Inorganic polybenzimidazole-polyvinylpyrrolidone-doped high-temperature proton exchange membrane and preparation method thereof

Abstract

The invention discloses an inorganic polybenzimidazole-polyvinylpyrrolidone doped high-temperature proton exchange membrane and a preparation method of the inorganic polybenzimidazole-polyvinylpyrrolidone doped high-temperature proton exchange membrane. The high-temperature proton exchange membrane comprises arylether type polybenzimidazole-polyvinylpyrrolidone and imidazolyl silicon dioxide, the mass percent of the imidazolyl silicon dioxide and the arylether type polybenzimidazole-polyvinylpyrrolidone is less than 5%, the imidazolyl silicon dioxide is obtained by modifying silicon dioxide by an imidazolyl silane coupling agent, and the arylether type polybenzimidazole-polyvinylpyrrolidone and the imidazolyl silicon dioxide are mixed to form the high-temperature proton exchange membrane. The imidazolyl silane coupling agent has a general formula Im-L-Si (OCH3) 3, Im represents imidazolyl, L represents a linking group, and L comprises an alkyl chain. The preparation process is simple, the raw material cost is low, and the prepared inorganic doped membrane doped with phosphoric acid has the advantages of excellent oxidation resistance, proton conductivity, high mechanical strength and the like, and has wide application prospects in high-temperature proton exchange membrane fuel cells.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials and fuel cell technology, and relates to a high-temperature proton exchange membrane of inorganic doped polybenzimidazole-polyvinylpyrrolidone and its preparation method. Background Technology

[0002] In recent years, with the continuous use of chemical fuels, global environmental pollution and energy shortages have become increasingly serious. Fuel cells, as a highly efficient and clean energy conversion technology, are gradually receiving widespread attention. Among them, high-temperature proton exchange membrane fuel cells (HT-PEMFCs) exhibit accelerated electrode reaction kinetics at operating temperatures of 120℃-200℃, resulting in higher output power and faster response speeds. Their core component, the high-temperature proton exchange membrane (HT-PEM), has garnered significant attention. A highly efficient and stable proton exchange membrane under high-temperature conditions is the core material basis for realizing HT-PEMFCs, playing a role in conducting protons and blocking cathode and anode reactants and electrons.

[0003] Polybenzimidazole (PBI), as the most widely used polymer, plays a major role in the framework and acid adsorption of proton exchange membranes (PEMs). In PA-doped PEMs, a large amount of PA doping is required to achieve high proton conductivity. Therefore, acid-adsorption groups, such as polyvinylpyrrolidone (PVP), can be introduced into the system. As a basic polymer containing nitrogen heterocycles, PVP can also serve as adsorption sites for PA, anchoring PA within the polymer network structure. Proton transfer is achieved through proton transfer between PA molecules and nitrogen heterocycles, or between PA molecules themselves. Besides the nitrogen atom in the pyrrole ring, the carbonyl group in PVP can also adsorb PA; therefore, adding PVP can effectively improve the PA adsorption capacity of the PEM. Although PVP provides good phosphate (PA) adsorption sites to improve proton conductivity, its strong hydrophilicity and poor mechanical properties (brittleness) reduce the overall stability of the composite membrane when blended with PBI.

[0004] To compensate for the insufficient mechanical properties of PVP, existing technologies introduce inorganic fillers (such as ionic liquids, graphitic carbon nitride, etc.) to form organic-inorganic blend membranes. However, this brings new problems: inorganic fillers tend to aggregate in the polymer matrix, disrupting the uniform structure of the membrane; the introduced inorganic fillers compete for the adsorption of phosphoric acid, resulting in a reduction in the amount of "free" phosphoric acid available for proton conduction, which in turn reduces the proton conductivity of the membrane.

[0005] In summary, existing technologies struggle to achieve a balance between the three key properties of high mechanical strength, excellent antioxidant stability, and high proton conductivity.

[0006] The statements herein provide only background information in relation to this invention and do not necessarily constitute prior art. Summary of the Invention

[0007] The purpose of this invention is to address the shortcomings of existing technologies by providing a novel high-temperature proton exchange membrane doped with inorganic materials such as polybenzimidazole and polyvinylpyrrolidone. This membrane not only achieves excellent mechanical strength and antioxidant stability through inorganic doping but also avoids the problem of decreased proton conductivity caused by doping, thereby achieving a comprehensive improvement in overall performance.

