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

Abstract

The application relates to a preparation method of a phosphoric acid / cystine functionalized MXene / polybenzimidazole composite high-temperature proton exchange membrane for high-temperature fuel cells, and relates to a preparation method of a high-temperature proton exchange membrane.The application aims to solve the problem of insufficient oxidation resistance of existing fuel cell proton exchange membranes, and the method is as follows: 1, preparing polybenzimidazole; 2, preparing cystine functionalized MXene; 3, preparing a proton exchange membrane in which the cystine functionalized MXene is compounded with OPBI, and then impregnating in a phosphoric acid solution, and the preparation is completed.The application designs the application of a cystine functionalized MXene / polybenzimidazole composite membrane for high-temperature fuel cells in HT-PEM, improves the conductivity and oxidation resistance of the proton exchange membrane, provides a basis for developing a novel and efficient HT-PEM, and the application is applied to the technical field of proton exchange membrane fuel cells.

Description

TECHNICAL FIELD

[0001] The application relates to a preparation method of a phosphoric acid / cystine functionalized MXene / polybenzimidazole composite high-temperature proton exchange membrane for a high-temperature fuel cell. BACKGROUND

[0002] About 65% of global 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 a clean and efficient energy source, plays an important role in the future energy system. Proton exchange membrane fuel cell (PEMFC) is one of the important technologies for hydrogen energy utilization, and has become a research hotspot in the field of hydrogen energy batteries due to its high energy conversion efficiency, fast start and adaptability to various application scenarios. PEMFC can be divided into low-temperature proton exchange membrane fuel cell (LT-PEMFC) and high-temperature proton exchange membrane fuel cell (HT-PEMFC) according to the working temperature. Among them, HT-PEMFC has a working temperature in the range of 100-200 DEG C, which not only improves the CO tolerance to a certain extent, but also simplifies the water and heat management system, so that the stability and efficiency of the fuel cell system are significantly improved. Therefore, HT-PEMFC has 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 cell. The performance of the proton exchange membrane determines the performance of the proton exchange membrane fuel cell. 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 oxidation resistance and poor long-term stability. How to further improve the oxidation resistance of HT-PEM and prolong its service life has become a key challenge. SUMMARY

[0004] The purpose of the application is to solve the problem of insufficient oxidation resistance of the existing fuel cell proton exchange membrane, and provide a preparation method of a phosphoric acid / cystine functionalized MXene / polybenzimidazole composite high-temperature proton exchange membrane for a high-temperature fuel cell and application thereof.

[0005] The preparation method of the 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:

[0006] I. Preparation of polybenzimidazole

[0007] Dissolve biphenyltetramine and 4,4-diphenyl ether dicarboxylic acid in polyphosphoric acid, stir at 100 DEG C under the protection of nitrogen, after complete dissolution, increase the temperature to 140 DEG C, continue to stir until the mixture is viscous, then pour into deionized water to obtain brownish silk, then wash with deionized water, then dry and polish into powder, add NaHCO3 solution for neutralization, then repeatedly wash with deionized water until neutral, filter, dry the obtained solid, and OPBI is obtained;

[0008] II. Preparation of cystine functionalized MXene

[0009] MXene dispersion liquid is prepared by taking Ti3AlC2 as a matrix and selectively etching the Al layer with hydrochloric acid; the MXene dispersion liquid is added to hydrochloric acid, and MXene hydrochloric acid solution is obtained after ultrasonic treatment; cystine hydrochloric acid solution is obtained by dissolving cystine in hydrochloric acid; the cystine hydrochloric acid solution is added dropwise into the MXene hydrochloric acid solution at room temperature and stirred, and after reaction for 24 hours, centrifugation is performed, and after washing with deionized water, the precipitate is collected, and cystine functionalized MXene is obtained after freeze-drying;

[0010] III. Preparation of phosphoric acid / cystine functionalized MXene / polybenzimidazole composite high-temperature proton exchange membrane

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

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

[0013] The application of the phosphoric acid / cystine functionalized MXene / polybenzimidazole composite high-temperature proton exchange membrane as a high-temperature fuel cell proton exchange membrane.

