Graft-modified polybenzimidazole proton exchange membrane and preparation method thereof

Abstract

The invention is applicable to the technical field of fuel cells, and provides a graft modified polybenzimidazole proton exchange membrane and a preparation method thereof, and the preparation method comprises the following steps: Step 1, synthesizing a halogenated bisulfonyl imide compound; step 2, synthesis of bis-sulfonylimide side group polybenzimidazole: dissolving OPBI in a proper amount of a polar solvent, adding a proper amount of LiH at 120 DEG C to activate OPBI for about 4-12 h, after complete activation, adding a mixture of a certain amount of halogenated bis-sulfonylimide compound and a proper amount of KI, and continuing to react for 24 h; after the reaction is finished, pouring the product into distilled water while the product is hot, fully washing with a proper amount of hydrochloric acid, washing off redundant hydrochloric acid with a proper amount of sodium carbonate, and completely drying to obtain the product bis-sulfonimido side group polybenzimidazole; and step 3, preparing the proton exchange membrane of the bis (sulfonyl) imide grafted polybenzimidazole. According to the scheme, raw materials are low in cost and easy to obtain, synthesis conditions are mature, the yield and feasibility are high, the product membrane conductivity is high, the output characteristic of a fuel cell is improved, and wide application prospects are achieved.

Description

Technical Field

[0001] This invention relates to the field of fuel cell technology, specifically to a graft-modified polybenzimidazole proton exchange membrane and its preparation method. Background Technology

[0002] Polybenzimidazole (PBI) polymer is an engineering plastic with excellent thermal stability, good mechanical properties, and superior proton conductivity and chemical stability at high temperatures, making it valuable for applications in fuel cells, aerospace, chemical machinery, protective clothing, and other fields.

[0003] However, for PBI to be formally applied in fuel cells, it still 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 mainly follows the Grotthuss mechanism, with protons hopping and conducting within the hydrogen bond network of PA-PBI. High levels of phosphoric acid doping (ADL) can achieve even better proton conductivity, but it also introduces two major problems: (1) Decreased mechanical properties: A large number of PA molecules enter the polymer chain, which will destroy the original hydrogen bonding and weaken the intermolecular interaction force, resulting in 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, which in turn affects the overall performance of the battery.

[0004] Based on the above technical problems, this application proposes a graft-modified polybenzimidazole proton exchange membrane and its preparation method, aiming to develop a PBI membrane 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 purpose of this invention is to provide a grafted modified polybenzimidazole proton exchange membrane and its preparation method, so as to provide a grafted modified polybenzimidazole polymer proton exchange membrane with excellent proton conductivity, which can be used as a proton exchange membrane for fuel cells to block the positive and negative electrodes.

[0006] To achieve the above objectives, the present invention provides the following technical solution: The first aspect of the present invention provides a method for preparing a graft-modified polybenzimidazole proton exchange membrane, comprising the following steps: Step 1, Synthesis of halobissulfonylimide compounds: The sulfonamide chemical was dissolved in an appropriate amount of anhydrous acetonitrile, and a strong base was added under nitrogen protection and stirred until homogeneous. The halosulfonyl chloride compound was dissolved in an appropriate amount of anhydrous acetonitrile and added to a double-necked flask through a constant pressure funnel. After reacting for 12 hours, the mixture was filtered. After the filtrate was completely evaporated using a rotary evaporator, an appropriate amount of dichloromethane was added, and the mixture was washed thoroughly, filtered again, and dried completely to obtain the halodisulfonylimide compound. Step 2, Synthesis of disulfonylimide-side-group polybenzimidazole: Dissolve OPBI in an appropriate amount of polar solvent, add an appropriate amount of LiH at 120℃ to activate OPBI for 4-12h, after complete activation, add a certain amount of halobissulfonylimide compound and an appropriate amount of KI mixture, and continue the reaction for 24h. After the reaction was completed, the product was poured into distilled water while hot, washed thoroughly with an appropriate amount of hydrochloric acid, and then washed away with an appropriate amount of sodium carbonate to remove excess hydrochloric acid. After complete drying, the product disulfonylimide side-group polybenzimidazole was obtained. The content of OPBI and halobissulfonylimide compounds is adjusted according to the grafting degree requirements. Step 3, Preparation of a proton exchange membrane grafted with bis(sulfonylimide) polybenzimidazole: The product from Step 2 was dissolved in an appropriate amount of polar solvent, and a film was prepared by casting. After thorough drying, a proton exchange membrane of disulfonylimide-grafted polybenzimidazole was obtained.