[0008] To achieve the above objectives, the present invention provides a high-temperature proton exchange membrane of inorganic doped polybenzimidazole-polyvinylpyrrolidone, comprising: aryl ether type polybenzimidazole (hereinafter referred to as OPBI)-polyvinylpyrrolidone, and imidazole-based silica, wherein the mass percentage of imidazole-based silica to aryl ether type polybenzimidazole-polyvinylpyrrolidone is less than 5%, and the imidazole-based silica is obtained by modifying silica with an imidazole-based silane coupling agent, wherein the imidazole-based silane coupling agent has the general formula Im-L--Si(OCH3)3, wherein Im represents an imidazole group, L represents a linking group, and L contains an alkyl chain.

[0009] Optionally, in the high-temperature proton exchange membrane, the mass percentage of imidazole silica and aryl ether polybenzimidazole-polyvinylpyrrolidone is 2% to 4%.

[0010] Optionally, the imidazole silane coupling agent comprises at least one of Im-(CH2)n-Si(OCH3)3 or Im-CO-NH-(CH2)n-Si(OCH3)3, wherein n is 2-6.

[0011] Optionally, in the aryl ether polybenzimidazole-polyvinylpyrrolidone, the mass percentage of aryl ether polybenzimidazole to polyvinylpyrrolidone is 1:2 to 2:1.

[0012] The present invention also provides a method for preparing a high-temperature proton exchange membrane based on the above-described inorganic doped polybenzimidazole-polyvinylpyrrolidone, comprising: Step S1: Surface modification of silica with imidazole silane coupling agent to obtain imidazole silica; Step S2: Imidazolium silica is co-doped with aryl ether polybenzimidazole-polyvinylpyrrolidone. Step S3, film formation.

[0013] Optionally, the film-forming method includes at least one of the following: casting, solution casting, blown film, or electrospinning.

[0014] Optionally, step S2 includes: Aromatic ether polybenzimidazole and polyvinylpyrrolidone were dissolved in a polar aprotic solvent to obtain a homogeneous solution; Imidazole-based silica was ultrasonically dispersed in a polar aprotic solvent; Mix the two together thoroughly. After film formation by casting, the polar aprotic solvent is removed by heating, and crosslinking is performed to obtain a high-temperature proton exchange membrane.

[0015] Optionally, the polar aprotic solvent comprises at least one of N,N-dimethylacetamide, N,N-dimethylformamide, N-methylpyrrolidone, or dimethyl sulfoxide.

[0016] Optionally, the polar aprotic solvent is removed by heating at a temperature of 40°C for 12 to 24 hours.

[0017] The present invention also provides a high-temperature proton exchange membrane fuel cell comprising: the above-mentioned inorganic doped polybenzimidazole-polyvinylpyrrolidone high-temperature proton exchange membrane.

[0018] Compared with the prior art, the technical solution of the present invention has at least the following beneficial effects: 1) Significantly improved mechanical strength: The inorganic rigid framework of imidazole silica (Im-SiO2) forms an organic-inorganic composite structure in the polymer matrix, which plays a reinforcing role, thereby improving the mechanical strength of the membrane material to withstand the physical stress during fuel cell operation.

[0019] 2) Enhance the antioxidant stability of the membrane to extend the service life of the fuel cell. Im-SiO2 has the ability to scavenge free radicals (·OH, HOO·), which can effectively slow down the oxidative degradation of polymer chains by Fenton's reagent.

[0020] 3) The proton conductivity is significantly improved, thus ensuring the high-performance output of the battery. A hydrogen bond network is formed between the imidazole groups on the Im-SiO2 surface and the amide groups of PVP, constructing a continuous and efficient proton transport channel. Furthermore, the imidazole groups themselves are also phosphate adsorption sites, increasing the overall phosphate adsorption capacity of the membrane rather than competitively consuming it. Therefore, inorganic doping not only does not reduce, but actually improves, the proton conductivity. Attached Figure Description

[0021] Figure 1 Mechanical strength and tensile strength diagrams of the surface-modified silica-doped polybenzimidazole-polyvinylpyrrolidone high-temperature proton exchange membrane materials prepared in Examples 1-4 with imidazole-silane coupling agents and the polybenzimidazole-polyvinylpyrrolidone membrane of Comparative Example 1.

[0022] Figure 2The oxidation stability of the surface-modified silica-doped polybenzimidazole-polyvinylpyrrolidone high-temperature proton exchange membrane materials prepared in Examples 1-4 with imidazole-silane coupling agents and the polyvinylpyrrolidone-polyethersulfone membrane of Comparative Example 1 is shown in the graphs within 96 h.

