEK. The use of sulfonated silica can not only achieve the grafting of silica and PEI through the cross-linking action of aliphatic diamine, but also the remaining sulfonic acid groups after grafting can improve the interfacial compatibility between silica and sulfonated PEEK. Finally, in addition to improving the stability of sulfonated PEEK film in solution, it can also improve the proton conductivity and high-temperature resistance of sulfonated PEEK film.

[0009] Optionally, the sulfonated silica is obtained by reacting silica with a mercapto-silane coupling agent to obtain mercapto-silica, and then oxidizing the mercapto-silica to obtain sulfonated silica. The mass ratio of silica to the mercapto-silane coupling agent is 1:(0.05 - 0.09).

[0010] By adopting the above technical solution, the mercapto-silane coupling agent introduces -SH groups on the surface of silica, and under the action of an oxidant such as hydrogen peroxide, sulfonic acid groups are generated by oxidation, realizing the sulfonation of silica.

[0011] Optionally, the mercapto-silane coupling agent includes one or both of 3-mercaptopropyltrimethoxysilane and 3-mercaptopropyltriethoxysilane.

[0012] By adopting the above technical solution, the silanes of 3-mercaptopropyltrimethoxysilane and 3-mercaptopropyltriethoxysilane can react with the surface hydroxyl groups of silica, thereby grafting mercapto groups onto the silica surface, and waiting for subsequent oxidation to generate sulfonic acid groups.

[0013] Optionally, the silica is prepared from orthosilicate ester, using polystyrene microspheres as a template, and aging and calcining through the sol-gel method.

[0014] By adopting the above technical solution, the sol-gel method prepares fine and uniform silica, and using polystyrene microspheres as a template to control the internal morphology of silica, making silica have a mesoporous structure, promoting sulfonation, and helping with the grafting and coating of PEI, and enhancing the selectivity, proton conductivity and high-temperature resistance of sulfonated PEEK film.

[0015] Optionally, the aliphatic diamine includes one or both of ethylenediamine and butanediamine.

[0016] By adopting the above technical solution, the structural lengths of ethylenediamine and butanediamine are appropriate and suitable as cross-linking agents to connect PEI and silica.

[0017] In a second aspect, a sulfonated PEEK film for a hydrogen fuel cell provided by the present application adopts the following technical solution: A preparation method of a sulfonated PEEK film for a hydrogen fuel cell, comprising the following steps: Dissolve PEI in a first solvent, add sulfonated silica after dissolving evenly, stir and disperse evenly, then add aliphatic diamine, continuously stir and then filter to obtain a PEI-grafted silica filler.

[0018] Dissolve sulfonated PEEK in a second solvent, add the PEI-grafted silica filler after dissolving evenly, stir and disperse evenly, defoam, coat on a substrate, and dry to remove the first solvent to obtain a sulfonated PEEK film.

[0019] By adopting the above technical solution, aliphatic diamine is used to connect PEI and silica to achieve grafting. And the sulfonated PEEK film is prepared by the solution casting method, which has simple operation and helps the PEI-grafted silica filler to be fully dispersed.

[0020] Optionally, the first solvent and the second solvent can be polar aprotic solvents, specifically one or more of N,N-dimethylacetamide, N,N-dimethylformamide, and dimethyl sulfoxide.

[0021] Optionally, the preparation method of the sulfonated silica comprises the following steps: Disperse silica in a third solvent, add a mercapto silane coupling agent, react under heating conditions, filter after the reaction ends, collect the solid, and then put the solid into an oxidant solution for reaction, filter after the reaction ends to obtain sulfonated silica.

[0022] By adopting the above technical solution, a mercapto group is introduced by using a silane coupling agent first, and then oxidized into a sulfonic acid group to improve the stability of the sulfonic acid group on the silica surface.

[0023] Optionally, the third solvent can be a mixed solvent of alcohol and water.

[0024] Optionally, the oxidant solution is a hydrogen peroxide solution.

[0025] Optionally, the preparation method of the silica comprises the following steps: Add orthosilicate ester to a mixed solvent of alcohol and water containing a catalyst, stir and hydrolyze, heat and evaporate to obtain a gel, dry, and calcine to obtain silica.

[0026] Optionally, the preparation method of the silica comprises the following steps: Soak polystyrene microspheres in a mixed solvent of alcohol and water, add a catalyst, then add orthosilicate ester, stir and hydrolyze, heat and evaporate to obtain a solid, dry, and calcine to obtain silica.

