Cross-linked phosphoric acid doped polysulfone proton exchange membrane and preparation method thereof

Abstract

The application discloses a crosslinking type phosphoric acid doped polysulfone proton exchange membrane and a preparation method, and particularly relates to the following steps: firstly, a modified polysulfone containing isocyanate groups at the end is prepared, then 4-hydroxyethyl benzaldehyde is added for reaction, and then the modified polysulfone is dissolved in N,N-dimethylacetamide, and p-aminobenzene propyl triazole is added dropwise for Schiff base reaction to prepare a modified polysulfone membrane material containing active hydrogen at the end; then the modified polysulfone membrane material is dissolved in dimethylacetamide, nitrogen is introduced, and hexamethylene diisocyanate is added, dried, demolded, washed, and finally soaked in a phosphoric acid solution, and the crosslinking type phosphoric acid doped polysulfone proton exchange membrane is prepared. According to the method, the phosphoric acid groups are far away from the polymer main chain, the influence of water on the main chain is reduced, the number of phosphoric acid binding sites is increased, the phosphoric acid doped polysulfone proton exchange membrane can maintain a high phosphoric acid doping amount, and in addition, the proton exchange membrane can maintain good dimensional stability under high ion conductivity.

Description

Technical Field

[0001] This invention belongs to the technical field of high-temperature proton exchange membrane preparation technology, specifically relating to a cross-linked phosphate-doped polysulfone proton exchange membrane, and also to a method for preparing the cross-linked phosphate-doped polysulfone proton exchange membrane. Background Technology

[0002] Proton exchange membrane fuel cells (PEMFCs), as a clean and efficient energy source, have attracted widespread attention from scholars and are considered an ideal green energy source for the future, resulting in extensive research and discussion. Compared to traditional PEMFCs, medium- and high-temperature PEMFCs refer to PEMFCs operating at temperatures between 100 and 200°C. The higher temperatures improve the platinum catalyst's tolerance to CO, extending its lifespan. The water-pipe operating system is also simpler, effectively reducing operating costs and demonstrating promising application prospects.

[0003] Phosphoric acid-doped high-temperature proton exchange membranes (PEMs) possess excellent proton conductivity and thermodynamic stability, making them the most widely studied medium- and high-temperature PEM materials and considered the most promising. The amount of phosphoric acid doping directly determines the proton conductivity of the PEM; however, excessively high doping levels reduce dimensional stability and shorten the membrane's lifespan. To balance the relationship between high proton conductivity and dimensional stability in phosphoric acid-doped high-temperature PEMs, polysulfone was used as the base material. Multiple phosphoric acid doping sites were introduced through structural design, resulting in long-side-chain phosphoric acid-doped PEMs with high phosphoric acid doping levels. This improved proton conductivity. Furthermore, a dense three-dimensional network structure was designed through chemical cross-linking, enabling the PEM to maintain good dimensional stability even at high proton conductivity. This approach balances the proton conductivity and dimensional stability issues of phosphoric acid-doped high-temperature PEMs and shows great application potential. Summary of the Invention

[0004] The purpose of this invention is to provide a cross-linked phosphate-doped polysulfone proton exchange membrane, which solves the problem of poor dimensional stability of traditional medium- and high-temperature proton exchange membranes under high proton conductivity.

[0005] Another object of the present invention is to provide a method for preparing the above-mentioned cross-linked phosphate-doped polysulfone proton exchange membrane.

[0006] The technical solution adopted in this invention is a cross-linked phosphate-doped polysulfone proton exchange membrane, the structural formula of which is:

[0007] .

