Acid-base composite high-temperature proton exchange membrane, preparation method and application thereof

Abstract

The application discloses an acid-base composite high-temperature proton exchange membrane and a preparation method and application thereof. The acid-base composite high-temperature proton exchange membrane is prepared by soaking a hydrogen-bond organic framework material containing carboxyl groups and polybenzimidazole after acid-base crosslinking, and then soaking in phosphoric acid. The hydrogen-bond organic framework material containing carboxyl groups is blended with polybenzimidazole, the carboxyl groups of the hydrogen-bond organic framework material can be crosslinked with polybenzimidazole, so that the mechanical strength of the composite membrane is improved; meanwhile, the hydrogen-bond organic framework material has ultrahigh specific surface area and hydrogen bonding, which provides huge storage space and binding force for phosphoric acid molecules, so that the proton conduction performance, phosphoric acid stability and high-temperature battery performance of the composite membrane are improved. Compared with the prior art, the novel acid-base composite high-temperature proton exchange membrane prepared by the application has higher proton conductivity at 100-200 DEG C, has higher mechanical strength, and the battery assembled based on the membrane can be stably operated at 100-200 DEG C.

Description

Technical Field

[0001] This application relates to an acid-base composite high-temperature proton exchange membrane, its preparation method, and its application, belonging to the fields of new materials technology and new energy technology. Background Technology

[0002] Hydrogen energy is a renewable and clean energy source that will gradually replace increasingly depleted fossil fuels, becoming an important part of the world's energy landscape. Fuel cells can convert hydrogen energy into electrical energy, and therefore have attracted widespread attention. Proton exchange membrane (PEM) fuel cells, using a proton exchange membrane as the electrolyte, are widely used in transportation power sources and stationary power plants due to their high energy conversion efficiency, low operating temperature, fast start-up, and long lifespan, making them the most commercially promising fuel cell technology. Currently, PEM fuel cells suffer from problems such as low environmental adaptability, low utilization efficiency of precious metal catalysts, high cost, and complex hydrothermal management systems. It is generally believed that increasing the operating temperature of the fuel cell is an effective solution to these problems. When the operating temperature of a PEM fuel cell is increased above 100℃, the cell reaction kinetics improve, the catalytic efficiency of the Pt catalyst increases, and the amount of Pt catalyst used can be significantly reduced; moreover, the tolerance of the Pt catalyst to CO increases exponentially with temperature; simultaneously, increasing the operating temperature reduces the requirements of the hydrothermal management system. However, excessively high temperatures (above 500℃) place stringent requirements on the materials used in the components of the PEM fuel cell. Therefore, developing high-temperature (100-500℃) proton exchange membrane fuel cells is of great significance. The most important challenge in developing high-temperature proton exchange membrane fuel cells is developing high-performance high-temperature proton exchange membranes.

[0003] Given the unique advantages of high-temperature proton exchange membrane fuel cells (PEMFCs), research on high-temperature PEMFCs has become a hot topic. Polybenzimidazole (PPI) is widely used in PEMFCs for high-temperature fuel cells due to its excellent thermal stability and mechanical strength. However, PPI itself has a weak proton transport capacity, requiring modification. One major method is to dope PPI with phosphoric acid to improve proton transport capacity, primarily by immersing the PPI membrane in phosphoric acid. However, there has always been a trade-off between proton conductivity and mechanical strength, making further improvements in battery performance difficult, and the problem of phosphoric acid loss remains unresolved. Therefore, how to simultaneously improve the mechanical properties and proton conductivity of the PPI while ensuring its thermal and dimensional stability is a pressing issue for application. Summary of the Invention

[0004] According to one aspect of this application, an acid-base composite high-temperature proton exchange membrane is provided, wherein the acid-base composite high-temperature proton exchange membrane is formed by cross-linking a carboxyl-containing hydrogen-bonded organic framework material and a polybenzimidazole acid-base mixture, followed by immersion in phosphoric acid.

[0005] The carboxyl-containing hydrogen-bonded organic framework material is selected from one of the structures shown in Formula I-1, Formula I-2, Formula I-3, and Formula I-4;

[0006]

[0007]

[0008] Optionally, the mass ratio of the carboxyl-containing hydrogen-bonded organic framework material to polybenzimidazole is 3:97 to 21:79.