[0027] By adopting the above technical solution, mesoporous silica is prepared using polystyrene microspheres as a template.

[0028] Optionally, the particle size of the polystyrene microspheres is 50 - 80 nm.

[0029] In summary, the present application has the following beneficial effects: 1. In the present application, silica plays a role in filling and reinforcing the internal structure of sulfonated PEEK, improving the mechanical properties of sulfonated PEEK, reducing its swelling property, enhancing the stability of the sulfonated PEEK film in solution, grafting PEI onto the silica, and having good interfacial compatibility between PEI and sulfonated PEEK, thereby reducing the agglomeration of silica and strengthening the structure of silica and sulfonated PEEK. The use of sulfonated silica can not only achieve the grafting of silica and PEI through the cross-linking action of aliphatic diamine, but also the remaining sulfonic acid groups after grafting can improve the interfacial compatibility between silica and sulfonated PEEK. Ultimately, in addition to improving the stability of the sulfonated PEEK film in solution, it can also improve the proton conductivity and high-temperature resistance of the sulfonated PEEK film.

[0030] 2. The present application further uses mesoporous silica, with polystyrene microspheres as a template, to control the internal morphology of silica, making the silica have a mesoporous structure, promoting sulfonation, and facilitating the grafting and coating of PEI, and enhancing the selectivity, proton conductivity, and high-temperature resistance of the sulfonated PEEK film. Specific Embodiments

[0031] The following further details the present application.

[0032] Preparation Example 1 A preparation method of sulfonated PEEK, comprising the following steps: Gradually pour PEEK powder of Zhongyan Polymer brand No. 770 into 98 wt% concentrated sulfuric acid, with the mass ratio of PEEK powder to concentrated sulfuric acid being 1:20. Continuously stir to dissolve the PEEK powder, then heat it to 40 °C through a water bath, sulfonate for 7 h, add ice water after sulfonation is completed, continue to stir for 12 h, filter and collect the precipitate, wash the precipitate with water until the pH is close to neutral, and dry to obtain sulfonated PEEK.

[0033] Preparation Example 2 A preparation method of silica, comprising the following steps: Prepare a mixed solvent of ethanol and water, where the mass percentage of ethanol is 90%. Add hydrochloric acid as a catalyst to the mixed solvent to make the pH of the mixed solvent 4. Gradually add tetraethyl orthosilicate, with the molar ratio of water to tetraethyl orthosilicate being 2. Stir and hydrolyze for 24 h, then heat and evaporate to obtain a gel. Dry the gel at 65 °C for 12 h to form a powder, and calcine it at 550 °C for 4 h to obtain silicon dioxide.

[0034] Preparation Example 3 A method for preparing silicon dioxide, comprising the following steps: Prepare a mixed solvent of ethanol and water, where the mass percentage of ethanol is 90%. Disperse polystyrene microspheres in the mixed solvent and soak for 12 h, then add hydrochloric acid as a catalyst to the mixed solvent to make the pH of the mixed solvent 4. Gradually add tetraethyl orthosilicate, with the molar ratio of water to tetraethyl orthosilicate being 2. Stir and hydrolyze for 24 h, then heat and evaporate to obtain a solid. Dry the solid at 65 °C for 6 h and calcine it at 600 °C for 5 h to obtain silicon dioxide.

[0035] Preparation Example 1 A method for preparing sulfonated silicon dioxide, comprising the following steps: Disperse the silicon dioxide obtained in Preparation Example 2 in a 92 wt% ethanol solution, add 3-mercaptopropyltrimethoxysilane, with the mass ratio of silicon dioxide to 3-mercaptopropyltrimethoxysilane being 1:0.05. React at 65 °C for 2 h. After the reaction, filter to collect the solid, then put the solid into a 20 wt% hydrogen peroxide solution and react at room temperature for 12 h. After the reaction, filter, wash, and dry to obtain sulfonated silicon dioxide.

[0036] Preparation Example 2 A method for preparing sulfonated silicon dioxide, comprising the following steps: Disperse the silicon dioxide obtained in Preparation Example 3 in a 92 wt% ethanol solution, add 3-mercaptopropyltrimethoxysilane, with the mass ratio of silicon dioxide to 3-mercaptopropyltrimethoxysilane being 1:0.05. React at 65 °C for 2 h. After the reaction, filter to collect the solid, then put the solid into a 20 wt% hydrogen peroxide solution and react at room temperature for 12 h. After the reaction, filter, wash, and dry to obtain sulfonated silicon dioxide.