[0008] Another technical solution adopted in this invention is a method for preparing a cross-linked phosphate-doped polysulfone proton exchange membrane, which is specifically implemented according to the following steps:

[0009] Step 1: Prepare modified polysulfone with isocyanate groups at the ends;

[0010] Step 2: Prepare modified polysulfone with aldehyde groups at the ends;

[0011] Step 3: Prepare a modified polysulfone membrane material with active hydrogen at the end;

[0012] Step 4: Prepare a cross-linked polysulfone membrane containing phosphate adsorption sites;

[0013] Step 5: Immerse the cross-linked polysulfone membrane material prepared in step 4 in a phosphoric acid solution to obtain a cross-linked phosphoric acid-doped polysulfone high-temperature proton exchange membrane.

[0014] The invention is further characterized in that,

[0015] In step 1, specifically: polysulfone is mixed with dimethylacetamide, and after it is completely dissolved, nitrogen gas is introduced for protection. Chloroethyl isocyanate and anhydrous SnCl4 are added, and the mixture is reacted at 50-60℃ for 24-30h to obtain modified polysulfone with isocyanate groups at the end.

[0016] The mass ratio of polysulfone, dimethylacetamide, chloroethyl isocyanate and anhydrous SnCl4 is 1:46.8:2.47:0.87.

[0017] In step 2, specifically: 4-hydroxyethylbenzaldehyde is added to the modified polysulfone obtained in step 1, and the mixture is reacted at 50-60℃ for 12 hours to obtain a mixed solution. The mixed solution is then precipitated with anhydrous ethanol to obtain modified polysulfone with aldehyde groups at the end.

[0018] In step 3, specifically: the modified polysulfone obtained in step 2 is dissolved in N,N-dimethylacetamide, and then p-aminophenyltriazole is added dropwise to carry out a Schiff base reaction to prepare a modified polysulfone membrane material with active hydrogen at the end.

[0019] The reaction temperature is 60-80℃, and the reaction time is 10-15h; the mass ratio of modified polysulfone, N,N-diethylacetamide, and aminophenyltriazole is 1:46.8:2.43:0.66.

[0020] In step 4, specifically: the modified polysulfone membrane material prepared in step 3 is dissolved in dimethylacetamide, nitrogen gas is introduced for 30 minutes, hexamethylene diisocyanate is added, and after mixing evenly, it is poured into a petri dish. The petri dish is placed in a vacuum drying oven at 70°C to dry. After the solvent evaporates, it is demolded with distilled water. The obtained film is washed several times alternately with anhydrous ethanol and distilled water, and after drying, cross-linked polysulfone membrane material is obtained.

[0021] The mass ratio of modified polysulfone membrane material, dimethylacetamide and hexamethylene diisocyanate is 1:46.8:0.90.

[0022] In step 5, the mass concentration of the phosphoric acid solution is 80-90%, the soaking temperature is 100-120℃, and the soaking time is 6-24h.

[0023] The beneficial effects of this invention are as follows:

[0024] The cross-linked phosphate-doped polysulfone proton exchange membrane prepared by the method of this invention reduces the influence of moisture on the polymer backbone due to the phosphate groups being far from the main polymer chain. Furthermore, the introduction of numerous phosphate binding sites allows the phosphate-doped polysulfone proton exchange membrane to maintain a high phosphate doping level; the CPS-PA-3 membrane, for example, achieves a phosphate doping rate of 13%. The cross-linked polysulfone membrane material formed by polymer cross-linking allows the proton exchange membrane to maintain excellent dimensional stability under high ionic conductivity. Simultaneously, based on the high phosphate doping level, it maintains excellent proton conductivity at high temperatures; the CPS-PA-3 membrane achieves an ionic conductivity of 118 mS / cm at 200°C, meeting the requirements of medium- and high-temperature fuel cells and demonstrating significant application value. Attached Figure Description

[0025] Figure 1 This is the infrared spectrum of the CPS-PA film prepared by the method of this invention;

[0026] Figure 2 This is a graph showing the relationship between water absorption rate and temperature for the CPS-PA membrane prepared by the method of this invention.

