Gel-state composite proton exchange membrane as well as preparation method and application thereof
By preparing gel-state composite proton exchange membranes using the sol-gel method, the problems of stability of high-temperature proton exchange membrane fuel cells at low temperatures and low conductivity at high temperatures were solved, enabling high-performance and stable operation of fuel cells over a wide temperature range.
Patent Information
- Application Number
- CN202511034823.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-07-25
- Publication Date
- 2025-12-12
AI Technical Summary
Existing high-temperature proton exchange membrane fuel cells exhibit poor membrane electrode stability at low temperatures and low proton conductivity at high temperatures, hindering their commercial development.
A gel-state composite proton exchange membrane was prepared using the sol-gel method. By combining microporous polymers with polybenzimidazole, stable confined nanopores were constructed to enhance proton conduction performance. Furthermore, multi-scale structural design was used to enhance PA retention capacity at low temperatures and improve membrane electrode stability at high temperatures.
This achievement improved proton conductivity at high temperatures, enhanced rapid start-up performance at low temperatures, broadened the operating temperature range of fuel cells, and improved electrochemical performance and stability.
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Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to a gel-state composite proton exchange membrane, a preparation method thereof and an application thereof in fuel cells. BACKGROUND
[0002] Proton exchange membrane fuel cells (PEMFCs) are one of the key directions of hydrogen energy industry development, and are considered as a potential source of green electrochemical energy due to their environmental friendliness and high energy conversion efficiency. Through electrochemical reactions, chemical energy in hydrogen fuel is converted into electrical energy, only emitting water as a byproduct, which can minimize environmental pollution. Phosphoric acid (PA) doped polybenzimidazole (PBI) has become one of the electrolyte materials for high-temperature proton exchange membrane fuel cells (HT-PEMFCs) operating under anhydrous conditions at a temperature range of 120 to 200°C, which can simplify water thermal management and significantly improve work efficiency. Meanwhile, the higher working temperature improves the reaction activity of the catalyst and increases the tolerance to CO or H2S contaminants in the hydrogen inlet stream (>1% CO at 150°C). Since 2005, Celtec@P1000 membranes have been produced by BASF in Germany. This series of polybenzimidazole membranes are made based on a sol-gel production process. However, when high-temperature proton exchange membrane fuel cells (HT-PEMFCs) are started at room temperature or work at a lower temperature, the PA in the membrane electrode will be lost with the generated liquid water, which will affect the efficient proton conduction capacity of the membrane and the good catalytic activity of the catalyst. Therefore, it is necessary to preheat to above 120°C to inhibit the loss of PA, which prolongs the start-up time of the fuel cell and increases the operation difficulty. Therefore, to broaden the working temperature of the proton exchange membrane fuel cell, the performance of the membrane needs to be improved. For HT-PEMFCs, the stability of the membrane electrode at low temperature and the efficient proton conduction of the membrane electrode at high temperature are one of the main factors hindering the commercial development of this type of cell. Therefore, it has become a research difficulty and hotspot for HT-PEMFCs.
[0003] Currently, many researchers have developed a series of unique composite membrane electrode materials to enhance the PA / water retention rate and proton conductivity at high temperature. For high temperature proton exchange membranes (HT-PEMs), the ideal filler material needs to meet the following conditions: first, high affinity with the HT-PEMs polymer backbone, conducive to compatibility; second, excellent thermal and chemical stability, suitable for complex environments; third, containing functional groups such as hydroxyl, amino, carboxyl, etc., which can effectively anchor the proton carrier; fourth, the size of the filler matches the nanoscale mass transfer channel in the HT-PEMs, promoting ion transport. To meet these requirements, researchers have developed covalent organic frameworks (COFs), metal-organic frameworks (MOFs), polyhedral oligomeric silsesquioxanes (POSS), and conjugated microporous polymers (CMPs) as organic filler materials for the preparation of mixed matrix composite proton exchange membranes. However, these materials often have poor processability, poor solubility, and tend to settle at the bottom when casting in solvents, which limits their application. SUMMARY
[0004] The purpose of the present application is to provide a gelable composite proton exchange membrane and its preparation method and application in fuel cells.
