A branched ionomer based on porphyrin, its preparation method and use as a binder

Abstract

The present application relates to fuel cell application technical field, especially to a kind of branched type ionomer based on porphyrin and its preparation method and as binder application.The preparation method includes the following steps: S1) by superacid catalytic polymerization reaction preparation porphyrin branched type polymer main chain;The monomer of the polymerization reaction includes porphyrin monomer, aromatic compound monomer and ketone monomer;S2) above-mentioned porphyrin branched type polymer main chain is sequentially deprotonated, quaternized, to obtain branched type ionomer based on porphyrin.The present application provides a series of branched type polymers based on porphyrin, introduce different molar quantities of porphyrin in polymer main chain, the polymer can be used as binder in fuel cell, the structure of polymer with porphyrin is conducive to the transmission of substance.And, using the interaction between porphyrin and platinum makes platinum catalyst better dispersion, improves the utilization of catalyst.

Description

Technical Field

[0001] This invention relates to the field of fuel cell application technology, and in particular to a porphyrin-based branched ionomer, its preparation method, and its application as a binder. Background Technology

[0002] Alkaline anion exchange membrane fuel cells (AEMFCs), as a promising clean energy technology, have attracted widespread attention due to their ability to use non-precious metal catalysts in an alkaline environment, significantly reducing manufacturing costs. However, their commercialization faces a core challenge—ARMFCs suffer from significant performance bottlenecks, particularly rapid voltage decay at high current densities. This bottleneck mainly stems from the slow electrode kinetics and limited mass transport at the multiphase interface of the catalytic system, especially the hydroxyl ion conduction efficiency and the supply capacity of reactant gases (such as oxygen). In-depth analysis reveals that the performance limitation is the result of a combination of factors: the inherent activity of the catalyst, the conductivity of the membrane, and, most importantly, the complex multiphase mass transfer process within the three-phase reaction zone. Among these, the ionomer binder, as a key component in constructing the three-phase reaction zone, plays a role far beyond ion conduction. Encapsulating the catalyst, it directly dominates the transport pathways of reactants and products. Therefore, a deep understanding and optimization of the chemical structure and microenvironment of the ionomer binder to overcome its internal oxygen transport limitations is the key to improving the overall performance of ARMFCs.

[0003] However, conventional linear ionomer binders have inherent limitations in promoting oxygen mass transfer: their dense polymer backbone and low free volume result in low solubility and diffusion coefficient of oxygen molecules within the ionomer phase, leading to significant oxygen transport resistance in the three-phase reaction region and becoming a key bottleneck restricting battery performance at high current densities. To overcome this transport limitation, research has shifted to developing high-performance ionomer binders from a molecular structure design perspective. A series of innovative strategies have been proposed, mainly including: introducing large-volume, hydrophobic groups into the side chains to artificially construct nanopores; designing rigid, twisted backbone structures to suppress chain segment stacking and increase molecular-level porosity; and developing self-microporous polymers with well-defined microporous structures as ionomer binder materials. Therefore, by precisely introducing branched structural units, whether as part of the side chains or the backbone, the regular arrangement of polymer chains can be systematically broken. This "structural branching" strategy has been proven to effectively build robust microporous properties and enhanced free volume, providing efficient transport channels for oxygen molecules and ultimately significantly improving the power output and operational stability of AEMFC. Summary of the Invention

[0004] In view of this, the technical problem to be solved by the present invention is to provide a porphyrin-based branched ionomer, a method for preparing the same, and its application as a binder. The prepared porphyrin-based branched ionomer can improve the performance of fuel cells when used as a binder.

[0005] This invention provides a method for preparing porphyrin-based branched ionomers, comprising the following steps:

[0006] S1) A porphyrin-branched polymer backbone is prepared by superacid-catalyzed polymerization; the monomers of the polymerization reaction include porphyrin monomers, aromatic monomers and ketone monomers;

[0007] S2) The main chain of the above porphyrin branched polymer is deprotonated and quaternized sequentially to obtain a porphyrin-based branched ionomer.

[0008] A schematic diagram of the preparation process is shown below. Figure 1 As shown.

[0009] Preferably, the aromatic compound monomer is selected from one or more of the following compounds:

[0010] .

[0011] In some specific embodiments, the aromatic compound monomer is selected from biphenyl, terphenyl, dimethylfluorene, 1,2-diphenylethane, trans-1,2-stilbene, cis-1,2-stilbene, and carbazole.

