Anion exchange membrane based on isopropyl piperidone and biphenyl and preparation method of membrane electrode

Abstract

The invention relates to an anion exchange membrane based on isopropyl piperidone and biphenyl and a preparation method of a membrane electrode, the preparation method comprises the following steps: respectively dissolving an aromatic monomer and IPD in a first solvent, and mixing to obtain a mixed solution, the aromatic monomer being BP or TP; dropwise adding an acidic initiator into the mixed solution for reaction at the reaction temperature of-5 DEG C to 0 DEG C to obtain a nitrogen heterocyclic ring polymer intermediate; adding a quaternization reagent into the nitrogen-containing heterocyclic ring polymer intermediate to realize quaternization modification of nitrogen atoms to obtain a quaternization ionomer; and forming a film to obtain the AEM film. The preparation method of the membrane electrode comprises the following steps: respectively forming a cathode catalyst layer and an anode catalyst layer on two opposite sides of an AEM membrane through ultrasonic spraying to obtain the MEA. The AEM membrane and the MEA obtained according to the invention have the characteristics of excellent stability and high water electrolysis performance, can significantly improve the efficiency and durability of AEMWE, and are suitable for the fields of hydrogen production by water electrolysis and the like.

Description

Technical Field

[0001] This invention relates to hydrogen production by water electrolysis, and more specifically to an anion exchange membrane and membrane electrode preparation method based on isopropylpiperidone and biphenyl. Background Technology

[0002] With the global energy structure shifting towards clean energy, hydrogen energy, as a highly efficient and clean secondary energy source, has seen its green production technology become a research hotspot. Electrolysis of water is considered the most promising green hydrogen production method, among which anion exchange membrane electrolysis (AEMWE) has attracted significant attention due to its high efficiency, low cost, and environmental friendliness. AEMWE technology combines the advantages of traditional alkaline water electrolysis (AWE) and proton exchange membrane electrolysis (PEMWE), utilizing hydroxide ions (OH-). - As a charge carrier, it operates under neutral or weakly alkaline conditions, avoiding the high cost associated with using precious metal catalysts. However, stability at high pH levels remains a major bottleneck limiting its commercial application. Currently, the main research focus of AEMs is on improving their ionic conductivity and chemical stability. Researchers have attempted to improve AEM performance through methods such as crosslinking, microphase separation, and organic / inorganic composites. However, existing AEMs exhibit poor stability and water electrolysis performance at high pH levels, mainly due to the following factors: First, degradation of quaternary ammonium salt cationic head groups. Commonly used quaternary ammonium salt cationic head groups in AEMs are prone to nucleophilic substitution or Hofmann elimination reactions under high pH conditions, leading to degradation of the cationic head groups and thus reducing the membrane's ionic conductivity and stability. Second, degradation of the polymer backbone. The polymer backbone of AEMs is also prone to degradation under high pH conditions, especially the backbone containing aromatic ether bonds, which is susceptible to C–O bond breakage, resulting in decreased membrane mechanical strength and performance degradation. Third, degradation caused by free radicals. During the operation of AEMs, superoxide anion radicals (O2) may be generated. - Reactive oxygen species, such as free radicals, attack the cationic head groups and polymer backbone of AEM, further accelerating membrane degradation. Fourth, the poor compatibility between the AEM membrane and other components in the membrane electrode (such as catalysts, ionomers, etc.) leads to poor mass (gas, water, etc.)-charge (electrons, charged ions) transfer within the electrode, resulting in increased interfacial resistance and loss of water electrolysis performance.

[0003] To address the aforementioned issues, AEMs based on aromatic polymer backbones have attracted widespread attention. For example, Zhuang Lin, Patric Jannasch, and others proposed using "ether-free" aromatic monomers such as biphenyl and terphenyl to undergo a metal-free, superacid-catalyzed Friedel-Crafts reaction with N-methyl-4-piperidinone, synthesizing a novel class of polyarylenepiperidine polymers. AEM films prepared using these polymers typically exhibit high OH content.- It exhibits good electrical conductivity and alkali resistance (Advanced Functional Materials, 2018, 28(2):1702758, Journal of Power Sources, 2018,390:165-167). However, these traditional polyarylene piperidine membranes still suffer from limited free radical scavenging ability of cationic head groups, and their performance will still degrade during long-term operation. Furthermore, their compatibility with other components of the membrane electrode has not been effectively optimized, making it difficult to meet the practical application requirements of AEMWE technology.