[0014] The composite membrane prepared by the application has a higher residual weight after Fenton reagent test, which shows that OPBI / MC has superior oxidation resistance stability, which is attributed to the sulfur-sulfur bond on cystine as a free radical scavenger. The thermal stability of OPBI / MC is superior to that of pure OPBI, which is due to the addition of functionalized MXene, which improves the thermodynamic properties of the electrolyte membrane material through the direct acid-base interaction of the carboxyl group of cystine with the imidazole ring of OPBI, and the optimized polymer electrolyte membrane material is not prone to main chain degradation under high temperature conditions. It is worth noting that all the prepared samples maintain good thermal stability at 200 DEG 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 improves the absorption amount of phosphoric acid, and the phosphoric acid group provides proton transport sites. The application provides a basis for developing new efficient HT-PEM, and provides a new idea for the development of hydrogen energy and fuel cell technology in the future. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 It is a synthesis route diagram of MXene and cystine functionalized MXene;

[0016] Figure 2 It is an infrared spectrum of OPBI and OPBI / MC proton exchange membrane in the application;

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

[0018] Figure 4 It is an oxidation resistance performance image of the proton exchange membrane;

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

[0020] Figure 6 It is a schematic diagram of the proton conductivity of the membrane at 100-180 DEG C in the application. DETAILED DESCRIPTION

[0021] Specific embodiment one: the preparation method of the phosphoric acid / cystine functionalized MXene / polybenzimidazole composite high-temperature proton exchange membrane for high-temperature fuel cell in the embodiment is carried out according to the following steps:

[0022] I. Preparation of polybenzimidazole

[0023] Dissolve biphenyltetramine and 4,4-diphenyl ether dimethyl acid in polyphosphoric acid, stir at 100℃ under nitrogen protection, after complete dissolution, increase the temperature to 140℃, continue to stir until the mixture is viscous, then pour into deionized water to obtain brownish silk, then wash with deionized water, then dry and grind into powder, add NaHCO3 solution for neutralization, then wash repeatedly with deionized water until neutral, filter, dry the obtained solid to obtain OPBI;

[0024] II. Preparation of cystine functionalized MXene

[0025] MXene dispersion liquid was prepared by taking Ti3AlC2 as matrix and using hydrochloric acid to selectively etch Al layer; MXene hydrochloric acid solution was obtained by adding MXene dispersion liquid into hydrochloric acid and ultrasonic treatment; Cystine hydrochloric acid solution was obtained by dissolving cystine in hydrochloric acid; Cystine functionalized MXene was obtained by adding cystine hydrochloric acid solution dropwise into MXene hydrochloric acid solution, stirring at room temperature, centrifuging after 24 hours of reaction, washing with deionized water, collecting the precipitate, and freeze-drying;

[0026] III. Preparation of phosphoric acid / cystine functionalized MXene / polybenzimidazole composite high-temperature proton exchange membrane

[0027] OPBI solution was obtained by dissolving OPBI with N,N-dimethylacetamide; Cystine functionalized MXene solution was obtained by dispersing cystine functionalized MXene in N,N-dimethylacetamide; Cystine functionalized MXene / polybenzimidazole composite membrane was obtained by adding cystine functionalized MXene solution dropwise into OPBI solution, stirring to mix uniformly, then pouring onto a horizontal glass plate to flow into a film, and drying; wherein the mass ratio of cystine functionalized MXene to OPBI is 1-15:100;

[0028] Phosphoric acid / cystine functionalized MXene / polybenzimidazole composite high-temperature proton exchange membrane was obtained by immersing the cystine functionalized MXene / polybenzimidazole composite membrane in phosphoric acid solution, wiping off the phosphoric acid solution on the surface of the composite membrane with filter paper after taking it out, and drying, thereby completing the preparation.

