Phosphonic acid grafted polybenzimidazole high-temperature proton exchange membrane and preparation method thereof

Abstract

The invention discloses a phosphonic acid grafted polybenzimidazole high-temperature proton exchange membrane and a preparation method thereof, and the preparation method comprises the following steps: mixing phosphoryl chloride and triphenylphosphine in a solvent, then heating and stirring under the condition of introducing nitrogen to prepare a grafting agent, mixing and stirring the grafting agent and polybenzimidazole in the solvent to prepare the phosphonic acid grafted polybenzimidazole high-temperature proton exchange membrane. The preparation method comprises the following steps: reacting hydroxyl on the surface of polybenzimidazole with phosphoric anhydride to form a phosphonic acid grafted polybenzimidazole solution, repeatedly washing the solution, filtering, drying, dissolving in a solvent, coating in a polytetrafluoroethylene mold plate, drying in a blast oven, soaking in a sulfuric acid solution after drying, and repeatedly washing with water until the solution is neutral, thereby obtaining the phosphonic acid grafted polybenzimidazole. The whole preparation process is simple, easy to master and operate and high in production efficiency, and the prepared product has excellent thermal stability, chemical stability, mechanical strength and proton conductivity in a high-temperature environment.

Description

Technical Field

[0001] The invention relates to the technical field of high-temperature proton exchange membrane preparation, in particular to a phosphonic acid grafted polybenzimidazole high-temperature proton exchange membrane and a preparation method thereof. Background Art

[0002] High-temperature proton exchange membrane is a key component of electrochemical devices such as fuel cells. It can separate protons produced by electrochemical reactions such as hydrogen and oxygen to generate electricity. Since fuel cells need to withstand harsh conditions such as high temperature, high pressure, and strong corrosion during operation, the preparation of high-temperature proton exchange membrane requires high thermal stability, acid and alkali resistance, good proton conductivity and mechanical strength.

[0003] Currently, there are many methods for preparing high-temperature proton exchange membranes, but the cost of preparing high-temperature proton exchange membranes by existing preparation methods is relatively high, resulting in high production costs of fuel cells. At the same time, the high-temperature proton exchange membranes prepared by existing preparation methods are not excellent in thermal stability, chemical stability, mechanical strength and proton conductivity.

[0004] Therefore, it is necessary to develop a suitable preparation method to prepare a high-temperature proton exchange membrane with excellent performance, so that it has excellent thermal stability, chemical stability, mechanical strength and proton conductivity. Summary of the invention

[0005] The purpose of the present invention is to improve the thermal stability, chemical stability, mechanical strength and proton conductivity of the high-temperature proton exchange membrane, and to propose a phosphonic acid grafted polybenzimidazole high-temperature proton exchange membrane and a preparation method thereof. The preparation process is simple, easy to master and operate, and has high production efficiency. The prepared product has excellent thermal stability, chemical stability, mechanical strength and proton conductivity in a high-temperature environment, and the preparation cost is low.

[0006] The purpose of the present invention can be achieved by the following technical solution: A phosphonic acid grafted polybenzimidazole high temperature proton exchange membrane, which is prepared by the following method: Step 1: mixing phosphoryl chloride and triphenylphosphine in a solvent, and then heating and stirring under nitrogen flow to prepare a grafting agent; Step 2: Mix the grafting agent in step 1 and polybenzimidazole in a solvent, and stir to react the hydroxyl groups on the surface of the polybenzimidazole with phosphoric anhydride to form a polybenzimidazole solution grafted with phosphonic acid; Step 3: repeatedly washing and filtering the phosphonic acid grafted polybenzimidazole solution formed in step 2, and then performing a drying operation to obtain the phosphonic acid grafted polybenzimidazole; Step 4: dissolving the phosphonic acid grafted polybenzimidazole prepared in step 3 in a solvent, coating the film on a polytetrafluoroethylene mold, and then drying the film in a forced air oven; Step 5: Soak the dried product in step 4 in a sulfuric acid solution, and then repeatedly wash with water until it becomes neutral, thereby obtaining a phosphonic acid-grafted polybenzimidazole high-temperature proton exchange membrane.