[0037] Preparation Example 3 A method for preparing sulfonated silicon dioxide, comprising the following steps: Disperse the silicon dioxide obtained in Preparation Example 3 in a 92 wt% ethanol solution, add 3-mercaptopropyltrimethoxysilane, with the mass ratio of silicon dioxide to 3-mercaptopropyltrimethoxysilane being 1:0.09. React at 65 °C for 2 h. After the reaction, filter to collect the solid, then put the solid into a 20 wt% hydrogen peroxide solution and react at room temperature for 12 h. After the reaction, filter, wash, and dry to obtain sulfonated silicon dioxide.

[0038] Example 1 A preparation method of sulfonated PEEK film for hydrogen fuel cells, comprising the following steps: Weigh 1 kg of sulfonated PEEK prepared in Preparation Example 1, 0.1 kg of PEI of Sabic grade 1000, 0.11 kg of sulfonated silica prepared in Preparation Example 1, and 0.03 kg of ethylenediamine.

[0039] Dissolve PEI in 1 L of N,N-dimethylacetamide. After dissolving evenly, add sulfonated silica and continuously stir and disperse evenly for 20 min. Then add ethylenediamine and continuously stir at 35 °C for 12 h and then filter to obtain PEI-grafted silica filler.

[0040] Dissolve sulfonated PEEK in 10 L of N,N-dimethylacetamide. After dissolving evenly, add 0.03 kg of PEI-grafted silica filler, continuously stir and disperse evenly for 20 min, and perform vacuum degassing. The obtained slurry is coated on a release substrate and dried at 70 °C for 24 h to remove N,N-dimethylacetamide. The obtained film is soaked in dilute sulfuric acid and water for 24 h respectively. After soaking, the film is peeled off to obtain a sulfonated PEEK film with a thickness of 60 μm.

[0041] Example 2 A preparation method of sulfonated PEEK film for hydrogen fuel cells, comprising the following steps: Weigh 1 kg of sulfonated PEEK prepared in Preparation Example 1, 0.1 kg of PEI of Sabic grade 1000, 0.15 kg of sulfonated silica prepared in Preparation Example 1, and 0.05 kg of ethylenediamine.

[0042] Dissolve PEI in 1 L of N,N-dimethylacetamide. After dissolving evenly, add sulfonated silica and continuously stir and disperse evenly for 20 min. Then add ethylenediamine and continuously stir at 35 °C for 12 h and then filter to obtain PEI-grafted silica filler.

[0043] Dissolve sulfonated PEEK in 10 L of N,N-dimethylacetamide. After dissolving evenly, add 0.07 kg of PEI-grafted silica filler, continuously stir and disperse evenly for 20 min, and perform vacuum degassing. The obtained slurry is coated on a release substrate and dried at 70 °C for 24 h to remove N,N-dimethylacetamide. The obtained film is soaked in dilute sulfuric acid and water for 24 h respectively. After soaking, the film is peeled off to obtain a sulfonated PEEK film with a thickness of 60 μm.

[0044] Example 3 A preparation method of sulfonated PEEK film for hydrogen fuel cells, comprising the following steps: Weigh 1 kg of sulfonated PEEK prepared in Preparation Example 1, 0.1 kg of PEI of Sabic grade 1000, 0.14 kg of sulfonated silica prepared in Preparation Example 1, and 0.4 kg of ethylenediamine.

[0045] Dissolve PEI in 1 L of N,N-dimethylacetamide. After dissolving evenly, add sulfonated silica and continuously stir for 20 min until dispersed evenly. Then add ethylenediamine and continuously stir at 35 °C for 12 h, and then filter to obtain PEI-grafted silica filler.

[0046] Dissolve sulfonated PEEK in 10 L of N,N-dimethylacetamide. After dissolving evenly, add 0.05 kg of PEI-grafted silica filler, continuously stir for 20 min until dispersed evenly, and then perform vacuum degassing. The obtained slurry is coated on a release substrate and dried at 70 °C for 24 h to remove N,N-dimethylacetamide. The obtained film is soaked in dilute sulfuric acid and water for 24 h respectively. After soaking, the film is peeled off to obtain a sulfonated PEEK film with a thickness of 60 μm.