[0004] In the preparation of MEAs, commonly used methods include the catalyst-coated substrate (CCS) method and the catalyst-coated membrane (CCM) method. The CCS method involves coating a catalyst slurry onto a gas diffusion layer (GDL) to form the MEA. The CCM method involves directly coating the catalyst onto an aerated polymer (AEM) and then forming the MEA using processes such as hot pressing. Comparatively, the CCM method has a lower ohmic resistance and is therefore widely used in water electrolysis, especially in proton exchange membrane electrolysis (PEMWE). However, in the AEMWE field, existing MEA preparation processes are still immature, suffering from problems such as poor compatibility between the AEM membrane and the catalyst / ionomer, membrane swelling during spraying, and catalyst detachment under high current. These issues lead to rapid performance degradation of the electrolyzer under operating test conditions, making it difficult to achieve the expected performance. Summary of the Invention

[0005] To address the problems of poor stability of AEM and performance degradation of MEA in the existing technology, the present invention aims to provide a method for preparing anion exchange membrane and membrane electrode based on isopropylpiperidone and biphenyl.

[0006] The method for preparing anion exchange membrane and membrane electrode based on isopropylpiperidone and biphenyl according to the present invention includes the following steps: S1, dissolving aromatic monomers and IPD in a first solvent and mixing them to obtain a mixed solution, wherein the aromatic monomer is BP or TP, and the molar ratio of aromatic monomer to IPD is 1:1.1-1:1.2; S2, adding an acidic initiator dropwise to the mixed solution to carry out the reaction at a reaction temperature of -5℃ to 0℃ to obtain a nitrogen-containing heterocyclic polymer intermediate; S3, dissolving the nitrogen-containing heterocyclic polymer intermediate in a second solvent, the second solvent being a polar solvent, adding a quaternizing agent to achieve quaternization modification of nitrogen atoms, and after the reaction, pouring the reaction solution into a third solvent to precipitate a solid precipitate to obtain a quaternized ionomer; S4, washing, drying and drying the quaternized ionomer to form a membrane to obtain an AEM membrane.

[0007] In a preferred embodiment, in step S2, the acidic initiator is a mixture of trifluoromethanesulfonic acid (TFSA) and trifluoroacetic acid (TFA) in a volume ratio of 8:1 to 15:1, and the molar ratio of the acidic initiator to the aromatic monomer is 8:1 to 12:1.

[0008] In a preferred embodiment, in step S2, the acid dropwise addition process needs to be controlled at a temperature below 5°C, and the dropwise addition process needs to be intermittent to control the reaction rate and avoid the instantaneous formation of a large amount of precipitate.

[0009] In a preferred embodiment, in step S3, the second solvent is DMSO and the quaternizing agent is CH3I.

[0010] In a preferred embodiment, in step S3, the third solvent is ethyl acetate.

[0011] In a preferred embodiment, in step S4, the quaternized ionomer is formed into an AEM film by casting.

[0012] In a preferred embodiment, the nitrogen-containing heterocyclic polymer intermediate is a PBIP-TA intermediate and the AEM membrane is a PBIP-QA membrane; or the nitrogen-containing heterocyclic polymer intermediate is a PTIP-TA intermediate and the AEM membrane is a PTIP-QA membrane.

[0013] The method for preparing a membrane electrode based on isopropylpiperidone and biphenyl according to the present invention includes the above-described preparation method, and further includes forming a cathode catalyst layer and an anode catalyst layer on opposite sides of an AEM membrane by ultrasonic spraying, thereby obtaining a MEA.

[0014] In a preferred embodiment, the cathode catalyst layer is formed by ultrasonically spraying a cathode catalyst slurry, which is composed of a Pt / C catalyst and a quaternized ammonium ionomer.

[0015] In a preferred embodiment, the cathode catalyst slurry is dispersed using an isopropanol / water mixed solvent.

