Preparation method of phosphoric acid / cystine functionalized MXene / polybenzimidazole composite high-temperature proton exchange membrane for high-temperature fuel cell

Abstract

The invention relates to a preparation method of a high-temperature proton exchange membrane, in particular to a preparation method of a phosphoric acid / cystine functionalized MXene / polybenzimidazole composite high-temperature proton exchange membrane for a high-temperature fuel cell. The invention aims to solve the problem of insufficient oxidation resistance of the existing fuel cell proton exchange membrane. The method comprises the following steps: 1, preparing polybenzimidazole; (2) preparing cystine functionalized MXene; and 3, preparing a cystine functionalized MXenen and OPBI compounded proton exchange membrane, and then dipping in a phosphoric acid solution. According to the application of the cystine functionalized MXene / polybenzimidazole composite membrane for the high-temperature fuel cell in HT-PEM, the conductivity and oxidation resistance of a proton exchange membrane are improved, a basis is provided for developing novel efficient HT-PEM, and the cystine functionalized MXene / polybenzimidazole composite membrane is applied to the technical field of proton exchange membrane fuel cells.

Description

Technical Field

[0001] The invention relates to a method for preparing a phosphoric acid / cystine functionalized MXene / polybenzimidazole composite high-temperature proton exchange membrane for a high-temperature fuel cell. Background Art

[0002] About 65% of the world's energy demand relies on non-renewable fossil fuels, which leads to greenhouse gas emissions, global warming and environmental degradation. With the growing global demand for clean energy, hydrogen energy, as an efficient, zero-emission clean energy, occupies an important position in the future energy system. Proton exchange membrane fuel cell (PEMFC) is one of the important technologies for hydrogen energy utilization. Due to its high energy conversion efficiency, rapid start-up and ability to adapt to a variety of application scenarios, it has become a research hotspot in the field of hydrogen energy batteries. PEMFC can be divided into low-temperature proton exchange membrane fuel cells (LT-PEMFC) and high-temperature proton exchange membrane fuel cells (HT-PEMFC) according to different operating temperatures. Among them, HT-PEMFC has an operating temperature in the range of 100-200℃, which not only improves CO tolerance to a certain extent, but also simplifies the water thermal management system, so that the stability and efficiency of the fuel cell system are significantly improved. Therefore, HT-PEMFC shows broad application prospects in the fields of hydrogen energy vehicles and distributed power generation.

[0003] Proton exchange membrane is the core component of proton exchange membrane fuel cells. The performance of proton exchange membrane determines the performance of proton exchange membrane fuel cells. In recent years, OPBI in polybenzimidazole has attracted widespread attention due to its good solubility and strong processability, but OPBI still has problems such as insufficient antioxidant performance and poor long-term stability. How to further improve the antioxidant performance of HT-PEM and extend its service life has become a key challenge. Summary of the invention

[0004] The purpose of the present invention is to solve the problem of insufficient antioxidant performance of existing fuel cell proton exchange membranes, and to provide a preparation method and application of a phosphate / cystine functionalized MXene / polybenzimidazole composite high-temperature proton exchange membrane for high-temperature fuel cells.

[0005] The preparation method of a phosphoric acid / cystine functionalized MXene / polybenzimidazole composite high temperature proton exchange membrane for a high temperature fuel cell of the present invention is carried out by the following steps:

[0006] 1. Preparation of polybenzimidazole

[0007] Dissolve benzyltetramine and 4,4-diphenyl ether dicarboxylic acid in polyphosphoric acid, stir at 100°C under nitrogen protection, and after complete dissolution, heat to 140°C, continue stirring until the mixture becomes viscous, and then pour into deionized water to obtain brown filaments, wash with deionized water, dry and grind into powder, add NaHCO3 solution for neutralization, and then repeatedly wash with deionized water until neutral, filter, and dry the obtained solid to obtain OPBI;

