Blending modified polybenzimidazole proton exchange membrane and preparation method thereof

Abstract

The invention is applicable to the technical field of fuel cells, and provides a blending modified polybenzimidazole proton exchange membrane and a preparation method thereof, and the preparation method comprises the following steps: S1, preparing 4-methyl-N-toluenesulfonyl benzene sulfonamide; s2, preparing 4, 4 '-[imino bis (sulfonyl)] dibenzoic acid; s3, preparation of PSI: dissolving CBSI and a proper amount of anhydrous lithium chloride in a proper amount of a mixed solution of pyridine, triphenyl phosphite and pyrrolidone, adding diamino molecules after complete dissolution, heating and stirring the solution for 12 h, pouring the solution into methanol, filtering and collecting a product, washing with water, and drying to obtain the product PSI; and S4, preparing the PSI / OPBI blended membrane. The blended membrane prepared by the invention has excellent proton conductivity and good mechanical properties, and meets the performance requirements of the proton exchange membrane of the fuel cell; moreover, the raw materials are low in cost and easy to obtain, the synthesis conditions are mature, the yield is high, the feasibility is high, and the application prospect is wide.

Description

Technical Field

[0001] The present invention relates to the technical field of fuel cells, in particular to a blended modified polybenzimidazole proton exchange membrane and a preparation method thereof. Background Art

[0002] Polybenzimidazole (PBI) polymer is an engineering plastic with excellent thermal stability, good mechanical properties, superior proton conductivity and chemical stability under high temperature conditions. It has application value in fuel cells, aerospace, chemical machinery, protective clothing and other fields.

[0003] For PBI to be officially used in fuel cells, it needs to be doped with phosphoric acid (PA). PA-doped PBI membranes (PA-PBI) exhibit excellent proton conductivity and stability under high-temperature, anhydrous conditions. Under anhydrous conditions, proton conduction in the PA-PBI system primarily follows the Grotthuss mechanism, with protons hopping across the hydrogen bond network of the PA-PBI. High levels of phosphoric acid doping (ADL) can achieve better proton conductivity, but also bring two major problems: (1) Deterioration of mechanical properties: A large number of PA molecules enter the polymer chain, which will destroy the original hydrogen bonding effect, weaken the intermolecular interaction force, and cause a significant deterioration of mechanical properties; (2) PA leaching: During the operation of the fuel cell, PA molecules migrate and are lost under the influence of water molecules. The proton conductivity decreases as PA is lost, thereby affecting the overall performance of the battery.

[0004] Therefore, it is urgent to develop PBI membranes with both high proton conductivity and good mechanical strength to meet the needs of applications such as fuel cells. Summary of the Invention

[0005] The present invention aims to provide a blended modified polybenzimidazole proton exchange membrane and a preparation method thereof, so as to provide a blended modified membrane having excellent proton conductivity and good mechanical properties, which can be used as a proton exchange membrane for fuel cells to isolate positive and negative electrodes.

