A composite high-temperature proton exchange membrane for fuel cells, its preparation method and application
By preparing a composite high-temperature proton exchange membrane and using dihydrogen phosphate and pentahydrogen phosphate to form a complex solid acid, the problem of phosphoric acid loss was solved, and the high proton conductivity and mechanical strength of the high-temperature proton exchange membrane were achieved, thus improving battery performance.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- DALIAN INSTITUTE OF CHEMICAL PHYSICS CHINESE ACADEMY OF SCIENCES
- Filing Date
- 2023-03-22
- Publication Date
- 2026-05-26
AI Technical Summary
Existing high-temperature proton exchange membrane fuel cells suffer from phosphoric acid loss, which leads to decreased mechanical strength and insufficient proton conductivity, affecting battery performance.
A composite high-temperature proton exchange membrane was used, with dihydrogen phosphate and pentahydrogen phosphate as solid acids. The complex solid acid Cs7(H4PO4)(H2PO4)8 was prepared by doping and impregnation methods to achieve uniform dispersion and continuous transport channels of proton conductors.
It improved proton conductivity, solved the problem of phosphoric acid loss, and enhanced battery performance and lifespan.
Smart Images
Figure CN116344878B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of proton exchange membrane fuel cell technology, specifically relating to a composite high-temperature proton exchange membrane for fuel cells, its preparation method, and its application. Background Technology
[0002] Proton exchange membrane fuel cells (PEMFCs) are energy conversion devices that directly convert chemical energy into electrical energy. As long as an oxidant and reductant are continuously supplied, they can continuously output electrical energy. High-temperature PEMFCs have advantages such as high energy efficiency, good CO tolerance, and a relatively simple hydrothermal management system, making them a current research hotspot. However, some problems hinder the development of high-temperature PEMFCs, with the fabrication of the high-temperature membrane, as the core and foundation of the cell, being the current technological bottleneck. When polybenzimidazole is used in high-temperature PEMFCs, it must be doped with as much phosphoric acid as possible to ensure high proton conductivity. However, high phosphoric acid doping can cause a rapid decrease in mechanical strength, increase the loss rate of phosphoric acid during cell operation, and thus affect the overall performance of the cell.
[0003] To address the aforementioned issues, patent CN112820922A discloses a method for preparing a ceramic particle-reinforced polyazole high-temperature proton exchange membrane. This proton exchange membrane exhibits good electrochemical performance, mechanical integrity, and durability. However, the increase in ceramic particles affects the membrane's mechanical properties. Furthermore, since ceramic particles cannot conduct protons, this method struggles to achieve high performance of the high-temperature proton composite membrane under non-humidified conditions. Patent CN111613820A discloses a method for dispersing phosphoric acid and sulfonated tungsten trioxide nanoparticles in a PI matrix. While this method offers higher proton conductivity, stability, high-temperature resistance, and oxidation resistance, phosphoric acid is still required for proton conduction within the membrane, necessitating consideration of phosphoric acid loss.
[0004] In summary, there is currently a lack of a high-temperature proton exchange membrane that combines high proton conductivity with no phosphate loss problem. Summary of the Invention
[0005] To address the shortcomings of existing technologies, this invention provides a composite membrane for high-temperature proton exchange membrane fuel cells, its preparation method, and its application. This membrane exhibits good proton conductivity but does not suffer from phosphoric acid loss.
[0006] To achieve the above objectives, the present invention adopts the following technical solution:
[0007] The present invention provides a composite high-temperature proton exchange membrane, the raw materials of which include polyethersulfone (PES), polyvinylpyrrolidone (PVP), and phosphate-type solid acids; wherein the phosphate-type solid acids include dihydrogen phosphate and pentahydrogen phosphate.
[0008] Based on the above technical solutions, preferably, the dihydrogen phosphate is one of KH2PO4 and CsH2PO4; the pentahydrogen phosphate is one of KH5(PO4)2 and CsH5(PO4)2.
[0009] Based on the above technical solution, the preferred method for preparing the dihydrogen phosphate is as follows: phosphoric acid is added to carbonate to react, the mass ratio of carbonate to phosphoric acid is 1:2, then ethanol is added and stirred to induce precipitation, finally filtered and washed with ethanol, and vacuum dried at 60-80℃ for 12-24h to obtain a white powdery solid.
