Gel type mixed matrix high-temperature proton exchange membrane based on metal organic framework loaded phosphoric acid and preparation method of gel type mixed matrix high-temperature proton exchange membrane

Abstract

The invention discloses a gel type mixed matrix high-temperature proton exchange membrane based on metal organic framework loaded phosphoric acid and a preparation method of the gel type mixed matrix high-temperature proton exchange membrane, a membrane material is prepared by adding turbid liquid of a metal organic framework MIL-101 (Cr) and water into a polybenzimidazole solution to form gel state mixed liquid and then scraping the membrane; mIL-101 (Cr) and deionized water are mixed in advance to form a uniform suspension, the suspension is slowly added into a polybenzimidazole solution, the dispersity of the MIL-101 (Cr) in a PBI matrix is improved and agglomeration is inhibited by utilizing a hydrolysis reaction of polyphosphoric acid (PPA), and phosphoric acid loaded in a cavity of the MIL-101 (Cr) can provide an extra micro-nano space and a proton conduction path, so that the performance of the composite material is improved. The acid doping level and the proton conductivity of the membrane are improved.

Description

Technical Field

[0001] The present invention relates to the field of high-temperature proton exchange membranes, and particularly to a MIL-101(Cr)@PBI gel-type mixed matrix high-temperature proton exchange membrane based on metal-organic framework loaded with phosphoric acid and a preparation method thereof. Background Art

[0002] A fuel cell is an energy conversion device that can convert the chemical energy of hydrogen energy into electrical energy. As an electrochemical device, a fuel cell consists of two electrodes (an anode and a cathode) where reactions occur and an electrolyte that allows ions to transfer from the anode to the cathode. The proton exchange membrane fuel cell (PEMFC) is considered one of the most suitable energy conversion technologies. The proton exchange membrane (PEM) is the core component of the PEMFC and has the functions of conducting H + , isolating hydrogen and oxygen, and blocking the internal electron transfer of the battery. Currently, the more maturely studied and commercially successful PEMs are still Nafion membranes. However, Nafion membranes are only applicable to low-temperature proton exchange membrane fuel cells (LT-PEMFCs) with an operating temperature not exceeding 80 °C. In 1996, Wainright et al. first reported the application of phosphoric acid (PA)-doped polybenzimidazole as a solid electrolyte in fuel cells in Electro-osmotic drag coefficient of water and methanol in polymer electrolytes at elevated temperatures, and showed that the proton conductivity of this proton exchange membrane depends on the phosphoric acid doping level (ADL) in the membrane. So far, polybenzimidazole (PBI) and its derivatives are still the main polymer materials for preparing high-temperature proton exchange membranes.

[0003] The phosphoric acid-doped polybenzimidazole (PA-PBI) membrane stands out among the candidate proton exchange membrane (PEM) materials due to its excellent proton conductivity and stability under high-temperature and anhydrous conditions. Among them, the proton conduction ability of the PA-PBI membrane highly depends on phosphoric acid, and a high ADL can achieve a better proton conductivity. There have been reports on various inorganic filler-doped polybenzimidazole membranes, such as SiO 2 、TiO 2 , carbon nanotubes, phosphotungstic acid, etc. However, these inorganic doping materials destroy the hydrogen bond structure in the membrane, resulting in a decrease in the amount of phosphoric acid adsorbed by the polymer, and thus the proton conductivity of the doped membrane does not increase significantly.

[0004] Currently, a new type of material - metal-organic frameworks (MOFs) - is a one-dimensional, two-dimensional, or three-dimensional network structure self-assembled by the coordination of metal ions or clusters and organic ligands. Due to the characteristics of MOF such as high porosity, easy structural tuning, and large specific surface area, and the good compatibility between MOF and proton exchange membranes, the hydrogen bond network or functional sites in the pores of MOF can effectively transfer protons, which has attracted great attention in the application of proton conduction. Therefore, more and more MOF-modified proton exchange membranes have been developed. Among them, MIL-101(Cr) has been widely concerned due to its high specific surface area, high porosity, good chemical stability, acid and alkali resistance, and high temperature resistance. Summary of the Invention

[0005] The purpose of the present invention is to provide a MIL-101(Cr)@PBI gel-type mixed matrix high-temperature proton exchange membrane based on metal-organic framework loaded with phosphoric acid and its preparation method.