[0012] Preferably, the ketone monomer is selected from one or more of the following compounds:

[0013] .

[0014] In some specific embodiments, the ketone monomer is selected from methylpiperidone, trifluoroacetophenone, 7-bromo-1,1,1-trifluoro-2-heptanone, indigo, and quinolinone.

[0015] Preferably, the reagent used for quaternization is selected from one or more of the following compounds:

[0016]

[0017] The porphyrin monomer is preferably porphyrin or tetraphenylporphyrin.

[0018] The molar ratio of the aromatic compound monomer to the ketone monomer is preferably 1:(1~2), more preferably 1:(1~1.5). Exemplary ratios can be 1:1, 1:1.1, 1:1.2, 1:1.3, 1:1.4, 1:1.5, 1:1.6, or any of the above values ​​as upper or lower limits. By controlling the molar amount of the ketone, the polymerization rate of the polymerization process can be adjusted.

[0019] The molar ratio of the porphyrin monomer to the aromatic compound monomer is preferably 1:(1~100), more preferably 1:(9~99). For example, it can be 1:9, 1:29, 1:39, 1:49, 1:69, 1:79, or any of the above values ​​as the upper or lower limit.

[0020] The preferred reaction temperature for the superacid-catalyzed polymerization reaction is 0~30℃. In some specific embodiments, the reaction temperature for the superacid-catalyzed polymerization reaction is 0℃ or room temperature.

[0021] The preferred reaction time for the superacid-catalyzed polymerization reaction is 3 to 24 hours, more preferably 3 to 12 hours. For example, it can be 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 11 hours, or 12 hours, or any of the above values ​​as the upper or lower limit. By controlling the reaction time, the molecular weight of the polymer can be controlled.

[0022] The catalyst for the superacid-catalyzed polymerization reaction preferably includes trifluoromethanesulfonic acid and trifluoroacetic acid.

[0023] The deprotonation is carried out in an alkaline solution.

[0024] The quaternization process uses aqueous solutions of compounds such as iodomethane and trimethylamine as quaternizing reagents.

[0025] The preferred temperature for the quaternization reaction is 30~100℃, more preferably 30~80℃. For example, it can be 30℃, 40℃, 50℃, 60℃, 70℃, 80℃, or any of the above values ​​as the upper or lower limit. Different degrees of quaternization can be achieved by controlling the heating temperature.

[0026] The present invention also provides porphyrin-based branched ionomers prepared by the above preparation method.

[0027] The structural formula of the above-mentioned porphyrin-based branched ionomers is shown in Formula I:

[0028]

[0029] Formula I

[0030] in,

[0031]

[0032] in, This refers to ketone monomers. In the compound structure, ketone monomers are residues after the carbonyl group has been removed. They are connected to porphyrin and aromatic monomers through the carbonyl group position.

[0033] Aromatic monomers can be attached to ketone monomers at any position of the phenyl group.

[0034] The present invention also provides the application of the porphyrin-based branched ionomer prepared by the above preparation method or the above porphyrin-based branched ionomer as a binder.

[0035] Specifically, the present invention provides a binder for use in alkaline fuel cells, which is prepared by dissolving the porphyrin-based branched ionomer prepared by the above preparation method in an organic solvent.

[0036] The present invention provides an adhesive prepared by dissolving the porphyrin-based branched ionomer prepared by the above preparation method in an organic solvent.

[0037] In some specific implementations, the prepared ionomer solution is used as a binder to formulate the catalyst ink, and then the catalyst ink is sprayed onto carbon paper or a membrane using CCS or CCM to form a catalyst layer.

[0038] The organic solvent is preferably one or more of dimethyl sulfoxide, N,N-dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide, 1-methyl-2-pyrrolidone, and methanol.

[0039] In some specific embodiments, the organic solvent is dimethyl sulfoxide, N,N-dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide, 1-methyl-2-pyrrolidone, or methanol, preferably a single solvent of dimethyl sulfoxide or N,N-dimethylformamide.

[0040] In some specific embodiments, the organic solvent is a mixture of methanol and dimethyl sulfoxide, methanol and N,N-dimethylformamide, or isopropanol and water, or a mixture of N,N-dimethylacetamide, isopropanol, and water.

[0041] The mass ratio of catalyst to ionomer in the catalyst ink is preferably 6:4 to 9:1, more preferably 3:1 to 8:1. For example, it can be 6:4, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, or any of the above values ​​as the upper or lower limit.