[0027] Figure 3 This is a graph showing the relationship between the swelling ratio and temperature of the CPS-PA film prepared by the method of this invention;

[0028] Figure 4 This is a graph showing the relationship between the proton conductivity and temperature of the CPS-PA membrane prepared by the method of this invention. Detailed Implementation

[0029] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0030] The preparation method of the cross-linked phosphate-doped polysulfone proton exchange membrane of the present invention is carried out according to the following steps:

[0031] Step 1: Prepare modified polysulfone (PS-EC) with isocyanate groups at the ends;

[0032] Specifically, polysulfone (PS) is mixed with dimethylacetamide. After the PS is completely dissolved, nitrogen gas is introduced for protection. Chloroethyl isocyanate and anhydrous SnCl4 are added, and the mixture is reacted at 50-60℃ for 24-30 hours to obtain modified polysulfone (PS-EC) with isocyanate groups at the end.

[0033] The mass ratio of polysulfone, dimethylacetamide, chloroethyl isocyanate and anhydrous SnCl4 is 1:46.8:2.47:0.87.

[0034] The chemical reaction equation for preparing PS-EC is shown in equation (1):

[0035] (1);

[0036] Step 2: Prepare modified polysulfone (PS-AL) with aldehyde groups at the ends.

[0037] Specifically, 4-hydroxyethylbenzaldehyde is added to the modified polysulfone obtained in step 1, and the mixture is reacted at 50-60℃ for 12 hours to obtain a mixture. The mixture is then precipitated with anhydrous ethanol to obtain modified polysulfone (PS-AL) with aldehyde groups at the end.

[0038] The mass ratio of polysulfone, dimethylacetamide, chloroethyl isocyanate, anhydrous SnCl4, and 4-hydroxyethylbenzaldehyde is 1:46.8:2.47:0.87:1.31.

[0039] The chemical reaction formula for preparing PS-AL is shown in formula (2):

[0040] (2);

[0041] Step 3: Prepare a modified polysulfone membrane material (PS-AZ) with active hydrogen at the end.

[0042] Specifically, the modified polysulfone obtained in step 2 is dissolved in N,N-dimethylacetamide, and then p-aminophenyltriazole is added dropwise to carry out a Schiff base reaction to prepare a modified polysulfone film material (PS-AZ) with active hydrogen at the end of the side chain.

[0043] The reaction temperature is 60-80℃, and the reaction time is 10-15h;

[0044] The mass ratio of PS-AL, N,N-dimethylacetamide, and aminophenyltriazole is 1:46.8:2.43:0.66;

[0045] The chemical reaction formula for preparing PS-AZ is shown in formula (3);

[0046] (3);

[0047] Step 4: Prepare a cross-linked polysulfone membrane material (CPS-AZ) containing phosphate adsorption sites.

[0048] Specifically, the modified polysulfone membrane PS-AZ prepared in step 3 was dissolved in dimethylacetamide, nitrogen gas was introduced for 30 minutes, hexamethylene diisocyanate (HDI) was added, and after mixing evenly, it was poured into a petri dish. The petri dish was placed in a vacuum drying oven at 70°C to dry. After the solvent evaporated, it was demolded with distilled water. The obtained film was washed several times with anhydrous ethanol and distilled water alternately. After drying, cross-linked polysulfone membrane (CPS-AZ) was obtained.

[0049] The mass ratio of modified polysulfone PS-AZ, dimethylacetamide, and hexamethylene diisocyanate was 1:46.8:0.90:

[0050] The chemical reaction formula for preparing CPS-AZ is shown in (4):

[0051] (4);

[0052] Step 5: Prepare a phosphoric acid-doped cross-linked polysulfone proton exchange membrane (CPS-PA).

[0053] Specifically, the modified cross-linked polysulfone membrane material CPS-AZ from step 4 is placed in a petri dish containing a phosphoric acid solution with a mass concentration of 80-90% and immersed at 100-120℃ for 6-24 hours to obtain a cross-linked phosphoric acid-doped polysulfone high-temperature proton exchange membrane (CPS-PA).

