Composite proton exchange membrane as well as preparation method and application thereof

Abstract

The invention relates to a composite high-temperature proton exchange membrane for a fuel cell, the composite high-temperature proton exchange membrane is obtained by compounding hyperbranched polyphenyl quinoxaline and linear polyphenyl quinoxaline, and the pore structure in the hyperbranched polyphenyl quinoxaline increases the free volume, improves the phosphoric acid doping level and the phosphoric acid retention capability, and improves the performance of the composite high-temperature proton exchange membrane. The linear polyphenylquinoxaline high-molecular polymer has good solubility and good film-forming property, and can enhance the mechanical properties and swelling resistance of the composite film material. The prepared composite high-temperature proton exchange membrane has improved phosphoric acid doping level, proton conduction performance, fuel cell performance and mechanical performance at the same time. The invention also relates to a preparation method of the composite high-temperature proton exchange membrane for the fuel cell and an application of the composite high-temperature proton exchange membrane in a high-temperature proton exchange membrane fuel cell.

Description

Technical Field

[0001] The present disclosure relates to the technical field of proton exchange membrane fuel cells, and in particular to a composite proton exchange membrane, a preparation method thereof, and applications thereof. Background Art

[0002] In recent years, proton exchange membrane fuel cells (PEMFCs) have attracted considerable attention as highly efficient energy conversion devices. The proton exchange membrane (PEM) is a core component of PEMFCs and significantly influences their performance. However, their stringent operating conditions, resulting in complex water and heat management and low catalyst efficiency, limit their application. Against this backdrop, high-temperature PEMs have garnered significant attention.

[0003] High-temperature proton exchange membranes typically use phosphoric acid (PA) instead of water for proton transport, offering advantages such as strong electrode reactivity and simplified hydrothermal management. Polybenzimidazole (PBI) doped with phosphate has been recognized as a classic high-temperature proton exchange membrane (HT-PEM) material. Due to its excellent performance under the harsh operating conditions of high temperature and low humidity, it has been a hot topic in high-temperature proton exchange membrane fuel cells (HT-PEMFCs) research, demonstrating broad application prospects. Although extensive research has been conducted on PA-doped PBI systems, the conflict between high proton conductivity and good mechanical properties has limited their development. This is because, to achieve excellent proton conductivity under high temperature and low humidity conditions, the PBI membrane material must be doped with large amounts of phosphate. However, extremely high levels of phosphate doping often lead to a decrease in the membrane's mechanical properties due to the "strong plasticization" effect of the phosphate molecules. Furthermore, the incorporation of large amounts of phosphate leads to supersaturation of the phosphate, resulting in its free state. Under external forces, these free phosphate molecules are susceptible to migration and loss, resulting in a significant decrease in proton conductivity and severely impacting device durability.

[0004] Polyphenylquinoxalines (PPQs) are a class of π-electron-deficient aromatic heterocyclic high-performance thermoplastics with excellent thermal stability and exceptional mechanical properties. Furthermore, due to the presence of basic nitrogen atoms in the backbone, PPQs have the potential to be doped with phosphoric acid. Compared to the parent polyphenylquinoxaline polymer, the large phenyl group in PPQs improves their solubility and processability. Studies have reported that PPQs exhibit excellent proton conductivity when appropriately doped. Furthermore, compared to other aromatic heterocyclic polymers such as PI, polybenzimidazole (PBI), and polybenzoxazole (PBO), PPQs are currently the only aromatic heterocyclic polymer that can be prepared and cyclized at room temperature. Furthermore, the structural diversity of PPQs themselves offers potential benefits. Hyperbranched polyphenylquinoxaline (HBPPQ), as a porous polymer, offers advantages such as high surface area, multifunctionality, and high stability. Linear polyphenylquinoxaline (PPQ) exhibits excellent resistance to heat, strong acids, and strong bases, making it a suitable matrix for high-temperature PEMs.

[0005] Therefore, it is possible to develop a new type of proton exchange membrane for high-temperature fuel cells through structural improvement based on the characteristics of polyphenylquinoxaline, so as to have excellent phosphoric acid doping amount, proton conductivity, fuel cell performance and mechanical properties. Summary of the Invention

[0006] This disclosure addresses the aforementioned challenges and aims to develop a unique composite membrane for HT-PEMFC applications. This composite membrane, composed of a flexible linear polyphenylquinoxaline (PPQ) matrix and a rigid, porous hyperbranched polyphenylquinoxaline (HBPPQ), significantly improves the membrane's dimensional and mechanical stability at high acid doping levels. Due to the unexpectedly good interfacial compatibility between HBPPQ and PPQ, the resulting membrane exhibits excellent uniformity and stability. Furthermore, the rich pore structure of this composite membrane significantly enhances PA doping and retention, contributing to high proton conductivity and superior fuel cell performance.

[0007] Specifically, in order to solve the above problems, the first aspect of the present disclosure provides a composite membrane comprising: Hyperbranched polyphenylquinoxaline; and linear polyphenylquinoxaline; The hyperbranched polyphenylquinoxaline and the linear polyphenylquinoxaline are blended to form an interpenetrating network structure, and the mass ratio of the hyperbranched polyphenylquinoxaline to the linear polyphenylquinoxaline is 1:4-4:1.

