A method for preparing a proton exchange membrane

Abstract

This invention provides a method for preparing a proton exchange membrane, comprising the following steps: mixing SPEEK-Na at a certain mass ratio... + Dissolve ABPBI in a mixed solvent and stir. The mixed solvent makes SPEEK-Na + SPEEK and ABPBI are dissolved simultaneously to form a homogeneous polymer mixture with a certain mass fraction. The homogeneous polymer mixture is then subjected to material molding to obtain an intermediate product. This intermediate product is subsequently post-treated in hydrogen peroxide solution, deionized water, and dilute sulfuric acid solution, and then washed with deionized water until neutral to obtain a SPEEK / ABPBI proton exchange membrane. This invention allows for the simultaneous dissolution of SPEEK and ABPBI in a solvent, followed by material molding and post-treatment to obtain a composite proton exchange membrane composed of SPEEK and ABPBI. The process is simple and easy to operate. The resulting composite membrane exhibits excellent mechanical strength, proton conductivity, and water absorption / retention and acid absorption / storage capabilities, demonstrating superior proton conductivity.

Description

Technical Field

[0001] This invention relates to polymer materials, and more specifically to a method for preparing a proton exchange membrane. Background Technology

[0002] Hydrogen energy is hailed as the next generation of clean energy, and proton exchange membrane fuel cells (PEMFCs) have attracted much attention as one of the most direct applications of hydrogen energy. The proton exchange membrane is considered the "chip" of PEMFCs, and its proton conductivity (σ) and mechanical properties are key indicators for evaluating the membrane. The proton conductivity largely depends on the water content within the membrane during battery system operation. Therefore, to ensure efficient operation of the stack, an external hydrothermal management device is generally required, which increases the size and cost of the stack system. Therefore, reducing the membrane's dependence on water and improving its mechanical properties are convenient and effective ways to reduce the size of the stack system while lowering costs. SPEEK is often considered as a proton exchange membrane material due to its low cost and high ion selectivity; however, its high swelling ratio and low proton conductivity at low humidity limit its further application.

[0003] The ideal approach at present is to blend it with other polymer electrolytes to reduce its dependence on water, thereby meeting the proton conductivity requirements under low humidity conditions. For example, Chinese patent 201110034247.1 discloses an acid-base crosslinked proton exchange membrane and its preparation, which blends sulfonated polyether ether ketone and polyether ether ketone-benzimidazole to obtain a mixed acid-base composite membrane.

[0004] The existing technology described above, which uses sulfonated polyetheretherketone (PEEK) and PEEK-benzimidazole to obtain an acid-base blended composite membrane, can improve the swelling rate and proton conductivity of SPEEK. However, the synthesis of PEEK-benzimidazole is complex and expensive, and the proton conductivity is still relatively low. It is not possible to obtain excellent proton conductivity at a low cost. Summary of the Invention

[0005] The purpose of this invention is to overcome the above-mentioned technical deficiencies and propose a method for preparing proton exchange membranes, thereby solving the technical problems of complex synthesis, high price, and relatively low proton conduction performance of polyether ether ketone-benzimidazole in the prior art.

[0006] To achieve the above-mentioned technical objectives, the present invention adopts the following technical solution:

[0007] This invention provides a method for preparing a proton exchange membrane, comprising the following steps:

[0008] A certain mass ratio of SPEEK-Na + Dissolve ABPBI in a mixed solvent and stir. The mixed solvent makes SPEEK-Na +It dissolves simultaneously with ABPBI to form a homogeneous polymer mixture with a certain mass fraction.

[0009] The polymer mixture homogeneous solution is subjected to material molding treatment to obtain an intermediate product;

[0010] The intermediate product was post-treated sequentially in hydrogen peroxide solution, deionized water, and dilute sulfuric acid solution, and then washed with deionized water until neutral to obtain the SPEEK / ABPBI proton exchange membrane.

[0011] In some embodiments, the mixed solvent in step one is a mixed solution of dimethyl sulfoxide / methanol / KOH.

[0012] In some embodiments, the mass ratio of dimethyl sulfoxide / methanol / KOH in the mixed solvent in step one is 40:24:1.