[0007] The further technical improvement of the present invention is that the solvents in step 1 and step 2 are one of dimethyl sulfoxide, N,N-dimethylacetamide, N-methylpyrrolidone, m-cresol, N,N-dimethylpropylene urea and diphenyl sulfone.

[0008] The further technical improvement of the present invention is that: in step 1, the molar ratio of phosphoryl chloride to triphenylphosphine is controlled at 1:0.4-0.8, the heating temperature is controlled at 60-90° C., and the stirring time is controlled at 20-40 min.

[0009] The further technical improvement of the present invention is that the molar ratio of the grafting agent to the polybenzimidazole in step 2 is controlled at 0.4-1:1, and the stirring time is controlled at 18-28 hours.

[0010] The further technical improvement of the present invention is that the drying method in step three is: the washed and filtered phosphonic acid grafted polybenzimidazole is placed in a 50-80°C environment for drying for 18-28 hours, and then transferred to a vacuum oven at 90-110°C for drying for 10-18 hours.

[0011] The further technical improvement of the present invention is that: in step 4, dimethyl sulfoxide is selected as the solvent, and after the phosphonic acid grafted polybenzimidazole is added with dimethyl sulfoxide, the density is controlled at 1-4 g / mL.

[0012] A further technical improvement of the present invention is that in step 4, the temperature of the blast oven is controlled at 50-80° C., and the drying time is controlled at 6-10 hours.

[0013] A further technical improvement of the present invention is that the concentration of the sulfuric acid solution in step five is controlled at 0.8-1.5 mol / L, and the soaking time is controlled at 10-18 h.

[0014] A further technical improvement of the present invention is that the preparation method specifically comprises the following steps: Step 1: mixing phosphoryl chloride and triphenylphosphine in a solvent, and then heating and stirring under nitrogen flow to prepare a grafting agent; Step 2: Mix the grafting agent in step 1 and polybenzimidazole in a solvent, and stir to react the hydroxyl groups on the surface of the polybenzimidazole with phosphoric anhydride to form a polybenzimidazole solution grafted with phosphonic acid; Step 3: repeatedly washing and filtering the phosphonic acid grafted polybenzimidazole solution formed in step 2, and then performing a drying operation to obtain the phosphonic acid grafted polybenzimidazole; Step 4: dissolving the phosphonic acid grafted polybenzimidazole prepared in step 3 in a solvent, coating the film on a polytetrafluoroethylene mold, and then drying the film in a forced air oven; Step 5: Soak the dried product in step 4 in a sulfuric acid solution, and then repeatedly wash with water until it becomes neutral, thereby obtaining a phosphonic acid-grafted polybenzimidazole high-temperature proton exchange membrane.

[0015] Compared with the prior art, the present invention has the following beneficial effects: (1) The present invention prepares a phosphonic acid grafted polybenzimidazole high-temperature proton exchange membrane. The entire preparation process is simple, easy to master and operate, and has high production efficiency. The prepared product has excellent thermal stability, chemical stability, mechanical strength and proton conductivity under high temperature environment.

[0016] (2) The present invention uses phosphoryl chloride and triphenylphosphine for preparation. Phosphoryl chloride and triphenylphosphine as grafting agents can make the bonds between polymer molecules more tightly bound, thereby enhancing the mechanical properties of the prepared high-temperature proton exchange membrane, and improving its durability and stability. In addition, phosphoryl chloride and triphenylphosphine as grafting agents have relatively low production costs. Using these materials can reduce manufacturing costs. Using phosphoryl chloride and triphenylphosphine as grafting agents can also effectively improve reaction efficiency. Through this preparation method, high-temperature proton exchange membranes can be mass-produced.