[0009] Optionally, the mass ratio of the carboxyl-containing hydrogen-bonded organic framework material to polybenzimidazole is selected from any value of 3:97, 5:95, 7:93, 9:91, 11:89, 13:87, 15:85, 17:83, 19:81, 21:79 or a range between any two of the above.

[0010] An appropriate ratio allows carboxyl-containing hydrogen-bonded organic framework materials to be uniformly dispersed in polybenzimidazole. Under the interaction of acid and base with polybenzimidazole, a cross-linked hydrogen bond network is formed, which improves mechanical strength. At the same time, the high specific surface area of ​​the hydrogen-bonded organic framework material can be used to increase the phosphoric acid loading, promote stable, uniform and efficient proton transport, and improve proton conductivity and battery performance.

[0011] According to another aspect of this application, a method for preparing the above-described acid-base composite high-temperature proton exchange membrane is provided, the method comprising the following steps:

[0012] (1) A mixture of carboxyl-containing hydrogen-bonded organic framework material, polybenzimidazole, and solvent is ultrasonically dispersed to obtain a casting solution;

[0013] (2) The casting film is pressed onto the substrate surface by scraping method, dried and soaked in phosphoric acid to obtain the acid-base composite high-temperature proton exchange membrane.

[0014] Optionally, in the casting solution, the sum of the mass fractions of the carboxyl-containing hydrogen-bonded organic framework material and the polybenzimidazole is 2.5-10%.

[0015] Optionally, the sum of the mass fractions of the carboxyl-containing hydrogen-bonded organic framework material and the polybenzimidazole is selected from any value of 2.5%, 4%, 5.5%, 7%, 8.5%, 10%, or a range between any two of the above.

[0016] Optionally, the solvent is selected from at least one of N,N-dimethylacetamide, N,N-dimethylformamide, and dimethyl sulfoxide.

[0017] Optionally, the solvent is selected from N,N-dimethylacetamide (DMAC) and / or dimethyl sulfoxide (DMSO).

[0018] In this application, N,N-dimethylacetamide (DMAC) and dimethyl sulfoxide (DMSO) exhibit better dispersibility for carboxyl-containing hydrogen-bonded organic framework materials and polybenzimidazole, and can be dispersed more easily.

[0019] Optionally, the ultrasonic dispersion time is 4 to 12 hours.

[0020] Optionally, the substrate is a glass substrate.

[0021] Optionally, the drying temperature is 50–80°C.

[0022] Optionally, the drying temperature is selected from any value of 50°C, 60°C, 70°C, 80°C, or a range between any two of the above.

[0023] Optionally, the soaking temperature is 60–100°C, and the soaking time is 2–4 days.

[0024] Optionally, the immersion temperature is selected from any value of 60°C, 70°C, 80°C, 90°C, 100°C, or a range between any two of the above.

[0025] Optionally, the soaking time is selected from any value of 2 days, 2.5 days, 3 days, 3.5 days, 4 days, or a range between any two of the above.

[0026] According to another aspect of this application, an application of the above-described acid-base composite high-temperature proton exchange membrane in a fuel cell is provided, wherein the operating temperature of the acid-base composite high-temperature proton exchange membrane is 100-200°C.

[0027] Optionally, the novel acid-base composite high-temperature proton exchange membrane is applied in fuel cells, with an applicable temperature of 100–200°C.

[0028] In this application, the composite high-temperature proton exchange membrane uses a polybenzimidazole membrane and a carboxyl-containing hydrogen-bonded organic framework material as its backbone. The carboxyl-containing hydrogen-bonded organic framework material contains carboxyl sites and can undergo acid-base crosslinking with polybenzimidazole. At the same time, it stores and binds phosphoric acid molecules through hydrogen bonding and its ultra-high specific surface area.