[0006] In the present invention, MIL-101(Cr) is pre-mixed with deionized water to form a uniform suspension, which is slowly added to the polybenzimidazole solution. By using the hydrolysis reaction of polyphosphoric acid (PPA), the dispersion of MIL-101(Cr) in the PBI matrix is improved and agglomeration is inhibited. Moreover, the phosphoric acid loaded inside the cavity of MIL-101(Cr) can provide additional micro-nano spaces and proton conduction paths, improving the acid doping level and proton conductivity of the membrane.

[0007] The technical solution of the present invention is as follows:

[0008] A MIL-101(Cr)@PBI gel-type mixed matrix high-temperature proton exchange membrane based on metal-organic framework loaded with phosphoric acid is prepared by adding a suspension of metal-organic framework MIL-101(Cr) and deionized water to a polybenzimidazole solution to form a gel-like mixture, and then by scraping the film.

[0009] Among them,

[0010] The average particle size of MIL-101(Cr) is 420 - 680 nm, the crystal is octahedral, and the smallest unit formed is a regular tetrahedron structure. These regular tetrahedron structures form a larger cage-like structure in space (as Figure 4 shown);

[0011] In the polybenzimidazole solution, the solvent is polyphosphoric acid; the weight-average molecular weight of polybenzimidazole is 50,000 - 110,000;

[0012] Technical principle: When a suspension of MIL-101(Cr) and deionized water is added to a polybenzimidazole solution, polyphosphoric acid in the polymer solution hydrolyzes to form phosphoric acid, which protonates some of the hydroxyl groups on the surface of MIL-101(Cr), inhibits the aggregation of MIL-101(Cr) particles, constructs a "MIL-phosphoric acid-PBI" multi-level interfacial cross-linked structure, and enhances the compatibility between the two phases. At the same time, the phase transformation from solution to gel state is completed, promoting the uniform dispersion of MIL-101(Cr) in the PBI matrix. After scraping the film, without additional phosphoric acid impregnation, the product has an acid doping level of 40 - 75 mol PA / PRU.

[0013] In the present invention, MIL-101(Cr) is prepared by the following method:

[0014] Cr(NO 3 ) 3 ·9H 2 O, a dicarboxylic acid ligand, a regulator, and deionized water are added to a reaction kettle and mixed evenly. A solvothermal reaction is carried out at 200 - 240 °C for 8 - 16 h, then cooled to room temperature, the supernatant is removed by centrifugation, and the solid product (green) is washed and dried under vacuum to obtain MIL-101(Cr);

[0015] The dicarboxylic acid ligand is selected from one or more of terephthalic acid (H 2 BDC), 2-aminoterephthalic acid (H 2 BDC-NH 2 ), and 1,2,4-benzenetricarboxylic acid (H 2 BDC-COOH);

[0016] The regulator is selected from one of sodium hydroxide, hydrofluoric acid, nitric acid, toluene, and tetramethylammonium hydroxide;

[0017] The specific operations of washing and vacuum drying are as follows: The solid product is mixed with hot DMF (N,N-dimethylformamide), and the resulting suspension is soaked in a water bath at 60 - 100 °C for 1 - 5 h (so that the water level is not lower than the liquid level of the suspension), then centrifuged, and the solid product is collected and washed 3 - 6 times repeatedly; then washed with hot ethanol 3 - 6 times by the same method, and finally dried in a vacuum oven at 120 °C to obtain MIL-101(Cr);

[0018] The temperature of hot DMF and hot ethanol is 60 - 100 °C.

[0019] The preparation method of the MIL-101(Cr)@PBI gel-type mixed matrix high-temperature proton exchange membrane based on metal-organic framework loaded with phosphoric acid according to the present invention is as follows:

[0020] (1) Under an inert gas atmosphere, an aromatic tetraamine monomer, a phenyl dicarboxylic acid monomer, and polyphosphoric acid (solvent and polycondensation agent) are mixed, and the temperature is raised to 120 - 190 °C with stirring for 25 - 35 h to carry out a polymerization reaction to obtain a polybenzimidazole solution;

[0021] Preferably, the molar ratio of the aromatic tetraamine monomer to the phenyl dicarboxylic acid monomer is 1:1;

[0022] Preferably, in the initial reaction system, the total concentration of the aromatic tetraamine monomer and the phenyl dicarboxylic acid monomer is 1 - 15 wt%;

[0023] The aromatic tetraamine monomer is selected from at least one of 3,3'-diaminobenzidine and 1,2,4,5-tetraaminobenzene;

[0024] The phenyl dicarboxylic acid monomer is selected from at least one of terephthalic acid and isophthalic acid;

[0025] (2) MIL-101(Cr) is mixed uniformly with deionized water to obtain a suspension; the polybenzimidazole solution obtained in step (1) is added to a reaction kettle, and then the suspension is added in batches, and stirred at 120 - 190 °C and 30 - 72 r / min for 4 - 12 h to obtain a gel-like mixed solution;

[0026] Preferably, the mass ratio of polybenzimidazole to MIL-101(Cr) is 100:5 - 50;

[0027] (3) The gel-like mixed solution obtained in step (2) is poured onto a substrate and scraped with a film scraping frame to obtain a gel-type mixed matrix high-temperature proton exchange membrane.