[0007] Preferably, the sulfonamide compound in Step 1 includes, but is not limited to, one or more of trifluoromethanesulfonamide, methanesulfonamide, benzenesulfonamide, and isopropylsulfonamide; the strong base in Step 1 includes, but is not limited to, one or more of potassium hydroxide, sodium hydroxide, and lithium hydroxide.

[0008] Preferably, the halosulfonyl chloride compound in Step 1 includes, but is not limited to, one or more of 3-chloropropanesulfonyl chloride, 3-bromopropanesulfonyl chloride, 2-chloroethanesulfonyl chloride, 2-bromoethylsulfonyl chloride, and 4-bromomethylbenzenesulfonyl chloride.

[0009] Preferably, the polar solvent in Step 2 includes, but is not limited to, one or more of N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, and N-methylpyrrolidone.

[0010] Preferably, LiH in Step 2 is replaced with NaH or KH.

[0011] Preferably, the hydrochloric acid in Step 2 is replaced with formic acid or acetic acid; and the sodium carbonate in Step 2 is replaced with sodium bicarbonate or ammonia.

[0012] Preferably, the molar ratio of the sulfonamide chemical, the strong base, and the halosulfonyl chloride compound in Step 1 is 1:2:1.

[0013] A second aspect of the present invention provides a grafted modified polybenzimidazole proton exchange membrane, which is prepared by the method described in the first aspect of the present invention.

[0014] This invention has at least the following beneficial effects: This invention provides a graft-modified polybenzimidazole proton exchange membrane and its preparation method. The raw materials are low in cost and readily available, the synthesis conditions are mature, the yield is high, the feasibility is high, and the product membrane has high conductivity, which improves the output characteristics of fuel cells. It can be applied to fuel cells and has broad application prospects. Attached Figure Description

[0015] Figure 1 This is a flowchart of the preparation method of the modified bis(sulfonyl)imide-side-group polybenzimidazole proton exchange membrane in Embodiment 1 of the present invention; Figure 2 For CFSI in Embodiment 1 of the present invention 1 H NMR spectrum; Figure 3 The FT-IR spectrum of CFSI in Embodiment 1 of the present invention; Figure 4 For OPBI, OPBI-CFSI, and CFSI in Embodiment 1 of this invention 1 H NMR spectrum; Figure 5 The FT-IR spectra of OPBI, OPBI-CFSI, and CFSI in Embodiment 1 of this invention; Figure 6 The graph shows the conductivity-electrochemical stability-temperature curves of the modified bis(sulfonyl)imide-side-group polybenzimidazole proton exchange membrane after phosphoric acid doping in Embodiment 1 of this invention. Figure 7 This is a graph showing the mechanical properties of the modified bis(sulfonyl)imide-side-group polybenzimidazole proton exchange membrane after phosphoric acid doping in Embodiment 1 of the present invention. Detailed Implementation

[0016] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Example 1

[0017] like Figure 1 As shown, this embodiment provides a method for preparing a grafted modified polybenzimidazole proton exchange membrane, including the following steps: 1) Dissolve 6.71 g (0.045 mol) of trifluoromethanesulfonamide in 100 mL of anhydrous acetonitrile. Under argon protection, add 5.0 g (0.09 mol) of potassium hydroxide and dissolve with stirring. Dissolve 8.59 g (0.045 mol) of 3-chloropropanesulfonyl chloride in anhydrous acetonitrile and add it to a double-necked flask through a constant pressure funnel. React at 120 °C overnight.

