A polymer nano-microsphere composite anion exchange membrane and its preparation method and use

Abstract

The present invention provides a polymer nanosphere composite anion exchange membrane, its preparation method, and its use, belonging to the field of anion exchange membrane fuel cell technology. The present invention prepares polymer nanospheres of varying particle sizes through aqueous dispersion polymerization and introduces these nanospheres into a semi-interpenetrating network anion exchange membrane to produce a polymer nanosphere-doped anion exchange membrane. The resulting polymer nanosphere composite anion exchange membrane exhibits excellent thermal stability and mechanical properties, improving the electrochemical performance of the anion exchange membrane and the performance of fuel cells assembled with the anion exchange membrane, thus demonstrating promising application prospects.

Description

Technical Field

[0001] The present invention belongs to the technical field of anion exchange membrane fuel cells, and in particular relates to a polymer nano-microsphere composite anion exchange membrane and a preparation method and application thereof. Background Art

[0002] Anion exchange membranes (AEMs) are the core components of anion exchange membrane fuel cells (AEMFCs). Their main function is to conduct anions (mainly OH - ) and isolate the fuel from the oxidant. Efficient ion conduction capability is crucial to improving the performance of fuel cells. In fuel cell components, AEMs need to have good chemical stability, withstand the effects of alkaline environments and electrochemical reactions, have certain mechanical strength and durability, withstand mechanical stress and wear from long-term operation, and also need to have good thermal stability within a certain temperature range. However, existing AEMs have problems such as low ion conductivity and insufficient long-term durability in high temperature, strong alkaline and low humidity environments, which hinder their development in the commercial market. Therefore, designing anion exchange membranes with high ionic conductivity is crucial for the development of anion exchange membrane fuel cells with good battery performance.

[0003] The literature (ACS Applied Materials & Interfaces, 2022, 14(33): 38132-38143) discloses an anion exchange membrane material (S1V1)3Q AEM prepared by cross-linking a branched polyethyleneimine with a PS-co-PVBC skeleton. However, the anion exchange membrane material has the following problems: (1) (S1V1)3Q AEM has a low ionic conductivity; (2) the peak power density is low, and its working performance in the battery needs to be further improved. Summary of the Invention

[0004] The purpose of the present invention is to provide a polymer nano-microsphere composite anion exchange membrane and a preparation method and use thereof.

[0005] The invention provides a composite anion exchange membrane, which is composed of polymer nano-microspheres and interpenetrating network anion exchange membrane. The mass ratio of the polymer nano-microspheres to the interpenetrating network anion exchange membrane is 0.1-10:100.

[0006] Furthermore, the mass ratio of the polymer nanospheres to the interpenetrating network anion exchange membrane is 0.5 to 6:100.

[0007] Furthermore, the mass ratio of the polymer nanospheres to the interpenetrating network anion exchange membrane is 1 to 2:100.

[0008] Furthermore, the average particle size of the polymer nanospheres is 100 to 1000 nm, preferably 500 to 830 nm, and more preferably 515.1 to 824.9 nm.

[0009] Furthermore, the polymer nanospheres are obtained by reacting a vinyl-containing halogenated aromatic hydrocarbon monomer, an initiator and a dispersant; the mass volume ratio of the vinyl-containing halogenated aromatic hydrocarbon monomer, the initiator and the dispersant is 10mL:0.1-0.2g:0.6-1g.

[0010] Furthermore, the vinyl-containing halogenated aromatic hydrocarbon monomer is 4-vinylbenzyl chloride; the initiator is an azo initiator, preferably azobisisobutyronitrile; the dispersant is polyvinylpyrrolidone; and the mass volume ratio of the vinyl-containing halogenated aromatic hydrocarbon monomer, the initiator and the dispersant is 10 mL: 0.11 g: 0.8 g.

[0011] Furthermore, the reaction is carried out under a nitrogen atmosphere; the solvent of the reaction is a mixture of an inorganic solvent and an organic solvent; the temperature of the reaction is 60 to 80° C., and the time is 4 to 16 hours.

[0012] Furthermore, the solvent of the reaction is a mixture of anhydrous ethanol and deionized water in a volume ratio of 15:4; the temperature of the reaction is 70° C., and the reaction time is 6 to 12 hours.

[0013] Furthermore, after the reaction is completed, the following purification step is further included: centrifuging the reaction solution, washing the solid with deionized water saturated with nitrogen atmosphere, and vacuum drying at 60° C. for 6 h to obtain polymer nanospheres.

[0014] Furthermore, the interpenetrating network anion exchange membrane is prepared according to the following steps:

[0015] (i) reacting a vinyl-containing aromatic hydrocarbon monomer, a vinyl-containing halogenated aromatic hydrocarbon monomer, and an initiator to obtain a copolymer;

[0016] (ii) reacting the copolymer with a quaternizing agent to obtain a quaternized copolymer;

[0017] (iii) reacting the quaternized copolymer with a cross-linking agent to obtain an interpenetrating network anion exchange membrane.