[0042] In this invention, the mass ratio of water to isopropanol in the catalyst ink is preferably 1:9 to 9:1; more preferably 1:9 to 1:5. For example, it can be 1:9, 1:7, 1:5, 1:3, 1:1, 3:9, 5:9, 7:9, 9:9, or any of the above values ​​as the upper or lower limit.

[0043] The mass fraction of the porphyrin-based branched ionomer in the organic solvent is preferably 1% to 30%, more preferably 1% to 20%. Further preferably, it is 1% to 10%, and by example, it can be 1%, 3%, 5%, 7%, 10%, or any of the above values ​​as the upper or lower limit.

[0044] In this invention, the catalyst loading in the catalyst layer is preferably 0.05~2.0 mg / cm³. 2 More preferably, it is 0.1~1.0 mg / cm³. 2 For example, it could be 0.05 mg / cm³. 2 0.1 mg / cm 2 0.5 mg / cm 2 1.0 mg / cm 2 1.5 mg / cm 2 2.0 mg / cm 2 The values ​​can be set as either upper or lower limits, or any of the above values ​​can be used as upper or lower limits. By controlling the catalyst loading, membrane electrode assemblies with different catalyst loadings can be obtained, allowing for a comparison of the performance of membrane electrode assemblies with different catalyst loadings when applied to fuel cells.

[0045] The present invention also provides a membrane electrode assembly, including a catalyst layer comprising a catalyst and the binder described above.

[0046] The catalyst loading in the catalyst layer is the same as described above, preferably 0.05~2.0 mg / cm³. 2 More preferably, it is 0.1~1.0 mg / cm³. 2 For example, it could be 0.05 mg / cm³. 2 0.1 mg / cm 2 0.5 mg / cm 2 1.0 mg / cm 2 1.5 mg / cm 2 2.0 mg / cm 2 Or, any of the above values ​​can be used as the upper or lower limit of the range.

[0047] In some specific embodiments, the membrane electrode assembly consists of an ion exchange membrane and catalyst layers on both sides, the catalyst layers containing a catalyst and a binder composed of ionomers.

[0048] The membrane electrode assembly with porphyrin ionomer provided by the present invention has the following advantages: on the one hand, the interaction between porphyrin and catalyst improves the dispersibility of catalyst, thereby improving catalyst utilization and mass transfer at interface; on the other hand, it has high electrical conductivity.

[0049] It should be noted that, for clarity and simplicity, the catalysts used in the fuel cell tests of this invention are platinum-carbon catalysts and platinum-ruthenium-carbon catalysts, but this does not mean that all catalysts in this invention are these catalysts. This invention is also applicable to various noble metal and non-noble metal-based catalysts.

[0050] Compared with the prior art, the present invention provides a method for preparing a porphyrin-based branched ionomer, comprising the following steps: S1) preparing a porphyrin-based branched polymer backbone by superacid-catalyzed polymerization reaction; wherein the monomers of the polymerization reaction include porphyrin monomers, aromatic compound monomers and ketone monomers; S2) sequentially deprotonating and quaternizing the above-mentioned porphyrin-based branched polymer backbone to obtain the porphyrin-based branched ionomer.

[0051] This invention provides a series of porphyrin-based branched polymers, incorporating different molar amounts of porphyrin into the polymer backbone. These polymers are used as binders in fuel cells, and the fuel cell performance of the ionomers was tested. When used as binders, the porphyrin-containing polymer structure facilitates mass transport. Furthermore, the interaction between porphyrin and platinum improves the dispersion of the platinum catalyst, enhancing catalyst utilization. Attached Figure Description

[0052] Figure 1 This is a schematic diagram of the preparation process of the porphyrin branched ionomer of the present invention;

[0053] Figure 2 The 1H NMR spectrum of the porphyrin branched ionomer prepared in Example 1 of this invention;

[0054] Figure 3 The surface morphology of GDEs prepared using porphyrin branched ionomers and porphyrin-free anionic ionomers as binders in Example 1 and Comparative Example 1 of this invention;

[0055] Figure 4 Electrochemical performance testing under different binder catalytic systems;

[0056] Figure 5 The Pt loading prepared by CCS in Example 1 and Comparative Example 1 of this invention is 0.5 mg / cm³. 2 Under the same ion exchange membrane conditions, the performance of membrane electrode assemblies for hydrogen-oxygen fuel cells based on different ionomers as binders was compared. Detailed Implementation

[0057] To further illustrate the present invention, a detailed description is provided below with reference to embodiments. However, it should be understood that these descriptions are merely for further illustrating the features and advantages of the present invention, and not for limiting the scope of the claims.