[0029] Specific implementation method two: the difference between this implementation method and specific implementation method one is that the mass ratio of biphenyltetramine, 4,4-diphenyl ether dimethyl acid and polyphosphoric acid in step one is 5.4:6.5:110. The others are the same as specific implementation method one.

[0030] Specific implementation method three: the difference between this implementation method and specific implementation method one or two is that the solution is washed with deionized water until the PH is 7 in step one, then dried and ground into powder. The others are the same as specific implementation method one or two.

[0031] Specific implementation four: the difference between this implementation and one of the specific implementations one to three is that the mass concentration of the NaHCO3 solution is 10%. The others are the same as one of the specific implementations one to three.

[0032] Specific implementation five: the difference between this implementation and one of the specific implementations one to four is that the OPBI is obtained by drying at 80°C for 24h in step one. The others are the same as one of the specific implementations one to four.

[0033] Specific implementation six: the difference between this implementation and one of the specific implementations one to five is that the ultrasonic treatment is performed under ice bath condition for 3.5h in step two. The others are the same as one of the specific implementations one to five.

[0034] Specific implementation seven: the difference between this implementation and one of the specific implementations one to six is that the cystine is dissolved in hydrochloric acid and stirred for 3h in step two. The others are the same as one of the specific implementations one to six.

[0035] Specific implementation eight: the difference between this implementation and one of the specific implementations one to seven is that the MXene hydrochloric acid solution and the cystine hydrochloric acid solution are mixed and stirred at 80°C for 24h in step two. The others are the same as one of the specific implementations one to seven.

[0036] Specific implementation nine: the difference between this implementation and one of the specific implementations one to eight is that the drying is performed at 80°C for 24h in step three. The others are the same as one of the specific implementations one to eight.

[0037] Specific implementation ten: the difference between this implementation and one of the specific implementations one to nine is that the mass concentration of the phosphoric acid solution is 85% in step three. The others are the same as one of the specific implementations one to nine.

[0038] Specific implementation eleven: the difference between this implementation and one of the specific implementations one to ten is that the step three is immersed in the phosphoric acid solution for 48h. The others are the same as one of the specific implementations one to ten.

[0039] The content of the present application is not limited to the content of each of the above-mentioned embodiments, and the combination of one or more specific embodiments can also achieve the purpose of the application.

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

[0041] I. Preparation of polybenzimidazole (OPBI)

[0042] Synthesis route of polybenzimidazole (OPBI):

[0043]

[0044] Biphenyltetramine (5.4 g) and 4,4-diphenyl ether dicarboxylic acid (6.5 g) were dissolved in polyphosphoric acid (110 g) in a 250 ml three-necked round-bottom flask, and stirred mechanically under nitrogen protection at 100 °C for 4 h until a homogeneous mixture was obtained. The temperature was then raised to 140 °C, and mechanical stirring was continued for 2-4 h until the solution became viscous. The solution was then poured into deionized water to obtain a brownish, filamentous polymer. After washing with deionized water several times to remove a large amount of acid, the polymer was dried and ground into powder. The powder was then added into a NaHCO3 solution (10 wt%) and neutralized for 24 h. After filtration, the solid was washed with deionized water until the pH of the filtrate was 7. The obtained solid was dried at 80 °C for 24 h to obtain the OPBI polymer.

[0045] II. Preparation of MXene and functionalized MXene

[0046] The preparation method of MXene and functionalized MXene is as shown in Figure 1 ;

[0047] MAX (Ti3AlC2) powder was used as the matrix, and a MXene dispersion solution (Ti3C2T x ) was prepared by selectively etching the Al layer with 12 M hydrochloric acid. 25 mL of MXene was added to 50 mL of 12 M hydrochloric acid, and ultrasonic treatment was performed in an ice bath for three and a half hours to obtain a MXene hydrochloric acid solution. 2 g of cystine was dissolved in 25 mL of 12 M hydrochloric acid and stirred for 3 h to obtain a cystine hydrochloric acid solution. The MXene hydrochloric acid solution and the cystine hydrochloric acid solution were mixed and stirred at 80 °C for 24 h. The solution was centrifuged, the precipitate was collected, and freeze-drying was performed to obtain cystine functionalized MXene (MC).

