Proton exchange membrane with composite structure and preparation method of proton exchange membrane

Abstract

The invention relates to the technical field of proton exchange membranes, and provides a composite structure proton exchange membrane and a preparation method thereof. The proton exchange membrane with the composite structure is obtained by casting hybrid proton exchange membrane slurry on a diaphragm, and the hybrid proton exchange membrane slurry is prepared from the following raw materials in percentage by weight: 0.1-1% of lithium niobate, 4-6% of perfluorosulfonic acid powder and 93-95% of a solvent, the tensile strength of the proton exchange membrane with the composite structure is 30.0 MPa or above, and the proton conductivity is 0.168 S cm <-1 > or above. According to the technical scheme, the problems of poor mechanical strength and stability of the proton exchange membrane under the condition of good proton conductivity in the prior art are solved.

Description

Technical Field

[0001] This invention relates to the field of proton exchange membrane technology, specifically to a composite structure proton exchange membrane and its preparation method. Background Technology

[0002] Proton exchange membrane fuel cells (PEMFCs) generally consist of an electrolyte, a cathode and an anode, and a Pt / C catalyst. The cathode and anode are typically metal plates with gas flow channels, and the electrolyte is usually a proton exchange membrane (PEM). The proton exchange membrane is the most crucial core component of PEMFCs, playing a vital role in the entire battery operation. The proton exchange membrane is typically an organic electrolyte membrane with cation exchange groups, with a thickness usually between 10 and 200 µm. While the widely used perfluorosulfonic acid proton exchange membrane exhibits excellent proton conductivity under low temperature and high humidity conditions, it still has several drawbacks, including high manufacturing cost, insufficient dimensional stability, low mechanical strength, and poor chemical stability.

[0003] Therefore, developing a proton exchange membrane that has good proton conductivity, as well as good mechanical strength and stability is of great significance for extending the service life of proton exchange membranes. Summary of the Invention

[0004] This invention proposes a composite proton exchange membrane and its preparation method, which solves the problem of poor mechanical strength and stability of proton exchange membranes in related technologies even when the proton conductivity is good.

[0005] The technical solution of the present invention is as follows: This invention proposes a composite proton exchange membrane, obtained by casting a hybrid proton exchange membrane slurry onto a diaphragm. The raw materials of the hybrid proton exchange membrane slurry are composed of the following components by weight percentage: Lithium niobate 0.1%~1%, perfluorosulfonic acid powder 4%~6%, solvent 93%~95%; The composite proton exchange membrane has a tensile strength of over 30.0 MPa and a proton conductivity of 0.168 S cm⁻¹. -1 above.

[0006] As a further technical solution, the solvent includes one or more of N-methylpyrrolidone, dimethyl sulfoxide, and N,N-dimethylformamide, preferably N-methylpyrrolidone.

[0007] As a further technical solution, the diaphragm is a polyethylene terephthalate diaphragm.

[0008] In this invention, polyethylene terephthalate membrane serves as the base membrane for the composite proton exchange membrane, providing excellent skeletal support and thus endowing the composite proton exchange membrane with good mechanical strength.

[0009] This invention proposes a method for preparing a composite proton exchange membrane, comprising the following steps: S1. Mix the lithium niobate, perfluorosulfonic acid powder and solvent evenly to obtain a hybrid proton exchange membrane slurry; S2. Immerse the diaphragm in a buffer solution, remove it, and dry it to obtain a pretreated diaphragm. S3. Cast the hybrid proton exchange membrane slurry onto the pretreated diaphragm on one or both sides, dry it, and then perform post-treatment to obtain the composite structure proton exchange membrane.

[0010] As a further technical solution, in step S1, when the mixture is homogeneous, the temperature is 140~160℃, for example, 140℃, 145℃, 150℃, 155℃, 160℃, preferably 150℃; the stirring speed is 400~600r / min, for example, 400r / min, 450r / min, 500r / min, 550r / min, 600r / min, preferably 500r / min; and the time is 3.5~4.5h, for example, 3.5h, 4h, 4.5h, preferably 4h.