[0018] Furthermore, in step (i), the vinyl-containing aromatic hydrocarbon monomer is styrene, the vinyl-containing halogenated aromatic hydrocarbon monomer is 4-vinylbenzyl chloride; the initiator is an azo initiator, preferably azobisisobutyronitrile; the molar ratio of the vinyl-containing aromatic hydrocarbon monomer to the vinyl-containing halogenated aromatic hydrocarbon monomer is 1:0.5-1.5; the mass percentage of the initiator is 0.5-1.5wt%; the reaction is carried out under a nitrogen atmosphere; the reaction temperature is 70-90°C, and the reaction time is 20-30 hours;

[0019] In step (ii), the reaction is carried out under a nitrogen atmosphere; the quaternizing agent is trimethylamine; the molar ratio of the vinyl-containing halogenated aromatic hydrocarbon monomer to the quaternizing agent in the copolymer is 1:0.1-1; the solvent for the reaction is an organic solvent; the reaction temperature is 70-90° C., and the reaction time is 4-6 hours;

[0020] In step (iii), the crosslinking agent is branched polyethyleneimine; the mass ratio of the quaternized copolymer to the crosslinking agent is 2 to 4:1; the reaction temperature is 10 to 40° C., and the reaction time is 1 to 3 hours.

[0021] Furthermore, in step (i), the molar ratio of the vinyl-containing aromatic hydrocarbon monomer to the vinyl-containing halogenated aromatic hydrocarbon monomer is 1:1; the mass percentage of the initiator is 1 wt%; the reaction temperature is 80° C., and the reaction time is 24 hours;

[0022] In step (ii), the molar ratio of the vinyl-containing halogenated aromatic hydrocarbon monomer to the quaternizing agent in the copolymer is 1:0.5; the solvent of the reaction is dimethyl sulfoxide; the reaction temperature is 80° C., and the reaction time is 5 hours;

[0023] In step (iii), the mass ratio of the quaternized copolymer to the cross-linking agent is 3:1; the reaction temperature is 20-30° C., and the reaction time is 2 hours.

[0024] Furthermore, after the reaction in step (i) is completed, the following purification step is further included: dissolving the reactant in toluene, precipitating with anhydrous ethanol, repeating the operation three times, and vacuum drying at 60° C. for 6 h to obtain a copolymer;

[0025] After the reaction in step (ii) is completed, the following purification steps are further included: vacuum drying at 60° C. for 12 hours, washing with anhydrous ethanol, and vacuum drying at 40° C. for 12 hours to obtain a quaternized copolymer.

[0026] The present invention also provides a method for preparing the composite anion exchange membrane, which comprises the following steps: reacting polymer nanospheres with an interpenetrating network anion exchange membrane, vacuum degassing, and drying to obtain the composite anion exchange membrane.

[0027] Furthermore, the reaction temperature is 10-40° C., and the reaction time is 0.5-1.5 hours.

[0028] Furthermore, the reaction temperature is 20-30° C. and the reaction time is 1 hour.

[0029] Furthermore, after the reaction is completed, the following purification step is also included: soaking the reactants in 1-bromopropane, reacting in vacuum at 20-30°C for 36 hours, drying, soaking in N2-saturated 1M NaOH solution at 20-30°C for 48 hours, and washing with N2-saturated deionized water to obtain a composite anion exchange membrane.

[0030] The present invention also provides use of the composite anion exchange membrane in preparing a fuel cell.

[0031] The anion exchange membrane material (S1V1) 3Q AEM reported in the literature (ACS Applied Materials & Interfaces, 2022, 14(33): 38132-38143) is the sample SV AEM of Comparative Example 1 of the present invention. Compared with (S1V1) 3Q AEM, the present invention achieves the following beneficial effects:

[0032] (1) The ionic conductivity of the composite anion exchange membrane of the present invention is better. (S1V1) 3Q AEM has only 106 mS cm at 80 °C. -1 The hydroxide conductivity of the composite anion exchange membrane of the present invention is significantly improved (the conductivity at 80 ° C is 112.8 mS cm) when the SPM and BPM contents are 2% and 1% respectively. -1 and 110.5 mS cm -1 ), which were increased by 9.20% and 6.97% respectively compared with the (S1V1)3Q AEM without nanospheres;

[0033] (2) As is well known to those skilled in the art, the peak power density of an anion exchange membrane is one of the important indicators for measuring its performance in a fuel cell. An increase in peak power density means that the anion exchange membrane can achieve a higher energy conversion efficiency per unit area, which is of great significance for the performance optimization and practical application of fuel cells. The composite anion exchange membrane of the present invention has a higher peak power density and better working performance in the battery. (S1V1) 3Q AEM at a current density of 270.80 mA cm-2 The peak power density is 150.33 mW cm -2 The composite anion exchange membrane SVBPM1AEM of the present invention is at a current density of 301.26 mA cm -2 When the peak power density is 158.61mW cm -2 SVSPM2AEM at a current density of 375.13 mA cm -2 The peak power density is 168.72 mW cm -2 The peak power densities of SVBPM1AEM and SVSPM2AEM were increased by about 5.51% and 12.23% respectively compared with the (S1V1)3Q AEM without nanospheres.

[0034] Experimental results show that the polymer nanosphere composite anion exchange membrane obtained by the present invention has good thermal stability and mechanical properties, improves the electrochemical properties of the anion exchange membrane and the performance of the fuel cell assembled with the anion exchange membrane, and has good application prospects.

[0035] Obviously, based on the above contents of the present invention, according to common technical knowledge and customary means in this field, without departing from the above basic technical ideas of the present invention, other various forms of modifications, replacements or changes can be made.