[0023] Figure 3 The fuel cell performance of the surface-modified silica-doped polybenzimidazole-polyvinylpyrrolidone high-temperature proton exchange membrane materials prepared in Examples 1-4 and the polybenzimidazole-polyvinylpyrrolidone membrane of Comparative Example 1 under hydrogen-oxygen conditions at 160°C without humidification is shown in the graphs. Detailed Implementation

[0024] The following detailed description, in conjunction with the accompanying drawings and specific embodiments, provides a further detailed explanation of the inorganic doped polybenzimidazole-polyvinylpyrrolidone high-temperature proton exchange membrane and its preparation method, as proposed in this invention. The advantages and features of this invention will become clearer from the following description. It should be noted that the accompanying drawings are in a very simplified form and use non-precise proportions, used only to facilitate and clarify the illustration of the embodiments of this invention. Please refer to the accompanying drawings to make the objectives, features, and advantages of this invention more apparent and understandable. It should be understood that the structures, proportions, sizes, etc., depicted in the accompanying drawings are only for illustrative purposes to aid those skilled in the art and are not intended to limit the implementation conditions of this invention. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in proportions, or adjustments to the size, without affecting the effects and objectives achieved by this invention, should still fall within the scope of the technical content disclosed in this invention.

[0025] Hydrophilic silica (SiO2) particles typically have a surface rich in hydroxyl groups (–OH), as shown in the following formula: It is prone to problems such as aggregation and poor dispersibility in organic matrices.

[0026] Imidazoles are nitrogen-containing heterocyclic compounds with basicity, coordination, and hydrogen bond acceptance capabilities, and are commonly used in catalysis, ionic liquids, and molecular recognition. Introducing imidazole groups into silane coupling agents can endow the SiO2 surface with basicity, coordination functionality, or ionic liquid properties.

[0027] This invention attempts to form Si–O–Si bonds on hydroxyl groups using imidazole silane coupling agents, which can introduce functional groups on the silicon surface and significantly improve oleophilicity, dispersibility, and subsequent chemical activity.

[0028] The structure of the imidazole silane coupling agent of the present invention comprises: 1) 3-Imidazolylpropylsilane (Im-CH2CH2CH2-Si(OCH3)3): It can be obtained by nucleophilic substitution of 3-chloropropyltrimethoxysilane (ClCH2CH2CH2-Si(OCH3)3) with imidazole.

[0029] 2) Urea-functionalized imidazole silane (Im-CO-NH-(CH2)n-Si(OCH3)3) can be obtained by reacting isocyanate with the amine of imidazole (Im) to generate a urea chain, which is then attached to a silane.

[0030] The common structural feature of the imidazole silane coupling agents of the present invention is that they are hydrolyzable triol silyl groups (Si(OCH3)3), which are hydrolyzed in a water / alcohol system to generate silanol (Si-OH), which then condenses with hydroxyl groups on the surface of SiO2 to form stable Si-O-Si bonds.

[0031] This invention provides a high-temperature proton exchange membrane of inorganically doped polybenzimidazole-polyvinylpyrrolidone (PVP), comprising: aryl ether type polybenzimidazole (OPBI)-polyvinylpyrrolidone (PVP), and imidazole-based silica, wherein the mass percentage of imidazole-based silica to aryl ether type polybenzimidazole-polyvinylpyrrolidone is less than 5%, and the imidazole-based silica is obtained by modifying silica with an imidazole-based silane coupling agent having the general formula Im-L--Si(OCH3)3, wherein Im represents an imidazole group, L represents a linking group, and L contains an alkyl chain, for example, -(CH2)n-. In some embodiments, the imidazole-based silane coupling agent comprises at least one of Im-(CH2)n-Si(OCH3)3 or Im-CO-NH-(CH2)n-Si(OCH3)3, wherein n is 2-6.

[0032] The imidazole-based silica is obtained by modifying hydrophilic silica with an imidazole-based silane coupling agent. Taking 3-imidazole propylsilane as an example, its modification of silica yields imidazole-based silica (Im-SiO2), as shown in the following equation: Im-SiO2 is an inorganic metal oxide material that exhibits resistance to hydroxyl radicals through redox cycles. . OH) and peroxy radicals (HOO) . The ability to remove phosphoric acid can improve the antioxidant stability of the composite membrane. Moreover, due to its inorganic rigid structure, an organic-inorganic structure is formed in the composite membrane, which can improve the mechanical strength of the composite membrane and reduce the swelling rate of the composite membrane after phosphoric acid doping.

[0033] The imidazole-based silane coupling agent comprises an imidazole group and a silyl ether group. The hydrogen bond network formed between the imidazole group and the amide group of polyvinylpyrrolidone (PVP) provides a continuous and efficient transport channel for proton transport, thereby improving the proton conductivity of the composite membrane.

[0034] The present invention also provides a method for preparing a high-temperature proton exchange membrane based on the above-described inorganic doped polybenzimidazole-polyvinylpyrrolidone, comprising: Step S1: Surface modification of silica with imidazole silane coupling agent to obtain imidazole silica (Im-SiO2).