[0005] To achieve the above-mentioned purposes, the present application adopts the following technical solutions:
[0006] In a first aspect, the present application provides a gelable composite proton exchange membrane, which is prepared by a method comprising the following steps:
[0007] (1) Under nitrogen protection, aromatic tetraamine monomer A and polycarboxylic acid monomer are pre-polymerized in polyphosphoric acid (PPA), and the reaction is stopped when the viscosity of the reaction system starts to increase, to obtain a microporous polymer precursor reaction solution containing a benzimidazole bridge; the aromatic tetraamine monomer A contains four amine groups a-d, wherein amine groups a and b, and amine groups c and d are located on the same or different aromatic rings, and amine groups a and b, and amine groups c and d are in ortho relationship; the polycarboxylic acid monomer contains at least three carboxyl groups;
[0008] (2) Under nitrogen protection, aromatic tetraamine monomer B and dicarboxylic acid monomer are subjected to polycondensation reaction in polyphosphoric acid, and after sufficient reaction, a viscous polybenzimidazole reaction solution is obtained; the aromatic tetraamine monomer B contains four amine groups e-h, wherein amine groups e and f, and amine groups g and h are located on different aromatic rings, and amine groups e and f, and amine groups g and h are in ortho relationship;
[0009] (3) blending the microporous polymer precursor reaction solution obtained in (1) and the polybenzimidazole reaction solution obtained in (2), further polymerizing in situ to obtain a uniform transparent solution, casting into a film after standing and defoaming, and standing the obtained wet film in air at room temperature, in the standing process, the polyphosphoric acid absorbs water in the air to dissociate into phosphoric acid, and after sufficient standing, a gel-state composite proton exchange membrane is obtained. The aromatic tetramine monomer A and the aromatic tetramine monomer B in the application are only used to distinguish the aromatic tetramine monomers used in different steps, and each of them is independent and can be the same or different.
[0010] The aromatic ring in the aromatic tetramine monomer A in the application can be a benzene ring, and the aromatic tetramine monomer A can contain one or more (such as two) benzene rings, and the four amine groups a-d can be located on the same benzene ring (such as 1, 2, 4, 5-benzene tetramine) or two by two on different benzene rings. In the specific embodiment, the aromatic tetramine monomer A can be selected from at least one of the compounds shown in formula I-1 and I-2, in formula I-1, -R1- is a chemical single bond (i.e. biphenyl structure), -CH2-O-, -O- (ether bond) or -CO- (carbonyl);
[0011]
[0012] The polycarboxylic acid monomer contains at least three carboxyl groups, such as three or four. In the specific embodiment, the polycarboxylic acid monomer can be selected from at least one of the compounds shown in formula II-1 to II-5:
[0013]
[0014] The aromatic ring in the aromatic tetramine monomer B in the application can be a benzene ring, and the aromatic tetramine monomer B can contain multiple (such as two) benzene rings, and the four amine groups e-h can be two by two on different benzene rings. In the specific embodiment, the aromatic tetramine monomer B can be selected from at least one of the compounds shown in formula III, in formula III, -R2- is a chemical single bond (i.e. biphenyl structure), -CH2-O-, -O- (ether bond) or -CO- (carbonyl);
[0015]
[0016] The dicarboxylic acid monomer contains two carboxyl groups. In the specific embodiment, the dicarboxylic acid monomer can be selected from at least one of the compounds shown in formula IV, in formula IV, -A- is selected from one of the chemical structures shown in ① to ⑧:
[0017] HOOC-A-COOH Ⅳ
[0018]
[0019] n is 2≤n≤18.
[0020] As preferred, the polyphosphoric acid is dried before use.
[0021] As preferred, the molar ratio of the aromatic tetramine monomer A and the polycarboxylic acid monomer is 2:1.
[0022] As preferred, in step (1), the total mass fraction of the aromatic tetramine monomer A and the polycarboxylic acid monomer in the prepolymerization system is 1-10%, such as 1%, 2%, 3%, 4%, 5%, 6%, 8%, etc., wherein the prepolymerization system refers to a reaction system composed of the aromatic tetramine monomer A, the polycarboxylic acid monomer, and the polyphosphoric acid.