[0047] Example 4 A preparation method of a sulfonated PEEK film for a hydrogen fuel cell.

[0048] The difference between this example and Example 3 is that the sulfonated silica is prepared in Preparation Example 2.

[0049] Example 5 A preparation method of a sulfonated PEEK film for a hydrogen fuel cell.

[0050] The difference between this example and Example 3 is that the sulfonated silica is prepared in Preparation Example 3.

[0051] Comparative Example 1 A preparation method of a sulfonated PEEK film, comprising the following steps: Dissolve 1 kg of sulfonated PEEK prepared in Preparation Example 1 in 10 L of N,N-dimethylacetamide. After dissolving evenly, perform vacuum degassing. The obtained slurry is coated on a release substrate and dried at 70 °C for 24 h to remove N,N-dimethylacetamide. The obtained film is soaked in dilute sulfuric acid and water for 24 h respectively. After soaking, the film is peeled off to obtain a sulfonated PEEK film with a thickness of 60 μm.

[0052] Comparative Example 2 A preparation method of a sulfonated PEEK film, comprising the following steps: Weigh 1 kg of sulfonated PEEK prepared in Preparation Example 1 and 0.018 kg of PEI of Sabic grade 1000.

[0053] Dissolve sulfonated PEEK and PEI in 10 L of N,N-dimethylacetamide. After uniform dissolution, perform vacuum degassing. Coat the resulting slurry on a release substrate and dry it at 70 °C for 24 h to remove N,N-dimethylacetamide. Immerse the obtained film in dilute sulfuric acid and water for 24 h respectively. After immersion, peel off the film to obtain a sulfonated PEEK film with a thickness of 60 μm.

[0054] Comparative Example 3 A preparation method of a sulfonated PEEK film, comprising the following steps: Weigh 1 kg of sulfonated PEEK prepared in Preparation Example 1, 0.018 kg of PEI of Sabic grade 1000, and 0.025 kg of silica prepared in Preparation Example 2.

[0055] Dissolve sulfonated PEEK in 10 L of N,N-dimethylacetamide. After uniform dissolution, add PEI and silica, continuously stir and disperse uniformly for 20 min, perform vacuum degassing. Coat the resulting slurry on a release substrate and dry it at 70 °C for 24 h to remove N,N-dimethylacetamide. Immerse the obtained film in dilute sulfuric acid and water for 24 h respectively. After immersion, peel off the film to obtain a sulfonated PEEK film with a thickness of 60 μm.

[0056] Performance testing Perform the following tests on the sulfonated PEEK films prepared in Examples 1-5 and Comparative Examples 1-3.

[0057] Swelling test: Cut the film into specimens with a length and width of 2 cm each. There are 2 specimens in total. Record the original length L d of the specimens. Immerse the specimens in water at 25 °C and 70 °C for 12 h respectively. Take them out, dry them, and measure the length L w of the specimens. According to the swelling rate = (L w - L d ) / L d , calculate the swelling rate of the film.

[0058] Vanadium ion permeation test: Place the film between two half-cells. Add a mixed solution of 1 mol / L VOSO 4 + and 2 mol / L H 2 SO 4 to the left half-cell, and add an equal volume of a mixed solution of 1 moL / L MgSO 4 + and 2 mol / L H 2 SO 4 to the right half-cell. Use a spectrophotometer to measure the absorbance in the right half-cell 24 h after the start of the experiment, and then calculate the vanadium ion concentration.

[0059] Proton conductivity test: Use an electrochemical test system to measure the resistance R of the film, and measure the thickness L and area S of the film. According to σ = L / (S·R), the proton conductivity σ of the film is calculated.

[0060] The above test results are shown in Table 1.

[0061] Table 1 Combined with the test analysis in Table 1, compared with the pure sulfonated PEEK film in Comparative Example 1, the swelling ratio of the sulfonated PEEK film in Example 3 is significantly lower, indicating that the film has higher stability in the solution, and the increase in the swelling ratio after soaking at 70 °C is smaller, indicating that the film has higher high-temperature resistance and durability. In addition, the sulfonated PEEK film in Example 3 has a lower vanadium ion concentration and a higher proton conductivity, indicating that the film has higher selectivity and is more suitable for use as a proton exchange membrane in hydrogen fuel cells.