[0036] The following is a detailed description of the present invention through specific embodiments in the form of examples. However, this should not be construed as limiting the scope of the present invention to the following examples. All technologies implemented based on the above-mentioned content of the present invention fall within the scope of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 Schematic diagram of the preparation of PVBC nanospheres and AEMs doped with nanospheres.

[0038] Figure 2 (a, b) XPS total spectra of SPM and BPM and (c, d) particle size diagrams of SPM and BPM.

[0039] Figure 3 (a, b) SEM images of SPM and BPM and (c, d) EDS images of the distribution of C and Cl elements in BPM.

[0040] Figure 4 This is the TGA-DTG curve of SPM.

[0041] Figure 5 Infrared spectra of SV, SVSPM1 and SVBPM1AEMs.

[0042] Figure 6(ac) Surface SEM images of SV, SVSPM1 and SVSPM6AEMs; (d) Cross-sectional SEM image of SVSPM6AEM; (e,f) Surface SEM images of SVBPM1 and SVBPM6AEMs; (g) EDS image of N element distribution in the cross section of SVSPM6AEM; (h) EDS image of N element distribution on the surface of SVBPM1AEM; (i) Actual image of SVSPM1.

[0043] Figure 7 TEM images of SV (a), SVSPM1 (c), SVSPM6 (d), SVBPM1 (g) and SVBPM6 (h) AEMs; 2D AFM phase images of SV (b), SVSPM1 (e), SVSPM6 (f), SVBPM1 (i) and SVBPM6 (j) AEMs.

[0044] Figure 8 (a, b) TGA-DTG curves of SV, SVSPM1, SVSPM6, SVBPM1 and SVBPM6 AEMs; (c, d) mechanical properties test diagrams of SV, SVSPMx and SVBPMy AEMs.

[0045] Figure 9 Water absorption rate of SVSPMx (a) and SVBPMy (c) AEMs at different temperatures; swelling test diagram of SVSPMx (b) and SVBPMy (d) AEMs at different temperatures.

[0046] Figure 10 (a, b) Ionic conductivity diagrams of SV, SVSPMx, and SVBPMy AEMs.

[0047] Figure 11 Figure 3. H2 / O2 fuel cell performance test of AEMFCs prepared from SV, SVBPM1 and SVSPM2AEMs at 60°C. DETAILED DESCRIPTION

[0048] The raw materials and equipment used in the present invention are all known products and are obtained by purchasing commercially available products.

[0049] 4-Vinylbenzyl chloride (VBC), azobisisobutyronitrile (AIBN), polyvinylpyrrolidone (PVP), styrene (St), branched polyethyleneimine (BPEI, average weight-average molecular weight Mw = 25000), and trimethylamine (TMA, 30% ethanol solution) were all purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0050] The "room temperature" referred to in the present invention is 25±5°C.

[0051] Example 1. Preparation of polymer nanosphere composite anion exchange membrane

[0052] 1. Preparation of PVBC nanospheres

[0053] Under a nitrogen atmosphere, 30 mL of VBC, 0.34 g of AIBN, and 2.4 g of PVP were added to a mixture containing 150 mL of anhydrous ethanol and 40 mL of deionized water, followed by stirring at 70°C. After 6 and 12 hours of reaction, 50 mL of the dispersion was collected and the solid layer removed by centrifugation. After washing and filtering three times with nitrogen-saturated deionized water, the mixture was vacuum-dried at 60°C for 6 hours to produce PVBC nanospheres of varying sizes. The prepared nanospheres of varying sizes were named Small PVBC Microspheres (abbreviated as SPM, obtained from the dispersion after 6 hours of reaction) and Big PVBC Microspheres (abbreviated as BPM, obtained from the dispersion after 12 hours of reaction).

[0054] 2. Preparation of PS-co-QPVBC-BPEI solution

[0055] (1) Synthesis of PS-co-PVBC: Purified St and VBC, as well as AIBN (1 wt% of the reaction monomers), were added to a 50 mL two-necked round-bottom flask equipped with a magnetic stirring bar according to a molar ratio (St:VBC = 1:1). After mixing, the round-bottom flask was purged with a dry nitrogen atmosphere for 30 min and then reacted at 80°C for 24 h. After the reaction was completed, the reactants were dissolved in toluene, and PS-co-PVBC was isolated by precipitation with anhydrous ethanol. The product was repeatedly dissolved in toluene three times and then purified by precipitation. The product was then dried in vacuum at 60°C for 6 h.

[0056] (2) Synthesis of PS-co-QPVBC: PS-co-PVBC (10 g) and trimethylamine (TMA) were dissolved in an excess of dimethyl sulfoxide (DMSO) under ultrasonic treatment (the molar ratio of VBC to TMA in PS-co-PVBC was 1:0.5). Then, the solution was stirred at 80°C for 5 h under a dry nitrogen purge. Afterwards, the product was vacuum-dried at 60°C for 12 h to remove DMSO to obtain a crude powder of PS-co-QPVBC. Finally, the crude PS-co-QPVBC powder was washed three times with anhydrous ethanol and vacuum-dried at 40°C for 12 h to obtain the product PS-co-QPVBC.

[0057] (3) PS-co-QPVBC-BPEI solution: The vacuum-dried PS-co-QPVBC powder and BPEI were dissolved in DMSO solution at a mass ratio of 3:1 and stirred at room temperature for 2 h to obtain a uniform PS-co-QPVBC-BPEI solution.