[0010] Based on the above technical solution, the preferred method for preparing the pentahydrogen phosphate is as follows: phosphoric acid is added to carbonate to react, the mass ratio of carbonate to phosphoric acid is 1:4, then ethanol is added and stirred to induce precipitation, finally filtered and washed with ethanol, and vacuum dried at 60-80℃ for 12-24h to obtain a white powdery solid.
[0011] Based on the above technical solutions, preferably, the mass ratio of PES to PVP is 4:1, the mass ratio of dihydrogen phosphate to PVP is 3:2, and the molar ratio of dihydrogen phosphate to pentahydrogen phosphate is 5:2.
[0012] Another aspect of the present invention provides a method for preparing the above-mentioned composite high-temperature proton exchange membrane, the method comprising the following steps:
[0013] (1) Dissolve PES in a strongly polar aprotic solvent and stir thoroughly to obtain solution S1;
[0014] (2) Add PVP to the solution S1 obtained in step (1) and stir thoroughly to obtain a mixed solution S2;
[0015] (3) Add dihydrogen phosphate powder to the mixed solution S2 obtained in step (2), and after ultrasonic treatment, stir thoroughly to obtain the molding liquid S3;
[0016] (4) The molding liquid S3 obtained in step (3) is poured onto a grooved flat glass and then dried to obtain a pure film M1.
[0017] (5) Heating pentahydrogen phosphate yields liquid-phase molten material S4;
[0018] (6) Immerse the pure membrane M1 obtained in step (4) in the molten material S4 obtained in step (5), then take it out and wipe it dry to obtain the composite high-temperature proton exchange membrane.
[0019] Based on the above technical solution, preferably, the mass fraction of PES in solution S1 in step (1) is 1.33-2.67%;
[0020] In step (2), the mass fraction of PVP in solution S2 is 0.33–0.67 wt.%.
[0021] In step (3), the mass fraction of dihydrogen phosphate in the molding liquid S3 is 0.33-2%.
[0022] Based on the above technical solutions, preferably, in step (1), the strongly polar aprotic solvent is one or more of N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), and N-methyl-2-pyrrolidone (NMP);
[0023] In steps (1), (2) and (3), the stirring method is magnetic stirring, the stirring power is 50-100W, and the stirring time is 0.5-1h.
[0024] In step (3), the ultrasonic power is 100-400W and the ultrasonic time is 0.5-1h;
[0025] In step (4), the drying temperature is 60-120℃ and the drying time is 24-48h;
[0026] In step (5), the heating temperature is 160-170℃ and the heating time is 2-4 hours.
[0027] In step (6), the immersion temperature is 160-170℃ and the immersion time is 12-24h.
[0028] In another aspect, the present invention provides a fuel cell membrane electrode, comprising the above-mentioned composite high-temperature proton exchange membrane.
[0029] The present invention also provides a fuel cell including the membrane electrode described above.
[0030] The beneficial effects of this invention are as follows:
[0031] (1) This invention uses two phosphate-type solid acids to prepare a composite membrane. Compared with doped membranes that only add dihydrogen phosphate or pentahydrogen phosphate, the addition of dihydrogen phosphate increases the operating temperature of the pentahydrogen phosphate doped membrane, and the addition of pentahydrogen phosphate increases the proton conductivity of the dihydrogen phosphate doped membrane. In the high-temperature proton exchange membrane of this invention, at a temperature of 140–190°C, there is an interaction between dihydrogen phosphate and pentahydrogen phosphate to generate another complex solid acid, Cs7(H4PO4)(H2PO4)8, achieving uniform dispersion of the proton conductor and forming a continuous proton transport channel within the membrane, thereby improving the proton conductivity.
[0032] (2) In the preparation method of this application, dihydrogen phosphate is first doped, followed by impregnation with pentahydrogen phosphate. The dihydrogen phosphate dispersed in the film by the doping method can anchor the pentahydrogen phosphate through interaction, while the impregnation method uses molten pentahydrogen phosphate to fill the voids in the dihydrogen phosphate in the film, which can effectively solve the problem of uneven distribution of dihydrogen phosphate caused by doping and establish an effective proton transport path in the film. At the same time, the impregnation method can also solve the structural change problem that occurs when directly doping pentahydrogen phosphate.