[0035] Step S2 involves co-doping imidazole-based silica with aryl ether-type polybenzimidazole-polyvinylpyrrolidone.

[0036] Specifically, it includes: Step a: Dissolve aryl ether polybenzimidazole and polyvinylpyrrolidone in a polar aprotic solvent to obtain a homogeneous solution; Step b: Imidazole-based silica is ultrasonically dispersed in a polar aprotic solvent; Step c: Mix the two together thoroughly.

[0037] The order of steps a and b is not important, and the polar aprotic solvents used can be the same or different. The polar aprotic solvent includes at least one of N,N-dimethylacetamide, N,N-dimethylformamide, N-methylpyrrolidone, or dimethyl sulfoxide.

[0038] Step S3, film formation.

[0039] Optionally, the film-forming method includes at least one of the following: casting, solution casting, blown film, or electrospinning.

[0040] In some embodiments, a casting method is used to form the film. After casting, the polar aprotic solvent is removed by heating, for example, at a temperature of 40°C, and held for 12 to 24 hours to obtain a high-temperature proton exchange membrane through crosslinking.

[0041] The present invention also provides a high-temperature proton exchange membrane fuel cell comprising: the above-mentioned inorganic doped polybenzimidazole-polyvinylpyrrolidone high-temperature proton exchange membrane.

[0042] The PVP used in the following embodiments is: In PVP, n=10000-12000, purchased from Aladdin Biochemical Technology Co., Ltd.

[0043] OPBI: In OPBI, n=800-1000, prepared in the laboratory: 3.238 g (15 mmol) of 3,3'-diaminobenzidine and 3.942 g (15 mmol) of 4,4'-diphenyl ether dicarboxylic acid were added to a 150 mL reaction flask, followed by 150 g of Eaton reagent (prepared by dissolving 50 g of phosphorus pentoxide in 500 g of methanesulfonic acid) as the reaction solvent. N2 was bubbled into the reaction system, and the mixture was mechanically stirred at 140 °C for 1.5 h to obtain a high-viscosity liquid. This liquid was then poured into deionized water to obtain a brown filamentous polymer. After washing repeatedly with deionized water to remove a large amount of acid, the polymer was dried and ground into powder. NaHCO3 solution (10 wt%) was then added for neutralization for 24 h, followed by washing with deionized water until the pH of the filtrate was 7. The resulting solid was dried at 120 °C for 12 h to obtain the OPBI polymer. Reference HsiuLi Lin et al., "Poly(benzimidazole)-epoxide crosslink membranes for high temperature protonexchange membrane fuel cells, International Journal of Hydrogen Energy (2012)".

[0044] The PBI-PVP refers to the process of dissolving OPBI and PVP together in NMP at a certain mass ratio (e.g., 2:1) and stirring until completely dissolved to form a homogeneous blend solution.

[0045] The Im-SiO2 used in this embodiment is: The surface-modified silica (Im-SiO2) was synthesized by reacting 3-imidazolium propylsilane with hydrophilic SiO2 nanoparticles: 0.6008 g (10 mmol) of SiO2 was added to 50 ml of organic solvents such as toluene and ethanol and ultrasonically dispersed. Then, 2.7242 g (10 mmol) of 3-imidazolium propylsilane was added, and the reaction was carried out with stirring at 60-80 °C for 12-16 h. After the reaction was completed, the reaction product was centrifuged and washed several times with ethanol in a vacuum filter. Finally, it was dried in an 80 °C oven for 24 h to completely remove the solvent, yielding surface-modified silica with imidazolium propylsilane coupling agent (Im-SiO2).

[0046] The 3-imidazolium propylsilane and the hydrophilic SiO2 nanoparticles were both purchased from Aladdin Biochemical Technology Co., Ltd.

[0047] Example 1 The preparation method of O / P-ImSiO2 high-temperature proton exchange membrane material is as follows: The mass ratio of surface-modified silica (Im-SiO2) to polybenzimidazole-polyvinylpyrrolidone (PBI-PVP) is controlled at 2:100, that is, 2% by mass of surface-modified silica (Im-SiO2) is added to PBI-PVP, based on the total mass of PBI-PVP. Specifically, OPBI (oxy-phenylene benzimazole) and polyvinylpyrrolidone (PVP) were first added to an N-methylpyrrolidone solution (mass ratio: OPBI:PVP = 2:1), and stirred at room temperature for 12 hours to dissolve. Then, imidazole-based silane coupling agent surface-modified silica (Im-SiO2) was added to the N-methylpyrrolidone solution, and stirred and ultrasonically dispersed at room temperature. The uniformly dispersed suspension of imidazole-based silane coupling agent surface-modified silica (Im-SiO2) was added to the above polybenzimidazole-polyvinylpyrrolidone solution, stirred at room temperature and ultrasonically dispersed to obtain an inorganic doped solution with a mass fraction of 10 wt% Im-SiO2 / OPBI-PVP. The film was formed by casting: the homogeneous solution was cast onto a glass plate, heated at 40°C for 24 hours, and the solvent was evaporated to obtain an inorganic doped polybenzimidazole-polyvinylpyrrolidone high-temperature proton exchange membrane. The inorganic doped membrane was immersed in 85 wt% phosphoric acid at room temperature for 1 hour and then removed to obtain the desired composite high-temperature proton exchange membrane.