[0028] The beneficial effects of the present invention are as follows:

[0029] Through the multiple synergistic effects of physical dispersion (suspension), chemical regulation (PPA hydrolysis), and interfacial bonding (hydrogen bond / coordination), the present invention realizes the highly uniform dispersion of MIL-101(Cr) in the PBI matrix; reduces the agglomeration phenomenon of MIL-101(Cr); and the compatibility of MIL-101(Cr) with the gel membrane is better, providing an effective method for developing high-performance MIL / PBI composite proton exchange membranes.

[0030] Due to the characteristics of high porosity, good chemical stability, and high temperature resistance of MIL-101(Cr), it provides additional micro-nano spaces and proton conduction paths for phosphoric acid, improving the proton conductivity and acid doping level of the proton exchange membrane. The proton exchange membrane provided by the present invention has a proton conductivity of up to 0.05 S / cm at 20 °C, a proton conductivity of up to 0.32 S / cm at 200 °C, and an acid doping level in the membrane of up to 64.86 mol PA / PRU. Brief Description of the Drawings

[0031] Figure 1 : Proton conduction performance diagrams of high-temperature membranes for comparative examples and examples.

[0032] Figure 2 : Morphology diagram of the mixed membrane of Example 2.

[0033] Figure 3 : Electron microscopy image of MIL-101(Cr).

[0034] Figure 4 : Schematic structural diagram of MIL-101(Cr). Detailed implementation manners

[0035] The present invention will be further described below through specific examples, but the protection scope of the present invention is not limited thereto.

[0036] In the following examples, MIL-101(Cr) was prepared as follows:

[0037] Cr(NO 3 ) 3 ·9H 2 O (4 g, 0.01 mol), terephthalic acid ligand (1.66 g, 0.01 mol), regulator HNO 3 (0.435 ml), and 48 mL of deionized water were added to a reaction kettle and mixed evenly. A solvothermal reaction was carried out at 220 °C for 8 h, and then cooled to room temperature. The supernatant was removed by centrifugation to obtain a green product; then hot DMF at 80 °C was added to a centrifuge tube and mixed evenly to obtain a suspension, which was placed in a water bath at 80 °C and soaked for 1.5 h. The water level was not lower than the liquid level of the suspension in the centrifuge tube, and then centrifuged to obtain a green solid, which was washed 5 times repeatedly; then washed 5 times with hot ethanol at 80 °C by the same method. Finally, the obtained MIL-101(Cr) was centrifuged and placed in a vacuum oven to be dried at 120 °C to obtain a MIL-101(Cr) solid.

[0038] Comparative Example 1:

[0039] The commercial PBI membrane provided by PBIPerformance company was immersed in 85 wt% phosphoric acid solution for 168 hours to complete acid doping, and a traditional PA / PBI membrane was prepared.

[0040] The traditional PA / PBI membrane obtained in Comparative Example 1 was analyzed and tested:

[0041] Experimental result: Phosphoric acid doping level: 7.73 mol PA / PRU.

[0042] Proton conductivity (without additional humidification): Conductivity at 25°C: 0.015 S / cm, conductivity at 80°C: 0.051 S / cm, conductivity at 200°C: 0.096 S / cm, conductivity at 240°C: 0.070 S / cm.

[0043] Comparative Example 2:

[0044] (1) Weigh 3.1358 g of 3,3'-diaminobenzidine monomer and 2.4312 g of terephthalic acid monomer respectively, pour them into a three-necked reaction kettle, and then add 180 g of solvent and polycondensation agent polyphosphoric acid to the reaction kettle. React under a nitrogen atmosphere, and use an oil bath heating method to raise the temperature to 180°C and react for 30 hours.

[0045] (2) Slowly add 27 ml of deionized water to the polymer solution multiple times. During the process, the temperature is 160°C and the stirring rate is 30 r / min to obtain a gel-like mixture.