[0023] As preferred, step (1) is specifically implemented as follows: under nitrogen protection, polyphosphoric acid, aromatic tetramine monomer A, and polycarboxylic acid monomer are added to a reaction container, and stirred at 80-120°C until completely dissolved (preferably batch feeding, and the feeding order can be determined according to the solubility of the substances during stirring and dissolving, such as first adding polyphosphoric acid and stirring and dissolving, then adding the less soluble monomer, and then adding the other monomer after stirring and dissolving to continue stirring and dissolving), and then heated to 140-160°C (more preferably 140-150°C, for example 150°C) for pre-polymerization, and the reaction is stopped when the viscosity of the reaction system starts to increase, to obtain a benzimidazole-bridged microporous polymer precursor reaction solution.
[0024] As preferred, in step (2), the molar ratio of the aromatic tetramine monomer B and the dicarboxylic acid monomer is 1:1.
[0025] As preferred, in step (2), the total mass fraction of the aromatic tetramine monomer B and the dicarboxylic acid monomer in the polycondensation reaction system is 1-10%, such as 1%, 2%, 3%, 4%, 5%, 6%, 8%, etc., wherein the polycondensation reaction system refers to a reaction system composed of the aromatic tetramine monomer B, the dicarboxylic acid monomer, and the polyphosphoric acid.
[0026] As preferred, step (2) is specifically implemented as follows: under nitrogen protection, polyphosphoric acid, aromatic tetramine monomer B, and dicarboxylic acid monomer are added to a reaction container, and stirred at 100-140°C until completely dissolved (preferably batch feeding, and the feeding order can be determined according to the solubility of the substances during stirring and dissolving, such as first adding polyphosphoric acid and stirring and dissolving, then adding the less soluble monomer, and then adding the other monomer after stirring and dissolving to continue stirring and dissolving), and then heated to 170-220°C (more preferably 180-200°C, for example 190°C), and the viscosity of the reaction system gradually increases, and the color deepens, and the reaction is stopped after 16-36h (preferably 20-30h, for example 24h) of reaction, and the temperature is reduced to 120-160°C for heat preservation, to obtain a viscous polybenzimidazole PBI polyphosphoric acid solution.
[0027] As a preference, in step (3), the feeding ratio of the microporous polymer precursor reaction solution to the polybenzimidazole reaction solution is 1:1-15, for example, 1:1, 1:3, 1:4, 1:5, 1:6, 1:8, 1:10, 1:15, etc., more preferably 1:3-10, and more further preferably 1:4-6, in terms of the mass of the monomers contained therein, wherein the mass of the monomers contained in the microporous polymer precursor reaction solution refers to the total mass of the aromatic tetraamine monomer A and the polycarboxylic acid monomer added for preparing the reaction solution, and the mass of the monomers contained in the polybenzimidazole reaction solution refers to the total mass of the aromatic tetraamine monomer B and the dicarboxylic acid monomer added for preparing the reaction solution.
[0028] As a preference, in step (3), the in-situ polymerization is carried out at 160-220°C for 4-24h under stirring to obtain a uniform transparent solution; more preferably, the polymerization temperature is 170-190°C, for example, 180°C, and the stirring reaction time is 10-14h, for example, 12h.
[0029] The casting into a film in step (3) refers to pouring the defoamed solution into a clean mold and using a film doctor with a height of 100-600μm (for example, 100, 200, 300, 400, 450, 500, 600μm) to obtain a wet film.
[0030] As a preference, in step (3), the obtained wet film is left to stand at room temperature in air with a humidity of 40-60%RH (for example, 50%RH) for 2-24h, preferably 8-12h, for example, 10h.
[0031] In a second aspect, the present application provides a preparation method of the gel-state composite proton exchange membrane of the first aspect, which comprises the following steps:
[0032] (1) Under nitrogen protection, the aromatic tetraamine monomer A and the polycarboxylic acid monomer are pre-polymerized in polyphosphoric acid, and the reaction is stopped when the viscosity of the reaction system begins to increase to obtain a microporous polymer precursor reaction solution containing a benzimidazole bridge; the aromatic tetraamine monomer A contains four amine groups a-d, wherein amine groups a and b, and amine groups c and d are located on the same or different aromatic rings, and amine groups a and b, and amine groups c and d are in an ortho relationship, respectively; the polycarboxylic acid monomer contains at least three carboxyl groups;
[0033] (2) Under nitrogen protection, the aromatic tetraamine monomer B and the dicarboxylic acid monomer are pre-polymerized in polyphosphoric acid, and the reaction is stopped when the viscosity of the reaction system begins to increase to obtain a microporous polymer precursor reaction solution containing a benzimidazole bridge; the aromatic tetraamine monomer B contains four amine groups e-h, wherein amine groups e and f, and amine groups g and h are located on the same or different aromatic rings, and amine groups e and f, and amine groups g and h are in an ortho relationship, respectively;
[0034] (3) blending the microporous polymer precursor reaction solution obtained in (1) and the polybenzimidazole reaction solution obtained in (2), further in-situ polymerizing to obtain a uniform transparent solution, and after standing and defoaming, casting into a film, and after standing at room temperature in air, the polyphosphoric acid is dissociated into phosphoric acid by absorbing moisture in air, and after sufficient standing, a gel composite proton exchange membrane is obtained.