[0018] 2) After the reaction is complete, filter the solution, use a rotary evaporator to completely dry the filtrate, add dichloromethane, wash thoroughly, filter to obtain white 3-chloropropanesulfonyl (trifluoromethylsulfonyl)imide, denoted as CFSI, and dry it in a 60℃ oven.

[0019] 3) Dissolve 4.0g of OPBI in an appropriate amount of N,N-dimethylacetamide (DMAC), add 0.50g of lithium hydride (LiH) to activate OPBI for about 4 hours. After complete activation, add 2.89g, 5.78g, 8.67g, and 11.56g of CFSI and an appropriate amount of KI respectively, and continue the reaction at 120℃ for 24 hours.

[0020] 4) After the reaction in 3) is complete, pour the product into distilled water while it is still hot, wash it thoroughly with hydrochloric acid, and then wash away the excess hydrochloric acid with sodium carbonate. After complete drying, the product with 10%, 20%, 30%, and 40% grafting degree of disulfonamide side-group polybenzimidazole (can be adjusted according to the grafting degree requirement) is obtained, denoted as OPBI-CFSI.

[0021] 5) Add the product obtained in 4) to DMAC, stir to dissolve, coat it into a membrane, and evaporate the membrane solvent to obtain a disulfonamide side-group polybenzimidazole proton exchange membrane. Example 2

[0022] This embodiment provides a method for preparing a grafted modified polybenzimidazole proton exchange membrane, comprising the following steps: 1) Dissolve 4.91 g (0.045 mol) methanesulfonamide in 100 mL of anhydrous acetonitrile. Under argon protection, add 0.09 mol potassium hydroxide and dissolve with stirring. Dissolve 8.59 g (0.045 mol) 3-chloropropanesulfonyl chloride in anhydrous acetonitrile and add it to a double-necked flask through a constant pressure funnel. React at 120 °C overnight.

[0023] 2) After the reaction is complete, filter the solution, use a rotary evaporator to completely dry the filtrate, add dichloromethane, wash thoroughly, filter to obtain 3-chloropropanesulfonyl (methylsulfonyl)imine, and dry it in a 60℃ oven.

[0024] 3) Dissolve 6g of OPBI in an appropriate amount of N,N-dimethylacetamide (DMAC), add 0.75g of lithium hydride (LiH) to activate OPBI for about 4h. After complete activation, add 1.02g, 2.04g, 3.06g, and 4.08g of 3-chloropropanesulfonyl (methylsulfonyl)imide and 6.6g of KI respectively, and continue the reaction at 120℃ for 24h.

[0025] 4) After the reaction in (3) is completed, pour the product into distilled water while it is still hot, wash it thoroughly with hydrochloric acid, wash off the excess hydrochloric acid with sodium carbonate, and dry it completely to obtain products with 10%, 20%, 30%, and 40% grafted disulfonylimide side-group polybenzimidazole.

[0026] 5) Add the product obtained in (4) to DMAC, stir to dissolve, coat it into a membrane, and evaporate the membrane solvent to obtain a disulfonamide side-group polybenzimidazole proton exchange membrane. Example 3

[0027] This embodiment provides a method for preparing a grafted modified polybenzimidazole proton exchange membrane, comprising the following steps: 1) Dissolve 4.91 g (0.045 mol) methanesulfonamide in 100 mL of anhydrous acetonitrile. Under argon protection, add 0.09 mol potassium hydroxide and dissolve with stirring. Dissolve 12.13 g (0.045 mol) 4-bromomethylbenzenesulfonyl chloride in anhydrous acetonitrile and add it to a double-necked flask through a constant pressure funnel. React at 120 °C overnight.

[0028] 2) After the reaction is complete, filter the solution, use a rotary evaporator to completely dry the filtrate, add dichloromethane, wash thoroughly, filter to obtain 4-bromomethylbenzenesulfonyl chloride (methylsulfonyl)imine, and dry it in a 60℃ oven.

[0029] 3) Dissolve 6g of OPBI in an appropriate amount of N,N-dimethylacetamide (DMAC), add 0.75g of lithium hydride (LiH) to activate OPBI for about 4h. After complete activation, add 1.65g, 3.3g, 4.95g, and 6.6g of 4-bromomethylbenzenesulfonyl chloride (methylsulfonyl)imide and an appropriate amount of KI mixture respectively, and continue the reaction at 120℃ for 24h.

