Graft modified polybenzimidazole proton exchange membrane and preparation method thereof

Abstract

The application is suitable for the field of fuel cell technology, and provides a grafted modified polybenzimidazole proton exchange membrane and a preparation method, which comprises the following steps: Step 1, synthesizing a halogenated bis-sulfonimide compound; Step 2, synthesizing a bis-sulfonimide side group polybenzimidazole: OPBI is dissolved in a proper amount of a polar solvent, OPBI is activated by adding a proper amount of LiH at 120 DEG C for about 4-12 h, after complete activation, a certain amount of the halogenated bis-sulfonimide compound is added and mixed with a proper amount of KI, and the reaction is continuously carried out for 24 h; after the reaction is completed, the product is poured into distilled water while hot, washed with a proper amount of hydrochloric acid, and then washed with a proper amount of sodium carbonate to remove the excess hydrochloric acid, and the product bis-sulfonimide side group polybenzimidazole is obtained after complete drying; Step 3, preparing a bis-sulfonimide grafted polybenzimidazole proton exchange membrane. The raw material cost of the scheme is low, the raw material is easy to obtain, the synthesis condition is mature, the yield is high, the feasibility is high, the product membrane has high conductivity, the output characteristics of the fuel cell are improved, and the scheme has a wide application prospect.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of fuel cells, in particular to a grafted modified polybenzimidazole proton exchange membrane and a preparation method. BACKGROUND

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

[0003] However, PBI needs to be doped with phosphoric acid (PA) for formal application in fuel cells. PA-doped PBI membrane (PA-PBI) has excellent proton conductivity and stability under high-temperature anhydrous conditions. Under anhydrous conditions, the proton conduction in the PA-PBI system mainly follows the Grotthuss mechanism, and the proton is conducted by jumping in the hydrogen bond network of PA-PBI. A high level of phosphoric acid doping amount (ADL) can achieve better proton conductivity, but also brings two problems:

[0004] (1) Mechanical property degradation: a large number of PA molecules entering the polymer chain will destroy the original hydrogen bond effect, weaken the intermolecular interaction force, and cause the mechanical property to deteriorate significantly;

[0005] (2) PA leaching: during the operation of the fuel cell, PA molecules migrate and lose under the influence of water molecules, and the proton conductivity decreases with the loss of PA, thereby affecting the overall performance of the cell.

[0006] Based on the above technical problems, the application provides a grafted modified polybenzimidazole proton exchange membrane and a preparation method, aiming to develop a PBI membrane with high proton conductivity and good mechanical strength to meet the needs of fuel cell applications. SUMMARY

[0007] The application aims to provide a grafted modified polybenzimidazole proton exchange membrane and a preparation method, which has excellent proton conductivity and can be used as a fuel cell proton exchange membrane to block the positive and negative electrodes.

[0008] To achieve the above-mentioned purpose, the application provides the following technical scheme: the first aspect of the application provides a preparation method of a grafted modified polybenzimidazole proton exchange membrane, comprising the following steps:

[0009] Step 1, synthesis of halogenated bis-sulfonylimide compound:

[0010] The sulfonamide compound is dissolved in a proper amount of anhydrous acetonitrile, a strong base is added under nitrogen protection, the mixture is stirred and mixed uniformly; the halogenated sulfuryl chloride compound is dissolved in a proper amount of anhydrous acetonitrile, and is added into the double-necked flask through a constant-pressure funnel, and after reaction for 12 h, filtration is performed;

[0011] After the filtrate is completely dried by using a rotary evaporator, a proper amount of dichloromethane is added, and after sufficient washing, filtration is performed again, and the halogenated disulfimide compound is completely dried to obtain the halogenated disulfimide compound;

[0012] Step 2, synthesis of a disulfimide side group polybenzimidazole:

[0013] The OPBI is dissolved in a proper amount of a polar solvent, and a proper amount of LiH is added to activate the OPBI at 120°C for 4-12 h; after complete activation, a certain amount of a halogenated disulfimide compound is added and mixed with a proper amount of KI, and the reaction is continued for 24 h;

[0014] After the reaction is completed, the product is poured into distilled water while hot, washed with a proper amount of hydrochloric acid, and then washed with a proper amount of sodium carbonate to remove excess hydrochloric acid; after complete drying, the product, a disulfimide side group polybenzimidazole, is obtained;

[0015] The content of the OPBI and the halogenated disulfimide compound is adjusted according to the requirement of the grafting degree.

[0016] Step 3, preparation of a proton exchange membrane of a disulfimide grafted polybenzimidazole:

[0017] The product of Step 2 is dissolved in a proper amount of a polar solvent, and a film is prepared by a casting method, and a proton exchange membrane of a disulfimide grafted polybenzimidazole is obtained after complete drying.