[0035] The preparation details of steps (1)-(3) are the same as those of the first aspect, and will not be repeated here.
[0036] In the above-mentioned staged polymerization process, the microporous polymer has good compatibility with PBI due to the similar structure, and a uniform casting solution can be obtained by in-situ polymerization reaction, and the film is prepared by PPA sol-gel method in one step.
[0037] In a third aspect, the present application provides the use of the gel composite proton exchange membrane of the first aspect in a fuel cell.
[0038] In a fourth aspect, the present application provides a membrane electrode, comprising a proton exchange membrane, wherein the proton exchange membrane is the gel composite proton exchange membrane of the first aspect.
[0039] In an embodiment, the membrane electrode further comprises an anode gas diffusion electrode and a cathode gas diffusion electrode, wherein the anode gas diffusion electrode and the cathode gas diffusion electrode are respectively HT-PEMFCs gas diffusion anode and HT-PEMFCs gas diffusion cathode, such as carbon cloth type or carbon paper type HT-PEMFCs gas diffusion anode and cathode.
[0040] The membrane electrode is generally obtained by pressing the anode gas diffusion electrode and the cathode gas diffusion electrode on both sides of the gel composite proton exchange membrane, respectively, and the pressing can be pressing by a clamp, cold pressing or hot pressing.
[0041] In a fifth aspect, the present application provides a fuel cell comprising the membrane electrode of the fourth aspect.
[0042] In an embodiment, the fuel cell uses hydrogen as fuel.
[0043] Compared with the prior art, the present application prepares a new type of composite proton exchange membrane, i.e., a composite film of benzimidazole bridged microporous polymer and polybenzimidazole, the preparation method is easy to mass produce, and the obtained homogeneous proton exchange membrane has ultra-high anhydrous proton conductivity and good high-temperature and low-temperature resistance.
[0044] Specifically, the application innovatively introduces a series of microporous polymers into the gel-state polybenzimidazole during the polymerization process to solve the processing and interface problems. The application uses polycarboxylic acid monomers as functional monomers, aromatic tetraamine monomers as bridging agents, and PPA as a solvent to prepare a microporous polymer precursor reaction solution by solvent thermal pre-polymerization; uses aromatic tetraamine monomers and dicarboxylic acid monomers as monomers and PPA as a solvent to prepare a high-viscosity PBI reaction solution by polycondensation reaction; on this basis, a gel-state composite proton exchange membrane is prepared by one-step sol-gel method through in-situ reaction of the two reaction solutions, which is easy to mass-produce. By virtue of the high specific surface area characteristics of the microporous polymer, the application realizes the uniform dispersion and construction of stable limited nano-pores by regulating the types and structures of monomers, and prepares a high-performance composite membrane, thereby improving the electrochemical performance and stability of the high-temperature proton exchange membrane fuel cell, and inhibiting the leakage, migration and volatilization of PA, etc., and widening the operating temperature range. The PA is enriched in the composite membrane to construct a proton transmission channel, the PA is limited in the microporous polymer pores to promote proton conduction, and the PA loss caused by the frequent start-stop of the cathode water production of the fuel cell is slowed down. At low temperature (<80℃), the existence of multiple N sites in the composite membrane can enhance the uptake of PA, the capillary action can enhance the retention capacity of PA, a proton rapid transmission channel can be constructed, and the cold start performance of the fuel cell can be improved; at high temperature (≥200℃), the rigid structure of the highly cross-linked microporous polymer enhances the stability of the membrane electrode, inhibits the movement of the molecular chain at high temperature, and limits the long-range migration thereof. The pore size (usually 0.5-2nm) is smaller than the free diffusion path of the PA molecule, the volatilization and migration of the PA can be inhibited by physical limitation, the membrane creep rate and pore collapse can be slowed down, and the working temperature and CO tolerance can be improved. Through the design of a multi-scale structure, the balance between rapid proton transmission and long-term stability at high temperature can be realized, and the needs of HT-PEMFCs or other energy devices can be met. BRIEF DESCRIPTION OF DRAWINGS
[0045] Figure 1 is a synthetic route map of the embodiment one of the application.