[0008] In one embodiment, the linear polyphenylquinoxaline has the following chemical structure: , Wherein, n represents the number of repeating units, and n=50-200; The Ar3 is selected from the following group: ; The Ar4 is selected from the following group: ; The Z is O or S.

[0009] In one embodiment, the chemical structure of the hyperbranched polyphenylquinoxaline is as follows: Wherein Ar1 is selected from the following group: , Wherein Ar2 is selected from the following group: , Wherein X is selected from the following group: , Wherein Y is selected from the following group: .

[0010] A second aspect of the present invention provides a composite proton exchange membrane comprising: The composite membrane according to the first aspect; and Phosphoric acid; The phosphoric acid is doped into the composite membrane, and the mass ratio of the phosphoric acid to the composite membrane is 3:1-5:1.

[0011] A third aspect of the present invention provides a method for preparing the composite membrane according to the first aspect, comprising: (a) polymerizing a diaziloyl monomer and a tetramine monomer in a solvent in the presence of an acidic catalyst to obtain a reaction solution containing linear polyphenylquinoxaline; (b) dissolving the triazil monomer and the tetramine monomer in a solvent in the presence of an acidic catalyst, and then adding the reaction solution containing the linear polyphenylquinoxaline obtained in step (a) above to the system to obtain a blended solution; (c) Casting the blended solution of step (b) into a membrane and polymerizing the trisulphuric acid monomer and the tetramine monomer during the membrane formation process to obtain the composite membrane.

[0012] In one embodiment, in the method of the third aspect: The chemical structure of the diazinon monomer in step (a) is selected from the following group: , wherein Z is O or S; and / or The tetraamine monomer in the step (a) is selected from the following group: and / or The solvent in step (a) is m-cresol, dimethyl sulfoxide or N-methylpyrrolidone; and / or The acidic catalyst in step (a) is formic acid, acetic acid or benzoic acid; and / or.

[0013] The polymerization reaction temperature in step (a) is 50° C. to 150° C.; and / or The molar ratio of the diaziloyl monomer to the tetramine monomer in step (a) is 1:1; and / or The step (a) is carried out under the protection of an inert gas; and / or The triphenyl monomer in step (b) is selected from the following group: wherein Y is H, F, Cl, Br or I; and / or The tetraamine monomer in the step (b) is selected from the following group: and / or The solvent in step (b) is m-cresol, dimethyl sulfoxide or N-methylpyrrolidone; and / or The acidic catalyst in step (b) is formic acid, acetic acid or benzoic acid; and / or The molar ratio of the triphenyl monomer to the tetramine monomer in step (b) is 1:5-5:1, preferably 1:2-2:1, more preferably 2:3; and / or The step (b) is carried out under the protection of an inert gas; and / or The casting and film formation in the step (c) is carried out at a temperature of 50°C-150°C, preferably by gradually increasing the temperature from 50°C to 150°C, more preferably by the following stepwise heating method: 3 days at 50°C, 4 hours at 80°C, 6 hours at 100°C, 10 hours at 120°C, and 4 hours at 150°C.

[0014] A fourth aspect of the present invention provides a method for preparing the composite proton exchange membrane according to the second aspect, comprising: The composite membrane according to the first aspect of claim or the composite membrane prepared by the method according to the third aspect is immersed in a phosphoric acid solution to obtain the composite proton exchange membrane.

[0015] In one embodiment, in the method of the fourth aspect: The phosphoric acid content in the phosphoric acid solution is 60-85% by weight; and / or The soaking time is 1-48 hours; and / or The soaking temperature is 20-120°C; and / or The soaking was continued until the weight became constant.

[0016] A fifth aspect of the present invention provides a high-temperature proton exchange membrane fuel cell, comprising: the composite proton exchange membrane according to the second aspect or the composite proton exchange membrane prepared by the method according to the fourth aspect.

[0017] The sixth aspect of the present invention provides use of the composite proton exchange membrane according to the second aspect or the composite proton exchange membrane prepared by the method according to the fourth aspect in a high-temperature proton exchange membrane fuel cell.

[0018] The special mechanism and beneficial technical effects of the present disclosure are as follows: Porous materials have a regular structure, are highly designable, can accommodate a variety of proton carriers, and can be easily assembled into excellent proton-conducting materials. Numerous studies have demonstrated that constructing continuous proton transport channels with pores is an effective strategy for improving the proton conductivity of HT-PEMs. Most studies have reported methods for constructing proton transport channels through molecular design and doping with microporous materials. However, these strategies also have limitations, as complex molecular structures and microporous materials are difficult to prepare. In contrast, directly preparing porous membranes with pore structures is considered a relatively simple approach to constructing proton channels. In theory, sufficient porosity can form a continuous pore network. However, it is important to note that high porosity alone is not sufficient for constructing stable and efficient proton channels. Instead, it may introduce excessive structural defects, compromising the overall membrane properties (such as mechanical strength and oxidation resistance). Therefore, stable (low porosity) and continuous pores are crucial for constructing optimal proton transport channels.

[0019] The gaps between polymer chains are defined as free volume (FFV), which plays a crucial role in the phosphoric acid doping level. There are various strategies to enrich the free volume, such as optimizing physicochemical properties and introducing pendant groups, manipulating branched structures, filling inorganic components, and combining with porous organic polymers. However, synthesizing membranes with large FFV is very difficult. Polymer blending is considered a relatively simple and efficient method, especially because the blending process is suitable for large-scale preparation, but it often has the disadvantage of being difficult to form a perfect homogeneous composite.