[0017] (3) In the present invention, by soaking the phosphonic acid grafted polybenzimidazole high temperature proton exchange membrane in sulfuric acid solution, on the one hand, the chemical resistance and stability of the exchange membrane can be improved, and the decomposition and aging of the exchange membrane can be reduced; on the other hand, the sulfuric acid solution contains a large amount of H+ ions, which can promote the proton transfer in the exchange membrane, and the sulfuric acid solution can improve the hydration performance of the exchange membrane, increase the hydration capacity of the exchange membrane and the diffusion rate of water molecules, thereby enhancing the electrical conductivity of the exchange membrane. DETAILED DESCRIPTION

[0018] The technical scheme of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0019] Embodiment 1 A phosphonic acid grafted polybenzimidazole high temperature proton exchange membrane is prepared by the following method: Step 1: mixing phosphoryl chloride and triphenylphosphine in dimethyl sulfoxide, wherein the molar ratio of phosphoryl chloride to triphenylphosphine is controlled at 1:0.6. When the molar ratio of phosphoryl chloride to triphenylphosphine is 1:0.6, the reaction rate of the two is faster, the reaction can be completed faster, and less by-products are generated. Subsequently, the mixture is heated to 80° C. and stirred for 30 minutes under nitrogen flow to prepare a grafting agent. Step 2: Mix the grafting agent and polybenzimidazole in a solvent, and control the molar ratio of the grafting agent to the polybenzimidazole to be 0.6:1. When the molar ratio is 0.6:1, less grafting agent is required, which can reduce the cost of material use, and stir for 24 hours to react the hydroxyl groups on the surface of the polybenzimidazole with phosphoric anhydride to form a phosphonic acid grafted polybenzimidazole solution; Step 3: repeatedly washing and filtering the phosphonic acid grafted polybenzimidazole solution formed in step 2. By repeatedly washing and filtering to remove residual substances in the solution, the quality and performance of the product can be improved, the influence of impurities on the product can be reduced, and the performance of the prepared high-temperature proton exchange membrane can be made better and more stable. After that, it is placed in a 60°C environment and dried for 24 hours, and then transferred to a vacuum oven at 100°C and dried for 14 hours to obtain the phosphonic acid grafted polybenzimidazole. First drying at 60°C and then drying at 100°C can make the surface of the material smoother, and the moisture in the material can be fully volatilized, reducing the moisture content, which is beneficial to improving the quality of the material; Step 4: dissolving the phosphonic acid grafted polybenzimidazole prepared in step 3 in dimethyl sulfoxide solvent, adding the phosphonic acid grafted polybenzimidazole to the dimethyl sulfoxide solvent, maintaining the solvent density at 3 g / mL, coating on a polytetrafluoroethylene mold, and then placing in a forced air oven at a temperature of 60° C. for 8 hours; Step 5: Soak the dried product in step 4 in a 1.2 mol / L sulfuric acid solution for 12 hours. Soaking the phosphonic acid grafted polybenzimidazole high temperature proton exchange membrane in the sulfuric acid solution can, on the one hand, improve the chemical resistance and stability of the exchange membrane and reduce the decomposition and aging of the exchange membrane. On the other hand, the sulfuric acid solution contains a large amount of H+ ions, which can promote the proton transfer in the exchange membrane, and the sulfuric acid solution can improve the hydration performance of the exchange membrane, increase the hydration capacity of the exchange membrane and the diffusion rate of water molecules, thereby enhancing the conductivity of the exchange membrane. Then, repeatedly wash with water until neutral to obtain a phosphonic acid grafted polybenzimidazole high temperature proton exchange membrane.

[0020] After testing, the high-temperature proton exchange membrane prepared in this embodiment has a linear swelling coefficient of 8.71% at room temperature and a tensile strength of 54.8 MPa. The TGA test results show that the total thermal weight loss rate of the proton exchange membrane in the range of 50°C to 240°C is 4.52%, and the proton conductivity measured at 160°C under anhydrous conditions is 0.078S / cm.