[0011] As a further technical solution, the buffer solution is a TA-Tris buffer solution, the pH value of the TA-Tris buffer solution is 7.5~9.5, for example, it can be 7.5, 8, 9.5, preferably 8, and the molar concentration of TA in the TA-Tris buffer solution is 0.5~2M, for example, it can be 0.5M, 1M, 1.5M, preferably 1.5M.

[0012] In this invention, the TA-Tris buffer is a tannic acid-tris(hydroxymethyl)aminomethane buffer. The preparation method of the TA-Tris buffer is as follows: pour TA powder into the Tris buffer and stir at 350 r / min for 3 h to mix it evenly to obtain the TA-Tris buffer.

[0013] In this invention, a polyethylene terephthalate (PET) membrane is immersed in a trimethylolaminomethane buffer solution containing tannic acid. The hydrogen bonds and van der Waals forces of tannic acid can be used to modify the PET membrane. The presence of tannic acid can enhance the hydrophilicity of the PET membrane, and the phenolic hydroxyl groups in tannic acid can form hydrogen bonds with the perfluorosulfonic acid powder in the hybrid proton exchange membrane slurry, which facilitates the effective bonding of the membrane and slurry components, thereby improving the interfacial stability of the overall composite proton exchange membrane.

[0014] As a further technical solution, in step S2, when immersing in the buffer solution, the temperature is 30~50℃, for example, it can be 30℃, 35℃, 40℃, 45℃, or 50℃, preferably 40℃, and the time is 1~3h, for example, it can be 1h, 2h, or 3h, preferably 2h.

[0015] As a further technical solution, in step S2, the drying temperature is 40~65℃, for example, 40℃, 45℃, 50℃, 55℃, 60℃, or 65℃, preferably 60℃, and the time is 4~6h, for example, 4h, 5h, or 6h, preferably 5h.

[0016] As a further technical solution, in step S3, the casting amount of the hybrid proton exchange membrane slurry is 0.1~0.2 g / cm³. 2 ; The drying process is divided into a first drying and a second drying. The temperature of the first drying is 60~90℃, for example, 60℃, 70℃, 80℃, 90℃, preferably 80℃, and the time is 10~14h, for example, 10h, 11h, 12h, 13h, 14h, preferably 12h; The temperature for the second drying is 110~130℃, for example, 110℃, 115℃, 120℃, 125℃, or 130℃, preferably 120℃, and the time is 1~2h, for example, 1h, 1.5h, or 2h, preferably 1.5h.

[0017] As a further technical solution, in step S3, the specific process of the post-processing is as follows: the diaphragm is soaked in sulfuric acid and hydrogen peroxide in sequence, taken out, cleaned, soaked in deionized water, and dried.

[0018] As a further technical solution, when soaking in sulfuric acid, hydrogen peroxide, or deionized water, the temperature is independently 60~90℃, for example, 60℃, 70℃, 80℃, or 90℃, preferably 80℃, and the time is independently 0.5~1.5h, for example, 0.5h, 1h, or 1.5h, preferably 1h.

[0019] As a further technical solution, the concentration of the sulfuric acid is 0.5~1.2 mol / L, for example, it can be 0.5 mol / L, 0.8 mol / L, 1 mol / L, 1.2 mol / L, preferably 1 mol / L, and the mass fraction of the hydrogen peroxide is 2.5%~3.5%, for example, it can be 2.5%, 3%, 3.5%, preferably 3%.

[0020] As a further technical solution, in the specific process of post-processing, the drying temperature is 60~90℃, for example, 60℃, 70℃, 80℃, 90℃, preferably 80℃, and the time is 10~14h, for example, 10h, 11h, 12h, 13h, 14h, preferably 12h.