[0029] In this application, the carboxyl groups of the hydrogen-bonded organic framework material can undergo acid-base crosslinking with polybenzimidazole, thereby improving the mechanical strength of the composite membrane. Simultaneously, the extremely high specific surface area of ​​the hydrogen-bonded organic framework material provides ample storage space for phosphoric acid molecules. Furthermore, the abundant hydrogen bonds in the hydrogen-bonded organic framework material also provide additional binding forces for phosphoric acid molecules, thus improving the proton conductivity and phosphoric acid stability of the composite membrane. Introducing the carboxyl-containing hydrogen-bonded organic framework material of this invention into the composite membrane not only improves the mechanical strength of the composite membrane but also enhances its proton conductivity, slows down phosphoric acid loss, and improves the battery's operational stability. The resulting composite proton exchange membrane is extremely dense and exhibits strong proton conductivity.

[0030] The beneficial effects that this application can produce include:

[0031] 1) This application introduces a carboxyl-containing hydrogen-bonded organic framework material into polybenzimidazole. The carboxyl-containing hydrogen-bonded organic framework material undergoes acid-base crosslinking with polybenzimidazole, which can form an effective crosslinking network in the composite film and improve the mechanical strength of the composite film.

[0032] 2) The hydrogen-bonded organic framework material provided in this application has an extremely high specific surface area, which provides a huge storage space for phosphate molecules, thereby improving the proton conduction performance of the composite membrane.

[0033] 3) The abundant hydrogen bonds in the hydrogen-bonded organic framework material provided in this application provide additional binding forces for phosphoric acid molecules, slowing down the loss rate of phosphoric acid in the composite membrane, improving the stability of battery operation, and having great application potential in the field of proton exchange membranes for high-temperature fuel cells. Attached Figure Description

[0034] Figure 1 The curves showing the change in proton conductivity of the high-temperature proton exchange membranes with temperature in Examples 1-6 and Comparative Examples 1-2 of this application are shown.

[0035] Figure 2 This is a graph showing the phosphate rejection rate of the high-temperature proton exchange membrane in Example 1 and Comparative Example 1 of this application. Detailed Implementation

[0036] The present application is described in detail below with reference to the embodiments, but the present application is not limited to these embodiments.

[0037] Unless otherwise specified, all raw materials used in the embodiments of this application were purchased through commercial channels.

[0038] The phosphoric acid absorption rate of the high-temperature proton exchange membrane was tested using a high-precision balance.

[0039] The tensile strength of high-temperature proton exchange membranes was tested using a universal testing machine.

[0040] The elongation at break of high-temperature proton exchange membranes was tested using a universal testing machine.

[0041] The proton conductivity of a high-temperature proton exchange membrane was tested using an electrochemical workstation.

[0042] In the embodiments of this application, room temperature refers to "25°C".

[0043] A method for preparing a composite high-temperature proton exchange membrane, the method comprising the following steps:

[0044] 1) The carboxyl-containing hydrogen-bonded organic framework material and polybenzimidazole were mixed in a solvent and ultrasonically dispersed to obtain a casting solution;

[0045] 2) Drop the casting solution onto the substrate and use a scraping method to evenly press the casting solution onto the substrate surface;

[0046] 3) Transfer the substrate to a vacuum oven to promote solvent evaporation and obtain a composite film;

[0047] 4) The composite membrane is immersed in a phosphoric acid solution to obtain a novel acid-base composite high-temperature proton exchange membrane.

[0048] Example 1

[0049] A method for preparing a composite high-temperature proton exchange membrane includes the following steps:

[0050] 1) Disperse 0.16g of carboxyl-containing hydrogen-bonded organic framework material I-2 in 4g of N,N-dimethylacetamide and sonicate for 1h to obtain dispersion A; disperse 0.84g of polybenzimidazole in 15g of N,N-dimethylacetamide and sonicate for 1h to obtain dispersion B; mix dispersion A and B and stir at room temperature for 24 hours to obtain casting solution;

[0051] 2) The casting solution is dropped onto the glass substrate, and the casting solution is evenly pressed onto the substrate surface using a scraping method;

[0052] 3) Transfer the substrate to an 80℃ vacuum oven to promote solvent evaporation and obtain a composite film;

[0053] 4) The composite membrane is immersed in phosphoric acid solution at 80°C for 2 days to obtain a novel acid-base composite high-temperature proton exchange membrane.