[0046] Figure 2 is a cross-sectional morphology map of the proton exchange membrane prepared in the embodiment one of the application, showing a layer-by-layer stacked structure.
[0047] Figure 3 is the anhydrous proton conductivity of the proton exchange membrane prepared in the application at different temperatures.
[0048] Figure 4 is the polarization curve and power density curve of the non-back pressure humidified proton exchange membrane fuel cell of the embodiment one and the comparative example one prepared in the application.
[0049] Figure 5 is the 200mA cm -2AC impedance plots and cell polarization curves and power density curves at 2.5 bar back pressure without humidification.
[0050] Figure 6 is the polarization curve and power density curve and AC impedance plot of the proton exchange membrane fuel cell prepared in Example 1 of the present application without back pressure humidification at more than 200℃.
[0051] Figure 7 is the polarization curve and power density curve and AC impedance plot of the proton exchange membrane fuel cell prepared in Example 1 of the present application without back pressure humidification at less than 100℃. DETAILED DESCRIPTION
[0052] In order to make the objectives, technical solutions and advantages of the present application clearer, the technical solutions will be further described clearly and completely by examples below. If no specific conditions are indicated in the examples, the conventional conditions or the conditions suggested by the manufacturers are adopted. If no manufacturers of the reagents or instruments are indicated, the conventional products that can be purchased in the market are adopted.
[0053] Example 1:
[0054] The three-necked reaction kettle was connected with nitrogen flow, and the polyphosphoric acid was preheated in the 80℃ air-drying oven for 0.5h. 40g of polyphosphoric acid was added, and the temperature was raised to 120℃ and stirred for 0.5h. Then 0.27g (1.28mmol) of 3,3'-diaminobenzidine was added, and after stirring to complete dissolution, 0.5g (0.64mmol) of meso-tetrakis(4-carboxyphenyl)porphyrin was added. After mechanical stirring for 5h to dissolve, the temperature was raised to 150℃ for reaction. After about 6h, the viscosity of the reaction system was observed to increase, and the reaction was stopped to obtain a microporous polymer precursor reaction solution with low viscosity.
[0055] 120g of polyphosphoric acid was added, and the temperature was raised to 120℃ and stirred for 0.5h. Then 2.14g (10mmol) of 3,3'-diaminobenzidine was added, and after stirring to complete dissolution, 1.66g (10mmol) of isophthalic acid was added. After mechanical stirring for 5h to dissolve, the temperature was raised to 190℃, and the viscosity of the reaction system gradually increased, and the color deepened. After about 24h, the reaction was completed, and the temperature was lowered to 140℃ for insulation, to obtain a viscous polybenzimidazole p-PBI polyphosphoric acid solution.
[0056] The above two solutions were mixed together, stirred at 180℃ for 12h, and then the obtained uniform transparent solution was poured onto a clean glass plate, uniformly scraped with a 450μm doctor blade, and hydrolyzed in 50%RH air for 10h to obtain a gel state CMP1-PBI composite membrane. Figure 1 The composite membrane exhibited uniformity without defects, which proved that the two polymers had good compatibility; Figure 2The cross section of the film presents a layered stack structure, and the upper and lower skin layers are dense structures, which are beneficial to store PA and slow down the leakage of PA.