[0006] To achieve the above objectives, the present invention provides the following technical solutions: In a first aspect, the present invention provides a method for preparing a blended modified polybenzimidazole proton exchange membrane, comprising the following steps: S1, preparation of 4-methyl-N-toluenesulfonylbenzenesulfonamide: Add p-toluenesulfonylamine and a strong base to a two-necked flask, add an appropriate amount of deionized water, heat and stir until the solution is clear, then add p-toluenesulfonyl chloride, continue the reaction under nitrogen protection, cool and filter, adjust the pH of the filtrate to 7 with an acidic solution, filter and collect the residue, and dry to obtain the product 4-methyl-N-toluenesulfonylbenzenesulfonamide, recorded as MBSI; S2, preparation of 4,4'-[iminobis(sulfonyl)]bisbenzoic acid: MBSI and sodium hydroxide were added to a two-necked flask, and an appropriate amount of deionized water was added. After heating and stirring until the solution was clear and transparent, an oxidant was added. After the reaction was completed, the filtrate was collected by filtration. The pH of the filtrate was adjusted to 7 with an acidic solution, and the solution was filtered and dried to obtain the product 4,4'-[iminobis(sulfonyl)]bisbenzoic acid, which was recorded as CBSI. S3, preparation of PSI: CBSI and an appropriate amount of anhydrous lithium chloride were dissolved in a mixed solution of appropriate amounts of pyridine, triphenyl phosphite, and pyrrolidone. After complete dissolution, a diamino molecule was added. The solution was heated and stirred for 12 h, then poured into methanol. The product was collected by filtration, washed with water, and dried to obtain the product PSI. S4, preparation of PSI / OPBI blend membrane: Appropriate amounts of PSI and polyether polybenzimidazole (OPBI) were dissolved in a polar solvent, and a film was prepared by a casting method, and then dried thoroughly to obtain a PSI / OPBI blend film. The mixed mass percentage of PSI and OPBI includes but is not limited to 10PSI / 90OPBI, 25PSI / 75OPBI, 50PSI / 50OPBI, and 60PSI / 40OPBI.

[0007] Preferably, the molar ratio of toluenesulfonylamide, strong base and toluenesulfonyl chloride in S1 is 2:2:1.

[0008] Preferably, the strong base in S1 includes but is not limited to one or more of potassium hydroxide, sodium hydroxide, and lithium hydroxide.

[0009] Preferably, the reaction temperature of S1 is 70-95° C., and the reaction time is controlled at 8-12 h.

[0010] Preferably, the molar ratio of MBSI, sodium hydroxide and oxidant in S2 is 1:1:4.5.

[0011] Preferably, the oxidant of S2 includes but is not limited to one or more of potassium permanganate, potassium dichromate, potassium chlorate, and hydrogen peroxide.

[0012] Preferably, the diamino molecules of S3 include but are not limited to one or more of 4,4'-diaminodiphenyl sulfone, 4,4'-dicarboxydiphenyl ether, 2,2-bis(4-aminophenyl)hexafluoropropane, 2,2'-(ethylenedioxy)bis(ethylamine), [2,2'-bifuran]-5,5'-dimethyldiamine, 4,4'-diphenylenediamine, naphthalene-2,6-diamine, and 1,4-phenylenediamine.

[0013] Preferably, the molar ratio of CBSI to diamino molecules in S3 is 1:1.

[0014] Preferably, the organic solvent of S4 includes but is not limited to one or more of N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, and N-methylpyrrolidone.

[0015] The second aspect of the present invention provides a blended modified polybenzimidazole proton exchange membrane, which is prepared by the method described in the first aspect of the present invention.

[0016] The present invention has at least the following beneficial effects: The present invention provides a blended modified polybenzimidazole proton exchange membrane and a preparation method. The prepared blended membrane has excellent proton conductivity and good mechanical properties, meeting the performance requirements of fuel cell proton exchange membranes. Moreover, the raw materials of the present invention are low in cost and readily available, the synthesis conditions are mature, the yield is high, the feasibility is high, and it has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a flow chart for preparing a modified proton exchange membrane by blending bissulfonylimide polyamide and polybenzimidazole in Example 1 of the present invention; Figure 2 is the PSI in Example 1 of the present invention 1 H NMR spectrum; Figure 3 is the FT-IR spectrum of PSI of PSI in Example 1 of the present invention; Figure 4 OPBI, OPBI / PSI, and PSI in Example 1 of the present invention 1 H NMR spectrum; Figure 5 FT-IR spectra of OPBI, OPBI / PSI, and PSI in Example 1 of the present invention: Figure 6 This is an SEM image of the blended modified membrane of the polybenzimidazole polymer prepared in Example 1 of the present invention; Figure 7 This is a graph comparing the electrochemical stability of the conductivity of the modified polybenzimidazole polymer blend membrane after phosphoric acid doping - temperature in Example 1 of the present invention; Figure 8 This is a graph showing the mechanical properties of the blended modified film of the polybenzimidazole polymer in Example 1 of the present invention before phosphoric acid doping; Figure 9 This is a graph showing the mechanical properties of the blended modified membrane of the polybenzimidazole polymer after phosphoric acid doping in Example 1 of the present invention. DETAILED DESCRIPTION

