A quinoline structure modified polybenzimidazole composite bio-based lignin sodium sulfonate doped phytic acid-phosphoric acid high-temperature proton exchange membrane and a preparation method and application thereof

Abstract

This invention belongs to the fields of high-temperature proton exchange membrane fuel cells and bio-based technologies. It discloses a quinoline-modified polybenzimidazole composite bio-based sodium lignosulfonate-doped phytic acid-phosphoric acid high-temperature proton exchange membrane, its preparation method, and its applications. The oxygen-rich functional groups of sodium lignosulfonate, the polyphosphate structure of phytic acid, and the nitrogen-containing sites in PBI / QL-PBI synergistically form a dense and stable three-dimensional hydrogen bond network, effectively anchoring phosphoric acid and constructing a continuous and efficient proton conduction channel. This exhibits a significant synergistic effect, promoting efficient proton migration under anhydrous high-temperature conditions, while simultaneously inhibiting phosphoric acid leakage and improving the membrane's oxidation resistance and mechanical properties. The method of this invention is simple, structurally controllable, and suitable for large-scale preparation. The resulting membrane achieves a proton conductivity of up to 0.18 S·cm under anhydrous conditions at 200-220℃. ‑1 It exhibits excellent stability under Fenton oxidation conditions and can be widely used in the field of high-temperature proton exchange membrane fuel cells.

Description

Technical Field

[0001] This invention relates to the fields of high-temperature proton exchange membrane fuel cells and bio-based technologies, specifically to a quinoline-modified polybenzimidazole composite bio-based sodium lignosulfonate-doped phytic acid-phosphate high-temperature proton exchange membrane, its preparation method, and its applications. Background Technology

[0002] High-temperature proton exchange membrane fuel cells (HT PEMFCs) have shown broad application prospects in distributed energy and vehicle power fields due to their advantages such as high operating temperature of 120-200℃, weak dependence on fuel purity and humidity, and strong catalyst resistance to CO poisoning. Polybenzimidazole (PBI) and its derivatives have become one of the most representative matrix materials for high-temperature proton exchange membranes due to their excellent thermal stability, chemical stability and mechanical properties. However, traditional PBI membranes often suffer from severe acid loss, weakened mechanical properties and insufficient long-term durability after phosphoric acid doping, which greatly limits their practical application.

[0003] To address the aforementioned issues, the introduction of functional fillers or structural design of the polymer backbone to regulate acid-base interactions within the membrane and establish stable proton conduction channels has become a key focus of high-temperature proton exchange membrane research. Sodium lignosulfonate, being a widely available, affordable biomass material rich in sulfonic acid and hydroxyl groups, can form a multi-hydrogen bond network structure with PBI and phosphate molecules, giving it unique advantages in improving phosphate retention and proton conduction performance. By introducing basic heterocyclic structures such as quinoline into the PBI backbone, the number density of basic sites within the membrane can be increased, intensifying the acid-base interaction effect, which is beneficial for increasing the phosphate doping amount and improving the structural stability of the membrane.

[0004] Sol-gel in-situ deposition technology can construct a continuous three-dimensional network structure within a polymer matrix, facilitating the construction of a more compact and homogeneous acid-base composite system. Leveraging the polyphosphate structure and strong complexing ability of phytic acid molecules, a mixed acid system of phytic acid and phosphoric acid can be introduced, potentially reducing acid loss and optimizing proton conduction pathways. This could lead to simultaneous improvements in conductivity and durability at high temperatures. This research, focusing on the key concept of "structural regulation—multi-component synergy—proton conduction mechanism optimization," systematically analyzes the structural evolution and performance improvement mechanisms of OPBI-based high-temperature proton exchange membranes through filler composites, main chain modification, and sol-gel construction strategies. This provides theoretical basis and experimental support for the development of high-performance, durable high-temperature proton exchange membrane materials, possessing significant scientific value and practical engineering application potential. Summary of the Invention

[0005] Based on the above, the present invention provides a method for preparing a high-temperature proton exchange membrane with excellent performance, tunable structure, simple preparation process, and suitability for large-scale production. This method employs an in-situ polymerization-sol-gel method, using polybenzimidazole containing a quinoline structure and pure polybenzimidazole as the main framework, introducing sodium lignosulfonate as a bio-based functional filler, and synergistically doping a phytic acid-phosphoric acid mixed acid system to construct a composite proton conduction system with a high-density hydrogen bond network.