[0008] Preparation of Cystine-functionalized MXene

[0009] Taking Ti3AlC2 as the matrix, MXene dispersion was prepared by selectively etching the Al layer with hydrochloric acid; the MXene dispersion was added to hydrochloric acid, and the MXene hydrochloric acid solution was obtained after ultrasonic treatment; cystine was dissolved in hydrochloric acid to obtain cystine hydrochloric acid solution; the cystine hydrochloric acid solution was added dropwise to the MXene hydrochloric acid solution at room temperature, stirred, reacted for 24 hours, centrifuged, washed with deionized water, and the precipitate was collected and freeze-dried to obtain cystine-functionalized MXene;

[0010] 3. Preparation of phosphate / cystine functionalized MXene / polybenzimidazole composite high temperature proton exchange membrane

[0011] OPBI is dissolved in nitrogen-nitrogen dimethylacetamide to obtain an OPBI solution; cystine-functionalized MXene is dispersed in nitrogen-nitrogen dimethylacetamide to obtain a cystine-functionalized MXene solution; the cystine-functionalized MXene solution is added dropwise to the OPBI solution and stirred to mix evenly, and then cast onto a horizontal glass plate to form a film, and after drying, a cystine-functionalized MXene and polybenzimidazole composite film is obtained; wherein the mass ratio of cystine-functionalized MXene to OPBI is 1 to 15:100;

[0012] The cystine functionalized MXene / polybenzimidazole composite membrane is immersed in a phosphoric acid solution, and the phosphoric acid solution on the surface of the composite membrane is wiped off with filter paper after being taken out. After drying, a phosphoric acid / cystine functionalized MXene / polybenzimidazole composite high temperature proton exchange membrane is obtained, and the preparation is completed.

[0013] The phosphate / cystine functionalized MXene / polybenzimidazole composite high-temperature proton exchange membrane of the present invention is used as a proton exchange membrane for a high-temperature fuel cell.

[0014] The composite membrane prepared by the present invention has a higher residual weight after Fenton's reagent test, which indicates that OPBI / MC has excellent antioxidant stability, which is attributed to the presence of sulfur-sulfur bonds on cystine as free radical scavengers. The thermal stability of OPBI / MC is better than that of pure OPBI. This is because the addition of functionalized MXene improves the thermodynamic properties of the electrolyte membrane material through the direct acid-base interaction between the carboxylic acid group of cystine and the imidazole ring of OPBI, and the optimized polymer electrolyte membrane material is not easy to degrade the main chain under high temperature conditions. It is worth noting that all prepared samples maintain good thermal stability at 200°C and meet the requirements of HT-PEMFC. The proton conductivity of the composite membrane material is also higher than that of pure OPBI, mainly because the two-dimensional sheet structure of cystine functionalized MXene increases the absorption of phosphoric acid, and the phosphoric acid group provides a proton transfer site. The present invention provides a basis for the development of new and efficient HT-PEM and provides new ideas for the future development of hydrogen energy and fuel cell technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 Schematic diagram of the synthesis route of MXene and cystine-functionalized MXene;

[0016] Figure 2 It is the infrared spectra of OPBI and OPBI / MC proton exchange membranes in the present invention;

[0017] Figure 3 is an atomic force microscope AFM image of the proton exchange membrane in the present invention, wherein Figure 3 (a) AFM image of OPBI / MC-1; Figure 3 (b) AFM image of OPBI / MC-7;

[0018] Figure 4 This is an image of the antioxidant properties of proton exchange membranes;

[0019] Figure 5 This is the thermogravimetric spectrum of the proton exchange membrane;

[0020] Figure 6 Schematic diagram of proton conductivity of the membrane at 100-180°C in the present invention. DETAILED DESCRIPTION

[0021] Specific implementation method 1: In this implementation method, a method for preparing a phosphoric acid / cystine functionalized MXene / polybenzimidazole composite high-temperature proton exchange membrane for a high-temperature fuel cell is carried out according to the following steps:

[0022] 1. Preparation of polybenzimidazole

[0023] Dissolve benzyltetramine and 4,4-diphenyl ether dicarboxylic acid in polyphosphoric acid, stir at 100°C under nitrogen protection, and after complete dissolution, heat to 140°C, continue stirring until the mixture becomes viscous, and then pour into deionized water to obtain brown filaments, wash with deionized water, dry and grind into powder, add NaHCO3 solution for neutralization, and then repeatedly wash with deionized water until neutral, filter, and dry the obtained solid to obtain OPBI;

[0024] Preparation of Cystine-functionalized MXene

[0025] Taking Ti3AlC2 as the matrix, MXene dispersion was prepared by selectively etching the Al layer with hydrochloric acid; the MXene dispersion was added to hydrochloric acid, and the MXene hydrochloric acid solution was obtained after ultrasonic treatment; cystine was dissolved in hydrochloric acid to obtain cystine hydrochloric acid solution; the cystine hydrochloric acid solution was added dropwise to the MXene hydrochloric acid solution at room temperature, stirred, reacted for 24 hours, centrifuged, washed with deionized water, and the precipitate was collected and freeze-dried to obtain cystine-functionalized MXene;

[0026] 3. Preparation of phosphate / cystine functionalized MXene / polybenzimidazole composite high temperature proton exchange membrane

[0027] OPBI is dissolved in nitrogen-nitrogen dimethylacetamide to obtain an OPBI solution; cystine-functionalized MXene is dispersed in nitrogen-nitrogen dimethylacetamide to obtain a cystine-functionalized MXene solution; the cystine-functionalized MXene solution is added dropwise to the OPBI solution and stirred to mix evenly, and then cast onto a horizontal glass plate to form a film, and after drying, a cystine-functionalized MXene and polybenzimidazole composite film is obtained; wherein the mass ratio of cystine-functionalized MXene to OPBI is 1 to 15:100;

[0028] The cystine functionalized MXene / polybenzimidazole composite membrane is immersed in a phosphoric acid solution, and the phosphoric acid solution on the surface of the composite membrane is wiped off with filter paper after being taken out. After drying, a phosphoric acid / cystine functionalized MXene / polybenzimidazole composite high temperature proton exchange membrane is obtained, and the preparation is completed.

[0029] Specific embodiment 2: This embodiment is different from specific embodiment 1 in that the mass ratio of benzyltetramine, 4,4-diphenyl ether dicarboxylic acid and polyphosphoric acid in step 1 is 5.4:6.5:110. The rest is the same as specific embodiment 1.

[0030] Specific implementation method 3: This implementation method is different from specific implementation method 1 or 2 in that: in step 1, deionized water is used to wash the solution until the pH value is 7, and then the solution is dried and ground into powder. The rest is the same as specific implementation method 1 or 2.

[0031] Specific embodiment 4: This embodiment differs from specific embodiments 1 to 3 in that the mass concentration of the NaHCO3 solution is 10%. The rest is the same as specific embodiments 1 to 3.

[0032] Specific embodiment 5: This embodiment is different from specific embodiments 1 to 4 in that: in step 1, OPBI is obtained by drying at 80° C. for 24 hours. The rest is the same as specific embodiments 1 to 4.

[0033] Specific embodiment 6: This embodiment is different from Specific embodiments 1 to 5 in that: in step 2, ultrasonic treatment is performed for 3.5 hours under ice bath conditions. The rest is the same as Specific embodiments 1 to 5.

[0034] Specific embodiment 7: This embodiment differs from Specific embodiments 1 to 6 in that: in step 2, cystine is dissolved in hydrochloric acid and stirred for 3 hours. The rest is the same as Specific embodiments 1 to 6.