[0013] In some embodiments, the intermediate product obtained by subjecting the polymer homogeneous solution to material molding treatment in the step includes:

[0014] The polymer-mixed homogeneous solution was electrospun at room temperature under set parameters to obtain SPEEK-Na+ / ABPBI nanofiber mat in the form of sodium sulfonate.

[0015] The material was hot-pressed to obtain a SPEEK-Na+ / ABPBI nanofiber membrane.

[0016] In some embodiments, the intermediate product is post-treated sequentially in hydrogen peroxide solution, deionized water, and dilute sulfuric acid solution, and then washed with deionized water until neutral to obtain the SPEEK / ABPBI proton exchange membrane, which includes:

[0017] The SPEEK-Na+ / ABPBI nanofiber membrane was sequentially post-treated in hydrogen peroxide solution, deionized water, and dilute sulfuric acid solution.

[0018] The membrane was then washed with deionized water until neutral to obtain the SPEEK / ABPBI composite nanofiber proton exchange membrane.

[0019] In some embodiments, the intermediate product obtained by subjecting the polymer homogeneous solution to material molding treatment in the step includes:

[0020] The homogeneous polymer mixture solution was poured into a flat dish and the temperature was gradually increased to completely evaporate the solvent, resulting in an intermediate product with the solvent evaporated.

[0021] In some embodiments, the intermediate product is post-treated sequentially in hydrogen peroxide solution, deionized water, and dilute sulfuric acid solution, and then washed with deionized water until neutral to obtain the SPEEK / ABPBI proton exchange membrane, which includes:

[0022] The intermediate product was post-treated in hydrogen peroxide solution, deionized water and dilute sulfuric acid solution in sequence.

[0023] The membrane was then washed with deionized water until neutral to obtain the SPEEK / ABPBI composite proton exchange membrane.

[0024] In some embodiments, a certain mass ratio of SPEEK-Na is added in the step. + Dissolve ABPBI in a mixed solvent and stir. The mixed solvent makes SPEEK-Na + Before dissolving ABPBI simultaneously to form a homogeneous polymer mixture with a certain mass fraction, the process includes an ABPBI preparation step, which is as follows:

[0025] The monomers 3,4-diaminobenzoic acid, phosphorus pentoxide, and methanesulfonic acid were added to the reaction vessel;

[0026] Then, the reaction is carried out under the protection of an inert gas and heated to obtain a viscous polymer liquid;

[0027] Then pour the viscous polymer liquid into a container filled with a large amount of deionized water to make it fibrous;

[0028] Then wash with plenty of deionized water and NaOH solution until neutral;

[0029] Finally, ABPBI is obtained by drying, weighing, and bagging for later use.

[0030] In some embodiments, a certain mass ratio of SPEEK-Na is added in the step. + Dissolve ABPBI in a mixed solvent and stir. The mixed solvent makes SPEEK-Na + Before dissolving simultaneously with ABPBI to form a homogeneous polymer mixture solution of a certain mass fraction, it also includes SPEEK-Na. + The preparation steps of SPEEK-Na + The preparation steps are as follows:

[0031] Polyetheretherketone (PEEK) is dissolved in concentrated sulfuric acid and reacted at a constant temperature for a period of time.

[0032] Then pour it into ice water and draw it to obtain polymer filaments;

[0033] Rinse again with deionized water until the aqueous solution is neutral;

[0034] Finally, the polymer was dried to obtain sulfonated polyether ether ketone;

[0035] The prepared sulfonated polyether ether ketone was placed in an aqueous NaOH solution and heated to react, causing the sulfonated polyether ether ketone to change from pale yellow to white;

[0036] Finally, wash thoroughly with deionized water until the solution is neutral, and dry to obtain SPEEK-Na. + Polymer salt.

[0037] In some embodiments, the intermediate product is post-treated sequentially in hydrogen peroxide solution, deionized water, and dilute sulfuric acid solution, and then washed with deionized water until neutral to obtain the SPEEK / ABPBI proton exchange membrane. The concentration of hydrogen peroxide solution is 3%, and the concentration of dilute sulfuric acid solution is 5%.