[0048] III. Phosphoric acid / 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 uniformly dispersed by ultrasonic treatment to obtain an MC solution. The two solutions were mixed and stirred uniformly, and the uniformly mixed solution was cast on a flat glass plate. Drying was performed at 80 °C for 24 h to obtain a cystine functionalized MXene / polybenzimidazole composite membrane. The cystine functionalized MXene / polybenzimidazole composite membrane was immersed in a 85% phosphoric acid solution for 48 h. After taking out, the phosphoric acid solution on the surface of the composite membrane was wiped off with filter paper, and drying was performed to obtain a phosphoric acid / cystine functionalized MXene / polybenzimidazole composite high-temperature proton exchange membrane.

[0050] In the mixed solution, the mass ratio of cystine-functionalized MXene to OPBI polymer was 1:100, 3:100, 7:100, 10:100, or 15:100, to prepare composite high-temperature proton exchange membranes with composite rates of 1%, 3%, 7%, 10%, and 15%, respectively, which were represented as OPBI / MC-1, OPBI / MC-3, OPBI / MC-7, OPBI / MC-10, and OPBI / MC-15.

[0051] Infrared spectra of OPBI and OPBI / MC, such as Figure 2 As shown, in all samples at 1015 cm -1 and 1600cm -1 The same characteristic peaks of aryl ether bonds and C=N stretching vibrations of the imidazole ring appeared at 659 cm⁻¹ as those of OPBI. -1 and 1285cm -1 The peaks at the positions represent SS and CS bonds, respectively, indicating that a composite film of MC and OPBI was successfully prepared.

[0052] Atomic force microscopy of composite high-temperature proton exchange membranes, such as Figure 3 As shown, Figure 3 a is the AFM image of OPBI / MC-1. Figure 3 b is an AFM image of OPBI / MC-7, where the brighter layers are 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 soaking in Fenton's reagent for 72 hours. Compared with the OPBI membrane, the composite high-temperature proton exchange membrane prepared in the example has a higher residual weight, which indicates that OPBI / MC has superior oxidative stability, attributed to the presence of sulfur-sulfur bonds on the side chains as free radical scavengers.

[0054] Figure 5 The TGA curves for OPBI and OPBI / MC are shown. The results indicate that the weight loss of the samples can be divided into two stages. The first stage, before 200℃, is mainly due to the loss of adsorbed water and solvent in the membrane. The second stage, after 500℃, is attributed to the degradation of the OPBI or OPBI / MC backbone. Furthermore, the thermal stability of OPBI / MC is observed to be superior to that of pure OPBI. This is because the acid-base interaction between cysteine ​​and OPBI effectively enhances the thermodynamic properties of the composite membrane. Notably, all prepared samples maintain good thermal stability at 200℃ and meet the requirements of HT-PEMFC.

[0055] Figure 6The proton conductivity of high temperature proton exchange membrane was shown at 100-180℃ without humidification. The proton conductivity increased with the increase of temperature and the content of cystine functionalized MXene. At 180℃, the proton conductivity of OPBI / MC-15 membrane was 3.0 times of that of OPBI membrane, which was due to the higher phosphoric acid absorption in OPBI / MC-15 membrane, and the two-dimensional functionalized MXene could effectively improve the absorption of phosphoric acid. The results showed that the cystine functionalized MXene / polybenzimidazole composite membrane could be used for HT-PEMFC.