[0020] In addition, the proton transport in PA-doped membranes generally follows the Grotthuss (proton hopping) mechanism, where protons move between ionized NH sites, PA molecules, and H2PO4 + / H2PO4 - Alternatively, a carrier mechanism may coexist with the Grotthuss mechanism, whereby protons bound to PAs or any available water molecules self-diffusion throughout the membrane.

[0021] It is precisely because of the above mechanism and in order to overcome the related defects that the present disclosure creatively utilizes the rigid porous structure of HBPPQ in the composite membrane to expand the chain spacing of PPQ, increase the free volume of the membrane, and enrich more PA molecules. At the same time, the composite membrane has abundant basic sites, which can form hydrogen bonds with more PA molecules, forming a long-range hydrogen bond network, providing continuous proton transfer sites, and facilitating enhanced proton conduction. The channels in the porous composite membrane shorten the proton conduction path and improve the path selectivity. Protons can quickly jump from one site to the next, thereby making the Ea value lower and the proton conductivity higher. In addition, the composite structure is composed of a flexible matrix PPQ and a rigid HBPPQ, which can be well blended to form an interpenetrating network structure. At high phosphoric acid doping levels, the dimensional-mechanical stability of the membrane can be significantly improved, and a two-dimensional, ordered pore structure can be formed.

[0022] It should be understood that the contents described in this section are not intended to identify the key or important features of the embodiments of the present disclosure, nor are they intended to limit the scope of the present disclosure. Other features of the present disclosure will become readily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 1 is the hydrogen nuclear magnetic resonance spectrum of the triphenyl monomer and the fluorine-containing triphenyl monomer of Example 1.

[0024] Figure 2 This is the hydrogen nuclear magnetic resonance spectrum of the diazolyl monomer of Example 1.

[0025] Figure 3 This is an infrared spectrum analysis chart of the hyperbranched polyphenylquinoxaline of Example 2.

[0026] Figure 4 This is a surface SEM image of the 50% HBPPQ-PPQ film of Example 3. The surface SEM image shows a flat and smooth surface with no obvious phase interface separation, indicating good dispersibility of HBPPQ and PPQ in the solvent and good compatibility between the two.

[0027] Figure 5 Figure 3 is a cross-sectional SEM image of the 50% HBPPQ-PPQ membrane of Example 3. The cross-sectional morphology of the membrane is a fibrous network, indicating the porous nature and abundant free volume of the membrane.

[0028] Figure 6 1 is a cross-sectional TEM image of the 50% HBPPQ-PPQ membrane of Example 3. This image shows that the membrane has long-range continuous proton conduction channels.

[0029] Figure 7 It is an infrared spectrum analysis chart of the composite membranes of Examples 3, 4, 5, and 6 and the membrane of Comparative Example 1.

[0030] Figure 8 3 and 4 are thermogravimetric analysis graphs of the hyperbranched polyphenylquinoxaline of Example 2, the composite membranes of Examples 3, 4, 5, and 6, and the membrane of Comparative Example 1.

[0031] Figure 9 It is a tensile analysis diagram of the composite films of Examples 3, 4, 5, and 6 and the film of Comparative Example 1.

[0032] Figure 10 The Nyquist curves of the composite membranes of Examples 3, 4, and 5 after doping with phosphoric acid (cell temperature 180°C, back pressure 50KPa, H2 / O2 flow rate 150 ml / min, current density 0.5A / cm 2 ).

[0033] Figure 11 The graph shows the relationship between the proton conductivity of the composite membrane doped with phosphoric acid in Examples 3, 4, and 5 and the temperature (the battery temperature is 180°C, the back pressure is 50KPa, the H2 / O2 flow rate is 150 ml / min, and the current density is 0.5A / cm 2 The figure shows that with the increase of HBPPQ content, the proton conductivity of the composite membrane is higher at the same temperature. The proton conductivity of the 70% HBPPQ-PPQ membrane in the anhydrous state at 180 °C is as high as 99 mS·cm -1 .

[0034] Figure 12 The performance of a fuel cell using a proton exchange membrane obtained by doping the composite membranes of Examples 3, 4, and 5 with phosphoric acid (cell temperature 180°C, back pressure 50 kPa, H2 / O2 flow rate 150 ml / min) shows that the power density of a 50% HBPPQ-PPQ membrane can reach a maximum of 940.5 mW / cm 2 . DETAILED DESCRIPTION

[0035] The following describes embodiments of the present disclosure in more detail. Although the present disclosure provides certain embodiments, it should be understood that the present disclosure can be implemented in various forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the present disclosure. It should be understood that the drawings and embodiments of the present disclosure are for illustrative purposes only and are not intended to limit the scope of protection of the present disclosure.

[0036] "Range" in this disclosure is defined in the form of a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundaries of a particular range. Ranges defined in this manner can be inclusive or exclusive of the end values ​​and can be arbitrarily combined, i.e., any lower limit can be combined with any upper limit to form a range. For example, if a range of 60-120 and 80-110 is listed for a particular parameter, it is understood that ranges of 60-110 and 80-120 are also expected. In addition, if the minimum range values ​​listed are 1 and 2, and if the maximum range values ​​listed are 3, 4, and 5, then the following ranges can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this disclosure, unless otherwise specified, the numerical range "ab" represents an abbreviation for any real number combination between a and b, where a and b are both real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" have been listed herein, and "0-5" is simply an abbreviation for these numerical combinations. In addition, when a parameter is expressed as an integer ≥ 2, it is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0037] Terms such as "first" and "second" used in this disclosure are used solely to distinguish between objects for clarity of description and do not limit the size, quantity, or other order of the objects they describe. Directional terms indicate orientations or positional relationships based on those shown in the accompanying drawings. These terms are used solely to facilitate the description of this disclosure and do not indicate or imply that the objects referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limiting this disclosure.

