Proton exchange membrane and preparation method and application thereof

Abstract

The invention relates to the technical field of fuel cells, in particular to a proton exchange membrane as well as a preparation method and application thereof. The preparation raw materials comprise polybenzimidazole powder, polyvinyl alcohol, phosphoric acid, a cross-linking agent and a solvent, and the addition amount of the polyvinyl alcohol is 10-30 wt% of the polybenzimidazole powder. According to the invention, polybenzimidazole powder and phosphoric acid are taken as phosphorylation reagents, polyvinyl alcohol is taken as a functional group introduction reagent, and through chemical modification and introduction of a flexible side chain, the proton conduction performance and mechanical strength of the proton exchange membrane are remarkably improved, and the proton exchange membrane is especially excellent in performance under low-humidity and high-temperature conditions; the invention is applicable to fuel cells.

Description

Technical Field

[0001] The present invention relates to the technical field of fuel cells, and specifically, to a proton exchange membrane, a preparation method thereof, and an application thereof. Background Art

[0002] As a clean energy technology with high efficiency, no pollution emissions, and a silent characteristic, hydrogen fuel cells exhibit significant advantages in the application scenario of new energy vehicles. However, during the actual operation of fuel cells, they need to experience frequent severe temperature fluctuations and periodic humidity changes. Such extreme working conditions can cause irreversible structural damage to the proton exchange membrane, thereby shortening the service life of the fuel cell stack. Especially when the working environment reaches the harsh conditions of high temperature (>105°C) and low humidity, there are still significant technical bottlenecks in the mechanical strength and proton conduction efficiency of existing proton exchange membrane materials, and there is an urgent need to develop a new generation of high-performance membrane materials. Although the current mainstream perfluorosulfonic acid-based proton exchange membranes have excellent conductivity under high humidity conditions (>193 mS / cm, 80°C / 95% RH), under low humidity or high temperature working conditions, due to the conformational change of hydrophilic groups and the breakage of the hydration network, their proton conductivity will drop sharply.

[0003] Chinese invention patent CN107834089B discloses a polyvinyl alcohol-phosphorylated chitosan composite membrane for high-temperature proton exchange membrane fuel cells, and provides a preparation method and an application of the above composite membrane. The film-forming raw materials of the proton exchange membrane include polyvinyl alcohol and phosphorylated chitosan. Phosphorylated chitosan (PCS) and polyvinyl alcohol (PVA) are chemically crosslinked to prepare a high-performance composite membrane. As a potential blend polymer, PVA has high hydrophilicity, strong water permeability, and low alcohol exchangeability, and can be used to improve the mechanical, chemical, and electrochemical properties of the PCS proton exchange membrane. By chemically crosslinking PVA and PCS with a crosslinking agent glutaraldehyde, the hydroxyl groups of PVA and the amino groups and hydroxyl groups of PCS form strong chemical bonds, further improving the conductivity and mechanical properties of the composite membrane, but the high-temperature resistance needs to be improved. Summary of the Invention

[0004] In a first aspect of the present invention, a proton exchange membrane is provided, and the preparation raw materials include: polybenzimidazole powder, polyvinyl alcohol, phosphoric acid, a crosslinking agent, and a solvent. The addition amount of the polyvinyl alcohol is 10-30 wt% of the polybenzimidazole powder.

[0005] Optionally, the addition amount of the polyvinyl alcohol is 15-25 wt% of the polybenzimidazole powder.

[0006] The mass ratio of the polybenzimidazole powder to the crosslinking agent is 10:(0.1-2).

[0007] Optionally, the mass ratio of the polybenzimidazole powder to the crosslinking agent is 10:(0.3-1).

[0008] The degree of polymerization of the polyvinyl alcohol is 1600 - 2500.

[0009] Optionally, the degree of polymerization of the polyvinyl alcohol is 1600 - 2000.

[0010] The mass - to - volume ratio of the polybenzimidazole powder to phosphoric acid is 1 g:(8 - 15) mL.

[0011] Optionally, the mass - to - volume ratio of the polybenzimidazole powder to phosphoric acid is 1 g:(8 - 12) mL.

[0012] The cross - linker includes at least one of glutaraldehyde, glyoxal, and formaldehyde.

[0013] The solvent includes at least one of γ - valerolactone, N,N - dimethylformamide, N - methylpyrrolidone, and dimethyl sulfoxide.