[0016] According to the present invention, an anion exchange membrane (AEM) and membrane electrode assembly (MEA) based on isopropylpiperidone and biphenyl are prepared by using ether-free aromatic hydrocarbons (BP or TP) and IPD as the main monomers, synthesizing a polyarylpiperidone polymer containing isopropyl side chains through electrophilic substitution polymerization. After quaternization modification, the AEM membrane is obtained. Then, an ultrasonic spraying technique is used to directly coat the catalyst layer onto the membrane surface to prepare the MEA. In polymer design, isopropyl side chains are introduced to protect the quaternary ammonium cationic head groups, enhancing resistance to high pH degradation and free radical attack, thus improving the stability of the AEM. The ratio of IPD to aromatic hydrocarbons is optimized to achieve a balance between membrane conductivity, ion exchange equivalent (IEC), and swelling properties, ensuring high conductivity and good mechanical properties. In particular, in process optimization, ultrasonic spraying is used to prepare a CCM-type MEA, improving the compatibility between the membrane and the catalyst / ionomer, reducing interfacial resistance, and increasing the current density of the electrolyzer. The final AEM membrane and MEA exhibit excellent stability and high water electrolysis performance, which can significantly improve the efficiency and durability of AEMWE and are suitable for fields such as hydrogen production by water electrolysis. Attached Figure Description

[0017] Figure 1 It is the PBIP prepared in Example 1 and the PTIP prepared in Example 2. 1 HNMR spectrum.

[0018] Figure 2 This is a cross-sectional scanning electron microscope (SEM) image of the AEM membrane.

[0019] Figure 3 The polarization curves of different anion exchange membranes (AEMs) in AEM electrolysis of water are shown.

[0020] Figure 4 Electrochemical impedance spectroscopy (EIS) spectra of different film samples are shown.

[0021] Figure 5 This is a test chart of the electrolytic water stability of the PBIP-QA type anion exchange membrane. Detailed Implementation

[0022] The preferred embodiments of the present invention are given below with reference to the accompanying drawings and described in detail.

[0023] The preparation method according to the present invention first includes dissolving an aromatic monomer and isopropylpiperidone (IPD) separately in a first solvent and then mixing them to obtain a mixed solution. The aromatic monomer is biphenyl (BP) or terphenyl (TP), and the molar ratio of the aromatic monomer to IPD is 1:1.1-1:1.2. In a preferred embodiment, the aromatic monomer is dissolved in the first solvent in a first centrifuge tube to obtain a first solution, and IPD is dissolved in the first solvent in a second centrifuge tube to obtain a second solution. The first and second solutions are then added to a double-walled glass reactor and stirred to obtain a mixed solution. In a preferred embodiment, the aromatic monomer is BP, and the first solvent is dichloromethane (DCM), with a mass ratio of approximately 1:2.5. In a preferred embodiment, the molar ratio of BP to IPD is 1:1.

[0024] The preparation method according to the present invention further includes adding an acidic initiator dropwise to a mixed solution for reaction at a reaction temperature of -5°C to 0°C to obtain a nitrogen-containing heterocyclic polymer intermediate. In a preferred embodiment, the acidic initiator is a mixture of trifluoromethanesulfonic acid (TFSA) and trifluoroacetic acid (TFA) at a volume ratio of 8:1 to 15:1. In a preferred embodiment, the molar ratio of the acidic initiator to the aromatic monomer is 8:1 to 12:1. In a preferred embodiment, the volume ratio of TFSA to TFA is 10:1. In a preferred embodiment, the acid dropwise addition process needs to be controlled at a temperature below 5°C (e.g., -3 to 2°C), and the dropwise addition process needs to be intermittent to control the reaction rate and avoid the instantaneous formation of a large amount of precipitate. In a preferred embodiment, the reaction temperature is -3°C, the stirring speed is increased to 450 rpm, and the reaction time is 3 hours. In a preferred embodiment, the nitrogen-containing heterocyclic polymer intermediate is a PBIP-TA intermediate corresponding to a biphenyl system or a PTIP-TA intermediate corresponding to a terphenyl system.