[0033] In summary, the composite membrane of the present invention has high conductivity and no phosphoric acid loss problem, resulting in batteries with superior performance and lifespan. Attached Figure Description
[0034] Figure 1 The temperature-varying XRD pattern of Cs7(H4PO4)(H2PO4)8 generated by mixing the two solid acids in Example 1 of this invention;
[0035] Figure 2 The graph shows the electrical conductivity of Cs7(H4PO4)(H2PO4)8 generated by mixing CsH2PO4 and the two corresponding solid acids in Example 1 as a function of temperature.
[0036] Figure 3 The images show the XRD patterns of the composite high-temperature proton exchange membranes prepared in Example 2 and Comparative Example 4. Detailed Implementation
[0037] The present invention will be further described below with reference to specific embodiments, but this does not limit the present invention in any way.
[0038] Example 1
[0039] A composite high-temperature proton exchange membrane for fuel cells is prepared according to the following steps:
[0040] Step 1: Add 6.8 mL of H3PO4 to 16.29 g of Cs2CO3 to react, then add 50 mL of ethanol and stir to induce precipitation. After filtration, wash the precipitate with ethanol and dry to obtain CsH2PO4 white powder solid.
[0041] Step 2: Add 13.6 mL of H3PO4 to 16.29 g of Cs2CO3 to react, then add 50 mL of ethanol and stir to induce precipitation. After filtration, wash the precipitate with ethanol and dry to obtain CsH5(PO4)2 white powder solid.
[0042] Step 3: Dissolve 0.4g of PES in 30g of DMAc and stir for 1h to obtain a PES solution. Add 0.1g of PVP to the PES solution and stir for 1h to obtain a mixed solution of PES and PVP. Add 0.15g of CsH2PO4 powder to the mixed solution, sonicate for 30min and stir for 12h to obtain a molding liquid. Pour the molding liquid onto a grooved flat glass plate and then dry at 80℃ for 24h to obtain a PES / PVP composite film doped with CsH2PO4.
[0043] Step 4: Place 20g of CsH5(PO4)2 in a glass petri dish and heat to obtain a liquid-phase molten material; immerse the composite membrane in the molten material, heat at 170℃ for 48h, and then remove and wipe dry to obtain the composite membrane.
[0044] Example 2
[0045] A composite high-temperature proton exchange membrane for fuel cells is prepared according to the following steps:
[0046] Step 1: Add 6.8 mL of H3PO4 to 16.29 g of Cs2CO3 to react, then add 50 mL of ethanol and stir to induce precipitation. After filtration, wash the precipitate with ethanol and dry to obtain CsH2PO4 white powder solid.
[0047] Step 2: Add 13.6 mL of H3PO4 to 16.29 g of Cs2CO3 to react, then add 50 mL of ethanol and stir to induce precipitation. After filtration, wash the precipitate with ethanol and dry to obtain CsH5(PO4)2 white powder solid.
[0048] Step 3: Dissolve 0.4g of PES in 30g of DMAc and stir for 1h to obtain a PES solution. Add 0.1g of PVP to the PES solution and stir for 1h to obtain a mixed solution of PES and PVP. Add 0.3g of CsH2PO4 powder to the mixed solution, sonicate for 30min and stir for 12h to obtain a molding liquid. Pour the molding liquid onto a grooved flat glass and then dry at 80℃ for 24h to obtain a PES / PVP composite film doped with CsH2PO4.
[0049] Step 4: Place 20g of CsH5(PO4)2 in a glass petri dish and heat to obtain a liquid-phase molten material; immerse the composite membrane in the molten material, heat at 170℃ for 48h, and then remove and wipe dry to obtain the composite membrane.
[0050] Comparative Example 1
[0051] A composite high-temperature proton exchange membrane for fuel cells is prepared according to the following steps:
[0052] Step 1: Add 6.8 mL of H3PO4 to 16.29 g of Cs2CO3 to react, then add 50 mL of ethanol and stir to induce precipitation. After filtration, wash the precipitate with ethanol and dry to obtain CsH2PO4 white powder solid.
[0053] Step 2: Add 13.6 mL of H3PO4 to 16.29 g of Cs2CO3 to react, then add 50 mL of ethanol and stir to induce precipitation. After filtration, wash the precipitate with ethanol and dry to obtain CsH5(PO4)2 white powder solid.
[0054] Step 3: Dissolve 0.5g of PES in 30g of DMAc and stir for 1h to obtain a PES solution. Add 0.15g of CsH2PO4 powder to the PES solution, sonicate for 30min and stir for 12h to obtain a molding liquid. Pour the molding liquid onto a grooved flat glass and then dry at 80℃ for 24h to obtain a PES composite film doped with CsH2PO4.