[0018] Preferably, the sulfonamide compound of Step 1 includes but is not limited to one or more of trifluoromethanesulfonamide, methanesulfonamide, benzenesulfonamide, and isopropyl sulfanilamide; and the strong base of Step 1 includes but is not limited to one or more of potassium hydroxide, sodium hydroxide, and lithium hydroxide.

[0019] Preferably, 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.

[0020] Preferably, 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.

[0021] Preferably, the LiH in Step 2 is replaced by NaH or KH.

[0022] Preferably, the hydrochloric acid of Step 2 is replaced by formic acid or acetic acid; the sodium carbonate of Step 2 is replaced by sodium bicarbonate or ammonia.

[0023] Preferably, the molar ratio of the sulfonamide compound of Step 1, the strong base and the halogenated sulfuryl chloride compound is 1:2:1.

[0024] The second aspect of the present application provides a graft-modified polybenzimidazole proton exchange membrane, which is prepared by the method of the first aspect of the present application.

[0025] The present application has at least the following beneficial effects:

[0026] The graft-modified polybenzimidazole proton exchange membrane and the preparation method provided by the present application have low raw material cost, are easy to obtain, have mature synthesis conditions, high yield and high feasibility, have high product membrane conductivity, improve the output characteristics of fuel cells, can be applied to fuel cells, and have wide application prospects. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 A preparation method flow chart of the modified bis-sulfonimide side group polybenzimidazole proton exchange membrane in the embodiment 1 of the present application;

[0028] Figure 2 A FT-IR spectrum of the CFSI in the embodiment 1 of the present application; 1 H NMR spectrum;

[0029] Figure 3 A FT-IR spectrum of the CFSI in the embodiment 1 of the present application;

[0030] Figure 4 A H NMR spectrum of the OPBI, OPBI-CFSI and CFSI in the embodiment 1 of the present application; 1 H NMR spectrum;

[0031] Figure 5 A FT-IR spectrum of the OPBI, OPBI-CFSI and CFSI in the embodiment 1 of the present application;

[0032] Figure 6 A conductivity-electrochemical stability-temperature curve of the modified bis-sulfonimide side group polybenzimidazole proton exchange membrane after phosphoric acid doping in the embodiment 1 of the present application;

[0033] Figure 7 A mechanical property curve of the modified bis-sulfonimide side group polybenzimidazole proton exchange membrane after phosphoric acid doping in the embodiment 1 of the present application. DETAILED DESCRIPTION

[0034] The technical solutions in the embodiments of the present application will be clearly and completely described below. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the present application. Embodiment 1

[0035] As shown in the following, the present embodiment provides a preparation method of a grafted and modified polybenzimidazole proton exchange membrane, comprising the following steps: Figure 1

[0036] 1) 6.71 g (0.045 mol) of trifluoromethanesulfonamide was dissolved in 100 mL of anhydrous acetonitrile, 5.0 (0.09 mol) of potassium hydroxide was added under argon protection, and 8.59 g (0.045 mol) of 3-chloropropylsulfonyl chloride was dissolved in anhydrous acetonitrile and added to a double-necked flask through a constant-pressure funnel, and the reaction was carried out at 120°C overnight.

[0037] 2) After the reaction was completed, the filtrate was completely dried by using a rotary evaporator, dichloromethane was added, and the white 3-chloropropylsulfonyl (trifluoromethylsulfonyl) imine was obtained by filtering after sufficient washing, and was marked as CFSI and dried in a 60°C oven.

[0038] 3) 4.0 g of OPBI was dissolved in an appropriate amount of N,N-dimethylacetamide (DMAC), 0.50 g of lithium hydride LiH was added to activate OPBI for about 4 h, and after complete activation, 2.89 g, 5.78 g, 8.67 g, and 11.56 g of CFSI mixed with an appropriate amount of KI were added, and the reaction was continued at 120°C for 24 h.

[0039] 4) After the reaction in 3) was completed, the product was poured into distilled water while hot, washed with hydrochloric acid, and the excess hydrochloric acid was washed away using sodium carbonate, and the product was obtained after complete drying, which was a 10%, 20%, 30%, and 40% grafting degree double-sulfonylimide side group polybenzimidazole (which can be adjusted according to the grafting degree requirement), and was marked as OPBI-CFSI.