[0025] The preparation method according to the present invention further includes dissolving a nitrogen-containing heterocyclic polymer intermediate in a second solvent, which is a polar solvent, adding a quaternizing agent to achieve quaternization modification of the nitrogen atoms, and then pouring the reaction solution into a third solvent to precipitate a solid precipitate, thereby obtaining the quaternized ionomer. In a preferred embodiment, the second solvent is dimethyl sulfoxide (DMSO), and the quaternizing agent is methyl iodoformane (CH3I). In a preferred embodiment, the quaternization reaction is carried out at room temperature for 24 hours under light-protected conditions. In a preferred embodiment, the third solvent is ethyl acetate, and the amount added is sufficient to completely precipitate the reaction product.

[0026] The preparation method according to the present invention further includes washing, drying, and then forming an AEM membrane based on isopropylpiperidone and biphenyl after washing the quaternized ionomer. In a preferred embodiment, the washing is performed at least three times, the drying temperature is 60°C, and the vacuum drying time is at least 24 hours. In a preferred embodiment, the AEM membrane is PBIP-QA, which is ground into powder before use for subsequent processing or characterization. In a preferred embodiment, the AEM membrane is formed by casting.

[0027] The preparation method according to the present invention further includes forming a cathode catalyst layer and an anode catalyst layer on opposite sides of an AEM membrane by ultrasonic spraying, respectively, to obtain a membrane electrode assembly (MEA). In a preferred embodiment, both the cathode and anode surfaces are symmetrically sprayed to form a membrane electrode assembly with a double-sided catalyst layer structure. In a preferred embodiment, the cathode catalyst layer is formed by ultrasonically spraying a cathode catalyst slurry, which is composed of a Pt / C catalyst and a PBIP-QA ionomer. In a preferred embodiment, the mass ratio of catalyst to ionomer is 70:30. The cathode catalyst slurry is dispersed using an isopropanol / water mixed solvent. In a preferred embodiment, the volume ratio of isopropanol to water is 3:1, and the ultrasonic time is not less than 30 minutes. In a preferred embodiment, the nozzle movement speed during the ultrasonic spraying process is 70 mm / s, the spraying frequency is 1 Hz, the spraying height is 10 cm, and the air pressure is controlled at 3.0 MPa. In a preferred embodiment, an infrared heating device is provided at the bottom of the membrane during the spraying process to maintain a temperature of 70°C to promote solvent evaporation. The catalyst is sprayed onto the membrane surface until the platinum loading reaches 0.5 mg / cm². After the membrane electrode coating is completed, it needs to be dried in a vacuum drying oven at 60℃ for 12 hours. The resulting MEA can be directly used in the assembly of anion exchange membrane electrolyzers and has excellent catalytic performance and interfacial stability.

[0028] Example 1: Preparation of poly(biphenyl-isopropylpiperidinone) PBIP

[0029]

[0030] PBIP is prepared from biphenyl (BP) and isopropylpiperidone (IPD). PBIP-TA represents the polymer structure before quaternization of the cationic group, and PBIP-QA represents the polymer structure after quaternization.

[0031] Weigh 1.082 g of biphenyl (BP) and 2.66 g of dichloromethane (DCM) and add them to the first centrifuge tube; weigh 1.14 g of isopropylpiperidone (IPD) and 1.33 g of dichloromethane (DCM) and add them to the second centrifuge tube.

[0032] Add the first and second centrifuge tubes sequentially into the double-walled glass reactor, attach the stirring rod, adjust the stirring speed of the reactor to 300 rpm, and stir for about 10 minutes to ensure that BP and IPD are fully dissolved and mixed.

[0033] Weigh 5.4 mL of trifluoromethanesulfonic acid (TFSA) and 0.455 mL of trifluoroacetic acid (TFA) into a graduated cylinder. Place the graduated cylinder containing the acid into an ice bath and keep the temperature below 5°C.

[0034] Take an appropriate amount of acid solution using a small-diameter dropper and slowly add it to the reaction vessel. Stop adding the acid solution when you observe the formation of a precipitate. Continue adding the acid solution after the precipitate disappears until the addition is complete, which takes about 20-30 minutes.