[0048] Example 2 The difference from Example 1 is that the mass ratio of the surface-modified silica with imidazole silane coupling agent is 3%. The specific preparation process of the composite film is as follows: The mass ratio of surface-modified silica (Im-SiO2) to polybenzimidazole-polyvinylpyrrolidone was controlled at 3:100, that is, 3% by mass of surface-modified silica (Im-SiO2) was added. Specifically, polybenzimidazole (OPBI) and polyvinylpyrrolidone (PVP) were first added to an N-methylpyrrolidone solution (mass ratio: OPBI:PVP = 2:1) and stirred at room temperature for 12 hours to dissolve. Then, imidazole-based silane coupling agent surface-modified silica (Im-SiO2) was added to the N-methylpyrrolidone solution and stirred and ultrasonically dispersed at room temperature. The uniformly dispersed suspension of imidazole-based silane coupling agent surface-modified silica (Im-SiO2) was added to the above polybenzimidazole-polyvinylpyrrolidone solution, stirred and ultrasonically dispersed at room temperature to obtain an inorganic doped solution with a mass fraction of 10 wt% Im-SiO2 / OPBI-PVP. The homogeneous solution was cast onto a glass plate using a casting method, heated at 40°C for 24 hours, and the solvent was evaporated to obtain an inorganic doped polybenzimidazole-polyvinylpyrrolidone high-temperature proton exchange membrane. The inorganic doped membrane was immersed in 85 wt% phosphoric acid at room temperature for 1 hour and then removed to obtain the desired composite high-temperature proton exchange membrane.

[0049] Example 3 The difference from Example 1 is that the mass ratio of the aminosilane coupling agent surface-modified silica added is 4%. The specific preparation process of the composite film is as follows: The mass ratio of surface-modified silica (Im-SiO2) to polybenzimidazole-polyvinylpyrrolidone was controlled to be 4:100, that is, 4% by mass of surface-modified silica (Im-SiO2) was added. First, polybenzimidazole (OPBI) and polyvinylpyrrolidone (PVP) were added to an N-methylpyrrolidone solution (mass ratio: OPBI:PVP = 2:1) and stirred at room temperature for 12 h to dissolve them. Then, imidazole-based silane coupling agent surface-modified silica (Im-SiO2) was added to the N-methylpyrrolidone solution and stirred at room temperature with ultrasonic dispersion. The uniformly dispersed suspension of imidazole-based silane coupling agent surface-modified silica (Im-SiO2) was added to the above polybenzimidazole-polyvinylpyrrolidone solution, stirred at room temperature and ultrasonically dispersed to obtain an inorganic doped solution with a mass fraction of 10 wt% Im-SiO2 / OPBI-PVP. The homogeneous solution was cast onto a glass plate using a casting method, heated at 40 °C for 24 h, and the solvent was evaporated to obtain an inorganic doped polybenzimidazole-polyvinylpyrrolidone high-temperature proton exchange membrane. The inorganic doped membrane was immersed in 85 wt% phosphoric acid at room temperature for 1 hour and then removed to obtain the desired composite high-temperature proton exchange membrane.

[0050] Example 4 The difference from Example 1 is that the mass ratio of the aminosilane coupling agent surface-modified silica added is 5%. The specific preparation process of the composite film is as follows: The mass ratio of surface-modified silica (Im-SiO2) to polybenzimidazole-polyvinylpyrrolidone was controlled to be 5:100, that is, 5% by mass of surface-modified silica (Im-SiO2) was added. First, polybenzimidazole (OPBI) and polyvinylpyrrolidone (PVP) were added to an N-methylpyrrolidone solution (mass ratio: OPBI:PVP = 2:1) and stirred at room temperature for 12 h to dissolve them. Then, imidazole-based silane coupling agent surface-modified silica (Im-SiO2) was added to the N-methylpyrrolidone solution and stirred at room temperature with ultrasonic dispersion. The uniformly dispersed suspension of imidazole-based silane coupling agent surface-modified silica (Im-SiO2) was added to the above polybenzimidazole-polyvinylpyrrolidone solution, stirred at room temperature and ultrasonically dispersed to obtain an inorganic doped solution with a mass fraction of 10 wt% Im-SiO2 / OPBI-PVP. The homogeneous solution was cast onto a glass plate using a casting method, heated at 40 °C for 24 h, and the solvent was evaporated to obtain an inorganic doped polybenzimidazole-polyvinylpyrrolidone high-temperature proton exchange membrane. The inorganic doped membrane was immersed in 85 wt% phosphoric acid at room temperature for 1 hour and then removed to obtain the desired composite high-temperature proton exchange membrane.