[0054] The chemical reaction formula for preparing CPS-PA is shown in (5):

[0055] (5);

[0056] The method of this invention uses polysulfone as a base, introduces long flexible side chains, introduces aldehyde groups at the ends of the side chains, and prepares a cross-linked polysulfone proton exchange membrane with high phosphoric acid doping through a cross-linking reaction. The prepared cross-linked polysulfone proton exchange membrane with high phosphoric acid doping can still maintain good alkali resistance and dimensional stability under high ionic conductivity, solving the problem of poor dimensional stability of traditional phosphoric acid doped polysulfone proton exchange membranes under high ionic conductivity, and can be used in practical applications of fuel cells.

[0057] Infrared spectra of PS-AL, PS-AZ, and CPS-AZ prepared by the method of this invention are as follows: Figure 1 As shown, in the PS-AL spectrum, all the characteristic absorption peaks of the polysulfone backbone appear, with a peak at 1490 cm⁻¹. -1 With 1585cm -1 The absorption peak that appears belongs to the main chain benzene ring, 1080 cm⁻¹ -1 1295 cm-1 and 1325 cm -1 The absorption peak at that point belongs to the main chain -SO2 - 1245 cm -1 With 1015 cm -1 The absorption peak at 1340 cm⁻¹ belongs to the phenoxy bond. -1 1701cm -1 and 3401cm -1 The characteristic absorption peak of carbamates appeared at 1544 cm⁻¹. -1 A new absorption peak appeared, caused by the coupling of the stretching vibration of the CN bond and the bending vibration of the NH bond. Three characteristic absorption peaks appeared at the terminal aldehyde group, with a peak at 1690 cm⁻¹. -1 The characteristic absorption peak of the aldehyde group is 2730 cm⁻¹. -1 The absorption peak belongs to the stretching vibration of the aldehyde group CH bond, 1212 cm⁻¹ -1 The peak at [location] belongs to an aromatic ether bond; in the PS-AZ infrared spectrum, in addition to the characteristic absorption peak of carbamates, there is also a peak at 1580 cm⁻¹. -1 The characteristic absorption peak of the nitrogen-nitrogen double bond appeared, and the characteristic absorption peak of the aldehyde group was observed at 1690 cm⁻¹. -1 and 2730cm -1 The characteristic absorption peak of the secondary amine at 1544 cm⁻¹ has disappeared; in the CPS-AZ infrared spectrum, the characteristic absorption peak of the secondary amine is... -1 The peaks have basically disappeared, and when CPS-AZ is immersed in DMSO solvent, it hardly dissolves. This evidence proves that cross-linked phosphate-doped polysulfone film has been successfully prepared.

[0058] Example 1

[0059] The preparation method of the cross-linked phosphate-doped polysulfone proton exchange membrane of the present invention is as follows:

[0060] Step 1: Add 1.00 g of polysulfone and 50.00 mL of dimethylacetamide to a four-necked flask. After the PS is completely dissolved, purge with nitrogen for protection. Add 2.00 mL of chloroethyl isocyanate and 2.0 mL of anhydrous SnCl4. Incubate at 60 °C for 24 h to obtain a clear and transparent intermediate product solution, which is the modified polysulfone (PS-EC) with isocyanate groups at the end.

[0061] Step 2, prepare modified polysulfone (PS-AL) with aldehyde groups at the ends, as follows:

[0062] Add 4-hydroxyethylbenzaldehyde to the solution obtained in step 1 and react at 50°C for 12 hours to obtain a mixture. Precipitate the mixture with anhydrous ethanol to obtain modified polysulfone (PS-AL) with aldehyde groups at the end.

[0063] The mass ratio of polysulfone, N,N-dimethylacetamide, chloroethyl isocyanate, SnCl4 and 4-hydroxyethylbenzaldehyde is 1:46.8:2.47:0.87:1.31.

[0064] Step 3: Prepare a modified polysulfone membrane material (PS-AZ) with active hydrogen at the end.