[0035] After the addition is complete, adjust the stirring speed to 450 rpm, set the reaction temperature to -3℃, and continue stirring for 3 hours.

[0036] After the reaction is complete, raise the reaction temperature to room temperature, stop stirring, observe the precipitate, and wash the reaction product with dichloromethane (DCM) to remove unreacted substances and byproducts.

[0037] The solvent was removed by rotary evaporation to obtain the PBIP-TA intermediate.

[0038] Take 1g of PBIP-TA intermediate, dissolve it in 25mL of dimethyl sulfoxide (DMSO), stir to dissolve, add 1mL of iodomethane, stir and react in the dark for 24 hours to form a brown solution.

[0039] The brown solution was slowly poured into excess ethyl acetate to precipitate.

[0040] After centrifugation, the solid product obtained by vacuum filtration is washed with deionized water to ensure that impurities are removed.

[0041] Repeat the washing step 3 times to ensure the purity of the product.

[0042] The cleaned product was placed in a vacuum oven at 60°C and dried for 24 hours.

[0043] After drying, the product is removed and allowed to cool naturally to room temperature.

[0044] The dried product was ground using a mortar and pestle to obtain the final PBIP-QA product.

[0045] The structure and purity of the product were confirmed by characterization using analytical techniques such as Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance (NMR).

[0046] Example 2: Preparation of poly(terphenyl-isopropylpiperidinone)PTIP

[0047]

[0048] PTIP is prepared from terphenyl (TP) and isopropylpiperidone (IPD). PTIP-TA represents the polymer structure before quaternization of the cationic group, and PTIP-QA represents the polymer structure after quaternization.

[0049] Weigh 1.082 g of terphenyl (TP) and 2.66 g of dichloromethane (DCM) and add them to the first centrifuge tube; weigh 0.763 g of isopropylpiperidone (IPD) and 1.33 g of dichloromethane (DCM) and add them to the second centrifuge tube.

[0050] Add the first and second centrifuge tubes sequentially into the double-walled glass reactor, attach the stirring rod, adjust the stirring speed of the reactor to 300 rpm, and stir for about 10 minutes to ensure that TP and IPD are fully dissolved and mixed.

[0051] Weigh 5.4 mL of trifluoromethanesulfonic acid (TFSA) and 0.455 mL of trifluoroacetic acid (TFA) into a graduated cylinder. Place the graduated cylinder containing the acid into an ice bath and keep the temperature below 5°C.

[0052] Use a small-diameter dropper to take an appropriate amount of acid solution from the graduated cylinder and slowly add it dropwise into the reaction vessel. Stop adding when you observe the formation of a precipitate. After the precipitate disappears, continue adding until the addition is complete, which takes about 20-30 minutes.

[0053] After the addition is complete, adjust the stirring speed to 450 rpm, set the reaction temperature to -3℃, and continue stirring for 3 hours.

[0054] After the reaction is complete, raise the reaction temperature to room temperature, stop stirring, observe the precipitate, and wash the reaction product with DCM to remove unreacted substances and byproducts.

[0055] The solvent was removed by rotary evaporation to obtain the PTIP-TA intermediate.

[0056] Take 1g of PTIP-TA intermediate and dissolve it in 19mL of dimethyl sulfoxide (DMSO). After stirring to dissolve, add 1mL of iodomethane and stir in the dark for 24 hours to form a brown solution.

[0057] The brown solution was slowly poured into excess ethyl acetate to precipitate.

[0058] After centrifugation, the solid product obtained by vacuum filtration is washed with deionized water to ensure that impurities are removed.

[0059] Repeat the washing step 3 times to ensure the purity of the product.

[0060] The cleaned product was placed in a vacuum oven at 60°C and dried for 24 hours.

[0061] After drying, the product is removed and allowed to cool naturally to room temperature.

[0062] The dried product was ground using a mortar and pestle to obtain the final PTIP-QA product.

[0063] The structure and purity of the product were confirmed by characterization using analytical techniques such as Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance (NMR).