[0051] Comparative Example 1 Prepare a high-temperature proton exchange membrane of polybenzimidazole-polyvinylpyrrolidone (OPBI-PVP).

[0052] The difference from Example 1 is that no imidazole silane coupling agent was added to modify the surface of the silica. The specific preparation process is as follows: Polybenzimidazole (OPBI) and polyvinylpyrrolidone (PVP) were added to an N-methylpyrrolidone solution (mass ratio: OPBI:PVP = 2:1) and stirred at room temperature for 4 hours to dissolve uniformly, yielding a homogeneous and transparent solution with a mass fraction of 10%. A film was formed by casting the homogeneous solution onto a glass plate and heating at 60°C for 20 hours to evaporate the solvent, thus obtaining a polybenzimidazole high-temperature proton exchange membrane. The membrane was then immersed in 85 wt% phosphoric acid at room temperature for 1 hour to obtain the desired high-temperature proton exchange membrane.

[0053] Comparative Example 2 Prepare a high-temperature proton exchange membrane of silica-doped polybenzimidazole-polyvinylpyrrolidone (SiO2 / OPBI-PVP).

[0054] The difference from Example 1 is the addition of hydrophilic silica. The specific preparation process is as follows: The mass ratio of hydrophilic silica (SiO2) to polybenzimidazole-polyvinylpyrrolidone (PVP) was controlled at 2:100, i.e., 2% hydrophilic silica (SiO2) was added. First, polybenzimidazole (OPBI) and polyvinylpyrrolidone (PVP) were added to an N-methylpyrrolidone solution (mass ratio: OPBI:PVP = 2:1) and stirred at room temperature for 12 hours to dissolve. Then, hydrophilic silica (SiO2) was added to the N-methylpyrrolidone solution and stirred and ultrasonically dispersed at room temperature until homogeneous. The homogeneous suspension of hydrophilic silica (SiO2) was added to the above polybenzimidazole-PVP solution, stirred and ultrasonically dispersed at room temperature until homogeneous, finally obtaining an inorganic doped solution with a SiO2 / OPBI-PVP mass fraction of 10 wt%. A film was formed using a casting method, casting the homogeneous solution onto a glass plate, heating at 40°C for 24 hours, and evaporating the solvent to obtain an inorganically doped polybenzimidazole-PVP high-temperature proton exchange membrane. The inorganic doped membrane was immersed in 85 wt% phosphoric acid at room temperature for 1 hour and then removed to obtain a composite high-temperature proton exchange membrane.

[0055] Comparative Example 3 Prepare polybenzimidazole (OPBI) high-temperature proton exchange membrane.

[0056] The difference from Comparative Example 2 is the absence of polyvinylpyrrolidone (PVP) and hydrophilic silica (SiO2). The specific preparation process is shown below: Polybenzimidazole (OPBI) was added to an N-methylpyrrolidone (NMP) solution and stirred at 80°C for 4 hours to dissolve it uniformly, yielding a homogeneous brown solution with an 8% (w / w) OPBI content. A film was formed by casting the homogeneous solution onto a glass plate and heating it in a 60°C oven for 20 hours to evaporate the solvent, thus obtaining a polybenzimidazole high-temperature proton exchange membrane. The membrane was then immersed in 85 wt% phosphoric acid at 150°C for 1 hour and 30 minutes to obtain the desired high-temperature proton exchange membrane.

[0057] Composite films with different doping levels were subjected to the following offline and online tests after being treated with phosphoric acid.

[0058] The mechanical strength of the obtained high-temperature proton exchange membrane was tested according to GB / T 20042.3-2022. Specific operating conditions were as follows: the mechanical properties of the membrane material were evaluated using a Shimadzu AGX-1kN microcomputer-controlled electronic universal testing machine, strictly following the ASTM D638 standard sample preparation specifications. The phosphate-doped membrane was cut into rectangular test samples with dimensions of 30mm in length and 10mm in width, each sample measuring 30*10mm. 2 The sample was subjected to a constant tensile force of 2 mm / min at room temperature until the sample membrane broke, and the data was recorded. Each membrane was tested at least 3 times and the average value was taken.