[0040] 5) The product obtained in 4) was added to DMAC, stirred and dissolved, coated into a film, and the film solvent was evaporated to obtain a double-sulfonylimide side group polybenzimidazole proton exchange membrane. Embodiment 2

[0041] The present embodiment provides a preparation method of a grafted and modified polybenzimidazole proton exchange membrane, comprising the following steps:

[0042] ​1) 4.91 g (0.045 mol) of methanesulfonamide was dissolved in 100 mL of anhydrous acetonitrile, 0.09 mol of potassium hydroxide was added under argon protection and dissolved under stirring, 8.59 g (0.045 mol) of 3-chloropropylsulfonyl chloride was dissolved in anhydrous acetonitrile and added to the double-necked flask through a constant-pressure funnel, and the reaction was carried out at 120°C overnight.

[0043] 2) After the reaction was completed, the filtrate was filtered and completely spin-dried using a rotary evaporator, dichloromethane was added, and after sufficient washing, 3-chloropropylsulfonyl (methylsulfonyl) imine was obtained by filtration and dried in a 60°C oven.

[0044] 3) 6 g of OPBI was dissolved in an appropriate amount of N,N-dimethylacetamide (DMAC), 0.75 g of lithium hydride LiH was added to activate OPBI for about 4 h, and after complete activation, 1.02 g, 2.04 g, 3.06 g, and 4.08 g of 3-chloropropylsulfonyl (methylsulfonyl) imine were added, respectively, and mixed with 6.6 g of KI, and the reaction was continued at 120°C for 24 h.

[0045] 4) After the reaction in (3) was completed, the product was poured into distilled water while hot, washed with hydrochloric acid, and the excess hydrochloric acid was washed away using sodium carbonate, and after complete drying, 10%, 20%, 30%, and 40% grafting degree double-sulfonimide side group polybenzimidazole was obtained.

[0046] 5) The product obtained in (4) was added to DMAC, stirred and dissolved, coated into a film, and after the solvent in the film was evaporated, a double-sulfonimide side group polybenzimidazole proton exchange membrane was obtained. Example 3

[0047] The present embodiment provides a preparation method of a graft-modified polybenzimidazole proton exchange membrane, comprising the following steps:

[0048] 1) 4.91 g (0.045 mol) of methanesulfonamide was dissolved in 100 mL of anhydrous acetonitrile, 0.09 mol of potassium hydroxide was added under argon protection and dissolved under stirring, 12.13 g (0.045 mol) of 4-bromomethylbenzenesulfonyl chloride was dissolved in anhydrous acetonitrile and added to the double-necked flask through a constant-pressure funnel, and the reaction was carried out at 120°C overnight.

[0049] 2) After the reaction was completed, the filtrate was filtered and completely spin-dried using a rotary evaporator, dichloromethane was added, and after sufficient washing, 4-bromomethylbenzenesulfonyl (methylsulfonyl) imine was obtained by filtration and dried in a 60°C oven.

[0050] 3) 6 g of OPBI was dissolved in an appropriate amount of N, N-dimethylacetamide (DMAC), 0.75 g of lithium hydride LiH was added to activate OPBI for about 4 h, after complete activation, 1.65 g, 3.3 g, 4.95 g, 6.6 g of 4-bromomethylbenzenesulfonyl chloride (methylsulfonyl) imide was added respectively, and an appropriate amount of KI was mixed, and the reaction was continued at 120°C for 24 h.

[0051] 4) After the reaction in (3) was completed, the product was poured into distilled water while hot, washed with hydrochloric acid, and then washed with sodium carbonate to remove excess hydrochloric acid. After drying, 10%, 20%, 30%, and 40% grafting degree double-sulfonamide side group polybenzimidazole was obtained.

[0052] 5) The product obtained in (4) was added to DMAC, stirred and dissolved, coated into a film, and the film solvent was evaporated to obtain a double-sulfonamide side group polybenzimidazole proton exchange membrane. Example 4

[0053] This example provides a preparation method of a graft-modified polybenzimidazole proton exchange membrane. The same as Example 1, the difference is that:

[0054] In Step 1, the sulfonamide compound is benzene sulfonamide; the strong base is sodium hydroxide; and the halogenated sulfuryl chloride compound is a mixture of 3-bromopropane sulfuryl chloride and 2-chloroethane sulfuryl chloride (mixture molar ratio is 1:1).

[0055] In Step 2, the polar solvent is N, N-dimethylformamide; NaH is used instead of LiH; formic acid is used instead of hydrochloric acid; and sodium bicarbonate is used instead of sodium carbonate. Example 5

[0056] This example provides a preparation method of a graft-modified polybenzimidazole proton exchange membrane. The same as Example 1, the difference is that:

[0057] In Step 1, the sulfonamide compound is isopropyl sulfonamide; the strong base is lithium hydroxide; and the halogenated sulfuryl chloride compound is a mixture of 2-bromoethyl sulfuryl chloride and 4-bromomethyl benzene sulfuryl chloride (mixture molar ratio is 2:1).