[0021] Embodiment 2 A phosphonic acid grafted polybenzimidazole high temperature proton exchange membrane is prepared by the following method: Step 1: mixing phosphoryl chloride and triphenylphosphine in dimethyl sulfoxide, wherein the molar ratio of phosphoryl chloride to triphenylphosphine is controlled to be 1:0.7. When the molar ratio of phosphoryl chloride to triphenylphosphine is 1:0.7, the reaction rate of the two is faster, the reaction can be completed faster, and the yield of the product is higher. Subsequently, the mixture is heated to 70° C. and stirred for 35 minutes under nitrogen flow to prepare a grafting agent. Step 2: Mix the grafting agent and polybenzimidazole in a solvent, and control the molar ratio of the grafting agent and the polybenzimidazole to be 0.8:1. When the molar ratio is 0.8:1, the grafting agent and the polybenzimidazole can fully react, and the yield of the formed graft copolymer is high. Stir for 26 hours to react the hydroxyl groups on the surface of the polybenzimidazole with phosphoric anhydride to form a phosphonic acid grafted polybenzimidazole solution; Step 3: repeatedly washing and filtering the phosphonic acid grafted polybenzimidazole solution formed in step 2. By repeatedly washing and filtering to remove residual substances in the solution, the quality and performance of the product can be improved, the influence of impurities on the product can be reduced, and the performance of the prepared high-temperature proton exchange membrane can be made better and more stable. After that, it is placed in a 70°C environment and dried for 20 hours, and then transferred to a vacuum oven at 105°C and dried for 12 hours to obtain the phosphonic acid grafted polybenzimidazole. The material surface can be made smoother and the drying speed can be accelerated. Step 4: dissolving the phosphonic acid grafted polybenzimidazole prepared in step 3 in dimethyl sulfoxide solvent, and adding the phosphonic acid grafted polybenzimidazole to the dimethyl sulfoxide solvent, the solvent density is maintained at 2.5 g / mL, coating on a polytetrafluoroethylene mold, and then placing in a forced air oven at a temperature of 70° C. for drying for 7 hours; Step 5: Soak the dried product in step 4 in a 1 mol / L sulfuric acid solution for 15 hours. Soaking the phosphonic acid grafted polybenzimidazole high temperature proton exchange membrane in the sulfuric acid solution can, on the one hand, improve the chemical resistance and stability of the exchange membrane and reduce the decomposition and aging of the exchange membrane. On the other hand, the sulfuric acid solution contains a large amount of H+ ions, which can promote the proton transfer in the exchange membrane, and the sulfuric acid solution can improve the hydration performance of the exchange membrane, increase the hydration capacity of the exchange membrane and the diffusion rate of water molecules, thereby enhancing the conductivity of the exchange membrane. Repeatedly wash with water until neutral to obtain a phosphonic acid grafted polybenzimidazole high temperature proton exchange membrane.

[0022] After testing, the high-temperature proton exchange membrane prepared in this embodiment has a linear swelling coefficient of 8.41% at room temperature and a tensile strength of 58.8 MPa. The TGA test results show that the total thermal weight loss rate of the proton exchange membrane in the range of 50°C to 240°C is 4.22%, and the proton conductivity measured at 160°C under anhydrous conditions is 0.073S / cm.

[0023] The preferred embodiments of the present invention disclosed above are only used to help explain the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to only specific implementation methods. Obviously, many modifications and changes can be made according to the content of this specification. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can understand and use the present invention well. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A phosphonic acid grafted polybenzimidazole high temperature proton exchange membrane, characterized in that: It is prepared by the following method: Step 1: mixing phosphoryl chloride and triphenylphosphine in a solvent, and then heating and stirring under nitrogen flow to prepare a grafting agent; Step 2: Mix the grafting agent in step 1 and polybenzimidazole in a solvent, and stir to react the hydroxyl groups on the surface of the polybenzimidazole with phosphoric anhydride to form a polybenzimidazole solution grafted with phosphonic acid; Step 3: repeatedly washing and filtering the phosphonic acid grafted polybenzimidazole solution formed in step 2, and then performing a drying operation to obtain the phosphonic acid grafted polybenzimidazole; Step 4: dissolving the phosphonic acid grafted polybenzimidazole prepared in step 3 in a solvent, coating the film on a polytetrafluoroethylene mold, and then drying the film in a forced air oven; Step 5: Soak the dried product in step 4 in a sulfuric acid solution, and then repeatedly wash with water until it becomes neutral, thereby obtaining a phosphonic acid-grafted polybenzimidazole high-temperature proton exchange membrane.