[0057] Example Two:
[0058] The three-necked reaction kettle was connected with nitrogen flow, and the polyphosphoric acid was preheated in an 80°C air-drying oven for 0.5 h. 45 g of polyphosphoric acid was added, and the temperature was raised to 120°C and stirred for 0.5 h. Then 0.364 g (1.28 mmol) of 1,2,4,5-benzene tetramine tetrahydrochloride was added, and after stirring to complete dissolution, 0.5 g (0.64 mmol) of meso-tetra(4-carboxyphenyl) porphine was added. After mechanical stirring for 5 h, the temperature was raised to 150°C for reaction. After about 6 h, it was observed that the viscosity of the reaction system began to increase, and the reaction was stopped. A low-viscosity microporous polymer precursor reaction solution was obtained.
[0059] The three-necked reaction kettle was connected with nitrogen flow, and the polyphosphoric acid was preheated in an 80°C air-drying oven for 0.5 h. 45 g of polyphosphoric acid was added, and the temperature was raised to 120°C and stirred for 0.5 h. Then 0.364 g (1.28 mmol) of 1,2,4,5-benzene tetramine tetrahydrochloride was added, and after stirring to complete dissolution, 0.5 g (0.64 mmol) of meso-tetra(4-carboxyphenyl) porphine was added. After mechanical stirring for 5 h, the temperature was raised to 150°C for reaction. After about 6 h, it was observed that the viscosity of the reaction system began to increase, and the reaction was stopped. A low-viscosity microporous polymer precursor reaction solution was obtained.
[0060] The two solutions were mixed together, stirred at 180°C for 12 hours, and then the uniform transparent solution was poured onto a clean glass plate, uniformly scraped with a 450μm scraper, and hydrolyzed in 50% RH air for 10 h to obtain a gel state CMP2-PBI composite film.
[0061] Example Three:
[0062] The three-necked reaction kettle was connected with nitrogen flow, and the polyphosphoric acid was preheated in an 80°C air-drying oven for 0.5 h. 45 g of polyphosphoric acid was added, and the temperature was raised to 120°C and stirred for 0.5 h. Then 0.364 g (1.28 mmol) of 1,2,4,5-benzene tetramine tetrahydrochloride was added, and after stirring to complete dissolution, 0.5 g (0.64 mmol) of meso-tetra(4-carboxyphenyl) porphine was added. After mechanical stirring for 5 h, the temperature was raised to 150°C for reaction. After about 6 h, it was observed that the viscosity of the reaction system began to increase, and the reaction was stopped. A low-viscosity microporous polymer precursor reaction solution was obtained.
[0063] The polyphosphoric acid solution of polybenzimidazole p-PBI was consistent with Example One.
[0064] The two solutions were mixed together, stirred at 180°C for 12 hours, and then the uniform transparent solution was poured onto a clean glass plate, uniformly scraped with a 450 μm doctor blade, and placed in 50% RH air for hydrolysis for 10 h to obtain a gel state CMP3-PBI composite film.
[0065] Example Four:
[0066] A three-necked reaction kettle was purged with nitrogen flow, and the polyphosphoric acid was preheated in an 80°C air-dried oven for 0.5 h. 35 g of polyphosphoric acid was added, and the temperature was raised to 120°C and stirred for 0.5 h. Then 0.364 g (1.28 mmol) of 1,2,4,5-benzene tetramine tetrahydrochloride was added, and after stirring until complete dissolution, 0.281 g (0.64 mmol) of 1,3,5-tris (4-carboxyphenyl) benzene was added. After mechanical stirring for 5 h, the temperature was raised to 150°C for reaction. After about 6 h, the viscosity of the reaction system was observed to increase, and the reaction was stopped to obtain a low-viscosity microporous polymer precursor reaction solution.
[0067] The polybenzimidazole p-PBI polyphosphoric acid solution was prepared in accordance with Example One.
[0068] The two solutions were mixed together, stirred at 180°C for 12 hours, and then the uniform transparent solution was poured onto a clean glass plate, uniformly scraped with a 450 μm doctor blade, and placed in 50% RH air for hydrolysis for 10 h to obtain a gel state CMP4-PBI composite film.
[0069] Comparative Example One:
[0070] The two solutions were mixed together, stirred at 180°C for 12 hours, and then the uniform transparent solution was poured onto a clean glass plate, uniformly scraped with a 450 μm doctor blade, and placed in 50% RH air for hydrolysis for 10 h to obtain a gel state CMP4-PBI composite film.