[0038] Compared with the prior art, the proton exchange membrane preparation method provided by the present invention involves simultaneously dissolving SPEEK and ABPBI in a solvent, forming a membrane through material molding, and then performing post-treatment to obtain a composite proton exchange membrane composed of SPEEK and ABPBI. The process is simple and easy to operate, and the resulting composite membrane has good mechanical strength, proton conductivity, and water absorption / retention and acid absorption / storage capabilities, exhibiting excellent proton conduction performance. Attached Figure Description

[0039] Figure 1 SEM images of SPEEK fiber mat, SPEEK / ABPBI fiber mat and their heat-pressed films;

[0040] Figure 2 The stress-strain tensile diagram of the SPEEK / ABPBI fiber membrane;

[0041] Figure 3 This is a diagram of proton conductivity. Detailed Implementation

[0042] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0043] To address the technical challenges of complex and expensive synthesis of polyetheretherketone-benzimidazole (PEEK-BENIZE), which also results in relatively low proton conductivity, this invention provides a method for preparing a proton exchange membrane. This method enables the preparation of SPEEK / ABPBI composite membranes. The process is simple and easy to operate, and the resulting composite membrane exhibits excellent mechanical strength, proton conductivity, and water absorption / retention, acid absorption / storage capabilities, demonstrating superior proton conductivity.

[0044] It should be noted that the proton exchange membrane preparation method described in this invention is applicable to, but not limited to, the preparation of proton exchange membranes for fuel cells. For ease of explanation, this invention will only use the application of the proton exchange membrane preparation method to the preparation of proton exchange membranes for fuel cells as an example. The principle of the proton exchange membrane preparation method applied to other types of equipment is essentially the same as that applied to the preparation of proton exchange membranes for fuel cells, and will not be described in detail here.

[0045] Example 1

[0046] In this embodiment, before the step of preparing the proton exchange membrane by blending, the synthesis of ABPBI is performed first, and the specific steps are as follows:

[0047] Add 3g of monomeric 3,4-diaminobenzoic acid, 6g of phosphorus pentoxide, and 20ml of methanesulfonic acid to a three-necked flask, then... 2 In a protected atmosphere, the mixture was reacted at 150°C for 4 hours to obtain a viscous polymeric liquid. While still hot, it was poured into a container filled with a large amount of deionized water to make it fibrous. Then, it was washed with a large amount of deionized water and NaOH aqueous solution until neutral. Finally, it was dried in a vacuum drying oven for 24 hours to obtain ABPBI, which was weighed and bagged for later use.

[0048] Understandably, ABPBI is a basic poly(2,5-benzimidazole).

[0049] It should be noted that ABPBI has excellent mechanical properties, and its proton conductivity is quite ideal under low humidity conditions after acid doping.

[0050] In this embodiment, before the step of preparing the proton exchange membrane by blending, SPEEK-Na is required first. + The specific steps of the synthesis for preparation are as follows:

[0051] Weigh 28 g of polyether ether ketone and dissolve it in 200 ml of 96%-98% concentrated sulfuric acid. React at 50°C for 8 hours. Then, while the solution is still hot, pour it into a large amount of ice water and draw it into a large amount of polymer filaments. Wash the filaments with a large amount of deionized water until the aqueous solution is neutral. Finally, place the polymer in a vacuum drying oven at 60°C for 48 hours to prepare SPEEK with a sulfonation degree of about 64%.

[0052] Understandably, polyether ether ketone is abbreviated as PEEK, and SPEEK is acidic sulfonated polyether ether ketone.

[0053] Then, the dried SPEEK was placed in 500 ml of a 1 M NaOH aqueous solution and heated at 50 °C for 24 h. The SPEEK changed from pale yellow to white. Finally, it was thoroughly washed with plenty of deionized water until the solution was neutral, and then dried in a vacuum drying oven at 60 °C for 24 h to obtain SPEEK-Na.+ The polymer salt is prepared for use. The SPEEK-Na obtained from the reaction... + It can effectively improve the compatibility of SPEEK and ABPBI and prevent ABPBI from precipitating due to acid-base reaction in SPEEK solution.