[0006] The preparation method of the quinoline-modified polybenzimidazole composite bio-based sodium lignosulfonate-doped phytic acid-phosphoric acid high-temperature proton exchange membrane of the present invention is as follows: (1) Mix 100g of phytic acid (HA) solution with 0.1g-3.32g of sodium lignosulfonate (SL) at room temperature for 10-30 minutes. When SL is completely dispersed in the phytic acid solution, add 110g of phosphorus pentoxide and mix evenly. Stir at 90℃-120℃ for 3-5 hours. When the phosphorus pentoxide is completely dissolved and a brownish-black homogeneous solution is formed, polyphosphoric acid containing sodium lignosulfonate and phytic acid is obtained. Pour it into a pre-dried glass container and seal it for later use. (2) Under nitrogen atmosphere protection, accurately weigh 1 mmol-5 mmol of 3,3'-diaminobenzidine (DAB), 1 mmol-5 mmol of 4,4'-dicarboxylic acid (OBA), and 0.1 mmol-2 mmol of quinoline-2,3-dicarboxylic acid into a 100 mL dry three-necked flask. Add 10-15 mL of the brown-black homogeneous solution prepared in step (1) as a solvent to the flask. Stir mechanically at 50-90℃ for 0.5-1 hours to mix and dissolve the drugs evenly. Then, raise the temperature of the reaction system to 120-160℃ and continue the reaction for 5-10 hours. Then, raise the temperature to 150-200℃ and continue the reaction for 5-10 hours to obtain a dark brown slurry solution. (3) Then, the membrane was laid by direct membrane laying method. The dark brown slurry solution prepared in step (2) was evenly coated on a clean glass plate at 80-100℃ and placed in a constant temperature and humidity chamber at 25℃-30℃ and 40%-55% to absorb water and form acid. After two weeks, a large amount of phosphoric acid formed by polyphosphoric acid absorbing water was observed on the surface of the membrane. The membrane was peeled off from the glass plate, the surface liquid was wiped dry, and it was further dried under vacuum at 80-100℃ for 20-24 hours to remove residual moisture. The sample obtained is the bio-based composite high temperature proton exchange membrane.

[0007] Based on the above technical solutions, the thickness of the high-temperature proton exchange membrane is 5~300μm.

[0008] Based on the above technical solutions, preferably, the thickness of the exchange membrane is 10~100μm.

[0009] By adopting the above technical solution, within this thickness range, the high-temperature proton exchange membrane can achieve both high proton conductivity and phosphate retention capacity.

[0010] This invention also protects the high-temperature proton exchange membrane prepared by the above method and its application in hydrogen-oxygen fuel cells.

[0011] This invention aims to provide favorable conditions for improving the proton conductivity and structural stability of polybenzimidazole (OPBI)-based high-temperature proton exchange membranes. A nitrogen-rich quinoline structure is introduced into the OPBI backbone via in-situ polymerization-sol-gel method, while simultaneously incorporating sodium lignosulfonate and synergistically doping a phytic acid-phosphate system. The heterocyclic nitrogen atoms in the quinoline structure can form strong interactions with phosphoric acid and phytic acid, thereby significantly enhancing the membrane's acid adsorption and retention capabilities. The abundant sulfonic acid groups and phenolic hydroxyl groups in sodium lignosulfonate further promote the construction of a hydrogen bond network. The synergistic effect of these multiple components helps to form continuous and stable proton conduction channels within the membrane, providing an efficient pathway for proton migration.

[0012] Compared with traditional PBI membranes, this system constructs a dense three-dimensional hydrogen bond network through the synergistic design of main chain structure regulation and multi-acid doping. This not only effectively promotes the synergistic transport of protons under the Grotthuss and Vehicle mechanisms, achieving rapid proton transfer, but also significantly improves the membrane's antioxidant and proton conduction properties, and inhibits durability and phosphate loss under high-temperature conditions, thereby enhancing the overall performance of high-temperature proton exchange membranes.

[0013] Compared with the prior art, the present invention has the following advantages: (1) Structural innovation: Quinoline structure is introduced into the main chain of OPBI through in-situ polymerization-sol-gel method, and sodium lignosulfonate and phytic acid are combined to achieve uniform distribution and chemical bonding of multifunctional groups at the molecular level, overcoming the problem of poor interfacial compatibility of traditional physical blending systems, and significantly improving the structural stability and integrity of the membrane.

[0014] (2) Performance synergy: Quinoline structure provides abundant nitrogen sites, sodium lignosulfonate and phytic acid provide a variety of oxygen- and phosphorus-containing functional groups. The three work together to construct a dense and continuous hydrogen bond network and proton conduction channel, realizing the synergistic effect of Grotthuss and Vehicle mechanisms, and significantly improving proton conduction performance and acid retention capacity under high temperature and low humidity conditions.

[0015] (3) Improved stability: Multi-site interaction (nitrogen site, sulfonic acid group, phosphate group) effectively enhances the binding ability of phosphoric acid, reduces acid loss at high temperature, and improves the membrane's antioxidant capacity, thermal stability and dimensional stability, ensuring the membrane's stable performance during long-term operation.