[0055] Step 4: Place 20g of CsH5(PO4)2 in a glass petri dish and heat to obtain a liquid-phase molten material; immerse the composite membrane in the molten material, heat at 170℃ for 48h, and then remove and wipe dry to obtain the composite membrane.
[0056] Comparative Example 2
[0057] A composite high-temperature proton exchange membrane for fuel cells is prepared according to the following steps:
[0058] Step 1: Add 6.8 mL of H3PO4 to 16.29 g of Cs2CO3 to react, then add 50 mL of ethanol and stir to induce precipitation. After filtration, wash the precipitate with ethanol and dry to obtain CsH2PO4 white powder solid.
[0059] Step 2: Dissolve 0.4g of PES in 30g of DMAc and stir for 1 hour to obtain a PES solution. Add 0.1g of PVP to the PES solution and stir for 1 hour to obtain a mixed solution of PES and PVP. Add 0.15g of CsH2PO4 powder to the mixed solution, sonicate for 30 minutes, and stir for 12 hours to obtain a molding liquid. Pour the molding liquid onto a grooved flat glass plate and then dry at 80℃ for 24 hours to obtain a PES / PVP composite film doped with CsH2PO4.
[0060] Comparative Example 3
[0061] A composite high-temperature proton exchange membrane for fuel cells is prepared according to the following steps:
[0062] Step 1: Add 13.6 mL of H3PO4 to 16.29 g of Cs2CO3 to react, then add 50 mL of ethanol and stir to induce precipitation. After filtration, wash the precipitate with ethanol and dry to obtain CsH5(PO4)2 white powder solid.
[0063] Step 2: Dissolve 0.4g of PES in 30g of DMAc and stir for 1 hour to obtain a PES solution. Add 0.1g of PVP to the PES solution and stir for 1 hour to obtain a mixed solution of PES and PVP. Cast the mixed solution onto a grooved flat glass plate and then dry at 80℃ for 24 hours to obtain a PES / PVP composite film.
[0064] Step 3: Place 20g of CsH5(PO4)2 in a glass petri dish and heat to obtain a liquid-phase molten material; immerse the composite membrane in the molten material, heat at 170℃ for 48h, and then remove and wipe dry to obtain the composite membrane.
[0065] Comparative Example 4
[0066] A composite high-temperature proton exchange membrane for fuel cells is prepared according to the following steps:
[0067] Step 1: Add 13.6 mL of H3PO4 to 16.29 g of Cs2CO3 to react, then add 50 mL of ethanol and stir to induce precipitation. After filtration, wash the precipitate with ethanol and dry to obtain CsH5(PO4)2 white powder solid.
[0068] Step 2: Dissolve 0.4g of PES in 30g of DMAc and stir for 1 hour to obtain a PES solution. Add 0.1g of PVP to the PES solution and stir for 1 hour to obtain a mixed solution of PES and PVP. Add 0.3g of CsH5(PO4)2 powder to the mixed solution, sonicate for 30 minutes and stir for 12 hours to obtain a casting liquid. Pour the casting liquid onto a grooved flat glass plate and then dry at 80℃ for 24 hours to obtain a composite membrane.
[0069] The conductivity of the composite membranes of Example 1 and the comparative example was tested, and the results are shown in Table 1.
[0070] Table 1. Conductivity of the composite films prepared in Example 1 and Comparative Examples 1-5
[0071]
[0072]
[0073] Depend on Figure 1 and Figure 2It can be seen that CsH2PO4 and CsH5(PO4)2 can generate the complex solid acid Cs7(H4PO4)(H2PO4)8 at temperatures of 140-190℃. Referring to Table 1, due to the addition of CsH5(PO4)2, the composite exhibits a much higher conductivity than pure CsH2PO4. Example 1 and Comparative Example 1 show the addition and absence of PVP, respectively. Because PVP has a certain acid absorption and solidification ability, the membrane without PVP exhibits significantly lower conductivity. Comparative Examples 2 and 3 show the use of only dihydrogen phosphate and only pentahydrogen phosphate, respectively. Doping with only dihydrogen phosphate results in uneven distribution, while impregnation with only pentahydrogen phosphate leads to high fluidity and easy loss; both composite membranes exhibit low conductivity. Comparative Example 4 uses a doping method to add pentahydrogen phosphate. Figure 3 The results show that after adding pentahydrogen phosphate by doping, some of the active hydrogens are taken away by PVP, reducing its proton conduction performance.