[0054] Example 2

[0055] A method for preparing a composite high-temperature proton exchange membrane includes the following steps:

[0056] 1) Disperse 0.05g of carboxyl-containing hydrogen-bonded organic framework material I-3 in 4g of N,N-dimethylformamide and sonicate for 1h to obtain dispersion A; disperse 0.95g of polybenzimidazole in 15g of N,N-dimethylacetamide and sonicate for 1h to obtain dispersion B; mix dispersions A and B and stir at room temperature for 24 hours to obtain casting solution;

[0057] 2) The casting solution is dropped onto the glass substrate, and the casting solution is evenly pressed onto the substrate surface using a scraping method;

[0058] 3) Transfer the substrate to a 60℃ vacuum oven to promote solvent evaporation and obtain a composite film;

[0059] 4) The composite membrane was immersed in a phosphoric acid solution at 60°C for 4 days to obtain a novel acid-base composite high-temperature proton exchange membrane.

[0060] Example 3

[0061] A method for preparing a composite high-temperature proton exchange membrane includes the following steps:

[0062] 1) Disperse 0.10g of carboxyl-containing hydrogen-bonded organic framework material I-4 in 2g of dimethyl sulfoxide and sonicate for 1h to obtain dispersion A; disperse 0.90g of polybenzimidazole in 7g of dimethyl sulfoxide and sonicate for 1h to obtain dispersion B; mix dispersion A and B and stir at room temperature for 24 hours to obtain casting solution.

[0063] 2) The casting solution is dropped onto the glass substrate, and the casting solution is evenly pressed onto the substrate surface using a scraping method;

[0064] 3) Transfer the substrate to a 50°C vacuum oven to promote solvent evaporation and obtain a composite film;

[0065] 4) The composite membrane is immersed in a phosphoric acid solution at 100°C for 2 days to obtain a novel acid-base composite high-temperature proton exchange membrane.

[0066] Example 4

[0067] A method for preparing a composite high-temperature proton exchange membrane includes the following steps:

[0068] 1) Disperse 0.12g of carboxyl-containing hydrogen-bonded organic framework material I-1 in 10g of N,N-dimethylformamide and sonicate for 1h to obtain dispersion A; disperse 0.88g of polybenzimidazole in 29g of dimethyl sulfoxide and sonicate for 1h to obtain dispersion B; mix dispersion A and B and stir at room temperature for 24 hours to obtain casting solution;

[0069] 2) The casting solution is dropped onto the glass substrate, and the casting solution is evenly pressed onto the substrate surface using a scraping method;

[0070] 3) Transfer the substrate to an 80℃ vacuum oven to promote solvent evaporation and obtain a composite film;

[0071] 4) The composite membrane is immersed in a phosphoric acid solution at 100°C for 2 days to obtain a novel acid-base composite high-temperature proton exchange membrane.

[0072] Example 5

[0073] A method for preparing a composite high-temperature proton exchange membrane includes the following steps:

[0074] 1) Disperse 0.03g of carboxyl-containing hydrogen-bonded organic framework material I-2 in 5g of N,N-dimethylformamide and sonicate for 1h to obtain dispersion A; disperse 0.97g of polybenzimidazole in 14g of dimethyl sulfoxide and sonicate for 1h to obtain dispersion B; mix dispersion A and B and stir at room temperature for 24 hours to obtain casting solution;

[0075] 2) The casting solution is dropped onto the glass substrate, and the casting solution is evenly pressed onto the substrate surface using a scraping method;

[0076] 3) Transfer the substrate to an 80℃ vacuum oven to promote solvent evaporation and obtain a composite film;

[0077] 4) The composite membrane is immersed in a phosphoric acid solution at 100°C for 2 days to obtain a novel acid-base composite high-temperature proton exchange membrane.