[0018] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0019] The present invention provides a method for preparing a blended modified polybenzimidazole proton exchange membrane, comprising the following steps: S1, preparation of 4-methyl-N-toluenesulfonylbenzenesulfonamide: Add p-toluenesulfonylamine and a strong base to a two-necked flask, add an appropriate amount of deionized water, heat and stir until the solution is clear, then add p-toluenesulfonyl chloride, continue the reaction under nitrogen protection, cool and filter, adjust the pH of the filtrate to 7 with an acidic solution, filter and collect the residue, and dry to obtain the product 4-methyl-N-toluenesulfonylbenzenesulfonamide, recorded as MBSI; S2, preparation of 4,4'-[iminobis(sulfonyl)]bisbenzoic acid: MBSI and sodium hydroxide were added to a two-necked flask, and an appropriate amount of deionized water was added. After heating and stirring until the solution was clear and transparent, an oxidant was added. After the reaction was completed, the filtrate was collected by filtration. The pH of the filtrate was adjusted to 7 with an acidic solution, and the solution was filtered and dried to obtain the product 4,4'-[iminobis(sulfonyl)]bisbenzoic acid, which was recorded as CBSI. S3, preparation of PSI: CBSI and an appropriate amount of anhydrous lithium chloride were dissolved in a mixed solution of appropriate amounts of pyridine, triphenyl phosphite, and pyrrolidone. After complete dissolution, a diamino molecule was added. The solution was heated and stirred for 12 h, then poured into methanol. The product was collected by filtration, washed with water, and dried to obtain the product PSI. S4, preparation of PSI / OPBI blend membrane: Appropriate amounts of PSI and polyether polybenzimidazole (OPBI) were dissolved in a polar solvent, and a film was prepared by a casting method, and then dried thoroughly to obtain a PSI / OPBI blend film. The mixed mass percentage of PSI and OPBI includes but is not limited to 10PSI / 90OPBI, 25PSI / 75OPBI, 50PSI / 50OPBI, and 60PSI / 40OPBI.

[0020] Furthermore, the molar ratio of toluenesulfonylamide, strong base, and toluenesulfonyl chloride in S1 is 2:2:1; the strong base in S1 includes but is not limited to one or more of potassium hydroxide, sodium hydroxide, and lithium hydroxide; the reaction temperature of S1 is 70-95° C., and the reaction time is controlled at 8-12 h; and the yield of MBSI is 60-85%.

[0021] Furthermore, the molar ratio of MBSI, sodium hydroxide and oxidant in S2 is 1:1:4.5; the oxidant in S2 includes but is not limited to one or more of potassium permanganate, potassium dichromate, potassium chlorate and hydrogen peroxide.

[0022] Furthermore, the diamino molecules of S3 include but are not limited to one or more of 4,4'-diaminodiphenyl sulfone, 4,4'-dicarboxydiphenyl ether, 2,2-bis(4-aminophenyl)hexafluoropropane, 2,2'-(ethylenedioxy)bis(ethylamine), [2,2'-bifuran]-5,5'-dimethyldiamine, 4,4'-diphenylenediamine, naphthalene-2,6-diamine, and 1,4-phenylenediamine; the molar ratio of CBSI to diamino molecules of S3 is 1:1.

[0023] Furthermore, the organic solvent of S4 includes but is not limited to one or more of N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, and N-methylpyrrolidone.