[0058] 3. Preparation of AEMs doped with PVBC nanospheres

[0059] To 47 mL of PS-co-QPVBC-BPEI solution (concentration of 1.4 g / 47 mL), 0.007 g of SPM was added and ultrasonically dispersed at room temperature for 1 hour to prepare a uniform dispersion. The dispersion was then vacuum degassed and poured onto a polytetrafluoroethylene (PTFE) plate and placed in an 80°C oven for reaction for 24 hours to prepare nanosphere-reinforced interpenetrating network AEMs. Subsequently, the AEMs were immersed in a round-bottom flask filled with excess 1-bromopropane and reacted under vacuum at room temperature for 36 hours to quaternize the unreacted BPEI. After that, the completely dried AEMs were soaked in a 1M NaOH solution saturated with N2 at room temperature for 48 hours (the NaOH solution was replaced every 24 hours and monitored with AgNO3 and HNO3 until no white precipitate was produced to ensure that the Cl in the membrane - and Br - Completely converted to OH - ), and then rinsed repeatedly with N2-saturated deionized water until neutral to remove excess OH - Finally, the prepared AEMs were stored in deionized water for future use. The prepared AEMs were named SVSPM0.5. The preparation process of AEMs doped with nanoparticles was as follows: Figure 1 shown.

[0060] According to the formula in Table 1 and referring to the preparation method of SVSPM0.5, the only difference is that the input amount of SPM is changed to prepare AEMs with different SPM contents: SVSPM1, SVSPM2, SVSPM4, and SVSPM6.

[0061] According to the recipe in Table 1, referring to the preparation method of SVSPM0.5, the only difference is that SPM is replaced by BPM and the input amount of BPM is changed to prepare AEMs with different BPM contents: SVBPM0.5, SVBPM1, SVBPM2, SVBPM4, and SVBPM6.

[0062] Table 1. Formulations of all AEMs

[0063]

[0064]

[0065] In Table 1, the concentration of the PS-co-QPVBC-BPEI solution was 1.4 g / 47 mL.

[0066] The following is the preparation method of the control sample.

[0067] Comparative Example 1: Preparation of AEM without Nanospheres

[0068] According to the formulation in Table 1 and referring to the preparation method of SVSPM0.5, an AEM without nanospheres was prepared and named SV AEM (see Table 1 for details).

[0069] The beneficial effects of the present invention are demonstrated by experimental examples below.

[0070] Experimental Example 1: Structural Characterization and Performance Testing of PVBC Nanospheres

[0071] 1. Experimental methods

[0072] (1) X-ray photoelectron spectroscopy (XPS): The elemental analysis of SPM and BPM was performed using a Thermo Scientific K-Alpha X-ray photoelectron spectrometer (Thermo, USA). The test voltage was 12 kV, the excitation source was Al Kα rays, and the spot size was 400 μm.

[0073] (2) Particle size analysis: The particle size of SPM and BPM was analyzed at room temperature using a Nano ZS90 nanoparticle size and zeta potential analyzer (Malvern, UK).

[0074] (3) Scanning electron microscopy (SEM): A microsphere suspension of a certain concentration was prepared and cast onto a 300-mesh copper grid. The suspension was then dried under vacuum at room temperature and its microphase separation structure was observed using a transmission electron microscope (Tecnai G2F20, Japan).

[0075] 2. Experimental results

[0076] (1) Structural characterization of PVBC nanospheres

[0077] like Figure 2 As shown in a and b, the XPS spectra of the two nanospheres show obvious C1s and Cl 2p peaks. Further calculations show that the Cl content in SPM and BPM is 5.66% and 6.10%, respectively, which is consistent with the Cl content in PVBC. Figure 2 As shown in Figures c and d, the average particle sizes of SPM and BPM are 515.1 nm and 824.9 nm, respectively. The above results indicate that PVBC nanoparticles with different particle sizes have been successfully prepared.

[0078] Furthermore, the microscopic morphology of nano-microspheres SPM and BPM with different particle sizes was observed by SEM. Figure 3 As shown in a and b, both SPM and BPM present a relatively uniform spherical morphology, and the particle size is consistent with the above-mentioned particle size analysis results, which confirms each other and shows that this study successfully prepared spherical SPM and BPM with different particle sizes. In addition, according to the EDS diagram of BPM ( Figure 3 c, d) It can be seen that the prepared nanospheres contain a large amount of evenly distributed C and Cl elements, further confirming the successful synthesis of PVBC nanospheres with different particle sizes.

[0079] (2) Thermal stability of PVBC nanospheres

[0080] This study took SPM as an example to investigate the thermal stability of PVBC nanoparticles. Figure 4 As shown, PVBC nanospheres exhibit three typical thermal degradation stages: the first stage, in the 30-150°C range, is attributed to the evaporation of a small amount of water from the PVBC microspheres; the second stage, in the 150-410°C range, is attributed to the thermal decomposition of chloromethyl groups on the PVBC polymer backbone and side chains; and the third stage, occurring above 410°C, is primarily due to the degradation of a large amount of the PVBC polymer backbone. In summary, the prepared PVBC nanospheres possess excellent thermal stability, meeting the requirements for use as a reinforcement material in the preparation of composite membranes.