[0046] (3) Pour the gel-like mixture onto a 25×50 cm glass plate substrate and scrape the film with a film scraping frame to obtain a gel-type high-temperature proton exchange membrane (thickness 240 μm).

[0047] Analytical tests were carried out on the obtained gel-type high-temperature proton exchange membrane:

[0048] The membrane performance of the gel-type high-temperature proton exchange membrane obtained in this example was tested. The experimental results: Proton conductivity at 200°C: 0.23 S / cm.

[0049] The acid doping level of the gel-type high-temperature proton exchange membrane obtained in this example is: 47.75 mol PA / PRU.

[0050] Example 1:

[0051] (1) Weigh 3.1358 g of 3,3'-diaminobenzidine monomer and 2.4312 g of terephthalic acid monomer respectively, pour them into a three-necked reaction kettle, and then add 180 g of solvent and polycondensation agent polyphosphoric acid to the reaction kettle. React under a nitrogen atmosphere, and use an oil bath heating method to raise the temperature to 180°C and react for 30 hours.

[0052] (2) Mix 0.648 g of MIL-101(Cr) compound with 27 mL of deionized water, and stir evenly by ultrasonic to obtain a suspension.

[0053] (3) Slowly add the suspension to the polymer solution in the reaction kettle multiple times. During the process, the temperature is 160°C and the stirring rate is 30 r / min to obtain a gel-like mixture.

[0054] (4) Pour the gel-like mixture onto a 25×50 cm glass plate substrate and scrape the film with a film scraping frame to obtain a gel-type mixed matrix high-temperature proton exchange membrane (thickness 240 μm).

[0055] Perform analysis and testing on the obtained gel-type mixed matrix high-temperature proton exchange membrane:

[0056] Perform membrane performance testing on the gel-type mixed matrix high-temperature proton exchange membrane obtained in this example. Experimental results: Proton conductivity at 200 °C: 0.30 S / cm.

[0057] The acid doping level of the gel-type mixed matrix high-temperature proton exchange membrane obtained in this example is: 65.22 mol PA / PRU.

[0058] Example 2:

[0059] (1) Weigh 3.1358 g of 3,3'-diaminobenzidine monomer and 2.4312 g of terephthalic acid monomer respectively, pour them into a three-necked reaction kettle, and then add 180 g of solvent and polycondensing agent polyphosphoric acid to the reaction kettle. React under a nitrogen atmosphere, and use an oil bath heating method to directly raise the temperature to 180 °C and react for 30 hours.

[0060] (2) Mix 0.408 g of MIL-101(Cr) compound with 27 mL of deionized water, and stir evenly by ultrasonic to obtain a suspension.

[0061] (3) Slowly add the suspension to the polymer solution in the reaction kettle multiple times. During the process, the temperature is 160 °C and the stirring rate is 30 r / min to obtain a gel-like mixture.

[0062] (4) Pour the gel-like mixture onto a 25×50 cm glass plate substrate and scrape the film with a film scraping frame to obtain a gel-type mixed matrix high-temperature proton exchange membrane (thickness 240 μm).

[0063] Perform analysis and testing on the obtained gel-type mixed matrix high-temperature proton exchange membrane:

[0064] Perform membrane performance testing on the gel-type mixed matrix high-temperature proton exchange membrane obtained in this example. Experimental results: Proton conductivity at 200 °C: 0.32 S / cm.

[0065] The acid doping level of the gel-type mixed matrix high-temperature proton exchange membrane obtained in this example is: 64.86 mol PA / PRU.

[0066] Example 3:

[0067] (1) Weigh 3.1358 g of 3,3'-diaminobenzidine monomer and 2.4312 g of terephthalic acid monomer separately, pour them into a three-necked reaction kettle, and then add 180 g of solvent and polycondensing agent polyphosphoric acid to the reaction kettle. React under a nitrogen atmosphere and use an oil bath heating method to raise the temperature to 180 °C and react for 30 hours.

[0068] (2) Mix 0.918 g of MIL-101(Cr) compound with 27 mL of deionized water, and stir evenly by ultrasonic to obtain a suspension.

[0069] (3) Slowly add the suspension to the polymer solution in the reaction kettle multiple times. During the process, the temperature is 160 °C and the stirring rate is 30 r / min to obtain a gel-like mixture.

[0070] (4) Pour the gel-like mixture onto a 25×50 cm glass plate substrate and scrape the film with a film scraping frame to obtain a gel-type mixed matrix high-temperature proton exchange membrane (thickness 240 μm).