[0024] Based on the above technical solutions, the present invention provides the following partial embodiments: Example 1

[0025] like Figure 1 As shown, this embodiment provides a method for preparing a blended modified polybenzimidazole proton exchange membrane, comprising the following steps: (1) Weigh 17.12 g (0.1 mol) of p-toluenesulfonylamine and 4.0 g (0.1 mol) of sodium hydroxide into a two-necked flask, add an appropriate amount of deionized water, and stir at 75 ° C until the solution is clear and transparent. Add 9.53 g (0.05 mol) of p-toluenesulfonyl chloride and continue to react for 12 hours under nitrogen protection. After the solution is cooled, filter it, adjust the pH of the filtrate to 7 with dilute hydrochloric acid solution, filter it, and collect the product 4-methyl-N-toluenesulfonylbenzenesulfonamide (MBSI) after drying. (2) Weigh 13.0 g (0.04 mol) of the product obtained in (1) and add it to a two-necked flask. Add 1.60 g (0.04 mol) of sodium hydroxide and an appropriate amount of deionized water, stir at 70°C, and after the drug is completely dissolved, add 28.44 g (0.18 mol) of potassium permanganate. After the solution changes from purple-red to brown, filter and collect the filtrate. Adjust the pH of the filtrate to 7 with dilute hydrochloric acid solution, filter the solution, and collect the product CBSI after drying. (3) Weigh 7.70 g (0.02 mol) of the product obtained in (2) and add it to a double-necked flask containing 40 mL of pyrrolidone (NMP), 30 mL of pyridine (Py) and 10.4 mL of triphenyl phosphite (TPP), add 5.12 g (0.02 mol) of 4,4'-diaminodiphenyl sulfone (DADS) and an appropriate amount of anhydrous LiCl, and heat to react for 12 h. Pour the product into cold methanol to obtain a white precipitate, filter, collect the filter residue, and wash it several times with methanol and UP water. After drying the product under reduced pressure at 120 ° C for 24 h, the final product, bis(4-carbonylbenzene) poly(4,4'-diaminodiphenyl sulfone sulfonyl) imide PSI, is obtained. (4) PSI and OPBI were dissolved in N,N-dimethylacetamide (DMAC) at mass percentages of 10:90, 25:75, 50:50, and 60:40, respectively, and coated by a casting method. The membrane solvent was evaporated to obtain a PSI / OPBI blend membrane, which can be used as a proton exchange membrane in fuel cells. Example 2

[0026] This embodiment provides a method for preparing a blended modified polybenzimidazole proton exchange membrane, comprising the following steps: (1) Weigh 17.12 g (0.1 mol) of p-toluenesulfonylamine and 4.0 g (0.1 mol) of sodium hydroxide into a two-necked flask, add an appropriate amount of deionized water, and stir at 75 °C until the solution is clear and transparent. Add 9.53 g (0.05 mol) of p-toluenesulfonyl chloride and continue the reaction for 12 h under nitrogen protection. After the solution is cooled, filter it. Adjust the pH of the filtrate to 7 with dilute hydrochloric acid solution and filter it. Collect the product 4-methyl-N-toluenesulfonylbenzenesulfonamide (MBSI) after drying. (2) Weigh 13.0 g (0.04 mol) of the product obtained in (1) and add it to a two-necked flask. Add 1.60 g (0.04 mol) of sodium hydroxide and an appropriate amount of deionized water, stir at 70°C, and after the drug is completely dissolved, add 28.44 g (0.18 mol) of potassium permanganate. After the solution changes from purple-red to brown, filter and collect the filtrate. Adjust the pH of the filtrate to 7 with dilute hydrochloric acid solution, filter the solution, and collect the product CBSI after drying. (3) The product obtained in (2) was added to a double-necked flask containing 40 mL of pyrrolidone (NMP), 30 mL of pyridine (Py) and 10.4 mL of triphenyl phosphite (TPP), and 0.02 mol of 4,4'-dicarboxydiphenyl ether and anhydrous LiCl were added. The mixture was heated to react for 12 h. The product was poured into cold methanol to obtain a white precipitate. The residue was filtered and collected. The residue was washed several times with methanol and UP water. The product was dried under reduced pressure at 120 °C for 24 h to obtain the final product, poly(bis(4-aminophenyl) ether-bis(4-carboxyphenylsulfonyl)imide)amide. (4) The product of (3) and PBI were dissolved in DMAC at mass percentages of 10:90, 25:75, 50:50, and 60:40, respectively, and coated by a cast method to form a membrane. The membrane solvent was evaporated to dryness to obtain a PSI / OPBI blend membrane, which can be used as a proton exchange membrane in fuel cells. Example 3