[0078] Example 6

[0079] A method for preparing a composite high-temperature proton exchange membrane includes the following steps:

[0080] 1) Disperse 0.21g of carboxyl-containing hydrogen-bonded organic framework material I-2 in 5g of N,N-dimethylformamide and sonicate for 1h to obtain dispersion A; disperse 0.79g of polybenzimidazole in 14g of dimethyl sulfoxide and sonicate for 1h to obtain dispersion B; mix dispersion A and B and stir at room temperature for 24 hours to obtain casting solution;

[0081] 2) The casting solution is dropped onto the glass substrate, and the casting solution is evenly pressed onto the substrate surface using a scraping method;

[0082] 3) Transfer the substrate to an 80℃ vacuum oven to promote solvent evaporation and obtain a composite film;

[0083] 4) The composite membrane is immersed in a phosphoric acid solution at 100°C for 2 days to obtain a novel acid-base composite high-temperature proton exchange membrane.

[0084] Comparative Example 1

[0085] A method for preparing a high-temperature proton exchange membrane, differing from Example 1 only in that it does not include a carboxyl-containing hydrogen-bonded organic framework material, specifically comprising the following steps:

[0086] 1) Disperse 1.0g of polybenzimidazole in 19g of N,N-dimethylacetamide, sonicate for 1h, and stir at room temperature for 24h to obtain casting solution;

[0087] 2) The casting solution is dropped onto the glass substrate, and the casting solution is evenly pressed onto the substrate surface using a scraping method;

[0088] 3) Transfer the matrix to an 80℃ vacuum oven to promote solvent evaporation;

[0089] 4) The membrane is immersed in a phosphoric acid solution at 80°C for 2 days to obtain a high-temperature proton exchange membrane.

[0090] Comparative Example 2

[0091] A method for preparing a high-temperature proton exchange membrane, differing from Example 4 only in that it does not include a carboxyl-containing hydrogen-bonded organic framework material, specifically comprising the following steps:

[0092] 1) 1.0 g of polybenzimidazole was dispersed in 39 g of dimethyl sulfoxide, ultrasonically dispersed for 1 h, and stirred at room temperature for 24 h to obtain the casting solution;

[0093] 2) The casting solution is dropped onto the glass substrate, and the casting solution is evenly pressed onto the substrate surface using a scraping method;

[0094] 3) Transfer the matrix to an 80℃ vacuum oven to promote solvent evaporation;

[0095] 4) The membrane is immersed in a phosphoric acid solution at 100°C for 2 days to obtain a high-temperature proton exchange membrane.

[0096] Performance Test 1

[0097] The phosphoric acid absorption rate, tensile strength, and elongation at break of the high-temperature proton exchange membranes in Examples 1-6 and Comparative Examples 1-2 (the test object was the composite membrane obtained in step 3) were tested respectively, and the test results are shown in Table 1.

[0098] Table 1

[0099] Example Phosphoric acid absorption rate / % Tensile strength / MPa Elongation at break / % Example 1 352.1 157.9 5.29 Example 2 310.9 135.2 4.82 Example 3 325.2 141.6 5.02 Example 4 332.9 149.8 5.12 Example 5 301.5 124.8 4.69 Example 6 321.2 152.8 4.36 Comparative Example 1 281.6 121.6 4.25 Comparative Example 2 252.7 112.0 3.98

[0100] Performance Test 2

[0101] The tensile strength and elongation at break of the high-temperature proton exchange membranes in Examples 1-6 and Comparative Examples 1-2 were tested respectively (the test object was the proton exchange membrane obtained in step 4), and the test results are shown in Table 2.

[0102] Table 2

[0103] Example Tensile strength / MPa Elongation at break / % Example 1 35.8 126.9 Example 2 28.6 110.2 Example 3 30.9 116.4 Example 4 32.1 121.2 Example 5 27.2 101.8 Example 6 30.2 102.9 Comparative Example 1 26.9 97.6 Comparative Example 2 23.7 92.1

[0104] Performance Test 3

[0105] The proton conductivity as a function of temperature of the high-temperature proton exchange membranes in Examples 1-6 and Comparative Examples 1-2 (the test object was the proton exchange membrane obtained in step 4) was tested respectively, and the test results are as follows: Figure 1 As shown.