[0058] There are no particular restrictions on the source of any raw materials used in this invention; they can be purchased from the market or prepared using conventional methods known to those skilled in the art.

[0059] Example 1

[0060] In step S1, biphenyl, tetraphenylporphyrin, and N-methylpiperidinone were fed in a molar ratio of 1:0.026:1.4, followed by the addition of dichloromethane. Subsequently, trifluoroacetic acid and trifluoromethanesulfonic acid were added sequentially under ice-water bath conditions (0 °C). After stirring for 12 h, the mixture was poured into methanol to precipitate, and the product was washed with methanol, filtered, and dried under vacuum to obtain the corresponding polymer backbone. The reaction equation is shown below:

[0061]

[0062] Step S2: Add the polymer from step S1 and a 1M aqueous solution of potassium carbonate to a flask. Heat and stir at 50 °C for 48 h, wash 4-5 times with pure water, filter, and vacuum dry for 24 h to obtain the corresponding deprotonated polymer backbone. The reaction equation is shown below:

[0063]

[0064] In step S3, the prepared deprotonated polymer, anhydrous potassium carbonate, and iodomethane are dissolved in dimethyl sulfoxide solution. After heating and stirring at 80 °C for 48 h, the product is precipitated in ethyl acetate. The product is then washed with ethyl acetate and water, filtered, and vacuum dried for 24 h to obtain the quaternized product. The reaction equation is shown below:

[0065]

[0066] In step S4, the quaternized polymer is dissolved in a mixed solution of isopropanol and water to prepare a membrane solution with a mass fraction of 8% to prepare a binder. Then, the binder is mixed with water, isopropanol, and platinum-carbon catalyst to prepare a catalyst ink. The catalyst ink is stirred, ultrasonicated, and then sprayed onto the gas diffusion layer for fuel cell testing.

[0067] Comparative Example 1

[0068] To compare the advantages of the ionomer membrane electrode assembly provided by this invention in fuel cell applications, a porphyrin-free polymer was prepared using the same synthesis method as in Example 1, and its advantages as a binder were then compared through battery performance analysis.

[0069] Chemical composition of porphyrin branched ionomers

[0070] 1) The chemical composition of the porphyrin-branched polymer was characterized by 1H NMR spectroscopy using an AVANCEIII 400 instrument. First, the product from step S2 of Example 1 was dissolved in deuterated dimethyl sulfoxide (DMSO) while trifluoroacetic acid was added dropwise. After the polymer was completely dissolved, the chemical structure of the product was characterized using a 400MHz liquid superconducting NMR spectrometer. Then, step S3 of Example 1 involved a quaternization reaction, in which the product was dissolved in DMSO while trifluoroacetic acid was added dropwise. After the polymer was completely dissolved, the product was characterized by 1H NMR spectroscopy, confirming the complete quaternization reaction.

[0071] 2) Results: Figure 2 The figures shown are the 1H NMR spectra of the products from steps S2 and S3 in Example 1, respectively. Figure 2 The chemical composition of the product in step S2 can be clearly characterized by 2a, where 9.6 ppm is the active hydrogen on piperidine, and 7.63 ppm, 7.56 ppm, 7.49 ppm, 7.35 ppm and 8.73 ppm are attributed to the hydrogen on biphenyl and tetraphenylporphyrin, respectively. This result shows that the superacid reaction was successfully carried out, and at the same time proves the successful introduction of tetraphenylporphyrin. Figure 2 In step 2b, the chemical composition of the product after the quaternization reaction in step S3 can be clearly characterized. Compared with step 2a, the active hydrogen at 9.6 ppm, which is attributed to piperidine, disappears, while a new chemical signal peak appears at 3.1 ppm. This is attributed to the hydrogen on the methyl group of the piperidine quaternary ammonium salt. Therefore, this proves that the quaternization reaction is complete.

[0072] Scanning electron microscopy testing of membrane electrode assembly

[0073] 1) The interface morphology of the membrane electrode assembly was characterized using a scanning electron microscope (SEM) of the Gemini SEM500. First, the membrane electrode assembly prepared in the examples was dried at 60 °C, and its morphology was characterized using a scanning electron microscope.