[0027] This embodiment provides a method for preparing a blended modified polybenzimidazole proton exchange membrane, which is the same as that of Example 1, except that: The strong base of S1 is potassium hydroxide; the reaction temperature of S1 is 70°C, and the reaction time is controlled at 8 hours.

[0028] The oxidizing agent for S2 is potassium dichromate.

[0029] The diamino molecule of S3 is 2,2-bis(4-aminophenyl)hexafluoropropane.

[0030] The organic solvent of S4 is N,N-dimethylformamide. Example 4

[0031] This embodiment provides a method for preparing a blended modified polybenzimidazole proton exchange membrane, which is the same as that of Example 1, except that: The strong base of S1 is lithium hydroxide; the reaction temperature of S1 is 80°C, and the reaction time is controlled within 10 hours.

[0032] The oxidant for S2 is potassium chlorate.

[0033] The diamino molecule of S3 is 2,2′-(ethylenedioxy)bis(ethylamine).

[0034] The organic solvent of S4 is dimethyl sulfoxide. Example 5

[0035] This embodiment provides a method for preparing a blended modified polybenzimidazole proton exchange membrane, which is the same as that of Example 1, except that: The strong base of S1 is potassium hydroxide; the reaction temperature of S1 is 90°C, and the reaction time is controlled at 10 hours.

[0036] The oxidant of S2 is hydrogen peroxide.

[0037] The diamino molecule of S3 is [2,2'-bifuran]-5,5'-diyldimethylamine.

[0038] The organic solvent of S4 is N-methylpyrrolidone. Example 6

[0039] This embodiment provides a method for preparing a blended modified polybenzimidazole proton exchange membrane, which is the same as that of Example 1, except that: The strong base of S1 is sodium hydroxide; the reaction temperature of S1 is 70°C, and the reaction time is controlled at 8 hours.

[0040] The oxidant of S2 is hydrogen peroxide.

[0041] The diamino molecule of S3 is 4,4'-diphenylenediamine.

[0042] The organic solvent of S4 is N,N-dimethylformamide. Example 7

[0043] This embodiment provides a method for preparing a blended modified polybenzimidazole proton exchange membrane, which is the same as that of Example 1, except that: The strong base of S1 is lithium hydroxide; the reaction temperature of S1 is 95°C, and the reaction time is controlled at 12h.

[0044] The oxidant for S2 is potassium permanganate.

[0045] The diamino molecule of S3 is naphthalene-2,6-diamine.

[0046] The organic solvent of S4 is N,N-dimethylformamide. Example 8

[0047] This embodiment provides a method for preparing a blended modified polybenzimidazole proton exchange membrane, which is the same as that of Example 1, except that: The strong base of S1 is sodium hydroxide; the reaction temperature of S1 is 70°C, and the reaction time is controlled at 12h.

[0048] The oxidant for S2 is potassium permanganate.

[0049] The diamino molecule of S3 is 1,4-phenylenediamine.

[0050] The organic solvent of S4 is N-methylpyrrolidone.

[0051] The yield of MBSI obtained in the above Examples 1-8 is 60-85%, and thus PSI and blended membranes with a higher yield can be obtained.

[0052] A series of relevant performance tests were conducted on the product prepared in Example 1 above, and the results are as follows: 1. Structural characterization of PSI: 1.1, prepare PSI through 1 H NMR (400 MHz, DMSO-d6) was used for characterization. The test results were as follows: Figure 2As shown in Figure 1, the characteristic hydrogen peak of the imide at a appears at 10.71 ppm; the characteristic hydrogen peaks of the CBSI monomer at d and e on the PSI polymer appear at 8.02 ppm and 7.96 ppm, respectively; and the characteristic hydrogen peaks of the DADS monomer at b and c appear at 7.54 ppm and 7.84 ppm, respectively. 1 H NMR analysis showed that PSI was successfully synthesized.