[0038] Unless otherwise specified, all embodiments and optional embodiments of the present disclosure can be combined with each other to form new technical solutions.

[0039] Unless otherwise specified, all steps of the present disclosure may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), which means that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0040] Unless otherwise stated, the words “comprises,” “includes,” “has,” “contains” or any other variations thereof mentioned in this disclosure are intended to cover a non-exclusive inclusion.

[0041] Unless otherwise specified, the indefinite articles "a" and "an" before an element or component in the present disclosure do not limit the quantity requirement (i.e., the number of times the element or component appears). Therefore, "a" or "an" should be interpreted as including one or at least one, and elements or components in the singular also include plural forms, unless the number is obviously intended to limit the singular form.

[0042] As mentioned above, there is an urgent need in the prior art to synthesize a new proton exchange membrane for high-temperature fuel cells that has excellent phosphoric acid doping amount, proton conductivity, fuel cell performance and mechanical properties.

[0043] Composite membrane To at least partially address one or more of the above-mentioned problems and other potential problems, a first exemplary embodiment of the present disclosure provides a composite membrane comprising: Hyperbranched polyphenylquinoxaline; and linear polyphenylquinoxaline; The hyperbranched polyphenylquinoxaline and the linear polyphenylquinoxaline are blended to form an interpenetrating network structure, and the mass ratio of the hyperbranched polyphenylquinoxaline to the linear polyphenylquinoxaline is 1:4-4:1.

[0044] Regarding the chemical structure of the linear polyphenylquinoxaline, the following structure can be typically adopted: , Wherein, n represents the number of repeating units, and n=50-200; The Ar3 is selected from the following group: ; The Ar4 is selected from the following group: ; The Z is O or S.

[0045] Regarding the chemical structure of the hyperbranched polyphenylquinoxaline, the following structure can be typically adopted: Wherein Ar1 is selected from the following group: , Wherein Ar2 is selected from the following group: , Wherein X is selected from the following group: , Wherein Y is selected from the following group: .

[0046] The mass ratio of the linear polyphenylquinoxaline to the hyperbranched polyphenylquinoxaline is 1:4-4:1, and can typically be 1:1, 1:2, 1:3, 1:4, 4:1, 3:1, 2:1 or any value therebetween.

[0047] The composite membrane can be used to further prepare a composite proton exchange membrane by doping with acid.

[0048] Composite proton exchange membrane In order to at least partially solve the above problems and one or more of other potential problems, a second exemplary embodiment of the present disclosure provides a composite proton exchange membrane comprising: The composite membrane according to the first exemplary embodiment; and Phosphoric acid; The phosphoric acid is doped into the composite membrane, and the mass ratio of the phosphoric acid to the composite membrane is 3:1-5:1.

[0049] The mass ratio of the phosphoric acid to the composite membrane may typically be 3:1, 4:1, 5:1 or any value therebetween.

[0050] Method for preparing composite membrane In order to at least partially solve the above problems and one or more of other potential problems, a third exemplary embodiment of the present disclosure provides a method for preparing the composite membrane according to the first exemplary embodiment, comprising: (a) polymerizing a diaziloyl monomer and a tetramine monomer in a solvent in the presence of an acidic catalyst to obtain a reaction solution containing linear polyphenylquinoxaline; (b) dissolving the triazil monomer and the tetramine monomer in a solvent in the presence of an acidic catalyst, and then adding the reaction solution containing the linear polyphenylquinoxaline obtained in step (a) above to the system to obtain a blended solution; (c) Casting the blended solution of step (b) into a membrane and polymerizing the trisulphuric acid monomer and the tetramine monomer during the membrane formation process to obtain the composite membrane.

[0051] Regarding the chemical structure of the diazinon monomer in step (a), a structure selected from the following group can be typically employed: , wherein Z is O or S; and / or Regarding the chemical structure of the tetraamine monomer in the step (a), it can be typically selected from the following group: and / or As for the solvent in step (a), m-cresol, dimethyl sulfoxide or N-methylpyrrolidone can be typically used; and / or As for the acidic catalyst in the step (a), formic acid, acetic acid or benzoic acid may be typically used; and / or

[0052] The temperature of the polymerization reaction in step (a) may typically be 50°C to 150°C. For example, it may be 50°C, 60°C, 70°C, 80°C, 90°C, 100°C, 110°C, 120°C, 130°C, 140°C, 150°C or any value therebetween; and / or The molar ratio of the diazolyl monomer to the tetramine monomer in step (a) is typically 1:1; and / or The step (a) is carried out under the protection of an inert gas; and / or Regarding the triphenyl monomer in step (b), it is typically selected from the following group: wherein Y is H, F, Cl, Br or I; and / or Regarding the tetraamine monomer in step (b), it is typically selected from the following group: and / or Regarding the solvent in step (b), it is typically m-cresol, dimethyl sulfoxide or N-methylpyrrolidone; and / or Regarding the acidic catalyst in step (b), it is typically formic acid, acetic acid or benzoic acid; and / or The molar ratio of the triphenyl monomer to the tetramine monomer in step (b) is typically 1:5-5:1, preferably 1:2-2:1, more preferably 2:3; and / or The step (b) is carried out under the protection of an inert gas; and / or The casting and film formation in the step (c) is carried out at a temperature of 50°C-150°C, preferably by gradually increasing the temperature from 50°C to 150°C, more preferably by the following stepwise heating method: 3 days at 50°C, 4 hours at 80°C, 6 hours at 100°C, 10 hours at 120°C, and 4 hours at 150°C.