[0074] 2) Results: Figure 3 The images shown are field emission scanning electron microscope (FESEM) images of the GDEs prepared in Example 1 and Comparative Example 1, respectively. Image 3a is an FESEM image of the GDE prepared in Comparative Example 1, and image 3b is an FESEM image of the GDE prepared in Example 1. (Comparison) Figure 3As shown in Figures 3a and 3b, by comparing the morphology images of membrane electrode assemblies with different binder catalyst systems, it is evident that the porphyrin-based branched ionomer prepared in Example 1 is more uniformly dispersed on the catalyst surface (3b). This uniform dispersion is beneficial to improving the mass transfer efficiency at the interface. Furthermore, it can be observed that the catalyst layer maintains good integrity without being damaged, demonstrating the advantages of this strategy in preparing membrane electrode assemblies.

[0075] Electrochemical performance testing of different catalytic systems

[0076] 1) Electrochemical performance under different catalytic systems (with different binders) was assessed using a standard three-electrode system on an electrochemical workstation (CHI7052E) via a rotating disk electrode. First, catalyst ink was prepared. Then, a platinum sheet and an Ag / AgCl electrode (saturated with KCl solution) were used as the counter and reference electrodes, respectively. The catalyst was uniformly coated on the surface of a glassy carbon disk electrode with a platinum loading of 0.1 mg cm⁻¹. -2 The electrode surface area is 0.196 cm². 2 Before testing, dissolved oxygen was removed by bubbling the 0.1 M KOH electrolyte with nitrogen (N2) for 1 hour. Subsequently, the electrolyte was tested at 50 mV s⁻¹ in the potential range of 0.05 to 1.20 V vs. RHE. -1 Cyclic voltammetry scans were performed at different speeds (2500 rpm, 2250 rpm, 1600 rpm, 1225 rpm, 900 rpm, 625 rpm, 400 rpm) and 5 mV s⁻¹ to clean the catalyst until a stable state was reached. Finally, the catalyst was cleaned in oxygen-saturated 0.1 M KOH solution at different speeds (2500 rpm, 2250 rpm, 1600 rpm, 1225 rpm, 900 rpm, 625 rpm, 400 rpm) and 5 mV s⁻¹. -1 The oxygen reduction reaction (ORR) polarization curve was recorded at the scan rate.

[0077] 2) Results: such as Figure 4 The figures show the LSV curves of the catalyst systems with binders prepared in Example 1 and Comparative Example 1. The catalyst system with binder prepared in Example 1 is denoted as QPBP-2.5@Pt / C, and the catalyst system with binder prepared in Comparative Example 1 is denoted as QPBP-0@Pt / C. Both catalyst systems have the same platinum loading. By comparing the LSV curves under different rotational speeds, it can be concluded that the catalyst system with porphyrin binder has a higher limiting current density compared to the porphyrin-free binder. This indicates that the porphyrin-containing binder catalyst system has a faster oxygen transport capacity. This is mainly because the introduction of porphyrin prepares a branched structure, which is beneficial for the formation of polymer micropores, thereby improving the polymer's oxygen transport capacity. Mass transport is beneficial for improving the performance of hydrogen-oxygen fuel cells.

[0078] Hydrogen-oxygen fuel cell performance testing

[0079] 1) First, the prepared membrane electrode assembly was immersed in a 1 M sodium hydroxide aqueous solution for 24 hours to completely convert the anions in the membrane electrode assembly into hydroxide ions, with the sodium hydroxide aqueous solution being changed multiple times during this period. Then, the membrane electrode assembly, now completely converted to hydroxide ions, was immersed in deionized water to wash away free ions, with the water being changed multiple times during this process. Finally, the membrane electrode assembly to be tested was sandwiched between two gas diffusion layers for testing. The performance of the hydrogen / oxygen fuel cell was tested using a Scribner 850E fuel cell testing system at 80 °C using a voltage sweep method. Hydrogen and oxygen were humidified at 80 °C, with the relative humidity on both sides adjusted to 100%. The gas flow rates on both sides were 1 L / min. -1 1.5 L min -1 The back pressure on both sides is 0.2 MPa. After the power output stabilizes, the battery voltage and power density at various current densities are recorded.