[0054] It should be noted that SPEEK is often considered as a proton exchange membrane material due to its low cost and high ion selectivity. However, its high swelling ratio and low proton conductivity at low humidity limit its further application. To address this, an alkaline ABPBI polymer was introduced into acidic SPEEK for blending, followed by electrospinning to obtain a blended fiber membrane. This nanofiber membrane optimizes the proton transport path and forms an acid-base ion crosslinking network, which can solve the water dependence of SPEEK membrane proton conductivity while improving the membrane's mechanical properties.

[0055] In this embodiment, after preparing SPEEK-Na + After using ABPBI material, proton exchange membranes are prepared by blending using electrospinning technology. The specific steps are as follows:

[0056] SPEEK / ABPBI composite fiber membranes were prepared using electrospinning technology, with a certain mass ratio of SPEEK-Na + ABPBI was dissolved in a mixed solution of dimethyl sulfoxide / methanol / KOH and magnetically stirred at 400 rpm for at least 48 hours to form a homogeneous polymer solution with a specific mass fraction. The polymer solution was then electrospun at room temperature under set parameters to obtain SPEEK-Na in the form of sodium sulfonate. + / ABPBI nanofiber mat. It was hot-pressed at 150℃ and 5 MPa for more than 1 hour to obtain SPEEK-Na. + / ABPBI nanofiber membrane.

[0057] Finally, the membrane was post-treated sequentially in 3% hydrogen peroxide solution, deionized water, and 5% dilute sulfuric acid solution for 1 hour, and then washed with deionized water until neutral to obtain the SPEEK / ABPBI nanofiber membrane. It was then dried in a vacuum oven, packaged, and stored for subsequent testing.

[0058] Understandably, the prepared membrane can form an ion cross-linking network internally, constructing abundant proton transport channels, effectively improving mechanical properties, reducing phosphoric acid doping levels, and also possessing excellent proton conductivity. It is a promising proton exchange membrane for fuel cells.

[0059] Furthermore, SPEEK-Na +The mass ratio of ABPBI to ABPBI is one of 1:1, 2:1, 3:1, 4:1, or 5:1. These are preferred mass ratios, but the mass ratio is not limited to these few. Other mass ratios that have the corresponding preparation effect are also acceptable.

[0060] It should be noted that the mass fraction in step one can be 9-15 wt.%, and the parameters for electrospinning the polymer solution can be 20 kV and 15 cm. Blending SPEEK and ABPBI and then electrospinning them can optimize the proton conduction channels through nanofibers and reduce the water dependence of SPEEK.

[0061] Example 2

[0062] In this embodiment, before the step of preparing the proton exchange membrane by blending, the synthesis of ABPBI is performed first, and the specific steps are as follows:

[0063] Add 3g of monomeric 3,4-diaminobenzoic acid, 6g of phosphorus pentoxide, and 20ml of methanesulfonic acid to a three-necked flask, then... 2 In a protected atmosphere, the mixture was reacted at 150°C for 4 hours to obtain a viscous polymeric liquid. While still hot, it was poured into a container filled with a large amount of deionized water to make it fibrous. Then, it was washed with a large amount of deionized water and NaOH aqueous solution until neutral. Finally, it was dried in a vacuum drying oven for 24 hours to obtain ABPBI, which was weighed and bagged for later use.

[0064] In this embodiment, before the step of preparing the proton exchange membrane by blending, SPEEK-Na is required first. + The specific steps of the synthesis for preparation are as follows:

[0065] Weigh 28 g of polyether ether ketone and dissolve it in 200 ml of 96%-98% concentrated sulfuric acid. React at 50°C for 8 hours. Then, while the solution is still hot, pour it into a large amount of ice water and draw it into a large amount of polymer filaments. Wash the filaments with a large amount of deionized water until the aqueous solution is neutral. Finally, place the polymer in a vacuum drying oven at 60°C for 48 hours to prepare SPEEK with a sulfonation degree of about 64%.

[0066] Then, the dried SPEEK was placed in 500 ml of a 1 M NaOH aqueous solution and heated at 50 °C for 24 h. The SPEEK changed from pale yellow to white. Finally, it was thoroughly washed with plenty of deionized water until the solution was neutral, and then dried in a vacuum drying oven at 60 °C for 24 h to obtain SPEEK-Na. + Polymer salts are available for later use.