[0081] Therefore, this study successfully synthesized PVBC nanoparticles SPM and BPM with different particle sizes, whose average particle sizes were 515.1nm and 824.9nm, respectively. The nanoparticles have good thermal stability and the initial thermal decomposition temperature is about 150℃, which meets the requirements for being used as a reinforcing material for the preparation of composite membranes.

[0082] Experimental Example 2: Structural Characterization of Polymer Nanosphere Composite Anion Exchange Membrane

[0083] 1. Experimental methods

[0084] (1) Transmission electron microscopy (TEM): AEMs were embedded in epoxy resin, cured, and vacuum-dried. Ultrathin sections (less than 100 nm thick) were prepared and placed on a 300-mesh copper grid. The microstructure was observed using a transmission electron microscope (Tecnai G2F20, Japan).

[0085] (2) Infrared spectroscopy (FTIR): The FTIR spectrum of the crushed and dried samples was measured using the KBr pellet method. Data were collected on a Fourier transform infrared spectrometer (Nicolet IS-50, Thermo Fisher Scientific, USA). The test was performed in transmission mode with a measurement range of 4000-600 cm -1 , step length is 4cm -1 .

[0086] (3) Scanning electron microscopy (SEM): Same as Experimental Example 1.

[0087] 2. Experimental results

[0088] Figure 5 The FTIR spectra of SV, SVSPM1 and SVBPM1AEMs are shown. It can be seen that the FTIR spectra of SV, SVSPM1 and SVBPM1AEMs are at 3380 and 1650 cm -1 The hydrophilic NH4 + Peak at 2925cm -1 Symmetrical stretching vibration peaks of -CH2 in the main chain of PS-co-PVBC polymer matrix and PVBC nanospheres appeared near 1450 and 1495 cm -1 The characteristic peaks of the carbon-carbon double bond on the benzene ring of the PS-co-PVBC polymer matrix and the PVBC nanospheres appeared at 1020 cm -1 Stronger CN peaks than those in SV AEM appeared near the surface of the nanospheres, indicating that an obvious chemical reaction occurred between -CH2Cl in the PVBC nanospheres and BPEI in the polymer matrix, indicating that PVBC nanospheres can be successfully introduced into SV AEM.

[0089] In this study, the microscopic morphology of the prepared AEMs doped with PVBC nanospheres was observed by SEM. Figure 6 As shown in d and i, the surface of the membrane doped with PVBC nanospheres is yellow and transparent, with a thickness of about 108.5 μm. The surface of the SV AEM without any nanospheres is smooth, dense and flat ( Figure 6 a). However, after adding PVBC nanospheres, the surface of SVSPMx and SVBPMyAEMs gradually became rougher with the increase of the amount of nanospheres added ( Figure 6 b, c, e, f). As the amount of microspheres added increases, obvious particles appear on the surface of the AEM. This is because some nanospheres aggregate after being added to the AEMs, causing the surface of the AEMs to become rough. As the number of aggregated nanospheres increases, they gradually precipitate from the membrane. In addition, the EDS images of the SVSPM6 AEM cross section and the SVBPM1 AEM surface ( Figure 6 As shown in Figures g and h, the uniform and dense distribution of nitrogen in the AEMs doped with PVBC nanospheres provides a structural foundation for the preparation of AEMs with high ionic conductivity. These results demonstrate that the preparation of AEMs by doping with nanospheres is feasible and that by adjusting the amount of PVBC microspheres added, AEMs with smooth surfaces and suitable thickness can be prepared.

[0090] Furthermore, this study selected SV, SVSPM1, SVSPM6, SVBPM1 and SVBPM6 AEMs, and observed the hydrophilic / hydrophobic phase separation structure of AEMs at the nanoscale before and after doping with PVBC nanospheres using TEM and AFM. Figure 7 As shown, all TEM and AFM images show alternating light and dark hydrophilic / hydrophobic regions within the AEMs. Dark regions represent hydrophilic regions within the AEMs, while light regions represent hydrophobic regions. In the SV AEMs, due to the absence of nanospheres, the polymer matrix is ​​tightly bound, resulting in a low degree of microphase separation. However, with the addition of an appropriate amount of nanospheres, the steric volume effect of the microspheres and the formation of nanoclusters (dark patches in the image) enhance the microphase separation within the AEMs, thereby promoting the formation of ion transport channels and improving the ion conduction efficiency of the membranes. However, when the nanosphere content is too high, the PVBC microspheres aggregate to form large clusters, leading to significant phase separation within the membranes. This may block ion transport channels or form "islands," hindering ion transport. Furthermore, the degree of microphase separation and nanocluster size in the BPM-doped membranes are larger than those in the SPM-doped membranes, which is attributed to the larger particle size of the nanospheres. These results indicate that the addition of PVBC nanospheres can regulate the degree of microphase separation in AEMs, thereby improving the size of ion transport channels. However, the degree of microphase separation in AEMs is directly related to the particle size and dosage of PVBC nanospheres. Therefore, by selecting the appropriate nanospheres and dosage, it is possible to construct AEMs with high ionic conductivity.

[0091] The above results show that this study successfully introduced PVBC nanospheres into AEMs, and the addition of SMP and BPM can increase the degree of microphase separation in AEMs. By changing the amount of nanospheres added, the size of the ion transport channels in AEMs can be effectively controlled.