[0080] 2) Results: such as Figure 5 The diagram shows a performance comparison of hydrogen-oxygen fuel cells using membrane electrode assemblies prepared by CCS in Example 1 and Comparative Example 1. The catalyst system of the binder prepared in Example 1 is designated QPBP-2.5@Pt / C, and the catalyst system of the binder prepared in Comparative Example 1 is designated QPBP-0@Pt / C. Both membrane electrode assemblies have the same catalyst loading and the same anion exchange membrane. The battery testing conditions are completely identical, except for the binder in the membrane electrode. Figure 4 The polarization curves show that the open-circuit voltages of the two membrane electrode assemblies are basically the same, indicating that the gas barrier properties of the two membrane electrode assemblies are similar. (Comparison) Figure 5 The power density curves of both methods show that when porphyrin-based anionic ionomers are used as binders, the peak power density of the fuel cell at 100% humidity is 1.09 W / cm². 2 In contrast, when porphyrin-free anionic ionomers were used as binders, the peak power density of the prepared membrane electrode assembly at 100% humidity was only 0.29 W / cm². 2 The superior performance of the membrane electrode assembly, determined by scanning electron microscopy (SEM) analysis of its cross-sectional morphology and electrochemical performance, can be attributed to the porphyrin-branched ionomer binder structure in the catalyst layer, which facilitates oxygen transport and more uniform dispersion on the catalyst. This synergistic effect promotes mass transfer, thereby enhancing battery performance. Furthermore, the battery performance of the two membrane electrode assemblies under different back pressures is noteworthy. When the back pressure increases to 0.2 MPa, the peak power density of the porphyrin-branched anion exchange membrane assembly is 1.75 W / cm². 2 In contrast, the membrane electrode assembly of the porphyrin-free anion exchange membrane exhibited lower cell performance, with a peak power density of 0.53 W / cm². 2.

[0081] By comparing the data in the above embodiments and comparative examples, it can be seen that the membrane electrode assembly based on porphyrin ionomers can achieve excellent fuel cell performance. This is of great significance for the practical application of fuel cells, as it can significantly reduce the total cost of fuel cell membrane stacks and optimize water management during battery operation, thereby reducing operating costs.

[0082] The above description of the embodiments is only for the purpose of helping to understand the method and core ideas of the present invention. It should be noted that those skilled in the art can make several improvements and modifications to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims

1. Application of porphyrin-based branched ionomers as binders for membrane electrode assemblies; The method for preparing the porphyrin-based branched ionomer includes the following steps: S1) A porphyrin-branched polymer backbone is prepared by superacid-catalyzed polymerization; the monomers of the polymerization reaction include porphyrin monomers, aromatic monomers and ketone monomers; S2) The main chain of the above porphyrin branched polymer is deprotonated and quaternized sequentially to obtain a porphyrin-based branched ionomer; The aromatic compound monomer is selected from one or more of the following compounds: ； The ketone monomer is: ； The reagent used for quaternization is selected from one or more of the following compounds: ； The porphyrin monomer is porphyrin or tetraphenylporphyrin; The molar ratio of the aromatic compound monomer to the ketone monomer is 1:(1~2). The molar ratio of the porphyrin monomer to the aromatic compound monomer is 1:(1~100).

2. The application according to claim 1, characterized in that, The reaction temperature of the superacid-catalyzed polymerization reaction is 0~30℃; The reaction time for the superacid-catalyzed polymerization reaction is 3-24 hours.

3. The application according to claim 1, characterized in that, The catalysts for the superacid-catalyzed polymerization reaction include trifluoromethanesulfonic acid and trifluoroacetic acid; The deprotonation is carried out in an alkaline solution; The quaternization process uses an aqueous solution of iodomethane and trimethylamine as the quaternization reagent.

4. An adhesive for use in membrane electrode assemblies, characterized in that, The porphyrin-based branched ionomer was prepared by dissolving it in an organic solvent. The method for preparing the porphyrin-based branched ionomer includes the following steps: S1) A porphyrin-branched polymer backbone is prepared by superacid-catalyzed polymerization; the monomers of the polymerization reaction include porphyrin monomers, aromatic monomers and ketone monomers; S2) The main chain of the above porphyrin branched polymer is deprotonated and quaternized sequentially to obtain a porphyrin-based branched ionomer; The molar ratio of the aromatic compound monomer to the ketone monomer is 1:(1~2). The molar ratio of the porphyrin monomer to the aromatic compound monomer is 1:(1~100). The aromatic monomers, ketone monomers, reagents used for quaternization, and porphyrin monomers are as described in claim 1.

5. A membrane electrode assembly comprising a catalyst layer, the catalyst layer comprising a catalyst and the binder of claim 4.

6. The membrane electrode assembly according to claim 5, characterized in that, The catalyst loading in the catalyst layer is 0.05~2.0 mg / cm³. 2 .

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