[0035] Specific embodiment eight: This embodiment differs from specific embodiments one to seven in that: in step two, the MXene hydrochloric acid solution and the cystine hydrochloric acid solution are mixed and stirred at 80° C. for 24 hours. The rest is the same as specific embodiments one to seven.

[0036] Specific embodiment 9: This embodiment is different from specific embodiments 1 to 8 in that: in step 3, drying is performed at 80° C. for 24 hours. The rest is the same as specific embodiments 1 to 8.

[0037] Specific embodiment 10: This embodiment differs from specific embodiments 1 to 9 in that the mass concentration of the phosphoric acid solution in step 3 is 85%. The rest is the same as specific embodiments 1 to 9.

[0038] Specific embodiment eleven: This embodiment differs from specific embodiments one to ten in that step three involves immersing in a phosphoric acid solution for 48 hours. The rest is the same as specific embodiments one to ten.

[0039] The content of the present invention is not limited to the content of the above-mentioned embodiments. The combination of one or several specific embodiments can also achieve the purpose of the invention.

[0040] Example 1: A method for preparing a phosphoric acid / cystine functionalized MXene / polybenzimidazole composite high temperature proton exchange membrane for a high temperature fuel cell:

[0041] 1. Preparation of polybenzimidazole (OPBI)

[0042] Synthesis route of polybenzimidazole (OPBI):

[0043]

[0044] Dissolve benzyltetramine (5.4 g) and 4,4-diphenyl ether dicarboxylic acid (6.5 g) in polyphosphoric acid (110 g), stir mechanically for 4 h at 100 ° C under nitrogen protection in a 250 ml three-necked round-bottom flask, and after obtaining a uniform mixture, raise the temperature to 140 ° C, continue to stir mechanically for 2-4 h, until the solution becomes viscous, pour it into deionized water, and obtain a brown filamentous polymer. Wash it with deionized water several times to remove a large amount of acid, dry it and grind it into powder, then add NaHCO3 solution (10 wt%) to neutralize it for 24 h, filter it, and wash the solid with deionized water until the pH value of the filtrate is 7; dry the obtained solid at 80 ° C for 24 h to obtain OPBI polymer.

[0045] 2. Preparation and functionalization of MXene

[0046] Preparation methods of MXene and functionalized MXene Figure 1 As shown;

[0047] Using MAX (Ti3AlC2) powder as the matrix, MXene dispersion (Ti3C2T x ). Add 25 mL of MXene to 50 mL of 12 M hydrochloric acid and ultrasonicate in an ice bath for three and a half hours to obtain a MXene hydrochloric acid solution. Dissolve 2 g of cystine in 25 mL of 12 M hydrochloric acid and stir for 3 hours to obtain a cystine hydrochloric acid solution; mix the MXene hydrochloric acid solution and the cystine hydrochloric acid solution and stir at 80 ° C for 24 hours. Centrifuge the solution, collect the precipitate, and freeze-dry to obtain cystine functionalized MXene (MC).

[0048] 3. Phosphate / cystine functionalized MXene / polybenzimidazole composite high temperature proton exchange membrane

[0049] A certain amount of OPBI powder was added to 20 mL of DMAC and stirred until completely dissolved to obtain an OPBI polymer solution; a certain amount of MC powder was added to 20 mL of DMAC and dispersed evenly by ultrasound to obtain an MC solution; after the above two liquids were mixed and stirred evenly, the uniform mixed solution was cast on a flat glass plate and dried at 80°C for 24 hours to obtain a cystine-functionalized MXene / polybenzimidazole composite membrane. The cystine-functionalized MXene / polybenzimidazole composite membrane was immersed in 85% phosphoric acid solution for 48 hours, and the phosphoric acid solution on the surface of the composite membrane was wiped off with filter paper after being taken out. After drying, a phosphoric acid / cystine-functionalized MXene / polybenzimidazole composite high-temperature proton exchange membrane was obtained.