[0071] Analyze and test the obtained gel-type mixed matrix high-temperature proton exchange membrane:

[0072] Test the membrane performance of the gel-type mixed matrix high-temperature proton exchange membrane obtained in this example. Experimental results: Proton conductivity at 200 °C: 0.30 S / cm.

[0073] The acid doping level of the gel-type mixed matrix high-temperature proton exchange membrane obtained in this example is: 74.78 mol PA / PRU.

[0074] Table 1 Membrane components of high-temperature membranes in the comparative example and the example

[0075]

Claims

1. A MIL-101(Cr)@PBI gel-type mixed matrix high temperature proton exchange membrane based on metal organic framework loaded with phosphoric acid, characterized in that: The membrane material is prepared by adding a suspension of metal organic framework MIL-101 (Cr) and water into a polybenzimidazole solution to form a gel-like mixed solution, and then scraping the mixed solution. in, The average particle size of MIL-101(Cr) is 420-680nm, and the crystal is octahedral. The smallest unit formed is a regular tetrahedral structure, which forms a larger cage-like structure in space. In the polybenzimidazole solution, the solvent is polyphosphoric acid; the weight average molecular weight of the polybenzimidazole is between 50,000 and 110,000.

2. The MIL-101(Cr)@PBI gel-type mixed matrix high temperature proton exchange membrane based on metal organic framework loaded phosphoric acid as claimed in claim 1, characterized in that: MIL-101(Cr) was prepared as follows: Cr(NO3)3·9H2O, diformic acid ligand, regulator and deionized water were added into a reaction kettle and mixed evenly, and a solvent thermal reaction was carried out at 200-240°C for 8-16 hours, and then cooled to room temperature, and the supernatant was removed by centrifugation. The solid product was washed and vacuum dried to obtain MIL-101(Cr); The dicarboxylic acid ligand is selected from one or more of terephthalic acid, 2-aminoterephthalic acid, and 1,2,4-benzenetricarboxylic acid; The regulator is selected from one of sodium hydroxide, hydrofluoric acid, nitric acid, toluene and tetramethylammonium hydroxide.

3. The MIL-101(Cr)@PBI gel-type mixed matrix high temperature proton exchange membrane based on metal organic framework loaded phosphoric acid as claimed in claim 2, characterized in that: The washing and vacuum drying operations are as follows: the solid product is mixed with hot DMF, the resulting suspension is immersed in a 60-100° C. water bath for 1-5 hours, then centrifuged, the solid product is collected and washed repeatedly 3-6 times; then washed with hot ethanol 3-6 times by the same method, and finally dried in a vacuum oven at 120° C. to obtain MIL-101(Cr); The temperature of hot DMF and hot ethanol is 60-100°C.

4. The method for preparing the MIL-101(Cr)@PBI gel-type mixed matrix high temperature proton exchange membrane based on metal organic framework loaded phosphoric acid as claimed in claim 1, characterized in that: The steps include: (1) In an inert gas atmosphere, an aromatic tetraamine monomer, a dicarboxylic acid phenyl monomer, and polyphosphoric acid are mixed, and the temperature is raised to 120 to 190° C. under stirring for a polymerization reaction for 25 to 35 hours to obtain a polybenzimidazole solution; The aromatic tetraamine monomer is selected from at least one of 3,3'-diaminobenzidine and 1,2,4,5-tetraaminobenzene; The dicarboxylic acid phenyl monomer is selected from at least one of terephthalic acid and isophthalic acid; (2) mixing MIL-101(Cr) and deionized water uniformly to obtain a suspension; adding the polybenzimidazole solution obtained in step (1) to a reaction kettle, and then adding the suspension in batches, stirring at 120-190° C. and 30-72 r / min for 4-12 hours to obtain a gel-like mixed solution; (3) Pour the gel-like mixed solution obtained in step (2) onto a substrate and scrape the membrane with a scraping frame to obtain a gel-type mixed matrix high-temperature proton exchange membrane.

5. The preparation method according to claim 4, characterized in that: In step (1), the molar ratio of the aromatic tetraamine monomer to the dicarboxylic acid phenyl monomer is 1:

1.

6. The preparation method according to claim 4, characterized in that: In the initial reaction system of step (1), the total concentration of the aromatic tetraamine monomer and the dicarboxylic acid phenyl monomer is 1 to 15 wt %.

7. The preparation method according to claim 4, characterized in that: In step (2), the mass ratio of polybenzimidazole to MIL-101(Cr) is 100:5-50.

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