[0014] The second aspect of the present invention provides a method for preparing a proton exchange membrane, comprising the following steps: mixing polybenzimidazole powder and phosphoric acid, performing a phosphorylation reaction, and obtaining phosphorylated polybenzimidazole through post - treatment; stirring and mixing the phosphorylated polybenzimidazole, polyvinyl alcohol, and a solvent, adding a cross - linker, and performing a cross - linking reaction to obtain a mixed solution; casting the mixed solution into a film, drying it, and then obtaining the proton exchange membrane through heat treatment.

[0015] By limiting the addition amount of polyvinyl alcohol to 10 - 30 wt% of the polybenzimidazole powder, the present invention can effectively improve the proton conductivity. After mixing polyvinyl alcohol with phosphorylated polybenzimidazole, a more uniform phosphoric acid adsorption network may be formed, enhancing the continuity of the proton transport channels, thereby improving the proton conductivity. Generally, a high phosphoric acid loading weakens the intermolecular interaction of polybenzimidazole molecular chains. Further research in the present invention finds that the mass ratio of the polybenzimidazole powder to the cross - linker is 10:(0.1 - 2), which can effectively balance the mechanical properties and conductive properties of the proton exchange membrane. It may be that the cross - linker and polyvinyl alcohol act synergistically to form a three - dimensional cross - linked structure with a specific structure, effectively reducing the loss of phosphoric acid, maintaining the mechanical properties of the membrane, and simultaneously enhancing the proton conductivity.

[0016] The degree of phosphorylation of the phosphorylated polybenzimidazole is 50 - 70%.

[0017] The temperature of the stirring and mixing is 80 - 100 °C, and the time is 2 - 5 h.

[0018] Optionally, the temperature of the stirring and mixing is 85 - 95 °C, and the time is 3 - 5 h.

[0019] The temperature of the phosphorylation reaction is 80 - 120 °C, and the time is 4 - 8 h.

[0020] The content of the solvent in the mixed solution is 88-92 wt%.

[0021] The drying temperature is 80-100 °C and the time is 20-30 h.

[0022] The thickness of the cast film is 50-100 μm.

[0023] Optionally, the thickness of the cast film is 50-80 μm.

[0024] The third aspect of the present invention provides an application of a method for preparing a proton exchange membrane, which is applied to the preparation of a fuel cell.

[0025] Beneficial effects

[0026] 1. By limiting the addition amount of polyvinyl alcohol to 10-30 wt% of the polybenzimidazole powder, the proton conductivity can be effectively improved.

[0027] 2. The degree of polymerization of polyvinyl alcohol is 1800-2500, which can improve the elongation at break and thermal properties of the proton exchange membrane.

[0028] 3. The mass ratio of polybenzimidazole powder to crosslinking agent is 10:(0.1-2), which can effectively balance the mechanical properties and conductive properties of the proton exchange membrane.

[0029] 4. The mass-volume ratio of polybenzimidazole powder to phosphoric acid is 1 g:(8-15) mL, which can improve the performance of the proton exchange membrane under low humidity and high temperature conditions.

[0030] 5. The degree of phosphorylation of phosphorylated polybenzimidazole is 50-70%, which can increase the thermal decomposition temperature of the proton exchange membrane to

[0031] above 270 °C. Specific embodiments

[0032] Example 1

[0033] A proton exchange membrane, the preparation raw materials: polybenzimidazole powder (U60, manufacturer: Changzhou Puwei), polyvinyl alcohol (1799, manufacturer: Anhui Wanwei), phosphoric acid (concentration: 85 wt%), crosslinking agent (glutaraldehyde) and solvent (dimethyl sulfoxide), the addition amount of polyvinyl alcohol is 20 wt% of the polybenzimidazole powder; the mass ratio of polybenzimidazole powder to crosslinking agent is 10:0.5; the mass-volume ratio of polybenzimidazole powder to phosphoric acid is 1 g:10 mL.