[0050] The mass ratio of cystine functionalized MXene to OPBI polymer in the mixed solution is 1:100, 3:100, 7:100, 10:100 or 15:100, and composite high-temperature proton exchange membranes with composite rates of 1%, 3%, 7%, 10% and 15% are prepared, respectively, and are represented by OPBI / MC-1, OPBI / MC-3, OPBI / MC-7, OPBI / MC-10 and OPBI / MC-15.

[0051] The infrared spectra of OPBI and OPBI / MC are as follows: Figure 2 As shown, in all samples at 1015 cm -1 and 1600cm -1 The characteristic peaks of aromatic ether bonds and C=N stretching vibration peaks of imidazole rings, which are the same as those of OPBI, appear at 659 cm -1 and 1285cm -1 The peaks at are SS and CS bonds, respectively, which indicates that the composite film of MC and OPBI was successfully prepared.

[0052] Atomic force microscopy of composite high temperature proton exchange membranes Figure 3 As shown, Figure 3 a is the AFM image of OPBI / MC-1, Figure 3 b is the AFM image of OPBI / MC-7, where the brighter layers are due to the presence of cystine-functionalized MXene in OPBI / MC.

[0053] All membranes were immersed in Fenton's reagent at an experimental temperature of 80 °C. Figure 4 The residual mass curve of the membrane after immersion in Fenton's reagent for 72 hours. Compared with the OPBI membrane, the composite high-temperature proton exchange membrane prepared in the embodiment has a higher residual weight, which indicates that OPBI / MC has superior oxidative stability, which is attributed to the presence of sulfur-sulfur bonds on the side chains as free radical scavengers.

[0054] Figure 5 The TGA curves of OPBI and OPBI / MC. The results show that the weight loss of the samples can be divided into two stages. The first stage is before 200°C, and the weight loss of the samples is mainly due to the loss of adsorbed water and solvent in the membrane. The second stage is after 500°C, and the weight loss of the samples is attributed to the degradation of the main chain of OPBI or OPBI / MC. In addition, it can be observed that the thermal stability of OPBI / MC is better than that of pure OPBI. This is because the acid-base interaction between cystine and OPBI effectively improves the thermodynamic properties of the composite membrane. It is worth noting that all prepared samples maintain good thermal stability at 200°C and meet the requirements of HT-PEMFC.

[0055] Figure 6The proton conductivity of high-temperature proton exchange membranes at 100-180°C without humidification is shown. The proton conductivity increases with increasing temperature and with the increase in the content of cystine-functionalized MXene. At 180°C, the proton conductivity of the OPBI / MC-15 membrane is 3.0 times that of the OPBI membrane. This is due to the higher phosphoric acid absorption in the OPBI / MC-15 membrane, and the two-dimensional functionalized MXene can effectively increase the absorption of phosphoric acid. The results show that the cystine-functionalized MXene / polybenzimidazole composite membrane can be used for HT-PEMFC.

Claims

1. A method for preparing a phosphate / cystine functionalized MXene / polybenzimidazole composite high-temperature proton exchange membrane for a high-temperature fuel cell, characterized in that: The method is carried out according to the following steps:

1. Preparation of polybenzimidazole Dissolve benzyltetramine and 4,4-diphenyl ether dicarboxylic acid in polyphosphoric acid, stir at 100°C under nitrogen protection, and after complete dissolution, heat to 140°C, continue stirring until the mixture becomes viscous, and then pour into deionized water to obtain brown filaments, wash with deionized water, dry and grind into powder, add NaHCO3 solution for neutralization, and then repeatedly wash with deionized water until neutral, filter, and dry the obtained solid to obtain OPBI; 2. Preparation of Cystine-functionalized MXene Using Ti3AlC2 as a matrix, a MXene dispersion was prepared by selectively etching the Al layer with hydrochloric acid; the MXene dispersion was added to hydrochloric acid and ultrasonically treated to obtain a MXene hydrochloric acid solution; cystine was dissolved in hydrochloric acid to obtain a cystine hydrochloric acid solution; The cystine hydrochloride solution was added dropwise to the MXene hydrochloride solution at room temperature and stirred, and the mixture was centrifuged after 24 hours of reaction. After washing with deionized water, the precipitate was collected and freeze-dried to obtain the cystine functionalized MXene.