[0092] Experimental Example 3: Performance Test of Polymer Nanosphere Composite Anion Exchange Membrane

[0093] 1. Experimental methods

[0094] (1) Thermal Stability Test: The thermal stability of AEMs was evaluated using a thermogravimetric analyzer (TGA, TA2950, ​​PE Company, USA). The test samples were vacuum dried (60°C) before testing. The test conditions were as follows: N2 atmosphere protection, a heating rate of 10°C / min, and a temperature range of 30–600°C.

[0095] (2) Mechanical Properties: 40 mm × 10 mm AEM specimens were removed from nitrogen-saturated deionized water and the excess water was removed with filter paper. Mechanical properties were then tested at room temperature. A universal testing machine (Instron 5567, Instron, USA) was used with a fixture gauge length of 20 mm and a loading rate of 10 mm / min. The same specimen was tested at least five times under the same conditions.

[0096] (3) Water absorption (WU) and swelling rate (SR) test: The WU and SR of AEMs were determined by measuring the changes in mass and length of completely dried AEMs (40 mm × 10 mm) before and after water absorption. After the AEMs specimens were dried to constant weight under vacuum at 80°C, they were weighed and their lengths were measured. The specimens were then immersed in deionized water at different temperatures (20°C, 40°C, 60°C, and 80°C) for 24 h, taken out, and the surface moisture was wiped off with filter paper before being weighed and their lengths measured. The WU and SR of AEMs were calculated using the following formula:

[0097]

[0098] In the formula, W wet and W dry represent the mass of completely wet and completely dry AEMs, respectively; L wet and L dry represent the lengths of completely wet and completely dry AEMs, respectively.

[0099] (4) Calculation of ion exchange capacity (IEC) and hydration number (λ): The ion exchange capacity reflects the number of exchangeable ions per unit mass of AEM and is generally determined by titration. - The membrane was immersed in 40 mL of 0.01 M hydrochloric acid (HCl) solution and stirred for 72 h to ensure that OH - Has been H + Neutralization. Subsequently, this study used phenolphthalein as an indicator to titrate the residual HCl solution after the membrane was soaked with a 0.01 M NaOH solution (calibrated with potassium hydrogen phthalate). The IEC of AEMs can be calculated using the following formula:

[0100]

[0101] Among them, m dis the mass of AEM completely dried to constant weight, V1 and V2 represent the volume of HCl solution used to soak AEM and the volume of NaOH solution used to titrate the residual HCl solution, respectively, and C0 represents the concentration of NaOH solution.

[0102] The number of water molecules (H2O) that can be absorbed by a single quaternary ammonium group in AEMs is expressed as the hydration number λ. The λ of AEMs can be calculated by the following formula:

[0103]

[0104] In the formula, WU (%) represents the water absorption rate of AEMs, IEC (meq.g -1 ) represents the ion exchange capacity of AEMs, and 18 represents the relative molecular mass of H2O.

[0105] (5) Calculation of ionic conductivity (σ): The ionic conductivity (σ) of AEMs strips (40 mm × 5 mm) was measured in deionized water at different temperatures (20°C, 40°C, 60°C, and 80°C) using an electrochemical workstation (CHI650E, Shanghai Chenhua Instrument Co., Ltd.) using the AC impedance method (test frequency 10 kHz-0.1 Hz, test voltage 10 mV, across the membrane plane). Ionic conductivity (σ) (mS·cm -1 ) is calculated using the following formula:

[0106]

[0107] In the formula, l (cm) represents the distance between the two electrodes, S (cm 2 ) represents the cross-sectional area of ​​the AEM spline, and R (kΩ) represents the in-plane impedance of the AEM spline.

[0108] (6) Preparation of membrane electrode (MEAs) and fuel cell performance test: MEA preparation: In order to test the battery performance of AEMs, a membrane electrode assembly (MEA) was prepared using the catalyst coating substrate (CCS) method. Specifically, a certain amount of Pt / C catalyst (Pt content of 40 wt%) was dispersed in 10 mL of isopropanol, and then an appropriate amount of membrane-forming liquid (solid content of membrane-forming liquid of 3 wt%, membrane-forming liquid / Pt / C = 3 / 5 (w / w) was added and blended with it and ultrasonicated for 1 hour to prepare a catalyst ink. The catalyst ink was evenly sprayed onto a 2 cm × 2 cm carbon paper (the Pt loading on the carbon paper was 0.5 mg cm) using an N2-driven spray gun. -2 Subsequently, the AEM was sandwiched between two sheets of CCS and a small hot press (60°C, 2 MPa, 2 min) was used to prepare sandwich MEAs.

[0109] Fuel Cell Performance Testing: After MEAs were assembled into single cells, cell performance was tested using a fuel cell testing station (Hephas Mini-L100, HEE, China) at 60°C and 40% relative humidity. There was no backpressure during the test, and pure H₂ and pure O₂ were introduced into the test station at flow rates of 250 mL / min and 350 mL / min, respectively.

[0110] 2. Experimental results

[0111] (1) Thermal stability and mechanical properties of SVSPMx and SVBPMy AEMs doped with PVBC nanospheres

[0112] The thermal stability of AEMs has an important impact on the operating stability of fuel cells. Figure 8 Figures a and b show the TGA-DTG curves of SV, SVSPM1, SVSPM6, SVBPM1, and SVBPM6 AEMs. These curves can be divided into three main stages: the first stage is the initial mass loss in the 30–150°C range, which is attributed to the evaporation of a small amount of water from the AEMs; the second stage is the mass loss in the 150–300°C range, which is attributed to the thermal decomposition of quaternary ammonium groups formed on the side chains of the polymer matrix and the reaction between the polymer matrix and PVBC microspheres and BPEI in the AEMs; and the third stage is the mass loss in the 300–500°C range. Overall, the initial degradation temperature of the quaternary ammonium groups in the nanosphere-doped SVSPMx and SVBPMy AEMs is around 150°C, which is higher than the upper operating temperature limit required for fuel cells, demonstrating good thermal stability sufficient for fuel cell operation.