2. The phosphonic acid grafted polybenzimidazole high temperature proton exchange membrane according to claim 1, characterized in that: The solvents in step 1 and step 2 are both one of dimethyl sulfoxide, N,N-dimethylacetamide, N-methylpyrrolidone, m-cresol, N,N-dimethylpropylene urea and diphenyl sulfone.

3. The phosphonic acid grafted polybenzimidazole high temperature proton exchange membrane according to claim 1, characterized in that: In step 1, the molar ratio of phosphoryl chloride to triphenylphosphine is controlled at 1:0.4-0.8, the heating temperature is controlled at 60-90° C., and the stirring time is controlled at 20-40 min.

4. The phosphonic acid grafted polybenzimidazole high temperature proton exchange membrane according to claim 1, characterized in that: In step 2, the molar ratio of the grafting agent to the polybenzimidazole is controlled at 0.4-1:1, and the stirring time is controlled at 18-28 hours.

5. The phosphonic acid grafted polybenzimidazole high temperature proton exchange membrane according to claim 1, characterized in that: The drying method in step three is: the washed and filtered phosphonic acid grafted polybenzimidazole is placed in a 50-80° C. environment for drying for 18-28 hours, and then transferred to a vacuum oven at 90-110° C. for drying for 10-18 hours.

6. The phosphonic acid grafted polybenzimidazole high temperature proton exchange membrane according to claim 1, characterized in that: In step 4, dimethyl sulfoxide is selected as the solvent, and after dimethyl sulfoxide is added to the phosphonic acid grafted polybenzimidazole, the density is controlled at 1-4 g / mL.

7. The phosphonic acid grafted polybenzimidazole high temperature proton exchange membrane according to claim 1, characterized in that: In step 4, the temperature of the blast oven is controlled at 50-80° C., and the drying time is controlled at 6-10 hours.

8. The phosphonic acid grafted polybenzimidazole high temperature proton exchange membrane according to claim 1, characterized in that: In step 5, the concentration of the sulfuric acid solution is controlled at 0.8-1.5 mol / L, and the soaking time is controlled at 10-18 hours.

9. A method for preparing a phosphonic acid grafted polybenzimidazole high temperature proton exchange membrane according to any one of claims 1 to 8, characterized in that: The preparation method specifically comprises the following steps: Step 1: mixing phosphoryl chloride and triphenylphosphine in a solvent, and then heating and stirring under nitrogen flow to prepare a grafting agent; Step 2: Mix the grafting agent in step 1 and polybenzimidazole in a solvent, and stir to react the hydroxyl groups on the surface of the polybenzimidazole with phosphoric anhydride to form a polybenzimidazole solution grafted with phosphonic acid; Step 3: repeatedly washing and filtering the phosphonic acid grafted polybenzimidazole solution formed in step 2, and then performing a drying operation to obtain the phosphonic acid grafted polybenzimidazole; Step 4: dissolving the phosphonic acid grafted polybenzimidazole prepared in step 3 in a solvent, coating the film on a polytetrafluoroethylene mold, and then drying the film in a forced air oven; Step 5: Soak the dried product in step 4 in a sulfuric acid solution, and then repeatedly wash with water until it becomes neutral, thereby obtaining a phosphonic acid-grafted polybenzimidazole high-temperature proton exchange membrane.