[0067] In this embodiment, after preparing SPEEK-Na + After using ABPBI material, a proton exchange membrane is prepared by blending via a casting method. The specific steps are as follows:

[0068] A certain mass ratio of SPEEK-Na + ABPBI was dissolved in a mixed solution of dimethyl sulfoxide / methanol / KOH and magnetically stirred at 400 rpm for more than 48 hours to form a homogeneous polymer mixture with a certain mass fraction. The mixture was then poured into a flat dish and heated from 80°C to 110°C to completely evaporate the solvent, yielding an intermediate product.

[0069] The intermediate product was treated sequentially in 3% hydrogen peroxide solution, deionized water, and 5% dilute sulfuric acid solution for 1 hour, and then washed with deionized water until neutral to proceed with the protonation process. SPEEK-Na + The sodium sulfonate is converted into sulfonate ions, and finally dried in a vacuum oven, then bagged and stored for subsequent testing.

[0070] Furthermore, SPEEK-Na + The mass ratio of ABPBI to ABPBI is one of 1:1, 2:1, 3:1, 4:1, or 5:1. These are preferred mass ratios, but the mass ratio is not limited to these few. Other mass ratios that have the corresponding preparation effect are also acceptable.

[0071] It should be noted that the mass fraction in step one can be 9-15 wt.%; in the operation of gradually increasing the temperature from 80℃ to 110℃, the temperature is increased by 20℃ every hour.

[0072] Compare with Example 1

[0073] In this comparative example, before the SPEEK fiber membrane preparation step, SPEEK preparation is required first. The specific steps are as follows:

[0074] Weigh 28 g of polyether ether ketone and dissolve it in 200 ml of 96%-98% concentrated sulfuric acid. React at 50°C for 8 hours. Then, while the solution is still hot, pour it into a large amount of ice water and draw it into a large amount of polymer filaments. Wash the filaments with a large amount of deionized water until the aqueous solution is neutral. Finally, place the polymer in a vacuum drying oven at 60°C for 48 hours to prepare SPEEK with a sulfonation degree of about 64%.

[0075] In this comparative example, SPEEK fiber membranes were prepared using electrospinning technology, and the specific steps are as follows:

[0076] A certain mass fraction of SPEEK was dissolved in a dimethyl sulfoxide solution and magnetically stirred at 400 rpm for more than 24 hours to form a homogeneous polymer solution with a certain mass fraction.

[0077] The polymer solution was then electrospun at room temperature under set parameters to obtain SPEEK nanofiber mat.

[0078] The SPEEK nanofiber membrane is obtained by hot-pressing it at 140℃ and 5MPa for more than 1 hour, then post-treating it in 3% hydrogen peroxide solution, deionized water and 5% dilute sulfuric acid solution for 1 hour in sequence, and then washing it with deionized water until neutral.

[0079] Dry in a vacuum oven, then bag and store for later testing.

[0080] It should be noted that SPEEK is an ionic polymer containing -SO3H in its main chain, making it a relatively ideal polymer electrolyte material with good thermal stability.

[0081] Compare with Example 2

[0082] In this comparative example, before the SPEEK fiber membrane preparation step, SPEEK preparation is required first. The specific steps are as follows:

[0083] Weigh 28 g of polyether ether ketone and dissolve it in 200 ml of 96%-98% concentrated sulfuric acid. React at 50°C for 8 hours. Then, while the solution is still hot, pour it into a large amount of ice water and draw it into a large amount of polymer filaments. Wash the filaments with a large amount of deionized water until the aqueous solution is neutral. Finally, place the polymer in a vacuum drying oven at 60°C for 48 hours to prepare SPEEK with a sulfonation degree of about 64%.

[0084] In this comparative example, SPEEK films were prepared using a casting film deposition technique, and the specific steps are as follows:

[0085] A certain mass fraction of SPEEK was dissolved in a dimethyl sulfoxide solution and magnetically stirred at 400 rpm for more than 24 hours to form a homogeneous polymer solution with a certain mass fraction.