[0113] AEMs are also affected by many external forces such as tension and pressure when serving in fuel cells, so they need to have sufficient mechanical properties to ensure the safety and stability of the battery. Figure 8 As shown in Figures c and d, compared to SV AEMs, the tensile strength of AEMs doped with PVBC nanospheres of varying particle sizes initially increases and then decreases with increasing microsphere content, while the elongation at break continuously decreases. Furthermore, at the same addition level, AEMs incorporating smaller-sized SPM microspheres exhibit slightly better mechanical properties than those incorporating larger-sized BPM microspheres. Taking all factors into consideration, AEMs incorporating 2% SPM (tensile strength and elongation at break of 12.89 MPa and 22.09%, respectively, for SVSPM2AEM) and 1% BPM (tensile strength and elongation at break of 12.31 MPa and 23.03%, respectively, for SVBPM1AEM) exhibit excellent mechanical properties, meeting the performance requirements of fuel cells for AEMs.

[0114] (2) Water absorption, swelling, and ion exchange capacity of SVSPMx and SVBPMy AEMs doped with PVBC nanospheres

[0115] The water absorption (WU) and swelling ratio (SR) of AEMs are important indicators of their dimensional stability. Figure 9 As shown, the WU and SR of all AEMs increase with increasing temperature, and the WU and SR of AEMs doped with nanospheres increase with increasing microsphere content. Membranes doped with BPM at the same content exhibit slightly greater WU and SR than membranes doped with SPM. This indicates that by doping with an appropriate amount of nanospheres, a balanced relationship between WU and SR can be achieved, ensuring that the AEMs possess both good ionic conductivity and dimensional stability.

[0116] Furthermore, this study measured the ion exchange capacity (IEC) and hydration number (λ) of SV, SVSPMx, and SVBPMy AEMs. Table 2 shows that the addition of nanospheres can improve the membrane IEC within a certain range. Furthermore, the IEC of SVSPMx and SVBPMy AEMs first increases and then decreases with increasing nanosphere loading. Therefore, by controlling the loading of PVBC nanospheres of varying particle sizes, the IEC and λ of the AEMs can be adjusted, thereby ensuring dimensional stability at appropriate water absorption levels, which is crucial for practical fuel cell applications.

[0117] Table 2. IEC, WU and λ of SV, SVSPMx and SVBPMy AEMs a Test temperature: 20℃)

[0118]

[0119] (3) Ionic conductivity of SVSPMx and SVBPMy AEMs doped with PVBC nanospheres

[0120] In fuel cells, the core role of anion exchange membranes is to transport OH - , so it needs to have good ion conductivity. Figure 10 The ionic conductivity of SV, SVSPMx and SVBPMy AEMs at different temperatures is shown in Figure 2. Figure 10As can be seen from a and b, the ionic conductivity of all AEMs increases with increasing temperature. At the same temperature, the ionic conductivity of AEMs doped with PVBC nanospheres is slightly higher than that of SV AEM. However, when the content of PVBC nanospheres is further increased, the ionic conductivity of AEMs shows a downward trend. In addition, when the microsphere doping amount is within the appropriate range, the ionic conductivity of SVBPMy AEMs at the same addition amount is slightly higher than that of SVSPMy AEMs. In general, when the SPM and BPM contents are 2% and 1%, respectively, the prepared SVSPM2 and SVBPM1 AEMs have the best ionic conductivity (the conductivity at 80°C is 112.8 mS cm -1 and 110.5 mS cm -1 ), which is a certain improvement compared with SV AEM (the conductivity at 80℃ is 103.3mS cm -1 ), which shows the promoting effect of doping with PVBC nanospheres on improving the ionic conductivity of AEMs.

[0121] (4) Fuel cell performance

[0122] Fuel cell performance testing is an essential step in verifying the practical application of AEMs. This study selected SV AEMs without PVBC nanospheres, SVSPM2 and SVBPM1 AEMs with better overall performance, assembled MEAs under the same conditions and tested their single cell performance (test conditions: 60°C, 40% RH, H2 as fuel, O2 as oxidant). Figure 11 As shown in the figure, the open circuit voltages of the three AEMs in the battery test were all higher than 0.9V, indicating that they have good gas barrier properties in the battery and can effectively prevent the crossover of H2 and O2, ensuring the safety of the battery. The test results show that the SV AEM has a high current density of 270.80mAcm -2 The peak power density is 150.33 mW cm -2 SVBPM1AEM at a current density of 301.26 mA cm -2 When the peak power density is 158.61mW cm -2 ; SVSPM2AEM at a current density of 375.13 mA cm -2 The peak power density is 168.72 mW cm -2 Compared with SV AEM, the peak power density of AEMs doped with PVBC nanospheres was improved. Overall, the peak power density of SVBPM1AEM and SVSPM2AEM increased by approximately 5.51% and 12.23% respectively compared with SV AEM, which proves that the addition of an appropriate amount of PVBC nanospheres can effectively improve the working performance of AEMs in batteries and demonstrates its application potential.