[0016] (4) Process feasibility: The method is simple and does not require complex equipment. It constructs a uniform structure network in situ. The resulting membrane material has a high thermal decomposition temperature, excellent mechanical properties and stable proton conduction capacity, which meets the practical application requirements of high-temperature proton exchange membrane fuel cells. Attached Figure Description

[0017] Figure 1 Flowcharts of the preparation of samples from comparative examples and Examples 1-5; Figure 2 This is an infrared image of the high-temperature proton exchange membrane described in an embodiment of the present invention; Figure 3 These are infrared images of the high-temperature proton exchange membranes described in Examples 3-5; Figure 4 These are TGA curves of the high-temperature proton exchange membranes described in the comparative examples and Examples 1-2 of this invention; Figure 5 TGA curves of the high-temperature proton exchange membranes described in Examples 3-5; Figure 6 This is a graph showing the proton conductivity of the high-temperature proton exchange membrane described in the comparative examples and Examples 1-2 of this invention; Figure 7 This is a proton conductivity diagram of the high-temperature proton exchange membrane described in embodiments 3-5 of this invention; Figure 8 These are durability diagrams of the high-temperature proton exchange membranes described in comparative examples and Examples 1-2 of the present invention; Figure 9 These are durability diagrams of the high-temperature proton exchange membranes described in Examples 3-5 of this invention. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0019] The quinoline 2,3-dicarboxylic acid, 4,4-dicarboxylic acid diphenyl ether, 3,3-diaminobenzidine, sodium lignosulfonate, phytic acid, and phosphoric acid used in this embodiment were all purchased directly from the market.

[0020] The concentration of the phytic acid (HA) solution used was 70%.

[0021] Comparative Example 1 Includes the following steps: (1) Preparation of polyphosphoric acid (PPA) without sodium lignosulfonate: 100g of phytic acid solution and 110g of phosphorus pentoxide were mixed evenly and stirred at 120℃ for 5 hours. When the phosphorus pentoxide was completely dissolved and a brownish-black homogeneous solution was formed, polyphosphoric acid containing sodium lignosulfonate and phytic acid was obtained. The homogeneous reaction solution was poured into a pre-dried glass container and sealed for storage.

[0022] (2) Accurately weigh 5 mmol of 3,3'-diaminobenzidine (DAB) and 5 mmol of 4,4'-dicarboxylic acid diphenyl ether (OBA) into a 100 ml three-necked flask, and add 10 ml of polyphosphoric acid (HA) and (SL) prepared by (1) into the flask. Stir mechanically at 80 °C for 1 hour, then raise the temperature to 160 °C and react for 8 hours, and continue to raise the temperature to 180 °C and react for 7 hours to obtain a hot slurry liquid.

[0023] (3) Then, the membrane was laid by direct membrane laying method. The hot slurry liquid was evenly coated on a clean glass plate at 100℃ and placed in a constant temperature and humidity chamber at 25℃-30℃ and 40%-55% to absorb water and form acid. After two weeks, a large amount of phosphoric acid formed by polyphosphoric acid absorbing water was observed on the surface of the membrane. The membrane was peeled off from the glass plate, the surface liquid was wiped dry, and it was further dried under vacuum at 100℃ for 24 hours to remove residual moisture. The membranes with different sodium lignosulfonate (SL) contents were named Gel-SL-HA-OPBI (A), where A represents sodium lignosulfonate content / highest sodium lignosulfonate content * 100%, that is, the prepared Gel-SL-HA-OPBI (A) high temperature proton exchange membrane was obtained.

[0024] Example 1 Includes the following steps: (1) Preparation of polyphosphoric acid (PPA) containing phytic acid and sodium lignosulfonate: 100g of phytic acid (HA) solution and 1.66g of sodium lignosulfonate (SL) were stirred at room temperature for 30 minutes until the sodium lignosulfonate (SL) was completely dispersed in the phytic acid solution. Then, 110g of phosphorus pentoxide was added and mixed evenly. The mixture was stirred at 120℃ for 5 hours. When the phosphorus pentoxide was completely dissolved and a brownish-black homogeneous solution was formed, polyphosphoric acid containing sodium lignosulfonate and phytic acid was obtained. The homogeneous reaction solution was poured into a pre-dried glass container and sealed for storage.

[0025] (2) Accurately weigh 5 mmol of 3,3'-diaminobenzidine (DAB) and 5 mmol of 4,4'-dicarboxylic acid diphenyl ether (OBA) into a 100 ml three-necked flask, and add 10 ml of polyphosphoric acid (HA) and (SL) prepared by (1) into the flask. Stir mechanically at 80 °C for 1 hour, then raise the temperature to 160 °C and react for 8 hours, and continue to raise the temperature to 180 °C and react for 7 hours to obtain a hot slurry liquid.

[0026] (3) Step 3 is the same as in Example 1, except that the amount of sodium lignosulfonate is changed.

[0027] Example 2 Includes the following steps: (1) Preparation of polyphosphoric acid (PPA) containing phytic acid and sodium lignosulfonate: 100g of phytic acid (HA) solution and 2.49g of sodium lignosulfonate (SL) were stirred at room temperature for 30 minutes until the sodium lignosulfonate (SL) was completely dispersed in the phytic acid solution. Then, 110g of phosphorus pentoxide was added and mixed evenly. The mixture was stirred at 120℃ for 5 hours. When the phosphorus pentoxide was completely dissolved and a brownish-black homogeneous solution was formed, polyphosphoric acid containing sodium lignosulfonate and phytic acid was obtained. The homogeneous reaction solution was poured into a pre-dried glass container and sealed for storage.