[0053] Method for preparing composite proton exchange membrane In order to at least partially solve one or more of the above problems and other potential problems, a fourth exemplary embodiment of the present disclosure provides a method for preparing the composite proton exchange membrane according to the second exemplary embodiment, comprising: The composite membrane according to the first exemplary embodiment or the composite membrane prepared by the method according to the third exemplary embodiment is immersed in a phosphoric acid solution to obtain the composite proton exchange membrane.

[0054] Typically: The phosphoric acid content in the phosphoric acid solution is 60-85% by weight; and / or The soaking time is 1-48 hours; and / or The soaking temperature is 20-120°C; and / or The soaking was continued until the weight became constant.

[0055] High-temperature proton exchange membrane fuel cells In order to at least partially solve one or more of the above-mentioned problems and other potential problems, the fifth exemplary embodiment of the present disclosure provides a high-temperature proton exchange membrane fuel cell, which includes: a composite proton exchange membrane according to the second exemplary embodiment or a composite proton exchange membrane prepared by the method according to the fourth exemplary embodiment.

[0056] Typically, the operating temperature of the high-temperature proton exchange membrane fuel cell is 120°C-180°C.

[0057] Application of composite proton exchange membrane To at least partially solve one or more of the above problems and other potential problems, the sixth exemplary embodiment of the present disclosure provides the composite proton exchange membrane according to the second exemplary embodiment or the composite proton exchange membrane prepared by the method according to the fourth exemplary embodiment.

[0058] The following examples are provided. The examples described below are illustrative and are intended only to explain the present disclosure and are not to be construed as limiting the present disclosure. Where specific techniques or conditions are not specified in the examples, the methods were performed according to those described in the literature in the art or according to the product specifications. Reagents or instruments used without manufacturer's indication are all commercially available conventional products. Example 1 - Synthesis of various monomers 1. Synthesis of Triazolyl Monomer (hereinafter referred to as Monomer of Formula A) Specific synthesis method: (1) 1,3,5-triphenylbenzene, phenylacetyl chloride, and anhydrous aluminum chloride (molar ratio of 1:3.05:3.10) were added to dichloromethane (solid content of the reaction system was 35%) and reacted in an ice bath under nitrogen atmosphere for 24 h. (2) Pour the solution obtained in step (1) into a 10% by mass aqueous solution of hydrochloric acid, stir and filter, wash the filter cake with deionized water until neutral, dry and pour the crude product into acetone and heat until completely dissolved, then cool and precipitate the product, collect the product and dry it; (3) The product obtained in step (2) is used as a raw material, poured into DMSO (solid content of the reaction system is 25%) and stirred until completely dissolved, then copper bromide (the molar ratio of copper bromide to the molar amount of the product obtained in step (2) is 3.05:1) is added as a catalyst, the reaction system is heated to 80°C and reacted for 24 hours, then the reaction solution is poured into a 10% hydrochloric acid aqueous solution, stirred and filtered, the filter cake is washed with deionized water until neutral, dried and poured into acetone to dissolve, filtered and the filtrate is poured into a hydrochloric acid aqueous solution, stirred and filtered to obtain a filter cake, then washed with deionized water until neutral, dried and collected to obtain the said tris-acyl monomer, whose chemical structure is as follows: Formula A.

[0059] 2. Synthesis of fluorinated triazide monomer (hereinafter referred to as monomer of formula B) Specific synthesis method: (1) Add 1,3,5-triphenylbenzene, p-fluorophenylacetyl chloride, and anhydrous aluminum chloride (molar ratio of 1:3.05:3.10) to dichloromethane (solid content of the reaction system is 35%); react in an ice bath under nitrogen atmosphere for 24 hours; (2) Pour the solution obtained in step (1) into a 10% hydrochloric acid aqueous solution, stir and filter, wash the filter cake with deionized water until neutral, dry and pour the crude product into acetone and heat until completely dissolved, then cool and precipitate the product, collect the product and dry it; (3) The product obtained in step (2) is used as a raw material, poured into DMSO (the solid content of the reaction system is 25%) and stirred until completely dissolved, and then copper bromide (the molar ratio of copper bromide to the molar amount of the product obtained in step (2) is 3.05:1) is added as a catalyst, the reaction system is heated to 80°C and reacted for 24 hours, and then the reaction solution is poured into a 10% hydrochloric acid aqueous solution, stirred and filtered, the filter cake is washed with deionized water until neutral, dried and poured into acetone to dissolve, filtered and the filtrate is poured into a hydrochloric acid aqueous solution, stirred and filtered to obtain a filter cake, and then washed with deionized water until neutral, dried and collected to obtain the fluorine-containing tris-acyl monomer; The structural formula of the obtained fluorine-containing triphenyl monomer is as follows: Formula B.