[0053] 1.2、FT-IR of PSI Figure 3 As shown, at 3361cm -1 The absorption peak at is attributed to the free -NH2 group; the sulfone group (-SO 2- ) have symmetric stretching and antisymmetric stretching vibration characteristic peaks at 1106 and 1080 cm -1 Appears at 3095cm -1 The characteristic peak of the stretching vibration of C=O is at 1674cm -1 and 1595, 1536, 1260cm -1 The peaks at 3 and 4 correspond to the stretching vibration of C=C benzene ring, the bending vibration of NH and the stretching vibration of CN respectively. FT-IR test results further prove the successful synthesis of PSI.

[0054] 2. Structural characterization of blend films: 2.1. Pass 1 H NMR spectroscopy was used to characterize the chemical structure of the blended films. Figure 4 As shown (the lines from top to bottom represent PSI, 60PSI / 40OPBI, 50PSI / 50OPBI, 25PSI / 75OPBI, 10PSI / 90OPBI, and OPBI, respectively). As the ratio of the polymer components changes, the characteristic peak originally attributed to PSI gradually becomes more prominent in the NMR curve, while the corresponding characteristic peak of OPBI gradually weakens, indicating an increase in the proportion of the PSI component in the blend film. In addition, the absorption peak of the imine on the benzimidazole ring of the OPBI polymer appears at 12.97 ppm. However, as the content of the PSI component in the blend film increases, this characteristic peak gradually weakens and eventually disappears. This is because the bissulfonyl imide group is Lewis acidic and, after blending with OPBI, forms hydrogen bonds with the Lewis basic -NH- on the imidazole ring. 1 H NMR test results showed that PSI and OPBI were successfully blended.

[0055] 2.2. The structures of OPBI membrane and four groups of OPBI / PSI blend membranes were characterized by FT-IR. The test results are shown in the figure below. Figure 5 The characteristic peak of the CN bond stretching vibration on the imidazole ring in OPBI polymer is at 1603 cm -1Appearance, 1201cm -1 The characteristic peak at 1674 cm is the stretching vibration of the phenyl ether bond. -1 Appearance, sulfone group (-SO 2- ) has a symmetrical stretching peak at 1106 cm -1 The characteristic peaks are more pronounced as the mass proportion of PSI polymer in the blend film increases. FT-IR analysis further demonstrates that the blend film was successfully prepared.

[0056] 2.3, SEM images of the blended films, such as Figure 6 It can be found that the surface of the membrane prepared by blending OPBI and PSI is also very dense, indicating that the PSI polymer and OPBI polymer have good compatibility. The membrane with a compact structure has a stronger ability to block the contact between the positive and negative electrode fuels and the oxidant.

[0057] 3. Proton conductivity of blend membrane: In addition to isolating the gas contact between the positive and negative electrodes, the proton exchange membrane (PEM) also needs to conduct protons during operation. The level of proton conductivity directly affects the output power and response speed of the fuel cell. Figure 7 As shown in the figure, the resistance of five groups of membranes at similar acid doping rates in the temperature range of 100-200 ℃ was tested, and the corresponding proton conductivity was calculated.

[0058] Because the ion migration rate of phosphoric acid increases with temperature before 160°C, the proton conductivity of all membranes increases with increasing test temperature. However, in the temperature range of 160-200°C, phosphoric acid molecules polymerize to form oligomers, resulting in a decrease in the membrane's proton conductivity.