[0064] Figure 1 The PBIP prepared in Example 1 and the PTIP prepared in Example 2 were dissolved in deuterated DMSO. 1 HNMR spectra. As shown in the figure, compared with the poly(biphenyl-N-methylpiperidinone) PBP and poly(terphenyl-N-methylpiperidinone) PTP synthesized using the traditional N-methylpiperidinone monomer, PBIP and PTIP clearly showed a –CH3 characteristic peak originating from the isopropyl side chain at 1.25 ppm, verifying the successful construction and effectiveness of the target polymer structure.

[0065] The PBIP and PTIP polymer powders prepared in Example 1 and Example 2, respectively, are typically used to prepare anion exchange membranes (AEMs) via casting. This method is a common technique and is presented here as an example, not a limitation. Specifically, the prepared polymer powder is dissolved in a high-boiling-point organic solvent such as dimethyl sulfoxide (DMSO) or N-methylpyrrolidone (NMP) to prepare an 8-10% (w / w) solution. This solution is then uniformly coated onto a glass plate using a doctor blade. Finally, the solvent is evaporated by heating, forming the final AEM membrane. The membrane thickness and dimensions can be controlled by adjusting the solution viscosity, dosage, and doctor blade spacing, depending on the application requirements.

[0066] Figure 2 These are cross-sectional scanning electron microscope (SEM) images from an atomizer. (a) is a low-magnification view showing the overall thickness of the PBIP membrane is approximately 62 μm. The membrane layer is uniform and continuous, with no obvious defects. (b) is a high-magnification view showing the internal density of the PBIP membrane, without pores or delamination, indicating good film-forming properties. (c) is a low-magnification view showing the overall thickness of the PTIP membrane is approximately 60 μm. (d) is a high-magnification view showing the PTIP membrane exhibits a dense and continuous characteristic, with no obvious defects or uneven areas. Therefore, both PTIP and PBIP membranes were successfully prepared, and the membrane thickness is uniform and can be precisely controlled at around 60 micrometers. This helps ensure the consistency and reliability of the results of water electrolysis testing and performance evaluation.

[0067] Take the dried AEM film, cut it to the required size (e.g., 5cm×5cm), place it on the ultrasonic spraying device platform, and use vacuum adsorption to fix the film surface to ensure it is flat and wrinkle-free.

[0068] Preparation of catalyst slurry: Weigh Pt / C (40 wt.%) catalyst and anionic ionomer (PBIP-QA or PTIP-QA ionomer solution) separately, mix them at a mass ratio of 70:30, add isopropanol / water mixed solvent (volume ratio of 3:1), and ultrasonically disperse for 30 minutes to obtain a uniform catalyst slurry.

[0069] Ultrasonic spraying equipment was used for spraying: the nozzle scanning rate was set to 70 mm / s, the spraying height to 10 cm, the air pressure to 3.0 MPa, and the spraying frequency to 1 Hz. The catalyst slurry was sprayed evenly layer by layer onto the AEM membrane surface until the specified loading (e.g., 0.5 mg / cm³) was achieved. 2 Pt).

[0070] During the spraying process, the temperature at the bottom of the film is maintained at 70°C by an infrared heating plate to promote rapid solvent evaporation and avoid slurry accumulation and uneven film surface.

[0071] After spraying, place the film along with the catalyst layer in a vacuum drying oven and dry at 60°C for 12 hours to ensure that the catalyst layer is fully cured and adhered.

[0072] Repeat the above operation to spray an anode catalyst layer (ultrasonic spraying of a catalyst slurry consisting of a non-precious metal catalyst and anionic ionomer) on the other side of the membrane to form a symmetrical MEA (Membrane Electrode Assembly).

[0073] The dried membrane electrode assembly is cut to the required size for use in assembling an AEM electrolyzer.