Claims

1. A method for preparing a phosphoric acid / cystine functionalized MXene / polybenzimidazole composite high-temperature proton exchange membrane for high-temperature fuel cells, characterized in that, The method is carried out in the following steps: I. Preparation of polybenzimidazole Dissolve biphenyl tetramine and 4,4-diphenyl ether dimethyl acid in polyphosphoric acid, stir at 100℃ under the protection of nitrogen, after complete dissolution, warm up to 140℃, continue to stir until the mixture is viscous, then pour into deionized water to obtain brownish silk, then wash with deionized water, then dry and grind into powder, add NaHCO3 solution for neutralization, then repeatedly wash with deionized water until neutral, filter, dry the obtained solid to obtain OPBI; II. Preparation of cystine functionalized MXene Take Ti3AlC2 as the substrate, and use hydrochloric acid to selectively etch the Al layer to prepare a MXene dispersion liquid; add the MXene dispersion liquid to hydrochloric acid, and obtain a MXene hydrochloric acid solution after ultrasonic treatment; dissolve cystine in hydrochloric acid to obtain a cystine hydrochloric acid solution; Drop the cystine hydrochloric acid solution into the MXene hydrochloric acid solution and stir at room temperature, centrifuge after 24 hours of reaction, wash with deionized water, collect the precipitate, and freeze-dry to obtain cystine functionalized MXene; III. Preparation of phosphoric acid / cystine functionalized MXene / polybenzimidazole composite high-temperature proton exchange membrane Dissolve OPBI in N,N-dimethylacetamide to obtain an OPBI solution; Disperse the cystine functionalized MXene in N,N-dimethylacetamide to obtain a cystine functionalized MXene solution; Drop the cystine functionalized MXene solution into the OPBI solution and stir to mix evenly, then pour onto a horizontal glass plate to flow into a film, and after drying, obtain a cystine functionalized MXene / polybenzimidazole composite membrane; the mass ratio of the cystine functionalized MXene to OPBI is 1-15:100; Immerse the cystine functionalized MXene / polybenzimidazole composite membrane in a phosphoric acid solution, wipe off the phosphoric acid solution on the surface of the composite membrane with filter paper after taking it out, and after drying, obtain a phosphoric acid / cystine functionalized MXene / polybenzimidazole composite high-temperature proton exchange membrane, i.e. complete the preparation.

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

110.

3. The method of claim 1, wherein the method is characterized by: In step one, wash with deionized water until the solution PH is 7, then dry and grind into powder.

4. The method of claim 1, wherein the phosphoric acid / cystine functionalized MXene / polybenzimidazole composite high-temperature proton exchange membrane for high-temperature fuel cells is characterized by, The mass concentration of the NaHCO3 solution is 10%.

5. The method of claim 1, wherein the method of preparing a phosphoric acid / cystine functionalized MXene / polybenzimidazole composite high-temperature proton exchange membrane for a high-temperature fuel cell is characterized by, In step one, dry at 80℃ for 24h to obtain OPBI.

6. The method of claim 1, wherein the method of preparing a phosphoric acid / cystine functionalized MXene / polybenzimidazole composite high-temperature proton exchange membrane for a high-temperature fuel cell is characterized by, In step two, ultrasonic treatment under ice bath conditions for 3.5h.

7. The method according to claim 1, wherein the method for preparing a phosphoric acid / cystine functionalized MXene / polybenzimidazole composite high-temperature proton exchange membrane for high-temperature fuel cells is characterized by, In step two, dissolve cystine in hydrochloric acid and stir for 3h.

8. The method of claim 1, wherein the method is characterized by: In step two, mix the MXene hydrochloric acid solution and the cystine hydrochloric acid solution and stir at 80℃ for 24h.

9. The method according to claim 1, wherein the method for preparing a phosphoric acid / cystine functionalized MXene / polybenzimidazole composite high-temperature proton exchange membrane for high-temperature fuel cells is characterized by, In step three, immerse the cystine functionalized MXene / polybenzimidazole composite membrane in a phosphoric acid solution for 48h.

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

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