[0086] Then, it is poured into a flat dish and heated from 80°C to 110°C to completely evaporate the solvent. Then, it is post-treated in 3% hydrogen peroxide solution, deionized water, and 5% dilute sulfuric acid solution for 1 hour, and then washed with deionized water until neutral to obtain the SPEEK membrane.

[0087] Dry in a vacuum oven, then bag and store for later testing.

[0088] The specific embodiments of the present invention described above do not constitute a limitation on the scope of protection of the present invention. Any other corresponding changes and modifications made in accordance with the technical concept of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing a proton exchange membrane, characterized in that, Includes the following steps: To prepare ABPBI, monomers 3,4-diaminobenzoic acid, phosphorus pentoxide, and methanesulfonic acid were added to a reaction vessel. The reaction was then heated under an inert gas atmosphere to obtain a viscous polymer liquid. The viscous polymer liquid was then poured into a container filled with a large amount of deionized water to make it fibrous. It was then washed with a large amount of deionized water and NaOH aqueous solution until neutral. Finally, ABPBI was obtained by drying, weighing, and bagging for later use. Preparation of SPEEK-Na + Polyether ether ketone (PEE ketone) was dissolved in concentrated sulfuric acid and reacted at a constant temperature for a period of time. The solution was then poured into ice water and drawn into fine polymer filaments. The filaments were then washed with deionized water until the solution was neutral. Finally, the polymer was dried to obtain sulfonated PEEK. The prepared sulfonated PEEK was then placed in a NaOH aqueous solution and heated to react, causing the sulfonated PEEK to change from pale yellow to white. Finally, the solution was thoroughly washed with deionized water until it was neutral and dried to obtain SPEEK-Na. + Polymer salts; A certain mass ratio of SPEEK-Na + Dissolve ABPBI in a mixed solvent and stir. The mixed solvent makes SPEEK-Na + It is dissolved simultaneously with ABPBI to form a homogeneous polymer mixture with a certain mass fraction. The mixed solvent is a mixed solution of dimethyl sulfoxide / methanol / KOH. The polymer mixture homogeneous solution is subjected to material molding treatment to obtain an intermediate product; The intermediate product was post-treated sequentially in hydrogen peroxide solution, deionized water, and dilute sulfuric acid solution, and then washed with deionized water until neutral to obtain the SPEEK / ABPBI proton exchange membrane.

2. The method for preparing a proton exchange membrane according to claim 1, characterized in that, The mass ratio of dimethyl sulfoxide / methanol / KOH in the mixed solvent is 40:24:

1.

3. The method for preparing a proton exchange membrane according to claim 1, characterized in that, The intermediate product obtained by subjecting the polymer homogeneous solution to material molding in the step includes: The polymer-mixed homogeneous solution was electrospun at room temperature under set parameters to obtain SPEEK-Na+ / ABPBI nanofiber mat in the form of sodium sulfonate. The material was hot-pressed to obtain a SPEEK-Na+ / ABPBI nanofiber membrane.

4. The method for preparing a proton exchange membrane according to claim 1, characterized in that, The intermediate product obtained by subjecting the polymer homogeneous solution to material molding in the step includes: The polymer homogeneous solution was poured into a flat dish and the temperature was gradually increased to completely evaporate the solvent, resulting in an intermediate product with the solvent evaporated.

5. The method for preparing a proton exchange membrane according to claim 4, characterized in that, In the next step, the intermediate product is sequentially post-treated in hydrogen peroxide solution, deionized water, and dilute sulfuric acid solution, and then washed with deionized water until neutral to obtain the SPEEK / ABPBI proton exchange membrane, which includes: The intermediate product was post-treated sequentially in hydrogen peroxide solution, deionized water, and dilute sulfuric acid solution. The membrane was then washed with deionized water until neutral to obtain the SPEEK / ABPBI composite proton exchange membrane.

6. The method for preparing a proton exchange membrane according to claim 1, characterized in that, In the step, the intermediate product is sequentially post-treated in hydrogen peroxide solution, deionized water, and dilute sulfuric acid solution, and then washed with deionized water until neutral to obtain the SPEEK / ABPBI proton exchange membrane. The mass concentration of hydrogen peroxide solution is 3%, and the mass concentration of dilute sulfuric acid solution is 5%.

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