[0059] The electrical conductivity of the four blend membranes was significantly improved compared to that of pure OPBI membranes at all temperature ranges. The bissulfonylimide polymer proton conductor PSI possesses strong proton dissociation capabilities, providing more protons within the blend membranes. Furthermore, compared to pure OPBI membranes, the hydrogen bonding interaction between PSI and OPBI enhances the hydrogen bonding network within the blend membranes after phosphoric acid doping, facilitating proton conduction within the membrane via a hopping mechanism. Consequently, the proton conductivity of the OPBI / PSI blend membranes was significantly improved.

[0060] 4. Mechanical properties of blended films: The mechanical properties of proton exchange membrane (PEM) have a direct impact on the preparation of membrane electrode and the long service life of fuel cells. In order to evaluate the mechanical properties of the blend, the mechanical properties of four groups of OPBI / PSI blend membranes before and after phosphoric acid doping were tested. The test results of the stress-strain curve of pure OPBI membrane are shown in Figure 2. Figure 8 and Figure 9shown.

[0061] Among them, the stress-strain curves of the five groups of membranes before phosphoric acid doping are as follows Figure 8 As shown, the mechanical properties of the blend films generally show an upward and then downward trend, with the 25PSI / 75OPBI group showing a significant improvement, with both tensile strength and elongation at break higher than those of pure OPBI. This is due to the good compatibility between OPBI and PSI polymers, the uniform distribution and cross-arrangement of the two polymers within the film, and the formation of a tight hydrogen bond network between PSI and OPBI molecules, which enhances the mechanical properties of the single OPBI polymer. However, the mechanical properties of the PSI polymer itself are inferior to those of OPBI, and as the content of the PSI component in the blend film increases, the mechanical properties of the blend film begin to decline.

[0062] The stress-strain curves of the blend films after phosphoric acid doping are shown in Figure 2. Figure 9 As shown, due to the plasticizing effect of phosphoric acid molecules on the polymers, the intermolecular hydrogen bonds within the polymers were significantly disrupted, resulting in a significant decrease in the tensile strength of all four OPBI / PSI blend films. The presence of free phosphoric acid molecules between the polymers significantly enhanced the mobility and flexibility of the polymer chains, resulting in a significant increase in the elongation at break of the films after acid doping. The tensile strength of the four blend films after phosphoric acid doping initially increased and then decreased. The good compatibility between OPBI and PSI polymers, as well as the formation of an intermolecular hydrogen bond network, contributes to the enhanced mechanical strength of the PA-doped films.

[0063] In summary, the present invention synthesizes CBSI, then reacts it with diamino molecules through an amidation-dehydration condensation reaction to produce a high-molecular-weight polymer (PSI) containing repeating bissulfonyl imide groups. PSI and polyether polybenzimidazole (OPBI) are dissolved in a polar solvent to form a membrane, which is then dried to produce a modified proton exchange membrane blended with the bissulfonyl imide polymer and polybenzimidazole. Compared to existing polybenzimidazole proton exchange membranes, the composite membrane of the present invention exhibits superior proton conductivity and good mechanical properties, meeting the performance requirements of fuel cell proton exchange membranes.

[0064] The present invention utilizes low-cost, readily available raw materials, a mature preparation method, high yield, and high feasibility. The resulting membrane exhibits high proton conductivity and excellent mechanical properties, making it suitable for use in proton exchange membrane fuel cells. The present invention also utilizes a simple method for preparing the blended modified membranes of polybenzimidazole polymers. Polyether polybenzimidazole (OPBI) is commercially mature and readily available, offering broad application prospects.

[0065] The above shows and describes the basic principles and main features of the present invention and the advantages of the present invention. It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the present invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the present invention. Therefore, the embodiments should be regarded as illustrative and non-restrictive in all respects. The scope of the present invention is defined by the appended claims rather than the foregoing description, and it is intended that all changes that come within the meaning and range of equivalents of the claims be embraced therein.