[0021] The working principle and beneficial effects of this invention are as follows: In the composite proton exchange membrane of this invention, a diaphragm is used as the base membrane to provide skeletal support. A hybrid proton exchange membrane slurry is cast onto the diaphragm to prepare a structurally stable composite proton exchange membrane. The hybrid proton exchange membrane slurry incorporates lithium niobate and perfluorosulfonic acid powder. The phosphate groups of lithium niobate and the sulfonic acid groups of the perfluorosulfonic acid powder interact to form continuous proton channels, effectively enhancing the proton transport performance of the composite proton exchange membrane. Furthermore, by combining lithium niobate, perfluorosulfonic acid powder, and the skeletal base membrane, the mechanical strength and structural stability of the composite proton exchange membrane are significantly improved while maintaining its good electrical conductivity. Attached Figure Description

[0022] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0023] Figure 1 This is a cross-sectional electron microscope image of the composite proton exchange membrane prepared in Example 3 of the present invention; Figure 2 This is a cross-sectional electron microscope image of the composite proton exchange membrane prepared in Example 7 of the present invention. Detailed Implementation

[0024] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0025] In the following examples and comparative examples, lithium niobate with a purity of 99%; perfluorosulfonic acid powder with a purity of 98% was purchased from Wuhan Lanabai Pharmaceutical Chemical Co., Ltd.; and N-methylpyrrolidone with a purity of 99.5% was purchased from Tianjin Hengxing Chemical Reagent Manufacturing Co., Ltd. The preparation method of TA-Tris buffer is as follows: pour TA powder into Tris buffer and stir at 350 r / min for 3 h to mix it evenly to obtain TA-Tris buffer; the pH value of TA-Tris buffer is 8, and the molar concentration of TA in TA-Tris buffer is 1.5M.

[0026] Example 1 The raw materials for hybrid proton exchange membrane slurries consist of the following components by weight percentage: Lithium niobate 0.1%, perfluorosulfonic acid powder 5%, N-methylpyrrolidone 94.9%; A method for preparing a composite proton exchange membrane includes the following steps: S1. Lithium niobate, perfluorosulfonic acid powder and N-methylpyrrolidone were stirred in a high-temperature reactor at 150°C at a stirring speed of 500 r / min for 4 h to obtain a hybrid proton exchange membrane slurry. S2. Immerse the polyethylene terephthalate membrane in TA-Tris buffer (TA-Tris buffer pH value is 8, and the molar concentration of TA in TA-Tris buffer is 1.5M) at 40℃ for 2 hours, remove it, and dry it at 60℃ for 5 hours to obtain the pretreated membrane. S3. The above-mentioned hybrid proton exchange membrane slurry is prepared at a concentration of 0.15 g / cm³. 2 The casting volume was cast onto a pretreated diaphragm on one side, dried at 80℃ for 12 hours, and then dried at 120℃ for 1.5 hours. The dried diaphragm was then immersed in 1 mol / L sulfuric acid at 80℃ for 1 hour, and then in 3% hydrogen peroxide at 80℃ for 1 hour. After removal, it was washed with deionized water, then soaked in deionized water at 80℃ for 1 hour, removed, and finally dried at 80℃ for 12 hours to obtain a composite proton exchange membrane.

[0027] Example 2 The only difference between this embodiment and Embodiment 1 is that, in this embodiment, the raw material of the hybrid proton exchange membrane slurry is composed of the following components by weight percentage: Lithium niobate 0.3%, perfluorosulfonic acid powder 5%, N-methylpyrrolidone 94.7%.

[0028] Example 3 The only difference between this embodiment and Embodiment 1 is that, in this embodiment, the raw material of the hybrid proton exchange membrane slurry is composed of the following components by weight percentage: Lithium niobate 0.6%, perfluorosulfonic acid powder 5%, N-methylpyrrolidone 94.4%; The cross-sectional electron microscope image of the composite proton exchange membrane prepared in Example 3 is shown below. Figure 1 As shown.