[0065] Specifically, modified polysulfone PS-AL is dissolved in N,N-dimethylacetamide, and after dissolution, p-aminobenzotriazole is added dropwise to prepare modified polysulfone (PS-AZ) with active hydrogen at the end of the side chain through Schiff base reaction.

[0066] The mass ratio of PS-AL, N,N-diethylacetamide, and aminophenyltriazole is 1:46.8:2.43:0.66.

[0067] Step 4: Prepare a cross-linked polysulfone membrane material (CPS-AZ) containing phosphate adsorption sites. The specific steps are as follows:

[0068] The modified polysulfone PS-AZ prepared in step 3 was dissolved in dimethylacetamide. After purging with nitrogen for 30 minutes, hexamethylene diisocyanate was added and mixed evenly. The mixture was then poured into a petri dish and placed in a vacuum drying oven at 70°C to dry. After the solvent evaporated, the film was demolded with distilled water. The film was washed several times with anhydrous ethanol and distilled water alternately. After drying, the cross-linked membrane material CPS-AZ was obtained.

[0069] Modified polysulfone PS-AZ, dimethylacetamide, and hexamethylene diisocyanate in a ratio of 1:46.8:0.90:

[0070] Step 5: The modified cross-linked polysulfone film CPS-AZ is placed in a petri dish containing a phosphoric acid solution with a mass concentration of 85% and immersed at 120°C for 6 hours to dope with phosphoric acid, thereby obtaining a cross-linked phosphoric acid-doped polysulfone high-temperature proton exchange membrane, denoted as CPS-PA-1 membrane, wherein the phosphoric acid doping rate is 5%.

[0071] Example 2

[0072] The preparation method of the cross-linked phosphate-doped polysulfone proton exchange membrane of the present invention includes the following specific steps:

[0073] Step 1: Preparation of modified polysulfone (PS-EC) with terminal isocyanate groups, the specific steps are as follows:

[0074] 1.00 g of polysulfone and 50.00 mL of dimethylacetamide were added to a four-necked flask. After the PS was completely dissolved, nitrogen gas was introduced for protection. 2.00 mL of chloroethyl isocyanate and 2.0 mL of anhydrous SnCl4 were added. The mixture was carried out at 60 °C for 24 h to obtain a clear and transparent intermediate product solution, which is the modified polysulfone (PS-EC) with isocyanate groups at the end.

[0075] Step 2, prepare modified polysulfone (PS-AL) with aldehyde groups at the ends, the specific steps are as follows:

[0076] Add 4-hydroxyethylbenzaldehyde to the solution obtained in step 1 and react at 55°C for 12 hours to obtain a mixture. Precipitate the mixture with anhydrous ethanol to obtain modified polysulfone (PS-AL) with aldehyde groups at the end.

[0077] The mass ratio of polysulfone, N,N-dimethylacetamide, chloroethyl isocyanate, SnCl4 and 4-hydroxyethylbenzaldehyde is 1:46.8:2.47:0.87:1.31.

[0078] Step 3, prepare a modified polysulfone membrane material (PS-AZ) with active hydrogen at the end, the specific steps are as follows:

[0079] Modified polysulfone PS-AL was dissolved in N,N-dimethylacetamide, and p-aminobenzotriazole was added dropwise after dissolution. Modified polysulfone (PS-AZ) with active hydrogen at the end of the side chain was prepared by Schiff base reaction.

[0080] The mass ratio of PS-AL, N,N-dimethylacetamide, and aminophenyltriazole is 1:46.8:2.43:0.66.

[0081] Step 4: Prepare a cross-linked polysulfone membrane material (CPS-AZ) containing phosphate adsorption sites. The specific steps are as follows:

[0082] The modified polysulfone PS-AZ prepared in step 3 was dissolved in dimethylacetamide. After purging with nitrogen for 30 minutes, hexamethylene diisocyanate (HDI) was added and mixed evenly. The mixture was then poured into a petri dish and placed in a vacuum drying oven at 70°C for a certain period of time. After the solvent evaporated, the film was demolded with distilled water. The film was washed several times with anhydrous ethanol and distilled water alternately. After drying, the cross-linked membrane material CPS-AZ was obtained.