[0030] 4) After the reaction in (3) is completed, pour the product into distilled water while it is still hot, wash it thoroughly with hydrochloric acid, wash off the excess hydrochloric acid with sodium carbonate, and dry it completely to obtain products with 10%, 20%, 30%, and 40% grafted disulfonylimide side-group polybenzimidazole.

[0031] 5) Add the product obtained in (4) to DMAC, stir to dissolve, coat it into a membrane, and evaporate the membrane solvent to obtain a disulfonamide side-group polybenzimidazole proton exchange membrane. Example 4

[0032] This embodiment provides a method for preparing a grafted modified polybenzimidazole proton exchange membrane, which is the same as in Embodiment 1, but with the following differences: In Step 1: the sulfonamide compound is benzenesulfonamide; the strong base is sodium hydroxide; the halosulfonyl chloride compound is a mixture of 3-bromopropanesulfonyl chloride and 2-chloroethanesulfonyl chloride (mixing molar ratio is 1:1).

[0033] In Step 2: the polar solvent is N,N-dimethylformamide; NaH is used instead of LiH; formic acid is used instead of hydrochloric acid; sodium bicarbonate is used instead of sodium carbonate. Example 5

[0034] This embodiment provides a method for preparing a grafted modified polybenzimidazole proton exchange membrane, which is the same as in Embodiment 1, but with the following differences: In Step 1: the sulfonamide compound is isopropyl sulfonamide; the strong base is lithium hydroxide; and the halosulfonyl chloride compound is a mixture of 2-bromoethylsulfonyl chloride and 4-bromomethylbenzenesulfonyl chloride (mixing molar ratio of 2:1).

[0035] In Step 2: the polar solvent is a mixture of dimethyl sulfoxide and N-methylpyrrolidone (mixing volume ratio of 3:1); KH is used instead of LiH; acetic acid is used instead of hydrochloric acid; and ammonia is used instead of sodium carbonate.

[0036] 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 3-chloropropanesulfonyl (trifluoromethylsulfonyl)imine (CFSI): 1.1 Usage 1 The product was characterized by ¹H NMR (400 MHz, DMSO-d6), and the test results are as follows: Figure 2 As shown, the methylene group (-CH) on CFSI 2- The electron-withdrawing effect of chlorine atoms and sulfone groups splits into three sets of peaks, which appear at 3.75 ppm, 3.10 ppm and 2.11 ppm, respectively.

[0037] 1.2. CFSI was further characterized by FT-IR spectroscopy, and the test results are as follows: Figure 3 As shown. Sulfone group (-SO 2- The characteristic peaks of asymmetric and symmetric tensile vibrations are at 1313 cm⁻¹. -1 and 1117cm -1 It appears in the location, and 1187cm -1 and 1049cm -1 The characteristic peaks at 620 cm⁻¹ represent the stretching vibrations of asymmetric CF and SNS bonds, respectively. -1It is the characteristic peak of the bending vibration of the CF bond.

[0038] In conclusion, 1 1H NMR and FT-IR test results indicate that CFSI was successfully prepared.

[0039] 2. Structural characterization of grafted membranes: 2.1 Usage 1 The chemical structures of the OPBI film and four groups of OPBI-CFSI grafted films were characterized by ¹H NMR (400MHz, DMSO-d6). The test results are as follows: Figure 4 As shown, the characteristic hydrogen peaks at positions d, e, and f on the benzimidazole ring of the OPBI molecule correspond to 8.04 ppm, 7.76 ppm, and 8.19 ppm in the spectrum, respectively; the characteristic hydrogen peaks at positions h and i on the diphenyl ether ring correspond to 8.29 ppm and 7.31 ppm in the spectrum, respectively; and the peak at 13.0 ppm corresponds to the vibrational peak of the imine (-NH-) on the imidazole ring. With the introduction of the CFSI side chain, the characteristic hydrogen peak at position h on the diphenyl ether ring of OPBI, which was originally at 8.29 ppm, gradually weakens, while the characteristic peak in the 8.04-8.19 ppm region gradually strengthens. This is because the strong electron-withdrawing effect of the disulfonyl imide group on the CFSI molecule reduces the electron cloud density and chemical shift at position h on the OPBI molecule. In addition, the characteristic peak of the methylene group at position c on the CFSI molecule shifts to a lower field and appears at 4.51 ppm. By comparing the area ratio of the methylene characteristic peak at position c to the hydrogen characteristic peak on the benzene ring at position i, the actual grafting degree of the OPBI-CFSI grafted membrane was calculated to be consistent with the theoretical grafting degree, and the four groups of OPBI-CFSI grafted membranes were successfully prepared.