[0029] Example 4 The only difference between this embodiment and Embodiment 1 is that, in this embodiment, the raw material of the hybrid proton exchange membrane slurry is composed of the following components by weight percentage: Lithium niobate 0.9%, perfluorosulfonic acid powder 5%, N-methylpyrrolidone 94.1%.

[0030] Example 5 The raw materials for hybrid proton exchange membrane slurries consist of the following components by weight percentage: Lithium niobate 1%, perfluorosulfonic acid powder 4%, N-methylpyrrolidone 95%; A method for preparing a composite proton exchange membrane includes the following steps: S1. Lithium niobate, perfluorosulfonic acid powder and N-methylpyrrolidone were stirred in a high-temperature reactor at 140°C at a stirring speed of 400 r / min for 4.5 h to obtain a hybrid proton exchange membrane slurry. S2. Immerse the polyethylene terephthalate membrane in TA-Tris buffer (TA-Tris buffer pH value is 8, and the molar concentration of TA in TA-Tris buffer is 1.5M) at 30℃ for 3h, take it out, and dry it at 60℃ for 5h to obtain the pretreated membrane. S3. The above-mentioned hybrid proton exchange membrane slurry is prepared at a concentration of 0.1 g / cm³. 2 The casting volume was cast onto a pretreated diaphragm on one side, dried at 60℃ for 14 hours, and then dried at 110℃ for 2 hours. The dried diaphragm was then immersed in 1.2 mol / L sulfuric acid at 60℃ for 1.5 hours, and then in 3% hydrogen peroxide at 60℃ for 1.5 hours. After removal, it was washed with deionized water, then immersed in deionized water at 60℃ for 1.5 hours, removed, and finally dried at 60℃ for 14 hours to obtain a composite proton exchange membrane.

[0031] Example 6 The raw materials for hybrid proton exchange membrane slurries consist of the following components by weight percentage: Lithium niobate 1%, perfluorosulfonic acid powder 6%, N-methylpyrrolidone 93%; A method for preparing a composite proton exchange membrane includes the following steps: S1. Lithium niobate, perfluorosulfonic acid powder and N-methylpyrrolidone were stirred in a high-temperature reactor at 160°C at a stirring speed of 600 r / min for 3.5 h to obtain a hybrid proton exchange membrane slurry. S2. Immerse the polyethylene terephthalate membrane in TA-Tris buffer (TA-Tris buffer pH value is 8, and the molar concentration of TA in TA-Tris buffer is 1.5M) at 50℃ for 1 hour, remove it, and dry it at 60℃ for 5 hours to obtain the pretreated membrane. S3. The above-mentioned hybrid proton exchange membrane slurry is prepared at a concentration of 0.2 g / cm³. 2 The casting volume was cast onto a pretreated diaphragm on one side, dried at 90℃ for 10 hours, and then dried at 130℃ for 1 hour. The dried diaphragm was then immersed in 0.5 mol / L sulfuric acid at 90℃ for 0.5 hours, and then in 3% hydrogen peroxide at 90℃ for 0.5 hours. After removal, it was washed with deionized water, then immersed in deionized water at 90℃ for 0.5 hours, removed, and finally dried at 90℃ for 10 hours to obtain a composite proton exchange membrane.

[0032] Example 7 The only difference between this embodiment and Embodiment 3 is the preparation method of the comparative example composite proton exchange membrane, which is different. Specifically: S1. Lithium niobate, perfluorosulfonic acid powder and N-methylpyrrolidone were stirred in a high-temperature reactor at 150°C at a stirring speed of 500 r / min for 4 h to obtain a hybrid proton exchange membrane slurry. S2. The above-mentioned hybrid proton exchange membrane slurry is prepared at a concentration of 0.15 g / cm³. 2 The casting volume was cast on one side of a polyethylene terephthalate membrane, dried at 80℃ for 12 hours, and then dried at 120℃ for 1.5 hours. The dried membrane was then immersed in 1 mol / L sulfuric acid at 80℃ for 1 hour, and then in 3% hydrogen peroxide at 80℃ for 1 hour. After removal, it was washed with deionized water, then immersed in deionized water at 80℃ for 1 hour, removed, and finally dried at 80℃ for 12 hours to obtain a composite proton exchange membrane. The cross-sectional electron microscope image of the composite proton exchange membrane prepared in Example 7 is shown below. Figure 2 As shown.