[0066] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a blended modified polybenzimidazole proton exchange membrane, characterized in that: The following steps are involved: S1, preparation of 4-methyl-N-toluenesulfonylbenzenesulfonamide: Add p-toluenesulfonylamine and a strong base to a two-necked flask, add an appropriate amount of deionized water, heat and stir until the solution is clear, then add p-toluenesulfonyl chloride, continue the reaction under nitrogen protection, cool and filter, adjust the pH of the filtrate to 7 with an acidic solution, filter and collect the residue, and dry to obtain the product 4-methyl-N-toluenesulfonylbenzenesulfonamide, recorded as MBSI; S2, preparation of 4,4'-[iminobis(sulfonyl)]bisbenzoic acid: MBSI and sodium hydroxide were added to a two-necked flask, and an appropriate amount of deionized water was added. After heating and stirring until the solution was clear and transparent, an oxidant was added. After the reaction was completed, the filtrate was collected by filtration. The pH of the filtrate was adjusted to 7 with an acidic solution, and the solution was filtered and dried to obtain the product 4,4'-[iminobis(sulfonyl)]bisbenzoic acid, which was recorded as CBSI. S3, preparation of PSI: CBSI and an appropriate amount of anhydrous lithium chloride were dissolved in a mixed solution of appropriate amounts of pyridine, triphenyl phosphite, and pyrrolidone. After complete dissolution, a diamino molecule was added. The solution was heated and stirred for 12 h, then poured into methanol. The product was collected by filtration, washed with water, and dried to obtain the product PSI. S4, preparation of PSI / OPBI blend membrane: Appropriate amounts of PSI and polyether polybenzimidazole (OPBI) were dissolved in a polar solvent, and a film was prepared by a casting method, and then dried thoroughly to obtain a PSI / OPBI blend film. The mixed mass percentage of PSI and OPBI includes but is not limited to 10PSI / 90OPBI, 25PSI / 75OPBI, 50PSI / 50OPBI, and 60PSI / 40OPBI.

2. The method for preparing a blended modified polybenzimidazole proton exchange membrane according to claim 1, wherein: The molar ratio of toluenesulfonylamide, strong base and toluenesulfonyl chloride in S1 is 2:2:

1.

3. The method for preparing a blended modified polybenzimidazole proton exchange membrane according to claim 1, wherein: The strong base S1 includes but is not limited to one or more of potassium hydroxide, sodium hydroxide, and lithium hydroxide.

4. The method for preparing a blended modified polybenzimidazole proton exchange membrane according to claim 1, wherein: The reaction temperature of S1 is 70-95° C., and the reaction time is controlled at 8-12 h.

5. The method for preparing a blended modified polybenzimidazole proton exchange membrane according to claim 1, wherein: The molar ratio of MBSI, sodium hydroxide and oxidant in S2 is 1:1:4.

5.

6. The method for preparing a blended modified polybenzimidazole proton exchange membrane according to claim 1, characterized in that: The oxidant of S2 includes but is not limited to one or more of potassium permanganate, potassium dichromate, potassium chlorate, and hydrogen peroxide.

7. The method for preparing a blended modified polybenzimidazole proton exchange membrane according to claim 1, characterized in that: The diamino molecules of S3 include but are not limited to one or more of 4,4'-diaminodiphenyl sulfone, 4,4'-dicarboxydiphenyl ether, 2,2-bis(4-aminophenyl)hexafluoropropane, 2,2'-(ethylenedioxy)bis(ethylamine), [2,2'-bifuran]-5,5'-dimethyldiamine, 4,4'-diphenylenediamine, naphthalene-2,6-diamine, and 1,4-phenylenediamine.

8. The method for preparing a blended modified polybenzimidazole proton exchange membrane according to claim 1, characterized in that: The molar ratio of CBSI to diamino molecules in S3 is 1:

1.

9. The method for preparing a blended modified polybenzimidazole proton exchange membrane according to claim 1, characterized in that: The organic solvent of S4 includes, but is not limited to, one or more of N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, and N-methylpyrrolidone.

10. A blended modified polybenzimidazole proton exchange membrane, characterized in that: The blended modified polybenzimidazole proton exchange membrane is prepared by the method according to any one of claims 1 to 9.

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