[0062] Compared with Comparative Example 2 and Comparative Example 3, Example 3 also shows higher stability, high-temperature resistance and selectivity, indicating that sulfonating silica and then grafting PEI onto silica to adjust the interfacial morphology of silica and improve the dispersibility of silica can improve the internal structure of the sulfonated PEEK film, thereby improving various application performances.

[0063] Compared with Example 3, Examples 4 and 5 perform better in terms of high-temperature resistance and selectivity, indicating that preparing mesoporous silica using polystyrene microspheres as a template can promote sulfonation and contribute to the grafting and coating of PEI, playing a role in improving the structure of the sulfonated PEEK film.

[0064] This specific embodiment is only an interpretation of the present application and does not limit the present application. Those skilled in the art can make modifications without creative contributions to this specific embodiment after reading this specification, but as long as they are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A sulfonated PEEK film for a hydrogen fuel cell, characterized in that: It is prepared from the following raw materials in parts by weight: Sulfonated PEEK 100 parts; PEI grafted silica filler 3-7 parts; The PEI grafted silica filler is formed by reacting PEI and sulfonated silica under the cross-linking action of aliphatic diamine, and the mass ratio of PEI, sulfonated silica and aliphatic diamine is 1:(1.1-1.5):(0.3-0.5).

2. The sulfonated PEEK film for a hydrogen fuel cell according to claim 1, characterized in that: The sulfonated silica is obtained by reacting silica with a mercapto-containing silane coupling agent to obtain mercapto-containing silica, and then the mercapto-containing silica is subjected to an oxidation reaction to obtain the sulfonated silica, wherein the mass ratio of the silica to the mercapto-containing silane coupling agent is 1:(0.05-0.09).

3. The sulfonated PEEK film for a hydrogen fuel cell according to claim 2, characterized in that: The mercapto-containing silane coupling agent includes one or both of 3-mercaptopropyltrimethoxysilane and 3-mercaptopropyltriethoxysilane.

4. The sulfonated PEEK film for a hydrogen fuel cell according to claim 2, characterized in that: The silicon dioxide is prepared from orthosilicate by aging and calcining through a sol-gel method using polystyrene microspheres as templates.

5. The sulfonated PEEK film for a hydrogen fuel cell according to claim 1, characterized in that: The aliphatic diamine includes one or both of ethylenediamine and butanediamine.

6. A method for preparing a sulfonated PEEK film for a hydrogen fuel cell according to any one of claims 1 to 5, characterized in that: The following steps are involved: PEI is dissolved in the first solvent, and after being evenly dissolved, sulfonated silica is added, stirred and dispersed evenly, and then fatty diamine is added, and the mixture is continuously stirred and filtered to obtain a PEI-grafted silica filler.

7. Dissolve the sulfonated PEEK in the second solvent, add the PEI grafted silica filler after it is evenly dissolved, stir and disperse evenly, degas, apply it on the substrate, dry and remove the first solvent, and obtain the sulfonated PEEK film.

8. The method for preparing a sulfonated PEEK film for a hydrogen fuel cell according to claim 6, characterized in that: The preparation method of the sulfonated silicon dioxide comprises the following steps: The silicon dioxide is dispersed in a third solvent, a mercapto-containing silane coupling agent is added, and the mixture is reacted under heating conditions. After the reaction is completed, the mixture is filtered and the solid is collected. The solid is then put into an oxidant solution for reaction. After the reaction is completed, the mixture is filtered to obtain sulfonated silicon dioxide.

9. The method for preparing a sulfonated PEEK film for a hydrogen fuel cell according to claim 7, characterized in that: The method for preparing silicon dioxide comprises the following steps: Orthosilicate is added into a mixed solvent of alcohol and water containing a catalyst, stirred for hydrolysis, heated for evaporation to obtain gel, dried, calcined to obtain silicon dioxide.

10. The method for preparing a sulfonated PEEK film for a hydrogen fuel cell according to claim 7, characterized in that: The method for preparing silicon dioxide comprises the following steps: The polystyrene microspheres are immersed in a mixed solvent of alcohol and water, a catalyst is added, and then orthosilicate is added, stirred for hydrolysis, heated for evaporation to obtain a solid, dried, and calcined to obtain silicon dioxide.

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