[0083] Modified polysulfone PS-AZ, dimethylacetamide, and hexamethylene diisocyanate in a ratio of 1:46.8:0.90:

[0084] Step 5: Prepare a phosphate-doped crosslinked polysulfone proton exchange membrane (CPS-PA). The specific steps are as follows:

[0085] The modified cross-linked polysulfone film CPS-AZ was placed in a petri dish containing a phosphoric acid solution with a mass concentration of 85% and immersed at 120°C for 18 hours to dope with phosphoric acid. Finally, a cross-linked phosphoric acid-doped polysulfone high-temperature proton exchange membrane was obtained, denoted as CPS-PA-2 membrane, in which the phosphoric acid doping rate was 10%.

[0086] Example 3

[0087] The preparation method of the cross-linked phosphate-doped polysulfone proton exchange membrane of the present invention includes the following specific steps:

[0088] Step 1: Preparation of modified polysulfone (PS-EC) with terminal isocyanate groups, the specific steps are as follows:

[0089] 1.00 g of polysulfone and 50.00 mL of dimethylacetamide were added to a four-necked flask. After the PS was completely dissolved, nitrogen gas was introduced for protection. 2.00 mL of chloroethyl isocyanate and 2.0 mL of anhydrous SnCl4 were added. The mixture was carried out at 60 °C for 24 h to obtain a clear and transparent intermediate product solution, which is polysulfone modified with isocyanate groups at the end of the side chain (PS-EC).

[0090] Step 2, prepare modified polysulfone (PS-AL) with aldehyde groups at the ends, the specific steps are as follows:

[0091] Add 4-hydroxyethylbenzaldehyde to the solution obtained in step 1 and react at 60°C for 12 h to obtain a mixture. Precipitate the mixture with anhydrous ethanol to obtain modified polysulfone (PS-AL) with aldehyde groups at the end.

[0092] The mass ratio of polysulfone, N,N-dimethylacetamide, chloroethyl isocyanate, SnCl4 and 4-hydroxyethylbenzaldehyde is 1:46.8:2.47:0.87:1.31.

[0093] Step 3: Prepare a modified polysulfone membrane material (PS-AZ) with active hydrogen at the end.

[0094] Specifically, modified polysulfone PS-AL is dissolved in N,N-dimethylacetamide, and after dissolution, p-aminobenzotriazole is added dropwise to prepare modified polysulfone (PS-AZ) with active hydrogen at the end of the side chain via Schiff base reaction.

[0095] The mass ratio of PS-AL, N,N-dimethylacetamide, and aminophenyltriazole is 1:46.8:2.43:0.66.

[0096] Step 4: Prepare a cross-linked polysulfone membrane material (CPS-AZ) containing phosphate adsorption sites. The specific steps are as follows:

[0097] The modified polysulfone PS-AZ prepared in step 3 was dissolved in dimethylacetamide. After purging with nitrogen for 30 minutes, hexamethylene diisocyanate (HDI) was added and mixed evenly. The mixture was then poured into a petri dish and placed in a vacuum drying oven at 70°C for a certain period of time. After the solvent evaporated, the film was demolded with distilled water. The film was washed several times with anhydrous ethanol and distilled water alternately. After drying, the cross-linked membrane material CPS-AZ was obtained.

[0098] Modified polysulfone PS-AZ, dimethylacetamide, and hexamethylene diisocyanate in a ratio of 1:46.8:0.90:

[0099] Step 5: Prepare a phosphate-doped crosslinked polysulfone proton exchange membrane (CPS-PA). The specific steps are as follows:

[0100] The modified cross-linked polysulfone film CPS-AZ was placed in a petri dish containing a phosphoric acid solution with a mass concentration of 85% and immersed at 120°C for 24 hours to dope with phosphoric acid. Finally, a cross-linked phosphoric acid-doped polysulfone high-temperature proton exchange membrane was obtained, denoted as CPS-PA-3 membrane, in which the phosphoric acid doping rate was 13%.