[0058] In Step 2, the polar solvent is a mixture of dimethyl sulfoxide and N-methyl pyrrolidone (mixture volume ratio is 3:1); KH is used instead of LiH; acetic acid is used instead of hydrochloric acid; and ammonia is used instead of sodium carbonate.

[0059] A series of related performance tests were conducted on the product prepared in Example 1 above, and the results are as follows:

[0060] 1. Structure characterization of 3-chloropropyl sulfuryl (trifluoromethyl sulfuryl) imine (CFSI):

[0061] 1.1, using1 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.

[0062] 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 tensile vibrations of asymmetric CF and SNS bonds, respectively. -1 It is the characteristic peak of the bending vibration of the CF bond.

[0063] In conclusion, 1 1H NMR and FT-IR test results indicate that CFSI was successfully prepared.

[0064] 2. Structural characterization of grafted membranes:

[0065] 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.

[0066] 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. -1 The 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.

[0067] 3. Proton conductivity of the grafted membrane:

[0068] like Figure 6 As shown in the results, 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 via hydrogen bonding, enhancing the hydrogen bond network within the phosphate-doped grafted membrane and facilitating proton migration through 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.

[0069] 4. Mechanical properties of the grafted membrane:

[0070] like Figure 7The mechanical properties of the OPBI film doped with phosphoric acid and the four OPBI-CFSI grafted films were tested.

[0071] The PA molecules have a "plasticizing effect" on the polymer, which will fully occupy the gap between the OPBI molecular chains and further cause the hydrogen bonds between the polymer molecules to be greatly destroyed, thus the tensile strength of the acid-doped film decreases. A large number of PA molecules occupy the free space of the polymer, significantly enhancing the mobility and flexibility of the polymer chain, thus the elongation at break of the acid-doped film is greatly improved.

[0072] In summary, the technical solution provided by the present application has low raw material cost, is easy to obtain, has mature synthesis conditions, high yield, high feasibility, high product membrane conductivity, improves the output characteristics of the fuel cell, and is expected to be applied to the fuel cell.

[0073] In addition, the preparation method of the grafted modified film of the polybenzimidazole polymer is simple, the polyether polybenzimidazole (OPBI) is commercially mature and can be stably obtained, the raw material cost of 3-chloropropyl sulfonimide (trifluoromethylsulfonyl) (CFSI) required for synthesis and preparation is low, the reaction conditions are mild, and the yield is relatively high.

[0074] The above shows and describes the basic principles and main features of the present application and the advantages of the present application. For those skilled in the art, it is obvious that the present application is not limited to the details of the above exemplary embodiments, and the present application can be implemented in other specific forms without departing from the spirit or essential characteristics of the present application. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting, and the scope of the present application is defined by the appended claims rather than the above description, and therefore all changes falling within the meaning and scope of the essential elements of the claims are intended to be included in the present application.

[0075] Although embodiments of the present application 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 present application, and the scope of the present application is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a graft-modified polybenzimidazole proton exchange membrane, characterized in that, Includes the following steps: Step 1, Synthesis of halobissulfonylimide compounds: The sulfonamide compound 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. The sulfonamide compound is trifluoromethanesulfonamide, and the halosulfonyl chloride compound is 3-chloropropanesulfonyl chloride; 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.

2. The method for preparing a grafted modified polybenzimidazole proton exchange membrane according to claim 1, characterized in that: The sulfonamide compound in Step 1 is one or more of trifluoromethanesulfonamide, methanesulfonamide, benzenesulfonamide, and isopropylsulfonamide; the strong base in Step 1 is one or more of potassium hydroxide, sodium hydroxide, and lithium hydroxide.

3. The method for preparing a grafted modified polybenzimidazole proton exchange membrane according to claim 1, characterized in that: The halogenated sulfonyl chloride compound in Step 1 is one or more of 3-chloropropanesulfonyl chloride, 3-bromopropanesulfonyl chloride, 2-chloroethanesulfonyl chloride, 2-bromoethylsulfonyl chloride, and 4-bromomethylbenzenesulfonyl chloride.

4. The method for preparing a grafted modified polybenzimidazole proton exchange membrane according to claim 1, characterized in that: The polar solvent in Step 2 is one or more of N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, and N-methylpyrrolidone.

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

6. The method for preparing a grafted modified polybenzimidazole proton exchange membrane according to claim 1, characterized in that: The hydrochloric acid in Step 2 can be replaced with formic acid or acetic acid; the sodium carbonate in Step 2 can be replaced with sodium bicarbonate or ammonia.

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

1.

8. A grafted and modified polybenzimidazole proton exchange membrane, characterized in that: The grafted modified polybenzimidazole proton exchange membrane is prepared by the method described in any one of claims 1 to 7.

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