[0028] (2) Accurately weigh 5 mmol of 3,3'-diaminobenzidine (DAB) and 5 mmol of 4,4'-dicarboxylic acid diphenyl ether (OBA) into a 100 ml three-necked flask, and add 10 ml of polyphosphoric acid (HA) and (SL) prepared by (1) into the flask. Stir mechanically at 80 °C for 1 hour, then raise the temperature to 160 °C and react for 8 hours, and continue to raise the temperature to 180 °C and react for 7 hours to obtain a hot slurry liquid.

[0029] (3) The specific steps are the same as those in Example 1, except that the amount of sodium lignosulfonate is changed, and the sample of Example 2 is obtained by step 3.

[0030] Example 3 The specific steps are as follows: (1) Preparation of polyphosphoric acid (PPA) containing phytic acid and sodium lignosulfonate: 100g of phytic acid (HA) solution and 2.49g of sodium lignosulfonate (i.e. the optimal ratio in Example 1) were stirred at room temperature for 30 minutes until sodium lignosulfonate (SL) was completely dispersed in the phytic acid solution. Then, 110g of phosphorus pentoxide was added and mixed evenly. The mixture was stirred at 120°C for 5 hours. When the phosphorus pentoxide was completely dissolved and a brownish-black homogeneous solution was formed, polyphosphoric acid containing sodium lignosulfonate and phytic acid was obtained. The homogeneous reaction solution was poured into a pre-dried glass container and sealed for storage.

[0031] (2) Using the in-situ polymerization sol-gel method, by changing the amount of quinoline-2,3-dicarboxylic acid (0.1 mmol-5 mmol) and the sum of 4,4-dicarboxylic acid diphenyl ether (OBA) (0.1 mmol-5 mmol), quinoline-structured polymers with different percentage contents were prepared by polymerizing with DAB at a 1:1 ratio. Under nitrogen atmosphere protection, 5 mmol of 3,3'-diaminobenzidine (DAB), 4.75 mmol of 4,4'-dicarboxylic acid diphenyl ether (OBA), and 0.25 mmol of quinoline-2,3-dicarboxylic acid were accurately weighed into a 100 mL dry three-necked flask. 15 mL of polyphosphoric acid (PPA) containing sodium lignosulfonate (SL) and phytic acid (HA) was added to the flask as a solvent, and the mixture was mechanically stirred at 90 °C for 1 hour to mix and dissolve the reagents evenly. Subsequently, the temperature of the reaction system was raised to 160 °C. The temperature was increased to 180℃ and the reaction was continued for 8 hours; then the temperature was further increased to 180℃ and the reaction was continued for 7 hours. A dark brown slurry solution was obtained.

[0032] (3) Then, the hot solution was poured onto a clean glass plate at 100°C using the direct film-laying method. It was placed in a constant temperature and humidity chamber at 25°C and 40% humidity to absorb water and form acid. After two weeks, the excess phosphoric acid formed by the polyphosphoric acid absorbing water on the surface was wiped clean and then placed in a vacuum drying oven at 100°C for 24 hours to remove residual moisture, thus obtaining the Gel-SL-HA-QLPBI (5%) composite membrane of Example 3.

[0033] Example 4 The specific steps include the following: (1) Preparation of polyphosphoric acid (PPA) containing phytic acid and sodium lignosulfonate: 100g of phytic acid (HA) solution and 2.49g of sodium lignosulfonate (i.e. the optimal ratio in Example 1) were stirred at room temperature for 30 minutes until sodium lignosulfonate (SL) was completely dispersed in the phytic acid solution. Then, 110g of phosphorus pentoxide was added and mixed evenly at a molar ratio of 1:6. The mixture was stirred at 120°C for 5 hours. When the phosphorus pentoxide was completely dissolved and a brownish-black homogeneous solution was formed, polyphosphoric acid containing sodium lignosulfonate and phytic acid was obtained. The homogeneous reaction solution was poured into a pre-dried glass container and sealed for storage.

[0034] (2) Using the in-situ polymerization sol-gel method, polymers with different percentage contents of quinoline structure were prepared by polymerizing the sum of quinoline-2,3-dicarboxylic acid (QL) (0.1 mmol-5 mmol) and 4,4-dicarboxylic acid (OBA) (1 mmol-5 mmol) with DAB in a 1:1 ratio. Under nitrogen atmosphere protection, 5 mmol of 3,3'-diaminobenzidine (DAB), 4.25 mmol of 4,4'-dicarboxylic acid (OBA), and 0.75 mmol of quinoline-2,3-dicarboxylic acid were accurately weighed into a 100 mL dry three-necked flask. 15 mL of polyphosphoric acid (PPA) containing sodium lignosulfonate (SL) and phytic acid (HA) was added to the flask as a solvent, and the mixture was heated to 90 °C. The reagents were mechanically stirred at ℃ for 1 hour to ensure uniform mixing and dissolution. Subsequently, the reaction temperature was raised to 160℃ and the reaction was continued for 8 hours; then further heated to 180℃ and the reaction was continued for 7 hours. A dark brown slurry solution was obtained.