[0101] The doping level of phosphoric acid (ADL) is measured by the doping rate of phosphoric acid, which is represented by ω (%), indicating the number of moles of phosphoric acid doped per gram of polymer film. The calculation formula is shown in (1). w and w 0 represents the mass of the membrane after absorbing phosphoric acid and the mass of the dry membrane, respectively.

[0102]

[0103] CPS-PA-1, CPS-PA-2, and CPS-PA-3 membrane samples were dried in a vacuum drying oven at 80℃, with a mass of m1. The membranes were then immersed in DMSO solution at 80℃ for 48 hours. After immersion, the membrane samples were dried in a vacuum drying oven at 80℃, with a mass of m2. The degree of crosslinking (DC, Degree of Crosslinking) was calculated using formula (2). m 1 and m 2. The mass of the membrane sample before and after immersion in DMSO.

[0104]

[0105] Table 1 shows the solubility and crosslinking degree of CPS-PA-1, CPS-PA-2, and CPS-PA-3 membranes in different solvents. Due to the formation of a three-dimensional network structure, the proton exchange membrane has high chemical stability. When immersed in organic solvents, the crosslinked parts of the proton exchange membrane will swell but will not dissolve, while the uncrosslinked parts will dissolve in the organic solvent. With the increase of phosphoric acid doping rate, the corresponding crosslinking degree increases accordingly, and the crosslinking degree of CPS-PA-3 membrane reaches 89.5%.

[0106] Table 1. Test results of membrane solubility and crosslinking degree in different solvents.

[0107] sample dichloromethane THF DMF DMSO DC (%) CPS-PA-1 - - - - 56.5 CPS-PA-2 - - - - 69.6 CPS-PA-3 - - - - 89.5

[0108] The relationship between the water absorption rate of CPS-PA membrane and temperature is as follows: Figure 2 As shown, moisture is an important condition for proton conduction in proton exchange membranes. CPS-PA-1, CPS-PA-2, and CPS-PA-3 membranes have phosphate groups far from the polymer backbone, so moisture has little effect on the polysulfone backbone, allowing them to maintain good dimensional stability even with high water absorption. As the phosphate doping rate increases, the number of binding sites with water molecules increases, leading to an increase in water absorption. Among them, the CPS-PA-3 membrane has a water absorption rate as high as 38.1% and 59.6% at room temperature and 85℃, respectively, showing excellent water absorption performance.

[0109] The water absorption swelling ratio of the CPS-PA membrane prepared in this invention as a function of temperature is shown in the following curve. Figure 3 As shown, because the hydrophilic groups of CPS-PA are far from the polymer backbone, the influence of water on the backbone is reduced. At the same time, the dense three-dimensional network structure enables the proton exchange membrane to maintain good dimensional stability even with high water absorption. This is beneficial to the dimensional stability of the proton exchange membrane. With the increase of cross-linking degree, the water absorption swelling rate of the proton exchange membrane decreases and the corresponding dimensional stability increases. However, the increase of phosphoric acid doping will lead to an increase in the water absorption swelling rate of the corresponding proton exchange membrane. The two factors ultimately result in the dimensional stability of CPS-PA-1, CPS-PA-2 and CPS-PA-3 membranes being very close. Among them, the water absorption swelling rate of CPS-PA-3 membrane is only 12.5%, which shows good dimensional stability.