[0060] 3. Synthesis of diazolyl monomer (hereinafter referred to as monomer of formula C) Specific synthesis method: (1) Phenyl ether and phenylacetyl chloride were used as the reaction raw materials, anhydrous aluminum chloride was used as the catalyst, and dichloromethane was used as the solvent. Under a nitrogen atmosphere, anhydrous aluminum chloride (25.2013 g, 189 mmol) was dispersed in dichloromethane solvent (40 mL), and then phenylacetyl chloride solution (27.8262 g, 180 mmol) was added dropwise. After the addition was completed, the mixture was stirred for about 30 minutes, and then a dichloromethane solution (40 mL) of phenyl ether (14.9453 g, 87 mmol) was added dropwise. The mixture was reacted under ice bath for 24 hours. After the reaction was completed, the resulting solution was poured into aqueous hydrochloric acid solution, stirred, and filtered. The filter cake was washed with deionized water until neutral. After drying, the crude product was poured into acetone and heated until completely dissolved. The product was then cooled to precipitate, and the product was collected and dried. (2) The obtained product was used as a raw material (14.9453 g, 54.1 mmol), poured into DMSO (110 mL) and stirred until completely dissolved. Then, copper bromide (24.1959 g, 10.8 mmol) was added as a catalyst, and the reaction system was heated to 80°C for 24 h. After the reaction was completed, the reaction solution was poured into a hydrochloric acid aqueous solution, stirred, and filtered. The filter cake was washed with deionized water until neutral, dried, and poured into acetone to dissolve. The filtrate was filtered and poured into a hydrochloric acid aqueous solution. After stirring, the filter cake was filtered and washed with deionized water until neutral. The product was collected after drying.

[0061] The structural formula of the obtained diazolyl monomer is as follows: Formula C.

[0062] Example 2 - Copolymerization of Trisulphonyl Monomer and Tetramine Monomer (Verification of Successful Hyperbranching Reaction) The trisulyl monomer and tetramine monomer of the above formula A were used as reaction raw materials, added to m-cresol (solid content of the reaction system was 1%) in a molar ratio of 2:3, and stirred to dissolve. Acetic acid (molar ratio of acetic acid to tetramine monomer was 2:1) was added as a catalyst. The reaction temperature was 70° C. and the reaction was carried out for 48 hours. After the reaction was completed, the mixture was poured into a methanol solution for precipitation, and the obtained product was filtered and dried to prepare a hyperbranched polyphenylquinoxaline.

[0063] The tetraamine monomer used in the above reaction is 3,3'-diaminobenzidine, whose structural formula is .

[0064] Figure 3 The structure of hyperbranched polyphenylquinoxaline was verified by infrared spectroscopy, and Figure 8 The high heat resistance demonstrated proves that the polymerization reaction occurred successfully, that is, the hyperbranched polymer was successfully prepared.

[0065] Example 3 - Preparation of 50% HBPPQ-PPQ composite membrane (1) Preparation of PPQ solution: Under nitrogen atmosphere, diazinon monomer (0.395 mmol, 0.1747 g) of formula C was added to m-cresol solvent (6 mL) and stirred until dissolved. 3,3'-diaminobenzidine (0.395 mmol, 0.0846 g) was then added and reacted at 120 °C for 6 h to prepare PPQ solution. The structure of the obtained PPQ is as follows: , n=71, obtained based on intrinsic viscosity test; (2) In situ introduction of PPQ solution during the synthesis of HBPPQ: Under nitrogen atmosphere, 3,3'-diaminobenzidine (0.377 mmol, 0.0807 g) and the monomer of formula A in Example 1 (0.251 mmol, 0.1764 g) were dissolved in m-cresol solvent (25 mL), and acetic acid (0.753 mmol, 0.0452 g) was added as a catalyst. After the catalyst was completely dissolved, the prepared PPQ solution was added to the reaction system and stirred for about 5-10 min. The blend solution was filtered and degassed, then poured into an ultra-flat surface dish, placed in an oven, and gradually heated from 50°C to 150°C (50°C for 3 days, 80°C for 4 hours, 100°C for 6 hours, 120°C for 10 hours, and 150°C for 4 hours). The solvent was gradually dried, peeled off from the ultra-flat surface dish, washed with methanol and deionized water, and dried to obtain a 50% HBPPQ-PPQ composite membrane. Example 4 - Preparation of 60% HBPPQ-PPQ composite membrane (1) Preparation of PPQ solution: Under nitrogen atmosphere, diazinon monomer (0.316 mmol, 0.1397 g) of formula C was added to m-cresol solvent (5 mL) and stirred until dissolved. Then, 3,3'-diaminobenzidine (0.316 mmol, 0.0677 g) was added and reacted at 80 °C for 12 h to prepare PPQ solution. (2) In situ introduction of PPQ solution during the synthesis of HBPPQ: Under nitrogen atmosphere, 3,3'-diaminobenzidine (0.453 mmol, 0.0972 g) and the monomer of formula A in Example 1 (0.302 mmol, 0.2124 g) were dissolved in m-cresol solvent (30 mL), and acetic acid (0.907 mmol, 0.0545 g) was added as a catalyst. After the catalyst was completely dissolved, the prepared PPQ solution was added to the reaction system and stirred for about 5-10 min. The blended solution was filtered and degassed, then poured into an ultra-flat surface dish, placed in an oven, and gradually heated from 50°C to 150°C (50°C for 3 days, 80°C for 4 hours, 100°C for 6 hours, 120°C for 10 hours, and 150°C for 4 hours). The solvent was gradually dried, peeled off from the ultra-flat surface dish, washed with methanol and deionized water, and dried to obtain a 60% HBPPQ-PPQ composite membrane.