[0074] Polarization curves and durability tests were performed using a Xinwei CE-4008Q-5V30A-SR eight-channel battery analyzer. Initially, the electrolyzer was stabilized at a low current density of 0.02 A / cm² for 30 minutes. Subsequently, a stepped loading method was used, gradually increasing the current density from 0.01 A / cm² to 4 A / cm², with each step lasting 1 minute, and the constant-current steady-state polarization response was recorded. A comparison of polarization curves of different anion exchange membranes (AEMs) in AEM electrolysis of water is shown below. Figure 3As shown, the membranes involved include the PBIP membrane and PTIP membrane prepared in this invention, the control membranes (PBP, PTP) without isopropyl structure, and the commercial membrane (PAP-TP-85). As can be seen from the figure, at the same current density, the voltage of the PBIP membrane and PTIP membrane is significantly lower than that of the control membrane and the commercial membrane. For example, the PBIP membrane exhibits excellent water electrolysis performance under the test conditions of 60 °C and 1 MKOH. At 4 A / cm², the voltage of the PBIP membrane is only 1.95 V, and at 1 A / cm², the voltage is 1.65 V. The voltage of the PTIP membrane is slightly higher than that of the PBIP membrane but still lower than that of the other membranes. This indicates that the PBIP and PTIP membranes based on the isopropylpiperidone and biphenyl / terphenyl structures can effectively reduce the voltage during water electrolysis and significantly improve the performance of AEM water electrolysis.

[0075] Electrochemical impedance spectroscopy (EIS) tests were performed in AEM electrolyzers with different membranes installed. Using a Bio-Logic VSP-300 electrochemical workstation, AC impedance data were acquired at a constant potential of 1.65 V, with a frequency range of 100 kHz to 0.1 Hz and an AC perturbation amplitude of 10 mV (rms). Comparisons of EIS spectra of different membrane samples are shown below. Figure 4 As shown, the membranes involved include the PBIP and PTIP membranes prepared in this invention, the control membranes (PBP and PTP) without isopropyl structure, and the commercial membrane (PAP-TP-85). As can be seen from the figure, the PBIP membrane has the smallest x-axis intercept in the high-frequency region of the EIS spectrum, indicating that it has the lowest sheet resistance; followed by the PTIP membrane, while the isopropyl-free PBP and PTP membranes and the commercial membrane have larger intercepts and higher sheet resistance. This further verifies that the PBIP and PTIP membranes containing isopropyl structure prepared in this invention have superior ion conduction performance, can reduce ohmic losses during electrolysis, and are comparable to… Figure 3 The polarization curve results corroborate each other, jointly demonstrating the advantages of the AEM membrane of the present invention in water electrolysis efficiency.

[0076] PBIP-QA type anion exchange membrane in 1 MKOH electrolyte solution, 1 A / cm 2 The stability of water electrolysis was tested at the operating current density. The results are as follows: Figure 5 As shown, after 500 hours of continuous high current density operation, the electrolytic cell voltage remained stable at approximately 1.8V, with a voltage decay rate as low as 50μV / h, indicating that the membrane possesses excellent durability.

[0077] Therefore, the method for preparing anion exchange membranes and membrane electrodes based on isopropylpiperidone and biphenyl according to the present invention has many advantages.

[0078] First, the synthesis steps are simple, requiring no special equipment, and all raw materials used are commercially available, making the process easy to scale up. This invention uses biphenyl (BP) and isopropylpiperidone (IPD) as the main monomers, and synthesizes the polymer by inducing an aromatic electrophilic polymerization reaction under simple acidic conditions. The acidic initiators used are commercially available trifluoromethanesulfonic acid (TFSA) and trifluoroacetic acid (TFA). The reaction does not require metal catalysts, high pressure, or complex conditions, and the entire synthesis can be completed with only temperature control and magnetic stirring equipment.

[0079] Secondly, the material utilization rate is high, the consumption during film formation and electrode preparation is low, and the process is easy to scale up. The synthesized PBIP-QA polymer has excellent film-forming properties and solubility, and can be directly used to prepare catalyst slurries and spray them onto the membrane surface. In the process of ultrasonic spraying to prepare membrane electrodes, only about 50~100µL of ionomer dispersion is needed per square centimeter of catalyst layer to achieve good coating, significantly reducing material consumption.

[0080] Third, the polymer coating does not cause electrode polarization or affect the active sites on the catalyst surface, ensuring reaction efficiency. The PBIP-QA polymer has a highly stable carbon-nitrogen quaternary ammonium structure, and the introduction of a hydrophobic biphenyl rigid backbone and isopropyl side chain in the molecular design helps to improve the stability of the ion conduction pathway; at the same time, the polymer does not form a dense or highly covering non-conductive layer, thus it will not shield the active sites or cause catalyst activity loss.