[0110] Proton conductivity, as the most important performance indicator for evaluating proton exchange membranes, is related to the doping rate of phosphate. Modified polysulfone containing ammonium groups can form a hydrogen bond network with phosphate ions. This hydrogen bond network determines the proton conductivity. Furthermore, using phosphate ions as the proton-conducting group, phosphate ions can ionize under anhydrous conditions, thereby enabling proton conduction. Figure 4The curves showing the change of proton conductivity of the proton exchange membrane with temperature are presented. As the phosphoric acid doping rate increases, the proton conductivity of the proton exchange membrane increases. The higher the temperature, the greater the proton conductivity. The increased mobility of the phosphate groups is beneficial to the ionization of hydrogen ions and thus to the conduction of protons. The proton conductivity of the CPS-PA-3 membrane reached 118 mS / cm at 200℃.

Claims

1. A cross-linked phosphoric acid doped polysulfone proton exchange membrane, characterized by, The structural formula is 。 2. The method for preparing a cross-linked phosphate-doped polysulfone proton exchange membrane according to claim 1, characterized in that, Specifically, the following steps are implemented: Step 1, preparation of modified polysulfone containing isocyanate groups at the end; Step 2, preparation of modified polysulfone containing aldehyde groups at the end; Step 3, preparation of modified polysulfone film material containing active hydrogen at the end; Step 4, preparation of cross-linked polysulfone film material containing phosphoric acid adsorption sites; Step 5, the cross-linked polysulfone film material prepared in step 4 is soaked in a phosphoric acid solution to obtain a cross-linked phosphoric acid doped polysulfone high temperature proton exchange membrane.

3. The method for preparing a cross-linked phosphate-doped polysulfone proton exchange membrane according to claim 2, characterized in that, In the step 1, the polysulfone is mixed with dimethylacetamide, and after complete dissolution, nitrogen protection is carried out, chloroethyl isocyanate and anhydrous SnCl4 are added, and the reaction is carried out at 50-60℃ for 24-30h to obtain modified polysulfone containing isocyanate groups at the end; The mass ratio of polysulfone, dimethylacetamide, chloroethyl isocyanate and anhydrous SnCl4 is 1:46.8:2.47:0.

87.

4. The method for preparing a cross-linked phosphate-doped polysulfone proton exchange membrane according to claim 2, characterized in that, In the step 2, 4-hydroxyethyl benzaldehyde is added to the modified polysulfone obtained in step 1, and the reaction is carried out at 50-60℃ for 12h to obtain a mixed solution, which is precipitated with anhydrous ethanol to obtain modified polysulfone containing aldehyde groups at the end.

5. The method for preparing a cross-linked phosphate-doped polysulfone proton exchange membrane according to claim 2, characterized in that, In the step 3, the modified polysulfone obtained in step 2 is dissolved in N,N-dimethylacetamide, and then p-aminobenzotriazole is added dropwise for Schiff base reaction to prepare modified polysulfone film material containing active hydrogen at the end.

6. The method for preparing a cross-linked phosphate-doped polysulfone proton exchange membrane according to claim 5, characterized in that, The reaction temperature is 60-80℃, and the reaction time is 10-15h; the mass ratio of modified polysulfone, N,N-dimethylacetamide, and aminobenzotriazole is 1:46.8:2.43:0.

66.

7. The method for preparing a cross-linked phosphate-doped polysulfone proton exchange membrane according to claim 2, characterized in that, In the step 4, the modified polysulfone film material prepared in step 3 is dissolved in dimethylacetamide, and after nitrogen is introduced for 30min, hexamethylene diisocyanate is added, and then the mixture is introduced into a culture dish, and the culture dish is placed in a vacuum drying oven at 70℃ for drying, and after the solvent is volatilized, the obtained film is washed with anhydrous ethanol and distilled water alternately for several times, and then dried to obtain a cross-linked polysulfone film material; The mass ratio of modified polysulfone film material, dimethylacetamide and hexamethylene diisocyanate is 1:46.8:0.

90.

8. The method for preparing a cross-linked phosphate-doped polysulfone proton exchange membrane according to claim 2, characterized in that, In the step 5, the mass concentration of the phosphoric acid solution is 80-90%, the soaking temperature is 100-120℃, and the soaking time is 6-24h.

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