[0066] Example 5 - Preparation of 70% HBPPQ-PPQ composite membrane (1) Preparation of PPQ solution: Under nitrogen atmosphere, diazinon monomer (0.237 mmol, 0.1047 g) of formula C was added to m-cresol solvent (4 mL) and stirred until dissolved. Then, 3,3'-diaminobenzidine (0.237 mmol, 0.0507 g) was added and reacted at 100 °C for 8 h to prepare PPQ solution. (2) In situ introduction of PPQ solution during the synthesis of HBPPQ: Under nitrogen atmosphere, 3,3'-diaminobenzidine (0.529 mmol, 0.1133 g) and the monomer of formula A in Example 1 (0.353 mmol, 0.2478 g) were dissolved in m-cresol solvent (35 mL), and acetic acid (1.058 mmol, 0.0635 g) was added as a catalyst. After the mixture was completely dissolved, the prepared PPQ solution was added to the reaction system and stirred for about 5-10 min. The mixed solution was filtered, degassed, and poured into an ultra-flat surface dish. The mixture was placed in an oven and gradually heated from 50°C to 150°C for 3 days to gradually dry the solvent. After peeling from the ultra-flat surface dish, it was washed with methanol and deionized water and dried to obtain a 70% HBPPQ-PPQ composite membrane.

[0067] Example 6 - Preparation of 80% HBPPQ-PPQ composite membrane (1) Preparation of PPQ solution: Under nitrogen atmosphere, diazinon monomer of formula C (0.158 mmol, 0.0699 g) was added to m-cresol solvent (3 mL) and stirred until dissolved. Then, 3,3'-diaminobenzidine (0.158 mmol, 0.0338 g) was added and reacted at 30 °C for 24 h to prepare PPQ solution.

[0068] (2) In situ introduction of PPQ solution during the synthesis of HBPPQ: Under nitrogen atmosphere, 3,3'-diaminobenzidine (0.605 mmol, 0.1295 g) and the monomer of formula A in Example 1 (0.403 mmol, 0.2832 g) were dissolved in m-cresol solvent (40 mL), and acetic acid (1.209 mmol, 0.0726 g) was added as a catalyst. After the catalyst was completely dissolved, the prepared PPQ solution was added to the reaction system and stirred for about 5-10 min. The blended solution was filtered and degassed, then poured into an ultra-flat surface dish, placed in an oven, and gradually heated from 50°C to 150°C (50°C for 3 days, 80°C for 4 hours, 100°C for 6 hours, 120°C for 10 hours, and 150°C for 4 hours). The solvent was gradually dried, peeled off from the ultra-flat surface dish, washed with methanol and deionized water, and dried to obtain an 80% HBPPQ-PPQ composite membrane.

[0069] Comparative Example 1 - Preparation of PPQ Film Under a nitrogen atmosphere, the diazinon monomer of formula C (0.790 mmol, 0.3493 g) was added to m-cresol solvent (11 mL) and stirred until dissolved. 3,3'-diaminobenzidine (0.790 mmol, 0.1692 g) was then added and reacted at 120°C for 6 h to prepare a PPQ solution. The PPQ solution was then poured into an ultra-flat watch glass and placed in an oven at 80°C for 4 h and 120°C for 10 h to gradually dry out the solvent. The PPQ film was peeled from the ultra-flat watch glass, washed with methanol and deionized water, and dried to obtain a PPQ film.

[0070] Preparation of composite proton exchange membrane The composite membranes of Examples 3-6 and the membrane of Comparative Example 1 were cut into regular small strips and immersed in 85 wt% phosphoric acid at 25°C for 24 hours. The membrane surfaces were then wiped with filter paper. Finally, the samples were dried at 120°C for 1 hour to remove moisture, yielding composite proton exchange membranes. The difference in mass before and after doping and the ratio of the mass of the undoped membrane represent the phosphoric acid doping rate.

[0071] The performance of the various proton exchange membranes obtained above was tested, and the results are shown in Table 1 below.

[0072] Table 1 Performance tests of various proton exchange membranes ( Note: The proton conductivity in the above table is based on the battery temperature of 180°C, the cathode and anode back pressure of 50KPa, and H 2 / O 2 The flow rate is The data is obtained under the test conditions of 150ml / min and no humidification; the fuel cell performance is obtained under the conditions of battery temperature 180℃ and anode back pressure 100Kpa, H 2 / O 2 Data obtained under test conditions with a flow rate of 150 ml / min and no humidification; PPQ membrane fuel cell performance after phosphoric acid doping Energy difference, when the current is 0.1A, the voltage has dropped below 0.1V, so the current density of 0.5A / cm cannot be measured. 2 Current density Electron conductivity and battery performance ).

[0073] The above results show that compared with pure PPQ membranes, all composite membranes exhibit higher phosphate doping levels and mechanical strength. Moreover, with the increase of HBPPQ content, under the same test conditions, the phosphate doping level of the composite membrane increases and the proton conductivity value increases, achieving significantly beneficial technical effects.