[0040] 2.2 The structures of the OPBI membrane and the four groups of OPBI-CFSI grafted membranes were characterized by FT-IR spectroscopy. The test results are as follows: Figure 5 As shown, the characteristic peak of the imine stretching vibration on OPBI appears at 3187 cm⁻¹. -1 At 1601 cm⁻¹, the characteristic peak of the stretching vibration of the carbon-nitrogen double bond (C=N) on the imidazole ring is observed. -1 The characteristic peak of the stretching vibration of the phenyl ether bond is visible at 1480 cm⁻¹. -1 The appearance was evident at 1313 cm. Compared to OPBI, all grafted membranes showed improvement at 1313 cm. -1 and 1117cm -1 Absorption peaks of sulfone group asymmetric and symmetric stretching vibrations appeared at all locations, and the absorption peaks became more pronounced with increasing grafting degree; all grafted films showed absorption peaks at 1187 cm⁻¹. -1 and 1049cm -1 Asymmetrical CF and SNS tensile vibrations were observed at 620cm. -1The peak at 800 cm⁻¹ is a characteristic peak of the CF bending vibration. Furthermore, as the grafting degree of the grafted membrane increases, the -NH₄⁻ on benzimidazole is reacted away, thus the peak at 800 cm⁻¹... -1 The absorption peak at that point shows a decreasing trend. FT-IR spectroscopy further confirms that CFSI was successfully grafted onto OPBI.

[0041] 3. Proton conductivity of the grafted membrane: like Figure 6 As shown, the test results indicate that the proton conductivity of all tested membranes initially increases and then decreases with increasing test temperature. In the 100-160 °C temperature range, the phosphate ion migration rate increases with temperature, thus the proton conductivity of the tested membrane reaches its highest value at 160 °C. As the temperature continues to rise, phosphate molecules undergo polymerization to form phosphate oligomers, thereby reducing the migration rate within the membrane and consequently decreasing the proton conductivity. All grafted membranes exhibit significantly higher proton conductivity than pure OPBI membranes across all temperature ranges. This is because the bissulfonylimide side-chain group possesses a strong proton dissociation capability, resulting in more proton conduction sites within the OPBI-CFSI grafted membrane. Furthermore, the bissulfonylimide group interacts with the OPBI benzimidazole ring through hydrogen bonding, enhancing the hydrogen bond network within the phosphate-doped grafted membrane and facilitating proton migration within the membrane via hydrogen bond breaking and recombination. In summary, grafting CFSI, a disulfonamide-type proton conductor, onto OPBI polymers to form a side chain structure can significantly enhance the membrane's ability to conduct protons.

[0042] 4. Mechanical properties of the grafted membrane: like Figure 7 As shown, the mechanical properties of the phosphate-doped OPBI film and four groups of OPBI-CFSI grafted films were tested.

[0043] PA molecules have a "plasticizing effect" on polymers, fully occupying the gaps between OPBI molecular chains, which leads to a significant disruption of intermolecular hydrogen bonds, thus reducing the tensile strength of the acid-doped film. Conversely, the large number of PA molecules occupying the free space of the polymer significantly enhances the mobility and flexibility of the polymer chains, resulting in a substantial increase in the elongation at break of the acid-doped film.

[0044] In summary, the technical solution provided by this invention has low raw material cost, readily available raw materials, mature synthesis conditions, high yield, high feasibility, and high membrane conductivity, which improves the output characteristics of fuel cells and is expected to be applied to fuel cells.