[0035] (3) Subsequently, the hot solution was poured onto a clean glass plate at 100°C using the direct film-laying method. It was placed in a constant temperature and humidity chamber at 25°C and 40% humidity to absorb water and form acid. After two weeks, the excess phosphoric acid formed by the polyphosphoric acid absorbing water on the surface was wiped clean, and then it was placed in a vacuum drying oven at 100°C for 24 hours to remove residual moisture, thus obtaining the Gel-SL-HA-QLPBI (15%) composite membrane of Example 4.

[0036] Example 5 The specific steps include the following: (1) Preparation of polyphosphoric acid (PPA) containing phytic acid and sodium lignosulfonate: 100g of phytic acid (HA) aqueous solution and 2.49g of sodium lignosulfonate (i.e. the optimal ratio in Example 1) were stirred at room temperature for 30 minutes until sodium lignosulfonate (SL) was completely dispersed in the phytic acid solution. Then, 110g of phosphorus pentoxide was added and mixed evenly. The mixture was stirred at 120°C for 5 hours. When the phosphorus pentoxide was completely dissolved and a brownish-black homogeneous solution was formed, polyphosphoric acid containing sodium lignosulfonate and phytic acid was obtained. The homogeneous reaction solution was poured into a pre-dried glass container and sealed for storage.

[0037] (2) Using the in-situ polymerization sol-gel method, quinoline-structured polymers with different percentage contents were prepared by varying the sum of the amounts of quinoline-2,3-dicarboxylic acid (QL) (0.1 mmol-5 mmol) and 4,4-dicarboxylic acid diphenyl ether (OBA) (0.1 mmol-5 mmol) with DAB in a 1:1 ratio. Under a nitrogen atmosphere, 5 mmol of 3,3'-diaminobenzidine (DAB), 4 mmol of 4,4'-dicarboxylic acid diphenyl ether (OBA), and 1 mmol of quinoline-2,3-dicarboxylic acid were accurately weighed into a 100 mL dry three-necked flask. 15 mL of polyphosphoric acid (PPA) containing sodium lignosulfonate (SL) and phytic acid (HA) was added to the flask as a solvent, and the mixture was mechanically stirred at 90 °C for 1 hour to ensure uniform dissolution. Subsequently, the reaction system temperature was raised to 160 °C and the reaction was continued for 8 hours; then the temperature was further raised to 180 °C and the reaction was continued for 7 hours. A dark brown slurry solution was obtained. (3) Subsequently, the hot solution was poured onto a clean glass plate at 100°C using the direct film-laying method. It was placed in a constant temperature and humidity chamber at 25°C and 40% humidity to absorb water and form acid. After two weeks, the excess phosphoric acid formed by the polyphosphoric acid absorbing water on the surface was wiped clean, and then it was placed in a vacuum drying oven at 100°C for 24 hours to remove residual moisture, thus obtaining the Gel-SL-HA-QLPBI (20%) composite membrane of Example 5.

[0038] In this invention, the phosphoric acid concentration is 65-85 wt.%. Preferably, the phosphoric acid concentration is 65, 70, 75, 80, or 85 wt.%, etc., to ensure that the polymer does not precipitate from the solution. The mass fraction of phosphoric acid relative to the polybenzimidazole polymer is 0-3000 wt.%, preferably 1000-2000 wt.%, to ensure that the resulting membrane simultaneously maintains mechanical stability and proton conductivity.

[0039] In this invention, drying is first carried out at 100°C for 24 hours, allowing the high-boiling-point solvent to evaporate slowly and ensuring that the phosphoric acid in the membrane is not lost during the drying process. Subsequently, drying is carried out at 120°C, 140°C, and 160°C for 2 hours respectively, ensuring that the phosphoric acid is not lost during the drying process while the solvent is completely removed.

[0040] The solution-in-situ composite phosphate-doped polybenzimidazole high-temperature proton exchange membrane prepared in this invention has a thickness of 5-300 μm. Preferably, the thickness is 10-100 μm. Within this thickness range, the high-temperature proton exchange membrane can balance surface conductivity and gas barrier properties. The thickness of the composite proton exchange membrane can be, for example, 30 μm, 40 μm, 80 μm, or 120 μm, etc., and those skilled in the art can set it within this range according to actual needs.

[0041] The phosphate-doped polybenzimidazole-based high-temperature proton exchange membranes prepared in the above embodiments and comparative examples were subjected to the following structural and performance tests.