[0033] Example 8 The only difference between this embodiment and Embodiment 3 is the preparation method of the comparative example composite proton exchange membrane, which is different. Specifically: S1. Lithium niobate, perfluorosulfonic acid powder and N-methylpyrrolidone were stirred in a high-temperature reactor at 150°C at a stirring speed of 500 r / min for 4 h to obtain a hybrid proton exchange membrane slurry. S2. Immerse the polyethylene terephthalate membrane in a phosphate buffer solution at 40°C for 3 hours, remove it, and dry it to obtain the pretreated membrane. S3. The above-mentioned hybrid proton exchange membrane slurry is prepared at a concentration of 0.15 g / cm³. 2 The casting volume was cast onto a pretreated diaphragm on one side, dried at 80℃ for 12 hours, and then dried at 120℃ for 1.5 hours. The dried diaphragm was then immersed in 1 mol / L sulfuric acid at 80℃ for 1 hour, and then in 3% hydrogen peroxide at 80℃ for 1 hour. After removal, it was washed with deionized water, then soaked in deionized water at 80℃ for 1 hour, removed, and finally dried at 80℃ for 12 hours to obtain a composite proton exchange membrane.

[0034] Comparative Example 1 The only difference between this comparative example and Example 3 is that lithium niobate was not added in this comparative example.

[0035] Comparative Example 2 The only difference between this comparative example and Example 3 is that lithium niobate is replaced with an equal amount of lithium tantalate in this comparative example.

[0036] Experimental Example The composite proton exchange membranes prepared in Examples 1-8 and Comparative Examples 1-2 were subjected to performance testing according to the following methods: (1) Mechanical property test: The composite proton exchange membrane was made into a rectangular strip with a length of 65 mm and a width of 15 mm. The tensile strength was tested using a universal tensile testing machine. During the test, the tensile speed was set to 5 mm / min and the original gauge length was 20 mm. The tensile strength was calculated by the following formula: In the formula, σ1 is the tensile strength (MPa), p is the maximum load (N), b is the width of the rectangular spline (mm), and d is the thickness of the rectangular spline (mm), with a thickness of 42μm.

[0037] (2) Proton conductivity test: The proton conductivity of the composite structure proton exchange membrane sample was tested at a temperature of 25℃ and a humidity of 100% RH.

[0038] (3) Water absorption rate test: The proton exchange membrane was dried in an oven at 80℃±2℃ for 24h, then removed and air-dried to room temperature. The mass of the composite proton exchange membrane was measured as m0 (g). The composite proton exchange membrane was then soaked in distilled water at 80℃ for 8h. The water on the surface of the composite proton exchange membrane was removed with filter paper. The mass of the proton exchange membrane was measured as m1 (g) within 30s. The water absorption rate Δm was calculated by the following formula: .

[0039] (4) Hydrolytic stability: A pre-dried composite proton exchange membrane with a mass of Wo (g) was immersed in deionized water at 80℃ for 48h. After immersion, the composite proton exchange membrane was dried at 80℃ for 8h and its mass was measured as Wt (g). The hydrolytic stability Wc value of the composite proton exchange membrane was calculated by the following formula: .

[0040] The test results are shown in Table 1: Table 1 Performance test results of the composite proton exchange membranes of Examples 1-8 and Comparative Examples 1-2

[0041] As can be seen from Table 1, compared with Comparative Examples 1-2, the composite proton exchange membranes prepared in Examples 1-6 have good mechanical properties, proton conductivity, water absorption rate, and hydrolytic stability. This indicates that in this invention, using polyethylene terephthalate membrane as the base membrane and simultaneously casting a hybrid proton exchange membrane slurry containing lithium niobate and perfluorosulfonic acid powder on the base membrane can form a stable interfacial transition layer, thus forming a stable composite proton exchange membrane. While maintaining good conductivity, it can improve the mechanical strength of the proton exchange membrane.