[0106] From Table 1, Table 2 and Figure 1 It can be seen that the composite high-temperature proton exchange membrane provided in this application improves the phosphoric acid absorption rate, thereby improving the proton conductivity; at the same time, due to the acid-base crosslinking interaction, the dimensional stability of the composite membrane is greatly improved, thereby improving the mechanical strength. A comparison between Example 6 and Example 1 shows that as the mass ratio of the carboxyl-containing hydrogen-bonded organic framework material to polybenzimidazole increases to a certain extent, the hydrogen-bonded organic framework material is prone to agglomeration, causing a decrease in membrane quality, which in turn affects the phosphoric acid absorption rate, proton conductivity, and mechanical strength.

[0107] Performance Test 4

[0108] The phosphate rejection rate of the high-temperature proton exchange membranes prepared in Example 1 and Comparative Example 1 (the test object was the proton exchange membrane obtained in step 4) was tested respectively, and the test results are as follows: Figure 2 As shown.

[0109] from Figure 2 As can be seen, the composite high-temperature proton exchange membrane provided in this application provides additional binding forces for phosphate molecules due to the abundant hydrogen bonds in the hydrogen-bonded organic framework material, thereby significantly slowing down the loss rate of phosphate in the composite membrane.

[0110] Performance Test 5

[0111] The performance of H2 / O2 fuel cells using high-temperature proton exchange membranes in Examples 1-6 and Comparative Examples 1-2 (the test object was the proton exchange membrane obtained in step 4) was tested respectively, and the test results are shown in Table 3.

[0112] Table 3

[0113] Example <![CDATA[Peak power density (mW cm -2 )]]> Example 1 782.8 Example 2 628.1 Example 3 682.2 Example 4 728.9 Example 5 599.3 Example 6 639.9 Comparative Example 1 428.2 Comparative Example 2 412.9

[0114] As can be seen from Table 3, the ultra-high specific surface area of ​​the hydrogen-bonded organic framework material provides a huge storage space for phosphoric acid molecules, thereby improving the proton conduction performance of the composite membrane and thus improving the performance of the H2 / O2 fuel cell of the composite membrane.

[0115] The above description is merely a few embodiments of this application and is not intended to limit this application in any way. Although this application discloses preferred embodiments as described above, it is not intended to limit this application. Any changes or modifications made by those skilled in the art without departing from the scope of the technical solution of this application using the disclosed technical content are equivalent to equivalent implementation cases and all fall within the scope of the technical solution.

Claims

1. An acid-base composite high-temperature proton exchange membrane, characterized in that, The acid-base composite high-temperature proton exchange membrane is made by cross-linking a carboxyl-containing hydrogen-bonded organic framework material with polybenzimidazole acid and base, followed by immersion in phosphoric acid. The carboxyl-containing hydrogen-bonded organic framework material is selected from one of the structures shown in Formula I-1 and Formula I-2; Equation I-1, Equation I-2; The mass ratio of the carboxyl-containing hydrogen-bonded organic framework material to polybenzimidazole is 3:97~21:

79.

2. The method for preparing the acid-base composite high-temperature proton exchange membrane according to claim 1, characterized in that, The preparation method includes the following steps: (1) A mixture of carboxyl-containing hydrogen-bonded organic framework material, polybenzimidazole, and solvent is ultrasonically dispersed to obtain a casting solution; (2) The casting film is pressed onto the substrate surface by scraping method, dried and soaked in phosphoric acid to obtain the acid-base composite high-temperature proton exchange membrane.

3. The preparation method according to claim 2, characterized in that, In the casting solution, the sum of the mass fractions of the carboxyl-containing hydrogen-bonded organic framework material and polybenzimidazole is 2.5-10%.

4. The preparation method according to claim 2, characterized in that, The solvent is selected from at least one of N,N-dimethylacetamide, N,N-dimethylformamide, and dimethyl sulfoxide.

5. The preparation method according to claim 2, characterized in that, The ultrasonic dispersion time is 4~12h.

6. The preparation method according to claim 2, characterized in that, The substrate is a glass substrate.

7. The preparation method according to claim 2, characterized in that, The drying temperature is 50~80℃.

8. The preparation method according to claim 2, characterized in that, The soaking temperature is 60~100℃, and the soaking time is 2~4 days.

9. The application of the acid-base composite high-temperature proton exchange membrane according to claim 1 in a fuel cell, characterized in that, The working temperature of the acid-base composite high-temperature proton exchange membrane is 100~200℃.

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