[0042] The appendix describes the chemical structure of the materials, specifically the infrared spectra of the bio-based sodium lignin sulfonate composite high-temperature proton exchange membranes prepared in comparative examples and Examples 2-5. Figure 2 As shown. From the FT-IR, we can obtain 1675 cm. -1 It is the C=N characteristic peak of the imidazole ring, 1261 cm⁻¹. -1 The infrared characteristic peaks are those of the imidazole ring and the characteristic peak of the C=C bond at 1400 cm⁻¹. Both peaks appear in all membranes, indicating that OPBI was successfully synthesized. (1110 cm⁻¹) -1 The peak at 3588 cm⁻¹ is a characteristic peak of ether bonds. As can be seen from the graph, the characteristic peak is more pronounced after adding SL. -1 and 887 cm -1 These are the characteristic infrared peaks of the phenolic hydroxyl (-OH) and sulfonic acid groups in sodium lignosulfonate. This indicates the successful introduction of SL into the Gel-SL-HA-OPBI composite membrane. Infrared spectroscopy confirms the successful preparation of the Gel-SL-HA-OPBI composite membrane. Figure 3 The composite films shown in Examples 3-5 are in infrared at 3324 cm⁻¹. -1 A distinct and broad absorption peak is observed near the membrane, primarily originating from the characteristic peaks of the phenolic hydroxyl (-OH) groups and the -NH bonds in the imidazole ring of sodium lignosulfonate. With increasing quinoline content, this absorption peak gradually broadens and exhibits a slight red shift, indicating that the abundant nitrogen-containing heterocyclic sites in the quinoline structure further enhance the hydrogen bond interaction between the polymer and phosphate within the membrane, facilitating the construction of a stable hydrogen bond network. The peak is observed at 1675 cm⁻¹ in FT-IR. -1 It is the C=N characteristic peak of the imidazole ring, 1261 cm⁻¹. -1 The infrared characteristic peaks of the imidazole ring and 1386 cm⁻¹ are... -1 The characteristic peak of the C=C bond appears at 1280 cm⁻¹, and both of these peaks appear in all membranes. -1 The peak at 2977 cm⁻¹ is a characteristic peak of ether bonds, indicating that the QLPBI polymer was successfully synthesized. The figure shows that the characteristic peak is more pronounced with the addition of SL, reaching 2977 cm⁻¹. -1 and 1043 cm -1 It is the methyl (-CH3) and sulfonic acid (-SO3) groups in sodium lignosulfonate. - The infrared characteristic peaks indicate the successful introduction of SL into the Gel-SL-HA-QLPBI composite membrane. Infrared spectroscopy confirms the successful preparation of the Gel-SL-HA-QLPBI composite membrane.

[0043] The thermogravimetric curves of the bio-based sodium lignin sulfonate composite polybenzimidazole high-temperature proton exchange membranes prepared in specific comparative examples and Examples 2-5 are shown below. Figure 4 and Figure 5 As shown in the figure, the heating was carried out under a nitrogen flow, with a heating range of 30°C to 800°C and a heating rate of 20°C / min. The figure shows that the composite film with sodium lignosulfonate or quinoline-doped phytic acid exhibits superior thermal stability compared to the PBI film without sodium lignosulfonate.

[0044] The proton conductivity of the bio-based sodium lignin sulfonate polybenzimidazole high-temperature proton exchange membranes prepared in the specific comparative examples and Examples 2-5 is as follows: Figure 4 As shown. The tests were performed on an SP-300 electrochemical workstation. From Figure 6 It can be seen that the proton conductivity of all membranes increases with increasing temperature. Furthermore, the proton conductivity of the comparative example at 180°C is 0.04 S cm⁻¹. -1 As the content of sodium lignosulfonate increases, the proton conductivity of the membrane increases accordingly. The Gel-SL(75%)-HA-OPBI membrane, with the highest SL content, achieves a proton conductivity of 0.18 S cm⁻¹. -1 That's almost four times that of the comparative membrane. Furthermore, such as... Figure 7 As shown, the proton conductivity of the composite membranes in Comparative Examples 3-5 gradually increased with increasing quinoline content. At 240°C, the proton conductivity of the composite membrane in Example 4 reached a maximum of 0.13 S / cm. -1 Compared to the low-content composite membrane of Example 3, which has a proton conductivity of 0.03 S / cm -1 Four times higher.

[0045] The Gel-SL-HA-QLPBI (15%) composite membrane in Example 4 achieved a proton conductivity of 0.12 S / cm at 180°C. -1 At 200℃, the proton conductivity is as high as 0.13 S / cm. -1 As the quinoline content increases, the composite membrane exhibits stronger hydrogen bond interactions with phosphoric acid and phytic acid due to the introduction of nitrogen-containing heterocyclic groups from the quinoline, and the presence of a large number of sulfonic acid groups (-SO3) in the composite sodium lignin sulfonate. - ) and phenolic hydroxyl groups (-OH) further participate in the construction of a multiple hydrogen bond network structure.