[0042] Comparing Example 3 with Examples 6-7 Figure 1 and Figure 2 In comparison, the composite proton exchange membrane prepared in Example 3 showed improved tensile strength, proton conductivity, and hydrolytic stability, while its end-face structure was more regular and stable. This indicates that treating the polyethylene terephthalate membrane with TA-Tris buffer can introduce tannic acid into the polyethylene terephthalate membrane, which is beneficial to the bonding between the polyethylene terephthalate membrane and the hybrid proton exchange membrane slurry, enhances the interfacial contact ability, and thus improves the overall mechanical strength of the composite proton exchange membrane.

[0043] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A composite structure proton exchange membrane obtained by casting a hybrid proton exchange membrane paste on a separator, characterized in that, The raw material of the hybrid proton exchange membrane slurry is composed of the following components in weight percentage: 0.1%~1% lithium niobate, 4%~6% perfluorosulfonic acid powder, 93%~95% solvent; The composite structure proton exchange membrane has a tensile strength of 30.0 MPa or more and a proton conductivity of 0.168 S cm -1 The above.

2. The composite structure proton exchange membrane according to claim 1, wherein, The solvent includes one or more of N-methyl pyrrolidone, dimethyl sulfoxide, N,N-dimethylformamide.

3. The composite structure proton exchange membrane according to claim 1, wherein, The diaphragm is a polyethylene terephthalate diaphragm.

4. A method for preparing a composite structured proton exchange membrane according to any one of claims 1 to 3, characterized in that The method comprises the following steps: S1, uniformly mix the lithium niobate, perfluorosulfonic acid powder and solvent to obtain a hybrid proton exchange membrane slurry; S2, immerse the diaphragm in a buffer solution, take it out, dry it to obtain a pretreated diaphragm; S3, one-sided or double-sided casting the hybrid proton exchange membrane slurry on the pretreated diaphragm, drying, post-processing to obtain the composite structure proton exchange membrane.

5. The method of claim 4, wherein the composite structure proton exchange membrane is prepared by the steps of: In step S1, when the mixture is uniformly mixed, the temperature is 140~160℃, the stirring speed is 400~600r / min, and the time is 3.5~4.5h.

6. The method of claim 4, wherein the composite structure proton exchange membrane is prepared by the steps of: The buffer solution is TA-Tris buffer solution, the pH value of the TA-Tris buffer solution is 7.5~9.5, and the molar concentration of TA in the TA-Tris buffer solution is 0.5~2M.

7. The method of claim 4, wherein the composite structure proton exchange membrane is prepared by the steps of: In step S2, when the diaphragm is immersed in the buffer solution, the temperature is 30~50℃, and the time is 1~5h.

8. The method of claim 4, wherein the composite structure proton exchange membrane is prepared by the steps of: In step S3, the casting amount of the hybrid proton exchange membrane slurry is 0.1-0.2 g / cm2 during casting. 2 ; When drying, it is divided into first drying and second drying; The temperature of the first drying is 60~90℃, and the time is 10~14h; The temperature of the second drying is 110~130℃, and the time is 1~2h.

9. The method for preparing a composite proton exchange membrane according to claim 4, characterized in that, In step S3, the specific process of post-processing is: immerse the diaphragm in sulfuric acid, hydrogen peroxide in turn, take it out, clean it, then immerse it in deionized water, and dry it.

10. The method of claim 9, wherein the composite structure proton exchange membrane is prepared by the steps of: When immersed in sulfuric acid, hydrogen peroxide and deionized water, the temperature is independently 60~90℃, and the time is independently 0.5~1.5h.

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