[0034] A method for preparing a proton exchange membrane: Mix 1 g of polybenzimidazole powder with phosphoric acid and carry out a phosphorylation reaction. After the reaction is completed, slowly pour the mixture into methanol for precipitation, filter and wash with deionized water until neutral, and then dry in vacuum at 60 °C for 24 h to obtain phosphorylated polybenzimidazole (phosphorylation degree 60%); Stir and mix phosphorylated polybenzimidazole, polyvinyl alcohol and 100 mL of solvent, add a crosslinking agent, and carry out a crosslinking reaction for 1 h to obtain a mixed solution; Cast the mixed solution into a film and dry in vacuum at 90 °C for 24 h to obtain a film with a thickness of about 70 μm, and obtain a proton exchange membrane through heat treatment (120 °C, 2 h); The temperature of the stirring and mixing is 90 °C and the time is 4 h.

[0035] The phosphorylation degree is calculated by the mass difference method: (m2 - m1) / m1 × 100%

[0036] m1: The mass before phosphorylation: 1 g;

[0037] m2: The mass after phosphorylation: 1.6 g;

[0038] Phosphorylation degree: (1.6 - 1) / 1 × 100% = 60%.

[0039] Example 2

[0040] The specific implementation method is the same as that of Example 1; The difference is that in Example 2: The mass ratio of the polybenzimidazole powder to the crosslinking agent is 10:1; The temperature of the stirring and mixing is 95 °C.

[0041] Example 3

[0042] The specific implementation method is the same as that of Example 1; The difference is that in Example 3: The mass ratio of the polybenzimidazole powder to the crosslinking agent is 10:0.3; The temperature of the stirring and mixing is 85 °C.

[0043] Example 4

[0044] The specific implementation method is the same as that of Example 1; The difference is that in Example 4: The mass ratio of the polybenzimidazole powder to the crosslinking agent is 10:0.3; The temperature of the stirring and mixing is 95 °C.

[0045] Example 5

[0046] The specific implementation method is the same as that of Example 1; The difference is that in Example 5: The mass ratio of the polybenzimidazole powder to the crosslinking agent is 10:1; The temperature of the stirring and mixing is 85 °C.

[0047] Performance test method

[0048] Perform performance tests on the proton exchange membranes prepared in the examples, and the test data are listed in Table 1.

[0049] Refer to GB / T 20042.3-2022: The new standard for testing proton exchange membranes of fuel cells, and test the proton conductivity (120 °C, 30% RH), thermal stability (thermal decomposition temperature), and mechanical strength (tensile strength, elongation at break).

[0050] Performance test data

[0051] Table 1

[0052]

Claims

1. A proton exchange membrane, characterized in that, The preparation raw materials include: polybenzimidazole powder, polyvinyl alcohol, phosphoric acid, a crosslinking agent and a solvent, and the addition amount of the polyvinyl alcohol is 10-30 wt% of the polybenzimidazole powder.

2. The proton exchange membrane according to claim 1, wherein The mass ratio of the polybenzimidazole powder to the crosslinking agent is 10:(0.3-1).

3. The proton exchange membrane according to claim 1, characterized in that, The degree of polymerization of the polyvinyl alcohol is 1600-2500.

4. The proton exchange membrane according to claim 1, wherein The mass-volume ratio of the polybenzimidazole powder to the phosphoric acid is 1 g:(8-15) mL.

5. A method for preparing a proton exchange membrane according to claim 2, characterized in that, It includes the following steps: Mix the polybenzimidazole powder and the phosphoric acid, carry out a phosphorylation reaction, and obtain phosphorylated polybenzimidazole through post-treatment; stir and mix the phosphorylated polybenzimidazole, polyvinyl alcohol and the solvent, add the crosslinking agent, and carry out a crosslinking reaction to obtain a mixed solution; cast the mixed solution into a film, and after drying, obtain a proton exchange membrane through heat treatment.

6. The preparation method of the proton exchange membrane according to claim 5, characterized in that, The temperature of the stirring and mixing is 85-95 °C, and the time is 3-5 h.

7. The preparation method of the proton exchange membrane according to claim 6, wherein The temperature of the phosphorylation reaction is 80-120 °C, and the time is 4-8 h.

8. The preparation method of the proton exchange membrane according to claim 7, wherein The content of the solvent in the mixed solution is 88-92 wt%.

9. The preparation method of the proton exchange membrane according to claim 8, characterized in that, The thickness of the film casting is 50-100 μm.

10. An application of the method for preparing a proton exchange membrane according to any one of claims 5-9, characterized in that, It is applied to the preparation of fuel cells.

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