[0046] The durability of the bio-based sodium lignin sulfonate polybenzimidazole high-temperature proton exchange membranes prepared in specific comparative examples and Examples 2-5 Figure 8As shown. The proton conductivity of the Gel-SL-HA-OPBI composite membrane was measured after being kept at 200℃ for 10 hours, and the acid loss rate was evaluated under high temperature and high humidity conditions. All Gel-SL-HA-OPBI composite membranes exhibited excellent durability. Compared with the Gel-SL (0%)-HA-OPBI (comparative) composite membrane without SL, the proton conductivity of the Gel-SL (75%)-HA-OPBI composite membrane remained at 0.13 S cm⁻¹ after long-term high-temperature testing. -1 The above demonstrates excellent phosphate retention. For example... Figure 9 As shown, the durability of the Gel-SL-HA-QLPBI (15%) composite membrane in Example 4 maintained a proton conductivity of 0.10 S cm⁻¹ after long-term high-temperature testing. -1 In the above-mentioned case, at a content of 1 mmol of quinoline-2,3-dicarboxylic acid, a relatively stable interaction network was formed between the acid molecules in the membrane and the polymer matrix, effectively inhibiting the degradation of proton conduction channels. Excellent phosphoric acid retention was observed. All membranes polymerized in situ exhibited excellent durability.

[0047] The phosphoric acid doping degree of the bio-based sodium lignin sulfonate composite polybenzimidazole high-temperature proton exchange membranes prepared in the comparative examples and Examples 2-5 is shown in Table 1. As can be seen from Table 1, the PA absorption rate of the membrane increases with the increase of sodium lignin sulfonate content. Controlling the amount of sodium lignin sulfonate, the PA doping degree of the PBI membrane reached 10 mol with the increase of quinoline-2,3-dicarboxylic acid content, which is nearly twice the PA absorption rate of the comparative example membranes. This is because the introduction of sodium lignin sulfonate rich in phenolic hydroxyl and sulfonic acid groups, along with the quinoline structure, helps to combine with phosphoric acid and phytic acid, thereby increasing the acid doping degree of the high-temperature proton exchange membrane.

[0048] The mechanical properties of the bio-based sodium lignin sulfonate polybenzimidazole high-temperature proton exchange membranes prepared in the specific comparative examples and Examples 2-5 are shown in Table 1. The content of sodium lignin sulfonate (SL) is likely the main factor affecting the Gel-SL-HA-OPBI composite membrane, gradually increasing with the increase of SL content. The tensile strength of the Gel-SL (0%)-HA-OPBI composite membrane without SL is only 0.22 MPa, exhibiting poor mechanical properties. When the SL content increases to 75%, the tensile strength of the Gel-SL (75%)-HA-OPBI composite membrane reaches 0.99 MPa, mainly because the abundant sulfonic acid groups, phenolic hydroxyl groups, and ether bonds in the SL molecule form multiple hydrogen bonds and ion pairs with the OPBI backbone and phytic acid / phosphate, enhancing the intermolecular chain interactions. In Examples 3-5, the quinoline content is likely the main factor affecting tensile properties; the tensile strength of the Gel-SL-HA-QLPBI composite membrane gradually increases with the increase of quinoline content. When the quinoline content reaches 20%, the tensile strength of the composite membrane reaches 1.29 MPa.

[0049] Table 1 Mechanical properties of high-temperature proton exchange membranes containing bio-based sodium lignosulfonate and polybenzimidazole The oxidation resistance of the bio-based sodium lignin sulfonate polybenzimidazole high-temperature proton exchange membranes prepared in Comparative Examples and Examples 2-5 is shown in Table 1. The Gel-SL-HA-OPBI (Comparative Example) composite membrane was immersed in Fenton's reagent (30% H2O2, 4 ppm Fe). 2+ In this study, oxidation stability was assessed by observing mass changes at regular intervals under room temperature conditions. After immersion in Fenton's reagent at 80°C for 120 h with and without SL, the residual mass of all composite membranes was above 60%, which was higher than that of the Gel-SL (0%)-HA-OPBI (comparative example) composite membrane without SL. Therefore, the composite membrane with added SL exhibited superior oxidation resistance. Furthermore, in Examples 3-5, the oxidation mass retention rate of the composite membranes showed a gradual upward trend with increasing quinoline content, indicating a significant enhancement in the material's antioxidant capacity. After 120 h of oxidation treatment, the mass retention rate of the Gel-SL-HA-QLPBI (20%) composite membrane reached 73.64%, significantly better than the samples with low quinoline content. This result demonstrates that the introduction of the quinoline structure effectively improves the membrane material's resistance to free radical attack.

[0050] In summary, sodium lignosulfonate molecules, rich in sulfonic acid and phenolic hydroxyl groups, can act as proton donors and hydrogen bond acceptors, forming multi-point interactions with imidazole nitrogen atoms and acid molecules on the OPBI molecular chain, thereby increasing the binding strength of acid molecules within the membrane. Phytic acid molecules, due to their high-density phosphate group structure, can act as multi-proton conduction nodes within the membrane, while their macromolecular properties effectively reduce acid migration. When phytic acid and phosphate coexist, a multi-level proton conduction and fixation system involving "phosphate-phytic acid-sodium lignosulfonate-OPBI / QL-PBI" can be constructed within the membrane. The introduction of the in-situ polymerization-reaction solution direct deposition method further promotes the synergistic effect among the above-mentioned components, enabling sodium lignosulfonate and the phytic acid / phosphate system to form a relatively stable cross-linked structure in the OPBI / QL-PBI matrix, thereby constructing a multi-hydrogen bond network structure. This structure not only enhances the continuity of the hydrogen bond network within the membrane but also helps to inhibit acid loss and improve the structural integrity of the membrane.