[0071] The gel state composite films prepared in the above examples and comparative examples were subjected to performance testing, and the testing methods were as follows:
[0072] Proton conductivity test: The composite film was placed between two platinum wire electrodes of a DH7002A electrochemical workstation, and the impedance of the film was determined by an alternating current impedance method. The frequency scanning range was 1 Hz to 1000 kHz, and the temperature interval was 10°C. The proton conductivity was calculated.
[0073] Single cell performance test: The commercial Basf carbon cloth type HT-PEMFCs gas diffusion anode and cathode (catalyst Pt loading is 1.0 mg cm -1 , and the effective area is 2 cm 2 ) and composite membrane were hot-pressed into membrane electrode at 0.5 MPa, 120 °C, and assembled into fuel cells with gasket frame. The single cell polarization curve and electrochemical impedance spectroscopy (EIS) were collected by DH7101B electrochemical workstation test system under dry H2 and O2 with a flow rate of 200 ml / min and different temperatures. The IV curve scanning rate is 5 mV s -1 , the frequency scanning range is 0.1 Hz-100 kHz, and the current density is 200 mA cm -2 .
[0074] Figure 3 The anhydrous proton conductivity of different membranes is shown, and the comparison of examples one and two shows that with the increase of microporous polymer content, the long-range migration of PA to the surface evaporation can be inhibited, the temperature of peak conductivity is increased, and the surface film high temperature resistance is enhanced; Figure 4 , Figure 5 and Figure 6 The fuel cell prepared in example one shows that the peak power reaches 1.70 W cm -2 at 200 °C, no back pressure humidification, 2.71 W cm -2 at 2.5 bar back pressure, and shows ultra-low internal resistance of the cell, and the temperature is further increased to 240 °C (1.76 W cm -2 ), and the performance does not decrease, while the base film without adding microporous polymer in comparative example one is only 1.21 W cm -2 , and the performance starts to decrease at 200 °C. Figure 7 It can still reach 0.45 W cm -2 at 20 °C cold start, showing excellent low temperature start-up performance.
Claims
1. A gel-state composite proton exchange membrane, characterized in that: The gel-state composite proton exchange membrane is prepared by a method comprising the following steps: (1) Under nitrogen protection, aromatic tetraamine monomer A and polycarboxylic acid monomer are prepolymerized in polyphosphoric acid until the viscosity of the reaction system begins to increase. The reaction is then stopped to obtain a microporous polymer precursor reaction solution with benzimidazole bridging. The aromatic tetraamine monomer A contains four amino groups a and b, wherein amino groups a and b, and amino groups c and d are located on the same or different aromatic rings, and amino groups a and b, and amino groups c and d are in an ortho-ortho relationship. The polycarboxylic acid monomer contains at least three carboxyl groups. (2) Under nitrogen protection, aromatic tetraamine monomer B and dicarboxylic acid monomer undergo polycondensation reaction in polyphosphoric acid, and after the reaction is complete, a viscous polybenzimidazole reaction solution is obtained; the aromatic tetraamine monomer B contains four amino groups eh, wherein amino groups e and f, and amino groups g and h are located on different aromatic rings, and amino groups e and f, and amino groups g and h are in an ortho-ortho relationship. (3) The microporous polymer precursor reaction solution obtained in (1) and the polybenzimidazole reaction solution obtained in (2) are mixed and further polymerized in situ to obtain a uniform and transparent solution. After standing and degassing, the solution is cast into a film. The resulting wet film is placed in the air at room temperature. During the standing process, polyphosphoric acid absorbs water from the air and decomposes into phosphoric acid. After standing for a while, a gel-state composite proton exchange membrane is obtained.
2. The gel-state composite proton exchange membrane as described in claim 1, characterized in that: In step (1), the molar ratio of aromatic tetraamine monomer A and polycarboxylic acid monomer is 2:1 based on the molar ratio of amine groups and carboxyl groups contained therein, and the total mass fraction of aromatic tetraamine monomer A and polycarboxylic acid monomer in the prepolymer system is 1-10%. The prepolymer system refers to a reaction system composed of aromatic tetraamine monomer A, polycarboxylic acid monomer and polyphosphoric acid. Step (1) is carried out as follows: Under nitrogen protection, polyphosphoric acid, aromatic tetraamine monomer A and polycarboxylic acid monomer are added to the reaction vessel and stirred at 80-120℃ until completely dissolved. Then, the temperature is raised to 140-160℃ and stirred for prepolymerization. The reaction is stopped when the viscosity of the reaction system begins to increase, and the reaction solution containing benzimidazole-bridged microporous polymer precursor is obtained.