[0123] From the above experimental results, it can be seen that by selecting the appropriate PVBC particle size and addition amount, the AEMs prepared have appropriate water absorption and swelling capacity, and have good thermodynamic stability and mechanical properties, which can meet the use requirements of fuel cells. Compared with undoped nanospheres, adding an appropriate amount of SPM or BPM can significantly improve the electrochemical performance of AEMs, and doping with an appropriate amount of SPM or BPM can significantly improve the performance of fuel cells assembled from AEMs. Among them, SVSPM2 and SVBPM1 AEMs prepared by adding 2% SPM or 1% BPM have high ionic conductivity, and the ionic conductivity at 80°C reaches 112.8mS cm -1 and 110.5 mS cm -1 , which are increased by 9.20% and 6.97% respectively compared with the undoped SV AEM. The peak power densities of SVBPM1 and SVSPM2 AEMs are 158.61 mW cm -2 and 168.72 mW cm -2 , which were increased by about 5.51% and 12.23% respectively compared with the SV AEM without nanospheres, demonstrating the advantages of the microsphere enhancement strategy in the preparation of efficient anion exchange membranes.

[0124] In summary, the present invention provides a polymer nanosphere composite anion exchange membrane, its preparation method, and use. The present invention prepares polymer nanospheres of varying particle sizes through aqueous dispersion polymerization and introduces these nanospheres into a semi-interpenetrating network anion exchange membrane to produce a polymer nanosphere-doped anion exchange membrane. The resulting polymer nanosphere composite anion exchange membrane exhibits excellent thermal stability and mechanical properties, improving the electrochemical performance of the anion exchange membrane and the performance of fuel cells assembled from the anion exchange membrane, demonstrating promising application prospects.

Claims

1. A composite anion exchange membrane, characterized in that The composite anion exchange membrane is composed of polymer nano-microspheres and interpenetrating network anion exchange membrane, wherein the mass ratio of the polymer nano-microspheres to the interpenetrating network anion exchange membrane is 2:

100. The average particle size of the polymer nanospheres is 515.1 nm; The polymer nanospheres are obtained by reacting a vinyl-containing halogenated aromatic hydrocarbon monomer, an initiator, and a dispersant; the mass volume ratio of the vinyl-containing halogenated aromatic hydrocarbon monomer, the initiator, and the dispersant is 10 mL: 0.1-0.2 g: 0.6-1 g; The interpenetrating network anion exchange membrane is prepared according to the following steps: (i) reacting a vinyl-containing aromatic hydrocarbon monomer, a vinyl-containing halogenated aromatic hydrocarbon monomer, and an initiator to obtain a copolymer; (ii) reacting the copolymer with a quaternizing agent to obtain a quaternized copolymer; (iii) The quaternized copolymer is reacted with a cross-linking agent to obtain an interpenetrating network anion exchange membrane.

2. The composite anion exchange membrane according to claim 1, characterized in that The vinyl-containing halogenated aromatic hydrocarbon monomer is 4-vinylbenzyl chloride; the initiator is an azo initiator; the dispersant is polyvinyl pyrrolidone; the mass volume ratio of the vinyl-containing halogenated aromatic hydrocarbon monomer, the initiator and the dispersant is 10 mL: 0.11 g: 0.8 g.

3. The composite anion exchange membrane according to claim 2, characterized in that The initiator is azobisisobutyronitrile.

4. The composite anion exchange membrane according to claim 1, characterized in that In step (i), the vinyl-containing aromatic hydrocarbon monomer is styrene, the vinyl-containing halogenated aromatic hydrocarbon monomer is 4-vinylbenzyl chloride; the initiator is an azo initiator; the molar ratio of the vinyl-containing aromatic hydrocarbon monomer to the vinyl-containing halogenated aromatic hydrocarbon monomer is 1:0.5-1.5; the mass percentage of the initiator is 0.5-1.5wt%; the reaction is carried out under a nitrogen atmosphere; the reaction temperature is 70-90°C, and the reaction time is 20-30 hours; In step (ii), the reaction is carried out under a nitrogen atmosphere; the quaternizing agent is trimethylamine; the molar ratio of the vinyl-containing halogenated aromatic hydrocarbon monomer to the quaternizing agent in the copolymer is 1:0.1-1; the solvent for the reaction is an organic solvent; the reaction temperature is 70-90° C., and the reaction time is 4-6 hours; In step (iii), the cross-linking agent is branched polyethyleneimine; the mass ratio of the quaternized copolymer to the cross-linking agent is 2-4:1; the reaction temperature is 10-40° C., and the reaction time is 1-3 hours.

5. The composite anion exchange membrane according to claim 4, characterized in that In step (i), the initiator is azobisisobutyronitrile.

6. A method for preparing the composite anion exchange membrane according to any one of claims 1 to 5, characterized in that: The method comprises the following steps: reacting polymer nano-microspheres with an interpenetrating network type anion exchange membrane, vacuum defoaming, and drying to obtain a composite anion exchange membrane.

7. The method according to claim 6, characterized in that The reaction temperature is 10-40° C. and the reaction time is 0.5-1.5 hours.

8. Use of the composite anion exchange membrane according to any one of claims 1 to 5 in the preparation of a fuel cell.

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