3. Preparation of phosphate / cystine functionalized MXene / polybenzimidazole composite high temperature proton exchange membrane Dissolve OPBI with dimethylacetamide to obtain an OPBI solution; Dispersing the cystine-functionalized MXene in N,N-dimethylacetamide to obtain a cystine-functionalized MXene solution; The cystine functionalized MXene solution is added dropwise to the OPBI solution and stirred to make it evenly mixed, and then cast onto a horizontal glass plate to form a film, and after drying, a cystine functionalized MXene and polybenzimidazole composite film is obtained; wherein the mass ratio of cystine functionalized MXene to OPBI is 1 to 15:100; The cystine functionalized MXene / polybenzimidazole composite membrane is immersed in a phosphoric acid solution, and the phosphoric acid solution on the surface of the composite membrane is wiped off with filter paper after being taken out. After drying, a phosphoric acid / cystine functionalized MXene / polybenzimidazole composite high temperature proton exchange membrane is obtained, and the preparation is completed.

2. The method for preparing a phosphoric acid / cystine functionalized MXene / polybenzimidazole composite high temperature proton exchange membrane for a high temperature fuel cell according to claim 1, characterized in that: In step 1, the mass ratio of benzyltetramine, 4,4-diphenyl ether dicarboxylic acid and polyphosphoric acid is 5.4:6.5:

110.

3. The method for preparing a phosphoric acid / cystine functionalized MXene / polybenzimidazole composite high temperature proton exchange membrane for a high temperature fuel cell according to claim 1, characterized in that: In step 1, the solution is washed with deionized water until the pH value is 7, and then dried and ground into powder.

4. The method for preparing a phosphoric acid / cystine functionalized MXene / polybenzimidazole composite high temperature proton exchange membrane for a high temperature fuel cell according to claim 1, characterized in that: The mass concentration of NaHCO3 solution is 10%.

5. The method for preparing a phosphoric acid / cystine functionalized MXene / polybenzimidazole composite high temperature proton exchange membrane for a high temperature fuel cell according to claim 1, characterized in that: In step 1, OPBI is obtained by drying at 80° C. for 24 h.

6. The method for preparing a phosphoric acid / cystine functionalized MXene / polybenzimidazole composite high temperature proton exchange membrane for a high temperature fuel cell according to claim 1, characterized in that: In step 2, ultrasonic treatment was performed in an ice bath for 3.5 h.

7. The method for preparing a phosphoric acid / cystine functionalized MXene / polybenzimidazole composite high temperature proton exchange membrane for a high temperature fuel cell according to claim 1, characterized in that: In step 2, cystine is dissolved in hydrochloric acid and stirred for 3 h.

8. The method for preparing a phosphoric acid / cystine functionalized MXene / polybenzimidazole composite high temperature proton exchange membrane for a high temperature fuel cell according to claim 1, characterized in that: In step 2, the MXene hydrochloric acid solution and the cystine hydrochloric acid solution are mixed and stirred at 80° C. for 24 h.

9. The method for preparing a phosphoric acid / cystine functionalized MXene / polybenzimidazole composite high temperature proton exchange membrane for a high temperature fuel cell according to claim 1, characterized in that: In step three, the cystine-functionalized MXene / polybenzimidazole composite membrane is immersed in a phosphoric acid solution for 48 hours.

10. The method for preparing a phosphoric acid / cystine functionalized MXene / polybenzimidazole composite high temperature proton exchange membrane for a high temperature fuel cell according to claim 1 or 9, characterized in that: The mass concentration of the phosphoric acid solution is 85%.

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