[0051] The embodiments described above are merely preferred embodiments of the present invention, and not all feasible embodiments of the present invention. Any obvious modifications made by those skilled in the art without departing from the principles and spirit of the present invention should be considered to be included within the scope of protection of the claims of the present invention.

Claims

1. A quinoline-structured modified polybenzimidazole composite bio-based sodium lignosulfonate-doped phytic acid-phosphate high-temperature proton exchange membrane, characterized in that, The proton exchange membrane uses polyphosphoric acid containing sodium lignosulfonate and phytic acid as the doped acid system and quinoline-modified polybenzimidazole as the matrix, with the sodium lignosulfonate uniformly dispersed in the polyphosphoric acid.

2. The quinoline-modified polybenzimidazole composite bio-based sodium lignosulfonate-doped phytate-phosphate high-temperature proton exchange membrane according to claim 1, characterized in that, The raw materials for preparing the proton exchange membrane include: 100g of phytic acid, 0.1g to 3.32g of sodium lignosulfonate, 110g of phosphorus pentoxide, 1mmol to 5mmol of 3,3'-diaminobenzidine, 1mmol to 5mmol of 4,4'-dicarboxylic acid diphenyl ether, and 0.1mmol to 2mmol of quinoline-2,3-dicarboxylic acid.

3. The quinoline-structure-modified polybenzimidazole composite bio-based sodium lignosulfonate-doped phytate-phosphate high-temperature proton exchange membrane according to any one of claims 1 to 2, characterized in that, The thickness of the proton exchange membrane is 5 μm to 300 μm.

4. The quinoline-modified polybenzimidazole composite bio-based sodium lignosulfonate-doped phytate-phosphate high-temperature proton exchange membrane according to claim 3, characterized in that, The thickness of the proton exchange membrane is 10 μm to 100 μm.

5. A method for preparing a quinoline-structured modified polybenzimidazole composite bio-based sodium lignin sulfonate-doped phytic acid-phosphate high-temperature proton exchange membrane as described in any one of claims 1 to 5, characterized in that, Includes the following steps: Step (1): Stir 100g of phytic acid solution with 0.1g to 3.32g of sodium lignosulfonate at room temperature. When the sodium lignosulfonate is completely dispersed in the phytic acid solution, add 110g of phosphorus pentoxide and mix evenly. Stir at 90℃ to 120℃ for 3h to 5h. When the phosphorus pentoxide is completely dissolved to form a brownish-black homogeneous solution, seal and store for later use to obtain polyphosphoric acid containing sodium lignosulfonate and phytic acid. Step (2): Under nitrogen atmosphere protection, add 1 mmol to 5 mmol of 3,3'-diaminobenzidine, 1 mmol to 5 mmol of 4,4'-dicarboxylic acid and 0.1 mmol to 2 mmol of quinoline-2,3-dicarboxylic acid to a 100 mL dry three-necked flask, add 10 mL to 15 mL of the brown-black homogeneous solution prepared in step (1) as solvent, and mechanically stir at 50℃ to 90℃ for 0.5 h to 1 h to mix and dissolve the drugs evenly. Then raise the temperature of the reaction system and continue the reaction to obtain a dark brown slurry solution. Step (3): Using the direct membrane laying method, the dark brown slurry solution prepared in step (2) is evenly coated onto a clean glass plate at 80℃~100℃. The plate is placed in a constant temperature and humidity chamber to absorb water and form acid. After two weeks, a large amount of phosphoric acid formed by polyphosphoric acid absorbing water appears on the surface of the membrane. The membrane is peeled off from the glass plate, the surface liquid is wiped dry, and the membrane is dried under vacuum at 80℃~100℃ for 20h~24h to remove residual moisture, thus obtaining the proton exchange membrane.

6. The preparation method according to claim 5, characterized in that, In step (1), the stirring time at room temperature is 10 min to 30 min.

7. The preparation method according to claim 5 or 6, characterized in that, In step (2), the temperature is first raised to 120℃~160℃ and the reaction continues for 5h~10h.

8. The preparation method according to claim 7, characterized in that, In step (2), the temperature is raised to 150℃~200℃ and the reaction continues for 5h~10h.

9. The preparation method according to claim 5, characterized in that, In step (3), the temperature of the constant temperature and humidity chamber is 25℃~30℃ and the humidity is 40%~55%.

10. The application of the quinoline-modified polybenzimidazole composite bio-based sodium lignin sulfonate doped with phytic acid-phosphoric acid high-temperature proton exchange membrane according to any one of claims 1 to 4 in hydrogen-oxygen fuel cells.

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