[0074] The foregoing examples are merely illustrative, serving to illustrate some of the features of the present disclosure. The appended claims are intended to be as broad as conceivable, and the examples presented herein are merely illustrative of selected implementations according to all possible combinations of embodiments. Therefore, it is the applicant's intention that the appended claims are not limited by the selection of examples illustrating the features of the present application. As used in the claims, the term "comprising" and its semantic variations logically encompass different and varied terms, such as, but not limited to, "consisting essentially of" or "consisting of." Where necessary, numerical ranges are provided, and these ranges also include subranges therebetween. Variations within these ranges will be self-evident to those skilled in the art and should not be considered to be dedicated to the public, but rather should be construed to be covered by the appended claims, to the extent possible. Furthermore, advances in science and technology will result in possible equivalents or sub-alternatives not currently contemplated due to linguistic inaccuracies, and such variations should be construed to be covered by the appended claims, to the extent possible.

Claims

1. A composite membrane comprising: Hyperbranched polyphenylquinoxaline; and linear polyphenylquinoxaline; in, The hyperbranched polyphenylquinoxaline and the linear polyphenylquinoxaline are blended to form an interpenetrating network structure, and the mass ratio of the hyperbranched polyphenylquinoxaline to the linear polyphenylquinoxaline is 1:4-4:

1.

2. The composite membrane according to claim 1, wherein the chemical structure of the hyperbranched polyphenylquinoxaline is as follows: wherein Ar1 is selected from the group consisting of: ， Wherein Ar2 is selected from the following group: ， Wherein X is selected from the following group: ， Wherein Y is selected from the following group: 。 3. The composite membrane according to claim 1 or 2, wherein the chemical structure of the linear polyphenylquinoxaline is as follows: ， in, n represents the number of repeating units, and n=50-200; The Ar3 is selected from the following group: ； Said Ar4 is selected from the following group ； The Z is O or S.

4. A composite proton exchange membrane comprising: The composite membrane according to any one of claims 1 to 3; and Phosphoric acid; in, The phosphoric acid is doped into the composite membrane, and the mass ratio of the phosphoric acid to the composite membrane is 3:1-5:

1.

5. A method for preparing a composite membrane according to any one of claims 1 to 3, comprising: (a) polymerizing a diaziloyl monomer and a tetramine monomer in a solvent in the presence of an acidic catalyst to obtain a reaction solution containing linear polyphenylquinoxaline; (b) dissolving the triazil monomer and the tetramine monomer in a solvent in the presence of an acidic catalyst, and then adding the reaction solution containing the linear polyphenylquinoxaline obtained in step (a) above to the system to obtain a blended solution; (c) Casting the blended solution of step (b) into a membrane and polymerizing the trisulphuric acid monomer and the tetramine monomer during the membrane formation process to obtain the composite membrane.

6. The method according to claim 5, wherein: The chemical structure of the diazinon monomer in step (a) is selected from the following group: , where Z is O or S; and / or The tetraamine monomer in step (a) is selected from the following group: and / or The solvent in step (a) is m-cresol, dimethyl sulfoxide or N-methylpyrrolidone; and / or The acidic catalyst in step (a) is formic acid, acetic acid or benzoic acid; and / or The polymerization reaction temperature in step (a) is 50° C. to 150° C.; and / or The molar ratio of the diaziloyl monomer to the tetramine monomer in step (a) is 1:1; and / or The step (a) is carried out under the protection of an inert gas; and / or The triphenyl monomer in step (b) is selected from the following group: wherein Y is H, F, Cl, Br or I; and / or The tetraamine monomer in step (b) is selected from the following group: and / or The solvent in step (b) is m-cresol, dimethyl sulfoxide or N-methylpyrrolidone; and / or The acidic catalyst in step (b) is formic acid, acetic acid or benzoic acid; and / or The molar ratio of the triphenyl monomer to the tetramine monomer in step (b) is 1:5-5:1, preferably 1:2-2:1, more preferably 2:3; and / or The step (b) is carried out under the protection of an inert gas; and / or The casting and film formation in the step (c) is carried out at a temperature of 50°C-150°C, preferably by gradually increasing the temperature from 50°C to 150°C, more preferably by the following stepwise heating method: 3 days at 50°C, 4 hours at 80°C, 6 hours at 100°C, 10 hours at 120°C, and 4 hours at 150°C.

7. A method for preparing the composite proton exchange membrane according to claim 4, comprising: The composite membrane according to any one of claims 1 to 3 or the composite membrane prepared by the method according to any one of claims 5 to 6 is immersed in a phosphoric acid solution to obtain the composite proton exchange membrane.

8. The method according to claim 7, wherein: The phosphoric acid content in the phosphoric acid solution is 60-85% by weight; and / or The soaking time is 1-48 hours; and / or The soaking temperature is 20-120°C; and / or The soaking was continued until the weight became constant.

9. A high-temperature proton exchange membrane fuel cell comprising: the composite proton exchange membrane according to claim 4 or the composite proton exchange membrane prepared by the method according to claim 7.

10. Use of the composite proton exchange membrane according to claim 4 or the composite proton exchange membrane prepared by the method according to claim 7 in a high-temperature proton exchange membrane fuel cell.

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