3. The gel-state composite proton exchange membrane as described in claim 1, characterized in that: In step (2), the molar ratio of aromatic tetraamine monomer B to dicarboxylic acid monomer is 1:1, and the total mass fraction of aromatic tetraamine monomer B and dicarboxylic acid monomer in the polycondensation reaction system is 1-10%. The polycondensation reaction system refers to a reaction system composed of aromatic tetraamine monomer B, dicarboxylic acid monomer and polyphosphoric acid. Step (2) is carried out as follows: Under nitrogen protection, polyphosphoric acid, aromatic tetraamine monomer B, and dicarboxylic acid monomer are added to the reaction vessel and stirred at 100-140℃ until completely dissolved. Then the temperature is raised to 170-220℃. The viscosity of the reaction system gradually increases and the color deepens. After the reaction is completed for 16-36 hours, the temperature is lowered to 120-160℃ and kept warm to obtain a viscous polybenzimidazole PBI polyphosphoric acid solution.
4. The gel-state composite proton exchange membrane as described in claim 1, characterized in that: In step (3), the feed ratio of the microporous polymer precursor reaction solution to the polybenzimidazole reaction solution is 1:1-15 (preferably 1:3-10) based on the ratio of the monomers contained therein. The monomer mass contained in the microporous polymer precursor reaction solution refers to the total mass of aromatic tetraamine monomer A and polycarboxylic acid monomer added to prepare the reaction solution. The monomer mass contained in the polybenzimidazole reaction solution refers to the total mass of aromatic tetraamine monomer B and dicarboxylic acid monomer added to prepare the reaction solution.
5. The gel-state composite proton exchange membrane as described in claim 1 or 4, characterized in that: In step (3), the in-situ polymerization is carried out by stirring at 160-220℃ for 4-24 hours to obtain a uniform and transparent solution; preferably, the polymerization temperature is 170-190℃ and the stirring reaction time is 10-14 hours.
6. The gel-state composite proton exchange membrane as described in claim 1, characterized in that: In step (3), the obtained wet film is placed in air with a humidity of 40-60%RH at room temperature for 2-24 hours.
7. A method for preparing a gel-state composite proton exchange membrane as described in any one of claims 1-6, comprising the following steps: (1) Under nitrogen protection, aromatic tetraamine monomer A and polycarboxylic acid monomer are prepolymerized in polyphosphoric acid until the viscosity of the reaction system begins to increase. The reaction is then stopped to obtain a microporous polymer precursor reaction solution with benzimidazole bridging. The aromatic tetraamine monomer A contains four amino groups a and b, wherein amino groups a and b, and amino groups c and d are located on the same or different aromatic rings, and amino groups a and b, and amino groups c and d are in an ortho-ortho relationship. The polycarboxylic acid monomer contains at least three carboxyl groups. (2) Under nitrogen protection, aromatic tetraamine monomer B and dicarboxylic acid monomer undergo polycondensation reaction in polyphosphoric acid, and after the reaction is complete, a viscous polybenzimidazole reaction solution is obtained; the aromatic tetraamine monomer B contains four amino groups eh, wherein amino groups e and f, and amino groups g and h are located on different aromatic rings, and amino groups e and f, and amino groups g and h are in an ortho-ortho relationship. (3) The microporous polymer precursor reaction solution obtained in (1) and the polybenzimidazole reaction solution obtained in (2) are mixed and further polymerized in situ to obtain a uniform and transparent solution. After standing and degassing, the solution is cast into a film. The resulting wet film is placed in the air at room temperature. During the standing process, polyphosphoric acid absorbs water from the air and decomposes into phosphoric acid. After standing for a while, a gel-state composite proton exchange membrane is obtained.
8. The application of the gel-state composite proton exchange membrane as described in any one of claims 1-6 in a fuel cell.
9. A membrane electrode comprising a proton exchange membrane, characterized in that: The proton exchange membrane is a gel-state composite proton exchange membrane as described in any one of claims 1-6.
10. A fuel cell comprising the membrane electrode assembly of claim 9.