[0045] Furthermore, the preparation method of the grafted modified film of the polybenzimidazole polymer of the present invention is simple. The polyether polybenzimidazole (OPBI) is commercially mature and can be stably obtained. The raw material cost of the 3-chloropropanesulfonyl (trifluoromethylsulfonyl)imide (CFSI) to be synthesized is low, the reaction conditions are mild, and the yield is high.

[0046] The foregoing has shown and described the basic principles, main features, and 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 invention can be implemented in other specific forms without departing from its spirit or basic characteristics. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

[0047] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a graft-modified polybenzimidazole proton exchange membrane, characterized by, Comprising the following steps: Step 1, synthesis of halogenated bis-sulfonamide compound: Dissolve sulfonamide chemicals in a suitable amount of anhydrous acetonitrile, add strong base under nitrogen protection, stir and mix uniformly; dissolve halogenated sulfuryl chloride compound in a suitable amount of anhydrous acetonitrile, add to the double-necked flask through a constant pressure funnel, filter after 12h of reaction; After the filtrate is completely dried by rotary evaporation, add a suitable amount of dichloromethane, wash thoroughly, filter again, and dry completely to obtain the halogenated bis-sulfonamide compound; Step 2, synthesis of bis-sulfonamide side group polybenzimidazole: Dissolve OPBI in a suitable amount of polar solvent, activate OPBI at 120℃ by adding a suitable amount of LiH for 4-12h, after complete activation, add a certain amount of halogenated bis-sulfonamide compound and a suitable amount of KI mixture, continue to react for 24h; After the reaction is completed, pour the product into distilled water while it is hot, wash with a suitable amount of hydrochloric acid, then wash off the excess hydrochloric acid with a suitable amount of sodium carbonate, and dry completely to obtain the product bis-sulfonamide side group polybenzimidazole; Wherein, the content of OPBI and halogenated bis-sulfonamide compound is adjusted according to the grafting degree requirement; Step 3, preparation of bis-sulfonamide grafted polybenzimidazole proton exchange membrane: dissolve the product of Step 2 in a suitable amount of polar solvent, prepare into a film by casting method, and dry completely to obtain the bis-sulfonamide grafted polybenzimidazole proton exchange membrane.

2. The method of claim 1, wherein the method is characterized by: The sulfonamide compound of Step 1 includes but is not limited to one or more of trifluoromethanesulfonamide, methanesulfonamide, benzenesulfonamide, and isopropyl sulfonamide; the strong base of Step 1 includes but is not limited to one or more of potassium hydroxide, sodium hydroxide, and lithium hydroxide.

3. The method of claim 1, wherein the method is characterized by: The halogenated sulfuryl chloride compound of Step 1 includes but is not limited to one or more of 3-chloropropane sulfuryl chloride, 3-bromopropane sulfuryl chloride, 2-chloroethane sulfuryl chloride, 2-bromoethyl sulfuryl chloride, and 4-bromomethyl benzene sulfuryl chloride.

4. The method of claim 1, wherein the method is characterized by: The polar solvent of Step 2 includes but is not limited to one or more of N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, and N-methyl pyrrolidone.

5. The method for preparing a grafted modified polybenzimidazole proton exchange membrane according to claim 1, characterized in that: NaH or KH is used instead of LiH in Step 2.

6. The method for preparing a grafted modified polybenzimidazole proton exchange membrane according to claim 1, characterized in that: Formic acid or acetic acid is used instead of hydrochloric acid in Step 2; sodium bicarbonate or ammonia water is used instead of sodium carbonate in Step 2.

7. The method for preparing a grafted modified polybenzimidazole proton exchange membrane according to claim 1, characterized in that: The molar ratio of sulfonamide chemicals, strong base, and halogenated sulfuryl chloride compound of Step 1 is 1:2:

1.

8. A graft-modified polybenzimidazole proton exchange membrane, characterized by: The graft-modified polybenzimidazole proton exchange membrane is prepared by the method of any one of claims 1-7.

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