[0059] Following GB / T 20042.3-2022, Fenton's reagent was prepared by mixing a solution containing 4 ppm FeSO4 and 3% H2O2. The pre-cut undoped sample film was then immersed at 80°C. Every 24 hours, the film was removed and rinsed with deionized water to remove the surface Fenton's reagent. The sample film was then dried in a 100°C oven and weighed. The residual mass percentage curve represents the oxidation stability.

[0060] According to GB / T 20042.5-2009, the polarization curve of the obtained high-temperature proton exchange membrane fuel cell was tested. The specific operating conditions were: single cell operating temperature of 160℃, anode feed of pure hydrogen, cathode feed of atmospheric pressure oxygen, and cathode / anode feed ratio of 1 / 1.

[0061] Test results are attached to the instruction manual. Figure 1-3 See Figure 1 The mechanical strength and tensile strength of the composite high-temperature proton exchange membranes of Examples 1 (O / P-ImS-2%), 2 (O / P-ImS-3%), 3 (O / P-ImS-4%), and 4 (O / P-ImS-5%) of this invention, and the high-temperature proton exchange membrane of Comparative Example 1 (O / P-2 / 1) were measured. As can be seen from the figures, after phosphoric acid doping, the mechanical strengths of Examples 1, 2, 3, 4, and Comparative Example 1 were measured to be 3.25 MPa, 4.71 MPa, 6.28 MPa, 4.06 MPa, and 3.08 MPa, respectively. The corresponding tensile strengths were 27.07%, 53.36%, 60.28%, 50.59%, and 45.34%, respectively. Compared with the film of Comparative Example 1, the inorganic doped composite films of Examples 1, 2, 3, and 4 of this invention have higher mechanical strength. It can be seen that this doping increases the tensile strength, proving that the inorganic rigid skeleton of Im-SiO2 forms an organic-inorganic composite structure in the polymer matrix, which plays a reinforcing role.

[0062] See Figure 2The oxidation stability of the composite high-temperature proton exchange membranes of Examples 1, 2, 3, and 4 of this invention, and the composite high-temperature proton exchange membrane of Comparative Example 2, were measured. A higher percentage of remaining mass indicates better oxidation stability. As shown in the graphs, the remaining mass of the doped membranes corresponding to Examples 1, 2, 3, 4, and Comparative Example 2 after 96 hours was 77.27%, 81.84%, 76.36%, 70.41%, and 71.73%, respectively, demonstrating a significant improvement in oxidation stability with smaller doping doses (2%-4%). ​​When the Im-SiO2 addition amount was too high (5%, Example 4), the improvement in oxidation stability weakened, even lower than that of the examples with lower addition amounts, indicating the existence of an optimal doping range. Furthermore, the improvement effect of unmodified SiO2 (Comparative Example 2) was also less than that of modified Im-SiO2 (Examples 1-3), demonstrating the necessity of surface imidazole functionalization.

[0063] See Figure 3 The proton conductivity diagrams of the high-temperature proton exchange membranes composited in Examples 1, 2, 3, and 4 of this invention, and the high-temperature proton exchange membrane of Comparative Example 3, were measured. As can be seen from the diagrams, at 0.1 A / cm... 2 The membrane electrode voltages measured for Examples 1, 2, 3, 4, and Comparative Example 1 were 0.765 V, 0.779 V, 0.776 V, 0.723 V, and 0.708 V, respectively. The fuel cell power densities measured for Examples 1, 2, 3, 4, and Comparative Example 1 were 76.5 mW / cm², respectively. -2 77.9 mW cm -2 77.6 mW cm -2 72.3 mW cm -2 70.8mW cm -2 At 0.5A / cm 2 The membrane electrode voltages measured for Examples 1, 2, 3, 4, and Comparative Example 1 were 0.627 V, 0.645 V, 0.535 V, 0.452 V, and 0.501 V, respectively. The fuel cell power densities measured for Examples 1, 2, 3, 4, and Comparative Example 1 were 313.5 mW / cm², respectively. -2 322.5 mWcm -2 267.5 mW cm -2 226.0 mW cm -2 250.5 mW cm -2 At 1.0 A / cm 2The membrane electrode voltages measured for Examples 1, 2, 3, 4, and Comparative Example 1 were 0.491 V, 0.529 V, 0.346 V, 0.271 V, and 0.276 V, respectively. The fuel cell power densities measured for Examples 1, 2, 3, 4, and Comparative Example 1 were 491.0 mW / cm², respectively. -2 529.0mW cm -2 346.0 mW cm -2 271.0 mW cm -2 276.0 mWcm -2 As can be seen, compared with the membrane of Comparative Example 1, the membrane electrodes prepared using the inorganic doped membranes (ImS-2%~ImS-4%) of Examples 1, 2 and 3 of this invention have lower polarization losses and higher fuel cell performance.