[0081] Fourth, the method has broad applicability and can be applied to various electrolysis systems, different catalysts, and electrode materials, demonstrating good versatility. The membrane electrode prepared by this invention employs ultrasonic spraying technology, which has advantages such as controllable spraying particle size, good coating uniformity, and strong adaptability. Combined with the good dispersibility and membrane adhesion of PBIP-QA polymer, it is compatible with various noble metal (such as Pt, Ir, Ru) or non-noble metal catalyst systems, and is also suitable for various electrode substrates such as carbon paper, metal foam, or titanium mesh.

[0082] In summary, the method for preparing anion exchange membranes and membrane electrodes based on isopropylpiperidone and biphenyl according to the present invention can effectively solve the problems of insufficient stability of AEM membranes and rapid performance degradation of MEAs in the prior art, laying the foundation for the industrial application of anion exchange membrane water electrolysis technology.

[0083] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of the invention. Various variations can be made to the above embodiments of the present invention. That is, all simple and equivalent changes and modifications made based on the claims and description of this invention fall within the protection scope of the claims. All aspects not described in detail in this invention are conventional technical content.

Claims

1. A method for preparing anion exchange membrane based on isopropylpiperidone and biphenyl, characterized in that, The preparation method includes the following steps: S1, the aromatic monomer and IPD are dissolved separately in the first solvent and then mixed to obtain a mixed solution, wherein the aromatic monomer is BP or TP, and the molar ratio of aromatic monomer to IPD is 1:1.1-1:1.2; S2, an acidic initiator is added dropwise to the mixed solution to carry out the reaction at a temperature of -5℃ to 0℃, to obtain a nitrogen-containing heterocyclic polymer intermediate; S3, the nitrogen-containing heterocyclic polymer intermediate is dissolved in a second solvent, which is a polar solvent. A quaternizing agent is added to achieve quaternization modification of nitrogen atoms. After the reaction, the reaction solution is poured into a third solvent to precipitate a solid precipitate, thus obtaining the quaternized ionomer. S4, after washing, drying and drying the quaternized ionomer, an AEM membrane is obtained.

2. The preparation method according to claim 1, characterized in that, In step S2, the acidic initiator is obtained by mixing TFSA and TFA in a volume ratio of 8:1 to 15:1, and the molar ratio of the acidic initiator to the aromatic monomer is 8:1 to 12:

1.

3. The preparation method according to claim 1, characterized in that, In step S2, the acid dropwise addition process must be controlled at a temperature below 5°C, and the dropwise addition process must be carried out intermittently to control the reaction rate and avoid the instantaneous formation of a large amount of precipitate.

4. The preparation method according to claim 1, characterized in that, In step S3, the second solvent is DMSO and the quaternizing agent is CH3I.

5. The preparation method according to claim 1, characterized in that, In step S3, the third solvent is ethyl acetate.

6. The preparation method according to claim 1, characterized in that, In step S4, the quaternized ionomer is formed into an AEM film by casting.

7. The preparation method according to claim 1, characterized in that, The nitrogen-containing heterocyclic polymer intermediate is a PBIP-TA intermediate, and the AEM membrane is a PBIP-QA membrane; or the nitrogen-containing heterocyclic polymer intermediate is a PTIP-TA intermediate, and the AEM membrane is a PTIP-QA membrane.

8. A method for preparing a membrane electrode based on isopropylpiperidone and biphenyl, characterized in that, The preparation method includes the preparation method according to any one of claims 1-7, and further includes forming a cathode catalyst layer and an anode catalyst layer on opposite sides of the AEM membrane by ultrasonic spraying, respectively, to obtain MEA.

9. The preparation method according to claim 8, characterized in that, The cathode catalyst layer is formed by ultrasonically spraying cathode catalyst slurry, which is composed of Pt / C catalyst and quaternized ammonium ionomer.

10. The preparation method according to claim 8, characterized in that, The cathode catalyst slurry is dispersed using a mixed solvent of isopropanol and water.

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