[0074] For anyone skilled in the art, many possible variations and modifications can be made to the technical solutions of this invention, or equivalent embodiments can be modified based on the disclosed technical content, without departing from the scope of the technical solutions of this invention. Therefore, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of this invention without departing from the content of the technical solutions of this invention should still fall within the protection scope of the technical solutions of this invention.
Claims
1. A method for preparing a composite high-temperature proton exchange membrane, characterized by, The preparation method includes the following steps: (1) Dissolve polyethersulfone in a strongly polar aprotic solvent and stir thoroughly to obtain solution S1; (2) Add polyvinylpyrrolidone to the solution S1 obtained in step (1) and stir thoroughly to obtain a mixed solution S2; (3) Add dihydrogen phosphate powder to the mixed solution S2 obtained in step (2), and after ultrasonic treatment, stir thoroughly to obtain the molding liquid S3; (4) The molding liquid S3 obtained in step (3) is poured onto a grooved flat glass and then dried to obtain a pure film M1; (5) Heating pentahydrogen phosphate yields a liquid-phase molten substance S4; (6) Immerse the pure membrane M1 obtained in step (4) in the molten material S4 obtained in step (5), then take it out and wipe it dry to obtain the composite high temperature proton exchange membrane.
2. The preparation method of the composite high-temperature proton exchange membrane according to claim 1, characterized in that, The dihydrogen phosphate is one of KH2PO4 and CsH2PO4; the pentahydrogen phosphate is one of KH5(PO4)2 and CsH5(PO4)2.
3. The method for preparing a composite high-temperature proton exchange membrane according to claim 1, characterized in that, The preparation method of the dihydrogen phosphate is as follows: phosphoric acid is added to the carbonate to react, the mass ratio of carbonate to phosphoric acid is 1:2, then ethanol is added and stirred to induce precipitation, finally filtered and washed with ethanol, and dried under vacuum at 60~80℃ for 12~24 h to obtain a white powdery solid.
4. The method for preparing the composite high-temperature proton exchange membrane according to claim 1, characterized in that, The method for preparing the pentahydrogen phosphate is as follows: phosphoric acid is added to the carbonate to react, with a mass ratio of carbonate to phosphoric acid of 1:
4. Then ethanol is added and stirred to induce precipitation. Finally, the mixture is filtered, washed with ethanol, and dried under vacuum at 60-80°C for 12-24 h to obtain a white powdery solid.
5. The method for preparing the composite high-temperature proton exchange membrane according to claim 1, characterized in that, The mass ratio of polyethersulfone to polyvinylpyrrolidone is 4:1, the mass ratio of dihydrogen phosphate to polyvinylpyrrolidone is 3:2, and the molar ratio of dihydrogen phosphate to pentahydrogen phosphate is 5:
2.
6. The method for preparing the composite high-temperature proton exchange membrane according to claim 1, characterized in that, In step (1), the mass fraction of polyethersulfone in solution S1 is 1.33~2.67%; In step (2), the mass fraction of polyvinylpyrrolidone in solution S2 is 0.33~0.67 wt.%; In step (3), the mass fraction of dihydrogen phosphate in the molding liquid S3 is 0.33~2%.
7. The method for preparing the composite high-temperature proton exchange membrane according to claim 1, characterized in that, In step (1), the strongly polar aprotic solvent is independently one or more of N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), and N-methyl-2-pyrrolidone (NMP); In steps (1), (2) and (3), the stirring method is magnetic stirring, the stirring power is 50~100 W, and the stirring time is 0.5~1 h; In step (3), the ultrasonic power is 100~400 W and the ultrasonic time is 0.5~1h; In step (4), the drying temperature is 60~120℃ and the drying time is 24~48 h; In step (5), the heating temperature is 160~170℃ and the heating time is 2~4 h; In step (6), the immersion temperature is 160~170℃ and the immersion time is 12~24 h.
8. A fuel cell membrane electrode assembly, characterized in that, Including the composite high-temperature proton exchange membrane prepared by the preparation method according to any one of claims 1-7.
9. A fuel cell, characterized in that, Includes the membrane electrode as described in claim 8.