[0064] In summary, this invention employs inorganic materials co-doped with polybenzimidazole-polyvinylpyrrolidone (PBI-PVP) to form a high-temperature proton exchange membrane. The inorganic material is obtained by surface-modifying silica (Im-SiO2) with an imidazole-based silane coupling agent. This invention cleverly resolves the contradiction between enhancing mechanical properties and maintaining high proton conductivity in traditional organic-inorganic composite membranes through molecular design that functionalizes the inorganic dopant with imidazole groups. Im-SiO2 not only acts as a reinforcing agent but also as a functional proton conductor, producing a synergistic effect with the PBI-PVP matrix. The preparation process of this invention is simple, with low raw material costs. The inorganic-doped membrane, after being doped with phosphoric acid, exhibits excellent antioxidant capacity, high proton conductivity, and strong mechanical strength, showing broad application prospects in high-temperature proton exchange membrane fuel cells.

[0065] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0066] Although the present invention has been described in detail through the preferred embodiments above, it should be understood that the above description should not be considered as a limitation of the present invention. Various modifications and substitutions to the present invention will be apparent to those skilled in the art after reading the above description. Therefore, the scope of protection of the present invention should be defined by the appended claims.

Claims

1. A high temperature proton exchange membrane of inorganic doped polybenzimidazole-polyvinylpyrrolidone, characterized by, The high-temperature proton exchange membrane comprises: an aromatic ether type polybenzimidazole-polyvinylpyrrolidone, and an imidazole-based silica, wherein the mass percentage of the imidazole-based silica to the aromatic ether type polybenzimidazole-polyvinylpyrrolidone is less than 5%, the imidazole-based silica is obtained by modifying silica with an imidazole-based silane coupling agent, and the imidazole-based silane coupling agent has a general formula of Im-L-Si(OCH3)3, wherein Im represents an imidazole group, L represents a linking group, and L comprises an alkyl chain.

2. The inorganically doped polybenzimidazole-polyvinylpyrrolidone high temperature proton exchange membrane according to claim 1, characterized in that, In the high-temperature proton exchange membrane, the mass percentage of the imidazole-based silica to the aromatic ether type polybenzimidazole-polyvinylpyrrolidone is 2% to 4%.

3. The inorganically doped polybenzimidazole-polyvinylpyrrolidone high temperature proton exchange membrane of claim 2, wherein, The imidazole-based silane coupling agent comprises at least one of Im-(CH2)n-Si(OCH3)3 or Im-CO-NH-(CH2)n-Si(OCH3)3, wherein n is 2 to 6.

4. The inorganically doped polybenzimidazole-polyvinylpyrrolidone high temperature proton exchange membrane of claim 1, wherein, The aromatic ether type polybenzimidazole-polyvinylpyrrolidone is formed by blending an aromatic ether type polybenzimidazole with a polyvinylpyrrolidone, and the mass percentage of the aromatic ether type polybenzimidazole to the polyvinylpyrrolidone is 1:1 to 2:

1.

5. A method for producing the inorganic-doped polybenzimidazole- polyvinylpyrrolidone high-temperature proton exchange membrane according to any one of claims 1 to 4, characterized by, The method comprises the steps of: Step S1, modifying silica with an imidazole-based silane coupling agent to obtain imidazole-based silica; Step S2, blending and doping the imidazole-based silica with an aromatic ether type polybenzimidazole-polyvinylpyrrolidone; Step S3, film forming.

6. The production method according to claim 5, wherein The film forming method of step S3 comprises at least one of a casting method, a solution casting method, a film blowing method, or electrospinning.

7. The production method according to claim 5, wherein In step S3, the film is formed by using the casting method, and after the film forming, the polar aprotic solvent is removed by heating, and a high-temperature proton exchange membrane is obtained by cross-linking.

8. The production method according to claim 5, wherein Step S2 comprises: dissolving the aromatic ether type polybenzimidazole and the polyvinylpyrrolidone in a polar aprotic solvent to obtain a homogeneous solution; ultrasonically dispersing the imidazole-based silica in the polar aprotic solvent; mixing and stirring the two to be uniform.

9. The production method according to claim 8, wherein The polar aprotic solvent comprises at least one of N,N-dimethylacetamide, N,N-dimethylformamide, N-methylpyrrolidone, or dimethyl sulfoxide.

10. A high temperature proton exchange membrane fuel cell, characterized by, The high-temperature proton exchange membrane comprises the inorganic doped polybenzimidazole-polyvinylpyrrolidone of any one of claims 1 to 4.

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